CA2053707A1 - Cheese packaging laminate - Google Patents
Cheese packaging laminateInfo
- Publication number
- CA2053707A1 CA2053707A1 CA 2053707 CA2053707A CA2053707A1 CA 2053707 A1 CA2053707 A1 CA 2053707A1 CA 2053707 CA2053707 CA 2053707 CA 2053707 A CA2053707 A CA 2053707A CA 2053707 A1 CA2053707 A1 CA 2053707A1
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- film
- multilayer laminate
- layer
- laminate according
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Abstract
ABSTRACT OF THE DISCLOSURE
A multilayer laminate comprises a machinable film with perforations defined therein, preferably of a propylene homopolymer or copolymer, and a second component film bonded to one side of the machinable film, such laminate providing the combined properties of machinability, high gas permeabili-ty and low moisture transmission while maintaining a substan-tially planar configuration.
2/901004.1/OLDFLDR
A multilayer laminate comprises a machinable film with perforations defined therein, preferably of a propylene homopolymer or copolymer, and a second component film bonded to one side of the machinable film, such laminate providing the combined properties of machinability, high gas permeabili-ty and low moisture transmission while maintaining a substan-tially planar configuration.
2/901004.1/OLDFLDR
Description
20~3707 CHEESE PACKAGING LAMINATE
The present invention is directed to a laminated structure useful in the packaging of food items, particularly soft cheeses.
Soft cheeses such as Camembert and Brie are current-ly packaged in a variety of different materials including polyethylenes with and without ethylene/vinyl-acetate copolymers, polypropylenes, nylon/polyethylene laminates, and polyester/polyethylene laminates. The oxygen and carbon dioxide transmission rates of such structures are of primary importance in the packaging of many soft cheeses, as well as other food items which require a packaging material of high gas permeability such as many fruits and vegetables. High oxygen permeability is of primary importance in the packaging of cheeses which, like Brie, require an aerobic atmosphere to support fungal growth on the surface of the cheese. Other cheeses respire COz in amounts that require a permeable packaging material in order to preclude gassing of the pack-age. In the case of produce packaging, regulation of the transmission of 2 and CO2 minimizes enzymatic browning of cut surfaces and the damaging effects of product anaerobio-sis.
However, in most cases, materials having the de-sired oxygen and carbon dioxide transmission rates required in the above-discussed applications also have minimal abuse resistance and machinability properties. Conversely, film structures which are abuse resistant and machinable generally 2/901004.1/OLDFLDR
20~3707 lack the gas permeability and sealing properties required by such applications.
The present application requires a structure which combines heat resistance, low extensibility and strength with high gas permeability and sealing. To prevent drying of the packaged food product, a low water vapor transmission rate is also required.
Such requirements were met by the structure of U.S.
Pat. No. 4,935,271 to Schirmer which discloses a multilayer laminate for use in the packaging of lettuce and the like having a first impermeable film of propylene homopolymer or copolymer having perforations defined therein, and a second permeable film bonded to the first film which includes a bonding layer of ethylene vinyl acetate copolymer and an outer heat sealable layer. In that laminate, machinability is provided by the polypropylene film which is perforated in order to render it permeable. The gas permeable second film contributes the properties of low moisture transmission and sealability to the overall structure. However, for the Schirmer structure, disposition of the soft, flexible second film adjacent the relatively stiff, heat set polypropylene, results in curling of the overall structure and, thus, poor machining performance.
SUMMARY OF THE INV~ENTION
It is thus an object of the present invention to provide an improved material for use in the packaging of soft cheeses which has a low moisture permeability and a high gas permeability.
It is still another object of the present invention to provide such an improved material for the packaging of cheese and the like which is machinable, having heat resis-tance, non-extensibility and strength.
2/901004. l/OLDFLDR
20~3707 It is a further object of the present invention to provide a packaging laminate having high gas permeability in addition to strength, heat resistance, and low extensibility which precludes moisture transmission and tends to remain in a planar configuration during processing.
These, as well as other objects, are achieved by providing a multilayer laminate comprising a first component of a strong, nonextensible film having perforations defined therein, and a second component film, bonded to the first component film, having high permeability and low moisture transmission and including a bonding layer and a layer which imparts stiffness to the second film.
Such objects are further achieved by providing a method of making a multilayer laminate comprising providing a perforated film preferably comprising a propylene homopolymer or copolymer, coextruding a second film having a bonding layer and an interior styrene butadiene layer, and bonding the second film to the perforated film.
DEFINITIONS
The term "ethylene copolymers" as used herein re-fers to copolymers of ethylene and vinyl acetate, alkyl acrylate or alpha-olefin. Also within the scope of the present definition are chemically modified derivatives of these materials.
The tern "EVA" as used herein designates ethylene/vinyl-acetate copolymers.
