JP3736615B2 - Heat-shrinkable polyester film - Google Patents

Description

【００５９】
表中の微粒子の添加量は、フィルム全重量に対する添加量を示す。
【００６０】
上記表１から明らかなように、実施例１及び２の本発明熱収縮性ポリエステル系フィルムは、いずれも、全光線透過率、ヘーズ及び内部ヘーズの要件を満たしており、良好なすりガラス調の外観を有するものであった。従って、本発明の熱収縮性ポリエステル系フィルムは、高品質で実用性が高く、特にすりガラス調の収縮ラベル用として好適である。
【００６１】
一方、比較例１〜２で得られた熱収縮性ポリエステル系フィルムは、すりガラス調の外観を有するもののフィルムを通して印刷物を見たとき小さい文字が見にくく、比較例３で得られた熱収縮性ポリエステル系フィルムは、すりガラス調の外観が劣っていた。このように比較例の熱収縮性ポリエステル系フィルムは、品質が劣り、実用性の低いものであった。
【００６２】
【発明の効果】
本発明の熱収縮性ポリエステル系フィルムによれば、印刷や加工を施さなくともすりガラス調の外観を有し、又充分な溶剤接着性が得られる。従って、ラベル用、特に商品価値の高いラベル用の熱収縮性ポリエステル系フィルムとして極めて有用である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat-shrinkable polyester film, and more particularly to a heat-shrinkable polyester film having a ground glass-like appearance.
[0002]
[Prior art]
As a sake bottle for gifts, ground glass bottles are mainly used, but in recent years the amount of used bottles has been reduced due to the fact that the bottles are easily scratched and cannot be used repeatedly. Instead, transparent glass bottles or PET bottles have been used. Attempts have been made to use a heat-shrinkable film label.
[0003]
Conventionally, heat-shrinkable films made of polyvinyl chloride, polystyrene, etc. have been mainly used as such labels (Japanese Patent Laid-Open No. 11-188817, etc.), but in recent years, polyvinyl chloride has been incinerated at the time of disposal. There is a problem of generation of chlorine-based gas at the time, and polystyrene has problems such as difficulty in printing. Recently, the use of a heat-shrinkable polyester film has attracted attention.
[0004]
Conventionally, when using these heat-shrinkable films, the film has been white-printed or sandblasted to finish it in frosted glass, but this is industrially disadvantageous in terms of high processing costs and long delivery times. there were.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a heat-shrinkable polyester film having a frosted appearance without being printed or processed.
[0006]
[Means for Solving the Problems]
As a result of earnest research to solve the problems of the prior art, the present inventor has found that the object can be achieved by setting the total light transmittance, haze and internal haze of the heat-shrinkable polyester film within a specific range. Based on this, the present invention has been completed.
[0007]
That is, the present invention is a film made of a polyester resin, wherein the total light transmittance of the film is 80 to 90%, the haze is 15 to 60%, and the internal haze is 50% or less of the haze. The heat-shrinkable polyester film characterized by the following.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The heat-shrinkable polyester film of the present invention has a total light transmittance of 80 to 90%, a haze of 15 to 60%, and an internal haze of 50% or less of the haze at a film thickness of 50 μm. It is characterized in that it achieves the above object.
[0009]
The heat-shrinkable polyester film of the present invention substantially comprises a polyester resin or a polyester resin and fine particles described later. As the polyester resin, for example, a polyester resin composition containing a polyester having a dicarboxylic acid component and a diol component as constituent components and a polyester elastomer can be preferably used. In the polyester resin composition, the blending ratio of the polyester and the polyester-based elastomer is usually about 50 to 97% by weight, particularly 70 to 95% by weight, and 3 to 50 for the latter with respect to the total amount of both. It is preferable that the amount be about 5% by weight, particularly about 5 to 30% by weight.
[0010]
Examples of the dicarboxylic acid component constituting the polyester include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid and decanedicarboxylic acid, and alicyclic rings such as cyclohexanedicarboxylic acid. What is necessary is just to use 1 type, or 2 or more types of well-known dicarboxylic acids, such as a formula dicarboxylic acid. In addition, as the diol component, one kind of known diols such as ethylene glycol, propylene glycol, triethylene glycol, butylene glycol, diethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, tetramethylene glycol ethylene oxide adduct or the like Two or more types may be used.
