US20050249902A1

US20050249902A1 - Compression over-molding container preforms

Info

Publication number: US20050249902A1
Application number: US10/841,773
Authority: US
Inventors: Brian Lynch; Thomas Nahill
Original assignee: Graham Packaging Pet Technologies Inc
Current assignee: Graham Packaging Pet Technologies Inc
Priority date: 2004-05-07
Filing date: 2004-05-07
Publication date: 2005-11-10

Abstract

A method of making a preform for blow molding a plastic container. In one embodiment, a tubular shell of plastic construction is provided, wherein the shell has a closed end and an open end. A plastic mold charge is then placed within the shell, and a preform body is compression molded within the shell such that the shell is secured to an outer surface of the preform body. In another embodiment, a tubular shell of plastic construction is provided wherein the shell is open at opposed ends, and a preform body is then compression molded externally around the shell. A preform for blow molding a plastic container includes a plastic shell and a plastic body that is compression over-molded to the plastic shell.

Description

The present invention is directed to compression molding preforms for subsequent blow molding as plastic containers, and more particularly to an article and a method for compression over-molding a preform within or around a pre-made shell.

BACKGROUND AND SUMMARY OF THE INVENTION

In the production of hollow plastic containers it is common to form a parison or preform, and then to blow mold the preform to achieve the final shape of a container. The preform typically is injection molded, and includes a body having a closed bottom end and a sidewall extending in a direction axially away from the closed bottom end. The preform also includes a neck, which axially terminates the sidewall to define an open end of the preform. The perform neck can have one or more threads for receiving a threaded closure to close the container.
A method in accordance with one aspect of the invention includes making a preform for blow molding a plastic container. According to the method, a tubular shell of plastic construction has a closed end and an open end. A plastic mold charge is placed within the shell, and a preform body is compression molded within the shell such that the shell is secured to an outer surface of the preform body.
In accordance with a second aspect of the invention, there is provided another method of making a preform for blow molding a plastic container. According to this method, a tubular shell of plastic construction is provided wherein the shell is open at opposed ends, and a preform body is compression molded externally around the shell.
An article in accordance with a third aspect of the invention includes a preform that is used in the blow molding of a plastic container. The preform includes a plastic shell and a plastic body that is compression over-molded to the plastic shell.

