The characteristics, composition and preparation of environment-friendly aqueous screen printing ink

Now, with the enhancement of environmental awareness, people are not only concerned with the quality of printed products, environmental characteristics are also an important factor in measuring print. For screen printing, there are many environmental factors that need attention, and ink is arguably the most important one. Therefore, people all advocate the use of environmentally friendly screen printing inks.

Environmental screen printing inks must meet the following requirements:

(1) It is non-toxic and harmless to humans and organisms and does not contain toxic elements;

(2) In the entire life cycle of the packaged product, the ink will not cause pollution to the human body and the environment or cause public hazards.

The ink satisfying the above two points mainly includes a UV ink and a water-based ink. The drying of the UV ink requires a special curing device, and the use of the water-based ink is similar to that of a common ink, so its application prospect is very wide. This article will discuss water-based screen printing inks.

First, the characteristics of water-based screen printing ink

Aqueous screen printing ink inherits many advantages of water-based ink, such as low toxicity (or non-toxic), no irritating odor, at the same time, its viscosity, pigment granules, fixation, etc. have the characteristics of general screen printing ink, so it is very suitable for Highly demanding screen printing. In general, the characteristics of aqueous screen printing inks are as follows:

(1) Non-irritating odor, non-flammable and non-explosive, and in compliance with environmental protection requirements, to a certain extent ensure the health of workers and contribute to safe production.
(2) It can be diluted with water, washed with water, convenient and practical.
(3) Solid content (10% to 50%) can be freely adjusted and mixed.
(4) Monochrome, multicolor, multicolor, color, gradient, and double-sided printing are all acceptable.
(5) The printing suitability is good, there will be no troubles such as traces, blisters, pinholes, spots, etc., the characters are clear, the dots are complete, and the three-dimensional effect is strong.
(6) Wide range of printing materials, such as paper products, stickers, corrugated boxes, fine arts, and various plastics and fabrics can be printed.

However, water-based screen printing inks also have some shortcomings, such as slow drying speed, high screen mesh screen printing, poor fixation of non-absorbent materials, etc.

Second, the composition of water-based screen printing ink

Water-based screen printing inks mainly consist of binders, pigments and various additives, mainly water as the solvent.

1. Binder

The binder in water-based ink consists of a water-soluble resin and an aqueous polymer emulsion. There are many kinds of water-based resins, such as rosin maleic acid resin, styrene maleic acid resin, acrylic acid copolymer, amino ethyl acrylate, etc.; polymer emulsion that is water-based dispersion resin, vinyl acetate copolymer, acrylic copolymer, polyurethane resin , epoxy resin and so on. At present, water-based acrylic resins are the most commonly used binders in aqueous screen printing inks.

2. pigment

Water-based screen printing inks mainly use organic or inorganic pigments with strong alkali resistance and good dispersibility in water systems. In addition to ordinary powder pigments, these pigments also include pigment filter cakes, aqueous dispersions of pigments, and easily dispersible pigments in water. Because of the poor resistance of the pigments to condensation, water-based inks require high quality pigments.

3. Solvent

Since the water's dissolving power and wetting ability are not large, it is necessary to use the corresponding cosolvents, such as ethanol, propanol (positive and negative), ethylene glycol monoacetic acid, and the like.

By adding auxiliaries, the disadvantages of the ink can be improved and its stability can be improved, the surface tension of the water-based ink can be reduced, the wetting of the plastic can be increased, and the dissolving resin can also be used to increase the drying speed. In addition, the resin is generally insoluble in water, and an appropriate alkaline substance must be added to make the resin soluble in water. Generally used amines, such as ethanolamine, depending on the pH value.

4. Additives

Many types of additives, such as thinners, dispersants, brighteners, defoamers, diluting agents, electrostatic agents, etc., to improve the printability of the ink.

Third, the preparation of water-based screen printing ink

When formulating water-based screen printing inks, it is necessary to consider the printing characteristics of screen printing, and also consider the environmental characteristics of ink, so as to achieve our goal. In general, the principle of preparation of aqueous screen printing inks is as follows:

(1) When the ink is on the printing plate, the conjunctiva should not be dried. When printing on the surface of the printing material, it is required to be quickly fixed and dried.

(2) The graphic of the ink formed on the surface of the substrate, and the dried imprint must have a good adhesion fastness.
(3) The ink should have the characteristics of being loose, short, soft, thin, and slippery to ensure that the ink is easily coated evenly on the printing plate, and it is easy to pass through the net when the force is applied. The graphic image of the printing product is clear and there is no sticky phenomenon.
(4) When the ink is coated on a printing plate, it must have a certain degree of stability, that is, the viscosity, viscosity and consistency of the ink change little with time, so as to ensure that the quality of the printing product is consistent and the printing proceeds smoothly.
(5) According to the printing object, the ink should have a certain color density.
(6) After the printing is finished, the ink on the printing plate should be easy to clean to ensure the effective recycling of the printing plate.

Fourth, summary

At present, although the three major problems of water-based screen printing inks (ie, drying problems, fixing problems, and full-water-based problems) have basically been solved, water-based inks still have many deficiencies. Among them, the drying time is still the most important issue in water-based ink applications, unless the printing press is equipped with enough drying equipment, or printing speed will be affected. In addition, aqueous screen printing inks contain a certain amount of solvents, and their shipping costs are also high when they are exported. These are problems that need to be solved.

However, water-based screen printing ink technology is rapidly developing and it is believed that some of the current problems will be resolved soon. Nowadays, more and more water-based inks are used in screen printing. This has prompted many ink manufacturers to invest heavily in the development of water-based screen printing inks. Along with the slow elimination of solvent-based inks, it is believed that the development of water-based screen printing inks It will be faster and faster.