JP2001527107A - Rigid foamed plastic molding having a dense skin layer - Google Patents

Abstract

  (57) [Summary] The present invention relates to a method for producing a rigid foamed plastic molded article having a dense outer skin layer. The polyisocyanate is added to the tertiary amine and, if desired, the pigment and reacted with the polyol and the polycarboxylic acid. The carbon dioxide released during the reaction of the carboxylic acid and the isocyanate is used as a blowing agent, which makes it possible to produce a compact having a dense skin layer firmly bonded to the cellular core of the compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL FIELD [0001] The present invention relates to a method for producing a rigid foam molded article having a dense skin layer, and a molded article produced by such a production method.

BACKGROUND OF THE INVENTION The formation of dense skin layers is often observed in the production of polyurethane foams. If the manufacturing method is performed in a mold, the formation of the skin layer is often enhanced by cooling the mold walls and applying pressure. Unfortunately, the shaped bodies produced in this way do not have a uniform density distribution, but are characterized by a sharp change from the densified skin layer towards the cell core, The skin layer
Often, they are not firmly bonded to the porous core.

When producing foams having a dense skin layer or outer region, a reaction mixture of a polyisocyanate, a polyol, additives and a low boiling liquid is used in practice. In this case, the pressure / temperature relationship in the outer region determines the formation of a dense skin layer. Due to the presence of the low boiling point liquid, a dynamic equilibrium is established between the liquid phase and the gas phase of the low boiling point liquid. This equilibrium is near the cooled mold wall on the liquid side, where no foam is formed.

[0004] The isocyanate-water reaction that proceeds with the production of carbon dioxide often leads to
It is known to be used for foam formation in polyurethane foam production.
However, this reaction is not used for the production of foams having a dense skin layer. This is because the reaction cannot be completely suppressed in the cooled outer zone and the carbon dioxide generated during the reaction does not condense on the cooled walls. In this way, only the production of high-density foams with incompletely dense skin layers is possible. In addition, obtaining a dense skin layer requires very careful catalyst selection,
Only by maintaining a difficult temperature profile so as to keep the evolution of carbon dioxide in the cold outer zone to a minimum.

[0005] Thus, the most common method so far for producing foams having a dense skin layer is to use a low-boiling liquid as a blowing agent. Low boiling liquids are
Either fluorocarbons or hydrogenated fluorocarbons, which are known to adversely affect the ozone layer of the global environment, can only be used to a limited extent in recent years. These compounds are being replaced by low boiling hydrocarbons, but the very high flammability of low boiling hydrocarbons requires very careful precautions in the production of foams.

[0006] According to the teaching of DE-A 43 33 569, foams having a dense skin layer can be produced by using carbon dioxide as blowing agent. This publication proposes using a carbamate to generate carbon dioxide. Carbamates prepared from alkanolamines and carbon dioxide are specifically described. Such carbamates are added to the polyisocyanate / polyol mixture and decompose inside the mold at relatively high temperatures during the molding and foaming process to produce carbon dioxide, but to cool the mold wall. In the vicinity, it remains without being decomposed. Unfortunately, the carbamate had to be prepared in a separate reaction,
Since an accurate temperature profile must be maintained in the mold during the foaming process,
This method is very complicated.

[0007] A very similar method has been proposed in US Pat. No. 5,451,612, in which the carbamate is replaced by a carbonate, especially an alkali metal carbonate or bicarbonate, the method generally comprising: It is carried out in the presence of water as blowing agent and optionally an acid source which releases carbon dioxide. However, this method relies on the high exotherm of the isocyanate / polyol reaction or the addition of an acid or acid source to promote rapid decomposition of the carbonate with the release of carbon dioxide.

(Disclosure of the Invention) (Problems to be Solved by the Invention) The problem to be solved by the present invention is to provide a rigid foam having a dense skin layer, which can be easily carried out using readily available raw materials. It is to provide a method of manufacturing.

The solution to this problem is described in the claims, wherein the carboxylic acid is used as a blowing agent and the isocyanate-free components in the composition are reduced to 0.1% before the reaction. 2
It is characterized by containing less than water by weight.

