A review of new environmentally friendly packaging printing varnishes (2)

China's printing and packaging industry commonly used glazing oil:
1UV (UV Curing) Varnish

2 Solvent-based coating oils include alcohol-soluble varnish

3 Waterborne Varnish Three categories.

In order to give everyone a clearer understanding of the coating glazing process of the printing system and its corresponding requirements, we need to first determine the most commonly used coating materials and compositions and their properties.

(1) Solvent-based oil-based coating

In general, many commercial printing plants can be used on ordinary printing units like ordinary offset printing inks.

The oil-based coating is similar in structure to an offset ink, except that it does not contain any colorant. Its ingredients are mineral oils, dry vegetable oils, coagulated alkyds, and a variety of additives. Oil-based coatings contain high levels of solids, about 60% to 85%. They are primarily chemically dried. They use oxygen from the air to oxidize unsaturated fatty acids in dry oils and alkyds. .

The characteristics of the use of oil-base coating are: the gloss of the printing is good; the coating process is as simple as using ordinary offset printing ink; the offset printing plate can be used for gluing the excavated window; relatively insensitive to the moist environment; There are no special requirements for ink fading characteristics.

The disadvantages are: the drying process is relatively slow; powder spraying is needed to prevent stickiness; coating coatings are relatively thin; yellowing is unavoidable; only special adhesives can be used for adhesion; ghosting cannot be eliminated problem.

Solvent type coating varnish is used to apply varnish to the surface of printed products. After passing through the drying tunnel, the solvent in the varnish is volatilized and the film forming material remains on the surface of the paper to form a bright film layer. The glazing oil is mostly heated by a far-infrared device, so it is also known as infrared glazing oil. This is the most widely applied glazing process in China. Its characteristics are low investment, low cost and suitability for general prints. The disadvantage is that there is a large amount of solvent volatilization, causing certain environmental problems and affecting the health of workers. . Despite this, China's current SMEs are still widely used solvent-based polish. The solvent-based coating is not divided into two types according to the solvent, including benzene-based solvent coating, alcohol-soluble coating coating, and is divided into varnishes and calendering oils (also known as polishing oils) according to different coating processes. Pressurized oil refers to the polishing and then the brightness is further increased by the calendering process to make it have a very bright mirror effect.

After the development of toluene-based solvent varnish in China, according to user requirements, alcohol-based varnish and pressure varnish were developed, which not only removed toxic solvents, but also further improved the gloss. Its performance index exceeded that of similar products imported from Taiwan.

2. Dispersion type water base coating

Water-soluble coating oil (or water-based coating oil), its biggest advantage is no smell, no toxicity, no environmental pollution, no solvent, can fundamentally improve the production environment, this coating oil is the nineties The development of environmentally friendly coating oil is very popular in developed countries. With the increasing demand for environmental protection and health at home and abroad, waterborne coating oil has become the development trend of printing.

The major component of a dispersion gloss material is a polymer dispersion, also referred to as a modified acrylate in a very finely distributed state. It is composed of full resin and water, of which synthetic resin accounts for 45% and water accounts for 55%. In general, synthetic resin is insoluble in water. Therefore, in this type of coating oil, water acts as a dispersing agent. Therefore, it should be fully stirred during use. This kind of coating oil is an environmentally friendly "green" material. The decentralized water-based coating has three types of high gloss, ordinary gloss and matt finish, and its glazing effect can basically meet the requirements of the printing designer.

The greatest advantage of using a dispersion coating is that the newly coated material can be stored for long periods of time.