BRIEF DESCRIPTION OF THE DRAWING

The invention, together with additional objects, features, advantages and aspects thereof, will be best understood from the following description, the appended claims and the accompanying drawings, in which:
FIG. 1A illustrates a compression molding apparatus according to one exemplary embodiment of the present invention in which a charge of preform material is located within a pre-made shell, which is inserted within a mold cavity;
FIG. 1B illustrates the compression molding apparatus of FIG. 1A wherein a core pin has been driven into the mold cavity to compression over-mold the preform material within the pre-made shell to produce a completed preform;
FIG. 2 illustrates the completed preform produced by the apparatus of FIG. 1B;
FIG. 2A illustrates an enlarged view of a sidewall of the preform of FIG. 2;
FIG. 2B illustrates an enlarged view of a sidewall according to an alternative embodiment of the present invention in which the preform material is multilayered;
FIG. 2C illustrates an enlarged view of a sidewall according to an alternative embodiment of the present invention in which the shell material is multilayered;
FIG. 3 illustrates a compression molding apparatus according to another exemplary embodiment of the present invention in which a charge of preform material is located within a compression mold cavity and a pre-made shell is loaded to a compression core pin;
FIG. 4 illustrates a preform produced by the apparatus of FIG. 3, in which the preform material is compression over-molded around the pre-made shell;
FIG. 5 illustrates a preform according to an alternative embodiment of the present invention wherein the pre-made shell is substantially tubular without a flange at an upper end thereof; and
FIG. 6 illustrates a preform according to an alternative embodiment of the present invention wherein the preform material has been compression molded within the pre-made shell.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In general, the present invention relates to a method of making a multi-layer parison or preform by compression molding, and to the resulting preform, wherein the preform is adapted subsequently to be molded into a plastic container. Referring now to the drawing figures, FIGS. 1A through 2C illustrate a first exemplary embodiment of the present invention. FIG. 1A illustrates a compression molding apparatus 10 that is used in accordance with a process of the present invention. The compression molding apparatus 10 includes a core pin 12 positioned above a compression mold 14. The compression mold 14 includes a closed bottom end 16, a body portion 18, and a finish portion 20 that define a mold cavity 22.
A pre-made component, liner, sleeve or shell 24 is placed in the compression molding apparatus 10 prior to compression molding. In the embodiment of FIG. 1A, the pre-made shell 24 preferably is composed of a relatively inexpensive polymeric material such as a regrind polymer, post consumer resin, lower IV material and the like. The shell 24 is circumferentially continuous and may be produced in an upstream manufacturing operation such as injection molding, thermoforming, cutting from swaged tube stock or the like. In any case, this embodiment involves loading the shell 24 all the way down into the mold cavity 22 of the mold 14, such that the top of the shell 24 is positioned just below the finish portion 20 of the mold 14.
A compression overmolding process follows, wherein a charge 26 of polymeric material is placed or fed into the mold cavity 22 within the interior of the shell 24. The charge 26 is soft or molten, and thereby conforms to and fills the lower end of the shell 24. The core pin 12 and mold 14 are positioned in vertical alignment, and the core pin 12 is moved into the mold 14 to compression mold the charge 26 over and within the interior of the shell 24. As shown in FIG. 1B, a preform body 28 is thus molded over the shell 24 between the core pin 12 and mold 14. Mold charge 26 can be of any suitable polymer intent, such as polyester, including polyethylene terephthalate (PET) and polyethylene naphthalate (PEN).
FIG. 2 illustrates a preform 30 produced by the apparatus and process described above. The preform 30 includes a closed bottom end 32 defined by a closed bottom end 32 a of the shell 24 and by a closed bottom end 32 b of the preform body 28. A sidewall 34 extends in a direction axially away from the closed bottom end 32, and terminates in an open end 36 opposite from the closed bottom end 32. The preform body 28 is formed within the shell 24, such that the shell 24 is secured to the outer surface of the preform body 28. The preform body 28 extends from the closed bottom end 32 to the open end 36 where the preform body 28 includes a finish portion 38 and a flange 40. In contrast, the shell 24 does not extend all the way from the closed bottom end 32 to the open end 36 but, rather, stops short at an open end 42 just beneath the flange 40 of the preform body 28.
FIGS. 2A-2C generally illustrate enlarged views of the sidewall 34 of the preform 30 of FIG. 2. FIG. 2A illustrates an enlarged portion of the sidewall 34 showing the shell 24 disposed on the outside of the preform body 28, wherein both the shell 24 and preform body 28 are of monolayer construction. FIG. 2B illustrates a sidewall 134 according to an alternative embodiment of the present invention wherein the shell 24 is of monolayer construction, but an alternative preform body 128 is composed of multiple layers, such as three layers as shown. Similarly, FIG. 2C illustrates another sidewall 234 according to another alternative embodiment of the present invention wherein the preform body 28 is a of monolayer construction, but an alternative shell 224 is composed of multiple layers, such as three layers as shown. In FIGS. 2B and 2C, the multiple-layers may be composed of, for example, outside layers of virgin PET and an interior layer of barrier resin such as nylon or ethylene vinyl alcohol (EVOH). In another example, the outside layers may be composed of different materials such as virgin PET and post consumer resin. A method for compression molding such stratified layers is disclosed in U.S. application Ser. No. 10/746,404, which is assigned to the assignee hereof and is incorporated by reference herein.
