CA1042286A - Polyethylene foam/polyurethane composites - Google Patents

Abstract

POLYETHYLENE FOAM/POLYURETHANE COMPOSITES

Abstract of the Invention Composite systems have now surprisingly been found which contain at least one layer of a polyethylene foam joined to at least one layer of a polyurethane without any adhesion-promoting intermediate layer.

Description

Mo-L503-G
LeA 15,745 ., ~O~Z8~
POI,YETIIYLENE FOAM/POLYURETHAWE COMPOSITES

Backqround of the Invention ~
Various -types of composites are already known. For example, German Offenlegungsschrift 1,704,647 describes composites consisting of foamed, thermoplastic materials in the form of strands, tapes, films, or mixtures thereof and foamed duroplastic materials, the proportion of thermoplastic foam being from 10 to 90%, by weight preferably from 50 to 75% by weight, of the composite foam mass. Polyethylene may be used ~ -; 10 as the foamed thermoplastic material, while polyurethane may be used as the foamed duroplastic material.
~ ;~
; The composite foams known from the prior art are produced by introducing the thermoplastic foam strands or tapes into a suitable vessel or container in a totally random arrangement to form a tangled ball of strands or tapes. This i.s followed by the addition of the hardenable and foamable duroplastic masses and by the known foaming process.
. '~ ', ;~ The composite foams produced in this way do not consist of a combination of various layers, instead the `
thermoplastic foam, for example, the polyethylene foam, is contained in the duroplastic foam in a random arrangement in the form of strands, tapes or films without any appreciable .. ... .
-~ adhesion.
`.! 'i Attempts have been made to combine polyethylene ~ 25 in compact form for example, in the form of polyethylene film, ~
;~ with polyurethane foam. It has been found that there is `J
.. `.:
little, if any, adhesion between the two plastics, so that -` polyethylene film may even be successfully used as a release ;~ film in the foam-molding of polyurethanes (cf. U.S. Patent ~ i;;

`~ LeA 15,745 .

1~4~36 Specifi.cation No. 3,487,Q~9~ it is desired to unite the polyethylene fi.lm with th polyure.thane foam, it is.necessary to take addi.tionaI measures. Thus, the art has reacted to the.base of adhesion promoters, such.as adhesives, in order to obtain an ade~uate le.vel of adhesion in the composite.
Th.e use of adhesion promoters is expensive because it involves ..
additional operations. Additionally, adhesion promoters are often expensive in and of themselves, so that, in each case, economic disadvantages are incurred by the use thereof.
The use of adhesion promoters further gives rise to the formation of an intermediate layer in the composite material which influences the physical properties of the composite.
l Accordingly, it is desirable to produce composites without i the use of adhesion promoters.

DESCRIPTION OF THE INVENTION

l Composite systems have now surprisingly been found I which contain a:t least one layer of a polyethylene foam ~ joined to at least one layer oE a polyurethane without any adhesion-promoting intermediate layer.

~¦ 20 Accordingly, the invention relates to composite . ' systems containing at least one layer of a cross-linked poly- .
ethylene foam bonded to at least one polyurethane layer, the polyethylene foam layer and the polyurethane layer being bonded together without adhesion promoters.
;`, ,25 The invention also relates to a process for the .l production of a composite material consisting essentially of polyethylene ~oam and polyurethane layers. The process :
comprises (a~ alpplying a polyurethane directly to a cross-linked polyethylene foam substrate, and (b~ allowing said ~ 30 polyurethane to harden.
LeA 15,745-Ca. ~ - 2 - .

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The composi,tes, of the i,nvention may be produced us;ing suhs.tantia,lly any polyethylene foam w.hich.has been produced usi.ng known ch:emical blo~in~ agents and cross-linked by irradi,ation ~ith high-energy rays, for example Co-90 rays or acceIerated electron ~eams, or by treatment with peroxides.
Processes for the production of polyethylene foams are known ; LeA 15,745 - 2a -'~ ~
~, ,, ; , . . . . ... . . ... . . . . . ` .

`

~ Z286 `~
(cf. German Offenlegungsschrift 1,~94,130 and U.S. Patent No. 3,098,831).

In these known processes, organic peroxides and -~
blowing agents are added to polyethylene and the mixture is r 5 extruded onto a sheet ~nder such conditions that no appreciable cross-linking or blowing agent decomposition takes place. ^
This sheet may then be heated in a hot-air oven initially to such an extent that the cross-linking reaction begins. As the temperature is further increased, the blowing agent -decomposes and the cross-linked polyethylene is foamed by the gas liberated thereby. ~; ;

Polvethylenes suitable for producing the foam are low-` pressure polyethylenes (d ^- 0.94 - 0.97 g/cc) and high- `
pressure polyethylenes(d - 0.91 to about 0.94 g/cc). It is generally preferable to use high-pressure polyethylenes.

Suitable peroxides include organic peroxides, such , .................................................................... .. ...
as dicumylperoxide, 2,5-dimethyl-2,5-dl-(tert.-butylperoxy)-hexane, 2,5-dimethyl-2,5-di-(tert.-butylperoxy)-hexyne, tert.-~` butyl hydroperoxide, cumyl-tert.-butylperoxide, di-tert.-butylperoxide, bis-[-tert.-butylperoxy isopropyl]-benzene and ' dicumylperoxide. Dicumylperoxide is the presently preferred peroxide. The peroxides are used in quantities of from 0.3 to 1.5% by weight based on the total mixture.

