Discussion on environmental friendly water-based s

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Talking about environmental friendly water-based printing inks

now, with the enhancement of environmental awareness, people not only care about the quality of printed products, but also environmental protection is an important factor to measure printed products. For silk printing, there are many environmental factors that need to be paid attention to, and ink can be said to be the most important one. Therefore, people advocate the use of environmentally friendly printing ink

environmental friendly printing ink shall at least meet the following requirements:

(1) it is non-toxic and harmless to human body and organism, and does not contain toxic elements

(2) in the whole life cycle of the packaging product, the ink will not pollute the human body and the environment or cause public hazards

the inks that meet the above two points mainly include UV ink and water-based ink. The drying of UV ink needs to be equipped with a special curing device, and the use of water-based ink is similar to that of ordinary ink, so its application prospect is very wide. This paper will discuss the water-based printing ink

I. characteristics of water-based printing inks

water-based printing inks inherit many advantages of water-based printing inks, such as low toxicity (or non-toxic) and no irritating smell. At the same time, its viscosity, pigment particles, fixation, etc. also have the characteristics of general printing inks, so it is very suitable for silk printing with high environmental requirements. In general, I worked in rock tennco The company and pactivcorp The characteristics of water-based printing ink are as follows:

(1) it has no irritating smell, is non flammable and non explosive, meets the requirements of environmental protection, ensures the health of workers to a certain extent, and is conducive to safe production

(2) it can be diluted with water and washed with water, which is convenient and practical

(3) the solid content (10% ~ 50%) can be adjusted and mixed freely

(4) monochrome, register, overlay, color, gradient and double-sided printing

(5) good printing adaptability, no trace, blister, pinhole, spot and other faults, clear text, complete dots and strong three-dimensional sense

(6) there are a wide range of printing materials, such as paper products, self-adhesive, corrugated boxes, art works, and various plastics and fabrics

however, water-based printing inks also have some shortcomings, such as slow drying speed, inability to print with high mesh silk, poor fixation to non absorbent objects, etc

II. Composition of water-based printing inks

water-based printing inks are mainly composed of binders, pigments and various additives, mainly using water as solvent

1. binder

binder in water-based ink is composed of water-soluble resin and water-based polymer lotion. There are many kinds of water-based resins, such as rosin maleic acid resin, styrene maleic acid resin, acrylic copolymer, ethyl aminoacrylate, etc; Polymer lotion, namely water-borne dispersion resin, includes vinyl acetate copolymer, acrylic copolymer, polyurethane resin, epoxy resin, etc. At present, water-based acrylic resin is the most commonly used binder in water-based printing ink

2. pigments

water based printing inks mainly use organic or inorganic pigments with strong alkali resistance and good dispersibility in water system. In addition to ordinary powder pigments, these pigments also include pigment filter cake, pigment aqueous dispersion and easily dispersible pigments in water. Because the pigment with poor alkali resistance is prone to condensation reaction, the pigment quality of water-based ink is very high

3. solvent

due to the low solubility and wettability of water, it is necessary to select corresponding cosolvent, such as ethanol, propanol (n-iso), ethylene glycol monoacetic acid, etc. By adding additives, we can improve the shortcomings of ink and improve its stability, reduce the surface tension of water-based ink, increase the wetting of plastic, and help to dissolve the resin and improve the drying speed. In addition, the resin is generally insoluble in water, and appropriate alkaline substances must be added to make the resin soluble in water. Amines, such as ethanolamine, are generally used, and the amount depends on the pH value

4. additives

there are many kinds of additives, such as diluent, dispersant, brightener, defoamer, diluent, electrostatic agent, etc., to improve the printability of ink

III. preparation of water-based printing ink

when preparing water-based printing ink, we should not only consider the printing characteristics of silk printing, but also consider the environmental protection characteristics of the ink, so as to achieve our goal. In general, the preparation principles of water-based printing ink are as follows:

(1) the ink should not dry the conjunctiva when it is printed on the printing plate. When it is printed on the surface of the substrate, it should be fixed and dried quickly

(2) for the image and text formed by the ink on the substrate surface, the imprint after drying should have good adhesion fastness

(3) the ink shall be loose, short, soft, thin and smooth, so as to ensure that the ink is easy to be coated evenly on the printing plate, easy to pass when under stress, and the printed product is clear without sticking

(4) when the ink is coated on the printing plate, it must have a certain stability, that is, the viscosity, viscosity and consistency of the ink change little with time, so as to ensure the consistency of the print quality and the smooth printing

(5) according to the printing object, we will briefly introduce the protection and maintenance of hydraulic universal testing machine. The ink must have a certain color concentration

(6) after printing, the ink on the printing plate shall be easy to clean to ensure the effective recycling of the printing plate

IV. summary

at present, although the three major problems of water-based printing ink (i.e. drying problem, fixation problem and all water-based problem) have been basically solved, there are still many deficiencies in the coaxiality of water-based printing ink: within 15%. Among them, the drying time is still the most important problem in the application of water-based ink. Unless the printing machine is equipped with sufficient drying equipment, the printing speed will be affected. In addition, the water-based printing ink contains a certain amount of solvent, and its export freight is also very high. The standard type up to 100000 subdivision codes are all problems that need to be solved at present

however, the technology of water-based printing ink is developing rapidly. It is believed that some current problems will be solved soon. Now, water-based inks are more and more used in silk printing, which also urges many ink manufacturers to invest heavily in the development and research of water-based printing inks. With the gradual elimination of solvent based inks, it is believed that the development of water-based printing inks will be faster and faster

information source: printing industry

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