GB2086342A

GB2086342A - Multilayer Containers

Info

Publication number: GB2086342A
Application number: GB8130919A
Authority: GB
Original assignee: Compagnie Francaise de Raffinage SA
Current assignee: Compagnie Francaise de Raffinage SA
Priority date: 1980-10-14
Filing date: 1981-10-13
Publication date: 1982-05-12
Also published as: FR2491825A1; IT8124400A0; FR2491825B1; IT1139643B; BE890700A; GB2086342B; ES8207042A1; ES506214A0; NL8104678A

Abstract

A co-extruded, blow-moulded container for milk comprises: a) a first outer layer of a thermoplastic polymer, such as high- density polyethylene, containing a filler, e.g. titanium dioxide, which inhibits light having a wavelength equal to or higher than 800 nanometres; and b) a second layer of the same polymer containing a filler, e.g. carbon black so that the second layer inhibits light having a wavelength less than 800 nanometres. A third layer of the same polymer may be located on the inner surface of the second layer, the third layer containing no filler or an "alimentary" filler, e.g. titanium dioxide.

Description

SPECIFICATION Container with Multilayer Wall The present invention relates to a container whose wall is constituted by at least two layers of the same polymer.

It is known to use containers, the walls of which are formed from several layers of different polymers, for the packing of products which are sensitive to light and/or to gases, such as atmospheric oxygen; particularly foodstuffs.

Thus French Patent No. 2 1 32 395 discloses a bottle formed from a layer of polyamide and layer of polyolefin onto which a dicarboxylic acid is grafted. This bottle is used in particular for the packaging of foodstuffs. This bottle is produced by the well-known process of coextruded blowmoulding. In this case, the protection from gases is obtained by the polyamide layer; polyethylene being permeable to gases.

The Applicant has established that for the packaging of products which are sensitive to light and to gases it is possible to produce containers with multilayer walls from the same polymer, and that these containers are distinguished advantageously from the known containers whose walls are formed from layers of different polymers.

The object of the present invention is thus to propose containers for the packaging of products which are sensitive to light and, possibly, to gases.

To this end, the invention relates to a container characterised in that its wall comprises at least: a) a first, outer layer of a thermoplastic polymer containing a filler so that said first layer is able to inhibit light rays with a wavelength equal to or higher than 800 nanometres; and b) a second layer of the same thermoplastic polymer containing a filler so that said second layer is able to inhibit light rays with a wavelength of less than 800 nanometres.

The two layers of the wall thus inhibit all light radiation and the effect of this radiation on the contents of the container is zero.

The inhibiting of radiation may be effected by reflection or by absorption.

The fact that the two polymers are identical eliminates the phenomenon of incompatibility which may arise when they are different; thus necessitating the presence of an adhesive layer.

The polymers which can be used to form the layers of the container according to the invention may be gas-permeable or gas-impermeable.

For example, they may be polyolefins such as high or low-density polyethylene, polypropylene or polybutylene.

The first layer may contain between 0.5 and 30% and, preferably, between 0.5 and 10% by weight of filler.

This latter may be particularly a filler which is white or very light in colour, such as titanium dioxide, calcium carbonate or zinc oxide.

As a result of its reflective capacity, it prevents any rise in the temperature of the product contained in the container under the action of light rays with a wavelength higher than 800 nanometres.

The second layer may contain between 0.01 and 20% and, preferably, between 0.1 and 5% by weight of filler.

This filler may be particularly carbon black.

The container according to the invention may be used for the packaging of all products which are liable to degrade under the action of light. In the case of foodstuffs, it is of course necessary for the polymer forming the layer in contact with the food to be of the type known as "alimentary".

It may also be necessary for the container to comprise an inner additional third layer of the same polymer, so as to prevent the food from coming into contact with the filler contained in the second layer, and for this third layer not to contain any filler or to contain a filler of "alimentary" type.

The container according to the invention may consist of three layers of high-density polyethylene (for example in the case in which it is intended for the packaging of milk): a) an outer first layer containing titanium dioxide; b) an intermediate second layer containing carbon black; and c) a an inner third layer which contains or does not contain titanium dioxide.

