JPH04212839A - Wrapping material for shredded cheese - Google Patents

Abstract

PURPOSE: To provide a packaging material comprising a polymer film useful for packaging shredded cheese by a molding/filling/sealing device and having hot and cold sealing properties even if a contaminant is present in the seal region of a package and also having low seal starting temp., toughness and severe use resistance. CONSTITUTION: A film comprises a center layer 16 containing an oxygen barrier material, the polyamide inner layers 14 arranged on the respective surfaces of the center layer 16, a sealant layer 20 containing an extremely low density polyethylene, a heat resistant outer layer 10 and the chemically modified polyolefin-containing intermediate layers arranged between the polyamide inner layer 14, a sealant layer 20 and an outer layer 10. This film can be bonded to an additional film to form a laminate and, according to circumstances, a trap print surface is provided.

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION This invention relates generally to the packaging film art, and more particularly to films and laminates useful for packaging food products such as cheese.

Form-fill-seal packaging is commonly used for packaging many items, including food products.
It is common practice to use what is known as a device. Vertical form-fill-seal (VFFS) equipment feeds flexible packaging material from a web into a tube forming machine that converts tubes from sheet material into vertically suspended, upwardly facing tubes with overlapping longitudinal edges. Make it into a tube shape with an opening. These overlapping edges are then vertically sealed together by means well known in the art;
The ends of the tube are sealed together by a pair of vertically spaced lateral heat seals. At this point the product to be packaged, such as shredded cheese, is weighed and filled into the tube. A second heat sealing operation is typically performed after the filled tube has advanced downwardly to complete the sealing of the product. Simultaneously with or immediately after the transverse heat sealing step, the tube is completely transversely severed by known cutting means at the intermediate space between a pair of vertically spaced transverse heat seals. The tube is then fed downward and the cycle is repeated successively to form a number of individually packaged products.

Alternatively, a single lateral heat seal formed by a pair of horizontally spaced sealing jaws is used to effectively form two vertically adjacent heat seals. It is possible. The seal is simultaneously or subsequently broken at a vertical line midway through the heat seal.

Horizontal form-fill-seal (HFFS) equipment is also well known in the art for packaging many items, including foodstuffs.

Flexible packaging materials useful in this and other applications generally must meet stringent requirements imposed by the particular food or other item being packaged.

[0006] For example, including low seal initiation temperatures,
Wide seal "window" packaging materials may be desirable.

[0007] Flexible materials have satisfactory abuse resistance to the physical and mechanical abuse imposed throughout the form-fill-seal system or other packaging system, as well as the subsequent abuse that the package may undergo during the distribution cycle. must also have.

[0008] Still another requirement of the packaging material, especially in the case of form-fill-seal systems, is good hot seal strength ("hot tack") with respect to lateral heat sealing.
tack)'') and cold (final) seal strength. The lateral seal is typically subjected to loading forces by an inserted product, such as a food product, immediately after the heat seal is formed. at least about 10 lb/in. A cold seal strength of is preferred.

[0009] If the food product is, for example, shredded cheese, contamination can occur in the area of the packaging material forming the final package seal. This effective containment of contamination should provide sufficient strength to the seal to keep the package intact throughout the distribution cycle.

[0010] When packaging oxygen- or moisture-sensitive products, there is yet another requirement for materials of this type: good, ie low oxygen and moisture vapor permeability.

[0011] In VFFS and HFFS processing, approximately 0.
Packaging materials with a coefficient of friction (cof) of less than 3 are preferred. The higher the cof value, the more difficult it becomes to flow packaging materials in these ways.

Related US Pat. No. 3,912,843 (B
Razier) is made of nylon, biaxially oriented polypropylene,
A flexible packaging film having a heat sealable polyolefin and saran layer is disclosed.

[0013] Related US Pat. No. 4,284,674, issued to Sheptak, discloses a multilayer film bonded with nylon on each side, each nylon layer then being coated with a chemically modified polyolefin. and has a central layer of ethylene-vinyl alcohol copolymer adhered to the ethylene-vinyl alcohol copolymer and yet another layer of primer material. The layer of primer material is a multiply film that provides toughness, flex crack resistance and moisture resistance.
The modified polyolefin is suitable for adhering the modified polyolefin to an outer layer of polypropylene or other material suitable for application.

Also related US Pat. No. 4,355,721, issued to Knott et al., discloses a coextruded multilayer sheet comprising a first layer of nylon, an EVOH barrier layer, another layer of nylon, an adhesive layer and another outer layer of, for example, high density polyethylene.

