Polyurethane prepolymers and methods for making and using same

Abstract

Urethane group-containing, isocyanate-terminated prepolymers are made from an organic polyisocyanate and a poly(propylene oxide) that has mainly primary hydroxyl groups and contains 90% by weight or more oxypropylene groups. The prepolymers are useful for making polyurethane elastomers when used in either a one-part, moisture cured process or as a component of a two-part elastomer-forming reactive system. The elastomers tend to have unexpectedly high tensile moduli at a given hard segment content.

Description

Atty Ref.: 157928.221087 (86221)POLYURETHANE PREPOLYMERS AND METHODS FOR MAKING AND USING SAMECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and all advantages of U.S. Provisional Patent Application No. 63 / 698,110 filed on 24 September 2024, the content of which is incorporated herein by reference.FIELD OF THE DISCLOSURE

[0002] This disclosure pertains to polyurethane prepolymers, methods for making those compositions and method for using them.BACKGROUND

[0003] Polyurethane prepolymers are urethane group-containing, isocyanate-terminated materials that can be cured by reaction with water or other curing agent to form an elastomeric polymer. The prepolymer is typically a reaction product of a polyether polyol having a hydroxyl equivalent weight of 350 to 3000 with an excess of a polyisocyanate. The polyether residues incorporated into the prepolymer impart elastomeric properties to the cured, elastomeric polymer.

[0004] Polyurethane prepolymers find utility in applications such as coatings, sealants and adhesives for windows and other uses, and as binders for particulate matter.

[0005] Elastomer systems based on polyurethane prepolymers fall generally into two types. The first type is known as a “one-component” or “1 K” system, that do not need to be mixed with a separate organic curing agent to cure. This avoids the complexity and the need for on-site mixing, metering and dispensing equipment which is expensive and / or impractical to bring to bear on certain specific applications. Instead, 1 K systems cure in the presence of atmospheric moisture and / or liquid water, which do not need to be metered nor mechanically mixed with the prepolymer. This curing can take place at ambient conditions, so a further advantage is that heating is not required to effect the cure.

[0006] The other major type of elastomer system is a “two-component” or “2K” system, in which the polyurethane prepolymer is mixed with a curing agent that contains an isocyanate-reactive organic compound such a polyols, a polyamine or an aminoalcohol.

[0007] Elastomeric polyurethanes made by curing polyurethane prepolymers compositions sometimes lack mechanical properties that are desired in particular applications. In particular, increases in tensile modulus are sometimes needed. Tensile modulus can be increased by increasing the hard segment content of the polyurethane prepolymer, effectively decreasing the proportion of polyether chains in the prepolymer. This is done, for example, by adding chain extenders or crosslinkers into the prepolymer recipe and / or by reducing the equivalent weight of the polyols used to make the prepolymer. These modifications have other effects which may be adverse in certain applications. Those effects include, for example, increased glass transitionAtty Ref.: 157928.221087 (86221) temperature, lower elongations, higher prepolymer viscosities, and poorer processability, among others.BRIEF SUMMARY

[0008] The disclosure in one aspect is a urethane group-containing isocyanate-term inated prepolymer having an isocyanate content of 5 to 15% by weight, which isocyanate-terminated prepolymer is liquid at 23°C and is a reaction product of reactants comprising: i) an organic poly isocyanate having an average of 1.8 to 3 isocyanate groups per molecule and an isocyanate content of 28 to 50% by weight and ii) one or more isocyanate-reactive materials, wherein the isocyanate-reactive materials comprise one or more polyether polyols having a hydroxyl number of 25 to 160 mg KOH / g, at least 50% by weight of the polyether polyols having a hydroxyl number of 25 to 160 mg KOH / g is one or more polypropylene oxide)s that contain at least 90% oxypropylene repeating units and in which at least 50% of the hydroxyl groups are primary hydroxyl groups having the structure - C(CH3)H-CH2-OH.

[0009] Elastomers made by curing the urethane group-containing, isocyanate-terminated prepolymers of the disclosure have unexpectedly high tensile moduli at a given hard segment content. This result is especially surprising when the polypropylene oxide) that contain at least 90% oxypropylene repeating units and in which at least 50% of the hydroxyl groups are primary hydroxyl groups having the structure -C(CH3)H-CH2-OH has a nominal functionality of 2 to 2.5, and particularly 2 to 2.2 or exactly 2. These polypropylene oxide)s contain few if any high functionality coupled species that can create branching and / or crosslinking when the elastomer is cured.

[0010] The disclosure is also a method for making the urethane group-containing, isocyanate- terminated prepolymer of the first aspect, comprising A) a step of producing a polypropylene oxide) comprising at least 90% oxypropylene repeating units and in which at least 50% of the hydroxyl groups are primary hydroxyl groups, the polypropylene oxide) having a hydroxyl number of 25 to 160 mg KOH / g, by homopolymerizing propylene oxide onto a polyhydroxylic starter in the presence of a polymerization catalyst having the general formulaM(R)3(R4)O or 1 wherein M is boron, aluminum, indium, bismuth or erbium, each R is independently a fluoroalkylsubstituted phenyl group, a fluoro-substituted phenyl group, a chlorosubstituted phenyl group, or a fluoro- and chloro-substituted phenyl group and optional R4is a functional group or functional polymer group and B) a step of reacting the polypropylene oxide) with an organic polyisocyanate having an average of 1.8 to 3 isocyanate groups per molecule and an isocyanate content of 28 to 50% by weight to produce the urethane group-containing isocyanate-terminated prepolymer.Atty Ref.: 157928.221087 (86221)

[0011] In a third aspect, the disclosure is a method of making a polyurethane elastomer, comprising applying a urethane group-containing, isocyanate-terminated prepolymer of the first aspect to a substrate and curing the applied urethane group-containing, isocyanate-terminated prepolymer by reaction with atmospheric moisture, liquid water or a combination of atmospheric moisture and liquid water to produce the polyurethane elastomer.

