Method for producing a thermoplastic copolymers from polycaprolactam and thermoplastic polyurethane

Abstract

The present invention relates to a process for preparing a thermoplastic copolymer from polycaprolactam and thermoplastic polyurethane (TPU), to thermoplastic copolymers thus obtained and to shaped articles formed from copolymers of this type.

Claims

1. A process for preparing a thermoplastic copolymer based on polycaprolactam and a thermoplastic polyurethane, the process comprising: preparing a liquid mixture comprising caprolactam and a thermoplastic polyurethane at a temperature T.sub.1; and admixing a polymerization catalyst to the liquid mixture to obtain a mixture comprising the caprolactam and the thermoplastic polyurethane in a mass ratio of caprolactam to thermoplastic polyurethane in the range from 3:1 to 1:4, and polymerizing at a temperature T.sub.2 of at most 175 C. to obtain the thermoplastic copolymer, wherein the thermoplastic polyurethane has a melting temperature T.sub.0 and is based on (i) an alkylene diisocyanate; (ii) an alkylenediol; and (iii) a polyalkylene ether.

2. The process according to claim 1, wherein the alkylene diisocyanate of (i) is selected from the group consisting of a C1 to C20 alkylene diisocyanate and a mixture of two or more thereof.

3. The process according to claim 1, wherein the alkylenediol of (ii) is selected from the group consisting of a C1 to C20 alkylenediol and a mixture of two or more thereof.

4. The process according to claim 1, wherein the polyalkylene ether of (iii) is selected from the group consisting of a poly(C1 to C20 alkylene) ether and a mixture of two or more thereof.

5. The process according to claim 1, wherein one or more of the components alkylene diisocyanate (i), alkylenediol (ii) and polyalkylene ether (iii) have a linear and/or cyclic alkylene moiety.

6. The process according to claim 1, wherein T.sub.0 is in the range from 155 to 280 C.

7. The process according to claim 1, wherein T.sub.1 is not more than T.sub.0.

8. The process according to claim 1, wherein T.sub.2 is in the range from 100 to 175 C.

9. The process according to claim 1, wherein the polymerization catalyst is a salt of caprolactam.

10. The process according to claim 1, further comprising admixing a polymerization activator to the liquid mixture.

11. The process according to claim 1, wherein the admixing the polymerization catalyst to the liquid mixture provides a mixture comprising the caprolactam and the thermoplastic polyurethane in a mass ratio of caprolactam to thermoplastic polyurethane in the range from 7:3 to 1:3.

12. The process according to claim 1, wherein the preparing of the liquid mixture and the admixing and polymerizing are carried out as a batch process or as a continuous process.

13. A thermoplastic copolymer based on polycaprolactam and a thermoplastic polyurethane based on (i) an alkylene diisocyanate; (ii) an alkylenediol; and (iii) a polyalkylene ether, wherein the copolymer comprises the thermoplastic polyurethane in an amount of 25 to 80 wt %, based on the sum total of the weights of the caprolactam and of the thermoplastic polyurethane which are present in the copolymer.

14. The thermoplastic copolymer according to claim 13, wherein the alkylene diisocyanate of (i) is selected from the group consisting of a C1 to C20 alkylene diisocyanate and a mixture of two or more thereof.

15. The thermoplastic copolymer according to claim 13, wherein the alkylenediol of (ii) is selected from the group consisting of a C1 to C20 alkylenediol and a mixture of two or more thereof.

16. The thermoplastic copolymer according to claim 13, wherein the polyalkylene ether of (iii) is selected from the group consisting of a poly(C1 to C20 alkylene) ether and a mixture of two or more thereof.

17. The thermoplastic copolymer according to claim 13, wherein one or more of the components alkylene diisocyanate (i), alkylenediol (ii) and polyalkylene ether (iii) have a linear and/or cyclic alkylene moiety.

18. The thermoplastic copolymer according to claim 13, wherein the copolymer comprises the thermoplastic polyurethane in an amount of 30 to 75 wt %, based on the sum total of the weights of the caprolactam and of the thermoplastic polyurethane which are present in the copolymer.

19. A thermoplastic copolymer, obtained or obtainable by the process according to claim 1.

20. A shaped article made of or obtainable from the thermoplastic copolymer according to claim 13.

Description

EXAMPLES

(1) The following starting materials are used in the experimental examples, and comparative examples, which follow:

(2) 1. Lactam:

(3) caprolactam, from BASF.
2. Thermoplastic polyurethanes (TPUs), obtained from BASF: Elastollan A1185A (TPU based on polytetrahydrofuran 1000; hexamethylene diisocyanate (HDI) and 1,6-hexanediol), annealed at 110 C. for 3 h; Elastollan L1185A (TPU based on polytetrahydrofuran, 4,4-diisocyanatodicyclohexylmethane (H12MDI) and 1,4-butanediol), annealed at 110 C. for 3 h; Elastollan E1170A (TPU based on polytetrahydrofuran 1000/2000, methylenediphenyl diisocyanate (MDI) and 1,4-butanediol), annealed at 110 C. for 3 h.
3. Polymerization catalyst: Brggolen C10 (17-19% sodium caprolactamate in caprolactam), from Brggemann KG, Heilbronn.
4. Polymerization activator: Brggolen C20 (80% hexamethylene-1,6-dicarbamoylcaprolactam in caprolactam), from Brggemann KG, Heilbronn.

