Poly (amino acid) rheology modifier compositions and methods of use

Abstract

Described are rheology modifier compositions comprising cross-linked poly(amino acid) and methods of their use in aqueous compositions.

1 . A rheology modifier comprising cross-linked poly(amino acid) microparticles, wherein the microparticles have a mean equivalent diameter when fully swollen in deionized water of up to about 1000 μm, as measured by laser diffraction. 
     
     
         2 . The rheology modifier of  claim 1 , wherein the cross-linked poly(amino acid) comprises a cross-linked amino acid homopolymer or copolymer. 
     
     
         3 . The rheology modifier of  claim 1 , wherein the cross-linked poly(amino acid) comprises a cross-linked blend of at least two members selected from the group consisting of amino acid homopolymers and copolymers. 
     
     
         4 . The rheology modifier of  claim 1 , wherein the cross-linked poly(amino acid) comprises a cross-linked member selected from the group consisting of D-γ-poly(glutamic acid), L-γ-poly(glutamic acid), D,L-γ-poly(glutamic acid), and combinations thereof. 
     
     
         5 . The rheology modifier of  claim 1 , wherein the cross-linked poly(amino acid) is prepared from a poly(amino acid) having a weight average molecular weight of from about 1000 to about 30,000,000 Daltons. 
     
     
         6 . The rheology modifier of any  claim 1 , wherein the cross-linked poly(amino acid) has a cross-link density of from one cross-link bond per ten monomer units up to one cross-link bond per about 100,000 monomer units. 
     
     
         7 . The rheology modifier of  claim 1 , wherein the cross-linked poly(amino acid) has a free swelling absorbency of from about 20 g to about 10,000 g water/g dry cross-linked poly(amino acid). 
     
     
         8 . The rheology modifier of  claim 1 , wherein the cross-linked poly(amino acid) is made from renewable starting materials. 
     
     
         9 . An aqueous composition comprising the rheology modifier of  claim 1 . 
     
     
         10 . The aqueous composition of  claim 9 , wherein the cross-linked poly(amino acid) has a concentration of 1 g/L to 100 g/L in the aqueous composition. 
     
     
         11 . Use of the rheology modifier of  claim 1  in a personal care or pharmaceutical formulation, topical drug formulation, skin care product, cosmetic, personal cleansing product, paint, coating, and ink, agrochemical formulation, food product, concrete or cement mix, household or industrial cleanser, or drilling fluid. 
     
     
         12 . A method of preparing a rheology modifier comprising:
 a) cross-linking a poly(amino acid) to produce a cross-linked poly(amino acid);   b) drying the cross-linked poly(amino acid); and   c) grinding the cross-linked poly(amino acid) to have a mean equivalent diameter when fully swollen in deionized water of up to about 1000 μm, as measured by laser diffraction.   
     
     
         13 . The method of  claim 10 , wherein the cross-linked poly(amino acid) is dispersed in water before the grinding step. 
     
     
         14 . The method of  claim 10 , wherein step a) and step b) are carried out simultaneously by heating a solution of the poly(amino acid) and a cross-linker in water at a temperature at which the water evaporates and the cross-linker crosslinks the poly(amino acid). 
     
     
         15 . A method of thickening an aqueous composition, comprising:
 a) dispersing the rheology modifier of  claim 1  into an aqueous composition to form a dispersion having a concentration of 1 g cross-linked poly(amino acid) per L to 100 g cross-linked poly(amino acid) per L; and   b) mixing the dispersion to thicken the aqueous composition.   
     
     
         16 . The method of  claim 15 , wherein the rheology modifier has an acidic pH and the dispersion pH is increased in step b). 
     
     
         17 . The method of  claim 15 , wherein the rheology modifier used in step a) has a concentration of cross-linked poly(amino acid) in water ranging from 1 g/L to 1000 g/L before addition to the aqueous composition. 
     
     
         18 . The method of  claim 15 , wherein the rheology modifier used in step a) comprises cross-linked poly(amino acid) dispersed in a hydrophobic medium at a concentration ranging from 1 g/L to 1000 g/L. 
     
     
         19 . The method of  claim 15 , wherein the rheology modifier used in step a) is dry poly(amino acid). 
     
     
         20 . The method of  claim 15 , further comprises adjusting the pH of the aqueous dispersion through addition of any alkali or acidic agent in step a) or step b).