[0012] In a fourth aspect, the disclosure is a process for producing a polyurethane elastomer, comprising combining the urethane group-containing, isocyanate-terminated prepolymer of the first aspect with a curing agent that comprises at least one organic curing agent selected from polyols, primary amines, secondary amines and aminoalcohols to form a reaction mixture, applying the reaction mixture to a substrate, and curing the reaction mixture to produce the polyurethane elastomer.DETAILED DESCRIPTION

[0013] The disclosure in one aspect is a urethane group-containing isocyanate-terminated prepolymer having an isocyanate content of 5 to 15% by weight, which isocyanate-terminated prepolymer is liquid at 23°C and is a reaction product of reactants comprising: i) an organic poly isocyanate having an average of 1.8 to 3 isocyanate groups per molecule and an isocyanate content of 28 to 50% by weight and ii) one or more isocyanate-reactive materials, wherein the isocyanate-reactive materials comprise one or more polyether polyols having a hydroxyl number of 25 to 160 mg KOH / g, at least 50% by weight of the polyether polyols having a hydroxyl number of 25 to 160 mg KOH / g is one or more polypropylene oxide)s that contain at least 90% oxypropylene repeating units and in which at least 50% of the hydroxyl groups are primary hydroxyl groups having the structure - C(CH3)H-CH2-OH.

[0014] Elastomers made by curing the urethane group-containing, isocyanate-terminated prepolymers of the disclosure have unexpectedly high tensile moduli at a given hard segment content. This result is especially surprising when the polypropylene oxide) that contain at least 90% oxypropylene repeating units and in which at least 50% of the hydroxyl groups are primary hydroxyl groups having the structure - C(CH3)H-CH2-OH has a nominal functionality of 2 to 2.5, and particularly 2 to 2.2 or exactly 2. These polypropylene oxide)s contain few if any high functionality coupled species that can create branching and / or crosslinking when the elastomer is cured.

[0015] The disclosure is also a method for making the urethane group-containing, isocyanate- terminated prepolymer of the first aspect, comprising A) a step of producing a polypropylene oxide) comprising at least 90% oxypropylene repeating units and in which at least 50% of the hydroxyl groups are primary hydroxyl groups, the polypropylene oxide) having a hydroxylAtty Ref.: 157928.221087 (86221) number of 25 to 160 mg KOH / g,by homopolymerizing propylene oxide onto a polyhydroxylic starter in the presence of a polymerization catalyst having the general formulaM(R)3(R4)0 or 1 wherein M is boron, aluminum, indium, bismuth or erbium, each R is independently a fluoroalkylsubstituted phenyl group, a fluoro-substituted phenyl group, a chlorosubstituted phenyl group, or a fluoro- and chloro-substituted phenyl group and optional R4is a functional group or functional polymer group and B) a step of reacting the polypropylene oxide) with an organic polyisocyanate having an average of 1.8 to 3 isocyanate groups per molecule and an isocyanate content of 28 to 50% by weight to produce the urethane group-containing isocyanate-terminated prepolymer. For purposes of this disclosure, the 0 or 1 subscript for optional R4is intended to indicate whether R4is present or not. When the subscript is 0, optional R4is absent. When the subscript is 1 , optional R4is present.

[0016] In a third aspect, the disclosure is a method of making a polyurethane elastomer, comprising applying a urethane group-containing, isocyanate-terminated prepolymer of the first aspect to a substrate and curing the applied urethane group-containing, isocyanate-terminated prepolymer by reaction with atmospheric moisture, liquid water or a combination of atmospheric moisture and liquid water to produce the polyurethane elastomer.

[0017] In a fourth aspect, the disclosure is a process for producing a polyurethane elastomer, comprising combining the urethane group-containing, isocyanate-terminated prepolymer of the first aspect with a curing agent that comprises at least one organic curing agent selected from polyols, primary amines, secondary amines and aminoalcohols to form a reaction mixture, applying the reaction mixture to a substrate, and curing the reaction mixture to produce the polyurethane elastomer.

[0018] The urethane group-containing, isocyanate-terminated prepolymer of the disclosure is a liquid at 23°C and has an isocyanate content of 5 to 15% by weight, alternatively from 8 to 12.5% alternatively from 9 to 11% by weight. It contains an average of 1 .8 to 4, alternatively from 2 to 3, alternatively from 2 to 2.5 aromatic isocyanate groups per molecule.

[0019] The urethane group-containing, isocyanate-terminated prepolymer is a reaction product of a starting organic poly isocyanate having an average of from 1 .8 to 3 isocyanate groups per molecule and an isocyanate content of from 28 to 50% by weight and a certain polyether polyol. The starting organic polyisocyanate may be a mixture of two or more organic polyisocyanates, in which case the mixture has an average of from 1.8 to 3 isocyanate groups per molecule and an isocyanate content of from 28 to 50% by weight. The isocyanate content of the starting organic polyisocyanate in some embodiments is from 28 to 40%, alternatively from 28 to 35% by weight.

[0020] The starting organic polyisocyanate or mixture thereof typically has a number average of from 2 to 2.5, alternatively from 2 to 2.3 isocyanate groups per molecule.Atty Ref.: 157928.221087 (86221)

[0021] Among the useful starting organic polyisocyanates are aromatic polyisocyanates such as m-phenylene diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, naphthylene- 1 ,5-diisocyanate, methoxyphenyl-2,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4’-diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyl-4-4'-biphenyl diisocyanate, 3,3'-dimethyldiphenyl methane-4,4'- diisocyanate, 4,4',4"-triphenyl methane triisocyanate, polymethylene polyphenylisocyanate (PMDI), toluene-2,4,6-triisocyanate and 4,4'-dimethyldiphenylmethane-2,2',5,5,-tetraisocyanate. Modified aromatic polyisocyanates that contain urethane, urea, biuret, carbodiimide, uretoneimine, allophanate or other groups formed by reaction of an isocyanate group are also useful. A specific example of a suitable aromatic polyisocyanate is MDI (any one or more isomers of diphenyl methane diisocyanate) or PMDI (or a mixture thereof that is commonly referred to as “polymeric MDI”), and so-called “liquid MDI” products that are mixtures of MDI and MDI derivatives that have biuret, carbodiimide, uretoneimine and / or allophonate linkages.

