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首页> 外国专利> High-density polyethylene (HDPE) prodn. - with procedure for changing process parameters to enable changeover from high-mol. wt. to low-mol. wt. HDPE without shut-down or cleaning

High-density polyethylene (HDPE) prodn. - with procedure for changing process parameters to enable changeover from high-mol. wt. to low-mol. wt. HDPE without shut-down or cleaning

机译：高密度聚乙烯（HDPE）产品-具有更改工艺参数的步骤，以实现从高分子量的转换。重量到低分子。重量HDPE无需停机或清洁

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A process is claimed for the prodn. of HDPE by catalytic gas-phase polymerisation of a mixt. of ethylene, hydrogen and comonomer in a fluid-bed reactor incorporating a gas distributor, with recirculation of unreacted gas mixt.. The special feature is that, from the steady-state condition for prodn. of a polymer suitable for the mfr. of large tubular prods. (HDPE-I), the system can be changed over directly to reaction conditions for the prodn. of a polymer suitable for the mfr. of film, fibres and injection mouldings (HDPE-II), by changing the catalyst and the comonomer but without shutting down or cleaning the system. This process comprises: (a) raising the hydrogen concn. in the gas circulation to a level corresp. to a hydrogen/ethylene mole ratio of 45-55 x 10 power(-3) mole/mole 36-42 hrs. before changeover, at a temp. of 84-96 deg.C and with continuous removal of off-gas at the rate of 1.7-5.1 x 10 power(-3) Nm3/m3 circulating gas, (b) stopping the addn. of catalyst, (c) emptying the catalyst metering system including instrument parts, washing with the new catalyst and filling with new catalyst, (d) stopping addn. of comonomer (e.g. butene-1) when monomer conversion has dropped to 20-30% of the normal level, (e) preparing for the change of comonomer, e.g. from butene-1 to propene, (f) adding a mixt. of N2/O2 to kill any residual reaction (at the same time as (d)), (g) flushing the reactor 2-4 times with ethylene, (h) establishing the required new hydrogen/ethylene ratio (the propene content is adjusted only after the start of polymerisation), (i) starting addn. of the new catalyst, with the circulating gas contg. less than 1 ppm oxygen and less than 3 ppm CO2, (j) lowering the reactor fill height to 90-94% of the normal level gradually over 1.4-1.8 hrs. (simultaneously with (b)), (k) raising the reactor temp. gradually to 94-96 deg.C starting with (b), (l) increasing the reactor level to 110-115% of normal for 15-35 mins. after stage (i), and (m) re-establishing the normal reactor level. USE/ADVANTAGE - The invention makes it possible to convert a continuous gas phase HDPE prodn. system directly from prodn. of high-mol. wt. polymer to prodn. of low-mol. wt. polymer (mol. wt. 300,000) by changing the catalyst and the comonomer but without shutting down or cleaning the system. This process reduces the amt. of transitional polymer with pinholes and inhomogeneities which is normally obtd. after changeover.
机译：要求保护该产品的过程。通过混合物的催化气相聚合制备高密度聚乙烯。在装有气体分配器的流化床反应器中回收乙烯，氢和共聚单体，并循环未反应的气体混合物。适用于制造的聚合物大型管状产品。 （HDPE-I），系统可以直接转换为产品的反应条件。适用于制造的聚合物通过更换催化剂和共聚单体而无需关闭或清洁系统，即可制成薄膜，纤维和注塑成型品（HDPE-II）。该过程包括：（a）提高氢气浓度。在气体循环中达到相应水平。氢/乙烯摩尔比为45-55 x 10幂（-3）摩尔/摩尔36-42小时。转换之前，暂时。温度为84-96摄氏度，并以1.7-5.1 x 10功率（-3）Nm3 / m3循环气体的速率连续去除尾气，（b）停止添加。 （c）排空包括仪器部件在内的催化剂计量系统，用新催化剂洗涤并用新催化剂填充，（d）停止添加。当单体转化率降至正常水平的20％至30％时，共聚单体（例如，丁烯-1）的用量;（e）为共聚单体的改变做准备，例如：从丁烯-1到丙烯，（f）添加混合物。 N2 / O2杀死任何残留反应（与（d）同时），（g）用乙烯冲洗反应器2-4次，（h）建立所需的新的氢/乙烯比（调整丙烯含量）仅在聚合开始之后），（i）开始加成。的新催化剂，并伴有循环气体。氧含量低于1 ppm且二氧化碳含量低于3 ppm，（j）在1.4-1.8小时内将反应器填充高度逐渐降低至正常水平的90-94％。 （与（b）同时），（k）提高反应器温度。从（b），（1）开始逐渐升高至94-96℃，在15-35分钟内将反应器水平增加至正常的110-115％。在阶段（i）和（m）之后，重新建立正常的反应堆高度。使用/优点-本发明使得可以转化连续气相HDPE产品。系统直接从产品。高摩尔。重量聚合物生产低摩尔。重量通过改变催化剂和共聚单体而无需关闭或清洁系统就可制得聚合物（摩尔重量，300,000）。这个过程减少了amt。通常带有针孔和不均匀性的过渡聚合物转换后。

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