CA1304187C - Butene-rich butene-1 propylene copolymer shrink film - Google Patents
Butene-rich butene-1 propylene copolymer shrink filmInfo
- Publication number
- CA1304187C CA1304187C CA000523640A CA523640A CA1304187C CA 1304187 C CA1304187 C CA 1304187C CA 000523640 A CA000523640 A CA 000523640A CA 523640 A CA523640 A CA 523640A CA 1304187 C CA1304187 C CA 1304187C
- Authority
- CA
- Canada
- Prior art keywords
- film
- butene
- propylene
- shrink
- weight
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/10—Homopolymers or copolymers of propene
- C08L23/12—Polypropene
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/10—Homopolymers or copolymers of propene
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/10—Homopolymers or copolymers of propene
- C08L23/14—Copolymers of propene
- C08L23/142—Copolymers of propene at least partially crystalline copolymers of propene with other olefins
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/18—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms
- C08L23/20—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms having four to nine carbon atoms
Abstract
ABSTRACT
A blend suitable for use in producing heat shrinkable, thermoplastic films of good clarity and good proaessability, comprises a mixture containing (i) 10 to 60% by weight of a butene-1/propylene copolymer, wherein the propylene comonomer content is from 5 to 40 mole percent, and (ii) 40 to 90% by weight of a propylene homopolymer or copolymer.
A blend suitable for use in producing heat shrinkable, thermoplastic films of good clarity and good proaessability, comprises a mixture containing (i) 10 to 60% by weight of a butene-1/propylene copolymer, wherein the propylene comonomer content is from 5 to 40 mole percent, and (ii) 40 to 90% by weight of a propylene homopolymer or copolymer.
Description
3~ t7 `-J
K-~8B~ (US~
JRD:kn BUTENE-RICH BUTENE-1-PROPYLENE COPOLYMER SH_INK FILM
Back~round of the Invention The present invention relates to films made from blends of thermoplastic polymer materials which have improved properties. More particularly the present invention relates to films made from blends of a propylene polymer with a butene-rich butene-1-propylene copolymer which are heat shrinkable and which have good clarity and good processability.
Thermoplastic blends for films are used as packaging material~
and in the area of shrink packaging, for objects that are packaged in thermoplastic shrink film. Shrink ~ilm is used in many applications, for example, for many types of packaging and wrapping articles such as toys, sporting goods, stationary, greeting cards, hardware, household products, office supplies and forms, phonograph records, industrial parts, computer floppy diskettes, and photo albums, etc. Heat is applied to the film and the film shrinks to conform to the shape of the article packaged therein.
~ any ~hermoplastic films shrink to some extent if they are subjected to elevated temperatures. Use is made of this characteristic by subjecting objects packaged in such fillns for a short time to elevated temperatures, e.g. e~posing them to a blast of heated air, or by irnmerslng in boiling water so that the ~ilm shrinksl thereby tightly enclosing the objects packaged therein. Examples are films fabricated from polyolefins or irradiated polyolefins.
Usually for most shrink film applications5 a film should exhibit a high shrink energy or contractile force when exposed to ele-vated temperatures~ In addition, the film should not only be heat shrinkable but have good ~clarity and be easily processed. Clarity is important ln the marketing aspect of the packaged goods so that the consumer c~n ascertain what he or she ia purchasing. Addi~ional advan-tages of shrink packaging made ~rom blends should include: (1) adds luster, enhances product appearance; (2) imparts contemporary image to ~ ~J
- 1.3~4~E~'7 the product; (3) helps the product sell itself; (4) keeps out dust and moisture so that the product doesn't become shop worn; (5) discourages shoplifters; (6) speeds production; (7) cuts labor and material costs;
(8) reduces labeling cost; (9) eases the training of opPrators;
(10) simplifies internal handling; (11) wraps unusual shapes with a oontour fit; (12) versatile--serves many packaging needs; and (13) excellent for bundling and multipackaging.
A shrink film should possess the following specific properties:
(1) the shrink force should be between 100 and 400 grams per inch at 10~C depending on the objects to be encased.
(2~ the percent shrinkage should be between 10 and 50% at 121C
depending on the objects to be encased.
~ 3) the film should have high clarity or optics.
(4) the modulus should be between ~0,000 and 350,000 psi depending upon the objects to be encased.
(5) machinab~lity: the coefficient of friction should be less than ,.,, 0~
~ 6) tear strength: the tear strength should be as high as possi-ble; typical is 3 to 15 grams per mil of film thickness and per inch o~
width.
(7) elongation: the elongation should be between 50 and 150%
depending on the objects to be encased.
Films may be oriented or unoriented. Oriented films may be obtained by stretching processes in which tensions capable of stretching the film are applied to the film, the directions of which form an angle of about 90 utilizing well known prior art techniques. These film stretching tensions may be applied sequentially~ as in the case if the film, after; forming, is subjected to stretching in a longitudinal direc-tions and thereafter tension is applied in a transverse direction to stretch the film transversely, or simultaneously, whereby longitudinal and transverse tensions are applied to the film at the same time ~.3~18~
resulting in a simultaneous longitudinal and transverse stretching of the film. Such processes are well known in the art and includes for example the ~Idouble-bubble~ method which comprises extrusion of material into a -tubular stalk, cooling of the tubular stalk, reheating and inflating of the tube and simultaneously drawing the inflated tube in a longitudinal direction thereby imparting biaxial orientation to the film.
