CA2137540A1 - Preparation of compact or cellular polyurethanes, polyisocyanate compositions containing urethane groups which can be used for this purpose, and their use - Google Patents

Abstract

The invention relates to a process for the preparation of compact or cellular polyurethanes by reacting relatively high-molecular-weight polyhydroxyl compounds with a liquid polyisocyanate com-position containing urethane groups in the presence or absence of chain extenders and/or crosslinking agents, the polyisocyanate composition being obtainable from mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates and linear, branched or cyclic, saturated or olefinically unsatur-ated, low-molecular-weight monoalcohols, to the liquid polyiso-cyanate compositions containing urethane groups which can be used for this purpose, and to their use for the preparation of prefer-ably highly crosslinked polyurethanes, in particular rigid PU
(molded) foams.

Description

`` ` 21375~0 .~

, _ , .
Preparation of compact or cellular polyurethanes, polyisocyanate compositions contA;ning urethane groups which can be used for this purpose, and their use The invention relates to a process for the preparation of compact or preferably cellular polyurethanes, in particular rigid poly-urethane (PU) foams, by reacting relatively high-molecular-weight polyhydroxyl compounds (a) with a liquid polyisocyanate composi-lO tion (b) contA; n; ~g bonded urethane groups in the presence orabsence of chain extenders and/or crosslinking agents (c), where this polyisocyanate composition (b) is itself obtA;nAhle by reacting a mixture of diphenylmethane Ai isocyanates (MDI) and polyphenylpolymethylene polyisocyanates, known as crude MDI, and 15 linear, branched or cyclic, ~aturated or oiefinically unsatura-ted, low-molecular-weight monoalcohols, expediently having 1 to 6 carbon atoms, to novel polyisocyanate compositions (b) of this type, and to their use for the preparation of preferably highly crosslinked polyurethanes, in particular rigid polyurethane 20 foams.
The preparation of compact or cellular polyurethanes, also abbreviated to PU below, preferably soft and elastic, semirigid or rigid polyurethane foams, by reacting relatively high-molecu-25 lar-weight polyhydroxyl compounds, preferably polyester- or in particular polyether-polyols, with organic and/or modified organ-ic polyisocyanates in the presence or absence of chain extenders and/or crosslinking agents is known and is described in numerous patents and other publications.
By way of example, reference may be made to Runststoff-Handbuch, Volume VII, Polyurethanes, Carl Hanser Verlag, Munich, Vienna, 1st Edition, 1966, edited by Dr. R. Vieweg and Dr. A. ~ochtlen, and 2nd Edition, 1983, edited by Dr. G. Oertel.
Compact and cellular polyurethanes are usually prepared by the two-component process, in which a component A cont~in;ng the rel-atively high-molecular-weight polyhydroxyl compounds, if desired chain extenders, crosslinking agents, blowing agents, catalysts, 40 auxiliaries and/or additives, and component B, which usually com-prises organic and/or modified organic polyisocyanates, are mixed vigorously and brought to reaction. Although the t-~ c~mponent process i8 widely used in industry, it still has deficiencies.
For example, an evident problem is the poor compati hi lity of the 45 polyhydroxyl component (A) and the polyisocyanate cnmronent (B), which occurs, in particular, in the reaction of highly functional polyether-polyols based on at least trifunctional initiator ~1375~0 molecules, for example glycerol, trimethylolpropane, pentaery_ thritol, sorbitol and sucrose, with crude MDI having a function-ality of greater than 2.5. This therefore requires longer stir-ring times before compatibility of the starting components i8 5 achieved owing to commencement of urethane formation or special mixing techniques, by means of which the sometimes coarse disper-sions of one ~tarting component in the other can be converted into fine emulsions. The polyurethane formation thus takes place at the beginning of a reaction from 2 heterogeneous phases to a 10 certain conversion, presumably due to the oligomers which become effective solubilizers, from which fine emulsions and/or true solutions are formed. This phase change is evident, for example, from the conversion of the yellow-brown, cloudy di~persions or emulsions into a dark-brown, clear solution.
There i8 thus a close relationship between the quality of the compact or cellular polyurethanes formed and the starting materi-als used, their physical and chemical properties, the mixing technigue used and the reaction mixture obtained, which can be in 20 the form, for example, of a coarse dispersion, fine emulsion or clear solution, or anywhere in between.

There has therefore been no lack of attempts to improve the mechanical properties of polyurethanes by a ~uitable choice of 25 starting materials or by modification thereof in order largely to overcome the abovementioned disadvantages.
Reference may be made, for example, to processes for the lique-faction of MDI isomer mixtures or processes for improving the 30 low-temperature shelf life of crude MDI, in particular crude MDI
having a relatively high content of MDI isomers, by partial reac-tion of the polyisocyanates with polyhydric alcohols.
According to DE-C-16 18 3~0 (US-A-3,644,457), this is achieved by 35 reacting 1 mol of 4,4'- and/or 2,4'-MDI with from 0.1 to 0.3 mol of tri-1,2-oxypropylene glycol and/or poly-1,2-oxypropylene gly-col having a molecular weight of up to 700.

According to G3-A-1,369,334, the modification is carried out in 40 two reaction steps and the modifier used is dipropylene glycol or polyoxypropylene glycol having a molecular weight of less than 2000.

DE-A-29 13 126 (U~-A-4,229,347) describes MDI compositions in 45 which from 10 to 35~ by weight of the isocyanate groups are reacted with a mixture of at least 3 alkylene glycols, one of Z1375~
.

these glycols being di-, tri- or a relatively high-molecular-weight polyoxypropylene glycol.

By contrast, the modifiers used in DE-A-24 04 166 5 (GB-A-1,430,455) are mixtures of a polyoxyethylene glycol or polyoxyethylene glycol mixture having a mean molecular weight of less than 650 and at least one alkylene glycol cont~;n;ng at least 3 carbon atoms.
10 DE-A-23 46 996 (GB-A-1,377,679) relates to MDI compositions in which from 10 to 35~ by weight of the isocyanate groups have been reacted with a commercially available polyoxyethylene glycol.
EP-A-10 850 uses a crude MDI composition comprising a mixture of 15 crude MDI with an MDI which has been modified by means of poly-oxyalkylene polyols having a functionality of from 2 to 3 based on polyoxypropylene-polyol and, if desired, polyoxyethylene-polyol having a molecular weight of from 750 to 3000.
20 According to DE-B-27 37 338 (UA-A 4,055,548), a liguid crude MDI
composition i8 obtained by combining crude MDI with a polyoxy-ethylene glycol having a mean molecular weight of from 200 to 600.

25 In DE-B-26 24 526 (GB-A-1,550,325), a crude MDI which has been prepared by a special process and contains from 88 to g5% by weight of MDI is reacted with polyoxypropylene glycol having a molecular weight in the range from 134 to 700.

30 DE-A-25 13 796 (GB-A-1,444,192) and DE-A-25 13 793 (GB-A-1,450,660) relate to crude MDI compositions in which the crude MDI has been modified by means of alkylene glycols or poly-oxyalkylene glycols in certain amounts.

35 Although said alkylene glycols or polyoxyalkylene glycols cause liquefaction of the 4,4'- or 2,4'-MDI isomers, which melt at 42 and 28 C respectively, it i8 disadvantageous that the polyisocyan-ate c~mpositions exhibit crystalline deposits after extended storage at temperatures around 10 C.
It is furthermore known that flexible PU foams can be produced using, as the polyisocyanate component, crude MDI compositions which have been modified by means of urethane groups.

