CA1051150A - Foam processing aid - Google Patents

Abstract

FOAM PROCESSING AID
Abstract of the Invention The use of acrylate polymers significantly reduces surface imperfections, decreases foam density and improves the cell structure of foamed plastics which find utility in numerous areas such as in packaging, construction, flooring, upholstery and carpet materials.

Description

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1~5~1150 FOAM PROCESSING AID
Cro~s-References to ~elated A lications _ PP _ _ None ack~round of the Invention This invention relates to improved cellular plastic materials and to a proceqs for making such materlals.
The ba~ic proce~ses for making a vinyl chloride polymer "sponge" or "foam" material from a plastisol are well known. In many of such processes, the plastlsol may be expanded or foamed and then heated to ~use or sinter the expanded vln~1 chloride polymer. The formation of the cellular qtructure may be accom-plished in various ways. One method of foaming a plastiæol is a process wherein a gas is dissolved in the pla~tisol under pressure. Upon release of the pre~sure, the dissolved gas expands in the plastisolJ forming a cellular mass. The plastisol may al~o be foamed by mechanically beating or whipping alr into the plastisol. Chemical blowlng agents capable of liberating a gas below a temperature at which the plastisol gels also have been extensively employed ln foaming or expanding plastisols. The mo~t common method~ however~ is the use of blowing agent~, such as the azodlcarbonamlde typeJ to foam an already fuqed plastisol.
Although other processes for expanding plastisols are available, the above-mentioned processing techniques are the most widely uqed.
In the past~ it has been difficult to control the density and cell size Or polymer foam~, whether formed from plastisols or by the techniques o~ calendered ~heet and extrusion techniques.
Since the vl~cosities of plastisols used in the manufacture of mechanically frothed foam materials are relatively low, the cellular 3tructure of the ungelled foam tends to collapse or ::

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breakdown i the foam is allowed to stand even for a short period of time before the plastisol is gelled and fused~
Also, degeneration of the cellular structure of the foamed plastisol has been experienced when the foamed material is heated to gel and fuse the plastisol. Additionally, if the plastisol has a low melt viscosity, the cell structure degenerates in a very short time period when azodicarbonamide-type blowing agents are used. Still further, extruded foams, unless narrowly controlled, will overblow at the die face and result in a large and irregular cell structure.
In accordance with the present invention, a particu-lar class of processing aids are provided which, when incor-porated in a foam formulation, contribute to stabilizing the structure of the foamed cells, reduce surface imperfections and decrease the density of certain foams, such as vinyl dry blend foams.
The following patents have been considered in the preparation of the present application:
U.S. 2,909,493 discloses a method for making cellu-:, .
lar vinyl chloride resins which comprises adding materials to . .
the plastisol which react in the plastisol to form thickening . . .
agents. The materials which are added to the plastisol, and which react with each other to form thickening agents within the plastisol, are an aliphatic acid and a material which reacts with the acid at a temperature below the gelling tem- ~;
perature of the plastisol (e.g. sodium hydroxide) to form a fatty acid soap.
U.S. 3,338,845 describes a process for the prepara-tion of foamed materials which comprises heating an organic ~ ~
isocyanate with a secondary amine, such reaction being carried ~;

out in the presence of a polyvinyl halide and an additional

-3-51~5~ `
substance which is reactable with the isocyanate. Such reactable material is certain disclosed alcohols and `~
naphthenic acids~ ~
U.S. 3,409,580 discloses a plastisol comprising a `
polyvinyl halide, a piasticizer therefor and a small amount of an amine which acts to improve Elow characteristics and froth stability of the plastisol. In addition to the amine, a naphthenic acid or an ether alcohol may be used.
U.S. 3,454,507 discloses the preparation of foamed ;
polyvinyl chloride compositions in the presence of a pore-size controlling additive which is a copolymer of at least one unsaturated compound and one compound which is a deriva-tive of a mono- or di-protic unsaturated acid. Typical copolymers disclosed are copolymers of methacrylates and fumarates and copolymers of a long chain alkyl ester of acrylic or methacrylic acid with an acrylic or methacrylic acid ester of a polyalkylene glycol. The copolymers may also comprise other comonomers such as ethyl acrylate and the like.
A typical additive comprises the reaction product of 2-ethylhexyl acrylate, ethyl acrylate and a polyethylene glycol methacrylate. At least one of the monomers utilized to prepare the pore size controlling additive must contain at least one polyoxyalkylene residue terminated with an alkyl, aryl, aralkyl, alkaryl or acyl group.
In accordance with the present invention there is provided a class of foam processing aids which include liquid homopolymers of alkyl acrylate esters wherein the alkyl radical is linear or branched chain and contains from 1 to about 24 carbon atoms, and liquid copolymers of an alkyl acrylate ester with a dissimilar alkyl acrylate ester.

