Process for the production of urethane-modified polyisocyanate using an oxyalkylated bisphenol
BACKGROUND OF THE INVENTION 
     This invention relates to a new process for the production of urethane-modified polyisocyanates which are particularly valuable starting materials in the production of polyurethane plastics. 
     Processes for the production of urethane-modified polyisocyanate preparations (i.e. isocyanate-terminated prepolymers or semiprepolymers), particularly those based on polyisocyanates or polyisocyanate mixtures of the diphenyl methane series (4,4&#39;-diisocyanatodiphenylmethane, mixtures thereof with 2,4&#39;- and, optionally 2,2&#39;-diisocyanatodiphenylmethane or phosgenation products of aniline/formaldehyde condensates which, in addition to these diisocyanates, contain higher homologs thereof), and a variety of different polyhydroxyl compounds are known to those skilled in the art. For example, such processes are described in European Patent Applications 10 850 and 66 130; German Offenlegungsschriften Nos. 23 47 207, 24 04 166, 25 13 793, 25 13 796, 26 20 222, 26 22 104, 27 32 182, 27 37 338, 28 04 375, 28 10 596, 28 15 579 and 29 13 126; U.S. Pat. No. 3,644,457; 4,055,548, 4,234,714 and 4,321,333 and also Great Britain No. 1,369,334. In general, the processes described in these publications are concerned with the liquefaction of diisocyanatodiphenylmethane (more particularly 4,4&#39;-diisocyanatodiphenylmethane) which is solid at room temperature or with a reduction in the tendency towards crystallization during storage at low temperatures of polyisocyanate mixtures of the diphenylmethane series which mixtures are liquid at room temperature. 
     SUMMARY OF THE INVENTION 
     It has now surprisingly been found that urethane-modified polyisocyanates based on organic polyisocyanates, particularly aromatic polyisocyanates, and more preferably on polyisocyanates or polyisocyanate mixtures of the diphenylmethane series and alkoxylation products of bisphenols of the type described in greater detail hereinafter have a reduced melting point and a reduced tendency towards crystallization during storage at low temperatures. These urethane-modified polyisocyanates may be used in the production of polyurethane plastics, particularly polyurethane moldings, having a homogeneous surface which have considerably improved mechanical properties, such as better thermal stability, greater rigidity and better green strength coupled with high flexibility and high breaking elongation. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates to a process for the production of urethane-modified polyisocyanate preparations having an NCO-content of from 5 to 45 wt. % in which organic polyisocyanates having an NCO-content of from 30 to 50 wt. % or mixtures of organic polyisocyanates having an average NCO-content of from 30 to 50 wt. % are reacted with organic polyhydroxyl compounds in quantities such that the NCO:OH equivalent ratio is maintained at from 2:1 to 50:1 during the reaction. The organic polyhydroxyl compounds used are alkoxylation products of bisphenols containing two alcoholic hydroxyl groups and having an OH-number in the range from 112 to 389 which bisphenols correspond to the formula ##STR1## in which R 1  represents a C 1  -C 4  -alkyl radical, chlorine or bromine, 
     R 2  and R 3  which may be the same or different, each represent hydrogen or C 1  -C 6  -alkyl radicals or, together with the carbon atom attaching the two aromatic rings, form a 5- to 7-membered cycloaliphatic hydrocarbon radical, and n=0 or an integer of from 1 to 4. Up to 90, preferably 50, hydroxyl equivalent percent of other organic polyhydroxyl compounds may be used in admixture with the alkoxylation products of bisphenols. 
     The urethane-modified polyisocyanates obtained by this process may be used as starting materials in the production of polyurethane plastics by the isocyanate polyaddition process. 
     Organic polyisocyanates having an NCO-content of from 30 to 50 wt. % or mixtures of organic polyisocyanates such as these having an average NCO-content of from 30 to 50 wt. % may be used as starting materials in the process of the present invention. Polyisocyanates containing aromatically bound isocyanate groups are preferably used. Examples of such polyisocyanates include: 2,4-diisocyanatotoluene; 2,6-diisocyanatotoluene; 1,ω-bis-(isocyanatophenyl)-alkanes such as 1,2-bis-(4-isocyanatophenyl)-ethane; alkyl-substituted and, more particularly, methyl-substituted diisocyanatodiphenylmethanes of the type described, for example, in European Patent Applications Nos. 24 665 and 46 556; and, preferably, polyisocyanates or polyisocyanate mixtures of the diphenylmethane series. Mixtures of polyisocyanates such as these may also be used in the practice of the present invention. The particularly preferred polyisocyanate mixtures of the diphenylmethane series are 4,4&#39;-diisocyanatodiphenylmethane, mixtures thereof with 2,4&#39;- and, optionally, 2,2&#39;-diisocyanatodiphenylmethane having a 2,4&#39;-diisocyanatodiphenylmethane content, based on the mixture as a whole, of up to 70 wt. % and preferably of up to 20 wt. %, the 2,2&#39;-diisocyanatodiphenylmethane content generally not exceeding 5 wt. %, and polyisocyanates of the type obtained by phosgenating aniline/formaldehyde condensates and which, in addition to the above-mentioned diisocyanatodiphenylmethane isomers, may contain different quantities of higher homologous polyisocyanates (generally 5 to 60 wt. %, based on the mixture as a whole). Diphenylmethane polyisocyanates or mixtures thereof, optionally in admixture with up to 50 NCO equivalent percent (based on the mixture as a whole), of other aromatic polyisocyanates, are preferably used as polyisocyanates in the process of the present invention. However, it is particularly preferred to use the polyisocyanates or polyisocyanate mixtures of the diphenylmethane series as the sole polyisocyanate component. 
     Reactants for the polyisocyanates are alkoxylation products of bisphenols corresponding to formula I containing two alcoholic hydroxyl groups and having an OH-number of from 112 to 389 and preferably from 200 to 354. It is preferred to use alkoxylation products of bisphenols corresponding to formula I in which n=0 and R 2  and R 3  are each methyl radicals. 
     Starting materials for the production of the above-mentioned alkoxylation products are, for example, 4,4&#39;-dihydroxydiphenylmethane; bisphenol A (4,4&#39;-dihydroxy-2,2-diphenylpropane); 3,3&#39;-dimethyl-4,4&#39;-dihydroxy-2,2-diphenylpropane; 3,3&#39;-di-n-hexyl-4,4&#39;-dihydroxy-2,2-diphenylpropane; 2,3,5,6,2&#39;,3&#39;,5&#39;,6&#39;-octachloro (or octabromo)-4,4&#39;-dihydroxy-2,2-diphenylpropane; 4,4&#39;-dihydroxy-2,2-diphenylhexane; 4,4&#39;-dihydroxy-2,2-diphenyloctane and 4,4&#39;-dihydroxy-1,1-diphenylcyclohexane. It is particularly preferred to use the alkoxylation products of bisphenol A in the process of the present invention. 
