JPH02263860A - Polyester composition - Google Patents

Abstract

PURPOSE:To provide a composition having excellent gas barrier property, aroma-retaining property, heat-sealing property, etc., and suitable for the linings of paper containers by compounding polyethylene terephthalate, modified polyethylene terephthalate and an ethylenic polymer in a specific ratio. CONSTITUTION:A composition comprises (A) 60-5 pts.wt., preferably 50-10 pts.wt., of polyethylene terephthalate having an intrinsic viscosity of preferably 0.6-1.4dl/g, (B) 20-80 pts.wt., preferably 30-70 pts.wt., of a modified polyethylene terephthalate containing 5-20mol%, preferably 5-15mol%, of a copolymerized component (preferably isophthalate) and having an intrinsic viscosity of preferably 0.6-1.4dl/g and (C) 30-10 pts.wt., preferably 25-10 pts.wt., of an ethylenic polymer (e.g. the Zn ionomer of ethylene-isobutyl acrylate-methacrylic acid copolymer) having a melt flow rate of preferably 0.1-100g/10min.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides heat sealability, flexibility, pinhole resistance,
This invention relates to a polyester composition with excellent fragrance retention and impact resistance. More specifically, the present invention relates to a polyester composition suitable as a packaging material that comes into direct contact with foods and drinks containing aroma components.

[Prior Art] In the field of food and beverage packaging, such as juice containers, the usage ratio of resin-coated paper cartons is rapidly increasing. Olefin polymers are widely used as resins used for this purpose from the viewpoint of heat sealability, flexibility, etc. However, olefin polymers are not suitable for gas barrier properties.
It has drawbacks in its properties and aroma retention, and when used as an inner layer resin that comes into direct contact with foods and drinks containing aroma components, it has the disadvantage that the taste and aroma change.

Although polyethylene terephthalate (hereinafter referred to as PET) has excellent aroma retention properties, it cannot be heat-sealed, so it was unsuitable as the inner layer resin for coating paper cartons as described above. 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 becomes poor if the time from filling to sealing becomes long. Therefore, it could not be said to be satisfactory as a product for high-temperature filling.

Furthermore, modified PET containing a considerable amount of copolymerized components such as isophthalic acid has better heat sealability than PET, but is inferior in flexibility and pinhole resistance, so it will not be used as a single material in the future. It was unsuitable for use as an inner layer material for paper containers.

[Problems to be Solved by the Invention] The present inventors took advantage of the excellent aroma retention properties of PET and studied a new resin for the inner layer of paper containers that does not have the above-mentioned drawbacks. As a result, we have found that a composition as described below is suitable as an inner layer material for paper containers.

It is therefore an object of the invention to provide a new resin composition based on PET.Another object of the invention is to provide a new resin composition based on PET.
The object of the present invention is to provide a resin composition that can be used satisfactorily for high-temperature filling when used as an inner layer material for paper containers, and has excellent heat-sealing properties, aroma retention properties, pinhole resistance, etc.

[Means for Solving the Problems] The present invention includes 760 to 5 parts by weight of PE and 5 to 2 parts by weight of copolymer component.
This is a polyester composition consisting of 720 to 80 parts by weight of modified PE containing 0 mol% and 30 to 10 parts by weight of ethylene polymer.

PET in the present invention is a polyester consisting essentially of ethylene glycol units and terephthalic acid units5, but if the proportion of copolymer components such as diethylene glycol is 4 mol% or less, it can be copolymerized with those copolymer components. It may be a combination. Such PET has an intrinsic viscosity of 0.6 to 1.4 dβ/g as measured with trifluoroacetic acid,
Especially 0.7 to 1. It is preferably about QdJ2/g.

The modified PET used in the present invention contains 5 to 2 copolymer components in addition to ethylene glycol units and terephthalic acid units.
It is copolymerized at a ratio of 0 mol%, preferably 5 to 15 mol%.

Copolymerization components include isophthalic acid, phthalic acid, 2.6
- Aromatic carboxylic acids such as naphthalenedicarboxylic acid, p-oxybenzoic acid, aliphatic or cycloaliphatic carboxylic acids such as adipic acid, sebacic acid, cyclohexanedicarboxylic acid, propylene glycol, 1,4-butanediol, 1 .4-Cyclohexane dimetatool, diethylene glycol, triethylene glycol and other diols can be mentioned. Among these copolymerizable components, isophthalic acid, 1,4-cyclohexane dimetatool, diethylene glycol, and the like are particularly preferred. These modified PE
As T, the intrinsic viscosity is 0.60 to 1.4 dJ2/
g, particularly preferably 0.7 to 1.0 dR,/g.

