JP2011122171A - Heat shrinkable polyester film and method of producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat shrinkable polyester film and a method of producing the same exhibiting good shrink finish property, a good shrink coated container reinforcing function, and good blocking resistance even in use for a full label, and having excellent film forming property and workability. <P>SOLUTION: The heat shrinkable polyester film satisfies following specifications (A)-(F): (A) a thermal shrinkage rate in hot water of 70°C is 10-50% in the maximum shrinkage direction; (B) a thermal shrinkage rate in hot water of 85°C is 75% or more in the maximum shrinkage direction and is 10% or less in the direction orthogonal to the maximum shrinkage direction; (C) a thermal shrinkage difference Δ (%) shown by an expression: Δ=X<SB>0</SB>-X<SB>10</SB>is 10-20% when a thermal shrinkage rate in hot water of 95°C is represented by X<SB>0</SB>(%) and a thermal shrinkage rate of a 10%-shrunk film in hot water of 95°C is represented by X<SB>10</SB>(%); (D) three-dimensional face coarseness SΔa is 0.008-0.04; (E) three-dimensional face coarseness SRz is 0.6-1.5 μm; and (F) a maximum thermal shrinkage stress value measured under a predetermined condition is 10 MPa or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable polyester film suitable for label use, and a heat-shrinkable label using the film.

  The heat-shrinkable plastic film is widely used for applications such as shrink wrapping and shrinkage labels by utilizing the property of shrinking by heating. Among them, stretched films such as polyvinyl chloride films, polystyrene films, and polyester films are used for labels, cap seals, and integrated packaging in various containers such as polyethylene terephthalate (PET) containers, polyethylene containers, and glass containers. (For example, Patent Document 1).

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

  On the other hand, the polystyrene film can be evaluated for its good finished appearance after shrinkage, but it has poor solvent resistance, and therefore, an ink having a special composition must be used for printing. In addition, polystyrene resins need to be incinerated at a high temperature and have a problem that a large amount of black smoke and off-flavor are generated during incineration.

  Polyester films without these problems are highly expected as shrink labels to replace polyvinyl chloride films and polystyrene films, and the amount of use tends to increase as the amount of PET container used increases.

  These heat-shrinkable films are once wound up into a roll after production, and are sent to a printing process of various designs in the form of this film roll. After the printing is finished, they are used for final products as necessary. It is slitted to fit the size of the label, etc., and the left and right ends of the film are overlapped and sealed by means such as solvent bonding to form a tubular body, and the tubular body is cut into a label, bag It is processed into the form. And inside a shrink tunnel (steam tunnel) of a type that attaches a label or bag to a container and blows steam to heat shrink, or a shrink tunnel (hot wind tunnel) of hot shrink that blows hot air Is placed on a belt conveyor and the like, and is heat-shrinked so as to be in close contact with the container.

  By the way, from the viewpoint of recycling, as the use of colored PET bottles is restricted, the demand for covering most of the bottle side surface with a label made of a heat-shrinkable polyester film instead of coloring the bottle itself (so-called full label) Applications) are also increasing. However, since the PET bottle has various side shapes and the outer diameter changes at an arbitrary height position, the required degree of shrinkage varies depending on the height position of the bottle even with one label covering one bottle. . For this reason, there is a need for a heat-shrinkable polyester-based film that has better shrinkage properties than conventional products and can exhibit excellent shrinkage finish even when used for coating bottles with complex side shapes.

  Furthermore, for example, in PET bottles for beverages, label mounting and shrinkage are often performed in a beverage filling line in order to improve productivity. Since such a filling line is high-speed, label mounting / shrinking is also fast, and shrinking tends to be performed in a short time. Therefore, the heat-shrinkable polyester film is also required to have physical properties that can withstand high-speed mounting and shrinkage performance that provides a high shrinkage rate in a short time.

  In addition, recently, labels used for various containers such as PET bottles are expected to have an effect of reinforcing these containers. However, labels obtained from conventional heat-shrinkable polyester films have not been able to satisfy such a reinforcing action.

  In addition, containers whose labels are covered and shrunk are often packed (packed, etc.) at a high temperature. However, particularly in the case of a full label, the labels are adhered (blocked) to each other between the packed containers. There was also.

  In addition, it is desired that the heat-shrinkable film is a film roll in which a long film is run at a high speed or is wound at a high speed from the viewpoint of improving productivity in the film forming process or the post-processing process. In order to cope with this, it is required that the slipperiness is good to some extent. When the slipperiness of the film is insufficient, a handling failure occurs at the time of running at high speed or winding. Specifically, for example, where the film is in contact with the guide roll when the film is running, the tension increases, scratches occur on the film surface, or wrinkles or acne defects (film In some cases, minute protrusions (which are formed without the air caught between them being removed) may occur.

JP-A-7-138388 (paragraph numbers 0001 to 0005)

  The present invention has been made in view of the above circumstances, and its purpose is to exhibit a good shrink finish even when used for a full label, as well as a function capable of reinforcing a shrink-coated container and a good blocking resistance. Furthermore, it is providing the heat-shrinkable polyester-type film excellent in film forming property and workability, and the heat-shrinkable label using this film.

The heat-shrinkable polyester film of the present invention that can achieve the above object has a gist in that it satisfies the following (A) to (E).
(A) About a sample of a heat-shrinkable polyester film cut into a 10 cm × 10 cm square shape, it was pulled up by dipping in 70 ° C. warm water for 5 seconds, and then dipped in water at 25 ° C. for 10 seconds. The heat shrinkage rate in the maximum shrinkage direction is 10 to 50%.
(B) About a sample of a heat-shrinkable polyester film cut into a 10 cm × 10 cm square shape, dipped in hot water at 85 ° C. for 5 seconds, and then dipped in water at 25 ° C. for 10 seconds. The heat shrinkage rate in the maximum shrinkage direction is 75% or more, and the heat shrinkage rate in the direction orthogonal to the maximum shrinkage direction is 10% or less.
(C) 95 ° C. hot water for a sample of a heat-shrinkable polyester film cut into a 10 cm × 10 cm square shape and a sample obtained by cutting a film that has been heat-shrinked 10% in the maximum shrinkage direction into a 10 cm × 10 cm square shape X ₀ (%) and X ₁₀ (%) are the heat shrinkage rates in the maximum shrinkage direction measured when immersed in water for 5 seconds and then immersed in water at 25 ° C. for 10 seconds. When the thermal shrinkage difference Δ (%) represented by the following formula (1) is 10 to 20%.
Δ = X ₀ −X ₁₀ (1)
(D) The three-dimensional surface roughness SΔa is 0.008 to 0.04.
(E) The three-dimensional surface roughness SRz is 0.6 to 1.5 μm.

  The heat-shrinkable polyester film preferably contains 0.02 to 0.5% by mass of lubricant particles having an average particle diameter of 0.01 to 4 μm.

  In addition, the heat-shrinkable polyester film was subjected to a test on the heat-shrinkage stress value in the direction after thermal shrinkage of 10% in the maximum shrinkage direction in hot air at a temperature of 90 ° C. and a blowing speed of 5 m / sec. When measured under the conditions of a single width of 20 mm and a chuck distance of 100 mm, the maximum heat shrinkage stress value is preferably 7 MPa or more.

Further, when the thickness shrinkage measurement in the maximum shrinkage direction of the heat-shrinkable polyester film was performed on a test piece having a length of 50 cm and a width of 5 cm, the thickness distribution defined by the following formula (2) was 6 % Is recommended.
Thickness distribution = [(maximum thickness−minimum thickness) / average thickness] × 100 (2)

In addition, the heat-shrinkable polyester film preferably has a melt specific resistance value at 275 ° C. of 0.70 × 10 ⁸ Ω · cm or less.

  In addition, a heat-shrinkable label using the heat-shrinkable polyester film is also included in the present invention.

  The heat-shrinkable polyester film of the present invention can obtain a beautiful shrink-finished appearance by shrinkage in a relatively low temperature range even when a high shrinkage rate is partially required. Moreover, the film forming property and workability are good. Furthermore, the heat-shrinkable label obtained from the heat-shrinkable polyester film of the present invention is excellent in the reinforcing effect of the coated container and the blocking resistance.

  Therefore, the heat-shrinkable polyester film and heat-shrinkable label of the present invention are suitable for various coated labels such as full labels such as PET bottles.

  The heat-shrinkable polyester film of the present invention is a single copolyester mainly composed of an ester unit formed from a known polyvalent carboxylic acid component and a polyhydric alcohol component, or a mixture of two or more polyesters. It is obtained by using.

  The heat-shrinkable polyester film of the present invention has a heat shrinkage rate measured under the above conditions (A) and (B) (A): 10% to 50%, (B): maximum shrinkage direction 75% or more and 10% or less in the direction perpendicular to the maximum shrinkage direction. If it is such a film, the heat-shrinkable label which becomes a high shrinkage rate by the process for a comparatively short time can be provided.

