JP6451381B2 - Coextruded multilayer film for deep drawing packaging - Google Patents

Description

  The present invention relates to a deep-drawing film that can be suitably used for packaging mainly sliced ham and sliced bacon, and a deep-drawn package.

In recent years, in the food industry, the reduction of waste due to environmental problems and the reduction in the amount of individual food products have been promoted rapidly along with the deep awareness of consumers, and even in deep-drawn packages such as sliced ham and sliced bacon, packaging There is a demand for a reduction in packaging material, that is, a reduction in thickness, which is nearly halved while maintaining the quality of the material.
In the process of manufacturing deep-drawn packages such as sliced ham and sliced bacon, the film is supplied to a deep-drawing machine and molded into the desired shape and size using a mold, and the contents such as sliced ham are placed in the deep-drawn part. , And heat-sealing and vacuum packaging using the lid material film supplied from above. Then, it cools and a film cut is carried out between each deep drawing part, and each deep drawing package is produced.
Furthermore, in these package applications, in accordance with the reduction of food per individual package, after producing each deep-drawn package, 3 to 4 packages were shifted and overlapped and bonded with a label tape to integrate them. Quad pack production is in progress.
In such a manufacturing process, if the packaging material film is thinned in accordance with the market demand, the rigidity (waist) of the film is lowered, or curling occurs due to heat sealing with the lid material. These problems of strength and deformation of individual packages not only lower the product value, including appearance, but also significantly deteriorate film production, alignment transportation of individual packages and orderly labeling at the manufacturing stage. To stop.

As a film for deep-drawing packaging, a polyester resin layer as an outer layer, a gas barrier layer made of nylon resin (Ny) or ethylene-vinyl acetate copolymer saponified material (EVOH) as an intermediate layer, and a polyolefin resin layer as an inner seal layer Multi-layer films having a wide range are generally used (for example, Patent Documents 1 to 4).
In these disclosed technologies, an amorphous polyester resin layer obtained by copolymerization with cyclohexanedimethanol or copolymerization with isophthalic acid, or an amorphous polyester obtained by solidifying a crystalline polyester in an amorphous state. By using the resin layer, the waist, gloss and transparency necessary for the deep-drawn package are provided.

However, the multilayer films of Patent Documents 1 to 3 all have a total film thickness of 120 μm or more, and the film has a waist. When the thickness is reduced in this configuration, the waist becomes insufficient and the shape of the package is lost.
In a multilayer film having a total film thickness of 50 to 150 μm and a ratio of the amorphous polyester resin layer thickness of the outer layer to the total film thickness of 40 to 60% disclosed in Patent Document 4, curling occurs due to heat sealing. .

  Moreover, although the technique which arrange | positions 2 layers 2 types of polyester resin layers in an outer layer is disclosed as a film for deep drawing (for example, patent documents 5-6), these are 200 micrometers-500 micrometers only by outer layer thickness. This is a technique for achieving film production with a total film thickness of 300 μm or more. These have a polyester resin layer thickness of 80% or more of the total film thickness in order to obtain the rigid properties required for gas pack applications in which an inert gas is sealed together with the contents. Thin film formation is difficult in terms of processing technology, and cannot be applied to the use of the present invention which is thin and requires barrier properties and pinhole resistance.

JP-A-7-096582 JP-A-8-281892 JP2003-136648 Patent 424749 Japanese Patent Laid-Open No. 10-100300 JP 10-034852 A

  An object of the present invention is to provide a packaging material and a packaging body having high rigidity and curl resistance as a deep-drawing packaging body without impairing transparency and gloss.

  As a result of intensive studies to solve the above problems, it has been found that the above problems can be solved by adopting a specific configuration, and the present invention has been completed.

  That is, the gist of the present invention is that the outer layer has at least three layers of an amorphous polyethylene terephthalate resin layer, the intermediate layer is a gas barrier layer, and the inner layer is an easy peel layer made of polyolefin resin, and the total film thickness is 40 μm or more and less than 120 μm The ratio of the thickness of the amorphous polyethylene terephthalate resin layer to the total film thickness is 40% or more and less than 75%.