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In a preferred embodi.ment of the present invention there is provided a composition comprising a foamed plastic and from about 0.025 to about 2.0 percent, based on the weight of said plastic, of a processing aid consisting of a liquid polymer of one or more alkyl acrylate esters wherein the alkyl radical in each of said esters contains from 1 -:
to about 24 carbon atoms, said polymer having a molecular weight of from about 2,000 to about 10,000 and being a homo ;
polymer of an alkyl acrylate ester or a copolymer consisting of an alkyl acrylate ester copolymerized with a dissimilar .
alkyl acrylate ester.
In a further embodiment of the present invention .-there is provided a method of improving the processability `
and characteristics of plastic foams which comprises incor~
porating therein from about 0.025 to about 2 percent, based .
on the weight of said plastic, of a processing aid consisting of a liquid polymer of one or more alkyl acrylate esters : ~
wherein the alkyl radical in each of said esters contains .. : :
~ .
from 1 ~o about 24 carbon atoms, said polymer having a molecu~
20 lar weight of from about 2,000 to about 10,000 and being a homopolymer of an alkyl acrylate ester or a copolymer consis- .- ~
ting of an alkyl acrylate ester copolymerized with a dissimilar :
alkyl acrylate ester. ~ .
'`: ':, ., Utilization of the processing aids provided by the present invention afford improved cell structure and stabilization thereof, reduction of surface imperfections of the foamed material and the preparation of foams having decreased density. ~:
The foam processing aids provided by the present invention include liquid homopolymers of alkyl ,'' `'' -4a- .

1~5~l~5~ -acrylate esters wherein the alkyl radical is linear or branched chain and contains from 1 to about 24 carbon atoms, and liquid copolymers of an alkyl acrylate ester with a dissimilar alkyl acrylate ester. Preferred alkyl acrylate homopolymers are those wherein the alkyl radical contains from about 3 to about 12 carbon atoms, e.g. polypropyl acrylate, polybutyl acrylate, polyhexyl acrylate, poly-octyl acrylate, polydecyl acrylate, polydodecyl acrylate.
The copolymers consist o-f ~1) from about 5 to about 95% by weight of an alkyl acrylate ester wherein the alkyl constituent contains from about 1 to about 12 carbon atoms and ~2) from about 95 to about 5% by weight of a dissimilar alkyl acrylate ester wherein the alkyl constituent contains from about 3 to about 24 carbon atoms. In a preferred embodiment of the invention, the processing aid consists of a copolymer of (1) from about 5 to about 95% by weight of an alkyl acrylate ester wherein the alkyl constituent contains from about 1 to about 12 carbon atoms and (2) from about -95 to about 5~ by weight of a dissimilar alkyl acrylate ester wherein the alkyl constituent contains from about 3 to about 18 carbon atoms. In a yet more preferred embodi-ment of the invention, the useful modifying copolymers con-sist of (1) from about 2~ to about 50% by weight of an alkyl acrylate ester wherein the alkyl constituent contains from about 2 to about S carbon atoms and (2) from about 80 to about 50% by weight of a dissimilar alkyl acrylate ester wherein the alkyl constituent contains from about 6 to about 12 carbon atoms.
The processing aids utilized herein are characterized , ~S~LS~ .
by their liquidity, ranging from free-flowing to viscous at room temperature or slight~.y above. The polymers have an average molecular weight of from about 2000 to about 1OJOOOJ a pref'erred molecular we~ght range being from about ~OGO to about 6000.
particularly useful molecular weight range is from about 3500 t~
about 5000.
Tough or rubbery acrylic materia].s such as those fre-quently used AS extenders or impact value modj.fiers are unsuitable for use as processing aids in accordance with the purposes of ~:
this invention. . .
Typical acrylic polymeric materials whlch are util.i~e~
as processin~ aids in accordance with the present invention i.nclude the following: ~ :
Copolymer of 50 parts of 2-ethylhexyl acrylate and :
50 parts of octadecyl acrylate (molecular weight - 4,040) Homopolymer of octadecyl acrylate (molecular weight =
2,470) Homopolymer of lauryl acrylate (molecular weight = 1,980) ..
Copolymer of 30 parts of ethyl acrylate and 70 parts of 2-ethylhexyl acrylate (molecular weight = 4,690) Copolymer of 30 parts of ethyl acrylate and 70 parts of 2-ethylhexyl acrylate (mo~.ecular weight = 3,600) ;
Homopolymer of propyl acrylate Homopolymer of butyl acrylate .. :
Homopolymer of heptyl acrylate Homopolymer of nonyl acrylate :-Homopolymer of decyl acrylate Homopolymer of tetradecyl acrylate Homopolymer of hexadecyl acrylate :

Copolymer of 85 parts of hexyl acrylate and 15 parts of propyl acrylate ... ..... . .. . .. . .

