Common knowledge of coatings: types of waterborne coatings for plastics

Core tip: at present, the varieties of water-based coatings that can be applied to plastic products in the market are similar to water-based wood coatings, mainly using water-soluble coatings and latex coatings According to the resin classification, there are mainly water-based acrylic acid, water-based single component polyurethane, water-based two-component polyurethane, etc in addition, there are also water-based UV curing types These varieties are mainly used on the surface of ABS, PS, PC / ABS, PVC and other polar plastics; for non-polar PE, PP and other base materials with very small surface tension, special pre-treatment is required, or chlorinated polyolefin resin is emulsified or modified by external emulsification or other methods Which is the price of Dajin diatom mud Recommended brief introduction: which is the price of Dajin diatom mud? How to buy genuine diatom mud? Guangdong diatom mud agent suggests placing a basin of cold water in the air conditioning room, so that the diatom mud wall can breathe effectively The feature of the breathing wall is obvious When the indoor air is dry, the diatom mud wall will release the absorbed water quickly Put it out to help regulate the indoor dry humidity It is suggested to place a basin of cold water in the air conditioning room, so that the wall of diatom mud can breathe effectively The feature of the wall that can breathe is obvious When the indoor air is relatively dry, the wall of diatom mud will absorb the water Paint Home News: at present, the market can be applied to the plastic products of water-based paint varieties and water-based wood coatings are similar, mainly using water-soluble paint and latex paint According to the resin classification, there are mainly water-based acrylic acid, water-based single component polyurethane, water-based two-component polyurethane, etc in addition, there are also water-based UV curing types These varieties are mainly used on the surface of ABS, PS, PC / ABS, PVC and other polar plastics; for non-polar PE, PP and other base materials with small surface tension, special surface treatment should be done at the early stage, or chlorinated polyolefin resin should be made water-borne by external emulsification or other modification methods (1) The acrylic resin for waterborne acrylic coating is mainly thermoplastic or thermosetting acrylic resin which is obtained by copolymerization of acrylic acid, methacrylic acid and its ester with vinyl monomers (such as styrene) and other acrylic resin modified by active crosslinkable functional group resin According to the state of resin in water, it can be divided into water soluble, water emulsion and latex acrylic coating The waterborne acrylic resin is composed of thickener, defoamer, drier, antifungal agent, corrosion inhibitor and other additives Plastic water-soluble acrylic acid needs water-soluble, its relative molecular weight will not be too large, otherwise it is difficult to be water-soluble Therefore, they are mostly made of thermal isotropy as a polymer material The film is formed by crosslinking, mainly by adding crosslinking resin (such as epoxy resin, phenolic resin, amino resin, etc.) to achieve external crosslinking The other is acrylic emulsion paint, which is generally divided into three types according to the latex used, namely, all acrylic emulsion paint, styrene acrylic emulsion paint and ethylene acrylic emulsion paint, of which the performance of all acrylic emulsion is the best The development and application of waterborne acrylate coating began in the 1950s and got J in the early 1970s It develops rapidly and is gradually applied in plastics It is one of the important varieties of waterborne coatings for plastics It has the characteristics of anti-corrosion, alkali resistance, light and weather resistance, good film-forming, good color retention, pollution-free, good construction performance, use safety, etc and it can be changed by A series of measures, such as the kinds of monomers and crosslinkers and the adjustment of the relative molecular mass of polymers, have changed the properties of the coatings However, there are some defects in waterborne acrylate coating, such as easy loss of light, water permeability, high water absorption, hot viscosity and cold embrittlement Since the 80s of the 20th century, waterborne acrylic composite emulsion has been developed to enhance the overall performance of the waterborne paint film (such as gloss, water resistance, adhesion, etc.) through the complementary advantages among components HJ The waterborne acrylate coating is modified by other resins or monomers Such as: epoxy resin modified water-based acrylate resin, water-based polyurethane acrylate resin, fluorine-containing or silicon-containing water-based acrylate resin, etc Some functional monomers are specially introduced in the emulsion polymerization process, so that waterborne acrylic emulsion and waterborne aluminum silver paste have good compatibility and compatibility, and help to guide and arrange the orientation and arrangement of water aluminum powder in the process of film formation, so as to obtain a very good waterborne plastic silver powder paint with good apparent effect Using nano silica as Picketing emulsifier and stabilizer, water based nano modified acrylate resin and coating were prepared by in-situ emulsifier free emulsion polymerization with butyl acrylate, styrene and special functional monomers, using water as the medium In the water-based nano modified resin, there is no free small molecule surfactant or modifier at all The film has good adhesion to the surface of plastic substrate such as PP, PE, PC, PVC, ABS, polyester, epoxy resin and so on The water-based plastic coating series products developed by using new polymer nano material synthesis technology to prepare polymer nano water dispersion can be widely used in the surface coating of plastic parts in the fields of home appliances, motorcycles, electric bicycles, toys, shoes and other fields, with the advantages of non combustion, non-toxic, non pollution, low cost, resource saving and energy saving (2) Waterborne polyurethane coating polyurethane contains strong polar isocyanate group (NCO), 0h and urea group In addition, hydrogen bond and van der Waals force can be formed between molecules, which has high cohesion and good adhesion to polar plastic surface For non-polar PE, PP and other plastics, in addition to the surface treatment of the plastics, the polyurethane resin can also be grafted with chain segments whose chemical properties, surface tension and solubility parameters are similar to those of the female non-polar resin Waterborne polyurethane