JPH1044344A - Laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate having excellent boilproofness and particularly useful for a boil sterilizing or retort sterilizing packaging material. SOLUTION: The laminate comprises at least one ethylene-vinyl acetate copolymer saponified material layer having heat of fusion (ΔH) of 1st RUN measured by a differential scanning calorimeter(DSC) satisfying ΔH(J/g) >=100-0.55Et, ethylene content (Et) of 20 to 50mol% and degree of saponification of 90mol% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate having a saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH) layer, and more particularly to a laminate of EVOH having excellent boil resistance and the like. About.

[0002]

2. Description of the Related Art Conventionally, as a food package using a multilayer structure, especially a multilayer film, contents are packaged (pouches).
After filling and sealing, there is a retort packaging material that is required to have a preservation effect equivalent to canning by performing high-temperature heat sterilization,
In the use of the packaging material, generally, a type including an aluminum foil and a transparent type including vinylidene chloride are known.

[0003] However, aluminum foil has the disadvantage that its contents cannot be checked because it is opaque. In addition, vinylidene chloride tends to be colored, and in order to obtain a desired oxygen gas barrier property, it is difficult to obtain a desired oxygen gas barrier property. A thickness of about 80 μm is required, and as a result, the packaging material takes on a yellow tint or the transparency is reduced. Therefore, at present, it is usually used at about 15 to 30 μm. There is a problem that has not been obtained.

Therefore, EVOH having excellent gas barrier properties is used.
There has been proposed a laminate for sterilizing boiling or retort using a resin composition comprising a polyamide resin having excellent moisture permeability. For example, Japanese Patent Publication No. 3-8944 discloses a multilayer film obtained by biaxially stretching a composition comprising EVOH and a polyamide, and the present applicant has proposed various compositions comprising a specific polyamide and EVOH ( JP-A-6-345919, JP-A-6-345920
JP-A-7-118469, JP-A-7-118469
No. 18470).

[0005]

However, in these compositions comprising EVOH and polyamide, it is necessary to blend EVOH and polyamide, and furthermore, depending on the state of blending, coloring and moldability may be reduced.
It is desired that a layer of VOH alone be used in a state of being laminated with another layer.

[0006]

The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, the heat of fusion (ΔH) of the first run measured by a differential scanning calorimeter (DSC) is shown in the following (1). ) Which satisfies the formula (E)
t) EV having 20 to 50 mol% and saponification degree of 90 mol% or more
The inventors have found that a laminate formed by laminating an OH layer has excellent boil resistance, and have completed the present invention. ΔH (J / g) ≧ 100−0.55 · Et (1) (where Et represents the ethylene content (mol%)) The heat of fusion (ΔH) is only for the EVOH layer. When the heat of fusion (ΔH) of the EVOH layer in the laminate was measured, the value was measured by peeling only the EVOH layer, and when it was unavoidable to measure as a laminate, the value was converted to a single EVOH layer. Value.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the laminate of the present invention will be specifically described. E used for the EVOH layer (A) of the present invention
As the VOH, the ethylene content is 20 to 50 mol%, further 28 to 48 mol%, and the saponification degree of the vinyl acetate component is 90%.
Mol% or more, and more preferably 95 mol% or more,
If the ethylene content is less than 20 mol%, the water resistance becomes insufficient, while if it exceeds 50 mol%, the barrier properties of gas and the like deteriorate, and if the saponification degree is less than 90 mol%, the water resistance and heat resistance are poor. It is unsuitable due to insufficient stability. The EVOH may further contain a small amount of α-olefins such as propylene, isobutene, α-octene, α-dodecene, α-octadecene, unsaturated carboxylic acids or salts thereof, partial alkyl esters, complete alkyl esters, nitriles, amides and anhydrides. Or a comonomer such as an unsaturated sulfonic acid or a salt thereof.