  Usually, in the process of covering and shrinking a label made of a heat-shrinkable film on a container or the like, the hot air tunnel described above is passed through hot air of about 120 to 200 ° C. and a wind speed of about 2 to 20 m / second in about 2 to 20 seconds. Moreover, in the steam tunnel, it is performed by passing through steam at about 75 to 95 ° C. and a pressure of about 0.5 to 20 MPa in about 2 to 20 seconds. A film in which all of the heat shrinkage ratios of (A) and (B) satisfy the above range is, for example, heat for covering most of the side surface of a container such as a PET bottle having a complicated side surface shape. Even if it is used as a shrinkable label, or as a heat shrinkable label for a container having a side shape that requires a very high shrinkage ratio for a label that covers the side (for example, a full label for a PET bottle or a glass bottle) Under such normal shrinking conditions, a very beautiful shrink-finished appearance can be achieved.

  That is, when the thermal shrinkage rate measured under the condition (A) is below the above range, the low temperature shrinkability becomes insufficient, and it is not preferable because the temperature at the time of label coating shrinkage needs to be increased. On the other hand, when the heat shrinkage rate measured under the condition (A) exceeds the above range, defects such as jumping of the label due to heat shrinkage (shifting upward due to rapid shrinkage of the film) tend to occur. . The thermal shrinkage rate measured under the condition (A) is preferably 15% or more and 40% or less.

  Further, when the thermal shrinkage rate in the maximum shrinkage direction measured under the condition (B) is lower than the above range, for example, when a shrinkage is applied to a PET bottle or the like as a label, a portion where a larger shrinkage rate is required. There is a tendency for insufficient shrinkage to occur (for example, at the mouth of a bottle). Preferably it is 78% or more. In addition, it is preferable that the thermal contraction rate of the maximum shrinkage direction measured on the conditions of (B) is 95% or less.

  Furthermore, when the thermal contraction rate (orthogonal direction thermal contraction rate) in the direction orthogonal to the maximum shrinkage direction measured under the condition (B) exceeds the above range, a poor appearance due to vertical shrinkage occurs. Note that “vertical sinking” means that the length of the label after shrinkage is uneven, so that the upper edge of the label after being shrunk on a PET bottle or the like draws a line that curves downward, or the lower edge is upward A poor appearance that draws a curved line. It is preferable that the orthogonal direction thermal shrinkage measured under the condition (B) is 7% or less.

In addition, the heat-shrinkable polyester film of the present invention has a heat shrinkage rate X ₀ (%) in the maximum shrinkage direction measured under the above condition (C) for the film before heat shrinkage, and the film before heat shrinkage is temporarily removed. With respect to a film that has been heat-shrinked 10% in the maximum shrinkage direction, when the thermal shrinkage rate in the maximum shrinkage direction measured under the above condition (C) is X ₁₀ (%), the heat shrinkage represented by the above formula (1) The rate difference Δ (%) is 10% or more and 20% or less. If the heat-shrinkable polyester film has the heat-shrinkage difference Δ within the above range, a heat-shrinkable label having a reinforcing effect on the coated container can be obtained.

With a heat-shrinkable label obtained from a heat-shrinkable polyester film having a heat shrinkage difference Δ that is less than the above range, the reinforcing effect of the container after coating shrinkage becomes insufficient. In the heat-shrinkable polyester film of the present invention, the preferred heat shrinkage difference Δ is 17% or less. The lower limit of the thermal shrinkage difference Δ is the thermal shrinkage rate X ₁₀ is because a value measured by using a film obtained by 10% heat shrinkage, never below 10%.

  By the way, in a normal heat-shrinkable polyester film, the final heat shrinkage rate (the first heat shrinkage rate is 10% and the second heat shrinkage when heat shrinkage is once again after 10% heat shrinkage). The ratio of the heat shrinkage rate Δ exceeds the above range when the film before heat shrinkage is completely shrunk under the same heat shrinkage conditions. ) In the film of the present invention, as will be described later, the composition of the polyester used in the film is made suitable, and the stretching condition of the film is controlled to ensure the heat shrinkage difference Δ within the above range. .

The above-mentioned “heat shrinkage rate in the maximum shrinkage direction” means the heat shrinkage rate in the direction in which the sample is most shrunk, and the maximum shrinkage direction and the orthogonal direction are the length of the square in the vertical or horizontal direction. That's it. The heat shrinkage rate (%) is obtained by measuring a 10 cm × 10 cm sample in warm water at 70 ° C. ± 0.5 ° C. under the heat shrinkage rate measured under the condition (A) and the heat measured under the condition (B). in hot water of 85 ° C. ± 0.5 ° C. in shrinkage, condition the thermal shrinkage rate X hot water of 95 ° C. ± 0.5 ° C. at _0, measured by the (C), 5 seconds immersion in each no load The film was immediately immersed in water at 25 ° C. ± 0.5 ° C. under no load for 10 seconds, and the lengths in the vertical and horizontal directions of the film were measured. × (Length before shrinkage−Length after shrinkage) ÷ (Length before shrinkage)
The value obtained according to

Further, the thermal shrinkage rate X ₁₀ used to calculate the thermal shrinkage difference Δ is measured as follows.

  First, a film that is heat-shrinked 10% in the maximum shrinkage direction is produced. A mold having two chucks facing each other is prepared so that only a pair of opposite ends of a rectangular film can be gripped. The heat-shrinkable polyester film is cut into a square or a rectangle parallel to the maximum shrinkage direction. The cut film is fixed with the above mold. Fixing is performed by gripping both ends of the film perpendicular to the maximum shrinking direction with chucks and loosening the film so that the ratio of the film length between chucks to the distance between chucks of the mold is 1: 0.9. Do it. After that, the film fixed on the mold was immersed in warm water at 95 ° C. ± 0.5 ° C. under no load for 5 seconds and heat-shrinked, and then immediately immersed in water at 25 ° C. ± 0.5 ° C. under no load. Soak for 10 seconds and pull up. The film is removed from the mold and the adhering water is removed to obtain a film thermally contracted by 10% in the maximum shrinkage direction.

A 10 cm × 10 cm sample is cut from the obtained film, and the heat shrinkage rate X ₁₀ is measured by using this sample in the same manner as the heat shrinkage rate X _0, and the heat shrinkage rate difference Δ is calculated by the above equation (1). calculate.

  In addition, the time from the production process of the film thermally contracted by 10% in the maximum shrinkage direction to the sample cutting process and the time from the sample cutting process to the heat shrinking process under the condition (C) are both It is desirable to make it as short as possible. In addition, when storing a film that has been heat-shrinked 10% in the maximum shrinking direction until the sample cutting step, and when storing the cut sample until the heat shrinking step, in an airless environment of 25 ° C. or less in an unstrained state. And avoid unnecessary heat shrinkage.

  Furthermore, the heat-shrinkable polyester film of the present invention has a three-dimensional surface roughness SΔa of 0.008 or more and 0.04 or less. By controlling SΔa within such a range, good film formability and workability can be ensured. The three-dimensional surface roughness SΔa can be measured with a three-dimensional roughness meter (for example, “ET-30K” manufactured by Kosaka Manufacturing Co., Ltd.).

  The three-dimensional surface roughness SΔa is a three-dimensional average inclination, and is defined by the following expression in a direction perpendicular to the direction at 150 points set in an arbitrary direction of the film in a plan view at intervals of 2 μm. The average slope Δa is measured and the measurement results at all these points are averaged. For example, the 150 points may be taken in the TD direction of the film (perpendicular to the traveling direction during film production), and the average inclination Δa may be measured in the MD direction of the film (traveling direction during film production).

[Where, f (x) represents a cross-sectional curve, and more specifically, the size of the unevenness at the coordinate x set in the measurement direction (positive when higher than the average line, negative when lower than the average line) ). L indicates the measurement length. ]

  If SΔa is too small, the running property during film production is lowered, and the film surface may be damaged during running. On the other hand, if SΔa is too large, the tear resistance of the film is deteriorated, and white powder is generated when the film travels, causing printing loss. A more preferable lower limit of SΔa is 0.01, and a more preferable lower limit is 0.012. A more preferable upper limit of SΔa is 0.035, and a more preferable upper limit is 0.03.

  In addition, the heat-shrinkable polyester film of the present invention has a three-dimensional surface roughness SRz of 0.6 μm or more and 1.5 μm or less. By controlling SRz within such a range, the blocking resistance after covering the container can be enhanced. The three-dimensional surface roughness SRz can be measured by a three-dimensional roughness meter (for example, “ET-30K” manufactured by Kosaka Manufacturing Co., Ltd.) in the same manner as the above SΔa.

  The three-dimensional surface roughness SRz is a three-dimensional ten-point average roughness. For each of 150 points set at 2 μm intervals in an arbitrary direction of the film in plan view, the weighted average roughness in a direction perpendicular to the direction. Rz is measured and the measurement results at all these points are averaged. For example, if the above 150 points are taken in the TD direction of the film (perpendicular to the running direction during film production) and the ten-point average roughness Rz is measured in the MD direction of the film (running direction during film production). Good.

  If SRz is too small, for example, when a full label is produced from a film and the container is coated and contracted, and the coated container is packaged (boxed or the like) at a high temperature, blocking becomes easy. On the other hand, if SRz is too large, the tear resistance of the film deteriorates, and white powder is generated during film running, causing printing loss. A more preferred lower limit of SRz is 0.65 μm, and a more preferred lower limit is 0.7 μm. A more preferable upper limit of SRz is 1.3 μm, and a more preferable upper limit is 1.0 μm.