The term "linear low density polyethylene" (LLDPE) as used herein includes that group of ethylene/alpha-olefin copolymers having limited side chain branching and which fall into a density range of 0.916 g/cc to 0.940 g/cc. Sometimes linear polyethylene in the density range from 0.926 g/cc to 2/901004.1/OLDFLDR
20~37~
0.940 g/cc is referred to as linear medium density polyethyl-ene (LMDPE). Typical brand names are Dowlex from Dow Chemi-cal Company, Ultzex and Neozex from Mitsui Petro Chemical Company, and Sclair from duPont. The alpha-olefin copolymers are typically butene-1, pentene-1, hexene-1, octene-1, etc.
The terms "very low density polyethylene" (VLDPE) and "ultra-low density polyethylene" (ULDPE) as used herein refer to ethylene/alpha-olefin copolymers which have a densi-ty of less than about 0.915 g/cc and, more specifically, usually 0.912 g/cc or below and may be below 0.89 g/cc.
Typical VLDPE resins are those designated DFDA by Union Car-bide and are believed to principally or usually have butene or isobutene as a comonomer. The very low density polyethyl-enes as compared to LLDPE, usually have significantly higher copolymer content and distinctly different properties making A them a distinct class of polymers. Typically, resins desig-nated "ULDPE" resins come from Dow and are believed to have octene as the comonomer. There is a slight difference in properties which is thought to be attributable to the comonomer. As used herein the term "linear ethylene/alpha-olefin copolymer having a density of less than 0.915 g/cc" encompasses both VLDPE and ULDPE.
The term "butadiene styrene copolymer" (BDS) is used herein to denote thermoplastic copolymers, especially block copolymers containing a major portion (greater than 50%) of styrene and a minor proportion (less than 50%) of butadiene comonomer.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention can be further understood by refer-ence to the drawing figures, wherein:
2/901004.1/OLDFLDR
20537~7 FIG. 1 is a schematic cross sectional view o~ one embodiment of the multilayer laminate of the present inven-tion; and FIG. 2 iS a schematic cross sectional view of anoth-er embodiment of a multilayer laminate in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is directed to a laminate for use in the packaging of soft cheese and other items which require a packaging material having the properties disclosed herein. The packaging of soft cheeses requires a packaging material having a low moisture transmission rate and a high gas transmission rate. Further, automation of the process requires the material to be machinable. Machinability may be defined as including the properties of strength, low extensi-bility, and heat resistance. Further, for a film to be ma-chinable it must be capable of maintaining a substantially planar configuration during many types of handling and pro-cessing. Typically, those materials having high gas permea-bilities do not demonstrate adequate machinability and vice-versa. The present invention meets all of the prerequisites of this application by first providing a machinable film which is strong, non-extensible and heat resistant, but also impermeable and nonsealable, and then perforating it, thereby rendering it permeable. In order to provide sealability while maintaining permeability and providing for a moisture impermeable structure, a permeable, heat sealable film is bonded to one side of the perforated film. Curling of the final laminate structure, which is expected when a highly permeable film is laminated onto a strong, non-extensible film, is precluded by including a stiffness imparting layer within the otherwise soft, permeable film. Relative gas and moisture transmission rates of the ultimate structure are 2/901004.1/OLDFLDR
determined by the size and number of perforations in the first, impermeable film, as well as the thickness and permea-bility of the second film.
Referring to Figure 1, the multilayer laminate 100 includes an first film 12 having perforations 14 therein. In the preferred embodiments, layer 12 comprises a propylene homopolymer (PP), although a propylene copolymer such as ethylene propylene copolymer (EPC) may be used. Various homopolymsrs and copolymers of polypropylene are commercially available and well known in the art. One film especially preferred for the present invention is a commercial film designated PY, supplied by the Cryovac Division af W. R.
Grace & Co.-Conn. Also within the scope of the present inven-tion are other machinable films. Generally, such films are first stretch-oriented and then heat set, that is, held in a stretched configuration and heated to some temperature higher than the original orientation temperature but below the melt temperature such that shrinkage will occur at such tempera-ture and not at the original orientation temperature. Such processing provides strength, low elongation and heat resis-tance. In addition to polypropylenes, polyesters and nylons may be oriented ~nd heat set to provide the properties needed for good machinability required by the present invention.
A coextruded second component film 16 is also de-picted in Figure 1. A web of film 16 is bonded to one side of film 12. It should be noted that although it is within the scope of the present invention to bond a web of film 16 to both sides of film 12, such is not necessary and is, gener-ally, not preferred. A second web of film 16 is not required to "balance out" the present structure and prevent curling of a machinable film about a relatively flexible, permeable film. Instead, the present film 16 is stiffened by an interi-or layer 20, discussed in greater detail below. However, lamination of a web of film 16 to both sides of film 12 may be preferred when it is desirable to provide heat sealable layers on both outer surfaces of the final structure such as 2/901004.1/OLDFLDR
-`` 20537~
when a BDS copolymer is employed for stiffness imparting layer 20, a further sealing layer is not required because of the wide sealing range provided by such material. Note that in Examples 3 and 5 below, an outer BDS layer serves as a heat sealable layer. In order to provide the requisite stiff-ness for the present application either two or more BDS lay-ers are required, or, if only one BDS layer is provided, it must be a relatively thick layer, comprising from about _%
to about _ % of the total thickness of film 16.
