JP3396962B2 - Heat shrinkable polyester composite film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable polyester type composite film which is preferably used as a packaging material used for coating, bundling, outer packaging, etc., and is particularly excellent in shrink finish and solvent adhesiveness and heat shrinkable. The present invention also relates to a heat-shrinkable polyester film that retains excellent strength and does not break or tear.

[0002]

2. Description of the Related Art A heat-shrinkable film utilizes various heat-shrinkability and shrinkage stress to make various containers such as bottles (including glass and plastic bottles) and cans, and long objects (pipes, bars, It is widely used for coating, bundling, or sheathing wood and various rods. Specifically, display,
Used to cover part or all of the cap, shoulder and body of the bottle for the purpose of protection, bundling and improvement of commercial value, or a plurality of boxes, bottles, plates, sticks, notebooks, etc. It is used for a skin package or the like in which each film is accumulated and packaged, or the film is brought into close contact with the object to be packaged. Actually, the heat-shrinkable film is formed into a tube and covered with a bottle, or after pipes are accumulated, heat-shrinking is performed for packaging or bundling.

Polyvinyl chloride, polystyrene, polypropylene and the like are usually used as the material for the heat-shrinkable film. However, these generally have poor heat resistance and cannot withstand boil treatment, retort treatment and the like.
For example, a film made of polyvinyl chloride has a problem that a gel of a polymer or an additive is apt to be generated during heat shrinkage, a pin pole is generated on the printed surface when printing is performed, and chlorine gas is generated when incinerated. Further, a film made of polystyrene has inferior weather resistance and solvent resistance, is prone to cracks, and has a problem that the dimensions of the film are not stable. Further, a film made of polypropylene has a problem that it has a poor shrinkage property in a low temperature range, and wrinkles or spots are apt to be generated in a shrinking part.

On the other hand, polyester is a very excellent material in terms of heat resistance, weather resistance and solvent resistance. However, on the other hand, it has the property of being easily crystallized at high temperatures and becoming brittle, so its strength decreases due to heat history in the processing steps (high temperature sterilization, etc.) after heat shrinkage, and due to external forces such as friction and impact. There is a drawback that scratches and tears are likely to occur. Therefore, under conditions where the film surface is susceptible to friction and shock, such as high-speed heat shrinkage processing and transport process after heat shrinkage, scratches and tears of the film frequently occur,
It was a very big problem in practical application.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to have excellent heat shrinkability and solvent adhesiveness, and at the time of heat shrinkage and after heat shrinkage. Another object of the present invention is to provide a heat-shrinkable polyester film capable of maintaining excellent strength even after undergoing the heat history of.

[0006]

The heat-shrinkable polyester-based composite film of the present invention, which has been able to solve the above-mentioned problems, comprises a polyester having an ethylene terephthalate unit of 80 mol% or more as an intermediate layer, and ethylene on both sides thereof. Polyesters having a terephthalate unit content of 80 mol% or less, a smaller number of ethylene terephthalate units than the polyester of the intermediate layer, and having the same or different chemical structures are laminated, and the polyester layers on both sides are used as a diol component. In addition to ethylene glycol that constitutes a polyethylene terephthalate unit, it is characterized by being composed of diethylene glycol and butanediol, and neopentyl glycol or cyclohexanedimethanol.

Here, the heat shrinkage at 100 ° C. in at least one of the longitudinal direction and the width direction of the film is 30.
%, And the heat-shrinkable polyester-based composite film having the following fracture rate in the direction orthogonal to the main shrinkage direction after crystallization treatment of 20% or less is a preferred embodiment of the present invention.