  In the film of the present invention, SΔa and SRz are controlled within the above range by containing a lubricant.

  Examples of the lubricant include inorganic particles (inorganic lubricant), organic salt particles, and polymer particles. Inorganic particles include carbonates (such as alkaline earth metal carbonates such as calcium carbonate, magnesium carbonate, and barium carbonate), sulfates (such as alkaline earth metal salts such as barium sulfate), and phosphates (lithium phosphate). Alkali metal phosphates such as calcium phosphate, alkaline earth metal phosphates such as magnesium phosphate) Oxide-based particles (aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, etc.), kaolin, talc, lithium fluoride Etc. can be exemplified. Among these, silica (silicon oxide) particles are preferable. Particularly preferred silica particles are aggregates formed by agglomerating primary particles. Such silica particles have good handling properties and are useful for obtaining a film with good transparency.

  Organic salt particles include oxalates (such as alkaline earth metal salts such as calcium oxalate) and terephthalate salts (such as alkaline earth metal salts such as calcium, magnesium and barium salts, zinc salts and manganese salts). Can be mentioned.

  Examples of the polymer particles include homopolymers or copolymers of vinyl monomers such as divinylbenzene, styrene, (meth) acrylic acid, polytetrafluoroethylene, benzoguanamine resin, thermosetting urea resin, thermosetting phenol resin, and the like. It is done. In particular, crosslinked polymer particles are preferred.

  The average particle size of these lubricants is preferably 0.01 μm or more and 4 μm or less, and more preferably 0.05 μm or more and 3.5 μm or less. When the average particle size of the lubricant is less than the above range, it becomes difficult to make SΔa equal to or more than the above lower limit value, and when the average particle size of the lubricant exceeds the above range, it becomes difficult to make SRz equal to or less than the above upper limit value. . In addition, the average particle diameter of a lubricant here is a nominal value of a lubricant maker, and is an average particle diameter measured about the particle | grains which grind | pulverized the aggregate of the primary particle and adjusted the particle diameter.

  Further, it is recommended that the amount of the lubricant added be adjusted so that it is 0.02% by mass or more and 0.5% by mass or less, and more preferably 0.03% by mass or more and 0.4% by mass or less in the total amount of the film. Is done. In addition, when the film has a plurality of layers as described later, the content of the lubricant with respect to the total amount of the two layers positioned on the outermost surface is 0.02% by mass or more and 0.5% by mass. Hereinafter, it may be adjusted so as to be more preferably 0.03 mass% or more and 0.4 mass% or less. If the addition amount of the lubricant is less than the above range, it is difficult to make SΔa equal to or more than the above lower limit value, and if the addition amount of the lubricant exceeds the above range, it becomes difficult to make SΔa less than the above upper limit value.

  Further, in the heat-shrinkable polyester film of the present invention, the heat-shrinkage stress value in the direction after the heat shrinkage of 10% in the maximum shrinkage direction was tested in hot air at a temperature of 90 ° C. and a blowing speed of 5 m / sec. When measured under the conditions of a single width of 20 mm and a chuck distance of 100 mm, the maximum heat shrinkage stress value is preferably 7 MPa or more. If the film has a maximum heat shrinkage stress value of 7 MPa or more, a heat-shrinkable label having a more excellent reinforcing effect of the covering container can be obtained. That is, in the heat-shrinkable label obtained from the film having the maximum heat-shrinkage stress value below the above range, the effect of reinforcing the covering container tends to be reduced. The maximum heat shrinkage stress value is more preferably 10 MPa or more, and further preferably 11 MPa or more.

The maximum heat shrinkage stress value is measured by the following method.
[1] A test piece having a length in the maximum shrinkage direction of 200 mm and a width of 20 mm is cut out from the heat-shrinkable polyester film.
[2] The inside of the heating furnace of a tensile testing machine (for example, “Tensilon” manufactured by Toyo Seiki Co., Ltd.) equipped with a hot air type heating furnace is heated to 90 ° C.
[3] Stop blowing and set the test piece in the heating furnace. The distance between chucks is set to 100 mm (constant), and the test pieces are set loosely so that the length between the chucks of the test pieces and the distance between chucks are 1: 0.9.
[4] The heating furnace door is quickly closed, and blowing (hot air with a temperature of 90 ° C. and a blowing speed of 5 m / sec) is resumed. The test piece is subjected to heat shrinkage by 10%, and the heat shrinkage stress after the heat shrinkage is detected and measured.
[5] The maximum value is read from the chart, and this is taken as the maximum heat shrinkage stress value (MPa).

  Further, the heat-shrinkable polyester film of the present invention preferably has a more uniform thickness, and when the thickness displacement measurement in the maximum shrinkage direction of the film is performed on a test piece having a length of 50 cm and a width of 5 cm, It is recommended that the thickness distribution defined in Equation (2) be 6% or less.

  The thickness distribution is 50 cm in length and 5 cm in width, and 10 test pieces having the maximum shrinkage direction of the film in the length direction are prepared. For each test piece, a contact-type thickness meter (for example, manufactured by Anritsu Corporation) is prepared. “KG60 / A”) is used to continuously measure the thickness in the length direction and output it to the chart. From the output results, the maximum thickness, the minimum thickness, and the average thickness are obtained, and the above formula (2 ) Is used to calculate the average thickness distribution of 10 test pieces.

  A film having a thickness distribution exceeding 6% is inferior in printability especially when printing a multicolored pattern in the printing process, and misalignment is likely to occur when a plurality of colors are superimposed. In addition, in order to produce a label from the film of the present invention, it is difficult to superimpose the bonded portions of the film when solvent-bonding to form a tube. Furthermore, in the film having a thickness distribution exceeding 6%, when wound in a roll shape in the film manufacturing process, a difference in partial winding hardness occurs, resulting in looseness and wrinkles of the film, In some cases, it cannot be used as a heat-shrinkable film. The thickness distribution is more preferably 5% or less, and particularly preferably 4% or less.

Furthermore, in the heat-shrinkable polyester film of the present invention, the melt specific resistance value at 275 ° C. is preferably 0.70 × 10 ⁸ Ω · cm or less. Thus, when a melt specific resistance value is small, when cooling the film melt-extruded from the extruder with the casting roll, the electrostatic adhesiveness of the film with respect to a roll can be improved. Therefore, the stability of solidification by cooling can be improved, and the casting speed (production speed) can be improved. The melting specific resistance value is more preferably 0.65 × 10 ⁸ Ω · cm or less, and further preferably 0.60 × 10 ⁸ Ω · cm or less.

  Further, when the melting specific resistance value is low and the electrostatic adhesion is high, the film quality can be improved. In other words, when the electrostatic adhesion is low, the film is incompletely cooled and solidified, and air locally enters between the casting roll and the film, resulting in pinner bubbles (streaky defects) on the film surface. However, if the electrostatic adhesion is excellent, the occurrence of the pinner bubble can be reduced, and the film appearance can be improved.

  In addition, when the melting specific resistance value is sufficiently low and the electrostatic adhesion is sufficiently high, the thickness of the film can be made uniform. That is, when the electrostatic adhesion to the casting roll is low, the thickness of the cast unstretched film becomes uneven, and the stretched film obtained by stretching the unstretched film further expands the thickness nonuniformity. However, when the electrostatic adhesion is sufficiently high, the thickness can be made uniform even in the stretched film.

  In order to control the melt specific resistance value of the film within the above range, it is desirable to include an alkaline earth metal compound and a phosphorus-containing compound in the film. The melting specific resistance value can be lowered only by the alkaline earth metal compound, but the melting specific resistance value can be remarkably lowered by the coexistence of the phosphorus-containing compound. Although it is not clear why the specific melt resistance can be significantly reduced by combining an alkaline earth metal compound and a phosphorus-containing compound, the amount of foreign matter can be reduced and the amount of charge carriers can be reduced by including a phosphorus-containing compound. It is estimated that it can be increased.

The content of the alkaline earth metal compound in the film, based on the alkaline-earth metal atom ^{M 2,} for example, 40ppm is preferably set to (by mass, hereinafter the same) or more, more preferably, to 50ppm or more, 60 ppm More preferably, the above is used. If the amount of the alkaline earth metal compound is too small, it tends to be difficult to lower the melting specific resistance value. Even if the content of the alkaline earth metal compound is excessively increased, the effect of reducing the melt specific resistance value is saturated, and rather adverse effects such as generation of foreign substances and coloring tend to increase. Therefore, the content of the alkaline earth metal compound, based on the alkaline-earth metal atom ^{M 2,} for example, preferably to 400ppm or less, more preferably, to less 350 ppm, and even more preferably from 300ppm or less.

