Curable silicone rubber composition

• US 5,516,832 A
• Filed: 11/03/1994
• Issued: 05/14/1996
• Est. Priority Date: 11/03/1994
• Status: Expired due to Fees

• Current Assignee: Dow Corning Corporation (Dow, Inc.)
• Original Assignee: Dow Corning Corporation (Dow, Inc.)
• Inventors: Gentle, Thomas M., Popa, Paul J., Hauenstein, Dale E., Kennan, Linda D.
• Primary Examiner(s): Michl, Paul R.
• Assistant Examiner(s): Rajguru, U. K.
• Application Number:
  US08/334,171
• Time in Patent Office: 558 Days
• Field of Search: 524/588, 524/492, 524/493, 524/494, 524/506, 524/497, 525/100, 525/103, 525/106, 525/476, 525/477, 525/478, 525/479
• US Class Current: 524/493
• CPC Class Codes: C08G 77/16 to hydroxyl groups
• CPC Class Codes: C08G 77/20 containing silicon bound to unsaturated aliphatic groups C08G77/045 takes precedence
• CPC Class Codes: C08G 77/24 halogen-containing groups
• CPC Class Codes: C08G 77/44 containing only polysiloxane sequences
• CPC Class Codes: C08G 77/70 Siloxanes defined by use of the MDTQ nomenclature
• CPC Class Codes: C08L 23/20 having four to nine carbon atoms
• CPC Class Codes: C08L 23/26 modified by chemical after-treatment
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 2666/04 Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
• 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

Abstract

The present invention relates to a peroxide-curable silicone rubber composition which, when cured, exhibits a reduced modulus and improved tear strength relative to prior art systems without sacrificing other desirable properties, such as high tensile strength of the cured rubber or storage stability of the uncured rubber base, said composition comprising:

(A) 100 parts by weight of a diorganopolysiloxane gum;

(B) 10 to 75 parts by weight a reinforcing filler;

(C) a polybutylene oligomer having a number average molecular weight of 200 to less than 900 and having functionality selected from the group consisting of epoxy, alkoxyphenylene, hydroxyl, carboxyl, anhydride and fully saturated; and, optionally,

(D) a hydroxy-terminated diorganopolysiloxane having a degree of polymerization of 2 to 50.

Claims

1. A composition comprising:

(A) 100 parts by weight of a diorganopolysiloxane gum;

(B) 10 to 75 parts by weight of a reinforcing filler;

(C) a polybutylene having a number average molecular weight of 200 to less than 900, said polybutylene being selected from the group consisting of

(i) polybutylene having functionality selected from the group consisting of epoxy, alkoxyphenylene, hydroxyl, carboxyl, and anhydride and

(ii) fully saturated polybutylene; and

(D) a hydroxy-terminated diorganopolysiloxane having a degree of polymerization of 2 to 50, wherein the ratio of said hydroxy-terminated diorganopolysiloxane (D) to said polybutylene (C) is 1;

5 to 5;

1 and a total of 0.02 to 0.5 part by weight of said components (C) plus (D) is present for each part of said filler (B).

2. The composition according to claim 1, wherein said diorganopolysiloxane (A) is selected from the group consisting of polydimethylsiloxane homopolymers, copolymers of dimethylsiloxane units and methylphenylsiloxane units, copolymers of dimethylsiloxane units and methyl-3,3,3-trifluoropropylsiloxane units and said hydroxy-terminated diorganopolysiloxane (D) is a hydroxy-terminated polydimethylsiloxane.

3. The composition according to claim 1, wherein said diorganopolysiloxane (A) is a linear polydimethylsiloxane in which up to 30 mole percent of other diorganosiloxane units are copolymerized with dimethylsiloxane units and said hydroxy-terminated diorganopolysiloxane (D) is a hydroxy-terminated polydimethylsiloxane.

4. The composition according to claim 1, further comprising a sufficient amount of an organic peroxide catalyst to cure said composition, wherein said diorganopolysiloxane (A) is a linear polydimethylsiloxane copolymer of dimethylsiloxane units with up to about 5 mole percent of methylvinylsiloxane units, said hydroxy-terminated diorganopolysiloxane (D) is a hydroxy-terminated polydimethylsiloxane and said polybutylene (C) is selected from the group consisting of epoxy functional polybutylene and fully saturated polybutylene.

5. The composition according to claim 4, wherein the degree of polymerization of said hydroxy-terminated diorganopolysiloxane (D) is 3 to 15.

6. The composition according to claim 5, wherein the number average molecular weight of said polybutylene (C) is 300 to 400.

12. A cured article prepared from the composition of claim 1.

13. A cured article prepared from the composition of claim 2.

14. A cured article prepared from the composition of claim 3.

15. A cured article prepared from the composition of claim 4.

16. A cured article prepared from the composition of claim 5.

17. A cured article prepared from the composition of claim 6.

7. A composition comprising:

(A) 100 parts by weight of a diorganopolysiloxane gum;

(B) 10 to 75 parts by weight of a reinforcing filler; and

(C) 0.02 to 0.5 parts by weight for each part of said filler (B) of a polybutylene having a number average molecular weight of 200 to less than 900, said polybutylene being selected from the group consisting of

(i) polybutylene having functionality selected from the group consisting of epoxy, alkoxyphenylene, hydroxyl, carboxyl, and anhydride and

(ii) fully saturated polybutylene.

8. The composition according to claim 7, wherein said diorganopolysiloxane (A) is selected from the group consisting of polydimethylsiloxane homopolymers, copolymers of dimethylsiloxane units and methylphenylsiloxane units, copolymers of dimethylsiloxane units and methyl-3,3,3-trifluoropropylsiloxane units.

9. The composition according to claim 7, wherein said diorganopolysiloxane (A) is a linear polydimethylsiloxane in which up to 30 mole percent of other diorganosiloxane units are copolymerized with dimethylsiloxane units.

10. The composition according to claim 7, further comprising a sufficient amount of an organic peroxide catalyst to cure said composition, wherein said diorganopolysiloxane (A) is a linear polydimethylsiloxane copolymer of dimethylsiloxane units with up to about 5 mole percent of methylvinylsiloxane units and said polybutylene (C) is selected from the group consisting of epoxy functional polybutylene and fully saturated polybutylene.

11. The composition according to claim 9, wherein the number average molecular weight of said polybutylene (C) is 300 to 400.

18. A cured article prepared from the composition of claim 7.

19. A cured article prepared from the composition of claim 10.