WO2000068000A1

WO2000068000A1 - Multilayer container for oxygen and light sensitive products

Info

Publication number: WO2000068000A1
Application number: PCT/US2000/012873
Authority: WO
Inventors: Guy Richards
Original assignee: Pechiney Emballage Flexible Europe SAS
Current assignee: Alcan Packaging Flexible France SAS
Priority date: 1999-05-11
Filing date: 2000-05-11
Publication date: 2000-11-16
Anticipated expiration: 2001-11-11
Also published as: AU5129900A

Abstract

A colored multilayer container having oxygen barrier properties is achieved by adding a colorant to the barrier layer and without the addition of colorant to the one or more structural layers thereof such that the structural layers remain uncontaminated by colorant. Inexpensive recycling of the present container is therefore facilitated because it may be mixed and recycled with non-colored containers to recover the structural materials therefrom and produce an aggregate of recycled structural material uncontaminated by colorant.

Description

MULTILAYER CONTAINER FOR OXYGEN AND LIGHT SENSITIVE PRODUCTS

1. Field of the Invention.

The present invention relates generally to a multilayer plastic container; particularly to a readily recyclable multilayer plastic container comprising a barrier layer capable of protecting contents from both oxygen and harmful light.

2. Background of the Invention.

Many products in need of packaging are susceptible to deterioration when in the presence of oxygen; especially foodstuff products. Beer is one example of a product susceptible to oxidative degradation. The packaging industry often constructs product containers to comprise an oxygen barrier material in order to limit oxygen migration into the container and, thus, the amount of oxygen capable of deteriorating the product. Glass and metal containers provide a good barrier to oxygen migration. However, plastic containers have become increasingly popular as a replacement for both glass and metal containers. Typical plastics employed as oxygen barriers include, for example, ethylene vinyl alcohol (EVOH), nylon and blends thereof. However, when used alone, oxygen barrier materials typically possess insufficient structural characteristics to protect a product from the rigors encountered during packaging, delivery and customer handling. Furthermore, the costs of known oxygen barrier materials are substantially higher than other materials typically used for product packaging such as, for example, polyethylene terephthalate (PET) and polypropylene (PP). Additionally, the oxygen barrier properties of known oxygen barrier materials are substantially diminished in the presence of moisture. This characteristic presents special problems for packaging oxygen sensitive liquid products such as beer. For these reasons, the packaging industry has turned to multilayer packages comprising at least one oxygen barrier layer and at least one structural layer to provide strength and moisture protection to the oxygen barrier material.

Multilayer packages often comprise an inner and outer layer of structural material encapsulating at least one internal intermediate layer of oxygen barrier material. A typical multilayer package may comprise inner and outer structural layers of PET protecting an intermediate oxygen barrier layer of EVOH. Multiple intermediate barrier layers may also be employed so that the multilayer package might comprise inner and outer structural layers protecting two barrier layers which are separated by a third layer of structural material. One or more layers are also often configured to have oxygen-scavenging capabilities such as by comprising the barrier of MXD6 nylon and cobalt.

In any of these or other known configurations, each oxygen barrier layer is protected on all sides from both physical contact and moisture. Thus a strong package capable of substantially limiting oxygen migration is obtained. Typical oxygen barriers may also limit migration of carbon dioxide gas which assists in retention of that gas within a beer bottle to prevent the beer from going flat. The barrier layer need only be as thick as necessary to provide the necessary level of barrier to oxygen and carbon dioxide. Multilayer containers are typically formed by injection molding a multilayer preform which is then stretch blow molded into the desired container. Multilayer injection molding has been described, for example, in U.S. Patent No. 4,712,990 to Kudert et al. the entirety of which is hereby incorporated by reference.

Although constructing containers from plastics provides many advantages over other materials, recycling of plastic containers presents new issues and problems not previously encountered with containers constructed from glass. For example, current recycling processes requires separation of the structural materials from the barrier materials. Because structural materials, both virgin and recycled, are used more widely and in greater quantities than oxygen barrier materials, recycling of plastic containers is usually accomplished by first sorting a plurality of containers according to the structural material of which they are comprised, then separating the barrier material from the structural material and combining the aggregate of the structural material from the containers. This aggregate is then processed into a form which may readily be reused. It has often been found desirable to color plastic containers for many purposes including aesthetics. Additionally, it is believed that some foodstuff products are susceptible to degradation in the presence of certain spectrums of light waves and that coloring the container walls with an appropriate color, as is known in the art, will prevent light waves of the undesirable spectrum from entering the container and deteriorating the food product. For example, it is thought that beer will deteriorate in the presence of light having wavelengths of electromagnetic radiation ranging from 300 to 500 nanometers. For one or both of these reasons, some prior containers such as glass beer bottles comprise colored container walls to block out light of those wavelengths. By way of specific example, glass beer bottles have traditionally been colored with an amber or emerald green coloring. To accomplish this coloring, prior plastic containers have employed color additives in the structural layers. However, the containers having colored structural material are not currently acceptable for recycling because they contaminate the clarity characteristic of the aggregate of recycled structural material. The reduced clarity of the aggregate causes a concomitant reduction in its value. For this reason, recycling personnel often discard colored bottles rather than allowing them to 'contaminate' the aggregate. Thus, current colored bottle configurations are not afforded the advantage of recycling.