Regardless of whether the preform body 28 or 128 or the shell 24 or 124, is individually composed of single or multiple layers, the preform 30 preferably is composed in a ratio of about 90% regrind polymer, post consumer resin, lower IV material, or the like and about 10% virgin polymer, which preferably is composed of about 10% polycarbonate, polycarbonate blends, PEN or PEN blends and about 90% PET for low cost, high temperature applications. More specifically, it is preferred that the shell be composed of about 10% high IV or high temperature polymeric material and about 90% low IV polymeric material. (IV is intrinsic viscosity measured according to ASTM D-5225-92.)
Referring now to FIGS. 3 through 5, there is illustrated a second exemplary embodiment of the present invention. FIG. 3 illustrates a compression molding apparatus 310 that is used in accordance with of this second embodiment of the present invention. The compression molding apparatus 310 includes a core pin 312 positioned above a compression mold 314. The compression mold 314 includes a closed bottom end 316, a substantially cylindrical body portion 318 and a finish portion 320 that together define a mold cavity 322. As with the embodiment of FIGS. 1A through 2C, this embodiment involves novel steps to produce a multi-layer preform.
A pre-made component, liner, sleeve, tube or shell 324 is loaded into the compression molding apparatus 310 prior to compression molding. In this embodiment, the pre-made shell 324 preferably is composed of any polymeric material, such as virgin PET or the like, that is amenable for use with containers—e.g., for holding contents for human consumption. The shell 324 may be produced by a process involving injection molding, thermoforming, cutting from swaged tube-stock or the like. In any case, this embodiment involves loading the shell 324 onto and around the core pin 312. The shell 324 includes a flange portion 323 that abuts a flanged portion of the core pin 312, and further includes an open bottom end 325. It is, however, contemplated that the bottom end 325 instead may be closed.
A compression overmolding process follows, wherein a charge 326 of polymeric material is placed or otherwise fed into the mold cavity 322. The charge 326 is soft or molten, and thereby conforms to and fills the lower end of the mold cavity 322. The core pin 312, with the shell 324 mounted thereto, and the mold 314 are positioned in vertical alignment, and the core pin 312 and shell 324 are moved into the mold 314 to compression mold the charge 326 over and around the exterior of the shell 324.
FIG. 4 illustrates a completed preform 330 produced by the apparatus and process described immediately above. The preform 330 includes a closed bottom end 332, a sidewall 334 extending in a direction axially away from the closed bottom end 332, and an open end 336 opposite of the closed bottom end 332. The compression molding of the charge 326 of FIG. 3 results in the formation of a preform body 328 over and around the exterior of the shell 324. The preform body 328 extends from the closed bottom end 332 to the open end 336, where the preform body 328 includes a finish portion 338 and a flange 340. In contrast, the shell 324 extends from its flange 323 at the open end 336 toward the closed bottom end 332, but stops just short at about a transition point between the sidewall 334 and the closed bottom end 332. In a modification of this embodiment, FIG. 5 illustrates a preform 430 having a shell 424 made by the process of the present invention, but not including the flange 323 of the shell 324 of FIG. 4. Rather, the shell 424 is a tubular-shaped component having an open upper end 423 opposite an open lower end 425.
As with the embodiment of FIGS. 1A through 2C, in this embodiment the preform body 328 and shell 324, or 424 may be composed of multi-layer materials. Moreover, the shell 324, or 424 preferably is composed of virgin polymer, and the preform body 328 composed of a regrind material, post consumer resin, low IV material or the like. Where the preform body 328 may be composed of multiple layers, it is preferable that the innermost layer, which partially defines the interior of the preform 330 or 430, be composed of a virgin polymer, and the other layers may be composed of regrind material or the like.
FIG. 6 illustrates a modification to the embodiment depicted in FIG. 2. Here, a preform 530 includes a preform body 528 that is partially circumscribed by a modified shell 524. The shell 524 of this embodiment includes a flange 523 that abuts a flange 540 of the preform body 528, and the shell 524 does not extend all the way from the flange 540 down and around a closed bottom end 532 of the preform. Rather, the shell 524 stops at about a transition point between the sidewall 534 of the preform 530 and the closed bottom end 532.
With all of the embodiments and modifications described above, the present invention provides a process for making a preform that is composed of layers of materials so as to reduce material costs yet optimize container properties such as strength and resistance to gas permeability.
There have thus been described a method and apparatus for compression overmolding a charge of polymeric material with respect to a pre-made sleeve, and a preform made by such method, that fully satisfy all of the objects and aims previously set forth. The present invention has been disclosed in conjunction with two exemplary presently preferred embodiments thereof, and a number of modifications and variations have been discussed. Other modifications and variations will readily suggest themselves to persons of ordinary skill in the art in view of the foregoing description. Directional words such as “lower”, “bottom”, and the like are employed by way of description and not limitation with respect to the upright orientations of the components illustrated in the drawings. The invention is intended to embrace all modifications and variations as fall within the spirit and broad scope of the appended claims.