[0008] The laminate of the present invention is such that the EVOH layer (A) is laminated on a substrate, and the substrate is not particularly limited. However, considering the packaging for sterilizing boil or retort, A highly transparent thermoplastic resin layer (B) is preferable, and it is particularly preferable to be any one of a polyolefin resin layer, a polyamide resin layer, a polyester resin layer, and a polystyrene resin layer. As such a polyolefin resin or polyamide resin, specifically, high density, medium density, low density polyethylene, vinyl acetate,
Acrylic acid ester, or butene, hexene, 4-
Polyethylene copolymerized with α-olefins such as methyl-1-pentene, ionomer resin, polypropylene homopolymer, polypropylene graft copolymerized with ethylene, or ethylene, hexene, 4-methyl-1
Polypropylene, poly-1-butene, poly-4-methyl-1-copolymerized with α-olefins such as pentene
Examples include polyolefin resins such as pentene, and polyamide resins such as nylon 6, nylon 6.12, nylon 6.66, nylon 6.9, nylon 6.12, nylon 12, nylon 6.4, and amorphous polyamide. Can be.

In laminating the EVOH layer (A) and the thermoplastic resin layer (B), a co-extrusion method such as a T-die method and an inflation method, a blow molding method, a co-injection method, a dry lamination method A known method such as a solution coating method or the like can be employed, and is not particularly limited, but an example of the production method will be described below.

When the laminate of the present invention is produced by a co-extrusion method, the EVOH layer (A) and the thermoplastic resin layer (B)
And an ordinary method of laminating the layers with an adhesive resin therebetween. As the adhesive resin, a resin obtained by modifying a polyolefin resin such as polypropylene, polyethylene, or a copolymer of monomers copolymerizable with ethylene (vinyl acetate, acrylate ester, etc.) by adding maleic anhydride or the like is used. , The resin temperature of the EVOH layer (A) is 190
To 260 ° C., preferably 210 to 250 ° C., (A)
/ Adhesive resin / (B), (B) / Adhesive resin / (A) /
Adhesive resin / (B) Multi-layer co-extrusion molding equipment
A laminate having good film appearance is obtained. When a polyamide-based resin is used as the thermoplastic resin layer (B), the adhesive resin may not be required when bonding with the EVOH layer (A).

Further, the above-mentioned laminate can be obtained by using a dry lamination method, an extrusion lamination method or the like. That is, the above (A) and (B)
Each layer is formed into a film in advance by an extruder or the like, and the respective layers are dry-laminated with a urethane-based adhesive resin or the like. Further, in order to obtain a laminate by a solution coating method, the above EVOH solution is used, and a mixed solvent of water and alcohol is used as a solvent at that time, and the amount of water is 30 to 70% by weight (the amount of alcohol is 70 to 30% by weight), preferably 40 to 6%.
The amount is 0% by weight (the amount of alcohol is 60 to 40% by weight). If the amount is less than 30% by weight or more than 70% by weight, a uniform solution is hardly obtained and the coating film becomes opaque.
Alcohols such as methanol, ethanol, n-
Propyl alcohol, iso-propyl alcohol, n-
Butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and the like,
n-Propyl alcohol and iso-propyl alcohol are preferably used.

The concentration of the EVOH in the EVOH solution is not particularly limited, and the EVOH can be applied in an arbitrary range and is usually preferably about 0.5 to 25% by weight. 20% by weight is most preferred. Such EV
In coating the OH solution on the surface of the substrate, a known method can be adopted, for example, a gravure coater, a reverse roll coater, an air knife coater, a spray, a brush coating, a bar coater, and the like. A reverse roll coater is used. After that, the substrate is heated and dried to form a coating layer of EVOH on the surface of the substrate. Ideally, when the EVOH solution is applied to paper and dried, the solution viscosity at the time of application of the EVOH solution and the subsequent The drying temperature may be arbitrarily selected from a range where the solution viscosity at the time of applying the EVOH solution is 50 to 1000 cps and a subsequent drying temperature is around 80 to 120 ° C. The time for drying is not particularly limited, but is usually appropriately selected from the range of 10 seconds to 10 minutes (more preferably, 30 seconds to 5 minutes). The thickness (after drying) of the EVOH coating layer is not particularly limited, but is preferably 1 to 50 μm, particularly preferably 2 to 10 μm.
Of Chakuryou (attached amount after drying) is preferably from 1 to 50 g / m ^2, more preferably from 2 to 10 g / m ^2.