43~4104A

~51~50 Copolymer of 25 parts of heptyl acrylate a~d 75 parts of nonyl acrylate Copolymer of 35 parts of amyl acrylate and 65 parts of dodecyl acrylate Copolymer of 45 parts of decyl acrylate and 55 parts of heptadecyl acrylate Copolymer of 15 parts of dodecyl acrylate and 85 parts of butyl acrylate Copolymer of 75 parts of dodecyl acrylate and 25 parts of pentadecyl acrylate ~:
Copolymer of 60 parts of nonyl acrylate and 40 parts of decyl acrylate Copolymer of 45 parts o~ ethyl acrylate and 55 parts .
of dodecyl acrylate Copplymer of 40 parts of ethyl acrylate and 60 parts of 2-ethylhexyl acrylate (molecular weight = 6,760) Homopolymer o~ lauryl acrylate (molecular weight = 8,930) Copolymer of 90 parts of methyl acrylate and 10 parts of butyl acrylate (molecular weight - 10,230) Copolymer of 80 parts of butyl acrylate and 20 parts of lauryl acrylate (molecular weight = 5,410) .~ .
Copolymer of 40 parts of butyl acrylate and 60 parts o~ lauryl acrylate (molecular weight = 6,790) Homopolymer of octadecyl acrylate (molecular weight =
3,200) Copolymer of 30 parts ethyl acrylate and 70 parts of 2-ethylhexyl acrylate (molecular weight = 4,760) Copolymer of 90 parts of ethyl acrylate and 10 parts of butyl acrylate (molecular weight = 5J320) Homopolymer of lauryl acrylate (molecular weight = 7,400) l~)5~ lS~ `
Homopolymer of methyl acrylate (molecular weight =
8,920) Copolymer of 90 parts of methyl acrylate and 10 parts -of butyl acrylate (molecular weight = 2,100) Homopolymer of methyl acrylate (molecular weight =
9,730) Homopolymer of lauryl acrylate (molecular weight =
9,500) The foamed materials which are used in the composi-tions of this invention may be any foamed materials. Such foams may be utilized in various techniques such as powder casting of plasticized dry blend foams, rotational molding of vinyl foam dry blends, injection molding of vinyl foams, calen-dered vinyl foams, low density vinyl -foams formed from plasti-sols, extrusion of rigid vinyl foams, extrusion and injection -molding of polyolefin foams and similar techniques. Any plas-tic materials capable of being formed into a foam composition are useful in the compositions of the present invention. ;
The concentration of the acrylate processing aid in ~
the polymer foam will vary with the particular polymer foam ;
system being used and with the size of the polymer particles, thus indicating that a surface phenomenon occurs. Generally, the amount of processing aid which is added will be from about 0.025 to about 2 percent by weight, based on the weight of the foam. Preferably, the processing aid is added at a level of from about 0.05 to about 0.25 percent in powder coat-ing formulations, from about 0.25 to about 0.75 percent in plastisol formulations, from about 0.05 to about 0.25 percent in calendering formulations, from about 0.05 to about 0.50 percent in extrusion formulations, from about 0.05 to about 0.50 percent in injection molding formulations and .
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from about 0.10 to about 0.75 percent in rotational molding formulations.
Illustrative of foamed thermoplastic materials which may be advantageously modified in accordance with the present invention include the polyacetals, polyacrylics, chlorinated polyethers, polyfluorocarbons, nylon molding com-pounds, polyolefins, polycarbonates, vinyl polymers and co~
polymers, urethane elastomers and the like. ~-Specifically, an important class of foamed polymers which are beneficially modified with the acrylic materials of the invention are those obtained from a polymerizable monomer compound having ethylenic unsaturation.
A particularly preferred class of foamed polymers which are used consist of the polymerized vinyl and vinylidene compounds, i.e., those having the CH2 = C ~ radical. Compounds having such a radical are, for example, the solid polymeric alkenes, such as polyethylene, polypropylene, polyisobutylene or ethylene/propylene copolymers; polymerized acrylyl and alkacrylyl compounds such as acrylic, fluoroacrylic and meth-acrylic acids, anhydrides, esters, nitriles and amides, for example, acrylonitrile, ethyl or butyl acrylate, methyl or ethyl methacrylate, methoxymethyl or 2-(2-butoxyethoxy)ethyl methacrylate, 2-(cyanoethoxy) ethyl 3-(3-cyanopropoxy) propyl acrylate or methacrylate, 2-(diethylamino)ethyl or 2-chloro-ethyl acrylate or methacrylate, acrylic anhydride or methacry-lic anhydride; methacrylamide or chloroacrylamide; ethyl or butyl chloroacrylate; the olefinic aldehydes such as acrolein, methacrolein and their acetals, the vinyl and vinylidene halides such as vinyl chloride, vinyl fluoride, vinylidene fluoride and l-chloro-l-fluoroethylene; polyvinyl ;
alcohol; the vinyl carboxylates such as vinyl acetate, "

