Abstract: A new polyurethane as well as a process for preparing same is disclosed. The new polyurethane contains therein a hard segment derived from at least one polyhydroxy substance selected from the group consisting of cellulosic substances, hemi-cellulosic substances and lignic substances, and is excellent in mechanical and thermal characteristics as compared with the existing polyurethanes. The new polyurethane can be prepared according to a method known per se, using the polyhydroxy substance alone or in mixture with a polyol compound as reactants to be polycondensed with a polyisocyanate.

Abstract: The present invention is directed to a process for the production of heat curable, flexible, polyurethane molded foams by the reacting inside a closed mold(a) polyisocyanates with(b) compounds having a molecular weight of 400 to about 10,000 and containing at least two isocyanate-reactive groups and(c) optionally chain lengthening and/or cross-linking agents in the molecular weight range of 32 to 399 and containing at least two isocyanate-reactive groups in the presence of(d) a catalyst based on carbonic acid diamide and(e) a blowing agent based on water, characterized in that1. the polyisocyanates (a) are based on diphenyl-methane diisocyanate which may optionally be alkyl substituted, toluylene diisocyanate, hexamethylene diisocyanate and/or isophorone diisocyanate,2. carbonic acid diamide is used in a quantity of 0.05 to 1.0 parts by weight, preferably about 0.3 to 0.7 parts by weight, based on 100 parts by weight of component (b),3.

Abstract: Polyisocyanate composition comprising:(A) 30-45% by weight of disphenylmethane diisocyanates;(B) 28-67% by weight of polymethylene polyphenylene polyisocyanates having more than two free isocyanate groups in the molecule; and(C) 3-27% by weight of a prepolymer from a diphenylmethane diisocyanate and a compound containing at least two isocyanate-reactive groups and having a molecular weight below 1000; the % by weight being calculated on the total amount of (A), (B) and (C) present in the composition; the number average isocyanate functionality of the composition being at least 2.3.The compositions show improved miscibility with rigid foam polyols resulting in processing benefits. Foams made from these compositions exhibit smaller cell size and lower thermal conductivity.

Abstract: This invention relates to a process for the production of elastic, open-cell flexible slabstock polyurethane foams comprising reacting at an isocyanate index less than about 80 one or more polyisocyanates selected from the group tolylene diisocyanates, hexamethylene diisocyanate, and isophorone diisocyanate, with compounds containing at least two isocyanate-reactive hydrogen atoms and having a molecular weight of about 400 to about 10,000, in the presence of water as blowing agent in a quantity of about 5 to about 15 parts by weight for every 100 parts by weight of the isocyanate-reactive compound. The process may optionally include chain-extending and crosslinking agents containing at least two isocyanate-reactive hydrogen atoms and having a molecular weight of about 32 to about 399, and may optionally be carried out in the presence of other blowing agents, catalysts, auxiliaries, and additives.

Abstract: Substantially water blown flexible polyurethane foams, based on methylene diphenyl isocyanates, having a density ranging from 15-45 kg/m.sup.3.Such foams may be obtained through a process substantially avoiding halocarbon blowing agents, which comprises reacting methylene diphenyl isocyanates with water and one or more isocyanate-reactive compounds selected from polyols and polyamines with a functionality of 2-4 and an average equivalent weight ranging from 750-5000, while the isocyanate index ranges from 10 to 60, and weight ratio of the isocyanate-reactive compound(s) to water is less than 20.

Abstract: A polyisocyanate composition, suitable for use in the production of elastomers by the RIM process, or foams, said composition being the product of reacting an imino-functional or enamine-containing compound having a molecular weight of at least 1000 with a stoichiometric excess of an organic polyisocyanate.

Abstract: The present invention is directed to a novel isocyanate mixture and the use thereof in producing a flexible polyurethane foam. The polyisocyanate mixture comprises(a) for 73 to 77% by weight of methylene bis(phenylisocyanate), said methylene bis(phenylisocyanate) having an isomer content as follows:(i) from about 30 to about 34% by weight of the 2,4' isomer,(ii) from about 60 to about 66% by weight of the 4,4'- isomer, and(iii) from about 3 to about 7% by weight, the 2,2' isomer, the percent of said isomers totaling 100%(b) from 23 to 27% by weight of higher functional methylene-bridged polyphenyl polyisocyanates, the percents of components (a) and (b) totaling 100%, and wherein said polyisocyanate mixture has an isocyanate group content of from about 30 to about 33.5 percent by weight.