Claims

1. A method of making a preform for blow molding a plastic container, which includes the steps of:

(a) providing a tubular shell of plastic construction, said shell having a closed end and an open end,

(b) placing a plastic mold charge within said shell, and

(c) compression molding a preform body within said shell such that said shell is secured to an outer surface of said preform body.

2. The method set forth in claim 1 wherein said step (b) includes placing said mold charge within said closed end of said shell.

3. The method set forth in claim 1 wherein said tubular shell is of multilayer plastic construction.

4. The method of claim 3 wherein said tubular shell is composed of about 10% high IV material and about 90% low IV material.

5. The method of claim 1 wherein said tubular shell is of single layer plastic construction.

6. The method of claim 5 wherein said tubular shell is composed of at least one of a regrind polymer, post consumer resin and a low IV material.

7. The method of claim 1 wherein said preform is composed of about 90% low cost material such as a regrind polymer, post consumer resin, lower IV material and the like, and is further composed of about 10% virgin material.

8. The method of claim 7 wherein said 10% virgin material is composed of about 10% polycarbonate, polycarbonate blends, PEN or PEN blends, and about 90% PET.

9. The method of claim 1 wherein said step (c) includes molding a preform finish integrally with said body and adjacent to but outside of said open end of said shell.

10. A preform for blow molding a plastic container wherein said preform is produced by the method of claim 1.

11. A method of making a preform for blow molding a plastic container, which includes:

(a) providing a tubular shell of plastic construction, said shell being open at opposed ends, and

(b) compression molding a preform body externally around said shell.

12. The method of claim 11 wherein said tubular shell is composed of a virgin polymer composed of about 10% polycarbonate, polycarbonate blends, PEN or PEN blends, and about 90% PET.

13. The method of claim 11 wherein said tubular shell includes a flange portion at one of said opposed ends.

14. The method of claim II wherein said tubular shell is composed of a multi-layer material including at least one layer of virgin polymer and at least one layer of a low cost material such as a regrind polymer, post consumer resin, lower IV material, and the like.

15. The method of claim 11 wherein said preform body is composed of a multi-layer material including at least one layer of virgin polymer and at least one layer of a low cost material such as a regrind polymer, post consumer resin, lower IV material, and the like.

16. The method of claim 11 wherein said preform is composed of about 90% low cost material such as a regrind polymer, post consumer resin, lower IV material, and the like and is further composed of about 10% virgin material.

17. The method of claim 11 further comprising loading said tubular shell to a core pin prior to said compression molding step.

18. The method of claim 11 wherein said step (b) includes molding a preform finish integrally with said preform body and adjacent to but outside of said open end of said shell.

19. A preform for blow molding a plastic container wherein said preform is produced by the method of claim 11.

20. A method of making a preform for blow molding a plastic container, said method includes:

providing a shell,

loading said shell to one of a compression mold cavity and a compression core pin,

introducing a softened polymer into said compression mold cavity, and

compression molding said softened polymer to said shell.

21. The method of claim 20 wherein said loading step includes loading said shell to said compression mold cavity and said introducing step includes introducing said softened polymer at least partially within said shell and said compression molding step includes compression molding said softened polymer at least partially within said shell.

22. The method of claim 21 wherein said shell is a substantially open-ended tubular-shaped component.

23. The method of claim 20 wherein said loading step includes loading said shell to said compression core pin and said compression molding step includes compression molding said softened polymer at least partially around said shell.

24. The method of claim 20 wherein said shell is a tubular-shaped component having a flange portion at one end thereof.

25. A preform for blow molding a plastic container wherein said preform is produced by the method of claim 20.

26. A preform for blow molding a plastic container, said preform including:

a plastic shell; and

a plastic body compression over-molded to said plastic shell.

27. The preform of claim 26 wherein said plastic body is compression over-molded at least partially around said plastic shell.

28. The preform of claim 26 wherein said plastic body is compression over-molded at least partially within said plastic shell.