Another common method for the biaxial orientation af -the film sheet comprises passing the film sheet through a series of rotating draw rollers which impart longitudinal directions stretch to the film and subsequently transversely drawing the longitudinally stretched film, for example, by passing it through a tenter frame wherein the film is stretched in a transverse direction.
In use, the film may be sealed around the product, formed into a bag, subjected to heat and shrunk tightly around the product. A variety of equipment is available Eor shrink packaging from ~anual as well as automatic systems~ These systems use single-wound or centerfolded Eilm. A sealing unLt and a s~rink tunnel are needed Eor shrink packaging. In a typical semi-automatic shrink packaging operation only three essential units are required--(l) a work surface for dispensing the film and inserting the product to be packaged, (2) an L-sealer, and (3) a heat tunnel.
For L-sealers, the film is supplied folded on a roll in widths to suit the need. By using folded film, the folded edge forms one side of the eventual package. The product to be packaged is inserted between the folded film and then moved to the heat sealing unit. Here an L-bar containing a hot wire ~ 3~ 8~7 3a - 67674-16 descends in both heat seals and cuts the ~front edge and trail-ing edge. The leading edge has already been sealed durirlg the heat sealing of the preceding package. The product is now in a loose film fitting bag closed on all four sides. I-t next travels on a conveyer through a shrink tunnel where the film is exposed to heat resulting in a ~ J~
3..~ 17 ~ 1S-~22 heated film shrinki.ng tightly around the product to provide an attractive, clear form fitting package.
U.S. Patent 3,900,534 discloses a biaxially oriented thermoplastic film struc~ure formed from a blend comprising polypropylene and polybutene homopolymers where the polybutene is present in a small amount of more than 10% but less than 2Q%
by weight.
U.S. Patent 3,634,553 discloses a heat shrinkable oriented thermoplastic film which comprises a blend of polypropylene and an ethylene/butene-1 copolymer.
European Patent Application 0,145,014A discloses a blend of a random copolymer of propylene and an alpha ole~in with 4 or more carbon atoms (i.e. perhaps butene-1), where the alpha olefin content in the copolymer is 8 to 30 mole~ (m%).
Single layer shrink films based on hlends of polybutylene with polypropylene are disclosed in Mobil Patents:
U.S. Patent No. 3,634,552 (1972), U.S. Patent No. 3,634,553 (1972), U.S. Patent No. 3,8~9,520 (1974) and U.S. Patent No.
3,900,534 (1975) and blends of polybutylene with ethylene vinyl acetate (EVA) and C2-Ca elastomer or polybutylene with low density polyethylene (LDPEJ and C2-Ca elastomer (where Ca is an a-ole~in ~omonomer) are disclosed in U.S. Patent No. ~,37~,888 (1983). Multilayers may include three layers (propylene-ethylene plus butene-1-ethylene plus etllylene-propylene rubber)/tie layer/linear low density ~, ' ,, . .
polyethylene (~LDPE) by Union Carbide, U.S. Patent No.
4,196,2~0 (1980) for frozen poultry and U.S. Patent No.
4,207,363 (1980) for primal meat cuts. Three layers oE propy-lene-ethylene/(EV~ ~ butene-l-ethylene)/propylene-ethylene, U.S. Patent No. 4,194,039 (1980) is known. Also, three layers (polyprop~lene + polybutylene)/EVA/irradiated EVA by Cryovac~
U~S. Patent No. 3,754,063 (1973), U.S. Patent No. 3,832,274 (1974), and U.S. Paten-t No. 3,891,008 (1975) for turkey bags are known.
Heretofore, polyvinyl chloride (PVC) has been used to produce good shrink films~ PVC has been shown to be much better in certain applications than the use of pol~olefins such as propylene polymers. This is because the use of polyolefins in shrink wrap results in a moderate to high shrink force which is undesirable in many applications. However, the use of polyolefins allows for the use of high speed automated packag-ing machinery with ease of control, lower cost, and less deposit from corrosion of equipment, which results ir~ less equipment maintenance than when using PVC. PVC, however, may produce a better lookin~ package because of the low shrink force and better optics. Also, the seal and shrink of PVC
films may take place over a much broader temperature range and tear strength may be better.
It has been desired to produce a blend for producing a heat shrinkable thermoplastic film with the film advantages of PVC but which is of low cost, can be used on a high speed automated packaging machine and which does not corrode equip~
ment. It is the butene-rich butene-l-propylene polymer blend film of the present invention which results in low shrink - 5a - 67674-26 force which is adjustable by the blending ra-ti.o, low shrink temperature, low stiffness wi-th better op-tics, and which does not corrode the equipment being used, is of lower cost and can be used on high speed automated packaging machines.
Summary of the Invention Applicant has surprisingly discovered a butene-rich butene-l-propylene copolymer which may be blended with a propy-lene polymer ('nomo-~.3~87 - 6 - ~1~15~3225 or copolymer) where the propylene comonomer content of the butene-1 propylene copolymer is from about 5 m~ to abo-lt 50 m%
and thus the butene-l content of the hukene l propylene copolymer is from about 60 m~ to about 95 m~ which may be blended for producing a heat shrinkable oriented thermoplastic film which also has good clarity and good processability.
Heretofore, no such butene-rich butene-l-propylene copolymers have been known which produce a heat æhrlnkable oriented thermoplastic film which has good clarity and good processability as well as not corroding equlpment which may be used on high æpeed automated packaging machines.
