JP2001253028A - Multilayered film and package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered film having excellent boil resistance in the deep draw vacuum packaging of food and capable of botaining a package good in the transparency of a seal part, and the package thereof. SOLUTION: The multilayered film is constituted by arranging a layer comprising a polyethylene resin, which is polymerized using a metallocene catalyst, having a density of 0.88-0.92 g/cm3 to a seal layer with a thickness of 2-15 μm, which has easy opening properties due to cohesive failure, as an adjacent layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly has excellent boil resistance in deep drawing vacuum packaging of foods,
The present invention relates to a multilayer film from which a package having good transparency of a seal portion can be obtained, and a package thereof.

[0002]

2. Description of the Related Art Multilayer films used in deep drawing vacuum packaging of foods are required to be easily openable (easy peeling property). Further, in applications involving boil processing, deformation and delamination may occur during boiling. It is required that the film be provided at the end of the package so as to be easily opened, and that the film be "opened" (unsealed portion) does not fuse. In order to provide such properties, in conventional multilayer films, an easy peel material containing a heat-resistant linear low-density polyethylene resin (hereinafter referred to as “LL”) as a main component is used for a seal layer. I have. Most of them are compositions in which LL, polypropylene (hereinafter, referred to as “PP”), polybutene-1 (hereinafter, referred to as “PB1”), and styrene resin are mixed.

[0003]

However, since the easy peel material comprising the above composition is a resin which easily develops spherulites by crystallization at the time of sealing, a frame seal (a seal at the outer peripheral portion of a pack product and a hot plate) And the face seal (the part inside the frame seal, the hot plate side (the upper side of the lid) is vacuum, the vacuum box side (the lower side of the bottom material) ) Has a drawback in that the transparency of the portion which is sealed by bringing the film into close contact with the hot plate at a differential pressure of 1 atm is deteriorated by opening to the atmosphere. In addition, when the easy peel material used for non-boiling is used for boiling, there is a problem that the easy peel strength tends to fluctuate before and after the boiling and that the kick portion of the easy peel is fused.

An object of the present invention is to provide a multilayer film and a package for deep drawing which can solve the above-mentioned problems.

[0005]

The above object is achieved by the following means.
Achieved by In other words, the sealing layer
It has an easy opening property, and its thickness is in the range of 2 to 15 μm.
And a density of 0.88 to 0.9 in the layer adjacent to the sealing layer.
2g / cm^Three Polymerized by Metallocene Catalyst
This is a multilayer film having a styrene resin layer. here
The seal layer is made of an ionomer, ethylene-acrylic acid
Copolymer, ethylene-ethyl acrylate copolymer, and
Selected from the group consisting of ethylene-methacrylic acid copolymers
50: 50-8 at least one kind of resin and PP
Consisting of resin blended in a ratio of 0:20, above
The low-density polyethylene whose adjacent layer is polymerized by a high-pressure method
To 30% by weight, and the seal layer
Rubitol compounds in the range of 100-5000 ppm
Includes adding. Also, seal layer, adjacent
Other layers except the layer are saponified with ethylene-vinyl acetate copolymer.
Material, polyamide, or polypropylene
At least one type of resin and co-extrusion molding
And from the outermost layer side, 12 nylon or 6 nylon / adhesive
Resin / 6-66 nylon / ethylene-vinyl acetate copolymer
Combined saponified material / adhesive resin / adjacent layer / seal layer or 1
2 nylon or 6 nylon / adhesive resin / ethylene-vinegar
Saponified acid vinyl copolymer / 6-66 nylon / adhesive
Resin / adjacent layer / seal layer
Biaxially oriented polypropylene, biaxially oriented polyethylene for outer layer
Group consisting of terephthalate and biaxially stretched polyamide
Dry-laminated resin film selected from
In addition, using the multilayer film described above,
0.91 to 0.93 g / cm
^Three , Linear low density polyethylene having a melting point of 115 to 125 ° C
Including packaging made by film sealing using resin
I have.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the present invention, the seal layer is a cohesive failure type easy peel material and its thickness needs to be 2 to 15 μm. If the thickness is less than 2 μm, the sealing layer may partially flow and be displaced by the temperature and pressure at the time of sealing, and a layer adjacent to the sealing layer may appear on the sealing surface. This is because the easy opening property is deteriorated and the peeled surface is easily fluffed. In particular, when the adjacent layer comes out on the surface, it is completely sealed, so that there is a problem that the opening property is extremely deteriorated.

