JPH05209116A - Packing material of polyester - Google Patents

Abstract

PURPOSE:To obtain a packing material of polyester having excellent fragrance retention, spreadability, impact resistance, etc., comprising an inner layer composed of a composition consisting of a specific copolymerized polyethylene terephthalate and an ethylene copolymer ionomer. CONSTITUTION:A packing material has a layer, made of a composition comprising (A) 70-95 pts.wt. copolymerized polyethylene terephthalate which is derived from A1: terephthalic acid and optionally isophthalic acid and A2: ethylene glycol and cyclohexanedimethanol (molar ratio of the former/the latter of 95/5 to 75/25) and has 180-240 deg.C endothermic peak by DSC and 10-40 joule/g endotherm, (B) 5-30 pts.wt. ionomer wherein COOH of ethylene/unsaturated carboxylic acid copolymer is at least partially neutralized with a metal cation (preferably bivalent ion), preferably further (C) a nonpolar ethylene (co)polymer (preferably straight-chain low-density polyethylene) and (D) an antioxidant, as an inner layer.

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 excellent in aroma retention, spreadability, impact resistance and the like, and more particularly to food and beverages and other packaging materials for substances containing aroma components. ..

[0002]

BACKGROUND OF THE INVENTION Packaging materials such as hollow containers, trays and lids, paper container inner layers, can inner surface coats, etc. may come into direct contact with foods and drinks such as juice and water. It is required to have excellent fragrance retention. Polyethylene terephthalate has been attracting attention as such a packaging material.

By the way, the material for the inner layer of the paper container is required to have excellent heat-sealing properties, spreadability, impact resistance and the like, and as the coating material for the inner surface of the can, it is required to have spreadability, impact resistance and can material. Although excellent adhesion is required, the conventionally known polyethylene terephthalate is
They did not always meet these high requirements. For example, a polyethylene terephthalate homopolymer derived only from terephthalic acid and ethylene glycol has insufficient heat sealability and impact resistance, and comprises terephthalic acid, ethylene glycol, and a small amount of a copolymerization component other than ethylene glycol. Crystalline copolymerized polyethylene terephthalate is not necessarily excellent in spreadability and impact resistance. Further, as a diol component, cyclohexanedimethanol is used in an amount of about 30 mol% to form P
Amorphous copolymerized polyethylene terephthalate, which is marketed under the ETG trade name, has a considerable level of spreadability and impact resistance, but it does not have sufficient aroma retention and is also sufficiently satisfactory in spreadability. Since it is not in a standard level and has poor heat resistance, there is a problem in using it for applications such as retort treatment and hot filling.

The present inventors have studied to solve the problems in the prior art as described above and to obtain a packaging material having excellent heat resistance and aroma retention, and having sufficient spreadability and impact resistance. When carried out, they 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. Came to do.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems in the prior art, and is a polyester excellent in aroma retention, spreadability, impact resistance and heat sealability. 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 cyclohexanedimethanol, the molar ratio of ethylene glycol and cyclohexanedimethanol being in the range 95/5 to 75/25, at 130 ° C. for 5 hours in nitrogen 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 It is characterized in that it has a layer formed from a polyester composition consisting of 1 part by weight, as a layer in contact with the contents.

Such polyester packaging material is excellent in aroma retaining property and spreadability, and is also excellent in impact resistance and heat sealing property.

[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 of a polyester composition including a copolymerized polyethylene terephthalate and an ethylene copolymer ionomer.

Copolymerized polyethylene terephthalate In the present invention, as copolymerized polyethylene terephthalate, copolymerized polyethylene terephthalate derived from terephthalic acid, ethylene glycol and cyclohexanedimethanol or terephthalic acid and isophthalic acid, ethylene glycol and cyclohexanedimethanol are used. Copolymerized polyethylene terephthalate derived from and is used.

It is desirable that the molar ratio of ethylene glycol and cyclohexanedimethanol is 95/5 to 75/25, preferably 92/8 to 83/17. When isophthalic acid is used, the amount of isophthalic acid is 10 relative to the total carboxylic acid (terephthalic acid + isophthalic acid).
It is desirable that the content is not more than mol%, preferably not more than 5 mol%. If the isophthalic acid content is too high, the cyclohexanedimethanol content must be reduced in order to obtain a copolymerized polyethylene terephthalate having an endothermic peak of 180 to 240 ° C. and an endothermic amount of 10 to 40 joules. The resulting copolymerized polyethylene terephthalate may not always have satisfactory 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, and ethylene as a diol component. A small amount of 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 or a direct polymerization method.