The film is subjected to metallic printing for a shrink label, made into a tube into a cylindrical shape, covered with a 300 ml round glass bottle container, and passed through a shrink tunnel. Passing condition of the shrink tunnel is 1 in zone 1
The residence time is 4.5 seconds at 00 ° C, and the second zone is 140 ° C.
And the residence time is 5 seconds. After aging the container thus coated with the label in an atmosphere of 60 ° C. for 24 hours,
Each sample was obtained by cutting the label into a sample with a width of 15 mm in the main shrinkage direction and pulling it in a tensile tester (STM-T manufactured by Toyo Baldwin Co., Ltd.) in a direction orthogonal to the main shrinkage direction in an atmosphere of -5 ° C. The breaking elongation of each is measured. Of these, those having a breaking elongation of 10% or less are regarded as initial breaking, and the breaking rate (%) is calculated based on the following formula. Breakage rate (%) = [number of initial fractured samples] / [number of measured samples] × 100 Further, the maximum shrinkage stress at 90 ° C. in the main shrinkage direction is preferably 1.7 kg / mm ² or less.

[0009]

As described above, the heat-shrinkable polyester composite film of the present invention comprises (i) a polyester having an ethylene terephthalate unit content of 80 mol% or more as an intermediate layer (hereinafter referred to as B).
(Ii) a polyester having ethylene terephthalate units of 80 mol% or less on both sides thereof and having less ethylene terephthalate units than the polyester of the intermediate layer and having the same or different chemical structure (hereinafter , A layer) may be abbreviated).

The polyester constituting the above-mentioned layer A is used from the viewpoint of imparting excellent solvent adhesiveness to the film.
It is necessary to set the upper limit of the ethylene terephthalate unit to 80 mol%. When the ethylene terephthalate unit exceeds 80 mol%, the solvent adhesiveness when the films are adhered by coating a non-chlorine solvent such as tetrahydrofuran on the film surface is not preferable. It is preferably 78 mol% or less, more preferably 75 mol% or less.

On the other hand, the polyester constituting the layer B has a lower limit of 80 mol% of ethylene terephthalate units from the viewpoint of imparting excellent mechanical properties to the film.
It is necessary to If it is less than 80 mol%, the mechanical properties of the film will be deteriorated, and when it is used as a label for glass bottles, the label will be impacted by rubbing or rubbing the bottles during filling of contents or transfer of products. If added, the label will be scratched or torn, and the commercial value will be significantly impaired. Preferably 83
It is at least mol%, more preferably at least 85 mol%. In order to effectively exhibit the characteristics of the A layer and the B layer described above, the polyester of the B layer needs to have more ethylene terephthalate units than the polyester of the A layer. The polyester contained in the A layer and the B layer is
It may be formed from the dicarboxylic acid component and the diol component described below.

As the above-mentioned dicarboxylic acid component, any of aromatic dicarboxylic acid, aliphatic dicarboxylic acid and alicyclic dicarboxylic acid can be used in addition to terephthalic acid which constitutes an ethylene terephthalate unit.

Examples of the aromatic dicarboxylic acid include benzenedicarboxylic acids such as isophthalic acid, orthophthalic acid and 5-tert-butylisophthalic acid; naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid;
4,4'-dicarboxydiphenyl, 2,2,6,6-
Dicarboxybiphenyls such as tetramethylbiphenyl-4,4'-dicarboxylic acid; 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid and its substitution product; 1,2-diphenoxyethane- 4,4'-dicarboxylic acid and its substitution products are exemplified. Further, as the aliphatic dicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, pimelic acid, suberic acid, undecanoic acid, dodecanedicarboxylic acid, brassylic acid, tetradecanedicarboxylic acid, Examples include tapsinic acid, nonadecanedicarboxylic acid, and docosanedicarboxylic acid. Furthermore, examples of the alicyclic dicarboxylic acid include 1,4-dicarboxycyclohexane and 1,3-dicarboxycyclohexane.

Next, as the diol component, in addition to ethylene glycol constituting the polyethylene terephthalate unit, any of aliphatic diol, alicyclic diol and aromatic diol can be used.

The above-mentioned aliphatic diols include diethylene glycol, propylene glycol, butanediol,
1,6-hexanediol, 1,10-decanediol, neopentyl glycol, 2-methyl-2-ethyl-1,3-propanediol, 2-diethyl-1,3-
Propanediol, 2-ethyl-2-n-butyl-1,
Examples include 3-propanediol. Examples of the alicyclic diol include 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol. Further, as the above aromatic diol, 2,2
-Ethylene oxide adducts of bisphenol compounds such as bis (4'-β-hydroxyethoxydiphenyl) propane and bis (4'-β-hydroxyethoxyphenyl) sulfone; xylylene glycol; polyalkylenes such as polyethylene glycol and polypropylene glycol Examples thereof include glycol.

