GB2168926A - Collapsible container made from ethylene propylene copolymer - Google Patents

Abstract

There is disclosed a substrate which may be employed in fabricating a dentifrice tube and which comprises two ethylene propylene copolymer layers 11, 16 having sandwiched therein between a metal foil 13 layer and a paper layer 15 all suitably adhered to one another. <IMAGE>

Description

SPECIFICATION Collapsible container made from ethylene propylene copolymer The present invention relates broadly to the container art, and is more particularly concerned with a collapsible dispensing container of laminated wall construction in the body portion thereof, whereby product permeation and absorption, and oxygen absorption are substantially prevented in all regions of the container structure susceptible thereto.

Collapsible tubes formed of metallic and plastic materials have long been known in the packaging field.

Extruded metal tubes are inherently brittle and repeated use not infrequently results in wall cracks so that the product is exuded from a location other than the essentially rigid dispensing orifice. Of the prior art metal tubes, aluminium tubes, while probably being the least brittle, are somewhat limited in their applications since up to the present time it has not been possible to apply to the interior surfaces thereof a completely satisfactory coating, when required to prevent attack and corrosion of the metal by alkaline or acid contents and contamination of the contents by the reaction products. Notwithstanding the relatively brittle nature of a metal tube, the mentioned internal coating operation requires an additional processing step which necessarily increases the cost of the final article.

Tubes formed of polyethylene and other plastic materials have enjoyed wide commercial success in the packaging of many products; however, certain other products after a time have been noted to deteriorate when contained therein. Plastics as exemplified by polyethylene are permeable to a degree when employed in the wall thicknesses used in tubular containers, and the essential oils embodied in most dentifrices for flavouring purposes are reduced in volume during storage of the container, rendering the dentifrice less palatable. Also, the plastic container wall absorbs oxygen over a period of time and ultimately may decompose the Product, which has actually been found to be the case with fluoride-containing toothpastes. A further disadvantage of a plastic tube resides in the inability of the surface to readily receive printing or decorative material.In addition, plastic tubes, as exemplified by polyethylene, have a memory effect; that is, they do not remain compressed when squeezed, a particular disadvantage for dentifrice tubes.

To counter the above problems, it has accordingly been proposed to provide a metallic foil barrier between the product and the polyethylene tube body. This would counter the compressibilíty problem in that the metal layer would impose its compressibility upon the plastic. In addition, the metallic foil barrier between the product and the polyethylene tube body would prevent the mentioned loss of essential oils and the absorption of oxygen. The metallic barrier has been suggested as an interlayer between facing sheets of polyethylene, and that a laminate be formed by heat with or without suitable adhesives.However, while a structure of this general character is effective to prevent some product permeation and oxygen absorption through the tube body, and particularly when the inner thermoplastic layer is a copolymer of ethylene olefin and a polar group containing monomer which is co-polymerisable therewith, there remains the possibility of product deterioration albeit to a much lesser extent.

Attention is directed to the following prior art: Brandt (U.S. Patent No. 3,295,725) discloses a tube which combines advantages of an aluminium tube with advantages of a plastic tube. This is a laminated collapsible dispensing container containing both a metallic barrier and a polyethylene inner wall. The thermoplastic layer is broadly described as polyolefin and copolymer of an olefin and a polar group containing monomer which is copolymerisable therewith.

This laminate overcomes the above described limitations, except for absorption of the essential oils from the dentifrices.

Marchak (Canadian Patent No. 728, 525) discloses a laminated tube containing an inner layer of polyethylene. He recognised the problem of absorption of flavour oil by the thermoplastic wall, and suggested the use of nylon to overcome this.

Cook (U.S. Patent No. 4,096,946) discloses a laminated package using vinylidene chloride as the inner layer, and an outer layer of copolymer of ethylene and propylene. However, this is not a tube; it contains no metal; and Cook did not make mention of the flavour barrier properties of the copolymer.

Anthony (U.S. Patent No. 4,207,363) discloses a laminate film used for packaging meats which contains a propylene ethylene copolymer as the outer layer. This also is not a tube; it contains no metal; and Anthony made no mention of the copolymer's flavour barrier properties.

In addition, Christensen (U.S. Patent No. 4,405,667), Ohtusuki (U.S. Patent No. 4,308,084), and Holloway (U.S. Patent No. 4,279,344) teach laminated packaging articles containing ethylene propylene copolymer.

However, none of these articles were tubes, and no mention was made of the copolymer's flavour barrier properties.

The present invention aims to provide a collapsible dispensing container of laminated wall construction in the body portion.

The present invention also aims to provide a tubular container having a plurality of adherent layers in the body portion thereof, one of said layers providing a barrier to product migration and oxygen absorption such as a metallic foil and another of said layers being ethylene propylene copolymer or mixture thereof varying in density and crystallinity. The ethylene propylene copolymer layer being innermost and preferably another such layer also being disposed as the outside layer with different additional laminae sandwiched therein between.

