CA1240097A - Linear ethylene copolymer - Google Patents
Linear ethylene copolymerInfo
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- CA1240097A CA1240097A CA000465836A CA465836A CA1240097A CA 1240097 A CA1240097 A CA 1240097A CA 000465836 A CA000465836 A CA 000465836A CA 465836 A CA465836 A CA 465836A CA 1240097 A CA1240097 A CA 1240097A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
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- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
- Organic Insulating Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A copolymer of ethylene with at least one C4-C20 .alpha.-olefin having the following characteristics (A) to (J):
(A) it has a melt flow rate of from 0.01 to 200 g/10 min., (B) it has a density (d) of from 0.850 to 0.930 g/cm3, (C) it has a composition distribution parameter (U) of not more than 50, (D) the amount of components having a degree of branch-ing of not more than 2/1000 carbons is more than 10% by weight based on the ethylene copolymer, (E) the amount of components having a degree of branch-ing of at least 30/1000 carbons is not more than 70% by weight based on the ethylene copolymer, (F) the ratio of the average block methylene chain length to the average methylene chain length is not more than 2.0, (G) it has n melting points measured by a differential scanning calorimeter (DSC) (where n=1 or n?3), in which the highest melting point (T1) among these DSC melting points is given by the following expression (i) (175 x d - 46)°C?T1?125°C (i), the difference between T1 and the lowest melting point (Tn) among the DSC melting points is given by the following expression (ii) 18°C<T1 - Tn?65°C (ii), and the difference between T1 and the second high-est melting point (T2) is given by the following expression (iii) 0°C<T1 - T2?20°C (iii), (H) when n?3 in the characteristic (G) above, the ratio of the amount of heat of crystal fusion (H1) at the highest melting point T1 to the total amount of heat of crystal fusion (HT) is given by the following expression 0<H1/HT?0.40, (I) it has a crystallinity of from 15 to 70%, and (J) it has a molecular weight distribution ?w/?n of from 2.5 to 10.
A copolymer of ethylene with at least one C4-C20 .alpha.-olefin having the following characteristics (A) to (J):
(A) it has a melt flow rate of from 0.01 to 200 g/10 min., (B) it has a density (d) of from 0.850 to 0.930 g/cm3, (C) it has a composition distribution parameter (U) of not more than 50, (D) the amount of components having a degree of branch-ing of not more than 2/1000 carbons is more than 10% by weight based on the ethylene copolymer, (E) the amount of components having a degree of branch-ing of at least 30/1000 carbons is not more than 70% by weight based on the ethylene copolymer, (F) the ratio of the average block methylene chain length to the average methylene chain length is not more than 2.0, (G) it has n melting points measured by a differential scanning calorimeter (DSC) (where n=1 or n?3), in which the highest melting point (T1) among these DSC melting points is given by the following expression (i) (175 x d - 46)°C?T1?125°C (i), the difference between T1 and the lowest melting point (Tn) among the DSC melting points is given by the following expression (ii) 18°C<T1 - Tn?65°C (ii), and the difference between T1 and the second high-est melting point (T2) is given by the following expression (iii) 0°C<T1 - T2?20°C (iii), (H) when n?3 in the characteristic (G) above, the ratio of the amount of heat of crystal fusion (H1) at the highest melting point T1 to the total amount of heat of crystal fusion (HT) is given by the following expression 0<H1/HT?0.40, (I) it has a crystallinity of from 15 to 70%, and (J) it has a molecular weight distribution ?w/?n of from 2.5 to 10.
Description
~2~
LINEAR ETH~LENE COPOLYMER
This invention relates to ethylene/C4-C20 ~-olefin copolymers which have new characteristics in regard to composition distribution, degree of branch-ing, randomness and crystallinity by DSC melting points and are not described in the prior literature. These copolymers have excellent transparency" impact strength, tear strength, blocking resistance, environ-mental stress cracking resistance, heat resistance and low-temperature heat sealability in a well-balanced comblnation when they have a density of at least 0.g0.
When their density is less than 0.90, these copolymers have particularly excellent transparency, impact strength and low-temperature heat sealability, and by incorporating them in various thermoplastic resins, they serve as an excellent modifier for improved impact strength and low-temperature heat sealability.
More specifically, this invention relates to a copolymer of ethylene with at least one C~-C2~ ~-olefin having the following characteristics (A) to (J):
(A) It has a melt flow rate, determined by ASTM D
1238E, of from 0.01 to 200 g/10 min.~
(B) it has a density of from 0.850 to 0.930 g/cm3, (C) it has a composition distribution parameter (U), defined by the ~ollowing equation (1) U=100 x (Cw/Cn - 1) ........ (1) wherein Cw is the weight average degree of branching, and Cn is the number average degree of branching J
of not more than 50, (D) the amount of components having a degree of branching of not more than 2/1000 carbons is not more than 10% by wei~ht based on the ethylene copolymer, (E) the amount of components having a degree of branching of at least 30/1000 carbons is not more than 70% by weight based on the ethylene ., . ,,., ~ -, :. .
copolymer, (F) the ratlo of the average block methylene chain length to the average methylene chain length is not more than 2.0, (G) lt has n melting points measured by a dif-ferential scanning calorimeter (DSC) (where n=l or n>3), in which the hip,hest melting point (Tl) among these DSC melting points is glven by the following expression (i) (175 x d - 46) C<Tl<125C (i) whereln d is the density (kg/cm3) of the copolymer, the difference between Tl and the lowest melting point (Tn) among the DSC melting points is given by the following expression (ii) 18C<Tl - Tn < 65C (ii), and the difference between Tl and the second highest melting point (T2) is given by the following expression (iii) 0C<Tl - T2 < 20C ~iii)$
provided that when the number of melting polnts is one (i,e., n=l), only the expression (i) ls applicable and the expressions (ii) and (iii) are not applicable, (H) when n>3 in the characteristic (G) above, the ratio of the amount of heat of crystal fusion (Hl) at the highest melting point Tl to the total amount of heat of crystal fusion (HT) is ~iven by : the following expression O<IIl/HT<0-40, (I) it has a crystallinity~ measured by an X-ray diffractlon method~ of from 15 to 70%, and (J~ it has a molecular weight distribution Mw/Mn where Mw is the weight average molecular wei~ht of the copolymer and Mn is the number average molecular weight of the copolymer, measured by gel permeation chromatography, of from 2.5 to 10.
Low-density polyethylene (to be sometlmes abbreviated as HP-LDPE) obtained by the high pressure process has been extensively used as rilms, hollow containers, ln~ection-molded articles, pipes~ steel pipe coatings, cable and wire coatings, foamed articles, etc. because of its pliability and relatively good transparency. However, since HP-LDPE has poor impact strength, tear strength and environmental stress cracking resistance (to be sometimes abbreviated as ESCR), it is not suitable for use in fields re~uirin~
materials which are excellent in these properties and have the aforesaid good properties in a well balanced combination.
On the other hand, low-density polyethylenes 20 (to be sometimes abbreviated as L-LDPE) obtained by co- -polymerizln~ ethylene with ~-olefins having at least 3 carbon atoms under medium to low pressure conditions have better mechanical strength, ESCR and transparency than HP~LDPE, and therefore attract interest as a sub-stitute of ~P-LDPE in some applications. But the mechanical stren~th and optical properties of L-LDPE
are still required to be improved, and it still does not have satisfactory heat sealability. Hence~ L-LDPE
cannot meet the recent requirement ~or hi~h strength which arises from the higher speeds of packagin~
machines such as bag-making machines and filing and packing machines or the reduced thickness of packing materialsO It has therefore been desired to develop materials which are excellent in these properties and at the same time have the inherent good propertles mentioned above in a well balanced combination.
An ethylene copolymer meetlng this require-ment was disclosed in U. S Patent No. 4J205,021 (cor-responding to Japanese Laid-Open Patent Publication No. 92887/1978). Investigations of the present in-ventors, however, show that the ethylene copolymer specifically disclosed in this patent has a somewhat broad composition distribution and cont;ains an un-negligible arnount of components having low crystal-linity and therefore does not have fully satisfactory composition distribution characteristics, and lts blocking resistance is still desired to be improved.
Japanese Laid-Open Patent Publication No.
10541/1982 (corresponding to U~S. Patent No. 4,405,774) propose~ an ethylene copolymer havin~ improved anti-blocking property which has a melt flow rate of 0.1 to 100 g/10 min.~ a density of 0.91 to 0.94 g/cm3 and a single DSC melting point, and in which the crystallinity (X) and the xylene absorption rate (Y) per unit amount of an amorphous portion have the relation Y<-0.80X +
0.67. The balance between the heat resistance and the low temperature heat sealability of this ethylene co-polymer is poor. Attempts to improve the low-temper-ature heat sealability result in a reduction in heat resistance, and attempts t~ improve the heat resistance result in a reduction in low-temperature heat seal-ability. In attition, the antiblocking property ofthis ethylene copolymer is not sufficient.
Japanese Laid-Open Patent Publication No.
12~809/1982 (corresponding to U.S. Patent No.4,438,238) proposes an ethylene/~-olefin copolymer having a specific long chain branchin~ index and a specific short chain branching distribution. The proposed co-polymer, however, has the dlsadvantage that its com-position distribution is broad and its transparency and impact strength are unsatisfactory. It cannot be a material having various excellent properties in a well-balanced combination.
Japanese Patent Publication No. 21212/1971 (corresponding to U.S. Patent No. 3,645,992) proposes a process for continuous production of a uniform random partially crystalline copolymer having a narrow molecular weight distribution in the presence of a vanadium-containing catalyst. The ethylene copolymer obtained by this process, however9 has an extremely narrow molecular weight dlstribution and an extremely low crystallinity. Even when this ethylene copolymer is used to produce films and sheets, it is difficult to obtain products having heat resistance and low-temperature heat sealability in a well-balanced com-bination. Furthermore, this copolymer has inferior antiblocking property.
The present inventors have extensively worked on the development of an ethylene eopolymer whieh has exeellent mechanieal properties, optleal properties, bloeking resistanee, heat ~esistanee and low-temper-ature heat sealability in a well-balaneed eombination.
First, they diseovered that in an ethylene eopolymer, particularly a copolymer of ethylene with a Cl~-C20 ~-olefin, the combination of parameters of composition distr~bution characteristics, the degree of branehing, randomness, DSC melting points, crystal-linity and molecular weight distribution is an important faetor for imparting the aforesaid exeellent properties and maintaining a good balance among them.
Further work based on this new finding has finally led to the diseovery that an ethylene/C4-C20 ~-olefin eopolymer having the eharaeteristics (A) to (J) stated above can be produeed, and has various excellent properties in a well balaneed eomblnation.
It has been found that when its density is at least 0.90 g/em3, this eopolymer has excellent transpareney, impact strength, tear strength, antiblocking property, environmental stress craeking resistance, heat resistanee and low-temperature heat sealability in a well balanced combination. It has further been found that when its density is less than 0.90 ~/cm3, this copolymer has excellent transparency, impact strength and low-temperature heat sealabillty and a broader molecular weight distribution and better moldability than the uniform random partially crystalline copolymer produced in the presence of a vanadium-containing catalyst, and by incorporating it into various termo-plastic resins, it serves as an excellent modifier for improved impact strength and low-temperature heat seal-ability.
It is an object of this invention thereforeto provide a new type of ethylene copolymersO
The above and other objects and advantages of this invention will become apparent from the follow-ing description.
The ethylene copolymer of this invention isdefined by the characteristics (A) to (J) which will be described below in detail.
The ethylene copolymer of this invention is a substantially linear copolymer of ethylene with an ~-olefin having 4 to 20 carbon atoms, preferably 4 to 18 carbon atoms, especially preferably 4 to 12 carbon atoms. At least one ~-olefin may be used. Examples of the ~-olefin are l-butene~ 1-pentene, l-hexene9 4-methyl-l-pentene3 l-heptene, l-octene, l-decene, 1-tetradecene, l-octadecene, and mixtures of these. When propylene, i.e. C3 ~-olefing is used, the resulting copolymer has poor tear strength, impact strength and environmental stress crackin~ resistance.
