JP5761281B2 - Method for producing white heat-shrinkable polyester film, white heat-shrinkable polyester film, and package - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method for producing a white heat-shrinkable polyester film, a white heat-shrinkable polyester film, and a package, and more specifically, a white heat-shrinkable polyester having a light-cutting property and suitable for label applications. The present invention relates to a method for producing a film, a white heat-shrinkable polyester film, and a package using a label.

  In recent years, stretched films made of polyvinyl chloride resin, polystyrene resin, polyester resin, etc. (so-called so-called, Heat-shrinkable film) has been widely used. Among such heat-shrinkable films, the polyvinyl chloride film has problems such as low heat resistance, generation of hydrogen chloride gas during incineration, and dioxin generation. In addition, polystyrene film has poor solvent resistance and must use ink with a special composition during printing, and must be incinerated at a high temperature, and a large amount of black smoke is generated with an unpleasant odor during incineration. There is a problem of doing. Therefore, polyester-based heat-shrinkable films that have high heat resistance, are easy to incinerate, and have excellent solvent resistance are widely used as shrink labels. The usage tends to increase with the increase.

  In addition, as the heat-shrinkable film, a film that is largely shrunk in the width direction is generally used from the viewpoint of handling during label production. Therefore, the conventional heat-shrinkable polyester film has been produced by stretching at a high magnification in the width direction in order to develop a sufficient shrinkage force in the width direction during heating.

  However, since the conventional heat-shrinkable polyester film is hardly stretched in the longitudinal direction perpendicular to the main shrinkage direction, the mechanical strength is low, and when it is covered by being shrunk on a plastic bottle or the like as a label, There is a defect that the label cannot be torn well along the perforation (that is, the perforation opening is poor). In addition, there is a problem that the tear resistance after storage when used as a label for a beverage container tends to be insufficient. Furthermore, in order to improve the perforation opening property of the heat-shrinkable polyester film, when the film is stretched in the longitudinal direction during production, the mechanical strength increases and the perforation opening property is improved to some extent, but in the longitudinal direction. Since the shrinkage force is expressed, when it is made to shrink and coat as a label on a PET bottle or the like, the appearance (shrinkage finishing property) is very poor.

  Therefore, in order to improve the perforation openability of the heat-shrinkable polyester film, a method of mixing an incompatible thermoplastic resin into the main raw material of the heat-shrinkable polyester film (Patent Document 1) is also proposed. .

Japanese Patent Application Laid-Open No. 2002-36312

  According to the method of mixing an incompatible thermoplastic resin in the main raw material of the heat-shrinkable polyester film described in Patent Document 1, although the perforation openability of the heat-shrinkable polyester film is improved to some extent, It is difficult to say that a heat-shrinkable polyester film having sufficient perforation-opening properties has been obtained. In addition, when the method described in Patent Document 1 is adopted, since the film can be stretched only in the width direction during production, a heat-shrinkable polyester film cannot be produced efficiently.

  An object of the present invention is to solve the problems of the conventional heat-shrinkable polyester film and to provide a white heat-shrinkable polyester film having a very good perforation opening property and a production method with high productivity. .

  Another object of the present invention is to provide a lightweight white heat-shrinkable polyester film that has light-cutting properties without printing or processing, and has an excellent aesthetic appearance even when printing is performed.

  As a result of intensive studies to solve the above problems, the present inventors have finally completed the present invention. That is, the present invention has the following configuration.

1. The following (1) to (4) comprising a polyester-based resin comprising ethylene terephthalate as a main constituent and containing at least 13 mol% of at least one monomer component that can be an amorphous component in all polyester resin components. A white heat-shrinkable polyester film, which is a production method for continuously producing a white heat-shrinkable polyester film that satisfies the above requirements, comprising the following steps (a) to (e): Manufacturing method.
(1) The hot water thermal shrinkage in the longitudinal direction when treated for 10 seconds in warm water at 80 ° C. is −2% or more and 4% or less ( 2 ) for 10 seconds in warm water at 95 ° C. The hot water thermal contraction rate in the width direction when treated is 50% or more and 80% or less.
(3) The perpendicular tear strength in the longitudinal direction per unit thickness after shrinking 10% in the width direction in warm water at 80 ° C. is 200 N / mm or more and 300 N / mm or less ( 4 ) It has a B layer with fewer cavities than the A layer on at least one side of the A layer to be contained, and the whiteness is 70 or more. (A) An unstretched film is 1 in the longitudinal direction at a temperature of 75 ° C. or more and 100 ° C. or less. (B) Longitudinal stretching step of stretching at a magnification of 1 to 1.8 times (b) A temperature of 110 ° C. or more and 150 ° C. or less with the film after longitudinal stretching held in the tenter by the clips at both ends in the width direction Intermediate heat treatment step (c) in which the film is subjected to heat treatment over a period of 5 seconds to 30 seconds at a positive cooling step in which the film after the intermediate heat treatment is actively cooled until the surface temperature becomes 70 ° C. or higher and 90 ° C. or lower ( d) After active cooling A transverse stretching step in which the film is stretched at a temperature of 65 ° C. or more and 90 ° C. or less at a magnification of 3.5 times or more and 5.0 times or less in the width direction. 1. A final heat treatment step in which heat treatment is performed at a temperature of 80 ° C. or higher and 100 ° C. or lower for a time of 5 seconds or longer and 30 seconds or shorter with the edge held by a clip. The method for producing a white heat-shrinkable polyester film according to the first aspect, wherein the solvent adhesive strength is 2 N / 15 mm width or more and 10 N / 15 mm width or less.
3. 3. The method for producing a white heat-shrinkable polyester film as described in the above item 1 or 2 , wherein the thickness unevenness in the longitudinal direction is 1% or more and 18% or less.
4). 4. The method for producing a white heat-shrinkable polyester film according to any one of the first to third aspects, wherein thickness unevenness in the width direction is 1% or more and 18% or less.
5. Thickness is 20 micrometers or more and 80 micrometers or less, The manufacturing method of the white heat-shrinkable polyester film in any one of said 1st- 4 characterized by the above-mentioned.
6). The main component of a monomer that can be an amorphous component in all the polyester resin components is one or more of neopentyl glycol, 1,4-cyclohexanedimethanol, and isophthalic acid. method for producing a white heat-shrinkable polyester film according to any one of 1 to 5.
7). An apparent density is 1.2 g / cm < ³ > or less, The manufacturing method of the white heat-shrinkable polyester film in any one of said 1-6 characterized by the above-mentioned.
8). A white heat-shrinkable polyester film produced by the method for producing a white heat-shrinkable polyester film according to any one of the first to seventh aspects.
9. A package comprising the white heat-shrinkable polyester film as described in the above item 8 as a base material, and a heat-shrinkable covering at least a part of the outer periphery with a perforation or a label provided with a pair of notches. body.

  The white heat-shrinkable polyester film of the present invention is highly shrinkable in the width direction, which is the main shrinkage direction, has high mechanical strength in the longitudinal direction perpendicular to the width direction, and has a perforation opening property when used as a label. When opening, it can be cut neatly along the perforation from the beginning of tearing to the completion of tearing. In addition, the stiffness (so-called “waist strength”) is high, and the wearability when the label is used is excellent. In addition, the processing characteristics during printing and tubing are good. Therefore, the white heat-shrinkable polyester film of the present invention can be suitably used as a label for a container such as a bottle. When used as a label, the white heat-shrinkable polyester film can be very efficiently used in a container such as a bottle within a short time. It can be worn, and when it is heat-shrinked after wearing, it can express a good finish with very little wrinkles and insufficient shrinkage, and the attached label expresses very good perforation opening Become. The package of the present invention has a good tearing condition of the coated label, and can be torn the coated label cleanly along the perforation with an appropriate force.

