JP2868802B2 - Multi-layer packaging material laminate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a laminate excellent in sealability and interlayer adhesion. More specifically, the present invention relates to a laminate suitable for forming a heat seal layer of a substrate such as paper, aluminum, and polyester.

[Conventional technology and its problems] Multilayer paper containers are widely used as containers for various fruit drinks, lactic acid bacteria drinks, and the like. Such a paper container is used by laminating a heat-sealable resin layer on an inner layer of paper, since heat sealing is performed at the time of packaging. On this occasion,
In order to improve gas barrier properties and light-shielding properties, an aluminum foil layer may be formed on the inner layer of paper, and a heat-sealing resin layer may be formed on the inner layer. In any case, an olefin-based polymer has been mainly used as such a heat-sealing resin. The olefin polymer has not only excellent heat sealing properties but also excellent flexibility, and has excellent features such as no pinholes even when subjected to bending. However, such a heat-sealing layer is also a layer that comes into direct contact with the contents such as food and drink, but in this case, the olefin-based polymer easily adsorbs aroma components, and depending on the type of the packaged product, the taste and aroma may be different. It had the disadvantage of changing.

On the other hand, polyethylene terephthalate (hereinafter referred to as PET) is excellent in scent retention, but poor in heat sealability, and is unsuitable for use as a resin for the inner layer of a paper container as described above. Modified PET, which contains a considerable amount of a copolymer component such as isophthalic acid, is superior to PET in terms of heat sealability, but is inferior in flexibility, pinhole resistance, etc. It has been difficult to use it as a resin for the inner layer of a container.

[Problems to be Solved by the Invention] The present inventors make use of the excellent heat sealability and fragrance retention properties of the modified PET, and modify the modified PE such as pinhole resistance.
A heat seal material with improved defects of T was studied. As a result, it has been found that the above-mentioned drawback is improved by forming a laminate having a specific three-layer structure, and the laminate is suitable as a material to be laminated on paper, aluminum, or a plastic film such as nylon or polyethylene terephthalate.

Therefore, an object of the present invention is particularly suitable for packaging foods and beverages having an aroma component, and is easy to be laminated on paper, aluminum, a plastic film, and the like, and is therefore excellent in heat sealability, pinhole resistance, and fragrance retention. It is an object of the present invention to provide a novel laminate capable of forming a paper container, a flexible packaging bag, and the like.
It is another object of the present invention to provide a laminate excellent in interlayer adhesion that can be easily produced by a coextrusion method.

[Means for Solving the Problems] The present invention provides (A) a modified polyethylene terephthalate layer containing 5 to 20 mol% of a copolymer component, (B) (B ₁ ) a partially or entirely unsaturated carboxylic acid or an anhydride thereof. low crystalline or an ethylene · alpha-olefin copolymer 75 to 95 wt% of amorphous grafted modified with objects, (B ₂₎ an ethylene copolymer composition layer comprising a tackifying resin 5 to 25 wt% And (C) a multilayer packaging material laminate in which a crystalline olefin-based polymer layer is formed in order, the (A) layer being a heat seal layer, and the (C) layer being a laminate layer on a substrate. About.

In the present invention, the layer which directly contacts food or drink when used as a packaging material, that is, the modified PET which becomes the heat seal layer, contains, in addition to the ethylene glycol unit and the terephthalic acid unit, a copolymer component of 5 to 20 mol%, Preferably 5
It is copolymerized at a ratio of 15 mol%. The copolymerization component may be contained on either side of the ethylene glycol unit and the terephthalic acid unit, or both may contain a copolymerization component. Examples of such a copolymerization component include isophthalic acid and phthalic acid. 2,6-naphthalenedicarboxylic acid, aromatic carboxylic acids such as p-oxybenzoic acid, adipic acid, sebacic acid, aliphatic or alicyclic carboxylic acids such as cyclohexanedicarboxylic acid, propylene glycol, 1,4- Examples thereof include diols such as butanediol, 1,4-cyclohexanedimethanol, diethylene glycol, and triethylene glycol. Among these copolymer components, isophthalic acid, 1,4-cyclohexanedimethanol, diethylene glycol and the like are particularly preferred. These modified PETs have an intrinsic viscosity of 0.60
To 1.4 dl / g, particularly preferably 0.7 to 1.0 dl / g. When the amount of the copolymer component is less than 5 mol%, the heat sealing property is poor, and when heat sealing is performed, a material having high sealing strength cannot be obtained. If the amount of the copolymer component exceeds 20 mol%, flexibility, elongation and the like are not sufficient, and breakage or the like due to pinholes or bending tends to occur.

