CA1118950A - Expanded thermoplastic synthetic resin and composition therefor - Google Patents

Abstract

Abstract of the disclosure:

A thermoplastic synthetic resin such as poly-ethylene or ethylene-vinyl acetate copolymer resin containing 0.1 to 10 wt. % of a specific additive selected from specific classes of compounds, namely saturated higher fatty acid amides, saturated higher aliphatic amines and complete esters of saturated higher fatty acids is found to be very suitable for production of expanded articles and can be easily formed into expanded articles with little shrinkage after expansion, free from creases on the surface or cracks on the cell walls, and having excellent characteristics such as good closed cellular characteristic, high compressive strength, low density, etc.

Description

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This invention relates to a novel thermoplastic synthetic resin composition suitable for manufacturing expanded products of various kinds, which contains at least one compound selected from specific classes of compounds.
This in~ention relates also to a process for expanding such a novel thermoplastic synthetic resin composition and to expanded products of a polyolefin resin obtained by such a process having excellent characteristics.
A thermoplastic synthetic resin of which expansion molding is difficult, for example, a polyolefin resin is known to be inferior in retentivity of gases such as of blowing agents as compared with such a resin as polystyrene resin.
Typical well-known methods of prior art for improve-ment of expandability of polyolefin resins may be classified - 15 broadly into four methods as follows:
(1) A method as disclosed by Japanese published examined patent applications No. 8840/1965 and No. 6278/1966, wherein the starting resin is subjected to crosslinking;

(2) A method as disclosed by U.S. Patent 3,810,964, wherein the starting resin is mixed with a resin other than polyolefin resins;
; ~3) A method as disclosed by Japanese published examined patent applications No. 4341~1960 and No. 19628/197~, wherein there is employed a blowing agent with a composition and components specifically selected; and (4) A method as disclosed by Japanese published examined patent applications No. 43997/1971 and No. 43998/1971, wherein there is added in the starting resin a partial ester of a specific polyhydric alcohol.
These methods, however, involve a number of drawbacks .. - ~ . . .

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and none of them are satisfactory in commercial application.
F~r example, according to the method (1), rheological flow properties of the resih can be improved, whereby it is possible to control resin temperature conditions optimum for melt-flow viscosity suitable fox expansion. However, the temperature control range can be improved only to a small extent and besides there is no improvement of retentivity of gases such as blowing agents at all. Thus, this method fails to give substantial improvement in the art. That is, even if expansion may proceed as intended, the resultant expanded product will suffer from immediate shrinkage to be converted directly to expanded products with high density.
Alternatively, even if the once shrinked expanded product may have a chance to be expanded again by the air impregnated thereinto, the creases, concavo-convex defoxmations on the surface or cracks on cell walls formed at the time of shrinkage cannot thereby be remedied. In consequence, no excellent expanded product can be obtained. For the same reason as mentioned above in connection with the method (1), the method (2) cannot he free from the same drawback. In addition it further involves the drawback that the desirable characteristics inherent in a polyolefin resin may be impaired. The method (3), especially that as disclosed by Japanese published examined patent application No~ 4341/1960, is now accepted as the most excellent method and has been practically used for commercial production of thick expanded articles. But this method cannot also be free from the problem of shrinkage or concavo-convex `deformations on the surface of the expanded products.
Furthermore, the specific blowing agents to be employed in this method are too expensive to be economical. Lastly, .` .

- 3 -, ,:
, . , -the partial esters used in the method (4) have insufficient effect of pxeventing shrinkage or cannot sufficiently be kneaded with the resin, whereby expansion moldability is lowered.
An object of the present invention is to provide a resin composition which can readily be formed into an expanded product with good quality from a synthetic resin which itself is difficultly formed into an expanded product with good quality due to excessive shrinkage phen~menon, particularly a polyolefin resin composition suitable for preparation of expanded products havlng a bulk density of lO to 200 kg/m3 and smooth surface, and being excellent in closed cellular structure as well as in compressive strength.
Another object of the present invention is to provide a novel expanded produck of a polyolefi~ resin having specific characteristics of an expanded product which cannot be obtained by any of prior art methods.
Still another object of the present invention is to provide a process for expansion of a thermoplastic resin which is capable of supplying economically expanded articles with low density, high closed cell percentage having excellent surface smoothness and compressive strength by preventing shrinkage in volume of the expanded products with lapse of time.
According to the present invention, thexe is provided a thermoplastic resin composition for manufacturing expanded products, comprising a thermoplastic synthetic resin and at least one compound selected from the group consisting of the compounds represented by the formulas ~I), (II) and ~III) as set forth below contained in said resin in an amount .: , :. , : , :
.~; , . . .

` of 0.1 to 10 % by weight based on the weight of said resin:
X

1 ~X' (I) wherein Rl is an alkyl group having 10 to 24 carbon atoms, X and X' each hydrogen atom, an alkyl group having 1 to 24 carbon atoms which may be substituted or a substituent containing a group of the formula-(~40)m~ wherein R4 is : . an alkylene group having 1 to 5 carbon atoms and m an integer of 1 to 10;

R2 ~ C - N ~ ~II) `yl wherein R2 is an alkyl group having 9 to 23 carbon atoms, ~ Y and Y' each hydrogen atom, an alkyl having 1 to 24 carbon atoms, an acyl having 10 to 24 carbon atoms or a substituent containing a group of the formula~(R40)m~ wherein R4 is an . alkylene group having 1 to 5 carbon atoms and m an integer of 1 to 10;

[R3~ -(OR4)k- ~ Z (~II) : O
wherein [R3] means plural alkyl or hydroxyalkyl groups `~ . corresponding in number to the integer Q, which may be the -.~ -same or different, each having 9 to 23 carbon atoms~ R4 an alkylene group having 1 to 5 carbon atoms, k an integer of : O to 7, Q an integer of 2 to 8 and æ a Q-valent residue of : Q-valent polyhydric alcohol f~om which Q hydroxyl groups are eliminated.
~ The expanded product obtained by using the composi-:. 25 tion of the present invention as mentioned above is also novel when a polyo efin resin is used as the thermoplastic resin.
~hus, the present invention also provides an expanded article .
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of a polyolefin resin, comprising an expanded product of a polyolefin resin containing at least one compound selected from the group consisting of the compounds represented by the ~ormulas (I), (II) and (III) as mentioned above in an amount of 0.1 to 10 % by weight based on said resin and having closed cellular characteris~ic value of 0 to 0.5 g/cm3, a bulk density of 10 to 200 kg/m3 and a compressive strength coefficient of 2.15 x 10 3 to 2.89 x 10 2.
~ In the accompanying drawings:
Fig. 1 shows the relationship of the volume change (ordinate) of the expanded product of the present invention (obtained in Experiment I) with lapse of time (abscissa) in which the marks o, o~ and ~ correspond to Sample No. 1 to No. 5, respectively;
Fig~ 2 compressive strength (at 25% compression) of several expanded products of polyethylene resin containing the additives according to the present invention and of poly-ethylene containing no additive plotted as ordinate versus bulk density of said products as abscissa;
Fig. 3 compressive strength (at 25% compression) of several expanded products of ethylene-vinyl acetate copolymer resin containing the additive and also o~ the same resin ` containing no additive plotted as ordinate versus bulk density of said products as abscissa (In Fig. 2 and ~ig. 3 the two straight lines in the drawings correspond to critical values 2.15 x 10 3 and 2.89 x 10 2, respectively.);
Fig. 4 the change in volume percentage (ordinate) of expanded products (obtained in Example 10 and Comparison example 1) based on the volumes immediately after expansion with lapse of tine 5abscissa); and ' - 6 -,;. . . .

