Flexographic printing process with wet on wet capability

Abstract

The Invention refers to a flexographic printing process with wet on wet capability based on controlled polymer or polymer segment precipitation that leads to gel formation of ink compounds by controlling the solubility parameter of the ink system. The mechanism to obtain a desirable wet on wet color trapping is the formation and/or presence of a gel in the applied ink film due to a controlled physicochemical mechanism of resin precipitation. This is accomplished either by controlling a change in the Hansen Solubility Parameter of the liquid in the ink through evaporation of some or all of a non-reactive and volatile solvent, or alternatively by use of a polymer comprised of two distinct and separate segments one of which is soluble in the monomer/oligomer mix and the other of which is not. The insoluble segments form a reversible gel that is broken to a liquid by shear in the application process, allowing application of a liquid ink, and is reestablished in the applied ink film in such a manner and with such strength as to allow overprinting in the wet on wet flexographic printing process.

1 - 27 . (canceled) 
     
     
         28 . A phase-changing printing ink comprising a non-reactive polymer, wherein the ink in a liquid state has a viscosity ranging from about 100 cps to about 4,000 cps, and the ink in a gel state has a hardness that can be measured by ASTM D2240-05. 
     
     
         29 . The ink according to  claim 28  wherein the non-reactive polymer is selected from the group consisting of ketonics, alkyl phenolic, acrylic, methacrylic, polyamide, epoxy-polyamide, modified maleic, modified phenolic, ketone formaldehydes, polyurethane, polyesters, polyvinyl butyrals and mixtures thereof. 
     
     
         30 . The ink according to  claim 28 , wherein the non-reactive polymer is present in an amount ranging from about 0.1% to about 10% by weight of the ink. 
     
     
         31 . The ink according to  claim 28 , wherein the ink in a liquid state has a viscosity lower than 1000 cps. 
     
     
         32 . The ink according to  claim 28 , wherein the ink is free of volatile organic compounds. 
     
     
         33 . The ink according to  claim 28 , further comprising materials selected from the group consisting of monomers, oligomers, diluents, colorants, additives, and photoinitiators. 
     
     
         34 . The ink according to  claim 28 , further comprising at least one non-reactive solvent, in an amount ranging from about 1% to about 15% by weight of the ink. 
     
     
         35 . The ink according to  claim 33 , wherein the monomers and/or oligomers are present in an amount ranging from about 15% to about 80% by weight of the ink. 
     
     
         36 . The ink according to  claim 33 , wherein the monomers are present in an amount ranging from about 0% to about 80% by weight of the ink. 
     
     
         37 . The ink according to  claim 33 , wherein the oligomers are present in an amount ranging from about 0% to about 80% by weight of the ink. 
     
     
         38 . The ink according to  claim 33 , wherein the oligomers are selected from the group consisting of radiation curable polyester acrylates, low viscosity epoxy acrylates, acrylic acrylates, polyurethane acrylates, amine acrylates, epoxidized soybean oil acrylates and mixtures thereof. 
     
     
         39 . The ink according to  claim 33 , wherein the monomers are selected from the group consisting of trimethylolpropane triacrylate (TMPTA), 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TRPGDA), ethoxylated (3) trimethylolpropane triacrylate (TMP3EOTA), ethoxylated (6) trimethylolpropane triacrylate (TMP6EOTA), ethoxylated (9) trimethylolpropane triacrylate (TMP9EOTA), propoxylated (6) trimethylolpropane triacrylate (TMP6POTA), propoxylated (3) glyceryl triacrylate (G3POTA), di trimethylolpropane triacrylate (DTMPTA), dipropylene glycol diacrylate DPGDA, ethoxylated (5) pentaerythritol tetraacrylate (PPTTA), propoxylated (2) neopentyl glycol diacrylate (NPG2PODA), ethoxylated (2) 1,6 hexanediol diacrylate (HD2EODA); cycloaliphatic epoxide, one or more polyfunctional cycloaliphatic epoxides and multifunctional vinyl ethers; and mixtures thereof. 
     
     
         40 . The ink according to  claim 28 , further comprising a non-reactive solvent selected from the group consisting of glycol ethers and glycol esters, alcohols, ketones, aromatic and aliphatic hydrocarbons, esters, and mixtures thereof. 
     
     
         41 . The ink according to  claim 39 , further comprising an organic gellant, in an amount ranging from about 1% to about 50% by weight of the ink. 
     
     
         42 . The ink according to  claim 28 , wherein the gel has a hardness lower than about 00/50/1. 
     
     
         43 . The ink according to  claim 42 , wherein the gel has a hardness lower than about 00/25/1. 
     
     
         44 . The ink according to  claim 42 , wherein the gel has a hardness of at least about 00/4/1. 
     
     
         45 . The ink according to  claim 42 , wherein the gel has a hardness of at least about 00/7/1. 
     
     
         46 . The ink according to  claim 42 , wherein the gel has a hardness of at least about 00/10/1. 
     
     
         47 . The ink according to  claim 28  wherein the temperature differential for the ink to transition from liquid to gel is less than about 80° C.