| abstract |
A method of producing self-contained pressure-sensitive copying material having a coating which contains both a particulate mineral color-developing material and microcapsules enclosing a solution of a colorless color former which is reactive with the color developing material to produce a colored product, in which the particles of color developing material (e.g. an acidic clay) and optionally the microcapsules as well, are treated with a protective agent to inhibit premature color development. The protective agent may be a self-crosslinkable polymer, such as an aminoplast polymer (e.g. a urea-formaldehyde or melamine-formaldehyde polymer), or a epichlorohydrin polymer (e.g. an aminoepichlorohydrin or an amide/aminoepichlorohydrin polymer), or an anionic surfactant (e.g. a lauryl sulphate salt or a sulphonated ricinoleic acid derivative, a dodecyl benzene sulphonate salt, or a dibutyl or dioctyl ester of sulphosuccinic acid), or a fluorine-containing paper sizing agent, or a non-self-crosslinkable polymer which is a wet-strength agent for paper (e.g. a polyethylene imine resin). |