Preparation And Modification Of Self-emulsifying Cellulose Acetate Waterborne Polymer Emulsion

Cellulose acetate is an organic acid derivative produced by esterification of natural cellulose with acetic acid.It has the advantages of non-toxic,renewable,flexible and abrasion-resistant film,and is often used as a modified resin,additive or film-forming substance used in various fields.Because cellulose acetate is insoluble in water,only soluble in organic solvents.In the application process,a large amount of volatile organic compounds(VOC)will be generated,causing environmental pollution,therefore,it is necessary to study the water-based cellulose acetate.In this paper,cellulose diacetate(CDA)was used as the substrate,ethylenediamine sodium sulfonate(AAS),dimethylolbutyric acid(DMBA)as the hydrophilic agent,and isophorone diisocyanate(IPDI)as the bridge linking agent under the action of the catalyst,through the reaction of-NCO in the bridging agent with—OH in CA and—OH,—NH2 in the hydrophilic agent,the hydrophilic carboxylic acid group(—COOH)and sulfonic acid group(—NaSO3)was introduced into the CA molecular chain.The sulfamate waterborne cellulose acetate emulsion(SWCA)and carboxylate sulfonate waterborne cellulose acetate emulsion(DSWCA)were prepared,and the prepared emulsions were characterized by structure and performance.In order to further improve the performance of the emulsion and coating film,in this thesis,modified DSWCA emulsion with polyurethane(WPU)emulsion,and the properties of the modified emulsion and its coating film were also studied.The main research contents of this paper are as follows:(1)Study on preparation and coating performance of sulfamate waterborne cellulose acetate emulsion(SWCA).SWCA emulsion was prepared by using AAS as hydrophilic agent and dibutyltindilaurate(DBTDL)as catalyst,in which the-NaSO3 was introduced into CDA by isophorone diisocyanate(IPDI).The effect of molar ratio of IPDI to AAS on the particle size and viscosity of SWCA emulsion,the apparent morphology and water resistance of coating films was investigated.The results showed that when the molar ratio of IPDI to AAS was 1.1,the SWCA emulsion was the most stable,and its microstructure showed an oil-in-water(O/W)core-shell structure.The particle size and dispersion coefficient(PDI)of the emulsion were the smallest,and were 128 nm and 0.112,respectively.At this point,the emulsion had the greatest apparent viscosity of 73.5 mPa·s.The obtained coating film was dense and flat,and exhibited significant hydrophobicity with a contact angle of 110.2°±2°.In addition,compared with CA.SWCA film exhibited a microcrystalline or sub-crystalline structure and the crystallinity of film was weakened,and the film had good heat resistance.(2)Study on the preparation and performance of carboxylate and sulfonate waterborne cellulose acetate emulsion(DSWCA).With low viscosity and relatively high solid content DSWCA emulsion was prepared by using AAS and DMBA as hydrophilic agent,CDA as base material,and 1,4-butanediol(BDO)as a small molecule chain extender,the hydrophilic carboxylic acid group(—COOH)and sodium sulfonate group(—NaSO3)were introduced into the CDA molecular chain under the catalysis of DBTDL,through the bridging agent IPDI.A carboxylic sulfonate waterborne cellulose acetate emulsion(DSWCA)with low VOC content,low viscosity,and relatively high solid content was finally prepared.The effects of reaction temperature,reaction time,DMBA content,AAS content and R value on the properties of DSWCA emulsion were explored,and the optimal conditions and material ratios for the synthesis of DSWCA were obtained.The results show that when the reaction temperature of the prepolymer and CA was 75?,the reaction time was 120 min,the R value of the whole system was 1.3,the DMBA and AAS content were respectively 7.12%and 4.35%,DSWCA emulsion had better performance,which was pale yellow and bluish,particle size was 105 nm,PDI was 0.029,solid content was 40.86%.TEM test showed that DSWCA emulsion particles had a spherical oil-in-water(O/W)core-shell structure.Compared with SWCA,the DSWCA coating film had lower crystallinity and significantly improved water resistance.(3)Preparation of DSWCA/WPU composite emulsion(B-WPC)and study on film properties.First,a polyether glycol N210,DMBA and IPDI were used as raw materials to prepare a WPU emulsion with flexible molecular chain and small particle size by a self-emulsifying method.The WPU emulsion was then used to modify the DSWCA emulsion by physical blending to obtain a composite emulsion B-WPC.The effects of WPU content on the properties of emulsions and coatings were investigated.The results show that When the mass fraction of WPU accounts for 25%of the mixed system,the solid content and average particle size of the B-WPC emulsion were 56.68%and 195.32 nm,respectively.The coating film hardness was B,the wear rate was 0.98%,the mechanical properties were the best,and the film formation time was 1.5 times shorter than WPU.SEM,AFM and contact angle test results show that the surface of the coating film was dense and smooth with a roughness of 2.847 nm and a static water contact angle of 94.6°,showing a certain degree of hydrophobicity.TEM shows that small particles of WPU were evenly dispersed in large particles of DSWCA.Comprehensive analysis of TGA and DTG shows that the thermal stability of the B-WPC composite coating film is better than that of the single DSWCA and WPU.