USE OF POLYAMIDE-MODIFIED METAL RESINATES IN PUBLICATION GRAVURE PRINTING INKS

Abstract: The product of the reaction of a metal resinate and an amine-reactive polymide is useful as the vehicle of plublication gravure printing inks, resulting in prints that have superior properties such as holdout, gloss, and colour development.

Description: This invention relates to printing inks. More particularly it relates to publication gravure printing inks. Inks conventionally used for the gravure printing of magazines, inserts and newspapers comprise a pigment, a solvent, and a metal resinate. These inks are deficient in gloss and holdout, particularly on poor quality uncoated stock. It has now been found that printability on low quality paper stock and gloss on coated paper stock can be improved with inks, preferably gravure printing inks, prepared with a novel modified metal resinate vehicle. The novel resinate is a polyamide-modified metal resinate. It is the reaction product of a metal resinate with an amine reactive polyamide. It is best prepared by reacting a metal resinate with an amine reactive polyamide in solution at an elevated temperature. The metal resinate is acidic and preferably has an acid value of 5 to 175. The polyamide is basic (due to amine functionality) and preferably has an amine value of 5 to 350. Suitable metal resinates include calcium, zinc, and magnesium salts of a resin, either alone or in combination with rosins, including dimerised rosin, polymerised rosin, maleated rosin, phenolated rosin, or their mixtures. Tall oil, gum rosin, or wood rosin can also be used in combination with the metal resinate. The resin used for forming the metal resinate is chosen from a carboxyl-functional hydrocarbon resin, preferably having a melting point above 100°C, a metallised phenol formaldehyde resin (calcium-zinc phenol formaldehyde resinate was used in the examples), a metallised carboxyl functional-phenol formaldehyde resin ester or a metallised maleinised dicyclo pentadiene hydrocarbon resin. Amine-reactive polyamides that are used to modify the metal resinate are reaction products of dimerised fatty acids; trimerised fatty acids; C₂-C₂₀ monobasic acids; diamines such as ethylene diamine, hexamethylene diamine, and neopentyl diamine; polyamines such as diethylene triamine and triethylene tetramine; and their mixtures. The reaction is essentially the amine-salt formation of the amino groups of the polyamide and the carboxyl groups of the metal resinate. The two ingredients are generally reacted in the ratio of 1-5 carboxyl equivalents of the metal resinate to 1 amine equivalent of the polyamide, and preferably the ratio is 2 carboxyl equivalents to 1 amine equivalent. The reaction temperature is generally 25 to 100°C, and preferably 70 to 90°C. Solvents suitable for use in the reaction include toluene, Lactol Spirits (Trade Mark for a mixture of heptane and toluene), Rotosolve (Trade Mark for a mixture of aliphatic and aromatic hydrocarbons), or mixtures thereof. These polyamide modified metal resinates have a higher viscosity than the unmodified metal resinates, enabling them to be used with low-cost solvents. Inks formulated with these products as the vehicles have improved holdout (non-penetration) properties on low quality porous paper stock. The invention will be illustrated by the following examples in which all parts and percentages are by weight unless otherwise specified. Example 1 (A) 500 Parts (0.345 equivalent) of a solution of calcium-zinc phenol formaldehyde resinate in toluene containing 60% of non-volatile material, 375 parts of toluene, and 202.5 parts of Lactol Spirits were charged into a two-liter round bottom flask equipped with stirrer, thermometer, and water-cooled condenser and stirred at room temperature. 75 Parts (0.1725 equivalent) of a 60% non-volatile solution in toluene of a polyamide based on dimerized fatty acids, tall oil fatty acid, and diethylene triamine and having an amine value of 238 was added. The mixture was stirred, heated to 80° C, and the temperature held at 80° C ± 5° C for one hour. The mixture was then discharged. The product had a Gardner-Holdt viscosity @25° C of Z4-5, a Gardner color @25° C of 12, and contained 30% of non-volatile material. (B) A publication gravure ink was made by the following procedure: 45 parts of a blue pigment base was admixed at room temperature with 55 parts of the product of part (A) and agitated until uniform. The viscous ink product was then reduced with 40/60 toluene/Lactol Spirits to print viscosity (18 seconds #2 steel cup). (C) The resulting blue ink was used to print insert stock. The quality of the print was excellent and superior to a print made with a conventional ink in both holdout and gloss. Example 2 The procedure of Example 1 was repeated except that the following ingredients were used: 500 parts (0.345 equivalent) of a solution of a calcium-zinc-magnesium resinate in 40/60 toluene/Lactol Spirits; 121 parts (0.275 equivalent) of a 55% solids solution in toluene of a polyamide prepared from dimerized fatty acids, soya fatty acid, and diethlyene triamine having an amine value of 340; 500 parts of toluene; and 310 parts of Lactol Spirits. The product had a Gardner-Holdt viscosity @25° C of Z4, a Gardner color @25° C of 12, and contained 25% of non-volatile material. As in Example 1, a publication gravure printing ink was formulated and used to print supplement stock. The results were comparable, that is, the print had excellent holdout and gloss. Example 3 The procedure of Example 1 was repeated with each of the following metal resinates instead of calcium-zinc resinate: calcium resinate and magnesium resinate. The results were comparable. Example 4 The procedure of Example 1 was repeated with each of the following polyamides instead of one prepared from dimerized fatty acids, tall oil fatty acid, and diethylene triamine: a polyamide prepared from dimer acids, propionic acid, triethylene tetramine, and ethylene diamine and a polyamide prepared from dimer acids, sebacic acid, tall oil fatty acid, and diethylene triamine. The results were comparable. Example 5 The procedure of Example 1 was repeated except that each of the following solvents was used instead of toluene/Lactol Spirits: toluene, Rotosolve, and Lactol Spirits. The results were comparable. Comparative Example For the purpose of comparison a publication gravure printing ink was formulated with 55 parts of unmodified calcium-zinc resinate containing 60% non-volatile material and 45 parts of blue pigment. The product was then cut to print viscosity with toluene/Lactol Spirits, and the blue ink product was used to print insert stock. The inks made from the products of Examples 1 and 2 were consistently better than the ink of this Example in printability of low quality paper stock, e.g., in holdout (non-penetration), gloss, and color development. The inks made from the products of Examples 1 and 2 also gave much better gloss on coated paper stock than did the product of the Comparative Example.