The invention is a packaging film, sheet or laminar structure (preferably oriented) which is a shrinkable thermoplastic film which has good clarity and good processability, comprising a mixture ~ontaining:
from about lO~ by welght to about 60% by weight (preferably 20 to 50% by weight, particularly about 35% by weight) butene-l-propylene ~opolymer where the propylene comonomer conten~ o~ the butene-1-propylene copolymer is from about 5 m% ~o about 40 m% ~preferably lO to 30 m%, partlcularly about 20 m%); and from about 40% by weight to about 90% by weight (preferably 50 to 80% by weight, particularly about 65% by weight) propylene homopolymer or copolymer.
Detailed ~escrlption of the Invention The polymer and copolymer components of the film composition of the present lnvention are blended together to form a substan~ially homogeneous resin mixture. Thls may be accomplished, for example, by tumbling the mixture in a fiher drum. The tumbled mixture is then melt compounded by an ex~ruder having good mlxing screw and pelletized ~hereaf-ter.
The blend is then extruded into a film utilizing a standard ~ 3~ 7 - 6a - 61~15~32~5 extruder and tubular or flat film die and as subsequently oriented utiliziny any one of a number of prior art film orientation techniques.
Various gauges of shrink film may be manufa~tured through utilizing a novel resin composltion of the present invention. The ~3Q~ 7 - 7 - 6767~-16 gauge may generally vary from about 0.10 mil to about 5 mils and preferably from about 0.5 mil to about 2.0 mils dependiny to a great extent upon the type of shrink packaging applica-tions for which the film is manufactured.
The following example as set forth to more clearly illustrate the present invention is not intended to limit the scope thereof.
Example 1 A butene-l-propylene copolymer, C-2756*, which con-tains 27 mole ~ (m~) of propylene comonomer was blended at a 15 weight ~ (w%) level with a Shell polypropylene random copoly-mer. This particular propylene copolymer had an ethylene comonomer content of l.0 wt%, however, -the ethylene content may vary considerably. Applicants blend was compared with (l) polypropylene random copolymer and with, (2) a blend of 15% of polybutylene (a butene-l-ethylene copolymer where the ethylene comonomer content was 0.75 wt~ with 85% of the polypropylene copolymer (1). Thi6 blend (2) of butene-1-ethylene copol~mer, where the ethylene comonomer content is 0.75 wt~ is patented in MobiL U.S. Patent No. 3,634,553 and is typical of compositions used heretofore. The polymers were blended utilixing a drum tumbler and subsequently fed into the hopper of the standard rotating screw extrusion apparatus which served to further mix and melt the blend, and then melt extruded and pelletized thereafter. The temperature of the melt within the extruder was maintained at about 465F.
The blend was subsequently extruded in the shape of a tube from a tubular die affixed to the outlet of an extruder, the die being maintained at a temperature of 370F. The tube *Trade-mark .~"7; .
'7 - 7a ~ 67674-16 was quenched to a temperature of about 60F which was substan-tially below the crystalline mel-ting points of the propylene polymer and the butene-l-propylene copolymer immediately upon emergence from the die. The extruded tube had an external diameter of about 2 inch and a wall thickness of about 20 mils.
Upon cooling, the tube was taken up by a set of draw rollers at about 12 ft/min and passed ,.~
~ 3~ t~
through a preheat oven where it was reheated. The temperature of the preheat oven was maintained at about 1000F. The heated tube was immediately rein~lated with air under pressure which expanded the heated tube by a ratio of about 5:1 in a transverse direction and a substantially similar ratio in the longitudinal direction. The expanded tube was subsequently collapsed by a pair of nip rollers operating at speeds higher than the rotational speeds of the draw rollers. The tube was passed to a set of windup rollers finally. Table 1 illustratPs the properties which resulted from this experiment.
:
~ 3~ 7 PROPERTIES OF SHRINK FILMS*
.
i ,~
PP** PP ~ 15% C2756PP + 15~ PB8240 Control Shrink @ 220 oF, %
Shrink @ 250 oF, %
10 MD 7 12.5 . 6.5 TD 14 20 15.5 Orientation Release Stress, psi MD 360 250 354 Contracti~e Stress psi MD 236 193 215 Haze, % 1.9-3.6 2.9-3.9 5 Tagent Modulus, psi 20 MD 303,700 222,760 247~860 , T~p 335,S80 237,140 255,3~0 Break Strength, psi MD 19,384 16,220 18l478 TD 17,483 169593 15,284 25Elongation, X MD 61 78 53 TD 40 88 $2 Tear Strength, g/mil MD 14 11.6 12.5 TD 13.7 13.6 11.9 *: Tubular OPP Film ~ 0.75 mil thickness **: A Random Copolymer @ I.O w% C2.
~T~c~de~ f~
L8'~
- 10 - ~1~15-32~5 Table 1 considers a polypropylene control which is a random copol~mer at 1.0 wt~ ethylene (Control I), a blend of 85~ polypropylene and 15% C-2756 which is applicant's invention with propylene comonomer content of the butene-1-propylene copolymer being 27 m% (Applican~ II), and a blend of polypropylene and ~5% PB8240 which represents the Mobil patent '553 material of a butene-1-ethylene copolymer where the ethylene comonomer ~ontent is 0.75 wt% (Mobil III). The shrink forces both expressed by orientation release s~ress and contrac~ive stress of applican~'s fllm, II were lower than those of the Mobil III film and is much lower than those o~
Con~rol I film. These lower shrink forces are desirable and, thus, make the butene-1-propylene copolymer modified polyolefins (polypropylene) film useful in many shrink packaging application where low shrink forc~ is required.