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Fig. S the change in weight percentage (ordinate) of expanded products (obtained in Example lO and Comparison example l) based on the weight immediately after expansion with lapse of time. (In Fig. 4 and Fig. S the marks o and -coxrespond to Example lO and Comparison example 1, respectively.) ~he specific eature of ~he present invention resides in use of at least one compound selected from the three classes of the compounds (I), (II) and (III) as mentioned above.
The first class of the compounds are higher alkyl amines and N-substituted derivatives ther~of as represented by the above specified formula (I). The alkyl group represented by Rl is required to have 10 to 24 carbon atoms, preferably 12 to 22 carbon atoms. It may either be straight chain, branched or alicyclic. But for the practical reason from economical standpoint such as commercial availability or cost, a straight chain alkyl having 12 to 22 carbon atoms may preferably be used. The alkyl amines (I) to be used in the present invention are inclusive of primary, secondary and tertiary amines. Thus, both of X and X' may be hydrogen atom, or one or both of them may be substituents.
Preferable examples of substituents are as follows:
: (a) an alkyl having 1 to 24 carbon atoms (b) -(CH2)n-NH2 (n is an integer of l to 22) i (c) -(CH2)n-N-H (R5 is an alkyl having l to 24 ; R5 carbon atoms) (d~ -(R40 ~ H
(e~ -(R40 ~ C-R5 (R5 is the same as defined above) O

~f~ -(CH2)n-l_(R40 ~ A (~ is hydroge~ atom or -C-R5) (g~ -(CH2)n-N-(R40 ~ A (A' is hydrogen atom or (R
R5) . . .

As preferable combinations of ~ a-~d ~' 9 when one - 5 of ~ and ~' is the group (a), the other is the group (b) or (c); when o~e o~ X ~nd X' is h~drogen atom or the group (d) .; or (e), the other is hydrogen atom or any of the groups (a) -: .to (g).
~ypical e~amples of the compounds according to the ; 10 ~ormula (I) may include dodecyl amine, tetradecyl amine, hexadecyl amine, octadecyl amine, eicosyl ami~e7 docosyl ; amine, N-methyl dodecyl amina, ~-methyl octadecyl amine, N-èthyl octadecyl amine, dodecyl propylene diamine, tetra-decyl propylene diamine, hexadecyl propylene diamins, octadecyl propylene diamine, ~-methyl he~adecyl propylene diamine, N,N'-dimethyl hexadecyl propylene diamine, N-methyl octadecyl propylene diamine, N,~'-dimethyl octadecyl propylene diamine, hexadecyl ethylene diamine, octadecyl ethylene diamine, N-methyl he~adecyl ethylene diamine9 N~methyl ; 20 octadecyl ethylene diamine, and the like~ Typical example~
` of the saturated higher aliphatic amine derivatives axe polyoxyethylene myrist~l amine, polyoxyethylene palmityl . amine, polyoxyethylene stearyl amine, polyoxypropylene palmityl - amine, polyo~ypropylene stearyl amine, miristyl ~mine acetate, : 25 palmityl amine acetate, stearyl amine acetate9 polyoxy ethylene lauryl amine mono(and di~)palmitate 9 polyoxyethylene :-'`~ lauryl amine mono(and di-)stearate, polyoxyethylene palmityl ~ .

~ ~r~b amine mono(and di-)palmitate, polyoxyethylene palmityl amine mono(and di-)stearate, polyoxyethylene stea~yl amine mo~o (and di-)palmitate, polyoxyethylene stearyl amine mono(and di-)stearate, N-methyl polyoxyethylene stearyl amine palmitate, ~-ethyl polyo~yethglene s-tearyl amine stearate9 lauryl mono (and di-)ethanolamine palmitate, lauryl mono5and di-)ethanol-amine stearate, palmityl mono(and di-~ethanolamine palmitate, palmityl mono(and di-)ethanolamine stearate, stearyl mono (and di-)ethanolamine palmitate, stearyl mono(and di-)ethanol-amine stearate, dodecyl propylene diamine o~yethylene addition product, hexadecyl propylene diamine oxyethylene addition product, octadecyl propylene diamine oxyethylene addition product, polyoxyethylene hexadecyl propylene diamine mono(and di-)palmitate, polyoxyethylene hexadecyl propylene diamine mono(and di-)stearate, polyoxyethylene octadecyl propylene diamine mono(and di-)palmitate, polyozyethylene octadecyl propylene diamine mono(and di-)~tearate, and the like.
lhe second class of the compounds are saturated -fatty acid amides and derivatives thereof as represented by ; 20 the formula (II) as specified above. ~he alkyl group R2 in the formula (II) is required to have 9 to 23 carbon atoms, ~ preferably 11 to 21 atoms~ and may be either straight chain, `~ branched o~ cyclic~ ~or the same practical reason as mentioned above in connection with R~, R2 ma~ preferably a straight chain alkyl having 11 to 21 carbon atoms~ Similarl~, each of Y and Y' may either be hydrogen atom or a substituent.
~s substituents, there may be mentioned an alkyl having 1 to 24 carbon atoms, an acyl having 10 to 24 carbon atoms or a group of the formula -(R40)mA2 (wherein m is an integer o~
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1 to 10 and A2 hydrogen atom, an alkyl having 1 to 24 carbon atoms or an acyl having 10 to 24 carbon a~oms).
Typical examples of the compounds (II) are lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, arachic acid amide (eicosyl amide), behenic acid amide (docosyl amide~, N-methyl stearic acid amide, N,N'-dimethyl stearic acid amide, di-lauric acid amide, di-palmitic acid amide, di-stearic acld amide, tri-lauric acid amide, tri-palmitic acid amide, tri-stearic acid amide, and so on. The saturated higher fatty acid amide derivatives may include lauric acid mono(and di-)ethanolamide, myristic acid mono(and di-)ethanolamide, palmitic acid mono(and di-)ethanol-amide, stearic acid mono(and di-)ethanolamide, arachic acid mono(and di-)ethanolamide, behenic acid mono(and di-)ethanol-amide, lignoceric acid mono(and di-)ethanolamide, lauric acid mono-isopropanolamide, palmitic acid mono-isopropanolamide, stearic acid mono-isopropanolamide, polyoxyethylene lauric acid amide, polyoxyethylene myristic acid amide, polyoxy-ethylene palmitic acid amide, polyoxyethylene stearic acid amide, polyoxyethylene arachic acid amide, di-lauric acid mono-ethanolamide, di-myristic acid mono-ethanolamide, di-palmitic acid mono-ethanolamide, di-stearic acid mono-`~ ethanolamide, di-arachic acid mono-ethanolamide, polyoxy-ethylene di-stearic acid amide, polyoxyethylene lauric acid 2~ amide-mono~stearate, polyoxyethylene stearic acid amide-mono-`~ stearate, etc.
~` The third group of the compounds are complete esters ` of saturated higher fatty acids as represented by the formula '.~
~` (III) as specified above. They are complete esters of poly-hydric alcohols of the formula Z(OH)Q and saturated fatty acids ,.

