JP2010149521A - Heat-shrinkable polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable polyester laminate film which is excellent in transparency, glossiness, processing suitability, and is easy to be formed. <P>SOLUTION: The heat-shrinkable polyester film is a laminate film which includes a base material film formed of polyester resin, and a surface layer formed on at least one surface of the base material film. The surface layer contains 0.05 wt.% to 30 wt.% of inorganic particles having 1 nm or larger to 300 nm or smaller of particle diameters and an anion antistatic agent. The haze value of the film is 2% or smaller. Glossiness at 45° of a measuring angle of at least one surface of the film is 200% or higher. Coefficients of the dynamic friction of one surface and the other surface of the film are 1.5 or smaller. The shrinkage percentage of the film in the main shrinkage direction when the film is dipped in a hot liquid at 95°C for 10 sec. is 50% or higher. The surface specific resistance of the film at a relative humidity of 65% or lower is 13 logΩ or lower. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable polyester film, and more particularly to a heat-shrinkable polyester film excellent in transparency and gloss.

  In recent years, it has the property of shrinking by heating for the purpose of packaging to improve the appearance of packaging, packaging to avoid direct impact of contents, label packaging that protects glass bottles or plastic bottles and displays products etc. Heat shrinkable plastic films are widely used. Plastic materials used for these purposes include stretched films such as polyvinyl chloride films, polystyrene films, and polyester films. Labels are used in various containers such as polyethylene terephthalate (PET) containers, polyethylene containers, and glass containers. And used for the purpose of cap seals or integrated packaging.

  However, the polyvinyl chloride film has problems such as low heat resistance, generation of hydrogen chloride gas during incineration, and dioxin. Further, when a heat-shrinkable vinyl chloride resin film is used as a shrink label for a PET container or the like, there is a problem in that the label and the container must be separated when the container is recycled.

  On the other hand, a polystyrene film can be evaluated for its good finished appearance after shrinkage, but it is poor in solvent resistance, so an ink with a special composition must be used for printing. In addition, heat-shrinkable films have recently been used in hot beverage PET bottle labels, but when stored in warming equipment such as hot-warmers, the heat-shrinkable polystyrene film comes into contact with hot wires that have become hot. There is a problem that the shrinkage label melts instantly. Furthermore, the polystyrene resin needs to be incinerated at a high temperature, and has a problem that a large amount of black smoke and off-flavor are generated at the time of incineration.

  A polyester film free from these problems (excellent in solvent resistance, heat resistance, and environmental suitability) is used as a shrink film instead of a polyvinyl chloride film or a polystyrene film.

  In order to produce labels and the like, the following methods are usually employed. That is, the raw polymer is continuously melt extruded to produce an unstretched film. Next, stretching is performed to obtain a film roll. While feeding out the film from this film roll, it is slit to a desired width and wound into a roll again. Subsequently, character information such as various product names and designs are printed. After the printing is finished, the tube is manufactured by overlapping and joining the left and right ends of the film by means such as solvent bonding (tubing process). The slit process and the printing process may be reversed in order. If the obtained tube is cut into a suitable length, it becomes a cylindrical label, and a bag can be manufactured by joining one open end of this cylindrical label.

  And the inside of the shrink tunnel (steam tunnel) of the type that covers the label or bag etc. on the container and blows and heat shrinks by steam, and the shrink tunnel (hot air tunnel) of the type that blows hot air and heat shrinks, A final product (labeled container) is obtained by making it pass on a belt conveyor or the like, and heat-shrinking a label, a bag, or the like so as to adhere to the container (see, for example, Patent Document 1).

  Transparency is mentioned as an important thing among the characteristics calculated | required as this film used for a container label. As described above, in many cases, character information and designs such as various product names are printed on the film used for the container label, but in the case of a transparent label, printing is often performed on the side in contact with the container. If the transparency is low, a clear printed pattern cannot be expressed. In addition, there is a problem that it is difficult to confirm the color and filling amount of contents such as beverages in a transparent container in a portion where printing is not performed.

  Among shrinkage label materials, polyester film has excellent gloss, but if this gloss is low, the product image may be adversely affected, for example, the sense of quality of the coated product may be impaired.

  Furthermore, as a processing method of the shrink film, there is a case in which a metal-like appearance is given to the label by performing vapor deposition processing of metal or the like. The side that comes into contact with the container is often processed, but when using a film with low transparency and gloss as described above, the surface of the coated container should be expressed so that it looks like a metal surface. Is difficult.

  As described above, improving the transparency and gloss of the shrinkable label film has the importance of improving the design and improving the product image. The present invention further enhances the transparency and gloss of an existing heat-shrinkable polyester film.

  In addition, since a conventionally known polyester film is an insulator, there is a problem that static electricity is easily generated and accumulated in the film. For example, static electricity that causes film wrapping around a roll in the film manufacturing process, film printing, adhesion between films, or electric shock to the human body becomes a factor that complicates the handling of the film. Moreover, since static electricity causes so-called printing mustaches, dirt on the film surface, and the like, it may induce a decline in commercial value. Therefore, a polyester film in which generation / accumulation of static electricity is suppressed is desired.