     The polyhydroxyl compounds used as reactants for the starting polyisocyanates are alkoxylation products containing alcoholic hydroxyl groups of starter molecules. The quantity of alkylene oxides used in carrying out this alkoxylation must be such that, on a statistical average, at least 90% and preferably all of the phenolic hydroxyl groups are converted into ether groups, so that at least 90 equivalent percent and preferably all of the hydroxyl groups of the alkoxylation products are alcoholic hydroxyl groups. The alkoxylation reaction may readily be carried out in such a way that hydroxyl-terminated polyether diols containing more than two incorporated alkylene oxide units per molecule and having a hydroxyl number of from 112 to 389 are formed. The alkylene oxides preferably used for the production of the alkoxylation products are ethylene oxide and/or propylene oxide in any order or mixtures of these alkylene oxides. The ethoxylation products and propoxylation products of bisphenol A having hydroxyl numbers in the above-mentioned range are particularly suitable for the process according to the present invention. 
     In addition to the above-mentioned alkoxylation products of bisphenols, other polyhydroxyl compounds may also be used in the process of the present invention in a quantity of up to 90 hydroxyl equivalent percent and preferably in a quantity of up to 50 hydroxyl equivalent percent, based on all the polyhydroxyl compounds. More particularly, the alkoxylation products of the bisphenols may be used in admixture with other polyhydroxyl compounds such as those described in the prior art publications cited above which have already been used for the modification of polyisocyanates of the diphenylmethane series. Accordingly, suitable polyhydroxyl compounds, which may optionally be used in combination with the polyhydroxyl alkoxylated bisphenols essential to the invention include simple glycols, preferably glycols containing ether groups and having an (average) molecular weight of from 62 to 700, such as ethylene glycol, 1,2-dihydroxypropane, 1,4-dihydroxybutane, polyethylene glycols and, in particular, polypropylene glycols. Linear or branched polyether polyols having a molecular weight in the range from 700 to 10,000 and preferably in the range from 2000 to 6000 such as the corresponding alkoxylation products of suitable low molecular weight starter molecules (e.g. the simple glycols just mentioned) or of suitable higher starter molecules such as glycerol or trimethylol propane. Mixtures of the above-mentioned low molecular weight and/or relatively high molecular weight polyhydroxyl compounds may of course be used together with the polyhydroxyl compounds essential to the present invention. It is also possible in principle to react successively the starting polyisocyanates with the alkoxylation products of bisphenols essential to the invention and then with the other polyhydroxyl compounds mentioned above or even in reverse order with those polyhydroxyl compounds. However, the process of the present invention is preferably carried out using only alkoxylated bisphenols of the type mentioned above. 
     In the processes of the present invention, the reactants are used in quantities such that the equivalent ratio of isocyanate groups to hydroxyl groups of the alkoxylated bisphenols and any optional polyhydroxyl compounds is from 2:1 to 50:1, preferably from 4:1 to 20:1. 
     The process of the present invention is generally carried out at a temperature in the range from 20° to 140° C. and preferably at a temperature in the range from 40° to 120° C. The reaction is generally carried out by combining the reactants at room temperature and then heating them to at most 140° C. and preferably to between 40° and 100° C. until the calculated NCO-content has been reached. It is also possible and, in some cases (particularly when the hydroxyl component has a relatively high melting point and poor solubility in the polyisocyanate) even preferred to heat the starting polyisocyanate or polyisocyanate mixture to a temperature of from 40° to 140° C. (preferably from 80° to 120° C.) and then to add the polyhydroxyl component either all at once or preferably in portions. In this connection, it is important to ensure that the temperature prevailing inside the reaction vessel does not exceed the upper limit of approximately 140° C. in order to avoid secondary reactions such as trimerization of the isocyanate groups. The resulting polyisocyanates containing urethane groups are generally so-called semiprepolymers, i.e. mixtures of unreacted starting polyisocyanate with urethane-modified NCO-prepolymers. It is only where low NCO:OH equivalent ratios within the ranges mentioned above are used that genuine NCO-prepolymers containing only very small quantities of unreacted starting polyisocyanate are formed almost exclusively in the process of the present invention. The NCO-content of the products obtained by the process of the present invention lies within the 5 to 45 wt. % limits mentioned above, depending upon the starting materials used and the quantitative ratios in which they are used. Where the preferred polyisocyanates or polyisocyanate mixtures of the diphenylmethane series are used, products having an NCO content of from 5 to 30 wt. % and, more particularly, from 18 to 28 wt. % are generally formed. 
     The products obtained by the process of the present invention generally have a lower melting point than the corresponding starting polyisocyanate. They may be used with advantage, optionally in admixture with other polyisocyanates of the type known to those skilled in polyurethane chemistry, for the production of polyurethane plastics. The products obtained by the process of the present invention may be used with particular advantage as the polyisocyanate component in the production of molded plastics by the &#34;RIM&#34; process, i.e. both for the production of rigid, semi-rigid and flexible integral foams and also for the production of the corresponding solid, i.e. at best microcellular, moldings having a gross density of from 0.8 to 1.4 and preferably from 0.9 to 1.2 g/cc. 
     In such applications, the products of the process of the present invention may be used either instead of or in admixture with the polyisocyanates normally used for this purpose. The organic compounds having isocyanate-reactive groups, other reactants and auxiliaries suitable for the production of polyurethanes as well as process parameters are known to those in the art. For example German Offenlegungsschriften Nos. 19 53 637, 21 21 670, 23 56 692, 23 63 452, 24 04 310, 24 27 273, 24 31 968, 23 07 589, 23 19 648, 30 12 126 and 31 47 736; U.S. Pat. Nos. 4,065,410 and 4,218,543 and published European Patent Applications (publication numbers) 17 928, 44 481 or 81 701 each disclose appropriate materials and process parameters for the production of polyurethanes. 
     The products obtained by the process of the present invention may of course also be used with advantage as polyisocyanate component in the production of polyurethane plastics, such as free-foamed rigid, semi-rigid or flexible polyurethane foams, either instead of or in admixture with the polyisocyanates previously used for that purpose. 
     The polyurethane plastics obtained using the products of the process of the present invention are distinguished by excellent mechanical properties. These polyurethanes may be used for the same applications as state-of-the-art polyurethane plastics. 
    