As the resin used for the seal layer, a combination of resins having easy-opening properties due to cohesive failure can be used as appropriate, but ionomers, ethylene-acrylic acid copolymers, ethylene-ethyl acrylate copolymers, and PP is mixed with at least one resin selected from the group consisting of an ethylene-methacrylic acid copolymer and 50:50 to 80:20.
A resin made of a resin blended at a ratio of 2 is preferably used. Such a combination of resins is preferable from the viewpoint of transparency. However, if the ratio of PP exceeds 50% by weight, the easy peel strength is weakened, and the possibility of breakage during storage and transportation is increased. In particular, when there is boil sterilization after packing, bag breakage is more likely to occur. When the ratio of PP is less than 20% by weight, the cohesive strength is not sufficiently reduced, so that the easy peel strength is high and the opening property tends to be poor.

The layer adjacent to the seal layer has a density of 0.
It is necessary to provide a polyethylene resin layer polymerized with a metallocene catalyst (single site catalyst) of 88 to 0.92 g / cm ³ . This is because the polyethylene-based resin using the metallocene catalyst has a feature that the molecular weight distribution is narrow, the uniformity is high, and the transparency is excellent, and the density is in the range of 0.88 to 0.92 g / cm ³ . Must be used. If the density is less than 0.88 g / cm ³ , the heat resistance is low and the possibility of causing problems in hot tack property during sealing (hot sealing strength) and heat resistance during boiling increases. On the other hand, if the density exceeds 0.92 g / cm ³ , spherulites are easily formed by crystallization at the time of heat sealing, which causes a problem that transparency is lowered. When the resin used for the seal layer is mainly composed of a polyethylene resin, the resin used for the layer adjacent to the seal layer is not particularly problematic using a normal polyethylene resin. In the case of an acid copolymer, an ethylene-ethyl acrylate copolymer, and an ethylene-methacrylic acid copolymer, a polyethylene resin polymerized with a metallocene catalyst in order to secure interlayer strength, particularly a density of 0.92 g / cm ³ It is preferable to use the following. Such resins are characterized by high strength and low pinhole resistance at low temperatures due to low elastic modulus, and are useful as films for deep drawing packaging. As the polyethylene resin polymerized by the metallocene catalyst used herein, a copolymer with an α-olefin such as butene-1, hexene-1, 4-methylpentene-1, and octene-1 is mainly used, but is not particularly limited.

The above-mentioned ionomer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer and ethylene-methacrylic acid copolymer include linear low-density polyethylene and high-pressure low-density polyethylene. Even when co-extruded with an ordinary polyethylene resin, it was difficult to develop interlayer strength, and it could not be used adjacently. The use of a similar resin or an ethylene-vinyl acetate copolymer as an adjacent layer of the seal layer containing the above-mentioned ionomer or the like as a main component easily provides an interlayer strength, but if the heat resistance of the adjacent layer is low, a boil treatment is performed. That the hot tack property in the
Since the unit cost of raw materials was relatively high, it was not used in films for boil processing. Therefore, in the present invention, a polyethylene-based polymerized using a metallocene catalyst, which has the required interlayer strength, has good hot tack properties, and has good pinhole resistance at low temperatures, and is also relatively low in cost. By using the resin for the adjacent layer, the above problem could be solved.

The polyethylene resin polymerized by using the metallocene catalyst in the adjacent layer may contain 2 to 30% by weight of a low-density polyethylene polymerized by a high-pressure method. By incorporating the high-pressure low-density polyethylene in the above range, the crystal of the polyethylene-based resin polymerized by the metallocene catalyst can be suppressed small, and the transparency can be further improved by microcrystallization. If the amount of the high-density low-density polyethylene is less than 2% by weight, the effect of improving transparency is small,
If it exceeds 30% by weight, transparency and strength are likely to be reduced.

