SAN (Styrene Acrylonitrile) resin with high nitrile content and narrow distribution and preparation method thereof

Abstract

The invention discloses SAN (Styrene Acrylonitrile) resin with high nitrile content and narrow distribution and a preparation method thereof. The SAN resin with high nitrile content and narrow distribution is a continuous thermal initiation body copolymer prepared from a reaction monomer in the presence of a mixed inertia solvent and a molecular weight regulator, wherein the nitrile content is more than or equal to 32 percent (mass); the melting index is less than 6 g / 10min (230 DEG C, 3.8 kg); and the molecular weight distribution index (Mw / Mn) is less than 2. In an SAN continuous thermal initiation body copolymerization method, the evaporation of acrylonitrile in the evaporation heat releasing process is reduced by adding the mixed inertia solvent into a copolymerization reaction system, so that the proportion of the acrylonitrile in fed materials is further lowered, and SAN resin with high nitrile content and narrow distribution is obtained.

Description

technical field [0001] The invention relates to the technical field of copolymerization of styrene and acrylonitrile in the petrochemical industry, in particular to a SAN resin with high nitrile content and narrow distribution and a preparation method thereof. Background technique [0002] SAN resin is a copolymer of styrene and acrylonitrile. It has good transparency, mechanical properties, chemical resistance and permeability resistance. It is mainly used in transparent structural materials or as a blending component of polymer alloys. [0003] The SAN copolymer is a quite complex mixture in terms of chemical composition, and the molecular weight size and distribution, the acrylonitrile content in the copolymer and other indicators have a great influence on the performance of the SAN resin. With the increase of acrylonitrile content in SAN resin, the mechanical properties, solvent resistance and temperature resistance of the resin have been greatly improved. At present, th...

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Problems solved by technology

[0007] But in engineering, for the characteristics of thermal initiation continuous bulk polymerization method, will prepare the SAN product of high nitrile content and narrow distribution, owing to having strengthened the ratio of acrylonitrile in the reaction feed, this will face the following problems: ( 1) The viscosity of the polymerization system of SAN resin with high nitrile content increases. At the same time, the increase of acrylonitrile content, because acrylonitrile is a polar group, and usually ethylbenzene is used as a solvent in the polymerization process, and ethylbenzene is a non-polar solvent, so Along with the raising of acrylonitrile content in SAN, ethylbenzene has become the bad solvent of SAN resin gradually, comprehensive these can cause the viscosity of reaction system to increase sharply, and this can bring to remove heat and mix difficulty, and reaction system appears inhomogeneous; (2 ) The improvement of acrylonitrile content in the reaction feed increases the probability of generating acrylonitrile homopolymer or ultra-high content acrylonitrile copolymer in the reactor, causing the distribution to widen, which will greatly deteriorate the mechanical properties and color of the material; ( 3) With the increase of acrylonitrile content in the reaction system, the more acrylonitrile monomer evaporates in the polymerization reactor, which will require a higher acrylonitrile content in the feed monomer composition of the reactor, which will further aggravate the aforementioned Two problems, forming a vicious circle, at the same time, the content of acrylonitrile in the evaporated gas phase is higher, which increases the probability of generating acrylonitrile homopolymer or copolymer with high acrylonitrile content in the condenser, these components are Insoluble gel-like polymer with very low thermal stability causing red and black spots on molded articles that spoil the appearance of the article

[0009] Therefore, in order to prepare SAN resin with high nitrile content and narrow distribution, it is necessary to solve the problems of wide distribution and yellow color caused by the increase of acrylonitrile content.

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