CA1093244A - Odorless catalysts for the synthesis of polyurethanes - Google Patents

Abstract

Abstract of the Disclosure The instant invention is directed to a process for the preparation of polyurethane resins by the reaction of compounds which contain at least two hydrogen atoms capable of reacting with isocyanates and having molecular weights of from 400 to 10,000, polyisocyanates and optionally chain lengthening agents, water and/or organic blowing agents in the presence of catalysts which contain tertiary nitrogen, the improvement wherein the catalyst used is a compound of the formula:

wherein n represents 2 or 3;
R represents a C1-C5 alkyl group;
Y represents R or ; and Z represents C2H5

Description

1093Z44 Mo-1620-G
LeA 16,442 ODORLESS CATALYSTS FOR THE
SYNTHESIS OF POLYURETHANES
Background of the Invention This application is a division of our copending application Serial No. 252,012 filed May 7, 1976.
Polyurethane foams with a wide variety of physical properties have long been produced on a technical scale by the isocyanate polyaddition process from compounds con-taining several active hydrogen atoms, and in particular 10 compounds containin~ hydroxyl and/or carboxyl group~s, poly-isocyanates and water and/or organic blowing agents with the optional addition of catalysts, emulsifiers and other additives [Angew. Chem. A, 59 (1948), page 257]. With suit-able choice of components, it i5 possible by this process 15 to obtain either elastic or rigid foams or any variations between these extremes.
Polyurethane foams are preferably produced by mixing the liquid components. The starting materials which are to be reacted together are either all mixed together 20 at once or an isocyanate prepolymer is first prepared from polyols and an excess of polyisocyanates, and this prepoly-mer is then foamed.
Tertiary amines have proved to be very suitable catalysts for the production of polyurethane foams, mainly 25 because they accelerate both the re~ction between the hydroxyl and/or carboxyl groups and the isocyanate groups and the reaction between water and isocyanate groups. In the one-shot process, the velocities of these reactions, which take place side by side, may be adjusted to each 30 other.

LeA 16,442 Additional cross-linking reactions accompany the foaming process to form allophanate, biuret and cy~nurate structures. In view of the complexity of the reactions, the catalysts must be suitably chosen to ensure that, on S the o~e hand, the various reactions will be synchronized and that, on the other hand, the catalyst will not be fixed too early in the process by being incorporated in the foam and will not subsequently accelerate hydrolytic degradation of the finished foam. Furthermore, the unpleasant odor of many of the tertiary amines frequently used in practice is a disadvantage if they are to be usecl in the production of foams.

In U.S. Patent 3,243,389, and German Offenlegungs-schrift 2,354,952, tertiary amines which contain Zerewitinoff-active hydrogen atoms are described as catalysts for isocya-nate polyaddition reactions. Howe~er, these compounds are gradually built into the polymer structure in the course of the foaming process. They are therefore no longer available at sufficiently high concentrations in the final stages of the reactions, especially in the marginal zone of the foams.
This insufficiency adversely affects the surface characteris-tics and the gelling properties of the polyurethane foams.

Description of the Invention The present invention relates to a process for the production of polyurethane resins, and preferably polyurethane foams, by the reaction of ta) compounds which contain at least two hydrogen atoms capable of reacting with isocyanates and which have molecular weights of from 400 to 10,000, (b) polyisocyanates,and (c) optionally, chain LeA 16,442 -2-lOg3Z44 lengthening agents, water and/or organic blowing agents, in the presence of catalysts which contain tertiary nitrogen atoms, which process is characterized in that the catalysts used are compounds of the formula:
R /R
~N-~CH2)n-N- (CH2)n-N
Y Z R

wherein n which may be the same or different represents 2 or 3;
R which may be the same or different, represents a Cl-C5 alkyl group;
Y represents R or -(CH2)n-N ~R ; and Z represents C2H5-0-C-.
o LeA 16,442~Ca-DIV -3-1~

~ 1093244 The catalysts used according to the present invention may be prepared in a known manner by the reaction of known amines corresponding to the following general formula:

N-(CH2)n / NH

wherein n, R and Y are as defined above; with acylating agents, such as carbon monoxide, carboxylic acids, acid amides, acid esters, acid anhydrides, chlorocarbonic acid esters, dialkyl or diaryl carbonates or dicarbonic acid diesters, and the like.

