Method for producing silicone elastomer molds

Abstract

Silicone compositions are described for the production of negative molds that include a silicone elastomer. The molds can be used in the production of molded articles.

1 . (canceled) 
     
     
         2 . (canceled) 
     
     
         3 . (canceled) 
     
     
         4 . A polyorganosiloxane composition X that can be cured into an elastomer by polycondensation reactions, wherein the composition X does not contain a metallic catalyst and comprises:
 a silicone base B comprising at least one polyorganosiloxane oil A that can be cured by a polycondensation reaction in a manner such as to form a silicone elastomer, and   a catalytic quantity of at least one polycondensation catalyst C which is an organic compound having a general formula (I):
                     
 in which the symbols R″, which are identical or different, represent aliphatic hydrocarbon radicals containing 6 to 10 carbon atoms. 
   
     
     
         5 . A negative mold MN produced from silicone elastomer by:
 a) preparing a polyorganosiloxane composition X that can be cured to produce an elastomer by polycondensation reactions, which does not contain a metallic catalyst, and comprising:
 a silicone base B comprising at least one polyorganosiloxane oil A that can be cured by a polycondensation reaction, and 
 a catalytic quantity of at least one polycondensation catalyst C, which is an organic compound having a general formula (I):
                     
 in which the symbols R″, which are identical or different, represent aliphatic hydrocarbon radicals containing 1 to 30 carbon atoms, 
 
   b) applying said polyorganosiloxane X to a master to be duplicated, optionally already covered with a release agent,   c) curing said polyorganosiloxane composition X in the presence of moisture supplied by ambient air or by a prior addition of water, in order to form the negative mold MN produced from silicone elastomer, which is an impression corresponding to the exterior contour of the master to be duplicated, and   d) separating the negative mold MN produced from silicone elastomer from the master to be duplicated.   
     
     
         6 . (canceled) 
     
     
         7 . A method of manufacturing a molded article, the method comprising: 
 a) preparing a negative mold comprising:
 i) preparing a polyorganosiloxane composition X that can be cured to produce an elastomer by polycondensation reactions, which does not contain a metallic catalyst, and comprising:
 a silicone base B comprising at least one polyorganosiloxane oil A that can be cured by a polycondensation reaction, and 
 a catalytically effective quantity of at least one polycondensation catalyst C, which is an organic compound having the general formula (I):
                     
 in which the symbols R″, which are identical or different, represent aliphatic hydrocarbon radicals containing 1 to 30 carbon atoms, 
 
 
 ii) applying said polyorganosiloxane X to a master to be duplicated, optionally already covered with a release agent, 
 iii) curing said polyorganosiloxane composition X in the presence of moisture supplied by ambient air or by a prior addition of water, in order to form the negative mold MN produced from silicone elastomer, which is an impression corresponding to the exterior contour of the master to be duplicated, and 
 iv) separating the negative mold MN produced from silicone elastomer from the master to be duplicated and 
   b) applying a reproduction material to the negative mold MN.   
     
     
         8 . The method of  claim 7 , further comprising:
 c) allowing the reproduction material to harden inside the negative mold MN produced from silicone elastomer, in order to produce a replica R of the master to be duplicated, and   d) separating the replica R from the negative mold MN produced from silicone elastomer, wherein steps c) and d) are performed sequentially after step b.   
     
     
         9 . The negative mold MN of  claim 5 , wherein in step c), the homogeneity of curing, as determined by measuring the Shore A hardness above and below the indenter and the difference is 2 or less. 
     
     
         10 . The method of  claim 7 , wherein the at least one polyorganosiloxane oil A comprises a reactive α,ω-dihydroxydiorganopolysiloxane polymer having the general formula:
                     
 in which the substituents R 
 1 , which may be identical or different, each represent a monovalent C 1  to C 13  hydrocarbon, which may or may not be saturated, which may or may not be substituted, aliphatic, cyclic or aromatic, and n has a sufficient value to provide the α,ω-dihydroxydiorganopolysiloxane polymer with a dynamic viscosity at 25° C. of 10 to 1000000 mPas. 
     
     
         11 . The method of  claim 10 , wherein the at least one polyorganosiloxane oil A has a dynamic viscosity at 25° C. of from 50 to 200000 mPas. 
     
     
         12 . The method of  claim 10 , wherein at least 60% by number of the radicals R 1  are methyl radicals. 
     
     
         13 . The method of  claim 10 , where the radicals R 1  that are not methyl radicals are phenyl and/or vinyl radicals. 
     
     
         14 . The method of  claim 7 , wherein the polyorganosiloxane composition X comprises:
 (a) a silicone base that is capable of hardening into a silicone elastomer in the presence of a catalyst by polycondensation reactions, comprising:
 for 100 parts by weight of at least one α, ω-dihydroxydiorganopolysiloxane A, 
 0.1 to 60 parts by weight of at least one curing agent AR, and 
 0.001 to 10 parts by weight of water, and 
   (b) a catalytically effective quantity of a polycondensation catalyst C.   
     
     
         15 . The method of  claim 14 , wherein the curing agent AR is:
 a) a silane with the general formula (2):
                     
 in which the symbols R 3 , which may be identical or different, represent alkyl radicals containing 1 to 8 carbon atoms, or C 3 -C 6  oxyalkylene radicals, 
 the symbols R 2  representing a saturated or unsaturated, linear or branched aliphatic hydrocarbon group, a saturated or unsaturated and/or aromatic, monocyclic or polycyclic carbocyclic group, and 
 k is equal to 0 or 1; and 
   b) partial hydrolysis and condensation products of a silane with formula (2).   
     
     
         16 . The method of  claim 14 , wherein 0.1 to 6 parts by weight of curing agent AR are used per 100 parts by weight of the at least one polyorganosiloxane oil A. 
     
     
         17 . The method of  claim 12 , wherein the compositions further comprises reinforcing fillers, semi-reinforcing fillers or packing fillers CH. 
     
     
         18 . The method of  claim 17 , wherein the reinforcing fillers are fumed silicas or precipitated silicones having a specific surface area, measured using a BET method, of at least 50 m 2 /g, a mean primary particle dimension of less than 0.1 µm (micrometers) and an apparent density of less than 200 g/liter. 
     
     
         19 . The method of  claim 17 , wherein the semi-reinforcing fillers or packing fillers are selected from ground quartz, calcined clays and diatomaceous earth and have a particle diameter of more than 0.1 µm.