Preparation method and separation method of low polymerization cyclic polymer

Abstract

The invention provides a preparation method of a low polymerization cyclic polymer, and the method comprises the following steps: (1-1) in an organic solvent A, terephthaloyl chloride and 1,4-butanediol undergo esterification reaction under the action of an alkali A to obtain a hydroxyl n-butyl terephthalate mixture (mixture 1), and (1-2) in an organic solvent B, the hydroxyl n-butyl terephthalatemixture (mixture 1) obtained in the step (1-1) and the terephthaloyl chloride undergo cyclization under the action of an alkali B to obtain a low polymerization cyclic polymer mixture (mixture 2). The method has the advantages of simple synthesis route and high atom utilization rate, and four low polymerization cyclic polymers (I) can be prepared by only two steps of reaction, the reaction conditions are mild, high temperature and high pressure steps are not required, and guarantee is provided for safe production.

Description

Technical field [0001] The invention relates to the technical field of compound preparation, in particular to a preparation method and a separation method of an oligomeric cyclic polymer. Background technique [0002] Polybutylene terephthalate, abbreviated as PBT, is a polymer of terephthalic acid and 1,4-butanediol. It is a thermoplastic polyester crystalline engineering plastic with excellent performance and is widely used Used in electronic appliances and accessories, auto parts, mechanical equipment and parts, etc. [0003] In the PBT production process, oligomeric cyclic compounds with the structure shown in formula (I) will be produced (generally common are cyclic dibutylene terephthalate, cyclic tributylene terephthalate Ester, cyclic tetra-polybutylene terephthalate, cyclic penta-polybutylene terephthalate), although the content of these compounds is very small, it is an important factor affecting the quality of PBT, which causes Extensive attention and research from the...

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Problems solved by technology

[0008] Although this method can obtain single product cyclic dipolybutylene terephthalate, its disadvantages are: 1) the synthetic route is loaded down with trivial details, from raw material to intermediate compound, needs 8~9 step chemical reactions, causes production The cycle is long and the production cost is increased; 2) Since there are many synthesis steps, and multiple steps are separated and purified by column chromatography, a large amount of waste water, waste liquid, and waste residue will inevitably be produced, which is not friendly to the environment and does not meet the requirements of green chemical industry; 3 ) needs to use palladium / carbon to carry out high-pressure catalytic hydrogenation deprotection, and the reaction conditions are harsh, which increases the danger of operation and is not conducive to safe production; Meet the requirements of atomic economy and green environmental protection

[0013] By this method, cyclic tetrapolybutylene terephthalate (VI) can be prepared with fewer reaction steps, but its disadvantage is that it needs to use palladium / carbon to carry out catalytic hydrogenation deprotection, and the reaction conditions Harsh, high risk of operation, not conducive to safe production

[0014] In summary, the above three methods can be seen, in the preparation method of the low-polymerization cyclic polymer in PBT by chemical synthesis disclosed in the prior art, the product is single, and lacks the method for preparing cyclic pentapolybutylene terephthalate. method, and has the defects of cumbersome synthetic route, long production cycle, unfriendly to the environment, and low production safety factor

[0015] In addition, the art lacks a method for simultaneously preparing and isolating low-polymerization cyclic polymers in various PBTs

At the same time, cyclic dibutylene terephthalate, cyclic tributylene terephthalate, cyclic tetrabutylene terephthalate and cyclic pentabutylene terephthalate Due to the similar structure of alcohol esters, the polarity gap of the substances is also small, which brings great difficulties to the subsequent separation.

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