`
., ~ ,. . . .
, having 10 to 24 carbon atoms. In the above formula, the symbol LR3] means plural alkyl groups comprehensively, each being attached to each ester linkage which is bonded to polyhydric alcohol residue represented by Z, and each having 9 to 23 carbon atoms. Also in this compound, straight chain alkyl having 11 to 21 carbon atoms is preferred. The co~plete esters may be modified by addition reaction to include polyoxyalkylene group of the formula -(OR4)k- in the molecule. The oxyalkylene group-OR4- may preferably oxyethylene or oxypropylene.
Typical examples of the compounds (III) are polyoxy-ethylene di-myristate, polyoxypropylene di-myristate, polyoxy-;~ ethylene di-palmitate, polyoxypropylene di-palmitate, poly-oxyethylene di-stearate, polyoxypropylene di-stearate, polyoxyethylene di-arachate, polyoxyethylene di-behenate, ethyleneglycol di-myristate, ethyleneglycol di-palmitate, ethyleneglycol di-stearate, ethyleneglycol di-arachate, ` ethyleneglycol di-behenate, lauric acid tri-glyceride, ;` myristic acid tri-glyceride, palmitic acid tri-glyceride, .~ . .
~ 20 stearic acid tri-glyceride, arachic acid tri-glyceride, ~. ~
~: 1,3-palmito-2-stearic acid glyceride, 1,3-stearo-2-myristic acid glyceride, sorbitane tetra-palmitate, sorbitane tetra-stearate, 12-hydxoxy stearic acid tri-glyceride, sorbitane tetra-12-hydroxystearate, mono-stearic acid-di-12-hydroxy-~.` 25 stearic acid tri-glyceride, polyoxyethylene glycerine tri-- stearate, polyoxye~hylene glycerine tri-12-hydroxystearate, polyoxyethylene sorbitane tetra-stearate, polyoxyethylene ` sorbitane tetra-12-hydroxystearate, mono-stearic acid-di-12-hydroxy sllearic acid polyoxyethylene tri-glyceride, and `` 30 the like.

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It is critically required in the present invention that at least one compound selected from the group of the compounds (I), (II) and (III) as described above should be contained in the thermoplastic synthetic resin in a total amount of 0.1 to 10 % by weight based on the weight of said resin.
Referring now to Experiments I to IV set forth below, the specific behavior of the compounds within the scope of the present invention when they are contained in an amount within the range as specified above is to be described.
Experiment I
Using an ethylene-vinyl acetate copolymer (EVATATE
D-2021, trade mark, produced by Sumitomo Chemical Co., Ltd.;
vinyl acetate content: 10 wt. %, density: 0.93, Melt Flow Index: 1.5) as base resin, various samples are prepared by adding t~e compounds as shown in Table 1 and each sample is fabricated into a non-stretched sheet with thickness of about 0~15 mm.
` ` T~ble 1 ;. . , Sample No Additives ` Parts per 100 parts Principal of resin Trade name component (by weight) Manufacturer 1 Amine A-B Octadecyl 2 Nippon Oils &
amine Fats Co., Ltd.
2 Fattv acid Stearic 2 Kao Soap amide T acid amide/ Co., Ltd.
palmitic acid amide 3 Hardened Stearic 5 "
oil acid tri-; glyceride

4 Span 85 Sorbitane 2 "
(reference) tri-oleate -(Control) - - -.

.: ' - 12 _ .

351~3 The gas permeability characteristics of these sheets - are measured according ko the following method:
Device: Gas-permeability measuring instrument ; (LYSSY-L100-3001 model, produced by LYSSY Co.) Gases to be permeated: Air; Dichlorotetrafluoro-ethane (blowing agent) Method: Gas permeability coefficient is determined - by measuring the time (seconds~ needed until the inner pressure of a vessel initially maintained at 0.2 Torr at about 30C is ~ .
increased to 0.4 Torr by the gas permeated through the sample sheet. The time is measured repeatedly until its value becomes : 15 approximately con~tant, and the average value of three measured values is divided ` . by the thickness of the sheet to give the gas permeability coefficient.
~' - The results of measurement are given in the following `~ 20 Table 2.
.` Table 2 Sample No.: 1 2 3 4 5 Additive : Amine Fatty Hardened Span 85 Control '`, AB acid oil (reference) - amide . ` T
`: Permeated `~i! gas ~- 1,2-dichloro-~` tetra- . 244 255 320 121 79 fluoro `~ ethane Air 340 350 380 490 320 . .
` unit: sec/mm ~, ' - 13 ~

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;"' ~': ', ' ,` , .' . `' `"' ' ' As apparently seen from Table 2, the compositions according to the present invention (Sample Nos. 1, 2 and 3) suppress noticeably permeability of blowing agent gas as compared with Control (Sample No. 5), while they suppress little permeability of the air. On the contrary, the composition of the reference (Sample No. 4) slightly suppresses permeability of the blowing agent gas, while t greatly suppresses permeability of the air.
Based on the presumption that the well-balanced permeabilities of the air and the blowing agent gas through the resin compositions of the present invention as shown in Table 2 might be reflected in expansion procedure to result in ideal expanded products, the present inventors have made experiments to apply these compositions for manufacturing expanded products of polyethylene and ethylene-vinyl acetate copolymer resin in spite of the fact that expansion molding of polyethylene resin under uncrosslinked state has been - deemed to be difficult and also that expansion molding with high closed cell percentage of ethylene-vinyl acetate copolymer resin has been substantially impossible.
The following ExperimentsII-IV illustrates the ~` results of these experiments.
: Experiment II
Each of the resin compositions according to Sample Nos. 1 to 5 as described in Experiment 1 is mixed with 0.1 part by weight of calcium stearate and 0.6 part by weight of calcium stearate and fed to an extruder (30 rnm~). The mixture is kneaded internally of the extruder together with 28 parts by weight of 1,2-dichlorotetrafluoroethane and the thus mixed - 30 resin is extruded into the air while being maintained at about li3LlB95~

