Method for stabilising silicone elastomer moulds

• US 6,747,079 B2
• Filed: 11/20/2002
• Issued: 06/08/2004
• Est. Priority Date: 03/24/2000
• Status: Expired due to Fees

• Current Assignee: Rhodia Chimie (Solvac SA)
• Original Assignee: Rhodia Chimie (Solvac SA)
• Inventors: Bressieux, Jérôme, Deforth, Thomas, Pusineri, Christian
• Primary Examiner(s): Moore, Margaret G.
• Application Number:
  US10/239,357
• Publication Number:
  US 20030149170A1
• Time in Patent Office: 566 Days
• Field of Search: 524/302, 524/748
• US Class Current: 524/302
• CPC Class Codes: C08K 5/3435 Piperidines
• CPC Class Codes: C08K 5/372 Sulfides , e.g. R-(S)x-R'
• CPC Class Codes: C08L 83/04 Polysiloxanes

Abstract

The invention concerns the use for increasing the life span of molds made of silicone elastomer crosslinking by polyaddition or polycondensation reaction, of an additive capable of stabilizing the silicone elastomer whereof the mold is constituted with respect to materials to be mouded, said additive corresponding the following formula (1) wherein R¹ and R² are linear or branched alkyl radicals or cycloaliphatic radicals having 1 to 40 carbon atoms. Preferably, said additive is methyl laurylthiopropionate. C₁₂H₂₅—S—CH₂—CH₂—CO—O—CH₃. The invention also concerns the corresponding silicone compositions and the resulting molds.

Claims

1. A method for increasing the longevity of molds made of silicone elastomer which crosslinks by a polyaddition or polycondensation reaction comprising using an additive capable of stabilizing the silicone elastomer constituting the mold with respect to the materials to be molded, the additive corresponding to the following formula (1):

in which R¹ and R² are linear or branched alkyl radicals or cycloaliphatic radicals having from 1 to 40 carbon atoms.

2. The method as claimed in claim 1, wherein R¹ and R² are such that R¹+R²≦

20.

3. The method as claimed in claim 2, wherein 6≦

R¹+R²≦

18.

4. The method as claimed in claim 2, wherein 10≦

R¹+R²≦

18.

5. The method as claimed in claim 1, wherein R¹ and R² are such that R¹+R²>

20.

6. The method as claimed in claim 5 for the molding of objects having reliefs with a depth or thickness of greater than or equal to 1 millimeter and with a width or diameter of less than 1 to 5 mm.

7. The method as claimed in claim 1, wherein the additive is employed at between 0.1 and 15% by weight with respect to the overall silicone composition.

8. The method as claimed in claim 7, wherein the additive is employed at between 0.2 and 10% by weight with respect to the silicone composition.

9. The method as claimed in claim 1, wherein the composition comprises another stabilization additive.

10. The method as claimed in claim 1, wherein the stabilization of the constituent silicone elastomers of molds is intended for the molding of polyester items in order to prevent, within the silicone elastomer, the polymerization of the styrene resulting from the polyester resin, without harming the polymerization at the core and at the surface of the polyester.

11. The method as claimed in claim 1, which makes it possible to obtain a number of molding operations per mold which is increased by more than 20% with respect to an additive-free elastomer.

12. A method for increasing the longevity of molds made of silicone elastomer which crosslinks by a polyaddition or polycondensation reaction, the method comprising using an additive capable of stabilizing the silicone elastomer constituting the mold with respect to the materials to be molded, the additive corresponding to the following formula (1):

in which R¹ and R² are linear or branched alkyl radicals or cycloaliphatic radicals having from 1 to 40 carbon atoms, wherein the additive comprises methyl lauryithiopropionate MeLTP;

C₁₂H₂₅—

S—

CH₂—

CH₂—

CO—

O—

CH₃.

13. A method for increasing the longevity of molds made of silicone elastomer which crosslinks by a polyaddition or polycondensation reaction, the method comprising using an additive capable of stabilizing the silicone elastomer constituting the mold with respect to the materials to be molded, the additive corresponding to the following formula (1):

in which R¹ and R² are linear or branched alkyl radicals or cycloaliphatic radicals having from 1 to 40 carbon atoms, wherein R¹ and R² are such that R¹+R²≦

20 and, further involving a second additive wherein R¹ and R² are such that R¹+R²>

20.

14. A method for increasing the longevity of molds made of silicone elastomer which crosslinks by a polyaddition or polycondensation reaction, the method comprising using an additive capable of stabilizing the silicone elastomer constituting the mold with respect to the materials to be molded, the additive corresponding to the following formula (1):

in which R¹ and R² are linear or branched alkyl radicals or cycloaliphatic radicals having from 1 to 40 carbon atoms, wherein the composition comprises another stabilization additive selected from the group consisting of;

phosphates,

sterically hindered phenols,

aromatic amines and HALS hindered amines,

metal thiophosphates,

metal salts with an oxidizing action,

additives comprising, in their structure, at least 2 groups of formula

15. The method as claimed in claim 14, wherein the composition comprises pentaerythritol tetra(laurylthiopropionate).

16. The method as claimed in claim 14, wherein the composition comprises an HALS hindered amine of N—

OR type, comprising at least one group;

in which R^y is hydrogen or a linear or branched C₁ to C₁₈ alkyl, optionally substituted by one or more phenyl groups, or a C₅ to C₆ cycloalkyl or benzyl, a is 0 or 1, and the R^x radicals, which are identical to or different from one another, are selected from the group consisting of linear or branched C₁ to C₃ alkyl, phenyl and benzyl radicals.

17. The method as claimed in claim 16, wherein the composition comprises a sebacate of formula:

the R^x radicals, which are identical to or different from one another, are selected from the group consisting of linear or branched C₁ to C₃ alkyl, phenyl and benzyl radicals.

18. The method as claimed in claim 17, wherein the composition comprises bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate.

19. A precursor silicone composition of a silicone elastomer which can be used for the formation of molds for the molding of polyester items, comprising, as a stabilization additive, at least one additive corresponding to the following formula (1):

in which R¹ and R² are linear or branched alkyl radicals or cycloaliphatic radicals having from 1 to 40 carbon atoms.

20. A silicone composition as claimed in claim 19, which comprises one or more additives.

21. A composition as claimed in claim 19, wherein the additive is employed at between 0.1 and 15% by weight with respect to the silicone composition.

22. A composition as claimed in claim 19, wherein the additive is employed at between 0.2 and 10% by weight with respect to the silicone composition.

23. A composition as claimed in claim 19, comprising:

(A) a diorganopolysiloxane oil exhibiting reactive groups selected from the group consisting of i) condensable, hydrolyzable or hydroxyl terminal groups and 2i) alkenyl groups, bonded to silicon;

(B) optionally a compound selected from the group consisting of silanes comprising condensable or hydrolyzable groups, in the case where (A) is selected from the group i), and of diorganopolysiloxane oil carrying hydrogen atoms, in the case where (A) is selected from the group 2i);

p1 (C) a catalyst;

(D) optionally any other additive conventionally used in the type of composition under consideration.

24. A method of molding an object, the method comprising molding the object with a mold made of a silicone elastomer which crosslinks by a polyaddition or a polycondensation reaction, wherein the silicone elastomer is stabilized with respect to the object being molded with an additive corresponding to the formula (1):

in which R¹ and R² are linear or branched alkyl radicals or cycloaliphatic radicals having 1 to 40 carbon atoms.