GB1292939A - Pressure-sensitive recording paper - Google Patents

Abstract

1292939 Microcapsules FUJI PHOTO FILM CO Ltd 19 April 1971 [27 Feb 1970] 22762/71 Heading C3R [Also in Divisions B8 and D2] Microcapsules for use in pressure-sensitive recording paper are prepared by dissolving a single wall-forming material capable of forming, or two or more wall-forming materials capable of reacting to form, a polymeric compound which is insoluble in both oil and water, in an oily liquid (defined) containing a colour-former and a first carrier solvent (defined) to prepare a solution, emulsifying the solution in a second solvent, which is a polar solvent, forming a continuous phase and miscible with the first solvent elevating the temperature of the emulsified system to transfer the wall-forming material or materials to the surface of the oil drops and to cause the wall-forming material or materials to form the polymeric compound on the surfaces of the oil drops, thereby producing the microcapsules containing the colour-former. Suitably, a catalyst to promote the wall-forming reaction is incorporated in the solution. It is preferred to use as the wall-forming materials a polyisocyanate or polyisothiocyanates and a polyamine, polycarboxylic acid, acid anhydride epoxy compound, polyol, polysulphide, lactone or lactam. Numerous solvents are listed for forming the solution. Water is the preferred second solvent. Protective colloids or surfaceactive agents may be used to emulsify the oily liquid. Examples of colour formers are triphenylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds and spiropyran compounds. The oily liquid is any liquid capable of being emulsified to formliquid drops in and immiscible with the second polar solvent, with the use of a surface-active agent or protective colloid, if necessary, andis suitably a chlorinated diphenyl, chlorinated paraffin, cotton seed oil, peanut oil, silicone oils, tricresyl phosphate, monochlorobenzene, kerosene, n-paraffins or iso-paraffins. In a typical example, crystal violet lactone is dissolved in a mixture of chlorinated diphenyl and kerosene and to the solution is added bisphenol A dissolved in a mixed solvent of acetone/ methylene chloride, xylylene diisocyanate and dibutyl tin laurate as catalyst. The resulting solution is poured into an aqueous solution of gum arabic with stirring to form an emulsion, followed by the addition of more water and heating to bring about the encapsulation. After cooling a styrene-butadiene latex, sodium alginate and cellulose powder is added as a binder to complete the preparation of a micro-capsule solution which may be applied to a support paper for use as a pressure-sensitive recording paper (see Divisions D1-D2).