JPH0418349A - Easy open material - Google Patents

Abstract

PURPOSE:To obtain a material easy to open and generating no rupture on the way of peeling by combining copolymerized polyester slightly different in compatibility to receive peel strength in a definite range and further using an improved polyethylene terephthalate film as a support film. CONSTITUTION:A film molded from polyester characterized by that a glycol group is mainly composed of an ethylene glycol group and a dibasic acid group consists of a terephthalate group and an isophthalate group and the mol ratio of the terephthalic acid component in the dibasic acid group is 0.75 - 0.96 and the mol ratio of the isophthalic acid group is 0.25 - 0.05 is used as a support base material and an easy release layer composed of low crystalline copolymerized polyester alone or a mixture of copolymerized polyester and non-crystalline copolymerized polyester is provided to the single surface of the film and a thermal adhesive layer composed of hot press adhesive crystalline copolymerized polyester is further provided on said layer to form a lid material.

Description

Detailed Description of the Invention <Industrial Field of Application> The present invention relates to a material that is mainly used as a lid material for plastic containers and has the property of being easily peelable. is provided with a peelable adhesive layer (B) that can be bonded by thermocompression, the peelable adhesive layer is composed of an easily peelable layer (I) and a thermally adhesive layer (II),
) has a peel strength of 0.8 to 1.5 (kg/15 am width), and is an easily peelable material consisting of three layers with a thermocompression adhesive layer (n) provided on the core layer (I). This invention relates to a laminate (hereinafter referred to as an easy-open material).

<Prior Art> Polycarbonate resins are excellent in heat resistance, one-dimensional stability, etc., and another property is that they are very excellent in fragrance retention. Taking advantage of this property, containers thermoformed from polycarbonate films or sheets have been widely used for food packaging.

However, as lid materials for polycarbonate containers, a thin film made of the same polycarbonate is currently used by heat-sealing it at a high temperature of 220° C. or higher. Although food containers with such a structure have excellent flavor retention, they cannot be easily opened, because the lid material and the container body are firmly heat-sealed. As a countermeasure to this problem, attempts have been made to use lid materials made of polyester or other films coated with adhesives such as polyethylene or ethylene/vinyl acetate copolymer # (EVA), but the If a general polyester film or nylon film is used as a supporting base material for the lid, it may corrode, weaken the adhesive strength, and cause the contents to seep out.
When trying to remove the lid quickly, problems such as the lid material breaking during peeling occurred, so this project failed without being put to practical use. Therefore, there is a strong desire for containers that can be easily opened.

<Problems to be Solved by the Invention> The present invention solves these problems by combining copolyesters with slightly different compatibility, and
By keeping the lt strength within a certain range and by using an improved polyethylene terephthalate film as the support film, we provide a material that is easy to open and does not break during peeling even if it is quickly peeled off. . More specifically, by laminating crystalline copolymerized polyesters with a glass transition point of 50°C or higher to form a thermal adhesive layer, corrosion by oils in the contents can be prevented, and isophthalic acid groups are copolymerized. By using a film (C) formed from polyethylene terephthalate as a supporting base material, we have succeeded in developing a material that is strong and can be opened easily.

Means for Solving Problems> The present invention provides a method in which the glycol group is mainly an ethylene glycol group, the dibasic acid group is composed of a terephthalic acid group (A) and an isophthalic acid group (B), and the terephthalic component in the dibasic acid is (
Using a film (C) formed from polyester having a molar ratio of ^) of 0.75 to 0.95 and a molar ratio of isophthalic acid component (B) of 0.25 to 0.05 as a supporting base material, On one side of the film, low crystalline copolyester (E) alone or the copolyester (E)
and an amorphous copolymerized polyester (F), and further provided on the core layer is a thermoadhesive layer (II) made of a thermocompression bondable crystalline copolymerized polyester (G).
). This is an easy-to-open lid material used for plastic containers. More specifically, when bonded by thermocompression to a polycarbonate film, the peel strength is 0.8.
~1.5 (kg/15m), and can be thermocompression bonded to food containers thermoformed from polycarbonate film, and also prevents oils in the container contents from seeping out and retains fragrance for a long time. The present invention relates to a lid material that can be maintained and that does not cause the lid material to tear during opening.