  The white heat-shrinkable polyester film of the present invention is lightweight and excellent in aesthetics, has light-cutting properties without printing or processing, and has excellent aesthetics even when printed.

  Moreover, the white heat-shrinkable polyester film of the present invention has an extremely high adhesive force when the front and back surfaces (or the same surface) are bonded with a solvent. Therefore, it can be suitably used for various coated labels including labels such as PET bottles.

It is explanatory drawing which shows the shape of the test piece in the measurement of a right-angled tear strength (In addition, the unit of the length of each part of the test piece in a figure is mm).

  The polyester used in the present invention is mainly composed of ethylene terephthalate. That is, it contains 50 mol% or more, preferably 60 mol% or more of ethylene terephthalate. Other dicarboxylic acid components constituting the polyester of the present invention include aromatic dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid and orthophthalic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid, And alicyclic dicarboxylic acid.

  When an aliphatic dicarboxylic acid (for example, adipic acid, sebacic acid, decanedicarboxylic acid, etc.) is contained, the content is preferably less than 3 mol%. A heat-shrinkable polyester film obtained by using a polyester containing 3 mol% or more of these aliphatic dicarboxylic acids is not preferred because the film stiffness at high speed mounting tends to be insufficient.

  Further, it is preferable not to contain a trivalent or higher polyvalent carboxylic acid (for example, trimellitic acid, pyromellitic acid, and their anhydrides). A heat-shrinkable polyester film obtained by using a polyester containing these polyvalent carboxylic acids is not preferred because it is difficult to achieve the required high shrinkage.

  Examples of the diol component constituting the polyester used in the present invention include aliphatic diols such as ethylene glycol, 1-3 propanediol, 1-4 butanediol, neopentyl glycol, and hexanediol, and 1,4-cyclohexanedimethanol. Examples thereof include aromatic diols such as alicyclic diols and bisphenol A.

The polyester used for the white heat-shrinkable polyester film of the present invention is a cyclic diol such as 1,4-cyclohexanedimethanol or a diol having 3 to 6 carbon atoms (for example, 1-3 propanediol, 1-4 butane). A polyester having a glass transition point (Tg) adjusted to 60 to 80 ° C. by containing one or more of diol, neopentyl glycol, hexanediol and the like.

  The polyester used in the white heat-shrinkable polyester film of the present invention is one or more kinds that can be an amorphous component in 100 mol% of the polyhydric alcohol component or 100 mol% of the polyvalent carboxylic acid component in the total polyester resin. The total of the monomer components is preferably 13 mol% or more, more preferably 15 mol% or more, still more preferably 17 mol% or more, and particularly preferably 20 mol% or more. Here, examples of the monomer that can be an amorphous component include neopentyl glycol, 1,4-cyclohexanedimethanol, isophthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,2- Diethyl 1,3-propanediol, 2-n-butyl 2-ethyl 1,3-propanediol, 2,2-isopropyl 1,3-propanediol, 2,2-di-n-butyl 1,3-propanediol, Among them, 1,4-butanediol and hexanediol can be mentioned. Among them, neopentyl glycol, 1,4-cyclohexanedimethanol and isophthalic acid are preferably used. However, if one or more kinds of monomer components that can be too amorphous components are increased, the heat shrinkage characteristics may be increased more than necessary or the mechanical characteristics may be insufficient. Or less, and more preferably 30 mol% or less.

  In the polyester used in the white heat-shrinkable polyester film of the present invention, a diol having 8 or more carbon atoms (for example, octanediol) or a trihydric or higher polyhydric alcohol (for example, trimethylolpropane, trimethylolethane, It is preferable not to contain glycerin, diglycerin and the like. In the white heat-shrinkable polyester film obtained by using polyester containing these diols or polyhydric alcohols, it is difficult to achieve a necessary high shrinkage rate.

  Moreover, it is preferable not to contain diethylene glycol, triethylene glycol, and polyethylene glycol as much as possible in the polyester used for the white heat-shrinkable polyester film of the present invention.

  In addition, in the resin forming the white heat-shrinkable polyester film of the present invention, various additives, for example, waxes, antioxidants, antistatic agents, crystal nucleating agents, viscosity reducing agents are used as necessary. Further, a heat stabilizer, a coloring pigment, an anti-coloring agent, an ultraviolet absorber and the like can be added. In the resin forming the white heat-shrinkable polyester film of the present invention, it is preferable to improve the workability (slidability) of the polyethylene terephthalate resin film by adding fine particles as a lubricant. Any fine particles can be selected. Examples of inorganic fine particles include silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate. Examples of the organic fine particles include acrylic resin particles, melamine resin particles, silicone resin particles, and crosslinked polystyrene particles. The average particle size of the fine particles can be appropriately selected as necessary within a range of 0.05 to 3.0 μm (when measured with a Coulter counter).

  As a method of blending the above particles into the resin forming the white heat-shrinkable polyester film, for example, it can be added at any stage of producing the polyester resin, but it can be added at the esterification stage or transesterification. After completion of the reaction, it is preferable to add as a slurry dispersed in ethylene glycol or the like at the stage before the start of the polycondensation reaction to advance the polycondensation reaction. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water using a vented kneading extruder and a polyester resin material, or a dried particle and a polyester resin material using a kneading extruder It is also preferable to carry out by a method of blending and the like.

  In the present invention, in order to obtain an appropriate whiteness, for example, it is preferable to contain fine cavities inside. For example, a foam material or the like may be mixed and extruded, but a preferable method is to obtain a cavity by mixing an incompatible thermoplastic resin in polyester and stretching it in at least one axial direction. The thermoplastic resin incompatible with the polyester used in the present invention is arbitrary, and is not particularly limited as long as it is incompatible with the polyester. Specific examples include polystyrene resins, polyolefin resins, polyacrylic resins, polycarbonate resins, polysulfone resins, and cellulose resins. In particular, a polystyrene resin or a polyolefin resin such as polymethylpentene or polypropylene is preferable because of the formation of cavities.

  Polystyrene resin refers to a thermoplastic resin containing a polystyrene structure as a basic component, and grafted or block copolymerized with other components in addition to homopolymers such as atactic polystyrene, syndiotactic polystyrene, and isotactic polystyrene. Modified resins, such as impact-resistant polystyrene resins and modified polyphenylene ether resins, and mixtures of thermoplastic resins having compatibility with these polystyrene resins, such as polyphenylene ether, are included.

  The polymethylpentene-based resin is a polymer having units derived from 4-methylpentene-1 at 80 mol% or more, preferably 90 mol% or more, and other components include ethylene units, propylene units, Examples include units derived from butene-1 units, 3-methylbutene-1, and the like. The melt flow rate of such polymethylpentene is preferably 200 g / 10 min or less, more preferably 30 g / 10 min or less. This is because when the melt flow rate exceeds 200 g / 10 min, it is difficult to obtain the effect of reducing the weight of the film.

  The polypropylene resin in the present invention also includes modified resins obtained by grafting or block copolymerizing other components in addition to homopolymers such as isotactic polypropylene and syndiotactic polypropylene.

  In preparing a polymer mixture obtained by mixing the polyester and the incompatible resin, for example, the chips of each resin may be mixed and melt-kneaded in an extruder and then extruded, or both resins may be preliminarily mixed by a kneader. The kneaded product may be further melt extruded from an extruder. Further, a chip obtained by adding a polystyrene resin in the polyester polymerization step and stirring and dispersing may be melt-extruded.