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viny~ chloroacetate, vinyl propionate, and vinyl 2-ethylhexa-noate; the N-vinyl imides such as N-vinyl phthalimide and N-vinyl succinamide; the N-vinyl lactams such as N-vinyl capro-lactam and N-vinyl butyrolactam; vinyl aromatic hydrocarbon :
compounds such as styrene, alphamethylstyrene, 2,4-dichloro-styrene, alpha- or beta-vinylnaphthalene, divinyl benzene an~ ~.
vinyl fluorene; the vinyl ethers such as ethyl vi.nyl ether or isobutyl vinyl ether; vinyl-substituted heterocyclic compounds :.
such as vinyl pyridine, vinyl pyrrolidone, vinylfuran or vi.nyl-thiophene; the vinyl or viny}idene ketones such as methyl vinyl ketone or isopropenyl ethyl ketone, vinylidene cyanide. Foams of homopolymers of the above compounds or copolymers and ter-polymer.s thereof are beneficially used in the compositions of the present i.nvention. Examples of such copolymers or terpolymers ..
are those obtained by polymerization of the following monomer mixtures; vinyl chloride/vinyl acetate, ethylene/vinyl chloride/
vinyl acetate, acrylonitrile/vinyl pyridine, styrene/methyl methacrylate, styrene/N-vinyl pyrrolidone, cyclohexyl metha-crylate/vinyl chloroacetate, acrylonitrile/vinylidene cyanide, m~thyl methacrylate/vinyl acet~te, ethyl acrylate/methacrylamide/
ethyl chloroacrylateJ vinyl chloride/vinylidene chloride/vinyl .
acetate. : .
Other foamed polymers of compounds having the ethylenic group, ~ C = C \ , are homopolymers, copolymers and terpolymers - ...
of alpha-, beta-olefinic dicarboxylic acids and derivatives thereof of such as the anhydrides, esters, amides, nitriles and imides, f`or example~ methylg butyl, 2-ethylhexyl or dodecyl fuma-rate or maleate; maleic, chloromaleic, citraconic or itaconic .:
anhydride; fumaronitrile, dichlorofumaronitrile or citracononitrile;
fumaride, maleamide or N-phenyl maleamide. Examples of parti -10- ~ .

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cularly useful polymers and terpolymers prepared from the alpha-, beta-olefinic dicarboxylic compounds are the copolymers of maleic anhydride and a vinyl compound such as ethylene, propylene, iso- :.
butylene, styrene, alpha ~ethylstyrene, vl.nyl acetate, vinyl propionate, methyl isopropenyl ketone, isobutyl vinyl ether, the copolymers o~ dialkyl fumarate such as ethyl or butyl fumarate and vinyl compounds such as styrene, vinyl acetate, vi.nylidene chloride, ethyl methacrylate, ac.rylonitrile and the li.kc.
The compounds Or the invention act as processing ai.ds for the foamed polymers and copolymers of unsaturated, cyclic esters of carbonic acid, ~or example, homopolymeric vinylene carbonate or the copolymers of v~.nylene carbonate with ethylenic ~-compounds such as ethylene, vinyl chloride, vinyl acetate, 1,3-butadiene, acrylonitrile, methacrvlonitrile, or the esters of methacrylic or acrylic acid.
The compoun~s of the invention are also used as pro-`` cessing aids for foams of polyarylcarbonate polymers such as thelinear polyarylcarbonates formed from diphenols or dihydroxy aromatic compounds including single and fused-r~ng nucleii with 2G two hydroxy groups as well as monohydroxy-substituted aromatic residues joined in pai.rs by various connecting linkages. Examples of the foregoing include dihydroxy benzenes, naph~a.lenes and the like, the dihydroxydiphenyl ethers, sulfones, alkanes, ketones and the like.
The compounds of the invention also act as processing aids for foamed polymers, copolymers or terpolymers of poly-merizable compounds having a plurali.ty of double bonds~ for ex-ample, rubbery~ con~ugated diene polymerizates such as homopoly-merized 3-butadiene, 2-chlorobutadiene or isoprene and linear copolymers or terpolymers such as butadiene/acrylonitrile, iso-.... ..

