GB750605A - Improvements in or relating to coating compositions and preparation thereof - Google Patents

Abstract

A stable coating composition comprises a dispersion of discrete particles of one or more coating materials in an aqueous dispersing medium, most of the particles having a longest dimension of at least 50 microns and being stabilized by the presence in the aqueous phase of a colloidal stabilizing agent selected from gums, cellulose derivatives, carbohydrates, water-soluble synthetic organic materials and colloidal inorganic materials. The coating materials include introcellulose, cellulose acetate and ethyl cellulose lacquers, synthetic resin enamels, solutions of polymerized synthetic resins, such as polyvinyl, polystyrene and polyacrylic resins, and urea - formaldehyde resins. More than one type or colour of coating material may be dispersed in the aqueous medium, the particles of different sorts not coalescing. Non-spherical particles, e.g. of tear-drop or filamentary shapes, may be produced under certain conditions. The aqueous medium may contain dyes, wetting agents, pigments, water-proofing agents, freezing point depressants and the like. Suspension stabilizers mentioned include methyl and ethyl cellulose, cellulose acetate phthalate, carboxy methyl cellulose and hydroxy ethyl cellulose, polyvinyl alcohol, gum tragacanth, locust bean gum, quince seed extract, bentonite, polystyrene ammonium maleate, polymethacrylic acid, gum arabic, gum cibara, gum karaya, sodium alginate, pectin, starches, water soluble urea-formaldehyde, fuller's earth, talc, barium sulphate, calcium carbonate, calcium sulphate, magnesium carbonate and diatomaceous earth. The inorganic materials require to be used in amounts of up to 25 per cent of the aqueous medium and to be finely divided, i.e. of colloidal dimensions. In Examples: (I) and (II) 100 parts of lacquers containing titanium dioxide or Indian red oxide and wet nitrocellulose, ester gum, castor oil, dibutyl phthalate, butyl alcohol, butyl acetate, methyl amyl acetate, toluol and xylol are dispersed in 50 parts of a 1 per cent solution of methyl cellulose, in a mixing kettle provided with a propeller agitator; (III) separate dispersions of white and red lacquers produced as above are mixed and the resulting mixture sprayed to give a coating in which the red and white particles are visible; (IV) and (V) 100 parts of enamels composed of chrome yellow or chrome green pigment, ureaformaldehyde resin in butyl alcohol, and soy bean alkyd resin in xylol are dispersed in 92 parts of tap water containing 0.55 parts of quince seed extract; (VI) equal parts of dispersions prepared according to Examples (IV) and (V) are stirred together and the resulting mixture sprayed on kraft and asphalt paper surfaces; (VII) and (VIII) 100 parts of oil paints containing Indian red oxide or chrome yellow pigment and linseed oil, oxidized sardine oil, mineral spirits, and cobalt and lead drier solutions are dispersed in 50 parts of tap water containing 1 per cent of high viscosity polyvinyl alcohol and 2.5 per cent of bentonite; (IX) equal parts of dispersions prepared according to Examples (VII) and (VIII) are stirred together; (X) 100 parts of coating material comprising titanium dioxide, polystyrene resin and xylol are added, with agitation, to a solution of 1 part of cellulose acetate phthalate in 49 parts of tap water adjusted to a pH of about 8.8 by addition of ammonium hydroxide; (XI) 100 parts of a lacquer composed of titanium dioxide, vinyl acetate polymer, toluol and methyl amyl acetate are added with mild agitation to 50 parts of a 2 per cent solution of soluble ethyl cellulose in tap water; (XII) a water-in-oil type emulsion is prepared by mixing equal parts of a 1 per cent solution of locust bean gum in tap water and an enamel composed of chrome green pigment, urea-formaldehyde resin in butyl alcohol, soy bean alkyd resin in xylol, and butyl alcohol, and 50 parts of this is mixed with agitation with 50 parts of a 2 per cent aqueous solution of a water-soluble ethyl cellulose. A dispersion of the emulsion in fairly large particles in the aqueous phase is formed; (XIII) a dispersion of an emulsion of a white enamel, formed by substituting titanium dioxide for the chrome green in the composition of Example (XII), is prepared by the method of that example, and equal parts of these green and white dispersions are mixed, and sprayed on kraft paper.ALSO:A stable coating composition comprises a dispersion of discrete particles of one or more coating materials in an aqueous dispersing medium, most of the particles having a longest dimension of at least 50 microns and being stabilized by the presence in the aqueous phase of a colloidal stabilizing agent selected from gums, cellulose derivatives, carbohydrates, watersoluble synthetic organic materials and colloidal inorganic materials. The coating materials include nitrocellulose, cellulose acetate and ethyl cellulose lacquers, synthetic and natural resin enamels, oil base paints made with linseed or other drying oils, solutions of polymerized synthetic resins, such as polyvinyl, polystyrene and polyacrylic resins, urea-formaldehyde resins, water-in-oil type emulsions of lacquers, enamels, paints and the like. More than one type or colour of coating material may be dispersed in the aqueous medium, the particles of different sorts not coalescing. Non-spherical particles, e.g. of tear-drop or filamentary shapes, may be produced under certain conditions. The aqueous medium may contain dyes, wetting agents, pigments, water proofing agents, freezing point depressants and the like. Suspension stabilizers mentioned include methyl and ethyl cellulose, cellulose acetate phthalate, carboxy methyl cellulose and hydroxy ethyl cellulose, polyvinyl alcohol, gum tragacanth, locust bean gum, quince seed extract, bentonite, polystyrene ammonium maleate, polymethacrylic acid, gum arabic, gum cibara, gum karaya, sodium alginate, pectin, starches, water-soluble urea-formaldehyde, Fullers' earth, talc, barium sulphate, calcium carbonate, calcium sulphate, magnesium carbonate and diatomaceous earth. The inorganic materials require to be used in amounts of up to 25 per cent of the aqueous medium and to be finely divided, i.e. of colloidal dimensions. In Examples (VII) and (VIII) 100 parts of oil paints containing Indian Red Oxide or chrome yellow pigment and linseed oil, oxidized sardine oil, mineral spirits, and cobalt and lead drier solutions are dispersed in 50 parts of tap water containing 1 per cent of high viscosity polyvinyl alcohol and 2.5 per cent of bentonite. In Example (IX) equal parts of dispersions prepared according to Examples (VII) and (VIII) are stirred together.