Film in the invention is preferably provided with less B layer having cavities than A layer on at least one surface of the A layer containing a large number of cavities therein. In order to achieve this configuration, different raw materials are charged into different extruders A and B, melted, bonded in a molten state before or in the T-die, and solidified in close contact with the cooling roll, and then described later. It is preferable to stretch by the method. At this time, it is preferable that the incompatible resin of the B layer is less than the A layer as a raw material. By doing so, there are few cavities in the B layer, the surface is less rough, and the film does not impair the aesthetics of printing. In addition, since there are portions where there are not many cavities in the film, the film does not become weak and the film has excellent wearability.

  Furthermore, the white heat-shrinkable polyester film of the present invention can be subjected to corona treatment, coating treatment, flame treatment, etc. in order to improve the adhesion of the film surface.

The white heat-shrinkable polyester film of the present invention is a film calculated by the following equation (1) from the length before and after shrinkage when treated for 10 seconds in warm water at 80 ° C. under no load. The heat shrinkage rate in the longitudinal direction (that is, the hot water heat shrinkage rate at 80 ° C.) is preferably −2% or more and 4% or less.
Thermal shrinkage rate = {(length before shrinkage−length after shrinkage) / length before shrinkage} × 100 (%)
... Formula (1)

  When the hot water thermal contraction rate in the longitudinal direction at 80 ° C. is less than −2% (that is, when it exceeds 2% by heat treatment), a good shrink appearance cannot be obtained when used as a bottle label. On the contrary, if the hot water thermal shrinkage rate in the longitudinal direction at 80 ° C. exceeds 4%, it is not preferred because distortion tends to occur during heat shrinkage when used as a label. Therefore, the hot water heat shrinkage in the longitudinal direction at 80 ° C. is preferably −2% or more and 4% or less, more preferably −1% or more and 3% or less, and more preferably 0% or more and 2% or less. Note that the measurement temperature of 80 ° C. is adopted as the process for attaching the label to the container, for example, the temperature corresponding to the actual label temperature when passing through the shrink tunnel by steam. A temperature of 80 ° C. is adopted in order to confirm that the above-mentioned problems are unlikely to occur.

  In addition, the white heat-shrinkable polyester film of the present invention is a film calculated from the length before and after shrinkage by the above formula (1) when treated for 10 seconds in 95 ° C. warm water under no load. The heat shrinkage in the width direction (that is, the hot water heat shrinkage at 95 ° C.) is preferably 50% or more and 80% or less.

  If the hot water thermal contraction rate in the width direction at 95 ° C. is less than 50%, the shrinkage amount is small, so that wrinkles and tarmi occur on the label after thermal contraction, which is not preferable. However, if the hot water thermal contraction rate in the width direction at 95 ° C. exceeds 80%, it is not preferable because when used as a label, the shrinkage tends to occur during thermal contraction, or so-called “jumping” occurs. Therefore, the hot water heat shrinkage in the width direction at 95 ° C. is preferably 50% or more and 80% or less, more preferably 52% or more and 78% or less, and more preferably 55% or more and 75% or less. Note that the measurement temperature of 95 ° C is adopted because the shrinkage potential in the width direction, which is the main shrinkage direction in which the film can be obtained at maximum, is a major concern of customers, and 95 ° C close to the boiling water temperature to represent it. Is adopted.

  The white heat-shrinkable polyester film of the present invention has a right-angled tear strength per unit thickness of 200 N / mm or more and 300 N / mm or less after shrinking 10% in the width direction in warm water at 80 ° C. Is preferred.

[Measurement method of right-angle tear strength]
The film is shrunk 10% in the width direction in hot water adjusted to 80 ° C., and then sampled as a test piece of a predetermined size according to JIS-K-7128. Thereafter, both ends of the test piece are gripped with a universal tensile tester, and the strength at the time of tensile fracture in the longitudinal direction of the film is measured under the condition of a tensile speed of 200 mm / min. Then, the right angle tear strength per unit thickness is calculated using the following formula (2).
Right angle tear strength = strength at tensile failure ÷ thickness ・ ・ ・ Equation (2)

  When the right-angled tear strength after shrinking 10% in the width direction in warm water at 80 ° C. is less than 200 N / mm, when used as a label, it may be easily broken by an impact such as dropping during transportation. On the other hand, if the right-angled tear strength exceeds 300 N / mm, the cut property (easy to tear) at the initial stage of tearing the label becomes unfavorable. In addition, the lower limit of the right-angled tear strength is more preferably 210 N / mm or more. Further, the upper limit value of the right-angled tear strength is more preferably 290 N / mm or less, and more preferably 280 N / mm or less.

  In the white heat-shrinkable polyester film of the present invention, the solvent adhesive strength is preferably 2 N / 15 mm width or more. If the solvent adhesive strength is less than 2 N / 15 mm width, it is not preferable because the label is easily peeled off after the heat shrinkage. The solvent adhesive strength is more preferably 3N / 15 mm width or more, and particularly preferably 4N / 15 mm width or more. Although the solvent adhesive strength is preferably high, the solvent adhesive strength is considered to be about 10 (N / 15 mm) at present as the upper limit in view of the performance of the film forming apparatus. Also, if the solvent adhesive strength is too high, when two films are solvent-bonded to form a label, a situation where the film is unnecessarily bonded to the film is likely to occur, and the productivity of the label may be reduced. Therefore, it may be 8.5 (N / 15 mm) or less, and even if it is 7 (N / 15 mm) or less, it does not matter at all.

  The thickness variation in the longitudinal direction (thickness variation when the measurement length is 10 m) is preferably 18% or less. When the thickness unevenness in the longitudinal direction is more than 18%, it is not preferable because printing unevenness is likely to occur during printing at the time of label production or shrinkage unevenness after heat shrinkage is likely to occur. The thickness variation in the longitudinal direction is more preferably 16% or less, and particularly preferably 14% or less. Although the thickness unevenness in the longitudinal direction is preferably as small as possible, the lower limit of the thickness unevenness is considered to be 5% or more in view of the performance of the film forming apparatus and ease of production, but the most preferable value is close to 0%. Yes 1% is considered to be the limit in terms of the performance of film forming equipment.

  In the white heat-shrinkable polyester film of the present invention, the thickness variation in the width direction (thickness variation when the measurement length is 1 m) is preferably 18% or less. If the thickness unevenness in the width direction is more than 18%, it is not preferable because printing spots are likely to occur during printing at the time of label production or shrinkage spots after heat shrinkage are likely to occur. The thickness variation in the width direction is more preferably 16% or less, and particularly preferably 14% or less. Although the thickness variation in the width direction is preferably as small as possible, the lower limit of the thickness variation is considered to be 4% or more in view of the performance of the film forming apparatus and ease of production, but the most preferable value is close to 0%. There is a limit of 1% on the performance of the film forming apparatus.

  The thickness of the white heat-shrinkable polyester film of the present invention is not particularly limited, but is preferably 20 μm or more and 80 μm or less, and more preferably 30 μm or more and 70 μm or less as the heat-shrinkable film for labels. In addition, when the white heat-shrinkable polyester film of the present invention has a laminated structure, the thickness of each layer is not particularly limited, but is preferably 2 μm or more.

