Foam printing

Foam printing (foam printing) is a printing process in which a special microsphere foaming ink is printed on a printing material, and the ink is heated and foamed and raised, and the ink is cooled and solidified into embossed characters or patterns after entering the drying tunnel to heat up.

The foaming agent in the foaming ink is different. Therefore, the printing process used is also different, and can be divided into two processes: microsphere foaming and grooved bottom foaming.

First, microsphere foam printing

The microspheres are the main components in the microsphere foaming inks. They are synthetic resin spheres with a diameter of 5 to 80 microns and are filled with a low-boiling solvent. After the sphere is heated, the low-boiling point solvent in the sphere vaporizes to increase the volume of the microsphere by 5 to 30 times. After the microsphere foaming ink is printed on the substrate, it is heated to 130° C. in the tunnel, within a few seconds. The microspheres in the ink expand to form countless small bubbles that form an embossed ink layer.

The main composition of the microsphere foaming ink is: acrylic and other resin copolymers, microspheres, urea, color paste and other components.

In the microsphere foaming ink, acrylate is used as a binder; microspheres are synthesized with vinylidene chloride, acrylonitrile, dibenzoyl peroxide, and other raw materials; urea can promote the expansion and diffusion of the microspheres when they are heated and vaporized, and at the same time Neutralizes the acidity of the color paste; the color paste consists of a slurry and an additive, and the slurry has a good structural viscosity and a printing effect.

Microsphere foam printing can be screen printing method, after low-temperature drying, then heating foaming.

Second, groove bottom foam printing

Groove base foaming ink is based on polyvinyl chloride resin, which dissolves the foaming agent in the liquid polymer. When the ink is heated, the foaming agent vaporizes, the ink layer forms countless tiny pores, and the foamed pattern is convex. people

The main components of the grooved foam ink are: polyvinyl chloride resin, calcium carbonate, dioctyl phthalate, dibasic aluminum phosphite, azodicarbonamide, and pigments.

After the above raw materials are fully ground, a paste-like resin is prepared and diluted with an appropriate amount of solvent.

Polyvinyl chloride resin is a binder in the grooved foam ink; calcium carbonate is used as a filler; dioctyl phthalate is a plasticizer for polyvinyl chloride resin, which increases the plasticity and fluidity of polyvinyl chloride resin during molding. Dibasic aluminum phosphite is a stabilizer; azodicarbonamide is a foaming agent; the decomposition temperature in plastics is 155-210°C, and the gas evolution is 190-220 ml / g. The ammonia gas is precipitated during decomposition. For carbon dioxide, the finer the pigment, the better for pigmentation.

Groove-bottom foam printing process is more complicated. The ink formulated into a paste shape is printed on the substrate and can be pressed on the embossing roll, embossing roll or grooved bottom embossing roll to produce embossing with different shapes. pattern.

Ditch bottom foaming process is divided into chemical foaming and mechanical foaming.

1. Chemical foaming is screen printed, dried, foamed, and cooled to form a pattern. It is the substrate that is specially printed with foaming ink and is input into the foaming machine to add it. The foaming agent is thermally decomposed to generate gas, and the ink layer foams. The amount of blowing agent and the degree of action of the blowing agent in the ink depends on its decomposition temperature.

2. Mechanical foaming adopts gravure printing method, embossing by embossing roller at the bottom of groove, heating by drying tunnel, shaping, and setting after cooling.

This foam printing product has very fine micropores, with gloss, light and soft, soft colors, good abrasion resistance, pressure resistance, water resistance, pattern embossing height, depends on embossing roller The pattern depth.

Foam printing has great practical value and can be used for Braille printing. Braille is the formation of words on the paper to form a protruding point, the blind people touch the protruding points by hand, relying on the sense of touch to read. The original blind literature and periodicals were specially prepared papers that were put into a model to pressurize and heat the thick paper to form raised four points, and can only be imprinted on one side. With foam printing, Braille readings can be printed not only on both sides of the paper, but also printed on the pattern, reducing the thickness of the blind writing and writing, the wear resistance of the dots, and the soft texture. Long-term reading does not hurt the fingers.

In the books and magazines can be used as a book cover and binding materials, can also be printed maps, with a three-dimensional sense. On the packing and decorating materials, a layer of artificial leather-like film can be formed, which can be comparable to natural leather. The wallpaper made by embossing on the bottom of the groove is a kind of cheap construction and decoration material.