  According to the deep-drawing co-extruded multilayer film of the present invention, it is possible to provide a deep-drawing film and a package that are firm and have good curl without losing transparency and gloss even when the film is thin. it can.

  Although the film of this invention is demonstrated in detail below, it is not limited to embodiment described below.

<Outer layer: Amorphous polyethylene terephthalate resin layer>
The outer layer of the film of the present invention is composed of an amorphous polyethylene terephthalate (PET) resin layer, and the crystalline polyester resin is solidified in an amorphous state in film formation to form a layer. Can be given rigidity, strength, moldability and gloss. In addition, since the cost is lower than that of a polyethylene terephthalate glycol (PETG) resin, which will be described later, even if the layer thickness ratio is increased, the economy is good, and the effect of imparting rigidity, strength, and moldability can be sufficiently exhibited. .
As the crystalline polyester resin, a resin having an ethylene terephthalate unit content of 80 mol% or more is used. The preferred content is 83 mol% or more, more preferably 85 mol% or more.

Moreover, the PET resin of the outer layer of the film of the present invention can be formed of a polyvalent carboxylic acid component and a polyhydric alcohol component described below.
As the polyvalent carboxylic acid component, any of aromatic dicarboxylic acid, aliphatic dicarboxylic acid, and alicyclic dicarboxylic acid is used in addition to terephthalic acid constituting the ethylene terephthalate unit.
Examples of aromatic dicarboxylic acids include benzenedicarboxylic acids such as isophthalic acid, orthophthalic acid, and 5-tert-butylisophthalic acid; naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid; 44-dicarboxydiphenyl and 2,2,6. Dicarboxybiphenyls such as 1,6-tetramethylbiphenyl-4,4′-dicarboxylic acid; 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid and substituted products thereof; 1,2-di Examples include phenoxyethane-4,4′-dicarboxylic acid and substituted products thereof.
Aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, pimelic acid, suberic acid, undecanoic acid, dodecanedicarboxylic acid, brassic acid, tetradecanedicarboxylic acid, tapsinic acid , Nonadecane dicarboxylic acid, docosane dicarboxylic acid and the like. Furthermore, examples of the alicyclic dicarboxylic acid include 1,4-dicarboxycyclohexane and 1,3-dicarboxycyclohexane.

As the polyhydric alcohol component, in addition to ethylene glycol constituting the polyethylene terephthalate unit, any of aliphatic diol, alicyclic diol and aromatic diol can be used.
Examples of the aliphatic diol include diethylene glycol, propylene glycol, butanediol, 1,6-hexanediol, 1,10-decanediol, neopentyl glycol, 2-methyl-2-ethyl-1,3-propanediol 2-diethyl- Examples include 1,3-propanediol and 2-ethyl-2-n-butyl-1,3-propanediol.
Examples of the alicyclic diol include 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol.
As aromatic diols, ethylene oxide adducts of bisphenol compounds such as 2,2-bis (4′-β-hydroxyethoxydiphenyl) propane and bis (4′-β-hydroxyethoxyphenyl) sulfone; xylylene glycol, etc. Is mentioned.
Moreover, polyalkylene glycols, such as polyethylene glycol and polypropylene glycol, etc. can also be used as a polyhydric alcohol component.

In order to prepare a PET resin using such a polyvalent carboxylic acid component and a polyhydric alcohol component, in order to improve the properties as a coextrusion film for deep drawing, one or more polyvalent carboxylic acid components or multiple polycarboxylic acid components are used. A combination of monohydric alcohol components can be used. The kind and content of the monomer component to be combined can be appropriately determined based on desired film characteristics, economy and the like.
The PET resin may be a single copolymer resin, or a mixture of two or more types of copolymer or homopolyester.
In particular, homopolyethylene terephthalate, polyethylene terephthalate copolymer, and the like can be suitably used from the viewpoint of economy.

