JP7404752B2 - Laminates for highly resistant packaging materials - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laminate forming a packaging material having excellent contents resistance and a method for manufacturing the same.

Conventionally, packaging materials used to package foods, pharmaceuticals, etc. have been used to suppress the deterioration and decay of the contents and to maintain their functions and properties by using gases such as water vapor, oxygen, and other gases that alter the quality of the contents. A laminate having gas barrier properties that blocks the intrusion of gas is generally used.

In the case of a laminate, a urethane two-component curing adhesive for dry lamination is generally used as the adhesive for forming the adhesive layer, even when used as a durable packaging material. However, many of the contents packaged with packaging materials contain alkaline substances, fragrances, surfactants, high-boiling organic solvents, etc., and packaging these contents may have an adverse effect on the adhesive layer for dry lamination. This may lead to a decrease in the laminate strength of the laminate, resulting in peeling.

In other words, in the case of packaging materials that require content resistance, the content resistance is required to prevent delamination (peeling) of the package due to the contents, but in general dry lamination, the lamination strength between the aluminum foil and the sealant layer is There has been a problem in that the amount decreases over time, resulting in delamination (peeling).

In order to cope with such a situation, various improvements have been made to adhesives used in lamination processing, and adhesives that are resistant to alcohol have been proposed (for example, Patent Document 1). Furthermore, as an adhesive, a laminate using maleic anhydride graft-modified polyethylene has been proposed as an adhesive that has excellent adhesion to a wide variety of transparent barrier films and aluminum foil, and has excellent content resistance. However, maleic anhydride graft-modified polyethylene has a problem of poor extrusion processability due to large neck-in during extrusion processing.

Patent No. 5915710

An object of the present invention is to provide a laminate that can be applied to packaging materials for contents that are subject to strong attacks. In addition, the maleic anhydride-grafted polyethylene used in the laminate, which has excellent adhesion to aluminum and a wide variety of transparent barrier films, has a high melt flow rate (hereinafter abbreviated as MFR) during extrusion processing. The objective is to solve the problem of poor extrusion processability due to large neck-in. Another object of the present invention is to solve the problem that wrinkles may appear in the laminate due to the need for heat treatment at high temperatures in order to develop adhesive strength.

In order to solve the above problems, the present invention includes a base material layer, an aluminum layer, an adhesive layer, and a thermoplastic resin layer that are laminated in this order from the surface side, the adhesive layer containing at least acid-modified polyethylene and low-density polyethylene, and , It is a melt coextrusion layer with an acid-modified polyethylene layer on the aluminum layer side and a low-density polyethylene layer on the thermoplastic resin layer side, and is sandwich laminated with the base material layer, aluminum layer, and thermoplastic resin layer. A highly resistant laminate for packaging material is provided.

According to the above-mentioned laminate for highly resistant packaging materials, acid-modified polyethylene and low-density polyethylene are used as adhesive layers between the aluminum layer and the thermoplastic resin layer, which are affected by the contents, and acid-modified polyethylene is used on the aluminum layer side. Content resistance can be obtained by arranging the layers, and neck-in during melt coextrusion can be reduced by arranging the low-density polyethylene layer on the thermoplastic resin layer side of the adhesive layer. It is possible to obtain a highly workable and highly durable laminate for packaging materials.

In the above-mentioned laminate for highly durable packaging materials, it is preferable that the acid-modified polyethylene layer is made of maleic anhydride graft-modified polyethylene, and the thermoplastic resin layer is made of linear low-density polyethylene. Content resistance and adhesion can be further improved, and processability can be further improved.

In the above-mentioned laminate for highly resistant packaging materials, the maleic anhydride graft-modified polyethylene exhibits a first melting point peak at 90°C to 100°C in differential scanning calorimetry, and continues from 50°C to the low temperature side by 20°C or more. It is preferable that the composition contains a component exhibiting a second melting point peak. Adhesive strength is developed at lower temperatures, and wrinkles can be suppressed during heat treatment.

In the above laminate for highly resistant packaging materials, the maleic anhydride graft modified polyethylene has a maleic anhydride graft ratio of 0.1 wt% or more and 1.0 wt% or less, and a density of 0.88 g/cm3 or more and 0.90 g/cm3 ^or more. cm ³ or less, and the melt flow rate is preferably 8.5 or more and 12.0 or less. When forming the adhesive layer, it is possible to form a film with higher smoothness.

In the laminate for highly resistant packaging materials, the maleic anhydride graft-modified polyethylene exhibits a broad first melting point peak near 100°C in differential scanning calorimetry, and two peaks between 110°C and 130°C. It is preferable to include a component exhibiting a second melting point peak with continuous peaks.