[0022] Further useful starting organic polyisocyanates include aliphatic polyisocyanates such as cyclohexane diisocyanate, 1,3- and / or 1 ,4-bis(isocyanatomethyl)cyclohexane, 1-methyl- cyclohexane-2,4-diisocyanate, 1 -methyl-cyclohexane-2,6-diisocyanate, methylene dicyclohexane diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate, any of which may be modified to contain urethane, urea, biuret, carbodiimide, uretoneimine, allophanate, isocyanurate or other groups formed by reaction of an isocyanate group.

[0023] The prepolymer is made by reacting the organic polyisocyanate with one or more isocyanate-reactive materials. The polyether polyols having a hydroxyl number of 25 to 160 mg KOH / g may constitute 40 to 85% of the weight of the reactants, i.e., the combined weight of the organic polyisocyanate(s) and all isocyanate-reactive materials.

[0024] The isocyanate-reactive materials include one or more polyether polyols having a hydroxyl number of from 25 to 160 mg KOH / g. At least 50% by weight of the polyether polyols having a hydroxyl number of from 25 to 160 mg KOH / g is one or more polypropylene oxide)s characterized by containing at least 90% oxypropylene (-O-CH(CH3)CH2-) repeating units, and in which at least 50% of the hydroxyl groups are primary hydroxyl groups having the structure - C(CH3)H-CH2-OH. In specific embodiments such polypropylene oxide)s may constitute at least 70%, alternatively at least 80%, alternatively at least 90%, alternatively at least 95% of the weight of the polyether polyols having a hydroxyl number of from 25 to 160 mg KOH / g. Such a polypropylene oxide) may constitute the entire weight of polyether polyols having a hydroxyl number of from 25 to 160 mg KOH / g. The polypropylene oxide) may constitute from 20 to 85% of the total weight of the reactants used to make the urethane group-containing isocyanate- terminated prepolymer.Atty Ref.: 157928.221087 (86221)

[0025] In specific embodiments, the polypropylene oxide) has a hydroxyl number of from 25 to 125 mg KOH / g, alternatively from 25 to 80 mg KOH / g, alternatively from 40 to 80 mg KOH / g. Oxypropylene repeating units comprise at least 90% of the total weight of the polyether polyol.

[0026] At least 50%, alternatively at least 60%, alternatively at least 65% of the of the hydroxyl groups of the polyether polyol are primary hydroxyl groups having the structure -C(CH3)H-CH2- OH. Up to 100%, alternatively up to 95%, alternatively up to 90%, alternatively up to 80%, alternatively up to 75% of the hydroxyl groups may be primary hydroxyl groups having that structure. Primary hydroxyl groups of this type are produced when a molecule of propylene oxide polymerizes at the chain end during the polymerization. Primary hydroxyl content can be determined NMR analysis of a trifluoroacetic anhydride derivative of the polyol.

[0027] The polypropylene oxide) may have an average nominal hydroxyl functionality of from 2 to 3, alternatively 2 to 2.5, alternatively 2 to 2.2. The nominal functionality is the average number of hydroxyl groups on the starter used to produce the polypropylene oxide).

[0028] A mixture of two or more such polypropylene oxide)s may be used.

[0029] The polypropylene oxide) can be conveniently made by polymerizing 1 ,2-propylene oxide onto a starter having two or more, alternatively 2 to 3, alternatively exactly 2, hydroxyl groups per molecule. A mixture of two or more starters may be used, in which case the starters may have an average hydroxyl functionality of from 2 to 3, alternatively from 2 to 2.5, alternatively from 2 to 2.2. A mixture of propylene oxide and another alkylene oxide such as ethylene oxide, 1,2-butylene oxide, 2-3, butylene oxide or tetrahydrofuran may be polymerized provided the product polyether polyol contains at least 90% by weight oxypropylene units. Polyether polyols formed by homopolymerizing 1 ,2-propylene oxide are most typical.

[0030] The polymerization of 1 ,2-propylene oxide is performed in the presence of a catalyst. The selection of catalyst affects the ratio of primary to secondary hydroxyl end groups that form. In some embodiments, the 1 ,2-propylene oxide is polymerized to form the starting polyether polyol in the presence of a polymerization catalyst having the general formulaM(R)3(R4)O or 1 wherein M is boron, aluminum, indium, bismuth or erbium, each R is independently a fluoroalkylsubstituted phenyl group, a fluoro-substituted phenyl group, a chloro-substituted phenyl group, or a fluoro- and chloro-substituted phenyl group and optional R4is a functional group or functional polymer group. Each R may be the same or different.

[0031] In particular embodiments, the polymerization catalyst has the general formulawherein M is boron, aluminum, indium, bismuth or erbium, R^ is a fluoroalkyl-substituted phenyl group and R^and R3each are a fluoroalkyl-substituted phenyl group, a fluoro-substituted phenylAtty Ref.: 157928.221087 (86221) group, a chloro-substituted phenyl group, or a fluoro- and chloro-substituted phenyl group provided that R^ , R^ and R^ are not all the same. Optional R4is a functional group or functional polymer group, if present. The M in the general formula may bear a positive charge.

[0032] The at least one fluoroalkyl substituent of a fluoroalkyl-substituted phenyl group may be, for example, a fluorine-substituted alkyl group having, for example, 1 to 5 carbon atoms. Fluorinesubstituted methyl groups are most typical. The alkyl groups contain at least one fluorine substituent and may have any greater number up to being perfluorinated. A specific example of a fluoroalkyl substituent includes a -CF3 moiety. In some embodiments the fluoroalkyl substituents are -CF3.