SUMMARY OF THE INVENTION

It is one of the principal objectives of the present invention to provide a colored plastic container susceptible of economic recycling.

It is another objective of the present invention to provide a colored plastic container having structural materials susceptible of economic recycling.

It is another objective of the present invention to provide a colored plastic container without added colorant to the structural material.

It is another objective of the present invention to provide a plastic container capable of blocking damaging light spectrums without added colorant in the structural layers. It is still another objective of the present invention to provide a plastic bottle having a colored oxygen barrier layer capable of blocking the passage of light spectrums damaging to the product within the container while retaining the necessary oxygen barrier properties.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a multilayer plastic container of the present invention. FIG. 2 is a cross sectional view of the container of FIG. 1. FIG. 3 is an exploded cross sectional view of a portion of the sidewall of the container 2.

FIG. 4 is a perspective view of a multilayer plastic preform of the present invention. FIG. 5 is a cross sectional view of the preform of FIG. 4.

DETAILED DESCRIPTION OF THE DRAWINGS

In one embodiment of the present invention depicted in FIG. 1, a multilayer plastic container 10 is depicted in the form of a bottle comprising a top end portion 12 having a crown finish 14 for receiving a closure (not depicted) to seal the container 10 after the intended product has been placed therein. A tapered neck portion 16 extends downward from the top end 12 of the container 10 widening as it extends from the neck portion 16 toward a rounded shoulder 18 that rounds into a body portion 20 of the container 10. The body portion forms a cylindrical wall 21, which is closed off by a bottom end portion 22 of the container 10. The bottom end 22 depicted in FIG. 2 is designed to withstand the internal pressure caused by a carbonated beverage which may be placed therein. While the container 10 is the present invention is particularly applicable to the form of a beer bottle, as depicted in FIGS. 1 and 2, the container 10 of the present invention is not to be limited to any particular configuration except as expressly limited by the claims. As best depicted in FIG. 3, the container 10 comprises three layers, namely an inner layer 24, a middle layer 26, and an outer layer 28. The present invention is equally applicable to any multilayer configuration comprising at least one structural layer and at least one barrier layer, all of which are contemplated. In one embodiment of the container 10 depicted in FIGS. 2 and 3, both the inner layer 24 and the outer layer 28 are constructed of a structural material, for example polyester such as PET, and the middle layer 26 is constructed of an oxygen barrier material, such as EVOH or nylon. Other materials consistent with the present invention are also contemplated. The middle layer 26 provides an oxygen and/or carbon dioxide barrier, which allows a product to be stored within the container 10 for a period of time without spoiling. Thus, the middle layer 26 may also be referred to herein as the barrier layer 26. Because known oxygen barrier materials are substantially more expensive than structural materials, the middle layer 26 is constructed to be only as thick as necessary to provide the necessary level of oxygen and carbon dioxide barrier. One or more of the layers 24, 26, 28 may also comprise oxygen-scavenging capabilities. Such capabilities are discussed in U.S. Patent No. 5,281,360 to Hong et al. the entirety of which is hereby incorporated by reference. Alternatively, the container 10 of the present invention could be accomplished with a single structural layer on either side of the barrier layer. Moreover, as discussed above, the container 10 may comprise multiple barrier layers consistent with the objectives of the present invention, any of which may be comprised of these oxygen- scavenging properties.

It will evident to one of ordinary skill in the art that regardless of the multilayer configuration in which the present invention is employed, adhesion between the barrier layer, or layers, and the structural layer, or layers, must exist in an amount sufficient to prevent delamination of the layers both as a preform 30 and throughout the useful life of the bottle 10 blown therefrom. Specific attention must be given to the affect that the colorant will have on the barrier material with regard to the ability of the structural material to adhere thereto. While many different barrier material compositions and structural material compositions are currently known to be susceptible of being processed, injected and blown to provide proper lamination between the barrier layer(s) and the structural layer(s), the colorant added to the barrier material may change the ability of the compositions to adhere one to the other and the compositions or processing must compensate for this change to assure that proper lamination is obtained. However, this adhesion must also be limited so that the barrier material will be separable from the structural material during recycling. In one embodiment, the adhesion between the barrier layer(s) and structural layer(s) is sufficient to prevent delamination throughout the life of the bottle 10, yet the barrier material separates from the structural material upon the bottle 10 being ground as part of the recycling process.

