Dispensing container made from an ethylene vinyl alcohol containing laminated material and the material therefor

74) Agent (s): Cabinet Lavoix.

63) Laminate based on a copolymer of ethylene and vinyl alcohol and dispensing container with application thereof.

fe /) Substrate of layers of materials comprising layers of ethylene-vinyl alcohol copolymer between which are sandwiched a layer of metal foil and a layer of paper, all stuck together in a suitable manner.

Application for the manufacture of tubes for toothpaste.

FR 2 575 412

D

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The present invention relates, in general, to container technology and, more particularly, a collapsible dispensing container whose wall is laminated in the body part thereof, whereby the penetration and absorption of the product , and oxygen uptake are largely avoided in all sensitive regions of the container structure.

Crushable tubes formed from metallic and plastic materials have been known for a long time in the field of packaging. The extruded metal tubes are inherently brittle, and their repeated use frequently leads to cracks in the wall, so that the product exudes from a place other than the substantially rigid dispensing orifice. Among the metal tubes of the prior art, aluminum tubes, although probably the least brittle, have quite limited applications, because so far it has not been possible to apply to their interior surfaces a completely satisfactory coating, when necessary to prevent attack and corrosion of the metal by alkaline or acidic contents and contamination of the content by the products of the reaction. Despite the relatively brittle nature of the metal tubes, the mentioned internal coating operation requires an additional processing step which necessarily increases the cost of the final article.

Tubes made of polyethylene and other plastics have had wide commercial success in the packaging of many products. However, it was noted that some other products deteriorate after some time when they are contained.

Plastics such as polyethylene are permeable to some extent when used in the wall thicknesses used in tubular containers and the essential oils found in most toothpastes to scent them see their volume reduced during storage of the container , which makes the dentifice less palatable. Likewise, the wall of the plastic container absorbs oxygen over time, and can ultimately decompose the product, which has been found to be the case with fluoride containing pastes. Another disadvantage of plastic tubes lies in the inability of the surface to easily receive a printing or decorative material. In addition, plastic tubes such as polyethylene, have a memory effect, that is to say that they do not remain compressed when crushed, which is a particular drawback for toothpaste tubes.

To overcome the above problems, it has therefore been proposed to provide a metal sheet as a barrier between the product and the body of the polyethylene tube. This would solve the compressibility problem, in the sense that the metal layer would impose its compressibility on the plastic. In addition, the metal sheet forming a barrier between the product and the polyethylene tube body would prevent the loss of essential oils and the absorption of oxygen mentioned above. Oh suggested using the metal barrier as an intermediate layer between outer layers of polyethylene, and forming a laminate by heating, with or without suitable adhesives. However, although a structure having this general character is effective in preventing a certain penetration of the product and an absorption of oxygen through the body of the tube, and in particular when the internal thermoplastic layer is a copolymer of ethylene and d 'A monomer containing polar groups which is copolymerizable with it, there remains the possibility of deterioration of the product, although to a much lesser extent.

Attention is drawn to the following prior art:

Brandt (US Patent No. 3,295,725) describes a tube which combines the advantages described above of aluminum tubes with the advantages of plastic tubes. It is a collapsible dispenser container containing both a metal barrier and an inner polyethylene wall. The thermoplastic layer is generally described as a polyolefin and a copolymer of an olefin and of a monomer containing polar groups which is copolymerizable with this olefin. This laminate overcomes the limitations described above, except for the absorption of essential oils from toothpastes. .

Marchak (Canadian Patent No. 728,525) describes a laminate tube containing an inner layer of polyethylene. He mentioned the problem of the absorption of odoriferous oil by the thermoplastic wall.

Sugimoto (US Patent No. 4,261,482) describes a collapsible laminate tube containing an ethylene-vinyl alcohol copolymer as the outer layer and an olefin as the inner layer. The function of the ethylene-vinyl alcohol copolymer is to serve as an oxygen barrier resin. This tube differs from the present invention in two important points. The first is that it does not contain a metal barrier as the central layer, and therefore does not have the advantages of a metal layer described above. Second, it does not include an ethylene-vinyl alcohol copolymer as a layer adjacent to the toothpaste. The results below will show the advantage of the ethylene-vinyl alcohol copolymer as a barrier for flavors when it is placed against the toothpaste.

