Low free mdi prepolymers for rotational casting

Abstract

Rotational cast polyurethane composition prepared from a prepolymer composition comprising: a) an isocyanate-terminated polyurethane prepolymer; and b) a curative agent comprising i) a polyol; ii) an aromatic diamine; iii) a thixotropic aliphatic amine; and iv) a thixotropic colloidal additive, wherein the prepolymer comprises a product produce by the reaction of a polyol with an organic diisocyanate monomer comprising 4,4′-diisocyanato diphenylmethane (MDI), and which prepolymer comprises less than 1.0% by weight of free MDI monomer, based on the total weight of the prepolymer, exhibits a range of enhanced physical properties compared to those obtained from prepolymers comprising a higher level of free MDI monomer.

What is claimed: 
     
         1 . A method for producing a polyurethane polymer, the method comprising subjecting to a rotational casting process a polyurethane prepolymer composition comprising:
 a) an isocyanate-terminated polyurethane prepolymer;
 wherein the isocyanate-terminated polyurethane prepolymer comprises a reaction product of an organic diisocyanate monomer and a polyol selected from the group consisting of ethylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, polytetramethylene ether glycol, polypropylene glycol, and dihydroxypolyesters, 
   the organic diisocyanate monomer comprises 4,4′-diisocyanato diphenylmethane, and which prepolymer comprises less than 1.0% by weight of free 4,4′-diisocyanato diphenylmethane monomer, based on the total weight of the prepolymer,   and   b) a curative comprising i) a polyol, ii) an aromatic diamine, iii) a thixotropic aliphatic amine, and iv) a thixotropic colloidal additive,   to provide the polyurethane polymer as a rotationally cast polyurethane layer.   
     
     
         2 . The method according to  claim 1  wherein the isocyanate-terminated polyurethane prepolymer a) comprises polytetramethylene ether glycol. 
     
     
         3 . The method according to  claim 1  wherein the curative comprises a polyol selected from the group consisting of ethylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butanediol, polytetramethylene ether glycol, polypropylene glycol, and a dihydroxypolyester. 
     
     
         4 . The method according to  claim 1  wherein the curative comprises an aromatic amine selected from the group consisting of 4,4′-methylene-bis-(3-chloro)aniline, 4,4′methylene-bis-(3-chloro-2,6-diethyl)aniline, diethyl toluene diamine, tertiary butyl toluene diamine, dimethylthio-toluene diamine, trimethylene glycol di-p-aminobenzoate, 1,2-bis(2-aminophenylthio)ethane, 4,4′-methylene bis(2-chloroaniline), 2,2′5-trichloro-4,4′-methylene-diamine, naphthalene-1,5-diamine, ortho-phenylene diamine, meta-phenylene diamine, para-phenylene diamine, toluene-2,4-diamine, dichlorobenzidine, diphenylether-4,4′-diamine, and mixtures thereof. 
     
     
         5 . The method according to  claim 1  herein the curative comprises a thixotropic aliphatic amine selected from the group consisting of ethylene diamine, 1,6-hexanediamine, 1,12-dodecane diamine, 1,4-cyclohexane diamine, isophorone diamine, diethylene triamine, triethylene tetramine, amine-terminated polyoxypropylenes, xylene diamine, and piperazine. 
     
     
         6 . The method according to  claim 1  wherein the curative comprises a thixotropic colloidal additive selected from the group consisting of fumed silica, clay, bentonite, and talc. 
     
