Knit Fabric Paint Printing Practice (2)

Knitted circular screen printing process is generally:

Full coating: semi-finished product → slit width → seam head → setting → printing → baking → setting → roll

Coating/Activity: Semi-Products → Profiles → Slits → Stereotypes → Printing → Baking → Washing → Drying → Stereotypes → Finished Products

3.1 The Choice of New Paint Printing Aids

The new paint additive for printing consists of the following four pillars: (1) excellent coating dispersion system (Dystar coating, etc.); (2) excellent self-crosslinking adhesive system (Germany, U.S. large companies, and self-made products); (3) Excellent printing paste systems (German, U.S. large companies, and self-manufactured species); (4) Excellent hand-tightness-adjusting auxiliary systems.

When coating printing processes, to obtain satisfactory results, mainly depends on these additives. Traditional paint printing products are of poor quality. Usually chemical knitted fabrics that do not meet the new printing technical standards are used. Because they are different from ordinary woven fabrics, many different practical problems arise when printing. The key issues are as follows: Narrative:

Additives and unreasonable printing process:

(1) Coating Dispersion System

After the study, the following conclusions were drawn: The pigments were ground to a particle size distribution range of 0.25-1.5 microns by a high-power Simplified Sand Mill at 0.25 microns, which would cause shading and color strength. decline. The particle size and distribution of the four paint pastes are shown in Table 1 and shown in Figure 1.

Table 1 Particle Size and Distribution of Four Pigments

In actual printing, the choice of paints focuses on price, color intensity, vividness, and fastness properties. After many years of research, we believe that Dystar's 1mperon system is the first choice for environmental protection or irreplaceable, and a large number of coatings produced in Shanghai can be selected.

(2) Adhesive system

The new self-crosslinking adhesives, the vast majority of PA series, a small amount of PU series. Regardless of the type of adhesive, when it comes to synthesis and selection, the first consideration is how to solve the contradictory problem of good hand and fastness. Followed by the transparency of the film, it directly relates to the vividness of printed products. There are many specific descriptions of the constituents of the adhesive and the types of different monomers, and their effects on the film, which are not described here.

After research, we believe that the important condition that the adhesive must meet is to obtain a good balance between adhesion and cohesion. The adhesion of the adhesive film to the fabric is consistent with the good cohesion of the adhesive. Should try to increase. If the adhesion is weak, or if it is weaker than the cohesion, the fastness of the surface of the printed fabric will be reduced to produce fade marks. If the cohesion is weak, the coating particles will be easily rubbed off.

Pigment printing adhesives should be heated under acidic conditions (pH 4) during the heating reaction. Dry hot air is the best fixing medium. Neither wet steam nor superheated steam is suitable as a fixing medium. Because it can only achieve about 60-80% of the fixation effect (as a result of hydrolysis, high-temperature steam contains 100% of water vapor), resulting in a decline in the color fastness index. The thickness of the general paint-printing adhesive after the film is formed is about 5-10 microns, which is difficult to observe with the naked eye. The coating is agglomerated and deposited in the film, so the adhesive force of the adhesive affects the adhesion of the film to the fiber. This process is mainly physisorption and is strengthened by hydrogen bonding. Certain kinds of binders, even under certain conditions, may even form true chemical bonds on the fibers. This is due to the fact that the polymer film has a film-forming agent. Special reaction groups formed. When we synthesize or use adhesives, we pay special attention to its glass transition temperature, in addition to its general indicators.