Other inventors have also used ethylene-vinyl alcohol copolymers in laminates as a barrier against oxygen, but they have also not recognized their effectiveness as a barrier for flavorings. In addition, the described article is not in any case a collapsible laminated tube containing a metal layer forming a barrier, we can consult, on this subject, patents of E, UA such as the following: Knott (4,239,829), Schroeder (4,254,169), Sakano (4,182,457), Sugi (3,620,435), Canio (4,284,671), Farrell (4,464,443), Farrel ( 4,425,410), and Kushida (3,958,721).

In addition, the inventors have also used an ethylene vinyl alcohol copolymer as part of the structure of a laminate, but this was not in the form of a collapsible tube containing a metallic barrier layer. In addition, these inventors have also not mentioned the excellent barrier properties for the flavors of this polymer. These in15 venturers include: Christensen (4,407,873), Christensen (4,406,667), Bair (4,400,428), Uehara (4,352,850), Matsuo (4,451,512), and Katayama (4,410,595).

An ethylene vinyl alcohol copolymer was also used as a thermal insulator by Sheptak (US

A. 4,284,674). Nor was it in the form of a collapsible laminate tube.

An important object of the present invention is therefore to provide a collapsible dispensing container, the body part of which has a laminated wall.

Another object of the invention consists in providing a tubular container, the body part of which comprises several adherent layers, one of these layers forming a barrier against the migration of the product and the absorption of oxygen, such as a metal sheet, and another of these layers being an ethylene vinyl alcohol copolymer or a mixture based thereon of variable density and crystallinity. This last layer being the most internal and preferably the most external with various additional layers taken in sand35 wich between them.

These additional layers include paper and suitable adhesives and binders, such as a co-polymer of ethylene and acrylic acid.

The collapsible dispensing container of the present invention can be constructed from the laminate substrate of the present invention with conventional and known apparatus. Examples of such apparatus are found in the US patent N⁹3,832,964, which is incorporated herein by reference.

Another object of the present invention is to provide a method of manufacturing laminate tubes in which a tubular body is formed of a barrier layer and an ethylene vinyl alcohol copolymer laminated thereon; the laminated tube body is then placed on a shaping element in position adjacent to a barrier element also placed on it.

Other objects and advantages of the invention will appear on reading the description which follows, given by way of example and made with reference to the accompanying drawings.

In the drawings, in which the same reference numbers are used to designate the same parts:

Figure 1 is a cross-sectional view of a fragment of a laminate substrate of the present invention Figure 2 is a side elevational view of a collapsible dispensing container embodying the new concepts of the invention, parts of the walls from the body being torn away to more fully illustrate the layered structure.

The thermoplastic material of the invention is an ethylene-vinyl alcohol copolymer.

Referring to Figure 1 of the drawings, a substrate 10 is shown in cross section, thus revealing the constituents of the sandwich form the laminate structure.

It can be seen that the lower layer 11 is an ethylene-vinyl alcohol copolymer. The second layer 12 above it is an adhesive layer which bonds the ethylene-vinyl alcohol copolymer layer 11 with the third layer 13 which is a metallic foil such as aluminum foil. The fourth layer 14 is another adhesive which fixes the other side of the layer of metal foil 13 by adhesion to a layer of paper 15. The upper layer 16 is an ethylene-vinyl alcohol copolymer.

The ethylene vinyl alcohol copolymer is particularly useful because it has very low flavor absorption characteristics, as can be seen from the following tables in which the ethylene vinyl alcohol copolymer is compared with polyethylene, the thicknesses layers or coating being the same.

TABLE I

FLAVOR CONTENT OF A TOOTHPASTE IN CONTACT WITH POLYMERS *

Ccncentraticn en arône

Toothpaste polymer (%) **

<td>None (witness)</td><td> 100</td>

<td>Ethylene vinyl alcohol</td><td></td>

<td>EF-F (Kuraray)</td><td> _ 100</td>

<td>Low density polyethylene</td><td> 15-19</td>

<td>Surlyn 1707</td><td> 10-14</td>

<td>Surlyn 1706</td><td> 5-9</td>

<td>Surlyn 1605</td><td> 5-9</td>

ί Contact time 15 minutes at 32.2 ° C,

Si Compared to the control in which no polymer was in contact with the toothpaste? the higher the concentration of the flavor, the more the polymer is inert. .

