DE2736685A1 - Weather-resistant polyurethane foam with compact skin, prodn. - using foaming mixt. contg. aromatic poly:isocyanate and (cyclo)aliphatic poly:isocyanate - Google Patents

Abstract

Foamed articles having a compact outer skin and a cellular core and integral density distributing across article cross-section, are prepd. by forming a reaction mixt. contg. polyisocyanates, polyhydroxyl cpds. and blowing agents, opt. mixed with further isocyanate-reacting cpds. activators and further auxiliaries, in a closed mould. Novelty comprises using polyisocyanate mixts. of polyisocyanates (I) contg. aromatically bonded NCO gps. with polisocyanates (II) contg. aliphatically or cycloaliphatically bonded NCO gps., in mol. ratio (I):(II) 95:5 to 50:50 (esp. 95:5 to 80:20). Rigid foams can be used for furniture and car-body parts, technical instruments and building units. Semirigid to soft foams can be used for safety-upholstery in cars, flexible shoe-soles and bumpers. The addn. of 5-50 (5-20) mol. % (II) to (I) prevents yellowing and improves gloss retention after weathering, yielding polyurethane foams suitable for outdoor use.

Description

Process for the production of foam moldings

The present invention relates to a new method of manufacture of weather-resistant, non-yellowing molded foams.

Foams based on polyisocyanates, e.g. polyurethane foams with a dense outer skin and a cellular core, as they are according to the method of Foaming in form (German Auslegeschriften 1 196 864 and 1 694 138 and French patent specification 1 559 325) are ideal for the series production of Light construction, e.g. for furniture, vehicle and house construction, or elastic Molded parts such as cushions, shock absorbers, shoe soles.

The polyurethane moldings are produced by the foamable Reaction mixture consisting of polyisocyanates, compounds containing at least 2 isocyanates carrying reacting hydrogen atoms and additives consists in closed, temperature-controlled molds are filled, in which it foams and - strongly compressed - stiffens.

The plastic fills the mold exactly and forms the inner surfaces of the mold exactly from.

The raw materials currently available on the market for the production of rigid polyurethane foams are based on the crosslinking of aromatic polyisocyanates with polyethers or Polyester polyols. Such moldings have a high level of mechanical value on how modulus of elasticity, heat resistance, impact strength they are used for many applications makes suitable, such as furniture parts, technical housings, window profiles and the like. A disadvantage of all of these molded parts is that they yellow due to weathering and additionally roughen the surface by chemical degradation, so that the molded parts must be provided with a protective layer of varnish for increased demands.

It is now known that polyurethanes, especially polyurethane paints, such a yellowing tendency based on aliphatic or alicyclic isocyanates do not show. The obvious thought, according to these experiences, too the production of polyurethane foams, in particular molded polyurethane foams, with integral density distribution, aliphatic or cycloaliphatic polyisocyanates to use, has so far failed due to catalysis. In the production of polyurethane foam moldings with. it is essential to conduct the catalysis in such a way that that after a short start time of the liquid reaction mixture the reaction begins and in a few seconds, in which the material foams and solidifies, completed is. This is the only way to ensure that the propellant condenses on the walls adjust the shape and evaporation of the blowing agent inside the molded part in such a way that that the typical integral density build-up of the molded part occurs. A subsequent one thermal treatment of the foam produced in the mold from the usual inert reactive systems based on polyhydroxyl compounds and aliphatic Polyisocyanates for the purpose of ending the isocyanate polyaddition reaction are not feasible way to molded bodies with compact outer skin, cellular core and integral The chemistry of the polyurethane foam moldings is different In this regard, basically differ from the chemistry of, for example, polyurethane paints, because lightfast coatings made of polyurethane paints based on aliphatic polyisocyanates and organic hydroxyl compounds are thermally aftertreated without difficulty (burned in) can be, so the inertia of the aliphatic isocyanates to compensate.

Surprisingly, it has now been found that when using Polyisocyanate mixtures, which are both polyisocyanates with aromatically bound isocyanate groups as well as polyisocyanates with aliphatically or cycloaliphatically bound isocyanate groups have weather-resistant, lightfast polyurethane foam moldings with integral density distribution and compact surface with good gloss retention already are accessible when the polyisocyanate component in the said mixtures with aliphatically or cycloaliphatically bound isocyanate groups in deficit is present, so that since the aromatic component is in excess, the aforesaid No catalysis problems appear. This finding is extremely surprising, because when using such polyisocyanate mixtures in which the aromatic component is in excess, no significant improvement in weather resistance, Lightfastness and gloss retention of the molded foams compared to those which are produced with the exclusive use of aromatic polyisocyanates, could be expected. Contrary to these expectations, it even turned out that one Increase in the proportion of the polyisocyanate component with aliphatic or cycloaliphatic bonded isocyanate groups via the ranges according to the invention defined below in addition, does not bring about any significant improvement in weather stability, but rather this rather when using the lower amounts of polyisocyanates according to the invention with aliphatically or cycloaliphatically bound isocyanate groups is optimal.

The production of such weatherproof polyurethane systems is of great importance for colored molded parts, as well as for molded parts that are exposed to outdoor weathering exposed unpainted.

The present invention relates to a method of production of molded foam bodies with a compact surface and cellular core as well as integral ones Density distribution over the cross section of the shaped body by foaming a foamable Reaction mixture of polyisocyanates, polyhydroxyl compounds, blowing agents, optionally mixed with other isocyanate-reactive compounds, Activators and other auxiliaries in a closed form under the conditions the Foam-molding, characterized in that the polyisocyanate component is mixtures from polyisocyanates containing aromatically bound isocyanate groups with aliphatic or polyisocyanates containing cycloaliphatically bonded isocyanate groups in Molar ratio (aromatically bound isocyanate groups): (aliphatic or cycloaliphatic bound isocyanate groups) = 95: 5 to 50:50 used.

The present invention also relates to those according to this process available foam moldings.

The evaluation of the color deviation after weathering is done with the help of the gray scale (DIN 54001 and SNV 195805). Assessment of weather stability is carried out on test specimens that have been weathered in the Weather-o-meter test. Before and after weathering, the gloss retention of the test specimens according to Gardner (DIN 67530) at a glancing angle of 600.

