| 摘要 |
Aqueous colloidal dispersions of methyl methacrylate polymers are prepared by adding 30-150% of the theoretical amount of ammonium hydroxide required to neutralize the polymer defined below to a mixture comprising water; an interpolymer of methyl methacrylate and either 1-8 by weight of polymer of acrylic and/or methacrylic acid or from 4-7% of maleic and/or itaconic acid and, optionallly, a further comonomer; and (where the second order transition temperature of the polymer is above 25 DEG C.) a comminution agent to render the interpolymer water-dispersible, and agitating the mixture at 40-100 DEG C. until the polymer is colloidally dispersed in the water, at least 95% by number of the polymer particles being within the range 0.01 to 0.1 micron in diameter. Optional monomer components of the interpolymer include alkyl acrylates or haloacrylates of 40016 carbon atoms, alkyl methacrylates of 6-16 carbon atoms, styrene, vinyl acetate and vinyl chloride. The comminution agent, which may also serve as a coalescing agent, is a liquid organic compound capable of swelling or dissolving the polymer, and is preferably watermiscible. Suitable comminution agents include alkanols and hydroxyalkanols, diacetone alcohol, furfuryl and tetrahydrofurfuryl alcohols, halo-alkanols, acetaldehyde, acetone, glycerol, glycidol, glycols, glycol diacetate, glycol ethers and ether-esters, m-dioxane, p-dioxane, and formic, acetic, butyric, pyruvic and dichloroacetic acids. The dispersions may include additional components, e.g. pigments; pigment extenders such as talc, mica, calcium carbonate or clays; pigment dispersing agents such as potassium tripolyphosphate; antifoam agents; mildew inhibitors; and thickening agents such as casein, polyvinyl alcohol, hydroxy ethyl cellulose and carboxy methyl cellulose. The dispersions are suitable for forming coatings or films and for sizing textiles.ALSO:Substrates, e.g. metal or wood, are provided with protective coatings by treating with a composition comprising an aqueous colloidal dispersion of an interpolymer containing units of methyl methacrylate and either 1 to 8% by weight of acrylic and/or methacrylic acid or 4 to 8% by weight of maleic and/or itaconic acid, at least 30 mole % of the acid component being in ammonium salt form and at least 95% by number of the dispersed polymer particles being within the range 0.01 to 0.1 micron in diameter. The interpolymer may also contain other units, e.g. of alkyl acrylates, haloacrylates or methacrylates, styrene, vinyl acetate or vinyl chloride. The required polymer particle size is obtained by a special process for neutralising the parent acid interpolymer (see Division C3), as a result of which the coating composition may contain an organic liquid, preferably water-miscible, e.g. an alkanol, hydroxyalkanol, haloalkanol, diacetone alcohol, furfuryl or tetrahydrofurfuryl alcohol, acetaldehyde acetone, glycerol, glycidol, a glycol or an ether or ether-ester thereof, glycol diacetate, m- or p-dioxane or formic, acetic, butyric, pyruvic or dichloroacetic acid. Optional components may be included, e.g. pigments; pigment extenders such as talc, mica, calcium carbonate or clays; pigment dispersing agents such as potassium tripolyphosphate; anti foam agents; mildew inhibitors; and thickening agents such as casein, polyvinyl alcohol, hydroxy ethyl cellulose and carboxymethyl cellulose. |