45 In EP-A-22 617, this i8 achieved by reacting a difunctional to trifunctional polyoxypropylene-polyoxyethylene-polyol cont~i~;ng at least 50S by weight of the polymerized oxyethylene groups with .

a mixture of MDI isomer6 and sub~equently diluting the resultant guasi-prepolymer with crude MDI. A particular di9advantage of the PU foams described iB their low tensile ~trength and tear propa- -gation ~trength.

Polyisocyanate mixtures based on crude MDI which have been modi-fied by means of urethane groups and contain from 12 to 30% by weight of NC0 groups are also described in EP-B-0 111 121 (US-A-4,478,960). The MDI or crude MDI is modified using a poly-10 oxypropylene-polyoxyethylene-polyol having a functionality of from 2 to 4, a hydroxyl number of from 10 to 65 and a content of polymerized ethylene oxide units of from 5 to 30~ by weight.
Using these polyisocyanate mixtures which have been modified by means of urethane groups, ~U foams having increased elongation at 15 break, improved tensile strength and tear propagation strength can be produced.
However, the modification of the MDI isomer mixtures and rela-tively highly functional crude MDI by means of low-molecular-20 weight alkanediols and/or oxyalkylene glycol~ and/or relativelyhigh-molecular-weight, at least difunctional polyoxyalkylene-polyols is severely restricted, since even partial reaction of these 6tarting materials causes a very considerable increase in the functionality and thus in the viscosity of the resultant 25 polyisocyanate c~mrositions which have been modified by means of urethane groups. The high viscosities of crude NDI compositions of this type mean that they can only be processed with difficulty in conventional metering and foAm;ng equipment.
30 EP-A-0 320 134 states that the compatibility of the polyhydroxyl component (A) and the polyisocyanate component (B) can be im-proved by using polyisocyanate compositions having a functional-ity of at least 2.3 which comprise, based on the total weight, from 30 to 45~ by weight of MDI, from 28 to 67~ by weight of 35 polyphenylpolymethylene polyisocyanates contA;ning more than 2 isocyanate groups and from 3 to 27% by weight of a prepolymer prepared from MDI and a compound contAi ni ng at least 2 radicals which react with isocyanate groups and having a molecular weight of less than 1000. Disadvantages of theQe MDI compositions are 40 their two-step preparation method and, as a consequence of the increase in viscosity, the fact that compounds ContA; n; ng at least 2 radicals which react with isocyanate groups can only be used in limited amounts.

45 In order to overcome these disadvantages, DE-A-39 28 330 (US-A-5,028,636) reacts MDI or crude MDI having an MDI content of at least 30~ by weight with substoichiometric amounts of at least 1375q~

one alkoxylation product obtained using monoalcohols having 8 to 24 carbon atoms, primary amines or organic carboxylic acids as initiator molecules. EP-A-031 650 describes the modification of MDI mixtures contA;ning at least 15% by weight of 2,4'-MDI by 5 means of a monohydric alcohol having 9 to 16 carbon atoms or a polyoxyalkylene alcohol contA; n; ng 1 to 58 alkylene oxide groups and an alkyl terminal group having 1 to 12 carbon atoms. Through incorporation of the relatively high-molecular-weight alkyl radi-cals or polyoxyalkylene groups into the crude MDI or MDI, the 10 adducts obtained are said to be effective in the form of an "internaln emulsifier and to improve the miscibility of polyoxy-alkylene-polyols and crude MDI compositions. However, these meas-ures do not adequately solve the main problem of incompatibility or immiscibility of highly functional, hydrophilic polyhydroxyl 15 compounds, in particular polyoxyalkylene-polyols, and hydrophobic polyisocyanates, in particular crude MDI.
It is an object of the present invention to improve the mechani-cal properties of compact snd cellular polyurethanes, preferably 20 rigid PU foams. To this end, it i8 an object to use measures which can readily be carried out industrially to improve the mis-cibility of the starting materials, preferably the miscibility of the polyhydroxyl component (A) and the polyisocyanate compo-nent (B).
We have found that, surprisingly, this object is achieved by increasing the content of urethane groups in the polyisocyanate composition, which allows the compatibility of polyisocyanate compositions based on MDI with polyhydroxyl compounds, preferably 30 polyether-polyols, to be improved, ~o that, for example, directly after c~mpo~ents (A) and (~) have been mixed, true solutions or fine emulsions are formed.
The present invention accordingly provides a process for the 35 preparation of compact or preferably cellular polyurethanes, in particular rigid polyurethane foams, by reacting a) relatively high-molecular-weight polyhydroxyl compounds con-tAin;ng at least two reactive hydrogen atoms with b) liquid, diphenylmethane diisocyanate-based polyisocyanate compositions contA;ning bonded urethane groups, in the presence or absence of c) chain extenders and/or crossl; nki ng agents, ` ~1375~

. . . --d) blowing agents, e) catalysts and 5 f) auxiliaries, wherein the polyisocyanate compositions (b) used are obtainable by reacting mixtures of diphenylmethane diisocyanates and poly-phenylpolymethylene polyisocyanates with a substoichiometric 10 amount of at least one linear, branched or cyclic, saturated or olefinically unsaturated, low-molecular-weight monoalcohol.
The present invention furthermore provides the liquid polyisocya-nate compositions contA;ning urethane groups which can be used 15 according to the invention, which are obtainable by reacting mix-tures of diphenylmethane diisocyanates and polyphenylpoly-methylene polyisocyanates with a substoichiometric amount of at least one linear, branched or cyclic, saturated or olefinically unsaturated, low-molecular-weight monoalcohol having 1 to 6 car-20 bon atoms as claimed in claim 6, and the use of these liquidpolyisocyanate compositions cont~ni~g urethane groups for the production of, in particular, rigid polyurethane foams as claimed in claim 10.
25 Partial reaction of crude MDI with the low-molecular-weight, monohydric alcohols allows the urethane group content, which is advantageously greater than or equal to 0.1 mol~kg of polyisocya-nate composition, to be increased as desired in accordance with requirements, for example its compatibility depending on the type 30 of polyhydroxyl component (A), without any excessive increase in the viscosity of the polyisocyanate composition (b) and thus without making its processibility more difficult or even impossi-ble. When the monohydric alcohols suitable according to the invention are used to form the urethane groups, crude MDI com-35 positions having a content of urethane groups of, for example,0.4 mol/kg are of low viscosity and preferably give clear solu-tions on mixing with the polyhydroxyl component (A), while crude MDI compo6itions having the 6ame urethane group content, but pre-pared using dihydric and/or trihydric alcohols are no longer pro-40 cessible in conventional foA~ng eguipment due to their highviscosity.

~eaction of the crude MDI with the monohydric alcohols reduces the functionality of the polyi~ocyanate composition ~b), but, 45 surprisingly, this measure has virtually no adverse effect on the mechanical properties of the resultant compact or cellular poly-urethanes, in particular rigid PU foams. The crucial factor for `` Z1375~0 this may well be that fine emulsions are rapidly converted into homogeneous solutions, or homogeneou5 solutions directly, which readily give reproducible polyurethanes of constant quality are already obtained at the beginning of the mixing operation from 5 the crude MDI compositions cont~;ning urethane groups and modi-fied according to the invention and the polyhydroxyl compon-ent (A), irrespective of the mixing guality of the mixing device.
In the case of rigid PU foams, it is not only the mechanical properties in general terms, but in particular its compressive 10 strength that has been improved by means of the process according to the invention.