In the present invention, an ethylene copolymer composition layer (B) is formed adjacent to the modified PET layer (A). The ethylene copolymer composition is a low-crystalline or amorphous ethylene / α-olefin copolymer (B ₁ ) partially or entirely graft-modified with an unsaturated carboxylic acid or an anhydride thereof.
And a resin composition layer containing two components of a tackifying resin (B ₂ ) as essential components.

The ethylene / α-olefin copolymer in the component (B ₁ ) is of low crystallinity or non-crystallinity, and has a crystallinity by X-ray diffraction of 20% or less, preferably 15% or less. . The ratio of ethylene to α-olefin in the copolymer is such that the ethylene is 60 to 90 mol%, preferably 70 to 85 mol%, and the α-olefin is 10 to 40 mol%, preferably
15 to 30 mol%. Here, as the α-olefin,
Examples thereof include propylene, 1-butene, 1-hexene, 1-octyne, 1-decene, and 4-methyl-1-pentene, with propylene or 1-butene being particularly preferred.

Such ethylene / α-olefin copolymers are partially or entirely kraft-modified with unsaturated carboxylic acids or anhydrides thereof. That is, the graft-modified copolymer itself may be used, or a composition of the graft-modified copolymer and the unmodified copolymer may be used.
The ethylene / α-olefin copolymer in the composition of the graft-modified copolymer and the unmodified copolymer may be the same or different. Any case be (B ₁₎ the amount of grafted and are unsaturated carboxylic acid or its anhydride in component from 0.03 to 7% by weight, preferably to so as to present about 0.5 to 5 wt%. Here, examples of the unsaturated carboxylic acid or anhydride thereof include acrylic acid, methacrylic acid, fumaric acid, nadic acid, maleic anhydride, itaconic anhydride, nadic anhydride and the like.

By using the modified product as described above as the component (B ₁ ), a product having excellent adhesion to the modified PET layer can be obtained.
In addition, when the modified PET layer is used as the seal layer, a stable seal can be obtained, and the pinhole resistance is improved.
Such an effect cannot be obtained by using a modified crystalline polyolefin in which part or all of the crystalline polyolefin is graft-modified with an unsaturated carboxylic acid or an anhydride thereof instead of the component (B ₁ ). .

The component (B ₁ ) has a melt flow rate at 190 ° C. and a load of 2160 g of 0.3 to 50 g / 10 min, particularly 0.5 to 20 g.
It is preferable to use one with g / 10 minutes in terms of extrusion processability, optical characteristics, and the like.

(B ₂ ) Examples of the tackifying resin include aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, aromatic hydrocarbon resins, polyterpene resins, rosins, styrene resins, and cumarone / indene resins. Can be

Examples of aliphatic hydrocarbon resins, 1-butene, isobutylene, butadiene, 1,3-pentadiene, isoprene, etc. polymers and the like mainly composed of C ₄ -C ₅ mono- or diolefins such as piperylene. Examples of the alicyclic hydrocarbon resin include a resin obtained by cyclizing and dimerizing a diene component in a spent C _{4 to} C ₅ fraction, a resin obtained by polymerizing a cyclic monomer such as cyclopentadiene, and an aromatic resin. Examples include resins obtained by hydrogenating a system hydrocarbon resin in the nucleus.
Examples of aromatic hydrocarbon resins include vinyl toluene,
Resins mainly containing C ₉ -C ₁₀ vinyl aromatic hydrocarbons such as indene and α-methylstyrene are exemplified. Examples of polyterpene resins include α-pinene polymer, β-pinene polymer, dipentene polymer, terpene
Phenol copolymers, α-pinene-phenol copolymers and the like can be mentioned. Rosins are gum rosin, wood rosin, rosins such as tall oil and modified products thereof,
Examples of the modified product include those subjected to modification means such as hydrogenation, disproportionation, dimerization, and esterification. Styrene-based hydrocarbon resins are polymers such as styrene, vinyltoluene, α-methylstyrene, and isopropenyltoluene.

The above-mentioned tackifier resin may be a resin modified by grafting with maleic anhydride, maleic ester or the like.

Among these tackifying resins, it is preferable to use an aliphatic hydrocarbon resin or an alicyclic hydrocarbon resin in view of the compatibility with the component (B ₁ ). (B ₁₎ component and (B ₂₎ blending ratio of the component, the former 75 to 95 wt%, with respect to preferably 80 to 90 wt%, the latter 5 to 25% by weight, preferably 10 to 20 wt%. When the blending ratio of the component (B ₂ ) is less than the above range, the interlayer adhesion does not become a large value,
On the other hand, if the compounding ratio is too large, the MFR becomes too high, making it difficult to produce a laminate by coextrusion, and the cohesive strength of the resin is reduced, and the interlayer adhesion after bending the film is reduced.

