GB1582463A - Multiple wall packaging material - Google Patents

Description

(54) MULTIPLE WALL PACKAGING MATERIAL (71) We, SCHOLLE CORPORATION, a corporation organised and existing under the laws of the State of Nevada, United States of America, of 200 West North Avenue, Northlake, State of Illinois 60164, United States of America, (assignee of WILLIAM RAYMOND SCHOLLE), do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a multiple wall packaging material.

It has become increasingly prevalent to package food and other products in non-metallic containers, such as containers and pouches made from thermoplastic material. One problem which arises with the usage of these materials is that many non-metallic materials, such as paper or thin films of polymeric materials, including polyethylene, are sufficiently permeable or porous to allow diffusion of atmospheric oxygen from the exterior of the container or package into the interior of the container.

In the packaging of many food products and other commerical products which are sensitive to or reactive with oxygen, it would be desirable to provide an inexpensive structural material which would effectively decrease the penetration of oxygen through the container wall. The contamination of food products as well as other commercial products with oxygen after packaging has many undesirable effects, including discoloration, deterioration, and spoilage of the product, resulting in significant loss in acceptable commercial shelf storage life.

It is well known in the plastics art and the commercial process of packaging products to incorporate minor concentrations of certain antioxidants into the polymer before polymerization, extrusion or other formation thereof, as well as to coat plastics films and paper with subsequent film layers which contain antioxidants. Such antioxidants tend to prevent oxidation of, and change of properties in, the polymer itself but do not actively react with oxygen.

C.W. Desaulniers, in U.S. 3,499,820, issued March 10, 1970, discloses a self-supporting laminate of polymeric films, including a first film of polymer, and a second film bonded to the first film and containing a filler of clay-like mineral having plate-like shapes. A third film of polymer is disposed adjacent to the second filler film. The self supporting laminate provides low permeability to gases, specifically oxygen, by mechanically interposing a plate-like mineral barrier film.

C.C. Kirk, T.E. Ferington, and R.S. Gregorian, in U.S. 3,539,437, issued November 10, 1970, disclose a self-supporting laminate film having a first sheet of flexible thermoplastic film and a second sheet of mineral filler selected from minerals consisting of vermiculite, mica, talc, and clay bonded to the first film. At least one additional film of a polymer is disposed on the second film. The bonded multiple ply laminate provides a mechanically impermeable mineral barrier plate-like structure reducing the permeability of gases through the laminate structure.

Schindler, in Austrian patent number 212,209 issued December 12, 1960, discloses a multiple ply laminate having a hydrophilic carrier layer, a layer adjacent to the hydrophilic carrier layer, which is impermeable to water vapor, to fatty substances, and to light and consists of a thermoplastic coating containing pigments of powdered metal and titanium dioxide. A third layer consisting of chlorinated rubber and a synthetic resin is bonded to the second layer, and a fourth layer of synthetic thermoplastic material provides a harness greater than any of the other layers.

A Russian patent 238,774, issued July 15, 1969, discloses an inert powder between a pair of parent materials, followed by a thermal welding step. The powders are silicon dioxide, metal oxides and the like.

The U.S. Patent No, 3,429,717 (Cook) discloses a multiple-ply film structure containing an organic antioxidant and solvent between two adjacent plies. The types of antioxidants disclosed, such as propyl gallate, however, do not react directly with oxygen and would not serve to chemically react with oxygen being transmitted between the plies.

The U.S.Patent No.2,979,410 (Parlour) and Canadian Patent No.569,215 disclose the concept of providing an edible antioxidant coating on the surface of the film that is wrapped over the food product, whereby the surface of the food becomes coated with the antioxidant to prevent deterioration. Certain oxygen reactive and edible compounds, however, such as ascorbic acid, tend to discolor upon being oxidized, thereby imparting an undesirable color to the packaging or the food.

In accordance with U.S. Patent No. 1,584,903, (Supplee) an oxygen reactive agent such as ferrous sulphate or stannous chloride is provided on an isolated interior wall of a container so as to absorb free oxygen present in the container.

