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How to improve the crosslinking density of the waterborne polyurethane resin?

by:Sinograce Chemical     2020-07-10
Waterborne polyurethane emulsion manufacturers of waterborne polyurethane coating to improve the mechanical properties and resistance to chemical media, change crosslinking performance significantly increase coating performance, so as to enlarge the range of coatings. At present, the crosslinking methods mainly include: (1) stated method, when the emulsion or some synthetic three faculties to join a small amount of degrees or higher faculties compounds form slightly crosslinked, or water to evaporate after can react with active group in molecular compounds crosslinking, such as amide/hydrazide cross-link. Olin companies in the United States recently developed the use of coupling agent on urine butanone as stated new technology. By using this technology can stable emulsion system, polyurethane skeleton of the latex particles containing butyl ketone group. When excessive diamine migrated to latex particles, and the urine butanone forming biuret reaction key, can induce the auxiliary crosslinking reaction. This auxiliary crosslinking reaction occurred within the latex particles, enlargement of latex particles of polyurethane molecular chain without affecting the stability of the emulsion, overcome the current one-component waterborne polyurethane coatings of low hardness, water resistance and solvent resistance of bad faults. (2) gas dry method, namely the use of oxygen in the air so that waterborne polyurethane chain unsaturated carbon carbon double bond oxidization crosslinking. (3) the foreign method, diplomatic method can significantly improve the coating performance, according to different crosslinking agent, the foreign modifying can be divided into the following several kinds: ( 1) N propyl organism compounds crosslinking n propyl organism is a good crosslinking agent of carboxyl, room temperature n propyl organism can produce fast reaction to form crosslinked with carboxyl, reactive as shown below. ( 2) Epoxy/connected under the condition of room temperature and moderate temperature can epoxy group and carboxyl and hydroxyl groups in the resin to chemical reaction, the reaction is as follows. This type of reaction can also be used in the emulsion synthesis light crosslinking for latex particles. ( 3) Siloxane/came special functional groups of siloxane emulsion and the reactive hydrolytic condensation and crosslinking, such as epoxy siloxane and latex particles of carboxyl reaction, reactive as follows. ( 4) More carbon 2 imine crosslinked carbonization with - imine COOH form crosslinking reaction, can be used as a crosslinking agent, waterborne coatings equation is as follows. ( 5) Metal ion crosslinking ammonium carbonate zirconium salt or ammonium carbonate zinc salt and resin crosslinking reaction of carboxyl of room temperature, the ionic bond has good heat resistance and alcohol resistance, after crosslinking film hardness and water resistance can be improved, the equation is as follows. Waterborne polyurethane emulsion is by adding nitrogen in the WPU before construction c organism, carbide imide, foreign agent such as melamine, coating film after its solvent resistance increased significantly. In addition to the crosslinking modification, can also in waterborne polyurethane system into other components, composite modification, this is an important way of promoting the polyurethane modified. At present, the polyurethane with hydroxymethyl cellulose, polyvinyl alcohol, vinyl acetate, styrene butadiene rubber, epoxy resin, polysiloxane and polymethyl methacrylate composite emulsion were studied. Among them, the three kinds of active compound emulsion research: epoxy resin modified is - in the polyurethane prepolymer NCO with the reaction of epoxy groups of epoxy resin chain, has greatly improved the comprehensive performance of polyurethane dispersion; Polysiloxane is commonly polysiloxane polyurethane and polyurethane block copolymer, has the very good mechanical properties, flexibility, performance and surface performance; Acrylate modified polyurethane ( PUA) Emulsion of polyurethane can be high tensile strength and impact strength, excellent flexibility and wear resistance, and good adhesion of polyacrylate, organic combination of low cost, preparation of high solid content, low cost of waterborne polyurethane resin. Both crosslinking modification and composite modification of polyurethane, they belong to a one-component polyurethane ( Or a set of crosslinker quantity few) , the coating performance is not ideal enough, also can use of one-component waterborne coating baking post-processing, such as to improve the coating performance. Want to get a higher performance of coating, must also adopt a two-component polyurethane system.
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