Graded crystallization of container finishes
A container, a container preform and a method of making the container or preform in which the finish of the preform or container is at least partially of crystallizable polymer construction, and has an end portion remote from the body of the preform or container, a capping flange adjacent to the body of the preform or container, and a mid portion between the end portion and the capping flange. The end portion of the finish forms an end surface, and the end and mid portions of the finish form continuous inner and outer surfaces. The polymer material in at least one of the end, inner and outer surfaces is crystallized, and crystallization in the finish in a direction perpendicular to such surface is graded from crystallization at the surface to an essential absence of crystallization at a position within the finish spaced from the surface.
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The present invention is directed to containers of molded polymer construction, and more particularly to crystallization at the container neck finish.
BACKGROUND AND SUMMARY OF THE INVENTIONContainers of crystallizable polymer construction—e.g., PET construction—are conventionally fabricated in an injection blow molding operation, in which a preform is fabricated by injection molding, and the preform is then subjected to a blow molding operation to form the container. The container finish is formed to final geometry or substantially final geometry in the injection molding operation, and generally is of amorphous polymer construction. The body of the container is subjected to stretching during the blow molding operation so that the body is of oriented polymer construction. It has been proposed to strengthen and rigidify the finish portion of the container by crystallizing all or selected portions of the neck finish. See, for example, U.S. Pat. Nos. 4,618,515, 4,928,835 and 6,217,818. The uncrystallized portions of the container body and finish are typically translucent, while the crystallized portion(s) of the finish contain spherulite that has a milky opaque appearance.
The term “crystallizable polymer” in the present application refers to any polymer that is capable of being crystallized. These polymers include not only polyesters such as PET, which is the crystallizable polymer most typically used to make containers, but also polyolefins such as polyethylenes and polypropylenes, polycarbonates and polyamides such as nylons. Thus, although specific embodiments of the invention are disclosed in conjunction with polyesters—i.e., PET—the invention is by no means limited specifically to this polymer or family of polymers.
Likewise, when referring in the present application to preforms or containers that are at least partly of crystallizable polymer construction, or to preforms or containers of crystallizable polymer construction, such language refers not only to containers that are entirely of crystallizable polymer construction, but also to multilayer containers in which inside and outside layers are of crystallizable polymer construction. Other intermediate layers of the container or preform may include barrier materials against migration of gases through the container walls, layers of process regrind and/or layers that include post consumer resin. These intermediate layers may be included only in the body of the container, such that the container finish is of unlayered polymer construction, or may extend into the finish of the container. See, for example, U.S. Pat. Nos. 4,550,043, 4,609,516, 4,781,954, 4,990,301 and 5,098,274.
It has been proposed to crystallize the entire finish of a PET container to improve dimensional stability of the container finish. However, such complete crystallization may induce shrinkage of the finish as a result of crystallization, which is unacceptable in the threaded section of the finish to which a container closure will ultimately be secured. Conversely, a completely amorphous finish is subject to softening and movement as the container is hot-filled and capped because the temperature of the container may rise above the glass transition temperature of the plastic. It is therefore an object of the present invention to provide a technique for selectively crystallizing portions of the container finish that substantially reduces or eliminates shrinkage of the finish as a result of crystallization, provides desired stability in the finish sealing and thread area where the container closure will ultimately be secured, and/or that reduces consumption of energy as compared with crystallization of the entire finish area. Other and more specific objects of the invention are to provide a preform for blow molding a hollow plastic container, a hollow plastic container, and a method for forming a hollow plastic container in which the container finish is selectively crystallized as described above.
These and other objects are achieved in accordance with the present invention by selectively crystallizing the neck finish of the preform or container in such a way as to achieve substantial crystallization in at least a first portion of the finish, substantially no crystallization in a second portion of the finish, and graded crystallization between the first and second portions of the finish. The term “graded crystallization” refers to a gradual transition between substantial crystallization and substantially no crystallization, as distinguished from a sharp or distinct non-graded pattern of contrast between crystallized and uncrystallized portions of the neck finish. The gradation of crystallization is continuous, and may be either linear or non-linear with distance.
