JP5125017B2 - Heat-shrinkable polyester film and method for producing the same - Google Patents

Description

  The present invention relates to a heat-shrinkable polyester film, and more particularly to a heat-shrinkable polyester film suitable for labeling applications such as PET bottles (polyethylene terephthalate (PET) bottles).

  As a heat-shrinkable film, particularly a heat-shrinkable film for labeling the body of a bottle, a film made of polyvinyl chloride, polystyrene or the like is mainly used. However, with regard to polyvinyl chloride, in recent years, the generation of chlorine-based gas at the time of incineration of discarded vinyl chloride products has become a problem. On the other hand, polystyrene has problems such as difficulty in printing on a polystyrene film. Furthermore, when collecting and recycling PET bottles, it is necessary to separate labels of resins such as polyvinyl chloride and polystyrene at the time of disposal. For this reason, polyester-based heat-shrinkable films that do not have these problems are attracting attention.

  A heat-shrinkable polyester film used as a bottle label is required to have perforation cutability and strength of an adhesive portion at the time of labeling in addition to general characteristics such as heat-shrinkability and tensile strength.

  The perforation cut property is required because a bottle perforation may be provided on the bottle label. When the product bottle is a beverage glass bottle, it is usually refrigerated. In this case, since label opening is performed at a low temperature, there is a problem that unsuccessful opening is likely to occur, and the demand for perforation cutability is high. In patent document 1, in order to improve perforation cut property, the temperature conditions at the time of extending | stretching are optimized in the manufacturing process of a heat-shrinkable polyester-type film. Although the perforation cutting property of the heat-shrinkable polyester film obtained by this method is somewhat improved, it is still insufficient.

  As a heat-shrinkable polyester film excellent in perforation cutability, Patent Document 2 discloses a heat-shrinkable polyester film having a predetermined hot water shrinkage ratio and breaking elongation. However, this heat-shrinkable polyester film is inferior in the strength of the adhesive part at the time of labeling, such as when the PET bottle falls when it is attached as a label, the adhesive part of the label peels off due to impact was there.

Therefore, in bottle label applications, heat-shrinkable polyester films are required to have excellent perforation cutting properties and the strength of adhesive portions during labeling.
JP 2003-268131 A JP-A-11-207818

  In view of the above circumstances, the problem to be solved by the present invention is to provide a heat-shrinkable polyester film excellent in perforation cutability and strength of an adhesive portion at the time of labeling.

  The heat-shrinkable polyester film of the present invention that has solved the above problems is a heat-shrinkable polyester film having a structure in which an X layer containing a polyester component M and a Y layer containing a polyester component N are alternately laminated. 1,3-dioxolane is coated slightly inside from one edge of one end of the film, the film is rolled up and the ends are overlapped to form a tube-shaped film label. When a plastic bottle is coated and heated at 80 ° C. for 2.5 seconds and then mounted, and when the 10 plastic bottles are dropped from a height of 1 m, all of the 10 plastic bottles have an X layer and a Y layer. It is characterized in that the film label is not damaged due to peeling between the films.

  In the heat-shrinkable polyester film of the present invention, the polyester component M contained in the X layer contains 70 to 99% by mass of polyester A and 1 to 30% by mass of polyester B, and the polyester component N contained in the Y layer contains polyester B70 to 70%. It is a preferable aspect that it contains 99 mass% and polyester A1-30 mass%. Further, it is preferable that the X layer and the Y layer have a structure in which 500 layers or more are alternately stacked.

  The heat-shrinkable polyester film of the present invention has a heat shrinkage ratio of 50% or more in the main shrinkage direction after being immersed in warm water at 95 ° C. ± 0.5 ° C. for 10 seconds, and a solvent adhesive strength of 2.0 N / 15 mm. These are heat-shrinkable polyester films having a tear propagation strength of 2.0 N or less, a breaking strength after immersion for 30 minutes in warm water of 60 ° C. ± 1 ° C. of 20 MPa or more, and a thickness of 5 to 100 μm. It is also expressed as

  The heat-shrinkable polyester film of the present invention is suitable for a bottle label, and a bottle label using the heat-shrinkable polyester film of the present invention is also included in the present invention.

