Coating printing has occupied an important position in the printing and dyeing industry around the world. According to data, in the 1990s, about 50% of the world’s production of printed fabrics were printed using paint printing technology, especially in the United States. Printing has reached about 80%; Western Europe also accounts for 60%; Japan’s proportion is lower than 10% to 15%; my country’s coating printing products have gradually increased from the original 20% to 35%, and are widely used in pure cotton fabrics and synthesis Fiber and its blended fabrics, knitted fabrics, etc. Paint printing is a printing process with a promising development in polyester-cotton blended textile printing. About 70% of domestic and foreign polyester-cotton blended textiles are made of paint printing.
With the development of the synthetic fiber industry, the mass production of various synthetic fibers and blended textiles is another challenge for coating printing. The paint itself has no affinity for fibers. The adhesive only relies on the adhesive to mechanically adhere the paint to the fiber surface to form a film, so that it can form a pattern after coloring and curing, and has a certain degree of firmness. As far as the principle of paint printing is concerned, it is suitable for all fiber printing, so the superiority of paint printing is more prominent. It has become a major field in textile printing and dyeing processing today, occupying half of the market. In addition, the coating printing process is simple and easy to learn, energy saving, low cost and environmental pollution, making it a widely adopted printing method that is valued by practitioners and enterprises. For those who are accustomed to using paint printing, they often ignore the choice of color paste components of the paint printing, and as a result, failure occurs during the printing process, especially when printing fine patterns. This article will focus on analyzing and introducing the problems of printing patterns such as seeping edges and unclear contours when printing polyester-cotton blended fabric paint.
Polyester-cotton blended textiles are a variety developed by my country in the early 1960s. The fiber has the characteristics of being crisp, smooth, fast drying, and durable, and is deeply loved by consumers. At present, the blended varieties have developed from the original ratio of 65% polyester to 35% cotton to blended fabrics of various different proportions such as 65:35, 55:45, 50:50, 20:80, etc. The purpose is to adapt to different levels. Consumer demand. However, due to the many differences in the physical structure and chemical properties of polyester fiber and cotton fiber, it is necessary to note that polyester fiber is a hydrophobic fiber. When printing, it is necessary to note that polyester fiber is a hydrophobic fiber. When printing pure polyester fiber or polyester cotton blended fabrics, no matter what kind of material is used. Printing methods (such as handmade tableboards, cloth-moving flat screen printing or round screen printing) often seeps into the edges of the printed fabric patterns, resulting in unclear contours, and the finer the pattern, the more serious the penetration problem.
I. Analysis of the causes of pattern seepage
Paint printing color paste belongs to an aqueous phase system or a galemized system. The ultrafine pigment particles in the paint color paste will follow the fibers along with the water molecules in the water emulsion. The capillary movement between the bundles causes diffusion, which then migrates to the edge of the pattern, causing seepage and causing unclear pattern outline. The schematic diagram of the permeation of the flower shape after printing is shown in Figure 1.
From the actual application, whether it is an emulsified paste or a synthetic thickener, it will be produced by printing polyester or polyester or cotton blended fabrics as the original paste of the paint printing color paste. Different degrees of permeation. Generally, the permeation of the thickener with a low solid content is more serious, because the water of paste with a low solid content is more likely to spread into the capillary in the fiber bundle. Permeation.
Although there are many reasons for affecting the clarity of the pattern profile, the main factors affecting the clarity of the printing paste on the clarity of the printing profile are the diffusion properties of the paste and the plasticity of the color paste.
1. Diffusion.
Diffusivity refers to the ability of the paste itself and its water-soluble parts to resist the capillary effect of the fabric, especially when printing hydrophobic (such as polyester-cotton blended fabrics) fibers, It seems more important. Generally, pastes with good flow properties are prone to diffusion. Pastes with low solid content and low viscosity have lower diffusion properties and are clearer in print shapes. However, in actual production, there are Although the printing paste is made of small consistency, its ability to resist impermeability is higher than that of other pastes with larger consistency, which means that the ability to resist impermeability has no direct relationship with the thickening effect of the paste. Paint printing paste All materials are water-absorbing polymers, and their thickening ability is directly related to their water-absorbing ability. Some people have found that under the same water absorption, the viscosity of various pastes is also very different, and the anti-permeability of pastes is as good as pastes. The water retention ability of the polymer particles in the material after absorbing water is related, that is, the properties of water in the polymer particles. There are three forms of water in the paste: ① Binding water that is bound to hydrogen bonds with the paste molecules but is not easy to free. ;② The embossed water that is embedded in the complex lattice of the paste molecules; ③ It can move freely to form permeable free water. The so-called water-bearing property of the paste is the hydration ability of the paste, and the water is free in the paste with poor water-bearing property. Movement will cause permeation, especially printing hydrophobic fabrics.
2. Plasticity of printing paste.
In order to ensure the clarity of the pattern, the paste must have a certain degree of plasticity, but The plasticity cannot be too high. If the plasticity of the paste is too high,
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