High impact resistant polyoxymethylene for extrusion blow molding

1. Method for the manufacturing of a container or parts of a container for volatile organic compounds (VOC) or compressed gases by extrusion blow molding a molding composition comprising:

a) at least one polyoxymethylene (A) having terminal groups comprised of hydroxyl groups,

b) at least one thermoplastic elastomer (B) and

c) at least one coupling agent (C);

wherein the coupling agent (C) couples the thermoplastic elastomer (B) to the polyoxymethylene (A) and comprises a polyisocyanate; and

wherein the molding composition has

a melt volume rate (MVR) of less than 3 g/10 min, determined according to ISO 1133 at 190° C. and 2.16 kg; and

a Charpy Notched Impact Strength (CNI) at 23° C., determined according to ISO 179-1/1eA (CNI), of higher than 15 kJ/m 2 , and

a complex shear viscosity η * of higher than 8000 Pas determined at 0.1rad/s and 190° C. according to ASTM D4440-08.

2. Method according to claim 1 , wherein at least 25% of the terminal groups of the polyoxymethylene (A) are hydroxyl groups.

3. Method according to claim 1 , wherein the polyoxymethylene (A) comprises at least 50 mol-% of —CH 2 O— repeat units.

4. Method according to claim 1 , wherein polyoxymethylene (A) is present in an amount ranging from 40 to 90 wt. % wherein the weight is based on the total weight of the molding composition.

5. Method according to claim 1 , wherein the complex shear viscosity η * ranges between 8100 and 100000 Pas.

6. Method according to claim 1 , wherein the coupling agent (C) is present in an amount ranging from 0.1 to 5 wt.-%, wherein weight-% is based on the total weight of the composition.

7. Method according to claim 1 wherein the thermoplastic elastomer (B) is selected from the group consisting of thermoplastic polyester elastomer (TPE-E), thermoplastic polyamide elastomer (TPE-A), thermoplastic polystyrene elastomer (TPE-S) which can be functionalized, thermoplastic polyolefin elastomer (TPE-O) which can be functionalized, thermoplastic polyurethane elastomer (TPE-U) and mixtures thereof.

8. Method according to claim 1 , wherein the thermoplastic elastomer (B) is present in an amount of 3 wt.-% to 50 wt.-%, wherein the weight is based on the total weight of the composition.

9. Method according to claim 1 , wherein the molding composition has a melt volume rate (MVR) of less than 2.5 g/10 min, determined according to ISO 1133 at 190° C. and 2.16 kg.

10. Method according to claim 1 , wherein the molding composition has a Charpy Notched impact Strength (CNI) at −40° C., determined according to ISO 179-1/1eA (CNI) of higher than 10 kJ/m 2 .

11. Method according to claim 1 , wherein the molding composition has a Charpy Notched Impact Strength (CNI) at 23° C., determined according to ISO 179-1/1eA (CNI) of higher than 20 kJ/m 2 .

12. Method according to claim 1 wherein the thermoplastic elastomer (B) is thermoplastic polyurethane elastomer (TPE-U).

13. Method according to claim 1 , wherein at least 50% of the terminal groups of the polyoxymethylene (A) are hydroxyl groups.

14. Method according to claim 13 , wherein the hydroxyl groups comprise hydroxyethylene groups.

15. Method according to claim 13 , wherein the thermoplastic elastomer (B) comprises a thermoplastic polyurethane elastomer, and wherein the container is a fuel tank or gas tank.