In the process according to the invention, polyisocyanate mixtures are used, which both polyisocyanates with aromatically bound isocyanate groups as well Polyisocyanates with aliphatically or cycloaliphatically bound isocyanate groups exhibit. The two are in these mixtures to be used according to the invention Polyisocyanate types are available in quantities that correspond to a molar ratio (aromatically bound Isocyanate groups): (aliphatic or

cycloaliphatically bound isocyanate groups) from 95: 5 to 50:50, preferably 95: 5 to 80:20 correspond. It is remarkable that the essential to the invention Effect of a significant increase in weather resistance already within of the preferred range mentioned of 5-20 mol% of aliphatic or cycloaliphatic bonded isocyanate groups comes into its own.

Any polyisocyanates can be used in the process according to the invention aromatically, aliphatically or cycloaliphatically bound isocyanate groups are used as they come e.g. from W.Siefgen in Justus Liebig's Annalen der Chemie, 562, Pages 75 to 136, are described, for example 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 any mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (DAS 1 202 785), 2,4- and 2,6-hexahydrotolylene diisocyanate and any mixtures of these isomers, hexahydro-1,3- and / or - 1,4-phenylene diisocyanate, perhydro-2,4'- and / or -4,4'-diphenylmethane diisocyanate, 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2,6-tolylene diisocyanate, and any Mixtures of these isomers, diphenylmethane-2,4'- and / or -4,4'-diisocyanate, naphthylene-1,5-diisocyanate, Triphenylmethane-4,4 ', 4 "-triisocyanate, polyphenyl-polymethylene polyisocyanates, such as they are obtained by aniline-formaldehyde condensation and subsequent phosgenation and e.g.

in British Patents 874,430 and 848,671 are, perchlorinated aryl polyisocyanates, such as those in the German Auslegeschrift 1,157,601, polyisocyanates containing carbodiimide groups, such as they are described in German patent specification 1 092 007, diisocyanates, such as them in american Patent 3 492 330 are described, Polyisocyanates containing allophanate groups, such as those in the British patent 994 890, Belgian patent 761 626 and the published Dutch Patent registration 7 102 524 are described, isocyanurate groups containing polyisocyanates, as for example in German patents 1 022 789, 1 222 067 and 1 027 394 as well as in the German Offenlegungsschriften 1 929 034 and 2 004 048 polyisocyanates containing urethane groups, such as are e.g.

in the Belgian patent 752 261 or in the American U.S. Patent 3,394,164, containing acylated urea groups Polyisocyanates according to German Patent 1,230,778, containing biuret groups Polyisocyanates, such as those in German Patent 1 101 394, in US Patent 3 124 605 and in French patent 7 017 514 Telomerization reactions produced polyisocyanates, such as those in the Belgian Patent specification 723 640 are described, polyisocyanates containing ester groups, as described, for example, in British patents 965,474 and 1,072,956, in American Patent 3 567 763 and in German Patent 1 231 688 are mentioned, Reaction products of the above isocyanates with acetals according to the German Patent Specification 1,072,385.

It is also possible to use the technical isocyanate production distillation residues containing isocyanate groups, if appropriate dissolved in one or more of the aforementioned polyisocyanates to be used. Further it is possible to use any mixtures of the aforementioned polyisocyanates.

The preferred aromatic polyisocyanates include those technical easily accessible polyisocyanates e.g. 2,4- and 2,6-toluylene diisocyanate as well as any mixtures of these isomers (TDI "), polyphenyl-polymethylene-polyisocyanate, as produced by aniline-formaldehyde condensation and subsequent phosgenation are ("raw MDI"), 2,4'- and 4,4'-diisocyanatodiphenylmethane and carbodiimide groups, Urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups containing aromatic polyisocyanates ("modified polyisocyanates").

The particularly preferred aromatic polyisocyanates include Reaction products of 4,4'-diisocyanatodiphenylmethane which are liquid at room temperature with insufficient amounts of organic polyhydroxyl compounds in the molecular weight range 62-700, preferably polypropylene glycols of the molecular weight range 134-700 according to U.S. Patent 3,644,457.

The preferred polyisocyanates with aliphatic or

cycloaliphatically bound isocyanate groups include hexamethylene diisocyanate, 4,4 '4,4'-diisocyanatodicyclohexylmethane and 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethyl-cyclohexane (Isophorone diisocyanate) or reaction products of these diisocyanates with deficient Amounts of polyhydroxyl compounds of the type exemplified below in molar NCO / OH ratio 2: 1 to 100: 1, preferably 4: 1 to 16: 1 at 200C a viscosity of 50-5000, preferably 100-1000 mPas and an NCO content of 10-38, preferably 25-32% by weight.

Reactants for the polyisocyanate component are in the invention Process any organic compounds with at least 2 opposite isocyanates reactive hydrogen atoms in the molecular weight range 62-10,000. at this The reactants for the polyisocyanate component are preferably organic polyhydroxyl compounds with aliphatically bound hydroxyl groups or

around mixtures of such polyhydroxyl compounds of a (medium) Molecular weight of preferably 150 to 4000, with individual component being one any mixture used often a below or above this preferred molecular weight ranges, within the above

have a broad range of molecular weights ranging from 62 to 10,000. The hydroxyl compounds which are preferably used generally have an OH functionality of 2 to 8, preferably 2 to 4, on.

The corresponding polyhydroxy polyethers are particularly preferred, possibly mixed with the simple ones corresponding to the statements made Alkane polyols used. The use of polyhydroxy polyesters or polythioethers, Polyacetals, polycarbonates or polyester amides with opposite isocyanate groups reactive groups with a molecular weight lying within the stated ranges is possible.