  The content of the phosphorus-containing compound in the film is preferably, for example, 10 ppm (mass basis, the same shall apply hereinafter) or more, more preferably 15 ppm or more, and more preferably 20 ppm or more, based on the phosphorus atom P. preferable. If the amount of the phosphorus-containing compound is too small, it may be difficult to sufficiently reduce the melt specific resistance value, and the amount of foreign matter generated may not be reduced. Even if the content of the phosphorus-containing compound is excessively increased, the effect of reducing the melt specific resistance value is saturated. Furthermore, since the production of diethylene glycol is promoted and it is difficult to control the production amount, the film properties may be different from those planned. Therefore, the content of the phosphorus-containing compound is preferably, for example, 500 ppm or less, more preferably 450 ppm or less, and further preferably 400 ppm or less, based on the phosphorus atom P.

When lowering the melt specific resistance value of the film with an alkaline earth metal compound and a phosphorus-containing compound, the mass ratio (M ² / P) of the alkaline earth metal atom M ² and phosphorus atom P in the film is 1.5 or more ( More preferably 1.6 or more, and even more preferably 1.7 or more. By setting the mass ratio (M ² / P) to 1.5 or more, the melt specific resistance value can be significantly reduced. When the mass ratio (M ² / P) exceeds 5.0, the amount of foreign matter generated may increase, the amount of foreign matter generated may increase, or the film may be colored. Therefore, the mass ratio (M ² / P) is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.0 or less.

  In order to further lower the melt specific resistance value of the film, it is desirable to contain an alkali metal compound in the film in addition to the alkaline earth metal compound and the phosphorus-containing compound. Alkali metal compounds cannot reduce the melt resistivity even if they are contained alone in the film, but they can significantly reduce the melt resistivity by adding to the coexistence system of alkaline earth metal compounds and phosphorus-containing compounds. Can do. The reason for this is not clear, but it is presumed that the melting specific resistance value is lowered by forming a complex of the alkali metal compound, alkaline earth metal compound, and phosphorus-containing compound.

The content of the alkali metal compound in the film, based on the alkali metal atom M ^1, for example, 0 ppm (mass basis, same hereinafter) or more and it is preferable that, more preferably, to 5ppm or more, 6 ppm or more and More preferably, it is particularly preferably 7 ppm or more. Even if the content of the alkali metal compound is increased too much, the effect of reducing the melt specific resistance value is saturated, and further, the amount of foreign matter generated increases. The content of this reason the alkali metal compound, based on the alkali metal atom ^{M 1,} for example, preferably be 100ppm or less, more preferably, to less 90 ppm, further preferably not more than 80 ppm.

  Examples of the alkaline earth metal compound include an alkaline earth metal hydroxide, alkoxide, aliphatic carboxylate (acetate, butyrate, etc., preferably acetate), aromatic carboxylate (benzoate), And salts with a compound having a phenolic hydroxyl group (such as a salt with phenol). Examples of the alkaline earth metal include magnesium, calcium, strontium, barium and the like (preferably magnesium). Preferred alkaline earth metal compounds include magnesium hydroxide, magnesium methoxide, magnesium acetate, calcium acetate, strontium acetate, barium acetate and the like, especially magnesium acetate. The alkaline earth metal compounds can be used alone or in combination of two or more.

Examples of the phosphorus-containing compounds include phosphoric acids (phosphoric acid, phosphorous acid, hypophosphorous acid, etc.) and esters thereof (alkyl esters, aryl esters, etc.), as well as alkylphosphonic acids, arylphosphonic acids, and esters thereof (alkyls). Ester, aryl ester, etc.). Preferred phosphorus compounds, such as phosphoric acid, aliphatic esters (alkyl esters of phosphoric acid of phosphoric acid; for example, phosphoric acid monomethyl ester, phosphoric acid monoethyl ester, phosphoric acid such as phosphoric acid monobutyl ester mono C _1-6 Phosphoric acid tri-C ₁ alkyl ester, phosphoric acid dimethyl ester, phosphoric acid diethyl ester, phosphoric acid dibutyl ester, etc. phosphoric acid diC _1-6 alkyl ester, phosphoric acid trimethyl ester, phosphoric acid triethyl ester, phosphoric acid tributyl ester, etc. _-6 alkyl esters), aromatic esters of phosphoric acid (such as mono-, di-, or tri-C _6-9 aryl esters of phosphoric acid such as triphenyl phosphate, tricresyl phosphate), aliphatic esters of phosphorous acid ( Alkyl esters of phosphorous acid and the like; for example, trimethyl phosphite, Mono-, di-, or tri-C _1-6 alkyl esters of phosphorous acid such as tributyl phosphite), alkyl phosphonic acids (C _1-6 alkyl phosphonic acids such as methyl phosphonic acid, ethyl phosphonic acid), alkyl phosphonic acids Esters (such as mono- or di-C _1-6 alkyl esters of C _1-6 alkylphosphonic acids such as dimethyl methylphosphonate and dimethyl ethylphosphonate), arylphosphonic acid alkyl esters (such as dimethyl phenylphosphonate, diethyl phenylphosphonate C) Mono- or di-C _1-6 alkyl esters of _6-9 aryl phosphonic acids), aryl phosphonic acid aryl esters (such as mono- or di-C _6-9 aryl esters of C _6-9 aryl phosphonic acids such as diphenyl phenylphosphonic acid) Etc. are examples That. Particularly preferred phosphorus-containing compounds include phosphoric acid and trialkyl phosphate (such as trimethyl phosphate). These phosphorus-containing compounds can be used alone or in combination of two or more.

  Examples of the alkali metal compound include alkali metal hydroxide, carbonate, aliphatic carboxylate (acetate, butyrate, etc., preferably acetate), aromatic carboxylate (benzoate), phenolic hydroxyl group And a salt with a compound having a salt (such as a salt with phenol). Examples of the alkali metal include lithium, sodium and potassium (preferably sodium). Preferred alkali metal compounds include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, lithium acetate, sodium acetate, potassium acetate and the like, especially sodium acetate.

  The heat-shrinkable polyester film of the present invention has an ester unit formed from a polyvalent carboxylic acid component and a polyhydric alcohol component as a main constituent unit.

  Polyvalent carboxylic acids for forming a polyvalent carboxylic acid component in the ester unit include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and orthophthalic acid; adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid And aliphatic dicarboxylic acids such as acids; alicyclic dicarboxylic acids; and the like, and ester-forming derivatives thereof.

  In addition, when using the above-mentioned aliphatic dicarboxylic acid, it is preferable that an aliphatic dicarboxylic acid component is less than 3 mol% in 100 mol% of polyvalent carboxylic acid components of a film. Although details will be described later, in the heat-shrinkable polyester film of the present invention, it is desirable to use an ethylene terephthalate unit as a main constituent unit in order to exhibit tear resistance, strength, heat resistance, and the like. Therefore, it is recommended that the polyvalent carboxylic acid component in the film is mainly a terephthalic acid component, but when the amount of the aliphatic dicarboxylic acid component is 3 mol% or more, the heat-shrinkable label obtained from the film In some cases, the rigidity (film waist) that can withstand high-speed mounting on the container cannot be obtained.

  Further, it is preferable not to use trivalent or higher polyvalent carboxylic acids (for example, trimellitic acid, pyromellitic acid, and anhydrides thereof). In the heat-shrinkable polyester film having these polyvalent carboxylic acid components, it may be difficult to obtain a sufficient heat shrinkage rate.

  As the polyhydric alcohol for forming the polyhydric alcohol component in the ester unit, ethylene glycol is used to form the ethylene terephthalate unit. Others, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-methyl-1,5-pentanediol, 2,2-diethyl Aliphatic diols such as -1,3-propanediol, alicyclic diols such as 1,4-cyclohexanedimethanol, dimer diols, alkylene oxide adducts of bisphenol compounds or derivatives thereof, and the like can be used in combination.

  In the film of the present invention, one or more of diols having 3 to 6 carbon atoms (for example, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, etc.) or 1,4-cyclohexanedi It is preferable to use a polyester having a glass transition temperature (Tg) adjusted to 60 to 75 ° C. using methanol.

  In particular, it is desirable to use a polyester combined with neopentyl glycol from the viewpoints of securing each heat shrinkage rate, improving the shrink-finished appearance, and securing the container reinforcing effect. In 100 mol% of the polyhydric alcohol component of the film, the amount of neopentyl glycol component is 15 mol% or more, preferably 18 mol% or more, and 27 mol% or less, preferably 25 mol% or less is recommended. . In the case of using a diol having 3 to 6 carbon atoms other than neopentyl glycol, in 100 mol% of the polyhydric alcohol component of the film, these diol components are 3 mol% or more, preferably 5 mol% or more, It is desired to be 15 mol% or less, preferably 13 mol% or less. In addition, when 1,4-cyclohexanedimethanol is used, the amount of 1,4-cyclohexanedimethanol component is 15 mol% or more, preferably 18 mol% or more, in 100 mol% of the polyhydric alcohol component of the film. 27 mol% or less, preferably 25 mol% or less is recommended.

  In addition, it is preferable not to use a diol having 8 or more carbon atoms (for example, octanediol) or a trihydric or higher polyhydric alcohol excluding the preferred polyhydric alcohols exemplified above. In the heat-shrinkable polyester film having these diol components and polyhydric alcohol components, it may be difficult to obtain a sufficient heat shrinkage rate.