In the present invention, the apparent density of the film is preferably 1.2 g / cm ³ or less, more preferably 1.18 g / cm ³ or less, and still more preferably 1.16 g / cm ³ or less. The fact that the apparent density is small and light is a great advantage in mass production, and the white heat-shrinkable polyester film of the present invention has a cavity inside, so that preferable light weight can be realized. In particular, by adopting the longitudinal-transverse stretching method described later, a larger area stretching ratio can be employed as compared with a conventional uniaxially stretched film having a cavity, and a smaller apparent density can be obtained. However, if the apparent density is too small, the strength of the film itself is impaired. Therefore, the apparent density is preferably 0.6 g / cm ³ or more, more preferably 0.7 g / cm ³ or more. .

  The molecular orientation ratio (MOR) in the present invention is preferably 3.5 or more and 4.1 or less. When the molecular orientation ratio is larger than 4.1, the molecular orientation in the longitudinal direction is low, and it is difficult to satisfy the right-angled tear strength in the longitudinal direction of the film. The preferred molecular orientation ratio is 4.0 or less, more preferably 3.9 or less. The molecular orientation ratio is preferably closer to 1, but it may be 3.5 or more in the present invention.

[Measurement method of molecular orientation ratio]
A sample of the film in the longitudinal direction × width direction = 140 mm × 100 mm was taken. And about the sample, molecular orientation ratio (MOR) was measured using the molecular orientation angle measuring apparatus (MOA-6004) by Oji Scientific Instruments.

  In order to satisfy the above characteristics, the film of the present invention may be composed of a single layer, but the layer structure is preferably A / B, B / A / B, or B / A / C. The thickness ratio of the A layer and the B layer is preferably A / B = 2/1 or more, more preferably 4/1 or more, and further preferably 6/1 or more. If it is less than 1/1, it is difficult to achieve both the aesthetics of printability and the reduction in apparent density. B / A / B is preferable for suppressing undesirable curling after the shrinkage treatment.

When the C layer is provided, the content of the cavities is arbitrary, but it is possible to add particles for controlling slippage between the bottle and the film during shrinkage.
The film of the present invention has a cushion rate of 10% or more, preferably 20% or more. If the cushion rate is low, the effect of preventing the bottle or bottle from being damaged is lowered.

  In the present invention, the total light transmittance is 40% or less, preferably 35% or less, more preferably 30% or less, and still more preferably 20% or less. If it exceeds 40%, the contents may be seen through or the printed matter may be difficult to see, which may be inferior in appearance. In the present invention, the whiteness is 70 or more, preferably 75 or more, more preferably 80 or more. If it is less than 70, the contents may be seen through or the printed matter may be difficult to see, and the appearance may be inferior.

  The film obtained by this invention can be made into a tube shape, and a film edge part can be joined. In that case, 1,3-dioxolane or a mixed solution with an organic solvent compatible with 1,3-dioxolane or a solvent or a swelling agent having a solubility parameter in the range of 8.0 to 13.8 is applied. It is preferable to bond by drying at a temperature of 70 ° C. or lower to obtain a tubular body before drying. Examples of the solubility parameter include those described in a solvent handbook (edited by the Japan Adhesive Association, published by Nikkan Kogyo Shimbun). The joint portion in the tube may have a width as narrow as possible from 50 mm or more and, of course, is appropriately determined according to the size of the container. A width of 5 mm is standard. Further, the joining portion may be joined in a single line shape, or may be formed by forming a plurality of linear joints over two or more. Since these joints do not damage the film base material, they retain the properties of the polyester polymer as they are and have protective properties such as impact resistance and bottle breakage resistance. It is good without a decrease in the degree of orientation due to shrinkage and no embrittlement phenomenon due to the subsequent heat treatment.

  The attachments using this tube include containers, bottles (including plastic bottles), and can sticks (pipes, sticks, wood, various sticks), preferably attached to bottles mainly composed of polyethylene terephthalate. Thus, recovery is facilitated, and even if a trace amount is mixed with the bottle raw material when the polyethylene terephthalate bottle is reused, it is effective because it is difficult to color.

  Although the manufacturing method of the white heat-shrinkable polyester film of this invention is not specifically limited, an example is given and demonstrated. The white heat-shrinkable polyester film of the present invention is a polyester containing ethylene terephthalate as a main component and containing at least 13 mol% of one or more monomer components that can be amorphous components in all polyester resin components. It can be obtained by melt-extruding the system raw material with an extruder to form an unstretched film, biaxially stretching the unstretched film by a predetermined method shown below, and heat-treating it. A plurality of resin composition raw materials can be coextruded in order to obtain a laminated unstretched film as necessary.

  When the raw material resin is melt-extruded, the polyester-based raw material is preferably dried using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer. After the polyester raw material is dried in such a manner, it is melted at a temperature of 200 to 300 ° C. and extruded into a film using an extruder. For this extrusion, any existing method such as a T-die method or a tubular method can be employed.

  And an unstretched film can be obtained by rapidly cooling the sheet-like molten resin after extrusion. In addition, as a method of rapidly cooling the molten resin, a method of obtaining a substantially unoriented resin sheet by casting the molten resin on a rotating drum from a die and rapidly solidifying it can be suitably employed.

  Furthermore, as will be described later, the obtained unstretched film is stretched in the longitudinal direction under predetermined conditions, and after the longitudinally stretched film is rapidly cooled, it is once heat-treated, and the heat-treated film is subjected to predetermined conditions. It is preferable to obtain the white heat-shrinkable polyester film of the present invention by stretching in the width direction under a predetermined condition and then heat-treating again after cooling. Hereinafter, a preferable film forming method for obtaining the white heat-shrinkable polyester film of the present invention will be described in detail in consideration of a difference from a conventional heat-shrinkable polyester film forming method.

As described above, conventionally, a heat-shrinkable polyester film has been produced by stretching only in a direction in which an unstretched film is desired to be shrunk (that is, the main shrinkage direction, usually the width direction). As a result of studying the conventional production method by the present inventors, it has been found that there are the following problems in the production of a conventional heat-shrinkable polyester film.
If the film is simply stretched in the width direction, as described above, the right-angled tear strength in the longitudinal direction is increased, and the perforation-opening property in the case of a label is deteriorated. In addition, it is difficult to increase the line speed of the film forming apparatus.
-If the method of extending | stretching to a longitudinal direction is employ | adopted after extending | stretching to the width direction, the contraction force of the width direction cannot fully be expressed, no matter what extending | stretching conditions are employ | adopted. In addition, the contraction force in the longitudinal direction is expressed at the same time, and when finished as a label, the finish after the shrinkage attachment becomes worse.
・ If a method of stretching in the width direction is used after stretching in the length direction, the contraction force in the width direction can be expressed, but the contraction force in the length direction is expressed at the same time. The finish of becomes worse.

Furthermore, based on the problems in the production of the above conventional heat-shrinkable polyester film, the present inventors further consider obtaining a white heat-shrinkable polyester film having good perforation opening and high productivity. As a result, the following is currently estimated and considered.
・ In order to improve the perforation of the perforated label, it is considered necessary to leave some molecules oriented in the longitudinal direction. In order to make it good, it is indispensable not to develop a contraction force in the longitudinal direction, and for that purpose, it is considered necessary to eliminate the tension state of molecules oriented in the longitudinal direction. When the portion having the above is provided, it works more advantageously with respect to the perforation opening, and unlike the uniaxially stretched film having a simple cavity, the area stretch ratio can be increased by the special longitudinal-lateral stretch method described below, and its effect That is expected to expand

From the above findings, the present inventors need to have “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” in the film in order to satisfy good perforation opening property and shrinkage finishing property at the same time. I came to think that there is. Then, a trial and error was carried out by paying attention to what kind of stretching would allow “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” to exist in the film. As a result, at the time of film production by the so-called longitudinal-lateral stretching method, which is stretched in the longitudinal direction after being stretched in the longitudinal direction, “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” by taking the following means: It is possible to obtain a white heat-shrinkable polyester film that simultaneously satisfies good perforation opening properties and shrink finish properties, and has devised the present invention.
(1) Control of longitudinal stretching conditions (2) Intermediate heat treatment after longitudinal stretching (3) Forced cooling of film after intermediate heat treatment (4) Control of transverse stretching conditions Hereinafter, each of the above-mentioned means will be sequentially described.