The polyolefins are preferably mixed with the cross-linking and blowing agents or their concentrates in an extruder, followed by molding at temperatures below the ` decomposition point of the peroxide. The average residence time in the extruder is about 5 minutes, so that the mixtures to be foamed do not undergo any appreciable crosslinking at ~ 30 this stage. The actual crosslinking reaction takes place at ;-`~ temperatures upwards of 160C, while the foaming reactions -;` LeA 15,745 ~3-1~ 36 take place at temperatures of from 190 to 250C.
In a preferred embodiment, the invention relates to composite systems produced using a radiation-crosslinked or peroxide-crosslinked polyethylene foam, preferably a 25 to 80~
crosslinked polyethylene foam. Polyethylene foams with a unit weight of from 20 to 200 kg/m3 are preferred.
Another necessary component of the instant invention is the polyurethane layer. The polyurethane may be cold-hardening, flexible or semi-flexible, as well as hard. In general, a reactive mixture of polyisocyanates and at least one compound containing at least two reactive hydrogen atoms or a polyurethane dispersion, solution, suspension or powder is -j applied to a layer of polyethylene foam, and left to harden in known manner.
The isocyanates suitable for use in polyurethane pro-duction in accordance with the invention include essentially any organic polyisocyanate, such as aliphatic, cycloaliphatic, araliphatic, axomatic and heterocyclic polyisocyanates of the type described for example by W. Siefgen in Justus Liebigs Annalen der Chemie, 562 pages 75 to 136. Specific examples in-clude ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, cyclobutane-1,3 diisocyanate, cyclohexane-1,3- and 1,4-diisocyanate and mixtures of these isomers l-isocyanato-3,3,5-trimethyl-5-isocyanato methyl cyclohexane (German Ausle~e-schrift 1,202,785) 2,4- and 2,6-hexahydrotolylene diisocyanate, ` and mixtures of these isomers; hexahydro-1,3 and/or 1,4-;, phenylene diisocyanate, perhydro-2,4' and/or 4,4'-diphenyl methane diisocyanate, 1,3- and 1,4-phenylene diisocyanate, 2,4-and 2,6-tolylene diisocyanate and mixtures of these isomers;
diphenyl methane 2,4'- and/or 4,4'-diisocyanate ` LeA 15,745-CA
, . . .

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1(~4;~2!36 naphthylene-1,5-diisocyanate, triphenyl methane-4,4',4"-triiso-cyanate, polyphenyl-polymethylene polyisocyanates, of the .
type obtained by condensing aniline with formaldehyde, ~-followed by phosgenation and described for exampl.e, in British Patents 874,430 and 848,671; perchlorinated aryl polyisocyanates o the type described for example, in German Auslegeschrift 1,157,601, polyisocyanates containing carbo-diimide groups of the type described in German Patent 1,092,007;
diisocyanates of the type described in U.S. Patent No.
3,492,330; polyisocyanates containing allophanate groups of ~.
the type described for example in British Patent 994,890 .
Belgium Patent 761,626 and published Dutch Patent Application 7,102,524; polyisocyanate containing isocyanurate groups of .:.the type described, for example in German Patents 1,022,789;
1,222,067 and 1,027,394 and in German Offenlegungsschrift Nos. 1,929,034 and 2,004,048 polyisocyanates contain.ing urethane groups of the type described for example in Belgian ~;
Patent 752,261 or in U.S. Patent 3,394,164; polyisocyanates .
; containing acylated urea groups according to German Patent 1,230,778; polyisocyanates containing biuret groups of the type described, for example, in German Patent 1,101,394, ~
; British Patent 889,050 and French Patent 7,017,514; polyiso- :
cyanates obtained by telomerization reactions of the type described, for example, in Belgian Patent 723,640; polyiso-cyanates containing ester groups of the type described, for example, in British Patents 965,474 and 1,072,956, U.S.
. Patent 3,567,763 and German Patent 1,231,688 and reaction `.:
;. products of the aforementioned isocyanates with acetals .
`. according to German Patent 1,072,385.

`. 30 It is also possible to use the isocyanate group-containing distillation residues accumulating in the production :~ of isocyanates on an industrial scale, optionally in solution :~
~ . .
~ Le~ 15,745 -5-

2~36 -: ~
in one or more of the aforementioned polyisocyanates. It is also possible to use mixtures of the aforementioned polyiso-cyanates.

In general, it is preferred to use readily available polyisocyanates, such as 2,4- and 2,6-tolylene diisocyanate, ~
and mixtures of these isomers ("TDI") polyphenyl-polymethylene i~ i polyisocyanates of the type obtained by condensing aniline ;;
with formaldehyde, followed by phosgenation ("crude MDL") and polyisocyanates containing carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups ("modified polyisocyanates"). ~;

Other suitable starting components suitable for polyurethane production in accordance with the invention are organic compounds with at least two isocyanate-reactive `
hydrogen atoms and molecular weight of from 400 to 10,000.
Such materials include compounds containing amino groups, thiol groups, hydroxyl groups or carboxyl groups. The poly- `
~ hydroxyl compounds are presently preferred with compounds i~ containing from 2 to 8 hydroxyl groups and molecular weights of from 800 to 10,000 preferably from 1000 to 6000 most preferred. Examples include, polyesters, polyethers, polythio-ethers, polyacetals, polycarbonates, polyester amides -1~ containing at least two, generally 2 to 8 but preferably 2 -~
to 4 hydroxyl groups, of the type generally known for the -~
production of homogeneous and cellular polyurethanes.

Suitablehydroxyl-group-containing polyesters include, reaction products of polyhydric, preferably dihydric ` and optionally, also trihydric, alcohols with polyvalent "
preferably divalent, carboxylic acids. Instead of using the ~0 free polycarboxylic acids, it is also possible to use the ~;~ corresponding polycarboxylic acid anhydrides or corresponding ' `, LeA 15,745 -6-10~221~
polycarboxylic acid esters of lower alcohols or mixtures thereof for producing the polyesters. The polycarboxylic acids may be aliphatic, cycloaliphatic, aromatic and/or heterocyclic and may optionally be substituted by, for example, halogen atoms, and/or they may be unsaturated. Examples of polycarboxyl acids of this type include succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acidr isophthalic acid, trimellitic acid, phthalic acid anhydride, tetrahydro~
phthalic acid anhydride, hexahydrophthalic acid anhydride, tetra-chlorophthalic acid anhydride, endomethylene tetrahydrophthalic acid anhydride, glutaric acid anhydride, maleic acid, maleic acid anhydride, fumaric acid, dimeric and trimeric fatty acids, such as oleic acid, optionally in admixture with monomeric fatty acids, terephthalic acid dimethyl ester, terephthalic acid-bis-glycol ester. Examples of suitable polyhydric alcohols include: ethylene glycol, 1,2- and 1,3-propylene ~-~ glycol 1,4- and 2,3-butylene glycol, 1,6-hexane diol, 1,8-; octane diol, neopentyl glycol, cyclohexane dimethanol (1,4- ;
bis-hydroxy methyl cyclohexane), 2-methyl-1,3-propane diol, glycerol, trimethylol propane, 1,2,6-hexane triol, 1,2,4-butane triol, trimethylol ethane, pentaerythritol, quinitoL mannitol ,~
; and sorbitol, methyl glycoside also diethylene glycol, tri-ethylene glycol, tetraethylene glycol, polyethylene glycols, dipropylene glycol, polypropylene glycols, dibutylene glycol and polybutylene glycols. The polyesters may also contain l some terminal carboxyl groups. It is also possible to use ¦ polyesters of lactones, for example, ~-caprolactone, or hydroxy carboxylic acids, for example, ~-hydroxy caproic acid.
The aforementioned polyvalent glycols (molecular weight 62 to 400) may also be additionally used as crosslinkers.

