Study Of Nanometer TiO₂ Modified Polyacrylic Copolymer Sizing Agent

Up to now,acrylic size has enhanced its property and sizing quality,but the acrylic size dosage in size formula is still limited and can't totally take the place of that of PVA,for its high moisture absorption and insufficient adhesion forces.Especially,PVA is used more or less in the size formula of extra high-count and high-density pure cotton,polyester/cotton,and etc. Corresponding to these problems,it is put forward in this thesis that to disperse nano TiO₂ particles fully in the acrylic monomer water solution,and then participates in synthesis of nano TiO₂ modified polyacrylic size at the nanometer level.This paper presents two steps for the study of nano TiO₂ modified polyacrylic size.Firstly, the molecular structure of the polyacrylic size was determined according to the requirement of size property,which should be:the branched main chain is three dimensional structure of～C—C—C—C—C—C～,with the branch chains containing:1) -COOH(-COONH-O) group, which increases the water solubility and desizing property of size.To decrease the moisture absorption,the side group shouldn't contain -CONH₂ or -CN groups,for their strong polar and high moisture absorption;2) -000R(R is alkyl) group,which makes synthetic size sufficient adhesion forces,good film forming ability,and -CH₃ group can adjust the molecule flexibility; so the monomers which are used in synthesizing the polyacrylic size should mainly include acrylic acid,ethyl acrylate,butyl acrylate,methyl methacrylate.However,the molecular structure includes not only the composition of the molecules,but also the proportion of each monomer.Aiming at this question,the composition of the molecules was studied in this paper by the orthogonal design of four factors and three levels,and the optimum scheme is A₃B₃C₁D₁, which was acrylic acid:ethyl acrylate:butyl acrylate:methyl methacrylate=15:50:20:10. Moreover,the synthetic conditions were optimized,and the novel nano TiO₂ modified polyacrylic size was synthesized at the optimized monomers' amount.The test results showed that the size has low viscosity(temperature 25℃,concentration 5%,viscosity 5.8mPa·s),high adhesion forces to T/C(94.1N).It also behaves well in yarn breaking strength(346.8cN), elongation(8.2%),wear resistance(110 times),and etc.Secondly,on the base of the optimizations of the monomers,the effects of nano TiO₂ amount on the size property and sizing quality were studied.On the consideration of process factors such as property and price,the optimum amount of nano TiO₂ was decided as 0.8%.The test results showed that the synthesized nano TiO₂ modified polyacrylic size has low viscosity(temperature 25℃, concentration 5%,viscosity 5.8mPa·s),high adhesion forces to T/C(96.2N).It also behaves well in yarn breaking strength(350.2cN),elongation(9%),wear resistance(158 times),and etc. Comparing its sizing performance with PVA,it was showed that:1) breaking strength was raised 5～10%;2) elongation was increased 10-15%;3) wearing resistance was improved 15～20%.Modification,dispersion and dispersion characterization were also researched,of which the results showed that:1) The comparatively ideal modified nano TiO₂ was processed by surface modifying nano TiO₂ with a certain amount oleic acid(the optimum amount was 0.2%).The infrared spectrum and thermo gravimetric curve showed that the chemical reaction between oleic acid and nano TiO₂ occurred,and it changed the surface property of nano TiO₂, which was beneficial to dispersion of nano TiO₂;2) When oleic acid was used to modify nano TiO₂,it can not only help disperse nano TiO₂,but also participate in the synthesis of the size. As a result,nano TiO₂ dispersed much good in synthesizing size.It will ensure the synthesis of the nano TiO₂ modified polyacrylic size,and help a lot in sizing yarns with nano TiO₂.But a further research should be carried out in modification and dispersion of nano TiO₂.Especially when the amount of nano TiO₂ is high,the stability of dispersed particles and liquid is not ideal, which limits the dosage of nano TiO₂ used in nano TiO₂ modified polyacrylic size.