Silicone rubber molded products and a method for producing same

• US 4,505,848 A
• Filed: 04/28/1983
• Issued: 03/19/1985
• Est. Priority Date: 05/25/1982
• Status: Expired due to Term

• Current Assignee: Ltd. Toray Silicone Company
• Original Assignee: Ltd. Toray Silicone Company
• Inventors: Kobayashi, Hideki
• Primary Examiner(s): Barr, Josephine L.
• Application Number:
  US06/489,443
• Time in Patent Office: 691 Days
• Field of Search: 252/511, 252/502, 252/510, 524/495, 524/496, 264/105, 428/447
• US Class Current: 252/511
• CPC Class Codes: B29C 70/882 partly or totally electrically conductive, e.g. for EMI shielding conductive floors or floor coverings H05F3/025; EMI shielding in general H05K9/00
• CPC Class Codes: B29K 2083/00 Use of polymers having silicon, with or without sulfur, nitrogen, oxygen, or carbon only, in the main chain, as moulding material
• CPC Class Codes: B29K 2105/16 Fillers
• CPC Class Codes: B29K 2105/24 crosslinked or vulcanised
• CPC Class Codes: B29K 2707/04 Carbon
• CPC Class Codes: B29K 2995/0005 Conductive
• CPC Class Codes: B29L 2031/3443 Switches
• CPC Class Codes: H01B 1/24 the conductive material comprising carbon-silicon compounds, carbon or silicon
• CPC Class Codes: H01C 10/106 on resistive material dispersed in an elastic material H01C10/103 and H01C10/12 take precedence; for electric switches H01H1/029
• CPC Class Codes: H01H 13/785 characterised by the material of the contacts, e.g. conductive polymers
• CPC Class Codes: H01H 2201/032 Conductive polymer; Rubber
• CPC Class Codes: H01H 2209/002 Materials
• CPC Class Codes: H01H 2229/046 Multi-colour or double shot injection moulding
• CPC Class Codes: H01H 2229/058 Curing or vulcanising of rubbers

Abstract

Cured unitary molded articles containing conductive and insulating silicone rubber components are prepared by tightly contacting a curable insulating silicone rubber composition comprising a curable silicone rubber containing substantially no carbon black and a nonacyl-type peroxide with a cured conductive silicone rubber component containing carbon black and which has been cured by an addition reaction in the presence of a platinum-type catalyst and molding the resultant composition at elevated temperatures to cure the insulating silicone rubber component and form a unitary cured silicone rubber article.

This invention also relates to cured silicone rubber articles prepared using the method of this invention.

Claims

1. A molded article consisting essentially of (A) a cured conductive silicone rubber containing from 5 to 75 weight percent carbon black, said component being cured by an addition reaction in the presence of a platinum type catalyst, and (B) a cured insulating silicone rubber component containing substantially no carbon black and which is cured by from 0.2 to 5.0 weight percent of a non-aryl peroxide, wherein said conductive and insulating components form a unitary article.

2. The molded article of claim 1 wherein the conductive silicone rubber component is cured by an addition reaction between a polyorganosiloxane containing at least 2 alkenyl groups and a polyorganohydrogensiloxane.

3. The molded article of claim 1 wherein the conductive silicone rubber component contains from 10 to 50 weight percent of conductive grade carbon black.

4. The molded article of claim 1 wherein the article forms a two-color keyboard pad.

5. The molded article of claim 1 wherein the article forms a zebra-type connector.

6. The molded article of claim 2 wherein the article forms a two-color keyboard pad.

7. The molded article of claim 2 wherein the article forms a zebra-type connector.

8. The molded article of claim 1 wherein the article forms an electrical contact.

9. The molded article of claim 2 where the article forms an electrical contact.

10. A method for preparing a unitary molded silicone rubber article comprising

(I) tightly contacting

(A) a cured conductive silicone rubber component containing from 5 to 75 weight percent carbon black, said component having been cured by an addition reaction in the presence of a platinum-type catalyst, and

(B) an uncured insulating silicone rubber component containing substantially no carbon black and from 0.2 to 5.0 weight percent of a nonacyl-type organoperoxide, and

(II) curing the insulating silicone rubber component at an elevated temperature to form a unitary silicone rubber article.

11. The method of claim 10 wherein the conductive silicone rubber component is cured by an addition reaction between a polyorganosiloxane containing at least two alkenyl groups and a polyorganohydrogensiloxane.

12. The method of claim 11 wherein said alkenyl groups are vinyl groups.

13. The method of claim 10 wherein said platinum-type catalyst is chloroplatinic acid.

14. The method of claim 11 wherein said cured conductive component contains from 10 to 50 weight % of conductive carbon black.

15. The method of claim 10 wherein said nonacyl-type organoperoxide is dicumyl peroxide or 2,5-dimethyl-2,5-di(t-butylperoxy)hexane.

16. The method of claim 10 wherein said uncured insulating silicone rubber component is cured at a temperature of from 120°

to 200°

C. for from 5 to 20 minutes.

17. The method of claim 10 wherein said insulating silicone rubber is post cured at a temperature of from 150°

to 260°

C. for from 1 to 24 hours.

18. The method of claim 10 wherein said insulating silicone rubber component contains a reinforcing silica filler.