According to the present invention a structural multiple ply wall for a product container comprises a first sheet ply comprising a cellulosic or polymeric material.

A fluid coating comprising an oxygen reactive sulfite compound, which may be present as an aqueous solution, removes atmospheric oxygen which diffuses adjacent to the coating.

The liquid or solution is disposed adjacent to a face of the first sheet ply. At least one second sheet ply has one face of one second sheet ply disposed adjacent to the fluid coating.

The second sheet ply can have a composition providing low oxygen permeability through the second sheet ply. One or more second sheet plies may be suitable adjacently disposed.

The first sheet ply, the fluid coating, and the second sheet ply are contiguously integrally disposed together, forming the structural multiple ply wall. The wall is suitable for providing at least a major proportion of a container wall area. The first sheet ply can typically be a wax impregnated cellulose sheet composition, polyethylene, or other sheet ply polymer such as polypropylene.

The sulphite compound comprises a water soluble salts or acid of silfite ion (S 0 5-), bisulfite ion (H S 03), meta bisulfite ion (S,05-) or hydrosulfite ion (S,Oj-) or a mixture thereof, preferably present as an aqueous sdlution. The sulfite solution can interface with the oxygen gas diffusing through the second sheet ply and the first sheet ply, and can chemically react with the atmospheric oxygen. Thus, the oxygen gas is prevented from diffusing through the first sheet ply into a product disposed adjacent to a first face of the first sheet ply.In addition, the sulfite solution does not discolor upon being oxidized and may evolve sulfur dioxide gas that may diffuse through the first sheet ply and kill or prevent growth of pathogenic organisms in food products.

An object of the invention is to provide a multiple ply wall for a product container having properties suitable for usage in a product container for food.

A preferred embodiment of the invention will now be described.

A structural multiple ply wall for a product container has a first sheet ply for contacting a product disposed adjacent to a first face of the first sheet ply. An oxygen reactive sulfite compound is provided which actively reacts with any atmospheric oxygen diffusing through the wall adjacent to the coating. The sulfite compound is disposed as a fluid coating adjacent to the second face of the first sheet ply. At least one second sheet ply has one face of one said second sheet ply disposed adjacent to the oxygen reactive sulfite compound.

The at least one second sheet ply can have a chemical composition providing low oxygen permeability through the at least one second sheet ply. The first ply, the sulfite composition, and the at least one second sheet ply are contiguously integrally disposed together forming the structural multiple ply wall. The wall is suitable for providing at least the major portion of the container wall area. The wall can be manufactured in continuous wide width web rolls for commercial applications. The continuous web rolls can then be fabricated into container products as are required.

The first sheet ply can be a sheet of a non-metalic material that is employed in packaging and includes cellulosic materials such as paper, fiberboard, waxed paper and fiberboard, and polymeric material such as polyethylene, polypropylene, polyisopropylethylene, polyisobutylethylene, polyvinylidene chloride, polyvinyl chloride, polystyrene, polyethylene terephthalate, polyethylene-2, 6-naphthalate, polyhexamethylene adipamide, a polymer of butene, vinyl acetate, methyl acrylate, 2-ethyl hexyl acrylate, isoprene, butadiene acrylamide. or ethyl acrylate N-methyl-n-vinyl acetamide, or a combination thereof. The specific first sheet ply may be selected to provide a low oxygen permeability through the ply for a specific product which is to be disposed adjacent to a face of the first sheet ply.The list of polymers is intended to be exemplary only since many others are known and can be employed in the practice of this invention.

The sulfite compound serves to combine chemically with oxygen and thus serves to remove atmospheric oxygen which may diffuse through the wall. The sulfite compound is preferably in the form of an aqueous solution, although solvents can be utilized in addition to water. The sulfite composition contains water soluble salt or acid of sulfite ion (S 03--) bisulfite ion (H S 03), meta bisulfite ion (S,Oj-), hydrosulfite ion (S,O,--), or a mixture thereof. The sulfite compound functions to remove oxygen gas which may diffuse through the exterior ply and the inner ply of the structural wall. The amount and concentration of the sulfite compound are the values required to lower the oxygen diffusion through the structural wall to the desired value.The solution is preferably buffered to an acid pH or otherwise acidified to increase reactivity.

