Synthesis of High Molecular Weight Nylon 6 by Anionic Polymerization of ε-Caprolactam. Mechanism and Kinetics

Ueda, Kazue; Nakai, Makoto; Hosoda, Masahiro; Tai, Kazuo

doi:10.1295/polymj.29.568

Cited by 25 publications

(15 citation statements)

References 24 publications

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“…20 Under the normal conditions of the polymerization, reaction 2 +-+ 3 (proton exchange between the reaction intermediate at the chain end and monomer molecule) is instantaneous. However, side reactions would sometimes occur in this reaction stage.…”

Section: Cyclic Dimermentioning

confidence: 99%

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Synthesis of High Molecular Weight Nylon 6 by Anionic Polymerization of ε-Caprolactam. Formation of Cyclic Oligomers

Ueda

Hosoda

Matsuda

et al. 1998

Polym J

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ABSTRACT:The formation of cyclic oligomers in the process of the anionic polymerization of E-caprolactam was studied. Cyclic oligomer contents increased with chain initiator concentration and decrease in catalyst concentration. Cyclic dimer content was much higher than that of cyclic trimer to cyclic hexamer and sensitively influenced by the concentrations of catalyst and chain initiator in comparison with cyclic trimer to cyclic hexamer. A mechanism is proposed in which cyclic dimer is peculiarly formed at the acyl-lactam terminal group.KEY WORDS Cyclic Oligomer/ Cyclic Dimer/ Nylon 6/ Anionic Polymerization/ E-Caprolactam/ Catalyst/ Chain Initiator / The anionic polymerization of e-caprolactam has been extensively investigated because of the high yield and rate of polymerization. 1 -4 Fundamental features such as various catalysts, 2 • 5 • 6 propagation mechanism, 7 -10 and kinetics 11 -16 are well known.The authors carried out systematic studies directed on high molecular weight nylon 6 and obtained stable high-molecular weight polymer (the weight average molecular weight, Mw=9.5 x 10 5 ) by controlling the water content in monomer and the concentration of the catalyst and chain initiator. 1 7 -19 The kinetic equations of their anionic polymerization are in agreement with the ideal rate equation. 20 The formation of cyclic oligomers in anionic polymerization of e-caprolactam has not been studied in detail. Cyclic oligomer content (up to heptamer) has been measured only in a few studies. 21 -23 The proposed mechanism of cyclic oligomer formation still seems insufficient. 24 This study deals with kinetic data of the cyclic oligomer formation in the polymerization as a function of the concentrations of catalyst and chain initiator. The mechanism of the formation is discussed. EXPERIMENT AL MaterialsIndustrial fiber grade e-caprolactam as monomer, ethyl magnesium bromide (EtMgBr; Aldrich Chemical Co., Inc.) as catalyst in 1.0 mo11-1 tetrahydrofuran solution and N-acetyl-e-caprolactam (Ac-CL; Tokyo Chemical Industry Co., Ltd.) as monofunctional chain initiator were used for polymerization. PolymerizationWater in e-caprolactam was removed to less than 0.013 mol¾ by bubbling dry argon gas for 5 h in a three-neck flask at 120°C. Water content was controlled by adding water to this e-caprolactam and measured by a Karl Fischer auto titration equipment (Hiranuma industrial Co., AQV-5S). The chain initiator was injected into ecaprolactam with controlled water content. The mixture of monomer and initiator was poured into a glass 186 tube (inside diameter 20 mm, volume 20 ml) dried beforehand by heating above l00°C under 10Pa vacuum. The catalyst (EtMgBr) solution was injected into the tube via a syringe, and the tube was sealed after unnecessary solvent was evaporated at 10 Pa. The polymerization was carried out with shaking in an oil bath at 150°C (thermostated at± l .0°C).Polymerization was stopped by quenching to dry ice/methanol temperature ( -73°C). The product was shaved with a boring machine and analyzed. Analy...

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Section: Cyclic Dimermentioning

confidence: 99%

“…1 7 -19 The kinetic equations of their anionic polymerization are in agreement with the ideal rate equation. 20 The formation of cyclic oligomers in anionic polymerization of e-caprolactam has not been studied in detail. Cyclic oligomer content (up to heptamer) has been measured only in a few studies.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of High Molecular Weight Nylon 6 by Anionic Polymerization of ε-Caprolactam. Formation of Cyclic Oligomers

Ueda

Hosoda

Matsuda

et al. 1998

Polym J

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“…Although a number of practical findings about the bulk polymerization of 6-caprolactam in the presence of various reinforcements have been collected 13) , the effect of preparation conditions on the structure and properties of the produced composites still remains an intriguing task, especially when alternative catalytic systems or fillers are attempted. As generally known, the anionic polymerization of caprolactam is initiated with strong bases able to form free lactam anions whose addition to N-acyllactam growth centers (created due to the action of suitable activators) brings about propagation of the polymer chain [13][14][15][16][17] . Frequently, sodium caprolactam is prepared by using sodium dihydridobis(2-methoxyethoxo)aluminate and sodium tetra(6-caprolactamo)aluminate.…”