The container 10 is molded from a preform 30, such as that depicted in FIG. 4, using conventional blow molding techniques. The preform 30 is made by an injection molding process such as that described in U.S. Patent No. 4,712,990 to Kudert et al. The preform 30 comprises a top portion 31 having a crown finish 32 (correlating to the container top portion 12 and container crown finish 14 respectively). A neck portion 33 (correlating to the container neck portion 16) extends downward from the top portion 31 and tapers into a body portion 34 (correlating to the container body portion 20). The preform body portion 34 extends from the preform neck portion 33 to a bottom 36 of the preform 30. Turning to FIG. 5, the preform 30 comprises a middle layer 37, surrounded by an inner structural layer 38 and an outer structural layer 39. The preform middle layer 37 comprises a colorant so that upon blow molding the preform 30 into the container 10 of the present invention, the container middle layer 26 will impart the desired color to the container 10. All known colorants are contemplated. It is recognized that a need to strike a balance between the colorant and the barrier properties of the container barrier layer 26 might arise because the addition of some colorants to a barrier material could reduce the barrier capabilities of the resulting container barrier layer 26. It has been found, however, that providing one or more of the layers of the container 10 with oxygen-scavenging properties will compensate for this reduction in barrier capabilities; if it occurs. So configured, one or more of the layers of the container 10, (the container middle layer 26 for example) will scavenge any oxygen which is allowed to migrate through the container barrier layer 26, including the excess oxygen which is allowed to migrate through the container barrier layer 26 due to its reduced barrier capabilities resulting from the addition of the colorant thereto. In another embodiment (not depicted), the container 10 could be configured to comprise two barrier layers wherein colorant is added to only a first of the two barrier layers so that the barrier capabilities of a second of the two barrier layers are left undiminished. In this embodiment, the outer of the two barrier layers could comprise the colorant to block out harmful light waves, as well as some oxygen, so that the barrier capabilities of the inner of the two barrier layers could be left undiminished and block substantially any oxygen which is allowed to migrate through the outer barrier layer. Other configurations will become apparent to one of ordinary skill in the art from the descriptions herein. As is known to one of ordinary skill in the art, the process of blow molding the preform 30 into the container 10 will stretch the preform middle layer 37 and reduce the thickness thereof such that the container middle layer 26 is thinner than the preform middle layer 37. The colored container middle layer 26 of the present invention is therefore thinned. A concomitant reduction in color intensity is also experienced and must be compensated for when calculating the color loading of the preform middle layer 37 to assure that the resulting preform 30 comprises the desired color intensity. Moreover, because the container middle layer 26 is kept as thin as possible, without allowing an unacceptable level of oxygen migration, the preform middle layer 37 will require a substantially large concentration of colorant therein, compared to the corresponding amount of colorant required in the relatively thicker structural layers of prior art colored containers, to obtain a comparable color intensity in the container 10. By way of example only, the thickness of the container barrier layer 26 is often only 1/15 the thickness of the container structural layers 26, 28.

The preform middle layer 37 may experience uneven amounts of stretching along the length thereof during blow molding. Specifically, a typical blow molding process, as is known in the art, will stretch the preform middle layer 37 in the neck portion 33 and the body portion 34 to produce the container neck portion 16 and container body portion 20 respectively. However, the preform top portion 31, and thus the layers 37, 38, 39 thereof, undergoes little or no stretching to produce the container top portion 12. Moreover, the preform layers 37, 38, 39 may experience more or less stretching in the preform neck portion 33 than in the preform body portion 34 to form the container 10 from the preform 30. As will be understood from the teachings herein, variations in stretching experienced along the length of the preform layers 37, 38, 39 could result in concomitant variations in color intensity in the resulting container 10. The variations in stretching experienced throughout various portions of the preform can be controlled by shaping and dimensioning the preform 30. Properly shaping the preform 30 can result in even stretching throughout the neck portion 16, the rounded shoulder 18 and the body portion 20 of the container 10 producing a uniformly colored container. Thus, the shape of the preform 30 may control the color intensity variations in the resulting container 10. Alternatively, the color intensity throughout the container 10 may also be controlled by varying the color intensity of the preform middle layer 37, such as by varying the amount of colorant added to the preform middle layer 37, to compensate for uneven stretching so that the container middle layer 26 will exhibit a uniform color intensity after blow molding. Because the human eye can only detect only a certain level of color intensity variation, some variation in stretching throughout the preform neck and body portions 33, 34 is allowable to obtain an apparently uniformly colored container 10. Conversely, desired variations in color intensity may be accomplished by controlling the shape and dimensions of the preform 30 or by controlling color intensity variations in the preform middle layer 37, as will be understood by one of ordinary skill in the art.

