CS252209B1 - A method for the non-waste preparation of a non-toxic activator for anionic lactam polymerization - Google Patents

Abstract

A method for producing non-toxic activators for the anionic polymerization of lactams from multifunctional isocyanates in a waste-free manner. The activators are prepared by reacting multifunctional isocyanates with lactams in an organic solvent at a molar equivalent ratio of lactam to isocyanate groups greater than one. Under these conditions, the mother liquors can be recycled multiple times, thereby achieving up to 100% yields and high purity of the product, which is suitable for the anionic polymerization of lactams.

Description

The invention relates to a process for the waste-free preparation of a non-toxic activator for the anionic polymerization of lactams.

In the manufacture of alkaline polyamide castings, polyfunctional isocyanates such as those described in USP 3,017,391 (1962) are preferably used as activators, which impart a high degree of toughness to the final product (U.S. Pat. No. 139,640), which is very important for this construction material.

However, isocyanates have a number of disadvantages. As reactants, they react very easily with acidic hydrogen such as water. Therefore, they are also degraded by air humidity. Their storage and handling therefore require special precautions. In addition, they are toxic and are likely to act mutagenically on animal cells. For this reason too, they need to be handled with great care, which presents some complications for the polyamide casting technology.

By reacting isocyanate groups with suitable reactants, activators (J. Stehlicek et al .: Coli. Czechosl. Chem. Commun. 32,371, 1967) can be prepared which are nontoxic and sufficiently inert to atmospheric moisture so that they do not require special storage, handling and handling measures. health safety. Such non-toxic activators with high stability to atmospheric humidity are, for example, products of multifunctional isocyanates with lactams, such as 4,4'-diisocyanate-diphenylmethane with ε-caprolactam or pyrrolidone. N-aryl and N-alkylcarbamoyllactams have the same activating effect as the corresponding isocyanates.

The preparation of alkyl and arylcarbamoyllactams is relatively simple and involves heating both components in a solvent. However, the solvent and part of the product are eliminated during the isolation. Since the anionic polymerization of lactam is extremely sensitive to impurities, the alkyl or arylcarbamoyllactams need to be purified for use as activators (see, e.g., U.S. Pat. No. AO 227 247,

J. Stehlíček et al. Coli. Czechosl. Chem. Commun. 29,1236,164; ibid 32,371, 1967). In doing so, additional solvent is consumed and further losses to the product occur.

These disadvantages can be overcome by a waste-free preparation process according to the invention, characterized in that the multifunctional isocyanates are reacted with lactams in a solvent, the ratio of lactam to isocyanates being at least 1.05: 1 in order to suppress side reactions. The product is then isolated and the mother liquors recirculated at least ten times. The quality of the products is sufficient for their use as activators of the anionic polymerization of lactams without any further purification.

The advantages of this process are that the nontoxic activator, which is much more resistant than the starting isocyanate to atmospheric moisture and which exhibits high cocatalytic efficiency, is obtained in high purity in a manner that generates no waste since the mother liquors after isolation are recirculated many times. This results in an almost 100% product yield, at high purity without the need for further purification operations, which are further advantages of the process of the invention.

Example 1

To a three-necked flask equipped with a stirrer, reflux condenser and dropping funnel, 25 g of ε-caprolactam was weighed and dissolved in 50 ml of toluene at about 80 ° C. To this solution was added a solution of 25 g MS Systanoate (4,4 ^L- diisocyanate diphenylmethane, manufactured by Synthesewerke, Schwarzheide, East Germany) in 50 mL toluene. Heat with stirring at gentle reflux for 2 hours. After this time, allow to cool to 25 ° C with stirring. The precipitated, crystalline product was filtered off, air-dried and dried for 12 hours at 50 ° C and 0.26 kPa. Melting point: 177-178 ° C. The mother liquors were returned to the next batch and the whole process repeated ten times. The overall yield of the activator was 99.2%. Toluene losses during filtration ranged from 5 to 10% per batch.

Example 2

4 kg of ε-caprolactam and 25 L of toluene were weighed into a 40 L enamelled duplicator pressure boiler, with heating and stirring on. After dissolution of caprolactam, 4 kg of 4,4'-diisocyanatodiphenylmethane was added. While stirring, it was heated to about 80 ° C over 2 hours, held at this temperature for 1 hour. Cooled to 20 ° C over the next 1 hour and the contents of the boiler drained to the filtering equipment. The mother liquors were returned to the next batch, the toluene losses made up to a volume of 25 L, the caprolactam concentration was determined and the amount of .epsilon.-caprolactam and the diisocyanate was weighed to the next batch so that the ratio of reactants, i.e. the.

-caprolactam: diisocyanate was 1.05: 1.

Example 3

In the diabetic polymerization reactor, 0.3 mol% of dilactamates and 0.3 mol% of the activator prepared according to the example (p, p-methylenebis (N-phenylcarbamoylhexahydro-2-azepinone)) were dissolved in a melt of 1 kg of ε-caprolactam at 130 ° C. ). The polymerization half-life was 8 min, the conversion was 97.2%, the polymer was insoluble in cresol, the impact strength was 24.7 J / cm, the notch toughness was 0.64 J / cm.

Example4

Similar to Example 1, an activator was prepared by reacting pyrrolidone with 2,4-diisocyanatotoluene and, analogously, piperidone with the same diisocyanate. The yields in both cases were 98.1% and 98.3% after the mother liquor recirculated ten times.

Example 5

In two duplicator boilers A and B, each 100 kg of ε-caprolactam was melted.

0.3 mol% of the dilactamates were added to the boiler and 1.2 kg of the activator prepared according to Example 1 were dissolved in the boiler B. Heat the contents of both boilers to 140 ° C and discharge through a mixer into plates (50x100x10) cm, 20x50 and 30x50 cm ) placed in a box tempered to 140 to 145 ° C. After 40 to 45 minutes, all molds were transferred to tempered boxes with a temperature gradient of 170 to 50 ° C over 8 to 12 hours.

The castings showed 96.8 to 97.2% polycaprolactam and were insoluble in cresol.

v 2

Impact toughness 2.50 to 2.53 J / cm Notch toughness 0.62 to 0.64 J / cm.

Claims (2)

A process for the waste-free preparation of a non-toxic activator for the anionic polymerization of lactams by reacting multi-fumed isocyanates with lactams in an organic solvent, characterized in that the ratio of molar equivalents of lactam to isocyanate functional groups is greater than 1. 2. Process according to claim 1, characterized in that the mother liquors are recirculated after isolation of the product.