The easily peelable layer (I) described here is a plastic film support (C1) and a polycarbonate surface bonded to a heat adhesive layer (n).
It acts as an adhesive to connect through.

When the package is opened, this layer <I> is peeled off.6 However, when peeled off, due to cohesive failure of layer (I>
．． It exhibits a peel strength of 5 (kg/15 aw+) and exhibits the ability to be easily opened. Further layers (
I) is a mixture of copolymerized polyester E or a mixture of this and polyester F [the weight ratio of the two is preferably 1 to 10 to 9 to 0, particularly preferably 4 to 10 to 6 to 0], for example, in a mixed solvent [ Toluene (60-80 parts by weight) / Methyl ethyl ketone (10-40 parts by weight) / Dimethylformamide (1-
20 parts by weight)] or [methylene chloride (50 to 90 parts by weight)/toluene (10 to 30 parts by weight)/methyl ethyl ketone (D to 20 parts by weight)] with a solid content of 10 to 40 parts by weight [especially 10 to 30 parts by weight] and gravure coated.

The plastic film support (C) is coated by known means such as reverse roll coating, kiss roll coating 1 bar coating, doctor knife coating, comma coating or air knife coating.
On top of that, the thickness after drying is 5 to 15 μm [If the thickness is less than 5 μm, the peel strength is weaker than 0.8 (kg / '15 + 111), and if it exceeds 15 μm, the peel strength is 1.5 (kg / 15 cities)
It is applied to make it stronger. The thermal adhesive layer (II) is made of crystalline copolymerized polyester (G) [
By using a glass transition point of 50°C or higher], the 4th layer (n) has the effect of preventing the contents in the container and the oils in the contents from seeping out and deteriorating the layer (I) at a temperature of about 55°C. Copolymerized polyester (G) was mixed with a mixed solvent [toluene (60
~90 parts by weight)/methyl ethyl ketone (40 to 10 parts by weight)] or [methylene chloride (50 to 90 parts by weight)/toluene (10 to 30 parts by weight)/methyl ethyl ketone (D
~20 parts by weight)] with a solid content of 10 to 30 parts by weight [especially 1
5 to 25 parts by weight] and provided on the plastic film support (C) by gravure coating, reverse roll coating, -1r roll coating, bar coating, doctor knife coating, comma coating, air knife coating, etc. On top of the layer (■), approximately 0.5 to 8 μm [particularly 1 to 5 μm; less than 1 μm is less effective in preventing corrosion by the contents and oils in the contents, and if it exceeds 5 μm, the peel strength is reduced. [leads to deterioration].

In addition, in order to prevent wrinkles in the film roll that tend to occur during winding after coating, fine polymer particles, for example, with a diameter of 1 to 10 μm, are added to the coating liquid for the easily peelable layer (I) and/or the thermal adhesive layer (n). cross-linked polyethylene or (cross-linked) polystyrene fine particles at a ratio of 0.5 to 10% of the solid content of the coating agent.
If parts by weight, preferably 2 to 7 parts by weight, are dispersed, winding can be easily performed.

Low crystalline copolyester used in the present invention (D is
The molar ratio of terephthalic acid and adipic acid as acid components is 5.
The ratio is about 0 to 90 to 50 to 10, and the glycol components include ethylene glycol, 1,4 butanediol,
The molar ratio of polyoxytetramethylene glycol is 10~
The ratio is approximately 40:70 to 50:20 to 10.

In the acid components, if terephthalic acid is less than 50 mol % and adipic acid is more than 50 mol %, crystallinity is impaired, blocking after coating becomes large, and processability becomes low, which is disadvantageous.