In Figure 1, an outer heat sealable layer is desig-nated at 22. Layer 22 is preferably an ethylene vinyl ace-tate copolymer and can be comprised of the same material as layer 18. A preferred EVA is Elvax 3165 from DuPont, which has a vinyl acetate content of about 18%. Layer 22 can also be a very low density polyethylene (VLDPE) or a VLDPE/EVA
blend.
Referring to Figure 2, a multilayer laminate 200 like that of Figure 1 is shown, but in which a filler layer 24' is disposed between reduced BDS layers 20'. Such struc-ture is preferred because it provides the stiffening proper-ties of the thick BDS layer 20 of Figure 1 above at less expense as the filler layer may be composed of a polymeric material which is less expensive than BDS. Such filler layer is preferably an ethylene~alpha-olefin copolymer. The pre-ferred resin for layer 24' is a VLDPE such as DFDA 1137 sup-plied by Union Carbide, although other materials having high gas permeability, such as high vinyl acetate EVA copolymers or EVA/VLDPE blends may also be employed.
Bonding reduced BDS layers 20' to filler layer 24' are intermediate tie layers 26', each comprising a polymeric adhesive and preferably a copolymer of ethylene, and more preferably an ethylene vinyl acetate copolymer (EVA). A
preferred EVA is one having a vinyl acetate content at about 18% by weight of the copolymer. Other polymeric materials may be used for layers 26' as long as they provide the neces-2/901004.1/OLDFLDR
2~53~07 when lap sealing, which requires the sealing of one surfaceof the laminate to the opposite surface, is required. Howev-er, while the provision of film 16 on only one side of film 12 allows only for fin sealing, wherein one surface of the laminate is sealed to itself, such sealing method advanta-geously subjects only the heat resistant film 12 to contact with the sealing jaws.
The film 16 of the present invention must include a bonding layer 18 for bonding film 16 to film 12. Preferably, bonding layer 18 comprises an ethylene vinyl acetate copolymer such as Elvax 3165, an 18% vinyl acetate EVA from DuPont. However, other materials which provide film 16 with a corona laminatable surface are also within the scope of the present invention. In a preferred embodiment, layer 18 com-prises a blend of EVA and antiblock, preferably about 80% of Elvax 3130, a 12% vinyl acetate EVA from DuPont, and about 20% of an antiblock masterbatch such as EPE-8160, a 90% poly-ethylene, 10% Syloid blend from Teknor Color. In an alterna-tive embodiment, bonding layer 18 is composed of a high vinyl acetate, low melting point EVA such as Alathon 3180 available from DuPont, having a melt index of between 23 and 27 grams/10 minutes, a vinyl acetate content by weight of be-tween about 27% and 29%, and a density of between about 0.948 g/cc and 0.954 g/cc.
Also required in film 16 is a layer 20 which im-parts stiffness to the otherwise pliant permeable film. As discussed above, it is this stiffness imparting layer which precludes curling of the final laminate structure 10. A pre-ferred material for layer 20 is a butadiene styrene (BDS) copolymer, although any material having the combined proper-ties of stiffness and high gas permeability is within the scope of the present invention. One example of a commercial-ly available resin for use in layer 20 is a BDS copolymer designated DK 10, one of the K-resin series available from Phillips Chemical Company. It should be noted that, although layer 20 is illustrated as an interior layer in Figure 1, 2/901004.1/OLDFLDR
20~3707 sary high gas permeability required by the present inven-tion. Blends of polymeric materials and polymeric adhesives can also be used for intermediate layers 26'. Further, it should be noted that tie layers may be employed as needed in film 16 for bonding adjacent layers which may otherwise be susceptible to delamination during handling. For example, in Example 2 below, tie layers are employed between an interior BDS layer and each of the bonding layer and the heat sealable layer.
Generally, perforated film 12 may be made by extrud-ing a polypropylene, ethylene propylene copolymer, polyester or nylon film, orienting and heat setting the film and perfo-rating same by means well known in the art such as flame or needle perforation. Multilayer film 16 can be made by stan-dard coextrusion techniques.
A web of multilayer film 16 is bonded to one side of perforated film 12 preferably by corona treating the bond-ing surfaces of both film 12 and film 16, and then, under some heat and pressure, adhering the two webs together.
Although it is within the scope of the present invention to corona treat only film 16 or only film 12, optimum lamination is achieved when both bonding surfaces are treated. The bond between the two films is designated at 40 in the drawings.
Other bonding techniques, including the use of conventional lamination adhesives, may also be used. Howev-er, bonding techniques in which a separate adhesive is uti-lized may be less desirable in that such adhesive may block the perforations of film 12.