  The heat-shrinkable polyester film of the present invention comprises a polyester component M containing 70 to 99% by mass of polyester A and 1 to 30% by mass of polyester B, and a polyester component N containing 70 to 99% by mass of polyester B and 1 to 30% by mass of polyester A. The melted polyester components M and N are put into separate extruders E and F, respectively, and molten polyester components M and N are put into a laminating apparatus to obtain a laminated body of polyester components X and Y. The laminated body is discharged from the laminating apparatus. The laminated body is guided from the laminating apparatus to a slit die so as to have a time from 45 seconds to 10 minutes until it adheres to the cooling roll, and is extruded onto a cooling film roll to obtain an unstretched sheet. It can manufacture by the method characterized by extending | stretching to the said, and the said method is also contained in this invention.

  According to the present invention, the heat-shrinkable polyester film has the general characteristics of heat-shrinkable polyester film such as heat-shrinkability and tensile strength, and is excellent in perforation cutting properties and the strength of the adhesive part at the time of labeling. Is provided. When the film of the present invention is a full bottle label, it is easy to peel off the label even at a low temperature, and causes a problem of label breakage when a beverage product in a PET bottle falls to the outlet in a vending machine. And can be suitably used as a bottle label.

  The present invention is a heat-shrinkable polyester film having a structure in which an X layer containing a polyester component M and a Y layer containing a polyester component N are alternately laminated, from one edge of one end of the film 1,3-Dioxolane is coated slightly inside, the film is rolled up and the ends are overlapped to form a tube-shaped film label. The film label is coated on a 500 mL plastic bottle and heated at 80 ° C. for 2.5 seconds. When 10 PET bottles are dropped from a height of 1 m, the film label is not damaged due to peeling between the X layer and the Y layer for all 10 PET bottles. This is a heat-shrinkable polyester film.

  The heat-shrinkable polyester film of the present invention has a structure in which X layers and Y layers are alternately laminated, and the X layer and Y layer are composed of different polyester components (polyester components M and N).

  The polyester components M and N can be selected to meet the object of the present invention in any combination as long as they have different thermal characteristics. It is preferable that the difference in glass transition temperature between the polyester components M and N is 3 ° C. or more and 100 ° C. or less, and the difference in heat of crystal fusion is 5 J / g or more and 100 J / g or less. The polyester component M is a crystalline polyester component having a glass transition temperature measured by DSC of −50 ° C. or more and less than 60 ° C. and a crystal melting heat of 5 J / g or more and 100 J / g or less. Is more preferably a substantially amorphous polyester component having a glass transition temperature of 60 ° C. or more and 150 ° C. or less and a heat of crystal fusion of 0 J / g or more and 3 J / g or less. The polyester components M and N as raw materials may be constituted by either a homopolymer or a copolymer, and may be a polyester composition containing two or more kinds of arbitrary polyesters.

  As a preferable combination of the polyester components M and N, the polyester component M includes 70 to 99 mass% of polyester A and 1 to 30 mass% of polyester B, and the polyester component N includes 70 to 99 mass% of polyester B and 1 to 30 mass% of polyester A. It is preferable to contain. Moreover, it is more preferable that the polyester component M contains 73-97 mass% of polyester A and 3-27 mass% of polyester B, and the polyester component N contains 73-97 mass% of polyester B and 3-27 mass% of polyester A. Furthermore, it is most preferable that the polyester component M contains 75-94 mass% of polyester A and 6-25 mass% of polyester B, and the polyester component N contains 75-94 mass% of polyester B and 6-25 mass% of polyester A.

  The polyester components M and N are preferably used in a mass ratio (polyester component M / N) of 97/3 to 3/97. If the mass ratio is outside this range, the layer structure becomes difficult to form, and a thermal shrinkage rate of 50% or more and a tear strength (tear propagation strength) of 2.0 N or less at 95 ° C. ± 0.5 ° C. at the same time. May be difficult to achieve.