The outer layer PET resin layer thickness of the film of the present invention is desirably 40% or more and less than 75% with respect to the total film thickness. By being 40% or more, good stiffness and curl resistance can be obtained for the film. If it is 75% or more, the thickness of the gas barrier layer of the intermediate layer and the seal layer of the inner layer cannot be ensured sufficiently, and their functions tend to be insufficient.
The lower limit thickness ratio is preferably 45% or more, and more preferably 50% or more. The upper limit thickness ratio is preferably 70% or less, and more preferably 65% or less.

<Outermost layer: Amorphous polyester resin layer>
In the film of the present invention, an amorphous polyester layer made of polyethylene terephthalate glycol (PETG) resin can be disposed on the outer side of the amorphous polyethylene terephthalate resin layer as an outer layer.
By disposing the PETG layer as the outermost layer, external haze due to oligomer precipitation on the surface of the outer amorphous PET layer is eliminated, and better gloss is obtained. In particular, the surface haze under heating at 130 ° C. or higher during sealing is significantly reduced, and transparency is improved.

  The PETG resin of the film of the present invention refers to a polyester resin in which 5 mol% or more of 1,4-cyclohexanedimethanol component is contained in 100 mol% of the polyhydric alcohol component. From the viewpoint of increasing the degree of amorphousness, it is desirable that 1,4-cyclohexanedimethanol is contained in an amount of 10 mol% or more, preferably 12 mol% or more, more preferably 15 mol% or more. On the other hand, if the 1,4-cyclohexanedimethanol component is too much, the impact strength of the film will decrease, so the upper limit is preferably 50 mol%, more preferably 47 mol% or less, and 45 mol. % Or less is more preferable.

  In the film of the present invention, considering the tear resistance, impact strength, heat resistance, etc., the content of the ethylene terephthalate unit in the unit of 100 mol% constituting the PETG resin used in the outermost layer is preferably 50 mol% or more, preferably Is preferably 55 mol% or more, more preferably 60 mol% or more. Therefore, 50 mol% or more of the terephthalic acid component in 100 mol% of the polyvalent carboxylic acid component, 50 mol% or more of less than 95 mol%, and further 55 mol% or more of 90 mol% in 100 mol% of the polyhydric alcohol component. It is desirable to contain it in mol% or less, particularly 60 mol% or more and 88 mol% or less.

  As other polyvalent carboxylic acid components and polyhydric alcohol components of the resin constituting the outermost layer of the film of the present invention, the same components as the amorphous polyethylene terephthalate resin layer of the outer layer can be used.

  The outermost PETG resin layer thickness of the film of the present invention is desirably 3% or more and 10% or less with respect to the total film thickness. When it is 3% or more, it is possible to impart a good gloss to the film, and when it exceeds 10%, the production cost increases and the industrial value decreases.

  For the outer PET resin layer and the outermost PETG resin layer, the layer interface can be observed by microscopic observation of the film cross section, and the layer thickness can be measured and calculated.

<Intermediate layer: Gas barrier layer>
The film of the present invention is desirably provided with an oxygen gas barrier property in the intermediate layer in order to prevent the food contained in the contents from being spoiled.
As the gas barrier layer, a polyamide resin (PA) layer, an ethylene-vinyl acetate saponified copolymer (EVOH) layer, or a mixed resin layer of PA and EVOH can be provided. Further, a single layer or a plurality of stacked layers may be used.

  The polyamide resin of the gas barrier layer is not particularly limited, but nylon resin (Ny) is preferably used from the viewpoint of gas barrier properties and pinhole resistance. For example, a polymer of a condensation unit such as 6 nylon, 66 nylon, 69 nylon, 6-66 nylon, 12 nylon, 11 nylon, 610 nylon, 612 nylon, 6I-6T nylon, MXD6 nylon, or two or more of these Mention may be made of copolymers and also mixtures thereof. Among them, it is preferable to use MXD6 nylon having high gas barrier property, 6 nylon or 6-66 nylon having high pinhole resistance.

  The EVOH resin of the gas barrier layer preferably has an ethylene content of 30 to 60 mol% and a saponification degree of 95% or more from the viewpoint of moldability and gas barrier properties.

