AU645711B2

AU645711B2 - Improved laminates and laminated tubes and packages for hard-to-hold products having volatile components

Info

Publication number: AU645711B2
Application number: AU22840/92A
Authority: AU
Inventors: Suzanne E. Schaefer
Original assignee: American National Can Co
Current assignee: Rexam Beverage Can Co
Priority date: 1987-12-14
Filing date: 1992-09-09
Publication date: 1994-01-20
Anticipated expiration: 2008-12-14
Also published as: AU645712B2; ZA889268B; AU2284092A; AU2284192A

Description

AUSTRALIA

Patents Act 64 571 1 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: r cc PHILLIPS ORMONDE FITZPATRICK Patent -nd Trade Mark Attorneys s. 'Collins Street Melb(orne 3000 AUSTRALIA o o Invention Title: IMPROVED LAMINATES AND LAMINATED TUBES AND PACKAGES FOR HARD-TO-HOLD PRODUCTS HAVING VOLATILE COMPONENTS Our Ref 304268 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): 006 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 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. Ther^ *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 suscep- -o tibility 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 coextrLded film containing Pre-r>? bi-I 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 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 S. layer of ethylene vinyl alcohol copolymer having first and second surfaces, a second covering layer on said first surface of said ethylene vinyl alcohol copolymer layer, a third adhesive S. layer on said second surface of said ethylene vinyl alcohol S. copolymer la,:sr, said third adhesive layer comprising a linear low density polyethylene and anhydride comprising active anhydride component equivalent to 0.13% to 0.40% maleic anhydride, and having a melt index, at 210 of between 3 and 9, and a fourth layer of linear low density polyethylene on said third layer opposite said first layer.

In a preferred embodiment, the sheet material includes a further adhesive layer of linear low density polyethylene adhered between the second covering layer and the first layer.

o .In a further embodiment, the present invention resides in a multiple layer sheet material comprising in order, a first layer comprising an olefin polymer or copolymer, a second adhesive layer comprising anhydride comprising active anhydride component equivalent to up to 0.60% maleic anhydride, and a third layer of ethylene vinyl alcohol which is in surface to surface contact with the second adhesive layer.

Still further, the present invention resides in a package made from the sheet materials described above, and methods for WDN 3 producing such a package.

The sheet materials of this embodiment of the invention include a sheet material comprising, from the inside surface thereof in the package outwardly a first layer of a polyolefin; a second adhesive layer comprising a polyethylene and about 0.10% to about 0.60%, preferably about 0.26% to about 0.40% (equivalent) of an anhydride, and having a melt index at 210°C of between 3 and 9; and a third layer of ethylene vinyl alcohol, the packaging sheet material being functional to retard iC transmission of the volatile component of, for example, methyl salicylate, acetone, acetic anhydride, undecylenic acid, ichthamnol coal tar derivative, or polyurethane prepolymer, through the sheet material, sufficient to provide for acceptable compositional stability of the volatile component in the product over the normal shelf life of the product. The composition of the first layer may, in some cases, be based on propylene. In other cases, it may be based on ethylene. Further, it may be based on a combination of ethylene and propylene. Preferably it comprises a copolymer of ethylene and up to 10% of an alpha 0 .20 olefin, having a carbon chain at least three carbon atoms long, S. and commonly referred to as linear low density polyethylene.

In fabrication of typical packages, portions of the sheet material are folded onto each othez 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 surface of the underlying layer is bonded to the lower surface of the overlying layer.

In another construction useful in making packages of sheet material of the invention, the same general container S* 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 39 to a second, and different packaging sheet material, such as a

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4 preformed rigid tray.

Another way of considering the invenion is that it 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 FIGURE 1 is a cross-section of a 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 in S. FIGURE 1 of application 26854/88. Thus layer 514 is EVOH.

Layer 516 is LLDPE. Layer 518 is an adhesive comprising a base resin of LLDPE and an anhydride modifier. Layer 519 is a covering layer over layer 514, and is provided primarily for the 25 purpose of physically protecting the EVOH in layer 514, though layer 519 may also serve other functions as well.

The embodiment shown in figure 1 is useful where 39

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5 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 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 hours at 100% relative humidity, preferably no more than 0.9 *99# 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 Sbased on propylene, butylene (including polyisobutylene) or a combination of the above; or other alpha olefins having a 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 -6from 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 Layer 519 may include other layers of materials which serve to protect or modify, or otherwise 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 I 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 depazting 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

2. A multiple layer sheet material according to claim 1 wherein said second covering layer comprises low density S polyethylene adhered by an intervening adhesive layer comprising linear low density polyethylene.
3. A multiple layer sheet material comprising in order, a first layer comprising an olefin polymer or copolymer, a second adhesive layer comprising anhydride comprising active anhydride component equivalent to up to 0.60% maleic anhydride, and a third layer of ethylene vinyl alcohol which is in surface to 25 surface contact with the second adhesive layer.
4. A multiple layer sheet material according to claim 3 wherein the composition of said first layer is based on propylene. A multiple layer sheet material according to claim 3 wherein the composition of said first layer is based on ethylene.
6. A multiple layer sheet material according to claim 3 wherein the composition of said first layer is based on a combination of ethylene and propylene.
7. A pacakge comprising the sheet material of claim 3, 39 wherein the first layer is towards the outside of the package WDN 8 and the third layer of ethylene vinyl alcohol is towards the inside of the package.
8. A package made with a sheet material of claim 1 or 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 S product over the normal shelf life of said product. *~de mo-ck. Li+k o- 6ec& k of
9. A package as-claimed in claim 3 wherein said second layer adheres said first layer of ethylene vinyl alcohol copolymer to a third polymer layer comprising an olefinic polymer selected Sfrom the gorup consisting of ethylene polymers and copolymers, propylene polymers and copolymers, butylene polymers and copolymers, including polyisobutylene, and combinations of the Y0 above polymers and copolymers.
10. A method of making a package, comprising: fabricating the sheet material of claim 1 or 3; fabricating said sheet material into a package 25 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.
11. A method of making a package, comprising: fabricating the sheet material of claim 1 or 4; fabricating said sheet material into a package enclosure by forming a tube comprising a lap seal, (c and with one end of said tube open; S39 placing a product in said package; and S- 9 closing said one end, to complete the fabricating, filling, and sealing of said package.
12. A multiple sheet layer material, according to claim 1 or 3, substantially as hereinbefore described with reference to Iay nn nof the vamples nr irawingR Q
13. A package, according to claim 8, substantially as <-!sure hereinbefore described with reference toLanyr one f the oamplcG-- 'Qr drawings.
14. A method, according to claim 10 or 11 substantially as heree d e w re I hereinbefore described with reference toj any ono of the- Oam- *ie *0 *so c l3- DATED: 9 September 1992 PHILLIPS ORMONDE FITZPATRICK Attorneys for: AMERICAN NATIONAL CAN COMPANY D /5 0319N A J WDN 10 ABSTRACT A multiple layer sheet material comprising a first layer of ethylene vinyl alcohol copolymer having first and second surfaces, a second covering layer on said first surface of said ethylene vinyl alcohol copolymer layer, a third adhesive layer on said second surface of said ethylene vinyl alcohol copolymer layer, said third adhesive layer comprising a linear low density polyethylene and anhydride comprising active anhydride component equivalent to 0.i3% to 0.40% maleic anhydride, and having a melt index, at 210°C., of between 3 and 9, and a fourth layer of linear low density polyethylene on said third layer opposite said first layer. S 55 S 39 WDN