The lower temperature boundary of liquid-phase synthesis of polyamide-6

Mizerovskii, L. N.; Bazarov, Yu. M.; Lytkina, N. I.

doi:10.1007/s10692-006-0057-5

Cited by 5 publications

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“…17 Mizerovskii further studied melt polymerization at a temperature 10−15 °C below the melting point of PA6. 18 Although the molten state can still be maintained at low temperature, it is a metastable state and is not suitable for large-scale application. In order to further realize the lowtemperature polymerization of PA6, some substances (lithium halide and ionic liquids) were added to form the lower melting point of the polymer.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Bazarov proved that CPL hydrolysis polymerization below the melting point of PA6 (210 °C) can effectively reduce the monomer content after equilibrium and recalculated the reaction equilibrium constant according to different water contents . Mizerovskii further studied melt polymerization at a temperature 10–15 °C below the melting point of PA6 . Although the molten state can still be maintained at low temperature, it is a metastable state and is not suitable for large-scale application.…”

Section: Introductionmentioning

confidence: 99%

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Sustainable Production of Polyamide 6 Fibers: Direct Melt Spinning and Efficient Reuse of Residual Oligomers during Polymerization

Zhang

et al. 2023

ACS Sustainable Chem. Eng.

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Direct melt spinning of PA6 from a polymerization reactor is currently unachievable in the industrial production of polyamide 6 (PA6) fibers because the hydrolysis polymerization of its monomer (caprolactam) is a reversible reaction which requires a boiling water extraction of oligomers from the polymer before melt spinning. Here, we proposed a polymerization method where the content of the cyclic dimer is controlled by reducing the temperature at the monomer ring-opening stage and the content of oligomers is monitored by rapid devolatilization through the polycondensation stage. As a result, the content of oligomers in PA6 is less than 1.5 wt % and the cyclic dimer is at 0.1–0.3 wt %, which are 80 and 48% lower than the values for the conventional PA6 production process. This allows for direct melt spinning of PA6 fibers at the industrial scale (spinning speed: 4000 m/min and a continuous production line of 10 kg/h), which reduces the production time from over 40 h to within 10 h, and the resource consumption reduces by over 30%. The resulting PA6 fibers show comparable mechanical and dyeing properties to those spun with the conventional multistep spinning method. In addition, the unreacted oligomers extracted during the polymerization stage can be directly reused in the polymerization, with no further treatment. This work provides an effective route to the sustainable production of PA6 fibers at the industrial scale, which significantly decreases the consumption of resources and the generation of chemical wastes while improving the production efficiency.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sustainable Production of Polyamide 6 Fibers: Direct Melt Spinning and Efficient Reuse of Residual Oligomers during Polymerization

Zhang

et al. 2023

ACS Sustainable Chem. Eng.

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“…% according to the data from differential scanning calorimetry [12,13], then the question of when it is better to go from 483 K to lower temperatures essentially boils down to the question of how it is possible to form cyclic oligomers after 1 or 2 h at 483 K in comparison to how many are formed after ~4 h of a decrease in the concentration of CL from ~32 to 20% at 453 K and after ~7 h from 46 to 20% at 443 K. We conducted two series of experiments to at least partially answer this question. …”

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Hydrolytic polymerization of caprolactam accompanied by crystallization of the polymer

Bazarov

Mizerovskii

2007

Fibre Chem

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678.675:66 09Caprolactam was polymerized in the presence of 3 wt. % water at 443-473 K, accompanied by crystallization of the melt of the polymer formed. It was found that the time of onset of crystallization of the melt is shifted to the region of lower degrees of conversion of caprolactam into a polymer, and the efficiency of the solid-phase stage of the reaction increases with a decrease in the temperature of synthesis.Two-stage (in melt and solid phase) synthesis of polycaproamide (PA-6) by hydrolytic polymerization of caprolactam (CL) is usually considered [1-6] a process that takes place in two different units: the liquid-phase stage takes place in the first and the solid-phase stage of the process takes place in the second.Moreover, in principle, the two-stage process can be conduced in one continuously operating unit with zones in which the polymerized mass is in different aggregate states. In this respect, we will discuss some features of polymerization of CL accompanied by crystallization of the polymer.The reaction and analyses of the polymerizates obtained were conducted as indicated in [7]. In some cases, the content of unreacted CL was determined by vacuum sublimation in a version similar to the one described previously in [8], while the low-molecular-weight compounds were determined by aqueous extractions combined with refractometric control of their concentration in the extract. The time phase separation began in the polymerized mixture was identified visually by the appearance of opalescence.*The kinetic curves of the change in the concentration of CL and amino groups during isothermal polymerization of the CLH 2 O system (100:3) at 443-483 K are shown in Figs. 1 and 2, respectively. The times at which phase separation begins (τ 1 ) are indicated by the arrows.At 483 K, the system remained liquid, and both equilibria (polycondensation and ringchain) were attained. At lower temperatures, the reaction mixture crystallized, and formation of a new phase with a decrease in the temperature was observed at lower values of the degree of conversion of CL and average degree of polymerization ( P ) of the polymer formed (Table 1).A comparison of the concentration of CL and the values of P attained at the time the polymer melt began to crystallize with the values of the equilibrium concentration of CL reported in the last two columns of Table 1, borrowed from [9], and the