The possible hydroxyl group-containing polyesters are e.g. reaction products of polyvalent, preferably divalent and optionally additionally trihydric alcohols with polybasic, preferably dibasic, carboxylic acids. Instead of the free polycarboxylic acids, it is also possible to use the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters of lower alcohols or mixtures thereof used to manufacture the polyester. The polycarboxylic acids can be aliphatic, be of a cycloaliphatic, aromatic and / or heterocyclic nature and optionally, e.g. by halogen atoms, substituted and / or unsaturated. As examples of this may be mentioned: succinic acid, adipic acid, suberic acid, azelaic acid, Sebacic acid, Phthalic acid, isophthalic acid, trimellitic acid, phthalic anhydride, tetrachlorophthalic anhydride, Tetrahydrophthalic anhydride, hexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, Glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimers and trimers Fatty acids such as acid, optionally mixed with monomeric fatty acids, dimethyl terephthalate, Terephthalic acid bis-glycol ester. The polyhydric alcohols are e.g. ethylene glycol, Propylene glycol- (1,2) and - (1,3), butylene glycol- (1,4) and - (2,3), hexanediol- (1,6), Octanediol (1,8), neopentyl glycol, cyclohexanedimethanol (1,4-bis-hydroxymethylcyclohexane), 2-methyl-1,3-propanediol, glycerine, trimethylolpropane, hexanetriol- (1,2,6), butanetriol- (1,2,4), Trimethylolethane, pentaerythritol, quinitol, mannitol and sorbitol, methyl glycoside, and more Diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols, dipropylene glycol, Polypropylene glycols, dibutylene glycol and polybutylene glycols in question. The polyester may have a proportion of terminal carboxyl groups. Also polyester made from lactones, e.g. caprolactone or hydroxycarboxylic acids, e.g. W-hydroxycaproic acid, can be used. The above-mentioned low molecular weight polyhydric alcohols can also be used as such will.

Also those preferred according to the invention, at least two, usually two to eight, preferably two to four, especially two up to three polyethers containing hydroxyl groups are those known per se Type and are e.g. by polymerizing epoxides such as ethylene oxide, propylene oxide, Butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin with itself, e.g. in the presence of BF3, or through the addition of these epoxides, optionally in a mixture or one after the other, with start components reactive hydrogen atoms such as alcohols or amines, e.g. water, ethylene glycol, propylene glycol- (1,3) or - (1,2) Trimethylolpropane, 4,4'-dihydroxydiphenylpropane, aniline, ammonia, xthanolamine, Xthylenediamine produced. Also succrose polyethers, such as those found in German Auslegeschrifts 1 176 358 and 1 064 938 are described come according to the invention in question. In many cases, those polyethers are preferred which are predominantly (up to 90% by weight, based on all existing OH groups in the polyether) have primary OH groups. Also polyethers modified by vinyl polymers, such as those produced by polymerization of styrene, acrylonitrile in the presence of polyethers (American patents 3,383,351, 3,304,273, 3,523,093, 3,110,695, German patent specification 1,152,536) likewise suitable, likewise polybutadienes containing OH groups.

Among the polythioethers are in particular the condensation products of thiodiglycol with itself and / or with other glycols, dicarboxylic acids, Formaldehyde, aminocarboxylic acids or amino alcohols are listed. Depending on the co-components The products are polythioether esters, polythioether esters, polythioether ester amides.

As polyacetals come e.g. those from glycols, such as diethylene glycol, Triethylene glycol, 4,4'-dioxethoxydiphenyldimethylmethane, hexanediol and formaldehyde possible connections in question. Also by polymerizing cyclic acetals suitable polyacetals can be produced according to the invention.

Polycarbonates containing hydroxyl groups are those of the known type into consideration, e.g. through implementation of diols such as propanediol (1,3), butanediol (1,4) and / or hexanediol (1,6), diethylene glycol, Triethylene glycol, tetraethylene glycol with diaryl carbonates, e.g. diphenyl carbonate or phosgene.

The polyester amides and polyamides include, for example, those made of polyvalent saturated and unsaturated carboxylic acids or their anhydrides and polyvalent ones saturated and unsaturated amino alcohols, diamines, polyamines and their mixtures recovered, predominantly linear condensates.

Also polyhydroxyl compounds already containing urethane or urea groups and optionally modified natural polyols, such as castor oil, carbohydrates, Strength, are usable. Also adducts of alkylene oxides with phenol-formaldehyde resins or urea-formaldehyde resins can be used according to the invention.

Representatives of these compounds to be used according to the invention are for example, in High Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology" by Saunders-Frisch, Interscience Publishers, New York, London, Volume I, 1962, pages 32-42 and pages 44-54 and Volume II, 1964, pages 5-6 and 198-199 as well as in the Kunststoff-Handbuch, Volume VII, Vieweg-Höchtlen, Carl-Hanser-Verlag, Munich, 1966, e.g. on the pages 45 to 71.

According to the invention, volatile organic substances are used as Propellant used. Examples of organic blowing agents are acetone, ethyl acetate, halogen-substituted alkanes such as methylene chloride, chloroform, xthylidene chloride, Vinylidene chloride, Monofluorotrichloromethane, chlorodifluoromethane, dichlorodifluoromethane, trichlorotrifluoroethane, also butane, hexane, heptane or diethyl ether in question. A driving effect can also by adding at temperatures above room temperature with the elimination of gases, for example nitrogen, decomposing compounds, e.g. azo compounds such as azoisobutyronitrile, can be achieved.

Further examples of propellants and details of their use of propellants are in the Kunststoffhandbuch, Volume VII, edited by Vieweg-Höchtlen, Carl-Hanser-Verlag, Munich 1966, e.g. on pages 108 and 109, 453 to 455 and 507 to 510.

In principle, water can also be used as a chemical paste are, although the inventive method preferably in the absence of added Water is carried out.

According to the invention, catalysts are also often used. as Catalysts to be used at the same time are those of the type known per se, e.g. tertiary amines such as triethylamine, tributylamine, N-methyl-morpholine, N-ethyl-morpholine, N-cocomorpholine, N, N, N ', N'-tetramethylethyldiamine, 1,4-diazabicyclo- (2,2,2) -octane, N-methyl-N'-dimethylaminoethyl piperazine, N, N-dimethylbenzylamine, bis (N, N-diethylaminoethyl) adipate, N, N-diethylbenzylamine, pentamethyldiethylenetriamine, N, N-dimethylcyclohexylamine, N, N, N ', N'-Tetramethyl-l, -butanediamine, N, N-dimethyl-B-phenylethylamine, 1,2-dimethylimidazole, 2-methylimidazole, tetramethylguanidine.

Tertiary hydrogen atoms which are active with respect to isocyanate groups Amines are e.g. triethanolamine, triisopropanolamine, N-methyl-diethanolamine, N-ethyl-diethanolamine, N, N-dimethylethanolamine and their reaction products with alkylene oxides, such as propylene oxide and / or ethylene oxide.

Silaamines with carbon-silicon bonds are also used as catalysts, as described, for example, in German patent specification 1 229 290, in question, e.g. 2,2,4-trimethyl-2-silamorpholine, 1,3-diethylaminomethyl-tetramethyl-disiloxane.