Section: Introductionmentioning

confidence: 99%

“…The polymerization is then effectively activated with a cyclic trimer of phenyl isocyanate. Chain propagation in the activated anionic polymerization of 6-caprolactam is accompanied by side reactions leading to the decay of both lactam anions and growth centres 17) . It may be expected that these reactions will be sensitive 13,18) to fillers, properties of their surfaces, surface sizing agents, adsorbed water, etc.…”

Section: Introductionmentioning

confidence: 99%

Composites of alkaline poly(6-caprolactam) and short glass fibers: one-step synthesis, structure and mechanical properties

Horský¹,

Kolařı́k

Fambri

1999

Angew. Makromol. Chem.

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If incorporation of short fibers precedes the polymerization process, their damage is reduced because the viscosity of a monomer is much lower than that of a corresponding polymer. One‐step preparation of composites also leads to essential energy savings since polymer fusion and melt mixing are eliminated. Structure and properties of poly(6‐caprolactam) matrix polymerized with the initiator/activator systems sodium dihydridobis(2‐methoxyethoxo)aluminate/cyclic trimer of phenyl isocyanate are affected by rising concentration of (γ‐aminopropyl)triethoxysilane sizing agent: polymerization is slower, but polymerization degree rises; yield strength and notched impact strength decrease, while crystallinity and modulus remain unaffected. When the initiation system sodium tetra(6‐caprolactamo)aluminate/cyclic trimer of phenyl isocyanate is alternatively used, the polymerization is somewhat faster, but the polymer is insoluble in m‐cresol due to side crosslinking reactions. Incorporated short glass fibers (SGF) (up to 13.2 vol.‐%) do not markedly affect the matrix properties. As expected, SGF decrease the compliance (increase the moduli) of composites, but do not affect the time dependence of the creep. Increasing the fraction of SGF also decreases the yield strength of composites, which indicates poor interfacial adhesion; the latter is only slightly improved by fiber sizing. Impact strength decreases with the fraction of as‐received SGF, while a moderate opposite trend can be seen for the composites containing silane treated fibers.

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“…This makes PA6 one of the main engineering materials in use today. According to different reports [10][11][12][13][14][15][16][17], there are three main parameters that govern the polymerization of APCL: the catalyst (type and concentration), activator (type and concentration), and also the initial polymerization temperature. In almost all published studies, this process has been carried out in an inert atmosphere.…”

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confidence: 99%

Polyamide from lactams by reactive rotational molding via anionic ring-opening polymerization: Optimization of processing parameters

Barhoumi¹,

Maazouz²,

Jaziri³

et al. 2013

Express Polym. Lett.

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A reactive rotational molding (RRM) process was developed to obtain a PA6 by activated anionic ring-opening polymerization of epsilon-caprolactam (APA6). Sodium caprolactamate (C10) and caprolactam magnesium bromide (C1) were employed as catalysts, and difunctional hexamethylene-1,6-dicarbamoylcaprolactam (C20) was used as an activator. The kinetics of the anionic polymerization of !-caprolactam into polyamide 6 was monitored through dynamic rheology and differential scanning calorimetry measurements. The effect of the processing parameters, such as the polymerization temperature, different catalyst/activator combinations and concentrations, on the kinetics of polymerization is discussed. A temperature of 150°C was demonstrated to be the most appropriate. It was also found that crystallization may occur during PA6 polymerization and that the combination C1/C20 was well suited as it permitted a suitable induction time. Isoviscosity curves were drawn in order to determine the available processing window for RRM. The properties of the obtained APA6 were compared with those of a conventionally rotomolded PA6. Results pointed at lower cycle times and increased tensile properties at weak deformation

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Synthesis of High Molecular Weight Nylon 6 by Anionic Polymerization of ε-Caprolactam. Mechanism and Kinetics

Abstract: ABSTRACT:Studies on the mechanism and kinetics of the anionic polymerization of e-caprolactam were carried out by observing the kinetic data. The kinetic data were obtained as the functions of the concentrations of the catalyst and chain initiator.

Cited by 25 publications

References 24 publications

Synthesis of High Molecular Weight Nylon 6 by Anionic Polymerization of ε-Caprolactam. Formation of Cyclic Oligomers

Synthesis of High Molecular Weight Nylon 6 by Anionic Polymerization of ε-Caprolactam. Formation of Cyclic Oligomers

Composites of alkaline poly(6-caprolactam) and short glass fibers: one-step synthesis, structure and mechanical properties

Polyamide from lactams by reactive rotational molding via anionic ring-opening polymerization: Optimization of processing parameters

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