(1) Control of longitudinal stretching conditions In the production of a film by the longitudinal-lateral stretching method of the present invention, in order to obtain the film roll of the present invention, substantially 1 in the longitudinal direction at a temperature of 75 ° C. or more and 100 ° C. or less. It is preferable to perform longitudinal stretching at a relatively low magnification of 1.1 times or more and 1.8 times or less as only the stepwise longitudinal stretching step.

  In addition, by longitudinally stretching at a low magnification as described above, it becomes possible to control the degree of orientation of the film in the longitudinal direction and width direction during the final heat treatment, the degree of molecular tension, and the intermediate heat set, which will be described later. As a result, it is possible to improve the perforation-opening property of the final film by acting that the film is provided with a cavity. If the draw ratio of the longitudinal stretching is less than 1.1 times, the merit of substantially longitudinal stretching cannot be utilized, the right-angled tear strength in the longitudinal direction increases, and the perforation opening property when used as a label may be impaired. So it is not so preferable. In addition, the number of initial breaks tends to increase, and it is difficult to increase the line speed of the film forming apparatus. When the draw ratio of the longitudinal drawing exceeds 1.8 times, preferable data can be obtained for the right-angled tear strength and the initial number of breaks, but the shrinkage in the longitudinal direction tends to increase, which is not so preferable.

  Further, although the thickness unevenness in the longitudinal direction increases as the stretching ratio in the longitudinal direction increases, according to the study by the present inventors, it tends to become maximum at about 2.5 times and then decrease. That is, the effect of reducing the thickness unevenness in the vertical direction can be obtained by setting the stretching ratio of the longitudinal stretching to a relatively low ratio of 1.1 to 1.8.

(2) Intermediate heat treatment after longitudinal stretching As described above, in order to make “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” exist in the film, it is preferable to thermally relax the molecules oriented in the longitudinal direction. However, conventionally, in the biaxial stretching of the film, if the film is subjected to a high temperature heat treatment between the first axis stretching and the second axis stretching, the film after the heat treatment is crystallized, so that the film is further stretched. It was technical common sense in the industry that it was not possible. However, as a result of trial and error by the inventors, in the longitudinal-lateral stretching method, longitudinal stretching is performed under certain conditions, and intermediate heat setting is performed under predetermined conditions according to the state of the film after the longitudinal stretching, Furthermore, by performing transverse stretching under predetermined conditions according to the state of the film after the intermediate heat setting, “molecules that are oriented in the longitudinal direction and do not contribute to contraction force” without causing breakage during transverse stretching. The surprising fact that it can be present in the film has been found.

  That is, in the production of a film by the longitudinal-lateral stretching method of the present invention, after longitudinally stretching an unstretched film, a temperature of 110 ° C. or higher and 150 ° C. or lower in a state where both ends in the width direction are held by clips in the tenter. It is preferable to perform heat treatment (hereinafter referred to as intermediate heat treatment) over a period of 5 seconds to 30 seconds. By performing such an intermediate heat treatment, “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” can be present in the film. As a result, when the label is used, the perforation is good and the shrinkage spots are not generated. A film that does not occur can be obtained. In any longitudinal stretching, “molecules that are oriented in the longitudinal direction and do not contribute to the shrinkage force” can not be present in the film. By carrying out the stretching, it is possible to allow “molecules that are oriented in the longitudinal direction and do not contribute to the shrinkage force” to be present in the film for the first time after the intermediate heat treatment. Then, by performing forced cooling and transverse stretching, which will be described later, the molecules are oriented in the width direction while maintaining the “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” formed in the film. It is possible to express the contraction force of

  Note that the temperature of the intermediate heat treatment is preferably 110 ° C. or higher and 150 ° C. or lower. If the lower limit of the temperature of the intermediate heat treatment is less than 110 ° C., the shrinkage force in the longitudinal direction of the film remains, and the longitudinal shrinkage rate of the film after stretching in the transverse direction is not preferable. Moreover, when the upper limit of the temperature of the intermediate heat treatment is higher than 150 ° C., the film surface layer is rough, which is not preferable. Therefore, the preferable temperature of the intermediate heat treatment is 110 ° C. or higher and 150 ° C. or lower, more preferably 115 ° C. or higher and 145 ° C. or lower, and further preferably 120 ° C. or higher and 140 ° C. or lower. Further, it is preferable to consider the temperature of the intermediate heat treatment somewhat depending on the raw material composition and the stretching ratio in the longitudinal direction.

  The intermediate heat treatment time is preferably 5 seconds or more and 30 seconds or less. If the intermediate heat treatment is longer than 30 seconds, the heat treatment can be performed at a low temperature, but the productivity is deteriorated. On the other hand, if it is shorter than 5 seconds, the shrinkage force in the longitudinal direction of the film remains, and the shrinkage ratio in the longitudinal direction of the film after stretching in the transverse direction becomes unfavorable. Therefore, the preferred intermediate heat treatment time is 5 seconds or more and 30 seconds or less, more preferably 7 seconds or more and 28 seconds or less, and further preferably 9 seconds or more and 26 seconds or less. Further, it is preferable to consider the temperature of the intermediate heat treatment somewhat depending on the raw material composition and the stretching ratio in the longitudinal direction.

  Moreover, when performing the intermediate heat treatment as described above, it is preferable to adjust the conditions for the intermediate heat treatment so that the heat shrinkage stress in the longitudinal direction of the film after the intermediate heat treatment is 0.5 MPa or less. By performing an intermediate heat treatment under such predetermined conditions, it becomes possible to control the degree of orientation in the longitudinal direction and width direction of the film and the degree of molecular tension during transverse stretching and final heat treatment, and thus the final film. It becomes possible to make the perforation openability of this.

(3) Forced cooling of film after intermediate heat treatment In the production of the film by the longitudinal-lateral stretching method of the present invention, the film subjected to the intermediate heat treatment as described above is not stretched as it is, but the temperature of the film is 70 ° C. or higher. It is preferable to quench rapidly so that it becomes below ℃. By applying such a rapid cooling treatment, a film having good perforation opening properties when used as a label can be obtained, which is preferable. In addition, the minimum of the temperature of the film after quenching is more preferable in it being 72 degreeC or more, and it is still more preferable in it being 74 degreeC or more. Moreover, the upper limit of the temperature of the film after quenching is more preferably 85 ° C. or less, and further preferably 80 ° C. or less.

  When the film is rapidly cooled as described above, if the temperature of the film after the rapid cooling remains above 90 ° C., the shrinkage rate in the width direction of the film becomes low, and the shrinkability when used as a label is insufficient. However, by controlling so that the temperature of the cooled film is 90 ° C. or less, it is possible to maintain a high shrinkage rate in the width direction of the film.

  Furthermore, when the film is rapidly cooled, if the temperature of the film after quenching remains above 90 ° C., the stress of transverse stretching performed after cooling tends to be small, and the thickness unevenness tends to be large. By performing rapid cooling so that the temperature of the film after cooling is 90 ° C. or lower, it is possible to increase the stress of transverse stretching performed after cooling and reduce the thickness unevenness in the width direction.