As may be seen from Table 1, Applicant II resulted in somewhat hlgher percent shrinkage at 220F then the polypropylene ControI I and percent shrinkage at least comparable to Mohll III. A~ a temperature o~ 250F, the percent shrinkage for Applicant II was hi.gher ~han eikher Control II or ~lobll III.
The modulus and break strength values of Applicant II
were quite acceptable. The haze or clarity value of Applicant II was bet~er than Mobil III and as good as Conkrol I. The other properties such as tear s~rength and elongation are very acceptable, as well.
K-~8B~ (US~
JRD:kn BUTENE-RICH BUTENE-1-PROPYLENE COPOLYMER SH_INK FILM
Back~round of the Invention The present invention relates to films made from blends of thermoplastic polymer materials which have improved properties. More particularly the present invention relates to films made from blends of a propylene polymer with a butene-rich butene-1-propylene copolymer which are heat shrinkable and which have good clarity and good processability.
Thermoplastic blends for films are used as packaging material~
and in the area of shrink packaging, for objects that are packaged in thermoplastic shrink film. Shrink ~ilm is used in many applications, for example, for many types of packaging and wrapping articles such as toys, sporting goods, stationary, greeting cards, hardware, household products, office supplies and forms, phonograph records, industrial parts, computer floppy diskettes, and photo albums, etc. Heat is applied to the film and the film shrinks to conform to the shape of the article packaged therein.
~ any ~hermoplastic films shrink to some extent if they are subjected to elevated temperatures. Use is made of this characteristic by subjecting objects packaged in such fillns for a short time to elevated temperatures, e.g. e~posing them to a blast of heated air, or by irnmerslng in boiling water so that the ~ilm shrinksl thereby tightly enclosing the objects packaged therein. Examples are films fabricated from polyolefins or irradiated polyolefins.
Usually for most shrink film applications5 a film should exhibit a high shrink energy or contractile force when exposed to ele-vated temperatures~ In addition, the film should not only be heat shrinkable but have good ~clarity and be easily processed. Clarity is important ln the marketing aspect of the packaged goods so that the consumer c~n ascertain what he or she ia purchasing. Addi~ional advan-tages of shrink packaging made ~rom blends should include: (1) adds luster, enhances product appearance; (2) imparts contemporary image to ~ ~J
- 1.3~4~E~'7 the product; (3) helps the product sell itself; (4) keeps out dust and moisture so that the product doesn't become shop worn; (5) discourages shoplifters; (6) speeds production; (7) cuts labor and material costs;
(8) reduces labeling cost; (9) eases the training of opPrators;
(10) simplifies internal handling; (11) wraps unusual shapes with a oontour fit; (12) versatile--serves many packaging needs; and (13) excellent for bundling and multipackaging.
A shrink film should possess the following specific properties:
(1) the shrink force should be between 100 and 400 grams per inch at 10~C depending on the objects to be encased.
(2~ the percent shrinkage should be between 10 and 50% at 121C
depending on the objects to be encased.
~ 3) the film should have high clarity or optics.
(4) the modulus should be between ~0,000 and 350,000 psi depending upon the objects to be encased.
(5) machinab~lity: the coefficient of friction should be less than ,.,, 0~
~ 6) tear strength: the tear strength should be as high as possi-ble; typical is 3 to 15 grams per mil of film thickness and per inch o~
width.
(7) elongation: the elongation should be between 50 and 150%
depending on the objects to be encased.
Films may be oriented or unoriented. Oriented films may be obtained by stretching processes in which tensions capable of stretching the film are applied to the film, the directions of which form an angle of about 90 utilizing well known prior art techniques. These film stretching tensions may be applied sequentially~ as in the case if the film, after; forming, is subjected to stretching in a longitudinal direc-tions and thereafter tension is applied in a transverse direction to stretch the film transversely, or simultaneously, whereby longitudinal and transverse tensions are applied to the film at the same time ~.3~18~
resulting in a simultaneous longitudinal and transverse stretching of the film. Such processes are well known in the art and includes for example the ~Idouble-bubble~ method which comprises extrusion of material into a -tubular stalk, cooling of the tubular stalk, reheating and inflating of the tube and simultaneously drawing the inflated tube in a longitudinal direction thereby imparting biaxial orientation to the film.
Another common method for the biaxial orientation af -the film sheet comprises passing the film sheet through a series of rotating draw rollers which impart longitudinal directions stretch to the film and subsequently transversely drawing the longitudinally stretched film, for example, by passing it through a tenter frame wherein the film is stretched in a transverse direction.
In use, the film may be sealed around the product, formed into a bag, subjected to heat and shrunk tightly around the product. A variety of equipment is available Eor shrink packaging from ~anual as well as automatic systems~ These systems use single-wound or centerfolded Eilm. A sealing unLt and a s~rink tunnel are needed Eor shrink packaging. In a typical semi-automatic shrink packaging operation only three essential units are required--(l) a work surface for dispensing the film and inserting the product to be packaged, (2) an L-sealer, and (3) a heat tunnel.