In the preferred embodiment, packaging film of the present invention is especially suitable for use in connec-tion with Kartridg-Pak or other types of vertical form fill seal machinery.
2/901004.1/OLDFLDR
2~3707 The invention may be further understood by refer-ence to Table 1 indicating specific laminate structures made in accordance with the present invention.
EXAMPLE
1 PP//EVA/BDS/EVA~tie)/VLDPE~EVA(tie)/BDS~EVA
2 PP//EVA/EVA(tie)/BDS/EVA(tie~¦EVA
The present invention is directed to a laminated structure useful in the packaging of food items, particularly soft cheeses.
Soft cheeses such as Camembert and Brie are current-ly packaged in a variety of different materials including polyethylenes with and without ethylene/vinyl-acetate copolymers, polypropylenes, nylon/polyethylene laminates, and polyester/polyethylene laminates. The oxygen and carbon dioxide transmission rates of such structures are of primary importance in the packaging of many soft cheeses, as well as other food items which require a packaging material of high gas permeability such as many fruits and vegetables. High oxygen permeability is of primary importance in the packaging of cheeses which, like Brie, require an aerobic atmosphere to support fungal growth on the surface of the cheese. Other cheeses respire COz in amounts that require a permeable packaging material in order to preclude gassing of the pack-age. In the case of produce packaging, regulation of the transmission of 2 and CO2 minimizes enzymatic browning of cut surfaces and the damaging effects of product anaerobio-sis.
However, in most cases, materials having the de-sired oxygen and carbon dioxide transmission rates required in the above-discussed applications also have minimal abuse resistance and machinability properties. Conversely, film structures which are abuse resistant and machinable generally 2/901004.1/OLDFLDR
20~3707 lack the gas permeability and sealing properties required by such applications.
The present application requires a structure which combines heat resistance, low extensibility and strength with high gas permeability and sealing. To prevent drying of the packaged food product, a low water vapor transmission rate is also required.
Such requirements were met by the structure of U.S.
Pat. No. 4,935,271 to Schirmer which discloses a multilayer laminate for use in the packaging of lettuce and the like having a first impermeable film of propylene homopolymer or copolymer having perforations defined therein, and a second permeable film bonded to the first film which includes a bonding layer of ethylene vinyl acetate copolymer and an outer heat sealable layer. In that laminate, machinability is provided by the polypropylene film which is perforated in order to render it permeable. The gas permeable second film contributes the properties of low moisture transmission and sealability to the overall structure. However, for the Schirmer structure, disposition of the soft, flexible second film adjacent the relatively stiff, heat set polypropylene, results in curling of the overall structure and, thus, poor machining performance.
SUMMARY OF THE INV~ENTION
It is thus an object of the present invention to provide an improved material for use in the packaging of soft cheeses which has a low moisture permeability and a high gas permeability.
It is still another object of the present invention to provide such an improved material for the packaging of cheese and the like which is machinable, having heat resis-tance, non-extensibility and strength.
2/901004. l/OLDFLDR
20~3707 It is a further object of the present invention to provide a packaging laminate having high gas permeability in addition to strength, heat resistance, and low extensibility which precludes moisture transmission and tends to remain in a planar configuration during processing.
These, as well as other objects, are achieved by providing a multilayer laminate comprising a first component of a strong, nonextensible film having perforations defined therein, and a second component film, bonded to the first component film, having high permeability and low moisture transmission and including a bonding layer and a layer which imparts stiffness to the second film.
Such objects are further achieved by providing a method of making a multilayer laminate comprising providing a perforated film preferably comprising a propylene homopolymer or copolymer, coextruding a second film having a bonding layer and an interior styrene butadiene layer, and bonding the second film to the perforated film.
DEFINITIONS
The term "ethylene copolymers" as used herein re-fers to copolymers of ethylene and vinyl acetate, alkyl acrylate or alpha-olefin. Also within the scope of the present definition are chemically modified derivatives of these materials.
The tern "EVA" as used herein designates ethylene/vinyl-acetate copolymers.
The term "linear low density polyethylene" (LLDPE) as used herein includes that group of ethylene/alpha-olefin copolymers having limited side chain branching and which fall into a density range of 0.916 g/cc to 0.940 g/cc. Sometimes linear polyethylene in the density range from 0.926 g/cc to 2/901004.1/OLDFLDR
20~37~
0.940 g/cc is referred to as linear medium density polyethyl-ene (LMDPE). Typical brand names are Dowlex from Dow Chemi-cal Company, Ultzex and Neozex from Mitsui Petro Chemical Company, and Sclair from duPont. The alpha-olefin copolymers are typically butene-1, pentene-1, hexene-1, octene-1, etc.
The terms "very low density polyethylene" (VLDPE) and "ultra-low density polyethylene" (ULDPE) as used herein refer to ethylene/alpha-olefin copolymers which have a densi-ty of less than about 0.915 g/cc and, more specifically, usually 0.912 g/cc or below and may be below 0.89 g/cc.
