Silicone elastomer material suitable for use in particular for making dental impressions

Abstract

Described are methods for preparing organopolysiloxane compositions that are capable of cross-linking and/or of hardening by polyaddition reactions so as to produce elastomers or materials made of silicone. Further described, is how the methods are useful for making a dental impression in the context of preparing prostheses.

1 . A method for reducing the blackening phenomena in a composition, the method comprising:
 (1) preparing a part A comprising:
 (a) at least 25% by weight, relative to the total weight of part A, of at least one stabilizer D selected from the group of starches, 
 (b) at least one polyorganosiloxane V having per molecule at least two alkenyl groups, which are each bonded to a silicon atom, and 
 (c) at least one catalyst C, which is a compound of a metal from the platinum group; 
   (2) preparing a part B comprising at least one polyorganosiloxane H having per molecule at least two hydrogen atoms, which are bonded to an identical or different silicon atom; and   (3) mixing part A and part B to form a composition X; and   wherein the composition X is crosslinkable and/or curable by polyaddition reactions, and takes the form of a two-component system S.   
     
     
         2 . The method as defined by  claim 1 , wherein the stabilizer D is present at from 30% to 45% by weight, relative to the total weight of said part A. 
     
     
         3 . The method as defined by  claim 1 , wherein the at least two alkenyl groups are vinyl groups. 
     
     
         4 . The method as defined by  claim 1 , wherein part A and/or part B comprises at least one compound selected from the group consisting of: a reinforcing filler Q1, a bulking filler Q2, a retarder or inhibitor I of polyaddition reactions, a polyorganosiloxane gum G having per molecule at least two alkenyl groups which are bonded to the silicon, and having a viscosity of greater than 1000 Pa·s at 25° C., a polydimethylsiloxane F used as diluent, a colorant K, a plasticizer P selected from the group consisting of liquid petroleum jelly and a paraffin, a wetting agent M, a silicone resin R, and a biocide N. 
     
     
         5 . The method as defined by  claim 4 , wherein the at least two alkenyl groups are vinyl groups. 
     
     
         6 . The method as defined by  claim 4 , wherein the wetting agent M is a surfactant. 
     
     
         7 . The method as defined by  claim 1 , wherein the stabilizer D is a corn starch. 
     
     
         8 . The method as defined by  claim 1 , wherein the composition X comprises at least two polyorganosiloxanes V having per molecule at least two alkenyl groups each bonded to a silicon atom, and having dynamic viscosities ×1 and ×2 at 25° C. in the ranges 10 to 1000 mPa·s and from 1000 to 150 000 mPa·s respectively. 
     
     
         9 . The method as defined by  claim 8 , wherein the at least two alkenyl groups are vinyl groups. 
     
     
         10 . The method as defined by  claim 1 , wherein parts A and B are mixed in weight ratios of between 1:10 to 1:1 respectively. 
     
     
         11 . The method as defined by  claim 1 , wherein parts A and B are mixed with 1 part of A and 5 parts of B. 
     
     
         12 . The method as defined by  claim 1 , wherein the compound V is a polyorganosiloxane which has per molecule at least two alkenyl groups bonded to the silicon, comprises:
 (a) at least two siloxyl units of formula:   
       
         
           
             
               
                 
                   
                     
                       T 
                       a 
                     
                      
                     
                       Z 
                       b 
                     
                      
                     
                       SiO 
                       
                         
                           4 
                           - 
                           
                             ( 
                             
                               a 
                               + 
                               b 
                             
                             ) 
                           
                         
                         2 
                       
                     
                   
                 
                 
                   
                     ( 
                     1.1 
                     ) 
                   
                 
               
             
           
         
         wherein:
 the symbols T are identical or different C 2 -C 6  alkenyl groups, 
 the symbols Z are identical or different monovalent hydrocarbon groups selected from the group consisting of an alkyl having 1 to 8 carbon atoms inclusive, optionally substituted by at least one halogen atom, and an aryl, 
 a is 1 or 2, b is 0, 1, or 2, and the sum a+b is 1, 2, or 3, and 
 
         (b) optionally at least one siloxyl unit of formula: 
       
       
         
           
             
               
                 
                   
                     
                       
                         Z 
                         c 
                       
                        
                       
                         SiO 
                         
                           
                             4 
                             - 
                             c 
                           
                           2 
                         
                       
                     
                     ; 
                   
                 
                 
                   
                     ( 
                     1.2 
                     ) 
                   
                 
               
             
           
         
       
       and
 wherein:
 the symbol Z has the same meaning as above and c is 0, 1, 2, or 3. 
 
 
     
     
         13 . The method as defined by  claim 1 , wherein:
 (1) part (A) comprises:
 at least two polyorganosiloxanes V having per molecule at least two alkenyl groups each bonded to a silicon atom, and having dynamic viscosities ×1 and ×2 at 25° C. in the ranges 10 to 1000 mPa·s and from 1000 to 150 000 mPa·s respectively, 
 at least 25% by weight, relative to the total weight of said part (A), of at least one stabilizer D selected from the group of starches, 
 a catalytically effective amount of at least one catalyst C which is a compound of a metal from the platinum group, 
 optionally at least one polyorganosiloxane gum G having per molecule at least two alkenyl, groups which are bonded to the silicon, and having a viscosity of greater than 1 000 000 mPa·s at 25° C., 
 optionally at least one reinforcing filler Q1 and/or one bulking filler Q2, 
 optionally at least one retarder or inhibitor I of polyaddition reactions, 
 optionally at least one polydimethylsiloxane F blocked at each of the chain ends by a trimethylsilyl unit and used as diluent, 
 optionally at least one colorant K, 
 optionally a paraffin P, 
 optionally at least one biocide N, 
 optionally at least one wetting agent M, 
 optionally at least one silicone resin R, and 
   (2) part B comprises no catalyst C and comprises:
 at least one compound H which is a polyorganosiloxane having per molecule at least three hydrogen atoms bonded to the silicon, 
 optionally at least one compound V which is a polyorganosiloxane having per molecule at least two alkenyl, groups bonded to the silicon, 
 optionally at least one stabilizer D selected from the group of starches, 
 optionally at least one polyorganosiloxane gum G having per molecule at least two alkenyl, groups which are bonded to the silicon, and having a viscosity of greater than 1 000 000 mPa·s at 25° C., 
 optionally at least one reinforcing filler Q1 and/or one bulking filler Q2, 
 optionally at least one retarder or inhibitor I of polyaddition reactions, 
 optionally at least one polydimethylsiloxane F blocked at each of the chain ends by a trimethylsilyl unit and used as diluent, 
 optionally at least one colorant K, 
 optionally a paraffin P, 
 optionally at least one biocide N, 
 optionally at least one wetting agent M imparting a hydrophilic nature to the surface of said elastomer E or said material M, and 
 optionally at least one silicone resin R. 
   
     
     
         14 . The method as defined by  claim 13 , wherein one or more alkenyl groups present in the composition are vinyl groups. 
     
     
         15 . The method as defined by  claim 1 , further comprising crosslinking and/or curing the composition X to obtain a material M or an elastomer E. 
     
     
         16 . The method as defined by  claim 1 , further comprising making dental impressions, pads employed in pad printing techniques, podiatric orthoses, or an impression of the auditory canal.