  Furthermore, the polyester components M and N are more preferably used in a mass ratio (polyester component M / N) of 90/10 to 10/90, and 85/15 to 60/40 or 40/60 to 15/85. Most preferably, it is used in

  Here, as polyester A, for example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polypentamethylene terephthalate, polyhexamethylene terephthalate, polyethylene-2,6-naphthalate (PEN) ) And other crystalline polyesters can be used. Further, based on these, an acid component and / or a glycol component described later may be copolymerized with 10 mol% or less in 100 mol% of the acid component and / or glycol component. Furthermore, based on polyethylene terephthalate (PET), dimer acid is copolymerized to 10 mol% or less (PET-D), or polyethylene-2,6-naphthalate (PEN) is copolymerized to 10 mol% or less of isophthalic acid. It is also possible to use. More preferred are PBT, PTT and PET-D.

As polyester B, for example, terephthalic acid as the acid component, a polyester based consisting et Ji glycol as a glycol component, the acid component and / or glycol component 100 mol% 5 mol% or more, preferably 6 mol% or more 40 Those obtained by copolymerizing different dicarboxylic acid components and / or glycol components of less than mol% can be used. Specific monomer components include, for example, dicarboxylic acid components such as aromatic dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, and orthophthalic acid, and aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid. And alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid. Examples of the glycol component include aliphatic diols such as propanediol, butanediol, neopentylglycol, and hexanediol; alicyclic diols such as 1,4-cyclohexanedimethanol, and aromatic diols.

  Polyester B is preferably a polyester obtained by copolymerizing 7 mol% or more and 35 mol% or less of neopentyl glycol and / or 1,4-cyclohexanedimethanol based on a polyester composed of terephthalic acid as an acid component and diethylene glycol as a glycol component. It is.

  The heat-shrinkable polyester film of the present invention has a structure in which X layers and Y layers are alternately laminated. The number of X layers and Y layers to be laminated is 500 in total including the X layers and Y layers. It is preferable that it is above, More preferably, it is 1000-100,000, Most preferably, it is 2000-20,000. When the total of the X layer and the Y layer is 500 layers or more, the perforation cut property is particularly excellent.

  The outermost layer of the heat-shrinkable polyester film may be either the X layer or the Y layer.

  In order to measure the number of laminated films, the X-layer and the Y-layer are dyed separately, and then the film cross-section is observed by TEM. However, as the number of layers increases, it becomes difficult to visually count even if the magnification of the TEM image is increased. Therefore, in this case, as will be described in detail later, a method of obtaining the number of layers by clarifying the degree of shading of an image using image analysis software and then digitizing (binarizing) the image is adopted.

  For the X layer and Y layer, conventionally known additives, for example, organic particles (eg, crosslinked acrylic particles, crosslinked styrene particles, silicone particles, etc.), inorganic particles (eg, silica, kaolin, clay, carbonic acid) Calcium, aluminum oxide, barium sulfate, zinc oxide, zinc sulfide, etc.), lubricants, stabilizers, colorants, antioxidants, antifoaming agents, antistatic agents, ultraviolet absorbers, and the like.

  Further, the heat-shrinkable polyester film of the present invention is a tube-like film in which 1,3-dioxolane is applied slightly inside from one edge of one side of the film, the film is rolled up and the ends are overlapped. When a 10 mL PET bottle is dropped from a height of 1 m when the film label is coated on a 500 mL PET bottle and heated at 80 ° C. for 2.5 seconds and then mounted, all 10 PET bottles are labeled. The film label is not damaged due to peeling between the X layer and the Y layer.

Specifically, 1,3-dioxolane is applied in a width of 2 ± 1 mm slightly from the edge of one side of one end of the film using a tube forming apparatus (application amount: 3.0 ± 0.3 g / m). ² ). Immediately roll up the film and glue the ends together to create a tubular film label. The size of the tube-shaped film label may be any size as long as it can be attached to a 500 mL plastic bottle without wrinkles. As a measure of the size of the film label, the folding diameter is 109 mm and the label length is about 90 mm.

  Perforations according to the actual product form are provided on the label. For example, using a sewing machine blade, holes having a length of 0.2 to 2.0 mm are disposed at intervals of 0.2 to 1.0 mm along a direction perpendicular to the main contraction direction of the label, and extend over the entire length of the label. One or two perforations of length are provided.