Such additional layers may comprise paper and suitable adhesive and bonding agents such as copolymer of ethylene and acrylic acid. The collapsible dispensing container of the present invention may be constructed from the laminated substrate of the present invention by conventional and known apparatuses. Examples of suitable equipment and a suitable method are claimed in U.S. Patent No. 3,832,964, which is incorporated herein by reference.

The procedure described in U.S. Patent No. 3,832,964 involves wrapping a sheet of flexible material (in the present case this will be the material of the present invention) about a mandrel and fastening overlapping side edges together to provide a tubular body having a longitudinal seam (which can be done readily with the material of the present invention because the materials of the inner and outer faces being the same can readily be bonded to each other) and then inserting and clamping one end of the formed body shell between an outer head structure element e.g. affording a neck and shoulders with an outer thread on the neck and an inner head structure element e.g. affording an inner neck and shoulders.

These components may conveniently be formed of or coated on their sheet contacting faces with the polymer of the outer layer of the laminate of the present invention.

A further object of the present invention is to provide a method of producing laminated tubes in which a tubular body is formed of a barrier layer and an ethylene propylene copolymer laminated thereto; the laminated tube body is then located on a forming member juxtaposed to a barrier member also positioned thereon.

The invention may be put into practice in various ways and a number of specific embodiments will be described to illustrate the invention with reference to the accompanying examples and drawings, in which: Figure 1 is a cross-sectional view of a fragmentary portion of a laminated substrate of the present invention; and Figure 2 is a side elevational view of a collapsible dispensing container embodying the novel concepts of the present invention, with portions of the body walls being broken away to more fully illustrate the laminated structure.

In the drawings like numerals are employed to designate like parts throughout the drawings.

Referring now first to Figure 1 of the drawings, a substrate 10 is shown in cross-section to reveal the components of the sandwich that go to make up the laminated configuration.

The.bottommost layer 11 is an ethylene propylene copolymer. Thes second layer 12 thereabove is an adhesive layer which joins the ethylene propylene copolymer layer 11 to a third layer 13 which is a metal foil such as aluminium foil. The fourth layer 14 is another adhesive that adhesively secures the other surface of the metal foil layer 13 to a paper layer 15. The topmost layer 16 is ethylene propylene copolymer.

The ethylene propylene copolymer is particularly useful because it has very low flavour absorption characteristics as can be seen from the following tables where ethylene propylene copolymer is compared with polyethylene where the thicknesses of the layers of coating are the same.

Example 1 Samples of polymer were tested by a single-side contact procedure (gravimetric-neat flavour oil). A 3/4 inch ( cms) diameter disk of the polymer to be tested is punched out and weighed. A 9 ml vial is filled with neat flavour oil. The disk of polymer is sealed over the top of the vial and the vial is inverted. The vial is aged for 2 weeks at 72"F ( C). The vial is inverted. The disk is removed, rinsed with water, dried and weighed to determine flavour oil uptake. The increase in weight (absorption) is given as a percentage of the original weight of the sample in Table 1 be[ow.

TABLE 1 Polymer absorption of neat flavour oil Polymer Weight Increase oJ Aluminium 0 Ethylene propylene copolymer 4.8 Rigidex 40 (British Petroleum) Low density polyethylene 5.5 Tenite 154 (Eastman) Low density polyethylene 5.6+0.14 Lupolen 1804H (BASF) High density polyethylene LR (USI) 5.9 lonomer 15.7 Surlyn 1707 (DuPont) lonomer 19.0 Surlyn 1605 (DuPont) lonomer 24.3 Surlyn 1706 (Dupont) Example,2 Samples of polymer were tested by a single-side contact procedure (gravimetric-flavoured dentifrice) using a conventional dental cream containing 0.84% by weight of a mint-peppermint oil blend. A 2 inch cms) diameter disk of the polymer to be tested is punched out and weighed.A 2 oz ( g) glass ointment jar is filled to within 1/16 inch ( mm) of the top. The disk of polymer is placed within an aluminium cap and the cap placed on the jar and the jar is sealed. The jar is aged for 3 months at 72"F ( "C). The disk is removed, rinsed in water, dried and weighed to determine the uptake of flavour oil. The amount of flavour oil absorbed by each polymer after that time relative to that absorbed by the low density polyethylene is given in Table 2. The value for the low density polyethylene was arbitrarily set at 100. It will be appreciated that the lower the number the less flavour is absorbed.

TABLE 2 Relative flavour absorption by polymers after contact with dentifrice for 3 months Polymer Flavour absorbed Ethylene propylene copolymer 59 Rigidex 40 (British Petroleum) High density polyethylene 84 LR (USI) Low density polyethylene 100+13 NA (USI) lonomer 893 Surlyn 1706 lonomer 1557 Surlyn 1707 lonomer 1672 Surlyn 1605 The adhesives may be a copolymer of ethylene and acrylic acid or methacrylic acid, or sodium or zinc salts thereof in a diluent system.

