Suspension polymerization method for polyvinyl chloride (PVC)

Abstract

The invention relates to a suspension polymerization method for PVC. The method comprises the following steps: a) adding a terminator to a PVC suspension polymerization system to terminate polymerization, performing centrifugation and separation and purifying a suspension polymerized aqueous-phase reaction mixture to obtain centrifugal mother liquor; b) taking the centrifugal mother liquor as a reaction raw material to be recycled to the PVC suspension polymerization system to carry out polymerization continuously; c) repeating the steps a) and b), wherein in the step a), controlling the equivalent concentration of polymerization inhibiting components in the centrifugal mother liquor at 7.8*10<-6>N to 3.1*10<-5>N. The method can accurately analyze the concentration and the residual dispersion amount of the polymerization inhibiting components in the centrifugal mother liquor, and remove obstacles for the reuse of the centrifugal mother liquor in the PVC suspension polymerization system, so that the centrifugal mother liquor can be efficiently reused in the suspension polymerization, thereby not only saving a lot of deionized water and further recycling a large amount of thermal energy and PVC resin and additives and being obvious in energy-saving effect, in addition, the production cost of PVC can be significantly reduced and economic benefits are good.

Description

technical field [0001] The invention relates to the field of polymer synthesis, in particular to a polyvinyl chloride suspension polymerization method. Background technique [0002] Polyvinyl chloride (PVC) resin is generally a resin produced by the homopolymerization of vinyl chloride monomer or the copolymerization of more than 50 wt.% of vinyl chloride and other monomers that can be copolymerized with vinyl chloride. Polyvinyl chloride resin is cheap and easy to adjust the hardness, so it can be processed by most processing methods. In addition, since polyvinyl chloride-based resins have various physical and chemical properties such as excellent mechanical strength, weather resistance, and chemical resistance, they are widely used in various products such as building materials, household goods, automotive interiors, furniture, etc. wait. [0003] More than 80% of polyvinyl chloride resins worldwide are produced by suspension polymerization. The production of polyvinyl ...

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Problems solved by technology

[0010] With the passage of time, many other problems have gradually emerged during the application of centrifuge mother liquor reuse technology. The application of the treatment method proposed in the above patent documents makes it difficult for the centrifuge mother liquor to be reused in polymerization production:

[0011] A. ATSC is a highly toxic substance and cannot be used in the production of polyvinyl chloride for food and medical purposes. In order to further improve the thermal stability of the resin, other components such as hindered phenol antioxidants need to be added to the terminator. Most of them use diethylhydroxylamine and hindered phenol composite non-toxic and environmentally friendly terminators, and no longer use the ATSC terminator disclosed in CN1654486A; and in order to shorten the reaction time and increase production capacity, most of them now use EHP and more efficient initiators, such as CNP compound ; Therefore, the terminator consumption and initiator corresponding relationship in the patent document CN1654486A are no longer applicable;

[0012] B. In the technical solution of the patent document CN1654486A, "the amount of dispersant decreased by 5% compared with the original amount" is a fixed value. This fixed value sometimes causes the amount of dispersant to be too small, and the dispersion system is abnormal, or sometimes the dispersant is left If the amount is too much, as time goes by, the accumulation of dispersant will occur, which will eventually lead to the decline of product quality;

[0013] C. In the patent document CN1654486A, the centrifuged mother liquor is filtered, and only the clear liquid obtained after filtration is reused. There is no clear filter pore size, and it does not involve the disposal of small particle resin after filtration.

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