The catalysts used according to the present invention are distinguished by their surprisingly powerful accelerating effect on the foaming process and by the fact that foams produced therefrom are odorless and have a surprisingly high resistance to hydrolysis. The compounds according to the present invention do not contain any active hydrogen atoms and therefore are not built into the polyurethane via main valency bonds, but remain active during the entire foaming process. The following is a typical example of the catalysts used according to the present invention:

\

N- (CH2)3 \h~

N- (CH2)3 LeA 16,442-Ca-DTV -4-lQ93Z44 The catalysts used according to the present invention are generally used in quantities of from 0.01 to 5 percent by weight and preferably from 0.1 to 1 percent, by weight, based on the foamable reaction mixture.

The starting components to be used according to the present invention include compounds containing at least two hydrogen atoms capable of reacting with isocyanates and generally having molecular weights of from 400 to 10,000.
These not only include compounds containing amino groups, thiol groups or carboxyl groups, but also include polyhydroxyl compounds (which are preferable) and, in particular compounds containing from 2 to 8 hydroxyl groups and especially those having molecular weights of from 800 to 10,000 and most preferably from 1000 to 6000. ~xamples of such polyhydroxyl materials include polyesters, polyethers, polythioethers, polyacetals, polycarbonates and polyester amides containing at least 2, generally from 2 to 8, and preferably from 2 to 4 hydroxyl groups, of the type generally known for the production of homogeneous and cellular polyurethanes.

Suitable polyesters with hydroxyl groups include, the reaction products of polyhydric, (preferably dihydric) LeA 16,442-~a-DIV -5-alcohols with the optional addition of trihydric alcohols, and polybasic (preferably dibasic) carboxylic acids.
Instead of free polycarboxylic acids, the corresponding polycarboxylic acid anhydrides or esters of lower alcohols or mixtures thereof may be used for preparing the poly-esters. The polycarboxylic acids may be aliphatic, cyclo-aliphatic, aromatic and/or heterocyclic and may be sub-stituted, e.g. by halogen atoms, and/or be u~saturated.
The following are mentioned as examples: succinic acid;
adipic acid; suberic acid; azelaic acid; sebacic acid;
phthalic acid; isophthalic acid; trimellitic acid; phthalic acid anhydride; tetrahydrophthalic acid anhydride; hexa-hydrophthalic acid anhydride; tetrachlorophthalic 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 mixed with monomeric fatty acids; dimethyltere-phthalate: bis-glycol terephthalate; and the like. The following are examples of suitable polyhydric alcohols:
ethylene glycol; propylene-1,2- and -1,3-glycol; butylene-1,4- and 2,3-glycol; hexane-1,6-diol; octane-1,8-diol;
neop~ntyl glycol; cyclohexane dimethanol (1,4-bis-hydroxy-methylcyclohexane); 2-methyl-propanecliol-(1,3~; glycerol;
trimethylolpropane; hexane-1,2,6-triol; butane-1,2,4-triol;
trimeth~lolethane; pentaerythritol; quinitol; mannitol;
sorbito:L; methyl glycoside; diethylene glycol; triethylene glycol; tetraethylene glycol; polyethylene glycols;
dipropylene glycol; polypropylene glycols; dibutylene gly-col; polybutylene glycols; and the like. The polyesters may also contain carboxyl end groups. Polyesters of LeA 16,442 -~-A~ ~

lactones; such as ~-caprolactone, or hydroxycarboxylic acids, e.~. ~-hydroxycaproic acid, may also be used.

The polyethers used according to the present invention, which contain at least two, generally from 2 to 8 and preferably 2 or 3 hydroxyl groups are also known and may be prepared, for example, by the polymerization of epoxides, such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichloro-hydrin, either alone for example in the presence of BF3, or by the addition of these epoxides, if desired as mix-tures or successi~ely, to starting components which contain reactive hydrogenatoms, such as water, alcohols, or amines.
Examples of alcohols and amines include: ethylene glycol, propylene-1,3- or -1,2-glycol, trimethylolpropane, 4,4'-dihydroxydiphenylpropane, aniline, ammonia, ethanolamine and ethylene diamine. Sucrose polyethers such as those described in German Auslegeschriften 1,176,358 and 1,064,938, may also be used according to the present invention. In many cases, it is preferred to use polyethers which contain predominant amounts of primary OH groups (up to 90~ by weight based on all the OH groups present in the polyether).
Polyethers modified by vinyl polymers are also suitable, for example, the compounds obtained by the polymerization of styrene or acrylonitrile in the presence of polyethers (U.S. Patents 3,383,351; 3,304,273; 3,523,0g3 and 3,110,695 and German Patent 1,152,536). Polybutadienes containing OH groups may also be used.