In order to suppress the growth of spherulites due to the crystallization of PP, a seal layer obtained by blending PP with an ionomer or the like contains 100% to 50% of a sorbitol compound as a nucleating agent.
It is effective to add it in the range of 00 ppm. 100
If it is less than ppm, the effect as a nucleating agent is small, and
If it exceeds 0 ppm, the sealing property is impaired, and the sealing strength tends to be reduced. Examples of the sorbitol compound include bis (p-methylbenzylidene) sorbitol and bis (p-ethylbenzylidene) sorbitol, but are not particularly limited. In addition to the polyethylene layer polymerized using a metallocene catalyst, which is a layer adjacent to the seal layer, it provides oxygen barrier properties, pinhole resistance, boil resistance, etc. necessary for bottom and lid materials for deep drawing packaging. For this purpose, it is effective to co-extrude a saponified ethylene-vinyl acetate copolymer, a polyamide resin, and PP. For imparting oxygen barrier properties, saponified ethylene-vinyl acetate copolymer is effective,
Food preservability is improved. However, when a high oxygen barrier is not required, a certain degree of oxygen barrier properties can be imparted by disposing a polyamide resin. It is effective to provide a polyamide resin for imparting strength, and it is effective to dispose PP to the outer layer on the side opposite to the seal layer for imparting boil resistance (in particular, prevention of curling during boiling).

When used as a bottom material for deep drawing, 12 nylon or 6 nylon / adhesive resin / 6-6-6 from the outermost layer side
6 nylon / Saponified ethylene-vinyl acetate copolymer /
Adhesive resin / adjacent layer / seal layer or 12 nylon or 6 nylon / adhesive resin / saponified ethylene-vinyl acetate copolymer / 6-66 nylon / adhesive resin / adjacent layer /
It is very effective to form a film that is laminated in the order of the sealing layer. Gloss and boil resistance can be imparted by using 12 nylon or 6 nylon as the outer layer resin, and pinhole resistance can be imparted by intermediate 6-66 nylon. The saponified ethylene-vinyl acetate copolymer is used for imparting oxygen barrier properties. The reason why the intermediate layer is made of 6-66 nylon is that the deep drawability is superior to that of 6 nylon and that the ethylene-vinyl acetate copolymer The co-extrusion is performed adjacent to the combined saponified layer, and the purpose is to keep the melting point low. As the outer layer resin, 12 nylon is better than 6 nylon because of its good gloss and low hygroscopicity, which is suitable for boiling.

When used as a deep drawing lid material, a saponified ethylene-vinyl acetate copolymer / polyamide resin layer is co-extruded with a seal layer to provide oxygen barrier properties and strength,
It is very useful to use a multilayer film obtained by dry laminating a film selected from biaxially oriented polypropylene, biaxially oriented polyethylene terephthalate, and biaxially oriented polyamide for the outermost layer in order to impart heat resistance during sealing. If a biaxially stretched film is not used for the lid material outer layer, the sealing heat in deep drawing packaging is applied from the lid material outer layer side, so that the film is sticky to the hot plate and the lid material is easily stretched, and the lid material is wrinkled. Phenomena tend to occur, which is likely to cause problems in appearance and storage.

The multilayer film of the present invention is used for deep drawing packaging.
When used as a bottom material or lid material, the seal on the mating side
The material has a density of 0.91 to 0.93 g / cm^Three, Melting point 1
Uses linear low-density polyethylene resin at 15-125 ° C
The package sealed with the film is heat-resistant when boiling.
Is good and the transparency is also good. Where density
Is 0.91 g / cm^ThreeOr less than 115 ° C
If the temperature is lower than the lower limit, the softening temperature decreases and the
Dangerous part (It is a kick to peel off the easy peel
(Unsealed portion), the bottom material and the lid material are easily fused. Density is 0.
93g / cm^Three Or melting point exceeds 125 ° C
If the softening temperature increases, the sealing temperature increases
The transparency of the seal part may be deteriorated,
Problems such as defects are likely to occur. Use here
The linear low-density polyethylene resin used is a copolymer component.
Α-olefin is butene-1, hexene-1, 4-methyl
Lupentene-1, octene-1 and the like are preferably used.
Wear. In addition, resin polymerized by metallocene catalyst can be used.
Wear. Note that the linear low-density polyethylene resin layer is
Crystallization may cause poor transparency
Low crystallinity or large spherulites in adjacent layers
Pile resin, and make the thickness of the layer as thin as possible
Preferably.