JP-A-2005-335111

  An object of this invention is to provide the heat-shrinkable polyester-type laminated film which is excellent in transparency, glossiness, and processability, and is easy to manufacture.

The present invention has the following configuration.
1. It is a laminated film having a base film made of a polyester-based resin and a surface layer provided on at least one surface of the base film, and the surface layer is an inorganic particle having a particle size of 1 nm or more and 300 nm or less. 30% by weight and an anionic antistatic agent, the haze value of the film is 2% or less, and the glossiness is 200% or more at a measurement angle of 45 ° on at least one side of the film. The coefficient of dynamic friction with the surface is 1.5 or less, the shrinkage rate in the main shrinkage direction is 50% or more when the film is immersed in hot water of 95 ° C. for 10 seconds, and the surface resistivity is 13 logΩ under a relative humidity of 65%. A heat-shrinkable polyester film characterized by:
2. The film has a haze value of 3% or less after being immersed in hot water of 90 ° C. for 10 seconds and contracted by 10% in the main contraction direction, and a glossiness of 190% or more at a measurement angle of 45 ° on at least one side of the film. The heat-shrinkable polyester film as described in the first item above.
3. The heat-shrinkable polyester film according to the first or second aspect, wherein the solvent adhesive strength of the film is 2 N / 15 mm or more.
4). 4. The heat-shrinkable polyester film according to any one of the first to third aspects, wherein the base film is mixed containing polyethylene terephthalate and a copolyester.
5). Surface layer, heat-shrinkable polyester film according to any one of the first to fourth, wherein the range of 0.0005 g / ^{m 2} or more 0.1 g / ^{m 2} in solid weight.
6). The heat-shrinkable polyester film according to any one of the first to fifth aspects, wherein the surface layer contains polyester and / or a polyester derivative.
7). The heat according to any one of the first to sixth aspects, which is formed by sequential biaxial stretching, simultaneous biaxial stretching, or uniaxial stretching in which a stretching ratio in a predetermined direction is 3.5 times or more. Shrinkable polyester film.

  According to the present invention, a heat-shrinkable polyester-based laminated film excellent in transparency, gloss, and processability can be provided at a low cost.

  Hereinafter, embodiments of the heat-shrinkable polyester-based laminated film of the present invention and the production method thereof will be described.

  The heat-shrinkable polyester film of the present invention has a surface layer on the surface of the polyester film substrate layer.

[Base material layer]
The heat-shrinkable polyester film is a single copolymer polyester mainly composed of an ester unit formed from a known polycarboxylic acid component and a polyhydric alcohol component, or a mixture of two or more polyesters. A heat shrinkable polyester film cut into a 10 cm × 10 cm square shape and having a shrinkage in the main shrinkage direction of 50% or more when immersed in hot water at 95 ° C. for 10 seconds. Say.
Shrinkage rate (%) = (size before heating−size after heating) / size before heating × 100

  When the film has a heat shrinkage rate of less than 50%, the film heat shrinkage rate is insufficient, and when the container is coated and shrunk, the film does not adhere to the container and an appearance defect occurs. A more preferable heat shrinkage rate is 52% or more, and further preferably 55% or more. However, if the heat shrinkage rate of the film is too large, spots are likely to occur during shrinkage processing, so it may be 100% or less, or 90% or less.

Such a heat-shrinkable polyester film will be described in detail.
As the dicarboxylic acid component constituting the polyester in the raw material composition used for the heat-shrinkable polyester film of the present invention, in addition to terephthalic acid constituting the ethylene terephthalate unit, any of aromatic dicarboxylic acid and alicyclic dicarboxylic acid Can be used.

  Examples of aromatic dicarboxylic acids include benzenecarboxylic acids such as isophthalic acid, orthophthalic acid, 5-tert-butylisophthalic acid and 5-sodium sulfoisophthalic acid; naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid; 4,4′- Dicarboxybiphenyls such as dicarboxydiphenyl, 2,2,6,6-tetramethylbiphenyl-4,4′-dicarboxylic acid; 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid and Examples thereof include 1,2-diphenoxyethane-4,4′-dicarboxylic acid and its substitutes.

  As fatty acid carboxylic acids, 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, Nonadecane dicarboxylic acid, docosane dicarboxylic acid, and substituted products thereof, 4,4′-dicarboxycyclohexane and substituted products thereof, and the like can be mentioned.

  As the diol component of the polyester contained in the raw material composition, any of aliphatic diols, alicyclic diols, and aromatic diols other than ethylene glycol constituting the polyethylene terephthalate unit can be used.

  Examples of the aliphatic diol include diethylene glycol, propylene glycol, butanediol, 1,6-hexanediol, 1,10-decanediol, neopentyl glycol, 2-methyl-2-ethyl-1,3-propanediol, and 2-diethyl. -1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, and the like. Examples of the alicyclic diol include 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol. Aromatic diols include ethylene oxide adducts of bisgenol compounds such as 2,2-bis (4'-β-hydroxyethoxyphenyl) sulfone; xylylene glycol and the like. Polyalkylene glycols such as polyethylene glycol and polypropylene glycol can also be used as the diol component.