The present invention embodies a number of aspects, that may be implemented separately from or in combination with each other.
In accordance with a first aspect of the invention, a preform for blow molding a hollow plastic container, which is at least partly of crystallizable polymer construction, includes a finish and a body integral with the finish. The finish has an end portion remote from the body, a capping flange adjacent to the body, and a mid portion between the end portion and the capping flange. The end and mid portions form a continuous outer surface and a continuous inner surface, with one of the inner and outer surfaces being crystallized throughout its length and the other of the inner and outer surfaces including at least a portion that is essentially uncrystallized. Crystallization in at least the mid portion of the finish is graded between the crystallized surface and the uncrystallized portion of the other surface. In accordance with another aspect of the present invention, the end and mid portions form a continuous outer surface that is crystallized throughout its length, and a continuous inner surface at least a portion of which is essentially uncrystallized. Crystallization in at least a mid portion of the finish is graded between the outer and inner surfaces, and between the mid portion of the finish and the capping flange. In accordance with a third aspect of the invention, at least the end portion of the finish is crystallized, and crystallization in the finish is graded from full crystallization at the end portion.
In accordance with yet another aspect of the present invention, a hollow plastic container of crystallizable polymer construction includes a finish and an integral body. The finish has an end portion remote from the body, a capping flange adjacent to the body, and a mid portion extending between the end portion and the capping flange. The end and mid portions form continuous outer and inner surfaces, with one of the outer and inner surfaces being crystallized throughout its length and the other of the inner and outer surfaces including at least a portion that is essentially uncrystallized. Crystallization in at least the mid portion of the finish is graded between the crystallized surface and the uncrystallized portion of the other surface. In accordance with another aspect of the invention, the end and mid portions of the container finish form a continuous outer surface that is crystallized throughout its length, and a continuous inner surface at least a portion of which is essentially uncrystallized. Crystallization in at least the mid portion of the container finish is graded between the outer and inner surfaces and between the mid portion and the capping flange. In accordance with a further object of the invention, at least the end portion of the finish is crystallized, and crystallization in the finish is graded from full crystallization at the end portion of the finish.
Yet another aspect of the present invention provides a method of making a hollow plastic container, which includes molding a preform of crystallizable polymer construction and blow molding the preform to form the hollow plastic container. Either prior to or subsequent to blow molding the preform, the finish is crystallized at one of the inner and outer surfaces of the finish in such a way that one surface is crystallized throughout its length and the other surface includes at least a portion that is essentially uncrystallized, with crystallization in at least the mid portion of the finish being graded between the surfaces. In accordance with a further aspect of the invention, crystallization of the finish of either the preform or the container is such that the outer surface of the finish is crystallized throughout its length and at least a portion of the inner surface is essentially uncrystallized. Crystallization in at least the mid portion of the finish is graded between the outer and inner surfaces and between the mid portion and the capping flange. In accordance with yet another aspect of the invention, crystallization at the finish is such that at least the end portion of the finish is crystallized, and crystallization in the finish is graded from crystallization at the end portion.
BRIEF DESCRIPTION OF THE DRAWINGSThe invention, together with additional objects, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:
Referring in particular to
In
Controlled crystallization in the embodiments of
Although the preferred embodiments of the invention have been discussed in conjunction with crystallizing the finish of the preform, which is preferred for process handling purposes, it will be understood that the crystallization operation could take place in the neck finish after the container is blown to final form. Such a modification would be particularly useful in situations in which the finish geometry is modified during the blow molding operation. Thus, crystallization in accordance with the present invention can be implemented on either amorphous or oriented finishes.
There has thus been described preforms, containers and methods of manufacture that fully implement all of the objects and aims previously set forth. The invention has been disclosed in conjunction with a number of presently preferred embodiments, and several additional modifications and variations have been discussed. Other modifications and variations will readily suggest themselves to persons of ordinary skill in the art. The invention is intended to embrace all such modifications and variations as fall within the spirit and broad scope of the appended claims.
