# US 4,400,481 A · Finisher and preserver for lithographic plates > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,400,481 A - Document ID: US4400481A - Status: Granted - Kind: A - Application number: 06/409,959 - Filed: 1982-08-20 - Granted: 1983-08-23 - Earliest claimed: 1980-11-05 - Assignees: Richardson Graphics Company - Inventors: Sunit S. Dixit; William V. Stansky, Jr. - Web page: https://patentgrep.com/patent/US4400481A ## CPC - B41N 3/08: Damping; Neutralising or similar differentiation treatments for lithographic printing formes; {Gumming or finishing solutions, fountain solutions, correction or deletion fluids, or on-press development (treatment of materials containing silver salts G03F7/063; developers per se for processing photosensitive materials G03F7/32)} - B41N: PRINTING PLATES OR FOILS (photosensitive material G03); MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM ## Abstract Finisher and preserver compositions are provided for desensitizing the non-image areas and protecting the image areas of lithographic plates of either the additive or the subtractive type that utilize substantially any type of exposure chemistry, the composition being useful for hand or machine finishing: they are also low in viscosity, are themselves unusually stable, preserve exposed plates for extended periods of storage time, and eliminate streaking on the plate to which they are applied to thereby substantially eliminate blinding problems during printing. Included in the finisher and preserver composition, which is a single phase aqueous system, are specific ratios of a blend of natural gum and synthetic hydrophilic resins, a preservative for the natural gum resin, a buffer system of phosphate and phosphoric acid, and a surfactant, with the balance being substantially entirely water. ## Claims ### Claim 1 A finisher and preserver for lithographic plates comprising a single-phase aqueous composition consisting essentially of: a blend of natural gum resin and synthetic hydrophilic resins in a total amount of between about 2 and 12 weight percent, based on the total weight of the aqueous composition, said resin blend including between about 1 and about 5 weight percent of the natural gum resin, between about 0.5 and about 5 weight percent of a cyclic amide synthetic hydrophilic resin, and between about 0.1 and about 2 weight percent of a polyacrylamide synthetic hydrophilic resin, all based on the total weight of the aqueous composition, wherein said resin blend includes a ratio of about 6 parts by weight of the natural gum resin, to about 3 parts by weight of the cyclic amide synthetic hydrophilic resin, to about 1 part by weight of the polyacrylamide synthetic hydrophilic resin, between about 0.05 and about 1 weight percent of a preservative for said natural resin, based on the total weight of the aqueous composition, a buffering system of phosphate and phosphoric acid, said buffering system being between about 0.5 and about 5 weight percent based on the total weight of the aqueous composition, a surfactant constituent in a total amount of between about 0.01 and about 0.2 weight percent, based on the total weight of the aqueous composition, and between about 85 and 95 weight percent water, based on the total weight of the aqueous composition, each of said blend of resins, preservatives, buffering system and surfactant constituent being in admixture with each other and being dissolved in said water in a single phase. ### Claim 2 (depends on 1) The finisher and preserver composition of claim 1, wherein said resin blend includes gum arabic as the natural gum resin and a modified polyacrylamide as the polyacrylamide synthetic resin. ### Claim 3 (depends on 1) The finisher and preserver composition of claim 1, wherein said resin blend includes polyvinylpyrrolidone as the cyclic amide synthetic hydrophilic resin. ### Claim 4 (depends on 1) The finisher and preserver composition of claim 1, wherein said polyacrylamide synthetic hydrophilic resin is partially hydrolyzed. ### Claim 5 (depends on 1) The finisher and preserver composition of claim 1, wherein said resin blend includes polyvinylpyrrolidone as the cyclic amide synthetic hydrophilic resin and a partially hydrolyzed polyacrylamide synthetic resin as the polyacrylamide synthetic hydrophilic resin. ### Claim 6 (depends on 1) The finisher and preserver composition of claim 1, wherein said resin blend includes gum arabic, polyvinyl pyrollidone, and a partially hydrolyzed polyacrylamide synthetic resin. ### Claim 7 (depends on 1) The finisher and preserver composition of claim 1, wherein said resin blend comprises between about 3 and 8 weight percent of the total aqueous composition. ### Claim 8 (depends on 1) The finisher and preserver composition of claim 1, wherein said preservative is sodium benzoate at a growth-inhibiting concentration. ### Claim 9 (depends on 1) The finisher and preserver composition of claim 1, wherein said buffering system includes trisodium phosphate and phosphoric acid. ### Claim 10 (depends on 1) The finisher and preserver composition of claim 1, wherein said buffering system maintains the composition at a pH between about 4.1 and 4.5. ### Claim 11 (depends on 1) The finisher and preserver composition of claim 1, wherein said buffering system includes monosodium phosphate, trisodium phosphate, and phosphoric acid. ### Claim 12 (depends on 1) The finisher and preserver composition of claim 1, wherein said buffering system includes between about 0.3 and 2 weight percent, based on the total weight of the aqueous composition, of each of trisodium phosphate and phosphoric acid. ### Claim 13 (depends on 1) The finisher and preserver composition of claim 1, wherein said buffering system includes monosodium phosphate, trisodium phosphate and phosphoric acid at a weight ratio of 1:3:3, respectively. ### Claim 14 (depends on 1) The finisher and preserver composition of claim 1, wherein said surfactant constituent includes generally equal parts by weight of an ethoxylate and of a polyether, and the total concentration of the surfactant constituent is between about 0.02 and 0.1 weight percent. ### Claim 15 (depends on 1) The finisher and preserver composition of claim 1, wherein said surfactant constituent includes a modified linear alcohol ethoxylate. ### Claim 16 (depends on 1) The finisher and preserver composition of claim 1, wherein said surfactant constituent includes a blend of a modified linear alcohol ethoxylate and a modified aliphatic polyether. ### Claim 17 (depends on 1) The finisher and preserver composition of claim 1, wherein said composition has a viscosity between about 20 and about 25 centipoises.