Example 1A

(4) The polymerization reaction was carried out in a dry atmosphere of nitrogen in a 250 mL round-bottom flask. Caprolactam (120 g) was dissolved at 170 C., followed by the admixture of 80 g of thermoplastic polyurethane (40 wt %) (Elastollan A1185A). The mixture was stirred at T.sub.1=170 C. for 30 min. Then, 23.1 g (11.6 wt %) of the catalyst (Brggolen C10) were introduced into the molten liquid mixture, starting the polymerization reaction. The anionic polymerization was carried out at T.sub.2=170 C. and stopped after 1 min by cooling the reactor off in ice-water (0 C.).

Example 1B

(5) Example 1A was repeated using Elastollan L1185A thermoplastic polyurethane instead of Elastollan A1185A.

Example 1C

(6) Examples 1A and 1B were repeated except that the thermoplastic polyurethane was dissolved at a temperature of 140 C. instead of 170 C., the mixture comprising caprolactam and the thermoplastic polyurethane is stirred for 30 min at T.sub.1=140 C. instead of at T.sub.1=170 C. and the polymerization reaction was carried out at T.sub.2=140 C. instead of at T.sub.2=170 C.

Example 2A

(7) The polymerization took place on a rheometer (Haake Polylab OS) in a 60 mL reaction chamber. The latter was heated to 170 C. and at the same time filled with 35 g of caprolactam (60 wt %) and 23.3 g of thermoplastic polyurethane (40 wt %) (Elastollan A1185A). The components were mixed at T.sub.1=170 C. for 10 min, followed by admixture of 6.71 g of catalyst (Brggolen C10) to start the anionic polymerization and carry it out at T.sub.2=170 C. The reaction mixture was kneaded for a further 15 min.

Example 2B

(8) Example 2A was repeated using Elastollan L1185A thermoplastic polyurethane instead of Elastollan A1185A.

Example 2C

(9) Examples 2A and 2B were repeated except that the thermoplastic polyurethane was mixed at a temperature of T.sub.1=140 C. instead of T.sub.1=170 C. and the polymerization reaction was carried out at a temperature of T.sub.2=140 C. instead of T.sub.2=170 C.

Example 3

(10) The thermoplastic copolymer based on polycaprolactam and a thermoplastic polyurethane was prepared on a twin-screw extruder (ZSK 32, L/D=56, Werner & Pfleiderer) whereto a heatable mixing tank was connected at zone 2. The extruder and mixing tank were ventilated with nitrogen in a continuous manner. Homogeneous, liquid mixture of 60 wt % caprolactam and 40 wt % thermoplastic polyurethane (Elastollan A1185A) was prepared in the mixing tank by heating and two hours of stirring. This mixture was temperature-regulated at T.sub.1=140 C. The copolymer was prepared by admixing 11.6 wt % of catalyst (Brggolen C10) into zone 1 of the extruder by solids metering at 60 C. and liquid metering of the caprolactam-polyurethane mixture into zone 2 at 170 C. Polymerization was achieved in zones 3-15 at T.sub.2=170 C. at a rotary speed of 200 rpm. The copolymer formed was pelletized by underwater separation and annealed at 80 C. Overall residence time in the extruder was about 3 min.

Example 4

(11) Example 3 was repeated except that the caprolactam-polyurethane mixture was premixed for 30 min instead of 2 h and metered into zone 2 of the extruder at T.sub.1=140 C. instead of T.sub.1=170 C. and the polymerization was carried out in zones 3-12 at T.sub.2=140 C. instead of T.sub.2=170 C. In addition, the temperature of the zones 13, 14 and 15 was set to 150 C., 160 C. and 170 C., respectively.

Example 5

(12) Example 3 was repeated except that the caprolactam-polyurethane mixture was premixed for 30 min instead of 2 h. In addition, the catalyst concentration was reduced to 5 wt %.

Comparative Example

(13) Example 3 was repeated except that Elastollan E1170A thermoplastic polyurethane was used instead of Elastollan A1185A and the caprolactam-polyurethane mixture was mixed at T.sub.1=180 C. instead of T.sub.1=140 C. and was metered into zone 2 at 180 C. instead of 170 C. In addition the temperature in zones 13-15 was set to T.sub.2=180 C. instead of T.sub.2=170 C.

