Process for achieving uniform, efficient distribution of hydrophobic materials through hydrophilic colloid layers and loaded latex compositions

A process of preparing a polymeric latex composition comprising

• (1) providing an aqueous latex consisting essentially of water as a continuous phase and from 0.1 to 20 percent by weight, based on total weight of the latex, of polymer particles of from 0.02 to 0.2 micron in average diameter as a dispersed phase, the polymer consisting essentially of
• (a) repeating units forming from 60 to 95 percent by weight of the polymer derived from at least one of
• (i) ethenic monomers of the formula ##STR40## where R is hydrogen, halogen or vinyl and
• R.sup.1 is hydrogen, halogen or methyl or, when R is hydrogen, cyano;
• (ii) styrene-type monomers of the formula ##STR41## where R.sup.2 is hydrogen or methyl,
• R.sup.3, R.sup.4 and R.sup.6 are hydrogen or lower alkyl of from 1 to 5 carbon atoms,
• R.sup.5 is hydrogen or with R.sup.4 constitutes the atoms necessary to complete a fused benzene ring or one of R.sup.5 and R.sup.6 is halomethyl;
• (iii) esters of 2-alkenoic acids having the formula ##STR42## where R.sup.7 is hydrogen or lower alkyl of from 1 to 5 carbon atoms,
• R.sup.8 is hydrogen, chlorine or lower alkyl of from 1 to 5 carbon atoms and
• R.sup.9 is alkyl or haloalkyl having from 1 to 20 carbon atoms, and
• (iv) vinyl acetate;
• (b) repeating units forming from 5 to 25 percent by weight of the polymer derived from a hydrophilic ethenic monomer having a molecular weight of at most 300 of the formula ##STR43## where R.sup.8 is as defined above,
• Q.sup.1 is --OM or a divalent organic radical which together with the carbonyl group of the formula forms an ester or amido linking group terminating in an ammonium or --SO.sub.3 M solubilizing group and
• M is hydrogen, ammonium or alkali metal;
• (c) repeating units forming from 0 to 10 percent by weight of the polymer derived from active methylene containing ethenic monomer exhibiting the formula ##STR44## where R.sup.12 is hydrogen, alkyl having from 1 to 12 carbon atoms or ##STR45## R.sup.13 is alkyl having from 1 to 10 carbon atoms, cycloalkyl having from 3 to 10 carbon atoms, phenyl or ##STR46## R.sup.14 is alkylene having from 1 to 10 carbon atoms and X.sup.1 is cyano or alkylcarbonyl having from 1 to 8 carbon atoms,
• provided that one and only one of R.sup.12 and R.sup.13 is always ##STR47## (d) repeating units forming from 0 to 3 percent by weight of the polymer derived from a crosslinking monomer having a molecular weight of at most about 300 and having at least two independently polymerizable vinyl groups;
• (2) providing a solution consisting essentially of a hydrophobic pesticide having a solubility in distilled water at 25.degree. C. of less than 0.5 percent, based on the weight of the water, dissolved in a water-miscible organic solvent in a concentration of from 0.1 to 20 percent by weight, based on total weight of the solution, wherein the water-miscible organic solvent is selected from those which can be dissolved in distilled water at 20.degree. C. to the extent of at least about 20 parts by volume in 80 parts by volume of water, having boiling points above about -10.degree. C., do not detrimentally react with aqueous latexes containing the polymer particles and do not dissolve more than about 5 weight percent of the polymer particles at 20.degree. C., and
• (3) gradually adding the aqueous latex to the solution of the hydrophobe and the water-miscible organic solvent employing a volume ratio of the aqueous latex to the solution of the hydrophobe and the water-miscible organic solvent of from 1:4 to 4:1 and a weight ratio of hydrophobe to the polymer particles of from 1:40 to 3:1 while retaining the hydrophobe in solution and the polymer particles dispersed so that (a) the hydrophobe and the polymer particles are brought into intimate association and (b) the water-miscible organic solvent is diluted with water to reduce the solubility of the hydrophobe in the resulting continuous phase and thereby drive the equilibrium distribution of the hydrophobe away from the resulting continuous phase toward the polymer particles of the dispersed phase, with the result being the loading of the dissolved hydrophobe into the polymer particles.

A process of preparing a polymeric latex composition comprising

• (1) providing an aqueous latex consisting essentially of water as a continuous phase and from 0.1 to 20 percent by weight, based on total weight of the latex, of polymer particles of from 0.02 to 0.2 micron in average diameter as a dispersed phase, the polymer particles being chosen from among those which, at 25.degree. C.,
• (a) are capable of forming a latex with water at a polymer particle concentration of from 10 to 20 weight percent, based on total weight of the latex,
• (b) exhibit no observable coagulation of the polymer particles when 100 ml of the latex is then mixed with an equal volume of a water-miscible organic solvent, stirred and allowed to stand for 10 minutes, and
• (c) contain from 2 to 25 percent by weight repeating units derived from hydrophilic ethenic monomers having a molecular weight at most of about 300, the monomers being capable of forming water-soluble homopolymers,
• (2) providing a solution consisting essentially of a hydrophobe which is methyl parathion having a solubility in distilled water at 25.degree. C. of less than 0.5 percent, based on the weight of the water, dissolved in the water-miscible organic solvent in a concentration of from 0.1 to 20 percent by weight, based on total weight of the solution, wherein the water-miscible organic solvent is selected from those which can be dissolved in distilled water at 20.degree. C. to the extent of at least about 20 parts by volume in 80 parts by volume of water, having boiling points above about -10.degree. C., do not detrimentally react with aqueous latexes containing the polymer particles and do not dissolve more than about 5 weight percent of the polymer particles at 20.degree. C.,
• (3) gradually adding the aqueous latex to the solution of the hydrophobe and the water-miscible organic solvent employing a volume ratio of the aqueous latex to the solution of the hydrophobe and the water-miscible organic solvent of from 1:4 to 4:1 and a weight ratio of hydrophobe to the polymer particles of from 1:40 to 3:1 while retaining the hydrophobe in solution and the polymer particles dispersed so that (a) the hydrophobe and the polymer particles are brought into intimate association and (b) the water-miscible organic solvent is diluted with water to reduce the solubility of the hydrophobe in the resulting continuous phase and thereby drive the equilibrium distribution of the hydrophobe away from the resulting continuous phase toward the polymer particles of the dispersed phase, with the result being the loading of the dissolved hydrophobe into the polymer particles.