    
     In the following Examples, all of the percentages quoted represent percentages by weight and all of the parts quoted represent parts by weight. 
     EXAMPLES 
     The following compounds were used to produce the urethane-modified polyisocyanate preparations (NCO-semiprepolymers) in the Examples which follow: 
     Polyisocyanate I: 4,4&#39;-diisocyanatodiphenylmethane (NCO-content: 33.6%). 
     Polyisocyanate II: A mixture of 60% of 4,4&#39;- and 40% of 2,4&#39;-diisocyanatodiphenylmethane (NCO-content: 33.5%). 
     Polyisocyanate III: A mixture of 83% of 4,4&#39;-diisocyanatodiphenylmethane, 7% of 2,4&#39;-diisocyanatodiphenylmethane and 10% of higher polyisocyanates of the diphenylmethane series (NCO-content: 31.8%). 
     Polyisocyanate IV: The crude phosgenation product of an aniline/formaldehyde condensate from which so much diisocyanatodiphenylmethane isomers had been distilled off that the distillation residue had a viscosity at 25° C. of 100 cP (NCO-content: 31%). 
     Diol I: 4,4&#39;-bis-[(2-hydroxyethoxy)phenyl]-2,2-propane obtained by the ethoxylation of bisphenol A (hydroxyl number 354). 
     Diol II: The propoxylation product of bisphenol A having an OH number of 320. 
     Diol III: The propoxylation product of bisphenol A having an OH number of 200. 
     Polyol IV: A polyether polyol having an OH number of 28 produced by the propoxylation of trimethylol propane, followed by ethoxylation of the propoxylation product (ratio by weight of PO to EO=87:13). 
     Diol V: Dipropylene glycol 
     Diol VI: Tripropylene glycol. 
     EXAMPLE 1 
     (Process according to the invention) 
     The starting polyisocyanates specified below were mixed at 25° C. with the diols identified below, after which the reaction mixtures were heated with stirring for 4 hours to 80° C. The NCO-prepolymers I to XIX described below were each obtained in this way, unless otherwise indicated. The NCO-contents indicated correspond to the values obtained by analysis. 
     NCO-semiprepolymer I: from polyisocyanate I (5.9 moles of NCO) and diol I (1 mole of OH). Viscosity (25° C.)=2600 mPas, NCO=22.4 wt. %. 
     NCO-semiprepolymer II: from polyisocyanate II (5.03 moles of NCO) and diol I (1 mole of OH). Viscosity (25° C.)=41800 mPas, (40° C.)=5300 mPas, NCO=20.0 wt. %. 
     NCO-semiprepolymer III: from polyisocyanate III (6.91 moles of NCO) and diol II (1 mole of OH). Viscosity (25° C.)=6390 mPas, NCO=22.5 wt. %. 
     NCO-semiprepolymer IV: from polyisocyanate IV (25 moles of NCO) and diol II (1 mole of OH). Viscosity (25° C.)=675 mPas, NCO=27.9 wt. %. 
     NCO-semiprepolymer V: from polyisocyanate III (8.83 moles of NCO) and diol III (1 mole of OH). Viscosity (25° C.)=1100 mPas, NCO=22.9 wt. %. 
     NCO-semiprepolymer VI: from polyisocyanate II (9.26 moles of NCO) and diol I (1 mole of OH). Viscosity (25° C.)=65,000 mPas, NCO=24.3 wt. %. 
     NCO-semiprepolymer VII: from polyisocyanate III (7.6 moles of NCO) and a mixture of diols I (0.08 mole OH) and II (0.84 mole OH). Viscosity (25° C.)=6000 mPas, NCO=22.6 wt. %. 
     NCO-semiprepolymer VIII: from polyisocyanate III (7.6 moles of NCO) and a mixture of diols I (0.1 mole OH) and II (0.9 mole OH). Viscosity (25° C.)=6200 mPas, NCO=22.9 wt. %. 
     NCO-semiprepolymer IX: from polyisocyanate III (6.91 moles NCO) and diol II (1 mole OH), heating for 2 hours to 80° C., addition to diol III (0.49 mole), stirring for 3 hours at 80° C. and further addition of isocyanate III (0.58 mole NCO). Viscosity (25° C.)=40,000 mPas, NCO=19.9 wt. %. 
     NCO-semiprepolymer X: from polyisocyanate III (6.91 moles NCO) and a mixture of diols II (1 mole OH) and III (0.44 mole OH), further addition of isocyanate III (0.55 mole NCO). Viscosity (25° C.)=47,000 mPas, NCO=19.8 wt. %. 
     NCO-semiprepolymer XI: from polyisocyanate III (9.31 moles NCO) and diol II (1 mole OH). Viscosity (25° C.)=830 mPas, NCO=24.5 wt. %. 
     NCO-semiprepolymer XII: from polyisocyanate I (11.99 moles NCO) and polyol I (1 mole OH). Viscosity (40° C.)=35 mPas, NCO=26.8 wt. %. 
     NCO-semiprepolymer XIII: from polyisocyanate III and diol II (4.76 moles NCO to 1 mole OH). NCO=20.6 wt. %. Viscosity (25° C.)=22,100 mPas. 
     NCO-semiprepolymer XIV: from polyisocyanate III (5.3 moles NCO) and diol II (0.78 mole OH) by combination at 25° C. and stirring for 3 hours at 80° C., followed by the addition of polyol IV (0.104 mole OH) and stirring for another 3 hours at 80° C. Viscosity (28° C.)=15,000 mPas, NCO=17.95 wt. %. 
     NCO-semiprepolymer XV: same formulation as for semiprepolymer XIV, except that diol II and polyol IV were added in the form of a mixture. Viscosity (25° C.)=8400 mPas, NCO=18.3 wt. %. 
     NCO-semiprepolymer XVI: from polyisocyanate III (3.78 moles NCO) and a mixture of diols I (0.12 mole OH) and II (0.7 mole OH) by combination at 25° C. and heating for 3 hours at 80° C., followed by the addition of polyol IV (0.094 mole OH) and heating for another 3 hours to 80° C. Viscosity (25° C.)=34,000 mPas, NCO=14.5 wt. %. 
     NCO-semiprepolymer XVII: from polyisocyanate I (20 moles NCO) and a mixture of diols I (1.08 mole OH) and V (1.08 mole OH). Viscosity (25° C.)=1200 mPas, NCO=23.7 wt. %. 
     NCO-semiprepolymer XVIII: from polyisocyanate III (20 moles NCO) and a mixture of diols II (1.08  mole OH) and V (1.08 mole OH). Viscosity (25° C.)=1650 mPas, NCO=24.2 wt. %. 
     NCO-semiprepolymer XIX: from polyisocyanate I (3.37 moles NCO) and a mixture of diols II (0.31 mole OH) and VI (0.08 mole OH). Viscosity (25° C.)=850 mPas, NCO=23 wt. %. 
     APPLICATION EXAMPLES 
     Examples 2 to 15 were carried out using a standard, commercially available piston metering unit equipped with a positively controlled mixing head (a Rimdomat® piston metering unit equipped with a plunger-cleaned throttle slide mixing head MQ of the type manufactured by the Hennecke Company of St. Augustin). The mold used was a closed aluminum mold internally measuring 500×350×4 mm of which the inner walls had been sprayed with a commercially available wax-based mold release agent (Acmos® 180 ST/5, a product of the Acmos Company). In each case, the internal temperature of the mold was 60° C. and the temperature of the starting materials 45° C. The mold filling time was 1.5 seconds in each case and the residence time in the mold 30 seconds. In all the Examples, the NCO-index was 110. 
     EXAMPLE 2 
     