~0C to effect expansion to obtain expanded products.
The density of the expanded products obtained is controlled to be 36 to 37 kg/m30 The volume of the resultant expanded product is thereafter continued to be measured day by day. On the other hand, for the expanded product after 10 days, there are conducted measurements of compressive strength, compression permanent set, compression creep, surface smoothness, maximum shrinkage of the expanded product after expansion, dimensional stability of the expanded product ànd closed cellular charac-teristic value (each measurement method is hereinafter described).
Fig. 1 shows the relationship of the volume change with lapse of time and Table 3 the results of the measurement ; 15 of various characteristics for each expanded product.
The-compressive strength coefficient is also determined from the formula (2) as hereinafter described and shown in Table 3 in bracket together with 25 % compressive strength (according to ~I~-K-6767), since the latter varies depending on the density of the expanded product, etc.
As is clear from the above results, the composition of the present invention can be expanded using a blowing agent to give feasibly expanded products with good quality o~ un-crosslinked polyethylene which has hikherto been deemed to be difficult in the prior art as well as expanded products with good quality of ethylene-vinyl acetate copolymer resin which cannot practically be prepared in the prior art.

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The concept of compressive strength coefficient is herein introduced to specify the novel expanded articles obtained by use of the composition according to the present invention. This is because apparent compressive strength as shown in Table 3 varies depending on bulk density of the expanded product and therefo~ it is not desirable to charac-terize the expanded product in terms of such an apparent compressive strength. As the result of numerous experiments, the present inventors were successful in generali~ation of the compressive strength relative to bulk density according to the following formula:
p = A x Dl 248 Y O............ (1) From the formula (1) is obtained:

Dl.248 Y o (2) wherein A represents compressive strength coefficient, P 25 %
compressive strength measured according to JIS-K-6767, D bulk density of expanded product, the value 1.248 is the index experimentally determined from numerous data, Y is parameter (1 ~ /100), a being percentage (wt.) of the component to be copolymerized in the resin (for example, vinyl acetate in ethylene-vinyl acetate copolymer)~ This specific compressive strength coefficient is hereinafter referred to as "A value".
Experiment III
Using a low density polyethylene (Asahi-Dow Poly-ethylene F-1920, trade mark, produced by Asahi-Dow Limited;
density: 0.919, Melt Flow Index 2.0) as base resin, the compositions 1 to 11 containing the additives and blowing agents as shown in Table 4, respectively, per 100 parts by weight of said resin are prepared by kneading similarly in .

.: .
. .

an extruder and sub~ected to extrusion expansion as in Experiment II. As nucleators, there are employed 0.06 parts by weight of calcium stearate and 0O36 parts by weight of calcium silicate in each composition. After 10 days after formation of expanded product, 25 % compressive strength is measured according to JIS-K 6767 for each expanded product .. .
from each composition to give the results as shown in Fig. 2, the numbers in Fig. 2 corresponding to those of the compositions.
Experiment IV
Using an ethylene-vinyl àcetate copolymer tEVATATE
K-2010, trade mark, produced by Sumitomo Chemical Co., Ltd.;
vinyl acetate content 25 wt.~, density: 0.95, Melt Flow Index: 3.0) as base resin, 0.1 part of calcium stearate and 0.6 part by weight of calcium silicate as nucleators and the additives and blowing agents as shown in Table 5, under other-wise the same conditions as in Experiment III, the compositions 12 to 20 are formed into expanded products. The results of measurement conducted similarly as in Experiment III are shown in Fig. 3, wherein the numbers correspond to those of the compositions.
, ' ;

Table 4 Compo-sition No _ Blowing agent (wt.parts~ _ Additive (wt.parts) _ _ . _ _ 1 Dichlorodifluoromethane (57) Fatty acid amide T(4.0 2 " t57) None 3 " (22) Fatty acid amide T(2.0) 4 " ~22) None " (5) Amine AB (1.0) 6 Butane (8) Hardened oil ~3.0) 7 " (8) ~one 8 " (6) Fatty acid amide T(0.5) 9 " (6) None l-chloro-l,l-difluoro-ethane (60) Hardened oil (2.0) 11 " (60) ~one .

Table 5 Compo-sition No. Blowing agent (wt.parts) Additive (wt.parts) 12 1,2-dichloro-tetrafluoro Amine AB (1.0) ethane (10) 13 Dichlorodifluoromethane (57) Fatty acid amide T(5.0) 14 " (57) No~e lS " (22) Fatty acid amide T(4.0) 16 .. (22) ~one 17 Butane (7) Hardened oil (2.0 18 '' (7) None 19 l-chloro-l,l-difluoro- Hardened oil (3.0) ethane (60) " (60) None .

-- 19 -- .

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As apparently seen from Fig. 2 and Fig. 3, the A
values of the expanded products obtain~d by use of the compositions of the prèsent invention are invariably within 2.15 x 10 3 to 2.89 x 10 2 even when the blowing agent employed may be varied. In contrast, the A values of the expanded products using no composition of the present invention are by far smaller than the range as specified above. While being not bound by any theory, this is probably due to the following reason. Blowing agent gases contained in the expanded products are rapidly dissipated therefrom at the stage immediately after expansion in case when no compo-sition of the present invention is employed, while the air penetrates into the expanded product considerably slowly.
Consequently, at the stage before complete solidification of the resin while it is hot, the expanded product is brought internally to a state undex reduced pressure, whereby it is compressed by atmospheric pressure to be shrinked. Thus, cooling is completed while giving deformations or cracks on cell walls. When the penetration of the air is slower than the cooling speed as mentioned above, the expanded product is cooled as it i6 to result in an expanded product with high density and having a large number of permanent creases remained on the expanded product. Even when the air may be penetrated more rapidly, simultaneously with reduction in pressure in the expanded product, to effect surface expansion of the expanded product, the deformations or cracks already formed on cell walls will prevent such surface expansion to make restoration to original volume difficult. This speculation is considered to be quite probable because the A values of the expanded products are greatly deteriorated.

.