  The polyester contained in the raw material composition is composed of the acid component and the diol component. In order to adjust the polyester, one or more acid components are used to improve the properties as a heat-shrinkable film. Alternatively, it is preferable to use a combination of diol components, and the type and content of the monomer components to be combined may be appropriately determined based on desired film characteristics, economy, and the like. The raw material composition contains one or more polyesters. When the contained polyester is one, it is a copolymerized polyester containing an ethylene terephthalate unit. When two or more kinds of polyesters are mixed, a mixture having a desired composition of a copolyester and a homopolyester is prepared. In general, copolymer polyesters have a low melting point, so that there are problems such as difficulty in handling at the time of drying. It is preferable to use a mixture. However, when the heat-shrinkable polyester film is used, 1 to 2 mol% of the entire polyester may be an aliphatic dicarboxylic acid unit. By controlling in this range, the start temperature of heat shrinkage can also be controlled in a preferable range.

  Any of the polyesters in the raw material composition can be produced by a conventional method. For example, the polyester is prepared using a direct esterification method in which a dicarboxylic acid and a diol are directly reacted; a transesterification method in which a dicarboxylic acid dimethyl ester is reacted with a diol, and the like. The adjustment may be performed by either a batch method or a continuous method.

In addition to the polyester, various known additives may be added to the raw material composition as necessary. For example, inorganic inert particles such as silica, calcium carbonate, kaolinite, alumina, talc and barium sulfate; organic inert particles such as benzoguanamine resin and polystyrene resin all have a particle size of about 0.001 to 10 μm. , By adding these, the slipperiness and blocking resistance can be improved. However, the addition of these particulate additives causes light scattering inside and outside the film and deteriorates transparency, and also causes the problem that light is diffusely reflected to reduce the gloss to roughen the film surface. Therefore, it is necessary to pay close attention to the shape and amount added.
Other additives include antistatic agents; anti-aging agents; ultraviolet absorbers; colorants, dyes and the like.

  The haze value of the film is preferably 2% or less. More preferably, it is 1.5% or less. When the haze value of the film exceeds 2%, the transparency is insufficient and it is difficult to satisfy the appearance quality. The haze value is preferably as small as possible, but may be 0.1% or more.

  About at least one surface of the film, the glossiness at a measurement angle of 45 ° is preferably 200% or more. More preferably, it is 210% or more. If it is less than 200%, it is difficult to give a high quality to the coated product, which is not preferable. However, if the glossiness is excessively increased, it is difficult to see the printed design or characters due to the reflection of light.

  The surface specific resistance value under a relative humidity of 65% of the film is preferably 13 logΩ or less. More preferably, it is 11.5 or less. If the surface specific resistance value under 65% relative humidity exceeds 13 log Ω, the handling value in each process is deteriorated, and the commercial value such as dirt due to static electricity may be impaired. However, if the surface specific resistance value is too small, there is a possibility that the transfer stain of the antistatic agent becomes prominent. Therefore, the surface specific resistance value may be 8 logΩ or more.

  The heat-shrinkable polyester film of the present invention can be suitably used for labeling for bottles, but preferably has a small haze value and a high glossiness after being subjected to heat-shrink mounting processing. . That is, the haze value of a film immersed in 90 ° C. hot water for 10 seconds and contracted by 10% in the main contraction direction is 3% or less, and the gloss of the film treated under the same conditions is 190% or more. Is preferred.

  When the haze value of a film which has been immersed in 90 ° C. hot water for 10 seconds and contracted 10% in the main contraction direction exceeds 3%, the transparency of the label after being subjected to heat-shrink mounting is insufficient, which is not preferable. More preferably, it is 2% or less. The smaller the haze value of a film immersed in 90 ° C. hot water for 10 seconds and shrinking 10% in the main shrinkage direction, the better, but it may be 0.2% or more.

  If the glossiness of a film immersed in 90 ° C. hot water for 10 seconds and contracted by 10% in the main shrinkage direction is less than 190%, the glossiness of the label after being subjected to heat shrinkage mounting becomes insufficient, which is not preferable. . More preferably, it is 195% or more. However, if it is attempted to increase the glossiness of the film which has been immersed in 90 ° C. hot water for 10 seconds and contracted by 10% in the main contraction direction, it will be difficult to see the printed pattern or characters due to reflection of light. .