Suitable polythioethers include, in particular, the condensation products obtained by the condensation of LeA 16,442 ~ -o ~

thiodiglycol on its own and/or with other glycols, dicar-boxylic acids, formaldehyde, aminocarboxylic acids or amino-alcohols. The products obtained are polythio mi~ed ethers, polythio ether esters or polythioether ester amides, depending on the cocomponents.

Suitable polyacetals include, for example, the compounds prepared from glycols (such as diethylene glycol, triethylene glycol, 4,4'-dioxethoxy-diphenyldimethylmethane and hexanediol) with formaldehyde. Polyacetals suitable for the purpose of the present invention may also be pre-pared by the polymerization of cyclic acetals.

Suitable polycarbonates with hydroxyl groups are known and include those which may be obtained by the reac-tion of diols (such as propane-1,3-dioll butane-1,4-diol and/or hexane-1,6-diol, diethylene glycol, triethylene glycol or tetraethylene glycol) with diarylcarbonates (e.g.
diphenylcarbonate) or phosgene.

The polyester amides and polyamides which may be used include, for example, the predominantly linear conden-sates obtained from polybasic saturated and unsaturated carboxylic acids or the anhydrides thereof and polyvalent saturated and un,afurated amino alcohols, diamines, poly-amines and mixtures thereof.

Polyhydroxyl -ompounds already containing ure-thane groups or urea groups and modified or unmodified natural polyols, such as castor oil, carbohydrates or starch, may also be used. Addition products of alkylene oxides and phenol-formaldehyde resins or alkylene oxides and LeA 16,442 -~

urea-formaldehyde resins are also suitable for the purpose of the present invention.

Representatives of these compounds which are to be used according to the present invention are known and have been described, for example, in High Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology", by Saunders-Frisch, Interscience Publishers, New York, Lond~n, Volume I, 1962, pages 32 - 42 and pages 44 - 54 and Vol. II, 1964, pages 5 - 6 and 198 - 199 and in Kunststoff-Handbuch, Vo]ume VII, Vieweg-Hochtlen, Carl-Hanser-Verlag, Munich, 1966, on pages 45 to 71.

One may, of course, also use mixtures of the above-mentioned compounds which have molecular weights of from 400 to 10,000 and contain at least two hydrogen atoms capable of reacting with isocyanates, such as mixtures of polyethers and polyesters.

Starting components which may optionally also be used according to the present invention include compounds having molecular weights of from 32 to 400 which contain at least two hydrogen atoms capable of reacting with isocya-nates. These also are compounds which contain hydroxyl groups and/or amino groups and/or thiol groups and/or carboxyl groups and preferably hydroxyl groups and/or amino groups, and they serve as chain lengthening agents or cross-linking agents. They generally contain from 2 to 8 hydrogen atoms which are reactive with isocyanates, and preferably contain 2 or 3 hydrogen atoms. The following are mentioned as examples of such compounds: ethylene glycol, LeA 16,442 A~ ~

~093Z4g propylene-1,2- and -1,3-glycol, butylene-1,4- and -2,3-glycol, pentane-1,5-diol, hexane-1,6-diol, octane-1,8-diol, neopentyl glycol, l,4-bis-hydroxymethylcyclohexane,

2-methyl-1,3-propanediol, glycerol, trimethylolpropane, hexane-1,2,6-triol, trimethylolethane, pentaerythritol, quinitol, mannitol and sorbitol, diethylene glycol, tri-ethylene glycol, tetraethylene glycol, polyethylene glycols having a molecular weight of up to 400, dipropy~ene glycol, polypropylene glycols having a molecular weight of up to 400, dibutylene glycol, polybutylene glycols having a molecular we.ight of up to 400, 4,4'-dihydroxydiphenyl propane, di-hydroxymethyl-hydroquinone, ethanolamine, diethanolamine, triethanolamine, 3-aminopropanol, ethylene diamine, 1,3-diaminopropane, 1-mercapto-3-aminopropane, 4-hydroxy- or 4-amino-phthalic acid, succinic acid, adipic acid, hydrazine, N,N'-dimethylhydrazine and 4,4'-diamino-diphenylmethane.