The metal foil is preferably aluminium foil.

The paper layer is desirably a kraft paper.

The thickness range of each of the layers is as follows: Ethylene propylene copolymer layer 11 - 0.5 mils to 3.0 mils (. . . mm to . . . mm), preferably 1.0 mils .... mm).

Adhesive layer 12 - sufficient to assure adherence.

Metal foil layer 13 - 0.5 mils to 2.0 mils (. . . mm to . . . mm), preferably 1.0 mils (. . . mm).

Adhesive layer 14 - sufficient to assure adherence.

Paper layer 15 - 1.5 mils to 2.5 mils (. . . mm to . mm), preferably 2.0 mils (. . . mm).

Ethylene propylene copolymer layer 16 - 3.5 mils to 5.0 mils (. . . mm to . .. mm), preferably 4.0 mils (...mm).

The topmost ethylene propylene copolymer layer 16 is adhered to the paper layer 15 by means of the application of sufficient heat and pressure to the substrate. In the event the application of heat and pressure is not appropriate a suitable adhesive is employed.

Figure 2 is an example of the laminated structure of a collapsible container with the layers being demonstrated as in Figure 1 with layer 11 being innermost and the other layers being of the same materials and in the same order as shown.

It is believed manifest from the foregoing that applicant has provided a collapsible container structure which substantially reduces the problems heretofore unsolved by the prior art. The laminated substrate and laminated shoulder piece 20 substantially eliminates product permeation and oxygen absorption.

The outer layer of an ethylene propylene copolymer is a thermoplastic capable of fusion during a side seaming step and granting adequate protection to the paper and metallic foil interlayer.The art of seaming of a collapsible dentifrice tube of the general type herein disclosed can- be seen in U.S. Patent No.

3,295,725, incorporated herein by reference.

However, the outer layer of ethylene propylene copolymer and paper may be eliminated if the foil barrier is of sufficient thickness to resist damage, and by flowing a thermoplastic material into the overlap side seam during the sealing thereof when such a system is employed.

Further, the outer layer may be paper in a three-ply laminate formed of paper, foil and an ethylene propylene copolymer as described. As the outermost and innermost layers are preferably the same, the folded edges of the tube produced from the substrate is conveniently heat bonded. A suitable adhesive can be used when heat bonding is not possible. This modification is in addition to the aforementioned four-ply laminate comprised of from outside to in, ethylene propylene copolymer, paper, foil and ethylene propylene copolymer.

It is contemplated that suitable adhesives will be employed between the laminae whenever necessary.

Ethylenepropylene copolymers can be employed for the shoulder piece, cap, neck, piston and in the construction of dispensing valves for other dentifrice dispensers, particularly in conjunction with the interior portions, exposed to the contained dentifrice, and, again, where required, compatible adhesives would naturally be employed.

Additionally when cast as a film on the interior surfaces of fibre drums used for the storage of fia voured'dentifrice, the material will retard flavour loss into the drums, thereby extending storage life.

Various modifications of the invention have been disclosed herein, and these and other changes can, of course, be effected without departing from the novel concepts of the present invention.

Claims (11)

1. A substrate of layers of materials comprising a first layer of an ethylene propylene copolymer, a second layer of metal foil, a third layer of paper and a fourth layer of an ethylene propylene copolymer.

2. A substrate as claimed in Claim 1 in which the first layer of the ethylene propylene copolymer is secured to the metal foil with an adhesive.

3. A substrate as claimed in Claim 1 or Claim 2 in which the third layer of paper is secured to the fourth layer of the ethylene propylene copolymer with an adhesive.

4. A substrate as claimed in Claim 2 or Claim 3 in which the adhesive is a copolymer of ethylene and acrylic acid.

5. A collapsible paste dispensing container of layers of materials comprising a first innermost layer of ethylene propylene copolymer, a second layer of metal foil, a third layer of paper and an outermost fourth layer of ethylene propylene copolymer

6. A container as claimed in Claim 5 in which the first layer of the ethylene propylene copolymer is secured to the metal foil with an adhesive.

7. A container as claimed in Claim 5 or Claim 6 in which the third layer of paper is secured to the fourth layer of the ethylene propylene copolymer with an adhesive.

8. A container as claimed in Claim 6 or Claim 7 in which the adhesive is a copolymer of ethylene and acrylic acid.

9. A container as claimed in any one of Claims 1 to 8 containing a composition containing one or more flavour oils.

10. A container as claimed in Claim 9 in which the composition is a dentifrice composition.

11. A package containing a composition containing one or more flavour oils, the interior surfaces of the package in contact with the said composition being afforded by ethylene propylene copolymer.