Emulsion polymerization process

Abstract

A method for preparing a silicone emulsion, more particularly a method for preparing a silicone emulsion with a low cyclic siloxane level and particle size control.

1 . A process for making a silicone emulsion comprising: 
 a) preparing a neutral aqueous surfactant by adding to water an anionic surfactant and a base, and mixing to form a uniform neutral aqueous surfactant having a pH of about 7;    b) forming a mixture of approximately equal portions of the surfactant and a polysiloxane;    c) homogenizing the mixture to form an emulsion, wherein the emulsion is homogenized until a desired particle size is achieved;    d) cooling the homogenized emulsion;    e) adding an acid to the cooled emulsion and condensing the emulsion to form a polymer, wherein the polymer is condensed until the viscosity reaches the desired level; and    f) neutralizing the condensed emulsion with an effective amount of a neutralizing agent    wherein the level of cyclic siloxanes in the emulsion is less than one percent by weight.    
     
     
         2 . The process of    claim 1   , comprising: 
 i) from about 0.3 to about 5 pbw of an anionic surfactant, from about 0.06 to about 1.1 pbw of a base and from about 30 to about 90 pbw water;    ii) from about 8 to about 65 pbw of a polysiloxane;    iii) from about 0.09 to about 1.5 pbw of an acid;    iv) an effective amount of a neutralizing agent to neutralize the emulsion to a pH of from about 6 to 8.5.    
     
     
         3 . The process of    claim 1   , wherein the mixture is homogenized at a pressure of from about 4,000 to about 12,000 psig.  
     
     
         4 . The process of    claim 1   , wherein the emulsion is cooled after homogenization to from about 15 to about 50° C.  
     
     
         5 . The process of    claim 1   , wherein the polymer viscosity is from about 100,000 to about 6,000,000 cps.  
     
     
         6 . The process of    claim 2   , wherein the anionic surfactant is alkylbenzenesulfonic acid.  
     
     
         7 . The process of    claim 6   , wherein the anionic surfactant is dodecylbenzenesulfonic acid.  
     
     
         8 . The process of    claim 1   , wherein the polysiloxane is a low viscosity silanol-stopped polymer of the formula:  
       OH—(R 2 SiO) x —H  
       wherein each R is independently a monovalent hydrocarbon radical;  
       and x is an integer, wherein x is chosen such that the viscosity is from about 15 to about 1000 centistokes.  
     
     
         9 . The process of    claim 8   , wherein each R is methyl.  
     
     
         10 . The process of    claim 1   , wherein the neutralizing agent is an alkanolamine of the formula:  
       (R 1 OH) 3 N  
       wherein R 1  is (C 1 -C 8 )alkyl.  
     
     
         11 . The process of    claim 10   , wherein the neutralizing agent is triethanolamine.  
     
     
         12 . The process of    claim 1   , wherein the particle size of the emulsion is from about 0.1 to about 2.0 microns.  
     
     
         13 . An emulsion formed the process of    claim 1   .  
     
     
         14 . A personal care composition comprising the emulsion formed by the process of    claim 1   .  
     
     
         15 . A silicone emulsion, comprising: 
 a) water;    b) a polysiloxane formed from a low viscosity silanol-stopped siloxane of the formula:    OH—(R 2 SiO) x —H    wherein each R is independently a monovalent hydrocarbon radical;    and x is an integer, wherein x is chosen such that the viscosity is from about 15 to about 1000 centistokes,    wherein the polysiloxane has a particle size of from about 0.1 to about 2.0 microns and a polymer viscosity of from about 100,000 to about 6,000,000 centipoise,    wherein the emulsion contains less than one percent by weight cyclic siloxanes.    
     
     
         16 . A personal care composition, comprising the emulsion of    claim 15   , a surfactant, a thickening agent, a colorant, a fragrance and water.