  In addition, when the film is rapidly cooled, if the temperature of the film after quenching remains below 70 ° C., the stretching stress of the film increases, and the film tends to break, which is not preferable. Therefore, the film temperature after the cooling step is preferably 70 ° C. or higher and 90 ° C. or lower, more preferably 72 ° C. or higher and 85 ° C. or lower, and further preferably 74 ° C. or higher and 80 ° C. or lower.

(4) Control of transverse stretching conditions In the production of a film by the longitudinal-lateral stretching method of the present invention, it is preferable to transversely stretch the film after longitudinal stretching, intermediate heat setting, and rapid cooling under predetermined conditions. That is, the transverse stretching can be performed at a temperature of 65 ° C. or more and 90 ° C. or less and a magnification of 3.5 times or more and 5.0 times or less in a state where both ends in the width direction are held by clips in the tenter. preferable. By performing transverse stretching under such predetermined conditions, the molecules are oriented in the width direction while maintaining the “molecules that are oriented in the longitudinal direction but do not contribute to the shrinkage force” formed by longitudinal stretching and intermediate heat setting. The shrinkage force in the direction can be expressed, and a film having a good perforation opening property when used as a label can be obtained. Further, by adopting the longitudinal-transverse stretching method, it is possible to give a larger area stretch ratio than a heat-shrinkable film having a simple uniaxially stretched cavity, and to further improve perforation opening. This improvement in perforation opening shows a good correspondence with a decrease in right-angled tear strength. The lower limit of the transverse stretching temperature is more preferably 67 ° C. or more, and further preferably 70 ° C. or more. Moreover, the upper limit of the temperature of transverse stretching is more preferably 85 ° C. or less, and more preferably 80 ° C. or less. On the other hand, the lower limit of the transverse stretching ratio is preferably 3.6 times or more, and more preferably 3.7 times or more. Further, the upper limit of the transverse stretching ratio is preferably 4.9 times or less, and more preferably 4.8 times or less. Adopting the longitudinal-transverse stretching method and making the area stretch ratio larger than that of the conventional uniaxial stretching method is preferable from the viewpoint of obtaining a smaller apparent density.

  Further, when the stretching temperature exceeds 90 ° C., the shrinkage rate in the longitudinal direction increases and the shrinkage rate in the width direction tends to decrease. However, by controlling the stretching temperature to 90 ° C. or less, the shrinkage rate in the longitudinal direction is reduced. It is preferable because it is easy to keep the shrinkage rate in the width direction high while keeping it low.

  Moreover, when the stretching temperature exceeds 90 ° C., the thickness variation in the width direction tends to increase, but by controlling the stretching temperature to 90 ° C. or less, the thickness variation in the width direction can be reduced.

  On the other hand, when the stretching temperature is lower than 65 ° C, the orientation in the width direction becomes too high and it is easy to break during transverse stretching. However, by controlling the stretching temperature to 65 ° C or more, reduction of breaking during transverse stretching is achieved. Is possible.

[Effects of manufacturing process conditions on film properties]
In producing the white heat-shrinkable polyester film of the present invention, it is very efficient by appropriately setting the conditions of the longitudinal stretching process, the intermediate heat treatment process, the forced cooling process, and the transverse stretching process as described above. In addition, it is considered that the film characteristics can be improved. In addition, among the characteristics of the film, important characteristics such as perpendicular tear strength in the longitudinal direction, thickness unevenness in the width direction, thickness unevenness in the longitudinal direction, and solvent adhesion strength are numerical values due to the combined action of a plurality of specific processes. May vary.

  That is, in the white heat-shrinkable polyester film of the present invention, it is preferable to adjust the right-angled tear strength in the longitudinal direction to 200 N / mm or more and 300 N / mm or less, more preferably, the right-angled tear strength in the longitudinal direction is 290 N / mm or less. More preferably, it is adjusted to 280 N / mm or less. For the right-angled tear strength in the longitudinal direction, it is particularly important to adjust the conditions of the longitudinal stretching process and the intermediate heat treatment process.

  Further, the white heat-shrinkable polyester film of the present invention is preferably adjusted to have a thickness variation in the width direction of 1% or more and 18% or less. The thickness variation in the width direction includes a longitudinal stretching step, an intermediate heat treatment step, and It is important to adjust the process conditions of the three processes called the transverse stretching process.

  In addition, the white heat-shrinkable polyester film of the present invention is preferably adjusted to have a thickness variation in the longitudinal direction of 1% or more and 18% or less. However, the thickness variation in the width direction includes the longitudinal stretching step and the intermediate heat treatment step. Adjustment of process conditions is important.

  The white heat-shrinkable polyester film of the present invention is preferably adjusted to have a solvent adhesive strength of 2 N / 15 mm or more and 10 N / 15 mm or less. A major factor in the solvent adhesive strength is the ratio of the amorphous raw material ratio on the film surface. When the amorphous raw material ratio is large, the solvent adhesive strength tends to increase. For example, in the examples described later, if the amorphous raw material ratio on the film surface is 40% by mass or more, the solvent adhesive strength is preferably 2N / 15 mm or more. However, if the amorphous raw material ratio becomes too large, the heat shrinkage characteristics may become too large, and therefore it is preferably 95% by mass or less. Generally, it can be said in terms of mol% of an amorphous monomer representing how much of one or more kinds of monomer components that can be an amorphous component in 100 mol% of a polyhydric alcohol component in a polyester resin on a film surface is included. For example, when it is 10 mol% or more, it is easy to make the solvent adhesive strength 2N / 15 mm or more, which is preferable. More preferably, it is 13 mol% or more of the film surface, and more preferably 20 mol% or more of the film surface, but if it is too large, the heat shrink property may become too large, so it may be 50 mol% or less, It is preferably 40 mol% or less, more preferably 30 mol% or less.

  The package of the present invention is formed by covering at least a part of the outer periphery with a label provided with a perforation based on the above white heat-shrinkable polyester film, and heat-shrinking the package. Examples of the object include plastic bottles for beverages, various bottles, cans, plastic containers such as confectionery and lunch boxes, and paper boxes (hereinafter collectively referred to as packaging objects). . In general, when a label based on a white heat-shrinkable polyester film is coated on these packaging objects by heat-shrinking, the label is heat-shrinked by about 2 to 15%. Adhere to. In addition, printing may be given to the label coat | covered with a packaging target object, and it does not need to be printed.

  The label can be made by applying an organic solvent slightly inside from the edge of one side of the rectangular film, and immediately rolling the film and bonding the edges together to form a label, or roll Apply the organic solvent slightly inside from the edge of one side of the film wound up in the shape of a film, immediately roll up the film, overlap the edges and adhere, cut the tube to make a label . As the organic solvent for adhesion, cyclic ethers such as 1,3-dioxolane or tetrahydrofuran are preferable. In addition, aromatic hydrocarbons such as benzene, toluene, xylene and trimethylbenzene, halogenated hydrocarbons such as methylene chloride and chloroform, phenols such as phenol, and mixtures thereof can be used.

  Next, the present invention will be specifically described by way of examples and comparative examples. However, the present invention is not limited to the modes of the examples, and may be appropriately selected without departing from the spirit of the present invention. It is possible to change.

The evaluation method used in the present invention is as follows.