43-~lO~A

~OS~S~ ' ' butylene/butadiene, butadiene/styrene; esters of saturated di-or poly-hydroxy compounds with olefinic carboxylic acids such as ethylene glycol dimethacrylate, triethylene glycol dicrotonate or glyceryl triacrylate; esters o~ olefinic alcohols with dicar-boxylic acids or with olefinic monocarboxylic acids such as diallyl adipate, divinyl succinateJ diallyl fumarate, allyl meth-acrylate or crotyl acrylate and other diethylenically unsaturated compounds ~uch as diallyl carbonate, divinyl ether or divinyl-benzene, as well as the crosslinked polymeric materials such as ~0 methyl methacrylate/diallyl methacrylate copolymer or butadiene/
styrene/divinyl benzene terpolymer.
The compounds of the present invention are well suited as processing aids for foamed resin compositions o~ the polyester type, for example, the linear polyesters which are obtained by the reaction of one or more polyhydric alcohols with one or ~ore alpha, beta-unsaturated polycarboxylic acids alone or in combi-nation with one or more saturated polycarboxylic acid compounds, or the crosslinked polyester resins which are obtalned by reacting a linear polyester with a compound containing a CH2 = C group. ~ :
The compounds o~ the present invention are processing aids for foamed epoxy resins. Such resins are condensation products formed by the reaction of a polyhydroxy compound and epichlorohydrin, which condensation products are subsequently cured by the addition of crosslinking agents. The hydroxy com~
pounds may be, ~or exampleJ ethylene glycol, 4,4l-isopropyli-denediphenol and similar materials. The crosslinking agent employed in the curing step may be a dicarboxylic compound such as phthalic anhydride or adipic acid, but is more generally a polyamine such as ethylene diamine, paraphenylamine diamine or diethylene triamine.

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Foamed polyurethanes are a class of polymer materials which are used in accordance with the present invention. The polyurethanes, like the above-mentioned polyesters, are materials which are employed i.n structural applications, ~or example, as insulating foams. Essentially, the polyurethanes are condensati.on products of a diis~cyanate and a compound having a molecular weight of at l.east 500 and preferably about 1500-500C and at least two reacti.ve hydrogen ions. The use~ul active-hydrogen containing compounds may be polyesters prepared from polycarboxylic acids and polyhydric alcohols, polyhydric polyalkylene ethers having at least two hydroxy groups, polythioether glycols, polyester-amides and similar materials.
The polyesters or polyester amides used for the pro-ducti.on of the polyurethane may be branched and/or linear, for example, the esters of adipic, sebasic, 6-aminocaproi.c, phthalic, isophthalic, terephthalic, oxalic, malonic, succinic, maleic, cyc].ohexane-1,2-dicarboxylic, cyclohexane-1,4-dicarboxylic, polyacrylic naphthalene-1,2-dicarkoxylic, fumaric or itaconic ~:
acids with po].yalcoho].s such as ethylene glycol, diethylene glycol, pentaglycol, gl.ycerol, sorbitol, triethanolamine and/or amino alcohols such as ethanolamine, 3-aminopropanol, and with mixtures of the above polyalcohols and amines.
The alkylene glycols and polyoxyalkylene or polythio-alkylene glycols used in the production of polyurethanes may be ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polythioethylene glycol, dipropylene glycol and the like.
Generally~ any of the polyesters, polyisocyanate-modified polyesters, polyester amides, polyisocyanate-modified polyester~
amides, alkylene glycols, polyisocyanate-modified alkylene glycols, ~S~L15~ ~
polyoxyalkylene glycols having three reactive hydrogen atoms, :
three reactive carboxylic and/or especially hydroxyl groups rnay be employed in the proAuction o~ polyurethanes. Moreover, any organic compound containing at least two radica~s selected from the group consisting of hydroxy and carboxy grouI)s may be employed.
The organic polyisocyanates useful for the production of polyurethanes include ethylene dilsocyanate, ethyl.idene dlisocyanate~ propylene-1,2 di.isocyanate, m-phenylene diisocyanate, 2,4-tolylene diisocyanate, triphenylmethane triisocyanate, or polyisocyanates in blocked or inactive form such as the bis-phenyl ~:
carbamates of tolylene diisocyanate and the like.
The compounds of the present invention are also ~Ise~ul as processing aids for fo~med linear polymers obta-Lned by the self-condensation of bifunctional compounds, for example, the polyethers which are derived by the self-condensation of dihy~ric alcohols such as ethylene glycol, propylene glycol or hexamethy- :~
lene glycol; the polyesters which are obtained by the self-con-densation of hydroxy acids such as lactic acid or 4 hydroxybutyri.c acid; the polyamides which are prepared by the self-condensati.on of aminocarboxyli.c acids such as 4-aminobutyric acid; the poly-anhydrides which are formed by the self-condensation of dicarboxylic acids such as sebasic or adipic acid.
The preferred foamed synthetic polymer materials which .
are used in the compositions of the present invention are the foamed vinyl halide polymersJ rigid and flexible polyurethane foams, foamed epoxy resins, ABS and GRS foamed rubbers. The vinyl halide polymers can be simple, mixed homopolymers of vinyl chlo-ride or polyvinylidene chloride, or copoly.ners or terpolymers in which the essential po].ymeric structure of polyvinyl chloride . ,- . .