Related US Pat. No. 4, issued to Hirt.
No. 398,635 discloses a medication package in which a coextruded multilayer sheet can have a structure that includes a layer of ethylene-vinyl alcohol copolymer sandwiched between adjacent layers of nylon; One may further adhere to a tie resin. The nylon layer may form either an outer surface or an inner layer, with additional layers of polymeric material added to each side of the sandwich structure, as one example.

Related US Pat. No. 4,405,667 issued to Christensen et al. discloses a packaging material for retort applications that includes a heat seal layer of linear low density polyethylene, seventh and ninth layers of nylon. and EV
Contains an 8th layer of OH.

[0017]Related US Pat. No. 4,407,873 issued to Christensen et al. discloses a packaging material for retort applications containing a heat seal layer of linear low density polyethylene, optionally between 0% and 80% a second layer of linear low density polyethylene, which may be blended with density polyethylene into the second layer; a third layer of anhydride-modified medium density polyethylene; a fourth layer of nylon; a fifth layer of ethylene-vinyl alcohol copolymer. layer, and a sixth layer of nylon.

Related US Pat. No. 4,421,823 (T
Heisen et al. disclose a laminate having an outer layer of polypropylene or polyester, an oxygen barrier layer and a polyethylene layer.

Related US Pat. No. 4,457,960, issued to Newsome, discloses a multilayer film having a central layer of barrier materials such as EVOH and EVOH blends. The film may be shrinkable, may be melt extruded, and may include an outer layer having a blend of linear low density polyethylene and ethylene-vinyl acetate copolymer.

Related US Patent No. 4, issued to Ohya et al.
No. 495,249 discloses a five-layer film comprising a central layer of a saponified copolymer of ethylene and vinyl acetate;
It has an outer layer of a mixture of linear low density polyethylene and ethylene-vinyl acetate copolymer, and two adhesive layers disposed between the center layer and the outer layer.

Related US Pat. No. 4,501,798 (K
oschak et al. disclose a film having a surface layer of nylon and ethylene copolymer and an inner layer of EVOH.

Related US Pat. No. 4,640,852 (O
The multilayer film disclosed by EVO
In addition to the layer of nylon on each side of the H layer, it has layers of modified polyethylene and linear low density polyethylene or propylene-ethylene copolymer.

Related US Pat. No. 4,683,170 (T
SE et al. discloses a film having a nylon surface layer, a heat sealable surface layer, and an inner layer of EVOH, adhesive, and polyethylene or polypropylene.

Related US Pat. No. 4,735,855 (W
offord et al. discloses a laminate having a central layer of oxygen barrier material, a polyamide on each surface of the central layer, a sealant layer, a second surface layer, and an intermediate adhesive layer.

Related US Pat. No. 4,746,562 (F
ant) discloses a film having a central layer of EVOH, a polyamide middle layer, an outer layer of linear low density polyethylene, and an adhesive layer.

Related German Patent No. 3035474 A1
(Schroeder) has an inner layer of EVOH, an outer layer of nylon and Surlyn(TM), and a Plexa
discloses a multilayer composition having an interlayer of R(TM).

[0027] It is an object of the present invention to provide a multilayer film or laminate suitable for the packaging of foods, especially foods such as shredded cheese, which can contaminate the sealed area of VFFS or HFFS pouches.

Another object of the present invention is to provide a multilayer film or laminate that has a wide sealing "window" including a low seal onset temperature.

Yet another object of the present invention is to provide a multilayer film or laminate that extends the shelf life of food products.

Yet another object of the invention is to provide a film or laminate with good abuse resistance.

Another object of the present invention is that even if the seal is contaminated with food, VFFS or HFF
An object of the present invention is to provide a packaging material that exhibits good hot and cold seal strength when used in S mode.

An additional object of the present invention is to provide a packaging material having a coefficient of friction of less than about 0.3.

SUMMARY OF THE INVENTION The present invention relates to a polymeric film comprising a central layer comprising an oxygen barrier material, an inner polyamide layer disposed on each surface of the central layer, a sealant layer comprising very low density polyethylene, and an outer heat resistant layer. , and an intermediate layer comprising a chemically modified polyolefin disposed between each inner polyamide layer and each of the sealant layer and the outer heat resistant layer.