Nitrogen-containing bases such as tetraalkylammonium hydroxides are also used as catalysts, also alkali hydroxides such as sodium hydroxide, alkali phenolates such as sodium phenolate or alkali metal alcoholates such as sodium methylate. Hexahydrotriazines can also be used as catalysts.

According to the invention, organic metal compounds, in particular organic tin compounds, can be used as catalysts.

The organic tin compounds are preferably tin (II) and / or Tin IV salts of carboxylic acids such as tin (II) acetate, tin (II-octoate, tin (II) ethylhexoate) and stannous laurate and the dialkyltin salts of carboxylic acids such as dibutyltin (IV) diacetate, Dibutyltin (IV) di-laurate, dibutyltin (IV) maleate or dioctyltin (IV) diacetate into consideration.

Further representatives of catalysts to be used according to the invention as well as details about the mode of operation of the catalytic converters can be found in the plastics manual, Volume VII, edited by Vieweg and Höchtlen, Carl-Hanser-Verlag, Munich 1966, e.g. described on pages 96 to 102.

The catalysts are usually used in an amount between about 0.001 and 10% by weight, preferably 0.5 to 2% by weight, based on the amount of compounds with at least two isocyanate-reactive hydrogen atoms of a molecular weight of 62 to 10,000 is used.

Although it is just one of the advantages of the method according to the invention is that according to the invention compared to the molded foams based on aromatic Prior art polyisocyanates particularly lightfast molded foams are accessible are, can in the process according to the invention to further increase this light fastness, especially when using polyhydroxy compounds containing Xther groups, Light stabilizers are also used. Such light stabilizers are optionally used preferably the polyol component in amounts of 0-10, preferably 0.5 to 5,% by weight based on the polyol component. Light stabilizers that can be used according to the invention are e.g .: I piperidine derivatives 4-benzoyloxy-, 4-salicyloyloxy-, 4-capryloyloxy-, 4-Steraroyloxy-, 4- (β-3, 5-di-tert-butyl-4-hydroxyphenylpropionyloxy) -, 4- (3,5-di-tert-butyl-4-hydroxybenzoyloxy) -2.2, 6,6-tetramethylpiperidine. 4-benzoyloxy-, 4-salicyloyloxy-, 4-stesroyloxy- and 4-tert. -Butylbenzoyl- 1,2,2,6,6-pentamethylpiperidine. Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) suberate, Bis- (2,2,6,6-tetramethyl-4-piperidyl) -dodecanedioate, bis- (1,2,2,6,6-pentamethyl-4-piperidyl) -sebacat. 4-capryloyloxy-1-propyl-2,2,6,6-tetramethylpiperidine. 4-capryloyloxy-1-allyl-2, 2,6,6-tetramethylpiperidine. 4-benzoxyamido, 4-acryloylamido and 4-stearoylamido-2,2,6,6-tetramethylpiperidine.

2,4,6-tris- (2,2,6,6-tetramethyl-4-piperidyloxy) -s-triazine, 2,4,6-tris- (1 , 2,2,6,6-pentamethyl-4-piperidyloxy) -s-triazine, 2,4,6-tris- (2,2,6,6-tetramethyl-4-piperidylamino) -s-triazine, 2,2,6,6-Tetramethyl-4-B-cyanoaethoxy-piperidine, 1,2,2,6,6-pentamethyl-4-lauroyloxy-piperidine, Triacetone amine oxime.

II Benzophenone derivatives 2,4-dihydroxy-, 2-hydroxy-4-methoxy-, 2-hydroxy-4-octoxy-, 2-hydroxy-4-dodecyloxy, 2-hydroxy-4-benzyloxy, 2-hydroxy-4,4'-dimethoxy, 2,4,4'-trihydroxy, 2,2'-dihydroxy-4,4'-dimethoxy-, 2,2'4,4'-tetrahydroxy-, 2,2'-dihydroxy-4-methoxy-, 2-hydroxy-2, 2-hydroxy-2'-carboxy-4-methoxy-, 2,2,2'-dihydroxy-4-octoxy- and 2,2'-dihydroxy-4-dodecyloxy-benzophenone.

III benzotriazole derivatives 2- (2'-hydroxy-5'-methylphenyl) -, 2- (2'-hydroxy-5'-tert.-butylphenyl) -, 2- (2'-Hydroxy-5'-tert-octylphenyl) -, 2- (2'-Hydroxy-3'-tert-butyl-5'-methylphenyl) -, 2- (2'-Hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chloro-, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl), 2- (2'-hydroxy 3 ', 5'-di-tert-butylphenyl) -5-chloro-, 2- (2'-hydroxy-3', 5'-di-tert-amylphenyl) -, 2- (2'-Hydroxy-3 ', 5'-di-tert-amylphenyl) -5-chloro-, 2- (2'-hydroxy-3'-sec-butyl-5'-tert-butylphenyl) - , 2- (2'-Hydroxy-3'-tert-butyl-5'-sec-butylphenyl) -, 2- (2 ', 4'-dihydroxyphenyl) -, 2- (2'-hydroxy-4'-methoxyphenyl) -, 2- (2'-hydroxy-4'-octoxyphenyl) -, 2- (2'-hydroxy-3 '- bC-phenyl2lthyl-5' -methylphenyl) - and 2- (2'-hydroxy-3'-; -phenylethyl-5'-methylphenyl) -5-chlorobenzotriazole.

IV Oxalanilide 2-ethyl-2'-ethoxy-, 2-ethyl-2'-ethoxy-5'-tert-butyl-, 2-ethyl-4-tert-butyl-2'-ethoxy-5'-tert-butyl, 2,2'-dimethoxy, 2,2'-diethoxy, 4,4'-dimethoxy, 4,4'-diethoxy, 2,4'-dimethoxy, 2,4'-diethoxy, 2-methoxy-2'-ethoxy, 2-methoxy-4'-ethoxy-, 2-ethoxy-4'-methoxy-, 2,2'-dioctoxy-5,5'-di-tert-butyl-, 2,2'-Didodecyloxy-5,5'-di-tert-butyl-, 2-ethyl-2'-octoxy-, 4'4'-di-octoxy-, 2-ethyl-2'-butoxy- and 4-methyl-4 4-methyl-4'-methoxyoxalanilide.