Claims
1-16. (canceled)
17. A hollow plastic container that is at least partially of crystallizable polymer construction and includes:
- a finish and a body integral with said finish,
- said finish having an end portion remote from said body, a capping flange adjacent to said body, and a mid portion between said end portion and said capping flange,
- said end and mid portions forming a continuous outer surface and a continuous inner surface,
- one of said inner and outer surfaces being crystallized throughout its length and the other of said inner and outer surfaces including at least a portion that is essentially uncrystallized,
- crystallization in at least said mid portion of said finish being graded between said crystallized surface and the uncrystallized portion of the other surface.
18. The container set forth in claim 17 wherein said outer surface is crystallized throughout its length and at least a portion of said inner surface is crystallized.
19. The container set forth in claim 18 wherein said end portion of said finish is crystallized throughout its thickness between said inner and outer surfaces.
20. The container set forth in claim 18 wherein crystallization in said end portion of said finish is graded between said outer and inner surfaces, being crystallized at said outer surface and essentially uncrystallized at said inner surface.
21. The container set forth in claim 17 wherein said inner surface is crystallized throughout its length and said outer surface is essentially uncrystallized.
22. The container set forth in claim 17 wherein said capping flange is essentially uncrystallized.
23. A hollow plastic container that is at least partially of crystallizable polymer construction and includes:
- a finish and a body integral with said finish,
- said finish having an end portion remote from said body, a capping flange adjacent to said body, and a mid portion between said end portion and said capping flange,
- said end and mid portions forming a continuous outer surface that is crystallized throughout its length, and a continuous inner surface at least a portion of which is essentially uncrystallized,
- crystallization in at least said mid portion of said finish being graded between said outer and inner surfaces and between said mid portion and said capping flange.
24. The container set forth in claim 23 wherein said end portion of said finish is crystallized throughout its thickness between said inner and outer surfaces.
25. The container set forth in claim 23 wherein crystallization in said end portion of said finish is graded between said outer and inner surfaces, being crystallized at said outer surface and essentially uncrystallized at said inner surface.
26. The container set forth in claim 23 wherein said capping flange is essentially uncrystallized.
27. A hollow plastic container that is at least partially of crystallizable polymer construction and includes:
- a finish and a body integral with said finish,
- said finish having an end portion remote from said body, a capping flange adjacent to said body, and a mid portion between said end portion and said capping flange,
- at least said end portion of said finish being crystallized, and crystallization in said finish being graded from crystallization at said end portion.
28. The container set forth in claim 27 wherein said end portion of said finish is crystallized throughout its thickness between said inner and outer surfaces.
29. The container set forth in claim 28 wherein graded crystallization in said finish extends into said mid portion of said finish.
30. The container set forth in claim 27 wherein crystallization in said end portion of said finish is graded between said outer and inner surfaces, being crystallized at said outer surface and essentially uncrystallized at said inner surface.
31. The container set forth in claim 27 wherein said end and mid portions of said finish form a continuous outer surface and a continuous inner surface, one of said inner and outer surfaces being crystallized throughout its length and the other of said inner and outer surfaces including at least a portion that is essentially uncrystallized.
32. The container set forth in claim 31 wherein crystallization in at least said mid portion of said finish is graded between said surfaces.
33. A hollow plastic container having a finish and an integral body,
- said finish having an end portion with an end surface, a capping flange adjacent to said body, and a mid portion between said end portion and said capping flange,
- said end and mid portions forming continuous inner and outer surfaces,
- said finish being crystallized at at least one of said end, inner and outer surfaces, and crystallization in said finish in a direction perpendicular to said at least one surface being graded from crystallization at said at least one surface to an essential absence of crystallization at a position within said finish spaced from said at least one surface.
