JP2812993B2 - Multilayer packaging material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a packaging material for containers excellent in heat sealability, flexibility, pinhole resistance, fragrance retention, and impact resistance. More specifically, the present invention relates to a heat-sealing packaging material for directly filling or packaging a food or the like containing an aroma component.

[Related Art] In the field of food and beverage packaging such as juice containers, the usage ratio of synthetic resin containers or resin-coated paper containers is rapidly increasing. As the resin used for this purpose, olefin polymers are widely used from the viewpoint of heat sealing properties, flexibility and the like. However, olefin polymers have drawbacks in gas barrier properties and fragrance retention properties, and when used as an inner layer resin that comes into direct contact with foods and beverages having fragrance components, there is a drawback that the taste and aroma change.

Polyethylene terephthalate (hereinafter referred to as PET) is excellent in fragrance retention, but cannot be heat-sealed, and thus is unsuitable as the resin for food and drink containers or the inner layer resin for coating paper containers as described above. On the other hand, blending a small amount of ethylene-based resin with PET improves flexibility and heat-sealing properties, but has the drawback that when filling the contents at high temperatures, the heat-sealing properties deteriorate as the time from filling to sealing increases. Therefore, it could not be said to be satisfactory for high-temperature filling.

Further, modified PET containing a considerable amount of a copolymer component such as isophthalic acid is superior in heat sealability to PET, but is inferior in flexibility, pinhole resistance, etc.
This simple substance was not suitable for use as a paper container inner layer material.

[Problems to be Solved by the Invention] The present inventors have studied a packaging material using a new material that does not have the above-mentioned disadvantages by utilizing the excellent fragrance retention and heat sealing properties of the modified PET. As a result, modified PE
It has been found that a laminate having a composition in which T and a specific ethylene copolymer are mixed at a fixed ratio as a heat seal layer is suitable for use as a packaging material. It is therefore an object of the present invention to provide a new packaging material based on modified PET. Another object of the present invention is to provide a packaging material which can be sufficiently used for high-temperature filling when used as a container, and is excellent in heat sealability, fragrance retention, pinhole resistance and the like.

[Means for Solving the Problems] The present invention comprises a surface base material layer and a heat seal layer, wherein the heat seal layer is composed of terephthalic acid, isophthalic acid and ethylene glycol and has a melting point of 205 to 240 ° C. 60-90 parts by weight of polymerized polyester and ethylene (meth)
A multilayer packaging material comprising a polymer composition comprising 10 to 40 parts by weight of an acrylic acid copolymer or a metal ionized product thereof. (Here, (meth) acrylic acid means acrylic acid or methacrylic acid, the same applies hereinafter.) The copolymer polyester used in the present invention contains a small amount of isophthalic acid units in addition to ethylene glycol units and terephthalic acid units. It is a copolyester having a melting point of 205 to 240 ° C, preferably 205 to 230 ° C. Melting point 205
When the temperature is lower than 0 ° C., the resins are easily fused and blocked during heating for drying or at the time of film molding, and industrial molding is difficult. Those having a melting point higher than 240 ° C. are copolymer polyesters having a low isophthalic acid content,
Due to the tendency to have crystallinity, there is a difficulty in heat sealing properties, and particularly, crystallization is promoted by hot water treatment, and therefore, there is a possibility that heat sealing properties may decrease during high-temperature filling.

The content of the isophthalic acid unit in the copolymerized polyester can be adjusted so that the melting point of the copolymerized polyester is in the above range. Usually, 5 to 20 mol% (total amount of isophthalic acid, terephthalic acid, ethylene glycol) ), Particularly preferably in the range of 5 to 15 mol%.

The ethylene / (meth) acrylic acid copolymer or the metal ionized product thereof used by being blended with the copolymerized polyester contains 75 to 97% by weight of ethylene, preferably 80 to 97% by weight.
95% by weight, the content of (meth) acrylic acid is 3 to 25% by weight,
It is preferably a copolymer of 5 to 20% by weight or a metal ionized product thereof, and such a copolymer contains a monomer such as a (meth) acrylate in a proportion of less than 5% by weight. You may. As metal ions, sodium,
Examples include lithium, potassium, calcium, magnesium, zinc, and aluminum. The degree of neutralization by these metals and ions is 80% or less, preferably 60% or less.

As such an ethylene copolymer, 190 ° C., 2
Melt flow rate at 160g load is 0.05-100g / 1
It is preferably 0 minutes, especially 0.1 to 50 g / 10 minutes.

The mixing ratio of the modified PET and the ethylene copolymer is, when the total amount thereof is 100 parts by weight, modified PET 60 to 90
The ethylene copolymer is used in an amount of 10 to 40 parts by weight, preferably 15 to 30 parts by weight, based on 70 to 85 parts by weight.
If the use ratio of the modified PET exceeds the above range, flexibility, pinhole resistance and the like are inferior, and the performance as a seal layer becomes insufficient. On the other hand, when the use ratio of the ethylene copolymer exceeds the above range, the fragrance retention, gas barrier properties, heat resistance, etc. are reduced, and it is not satisfactory as a packaging material that comes into direct contact with food and drink having an aroma component. I can't say.

In the present invention, up to 10 parts by weight of another ethylene-based polymer may be further added to the total of 100 parts by weight of the modified PET and the ethylene copolymer. Examples of the ethylene-based polymer include high-density or low-density polyethylene, a main amount of ethylene and an α-olefin having about 3 to 12 carbon atoms, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecane, copolymers of various densities with 4-methyl-1-pentene, etc., copolymers of a major amount of ethylene and a polar vinyl monomer and / or carbon monoxide, and these as base polymers, Examples thereof include a copolymer obtained by grafting a polar vinyl monomer. Two or more of these copolymer component monomers can be used in combination to form a ternary or higher multi-component copolymer. Examples of the polar vinyl monomer include carboxylic acid unsaturated esters such as vinyl acetate and vinyl propionate.