Abstract: The present invention is directed to a reactive mixture for use in preparing a flexible polyurethane foam and to the foams produced therefrom. The reactive mixture broadly comprises(A) from more than 0 up to 3 parts by weight per 100 parts by weight of components (B) and (C) of an amine of the formula:H.sub.2 N--R--NH.sub.2where R is a C.sub.4 to C.sub.10 straight or branched alkylene group, or a C.sub.4 to C.sub.15 alicyclic group,(B) from 0 to 30% by weight of a polyoxyalkylene polyamine having a molecular weight of from about 400 to about 5000 and containing from 2 to 3 primary amino groups, and(C) from 700 to 100% by weight of one or more polyether polyhydroxyl compounds having hydroxyl functionalities from about 2 to 3 and molecular weights of from about 1000 to about 10,000, the percents of components (B) and (C) totalling 100%.

Abstract: Rigid polyurethane foams are obtained by reacting an isocyanate-reactive component containing at least two isocyanate-reactive hydrogen atoms, having a molecular weight of from 32 to 10,000 or a mixture thereof, with a polyisocyanate composition comprising(a) 30 to 70 pbw of polymethylene polyphenyl polyisocyanate with an iscocyanate content of from 29 to 32%,(b) 30 to 70 pbw of a compound having 30 to 42% by weight isocyanate content obtained by reacting 2,4- and/or 2,6-tolylene diisocyanate with an active hydrogen containing compound, thereafter initiating a reaction in the presence of trimerization catalyst, if necessary diluted with 2,4- and/or 2,6-tolylene diisocyanate,(c) 0 to 30 pbw of other isocyanate compounds in the presence of water and/or organic blowing agents, catalysts and surfactants.

Abstract: The present invention is directed to a process for the preparation of cold setting, flexible, polyurethane, molded foams in a closed mold by reacting a polyisocyanate with a high molecular weight polyol in the presence of about 5 to 15, preferably about 6 to 12 parts by weight of water, based on the weight of the high molecular weight polyol at an isocyanate index below 70.

Abstract: The present invention is directed to a novel isocyanate mixture and the use thereof in producing a flexible polyurethane foam. The polyisocyanate mixture comprises(a) from 73 to 77% by weight of methylene bis(phenylisocyanate), said methylene bis(phenylisocyanate) having an isomer content as follows:(i) from about 30 to about 34% by weight of the 2,4' isomer,(ii) from about 60 to about 66% by weight of the 4,4'-isomer, and(iii) from about 3 to about 7% by weight, the 2,2' isomer, the percent of said isomers totaling 100%,(b) from 23 to 27% by weight of higher functional methylene-bridged polyphenyl polyisocyanates, the percents of components (a) and (b) totaling 100%, and wherein said polyisocyanate mixture has an isocyanate group content of from about 30 to about 33.5 percent by weight.

Abstract: Molded flexible polyurethane foam is prepared by reacting a polyol with a urea-biuret modified polyisocyanate mixture which is composed of toluene diisocyanate and polymeric diphenylmethane diisocyanate.

Abstract: There are provided low temperature, storage stable, liquid mixtures of (1) isocyanato-containing prepolymers obtained from the reaction of linear and/or slightly branched polyols and a polyisocyanate characterized by a methylene group --CH.sub.2 -- bonded to two benzenoid nuclei, and (2) a non-hydroxyl-containing flow modifier which is compatible with the said prepolymer. Novel liquid mixtures thus prepared exhibit little tendency to crystallize or phase separate when stored for prolonged periods of time, i.e., well below room temperature for several days.

Abstract: This invention relates to a class of alkenylated toluenediisocyanates having at least one alkenyl group ortho to an isocyanate group. More particularly the toluendiisocyanates are represented by the formula: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are hydrogen, C.sub.1-3 aliphatic, phenyl, halogen or alkoxy radicals, or R.sub.2 and R.sub.4 or R.sub.5 are bridged via an alkylene radical --(CH.sub.2).sub.y --wherein y=2 to 5, and x is one or two provided that in said formula at least one of R.sub.1, R.sub.2, R.sub.3, R.sub.4 or R.sub.5 is C.sub.1 or greater.The above described alkenylated toluenediisocyanates have been found to be well suited for preparing crosslinkable condensation polymers by providing pendant unsaturation for post curing and polymerization. They are also well suited for preparing polyurethane and polyurea elastomer systems.