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Formulation                                                               
2A      2B      20                                                        
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100     100     100       parts of a polyether                            
                          triol having an OH number                       
                          of 28, obtained by the                          
                          blockwise addition of 83%                       
                          of propylene oxide and                          
                          then 17% of ethylene oxide                      
                          onto trimethylol propane                        
                          were combined with                              
22      24      30        parts of a mixture of 65                        
                          parts of 3,5-diethyl-2,4-                       
                          tolylene diamine (amine                         
                          I),                                             
0.1     0.1     0.1       part of triethylene                             
                          diamine,                                        
0.1     0.1     0.1       part of dimethyl tin                            
                          dilaurate and                                   
61.7    68.9    80.7      parts of NCO-semi-                              
                          prepolymer II.                                  
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     The following properties were obtained: 
     
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Unit weight    2A        2B        2C                                     
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(kg/m.sup.3, DIN 53420)                                                   
               1083      1100      1094                                   
Tensile strength (MPa,                                                    
               24 ± 0.8                                                
                         25.7 ± 2                                      
                                   30.9 ± 1.6                          
DIN 53 504)                                                               
Breaking elongation (%,                                                   
               223 ± 3                                                 
                           207 ± 15                                    
                                   202 ± 8                             
DIN 53504)                                                                
Sag value (1/2 h,                                                         
               13.5      7.5       6.5                                    
160° C) (mm)                                                       
E-modulus in flexure                                                      
               173       238       320                                    
(MPa, ASTM-D 790)                                                         
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     EXAMPLE 3 
     
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Formulation:                                                              
3A      3B                                                                
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100     100       parts of the polyether triol used                       
                  in Example 1 were combined with                         
40      55        parts of a mixture of 50% of                            
                  3,5-diethyl-3&#39;,5&#39;-diisopropyl-                          
                  4,4&#39;-diaminodiphenylmethane, 25% of                     
                  3,5,3&#39;,5&#39;-tetraethyl-4,4&#39;-diamino-                      
                  diphenylmethane and 25% of                              
                  3,5,3&#39;,5&#39;-tetraisopropyl-4,4&#39;-                          
                  diaminodiphenylmethane,                                 
0.1     0.1       part of triethylene diamine                             
0.1     0.1       part of the tin catalyst used in                        
                  Example 2 and                                           
58.9    77.6      parts of NCO-prepolymer I.                              
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     The following properties were obtained (same test methods as in Example 2): 
     
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                 3A      3B                                               
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Unit weight (kg/m.sup.3)                                                  
                   1102      1081                                         
Tensile strength (MPa)                                                    
                   32.5 ± 2.5                                          
                             33.2 ± 1.5                                
Breaking elongation (%)                                                   
                   288 ± 15                                            
                             245 ± 7                                   
Sag value (1/2 h,    2       2.5                                          
160° C.) (mm)                                                      
E-modulus in flexure (MPa)                                                
                    228      395                                          
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     EXAMPLE 4 
     
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Formulation:                                                              
4A    4B        4C      4D                                                
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100   100       100     100     parts of the poly-                        
                                ether triol of                            
                                Example 2 were                            
                                combined with                             
22    25        30      33.5    parts of amine I                          
                                from Example 2,                           
0.1   0.1       0.1     0.1     part of triethylene                       
                                diamine,                                  
0.1   0.1       0.1     0.1     part of the same                          
                                tin catalyst as in                        
                                Example 2 and                             
59.9  67.0      78.1    85.2    parts of the                              
                                NCO-semiprepolymer                        
                                III.                                      
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     The following properties were obtained (same test methods as in Example 2): 
     
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             4A    4B        4C      4D                                   
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Unit weight (kg/m.sup.3)                                                  
               1073    1080      1074  1082                               
Tensile strength (MPa)                                                    
               23.5    26.5      29.5  30.5                               
Breaking elongation (%)                                                   
               224     223       201   184                                
Sag value (1/2 h,                                                         
                9       7         4     4                                 
160 ° C.) (mm)                                                     
E-modulus in flexure                                                      
               196     269       376   438                                
(MPa)                                                                     
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     EXAMPLE 5 
     (Comparison) 
     This Example 5 is a comparison with Example 4. Instead of an NCO-semiprepolymer according to the invention, a standard commercially available product was used. 
     