It is furthermore sdvantageous that the Dy; ~ reaction tempera-ture which occurs during the preparation of the rigid PU foam can 15 be significantly reduced, so that discoloration or tarring of the core of the rigid PU foam is prevented.
The following details apply to the novel process for the prepara-tion of the compact or preferably cellular polyurethanes, in par-20 ticular rigid PU foams, and to the starting materials which can be used for this purpose:
a) Suitable relatively high-molecular-weight polyhydroxyl com-pounds (a) usually have a functionality of from 2 to 8 and a molecular weight of from 400 to B000, the flexible polyure-thanes expediently being prepared using polyhydroxyl com-pounds having a functionality of, preferably, from 2 to 3 and a molecular weight of, preferably, fro~ 2400 to 7200, in par-ticular from 3200 to 6000, and rigid polyurethanes ex-pediently being prepared using polyhydroxyl compounds having a functionality of, preferably, from 3 to 8, in particular from 3 to 6, and a molecular weight of, preferably, from 400 to 3600, in particular from 1200 to 3200. Preferred poly-hydroxyl compounds are linear and/or branched polyester-polyols, in particular polyoxyalkylene-polyols. However, polymer-modified polyoxyalkylene-polyols, polyoxyalkylene-polyol dispersions and other hydroxyl-cont~ n~ ng polymers and polycondensates having the abovementioned functionalities and molecular weights, for example polyester-amides, polyacetals and/or polycarbonates, in particular those prepared from di-phenyl carbonate and 1,6-hexanediol by transe6terification, or mixtures of at least two of said relatively high-molecu-lar-weight polyhydroxyl compounds, are also suitable.

Suitable polyester-polyols may be prepared, for example, from organic dicarboxylic acids having from 2 to 12 carbon atoms, preferably aliphatic dicarboxylic acids having from 4 to -` .. ' 2137~g~

6 carbon atoms and polyhydric ~lcohols, preferably alkane-diols, having from 2 to 12 carbon atoms, preferably from 2 to 6 carbon atoms and/or dialkylene glycols. Example6 of suit- -able dicarboxylic acids are succinic acid, glutaric acid, adipic acid, 8uberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid and terephthalic acid. The dicarboxy-lic acids may be used either individually or mixed with one another. The free dicarboxylic acids may also be replaced by the corresponding dicarboxylic acid derivatives, for example dicarboxylic esters of alcohols having 1 to 4 carbon atoms or dicarboxylic anhydrides. Preference is given to dicarboxylic acid mixtures comprising succinic acid, glutaric acid and adipic acid in ratios of, for eXAmrle~ from 20 to 35: 35 to 50: 20 to 32 parts by weight, and in particular adipic acid. Examples of dihydric and polyhydric alcohols, in par-ticular alkanediols and dialkylene glycols, are ethanediol, diethylene glycol, 1,2- and 1,3-propanediol, dipropylene gly-col, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, l,10-decanediol, glycerol and trimethylolpropane. Preference is given to ethanediol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and mixtures of at least two of said alkanediols, in particular mixtures of 1,4-butane-diol, 1,5-pentanediol and 1,6-hexanediol. ~urthermore, poly-ester-polyols made from lactones, eg. -caprolactone or hydroxycarboxylic acids, eg. ~-hydroxycaproic acid, may also be employed.
The polyester-polyols may be prepared by polycondensing the organic, eg. aromatic and preferably aliphatic polycarboxylic acids and~or derivatives thereof and polyhydric alcohols and/
or alkylene glycols without using a catalyst or preferably in the presence of an esterification catalyst, expediently in an inert gas atmosphere, eg. nitrogen, helium, argon, inter alia, in the melt at from 150 to 250-C, preferably from 180 to 220 C, at atmospheric pressure or under reduced pressure until the desired acid number, which is advantageously less than 10, preferably less than 2, is reached. In a preferred ~m~o~iment, the esterification mixture is polycondensed at the abovementioned temperature under atmospheric pressure and subsequently under a pressure of less than 500 mbar, prefer-ably from 50 to 150 mbar, until an acid number of from 80 to 30, preferably from 40 to 30, has been reached.
Examples of suitable esterification catalysts are iron, cadmium, cobalt, lead, zinc, antimony, magnesium, titanium and tin catalysts in the form of metals, metal oxides or metal salts. However, the polycondensation may also be ` - ~137S4~

carried out in the liquid phase in the presence of diluents and/or entrainers, eg. benzene, toluene, ~ylene or chloroben-zene, for removal of the water of condensation by azeotropic distillation.
The polyester-polyols are advantageously prepared by polycon-densing the organic polycarboxylic acids and/or derivatives thereof with polyhydric alcohols in a molar ratio of from 1:1 to 1.8, preferably from 1:1.05 to 1.2.
The polyester-polyols obtained preferably have a functional-ity of from 2 to 4, in particular from 2 to 3, and a molecu-lar weight of from 800 to 3600, preferably from 1200 to 3200, in particular from 1800 to 2500.
However, the preferred polyhydroxyl compounds are polyoxy-alkylene-polyols prepared by conventional processes, for example by anionic polymerization using AlkAli metal hydroxides such as sodium hydroxide or potassium hydroxide, or ~lkali metal AlkQxides, such as sodium methoxide, sodium ethoxide, potassium ethoxide or potassium isopropoxide as catalysts and with addition of at least one initiator molecule contAining from 2 to 8, preferably 2 or 3, reactive hydrogen atoms in bound form for the preparation of polyoxy-alkylene-polyols for flexible polyurethanes and preferably from 3 to 8 reactive hydrogen atoms in bound form for the preparation of polyoxyalkylene-polyols for semirigid and rigid polyurethanes, or by cationic polymerization using Lewis acids, such as antimony pentachloride, boron fluoride etherate, inter alia, or bleaching earth as catalysts, from one or more alkylene oxides having from 2 to 4 carbon atoms in the alkylene moiety.
Examples of suitable alkylene oxides are tetrahydrofuran, 1,3-propylene oxide, 1,2- and 2,3-butylene oxide and preferably ethylene oxide and 1,2-propylene oxide. The alkylene oxides may be used individually, alternatively one after the other or as mixtures. Examples of ~uitable initia-tor molecules are water, organic dicarboxylic acids, ~uch as ~uccinic acid, adipic acid, phthalic acid and terephthalic acid, aliphatic and aromatic, unsubstituted or N-mono-, N,N-and N,N'-dialkyl-substituted diamines having from 1 to 4 carbon atoms in the alkyl moiety, such as unsubstituted or mono- or dialkyl-substituted ethylenediamine, diethylene-triamine, triethylenetetramine, 1,3-propylenediamine, 1,3-and 1,4-butylenediamine, 1,2-, 1,~-, 1,4-, 1,~- and 1,6-hexamethylenediamine, phenylenediamines, 2,3-, 2,4- and ~13~5~