Here again, mixtures of various compounds which have molecular weights of from 32 to 400 and contain at least two hydrogen atoms capable of reacting with isocya-nates may be used.

The starting isocyanates used according to the present invention include aliphatic, cycloaliphatic, arali-phatic, aromatic and heterocyclic polyisocyanates, such as those described, for example, by W. ~,iefken in Justus Liebigs Annalen der Chemie, 562, pages 75 to 136. Examples include ethylene diisocyanatei tetramethylene-1,4-diisocyanate; hexamethylene-1,6-diisocyanate; dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate; cyclohexane-LeA 16,442 -I~-A ~o 1,3- and -1,4-di.isocyanate and mixtures of these isomers;
l-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (German Auslegeschrift 1,202,785, U.S. Patent 3,401,190);
hexahydrotolylene-2,4- and -2,6-diisocyanate and mixtures of these isomers; hexahydrophenylene-1,3- and/or -1,4-diisocyanate; perhydrodiphenylmethane-2,4'- and/or 4,4'-diisocyanate; phenylene-1,3- and -1,4-diisocyanate;
tolylene-2,4- and -2,6-diisocyanate and mixture~ of these isomers; diphenylmethane-2,4'- and/or -4,4'-diisocyanate;
naphthylene-1,5-diisocyanate; triphenylmethane-4,4',4"-triisocyanate; polyphenyl-polymethylene polyisocyanates, which may be obtained by aniline-formaldehyde condensati.on followed by phosgenation and which have been described, for example, in British Patents 874,430 and 848,671;
lS _- and p-isocyanatophenyl-sulphonylisocyanates as described in U.S. Patent 3,454,606; perchlorinated aryl polyisocyanates, such as the compounds described in U.S. Patent 3,277,138;
polyisocyanates containing carbodiimide groups as described in U.S. Patent 3,152,162; the diisocyanates described in U.S. Patent 3,492,330; polyisocyanates containing allopha-nate groups as described, for exampl.e, in British Patent 994,890, Belgian Patent 761,626 and published Dutch Patent Application No. 7,102,524; polyisocyanates containing iso-cyanurate groups as described, for example, in U.S. Patent

3,001,973, in German Patents 1,022,789; 1,222,0fi7 and 1,027,,94 and in German Offenlegungcschriften 1,929,034 and 2,004,048; polyisocyanates containinq urethane groups as described in Belgian Patent 752,261 or in U.S. Patent 3,394,164; polyisocyanates containirq acylated urea groups as described in German Patent No. 1,210,/78 ~ol~isocyanates LeA 16,442 -lA-~093244 containing biuret groups as described in U.S. Patents 3,124,605 and 3,201,372 and in British Patent 889,050;
polyisocyanates prepared by telomerization reactions as described in U.S. Patent 3,644,106; polyisocyanates con-taining ester groups, such as those described in BritishPatents ~65,474 and 1,072,956, in U.S. Patent 3,567,763 and in German Patent 1,231,688; reaction products of the above-mentioned isocyanates with acetals as described in German Patent No. 1,072,385; and polyisocyanates containing polymeric fatty acid residues as described in U.S. Patent 3,455,883.

The distillation residues obtained from commercial production of isocyanates and still containing isocyanate groups may also be used, if desired as solutions in one or more of the above-mentioned polyisocyanates. Mixtures of the above-mentioned polyisocyanates may also be used.

As a rule, it is particularly preferred to use readily available polyisocyanates such as tolylene-2,4-and -2,6-diisocyanate and mixtures of these isomers ("TDI");
polyphenyl-polymethylene polyisocyanates which may be pre-pared by aniline-formaldehyde condensation followed by phosgenation ("crude MDI"); and, polyisocyanate containing carbod imide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups ("modi~ied polyisocyanates").