  Moreover, although it is not a polyhydric alcohol, you may use some lactones represented by (epsilon) -caprolactone. Lactones are ring-opened and become units having ester bonds at both ends.

  Considering the tear resistance, strength, heat resistance and the like of the film, it is preferable to select the ethylene terephthalate unit to be 50 mol% or more in 100 mol% of the constituent unit of the heat-shrinkable polyester film. Therefore, in 100 mol% of the polyvalent carboxylic acid component, the terephthalic acid component (component consisting of terephthalic acid or its ester) is 50 mol% or more, and in 100 mol% of the polyhydric alcohol component, the ethylene glycol component is 50 mol% or more. It is preferable to do. As for an ethylene terephthalate unit, 55 mol% or more is more preferable, and 60 mol% or more is further more preferable.

  The polyester constituting the heat-shrinkable polyester film can be produced by melt polymerization according to a conventional method, but a so-called direct polymerization method in which an oligomer obtained by directly reacting a polyvalent carboxylic acid and a polyhydric alcohol is polycondensed. Examples include a so-called transesterification method in which a methyl ester of a polyvalent carboxylic acid and a polyhydric alcohol are transesterified and then polycondensed, and any production method can be applied. Moreover, the polyester obtained by another polymerization method may be sufficient. The polymerization degree of polyester is preferably 0.3 to 1.3 dl / g in terms of intrinsic viscosity.

  As the polymerization catalyst, various conventional catalysts can be used. For example, titanium-based catalyst, antimony-based catalyst, germanium-based catalyst, tin-based catalyst, cobalt-based catalyst, manganese-based catalyst, etc., preferably titanium-based catalyst (titanium tetrabutoxide) Etc.), antimony catalysts (such as antimony trioxide), germanium catalysts (such as germanium dioxide), cobalt catalysts (such as cobalt acetate), and the like.

  The addition time of the alkali metal compound, alkaline earth metal compound, and phosphorus-containing compound is not particularly limited, and any of before the esterification reaction, during esterification, from the end of esterification to the start of the polymerization process, during polymerization, and after polymerization. However, it is preferably at any stage after the esterification step, more preferably from the end of the esterification to the start of the polymerization step. When an alkaline earth metal compound and a phosphorus-containing compound (and an alkali metal compound if necessary) are added after the esterification step, the amount of foreign matter generated can be reduced as compared with the case where it is added before that.

  Moreover, antioxidants, ultraviolet absorbers, antistatic agents, colorants, antibacterial agents, and the like can be added as necessary.

  The polyester film can be obtained by a known method to be described later. In the heat-shrinkable polyester film, as a means for containing a plurality of components in the film, copolymerization is performed and the copolymerized polyester is used alone. There is a method and a method of blending different kinds of homopolyesters or copolymerized polyesters.

  In a system in which a copolyester is used alone, a copolyester obtained from a polyhydric alcohol having a predetermined composition and a polyvalent carboxylic acid having a predetermined composition may be used. On the other hand, a method of blending polyesters having different compositions can be preferably employed because the characteristics of the film can be easily changed simply by changing the blend ratio, and it can be used for industrial production of a wide variety of films.

  Specifically, in the blending method, it is preferable to use a blend of two or more polyesters having different Tg. Three or more polyesters may be blended.

  In addition, by blending and using 2 or more types of polyesters, for example, there is a concern that the polyesters are not compatible with each other and the film is whitened. However, normally, in the film extrusion process described later, transesterification reaction occurs when heated, and as a result of the polyester contained in the film becoming a copolymerized polyester, it has been found that the above troubles such as whitening can be avoided. ing. Such copolymerization by transesterification can be confirmed from the fact that Tg measured by a known method is a single value for a film obtained from two or more polyester blends having different Tg.

  As a method of adding a lubricant used to set SΔa and SRz to the above predetermined values, a method of adding and dispersing at any stage of a polymerization process of a polyester used as a film material; a polyester chip obtained after polymerization and a lubricant are mixed. A method of preparing a master batch chip mixed with a lubricant in advance by a melt extrusion method to form a chip and using this to produce a film can be preferably employed. When blending a plurality of types of polyester chips to obtain the film of the present invention, it is not necessary to add a lubricant to all types of polyester chips, for example, adding only one type of polyester chip. It doesn't matter.

  As a specific method for producing a film, the raw material polyester chips are dried using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer, and extruded into a film at a temperature of 200 to 300 ° C. using an extruder. . Alternatively, an undried polyester raw material chip is similarly extruded into a film while removing moisture in a vented extruder. Any existing method such as a T-die method or a tubular method may be used for extrusion. After extrusion, it is cooled rapidly to obtain an unstretched film. The unstretched film here includes a film on which a tension necessary for feeding the film in the production process is applied.

  The film of the present invention may be a film composed of a single layer, but may be a laminated film in which two or more layers (for example, two layers, three layers, four layers, etc.) are laminated. In the case of a laminated film, polyesters having the same composition may be adopted for each layer, but it is also preferable to use polyesters having different compositions for each layer. In the case of three layers, it is also recommended to use a polyester having the same composition for both outer layers and a polyester having another composition for the central layer. In this case, all the layers may contain the lubricant, but it is also preferable that only the outermost layer (two layers located on the outermost surface) contain the lubricant. The lamination method in the case of forming such a laminated film is not particularly limited. For example, a method of obtaining the above-mentioned unstretched film by a known coextrusion method or the like can be employed.

  In addition, as described above, an electrode is disposed between the extruder and the casting roll, a voltage is applied between the electrode and the casting roll, and the film can be electrostatically adhered to the roll. Recommended in terms of uniform distribution.

  Stretching is performed on the unstretched film. The stretching treatment may be performed continuously after cooling with the above-described casting roll or the like, or may be wound up into a roll after cooling and then performed. Since it is practical in terms of production efficiency that the maximum shrinkage direction is the film transverse (width) direction, an example of a stretching method in the case where the maximum shrinkage direction is the transverse direction will be shown below. Even when the maximum shrinkage direction is the longitudinal (longitudinal) direction of the film, the film can be stretched according to ordinary operations such as changing the stretching direction by 90 ° in the following method.

If the thickness distribution of the heat-shrinkable polyester film is made uniform and not more than the above upper limit value, when stretching in the transverse direction using a tenter or the like, a preheating step can be performed prior to the stretching step. Preferably, in this preheating step, the film surface temperature is Tg + 0 at a low wind speed so that the thermal conductivity coefficient is 0.00544 J / cm ² · sec · ° C. or less (0.0013 calories / cm ² · sec · ° C.). Heating is preferably performed until a certain temperature within a range of from ° C to Tg + 60 ° C is reached.

  Stretching in the transverse direction is performed at a predetermined temperature within a range of Tg-5 ° C to Tg + 15 ° C. In the film of the present invention, the heat shrinkage rate of (A) and (B) and the heat shrinkage rate difference Δ are within the above range, and further, the maximum heat shrinkage stress value is within the above range. The stretching may be performed in two or more stages. Hereinafter, a case where stretching is performed in two stages will be described as an example.

  First, the first stage of stretching is performed. The draw ratio is 4.4 times or more and 6.0 times or less, preferably 4.8 times or more and 5.5 times or less with respect to the unstretched film. The stretching temperature in the first stage is the above temperature (a predetermined temperature within the range of Tg-5 ° C to Tg + 15 ° C).

  Next, it is preferable to perform heat setting in a state where the film is tensioned in the stretching direction. It is recommended that the tension rate at that time be 1% or more and 6% or less, preferably 2% or more and 5% or less, with respect to the first stretched film. Also, the heat setting temperature is the same as the first stage stretching temperature or within the above temperature range, it is about 1-5 ° C. lower than the first stage stretching temperature, and the heat setting time is 0.5 seconds. It is desirable that the time is not less than 5 seconds, preferably not less than 1 second and not more than 3 seconds.

  Next, the second stage of stretching is performed. The draw ratio is 1.1 times or more and 1.5 times or less (preferably 1.3 times or less) with respect to the film after heat setting (after the first-stage drawing when heat setting is not performed). The stretching temperature in the second stage is preferably the same as the heat setting temperature, or preferably about 1 to 5 ° C. lower than the heat setting temperature within the above temperature range.

  Thereafter, the film is cooled to obtain a heat-shrinkable polyester film, preferably with slight tension applied to the film. The tension rate during cooling is preferably 0.1 to 3% with respect to the stretched film in the second stage.

  In addition, when making the process of extending | stretching into 3 steps | paragraphs, it is desirable to put the said heat setting process between 2nd step | stretching and 3rd step | stretching. What is necessary is just to determine the conditions of a heat setting process according to said heat setting conditions. Further, the stretching conditions at the third stage may be determined according to the stretching conditions at the second stage.

  From the viewpoint of controlling the heat shrinkage rate of the film, it is preferable that the number of stretching steps is large. However, if the number of steps is too large, it is difficult to design a stretching facility in industrial production. It is desirable to have 4 or less steps.

