JP3192754B2 - Polyester packaging material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester packaging material having excellent scent retention, spreadability, impact resistance and the like, and more particularly to a packaging material for foods and drinks and other substances containing fragrance components. .

[0002]

BACKGROUND OF THE INVENTION Packaging materials such as hollow containers, trays and lids, inner layers of paper containers, inner coats of cans, etc., may come into direct contact with foods and drinks such as juice and water. It is required to be excellent in scent retention and the like. Attention has been paid to polyethylene terephthalate as such a packaging material.

[0003] By the way, the inner layer material of the paper container is required to be excellent in heat sealability, spreadability, impact resistance, and the like. Although excellent adhesion is required, conventionally known polyethylene terephthalate is
They did not always meet these advanced requirements. For example, a polyethylene terephthalate homopolymer derived from only terephthalic acid and ethylene glycol has insufficient heat sealability and impact resistance, and uses a small amount of terephthalic acid, ethylene glycol, and a copolymer component other than ethylene glycol. Crystalline copolymerized polyethylene terephthalate is not always excellent in spreadability and impact resistance. Further, as a diol component, cyclohexanedimethanol is used in an amount of about 30 mol%
Amorphous copolymerized polyethylene terephthalate marketed under the trade name of ETG has a considerable level of spreadability and impact resistance, but does not have sufficient fragrance retention and can be sufficiently satisfied with respect to spreadability. Since it is not at a standard level and has poor heat resistance, there is a problem in use in applications such as retort treatment and hot filling.

[0004] The present inventors have studied to solve the above-mentioned problems in the prior art, and to obtain a packaging material which is excellent in heat resistance and fragrance retention and shows sufficient spreadability and impact resistance. As a result, they have found that a polyester composition comprising a copolymerized polyethylene terephthalate having a specific composition and specific physical properties and a specific ethylene copolymer ionomer has excellent properties, and completed the present invention. I came to.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide a polyester excellent in fragrance retention, spreadability, impact resistance, heat sealability and the like. It is intended to provide packaging materials.

[0006]

SUMMARY OF THE INVENTION The polyester packaging material according to the present invention comprises:
Derived from terephthalic acid and optionally isophthalic acid, ethylene glycol and cyclohexane dimethanol, the molar ratio of ethylene glycol to cyclohexane dimethanol is in the range of 95/5 to 75/25 at 130 ° C. for 5 hours in nitrogen After heating at 70 to 95 parts by weight of a copolymerized polyethylene terephthalate having an endothermic peak measured by DSC at 180 to 240 ° C. and an endothermic amount of 10 to 40 joules / g, and an ethylene copolymer ionomer 5 to 30 And a layer formed from a polyester composition consisting of parts by weight and a polyester composition comprising the polyester composition as a layer in contact with the contents.

[0007] Such a polyester packaging material is excellent in fragrance retention and spreadability, and is also excellent in impact resistance, heat sealability and the like.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The polyester packaging material according to the present invention will be specifically described below. The polyester packaging material according to the present invention has a layer formed from a polyester composition comprising a copolymerized polyethylene terephthalate and an ethylene copolymer ionomer.

[0009] In the copolymerization of polyethylene terephthalate present invention, as copolymerized polyethylene terephthalate, and terephthalic acid, and polyethylene terephthalate copolymer or terephthalic acid and isophthalic acid are derived from ethylene glycol and cyclohexanedimethanol, ethylene glycol and cyclohexane dimethanol And copolymerized polyethylene terephthalate derived from

The molar ratio between ethylene glycol and cyclohexanedimethanol is preferably from 95/5 to 75/25, more preferably from 92/8 to 83/17. When isophthalic acid is used, isophthalic acid is used in an amount of 10 to the total carboxylic acid (terephthalic acid + isophthalic acid).
It is desirably at most 5 mol%, preferably at most 5 mol%. If the isophthalic acid content is too large, the endothermic peak is 180 to 240 ° C., and in order to obtain a copolymerized polyethylene terephthalate having an endothermic amount of 10 to 40 joules, it is necessary to reduce the cyclohexane dimethanol content. The resulting copolymerized polyethylene terephthalate may not always have sufficient spreadability and impact resistance.

The copolymerized polyethylene terephthalate of the present invention may contain a small amount of a dicarboxylic acid other than terephthalic acid and isophthalic acid, such as 2,6-naphthalenedicarboxylic acid, as a dicarboxylic acid component. A small amount of a diol other than glycol and cyclohexanedimethanol, such as diethylene glycol, may be contained.

The copolymerized polyethylene terephthalate according to the present invention can be produced by a conventionally known method such as a transesterification method and a direct polymerization method.