The content of the ~-olefin units constitut-ing the ethylene copolymer of this invention is optionally within the range which meets the specific composition distribution defined by the characteristics (C), (D) and (~) glven hereinabove. Usually, it is 0.5 to 40 mole%, preferably 0.5 to 30 mole%, and especially preferably 1.5 to 2.0 mole%.
The ethylene copolymer of the invention has a substantially llnear structure. The substantially linear structure, as referred to herei~, means a linear structure having branches ~ased on the ~-olefin but being free from long chain branches and crosslinkages.
This is confirmed by the fact that the ethylene co-polymer completely dissolves in n-decane at 130C.
The ethylene copolymer of this invention has a melt flow rate (MFR) of from 0.01 to 200 g/lO min., preferably from 0.05 to 150 gJlO min. [characteristic (A)].
The MFR is measured in accordance with AST~
Dl238E. If the MFR exceeds 200 g/lO min., the ethylene copolymer has poor moldability and mechanical strength.
If it is less than 0.01 g/10 min., its moldabiliky is also deteriorated undesirably.
The ethylene copolymer of this invention has a density of from o.850 to 0.930 g/cm3, preferably 0.880 to 0.930 g/cm3 [characteristic (B)].
The density is measured in accordance with ASTM D1505. If the density exceeds 0.930 g/cm3, the transparency3 tear strength, impact strength and low temperature heat sealability of the copolymer are deteriorated, and if it is less than 0.850 g/cm3, the antiblocking property of the copolymer becomes poor.
The ethylene copolymer of this invention has a composition distribution parameter (U), defined by the following equation U = 100 x (Cw/Cn 1) .......... (1) wherein Cw represents a weight average degree of branching and Cn represents a number a~erage degree of branching, of not more than 50, for example O<U<50, preferably not more than 40, more preferably not more than 30 ~charac-teristlc (C)].
U is a parameter showlng the distribution of components of the copolymer which is irrelevant to its molecular weight. As the characteristics (D), (E), (F), (G), etc. to be described below, it is an important characteristic which specifies the structure of the copolymer of this inventionO If U exceeds 50, the composition distribution of the copolymer is too broad, and the copolymer has poor transparency, tear strength, impact strength, blocking reslstance and low-temperature heat sealability. It is diff`icult therefore to provide the desired excelLent propertles in a well balanced combination.
Cw and Cn used in e~uation (:L) for calculat-ing U are determlned by the followlng method.
The copolymer (10 ~) is added to about 2liters of a mlxture of p-xylene and butyl Cellosolve~
(80:20 by volume) and the mixture is heated at about 130C in the presence of 2,5-di-tert.butyl-4-methyl-phenol (0.1% by weight based on copolymer) as a heatstabilizer. Then, about 1 kg of diatomaceous earch (tradename Ce~lte~#560, made by Johns-Manville Company, U. S. A.) is added to the resulting solution, and the mixture is cooled to room temperature with stirring.
This operation results in coating the copolymer on diatomaceous earth. Then, the entire mixture is filled in a jacketed c~lindrical column (diameter about 3 cm) which is set perpendicularly. While the column is maintained at a temperature of 30C, a solvent havlng the same composition as the above mixed solvent in the same volume as a solution flowing from the bottom of the column is passed (about 1 liter/hr) through the solumn from its top. The solution flowing out from the bottom of the column is collected in a receiver. To the collected solution is added methanol in an amount twice the volume of the collected solution to precipi-tate the eluted copolymer. After confirming that upon addition of methanol, the copolymer no longer precipi-tates, the flowing of the solution is stopped. The temperature of the column is then raised to 35C, and the flowing of the solution and the passing of the mixed solvent are resumed and continued until the copolymer no longer flows out. The foregoing operation is carried out at intervals of 5C until the operation is finally carried out at 120C. The copolyMer frac~
tions precipitated from methanol are separated by ~i]tration and dried to obtain fractions.
The welght of each of the fractions is then measured, and the degree of branching per lO00 carbons [C] of each of the fractions is determined by the 3C-NMR method shown below with regard to the charac-teristic (D).
Since the degree of branching per 1000 carbons [C] of the fraction decreases as the eluting temperature rises, the cumulative weight fractions [I(~)] are ealeulated in the deereasing order of the eluting temperature. Under the assumption that the number of branehes per 1000 earbons [C] and the eumula-tive weight fraetion [I(w)] in eaeh fraetionated por-tion follow the integral funetion of the logarithmie normal distribution, whieh is the following equation (2~, parameters ~ and CO e~uation (2) are determined by using the method of least square.
p[ ~2(~n C/CO) ~ d~nC) ~2) and CO are given by the following equations.
~2 = 2 ~n(Cw/Cn) (3) CO = Cw-Cn (~) Thus, Cn and Cw ean be easily ealeulated.
The amount of components havin~ a degree of branehing of not more than 2/1000 carbons (not more than 2 branehes per 1000 earbons of the main ehain of the eopolymer) is not more than 10% by welght, for example lO to 0% by wei~ht~ preferably not more than 5% by weight, more preferably not more than 3% by weight [characteristic (D)~.
The characteristie (D) is a parameter which means that the amount of components which have too ~ 10 --small a degree of branches bonded to the main chaln of the copolymer is small9 and which together with the composition distribution parameter U, specifies the structure of the ethylene copolymer of this invention.
If the copolymer contains more than 10,~ by weight of components having a degree of branching of not more than 2/lO00 C, it has poor transparency, tear strength, impact strength~ and low temperature heat sealability~ and it is difficult to provide the desired excellent properties in a well balanced combination.
The degree of branching, as used herein, denotes the number of branches per 1000 carbons in the copol~mer chain, and is determined in accordance with the method disclosed in G. J. Ray, P. E. Johnson and J. R. Knox, Macromolecules, 10, 713 (1977) from the area lntensity of a signal of methylenic carbon adjacent to a branch observed by the l3C-NMR spectrum. For example, when the comonomers are a copolymer of butene-l and 4-methylpentene-l, the positions of the chemical shifts of the slgnals assigned to the above meth~lenic carbons are respectively 33~8 ppm and 34~5 ppm with TMS (tetra-methylsilane) as a standardO
In the ethylene copolymer of this invention, the amount of components having a degree of branching of at least 30/lO00 carbons is not more than 70% by weight, for example 70 to 0% b~ weight, preferably not more than 20% by weight, more preferably not more than 5% by weight [characteristic (E)].
The characteristic (E) is a parameter which means that the amount o~ components having a main chain structure ln which the number of branches bonded to the main chaln of the copolymer is too large is amall. It is an important characterlstic which together with the composition distribution parameter U [characterlstic (C)] and the branching degree condition tcharacteristic ~D)]~ specifles the structure of the copolymer of this invention. If the amount of components having at least 30 branches/1000 C exceeds 70% by weight, the copolymer has deteriorated antiblocking property and tends to soil an object with which it makes contact.
The amounts o~ components ha~in~ not more than 2 branches/1000 carbons and components having at least 30 branches/1000 carbons are determined as fol-lows:- The relation between the cumulative weight fractions and the degrees of branching obtained from the fractionation of the copolymer per~ormed in determining U with regard to the characteristic (C) is plotted on a graph, and the points corresponding to two branches/1000 C and 30 branches/1000 C on the graph are interpolated; The cumulative weight fractions cor-responding to these points are determined based on the results3 and the above amounts can thus be determined.
The ethylene copolymer of this invention has an n-decanesoluble content at 23C of usually 0 to 60%
by weight, preferably 0 to 5~ by weight3 more prefer-ably 0 to 2% by weight. The n-decane-soluble content, as referred to herein, is determined by dissolving lOg of the ethylene copolymer in 1 llter of n-decane at 130C in the presence of 2,5-tert butyl-4-methylphenol as a heat stabilizer, maintaining the solution at 130C
for 1 hour~ cooling the solution to 23C at a rate o~
1C/min., measuring the wei~ht of the precipitated ethylene copolymer, substracting the measured weight from lOg, and calculating the percentage of the dlf-ference based on lOg.
In the ethylene copolymer of this invention, the ratio of the average block methylene chain length to average methylene chain length is not more than 2.0, for example 2.0 to 1.0, preferably 1.7 to 1.0, more preferably 1.5 to 1.0 [characterlstic (F~].
This characteristic (F) is a parameter ~hichshows the random structure of ethylene and the d-olefin in the molecular chains of the copolymer, and is one of the important characteristics which together with the characteristics (C) to (E), specifies ~he structure of the ethylene copolymer of this invention. If the ratio exceeds 2.0, the copolymer has inferior transparency, tear strength, impact strength, blockin~ resistance and low-temperature heatsealabilityg and it is difficult to provide the desired excellent properties in a well balanced combination.
In the present invention, the above ratio in characteristic (~) is determined from the average methylene chain length calculated by using 13C~NMR and the average block methylene chain length calculated by excluding the case where the number of methylene groups between two adjacent branches is not ~ore than 6, and defined as the ratio of the average block methylene chain length to the average methylene chain length. The blocX methylene chain length is the number of methylene groups between branches determined from the signals of the third and four-th and subsequent methylenic carbons observed when the number of methylene groups between branches is at leas~ 7. The positions of the chemical shifts of the signals assigned to the third and fourth and subsequent methylenes are 30.1 ppm and 29.6 ppm, respectively, with TMS as a standard.
The ethylene copolymer of this invention has n melting points measured by a differential scanning calorimeter (DSC) (where n=l or n>3), and the hlghest melting point (Tl) among these DSC melting point or points is given by the following expression (i) (i) (175 x d 46) C<Tl<1?5 C, preferably (175 x d - 45) C<Tl<113C.
wherein d is the density (g/cm3) of the copolymer.
The difference between Tl and the lowest melting poiint (T ) among the DSC melting points is given by the following expression (ii) (ii) 18~,Tl - Tn<65C, preferably 18C<Tl - Tn<50C, more preferably 18 C<Tl ~ I'n<30 C
and the difference between Tl and the second highest melting point (T2) is ~iven by the following expression (lii) (iii) 0 C<T1 - T2<20 C, preferably 0 C<Tl - T2<15 C, more preferably 2C<Tl - T2_10C~
when the number of melting points is one (i.e., n=1), only the expression (i) is applicable and expressions (ii) and (iii) are not applicable.
The above DSC melting points and their relation are a parameter which together with the characteristic (H) described below, has to do with the crystallinity characteristics of the ethylene copolymer of this invention. Th~s parameter is one of the important characteristics which together with the characteristics already described above~ specifies the structure of the copolymer of this invention. If Tl in the characteristic ~G) is less than (175 x d - 46)C
(d is as defined above) ? the copolymer has reduced heat resistanceO If T1 is higher than 125C, the trans~
parency and low-temperature heat sealability of the copolymer are inferior. When Tl - Tn is higher than 65C or Rl - T2 exceeds 20C, the tear strength, impact strength and low-temperature heat sealability of the copolymer are deteriorated, and it is difficult to provide the desired excellent properties in a well balanced combination.
In the present invention, the DSC melting points ln characteristic (G) and the amount of heat of crystal fusion (Hl) and the amount of heat o~ crystal fusion (HT) are measure~d and determined by the follow-ing methods.
Using a differential scanning calorimeter, 3 mg of a sample is melted at 200C for 5 minutes.
Then, the temperature is lowered to 20C at a rate of 10C/min. rrhe sample is then maintained at this temperature for 1 minute, and again heated to 150C
at a rate of 10C/min. Thus, a DSC endothermic curve is obtained.
Figures 1 and 2 accompanying this application are charts showin~ examples of DSC endothermic curves of the ethylene copolymers of this invention.
