Process for the production of dispersions of hydrophobic particulate solids (e.g. pesticides) and the particulate dispersions thus obtained

Claim 2

A dispersion in an aqueous medium of a non-polymeric hydrophobic particulate solid substantially all the particles of which have a size less than 100 microns, the dispersion containing a block or graft copolymer the molecule of which comprises at least one component (A), of molecular weight at least 250, which is solvated by the aqueous medium and at least one other component (B), of molecular weight at least 500 and having a minimum degree of hydrophobicity as hereinbefore defined, which is associated with the particulate solid, the total weight ratio of components A to components B in the copolymer being from 1:10 to 10:1 and the ratio of the number of individual components A to individual components B in the copolymer molecule being from 10:1 to 1:2.

Claim 3

A dispersion as claimed in claim 1, wherein the hydrophobic particulate solid is a pesticide, in particular a fungicide, an insecticide, a bactericide or a herbicide.

Claim 4

A dispersion as claimed in claim 1 or claim 2, containing a graft copolymer of the structure An B, wherein a plurality of solvatable A components are attached at intervals to a polymer backbone constituting the hydrophobic, associatable B component and wherein the A components provide a slight weight excess over the B components.

Claim 5

A dispersion as claimed in claim 3, wherein in the graft copolymer:- (i) the weight ratio of the A components to the B components is from 1.1:1 to 2:1; (ii) the number ratio of the A components to the B components is from 3:1 to 10:1; (iii) the molecular weight of each A component is at least 500,of each B component at least 1000, and of the copolymer as a whole at least 5000.

Claim 6

A dispersion as claimed in any one of claims 1 to 4, wherein the A component of the block or graft copolymer is selected from polyethylene glycol, poly(vinylpyrrolidone), poly(acrylamide) and poly(vinyl alcohol) and the B component is selected from polymers and copolymers of styrene, methyl methacrylate, ethyl acrylate, 2-ethylhexyl acrylate, lauryl methacrylate and vinyl acetate, polyesters, polyamides and oligomers of aliphatic monohydroxy-monocarboxylic acids.

Claim 7

A dispersion as claimed in claims 1 or claims 2, wherein the block or graft copolymer is the product of esterification of a polyethylene glycol with a high molecular weight monocarboxylic acid, or an alkyd resin formed from a polyethylene glycol, a polycarboxylic acid and optionally other polyhydric alcohols.

Claim 8

A dispersion as claimed in any one of claims 1 to 6, wherein there is additionally present a polymer of molecular weight at least 1000 which is soluble in the aqueous medium, the concentration of the soluble polymer in the aqueous medium being at least 0.01% by weight..

Claim 9

A process for the production of a dispersion as claimed in any one of claims 1 to 7, comprising dispersing a non-polymeric hydophobic solid in an aqueous medium in the form of particles substantially all of which are of a size less than 100 microns, in the presence in the aqueous medium of a block or graft copolymer the molecule of which comprises at least one component (A), of molecular weight at least 250, which is solvatable by the aqueous medium and at least one other component (B), of molecular weight at least 500 and having a minimum degree of hydrophobicity as hereinbefore defined, which becomes associated with the particulate solid, the total weight ratio of components A to components B in the copolymer molecule being from 1:10 to 10:1 and the ratio of the number of individual components A to individual components B in the copolymer molecule being from 10:1 to 1:2.

Claim 10

A process as claimed in claim 8, wherein the hydrophobic solid is dispersed in the aqueous medium by comminution of coarse particles of the solid in the presence of the aqueous medium and of the block or graft copolymer.

Claim 11

A process as claimed in claim 9 or claim 10, wherein there is subsequently incorporated into the dispersion so obtained, in a concentration of at least 0.1% by weight in the aqueous medium, a polymer of molecular weight at least 1000 which is soluble in the aqueous medium.