Impact-Resistant Polyurethane
The present invention teaches a new process to produce novel, hard, optically clear, impact-resistant polyurethane polymers that are characterized by excellent thermo mechanical properties and chemical resistance, and the polymers made as a result of such a process. The polyurethanes are made by reacting a) a prepolymer made by reacting a polyisocyanate with a primary amine-terminated polyether with an amine functionality of about 2 and a molecular weight of >1000, and in which the free —NCO content of the resulting prepolymer is >18% by weight; with b) (i) a polyol having an average hydroxyl functionality greater than 2 and an average hydroxyl equivalent weight of from about 400 to about 1,000, and (ii) a curing agent that has isocyanate reactive groups, a functionality of 2 to 3 and a molecular weight of <400. More preferably the prepolymer is made by reacting a cycloaliphatic polyisocyanate with a primary amine terminated polyether diamine of 2000 to 4000 molecular weight, the polyol is either a polyester polyol triol with a molecular weight of between about 540 and 900, or a polyether glycol with a molecular weight of between about 650 and 2000, and the curing agent is either dianhydrohexitol, an aromatic diamine, or a cyclohexanedimethanol.
1 . A polyurethane comprising the reaction product of:
a) a prepolymer made by reacting a stoichiometric excess of an aliphatic isocyanate with a primary amine-terminated polyether with an amine functionality of about 2 and a molecular weight of >1000, and in which the free —NCO content of the resulting prepolymer is >18% by weight; and
b) the reaction product of the prepolymer formed in step with (i) a polyol having an average nominal hydroxyl functionality greater than 2 and an average hydroxyl equivalent weight of from about 400 to about 1,000, and (ii) a curing agent that has isocyanate reactive groups, a functionality of 2 to 3 and a molecular weight of <400.
2 . The polyurethane according to claim 1 wherein the primary amine-terminated polyether has a molecular weight of 2,000 to 4,000 and the prepolymer has a free —NCO content of about 18% to 23% by weight.
3 . The polyurethane according to claim 2 wherein the polyol is selected from the group consisting of (a) a polyester polyol triol with a molecular weight of between about 540 and 900, or (b) a polyether glycol with a molecular weight of between about 650 and 2000.
4 . The polyurethane according to claim 3 wherein the curing agent is selected from the group consisting of (a) dianhydrohexitol (b) aromatic diamines and c) cyclohexanedimethanols
5 . The polyurethane according to claim 2 wherein the polyol is selected from the group consisting of (a) a polyester polyol triol with a molecular weight of between about 540 and 900, or (b) a polyether glycol with a molecular weight of between about 650 and 2000.
6 . The polyurethane according to claim 1 which has the following physical characteristics:
(i) a Vicat softening point (ASTM D 1525, Version A, load=10N) of >98° C.,
(ii) a hardness of >75 (ASTM D 2240-00, D durometer), and
(iii) an optical transmittance of >83%. 7. The polyurethane according to claim 5 wherein the curing agent is dianhydrohexitol.
8 . The polyurethane according to claim 5 wherein the curing agent is an aromatic diamine.
9 . The polyurethane according to claim 5 wherein the curing agent is a cyclohexanedimethanol.
10 . The polyurethane according to claim 7 wherein the polyol is a polyether glycol with a molecular weight of between about 650 and 2000.
11 . A process comprising:
a) forming a prepolymer made by reacting a stoichiometric excess of aliphatic polyisocyanate with a primary amine-terminated polyether with an amine functionality of about 2 and a molecular weight of >1000, and in which the free —NCO content of the resulting prepolymer is >18% by weight; and
b) reacting the prepolymer formed in step with (i) a polyol having an average nominal hydroxyl functionality greater than 2 and an average hydroxyl equivalent weight of from about 400 to about 1,000, and (ii) a curing agent that has isocyanate reactive groups, a functionality of 2 to 3 and a molecular weight of <400.
12 . The process according to claim 11 wherein the primary amine-terminated polyether has a molecular weight of 2,000 to 4,000 and the prepolymer has a free —NCO content of about 18% to 23% by weight.
13 . The process according to claim 11 wherein the polyol is selected from the group consisting of (a) a polyester polyol triol with a molecular weight of between about 540 and 900, or (b) a polyether glycol with a molecular weight of between about 650 and 2000.
14 . The process according to claim 11 wherein the curing agent is selected from the group consisting of (a) dianhydrohexitol, (b) aromatic diamines and c) cyclohexanedimethanol.
15 . The process according to claim 12 wherein the polyol is selected from the group consisting of (a) a polyester polyol triol with a molecular weight of between about 540 and 900, or (b) a polyether glycol with a molecular weight of between about 650 and 2000.
16 . The process according to claim 15 wherein the curing agent is selected from the group consisting of (a) dianhydrohexitol and (b) aromatic diamines and c cyclohexanedimethanol.
17 . The process according to claim 16 wherein the curing agent is dianhydrohexitol.
18 . The process according to claim 17 wherein the polyol is a polyether glycol.
19 . The process according to claim 16 wherein the curing agent is an aromatic diamine.
20 . The process according to claim 16 wherein the curing agent is a cyclohexanedimethanol.
21 . The process according to claim 19 wherein the polyol is a polyether glycol.
22 . The process according to claim 13 wherein the curing agent is selected from the group consisting of (a) dianhydrohexitol and (b) aromatic diamines and c) cyclohexanedimethanol.