[0034] Another aspect of the present invention is a method for producing a film that includes a central layer comprising an oxygen barrier material, a polyamide inner layer disposed on each surface of the central layer, a sealant layer comprising ultra-low density polyethylene, and a heat resistant coextruding a polyamide outer layer and an intermediate layer comprising a chemically modified polyolefin disposed between each inner polyamide layer and each of the sealant layer and the heat resistant outer layer; extruding through a pedestal extruder;
joining the extruded layers at a die to form a complete coextrusion; drawing the coextrudate from the die; quenching the coextrudate; and rolling the coextrudate. Consists of taking.

Still another aspect of the invention, the laminate comprises a central layer comprising an oxygen barrier material, a polyamide inner layer disposed on each surface of the central layer, a sealant layer comprising very low density polyethylene, polyamide, polypropylene. , an outer layer comprising a polymer material selected from the group consisting of polyester, polycarbonate, high density polyethylene, linear low density polyethylene, and copolymers and mixtures thereof, and between the polyamide inner layer and each of the sealant layer and the outer layer, It consists of a polymeric film with an intermediate layer comprising a chemically modified polyolefin, and a support adhered to the polymeric outer layer of the polymeric film and comprising polyester or polypropylene.

Definition [0036] As used herein, "oxygen barrier material" preferably refers to
An oxygen permeability (ASTM D3) of less than about 100 cc/m2 in 24 hours at 3°F (STP), more preferably less than about 10 cc/m2 in 24 hours at 73°F (STP).
985). Materials of this type include, for example, ethylene-vinyl alcohol copolymers and vinylidene chloride copolymers. It should be noted that polyamides are useful to some extent in providing oxygen barrier properties.

[0037] "Polyamide" as used herein is
Refers to a high molecular weight polymer having amide bonds along the molecular chain, and more specifically refers to synthetic polyamides such as various nylons.

As used herein, "ethylene-vinyl alcohol copolymer" refers to a vinyl alcohol copolymer having an ethylene comonomer and made, for example, by hydrolysis of vinyl acetate copolymers or chemical reaction of polyvinyl alcohol. As used herein, "polyolefin" refers to polyethylene, a small amount of comonomer,
For example, it broadly includes ethylene copolymers with vinyl acetate, ethylene-alpha-olefin copolymers (LLDPE), polypropylene, polybutene, and other resins that fall into the "polyolefin" family category.

[0039] As used herein, "very low density polyethylene" generally has a density of 0.880 to 0.915 g/cm3.
refers to a linear ethylene-α-olefin copolymer produced by a catalytic reaction and having a density of .

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic cross-section of a preferred embodiment of the film of the present invention. The film structure is (outside) A/B/C/
It relates to a multilayer composite material having a generalized structure of D/C/B/E (inside). Here, A is a heat-resistant outer layer, B is an adhesive intermediate layer, C is a polyamide inner layer, D is an oxygen barrier layer, and E is a sealant layer.

The outer layer 10 serves as a heat-resistant layer and an abuse-resistant layer and is preferably made of nylon 6, nylon 6,66,
Polyamides such as nylon 6,12 or nylon 6,10. Resins available on the market include Allied's Capron 8207F and BASF's Ultr.
amide C35. When used as the outermost layer of a packaging material, layer 10 must have sufficient heat resistance to withstand the longitudinal and transverse sealing operations that are part of a typical form/fill/seal process. Polyamides such as nylon 6 and nylon 6,66 provide good flex crack resistance and resistance to pinhole formation. Other suitable materials for layer 10 include polyester, polypropylene, polycarbonate, and high density polyethylene.

Oxygen barrier layer 16 is preferably an ethylene-vinyl alcohol copolymer such as Soarnol ET available from Nippon Gosei. This material exhibits low oxygen barrier properties at high humidity and excellent oxygen barrier properties at low humidity.

Adjacent to either side of the barrier layer 16 is a polyamide inner layer 14, preferably made of nylon 6.

Sealant layer 20 is preferably a very low density polyethylene (VLDPE) such as Attane 4004 available from Dow. This material is sometimes called very low density polyethylene. Particularly preferred VLDP
E has a density ranging from 0.900 to 0.910 g/cm3. Another suitable material is an ionomer, a copolymer of ethylene and acrylic or methacrylic acid neutralized with a metal salt. Other suitable sealant materials include polyolefins, ethylene-α-olefin copolymers and blends thereof.

