A method of modifying the polycaproamidefibre Megalon is plvposed," it consists of introducing a stage of preliminw'v heat treatment of a solution of the monomer in the graftThe cotton-like fibre Megalon prepared by graft polymerization --the graft copolymer ofpolycaproamide (PCA) and polyhydroxyethyl methacrylate (PHEMA) --has valuable properties: its water-retaining characteristics are close to cotton fibre, and its strength and wear resistance are better than cotton fibre [ 1, 2]. The problem of intensifying the existing technological process for manufacture of Megalon fibre, that is, to create economically efficient, environmentally progressive, and low-waste technology, is of both practical and scientific interest.We developed a method of manufacturing the graft copolymer of PCA with PHEMA (GCP) which allows reducing the concentration ofhydroxyethyl methacrylate (HEMA) in the initial solution by two times, increasing the amount of graft polymer, and repeatedly using the solution of the monomer without strengthening, significantly decreasing its concentration in wastewaters and increases the degree of conversion (HEMA) from 6 to 70%. This result is obtained by introducing a stage ofprelilninary heat treatment of the monomer solution in synthesis of GCP [3].In investigating the effect of the temperature and duration of heat treatment of the monomer solution on the amount of graft polymer, we found that heating the monomer solution at 65~ for less than 10 rain does not produce the desired results. Heat treatment of the nlonolner solution for more than 20 min at 75~ is not expedient, since the amount of graft polymer virtually does not change but a large amount of homopolymer is formed on the fibre, which is unacceptable.The results obtained are due to the fact that HEMA is oligomerized when heated, and the number of units in the oligomer is a function of the temperature and duration of heat treatment of the monomer solution. This in turn affects subsequent graft polymerization, in particular, the amount of graft polymer and homopolymer. We will discuss this problem in subsequent publications.Our studies showed that the optimum conditions of preliminary heat treatment of the monomer solution are heating for 15 rain at a temperature of 70~ Data on the yield of graft polymer, conversion of the monomer, efficiency of the graft polymerization reaction, and concentration of PHEMA in wastewaters in using this method of synthesis of GCP are reported in Fig. 1 and Table 1.Increasing the concentration of the starting monomer solution above 0.83 M was not associated with a significant increase in the amount of graft polymer. This is because a side homopolymerization reaction, caused by the formation of oligomers with a large number of units during preliminary heat treatment of the monomer solution, intensely takes place in addition to the basic graft polymerization reaction when a monomer solution with a concentration higher than 0.83 M is used.The increase in the amount of GCP on the second and third use of the monomer s...
A heat-treated solution ofhydroxyethyl methacrylate (HEMA) was investigated by the bromide--bromate method, gas-liquid chromatography, and NMR spectroscopy. A scheme of thermal polymerization of HEMA was proposed. Hypotheses were advanced concerning the mechanism of graft polymerization of HEMA oligomers to polycaproamide.The increase in output of the graft copolymer of polycaproamide (PCA) with polyhydroxyethyl methacrylate (PSP) is due to addition of the stage of preliminary heat treatment of a solution of the monomer to fabrication of the modified fibre [1]. We carefully investigated the preliminary stage of heat treatment of the monomer solution to determine the scheme of this process.Alkylene glycol methacrylic esters exhibit elevated polymerization activity. The possibility of thermal self-initiation has only been established for several monomers which generate sufficiently stabilized radicals [2, 3]. For this reason, a hypothesis was advanced concerning polymerization ofhydroxyethyl methacrylate (HEMA) during heat treatment of an aqueous solution of the compound with no catalyst. To confirm this version, a solution of HEMA was investigated by the bromide--bromate method, gas-liquid chromatography, and NMR spectroscopy. Heat treatment of the monomer solution was conducted for 15 min at a temperature of 70~The chromatographic analysis was conducted on a Tsvet-500 chromatograph with a flame-ionization detector and a glass column 2 m long with a 3-ram internal diameter, 1.5% OV-1 on Shimalitew for (80-100) min in isothermal temperature programming conditions using a UD-2M differential amplifier. The components of the solution were identified with reference substances and with the data from gas-liquid chromatographic analysis of HEMA reported in [4]. The results of the studies are reported in Table 1.The new signals with a retention time of 12 to 16 min were assigned to hydroxyethyl methacrylate oligomers. In the NMR spectroscopic study, ~H and 13C nuclear resonance was used. The spectra were recorded in solutions (1H and 13C). To obtain a more complete picture of polymerization of HEMA, D20, deuterated dimethyl sulfoxide (d 6 -DMSO), and hexachlorobutadiene (HCB) were used as solvents. The samples were heated in a thermostat or directly in the spectrometer detector. The spectra were primarily recorded in the accumulation mode with pulsed excitation and Fourier transformation. Broad-band decoupling of protons was used in recording the ~3C spectra. The study was conducted on Broker MSL-30 (FRG) and Varian T-60 (USA) spectrometers.The study of HEMA in heating for 5 min to 3 h gave the following results. The lines in the 13C NMR spectrum of the starting monomer had the following chemical shifts (& ppm Volgograd State Technical University.
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