Such a copolymerized polyethylene terephthalate is heated in a nitrogen atmosphere at 130 ° C. for 5 hours and then subjected to DSC.
(Differential scanning calorimeter) has an endothermic peak of 180 to 2
The temperature is 40 ° C, preferably 190 to 230 ° C, and the heat absorption is 10 to 40 joules / g, preferably 15 to 35 joules / g. When the copolymerized polyethylene terephthalate is heated at 130 ° C. for 5 hours, the copolymerized polyethylene terephthalate is sufficiently crystallized. In many cases, the endothermic peak is not detected in the copolymerized polyethylene terephthalate according to the present invention unless the above heat treatment is performed. In addition, the above-mentioned PETG does not crystallize even after the heat treatment at 130 ° C. for 5 hours, and thus does not show an endothermic peak. When measured under such conditions, the copolymerized polyethylene terephthalate having no endothermic peak has insufficient scent retention and poor heat resistance. On the other hand, those having an endothermic peak temperature or an endothermic amount exceeding the above ranges have low elongation, tensile strength, impact strength and the like when formed into a film, and do not exhibit excellent performance as a paper container inner layer material or can coating material.

Ethylene copolymer ionomer The ethylene copolymer ionomer used in the present invention is:
An ionomer in which at least a part of the carboxyl groups of the ethylene-unsaturated carboxylic acid copolymer is neutralized with a metal cation.

The ethylene-unsaturated carboxylic acid copolymer constituting the ethylene copolymer ionomer used in the present invention is a copolymer of ethylene and an unsaturated carboxylic acid. Unsaturated carboxylic acids having 3 to 8 carbon atoms, specifically, acrylic acid, methacrylic acid, fumaric acid, itaconic acid, maleic anhydride, monomethyl maleate, monoethyl maleate and the like are used. Among these unsaturated carboxylic acids, acrylic acid, methacrylic acid and maleic anhydride are particularly preferably used.

The ethylene-unsaturated carboxylic acid copolymer used in the present invention may contain a third component in addition to ethylene and the unsaturated carboxylic acid as described above. Is a polar vinyl compound having about 3 to 12 carbon atoms, such as an unsaturated carboxylic acid ester such as methyl acrylate, ethyl acrylate, i-butyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, Vinyl esters such as vinyl acetate are used.

In the ethylene-unsaturated carboxylic acid copolymer used in the present invention, ethylene is present in an amount of 60 to 99% by weight, preferably 70 to 99% by weight, and the unsaturated carboxylic acid is present in an amount of 1 to 30% by weight. %, Preferably 2 to 20% by weight
Is preferably present in an amount of

When the ethylene-unsaturated carboxylic acid copolymer contains a third component in addition to the ethylene component and the unsaturated carboxylic acid component, the third component may contain up to 39% by weight, preferably up to 30% by weight. Desirably it is present in an amount.

In the ionomer used in the present invention, at least a part of the carboxyl groups in the above-mentioned ethylene-unsaturated carboxylic acid copolymer is neutralized with a metal cation.

Such metal ions include Na ⁺ ,
K ⁺ , Li ⁺ , Ca ²⁺ , Mg ²⁺ , Zn ^{2 +} , Cu ²⁺ , C
Monovalent to trivalent metal cations such as o ²⁺ , Ni ²⁺ , Mn ²⁺ , and Al ³⁺ are mentioned. Of these, Zn ²⁺ ,
Divalent ions such as Mg ²⁺ are preferable. When an ionomer containing these divalent ions is used, crystallization of the copolymerized polyethylene terephthalate is not promoted, so that the heat sealing property does not change with time, and furthermore, the spreadability is improved. A polyester composition having excellent properties and impact resistance can be obtained.

Generally, such an ionomer is obtained by copolymerizing ethylene, an unsaturated carboxylic acid and, if necessary, a third component to obtain an ethylene-unsaturated carboxylic acid copolymer, Neutralizing at least a part of the carboxyl groups of the copolymer with metal ions, or copolymerizing ethylene, an unsaturated carboxylic acid ester and, if necessary, a third component, and It can be obtained by saponifying at least a part of the saturated carboxylic acid ester component.

In particular, in the present invention, a copolymer obtained by copolymerizing ethylene, an unsaturated carboxylic acid and, if necessary, a third component by a high-pressure radical polymerization method is used as a base, and one of the carboxyl groups of the copolymer is used. An ionomer partially or wholly neutralized with a metal cation is preferably used. It is desirable that the degree of neutralization is usually about 5 to 100%, preferably about 10 to 90%. The melting point of such an ionomer is generally about 70 to 105 ° C. The melt flow rate (MFR) of the ionomer measured at 190 ° C. under a load of 2160 g is 0.01 to 1000 dg / min.
In particular, it is preferably 0.1 to 200 dg / min.