For L-sealers, the film is supplied folded on a roll in widths to suit the need. By using folded film, the folded edge forms one side of the eventual package. The product to be packaged is inserted between the folded film and then moved to the heat sealing unit. Here an L-bar containing a hot wire ~ 3~ 8~7 3a - 67674-16 descends in both heat seals and cuts the ~front edge and trail-ing edge. The leading edge has already been sealed durirlg the heat sealing of the preceding package. The product is now in a loose film fitting bag closed on all four sides. I-t next travels on a conveyer through a shrink tunnel where the film is exposed to heat resulting in a ~ J~
3..~ 17 ~ 1S-~22 heated film shrinki.ng tightly around the product to provide an attractive, clear form fitting package.
U.S. Patent 3,900,534 discloses a biaxially oriented thermoplastic film struc~ure formed from a blend comprising polypropylene and polybutene homopolymers where the polybutene is present in a small amount of more than 10% but less than 2Q%
by weight.
U.S. Patent 3,634,553 discloses a heat shrinkable oriented thermoplastic film which comprises a blend of polypropylene and an ethylene/butene-1 copolymer.
European Patent Application 0,145,014A discloses a blend of a random copolymer of propylene and an alpha ole~in with 4 or more carbon atoms (i.e. perhaps butene-1), where the alpha olefin content in the copolymer is 8 to 30 mole~ (m%).
Single layer shrink films based on hlends of polybutylene with polypropylene are disclosed in Mobil Patents:
U.S. Patent No. 3,634,552 (1972), U.S. Patent No. 3,634,553 (1972), U.S. Patent No. 3,8~9,520 (1974) and U.S. Patent No.
3,900,534 (1975) and blends of polybutylene with ethylene vinyl acetate (EVA) and C2-Ca elastomer or polybutylene with low density polyethylene (LDPEJ and C2-Ca elastomer (where Ca is an a-ole~in ~omonomer) are disclosed in U.S. Patent No. ~,37~,888 (1983). Multilayers may include three layers (propylene-ethylene plus butene-1-ethylene plus etllylene-propylene rubber)/tie layer/linear low density ~, ' ,, . .
polyethylene (~LDPE) by Union Carbide, U.S. Patent No.
4,196,2~0 (1980) for frozen poultry and U.S. Patent No.
4,207,363 (1980) for primal meat cuts. Three layers oE propy-lene-ethylene/(EV~ ~ butene-l-ethylene)/propylene-ethylene, U.S. Patent No. 4,194,039 (1980) is known. Also, three layers (polyprop~lene + polybutylene)/EVA/irradiated EVA by Cryovac~
U~S. Patent No. 3,754,063 (1973), U.S. Patent No. 3,832,274 (1974), and U.S. Paten-t No. 3,891,008 (1975) for turkey bags are known.
Heretofore, polyvinyl chloride (PVC) has been used to produce good shrink films~ PVC has been shown to be much better in certain applications than the use of pol~olefins such as propylene polymers. This is because the use of polyolefins in shrink wrap results in a moderate to high shrink force which is undesirable in many applications. However, the use of polyolefins allows for the use of high speed automated packag-ing machinery with ease of control, lower cost, and less deposit from corrosion of equipment, which results ir~ less equipment maintenance than when using PVC. PVC, however, may produce a better lookin~ package because of the low shrink force and better optics. Also, the seal and shrink of PVC
films may take place over a much broader temperature range and tear strength may be better.
It has been desired to produce a blend for producing a heat shrinkable thermoplastic film with the film advantages of PVC but which is of low cost, can be used on a high speed automated packaging machine and which does not corrode equip~
ment. It is the butene-rich butene-l-propylene polymer blend film of the present invention which results in low shrink - 5a - 67674-26 force which is adjustable by the blending ra-ti.o, low shrink temperature, low stiffness wi-th better op-tics, and which does not corrode the equipment being used, is of lower cost and can be used on high speed automated packaging machines.
Summary of the Invention Applicant has surprisingly discovered a butene-rich butene-l-propylene copolymer which may be blended with a propy-lene polymer ('nomo-~.3~87 - 6 - ~1~15~3225 or copolymer) where the propylene comonomer content of the butene-1 propylene copolymer is from about 5 m~ to abo-lt 50 m%
and thus the butene-l content of the hukene l propylene copolymer is from about 60 m~ to about 95 m~ which may be blended for producing a heat shrinkable oriented thermoplastic film which also has good clarity and good processability.
Heretofore, no such butene-rich butene-l-propylene copolymers have been known which produce a heat æhrlnkable oriented thermoplastic film which has good clarity and good processability as well as not corroding equlpment which may be used on high æpeed automated packaging machines.
The invention is a packaging film, sheet or laminar structure (preferably oriented) which is a shrinkable thermoplastic film which has good clarity and good processability, comprising a mixture ~ontaining:
from about lO~ by welght to about 60% by weight (preferably 20 to 50% by weight, particularly about 35% by weight) butene-l-propylene ~opolymer where the propylene comonomer conten~ o~ the butene-1-propylene copolymer is from about 5 m% ~o about 40 m% ~preferably lO to 30 m%, partlcularly about 20 m%); and from about 40% by weight to about 90% by weight (preferably 50 to 80% by weight, particularly about 65% by weight) propylene homopolymer or copolymer.
Detailed ~escrlption of the Invention The polymer and copolymer components of the film composition of the present lnvention are blended together to form a substan~ially homogeneous resin mixture. Thls may be accomplished, for example, by tumbling the mixture in a fiher drum. The tumbled mixture is then melt compounded by an ex~ruder having good mlxing screw and pelletized ~hereaf-ter.
