Synthesis And Performance Of Waterborne Polyurethane Polyacrylate Containing Sulfonated Soft Segment

Because of scarcity of the oil resources and environment pollution, waterborne polyurethane has been attracting the attention of people from the solvent-based polyurethane. Waterborne polyurethane has advantages such as environmental friendliness, good flexibility and wearability, so it has been widely used coatings, package printing, adhesives, leather and papermaking. According to the market requirement of soft package, the waterborne polyurethane used for cigarette case package is required to be nontoxic, and the volatile organic solvents (VOC) content absolutely accorded with the new national standard of cigarette case package. Waterborne polyurethane is a kind of block polymer with soft and hard segment, the excellent properties such as heat resistance, flexibility and wearability of waterborne polyurethane are from the reaction between hard and soft segments. Waterborne polyurethane emulsion containing sulfonic groups (SWPU) with high solid content and good stability was prepared using polyester glycol containing sulfonic group (SPD205) as soft segment, isophorone diisocyanate (IPDI) as hard segment, ethylene diamine sulfonate (A95) as hydrophilic chain extender,1,4-butanediol (BDO) as chain extender, and hydroxyl ethyl acrylate (HEA) as a capping agent. Both butyl acrylate (BA) and methyl methacrylate (MMA) monomer were used to modified SWPU by copolymerizing in the seed emulsion, therefore, the sulfonated waterborne polyurethane-polyacrylate (SWPUA) was obtained and the performance of the emulsion and the films were improved. The polymerizable acrylate monomers were added to act as solvent during the SWPU preparation, and the high viscosity of polyurethane prepolymer can be overcomed, so the sulfonated waterborne polyurethane-polyacrylate (SWPUA) with core-shell structure was synthesized successfully during the preparation process without adding any organic solvents. By this method, the emulsification can be controlled conveniently, solid content of the SWPUA emulsion is as high as 54% and the storage stability is good. This emulsion product is environmental friendly water-based polymer materials without VOC, especially it does not contain neutralizer triethylamine, thus it can be applied in package printing for PET and aluminum foil paper with high gloss in cigarette case package. This paper studies the preparation and properties of SWPUA emulsion and its films of different material ratio, and the optimal formula of preparation SWPUA emulsion were determined. The main research content of this article is as follows:(1) The structure of polyurethane was characterized by fourier transform infrared spectroscopy (FTIR), the result showed SWPUA was successfully obtained. The test result of transmission electron microscope (TEM) showed that SWPUA latex particle has core-shell structure and uniform distribution of particle size, the average particle size is no more than100nm. The scanning electron microscope (SEM) photograph shows that the film surface is smooth and the introduction of PA can reduce the irregularity on the film surface, which make the film surface more smooth. Contact angle test result showed that the introduction of PA can increase the water resistance of films. Thermogravimetric analysis (TG) indicated the decomposition temperature of hard segment of SWPU is 326? and the decomposition temperature of soft segment is 405?. The TG show that the heat resistance can be improved with the increase of PA content.(2) The influence of different R value on SWPU emulsion and films was studied. The result shows that different mechanical properties of SWPU films can be obtained by changing the ratio of soft and hard segments when SPD205 content is 40%. With the increase of R value, elongation at break of SWPU film decreased and the tensile strength of the films increased. The frozen sTab.ility and storage sTab.ility of emulsion are excellent when the R value is 1.4 and the emulsion can be stored for more than 12 months.(3) The influence of different SPD205 content on SWPU emulsion and films was studied. The shows that when SPD205 content is 40%, the emulsion performance is the best, the emulsion has good appearance, and the average particle size is no less than 36.8 nm. With the introduction of PA, the average particle size of the emulsion increases gradually. The influence of different PA content on SWPUA emulsion and films were also studied. With the increase of PA content, the tensile strength of SWPUA films increases from 5.658 MPa to 5.658 MPa gradually while the elongation at break of the films decreased from 375% to 242%. When the PA content is 30%, the water absorption of SWPUA films is the lowest and the SWPUA emulsion has the best sTab.ility.(4) The influence of initiator KPS content on the reaction was studied. The results show that the total conversion rate is highest when the KPS content is 1.5% of the total mass of MMA and BA. In this case, the emulsion is the most stable. The performance of the waterborne colored paint prepared with this SWPUA emulsion is excellent and it can be used for cigarette packaging.