Among the endothermic peaks in the DSC
endothermic curve, T1 in Figure 1 appearing as a peak on the highest temperature side or as a shoulder or Tl in Figure 2 (the intersecting point of tangential lines drawn at the deflection point P1 on the high temper-ature side of the shoulder and the deflection point P2 on the low temperature side of the shoulder) is the highest melting point (T1). As shown in Figures 1 and
LINEAR ETH~LENE COPOLYMER
This invention relates to ethylene/C4-C20 ~-olefin copolymers which have new characteristics in regard to composition distribution, degree of branch-ing, randomness and crystallinity by DSC melting points and are not described in the prior literature. These copolymers have excellent transparency" impact strength, tear strength, blocking resistance, environ-mental stress cracking resistance, heat resistance and low-temperature heat sealability in a well-balanced comblnation when they have a density of at least 0.g0.
When their density is less than 0.90, these copolymers have particularly excellent transparency, impact strength and low-temperature heat sealability, and by incorporating them in various thermoplastic resins, they serve as an excellent modifier for improved impact strength and low-temperature heat sealability.
More specifically, this invention relates to a copolymer of ethylene with at least one C~-C2~ ~-olefin having the following characteristics (A) to (J):
(A) It has a melt flow rate, determined by ASTM D
1238E, of from 0.01 to 200 g/10 min.~
(B) it has a density of from 0.850 to 0.930 g/cm3, (C) it has a composition distribution parameter (U), defined by the ~ollowing equation (1) U=100 x (Cw/Cn - 1) ........ (1) wherein Cw is the weight average degree of branching, and Cn is the number average degree of branching J
of not more than 50, (D) the amount of components having a degree of branching of not more than 2/1000 carbons is not more than 10% by wei~ht based on the ethylene copolymer, (E) the amount of components having a degree of branching of at least 30/1000 carbons is not more than 70% by weight based on the ethylene ., . ,,., ~ -, :. .
copolymer, (F) the ratlo of the average block methylene chain length to the average methylene chain length is not more than 2.0, (G) lt has n melting points measured by a dif-ferential scanning calorimeter (DSC) (where n=l or n>3), in which the hip,hest melting point (Tl) among these DSC melting points is glven by the following expression (i) (175 x d - 46) C<Tl<125C (i) whereln d is the density (kg/cm3) of the copolymer, the difference between Tl and the lowest melting point (Tn) among the DSC melting points is given by the following expression (ii) 18C<Tl - Tn < 65C (ii), and the difference between Tl and the second highest melting point (T2) is given by the following expression (iii) 0C<Tl - T2 < 20C ~iii)$
provided that when the number of melting polnts is one (i,e., n=l), only the expression (i) ls applicable and the expressions (ii) and (iii) are not applicable, (H) when n>3 in the characteristic (G) above, the ratio of the amount of heat of crystal fusion (Hl) at the highest melting point Tl to the total amount of heat of crystal fusion (HT) is ~iven by : the following expression O<IIl/HT<0-40, (I) it has a crystallinity~ measured by an X-ray diffractlon method~ of from 15 to 70%, and (J~ it has a molecular weight distribution Mw/Mn where Mw is the weight average molecular wei~ht of the copolymer and Mn is the number average molecular weight of the copolymer, measured by gel permeation chromatography, of from 2.5 to 10.
Low-density polyethylene (to be sometlmes abbreviated as HP-LDPE) obtained by the high pressure process has been extensively used as rilms, hollow containers, ln~ection-molded articles, pipes~ steel pipe coatings, cable and wire coatings, foamed articles, etc. because of its pliability and relatively good transparency. However, since HP-LDPE has poor impact strength, tear strength and environmental stress cracking resistance (to be sometimes abbreviated as ESCR), it is not suitable for use in fields re~uirin~
materials which are excellent in these properties and have the aforesaid good properties in a well balanced combination.
On the other hand, low-density polyethylenes 20 (to be sometimes abbreviated as L-LDPE) obtained by co- -polymerizln~ ethylene with ~-olefins having at least 3 carbon atoms under medium to low pressure conditions have better mechanical strength, ESCR and transparency than HP~LDPE, and therefore attract interest as a sub-stitute of ~P-LDPE in some applications. But the mechanical stren~th and optical properties of L-LDPE
are still required to be improved, and it still does not have satisfactory heat sealability. Hence~ L-LDPE
cannot meet the recent requirement ~or hi~h strength which arises from the higher speeds of packagin~
machines such as bag-making machines and filing and packing machines or the reduced thickness of packing materialsO It has therefore been desired to develop materials which are excellent in these properties and at the same time have the inherent good propertles mentioned above in a well balanced combination.
An ethylene copolymer meetlng this require-ment was disclosed in U. S Patent No. 4J205,021 (cor-responding to Japanese Laid-Open Patent Publication No. 92887/1978). Investigations of the present in-ventors, however, show that the ethylene copolymer specifically disclosed in this patent has a somewhat broad composition distribution and cont;ains an un-negligible arnount of components having low crystal-linity and therefore does not have fully satisfactory composition distribution characteristics, and lts blocking resistance is still desired to be improved.
Japanese Laid-Open Patent Publication No.
10541/1982 (corresponding to U~S. Patent No. 4,405,774) propose~ an ethylene copolymer havin~ improved anti-blocking property which has a melt flow rate of 0.1 to 100 g/10 min.~ a density of 0.91 to 0.94 g/cm3 and a single DSC melting point, and in which the crystallinity (X) and the xylene absorption rate (Y) per unit amount of an amorphous portion have the relation Y<-0.80X +
0.67. The balance between the heat resistance and the low temperature heat sealability of this ethylene co-polymer is poor. Attempts to improve the low-temper-ature heat sealability result in a reduction in heat resistance, and attempts t~ improve the heat resistance result in a reduction in low-temperature heat seal-ability. In attition, the antiblocking property ofthis ethylene copolymer is not sufficient.
Japanese Laid-Open Patent Publication No.
12~809/1982 (corresponding to U.S. Patent No.4,438,238) proposes an ethylene/~-olefin copolymer having a specific long chain branchin~ index and a specific short chain branching distribution. The proposed co-polymer, however, has the dlsadvantage that its com-position distribution is broad and its transparency and impact strength are unsatisfactory. It cannot be a material having various excellent properties in a well-balanced combination.
Japanese Patent Publication No. 21212/1971 (corresponding to U.S. Patent No. 3,645,992) proposes a process for continuous production of a uniform random partially crystalline copolymer having a narrow molecular weight distribution in the presence of a vanadium-containing catalyst. The ethylene copolymer obtained by this process, however9 has an extremely narrow molecular weight dlstribution and an extremely low crystallinity. Even when this ethylene copolymer is used to produce films and sheets, it is difficult to obtain products having heat resistance and low-temperature heat sealability in a well-balanced com-bination. Furthermore, this copolymer has inferior antiblocking property.
The present inventors have extensively worked on the development of an ethylene eopolymer whieh has exeellent mechanieal properties, optleal properties, bloeking resistanee, heat ~esistanee and low-temper-ature heat sealability in a well-balaneed eombination.
First, they diseovered that in an ethylene eopolymer, particularly a copolymer of ethylene with a Cl~-C20 ~-olefin, the combination of parameters of composition distr~bution characteristics, the degree of branehing, randomness, DSC melting points, crystal-linity and molecular weight distribution is an important faetor for imparting the aforesaid exeellent properties and maintaining a good balance among them.
Further work based on this new finding has finally led to the diseovery that an ethylene/C4-C20 ~-olefin eopolymer having the eharaeteristics (A) to (J) stated above can be produeed, and has various excellent properties in a well balaneed eomblnation.
It has been found that when its density is at least 0.90 g/em3, this eopolymer has excellent transpareney, impact strength, tear strength, antiblocking property, environmental stress craeking resistance, heat resistanee and low-temperature heat sealability in a well balanced combination. It has further been found that when its density is less than 0.90 ~/cm3, this copolymer has excellent transparency, impact strength and low-temperature heat sealabillty and a broader molecular weight distribution and better moldability than the uniform random partially crystalline copolymer produced in the presence of a vanadium-containing catalyst, and by incorporating it into various termo-plastic resins, it serves as an excellent modifier for improved impact strength and low-temperature heat seal-ability.
It is an object of this invention thereforeto provide a new type of ethylene copolymersO
The above and other objects and advantages of this invention will become apparent from the follow-ing description.
The ethylene copolymer of this invention isdefined by the characteristics (A) to (J) which will be described below in detail.
The ethylene copolymer of this invention is a substantially linear copolymer of ethylene with an ~-olefin having 4 to 20 carbon atoms, preferably 4 to 18 carbon atoms, especially preferably 4 to 12 carbon atoms. At least one ~-olefin may be used. Examples of the ~-olefin are l-butene~ 1-pentene, l-hexene9 4-methyl-l-pentene3 l-heptene, l-octene, l-decene, 1-tetradecene, l-octadecene, and mixtures of these. When propylene, i.e. C3 ~-olefing is used, the resulting copolymer has poor tear strength, impact strength and environmental stress crackin~ resistance.
The content of the ~-olefin units constitut-ing the ethylene copolymer of this invention is optionally within the range which meets the specific composition distribution defined by the characteristics (C), (D) and (~) glven hereinabove. Usually, it is 0.5 to 40 mole%, preferably 0.5 to 30 mole%, and especially preferably 1.5 to 2.0 mole%.
The ethylene copolymer of the invention has a substantially llnear structure. The substantially linear structure, as referred to herei~, means a linear structure having branches ~ased on the ~-olefin but being free from long chain branches and crosslinkages.
This is confirmed by the fact that the ethylene co-polymer completely dissolves in n-decane at 130C.
The ethylene copolymer of this invention has a melt flow rate (MFR) of from 0.01 to 200 g/lO min., preferably from 0.05 to 150 gJlO min. [characteristic (A)].
The MFR is measured in accordance with AST~
Dl238E. If the MFR exceeds 200 g/lO min., the ethylene copolymer has poor moldability and mechanical strength.
If it is less than 0.01 g/10 min., its moldabiliky is also deteriorated undesirably.
The ethylene copolymer of this invention has a density of from o.850 to 0.930 g/cm3, preferably 0.880 to 0.930 g/cm3 [characteristic (B)].
The density is measured in accordance with ASTM D1505. If the density exceeds 0.930 g/cm3, the transparency3 tear strength, impact strength and low temperature heat sealability of the copolymer are deteriorated, and if it is less than 0.850 g/cm3, the antiblocking property of the copolymer becomes poor.
The ethylene copolymer of this invention has a composition distribution parameter (U), defined by the following equation U = 100 x (Cw/Cn 1) .......... (1) wherein Cw represents a weight average degree of branching and Cn represents a number a~erage degree of branching, of not more than 50, for example O<U<50, preferably not more than 40, more preferably not more than 30 ~charac-teristlc (C)].
U is a parameter showlng the distribution of components of the copolymer which is irrelevant to its molecular weight. As the characteristics (D), (E), (F), (G), etc. to be described below, it is an important characteristic which specifies the structure of the copolymer of this inventionO If U exceeds 50, the composition distribution of the copolymer is too broad, and the copolymer has poor transparency, tear strength, impact strength, blocking reslstance and low-temperature heat sealability. It is diff`icult therefore to provide the desired excelLent propertles in a well balanced combination.
Cw and Cn used in e~uation (:L) for calculat-ing U are determlned by the followlng method.
The copolymer (10 ~) is added to about 2liters of a mlxture of p-xylene and butyl Cellosolve~
(80:20 by volume) and the mixture is heated at about 130C in the presence of 2,5-di-tert.butyl-4-methyl-phenol (0.1% by weight based on copolymer) as a heatstabilizer. Then, about 1 kg of diatomaceous earch (tradename Ce~lte~#560, made by Johns-Manville Company, U. S. A.) is added to the resulting solution, and the mixture is cooled to room temperature with stirring.