Such copolymerized polyethylene terephthalate is heated at 130 ° C. for 5 hours in nitrogen and then DSC is added.
Endothermic peak measured by (differential scanning calorimeter) is 180-2
The temperature is 40 ° C., preferably 190 to 230 ° C., and the endothermic amount is 10 to 40 Joule / g, preferably 15 to 35 Joule / 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 of the copolymerized polyethylene terephthalate according to the present invention cannot be detected unless the above heat treatment is performed. The PETG described above does not crystallize even if it is heat-treated at 130 ° C. for 5 hours, and therefore no endothermic peak appears. Copolymerized polyethylene terephthalate, in which no endothermic peak is observed when measured under such conditions, does not have sufficient aroma retention and is inferior in heat resistance. On the other hand, when the endothermic peak temperature or the endothermic amount exceeds the above range, elongation, tensile strength, impact strength and the like when formed into a film are small, and it does not show excellent performance as a paper container inner layer material or a can coat material.

Ethylene Copolymer Ionomer The ethylene copolymer ionomer used in the present invention is
At least a part of the carboxyl groups of the ethylene-unsaturated carboxylic acid copolymer is an ionomer 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. The unsaturated carboxylic acid is An unsaturated carboxylic acid having 3 to 8 carbon atoms, specifically acrylic acid, methacrylic acid, fumaric acid, itaconic acid, maleic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, or the like is 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 above-mentioned unsaturated carboxylic acid. As such a third component, Is a polar vinyl compound having about 3 to 12 carbon atoms such as methyl acrylate, ethyl acrylate, i-butyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, unsaturated carboxylic acid ester such as methyl methacrylate, A vinyl ester such as vinyl acetate is 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 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 unsaturated carboxylic acid component, the third component is up to 39% by weight, preferably up to 30% by weight. It is desirable to be present in an amount.

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

Examples of such metal ions include Na ⁺ ,
^{K +, Li +, Ca 2+} , Mg 2+, Zn 2 +, Cu 2+, C
Examples thereof include monovalent to trivalent metal cations such as o ²⁺ , Ni ²⁺ , Mn ²⁺ and Al ³⁺ . Of these, especially Zn ²⁺ ,
Divalent ions such as Mg ²⁺ are preferable, and when an ionomer containing these divalent ions is used, crystallization of the copolymerized polyethylene terephthalate is not promoted, and therefore the heat-sealing property does not change with time and spreads. A polyester composition having excellent properties and impact resistance can be obtained.

Such an ionomer is generally obtained by copolymerizing ethylene, an unsaturated carboxylic acid and, if necessary, a third component into an ethylene-unsaturated carboxylic acid copolymer. At least a part of the carboxyl groups of the copolymer is neutralized with a metal ion, or ethylene is copolymerized with an unsaturated carboxylic acid ester and, if necessary, a third component, and the copolymer obtained is It can be obtained by saponifying at least a part of the saturated carboxylic acid ester component.

Particularly, 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 this copolymer is used. An ionomer whose part or all is neutralized with a metal cation is preferably used. The degree of neutralization is usually 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.
It is particularly preferably 0.1 to 200 dg / min.

The copolymerized polyethylene terephthalate and the ionomer are 70 to 95 parts by weight of the copolymerized polyethylene terephthalate when the total amount is 100 parts by weight.
Preferably, the amount of ionomer is 5 to 80 parts by weight.
It is desired to be used in an amount of -30 parts by weight, preferably 10-20 parts by weight. When the amount of the ionomer used is too small, the resulting polyester composition has insufficient impact resistance and spreadability, and when the amount used is too large, the heat resistance and aroma retention of the obtained polyester composition are impaired. Sometimes

Non-Polar Ethylene Polymer In the present invention, the polyester composition for forming the polyester packaging material comprises a non-polar ethylene (co) polymer in addition to the copolymerized polyethylene terephthalate and the ethylene copolymer ionomer as described above. It may contain a small amount of coalescence. A polyester packaging material comprising such a polyester composition containing an ethylene (co) polymer is excellent in heat sealability and processability.

