Modification of acrylic adhesives
Polyacrylate is a kind of polymer with a variety of properties, and a wide range of uses, the emulsion is generally methyl acrylate, ethyl acrylate, or butyl acrylate as the main monomer, and methacrylate monomer, styrene, acrylonitrile copolymerization emulsion formation. By improving the structure of the polymer or the polymerization method, the properties of the modified acrylate adhesive are more excellent.
1. Modification of silicone
Organosilicone resin has excellent high and low-temperature resistance and water resistance. Modification of polyacrylate emulsion adhesives by organosilicon has become a hot research topic in recent years. Organofunctional alkoxy silane is widely used in adhesives, sealants, and coatings as a bonding accelerator and crosslinking agent. Experts have studied a special water-based system of organosilane Wz-A in the application of water emulsion polyacrylic sealant, this water-based silane can significantly improve the mechanical properties and bonding properties of sealant without changing the stability of the product, the addition of Wz-A in 0.8%-1.6% is more appropriate. Experts through the emulsion polymerization method, using hydroxy-silicone oil and silane coupling agents A-151 and KH-570 for chemical modification of acrylate, with the silane coupling agent in the carbon-carbon double bond and siloxane structure to connect hydroxy-silicone oil and acrylate, the results found that through KH-570 modified acrylate emulsion adhesive in the performance has been significantly improved. Vinyl-modified silicone emulsion was prepared by ring-opening polymerization of octamethylcyclotetrasiloxane and vinyl-terminated silane coupling agent. When the reaction temperature is 80℃, the catalyst is dodecylbenzene sulfonic acid, and the silane coupling agent is A-151, the core-shell emulsion has A high conversion rate of vinyl-modified silicone emulsion monomer and good emulsion stability. Using the emulsion as seed emulsion to modify polyacrylate emulsion, a kind of printing adhesive with good softness and the color fastness can be prepared.
2. Epoxy Modification
By grafting copolymerization of acrylic ester and epoxy resin, the epoxy group can be crosslinked under the action of the curing agent, so that the system can finally form an interpenetrating network structure with epoxy resin crosslinked network as the skeleton and acrylic resin through it. The modified polyacrylate emulsion has the characteristics of high strength of epoxy resin, good adhesion, excellent weather resistance of acrylate, and good flexibility. Chemical experts use core-shell polymerization technology, the mass fraction of epoxy resin is 30%, copolymer glass temperature is 243.15K, can prepare curable emulsion pressure sensitive adhesive, curing of aluminum alloy bonding strength up to 10MPa, adjust the proportion of epoxy resin and polymer glass temperature, can change the performance of pressure sensitive adhesive. The epoxy resin was added into the polymerization system, and the epoxy resin-modified vinegar-propyl emulsion adhesive was prepared by emulsion polymerization. The bonding strength, film-forming properties, film hardness, and stain resistance of the adhesive were improved to different degrees. The product can produce good results when used as an adhesive.
3. Blending modification
The acrylic adhesive modified by crosslinking and copolymerization sometimes has some shortcomings such as poor weather resistance, low temperature, and poor stability. Experts used benzoxazine with high heat resistance and acrylic copolymerization emulsion to get the excellent performance of modified polyacrylate adhesive. Under the action of heating and catalyst, the ring-opening polymerization of benzoxazine was carried out to form a nitrogen-containing network structure similar to phenolic resin. After curing, the adhesive formed an interpenetrating network structure. The modified adhesive obtained has the characteristics of high-temperature resistance, dimensional stability, flame retardant, and environmental friendliness. The use of benzoxazine improved the heat resistance of the substrate, and the substrate made of modified adhesive could not be stratified or bubbled in the tin bath at 350℃ for 10s.
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