Mechanical method and apparatus for removing polycarprolactam dimers

Abstract

The invention discloses a mechanical method for removing polycarprolactam cyclic oligomer. The method comprises the following steps: (1) cooling caprolactam concentrate which has undergone triple effect evaporative concentration and has a temperature of 110 to 130 DEG C for crystallization, and carrying out stirring with a stirrer when the temperature of the caprolactam concentrate drops to 50 to 95 DEG C; (2) prefiltering the cooled concentrate, carrying out pressurization with a pressurization device until the concentrate has a pressure of 0.4 to 0.6 MPa, and allowing the concentrate to enter into aplate and frame type filter press for press filtration so as to obtain clear liquid of the caprolactam concentrate; (3) storing the clear liquid in a clear liquid storage tank, adding the clear liquid of the caprolactam concentrate into a fresh caprolactam storage tank through a metering pump, mixing the clear liquid with fresh caprolactam, and allowing an obtained mixture to enter into a polymerization reactor. The method provided in the invention enables flow for removing polycarprolactam cyclic oligomer to be simplified and a high removal rate of annular oligomers in the caprolactam concentrate to be obtained; the apparatus in the invention has the advantages of a large filtering area, a strong capability of bearing pollutants, convenience in cleaning and low cost.

Description

Technical field [0001] The present invention involves a mechanical filtering field of solution, which specifically involves a mechanical method and device that removes polycamide diocol. Background technique [0002] At present, the aggregation technology of domestic industrialized production nylon 6 slices is generally used. Generally, the hydrolytic polymerization process of lactide is used. The hydrolytic polymerization reaction of lactide is a reversible and balanced chemical reaction.The balance state of a low -molecular quantitative compound and polymer quantitative compound is over. The low molecular quantum compound part is composed of the self, water, and other compounds of the ingredients, water, and other compounds. The polymer quantum compound part is polyamide.Low molecular weight substances will bring a series of problems during the formation of polymer processing, so the low molecular substance must be removed through the heat water extraction solid polymer section...

AI Technical Summary

Problems solved by technology

Among them, the remarkable characteristic of cyclic oligomer is high melting point, the melting point of cyclic oligomer is about 348 ℃, which exceeds the melting point of polyamide; secondly, cyclic oligomer is in water, caprolactam melt and other organic solvents Moderately low solubility; in addition, cyclic oligomers are less reactive than caprolactam

[0004] When using the "evaporation-concentrated solution polymerization method" to produce nylon 6 polyester chips, the oligomer content is about 8 to 15% of the extract is subjected to three-effect evaporation and concentration, when the concentration reaches about 80%. , the concentrated solution is directly mixed with fresh monomers into the polymerization reactor, and the polymerization is carried out directly under high pressure conditions. This process saves the distillation process and realizes no residue discharge from the polymerization device. However, because the concentrated solution contains about 3% Oligomers, specifically including cyclic oligomers and linear oligomers, when mixed with fresh caprolactam for polymerization, due to the influence of the characteristics of cyclic oligomers, ring-opening polymerization cannot be re-opened, if not removed These substances will seriously affect the post-processing procedures such as spinning and molding of nylon 6, especially the clogging of components in the spinning process is particularly serious, causing the pressure of components to rise rapidly and frequent replacement of components

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