V Phenyl salicylate and derivatives Phenyl salicylate, 4-tert-butylphenyl salicylate, 4-tert-octylphenyl salicylate.

VI Cinnamic acid ester derivatives a-cyano-β-methyl-4-methoxycinnamic acid methyl ester a-cyano-ß-methyl-4-methoxycinnamic acid butyl ester, a-cyano-ß-phenyl-zintic acid ethyl ester, Isooctyl α-cyano-ß-phenylzimate.

VII malonic ester derivatives 4-methoxy-benzylidenemalonic acid dimethyl ester, 4-Methoxybenzylidenemalonic acid diethyl ester, 4-butoxy-benzylidenemalonic acid dimethyl ester.

The aforementioned light stabilizers are preferred individually, however also used in any combination according to the present invention. Particularly Benztriazole derivatives are preferably used, in particular 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole.

According to the invention, surface-active additives (emulsifiers and foam stabilizers) can also be used.

As a flnulCatoren z. B. the sodium salts of castor oil sulfonates or of fatty acids or salts of fatty acids with amines such as oleic diethylamine or diethanolamine stearic acid. Also alkali or ammonium salts of sulfonic acids such as dodecylbenzenesulfonic acid or dinaphthylmethanedisulfonic acid or else of fatty acids such as ricinoleic acid or of polymeric fatty acids can be used as surface-active Additives are also used.

Water-soluble polyether siloxanes are primarily used as foam stabilizers in question. These compounds are generally constructed in such a way that a copolymer of ethylene oxide and propylene oxide is linked to a polydimethylsiloxane radical. Such foam stabilizers are z. B. in the American patent specification 2,764,565 described.

According to the invention, reaction retarders, 2. B.

acidic substances such as hydrochloric acid, sulfuric acid, phosphoric acid or organic 5 euro halides, furthermore cell regulators the in itself known type such as paraffins or fatty alcohols or dimethylpolysiloxanes and pigments or dyes and flame retardants of the type known per se, e.g. B. Tris-choräthy1-phosphate or ammonium phosphate and polyphosphate, as well as stabilizers against anti-aging and weather influences, wcichers and fungistatic and bacteriostatic effects Substances and fillers such as barium sulfate, kieselguhr, soot or SchlEmml; reide are also used been.

Further examples of optionally also to be used according to the invention surface-active additives and foam stabilizers as well as cell regulators, reaction retarders, Stabilizers, flame retardants, plasticizers, dyes and fillers as well as fungistatically and bacteriostatically active substances and details About the use and effect of these additional means are in the plastic manual, Volume VII, edited by Vieweg and Itöchtlen, Carl-IIanscr-Verlag, llUnchen 1966, e.g. B. on pages 103-113 described.

When carrying out the method according to the invention can also the per se known external or internal mold release agents are used, wherein "External mold release agents" are to be understood as meaning, in particular, waxes or metal soaps are, while as internal mold release agents ", for example, the mold release agents according to US-PS 3,726,952, GB-PS 1,365,215, DT-OS 2,356,692, DT-OS 2,363,452, DT-OS 2,404 310, DT-OS 2 427 273, DT-OS 2 431 968 or GB-PS 1 420 293 can be used.

To carry out the process according to the invention, the reaction components are according to the one-step process known per se, the prepolymer process or the so-called Semiprepolymer process brought to implementation, wherein machine facilities are often used, e.g. those used in the American U.S. Patent 2,764,565. Details of processing facilities, which are also suitable according to the invention are in the Kunststoff-Handbuch, Volume VII, published by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich 1966, e.g. on described on pages 121 to 205.

The process according to the invention is carried out in closed molds. The reaction mixture is introduced into a mold. Comes as a molding material Metal, e.g. aluminum or plastic, e.g. epoxy resin in question. Foams in the mold the foamable reaction mixture and forms the shaped body. In general when the method according to the invention is carried out, the form becomes such Amount of the foamable reaction mixture entered that with free expansion would lead to a foam whose volume is greater than the internal volume of the Is shape and preferably corresponds to 120 to 1000 8 of the volume of the shape. In this Case is worked under the so-called "overcharging"; such a procedure is known, for example, from U.S. Pat. No. 3,178,490 or from U.S. Pat. No. 3,182,104.

The reactants come when the process according to the invention is carried out otherwise preferably in quantities that correspond to an "NCO number" from 90-120, preferably 100-110, although also works in particular above an NCO figure of 120 for example at the same time Use of trimerization catalysts, for example alkali acetates, possible for the purpose of trimerization of the excess NCO groups with formation of isocyanurate were. However, this last-mentioned embodiment is less preferred. Under "NCO number" is in the above context the ratio of the NCO groups to all in the reaction mixture to understand existing groups which are reactive towards NCO groups.

In this context, an NCO figure of 100 means the presence equivalent amounts of NCO groups and isocyanate-reactive groups Groups.

The inventive method allows both the production of soft, semi-hard or hard molded foams with a dense, cellular skin Core and integral density distribution, including a continuous increase in density is to be understood from the mold core to the outside.

The question of the hardness of the process products according to the invention is in primarily depending on the functionality and the chain length of the invention Process used starting materials, i.e. the degree of branching of these starting substances. The experience according to the invention is preferably used to produce rigid molded foams.

The products of the process can be prepared in a hard setting of furniture parts, vehicle body parts, technical devices and components Find use, as well as in semi-hard to soft setting for the production of Safety upholstery in the automotive industry, elastic shoe soles, impact fiber, etc.

The method according to the invention is described by way of example below. The specified parts are by weight, unless otherwise stated. The percentages represent weight 8 percent.

Example 1 (aromatic isocyanate) 100 parts by weight. a polyol mixture the OH number 594 and a viscosity at 25 ° C of 1650 mPa.s, consisting of 70 parts by weight. of a polyether with an OH number of 830, which is obtained by adding propylene oxide to trimethylolpropane has been obtained and 30 parts by weight. of a polyether with an OH number of 42, which by Addition of a mixture of propylene oxide and Äthylencsid to a mixture of trimethylolproFar. and propylene glycol (molar ratio 3: 1) was obtained, 1 part by weight. a polysiloxane-polyalkylene oxide block copolymer as a foam stabilizer, 0.6 part by weight. Tetramethylguanidine as a catalyst, 3.0 parts by weight. Dimethylbenzylamine as a catalyst, 10.0 parts by weight. Monofluorotrichloromethane, 213.0 Parts by weight of a polyisocyanate with an NCO content of 23%, which was obtained was made by reacting 5 moles of diphenylmethane-4,4'-diisocyanate and one mole of tripropylene glycol.