[0014]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the contents of the examples. The contents of the abbreviations in the following description are as follows. Metallocene LL: Linear low-density polyethylene polymerized by a metallocene catalyst 12 Ny: 12 nylon resin EVOH: Saponified ethylene-vinyl acetate copolymer resin 6 Ny: 6 nylon resin 6-66 Ny: 6-66 nylon resin

AD: acid-modified polyolefin PET: polyethylene terephthalate EAA: ethylene-acrylic acid copolymer EMAA: ethylene-methacrylic acid copolymer OPP: biaxially oriented polypropylene film CPP: unoriented polypropylene film EVA: ethylene-vinyl acetate Polymer IO: ionomer resin

(Embodiment 1) Hereinafter, the thickness in parentheses indicates the thickness of each layer.
The unit of expression is μm. Bottom material: Multi-layer film with the following layer composition is formed by co-extrusion
did. 12Ny / AD / EVOH / 6-66Ny / AD / metallocene LL / seal layer (20) (20) (20) (50) (10) (70) (10) Metallocene LL: density 0.903 g / cm^Three  Sealing layer: EAA 60% by weight + PP 40% by weight Lid material: Multi-layer of the following layer structure obtained by dry laminating OPP
FilmLL: density 0.921 g / cm^Three, Melting point 125 ° C

(Example 2) Bottom material: Multi-layer film having the following layer constitution is formed by co-extrusion.
did. 6Ny / AD / 6-66Ny / EVOH / AD / metallocene LL / seal layer (20) (20) (20) (50) (10) (70) (10) Metallocene LL: density 0.907 g / cm^Three  Sealing layer: EEA 65% by weight + PP 35% by weight Lid material: The following layer structure obtained by dry laminating PET film.
Multilayer film PET // 6Ny / AD / EVOH / 6-66Ny / AD / EVA / sealing layer (12) (5) (10) (10) (10) (5) (20) (10) Sealing layer: LL density 0.918g / cm^Three, Melting point 12
0 ° C

(Example 3) Bottom material: A multilayer film having the following layer constitution is formed by a coextrusion method.
did.Metallocene LL: density 0.918 g / cm^Three  Seal layer: 70% by weight of IO + 30% by weight of PP and sorbitol
Cover material: Domestic biaxially stretched nylon film (ONy) and LL
Lined film with the following compositionLL: density 0.920 g / cm^Three, Melting point 120 ° C

(Example 4) Bottom material: Multilayer of the following layer constitution obtained by dry laminating CPP
Film CPP // EVOH / 6-66Ny / AD / (Metallocene LL
(90) + LDPE (10)) / Seal layer (50) (20) (30)
 (10) (50) (10) Metallo
Sen LL: density 0.918 g / cm^Three  Sealing layer: EMAA 60% by weight + PP 40% by weight Lid material: The following layer structure obtained by dry laminating each film.
FilmLL: density 0.910 g / cm^Three, Melting point 115 ° C

(Example 5) Bottom material: A multilayer film having the following layer structure is formed by coextrusion.
did. 12Ny / AD / EVOH / 6-66Ny / AD / metallocene LL / seal layer (20) (20) (20) (50) (10) (70) (10) Metallocene LL: density 0.903 g / cm^Three  Seal layer: LL density 0.920 g / cm^Three, Melting point 1
17 ° C Lid: OPP dry-laminated, multi-layer with the following layer configuration
Film OPP // EVOH / 6-66Ny / AD / metallocene LL / seal layer (20) (10) (20) (10) (25) (5) Metallocene LL: density 0.903 g / cm^Three  Seal layer: EAA 60% by weight + PP 40% by weight