The heat-shrinkable polyester film in the present invention is preferably a laminated film having a base film made of a polyester resin and a surface layer provided on at least one surface of the base film. Solid surface layer fraction is 0.0005 g / ^{m 2} or more 0.1 g / ^{m 2} or less. When it is less than 0.0005 g / m ² , the slipperiness of the film is insufficient, which is not preferable. On the other hand, if it exceeds 0.1 g / m ² , the transparency is inhibited, which is not preferable. The lower limit is more preferably at most 0.0008 g / ^{m 2} or more, still more preferably 0.001 g / ^{m 2} or more. The upper limit is more preferably not more than 0.09 g / ^{m 2,} more preferably not more than 0.085 g / ^{m 2.}

  It is preferable that the dynamic friction coefficient of one surface and the other surface of the film is 1.5 or less. More preferably, it is 1.2 or less. If it exceeds 1.5, wrinkles and acne-like defects at the time of winding are likely to occur, which is not preferable. However, if the coefficient of dynamic friction is too small, there is a risk that the end face will be uneven at the time of winding.

  The solvent adhesive strength of the film is preferably 2 N / 15 mm or more. More preferably, it is 2.2 N / 15mm or more, More preferably, it is 2.4 N / 15mm or more. When the solvent adhesive strength is less than 2 N / 15 mm, it causes a problem such as peeling of the bonded portion, which is not preferable. However, if the solvent adhesive strength is too high, the adhesive portion may be deformed or the inner surface of the label may be blocked due to the penetration of the adhesive solvent.

The raw material composition is formed into a film by a known method (for example, an extrusion method or a calendar method). The shape of the film is, for example, a flat shape or a tube shape, and is not particularly limited. As the stretching method, for example, a known method such as a roll stretching method, a long gap stretching method, a tenter stretching method, or a tubular stretching method can be employed. In any of these methods, stretching may be performed by sequential biaxial stretching, simultaneous biaxial stretching, uniaxial stretching, and combinations thereof. In the biaxial stretching, stretching in the vertical and horizontal directions may be performed simultaneously, or either one may be performed first. The draw ratio is arbitrarily set in the range of 1.0 to 7.0 times, and the magnification in a predetermined direction is preferably 3.5 times or more.
In the stretching step, preheating is preferably performed at a temperature not lower than the glass transition temperature (Tg) of the polymer constituting the film and not higher than Tg + 80 ° C., for example. In the heat setting at the time of stretching, for example, it is recommended to pass the heating zone at 30 to 150 ° C. for about 1 to 30 seconds after stretching. Further, after stretching the film, it may be stretched at a predetermined degree before or after heat setting. Further, after the stretching, a step of cooling while keeping the stretched or tensioned state while applying stress to the film, or a step of cooling after releasing the tensioned state following the treatment may be added. The thickness of the obtained film is preferably in the range of 6 to 250 μm.

  In the present invention, a surface layer is preferably laminated on at least one surface of such a base material layer.

  Usually, heat-shrinkable polyester film for labels gives the slipperiness required for film handling by containing a particle lubricant in the base material layer and controlling the shape, amount, and distribution of the particles. is doing. However, in the present invention, since the transparency and gloss need to be maintained within a certain range, the addition of the particle lubricant is limited, so that the slipperiness may be insufficient. In the present invention, by laminating an easy-sliding layer containing a particle lubricant on the surface, transparency and gloss can be maintained within a certain range, and a heat-shrinkable polyester film that can achieve both slipperiness necessary for film production and handling can be obtained. I found.

It is recommended that the surface layer component contains a resin component having the function of a binder. Examples of the resin component include polyester resins, polyamide resins, polyurethane resins, epoxy resins, phenol resins, acrylic resins, polyvinyl acetate resins, polyolefin resins such as polyethylene and polypropylene, and copolymers thereof. Or a modified resin, a cellulose resin, etc. are mentioned. Further, it is desirable that the resin used as the binder in the present invention is essentially water-insoluble so that it does not easily affect the slipperiness due to moisture absorption.
In particular, the resin component having a binder function in the surface layer component is preferably a polyester and / or a polyester derivative, and a hydrophobic copolymerized polyester resin is preferably used as a backbone polymer. The graft polymerization reaction product obtained by graft polymerization of the polyester resin with a radical polymerizable monomer in an organic solvent, adding water and distilling off the organic solvent is excellent in adhesion and water resistance, and is a water-dispersed resin. It is a form, which is preferable from the viewpoint of work environment and applicability, and is also recommended because it is difficult to inhibit adhesion between films due to a solvent required for label processing. As a preferable polyester resin component of the trunk polymer, an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid or 2,6-naphthalenedicarboxylic acid, an aliphatic dicarboxylic acid such as adipic acid, azelaic acid or sebacic acid as a dicarboxylic acid component In addition to the component selected from the components, it is preferable to contain about 0.5 to 10 mol% of a component having a polymerizable unsaturated double bond such as fumaric acid, maleic acid, and 2,5-norbornene dicarboxylic acid. The glycol component is selected from aliphatic diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and alicyclic glycols such as 1,4-cyclohexanedimethanol. It is preferable to contain a component. The graft site is composed of a polymerizable unsaturated monomer, but preferably contains a component selected from fumaric acid, maleic acid, maleic anhydride, acrylic acid, methacrylic acid and the like.