  Subsequently, the film is coated on a 500 mL PET bottle (round shape, body diameter 62 mm, minimum neck diameter 25 mm), and a steam tunnel is used to pass the tube-shaped film label through a passage time of 2.5 seconds and a zone temperature of 80. Attach to a 500 mL PET bottle by heat shrinking at 0 ° C.

  When 10 PET bottles equipped with this label are prepared and dropped from a height of 1 m, the film label may not be damaged due to peeling between the X layer and the Y layer for all 10 bottles. Essential in the present invention. Such a film label that does not cause damage in the drop test does not cause a problem of damage to the label particularly when a beverage product in a plastic bottle is dropped at an outlet in a vending machine.

  Here, damage to the film label due to peeling between the X layer and the Y layer includes, as an example, that the label is peeled off due to delamination between the X layer and the Y layer, particularly in the solvent adhesion portion.

  The heat-shrinkable polyester film as described above has a heat shrinkage rate of 50% or more in the main shrinkage direction after being immersed in warm water of 95 ° C. ± 0.5 ° C. for 10 seconds, and a solvent adhesive strength of 2.0 N / It has a characteristic that it is 15 mm or more, the tear propagation strength is 2.0 N or less, and the breaking strength after immersion for 30 minutes in warm water of 60 ° C. ± 0.5 ° C. is 20 MPa or more. In this invention, it discovered that the subject which this invention tends to solve can be solved only by the heat-shrinkable polyester-type film which has such a characteristic.

(Heat shrinkage)
The heat-shrinkable polyester film of the present invention has a hot-water heat shrinkage rate of 50% or more in the maximum shrinkage direction when immersed in warm water at 95 ° C. ± 0.5 ° C. for 10 seconds in a no-load state. Has characteristics. If the heat shrinkage rate is less than 50%, the label may not be successfully attached to the container due to insufficient heat shrinkage force. The thermal contraction rate is preferably 55% or more, more preferably 60% or more. In particular, when the heat shrinkage rate is 60% or more, it is possible to attach the label very easily even on a difficult part such as a shoulder of a bottle. On the other hand, the upper limit of the heat shrinkage rate is 98% as a technical limit, but is preferably 90% or less, more preferably 85% or less. In particular, when the heat shrinkage rate is 85% or less, the occurrence of label jumping due to the excessively large shrinkage force of the label when the bottle is placed on the bottle for heat shrinkage is extremely suppressed.

  In addition, the heat-shrinkable polyester film of the present invention has a hot-water heat shrinkage rate of 10% or more and 50% in the main shrinkage direction when treated by immersing in hot water at 70 ° C. ± 0.5 ° C. for 10 seconds under no load. % Or less is preferable. When the heat shrinkage rate is less than 10%, the shrinkability is insufficient, and the shrinking process needs to be performed at a higher temperature. If the thermal shrinkage rate exceeds 50%, a label jumping phenomenon may occur when the bottle is placed on a bottle and heated and shrunk, because the shrinkage force of the label is too great.

  Here, the hot water heat shrinkage ratio is obtained by measuring the length of the film before and after the dipping treatment, and using the formula of (length before shrinkage−length after shrinkage) / length before shrinkage) × 100 (%). This is the required value. Moreover, the main shrinkage direction means a direction having a high hot water heat shrinkage rate in the longitudinal direction and the transverse direction.

  In addition, when measuring the heat shrinkage rate, the film is immersed in water at 25 ° C. ± 0.5 ° C. after being immersed in warm water at a predetermined temperature for a predetermined time so as not to give an excessive heat history to the film. So that the film cools.

  The heat-shrinkable polyester film of the present invention has a characteristic that the solvent adhesive strength is 2.0 N / 15 mm or more. The solvent adhesive strength is preferably 2.5 to 20 N / 15 mm, and preferably 2.8 to 10 N / 15 mm. Here, the solvent adhesive strength is a value determined as follows.

Apply 1,3-dioxolane with a width of 2 ± 1 mm slightly inside from the edge of one side of the film (coating amount: 3.0 ± 0.3 g / m ² ). They are bonded together and processed into a tube (processing speed: 10 mm / min). The tube is cut open so that the bonded portion is in the center, and a film-like test piece (n = 10) having a length of 100 mm and a width of 15 mm is cut out so that the bonded portion is in the center. This film-like test piece was set in a tensile tester (“STM-T” manufactured by Baldwin) with a distance between chucks set to 50 mm so that the solvent adhesion portion was positioned at the center of the chucks. A tensile test is performed under the conditions of ° C and a tensile speed of 200 mm / min, and the peel strength of the bonded portion is measured. This peel strength is the solvent adhesive strength.