According to the present invention, water and/or readily volatile organic substances may be added as blowing agents. Suitable organic blowing agent1 inclu-le: acetone, LeA 16,442 ~1 ..

ethyl acetate; halogenated alkanes, such as methylene chloride, chloroform, ethylidene chloride, vinylldene~
chloride, monofluorotrichloromethane, chlorodifluoro-methane and dichlorodifluoromethane; butane; hexane;
heptane; diethyl ether; and the like. Compounds which decompose at temperatures above room temperature to liberate gases, such as nitrogen, may also act as blowing agents. Examples include azo compounds, such a~s azoiso-butyric acid nitrile. Other examples of blowing agents and details concerning the use of blowing agents may be found in Kunststoff-Handbuch, Volume VII, published by Vieweg and ~ochtlen, Carl-Hanser-Verlag, Munich 1966, on pages 108 and 109, 453 to 45S and 507 to 510.

Known catalysts may, of course, be used in addi-tion to the compounds according to the present invention.

Surface active additives, such as emulsifiers andfoam stabilizers, may also be used according to the present invention. Suitable emulsifiers are, for example, the sodium salts of castor oil sulphonates or salts of fatty acids with amines, such dS oleic acid diethylamine or stearic acid diethanolamine. Alkali metal or ammonium salts of sulphonic acids, such as dodecylbenzenesulphonic acid or dinaphthylmethane disulphonic acid, or of fatty acids, such as ricinoleic acid, or of polymeric fatty acids, may also be used as surface active additives.

Particularly suitable foam stabilizers are the polyether siloxanes, especially those which are water-soluble. The structure of these compounds is generally such that a copolymer of ethylene oxide and propylene LeA 16,442 oxide is connected to a polydimethylsiloxane group. Foam stabilizers of this type have be~n described in U.S. Patents 2,834,748; 2,917,480 and 3,629,308.

According to the present invention, the following substances may also be added: reaction retarders, e.g.
compounds which are acid in reaction, such as hydrochloric acid or organic acid halides; known cell regulators such as paraffins or fatty alcohols or dimethylpolysiloxanes;
pigments or dyes; flame retarding agents, such as tris-chloroethylphosphate, tricresylphosphate or ammonium phc,s-phate or polyphosphate; stabilizers against ageing and weathering; plasticizers; fungistatic and bacteriostatic substances; and fillers, such as barium sulphate, kieselguhr, carbon black or whiting.

Other examples of surface active additives, foam stabilizers, cell regulators, reaction retarders, stabilizers, flame retarding substances, plasticizers, dyes, fillers and ungistatic and bacteriostatic substances which may also be used according to the present invention, as well as methods of using them and their mode of action have been described in Kunststoff-Handbuch, Volume VII, published by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich 1966, on pages :L03 to 113.

According to the present invention, the starting materi~lls are reacted together by the known one-shot pro-cess, prepolymer process or semi-prepolymer process, in mahy cases using mechanical devices, such as those described in U.S. Patent 2,764,565. Details concerning processing apparatus which may also be used according to the present LeA 16,442 -~

invention may be found in Kunststoff-Handbuch, Volume VII, published by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich, 1966, pages 121 to 205.

According to the present invention, production of foams is in many cases carried out by the process of foam-ing in the mold. In this process, the reaction mixture is introduced into a mold made of a metal, (e.g. aluminum) or of plastic (e.g. an epoxide resin) in which it foams ~:o form the shaped product. This process of foaming in the mold may be carried out to produce a product with a cellular structure on its surface or it may be carried out so that the product has a compact skin and cellular core. Accord-ing to the present invention, either result may be achieved by either introducing just sufficient foamable reaction mixture into the mold or by introducing a larger quantity of reaction mixture than is necessary for filling the interior of the mold with foam. The latter method is known as "overcharging". A procedure for carrying it out has been disclosed, for example, in U.S. Patents 1,178,490 and 3,182,104.

The process of foaming in the mold is in many cases carried O-lt with the aid of so-called "external mold release agents" which are known, such as silicon oils, but so-called "internal mold release agents" may also be used, if desired as mixtures with external mold release agents, ~or example, those disclosed in German Offenlegungsschriften 2,121,670 and 2,307,589.

Cold setting foams may also be produced according to the present invention (see, e.g., British Patent No.
1,162,517, German Offenlegungsschrift No. 2,153,086).
A LeA 16,442 -~r ~093244 The foams may, of course, be produced by a process of block foaming or by the known double conveyor belt process.

The products of the process are flexible, semi-flexible or hard foam resins which contain urethane groups.They are used for the conventional purposes of such pro-ducts as mattresses and upholstery material for the furni-ture and motor car industry, for the manufacture of pro-tective padding of the type used in the motor car industry and as insulating materials in general and for insulation against cold or heat in particular in the building indus-try or the refrigeration industry.