2,6-tolylenediamine and 4,4'-, 2,4'- and 2,2 ~ - diAm; no~; -phenylmethane.
Other suitable initiator molecules are alkanola~nes, eg.
ethanolamine, N-methyl- and N-ethyl-ethanolamine, ~ kAnol-amines, eg. diethanol~jne, N-methyl- and N-ethyl-diethanol-amine, and trialkanol~m;nes, eg. triethanolPm~ne, and ammonia. Preference is given to polyhydric alcohols, in par-ticular dihydric to octahydric alcohols and/or alkylene gly-0 c015, eg. ethanediol, 1,2- and 1,3-propanediol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, pentaerythritol, sorbitol and sucrose or mixtures of at least two polyhydric alcohols.
The polyoxyalkylene-polyols, preferably polyoxypropylene- and polyoxypropylene-polyoxyethylene-polyols, have a functional-ity of from 2 to 8 and molecular weights of from 400 to 8000, where, as stated above, polyoxyalkylene-polyols having a functionality of from 2 to 3 and a molecular weight of from 2400 to 7200 are preferred for flexible polyurethanes and polyoxyalkylene-polyols having a functionality of from 3 to 8 and a molecular weight of from 400 to 3600 are preferred for rigid polyurethanes, and suitable polyoxytetramethylene gly-cols have a molecular weight of from 400 to approxi-mately 3500.

Other suitable polyoxyalkylene-polyols are polymer-modified polyoxyalkylene-polyols, preferably graft polyoxyalkylene-polyols, in particular those based on styrene and/or acrylo-nitrile and prepared by in situ polymerization of acrylo-nitrile, styrene or preferably mixtures of styrene and acrylonitrile, for example in a weight ratio of from 90:10 to 10:90, preferably from 70:30 to 30:70, expediently in the abovementioned polyoxyalkylene-polyols by a method similar to that of German Patents 11 11 394, 12 22 669 (US 3,304,273, 3,383,351 and 3,523,093), 11 52 536 (GB 1,040,452) and 11 52 537 (GB 987,618), and polyoxyalkylene-polyol disper-6ions which contain, as the disperse phase, usually in an amount of from 1 to 50~ by weight, preferably from 2 to 25 by weight, for example polyureas, polyhydrazides, poly-urethanes containing tert-amino groups in bound form, and/or melamine and are described, for example, in EP-B-011 752 (US 4,304,708), US-A-4,374,209 and DE-A-32 31 497.

Like the polyester-polyols, the polyoxyalkylene-polyols can be used individually or in the form of mixtures. Furthermore, they may be mixed with the graft polyoxyalkylene-polyols or - ~13754~

polyester-polyol6 and the hydroxyl-contAin~ng polyester-amides, polyacetals and/or polycarbonates. ~YAmrles of mix-tures which have proven highly suitable for flexible polyure_ thanes are those having a functionality of from 2 to 3 and a molecular weight of from 2400 to 8000 which contain at least one polyoxyalkylene-polyol and at least one polymer-modified polyoxyalkylene-polyol from the group consi~ting of graft polyoxyalkylene-polyols or polyoxyalkylene-polyol dispersions contA;n~ng, as disperse phase, polyureas, polyhydrazides or polyurethanes contA;n;ng bonded tertiary amino groups.

Examples of suitable hydroxyl-cont~Ain;ng polyacetals are the compounds which can be prepared from glycols, ~uch as diethylene glycol, triethylene glycol, 4,4'-dihydroxyethoxy-diphenyldimethylmethane, hexanediol and formaldehyde. Suit-able polyacetals can also be prepared by polymerizing cyclic acetals.
Suitable hydroxyl-contA;ning polycarbonates are those of a conventional type, which can be prepared, for example, by reacting diols, such as 1,3-propanediol, 1,4-butanediol and/
or 1,6-hexanediol, diethylene glycol, triethylene glycol or tetraethylene glycol, with diaryl carbonates, eg. diphenyl carbonate, or phosgene.
The polyester-A~;des include, for example, the pre~om~nantly linear condensates obtained from polybasic, saturated and/or unsaturated carboxylic acids or anhydrides thereof and poly-hydric, saturated and/or unsaturated amino alcohols, or mix-tures of polyhydric alcohols and A~i no alcohols and/or poly-amines.

b) The organic polyisocyanates used according to the invention are liguid, diphenylmethane diisocyanate-based polyisocyanate compositions (b) contAin;ng urethane groups which are obtain-able by reacting mixtures of diphenylmethane diisocyanates (MDI) and polyphenylpolymethylene polyisocyanates, usually k~own as crude MDI, with a substoichiometric amount of at least one linear, branched or cyclic, saturated or olefinic-ally unsaturated, low-molecular-weight monoalcohol.

Suitable crude MDI grades advantageously have, in addition to higher homologs, a content of MDI isomers of from 30 to 95S
by weight, preferably from 35 to 80~ by weight, 3ased on the total weight, and NCO contents of from approximately 30 to 213~5~
. _ 32% by weight. Highly suitable are crude MDIs which contain or preferably comprise, based on the total weight:

bIl)from 29 to 65% by weight, preferably from 33 to 60% by weight, of 4,4'-MDI, bI2)from 1 to 30% by weight, preferably from 2 to 20% by weight, of 2,4'-MDI, bI3)from 0 to 4% by weight, preferably from 0.5 to 2.5% by weight, of 2,2'-MDI and bI4)from 70 to 5% by weight, preferably from 65 to 20% by weight, of at least trifunctional polyphenylpolymethylene polyisocyanates.
For the purposes of the present invention, liguid polyiso-cyanate compositions cont~ining urethane groups which can be used according to the invention are also taken to mean poly-isocyanate compositions obtained by reacting mixtures of MDI
isomers with the low-molecular-weight monoalcohol~ and subse-quently blending the resultant MDI mixtures contAining ure-thane groups with the abovementioned crude MDI and/or the crude MDI compositions contAining urethane groups prepared according to the invention or by blending the crude MDI com-positions ocntAining urethane groups prepared according to the invention with MDI mixtures and/or MDI mixtures contain-ing urethane groups.

Suitable mixtures of MDI isomers expediently contain or pre-ferably comprise, based on the total weight bIIl) from 90 to 48% by weight, preferably from B0 to 60% by weight, of 4,4'-MDI, bII2) from 10 to 48~ by weight, preferably from 20 to 40% by weight, of 2,4'-MDI and bII3) from 0 to 4% by weight, preferably from 0 to 2.5% by weight, of 2,2'-MDI.