; - Whereas, in the expanded product prepared from the composition of the present invention, the resin can be solidified with very small extent of shrinkage by permitting blowing agent gases to be replaced by the air while maintain-ing the ratio of both gases permeated suitably. As the result, the expanded product can be free from deformations or cracks on the cell walls to exhibit not only the excellent compres-sive strength coefficient but also excellent surface smoothness.
; If the specific compound of the present invention is used in less than 0.1 wt. % based on the resin, no significant e~fect can be obtained. On the contrary, an amount in excess - of 10 wt. % does not necessarily lead to improvement of the effect but in some cases may cause an adverse effect on the -rheological flow properties of the composition itself.
Accordingly, the amount of the specific compound added is generally selected from about 0.5 to 7 wt. % from economical standpoint. There is no significant change in the amount of the compound added when it is in the composition or when it is in the expanded product, and it is calculated as a total amount of the specific compounds employed based on the weight of the resin.
For the purpose of the invention, there may be employed either a single compound or a combination of two or more compounds selected from those as mentioned above~ The compound may be incorporated in the resin by any method but ` it is desirable to contain the compound in the resin so that ~ said compound may be dispersed as homogeneously as possible - in the resin when the cc,m~osition is formed into an expanded ` - product.
In accordance with the present invention, there is "
; - 21 -s~

also provided a process for expandiny a thermoplastic synthetic resin, which comprises incorporating at least one compound selected from the group consisting of the compounds of the formulas (I), (II) and (III) as described above in the thermoplastic synthetic resin in an amount of 0.1 to 10 % by weight based on said resin together with a suitable amount of a blowing agent under the condition maintained at a temperature in the range from about 15 to 300~C to form an expandable resin composition and then allowing said resin composition to expand utilizing the expanding force of the blowing agent contained therein.
In the process as specified above, the compounds may be incorporated in the resin by so called impregnation method wherein a substance to be incorporated is contacted with resin lS particles and said substance is impregnated into the resin by controlling the pressure and the temperature. Alternatively, there may also be employed so called kneading method wherein the resin and the substance to be incorporated are subjected to mixing and kneading. Furthermore, a combination of both methods may also be applicable. The substances to be incorporated may either be simultaneous or stepwise. These operations may be conducted under well known conditions, namely at a temperature in the range from 15 to 300C and a pressure of 0.05 to 300 kg/cm2 (gauge).
The expanding force of blowing agent used in this process is obtained through phase transfer (from li~uid phase to gas phase), volume expansion of blowing agent and decompo-sition of blowing agent (from solid to gas), and therefore the conditions are determined depending on the blowing agent employed and expanding operations. For example, when a physical _ 22 ~

.
.

blowing agent is used in extrusion expansion, a resin kneaded for temperature adjustment at a temperature of about 60 to 280C under a pressure of 5 to 200 kg/cm2 can be extruded into the atmosphere at a temperature of about 20C and under pressure of 1 atm. to obtain sufficient expanding force.
Alternatively, when a physical blowing agent is used in cavity expansion, a resin containing a blowing agent is filled in a cavity and the cavity is heated under conditions at a temperature of about 115C under pressure of 0.23 kg/cm2 (gauge).
The specific feature of the process according to the present invention resides in allowing a the~moplastic - synthetic resin composition containing 0.1 to 10 wt. % of-at least one compound as specified by the formulas (I), ~II) and (III) to expand with a blowing age~t which is also contained in said resin. This is because, in the absence of the specific compound, the expanded product suffers from shrinkage in the course of preparation and with lapse of time, as explained with reference to Fig. 1 to 3 and Table 3, thereby giving only expanded products with high density, having much concavo-convex deformations or creases or being very low in closed cell percentage. In particular, no expanded product ;~ with excellent compressive strength can be obtained in the absence of the specific compound.
Similarly as described in connection with the composition of the present invention, an amount of the specific compound less than 0.1 wt. ~ fails to give the effect of the - invention, while an amount exceeding 10 wt. ~ may cause adverse effect rather than better results. The specific compounds may also be used either singly or in a mixture of , .

935~

two or more compounds. The preferable total amount of the specific compounds falls also within 0.5 to 7 wt. %. They can be contained in the resin in any conventional manner, but it is desirable to disperse the compounds as homogeneously as possible throughout the entire resin.
As blowing agents to be used in the present invention, .. .
volatile organic blowing agents and thermally decomposable gas-releasing chemical blowing agents are available. Preferably, there may be employed volatile organic blowing agents having boiling point (at 1 atm.) not higher than melting point o~ th~
base resi~, such as trichlorofluoromethane, dichlorodifluoro-methane, dichlorofluoromethane, chlorodifluoromethane, 1,1',2-trichlorotrifluoroethane, l,2-dichlorotetrafluoroethane, l-chlorotrifluoroethane, l-chloro-l,l'-difluoroethane, 1,1 t _ difluoroethane, octafluorodichlorobutane, propane, butane, butene, propylene, pentane, etc. ~hen the base resin to be expanded is a non-crosslinked polyolefin resin, it is preferred to select a volatile blowing agent from those as enumerated above having a Kauri-Butanol value in the range of 10 to 25 as determined by the method according to ASTM-D-1133-61.
These blowing agents may be employed generally in an amount in the range from 5 to 70 % by weight based on the resin depending on the desired density of expanded products.
The process of the present invention is expected to be most advantageously be applied in the field of so called continuous extrusion expansion. In this case, for example, the base resin, the specific compound and blowing agent are fed into an extruder heated at a temperature higher than melting point of the base resin (generally about 120 to 280C), kneaded under a pressure generally of about 50 to 300 kg/cm2 .

therein, then said mixture is adjusted to a temperature suitable for expansion in the range from the melting point of the base resin to the temperature lower by 50C than the melting point (generally about 60 to 200C) before being extruded through an orifice to the outside at about 25~C
under atmospheric pressure, thereby accomplishing expansion ..
simultaneously with extrusion, followed ~y cooling to produce expanded articles. This technique is economical in continuous expansion of a large amount of resins. In particular, by use of the specific compound of the prèsent invention, it is rendered possible to select a blowing agent from a large number of less expensive compounds which have hitherto been insufficient in expandability when used alone as klowing agents. To speak one typical example, in place of an expensive blowing agent 1,2-dichlorotetrafluo~oethane, there can be employed less expensive blowing agents such as dichlorodifluoro-methane, propane or butane to a great economical advantage.
The thermoplastic synthetic resin to be used in the present invention refer to all polymers, copolymers and mixed polymers which can be subjected to melt fabrication. In particular, thermoplastic synthetic resins which can be improved in expandability by addition of the specific compound ~f the present invention are those which will undergo shrinkage when expanded due to the greater ratio S'/S exceeding 1 of permeating speed ~S') of volatile hydrocarbon or fluorocarbon gas through said resin film to that (S) of the air (at the time of expansion as estimated by ~ig~ 4 and ~ig. 5). More specifically, they may include crosslinked or non-crosslinked polyolefin resins such as ethylene homopolymers (e.g. high density polyethylene, medium density polyethylene or low - , :