[0033] A fluoroalkyl-substituted phenyl group can be substituted with 1 to 5 fluoroalkyl groups. The fluoroalkyl groups can occupy any of the positions on the phenyl ring. In some embodiments, a fluoroalkyl-substituted group is substituted with 2 fluoroalkyl groups, which may be positioned at the 2 and 5 carbons or the 3 and 5 carbons. In specific embodiments, a fluoroalkyl-substituted phenyl group is 2,5- or 3,5-bis(trifluoromethyl)phenyl. In some embodiments, a fluoroalkyl- substituted phenyl group may be substituted to include other groups in addition to the at least one fluoroalkyl group, e.g., a fluorine atom and / or chlorine atom that replaces at least one hydrogen of the phenyl group.

[0034] A fluoro-substituted phenyl group is substituted with 1 to 5 fluorine atoms, a chloro- substituted phenyl group is substituted with 1 to 5 chlorine atoms and a fluoro- and chloro- substituted phenyl group is substituted with at least one fluoroine atom and at least one chlorine atom, in each case being substituted with no fluoroalkyl groups. A Examples of R groups, in addition to 2,5- and 3,5-bis(trifluoromethyl)phenyl, include

[0035] With respect to optional R4, the functional group or functional polymer group may be a Lewis base that forms a complex with the Lewis acid catalyst. By functional group or functional polymer group it is meant a molecule that contains at least one of the following: water, an alcohol, an alkoxy (examples include a linear or branched ether and a cyclic ether), a linear or branchedAtty Ref.: 157928.221087 (86221) ether, a cyclic ether, an aldehyde, a ketone, an ester, an organosilane, an organosiloxane, an oxime, and substituted analogs thereof. Each of the alcohol, linear or branched ether, cyclic ether, aldehyde, ketone, ester, alkoxy, organosilane, organosiloxane, and oxime may include 2 to 20 carbon atoms, 2 to 12 carbon atoms, 2 to 8 carbon atoms, and / or 3 to 6 carbon atoms.

[0036] For example, the functional group or functional polymer group may have the formula (OYmH)n, wherein O is oxygen, H is hydrogen, Y is alkylene, m is zero or one and n is an integer (e.g., an integer from 1 to 100). However, other known functional groups or functional polymer groups combinable with the Lewis acid catalyst can be used.

[0037] Suitable R4groups include diethyl ether, cyclopentyl methyl ether, methyl tert / a / y-butyl ether, tetrahydrofuran, tetrahydropyran, 1 ,4-dioxane, acetone, methyl isopropyl ketone, isopropyl acetate, and isobutyl acetate.

[0038] Methods for making such catalysts are described, for example, in PCT / US2018 / 050995 and PCT / US2018 / 051001, both filed 14 September 2018.

[0039] Examples of suitable Lewis acid catalysts as described above include tris(pentafluorophenyl) borane, (2,5-bis(trifluoromethyl)phenyl)bis(3,5-bis(trifluoromethyl) phenyl)borane, bis(2,5-bis(trifluoromethyl)phenyl)(3,5-bis(trifluoromethyl) phenyl)borane, bis(3,5-bis(trifluoromethyl)phenyl)(2,3,5,6-tetrafluoro-4-(trifluoromethyl) phenyl)borane, bis(3,5- bis(trifluoromethyl)phenyl)(pentachlorophenyl)borane, any of which may be complexed with a functional group or functional polymer group R4.

[0040] The polypropylene oxide) polyol may contain acetal linkages. Strong Lewis acid catalysts such as those having the structure M(R)3(R4)Qor1 or M(R”' )-|(R2)^(R3)^ (R4)QOR cancatalyze the isomeration of propylene oxide to form an aldehyde, which in turn functions as a coupling agent for the polypropylene oxide) polyol. This produces coupled polyethers containing an acetal linkage. Such coupled polyethers form all or a portion of the polypropylene oxide) polyol. In cases in which the starter has 3 or more hydroxyl groups, this coupling reaction produces coupled polyethers that have functionalities of 4 or greater. When the starter has exactly 2 hydroxyl groups, the coupling reaction produces coupled polyethers that remain difunctional.

[0041] The polypropylene oxide)s may be the only isocyanate-reactive material reacted with the organic poly isocyanate to produce the prepolymer. However, other isocyanate-reactive materials are optionally used. These include, for example, chain extenders, crosslinkers, other polyether polyols having hydroxyl numbers of from 25 to 160 mg KOH / g; and polyols having hydroxyl numbers greater than 160 and less than 374 mg KOH / g.

[0042] If used at all, the amount of chain extender and / or crosslinker is generally such that no greater than 0.5 equivalents, alternatively no greater than 0.25 equivalents, alternatively no greater than 0.1 equivalents of hydroxy, primary amine and secondary amine groups combinedAtty Ref.: 157928.221087 (86221) are provided by the chain extender and / or crosslinker per equivalent of isocyanate groups in the starting organic polyisocyanate.

[0043] A chain extender for purposes of this disclosure is a compound having exactly two isocyanate-reactive groups per molecule and an equivalent weight per isocyanate-reactive group of less than 150, alternatively less than 125, alternatively less than 75 g / equivalent. The isocyanate-reactive groups may be hydroxyl and / or primary and / or secondary amino groups.

[0044] Examples of hydroxyl group-containing chain extenders and crosslinkers include 1 ,2- ethane diol, 1,2- or 1,3-propane diol, 1,4-butane diol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol, ethylene diamine, piperazine, piperazine, N-(2-aminoethyl)piperazine, N,N’-bis(2-aminoethyl)piperazine, cyclohexane diamine (including any one or more of the 1,2-, 1,3- and 1,4- isomers), bis(aminomethyl)cyclohexane (including any one or more of the 1,2-, 1,3- and 1,4- isomers) and bis(2-aminoethyl)cyclohexane; toluene diamine, diethyltoluenediamine, methylenediphenyldiamine phenylene diamine and bis(aminomethyl)benzene, glycerin, trimethylolpropane, trimethylolethane, erythritol, pentaerythritol, monoethanolamine, triethanolamine, diethanolamine, diethylene triamine, triethylene tetraamine, tetraethylenepentaamine, and alkoxylates of any of the foregoing having a hydroxyl equivalent weight of less than 150.