WO 93/15121 discloses a process for the preparation of amine-containing plastics with the release of carbon dioxide, in which polyfunctional isocyanates, carboxylic acids and optionally alcohols are converted to tertiary amines, especially heteroaromatics. React in the presence of an amine. According to this publication, the composition described is suitable for processing by the RIM method and makes it possible to produce standard molded bodies of integral foam.
However, this publication does not give any details on the production of the monolithic foam, and in particular does not describe properties relating to the outer region. Also, this publication does not state that the disclosed compositions allow for the production of integral foams with pigments or fillers.

In the context of the present invention, a “rigid foam” is understood to be a foam which exhibits a moderate or high resistance to deformation under compressive stress. In particular, the rigid foam according to the invention has at least 15 kPa (at 10% compression) according to DIN 53421
"Hard foam" (harter Schaumstoff) or "semi-rigid foam" (halbharter Schau) according to DIN 7726 (2.1.1 and 2.1.2)
mstoff). A rigid foam having a "dense skin layer" is a monolithic or structural foam having an outer region that has a higher density (substantially the density of the base polymer) than the foam core as a result of the molding process. Understood. DIN
According to 7726, the density (total density) of such a one-piece foam averaged over the core and the outer region is of the order of 100 kg / m ³ or more.

The polyurethane binder used according to the invention is at least one polyol or polyamine with at least one polyisocyanate, at least one carboxylic acid, and optionally added as blowing agent for foam formation. It consists essentially of very small amounts of water reaction products. Instead of polyols and polycarboxylic acids, hydroxycarboxylic acids or amine carboxylic acids can also be used.

[0013] Polyisocyanates are polyfunctional. Suitable polyfunctional isocyanates include 1
It preferably contains up to 2 to 5, more preferably up to 4 and even more preferably 2 or 3 isocyanate groups on average per molecule. The polyisocyanates used can be aromatic, cycloaliphatic or aliphatic isocyanates.

An example of a suitable aromatic polyisocyanate is toluene diisocyanate (TDI
Isomer (pure isomer or a mixture of isomers), naphthalene-1,5-diisocyanate, diphenylmethane-4,4′-diisocyanate (MDI), diphenylmethane-2,4′-diisocyanate, and It is a mixture of 4'-diphenylmethane diisocyanate and its 2,4 'isomer or a mixture of 4,4'-diphenylmethane diisocyanate and a relatively high functionality oligomer (crude MDI). Examples of suitable cycloaliphatic polyisocyanates are the hydrogenation products of the aromatic diisocyanates such as 4,4'-dicyclohexylmethane diisocyanate (H ₁₂ M
DI), 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (isophorone diisocyanate, IPDI), cyclohexane-1
, 4-diisocyanate, hydrogenated xylylene diisocyanate (H ₆ MDI), m
-Or p-tetramethylxylylene diisocyanate (m-TMXDI, p-
TMXDI), and dimeric fatty acid diisocyanates. Examples of aliphatic polyisocyanates include hexane-1,6-diisocyanate (HDI), 1,6-diisocyanato-2,2,4-trimethylhexane, 1,6-diisocyanato-2,4,4-trimethylhexane, butane it is a 1,4-diisocyanate and 1,12-dodecane diisocyanate (C ₁₂ DI).

[0015] Aromatic isocyanates, preferably diphenylmethane diisocyanate (pure isomer or a mixture of 2,4'- and 4,4'-isomers), or carbodiimide liquefied MDI (for example, commercially available as Isonate 143L; ), Ie, a mixture of isomers / oligomers of MDI (for example,
(Available commercially as API or Desmodur VK) is generally preferred. So-called “quasi prepolymers”, ie, the reaction products of MDI or TDI with low molecular weight diols (eg, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol or triethylene glycol) can also be used. Such pseudoprepolymers are known to be mixtures of the above reaction products with monomeric diisocyanates. Surprisingly, even aliphatic and cycloaliphatic isocyanates can react quickly and completely at room temperature to form the foams of the present invention. In addition to the above-mentioned aliphatic and cycloaliphatic isocyanates, it is also possible to use these isocyanates, in particular the isocyanurated or biuretized products of HDI and IPDI.

Suitable polyols are preferably liquid polyhydroxy compounds having 2 or 3 hydroxyl groups per molecule, for example from 200 to 6000, preferably from 400 to 3
Bifunctional and / or trifunctional polypropylene glycol with a molecular weight of 000. Statistical or block copolymers of ethylene oxide and propylene oxide can also be used. Another group of polyethers which are preferably used are, for example, polytetramethylene glycols which are produced by the acidic polymerization of tetrahydrofuran, which have a molecular weight of from 200 to 6000, preferably from 400 to 4000.

