JPH0732478A - Delustered heat shrinkable polyester film - Google Patents

Abstract

PURPOSE:To provide delustered heat shrinkable polyester film, very seldom in defects, such as wrinkle, strain, shrinkage spots and the like which are generated when the film is shrinked by heat, and provided with beautiful finishing appearance. CONSTITUTION:In a delustered heat shrinkable polyester film, the degree of heat shrinkage in a main shrinking direction at 100 deg.C is 40% or more and the same in a direction orthogonal to the main shrinking direction is 20% or less while the degree of heat shrinkage when the film is heated for 10sec employing hot air of 100 deg.C to shrink it 40% by heat in the main shrinking direction of the film and, thereafter, the film is heated by hot air of 130 deg.C for 10sec is 12% or more and the glossiness of the film is 150% or less.

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 film which is suitable as a packaging material used for coating, binding, exterior packaging, etc. In particular, the present invention relates to a matte heat-shrinkable polyester film having few defects such as wrinkles, distortion, and shrinkage spots when heat-shrinked, having a beautiful finished appearance.

[0002]

2. Description of the Related Art Heat-shrinkable films are used for coating various containers such as bottles (including glass and plastic bottles) and cans; and for coating long objects such as pipes, rods, wood and various rod-shaped bodies, It is used for bundling and exterior. For example, such a heat-shrinkable film is used to cover a part or the whole of the bottle cap, shoulder, and body for the purpose of marking, protection, bundling, improvement of commercial value and the like. Heat-shrinkable film can also be used for boxes, bottles, plates,
It is also used for the purpose of accumulating and packing a plurality of sticks, notebooks, etc., and for the purpose of closely adhering a film to an object to be packaged and packaging with the film (skin package). In the above application, the shrinkability and shrinkage stress of the film are utilized.

Polyvinyl chloride, polystyrene, polyethylene, chlorinated rubber and the like are used as the material of the film. Usually, the above-mentioned film is molded into a tube, and the tube-shaped film is put on a bottle, or after pipes are accumulated and the tube-shaped film is put on the bottle, it is heat-shrinked to wrap or bind the film. To do.

However, the conventional heat-shrinkable film has poor heat resistance and cannot be subjected to high-temperature boil treatment or retort treatment (high-temperature sterilization treatment for producing retort food). For example, when subjected to retort processing, conventional films break during processing.

Conventional films also have poor adhesion to ink. For example, even if a polyvinyl chloride film is printed, a good printing state cannot be obtained due to poor adhesion between the ink and the film. Furthermore, since the polyvinyl chloride film lacks heat resistance, gels of polymers and additives are likely to be partially formed during film formation, which causes pinholes on the printed surface. .

The above-mentioned conventional film shrinks with time after the film is manufactured. Therefore, the contraction causes a change in the printing pitch, and high-precision printing cannot be performed.

On the other hand, a heat-shrinkable film using polyester, which is excellent in heat resistance, weather resistance and solvent resistance, has been proposed. However, this heat-shrinkable polyester film has problems that the heat shrinkage in a desired direction is insufficient, or the heat shrinkage in a direction orthogonal to the direction cannot be reduced. It was Such a problem can be solved by optimizing the copolymerization composition of the raw material polyester, as disclosed in, for example, JP-A-63-156833.

However, the films obtained by these methods also have a problem that the shrinking speed is too fast, and when the film is heat-shrinked, wrinkles, distortions, shrinkage spots, etc. occur on the film, which is beautiful. There was a drawback that the appearance was difficult to obtain.

Furthermore, recently, since the image of the product has been upgraded to obtain a product having a better appearance than other similar products, a matte heat shrinkable film has been commercialized. Was wanted.

[0010]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned conventional problems, and an object thereof is to obtain a sufficiently large heat shrinkage ratio and to provide wrinkles, distortions, and shrinkage spots when heat shrinks. It is an object of the present invention to provide a heat-shrinkable polyester film having a matte appearance, a beautiful appearance, and a minimal number of defects.

[0011]

The matte polyester film of the present invention has a heat shrinkage at 100 ° C. of 40% or more in the main shrinkage direction and 20% or less in the direction orthogonal to the main shrinkage direction. Yes, the film was heated for 10 seconds using hot air at 100 ° C. to shrink the film by 40% in the main shrinking direction, and then was heated for 10 seconds using hot air at 130 ° C.
The heat shrinkage rate when heated for 2 seconds is 12 in the main shrinkage direction.
% Or more and the gloss of the film is 150% or less.

The present invention will be described in detail below.