Further, when terephthalic acid is more than 90 mol% and adipic acid is less than 10 mol%, the crystallinity can be kept within 20%.
Not only is this inappropriate, but the low-temperature sealing properties also deteriorate. Furthermore, ethylene glycol is 10 mol% in the glycol component.
When the amount is less than 40 mol %, the adhesive strength is decreased, and when it is 40 mol % or more, the crystallinity is too large and the adhesive strength is decreased. 1.4-
Butanediol is used to make the structure irregular and lower the melting point and crystallinity, so if it is out of the above range, it will have a negative effect on adhesive strength and blocking.
Polyoxytetramethylene glycol is also blended to control crystallinity, and if it is less than 10 mol%, the crystallinity will be insufficient, and if it is more than 30 mol%, the crystallinity will be too large. Therefore, it is necessary to adjust the crystallinity and glass transition point appropriately.

The amorphous copolymerized polyester B provided for layer (I) is
The molar ratio of terephthalic acid and sepathic acid as acid components is 50.
~90:50~10, and the molar ratio of ethylene glycol and neopentyl glycol as glycol components is
A ratio of 50 to 90 to 50 to 10 is used. If the acid component contains less than 50 mol% of terephthalic acid and more than 50 mol% of sepathic acid, it will become crystalline, and if the degree of crystallinity is less than a few % and is not substantially amorphous, it will lead to a decrease in adhesive strength. If the content of terephthalic acid exceeds 90 mol % and the content of sepathic acid is less than 10 mol %, the low-temperature sealing properties tend to deteriorate. Furthermore, in the glycol component, ethylene glycol is 5
Less than 0 mol% and 50 mol% neopentyl glycol
If it exceeds this value, it will become crystalline, which will reduce the adhesive strength and hinder smooth peeling. Furthermore, if the ethylene glycol content is more than 90 mol% and the neopentyl glycol content is less than 10 mol%, the solubility in solvents will decrease and processability will deteriorate.For this reason, the copolymerized polyester will be substantially amorphous. Therefore, a composition having a glass transition point of 20°C or less is selected.

The layer (Il) described in the present invention is composed of a low-crystalline copolyester (E) or a mixture of this copolyester (E) and an amorphous copolyester (F). (F) is used to soften the entire layer (I). Therefore, the weight ratio of copolyester (E) and (F) is 1 to 10.
vs. 9-0. If only the amorphous copolyester (F) is used for the easily peelable layer (I), it will be too soft and the layer (I) will be too soft.
I) The coating cannot be applied uniformly.

Copolymerized polyester (
G) uses terephthalic acid and isophthalic acid as acid components, the molar ratio of both is 30 to 70:70 to 30, and the molar ratio of ethylene glycol and neopentyl glycol used as glycol components is 30 to 60: 70-4
0, and the glass transition point of the copolymer is 50°C or higher.

If the acid component contains less than 30 mol% of terephthalic acid and more than 70 mol% of isophthalic acid, the glass transition point will be lowered and the heat resistance will be lowered. Also, terephthalic acid is 70
If the amount of isophthalic acid exceeds 30 mol%, the glass transition point becomes too high and the low-temperature sealability deteriorates. Furthermore, in the glycol component, ethylene glycol is 3
less than 0 mol% and neopentyl glycol or 70%
If it exceeds mol%, the degree of crystallinity will decrease and heat resistance will decrease. Furthermore, if the ethylene glycol content exceeds 60 mol% and the neopentyl glycol content exceeds 30 mol%, the solubility in the solvent decreases, resulting in poor processability.

The glass transition point of the copolymerized polyester (G) is 50°C or higher. In midsummer, the temperature inside a transport vehicle can rise to over 50°C, and if a copolyester with a glass transition point of 50°C or lower is used, the contents or oil stains in the contents will not occur in such an environment. It is difficult to completely prevent leakage.

The copolymerized polyester (E) used in the present invention, the substantially amorphous copolyester (F), and the crystalline copolymerized polyester [G) all have molecular weights of 1oooo to 3.
The molecular weight is preferably about 0,000.
If it is less than 0, wetting to the plastic film support layer will be poor, and if it exceeds 30,000, the cohesive force will be too large, resulting in poor adhesion.

Next, the support film (C) used in the present invention will be explained in detail.

When the above-mentioned peelable layer D [easy peel layer (■) + thermal adhesive layer (■)] is installed on a commercially available general polyethylene terephthalate film or nylon film, it can be quickly bonded to a plastic container, such as a polycarbonate container, after being thermally bonded. If an attempt is made to peel off the film, a problem may occur in which the film support is torn due to the formation of a thermally bonded portion during the peeling process.

