JP2564643B2 - Packaging material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyester composition having excellent heat sealability, flexibility, pinhole resistance, aroma retention, and impact resistance. More specifically, the present invention relates to a packaging material suitable for a container in which a specific polyester composition is used as a heat-sealing layer and which comes into direct contact with food or drink containing an aroma component.

[Prior Art] In the field of food and drink packaging such as juice containers, the use ratio of resin-coated paper containers is rapidly increasing. As a resin used for this purpose, an olefin polymer is widely adopted from the viewpoint of heat sealability, flexibility and the like. However, olefin-based polymers have drawbacks in gas barrier properties and aroma retention properties, and when used as an inner layer resin that comes into direct contact with foods and drinks having an aroma component, they have the drawback of changing taste and aroma.

Polyethylene terephthalate (hereinafter referred to as PET) has an excellent fragrance-retaining property, but cannot be heat-sealed, so that it was unsuitable as the above-mentioned inner layer resin for paper container coating. On the other hand, if a small amount of ethylene resin is blended with PET, the flexibility and heat sealability are improved, but when filling the contents at high temperature, the heat sealability deteriorates if the time from filling to sealing becomes long. Therefore, it cannot be said to be satisfactory for high temperature filling.

Further, modified PET containing a considerable amount of a copolymerization component such as isophthalic acid is superior to PET in terms of heat sealability, but is inferior in flexibility, pinhole resistance and the like. It was unsuitable for use as a paper container inner layer material.

[Problems to be Solved by the Invention] The present inventors have made a study on a new paper container inner layer resin which does not have the above-mentioned drawbacks by taking advantage of the excellent aroma retaining property of PET. As a result, they have found that a composition as described below is suitable as a paper container inner layer material.

Therefore, an object of the present invention is to provide a packaging material having a PET-based new resin composition as a heat-sealing layer. Another object of the present invention is to provide a packaging material that can be sufficiently used for high-temperature filling when laminated on a paper container and is excellent in heat sealability, aroma retention, pinhole resistance and the like. .

[Means for Solving the Problems] The present invention includes 60 to 5 parts by weight of PET, 20 to 80 parts by weight of modified PET containing 5 to 20 mol% of a copolymerization component, and an ethylene-based polymer 30.
It is a packaging material having a heat-sealing layer of a polyester composition comprising 10 to 10 parts by weight.

The PET in the present invention is a polyester essentially consisting of ethylene glycol units and terephthalic acid units, but it contains 4 mol% of a copolymerization component such as diethylene glycol.
A copolymer with these copolymer components may be used as long as it has the following proportions. As such a PET, one having an intrinsic viscosity measured with trifluoroacetic acid of 0.6 to 1.4 dl / g, particularly about 0.7 to 1.0 dl / g is preferable.

The modified PET used in the present invention has a copolymerization component of 5 to 20 in addition to the ethylene glycol unit and the terephthalic acid unit.
It is one that is copolymerized in a proportion of mol%, preferably 5 to 15 mol%. As the copolymerization component, isophthalic acid,
Aromatic carboxylic acids such as phthalic acid, 2,6-naphthalenedicarboxylic acid, p-oxybenzoic acid, aliphatic or alicyclic carboxylic acids such as adipic acid, sebacic acid, cyclohexanedicarboxylic acid, propylene glycol, 1, Examples thereof include diols such as 4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol and triethylene glycol. Among these copolymerization components, isophthalic acid, 1,4-cyclohexanedimethanol, diethylene glycol and the like are particularly suitable. As the modified PET, one having an intrinsic viscosity of 0.60 to 1.4 dl / g, particularly 0.7 to 1.0 dl / g is preferable.

Examples of the ethylene-based polymer used in the present invention include high-density or low-density polyethylene, a main amount of ethylene and an α-olefin having about 3 to 12 carbon atoms, such as propylene, 1
Copolymers of various densities with butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecane, 4-methyl-1-pentene, etc., major amounts of ethylene and polar vinyl monomers and / or Examples thereof include copolymers with carbon monoxide, copolymers obtained by using these as base polymers and grafting polar vinyl monomers, and the like. Further, two or more of these copolymerization component monomers may be used in combination to form a ternary or higher multicomponent copolymer. As the polar vinyl monomer, vinyl acetate, unsaturated carboxylic acid ester such as vinyl propionate, methyl acrylate, ethyl acrylate, n-butyl acrylate,
Unsaturated carboxylic acid esters such as isobutyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, diethyl maleate, glycidyl acrylate and glycidyl methacrylate, acrylic acid, methacrylic acid and itaconic acid. Saturated carboxylic acid, its lithium salt, sodium salt, magnesium salt,
Unsaturated carboxylic acid salts such as zinc salts, maleic anhydride,
Examples thereof include unsaturated carboxylic acid anhydrides such as itaconic anhydride and tetrahydrophthalic anhydride. In the case of a copolymer with an unsaturated carboxylic acid salt, some or all of the carboxyl groups of the ethylene-unsaturated carboxylic acid copolymer or ethylene-unsaturated carboxylic acid-unsaturated carboxylic acid ester terpolymer So-called ionomer resins neutralized with metal ions such as sodium and zinc can be used.