In order to prepare the polyester used in the above-mentioned A layer and B layer by using such a dicarboxylic acid component and a diol component, one or more dicarboxylic acid components may be added in order to improve the properties as a heat-shrinkable film. Alternatively, it is preferable to use a combination of diol components. The type and content of the monomer components to be combined may be appropriately determined based on desired film characteristics, economic efficiency and the like.

As the polyester, a single copolymer resin may be used, or a mixture of two or more copolymers or homopolyesters may be used. From an economic point of view, it is recommended to use a mixture of polyethylene terephthalate and copolyester.

Here, the chemical structures of the polyesters used in the A and B layers may be the same or different. Further, the B layer may be polyester containing only polyethylene terephthalate.

The above polyester can be produced by a known method, and as such an example, a direct esterification method in which a dicarboxylic acid and a diol are directly reacted;
Examples thereof include a transesterification method in which a dicarboxylic acid dimethyl ester is reacted with a diol. The preparation may be performed by either a batch method or a continuous method.

The heat-shrinkable polyester-based composite film of the present invention contains various known additives, if necessary, in addition to the polyester having the above composition. Such examples include titanium dioxide, particulate silica, kaolin,
Lubricants such as calcium carbonate; antistatic agents; antiaging agents;
UV inhibitors; colorants (dyes, etc.) are included. The intrinsic viscosity of the A layer and the B layer having the above composition is 0.50 to
It is preferably 1.3 d / g.

The method for producing the polyester-based composite film consisting of the A layer and the B layer is not particularly limited as long as a film satisfying the above requirements can be formed, and examples thereof include a multilayer extrusion method and an extrusion laminating method. ,
From an economical point of view, it is recommended to use the multi-layer extrusion method. The shape of the film is not particularly limited, and a flat surface,
It is formed in a tube shape or the like. The obtained film is stretched in a predetermined one direction (main stretching direction) by a known stretching method such as a roll stretching method, a long gap stretching method, a tenter stretching method and a tubular stretching method. In either method, the stretching is carried out by sequential biaxial stretching, simultaneous biaxial stretching, uniaxial stretching and a combination thereof. When biaxial stretching is used, stretching in the machine and transverse directions may be carried out simultaneously, but in order to obtain a more excellent stretching effect, a sequential biaxial stretching method in which either one is stretched first is used. Recommended. In that case, whichever of the longitudinal and lateral stretching order may be performed first. The draw ratio is preferably 2.5 times to 7.0.
Times, more preferably 3.0 times to 6.0 times, even more preferably 4.0 times to 6.0 times, and most preferably 4.0 times.
It is 5 to 6.0 times. In the direction orthogonal to the main stretching direction, stretching is preferably performed in the range of 1.0 to 2.0 times, more preferably 1.1 to 1.8 times. Either may be first in the order of this stretching. By stretching in a direction orthogonal to the main stretching direction, the impact resistance of the film is improved and the property of being easily torn in one direction is relaxed. When the stretching ratio in the right-angled direction exceeds 2 times,
The heat shrinkability in the direction orthogonal to the main shrinkage direction becomes too large, and the result of the heat shrinkage becomes uneven in a wavy state. The film stretched at the above ratio has a shrinkage ratio in the direction orthogonal to the shrinkage ratio in the main direction of preferably 15% or less, more preferably 8 to 10.
It is 9% or less, more preferably 7% or less. The film stretched in this way has the advantage that the finish when heated is uniform.

At the time of stretching, the heat setting method is usually used. Specifically, after stretching, 30 ° C. to 10 ° C.
It is recommended to pass a heating zone of 0 ° C. for about 1 to 30 seconds. By performing such heat setting, it is possible to prevent the dimensional change of the film under high temperature in summer. After the stretching of the film and before or after the heat setting, the stretching may be performed at a predetermined degree. In that case, the stretching is performed at a ratio of up to 70% of the film length. In particular, it is preferable to extend in the main direction, and it is better not to extend in the non-contraction direction (direction orthogonal to the main contraction direction).