In addition, metals, metal oxides, inorganic oxides other than metals can be deposited on the surface of the heat-shrinkable polyester film of the present invention, and the laminated surface layer is an adhesive between the deposited layer and the film. Has the effect of improving the sex. In particular, the main component is a water-dispersible thermoplastic polyurethane, which is obtained from a polyester polyol, diisocyanate, and optionally a low molecular weight compound having two or more active hydrogens, and the polyester polyol is 5 A dicarboxylic acid containing an aliphatic dicarboxylic acid; and a glycol obtained from glycols are desirable because they have good adhesion.

  Furthermore, in the present invention, a particle lubricant is added to the aqueous resin dispersion, and as the particle lubricant, cucumber, chalk, heavy coal cal, light coal cal, basic magnesium carbonate, dolomite, special calcium carbonate, kaolin, calcined Clay, pyrophyllite, bentonite, cerisalite, zeolite, nepheline cynite, talc, attapuljanite, synthetic aluminum silicate, synthetic calcium silicate, diatomaceous earth, quartzite powder, fine silicate, anhydrous fine silicate, aluminum hydroxide, barite, sedimentation There are various kinds of inorganic particles such as barium sulfate, natural gypsum, gypsum, calcium sulfite, and inert particles such as benzoguanamine resin and polystyrene resin. Any of these may be used in relation to transparency, gloss and slipperiness. Particularly preferred are natural and synthetic products of silicic acid. So-called colloidal silica can be particularly preferably used. The particle size is preferably 0.001 μm to 0.3 μm. If the particle diameter is less than 0.001 μm, it must be used in a large amount, and it tends to be difficult to express slipperiness. When the particle diameter exceeds 0.3 μm, coarse protrusions are generated, resulting in problems such as poor smoothness and impairing printing processing and label processing suitability. Also, depending on the method of bar coating or the like, if the particle size is large, there is a problem that the coating cannot be performed normally due to clogging or the like at the time of coating. In addition, although the said particle size is a particle size measured by the Coulter counter method, the measuring method of the average particle diameter of the particle | grains in a film surface layer is mentioned later. The amount added varies depending on the shape, particle diameter and surface layer thickness and is not limited, but it is preferably used in the range of 0.05 to 30% by weight in the surface layer. If it is less than 0.05% by weight, the slipperiness becomes insufficient, so that blocking between the films tends to occur, and if it exceeds 30% by weight, the transparency and glossiness tend to deteriorate.

  It is preferable to use a low-boiling organic solvent for the coating solution in order to impart wettability of the solution and drying property after coating. Isopropanol is usually used as the organic solvent. When blending, the concentration of isopropyl alcohol must be 56% or less. If the concentration exceeds 56%, the aggregation of inert particles tends to occur, and problems such as slippage deterioration due to particle dropping after coating are likely to occur, which is not preferable.

  Another feature of the film according to the present invention is that an anionic antistatic agent is present on at least one surface of the surface. Even if an anionic antistatic agent is included in the film raw material by kneading or the like, generation and accumulation of static electricity can be suppressed if the anionic antistatic agent oozes from the inside of the film to the surface. However, since the glass transition temperature of the polyester constituting the film is generally high, the anionic antistatic agent is often difficult to ooze out on the film surface at room temperature and in the vicinity thereof, and sufficiently suppresses the generation and accumulation of static electricity. It tends to be impossible. In addition, since the film forming temperature for producing the film according to the present invention produced by stretching the resin is relatively high, and the reaction activity of the polar group of the polyester is high, the film raw material is antistatic. When an agent is blended, deterioration of the polyester is promoted at the time of film formation, so that the physical properties of the film may be lowered and coloring may occur.

The amount of the anionic antistatic agent present on the film surface is preferably 0.001 to 0.5 g / m ² . If the amount of the anionic antistatic agent is less than the above range, the antistatic effect may not be sufficiently secured. On the other hand, when the amount of the anionic antistatic agent exceeds the above range, the transparency and blocking resistance of the film may be lowered.

  The anionic antistatic agent preferably has an alkyl group and has 10 to 20 carbon atoms. With such an antistatic agent, for example, even if there is scattering or disappearance due to heat in film production or secondary processing of the film, the amount of the scattering or the like can be kept low. Moreover, when carbon number exceeds 20, the antistatic effect of antistatic agent itself may be inadequate. More preferable anionic antistatic agents are those having 12 to 18 carbon atoms.

  The anionic antistatic agent in the present invention can be selected from known antistatic agents, and sulfuric acid such as higher alcohol sulfates, sulfates of alkylphenol ethylene oxide adducts, alkylsulfonates, and alkylallylsulfonates. And sulfonic acid derivatives. More specifically, alkyl sulfonate, alkyl benzene sulfonate, alkyl sulfate ester salt, alkyl ethoxy sulfate ester salt, and alkyl phosphate ester salt are exemplified. Suitable anionic antistatic agents include, for example, dodecyl sulfonate and dodecyl benzene sulfonate.

  Antistatic agents often do not have good compatibility with silicic acid particles, and it is preferable to adjust the solid content of the antistatic agent to an appropriate range. The appropriate range is often influenced by the characteristics resulting from the type and amount of the content of the coating solution, and can be determined while confirming the effect each time. For example, in the case of dodecyl sulfonate, when the solid content reaches 40%, the silicic acid particles may be easily aggregated.