The blend is then extruded into a film utilizing a standard ~ 3~ 7 - 6a - 61~15~32~5 extruder and tubular or flat film die and as subsequently oriented utiliziny any one of a number of prior art film orientation techniques.
Various gauges of shrink film may be manufa~tured through utilizing a novel resin composltion of the present invention. The ~3Q~ 7 - 7 - 6767~-16 gauge may generally vary from about 0.10 mil to about 5 mils and preferably from about 0.5 mil to about 2.0 mils dependiny to a great extent upon the type of shrink packaging applica-tions for which the film is manufactured.
The following example as set forth to more clearly illustrate the present invention is not intended to limit the scope thereof.
Example 1 A butene-l-propylene copolymer, C-2756*, which con-tains 27 mole ~ (m~) of propylene comonomer was blended at a 15 weight ~ (w%) level with a Shell polypropylene random copoly-mer. This particular propylene copolymer had an ethylene comonomer content of l.0 wt%, however, -the ethylene content may vary considerably. Applicants blend was compared with (l) polypropylene random copolymer and with, (2) a blend of 15% of polybutylene (a butene-l-ethylene copolymer where the ethylene comonomer content was 0.75 wt~ with 85% of the polypropylene copolymer (1). Thi6 blend (2) of butene-1-ethylene copol~mer, where the ethylene comonomer content is 0.75 wt~ is patented in MobiL U.S. Patent No. 3,634,553 and is typical of compositions used heretofore. The polymers were blended utilixing a drum tumbler and subsequently fed into the hopper of the standard rotating screw extrusion apparatus which served to further mix and melt the blend, and then melt extruded and pelletized thereafter. The temperature of the melt within the extruder was maintained at about 465F.
The blend was subsequently extruded in the shape of a tube from a tubular die affixed to the outlet of an extruder, the die being maintained at a temperature of 370F. The tube *Trade-mark .~"7; .
'7 - 7a ~ 67674-16 was quenched to a temperature of about 60F which was substan-tially below the crystalline mel-ting points of the propylene polymer and the butene-l-propylene copolymer immediately upon emergence from the die. The extruded tube had an external diameter of about 2 inch and a wall thickness of about 20 mils.
Upon cooling, the tube was taken up by a set of draw rollers at about 12 ft/min and passed ,.~
~ 3~ t~
through a preheat oven where it was reheated. The temperature of the preheat oven was maintained at about 1000F. The heated tube was immediately rein~lated with air under pressure which expanded the heated tube by a ratio of about 5:1 in a transverse direction and a substantially similar ratio in the longitudinal direction. The expanded tube was subsequently collapsed by a pair of nip rollers operating at speeds higher than the rotational speeds of the draw rollers. The tube was passed to a set of windup rollers finally. Table 1 illustratPs the properties which resulted from this experiment.
:
~ 3~ 7 PROPERTIES OF SHRINK FILMS*
.
i ,~
PP** PP ~ 15% C2756PP + 15~ PB8240 Control Shrink @ 220 oF, %
Shrink @ 250 oF, %
10 MD 7 12.5 . 6.5 TD 14 20 15.5 Orientation Release Stress, psi MD 360 250 354 Contracti~e Stress psi MD 236 193 215 Haze, % 1.9-3.6 2.9-3.9 5 Tagent Modulus, psi 20 MD 303,700 222,760 247~860 , T~p 335,S80 237,140 255,3~0 Break Strength, psi MD 19,384 16,220 18l478 TD 17,483 169593 15,284 25Elongation, X MD 61 78 53 TD 40 88 $2 Tear Strength, g/mil MD 14 11.6 12.5 TD 13.7 13.6 11.9 *: Tubular OPP Film ~ 0.75 mil thickness **: A Random Copolymer @ I.O w% C2.
~T~c~de~ f~
L8'~
- 10 - ~1~15-32~5 Table 1 considers a polypropylene control which is a random copol~mer at 1.0 wt~ ethylene (Control I), a blend of 85~ polypropylene and 15% C-2756 which is applicant's invention with propylene comonomer content of the butene-1-propylene copolymer being 27 m% (Applican~ II), and a blend of polypropylene and ~5% PB8240 which represents the Mobil patent '553 material of a butene-1-ethylene copolymer where the ethylene comonomer ~ontent is 0.75 wt% (Mobil III). The shrink forces both expressed by orientation release s~ress and contrac~ive stress of applican~'s fllm, II were lower than those of the Mobil III film and is much lower than those o~
Con~rol I film. These lower shrink forces are desirable and, thus, make the butene-1-propylene copolymer modified polyolefins (polypropylene) film useful in many shrink packaging application where low shrink forc~ is required.
As may be seen from Table 1, Applicant II resulted in somewhat hlgher percent shrinkage at 220F then the polypropylene ControI I and percent shrinkage at least comparable to Mohll III. A~ a temperature o~ 250F, the percent shrinkage for Applicant II was hi.gher ~han eikher Control II or ~lobll III.
The modulus and break strength values of Applicant II
were quite acceptable. The haze or clarity value of Applicant II was bet~er than Mobil III and as good as Conkrol I. The other properties such as tear s~rength and elongation are very acceptable, as well.
Claims (5)
1. A single-layer heat shrinkable, thermoplastic film or sheet, formed from a blend comprising a mixture of:
(i) from 10 to 60% by weight of a butene-1/propylene copolymer, wherein the propylene comonomer content is from 10 to 30 mole percent; and (ii) from 40 to 90% by weight of a propylene polymer.