Further, after the above stretching, by adding a step of cooling while applying stress to the film while keeping the stretched or tensioned state, or a step of continuously cooling after releasing the tensioned state after the treatment. The shrinkage characteristics of the film due to heating can be made better and stable.

In the stretching step, it is preferable to preheat at a temperature not lower than the average glass transition temperature (Tg) of the polymer constituting the film and not higher than [Tg + 80 ° C.]. When preheating in such a temperature range,
It is possible to control the heat shrinkage in the direction orthogonal to the main shrinkage direction. After that, by heating in a temperature range of 80 ° C. ± 25 ° C., the heat shrinkage rate in the orthogonal direction can be almost minimized.

In order to improve the rupture rate, which will be described later, the temperature (t ₁ ) in the first half and the temperature (t) in the second half of the stretching process are used.
It is recommended to set ₂ ) differently. Preferably, t ₂ is [1 / 2t ₁ +10] (° C.) or more.

In the heat-shrinkable polyester composite film of the present invention thus produced, the heat shrinkage at 100 ° C. in at least one of the longitudinal direction and the width direction of the film is 30% or more. It is a preferred embodiment of the present invention. When the shrinkage ratio is less than 30%, when the film is heat-shrinked by covering the surface of the irregularly-shaped packaged product, the necessary shrinkage ratio in each part cannot be obtained, and if sufficient shrinkage is to be obtained, It needs to be heated to a high temperature. However, since the heat resistance of the packaged item is also limited, the application range is only narrowed,
Not preferable.

In the present invention, the rupture rate (-5 ° C.) obtained by the above method after the crystallization treatment in the direction orthogonal to the main shrinkage direction exhibiting a higher shrinkage rate is preferably 20% or less. . When the breaking rate exceeds 20%, when the film of the present invention is used as a label for glass bottles,
When filling or transferring the contents, the bottles are struck or rubbed against each other and a force such as impact or friction is applied to the label, and the label is scratched or torn. The breakage rate is more preferably 15% or less, and even more preferably 10% or less.

Further, in the present invention, 90 in the main shrinkage direction.
The maximum shrinkage stress of the film at ℃ is 1.7kg / m
It is preferably m ² or less, more preferably 1.5
It is not more than kg / mm ² . This contraction stress is 1.7 kg /
A film having a size of more than mm ² is not preferable because when it is shrunk for a label, the container is deformed, the label is distorted, the shrinkage unevenness is generated, and the commercial value is significantly reduced.

The total thickness of the composite film of the present invention is 20 to 1
00 μm is preferable and 25 to 75 μm is more preferable.
When it is less than 20 μm, mechanical properties such as strength and waist are insufficient, which is not preferable, while when it exceeds 100 μm, mechanical properties become excessive and economically disadvantageous.

The thickness ratio of the A layer and the B layer in the composite film of the present invention is A layer / B layer = 0.01 / 0.99-0.
9 / 0.1 is preferable, 0.05 / 0.95-0.8 /
0.2 is more preferable. Here, the thickness of layer B is the total thickness of both the front and back sides, and the thickness of both sides may be the same or different.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any modification or implementation is within the scope of the present invention without departing from the gist thereof. It is included in the technical scope of.

[0032]

[Examples] The methods for measuring and evaluating the heat shrinkage rate, breakage rate, maximum shrinkage stress, shrinkage finish, transport test breakage rate, and solvent adhesiveness used in the following examples are as follows. (1) Heat shrinkage rate The shrinking direction of the film is the long side, and the sample is cut so that the width is 15 mm, and the sample is 200 mm in the long side direction.
Mark the mark in the gap. The sample is heated to the specified temperature (10
Apply hot air (0 ° C) for 1 minute to heat, and measure the amount of change in the distance between the marked lines. The percentage of this change amount to the original length was defined as the heat shrinkage rate (%). In addition, in Table 1 described later, MD
Represents the heat shrinkage in the stretching direction, and TD represents the heat shrinkage in the width direction.