Other suitable polyols are liquid polyesters, which are dicarboxylic or tricarboxylic acids (eg, adipic, sebacic, glutaric, azelaic, hexahydrophthalic or phthalic acids) Molecular weight diols or triols (eg, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, butane-1,4-diol, hexane-1,6-diol, decane-1,10-diol, glycerol or triol) (Methylolpropane). Another group of polyols that are suitable for use in the present invention are e-caprolactone-based polyesters known as "polycaprolactones".

However, polyester polyols of oleochemical origin can also be used. The oleochemical polyester polyol completely opens the epoxidized triglyceride of the fat mixture comprising at least partially olefinically unsaturated fatty acids, for example, with one or more alcohols containing 1 to 12 carbon atoms, It is then obtained by partially transesterifying the triglyceride derivative to form an alkyl ester polyol containing from 1 to 12 carbon atoms in the alkyl group. Other suitable polyols are polycarbonate polyols and dimer diols (Henkel K
GaA), and castor oil and its derivatives. For example, hydroxy-functional polybutadienes known under the trade name Poly-bd can also be used as polyols for the compositions of the present invention. In one particular embodiment, the polyol component is a diol / triol mixture of polyether- and polyester polyols.

The carboxylic acids used according to the invention react with isocyanates with the release of carbon dioxide in the presence of a catalyst to form amides. That is, the carboxylic acid has two functions of participating in the formation of the polymer skeleton and also acting as a blowing agent by releasing carbon dioxide.

“Carboxylic acids” are understood to be acids containing one or more, preferably up to three, carboxyl groups (—COOH) and at least 2, preferably 5 to 400, carbon atoms. . The carboxyl group may be linked to a saturated or unsaturated, linear or branched alkyl or cycloalkyl group, or to an aromatic group. The carboxylic acids may contain other groups, such as ether, ester, halogen, amide, amino, hydroxy, urea groups and the like. However, preference is given to carboxylic acids which can be easily formulated as liquids at room temperature, for example natural fatty acids or mixtures of fatty acids, terminal COOH polyesters, polyethers or polyamides, dimeric and trimer fatty acids.

Examples of carboxylic acids are acetic acid, valeric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, isopalmitic acid, arachiic acid, behenic acid, serotonic acid And palmitoleic acid, oleic acid, elaidic acid, petroselinic acid, erucic acid, linoleic acid, linolenic acid and gadolinic acid which are mono- or polyunsaturated acids. Other suitable carboxylic acids are adipic, sebacic, isophthalic, terephthalic, trimellitic, phthalic, hexahydrophthalic, tetrachlorophthalic, oxalic, muconic, succinic, fumaric, ricinoleic. , 12-hydroxystearic acid, citric acid, tartaric acid, dimer or trimer unsaturated fatty acids, optionally mixtures of these with monomeric unsaturated fatty acids, and optionally partial esters of these compounds.

Esters of polycarboxylic acids or carboxylic acid mixtures containing both COOH and OH groups, such as TMP [C ₂ H ₅ —C (CH ₂ OH) ₃ ], glycerol, pentaerythritol, sorbitol, glycols and Esters of alkoxylates with adipic acid, sebacic acid, citric acid, tartaric acid or grafted or partially esterified carbohydrates (sugars, starch, cellulose), and also the ring-opening products of epoxides with polycarboxylic acids can be used. it can.

“Carboxylic acid” includes not only aminocarboxylic acid but also preferably “hydroxycarboxylic acid”. "Hydroxycarboxylic acid" means monohydroxymonocarboxylic acid, monohydroxypolycarboxylic acid, polyhydroxymonocarboxylic acid and polyhydroxypolycarboxylic acid, and preferably has 1 to 9, preferably 1 to 9, HC groups, particularly aliphatic groups. Contains 2 to 3 hydroxyl or carboxyl groups and also includes the corresponding hydroxyalkoxycarboxylic acids having 2 to 600, preferably 8 to 400, more preferably 14 to 120 carbon atoms. Polyhydroxymonocarboxylic acids and polyhydroxypolycarboxylic acids, including the corresponding hydroxyalkoxycarboxylic acids, combine to form polyhydroxy fatty acids. Preferred dihydroxy fatty acids and their preparation are described in DE-OS 3 318 596 and EP 237
959, and are particularly referred to.

