Granted Patent B2

US 9,808,983 · App. 14/475,096 · Granted Nov 7, 2017

Abstract

Claims (27)

1. A method of producing a multilayer vessel, the method comprising the steps of

extruding an inner-layer formulation, a core-layer formulation, and an outer-layer formulation to form an inner parison, an outer parison, and a core parison configured to have a core-parison density different than each of an inner-parison density of the inner parison and an outer-parison density of the outer parison,

aligning the inner parison, the core parison, and the outer parison to cause the core parison to be located between the inner parison and the outer parison to cause the core parison to surround the inner parison and to be surrounded by the outer parison to form a multilayer tube,

placing the multilayer tube in a mold cavity formed in a mold, and

expanding the multilayer tube to cause the multilayer tube to deform so that the outer parison engages an inner surface of the mold and a multilayer vessel having an interior region formed therein is provided and to transform the core parison into a core layer having a core-layer density,

wherein a ratio of the core-layer density of the multilayer vessel to the core-parison density of the multilayer tube is in a range of about 1 to about 2.

2. The method of claim 1 , wherein a ratio of the core-layer density to the core-parison density is in a range of about 1.0 to about 1.25.

3. The method of claim 2 , wherein a ratio of the core-layer density to the core-parison density is in a range of about 1.0 to about 1.1.

4. The method of claim 3 , wherein a ratio of the core-layer density to the core-parison density is about 1.

5. The method of claim 1 , wherein the multilayer vessel has a vessel density, the multilayer tube has a tube density, and a ratio of the vessel density to the tube density is in a range of about 1.0 to about 1.9.

6. The method of claim 5 , wherein the ratio of the vessel density to the tube density is in a range of about 1.0 to about 1.25.

7. The method of claim 6 , wherein the ratio of the vessel density to the tube density is about 1.

8. The method of claim 1 , wherein each of the inner layer, outer layer, and core layer comprise a polymeric material.

9. The method of claim 1 , wherein the core-layer formulation comprises a polyethylene.

10. The method of claim 9 , wherein the polyethylene is high density polyethylene (HDPE).

11. The method of claim 10 , wherein the HDPE is a HDPE hexene copolymer.

12. The method of claim 1 , wherein the core-layer formulation comprises one or more high density polyethylene base resins (HDPE).

13. The method of claim 12 , wherein the HDPE is unimodal.

14. The method of claim 13 , wherein the unimodal HDPE is a unimodal, high-melt strength HDPE.

15. The method of claim 14 , wherein the unimodal, high-melt strength HDPE is electron beam modified.

16. The method of claim 15 , wherein the electron beam modified unimodal, high-melt strength HDPE has long chain branching and a melt index of about 0.25 g/10 min.

17. The method of claim 1 , wherein the core-layer formulation comprises about 97% to about 99.9% HDPE base resin.

18. The method of claim 17 , wherein the core-layer formulation comprises a nucleating agent.

19. The method of claim 18 , wherein the nucleating agent is about 0.1% to 15% (w/w) of the core-layer formulation.

20. The method of claim 19 , wherein the core-layer formulation lacks talc.

21. The method of claim 19 , wherein the core-layer formulation further comprises a slip agent.

22. The method of claim 21 , wherein the slip agent is about 0% to 3% (w/w) of the core-layer formulation.

Assignments (32)