(2) Breakage rate at -5 ° C after crystallization treatment The film was subjected to metallic printing for shrink labels, made into a cylindrical tube, covered with a 300 ml round glass bottle container, and passed through a shrink tunnel. Let The conditions for passing through the shrink tunnel were such that the first zone had a residence time of 4.5 seconds at 100 ° C., and the second zone had a residence time of 5 seconds at 140 ° C. The container thus coated with the label was aged in an atmosphere of 60 ° C. for 24 hours, and then the label was cut into a width of 15 mm in the main shrinkage direction to obtain a sample (n = 2).
0), the breaking elongation of each sample was measured by pulling with a tensile tester (STM-T manufactured by Toyo Baldwin Co., Ltd.) in a direction orthogonal to the main shrinkage direction in an atmosphere of −5 ° C. Of these, those having a breaking elongation of 10% or less were regarded as initial breaking, and the breaking rate (%) was calculated based on the following formula. Breakage rate (%) = [number of initial fractured samples] / [number of measured samples] × 100

(3) Maximum shrinkage stress Length of the film in the main shrinkage direction: 150 mm, width: 15 m
Cut into m to make a sample, and this sample is 100 m
The sample was set on the upper and lower chucks of a tensile tester (STM-T manufactured by Toyo Baldwin Co., Ltd.) with a marked line of m set to 100 mm. Then, it was treated in hot air at 90 ° C. for 3 minutes, and the maximum value of the shrinkage stress during that time was defined as the maximum shrinkage stress.

(4) Shrinkage Finish In the same manner as in (2) above, the shrinkage finish of the label passed through the shrink tunnel was visually evaluated from the viewpoint of wrinkles, print distortion, and print density due to shrinkage unevenness.

(5) Transport Test Breakage Occurrence Rate In the same manner as in (2) above, 2400 containers each coated with a label that passed through the shrink tunnel were prepared.
Pack 12 containers for each cardboard box,
The containers were stacked on a track with the label surfaces of each container touching each other, and reciprocated over a distance of 700 km. After transportation, the label was inspected for breakage, and the occurrence rate was calculated.

(6) The solvent-adhesive film was rolled into a tube, and tetrahydrofuran (coating amount: 5 g / m ² ) was applied to the bonding surface, and the tube was bonded at room temperature. Width of this tubular sample:
It was cut into 15 mm and the peel strength (g / 15 mm) at 90 ° C. on the joint surface was measured 10 times by a tensile tester (STM-T manufactured by Toyo Baldwin Co., Ltd.), and the solvent adhesion was evaluated by the average value. . According to this evaluation method, at a practical level, solvent adhesion: a value of 400 g / 15 mm or more is required.

Example 1 Resin for layer A: dicarboxylic acid component terephthalic acid unit: 100 mol% diol component ethylene glycol unit: 67 mol% diethylene glycol unit: 2 mol% neopentyl glycol: 21 mol% butanediol: 10 mol % Silicon dioxide (average particle size 2.4 μm): 0.05 wt% Intrinsic viscosity: 0.75 dl / g Resin for B layer: Dicarboxylic acid component terephthalic acid unit: 100 mol% Diol component ethylene glycol unit: 88 mol% di Ethylene glycol unit: 2 mol% Neopentyl glycol: 10 mol% Intrinsic viscosity: 0.75 dl / g

The above polyesters A and B were melt-extruded by separate extruders. The obtained melt was merged between dies, and the melt having a three-layer structure of A / B / A was rapidly cooled by a cooling roll to obtain a film having a total thickness of 188 μm. This unstretched film was preheated at 95 ° C. and then stretched 4.7 times in the transverse direction. The temperature condition during stretching is set to 80 ° C. until half of the whole process, and the remaining half is 9
It was set to 0 ° C. After stretching, the film was cooled to 40 ° C. while keeping it in a tension state to obtain a heat-shrinkable film having a total thickness of 40 μm (thickness ratio of A / B / A layer = 1/2/1). Regarding the film thus obtained, the above (1) to
Table 1 shows the results of examining the characteristics of (6).

