Dual-cure silicone compounds exhibiting elastomeric properties

• US 7,105,584 B2
• Filed: 04/14/2004
• Issued: 09/12/2006
• Est. Priority Date: 04/18/2003
• Status: Active Grant

• Current Assignee: NSCG, Inc.
• Original Assignee: NSCG, Inc.
• Inventors: Raleigh, Ronald J. Jr., Chambers, Brian R., Hannah, Steven L.
• Primary Examiner(s): BERMAN, SUSAN W
• Application Number:
  US10/823,942
• Publication Number:
  US 20040209972A1
• Time in Patent Office: 881 Days
• Field of Search: 528/33, 522/99
• US Class Current: 522/99
• CPC Class Codes: C08J 2383/04 Polysiloxanes
• CPC Class Codes: C08J 3/243 Two or more independent types of crosslinking for one or more polymers
• 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 83/08 containing silicon bound to organic groups containing atoms other than carbon, hydrogen and oxygen

Abstract

A dual-cure silicone composition is provided that is useful to make an encapsulating/potting compound. The dual-cure silicone exhibits both UV- and moisture-initiated curing mechanisms, with the UV-initiated curing mechanism providing very rapid curing compared to conventional dual-cure silicones. The dual-cure silicone is an elastomeric material on curing. In a preferred embodiment, the dual-cure silicone composition is made from a mixture of a first polysiloxane component having terminal mercapto and alkoxy functionality, and a second polysiloxane component having terminal vinyl and alkoxy functionality. Methods of making the first and second polysiloxane components also are disclosed.

Claims

1. A dual-cure silicone composition comprising a first polysiloxane component and a second polysiloxane component, said first polysiloxane component being a polyorganosiloxane having terminal mercapto functionality, said second polysiloxane component being a polyorganosiloxane having terminal vinyl and oximo functionality, wherein the terminal vinyl functionality of said second polysiloxane component is not provided in the form of a (meth)acrylic group.

2. A dual-cure silicone composition according to claim 1, said second polysiloxane component having the structure:

3. A dual-cure silicone composition according to claim 2, wherein R₅ and R₆ each is a low order alkyl moiety.

4. A dual-cure silicone composition according to claim 2, wherein R₅ is methyl and R₆ is ethyl.

5. A dual-cure silicone composition according to claim 2, wherein n for said second polysiloxane component is greater than about 50.

6. A silicone composition according to claim 1, said first polysiloxane component being dimethylmercapto terminated polydimethylsiloxane.

7. A dual-cure silicone composition according to claim 1, said first polysiloxane component also having terminal alkoxy functionality.

8. A dual-cure silicone compound according to claim 1, said first polysiloxane component having the following structure:

9. A dual-cure silicone composition according to claim 8, wherein n for said first polysiloxane component is greater than about 50.

10. A silicone composition according to claim 1, further comprising at least one of a) a vinylmethylsiloxane copolymer that is trimethyl terminated and having vinyl functionality pendent to the polymer backbone, or b) a dimethylvinyl terminated polydimethylsiloxane.

11. A dual-cure silicone composition according to claim 1, said first polysiloxane component having terminal mercapto functionality at both ends thereof.

12. A dual-cure silicone composition according to claim 1, said second polysiloxane component having terminal vinyl and oximo functionality at both ends thereof.

13. A dual-cure silicone composition according to claim 1, further comprising a photoinitiator.

14. A dual-cure silicone composition according to claim 1, further comprising a water curing catalyst.

15. A dual-cure silicone composition according to claim 8, said second polysiloxane component having the structure:

16. A dual-cure silicone composition according to claim 15, wherein R₅ and R₆ each is a low order alkyl moiety.

17. A dual-cure silicone composition according to claim 15, wherein R₅ is methyl and R₆ is ethyl.

18. A dual-cure silicone composition according to claim 15, wherein n for both said first and second polysiloxane components is greater than 50.

19. A dual-cure silicone composition according to claim 15, wherein n is substantially the same for both said first and said second polysiloxane components.

20. A dual-cure silicone composition according to claim 1, said first and second polysiloxane components being present in a nominal equivalent weight ratio of 1:

1.

21. A dual-cure silicone composition according to claim 1, said first and second polysiloxane components being present in a nominal equivalent weight ratio in the range of 0.7:

1 to 1.3;

1.

22. A dual-cure silicone composition according to claim 21, wherein the equivalent weight ratio between said first and second polysiloxane components is calculated taking account of any residual excesses of mercapto-functional and vinyl-functional silanes still present in the composition, which were used in preparing the respective first and second polysiloxane components.

23. A dual-cure silicone composition according to claim 1, further comprising a plasticizer.

24. A dual-cure silicone composition according to claim 1, said composition being effective such that a layer of said composition having a uniform total thickness of 0.1 inches exhibits at least 70 percent total curing, based on a UV-initiated curing mechanism, following two seconds of exposure to direct UV radiation having an average UV intensity of 151–

185 mW/cm² measured at the surface of the layer.

25. A dual-cure silicone composition according to claim 1, said compound being effective to produce an elastomeric compound on curing said composition.

26. A dual-cure silicone composition according to claim 1, said composition exhibiting both a UV-initiated crosslinking mechanism and a moisture-initiated crosslinking mechanism, wherein a layer of said composition having a uniform total thickness of 0.1 inches exhibits at least 70 percent total curing, based on the UV-initiated curing mechanism, following two seconds of exposure to direct UV radiation having an average UV intensity of 151–

185 mW/cm² measured at the surface of the layer.

27. A dual-cure silicone composition according to claim 26, wherein a layer of said composition having a uniform total thickness of 0.4 inches exhibits at least 90 percent total curing, based on the UV-initiated curing mechanism, following two seconds of exposure to direct UV radiation having an average UV intensity of 151–

185 mW/cm² measured at the surface of the layer.