United States Patent:  6,096,345

Assignee:  ISP Investments Inc. (Wilmington, DE)

Filed:  January 22, 1998

This invention relates to a composition containing an active chemical and a particulate polysaccharide matrix having improved water dispersibility and dispersion stability in aqueous solutions by the incorporation of a copolymer of a N-vinyl lactam monomer and a hydrophobic comonomer. The improved properties of the matrix promotes its use as a dispersing agent in a wide variety of formulations where soil and skin substantivity or sustained release of the active chemical is required, as in pharmaceutical, pre- and post-emergent agrochemical and cosmetic formulations. The invention also pertains to the preparation and use of formulations based on the use of polysaccharide/copolymer matrix of this invention.

THE INVENTION

In accordance with the present invention there is provided a free flowing granular composition comprising an active agricultural, cosmetic or pharmaceutical chemical uniformly dispersed on a matrix of naturally occurring or modified polysaccharide particles infused with a copolymer of excess N-vinyl lactam monomer and a minor amount of a water insoluble comonomer. The present copolymer can be optionally crosslinked up to 2% with conventional polyfunctional crosslinking agents such as a polyolefin, polyacrylate, polyalkenyl ether, ethyledinevinyl pyrrolidone, divinylimidazolidone and the like.

The N-vinyl lactam monomer of the present invention is a cyclic amide containing from 4 to 6 ring carbon at oms and which is optionally substituted on the ring with lower alkyl of 1 to 4 carbon atoms. The lactam component of the copolymer also includes mixtures of such N-vinyl lactams. Representative examples of monomer are N-vinyl pyrrolidone, N-vinyl caprolactam, N-vinyl methyl pyrrolidone, N-vinyl ethyl pyrrolidone, N-vinyl methyl caprolactam and the like. Of these monomers, N-vinyl pyrrolidone and mixtures of N-vinyl pyrrolidone and N-vinylcaprolactam are preferred.

The hydrophobic comonomer of the copolymer is a polymerizable compound containing an olefinically unsaturated group, preferably a terminal unsaturated group, and is most preferably an oxygen-containing comonomer. The comonomer as well as the lactam monomer, can be quaternized or non-quaternized for the purposes of this invention, including mono-, di- and tri-lower alkyl ammonium halide salts, halide salts, sulfonate salts and phosphate salts. Examples of other suitable hydrophobic compounds include the lower alkylamino lower alkyl acrylates and methacrylates, C₄ to C₈ .alpha.-olefins, lower alkyl vinyl ethers, maleic acid and inorganic salts of said acid, N-vinyl imidazolone, N-vinyl imidazol and mixtures of these compounds as the comonomer species of the invention, such as for example mixtures of N-vinyl imidazolone or N-vinyl imidazol with dimethylamino ethyl methacrylate. Of the above comonomers, alkylamino alkylmethacrylates, particularly dimethylamino lower alkyl methacrylate and dimethylamino lower alkyl methacrylamide are preferred and the ethyl and propyl methacrylate and methacrylamide are particularly preferred.

The concentration of hydrophilic lactam component with respect to hydrophobic component in the copolymer can vary between about 60 and about 98.5 wt. %, and is preferably between about 70 and about 95 wt. %. The weight ratio of hydrophilic to hydrophobic monomer is preferably between about 4:1 and about 8:1. In this invention, the presence of the hydrophobic monomer component is critical for providing the improved soil, hair or skin substantivity desired in the matrix product when applied in aqueous solution. The hydrophobic comonomer also contributes to the improved dispersibility of the matrix/active mixture. Specifically, the polysaccharide, e.g. starch, when combined with the copolymer of this invention, has an altered tertiary structure in which the intramolecular hydrogen bonding, normally present in the unaltered state, is disrupted by the introduction of hydrophobic monomer units which interact with the hydrophobic segment of the starch; thus, exposing the hydrophilic segment of the copolymer for hydrogen bonding with water. Consequently, intramolecular bonding is inhibited and replaced by hydrogen bonding with water which is responsible for the significantly improved dispensability of the present matrix composition.

The matrices of the invention contain between about 5 and about 95 wt. % polysaccharide, preferably between about 15 and about 85 wt. % polysaccharide, with respect to copolymer, although a concentration of between 45 and 55 wt. % polysaccharide is most preferred.