This operation results in coating the copolymer on diatomaceous earth. Then, the entire mixture is filled in a jacketed c~lindrical column (diameter about 3 cm) which is set perpendicularly. While the column is maintained at a temperature of 30C, a solvent havlng the same composition as the above mixed solvent in the same volume as a solution flowing from the bottom of the column is passed (about 1 liter/hr) through the solumn from its top. The solution flowing out from the bottom of the column is collected in a receiver. To the collected solution is added methanol in an amount twice the volume of the collected solution to precipi-tate the eluted copolymer. After confirming that upon addition of methanol, the copolymer no longer precipi-tates, the flowing of the solution is stopped. The temperature of the column is then raised to 35C, and the flowing of the solution and the passing of the mixed solvent are resumed and continued until the copolymer no longer flows out. The foregoing operation is carried out at intervals of 5C until the operation is finally carried out at 120C. The copolyMer frac~
tions precipitated from methanol are separated by ~i]tration and dried to obtain fractions.
The welght of each of the fractions is then measured, and the degree of branching per lO00 carbons [C] of each of the fractions is determined by the 3C-NMR method shown below with regard to the charac-teristic (D).
Since the degree of branching per 1000 carbons [C] of the fraction decreases as the eluting temperature rises, the cumulative weight fractions [I(~)] are ealeulated in the deereasing order of the eluting temperature. Under the assumption that the number of branehes per 1000 earbons [C] and the eumula-tive weight fraetion [I(w)] in eaeh fraetionated por-tion follow the integral funetion of the logarithmie normal distribution, whieh is the following equation (2~, parameters ~ and CO e~uation (2) are determined by using the method of least square.
p[ ~2(~n C/CO) ~ d~nC) ~2) and CO are given by the following equations.
~2 = 2 ~n(Cw/Cn) (3) CO = Cw-Cn (~) Thus, Cn and Cw ean be easily ealeulated.
The amount of components havin~ a degree of branehing of not more than 2/1000 carbons (not more than 2 branehes per 1000 earbons of the main ehain of the eopolymer) is not more than 10% by welght, for example lO to 0% by wei~ht~ preferably not more than 5% by weight, more preferably not more than 3% by weight [characteristic (D)~.
The characteristie (D) is a parameter which means that the amount of components which have too ~ 10 --small a degree of branches bonded to the main chaln of the copolymer is small9 and which together with the composition distribution parameter U, specifies the structure of the ethylene copolymer of this invention.
If the copolymer contains more than 10,~ by weight of components having a degree of branching of not more than 2/lO00 C, it has poor transparency, tear strength, impact strength~ and low temperature heat sealability~ and it is difficult to provide the desired excellent properties in a well balanced combination.
The degree of branching, as used herein, denotes the number of branches per 1000 carbons in the copol~mer chain, and is determined in accordance with the method disclosed in G. J. Ray, P. E. Johnson and J. R. Knox, Macromolecules, 10, 713 (1977) from the area lntensity of a signal of methylenic carbon adjacent to a branch observed by the l3C-NMR spectrum. For example, when the comonomers are a copolymer of butene-l and 4-methylpentene-l, the positions of the chemical shifts of the slgnals assigned to the above meth~lenic carbons are respectively 33~8 ppm and 34~5 ppm with TMS (tetra-methylsilane) as a standardO
In the ethylene copolymer of this invention, the amount of components having a degree of branching of at least 30/lO00 carbons is not more than 70% by weight, for example 70 to 0% b~ weight, preferably not more than 20% by weight, more preferably not more than 5% by weight [characteristic (E)].
The characteristic (E) is a parameter which means that the amount o~ components having a main chain structure ln which the number of branches bonded to the main chaln of the copolymer is too large is amall. It is an important characterlstic which together with the composition distribution parameter U [characterlstic (C)] and the branching degree condition tcharacteristic ~D)]~ specifles the structure of the copolymer of this invention. If the amount of components having at least 30 branches/1000 C exceeds 70% by weight, the copolymer has deteriorated antiblocking property and tends to soil an object with which it makes contact.
The amounts o~ components ha~in~ not more than 2 branches/1000 carbons and components having at least 30 branches/1000 carbons are determined as fol-lows:- The relation between the cumulative weight fractions and the degrees of branching obtained from the fractionation of the copolymer per~ormed in determining U with regard to the characteristic (C) is plotted on a graph, and the points corresponding to two branches/1000 C and 30 branches/1000 C on the graph are interpolated; The cumulative weight fractions cor-responding to these points are determined based on the results3 and the above amounts can thus be determined.
The ethylene copolymer of this invention has an n-decanesoluble content at 23C of usually 0 to 60%
by weight, preferably 0 to 5~ by weight3 more prefer-ably 0 to 2% by weight. The n-decane-soluble content, as referred to herein, is determined by dissolving lOg of the ethylene copolymer in 1 llter of n-decane at 130C in the presence of 2,5-tert butyl-4-methylphenol as a heat stabilizer, maintaining the solution at 130C
for 1 hour~ cooling the solution to 23C at a rate o~
1C/min., measuring the wei~ht of the precipitated ethylene copolymer, substracting the measured weight from lOg, and calculating the percentage of the dlf-ference based on lOg.
In the ethylene copolymer of this invention, the ratio of the average block methylene chain length to average methylene chain length is not more than 2.0, for example 2.0 to 1.0, preferably 1.7 to 1.0, more preferably 1.5 to 1.0 [characterlstic (F~].
This characteristic (F) is a parameter ~hichshows the random structure of ethylene and the d-olefin in the molecular chains of the copolymer, and is one of the important characteristics which together with the characteristics (C) to (E), specifies ~he structure of the ethylene copolymer of this invention. If the ratio exceeds 2.0, the copolymer has inferior transparency, tear strength, impact strength, blockin~ resistance and low-temperature heatsealabilityg and it is difficult to provide the desired excellent properties in a well balanced combination.
In the present invention, the above ratio in characteristic (~) is determined from the average methylene chain length calculated by using 13C~NMR and the average block methylene chain length calculated by excluding the case where the number of methylene groups between two adjacent branches is not ~ore than 6, and defined as the ratio of the average block methylene chain length to the average methylene chain length. The blocX methylene chain length is the number of methylene groups between branches determined from the signals of the third and four-th and subsequent methylenic carbons observed when the number of methylene groups between branches is at leas~ 7. The positions of the chemical shifts of the signals assigned to the third and fourth and subsequent methylenes are 30.1 ppm and 29.6 ppm, respectively, with TMS as a standard.
The ethylene copolymer of this invention has n melting points measured by a differential scanning calorimeter (DSC) (where n=l or n>3), and the hlghest melting point (Tl) among these DSC melting point or points is given by the following expression (i) (i) (175 x d 46) C<Tl<1?5 C, preferably (175 x d - 45) C<Tl<113C.
wherein d is the density (g/cm3) of the copolymer.
The difference between Tl and the lowest melting poiint (T ) among the DSC melting points is given by the following expression (ii) (ii) 18~,Tl - Tn<65C, preferably 18C<Tl - Tn<50C, more preferably 18 C<Tl ~ I'n<30 C
and the difference between Tl and the second highest melting point (T2) is ~iven by the following expression (lii) (iii) 0 C<T1 - T2<20 C, preferably 0 C<Tl - T2<15 C, more preferably 2C<Tl - T2_10C~
when the number of melting points is one (i.e., n=1), only the expression (i) is applicable and expressions (ii) and (iii) are not applicable.
The above DSC melting points and their relation are a parameter which together with the characteristic (H) described below, has to do with the crystallinity characteristics of the ethylene copolymer of this invention. Th~s parameter is one of the important characteristics which together with the characteristics already described above~ specifies the structure of the copolymer of this invention. If Tl in the characteristic ~G) is less than (175 x d - 46)C
(d is as defined above) ? the copolymer has reduced heat resistanceO If T1 is higher than 125C, the trans~
parency and low-temperature heat sealability of the copolymer are inferior. When Tl - Tn is higher than 65C or Rl - T2 exceeds 20C, the tear strength, impact strength and low-temperature heat sealability of the copolymer are deteriorated, and it is difficult to provide the desired excellent properties in a well balanced combination.
In the present invention, the DSC melting points ln characteristic (G) and the amount of heat of crystal fusion (Hl) and the amount of heat o~ crystal fusion (HT) are measure~d and determined by the follow-ing methods.
Using a differential scanning calorimeter, 3 mg of a sample is melted at 200C for 5 minutes.
Then, the temperature is lowered to 20C at a rate of 10C/min. rrhe sample is then maintained at this temperature for 1 minute, and again heated to 150C
at a rate of 10C/min. Thus, a DSC endothermic curve is obtained.
Figures 1 and 2 accompanying this application are charts showin~ examples of DSC endothermic curves of the ethylene copolymers of this invention.
Among the endothermic peaks in the DSC
endothermic curve, T1 in Figure 1 appearing as a peak on the highest temperature side or as a shoulder or Tl in Figure 2 (the intersecting point of tangential lines drawn at the deflection point P1 on the high temper-ature side of the shoulder and the deflection point P2 on the low temperature side of the shoulder) is the highest melting point (T1). As shown in Figures 1 and
2~ a plurality of ~SC points are designated as T1, T2, ... Tn from the high temperature side to the low temperature side. T2 is thus the second highest melt-ing point, and Tn is the lowest meltin~ point. Where n is 1, only T1 exists.
On the other hand, as shown in Fiogures 1 ~nd 2, the amount of heat of a portion defined by the straight line connecting the points at 60 C and 130 C
of the endothermic curve (the base line A-A' in the drawings) and the endothermic curve between them is defined as the total amount of heat of crysta] fusion (HT). Furthermore, as shown in Figure 1, when the highest melting point (Tl) appears as a peak3 a per-pendicular C3 is drawn from the minimum point B of the curve immediately on the low temperature side of T1 to the temperature axis of co-ordinates, and the amount of heat of ~he hatched portion defined by the per-pendicular C3, the base line A-A' (the portion C2 in the drqwing) and the endothermic curve (the curve por-tlon C1 between A and B ln the drawing) is defined asthe amount of heat of crystal fusion (H1) at the highest meltlng point (Tl). When the highest meltlng ~oint (Tl) appears as a shoulder as shown in Fi~ure 2, a perpendicular C3 is drawn from the intersecting point B' of tangential lines drawn at the deflection point P2 immediately on the low temperature side Or the shoulder and the deflection point P3 on the high temperature side of T2 to the temperature axis of co-ordinates, and the amount of heat of the hatchedportion de~ined by the perpendicular C3, the base line A-A' (the portion C2 in the drawing) and the endo thermic curve (the curve portion Cl between A and the intersection B" of the curve and the extension of C3) is defined as the amount of heat of crystal fusion (Y.l) at the highest melting point (Tl).
In the ethylene copolymer of this invention, the ratio of the amount of heat of crystal fusion (H1 as defined above) at the highest melting point (T1) among the DSC melting points to the total amount of heat Or crystal fusion (HT as defined.above) is o<H1<HT<0.40, preferably O.Ol<Hl/HT<0.35 [characteristic (H)]. This characteristic is applicable only where n>3 in the characteristic (G).
The ratio of the amounts of heat of fusion, Hl/HT, in the characteristic (H) is related to the crystallinity characteristics by DSC melting points Or the ethylene copolymer Or this invention together with the characteristic (G). If the Hl/HT ratio exceeds 0.40, the tear strength, impact strength and low-temperature heat sealability Or the copolymer are deteriorated. In combination with the other character-istics, this characteristic (H) serves to provide the desired excellent properties of the copolymer of this invention in a well balanced cornbination.
The ethylene copol~mer of this invention has a crystallinity, measured by an X-ray diffraction method, of 15 to 70%, ~referably 30 to 70%, more ~referably 40 to 65% [characteristlc (I)]. If the crystallinity is too high beyond 70%, the tear strength, impact strength and low-temperature heat sealability of the copolymer are reduced. If it is too low below 15%, the copolymer has drastically reduced antiblocking propekrty and heat resistance. Accordingly~ it should be within the above-specifled range.
