Study On The Preparation Of Anionic Waterborne Polyurethane With High Solid Content And The Bonding And Film-Forming Mechanism As Shoes Adhesives

Waterborne polyurethane (WPU) is a new type of polyurethane system with water as the dispersion medium. Because WPU is non-toxic, environmentally friendly and safe, it has attracted widespread attention at home and abroad. The application of waterborne polyurethane as shoe adhesives has become a hotspot of recent research due to the excellent flexibility, impact resistance, abrasive resistance and low temperature resistance. The authors prepared series of anionic waterborne polyurethane latex by composite modification, and a detailed study of the structure and properties of complex systems to explore the mechanism of their synergy. The main content of this paper is as followings:1.A water-based polyurethane adhesive was prepared. -COOH content has great effect on the water resistance, mechanical property and stability of WPU. The tensile strength of the WPU films increased with the increasing -COOH content while the water resistance decreased. The emulsion is unstable when w(COOH) is less than 1.45%. Increasing TMP content can improve water resistance and mechanical property of WPU films, the proper w(TMP) is 2%. The tensile strength of the WPU films increased with the increasing -NCO/-OH molar ratio. WPU with better combination property can be obtained when w(-COOH) is 1.60%,-NCO/-OH molar ratio is 1.4 and w(TMP) is 1.0%. T-style peeling strength increased with the increasing solid content of WPU adhesive. T-style peeling strength increased and then decreased with the increasement of n(NCO)/n(OH), COOH content, TMP content and molecular weight of polyurethane. When the WPU with solid content of 35% is used as leather adhesive, the T-style peeling strength is 12 N/(2.5cm). The polyurethane adhesive need to be further modified.2.A sery of modified waterborne polyurethane was prepared with BDO as chain extender, HEA as endcapper, MMA and BA as monomers and AIBN as initiator. The solid content of prepared waterborne polyurethane is more than 40%. After modification, the drying rate of WPU adhesive and the bonding strenghth can be both improved. On the other hand, production cost of waterborne polyurethane decreased. FTIR analysis indicates that acrylate has reacted. The morphology of emulsion were observed by Transmission Electron Microscope(TEM). TEM images display that the particles were well dispersed. The particle size of WPU increased and the distribution width becomes wider after the modification.TG analysis indicates that crosslinking degree and thermal stability of WPU modified with acrylate is increased. DMA showed that the modified WPU has a higher glass transition temperature. The adhesion, water resistance and thermal stability were improved by the increasing HEA and acrylate dosage. T-style peeling strength is 52.9 N/(2.5cm) as the mass ratio of MMA and BA is 4:2. The tensile strength of the WPU films is 19.6MPa, the elongation at break is 533.7%, the adhesive has good mechanical property and flexibility. BDO as chain extender can improve mechanical property of WPU, the proper w(BDO) is 1.5%. When the w(-COOH) is 1.6%, w(TMP) is 1.0%, w(HEA) is 4%, w(PA) is 30%, m(MMA):m(BA) is 4:2 and w(BDO) is 1.5%, The modified WPU has good water resistance, thermal resistance and flexibility, the bonding strength can reach 52.9 N/(2.5cm). The solid content of WPU with acrylate can reach 45%, which can improve the drying rate of WPU adhesive.With the increasing of the molecular of soft segments, the phase inversion delays. The decrease of NCO/OH molar ratio, increase of carboxyl content, HEA content and neutralization degree will increase the viscosity of system and more water was needed for the phase inversion.3. The natural glucose was introduced to the polyurethane mainchain as crosslinker, the waterborne polyurethane with solid content of 50% can be prepared. Combination property of the modified waterborne polyurethane can be improved evidently.The FTIR test results indicated that the glucose has been introduced into the main chain of polyurethane. XRD indicated that the degree of crystallinity decreased after the glucose has been introduced to the polyurethane, which showed the glucose has reacted with -NCO . With the increasing of glucose content, the stability WPU decreased. The WPU is stable when solid content of WPU is less than 60%. Dynamic rheological investigation showed that loss modulus(G'') and storage modulus(G′) both increased with oscillation frequency. Viscosity of the polyurethane emulsion increased and then decreased with the increasement of glucose content.The decomposition temperature of WPU films increased with increasing glucose content. Surface free energies decreased with addition of glucose and the medium resistance of WPU films is improved. Water and solvent absorption decreased with increasing R value. The tensile strength of the WPU films increased and the elongation at break decreased with increasing glucose content. As the glucose content increases from 0% to 4.68%, the T-style peeling strength increases 57.3N/(2.5cm) to 116.1 N/(2.5cm). The curing time of WPU samples were decreased with increasing glucose content. The bonding mechanism of WPU adhesives was investigated.4. The glucose was introduced to the polyurethane mainchain as crosslinker, the deionized water and carboxy styrene-butadiene latex were added to the polyurethane system and the waterborne polyurethane with solid content of 50% can be prepared. The effect of carboxy styrene-butadiene latex on properties of the waterborne polyurethane was studied in this chapter and synergistic action between waterborne polyurethane and carboxy styrene-butadiene latex was investigated. TEM photos show that WPU emulsion and CSBL werewell-dispersed with round appearance. The average particle size of WPU emulsion increases from 58.45nm to 70.7nm with increasing w(glucose). WPU emulsified by CSBL has bimodal distribution. The synthesis mechanism of WPU was investigated.The rheological behavior of polyurethane emulsion was studied. WPU emulsion exhibiting pseudoplastic liquid behavior. WPU emulsion with high solid content of 60% has thixotropy, while WPU emulsion with low solid content has no obvious thixotropy. When CSBL content increases, the WPU will be well emulsified, so the thermal stability of WPU increases. Compared with WPU and CSBL films without modification, mechanical property of polyurethane films modified by carboxy styrene-butadiene latex increased obviously. T-style peeling strength of the modified adhesive reach maximum when the w(CSBL) is 50%.