Study On Allyl Etherification Pretreatment Of Starch For Preparing The Grafted Starch As Sizing Agents

Through allyl etherification pretreatment of starch, an attempt had been made to enhance the graft efficiency and improve the properties of grafted starch used as warp sizing agents before the graft copolymerization between starch and vinyl monomers. By allyl etherification pretreatment of introducing polymerisable double bonds onto starch, graft copolymerization reactions between starch and acrylic acid/methyl acrylate were both carried out in aqueous dispersion to synthesize allyl starch graft PAA (AS-g-PAA) and allyl starch graft PMA (AS-g-PMA) for warp sizing. Furthermore, the influence of allyl etherification pretreatment on the graft efficiency of AS-g-PAA and AS-g-PMA and behaviors of AS-g-PMA was surveyed. In addition, the degree of substitution (DS) of allyl starch was adjusted through varying the feeding ratio of etherifying agent to starch. The intrinsic relation between the DS value of allyl starch and the graft efficiency and behaviors of grafted starch sizing agents was systematically studied.The experimental results indicated that, by introducing allyl groups onto starch before the copolymerization, the etherification pretreatment can enhance the graft efficiency of AS-g-PAA and AS-g-PMA by about 10% -20% when the degree of substitution (DS) of allyl starch was in a range of 0.01 to 0.068. The adhesion to fibers and film behaviors of AS-g-PMA were also remarkably improved. The experiments prove that proper DS value of AS-g-PMA was in the range of 0.011 to 0.023. Obviously, not only does allyl etherification pretreatment of starch supply a convenient way to enhance the graft efficiency, but also it broadens the serviceability of grafted starch.The paper also clarified the influence of such technological variables as sodium hydroxide amount, water content in water-isopropyl alcohol medium, allyl chloride concentration, reaction temperature and reaction time on allyl etherification reaction efficiency. The experimental result demonstrated that the variables considered showed evident effect on the reaction efficiency. For the etherification, a condition of 1.5:1 for the molar ratio of sodium hydroxide to allyl chloride, 20% for the water content, and at 30℃under 24h reaction is sufficient to retain the reaction efficiency above 50%.Moreover, the effects of blending ratio of AS-g-PMA to PVA1799 on blending film behaviors and adhesion to fibers were also investigated. And sizing properties of AS-g-PMA were primarily studied. The possibility of using AS-g-PMA to substitute PVA component was evaluated by contrast experiments. The results of experiment show that compared with the conventional size formulation used in modern sizing engineering AS-g-PMA can largely reduce the usage of PVA while the quality of sizing yarns doesn't fall.