Injection molded preform, method of treating same and container formed therefrom

• US 4,928,835 A
• Filed: 01/31/1989
• Issued: 05/29/1990
• Est. Priority Date: 01/31/1989
• Status: Expired due to Term

• Current Assignee: Graham Packaging Pet Technologies Inc (Graeme Richard Hart, MBA)
• Original Assignee: Continental Pet Technologies Inc (O-I Glass, Inc.)
• Inventors: Armstrong, Ralph, Collette, Wayne N.
• Primary Examiner(s): Weaver, Sue A.
• Application Number:
  US07/304,469
• Time in Patent Office: 483 Days
• Field of Search: 215/1 C, 215/31, 428/35.7, 428/36.6, 428/36.7, 428/36.92, 428/542.8, 264/25, 264/235, 264/346, 264/520, 264/521, 264/532, 264/535
• US Class Current: 215/42
• CPC Class Codes: B29C 2949/0715 the preform having one end closed
• CPC Class Codes: B29C 2949/0773 Threads
• CPC Class Codes: B29C 2949/0862 Crystallinity
• CPC Class Codes: B29C 2949/0863 at the neck portion
• CPC Class Codes: B29C 2949/0864 at the flange portion
• CPC Class Codes: B29C 2949/0872 Weight
• CPC Class Codes: B29C 49/06 Injection blow-moulding
• CPC Class Codes: B29C 49/6445 through the preform length
• CPC Class Codes: B29C 49/6462 by masking
• CPC Class Codes: B29C 71/0063 for changing crystallisation
• CPC Class Codes: B29K 2067/00 Use of polyesters or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2667/00 Use of polyesters or derivatives thereof for preformed parts, e.g. for inserts
• CPC Class Codes: Y10S 264/908 Crystallizing of neck portion of hollow article or hollow preform
• CPC Class Codes: Y10T 428/1352 Polymer or resin containing [i.e., natural or synthetic]
• CPC Class Codes: Y10T 428/1397 Single layer [continuous layer]

Abstract

A polyester preform which is injection molded preferably of PET and wherein the preform is provided with a molded neck finish or neck portion inlcuding threads which are molded to a high tolerance and wherein the neck finish may receive a closure cap of the type having a tamper indicating band which engages over a retaining bead also molded to a high tolerance as part of the neck finish. In order to maintain the container which is blow molded from the preform in axial alignment with the neck finish and thus eliminate the perpendicularity problem, a ring of the preform immediately below the flange which functions as the capping ring, is heated to a high temperature and crystallized. In a like manner, the end sealing surface is also heated to a high temperature and crystallized. The remainder of the neck finish remains in its amorphous state without disturbing the configuration of either the threads or the retaining bead. This combination of crystallized portions with the remainder of the neck finish remaining amorphous assures a high quality connection between a closure cap, whether the closure cap is formed of plastic or metal, while providing the end sealing surface with a hard tough finish resisting deformation and at the same time reducing the closure cap removal torque.

Claims

1. A plastic preform for forming a hollow blow molded plastic container, said preform being of an injection molded construction and including a neck finish, said neck finish terminating at a free end in an end sealing surface and having remote from said end sealing surface a lower flange with there being high tolerance molded threads between said end sealing surface and said flange, said preform also including a container shoulder forming portion next to said flange remote from said threads, and a body forming portion, a part of said shoulder forming portion being a crystallized part and of a greater strength than adjacent parts of said preform, said preform being further improved by said end sealing surface being also crystallized, and said threads being free of added crystallization with said threads remaining as formed.

2. A preform according to claim 1 wherein the crystallization of said end sealing surface is to a depth on the order of 0.5 to 1.0 mm.

3. A preform according to claim 1 wherein the percent of crystallinity of said end sealing surface is on the order of 30-45% as compared to 5-10% for the threads.

4. A preform according to claim 1 wherein said threads are interrupted.

5. A preform according to claim 1 wherein said threads are separate threads for engagement by closure lugs.

6. A preform according to claim 1 wherein said plastic is a polyester.

7. A preform according to claim 1 wherein said plastic is PET.

8. A method of improving a plastic preform of the injection molded type having a neck finish including an end sealing surface, high tolerance external thread means, and a capping flange, said method comprising the steps of separately heating said end sealing surface and an annular region closely below but spaced from said capping flange to a high crystallization temperature while maintaining said preform between said crystallized end sealing surface and said crystallized annular region untreated whereby said end sealing surface becomes dense and exhibits a lowered friction co-efficient while said thread means maintain their as molded high tolerance.

9. A method according to claim 8 wherein said end sealing surface is heated to a temperature of 350°

±

50°

F.

10. A method according to claim 8 wherein said end sealing surface is heated to a temperature of 350°

±

50°

F. for a period of 15-25 seconds.

11. A method according to claim 8 wherein said end sealing surface is heated to a temperature of 350°

±

50°

F. for a period of 15-25 seconds, and crystallized to a depth of 0.5-1.0 mm.

12. A method according to claim 8 wherein said end sealing surface is heated to a temperature of 350°

±

50°

F. by passing the end sealing surface 1.0-2.0 mm below a flat strip heater maintained at a temperature on the order of 700°

-800°

F.

13. A blow molded plastic container comprising a neck portion, a shoulder portion leading from said neck portion to a tubular body, and said tubular body being closed by a bottom portion, a crystallized ring portion between said neck portion and said shoulder portion maintaining axial alignment of said tubular body with said neck portion, said neck portion having an open end defined by a crystallized end sealing surface and said neck portion between said crystallized end sealing surface and said crystallized ring portion being a non-treated amorphous region and including thread means for receiving a closure.

14. A container according to claim 13 wherein said crystallized end sealing surface is crystallized for a depth of 0.5 to 1.0 mm.

15. A container according to claim 13 wherein said crystallized end sealing surface is crystallized for a depth of 0.5 to 1.0 mm at a crystallinity of 30-45%.

16. A container according to claim 13 wherein there is a closure tamper band retaining bead below said thread means.

17. A container according to claim 13 wherein said thread means are in the form of a multiple start thread arrangement.

18. A container according to claim 17 wherein said container is closed by a metal closure cap having plural lugs engaging said multiple start thread arrangement.

19. A container according to claim 17 wherein there is a closure tamper band retaining bead below said thread means.