The at least one second sheet ply has one face of one said second sheet ply disposed adjacent to the sulfite compound. The material of the second sheet ply can be selected to provide as low oxygen permeability as is required for the product container application.

Polyvinylidene chloride can be selected for the one or more second sheet plies in the multiple ply wall, since it is well known to have a low oxygen permeability. Other polymeric compositions can be selected, as are required. The individual sheet plies of a multiple ply wall may be identical or dissimilar, being provided with sealing means. In selecting the combination of first sheet ply and second sheet ply, consideration must be given to the problem of providing chemically compatible and physically sealable sheet ply chemical compositions which provide a multiple ply wall having suitable commercial storage life. The problems of sealing multiple plies together to form a wall suitable for container construction are well known in the packaging art and are to be solved in known manner.

In addition to the function of removing atmospheric oxygen which may diffuse through the wall, the use of'sulfide ions offers additional advantages in this environment in comparison with other oxygen reactive antioxidants. Although ascorbic acid conventionally serves as an antioxidant in foods, for example, an oxidized solution thereof would tend to discolor and turn brown, thus adversely affecting the appearance of the container. The sulfite solutions, however, remain clear and colorless upon oxidation and do not form byproducts that may be harmful to food.

In addition, sulfite compounds tend to decompose to produce sulfur dioxide gas. The evolved gas, in turn, serves to destroy many types of harmful or pathogenic organisms associated with food products, such as bacteria and fungi. In fact, many food products and containers are surface treated with sulfur dioxide gas to insure sanitation of the product. In the case of the present invention, any gas which may diffuse through the first sheet ply of the container will contain a significant amount of sulfur dioxide gas as well as nonreactive gases such as nitrogen, which will aid in the preservation of the product and minimize surface discoloration that otherwise would occur because of oxidation.

As one example of the invention, the second sheet ply may comprise polyvinylide chloride which is preferably coated with a polymer to insure a good heat seal, such as a polyolefin or ethylene vinyl acetate copolymer. The first sheet ply could consist of polyethylene or ethylene vinyl acetate copolymer. Since the second sheet ply is relatively non-porous in comparison to the first sheet ply, any sulfur dioxide gas generated by the sulfite composition would tend to migrate toward and through the first sheet ply and into at least surface contact with the contained product, while any oxygen penetrating the second sheet ply would be eliminated.

The multiple ply wall of the present invention is advantageously used in the packaging of food products which are sensitive to or reactive with oxygen. The removal of oxygen tending to pass through the wall from the exterior serves, for example, greatly to reduce surface discoloration of solid or semisolid foods, while the sulfur dioxide gas evolved from the sulfite compounds acts as a preservative.

The composite material of the present invention may be fabricated into the form of containers, bags, pouches and the like, the food product may be inserted or poured therein, and the container may be sealed to provide an air tight enclosure. Such containers are particularly useful in packaging liquids. such as wine, semisolids, such as tomato paste or ketchup.

The following is an example of a suitable sulfite composition for use in connection with the present invention: Example Water 100.00 grams Sodium bisulfite 30.00 grams Citric acid (buffered to pH = 3.3) 1.50 grams The above example utilizes sodium bisulfite, embodied in a formulation of distilled water and citric acid as a buffer. The listed inorganic sulfite, bisulfite and other sulphite salts may be likewise utilized. The concentration of these compounds are those which are required to produce the desired rate of removal of diffusing oxygen.

Thickeners other than carboxymethyl cellulose may be utilized, including pectin and sodium alginate. The thickeners must of course be chemically compatible and stable in the desired sulfite coatings.

The structural multiple ply wall of this invention especially facilitates convenience packaging of food products, which by law or other regulation cannot contain or be exposed to specified antioxidants and the like chemicals in amounts in excess of specified levels. In particular, a package can be fabricated fully compatible with the packaged food, having a second sheet ply providing resistance to oxygen penetration and an adjacent fluid coating providing for the removal of atmospheric oxygen which diffuses through the second sheet ply. In this manner, protection from oxidation can be provided for the packaged food without subjecting the food itself to antioxidant materials.