Abstract: A method for manufacturing polyurethane foam by mixing (a) polyisocyanate, (b) polyol, (c) blowing agent, (d) catalyst and, as required (e) surface active agent, filler, or other such additive, the said method being characterized in that the polyisocyanate (a) is a prepolymer with isocyanate end groups produced from a polyester polyol and a blended polyisocyanate component comprising 45-95 weight % of diphenylmethane diisocyanate and 55-5 weight % of a polymethylene polyphenyl polyisocyanate with a functionality of 3 or more.

Abstract: Polyurethanes containing uretdione rings are produced by reacting a polyisocyanate containing a uretdione ring with a relatively high molecular weight dihydroxyl compound in the presence of a bismuth salt of an organic carboxylic acid and a low molecular weight aromatic diamine. The low molecular weight aromatic diamine is used in a quantity which is 5 to 10 times the quantity of bismuth salt used. These solid polyurethanes are formed in relatively short reaction times and possess outstanding mechanical properties.

Abstract: The present invention is directed to a process for the production of light-resistant, optionally foamed elastomeric molded polyurethanes by reacting(a) organic polyisocyanates which are either mixtures of isophorone diisocyanate with polyisocyanates containing isocyanurate groups and based on 1,6-diisocyanatohexane or mixtures of IPDI with polyisocyanates containing isocyanurate groups and based on 1,6-diisocyanato-hexane and IPDI with organic compounds containing isocyanate-reactive groups in the presence of catalysts, wherein the components are reacted together inside closed molds in an isocyanate index of about 70 to 130.The present invention is additionally directed to the elastomeric polyurethanes prepared by this process.

Abstract: Microcellular foamed or reaction injection molded polyurethane/polyurea elastomers are prepared by reacting an aliphatically bound polyisocyanate, a primary or secondary amine terminated polymer, and an aliphatic diamine chain extender represented by the formulas: ##STR1## wherein A is represented by the group ##STR2## each R, R.sub.1 and R.sub.2 are independently hydrogen or an alkyl group having from 1 to about 4 carbon atoms, x has a value from zero to about 4; y has a value of 1 or 2; z has a value of zero or 1; and when y is 2, z is zero and the sum of y and z is 2 and ##STR3## wherein R is H or alkyl of 1 to 4 carbon atoms and A and A' are NH.sub.2 or H with the provisos that in each ring either A or A' is NH.sub.2, not both and when A or A' is NH.sub.2 then the R attached to that carbon atom is H.

Abstract: Lactones and lactams are utilized in the preparation of urethane modified prepolymers based on diphenylmethane diisocyanate, uretonimine-modified diphenylmethane diisocyanate. The prepolymers are then employed to prepare microcellular foams suitable for shoe soles and cast polyurethane products.

Abstract: A method for producing liquid isocyanurate modified Polymeric MDI composition containing a high two-ring MDI content, and foams made therefrom is described. The method comprises trimerizing a polymeric MDI in the presence of catalytically effective amount of a trimerization catalyst to form an isocyanurate containing polyisocyanate having a viscosity of about 100,000 mPas. The trimerization catalyst is thereafter deactivated and the isocyanurate-modified polyisocyanate is blended with a methylene bis(phenylisocyanate) (MDI) to form a final product having a two-ring content of about 60 percent of the total ring content and a viscosity comparable to polymeric MDI. Foams produced using this liquid isocyanurate modified polymeric MDI are of a substantially lighter color than those produced from standard polymeric MDI.

Abstract: A process for the preparation of liquid polymethylene polyphenylene polyisocyanate blends containing carbodiimide-uretonimine isocyanate linkages, containing a high two-ring methylene bis(phenylisocyanate) content, and light colored polyurethane foams made therefrom. The process is comprised of reacting polymethylene polyphenylene polyisocyanate with a catalytically effective amount of a carbodiimide-uretonimine promoting compound at a temperature sufficient to promote the formation of carbodiimide-uretonimine linkages and an isocyanate content of about 25 percent and the desired viscosity is reached, and then reacting that product to deactivate the carbodiimide-uretonimine catalyst, and finally blending two ring methylene bis(phenylisocyanate) with the product to produce a mixture having a two ring isocyanate content of about 60 percent of the total ring content and a viscosity comparable to standard polymeric MDI.