In applying the EVOH solution, an adhesive (anchor coat) layer is usually provided on the surface of the substrate. As such an adhesive, an organic titanium-based adhesive, 2
Liquid-reactive polyurethane adhesives, polyester / isocyanate-based adhesives and the like can be mentioned, and two-liquid reactive polyurethane-based adhesives are preferably used.

In such a laminate, the thickness of each layer cannot be determined unconditionally depending on the type of the laminate. However, in the case of a film packaging material for boil sterilization or retort sterilization,
(A) is 5 to 250 μm, preferably 10 to 100 μm
m, more preferably 10 to 80 μm, and (B)
It is 8 to 200 μm, preferably 10 to 100 μm, and more preferably 12 to 50 μm. Thus, a laminate in which the EVOH layer is formed on the surface of the base material (on which the primer layer and the adhesive resin layer are provided if necessary) is obtained. The heat of fusion (ΔH) of 1st Run measured by a scanning calorimeter (DSC) satisfies the following formula (1).
t) The most characteristic feature is that it comprises a saponified layer of an ethylene-vinyl acetate copolymer having 20 to 50 mol% and a saponification degree of 90 mol% or more. ΔH (J / g) ≧ 100−0.55 · Et (1) (Et represents ethylene content (mol%))

That is, when the heat of fusion (ΔH) of the 1st Run of the EVOH layer formed on the surface of the base material measured by a differential scanning calorimeter (DSC) is smaller than (100−0.55 · Et), The antifouling property, chemical resistance, water resistance, etc. are insufficient, and it is impossible to expect the effects of the present invention. The method for obtaining the EVOH layer satisfying the above conditions is not particularly limited, and includes a method of rolling the surface of the EVOH layer of the laminate with a heating roller, a method of heating the surface of the EVOH layer with a flame, a heating wire, or the like; Body) at a constant temperature, and generally, EVO.
It is practical to heat the H layer (laminate) at a constant temperature, and such a method will be described in detail.

The heat treatment temperature is selected from the range of 60 to 180 ° C., and the heat treatment time is also selected from the range of 0.5 to 1500 minutes (further, 1 to 600 minutes). ) And (3) are preferably subjected to heat treatment. 230-1.6 Et ≧ T ≧ 80−0.5 · Et (2) t ≧ exp (20,000 / T ² ) (3) (where Et is the ethylene content (mol%), T represents a heat treatment temperature (° C.), and t represents a heat treatment time (minutes). That is, in the above formula (2), T> 230−1.6 Et
When T <80−0.5 · Et, the barrier properties and water resistance of gas and the like become insufficient at the time of T <80−0.5 · Et. e
Also, when xp (20,000 / T ² ), the barrier properties of gas and the like and the water resistance become insufficient, which is not preferable.

Each layer of the laminate of the present invention contains a plasticizer, a stabilizer, a surfactant, a crosslinkable substance (epoxy compound, polyvalent metal, inorganic or organic polybasic acid or salt thereof), filler,
Coloring agent, fiber as reinforcing material (glass fiber, carbon fiber, etc.), matting agent (talc, silica powder, polyethylene,
Resin fine particles such as polyurethane) may be blended as long as the effects of the present invention are not impaired. The laminate of the present invention thus obtained is, in addition to (A) / (B),
(B) / (A) / (B), (B) / (A) / (B ′),
(B) / (A) / (B) / (B '), (B) / (A) /
(B ′) / (B ″), etc., and when the obtained laminate of the present invention is used as a film wrapping material, particularly a film wrapping material for boil sterilization or retort sterilization treatment, Features are exhibited. Examples of uses of the film packaging material include lid materials, pouches, vacuum packaging, skin packs, deep drawing packaging, and rocket packaging.

