BLOW MOLDED PLASTIC CONTAINER AND GAS STORAGE TANK COMPRISING THE BLOW MOLDED PLASTIC CONTAINER AS A LINER

Abstract

The present invention relates to a blow molded plastic container and to a polymer composition from which the blow molded plastic container is made. The blow molded plastic container comprises a pinched seamline and is made by an extrusion blow molding process comprising a pinch step. The present invention also relates to a gas storage tank, comprising the blow molded plastic container as a liner. The polymer composition comprises (a) a polyamide consisting of a copolyamide consisting of repeat units derived from lactam, diamine and dicarboxylic acid, and optionally chain stoppers or branching units or a combination thereof, or of a blend of at least two polyamides, comprising at least one polyamide comprising repeat units derived from lactam, and at least one polyamide comprising repeat units derived from diamine and dicarboxylic acid, and comprising 75-97.5 mole % caprolactam and 1-12 mole % monomer having an aromatic ring, (b) a heat stabilizer and (c) impact modifier.

Claims

1. A blow molded plastic container for a fuel tank liner comprising a pinched seam line, wherein the tank is made of a polymer composition comprising: a. polyamide (A) consisting of a copolyamide (A1) consisting of repeat units derived from lactam, diamine and dicarboxylic acid, and optionally chain stoppers or branching units or a combination thereof, or a blend (A2) of at least two polyamides, comprising at least one polyamide comprising repeat units derived from lactam, and at least one polyamide comprising repeat units derived from diamine and dicarboxylic acid, wherein the polyamide (A) comprises 75-97.5 mole % of repeat units derived from caprolactam and 1-12 mole % of repeat units derived from monomer having an aromatic ring, relative to the total molar amount of lactam, diamine and dicarboxylic acid; b. a heat stabilizer; and c. an impact modifier.

2. The blow molded plastic container according to claim 1, wherein the heat stabilizer is selected from primary antioxidants, secondary antioxidants and metal halides; and mixtures or combinations thereof; and preferably comprises a metal halide stabilizer.

3. The blow molded plastic container according to claim 1, wherein the heat stabilizer (b) is present in an amount of 0.05-3 wt. %, preferably 0.1-2.5 wt. %, more preferably 0.1-2 wt. %, relative to the total weight of the polymer composition.

4. The blow molded plastic container according to claim 1, wherein the impact modifier (c) is present in an amount of 1-40 wt. %, preferably 5-30 wt. %, relative to the total weight of the polymer composition.

5. The blow molded plastic container according to claim 1, wherein the polymer composition comprises 0.01-5 wt. %, preferably 0.1-3 wt. % nigrosine (d), relative to the total weight of the polyamide composition.

6. The blow molded plastic container according to claim 1, comprising (e) a nucleating agent; preferably comprising micro-talcum.

7. The blow molded plastic container according to claim 4, wherein the nucleating agent (e) is present in an amount of 0.001-3 wt. %, preferably 0.01-1 wt. %, wherein the weight percentages are relative to the total weight of the polymer composition.

8. The blow molded plastic container according to claim 1, wherein the polyamide comprises repeat units derived from monomer having an aromatic ring in an amount of 1-10 mole %, preferably 2-8 mole %, relative to the total molar amount of lactam, diamine and dicarboxylic acid in the polyamide.

9. The blow molded plastic container according to claim 1, wherein the polyamide comprises a semi-aromatic polyamide selected from either amorphous semi-aromatic polyamides or semi-crystalline semi-aromatic polyamides having a melting temperature of at most 250° C., or a combination thereof.

10. The blow molded plastic container according to claim 1, wherein the polyamide in the polymer composition has a melting temperature of at most 250° C., preferably a melting temperature of at least 200° C. and most 240° C.

11. The blow molded plastic container according to claim 1, wherein the polymer composition comprises either (f) reinforcing fibers in an amount of at most 20 wt. %, preferably at most 10 wt. %; or (g) inorganic fillers in an amount of at most 20 wt. %, preferably at most 10 wt. %; or (h) one or more further additives in a total amount of at most 20 wt. %, preferably at most 10 wt. %; or any combination thereof, wherein the total amount of the combination is at most 30 wt. %, preferably at most 25 wt. % and more preferably at most 20 wt. %, and wherein the weight percentages are relative to the total weight of the polymer composition.

12. An extrusion blow molding process for making a blow molded plastic container comprising an extrusion step and a molding step, comprising extruding a polymer melt of a polymer composition thereby forming a hot parison from the polymer melt; closing a mold around the hot parison, while blowing a gas into the hot parison, thereby expanding the hot parison and pressing it against a mold cavity until it cools and solidifies to form an expanded part, and pinching-off parts from the expanded part, thereby forming a pinched plastic container; wherein the polymer composition is a polymer composition as described in claim 1.