The following Examples illustrate the invention without restricting it.

(Unless otherwise indicated, the quantities given are parts by weight or percentages by weight).

LeA 16,442 :~093244 Example 1 178.2 g (1.1 mol) of diethyldicarbonate are added to 187 g of N,N-bis-(3-dimethylamino-n-propyl)-amine (degree of purity 87.6%) in an apparatus equipped with stirrer, condenser, thermometer and dropping funnel in the course of 22 minutes while the temperature is maintained at 40C by means of an ice bath. Evolution of carbon dioxide sets in when about one third of the acylating agent has béen added and it is completed quantitatively within 12 minutes. Stirring is then continued for 30 minutes at 40C.
35 g of ethanol are distilled off in a water-jet vacuum and 227 g at 0.2 Torr and a temperature of from 95 to 105C.
On redistillation, this distillate yields 183 g of purest N,N-bis-(dimethyl-amino-n-propyl)-carbamic acid ethyl ester:

N-(CH2)3 CH3 N- ~

CH3 / \ C2H5 N-(CH2)3 (= 80.7% of the theoretical yield).
The structure of the compound is confirmed by the IR and NMR spectra and by elemental analysis.

LeA 16,442-Ca-DIV -17-10~3Z~4 Example 2 50 parts, by weight, of a polypropylene glycol wh-ch has been started on trimethylolpropane and modified with ethylene oxide to result in 60% of primary hydroxyl end groups and an OH number of 28, 50 parts, by weight, of a polypropyleneglycol which has been started on trimethylol-propane and modified with ethylene oxide to result in 70%
of primary hydroxyl end groups and which has been grafted with acrylonitrile and styrene in proportions of 60:40 and has an OH number of 28, 2.7 parts, by weight, of water, 1.0 part, by weight, of siloxane 1 from German Offenlegungs-schrift 2,221,811, 0.1 part, by weight, of a polyether polysiloxane marketed by TH. Goldschmidt AG, Essen BRD, under the trade name "Tegostab B 2909", 2.0 parts, by weight, of the catalyst according to Example 1, 34.0 parts, by weight, of a tolylene diisocyanate mixture (2,4- and 2,6-isomer in proportions, by weight, of 80:20) and 20.0 parts, by weight, of a polyphenyl-polymethylene polyisGcyanate which has been obtained by aniline-formaldehyde condensation followed by phosgenation are reacted together in a mold.

A molded foam with the following mechanical proper-ties is obtained:
Gross density DIN 53420 (kg/m3) 42 Tension test DIN 53571 (KPa) 160 Elongation at break DIN 53571 (%) liO
Compression test DIN 53577 (KPa) 3.9 LeA 16,552-Ca-DIV -18-_ ~0~3244 Example 3 90 g of a polyether having a molecular weight of 4800 which has been prepared by chemical addition of propylene oxide (87%) and ethylene oxide (13%) to trimethylol-propane are mixed with 0.5 g of the compound according to Example 1, 5 g of triethanolamine, 2 g of tall oil and 2.5 g of water.

This mixture and 60 g of a polyphenylpolymethylene polyisocyanate which has been obtained by phosgenation of an aniline-formaldehyde condensate and has an isocyanate content of 31% are vigorously mixed in a mixing head and left to foam in a mold. The resulting foam has the following mechanical properties;

Density (kg/m3) : 61 Tensile strength (KPa) : 155 Elongation at break (~ : 60 Compression resistance (KPa) at 40~ compression : 16.3 Residual pressure deformation (%) at 50% compression : 7 LeA 16,442-Ca-DIV -19-

Claims (2)

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

1. In a process for the preparation of polyurethane resins by the reaction of compounds which contain at least two hydrogen atoms capable of reacting with isocyanates and having molecular weights of from 400 to 10,000, polyisocyanates and optionally chain lengthening agents, water and/or organic blowing agents in the presence of catalysts which contain tertiary nitrogen, the improvement wherein the catalyst used is a compound of the formula:

wherein n represents 2 or 3;
R represents a C1-C5 alkyl group;
Y represents R or ; and Z represents .

2. A process according to Claim 1, in which each n is 3, Y is R and each R is a methyl group.

LeA 16,442-Ca