(i) from 10 to 60% by weight of a butene-1/propylene copolymer, wherein the propylene comonomer content is from 10 to 30 mole percent; and (ii) from 40 to 90% by weight of a propylene polymer.
2. A film or sheet according to Claim 1 wherein the blend comprises from 20 to 50% by weight of (i) and from 50 to 80% by weight of (ii).
3. A film or sheet according to Claim 1 wherein the blend comprises about 35% by weight of (i), wherein the propylene comonomer content is about 20 mole percent, and about 65% by weight of (ii).
4. A film or sheet according to Claim 1 wherein the propylene polymer (ii) is a propylene homopolymer or a copolymer of propylene and ethylene.
5. A film or sheet according to Claim 1, 2, or 4 which is an oriented film or sheet.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US80134485A | 1985-11-25 | 1985-11-25 | |
| US801,344 | 1985-11-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1304187C true CA1304187C (en) | 1992-06-23 |
Family
ID=25180858
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000523640A Expired - Lifetime CA1304187C (en) | 1985-11-25 | 1986-11-24 | Butene-rich butene-1 propylene copolymer shrink film |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4769421A (en) |
| CA (1) | CA1304187C (en) |
Families Citing this family (36)
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|---|---|---|---|---|
| DE3814942A1 (en) * | 1988-05-03 | 1989-11-16 | Hoechst Ag | HOT-SEALANT SHRINK FILM BASED ON POLYPROPYLENE, METHOD FOR THE PRODUCTION THEREOF, AND ITS USE IN FOAM PACKAGING LABELS |
| DE3821581A1 (en) * | 1988-06-25 | 1989-12-28 | Hoechst Ag | TRANSPARENT SHRINK FILM BASED ON POLYPROPYLENE, METHOD FOR THE PRODUCTION THEREOF AND THEIR USE FOR SHRINK FETTIQUETTES |
| DE3917652A1 (en) * | 1989-05-31 | 1990-12-06 | Hoechst Ag | MULTILAYER TRANSPARENT POLYOLEFIN FILM FOR THE SCHRUMPFETIKETTIERANWENDUNG |
| IT1243430B (en) * | 1990-09-28 | 1994-06-10 | Himont Inc | COMPOSITIONS OF PROPYLENE CRYSTALLINE POLYMERS HAVING LOW TEMPERATURE |
| TW221700B (en) * | 1990-11-01 | 1994-03-11 | Himont Inc | |
| JP3046373B2 (en) * | 1991-03-20 | 2000-05-29 | 三井化学株式会社 | Polybutene resin laminate |
| USH1274H (en) | 1991-03-29 | 1994-01-04 | Shell Oil Company | Polypropylene-polybutylene heat sealable laminated packaging film with improved optics |
| US5549943A (en) * | 1992-09-23 | 1996-08-27 | Viskase Corporation | Heat shrinkable nylon food casing with a polyolefin core layer |
| US5698279A (en) * | 1992-09-23 | 1997-12-16 | Viskase Corporation | Heat shrinkable nylon food casing having a functionalized ethylenic polymer core layer |
| US5691043A (en) † | 1994-07-15 | 1997-11-25 | Mobil Oil Corporation | Uniaxially shrinkable biaxially oriented polypropylene film and its method of preparation |
| US6436496B1 (en) * | 1998-11-06 | 2002-08-20 | Avery Dennison Corporation | Halogen-free, printable, multilayered shrink films and articles encapsulated therein |
| US7244481B2 (en) | 2001-06-18 | 2007-07-17 | Viskase Companies, Inc. | Nylon food casing having a barrier core layer |
| KR20040045866A (en) * | 2001-10-17 | 2004-06-02 | 애버리 데니슨 코포레이션 | Multilayered shrink films and articles encapsulated therewith |
| US7045566B2 (en) * | 2002-11-12 | 2006-05-16 | E.I. Du Pont De Nemours And Company | Moisture and gas permeable non-porous ionomeric films |
| US7615270B2 (en) * | 2002-11-12 | 2009-11-10 | E. I. Du Pont De Nemours And Company | Films comprising a liquid-absorbant inner layer and an impermeable outer layer |
| US20040173492A1 (en) | 2003-03-05 | 2004-09-09 | Kane James P. | Reclosable packages and method for forming, filling and sealing such packages |
| US7892391B2 (en) * | 2004-01-29 | 2011-02-22 | E. I. Du Pont De Nemours And Company | Compositions of ethylene/vinyl acetate copolymers for heat-sealable easy opening packaging |
| CN101023129A (en) * | 2004-05-12 | 2007-08-22 | 纳幕尔杜邦公司 | Ionomer compositions suitable for use in antifog applications |
| AU2005304620A1 (en) * | 2004-11-08 | 2006-05-18 | E.I. Dupont De Nemours And Company | Toughened polyamide for food packaging and health care applications |
| US7781506B2 (en) * | 2007-01-26 | 2010-08-24 | E.I. Du Pont De Nemours And Company | Poly(vinyl alcohol) composition comprising a polyol |
| US20080188622A1 (en) * | 2007-02-01 | 2008-08-07 | Sumitomo Chemical Company, Limited | Propylene-based copolymer material, film made therefrom, and method for producing propylene-based copolymer material |