  The heat-shrinkable polyester film of the present invention has a characteristic that the tear propagation strength is 2.0 N or less. The tear propagation strength is preferably 0.2 to 1.9N, and more preferably 0.5 to 1.8N.

Here, the tear propagation strength is a light load manufactured by Toyo Seiki Seisakusho Co., Ltd. based on JIS K7128-2 (1998). A value obtained by measurement using a tear tester.

  The heat-shrinkable polyester film of the present invention has a characteristic that the breaking strength after being immersed in warm water at 60 ° C. ± 1 ° C. for 30 minutes is 20 MPa or more. The breaking strength is preferably 30 to 200 MPa, and more preferably 40 to 150 MPa. Here, the breaking strength is a value obtained as follows.

  A film label having a folding diameter of 87.5 mm and a label length of 120 mm is placed on a 250 mL steel can (outer diameter 53 mm, height 133 mm) and immersed in hot water at 80 ° C. for 10 seconds to shrink-fit the label on the can ( About 5% shrinkage). The steel can with the label is immediately transferred into warm water of 60 ° C. ± 1 ° C. and immersed for 30 minutes. A sample is cut out from the label of the steel can, and the film before heat treatment according to JIS-K-7127 (1999) (test piece is type 2. However, distance between chucks: 20 mm, pulling speed: 200 mm / min) A tensile test is performed in a direction perpendicular to the maximum shrinkage direction. The test piece has a length of 100 mm (a direction orthogonal to the maximum shrinkage direction of the film) and a width of 15 mm. Test conditions are a distance between chucks of 20 mm, a temperature of 23 ° C., and a tensile speed of 200 mm / min. The strength when ruptured during the test is defined as the rupture strength.

The heat-shrinkable polyester film used in the present invention preferably has a melting specific resistance value at a temperature of 275 ° C. of 0.70 × 10 ⁸ Ω · cm or less. When such a film is used, as will be described in detail below, the uniformity of the film thickness can be improved, and the printability on the film and the workability when processing the film into a form that can be mounted on a container. (Stable workability) can be improved.

  That is, in the present invention, when the film melt-extruded from the extruder is cooled by a conductive cooling roll (such as a casting roll), an electrode is disposed between the extruder and the casting roll, and the film is interposed between the electrode and the casting roll. A voltage is applied (that is, electricity is applied to the film from the electrode), and the film is electrostatically adhered to the roll. When the melting specific resistance value is small, the adhesion (electrostatic adhesion) between the film and the roll can be enhanced. If the electrostatic adhesion to the roll is low, the thickness of the cast unstretched film becomes non-uniform, and in the stretched film obtained by stretching this unstretched film, the thickness non-uniformity is further expanded. If the electrostatic adhesion is sufficiently high, the stretched film can be made uniform in thickness.

  When the uniformity of the film thickness is increased, color misregistration can be prevented and printability can be improved when multicolor printing in which a plurality of colors are superimposed is applied to the film.

  In addition, when the uniformity of the film thickness is increased, it is easy to superimpose the bonded portions when processing the film into a tube or the like by solvent bonding. In addition, when multicolor printing is performed on the film, wrinkles can be prevented from easily entering the film, and the film can be prevented from meandering during traveling, thereby improving workability (stable workability).

  Further increasing the uniformity of the film thickness can prevent partial differences in winding hardness when the film is wound in a roll shape, causing looseness and wrinkles on the film, greatly impairing the appearance of the film. Can be prevented.

  If the melt specific resistance value is lowered to increase the electrostatic adhesion, not only the uniformity of the film thickness can be increased, but also the productivity of the film can be increased and the appearance of the film can be improved. That is, when the electrostatic adhesion is high, the stability of cooling and solidification of the film can be increased, and the casting speed (production speed) can be increased. Also, if electrostatic adhesion is high, cooling and solidification of the film will be incomplete, and air will enter locally between the roll and the film, preventing pinner bubbles (streaky defects) on the film surface. The film appearance can be enhanced.

