Study On Amplification And Modification Of Waterborne Polyurethane Adhesive For Footwear

Waterborne polyurethane(WPU)adhesive has the advantage of harmlessness and few environmental pollution for its solvent is mainly water.As the world pays more and more attention on environmental protection and the laws and statute are becoming mature,developing WPU adhesive is highly demanded by shoemaking industry.However,those domestic researches on novel WPU adhesive for footwear are mostly restrained in the phase of lab scale preparation and only a few of them have reached to the phase of pilot scale preparation or manufacturing.And there is no report about manufacturing and applying WPU adhesive to shoemaking product line in industry.There exists several reasons that restrain the development of WPU adhesive,such as unstable properties when amplificating,insufficient initial adhesion strength,poor infiltration effect and bacterial corrupting.In order to overcome the problems of WPU adhesive mentioned above,studies were taken and solutions were provided in this research.In the aspect of amplification preparation,nano-Si O2 is chosen from nano-Si O2 and nano-Ca CO3 to modify WPU adhesive,as a choice for amplification preparation.Through optimization of multiple processing such as temperature controlling and solvent adding methodologys,WPUNS adhesive with 2wt% of nano-Si O2 was successfully prepared in lab scale(1L level and 2L level)and in pilot scale(10L level and 20 L level).Compared with the WPUNS adhesive made within 2L level,the WPUNS adhesive made in the pilot scale preparation has the same emulsion properties and adhesive properties,higher film mechanical properties,better heat resistance,higher water contact angle,and higher water sorption.In general,properties of prepared WPUNS adhesive meet the demands of shoemaking production and the requirements in adhesive for footwear.In order to improve the initial adhesion strength of WPU adhesive for footwear,a new blocked waterborne polyurethane curing agent(BWP)was synthesized with 4-hydroxypyridin as blocking agent,and its structure was confirmed the same as designed.The BWP was mixed with the WPUNS to prepare into a series of WPUNS/BWP adhesive for footwear with different concentration of curing agent BWP.The study showed that when the blocking agent is 12 mol% to the NCO group in the BWP,the WPUNS/BWP-12 adhesive had the best adhesive property and its initial adhesion strength could reach to 5.51 k N·m-1 without using the surface treating agent,which was comparable with the solvent-based PU adhesives product.The target of improving initial adhesion strength of the original WPUNS adhesive for footwear was basically accomplished.Meanwhile,the film of WPUNS/BWP adhesive had better thermal resistance,higher mechanical properties,higher water contact angles and higher water absorption when compared with the film of WPUNS adhesive.In order to overcome the problem of the bacterial corruption of WPU adhesive for footwear,an antibacterial methacrylate monomer derived from thiazole(MEMT)was synthesized with 5-hydroxymethylthiazole(5-HMT)and 2-isocyanatoethyl methacrylate(IEMA),and its structure was confirmed the same as designed.A polyurethane/ antibacterial polymethacrylate(PU/APMA)waterborne adhesive for footwear was successfully prepared by incorporation of MEMT.The study showed that when the MEMT was 15wt%,the antibacterial rates of the PU/APMA waterborne adhesive against Escherichia coli and Staphylococcus aureus were more than 99%,which indicated that adhesive had an outstanding antibacterial property.Furthermore,this adhesive had the best emulsion properties,adhesive properties and mechanical properties of the film,but lower thermal resistance among all of the PU/APMA adhesives.