[0045] Optional polyether polyols having hydroxyl numbers of 25 to 160 mg KOH / g include, for example poly(ethylene oxide) homopolymers; copolymers of propylene oxide and ethylene oxide containing less than 90% by weight oxypropylene units (such as from 40 to 85%, alternatively from 40 to 75% oxypropylene units, and polypropylene oxide) homopolymers in which fewer than 50% (such as from 0 to 20%, alternatively from 0 to 15%) of the hydroxyl groups are primary.

[0046] Other polyols having hydroxy numbers of greater than 125 and less than 374 mg KOH / g include, for example, polyether polyols, polyester polyols, polyacrylate polyols, polybutadiene polyols and the like.

[0047] Polyols having hydroxyl numbers of greater than 160 and less than 374 mg KOH / g, other than the specific polypropylene oxide) described above may constitute at most 42.5%, alternatively from 0 to 25%, alternatively from 0 to 10%, alternatively from 0 to 15% of the total weight of reactants used to make the prepolymer, and most typically are excluded from the prepolymer-forming reaction.

[0048] An excess of the organic polyisocyanate is reacted with the isocyanate-reactive material(s), including the specific polypropylene oxide) described above, to produce the isocyanate-terminated prepolymer. The reaction is conveniently performed at a temperature of 25 to 90°C under dry conditions. The reaction is continued until the isocyanate-reactive groups of the starting isocyanate-reactive materials are consumed and the reaction product attains a constant isocyanate content.Atty Ref.: 157928.221087 (86221)

[0049] The prepolymer-forming reaction may be performed in the presence of a urethane catalyst. The urethane catalyst is a material which catalyzes the reaction of a hydroxyl group with an isocyanate group. Suitable urethane catalysts include, for example, tertiary amines, cyclic amidines, tertiary phosphines, various metal chelates, acid metal salts, strong bases, various metal alcoholates and phenolates and metal salts of organic acids. Catalysts of most importance are tertiary amine catalysts, cyclic amidines, and tin catalysts. Examples of tertiary amine catalysts include trimethylamine, triethylamine, N-methylmorpholine, N-ethylmorpholine, N,N- dimethylbenzylamine, N,N-dimethylethanolamine, N,N,N',N'-tetramethyl-1 ,4-butanediamine, N,N-dimethylpiperazine, 1 ,4-diazobicyclo-2,2,2-octane, bis(dimethylaminoethyl)ether, triethylenediamine, dimethyldimorpholino ether and dimethylalkylamines where the alkyl group contains 4 to 18 carbon atoms. Mixtures of these tertiary amine catalysts are often used. Examples of tin catalysts are stannic chloride, stannous chloride, stannous octoate, stannous oleate, dimethyltin dilaurate, dibutyltin dilaurate, other tin compounds of the formula SnRn(OR)4.n, wherein R is alkyl or aryl and n is from 0-2, and the like.

[0050] The prepolymer may have a hard segment content of 15 to 60% by weight. In specific embodiments, the hard segment content may be at least 20%, alternatively at least 25%, alternatively at least 30% ,and may be up to 50%, alternatively up to 45%, in all cases by weight. Hard segment content is calculated from the weights of starting materials, as follows:

[0051] Hard segment (%) = 100% x (wtjS0Cyanafe+ wtChajnextender plus crosslinker) *extender plus crosslinker+^polyol), wherein wtjS0Cyana eis the weight of all organic polyisocyanates, wtQ|aii extender plus crosslinker the combined weight of all chain extenders and crosslinkers, tp0|y0| includes the weight of all polyols having a hydroxyl number of less than 374 mg KOH / g (including the specific polypropylene oxide) described above).

[0052] The urethane group-containing, isocyanate-terminated prepolymer composition may be combined with other components, as may be useful or desired for specific applications. One useful additional component is a catalyst for the reaction of an isocyanate group and water. Urethane catalysts as described above are generally useful for this purpose, although some catalysts favor the water- isocyanate reaction more than others. Dimorpholinodiethyl ether is especially suitable for moisture-curing applications. Such catalysts are used in catalytically effective amounts. Another useful component is an acid chloride, particularly benzoyl chloride or substituted benzoyl chloride, which may function as a stabilizer. Other useful components include a colorant, a plasticizer, a solvent, a diluent or a particulate filler.

[0053] The urethane group-containing, isocyanate-terminated prepolymer is useful for making polyurethane elastomers. Elastomers are produced by reacting the prepolymer with a curing agent that is reactive towards isocyanate groups.Atty Ref.: 157928.221087 (86221)

[0054] In certain embodiments the urethane group-containing isocyanate-terminated prepolymer composition is moisture-cured. The curing agent is water, which may be atmospheric moisture, liquid water or a combination of both. In such a moisture-cured system, other curing agents such as chain extenders, crosslinkers, polyols and the like generally are not combined with the urethane group-containing isocyanate-terminated prepolymer composition during the curing process. Instead, the prepolymer composition is exposed to atmospheric moisture and / or liquid water. The water reacts with isocyanate groups in the prepolymer to produce the elastomer. Such moisture-cured systems have the advantage of not requiring the moisture-curable isocyanate- terminated prepolymer composition to be mixed with a curing agent (other than water), so the costs of the curing agent and mixing equipment are avoided. Another advantage is long open times (especially when cured with atmospheric moisture), which allows the urethane group- containing, isocyanate-terminated prepolymer composition to be applied and worked before it hardens.

[0055] Applications in which the urethane group-containing, isocyanate-terminated prepolymer composition is moisture-cured include, for example, window sealants such as sealants for automotive and other vehicular windshields; general purpose sealants, construction sealants and adhesives and the like. In each of these applications, it is typical to apply the moisture-curable isocyanate-terminated prepolymer composition and cure it by exposure to atmospheric moisture.