As for the application quantity of the aqueous dispersion liquid apply | coated to a polyester film, 0.005-5 g / m < ² > is preferable with respect to the film after biaxial stretching. In the case of less than 0.005 g / m ^2, the force for fixing the inert particles becomes weak and the durability performance is deteriorated. When it is applied over 5.0 g / m ² , the slipperiness is deteriorated.

  As a method for forming the surface layer on the substrate, a method of coating the substrate with an aqueous solution is usually employed. The coating method is not limited, but an optimal method may be selected depending on the coating amount and viscosity of the coating liquid to be used. A reverse roll coating method, a roll knife coating method, a die coating method, or the like may be employed.

  The drying and heat treatment conditions during coating depend on the coating thickness and equipment conditions, but they can be sent immediately to the stretching process in the perpendicular direction without any drying process and dried in the preheating zone or stretching zone of the stretching process. preferable. In such a case, it is normally performed at about 50 to 250 ° C. If necessary, before forming the surface layer, the base film may be subjected to an anchoring treatment using a corona discharge treatment, other surface activation treatment or a known anchor treatment agent.

In order to produce a film having a surface layer in the present invention, a coating solution is applied to at least one surface of a melt-extruded unstretched polyester film or uniaxial polyester film, and then the coated film is biaxially stretched or An in-line coating method including a step of uniaxial stretching is preferred.

  Below, the tube process at the time of using the film obtained by said method as a label is demonstrated. When producing a label from the heat-shrinkable polyester film of the present invention, a tube-forming process is carried out. In this case, a solvent such as 1,3-dioxolane or tetrahydrofuran is used from the viewpoint that the solvent is often used for adhesion. Is preferably applied to one surface of the film, and the other surface of the film is pressure-bonded to the coated surface and peeled in the main shrinkage direction. When the amount is insufficient, there is a risk of peeling of the label adhesive portion when the label is heat-shrinked or when handling a beverage bottle.

  Hereinafter, the present invention will be described in detail by way of examples. The film properties obtained in each example were measured and evaluated by the following methods.

(1) Thermal contraction rate in the maximum shrinkage direction The film is cut into a 10 cm × 10 cm square along the longitudinal direction and the orthogonal direction, and treated in warm water at 95 ° C. ± 0.5 ° C. for 10 seconds under no load. Then, after heat shrinking, the sample was immediately immersed in water at 25 ° C. ± 0.5 ° C. for 10 seconds, then the lengths of the sample in the vertical and horizontal directions were measured and determined according to the following formula. The direction with the largest shrinkage rate was defined as the maximum shrinkage direction.
Thermal shrinkage (%) = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)

(2) Haze Haze was measured using a haze meter (manufactured by Nippon Seimitsu Co., Ltd.) according to JIS K7136.

(3) Glossiness Glossiness (gloss) was measured at a measurement angle of 45 degrees using a gloss meter “VG2000” (manufactured by Nippon Denshoku Industries Co., Ltd.) according to JIS Z8741.

(4) Dynamic friction coefficient The dynamic friction coefficient μd on one side and the other side of the film was measured in an environment of 23 ° C. and 65% RH in accordance with JIS K-7125.

(5) Surface specific resistance Using a surface specific resistance measuring instrument (main body: R8340, sample box: R12704) manufactured by Advantest Co., Ltd., measured in an atmosphere with an applied voltage of 100 V, 23 ° C., 65% RH, and the reading of the measuring instrument Was the surface resistivity.

(6) Solvent bond strength 1,3-dioxolane was applied to the stretched film with a cotton swab with a coating amount (5 ± 0.3) g / m ² and a coating width of 5 ± 1 mm, and the two sheets were bonded together to provide a seal. gave. Cut the seal part to a width of 15 mm in each direction perpendicular to the main stretching direction (main shrinking direction) of the film, set it on the Baldwin Co., Ltd. Universal Tensile Tester STM-50, and pull it by 90 ° peel test. It was measured at a speed of 200 mm / min.

Particle size of particles contained in the coat layer The coated surface of the obtained film was magnified using a laser microscope (LEXT OLS3000 manufactured by Olympus) to measure the particle size of 20 randomly selected particles. The average particle diameters of the particles corresponding to each of the silicas a, b, and c described in the examples were determined. The particle size was measured in the direction in which the particle size of each particle was measured to the maximum.

The base material layer polyester resin was obtained by the following method.
(Polyester synthesis example 1)
In a stainless steel autoclave equipped with a stirrer, thermometer and partial reflux condenser, 100 mol% of dimethyl terephthalate (DMT) as a dicarboxylic acid component, 72 mol% of ethylene glycol (EG) as a glycol component and neopentyl glycol (NPG) 30 mol% is charged so that glycol is 2.2 times the molar ratio of the methyl ester, 0.05 mol of zinc acetate as a transesterification catalyst (based on the acid component), and as a polycondensation catalyst 0.025 mol of antimony trioxide (based on the acid component) was added, and the ester exchange reaction was carried out while distilling off the produced methanol out of the system. Thereafter, a polycondensation reaction was performed at 280 ° C. under a reduced pressure condition of 26.7 Pa to obtain a polyester (A).