In one embodiment of the present invention, the colorant mixed with the preform middle layer 37 is sufficient in color and intensity to assure that the resulting container 10 blow molded therefrom is provided with a sufficient color and color intensity to substantially block out any spectrum of light which may deteriorate or otherwise damage a beer product. Consistent with this embodiment, the colorant may provide the container 10 with, by way of example only, an amber or emerald green color, as is known in the art, to protect beer from substantial degradation due to light waves such as those having wavelengths of electromagnetic radiation from 300 to 500 nanometers.

Current recycling processes typically involve separating the structural materials from the barrier materials and then processing the structural materials into a recycled aggregate for reuse. When the container 10 of the present invention is thus recycled, the colorant that imparts the desired color to the container 10, remains with the barrier material at all times. The structural material remains uncolored. Recycling the container 10 of the present invention will therefore result in an aggregate of structural material uncontaminated by color. The present colored container 10 may therefore be mixed and recycled with uncolored containers without fear that the resultant aggregate of structural material will be contaminated with colorant resulting in a lower economic value of that aggregate.

EXAMPLE

A three-layer coinjection molded preform was coinjected on a BMB 380 injection apparatus equipped for multicavity, multilayer coinjection molding. The preform comprised inner and outer structural layers and a middle layer. The structural layers and were PET, specifically Shell 7207. The middle layer was a dry blend of EVOH and colorant wherein the EVOH/colorant blend constituted approximately 5% by weight of the preform. The EVOH was Evalca LCE-105A and the colorant was Allied OC600010PPNP green color concentrate. The colorant was dry-blended into the EVOH in the range of from 1-5% by weight of colorant. The PET was injected at between 500-550°F and the EVOH/colorant blend was injected at between 400-440°F. The preform was injected and cooled in approximately a 30- second cycle time. The preform was stretch blow molded to form a container having a substantially uniform green color throughout the container.

From the foregoing description, it will be apparent that the container of the present invention has a number of advantages, some of which have been described above and others of which are inherent in the container of the present invention. Also, it will be understood that modifications can be made to the container of the present invention without departing from the teachings of the invention. Accordingly the scope of the invention is only to be limited as necessitated by the accompanying claims.

Claims

CLAIMSWe claim:

1. A multilayer container for a foodstuff susceptible to oxidative degradation, comprising: a structural layer; and a barrier layer adjacent to the structural layer; wherein the barrier layer comprises a colorant providing a color thereto and the container being sufficiently impermeable to oxygen so as to limit oxidative degradation of the foodstuff.

2. The container of claim 1 wherein the barrier layer substantially blocks passage of light waves susceptible of deteriorating the foodstuff.

3. The container of claim 2 wherein the barrier layer substantially blocks passage of electromagnetic radiation having wavelengths between 300 nanometers and 500 nanometers.

4. The container of claim 3 wherein the color of the barrier layer is substantially one of amber or emerald green.

5. The container of claim 1 wherein the barrier layer comprises EVOH.

6. The container of claim 1 wherein the barrier layer comprises nylon.

7. The container of claim 1 wherein the barrier layer is capable of scavenging oxygen.

8. The container of claim 5 wherein the barrier layer comprises colorant in an amount of from 1 %-5% by weight.

9. The container of claim 1 wherein the structural layer comprises PET.

10. The container of claim 1 wherein the structural layer comprises polypropylene.

11. A multilayer container comprising: a recyclable structural layer; and a colored barrier layer adjacent to the structural layer; wherein the colored barrier layer substantially blocks passage of light waves susceptible of deteriorating a foodstuff located within the container.

12. The container of claim 11 wherein the colored barrier layer sufficiently impedes ingress of oxygen into the container so as to limit oxidative degradation of the foodstuff.

13. The container of claim 11 wherein the colored barrier layer substantially blocks passage of electromagnetic radiation having wavelengths between 300 nanometers and 500 nanometers.

14. The container of claim 13 wherein the color of the colored barrier layer is substantially one of amber or emerald green and the foodstuff is beer.

15. The container of claim 11 wherein the colored barrier layer comprises EVOH.

16. The container of claim 11 wherein the colored barrier layer comprises nylon.

17. The container of claim 11 wherein the colored barrier layer is capable of scavenging oxygen.

18. The container of claim 15 wherein the colored barrier layer comprises a colorant in an amount of from l%-5% by weight.

19. The container of claim 11 wherein the structural layer comprises PET.

20. A multilayer container comprising: a recyclable structural layer; and a barrier layer adjacent to the structural layer and capable of blocking the passage of electromagnetic radiation having wavelengths of between 300 nanometers and 500 nanometers.