[Thermal shrinkage (hot water thermal shrinkage)]
The film is cut into a 10 cm × 10 cm square, heat-shrinked by treatment in warm water at a predetermined temperature ± 0.5 ° C. for 10 seconds under no load condition, and then measured in the vertical and horizontal dimensions of the film. In accordance with the following formula (1), the thermal shrinkage rate was determined. The direction in which the heat shrinkage rate is large was taken as the main shrinkage direction.
Thermal shrinkage rate = {(length before shrinkage−length after shrinkage) / length before shrinkage} × 100 (%)
... Formula (1)

[Measurement method of right-angle tear strength]
The film is shrunk 10% in the width direction in hot water adjusted to 80 ° C., and then sampled as a test piece of a predetermined size according to JIS-K-7128. Thereafter, both ends of the test piece are gripped with a universal tensile tester, and the strength at the time of tensile fracture in the longitudinal direction of the film is measured under the condition of a tensile speed of 200 mm / min. Then, the right angle tear strength per unit thickness is calculated using the following formula (2).
Right angle tear strength = strength at tensile failure ÷ thickness ・ ・ ・ Equation (2)

[Whiteness]
The degree of whiteness was measured according to JIS-L1015-1981 method using Z-1001DP manufactured by Nippon Denshoku Industries Co., Ltd.

[Total light transmittance]
The total light transmittance was calculated | required by Nippon Denshoku Industries Co., Ltd. product NDH-1001DP.

[Thickness unevenness in the width direction]
The film was sampled into a wide band with a length of 40 mm and a width of 1.2 m, and was measured in the width direction of the film sample at a speed of 5 (m / min) using a continuous contact thickness gauge manufactured by Micron Measuring Instruments Co., Ltd. The thickness was continuously measured along (measurement length was 500 mm). The maximum thickness at the time of measurement was Tmax., The minimum thickness was Tmin., The average thickness was Tave., And the thickness unevenness in the longitudinal direction of the film was calculated from the following formula (3).
Thickness unevenness = {(Tmax.−Tmin.) / Tave.} × 100 (%) (3)

[Longitudinal thickness unevenness]
The film was sampled into a long roll of 12 m long × 40 mm wide, and along the longitudinal direction of the film sample at a speed of 5 (m / min) using a continuous contact thickness gauge manufactured by Micron Measuring Instruments Co., Ltd. The thickness was continuously measured (measurement length was 10 m). The maximum thickness at the time of measurement was Tmax., The minimum thickness was Tmin., The average thickness was Tave., And the thickness variation in the longitudinal direction of the film was calculated from the above equation (3).

[Solvent adhesive strength]
Sealing was performed by applying 1,3-dioxolane to the stretched film and bonding the two together. Thereafter, the seal portion is cut to a width of 15 mm in a direction orthogonal to the main shrinkage direction of the film (hereinafter referred to as the orthogonal direction), and set in a universal tension tester STM-50 manufactured by Baldwin Co., Ltd. A 180 ° peel test was performed at 200 mm / min. And the tensile strength at that time was made into solvent adhesive strength.

[Apparent density of film]
Four films were cut into 5.0 cm squares and used as samples. Four samples of this sample were overlapped, and the total thickness was measured at 10 points using a micrometer with four significant figures, and the average value of the total thickness was determined. The average value was divided by 4 and rounded to 3 significant figures to obtain an average thickness t (μm) per sheet. The mass w (g) of the four samples was measured using an automatic upper balance with four significant digits, and the apparent density was determined from the following equation (4). The apparent density was rounded to 3 significant figures.
Apparent density (g / cm ³ ) = w / (5.0 × 5.0 × t × 10 ⁻⁴ × 4)
= W × 100 / t Expression (4)

[Molecular orientation ratio]
A sample of the film in the longitudinal direction × width direction = 140 mm × 100 mm was taken. And about the sample, molecular orientation ratio (MOR) was measured using the molecular orientation angle measuring apparatus (MOA-6004) by Oji Scientific Instruments.

[Shrinkage distortion at the label]
A cylindrical label (a label with the main shrinkage direction of the heat-shrinkable film as the circumferential direction) was prepared by adhering both ends to the heat-shrinkable film with dioxolane. After that, using a Fuji Astec Inc steam tunnel (model: SH-1500-L), a 500 ml PET bottle with a transit time of 2.5 seconds and a zone temperature of 80 ° C. (body diameter 62 mm, minimum neck diameter 25 mm) The label was attached by heat shrinking. At the time of mounting, the neck portion was adjusted so that a portion with a diameter of 40 mm was one end of the label. As an evaluation of the finishing property after shrinkage, the strain in the 360 degree direction on the attached label was measured using a gauge, and the maximum value of the strain was obtained. At that time, the standard was as follows.
○: Maximum strain of less than 2 mm ×: Maximum strain of 2 mm or more

[Label adhesion]
The label was attached under the same conditions as those described above for measuring shrinkage finish. Then, when the attached label and the PET bottle were lightly twisted, it was evaluated as “◯” if the label did not move, or “x” if it slipped through or the label and the bottle were displaced.

[Perforation opening]
A label having a perforation in a direction perpendicular to the main shrinkage direction in advance was attached to a PET bottle under the same conditions as those for measuring the shrinkage finish. However, the perforations were formed by putting holes having a length of 1 mm at intervals of 1 mm, and two perforations were provided in the longitudinal direction (height direction) of the label over a width of 22 mm and a length of 120 mm. The bottle is then filled with 500 ml of water, refrigerated to 5 ° C., tearing the perforation of the bottle label immediately after removal from the refrigerator with the fingertips, tearing it cleanly along the perforation in the vertical direction, and removing the label from the bottle The number of pieces that could be removed was counted, and the perforation unsuccessful rate (%) was calculated by subtracting the number from 50 samples.

  Moreover, the polyester used for the Example and the comparative example is as follows.

Polyester 1: Polyester composed of 70 mol% ethylene glycol, 30 mol% neopentyl glycol and terephthalic acid (IV 0.72 dl / g)
Polyester 2: Polyethylene terephthalate (IV 0.75 dl / g)
Polyester 3: Polyester composed of 70 mol% ethylene glycol, 30 mol% 1,4-cyclohexanedimethanol and terephthalic acid (IV 0.75 dl / g)

[Example 1]
The above-mentioned polyester 1 and polyester 2 were mixed at a weight ratio of 90:10 to obtain a raw material for the B layer. The raw material of layer A is the same as described above. When mixing polyester 1 and polyester 2 at a weight ratio of 90:10, polystyrene resin (G797N made by Nippon Polystyrene) 10% by weight and titanium dioxide (TA-300 made by Fuji Titanium) 10% by weight Added and mixed. The raw materials of layer A and layer B are put into separate twin screw extruders, mixed, melted and joined together with a feed block, melted and extruded at 280 ° C from a T-die, and cooled to a surface temperature of 30 ° C. The film was wound around a rotating metal roll and rapidly cooled to obtain an unstretched film having a thickness of 240 μm and a B / A / B laminated structure (B / A / B = 60 μm / 120 μm / 60 μm).

  And the 240-micrometer-thick unstretched film obtained as mentioned above was guide | induced to the longitudinal stretch machine which has arrange | positioned several roll groups continuously, and was extended | stretched to the vertical direction using the rotational speed difference of a roll. That is, after pre-heating an unstretched film on a preheating roll until the film temperature reaches 85 ° C., between a low-speed rotating roll set to a surface temperature of 85 ° C. and a high-speed rotating roll set to a surface temperature of 30 ° C. Then, the film was longitudinally stretched 1.5 times using the difference in rotational speed.

  Thereafter, the unstretched film was heat-set for 10 seconds at 130 ° C. and a wind speed of 18 m / s with the clips held at both ends in the width direction in the tenter, and the film was guided to the cooling zone to The film was actively cooled by blowing low-temperature air until the temperature reached 80 ° C., and the cooled film was guided to the transverse stretching zone, and stretched 4.0 times in the width direction (lateral direction) at 75 ° C.

