Microgel and external compositions containing the same

Abstract

The present invention provides a microgel having a mean particle size of 0.1-1,000 μm, the microgel being produced from a gel which is formed by use of a hydrophilic compound capable of forming a gel. An external composition containing the microgel provides an excellent sensation during use; i.e., the composition provides neither sticky sensation during use nor frictional sensation. Furthermore, even when a large amount of a pharmaceutical ingredient, such as a whitening ingredient, or a salt is incorporated into the composition, the viscosity of the composition is not lowered, and the composition exhibits excellent viscosity increasing property. In addition, the composition exhibits long-term stability, without inviting separation of water.

1 . A microgel having a mean particle size of 0.1-1,000 μm, the microgel being produced from a gel which is formed by use of a hydrophilic compound capable of forming a gel.  
     
     
         2 . A microgel having a mean particle size of 0.1-1,000 μm, the microgel being produced from a gel which is formed by use of a hydrophilic compound capable of forming a gel and a viscosity increasing compound incapable of forming a gel.  
     
     
         3 . A microgel as described in  claim 2 , wherein the viscosity increasing compound incapable of forming a gel is one or more viscosity increasing compounds selected from the group consisting of xanthan gum, succinoglycan, polyacrylic acid, polyethylene glycol, polyacrylamide, and a polyalkylacrylamide/polyacrylamide copolymer.  
     
     
         4 . A microgel as described in any one of claims  1  through  3 , wherein the hydrophilic compound capable of forming a gel is one or more hydrophilic compounds selected from the group consisting of agar, carrageenan, curdlan, gelatin, gellan gum, and alginic acid.  
     
     
         5 . A microgel as described in any one of claims  1  through  4 , which has a viscosity of 2,000-1,000,000 mPa·s (B-type viscometer, 25° C.)  
     
     
         6 . A process for producing a microgel of  claim 1 , which process comprises dissolving in an aqueous solvent a hydrophilic compound capable of forming a gel; causing the resultant mixture to form a gel; and pulverizing the gel into a microgel having a mean particle size of 0.1-1,000 μm.  
     
     
         7 . A process for producing a microgel of  claim 2 , which process comprising dissolving in an aqueous solvent a hydrophilic compound capable of forming a gel and a viscosity increasing compound incapable of forming a gel; causing the resultant mixture to form a gel; and pulverizing the gel into a microgel having a mean particle size of 0.1-1,000 μm.  
     
     
         8 . An external composition comprising a microgel of any one of claims  1  through  5 .  
     
     
         9 . An external composition as described in  claim 8 , further comprising a pharmaceutical ingredient and/or a salt.  
     
     
         10 . An external composition as described in  claim 9 , wherein the pharmaceutical ingredient is a whitening ingredient.  
     
     
         11 . An external composition as described in  claim 10 , wherein the whitening ingredient is one or more whitening ingredients selected from the group consisting of L-ascorbic acid, an L-ascorbic acid derivative, arbutin, glutathione, tranexamic acid, a tranexamic acid derivative, a placenta extract, and a vegetable extract exhibiting whitening effect.  
     
     
         12 . An external composition as described in any one of claims  9  through  11 , wherein the amount of the pharmaceutical ingredient and/or the salt is 0.01-20 mass % of the total of the composition.  
     
     
         13 . An external composition as described in any one of claims  8  through  12 , which is a cosmetic composition.  
     
     
         14 . An external composition as described in any one of claims  8  through  12 , which is a hair dye.