In this case, the thickness of the outer layer may be between 50 and 400 microns, that of the intermediate layer between 100 and 300 microns, and the thickness of the inner layer between 50 and 400 microns.

As already mentioned above, these containers may be produced by the coextruded blowmoulding process, in which each layer is obtained from a separate extruder when the polymers forming these layers contain different fillers.

In the case in which the polymers forming two layers are filled in identical manner (as in the case of the abovedescribed milk bottles), the container may be produced using two extruders for three layers.

In fact, the presence of titanium dioxide does not affect the milk in contact with the inner layer.

The following example, which is in no way restrictive, is intended to illustrate the invention.

Example This Example concerns the description of a container according to the invention and its application to the packaging and conserving of milk.

By means of coextrusion, three-layer bottles are produced in high-density polyethylene, with a density of d=0.960, with a number-average molecular mass My=1 3,000 and with a weightaverage molecular mass Mw=1 20,000.

The outer layer has a thickness of approximately 100 microns and contains 3% by weight of titanium dioxide.

The intermediate layer has a thickness of 300 microns approximately and contains 2% by weight of carbon black.

The inner layer is identical to the outer layer.

These bottles are filled with milk presterilised at 1 300C for 4 seconds. After the bottles have been sealed with a cap consisting of a complex of aluminium (thickness 50 microns) and of polyethylene containing, in the grafted state, less than 5% by weight of acrylic acid (thickness 50 microns), the bottles are brought to a temperature of 1200C for 20 minutes.

These bottles are exposed to natural light for 3 months at about 300C.

At the end of this period the milk is still of excellent quality, which is not the case with bottles consisting of a layer of polyethylene without filler, in which the conservation of milk is for about 2 days.

It has to be pointed out that the bottles tested are air-permeable bottles and that the milk contains oxygen. It is believed that oxidation reactions do not occur because there is no catalysis of oxidation reactions by light, as a result of the presence of the fillers contained in the different layers of polymer.

Claims

1. A container characterised in that its wall comprises at least: a) a first, outer layer of a thermoplastic polymer containing a filler so that said first layer is able to inhibit light rays with a wavelength equal to or higher than 800 nanometres; and b) a second layer of the same thermoplastic polymer containing a filler so that said second layer is able to inhibit light rays with a wavelength of less than 800 nanometres.

2. A container as claimed in claim 1 wherein the polymer is a high or lowdensity polyethylene, polypropylene or polybutylene.

3. A container as claimed in claim 1 or claim 2 wherein the filler of the first layer is titanium dioxide, calcium carbonate or zinc oxide.

4. A container as claimed in any one of the preceding claims wherein the first layer contains between 0.5 and 30% by weight of filler.

5. A container as claimed in claim 4 wherein the first layer contains between 0.5 and 10% by weight of filler.

6. A container as claimed in any one of the preceding claims wherein the filler of the second layer is carbon black.

7. A container as claimed in any one of the preceding claims wherein the second layer contains between 0.01 and 20% of filler.

8. A container as claimed in claim 7 wherein the second layer contains between 0.1 and 5% of filler.

9. A container as claimed in any one of the preceding claims wherein its wall comprises an additional inner layer of the same polymer.

10. A container for the packaging of a foodstuff, particularly milk, characterised in that its wall consists of three layers of high density polyethylene: a) a first, outer layer containing from 0.5 to 30% by weight of titanium dioxide and having a thickness of between 50 and 400 microns; b) a second,intermediate layer containing from 0.01 to 20% by weight of carbon black and having a thickness of between 100 and 300 microns; and c) a third, inner layer, optionally containing from 0.5 to 30% by weight of titanium dioxide, having a thickness of between 50 and 400 microns.

11. A container as claimed in any one of the preceding claims when produced by coextruded blow-moulding.

12. A container as claimed in claim 1 or claim 10 substantially as hereinbefore described.

13. Foodstuff, particularly milk, when packaged in a container as claimed in any one of the preceding claims.