In the laminate for highly resistant packaging materials according to the preceding item, the maleic anhydride graft modified polyethylene has a maleic anhydride graft ratio of 0.1 wt% or more and 1.0 wt% or less, and a density of 0.90 g/cm ³ or more and 0.92 g /cm ³ or less, and the melt flow rate is preferably 5.5 or more and 7.5 or less. When forming the adhesive layer, it is possible to form a film with higher smoothness.

In the above-mentioned laminate for highly durable packaging materials, it is preferable that the layer thickness ratio of the maleic anhydride graft-modified polyethylene and the melt coextruded low-density polyethylene in the adhesive layer is 25:75 to 75:25. Neck-in can be effectively reduced, and the amount of expensive maleic anhydride graft-modified polyethylene used can be suppressed.

In the above-mentioned laminate for highly durable packaging materials, it is preferable that the linear low-density polyethylene has a density of 0.915 g/cm ³ or more and 0.940 g/cm ³ or less.

In the above-mentioned laminate for highly durable packaging materials, the low-density polyethylene has a density of 0.910 g/cm ³ or more and 0.930 g/cm ³ or less, and a melt flow rate of 6.0 or more and 8.5 or less. It is preferable to do so.

The present invention also provides a method for producing a laminate in which a base material layer, an aluminum layer, an adhesive layer, and a thermoplastic resin layer are laminated in this order, the adhesive layer being an acid-modified polyethylene layer on the aluminum layer side, and a thermoplastic resin layer being laminated on the aluminum layer side. A low-density polyethylene layer is arranged on the resin layer side, and the layer thickness ratio is 25:75 to 75:25 by melt coextrusion, and the base material layer, the aluminum layer, and the thermoplastic This is a method for producing a highly resistant packaging material laminate, which is characterized by sandwich laminating the present invention with a resin layer.

According to the present invention, it is possible to obtain a highly resistant packaging material laminate that has high content resistance and can be applied to packaging materials for content that is subject to strong attacks on packaging materials, such as hair coloring agents, hypochlorous acid water, and fragrances. . Furthermore, by making the adhesive layer contain acid-modified polyethylene and low-density polyethylene, it is possible to reduce neck-in during melt coextrusion lamination, and it is also possible to suppress the occurrence of wrinkles during heat treatment, improving processability. can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of one form of the laminated body for highly durable packaging materials of this invention. FIG. 2 is a diagram showing an example of DSC measurement of maleic anhydride graft-modified polyethylene. It is a figure which shows the DSC measurement example of another maleic anhydride graft modified polyethylene. FIG. 4 is an enlarged view of the DSC measurement example of FIG. 3;

Embodiments of the present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the embodiments described below.

FIG. 1 is a schematic cross-sectional view of one form of the highly durable laminate for packaging materials of the present invention. The laminate 1 of this embodiment includes a base material layer 2, a printing ink layer 3, an adhesive layer 4, an aluminum layer 5, a maleic anhydride graft-modified polyethylene layer 6 which is an acid-modified polyethylene layer, and a low-density polyethylene layer 7. It has a structure in which an adhesive layer 9 and a linear low-density polyethylene layer 8, which is a thermoplastic resin layer, are sequentially laminated and bonded.

Here, the maleic anhydride graft modified polyethylene layer 6 and the low density polyethylene layer 7 are laminated by melt coextrusion. The base material layer 2, printing ink layer 3, adhesive layer 4, aluminum layer 5, and linear low-density polyethylene layer 8 are laminated and bonded together by sandwich lamination.

Maleic anhydride graft-modified polyethylene is preferably used in the present invention as one of acid-modified polyethylenes. Maleic anhydride graft-modified polyethylene is polyethylene obtained by graft-modifying polyethylene with maleic anhydride. As shown in FIG. 2, the maleic anhydride graft-modified polyethylene used in the present invention exhibits a first melting point peak at 90° C. to 100° C. when differential scanning calorimetry (DSC measurement) is performed, and It is preferable to include a component exhibiting a continuous second melting point peak of 20°C or more on the low temperature side from 50°C.

By having the second melting point peak on the low temperature side, adhesiveness is developed from low temperatures, so it is possible to suppress the generation of wrinkles during heat treatment.

Furthermore, as shown in FIG. 3 and a partially enlarged FIG. It is also preferable to include a component that exhibits a first melting point peak and a second melting point peak with two consecutive peaks between 110°C and 130°C.

Further, the maleic anhydride graft ratio of the maleic anhydride graft-modified polyethylene is preferably 0.1 wt% or more and 1.0 wt% or less. If it is less than 0.1 wt%, it tends to lead to a decrease in laminate strength, and if it exceeds 1.0 wt%, water adsorption increases, leading to foaming, which can cause high costs and yellowing. In addition, it tends to stick to the extruder and die metal, which may cause burns and reduce workability.

