AU645712B2 - Improved laminates and laminated tubes and packages for hard-to-hold products having volatile components - Google Patents

Description

AUSTRALIA

Patents Act 6 4 5 7 1 2 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: American National Can Company Actual Inventor(s): Suzanne E. Schaefer Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Attorneys 367 Collins reet Melbomrne 3000 AUSTRALIA Invention Title: IMPROVED LAMINATES AND LAMINATED TUBES AND PACKAGES FOR HARD-TO-HOLD PRODUCTS HAVING VOLATILE COMPONENTS Our Ref 304255 POF Code: 50689/81711 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): 6006 This application is a divisional from Australian application 26854/88, the entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION This invention pertains to laminated sheet materials used for packaging. Such sheet materials are commonly known for their use in making bags, pouches, and tubes. The sheet materials of the invention can be used for making any of these types of packages. This particular description will *be addressed primarily to the discussion of the sheet e materials as they relate to packaging products in lap seamed tubes.

Laminated sheet materials of the variety disclosed herein, and especially those containing a layer of metal foil, have been used for packaging such materials as toothpaste, foods, and certain chemical compounds. There remain certain products which have not heretofore been packaged in multiple layer sheet materials of the type 20 disclosed in the invention because of the package's susceptibility, to being chemically attacked by the contained product. Particularly troublesome, and addressing now the problem addressed by the inventors herein, are those compounds which use especially volatile, and chemically active, materials such as methyl salicylate.

-2- Multiple layered sheet materials containing a layer of metal foil are described and claimed in parent application 26854/88. In one embodiment, the present invention corresponds essentially to the five outermost layers of the embodiments described in Australian application 26854/88.

The sheet materials of this embodiment of the invention comprises essentially a five layer coextruded film containing outer surface layers of low density polyethylene and linear low density polyethylene, a core layer of ethylene vinyl alcohol, and adhesive layers, on either side of the ethylene vinyl alcohol layer, intervening between the ethylene vinyl alcohol and the respective surface layers. The same parameters and limitations as described in Australian :i15 application 26854/88 apply to the five layer sheet material.

This sheet material may be made, and preferably is made, by a coextrusion process.

Accordingly, one embodiment of the present invention resides in a multiple layer sheet material comprising a first layer of ethylene vinyl alcohol copolymer, a second layer comprising an olefinic polymer composition on a first side of said %tylene vinyl alcohol copolymer layer, a third layer of linear low density polyethylene on a second side of said ethylene vinyl alcohol layer, and a fourth adhesive layer between said ethylene vinyl alcohol layer and said third layer respectively.

In a preferred embodiment, the sheet material includes a further adhesive layer adhered between the first layer and the third layer.

The present invention further resides in a pacakge made from the sheet materials described above, and methods for producing such a package.

In fabrication of typical packages, portions of the sheet material are folded onto each other in a tubular configuration in formation of a lap seam, wherein an upper surface of an underlying layer is in facing contact with a lower surface of an overlying layer. A seal is fabricated by means of heating the sheet materials such that the upper 39 surface of the underlying layer is bonded to the lower surface WDN 3

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of the overlying layer.

In another construction useful in making packages of sheet material of the invention, the same general container shape may be fabricated using fin seals wherein portions of the same surface are brought into facing contact with each other to make the closure seals.

In still other cases, the sheet material of the invention may be used in combination with other sheet structures to fabricate less than the entire package structure. In these cases, the sheet material of the invention is typically seen as a closure, cover, or other type of lid material which is bonded to a second, and different packaging sheetmaterial, such as a preformed rigid tray.

Another way of considering the invenion is that it i15 provides, in two layers, one of ethylene vinyl alcohol and the other of the anhydride modified polyethylene composition, preferably linear low desntiy polyethylene, a composite barrier structure capable of holding products having one or more of the recited hard-to-hold components.

The thus made packages of the invention are entirely satisfactory, and are preferred, for packaging products having volatile components.

BRIEF DESCRIPTION OF THE DRAWING •2.25 FIGURE 1 is a cross-section of a less complex multiple layer film of the invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Figure 1 corresponds to figure 5 of Australian application 26854/88. With respect to the numbering of FIGURE 1, the last two digits of the layer numbers in FIGURE 1 correspond to the two digit numbers given for similar layers i:n FIGURE 1 of application 26854/88. Thus layer 514 is EVOH.

Layer 516 is LLDPE. Layer 518 is an adhesivekcomprising' a base resin of LLDPE and an anhydride modifier. Layer 519 is a covering layer over layer 514, and it provided primarily for the purpose of physically protecting the EVOH in layer 514, though layer 519 may also serve other functions as well.

39 The embodiment shown in figure 1 is useful where WiN u' \WN 4 14,705-1 Patent the extremely high barrier properties of the foil layer are not necessarily needed. Without the requirement for the foil layer, it is seen that the sheet material can be substantially less complex. Indeed, if covering layer 519 is polymeric, it is possible to make the sheet material at FIGURE 1 by a one step process of coextrusion.