The ethylene polymer used in the present invention includes high-density or low-density polyethylene, a major 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, l-dodecane, 4-methyl-1-pentene, etc., with major amounts of ethylene and polar and nil monomers and/or - Copolymers with carbon oxide, copolymers made of these as base polymers and grafted with polar vinyl monomers, etc. can be exemplified. Furthermore, two or more of these copolymerization component monomers can be used in combination to form a ternary or more multicomponent copolymer. The polar monomers include unsaturated carboxylic acid esters such as vinyl acetate and vinyl propionate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate,
Unsaturated carboxylic acid esters such as methyl methacrylate, ethyl methacrylate, diethyl maleate, glycidyl acrylate, glycidyl methacrylate, acrylic acid,
unsaturated carboxylic acids such as methacrylic acid and itaconic acid,
Examples thereof include unsaturated carboxylic acid salts such as lithium salt, sodium salt, magnesium salt, and zinc salt, and unsaturated carboxylic acid anhydrides such as maleic anhydride, itaconic anhydride, and tetrahydrophthalic anhydride. In the case of a copolymer with an unsaturated carboxylic acid salt, an ethylene-unsaturated carboxylic acid copolymer or an ethylene-unsaturated carboxylic acid copolymer
A so-called ionomer resin in which part or all of the carboxyl groups of an unsaturated carboxylic acid ester terpolymer is neutralized with metal ions such as sodium and zinc can be used.

As such an ethylene polymer, 190°C, 21
Melt flow rate at 60g load is 0.1-10
0 g/10 min, especially 0.3 to 50 g/IQ min is preferable.

The mutual blending ratio of PET, modified PET, and ethylene polymer is P
ET is 60 to 5 parts by weight, preferably 50 to 10 parts by weight,
20 to 80 parts by weight of modified PET, preferably 30 to 70 parts by weight
The amount of the ethylene polymer is 30 to 10 parts by weight, preferably 25 to 10 parts by weight. If the amount of the ethylene polymer used is less than the above range, the composition will not have sufficient impact resistance, flexibility, etc., and molded products such as films may tear or
It is undesirable because it tends to cause problems such as wrinkles. On the other hand, if the amount added is too large, properties such as fragrance retention and heat resistance will deteriorate, so it is necessary to keep it within the above range. be.

The amount of PET and modified PET to be used is determined from the viewpoints of pinhole resistance, heat sealability, fragrance retention, etc. of the composition, and if the amount of modified PET used is less than the above range, the heat sealability will be poor. (Unfavorable) It is not preferable to use it as an inner layer material of high-temperature filling paper containers because it may not be possible to obtain a material with high heat sealing strength.On the other hand, modified PET
If the usage ratio of .

Additives such as oxidation stabilizers, slip agents, anti-blocking agents, and colorants can be appropriately blended into the composition of the present invention.

The composition of the present invention can be suitably used as a packaging material that requires heat sealing. At this time, it is laminated to other materials,
The composition of the present invention can be used as an inner layer. Examples of other materials that can be laminated include metal, paper, 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 of the present invention may contain, for example, 10 layers.
Thicknesses such as ~200μ can be used.

[Example] Crystalline polyethylene terephthalate (manufactured by Mitsuibet Co., Ltd.)
J-135) Modified polyethylene terephthalate containing 45% by weight and 10% by mole of isophthalic acid (isophthalic acid/terephthalic acid/ethylene glycol = 10/40150)
40% by weight and 10% by weight of Zn ionomer (isobutyl acrylate) of ethylene-isobutyl acrylate-methacrylic acid copolymer, 10% by weight of methacrylic acid, and 15% by weight of ethylene-isobutyl acrylate-methacrylic acid copolymer, 15% by weight of Zn ionomer (isobutyl acrylate), 15% by weight of ethylene-isobutyl acrylate-methacrylic acid copolymer, and 15% by weight of ethylene-isobutyl acrylate-methacrylic acid copolymer were mixed in a 30 mm diameter biaxial kneading rock in the same direction. The mixture was mixed and granulated at 270°C. Incidentally, before this mixing and granulation operation, each resin was sufficiently dried with heated nitrogen.

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

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

2-3, 1-3 crystalline polyethylene terephthalate, isophthalic acid 1
Modified polyethylene terephthalate containing 0 mol% and an ethylene copolymer were used as raw materials in the proportions shown in Table 1, mixed in the same manner as in Example 1, and the physical properties were evaluated. The results are shown in Table 2 and Table 3 together with Example 1.

From the results shown in Tables 2 and 3, the composition of the present invention not only has excellent heat-sealing properties and heat-sealing strength, but also has excellent flexibility and crystallinity with excellent aroma retention and gas barrier properties. Since it contains an appropriate amount of PET, it is found that it is a material suitable as a resin for the inner layer of containers for high-temperature filling of food and beverages containing aroma components.

[Effects of the Invention] According to the present invention, by blending three component resins in a specific ratio, PE with excellent gas barrier properties and fragrance retention properties can be obtained.
A polyester composition that retains the properties of T resin and has excellent heat sealability, pinhole resistance, and impact resistance can be obtained. Such compositions are particularly suitable for use in areas that come into direct contact with food and drink. For example, when used in the inner layer of a paper carton, pinholes or tears do not occur even when folded or the like, and sufficient heat-sealing strength can be obtained even when the inner layer is filled at high temperatures. Since it has a slight adsorption property for aromatic components such as limonene, even if it is filled with aromatic component-containing drinks such as orange juice, there is little change in taste, aroma, etc. over time.

Claims (1)

[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 copolymer components, and 30 to 1 part by weight of ethylene polymer
A polyester composition consisting of 0 parts by weight.