Alkali release solution for gravure printing ink compositions and release method using the same

A release method for releasing a printed layer formed on a shrink PET base material and constituted by a gravure printing ink composition for label surface printing that satisfies a or b below, using an alkali release solution containing a basic compound, a polyoxyalkylene alkyl derivative, and water:

• a) when the gravure printing ink composition for label surface printing does not contain vinyl chloride resin,
• it is a gravure printing ink composition for label surface printing that contains a pigment, a binder resin containing cellulose resin and urethane resin, and an organic solvent, wherein a ratio by mass of solids content of polyurethane resin and cellulose resin is 5/95 to 95/5 (polyurethane resin:cellulose resin);
• or
• b) when the gravure printing ink composition for label surface printing contains a vinyl chloride resin,
• it is a gravure printing ink composition for label surface printing that contains a pigment, a vinyl chloride resin, and a polyurethane resin, wherein a content of the vinyl chloride resin, based on a ratio by mass of solids content of vinyl chloride resin and urethane resin, is 1.73 parts by mass or lower relative to the urethane resin representing 1.00 part by mass.

A method for releasing a printed layer formed on a shrink PET base material, comprising:

• providing a shrink PET base material on which a printed layer constituted by a gravure printing ink composition is formed by label surface printing, wherein the gravure printing ink composition satisfies a) or b) below:
• a) when the gravure printing ink composition does not contain vinyl chloride resin, the composition contains a pigment, a binder resin containing cellulose resin and urethane resin, and an organic solvent, wherein a ratio by mass of solids content of polyurethane resin and cellulose resin is 5/95 to 95/5 (polyurethane resin/cellulose resin);
• or
• b) when the gravure printing ink composition contains a vinyl chloride resin, the composition contains a pigment, a vinyl chloride resin, and a polyurethane resin, wherein a content of the vinyl chloride resin, based on a ratio by mass of solids content of vinyl chloride resin and urethane resin, is 1.73 parts by mass or lower relative to the urethane resin representing 1.00 part by mass;
• placing the printed layer on the shrink PET base material in an alkali release solution containing a basic compound, a polyoxyalkylene alkyl derivative, and water to release or separate the printed layer from the shrink PET bse material to the alkali release solution;
• and
• recover the printed layer-released shrink PET base material.