In the present invention, a crystalline olefin-based polymer layer (C) to be a laminate layer to a packaging material substrate is further formed adjacent to the layer (B). Crystalline olefin-based polymers are those having an α-olefin such as ethylene or propylene as a main component and usually having a degree of crystallinity of 25% or more, high pressure polyethylene, linear low density polyethylene, high / medium density polyethylene, acetic acid High-pressure ethylene copolymers containing small amounts of vinyl, (meth) acrylic acid, (meth) acrylic acid esters, and the like as copolymerization components, and polypropylene. Among them, it is preferable to use high-pressure polyethylene or linear low-density polyethylene for reasons of moldability, cost and thermal stability. As these crystalline olefin polymers, the ethylene polymer has a melt flow rate at 190 ° C. and a load of 2160 g of 0.5 to 100 g / 10 minutes, particularly 1.0 to 10 g.
It is preferable to use a propylene polymer having a melt flow rate of 0.2 at 230 ° C. and a load of 2160 g.
It is preferable to use one having 5 to 100 g / 10 minutes, particularly 1.0 to 20 g / 10 minutes.

The laminate of the present invention can be produced by a co-extrusion method. The thickness of each layer is arbitrary, but (A) 5 to 40 mμ, preferably 10 to 20 mμ for the modified PET layer, (B) 2 to 30 mμ, preferably 5 to 20 mμ for the ethylene copolymer layer, and (C) crystallinity. Olefin polymer layer 5 ~ 40mμ, preferably 10
It is desirable to set it to 〜20 μm. By adopting such a layer configuration, even when laminated by a co-extrusion method, not only is the interlayer adhesion excellent, but also the curling tendency of the laminate based on the difference in resin shrinkage upon cooling can be suppressed to a negligible level. it can. In addition, the laminate has appropriate flexibility and stiffness, and is easy to handle. When such a laminate is heat-sealed between the layers (A), the denaturation of a single layer
Compared to the case of heat sealing between PETs, there is no variation in the seal, and a stable seal can be obtained. Further, the tendency to generate pinholes in bending can be significantly reduced. Each of the inner and outer layers of the film may contain additives such as an antioxidant and a slip imparting agent, if necessary.

The laminate of the present invention is formed on a crystalline olefin polymer layer (C) via an adhesive layer through paper, aluminum, nylon, or PET.
Adhesive substrates are used to produce multilayer packaging materials. At this time, since the laminate of the present invention has a crystalline olefin-based polymer layer that can be easily laminated, the intended multilayer packaging material can be easily obtained by a method of dry lamination or sandwich lamination. . For example, a multilayer packaging material obtained by laminating the laminate of the present invention on a substrate containing a paper layer as described above can be used as a paper container material.

[Effects of the Invention] According to the present invention, it is possible to provide a laminate excellent in fragrance retention, heat sealability, and pinhole resistance. By laminating this laminate on another base material, it can be suitably used as various packaging materials, particularly for packaging of foods and beverages having an aroma component.

[Example] Example 1 Maleic anhydride (EBR, crystallinity 10%, MFR 3.5 g / 10 min) containing 100 parts by weight of an ethylene / 1-butene copolymer having a 1-butene content of 15 mol% was added. MAH) 0.5 part by weight, 0.15 parts by weight of 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane-3 as a radical polymerization initiator were added, and the resulting mixture was extruded (40 mmφ extruder, L / D = 28, denaturation temperature 2
The mixture was kneaded at 00 to 240 ° C at a screw rotation speed of 40 / min) to synthesize a maleic anhydride graft-modified ethylene / 1-butene copolymer. Ethylene-propylene copolymer (EP: 15% by weight of this maleic anhydride-modified product and 20% by mole of propylene)
R, 70% by weight of crystallinity 3%, MFR 1.0g / 10min) and 15% by weight of hydrogenated petroleum resin (Alcon p-125 manufactured by Arakawa Chemical) are mixed in advance and fed to a 65mmφ single screw extruder. It was melt mixed and granulated at 200 ° C. This mixture was used as a resin for layer B.

As the resin for the layer A, a modified polyethylene terephthalate containing 10 mol% of isophthalic acid (isophthalic acid / terephthalic acid / ethylene glycol = 10/40/50 molar ratio) was used.
As the resin for the C layer, a high-pressure low-density polyethylene having an MFR of 1.6 g / 10 minutes was used.

