Coatings are widely used in automobiles, furniture, construction, etc., which can not only improve their aesthetics, but also provide certain protection and extend their service life. In the process of social and economic development, coatings play an increasingly important role, and people pay very high attention to the performance and quality of coatings. At present, people’s living standards are getting higher and higher, their awareness of environmental protection is gradually increasing, they cherish the use of resources more and more, and they have very strict quality requirements for coating products. The world’s coatings industry is moving towards the 4E of economy, ecology, energy and efficiency.” Development in principle. The main raw material of acrylic paint is methacrylate or acrylate, and mixed resin is made into acrylic resin base material. This article conducts research and analysis on the performance and application of acrylic paint.
Acrylic resin
Acrylic resin is a copolymer composed of methacrylate, acrylate and vinyl monomers. Compared with other synthetic polymer resin materials, acrylic resin materials have very obvious advantages, such as In terms of light resistance, weather resistance, durability, heat resistance, etc., it will not discolor at 230°C and has good acid and alkali corrosion resistance. It is increasingly used in automobiles, home appliances, construction, plastic products, etc. Combining different resin structures and production processes, acrylic numerical paints can be divided into several different types.
The relationship between the structure and performance of acrylic resin
On the one hand, it is stability, includingUV resistance, acid and alkali resistance, chemical corrosion resistance, etc. Due to the presence of a-H, acrylate resins have lower oxidation resistance and UV resistance than methacrylate resins. Acrylic resin has C-C bonds as its main chain and has very good resistance to oxidation, acid and alkali, and hydrolysis. On the other hand, there are mechanical properties. The mechanical properties of acrylic resin include elongation, hardness, toughness, etc. These properties are largely affected by the density of polymer molecular structure. As the side chains grow, the tensile strength and hardness of acrylic resin will decrease significantly, and the elongation and softness will increase significantly. Polymethacrylate has a methyl group at the a-position, which greatly limits the rotational movement of the C-C main chain. There is no a-methyl group in polyacrylate, and each chain can rotate around the main chain. This is why polymethacrylate has good hardness and tensile strength, but poor flexibility and extensibility compared to polyacrylate. .
Synthesis of acrylic resin
Acrylic resin uses free radical reaction as the basic reaction, which can be divided into three processes: chain initiation, chain growth and chain termination. The whole process is also accompanied by chain transfer. In the process of synthesizing thermoplastic acrylic resin, it is necessary to control the molecular weight and molecular weight distribution. Although the mechanical properties of the paint film will be significantly improved as the molecular weight increases, the solution viscosity of the paint film will also increase significantly. Reduce the solid content. In addition, as the molecular weight increases, it is easy to reduce its solubility. The molecular weight of thermoplastic acrylic resin currently used commercially is around 80,000~90,000.
Molecular weight and molecular weight distribution are also easily affected by factors such as monomer feeding method and initiator type. When benzoyl peroxide is selected as the initiator, benzoyl free radicals will decompose and become highly active wave-type free radicals, which are prone to branching reactions and deprive hydrogen atoms of monomers or polymer molecular chains, especially as the As the temperature increases, above 130°C, a large number of branches will appear, increasing the molecular weight distribution. In terms of monomer feeding methods�For automotive topcoats, etc., choose polyisocyanate as the curing agent, which can be used in automotive topcoats, building exterior wall coatings, etc. Choose polyamines or polybasic acids as the curing agent, which can be used in can spraying, etc. Choose epoxy resin as the curing agent It can be used in can spraying, etc. If melamine resin is selected as the curing agent, it can be used in the bottom and middle layer coatings. It also has a very good application effect in furniture metal coatings.
Water-based acrylic paint is divided into thermoplastic acrylic latex paint, thermosetting acrylic There are two types of ester latex paints. Thermoplastic acrylate latex paint is mainly used in building exterior wall coatings, water-based road marking paints, metal anti-corrosion coatings, etc. Thermosetting acrylate latex paints are available in emulsion type, water dilutable and aqueous solution types. Emulsion type It is used in road sign paint, building interior and exterior wall coatings, etc.; water-dilutable paint is mainly used in automotive electrophoretic primers, aluminum door and window frames, etc.; water-soluble paint is mainly used in automotive primers, household parts coating, etc.
Solvent-free acrylic coatings mainly refer to thermosetting UV-curable coatings There are two types of thermosetting acrylic powder coatings. Among them, ultraviolet curing coatings are used in optical fiber coatings, wood coatings, plastic coatings, etc.; acrylic powder coatings are used in guardrail coatings, aluminum wheel hub coatings, etc., and are currently being used in automobile hoods. Varnish and other fields.
Water-based acrylic paint
Water-based coating technology started late. At present, its technology has gradually matured and has the characteristics of environmental protection and energy saving. It has gradually developed into a main development direction of modern coatings. At present, its varieties, functions and uses are becoming more and more perfect. Among the water-based coatings currently developed, in terms of curing temperature, there are latex paints abroad that can be cured at a temperature of 2°C. In terms of application scope, architectural coatings are the most widely used, and water-based polyurethane coatings have been successfully developed. The successful development of acrylic emulsion laid a good foundation for the realization of water-based coatings. In the actual application process, acrylic emulsion has good performance and is pollution-free. It can also be configured into a coating with excellent construction performance, and the safety of use can be effectively guaranteed. The composition of water-based acrylate is relatively simple, and it is currently difficult to meet the actual needs of the high-performance audio and video field. Using epoxy resin to modify acrylic resin, you can get water-based anti-corrosion and anti-rust coatings with good performance. Using silicone-modified acrylic phenol, you can also get water-based architectural coatings with excellent performance.
Acrylic coatings have excellent performance in practical applications and are used in automobile decoration, home appliances, machinery, and instruments , construction, leather and other fields, it is a new type of high-quality coating, including solvent-based acrylate coatings, water-based acrylic coatings, solvent-free acrylic coatings and other different types. In actual use, acrylic coatings can Combined with actual needs, different curing agents are added to give it different properties and better meet usage requirements.
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