For the lid material of the present invention, a method of heat-sealing a container made of a thermoplastic resin layer such as polypropylene laminated with an EVOH layer by a heat sealing method is suitably used. The lid material of the present invention is excellent in transparency and can be opened while checking the contents. The pouches of the present invention are used in the form of a three-side seal, a four-side seal, a pillow, a gusset, a standing pouch, and the like.

The laminate of the present invention can exhibit excellent properties as a container such as a cup or a tray in addition to the above-mentioned film packaging. As a method for forming a container, a sheet is formed by co-extrusion molding, heat-softened, and then formed into a predetermined container by a vacuum forming method, a plug assist forming method, a pressure forming method, a CD method, or an injection molding method. And any other method. The laminate of the present invention can be formed into a tube or bottle by blow molding.

The container using the laminate of the present invention in the form of a lid material, a pouch, a tray, a cup or a bottle or a tube can be subjected to a hot water heating treatment known as a retort sterilization treatment or a boil sterilization treatment. For the retort treatment, various methods such as a recovery method, a displacement method, a steam method, a shower method, and a spray method are employed. Containers such as lids, pouches, trays, cups or bottles and tubes made of the laminate of the present invention are filled with foods such as soup, pork juice, meat sauce, oden, pilaf, udon, sweet and sour pork, hamburger steak, cooked curry and the like. In this state, the retort sterilization treatment can be performed.

[0021]

EXAMPLES The method of the present invention will be specifically described below with reference to examples. In the following, “%” means on a weight basis unless otherwise specified. Example 1 Ethylene content 35 mol%, degree of saponification 99.8 mol%,
MI (melt index) = 3.0 (210 ° C., 21
(60 g load) as an EVOH layer (A), while a thermoplastic resin layer (B) and a polyamide resin layer (B1) containing 90% by weight of a nylon-6 resin and 10% by weight of an amorphous polyamide and an ethylene graft. (B1) / (A) / adhesive resin (carboxylic acid-modified polypropylene) / (B2) [15 μm / 15 μm / 10 μm / 4 from a T-die set at a temperature of 250 ° C. using a mold-type polypropylene layer (B2).
0 μm thickness configuration] and cooled by a chill roll that circulates cooling water to form a flat 3
A layer laminate was produced. The heat of fusion (ΔH) of the EVOH layer in the laminate measured by a differential scanning calorimeter (DSC) was 78 J / g.

Next, the obtained laminate was passed through a hot-air dryer at 110 ° C. for 5 minutes to perform a heat treatment to obtain a laminate of the present invention. Heat of fusion (ΔH) of 1st Run measured by differential scanning calorimetry (DSC) of the EVOH layer of such a laminate
Is 87 J / g, and (ΔH) is 100−0.55 · Et = 100−0.55 calculated from the above equation (1).
× 35 = 80.75, which satisfied the expression (1). The heat of fusion (ΔH) was measured by peeling the EVOH layer from the laminate, and the same applies hereinafter. The heat treatment conditions at this time [heat treatment temperature (T) = 110 ° C., heat treatment time (t) = 10 minutes]
The expressions (2) and (3) were also satisfied.
Using the obtained laminate, the boil resistance was evaluated as follows. (Boil resistance) The laminated body obtained above was subjected to 9
After performing the boil sterilization treatment at 5 ° C. for 30 minutes, the appearance (whether whitened), the haze value, and the gas barrier property of the laminate after standing at room temperature for 30 minutes were measured.