When the total amount of the copolymerized polyethylene terephthalate and the ionomer is 100 parts by weight, the copolymerized polyethylene terephthalate contains 70 to 95 parts by weight,
Preferably in an amount of 80 to 90 parts by weight, the ionomer is 5
It is desirable to use in an amount of from 30 to 30 parts by weight, preferably from 10 to 20 parts by weight. If the amount of the ionomer used is too small, the resulting polyester composition has insufficient impact resistance and spreadability, and if the amount is too large, the heat resistance and fragrance retention of the obtained polyester composition are impaired. May be

Nonpolar Ethylene Polymer In the present invention, the polyester composition for forming the polyester packaging material may be a nonpolar ethylene (co) polymer in addition to the copolymerized polyethylene terephthalate and the ethylene copolymer ionomer described above. It may contain a small amount of coalescence. A polyester packaging material made of a polyester composition containing such an ethylene (co) polymer has excellent heat sealability and processability.

Examples of the ethylene polymer include a homopolymer of ethylene or a copolymer of ethylene with an α-olefin having about 3 to 12 carbon atoms, such as propylene, 1-butene, 1-hexene, and 4-methyl-1-pentene. Polymers. Of these, linear low density polyethylene is particularly preferred.

Such an ethylene polymer has a total of 100% of copolymerized polyethylene terephthalate and ionomer.
It is preferably used in an amount of 10 parts by weight or less, preferably 1 to 5 parts by weight, based on parts by weight.

An additive such as an antioxidant may be added to such a polyester composition. Particularly, a hindered phenol-based stabilizer known as Irganox 1010, 1076 or the like under the trade name of 0.05-1.
By blending about 0 part by weight, particularly preferably about 0.2 to 1.0 part by weight, yellow discoloration of the composition can be prevented and impact resistance can be improved, and a multilayer structure such as a paper container inner layer material can be obtained. When heat sealing is performed using the inner layer material or a single layer packaging material, excellent heat sealing properties can be maintained by such a compounding.

The polyester packaging material according to the present invention has a layer formed from the above polyester composition as a layer in contact with an aroma component-containing material such as juice, soy sauce, detergent, oil and the like.

The layer formed from such a polyester composition is preferably used as a paper container inner layer material, a metal can coating material, a hollow bottle, a tray, a lid material, and the like, and is laminated with another plastic material or a metal foil. Being
It is used as an inner layer material of a multi-layer packaging container, and is further used as a single-layer packaging material such as a bag in box.

[0030]

The polyester packaging material of the present invention has a layer formed from the above polyester composition as an inner layer, and has a fragrance retention property, heat resistance, spreadability, impact resistance,
Excellent heat sealability. For example, when a layer formed from the polyester composition as described above is used as an inner layer material of a paper container, it has excellent heat sealing properties in addition to fragrance retention, heat resistance, etc., and breaks into a large container. It has excellent strength and is suitable as a beverage container. Further, when used as a metal can inner surface coat, it has excellent spreadability, so that a protective inner surface coating with good adhesion can be obtained even by drawing or ironing. Also, good performance is maintained when the container is subjected to heat sterilization.

The packaging material of the present invention is particularly suitable for packaging foods and drinks as described above because of its excellent fragrance preserving property. In addition, the packaging material for packaging substances having fragrance components such as oily substances and detergents is also used. When used, the effect is obtained that the fragrance component is less likely to leak to the outside or to be reduced by being absorbed by the packaging material. Further, since the layer formed from the polyester composition according to the present invention does not itself have an odor, the odor does not reach the contents.

[0032]

【Example】

[0033]

Example 1 Terephthalic acid 9 as a dicarboxylic acid component
Using 7 mol% and 3 mol% of isophthalic acid, 84 mol% of ethylene glycol and 1,4-
Copolymerized polyethylene terephthalate produced by a transesterification method using 16 mol% of cyclohexanedimethanol (a sample heated at 130 ° C. for 5 hours under a nitrogen atmosphere was measured by DSC at a temperature rising rate of 10 ° C./min under a nitrogen atmosphere). The endothermic peak is at 199 ° C. and the endothermic amount is 29.
82 wt%), 15 wt% Zn ionomer of ethylene-methacrylic acid copolymer (methacrylic acid content 15 wt%, Zn neutralization 60%), and linear low density polyethylene (density 0. 920 g / cm ³ , MFR
20 dg / min) and 3% by weight, respectively, were sufficiently dried with heated nitrogen.
After melt-kneading at 0 ° C., the mixture was granulated to prepare a pellet-like polyester composition. At the time of this mixed granulation, Irganox 1010 (trade name, manufactured by Ciba Geigy, an antioxidant) was added in an amount of 0.4 parts by weight per 100 parts by weight of the composition.
Parts by weight were added.