43 410~A

~51~5~ : -is interspersed at intervals with res~dues of other ethylenically unsaturated compounds copolymerizable therewith. The essential properties of the polymeric structure of polyvinyl ch~ oride is retained if not more than about 40 percent of a comonomer is copolymerized therewith. Especlally preferred copolymers include ethylene/vinyl chloride and vinyl chloride/acry~onitrile copolymers.
Especially preferred terpolymers include ethylene/vinyl chloride/
acrylonitrile, ethylene/vinyl chloride/acr~lic acid and ethylene/
vinyl chloride/acrylamide terpolymers.
Accordingly~ it is apparent that the processing aids of the present invention may be used with ~ny plastic material whether thermoplastic or thermoset in charact~r.
The polymer formulations which are used in accordance with the present invention may contain various conventional ad-ditives such as fillers~ extenders, crosslinking agents and colorants. Minor amounts of stabilizers, for example, are usually incorporated to reduce the effects of heat and ]ight.
The foamed composition may be formed from a self-blowirlg polymer or the polymer may be blown by chemical or mechnaical ~0 means or by the use of compressed gas. Fillers which are frc-quently employed to lower the cost of the finished material and to modify its properties include calcium carbonate and magnesium silicate. When fillers are employed, they are generally present in an amount of up to about 150 parts by weight of ~iller per 100 parts by weight of polymer formulation.
Where a colored or tinted composition is desired, colo-rants or color-pigments are incorporated in amounts of from about one to about five parts by weight to 100 parts by weight of polymer.
Surfactants such as silicones are normally added to ~0 foam formulations which are mechanically frothed. The surfactants reduce the surface tension of the foam and thereby increase the air or gas entrapment characteristics of the ~oam.

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The acrylate processing aids described herein and the methods of their production are well known to those skilled in the art. The polymers can be obtained ~or example, by solution polymerization of a monomer or a mixture of two monomers in an inert organic diluent while in contact with a peroxidic catalyst.
Another method for preparing the disclosed processing aids is by a mass polymerization process wherein a monomeric ingredient or mixture of monomeric ingredients is mixed with a polymeri-zation catalyst at a temperature sufficient to cause ~olymeri-zation. Emulsion polymerization procedures which entail poly-meriæing a monomer or a mixture of monomers as an emulsion in the presence of a suitable emulsifying agent are also suitable for the preparation of the processing aids of this invention.
In the emulsion polymerization procedure, which is the preferred process for preparing the acrylate resins~ polymerization of the monomer or mixture of monomers is effected in the presence of water which contains dissolved therein a suitable catalyst and an emulsion stabiliæing agent. Examples of suitable catalysts include ammonium persulfate, benzoyl peroxideJ hydrogen peroxide, sodium perborate and other water-solubles of peroxy acids. I'he peroxy compounds useful as catalysts may be present in amounts from about 0.02 to about 2.0 percent by weight of the polymerizable compounds. Illustrative of the emulsion stabilizing agents useful in this process are various wetting agents, which are in general organic compounds containing both hydrophobic and hydro-philic radicals such as sodium alkyl sulfate, sulfated aromatic ether alcohols, sodium akyl aryl sul~onates, ~atty alcohol sul-fates, sorbitan trioleate and the like. The emulsion polymerization is ordinarily carried out at a temperature in the range of ~rom ~0 65co to 95C. depending upon the nature of the polymerization system and the particular catalyst used.

1(3 S~L5~1t The invention will be more readily understood by refe-rence to the fol.Lowing examples in which parts are ~iven by wei~ht unless otherwise stated. There are, of courseJ many other forms of this invention which will become obvious to one skiLled in the art once the invention has been fully disclosed and lt w-ill accordingly be re~ognized that these examples are given for the -~
purpose o~ illustrating specific embodiments of the inventlon only and ~re not to b~ con~trued as limiting the scope of this inven~
tion in any way.
In the following examples, all proportions of mater~als are given in parts by weight.

