The Synthesis And Performance Research Of Composite-modified Starch

The composite-modified starch was prepared by cross-linked etherification, cross-linked graft co-polymerization using starch, chloroacetic acid, acryl acid, methacrylic acid and crosslinker as raw material. The application of composite-modified starch in the petroleum industry field as filtration control agent, gelling agent etc.The optimal synthesis conditions for carboxymethyl starch is as follows:85wt%ethanol as solvent, the quality ratio of solvent to starch is about5:1, the molar ratio of chloroacetic acid to starch is more than0.6, the molar ratio of NaOH to chloroacetic acid is about1.6, the amount of crosslinker is12.5wt%to starch, the reaction temperature is controlled in the range of52℃～58℃, and the reaction time is90min.The optimal synthesis conditions for starch-methacrylic acid graft co-polymer is as follows:the quality ratio of starch to methacrylic acid is about1:2, the neutralization degree of NaOH to methacrylic acid is75%, the amount of initiators is12.5wt%to starch, the amount of crosslinker is10wt%to starch, the reaction temperature is55℃, and the reaction time is3h.The optimal synthesis conditions for starch-acrylic acid graft co-polymer is as follows: the quality ratio of water to starch is about8:1, the gelatinization temperature is76℃, the gelatinization time is30min, the quality ratio of methacrylic acid to starch is about3:1, the neutralization degree of NaOH to methacrylic acid is75%, the quality ratio of initiators to starch is1:100, the reaction temperature is56℃, and the reaction time is3h. The synthesized starch-acrylic acid graft co-polymer under such conditions is with the largest water absorption times of137.7.Performance evaluation of high substituted high viscous carboxymethyl starch showed good filtration controlling and thicken property in fresh mud,4%salt mud and saturated salt mud, which are higher than the request of middle viscous carboxymethyl starch.Performance evaluation of starch-methacrylic acid graft co-polymer showed good filtration controlling and thicken property along with the increase of concentration in mud. All of the properties of the unaged mud are better that of aged mud. The starch-methacrylic acid graft co-polymer also displayed certain salt resistance and thermal resistance.