     
         7 . The method according to  claim 1  wherein the polyurethane prepolymer composition comprises
 a) an isocyanate-terminated polyurethane prepolymer prepared by reacting an organic diisocyanate monomer with a polyol, which prepolymer comprises a reaction product of polytetramethylene ether glycol and 4,4′-diisocyanato diphenylmethane; 
 and 
 b) a curative comprising, based on the total weight of the curative:
 i) about 10 wt % to about 90 wt % of a polyol selected from the group consisting of ethylene glycol, diethylene glycol, dipropylene glycol, 1,3-butanediol, polytetramethylene ether glycol and polypropylene glycol; 
 ii) about 10 wt % to about 90 wt % of an aromatic diamine selected from the group consisting of 4,4′-methylene-bis-(3-chloro)aniline, 4,4′methylene-bis-(3-chloro-2,6-diethyl)aniline, diethyl toluene diamine, tertiary butyl toluene diamine, dimethylthio-toluene diamine, trimethylene glycol di-p-aminobenzoate, 1,2-bis(2-aminophenylthio)ethane, 4,4′-methylene bis(2-chloroaniline), 2,2′5-trichloro-4,4′-methylene-diamine, naphthalene-1,5-diamine, ortho-phenylene diamine, meta-phenylene diamine, para-phenylene diamine, toluene-2,4-diamine, dichlorobenzidine, diphenylether-4,4′-diamine, and mixtures thereof; 
 iii) about 0.1 wt % to about 1.5 wt % of a thixotropic aliphatic amine selected from the group consisting of ethylene diamine, 1,6-hexanediamine, 1,12-dodecane diamine, 1,4-cyclohexane diamine, isophorone diamine, diethylene triamine, triethylene tetramine, amine-terminated polyoxypropylenes, xylene diamine, and piperazine; and 
 iv) about 1.0 wt % to about 10 wt % of a thixotropic colloidal additive selected from the group consisting of fumed silica, clay, bentonite, and talc, 
 wherein the total active hydrogen content of the curative agent is equal to about 80-115% of the total isocyanate content of the isocyanate-terminated polyurethane prepolymer. 
 
 
     
     
         8 . The method according to  claim 7  wherein the polyurethane prepolymer composition comprises
 a) an isocyanate-terminated polyurethane prepolymer prepared by reacting an organic diisocyanate monomer with a polyol, in a mole ratio of organic diisocyanate monomer to polyol ranging from about 1.7:1 to about 4:1; and 
 b) a curative agent comprising
 i) about 30 to about 60 wt % of the polyol; 
 ii) about 20 to about 80 wt % of the aromatic diamine; 
 iii) about 0.2 to 0.7 wt % of the thixotropic aliphatic amine; and 
 iv) about 2 to about 5 wt % of the thixotropic colloidal additive, 
 
 wherein the total active hydrogen content of the curative agent is equal to about 90-95% of the total isocyanate content of the isocyanate-terminated polyurethane prepolymer. 
 
     
     
         9 . A rotationally cast polyurethane layer obtained by a method comprising subjecting to a rotational casting process a polyurethane prepolymer composition comprising:
 a) an isocyanate-terminated polyurethane prepolymer;
 wherein the isocyanate-terminated polyurethane prepolymer comprises a reaction product of an organic diisocyanate monomer and a polyol selected from the group consisting of ethylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, polytetramethylene ether glycol, polypropylene glycol, and dihydroxypolyesters, 
   the organic diisocyanate monomer comprises 4,4′-diisocyanato diphenylmethane, and which prepolymer comprises less than 1.0% by weight of free 4,4′-diisocyanato diphenylmethane monomer, based on the total weight of the prepolymer,   and   b) a curative comprising i) a polyol, ii) an aromatic diamine, iii) a thixotropic aliphatic amine, and iv) a thixotropic colloidal additive.   
     
     
         10 . The rotationally cast polyurethane layer according to  claim 9  wherein the isocyanate-terminated polyurethane prepolymer a) comprises polytetramethylene ether glycol. 
     
     
         11 . The rotationally cast polyurethane layer according to  claim 9  wherein the curative comprises a polyol selected from the group consisting of ethylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butanediol, polytetramethylene ether glycol, polypropylene glycol, and a dihydroxypolyester. 
     
     
         12 . The rotationally cast polyurethane layer according to  claim 9  wherein the curative comprises an aromatic amine selected from the group consisting of 4,4′-methylene-bis-(3-chloro)aniline, 4,4′methylene-bis-(3-chloro-2,6-diethyl)aniline, diethyl toluene diamine, tertiary butyl toluene diamine, dimethylthio-toluene diamine, trimethylene glycol di-p-aminobenzoate, 1,2-bis(2-aminophenylthio)ethane, 4,4′-methylene bis(2-chloroaniline), 2,2′5-trichloro-4,4′-methylene-diamine, naphthalene-1,5-diamine, ortho-phenylene diamine, meta-phenylene diamine, para-phenylene diamine, toluene-2,4-diamine, dichlorobenzidine, diphenylether-4,4′-diamine, and mixtures thereof. 
     