13. The blow molding process according to claim 12, wherein the sum of the extrusion time Te needed for the extrusion step and the mold closing time Tmc needed for the molding step is at least 5 seconds.

14. Fuel tank comprising a liner and a reinforcing mantle around the liner, wherein the liner is a blow molded plastic container according to claim 1.

Description

EXAMPLES

[0082] Materials Used

[0083] Polyamide 1 PA6 with a relative viscosity of 2.5

[0084] Polyamide 2 PA-6I/6T amorphous semi-aromatic polyamide, Tg 125° C.

[0085] Polyamide 3 PA-6/6T, semi-crystalline semi-aromatic polyamide, Tm 205° C.

[0086] Polyamide 4 PA-6/IPDT copolymer

[0087] Impact modifier maleic anhydride (MAH) grafted ethene copolymer

[0088] Nucleating agent Micro-talcum; Median diameter of 0.50 micrometer

[0089] Heat stabilizer A CuI/KI

[0090] Heat stabilizer B Irganox 1098

[0091] Compositions

[0092] For the preparation of the compositions use was made of a twin-screw extruder, wherein the components were first dry-blended and then melt-mixed in the extruder while applying standard conditions for polyamide 6 compounds.

[0093] Preparation of Blow Molded Containers

[0094] Blow molded containers were prepared on a lab scale blow molding machine. Herein the polymer compositions were melt extruded through a circular orifice, thereby forming a parison from the molten polymer, and the parison was expanded by pressurized gas and pressed against a mold cavity while the mold closed and pinched of the end parts. Meanwhile the expanded parison cooled and solidified to form a molded and pinched container. Then the mold was opened, and the molded and pinched container was ejected from the mold. In a first series of experiments, the extrusion time Te was 27 seconds and the mold closing time Tmc was 7 seconds, resulting in a combined processing time Te+Tmc of 34 seconds. In a second series of experiments, the extrusion time Te was 14 seconds and the mold closing time Tmc was 1 second, resulting in a combined processing time Te+Tmc of 15 seconds.

[0095] Testing method for mechanical strength of the pinch line.

[0096] The pinch line strength was tested in following manner: first a section of pinch line was cut from the blow molded container. Then this section was bended by hand or in a vice inside-out and checked whether it broke. When it was easy to break, the result reported was ‘break’. When it was difficult to break, the result reported was ‘no break’.

[0097] The compositions and test results for the various Examples I-VIII according to the invention and Comparative Experiments A-F are listed in Tables 1 and 2. Herein IM is impact modifier; Mole % AM: is mole % of a monomer containing an aromatic group; and Mass % Stab is the weight percentage of heat stabilizer.

TABLE-US-00001 TABLE 1 First series of compositions and test results at ‘Condition 1’ for Comparative Experiments A-C and Examples I-IV. Com- ponents CE-A CE-B CE-C EX-I EX-II EX-III EX-IV PA #1 77 71.9 76.4 71.4 66.73 71.45 66.67 PA #2 5 5 10 5 10 IM 23 23 23 23 23 23 23 Stab-A 0.17 0.17 0.17 0.17 0.17 Stab-B 0.33 0.33 0.33 0.16 MB 0.1 0.1 0.1 0.1 0.05 Total 100 100 100 100 100 100 100 Mole % 0 3.12 0 3.14 6.32 3.08 6.07 AM Mass % 0 0 0.5 0.5 0.17 0.5 0.33 Stab Results break break break no no no no at break break break break Condition 1 Condition 1: total processing time Te + Tmc 34 seconds

TABLE-US-00002 TABLE 2 Second series of compositions and test results at ‘Condition 2’ for Comparative Experiments D-F and Examples V-VIII. CE- CE- CE- EX- EX- EX- EX- D E F V VI VII VIII PA #1 77 69 76.41 71.41 66.74 46.67 PA #2 5 5 10 PA #3 76.51 PA #4 30 IM 23 23 23 23 23 23 23 Stab-A 0.16 0.16 0.16 0.16 0.16 Stab-B 0.33 0.33 0.33 0.17 Micro- 0.1 0.1 0.1 0.1 talcum 100 100 100 100 100 100 100 Mole % 0 3.12 0 3.16 6.35 4.63 7.15 AM Mass % 0 0 0.49 0.49 0.16 0.49 0.33 Stab Result at break break break no no no no Condition break break break break 2 Condition 2: total processing time Te + Tmc 15 seconds