When the PA layer is provided, the layer thickness is 2 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and 25 μm or less, preferably 20 μm or less, more preferably 15 μm or less. When it is 2 μm or more, good gas barrier properties and pinhole resistance can be obtained, and when it is 25 μm or less, good cutting properties in a deep-drawing packaging machine can be obtained.
When the EVOH layer is provided, the layer thickness is preferably 1 μm or more and 20 μm or less, and more preferably 2 μm or more and 10 μm or less. When the thickness is 1 μm or more, good oxygen gas barrier properties are obtained, and when it exceeds 20 μm, pinhole properties may be impaired.

<Intermediate layer: EVA layer, PE layer>
In the film of the present invention, an ethylene-vinyl acetate copolymer (EVA) layer or a polyethylene (PE) layer can be disposed in the intermediate layer for the purpose of imparting flexibility.
Although the ethylene content of EVA is not particularly limited, it is preferably 1.5 mol% or more and 20 mol% or less, preferably 3 mol% or more and 15 mol% or less from the viewpoint of film formation stability. Is more preferable.
The resin for the PE layer is not particularly limited. For example, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), or a mixture thereof can be used.

<Intermediate layer: Adhesive resin layer>
In the film of the present invention, at least one layer can be disposed between the outer layer and the intermediate layer and between the inner layer and the intermediate layer. Also, from the viewpoint of further increasing the interlayer adhesive strength, between the EVOH layer and the PE layer, between the PA layer and the PE layer, between the amorphous PET layer and the EVOH layer, and between the amorphous PET layer and the PA layer. It is preferable to arrange.
The adhesive resin to be used is not particularly limited as long as various resin layers constituting each layer can be bonded with a required strength. A polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof is preferable. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid and the like.
In addition, unsaturated carboxylic acid esters and anhydrides can be used as adhesive resins, and derivatives such as methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, butyl methacrylate, vinyl acetate, Glycidyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, sodium acrylate and the like can be used.

  As a commercially available adhesive resin, the Mitsui Chemicals Co., Ltd. make and brand name Admer are mentioned, for example, These can be used conveniently. Above all, when bonding PP layer, PE layer, EVOH layer and PET resin layer, special polyolefin-based ones and polyethylene elastomer-based ones are useful. Furthermore, when bonding EVOH layer, PP layer and PE layer The LLDPE type or PP type can be preferably used.

<Inner layer: Easy peel layer>
The resin constituting the easy peel (EP) layer, which is the inner seal layer of the film of the present invention, is not particularly limited as long as it has an easy peel function, and a mixture of two incompatible polyolefin resins is used. I can do it.
For example, a mixture of linear low density polyethylene (LLDPE) and polybutene (PB), a mixture of ethylene-vinyl acetate copolymer (EVA) and polypropylene (PP), a mixture of PP and low density polyethylene (LDPE), PP and Examples include mixing of ionomer (IO), mixing of PP and ethylene-acrylic acid copolymer (EAA), mixing of PP and ethylene-methyl methacrylate copolymer (EMMA), and the like. Among them, a mixture of LLDPE and PB or a mixture of PP and LDPE can be preferably used.

The EP layer thickness is 2 μm or more, preferably 3 μm or more, more preferably 4 μm or more, and 15 μm or less, preferably 12 μm or less, more preferably 10 μm or less, from the viewpoint of film formability and peel appearance. desirable.
When the EP layer thickness is 2 μm or more, stable film-forming properties can be obtained, and when the EP layer thickness is 15 μm or less, fluffing and film residue hardly occur at the time of peeling, and a good peeling appearance can be obtained.

  The easy peel strength (peel strength) of the EP layer may be any strength as long as it causes cohesive failure during peeling and the peeled surface is not fluffed. 0 N / 15 mm width or more, more preferably 1.2 N / 15 mm width or more, 5.0 N / 15 mm width or less, preferably 4.5 N / 15 mm width or less, more preferably 4.0 N / 15 mm width or less. .