Polyol mixture and blowing agent are used with the isocyanate mixture a 2-component dosing mixer and mixed in a closed, temperature-controlled Metal form registered. The temperature of this mold is 600C. After 5 minutes the molded part is removed from the mold. The molded part has a total pipe density of 0.6 g / cm³ and a material thickness of 10 mm as well as a solid edge zone on both sides. The molded part is exposed to outdoor weathering for 30 days. Then the Color deviation from the blank sample with the gray scale according to DIN 54001 and SNV 195805 certainly. The deviation in color corresponds to gray level 1. Another test specimen from the molded part will rest in the Weather-o-meter for 200 hours weathered and then the gloss retention by the Gardner method at a glancing angle of 600 according to DIN 67530. The gloss retention is 20%.

Example 2 (5 mol% aliphatic isocyanate) 100.0 parts by weight. one Polyol mixture with an OH number of 594 and a viscosity at 250C of 1650 mPa.s. from 70.0 parts by weight

of a polyether with an OH number of 830, which is produced by the addition of propylene oxide has been obtained on trimethylolpropane, and 30.0 parts by weight. of a polyether OH number 42, which is obtained by adding a mixture of propylene oxide and ethylene oxide on a mixture of trimethylolpropane and propylene glycol (molar ratio 3: 1) was, 1.0 part by weight a Polys i loxane-polyalkylene oxide block copolymer as Foam stabilizer, 0.6 part by weight. Tetramethylguanidine as a catalyst, 3.0 parts by weight. Dimethyl-benzylamine 10.0 parts by weight. Monofluorotrichloromethane 210.7 parts by weight. one Polyisocyanate mixture, consisting of 202.0 parts by weight. a semi-prepolymer which by reacting 5 moles of diphenylmethane-4,4'-diisocyanate and 1 mole of tripropylene glycol was obtained, and has an NCO content of 23%, and 8.7% by weight of a polyisocyanate, which was prepared by prepolymerizing 7.74 moles of a polyol from trimethylol propane and propylene oxide, OH number 378, and 1.47 mol of a polyester made from castor oil and cyclohexanone formaldehyde condensate, OH number 165, with 121.9 mol of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (Isophorone diisocyanate). The prepolymer has an NCO content of 28.2%.

Polyol mixture, blowing agent and isocyanate mixture are, as in example 1, mixed with the aid of a 2-component metering mixer and in a closed, tempered metal mold is filled. The temperature of this form is 600C. The molded part is demolded after 5 minutes, it has a solid on both sides Edge zone and a total density of 0.6 g / cm³. The molding will last for 30 days free hosted and compared with the O sample. The change in color, measured with the The gray scale according to DIN 54001 and SNV 195805 is gray level 2. The one according to the example 1 certain gloss retention is 35%.

Example 3 (10 mol% aliphatic isocyanate) 100.0 parts by weight. one Polyol mixture with an OH number of 594 and a viscosity of 1650 mPa.s at 25 ° C from 70 parts by weight. of a polyether with an OH number of 130, which is produced by the addition of propylene oxide of trimethylolpropane has been obtained, and 30 parts by weight. of a polyether OH number 42, which is obtained by adding the mixture of propylene oxide and ethylene oxide obtained a mixture of trimethylolpropane and propylene glycol (molar ratio 3: 1) was, 1.0 part by weight. a polysiloxane-polyalkylene oxide block copolymer as a foam stabilizer, 0.6 part by weight Tetramethylguanidine as a catalyst, 3.0 parts by weight. Dimethyl benzylamine as a catalyst, 10.0 parts by weight. Monofluorotrichloromethane.

208.5 parts by weight. of a polyisocyanate mixture consisting of 191 parts by weight. of a semi-prepolymer, which by reaction of 5 moles of diphenylmethane-4,4'-diisocyanate and 1 mol / tripropylene glycol was obtained and has an NCO content of 23%, and 17.5 parts by weight. a prepolymer, which is formed from 7.74 moles of a polyol, made from trimethylolpropane and propylene oxide, OH number 378, 1.47 moles of one Polyester with OH number 165, formed from castor oil and cyclohexanone formaldehyde condensate and 121.9 moles of isophorone diisocyanate, with an NCO content of 28.2%. Like in the example 1, a molded part is made from the polyols, blowing agents and polyisocyanates manufactured. After 30 days of outdoor exposure, the color deviation of the weathered molded part compared with the O-sample and with the help of the gray scale (DIN 54001, SNV 195805). The gray level 3 is obtained. The one according to the example 1 certain gloss retention is 70%.

Example 4 (20 mol% aliphatic isocyanate) 100 parts by weight. one Polyol mixture with an OH number of 594 and a viscosity at 250C of 1650 mPa.s. from 70 parts by weight.

of a polyether with an OH number of 830, which is produced by the addition of propylene oxide of trimethylolpropane was obtained, and 30 parts by weight. of a polyether of the OH number 42, which is produced by adding a mixture of propylene oxide and ethylene oxide to a mixture from trimethylolpropane and propylene glycol (molar ratio 3: 1) was obtained, 1 part by weight of a polysiloxane polyalkylene oxide block copolymer as a foam stabilizer, 0.6 Parts by weight Tetramethylguanidine as a catalyst, 3 parts by weight. Dimethylbenzylamine as Catalyst, 10 parts by weight.

