Stabilized emulsion inks

#BACKGROUND OF THE INVENTION

#Typical emulsion inks have emulsified droplets of alcohol or water stabilized with surfactants within a matrix of an oil and an oil soluble resin. Some difficulties encountered with emulsion inks have included a difficulty in controlling and reproducing emulsions. In addition, emulsion inks have tended to breakdown either on storage or prematurely during milling on an ink press which results in poor image density and difficulty in transferring ink from roll to roll. Extremely stable ink emulsions, however, have tended to give poor printing results of high background. Accordingly, this invention is directed to emulsion inks which obviate or reduce the above problems.

#This invention is directed to stabilized alcohol or water in oil ink emulsions and more particularly to said emulsions comprising: (a) a coloring amount of a pigment, (b) from 20 to 40% by weight resin of a block or graft copolymer having one type of polar segment miscible with water and alkyl alcohols from 2 to 6 carbon atoms, and another type of non-polar segment which can be absorbed on the pigment and which are miscible with the non-polar components of the ink, said copolymer having a number average molecular weight of from 20,000 to 40,000 and (c) a vehicle for said resin and pigment comprising polar and non-polar solvents.

#The following examples will serve to illustrate the invention and preferred embodiments thereof. All parts and percentages in said examples and elsewhere in the specification and claims are by weight unless otherwise specified.

#A styrene-vinyl pyrrolidone block copolymer is obtained by using a trisperoxide as the reaction initiator. The polymerization of styrene at 75.degree. C gives polystyrene terminated with two peroxy groups. The peroxy end groups of the macromolecules are used for initiation of n-vinylpyrrolidone polymerization at 100.degree. C.

#A polystyrene-poly (vinylpyridine) block copolymer was parpared by anionic polymerization by the method of Grosius et al, Makromol, Chem., 132, 35 (1970) using cumylpotassium as the initiator in tetrahydrofuran as the solvent. The poly (vinylpyridine) blocks were quaternized by addition of hydrogen bromide or linear alkyl bromides to the copolymer in solution in tetrahydrofuran. To this solution was added an equal amount by volume of benzene, the mixture condensed to 10% solids by rotary evaporization and the polymer was purified by precipitation into hexane.