The present invention was developed as a result of various studies to solve these problems.
It has been found that a film made of modified polyethylene terephthalate in which isophthalic acid groups (B) are copolymerized with terephthalic acid groups (A) in the ratio described below should be used.

That is, in the modified polyethylene terephthalate used in the present invention, the glycol group is mainly an ethylene glycol group, and the molar ratio of the component (^) in the dibasic acid group is 0.75.
0.95 to 0.95, molar ratio of component (8) 0.25 to 0
,05, preferably the molar ratio of component (A) is 0.83 to 0.93, and the molar ratio of component (8) is 0.17 to 0.0.
It is made of polyester with a rating of 1.

Incidentally, the glycol mainly consists of ethylene glycol, and even if about 2 to 3% of diethylene glycol, which is sometimes produced during polymerization, is contained in the polyester as a glycol component, it will not cause any problem in carrying out the present invention. .

The film support (C) used in the present invention is a film obtained by melting polyester, extruding it through a die, and casting it on a casting drum. Preferably, this cast (unstretched) film is rolled in both the vertical and horizontal directions. Stretched 2.7 to 3.8 times, and further stretched 1
It is a biaxially stretched film heat-set in the range of 60°C to 230°C, more preferably a film stretched 2.8 to 3.5@C and heat-set in the range of 180°C to 220°C.

If the molar ratio of the isophthalic acid groups copolymerized to the modified polyethylene terephthalate to the dibasic acid groups is less than 0.05, the improvement effect of the film will be insufficient, and even if the lid material adhered to the container is quickly peeled off. Bifurcations may occur in the lid material during peeling, and if it is larger than 0.25, the film will lack heat resistance, and the easy-peel layer (N) and/or thermal adhesive layer (N) may be separated from the film support. It may hold its shape well when coated on top, but it becomes difficult to coat.

Further, the modified polyethylene terephthalate film is stretched 2.7 to 3.8 times in the vertical and horizontal directions, and further heat-set in the range of 160 to 230 degrees Celsius, more preferably 2.8 to 3.5 times. By stretching the film twice and heat-setting it in the range of 180° C. to 220° C., it is possible to obtain an excellent film or sheet that has excellent heat resistance during coating and does not break during peeling even if it is quickly peeled off.

The easy-open material according to the present invention is effective as a lid material for packaging foods containing oils, and is particularly suitable for use in instant solid curry.

The present invention will be described in detail below with reference to Examples.

The test methods in the examples are as follows.6 Test 1
．． Measurement of peel strength〉 The obtained lid material was cut into 15 square pieces, and using a heat sealer made by Tester Sangyo @, the pressure was 3 kg and the temperature was 100”C.
120°C, 140°(:, 160°C, 180"C:
Five samples were prepared by thermocompression bonding to a polycarbonate film (thickness: 120 μm) for 1.5 seconds at each temperature of : and 200'C. After cooling sufficiently, using a tensile tester T CM-100 model manufactured by Minebea ■, peeling at 180''C and tensile speeds of 200 and 500 (am/min), !j
The separation strength was measured.

Test 2: Leakage test of instant solid curry〉 Instant solid curry was placed in a thermoformed container made of polycarbonate film.
Pack 100 g of S&B dinner curry (medium spicy) and seal the layer (II) side of the container and lid using a cup sealer manufactured by Tester Sangyo ■ at a temperature of 160°C and a pressure of 3kg/-・f.
A sample was prepared by thermocompression bonding for 5 seconds. Thereafter, the container was placed diagonally in a constant temperature bath at an ambient temperature of 55° C., and leakage of the instant solid curry was observed.

Reference example> The copolymer used in the example was produced by a conventional method,
Its composition, crystallinity, molecular weight and glass transition point are as follows.