Monofluorotrichloromethane, 204.9 parts by weight. a polyisocyanate mixture, consisting of 170 parts by weight. of a semi-prepolymer, which by reacting 5 Mole of diphenylmethane-4,4'-diisocyanate and 1 mole of tripropylene glycol was obtained and has an NCO content of 23%, and 34.9 parts by weight. a polyisocyanate, which was obtained by reacting 7.74 moles of a polyol formed from trimethylolpropane and propylene oxide, OH number 378, and 1.47 moles of a polyester formed from castor oil and cyclohexanone formaldehyde condensate and 121.9 moles of isophorone diisocyanate, with one Isocyanate content of 28.2%. As described in Example 1, polyol, blowing agent and polyisocyanate mixed and mixed with the aid of a 2-component metering mixer entered in a closed mold heated to 60 ° C. After demolding the The molded part, which has a compact cover layer on all sides, is the molded part Exposed to outdoor weathering for 30 days. The weathered sample is measured using the Gray scale according to DIN 54001 and SNV 195805 compared to the O-sample. Of the Weathered test specimens show the gray level 3. The gloss retention determined according to Example 1 is 90 Example 5 (10 mol% aliphatic isocyanate and 0.6% by weight UV stabilizer) 100 parts by weight. a polyol mixture with an OH number of 594 and a viscosity at 250C of 1650 mpa.s, consisting of 70 parts by weight.

of a polyether with an OH number of 830, which is produced by the addition of propylene oxide of trimethylolpropane has been obtained, and 30 parts by weight. of a polyether OH number 42, which is obtained by adding a mixture of propylene oxide and ethylene oxide at obtained a mixture of trimethylolpropane and propylene glycol (molar ratio 3: 1) was, 1 part by weight a polysiloxane-polyalkylene oxide block copolymer as a foam stabilizer, 0.6 part by weight Tetramethylguanidine as a catalyst, 3 parts by weight. Dimethyl benzylamine as a catalyst, 10 parts by weight. Monofluorotrichloromethane, 208 parts by weight. a polyisocyanate mixture, consisting of 191 parts by weight. of a semi-prepolymer, which by reacting 5 Mole of diphenylmethane-4,4'-diisocyanate and 1 mole of tripropylene glycol was obtained, with an NCO content of 32% and 17.5 parts by weight. of a prepolymer obtained was formed by reacting 7.74 moles of a polyol from trimethylolpropane and propylene oxide, OH number 378, 1.47 moles of a polyester with OH number 165 from castor oil and cyclohexanone formaldehyde condensate and 121.9 mol of isophorone diisocyanate, NCO content = 28.2%.

2 parts by weight. a UV stabilizer (2 (2'-hydroxy-3'5'-di-tert-butyl-phenyl) -5-chlorobenzotriazole).

The UV stabilizer is pre-dissolved in the monofluorotrichloromethane propellant and then polyol mixture, blowing agent and isocyanate mixture are means a 2-component metering mixer and mixed as described in Example 1, filled into a closed, tempered metal mold. The temperature of the mold is 6O0C. After 5 min.

the molded part is removed from the mold. The molded part has an overall bulk density of 0.6 g / cm³ and a compact, cell-free skin that is closed on all sides. The molding is exposed to outdoor weathering for 30 days and the reduction in color in comparison to an O-sample with the help of the gray scale DIN 54001 and SNV 195805 determined. The color deviation corresponds to gray level 3. Further test specimens from the molded part were exposed in the weather-o-meter test and after a weathering period rated by the Gardner gloss method of 200 hours. The test specimens have a 78% gloss retention after 200 h. (Test according to Gardner DIN 67530 at a glancing angle of 600).

Example 6 (10 mol% aliphatic isocyanate and 1.2% by weight UV stabilizer) 100 parts by weight. a polyol mixture with an OH number of 594 and a viscosity at 250C of 1650 mPa.s, consisting of 70 parts by weight.

of a polyether with an OH number of 830, which is produced by the addition of propylene oxide of trimethylolpropane has been obtained, and 30 parts by weight. of a polyether OH number 42, which is obtained by adding a mixture of propylene oxide and ethylene oxide on a mixture of trimethylolpropane and propylene oxide (molar ratio 3: 1) was, 1 part by weight a polysiloxane-polyalkylene oxide block copolymer as a foam stabilizer, 0.6 part by weight Tetramethylguanidine as a catalyst, 3 parts by weight.

Dimethyl-benzylamine as a catalyst, 10 parts by weight. Monofluorotrichloromethane, 4 parts by weight. a UV stabilizer 2- (2'-hydroxy-3'5'-di-tert-butyl-phenyl) -5-chlorobenzotriazole, 108.5 parts by weight. of a polyisocyanate mixture consisting of 191 parts by weight. one Semiprepolymers, which by reacting 5 moles of diphenylmethane-4,4'-diisocyanate and 1 mole of tripropylene glycol was obtained, having an NCO content of 23% and a Prepolymer formed from 7.74 moles of a polyol from trimethylolpropane and propylene oxide (OH number 378) and 1.47 moles of a polyester formed from castor oil and cyclohexanone formaldehyde condensate with an OH number of 165 and 121.9 mol of isophorone diisocyanate, NCO content = 28.2%.

The UV stabilizer is pre-dissolved in the monofluorotrichloromethane propellant and the polyol mixture, blowing agent and isocyanate, as described in Example 1, mixed with the aid of a metering mixer and transferred to a closed, temperature-controlled Form registered. Mold temperature = 6O0C. After 5 minutes, the molded part becomes the mold taken. The molded part has a cover layer that is closed on all sides and one Total density of 0.6 g / cm3. The molded part is exposed to outdoor weathering for 30 days. The color change is then measured using the gray scale according to DIN 54001 and SNV 195805 determined in comparison to the O-sample. The gray level 4 is obtained Example 1 certain gloss retention is 80%.

Example 7 (5 mol% aliphatic isocyanate and 0.6% by weight UV stabilizer) 100 parts by weight. a polyol mixture with an OH number of 594 and a viscosity at 250C of 1650 mPa.s, consisting of 70 parts by weight.

of a polyether with an OH number of 830, which is produced by the addition of propylene oxide of trimethylolpropane has been obtained, and 30 parts by weight. of a polyether OH number 42, which is obtained by adding a mixture of propylene oxide and ethylene oxide on a mixture of trimethylolpropane and propylene glycol (molar ratio 3: 1) was, 1 part by weight a polysiloxane-polyalkylene oxide block copolymer as a foam stabilizer, 0.6 Parts by weight Tetramethylguanidine as a catalyst, 3 parts by weight. Dimethylbenzylamine as Catalyst, 2 parts by weight. a UV stabilizer 2- (2'-hydroxy-3'5'-di-tert-butyl-phenyl) -5-chlorobenzotriazole, 10 parts by weight.

