Molding polyamides, methods for the production thereof, and use thereof

Abstract

The present invention relates to novel cast polyamides, to processes for production thereof and to the use thereof.

Claims

1. A cast polyamide comprising a reaction product of: a) a catalyst for the anionic polymerization of lactams; b) an activator for the anionic polymerization of lactams, wherein the activator is at least one compound selected from the group consisting of biurets, and uretdiones; c) at least one coactivator selected from the group consisting of tert-amines; and d) a lactam, wherein the components a), b), c) and d) are combined and cast at a temperature of 80° C. to 130° C.

2. The cast polyamide as claimed in claim 1, wherein the catalyst is at least one compound selected from a group consisting of lactam magnesium halides, alkali metal aluminodilactamates, alkali metal and/or alkaline earth metal lactamates, potassium lactamates, and magnesium lactamates.

3. The cast polyamide as claimed in claim 1, wherein the activator is at least one biuret.

4. The cast polyamide as claimed in claim 1, wherein the activator is at least one uretdione.

5. The cast polyamide as claimed in claim 1, wherein: the coactivator is triethylenediamine; the lactam corresponds to lactams of the general formula ##STR00010##  where R is an alkylene group having 3 to 13 carbon atoms; and the combined components are cast in an injection casting, stationary casting, or rotary casting process.

6. The cast polyamide as claimed in claim 1, wherein the components a), b) and c) are present in the following proportions based on the lactam: a) 0.1 to 3% by weight, b) 0.1 to 2% by weight, and c) 0.0005 to 02% by weight.

7. A process for producing the cast polyamide as claimed in claim 1, the process comprising: mixing at least one lactam melt with the catalyst a) to produce a first mixture, mixing at least one lactam melt with the activator b) to produce a second mixture, at least one of: mixing a lactam melt with the coactivator c) to produce a third mixture, and mixing the coactivator c) with at least one of: the first mixture of lactam melt and catalyst a), and the second mixture of lactam melt and activator b), and combining the first mixture, the second mixture, and if the first and/or second mixture does not contain the coactivator c), also the third mixture at a temperature of 80° C. to 130° C. to produce a reaction mixture for polymerizing the lactam melts, and casting the reaction mixture at the temperature of 80° C. to 130° C.

8. A roller, a semifinished product or a sheet for mechanical engineering prepared with a polyamide according to claim 1.

9. The cast polyamide as claimed in claim 1, wherein: the catalyst is at least one compound selected from a group consisting of lactam magnesium halides, alkali metal aluminodilactamates, alkali metal and/or alkaline earth metal lactamates, potassium lactamates and magnesium lactamates; the activator is at least one compound selected from the group consisting of biurets, and uretdiones; the lactam corresponds to compounds of general formula ##STR00011##  where R is an alkylene group having 3 to 13 carbon atoms; and the temperature is 80° C. to <130° C.

10. The cast polyamide as claimed in claim 9, wherein components a), b) and c) are present in the following amounts based on the lactam: a) 0.1 to 3% by weight, b) 001 to 2% by weight, and c) 0.0005 to 02% by weight.

11. The cast polyamide as claimed in claim 10, wherein the temperature is 110° C. to 130° C.

12. The cast polyamide as claimed in claim 11, wherein; the coactivator is triethylenediamine; the activator is at least one biuret; and the lactam is at least one of caprolactam and laurolactam.

13. The cast polyamide as claimed in claim 11, wherein: the coactivator is triethylenediamine; the activator is at least one uretdione; and the lactam is at least one of caprolactam and laurolactam.

14. The cast polyamide as claimed in claim 9, wherein: components a), b) and c) are present in the following amounts based on the lactam: a) 0.2 to 1.5% by weight, b) 0.5 to 1% by weight, and c) 0.005 to 0.1% by weight; and the activator is at least one of: hexamethylene diisocyanate biuret and toluene diisocyanate uretdione; the catalyst is sodium caprolactamate; and the temperature is 110° C. to 130° C.

15. The cast polyamide as claimed in claim 1, wherein the cast polyamide is produced by reaction of at least: a) sodium lactamate as an 18-20% by weight caprolactam solution, b) at least one activator selected from the group consisting of a uretdione based on 2,4-diisocyanatotoluene, and a biuret of the formula (IV) ##STR00012##  with p=6, c) triethylenediamine, and d) caprolactam.

16. The cast polyamide as claimed in claim 15, wherein: the cast polyamide is produced by reaction of components a), b), c) and d); components a), b) and c) are present in the following amounts based on the lactam: a) 1 to 2% by weight, b) 0.5 to 1% by weight, and c) 0.005 to 0.1% by weight; and the temperature is 110° C. to 130° C.

Description

WORKING EXAMPLES

Reagents

(1) Dry caprolactam (EP>69° C.) from Lanxess Deutschland GmbH

(2) Addonyl® 8108 activator, a hexamethylene diisocyanate (HDI) biuret, 70% in N-ethylpyrrolidone, commercially available from Rhein Chemie Rheinau GmbH,

(3) Addonyl® Kat NL from Rhein Chemie Rheinau GmbH, about 18% sodium caprolactamate in caprolactam.

(4) Addocat® 105=a triethylenediamine in dipropylene glycol, commercially available from Rhein Chemie Rheinau GmbH

(5) Addolink® TT=a TDI uretdione from Rhein Chemie Rheinau GmbH

(6) Equipment:

(7) The apparatus used to prepare the melt consisted of: 2 three-neck flasks (500 ml), heated in an oil bath 2 precision glass stirrers with sleeves 2 gas caps, 1 with and 1 without a tap 1 vacuum pump with cold trap and manometer.

(8) The apparatus used to measure the temperature consisted of: Testo 175-T3 temperature measuring instrument with IR serial interface thermocouple to remain in the hardened sample 600 ml beaker (high mold) and a heater for the beaker (metal block, oil bath).
Procedure and Measurement:

(9) Flask A was charged with 196.8 g of caprolactam and 3.2 g of activator, Flask B with 192 g of caprolactam, 8 g of Addonyl® Kat NL catalyst and, in the case of the inventive experiments, with 0.2 g of Addocat®105.

(10) The melts from flasks A and B were prepared at 110-130° C. (±2° C.) in an oil bath under reduced pressure (<15 mbar) for 20 minutes.

(11) After venting with nitrogen, components from flask A and flask B were combined in a three-neck flask, stirred briefly and transferred to the 600 ml beaker.

(12) The mold temperature (beaker) was 160° C. The polymerization time was generally 10-20 minutes.

(13) TABLE-US-00001 No coactivator With coactivator Pot life (s)/ Pot life (s)/ Activator in flask A experiment number experiment number Addonyl ® 8108 (115° C.*) 550/C1 400/I1 Addonyl ® 8108 (135° C.*) 190/C2 200/C3 Addolink ® TT (125° C.*) 700/C4 580/I2 C1, C2, C3 and C4 = comparative example, I1 and I2 = inventive *Starting temperature of the polymerization melt

(14) The examples show that the inventive composition leads to short pot lives even at temperatures below 130° C., where the polymerization proceeds slowly. In this way, it is possible to achieve shorter cycle times in the production of cast moldings by the different shaping processes, such as stationary, rotary or injection casting processes, combined with improved properties of the castings.

(15) At temperatures above 130° C., the coactivator has no effect, as shown by comparative examples C2 and C3. These high starting temperatures are avoided, however, in the production of cast polyamide, since the polymerization can proceed in an uncontrolled manner and thus worsen the properties of the castings. In addition, the energy demand is higher here.