STABLE HECTOGRAPH COMPOSITIONS, TRANSFER ELEMENTS AND PROCESSES

摘要

STABLE HECTOGRAPH COMPOSITIONS, TRANSFER ELEMENTS AND PROCESSES Solvent hectograph compositions which are resistant to rapid thickening and gelling during storage in the presence of ambient humidity comprising a cellulose ether film-forming binder material, at least one oleagineous material which is substantially incompatible with said binder material and a major amount by weight of particulate spirit-soluble solid hectograph imaging material, the volatile solvent for said binder material being a lower aliphatic ester which is a substantial non-solvent for said imaging material and which has a partial miscibility with water, the process of making such compositions and the process of producing pressure-sensitive transfer elements from said compositions. Solvent hectograph compositions and pressure-sensitive transfer sheets coated therewith have been proposed for several years as replacements for the more conventional hot-melt hectograph compositions and transfer elements. Such solvent compositions include resinous binder materials in place of wax binder materials, and volatile organic solvents as vehicles to maintain the compositions at a suitable viscosity for coating onto a flexible foundation such as paper or plastic film. Reference is made to U. S. Patents 3,177,086 and 3,767,450 and to British Patents 833,631 and 973,362 as representative of various solvent hectograph compositions and transfer elements. Among the problems encountered with prior-known solvent hectograph compositions are the government regulations which now preclude or restrict the use of certain volatile solvents as dangerous to the health of workers, such as the chlorinated aliphatics, or as pollutants to the atmosphere, such as aromatic hydrocarbon materials including toluene and xylene. However, a more technical problem over the years has been the instability of solvent hectograph compositions based upon cellulose ether binder materials whereby such compositions undergo an increase in viscosity and become gelled after a fairly short period of time, frequently one or two days, so that they are no longer coatable. Thus, they had to be prepared in small batches capable of being used immediately, and the coating procedure could not be interrupted for long periods of time for equipment repair without possible gelling of the composition in the ink pan on the apparatus. Their poor shelf life is caused by the absorption of ambient moisture from the atmosphere, which moisture apparently causes a swelling and thickening of the cellulose ether binder material and/or a plasticizing action between the oily ink vehicles and the binder material.