The crystallinity of the ethylene copolymer is determined by the X-ray diffraction method. This method uses a straight line connecting diffraction angles 7 to 31.5 as a background~ and otherwise fol-lows the method described in the literature [S. L.
Aggarwal and G. P. Tilley: J. Polym. Sci., 18, 17 (1955)].
In the ethylene copolymer of this invention, the molecular weight distribution Mw/Mn wherein Mw is the weight average molecular weight of the copolymer and Mn is the number average molecular weight is given 0 by the following expressions [characteristic (J)].
2.5<Mw/Mn<10, ~referably 2.5<MwtMn<7~
more preferably 2.5<Mw/Mn<5.
If the molecular weight distribution of the ethylene copolymer exceeds 10, its impact strength and environmental stress cracking resistance are markedly reduced~ and i~ it less than 2.5, its moldability is deteriorated.
The molecular weight distribution Mw/Mn is measured by GPC (gel-permeation chromatography) under the following conditions.
Device: Model 150C, made by Waters Co.
Column: TSK GMH-6 (6 mm 0 x 600 mm) made by Toyo Soda Co., Ltd.
Solvent: ortho-dichlorobenzene (ODCB) Temperature: 135 C
Flow rate: 1.0 ml/min.
InJecting concentration: 30 mg/20 ml ODCB
(the amount inJected 40() microliters) The column elution volume is corrected by the universal method using standard polystyrene made by Toyo Soda Co., Ltd. and Pressure Chemic:al Co.
The copolymer of this invention can be produced~ for example, by copolymerizing ethylene with at least one CL~-C20 ~-olefin in the presence of a catalyst composition composed of (a) a titanlum component containing titanium~
magnesium and halogen as essential ingredients and obtalned by treating (a 1) a highly active solid component having a specific surface area of at least 50 m2/g with (a-2) an alcohol, Ga II~G l'llt, ~,n~
_ 18 -(c) a halogen compound component~
so that a copolymer having the aforesaid character-istics is formed ~when a part or the whole of the com-ponent (b) of the catalyst composition is an organo-aluminum compound containing halogen, the component (c)can be omitted).
The hi~hly active solid cornponent (a-l) is a component whlch can be itself be used as a highly active titanium catalyst component, and is well known.
Basically9 the component (a-l) can be obtained by reacting a magnesium compound and a titanium compound with or without an auxiliary reagent so as to obtain a solld component having a high specific surface area.
The solid component (a-l) has a specific surface area f at least about 50 m2/~, for example about 50 to about 1000 m2/~, and preferably about 80 to about 900 m /g. Generally, the solid component (a-l) contains about 0.2 to about 1~% by weight, preferably about 0.3 to about 15% by weight, of titanium, and has a halogen/
titanium atomic ratio of from about 4 to about 300, preferably from about 5 to about 200, and a magnesium/
titanium atomic rat~o of from about 1~8 to about 2009 preferably from about 2 to about 120.
The component (a-l) may contain other elements, metals, ~unctional groups, electron donors~
etc. in addition to the essential ingredients. For ~xample, aluminum and silicon may be used as the other elements and metals. Examples of the functional groups are al~oxy and aryloxy groups. Examples of the electron donors are ethers, carboxylic acids, esters and ketones. One preferred example of the method of producing the solid component (a-1) is a method which comprises treating a complex of a magnesium halide and an alcohol with an organic metal compound, for example an organoaluminum compound such as a trialkylaluminum or an alkyl aluminum halide, and reacting the treated product with a titanium compound. The details of this method are descrlbed in the specification of U. S.
Patent No~ 4,071,674, for example.
The alcohol (a-2) used to treat the highly active solid componen-t (a-l) may be an aliphatic, alicyclic or aromatic alcohol which may haYe a sub-stituent such as an alkoxy group. Specific examples of the alcohol are methanol, ethanol, n-propanol, iso-propanol, tert-butanol, n-hexanol, n-octanol, 2-ethylhexanol, n-decanol, oleyl alcohol" cyclopentanol, cyclohexanol, benzyl alcohol, isopropylbenzyl alcohol, cumyl alcohol and methoxyethanol. Aliphatic alcohols havlng 1 to 18 carbon atoms are especially preferred.
Treatment with the alcohol ls pre~erably carried out in an inert hydrocarbon such as hexane and heptane. ~or example, it is preferred to suspend the solld component (a-1) in the inert hydrocarbon to a concentration of 0.005 to 0.2 mole/llter, especially 0.01 to V.1 mole/liter, and to contact it with the alcohol in an amount of 1 to 80 moles, especially 2 to 50 moles, per titanium atom in the solid component (a-l). The reaction conditions can be properly selected depending upon the kind of the alcohol. For example, the reaction can be carried out at a temper ature of about -20 to about +100C, preferably about -10 to about ~100C, for several minutes to about 10 hours, preferably about 10 minutes to about 5 hours.
As a result of the alcohol treatment, the alcohol (a-2) is taken in the form of an alcohol and/or alkoxy group in the solid component (a-l)O Preferably, the amount of the alcohol (a-2) so taken into the component (a-l) ls 3 to 100 moles, especially 5 to ~0 moles3 per titanium atom. By this reaction, a part of titanium is sometimes liberated from the solid component (a-l)O
When such a solvent-soluble component exists, the resultlng titanium catalyst component is preferably washed with an inert solvent after the reaction, and then used for the polymerization.
The organoaluminurr~ compound component (b) to be used together with the tltanlum component (a) ls typically a compound of the ~eneral formula RnAlX3 n (wherein R represents a hydrocarbon ~roup, for example a Cl-C15 alkyl ~roup or a C2-C8 alkenyl group, X
represents a halo~en atom3 and O<n<3). Speciflc examples include trialkyl aluminums such as triethyl aluminum and triisobutyl aluminum; dialkyl aluminum halides such as diethyl aluminum chloride and diiso-butyl aluminum chloride; alkyl aluminum sesquihalidessuch as ethyl aluminum ses~uichloride and ethyl aluminum ses~uibromide; and alkyl aluminum dichloride such as ethyl aluminum dichloride. When the halo~en compound component (c) is not used9 it is desirable to use the component (b) so that in its general formula3 n is preferably 1.5<n<2.0, more preferably from 1.5<n<1.8 as an average composition.
The halogen compound component (c) iS9 for example, a halogenated hydrocarbon such as ethyl chloride or isopropyl chloride, or silicon tetra-chloride which can act as a halogenating agent for the component (b). When the component ~c) is used, its amount is preferably such that the total amount of the halogens in the components (b) and (c) is from 0.5 to 2 atoms, particularly from 1 to 1.5 atoms, per aluminum atom in the component (b).
The copolymerization of ethylene with the C4-C20 ~-olefin can be carried out in the liquid or vapor phase in the presence of the catalyst composition composed of components (a), (b) and (c) described above in the presence or absence of an inert diluent such as an inert hydrocarbon at a temperature of, for example, 0 to about 300C. In particular, the desired ethylene copolymer can be easily obtained by performin~ the copolymerization in the presence of an inert hydro-carbon under conditlons in which the resultin~ ethylene copolymer dissolves, at a temperature of3 for example, about 120 to 300 C~ preferably about 130 to 250 C.
The ratio between ethylene and the Cl~-C20 -olefln can be properly selected.
In performing the copolymeriYation, the amount of the titanium catalyst component (a) used is, for example, about 0.0005 to about 1 millimole/liter, preferably about 0.001 to about 0.1 mole/liter, calculated as titanium atom~ The amount of the organo-alwninum compound (b) is that which serves to maintain polymerization activity~ Desirablyj it is used so that the Al/Ti atomic ratio becomes from about 1 to about 2,000, preferably from about lO to about 500. The polymerization pressure is generally atmospheric pres-sure to about 100 kg/cm 3 especially abo~t ~ to about 5 kg/cm2.
The ethylene copolymers of this invention have better transparency, impact strenth~ tear strength, blockin~ resistance, low-temperature heat sealability, heat resistance and ESCR than not only HP-LDPE but also conventional L-LDPE, and retain these excellent properties in a well balanced combination~
Accordingly, they are especlally suitable for use as pac~aging fllms. These copolymers can be processed into various articles such as fllms, containers, plpes, tubes and household goods by various molding methods such as T-die molding, inflation film molding, blow molding, in~ection molding and extrusion. Various types of composite fllms can be formed by extrusion coating on other films or by coextrusion. They can also be used as steel pipe coatings, cable coatin~s or foamed articles. The copolymers of this inventlon ma~
be used as blends with other thermoplastic resins~ for example polyolefins such as HP-LDPE~ medium-density polyethylene, high-density polyethylene, polypropylene;
poly-1-butene, poly-4-methyl-1-pentene, ethylene/
propylene or 1-butene copolymers which have low crystallinity or are amorphousJ and propylene/l-butene copolymerO It is also ~ossible to incorporate ~etroleum resins, waxes, heat stabilizers, weather stabilizers, antistatic agents, antiblockin~ a~ents, slip agents9 nucleating a~ents~ pi~ments, dyes, inorganic or organic fillers, synthetic rubbers, natural rubbers, etc. into the copolymers of this invention.
~ mong the ethylene copolymers of this inven-tion, those havin~ a density of less than 0.90 ~/cm3 have particularly excellent transparency, impact strength and low-temperature sealability. They can be used in the same a~plications as those havin~ a density of at least 0.90 ~/cm3. But when these low~density copolymers are incorporated in various thermoplastic resins, the impact stren~th, low-temperature impact strength and low-temperature heat sealability of these thermoplastic resins can be improved greatly. Ac-cordingly3 they can be used as excellent modifiers for the thermoplastic resins. For use as modifiers for the thermoplastic resins, the ethylene copolymer may be used without modification. If desired, however, it can be used as a modi~ied productO Examples of the modified product are modlfied ethylene copolymers obtained by graft copolymerizin~ the ethylene copolymer with aromatic unsaturated hydrocarbons such as styrene, ~-methylstyrene, vinyltoluene and indene; and modified ethylene copolymers obained by graft copolymerizing the ethylene copolymer with unsaturated carboxylic acids and the anhydrides or esters thereof, such as acrylic acld, methacrylic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, endocis-5,6-dicarboxy-2-norbornene, methyl-endocis-5,6-dlcarboxy-2-norbornene, maleic anhydride, citraconic anhydride, itaconic anhydride, endocis-2-norbornene-5,G-dicarboxylic anhydride, methyl acrylate, methyl methacrylate, dimethyl maleate, dimethyl fumarate, dimethyl citraconate, dimethyl itaconate and dimethyl endocis~2-norbornene 5,6-dicarboxylate. The content of the modifylng component in the modified ethylene copolymer ls usually 0.01 to 100 parts by weight, preferably 0.1 to 50 parts by weightg per 100 parts by weight of the ethylene copolymer. The proportion of the ethylene copolymer or the modified ethylene co-polymer to be incorporated is usually 0.1 to 100 parts by weight, preferably 002 to 50 parts by wei~ht, per lO0 parts by weight of the thermoplastic resinO
Various thermoplastic resins can be modified by the ethylene copolymers of this invention or their modified products~ Examples include the above-exemplified polyolef`ins, styrene polymers such as polystyrene, poly(~-methylstyrene) 9 acrylonitrile/
styrene copolymer and acrylonitrile/butadiene/styrene copolyrner, polyesters such as polyethylene tere-phthalate and polybutylene terephthalate, polyamides such as polycaprolactoate, polyhexamethyl~ne adipamide, polyhexamethylene sebacamide and polydecamethylene adipamlde, polyarylene oxides such as poly(2,6-dimethylphenylene oxide), polyoxymethylene and poly-carbonate.
The thermoplastic resln composition modified by the incorporation of the ethylene copolymer or the modified ethylene copolymer may further include heat stabilizers, weatherability stabilizers, antistatic agents, antiblocking agents, lubricants~ nucleating agents, pigments, dyes, and inorganic or organic fillers as required.
