E-Caprolactam polymers

O. Kamigaito, Synthesis of nylon 6-clay hybrid by montmorillonite intercalated with e-caprolactam,/. Polym. Sci. Pdym. Chem. 1993, 31, 983-986 (c) Y. Kojima,... 

On an industrial scale, PA-6 is synthesized from e-caprolactam with water as the initiator. The process is very simple if the reaction is earned out at atmospheric pressure. The polymerization is earned out in a VK-reactor (Fig. 3.23), which is a continuous reactor without a stirrer, with a residence time of 12-24 h at temperatures of 260-280°C.5,28 Molten lactam, initiator (water), and chain terminator (acetic acid) are added at the top and the polymer is discharged at the bottom to an extruder. In this extruder, other ingredients such as stabilizers, whiteners, pigments, and reinforcing fillers are added. The extruded thread is cooled in a water bath and granulated. The resultant PA-6 still contains 9-12%... 

FIG. 5 Model of alkylammonium-exchanged clay swollen by monomer or polymer precursors such as styrene, e-caprolactam, and epoxide. 

Polyamide 6 is produced by ring opening polycondensation of e- caprolactame. If no other reactants are used, the polymer chains contain one carboxylic acid and one amine end group. 

The details of the anionic polymerization of nylon 6 have been extensively reviewed (1-8) and will only be discussed briefly as they affect the star-polymerization of nylon 6. Nylon 6 is polymerized anionically in a two-step process (Figure 1). The first step, creation of the activated species 3, is the slow step. The e-caprolactam monomer reacts in the presence of a strong base (such as sodium hydride) to form the caprolactam anion 2. This anion reacts with more caprolactam monomer to form 3. The reaction of this activated species with lactam anions occurs rapidly to form the nylon 6 polymer 4. 

Apart from the uses in the production of e-caprolactam, the Beckmann rearrangement has been used industrially in the synthesis of various APIs (Active Pharmaceutical Ingredient) or other compounds with economical value (essentially monomers for the production of polymers). A survey of the bulk reaction scaled in the GMP facilities at... 

It should be noted that there is an ambiguity here in that poly(6-aminocaproic acid) and poly(e-caprolactam) are one and the same polymer. The same polymer is produced from two different monomers—a not uncommonly encountered situation. 

Poly(e-caprolactam) orpoly(e-aminocaproic acid) depending on the source of polymer Poly[imino(l-oxohexane-l,6-diyl)]... 

Special terminology based on trade names has been employed for some polymers. Although trade names should be avoided, one must be familiar with those that are firmly established and commonly used. An example of trade-name nomenclature is the use of the name nylon for the polyamides from unsubstituted, nonbranched aliphatic monomers. Two numbers are added onto the word nylon with the first number indicating the number of methylene groups in the diamine portion of the polyamide and the second number the number of carbon atoms in the diacyl portion. Thus poly(hexamethylene adipamide) and polyfhexamethylene sebacamide) are nylon 6,6 and nylon 6,10, respectively. Variants of these names are frequently employed. The literature contains such variations of nylon 6,6 as nylon 66, 66 nylon, nylon 6/6, 6,6 nylon, and 6-6 nylon. Polyamides from single monomers are denoted by a single number to denote the number of carbon atoms in the repeating unit. Poly(e-caprolactam) or poly(6-aminocaproic acid) is nylon 6. 

The overall rate of conversion of e-caprolactam to polymer is higher than the polymerization rate of e-aminocaproic acid by more than an order of magnitude [Hermans et al., 1958, I960]. Step polymerization of e-aminocaproic acid with itself (Eq. 7-57) accounts for only a few percent of the total polymerization of e-caprolactam. Ring-opening polymerization (Eq. 7-58) is the overwhelming route for polymer formation. Polymerization is acid-catalyzed as indicated by the observations that amines and sodium e-aminocaproate are poor initiators in the absence of water and the polymerization rate in the presence of water is first-order in lactam and second-order in COOH end groups [Majury, 1958]. 

It has become the custom to name linear aliphatic polyamides according to the number of carbon atoms of the diamine component (first named) and of the dicarboxylic acid. Thus, the condensation polymer from hexamethylenedi-amine and adipic acid is called polyamide-6,6 (or Nylon-6,6), while the corresponding polymer from hexamethylenediamine and sebacoic acid is called polyamide-6,10 (Nylon-6,10). Polyamides resulting from the polycondensation of an aminocarboxylic acid or from ring-opening polymerization of lactams are indicated by a single number thus polyamide-6 (Nylon-6) is the polymer from c-aminocaproic acid or from e-caprolactam. 

Problem 16.56 Indicate the reactions involved and show the structures of the following condensation polymers obtained from the indicated reactants (a) Nylon 66 from adipic acid and hexamethylene diamine (b) Nylon 6 from e-caprolactam (c) Dacron from methyl terephthalate and ethylene glycol (d) Glyptal from glycerol and terephthalic acid (e) polyurethane from diisocyanates and ethylene glycol. ... 

The mechanochemical polycondensation reaction has been studied using heterochain polymer systems—polyethylene terephthalate poly-(e-caprolactam), cellulose, etc.—characterized by end groups that can be activated to increase their own number by mechanochemical destruction of corresponding polymers. The mechanochemical destruction was done in the presence of some suitable condensing agents, such as aliphatic and aromatic diamines and fatty acid dichlorides. 

To establish the identity of the —CO—NH— links, a comparative recording was made between 2000 and 4000 cm-1, a range that is specific for those groups. Samples of pure poly (e-caprolactam) and a copolymer synthesized mechanochemically were used. The reaction time exerted a decisive influence on the polymer structure. The products obtained after short milling times (less than 20 hours) gave bands characteristic of the support polymer and a succession of new bands... 

A peculiarity of the anionic activated polymerization process for e-caprolactam is that it proceeds at temperatures below the polymer melting point. This leads to superposition of the polymerization process and crystallization of the newly synthesized polymer. 

The rate of polymer synthesis in co-dodecalactam polymerization is proportional to the first power of the catalyst concentration (in contrast to e-caprolactam, where the rate is second-order in the catalyst concentration when the concentrations of an activator and the catalyst are equal). If the system Na-caprolactam/Na-acetyl e-caprolactam is used in equimolar ratio as the catalyst/activator mixture and the range of concentrations is [C] = 0.35 -1.5 mol% (or 0.0175 - 0.075 mol/1), the dependence of the constant ko on [C] is as follows ... 

Modelling non-isothermal crystallization is the next important step in a quantitative description of reactive processing. This is particularly important, because crystallization determines the properties of the end product. Therefore, the development the spatial distribution of crystallinity, a, and temperature, T, with time throughout the volume of the reactive medium must be calculated. It is also noteworthy that crystallization and polymerization processes may occur simultaneously. This happens when polymerization proceeds at temperatures below the melting point of the newly formed polymer. A typical example of this phenomenon is anionic-activated polymerization of e-caprolactam, which takes place below the melting temperature of polycaproamide. 

Although the polymerization of e-caprolactam was described above, there is no difference in principle from the process flow sheets for centrifugal molding of items from other polymers and oligomers. Nevertheless, in most cases, the high temperatures used in lactam polymerization are not required, and the flow sheet as a whole is simplified. In industrial practice, poly(methyl methacrylate) pipes,172 and sheets of polyurethanes and unsaturated polyesters are obtained by centrifugal casting. 

Log P (Polymer) for Poly(dimethylsiloxane), Polyethylene -co-vinyl acetate), 40 VA, Poly(e-caprolactone), and Poly(e-caprolactam-co-e-caprolactone)... 

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