  After that, after the laterally stretched film is guided to the final heat treatment zone in the tenter in a state where both ends in the width direction are held by the clips, in the final heat treatment zone, the film is heat treated at a temperature of 85 ° C. for 10 seconds. Cooling, cutting and removing both edges, and winding in a roll with a width of 400 mm, a biaxially stretched film of about 45 μm (skin layer / core layer / skin layer thickness: 10 μm / 25 μm / 10 μm) is predetermined. Was continuously produced over the entire length. And the characteristic of the obtained film was evaluated by the above-mentioned method. The evaluation results are shown in Table 3. The obtained biaxially stretched film became a film having preferable heat shrinkage characteristics, preferable right-angled tear strength, light weight, and high whiteness, which was very preferable overall.

[Example 2]
In Example 1, heat shrinkability was achieved by the same method as in Example 1 except that the crystalline resin (FO-50F ground polymer) was changed to 10% by weight instead of 10% by weight of the polystyrene resin added to the raw material of the A layer. Films were produced continuously. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3.
As in Example 1, a good film was obtained.

[Example 3]
In Example 1, the heat-shrinkable film was continuously formed in the same manner as in Example 1 except that polyester 3 and polyester 2 were mixed at a weight ratio of 90:10 with the raw material resins of layer A and layer B to be fed into the extruder. Manufactured. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3. As in Example 1, a good film was obtained.

[Example 4]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the thickness of the unstretched film was 180 μm, the stretch ratio in the longitudinal stretching step was 1.1 times, and the temperature in the intermediate heat treatment step was changed to 125 ° C. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3. The right-angled tear strength was slightly high and the perforation failure rate was slightly high, but it was favorable overall.

[Example 5]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the thickness of the unstretched film was 272 μm, the stretch ratio in the longitudinal stretching step was 1.7 times, and the temperature in the intermediate heat treatment step was changed to 140 ° C. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3. The right-angled tear strength was small, and it was extremely preferable overall because of excellent perforation openability.

[Example 6]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the film surface temperature was cooled only to 90 ° C. in the forced cooling step. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3. Although the thickness unevenness in the width direction was slightly large, it was preferable overall.

[Example 7]
The raw material of the B layer The heat-shrinkable film was continuously formed in the same manner as in Example 1 except that the weight ratio of polyester 1 and polyester 2 was changed to 90:10 and the weight ratio of polyester 1 and polyester 2 was changed to 30:70. Manufactured. And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3. Although the solvent adhesive strength was low, it was preferable overall.

[Example 8]
The film was formed under the same conditions as in Example 1 except that the amount of addition of titanium dioxide (A-300 Fuji Titanium) in layer A was changed to 14% by weight with respect to Example 1. An axially stretched film was continuously produced over a predetermined length. And the characteristic of the obtained film was evaluated by the above-mentioned method. The evaluation results are shown in Table 3. The whiteness was high and it was preferable overall.

[Comparative Example 1]
In the same manner as in Example 1, the thickness of the unstretched film was adjusted to 170 μm, and the transverse uniaxial stretching was performed by eliminating the longitudinal stretching step, the intermediate heat treatment step, and the forced cooling step to obtain a lateral uniaxially stretched film having a thickness of 45 μm. . And the characteristic of the obtained film was evaluated by the same method as Example 1. The evaluation results are shown in Table 3. Since the transverse uniaxially stretched film had a larger MOR value than the biaxially stretched film of Example 1, it was not preferable because it had a high right-angle tear strength and a large perforation unsealability rate.

[Comparative Example 2]
A biaxially stretched film was obtained in the same manner as in Example 1 except that the temperature of the intermediate heat treatment was changed to 100 ° C. Compared with the biaxially stretched film of Example 1, the biaxially stretched film had a large hot water shrinkage ratio in the longitudinal direction, and the shrinkage distortion at the label was noticeably undesirable.

  Since the white heat-shrinkable polyester film of the present invention has excellent properties such as perforation opening, light-cutting properties, and lightness, it can be suitably used for labeling applications such as bottles, A packaging body such as a bottle obtained by using the film as a label has a beautiful appearance.

F ・ ・ Film

Claims (9)

The following (1) to (4) comprising a polyester-based resin comprising ethylene terephthalate as a main constituent and containing at least 13 mol% of at least one monomer component that can be an amorphous component in all polyester resin components. A white heat-shrinkable polyester film, which is a production method for continuously producing a white heat-shrinkable polyester film that satisfies the above requirements, comprising the following steps (a) to (e): Manufacturing method.
(1) The hot water thermal shrinkage in the longitudinal direction when treated for 10 seconds in warm water at 80 ° C. is −2% or more and 4% or less ( 2 ) for 10 seconds in warm water at 95 ° C. The hot water thermal contraction rate in the width direction when treated is 50% or more and 80% or less.
(3) The perpendicular tear strength in the longitudinal direction per unit thickness after shrinking 10% in the width direction in warm water at 80 ° C. is 200 N / mm or more and 300 N / mm or less ( 4 ) It has a B layer with fewer cavities than the A layer on at least one side of the A layer to be contained, and the whiteness is 70 or more. (A) An unstretched film is 1 in the longitudinal direction at a temperature of 75 ° C. or more and 100 ° C. or less. (B) Longitudinal stretching step of stretching at a magnification of 1 to 1.8 times (b) A temperature of 110 ° C. or more and 150 ° C. or less with the film after longitudinal stretching held in the tenter by the clips at both ends in the width direction Intermediate heat treatment step (c) in which the film is subjected to heat treatment over a period of 5 seconds to 30 seconds at a positive cooling step in which the film after the intermediate heat treatment is actively cooled until the surface temperature becomes 70 ° C. or higher and 90 ° C. or lower ( d) After active cooling A transverse stretching step in which the film is stretched at a temperature of 65 ° C. or more and 90 ° C. or less at a magnification of 3.5 times or more and 5.0 times or less in the width direction. A final heat treatment step in which heat treatment is performed at a temperature of 80 ° C. or higher and 100 ° C. or lower for a time of 5 seconds or longer and 30 seconds or shorter in a state where the edge is held by a clip. 2. The method for producing a white heat-shrinkable polyester film according to claim 1, wherein the solvent adhesive strength is 2 N / 15 mm width or more and 10 N / 15 mm width or less. The method for producing a white heat-shrinkable polyester film according to claim 1 or 2 , wherein the thickness unevenness in the longitudinal direction is 1% or more and 18% or less. The method for producing a white heat-shrinkable polyester film according to any one of claims 1 to 3 , wherein thickness unevenness in the width direction is 1% or more and 18% or less. The method for producing a white heat-shrinkable polyester film according to any one of claims 1 to 4 , wherein the thickness is 20 µm or more and 80 µm or less. 2. The main component of a monomer that can be an amorphous component in all the polyester resin components is one or more of neopentyl glycol, 1,4-cyclohexanedimethanol, and isophthalic acid. method for producing a white heat-shrinkable polyester film according to any one of 1 to 5. An apparent density is 1.2 g / cm < ³ > or less, The manufacturing method of the white heat-shrinkable polyester film in any one of Claims 1-6 characterized by the above-mentioned. A white heat-shrinkable polyester film produced by the method for producing a white heat-shrinkable polyester film according to any one of claims 1 to 7 . A package comprising the white heat-shrinkable polyester-based film according to claim 8 as a base material, and a heat-shrinkable covering at least part of the outer periphery with a perforation or a label provided with a pair of notches. body.