The following examples illustrate the present invention more specifically.
The properties of the ethylene co~olymer obtained by this invention were evaluated by the fol-lowing methods.
Speclfically, the copolymer was formed into a film having a width of 350 mm and a thlckness of 50 microns by means of a commercial tubular fllm rorming machlne for high-pressure polyethylene (manufactured by Modern Machinery Company) under the following conditions.
Resin temperature: 180C
Screw rotating speed: 100 rpm Die diameter: 100 mm Die slit width: 0.7 mm The resulting film was evaluated by the following methods.
Haze t%) In accordance with ASTM D 1003 Impact strength (kg-cm/cm) Mewasured by a film impact tester made by Toyo Seiki Co., Ltd. The spherical surface of the impact head had a diameter of l inch.
Elmend_rf tear strength (kOE/Cm) In accordance with ASTM D1922.
BlockinK value (g) Measured substantially in accordance wlth ASTM D1893. The peeling bar was made of glass, and the peeling speed was adjusted to 20 cm/min.
Heat seal startin~ temperature ~C) Using a heat sealer made by Toyo Tester Co., Ltd., two films were heat-sealed over a l cm width at a given temperature (to be referred to as the heat seal temperature) under a pressure of 2 kg/cm2 for a sealing time of 1 second. From the two films integrated by heat sealing, a rectan~ular test sample having a width of 15 mm and a length of 60 mm was cut out. One short side of the test sample was heat-sealed and the other short side was left open. By using a tensile tester, the two open ends of the test sample were clamped by an air chuck and pulled at a pulling speed of 300 mm/min. at room temperature to perform a peeling test.
At this time, the sample was observed to determine whether the breakage was due to peeling or occurred at parts other than the heat-sealed surface.
The above operation was repeated at varying heat seal temperatures, and the heat seal temperature at which the breakage be~an to occur at the parts other than the heat-sealed surface was defined as the heat seal starting temperature.
Example 1 Preparation of a catalyst In an atmosphere of nitrogen, 1 mole of com~
mercial anhydrous magnesium chloride was suspended in 2 liters of puri~ied dehydrated hexane, and with stir-ring, 6 moles of ethanol was added dropwise over 1 hour. Then, the reaction was carried out at room temperature for 1 hour. To the reaction mixture was added dropwise 2.6 moles of diethyl aluminum chloride at room temperature, and the mixture was stirred for 2 hours. Then, 6 moles of titanium tetrachloride was added, and the mixture was heated to 80C. The reac-tion was carrled out at this temperature for 3 hours with stirring. After the reaction, the solld portion was separated, and repeatedly washed with purified hexane. The solid (designated A-1) had the following composition.
Ti ~ Cl Mg Al OEt ) (wt.%)
On the other hand, as shown in Fiogures 1 ~nd 2, the amount of heat of a portion defined by the straight line connecting the points at 60 C and 130 C
of the endothermic curve (the base line A-A' in the drawings) and the endothermic curve between them is defined as the total amount of heat of crysta] fusion (HT). Furthermore, as shown in Figure 1, when the highest melting point (Tl) appears as a peak3 a per-pendicular C3 is drawn from the minimum point B of the curve immediately on the low temperature side of T1 to the temperature axis of co-ordinates, and the amount of heat of ~he hatched portion defined by the per-pendicular C3, the base line A-A' (the portion C2 in the drqwing) and the endothermic curve (the curve por-tlon C1 between A and B ln the drawing) is defined asthe amount of heat of crystal fusion (H1) at the highest meltlng point (Tl). When the highest meltlng ~oint (Tl) appears as a shoulder as shown in Fi~ure 2, a perpendicular C3 is drawn from the intersecting point B' of tangential lines drawn at the deflection point P2 immediately on the low temperature side Or the shoulder and the deflection point P3 on the high temperature side of T2 to the temperature axis of co-ordinates, and the amount of heat of the hatchedportion de~ined by the perpendicular C3, the base line A-A' (the portion C2 in the drawing) and the endo thermic curve (the curve portion Cl between A and the intersection B" of the curve and the extension of C3) is defined as the amount of heat of crystal fusion (Y.l) at the highest melting point (Tl).
In the ethylene copolymer of this invention, the ratio of the amount of heat of crystal fusion (H1 as defined above) at the highest melting point (T1) among the DSC melting points to the total amount of heat Or crystal fusion (HT as defined.above) is o<H1<HT<0.40, preferably O.Ol<Hl/HT<0.35 [characteristic (H)]. This characteristic is applicable only where n>3 in the characteristic (G).
The ratio of the amounts of heat of fusion, Hl/HT, in the characteristic (H) is related to the crystallinity characteristics by DSC melting points Or the ethylene copolymer Or this invention together with the characteristic (G). If the Hl/HT ratio exceeds 0.40, the tear strength, impact strength and low-temperature heat sealability Or the copolymer are deteriorated. In combination with the other character-istics, this characteristic (H) serves to provide the desired excellent properties of the copolymer of this invention in a well balanced cornbination.
The ethylene copol~mer of this invention has a crystallinity, measured by an X-ray diffraction method, of 15 to 70%, ~referably 30 to 70%, more ~referably 40 to 65% [characteristlc (I)]. If the crystallinity is too high beyond 70%, the tear strength, impact strength and low-temperature heat sealability of the copolymer are reduced. If it is too low below 15%, the copolymer has drastically reduced antiblocking propekrty and heat resistance. Accordingly~ it should be within the above-specifled range.
The crystallinity of the ethylene copolymer is determined by the X-ray diffraction method. This method uses a straight line connecting diffraction angles 7 to 31.5 as a background~ and otherwise fol-lows the method described in the literature [S. L.
Aggarwal and G. P. Tilley: J. Polym. Sci., 18, 17 (1955)].
In the ethylene copolymer of this invention, the molecular weight distribution Mw/Mn wherein Mw is the weight average molecular weight of the copolymer and Mn is the number average molecular weight is given 0 by the following expressions [characteristic (J)].
2.5<Mw/Mn<10, ~referably 2.5<MwtMn<7~
more preferably 2.5<Mw/Mn<5.
If the molecular weight distribution of the ethylene copolymer exceeds 10, its impact strength and environmental stress cracking resistance are markedly reduced~ and i~ it less than 2.5, its moldability is deteriorated.
The molecular weight distribution Mw/Mn is measured by GPC (gel-permeation chromatography) under the following conditions.
Device: Model 150C, made by Waters Co.
Column: TSK GMH-6 (6 mm 0 x 600 mm) made by Toyo Soda Co., Ltd.
Solvent: ortho-dichlorobenzene (ODCB) Temperature: 135 C
Flow rate: 1.0 ml/min.
InJecting concentration: 30 mg/20 ml ODCB
(the amount inJected 40() microliters) The column elution volume is corrected by the universal method using standard polystyrene made by Toyo Soda Co., Ltd. and Pressure Chemic:al Co.
The copolymer of this invention can be produced~ for example, by copolymerizing ethylene with at least one CL~-C20 ~-olefin in the presence of a catalyst composition composed of (a) a titanlum component containing titanium~
magnesium and halogen as essential ingredients and obtalned by treating (a 1) a highly active solid component having a specific surface area of at least 50 m2/g with (a-2) an alcohol, Ga II~G l'llt, ~,n~
_ 18 -(c) a halogen compound component~
so that a copolymer having the aforesaid character-istics is formed ~when a part or the whole of the com-ponent (b) of the catalyst composition is an organo-aluminum compound containing halogen, the component (c)can be omitted).
The hi~hly active solid cornponent (a-l) is a component whlch can be itself be used as a highly active titanium catalyst component, and is well known.
Basically9 the component (a-l) can be obtained by reacting a magnesium compound and a titanium compound with or without an auxiliary reagent so as to obtain a solld component having a high specific surface area.
The solid component (a-l) has a specific surface area f at least about 50 m2/~, for example about 50 to about 1000 m2/~, and preferably about 80 to about 900 m /g. Generally, the solid component (a-l) contains about 0.2 to about 1~% by weight, preferably about 0.3 to about 15% by weight, of titanium, and has a halogen/
titanium atomic ratio of from about 4 to about 300, preferably from about 5 to about 200, and a magnesium/
titanium atomic rat~o of from about 1~8 to about 2009 preferably from about 2 to about 120.
The component (a-l) may contain other elements, metals, ~unctional groups, electron donors~
etc. in addition to the essential ingredients. For ~xample, aluminum and silicon may be used as the other elements and metals. Examples of the functional groups are al~oxy and aryloxy groups. Examples of the electron donors are ethers, carboxylic acids, esters and ketones. One preferred example of the method of producing the solid component (a-1) is a method which comprises treating a complex of a magnesium halide and an alcohol with an organic metal compound, for example an organoaluminum compound such as a trialkylaluminum or an alkyl aluminum halide, and reacting the treated product with a titanium compound. The details of this method are descrlbed in the specification of U. S.
Patent No~ 4,071,674, for example.
The alcohol (a-2) used to treat the highly active solid componen-t (a-l) may be an aliphatic, alicyclic or aromatic alcohol which may haYe a sub-stituent such as an alkoxy group. Specific examples of the alcohol are methanol, ethanol, n-propanol, iso-propanol, tert-butanol, n-hexanol, n-octanol, 2-ethylhexanol, n-decanol, oleyl alcohol" cyclopentanol, cyclohexanol, benzyl alcohol, isopropylbenzyl alcohol, cumyl alcohol and methoxyethanol. Aliphatic alcohols havlng 1 to 18 carbon atoms are especially preferred.
Treatment with the alcohol ls pre~erably carried out in an inert hydrocarbon such as hexane and heptane. ~or example, it is preferred to suspend the solld component (a-1) in the inert hydrocarbon to a concentration of 0.005 to 0.2 mole/llter, especially 0.01 to V.1 mole/liter, and to contact it with the alcohol in an amount of 1 to 80 moles, especially 2 to 50 moles, per titanium atom in the solid component (a-l). The reaction conditions can be properly selected depending upon the kind of the alcohol. For example, the reaction can be carried out at a temper ature of about -20 to about +100C, preferably about -10 to about ~100C, for several minutes to about 10 hours, preferably about 10 minutes to about 5 hours.
As a result of the alcohol treatment, the alcohol (a-2) is taken in the form of an alcohol and/or alkoxy group in the solid component (a-l)O Preferably, the amount of the alcohol (a-2) so taken into the component (a-l) ls 3 to 100 moles, especially 5 to ~0 moles3 per titanium atom. By this reaction, a part of titanium is sometimes liberated from the solid component (a-l)O
When such a solvent-soluble component exists, the resultlng titanium catalyst component is preferably washed with an inert solvent after the reaction, and then used for the polymerization.
The organoaluminurr~ compound component (b) to be used together with the tltanlum component (a) ls typically a compound of the ~eneral formula RnAlX3 n (wherein R represents a hydrocarbon ~roup, for example a Cl-C15 alkyl ~roup or a C2-C8 alkenyl group, X
represents a halo~en atom3 and O<n<3). Speciflc examples include trialkyl aluminums such as triethyl aluminum and triisobutyl aluminum; dialkyl aluminum halides such as diethyl aluminum chloride and diiso-butyl aluminum chloride; alkyl aluminum sesquihalidessuch as ethyl aluminum ses~uichloride and ethyl aluminum ses~uibromide; and alkyl aluminum dichloride such as ethyl aluminum dichloride. When the halo~en compound component (c) is not used9 it is desirable to use the component (b) so that in its general formula3 n is preferably 1.5<n<2.0, more preferably from 1.5<n<1.8 as an average composition.
The halogen compound component (c) iS9 for example, a halogenated hydrocarbon such as ethyl chloride or isopropyl chloride, or silicon tetra-chloride which can act as a halogenating agent for the component (b). When the component ~c) is used, its amount is preferably such that the total amount of the halogens in the components (b) and (c) is from 0.5 to 2 atoms, particularly from 1 to 1.5 atoms, per aluminum atom in the component (b).