(Synthesis Examples 2-3)
By the same method as in Synthesis Example 1, polyesters (B) to (C) shown in Table 1 were obtained. In addition,
In the table, NPG is neopentyl glycol, BD is 1,4-butanediol, and DEG is diethylene glycol.

As the inorganic lubricant, SiO ₂ particles (indefinite shape, average particle size 2.4 μm) were used, and a master batch (D) added with 0.7% by mass in polyester (A) was used. The lubricant was added in advance by dispersing the lubricant in ethylene glycol and polymerizing by the above method.

Moreover, the aqueous dispersion (E) of copolyester resin was obtained with the following method.
<Preparation of hydrophobic copolyester>
In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 345 parts of dimethyl terephthalate (DMT) as a dicarboxylic acid component, 211 parts of 1,4 butanediol (BD) as a glycol component, ethylene glycol ( (EG) 270 parts and 0.5 part of tetra-n-butyl titanate as a polymerization catalyst were charged, and a transesterification reaction was performed from 160 ° C. to 220 ° C. over 4 hours. Next, 14 parts of fumaric acid and 160 parts of adipic acid were added as dicarboxylic acid components, and the temperature was raised from 200 ° C. to 220 ° C. over 1 hour to carry out an esterification reaction. Next, the temperature was raised to 255 ° C., and the pressure of the reaction system was gradually reduced, followed by reaction for 1 hour 30 minutes under a reduced pressure of 0.22 mmHg to obtain a hydrophobic copolyester. The obtained hydrophobic copolyester had a weight average molecular weight of 20,000 and was pale yellow and transparent.

<Grafting of radically polymerizable monomer>
In a reactor equipped with a stirrer, a thermometer, a reflux device and a quantitative dropping device, 75 parts of the hydrophobic copolymer polyester, 56 parts of methyl ethyl ketone and 19 parts of isopropyl alcohol are heated and stirred at 65 ° C. The polymerized polyester was dissolved. After the hydrophobic copolyester was completely dissolved, 15 parts of maleic anhydride (MA) as a radical polymerizable monomer was added to the polyester solution. Next, a solution prepared by dissolving 10 parts of styrene (ST) as a radical polymerizable monomer and 1.5 parts of azobisdimethylvaleronitrile as a graft polymerization initiator in 12 parts of methyl ethyl ketone was dropped into the polyester solution at 0.1 ml / min. The stirring was continued for another 2 hours. After sampling for analysis from the reaction solution, 5 parts of methanol was added. Next, 300 parts of water and 15 parts of triethylamine were added to the reaction solution and stirred for 1 hour. Thereafter, the reactor internal temperature was raised to 100 ° C., and methyl ethyl ketone, isopropyl alcohol, and excess triethylamine were distilled off to obtain a polyester-based graft copolymer aqueous dispersion (E) having a solid content of 25%. The polyester graft copolymer was light yellow and transparent and had a glass transition temperature of -10 ° C.

Moreover, the aqueous dispersion (F) of copolyester resin was obtained with the following method.
The coating solution used in the present invention was prepared according to the following method. A reaction vessel was charged with 95 parts by weight of dimethyl terephthalate, 95 parts by weight of dimethyl isophthalate, 35 parts by weight of ethylene glycol, 145 parts by weight of neopentyl glycol, 0.1 part by weight of zinc acetate and 0.1 part by weight of antimony trioxide. The transesterification was carried out over 3 hours. Next, 6.0 parts by mass of 5-sodium sulfoisophthalic acid was added, and esterification was performed at 240 ° C. over 1 hour, and then at 250 ° C. under reduced pressure (10 to 0.2 mmHg) over 2 hours. A polycondensation reaction was performed to obtain a copolyester resin having a number average molecular weight of 19,500.
300 parts by mass of the obtained copolyester resin and 140 parts by mass of butyl cellosolve were stirred at 160 ° C. for 3 hours to obtain a viscous melt, water was gradually added to the melt, and a uniform light white color was added after 1 hour. An aqueous dispersion (F) of a copolymerized polyester resin having a solid content concentration of 30% was obtained.

Example 1
(1) Polyester resin and unstretched film Each preliminarily dried polyester composition shown in Table 1 was mixed with 75 wt% of polyester A, 10 wt% of B, and 15 wt% of C in a hopper directly above the extruder. , While continuously feeding separately with a fixed screw feeder, mixing in this hopper, melt extrusion with a single screw extruder at 275 ° C., quenching on a chill roll with a surface temperature of 25 ° C., and having a thickness of 200 μm An unstretched film was obtained.

