Production of radiation curable microcapsular coating compositions, pressure-sensitive transfer paper and its production

A process for producing a liquid coating composition for use in the manufacture of pressure-sensitive carbonless transfer papers, said liquid coating composition being characterized by being curable by radiation to a dry, solid, tack-free resin, said radiation being a combination of ultraviolet radiation and infra-red radiation, said liquid coating composition being further characterized by containing microcapsules having a hydrophobic core material, comprising the steps of:

• (a) preparing an emulsion containing droplets of a hydrophobic emulsion component dispersed in a hydrophilic emulsion component, said hydrophobic emulsion component comprising a chromogenic material in a hydrophobic liquid, said chromogenic material being soluble in said hydrophobic liquid, said hydrophobic emulsion component additionally containing a first-wall forming material capable of reacting by condensation polymerization with a second wall-forming material to form a polymeric capsule wall, said first wall-forming material being soluble in said hydrophobic emulsion component, said polymeric capsule wall being substantially insoluble in said hydrophilic and said hydrophobic emulsion components, said hydrophilic emulsion component comprising an emulsifier dispersed in a radiation curable hydrophilic liquid, said radiation curable hydrophilic liquid comprising water and at least one polar compound selected from the group consisting of N-vinyl-2-pyrrolidone, acrylamide, N-methylolacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, diacetone acrylamide, 2-acrylamido-2-acrylamido-2-methylpropanesulfonic acid, polyethylene glycol monoacrylates, polyethylene glycol polyacrylate, polyvinyl alcohol acrylate, starch acrylate, cellulose acrylate, quarternary ammonium salt derivatives of dimethylaminoethyl acrylate and methacrylate and mixtures thereof, said emulsion additionally containing said second wall-forming material;
• (b) subjecting said emulsion, with stirring, to a temperature of from about 0.degree. C. to about 70.degree. C. for a period of time from about 1 hour to about 16 hours, said temperature and said time being sufficient to substantially completely polymerize said first and second wall-forming materials thereby forming a dispersion of microcapsules in said hydrophilic emulsion component, said microcapsules having capsule walls substantially impermeable to said hydrophilic and said hydrophobic emulsion components;
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• (c) adding a photoinitiator to said dispersion of microcapsules.

A process for producing a pressure-sensitive transfer paper comprising the steps of:

• (a) preparing an emulsion containing droplets of a hydrophobic emulsion component dispersed in a hydrophilic emulsion component, said hydrophobic emulsion component comprising a chromogenic material in a hydrophobic liquid, said chromogenic material being soluble in said hydrophobic liquid, said hydrophobic emulsion component additionally containing a first wall-forming material capable of reacting by condensation polymerization with a second wall-forming material to form a polymeric capsule wall, said first wall-forming material being soluble in said hydrophobic emulsion component, said polymeric capsule wall being substantially insoluble in said hydrophilic and said hydrophobic emulsion components, said hydrophilic emulsion component comprising an emulsifier dispersed in a radiation curable hydrophilic liquid, said radiation curable liquid comprising water and at least one radiation curable polar component, said emulsion additionally containing said second wall-forming material;
• (b) subjecting said emulsion, with mixing, to temperature conditions for a period of time sufficient to polymerize said first and second wall-forming materials thereby forming a dispersion of microcapsules in said hydrophilic emulsion component, said microcapsules having a hydrophobic core material and capsule walls substantially impermeable to said hydrophilic and said hydrophobic emulsion components;
• (c) adding a photoinitiator to said dispersion of microcapsules;
• (d) applying said dispersion of said microcapsules to a paper substrate;
• and
• (e) setting said dispersion of said microcapsules by subjecting said dispersion on said paper substrate to radiation for a period of time sufficient to cure said radiation curable hydrophilic liquid to a dry, solid, tack-free resinous film on said paper substrate, said radiation being a combination of ultraviolet radiation and infra-red radiation.