[0056] Another application in which the urethane group-containing, isocyanate-terminated prepolymer is moisture-cured is in making composite articles by combining the prepolymer with particulate materials, and curing the prepolymer. The particulate matter can be, for example, an inorganic material such as sand, concrete or clay (such as to produce composites for foundry applications); lignocellulosic particles such as sawdust (such as for producing products such as wood board); reground foam when concerned with foam rebond; cork or rubber (such as polyurethane, styrene-butadiene, polymerized ethylene-propylene diene (EPDM), neoprene, ethylene vinyl acetate copolymer (EVA), granulated cork, granulated polyvinylchloride, (to produce articles such as roof or floor tiles, certain component parts of a sports track or surfaces, playground surfaces or other types of recreational or hobby mats or flooring, and composite articles used for traffic management including barriers, curbs, speed bumps) and such like. The particulate material may have sizes within a range of from 0.1 to 15 mm, alternatively from 1 to 8 mm as measured by sieving methods.

[0057] Such composites can be made by forming a polyurethane elastomer precursor composition that comprises the particulate material which is wetted and coated with the prepolymer of the disclosure. The polyurethane elastomer precursor composition may comprise, for example, from 50 to 95% by weight of the particles and from 5 to 50% by weight of the prepolymer of the disclosure, based on their combined weights. The mixture may be compression molded at room temperature or elevated temperatures. Alternatively, the prepolymer may beAtty Ref.: 157928.221087 (86221) combined with the particles at the jobsite where the composite is to be produced, especially in cases of large, rubberized surface installations such as playgrounds, running tracks, pathways, sports courts, etc. It is often desirable to produce a colored elastomer; in such cases it is convenient to provide a moisture-curable isocyanate-terminated prepolymer composition that already contains the colorant(s), or else to provide a separate colorant composition which is combined with the moisture-curable isocyanate-terminated prepolymer composition and the particulate material at the jobsite to produce the colored. A colorant composition may be a concentrate in an additional quantity of moisture-curable isocyanate-terminated prepolymer composition or in a diluent or solvent.

[0058] The polyurethane elastomer precursor composition may be applied to a substrate by, for example, pouring, spraying, pumping, shoveling or otherwise. The applied polyurethane elastomer precursor composition is then moisture-cured in specific embodiments. Liquid water may be sprayed onto the surface of the applied polyurethane elastomer precursor composition, enough water being applied to consume the isocyanate groups of the prepolymer. It may be desirable to provide an excess of liquid water over that needed to consume the isocyanate groups. Alternately, the applied polyurethane elastomer precursor composition can be cured by exposure to atmospheric moisture. It is within the scope of the disclosure to partially cure the applied polyurethane elastomer precursor composition with liquid water and partially cure it with atmospheric moisture.

[0059] The urethane group-containing, isocyanate-terminated prepolymer can also be used in so-called two-part or 2K systems in which the prepolymer is cured to produce a polyurethane elastomer by combining it with a curing agent that contains a polyol, aminoalcohol or a polyamine that has two or more primary or secondary amino groups and curing the resulting reaction mixture. The curing agent may include, for example a chain extender and / or crosslinker as described hereinbefore, and / or one or more polyols that have a hydroxyl number of, for example, 374 mg KOH / g or less.

[0060] The urethane group-containing, isocyanate-terminated prepolymer may be combined with enough of such a curing agent to provide at least 0.8 or at least 0.9 equivalents of hydroxyl and / or primary or secondary amino groups per equivalent of isocyanate groups in the prepolymer. However, it is within the scope of the disclosure to partially cure the prepolymer of the disclosure with such a curing agent and to perform further curing by reaction with atmospheric moisture and / or liquid water. For example, the prepolymer may be combined with enough of such a curing agent to provide 0.01 to 0.5, especially 0.01 to 0.25 or 0.01 to 0.1 equivalents of hydroxyl and / or primary or secondary amino groups per equivalent of isocyanate groups in the urethane group- containing, isocyanate-terminated prepolymer, partially cured by reaction of the prepolymer with the curing agent, supplemented by additional curing with atmospheric moisture or liquid water.Atty Ref.: 157928.221087 (86221)

[0061] Examples of other polyurethane elastomer products that can be produced by curing the prepolymer of the disclosure include a variety of flexible materials typically exhibiting an elongation to break of at least 100% as measured according to ASTM D638. Such an elastomer product of the disclosure may be a static or dynamic type, static elastomers being products which are not subject to regular deformation during use (such as gasketing materials and certain types of rollers) and dynamic elastomers being products that are subjected to regular and repeated deformation as they are used. Such an elastomer product may be, for example, a gasket or seal, tubing, a roller for many applications such as coating rollers, nip rollers, drive belts, squeeze rollers, business machine rollers, a pulley, a conveyor wheel, a fork truck wheel, a tricycle wheel, a caster wheel, an industrial tire, a rod wiper, a snow plow blade, a chute or cyclone liner, or an agitator blade, among many others.

[0062] Such an elastomer may be non-cellular, cellular or microcellular. A cellular or microcellular elastomer can be formed by incorporating a physical and / or chemical blowing agent into the reaction mixture and curing the reaction mixture under conditions that the blowing agent produces a gas that becomes trapped in the cured material to produce cells. Alternatively or in addition, air, carbon dioxide, nitrogen or other gas can be whipped into the reaction mixture to form a froth, which is cured to form a cellular, or microcellular elastomer.

[0063] When making elastomers or other molded or shaped product, curing may take place in a mold or other form, which may be open or closed. It may be performed on a belt or other apparatus. The reaction mixture may be formed into a layer on a substrate and cured thereon to form a composite. A fibrous material may be impregnated with the reaction mixture, after which the reaction mixture is cured in place to form a fiber-reinforced composite.