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Formulation:                                                              
5A    5B      5C      5D                                                  
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100   100     100     100   parts of the polyether triol                  
                            used in Example 2 were                        
                            combined with                                 
22    25      30      33.5  parts of amine I from Example                 
                            2,                                            
0.1   0.1     0.1     part of triethylene diamine,                        
0.1   0.1     0.1     0.1   part of the same tin catalyst                 
                            as in Example 2, and                          
55.6  62.6    72.9    79.9  parts of an isocyanate having                 
                            an NCO-content of 24.5%                       
                            obtained by reacting                          
                            polyisocyanate III with                       
                            dipropylene glycol.                           
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     The following properties were obtained (same test methods as in Example 2): 
     
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               5A    5B      5C      5D                                   
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Unit weight (kg/m.sup.3)                                                  
                 1083    1085    1098  1085                               
Tensile strength (MPa)                                                    
                 23.5    25      28    29                                 
Breaking elongation (%)                                                   
                 254     241     226   205                                
Sag value (1/2 h,                                                         
                  10      7       4     5                                 
160° C.) (mm)                                                      
E-modulus in flexure (MPa)                                                
                 181     229     329   406                                
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     EXAMPLE 6 
     
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Formulation:                                                              
6A    6B      6C      6D                                                  
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100   100     100     100   parts of a filler polyol (OH                  
                            number 28) of 20 parts of a                   
                            styrene/acrylonitrile copoly-                 
                            mer of 60% acrylonitrile and                  
                            40% styrene and 80 parts of a                 
                            polyether triol (OH number                    
                            35) obtained by the addition of               
                            83% propylene oxide and 17%                   
                            ethylene oxide onto trimethylol               
                            propane were combined with                    
19    22      25      30    parts of amine I from Example                 
                            2,                                            
0.1   0.1     0.1     0.1   part of triethylene diamine,                  
0.1   0.1     0.1     0.1   part of the same tin catalyst                 
                            as in Examp1e 2, and                          
53.6  59.9    67      78.1  parts of NCO-semiprepolymer                   
                            III.                                          
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     The following properties were obtained (same test methods as in Example 2): 
     
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               6A    6B      6C      6D                                   
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Unit weight (kg/m.sup.3)                                                  
                 1056    1080    1099  1099                               
Tensile strength (MPa)                                                    
                 25.8     29     34.1  35.5                               
Breaking elongation (%)                                                   
                 184     169     184   140                                
Sag value (1/2 h, 160° C.) (mm)                                    
                  16      10      6     8                                 
E-modulus in flexure (MPa)                                                
                 318     385     492   637                                
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     EXAMPLE 7 
     (Comparison) 
     This Example 7 is a comparison with Example 6. Instead of an NCO-prepolymer according to the invention, a standard commercially available NCO-semiprepolymer was used. 
     
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Formulation:                                                              
7A    7B      7C      7D                                                  
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100   100     100     100   parts of the filler polyol                    
                            used in Example 6 were com-                   
                            bined with                                    
19    22      25      30    parts of amine I from Example                 
                            2,                                            
0.1   0.1     0.1     0.1   part of triethylene diamine,                  
0.1   0.1     0.1     0.1   part of the same tin catalyst                 
                            as in Example 2 and                           
49.5  55.6    62.0    72.9  parts of the same isocyanate                  
                            as was used in Example 5.                     
______________________________________                                    
 
    
     The following properties were obtained (same test methods as in Example 2): 
     
         ______________________________________                                    
               7A    7B      7C      7D                                   
______________________________________                                    
Unit weight (kg/m.sup.3)                                                  
                 1073    1072    1075  1083                               
Tensile strength (MPa)                                                    
                 25.7    27       27    30                                
Breaking elongation (%)                                                   
                 183     183     176   172                                
Sag value (1/2 h, 160° C.) (mm)                                    
                  15     10       7     3                                 
E-modulus in flexure (MPa)                                                
                 279     362     435   551                                
______________________________________                                    
 
    
     EXAMPLE 8 
     In Example 8, a polyether containing terminal aromatic amino groups was used instead of the polyether triols of Examples 2 to 7. 
     
         ______________________________________                                    
Formulation:                                                              
8A    8B      8C                                                          
______________________________________                                    
100   100     100     parts of an aminopolyether having                   
                      an NH-number of 47.0 (mg KOH/g)                     
                      and a viscosity (25° C.) of 12,000           
                      mPas was combined with the                          
                      materials listed below. This                        
                      aminopolyether was obtained by the                  
                      basic hydrolysis of the terminal                    
                      NCO-groups of an NCO-prepolymer                     
                      according to German Offen-                          
                      legungsschrift 31 31 252. The                       
                      NCO-prepolymer itself had an                        
                      NCO-content of 3.6% and was the                     
                      thin-layered reaction product of                    
                      2,4-diisocyanato-toluene and a                      
                      polyether mixture of 2 parts of a                   
                      polyether produced from a mixture                   
                      of trimethylol propane and water                    
                      by the addition of propylene oxide                  
                      and then ethylene oxide and having                  
                      an OH-number of 56, a function-                     
                      ality of 2.4 and a molecular                        
                      weight of 2400 and 1 part of a                      
                      polyether produced from glycerin                    
                      by the blockwise addition of                        
                      propylene oxide, ethylene oxide,                    
                      propylene oxide and again ethylene                  
                      oxide and having an OH-number of                    
                      35, a functionality of 3 and a                      
                      molecular weight of 4800.                           
22    25      30      parts of amine I from Example 2,                    
0.1   0.1     0.1     part of triethylene diamine,                        
0.1   0.1     0.1     part of the same tin catalyst as                    
                      in Example 2 and                                    
67.2  73.9    84.6    parts of NCO-semiprepolymer III                     
                      were added.                                         
______________________________________                                    
 