Preferred low-molecular-weight monoalcohols for the prepara-tion of the liguid diphenylmethane diisocyanate-based poly-isocyanate compositions (b) contAining bonded urethane groups are those having 1 to 6 carbon atoms, in particular 1 to 3 carbon atoms, from the group consisting of linear or branched, ~aturated, monohydric alcohols. It is also possible , ~ 21375~0 to use linear or branched, olefinically unsaturated, monohyd-ric alcohols having 3 to 6 carbon atoms and saturated or ole-finically unsaturated, cyclic, monohydric alcohols having 4 to 6 carbon atoms, preferably 5 or 6 carbon atoms. Specific mention may be made, by way of example, of the following:
linear and branched, ~aturated monoalcohols, eg. methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol and n-hexanol and the corresponding ctructurally isomeric mono-hydric alcohols, linear and branched, olefinically unsaturat-ed monoalcohols, eg. allyl alcohol, 2-methyl-2-propen-1-ol, 2- and 3-buten-1-ol, and cyclic, saturated or olefinically unsaturated monoalcohols, eg. cyclobutanol, cyclopentanol, cyclopentenol, cyclohexanol and cyclohexenol. Monoalcohols which have proven highly successful snd are therefore pre-ferred are methanol, ethanol, n-propanol, isopropanol and allyl alcohol. The low-molecular-weight monoalcohols can be employed in technical-grade or preferably pure form, individ-ually or as mixtures of at least two monoalcohols.
As mentioned above, the compatibility of the polyhydroxyl component (A) and the polyisocyanate component (B) depends on the type of the polyhydroxyl component (A) and the content of urethane groups in the polyisocyanate crmronent (B), which is expediently at least 0.1 mol, preferably from 0.1 to 2 mol, in particular from 0.4 to 1 mol, of urethane groups per kg of polyisocyanate composition. If the polyisocyanate composition has a urethane group content of from 0.1 to 0.3 mol/kg, a fine emulsion which is very rapidly converted into a clear, homogeneous mixture is in some cases initially formed on mix-ing the polyhydroxyl component (A) and the polyisocyanatecomponent (~), depending on the type of the polyhydroxyl com-ponent (A), while polyisocyanate compositions have a ure-thane group content of approximately 0.4 mol/kg or greater usually form clear solutions directly on mixing. The polyiso-cyanate compositions cont~in~ng urethane groups which havebeen modified according to the invention by means of monohyd-ric alcohols usually have, in the range from 0.4 to 1 mol of urethane groups/kg, a viscosity, measured at 23-C by means of a Haake viscometer, of from 1000 to 3000 mPa-s and are there-fore readily processible, while analogous polyisocyanatec~mrositions having the ~ame urethane group content/kg, but modified, for example, by mean~ of dipropylene glycol, are already solid.
-The polyisocyanate compositions according td the inventionhaving a urethane group content of from 0.1 to 2 mol/kg usu-ally have a content of NC0 groups of from 18 to 30% by . -, , 213~5qO

weight, preferably from 24 to 28% by weight, based on the total weight.
The novel crude MDI romrositions cont~in~ng urethane groups can be used for the preparation of any, preferably highly crosslinked polyisocyanate polyaddition products. They have proven particularly successful and are therefore preferred for the preparation of polyisocyanate polyaddition products for wbose preparation relatively highly functional polyiso-cyanates, for example those having a functionality of at least 2.5, must be mixed with polyhydroxyl components (A) contA; ni ng polyoxyalkylene-polyols having a functionality of at least 3 and a hydroxyl number of at least 250, preferably at least 350. Polyisocyanate polyaddition products of this type are in particular crosslinked PV elastomers and rigid PU
(molded) foams.
c) The compact or cellular polyurethanes can be prepared by the novel process in the presence or absence of chain extenders and crosslinking agents (c). In the preparation of flexible, compact or cellular polyurethanes, the addition of chain extenders, crossljnking agents or, if desired, mixtures thereof may prove advantageous for modification of the me-chanical properties, for example the hardness. In the produc-tion of rigid PU foams, the use of chain extenders and/or crosslinking agents (c) is usually unnecessary. Chain extend-ers which can be used are difunctional compounds, and cross-linking agents which can be used are trifunctional and higher functional compounds, in each case having a molecular weight of less than 400, preferably from 62 to approximately 300.
Specific examples of chain extenders which may be mentioned are alkanediols, for example those having 2 to 6 carbon atoms in the alkylene radical, eg. ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol, and dial-kylene glycols, eg. diethylene glycol, dipropylene glycol and dibutylene glycol, and specific exampleg of crosslinki~g agents which can be used are alkanolamines, eg. ethanolamine, dialkanolamines, eg. diethanolamine, and trialkanolamines, eg. triethanolamine and triisopropanolam;ne, trihydric and polyhydric alcohols, eg. glycerol, trimethylolpropane and pentaerythritol, and aliphatic and/or aromatic diamines, eg.
1,2-ethanediamine, 1,4-butanedi~ine~ 1,6-hexanediamine, 2,3-, 2,4- and/or 2,6-tolylenediamine, 4,4'-diaminodiphenyl-methane, 3,5-diethyl-2,4- and/or 2,6-tolylenediamine, 3,3'-di- and/or 3,3',5,5'-tetraalkyl-3,3-diaminodiphenyl-methanes, eg. tetraisopropyl-4,4'-diaminodiphenylmethane.
Other suitable chain extenders or crosslin~;ng agents are 213754~

low-molecular-weight ethoxylation and/or propoxylation prod-ucts, eg. those having molecular weights of up to approxi-mately 400, of the abovementioned polyhydric alcohols, alkylene glycols, alkanolamines and diamines.
S
Preferred chain extenders are alkanediols, in particular 1,4-butanediol and/or 1,6-hexanediol, alkylene glycols, in particular ethylene glycol and propylene glycol, and pre-ferred crosslink;ng agents are trihydric alcohols, in partic-ular glycerol and trimethylolpropane, dialkanolamines, in particular diethanolamine, and trialkanolamines, in particu-lar triethanolamine.
The chain extenders and/or crossl1nking agents preferably used for the preparation of flexible, compact or cellular polyurethanes can be employed, for example, in amounts of from 2 to 60~ by weight, preferably from 10 to 40~ by weight, based on the total weight of formative components (a) and (c).
d) The blowing agent (d) for the preparation of the cellular polyurethanes, preferably rigid PU foams, i8, in particular, water, which reacts with isocyanate groups to form carbon dioxide. The amounts of water expediently employed are from 0.1 to 8 parts by weight, preferably from 1 to 5 parts by weight, in particular from 1.5 to 3 parts by weight, based on 100 parts by weight of the polyhydroxyl compounds (a).
Other suitable blowing agents are liquids which are inert toward the liquid polyisocyanate compositions (b) modified by means of urethane groups and which have boiling points of below 100 C, preferably below 50 C, in particular from -50-C
to 30 C, at atmospheric pressure, 80 that they evaporate under the conditions of the exothermic polyaddition reaction, and mixtures of these physical blowing agents and water.
Examples of preferred liquids of this type are alkanes, eg.
heptane, hexane, n- and isopentane, preferably technically-grade mixtures of n- and isopentanes, n- and isobutane and propane, cycloalkanes, ~uch as cyclopentane and/or cyclo-hexane, ethers, eg. furan, dimethyl ether and diethyl ether, ketones, eg. acetone and methyl ethyl ketone, alkyl carboxylates, such as methyl formate, dimethyl oxalate and ethyl acetate, and halogenated hydrocarbons, such as methy-lene chloride, dichloromonofluoromethane, difluoromethane, trifluoromethane, difluoroethane, tetrafluoroethane, chloro-difluoroethanes, 1,1-dichloro-2,2,2-trifluoroethane, 2,2-di-chloro-2-fluoroethane and heptafluoropropane. It is also 213~540 ~ . .

possible to use mixtures of these low-boiling liquids with one another and/or with other substituted or unsubstituted hydrocarbons. Also suitable are organic carboxylic acids, eg.
formic acid, acetic acid, oxalic acid, ricinoleic acid and carboxyl-cont~in~ng compounds.
Other blowing agents (d) which can be used are compounds which are pulverulent at room t~p~rature and which decompose at elevated temperature through eli mi n~tion of gases, eg.
steam, carbon dioxide, carbon monoxide, oxygen or nitrogen.
Specific examples which may be mentioned are silica gels, bicarbonates, ammonium formate, oxalic acid derivative~, urea and urea derivatives, peroxides and preferably azo compounds, eg. azoisobutyronitrile and azodicarbon~mide, hydrazines, eg.