The ethylene polymer is a homopolymer of ethylene or a copolymer of ethylene and an α-olefin having about 3 to 12 carbon atoms, such as propylene, 1-butene, 1-hexene, 4-methyl-1-pentene. Polymers may be mentioned. Of these, linear low density polyethylene is particularly preferable.

Such an ethylene polymer has a total of 100 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.

Additives such as antioxidants may be added to such a polyester composition. In particular, the hindered phenol stabilizers known under the trade name Irganox 1010, 1076 etc. are added in an amount of 0.05-1.
By blending in an amount of about 0 parts by weight, particularly preferably 0.2 to 1.0 parts by weight, yellowing of the composition can be prevented and impact resistance can be improved. When heat sealing is performed using an inner layer material or a single layer packaging material, such a composition can maintain excellent heat sealing properties.

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

A 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. Has been
It is used as an inner layer material for a multi-layer packaging container, and is also used as a single layer packaging material such as a bag in box.

[0030]

EFFECT OF THE INVENTION The polyester packaging material of the present invention has a layer formed of the above polyester composition as an inner layer, and has a fragrance retaining 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 is excellent in heat sealability in addition to aroma retention, heat resistance, etc. It has excellent strength and is suitable as a beverage container. Further, when used as an inner surface coat of a metal can, since it has excellent spreadability, a protective inner surface coating having good adhesion can be obtained even by drawing or ironing. Also, good performance is maintained even when the container is heat-sterilized.

The packaging material of the present invention is particularly suitable for packaging foods and drinks as described above because it has excellent aroma retaining property, but in addition to this, packaging of a substance having an aroma component such as an oily substance or detergent is also used. When used for, the effect that the aroma component is less likely to be leaked to the outside or absorbed by the packaging material to be reduced is obtained. In addition, the layer formed from the polyester composition according to the present invention does not have an odor by itself, so that the odor does not reach the contents.

[0032]

【Example】

[0033]

Example 1 As a dicarboxylic acid component, terephthalic acid 9
7 mol% and 3 mol% isophthalic acid were used, and as the diol component, ethylene glycol 84 mol% and 1,4-
Copolymerized polyethylene terephthalate produced by the transesterification method using 16 mol% of cyclohexanedimethanol (a sample heated at 130 ° C. for 5 hours in a nitrogen atmosphere was measured by DSC at a temperature increase rate of 10 ° C./min in a nitrogen atmosphere. The endothermic peak is 199 ° C and the endothermic amount is 29
Joules / g) 82 wt%, ethylene-methacrylic acid copolymer Zn ionomer (methacrylic acid content 15 wt%, Zn neutralization degree 60%) 15 wt%, and linear low density polyethylene (density 0. 920g / cm ³ , MFR
20 dg / min) 3% by weight, and sufficiently dried with heated nitrogen, and then, with a 44 mmφ same-direction biaxial kneader, 26
After melt-kneading at 0 ° C., the mixture was granulated to prepare a pelletized 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 per 100 parts by weight of the composition.
Parts by weight was added.

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

The tensile stress at break and elongation at break of this film were measured. The measurement results are shown in Table 1. Further, the breaking energy of this film was measured with a film impact tester manufactured by Toyo Seiki.

The results are shown in Table 2. Further, this film was heat-sealed with a bar sealer manufactured by Toyo Seiki and its peel strength was measured. The results are shown in Table 3.

Furthermore, this film is cut into 3 cm × 3 cm
And dipped in 100% liquid d-limonene, which is an aroma component,
It was left in a constant temperature bath at 23 ° C. After the specified time, remove the film.
Protrude 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 in the film
Table 4 shows the measured results. In Table 4, low density poly
Ethylene (LDPE, density 0.920 g / cm ³, MFR
 1.6dg / min) 40μm thick film
The same measurement results are shown.

[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 21,4-cyclohexanedimethanol as the diol component.
Copolyethylene terephthalate produced using mol% (the endothermic peak measured by DSC at a temperature rising rate of 10 ° C./min in a nitrogen atmosphere at 130 ° C. for 5 hours is 195 ° C., The endothermic amount is 22J
/ G) was used in the same manner as in Example 1 to produce a film having a thickness of 40 μm.