[0064] In addition to being useful for producing polyurethane elastomers, the urethane group- containing, isocyanate-terminated prepolymer composition is useful for preparing polyurethane foam, structural polymers and other types of polymers that contain linkages produced in a reaction of an isocyanate group with another isocyanate group or other isocyanate-reactive group.

[0065] The following examples are provided to illustrate the disclosure, but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated.

[0066] KOH Polyol A is a diol made by polymerizing homopropylene oxide in the presence of potassium hydroxide a diol initiator to a hydroxyl number of 56.5 mg KOH / g. 5% of the hydroxyl groups are primary.

[0067] KOH Polyol B is a diol made by homopolymerizing propylene oxide in the presence of potassium hydroxide and a diol initiator to a hydroxyl number of 56.5 mg KOH / g. 5% of the hydroxyl groups are primary. It differs from KOH Polyol A in having a reduced number of unsaturated species.Atty Ref.: 157928.221087 (86221)

[0068] DMC Polyol A is a diol made by homopolymerizing propylene oxide in the presence of a diol initiator to a hydroxyl number of 55.8 mg KOH / g, using a modified zinc hexacyanocobaltate DMC catalyst as described in WO2018209069. 8% of the hydroxyl groups are primary.

[0069] Polyol 1 is a diol made by homopolymerizing propylene oxide in the presence of tripropylene glycol and an adduct of bis(3,5-bis(trifluoromethyl)phenyl)(2,4,6- trifluorophenyl)borane with one mole of tetrahydrofuran and one mole of water. The bis(3,5- bis(trifluoromethyl)phenyl)(2,4,6-trifluorophenyl)borane is obtainable by the method described in W02020 / 068494. A 15% solution of the catalyst in a 431 molecular weight, difunctional homopolymer of propylene oxide is formed. 37.5 parts of tripropylene oxide are charged to a pressure reactor, together with enough of the catalyst solution to provide 11 mg of tris(pentafluorophenyl)borane). The reactor contents are heated to 80°C and propylene oxide is added at a rate of 2 mUminute. Enough of the catalyst solution to provide another 84 mg of catalyst are added during the propylene oxide addition. The reactor contents are digested for 20 minutes after the propylene oxide addition is completed. The reactor contents are then sparged with nitrogen before collecting the product. Polyol 1 has a hydroxyl number of 56 mg KOH / g as measured according to ASTM 4274-16. 53% of the hydroxyl groups are primary by proton NMR. A portion of Polyol 1 contains acetal linkages. The average functionality of Polyol 1 is approximately 2.0.

[0070] Polyol 2 is a diol made by homopolymerizing propylene oxide in the presence of tripropylene glycol and tris(pentafluorophenyl) borane. 2.17 g of the catalyst is dissolved in 11 .61 g of a 431 molecular weight, difunctional homopolymer of propylene oxide, 86 mg water and 0.61 g tetrahydrofuran. 373.5 parts of tripropylene oxide are charged to a pressure reactor, together with enough of the catalyst solution to provide 18 mg of tris(pentafluorophenyl)borane). The reactor contents are heated to 80°C and propylene oxide is added at a rate of 2 mL / minute. Enough of the catalyst solution to provide another 33 mg of catalyst are added during the propylene oxide addition. The reactor contents are digested for 43 minutes after the propylene oxide addition is completed. The reactor contents are then sparged with nitrogen before collecting the product. Polyol 2 has an OH number of 56.3 mg KOH / g. 66% of its hydroxyl groups are primary. A portion of Polyol 2 contains acetal linkages. The average functionality of Polyol 2 is approximately 2.0.Examples 1-2 and Comparative Samples A-C

[0071] Prepolymers are made from each of KOH Polyols A and B, DMC-like Polyol A and Polyols 1 and 2 by reacting 61.24 parts of the respective polyol with 38.72 parts of a mixture of MDI (diphenylmethane diisocyanate) and a polymeric MDI until a constant isocyanate content is obtained, as measured by ASTM D2572. 0.04 parts of dimorpholinodiethyl ether catalyst is mixedAtty Ref.: 157928.221087 (86221) into each of the resulting prepolymers to produce comparative urethane group-containing, isocyanate-terminated prepolymer compositions A-C and Examples 1 and 2, respectively.

[0072] The compositions are stored overnight in a dry box. The isocyanate content of each is then measured by titration and viscosity measured at 25°C measured using a rheometer having a 40-mm cone and a Peltier plate.

[0073] Open time and tack free time of each of the urethane group-containing, isocyanate- terminated prepolymer compositions are measured by applying a 76-mm film of the composition onto a cleaned glass test strip. The samples are moisture cured in a humidity chamber set at 25°C and 50% relative humidity, monitoring the cure according to ASTM D5895 using a BYK drying time recorder.

[0074] Tensile testing is performed on 10-mil films produced by coating the urethane group- containing, isocyanate-terminated prepolymer compositions onto a polypropylene sheet and curing the coatings at 25°C and 50% relative humidity for 7 days. The films are separated from the polypropylene sheet and tested according to ASTM 1708 at a testing speed of 12.7 cm / minute.

[0075] Results of the testing are as indicated in Table 1.Atty Ref.: 157928.221087 (86221)Table 1

[0076] As the data in Table 1 shows, very substantial increases in tensile modulus are obtained with the disclosure, with little or no significant change to other properties. The improvement in tensile modulus is especially pronounced in Example 2, in which the starting polyol has a highest proportion of primary hydroxyl groups.Examples 3 and 4 and Comparative Samples D-F

[0077] Prepolymers are made from each of KOH Polyols A and B, DMC Polyol A and Polyols 1 and 2 by reacting 59.99 parts of the respective polyol with 40 parts of a mixture of the 4,4’- and 2,4’-isomers of MDI and a polymeric MDI, until a constant isocyanate content is obtained. 0.006 parts of benzoyl chloride is mixed into each of the resulting prepolymers to produce comparative urethane group-containing, isocyanate-terminated prepolymer compositions D-F and Examples 3 and 4, respectively.