The polyethers containing at least two, generally two to eight, preferably two to three hydroxyl groups suitable .
~ LeA 15,745 -7-. , :

~4Z~86 -:-for use in accordance with the invention are also known and may be obtained, for example, by the polymerization of ;epoxides, such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin in the presence of BF3, or by the chemical addition of these epoxides, optionally in admixture or successively, to starter ~ --components containing reacti~e hydrogen atoms, such as alcohols or amines, for example, water, ethylene glycol, ,~
1,3- or 1,2-propylene glycol, trimethylol propane, 4,4'-di-hydroxy diphenyl propane, aniline, ammonia, ethanol amine and ethylene diamine. Sucrose polyethers of the type described, for example in German Auslegeschrift Nos. 1,176,358 and 1,064,938 may also be used in accordance with the invention.
In many cases, it is preferred to use polyethers of the type ~, 15 predominantly containing primary OH-groups (up to 90~ by weight, based on all the OH-groups present in the polyether).
Polyethers modi~ied by vinyl polymers of the type formed, for example, by polymerizing styrene and acrylonitrile in the presence of polyethers(U.S. Patent No. 3,383,351; 3,304,273;
`, 20 3,523,093 and 3,110,695 and German Patent 1,152,536) are also `
suitable, as are polybutadienes containing OH-groups.

Among the polythio ethers, reference is in j particular made to the condensation products of thio diglycol ,ii ..
.' f with itself and~or with other glycols, dicarboxylic acids, ` 25 formaldehyde, amino carboxylic acids or amino alcohols. The products are polythio mixed ethers, polythio ether esters, polythio ether ester amides, depending upon the cocomponents.

Examples of suitable polyacetals are the compounds .
`' which may be obtained from glycols, such as diethylene glycol, ~ , 30 triethylene glycol, 4,4'-dioxethoxy diphenyl dimethyl methane hexane diol, and formaldehyde. Polyacetals suitable LeA 15,745 -8-~4;~Z8~ : :
for use in accordance with the invention may also be obtained by polymerizing cyclic acetals. -;

Suitable polycarbonates containing hydroxyl groups are those which may be obtained, for example, by reacting diols, such as 1,3-propane diol, 1,4-butane diol, and/or 1,6-hexane diol, diethylene glycol, triethylene glycol or tetraethylene glycol with diaryl carbonates, for example, diphenyl carbonate or phosgene.

The polyester amides and polyamides include the predominantly llnear condensates obtained from polyvalent saturated and unsaturated carboxylic acids or their anhydrides and polyhydric, saturated and unsaturated amino alcohols, diamines, polyamines and mixtures thereof.

Polyhydroxyl compounds already containing urethane or urea groups and modi~ied natural polyols, such as castor oil, carbohydrates and starch, may also be used~ Addition products of alkylene oxides with phenol-formaldehyde resins or even with urea-formaldehyde resins may also be used in accordance with the invention.

Examples of the many types of compounds suitable for use in accordance with the invention are described for example, in High Polymers, Vol. XVI. "Polyurethanes, Chemistry and Technology", by Saunders and Frisch, Interscience Publishers, New York, London, Vol. I, 1962, pages 32 to 42 and pages 44 to 54, and Vol. II, 1964, pages 5 to 6 and 198 to 199 and also in Kunststoff-Handbuch, Vol. VII, Vieweg-Hochtlen, Carl-E~anser-Verlag, Munich 1966, for example on pages 45 to 71.
I :
In many instances, catalysts may also be used to produce the polyurethanes used herein. Suitable catalysts ;

LeA 15,745 -9-include tertiary amines, sucll as trie-thyl amine, tributyl amine, N-methyl morpholine, N-ethyl morpholine, N-coco ::
morpholine, N,N,N',N'-tetramethyl ethylene diamine, 1,4-diazabicyclo-(2,2,2)-octane, N-methyl-N'-dimethyl amino ethyl piperazine, N,N-dimethyl benzyl amine, bis-(N,N-diethyl amino . -~
ethyl)-adipate, N,N-diethyl benzyl amine, pentamethyl di- :
ethylene triamine, N,N-dimethyl cyclohexyl amine, N,N,N',N'- :
tetramethyl-1,3-butane diamine, N,N-dimethyl-~-phenyl ethyl amine, 1,2-dimethyl imidazole and 2-methyl imidazole.

Tertiary amines containing isocyanate-reactive hydrogen atoms may also be used and include triethanolamine, ~
triisopropanolamine, N-methyl-diethanolamine, N-ethyl-diethanol- .. ; .
amine, N,N-dimethyl ethanolamine and their reaction products with alkylene oxides, such as propylene oxide and/or ethylene ~ ~
oxide. `:

Other suitable catalysts include silaamines with ;.
~ .;, . .
carbon-silicon bonds of the type described in German Patent .~ " .
1,229,290. Specific examples include 2,2,4-trimethyl-2- !~' silamorpholine and 1,3-diethylaminomethyl tetramethyl disilo- ~ :
xane. .
j,, .... ~ . ~
Other suitable catalyst include nitrogen-containing ~ :
bases, such as tetraalkyl ammonium hydroxides. Alkali .-hydroxides such as sodium hydroxide, alkali phenolates, such as sodium phenolate or alkali alcoholates, such as sodium .;: :
25 methylate, and hexahydrotriazines may also be used as I catalysts.
.
Organo metallic compounds, especially organo tin :.
compounds, may also be used as catalyst. Preferred organo tin compounds are tin (II) salts of carboxylic acids, such as tin (II) acetate, tin (II) octoate, tin (II) ethyl r .... ..

"~' ~. LeA 15,745 -10- :

~04Z;~8~i ~
hexoate and tin (II) laurate~ and the dialkyl tin salts of carboxylic acids, such as dibutyl tin diacetate, dibutyl ' tin dilaurate, dibutyl tin maleate or dioctyl tin diacetate.

Further examples o~ catalysts suitable for use in accordance with the invention and details on the way in which : the catalysts work may be found in Kunststoff-Handbuch, Vol.VII, published by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich 1966, for example on pages 96 to 102.

