The Study On Optimization Of POM Devolatilization Process

Polyformaldehyde manufacturing technique is divided into two types:homopolyformaldehydemanufacturingtechniqueandcopolyoxymethylene manufacturing technique.A company takes the copolyoxymethylene manufacturing technique combined with 3-oxetanil methyl and a little of dioxolane（2%⁵%）or other cyclic ethers.Both ends of the newly-prepared polyformaldehyde molecular chain contain some unstable hemiacetal end groups（-OCH₂-OH）.The ends are sealed,but because there still are some unstable end groups and H⁺in the polymer,the polyformaldehyde molecules will cause the molecular chains to be degraded and broken in the influence of thermal oxidation to form some free radicals,which will further trigger the molecule chains to be broken,release methanal and influence the processing in the following course.The devolatilized volatile components are isolated the components of low molecular weight in the polymer.At present,methods of devolatilization are mainly taken the twin-screw extruder in high temperature and devolatilized the volatiles by the way of vacuum suction.The degree and speed of devolatilization are influenced by the interfacial concentration difference,interfacial area,the diffusivity of the volatiles in the polymer,and the nucleating and growth of the bubbles in the polymer fusion.In this article,by theoretical analysis,according to the current technique conditions,we researched the twin-screw extruder for devolatilization.We moved two groups of screw elements forward to increase material melting intermixing section length,and moved a group of kneading blocks backward to strengthen the material mixing degree so as to improve exhaust effect.Meanwhile,we added the aqueous solution of triethylamine into the system to enhance the effect of foam devolatilization.Through technical innovation,the contents of volatiles in the products have decreased from mean 0.46%to mean 0.3%,and the datum was stable,formaldehyde emission of the products has reduced greatly and the effect of original design has been realized.In summary,this paper mainly analyzed the POM melt devolatilization process to determine the influence factors of devolatilization and prilling of a company,design and implementation of production process,and examine the effectiveness of devolatilization,and solved the problem that volatile components of production in a company is higher,the formaldehyde odor in long storage is heavier.