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

Breakthrough 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, as the copolymerized polyethylene terephthalate, 86 mol% of terephthalic acid and 14 mol% of isophthalic acid were used as the dicarboxylic acid component and ethylene glycol was used as the diol component. Terephthalate (an endothermic peak measured by DSC at a temperature rising rate of 10 ° C./min in a nitrogen atmosphere at 130 ° C. for 5 hours was 217 ° C. and its endothermic amount was 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 elongation at break of the film thus obtained were measured before and after the retort treatment, and the results are shown in Table 1. Table 2 shows the results of measuring the breakthrough impact energy with a film impact tester.

[0043]

Comparative Example 2 Pellets of copolymerized polyethylene terephthalate prepared by using terephthalic acid as the dicarboxylic acid component and 70 mol% of ethylene glycol and 30 mol% of 1,4-cyclohexanedimethanol as the diol component were mixed with nitrogen. When heated at 130 ° C. for 5 hours in the atmosphere, the pellet was vigorously blocked.

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

40 μm was obtained in the same manner as in Example 1 except that such a copolymerized polyethylene terephthalate was used.
A thick film was obtained. The limonene absorption test of this film is shown in Table 4.

When this film was subjected to retort treatment in the same manner as in Example 1, it was found that the film after treatment was severely deformed, and it was not practical in terms of heat resistance as a retort packaging material.

[0047]

Comparative Example 3 The d-limonene absorption test described in Example 1 was performed on a 40 μm thick film formed from the copolymerized polyethylene terephthalate used in the Comparative Example below. That is, terephthalic acid was used as the dicarboxylic acid component, ethylene glycol 70 mol% and 1,4-cyclohexanedimethanol 30 as the diol component.
Mol% and prepared on the film formed from the copolymerized polyethylene terephthalate used in Comparative Example 2.

The results are shown in Table 4.

[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 a slight film elongation even after retort treatment. Not only that, it has excellent flexibility, less absorption of aroma components, and excellent aroma retention. Therefore, the polyester packaging material of the present invention is a packaging container for food and drink containing an aroma component (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 The procedure of Example 1 was repeated except that terephthalic acid was used as the dicarboxylic acid component as the copolymerized polyethylene terephthalate, and 91 mol% of ethylene glycol and 9 mol% of 1,4-cyclohexanedimethanol were used as the diol component. Copolymerized polyethylene terephthalate (a sample heated in a nitrogen atmosphere at 130 ° C. for 5 hours was measured by DSC in a nitrogen atmosphere at a temperature rising rate of 10 ° C./min, where the endothermic peak was 230 ° C.
A film having a thickness of 40 μm was produced in the same manner as in Example 1 except that (amount g) was used.

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

[0056]

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

Table 5 shows the tensile stress at break and elongation at break of the film thus obtained, the breaking impact energy by a film impact tester, and the heat seal strength. In this example, since no antioxidant was blended, it had heat sealability, but it did not reach the results of Examples 1 to 3. Further, Table 6 shows the weight increase due to the absorption of d-limonene measured by the same method as in Example 1.

[0058]

[Table 5]

[0059]

[Table 6]

Further, the films obtained in Examples 2, 3 and Comparative Example 1 were allowed to stand 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. The heat seal strength (N / 15 mm) was measured.

The results are shown in Table 7.

[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 being stored under high temperature and high humidity, and is excellent as a packaging material.

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Claims (5)

[Claims] 1. Derived from terephthalic acid and optionally isophthalic acid, ethylene glycol and cyclohexanedimethanol, the molar ratio of ethylene glycol and cyclohexanedimethanol being 95/5 to 75/25.
Copolymerized polyethylene terephthalate 70-95 having an endothermic peak of 180 to 240 ° C. measured by DSC after heating in nitrogen at 130 ° C. for 5 hours and an endothermic amount of 10 to 40 joules / g. A polyester packaging material, characterized by having a layer formed from a polyester composition consisting of 5 parts by weight of ethylene copolymer and 5 to 30 parts by weight of ethylene copolymer as a layer in contact with the contents. 2. The polyester composition further comprises a non-polar ethylene polymer or a non-polar ethylene copolymer in an amount of 10 parts by weight or less based on 100 parts by weight of the total amount 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 linear low density polyethylene.
The packaging material described in. 4. The polyester composition contains an antioxidant in an amount of 0.05 to 1.0 with respect to 100 parts by weight of the polyester composition.
Polyester packaging material according to claim 1 or 2, characterized in that it is included in an amount of parts by weight. 5. The polyester packaging material according to claim 1, wherein the ethylene copolymer ionomer is a divalent metal ionomer.