  In this transverse stretching step, it is preferable to use equipment that can reduce the fluctuation of the film surface temperature. That is, the stretching process includes a preheating process before stretching, a stretching process, a heat treatment process after stretching, a relaxation process, a restretching process process, and the like. In particular, in the preheating process, the stretching process, and the heat treatment process after stretching. The fluctuation range of the surface temperature of the film measured at an arbitrary point is preferably within an average temperature ± 1 ° C., and more preferably within an average temperature ± 0.5 ° C. If the fluctuation range of the surface temperature of the film is small, the film is stretched or heat-treated at the same temperature over the entire length of the film, so that the heat shrinkage behavior and other physical properties become uniform.

  As a stretching method, not only horizontal uniaxial stretching with a tenter, but also stretching in the longitudinal direction by 1.0 to 4.0 times, preferably 1.1 to 2.0 times may be performed. When biaxial stretching is performed in this manner, either sequential biaxial stretching or simultaneous biaxial stretching may be performed, and restretching may be performed as necessary. Further, in the sequential biaxial stretching, any method such as vertical and horizontal, horizontal and vertical, vertical and horizontal and horizontal and vertical and horizontal may be used as the order of stretching. Even when these longitudinal stretching steps or biaxial stretching steps are adopted, it is preferable to minimize the fluctuation of the film surface temperature as much as possible in the preheating step, the stretching step and the like, similarly to the transverse stretching.

As equipment that can reduce the fluctuation of the film surface temperature, for example, an inverter is attached to control the wind speed of the hot air that heats the film, and the equipment that can suppress the fluctuation of the wind speed, or a heat source of 500 kPa or less (5 kgf / cm ^2). The following is a facility that can suppress the temperature fluctuation of hot air using the low-pressure steam.

Focusing on the point of suppressing the internal heat generation of the film accompanying stretching and reducing the film temperature unevenness in the width direction, the heat transfer coefficient of the stretching process is 0.00377 J / cm ² · sec · ° C. cm ² · sec · ° C.) or higher. 0.00544 to 0.00837 J / cm ² · sec · ° C. (0.0013 to 0.0020 calories / cm ² · sec · ° C.) is more preferable.

  The thickness of the heat-shrinkable polyester film of the present invention is not particularly limited. For example, the heat-shrinkable polyester film for labels is preferably 10 to 100 μm, and more preferably 20 to 60 μm.

  Even if the heat-shrinkable label obtained using the heat-shrinkable polyester film of the present invention is used for a full label such as a PET bottle (a label that partially requires a high shrinkage rate), it has a good shrink-finished appearance. Can be presented. In addition, a high contraction rate can be achieved in a short time. Furthermore, it also has an effect of reinforcing a container such as a PET bottle that has undergone coating shrinkage.

  In order to use the heat-shrinkable polyester film as a heat-shrinkable label, for example, the heat-shrinkable film before shrinkage is stored for a predetermined time in an environment where temperature and humidity are controlled, and is taken out, and a known tubular molding apparatus is used. Is used to apply an adhesive solvent with a predetermined width slightly inward from the edge of one side of one end of the film, and the film is immediately rolled up, the ends are overlapped and bonded, and processed into a tube. This tube can be cut into a predetermined length to obtain the heat-shrinkable label of the present invention.

  The film can be bonded using a melt bonding method in which a part of the film is melted, but it is preferable to use a solvent from the viewpoint of suppressing fluctuations in the thermal shrinkage characteristics of the label. Examples of solvents that can be used include aromatic hydrocarbons such as benzene, toluene, xylene, and trimethylbenzene; halogenated hydrocarbons such as methylene chloride and chloroform; phenols such as phenol; furans such as tetrahydrofuran; -Organic solvents such as oxolanes such as dioxolane; among others, 1,3-dioxolane is preferable in view of high safety.

  The above heat-shrinkable label can be coated after being mounted on a container such as a PET bottle and then heat-shrinked by a known heat-shrinking means (such as a hot air tunnel or a steam tunnel) as described above.

  The PET bottle coated and shrunk with the heat-shrinkable label of the present invention has a weight of about 30% less than that of a conventional PET bottle. It is reinforced to such an extent that it can be handled in the same way. In this case, it is preferable that 75% or more of the body surface area of the PET bottle is covered with a label.

  For example, in the label obtained as follows from the heat-shrinkable film of the present invention, the bottle diameter change rate measured by the method described below is preferably 10% or less, more preferably 7% or less, and an excellent container Can exert a reinforcing effect.

1,3-dioxolane was applied in a width of 3 ± 1 mm slightly from the edge of one surface of one end of the film (coating amount: 3.0 ± 0.3 g / m ² ), and the ends were overlapped, Cut into a size of 14 cm in length and 6.7 cm in diameter to obtain a cylindrical label. A 500 mL round PET bottle with a mass of 20.5 g [height 21 cm, center (body) diameter 6.5 cm] was filled with 500 mL of water and sealed, and the above cylindrical label was attached to the zone. The label is shrunk by passing through a steam tunnel at a temperature of 85 ° C. in 2.5 seconds. The diameter (W ₁ ) of the center of the bottle when a load of 15 kg is applied in the compression mode using “Strograph V10-C” manufactured by Toyo Seiki Co., Ltd. is applied to the center of the side surface of the label-coated bottle thus obtained. Measure and obtain the bottle diameter change rate (%) according to the following formula.
Bottle diameter change rate (%) = 100 × (W ₁ −W ₂ ) / W ₂
Here, W ₂ is the diameter of the front of the bottle central portion to apply a load.

  It should be noted that a label with a bottle diameter change rate exceeding 10% is not preferable because, for example, when a coated container falls in a vending machine, the container is likely to be deformed and may cause clogging. .

  Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are not intended to limit the present invention, and modifications and implementations within the scope of the present invention are included in the present invention. In addition, "ppm" used in a present Example is a mass reference | standard. Moreover, the measuring method of the physical property of the film obtained by the Example and the comparative example is as follows.

(1) Thermal shrinkage rate After the film is cut into a 10 cm × 10 cm square and immersed in warm water at the temperatures of the following (A), (B) and (C) for 5 seconds under no load condition and thermally contracted The sample is immersed in water at 25 ° C. ± 0.5 ° C. for 10 seconds, pulled out from the water, measured in the vertical and horizontal directions, and determined according to the following formula.
Heat shrinkage rate (%) = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)
Here, (A): 75 ° C. ± 0.5 ° C., (B): 85 ° C. ± 0.5 ° C., (C): 95 ± 0.5 ° C. The direction with the largest shrinkage rate is defined as the maximum shrinkage direction.

(2) Difference in heat shrinkage ratio A mold having two chucks facing each other is prepared so that only a pair of opposed ends of a rectangular film can be gripped. The heat-shrinkable polyester film is cut into a square or a rectangle parallel to the maximum shrinkage direction. The cut film is fixed with the above mold. Fixing is performed by gripping both ends of the film perpendicular to the maximum shrinking direction with chucks and loosening the film so that the ratio of the film length between chucks to the distance between chucks of the mold is 1: 0.9. Do it. After that, the film fixed on the mold was immersed in warm water at 95 ° C. ± 0.5 ° C. under no load for 5 seconds and heat-shrinked, and then immediately immersed in water at 25 ° C. ± 0.5 ° C. under no load. Soak for 10 seconds and pull up. The film is removed from the mold and the adhering water is removed to obtain a film thermally contracted by 10% in the maximum shrinkage direction. Thereafter, this film is placed in an airless state in an environment of 25 ° C. or lower and subjected to the next step in as short a time as possible.

The film was cut into a 10 cm × 10 cm square, immersed in warm water of 95 ± 0.5 ° C. for 5 seconds under no load, and thermally contracted, then in water of 25 ° C. ± 0.5 ° C. for 10 seconds. It was immersed and withdrawn from in the aqueous measuring the longitudinal and lateral length of the sample, the maximum shrinkage direction heat shrinkage percentage X ₁₀ in accordance with heat shrinkage factor calculation formula of the. Further, the maximum shrinkage direction of the heat shrinkage rate obtained under the condition of (C) above (1) to X _0. From these values, the heat shrinkage rate difference Δ (%) is calculated according to the above equation (1).

(3) Three-dimensional surface roughness SΔa, SRz
The surface of the sample film is stylused (measurement length: 1 mm, cut-off value: 0.25 mm) along the MD direction of the film. As the stylus, a stylus type three-dimensional roughness meter (“ET-30K” manufactured by Kosaka Manufacturing Co., Ltd.) is used (needle radius: 2 μm, load: 30 mg). The unevenness profile of 1 mm in length obtained by this stylus is divided into 500 points at a pitch of 2 μm, and the height of each point is taken into a three-dimensional roughness analyzer (“AT-30K” manufactured by Kosaka Manufacturing Co., Ltd.). Make it.

  The same operation as described above is continuously performed 150 times (that is, 0.3 mm in the TD direction of the film) at intervals of 2 μm in the TD direction of the film. Then, SΔa and SRz are obtained by causing the analyzer to calculate.