The catalysts are generally used in a quantity of ..
from about 0.001 to 10% by weight, based on the quantity of ~:~
the organic compounds containing at least two isocyanate-! . reactive hydrogen atoms with a molecular weight of from 400 to 10,000.

l It is also possible to use reaction retarders such , 15 as acid-reacting substances, e.g. hydrochloric acid or organic acid halides in producing the polyurethane component. Pigments or dyes and flameproofing agents such as tris-chloroethyl phosphate or ammonium phosphate and polyphosphate, stabilizers .
against ageing and weathering, plasticizers, fungistatic and bacteriostatic compounds and fillers, such as barium sulphate, kieselguhr, carbon black or whiting, may also be used.
i'.
" Other examples of reaction retarders, stabilizers, flameproofing agents, plasticizers, dyes, fillers and fungi-static and bacteriostatic compounds optionally used in accordance with the invention, and also details on the way : additives of this type are used and the way in which they work, may be found in Kunststoff-Handbuch, Vol. VI, published by Vieweg-Hochtlen, Carl-Hanser-Verlag, Munich 1966, for example, on pages 103 to 113.
-, :: 30 The reaction components ofthe polyurethane can be : LeA 15,745 -11-. ~,, , ,,,, , . . .
: , . ~ . , , ~ ,, , , ~ .
:- . , : .: ., - ,: , ~ . . . .
~, . .

~O~Z2~6 ~ :
reacted by the one-stage process, by the prepolymer process or by the semi-prepolymer process. In many cases machines, of the type described in ~S. Patent No. 2,764,565 are used.
Particulars of processing machines which may also be used in accordance with the invention may be found in Kunststoff Handbuch, Vol. VI, published by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich 1966, for example on pages 121-205.
.
According to the instant invention, polyurethane dispersions may also be applied to the polyethylene foam.
Suitable dispersions include dispersions both of cationic and of anionic polyurethanes.
..',~
Cationic polyurethanes suitable for use in accordance with the invention are obtained, for example, ; in accordance with German Auslegeschrift No. 1,270,276. As 15 disclosed therein, at least one component with one or more basic tertiary nitrogen atoms is used in the synthesis of the polyurethane and the basic tertiary nitrogen atoms in the polyurethane are reacted with alkylating agents or organic or inorganic acids. In principle, the basic nitrogen atoms may , 20 be sikuated anywhere in the polyurethane macromolecule.
.~ i Conversely, it is also possible to react polyure-thanes containing reactive halogen atoms capable of quarter-nization with tertiary amines~ Cationic polyurethanes may also be obtained by chain-extending quarternization, for example, by producing dihalogen urethanes from relatively high molecular weight diols and isocyanates containing reactive halogen atoms or diisocyanates and halogen alcohols and reacting the dihalogen urethanes thus produced with `;
ditertiary amines. Conversely, diamino urethanes may be ~30 produced from compounds containing two isocyanate groups -~
and tertiary amino alcohols, and subsequently reacted with ; LeA 15,745 -12-, , ,~ , , . ~ , . , :, . . :. : ~ .. . .

~V~Z136 reactive dihalogen compounds. The cationic polyurethane mass may, of course, also be produced from a cationic salt-like starting component, for example a quarternized basic polyether or an isocyanate containing quaternary nitrogen. These production methods are described, for example, in German Auslegeschrift No. 1,184,946; 1,178,586 and 1,179,363, in U.S. Patent No. 3,686,108 and in Belgian Patents 653,223;
658,026 and 636,799. The starting materials suitable for synthesizing the salt-like polyurethanes are known in the ; 11) art and are also mentioned in these publications.

A suitable cationic dispersion in a mixture of dimethyl formamide and water may be prepared for example as follows: A polyester with terminal hydroxyl groups is reacted with a diisocyanate to form a prepolymer, diluted with dimethyl formamide and is then further reacted with N-methyl diethanolamine. This is followed by quarternization with dichlorodurol (1,4-bis- tchloromethyl)-benzene) and by the addition of phosphoric acid and a mixture of equal quantities of dimethyl formamide and water.

2- Anionic polyurethane(urea) dispersions may be prepared by known processes. Suitable anionic polyurethanes are described for example, in German Auslegeschrift No. 1,237,306 in German Offenlegungsschrift Nos. 1,570,556; 1,720,639 and 1,495,847. In addition to the usual glycols and diamines, compounds containing either anionic groups or groups which may subsequently be converted into anionic groups, are used, as in the production oE cationic dispersions. Compounds of this type include, hydroxy and mercapto acids, such as glyceric acid, citric acid or uric acid, amino acids, such as diamino naphthoic acid, hydroxy and carboxy sulphonic acids, such as 2-hydroxy ethanesulphonic acid or p-sulpho-benzoic acid; amino sulphonic acids, such as hydrazine di-LeA 15,745 -13-1~4~
sulphonic acid, 2,4-diamino toluene-5-sulphonic acid or amino ethyl amino ethane sulphonic acid; derivatives of phosphinic acid, phosphonous acids, phosphonic acids, and phosphoric acids, esters of phosphorous and phosphoric acid and their thioana-logues for example phosphoric acid-bis-propylene glycol ester;
and hydrazine dicarboxylic acids and diaminoamidocarboxylic acids or salts thereof, such as sodium phthalate-bis-N,N-(~-aminopropyl) amide.
The anionic dispersions may also be prepared from polyurethanes containing free hydroxyl and/or amino groups by reacting th~m with aliphatic and/or aromatic aldehydes and, simultaneously or subsequently, with a metal sulphite, metal hydrogen sulphite, metal amino carboxylate or metal amino sulphate. Finally, another possibility is to react polyure~
thanes containing free hydroxyl and/or amino groups with cyclic compounds containing from three to seven ring members and salt-like groups or groups capable of salt formation after ring opening (c~ German Auslegeschrift 1,237,306)~ Compounds of this type include sultones, such as 1,3-propane sultone~ 1~4 butane sultone or 1,8~naphth sultone, lactones, such as propiolactone or y~butyrolactone and dicarboxylic acid anhy-drides, such as succinic acid anhydride.
Cationic or anionic polyurethanes suitable for use in the process according to the in~ention may also be synthe~
~. 25 sized by formaldehyde polycondensation in accordance with '. German Offenlegungsschrift 1,77Q,068. In this process~
relati~ely high molecular weight polyisocyanates are reacted with an excess of compounds containing terminal methylol groups .`, (for example, amine~fo.rmaldehyde resins or phenol~formaldehyde :`, 30 resins~, The reaction product containing methylol groups is then dispersed in ~ater. Finally, . ~ .
~14-LeA 15,745-CA

zzæ6 ,~ -, the resulting dispersion i5 crosslinked by heat treatment to form methylene bridges.

