Organic alkali compound as pH value regulating agent for preparing polyvinyl chloride (PVC) resin

Abstract

The invention relates to an organic alkali compound as a pH value regulating agent for preparing polyvinyl chloride (PVC) resin and belongs to the technical field of polymer preparation. In the technical process of preparing general PVC resin products by a suspension method, organic alkali compounds such as trimethylamine, triethylamine, tripropylamine, pyridine and picoline are selected as the pH value regulating agent for replacing the traditional inorganic alkali or inorganic salt compounds such as NaOH, NaHCO3, NH4HCO3 and tricalcium phosphate; the addition quantity of the pH value regulating agent is metered according to the mass ratio, the chloroethylene monomer: the pH value regulating agent is 1:0.00014-0.00036; and the addition quantity of aqueous emulsion type terminating agents ZRT-6 is metered according to the mass ratio, and the chloroethylene monomer:ZRT-6 is 1:0.0008-0.001. The aqueous emulsion type terminating agents ZRT-6 is selected for eliminating the harm of chloride ions and improving the particle characteristic and the thermal stability of PVC resin products.

Description

technical field [0001] In the process of preparing general-purpose polyvinyl chloride (PVC) resin products by the suspension method, the present invention selects an organic base compound as a pH regulator to eliminate the harm of chloride ions and improve the particle characteristics of PVC resin products. Technical field of polymer preparation. Background technique [0002] Introduction to the technical literature on the pH value regulator used in the production of PVC resin published in the past: [0003] In the process of PVC resin products, the pH regulator is an indispensable auxiliary. The substances used mainly include strong bases, strong bases and weak salts, weak bases and weak salts, etc., such as NaOH, NaHCO 3 , NH 4 HCO 3 , tricalcium phosphate and other compounds, currently widely recognized by the industry and widely used in production is NH 4 HCO 3 , The pH regulator has a great influence on the polymerization reaction rate and resin quality, especially...

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Problems solved by technology

However, when the sodium bicarbonate solution is used for acid neutralization, it is easy to decompose and produce carbon dioxide to accumulate in the reflux condenser, which greatly affects the heat exchange capacity of the reflux condenser and brings inconvenience to normal production.

[0009] Tricalcium phosphate is a strong base and weak acid salt. It is used as a pH regulator in the production of vinyl chloride suspension polymerization. It shows the adverse effect of calcium ions on the dispersant. In addition, calcium ions are easy to deposit and cause fouling of the PVC slurry stripping tower. and clogging; PVC resin produced with tricalcium phosphate solution has a relatively high apparent density and poor oil absorption rate, which eventually leads to poor particle characteristics of the resin

[0010] Ammonium bicarbonate is used as the pH regulator in the production process, and the solution is a buffer solution, which has more advantages than sodium hydroxide solution in the polymerization system, and is not easy to cause the solution to be acidic or alkaline; NH 4 HCO 3 The disadvantage as a pH adjuster is that NH 4 HCO 3 Unstable and easy to decompose, volatilize quickly, decompose into ammonia, carbon dioxide and water vapor, resulting in errors when preparing solutions and inaccurate measurement; decomposition produces carbon dioxide and accumulates in the reflux condenser; reacts with hydrogen chloride to form compound salt NH 4 Cl, the dissociation of chlorine ions in water has a strong pitting corrosion effect, causing corrosion damage to equipment and auxiliary equipment

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