Synthesis And Propertiers Of Novel Waterborne Polyurethane For Adhesives

Conventional solvent-based adhesive more contains a large number of organic solvents, all of it would volatile into the atmosphere in process of synthesis and application, this will hidden fire disaster in the work environment, and cause huge pollution for the global environment, and also cause occupational disease of shoemaking work. The water-borne polyurethane (WPU) adhesive refers to polyurethane soluble in water or dispersed in water formed adhesives, also called stream or water-based polyurethane. Bonding performance of this adhesive is good, ferric phy-sical adjustable range of big, can be used in a variety of base material adhesive.Prepare polyurethane emulsion used aliphatic diisocyanate and aromatic diisocyanate. The mechanical properties of aromatic polyurethane Materials is good, but it's easily become yellow, benzene structure of aromatic diisocyanate makes thermal activation temperature of water dispersible liquid higher. Hydrolysis resistance, good stability, anti-yellowing of aliphatic polyurethane is better than aromatic polyurethane's. Secondly, the reactivity of reaction between groups isocyanate and water was lower than aromatic polyurethane's, and preparation technology of aliphatic polyurethane was easy to control, the isocyanate group of aromatic polyurethane connected to the benzene rings, due to products by sunshine easy oxidized into hydroquinone and turns to yellow, but products of aliphatic Style have a good performance of resistance to sunshine. With IPDI raw WPU adhesives have little reported, less research in enough detail. This paper studies the influences of different process condition, different raw material matching in emulsion stability of WPU, properties of membranous, plastic mechanics performance and heat-resistant property. In this paper, series of waterborne polyurethane were successfully synthesized by polypropylene glycol (PPG), isophorone diisocyanate(IPDI) and dimethylol propionic acid(DMPA) as primary materials. The catalyst was dibutyltin dilaurate. Triethylamine(TEA) were added for neutralization reaction, and the ethylene diamine (EDA) used as the secondary chain extender was added. Analyzes the mechanism of polyurethane synthesis; The influence of vacuum reaction time, reaction temperature, DMPA content, n-NCO/n-OH and the extent of neutralization on the performance of waterborne polyurethane emulsions and films were discussed. we test structure characterization and heat resistance, crystallization properties of WPU film by FTIR and TG, X-RD. The main research papers were summarized in the following statements.(1) Use IDPI, PPG 1000, DMPA as main raw materials synthesis water-borne polyurethane, by single factor experiment show that the best process:best dehydration temperature of PPG is 120℃, and best time for 40mins.The best reaction temperature between 100℃and 110℃,and best reaction time is 2 hours. The best neutralizing temperature is 50℃, and time is 30mins.(2) R value is the molar ratio between -NCO and -OH. R value on the performance of WPU influence. By single factor experiment indicate that the best ratio between n(-NCO) and n(-OH) is 1.6:1, at this time WPU emulsion have the best stability, stability time is big than 180 days. Adhesive ability at optimal, the end stripping can reach 9.6 N/mm. and the heat resistance is arrived optimal.(3) DMPA as the hydrophilic agent of WPU have a important influence in the adhesive. By single factor experiment indicate that:the Optimum quality ratio of DMPA is 4.5%. At this condition the emulsion content arrived 45%, overestimate content can reduce the transportation cost, improve adhesive utilization. Emulsion stability is longer than 120 days; Yellow index of less than 13%. As DMPA content increased, the bibulous rate of WPU film is bigger, water hygroscopicity is moderate. End peel strength reached at 8.6 N/mm, this is because-COO- has strong polarity, it can product hydrogen bond with substrate, increase the end peel strength. If DMPA content too high, it will cause molecules difficulty moving and unfavorable to peel strength instead of improving. At the same time, DPMA will reduce film crystallization degree, increasing polyurethane molecular microfacies separation degree, enhancing film thermal decomposition of temperature.(4) Best neutralization degree range in 90% to 100%, right now the water-borne polyurethane can maintain optimal emulsion stability.(5) Compared with common adhesive from market, test results show that:Self-made product performance has been close to Bayer's products. It solves problems of organic solvents volatile organic compounds (VOC) and harmful gas pollutants (HAPs) from traditional adhesive.