Paint printing how to choose polyester cotton fabric printing paste

Paint printing has occupied an important position in the printing and dyeing industry all over the world. According to relevant data, in the 1990s, about 50% of the world's printed fabrics were printed using a paint printing process, especially in the United States. The proportion of these accounts for about 80%; Western Europe also accounts for 60%; Japan has a low percentage of about 10% to 15%; China's paint printing as the main process of printing varieties also gradually increased from the original 20% to 35%. It has become one of the main printing processes for synthetic fibers and their blended fabrics and knitted fabrics. In particular, for a large number of garment printing products, in particular printed garments, only manual platen printing can be used. Since many small-scale printing enterprises do not have post-printing equipment (such as steaming and washing equipment), they are generally Avoiding dye printing methods, the preferred method is paint printing. For those who are accustomed to paint printing, they often ignore the choice of paint paste colorants and use coating printing paste freely. As a result, they will encounter some difficulties and thorny issues in printing, especially printing. Fine patterns are more likely to appear. This article describes the printing of polyester-cotton blend fabric paint, why the edge of the printing pattern appears to be infiltrated, the profile is not smooth defects?

Analysis of Causes of Pattern Penetration

1.1 Hydrophobicity of Polyester Fiber

Paint printing pastes are either aqueous systems or semi-emulsified systems. Ultrafine pigment particles in the paint paste will spread as the moisture in the aqueous emulsion moves along the capillary between the fiber bundles, and then migrate towards the edge of the pattern, causing bleed out and causing the outline of the pattern to be unclear.

From the actual application, whether emulsified paste or synthetic thickener, as the raw paste of paint printing paste to print polyester or polyester-cotton blended fabric will have varying degrees of osmosis phenomenon. In general, the permeation phenomenon of the low solid content all-aqueous synthetic thickener is more serious because water in the low solid content paste easily diffuses into the capillaries in the fiber bundle and causes osmosis. Although there are many reasons that affect the sharpness of the outline of a pattern, the factors that determine the influence of the printing paste on the definition of the printed outline are mainly the diffusion properties of the paste and the plasticity of the color paste. Diffusion refers to the resistance of the paste itself and the water-soluble substances it contains to the capillary effect of the fabric, especially when printing hydrophobic fibers (such as polyester-cotton blended fabrics), this factor becomes even more important. Generally, pastes with good flowability are prone to diffusion. In general, pastes with a solid content and a low viscosity will have lower diffusion performance and the printed pattern will be clearer. However, in actual production, it is often found that some pastes formulated with pastes have a smaller consistency, but the ability to resist osmosis is higher than other pastes with a higher consistency, which indicates the ability to resist osmosis and paste The thickening effect of the material is not directly related. Paint printing paste is a category of water-absorbing polymers. Its thickening ability is directly related to water absorption capacity. Some experiments have found that the viscosity of various pastes varies greatly with the same water absorption. The impermeability of the paste is related to the water-retaining ability of the polymer particles in the paste, ie, the nature of the water in the polymer particles. The presence of water in the paste has three forms: 1 binding water that is not easily released by the hydrogen bond of the paste molecule; 2 cohesive water entrained in the complex lattice of the paste molecule; 3 is free to move and constitutes Permeabilized free water.

The so-called paste holding water, that is to say the hydration capacity of the paste, the water moves freely in the paste with poor water holding capacity, it will have a phenomenon of osmosis. This phenomenon can occur especially when printing hydrophobic fabrics.

1.2 The plasticity of printing paste

In order to ensure the clarity of the pattern, the paste must have a certain plasticity, but the plasticity can not be too high. The paste with high plasticity and paste preparation makes it difficult to completely fill all parts of the screen mesh during printing, especially at the fine pattern of the pattern, thereby affecting the print uniformity of the pattern of the land.

2 anti-permeability control methods

Full water-based paint printing system will often appear osmotic phenomenon, affecting the contour finish. For this purpose, a semi-emulsifying paint printing system should be adopted, and at the same time, a rheology improving additive for preventing the bleeding of the printing paste, such as Printrite PM (produced by BF Goodrich, USA), should be added to the printing paste to increase the use of the synthetic thickener as the raw paste. The flow properties of printing pastes prevent the bleeding of printing pastes and reduce the penetrating performance of printing pastes.

This is why current printing and dyeing plants are still using emulsifying paste as a thickener for paint printing pastes, because emulsified pastes have a lower viscosity than static ones under mechanical shearing force, and when shearing force is eliminated, It can quickly return to its original approximate value. Therefore, the emulsified paste has less thixotropy and is advantageous for printing clear-cut patterns. Although emulsifying paste has good printing performance, it is formed with high-boiling white flame oil, water, and emulsifier under high-speed stirring, which is not only costly, but also releases a large amount of oil mist during drying or baking after printing. The smell is serious. It not only pollutes the environment but also wastes energy. It also easily causes fire. It becomes more and more necessary to develop a low-solvent or solvent-free thickener. China began to develop anti-permeation special pastes from the late 1970s. For example, the Zhejiang Silk Science Research Institute developed a special anti-permeation paste that can effectively prevent the occurrence of printing paste bleed. It uses non-ionic emulsifiers to rapidly disperse oil droplets into fine particles with a narrow and uniform particle size distribution of 1 μm or less, and to add auxiliary agents such as assistants for assistance and feel modifiers. Finally, low-solid electrolytes are added. The synthetic paste is compounded into a special impervious paste, and its performance with semi-emulsified paste is shown in Table 1. According to the above theoretical discussion,

The following printing paste formula should be selected:
Anti-permeation special printing paste prescription (%):
Coating X
Acrylic or Polyurethane Adhesive 15~18
Anti-permeation special paste 80
Take FS-200 thickener to mix printing paste as an example:
Paste preparation (%):
FS- 200 2.5 ─── ┐
├─┐
Water 83.5 ───┘ ├─┐
Adhesive pH-400A 10 ─────┘ │
Paint Red FFG 4 ───────┘

Reprinted from: Global Textile Network