(Comparative Example 1) Bottom material: A multilayer film having the following layer structure was formed by coextrusion.
did. 12Ny / AD / EVOH / 6-66Ny / AD
/ LL / seal layer (20) (20) (20) (50)
 (10) (70) (10) LL: Density 0.920 g / cm^Three  Sealing layer: EAA 60% by weight + PP 40% by weight Lid material: Multi-layer of the following layer structure obtained by dry laminating OPP
FilmSeal layer: LL density 0.921 g / cm^Three, Melting point 12
5 ℃

(Comparative Example 2) Bottom material: A multilayer film having the following layer structure was formed by coextrusion.
did. 12Ny / AD / EVOH / 6-66Ny / AD / metallocene LL / seal layer (20) (20) (20) (50) (10) (60) (20) Metallocene LL: density 0.903 g / cm^Three  Sealing layer: EAA 60% by weight + PP 40% by weight Lid material: Multi-layer of the following layer structure obtained by dry laminating OPP
FilmSeal layer: LL density 0.921 g / cm^Three, Melting point 12
5 ℃

(Comparative Example 3) Bottom material: A multilayer film having the following layer structure was formed by coextrusion.
did. 12Ny / AD / EVOH / 6-66Ny / AD / metallocene LL / seal layer (20) (20) (20) (50) (10) (70) (10) Metallocene LL: density 0.933 g / cm^Three  Sealing layer: EAA 60% by weight + PP 40% by weight Lid material: Multi-layer of the following layer structure obtained by dry laminating OPP
FilmSeal layer: LL density 0.921 g / cm^Three, Melting point 12
5 ℃

(Comparative Example 4) Bottom material: A multilayer film having the following layer structure was formed by coextrusion.
did. 12Ny / AD / EVOH / 6-66Ny / AD / metallocene LL / seal layer (20) (20) (20) (50) (10) (70) (10) Metallocene LL: density 0.903 g / cm^Three  Seal layer: 60% by weight of LL + 40% by weight of PB-1 Lid: Multi-layer of the following layer structure obtained by dry laminating OPP
FilmSeal layer: LL density 0.921 g / cm^Three, Melting point 12
5 ℃

(Comparative Example 5) Bottom material: A multilayer film having the following layer structure was formed by coextrusion.
did. 12Ny / AD / EVOH / 6-66Ny / AD
/ Metallocene LL / Seal layer (20) (20) (20)
 (50) (10) (70) (10) Metallocene
LL: density 0.903 g / cm^Three  Sealing layer: EAA 60% by weight + PP 40% by weight Lid material: Multi-layer of the following layer structure obtained by dry laminating OPP
FilmSeal layer: LL density 0.918 g / cm^Three, Melting point 10
6 ℃

(Comparative Example 6) Bottom material: A multilayer film having the following layer structure was formed by coextrusion.
did. 12Ny / AD / EVOH / 6-66Ny / AD / metallocene LL / seal layer (20) (20) (20) (50) (10) (70) (10) Metallocene LL: density 0.903 g / cm^Three  Sealing layer: EAA 60% by weight + PP 40% by weight Lid material: Multi-layer of the following layer structure obtained by dry laminating OPP
FilmSeal layer: LL density 0.935 g / cm^Three, Melting point 12
4 ℃

<Evaluation method> A deep drawing packaging machine ("FV630" manufactured by Omori Machinery Co., Ltd.)
0 "), the bottom material was drawn, filled with grilled pork (400 g) as the content, and heat-sealed at a temperature of 140 ° C. ×
Vacuum packed in 1.6 seconds. Next, this vacuum packaged product is 95
A boil at 20 ° C. for 20 minutes was performed. Sealability: Does not cause damage such as burning to contents 1
Those that can be sealed at a temperature of 40 ° C. or lower were rated as ○, and those that required 140 ° C. or higher were rated as Δ. Transparency: も の indicates that the seal portion has good transparency and no problem, Δ indicates that the seal portion has partially poor transparency, and X indicates the entire poor seal portion. Easy peelability: ○ indicates no problem such as fluffing, and × indicates problematic and practically problematic. Fusing resistance: も の indicates that no kick portion was fused by heat sealing, and △ indicates partially fused.