The copolymerization of ethylene with the C4-C20 ~-olefin can be carried out in the liquid or vapor phase in the presence of the catalyst composition composed of components (a), (b) and (c) described above in the presence or absence of an inert diluent such as an inert hydrocarbon at a temperature of, for example, 0 to about 300C. In particular, the desired ethylene copolymer can be easily obtained by performin~ the copolymerization in the presence of an inert hydro-carbon under conditlons in which the resultin~ ethylene copolymer dissolves, at a temperature of3 for example, about 120 to 300 C~ preferably about 130 to 250 C.
The ratio between ethylene and the Cl~-C20 -olefln can be properly selected.
In performing the copolymeriYation, the amount of the titanium catalyst component (a) used is, for example, about 0.0005 to about 1 millimole/liter, preferably about 0.001 to about 0.1 mole/liter, calculated as titanium atom~ The amount of the organo-alwninum compound (b) is that which serves to maintain polymerization activity~ Desirablyj it is used so that the Al/Ti atomic ratio becomes from about 1 to about 2,000, preferably from about lO to about 500. The polymerization pressure is generally atmospheric pres-sure to about 100 kg/cm 3 especially abo~t ~ to about 5 kg/cm2.
The ethylene copolymers of this invention have better transparency, impact strenth~ tear strength, blockin~ resistance, low-temperature heat sealability, heat resistance and ESCR than not only HP-LDPE but also conventional L-LDPE, and retain these excellent properties in a well balanced combination~
Accordingly, they are especlally suitable for use as pac~aging fllms. These copolymers can be processed into various articles such as fllms, containers, plpes, tubes and household goods by various molding methods such as T-die molding, inflation film molding, blow molding, in~ection molding and extrusion. Various types of composite fllms can be formed by extrusion coating on other films or by coextrusion. They can also be used as steel pipe coatings, cable coatin~s or foamed articles. The copolymers of this inventlon ma~
be used as blends with other thermoplastic resins~ for example polyolefins such as HP-LDPE~ medium-density polyethylene, high-density polyethylene, polypropylene;
poly-1-butene, poly-4-methyl-1-pentene, ethylene/
propylene or 1-butene copolymers which have low crystallinity or are amorphousJ and propylene/l-butene copolymerO It is also ~ossible to incorporate ~etroleum resins, waxes, heat stabilizers, weather stabilizers, antistatic agents, antiblockin~ a~ents, slip agents9 nucleating a~ents~ pi~ments, dyes, inorganic or organic fillers, synthetic rubbers, natural rubbers, etc. into the copolymers of this invention.
~ mong the ethylene copolymers of this inven-tion, those havin~ a density of less than 0.90 ~/cm3 have particularly excellent transparency, impact strength and low-temperature sealability. They can be used in the same a~plications as those havin~ a density of at least 0.90 ~/cm3. But when these low~density copolymers are incorporated in various thermoplastic resins, the impact stren~th, low-temperature impact strength and low-temperature heat sealability of these thermoplastic resins can be improved greatly. Ac-cordingly3 they can be used as excellent modifiers for the thermoplastic resins. For use as modifiers for the thermoplastic resins, the ethylene copolymer may be used without modification. If desired, however, it can be used as a modi~ied productO Examples of the modified product are modlfied ethylene copolymers obtained by graft copolymerizin~ the ethylene copolymer with aromatic unsaturated hydrocarbons such as styrene, ~-methylstyrene, vinyltoluene and indene; and modified ethylene copolymers obained by graft copolymerizing the ethylene copolymer with unsaturated carboxylic acids and the anhydrides or esters thereof, such as acrylic acld, methacrylic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, endocis-5,6-dicarboxy-2-norbornene, methyl-endocis-5,6-dlcarboxy-2-norbornene, maleic anhydride, citraconic anhydride, itaconic anhydride, endocis-2-norbornene-5,G-dicarboxylic anhydride, methyl acrylate, methyl methacrylate, dimethyl maleate, dimethyl fumarate, dimethyl citraconate, dimethyl itaconate and dimethyl endocis~2-norbornene 5,6-dicarboxylate. The content of the modifylng component in the modified ethylene copolymer ls usually 0.01 to 100 parts by weight, preferably 0.1 to 50 parts by weightg per 100 parts by weight of the ethylene copolymer. The proportion of the ethylene copolymer or the modified ethylene co-polymer to be incorporated is usually 0.1 to 100 parts by weight, preferably 002 to 50 parts by wei~ht, per lO0 parts by weight of the thermoplastic resinO
Various thermoplastic resins can be modified by the ethylene copolymers of this invention or their modified products~ Examples include the above-exemplified polyolef`ins, styrene polymers such as polystyrene, poly(~-methylstyrene) 9 acrylonitrile/
styrene copolymer and acrylonitrile/butadiene/styrene copolyrner, polyesters such as polyethylene tere-phthalate and polybutylene terephthalate, polyamides such as polycaprolactoate, polyhexamethyl~ne adipamide, polyhexamethylene sebacamide and polydecamethylene adipamlde, polyarylene oxides such as poly(2,6-dimethylphenylene oxide), polyoxymethylene and poly-carbonate.
The thermoplastic resln composition modified by the incorporation of the ethylene copolymer or the modified ethylene copolymer may further include heat stabilizers, weatherability stabilizers, antistatic agents, antiblocking agents, lubricants~ nucleating agents, pigments, dyes, and inorganic or organic fillers as required.
The following examples illustrate the present invention more specifically.
The properties of the ethylene co~olymer obtained by this invention were evaluated by the fol-lowing methods.
Speclfically, the copolymer was formed into a film having a width of 350 mm and a thlckness of 50 microns by means of a commercial tubular fllm rorming machlne for high-pressure polyethylene (manufactured by Modern Machinery Company) under the following conditions.
Resin temperature: 180C
Screw rotating speed: 100 rpm Die diameter: 100 mm Die slit width: 0.7 mm The resulting film was evaluated by the following methods.
Haze t%) In accordance with ASTM D 1003 Impact strength (kg-cm/cm) Mewasured by a film impact tester made by Toyo Seiki Co., Ltd. The spherical surface of the impact head had a diameter of l inch.
Elmend_rf tear strength (kOE/Cm) In accordance with ASTM D1922.
BlockinK value (g) Measured substantially in accordance wlth ASTM D1893. The peeling bar was made of glass, and the peeling speed was adjusted to 20 cm/min.
Heat seal startin~ temperature ~C) Using a heat sealer made by Toyo Tester Co., Ltd., two films were heat-sealed over a l cm width at a given temperature (to be referred to as the heat seal temperature) under a pressure of 2 kg/cm2 for a sealing time of 1 second. From the two films integrated by heat sealing, a rectan~ular test sample having a width of 15 mm and a length of 60 mm was cut out. One short side of the test sample was heat-sealed and the other short side was left open. By using a tensile tester, the two open ends of the test sample were clamped by an air chuck and pulled at a pulling speed of 300 mm/min. at room temperature to perform a peeling test.
At this time, the sample was observed to determine whether the breakage was due to peeling or occurred at parts other than the heat-sealed surface.
The above operation was repeated at varying heat seal temperatures, and the heat seal temperature at which the breakage be~an to occur at the parts other than the heat-sealed surface was defined as the heat seal starting temperature.
Example 1 Preparation of a catalyst In an atmosphere of nitrogen, 1 mole of com~
mercial anhydrous magnesium chloride was suspended in 2 liters of puri~ied dehydrated hexane, and with stir-ring, 6 moles of ethanol was added dropwise over 1 hour. Then, the reaction was carried out at room temperature for 1 hour. To the reaction mixture was added dropwise 2.6 moles of diethyl aluminum chloride at room temperature, and the mixture was stirred for 2 hours. Then, 6 moles of titanium tetrachloride was added, and the mixture was heated to 80C. The reac-tion was carrled out at this temperature for 3 hours with stirring. After the reaction, the solld portion was separated, and repeatedly washed with purified hexane. The solid (designated A-1) had the following composition.
Ti ~ Cl Mg Al OEt ) (wt.%)
3.7 67.0 20.0 0.~ .8 -Ethanol ~500 millimoles) was added at room temperature to 50 millimoles, calculated as Ti, of A-l suspended in puriPied hexane. The mixture was heated to 80C, and reacted for 1 hour. After the reaction, the reaction mixture was cooled to room temperature, and 150 millimoles of triethyl aluminum was added.
The reaction was carrled out Yor 1 hour wit~l stirring After the reaction, the solid portion was repeatedly washed with purified hexane. The resulting catalyst (B-1) had the following composition.
) Ti Cl Mg Al OEt (wt.%) 2.859.3 13.7 0.5 23.6 _ *) The resulting solid was decomposed and extracted with H2O-acetone, and then quantitatively deterrnined as ethanol by gas chromatography.
Polymerization A 200-liter continuous polymerization reactor was charged continuously with 100 liters/hr of purified dehydrated hexane~ 15 millimoles/hr of ethyl alumlnum sesquichloride and 1~0 millimole/hr, as Ti~ of the catalyst (B-l) obtained as above, and 13 kg/hr of ethylene, 13 kg/hr of 4-methyl-l-pentene and 30 liters/
hr of hydrogen were slmultaneously fed continuously into the reactor. The monomers were copolymerized at a polymerizati.on temperature Or 165C and a total pres-sure of 30 kg/cm2 with a residence time of l hour whlle maintaining the concentration of the copolymer in the hexane solvent at 130 gtliter. The catalytic activity corresponded to 13,000g of the copolymer/mmole of Ti.
The properties of the copolymers were evaluated, and the results are shown in Table 2.
Examples 2 to 6 Continuous copolymerizatlon was carried out in the same way as ln Example 1 using the same reactor and the same catalyst component (B-l) as in Example 1 except that the types of the organoaluminum component and the alpha-ole~in were changed as shown in Table lo The polymerization conditions are shown in Table 1, and the various properties of the copolymers are shown in Tables 2 and 3.
Comparative Example l Example l was repeated except that instead of (B~ (A-l) be~ore reaction with ethanol was used as ' ~' ', : ~ ' , , a Ti catalyst component. The catalytic activity was l9,100g of the copolymer/mmole of Ti. The properties of the copolymer are shown in Table 3. The resulting copolymer had a slightly broad composition distribution and contained a highly crysta]line port;ion and a portion having a low crystallinity. Hence, its anti-blocking property was insufficient.
Comparative Example 2 In the procedure of ~xample 1 9 20 mmoles/lhr of triethyl aluminum was u~ed as the organoaluminum component, 0.42 mmole/hr, as Ti atom, of (A-1) before reaction with ethanol was used instead of (B-l) as the Ti catalyst component, and 13 kg/hr of ethylene, and 30 kg/hr of 4-methyl-1-pentene were continuously fed together with 40 litersJhr of hydro~en, and polymerized. The catalytic activity corresponded to 31,000~ of the copolymer/mmole of Ti.
The properties of the copolymer are shown in Table 3.
The resulting polymer had a considerably broad composition distribution and contained large amounts of a highly crystalline portion and a low crystalline portion. Hence, it had poor transparency, antiblocking property and low-temperature heat seal-ability.
Com~arative Example 3 A 2-liter autocalve was charged with 0.8 liter of purified dehydrated hexane and 0.2 liter of
The reaction was carrled out Yor 1 hour wit~l stirring After the reaction, the solid portion was repeatedly washed with purified hexane. The resulting catalyst (B-1) had the following composition.
) Ti Cl Mg Al OEt (wt.%) 2.859.3 13.7 0.5 23.6 _ *) The resulting solid was decomposed and extracted with H2O-acetone, and then quantitatively deterrnined as ethanol by gas chromatography.