~1~8~

density polyethylene or a mixture thereof), ethylenic copol~mers having ethylene content of 50 % or more (e.g.
ethylene-vinyl acetate`copolymerr ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid ester copolymer,

5 a metallic salt of an ethylene-acrylic acid copolymer, ethylene-propylene copolymer, ethylene-vinyl chloride .
copolymer), polypropylene and polybutene-l. Among them, polyethylene resin and ethylene-vinyl acetate copolymer are preferably used. The polyolefin resin to be employed in the present invention may have a melt index which is not specifically limited but generally within the range from 0.3 to 45. When it is desired to employ a crosslinked poly-olefin resin, it may be prepared by conventional method by effecting crosslinking using a crosslinking agent such as organic peroxides or irradiation of electron beam~
The resin composition of the present invention may further contain, if desired, other inorganic or organic .
additi~es such as pigments, fire-retardants, lubricants, anti-oxidants, UV-absorbers, nucleators, anti-static agents or others in an amount of preferably no more than 3 % by weight based on the weight of the resin. In particular, it is preferable to use a small amount (not more than 1 ~ by weight) of nucleators such as talc or a fatty acid metal salt in order to control uniformly the cell distribution in the resultant expanded product.

.
..

The present invention is fuxther illustrated with re~erence to the following Examples an~ Comparison Examples.
The measuremen~ of characteristic values and evaluation of these values herein mentioned are conducted by the methods and the criteria, respectively, as set foxth below.
1. Compressive strength and compressive strength coefficient a) 25~ compressive strength (P):
Compressive stxength at the time of 25%
compression is measured according to JIS-K-6767.
b) compressive strength coefficient (A):
This value is calculated by the formula (2) as mentioned above from the above compressive strength (P) and bulk density (D) of expanded product.
2. 50% compression permanent set:
According to JIS-K-6767 (at the time of 50 compression).
3. Compression creep: ~
According to JIS-K-6767 (under area load of O.l Kg/cm2 24 hour) 4. Surface smoothness: ~
The surface of expanded product is measl1red over 10 cm length by coarseness measuring instrument to detect creases or concavo-convexes with width of 0.5 mm or more and c the number detected is calculated per 1 cm length.

.

3~

Feeding characteristic through extruder:
Change in amount extruded per one minute when performing extrusion by 30 mm~
extruder is expressed by variance percentage (n=15).
- Maximum minimum . ~ amount amount : Variance percentage = x 100 Average am~unt

6. Maximum shrinkage:
Volume of expanded product is measured (by water-sink method) every day for 20 days ater expansion and maximum shrinkage is calculated by the following formula:
- - Volume of expanded product Maximum = 1 on the day when it is minimum x 100 shrinkage Volume of expanded product immediately after expansion

7; Dimensional stability: .
`,` From the result of measurement 6. as mentioned above, dimensional stability is calc.ulated by the following formula:

Dimensional stabillty = ~ ~ x 100 (wherein V0 lS volume of expanded product immediately after expansion and V20 that after 20 days.)

8. Closed cellular characteristic value:
.. In water in a vessel having water volume sufficient to sink sample in water and a function to be sealed is sunk an expanded . 25 product sample of 15 mm x 15 mm x 100 mm , (volume: V; weight: Wo) to be held therein, .~
.

5~

followed by sealing of the vessel.
Subsequently, the inner pressure in the vessel is reduced to 460 mm Hg and left to stand for 10 minutes. Then, the inner pressure in the vessel is restored to atmospheric and the sample is taken ou~O
The samplP is calmly dipped in pure methanol for about 2 seconds, ~ollowed by wipe-off of the moisture adhered on the surface, dried in a drler at 60C for 5 minutes and thereafter - its weight (W13 is measured.
Closed cellular characteristic value is - calculated by the following formula:
Closed cellular W1 - W0-characteristic - -value (g/cm3) V

9. Criteria for evaluation:
Each evaluation item is rated according to . the ranks as shown in the following Table:
Evaluation item Ranks _ a b . c d (excellent) (good) (passable) _ (bad) 1. Compressive 8.0 x 10 3 4.0 x 10 3 2.15 x 10 3 less than 3 strength or more or more, or more, 2.15 x 10 coefficient less than less than ` 8.0 x 10 3 4.0 x 10 3 2. 50% compres- less than 5 or more, 15 or more, 30 or more sion 5 to 0 less than less than : permanent 15 30 set (%) ` 3. Compressive less than 5 or more, 10 or more 20 or more - creep (%) 5 to 0 less than less than ` 10 20 4. Surface less than 3 or more, 6 or more, 10 or more : smoothness 3 to 0 less than less than (number/cm) 6 10 -. , ; , . -. , 35~

Evaluation item Ranks a b c d (excellent) (good) (passable) (bad) 5. Feeding less than 5 or more, 10 or more, 15 or more character- 5 to 0 less than less than istic of 10 15 extruder ~) 6. Maximum less than 10 or more, 15 or more, 20 or more shrinkage 10 to 0 less than less than ~) 15 20 7. Dimensional less than 5 or more, 10 or more, 15 or more stability 5 to 0 less than less than (%) 10 15 8. Closed less than 0.010 or 0.02S or 0.50 or cellular 0.010 to 0 more, less more, less more charac- than 0.025 than 0.50 teristic (g/cm3) ;

Overall evaluation is rated from the ranks as set forth above according to the following ranks:
a (excellent) ..... when there are at least two excellent marks with no bad or passable mark b (good) .......... when there is at least one good mark with no bad mark and not more than two passable marks c (passable) ...... when there are three or more passable marks with no bad mark d (bad) ........... when there is one or more bad mark The details of the thermoplastic synthetic resins and the specific compounds employed in the following Examples and Comparison Examples are listed below.
Thermoplastic resins: -.
Resin A: low density polyethylene produced by Asahi-Dow Limited, F-1920, trade mark, density. 0.919 g/cc, MI: 2.0 g/10 min.
Resin B: ethylene-vinyl acetate copolymer produced by Sumitomo Chemical Co., Ltd., EVATATE

:

'3~

D-2021, trade mark, vinyl acetate content~ 10 wt.~, density: 0.93 g/cc, MI~ 1.5 g/10 min.
Resin C: ethylene-vinyl acetate copolymer produced by Sumitomo Chemical Co., Ltd., EVATATE R-2010, trade mark, vinyl acetate content: 25 wt.%, density: 0.95 g/cc, MI:
- 3.0 g/10 min.
Additives (Nos. 1 - 18: speci~ic compounds of the invention; Nos. 19 - 31: reference compounds) - Trade name of No. additives Manufacturer Name of the compounds 1 Fatty acid Kao Soap Co., Stearic acid amide and amide T Ltd. palmitic acid amide (mixture) 2 Amine BB Nippon Oils ~ Dodecyl amine Fats Co., Ltd.
3 Amine AB " Octadecyl amine 4 N-methyl- " N-methyloctadecyl amine octadecyl amine 5 ~sfaæol ~20 " Stearyl propylene diamine 6 Naimine S-202 Kao Soap Polyoxyethylene octa-Co., Ltd. decyl amine (2 moles of oxyethylene added) 7 Naimine S-210 " Polyoxyethylene octa-decyl amine (10 moles of oxyethylene added) 8 Denon 331 P Marubishi Polyoxyethylene stearyl Petrochemical amine mono- and di-Co. stearate (mixture) 9 Esoduomine Lion Fat ~ Polyoxyethylene stearyl T-13 Oil Co., ~td. and palmityl diamine (mixture: 3 moles of oxyethylene added)

10 Resicoat 1936 " Oxyethylene stearyl and palmityI diamine (mixture:
one mole of oxyethylene added) 35~:7 Trade name of No. additives Manufacturer _Name of the compounds -

11 Fatty acid Kao Soap Co., Lauric acid amide amide C Ltd.

12 Amizol SDE Kawaken Fine 1:1-type stearic acid Chemical Co., diethanolamide Ltd.

13 Amizol SME " l:l-type stearic acid mono-ethanolamlde

14 Amizol LME " l:l-type lauric acid mono-ethanolamide

15 Fatty acid Kao Soap Co., Palmitic acid amide amide P Ltd.

16 Hardened oil " Stearic acid triglyceride

17 Kao wax 85 " 12-hydroxy stearic acid powder triglycerlde

18 -Unister-~-275 Nippon Oils & Ethyleneglycol distearate Fats Co~, Ltd.

19 Syntolex " Sodium lauryl sulfate

20 Atmos-150 Kao Soap Co., Stearic acid mono- and Ltd. di-glyceride

21 Cation Nippon Oils & Octadecyl dimethylbenzyl S2-100 Fats Co., Ltd. ammonlum chloride

22 Noion " Polyoxyethylene nonyl SN-204.5 phenol ether

23 Caproic Kanto Chemical Caproic acid amide acid amide Co., Ltd.

24 Span 85 Kao Soap Co., Sorbitane trioleate Ltd.

25 Triphenyl Kanto Chemical Triphenyl carbinol carbinol Co., Ltd.

26 1,2-diphenyl " 1,2-diphenyl ethylene~
ethylene- . diamine diamine

27 Phthalamide " Phthalamide

28 Lunac S-30 Kao Soap Co., Stearic acid - Ltd.

:-Trade name of No. additives _ Manufacturer Name of the compounds

29 Zinc stearate Sakai Zinc stearate - Chemi~al Co., Ltd.

30 Fatty acid Kao Soap CoO, Oleic acid amide amide 0 htd.

31 Alfro P-10 Nippon Oils & Erucic amide E'ats Co., Ltd.

Examples 1 - 18 and Comparison examples 1 - 14 To 100 parts by weight of Resin B are added various additives as shown in Table 6, 0.1 part by weight of calcium stearate, 0.6 part by weight of calcium silicate and 22 parts by weight of a volatile blowing agent dichlorodifluormethane.
Each mixture is kneaded by means of a 30 mm single screw extruder equipped with a round orifice of 5 mm in diameter and heated at 190C. By adjusting the resin temperature in the orifice at 90C, extrusion expansion is carried out for each mixture to prepare an expanded product thereof. These expanded products are subjected to evaluation test as described above to give the results as shown in Table 6. Table 6 clearly shows that the expanded products of Examples 1 to 18 containing the compounds of the formulas (I) to (III) exhibit superior values to those of Comparison example 1 containing no additive and Comparison examples 2 to 14 containing other compounds than those of the formulas ~I) to (III).
The vol~nes and weights cf the expanded products obtained in Example 10 and Comparison example 1 are continued to be measured every day for about one month, respectively, ; and the percentages of volumes and the weights based on those immediately after expansion are plotted versus lapse of time (days) in Fig. 4 and Fig. 5.

-:: , , .

3~

As apparently seen from Fig. ~ and Fig. 5, the expanded product of Example 10 is reduced in weight with lapse of time, while its volume i5 not redu~ed with small shrinkage and good restorability. In contrast, the expanded product of Comparison example 1 suffers from abrupt and noticeable shrinkage with reduction in weight and its volume restored with lapse of time is at st about 60 ~.

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Examples l9 - 27 and Comparison examples 15 - 17 Expanded products are prepared similarly as described in Examples l - 18 except that lO0 parts by weiyht of Resin A are used as base resin, 0.06 parts by weight of calcium stearate a~d 0.36 part by weight of calcium silicate powders as nucleators and the blowing agents D, E
.. .
and F as shown in Table 7 in amounts of 22, 20 and 8 parts by weight, respectively, and that the resin temperature in the orifice is controlled at 104C. From the results shown in Table 7, it is clearly seen that Examples 19 to 27 give better results than Comparison examples 15 to 17 when various blowing agents D, E and F are employed.

.

-35~

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Examples 28 - 36 and Comparison examples 18 - 21 Using lO0 parts by weight of Resin C as base resin, blowing agents D, E, G and H as shown in Table 8 in amounts of 22, 20, 28 and 26 parts by weight, respectively, and the ~dditives as shown in Table 8 in amounts indicated therein, and also adjusting the resin temperature in the orifice at 78C, under otherwise the same conditions as described in Examples l to 18, various expanded products are prepared.
The results are shown in Table 5, which clearly shows that Examples 28 to 36 give better results than Comparison examples 18 to 21 even when there is employed Resin C of an ethylene-vinyl acetate copolymer with higher vinyl acetate content from whi.ch a volatile blowing agent is l~able to be readi y escaped.

.

~ - 4~ -, 9~

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::!

Examples 37 - 39 and Comparison examples 22 - 2~
According to the same procedure as in Examples 1 - 18 except for the specific compounds and their amounts and the amounts of dichlorodifluoromethane as shown in Table 9, various expanded products are prepared. The results as shown in Table 9 indicate that the products of Examples 37 - 39 are better in expansion moldability and physical properties of the resultant expanded products than those of the Comparative examples even when the amounts of the blowing agent are greatly changed as shown in Table 9.