[0040]

[Table 1]

As is apparent from Table 1, the film obtained in this example is excellent in solvent adhesiveness and also has good shrink finish. In addition, since it retains its strength even after crystallization due to hot filling after shrinkage and heat history due to past-rise, etc., it does not cause film scratches or tears due to vibration or shock during transportation of processed products. From this, it can be seen that the film is very practical as a label film.

[0042] the same manner as in Example 1 except that the Comparative Example 1 B layer base resin and the same composition as the A layer base resin to give a heat-shrinkable film of Comparative Example 1. The characteristic results of the obtained film are also shown in Table 1.

As is clear from Table 1, the film of Comparative Example 1 has good solvent adhesion and shrink finish, but has a high rupture rate after the crystallization treatment. It can be seen that this is inferior in practicality because the label is often scratched or torn due to vibration or shock during transportation.

Comparative Example 2 The procedure of Example 1 was repeated except that the resin for A layer contained 0.05% by weight of silicon dioxide having the same composition as the resin for B layer and having an average particle size of 2.4 μm. A heat-shrinkable film of Comparative Example 2 was obtained. The characteristic results of the obtained film are also shown in Table 1. As is clear from Table 1, the film of Comparative Example 2 is excellent in mechanical properties, but is inferior in solvent adhesiveness, so that the solvent adhesive method cannot be applied. It was examined whether or not it could be used as a label by bonding with an adhesive instead of the solvent bonding method, but it was found to be extremely unpractical because of its poor shrink finish.

Example 2 Resin for layer A: dicarboxylic acid component terephthalic acid unit: 95 mol% sebacic acid: 5 mol% diol component ethylene glycol: 72 mol% diethylene glycol: 2 mol% cyclohexanedimethanol: 21 mol% butanediol : 5 mol% Spherical silica having an average particle size of 2 μm: 0.05% by weight Intrinsic viscosity: 0.75 dl / g Resin for B layer: Intrinsic viscosity: 0.75 dl / g polyethylene terephthalate

The heat treatment of Example 2 was performed in the same manner as in Example 1 except that the polyesters of the A layer and the B layer were used and the ratio of the thickness of A layer / B layer / A layer was 1/1/1. A shrinkable film was obtained. The characteristic results of the film thus obtained are also shown in Table 1. Like the heat-shrinkable film of Example 1, when used as a label, the heat-shrinkable film of Example 2 has excellent solvent adhesion and good shrink finish, and vibrations and impacts during transportation of the product. Since the film is not scratched or torn due to, for example, it can be seen that it is very practical.

[0047] the same manner as in Example 2 except that the Comparative Example 3 B-layer resin was the same composition as the A layer base resin to give a heat-shrinkable film of Comparative Example 3. The characteristic results of the obtained film are also shown in Table 1. As is clear from Table 1, the heat-shrinkable film of Comparative Example 3 has a good heat-shrink finish, but has a large rupture rate after the crystallization treatment, and the label breaks during transportation of the product. It turns out that it is very inferior in practical use.

Comparative Example 4 As the resin for layer A, spherical silica having an average particle diameter of 2 μm:
Containing 0.05% by weight, intrinsic viscosity: 0.75 dl / g
A heat-shrinkable film of Comparative Example 4 was obtained by the same method as in Example 2 except that the polyethylene terephthalate of Example 1 was used. The characteristic results of the obtained film are also shown in Table 1.
As is clear from Table 1, the heat shrinkable film of Comparative Example 4 has
The heat shrinkage was low and the quality was low.

Example 3 Resin for Layer A Polyethylene terephthalate (polyester A) below: 30% by weight Spherical silica having an average particle size of 2 μm: 0.12% by weight Intrinsic viscosity: 0.75 dl / g Polyester (polyester B) having the following composition ): 62% by weight Terephthalic acid as dicarboxylic acid: 100 mol% Ethylene glycol as diol component: 53% Diethylene glycol: 2 mol% Neopentyl glycol: 45 mol% Intrinsic viscosity: 0.75 dl / g Polybutylene terephthalate (Polyester C): 8% by weight Intrinsic viscosity: 1.10 dl / g Resin for layer B A: 85% by weight Polyester B: 10% by weight Polyester C: 5% by weight

A heat-shrinkable film of Example 3 was obtained by the same method as in Example 1 except that the layers A and B were used. The characteristic results of the obtained film are also shown in Table 1. As is clear from Table 1, the heat-shrinkable film of Example 3 had high quality and high practicality, like the film of Example 1.

