CS217874B1 - Process for polymerization and copolymerization of dried low molecular weight water extractable fractions from the production of polyamide 6 - Google Patents

Abstract

The invention relates to a method for the polymerization and copolymerization of dried low-molecular water-extractable fractions from the production of polyamide 6 and/or cyclic oligomers of 6-caprolactam, the essence of which is that salts of anhydrous phosphoric acid with lactams of the general formula H3PO4.Iffl^CHgbrCO, where x is 3 to .1, are used as initiators in a concentration of 0.1 to 10 mol% at temperatures of 200 to 340 °C. The polymerization can be carried out in the presence of ω-amino acid lactams of the general formula where x is 3 to 11, or mixtures thereof. The invention can be used in the utilization of low-molecular water-extractable fractions that are lost in the production of polyamide 6.

Description

The invention relates to a process for the polymerization and copolymerization of low-molecular-weight water-extractable moieties which are dispensed with in the production of polyamide 6 or cyclic oligomers of 6-caprolactam.

In the polymerization of 6-caprolactam, unlike the polymerization of lactams β, a higher number of carbons per cycle than an honor equilibrium product is formed, which in addition to the polymer also contains unreacted monomer and cyclic and linear oligomers. For both fiber and other polyamide 6 applications, both monomer and oligomers need to be removed from the reaction product by extraction of a number of solvents, the most commonly used of which is water. Therefore, this part of the reaction product is referred to as water extractable fractions. Their equilibrium content and composition depend on temperature. At temperatures used in the production of polyamide 6 (i.e. 220 to 280 ° C), the water extractable fractions constitute 6 to 12% and consist largely (2/3 to 3/4) of 6-caprolactam. The remainder consists of oligomers, predominantly (9/10) cyclic. Of these, the cyclic dimer of 6-caprolactam is the most prominent.

The utilization of water-extractable fractions containing valuable polyamide-forming raw materials is an economically important task. Many procedures have been suggested for their processing; most are based on the regeneration of only the monomer, for example by distillation. Also, the cyclic oligomers can be overheated by cleavage in the presence of strong acids or by catalytic gas-phase cleavage. However, the regenerated 6-caprolactam is usually not sufficiently read and reduces the quality of the resulting product, i.e. polyamide 6.

The most efficient use of the water extractable fractions (after the water has been removed by concentration) should be their direct treatment by polymerization. Japanese Patent 72 24,676 and Hungarian Patent 332 (1968) protect their direct processing by addition to an excess of 6-caprolactam and subsequent anionic polymerization.

Direct hydrolytic polymerization treatment has not been utilized yet, since the cyclic oligomers present, especially the cyclic dimer of 6-caprolactam, reduce the rate of hydrolytic polymerization to such an extent that at technologically normal polymerization times (i.e. within 24 hours) an equilibrium polymer of sufficient polymerization degree cannot be obtained. For example, at 260 ° C, the monomer-oligomer-polymer equilibrium is reached after 20 hours of polymerization (initiator of 2 mol% of 6-aminocaproic acid). When 5 mol% of the cyclic dimer of 6-caprolactam is added to the same starting mixture, equilibrium is not reached after 70 hours at the same temperature. Polymerization of a mixture of 6-caprolactam and its oligomers by the action of water in combination with phosphoric acid is also less effective (Chem. Industry 26, 125 (1976)).

These drawbacks are overcome by a process for the polymerization and copolymerization of dried low molecular weight water extractables from the production of polyamide 6 having a water content of less than 0.2% by weight containing 6-caprolactam and its cyclic and linear oligomers and / or cyclic oligomers of 6-caprolactam of the formula NH-CO (CH 2) g] n, wherein n is 2 to 9, according to the invention, characterized in that the initiator used is the anhydrous phosphoric acid salt and the lactams of the ω-amino acids of the general formula H3FO4.NH- (CH2) _X- CO, wherein x is 3 to 11, preferably 8 salts of 6-caprolactam with anhydrous phosphoric acid at a concentration of 0.1 to 10 mol% at temperatures of 200 to 340 ° C. Further, the polymerization of the water-extractable moieties can be carried out in the presence of the ω-amino acid lactams of the general formula NH- (CH ₂ ) _X -CO, wherein x is 3 to 11, preferably 6-caprolactam, or mixtures thereof. When using 6-caprolactam, the resulting product is polyamide 6, while other lactams produce copolymers of these lactams with 6-caprolactam, while using a mixture of lactams gives ter- and multipolymers. according to the invention, compared to their hydrolytic polymerization, they are of an order of magnitude faster and the cyclic oligomers contained in the water extractable fractions are not a retarding component of the polymerization of 6-caprolactam or ω-amino acid lactams, respectively.

Another advantage of the process is that phosphoric acid remains incorporated into the polymer or copolymer chain and thus reduces the flammability of the polyamides. Said property is more pronounced with decreasing polymerization degree, i.e. with increasing initiator concentration. _t . C

The preparation of lactam salts with anhydrous phosphoric acid is described in the author's certificate No. 208 506.

The process according to the invention is described in more detail below on several exemplary embodiments.

*

He did

To the glass ampoule, 5% (w / w) water extractable fractions from polyamide fiber production 6 were added to the dried (water content 0.15 wt.%). The mixture was evacuated at 20 ° C / 13 Pa for 2 hours and sealed at this pressure. After 12 hours of polymerization at 240 ° C, an equilibrium polymer of 6-caprolactam (polymer content after extraction with water and drying to constant weight equal to 89.8 56) was obtained with a polymerization stage of 48 (polymerization stage P calculated from viscosimetric measurement of polymer solution in m- cresol at 25 ° C using the Huggins constant k * * 0.4 according to P * 119. W ^, _> 34 _> where [η] stands for the limit viscosity number (intrinsic viscosity (in dl / g)). When the initiator was used in an amount of 0.26% by weight, 81.56 polyamide 6 having a polymerization degree of 320 were obtained at this temperature and time.