<Multilayer film configuration>
It has at least three layers of an amorphous polyethylene terephthalate resin layer as an outer layer, a gas barrier layer as an intermediate layer, and an easy peel layer made of polyolefin resin as an inner layer, and has a total film thickness of 40 μm or more and less than 120 μm. There is no particular limitation as long as the ratio of the terephthalate resin layer thickness is 40% or more and less than 75%.

For example, abbreviations are used for each layer, amorphous PET resin layer (A), PA layer (B), EVOH layer (C), EVA layer or PE layer (D), easy peel layer (E), PETG layer (F) And the adhesive resin layer (G), the following layer structure can be formed.
(1) A / G / B / C / G / E
(2) A / G / B / C / G / D / E
(3) A / G / C / B / G / D / E
(4) A / G / C / B / G / E
(5) A / G / B / C / B / G / D / E
(6) A / G / B / F / C / G / D / E
(7) F / A / G / B / C / G / E
(8) F / A / G / B / C / G / D / E
(9) F / A / G / C / B / G / D / E
(10) F / A / G / C / B / G / E
(11) F / A / G / B / C / B / G / D / E
(12) F / A / G / B / G / C / G / D / E
Among the above, a preferable layer configuration is (8), (9), (10) or (11), and more preferably (8), (9) or (11).

  The film of the present invention can be produced using a known method. For example, an extrusion lamination method, a coextrusion inflation method, a coextrusion T die method, and the like can be used, and it is particularly preferable to use a coextrusion T die method.

<Deep drawn package>
The film of the present invention can be used for a deep drawn package by molding. In particular, when the film of the present invention is used as a bottom material of a deep drawn package, a good deep drawn package can be obtained.
The lid material is not particularly limited as long as easy peel properties can be obtained. For example, a lid material obtained by dry laminating an expanded polypropylene resin film (OPP), a transparent vapor-deposited polyethylene terephthalate film, and a linear low density polyethylene (LLDPE) film, or an expanded polyethylene terephthalate (OPET) film and EVLD or Ny containing LLDPE A laminate obtained by dry laminating a coextruded film as a layer can be mentioned.

Examples of the present invention will be described below, but the present invention is not limited thereto.
<Production of multilayer film>
A multilayer film having a layer structure shown in each example was produced by a coextrusion method. The component of each layer was shown using the following abbreviations.
(Each layer component)
PET: Polyethylene terephthalate homopolymer PETG: PETG manufactured by Eastman Chemical Co.
Adhesive resin: Unsaturated carboxylic acid-modified polyolefin resin Ny: 6-66 copolymer nylon Nylon 66 ratio 15%
EVOH1: Saponified ethylene-vinyl acetate copolymer 38 mol of ethylene
EVOH2: Saponified ethylene-vinyl acetate copolymer 32 mol of ethylene
LL: Linear low density polyethylene EVA: Ethylene-vinyl acetate copolymer EP: Mixture of linear low density polyethylene (60%) and polybutene (40%)

Example 1
PET (33 μm) / adhesive resin (4 μm) / Ny (5 μm) / EVOH1 (5 μm) / adhesive resin (4 μm) / LL (5 μm) / EP (4 μm)
Total thickness 60μm

(Example 2)
PET (33 μm) / adhesive resin (4 μm) / EVOH1 (5 μm) / Ny (5 μm) / adhesive resin (4 μm) / LL (5 μm) / EP (4 μm)
Total thickness 60μm

Example 3
PETG (3 μm) / PET (30 μm) / Adhesive resin (4 μm) / Ny (5 μm) / EVOH1 (5 μm) / Adhesive resin (4 μm) / LL (5 μm) / EP (4 μm)
Total thickness 60μm

(Example 4)
PETG (3 μm) / PET (30 μm) / Adhesive resin (4 μm) / EVOH2 (5 μm) / Adhesive resin (4 μm) / EVA (10 μm) / EP (4 μm)
Total thickness 60μm

(Example 5)
PETG (1 μm) / PET (23 μm) / Adhesive resin (3 μm) / Ny1 (3 μm) / EVOH1 (3 μm) / Adhesive resin (3 μm) / LL (2 μm) / EP (2 μm)
Total thickness 40μm