Further, it is preferable that the layer thickness ratio of the maleic anhydride graft-modified polyethylene and the low-density polyethylene melt-coextruded in the adhesive layer 9 is 25:75 to 75:25. If the ratio of maleic anhydride graft-modified polyethylene 6 is less than 25:75, there is a possibility that the adhesiveness may become unstable. Furthermore, if the ratio of low density polyethylene 7 is less than 75:25, there is a risk that the effect of improving neck-in may be lost. Furthermore, the ratio of maleic anhydride graft-modified polyethylene increases too much, and the price thereof is about four times higher than that of general extrusion resins, which is disadvantageous in terms of cost.

As the resin forming the base layer 2, polyester resins, polyamide resins, polyolefin resins, etc. that are commonly used for this type of packaging material may be used. For example, polyester resins include polyethylene terephthalate (PET), Examples include polyester resins such as polyethylene naphthalate (PEN), polyethylene-2,6-naphthalate, polybutylene terephthalate, and copolymers thereof.

Although the printing ink layer 3 is not essential, when it is necessary to display information on a laminate or a pouch, it can be provided by printing with a known gravure ink or the like, although this is not particularly limited.

Examples of the resin constituting the thermoplastic resin layer include linear low-density polyethylene, polyethylene, polypropylene, epoxy resin (EP), ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, and ethylene-methacrylic acid. Examples include ester copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, and metal crosslinked products thereof. Among these, linear low density polyethylene is preferred. As these thermoplastic resins, one type may be used alone, or two or more types may be used in combination.

The present invention will be explained in more detail below using Examples. The results of each Example and Comparative Example are summarized in Tables 1 and 2.

<Example 1>
(laminate)
・Base material: Polyester film (thickness 12 μm, FE2001, manufactured by Futamura Chemical Co., Ltd.) ・Adhesive: Main agent (A525, manufactured by Mitsui Chemicals, Inc.), curing agent (A52, manufactured by Mitsui Chemicals, Inc.) ・Aluminum Layer: Aluminum base material (thickness 7 μm, 1N30, manufactured by Toyo Aluminum Co., Ltd.)
・Adhesive layer: Maleic anhydride graft modified polyethylene (M605, manufactured by Mitsubishi Chemical Corporation, first melting point peak 98°C, second melting point peak 50°C, density 0.88 g/cm ³ , MFR 10 g/cm ³ )
: Low density polyethylene (LC600A, manufactured by Japan Polyethylene Co., Ltd., melting point 106°C, density 0.918g/cm ³ , MFR 7.0g/cm ³ )
・Thermoplastic resin layer: (linear low-density polyethylene, MZ434, manufactured by Tamapoly Co., Ltd., film thickness 80 μm)
- The maleic anhydride graft modified polyethylene and low density polyethylene of the adhesive layer were each melt-coextruded to a thickness of 10 μm, and the base material, adhesive, aluminum layer, adhesive layer, and thermoplastic resin layer were sandwich laminated.
- Confirmation of neck-in: A T-die width of 360 mm (air gap 120 mm) was used during melt coextrusion, and the resin width after extrusion was 303 mm. As a reference, when low density polyethylene was not used in the adhesive layer and a single layer of M605 was used, the resin width after extrusion was 253 mm, and it was confirmed that neck-in can be improved by melt coextruding low density polyethylene.
- After lamination, it was heated at 140° C. for 15 seconds so as to be wrapped around a heater roll to produce a laminate.

(pouch)
The produced laminate was sealed at the end to form a three-sided pouch, and a storage test was conducted by filling the pouch with the following contents.
・Contents: 1 hair color ・Storage conditions: Temperature 50°C, humidity not controlled.
・Storage period: 4 conditions: 2 weeks, 1 month, 2 months, and 3 months.

(evaluation)
A test sample with a width of 15 mm was cut out from the pouch after storage, and the adhesive strength (based on JIS K7127) between the aluminum layer and the adhesive layer was measured at a tensile speed of 300 m/min.
・Measuring device: RTF-1250 (manufactured by A&D Co., Ltd.)

<Example 2>
- Samples were prepared and evaluated in the same manner as in Example 1, except that the content was fragrance.

<Example 3>
- Sample preparation and evaluation were performed in the same manner as in Example 1, except that the content was hypochlorite.