     
         13 . The rotationally cast polyurethane layer according to  claim 1  herein the curative comprises a thixotropic aliphatic amine selected from the group consisting of ethylene diamine, 1,6-hexanediamine, 1,12-dodecane diamine, 1,4-cyclohexane diamine, isophorone diamine, diethylene triamine, triethylene tetramine, amine-terminated polyoxypropylenes, xylene diamine, and piperazine. 
     
     
         14 . The rotationally cast polyurethane layer according to  claim 9  wherein the curative comprises a thixotropic colloidal additive selected from the group consisting of fumed silica, clay, bentonite, and talc. 
     
     
         15 . The rotationally cast polyurethane layer according to  claim 1  wherein the polyurethane prepolymer composition comprises
 a) an isocyanate-terminated polyurethane prepolymer prepared by reacting an organic diisocyanate monomer with a polyol, which prepolymer comprises a reaction product of polytetramethylene ether glycol and 4,4′-diisocyanato diphenylmethane; 
 and 
 b) a curative comprising, based on the total weight of the curative:
 i) about 10 wt % to about 90 wt % of a polyol selected from the group consisting of ethylene glycol, diethylene glycol, dipropylene glycol, 1,3-butanediol, polytetramethylene ether glycol and polypropylene glycol; 
 ii) about 10 wt % to about 90 wt % of an aromatic diamine selected from the group consisting of 4,4′-methylene-bis-(3-chloro)aniline, 4,4′methylene-bis-(3-chloro-2,6-diethyl)aniline, diethyl toluene diamine, tertiary butyl toluene diamine, dimethylthio-toluene diamine, trimethylene glycol di-p-aminobenzoate, 1,2-bis(2-aminophenylthio)ethane, 4,4′-methylene bis(2-chloroaniline), 2,2′5-trichloro-4,4′-methylene-diamine, naphthalene-1,5-diamine, ortho-phenylene diamine, meta-phenylene diamine, para-phenylene diamine, toluene-2,4-diamine, dichlorobenzidine, diphenylether-4,4′-diamine, and mixtures thereof; 
 iii) about 0.1 wt % to about 1.5 wt % of a thixotropic aliphatic amine selected from the group consisting of ethylene diamine, 1,6-hexanediamine, 1,12-dodecane diamine, 1,4-cyclohexane diamine, isophorone diamine, diethylene triamine, triethylene tetramine, amine-terminated polyoxypropylenes, xylene diamine, and piperazine; and 
 iv) about 1.0 wt % to about 10 wt % of a thixotropic colloidal additive selected from the group consisting of fumed silica, clay, bentonite, and talc, 
 
 wherein the total active hydrogen content of the curative agent is equal to about 80-115% of the total isocyanate content of the isocyanate-terminated polyurethane prepolymer. 
 
     
     
         16 . The rotationally cast polyurethane layer according to  claim 15  wherein the polyurethane prepolymer composition comprises
 a) an isocyanate-terminated polyurethane prepolymer prepared by reacting an organic diisocyanate monomer with a polyol, in a mole ratio of organic diisocyanate monomer to polyol ranging from about 1.7:1 to about 4:1; and 
 b) a curative agent comprising
 i) about 30 to about 60 wt % of the polyol; 
 ii) about 20 to about 80 wt % of the aromatic diamine; 
 iii) about 0.2 to 0.7 wt % of the thixotropic aliphatic amine; and 
 iv) about 2 to about 5 wt % of the thixotropic colloidal additive, 
 
 wherein the total active hydrogen content of the curative agent is equal to about 90-95% of the total isocyanate content of the isocyanate-terminated polyurethane prepolymer. 
 
     
     
         17 . The rotationally cast polyurethane layer according to  claim 9  having a hardness in the range of 40 to 70 Shore A. 
     
     
         18 . The rotationally cast polyurethane layer according to  claim 9  having a hardness in the range of 70 to 95 Shore A. 
     
     
         19 . The rotationally cast polyurethane layer according to  claim 9  having a hardness of 80 Shore A or lower. 
     
     
         20 . A roll or wheel comprising a rotationally cast polyurethane layer according to  claim 9 .