can also be divided into 3 types: polyurethane aqueous solution, polyurethane aqueous dispersion and polyurethane emulsion Polyurethane aqueous solution is rarely used in coatings, and the latter two are sometimes referred to as polyurethane emulsion or polyurethane water dispersions According to the composition, it can be divided into single component and two component The single component belongs to thermoplastic resin, and the polymer does not cross-linking in the film forming process, which is convenient for construction The two-component waterborne polyurethane coating is composed of water-borne polyols containing active NCO curing agent component and active hydrogen (hydroxyl) which can react with NCO Before construction, the two components are mixed evenly, and cross-linking reaction occurs in the film forming process The coating has good performance ① One component waterborne polyurethane coating one component waterborne polyurethane coating is the earliest used waterborne polyurethane coating, with high elongation at break (up to 800%) and appropriate strength (20 MPa), and can be dried at room temperature Because high molecular weight polymer can not form good and stable water dispersion, the traditional one component waterborne polyurethane coating is usually low molecular weight or low crosslinking degree And there are hydrophilic groups in the structure If the salt forming agent can not escape completely during the drying and curing process, the hydrophilic groups will remain in the system, and the water resistance of the coating film is poor Moreover, the chemical resistance and solvent resistance of one component polyurethane water dispersion coating are poor, and the hardness, surface luster and brightness of the coating are low Machinery for further improvement of one component waterborne polyurethane coating As for chemical resistance, reactive groups can be introduced for cross-linking or composite modified base materials to improve coating performance Multi functional reactants such as polyols, polyisocyanates and polyamines can be selected to synthesize waterborne polyurethane dispersion with cross-linking structure; internal cross-linking agents such as carbodiimide, methylimide and azacyclopropane can be added; thermally activated cross-linking and self-oxidation are used Chemical crosslinking, etc Combined with epoxy resin, the higher branching degree of epoxy resin is introduced to the polyurethane main chain, which can improve adhesion, drying rate, film hardness and water resistance of emulsion coating Composite emulsion with low surface energy, high temperature resistance, water resistance, weatherability and permeability is prepared by compounding with polysiloxane, and compounded with arenoic acid, and the tensile strength and impact resistance of polyurethane are higher Excellent flexibility and wear resistance, combined with good adhesion and appearance and low cost of acrylic resin, prepare high solid content and low cost polyurethane acrylic acid (PUA) composite emulsion ② Two component waterborne polyurethane coating two component waterborne polyurethane coating has the reaction of water and one NCO, the drying speed is slow, and bubbles are easily produced in the coating process Through the research, we can use the different reaction rate of one nc0 with water and one Oh, and choose the appropriate water-borne polyol and curing agent to obtain the two-component waterborne polyurethane coating with practical value The gloss, hardness, chemical resistance and durability of the coating can be equivalent to that of the solvent type two-component In order to obtain a practical coating with uniform surface and internal quality, the two-component polyurethane water dispersion coating should also meet the following two conditions: (1) the polyol system should have the emulsifying ability, so as to ensure that the polyurethane curing agent (especially the curing agent without hydrophilic modification) is easy to emulsify after the two components are mixed, which has the dispersing function, so that the particle size of the dispersion is as small as possible, so as to be more effective in water Good mixing and diffusion; (2) the viscosity of curing agent should be as small as possible, so as to reduce the amount of organic solvent, even without organic solvent, and at the same time, it can ensure that it is well mixed with components containing hydroxyl In order to obtain the waterborne polyurethane coating with better comprehensive properties, the two-component waterborne polyurethane needs to be improved in the aspects of monomer and auxiliary agent, synthesis process, cross-linking technology and optimization of composite At present, it mainly includes acrylic acid modification, epoxy resin modification, organic silicon or fluorine modification, nano material composite modification system, etc Due to the excellent performance of water-based two-component polyurethane compared with other water-based coatings, it can meet the coating performance requirements of most plastic varieties, and will be one of the main varieties of water-based plastic coatings in the future (3) UV curable waterborne coatings are generally composed of water-based oligomers, photoinitiators, additives and water Under the action of photoinitiator, the unsaturated functional groups of water-based oligomers were polymerized by UV irradiation This kind of unsaturated resin is mainly obtained by unsaturated functionalization of common resins According to the chemical structure and composition of the oligomer, it can be divided into four categories: unsaturated polyester, polyurethane acrylate (PUA), polyacrylate and polyester acrylate They can be water-soluble or emulsion or hydrosol Among them, PUA coating has the best comprehensive performance, good hand feel, flexibility, high impact resistance and tensile strength Compared with traditional solvent based coatings, water-based coatings for plastics have great advantages in safety, environmental protection and VOC emission, but their construction surface is narrow, and they have special requirements in paint mixing, mixing, spraying, drying, transportation, storage and other links, so there are still many problems in the promotion and application However, it is the general trend to reduce the emission of industrial wastes and energy consumption Waterborne coatings will gradually become the preferred coating materials for environmentally conscious customers and enterprises Home of coatings is specialized in coatings, diatom mud, paint coating, coating technology, fire retardant coating news and coating, diatom mud, paint coating, coating technology, fire retardant coating decoration knowledge and decoration renderings,