Oil-containing microcapsules and method for their production

Abstract

Method of producing microcapsules containing hydrophobic oily liquid, which comprises, in producing microcapsules by complex coacervation, using gelatin, as at least one hydrophilic colloid, adding an aqueous solution of shock preventing agent at a temperature lower than the gelling point of gelatin in order to prevent a rise in viscosity due to reaction of gelatin and aldehyde during hardening pretreatment and rapidly accomplishing hardening pretreatment.

What is claimed is:  .[.1. In a method for producing oil-containing mononuclear microcapsules by emulsifying a water-immiscible oil and an aqueous solution of a hydrophilic colloid to obtain a first sol ionizable in water, by 
     
        integer..]. 2. The method of claim .[.1.]. .Iadd.32 .Iaddend.wherein the amount of said polyelectrolyte is from 1/12 to 1/2 by weight based on the 
     
     
        total amount of hydrophilic colloids present. 3. The method of claim .[.1.]. .Iadd.32 .Iaddend.wherein said modified cellulose is selected from the group consisting of carboxymethyl cellulose, carboxyethyl cellulose, 
     
     
        cellulose sulfate, cellulose phosphate and a metal salt thereof. 4. The method of claim .[.1.]. .Iadd.32 .Iaddend.wherein in said anionic starch derivative is selected from the group consisting of carboxymethyl starch, carboxyethyl starch, starch sulfate, starch phosphate and starch xanthate. 
     
     
        . The method of claim .[.1.]. .Iadd.32 .Iaddend.wherein said 
     
     
        polyelectrolyte is an anionic acid polysaccharide. 6. The method of claim .[.1.]. .Iadd.32 .Iaddend.wherein said polyelectrolyte is a hydroxyethyl 
     
     
        cellulose derivative. 7. The method of claim .[.1.]. .Iadd.32 .Iaddend.wherein said polyelectrolyte is a vinylbenzene sulfonate 
     
     
        copolymer. 8. The method of claim .[.1.]. .Iadd.32 .Iaddend.wherein said 
     
     
        polyelectrolyte is an acrylic acid copolymer. 9. The method of claim .[.1.]. .Iadd.32 .Iaddend.wherein said microcapsules contain a colorless 
     
     
        leuco dye capable of forming a color dye when contacted with clay. 10. Oil-containing microcapsules produced according to the method of claim 
     
     
        .[.1.]. .Iadd.32. .Iaddend. 11. Oil-containing microcapsules produced 
     
     
        according to the method of claim 9. 12. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein said condensate of naphthalene sulfonic acid 
     
     
        and Formalin has a degree of polymerization ranging from 5 to 9. 13. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein said vinyl-benzene sulfonate in said vinyl-benzene sulfonate copolymer is present in an 
     
     
        amount of from 45 to 95 mol percent. 14. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein said vinyl-benzene sulfonate in said vinyl-benzene sulfonate copolymer is present in an amount of from 60 to 85 
     
     
        mol percent. 15. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein the molecular weight of said vinyl-benzene sulfonate copolymer ranges from 
     
     
        10,000 to 3,000,000. 16. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein the molecular weight of said vinyl-benzene sulfonate copolymer 
     
     
        ranges from 100,000 to 1,000,000. 17. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein said acrylic acid in said acrylic acid 
     
     
        copolymer is present in an amount of from 40 to 95 mol percent. 18. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein said acrylic acid in said acrylic acid copolymer is present in an amount of from 50 to 85 mol 
     
     
        percent. 19. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein said acrylic acid copolymer has a molecular weight of from 6,000 to 2,000,000. 
     