[0027]

[Table 1]

Table 1 shows that Examples 1 to 5 of the present invention have no problem in any of the characteristics. On the other hand, it can be seen that Comparative Example 1 in which the resin used in the layer adjacent to the seal layer of the bottom material is not LL polymerized with a metallocene catalyst has no transparency. In Comparative Example 2, since the thickness of the easy peel layer is large, fluffing is likely to occur at the time of opening, and good easy peel properties cannot be obtained. In Comparative Example 3, since the density of the metallocene LL resin was high, crystallization was easy during sealing, and the transparency was poor. In Comparative Example 4, since the resin having high crystallinity of LL and PB-1 was used for the easy peel layer, transparency was hardly obtained. Comparative Example 5 had a density of 0.918 g / c for the mating sealing material.
Since LL having m ³ and a melting point of 106 ° C. was used, when the package was manufactured, the kick portion of the easy peel portion was partially fused. Further, in Comparative Example 6, the other party sealing material had a density of 0.3.
Since 935 g / cm ³ of LL is used, it can be seen that when a package is produced, the sealing properties and the transparency of the sealed portion are inferior.

[0029]

As described above, according to the multilayer film of the present invention, an easy peel type package for a boil having good heat resistance, good transparency, easy peel appearance and good pinhole resistance is provided. It became possible to obtain.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 23/08 C08L 23/08 23/12 23/12 23/26 23/26 F-term (Reference) 3E086 AD19 AD23 BA04 BA15 BA33 BA35 BB21 BB41 BB51 4F100 AH02A AK03 AK04B AK06B AK06E AK07A AK07C AK07E AK42E AK46C AK48D AK48E AK69C AK70A AK71A AL05A AL05B AL07 AR00A BA02 BA03 BA04 BA05 BA07 BA10A BA10C BA10E BA15 EH20 EJ38E GB23 JA13B JA20A JJ03 JK14 JL12 JL12A JL14 JL14A JN01 YY00A YY00B 4J002 BB071 BB081 BB122 BB231 GF00 GG02

Claims (8)

[Claims] 1. A metallocene catalyst having a seal layer having an easy-opening property due to cohesive failure, a thickness in a range of 2 to 15 μm, and a density of 0.88 to 0.92 g / cm ^{3 in} a layer adjacent to the seal layer. Multilayer film comprising a polyethylene resin layer polymerized by the method described above. 2. The sealing layer is made of an ionomer, ethylene-
At least one resin selected from the group consisting of acrylic acid copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methacrylic acid copolymer, and a polypropylene resin in a ratio of 50:50 to 80:20. The multilayer film according to claim 1, comprising a blended resin. 3. The multilayer film according to claim 1, wherein the low-density polyethylene polymerized by a high-pressure method is added in a range of 2 to 30% by weight to the adjacent layer of the sealing layer. 4. A sorbitol-based compound in a sealing layer
4. The multilayer film according to claim 1, wherein said multilayer film is added in the range of 0 to 5000 ppm. 5. A multilayer film obtained by co-extrusion of a sealing layer, an adjacent layer and another layer, wherein the other layer is ethylene-based.
The multilayer film according to any one of claims 1 to 4, wherein at least one resin selected from the group consisting of a saponified vinyl acetate copolymer, polyamide, and polypropylene is provided and co-extruded. 6. Nylon or 6 nylon / adhesive resin / 6-66 nylon / saponified ethylene-vinyl acetate copolymer / adhesive resin / adjacent layer / seal layer or 12 nylon or 6 from the outermost layer side 6. The multilayer film according to claim 5, wherein the film is laminated in the order of nylon / adhesive resin / saponified ethylene-vinyl acetate copolymer / 6-66 nylon / adhesive resin / adjacent layer / seal layer. 7. A multilayer film comprising a resin film selected from the group consisting of biaxially-stretched polypropylene, biaxially-stretched polyethylene terephthalate, and biaxially-stretched polyamide, as the outermost layer, being dry-laminated. 8. The multilayer film for deep drawing according to claim 1, wherein a density of 0.91 is set as a mating seal material.
A package formed by sealing a film using a linear low-density polyethylene resin having a melting point of 115 to 125 ° C. and a melting point of 0.93 g / cm ³ .