| CA2577380A1 (en) * | 2007-02-06 | 2008-08-06 | Hood Packaging Corporation | Easy opening shrink wrapper for product bundle |
| US7834089B2 (en) | 2007-05-08 | 2010-11-16 | E. I. Du Pont De Nemours And Company | Ionomeric ethylene vinyl alcohol compositions |
| US20090274856A1 (en) * | 2008-05-01 | 2009-11-05 | Chou Richard T | Compositions comprising ethylene acid copolymers and functional ethylene copolymers |
| PL2421378T3 (en) | 2009-04-20 | 2013-10-31 | Dsm Ip Assets Bv | Tubular film for foodstuff casing and a foodstuff casing produced from the film |
| US20110024433A1 (en) | 2009-07-30 | 2011-02-03 | E.I. Du Pont De Nemours And Company | Thermal insulation unit |
| US20110143003A1 (en) | 2009-12-16 | 2011-06-16 | E. I. Du Pont De Nemours And Company | Non-porous moisture and gas permeable films |
| PT2558627T (en) | 2010-04-12 | 2019-01-11 | Nicolon Corp Doing Business As Tencate Geosynthetics North America | Polypropylene yarn having increased young's modulus and method of making same |
| US20110300273A1 (en) | 2010-06-03 | 2011-12-08 | E.I. Du Pont De Nemours And Company | Non-Porous Moisture and Gas Permeable Films |
| GB2494616B (en) | 2011-08-12 | 2014-05-07 | Innovia Films Ltd | In-mould labelling |
| US20150011697A1 (en) | 2013-07-03 | 2015-01-08 | E I Du Pont De Nemours And Company | Melt-processible vinyl fluoride interpolymers of low crystallinity |
| US9777145B2 (en) | 2013-12-20 | 2017-10-03 | E. I. Du Pont De Nemours And Company | Anti-fogging films based on ethylene copolymer compositions |
| JP2017516686A (en) | 2014-05-20 | 2017-06-22 | イー・アイ・デュポン・ドウ・ヌムール・アンド・カンパニーＥ．Ｉ．Ｄｕ Ｐｏｎｔ Ｄｅ Ｎｅｍｏｕｒｓ Ａｎｄ Ｃｏｍｐａｎｙ | Collation shrink film protection structure |
| WO2016025663A1 (en) | 2014-08-13 | 2016-02-18 | E. I. Du Pont De Nemours And Company | Multilayer structure comprising polypropylene |
| WO2016094281A1 (en) | 2014-12-11 | 2016-06-16 | E. I. Du Pont De Nemours And Company | Stretch wrapping film |
| US11401389B2 (en) | 2018-05-24 | 2022-08-02 | E. I. Du Pont De Nemours And Company | Transparent fluoropolymer films |
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| US3808304A (en) * | 1964-03-18 | 1974-04-30 | Grace W R & Co | Oriented blends of polypropylene and polybutene-1 |
| GB1113380A (en) * | 1966-06-03 | 1968-05-15 | Mobil Oil Corp | Thermoplastic polymer blend compositions |
| US3754063A (en) * | 1970-03-23 | 1973-08-21 | Grace W R & Co | Method for casting an inflated tubular polyethylene film with mixed polymer of polypropylene-polybutene-1 |
| US3849520A (en) * | 1973-01-17 | 1974-11-19 | Mobil Oil Corp | Resinous blend and oriented shrink film comprising polypropylene,polybutene and ethylene/butene copolymer |
| US3900534A (en) * | 1973-05-07 | 1975-08-19 | Mobil Oil Corp | Thermoplastic films based on blends of polypropylene and polybutene |
| US3832274A (en) * | 1973-06-06 | 1974-08-27 | Lord Corp | Fast curing adhesives |
| US3891008A (en) * | 1973-12-26 | 1975-06-24 | Grace W R & Co | Multi-layer thermoplastic film and method of making same |
| GB1566239A (en) * | 1977-09-26 | 1980-04-30 | Mitsui Petrochemical Ind | Thermoplastic filmforming olefin polymer composition |
| US4196240A (en) * | 1978-01-18 | 1980-04-01 | Union Carbide Corporation | Heat shrinkable multilayer packaging film of blended copolymers and elastomers |
| CA1178414A (en) * | 1978-02-08 | 1984-11-27 | Toyo Boseki Kabushiki Kaisha (Trading Under The Name Of Toyobo Co., Ltd.) | Packaging material having excellent seal packaging property |
| US4207363A (en) * | 1978-03-29 | 1980-06-10 | Union Carbide Corporation | Flexible heat-shrinkable multilayer film for packaging primal meat |
| US4194039A (en) * | 1978-04-17 | 1980-03-18 | W. R. Grace & Co. | Multi-layer polyolefin shrink film |
| US4379883A (en) * | 1979-12-21 | 1983-04-12 | Hercules Incorporated | Chemically-initiated inverse emulsion polymerization with Na, Li/Cl, Br salt |
| JPS6038414A (en) * | 1983-08-12 | 1985-02-28 | Mitsui Petrochem Ind Ltd | Thermoplastic resin copolymer |
| JPS60127133A (en) * | 1983-12-14 | 1985-07-06 | Sumitomo Chem Co Ltd | Film for shrink package |
-
1986
- 1986-11-24 CA CA000523640A patent/CA1304187C/en not_active Expired - Lifetime
-
1987
- 1987-05-12 US US07/048,853 patent/US4769421A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| US4769421A (en) | 1988-09-06 |
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