Cross-linkable thermoplastic polyurethanes
The invention provides a cross-linkable mixture of thermoplastic polyurethanes and ethylenic unsaturated compounds and thermoset materials that can obtained therefrom. The invention also provides application of the cross-linkable mixtures and processes in a solvent-less coating process.
1. A cross-linkable mixture comprising ethylenically unsaturated compounds and a thermoplastic polyurethane with a number average molecular weight of 5000 to 10000, and wherein the thermoplastic polyurethane contains radically polymerizable unsaturated groups at ends of the thermoplastic polyurethane; wherein the thermoplastic polyurethane is urea-free, isocyanurate-free, oxazolinyl-free and functional radically-polymerizable pendant group free and is obtained by reacting one or more polyfunctional isocyanates, one or more polyfunctional polyols, one or more monofunctional alcohols or amines comprising radically-polymerizable unsaturation(s) and one or more diol chain extenders; and wherein the mixture does not contain any additional non-reactive solvent; wherein the amount of alcohol or amine comprising radically polymerizable unsaturations is between 0.08 mmole and 0.35 mmole per gram of cross-linkable mixture; and wherein the amount of thermoplastic polyurethane is between 45 and 70% by weight and the amount of ethylenically unsaturated compound is between 30 and 55% by weight, based on the total cross-linkable mixture; and further wherein the thermoplastic polyurethane is obtained in the absence of a triol having a molecular weight less than 400.
2. The cross-linkable mixture according to claim 1 , wherein the alcohol or amine comprising radically polymerizable unsaturations is selected from the group consisting of polyalkylene glycol mono methacrylates and polyalkylene glycol mono acrylates and combinations thereof.
3. The cross-linkable mixture according to claim 1 , wherein said ethylenically unsaturated compound is selected from the group consisting of mono acrylates and mono methacrylates and combinations thereof.
4. The cross-linkable mixture according to claim 1 , wherein the mixture has a viscosity of between 5 and 200 Pas at a temperature between 20 and 80° C.
5. The cross-linkable mixture according to claim 1 , wherein the thermoplastic polyurethane has a hard block content between 7and 60% by weight.
6. The cross-linkable mixture according to claim 1 , wherein the thermoplastic polyurethane chain has a number average molecular weight of 5000 to 8000.
7. A method of preparing a cross-linkable mixture, comprising: a. providing at least one polyfunctional isocyanate; b. providing at least one polyfunctional polyol; c. providing at least one low molecular weight diol; d. providing at least one radically polymerizable unsaturated alcohol or amine; e. providing at least one ethylenically unsaturated compound; f. blending the compounds provided in steps a to e and reacting the compounds provided in steps a to d, wherein blending and reacting the compounds results in a thermoplastic polyurethane with a number average molecular weight of 5,000 to 10,000; wherein the method is carried out in the absence of any additional non-reactive solvent; wherein the amount of alcohol or amine comprising radically polymerizable unsaturations is between 0.08 mmole and 0.35 mmole per gram of cross-linkable mixture; and wherein the amount of thermoplastic polyurethane is between 45 and 70% by weight and the amount of ethylenically unsaturated compound is between 30 and 55% by weight, based on the total cross-linkable mixture; and further wherein the method is carried out in the absence of a triol having a molecular weight less than 400.
8. The method of preparing a cross-linkable mixture according to claim 7 , wherein the thermoplastic polyurethane has a number average molecular weight of 5000 to 8000.
9. A process for preparing a thermoset material, comprising a step of cross-linking the mixture as defined in claim 1 .
10. The process according to claim 9 , wherein the crosslinking is initiated via a thermal route or via an actinic route.
11. A process for preparing a coating comprising a step of applying the cross-linkable mixture as defined in claim 1 onto a substrate and subsequent cross-linking onto said substrate.
12. The process according to claim 11 , wherein the cross-linking is either thermal, ultraviolet or electron beam activated.
13. The process according to claim 11 , wherein the coating is a synthetic leather coating.