Cosmetic oil thickener and oil-soluble copolymer

Abstract

The invention provides a novel oil thickener that can impart a thickening effect for oils used in cosmetics, and a novel oil-soluble copolymer that can be used as the thickener.The cosmetic oil thickener of the invention is an oil-soluble copolymer having a monomer unit composed of a hydrophilic monomer, a monomer unit composed of an easily-crystallizing hydrophobic monomer, and a monomer unit composed of a poorly-crystallizing hydrophobic monomer.

1 . A cosmetic oil thickener which is an oil-soluble copolymer having a monomer unit composed of a hydrophilic monomer, a monomer unit composed of an easily-crystallizing hydrophobic monomer, and a monomer unit composed of a poorly-crystallizing hydrophobic monomer. 
     
     
         2 . The thickener according to  claim 1 , wherein the easily-crystallizing hydrophobic monomer is a monomer of 8 or more carbon atoms that is a solid at ordinary temperature, and the poorly-crystallizing hydrophobic monomer is a monomer of 8 or more carbon atoms that is a liquid at ordinary temperature. 
     
     
         3 . The thickener according to  claim 1 , wherein the hydrophilic monomer is at least one monomer selected from among the following formula 1 and formula 2: 
       
         
           
           
               
               
           
         
         where, 
         R 1  is a hydrogen atom, a glyceryl group, a straight-chain or branched hydroxyalkyl group of 1 to 4 carbon atoms, or a polypropyleneglycol group represented by —(C 3 H 6 O) n H where n is an integer of 2 to 10, and 
         R 2  is a hydrogen atom or a methyl group, 
       
       
         
           
           
               
               
           
         
         where, 
         R 3  is a hydrogen atom or a methyl group, and 
         R 4  is a straight-chain or branched alkyl or hydroxyalkyl group of 1 to 4 carbon atoms, or a substituent of the following formula 3: 
       
       
         
           
           
               
               
           
         
       
     
     
         4 . The thickener according to  claim 1 , wherein the easily-crystallizing hydrophobic monomer is a monomer of the following formula 4: 
       
         
           
           
               
               
           
         
         where, 
         R 5  is a straight-chain alkyl group of 16 to 22 carbon atoms, and 
         R 6  is a hydrogen atom or a methyl group. 
       
     
     
         5 . The thickener according to  claim 1 , wherein the poorly-crystallizing hydrophobic monomer is a monomer of the following formula 5: 
       
         
           
           
               
               
           
         
         where, 
         R 7  is a branched alkyl group of 18 or fewer carbon atoms, or a straight-chain alkyl group of 12 or fewer carbon atoms, and 
         R 8  is a hydrogen atom or a methyl group. 
       
     
     
         6 . The thickener according to  claim 3 , wherein the monomer of formula 1 is at least one selected from among 2-hydroxyethyl (meth)acrylate, glyceryl (meth)acrylate, PPG-6 (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-2-methylpropyl (meth)acrylate and (meth)acrylic acid, and the monomer of formula 2 is at least one selected from among N-(2-hydroxyethyl) (meth)acrylamide, N-isopropyl(meth)acrylamide and 2-(meth)acrylamide-2-methylpropanesulfonic acid. 
     
     
         7 . The thickener according to  claim 4 , wherein the monomer of formula 4 is at least one selected from among cetyl (meth)acrylate, stearyl (meth)acrylate and behenyl (meth)acrylate. 
     
     
         8 . The thickener according to  claim 5 , wherein the monomer of formula 5 is at least one selected from among hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate and isostearyl (meth)acrylate. 
     
     
         9 . The thickener according to  claim 1 , wherein the oil-soluble copolymer contains the monomer unit of the hydrophilic monomer in a range of 30 to 50 mol %, contains the monomer unit of the easily-crystallizing hydrophobic monomer in a range of 40 to 65 mol % and contains the monomer unit of the poorly-crystallizing hydrophobic monomer in a range of 5 to 15 mol %. 
     
     
         10 . The thickener according to  claim 1 , wherein the molar ratio of the monomer unit of the easily-crystallizing hydrophobic monomer and the monomer unit of the poorly-crystallizing hydrophobic monomer in the oil-soluble copolymer is 5:1 to 8:1. 
     
     
         11 . The thickener according to  claim 1 , wherein the weight-average molecular weight of the oil-soluble copolymer is 9000 to 80,000. 
     
     
         12 . An oil-based cosmetic containing a thickener according to  claim 1  and an oil. 
     
     
         13 . An oil-soluble copolymer having:
 a monomer unit composed of at least one hydrophilic monomer selected from among the following formula 1 and formula 2,   a monomer unit composed of an easily-crystallizing hydrophobic monomer of formula 4, and   a monomer unit composed of a poorly-crystallizing hydrophobic monomer of formula wherein formulas 1, 2, 4, and 5 are as follows:   
       
         
           
           
               
               
           
         
         where, 
         R 1  is a hydrogen atom, a glyceryl group, a straight-chain or branched hydroxyalkyl group of 1 to 4 carbon atoms, or a polypropyleneglycol group represented by —(C 3 H 6 O) n H where n is an integer of 2 to 10, and 
         R 2  is a hydrogen atom or a methyl group, 
       
       
         
           
           
               
               
           
         
         where, 
         R 3  is a hydrogen atom or a methyl group, and 
         R 4  is a straight-chain or branched alkyl or hydroxyalkyl group of 1 to 4 carbon atoms, or a substituent represented by the following formula 3: 
       
       
         
           
           
               
               
           
         
         where, 
         R 5  is a straight-chain alkyl group of 16 to 22 carbon atoms, and 
         R 6  is a hydrogen atom or a methyl group, 
       
       
         
           
           
               
               
           
         
         where, 
         R 7  is a branched alkyl group of 18 or fewer carbon atoms, or a straight-chain alkyl group of 12 or fewer carbon atoms, and 
         R 8  is a hydrogen atom or a methyl group.