Method for preparing an emulsion with high-viscosity organic phase

Abstract

The invention concerns a method for preparing an oil-in-water emulsion whereof the organic phase has a viscosity not less than 1 Pa.s, which consists in using an aqueous phase comprising at least a heat-thickening polymer having a viscosity jump between 25 and 80° C. so that the value of the ratio log 10 (viscosity at 80° C.)/log 10 (viscosity at 25° C.) is at least equal to 1, preferably at least equal to 2, the variation in viscosity being reversible; the amount of heat-thickening polymer being such that the aqueous phase viscosity is 0.2 to 5 times that of the organic phase at the temperature for preparing the emulsion; the latter being not less than the thickening temperature of the heat-thickening polymer.

1 . A process for preparing an oil-in-water emulsion, the organic phase of which has a viscosity of greater than or equal to 1 Pa.s, in which an aqueous phase is used comprising at least one heat-induced thickening polymer displaying a jump-in viscosity between 25 and 80° C. such that the value of the ratio log 10  (viscosity at 80° C.)/log 10  (viscosity at 25° C.) is at least equal to 1 and preferably at least equal to 2, the variation in viscosity being reversible; the amount of heat-induced thickening polymer being such that the viscosity of the aqueous phase is from 0.2 to 5 times that of the organic phase at the emulsion preparation temperature; said temperature being greater than or equal to the thickening temperature of the heat-induced thickening polymer.  
     
     
         2 . The process as claimed in the preceding claim, characterized in that a heat-induced thickening polymer of comb structure is used, consisting of a polymer skeleton onto which are grafted at least two identical or different polymeric side segments, and for which either the polymer skeleton or the side segments have a lower critical solution temperature of between 25 and 80° C.  
     
     
         3 . The process as claimed in either of the preceding claims, characterized in that a heat-induced thickening polymer for which the polymer skeleton of the polymer has a lower critical solution temperature of between 25 and 80° C. is used.  
     
     
         4 . The process as claimed in either of claims  1  and  2 , characterized in that a heat-induced thickening polymer for which the polymeric side segments of the polymer have a lower critical solution temperature of between 25 and 80° C. is used.  
     
     
         5 . The process as claimed in one of the preceding claims, characterized in that a polymer is used comprising several polymers arranged together so as to form a crosslinked structure in which the polymer segments thereof having the lower critical solution temperature contain the crosslinking nodes and at least some of the segments thereof not having a lower critical solution temperature of between 25 and 80° C. establish the connections between said nodes.  
     
     
         6 . The process as claimed in one of  claims 1  to  3 , characterized in that a heat-induced thickening polymer is used, the segments of which not having alower critical solution temperature of between 25 and 80° C. are water-soluble at least in this temperature range.  
     
     
         7 . The process as claimed in one of the preceding claims, characterized in that a heat-induced thickening polymer is used, the polymer segments of which not having a lower critical solution temperature are water-soluble in the temperature range for preparation of the emulsion.  
     
     
         8 . The process as claimed in one of the preceding claims, characterized in that a heat-induced thickening polymer is used, the polymer segment of which not having a lower critical solution temperature is a polymer of water-soluble ethylenic type.  
     
     
         9 . The process as claimed in the preceding claim, characterized in that a heat-induced thickening polymer derived from the polymerization of water-soluble ethylenic monomers of vinyl, acrylic, styrene or diene type and/or of vinyl ester type is used.  
     
     
         10 . The process as claimed in one of the preceding claims, characterized in that a heat-induced thickening polymer whose polymer segments have a molecular weight at least greater than 1 000 g/mol is used.  
     
     
         11 . The process as claimed in one of the preceding claims, characterized in that a heat-induced thickening polymer whose polymer segments are derived from the polymerization of acrylic acid and/or 2-acrylamidomethylpropanesulfonic acid is used.  
     
     
         12 . The process as claimed in one of the preceding claims, characterized in that a heat-induced thickening polymer the polymer segments of which having a lower critical solution temperature of between 25 and 80° C. are derived from polyalkoxylated polymers is used.  
     
     
         13 . The process as claimed in the preceding claim, characterized in that a heat-induced thickening polymer whose polymer segments contain at least 5 oxyalkylenated units is used.  
     
     
         14 . The process as claimed in any one of the preceding claims, characterized in that a heat-induced thickening polymer chosen from the following is used: 
 polymer prepared from PEO-PPO-PEO triblocks and from acrylic acid (respective molar percentages: 2.3%, 97.7%), preferably by direct grafting,    polymer prepared from PEO-PPO-PEO triblock macro-monomer and from acrylic acid (respective molar percentages: 1.6%, 98.4%), preferably by copolymerization,    polymer prepared from PEO-PPO-PEO triblock macro-monomer and from acrylic acid (respective molar percentages: 3%, 97%), preferably by copolymerization, and/or    polymer prepared from PEO-PPO-PEO triblock macro-monomer and from acrylic acid (respective molar percentages: 2%, 98%), preferably by copolymerization.    
     
     
         15 . The process as claimed in any one of the preceding claims, characterized in that an amount of heat-induced thickening polymer is used such that the viscosity of the aqueous phase is from 0.5 to 2 times that of the organic phase, at the preparation temperature of said emulsion.  
     
     
         16 . The process as claimed in one of the preceding claims, characterized in that a content of heat-induced thickening polymer of between 0.5% and 5% by weight of the aqueous phase and preferably between 1% and 3% by weight of the aqueous phase is used.  
     
     
         17 . The process as claimed in one of the preceding claims, characterized in that an organic phase with a viscosity of at least 5 Pa.s and preferably between 5 and 500 Pa.s is used.  
     
     
         18 . The process as claimed in one of the preceding claims, characterized in that an organic phase chosen from mineral oils, alkyd resins, polyisocyanates and high molecular weight silicones is used; these compounds being alone or as a mixture.  
     
     
         19 . The process as claimed in one of the preceding claims, characterized in that an organic phase comprising at least one hydrophobic active material is used.  
     
     
         20 . The process as claimed in one of the preceding claims, characterized in that an organic phase comprising a dispersed internal aqueous phase is used.  
     
     
         21 . The process as claimed in  claim 20 , characterized in that an internal aqueous phase comprising at least one hydrophilic active material is used.  
     
     
         22 . The process as claimed in either of claims  20  and  21 , characterized in that an internal aqueous phase/organic phase weight ratio of between 10/90 and 90/10 and preferably between 30/70 and 80/20 is used.  
     
     
         23 . The process as claimed in one of the preceding claims, characterized in that the organic phase/aqueous phase weight ratio, or the weight ratio of the internal aqueous phase and organic phase combination/aqueous phase, is between 10/90 and 90/10 and preferably between 30/70 and 80/20.  
     
     
         24 . The process as claimed in one of the preceding claims, characterized in that the following are mixed with stirring:  
       the organic phase comprising: 
 optionally at least one hydrophobic active material,  
 optionally the dispersed internal aqueous phase optionally comprising at least one hydrophilic active material and optionally at least one additive; the combination of internal aqueous phase and organic phase comprising at least one nonionic surfactant and/or at least one amphiphilic block polymer, and/or at least one cationic surfactant; and  
 the aqueous phase comprising:  
 optionally at least one hydrophilic active material,  
 at least one polyalkoxylated nonionic surfactant and/or at least one nonionic amphiphilic polymer and/or at least one anionic surfactant and/or at least one anionic amphiphilic polymer,  
 at least one heat-induced thickening polymer,  
 optionally at least one additive and optionally at least one thickening polymer;  
 the emulsion preparation temperature being greater than or equal to the thickening temperature of the heat-induced thickening polymer.