TABLE II

ABSORPTION BY POLYMERS OF AN UNDILUTED AROMATIC OIL (Total immersion 2 weeks)

Weight increase polymer (%)

<td>Ethylene vinyl alcohol EF-F (Kuraray)</td><td> 0</td>

<td>Low density polyethylene</td><td></td>

<td>(USI)</td><td> 10</td>

<td>Surlyn 1707 (DuPont)</td><td> 15</td>

<td>Surlyn 1605 (DuPont)</td><td> 19</td>

<td>Surlyn 1706 (DuPont)</td><td> 24</td>

TABLE III

RELATIVE ABSORPTION OF FLAVOR BY POLYMERS AFTER CONTACT WITH THE. TOOTHPASTE

DURING THREE MONTHS* *

Polymer Aroma absorbed by the polymer **

Ethylene vinyl alcohol

EF-F (Kuraray) '12

Low density polyethylene (USI) 100 -13

Surlyn 1706 (DuPont) 893

Surlyn 1707 (DuPont) 1557

Surlyn 1605 (DuPont) 1672 * at 32.2 ° C,

Sut compared to low density polyethylene which has been arbitrarily set as equal to 100; the lower the number, the lower the amount of flavor absorbed.

It is contemplated that, within the scope of the invention, the adhesives may be a copolymer of ethylene and acrylic acid or methacrylic acid, or the sodium or zinc salts thereof in a diluent system .

The metal sheet is preferably an aluminum foil.

The paper layer is advantageously kraft paper.

The range of thicknesses for each sheet is as follows:

layer of ethylene-vinyl alcohol copolymer 11:

12.7 to 76.2 microns (0.5 to 3.0 thousandths of an inch), preferably- 25.4 microns (1.0 thousandths of an inch), adhesive layer 12. Sufficient to ensure adhesion, metallic foil layer 13: 12.7 microns at

50.8 microns (0.5 to 2.0 thousandths of an inch), preferably 25.4 microns (1.0 thousandths of an inch), adhesive layer 14: sufficient to ensure adhesion, paper layer 15: 38.1 microns at 63.5 microns (1.5 to 2.5 thousandths of an inch), preferably 50.8 microns (2.0 thousandths of an inch), layer of ethylene-vinyl alcohol copolymer 16:

88.9 microns to 127 microns (3.5 to 5.0 thousandths of an inch), preferably 101.6 microns (4.0 thousandths of an inch).

The upper ethylene-vinyl alcohol copolymer layer 16 adheres to the paper layer 15 by applying a sufficient amount of heat and pressure to the substrate. When the application of heat and pressure is inappropriate, an adequate adhesive should be used.

Figure 2 is an example of the layered structure of a collapsible container in which the layers are designated as in Figure 1, layer 11 being the innermost and the other layers being made of the same materials and being placed in the same order than the one shown.

It is clear from the above that the Applicant has provided a collapsible container structure which significantly reduces the problems hitherto not resolved by the prior art. The laminate substrate and the shoulder piece 20 virtually eliminates product penetration and oxygen uptake.

The outer layer of an ethylene-vinyl alcohol copolymer is a thermoplastic material capable of melting during a lateral welding stage and providing adequate protection for the paper and the metallic intermediate sheet. The technique of welding a collapsible toothpaste tube of the general type described in this specification is described in the US Patent

A. No. 3.295.725, incorporated in the present memorandum for reference. However, the outer layer of ethylene vinyl alcohol copolymer and paper can be removed, if the metal foil barrier is thick enough to resist damage, and by flowing a thermoplastic material in the side weld with overlap during its sealing when using such a system.

In addition, the outer layer may be paper in a three-layer laminate formed from paper, metal foil and ethylene-vinyl alcohol copolymer as described. Since the outermost layer and the innermost layer are preferably identical, the folded edges of the tube produced from the substrate are conveniently bonded by the action of heat.

A suitable adhesive can be used, when heat bonding is not possible. This variant is added to the 4-layer laminate mentioned above, consisting, from outside to inside, of an ethylene-vinyl alcohol copolymer, of paper, of metallic foil and of ethylene-vinyl alcohol copolymer.

It is envisaged to use suitable additives between the layers if necessary.

Ethylene vinyl alcohol copolymers can be used for shoulder pieces, plugs. necks, pistons and in the construction of dispensing valves for other toothpaste dispensers, in particular in the internal parts exposed to the toothpaste contained, and, here again, naturally, if necessary, compatible adhesives will be used. In addition, when cast as a film on the interior surfaces of plywood barrels used for the storage of scented toothpaste, the material will further delay the loss of aroma in the barrels, thereby extending the shelf life.