The melting specific resistance value is preferably 0.65 × 10 ⁸ Ω · cm or less, more preferably 0.60 × 10 ⁸ Ω · cm or less.

  In order to control the melt specific resistance value within the above range, it is desirable to contain 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. It is not clear why the melting specific resistance value can be remarkably lowered by combining the alkaline earth metal compound and the phosphorus-containing compound. However, the inclusion of the phosphorus-containing compound can reduce the amount of foreign matter and charge carriers. It is estimated that the amount of can be increased.

The content of the alkaline earth metal compound in the film is, for example, 20 ppm (mass basis) or more, preferably 40 ppm (mass basis) or more, more preferably 50 ppm (mass basis), based on the alkaline earth metal atom M ^2. ) Or more, particularly 60 ppm (mass basis) or more. If the amount of the alkaline earth metal compound is too small, the melting specific resistance value cannot be lowered. Note that 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 adverse effects such as generation of foreign substances and coloring are increased. Therefore, the content of the alkaline earth metal compound is, for example, 400 ppm (mass basis) or less, preferably 350 ppm (mass basis) or less, more preferably 300 ppm (mass basis) or less, based on the alkaline earth metal atom M ^2. It is.

  The content of the phosphorus compound in the film is, for example, 5 ppm (mass basis) or more, preferably 20 ppm (mass basis) or more, more preferably 40 ppm (mass basis) or more, particularly 60 ppm (mass) based on the phosphorus atom P. Standard) or more. If the amount of the phosphorus compound is too small, the melting specific resistance cannot be lowered sufficiently, and the amount of foreign matter generated cannot be reduced. Even if the content of the phosphorus compound is increased too much, 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 physical properties of the film may be different from those planned. Therefore, the content of the phosphorus compound is, for example, 500 ppm (mass basis) or less, preferably 450 ppm (mass basis) or less, more preferably 400 ppm (mass basis) or less, particularly 350 ppm (mass basis), based on the phosphorus atom P. It is as follows.

When lowering the melt resistivity value of the film with an alkaline earth metal compound and a phosphorus compound, the mass ratio (M ² / P) between the alkaline earth metal atom M ² and the phosphorus atom P in the film is 1.2 or more ( Preferably it is 1.3 or more, more preferably 1.4 or more. By setting the mass ratio (M ² / P) to 1.2 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 increases or the film is colored. Therefore, the mass ratio (M ² / P) is 5.0 or less, preferably 4.5 or less, and more preferably 4.0 or less.

  In order to further reduce 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 by adding to the coexistence system of alkaline earth metal compounds and phosphorus-containing compounds, the melt resistivity can be significantly reduced. Can do. Although it is not clear about the reason, it is presumed that the melting specific resistance value is lowered by forming a complex of the alkali metal compound, the alkaline earth metal compound, and the phosphorus-containing compound.

The content of the alkali metal compound in the film is, for example, 0 ppm (mass basis) or more, preferably 5 ppm (mass basis) or more, more preferably 6 ppm (mass basis) or more, based on the alkali metal atom M ^1. 7 ppm (mass basis) or more. Even if the content of the alkali metal compound is excessively increased, the effect of reducing the melt specific resistance value is saturated, and further, the amount of foreign matter generated is increased. Therefore, the content of the alkali metal compound is, for example, 100 ppm (mass basis) or less, preferably 90 ppm (mass basis) or less, more preferably 80 ppm (mass basis) or less, based on the alkali metal atom M ¹ .