Intermediate connection layers 12 and 18 are each inner layer 1
4 and the outer layer 10 and the inner layer 14 and the sealament layer 20, respectively. These intermediate tie layers may be the same or different from each other and may be made from a wide range of chemically modified materials based on ethylene-vinyl acetate copolymers, polypropylene, low-density polyethylene, linear low-density polyethylene, and very low-density polyethylene. and anhydride-grafted polyolefins. A commercial example of this type of material is Plexar, D, available from Quantum.
It is commercially available under the name of CXA series available from uPont. A preferred commercially available resin is Byn
el CXA 3095, i.e. DuPont
A chemically modified ethylene-vinyl acetate copolymer available from

The films of the invention have good optical properties including clarity and high gloss, good color retention (in meat products),
Provides long shelf life and hot and cold seal strength even in case of contaminated seals.

The film according to the present invention contains various resins.
It can be produced by extruding through ~7 extruders. The extrudate is passed through a die where the layers are joined to form a complete coextrudate. The multilayer composite material exits the die lip and is hot blown and then cooled.

[0048] The two streams of resin can be split to provide the inner polyamide layer and the intermediate adhesive layer. If layers 12 and 18 are comprised of different resins, an additional extruder is used.

For use in VFFS or HFFS processing, 2
:Hot blow the film to a blow up ratio of 1 to 3:1. Optionally, the ethylene-vinyl acetate copolymer adhesive layers 12 and 18 may be crosslinked by irradiating the film if this type of resin is used for the adhesive layer. The film can also be chemically crosslinked with commercially available chemical crosslinking agents.

To re-stretch the film, longitudinal stretching, calendering, and/or tentering may be performed.

FIG. 2 shows an alternative embodiment in which the support 30 can be laminated to the film of the invention with a conventional adhesive 32. The support is glued with the outer layer 10 of the film. When practicing this embodiment, layer 10 is not the outermost surface of the final laminate. In this case, the choice of suitable materials for layer 10 is wide and includes ethylene-based materials such as linear low density polyethylene (LLDPE) (eg Dowlex 2044A).
Alpha-olefins or other materials that do not necessarily have the abuse or heat resistance of polyamides for VFFS and HFFS processing are included. LLDPE adds pinhole resistance and advantageous mechanical properties to the final laminate.

Typical commercially available supports are polyester or polypropylene films with or without an internal coating of vinylidene chloride copolymer (Saran). The coating increases the oxygen barrier properties of the entire laminate, especially in conditions of high relative humidity. The inner surface of the polyester or polypropylene support is optionally trap printed.

The films or laminates of the invention are particularly suitable for packaging cheese products such as shredded cheese.

[0054]

EXAMPLES The invention will be better understood with reference to the following examples, which are presented in Table 2. These examples were made by extruding the various resins indicated through separate extruders. The exceptions are when the polyamide inner layer is extruded as a separate stream from a single extruder, and when the two tie layers are similarly extruded as separate streams from a single extruder.

In each example, the extrudates were joined in the apparatus and entered the coextrusion die. The resulting composite was removed from the die lip and hot blown at a ratio of 2:1 to 3:1. The hot blown film was then cooled and then crushed into mill logs and cut to the desired width using a Dusenbury slitter.

The resulting films of Examples 1-5 and 7 and 8 had a total thickness of about 2.0 mils. The films of Examples 6, 9 and 10 each had a final thickness of 2.5 m.
il and 3.0 mil. Films of the present invention preferably have a thickness of 1.0 to 5.0 mils.

Table 1 identifies the resins used in the examples in Table 2.

[0058]

[Table 1]

"EVOH" is an ethylene-vinyl alcohol copolymer. "LLDPE" is linear low density polyethylene. "VLDPE" is very low density polyethylene, as used in Examples 1-9, to represent the sealant or food contact layer of the film. "I" is an ionomer. The modification in “I1” is 5,000p
pm's Superfine Superfloss (
TM) (commercially available anti-blocking agent from Johns Manville). All commercially available polyamides listed are nylon 6.

[0060]

[Table 2]

In each example, the numbers listed below each layer are the percentage of the film structure formed by the respective layer.

[0062] In each of Examples 1-3 and 6-10, the sealant layer (VLDPE) has a small percentage (3
~4%) of Ampacet 10853. This is a polyethylene masterbatch containing 6‰ (parts per thousand) of an antiblocking agent (diatomaceous earth).

In Example 1, the sealant layer was first coated with Att.
Attane 4001 (Dow) was used, but the foam was unstable, so Attane 4004 was used instead.

