Study On The Preparation Of Emulsion Type Sizing Agent And Its Effects On Printability

In recent years, printing industry demands higher standards of the surface strengthand printability of paper. The common starch surface sizing agent is cheap, but its sizingeffect is unsatisfactory. Synthetic polymer surface sizing agents such as styrene acrylicemulsions （SAE）, polyurethane dispersions （PUD） could get good water resistingproperty, but their enhancement of the surface strength is not obviously. Thevulnerability of the anionic synthefic polymer sizing agent was caused by theinteruption of cationic impurities in water, which is bad for sizing.A cationic type starch graft copolymerization emulsion surface sizing agent （CSCE）with low price and excellent properties was synthesized in this paper. During thesynthesis of CSCE, the enzyme converted cation starch （CS-8） was used as the skeleton,and H₂O₂-FeSO₄redox initiator system was as initiator. Styrene （St）, butyl acrylate（BA）, functional monomer acrylamide （AM） and cationic monomer methyl acryloyloxygen ethyl trimethyl ammonium chloride （DMC） were copolymerized to cation starchskeleton by grafting copolymerization. The optimum condition of synthesizing CSCEwas discussed, and the product in the optimum condition was characterized by IRspectrum and its physical performance was tested. The results showed that the optimumconditions of synthesizing CSCE were as follows: m （starch）: m （St+BA）=1:2, m（St）: m （BA）=2:1, the dosage of initiator3.2%, m（FeSO₄）: m （H₂O₂）=2:100, AM4%, DMC2.8%, reaction temperature80℃, reaction time3.5h. The testing resultsshowed that the starch graft copolymer emulsion was the random copolymer of starchand four kinds of monomers, pH was3⁴, solid content was30±1%, charge densitywas mmol.g^-1and viscosity was less than20mpa.s.The application of CSCE in the board paper, the compound sizing conditions ofoxidized starch and CSCE, and the effects of reaction conditions on sizing performanceof CSCE were studied. The results showed that, when the ratio of the oxidized starch toCSCE was4:96, sizing concentration was5%, and pH was6, paper Cobb value wasreduced to21.6g/m²and ring crush index was11.44N.m/g, increased by32.56%compared with base paper. Grafting crosslinking monomer AM and cationic monomerDMC can improve sizing performance of the starch graft copolymerization emulsionand enhance ring crush strength of sizing paper.The application of CSCE in offset paper and its influence on printability were studied. In experiments, IGT printability tester was applied in six color proofing ofyellow（Y）, magenta （M）, Cyan （C）, red （R）, green （G）, blue （B）, paper fielddensity and the three stimulus value were measured with a spectrophotometer, thecorresponding color gamut graph was drawn according to the chromaticity coordinatecalculated, and the effect of CSCE on the paper printability was explored. The resultsshowed that while oxidized starch, SAE and CSCE were exclusively used, the effects ofCSCE on improving offset paper printability and paper color performance was best, andthe effect of compound sizing of using oxidized starch and CSCE was better than that ofusing oxidized starch and SAE surface sizing agent.The innovation of this essay is that CESE was synthesized through free emulsionpolymerization, using several monomers on cationic sharch grafted modification, and itseffect on paper surface performance and printability was studied, which provides thebasis for the development of new products and its application.