It is also possible in the process according to the invention to use dispersions of the type described in German Offenlegungsschrift Nos. l,953,3~5; l,953,348 and 1,953,349.
The dispersions disclosed therein are aqueous dispersions of ionic emulsion polymers obtained by the radical emulsion polymerization of olefinically unsaturated monomers in the presence of cationic or anionic oligo urethanes or poly-urethanes.

Dispersions of cationic and anionic polyurethanes which actually contain chemical cross links when they are used, are also suitable.

It is also possible to apply polyurethane suspensions lS to the polyethylene foam. Crosslinked polyurethane particles o~ this type may be produced by a variety of different methods known in principle to one skilled in the art. In general, crosslinked polyurethane particles may be prepared in the form of a suspension in suitable organic solvents, or in waker, or even in the absence of a liquid medium. In addition, it is possible to obtain crosslinked particles by suitably selecting the reaction components, or by initially preparing predominantly linear thermoplastic particles which are sub-sequently crosslinked.

There are a number of processes for producing finely divided polyurethanes in aqueous media. For example, a solution of a polyurethane in a water-immiscible solvent may be dispersed in water using an emulsifier and the organic solvent removed by distillation. In one preferred method, ionically and/or hydrophilically modified polyurethanes are mixed with water in the presence or absence of a solvent.
;'` ..
LeA 15,745 -15- ~

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In one preferred modification of this process, polyurethane prepolymers with terminal isocyanate or methylol groups are used, the reaction being carried out in highly concentrated solutions or even in the complete absence of solvents. The coarse emulsions initially formed are converted by reaction of the isocyanate groups with water or diamines or polyamines dissolved in the aqueous phase into high molecular weight polyurethane urea suspensions, accompanied by chain extension ~-and crosslinking. The chain extension of prepolymers con- -taining methylol groups may be obtained, for example, by heating or by reducing the pH-value.
~, -".
Suitable suspensions may also be prepared by .-: ,:
spraying high molecular weight polyurethanes or their reactive ~

precursors into water or organic non-solvents. ;
, In principle, any of the methods which have been ;~-proposed for the production of polyurethane dispersions or latices may also be used for preparing polyurethane suspen-sions, providing measures are taken to ensure that these ;
suspensions do not coalesce through sedimentation or under the effe~t of shear orces. This means that a primary sus-pension which is not yet of adequately high molecular weight -, .
has to be kept in motion until the dispersed particles have ` become tack-free. To cross-link the dispersed particles, it is possible either (1) to start with more than bifunctional ;;
starting materials, i.e. to use, for example, branched poly-esters or polyethers, triisocyanates or triols in the synthesis of the polyurethane, or (2) to react an initially linear NCO-prepolymer, i.e. an NCO-prepolymer prepared from bifunctional components, with higher functional amines to form a cross-linked polyurethane urea. However, crosslinked particles mayalso be synthesized from purely bifunctional components by working under conditions which promote branching, for example, LeA 15,745 -16-~42Z86 by adding catalysts which promote isocyanate trimerization or the formation of allophanate or biuret structures. In the presence of water and/or diamines, the use of more than equivalent quantities of isocyanate relative to the hydroxyl or amine compounds present is sufficient to produce cross-linking. Linear high molecular weight polyurethanes may also be subsequently crosslinked in the form of a suspension in a liquid medium or even in powder form, for example, by treat-` ment with polyisocyanates or formaldehyde or formaldehyde donors. Products containing basic groups may be crosslinkedfor example, with polyfunctional quarternizing agents or acids, while products containing acid groups may be crosslinked with metal oxides or polyamines. Polyurethanes containing unsat-urated double bonds may be crosslinked, for example, with known radical formers, or sulphur, polymercaptans and other, at least bifunctional, agents capable of reacting with double bonds.
.' The production of crosslinked polyurethane paxticles in the absence of solvents may be carried out by pulverizing polyurethane elastomers, for example, in an impact pulverizer.
It is particularly favorable to pulverize the elastomer immediately after it has been produced at which time, although tack-free, it has not yet completely reacted so that dispersion may be obtained without excessive energy consumption.

A detailed description of the production of cross-linked ionic polyurethane suspensions may be found, for ex-ample, in United States Patent 3,479,310, Canadian Patent 837,174, British Patent 1,158,088, United States Patents ' 3,714,095 and 3,622,S27, British Patent 1,175,339 and United States Patent 3,756,992.

The composite systems according to the invention may also be produced by applying a polyurethane powder to the poly-LeA 15,745 -17-z~
ethylene foams. Polyurethane powders with melting points or ranges of from 110 to 250C, preferably from 110 to 190C, .. . ... . .. ..
are particularly suitable for coating and lining the poly-ethylene foams. In addition, the trend of the intrinsic melt index (IMI) curv~s should resemble the upwardly sloping arm of a parabola so that the IMI-value changes from 2 g. per -~
10 minutes to 50 g. per 10 minutes within a temperature range from 5 to 50~C, preferably from 10 to 40C.

In addition, polyurethane(ureas) suitable for coat- -ing should have an ionic group content of 1 to 15 milliequiva-lents per 100 g., and a volume resistance of 101 to 1014 ,: :
ohm.cm. ~
~ .
According to the invention, the polyurethane(urea) ~-;
` powders which have:
(1) a smooth, spherical surface;
(2) an average diameter of from 5 to 200~

(3) an ionic group content of from 1 to 15 milliequiva- ;
lents per 100 g.; and

(4) a volume resistance of 101 to 1014 ohm.cm; and in which

(5) the trend of the respective IMI~curves at temperatures in the range from 110 to 250C represents the upwardly sloping arm of a parabola, the IMI-value changing from 2 g. per 10 minutes to 50 g. per 10 minutes with-in a temperature range from 5 to 50C;
are applied dry to the polyethylene foam, subsequently sintered -l and/or melted by the action of heat, optionally followed by j calendering.
., .
The polyurethane(urea) powders useable in accordance with the invention may be obtained by reacting NCO prepolymers containing ionic groups with primary and/or secondary diamines .. ' .
~ LeA 15,745 -18- ~;

