Application of Organosiloxanes in Coatings Analytical Coating Resin Adhesion to the substrate surface is usually negligible, especially when the polymeric resin does not bond with the substrate surface with chemical affinity. Usually, manual peeling with mechanical force or partial automatic delamination at the edge of the facility are signs of poor adhesion. In addition, moisture, acids, or bases often further accelerate the failure of the adhesion. Organosiloxane is a kind of silane coupling agent, and its general chemical formula is Y(CH2)nSiX3. Among them, n is 0-3; X is a hydrolyzable group that can react with inorganic substrates, mainly alkoxy groups; Y is an organic group that can react with organic materials, mainly including vinyl, amino, Functional groups such as epoxy group and mercapto group. When organosiloxane acts, the X group is hydrolyzed to generate silanol, which reacts with the hydroxyl group on the surface of the inorganic substrate to form siloxane. Through the Y group, the purpose is to chemically react with the organic matter and chemically react with the inorganic substrate. The material and organic matter are connected together to improve the performance of the coating, increase the bonding strength, and play the role of coupling.
There are three main ways to use organosiloxane as an adhesion promoter for coatings:
(1) As a substrate treatment agent: usually add 3-10% organosiloxane, a mixed solvent composed of water and solvent, and mix it by cold blending, and then treat the substrate to act as an adhesion promoter;
(2) As a reactive monomer: blend 0.5-5% of organosiloxane with conventional monomers of synthetic resins, and then carry out copolymerization reaction, so that the structure of the resin is inserted into the siloxane structure, and the siloxane plays a role The role of crosslinking agent, promote the adhesion of resin and substrate, improve the mechanical properties and water resistance of resin, etc.;
(3) As a post-additive additive: add organosiloxane monomer to the resin at 0.2-5% of the solid content of the resin, and after an induction period of about 12 hours, then mix the resin with other additives and The filler is mixed and ground to prepare the coating, thereby improving the adhesion of the coating to the substrate. Some examples of current specific applications include: as a substrate treatment agent, blending aminosiloxane with mixed solvents such as water, isopropanol, butanol, and butyl cellosolve, wherein the amount of water is the amount required by the silicone Determine the amount of water for pre-hydrolysis, spray, dip or brush the surface of the cleaned substrate to obtain a coating with a thickness of 2-3 microns, let the surface dry, and apply the surface coating within 24 hours to achieve enhanced coating adhesion. Focus on the function; as the application of polymer copolymerization modified monomer, pre-emulsify vinyl siloxane, and conventional acrylate monomer, and then initiate copolymerization by the initiator to obtain siloxane-modified acrylate emulsion , during the drying and film-forming process of the modified emulsion, the siloxane will be hydrolyzed and condensed, so that the acrylate chain segments can be condensed to obtain a Si-O-Si cross-linked structure through the condensation between silanols, which plays a role in cross-linking. The role of the monomer. Or in the process of preparing polyurethane, use amino or epoxy-containing siloxane and isocyanate group to carry out capping reaction, and introduce siloxane into the chain segment of polyurethane to play the function of modifying monomer; as a post-additive additive For the application of the epoxy resin, after the preparation of the epoxy resin, add the amino-containing siloxane, use the grafting reaction of the amino group and the epoxy group to introduce the siloxane group, and then introduce a small amount of water mixed solvent to hydrolyze the siloxane and then carry out Condensation to get the designed structure, and then introduce coating additives and various fillers to grind and disperse to prepare coatings with improved properties.
Due to their unique structural features, organosiloxanes have been widely used by manufacturers of industrial resins and adhesives to modify the adhesion of resins and coatings to substrates and enhance other mechanical properties. In the future, it is imperative to study multifunctional and multi-variety modified organosiloxanes in coatings, so as to prepare coatings with better performance and improve the variety and performance of coatings.