(Example 6)
PETG (3 μm) / PET (40 μm) / Adhesive resin (3 μm) / Ny1 (3 μm) / EVOH1 (3 μm) / Adhesive resin (3 μm) / LL (3 μm) / EP (2 μm)
Total thickness 60μm

(Comparative Example 1)
PETG (33 μm) / Adhesive resin (4 μm) / Ny (5 μm) / EVOH1 (5 μm) / Adhesive resin (4 μm) / LL (5 μm) / EP (4 μm)
Total thickness 60μm

(Comparative Example 2)
PETG (3 μm) / PET (10 μm) / Adhesive resin (5 μm) / Ny (6 μm) / EVOH1 (8 μm) / Adhesive resin (5 μm) / LL (18 μm) / EP (5 μm)
Total thickness 60μm

(Comparative Example 3)
PETG (2 μm) / PET (15 μm) / Adhesive resin (4 μm) / Ny (3 μm) / EVOH1 (4 μm) / Adhesive resin (4 μm) / LL (3 μm) / EP (5 μm)
Total thickness 40μm

<Production of deep-drawn package>
Using a deep-drawing packaging machine (FV6300 manufactured by Omori Machine Industry Co., Ltd.), using a multilayer film produced in each example as a film for a bottom material under the conditions of a molding heating temperature of 90 ° C. and a molding time of 1.5 seconds, a diameter of 98 mm, It was molded into a cylindrical shape with a drawing depth of 5 mm, and sliced ham having a diameter of 95 mm and 35 g was vacuum packaged to produce a package body having a length of 100 mm and a width of 80 mm.

For the lid material, the following laminate was produced by the dry lamination method. “//” represents adhesion by a dry laminating method.
OPP (30 μm) // Transparent deposition PET (12 μm) // LLDPE (40 μm)
OPP: Biaxially stretched polypropylene film Transparent deposition PET: Toyo Melarizing VM-PET
LLDPE: Linear low density polyethylene film

<Evaluation method>
The following evaluation was performed and the results are shown in Table 1.
(Heat seal curl)
Observation was made within 5 minutes after the package was prepared, and the case where the heat seal part was flat or the curl height was less than 5 mm was evaluated as “◯”, and the curl height was evaluated as “x”.

(Haze inside film)
Internal haze was measured as an evaluation of the transparency of the film.
Dioctyl phthalate was applied to the surface of the inner layer of the film, the film was sandwiched between slide glasses, and the internal haze was measured according to JIS-K 7105.

From Table 1, Examples 1 to 6 had good deep drawability, almost no curling of the heat seal part of the package, and the packs were easy to align when a label was applied.
On the other hand, in Comparative Examples 1 to 3, the heat seal part curls on the bottom material side, so the packaging body is not aligned and conveyed well in the labeler of the packaging line, and the label of the multiple packs cannot be bent or pasted. Happened.
The transparency was good in Examples 3 to 6 and Comparative Examples 1 to 3 in which an amorphous polyester resin layer was arranged in the outermost layer.

  According to the coextrusion multilayer film for deep drawing of the present invention, it is possible to provide a thin film that is firm and has good curl without impairing transparency and gloss, and the amount of waste is reduced to half that of the current product. The industrial value is high.

Claims (2)

Amorphous polyester resin layer as the outermost layer, amorphous polyethylene terephthalate resin layer to the outer layer, a gas barrier layer on the intermediate layer has at least four layers of easy peel layer comprising a polyolefin resin in the inner layer than the film total thickness is 40μm or more 120μm a deep drawn extruded multilayer film co molding Ru der, 10% or less the ratio is 3% or more of the amorphous polyester resin layer to the total film thickness, of the amorphous polyethylene terephthalate resin layer to the film total thickness A coextruded multilayer film for deep drawing, wherein the ratio is 40% or more and less than 75%. Deep draw packaging material produced using multi-layered film of claim 1 Symbol placement.