4,4~-oxybis(benzenesulfohydrazide) and diphenyl ~ulfone 3,3'-disulfohydrazide, semicarbazides, eg. p-tolylenesulfo-nylsemicarbazide, and triazoles, eg. 5-morpholyl-1,2,3,4-thiatriazole.

Preferred blowing agents are chlorodifluoromethane, chlorodi-fluoroethanes, dichlorofluoroethanes, pentane mixtures, cyclopentane, cyclohexane and in particular water, and mix-tures of at least two of these blowing agents, eg. mixtures of water and cyclopentane, mixture~ of chlorodifluoromethane and 1-chloro-2,2-difluoroethane and, if desired, water.
Chlorofluorocarbons, which damage the ozone layer, are not used as blowing agents.

The requisite amount of physical blowing agents can readily be determined experimentally depending on the foam density required and any water employed and is from about O to 25 parts by weight, preferably from O to 15 parts by weight, per 100 parts by weight of the polyhydroxyl compounds (a). It may be expedient to mix the polyisocyanate composition (b) contAini~g bonded urethane groups with the inert physical blowing agent and thus to reduce its viscosity.
e) If the compact or cellular polyurethanes are prepared in the presence of catalysts, preferred compounds for this purpose are those which greatly accelerate the reaction of the hydroxyl-contAining compounds of formative component (a) and, if used, (c) with the liquid, MDI-based polyisocyanate com-positions (b) containing bonded urethane group~. Suitable compounds are organometallic compounds, preferably organotin compounds, such as tin(II) ~alt~ of organic carboxylic acids, eg. tin(II) acetate, tin(II) octanoate, tin(II) ethylhexan-oate and tin(II) laurate, and the dislkyltin(IV) ~alts of ` - 21~S9U
. .

organic carboxylic acids, eg. dibutyltin diacetate, dibutyl_ tin dilaurate, dibutyltin maleate and dioctyltin diacetate, and highly ba8ic amines, for example ~m;dines, eg. 2,3-dime-thyl-3,4,5,6-tetrahydropyr~ mi dine, tertiary amines, eg. tri-ethylamine, tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl- and N-cyclohexylmorpholine, N,N,N',N'-tetramethyl-ethylenediamine, N,N,N',N'-tetramethylbutanediamine, N,N,N',N'-tetramethyl-1,6-hexanedi~mine~ di(4-dimethylamino-cyclohexyl)methane, pentamethyldiethylenetriamine, tetra-methyldiaminoethyl ether, bis(dimethylaminopropyl)urea,dimethylpiperazine, 1,2-dimethylimidazole, 1-azabicy-clo[3.3.0]octane and preferably 1,4-diazabicyclo[2.2.2]oct-ane, and alkanolamine compounds, such as triethanolamine, trii~opropanol~mine, N-methyl- and N-ethyldiethanolamine and dimethylethanolamine.
Other suitable catalysts are: tris(dialkylam;noalkyl)-s-hexa-hydrotriazines, in particular tris(N,N-dimethylaminoprop-yl)-s-hexahydrotriazine, tetraalkylammonium hydroxides, such as tetramethylammonium hydroxide, Al kal ~ metal hydroxides, such as sodium hydroxide, and Alk~li metal alkoxides, such as sodium methoxide, sodium ethoxide, potassium ethoxide and potassium isopropoxide, and al kAl i metal salts of long-chain fatty acids having 10 to 20 carbon atoms and possibly pendant OH groups, and combinations of the organometallic compounds and highly basic amines. It i8 preferred to use from 0.001 to 5S by weight, in particular from 0.05 to 2% by weight, of catalyst or catalyst combination, based on the weight of the polyhydroxyl compound (a).
f) Auxiliaries (f) can, if desired, also be incorporated into the reaction mixture for the preparation of the compact and cellular polyurethanes. Examples which may be mentioned are surfactants, foam stabilizers, cell regulators, fillers, dyes, pigments, flameproofing agents, antihydrolysis agents and fungistatic and bacteriostatic substances.

Examples of suitable surfactants are compounds which serve to support homogenization of the starting materials and may also regulate the cell structure. Specific examples are emulsi-fiers, such as the sodium salts of castor oil sulfates, or of fatty acids, and the salts of fatty acids with ~mi nes, for example diethylamine oleate, diethanolamine stearate and diethanolamine ricinoleate, 6alts of sulfonic acids, eg.
alkali metal salts or ammonium salts of dodecylbenzene- or dinaphthylmethanedisulfonic acid and ricinoleic acid; foam stabilizers, such as siloxane-oxyalkylene copolymers and - 213754~

other organopolysiloxanes, oxyethylated alkylphenols, oxy-ethylated fatty alcohols, paraffin oils, castor oil esters, ricinoleic acid esters, Turkey red oil and groundnut oil, and cell regulators, such as paraffins, fatty alcohols and di-methylpolysiloxanes. Suitable compounds for improving theemulsification action, the cell structure and/or stabilizing the foam are furthermore oligomeric polyacrylates ContAi ni ng polyoxyalkylene and fluoro~lkAne radicals a~ side groups. The surfactants are usually used in amounts of from 0.01 to 5 parts by weight, based on 100 parts by weight of the poly-hydroxyl compounds (a).
For the purposes of the present invention, fillers, in par-ticular reinforcing fillers, are conventional organic and inorganic fillers and reinforcing agents. Specific examples are inorganic fillers, such as silicate minerals, for example phyllosilicates, such as antigorite, serpentine, hornblendes, amphiboles, chrysotile, talc; metal oxides, such as kaolin, aluminum oxides, aluminum silicate, titanium oxides and iron oxides, metal salts, such as chalk, barytes and inorganic pigments, ~uch as cadmium ~ulfide, zinc 6ulfide and glass particles. Examples of suitable organic fillers are carbon black, melamine, colophony, cyclopentadienyl resins and graft polymers.
The inorganic and organic fillers may be used individually or as mixtures and are advantageously introduced into the reac-tion mixture in amounts of from 0.5 to 50% by weight, prefer-ably from 1 to 40% by weight, based on the weight of components (a) to (c).

Examples of suitable flameproofing agents are tricresyl phos-phate, tris(2-chloroethyl) phosphate, tris(2-chloropropyl) phosphate, tris(l,3-dichloropropyl) phosphate, tris(2~3-di bromopropyl) phosphate and tetrakis(2-chloroethyl)ethylene diphosphate.
In addition to the abovementioned halogen-substituted phos-phates, it is also possible to use inorganic flameproofing agents, ~uch as red phosphorus, aluminum oxide hydrate, anti-mony trioxide, arsenic oxide, ammonium polyphosphate, expand-able graphite and calcium sulfate, or cyanuric acid deriva-tives, eg. mel~;ne, or mixtures of two or more flameproofing agents, eg. ammonium polyphosphates and melamine and/or expandable graphite and, if desired, starch, in order to flameproof the compact or cellular polyurethanes prepared ac-cording to the invention. In general, it has proven expedient - 21~75~0 . .

to use from 5 to S0 parts by weight, preferably from 5 to 25 parts by weight, of said flameproofing agents or mixtures per 100 parts by weight of components (a) to (c).
Further details on the other conventiopal auxiliaries men-tioned above can be obtained from the specialist literature, for eYAmrle from the monograph by J.~. Saunders and R.C Frisch, High Polymers, Volume XVI, Polyurethanes, Parts 1 and 2, Interscience Publishers 1962 and 1964 respectively, or Runststoff-~andbuch, Polyurethane, Volume VII, Carl-Hanser-Verlag, Munich, Vienna, 1st and 2nd Editions, 1966 and 1983.