    
     The following properties were obtained (same test methods as in Example 2): 
     
         ______________________________________                                    
               8A      8B      8C                                         
______________________________________                                    
Unit weight (kg/m.sup.3)                                                  
                 1104      1079    1076                                   
Tensile strength (MPa)                                                    
                 29.9      36.6    41.5                                   
Elongation (%)   142       142     116                                    
Sag value (1/2 h, 160° C.) (mm)                                    
                  12        8       3                                     
E-modulus in flexure (MPa)                                                
                 452       638     779                                    
______________________________________                                    
 
    
     EXAMPLE 9 
     (Comparison) 
     This Example 9 is a comparison with Example 8. Instead of an NCO-semiprepolymer according to the invention, a standard commercially available product was used. 
     
         ______________________________________                                    
Formulation:                                                              
9A     9B      9C                                                         
______________________________________                                    
100    100     100       parts of the aminopolyether used                 
                         in Example 8 were combined with                  
22     25      30        parts of amine I from Example 2,                 
0.1    0.1     0.1       part of triethylene diamine,                     
0.1    0.1     0.1       part of the same tin catalyst as                 
                         in Example 2 and                                 
62.3   68.2    78.8      parts of the same isocyanate used                
                         in Example 5.                                    
______________________________________                                    
 
    
     The following properties were obtained (same test methods as in Example 2): 
     
         ______________________________________                                    
               9A      9B      9C                                         
______________________________________                                    
Unit weight (kg/m.sup.3)                                                  
                 1062      1061    1079                                   
Tensile strength (MPa)                                                    
                  31        31      33                                    
Elongation (%)   182       176     158                                    
Sag value (1/2 h, 160° C.) (mm)                                    
                  14        9       4                                     
E-modulus in flexure (MPa)                                                
                 417       480     651                                    
______________________________________                                    
 
    
     EXAMPLES 10 AND 11 
     
         ______________________________________                                    
Formulations:                                                             
10A   10B     11A     11B                                                 
______________________________________                                    
100   100     --      --    parts of the polyether triol                  
                            used in Example 2 or                          
--    --      100     100   parts of a polyether triol                    
                            obtained by the blockwise                     
                            addition of 80% of propylene                  
                            oxide and 20% of ethylene                     
                            oxide onto 1,2-propane diol                   
                            (OH number 28) were com-                      
                            bined with                                    
40    55      --      --    parts of the amine used in                    
                            Example 3 or                                  
--    --      22      30    parts of amine I from Example                 
                            2,                                            
0.1   0.1     0.1     0.1   part of triethylene diamine,                  
0.1   0.1     0.1     0.1   part of the same tin catalyst                 
                            as in Example 2 and                           
57.5  76.0    61.1    78.8  parts of the                                  
                            NCO-semiprepolymer III.                       
______________________________________                                    
 
    
     The following properties were obtained (same test methods as in Example 2): 
     
         ______________________________________                                    
           10A    10B      11A      11B                                   
______________________________________                                    
Unit weight (kg/m.sup.3)                                                  
             1078     1068     1091   1084                                
Tensile strength (MPa)                                                    
             26.4 ±                                                    
                      31.4 ±                                           
                               29.5 ±                                  
                                      28.1 ±                           
             0.8      2.5      1.5    3.5                                 
Breaking elongation                                                       
             253 ± 3                                                   
                      220 ± 3                                          
                               307 ± 13                                
                                      219 ± 27                         
(%)                                                                       
Sag value (1/2 h,                                                         
              6        2        9     3.5                                 
160° C.) (mm)                                                      
E-modulus in flexure                                                      
             265      411      263     424                                
(MPa)                                                                     
______________________________________                                    
 
    
     EXAMPLE 12 
     
         ______________________________________                                    
Formulation:                                                              
12A    12B     12C                                                        
______________________________________                                    
100    100     100       parts of the polyether triol of                  
                         Example 2 were combined with                     
22     25      30        parts of amine I from Example 2,                 
0.1    0.1     0.1       part of triethylene diamine,                     
0.1    0.1     0.1       part of the same tin catalyst as                 
                         in Example 2 and                                 
59.9   67.0    78.1      parts of NCO-semiprepolymer V.                   
______________________________________                                    
 
    
     The following mechanical values were obtained (same test methods as in Example 2): 
     
         ______________________________________                                    
              12A     12B      12C                                        
______________________________________                                    
Unit weight (kg/m.sup.3)                                                  
                1089      1068     1100                                   
Tensile strength (MPa)                                                    
                18.3 ± 0.9                                             
                          26.1 ± 1                                     
                                   28.4 ± 1.4                          
Breaking elongation (%)                                                   
                109 ± 4                                                
                           230 ± 7                                     
                                   226 ± 9                             
Sag value (160° C., 1/2 h)                                         
                10.5       11       7                                     
(mm)                                                                      
E-modulus in flexure (MPa)                                                
                 152      229      297                                    
______________________________________                                    
 
    
     EXAMPLE 13 
     
         ______________________________________                                    
Formulation:                                                              
13A    13B     13C                                                        
______________________________________                                    
100    100     100       parts of the polyether triol of                  
                         Example 2 were combined with                     
22     25      30        parts of amine I from Example 2,                 
0.1    0.1     0.1       part of triethylene diamine,                     
0.1    0.1     0.1       part of the same tin catalyst as                 
                         in Example 2 and                                 
56     65      74        parts of NCO-prepolymer II.                      
______________________________________                                    
 
    
     The following properties were obtained (same test methods as in Example 2): 
     
         ______________________________________                                    
               13A     13B     13C                                        
______________________________________                                    
Unit weight (kg/m.sup.3)                                                  
                 1050      1070    1050                                   
Tensile strength (MPa)                                                    
                  21        23      27                                    
Elongation (%)   310       300     260                                    
Sag value (1/2 h, 160° C.) (mm)                                    
                  17        8       7                                     
E-modulus in flexure (MPa)                                                
                 150       210     290                                    
______________________________________                                    
 