Typical VLDPE resins are those designated DFDA by Union Car-bide and are believed to principally or usually have butene or isobutene as a comonomer. The very low density polyethyl-enes as compared to LLDPE, usually have significantly higher copolymer content and distinctly different properties making A them a distinct class of polymers. Typically, resins desig-nated "ULDPE" resins come from Dow and are believed to have octene as the comonomer. There is a slight difference in properties which is thought to be attributable to the comonomer. As used herein the term "linear ethylene/alpha-olefin copolymer having a density of less than 0.915 g/cc" encompasses both VLDPE and ULDPE.
The term "butadiene styrene copolymer" (BDS) is used herein to denote thermoplastic copolymers, especially block copolymers containing a major portion (greater than 50%) of styrene and a minor proportion (less than 50%) of butadiene comonomer.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention can be further understood by refer-ence to the drawing figures, wherein:
2/901004.1/OLDFLDR
20537~7 FIG. 1 is a schematic cross sectional view o~ one embodiment of the multilayer laminate of the present inven-tion; and FIG. 2 iS a schematic cross sectional view of anoth-er embodiment of a multilayer laminate in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is directed to a laminate for use in the packaging of soft cheese and other items which require a packaging material having the properties disclosed herein. The packaging of soft cheeses requires a packaging material having a low moisture transmission rate and a high gas transmission rate. Further, automation of the process requires the material to be machinable. Machinability may be defined as including the properties of strength, low extensi-bility, and heat resistance. Further, for a film to be ma-chinable it must be capable of maintaining a substantially planar configuration during many types of handling and pro-cessing. Typically, those materials having high gas permea-bilities do not demonstrate adequate machinability and vice-versa. The present invention meets all of the prerequisites of this application by first providing a machinable film which is strong, non-extensible and heat resistant, but also impermeable and nonsealable, and then perforating it, thereby rendering it permeable. In order to provide sealability while maintaining permeability and providing for a moisture impermeable structure, a permeable, heat sealable film is bonded to one side of the perforated film. Curling of the final laminate structure, which is expected when a highly permeable film is laminated onto a strong, non-extensible film, is precluded by including a stiffness imparting layer within the otherwise soft, permeable film. Relative gas and moisture transmission rates of the ultimate structure are 2/901004.1/OLDFLDR
determined by the size and number of perforations in the first, impermeable film, as well as the thickness and permea-bility of the second film.
Referring to Figure 1, the multilayer laminate 100 includes an first film 12 having perforations 14 therein. In the preferred embodiments, layer 12 comprises a propylene homopolymer (PP), although a propylene copolymer such as ethylene propylene copolymer (EPC) may be used. Various homopolymsrs and copolymers of polypropylene are commercially available and well known in the art. One film especially preferred for the present invention is a commercial film designated PY, supplied by the Cryovac Division af W. R.
Grace & Co.-Conn. Also within the scope of the present inven-tion are other machinable films. Generally, such films are first stretch-oriented and then heat set, that is, held in a stretched configuration and heated to some temperature higher than the original orientation temperature but below the melt temperature such that shrinkage will occur at such tempera-ture and not at the original orientation temperature. Such processing provides strength, low elongation and heat resis-tance. In addition to polypropylenes, polyesters and nylons may be oriented ~nd heat set to provide the properties needed for good machinability required by the present invention.
A coextruded second component film 16 is also de-picted in Figure 1. A web of film 16 is bonded to one side of film 12. It should be noted that although it is within the scope of the present invention to bond a web of film 16 to both sides of film 12, such is not necessary and is, gener-ally, not preferred. A second web of film 16 is not required to "balance out" the present structure and prevent curling of a machinable film about a relatively flexible, permeable film. Instead, the present film 16 is stiffened by an interi-or layer 20, discussed in greater detail below. However, lamination of a web of film 16 to both sides of film 12 may be preferred when it is desirable to provide heat sealable layers on both outer surfaces of the final structure such as 2/901004.1/OLDFLDR
-`` 20537~
when a BDS copolymer is employed for stiffness imparting layer 20, a further sealing layer is not required because of the wide sealing range provided by such material. Note that in Examples 3 and 5 below, an outer BDS layer serves as a heat sealable layer. In order to provide the requisite stiff-ness for the present application either two or more BDS lay-ers are required, or, if only one BDS layer is provided, it must be a relatively thick layer, comprising from about _%
to about _ % of the total thickness of film 16.
In Figure 1, an outer heat sealable layer is desig-nated at 22. Layer 22 is preferably an ethylene vinyl ace-tate copolymer and can be comprised of the same material as layer 18. A preferred EVA is Elvax 3165 from DuPont, which has a vinyl acetate content of about 18%. Layer 22 can also be a very low density polyethylene (VLDPE) or a VLDPE/EVA
blend.