As the dicarboxylic acid component constituting the polyester used in the present invention, any of aromatic dicarboxylic acids including terephthalic acid constituting the ethylene terephthalate unit, aliphatic dicarboxylic acids and alicyclic dicarboxylic acids can be used. Can be done. Aromatic dicarboxylic acids other than terephthalic 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′-dicarboxylate. Dicarboxybiphenyls such as diphenyl and 2,2,6,6-tetramethylbiphenyl-4,4'-dicarboxylic acid; 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid and substitution thereof Body; 1,2
-Diphenoxyethane-4,4'-dicarboxylic acid and substituted products thereof. 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, brassic acid, tetradecanedicarboxylic acid, tapsinic acid, nonadecanedicarboxylic acid, doco Examples include sandicarboxylic acid and substitution products thereof. As the alicyclic dicarboxylic acid, 4,
4'-dicarboxycyclohexane and its substitution products.

As the diol component constituting the polyester used in the present invention, any of aliphatic diols such as ethylene glycol constituting an ethylene terephthalate unit, alicyclic diols and aromatic diols can be used. Aliphatic diols other than ethylene glycol 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-
Examples include ethyl-2-n-butyl-1,3-propanediol. Examples of the alicyclic diol include 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol. Examples of aromatic diols include ethylene oxide adducts of bisphenol compounds such as 2,2-bis (4′-β-hydroxyethoxydiphenyl) propane and bis (4′-β-hydroxyethoxyphenyl) sulfone; xylylene diglycol, Examples include polyalkylene glycol such as polyethylene glycol and polypropylene glycol.

The polyester used in the present invention can be formed from the above dicarboxylic acids and diols. In order to prepare the polyester, it is usually preferable to use one or more dicarboxylic acids and diols in combination, respectively, whereby the properties as a heat-shrinkable film can be improved. The types and contents of the dicarboxylic acid component and the diol component used in combination can be appropriately determined based on desired film characteristics, economic efficiency and the like.

The heat-shrinkable polyester film of the present invention is a composition containing at least one polyester obtained from the above dicarboxylic acid component and diol component. In the heat-shrinkable polyester film of the present invention, it is preferable that 40 to 90 mol% of the whole polyester contained is an ethylene terephthalate unit. When the content of the ethylene phthalate unit is less than 40 mol% of the total polyester, the heat resistance of the obtained film may be reduced, and when it exceeds 90 mol%, the finished state of the obtained film after shrinkage may be reduced. May be defective.

Any of the polyesters used in the present invention can be manufactured by conventional methods. For example, a direct esterification method in which a dicarboxylic acid and a diol are directly reacted;
A polyester or a copolyester is prepared by a transesterification method or the like in which a dicarboxylic acid dimethyl ester is reacted with a diol. Each of these methods may be a batch method or a continuous method.

In general, the copolyester has a low melting point, so that it has a problem that it is difficult to handle when dried. Therefore, the copolyester is preferably used as a mixture with the homopolyester. Examples of the homopolyester include polyethylene terephthalate, polyethylene naphthalate, and poly (1,4-cyclohexene dimethylene terephthalate), and polyethylene terephthalate is particularly preferable in that it is economical because it is inexpensive.

The polyester composition used in the present invention contains inorganic fine particles or organic fine particles insoluble in the composition in order to reduce the glossiness of the resulting film to 150% or less and to give a matte tone. An incompatible thermoplastic resin is added to the composition.

Examples of the inorganic fine particles insoluble in the polyester composition include metal oxides such as silica, alumina, titanium oxide and zirconia; complex oxides of metals such as kaolin, talc, sericite and zeolite; calcium carbonate, barium carbonate and the like. Examples thereof include fine particles of a carbonate of a metal; a sulfate of a metal such as calcium sulfate and barium sulfate; and a phosphate of a metal such as calcium phosphate. Examples of the organic fine particles include fine particles made of a crosslinked polymer such as polystyrene, polyacrylic, silicone, and melamine.

Examples of the thermoplastic resin which is incompatible with the polyester composition include polyolefin resin, polyacrylic resin, polycarbonate resin, polysulfonic acid resin, polyamide resin, polyacrylate resin and the like.

The above-mentioned insoluble fine particles or incompatible resin is
They may be used alone or in combination of two or more.

The content of the insoluble fine particles or the incompatible resin in the polyester composition should be appropriately selected depending on the glossiness required in the market or the components to be mixed.
Generally, in the case of using insoluble fine particles, it is 0.3 to 3
% By weight, 2 to 10% by weight when using an incompatible resin
It is preferably contained in the polyester composition in a ratio of about a certain degree. By containing the insoluble fine particles or the incompatible resin in such a content ratio in the polyester composition, the resulting film has a gloss of 150% or less, and when the film is printed, the film has a matte finish. A good-looking appearance is obtained.