Monofluorotrichloromethane, 219.2 parts by weight. a polyisocyanate mixture, that consists of 202 parts by weight. a semi-prepolymer, which by reaction of 5 moles of diphenylmethane-4,4'-diisocyanate and 1 mole of tripropylene glycol were obtained, NCO content = 23%, and 17.2 parts by weight. a prepolymer formed from 2 Mole of 1,6-hexamethylene diisocyanate, and one mole of dipropylene glycol, NCO content = 14.2 %. The polyol mixture and blowing agent are mixed with the isocyanate mixture using a two-component metering mixer mixed as described in Example 1, and in a closed, temperature-controlled Shape filled. Mold temperature = 6O0C. After 5 minutes, the molded part is removed from the mold.

The molded part has a closed, compact outer skin and has a total density of 0.6 g / cm³.

The molded part is exposed to outdoor weathering for 30 days and then the color intensification using the gray scale according to DIN 54001 and SNV 195805 in comparison determined to the O-sample.

The color deepening corresponds to gray level 3. Further test specimens from the molded part were weathered for 200 hours in the weather-o-meter test. Afterward the gloss retention is determined according to Gardner. The gloss retention according to Gardner (DIN 67430, gloss angle 600) is 92%.

Example 8 (10 mol% aliphatic isocyanate and 0.6% by weight UV stabilizer) 100 parts by weight. a polyol mixture with an OH number of 594 and a viscosity at 250C of 1650 mPa.s, consisting of 70 parts by weight.

of a polyether with an OH number of 830, which is produced by the addition of propylene oxide has been obtained on trimethylolpropane, and 30 parts by weight. of a polyether OH number 42, which is obtained by adding a mixture of propylene oxide and ethylene oxide on a mixture of trimethylolpropane and propylene glycol (molar ratio 3: 1) was, 1 part by weight a polysiloxane-polyalkylene oxide block copolymer as a foam stabilizer, 0.6 part by weight Tetramethylguanidine as a catalyst, 3 parts by weight. Dimethylbenzylamine as a catalyst, 2 parts by weight. of a UV stabilizer 2- (2'Hydroxy-3'5'-di-tert-butyl-phenyl) -5-chloro-benzotriazole, 10 parts by weight.

Monofluorotrichloromethane.

225.7 parts by weight. a polyisocyanate mixture consisting of 191.3 Parts by weight of a semi-prepolymer, which by reacting 5 moles of diphenylmethane-4,4'-diisocyanate and 1 mole of tripropylene glycol was obtained, and 34.3 parts by weight. a semi-prepolymer, this was obtained by reacting 2 moles of 1,6-hexamethylene diisocyanate and 1 mole Dipropylene glycol, NCO content = 14.2%.

The UV stabilizer is pre-dissolved in the monofluorotrichloromethane. Afterward polyol mixture, blowing agent and isocyanate mixture are created using a 2-component metering mixer mixed and poured into a closed metal mold heated to 600C. After 5 minutes, the molding becomes the Taken from the shape. The molding has an all-round coated top layer and a total density of 0.6 g / cm³. The molded part is then left outdoors for 30 days, and the change the color using a gray scale according to DIN 54001 and SNV 195805 in comparison determined to the O-sample.

The yellowing corresponds to the gray level 3. The determined according to Example 1 Gloss retention is 95%.

Example 9 (10 mol% aliphatic isocyanate and 0.7% by weight UV stabilizer) 100 parts by weight. a polyol mixture with an OH number of 594 and a viscosity at 250C of 1650 mPa.s, consisting of 70 parts by weight.

of a polyether with an OH number of 830, which is produced by the addition of propylene oxide of trimethylolpropane has been obtained, and 30 parts by weight. of a polyether OH number 42, which is obtained by adding a mixture of propylene oxide and ethylene oxide on a mixture of trimethylolpropane and propylene glycol (molar ratio 3: 1) was, 1 part by weight a polysiloxane-polyalkylene oxide block copolymer as a foam stabilizer, 0.6 part by weight Tetramethylguanidine as a catalyst, 3 parts by weight. Dimethylbenzylamine as a catalyst, 2 parts by weight.

UV stabilizer 2- <2'-hydroxy-3 ', 5'-di-tert-butyl-phenyl) -5-chlorobenzotriazole, 10 parts by weight. Monofluorotrichloromethane.

176.4 parts by weight. of a polyisocyanate mixture consisting of 142 parts by weight. of a polyisocyanate obtained by phosgenation of aniline-formaldehyde condensates was obtained, NCO content = 31%, and 34.4 parts by weight. a prepolymer which obtain was made by reacting 2 moles of 1,6-hexamethylene diisocyanate and 1 mole of dipropylene glycol, NCO content = 14.2%.

The UV stabilizer is pre-dissolved in the monofluorotrichloromethane.

This is followed by a polyol mixture, blowing agent and isocyanate mixture mixed by means of a 2-component metering mixer, as described in Example 1 is, and poured into a closed tempered metal mold. The mold temperature is 6O0C. After 5 minutes, the molded part is removed from the mold. The molding has a top layer that is closed on all sides and a total density of 0.6 g / cm³. The molded part is exposed to the elements for 30 days. Then the color retention determined using the gray scale, DIN 54001 and SNV 195805 in comparison to the O-sample. The color of the weathered sample corresponds to gray level 4. The one according to the example 1 certain gloss retention is 80%.

Claims (3)

Claims 1. experienced for the production of foam moldings with compact surface and cellular core as well as integral density distribution over the cross section of the shaped body by foaming a foamable reaction mixture from polyisocyanates, polyhydroxyl compounds, blowing agents, optionally in a mixture with other isocyanate-reactive compounds, activators and other auxiliaries in a closed mold under the conditions of foam molding, thereby characterized in that the polyisocyanate component is mixtures of aromatically bound Polyisocyanates containing isocyanate groups with aliphatic or cycloaliphatic Polyisocyanates containing bonded isocyanate groups in a molar ratio (aromatic bound isocyanate groups): (aliphatically or cycloaliphatically bound isocyanate groups) = 95: 5 to 50:50 used. 2. The method according to claim 1, characterized in that as Polyisocyanate with aliphatically or cycloaliphatically bound isocyanate groups Hexamethylene diisocyanate, 4,4'-diisocyanatodicyclohexylmethane or 1-isocyanato-3,3, 5-trimethyl-5-isocyanato-methyl-cyclohexane and / or. Reaction products containing urethane groups and isocyanate groups these diisocyanates are used with insufficient amounts of polyhydroxyl compounds. 3. According to claim 1 and 2 obtainable foam moldings.