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tj~

Example 40 In polyethylene resin ~F-2130, trade mark, produced by Asahi-Dow Limlted, density: 0.921 g/cc, MI: 3.0 g/10 min.), there are added by kneading 0.45 % by weight of dicumyl peroxide as crosslinking agent and 1.5 ~ by weight of stearic acid amide tFatty acid amide T, trade mark, produced by Kao Soap Co., Ltd.) and the mixture is subjected to crosslinking reaction. The resultant crosslinked polyethylene resin particles (spherical with diameter of 1.5 mm) with gel content of 61 ~ are impregnated in an autoclave with dichlorodifluoro-methane under pressurization with heating and thereafter cooled.
The expandable crosslinked polyethylene resin particles thus obtained are found to contain 14 wt.~ of dichlorodifluoro-methane. These particles are placed in a pressure-type expand~
ing vessel wherein they are allowed to expand while passing steam of 0.23 Kg/cm2.G for 45 seconds to obtain primarily expanded particles with density of 100 Kg/m3. Subsequently, these primarily expanded particles are placed in an autoclave and, under pressurization with the air at 10 Kg/cm2.G, heat treatment is conducted at 80C for 15 hours to increase inner pressure in the cells, follo~ed by passing of steam of 0.32 Kg/cm2 to effect expansion to obtain secondarily expanded particles with density of 27 Kg/m . After increasing the inner pressure in the cells of these secondarily expanded particles, they are filled under compression in a cavity in a molding machine (ECHO-120 model, produced by Toyo Machinery & Metal Co., Ltd.) and subjected to expansion fusion molding by heating with steam of 1.1 Kg/cm2.G. The density of the molded expanded product is found to be 25 Kg/m3 and have a closed cellular characteristic value of less than 0.01.

.

Comparison example 25 Example 40 is repeated except that no stearic acid amide is added. The resultant primarily expanded particles are found to have a density of 111 Kg/m3, while the secondarily expanded articles a density of 31 Kg/m . The expanded particles have higher density as compared with those of Example 40 and said particles are found to have relatively large number of creases. When the secondarily expanded particles are molded - similarly as in Example 40, the expanded product obtained is found to have a density of 30 Kg/m3. It is also inferior in closed cell percentage and compressive strength to that of Example 40. The life of beads impregnated with blowing agent for retaining desirable expandability is also shorter by one hour as compared with those of Example 40.
Example 41 Using a mixed resin comprising 60 parts by weight of a high density polyethylene (Suntec S-360, trade mark, produced by Asahi Kasei Kogyo Kabushiki Kaisha, density: 0.950 gjcc) and 40 parts by weight of an ionomer (Surly~ A 1706, trade mark, produced by E.I. du Pont de Nemours, Inc.), 1.5 parts by weight of stearic acid amide as specific additive (Fatty acid amide T, trade mark, pxoduced by Kao Soap Co., htd.), 0O3 part by weight of calcium silicate powders as nucleators and 27 parts by weight of dichlorodifluoromethane as volatile blowing agent are kneaded with said mixed resin in a 30 mm single screw extruder equipped with an orifice with diameter of 5 mm and heated at 220C. While adjusting the resin temperature in the orifice at 122C, extrusion expansion is conducted to obtain expanded product having excellent characte~istics such as closed cel1ular characteristic of 0.005 g/cm3, density of .

:

lllB9~0 .
., 23 Kg/m3, compressive strength coefficient of 2.01 x 10 2 and maximum expansion shrinkage of 0.2 %.
Example 42 Example 41 is repeated except that the base resin . 5 of high density polyethylene is replaced by isotactic poly-propylene (Chisso Pol~pro 1011, trade mark, produced by Chisso . .
Corporation) and the resin temperature in the orifice is adjusted at 135C. The expanded product obtained is found to have excellent characteristics such as closed cellular characteristic. Of 0.008 g/cm3, density of 21 Kg/m3, compressive strength coefficient of 2.10 x 10 2 and maximum expansion shrinkage of 0.1 ~.

- 49 ~

.
.

Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Expandable olefin polymer compositions utilizing volatile organic blowing agents having an atmospheric boiling point not higher than the melting point of the olefin polymer employed, comprising an olefin polymer and at least one compound selected from the group consisting of the compounds represented by the formulas (I), (II) and (III) as set forth below contained in said polymer in an amount of 0.1 to 10 percent by weight based on the weight of said polymer:

(I) wherein R1 is an alkyl group having 10 to 24 carbon atoms, X and X' each hydrogen atom, an alkyl group having 1 to 24 carbon atoms which may be substituted or a substituent containing a group of the formula -(R4O)m- wherein R4 is an alkylene group having 1 to 5 carbon atoms and m an integer of 1 to 10;

(II) 28,022-F

wherein R2 is an alkyl group having 9 to 23 carbon atoms, Y and Y' each hydrogen atom, an alkyl having 1 to 24 carbon atoms, an acyl having 10 to 24 carbon atoms or a substituent containing a group of the formula -(R4O)m-wherein R4 is an alkylene group having 1 to 5 carbon atoms and m an integer of 1 to 10;

(III) wherein [R3] means plural alkyl or hydroxyalkyl groups corresponding in number to the integer ?, which may be the same or different, each having 9 to 23 carbon atoms, R4 an alkylene group having 1 to 5 carbon atoms, k an integer of 0 to 7, ? an integer of 2 to 8 and Z a ?-valent residue of ?-valent polyhydric alcohol from which ? hydroxyl groups are eliminated.

2. Composition of Claim 1 wherein the polymer is polyethylene or an ethylene-vinyl acetate copolymer.

3. An expanded article of an olefin polymer comprising an expanded product of an olefin polymer con-taining a volatile organic blowing agent and at least one compound selected from the group consisting of the compounds represented by the formulas (I), (II) and (III) as set forth in Claim l in an amount of 0.1 to 10 percent by weight based on the weight of said resin and having a closed cellular characteristic value of 0 to 0.5 g/cm3, a bulk density of 10 to 200 kg/m and a compressive strength coefficient of 2.15 x 10 3 to 2.89 x 10 2,

4. Article of Claim 3 wherein the polyolefin resin is polyethylene or an ethylene-vinyl acetate polymer.

28,022-F

5. A process for expanding an olefin polymer composition, which comprises incorporating at least one compound selected from the group consisting or the com-pounds of the formulas (I), (II) and (III) as set forth in Claim 1 in an olefin polymer in an amount of 0.1 to 10 percent by weight based on the weight of said polymer together with a volatile organic blowing agent under the condition maintained at a temperature in the range from about 15 to 300°C to form an expandable polymer composition and then allowing said polymer composition to expand utilizing the expanding force of the blowing agent contained therein.

6. Process of Claim 5 wherein the polymer is polyethylene, an ethylene-vinyl acetate copolymer or polypropylene.

7. Process of any Claims 5 to 8 wherein the polymer composition is expanded by extrusion foaming by means of an extruder.

28,022-F