[0011]
The polyester elastomer is, for example, a polyester block copolymer comprising a high melting crystalline polyester segment (Tm 200 ° C. or higher) and a low melting point soft polymer segment (Tm 80 ° C. or lower) having a molecular weight of 400 or more, preferably 400 to 8000. Polyester elastomers using polylactones such as poly-ε-caprolactone for the low melting point soft polymer segment are particularly preferred.
[0012]
In order to achieve the specific total light transmittance, haze and internal haze of the film of the present invention and to give the film a ground glass appearance, for example, fine particles such as inorganic lubricant and organic lubricant are added to the film weight in the film. It is suitable to contain 0.1 to 10% by weight, preferably 0.5 to 5% by weight. When the content of the fine particles is less than 0.1% by weight, it tends to be difficult to obtain a ground glass-like appearance. On the other hand, when the content exceeds 10% by weight, the unevenness of the film surface tends to increase and the appearance tends to deteriorate. It is in.
[0013]
The fine particles may be added before polyester polymerization, but are usually added after polyester polymerization. Examples of the inorganic lubricant added as fine particles include known inert particles such as kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, titanium oxide, calcium phosphate, and carbon black.
[0014]
Similarly, as the organic lubricant added as fine particles, a high-melting-point organic compound that is insoluble when the polyester resin is melt-formed can be used. The melting point (Tm) of the high melting point organic compound needs to be higher than the temperature at the time of melt film formation, and the organic compound must maintain the shape at the temperature. Specific examples of the high melting point organic compound include, for example, a crosslinked polymer such as a polymethacrylic acid ester-based crosslinked product and benzoguanamine.
[0015]
The average particle size of the fine particles contained in the film is usually preferably in the range of 0.001 to 15.0 μm. When the particle size is less than 0.001 μm, it tends to be difficult to obtain a ground glass-like appearance, while when it exceeds 15 μm, the unevenness of the film surface tends to increase and the appearance tends to deteriorate. The particle size is more preferably 0.5 to 12 μm, and particularly preferably 1 to 10 μm. Here, the average particle diameter of the fine particles is measured by a Coulter counter method.
[0016]
Moreover, this invention film may contain additives, such as a stabilizer, a coloring agent, antioxidant, and an antistatic agent, as needed.
[0017]
The polyester film of the present invention needs to have a total light transmittance of 80 to 90% as measured in accordance with JIS K 7105-A. If the transmittance is less than 80%, it is difficult to see the printing applied to the film, while if it exceeds 90%, it becomes difficult to obtain a predetermined haze, and therefore neither is preferable. The transmittance is particularly preferably 85 to 90%.
[0018]
In addition, the film of the present invention needs to have a haze of 15 to 60% as measured according to JIS K 7105-A. If the haze is less than 15%, a ground glass-like appearance cannot be obtained. On the other hand, if it exceeds 60%, it is difficult to see small letters when the film surface is printed and viewed from the opposite side. .
[0019]
Furthermore, in the film of the present invention, it is necessary that the internal haze measured according to JIS K 7105-A is 50% or less of the haze, that is, (internal haze) ≦ (haze) × 0.5. It is. Based on this requirement, in the film of the present invention, by increasing the external haze [= (haze) − (internal haze)] and reducing the internal haze, the ground glass-like appearance and the design can be made compatible. Can be suitably achieved.
[0020]
As long as this internal haze requirement is satisfied, the heat-shrinkable polyester film of the present invention may be a single layer, but in the case of a single layer, it is not always easy to set the internal haze to 50% or less of the haze, In order to satisfy this requirement, it is necessary to select various kinds of fine particles, addition amount, and particle size.
[0021]
Therefore, the film of the present invention is preferably a laminated film composed of at least two layers of a fine particle added layer and a layer not containing fine particles. The content of fine particles in such a laminated film is the content with respect to the total film weight including the fine particle added layer and the layer not containing fine particles.
[0022]
As such a laminated film, for example, a two-layer laminated film in which a fine particle-added layer is provided on the surface side and a layer not containing fine particles is provided on the inner surface side, a fine particle-added layer is provided on the surface side, an intermediate layer and an inner surface Examples thereof include a laminated film having a three-layer structure in which a layer not containing fine particles is provided on the side. In the case of a laminated film provided with a layer that does not contain fine particles on the inner surface side, even if printing is performed on the inner surface side, it is difficult to read small letters or the color changes, and the design properties are impaired. Will not occur.