1al4~6 (containing aliphatic amino groups) and/or dicarboxylic acid-bis-hydrazides in the presence of water. The NH:NCO-ratio in the chain-extending reaction is preferably from 0.1 to 0.95 and, most preferably from 0.25 to 0.85. The ionic group ! 5 content of the NCO prepolymers should be such that the end-! products show the required ionic group content of from 1 to 15 milliequivalents, preferably 2 to 10 milliequivalents, per 100 g.
It is preferred initially to prepare a solution of the prepolymer containing both isocyanate groups and also ionic groups in oxganic solvents, to combine this solution with an aqueous solution of the chain extender and finally to remove ! the organic solvent, preferably by distillation~ In this way, the powders used in accordance with the invention are obtained in the form of a sedimenting, aqueous dispersion.
One particular advantage of this embodiment is that it is not essential to use high~speed stirrers. The NCO-prepolymer may be combined with the chain extender simply by stirring the two components together at low speeds.
The aforementioned prepolymers containing both free isocyanate groups and also ionic groups, are known compounds in the production of emulsifier-free polyurethane dispersions.
It is preferred to use NCO-prepolymers of the type which have an average molecular weight of from 300 to 25,000, more ', 25 especially from 800 to 15,000 and particularly from 20Q~ to 7000, 'he properties of the polyurethane foam powders ob=
' l tained in this way may be specifically varied within wide limits by suitable measures. This applies above all to the `~ 30 hardness and size o~ the particles~
,1 The first possibility of influenciny the property spectrum lies in the synthesis of the isocyanate~group-con-` LeA 15,745-CA

z~ :
tainin~ ionic preadduct~ Synthesis is carried out by known methods (Belg~an Patent Specification 653,223 and 730,543) using the starting materials mentioned in those patent speci-fications. In addition to the compounds mentioned therein, however, it is also possi~le to use as relatively high molecular weight substances containing reactive hydrogen atoms compounds containing amino groups of the type described in French Patent Nos. 1,361,810 and 1~300,981, in German Auslegeschrift No.
1,122,254 and United States Patent 2,888,439.
The size of the particles is essentially determined by the ionic groups content of the preadduct, while their hard-ness is predominantly determined by the chemical nature of the polyisocyanates and compounds containing reactive hydrogen , atoms used in the production of the NCO~prepolymers~ If these compounds axe c~nfined to those with low molecular weiyhts of up to about 500, relatively hard polyurethanes are obtained, whereas in cases where compounds with reIatively hi~h moleculax weights of up to about 10,000 are used, softer products are obtained, Since preadduat formation is caxried out with relatively large excesses of isocyanate (the molar xatio o~
the NC~-~roups to the reactive hydrogen atoms is best between 4:1 and 1.1:1~ preferably between 2;1 and 1~4:1~ In other words, since the molecular weights of the pxepolymers do not become Very hi~h, there is no need for strict linearity in the l .
I 25 structure of the chain~ However, the powders are preferably ;I prepared from linear NCO~prepolymers with two terminal ali~

;~ phatic isocyanate ~roups~

~ To this end, a solution of the prepolymer is 'l preferably reacted with an aqueous solution or dispexsion of the chain extender~ In exceptional cases, the chain extender , may also be added during dispersion in solution in an or~anic :~ solvent~ Basically, the polyurethane powders used in ac-., LeA 15,745-CA

~042~86;
cordance with the invention may be produced by the processes described in Belgian Patent Nos. 653,223 and 730,543 for producing emulsifier-~ree polyurethane dispersions.

Suitable chain extenders are, in particular, primary and/or secondary diamines containing aliphatic amino groups, and dicarboxylic acid-bis-hydrazides. (So far as chain ex-tenders of the second kind are concerned, it may be assumed that the amino groups in the 3-position to the carbonyl groups react primarily with the NCO-prepolymer so that the dicarboxylic acid-bis-hydrazides may be regarded, in broad terms, as bifunc-tional chain extenders). Suitable diamines are, in particular, those with a molecular weight below 250, such as ethylene diamine, 1,2-propylene diamine, N-methyl propylene diamine, ~ -butylene diamine, hexamethylene diamine, piperizine, 2-methyl piperizine, dimethyl piperizines, N,N'-dimethyl ethylene diamine, N,N'-diethyl diethylene diamine, N,N'-diisopropyl-1,2-propylene diamine, N,N'-bis-hydroxy ethyl ethylene diamine, N-hydroxy ethyl ~thylene diamine, N-hydroxy propyl ethylene `
diamine, N,N'-bis-(hydroxy propyl)-ethylene diamine, N,N'-1 20 dimethyl hexamethylene diamine, 1,3-propylene diamine, ~
bis-amino propyl sulphide, ~,~'-bis-amino propyl methyl amine, `
N,N-bis-(~-amino propyl)-aniline, N,N-bis-(~-amino propyl)-.. . ..
_-tolidine, and the like. Other suitable chain extenders , include ether diamines and ester diamines, also diamines of ~¦ 25 the type formed during the hydrogenation of cyanoethylated diols and bifunctional dihydroxy polyesters or dihydroxy polyethers.

The diamines may be used in the form of their salts, for example carbonates or acetates. Salt formation need only be partial, for example, to improve solubility. Salt forma-tion on the primary amino group results in a reduction ~n -; reactivity. -~ LeA 15,745 -21- -- ~

~2~86 Examples of suitable dicarboxylic acid--bis- -hydrazides include b:is-hydrazides of low molecular weight di-carboxylic acids with a molecular weight below 250, such as carbonic acid-bis-hydrazide, oxalic acid-bis-hydrazide, -~
succinic acid-bis-hydrazide, adipic acid-bis-hydrazide, phthalic acid-bis-hydrazide, terephthalic acid-bis-hydrazide, tetrahydrophthalic acid-bis-hydrazide and the like. sifun-ctional polyesters with terminal carboxylic acid hydrazide groups may also be used.

Solvents suitable for use in the production of `
the products employed in accordance with the invention may -be water-miscible compounds with a boiling point below ~;~ 100C, such as acetone, methyl ethyl ketone, tetrahydrofuran or acetic acid ethyl ester. Water-imMiscible solvents may also be used providing the reactants are intensively admixed by appropriate stirring. Solvents oE this type are, for example, benzene or toluene. Solvents with a boiling point above 100C such as toluene, to which reference has `
just been made, or even chlorobenzene, dimethyl formamide -or dimethyl sulphoxide, may also be used, although their ^
removal from the end-products generally involves more expense.