    
     EXAMPLE 14 
     
         ______________________________________                                    
Formulation:                                                              
14A    14B     14C                                                        
______________________________________                                    
100    100     100       parts of the polyether triol of                  
                         Example 2 were combined with                     
22     25      30        parts of amine I from Example 2,                 
0.1    0.1     0.1       part of triethylene diamine,                     
0.1    0.1     0.1       part of the same tin catalyst as                 
                         in Example 2 and                                 
41     44      50        parts of NCO-prepolymer IV.                      
______________________________________                                    
 
    
     The following properties were obtained (same test methods as in Example 2): 
     
         ______________________________________                                    
                14A     14B     14C                                       
______________________________________                                    
Unit weight (kg/m.sup.3)                                                  
                  1100      1090    1090                                  
Tensile strength (MPa)                                                    
                   24        26      68                                   
Breaking elongation (%)                                                   
                  170       165     155                                   
Sag value (1/2 160° C.) (mm)                                       
                   6         5       2                                    
E-modulus in flexure (MPa)                                                
                  180       240     280                                   
______________________________________                                    
 
    
     EXAMPLE 15 
     
         ______________________________________                                    
Formulation:                                                              
15A    15B     15C                                                        
______________________________________                                    
100    100     100       parts of the polyether triol of                  
                         Example 2 were combined with                     
25     25      30        parts of amine I from Example 2,                 
0.1    0.1     0.1       part of triethylene diamine,                     
0.1    0.1     0.1       part of the same tin catalyst as                 
                         in Example 2 and                                 
56     65      74        parts of NCO-semiprepolymer VI                   
______________________________________                                    
 
    
     The following properties were obtained (same test methods as in Example 2): 
     
         ______________________________________                                    
                15A     15B     15C                                       
______________________________________                                    
Unit weight (kg/m.sup.3)                                                  
                  1060      1050    1050                                  
Tensile strength (MPa)                                                    
                   23        25      29                                   
Breaking elongation (%)                                                   
                  290       280     240                                   
Sag value (1/2 h, 160° C.) (mm)                                    
                   14        12      6                                    
E-modulus in flexure (MPa)                                                
                  170       220     210                                   
______________________________________                                    
 
    
     EXAMPLE 16 
     In contrast to Examples 2 to 15, Example 16 was carried out using a 2 liter-Rimdomat, a high-pressure apparatus manufactured by the Hennecke Company of St. Augustin with a mixing head of the type manufactured by the Krauss-Maffei Company of Munich. The working pressure was 180 bars on both components. The temperature of the starting materials was 40° C. The mold which was a steel mold internally measuring 200×200×4 mm, with the inner walls sprayed with the standard commercially available mold release agent as in Examples 2 to 15 was at a temperature of 60° C. The filling time was 1.5 seconds and the residence time in the mold was 60 seconds. 
     
         ______________________________________                                    
Formulation:                                                              
16A   16B    16C                                                          
______________________________________                                    
77    77     77       parts of the polyether triol of                     
                      Example 2 were combined with                        
23    23     23       parts of amine I from Example 2,                    
0.2   0.2    0.2      part of the same tin catalyst as                    
                      in Example 2,                                       
0.6   0.6    0.6      part of a 33% solution of                           
                      triethylene diamine in dipropylene                  
                      glycol,                                             
58.8  --     --       parts of semiprepolymer III (Index                  
                      105),                                               
--    67.2   --       parts of semiprepolymer XIII                        
                      (Index 105) and                                     
--    --     55       parts of the isocyanate used in                     
                      Example 5                                           
______________________________________                                    
 
    
     The following mechanical properties were obtained: 
     
         ______________________________________                                    
                16A     16B     16C                                       
______________________________________                                    
Unit weight (kg/m.sup.3)                                                  
                  1093      1102    1100                                  
DIN 53 420)                                                               
Tensile strength RT (MPa,                                                 
                   29       32.9    26                                    
DIN 53 504)                                                               
Breaking elongation (%,                                                   
                  269       224     250                                   
DIN 53 504)                                                               
Tear propagation resistance                                               
                  106       59.8    65                                    
(kN/m, DIN 53 515)                                                        
Shore D hardness   59        68     58                                    
(DIN 53 505)                                                              
Modulus at 50%    14.1      18.4    14.2                                  
(MPa, DIN 53 504)                                                         
Modulus in flexure RT                                                     
                  414       585     350                                   
(MPa, ASTM D-790)                                                         
______________________________________                                    
 
    
     EXAMPLE 17 
     A semi-rigid integral foam having a density of 700 was produced from the following formulations: 
     
         ______________________________________                                    
17A   17B     17C                                                         
______________________________________                                    
95    95      95      parts of a polyether triol having                   
                      an OH number of 27 obtained by the                  
                      blockwise addition of 78% of                        
                      propylene oxide and then 22% of                     
                      ethylene oxide onto trimethylol                     
                      propane were combined with                          
23.5  23.5    23.5    parts of ethylene glycol,                           
15    15      15      parts of dichloromethane,                           
0.1   0.1     0.1     part of triethylene diamine,                        
0,15  0,15    0,15    parts of the same tin catalyst as in                
                      Example 2                                           
278                   parts of the isocyanate used in                     
                      Example 5 or                                        
      292             parts of the commercially                           
                      available isocyanate having an NCO                  
                      content of 23% obtained by reacting                 
                      4,4&#39;-diisocyanatodiphenylmethane                    
                      with tripropylene glycol or                         
              276     parts of NCO-semiprepolymer III.                    
______________________________________                                    
 
    
     The components were intensively mixed and the reaction mixture was introduced into a closed steel mold internally measuring 20×20×1 cm which had been heated to 50° C. and of which the inner walls have been sprayed with the same standard commercially available release agent used in Examples 2 to 15. 
     The following properties were obtained (same test methods as in Example 16): 
     