[0023]
Here, in the film of the present invention, the inner surface side refers to the side facing the bottle or bottle when used as a bottle or bottle label, and the surface side refers to the opposite side of the inner surface side.
[0024]
Further, the heat-shrinkable polyester film of the present invention has a maximum surface roughness height (SRmax) of 2.0 to 8.0 μm and a center plane average roughness (SRa) of 0.20 to 0. .5 μm is preferable. If SRmax or / and SRa are within the above range, the slipping of the film is good, the frequency of occurrence of troubles during processing is low, and the surface roughness is not substantially generated.
[0025]
The hot water shrinkage of the film of the present invention is preferably 50% or more at a treatment temperature of 95 ° C. and a treatment time of 10 seconds in the main shrinkage direction, more preferably from 50 to 75%. If the shrinkage rate is less than 50%, there is a tendency for label shrinkage to occur in the narrow part of the bottle or bottle. On the other hand, if the shrinkage rate exceeds 75%, the shrinkage rate is large. In some cases, neither is preferable. Here, the main shrinkage direction means a direction having a large heat shrinkage rate.
[0026]
The hot water shrinkage of the film of the present invention is preferably 0 to 10% at a treatment temperature of 95 ° C. and a treatment time of 10 seconds in a direction perpendicular to the main shrinkage direction. If the shrinkage rate is less than 0%, the lateral wrinkles of the label generated during the shrinkage tend to be difficult to disappear. On the other hand, if the shrinkage rate exceeds 10%, the vertical shrinkage of the label increases and the amount of film used increases. Since this causes problems, neither is preferable. The shrinkage rate is more preferably 1 to 7%.
[0027]
The glass transition temperature Tg of this invention film is about 50-90 degreeC normally, Preferably it is 55-85 degreeC, More preferably, it is the range of 55-80 degreeC. If Tg is within this range, the low temperature shrinkage is sufficient and the natural shrinkage is not too large, and the label finish is good.
[0028]
The film of the present invention includes aromatic hydrocarbons such as benzene, toluene, xylene and trimethylbenzene, halogenated hydrocarbons such as methylene chloride and chloroform, phenols such as phenol, furans such as tetrahydrofuran, 1,3-dioxolane and the like. It preferably has solvent adhesion with an organic solvent such as oxolanes. In particular, from the viewpoint of safety, it is more preferable to have solvent adhesion by 1,3-dioxolane.
[0029]
In order to impart solvent adhesion to the film of the present invention, for example, it is effective to copolymerize polyester with a low Tg component.
[0030]
Next, the manufacturing method of the film of this invention is demonstrated.
[0031]
After drying polyester, copolymer polyester, polyester-based elastomer, etc. containing an appropriate amount of inorganic lubricant as fine particles as necessary using a normal hopper dryer, paddle dryer, vacuum dryer, etc., a temperature of 200 to 320 ° C. Extrude with In the case of a laminated film, coextrusion is performed. In extruding, an existing method such as a T-die method or a tubular method may be used.
[0032]
After extrusion, the film is rapidly cooled to obtain an unstretched film. In the case of the T-die method, it is preferable to use a so-called electrostatic application adhesion method at the time of rapid cooling because a film with less thickness unevenness can be obtained thereby.
[0033]
The obtained unstretched film is uniaxially stretched or biaxially stretched so that the finally obtained film satisfies the constituent requirements of the present invention.
[0034]
As the stretching method, in addition to the method of stretching only in the longitudinal axis of the roll or stretching only in the lateral direction with a tenter, the known biaxial stretching is strongly stretched in either the longitudinal or lateral direction, and the other is as much as possible. It is also possible to stretch it small. Moreover, you may redraw as needed. The longitudinal direction means the film take-up direction.
[0035]
In the above stretching, the film is stretched at least 2.0 times in the main shrinkage direction, preferably 2.5 to 6.0 times, and if necessary, about 1.1 to 2.0 times in the direction perpendicular to the main shrinkage direction. Drawing is followed by heat treatment. If the stretching in the main shrinkage direction is less than 2.5 times, a sufficient shrinkage rate cannot be obtained, and if it exceeds 6.0 times, the shrinkage rate does not increase any more.