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“…This effect can be used to decrease the temperature boundary of the polymer remaining in the state of a melt for a long time in liquid-phase synthesis by hydrolytic polymerization of caprolactam (CL) [3].…”

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“…However, since the concentration of halides necessary for reducing T m by 0-0°C (3.5⋅0 --3.0⋅0 -mole per mole of monomeric unit [3]) is comparable to the concentration of water in the reaction mixture, and the possibility of practical implementation of the idea is a function of the degree to which the electrolyte affects the condensation equilibrium in the PCAH O system, which determines the molecular weight of the polymer obtained.…”

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Condensation equilibrium in the polycaproamide—water—LiCl system

Bazarov

Mizerovskii

2006

Fibre Chem

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It was found that in the conditions of hydrolytic polymerization of caprolactam, the equilibrium degree of polymerization of the polymer obtained decreases significantly with an increase in the LiCl content from 1 to 5 wt. %. It was shown that the regulating effect of this electrolyte can be quantitatively described in hypothesizing the existence of the following equilibrium in the meltwith a constant equal to 6.7-12.6 base-mole/mole at 523 K and melt equilibrium moisture content of 6.5⋅10 -2 mole/base-mole.It was shown a long time ago [, ] that lithium halides are among the salts that significantly and reversibly reduce the melting point (T m ) of polycaproamide (PCA). This effect can be used to decrease the temperature boundary of the polymer remaining in the state of a melt for a long time in liquid-phase synthesis by hydrolytic polymerization of caprolactam (CL) [3].However, since the concentration of halides necessary for reducing T m by 0-0°C (3.5⋅0 --3.0⋅0 -mole per mole of monomeric unit [3]) is comparable to the concentration of water in the reaction mixture, and the possibility of practical implementation of the idea is a function of the degree to which the electrolyte affects the condensation equilibrium in the PCAH O system, which determines the molecular weight of the polymer obtained.The data in [4] on the high dehydrating power and participation in complexation with amines cast doubt on the neutrality of lithium halides with respect to this equilibrium. We will discuss the results of a preliminary study of this condensation equilibrium with respect to the PCAH OLiCl system.The reaction was conducted* in evacuated ampuls at 5 3 K in the presence of % H O and -5% LiCl of the weight of CL. The moisture content of the LiCl, determined by the Fischer method, was 3.9 wt. %, and the duration of the reaction was 0 h, in agreement with the data in [5].To be able to neglect the amount of water passing from the solution into the gas phase, the volume of the gas phase was decreased to ~0% of the volume of the melt by adding a glass insert, as previously proposed in [6].The content of water-soluble products in the polymerizates, dried to a constant weight at 333 K and residual pressure of 67 Pa, was determined by extraction with boiling water for h at a ratio of :00 and drying the polymer to a constant weight in the same conditions.The degree of polymerization of PCA free of oligomers and electrolyte was calculated from the results of determining the relative viscosity of a solution with a concentration of g per 00 ml of solvent in 95.6% H SO 4 at 93.0±0. K.The results of the experiment and subsequent calculations are summarized in Table .

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The lower temperature boundary of liquid-phase synthesis of polyamide-6

Cited by 5 publications

References 28 publications

Sustainable Production of Polyamide 6 Fibers: Direct Melt Spinning and Efficient Reuse of Residual Oligomers during Polymerization

Sustainable Production of Polyamide 6 Fibers: Direct Melt Spinning and Efficient Reuse of Residual Oligomers during Polymerization

Hydrolytic polymerization of caprolactam accompanied by crystallization of the polymer

Condensation equilibrium in the polycaproamide—water—LiCl system

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