  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 compound 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 (alkyl esters). And aryl esters). Preferable phosphorus compounds include phosphoric acid, aliphatic esters of phosphoric acid (phosphoric acid alkyl esters, etc .; for example, phosphoric acid monomethyl ester, phosphoric acid monoethyl ester, phosphoric acid monobutyl ester, phosphoric acid mono C _1-6 Phosphoric acid tri-C ₁ such as alkyl ester, phosphoric acid dimethyl ester, phosphoric acid diethyl ester, phosphoric acid dibutyl ester, phosphoric acid diC _1-6 alkyl ester, phosphoric acid trimethyl ester, phosphoric acid triethyl ester, phosphoric acid tributyl ester _-6 alkyl esters, etc.), 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; for example, trimethyl phosphite, tributyl phosphite Mono-, di-, or tri-C _1-6 alkyl esters of phosphorous acid such as, alkyl phosphonic acids (C _1-6 alkyl phosphonic acids such as methyl phosphonic acid, ethyl phosphonic acid), alkyl phosphonic acid alkyl esters (methyl phosphonic acid) dimethyl, a C _1-6 mono- or di-C _1-6 alkyl esters of alkyl phosphonic acid such as ethylphosphonic acid dimethyl), aryl phosphonic acid alkyl ester (phenylphosphonic acid dimethyl, C _6-9 aryl such as phenyl phosphonic acid diethyl Examples include phosphonic acid mono- or di-C _1-6 alkyl esters), arylphosphonic acid aryl esters (such as C _6-9 arylphosphonic acid mono- or di-C _6-9 aryl esters such as phenylphosphonic acid diphenyl), and the like. . Particularly preferred phosphorus compounds include phosphoric acid and trialkyl phosphate (such as trimethyl phosphate). These phosphorus 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 alkaline earth 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 thickness of the heat-shrinkable polyester film of the present invention is preferably 5 to 100 μm, and more preferably 20 to 50 μm.

  The heat-shrinkable polyester film of the present invention can be labeled by a conventionally known method. As an example, a heat-shrinkable polyester film cut to a desired width is appropriately printed, and the right and left ends of the film are overlapped and bonded together by solvent adhesion or the like to produce a tube film. The tube film is cut into an appropriate length to obtain a tube-shaped label. Alternatively, one opening of this tubular label is joined to form a bag-like label.

  These labels are perforated by a conventional method, and then covered with a plastic bottle. The plastic bottle is placed on a belt conveyor or the like, and steam is blown into a contracting tunnel (steam tunnel) or hot air is blown. Pass the inside of the type of shrinking tunnel (hot air tunnel). The label is attached to a bottle container such as a plastic bottle by the thermal contraction of the label when passing through these tunnels.

  Next, the manufacturing method of the heat-shrinkable polyester film of the present invention will be described. Although there is no restriction | limiting in particular in the manufacturing method of the heat-shrinkable polyester film of this invention, For example, polyester component M containing 70-99 mass% of polyester A and 1-30 mass% of polyester B, and 70-99 mass% of polyester B, and polyester A1 Polyester component N containing ˜30% by mass is charged into separate extruders E and F, respectively, and melted polyester components M and N are charged into a laminating apparatus to obtain a laminate of polyester components M and N. The laminated body is guided from the laminating apparatus to a slit die so that the time from when the laminated body is discharged from the laminating apparatus until it is in close contact with the cooling roll is extruded from the laminating apparatus to the cooling roll, and an unstretched sheet is formed. And can be produced by a method of stretching the unstretched sheet at least uniaxially (one of the production lines It is shown in FIG. 1).

  More specifically, the polyester as a raw material is first dried using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer.

  A predetermined amount of polyester A and polyester B are mixed to prepare polyester component M and polyester component N. There is no restriction | limiting in particular as a mixing method of polyester, A chip blend method, a masterbatch method, etc. are employable. It is known that even when two or more kinds of polyester components are blended, there is a strong tendency to transesterify and copolymerize due to the heat history during melt extrusion.

  Polyester component M and polyester component N are charged into separate extruders E and F, respectively, and melted. The melting temperature is not particularly limited as long as it does not cause deterioration or deterioration for each resin. As one index, when the composition exhibits crystallinity, the melting point + (5 ° C. to 30 ° C.) is preferable, and when the composition exhibits amorphous property, the softening temperature + (20 ° C. to 150 ° C.) is preferable. .

  The melted polyester components M and N are guided to a laminating apparatus in a molten state, and a laminated body is formed. Examples of the laminating apparatus include a feed block, a multi-manifold die, and a static mixer. Of these, it is preferable to use a static mixer, and it is more preferable to use a combination of a feed block and a static mixer because stacking of several hundred layers can be easily achieved.