[0078] These compositions are tested in the same manner as described before, with results as indicated in Table 2.Atty Ref.: 157928.221087 (86221)Table 2

[0079] As with the previous set of examples, large gains in tensile modulus are seen with the disclosure, in particular with Example 4, in which the starting polyol has the highest proportion of primary hydroxyl groups.

Claims

Atty Ref.: 157928.221087 (86221)CLAIMSWhat is claimed is:

1. A urethane group-containing isocyanate-terminated prepolymer having an isocyanate content of 5 to 15% by weight, which isocyanate-terminated prepolymer is liquid at 23°C and is a reaction product of reactants comprising: i) an organic poly isocyanate having an average of 1.8 to 3 isocyanate groups per molecule and an isocyanate content of 28 to 50% by weight; and ii) one or more isocyanate-reactive materials, wherein the isocyanate-reactive materials comprise one or more polyether polyols having a hydroxyl number of from 25 to 160 mg KOH / g, at least 50% by weight of the polyether polyols having a hydroxyl number of from 25 to 160 mg KOH / g is one or more polypropylene oxide)s that contain at least 90% oxypropylene repeating units and in which at least 50% of the hydroxyl groups are primary hydroxyl groups having the structure -C(CH3)H-CH2-OH.

2. The urethane group-containing isocyanate-terminated prepolymer of claim 1 wherein at least 75% by weight of the polyether polyols is the one or more polypropylene oxide)s comprising at least 90% oxypropylene repeating units in which at least 50% of the hydroxyl groups are primary hydroxyl groups having the structure -C(CH3)H-CH2-OH.

3. The urethane group-containing isocyanate-terminated prepolymer of claim 1 wherein at least 95% by weight of the polyether polyols is the one or more polypropylene oxide)s comprising at least 90% oxypropylene repeating units in which at least 50% of the hydroxyl groups are primary hydroxyl groups having the structure -C(CH3)H-CH2-OH.

4. The urethane group-containing isocyanate-terminated prepolymer of any one preceding claim wherein the one or more polypropylene oxide)s that contain at least 90% oxypropylene repeating units and in which at least 50% of the hydroxyl groups are primary hydroxyl groups having the structure -C(CH3)H-CH2-OH has a nominal hydroxyl functionality of from 2 to 2.2.

5. The urethane group-containing isocyanate-terminated prepolymer of any one preceding claim wherein at least a portion of the one or more polypropylene oxide)s that contain at least 90% oxypropylene repeating units and in which at least 50% of the hydroxyl groups are primary hydroxyl groups having the structure -C(CH3)H-CH2-OH contains an acetal linkage.Atty Ref.: 157928.221087 (86221)6. The urethane group-containing isocyanate-term inated prepolymer of any one preceding claim wherein one or more polyether polyols having a hydroxyl number of from 25 to 160 mg KOH / g constitute from 40 to 85% of the weight of the reactants.

7. The urethane group-containing isocyanate-terminated prepolymer of any one of claims 1-3 wherein the reactants further comprise at least one chain extender and / or crosslinker.

8. The urethane group-containing, isocyanate-terminated prepolymer of any one preceding claim wherein the organic isocyanate is any one or more of diphenyl methane diisocyanate, polymeric MDI, and an MDI derivative having biuret, carbodiimide, uretoneimine and / or allophonate linkages.

9. A prepolymer composition comprising a urethane group-containing, isocyanate- terminated prepolymer of any one preceding claim and a urethane catalyst.

10. A prepolymer composition comprising a urethane group-containing, isocyanate- terminated prepolymer of any one of claims 1-5 and from 0.001 to 0.025 weight percent of a carboxylic acid chloride, based on the combined weight of the urethane group-containing, isocyanate-terminated prepolymer and the carboxylic acid chloride.

11. A prepolymer composition of claim 6 or 7, further comprising one or more of a colorant, a plasticizer, a solvent, a diluent or a particulate material.

12. A method for making the urethane group-containing isocyanate-terminated prepolymer of any one preceding claim, comprisingA) producing a polypropylene oxide) comprising at least 90% oxypropylene repeating units and in which at least 50% of the hydroxyl groups are primary hydroxyl groups, the polypropylene oxide) having a hydroxyl number of from 25 to 160 mg KOH / g, by homopolymerizing propylene oxide onto a polyhydroxylic starter in the presence of a polymerization catalyst having the general formulaM(R)3(R4)0 or 1 wherein M is boron, aluminum, indium, bismuth or erbium, each R is independently a fluoroalkylsubstituted phenyl group, a fluoro-substituted phenyl group, a chlorosubstituted phenyl group, or a fluoro- and chloro-substituted phenyl group and optional R4is a functional group or functional polymer group; andAtty Ref.: 157928.221087 (86221)B) reacting the polypropylene oxide) with an organic poly isocyanate having an average of from 1 .8 to 3 isocyanate groups per molecule and an isocyanate content of 28 to 50% by weight to produce the urethane group-containing isocyanate-terminated prepolymer.

13. The method of claim 12 wherein the polyhydroxylic starter is a diol.

14. A method of making a polyurethane elastomer, comprising applying a urethane group-containing, isocyanate-terminated prepolymer of any one of claims 1-8 or a prepolymer composition of any one of claims 9-11 to a substrate and curing the applied urethane group- containing, isocyanate-terminated prepolymer by reaction with atmospheric moisture, liquid water or a combination of atmospheric moisture and liquid water to produce the polyurethane elastomer.

15. A process for producing a polyurethane elastomer, comprising combining the urethane group-containing, isocyanate-terminated prepolymer of any one of claims 1-8 or a prepolymer composition of any one of claims 9-11 with a curing agent that comprises at least one organic curing agent selected from polyols, primary amines, secondary amines and aminoalcohols to form a reaction mixture, applying the reaction mixture to a substrate, and curing the reaction mixture to produce the polyurethane elastomer.

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