Copolymerized polyester (Polymer E) Tephthalic acid 5.9 mol%, adipic acid 4.1 mol%,
Ethylene glycol 3.0 mol%, 14-butanediol 5.8 mol% and polyoxytetramethylene glycol (molecular weight 2500) 1.2 mol% Molecular weight approximately 25000 Crystallinity approximately 20% Glass transition point -20°C Copolymerization Polyester (Polymer F) Terephthalic acid 5.0 mol%, Isophthalic acid 50 mol%,
Ethylene glycol 4.5 mol%, neopentyl glycol 55 mol% Molecular weight Approximately 25,000 Crystallinity Amorphous glass transition point 8°C Copolymerized polyester polymer G) Terephthalic acid 70 mol%, Sehasic acid 30 mol C30,
Ethyl diglycol 56 mol%, neopentyl glycol 44 mol% Molecular weight approximately 20,000 Crystallinity approximately 30% Glass transition point 67°C <Example 1> Polymer E was mixed with 79 parts of toluene and 16 parts of methyl ethyl getone.
7 parts of dimethylformamide and 5 parts of dimethylformamide.
A coating MD was prepared by heating to 0''C and dissolving over 30 minutes to have a solid content of 10% by weight.

After cooling this coating liquid to room temperature, it is made of modified polyethylene terephthalate in which 10 mol% of isophthalic acid groups are copolymerized in dibasic acid groups.
It was applied using a Mayer bar (No. 40) on one side of a 20 μm thick film that had been stretched 3 times and 3.5 times in the horizontal direction and further heat-set at 220°C. When dried at a temperature of 100℃ (about 1 minute), the first layer was 7μ.
A sample of mH strength was obtained.

Next, Polymer G was dissolved in a mixed solvent consisting of toluene (80 parts) and 20 parts of methyl ethyl ketone with stirring to prepare a coating liquid J having a solid content of 20% by weight. This coating liquid E
was further coated with a Mayer bar (No. 10) on top of the first layer of the previously processed film, and similarly dried at a drying temperature of 100°C to form a layer (2) with a thickness of 2.5 μm. Obtained.

Evaluation tests were conducted on the samples thus obtained. The peel strength according to Test 1 was measured at various temperatures from 100℃ to 200℃ and 2
At each peeling rate of 00 and 500 (fflI!/min), the peeling rate was 0.90 to 0.95 (kg/15+u+width), and all the peeling occurred in the first layer made of Polymer E. Also, the peeling was due to cohesive failure, but since Polymer E was a thin layer and Polymer G and Polymer E of the thermal adhesive layer (Layer Ⅰ) remained on the polycarbonate film, the failure (peeling M) occurred. The surface was not noticeable.

Note that there was no case of the lid material breaking during peeling in any of the samples under any of the test conditions.

In Test 2, the instant solid curry was left to stand for 3 weeks, but there was no leakage at all.

Comparative Example 1> Coating JH prepared in Example 1 was applied using the same Maya bar and drying conditions as in Example 1. ) with a thickness of 7 μm.
A layer was provided, and coating liquid J prepared in Example 1 was applied under the same conditions as in Example 1 to obtain a 2.5 μm thick sample of the 2nd layer. Evaluation tests were conducted on the samples thus obtained. The peel strength in Test 1 was 0.90 to 0.95 (dazzle/15 circles) at each temperature of 100 ° C to 200 ° C and at each peel speed of 200 and 500 (rounds / minute),
Two out of five samples peeled at a peeling speed of 200 m/min, and five out of five samples peeled at a peeling speed of 500° C.m/min, all of which broke during peeling.

Comparative Example 2> Only the support film used in Comparative Example 1 was changed from a commercially available biaxially oriented polyethylene terephthalate film to a commercially available biaxially oriented nylon 6 film. 7μm th layer and 2.5μ
A sample was obtained in which the m-th layer was provided.

Evaluation tests were conducted on the samples thus obtained. The peel strength in Test 1 was 0.8 at each temperature of 100°C to 200°C and at each peeling speed of 200 and 500 (mm/min).
5 to 0.95 (kg / 15 width), and the sample peeled at a peeling speed of 20011 m+/min broke 3 out of 5, and the samples peeled at 500 m/min broke 5 out of 5 during peeling. occurred.

<Example 2> Coating liquid K was prepared by dissolving polymer E in methylene chloride so that the solid content was 33% by weight. On the other hand, Polymer F was dissolved in methylene chloride and a coating liquid was prepared so that the solid content was 33% by weight.Next, coating liquids K and L were mixed, toluene and methyl ethyl ketone were added, and coating liquid M was prepared.
was prepared.