(2) Preparation of coating liquid 29.8% of the total water, 30% of isopropyl alcohol, water dispersion of copolymerized polyester resin (E) and colloidal silica (a) ("Snowtex MP2040" Nissan Chemical Industrial) was mixed so that the solid content was 15%, and colloidal silica (b) ("Snowtex OS" manufactured by Nissan Chemical Industries, Ltd.) was mixed to a solid content of 10%, and dodecyl sulfonate was mixed with 30% solid content. The liquid adjusted to% was added so as to be 10% of the whole, prepared and used as a coating liquid.

(3) Manufacture of coated film While applying the coating solution prepared in (2) to the unstretched film obtained in (1) by the bar coating method, it is continuously led to a tenter and preheated until the film temperature reaches 98 ° C. Then, the film was stretched 5.0 times in the transverse direction at a temperature of 77 ° C. Next, heat treatment was performed at 78 ° C. for 14 seconds to obtain a heat-shrinkable polyester film having a coating amount of 0.01 g / m ² and a thickness of 40 μm. The physical properties of the obtained film are shown in Table 2.

(Example 2)
The same method as in Example 1 except that the colloidal silica (b) is 10% based on the solid content and the colloidal silica (c) (“Snowtex MP3040” manufactured by Nissan Chemical Industries) is 15% based on the solid content. A heat-shrinkable polyester film was obtained.
The physical properties of this film are shown in Table 2.

Example 3
Polyester resin in water dispersion (F) and silica (d) ("Silicia 310" manufactured by Fuji Silysia) 0.6% solids, colloidal silica (e) ("Snowtex OL")
Nissan Chemical Co., Ltd.) is mixed to a solid content of 10%, dodecyl sulfonate is added to a solid content of 2.5%, an IPA 30 wt% aqueous dispersion is prepared, A heat-shrinkable polyester film was obtained in the same manner as in Example 1 except that the coating amount was 0.05 g / m ² by the reverse coating method.
The physical properties of this film are shown in Table 2.

(Comparative Example 1)
A polyester composition in which 75% by weight of polyester A shown in Table 1 and 10% by weight of B, 9% by weight of C, 9% by weight of C, and 6% by weight of D were melt-extruded as a base material layer and separately coated is shown. Samples were prepared and evaluated in the same procedure as in Example 1. The physical properties of this film are shown in Table 2.

(Comparative Example 2)
Samples were prepared and evaluated in the same procedure as in Example 1 except that coating was not performed. The physical properties of this film are shown in Table 2.
However, when this sample was taken up into a roll using a paper tube, the sample was wrinkled due to lack of slipperiness, and further, blocking between films occurred.

(Comparative Example 3)
Samples were prepared and evaluated in the same procedure as in Example 1 except that the amount of colloidal silica added was changed. The physical properties of this film are shown in Table 2.
The obtained film was not suitable for practical use due to lack of slipperiness.

(Comparative Example 4)
A sample was prepared and evaluated in the same procedure as in Example 1 except that a 40% solid content of dodecyl sulfonate was used. The physical properties of this film are shown in Table 2. The obtained film surface layer particles showed an increase in particle size due to aggregation, dropout occurred in some of the particles, lack of slipperiness, and were not suitable for practical use.

  The heat-shrinkable polyester film of the present invention has excellent transparency and glossiness, slipperiness necessary for production and handling, and antistatic properties, excellent processing suitability, and suitable for label use and utility value. Is high.

Claims (7)

It is a laminated film having a base film made of a polyester-based resin and a surface layer provided on at least one surface of the base film, and the surface layer is an inorganic particle having a particle size of 1 nm or more and 300 nm or less. 30% by weight and an anionic antistatic agent, the haze value of the film is 2% or less, and the glossiness is 200% or more at a measurement angle of 45 ° on at least one side of the film. The coefficient of dynamic friction with the surface is 1.5 or less, the shrinkage rate in the main shrinkage direction is 50% or more when the film is immersed in hot water of 95 ° C. for 10 seconds, and the surface resistivity is 13 logΩ under a relative humidity of 65%. A heat-shrinkable polyester film characterized by:   The film has a haze value of 3% or less after being immersed in hot water at 90 ° C. for 10 seconds and contracted by 10% in the main contraction direction, and has a glossiness of 190% or more at a measurement angle of 45 ° on at least one side of the film. The heat-shrinkable polyester film according to claim 1.   The heat-shrinkable polyester film according to claim 1 or 2, wherein the solvent adhesive strength of the film is 2 N / 15 mm or more. The heat-shrinkable polyester film according to any one of claims 1 to 3, wherein the base film is mixed containing polyethylene terephthalate and a copolyester. The heat-shrinkable polyester film according to any one of claims 1 to 4, wherein the surface layer has a solid mass of 0.0005 g / m ² or more and 0.1 g / m ² . The heat-shrinkable polyester film according to any one of claims 1 to 5 , wherein the surface layer contains polyester and / or a polyester derivative. The heat shrink according to any one of claims 1 to 6, wherein the film is subjected to sequential biaxial stretching, simultaneous biaxial stretching, or uniaxial stretching in which a stretching ratio in a predetermined direction is 3.5 times or more. Polyester film.