Abstract: Polyoxyalkylene surfactants for cellular foams can be prepared by reacting a polyoxyalkylene adduct and an esterified unsaturated dibasic acid in the presence of a free-radical initiator.

Abstract: A system for use in making molded polyurethane objects by an open or closed casting process, said system comprising(A) an aromatic polyisocyanate; and(B) an active hydrogen-containing composition comprising(i) a polyhydric alcohol having an average molecular weight in the range of about 1000 to about 8000 and an average functionality of about 2 to about 4;(ii) a polyhydric alcohol having 2 to 12 carbon atoms and an average functionality of about 2 to about 3; and(iii) a secondary monoamine of the formulaR--NH--R'wherein R and R' are independently saturated aliphatic groups having 1 to 20 carbon atoms, provided that said secondary monoamine contains at least 4 carbon atoms.

Abstract: Polyisocyanurate foams are prepared by reacting together an organic polyisocyanate, a blowing agent, a trimerization catalyst, and a minor amount of a polyol mixture prepared by digesting polyalkylene terephthalate, particularly polyethylene terephthalate, with a polyol, especially a glycol. Laminates of such foams exhibit a high degree of fire resistance, low smoke evolution on combustion, low foam friability and high compressive strength.

Abstract: An antibackslide treatment for a cross-country ski consists of a polyurethane containing a filler or closed-pore structure and which combined hydrophobicity with an elastic character which varies depending upon the velocity of its deformation. During the propulsion phase where the velocity of deformation is low, the treatment has viscoelastic characteristics whereas during the sliding phase when the velocity of deformation is high, the treatment has more elastic properties.

Abstract: The present invention is directed to a process for the production of urea- and/or biuret-modified polyisocyanates by reacting organic polyisocyanates with a mixture of high molecular weight isocyanate-reactive compounds and low molecular weight isocyanate-reactive compounds, wherein at least 25% of the isocyanate-reactive groups are primary amino groups. The present invention is further directed to the products obtained by this process and their use for the production of polyisocyanate polyaddition products, especially for the preparation of molded articles by the RIM process.

Abstract: Oxazolidone-containing isocyanurate foams characterized by thermal stability at a temperature of about 140.degree. C. or higher. These foams are produced by reacting at least one polyisocyanate with at least one polyepoxide in the presence of catalyst, surfactant, and blowing agent.

Abstract: This invention is a closed cell, rigid polyurethane-modified polyisocyanurate foam containing from about 10 to about 80 percent by weight of the foam of fly ash, which polyurethane-modified polyisocyanurate foam is prepared from a polyurethane-modified polyisocyanurate foam-forming composition which, when foamed to a density of about 1.75 pounds per cubic foot in the absence of the fly ash, forms a foam having a compressive modulus of about 150 to 325 pounds per square inch.

Abstract: Improved crack-free rigid cellular polyisocyanurate polymers are disclosed that are derived from the reaction of an organic polyisocyanate combination comprising two particular types of polymethylene polyphenyl polyisocyanates (a) and (b), a trimerization catalyst, minor amount of a polyol, a surfactant, and an inert volatile blowing agent having a boiling point from about 30.degree. C. to about 90.degree. C.The novel rigid foams are particularly useful in preparing high molded bodies of foam by making multiple pours or lifts on top of each other in a mold. The resultant molded body comprises a multiple of molded parts firmly fused to each other and crack-free. Such high molded bodies and process therefor are particularly useful in the insulation of ships.

Abstract: Reinforced cellular or noncellular molded polyurethane parts are prepared by heating a mixture of reinforcing materials and a heat-curable composition of polyisocyanates and polyols in an open or closed mold, said composition being storage-stable at room temperature and containing, optionally, auxiliaries and additives. In said composition, the polyisocyanate is dispersed in the form of discreet particles having particle diameters from 0.1 to 150 .mu.m in the polyol and the polyisocyanate particles are deactivated on their surfaces such that from 0.01 to 20 equivalent percent of the total available isocyanate groups are deactivated and such that the ratio of free isocyanate groups to hydroxyl groups is from 0.7:1 to 2.5:1.The polyurethane molded parts are suitable for use as self-supporting trim parts, reinforcement parts, or molded parts for various applications.

