The Dow Chemical Company

Walter L Garrett

Ralph G Czerepinski

Ralph E Friedrich

Czerepinski, Ralph G

Aqueous solutions are provided for treating image-bearing lithographic plates. These solutions include as an active polymer component:

Image-bearing lithographic plates with desensitizing coating

A method for treating imaged lithographic printing plates with a solution comprising (1) water, (2) an active polymer component for rendering non-image areas of a lithographic printing plate hydrophilic, comprised of a polyacrylamide-based polymer or copolymer or a blend of polyacrylamide and polyacrylic acid, or the like, said polymer or copolymer or blend having an average molecular weight of from about 5,000 to about 10.sup.6 and having from about 3 to about 70 percent of the carbonyl sites as carboxyl groups, said active polymer component being present in an amount of from about 3 to about 30 weight percent of active polymer component, based on the weight of the active polymer component and the water, and (3) a suitable polyoxyalkylene glycol in an amount which is effective to reduce tackiness while the composition is drying and which does not adversely affect the printing properties of a plate treated with said composition, said polyoxyalkylene glycol being selected from the group consisting of (a) a polyethylene glycol with an average molecular weight of about 200 to about 800; (b) a polypropylene glycol with an average molecular weight of about 200 to about 600; (c) a mixture of components from (a) and (b); (d) a triether of glycerine with a mixture of polypropylene and polyethylene oxides; and (e) a triether of glycerine with polypropylene oxides. The solution is particularly suited for treating imaged lithographic printing plates since, unlike earlier solutions, it does not go through a tacky state when drying.

Method for treating imaged lithographic printing plates

Method of treating image-bearing lithographic plates

Aqueous solutions are provided for treating imagebearing lithographic plates. These solutions include as an active polmyer component:

Method of desensitizing image-bearing lithographic plates

An aqueous solution is provided which is suitable for use as a desensitizing gum for treating imaged lithographic printing plates, comprising (1) water, (2) an active polymer component for rendering non-image areas of a lithographic printing plate hydrophilic, comprised of a polyacrylamide-based polymer or copolymer or a blend of polyacrylamide and polyacrylic acid, or the like, said polymer or copolymer or blend having an average molecular weight of from about 5,000 to about 10.sup.6 and having from about 3 to about 70 percent of the carbonyl sites as carboxyl groups, said active polymer component being present in an amount of from about 3 to about 30 weight percent of active polymer component, based on the weight of the active polymer component and the water, and (3) a suitable polyoxyalkylene glycol in an amount which is effective to reduce tackiness while the composition is drying and which does not adversely affect the printing properties of a plate treated with said composition, said polyoxyalkylene glycol being selected from the group consisting of (a) a polyethylene glycol with an average molecular weight of at least about 200; (b) a polypropylene glycol with an average molecular weight of at least about 200; (c) a mixture of components from (a) and (b); (d) a triether of glycerine with a mixture of polypropylene and polyethylene oxides; and (e) a triether of glycerine with polypropylene oxides. The solution is particularly suited for treating imaged lithographic printing plates since, unlike earlier solutions, it does not go through a tacky state when drying.

Composition suitable for use as desensitizing gumming solution for

Precipitation at relatively high pH levels, e.g. above about 4 or more, in an acidic water/alcohol type fountain composition containing polyvalent metal cations and, as an active polymer component for rendering the non-image areas of a lithographic plate hydrophilic, a polyacrylamide-based polymer having a weight average molecular weight (M.sub.w) of from about 5,000 to about 1,000,000 and having from about 3 to about 70 percent of the carbonyl sites as carboxyl groups, or a blend of polyacrylamide and polyacrylic acid, or the like, is controlled by providing in the fountain composition an effective amount of an organic chelating agent for polyvalent metal cations which is substantially inert with respect to the active polymer component. The suitable chelating agents are further characterized in that at 25.degree. C, each (A) has a 1:1 stability constant with zinc of at least about 10.sup.7.5 ; (B) has a solubility of at least about 0.001 moles per liter in the water/alcohol solvent system over the pH range of from about 3 to about 7; and (C) when in a stable complexed form with polyvalent metal cation(s), has a solubility of at least about 0.001 moles per liter in the water/alcohol solvent system over the pH range of from about 3 to about 7. A preferred chelating agent is the pentasodium salt of diethylenetriaminepentaacetic acid.

Fountain compositions for use in lithographic printing comprising

Cured phenolic resole bodies including foams which are generally non-corrosive are prepared by including in the curable mixture an inorganic alkali-containing particulate solid such as certain glasses.

Growing community of inventors

Freeland, MI, United States of America

Walter L Garrett