(4) Maximum heat shrinkage stress value Measured using a tensile tester with a heating furnace (“Tensilon” manufactured by Toyo Seiki Co., Ltd.). From the film before heat shrinkage, a sample having a length in the maximum shrinkage direction of 200 mm and a width of 20 mm was cut out, the blowing of the tensile tester that had been heated to 90 ° C. in advance was stopped, and the distance between the chucks was set to 100 mm. The test piece was loosened and attached so that the length between chucks of the test piece and the distance between chucks were 1: 0.9, and then the door of the heating furnace was quickly closed, and air blowing (temperature 90 ° C., blowing speed) The contraction stress detected when the hot air of 5 m / sec is supplied from the back, left and right directions) is measured, and the maximum thermal contraction stress value (MPa) after 10% contraction is determined from the measurement chart.

(5) Thickness distribution Ten test pieces having a length of 50 cm and a width of 5 cm and having the maximum shrinkage direction of the film as the length direction were prepared. For each test piece, a contact-type thickness meter (for example, “anritsu” KG60 / A "etc.), the thickness in the length direction is continuously measured and output to the chart. From the output results, the maximum thickness, the minimum thickness, and the average thickness are obtained, and the above formula (2 ) Is used to calculate the thickness distribution, and the average value of the thickness distributions of the ten test pieces is obtained to obtain the thickness distribution of the film.

(6) Melting specific resistance value A pair of electrode plates are inserted into a sample (film) melted at a temperature of 275 ° C., and a voltage of 120 V is applied. The current at that time is measured, and the melt specific resistance value Si (Ω · cm) is calculated based on the following equation.
Si = (A / I) × (V / io)
Here, A: electrode area (cm ² ), I: distance between electrodes (cm), V: voltage (V), io: current (A).

(7) Shrinkage finish The film was printed in three colors with grass, gold and white inks manufactured by Toyo Ink Mfg. Co., Ltd., and stored in an environment controlled at a temperature of 30 ± 1 ° C. and a relative humidity of 85 ± 2% for 250 hours. Then, using a tube-shaped forming device, 1,3-dioxolane was applied in a width of 3 ± 1 mm slightly from the edge of one side of one end of the film (coating amount: 3.0 ± 0.3 g / m ^2). ) Immediately roll up the film, overlap the ends and bond to a tube, and wind it in a flattened state. This tube is cut into a cylindrical label having a height of 14 cm and a diameter of 6.7 cm. This label is attached to a 500 mL round PET bottle filled with water [height 21 cm, center (body) diameter 6.5 cm], and inside the steam tunnel (SH-1500-L) manufactured by Fujistec. The entire amount of the label is allowed to pass through under the conditions of a tunnel transit time of 2.5 seconds and a zone temperature of 85 ° C. (n = 20). The degree of shrinkage finish is judged visually and the shrinkage finish is evaluated in two stages. The criteria are: ○: none of wrinkles, jumping up, or insufficient shrinkage occurs, x: wrinkles, jumping up, or insufficient shrinkage occurs.

(8) Container reinforcement effect Using a tube-shaped forming device, 1,3-dioxolane was applied in a width of 3 ± 1 mm from the edge of one side of one end of the film (coating amount: 3.0 ± 0.3 g). / M ² ) Immediately roll the film, overlap the ends and bond to a tube, and wind it in a flattened state. This tube is cut into a cylindrical label having a height of 14 cm and a diameter of 6.7 cm. Mass: 20.5 g of a 500 mL round PET bottle [height 21 cm, center (body) diameter 6.5 cm] was filled with 500 mL of water and sealed, and then the above cylindrical label was attached to it. Through the steam tunnel (SH-1500-L) manufactured by Fujistec, the label is shrunk by passing the entire amount of the label under conditions of a tunnel passage time of 2.5 seconds and a zone temperature of 85 ° C.

The diameter (W ₁ ) of the center of the bottle when a load of 15 kg is applied in the compression mode using “Strograph V10-C” manufactured by Toyo Seiki Co., Ltd. is applied to the center of the side surface of the label-coated bottle thus obtained. Measure and obtain the bottle diameter change rate (%) according to the following formula.
Bottle diameter change rate (%) = 100 × (W ₁ −W ₂ ) / W ₂
Here, W ₂ is the diameter of the front of the bottle central portion to apply a load.

(9) Blocking resistance All the label-coated PET bottles obtained by the shrinkage finishing test are sequentially placed in a cardboard box (3 × 4 = 12 bottles) so that the labels come into contact with each other at a high temperature immediately after the test. Pack it in a box. The cardboard box is stored in a room controlled at 40 ± 1 ° C. for 24 hours and then taken out, and the degree of blocking between the labels is evaluated in three stages. Evaluation criteria are: ○: no blocking, Δ: blocking, but no trace left when peeled, x: blocking, trace left when peeled, ○ and Δ are acceptable.

(10) Runnability and tear resistance of film The film is slit into a width: 100 mm and a length: 100 m to form a tape. After winding this tape into a roll, the tape is pulled out from the roll, and is wound around metal guide rolls arranged at intervals of 0.2 m, and then connected to a winding roll. Thereafter, the entire tape is run at a speed of 100 m / min and wound on a winding roll. The amount of scratches on the tape surface after running and the amount of white powder generated on the guide roll surface are visually observed and evaluated according to the following criteria.

[Running]
1: considerable scratches, 2: many scratches, 3: slight scratches, 4: little scratches, 5: no scratches generated,
[Tear resistance]
1: White powder is generated very much, 2: White powder is generated frequently, 3: White powder is generated slightly, 4: White powder is almost not generated, and 5: White powder is not generated.

Synthesis example 1
The esterification reactor is charged with 100 mol% of dimethyl terephthalate as a polyvalent carboxylic acid and 100 mol% of ethylene glycol as a polyhydric alcohol at a ratio 2.2 times (molar ratio) with respect to the polyvalent carboxylic acid. Antimony oxide was charged at the same time to 0.04 mol% with respect to polyvalent carboxylic acids and 81 ppm in terms of Mg atoms with respect to the polyester forming magnesium acetate tetrahydrate, and the temperature was raised to 230 ° C while stirring. Warm and the transesterification was carried out at normal pressure for 120 minutes. The transesterification reaction was completed when a predetermined amount of methanol was distilled off. After completion of the transesterification reaction, trimethyl phosphate was added to 58 ppm with respect to the polyester formed in terms of P atom, the temperature was raised to 280 ° C. while reducing the pressure over 85 minutes, and the melt viscosity was about 7000 poise. Polyester A was obtained by performing a polycondensation reaction for 40 minutes.

Synthesis Examples 2-7
In the same manner as in Synthesis Example 1, polyesters B to G shown in Table 1 were synthesized. In Synthesis Examples 2 and 3, polyesters B and C were obtained by using antimony trioxide as a polymerization catalyst so that the Sb atom was 160 ppm with respect to the polyester. In Synthesis Example 4, polyester D was obtained using titanium tetrabutoxide as a polymerization catalyst so that the Ti atom was 90 ppm with respect to the polyester. Furthermore, in Synthesis Example 6, cobalt acetate tetrahydrate was used as a polymerization catalyst so that Mg atoms were 20 ppm relative to the polyester, and titanium tetrabutoxide was used so that Ti atoms were 15 ppm relative to the polyester. Polyester F was obtained. In Synthesis Example 7, the polymerization catalyst was the same as in Synthesis Example 1, and polyester G was obtained.

  Table 1 shows polyesters A to G obtained in Synthesis Examples 1 to 7. In Table 1, DMT: dimethyl terephthalate, DMN: dimethyl naphthalate, EG: ethylene glycol, NPG: neopentyl glycol, BD: 1,4-butanediol, CHDM: 1,4-cyclohexanedimethanol, PPG: propanediol It is.

  As for the lubricant, in polyester A or polyester E, silica having an average particle diameter of 1.8 μm (“Sicilia 350” manufactured by Fuji Silysia), silica having an average particle diameter of 0.007 μm, or an average particle as an inorganic lubricant A master batch to which 0.7% by mass of silica having a diameter of 5.80 μm was added was manufactured in advance and added to the film. Production of polyester A or polyester E blended with silica was carried out by dispersing the silica in ethylene glycol during the polymerization. Incidentally, film No. described later. The silica in each film except 5 (Experiment 5) was introduced by the silica-containing polyester A, and the film no. The silica in 5 is introduced by the silica-containing polyester E.

Experiment 1
After separately preliminarily drying polyester A, silica-blended polyester A, polyester chip B, and polyester D in the proportions shown in Table 2, melt extrusion at 280 ° C. using a single-screw extruder (T die) Thereafter, the film was rapidly cooled with a casting roll to obtain an unstretched film having a thickness of 260 μm. This unstretched film was preheated at 100 ° C. for 3 seconds, and then stretched in the transverse direction (film width direction) with a tenter. Stretching was performed by first stretching 4.75 times at 77 ° C. (first stage), then tensioning 3% of the film width at the end of the first stage at 77 ° C. for 5 seconds (heat setting), then 75 ° C. The film was stretched (second stage) to 1.1 times the film width at the end of heat setting. Next, the film was cooled while applying a tension of 1% with respect to the film width at the end of the second stage of stretching, and a polyester film No. 5 having a thickness of 50 μm. 1 was obtained. The evaluation results of the obtained film are shown in Tables 4 and 5.

