As a rapidly developing "green" new technology, ultraviolet curing (Uv curing) has become an important type of radiation curing technology. According to experts from the China Epoxy Resin Industry Association, UV-curable coatings (UvCC) are energy-saving and environmentally friendly coatings developed in the 1960s. After UV irradiation, they will undergo photochemical reactions and liquid oligomers (including monomers) The coating undergoes crosslinking polymerization to form a solid coating instantly. Especially because of environmental protection, UVCC can be widely used and developed, people feel its unique advantages of energy saving and environmental protection, excellent coating performance, high production efficiency and so on.
The main components of UVCC include crosslinkable polymerizable prepolymer (photoactive oligomer), reactive diluent (photoactive monomer), photoinitiator, additives (leveling agent, defoamer, matting agent, surface Slip agent). Among them, oligomer is one of the components with the largest proportion in light-cured products. As the base resin of light-cured formulations, it determines the basic properties of cured products (including hardness, flexibility, adhesion, optical properties, aging resistance, etc.) ), mainly including unsaturated polyester resins, epoxy acrylates, urethane acrylates, polyesters, and acrylated polyacrylates; photoactive monomers are also important components, and traditional solvent-based coatings usually require the addition of organic solvents to It plays a role in adjusting the viscosity. These organic solvents generally do not participate in the film formation reaction. Volatilization into the air during film formation will cause environmental pollution. In the photocuring system, the photoactive monomer (active diluent) not only plays a role in adjusting the system The role of viscosity, and usually can participate in the curing film formation reaction, rarely evaporate into the air, giving the system environmental protection characteristics, currently the most widely used reactive diluent is (meth) acrylates; photoinitiator is UVCC The key component, whose role is to generate active groups that initiate the curing reaction, is generally divided into free radical polymerization photoinitiators and cationic polymerization photoinitiators. Free radical photoinitiators are divided into two types: cracking type and hydrogen abstraction type; actual In the application, the light curing system often needs to add various additives to meet other requirements. For example, pigments need to be added to the colored system (color paint, ink, etc.). In order to achieve good flow leveling, the leveling agent needs to be added. In order to suppress the formation of bubbles in the system, antifoaming agents are often added, and the matting agent is added to reduce the gloss of the cured film.
UVCC has the advantages of fast curing speed and environmental friendliness, so it has developed rapidly in various industries. The substrates it adapts to have expanded from the earliest wood to paper, plastic, metal, stone, cement, fabric, leather, etc. Experts from the China Epoxy Resin Industry Association said that its current application area is first of all coatings, mainly including: First, paper glazing coatings, paper glazing coatings are a kind of varnish, generally known as light curing varnish, suitable for Coating decoration of book covers, advertising posters, product packaging cartons, decorative paper bags, etc., giving products high gloss, abrasion resistance, water resistance, and enhancing product aesthetics; second, wood coatings, UVCC was originally used for wood coatings Now, woodware UVCC is one of the light-curing products with larger output. According to the use occasion and quality requirements, woodware UVCC can be divided into parquet floor coating and decorative plate coating; third is plastic coating, generally including ordinary plastic coating and engineering plastic Coatings can give ordinary plastics such as polystyrene products, organic glass, polyester film products and other friction-resistant and scratch-resistant properties, and phenolic products, ABS products and other engineering plastics with high hardness, high gloss, beautiful performance, etc. Flooring, UVCC can give it not easy to scratch, wear-resistant, low gloss, beautiful and other properties; Fourth, it is widely used in metal sign decoration, cans processing, metal trim manufacturing, aluminum alloy doors and windows protection and steel pipe temporary coating protection, etc. Mainly play a protective role on products; Fifth, optical fiber coatings, foreign countries began in the 1970s, the domestic Hubei Institute of Chemistry and Xi'an Jiaotong University have made special research in this regard, the main function is to protect quartz glass drawn into fibers The strength and prevention of environmental pollution, and give each fiber a different color; Sixth is its guest coating, which can be used for the coating of glass, leather, ceramics, silicate stone, optical discs, etc.
UVCC was originally used for wood coating. With the continuous development and improvement of technology, its scope of application has become more and more extensive. The study of applying UVCC to leather finishing started abroad in the 1970s, and research in this area in China is still relatively rare. Compared with traditional leather finishing agents, the advantages of UVCC applied to leather finishing are: the curing speed is greatly improved, the drying time is even less than 1min, the possibility that the wet film adheres to the dust and the glossiness is reduced is greatly reduced; the solvent volatilization is greatly Reduced; low curing temperature; excellent gloss and aesthetics of the coating film; avoid the use of crosslinking agents such as formaldehyde in the leather finishing agent, play an environmental protection role, in line with the development direction of ecological leather; can be used for leather finishing, can also be used for For artificial leather and synthetic leather, the equipment requirements are simple. The leather making process using Uv paint generally includes the following steps: leather (synthetic leather)-ironing-UVCC primer-radiation curing-IVa top coating-radiation curing. Experts from the China Epoxy Resin Industry Association said that with the continuous development of society and the enhancement of environmental awareness, more attention has been paid to the development of environmentally friendly technologies and chemicals that are less harmful to the environment and harmless to the human body. UV curing technology is a new type Environmentally friendly technology, I believe its application in leather finishing will become a major trend, Uv leather finishing agent will also become one of the research hotspots in leather finishing agent.