Referring to Figure 2, a multilayer laminate 200 like that of Figure 1 is shown, but in which a filler layer 24' is disposed between reduced BDS layers 20'. Such struc-ture is preferred because it provides the stiffening proper-ties of the thick BDS layer 20 of Figure 1 above at less expense as the filler layer may be composed of a polymeric material which is less expensive than BDS. Such filler layer is preferably an ethylene~alpha-olefin copolymer. The pre-ferred resin for layer 24' is a VLDPE such as DFDA 1137 sup-plied by Union Carbide, although other materials having high gas permeability, such as high vinyl acetate EVA copolymers or EVA/VLDPE blends may also be employed.
Bonding reduced BDS layers 20' to filler layer 24' are intermediate tie layers 26', each comprising a polymeric adhesive and preferably a copolymer of ethylene, and more preferably an ethylene vinyl acetate copolymer (EVA). A
preferred EVA is one having a vinyl acetate content at about 18% by weight of the copolymer. Other polymeric materials may be used for layers 26' as long as they provide the neces-2/901004.1/OLDFLDR
2~53~07 when lap sealing, which requires the sealing of one surfaceof the laminate to the opposite surface, is required. Howev-er, while the provision of film 16 on only one side of film 12 allows only for fin sealing, wherein one surface of the laminate is sealed to itself, such sealing method advanta-geously subjects only the heat resistant film 12 to contact with the sealing jaws.
The film 16 of the present invention must include a bonding layer 18 for bonding film 16 to film 12. Preferably, bonding layer 18 comprises an ethylene vinyl acetate copolymer such as Elvax 3165, an 18% vinyl acetate EVA from DuPont. However, other materials which provide film 16 with a corona laminatable surface are also within the scope of the present invention. In a preferred embodiment, layer 18 com-prises a blend of EVA and antiblock, preferably about 80% of Elvax 3130, a 12% vinyl acetate EVA from DuPont, and about 20% of an antiblock masterbatch such as EPE-8160, a 90% poly-ethylene, 10% Syloid blend from Teknor Color. In an alterna-tive embodiment, bonding layer 18 is composed of a high vinyl acetate, low melting point EVA such as Alathon 3180 available from DuPont, having a melt index of between 23 and 27 grams/10 minutes, a vinyl acetate content by weight of be-tween about 27% and 29%, and a density of between about 0.948 g/cc and 0.954 g/cc.
Also required in film 16 is a layer 20 which im-parts stiffness to the otherwise pliant permeable film. As discussed above, it is this stiffness imparting layer which precludes curling of the final laminate structure 10. A pre-ferred material for layer 20 is a butadiene styrene (BDS) copolymer, although any material having the combined proper-ties of stiffness and high gas permeability is within the scope of the present invention. One example of a commercial-ly available resin for use in layer 20 is a BDS copolymer designated DK 10, one of the K-resin series available from Phillips Chemical Company. It should be noted that, although layer 20 is illustrated as an interior layer in Figure 1, 2/901004.1/OLDFLDR
20~3707 sary high gas permeability required by the present inven-tion. Blends of polymeric materials and polymeric adhesives can also be used for intermediate layers 26'. Further, it should be noted that tie layers may be employed as needed in film 16 for bonding adjacent layers which may otherwise be susceptible to delamination during handling. For example, in Example 2 below, tie layers are employed between an interior BDS layer and each of the bonding layer and the heat sealable layer.
Generally, perforated film 12 may be made by extrud-ing a polypropylene, ethylene propylene copolymer, polyester or nylon film, orienting and heat setting the film and perfo-rating same by means well known in the art such as flame or needle perforation. Multilayer film 16 can be made by stan-dard coextrusion techniques.
A web of multilayer film 16 is bonded to one side of perforated film 12 preferably by corona treating the bond-ing surfaces of both film 12 and film 16, and then, under some heat and pressure, adhering the two webs together.
Although it is within the scope of the present invention to corona treat only film 16 or only film 12, optimum lamination is achieved when both bonding surfaces are treated. The bond between the two films is designated at 40 in the drawings.
Other bonding techniques, including the use of conventional lamination adhesives, may also be used. Howev-er, bonding techniques in which a separate adhesive is uti-lized may be less desirable in that such adhesive may block the perforations of film 12.
In the preferred embodiment, packaging film of the present invention is especially suitable for use in connec-tion with Kartridg-Pak or other types of vertical form fill seal machinery.
2/901004.1/OLDFLDR
2~3707 The invention may be further understood by refer-ence to Table 1 indicating specific laminate structures made in accordance with the present invention.
EXAMPLE
1 PP//EVA/BDS/EVA~tie)/VLDPE~EVA(tie)/BDS~EVA
2 PP//EVA/EVA(tie)/BDS/EVA(tie~¦EVA
3 PP//E~A/BDS¦EVA(tie)¦VLDPE/EVA~tie)/BDS¦EVA/BDS
PP//EVA/BDS
In the laminate of Example 3, about 20~ of the EVA
of bonding layer comprised an antiblocking agent masterbatch which had been preblended with the EVA prior to extrusion.