[0051] the same manner as in Example 3 except that Comparative Example 5 B layer base resin and the same composition as the A layer base resin to give a heat-shrinkable film of Comparative Example 5. The characteristic results of the obtained film are also shown in Table 1. As is clear from Table 1, the heat-shrinkable film of Comparative Example 5 has good solvent adhesion and shrink finish, but when used as a label, label breakage occurs during transportation of the product, so that it is inferior in practicality. It turned out to be a thing.

Comparative Example 6 A heat-shrinkable film of Comparative Example 6 was obtained in the same manner as in Example 3 except that the resin for layer A had the same composition as the resin for layer B. The characteristic results of the obtained film are also shown in Table 1. As is clear from Table 1, the heat-shrinkable film of Comparative Example 6 had good mechanical properties, but was inferior in practicality because it had poor solvent adhesion and shrink finish.

[0053]

Since the heat-shrinkable polyester-based composite film of the present invention is constituted as described above, it has excellent heat-shrinkability and solvent adhesion, and also has excellent shrink finish.
Since excellent strength can be maintained even after heat shrinkage, no tearing or tearing occurs. Therefore, it is useful in a wide range of packaging materials, including shrink films for labels, and has a very high utility value.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Isaka 2-2-8 Dojimahama, Kita-ku, Osaka Toyo Spinning Co., Ltd. Head Office (56) Reference JP-A-60-232948 (JP, A) JP-A-SHO 60-253545 (JP, A) JP 4-278347 (JP, A) JP 59-76226 (JP, A) JP 51-28885 (JP, A) JP 7-311547 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (3)

(57) [Claims] 1. A polyester having an ethylene terephthalate unit of 80 mol% or more is used as an intermediate layer, and the ethylene terephthalate unit is 80 mol% or less on both sides thereof, and the number of ethylene terephthalate units is less than that of the polyester of the intermediate layer, and the same or different der those polyester is laminated consisting of chemical structure is, the polyester layer of the both sides, as the diol component, Po
Ethylene glycol constituting the ethylene terephthalate unit
In addition to Cole, diethylene glycol and butanedio
And neopentyl glycol or cyclohexane dime
A heat-shrinkable polyester-based composite film , which is composed of a tonol . 2. The film has a thermal shrinkage at 30 ° C. of at least 30% in at least one of the longitudinal direction and the width direction of the film, and the following rupture rate in the direction orthogonal to the main shrinkage direction after crystallization treatment. The heat-shrinkable polyester-based composite film according to claim 1, which is 20% or less. The film is subjected to metallic printing for shrink labels, made into a tube into a cylindrical shape, covered with a 300 ml round glass bottle container, and passed through a shrink tunnel. The conditions for passing through the shrink tunnel are 100 ° C in the first zone and a residence time of 4.5 seconds,
The second zone has a residence time of 5 seconds at 140 ° C. The container coated with the label in this way was aged in an atmosphere of 60 ° C. for 24 hours, and then the label was cut into a sample having a width of 15 mm in the main shrinking direction to obtain a sample, which was orthogonal to the main shrinking direction in an atmosphere of −5 ° C. The breaking elongation of each sample is measured by pulling in a direction with a tensile tester (STM-T manufactured by Toyo Baldwin Co., Ltd.). Of these, the breaking elongation is 1
A fracture rate (%) of 0% or less is regarded as the initial fracture, and the fracture rate (%) is calculated based on the following equation. Breakage rate (%) = [number of initial fractured samples] / [number of measured samples] × 100 3. The heat-shrinkable polyester-based composite film according to claim 2, wherein the maximum shrinkage stress at 90 ° C. in the main shrinkage direction is 1.7 kg / mm ² or less.