Yu. M. Bazarov

Prospects for Perfecting Production Technology for Polycaproamide Used in Production of Textile and Industrial Fibres. Part I

The correlation between the strength indexes of polycaproamide (PA-6) fibres with the molar mass of the polymer and degree of nonlinearity of its macromolecules is discussed. The causes of breaking of branched PA-6 chains in modern technology for synthesis and preparation of the fibres for spinning are analyzed. Possible directions in improving these technologies are advanced.

Calculated and experimental investigation of the combined drying and monomer removal process of polyamide-6 in a batch apparatus

The experimental studies of the periodic process of drying polyamide-6 granulate combined with the elimination of monomer from granules (demonomerization) in one device have been performed. The mathematical model for the combined polyamide-6 drying–demonomerization process in a batch apparatus that helps to predict the change in the caprolactam and water contents in polyamide-6 granules and in the gas phase, the polymer and gas temperatures was proposed. The experimental data were compared with the calculations according to the developed mathematical model.

Rational Use of Cyclic Oligomers Formed During Hydrolytic Polymerization of Caprolactam

It was established experimentally that addition of the calculated amount of the cyclic oligomers isolated from extraction waters after treatment of equilibrium industrial granulate PA-6 to the initial reaction mixture during the hydrolytic polymerization of caprolactam leads to an increase in the degree of transformation of caprolactam into the sections of the linear chains. It was shown that the use of regenerated caprolactam, obtained by the technology used in OAO “KuibyshevAzot”, in the synthesis of PA-6 is a technologically safe and economically favorable method of using the cyclic oligomers formed during hydrolytic polymerization of caprolactam.

Emulsion Hydrolytic Polymerization of Caprolactam

Emulsion hydrolytic caprolactam polymerization method is proposed as an alternative to existing instrumental-technological solutions to production of fibre-forming polyamide-6 in a melt. The conditions for implementing a single- and a two-stage polymerization process and characteristics of the synthesized polymers are given. It is shown that emulsion polymerization at a temperature below the polymer melting point can be used to produce high-molecular polyamide 6 with a near-equilibrium content of low-molecular compounds.

The Importance of Long-Term Observations in Assessing the Strength of Polycaproamide Fibre

According to long-term observations, rewinding and slubbing operations have almost no effect on the unit strength of complex and slubbed polycaproamide fibres but affect the relative elongation at break. The stability of the deformation-strength properties of the fibres in time, assessed with the values of the coefficients of variation, during the manufacturing process, including slubbing, improves significantly. The fibre strength is not a function of fluctuations in the content of low-molecular-weight compounds in the initial polymer and its relative viscosity, spinning temperature, and elementary fibre thickness in the undrawn fibre in contrast to the moisture content of polymer going to spinning and the degree of orientational drawing of the fibre.

Some characteristics of low-temperature hydrolytic polymerization of caprolactam

Spontaneous crystallization of linear PCA chains during low-temperature hydrolytic polymerization of caprolactam (CL) is only observed when the temperature of synthesis is decreased to 473 K. At T = 473 K, hydrolytic polymerization of CL takes place in three successive regimes: purely liquid-phase, mixed (liquid and solid-phase), and purely solid-phase, and the proportion of CL converted into linear chain units in the second regime of the reaction increases from 1.8 to 18.2% with a decrease in the synthesis temperature from 473 to 443 K. The efficiency of the solid-phase stage of the process and low-temperature hydrolytic polymerization of CL as a whole increases with an increase in the degree of crystallinily of the PCA formed, and of the two reactions which take place in the amorphous phase of the polymer — polymerization of CL or polycondensation of linear chains — the first is relatively faster.

Dyeing of polyamide granulate with preliminary treatment with acetic acid solution

It was found that preliminary treatment of PCA granulate with a dilute solution of CH3COOH sharply increases the rate and degree of sorption of acid dyes by PCA granulate. A technological regime for dyeing PCA granulate with acid dyes was proposed and approved in industrial conditions; it allows increasing the intensity of the color by several times with almost total extraction of the dye from the bath.

Structure of the molecular-weight regulator and the mechanism of after-polyamidation of polycaproamide

where K is the constant of amide equilibrium, The disturbance of this equilibrium in the technological operations during the p=eparation of the.polycaproamide (PCA) for spinning causes a change in the ~polymerization P of the polymer. In the course of the transition from th Lons of caprolactam polyamidation to the conditions of spinning the numerator of Eq.(1) undergoes a change by a factor of four to I0 while the denominator varies by only 20-30% [i] so that the melting of the PCA in the spinning head always results in an increase in ~, i.e. in a reaction of after-polyamidation.