The method of mixing the fine particles and / or the incompatible resin with the polyester and / or the copolyester is not particularly limited. For example, there is a method of blending in the production process of polyester or copolyester, a method of blending at the time of film formation, and the blending form thereof includes a method of directly blending the insoluble fine particles or the incompatible resin, or a high concentration master. There is a method of preparing a batch in advance and blending the master batch.

The intrinsic viscosity when the various components of the polyester composition are mixed is preferably 0.50 to 1.3 d / g. If the intrinsic viscosity is less than 0.50 d / g, the strength of the obtained film may be insufficient, and if it exceeds 1.3 d / g, the strength of the obtained film may not rise above a certain level. And, there is a risk of being economically disadvantageous.

The above polyester composition is formed into a film by a known method (for example, extrusion method, calendar method). The shape of the film is, for example, a plane shape or a tube shape, and is not particularly limited. The obtained film is, for example, stretched in a predetermined one direction (main stretching direction) in a range of 2.5 to 7.0 times, preferably 3.0 to 6.0 times under predetermined conditions described later. To be done. 4.0
Double to 6.0 is more preferable, and 4.5 to 6.0 is most preferable. In the direction orthogonal to the main stretching direction, 1.
It is stretched in the range of 0 to 2.0 times, preferably 1.1 to 1.8 times. Either may be first in the order of this stretching. Stretching in the main stretching direction is performed to obtain a high heat shrinkage ratio in this direction. Stretching in the direction orthogonal to the main stretching direction is performed in order to improve the impact resistance of the obtained film and to alleviate the property of being easily torn in one direction. 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 finish when heat-shrinked becomes uneven in a wavy state. The film stretched at the above ratio is usually
The shrinkage in the direction orthogonal to the shrinkage in the main stretching direction is preferably 15% or less, more preferably 8 to 9% or less, and further preferably 7% or less. The film having such a shrinkage ratio has a uniform finish when subjected to heat treatment.

As a stretching method, a usual method is adopted. Examples thereof include roll stretching method, long gap stretching method, tenter stretching method, and tubular stretching method. In any of these methods, the stretching is performed by sequential biaxial stretching and simultaneous biaxial stretching.
Axial stretching, uniaxial stretching, and combinations thereof can be performed. In the above-mentioned biaxial stretching, stretching in the longitudinal and transverse directions may be performed simultaneously, but sequential biaxial stretching in which either one is performed first is effective, and the longitudinal and lateral directions may be performed first.

During the stretching, for example, the film is heated at a temperature not lower than Tg of the polyester constituting the film, for example, not lower than Tg and not higher than (Tg + 80 ° C.). When this heating is performed during the stretching in the main stretching direction (which becomes the “main shrinkage direction”), heat shrinkage in the direction orthogonal to the direction (main shrinkage direction) can be suppressed. When the temperature range is (Tg + 80 ° C. ± 25 ° C.), the heat shrinkage ratio in the direction orthogonal to the main shrinkage direction is almost the minimum.

After the above stretching, the following operations such as heat setting, stretching and cooling can be preferably performed.

After stretching the film, heat setting is usually performed. For example, after stretching the film,
It is recommended to pass the film through a heating zone of 30 ° C to 150 ° C for about 1 to 30 seconds. This is called heat set. By performing this heat setting, it is possible to prevent the dimensional change of the film under high temperature and high humidity conditions such as high temperature in summer.

After stretching the film, before heat-setting, or after heat-setting, further cooling while stressing the film while keeping it in a stretched or tensioned state, or following the treatment. By continuing to cool after releasing the tension,
The shrinkage property of the obtained film upon heating becomes better and stable.

In the heat-shrinkable polyester film of the present invention thus obtained, the heat shrinkage ratio (primary heat shrinkage ratio) in the main shrinkage direction at 100 ° C. is 40% or more. If the heat shrinkage ratio is less than 40%, when the film is heat-shrinked along the surface of the irregularly-shaped package, the necessary shrinkage cannot be achieved in detail, and the primary heat It would have to be heated to high temperatures to achieve the shrinkage. On the other hand, since the heat resistance of the packaged object is also limited, the application range of the film is narrowed, which is not preferable.

In the heat-shrinkable polyester film of the present invention, the heat shrinkage at 100 ° C. in the direction orthogonal to the main shrinkage direction is 20% or less, preferably 15% or less, and preferably 10% or less. It is more preferable that there is. When the heat shrinkage rate of the film exceeds 20%, when the film is used as a label for shrinking, the film greatly shrinks along the longitudinal direction of the container,
Distortion and curling of the edges occur, which is not preferable.