The polyurethane powders used in accordance with r~I the invention are preferably prepared as follows:
The ionic NCO-prepolymers are synthesized from known di-,... .
hydroxyl compounds with a molecular weight of from 500 to -5000, diisocyanates and, optionally, chain extenders, using such an excess of diisocyanate that the adduct contains ~!
from 1 to 4% by weight of Eree NCO-groups. The NCO-pre-polymer also contains 1 to 15 milliequivalents per 100 g of quarternary nitrogen or carboxylate or sulphonate groups.

. .~ . .
~ ` LeA 15,745 -22-~4Z~86 The 3Q to 90% by weight solutions o~ the ionic NCO-prepoly-mer in acetone (yiscosity at 5QC: approximately 3a to 8QQ0 cPJ are mixed with aqueous solutions of aliphatic diamines containing primary and/or secondary amino groups. The acetone is then distilled off, and the polyurethane urea powder is obtained in the ~orm of an aqueous sedimenting dispersion The end-product may be obtained in pure form by straightfor~ard filtration. Although it may be redispersed in water at any later stage, the dry powder is preferably applied by the dry knife or screen process.
During the chain-extending reaction, the aqueous solution may be added to the acetone solution or the acetone solution added to the aqueous solution, in both cases with stirring.
Mixing is preferably carried out continuously in suitable apparatus by introduciny the two solutions into a mLxing vessel, for example by means of pumps. In the most simple case, the mixing vessel is equipped with a stirrer and an overflow through which the aqueous-acetone dispersion flows into a distillation apparatus. The dispersion temperature is from 20 to 60C, preferably from 35 to 55C. The quantity of water required for dispersion, in which the diamine is dissolved, is from 0.8 to 3 times, preferably 1 to 2 times the quantity of the ionic NCO-prepolymer.

Further details as to the production of polyurethane powder of the type disclosed herein are disclosed in U. S.
Patent No. 3,868,350. `
. , .
`~ For continuous high-throughput mixing, it is ;~ preferred to use high-speed stirrers or even mixers of the type which enahle high shear forces to be applied. Suitable machines, such as screw machines, multiple-shaft screws, LeA 15,745-Ca. - 23 -,' ~
','. J~ :

~O~ZZ86 internal mixers, high-pressure or low-pressure mixing chambers with countercurrent mixing or ul-trasonic dispersers, are known to those skilled in the art. With apparatus of this type, it is preferred to use 70 to 90% solutions, although it is even possible to work in the complete absence of solvents given adequately free-flowing prepolymers.

The properties of the polyurea powders initially accumulating in the form of suspensions may be specifically influenced not only by the chemical composition of the poly- -isocyanate preadduct, but also by the dispersion conditions.
The most important factors are: the type and quantity of chain extender, the quantity of water, the type and quantity of organic solvent, the pH-value and the reaction temperatures which may be varied from about 0C up to the boiling point of the organic solvent, the reaction optionally being carried out under pressure.
!! ` :
Another important factor is the way in which the a~ueous and organic phases are mixed, i.e. whether this mixing is carried out substantially simultaneously, for example in a continuous mixer, or whether the organic phase is added to the aqueous phase or the aqueous phase to the organic phase. However, it is emphasized that, even , with simple means, it is possible to obtain useful products, for example, by allowing the aqueous phase to flow into the . .
` 25 organic phase with stirring using a normal stirrer. The , organic solvent is removed by distillation after or during ~^
mixing. The end-powder is obtained by filtration from the aqueous polyurethane dispersion formed. Again the details of these types of powders are disclosed in U.S. Patent ; 30 3,868,350.

The polyurethane powder is applied to the poly~thylene LeA 15,745 -24-22~6 foam by conventional coating techniques, such as, fixed coating systems, such as air-knife coaters; rubber blanket coaters; and primarily doctor roll coaters, and roll or reverse-roll coaters.

The coating may be colored or pigmented, if desired, in different ways. The polyurethane powders are preferably mixed before application with powder-form pigments or fillers, such as carbon black, titanium dioxide, aluminum bronze, iron or cadmium pigments.
.,.
The composite systems according to the invention , are eminently suitable for the production of travel goods, .; , "! leather substitutes, floor coverings and are also used, ~
'! :~.`
for example, in the clothing industry, or for example, in lacquered form and deep-drawn in the car industry as crashpads. j~
f ;:::
Application of the polyurethane reaction mixture '~ to the polyethylene foam, which may be used, for example, ~' in the orm of a sheet of foam, is by no means critical ~

and may be carried out in any way. It is, of course, even :
,. ,~, ~ 20 possible to use machines for this purpose. ~ ~
.: , :
' The composite systems according to the invention contain at least one layer of a polyethylene foam joined to a layer of a polyurethane. The invention also encompasses -composite systems containing several such combinations. In this connection, it is essential that the layer of polyethylene foam and the layer of polyurethane should always be joined together in the absence of adhesion promoters.

: :

, ~
, . . .
LeA 15,745 -25~

After its preparation, a polyurethane polymer (I) derived from lO0 parts by weigh~ of butane diol adipate 9.5 parts by weight of 1,4-butane diol 37.5 parts by weight of 4,4'-diphenyl methane diisocyanate is co-extruded with l~ of SiO2, pelle~ized and subsequently ground-up, under nitrogen, into a powder. Particles less than 200~ in size are separated off from the powder. Th~y are sifted, or evenly scattered, through a sieve onto a dicumylperoxide-crosslinked, azodicarbonimide-blown, con-tinously produced polyethylene ~oam (unit weight 35 kg/m3) with (a) a sliced surface and (_) an unsliced surface, and ~
~, 15 sinteredtogether in an IR-field at temperatures of from ;~ ;
170 to 175C (from 25 to 30C above the sintering range of ;~
the polyurethane polymer) to form coherent films. This procedure may be repeated several times, and it is recommended to apply no less than 50 g/m2 per article. The upper weight limit is imposed by the heat capacity of the IR-field.
Bonding was tested in accordance with DIN 53 357. During the test the polyethylene ~oam and the polyurethane layer could not be :
separated. The test was ~inished when material breakout occurred L
', in the polyethylene foam.
i 25 EXAMPLE 2 ., '~
A polyurethane prepolymer (II) derived from 50 parts by weight of ethylene-butylene-glycol ` adipate 50 parts by weight of hexanediol polycarbonate 3 13 parts by weight of 1,4-butane diol and 48 parts by weight of 4,4'-diphenyl urethane diisocyanate is dissolved to form a 25% solution in a mixture of 3 parts, Le A 15 745 - 26 - `~