As such an ethylene-based polymer, those having a melt flow rate of 0.1 to 100 g / 10 minutes, particularly 0.3 to 50 g / 10 minutes are preferable.

Additives such as an oxidation stabilizer, a slip agent, an antiblocking agent, and a coloring agent can be appropriately added to the above-mentioned polymer composition layer which is a heat seal layer.

The packaging material of the present invention is obtained by laminating the heat seal layer on a base material layer. Examples of the base material layer include one or multiple layers of metal, paper, and various thermoplastic resins such as PET, polyamide, polycarbonate, ethylene / vinyl alcohol copolymer, polyvinylidene chloride, and polyolefin. In such a multilayer packaging material, the polymer composition layer of the present invention, which is a heat seal layer, can be used in a thickness of, for example, 10 to 200 μm.

[Effects of the Invention] The multilayer packaging material of the present invention has gas barrier properties, fragrance retention properties,
Excellent heat sealability, pinhole resistance and impact resistance. Therefore, in the case where the heat seal layer portion is used as a container that comes into contact with food and drink as an inner layer, for example, pinholes are not generated or broken even when bent as in a paper container, and high-temperature filling is performed. However, the heat sealing layers have sufficiently high sealing strength and excellent sealing properties. Further, since the property of adsorbing the fragrance component such as limonene is slight, even if the fragrance component-containing food or drink such as orange juice is filled, there is little change over time in taste, fragrance and the like.

[Example] Example-1 75% by weight of a modified polyethylene terephthalate (isophthalic acid / terephthalic acid / ethylene glycol = 10/40/50, melting point 210 ° C) containing 10 mol% of isophthalic acid and ethylene-methacrylic acid copolymer Each 25% by weight of Zn ionomer (12% by weight of methacrylic acid, 30% of neutralization of Zn) is sufficiently dried with heating nitrogen, and then 270 ° C. in a 30 mmφ same-direction biaxial kneader.
Was granulated and mixed. In addition, at the time of this mixed granulation, 2000 ppm of Irganox-1010 (registered trademark, an antioxidant manufactured by Ciba Geigy) was added as a stabilizer. The granulated mixture was dried again and formed into a film with a blow-up ratio of 1.9 and a resin temperature of 260 ° C. using a 30 mmφ inflation molding machine. The film thickness 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, the other portion of the same film was immersed in hot water at 75 ° C. for 3 minutes and dried, and then heat-sealed similarly to measure the strength. Table 3 shows the heat seal strength before and after the hot water treatment.

Further, this film was cut into 3 cm × 3 cm, immersed in a 100% solution of D-limonene, and allowed to stand at room temperature. After a predetermined time, the film was taken out, the surface was quickly wiped with filter paper, measured on the weight of the film, and the weight increase due to the absorption of limonene in the film was measured. The results are shown in Table-4.

Example 2 A polyethylene terephthalate containing 10 mol% of isophthalic acid, and a Zn ionomer of an ethylene-methacrylic acid copolymer (methacrylic acid 9% by weight, Zn neutralization degree 20%) were mixed with 80/2.
At a ratio of 0% by weight, granulation, mixing and film formation were performed in the same manner as in Example 1, and the physical properties of the obtained film were evaluated in the same manner as in Example 1. The results are shown in Tables 2, 3 and 4.

Comparative Example-1 Instead of the modified polyethylene terephthalate of Example 1, crystalline polyethylene terephthalate (intrinsic viscosity 0.75)
The Zn ionomer of the same ethylen-methacrylic acid copolymer as used in Example 1 was granulated and mixed at the ratio shown in Table 1 to form a film, and the physical properties of the obtained film were measured in Example 1. The evaluation was performed in the same manner as described above. The results are shown in Tables 2, 3 and 4 together with Examples 1 and 2.

Comparative Examples 2 to 3 Zn of the same modified polyethylene terephthalate and ethylene-methacrylic acid copolymer as used in Example 1
Example using ionomers as raw materials in proportions in Table 1
Mixing and film formation were performed in the same manner as in Example 1, and the physical properties of the obtained film were evaluated. The results are shown in Tables 2, 3 and 4.

From the results in Table 2, Table 3, and Table 4, the resin composition used in the packaging material of the present invention has excellent heat sealability and heat seal strength, and particularly high heat seal even in heat seal after hot water treatment. In addition to showing strength, it is excellent in flexibility, has little absorption of aroma components, and has excellent fragrance retention and gas barrier properties, so it is used as a resin for the inner layer of high-temperature containers for foods and beverages containing aroma components. It turns out that it is a suitable material.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B32B 27/00-27/42 C08L 67/00-67/08 B65D 65/00-65/46 C09J 133 / 00-133/26 C09J 167/00-167/08 C08L 33/00-33/26

Claims (1)

(57) [Claims] 1. A heat-sealing layer comprising a surface base material layer and a heat-sealing layer, wherein said heat-sealing layer comprises 60 to 90 parts by weight of a copolyester having a melting point of 205 to 240 ° C. and comprising terephthalic acid, isophthalic acid and ethylene glycol. , Ethylene ・ (meta)
A multilayer packaging material comprising a polymer composition comprising 10 to 40 parts by weight of an acrylic acid copolymer or a metal ionized product thereof.