<Example 4>
A laminate was produced in the same manner as in Example 1 except that the adhesive layer had the following configuration.
・Adhesive layer: Maleic anhydride graft modified polyethylene (first melting point peak 108°C, second melting point peak 122°C, density 0.91g/cm ³ , MFR 6.5g/cm ³ )
: Low density polyethylene (LC600A, manufactured by Japan Polyethylene Co., Ltd., melting point 106°C, density 0.918g/cm ³ , MFR 7.0g/cm ³ )

(pouch)
The produced laminate was sealed at the end to form a three-sided pouch, and a storage test was conducted by filling the pouch with the following contents.
・Contents: Acetone ・Storage conditions: Temperature 50℃, humidity not controlled.
・Storage period: 1 week.

(evaluation)
-Evaluation was performed in the same manner as in Example 1.

<Comparative example 1>
- A three-way pouch similar to that in Example 1 was prepared except that the adhesive layer was an ordinary adhesive for dry laminate, and one hair color was filled in the pouch, and the pouch was stored and evaluated in the same manner as in Example 1.

<Comparative example 2>
- A three-way pouch similar to that in Example 4 was prepared except that the adhesive layer was a normal adhesive for dry lamination, and the pouch was filled with acetone and stored and evaluated in the same manner as in Example 4.

As is clear from Tables 1 and 2, in the laminate of the present invention, no decrease in adhesive strength was observed even after storage of contents with strong attack, and the results were good. On the other hand, in the comparative example, the adhesive strength decreased significantly.

1... Laminate 2... Base material layer 3... Printing ink layer 4... Adhesive layer 5... Aluminum layer 6... Maleic anhydride graft modified polyethylene layer 7... Low density Polyethylene layer 8...Linear low density polyethylene layer 9...Adhesive layer

Claims (8)

A base material layer, an aluminum layer, an adhesive layer, and a thermoplastic resin layer are laminated in this order from the surface layer side, the adhesive layer containing at least acid-modified polyethylene and low-density polyethylene, and an acid-modified polyethylene layer on the aluminum layer side, It is a melt coextrusion layer with a low density polyethylene layer placed on the thermoplastic resin layer side, and is sandwich laminated with a base material layer, an aluminum layer, and a thermoplastic resin layer.
The acid-modified polyethylene layer is made of maleic anhydride graft-modified polyethylene, and the thermoplastic resin layer is made of linear low-density polyethylene,
A laminate for highly durable packaging material, characterized in that the adhesive layer has a layer thickness ratio of melt coextrusion of maleic anhydride graft modified polyethylene and low density polyethylene of 25:75 to 75:25 . The maleic anhydride graft-modified polyethylene contains a component that exhibits a first melting point peak at 90° C. to 100° C. and a second melting point peak continuous from 50° C. to the low temperature side by 20° C. or more in differential scanning calorimetry. The highly durable laminate for packaging material according to claim 1 . The maleic anhydride graft modified polyethylene has a maleic anhydride graft ratio of 0.1 wt% or more and 1.0 wt% or less, a density of 0.88 g/cm ³ or more and 0.90 g/cm ³ or less, and a melt flow rate of The highly durable laminate for packaging material according to claim 1 or 2, wherein the laminate has a resistance of 8.5 or more and 12.0 or less. The maleic anhydride graft-modified polyethylene exhibits a broad first melting point peak near 100°C in differential scanning calorimetry, and a second melting point peak with two consecutive peaks between 110°C and 130°C. The laminate for highly resistant packaging material according to claim 1 , characterized in that it contains a component. The maleic anhydride grafting ratio of the maleic anhydride graft modified polyethylene is 0.1 wt% or more and 1.0 wt% or less, the density is 0.90 g/ ^cm3 or more and 0.92 g/ ^cm3 or less, and the melt flow rate is The highly durable laminate for packaging material according to claim 1 or 4, wherein the laminate has a resistance of 5.5 or more and 7.5 or less. The laminate for highly durable packaging materials according to any one of claims 1 to 5 , wherein the linear low-density polyethylene has a density of 0.915 g/cm ³ or more and 0.940 g/cm ³ or less. . 7. The low density polyethylene has a density of 0.910 g/cm ³ or more and 0.930 g/cm ³ or less, and a melt flow rate of 6.0 or more and 8.5 or less. The highly resistant laminate for packaging materials according to any one of the above. A method for producing a laminate in which a base material layer, an aluminum layer, an adhesive layer, and a thermoplastic resin layer are laminated in this order, the adhesive layer having an acid-modified polyethylene layer on the aluminum layer side and a low-density polyethylene layer on the thermoplastic resin layer side. Each polyethylene layer is arranged and formed by melt coextrusion so that the layer thickness ratio is 25:75 to 75:25, and sandwich laminated with the base material layer, the aluminum layer, and the thermoplastic resin layer. A method for producing a laminate for highly resistant packaging material, characterized by laminating the laminate.

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