The functional barrier properties of the sheet material of FIGURE 1 are generally provided by the EVOH layer 514, especially concerning barriers to transmission of oxygen and 10 methyl salicylate. Layer 516 provides a substantial barrier to the transmission of moisture, having a moisture vapor transmission rate of no more than about 0.9 grams/645 cm 2 -24 S. hours at 100% relative humidity, preferably no more than 0.9 grams/ 645 cm 2 24 hours. The composition of layer 516, is preferably based on an olefin polymer or .copolymer. A preferred olefin is an ethylene, as polymer or copolymer, but the composition may, alternatively, be based on propylene, butylene (including polyisobutylene) or a combination of the above; or other alpha olefins having a 20 primary monomer containing at least three carbon atoms.

The composition of covering layer 519 may be selected with respect to its capability to serve as a barrier to transmission of a selected material. Its primary function, however, is usually that of protecting EVOH layer 514 from physical abuse when it is used as the outside layer of the package, and from physical attack by the components of the product when it is used toward the inside of the package 5 14,705-1 Patent from layer 514. Indeed, covering layer 519 may include a multiple layer structure including another adhesive layer, such as an adhesive polyethylene, especially a linear low density polyethylene, containing at least about 0.10%, preferably at least about 0.13%, most preferably at least about 0.20% maleic anhydride equivalent, adjacent EVOH layer 514 Lc-yer 519 may include other layers of materials which serve to protect or modify, or otherwise 0. •10 enhance, or make more effective, the properties of the EVOH.

To that end, and especially with respect to using layer 516 toward the inside of the package, the sheet material of FIGURE 1 is seen to be useful for packaging a variety of products which benefit from the barrier properties of EVOH, yet require substantial levels of adhesion between adhesive layer 518 and EVOH layer 514.

With the sheet materials of the illustrated embodiments having thus been disclosed, it is seen that several and various modifications may be made to the invention without departing from the spirit and scope of the concept. Thus the invention should be interpreted, not only with respect to the illustrated embodiments, but more appropriately in light of the appended claims.

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Claims (7)

1. A multiple layer sheet material comprising a first layer of ethylene vinyl alcohol copolymer, a second layer comprising an olefinic polymer composition on a first side of said ethylene vinyl alcohol copolymer layer, a third layer of linear low density polyethylene on a second side of said ethylene vinyl alcohol layer, and a fourth adhesive layer between said ethylene vinyl alcohol layer and said third layer respectively.

2. A multiple layer sheet material according to claim i and sPc.oc c\ including a fifth adhesive layer between said first andiyhi-zd layers.

3. A multiple layer sheet material according to claim 2 wherein the compositions of said fourth and fifth layers comprise linear low density polyethylene and anhydride i15 comprising active anhydride component equivalent to between 0.13% and 0.40% maleic anhydride.

4. A package made with a sheet material of claim 1 to 3 and including therein a product comprising a volatile component selected from the group consisting of methyl salicylate, acetic anhydride, acetone, undecylenic acid, ichthamnol, and polyurethane prepolymers, and wherein said sheet material is functional to retard transmission of said volatile component through said sheet material, sufficient to provide for normal compositional stability of said volatile component in said product over the normal shelf life of said product.

5. A method of making a package, comprising: fabricating the sheet material according to any one of claims 1 to 3; fabricating said sheet material into a package enclosure by bringing portions of said sheet material in facing relationship and forming heat seals about contiguous portions thereof, leaving one side of said package open; placing a product in said package; and closing said one side of said package, to complete the fabricating, filling, and sealing of said package.

6. A method of making a package, comprising: fabricating the sheet material according to any one of claims 1 to 3;

39. i(b) fabricating said sheet material into a package enclosure I ft S WDN -7 7 by forming a tube comprising a lap seal, and with one end of said tube open; placing a product in said package; and closing said one end, to complete the fabricating, filling, and sealing of said package. 7. A sheet material, according to claim 1 substantially as hereinbefore described with reference to the drawing. 8. A package according to claim 4 substantially as hereinbefore described with reference to the drawing. 9. A method according to claim 5 or 6 substantially as hereinbefore described with reference to the drawing. DATED: 9 September 1992 S PHILLIPS ORMONDE FITZPATRICK Attorneys for: n AMERICAN NATIONAL CAN COMPANY 9* 9 0466N 9* 9*4* 39 8 WDN ABSTRACT A multiple layer sheet material comprising a first layer of ethylene vinyl alcohol copolymer, a second layer comprising an olefinic polymer composition on a first side of said ethylene vinyl alcohol copolymer layer, a third layer of linear low density polyethylene on a second side of said ethylene vinyl alcohol layer, and a fourth adhesive layer between said ethylene vinyl alcohol layer and said third layer respectively. 2 e OS *1 39 39 WDN