34. A method of making a hollow plastic container, which comprises the steps of:
- (a) molding a preform at least partially of crystallizable polymer construction including a finish and a body integral with said finish, said finish having an end portion remote from said body, a capping flange adjacent to said body, and a mid portion between said end portion and said capping flange, said end and mid portions forming continuous inner and outer surfaces,
- (b) blow molding said preform to form a hollow plastic container, and
- (c) either prior to or subsequent to said step (b), crystallizing said finish at one of said inner and outer surfaces in such a way that said one surface is crystallized throughout its length and the other of said inner and outer surfaces includes a portion that is essentially uncrystallized, and such that crystallization in at least said mid portion is graded between said surfaces.
35. A method of making a hollow plastic container, which comprises the steps of:
- (a) molding a preform at least partially of crystallizable polymer construction including a finish and a body integral with said finish, said finish having an end portion remote from said body, a capping flange adjacent to said body, and a mid portion between said end portion and said capping flange, said end and mid portions forming continuous inner and outer surfaces,
- (b) blow molding said preform to form a hollow plastic container, and
- (c) either prior to or subsequent to said step (b), crystallizing said finish in such a way that said outer surface is crystallized throughout its length and at least a portion of said inner surface is essentially uncrystallized, and such that crystallization in at least said mid portion of said finish is graded between said outer and inner surfaces and between said mid portion and said capping flange.
36. A method of making a hollow plastic container, which comprises the steps of:
- (a) molding a preform at least partially of crystallizable polymer construction including a finish and a body integral with said finish, said finish having an end portion remote from said body, a capping flange adjacent to said body, and a mid portion between said end portion and said capping flange, said end and mid portions forming continuous inner and outer surfaces,
- (b) blow molding said preform to form a hollow plastic container, and
- (c) either prior to or subsequent to said step (b), crystallizing said finish in such a way that at least said end portion of said finish is crystallized, and crystallization in said finish is graded from crystallization of said end portion.
37. A hollow plastic container having a finish and an integral body, said finish having a first portion that is crystallized, a second portion that is substantially uncrystallized, and a third portion extending between said first and second portions in which crystallization is graded from crystallization in said first portion and substantial uncrystallization in said second portion.
38. The container set forth in claim 37 wherein said crystallized first portion of said finish is an outer surface portion of said finish.
39. The container set forth in claim 37 wherein said crystallized first portion of said finish is an inner surface portion of said finish.
40. The container set forth in claim 37 wherein said crystallized first portion of said finish is an end surface portion of said finish.
41. The container set forth in claim 37 wherein said finish has an end portion remote from said body and a mid portion contiguous with said end portion between said end portion and said body, and wherein said crystallized first portion of said finish comprises said end portion of said finish.
42. The container set forth in claim 41 wherein said end portion of said finish also includes at least part of said graded third portion of said finish.
43. The container set forth in claim 41 wherein said mid portion of said finish includes said graded third portion of said finish.
44. The container set forth in claim 37 wherein said finish has an end portion remote from said body, and a mid portion contiguous with said end portion between said end portion and said body, and wherein said crystallized first portion of said finish comprises said mid portion of said finish.
45. The container set forth in claim 44 wherein said crystallized first portion of said finish also includes said end portion of said finish.
46. The container set forth in claim 44 wherein said end portion of said finish includes said substantially uncrystallized second portion of said finish.
47. The container set forth in claim 46 wherein said finish includes a capping flange between said mid portion and said body, said crystallized first portion of said finish including said capping flange.
48. A hollow plastic container that is at least partially of crystallizable polymer construction and includes:
- a finish and a body integral with said finish,
- said finish having a first end portion remote from said body, a second end portion adjacent to said body, and a mid portion between said end portions,
- said first end and mid portions forming a continuous outer surface and a continuous inner surface,
- one of said inner and outer surfaces being crystallized throughout its length and the other of said inner and outer surfaces including at least a portion that is essentially uncrystallized,
- crystallization in at least said mid portion of said finish being graded between said crystallized surface and the uncrystallized portion of the other surface.