In order to prepare the compact or cellular polyurethanes, the liquid polyisocyanate compositions (b) contA~ni~g bonded urethane 15 groups, the relatively high-molecular-weight polyhydroxyl com-pounds (a) and, if desired, chain extenders and/or crossl;nk;ng agents (c) can be reacted in the absence or preferably presence of catalysts (e) and auxiliaries (f) and in the presence of blow-ing agents (d) for the formation of cellular polyurethanes at 20 from 0 to 100 C, preferably from 15 to 80 C, in such mixing ratios that from 0.5 to 2, preferably from 0.8 to 1.3, in particular approximately one, reactive hydrogen atom(s) bonded to formative component (a) and, if used, (c) are present per NC0 group and, if water is used as blowing agent, the molar ratio between the num-25 ber of equivalents of water and the number of eguivalents of NC0 groups is from 0.5 to 5 : 1, preferably from 0.7 to 0.95 : 1, in particular from 0.75 to 0.85 : 1.

The compact and cellular polyurethanes can be prepared by the 30 prepolymer process or preferably by the one-shot process by mix-ing two cnmronents (A) and (B), where formative components (a) and, if used, (c), (d), (e) and (f) are combined to form the polyhydroxyl component (A) and the polyisocyanate component (B) comprises the diphenylmethane diisocyanate-based polyisocyanate 35 composition (b) contAining bonded urethane groups, if desired mixed with (f) and inert, physical blowing agents. Since the polyol component (A) and the polyisocyanate component (B) have very good shelf lives, they need only be mixed intensively before preparation of the compact or cellular polyurethanes. The reac-40 tion mixture can be brought to reaction in open or closed molds, expediently at from 15 to 80-C.

In order to prepare cellular polyurethanes, eg. flexible, semi-rigid or preferably rigid polyurethane foams, preferably PU
45 molded foams, the foamable reaction mixture can be introduced into an expediently metallic, t~mperature-controllable, open or closed mold at, for example, from 15 to 80 C, preferably at from 2137s4a 18 to 45 C. The mold tPmperature i5 u~ually from 20 to 90 C, pre-ferably from 35 to 70 C. The reaction mixture is allowed to cure in the closed mold, usually with compaction, for example with degrees of compaction of from 1.1 to 8, preferably from 2 to 6, 5 in particular from 2.5 to 4. The novel process i8 also suitable for the production of polyurethane slabstock foams.
The compact polyurethanes generally have densities of from 1.0 to 1.2 g/cm3, products of higher density being obtained with addition lO of reinforcing materials and/or fillers. Cellular elastomers and PU structural foams usually have densities of from 240 to less than 1000 g/l, densities of from 400 to 600 g/l being preferred.
The flexible, ~emirigid and preferably rigid PU foams expediently have densitie~ of from 30 to 80 g/l, preferably from 35 to 15 60 g/l.
The compact polyurethanes prepared by the novel proce~s are used, for example, in the automotive, construction and furniture indus-tries, for example as rain gutters, side strips, cover panels and 20 table edges; the cellular PU elastomers are used, for example, as damping elements, sun visors, armrests, shoe inners and shoe soles; and the PU foams are used, for example, as cushioning materials, ~afety covers, furniture housings, for foam-filling refrigeration equipment housings, for example chest freezers and 25 refrigerators, hot-water eguipment, district heating pipes and cavities of all types, and for rock con~olidation.

~YA~ples 30 Preparation of the liquid polyisocyanate compositions cont~;ning urethane groups Example 1 35 0.1 part by weight of benzoyl chloride was added with stirring to 4000 parts by weight of crude MDI having an NC0 content of 314 by weight and a content of MDI isomers of 40~ by weight under a nitrogen atmosphere in a reactor fitted with stirrer, reflux con-denser and feed and withdrawal device for gases, the reaction gO mixture was warmed to 50 C, and 211 parts by weight of isopropanol were added dropwise at this temperature over a period of 30 min-utes, during which the reaction temperature rose to 70-C. The reaction mixture was then warmed to 80-C and the reaction was com-pleted at this temperature in 2 hours, giving a clear, flowable 45 polyisocyanate composition having a urethane group content of 0.84 mol/kg, and an NC0 content of 25.94 by weight and a " - 213 75~

viscosity at 23 C of 2100 mPa-s, measured using a Haake viscometer (Rotovisko RV 20 type).

By varying the amount of i~opropanol, polyisocyanate c~mrositions 5 having different concentrations of urethane groups were prepared analogously.

The amount of isopropanol used, the percentage contents of ure-thane and isocyanate groups and the viscosity of the polyiso-10 cyanate compositions and their miscibility with trioxypropyleneglycol are shown in Table 1.

Examples 2 and 3 15 The procedure was similar to that of ~x~mrl e 1, but the isoprop-anol was replaced as monohydric alcohols by methanol snd allyl alcohol in the amounts shown below.

Comparative Example I
The procedure was similar to that of Example 1, but the isoprop-anol was replaced by difunctional dipropylene qlycol.

Miscibility with polyoxyalkylene-polyols In order to test the miscibility, e~uimolar amounts of the crude MDI compositions cont~i ni ng urethane groups and trioxypropylene glycol (TPG) were mixed at 23 C.

30 The test substance u ed in place of polyoxyalkylene-polyols was trioxypropylene glycol, since this compound has a similar hyd-roxyl number to rigid foam polyoxyalkylene-polyols, but has low viscosity and is therefore more ~uitable for mixing trials of this type than, for example, sucrose-based polyoxyalkylene-35 polyols, which have high viscosity.

~ 1 3 7 5 .
D~r A-trlenge~iell-Cn~2t930503 K J

E~ U o O

L ~ o ~ V C
c , O a ~ ' ~ L

tJ' ~ 0 -- _ '~ 0 ~ C

., -- ~ .
O r p~ O ~ ~ ~ ~~D O ~

-- '' 3 V~ ~ --4 ~ 0 ~ ~

o c ~ ~
C
o~ ~ o~ ~ 0 ~ O Ltl N N
O O O O O O O ~ O O O ~1 0 0 0 0 r 3 C ~ '--3 ~ ~ ~ o .-1 ~D 0 o ~

O ~ C

h ,_ ~ c c ~a ~ H

213~540 Preparation of cellular polyurethanes ~Yamp]e 4 Rigid PU foam Polyhydroxyl c~mronent (A): a mixture comprising 0 93 parts by wt.of trioxypropylene glycol (hydr number 584), 2.4 parts by wt.of polysiloxane foam ~t~hil~zer (Tegostab~B8406 from Goldschmidt AG), 1.9 parts by wt.of dimethylcyclohexylamine and 2.7 parts by wt.of water.
Polyisocyanate component (2)s Crude MDI composition having a urethane group content of 20 0.79 mol~kg, an NCO content of 26% by weight and a viscosity at 23 C of 1990 mPas, measured using a Haake viscometer, Rotovisko RV 20 type, prepared as described under Example 1 by reacting 200 parts by weight of isopropanol with 4000 parts by weight of the crude MDI described in ~YAmrle 1.
In order to prepare the rigid PU foam, 100 parts by weight of the polyhydroxyl component (A) and 229 parts by weight of the polyisocyanate component (B) were mixed vigorously at 23 C, and the clear reaction mixture was transferred into a plastic bucket, 30 where it was allowed to expand.
~mp~rative Example II

Polyhydroxyl component (A): as in Example 4 Polyisocyanate component (D): crude MDI hav$ng an NCO content of 31~ by weight and an MDI isomer content of 40~ by weight.

