Hot melt flexographic inks and method of preparing same

A solvent-free, flexographic printing ink which is solid at room temperature, the ink comprising:

• (A) a pigment;
• (B) an ethylene-acrylic acid copolymer;
• (C) a highly branched hydrocarbon wax;
• (D) a solid linear alcohol at room temperature;
• (E) one or more hyperdispersant(s);
• and,
• (F) a dicyclohexylphthalate;
• wherein, the ink has a melting point of about 75° C. or greater, and when heated to a temperature between about 90° C. and about 135° C., forms a molten ink which has a viscosity between about 100 cps and about 1200 cps.

A solvent-free, flexographic printing ink which is solid at room temperature, the ink comprising:

• (A) a pigment;
• (B) an ethylene-vinyl acetate copolymer;
• (C) a polyethylene homopolymer wax;
• (D) a solid linear alcohol at room temperature;
• (E) one or more hyperdispersant(s);
• and,
• (F) a dicyclohexylphthalate;
• wherein, the ink has a melting point of about 75° C. or greater, and when heated to a temperature between about 90° C. and about 135° C., forms a molten ink which has a viscosity between about 100 cps and about 1200 cps.

A method of melt flexographic printing comprising:

• (I) providing an ink which is solid at room temperature, the ink consisting essentially of:
• (A) a pigment;
• (B) a thermoplastic binder selected from the group consisting of an ethylene copolymer, a hydrocarbon resin, and a combination thereof;
• (C) a wax selected from the group consisting of a highly branched hydrocarbon wax, a polyethylene homopolymer wax, an oxidized polyethylene wax, an animal wax, a vegetable wax and combinations thereof;
• (D) a solid linear alcohol at room temperature;
• and,
• (E) a dispersing agent;
• and, optionally,
• (F) a solid plasticizer;
• (II) heating the ink to a temperature between about 90° C. and about 135° C. to form a molten ink which has a viscosity between about 100 cps and about 1200 cps;
• (III) applying the molten ink to a heated anilox roller in operational contact with a surface of a heated flexographic printing plate;
• and
• (IV) printing the applied molten ink onto a substrate.

A method for preparing a flexographic printing ink for hot melt flexographic printing comprising:

• (I) preparing a molten pigment dispersion from a component mixture in a mixer/grinder which is heated to a temperature above the melting point of the component mixture, wherein the component mixture consists essentially of:
• (A) a pigment;
• (B) a solid linear alcohol at room temperature;
• and,
• (C) a dispersing agent;
• and, optionally,
• (D) a solid plasticizer;
• (II) preparing a molten varnish from a second component mixture in a second mixer which is heated to a temperature above the melting point of the second component mixture, wherein the second component mixture consists essentially of:
• (E) a thermoplastic binder selected from the group consisting of an ethylene copolymer, a hydrocarbon resin, and a combination thereof;
• and,
• (F) a wax selected from the group consisting of a highly branched hydrocarbon wax, a polyethylene homopolymer wax, an oxidized polyethylene wax, an animal wax, a vegetable wax and combinations thereof;
• and
• (III) adding the pigment dispersion to the molten varnish and mixing in the second mixer to form a homogeneous molten ink which has a viscosity between about 100 cps and about 1200 cps at a temperature between about 90° C. and about 135° C.