SU960197A1 - Process for extracting polyamides - Google Patents

Description

(54) METHOD OF POLYAMIDE EXTRAGATION

one

The invention relates to the extraction of polyamides, in particular the removal of monomers and low molecular weight compounds from polyamides by treating them with aqueous solutions of stable free radicals.

Polyamides of JD -aminocarboxylic acids or their derivatives, alone or in. mixtures with other polyamides contain some amount of unreacted jg aminocarboxylic acids, lactams, or 1 low molecular weight condensation products, which are formed during storage or processing, for example, upon production of polyamide yarns. 5 With a high content of low molecular weight compounds, the processing of polyamides is difficult.

A known method of removing low molecular weight compounds (NMS) from polyamide-20s by treating polyamide chips with hot or boiling water l.

The HMC content is reduced to 0.5-1% by weight. However, while observing

A significant reduction in the polymer, which is manifested in the deterioration of the mechanical properties of products based on it, for example during the molding and drawing of filaments.

There are several ways to prevent the polyamide (Y) from being yellowed by treating it in order to remove NMS.

Known methods of processing polyamides with aqueous solutions of morpholine or its derivatives are concentrations of O, O01O, 5 wt.% 2, aqueous solutions of hydrazine and its derivatives 3, aqueous solutions of sodium sulfide, O content, 01-10 wt.% Of the latter 14.

The disadvantage of these methods is either the use of scarce substances, or the formation of salts, which must be additionally removed.

. Na1 | closer to the invention in its technical essence and the achieved positive effect is the method of extracting polyamides containing low molecular weight compounds by circulating & 6 by working the polymer with hot water; containing hydrazine with a concentration of 10-100 mg / l, 1 fi 50-80 C 5}. The disadvantage of this method is that hydrazine belongs to toxic compounds, therefore, their ingestion under industrial conditions is sharply limited. The aim of the invention is to reduce the toxicity of the extraction and drying process, as well as to preserve the "physical and mechanical properties of the polymer during its processing into filaments. The goal is achieved by the extraction method. polyamides containing their low molecular weight compounds (10-12% by weight), by treating the polymer crumb of the mountains -. whose water comprising a nitrogen-containing compound selected from the group containing 2,2,6,6-tetramethyl-4-hydroxypiperidine -1-oxyl, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, 2 , 2,4,5,5-pentamethyl-3-imidazol-3-oxide-1-oxide, in the amount of 10 -10% by weight of water 1 HI 9O-100 C. The method is carried out as follows. . In a vertical tank filled with polyamide chips containing up to 12% by weight of HMC, a hot (9010 C) aqueous solution from a chemical compound with a concentration of 10 - is fed. and incubated for 1-2 hours. The solution is cooled and then poured, a new batch is poured, again pushed for 3 h. A fresh solution is poured in for the third time and held for 4-5 h. The total process time for cooling and draining water is 15-20 h. As a result, a white polymer crumb is obtained with a HMC content of 0.5-1 HPC. Then polymer crumb

Without additives.-4

10 1O 10

.-g .f 10

179.4

144

112

96

Claims (5)

103 7 .4 are dried for 15-17 hours until the moisture content is LO, O5-0.5 weight. A thread of the required thickness is formed from the dried polymer. The thread has a permeability when stretching compared to a conventional one, i.e. It has significantly fewer breaks during stretching and intrapacking defects, for example breaks of elementary fibers. 1. Polyamide crumbs Example obtained from f-caprolactam c. The chemical conditions containing 10% by weight of HMC are placed in a vertical tank and filled with an aqueous solution of 2.2.6.6-heterramethyl-4-hydroxypiperidine-1-oxyl with a concentration of 10% by weight and a temperature of 90 C. The solution is maintained for 1-2 hours, cooled to room temperature, drained. A fresh portion of the hot solution of the nitroxyl radical is poured, kept for 3 hours. A third portion of the fresh solution is held in 4-5 hours. The content of HMC is 0.5 wt.%. Similarly, treatment with solutions of other nitroxyl radicals is carried out. The crumb is washed, dried for 14 hours until the water content in the crumb is 0.050, 5 wt.%, Molded on a PP-70OO machine into a 29 Tex string and then stretched on a KV-15O-44 machine. . The resulting yarn 29 tex is white, while the yarn obtained from the crumb without treatment with the proposed solutions has a yellowish tint. The table shows the data on the permeability of the yarn obtained in the process of stretching and winding. The nitrogen-containing compounds used for the extraction belong to the 3 claos of moderately hazardous chemical compounds. From the plates it can be seen that when the proposed compounds are added to the water upon removal of the NMS from polyamide, the thread breaks during drawing decrease by almost 2 cuts, and the breaks of the elementary fibers are reduced by 1.5 times. The invention of the method of extracting polyamides containing izomkolekulyarnyh compounds by treating polymer chips with hot water, including nitrogen-containing compound, JSpB heated, characterized in that, in order to reduce the toxicity of the process of extraction and drying and preserve the physicomechanical properties during their processing threads, as the nitrogen-containing compound, are used compounds selected in the groups containing 2,2,6,6-tetramethyl-4-oxoPvrvDIN-1- .OXIL, 2,2,6, in-tetrametyp-4 "-ox-piperidine-1 -oxip, 2,2,4,5,5 pentame TV1K -3-vmidazoliv-3-hydroxy) -1-oxysh1, in the amount by weight of water. Sources of information {% 4ation, taken into account in the examination 1. US patent number 3373145, cl. 260-78, publ. 1968. 2. Japanese Patent N 10349, cl. 25H62, published. 1966. 3. The patent of Germany Ms 109464, cl. 39 S 1O, pub. 1963. 4. Japanese Patent No. 7950, class 26СЗ, pub. 1969. 5. US patent number 2978439, cl. 26О-78, published. 1961 (prototype).