Abstract: Polyaddition products containing urethane groups are produced by reacting an isocyanate group containing distillation residue with a compound having a molecular weight less than 600 containing at least two alcoholic hydroxyl groups. The distillation residue is obtained in the commercial production of tolylene diisocyanate. The distillation residue and hydroxyl compound are reacted in amounts such that the NCO/OH equivalent ratio is less than 1.5:1. The polyaddition reaction is carried out at a temperature in the range of 50.degree. to 220.degree. C. The reaction is carried out in a reaction screw extruder preferably having self-cleaning screw geometry. The polyaddition products are useful as molding compositions, reactive fillers and starting materials in the production of flame-resistant polyurethane plastics.

Abstract: Polyoxyalkylene surfactants for cellular foams can be prepared by reacting a polyoxyalkylene adduct and an esterified unsaturated dibasic acid in the presence of a free-radical initiator.

Abstract: Polyisocyanurate foams are prepared by reacting together an organic polyisocyanate, a blowing agent, a trimerization catalyst, and a minor amount of a polyol blend comprising(a) about 5 percent to about 95 percent by weight of said blend of an alkylene oxide adduct of an aromatic amine of the formula ##STR1## wherein Z is a divalent aromatic radical, x, x', y, and y' each independently have an average value from about 1 to about 5, and each R is independently selected from the group consisting of hydrogen, alkyl or aryl, provided that the adduct is capped with ethylene oxide units, and(b) about 5 percent to about 95 percent by weight of said blend of an aromatic polyester polyol having a molecular weight of from about 150 to about 5,000. Laminates of such foams exhibit a high degree of fire resistance, low foam friability, high compressive strength, and excellent facer adhesion.

Abstract: Flexible polyurethane foams having improved flame resistance and "guide factor" are prepared by reacting a copolymer polyahl, isocyanate-terminated prepolymer containing a cotrimer of MDI and a blowing agent.

Abstract: Trimerized isocyanates having improved solubility in polyisocyanates are prepared by reacting a polyisocyanate with a low equivalent weight polyol to form a first prepolymer, forming a cotrimer from said first prepolymer by reaction of same with diphenylmethane diisocyanate or polymeric derivatives thereof, and forming a second isocyanate terminated prepolymer by reacting said cotrimer with a second low equivalent weight polyol. The resulting cotrimer can be diluted in a polyisocyanate and used to prepare polymers, particularly polyurethane foams, having excellent properties.

Abstract: The present invention relates to a process for the production of foams containing urethane groups by reacting polyether polyols with polyisocyanates in the presence of water and in the presence of an alkaline catalyst, a compound containing a labile halogen atom and, optionally, a tertiary nitrogen containing chain extender.The present invention also relates to the foams obtainable by this process.

Abstract: This invention relates to alkylated vicinal toluenediamines and their use as chain extenders in the preparation of polyurethane elastomers.

Abstract: Polyoxyalkylene surfactants for cellular foams can be prepared by reacting a polyoxyalkylene adduct and an esterified unsaturated dibasic acid in the presence of a free-radical initiator.

Abstract: The subject invention relates to alkylene oxide adducts of aniline prepared by reacting an alkylene oxide with an aniline in the presence of preferably at least 0.1 part of alkali metal hydroxide per 100 parts by weight of aniline.The resulting compositions may be used in the preparation of polyurethane products, such as rigid polyurethane foams, and may also be used as nonionic surfactants.

Abstract: Isocyanate-reactive compounds are prepared by the reaction of TDI distillation residue with a polyol in such proportions as to obtain a reaction product having an OH-number (mg KOH/g) of about 200 to about 700. The TDI distillation residue is obtained from the distillation of the product of phosgenating toluene diamine to the corresponding toluene diisocyanate and has a toluene diisocyanate content of about 30% to about 70% by weight. The isocyanate-reactive compounds are useful in polyurethane formulations.

Abstract: Polyoxyalkylene surfactants for cellular foams can be prepared by reacting a polyoxyalkylene adduct and an esterified unsaturated dibasic acid in the presence of a free-radical initiator.

Abstract: Diphenylmethane diisocyanate-based liquid polyisocyanate mixtures containing urethane groups and having an isocyanate content of from 12 to 30 percent by weight are obtained by reaction of a polyoxypropylene polyoxyethylene polyol containing 5 to 30 percent by weight of oxyethylene with diphenylmethane diisocyanate-based isocyanates. These polyisocyanate mixtures are storage stable at low temperature and yield flexible polyurethane foams having improved mechanical properties.