     
         0. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein said acrylic acid in said acrylic acid copolymer has a molecular weight of from 50,000 
     
     
        to 1,000,000. 21. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein said hydrophilic colloid is a member selected from the .[.roup.]. .Iadd.group .Iaddend.consisting of gelatin, casein, alginate, gum arabic, styrene-maleic anhydride copolymers, and polyethylene-maleic anhydride 
     
     
        copolymers. 22. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein the addition of said polyelectrolyte takes place at a temperature of below 
     
     
        20° C. 23. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein the addition of said polyelectrolyte takes place at a temperature of below 
     
     
        15° C. 24. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein 
     
     
        said pH is 7.0. 25. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein 
     
     
        said pH is 7.5. 26. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein 
     
     
        said pH is 8.0. 27. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein 
     
     
        said pH is 10.0. 28. The method of claim 4, wherein the cellulose of said anionic starch derivative has a degree of polymerization ranging from 50 
     
     
        to 500. 29. The method of claim 4, wherein the cellulose of said anionic starch derivative has a degree of esterification or etherification of from 
     
     
        0.5 to 1.2. 30. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein the 
     
     
        adjustment of pH occurs before addition of the hardening agent. 31. The method of claim .[.1.]. .Iadd.32.Iaddend., wherein the adjustment of pH occurs after the addition of the hardening agent. .Iadd. 32. In a method for producing oil-containing microcapsules by: (a) emulsifying a water-immiscible oil and an aqueous solution containing gelatin and another hydrophilic colloid, or   (b) emulsifying a water-immiscible oil and an aqueous solution of a hydrophilic colloid to obtain a first sol, ionizable in water and admixing said first sol and an aqueous solution of a hydrophilic colloid to obtain a second sol, ionizable in water and having an electric charge opposite to that of said first sol, one of said colloids being gelatin,   (c) adding water to either emulsion derived from (a) or (b) and/or adjusting the pH thereof to cause coacervation, thus to obtain coacervates, wherein the complex colloids are deposited around the individual oil drops,   (d) cooling the coacervates to cause gelation thereof, and converting the pH to alkalinity, and   (e) adding a hardening agent to the system and adjusting the pH thereof to a range of from 7 to 11, the improvement which comprises: adding an aqueous solution of a polyelectrolyte having anionic functional groups to the dispersion containing said coacervates at a temperature lower than the gelling point of the gelatin, in an amount sufficient to prevent a rise in viscosity thereof,   said addition being made after gelation of the coacervates has occurred and before the adjustment of said pH to a range of from 7 to 11 and the adding of said hardening agent to the system has occurred, and   said adjusting of said pH occurring before, after, or simultaneously with the addition of said hardening agent,   said polyelectrolyte being a member selected from the group consisting of   a modified cellulose comprising polysaccharides having beta-1,4-glucoside bonds of glucoses and having anionic functional groups,   an anionic starch derivative composed of a linear polysaccharide amylose formed by only alpha-1,4 bonds of D-glucose, and a branched polysaccharide amylopectin formed by mainly alpha-1,4 bonds of D-glucose and a partially side chain branched by alpha-1,6 bonds,   an anionic acid polysaccharide, obtained by polycondensing linearly D-galacturonic acid between the alpha-1,4 bonds thereof, said acid polysaccharide containing pectin, pectic acid, and pectinic acid,   a condensate of naphthalene sulfonic acid and formalin, which condensate is represented by the formula: ##SPC5## wherein X is a hydrogen atom, an alkali metal, or an ammonium group, and n is a positive integer,     a hydroxyethyl cellulose derivative selected from the group consisting of the carboxymethyl ether of hydroxyethyl cellulose, hydroxyethyl cellulose sulfate, and hydroxyethyl cellulose phosphate,   a vinyl-benzene sulfonate copolymer selected from the group consisting of a vinylbenzene sulfonate-acryloylmorpholine copolymer, a vinylbenzene sulfonate-morpholino-methylacrylamide copolymer, a vinylbenzene sulfonate acrylamide copolymer, a vinylbenzene sulfonate-vinylpyrrolidone copolymer, and a vinylbenzene sulfonate-methyloxymethylacrylamide; said copolymer having the following group within its molecular structure: ##SPC6## wherein M is an alkali metal and n is a positive integer, and     an acrylic acid copolymer selected from the group consisting of an acrylic acid acryloylmorpholine copolymer, an acrylic acid-morpholinomethylacrylamide copolymer, an acrylic acid-acrylamide copolymer, an acrylic acid-vinylpyrrolidone copolymer, and an acrylic acid-methoxymethylacrylamide copolymer, said copolymer having the following group within its molecular structure: ##EQU3## wherein X is a hydrogen atom or an alkali metal and n is a positive integer. .Iaddend.