Further, the film of the present invention is heated with hot air at 100 ° C. for 10 seconds, and the film is heated in the main shrinkage direction to 40 ° C.
After the heat shrinkage of 10%, the heat shrinkage in the main shrinkage direction (secondary heat shrinkage) when heated with hot air of 130 ° C. for 10 seconds is 12% or more, and preferably 14% or more. If the secondary heat shrinkage ratio is less than 12%, defects such as wrinkles, distortions, and shrinkage unevenness occur in the film when heat-shrinked, and a beautiful appearance cannot be obtained, which is not preferable.

The heat-shrinkable polyester film of the present invention has a gloss of 150% or less. By controlling the glossiness of the film to 150% or less, when the film is printed, it is possible to suppress the excessive gloss of the printing surface, and it becomes matte, and the print is easy to see, giving a high-class feeling to the printed matter. . The gloss of the film is 120%
The following is more preferable. The gloss of the film is 1
The content of 50% or less can be achieved by blending the above-mentioned polyester composition with the above-mentioned insoluble inorganic fine particles or organic fine particles, or an incompatible thermoplastic resin.

The plane orientation coefficient of the film of the present invention is 100.
It is preferably × 10 ⁻³ or less. Plane orientation coefficient is 10
When it exceeds 0 × 10 ⁻³ , the strength of the obtained film is lowered and the film is apt to be broken even by a small amount of external damage. When such a film is wound around the outer surface of a bottle and used as a reinforcing material, a sufficient reinforcing effect cannot be obtained.

The birefringence of the film of the present invention is 15 × 1.
It is preferably 0 ^{−3 to} 160 × 10 ⁻³ . When the birefringence is less than 15 × 10 ⁻³ , the heat shrinkage and shrinkage stress in the main shrinkage direction of the obtained film are low. When the birefringence exceeds 160 × 10 ⁻³ , the obtained film is easily broken by external scratches and the impact strength becomes low, so that the film is not practical.

The thickness of the film of the present invention is 6 to 250 μm.
It is preferably in the range of. Film thickness is 6 μm
If less than 250 μm, the strength of the film may be insufficient and handling may be difficult. If more than 250 μm,
There is a risk that the strength of the film will not rise above a certain level and it will be economically disadvantageous.

[0039]

EXAMPLES The present invention will be described below with reference to examples. The measurement methods used in this example and comparative examples are shown below.

(1) Primary heat shrinkage rate The film is cut into a width of 15 mm to obtain a tape-shaped sample, and a marked line is drawn in a gap of 200 mm in the longitudinal direction. This sample is heated with hot air at 100 ° C. for 1 minute, and the shrinkage rate is measured.

(2) Secondary heat shrinkage ratio The film was fixed to a metal frame with a slack of 40% with respect to the length of the film in the main shrinkage direction, and 100
The film is shrunk to a state where the slack is eliminated by heating with hot air at 0 ° C. for 10 seconds. This heat-shrinkable film is cut into a tape-shaped sample with a width of 15 mm, and a marked line is drawn in a gap of 200 mm in the longitudinal direction. This sample is heated with hot air at 130 ° C. for 10 seconds, and the shrinkage rate is measured.

(3) Finished state after shrinkage After printing a shrinkable label on the film and forming it into a cylindrical shape (tube), 1.5 L capacity rectangular PET
I covered the bottle and passed through the shrink tunnel. The conditions of 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 finished state of shrinkage of the obtained label was visually determined (for wrinkles, print distortion, and print density due to shrinkage unevenness).

(4) Glossiness A gloss value of 45 ° was measured with a gloss meter manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS Z 8741.

(Example 1) 95 mol% of terephthalic acid and 5 mol% of adipic acid as dicarboxylic acid, 68 mol% of ethylene glycol as diol component, 2 mol% of diethylene glycol, and 30 mol% of 1,4-cyclohexanedimethanol And a polyester composition containing 0.5% by weight of silicon dioxide having an average particle diameter of 2.4 μm as a glossiness adjusting agent and having an intrinsic viscosity of 0.70 d / g was melt extruded at 290 ° C. to obtain a film having a thickness of 200 μm. Got Table 1 shows the components and contents of the polyester composition and the gloss adjusting agent. Table 1 also shows the polyester compositions and glossiness adjusting agents used in Examples 2 to 4 and Comparative Examples 1 to 5. This unstretched film was preheated at 120 ° C. for 6 seconds and then stretched 5.0 times in one predetermined direction. The temperature conditions at the time of stretching were set to 80 ° C. up to ½ of all steps, and to 90 ° C. for the remaining ½. After stretching, heat treatment was performed at 95 ° C. for 5 seconds. At the time of this heat treatment, relaxation treatment of 3% in the lateral direction and 0.2% in the longitudinal direction was performed to obtain a heat-shrinkable film having a thickness of 40 μm. With respect to the obtained heat-shrinkable film, the primary heat shrinkage rate, the secondary heat shrinkage rate, the finished state after shrinkage, and the glossiness were measured by the above method, and the results are shown in Table 2. Examples 2-4
The results of Comparative Examples 1 to 5 are also shown in Table 2.

