High-nitrile SAN resin and production method thereof

Abstract

The invention relates to a production method of high-nitrile SAN resin. The method comprises the specific steps of (a) mixing acrylonitrile with part of styrene cinnamene to obtain a mixture A, then mixing the mixture A with a circulating material and a condensation circulating material outside a reactor in a static mixer through a metering pump so as to obtain a mixture B, and then continuously leading the mixture B to the reactor; and enabling the rest of the styrene to be pumped into a steam condenser at the top of a reaction kettle through the metering pump, to be in contact with steaming air flows of the reactor, and to be mixed with condensation steam to become a condensation circulating material, and enabling the condensation circulating material to enter the reactor through a static mixer ; (c) polymerizing a reaction mixture at 140-160 DEG C in the reactor for 1.5-2.5 hours so as to obtain an SAN copolymer; and (d) performing two-stage devolatilization in a devolatilization machine, and performing pelleting in a pelletizer, so as to obtain the high-nitrile SAN resin with narrow distribution. According to the high-nitrile SAN resin produced by the method disclosed by the invention, the percentage by mass of acrylonitrile is greater than or equal to 32%, the melt indexes of products are smaller than 6g / 10min(230 DEG C, 2.16Kg), and the yellow index of the products is smaller than 12.

Description

technical field [0001] The invention belongs to the copolymerization technology of styrene and acrylonitrile in the field of petrochemical industry, especially the copolymerization technology under high acrylonitrile content. More specifically, it is about a thermally initiated bulk copolymerization method of styrene and acrylonitrile that introduces part of styrene monomer in the evaporative condenser to quickly condense steam and mixes it with high-concentration acrylonitrile for the purpose of quickly condensing steam , Control the concentration of acrylonitrile in the condenser, avoid the self-polymerization of acrylonitrile, reduce the color of the polymer, so as to prepare SAN resin with high nitrile content and low yellowness. 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 ...

AI Technical Summary

Problems solved by technology

[0008] But in engineering practice, for the characteristics of conventional thermal initiation continuous bulk polymerization method, will prepare the SAN product of high nitrile content, 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

According to experiments, high nitrile SAN resin is prepared in the existing equipment, and the tensile properties, impact strength and yellow index of the obtained product are difficult to achieve satisfactory results

Therefore, it is difficult to prepare SAN resin with high nitrile content and narrow distribution. It is necessary to improve the existing polymerization method to solve the problem caused by the evaporation and heat removal of acrylonitrile

According to the results of literature research, there are few literature reports on the preparation method of SAN resin with high nitrile content. In Chinese patent CN85106459A, a process for continuous bulk polymerization of styrene and acrylonitrile is disclosed. Acrylonitrile in the copolymer of its embodiment 5 With a content of 33%, it is a high nitrile content SAN resin, but its distribution and yellowness index are not specified

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