100 parts by weight of the polyhydroxyl c~mponent (A) and 40 188 parts by weight of the polyisocyanate component (B) were mixed and allowed to expand as described in Example 4.

` 2~13 7~40 :

Table 2 .

Mechanical properties of the rigid PU foams, prepared as 5 described in Example 4 and Comparative ~yA~rle II

Mechanical properties Ex. 4 Comp. Ex. II
Density [g/l] 52.5 47.1 10 Thermal conductivity, lmW/mR~ 20.1 21.5 measured using a Hesto la_bda control A 50-A
Proportion of closed cells, [%] 87 88 measured using a Beckmann air comparative pycnometer, Model 930 Compressive strength in accordance with 494 306 DIN 53421 tkPa]
iml-m reaction t~mr~rature [oc] 181 206 in the foam core, measured using a Cr-Ni thermocouple with a thickness 20 of 0.2 mm.

Example 5 Rigid PU foam Polyhydroxyl component (A): a mixture comprising 81.6 parts by wt.of a glycerol-initiated polyoxypropylene-polyol having a hydroxyl number ~of 400, 9.9 parts by wt.of trioxypropylene glycol, 2.5 parts by wt.of polysiloxane foam ~tabilizer (polyurax~ SR 321 from Union Carbide), 2.0 parts by wt.of dimethylcyclohexylamine and 3.0 parts by wt.of water.

Polyisocyanate component (B)s as in Example 4 In order to prepare the rigid PU foam, 100 parts by weight of the polyhydroxyl rnmponent (A) and 179 parts by weight of the 40 polyisocyanate component (B) were mixed as in Example 4 and allowed to expand freely.

Comr~Fative Example III

45 Polyhydroxyl ~mponent (A): as in Example 5 `~ 213754~
.
.
. . .
Polyisocyanate c~mronent (B): as in ComrArative ~Y~mple II

100 parts by weight of the polyhydroxyl r~mrQnent (A) and 152 parts by weight of the polyisocyanate c~mponent (~) were S mixed and allowed to expand as in Example 4.

Table 3 Hechanical properties of the rigid PU foams, prepared as 10 described in Example 5 and C- ,~rative Example III

Mechanical properties Ex. 5 Comp.
Ex. III
15 Density [g/l] 44.6 40.8 Thermal conductivity, [mW/mR] 20.9 22.1 measured using a Hesto lambda control A 50-A
Proportion of closed cells, [%] 89 89 measured using a Beckmann air 20 comparative pycnometer, Model 930 Compressive strength in accordance with 368 287 DIN 53421 [kPa]

Example 6 Compact PU molding composition 100 parts by wt.of a polyoxypropylene glycol having a hydroxyl number of 105 prepared by polyaddition of 3 1,2-propylene oxide onto 1,2-propanediol were dried for 2 hours at 100 C under reduced pressure (about 10 mbar) and then mixed with 0,1 part by wt. of dibutyltin dilaurate.

33 parts by wt. of the flowable, crude HDI/i80propanol-based polyisocyanate composition described in Example 1, having an NCO content of 25.9%
by weight, were added at 23 C with vigorous stirring using a prDpeller ~tirrer.

` ~13754~

The reaction mixture was transferred into a metallic mold having the internal dimensions 20xlOx0.5 cm which was held at a temperature of 50 C, and allowed to react there, ~nd the PU
elastomer formed was demolded after one hour.
A clear, bubble-free, dark-brown PU sheet was obtained on which the following mechanical properties were measured:
Tear strength [N/mm2] 0.92 10 Elongation at break [~]: 102 C; rative Example IV
The procedure was similar to that described in Example 6, but the 15 flowable crude MDI/isopropanol-based polyi~ocyanate composition was replaced by unmodified crude MDI having ~n NCO content of 31%
by weight.
An inhomogeneous, yellow-brown PU sheet cont~i~jng numerous gas 20 bubbles was obtained on which the following mechanical properties were measured:
Tear strength [N/mm2] 0.26 Elongation at break [~]: 44

Claims (10)

1. A process for the preparation of compact or cellular poly-urethanes by reacting a) relatively high-molecular-weight polyhydroxyl compounds containing at least two reactive hydrogen atoms with b) liquid, diphenylmethane diisocyanate-based polyisocyanate compositions containing bonded urethane groups, in the presence or absence of c) chain extenders and/or crosslinking agents, d) blowing agents, e) catalysts and f) auxiliaries, wherein the polyisocyanate compositions (b) used are obtain-able by reacting mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates with a substoi-chiometric amount of at least one linear, branched or cyclic, saturated or olefinically unsaturated, low-molecular-weight monoalcohol.

2. A process as claimed in claim 1, wherein the relatively high-molecular-weight polyhydroxyl compounds (a) have a function-ality of from 2 to 8 and a molecular weight of from 400 to 8000, and the chain extenders and/or crosslinking agents (c) have a functionality of from 2 to 5 and a molecu-lar weight of less than 400.

3. A process as claimed in claim 1, wherein the mixture of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates which can be used for the preparation of the polyisocyanate compositions (b) has a diphenylmethane diiso-cyanate isomer content of from 30 to 95% by weight.

4. A process as claimed in claim 1, wherein the low-molecular-weight alcohols which can be used for the preparation of the polyisocyanate compositions (b) have 1 to 6 carbon atoms.

5. A process as claimed in claim 1, wherein 1 kg of polyisocya-nate composition contains from 0.1 to 2 mol of urethane groups.

6. A liquid polyisocyanate composition containing urethane groups, obtainable by reacting a mixture of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates with a substoichiometric amount of at least one linear, branched or cyclic, saturated or olefinically unsaturated monoalcohol having 1 to 6 carbon atoms.

7. A liquid polyisocyanate composition containing urethane groups as claimed in claim 6,which is prepared using a mix-ture of diphenylmethane diisocyanates and polyphenylpoly-methylene polyisocyanates containing from 30 to 95% by weight of diphenylmethane diisocyanate isomers.

8. A liquid polyisocyanate composition containing urethane groups as claimed in claim 6, which contains from 0.1 to 2 mol of urethane groups per kg.

9. A liquid polyisocyanate composition containing urethane groups as claimed in claim 6, wherein the monoalcohols used are methanol, ethanol, n-propanol, isopropanol and/or allyl alcohol.

10. The use of a liquid polyisocyanate composition containing urethane groups as claimed in claim 6 for the production of rigid polyurethane foams.