This example lllustrates the effect on foam density of an acrylate copolymer of the i.nvention ~ethyl acry].ate/~-ethylhexyl acrylate, 30/70) in flame retarded PVC dry blend ~oams.
The ~llowing resi.n formulations are prepared:
Batch I,~,redlent =~
Polyvinyl chloride resin 100 ~OG 100 2 ' 5 5 5 Stab~lizer 3 3 Blow~ng agent 4 4 4 Filler 20 20 20 s Acrylate ~opolymer ---- 0.1 0.1 .. .. .
Santicizer 711, a mixed phthalate prepared from a mixture of C~ C~, Cll alcohols and phthalic anhydride. Presently availab:L~ from Monsanto Company.
~ DyphosR, ~National Lead) - dibasic lead pho~phite KemporeR SD125 - azodicarbonamide (50~ active) DuramiteR - CaC03 Ethylacrylate/2-ethylhexyl acrylate copolymer (30/70) -.. . .
~1315115~
The resin batches are prepared using a spatula mix in the follo~Jing sequence.
1. Heat liquids to 50C. for 10 min.
2. Heat resin for 10 min. at 77C.
3. Add liquids to resinJ mix and dry for 10 min. -. Add CaCn~ and (Rt 77C.) Batch No. 1 ~or 30 min.; Batch No. 2 for 30 min.: Batch No. 3 for 40 min.
The foam densities (processed at 1~5C.) are as follow~:
; Batc~ No. 1: 29.5 lbs. per cu.ft.
Batch No. 2: 24.2 lbs. per cu.ft. ;
Batch No. 3: 23.7 lbs. per cu.ft.
The data indicate that addition of the acrylate co-polymer lowered the foam density (thus affording a f~am having enhanced rebound characteristics) and that overdrying ~Batch No. 3) did not adversely affect the blend. By using the acrylate copolymer, a drier blend is obtainable which is casier to work with in powder coating operations. The problem of foam deterl- ~
oration at longer drying times is t!hus overcome. :
Similar advantageous results are afforde~ when processing aids other than di~2-ethylhexyl acrylate are used, especially medium to long chain alkyl acrylates, and when other polymers are substituted for PVG, i.e. polyurethanes, rubbery foams, polycarbonates and polyester foams.

This example illustrates the effect of acrylate co-polymer concentration on cell structure and ~o~m density of flame retarded PVC dry blend foam.

-~S~lSal PVC foam samples are prepared by spatula mixing using the following procedure:
. Dry lngredients are heated for 10 min. ~t 77C. and liqui.d ingredients are heated for 10 min. at 50C. The dry in gredients are then combined with the liquid ingredients ~nd sp~tula mixed. The ingredients are further blended for 10 min.
at 11'7C. and ~lame retardant ls added. The total mlx i.~ then dried an additional 15 mln. at 77C. The dr~e~ blend~ ~re then fused for 5 min. at 185C.
The followi.ng formulations are prepared in the above-described manner:
Batch Ingredient No.l No.2 ~R~ No.4 No.5 Polyvinylchloride resin100 100 100 100 100 Plasticizer 25 25 25 25 25 Plasticizer 25 25 25 25 25 Stabi.lizer 3 ~ ~ 3 3 Blwoing Agent 4 4 4 4 4 Flame retard~nt 20 20 20 ~0 20 2Q Acrylate copolymer ____ 0.05 0.1 0.25 0-5 Density ~ cu.ft. ~ 29.0 .26.5~4.720.726.0 SanticizerR 711 (Monsanto) - mixed C7_ll phthalate esters SanticizerR 148 (Monsanto) - isodecyl diphenyl phosphate DyphosR (Na~ional Lead) - dibasic lead phosphitc KemporeR SD125 (50~ active) PhosgardRLSV (Monsanto) - propri.etary phosphoru~ Lormula-tion presently av~ilable -Ethy~ acryl~te/2-ethylhexyl acrylate (30/70) The data indicate that addition of ac~ylate copolymer ~0 lowered foam den~ity at acrylate concentrations of 0.05,.0~1 and 0.25 parts. At 0.5 part~ acrylate, the foam den6ity increa~ed.