Example 2 A three-layer laminate was obtained in the same manner as in Example 1, except that the ethylene content of EVOH was changed to 45 mol%. Differential scanning calorimeter (DSC) of the EVOH layer in such a laminate
The heat of fusion (ΔH) of 1stRun measured at 74 J
/ G. Next, the obtained laminate was passed through a hot-air dryer at 110 ° C. for 5 minutes to perform a heat treatment to obtain a laminate of the present invention, and the boil resistance was similarly examined. The heat of fusion (ΔH) of the 1st Run measured by a differential scanning calorimeter (DSC) of the EVOH layer of such a laminate is 77 J / g, and the (ΔH) is 100-0.
55 · Et = 100−0.55 × 45 = 75.25, thereby satisfying the expression (1). In this case, the heat treatment conditions [heat treatment temperature (T) = 110]
° C, heat treatment time (t) = 10 minutes] also satisfied the above expressions (2) and (3).

Example 3 Boil resistance was examined in the same manner as in Example 1 except that the heat treatment was performed at 150 ° C. for 4 minutes. In this case, the heat treatment conditions [heat treatment temperature (T) = 1]
50 ° C., heat treatment time (t) = 4 minutes] also satisfied the expressions (2) and (3).

Example 4 Boil resistance was examined in the same manner as in Example 1, except that the heat treatment was performed at 70 ° C. for 90 minutes. In this case, the heat treatment conditions [heat treatment temperature (T) = 7
0 ° C., heat treatment time (t) = 90 minutes] also satisfied the expressions (2) and (3).

Example 5 In Example 1, the laminate was prepared as follows: (A) / (B1) / adhesive resin (carboxylic acid-modified polypropylene) / (B2) [15 μm
m / 15 μm / 10 μm / 40 μm thickness configuration], and the boil resistance was similarly examined.

Example 6 The EVOH of Example 1 was dissolved in water / isopropyl alcohol (mixing weight ratio = 1/1) to form a 12% by weight solution, and anchored to one surface of a stretched nylon film (B1) having a thickness of 14 μm. Thickness after drying is 5 μm (6 g / m ² after drying) via a treating agent (Nippon Synthetic Chemical Industry Co., Ltd., Nichia Polyester LP033, 0.5 g / m ² after drying).
The EVOH (A) is applied so that a non-stretched polypropylene film (B2) having a thickness of 25 μm is dry-laminated through the same anchoring agent as described above to obtain (B1) / (A) / A laminate of (B2) was obtained. The heat of fusion (ΔH) of the first run of the EVOH layer in the laminate measured by a differential scanning calorimeter (DSC) was 77 J / g. Next, the obtained laminate was passed through a hot-air dryer at 110 ° C. for 5 minutes to perform a heat treatment to obtain a laminate of the present invention, and the boil resistance was similarly examined. EV of such a laminate
1st of OH layer measured by differential scanning calorimeter (DSC)
The heat of fusion (ΔH) of Run is 86 J / g,
H) is 100-0.55 calculated from the above equation (1).
Et = 100−0.55 × 35 = 080.75, which satisfied the expression (1). The heat treatment conditions (heat treatment temperature (T) = 110 ° C., heat treatment time (t) = 10 minutes) at this time also satisfied the above expressions (2) and (3).

Example 7 The same procedure as in Example 6 was carried out except that EVOH was pre-molded to a thickness of 15 μm.
m EVOH film (heat of fusion (ΔH) of 1st Run measured by differential scanning calorimeter (DSC) is 78 J / g)
As a stretched nylon film with a thickness of 14 μm (B1)
Then, the unstretched polypropylene film (B2) having a thickness of 25 μm was dry-laminated through the same anchoring agent as above to obtain a laminate of (B1) / (A) / (B2). Next, the obtained laminate was passed through a hot-air dryer at 110 ° C. for 5 minutes to perform a heat treatment to obtain a laminate of the present invention, and the boil resistance was similarly examined. EVO of such a laminate
1stR measured by differential scanning calorimeter (DSC) of layer H
The heat of fusion (ΔH) of un is 86 J / g, which is (ΔH)
Is 100−0.55 · E calculated from the above equation (1).
It was larger than t = 100−0.55 × 35 = 080.75, thereby satisfying the expression (1). Further, the heat treatment conditions (heat treatment temperature (T) = 110 ° C., heat treatment time (t) = 10 minutes) at this time are also the same as those in the above formula (2) and (3).
The expression was also satisfied.