The granulated polyester composition was dried again, and formed into a film at a resin temperature of 270 ° C. by a cast film forming machine of a 65 mmφ extruder to obtain a film having a thickness of 40 μm.

The tensile stress at break and the elongation at break of this film were measured. Table 1 shows the measurement results. The impact energy of this film was measured using a film impact tester manufactured by Toyo Seiki.

Table 2 shows the results. Further, the film was heat-sealed with a bar sealer manufactured by Toyo Seiki, and the peel strength was measured. Table 3 shows the results.

Further, the film was cut into 3 cm × 3 cm.
Immersion in 100% d-limonene liquid
It was left in a thermostat at 23 ° C. After a predetermined time, remove the film
And quickly wipe the surface with filter paper to reduce the weight of the film.
Measure the weight increase due to the absorption of limonene into the film
Table 4 shows the measurement results. Table 4 shows the low density poly
Ethylene (LDPE, density 0.920g / cm ^Three, MFR
 (1.6 dg / min) for a 40 μm thick film.
The measurement results are shown below.

[0038]

Example 2 In Example 1, terephthalic acid was used as the dicarboxylic acid component as the copolymerized polyethylene terephthalate, and 79 mol% of ethylene glycol and 1,4-cyclohexanedimethanol 21 were used as the diol component.
The endothermic peak of the copolymerized polyethylene terephthalate produced using the mol% (heated at 130 ° C. for 5 hours in a nitrogen atmosphere at a heating rate of 10 ° C./min in a nitrogen atmosphere by DSC is 195 ° C., The heat absorption is 22J
/ G) was prepared in the same manner as in Example 1 except that the film thickness was 40 µm.

The film thus obtained was measured for tensile stress at break and elongation at break. At the same time, the other part of the same film is autoclaved at 120 ° C for 3 hours.
The film was retorted for 0 minutes, and the tensile stress at break and the elongation at break of this film were measured. Table 1 shows the measurement results.

Further, the breaking impact energy was measured by a film impact tester, and the results are shown in Table 2. Further, the results of measuring the heat seal strength are shown in Table 3, and the results of the limonene absorption test are shown in Table 4.

[0041]

Comparative Example 1 In Example 1, copolymerized polyethylene produced by using 86 mol% of terephthalic acid and 14 mol% of isophthalic acid as dicarboxylic acid components as the copolymerized polyethylene terephthalate and using ethylene glycol as the diol component Terephthalate (The endothermic peak of a sample heated at 130 ° C. in a nitrogen atmosphere for 5 hours at a heating rate of 10 ° C./min in a nitrogen atmosphere is 217 ° C. and the endothermic amount is 38 J / g) A film having a thickness of 40 μm was produced in the same manner as in Example 1 except that the film was used.

The tensile stress at break and the elongation at break of the film thus obtained before and after the retort treatment were measured, and the results are shown in Table 1. Table 2 shows the results of measurement of the breakthrough impact energy with a film impact tester.

[0043]

Comparative Example 2 Copolymerized polyethylene terephthalate pellets produced using terephthalic acid as a dicarboxylic acid component and 70 mol% of ethylene glycol and 30 mol% of 1,4-cyclohexanedimethanol as a diol component were mixed with nitrogen. Upon heating at 130 ° C. for 5 hours in an atmosphere, the pellets were severely blocked.

A part of the blocked sample was cut out and measured by DSC at a heating rate of 10 ° C./min in a nitrogen atmosphere. As a result, no endothermic peak appeared and the copolymerized polyethylene terephthalate did not crystallize.

The procedure of Example 1 was repeated, except that the copolymerized polyethylene terephthalate was used.
A thick film was obtained. Table 4 shows the limonene absorption test of this film.

When this film was retorted in the same manner as in Example 1, it was found that the film after the treatment was severely deformed, and was not practical as a retort wrapping material because of its heat resistance.

[0047]

Comparative Example 3 The d-limonene absorption test described in Example 1 was performed on a 40 .mu.m thick film formed from the copolymerized polyethylene terephthalate used in the following comparative example. That is, terephthalic acid was used as a dicarboxylic acid component, and 70 mol% of ethylene glycol and 1,4-cyclohexanedimethanol 30 were used as diol components.
% Of the copolymerized polyethylene terephthalate used in Comparative Example 2 which was prepared using the same procedure.