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Accordingly, lowered foam densities are afforded at acrylate concentrations of less than 0.5 parts. Additionally, visual and microscopic observation of the prepared foams indicate that, although 0.25 parts acrylate copolymer affords the lowest density of the above batches, the cell size was equiva-lent to the cell size of the control. At ~.1 parts acrylate copolymer, the cell structure is much improved (i.e. uniform) and at a 20 percent lower density than the control.
Similar results are afforded when PVC is substituted by polyolefins, e.g. polyethylene, and epoxy foams.
While the invention has been described hereinabove with regard to certain illustrative embodiments, it is not so limited since many modifications and variations are possible in the light of the above teachings. It is understood there- ;
fore that -the invention may be practiced otherwise than as ;
specifically described without departing from the spirit and scope of the invention.

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~:.

Claims (16)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A composition comprising a foamed plastic and from about 0.025 to about 2.0 percent, based on the weight of said plastic, of a processing aid consisting of a liquid polymer in one or more alkyl acrylate esters wherein the alkyl radical in each of said esters contains from 1 to about 24 carbon atoms, said polymer having a molecular weight of from about 2,000 to about 10,000 and being a homopolymer of an alkyl acrylate ester or a copolymer consisting of an alkyl acrylate ester copolymerized with a dissimilar alkyl acrylate ester.

2. A composition comprising a foamed plastic and from about 0.025 to about 2.0 percent, based on the weight of said plastic, of a processing aid consisting of a liquid copolymer of (1) from about 5 to about 95% by weight of an alkyl acry-late ester wherein the alkyl constituent contains from about 1 to about 12 carbon atoms and (2) from about 95 to about 5% by weight of a dissimilar alkyl acrylate ester wherein the alkyl constituent contains from about 3 to about 18 carbon atoms, said copolymer having a molecular weight from about 2,000 to about 10,000.

3. A composition comprising a foamed plastic and from about 0.025 to about 2.0 percent, based on the weight of said plastic, of a processing aid consisting of a liquid copolymer of (1) from about 20 to about 50% by weight of an alkyl acry-late ester wherein the alkyl constituent contains from about 2 to about 8 carbon atoms and (2) from about 80 to about 50%
by weight of a dissimilar alkyl acrylate ester wherein the alkyl constituent contains from about 6 to about 12 carbon atoms, said copolymer having a molecular weight from about 2,000 to about 10,000.

4. The composition of claim 1, 2 or 3 wherein said plastic is thermoplastic.

5. The composition of claim 1, 2 or 3 wherein said plastic is a polymer of a vinyl halide.

6. The composition of claim 1, 2 or 3 wherein said plastic is polyvinylchloride.

7. The composition of claim 1, 2 or 3 wherein said plastic is a polymer of an olefin.

8. The composition of claim 1, 2 or 3 wherein said plastic is polyethylene.

9. The composition of claim 1, 2 or 3 wherein said plastic is a thermosetting plastic.

10. The composition of claim 1, 2 or 3 wherein said plastic is an epoxy resin.

11. The composition of claim 1, wherein said copolymer is ethyl acrylate/2-ethylhexyl acrylate.

12. The composition of claim 1, 2 or 3 wherein the processing aid is present in an amount of from about .05 to about .75%.

13. Method of improving the processability and charac-teristics of plastic foams which comprises incorporating therein from about 0.025 to about 2 percent, based on the weight of said plastic, of a processing aid consisting of a liquid polymer of one or more alkyl acrylate esters wherein the alkyl radical in each of said esters contains from 1 to about 24 carbon atoms, said polymer having a molecular weight of from about 2,000 to about 10,000 and being a homopolymer of an alkyl acrylate ester or a copolymer consisting of an alkyl acrylate ester copolymerized with a dissimilar alkyl acrylate ester.

14. Method of improving the processability and characteristics of plastic foams which comprises incorporating therein from about 0.025 to about 2 percent, based on the weight of said plastic, of a processing aid consisting of a liquid copolymer of (1) from about 5 to about 95% by weight of an alkyl acrylate ester wherein the alkyl constituent con-tains from about 1 to about 12 carbon atoms and (2) from about 95 to about 5% by weight of a dissimilar alkyl acrylate ester wherein the alkyl constituent contains from about 3 to about 18 carbon atoms, said copolymer having a molecular weight from about 2,000 to about 10,000.

15. Method of improving the processability and characteristics of plastic foams which comprises incorporating therein from about 0.025 to about 2 percent, based on the weight of said plastic, of a processing aid consisting of a liquid copolymer of (1) from about 20 to about 50% by weight of an alkyl acrylate ester wherein the alkyl constituent con-tains from about 2 to about 8 carbon atoms and (2) from about 80 to about 50% by weight of a dissimilar alkyl acrylate ester wherein the alkyl constituent contains from about 6 to about 12 carbon atoms, said copolymer having a molecular weight from about 2,000 to about 10,000.

16. A method as defined in claim 13, 14 or 15 wherein the said processing aid is present in an amount of from about .05 to about .75%.