Comparative Example 1 In Example 1, the heat treatment of the laminate was not performed (the heat of fusion was 78 J / g, and 100−0.55 · Et = 100−0.05 calculated from the above equation (1)). 55 × 35
= Smaller than 80.75 and deviates from the relationship of equation (1)) to obtain a laminate, which was similarly evaluated. Table 1 shows the evaluation results of the examples and the comparative examples.

[0030]

[Table 1] Appearance haze valueGas barrier properties Transmittance α Transmittance β Example 1 No whitening 4.1 0.7 0.8 〃 2 No whitening 3.6 2.1 2.1 〃 3 No whitening 3.9 0.7 0.7 ４ 4 No whitening 3.2 0.7 0.7〃5 No whitening 6.1 0.7 0.9〃6 No whitening 2.5 1.3 1.5〃 7 No whitening 3.6 0.7 0.7 Comparative Example 1 Whitening occurred 16.1 0.8 13.8  Note) Permeability α is the oxygen permeability before boil treatment (cc / m^TwoDay • atm), and the transmittance β indicates the oxygen permeability after boil treatment (same as above).

Example 8 Using the laminates obtained in Examples 1 to 7 as lids, heat bonding was carried out using a heat sealer with a polypropylene layer as the inner surface, in a cup-shaped container made of water containing water. The obtained retort container is steam-sterilized (Yamato Scientific Co., Ltd.)
Autoclave SM-31) at 121 ° C for 30 minutes. Immediately after the retort treatment, the lid film was transparent and had a good appearance without corrugations.

Example 9 The laminates obtained in Examples 1 to 7 were heat-sealed in a pouch shape, water was poured therein, and the mouth portions were heat-sealed. This was subjected to the same retort sterilization treatment as in Example 8. Immediately after the retort treatment, the pouch was transparent and had good appearance without any wave pattern.

[0033]

The laminate of the present invention has a differential scanning calorimeter (D
Since the heat of fusion measured in SC) uses a specific EVOH layer, it has excellent boil resistance and is particularly useful for packaging materials for sterilizing boil or retort.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B32B 27/34 B32B 27/34 B65D 81/24 B65D 81/24 J

Claims (8)

[Claims] 1. An ethylene content (Et) satisfying the following formula (1) having an ethylene content (Et) of 20 to 50 mol% and a saponification degree of 90 mol%, wherein the heat of fusion (ΔH) of the first run measured by a differential scanning calorimeter (DSC) is: A laminate comprising at least one saponified ethylene-vinyl acetate copolymer layer (A). ΔH (J / g) ≧ 100−0.55 · Et (1) (Et represents ethylene content (mol%)) 2. The laminate according to claim 1, wherein the saponified ethylene-vinyl acetate copolymer layer (A) is heat-treated under the conditions satisfying the following formulas (2) and (3). . 230-1.6 Et ≧ T ≧ 80−0.5 · Et (2) t ≧ exp (20,000 / T ² ) (3) (where Et is the ethylene content (mol%), T represents a heat treatment temperature (° C.), and t represents a heat treatment time (minutes). 3. The laminate according to claim 1, wherein the thermoplastic resin layer (B) is laminated. 4. The laminate according to claim 3, wherein the thermoplastic resin layer (B) is any one of a polyolefin resin layer, a polyamide resin layer, a polyester resin layer, and a polystyrene resin layer. 5. The laminate according to claim 1, wherein the thickness of the saponified ethylene-vinyl acetate copolymer layer (A) is 1 to 200 μm. 6. The laminate according to claim 1, wherein the laminate has at least a (B) / (A) / (B) laminate structure. 7. The laminate according to claim 1, which is used for a multilayer film for sterilizing boiling or retort. 8. The laminate according to claim 1, wherein the laminate is used for a container, a pouch, or a lid for sterilizing boiling or retort.