Abstract: There are provided low temperature, storage stable, liquid mixture of (1) isocyanato-containing prepolymers obtained from the reaction of linear and/or slightly branched polyols and a polyisocyanate characterized by a methylene group --CH.sub.2 -- bonded to two benzenoid nuclei, and (2) a non-hydroxyl-containing flow modifier which is compatible with the said prepolymer. Novel liquid mixtures thus prepared exhibit little tendency to crystallize or phase separate when stored for prolonged periods of time, i.e., well below room temperature for several days.

Abstract: Addition of controlled amounts of water to the reaction mixture produced by phosgenation of a mixture of polymethylene polyphenyl polyamines (and like polyamines produced by condensation of formaldehyde and aromatic amines) prior to complete removal of excess phosgene gives rise to the corresponding polymethylene polyphenyl polyisocyanates having significantly improved properties. Not only is the color of the product, and of polyurethane foams prepared therefrom, significantly lighter but the proportion of higher molecular weight products is significantly less and the viscosity is less. No undesirable by-products are introduced into the polyisocyanate as a result of the process.

Abstract: Spherical porous polyimide powder having an average particle diameter of 1 to 20 .mu.m which is infusible and insoluble in organic solvents is produced by polymerizing an aromatic tetracarboxylic acid dianhydride and an aromatic polyisocyanate in an organic solvent at a temperature of 100.degree. to 200.degree. C. and in the presence of a tertiary amine catalyst to form polyimide particles in the form of slurry, filtering or centrifuging said polyimide particles, and washing the resulting polyimide particles with an organic solvent.

Abstract: The present invention is directed to polyisocyanate mixtures which are liquid and stable in storage at room temperature and which have an NCO-content of from 36.5 to 45% by weight, consisting essentially of a mixture of from 25 to 70 parts by weight of partly trimerized 2,4-diisocyanatotoluene with from 30 to 75 parts by weight of unmodified 2,4-and/or 2,6-diisocyanatotoluene, a process for the production of these mixtures by mixing the individual components and the use of the mixtures as a synthesis component in the production of polyurethane plastics by the isocyanate-polyaddition process.

Abstract: A polyurethane foam produced by the reaction of a polyisocyanate and a polyether polyol in the presence of a catalyst, a cell regulating agent and water as a blowing agent, the polyether polyol of which consists of a halogenated polyether polyol (I) of the general formula: ##STR1## wherein x is a number of 0 to 7; y is a number of 2 to 3; A is a saturated or unsaturated, brominated polyol residue having a number of functional groups of y; R is hydrogen or an alkyl group having 1 to 5 carbon atoms and (II) a polyether polyol having a number of functional groups of 2 to 8, a weight ratio of the added amounts of propylene oxide and ethylene oxide within the range of about 75 to 95/25 to 5 and a hydroxyl number of about 20 to 100 mgKOH/g, whereby a weight ratio of (I) to (II) is about 95 to 25/5 to 75 and the amount of water is about 5 to 20 parts by weight against 100 parts by weight of the polyol component.

Abstract: The invention is a method of making a molded reaction injection molded elastomer. The reaction injection molded (RIM) elastomer is made by injecting via a RIM machine into a mold cavity of the desired configuration, a formulation comprising in the first stream amine terminated polyethers of greater than 1,500 molecular weight, a chain extender, and in the second stream methylene bis(phenylisocyanate) with a 2,4' isomer of greater than about 10%. RIM elastomers are useful, for example, for automobile body parts.

Abstract: The invention relates to reaction injection molded elastomers containing a major amount of polyurea linkages derived from high molecular weight amine terminated polyethers, an aromatic diamine chain extender and a polyisocyanate. The reaction injection molded (RIM) elastomers of this invention are useful, for example, as automobile body parts.

Abstract: Storage stable heterogeneous systems which may be processed at low temperatures to form polyurethanes are made by mixing a specific quantity of a high molecular weight polyhydroxyl compound with a specified quantity of a 4,4'-diphenyl methane uret dione diisocyanate corresponding to a specified formula or a corresponding modified diisocyanate. A lead and/or tin catalyst is also included.