Example 2

56 wt. of a mixture of 6-caprolactam (98 56 mol) with H 3 PO 4 .NH-TcHg 1 4 -CO (25 56 mol) was mixed with 8 20 56 wt. dried, to a water content of 0.18% by weight, of water extractables and polymerized as described in Example I. After 3 hours of polymerization at 260 ° C, 69% of polyamide 6 having a polymerization degree of 78 was obtained; after 12 hours of polymerization, an equilibrium polymer (polymer content 89 56) having a polymerization degree of 110 was obtained.

Example 3

A mixture of 93 56 mol of 6-caprolactam, 5 mol of cyclic dimar of 6-caprolactam and 2 56 mol

After 3 hours of polymerization at 260 DEG C., 72 56 polyamide 6 having a degree of polymerization of 77 were obtained; after 12 hours of polymerization at 260 DEG C., an equilibrium polymer was obtained. (polymer content 89.2 56) having a polymerization degree of 100.

Example

A mixture of 98 56 moles of cyclic dimar of 6-caprolactam and 2 56 moles of H 2 PO 3 .NH-CH 2 Cl 5-00 was polymerized at 340 ° C as described in Example 1. After 30 minutes of polymerization, 76 56 polyamide 6 were obtained. If it was under the same conditions instead of H3PO4.

.NH- (CH ₂₎ 5 to 00 used 6-aminocaproic acid (initiator hydrolytic polymerization), gave only 40 56 polyamide 6 having a polymerization degree '77.

Example 5

To a mixture of 48 56 moles of 6-caprolactam, 50 56 moles of 12-dodecanlactam and 2556 moles of H 3 PO 4 .NH-CH 2 Cl 2 was added 20 wt. dried water extractables β with water content 0.18 56 wt. The polymerization was carried out at 260 ° C according to the method of Example 1. An equilibrium copolymer (content of copolymers after extraction with methanol and drying to a constant weight of 91 56) with an intrinsic viscosity [η] = 1.0 dl / g was obtained after 18 hours of polymerization.

Example 6

To a mixture of 35 mole% 6-caprolactam, 48% 12-dodecanlactam and 2 mole% H ³ PO 4 .alpha .- (CH 3 TiO 4) was added 15 mole% cyclic dimer of 6-caprolactam and polymerized at 270 ° C according to Example 1. Equilibrium copolymer (92.356) having an intrinsic viscosity [η] = 1.1 dl / g was obtained after 18 hours of copolymerization.

Example 7

A mixture of 88 mol% of 12-dodecanlactam, 0.5 mol% of H 3 PO 4 .H 2 O - (CH 3 Ti-CO and 11.5 mol% of cyclic dimer of 6-caprolactam was polymerized at 320 ° C as described in Example 1. After 15 hours of polymerization an equilibrium copolymer (content of copolymers 96 56) having an intrinsic viscosity of Q1 = 2.0 dl / g was obtained.

Example 6

To a mixture of 24% of 6-caprolactam. 33 mole% of 8-octanlactam, 33 mole% of 12-dodecanlactam and 10 mole% of H 3 PC 4 · NH-CH 3 -CO 2 were added 10 wt. water-extractable fractions 8 with a water content of 0.18 wt. and polymerization at 220 < C > C was carried out according to Example 1. An equilibrium terpolymer was obtained after 5 hours (copolymer content 9516).

Example 9

A mixture of 80 mol% of 6-caprolactam, 10 mol% of cyclic dimer of 6-caprolactam and 10 mol%

H3PO4.fH- (CHgTy-CO) was polymerized at 240 ° C as described in Example 1. After eight hours of polymerization, 76% of the copolymers with an intrinsic viscosity [η] = 0.3 dl / g were obtained.

Example 10

16 wt. of a mixture of 6-caprolactam (90 16 mol), 2-pyrrolidone (556 mol) and H 3 PO 4. 1 H-XGHgTg-CO (516 mol) was mixed with 20 56 wt. dried water-extractable fractions from the production of polyamide 6 (water content 0.18 16 wt.) and polymerized as described in Example 1. After eight hours of polymerization at 240 ° C, 87.5 16 copolymers having an intrinsic viscosity were obtained. 0.5 dl / g.

Claims (2)

OBJECT OF THE INVENTION t CLAIMS 1. A process for the polymerization and copolymerization of dried low molecular weight water extractables from the production of polyamide 6 comprising 6-caprolactam and its cyclic and linear oligomers and / or cyclic oligomers of 6-caprolactams of the general formula [NH-CHCH3] -CQln, where n is 2 to 9, characterized in that the initiator used is the anhydrous phosphoric acid salt of the lactams of the general formula HjPC ^NH-TcHgT ^-CO, where x is 3 to 11, at a concentration of 0.1 to 10 16 mol, at temperatures 200 DEG-340 DEG. 2. A process according to claim 1, wherein the polymerization and copolymerization of the dried low molecular weight water extractables from the production of polyamide 6 and / or the cyclic oligomers of the 6-caprolactams of the general formula [NH-CCH3] -CO2, where n is 2 to 9, is carried out in the presence of lactams of the general formula (NH-CCH3) -CO, where x is from 3 to 11, or mixtures thereof.