The antiblocking agent used included 90% low density polyeth-ylene blended with 10% of a colloidal silica. Such structure was tested for water vapor transmission and 2 and CO2 permeability. The water vapor transmission rate averaged about 2.73 grams/100 in.2 over 24 hrs. at 100F and 100%RH. The oxygen transmission rate averaged about 4858.9 cm3/mZ-atm.-24 hrs. at 73F. The carbon dioxide transmis-sion rate averaged about 30204.0 cm3/m2-atm.-24 hrs. at Although the outer permeable films, generally 16, of the present invention are represented as composites of varying numbers of layers, it is to be understood that the relative thickness of any film 16 is not necessarily a func-tion of the number of layers comprising such. For example, the permeable film of Example 4 above may have a thickness as 2/901004.1/OLDFLDR
20~3707 great as that of Example 1. In Example 1, the VLDPE core is included in order to add bulk between the stiffness imparting BDS layers at a reduced cost. In Examples 4 and 5 the BDS
layer is thickened in order to provide the thickness and stiffness of the film of Example 1.
Although the present invention has been described by reference to the specific embodiments and examples, a latitude of modification change and substitution is intended in the f~regoing disclosure, those skilled in the art would readily understand that modifications may be made by one skilled in the art after a review of this description without departing from the spirit and scope of the claims which fol-low.
2/901004.1/OLDFLDR
In the laminate of Example 3, about 20~ of the EVA
of bonding layer comprised an antiblocking agent masterbatch which had been preblended with the EVA prior to extrusion.
The antiblocking agent used included 90% low density polyeth-ylene blended with 10% of a colloidal silica. Such structure was tested for water vapor transmission and 2 and CO2 permeability. The water vapor transmission rate averaged about 2.73 grams/100 in.2 over 24 hrs. at 100F and 100%RH. The oxygen transmission rate averaged about 4858.9 cm3/mZ-atm.-24 hrs. at 73F. The carbon dioxide transmis-sion rate averaged about 30204.0 cm3/m2-atm.-24 hrs. at Although the outer permeable films, generally 16, of the present invention are represented as composites of varying numbers of layers, it is to be understood that the relative thickness of any film 16 is not necessarily a func-tion of the number of layers comprising such. For example, the permeable film of Example 4 above may have a thickness as 2/901004.1/OLDFLDR
20~3707 great as that of Example 1. In Example 1, the VLDPE core is included in order to add bulk between the stiffness imparting BDS layers at a reduced cost. In Examples 4 and 5 the BDS
layer is thickened in order to provide the thickness and stiffness of the film of Example 1.
Although the present invention has been described by reference to the specific embodiments and examples, a latitude of modification change and substitution is intended in the f~regoing disclosure, those skilled in the art would readily understand that modifications may be made by one skilled in the art after a review of this description without departing from the spirit and scope of the claims which fol-low.
2/901004.1/OLDFLDR
Claims (22)
1. A multilayer laminate comprising:
a) an first component film having perfora-tions defined therein; and b) a gas permeable second component film, bonded to one side of the first component film, the second component film including a bonding layer and at least one layer comprising butadiene styrene copolymers.
a) an first component film having perfora-tions defined therein; and b) a gas permeable second component film, bonded to one side of the first component film, the second component film including a bonding layer and at least one layer comprising butadiene styrene copolymers.
2. A multilayer laminate according to claim wherein said first component film comprises a propylene homo-polymer or copolymer.
3. A multilayer laminate according to claim wherein the bonding layer of the second component film com-prises an ethylene vinyl acetate copolymer.
4. A multilayer laminate according to claim further including an outer heat sealable layer on the second component film.
5. A multilayer laminate according to claim 4 wherein said outer heat sealable layer comprises an ethylene vinyl acetate copolymer.
6 A multilayer laminate according to claim 5 wherein the outer heat sealable layer of the second component film is the same material as that of the bonding layer.
7. A multilayer laminate according to claim 4 wherein the outer heat sealable layer of the second component film comprises a very low density polyethylene.
2/901004.1/OLDFLDR
2/901004.1/OLDFLDR
8. A multilayer laminate according to claim 4 wherein the outer heat sealable layer of the second component film comprises a butadiene styrene copolymer.
9. A multilayer laminate according to claim wherein the bonding layer of the second component film com-prises a blend of ethylene vinyl acetate copolymer and an antiblocking agent master batch
10. A multilayer laminate according to claim 9 wherein the bonding layer of the second component film com-prises a blend of about 80% ethylene vinyl acetate copolymer and about 20% of an antiblocking agent master batch.
11. A multilayer laminate according to claim wherein the first component perforated film comprises a polyester.
12. A multilayer laminate according to claim wherein the first component perforated film comprises a nylon.
13. A multilayer laminate according to claim wherein the first component perforated film is oriented.
14. A multilayer laminate according to claim 13 wherein the first component film is oriented and heat set.
15. A multilayer laminate according to claim wherein said second component film comprises at least two layers comprising butadiene styrene copolymers and further including a filler layer disposed between two of said at least two butadiene styrene layers.