Table 4 shows the results.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

From Table 1, Table 2, Table 3 and Table 4, the polyester packaging material of the present invention is excellent in film elongation, film breaking impact strength and heat sealability, and shows slight film elongation even after retort treatment. In addition, it is understood that it is excellent in flexibility, has little absorption of fragrance components, and is excellent in fragrance retention. For this reason, the polyester packaging material of the present invention is a food and beverage packaging container (paper container,
It can be seen that the material is suitable for a layer in contact with food and drink such as a plastic container and a metal can.

[0054]

Example 3 In Example 1, copolymerized polyethylene terephthalate was produced using terephthalic acid as a dicarboxylic acid component and 91 mol% of ethylene glycol and 9 mol% of 1,4-cyclohexanedimethanol as a diol component. The endothermic peak of the copolymer polyethylene terephthalate (230 ° C., measured at a heating rate of 10 ° C./min in a nitrogen atmosphere by a DSC at 130 ° C. for 5 hours in a nitrogen atmosphere) is 230 ° C., and the heat absorption amount is 31 J /
g) was used to produce a film having a thickness of 40 μm in the same manner as in Example 1.

Table 5 shows the tensile stress at break and the elongation at break of the film thus obtained, the breaking energy by a film impact tester, and the heat sealing strength. Further, d was measured in the same manner as in Example 1.
Table 6 shows the weight increase due to limonene absorption.

[0056]

Example 4 Terephthalic acid 92 as a dicarboxylic acid component
Mol% and 8 mol% of isophthalic acid, and 88 mol% of ethylene glycol and 12 mol% of 1,4-cyclohexanedimethanol as diol components.
The endothermic peak of the sample heated at 30 ° C. for 5 hours measured by DSC at a temperature rising rate of 10 ° C./min in a nitrogen atmosphere is 203
° C and its endotherm is 25 J / g) 85% by weight
And Zn ionomer of ethylene-methacrylic acid copolymer (methacrylic acid content 15% by weight, Zn neutralization degree 60%)
15% by weight was melt-kneaded at 250 ° C. in a 65 mmφ single screw extruder (with a tip dalmage type mixing section), and then granulated to prepare a pellet-like polyester composition. To form a film having a thickness of 40 μm.

Table 5 shows the tensile strength at break and elongation at break of the film thus obtained, the breaking energy by a film impact tester, and the heat sealing strength. In this example, since an antioxidant was not blended, there was a heat sealing property, but the results were not as good as those of Examples 1 to 3. Table 6 shows the weight increase due to the absorption of d-limonene measured in the same manner as in Example 1.

[0058]

[Table 5]

[0059]

[Table 6]

Further, the films obtained in Examples 2, 3 and Comparative Example 1 were left at 40 ° C. and 75% relative humidity for a predetermined period and then heat-sealed at 170 ° C. under the conditions shown in Table 3. And heat seal strength (N / 15 mm).

Table 7 shows the results.

[0062]

[Table 7]

From Table 7, it can be seen that the polyester packaging material of the present invention has a small decrease in heat sealability even after storage under high temperature and high humidity, and is excellent for use as a packaging material.

Claims (5)

(57) [Claims] 1. Derived from terephthalic acid and optionally isophthalic acid, ethylene glycol and cyclohexane dimethanol, the molar ratio of ethylene glycol to cyclohexane dimethanol being 95/5 to 75/25.
The endothermic peak measured by DSC after heating in nitrogen at 130 ° C. for 5 hours is 180 to 240 ° C. and the endothermic amount is 10 to 40 joules / g. A polyester packaging material, comprising, as a layer in contact with the contents, a layer formed from a polyester composition consisting of: by weight, and 5 to 30 parts by weight of an ethylene copolymer ionomer. 2. The polyester composition further comprises a nonpolar ethylene polymer or a nonpolar ethylene copolymer in an amount of 10 parts by weight or less based on 100 parts by weight of the total of the copolymerized polyethylene terephthalate and the ethylene copolymer ionomer. The packaging material according to claim 1, wherein: 3. The non-polar ethylene polymer or non-polar ethylene copolymer is a linear low-density polyethylene.
The packaging material according to the above. 4. A polyester composition comprising an antioxidant in an amount of 0.05 to 1.0 based on 100 parts by weight of the polyester composition.
3. The polyester packaging material according to claim 1, wherein the polyester packaging material is contained in an amount of part by weight. 5. The polyester packaging material according to claim 1, wherein the ethylene copolymer ionomer is a divalent metal ionomer.