Experiment 2
An unstretched film having a thickness of 260 μm was obtained in the same manner as in Experiment 1 except that the mixing ratio of the polyester chips was changed as shown in Table 2. The unstretched film was stretched in the same manner as in Experiment 1, and the polyester film No. 50 having a thickness of 50 μm was applied. 2 was obtained. The evaluation results of the obtained film are shown in Tables 4 and 5.

Experiment 3
An unstretched film having a thickness of 260 μm was obtained in the same manner as in Experiment 1 except that the mixing ratio of the polyester chips was changed as shown in Table 2. The unstretched film was stretched in the same manner as in Experiment 1 except that the conditions shown in Table 3 were changed. 3 was obtained. The evaluation results of the obtained film are shown in Tables 4 and 5.

Experiment 4
An unstretched film having a thickness of 260 μm was obtained in the same manner as in Experiment 1 except that the mixing ratio of the polyester chips was changed as shown in Table 2. The unstretched film was stretched in the same manner as in Experiment 1 except that the conditions shown in Table 3 were changed. 4 was obtained. The evaluation results of the obtained film are shown in Tables 4 and 5.

Experiment 5
An unstretched film having a thickness of 260 μm was obtained in the same manner as in Experiment 1 except that the mixing ratio of the polyester chips was changed as shown in Table 2. The unstretched film was stretched in the same manner as in Experiment 1 except that the conditions shown in Table 3 were changed. 5 was obtained. The evaluation results of the obtained film are shown in Tables 4 and 5.

Experiment 6
An unstretched film having a thickness of 260 μm was obtained in the same manner as in Experiment 1 except that the mixing ratio of the polyester chips was changed as shown in Table 2. The unstretched film was stretched in the same manner as in Experiment 1 except that the conditions shown in Table 3 were changed. 6 was obtained. The evaluation results of the obtained film are shown in Tables 4 and 5.

Experiment 7
An unstretched film having a thickness of 260 μm was obtained in the same manner as in Experiment 1 except that the mixing ratio of the polyester chips was changed as shown in Table 2. The unstretched film was stretched in the same manner as in Experiment 1 except that the conditions shown in Table 3 were changed. 7 was obtained. The evaluation results of the obtained film are shown in Tables 4 and 5.

Experiment 8
Three-layered laminated polyester film No. 2 comprising both outer layers and a central layer. 8 was obtained. In the center layer, polyester A polyester C and polyester D chips, each of which was preliminarily dried separately, were mixed at a ratio shown in Table 2. In addition, chips of polyester A, silica-blended polyester A and polyester F, which were separately preliminarily dried, were mixed and used in the ratios shown in Table 2 for both outer layers. These mixed polyester chips were co-extruded at 280 ° C. using a single-screw extruder having a T die, and then rapidly cooled with a casting roll, so that both outer layers had a thickness of 65 μm and a central layer had a thickness of 130 μm. An unstretched film having a layer structure was obtained. The unstretched film was stretched in the same manner as in Experiment 1 except that the conditions shown in Table 3 were changed. The thickness was 50 μm (the thickness of both outer layers was 12.5 μm and the thickness of the center layer was 25 μm. ) Laminated polyester film No. 8 was obtained. The evaluation results of the obtained film are shown in Tables 4 and 5.

Experiment 9
An unstretched film having a thickness of 260 μm was obtained in the same manner as in Experiment 1 except that the mixing ratio of the polyester chips was changed as shown in Table 2. The unstretched film was stretched in the same manner as in Experiment 1 except that the conditions shown in Table 3 were changed. 9 was obtained. The evaluation results of the obtained film are shown in Tables 4 and 5.

Experiment 10
An unstretched film having a thickness of 260 μm was obtained in the same manner as in Experiment 1 except that the mixing ratio of the polyester chips was changed as shown in Table 2. The unstretched film was stretched in the same manner as in Experiment 1 except that the conditions shown in Table 3 were changed. 10 was obtained. The evaluation results of the obtained film are shown in Tables 4 and 5.

Experiment 11
An unstretched film having a thickness of 260 μm was obtained in the same manner as in Experiment 1 except that the mixing ratio of the polyester chips was changed as shown in Table 2. The unstretched film was stretched in the same manner as in Experiment 1 except that the conditions shown in Table 3 were changed. 11 was obtained. The evaluation results of the obtained film are shown in Tables 4 and 5.

  In Table 2, when silica is blended in the film or the layer constituting the film, the amount of polyester A is the total amount of polyester A in the amount of polyester A and the polyester A in the silica-blended polyester A chip. The amount of E represents the total amount of polyester E in the amount of polyester E chip and silica-containing polyester E chip. “Silica particles” indicate the content relative to the total amount of the film in the case of a single layer film, and the content relative to the total amount of each outermost layer in the case of a three-layer film.

  In Table 3, the draw ratio at the first stage of stretching is the ratio to the film width, the tension ratio at the time of heat setting is the ratio to the film width after the first stage of stretching, and the stretch ratio at the second stage of stretching. Is the ratio to the film width after heat setting (after the first stage stretching if heat setting is not performed), and the tension ratio during cooling is the ratio to the film width after the second stage stretching. In addition, film No. In 4, 9, and 10, the heat setting tension rate “0%” indicates that no heat setting process is provided, and the tension rate “0%” during cooling indicates that no tension is applied after the second stage of stretching. It means that the film was cooled.

Claims (9)

A heat-shrinkable polyester film, which satisfies the following (A) to (F).
(A) About a sample of a heat-shrinkable polyester film cut into a 10 cm × 10 cm square shape, it was pulled up by dipping in 70 ° C. warm water for 5 seconds, and then dipped in water at 25 ° C. for 10 seconds. The heat shrinkage rate in the maximum shrinkage direction is 10 to 50%.
(B) About a sample of a heat-shrinkable polyester film cut into a 10 cm × 10 cm square shape, dipped in hot water at 85 ° C. for 5 seconds, and then dipped in water at 25 ° C. for 10 seconds. The heat shrinkage rate in the maximum shrinkage direction is 75% or more, and the heat shrinkage rate in the direction orthogonal to the maximum shrinkage direction is 10% or less.
(C) 95 ° C. hot water for a sample of a heat-shrinkable polyester film cut into a 10 cm × 10 cm square shape and a sample obtained by cutting a film that has been heat-shrinked 10% in the maximum shrinkage direction into a 10 cm × 10 cm square shape X ₀ (%) and X ₁₀ (%) are the heat shrinkage rates in the maximum shrinkage direction measured when immersed in water for 5 seconds and then immersed in water at 25 ° C. for 10 seconds. When the thermal shrinkage difference Δ (%) shown by the following formula is 10 to 20%.
Δ = X ₀ -X ₁₀
(D) The three-dimensional surface roughness SΔa is 0.008 to 0.04.
(E) The three-dimensional surface roughness SRz is 0.6 to 1.5 μm.
(F) The heat shrinkage stress value in this direction of the film after the heat shrinkage of 10% in the maximum shrinkage direction is as follows: in a hot air with a temperature of 90 ° C. and a blowing speed of 5 m / sec, a test piece width of 20 mm and a chuck distance of 100 mm. When measured with, the maximum heat shrinkage stress value is 10 MPa or more.   The heat-shrinkable polyester film according to claim 1, wherein 0.02 to 0.5% by mass of lubricant particles having an average particle diameter of 0.01 to 4 µm is contained.   The polyester constituting the film is composed of 50 mol% or more of ethylene glycol, 15 to 27 mol% of neopentyl glycol or 1,4-cyclohexanedimethanol, propylene glycol, 1,4-butanediol and 100 mol% of the polyhydric alcohol component. The heat-shrinkable polyester film according to claim 1 or 2, which is obtained by using 3 to 15 mol% of one or more selected from the group consisting of 1,6-hexanediol. The heat according to any one of claims 1 to 3, wherein when the thickness displacement measurement in the maximum shrinkage direction of the film is performed on a test piece having a length of 50 cm and a width of 5 cm, the thickness distribution specified below is 6% or less. Shrinkable polyester film.
Thickness distribution = [(maximum thickness−minimum thickness) / average thickness] × 100 The heat-shrinkable polyester film according to any one of claims 1 to 4, wherein a melt specific resistance value at 275 ° C is 0.70 × 10 ⁸ Ω · cm or less.   A heat-shrinkable label using the heat-shrinkable polyester film according to claim 1.   A method for producing the heat-shrinkable polyester film according to any one of claims 1 to 5, wherein the film is stretched after subjecting the melt-extruded unstretched polyester film to a first-stage stretching treatment. A method for producing a heat-shrinkable polyester film, wherein the film is heat-set in a state of being tensioned in a direction, and further subjected to a second-stage stretching treatment to perform biaxial stretching or uniaxial stretching.   The draw ratio at the time of first-stage stretching is 4.4 to 6.0 times that of an unstretched film, and the tension ratio at the time of heat setting is 1 for the film after first-stage stretching. The production of the heat-shrinkable polyester film according to claim 7, wherein the stretch ratio in the second-stage stretching is 1.1 to 1.5 times that of the film after heat setting. Method.   The manufacturing method of the heat-shrinkable polyester film of Claim 7 or 8 which cools a film, applying tension | tensile_strength with the tension rate of 0.1 to 3% with respect to the film after the 2nd step | stretch of extending | stretching.