Polymerization A 200-liter continuous polymerization reactor was charged continuously with 100 liters/hr of purified dehydrated hexane~ 15 millimoles/hr of ethyl alumlnum sesquichloride and 1~0 millimole/hr, as Ti~ of the catalyst (B-l) obtained as above, and 13 kg/hr of ethylene, 13 kg/hr of 4-methyl-l-pentene and 30 liters/
hr of hydrogen were slmultaneously fed continuously into the reactor. The monomers were copolymerized at a polymerizati.on temperature Or 165C and a total pres-sure of 30 kg/cm2 with a residence time of l hour whlle maintaining the concentration of the copolymer in the hexane solvent at 130 gtliter. The catalytic activity corresponded to 13,000g of the copolymer/mmole of Ti.
The properties of the copolymers were evaluated, and the results are shown in Table 2.
Examples 2 to 6 Continuous copolymerizatlon was carried out in the same way as ln Example 1 using the same reactor and the same catalyst component (B-l) as in Example 1 except that the types of the organoaluminum component and the alpha-ole~in were changed as shown in Table lo The polymerization conditions are shown in Table 1, and the various properties of the copolymers are shown in Tables 2 and 3.
Comparative Example l Example l was repeated except that instead of (B~ (A-l) be~ore reaction with ethanol was used as ' ~' ', : ~ ' , , a Ti catalyst component. The catalytic activity was l9,100g of the copolymer/mmole of Ti. The properties of the copolymer are shown in Table 3. The resulting copolymer had a slightly broad composition distribution and contained a highly crysta]line port;ion and a portion having a low crystallinity. Hence, its anti-blocking property was insufficient.
Comparative Example 2 In the procedure of ~xample 1 9 20 mmoles/lhr of triethyl aluminum was u~ed as the organoaluminum component, 0.42 mmole/hr, as Ti atom, of (A-1) before reaction with ethanol was used instead of (B-l) as the Ti catalyst component, and 13 kg/hr of ethylene, and 30 kg/hr of 4-methyl-1-pentene were continuously fed together with 40 litersJhr of hydro~en, and polymerized. The catalytic activity corresponded to 31,000~ of the copolymer/mmole of Ti.
The properties of the copolymer are shown in Table 3.
The resulting polymer had a considerably broad composition distribution and contained large amounts of a highly crystalline portion and a low crystalline portion. Hence, it had poor transparency, antiblocking property and low-temperature heat seal-ability.
Com~arative Example 3 A 2-liter autocalve was charged with 0.8 liter of purified dehydrated hexane and 0.2 liter of
4-methyl-1-pentene, and the inside of the autoclave was pur~ed with nitrogen. Then, 2.0 mmoles of triethyl aluminum, and 0.02 mmole, calculated as Ti atom, of the Ti catalyst used in Comparative ~xamples 2 and 3 were introduced into the autoclave. Subsequently, hydrogen was introduced to a pressure of 0.6 kg/cm2.
Ethylene was then added to a total pressure of 2.5 kg/cm2. While the polymerization temperature was maintained at 70C 3 the polymerization was carried out _ 2~
~or 2 hours. There was obtained 295g of a copolymerO
The catalytic activity corresponded to 14,800g of the copolymer/mmole of Ti.
The properties of the resulting copolymer are shown in Table 3O
The polymer obtained had a very broad com-position distribution and showed a single melting point at 124.5C. Hence3 it had poor low-heat sealability.
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Ethylene was then added to a total pressure of 2.5 kg/cm2. While the polymerization temperature was maintained at 70C 3 the polymerization was carried out _ 2~
~or 2 hours. There was obtained 295g of a copolymerO
The catalytic activity corresponded to 14,800g of the copolymer/mmole of Ti.
The properties of the resulting copolymer are shown in Table 3O
The polymer obtained had a very broad com-position distribution and showed a single melting point at 124.5C. Hence3 it had poor low-heat sealability.
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Claims (3)
1. A copolymer of ethylene with at least one C4-C20 .alpha.-olefin having the following characteristics (A) to (J):
(A) it has a melt flow rate, determined by ASTM
D 1238E, of from 0.01 to 200 g/10 min., (B) it has a density of from 0.850 to 0.930 g/cm3, (C) it has a composition distribution parameter (U), defined by the following equation (1) U=100 x (Cw/Cn - 1) ..... (1) wherein Cw is the weight average degree of branching, and Cn is the number average degree of branching, of not more than 50, (D) the amount of components having a degree of branching of not more than 2/1000 carbons is more than 10% by weight based on the ethylene copolymer, (E) the amount of components having a degree of branching of at least 30/1000 carbons is not more than 70% by weight based on the ethylene copolymer, (F) the ratio of the average block methylene chain length to the average methylene chain length is not more than 2.0, (G) it has n melting points measured by a dif-ferential scanning calorimeter (DSC) (where n=1 or n?3), in which the highest melting point (T1) among these DSC melting points is given by the following expression (i) (175 x d - 46)°C?T1?125°C (i) wherein d is the density (g/cm3) of the copolymer, the difference between T1 and the lowest melting point (Tn) among the DSC melting points is given by the following expression (ii) 18°C<T1 - Tn?65°C (ii), and the difference between T1 and the second highest melting point (T2) is given by the following expression (iii) 0°C<T1 - T2?20°C (iii), provided that when the number of melting points is one (i.e., n=1), only the expres-sion (i) is applicable and the expressions (ii) and (iii) are not applicable, (H) when n?3 in the characteristic (G) above, the ratio of the amount of heat of crystal fusion (H1) at the highest melting point T1 to the total amount of heat of crystal fusion (HT) is given by the following expression O<H1/HT?0.40, (I) it has a crystallinity, measured by an X-ray diffraction method, of from 15 to 70%, and (J) it has a molecular weight distribution ?w/?n where ?w is the weight average molecular weight of the copolymer and ?n is the number average molecular weight of the copolymer, measured by gel permeation chromatography, of from 2.5 to 10.
(A) it has a melt flow rate, determined by ASTM
D 1238E, of from 0.01 to 200 g/10 min., (B) it has a density of from 0.850 to 0.930 g/cm3, (C) it has a composition distribution parameter (U), defined by the following equation (1) U=100 x (Cw/Cn - 1) ..... (1) wherein Cw is the weight average degree of branching, and Cn is the number average degree of branching, of not more than 50, (D) the amount of components having a degree of branching of not more than 2/1000 carbons is more than 10% by weight based on the ethylene copolymer, (E) the amount of components having a degree of branching of at least 30/1000 carbons is not more than 70% by weight based on the ethylene copolymer, (F) the ratio of the average block methylene chain length to the average methylene chain length is not more than 2.0, (G) it has n melting points measured by a dif-ferential scanning calorimeter (DSC) (where n=1 or n?3), in which the highest melting point (T1) among these DSC melting points is given by the following expression (i) (175 x d - 46)°C?T1?125°C (i) wherein d is the density (g/cm3) of the copolymer, the difference between T1 and the lowest melting point (Tn) among the DSC melting points is given by the following expression (ii) 18°C<T1 - Tn?65°C (ii), and the difference between T1 and the second highest melting point (T2) is given by the following expression (iii) 0°C<T1 - T2?20°C (iii), provided that when the number of melting points is one (i.e., n=1), only the expres-sion (i) is applicable and the expressions (ii) and (iii) are not applicable, (H) when n?3 in the characteristic (G) above, the ratio of the amount of heat of crystal fusion (H1) at the highest melting point T1 to the total amount of heat of crystal fusion (HT) is given by the following expression O<H1/HT?0.40, (I) it has a crystallinity, measured by an X-ray diffraction method, of from 15 to 70%, and (J) it has a molecular weight distribution ?w/?n where ?w is the weight average molecular weight of the copolymer and ?n is the number average molecular weight of the copolymer, measured by gel permeation chromatography, of from 2.5 to 10.
2. The copolymer of claim 1 wherein the propor-tion of the .alpha.-olefin is 0.5 to 40 mole%.
3. The copolymer of claim 1 wherein the com-position distribution parameter U is 0<U?40.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP196,081/83 | 1983-10-21 | ||
| JP58196081A JPS6088016A (en) | 1983-10-21 | 1983-10-21 | Ethylene copolymer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1240097A true CA1240097A (en) | 1988-08-02 |
Family
ID=16351882
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000465836A Expired CA1240097A (en) | 1983-10-21 | 1984-10-19 | Linear ethylene copolymer |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4668752A (en) |
| EP (1) | EP0141597B1 (en) |
| JP (1) | JPS6088016A (en) |
| AT (1) | ATE50584T1 (en) |
| CA (1) | CA1240097A (en) |
| DE (1) | DE3481424D1 (en) |
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| GB1355245A (en) * | 1970-05-29 | 1974-06-05 | Mitsui Petrochemical Ind | Non-elastic ethylene copolymers and their preparation |
| US4071674A (en) * | 1972-09-14 | 1978-01-31 | Mitsui Petrochemical Industries Ltd. | Process for polymerization or copolymerization of olefin and catalyst compositions used therefor |
| JPS5952643B2 (en) * | 1977-01-27 | 1984-12-20 | 三井化学株式会社 | ethylene copolymer |
| DE2801541A1 (en) * | 1978-01-14 | 1979-07-19 | Hoechst Ag | AETHYLENE COPOLYMERS AND THEIR USE FOR THE PRODUCTION OF FILMS |
| IT1110494B (en) * | 1978-08-02 | 1985-12-23 | Montedison Spa | ETHYLENE POLYMERS AND PROCEDURE FOR THEIR PREPARATION |
| JPS6011925B2 (en) * | 1978-10-18 | 1985-03-29 | 三井化学株式会社 | Method for producing ethylene copolymer |
| JPS5558210A (en) * | 1978-10-26 | 1980-04-30 | Nippon Oil Co Ltd | Production of copolymer |
| DE2847986A1 (en) * | 1978-11-04 | 1980-05-22 | Huels Chemische Werke Ag | METHOD FOR PRODUCING POWDER-SHAPED, THERMOPLASTIC COPOLYMERS FROM AETHYLENE AND BUTEN- (1) |
| JPS603323B2 (en) * | 1978-12-11 | 1985-01-28 | 三井化学株式会社 | Polymerization method of olefins |
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| JPS57105411A (en) * | 1980-12-23 | 1982-06-30 | Mitsubishi Petrochem Co Ltd | Ethylenic copolymer |
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| JPS57153004A (en) * | 1981-03-19 | 1982-09-21 | Nippon Oil Co Ltd | Production of silane-crosslinked polyolefin |
| FR2509315A1 (en) * | 1981-07-10 | 1983-01-14 | Charbonnages Ste Chimique | HETEROGENEOUS COPOLYMERS OF ETHYLENE FOR THE MANUFACTURE OF FILMS |
| IT1210855B (en) * | 1982-02-12 | 1989-09-29 | Assoreni Ora Enichem Polimeri | LINEAR STRUCTURE ETHYLENE POLYMERS AND PROCESSES FOR THEIR PREPARATION. |
| JPS5975910A (en) * | 1982-10-25 | 1984-04-28 | Mitsui Petrochem Ind Ltd | Ethylene copolymer |
-
1983
- 1983-10-21 JP JP58196081A patent/JPS6088016A/en active Granted
-
1984
- 1984-10-19 DE DE8484307212T patent/DE3481424D1/en not_active Expired - Lifetime
- 1984-10-19 AT AT84307212T patent/ATE50584T1/en not_active IP Right Cessation
- 1984-10-19 EP EP84307212A patent/EP0141597B1/en not_active Expired - Lifetime
- 1984-10-19 CA CA000465836A patent/CA1240097A/en not_active Expired
- 1984-10-22 US US06/663,557 patent/US4668752A/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP0141597B1 (en) | 1990-02-28 |
| JPS6088016A (en) | 1985-05-17 |
| JPH0336042B2 (en) | 1991-05-30 |
| EP0141597A1 (en) | 1985-05-15 |
| US4668752A (en) | 1987-05-26 |
| DE3481424D1 (en) | 1990-04-05 |
| ATE50584T1 (en) | 1990-03-15 |
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