49. A hollow plastic container that is at least partially of crystallizable polymer construction and includes:
- a finish and a body integral with said finish,
- said finish having a first end portion remote from said body, a second end portion adjacent to said body, and a mid portion between said end portions,
- said first end and mid portions forming a continuous inner surface at least a portion of which is essentially uncrystallized,
- crystallization in at least said mid portion of said finish being graded between said outer and inner surfaces and between said mid portion and said second end portion.
50. A hollow plastic container that is at least partially of crystallizable polymer construction and includes:
- a finish and a body integral with said finish,
- said finish having a first end portion remote from said body, a second end portion adjacent to said body, and a mid portion between said end portions,
- at least said first end portion of said finish being crystallized, and crystallization in said finish being graded from crystallization at said first end portion.
51. A hollow plastic container having a finish and an integral body,
- said finish having a first end portion with an end surface spaced from said body, a second end portion adjacent to said body, and a mid portion between said end portions,
- said first end and mid portions forming continuous inner and outer surfaces,
- said finish being crystallized at at least one of said end, inner and outer surfaces, and crystallization in said finish in a direction perpendicular to said at least one surface being graded from crystallization at said at least one surface to an essential absence of crystallization at a position within said finish spaced from said at least one surface.
52. A method of making a hollow plastic container, which comprises the steps of:
- (a) molding a preform at least partially of crystallizable polymer construction including a finish and a body integral with said finish, said finish having a first end portion remote from said body, a second end portion adjacent to said body, and a mid portion between said end portions, said first end and mid portions forming continuous inner and outer surfaces,
- (b) blow molding said preform to form a hollow plastic container, and
- (c) either prior to subsequent to said step (b), crystallizing said finish at one of said inner and outer surfaces in such a way that said one surface is crystallized throughout its length and the other of said inner and outer surfaces includes a portion that is essentially uncrystallized, and such that crystallization in at least said mid portion is graded between said surfaces.
53. A method of making a hollow plastic container, which comprises the steps of:
- (a) molding a preform at least partially of crystallizable polymer construction including a finish and a body integral with said finish, said finish having a first end portion remote from said body, a second end portion adjacent to said body, and a mid portion between said end portions, said first end and mid portions forming continuous inner and outer surfaces,
- (b) blow molding said preform to form a hollow plastic container, and
- (c) either prior to or subsequent to said step (b), crystallizing said finish in such a way that said outer surface is crystallized throughout its length and at least a portion of said inner surface is essentially uncrystallized, and such that crystallization in at least said mid portion of said finish is graded between said outer and inner surfaces and between said mid portion and said second end portion.
54. A method of making a hollow plastic container, which comprises the steps of:
- (a) molding a preform at least partially of crystallizable polymer construction including a finish and a body integral with said finish, said finish having a first end portion remote from said body, a second end portion adjacent to said body, and a mid portion between said end portions, said first end and mid portions forming continuous inner and outer surfaces,
- (b) blow molding said preform to form a hollow plastic container, and
- (c) either prior to or subsequent to said step (b), crystallizing said finish in such a way that at least said first end portion of said finish is crystallized, and crystallization in said finish is graded from crystallization of said first end portion.
55. A hollow plastic container that is at leas partially of crystallizable polymer construction and including a finish and a body integral with said finish,
- said finish having an end portion remote from said body, a capping flange adjacent to said body, and a mid portion between said end portion and said capping flange,
- at least a portion of said end portion, said mid portion or both said end portion and said mid portion being crystallized, and said capping flange being essentially free of crystallization.
56. The container set forth in claim 55 wherein at least a portion of said crystallization is graded.
Type: Application
Filed: Jan 11, 2006
Publication Date: May 25, 2006
Applicant: Graham Packaging PET Technologies, Inc. (York, PA)
Inventors: Thomas Nahill (Amherst, NH), Keith Barker (Candia, NH), Brian Lynch (Merrimack, NH)
Application Number: 11/329,234
International Classification: B32B 27/08 (20060101);