[0036]
The heat treatment is usually performed under tension fixation, but it is also possible to perform relaxation or tentering of 20% or less at the same time. As a heat treatment method, an existing method such as a method of contacting with a heating roll or a method of gripping a clip in a tenter may be used.
[0037]
During the stretching step, before or after stretching, one or both sides of the film may be subjected to corona discharge treatment to improve the adhesion of the film to the printed layer and / or the adhesive layer.
[0038]
In addition, during the stretching step, it is possible to apply on one or both sides of the film before or after stretching to improve the adhesion, release properties, antistatic properties, slipperiness, light shielding properties, etc. of the film. .
[0039]
The thickness of the film of the present invention is preferably in the range of 15 to 300 μm, more preferably 25 to 200 μm. In addition, when the film of the present invention is in the form of, for example, a two-layer laminated film of a fine particle added layer and a layer not containing fine particles, the fine particle added layer is preferably in the range of 7 to 150 μm, more preferably 12 to 50 μm. The layer containing no fine particles is preferably in the range of 7 to 150 μm, more preferably 12 to 50 μm.
[0040]
The heat-shrinkable polyester film of the present invention can be suitably used as a heat-shrinkable label for transparent glass bottles, PET bottles and the like. As a usage method in this case, for example, on the inner surface side of the film of the present invention, if necessary, a product name, a logo mark, a cautionary note, etc. or coloring is printed, then the film is rolled into a cylindrical shape, and both ends are A cylindrical heat-shrink label is obtained by solvent bonding. Next, the heat-shrink label is supplied to an automatic label mounting device, and continuously attached to an object to be attached such as a bottle or a bottle, and is passed through a steam tunnel to be shrunk and the label is attached to the object to be attached. Install it.
[0041]
【Example】
Hereinafter, although an example and a comparative example are given and the present invention is explained still more concretely, the present invention is not limited by these examples.
[0042]
Various characteristics in each example are obtained by the following methods.
[0043]
(1) Total light transmittance and film haze Measured according to JIS K 7105-A using a haze measuring instrument “NDH-1001DP” manufactured by Nippon Denka Kogyo Co., Ltd.
[0044]
(2) Zedel oil is applied to both sides of the internal haze film, sandwiched between two glass plates, and measured according to JIS K 7105-A using a Nippon Electric Decoration Co., Ltd. haze measuring instrument “NDH-1001DP”. did.
[0045]
(3) Maximum height of surface roughness (SRmax) and center surface average roughness (SRa) of film
The measurement was performed under the conditions of a cutoff of 80 μm and a drive speed of 100 μm / s using a three-dimensional fine shape measuring instrument “ET-30HK” manufactured by Kosaka Laboratory.
[0046]
(4) Heat shrinkage rate The film is cut into a 10 cm × 10 cm square, and immersed in warm water of 95 ± 0.5 ° C. for 10 seconds under a no-load condition and thermally contracted. The dimensions were measured, and the thermal shrinkage rate was determined according to the following formula.
[0047]
Thermal shrinkage rate (%) = [(length before shrinkage−length after shrinkage) / length before shrinkage] × 100
Moreover, the direction with a large heat shrinkage rate was defined as the main shrinkage direction.
[0048]
(5) Solvent adhesiveness 1,3-dioxolane is used to join the film into a tube shape, the tube-like body is cut into a width of 15 mm in the direction perpendicular to the flow direction during processing, and a sample is taken. A film that was pulled and peeled in the above direction to obtain a sufficient peel resistance was defined as solvent adhesion “◯”.
[0049]
(6) Tg (glass transition point)
Using DSC (model: “DSC220”) manufactured by Seiko Denshi Kogyo Co., Ltd., 10 mg of an unstretched film was heated from −40 ° C. to 120 ° C. at a heating rate of 20 ° C./min, and an endothermic curve obtained. I asked more. A tangent line was drawn before and after the inflection point of the endothermic curve, and the intersection was defined as Tg (glass transition point).
[0050]
The polyesters used in the examples and comparative examples are as follows.