         ______________________________________                                    
                17A     17B     17C                                       
______________________________________                                    
Unit weight (kg/m.sup.3)                                                  
                  694       710     698                                   
Shore D hardness  60        53      65                                    
E-modulus in flexure (MPa)                                                
+120° C.   15        21      12                                    
RT                281       252     357                                   
Tensile strength  9.1       7.6     9.1                                   
Breaking elongation (%)                                                   
                  71.3      71.0    59                                    
Sag value (160° C./30 mins.)                                       
                  12.8      12.7    9.3                                   
(mm)                                                                      
______________________________________                                    
 
    
     Examples 17A and 17B are comparison Examples. 
     EXAMPLE 18 
     
         ______________________________________                                    
Formulation:                                                              
95        parts of the polyether triol of Example 15,                     
23.5      parts of ethylene glycol,                                       
10        parts of dichloromethane,                                       
0.1       part of triethylene diamine and                                 
0.12      part of the tin catalyst of Example 1                           
______________________________________                                    
 
    
     were intensively mixed at room temperature and the resulting mixture subsequently mixed with one of the following isocyanates: 
     A: 253 parts of the commercially available isocyanate used in Example 5 (for comparison) 
     B: 279 parts of NCO-semiprepolymer III 
     C: 279 parts of NCO-semiprepolymer VII 
     D: 279 parts of NCO-semiprepolymer VIII 
     E: 279 parts of NCO-semiprepolymer IX 
     F: 279 parts of NCO-semiprepolymer X 
     G: 270 parts of NCO-semiprepolymer XI (0.2 part of triethylene diamine, 0.18 part of the Sn catalyst of Example 2) 
     H: 250 parts of NCO-semiprepolymer XII. 
     The resulting reaction mixture was subsquently introduced into the steel mold described in Example 17 heated to 60° C. and left to harden therein. The residence time in the mold was 2 minutes. 
     Example 18A is a Comparison Example. 
     The mechanical properties of each product are given in Table 1. 
     
                                           TABLE 1*                                
__________________________________________________________________________
                 18A                                                      
                    18B                                                   
                       18C                                                
                          18D                                             
                             18E                                          
                                18F                                       
                                   18G                                    
                                      18H                                 
__________________________________________________________________________
Unit weight      1005                                                     
                    1002                                                  
                       998                                                
                          1012                                            
                             1000                                         
                                1013                                      
                                   1005                                   
                                      1007                                
Shore D hardness 66 71 69 70 71 73 69 70                                  
E-modulus in flexure (MPa) RT                                             
                 361                                                      
                    594                                                   
                       579                                                
                          564                                             
                             559                                          
                                727                                       
                                   396                                    
                                      494                                 
120° C.   13 16 17 13 11 8  17 16                                  
E-modulus (MPa) from                                                      
                 275                                                      
                    464                                                   
                       448                                                
                          446                                             
                             470                                          
                                598                                       
                                   353                                    
                                      360                                 
tensile testing                                                           
Breaking elongation (%)                                                   
                 36 57 7.7                                                
                          26 68 64 19.3                                   
                                      10                                  
Tensile strength (MPa)                                                    
                 12.6                                                     
                    17.4                                                  
                       12.9                                               
                          16.4                                            
                             14.9                                         
                                18.0                                      
                                   13.9                                   
                                      14.1                                
Sag value (160° C./30 mins.) (mm)                                  
                 10.4                                                     
                    10.7                                                  
                       7.3                                                
                          10.4                                            
                             14.6                                         
                                8.3                                       
                                   8.1                                    
                                      5.2                                 
__________________________________________________________________________
 *(Same test methods as in Example 16, Emodulus according to DIN 53504).  
 
    
     EXAMPLE 19 
     
         ______________________________________                                    
Formulation:                                                              
19A    19B                                                                
______________________________________                                    
100    100      parts of a polyol mixture having an                       
                OH number of 56 and a viscosity (25° C.)           
                of 850 mPas, produced by mixing                           
          (a) 100 parts of a polyether (OH                                
              number 35) produced by the                                  
              addition of 82.5% of propylene                              
              oxide and 17.5% of ethylene                                 
              oxide onto trimethylol propane                              
              with                                                        
          (b) 10 parts of a polyether (OH                                 
              number l50) produced by the                                 
              addition of 87% of propylene                                
              oxide and 13% of ethylene oxide                             
              onto propylene glycol,                                      
1.4    1.4      parts of a solution of 20 wt. %                           
                potassium acetate and 80 wt. %                            
                dipropylene glycol,                                       
200    --       parts of the commercially available                       
                isocyanate used in Example 5 or                           
--     200      parts of NCO-semiprepolymer XII were                      
                combined.                                                 
______________________________________                                    
 
    
     Solid, 10 mm thick moldings (200×200×10 mm) were cast from the intensively stirred mixture in the steel mold described in Example 17 (T=70° C.) and hardened (residence time in the mold: 1 minute), NCO-index=1213 (19A) and 1280 (19B). 
     Example 19A is a Comparison Example. 
     The following properties were obtained (same test methods as in Example 16): 
     
         ______________________________________                                    
                 19A      19B                                             
______________________________________                                    
Unit weight (kg/m.sup.3)                                                  
                   1158       1213                                        
Heat distortion temperature                                               
                   191        238                                         
(°C.)                                                              
Modulus in flexure 0.31 MPa,                                              
heating rate 50° C./h, sag (10 mm)                                 
Modulus in shear (MPa)  20° C.                                     
                   503        568                                         
(DIN 53 445)100° C.                                                
                   288        329                                         
180° C.     153        207                                         
Modulus in shear 180° C./20° C.                             
                   0.30       0.36                                        
Linear expansion   1.35 × 10.sup.-6                                 
                              0.85 × 10.sup.-6                      
______________________________________                                    
 
    
     The moldings produced in accordance with 19B showed a higher heat distortion temperature and higher shear modulus values than the moldings produced with a standard commercially available isocyanate. The improvement in the linear expansion coefficient of the moldings produced in accordance with the invention over the comparison moldings was particularly noticeable. This is of considerable significance for the production of, for example, metal-containing composite materials in which the plastic is required to have a linear expansion coefficient of less than 10 -6 . 
     Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.