The polyhydroxy fatty acids used according to the invention are preferably derived from fatty acids of natural origin. Thus, polyhydroxy fatty acids generally contain an even number of carbon atoms in the backbone and are unbranched. Those with a chain length of 8 to 100 carbon atoms, in particular 14 to 22 carbon atoms, are particularly suitable. For industrial use, natural fatty acids are most commonly used in industrial mixtures. Such a mixture preferably contains partially oleic acid.

In addition, the polyhydroxy fatty acids may include other saturated, monounsaturated and polyunsaturated fatty acids. In principle, mixtures of different chain lengths, which may also contain polyhydroxyalkoxycarboxylic acids with saturates or double bonds, are also used for the preparation of polyhydroxy fatty acids or polyhydroxyalkoxy fatty acids suitable for use in the present invention. can do. Therefore, not only pure polyhydroxy fatty acids but also mixed products obtained from animal fats or vegetable oils containing 40% or more, preferably 60% or more of monounsaturated fatty acids after the treatment (ester decomposition, purification step) Suitable for the present invention. Examples of such mixed products are commercially available natural substances, for example 67% oleic acid, 2% stearic acid, 1% heptadecanoic acid, 10% saturated acids of chain length C ₁₂ -C _{16, 12%} linoleic acid and 18 Beef fat having a chain length distribution of 2% saturated acid having more than one carbon atom, or a new sunflower having a composition of about 80% oleic acid, about 5% stearic acid, about 8% linoleic acid and about 7% palmitic acid Oil (NSb). These products can be distilled briefly after ring opening to reduce the unsaturated acid ester component. Further purification steps (eg, relatively long distillations) are also possible.

The polyhydroxy fatty acids used according to the invention are preferably monounsaturated fatty acids, for example 4,5-tetradecenoic acid, 9,10-tetradecenoic acid, 9,10-pentadecenoic acid, 9,10-hexadecenoic acid 9,10-heptadecenoic acid, 6,7-octadecenoic acid, 9,10-octadecenoic acid, 11,12-octadecenoic acid, 1
It is derived from 1,12-eicosenoic acid, 11,12-docosenoic acid, 13,14-docosenoic acid, 15,16-tetracosenoic acid and 9,10-xymenic acid. Of these, oleic acid (9,10-octadecenoic acid) is preferred. Both cis and trans isomers of all of the above fatty acids are suitable.

Also suitable are polyhydroxy fatty acids derived from the less common unsaturated fatty acids, such as decyl-12-enoic acid, stilingsaeure, dodecyl-9-ene. Acid, ricinoleic acid, petroselinic acid, vaccenic acid, eleostearic acid, punicic acid, ricanoic acid, parinaric acid, gadolinic acid, arachidonic acid, 5-eicosenoic acid, 5-docosenoic acid, setrenic acid,
5,13-docosadienoic acid, and / or nervonic acid.

Also suitable are polyhydroxy fatty acids obtained from the isomerization products of natural unsaturated fatty acids. The polyhydroxy fatty acids produced in this way differ only in the position of the hydroxy or hydroxyalkoxy group in the molecule. Polyhydroxy fatty acids are usually present as a mixture. Natural fatty acids, which are natural substances, are preferred as starting materials in the present invention, but this does not mean that synthetic carboxylic acids of the corresponding number of carbon atoms are not suitable.

[0029] The hydroxyalkoxy group of the polyhydroxy fatty acid is derived from the polyol used to open the ring of the epoxidized fatty acid derivative. Preference is given to polyhydroxy fatty acids whose hydroxyalkoxy groups are derived from primary dihydric alcohols having up to 24, in particular up to 12, carbon atoms. Suitable diols are propanediol, butanediol, pentanediol, hexanediol, dodecanediol, preferably ethane-1,2-diol, butane-1,4-diol, hexane-1,6-diol, 2-40 Polypropylene glycol, polybutanediol and / or polyethylene glycol having a degree of polymerization. Polypropylene glycol and / or polytetrahydrofurandiol and its copolymers are also particularly suitable diol compounds, especially if they have a degree of polymerization of about 2 to 20. However, triols or higher alcohols such as glycerol and trimethylolpropane and their adducts with ethylene oxide and / or propylene oxide up to a molecular weight of 1500 can also be used for ring opening. In this case, a polyhydroxy fatty acid having more than 2 hydroxy groups per molecule is obtained.

