D_4乳液聚合反应条件及封端剂的研究

Study of Reaction Conditions and End-blocking Agent in D_4 Ring-opening Polymerization

以八甲基环四硅氧烷(D4)为原料,甲基丙烯酸-2-羟乙基酯(HEMA)为封端剂,十二烷基苯磺酸(DBSA)为催化剂,制备了分子链端含双键的有机硅乳液,比较了加料工艺对乳液稳定性和乳胶粒粒径的影响,考察了乳液固体质量分数、反应温度、反应时间、封端剂用量及加入时间对D4转化率和聚硅氧烷摩尔质量的影响。结果表明:采用连续滴加单体法制备的乳液透光率大、稳定性好,乳胶粒的粒径小;乳液固体质量分数越大、反应时间越长,D4转化率越高、聚硅氧烷摩尔质量越大;温度高于80℃时,聚硅氧烷的摩尔质量随温度升高而降低,D4转化率变化不明显;缩短反应时间可以获得聚硅氧烷摩尔质量较小的有机硅乳液;D4滴完2 h后加入HEMA,D4转化率高,聚硅氧烷摩尔质量较小;HEMA用量增大,聚硅氧烷摩尔质量显著下降,对D4转化率影响不大。

The silicone latex with vinyl terminal groups was synthesized by ring -opening polymerization of oetamethyleyclotetrasiloxane （ D4） by continuous addition of monomer using dodecyl benzene sulfonic acid （DBSA） as catalyst, methacrylic acid 2 - hydroxyethyl ester as end-blocking agent. The influences of the reaction conditions on D4 ring-opening polymerization including solid mass fraction, reaction temperature, reaction time, the amount of capping agent and adding time were studied. The results showed that latex particles by continuous addition of monomer were small, light transmittance was good and the emulsion stable. The greater the mass fraction of solids emulsion and the longer reaction time resulted in higher D4 conversion rate, and greater molar mass of the polysiloxane. When the temperature is higher than 80℃, the molar mass of the polysiloxane is lower with increasing temperature, while the D4 conversion rate is not change significantly. Shorter the reaction time produced, smaller mole mass polysiloxane emulsion. After D4 was added for 2 hours, adding HEMA gave higher D4 conversion rate and smaller molar mass polysiloxane. When HEMA amount increases, the molar mass of polysiloxane declined significantly, but had little effect on D4 conversion rate.