Pressure-sensitive copying paper

DETAILED DESCRIPTION We claim: 1.
Pressure-sensitive copying paper comprising base paper neutral- or alkaline-sized with an alkyl ketene dimer and carrying on one surface a coating of pressure-rupturable microcapsules containing an oil solution of chromogenic material and on the other surface a coating of an acid clay colour developer composition, characterized in that an extracted and isolated non-particulate soy protein polymer is carried by the base paper and/or is present in the microcapsule coating.
2.
Pressure-sensitive copying paper as claimed in claim 1, wherein the soy protein polymer is chemically modified carboxylation or hydrolyzation.




Description:
This invention relates to pressure-sensitive copying paper, also known as carbonless copying paper.
Pressure-sensitive copying paper sets may be of various types.
The commonest, known as the transfer type, comprises an upper sheet (usually referred to as a CB or coated back sheet), coated on its lower surface with microcapsules containing a solution in an oil solvent of at least one chromogenic material and a lower sheet (usually referred to as a CF or coated front sheet) coated on its upper surface with a colour developer composition.
If more than one copy is required, one or more intermediate sheets (usually referred to as CFB or coated front and back sheets) are provided, each of which is coated on its lower surface with microcapsules and on its upper surface with colour developer composition.
Pressure exerted on the sheets by writing, typing or other imaging pressure ruptures the microcapsules, thereby releasing chromogenic material solution onto the colour developer composition and giving rise to a chemical reaction which develops the colour of the chromogenic material and so produces an image.
The present invention is particularly concerned with pressure-sensitive copying paper of the CFB type.
A potential problem with such paper is that any free chromogenic material solution in the microcapsule coating may migrate through the paper into contact with the colour developer coating, with the result that premature colouration occurs