Instead of polyols as hydroxy-containing compounds, hydroxycarboxylic acids such as citric acid, ricinoleic acid, 12-hydroxystearic acid, lactic acid and the like can also be used for ring opening. In this case, an ester group is formed instead of an ether group. In addition, amines, hydroxy-containing amines and aminocarboxylic acids can also be used for ring opening.

However, dihydroxy fatty acids prepared from diols are particularly preferred.
Such dihydroxy fatty acids are liquid at room temperature and can be easily mixed with other reactants. The dihydroxy fatty acids in the present invention are understood to be either the ring-opened products of epoxidized unsaturated fatty acids with water and the corresponding ring-opened products with diols and their cross-linked products with other epoxide molecules. Ring opening products with diols are, to a lesser extent, referred to as dihydroxyalkoxy fatty acids. Preferably, the hydroxy or hydroxyalkyl group has at least one
One, preferably at least three, more preferably more at least six CH ₂ units, apart from carboxy groups. Preferred dihydroxy fatty acids are 9,10-dihydroxypalmitic acid, 9,10-dihydroxystearic acid and 13,
14-dihydroxybehenic acid and its 10,9- and 14,13-isomers.

Polyunsaturated fatty acids such as linoleic acid, linolenic acid and ricinic acid (Ricini
nsaeure) are also suitable. An example of an aromatic carboxylic acid is cinnamic acid.

If it is intended to initiate the release of carbon dioxide at temperatures as low as room temperature, it is desirable to use amino-substituted pyridines and / or N-substituted imidazoles as catalysts. Particularly suitable are 1-methylimidazole, 2-methyl-1-vinylimidazole, 1-allylimidazole, 1-phenylimidazole, 1,2,4,5-tetramethylimidazole, 1- (3-aminopropyl ) Imidazole, pyrimidazole, 4-dimethylaminopyridine, 4-pyrrolidinopyridine, 4-morpholinopyridine, 4-methylpyridine and N-dodecyl-
2-methylimidazole.

The abovementioned starting materials for the PU (polyurethane) binder, ie polyisocyanates, polyols, polyamines, carboxylic acids and amine catalysts are used in the following amounts: For each equivalent of isocyanate, a mixture of carboxylic acid and alcohol (alcohol to carboxylic acid ratio 20: 1 to 1:20) 0.1 to 1 equivalent, preferably 0.1
To 0.8 equivalents, and 0.0001 to 0.5 equivalents of the amine catalyst, preferably 0.0
Use from 01 to 0.1 equivalents. If the alcohol or polyamine does not participate in the reaction, ie if the isocyanate reacts with the carboxylic acid, the following rules apply: per equivalent of isocyanate 0.1 to 1 equivalent of carboxylic acid, preferably 0.
. 8 to 1 equivalent, and 0.0001 to 0.5 equivalent, preferably 0 to 3 equivalents of tertiary amine catalyst.
. Use 001-0.1 equivalents. When using polycarboxylic acids, hydroxycarboxylic acids or aminocarboxylic acids, it is not necessary to add a polyol.

When the polyfunctional isocyanate is mainly reacted with a hydroxycarboxylic acid,
The amine should be used in a concentration of preferably 0.05 to 15% by weight, more preferably 0.5 to 10% by weight, based on the sum of the hydroxycarboxylic acid and the isocyanate.

In addition to the above pyridine and imidazole derivatives, other catalysts, especially organometallic compounds such as tin (II) salts of carboxylic acids, strong bases such as alkali metal hydroxides,
Alkali metal alcoholates and phenolates such as di-n-octyltin mercaptide, dibutyltin maleate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dichloride, dibutyltin bis-dodecylmercaptide, tin (II) acetate, tin (II) Ethylhexoate, tin (II) diethylhexoate, or lead phenylethyldithiocarbamate can also be added. If certain carboxylic acids are used, such as hydroxycarboxylic acids and aminocarboxylic acids, the organometallic catalyst can be used by itself. DABCO, TMR
-2 (Air Products) (a quaternary ammonium salt dissolved in ethyl glycol) can be mentioned as a trimerization catalyst.