Example 6

(14) Example 3 was repeated except that 40 wt % of caprolactam and 60 wt % of thermoplastic polyurethane were used instead of 60 wt % of caprolactam and 40 wt % of thermoplastic polyurethane and caprolactam and thermoplastic polyurethane were premixed for 30 min instead of 2 hours.

Example 7

(15) Example 3 was repeated except that 5.1 wt % of activator (Brggolen C20) was added to the caprolactam-polyurethane mixture into the mixing container.

Example 8

(16) The thermoplastic copolymer based on polycaprolactam and a thermoplastic polyurethane was prepared on a twin-screw extruder (ZSK 32, L/D=56, Werner & Pfleiderer) ventilated with nitrogen in a continuous manner. The copolymer was prepared by solids metering of 40 wt % of thermoplastic polyurethane (Elastollan A1185A) into zone 1 (120 C.) and melting in zones 2 (160 C.), 3 (220 C.) and 4 (180 C.) with subsequent liquid metering of 60 wt % of caprolactam into zone 5 (140 C.). Subsequent zones were heated to 170 C. and the polymerization was started by admixing 11.6 wt % of catalyst (Brggolen C10) into zone 7 by solids metering. Overall residence time in the extruder was about 3 min. The copolymer formed was pelletized by underwater separation and annealed at 80 C.

Example 9

(17) Example 8 was repeated except that 40 wt % of caprolactam and 60 wt % of thermoplastic polyurethane (A1185A) were used instead of 60 wt % of caprolactam and 40 wt % of thermoplastic polyurethane.

(18) Determination of Bursting Strength

(19) Bursting strength was determined on shaped articles in the form of hoses having an outer diameter of 8.2 mm and a wall thickness of 8.2 mm. For this purpose, hose samples 30 cm in length were sealed at one end and connected at the other end to a compressed air supply via a control valve. The pressure in the hose sample was raised gradually (at about 30 bar/15 s) to bursting in a chamber temperature-controlled to 23 C. or 70 C. The bursting pressure was recorded as was the time to bursting, because a pre-burst inflation of the hoses can be inferred therefrom. Each test was repeated three times.

(20) TABLE-US-00001 TABLE 1 Example Comparative 3 4 5 6 7 8 9 example caprolactam/ 60 60 60 40 60 60 40 60 wt % Brggolen C10/ 11.6 11.6 5 11.6 11.6 11.6 11.6 11.6 wt % Brggolen C20/ 5.1 wt % Elastollan 40 40 40 60 40 40 60 A1185A/ wt % Elastollan 40 E1170A/ wt % temperature of 140 140 140 140 140 180 mixer/ C. premix time/min 120 30 30 30 30 120 temperature of 60 60 60 60 60 120 120 60 zone 1/ C. temperature of 170 140 170 170 170 160 160 180 zone 2/ C. temperature of 170 140 170 170 170 220 220 170 zone 3/ C. temperature of 170 140 170 170 170 180 180 170 zone 4/ C. temperature of 170 140 170 170 170 140 140 170 zone 5/ C. temperature of 170 140 170 170 170 170 170 170 zones 6-12/ C. temperature of 170 150 170 170 170 170 170 180 zone 13/ C. temperature of 170 160 170 170 170 170 170 180 zone 14/ C. temperature of 170 170 170 170 170 170 170 180 zone 15/ C. temperature of 200 200 200 200 200 200 200 200 dieplate/ C. rotary speed/ 200 200 200 200 200 200 200 200 rpm throughput/kg/h 15 15 15 15 15 15 15 15 total residence 3 3 3 3 3 3 3 3 time/min

(21) The present examples are clear in demonstrating the surprising effects associated with the process of the present invention. Owing to the specific TPU copolymer provided as per b), the polymerization of process step d) is performable at an advantageously low temperature T.sub.2 of not more than 175 C., as apparent from Examples 1 to 9, which are in accordance with the present invention. By contrast, the step of providing a TPU copolymer based on an aromatic diisocyanate such as, for example, MDI requires a polymerization temperature of about 180 C., as apparent from the comparative example.

REFERENCES CITED

(22) G. S. Yang et al., Preparation and characterisation of thermoplastic polyurethane elastomer and polyamide 6 blends by in situ anionic ring-opening polymerization of epsilon-caprolactam, Polymer Engineering and Science 2006, 46, pp. 1196-1203 G. S. Yang et al. A novel approach to the preparation of thermoplastic polyurethane elastomer and polyamide 6 blends by in situ anionic ring-opening polymerisation of -caprolactam, Polym. Int. 2006, 55, pages 643-649 DE 10 2006 036 539 A1