[0051]
Polyester A: polyethylene terephthalate (IV; 0.75),
Polyester B: Polyester (IV; 0.72) comprising 100 mol% terephthalic acid, 70 mol% ethylene glycol and 30 mol% neopentyl glycol,
Polyester elastomer C: Polyester block copolymer comprising 70% by weight of polybutylene terephthalate and 30% by weight of poly-ε-caprolactone (reduced viscosity (ηsp / c); 1.30).
[0052]
The fine particles used in Examples and Comparative Examples are as follows.
[0053]
Fine particles a: “Eposter MA1010” (polymethacrylate cross-linked particles, average particle size 10 μm); manufactured by Nippon Shokubai Co., Ltd., trade name,
Fine particles b: “Eposta MA1006” (polymethacrylate cross-linked particles, average particle size 6 μm); manufactured by Nippon Shokubai Co., Ltd., trade name,
Fine particles c: Amorphous cyloid (silica particles, average particle size 1.5 μm); manufactured by Fuji Silysia Co., Ltd.
[0054]
Example 1
As shown in Table 1, as a core layer (inner side layer), a polyester resin composition in which 31% by weight of polyester A, 49% by weight of polyester B, and 20% by weight of polyester elastomer C are mixed is used as a skin layer ( As a surface layer), a polyester resin composition prepared by adjusting fine particles a to 2 parts by weight with respect to 98 parts by weight of a mixture of 31% by weight of polyester A, 49% by weight of polyester B and 20% by weight of polyester elastomer C While being laminated at 280 ° C. from a T die so that the core layer / skin layer has a thickness ratio of 25 μm / 25 μm, it was melt coextruded and quenched with a chill roll to obtain an unstretched laminated film.
[0055]
The unstretched laminated film was stretched 4.0 times in the transverse direction at a film temperature of 70 ° C. with a tenter to obtain a heat-shrinkable polyester film having a total thickness of 50 μm.
[0056]
Example 2 and Comparative Examples 1-3
As shown in Table 1, a heat-shrinkable polyester film having a total thickness of 50 μm was obtained in the same manner as in Example 1 except that the type and amount of fine particles were changed.
[0057]
Table 1 shows the types and amounts of fine particles and various characteristics of the films obtained in Examples 1 and 2 and Comparative Examples 1 to 3.
[0058]
[Table 1]

[0059]
The addition amount of fine particles in the table indicates the addition amount relative to the total weight of the film.
[0060]
As is apparent from Table 1 above, the heat-shrinkable polyester films of Examples 1 and 2 all satisfy the requirements of total light transmittance, haze and internal haze, and have a good ground glass appearance. It was what had. Therefore, the heat-shrinkable polyester film of the present invention has high quality and high practicality, and is particularly suitable for a ground glass-like shrink label.
[0061]
On the other hand, the heat-shrinkable polyester film obtained in Comparative Examples 1 and 2 has a ground glass-like appearance, but when the printed material is viewed through the film, it is difficult to see small letters, and the heat-shrinkable polyester film obtained in Comparative Example 3 is used. The film was inferior in frosted glass appearance. Thus, the heat-shrinkable polyester film of the comparative example was inferior in quality and low in practicality.
[0062]
【The invention's effect】
According to the heat-shrinkable polyester film of the present invention, it has a frosted appearance without printing or processing, and sufficient solvent adhesiveness can be obtained. Therefore, it is extremely useful as a heat-shrinkable polyester film for labels, particularly for labels with high commercial value.

Claims (4)

A label film for a bottle or bottle made of a polyester resin, which is a laminated film comprising at least two layers of a fine particle added layer and a layer not containing fine particles, and a layer not containing fine particles provided on the inner surface side of the label, The total light transmittance is 80 to 90%, the haze is 15 to 60%, the internal haze is 50% or less of the haze , and the hot water shrinkage rate is 95 ° C. in the main shrinkage direction. A heat-shrinkable polyester film characterized by being 50% or more at a treatment time of 10 seconds and 0 to 10% in a direction orthogonal to the main shrinkage direction . The heat-shrinkable polyester film according to claim 1, wherein the film contains 0.1 to 10% by weight of fine particles with respect to the film weight. The heat-shrinkable polyester film according to claim 2, wherein the average particle size of the fine particles is in the range of 0.001 to 15.0 µm. The heat-shrinkable polyester film according to any one of claims 1 to 3 , which is solvent-bondable with 1,3-dioxolane.