[0037] Also suitable are aliphatic tertiary amines, especially those having a ring structure. Among the tertiary amines, those which additionally have an isocyanate-reactive group, in particular a hydroxyl group and / or an amino group, are suitable. Examples of such tertiary amines are dimethylmonoethanolamine, diethylmonoethanolamine, methylethylmonoethanolamine, triethanolamine, trimethanolamine, tripropanolamine, tributanolamine, trihexanolamine, tripentanolamine. , Tricyclohexanolamine, diethanolmethylamine, diethanolethylamine, diethanolpropylamine, diethanolbutylamine, diethanolpentylamine, diethanolhexylamine, diethanolcyclohexylamine, diethanolphenylamine and their ethoxylated and propoxylated products, diaza Bicyclooctane (Dabco), triethylamine, dimethylbenzylamine (Desmorapid DB, BAYER AG), bis Dimethylaminoethyl ether (Catalyst AI, manufactured by UCC), tetramethylguanidine, bis-dimethylaminomethylphenol, 2,2′-dimorpholine diethyl ether, 2- (2-dimethylaminoethoxy) -ethanol, 2-dimethylaminoethyl -3-dimethylaminopropyl ether, bis- (2-dimethylaminoethyl) -ether, N, N-dimethylpiperazine, N- (2-hydroxyethoxyethyl) -2-azanorbornane, Texacat DP-914 (Texace Chemical ), N, N, N, N-tetramethylbutane-1,3-diamine, N, N, N, N-tetramethylpropane-1,3-diamine and N, N, N, N-tetramethylhexane -1,6-diamine.

The catalyst can also be used in oligomerized or polymerized form, for example, as N-methylated polyethyleneimine.

The process for producing a rigid foam having a dense outer skin layer according to the invention can only be carried out in the presence of a minimum amount of water in the system. If the system is treated without pigments, the water content must be less than 0.2%. Pigment-containing or filler-containing binder mixtures are more sensitive to even traces of water. In such cases, the water content should preferably be less than 0.1%.

In addition to the amide groups from the carboxylic acid / isocyanate reaction, the polyurethane binder of the shaped bodies produced according to the invention also contains urethane groups from the reaction of isocyanates with polyols and / or polyhydroxycarboxylic acids. Also,
The moldings also contain very small amounts of urea groups from the reaction of isocyanates in the system with small amounts of water, polyamines or aminocarboxylic acids. The moldings additionally contain ester or ether groups from the polyols used.

Since the carboxylic acid / isocyanate reaction is mainly used to generate the blowing agent, the production of the foam of the present invention is almost independent of the water content in the fillers and pigments. Thus, the properties of the molding, in particular the pore structure, and therefore the density of the core material and the compactness of the skin layer, are very constant.

The amounts of the reactant polyisocyanates, polyols and carboxylic acids are chosen such that the polyisocyanates are used in excess. The equivalent ratio of NCO to OH groups is 5
From 1 to 1, preferably from 2: 1 to 1.2: 1, with an isocyanate excess of 5 to 50% being particularly preferred.

In one preferred embodiment of the shaped body produced according to the invention, the shaped body is colored. For that purpose, pigments are used. Preferably, the pigment is used in the form of a paste, that is, a pigment which is very finely dispersed in one of the reactants, generally a polyether polyol. An example of such a paste is Bayflex-F from Rheinchemie.
arbpasten (pigment paste).

It may be advantageous to use foam stabilizers known per se, for example siloxane hydroxyalkylene copolymer-based foam stabilizers, for example those of the type marketed by Goldschmidt under the trade name of Tegostab. Basically, other silicone-free stabilizers, such as LK-221, LK-223 and LK-443 (all Air-
Products) can also be used.

If each component of the binder system has a relatively high water content, it is advantageous to use a desiccant in the form of a molecular sieve paste. If the water content is very high, the components will have to be pre-dried.

A release agent known per se can be used for the mold in order to facilitate release of the molded article after the production. Examples of release agents are Acmos release agents for PUR (codenames: 35-5001, 39-4487, 37-3200 and 36-3182). However, in many cases, it will be sufficient to coat the mold with a fluoropolymer (Teflon® coating) as a release agent.