The polysaccharides of the present invention are in the form of free flowing particles having an average diameter of from about 10 to about 350 microns (.mu.), preferably from 15 to 200.mu.. Suitable polysaccharides are naturally occurring and modified forms thereof which include cornstarch, potato starch, oxidized starches, methyl cellulose hydroxy propyl cellulose, calcium carboxycellulose and other types generally regarded as water insoluble or only slightly miscible with water. The infusion of the copolymer in the polysaccharide reduces its hydrophobicity and promotes dispersibility of the matrix in an aqueous medium to provide liquid sprays of up to 20% suspended solids which are stable for extended periods of up to several days. Particularly, the use of copolymer in the polysaccharide, e.g. starch, is capable of increasing the dispersibility of the later in aqueous solution up to ten fold in some cases and generally provides a dispersibility improvement between 10 and 90%, depending upon the copolymer selected for infusion.

The modified matrix of the present invention, because of its hydrophobic-hydrophilic moieties, provides compatibility with a wide variety of conventional agrochemical agents including plant growth regulants, fertilizers, pre- and post-emergent herbicides, pesticides, fungicides, nematocides, etc. as well as topical pharmaceutical chemicals and personal care agents for skin and hair conditioning, such as creams and lotions for treating skin disorders, e.g. acne, denture adhesives, mouth washes, tooth whiteners, shampoos, hair sprays, sunscreens, moisturizers, toning agents, defoliating agents, depilatating agents, hair and skin bleaching agents, hair dyes, soaps and the like and commercial laundry detergents and disinfectants. Theoretically, the concentration of the active component can be employed at about the recommended dosage, however because of the resistance to leaching and the improved substrate substantivity provided by the present matrix, somewhat smaller dosages can be effective. Generally, the weight ratio of active component to matrix is between about 1:0.1 and about 1:10, preferably between about 1:0.5 and about 1:5, on a dry basis. Examples of specific agriculturally active chemicals suitably employed herein are disclosed in columns 3 through 8 of U.S. Pat. No. 5,176,736, issued January, 1993, which agrochemicals are incorporated herein by reference.

For active components having a low dispersibility in water, the present matrix composition preferably contains from about 1 to about 20 wt. of an oxygen containing dispersant aid, based on 100% active. Such dispersant aids include lignin sulfonate, naphthalene sulfonate/formaldehyde condensate, sodium C₁₀ to C₁₄ succinate or sulfate, such as sodium lauryl succinate or sodium lauryl sulfate, the sodium salts of ethoxylated acrylates or methacrylates, lower alkyl vinyl ether/maleic acid half ester salts, naphthalene sulfonate/formaldehyde condensate, polyanionic polymers such as acrylates, and other conventional dispersant aids conventionally employed for the active pharmaceutical, agricultural or personal care chemicals.

Starch has been used as a binder/disintegrant in solid, water dispersible granules or solid compositions which provide sustained release of the active chemical as disclosed in U.S. Pat. No. 4,911,952. However, the patented process for preparing the granules containing the active component requires starch pregelatinization and extrusion of the starch and active at high temperatures and pressures which automatically excludes the incorporation of temperature sensitive active ingredients. Conversely, the present process with the modified polysaccharide eliminates pregelatinization and enables extrusion of active/matrix at ambient temperature, as illustrated in Examples 7-9 which follow.

More specifically, the free flowing matrix/active solids of this invention are prepared under ambient conditions by forming a 10 to 80% aqueous slurry of active/dispersant mixture to which is added the polysaccharide/copolymer in the concentrations discussed above. The polysaccharide/copolymer is formed by intimate mixing of the copolymer, polysaccharide and from about 20 to about 80 wt. % water until a uniform composition is attained. This composition can be predried and ground to the desired particle size or the polysaccharide in a desired particle size can be used initially. The slurry of active, optional dispersant and modified polysaccharide is formed under ambient conditions with constant agitation for a period of from about 0.25 to about 2 hours. After a uniform mixture is formed, it is allowed to stand for 1-5 minutes to assure that no settling occurs and is then subjected to drying. The particle size of the resulting dried product can be further reduced, if necessary, by recrushing or pulverizing the dried product, after which it can be stored in suitable containers until ready for dilution to prepare a liquid spray, or it can be used as a concentrated paste or employed as a dust or in any other form desired by the formulator.

Claim 1 of 20 Claims

1. A free flowing particulate matrix suitable as a substrate for an active chemical which comprises polysaccharide infuse with a copolymer derived from a major amount of hydrophilic N-vinyl lactam monomer containing 4 to 8 ring carbon atoms, optionally substitued on the ring with C₁ to C₄ alkyl and a minor amount of a hydrophobic C₁ to C₄ alkyl amino, C₁ to C₄ alkyl-acrylate or methacrylate comonomer.

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