The resins A, B, and C were supplied to a three-layer cast film forming machine, and a three-layer film was obtained using a feed block.
The film forming conditions are as follows.

Table 1 shows the interlaminar adhesive strength between layer A (modified PET layer) and layer B (adhesive resin layer) of the obtained film, and Table 2 shows the breaking strength and elongation at break of the film. Table 3 shows the heat sealing strength using the competitor as a sealing layer.

As is clear from the results of Tables 1 to 3, the A layer and the B layer have a sufficient adhesive strength as a general packaging material. In addition, while the elongation is 0 in the modified PET single layer film,
The three-layer film of the present invention has a moderate elongation, and its heat seal strength is stable over a wide sealing temperature range from a low temperature to a high temperature.

Example 2 A film was prepared and evaluated in exactly the same manner as in Example 1 except that an ethylene-methacrylic acid copolymer (methacrylic acid 9% by weight, MFR 3 g / 10 minutes) was used as the resin for the C layer. The results are shown in Tables 1 to 3. This film also has good performance as a material for a seal layer, such as interlayer adhesion, elongation at break of the film, and heat seal strength.

Example 3 Polypropylene (Mitsui Petrochemical F6
07, MFR 6.0 g / 10 min) to obtain a three-layer film in exactly the same manner as in Example 1. The interlayer between B / C of this film was not peelable. In addition, Table 1 and Table 3 show the interlayer adhesive strength between A and B and the heat sealing strength using the A surface (modified PET resin) as a seal layer.

Comparative Example 1 Using a cast film molding machine having a 65 mmφ extruder, a monolayer film of modified polyethylene-terephthalate (isophthalic acid / terephthalic acid / ethylene glycol = 10/40/50) containing 10 mol% of isophthalic acid was obtained. . The film forming temperature was 270 ° C., and the film thickness was 50 μm.
Table 1 shows the strength, elongation and heat sealability of this film.
2 and Table 3 respectively. This film has no elongation, and a modified PET single-layer film has a problem as a sealing layer of a flexible packaging material.

Comparative Example 2 Maleated modified linear low-density polyethylene (maleic anhydride content: 0.4% by weight, MFR 4.0 g / 10 min) as resin for layer B
And a three-layer cast film was obtained in the same manner as in Example 1, except that the resin temperature during the formation of the B layer was 220 ° C. The total thickness of the film is 50 μm, and the thickness composition ratio of each film layer is A / B / C = 1/1/1.

The interlaminar adhesive strength between layer A (modified polyethylene terephthalate layer) and layer B (LLPPE-based adhesive resin layer) of this film, and the heat seal strength using the layer A as a seal layer are shown in Table 1.
1 and Table-3.

The adhesive strength between the layer A and the layer B of this film is low, and is insufficient as a seal layer of a flexible packaging material that is frequently repeatedly bent.

Comparative Example 3, Comparative Example 4 The maleic anhydride graft-modified product (maleic anhydride-modified EPR), ethylene-propylene copolymer (EPR) and hydrogenated petroleum resin (Arakawa Chemical Co., Alcon P-125) in Example 1 were used. Blend as follows, melt-mix and granulate
This was used as a layer resin.

As the resin for layer A and the resin for layer C, the same modified PET and MFR 1.6 g / 10 min high pressure method low density polyethylene as used in Example 1 were used. Machine, total thickness 50μm, A / B /
A film having a thickness ratio of C = 1/1/1 was obtained. The molding conditions were the same as in Example 1 except that the resin temperature in the extruder for layer B in Comparative Example 4 was 180 ° C.

Table 1 shows the measurement results of the interlayer adhesion strength between A / B of the film of Comparative Example 3. The value is smaller than that of Examples 1 to 3, and is insufficient as a sealing layer of a flexible packaging bag to which bending is applied.

In Comparative Example 4, the fluidity of the intermediate layer B layer resin was too large, and the thickness was small at the center of the die and large at both ends. Only a film having a nonuniform thickness of the B layer was obtained. Did not.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B32B 27/08 B32B 27/32 B32B 27/36

Claims (1)

(57) [Claims] (A) a modified polyethylene terephthalate layer containing 5 to 20 mol% of a copolymer component; (B) (B ₁ ) a low crystal partially or entirely graft-modified with an unsaturated carboxylic acid or an anhydride thereof; An ethylene / α-olefin copolymer of 75 to 95% by weight, (B ₂ ) a tackifier resin of 5 to 25% by weight, an ethylene copolymer composition layer, and (C) a crystalline olefin. A multi-layer packaging material laminate comprising: a series of polymer layers formed in order; a layer (A) serving as a heat seal layer; and a layer (C) serving as a laminate layer on a substrate.