Claims: A printing ink comprising a metal resinate, a pigment and a solvent, characterised in that the metal resinate is a reaction product of (a) a metallised carboxy functional hydrocarbon resin, a metallised phenol formaldehyde resin, a metallised phenol formaldehyde resin ester or a metallised maleinised dicyclo pentadiene hydrocarbon resin, with (b) an amine reactive polyamide which polyamide is derived from dimerised fatty acids, trimerised fatty acids, C₂₋₂₀ monobasic acids, diamines or polyamines or mixtures thereof. A printing ink according to claim 1 wherein the metal is calcium, zinc, magnesium, or a mixture thereof. A printing ink according to claims 1 or 2, wherein the metal resinate is in combination with rosin, dimerised rosin, polymerised rosin, maleated rosin or phenolated rosin. A process for the preparation of a printing ink according to claims 1 to 3 which comprises the step of reacting an acidic metal resinate chosen from a metallised carboxy functional hydrocarbon resin, a metallised phenol formaldehyde resin, a metallised phenol formaldehyde resin ester or a metallised maleinised dicyclo pentadiene hydrocarbon resin in solution with an amine reactive polyamide in solution which polyamide is derived from dimerised fatty acids, trimerised fatty acids, C₂₋₂₀ monobasic acids, diamines or polyamines or mixtures thereof at a temperature within the range of about 25° to 100°C and admixing the reaction product with a pigment and a solvent. A process according to claim 4 wherein the temperature is within the range of about 70° to 90°. A process according to claims 4 or 5 wherein the ratio of amounts is about 1-5 carboxyl equivalents of the metal resinate to 1 amine equivalent of the polyamide. A process according to claim 6 wherein the ratio of amounts is 2 carboxyl equivalents of the metal resinate to 1 amine equivalent of the polyamide. A process according to any of claims 4 to 7 in which the metal resinate has an acid value of 5 to 175 and the polyamide has an amine value of 5 to 350.

Inventors: JANUSZ, EDWARD G.
Applicants: SUN CHEMICAL CORPORATION
Application year: 1986
Main classification: C08G81
IPC codes: C08G69, C08G8, C09D11, C08G81