As such an ethylene polymer, 190 ℃, 2160g
A melt flow rate under load of 0.1 to 100 g / 10 minutes, particularly 0.3 to 50 g / 10 minutes is preferable.

The mutual blending ratio of PET, modified PET and ethylene polymer is such that when the total amount of these is 100 parts by weight, PET is 60
-5 parts by weight, preferably 50-10 parts by weight, modified PET 20-8
0 parts by weight, preferably 30 to 70 parts by weight, and the ethylene polymer is 30 to 10 parts by weight, preferably 25 to 10 parts by weight. When the amount of the ethylene-based polymer used is less than the above range, the composition has insufficient impact resistance, flexibility, and the like, and a packaging material such as a film is apt to suffer from trouble such as tearing and wrinkling, which is not preferable. On the other hand, if the amount of addition is too large, properties such as aroma retention and heat resistance deteriorate, so it is necessary to control the content within the above range.

The amount of PET and modified PET used is determined from the viewpoint of the composition's pinhole resistance, heat sealability, aroma retention, etc., and if the amount of modified PET used is less than the above range, the heat sealability will be poor. Unfortunately, it is not preferable to use it as an inner layer material of a high-temperature filling paper container, because it may not be possible to obtain a material having a high heat seal strength. On the other hand, when the ratio of the modified PET used is more than the above range, the flexibility of the composition, the elongation, etc. are not sufficient, and the damage due to pinholes or bending is likely to occur, and for use as a packaging material,
It required some ingenuity.

Additives such as an oxidation stabilizer, a slip agent, an anti-blocking agent, and a colorant can be appropriately added to the polyester composition used as the heat-sealing layer of the packaging material of the present invention.

The packaging material of the present invention has a constitution in which a polyester composition is used as an inner layer and is laminated on another material, and can be suitably used in a field requiring heat sealing. Examples of other materials that can be laminated include metals, papers, various thermoplastic resins such as PET, polyamide, polycarbonate, ethylene / vinyl alcohol copolymer, polyvinylidene chloride, polyolefin, and other single-layer or multi-layer materials. can do. In such a multilayer packaging material, the composition layer of the present invention can be used in a thickness such as 10 to 200 μ.

Example 1 Modified polyethylene terephthalate containing 45% by weight of crystalline polyethylene terephthalate (J-135 manufactured by Mitsui Pet Co., Ltd.) and 10 mol% of isophthalic acid (isophthalic acid / terephthalic acid / ethylene glycol = 10/40/50). 40% by weight and 15% by weight of Zn ionomer of ethylene-isobutyl acrylate-methacrylic acid copolymer (10% by weight of isobutyl acrylate, 10% by weight of methacrylic acid and 60% of neutralization degree)
mmφ Same direction biaxial kneader was used to mix and granulate at 270 ° C. still,
Prior to this mixing and granulating operation, each resin was thoroughly dried with heated nitrogen.

This granulated mixture is dried again, and blow-up ratio 2.0, resin temperature 265 ° C with a 30 mmφ inflation molding machine.
It was formed into a film. The thickness of the film was 40 μm.

The tensile stress at break and elongation at break of this film were measured. Table 2 shows the results. Further, this film was heat-sealed with a bar sealer manufactured by Toyo Seiki, and the peel strength was measured. At the same time, another portion of the same film was immersed in hot water at 75 ° C. for 3 minutes, dried and then heat-sealed in the same manner, and the strength was measured. Table 3 shows the heat seal strength before and after the hot water treatment.

Examples 2-3, Comparative Examples 1-3 Crystalline polyethylene terephthalate, isophthalic acid
The modified polyethylene terephthalate containing 10 mol% and the ethylene copolymer were used as raw materials in the proportions shown in Table 1, and mixed in the same manner as in Example 1 to evaluate the physical properties. The results are shown in Tables 2 and 3 together with Example 1.

From the results of Table-2 and Table-3, the packaging material of the present invention is not only excellent in heat sealability and heat seal strength, but also excellent in flexibility, crystallinity excellent in aroma retention and gas barrier property. Since it contains PET in an appropriate amount, it can be seen that it is a material suitable as a packaging material for a high temperature filling container of food and drink containing an aroma component.

[Effects of the Invention] According to the present invention, by using a polyester composition in which a resin of three components is blended in a specific ratio as a heat-sealing layer, the characteristics of a PET resin excellent in gas barrier property and aroma retention are maintained. In addition, heat sealability, pinhole resistance,
A packaging material having excellent impact resistance can be obtained. Such a packaging material is particularly suitable for use in a portion that comes into direct contact with food and drink. For example, when this polyester composition is used for the inner layer of a paper container, pinholes and tears do not occur even by bending and the like, and sufficient heat seal strength can be obtained even when the contents are hot-filled. it can.
Further, since it has a slight property of adsorbing an aroma component such as limonene, even if it is filled with an aroma component-containing food or drink such as orange juice, there is little change with time in taste, aroma and the like.

Claims (1)

(57) [Claims] 1. 60 to 5 parts by weight of polyethylene terephthalate, 20 to 80 parts by weight of modified polyethylene terephthalate containing 5 to 20 mol% of a copolymerization component, and 30 to 10 of an ethylene polymer.
A packaging material comprising a polyester composition composed of parts by weight as a heat-sealing layer.