Polymer Compositions

• US 20100168325A1
• Filed: 04/30/2008
• Published: 07/01/2010
• Est. Priority Date: 05/01/2007
• Status: Active Grant

• Current Assignee: Dow Silicones Corporation (Dow, Inc.)
• Original Assignee: Dow, Inc.
• Inventors: Gough, Helen L., O'Hare, Sarah, Mackinnon, Iain A., Durand, Geraldine
• Granted Patent: US 8,481,640 B2
• Time in Patent Office: Days
• US Class Current: 524/588
• CPC Class Codes: C08G 77/46 containing polyether sequences
• CPC Class Codes: C08K 5/54 Silicon-containing compounds C08K5/0091 takes precedence
• CPC Class Codes: C08L 2666/44 Silicon-containing compounds
• CPC Class Codes: C08L 83/00 Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
• CPC Class Codes: C08L 83/04 Polysiloxanes
• CPC Class Codes: C08L 83/12 containing polyether sequences

Abstract

The invention relates to a water-insoluble hydrophilic polymer network comprising polyorganosiloxane polyoxyalkylene block copolymer moieties characterised that they are linked to each other through an organosilicon cross-linking moiety, provided that the cross-linking moiety forming the links between polyorganosiloxane polyoxyalkylene block copolymer moieties result from an addition reaction between cross-linking sites present on the polyorganosiloxane polyoxyalkylene block copolymer moieties prior to formation of the hydrophilic polymer network, selected from silicon-bonded hydrogen atoms and aliphatically unsaturated groups, and reactive groups present on the cross-linking moiety prior to formation of the hydrophilic polymer network. Also disclosed is a process for making the polymer network, and a curable composition able to be reacted into such polymer network.

Claims

1. A water-insoluble hydrophilic polymer network comprising polyorganosiloxane polyoxyalkylene block copolymer moieties characterised that they are linked to each other through an organosilicon cross-linking moiety, provided that the cross-linking moiety forming the links between polyorganosiloxane polyoxyalkylene block copolymer moieties result from an addition reaction between cross-linking sites present on the polyorganosiloxane polyoxyalkylene block copolymer moieties prior to formation of the hydrophilic polymer network, selected from silicon-bonded hydrogen atoms and aliphatically unsaturated groups, and reactive groups present on the cross-linking moiety prior to formation of the hydrophilic polymer network able to react with the cross-linking sites on the block copolymer.

2. A water-insoluble hydrophilic polymer network according to claim 1, wherein the polyorganosiloxane polyoxyalkylene block copolymer moiety has the form PS-(A-PO)_m-(A-PS)_n wherein PS represents a polyorganosiloxane block, PO represents a polyoxyalkylene block, A represents a divalent radical and m and n have a value of at least 1.

3. A water-insoluble hydrophilic polymer network according to claim 2, the polyorganosiloxane polyoxyalkylene block copolymer moiety has the form PS-(A-PO-A-PS)_n wherein PS represents a polyorganosiloxane block, PO represents a polyoxyalkylene block, A represents a divalent radical and n has a value of at least 1.

4. A water-insoluble hydrophilic polymer network according to claim 2 wherein the cross-linking sites of the polyorganosiloxane polyoxyalkylene block copolymer prior to formation of the network are silicon-bonded hydrogen atoms.

5. A water-insoluble hydrophilic polymer network according to claim 2 wherein the cross-linking sites of the polyorganosiloxane polyoxyalkylene block copolymer prior to formation of the network are situated on terminal silicon atoms of the terminal polyorganosiloxane blocks.

6. A water-insoluble hydrophilic polymer network according to claim 2 each PS block independently is a polydiorganosiloxane with a degree of polymerisation of from 4 to 40 siloxane units.

7. A water-insoluble hydrophilic polymer network according to claim 2 wherein each PS block is a polydimethylsiloxane block.

8. A water-insoluble hydrophilic polymer network according to claim 2 wherein each PO block independently is a polyoxyalkylene group of which at least 50% are oxyethylene groups.

9. A water-insoluble hydrophilic polymer network according to claim 2 wherein each PO block independently is a polyoxyethylene block with a degree of polymerisation of from 4 to 40 oxyethylene units.

10. A water-insoluble hydrophilic polymer network according to claim 2 wherein each A group is independently selected from a divalent alkylene group and a divalent polyorganosiloxane group terminated by diorganosilylalkylene groups.

11. A water-insoluble hydrophilic polymer network according to claim 2 wherein the organosilicon cross-linking moiety is a branched polyorganosiloxane bonded to at least three polysiloxane polyoxyalkylene block copolymer moieties.

12. A water-insoluble hydrophilic polymer network according to claim 2 wherein it also contains a reinforcing filler.

13. A water-insoluble hydrophilic polymer network according to claim 2 whereof the surface becomes more hydrophilic upon wetting with water and reversibly becomes more hydrophobic on drying of the hydrophilic polymer network surface after being wetted with water, as shown by the contact angle of a water droplet on the surface of the hydrophilic polymer network decreasing with time after application of the water droplet to the surface and increasing upon drying.

14. A process for preparing a water-insoluble hydrophilic polymer network according to claim 2 comprising reacting a polyorganosiloxane polyoxyalkylene block copolymer having at least two reactive groups X, selected from silicon-bonded hydrogen atoms and aliphatically unsaturated groups, with an organosilicon cross-linking agent having at least two groups Y reactive with the groups X via addition reaction, provided that if the polyorganosiloxane polyoxyalkylene block copolymer has only two reactive groups X per molecule the cross-linking agent has on average more than two reactive groups Y per molecule.

15. A process according to claim 14 wherein X and Y are selected from silicon-bonded hydrogen atoms and aliphatically unsaturated groups, one being X and the other being the corresponding Y to react therewith via addition reaction.

16. A process according to claim 15 wherein the reactive groups X are Si—

H groups and the cross-linking agent contains ethylenically unsaturated groups Y.

17. A process according to claim 16, wherein the cross-linking agent is a branched siloxane comprising one or more Q units of the formula (SiO_4/2), from 0 to 250 D units of the formula R^b₂SiO_2/2 and M units of the formula R^aR^b₂SiO_1/2, wherein the R^a and R^b substituents are selected from alkyl and alkenyl groups having 1 to 6 carbon atoms, at least three R^a substituents in the branched siloxane being alkenyl units.

18. A process according to any of claim 17 wherein the polyorganosiloxane polyoxyalkylene block copolymer and the cross-linking agent are reacted in the presence of a catalyst comprising a platinum group metal.

19. A process according to claim 18 wherein the cross-linking agent and copolymer are reacted in the presence of a polyorganosiloxane having the same reactive groups X as the copolymer, so that the polyorganosiloxane is reacted into the water-insoluble hydrophilic polymer network.

20. A polymer composition curable to a water-insoluble hydrophilic polymer network according to claim 1 comprising a polyorganosiloxane polyoxyalkylene block copolymer having at least two reactive groups X as defined above, an organosilicon cross-linking agent, which has at least two groups Y reactive with the said groups X via addition reaction, provided that if the polyorganosiloxane polyoxyalkylene block copolymer has only two reactive groups X per molecule an organosilicon cross-linking agent having on average more than two reactive groups Y per molecule is present.

21. A polymer composition according to claim 20 suitable for use in a process according to claim 14.