16. A multilayer laminate according to claim 15 wherein said filler layer comprises very low density polyeth-ylene.
2/901004.1/OLDFLDR
2/901004.1/OLDFLDR
17. A multilayer laminate according to claim 15 wherein said filler layer comprises ethylene vinyl acetate copolymer.
18. A multilayer laminate according to claim 15 wherein said filler layer comprises a blend of very low densi-ty polyethylene and ethylene vinyl acetate copolymer.
19. A multilayer laminate according to claim 15 further including additional layers disposed between said filler layer and each of said two butadiene styrene layers, said additional layers bonding each of said butadiene styrene layers to said filler layer.
20. A method of making a multilayer laminate com-prising:
a) providing a first film;
b) perforating said first film;
c) coextruding a second film having a bonding layer and at least one layer comprising butadiene styrene copolymers; and d) bonding a web of the second film to the perforated film.
a) providing a first film;
b) perforating said first film;
c) coextruding a second film having a bonding layer and at least one layer comprising butadiene styrene copolymers; and d) bonding a web of the second film to the perforated film.
21. A method according to claim 20 including the step of corona treating the second film at its bonding sur-face prior to bonding a web thereof to the perforated film.
22. A method of making a multilayer laminate com-prising:
a) providing a perforated, machinable film;
2/901004.1/OLDFLDR
b) coextruding a second film having a bonding layer and at least one layer for imparting stiffness to said second film; and c) bonding a web of the second film to one side of the perforated film.
2/901004.1/OLDFLDR
a) providing a perforated, machinable film;
2/901004.1/OLDFLDR
b) coextruding a second film having a bonding layer and at least one layer for imparting stiffness to said second film; and c) bonding a web of the second film to one side of the perforated film.
2/901004.1/OLDFLDR
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US61481990A | 1990-11-16 | 1990-11-16 | |
| US614,819 | 1990-11-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2053707A1 true CA2053707A1 (en) | 1992-05-17 |
Family
ID=24462843
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2053707 Abandoned CA2053707A1 (en) | 1990-11-16 | 1991-10-18 | Cheese packaging laminate |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JP3043868B2 (en) |
| AU (1) | AU658375B2 (en) |
| CA (1) | CA2053707A1 (en) |
| ZA (1) | ZA918226B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6316067B1 (en) | 1993-04-09 | 2001-11-13 | Curwood, Inc. | Cheese package, film, bag and process for packaging a CO2 respiring foodstuff |
| US6511688B2 (en) | 1993-04-09 | 2003-01-28 | Curwood, Inc. | Cheese package, film, bag and process for packaging a CO2 respiring foodstuff |
| EP1749656A1 (en) | 2005-08-05 | 2007-02-07 | Curwood, Inc. | A polyester and polyamide blend containing article for packaging a CO2 respiring foodstuff |
| US11642867B2 (en) * | 2012-01-06 | 2023-05-09 | Amcor Flexibles France | Packaging sheet, packaging and associated manufacturing method |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ATE66179T1 (en) * | 1986-10-29 | 1991-08-15 | Grace W R & Co | MULTI-LAYER HIGH MOISTURE AND GAS PERMEABLE PACKAGING FILM. |
| US4935271A (en) * | 1988-09-06 | 1990-06-19 | W. R. Grace & Co.-Conn. | Lettuce packaging film |
| US5110677A (en) * | 1990-10-01 | 1992-05-05 | W. R. Grace & Co.-Conn. | Lettuce packaging film |
-
1991
- 1991-10-15 ZA ZA918226A patent/ZA918226B/en unknown
- 1991-10-18 CA CA 2053707 patent/CA2053707A1/en not_active Abandoned
- 1991-11-08 AU AU87716/91A patent/AU658375B2/en not_active Ceased
- 1991-11-15 JP JP3300468A patent/JP3043868B2/en not_active Expired - Lifetime
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6316067B1 (en) | 1993-04-09 | 2001-11-13 | Curwood, Inc. | Cheese package, film, bag and process for packaging a CO2 respiring foodstuff |
| US6511688B2 (en) | 1993-04-09 | 2003-01-28 | Curwood, Inc. | Cheese package, film, bag and process for packaging a CO2 respiring foodstuff |
| EP1749656A1 (en) | 2005-08-05 | 2007-02-07 | Curwood, Inc. | A polyester and polyamide blend containing article for packaging a CO2 respiring foodstuff |
| US11642867B2 (en) * | 2012-01-06 | 2023-05-09 | Amcor Flexibles France | Packaging sheet, packaging and associated manufacturing method |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04269533A (en) | 1992-09-25 |
| ZA918226B (en) | 1992-07-29 |
| AU8771691A (en) | 1992-05-21 |
| JP3043868B2 (en) | 2000-05-22 |
| AU658375B2 (en) | 1995-04-13 |
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Legal Events
| Date | Code | Title | Description |
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| EEER | Examination request | ||
| FZDE | Dead |