According to Example 1, the secondary heat shrinkage was high, the shrinkable label had a good finished state after shrinking, the gloss was low, and a matte appearance was obtained when printed on the back surface. A highly practical heat-shrinkable film was obtained.

(Comparative Example 1) The compounding amount of silicon dioxide was set to 0.
A heat-shrinkable polyester film was obtained in the same manner as in Example 1 except that the amount was 05% by weight.

In Comparative Example 1, the finished state after shrinkage as a shrinkable label is good, but the glossiness is high and the gloss is excessively strong even when printing on the back side, so that it does not have a matte tone. As a result, a heat-shrinkable film was obtained, which was inferior to the heat-shrinkable film No. 1 in quality.

Comparative Example 2 A heat-shrinkable film was obtained in the same manner as in Example 1 except that the composition of the copolyester was changed as shown in Table 1.

Comparative Example 2 is excellent in that it has a low glossiness and has a good matte appearance when printed on the back surface, but since it has a low secondary thermal shrinkage, it is used as a shrinkable label. A heat-shrinkable film having a poor finished state after shrinkage was obtained.

(Examples 2 to 4) The heat shrinkability was the same as in Example 1 except that a polyester composition having the composition shown in Table 1 and a gloss adjusting agent were used. I got a film.

In each of Examples 2 to 4, the finished state after shrinkage as a shrinkable label was good, the glossiness of the film was low, and the matte appearance was good when printed on the back surface. A heat-shrinkable film having high practicability was obtained.

Comparative Example 3 A heat-shrinkable film was obtained in the same manner as in Example 2 except that the gloss adjusting agent was not added.

Comparative Example 4 A heat-shrinkable film was obtained in the same manner as in Example 3 except that the gloss adjusting agent was not added.

Comparative Example 5 A heat-shrinkable film was obtained in the same manner as in Example 4, except that the gloss adjusting agent was not added.

In Comparative Examples 2 to 4, the shrinkable finish as a shrinkable label is good, but the glossiness is high, and even when the back surface printing is performed, the gloss is excessively strong so that the matte tone does not appear. A heat-shrinkable film was obtained that was inferior to the heat-shrinkable films of Nos. 1 to 4 in terms of high quality.

[0056]

[Table 1]

The abbreviations and * to *** in Table 1 indicate the following: T: terephthalic acid IPA: isophthalic acid SA: sebacic acid AA: adipic acid AZ: azelaic acid EG: ethylene glycol DEG: diethylene glycol CHDM: 1,4-Cyclohexanedimethanol NPG: Neopentyl glycol *: RV 2.87 **: MI 7 g / 10 minutes ***: Polycarbonate resin containing bisphenol A as a phenol component

[0058]

[Table 2]

[0059]

EFFECT OF THE INVENTION The heat-shrinkable film of the present invention has a beautiful appearance with very few defects such as wrinkles, distortions and shrinkage spots when the film is heat-shrinked. The heat-shrinkable film of the present invention also has a low glossiness of the film, and when backside printing is performed, good matte printing can be obtained. INDUSTRIAL APPLICABILITY The heat-shrinkable film of the present invention is useful as various packaging materials including a shrinkable film for labels and has high utility value.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B29K 105: 02 B29L 7:00 C08L 67:00 (72) Inventor Tsutomu Isaka Kita-ku, Osaka City, Osaka Prefecture 2-8 Dojimahama Toyobo Co., Ltd. Head Office

Claims (1)

[Claims] 1. A matte heat-shrinkable polyester film having a heat shrinkage at 100 ° C. of 40% or more in the main shrinkage direction and 20% or less in a direction orthogonal to the main shrinkage direction, After heating for 10 seconds using hot air of 100 ° C. to shrink the film by 40% in the main shrinking direction, 130 ° C.
The polyester film having a heat shrinkage of 12% or more in the main shrinkage direction and a film gloss of 150% or less when heated for 10 seconds using the hot air.