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可乳化异氰酸酯的合成、表征及其性能研究

Synthesis, Characterization and Properties of Emulsifiable Isocyanate

  • 摘要: 采用蓖麻油酸(RA)通过酰氯化反应与聚乙二醇单甲醚(MPEG)制备了共聚物MPEG-RA,并将所制备的MPEG-RA作为虚拟的“壳”通过羟基引入到多苯基多亚甲基多异氰酸酯(PAPI)中,构建虚拟的“核(PAPI)-壳(MPEG-RA)”结构制备可乳化异氰酸酯(MPEG-RA-PAPI),以提高异氰酸酯的稳定性及水分散性;然后将所制备的MPEG-RA-PAPI应用于木材胶黏剂中制备胶合板。采用傅里叶红外光谱仪、化学滴定分析、激光粒径仪等手段对所制备的MPEG-RA及MPEG-RA-PAPI的化学结构、活性基团(—N=C=O)含量稳定性、水分散性等进行分析。研究结果表明:所制备的MPEG-RA-PAPI即为预设的“核-壳”分子结构;MPEG-RA-PAPI(R=n—NCO/n—OH=40)中含—NCO约为24%,储存一个月后—NCO含量基本没有减少;MPEG-RA-PAPI(R=40)乳液储存8 h后含—NCO约为14%,明显高于MPEG-PAPI(约为4%),说明该结构提高了异氰酸酯的稳定性及水分散性;将所制备的MPEG-RA-PAPI应用于胶合板,当MPEG-SA-PAPI添加量为20%时能显著提高胶合板的耐水性,胶合干强度为1.80 MPa、II类湿强度为0.98 MPa、I类湿强度为0.77 MPa,使用期达到近5 h。

     

    Abstract: Polyaryl polymethylene isocyanates(PAPI) had been gradually attracted attention owing to their extremely high chemical activity, while their high chemical activity and poor water dispersibility limited the use of isocyanates. In this work, MPEG-RA was prepared by reaction of acyl chlorination of ricinoleic acid(RA) with polyethylene glycol monomethyl ether(MPEG), and the as-prepared MPEG-RA was introduced into PAPI as a virtual 'shell' through hydroxyl groups to build a virtual 'core(PAPI)-shell(MPEG-RA)' structure to prepare emulsifiable isocyanate(MPEG-RA-PAPI), which could improve the stability and water dispersibility of isocyanate. Then, the prepared MPEG-RA-PAPI was applied as wood adhesive to prepare plywood. The chemical structure, active group(-NCO) content stability and water dispersibility of the prepared MPEG-RA and MPEG-RA-PAPI were analyzed by Fourier transform infrared spectroscopy, chemical titration analysis, and laser particle size analyzer. The results showed that the prepared MPEG-RA-PAPI was the preset'core-shell' molecular structure. The prepared MPEG-RA-PAPI(R=n-NCO/n-OH=40) contained about 24% -NCO, and the content of -NCO did not decrease after one month of storage. The -NCO content of MPEG-RA-PAPI(R=40) emulsion was about 14% after storage for 8 h, which was significantly higher than that of MPEG-PAPI(about 4%), indicating that the structure improved the stability and water dispersibility of isocyanate. The prepared MPEG-RA-PAPI was applied to plywood. When the addition amount of MPEG-SA-PAPI was 20%, the water resistance of plywood could be significantly improved, the dry bonding strength was 1.80 MPa, the type II wet strength was 0.98 MPa, the type I wet strength was 0.77 MPa, and the working life reached nearly 5 h.

     

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