Preparation And Properties Of Silicone Modified Waterborne Polyurethane Coating Agent

Waterborne polyurethane which is one of the prior choice material in fabric coating agents, has advantages of good filming, flexibility, friction, adhesive fastness to fabric and environmental. However, the water resistance of it is poor, moreover, it requires additional cross-linking agent as being used to coat fabric, the operation is cumbersome and less environmental. In view of this, the self-crosslinking agent was applied to prepare the self-crosslinking waterborne polyurethane in this paper, then on this basis, the crosslinking silicone modified polyurethane was synthesized with silicone monomer, which needed no external crosslinking agent, and reached excellent water resistance, permeability and feel of the coated fabric. The paper is divided into three parts:Part one: The emulsion of self cross-linking liphatic waterborne polyurethane was synthesized with prepolymer prepared by isophorone diisocyanate and poly propylene oxide polyether and chain extenders such as dimthylol propionic acid (DMPA), trimethycolpropane (TMP), 1,4-butanediol (BDO). The effect of reaction temperature and time on the conversion of—NCO and the influences of these factors such as initial R value(n(—NCO)/n(—OH)), dosages of hydrophilic monomer and self-crosslinking monomer on the properties of polyurethane emulsion and its film were investigated, and the self cross-linking liphatic waterborne polyurethane was applied to coat the fabric , the hydrostatic pressure, washing resistant to the coated fabric were tested. The results showed: the optimal conditions for synthesis of cross-linking waterborne polyurethane was that pre-polymerization temperature was 80℃,reaction time was 2h, hydrophilic chain extending reaction temperature was 85℃, reaction time was 2h, the dosage of hydrophilic monomer was 4%, the dosage of self-crosslinking monomer was 40%.The the hydrostatic pressure of fabric coated with self cross-linking waterborne polyurethane was 239mm and its washing resistance was 26 times. The water resistance and washing resistant of fabric coated with self cross-linking waterborne polyurethane were improved obviously compared with non-modified polyurethane, and matching the performance of plus cross-linking waterborne polyurethane.The part two: The emulsion of self cross-linking silicone-modified waterborne polyurethane(Si-WPU) was synthesized with prepolymer prepared by isophorone diisocyanate, polyether210 and polyethersiloxanediol (PESO) and chain extender such as dimthylol propionic acid (DMPA), trimethycolpropane (TMP), 1,4-butanediol (BDO). The effects of the dosage and molecular weight of PESO on the properties of modified polyurethane emulsion and its film were investigated; FT-IR was used to characterize the structure of silicone-modified polyurethane; And self cross-linking silicone-modified waterborne polyurethane was applied to coat the fabric, the hydrostatic pressure, stiffness of fabric coated with Si-WPU were tested. The results showed: the emulsion of Si-WPU had good stability and a small size of particle, the water resistance and mechanical properties of the Si-WPU film were good when the molecular weight of PESO was 4600 and the amount of PESO was 6%; The FT-IR analysis showed that the Silicon chains had been grafted to the polyurethane molecular chains; The hydrostatic pressure and stiffness of the fabric coated with Si-WPU were 322 and 2.98 respectively. The hydrostatic pressure and fell of the fabric coated with polyurethane modified by polyethersiloxanediol were increased obviously compared with non-modified polyurethane.Part three: Self-made self-crosslinking silicone-modified waterborne polyurethane was applied to coat the cotton fabrics, the effects of dosage of caoting agent,curing temperature and curing time on the properties of coated cotton fabric were investigated, and the coating process conditions were optimized, the performance of fabric coated with self-made silicone-modified waterborne polyurethane was tested, and compared with non-modified waterborne polyurethane and commercially available silicone-modified waterborne polyurethane. The results showed that the optimization conditions of coating process with self-crosslinking silicone-modified waterborne polyurethane were that caoting agent dosage was 10 g/m2, cured at 140℃for 3min.Compared with non-modified waterborne polyurethane, cotton fabric coated with the silicone-modified waterborne polyurethane has better water resistance, permeability and softness.