Synthesis Of Anionic Self-crosslinking Styrene-acrylate Copolymer Latex And Application In Papermaking Surface Sizing

Styrene-acrylate copolymer emulsion is used as surface sizing agent due to its’ simpleproduction process, low cost, good ink absorbency and film-forming performance. Thedomestic research started late and compared with a few big foreign chemical companies,there’s still a long way to go, such as poor water resistance, easy foaming, etc. So, it’snecessary to develop polymer surface sizing agent of high efficiency and low prize.In this paper, firstly, the laboratory research of synthesis of styrene-acrylate copolymeremulsion surface sizing agent was adopted based on Minitab software and experiment. Then,styrene-acrylic emulsion synthesis process and formula optimization were determined fromproduct development angle. Pre-emulsified semi-continuous seed emulsion polymerizationmethod was systematically investigated. Fine emulsion polymerization process was explored.The weight ratio of hard and soft monomer, emulsifier, initiator, self-crosslinking and functionalmonomer on emulsion properties ware investigated respectively. Several testing methods suchas FT-IR, Malvern Zetasizer Nano particle size analyzer， and DSC were adopted tocharacterize the emulsion. The emulsion was mixed with anionic starch as surface sizingagent to size copy base paper and the experiments showed that emulsion synthesized underconditions optimized gave the best sizing efficiency. In this thesis, some novel discussionabout multipurpose optimal synthesis method, per-emulsified seeded emulsion polymerizationprocess and self-crosslinking system were proposed.Base on Minitab software, the comprehensive factors were analyzed and themultipurpose optimal synthesis project was obtained by Plackett-Burman design,Box-Benhnken design, response optimizer combined with experiments. The optimal synthesisproject as follows: monomer mass ratio (ST+MMA)/(BA)1:1, rotate speed30rpm, reactiontemperature78℃, dosage of emulsifiers1.97%, functional monomer2.17%and initiator0.51%. The experiments showed paper Cobb value, viscosity, solid content fitness were96.33%,92.78%,98.39%agreeing well with predicted value. With the synthesis optimalproject that under rotate speed of magnetic stirring apparatus in pre-emulsification process,synthesis temperature78～80oC, feeding speed4h～4.5h, rotate speed30～60rpm,7～8wt%of pre-emulsion to prepare seed emulsion,1/3wt%initiator used in base and the remainder added continuously, high polymerization stability, monomer conversion rate, andemulsion with good combination properties was obtained. The high polymerization stabilityand small average particle size were obtained under the conditions of ultrasonic processingtime15min, co-stabilizer CA dosage2wt%in fine emulsion polymerization process. With theincrease of self-crosslinking N-MA dosage, the polymer crosslinking degree was significantlyincreased. When the dosage is2.5wt%, emulsion with good water resistance was obtained andsuitable viscosity was obtained. The synthesis emulsion using in paper surface sizing showedthat paper water resistance enhanced obviously, and paper tensile strength and burstingstrength can enhanced from a certain extent.