Method for preparing polyvinyl chloride resin with reduced leather diaphragm and improved porosity

Abstract

The invention provides a method for preparing a polyvinyl chloride resin with reduced leather diaphragm and improved porosity, which comprises the following steps of: (1) putting water, a dispersant A, a dispersant B, a chain transfer agent, a pH regulator, a vinyl chloride monomer and an initiator into a reaction kettle to perform polymerization when the stirring power per unit volume is 0.70 to 0.90 kw / m3; (2) when the polymerization conversion is 12 to 20 percent, adding a dispersant C to perform the polymerization continuously when the stirring power per unit volume is changed to be 0.9 to 1.40 kw / m3; and 3) when the polymerization conversion is 30 to 45 percent, adding the dispersant C, performing the polymerization continuously when the stirring power per unit volume is changed to be 1.00 to 1.60 kw / m3, and ending the reaction when the polymerization pressure is reduced to be 0.15 to 0.30 MPa to obtain a product. The PVC resin prepared by the method has fewer leather diaphragms on particle surfaces, and has loosened and porous interior, high porosity and even pore distribution, and the absorptive amount of a plasticizer is high.

Description

technical field [0001] The invention relates to a method for preparing polyvinyl chloride resin by adopting a suspension polymerization method. Background technique [0002] Polyvinyl chloride (PVC) resin is generally a white powder with a particle size range of 100-200um. In addition to the molecular weight index, the most important performance of PVC resin is the particle characteristics, which are reflected in the index as the average particle size and its distribution, apparent density, plasticizer absorption rate, sieving rate, etc., which directly affect the melt fluidity of the resin during processing. , plasticizing time, appearance of the product, etc. PVC resin is widely used in the manufacture of pipes, pipe fittings, sheets, films and other fields, and can be further chlorinated to produce chlorinated polyvinyl chloride resin (CPVC). PVC resin has high porosity and uniform distribution, less film, suitable particle size range and concentrated distribution, good...

AI Technical Summary

Problems solved by technology

This technology uses a special type of dispersant, the operation is complicated, and it is difficult to control the granulation process.

[0006] At the same time, B.F.Goodrich Chemical Company also introduced a new additive that can adjust the molecular weight of the resin and improve the porosity of the resin, US 4,963,592, such as 2-mercaptophenylpropanthiazole, 2-mercaptophenylpropanoxazole, 2-mercaptophenylpropanoid imidazole, etc., but this kind of additive is easy to make the resin particles too thick, beyond the normal range

[0007] Domestic Zhejiang University published a patent for the production of skinless resin, CN 87,1,01663A, using magnesium hydroxide as the main dispersant, two types of porosity regulators with different properties as auxiliary dispersants, and water-soluble inorganic salts as auxiliary agents , carry out suspension polymerization of vinyl chloride, prepare loose, non-grafted copolymer film and polyvinyl chloride particles with high apparent density, and reduce the method of sticking, but the resin particles are very thick and cannot be applied in practice

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