After prolonged use or washing, fabrics may experience wrinkling, fuzzing, and other issues. Most untreated fabrics have poor waterproof and moisture permeability, and cannot provide a comfortable wearing experience. Textile finishing agents can solve these problems. Textile coating finishing agent is a polymer compound uniformly applied to the surface of a fabric. It forms one or more layers of thin films on the surface of the fabric through adhesion, which can improve the appearance of the fabric, increase the fabric style with special functions such as waterproofing, moisture permeability, flame retardancy, and UV resistance, and explore new uses of textiles. There are also many types of coating agents used for coating finishing.
Commonly used are high molecular polymers such as latex, waterborne polyurethane, polyacrylate, and polyethylene. Among these coating agents, polyacrylate and waterborne polyurethane resins have developed particularly significantly in recent years. Polyacrylate is a copolymer of different acrylic monomers, which can have different physical and mechanical properties due to the different raw material monomers used; Waterborne polyurethane is formed by adding compounds containing diisocyanate groups to polyols or other compounds containing active hydrogen, and there are no by-products in the reaction. In previous years, most of the coating agents used in domestic fabric coating processing were imported. In recent years, chemical manufacturers and research institutions in China have tried to produce high-level coating agents, which has created favorable conditions for the development of fabric coating technology in China.
To improve the performance of waterborne polyurethane coatings, a sealing agent can be added during the preparation process, which reacts with some isocyanate groups in the prepolymer to form urethane bonds. Under heating conditions, the isocyanate bonds generated by the cleavage of the urethane bonds then react with hydroxyl groups on the fabric to form polyurethane esters, thereby increasing the adhesion between the polyurethane coating and the fabric. Waterproof and breathable polyurethane films and coatings have become one of the research focuses of researchers due to their ability to both waterproof and breathable. Waterproof and breathable refers to polymer materials that do not allow liquids such as water droplets to pass through, but can ensure the free passage of water vapor. With the gradual improvement of people's living standards, the demand for waterproof and breathable clothing, shoes and hats and other fabrics is growing rapidly. The elasticity of polyurethane is similar to that of rubber, derived from the long chain structure of large molecules, the free rotation of single bonds in the chain, and appropriate crosslinking between molecular chain segments. Therefore, when selecting a polyurethane finishing agent with a known structure, increasing the crosslinking degree through appropriate formula and finishing process is beneficial for improving resilience. But excessive cross-linking can reduce resilience. A finishing agent made by adjusting the ratio of soft and hard segments on the main chain of polyurethane molecules can adjust the softness and stiffness of the fabric after treatment. Polyurethane grafted with organic silicon is a good finishing agent.
Common methods for coating finishing
The transfer film forming method involves first coating the slurry on transfer media such as silicone or other resin treated transfer paper, rubber tape, etc., then overlaying the transfer media coated with the slurry with the fabric, rolling and pressing the slurry to transfer to the fabric, and then drying, cooling, and other processes to separate the paper from the fabric coating to obtain the coated fabric. This film forming process is more suitable for finishing light and thin fabrics that cannot withstand tension. Heat thermoplastic polyurethane to a molten state, apply it to the fabric, cool it, and form a thin film on the surface of the fabric. The bonding method is mainly used for the finishing of thicker fabric products such as indoor decorative fabrics. The production process is to use adhesive to stick the film onto the surface of the fabric, and through rolling, it is firmly adhered to the fabric as a whole.
Direct coating uses a scraper to coat the resin into a continuous film to achieve waterproofing, wind resistance, and yarn fixation effects. According to different film forming methods, it can be divided into dry and wet coating.
Dry coating dissolves the coating agent in water or organic solvents, adds certain additives to make a coating slurry, and directly and evenly applies it to the fabric with a scraper. Then, it is heated, dried, and baked to evaporate the water and solvent. The coating agent forms a tough film on the surface of the fabric through its own cohesion or resin cross-linking.
After evenly coating the coating agent on the fabric, the wet coating removes solvent DMF through a water coagulation bath, and then removes impurities such as solvent additives through a water washing bath, forming a microporous film on the fabric. The hot melt coating heats and melts the PUR hot melt adhesive, injects it into the adhesive groove, squeezes the PUR into the hole of the rotating carving roller through a scraper, pressurizes, and transfers the adhesive from the hole to the film. After being pressed by the composite roller, it adheres to the substrate, curls under a certain tension and pressure, and matures under a certain temperature and humidity condition.
The adhesive coating overlaps the resin with the substrate coated with adhesive, which is then pressed and rolled to form a cohesive layer, or the resin film is melted at high temperature and then laminated with the substrate, and then pressed and rolled to form a cohesive layer. The coating film is thicker. The transfer coating is first coated with coating slurry on the silicone treated transfer paper, and then overlaid with the substrate. It is dried, flattened, and cooled under very low tension conditions, and then separated from the coated fabric.
Zhejiang Chaoyu New Material Technology Co., Ltd
Suzhou Chaoyu Textile Chemical Co., Ltd