The composition of coating liquid M is such that the solvent is 70 parts of methylene chloride, 20 parts of toluene, and 10 parts of methyl ethyl ketone, the solid content is 26% by weight, and the weight ratio of polymer E and polymer F in the solid content is 1:1. A certain coating liquid N was prepared.

On the other hand, as a support film, modified polyethylene terephthalate copolymerized with 17 mol% of isophthalic acid groups was melted, cast on a cooling drum,
．． The film was stretched 9 times and 3.3 times in the transverse direction, and then heat-set at 185° C. to obtain a film with a thickness of 38 μm.

Applying coating liquid N to the film using a comma coater,
It was dried at 110° C. to form a first layer having a thickness of 8 μm.

Next, coating liquid J was applied onto the previously processed layer (I) using a gravure coater, and dried at 110''C to form a 2.5 μm thick layer (1).

Evaluation tests were conducted on the samples thus obtained.

The peel strength in Test 1 was 1.1 to 1.3 (kg/15 m+width) at each temperature of 100°C to 200°C and each peeling speed of 200 and 500 (m+/min). There was no tearing of the material at all regardless of the test conditions, and in Test 2, an instant solid curry leakage test, no leakage occurred even though the material was left for 3 weeks.

<Example 3> Fine particle cross-linked polystyrene (manufactured by Sumitomo Chemical ■, Fine Pearl PB-30006E) was added to the coated MN obtained in Example 2.
) were mixed and dispersed to give a coating liquid P of 3.5% by weight based on the solid content of the copolymerized polyester.

As a support film, modified polyethylene terephthalate copolymerized with mol% of inphthalic acid groups was melted, cast on a cooling drum, and further stretched 3.0 times in the vertical direction and 3.1 times in the horizontal direction, and then A 25 μm film was prepared by heat setting at ℃.

Next, coating liquid P was applied on the film using a comma corner, and coating liquid J was dried at 110°C using a gravure coater to form a first layer of 8 μm and a layer of 3.5 μm.
The second layer was established.

The peel strength according to Test 1 was 1.1 to 1.3 (kg7" 1511 f+
(width), and the lid material never broke during peeling, regardless of the test conditions.

<Effects of the Invention> The easy-open lid of the present invention is as described above,
Oil resistance is achieved by providing an easily peelable layer (I) and an oil-resistant thermal adhesive layer (II> on the film support [C), and by using a polyethylene terephthalate film copolymerized with isophthalic acid groups as the film support. A highly practical laminate film that is easy to open and that does not tear the film support even when opened quickly is obtained.6 Patent Applicant: Teijin Ltd. Corporate Procedural Amendment August 21, 1990

Claims (1)

[Claims] 1) The glycol group is mainly an ethylene glycol group, 2
The basic acid groups are terephthalic acid group (A) and isophthalic acid group (B
), the molar ratio of component (A) in the dibasic acid group is 0.75 to 0.95, and the molar ratio of component (B) is 0.25.
A laminate in which a peelable adhesive layer (D) is provided on one side of a film (C) formed from polyester having a molecular weight of 0.05 to 0.05. 2) The polyester film (C) is stretched 2.7 to 3.8 times vertically and horizontally, and stretched at 160°C to 23°C.
The laminate according to claim 1, which is heat-set at 0°C. 3) The peelable adhesive layer (D) is composed of an easily peelable layer (I) and a thermal adhesive layer (II), and the easily peelable layer is composed of a film (C).
), and the easily peelable layer (I)
is a low-crystalline copolymerized polyester (E) alone or a mixture of the copolymerized polyester (E) and an amorphous polyester (F), and the thermoadhesive layer (II) is thermocompression bondable and crystalline. The laminate according to claim 1, comprising a polyester copolyester (G). 4) Claim 1: After the laminate and the lid of the container are thermocompression bonded to the plastic container, the peel strength between the lid and the plastic container is in the range of 0.8 to 1.5 kg/15 mm width.
The easily peelable laminate described in .