The moldings according to the invention are used in various industrial fields, preferably for the interiors of vehicles, in particular motor vehicles, trucks, motorhomes or trailer houses, rail vehicles, ships and aircraft, and buildings.

(Examples) The present invention will be specifically described by the following examples. Example 1 a) Polyol component% by weight Polypropylene glycol (Mn400) 18.5 Glycerol 14.1 Dipropylene glycol 32.6 Rapeseed oil fatty acid 21.2 Tegostab B8404 (Goldschmidt) 1.3 N-Methylimidazole 0.6 Dibutyltin dithio Glycolate 0.1 Na-Al silicate paste 5.8 Bayflex N (black paste) 5.8 b) Isocyanate component Diphenylmethane-4,4'-diisocyanate (crude MDI) 165

The polyol and the isocyanate component were mixed in the above ratio, and the resulting mixture was introduced into a mold coated with a release agent. The mold was designed to be closed by a cover. After 30 minutes, a foam having a dense skin layer firmly bonded to the cellular foam,
Removed from the mold. The outer skin layer has a thickness of up to about 1 mm and the molded body has a total weight of 140 kg /
It had a density of m ³ .

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Gilvia Sauf, Germany-Day 40472 Düsseldorf, Recklinghauser Straße 5 (72) Inventor Andreas Heidbleder Germany-Day 40593 Düsseldorf, Urdenbacher Dorfstr. 9 (72) Inventor Hans-Peter Kohlstadt Federal Republic of Germany Day 42549 Felbert, Wilchovstrasse 16a F-term (reference) 4J034 BA05 BA08 CA01 CA03 CA04 CA05 CA21 DB03 DB04 DB05 DC00 DF01 DF11 DF12 DF16 DF17 DG03 DG04 DG05 DG06 HA01 HA02 HA07 HA11 HC03 HC12 HC13 HC16 HC22 KA01 KD11 MA01 NA09 QB16 QC02 QD03 RA10 RA12

Claims (13)

[Claims] 1. reacting a) a polyisocyanate with b) a polyol, c) a carboxylic acid, d) a tertiary amine as a catalyst, and optionally another catalyst, e) optionally a pigment and a filler, A method for producing a rigid foamed plastic molded article having a dense skin layer, wherein the water content of b) to e) is less than 0.2% by weight. 2. The polyisocyanates used are difunctional, trifunctional or higher polyfunctional aliphatic, cycloaliphatic or aromatic isocyanates and / or oligomers containing free isocyanate groups prepared therefrom. The production method according to claim 1, which is a chemical product. 3. The polyisocyanate is a mixture of homologs, isomers and / or oligomers of diphenylmethane diisocyanate (MDI, as crude product)
The method according to claim 2, wherein 4. The method according to claim 1, wherein the polyol is selected from the group consisting of polyether diols, polyether triols, polyester diols, branched polyester polyols, natural triglycerides, and mixtures thereof. 5. The method according to claim 1, wherein the carboxylic acid is selected from the group consisting of natural fatty acids or derivatives thereof. 6. The method according to claim 1, wherein an amino-substituted pyridine and / or N-substituted imidazole is used as a catalyst together with an organometallic catalyst, if desired. 7. Airtightness wherein a) a polyol component, a carboxylic acid component, a catalyst and optionally a pigment and a filler are uniformly mixed, b) a polyisocyanate component is then added, and c) a mold release agent is applied as required. Introducing the resulting mixture into a mold, d) closing the mold and then reacting the polyisocyanate with a polyol and a carboxylic acid to form a foam; e) removing or demolding the molding from the mold The method according to claim 1. 8. Steps a) to d) are carried out at a temperature of 10 to 35 ° C., preferably at room temperature (
The method according to claim 7, which is performed at about 18 to 25 ° C). 9. The method according to claim 7, wherein the mold is cooled in step d). 10. A foamed polyurethane molded article having a dense skin layer produced by the production method according to claim 1. 11. The molded article according to claim 10, wherein the density of the cell core is 50 to 400 kg / m ³ . 12. The shaped body according to claim 10, wherein the density of the outer region is substantially the same as the density of the base polymer. 13. Use of a shaped body according to any of claims 10 to 12 for the interior of vehicles, especially cars, trucks, campers or trailer houses, rail vehicles, ships and aircraft, and buildings.