Method for producing a thermosetting polyurethane from a thermoplastic polyurethane and thermoset polyurethane obtainable using said method
View Patent ↗A method for producing thermosetting polyurethane after transformation from thermoplastic polyurethane with a hydrolyzable organo-silane which is grafted onto macromolecules of said thermoplastic polyurethane by means of a bonding agent. Said organo-silane has general formula (I), wherein R 1 ,R 2 ,R 3 =aliphatic alkyl, aromatic alkyl; n>1; R4 is an organic radical which can react with said bonding agent which comprises at least two isocyanate functions and the thermoplastic polyurethane obtained can, after transformation, become automatically cross-linked by coming into contact with water molecules in order to become thermosetting. The invention also relates to a product which can be obtained according to the inventive method.
1. Method for producing a polyurethane that can be thermoset after processing, said method comprising
mixing a thermoplastic polyurethane and a cross-linking agent comprising at least two isocyanate functions and
adding to the mixture a hydrolysable organosilane-having the general formula;
where R 1 , R 2 , R 3 =aliphatic alkyl, aromatic alkyl;
n≧1; and
R 4 is an organic radical capable of reacting with the cross-linking agent;
whereby the hydrolysable silane is grafted onto the macromolecules of the thermoplastic urethane via an allophanate linkage.
2. Method as claimed in claim 1 , wherein R 4 is selected from the group consisting of primary amino, secondary amino, thio, hydroxy, phenoxy and epoxy.
3. Method as claimed in claim 1 , characterized in that the cross-linking agent is a diisocyanate with the general formula:
O═C═N—R 5 —NαC═O
where R 5 =organic radical.
4. Method as claimed in claim 1 , characterized in that the organosilane is aminopropyltrimethoxysilane.
5. Method as claimed in claim 1 , characterized in that the diisocyanate is selected from the group comprising of aromatic, cycloaliphatic and aliphalic diisocyanates and their dimers.
6. Method as claimed in claim 5 , characterized in that the aromatic diisocyanate is selected from the group consisting of TDI (1,3-diisocyanatomethyl-benzene), 2,4′-MDI (1-isocyanato-2-(4-isocyanatophenyl) methylbenzene), 4,4′MDI (1,1-methylene bis (4-isocyanatobenzene)), 2,4-TDI (2,4diisocyanato-1-methylbenzene) and PPDI (1,4-diisocyanatobenzene) or their dimers.
7. Method as claimed in claim 5 , characterized in that the cycloaliphatic diisocyanate is H 12 MDI (1,1-methylene bis (4-isocyanalocyclohexane)).
8. Method as claimed in claim 1 , characterized in that the concentration or cross-linking agent is between 0.1 and 30% by weight or thermoplastic polyurethane.
9. Method as claimed in claim 1 , characterized in that the concentration or organosilane is between 0.05 and 15% by weight or thermoplastic polyurethane.
10. Method as claimed in claim 1 , the mixture of thermoplastic polyurethane and cross-linking agent is reacted at temperatures between 120 and 220° C. to produce a reagent TPU;
the reagent TPU mixture is then brought into contact with the organosilane; and
the resulting grafted TPU is then recovered.
11. Method as claimed in claim 10 , characterized in that the grafted thermoplastic polyurethane obtained is subsequently granulated or immediately processed.
12. A polyurethane capable of being thermoset after processing obtained using the method of claim 10 .
13. Polyurethane capable of being thermosot after processing obtained using the method described in claim 1 .
14. A method as claimed in claim 1 , wherein the concentration of cross-linking agent is 4% by weight of thermoplastic polyurethane.
15. A method as claimed in claim 1 , wherein the concentration of organosilane is 2% by weight of thermoplastic polyurethane.