The structural multiple ply wall may be produced at low cost as a continuous commercial mill material roll from which product containers may be formed.

WHAT WE CLAIM IS: 1. A structural multiple ply wall for a product container, said wall comprising: a first sheet ply comprising a cellulosic or polymeric material; a fluid coating containing a material for chemically reacting with atmospheric oxygen when said oxygen contacts said fluid coating, said fluid coating being disposed adjacent to a face of said first sheet ply and said material comprising a water soluble salt or acid of sulfite ion (S 03-), bisulfite ion (H S 03), meta bisulfite ion (S205-) or hydrosulfite ion S2Oa-) or a mixture thereof; and at least one second sheet ply comprising polymeric material having one face of one said second sheet ply disposed adjacent to said fluid coating; said first ply, said fluid coating, and said at least one second sheet ply being contiguously integrally disposed together, forming said structural multiple ply wall, said wall being suitable for providing at least the major proportion of the container wall area.

2. A wall as claimed in claim 1 wherein said at least one second sheet ply comprises polyvinylidene chloride.

3. A wall as claimed in claim 1 or claim 2 wherein said first sheet ply comprises polyethylene.

4. A wall as claimed in any one of claims 1 to 3, wherein said salt is a sodium salt.

5. A wall as claimed in any one of claims 1 to 4, in which the fluid coating is substantially as described in the foregoing Example.

6. A product container formed at least in part from a wall as claimed in any one of claims 1 to 5, wherein the first ply forms an inner ply and the second ply forms an outer ply of the container.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. and citric acid as a buffer. The listed inorganic sulfite, bisulfite and other sulphite salts may be likewise utilized. The concentration of these compounds are those which are required to produce the desired rate of removal of diffusing oxygen. Thickeners other than carboxymethyl cellulose may be utilized, including pectin and sodium alginate. The thickeners must of course be chemically compatible and stable in the desired sulfite coatings. The structural multiple ply wall of this invention especially facilitates convenience packaging of food products, which by law or other regulation cannot contain or be exposed to specified antioxidants and the like chemicals in amounts in excess of specified levels. In particular, a package can be fabricated fully compatible with the packaged food, having a second sheet ply providing resistance to oxygen penetration and an adjacent fluid coating providing for the removal of atmospheric oxygen which diffuses through the second sheet ply. In this manner, protection from oxidation can be provided for the packaged food without subjecting the food itself to antioxidant materials. The structural multiple ply wall may be produced at low cost as a continuous commercial mill material roll from which product containers may be formed. WHAT WE CLAIM IS:

1. A structural multiple ply wall for a product container, said wall comprising: a first sheet ply comprising a cellulosic or polymeric material; a fluid coating containing a material for chemically reacting with atmospheric oxygen when said oxygen contacts said fluid coating, said fluid coating being disposed adjacent to a face of said first sheet ply and said material comprising a water soluble salt or acid of sulfite ion (S 03-), bisulfite ion (H S 03), meta bisulfite ion (S205-) or hydrosulfite ion S2Oa-) or a mixture thereof; and at least one second sheet ply comprising polymeric material having one face of one said second sheet ply disposed adjacent to said fluid coating; said first ply, said fluid coating, and said at least one second sheet ply being contiguously integrally disposed together, forming said structural multiple ply wall, said wall being suitable for providing at least the major proportion of the container wall area.

2. A wall as claimed in claim 1 wherein said at least one second sheet ply comprises polyvinylidene chloride.

3. A wall as claimed in claim 1 or claim 2 wherein said first sheet ply comprises polyethylene.

4. A wall as claimed in any one of claims 1 to 3, wherein said salt is a sodium salt.

5. A wall as claimed in any one of claims 1 to 4, in which the fluid coating is substantially as described in the foregoing Example.

6. A product container formed at least in part from a wall as claimed in any one of claims 1 to 5, wherein the first ply forms an inner ply and the second ply forms an outer ply of the container.