Caprolactam oligomers

Many analytical techniques are in use for the qualitative and quantitative evaluation of monomers and oligomers extracted from PA6 (GC, differential refrac-tometry, IR, PC, SEC, HPLC, RPLC, etc.). FTIR has been used for quantitative analysis of caprolactam oligomer content (extract %) in polyamide-6 [113], The method, which involves a 3h extraction in boiling methanol, is suitable for process control and plant environment. Kolnaar [114] has used FTIR characterisation of fractional extracts with pentane, hexane, and heptane of HDPE for blow moulding applications. Vinyl acetate in packaging film has similarly been determined by quantitative FUR. 

SYNS AKULON ALK. MID AMILAN CM 1001 6-AMINOHEXANOIC ACID HOMOPOLYMER BONAMID CAPRAN 80 CAPROAMIDE POLYMER CAPROLACTAM OLIGOMER 0-CAPROL.ACTAM POLYMERS (GERMAN) CAPRON CHEMLON DANAMID DULL 704 DURETHAN BK ERTALON 6SA GRILON HEXAHYDRO-2H-AZEPIN-2-ONE HOMOPOLYMER ITAMID KAPROLIT KAPROLON KAPROMIN KAPRON MARAN iT. F 114 METAMID MIRAMID WM 55 NYLON-6 ORGAMIDE PA 6 (polymer) PLASKON 201 POLICAPRAN POLYAMIDE 6 POLY(e-... 

PVA, CMC, caprolactam oligomers, ethoxylated products, sulfonates, polyacrylic acid or adipic acid copolymers... 

The resulting amino acid then condenses in a stepwise manner to form the growing polymer chain. As in direct polymerization, cycHc oligomers are also formed hence, caprolactam (qv) can be formed in the reverse of the reaction just shown above. 

The cyclic oligomers are only slightly soluble in water and dilute solutions of caprolactam. They tend to separate out from die extracted waste during die process of concentration and chemical purification of die caprolactam. The cyclic oligomers tend to form on the walls of the equipment used in die process equipment. 6-Aminocaproic acid or sodium 6-aminocaproate may also be found in die oligomeric waste, especially if sodium hydroxide is used to initiate die caprolactam polymerization. 

Synthesis of PDMS-b-(e-caprolactam) ABA block copolymers was reported 343 In these reactions, anhydride-terminated PDMS oligomers were used to initiate the polymerization of -caprolactam in the presence of a catalytic amount of sodium hydride in melt at 130 °C. Under these conditions, the reaction was reported to be completed in... 

Reflux extraction of additives and wax from polyolefins was reported [116]. Subsequently, the additives were adsorbed onto an adsorbent (Florisil) and the wax was removed from the extract before chromatography. Boiling extractions of SBR are described in ASTM D 1416-89 1 g of rubber is extracted by boiling in two 100 mL portions of 75/25 vol% isopropyl alcohol/toluene. Reflux heating with strong solvents, such as THF, dichloromethane or chloroform has been reported [117]. Reflux extraction has also been used for the 3 h extraction of caprolactam and oligomers from PA6 in boiling methanol. 

On-line SFE-pSFC-FTIR was used to identify extractable components (additives and monomers) from a variety of nylons [392]. SFE-SFC-FID with 100% C02 and methanol-modified scC02 were used to quantitate the amount of residual caprolactam in a PA6/PA6.6 copolymer. Similarly, the more permeable PS showed various additives (Irganox 1076, phosphite AO, stearic acid - ex Zn-stearate - and mineral oil as a melt flow controller) and low-MW linear and cyclic oligomers in relatively mild SCF extraction conditions [392]. Also, antioxidants in PE have been analysed by means of coupling of SFE-SFC with IR detection [121]. Yang [393] has described SFE-SFC-FTIR for the analysis of polar compounds deposited on polymeric matrices, whereas Ikushima et al. [394] monitored the extraction of higher fatty acid esters. Despite the expectations, SFE-SFC-FTIR hyphenation in on-line additive analysis of polymers has not found widespread industrial use. While applications of SFC-FTIR and SFC-MS to the analysis of additives in polymeric matrices are not abundant, these techniques find wide application in the analysis of food and natural product components [395]. 

The polymerization of caprolactam to nylon 6 is an example of a step polymerization that does not lose a molecule of water. Oligomers can be isolated at any time, which is clearly a step reaction. If we recall that it is actually the polymerization of 6-aminocaproic acid, then we can see that it is indeed a step polymerization with loss of water. 

Caprolactams can be prepared by intramolecular nucleophilic cleavage of support-bound 6-aminohexanoates (Entry 9, Table 15.35). The yields of such reactions are usually not high, even if reactive esters are used for attachment to the support. High loading should be avoided to prevent the formation of oligomers by intermolecular nucleophilic cleavage. 

Copolymers. Copolymers from mixtures of different bisphenols or from mixtures of dichlorosulfone and dichlorobenzophenone have been reported in the patent literature. Bifunctional hydroxyl-terminated polyethersulfone oligomers are prepared readily by the polyetherification reaction simply by providing a suitable excess of the bisphenol. Block copolymers are obtained by reaction of the oligomers with other polymers having end groups capable of reacting with the phenol. Multiblock copolymers of BPA-polysulfone with polysiloxane have been made in this way by reaction with dimethyl amino-terminated polydimethylsiloxane the products are effective impact modifiers for the polyethersulfone (79). Block copolymers with nylon-6 are obtained when chlorine-terminated oligomers, which are prepared by polyetherification with excess dihalosulfone, are used as initiators for polymerization of caprolactam (80). 

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. 

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