by weight, of dimethyl formamide and 2 parts by weight of methyl ethyl ketone The solution is pigmented with a standard colored pigment and coated in a thickness of 60 g/m2 onto a standard separation layer, followed by drying in the usual way. The polyurethane polymer I from Example l is sifted onto this film in a layer thickness of 100 g/m2.
and sintered in the same way as described above. A dicumyl-peroxide-crosslinked, azodicarbonamide-blown, continuously manufactured polyethylene foam (unit weight 35 kg/m ) with (a) a sliced surface and`(b~ an unsliced surface, is placed on the surface of the sintered polyurethane polymer I Gentle pressure is applied and after cooling the combination of . polyurethane polymer II/polyurethane polymerI/polyethylene foam mechanically lifted off the separation layer Bondin~ is tested in accordance with DIN 53 357.
. ~ :
Material breakout occurred in the polyethylene foam ;, A polyurethane polymer III in powder form~ derived ;~
from:
482~5 g of hexane polycarbonate i 76 ~ o~ 1,6~diisocyanato hexane .1 .

- ~ ~ 2 ~ ~ S-CH2~cH2-OH

: 3.4 g of . H

., .

LeA 15,745-CA -27-`''`~
.

:

596.5 g of ace-tone 4 g of N-methyl diethanol amine 3.1 ml of dimethyl sulphate and produced according to U~S. Patent No. 3,868,350 is coated in dry form onto a dicumyl~peroxide-crosslinked, azodicarbonamide-blown, continuously~produced polyethylene ` foam (unit weight 35 kg/m3) with (a) a sliced surface and (b) an unsliced surface, and sintered in a hot air oven at 25 to 30~C above the sintering range of the polyurethane polymer to form a homogeneous film in a coating thic~ness of at least 50 g/m2.

It is surprising that, in this example, the oven temperature was approximately 200C and the residence time approximately 10 minutes.
', ', ' :, Bonding is tested in accordance with DIN 53 357.
Material breakout occurs in the polyethylene foam.

4040 g of butane diol polyadipate (OH-number 64) are reacted with 114 g of 4,4'-diphenyl methane diisocyanate ;-in 5180 g of perchloroethylen~. A prepolymer with an NCO-content of 1.85~ is formed. 40 g of 4,4'-diamino diphenyl -~
methane dissolved in 150 g of dioxane are introduced into 896 g of this prepolymer by means of a gear pump. After intensive mixing in a suitable mixing head, the reaction mixture is sprayed onto a chemically-blown, peroxide-crosslinked ` polyethylene foam. Spraying may be carried out, for example, , . .,~ . .
with a Transpol 201 Pistole (Registered Trademark).
:"~
; After coating, the composite is left for 30 minutes at 80C in a drying cabinet. -~
:' LeA 15,745 -28-sonding was tested in accordance with DIN 53 357.
Material breakout occurred in the polyethylene foam.

100 parts by weight of an ethane diol polyadipate (OH-number 56.2, acid number 0.7) were dehydrated _n vacuo at 135C and then stirred at 100C with 18 parts naphthylene ;
diisocyanate. After a few minutes, the temperature reaches 126C. The reaction mixture was degassed by brief evacuation i and was then intensively mixed with 2 parts, by weight of 1,4-butane diol. The hot reaction mixture (125C) was poured in a layer thickness of 3 mm onto a peroxide-cross- `-~
linked, chemically-blown continuously produced polyethylene foam, and the composite formed subsequently tempered for 13 hours at 110C. After cooling, the composite material shows high strength and firm bonding which was tested in aeeordanee with DIN 53 357. Material breakout oecurred in the polyethylene foam.

A reaetive mixture of:
455 parts of fatty-aeid-based polyester mixed with ~ ;
ketone resin `
90 parts of a moleeular sieve ~zeolite = a sodium aluminium silic~te) 395 parts of barium sulphate 32 parts of hydrogenated castor oil 600 parts of diacetone alcohol 60 parts of pigment (for example, mixture of titanium dioxide, iron oxide and chromium oxide) and 185-220 parts of diphenyl methane diisocyanate is applied by means of a standard compressed air spray gun to peroxide-erosslinked, ehemieally-blown, eontinuously produeed polyethylene foam. El~sticity may be influeneed by : ,. -: .:::, , .
LeA 15,745 -29- ~

~L~4~2B6 ; varying the isocyanate component. The reactive mixture takes about 12 hours to harden. ~
~; .
Bonding was tested in accordance with DIN 53 357.
Material breakout occurred in the polyethylene foam. ..

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Claims (8)

The embodiments of the invention in which exclusive property or privilege is claimed are defined as follows:

1. A composite consisting essentially of: (a) at least one layer of a crosslinked polyethylene foam, bonded to (h) at least one layer of a homogeneous polyurethane, said layers being bonded directly to each other in the absence of adhesion promoters.

2. In a process for the production of a composite material consisting essentially of polyethylene foam and polyurethane layers, the process comprising (a) applying a polyurethane directly to a cross-linked polyethylene foam substrate, and (b) allowing said polyurethane to harden.

3. The process of Claim 2, wherein said applied polyurethane is a reactive mixture of a polyisocyanate or polyisocyanates and at least one compound containing at least two reactive hydrogen atoms.

4. The process of Claim 3, wherein step (b) comprises heating the composite.

5. The process of Claim 2, wherein said applied polyurethane is selected from the group consisting of polyurethane dispersions, polyurethane solutions, polyurethane suspensions and polyurethane powders.

6. The process of Claim 5 wherein said applied polyurethane is a polyurethane powder which has (1) a melting point of from 110 to 250°C, (2) a smooth spherical surface, (3) an average diameter of from 5 to 200 microns, (4) an ionic group content of from 1 to 15 milliequivalents per 100 grams, (5) a volume resistance of 1010 to 1014 ohm.
cm; and in which (6) the trend of the respective IMI curves at temperatures in the range from 110 to 250°C represents the upwardly sloping arm of a parabola, the IMI value changing from 2 grams per 10 minutes to 50 grams per 10 minutes within a temperature range from 5 to 50°C; which polyurethane powder is applied dry to the polyethylene foam and subsequently sintered and/or melted by the action of heat.

7. The process of Claim 6 wherein the sintering or melting process is followed by calendering.

8. The process of Claim 6 wherein said polyurethane powder has a melting point of from 110 to 190°C.