In each of Examples 4 and 5, the ionomer sealant layer contained a small percentage of Superfine S
upperfloss(TM) (Johns Manv
ille anti-blocking agent).

The nylon outer layers of Examples 6, 9, and 10 also contained small amounts of slip and antiblock agents.

The coextruded films of Examples 1 to 5, 7, and 8 were each made of 75 gauge biaxially oriented polypropylene,
B523™ (available from Hercules)
The substrate was laminated by conventional means.

The coextruded films of Examples 1-5, 7, and 8 were also each coated with a 48-gauge polyester support Mylar.
™ (available from DuPont).

The coextruded films of Examples 1-5, 7, and 8 were also each coated with a 50-gauge coated polyester support Scotchpar 2708™.
(Minnesota Mining and
(available from Manufacturing Co., Ltd.).

For each laminate thus formed, the coextruded film support was adhered at the interface between the support and the outer layer of the coextruded film.

Although this invention has been described in terms of preferred embodiments, it will be appreciated that modifications and changes may be made therein without departing from the principle and scope of the invention, as will be readily apparent to those skilled in the art. . Accordingly, such modifications and changes are considered to be within the scope of the claimed invention. For example, although the preferred method of making the polymeric films of the present invention is a coextrusion method, other methods such as extrusion coating and conventional lamination can also be used to join the layers of the polymeric film.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a preferred embodiment of the polymer film of the present invention.

FIG. 2 is a schematic cross-sectional view of a preferred embodiment of the laminate of the present invention.

[Explanation of symbols]

10 Outer layer 12 Intermediate (connection) layer 14 Inner layer 16 Oxygen barrier layer (center layer) 18 Middle (connection) layer 20 Sealant layer 30 Support 32 Adhesive

Claims (11)

[Claims] 1. A polymer film comprising the following layers a to e: (a) a central layer comprising an oxygen barrier material; (b) an inner polyamide layer disposed on each surface of the central layer; (c) a sealant layer comprising very low density polyethylene;
(d) a heat resistant outer layer; and (e) an intermediate layer disposed between each polyamide inner layer and each of the sealant layer and the heat resistant outer layer and comprising a chemically modified polyolefin. 2. The laminate of claim 1, wherein the oxygen barrier material comprises an ethylene-vinyl alcohol copolymer. 3. The laminate of claim 1, wherein the polyamide inner layer comprises nylon 6. 4. A laminate according to claim 1, wherein the heat-resistant outer layer is a polymeric material taken from the group consisting of polyamide, polyester, polypropylene, polycarbonate, high density polyethylene, and copolymers and mixtures thereof. Claim 5: Claim 1 further comprising a small amount of anti-blocking agent.
Sealant layer as described in . 6. The chemically modified polyolefin comprises a polyolefin selected from the group consisting of ethylene-vinyl acetate copolymer, polypropylene, low density polyethylene, linear low density polyethylene, and very low density polyethylene. The laminate according to 1. 7. A method for producing a laminate comprising the following steps a to e. (a) a central layer comprising an oxygen barrier material, a polyamide inner layer disposed on each surface of the central layer, a sealant layer comprising very low density polyethylene, a heat resistant outer layer, and a polyamide inner layer and each of the sealant layer and the heat resistant outer layer; (b) coextruding an intermediate layer comprising a chemically modified polyolefin disposed between said layers, said layer being extruded through several extruders; (c) drawing the coextrudate from the die; (d)
) quenching the coextrudate; and (e)
Winding the coextrudate into rolls. 8. The method of claim 7, wherein the adhesive layer and the sealant layer are crosslinked. 9. The method of claim 7, wherein the coextrudate is stretched in the machine direction. 10. A laminate comprising the following a and b. (a) Polymer film having the following layers: (i)
a central layer comprising an oxygen barrier material; (ii) a polyamide inner layer disposed on each surface of the central layer; (iii) a sealant layer comprising a very low density polyethylene; (iv) a polyamide, polypropylene, polyester, polycarbonate, high density polyethylene,
an outer layer comprising a polymeric material selected from the group consisting of linear low density polyethylene, and copolymers and mixtures thereof; (v) a polyamide inner layer disposed between the inner polyamide layer and each of the sealant layer and the outer layer and chemically modified an intermediate layer comprising a polyolefin; and (b) an outer polymer layer of the polymer film;
Support comprising polyester or polypropylene. 11. The laminate of claim 10 further comprising a coating of vinylidene chloride copolymer on the inner surface of the support.