The static mixer in the present invention is adjacent to an element having a shape obtained by twisting and bending a horizontally long rectangular plate so that an angle (torsion angle) between its short sides is 45 degrees to 270 degrees. It is the in-pipe mixing device arranged alternately so that the short sides of the elements intersect. When the molten resin passes through one element, the resin is divided into two layers, and each resin layer is twisted in the direction opposite to the turning direction of the element. Further, when passing through the next element, the resin is divided and twisted in the same manner, and divided into four layers. Therefore, when the resin component M and the resin component N are laminated one by one and introduced into the static mixer, theoretically, if the short side of the first element is horizontal to the lamination surface, it passes through n elements. Then the 2 ⁿ layer, but the short side of the first element is 2 ^{n + 1} layer as long perpendicular to the laminated surface, in fact, the flow channel diameters and lengths, twist angles of the element, the torsional gradient, the discharge of the resin The amount may vary due to the influence of melting characteristics such as the viscosity and surface tension of each resin.

  The L / D (pipe length / pipe inner diameter) ratio of the elements of the static mixer is preferably in the range of 1.0 to 3.0, more preferably in the range of 1.4 to 2.0. If the L / D ratio is smaller than 1.0, the resin dividing efficiency is deteriorated, and if it exceeds 3.0, the residence time of the resin passing through the mixer becomes longer, which is not practical.

  The torsion angle of the static mixer element is 45 degrees or more. This is because if the twist angle is less than 45 degrees, the twist of the resin layer becomes insufficient. The twist angle is more preferably 90 degrees or more, and further preferably 135 degrees or more. The upper limit of the twist angle is preferably 315 degrees. If it exceeds 315 degrees, a uniform laminated structure cannot be obtained due to excessive twisting. The twist angle is preferably 270 degrees or less, and more preferably 215 degrees or less. Note that the fact that a uniform laminated structure cannot be obtained means that the laminated structure is disturbed, for example, the laminated layers are wavy.

  Further, when the side surface of the static mixer pipe is cut and developed in the resin traveling direction, the angle formed by the straight line following the joint between the pipe inner wall and the element and the resin traveling direction, that is, the torsional gradient of the element is 27 More than the degree is preferable. If this twist gradient is less than 27 degrees, the twisting effect of the resin layer is small, and the L / D ratio must be increased in order to give a sufficient twist to the resin, which is not practical. The twist gradient is more preferably 38 degrees or more, and further preferably 42 degrees or more. On the other hand, when the torsional gradient exceeds 65 degrees, the turbulent flow of the resin becomes violent and the laminated structure is disturbed. The twist gradient is more preferably 54 degrees or less, and further preferably 50 degrees or less.

  The preferred shape of the elements of the static mixer can be appropriately selected according to the discharge amount and melting characteristics of the resin, and a plurality of elements having different shapes corresponding to changes in the melting characteristics of the resin passing through the static mixer. Can also be used in combination. The most preferred elements have L / D = 1.5, a twist angle of 180 degrees, and a twist gradient of 46 degrees.

  The arrangement of the elements of the static mixer is preferably changed alternately so that the twisting directions of the elements are right turn, left turn, and right turn. This is because a uniform laminated structure can be obtained. It is also preferable to arrange adjacent elements so as to intersect at right angles in order to obtain a uniform laminated structure.

  The number of elements of the static mixer is preferably 4 or more, more preferably 6 or more, and still more preferably 8 or more. The film of the present invention has a laminated structure, and the number of layers is particularly preferably 500 or more as described later. When the number of elements is 8 or more, a laminated structure of 500 or more layers is ensured. Easy to obtain. On the other hand, if the number of elements becomes too large, the laminated structure tends to be disturbed. Therefore, the number of elements is preferably 24 or less, more preferably 18 or less, and even more preferably 14 or less. . For example, when the mass ratio of the polyester component is 8/2 (M / N), the number of elements is preferably 8 to 14, and more preferably 10 to 12.

  The structure of the static mixer described above is one typical example, the shape and arrangement are changed without departing from the object of the present invention, and another device is arranged before and after the static mixer and between the elements. Of course, it is possible. For example, two or more rows of static mixers smaller in diameter than the resin pipe may be arranged in parallel in the pipe. Another resin may be merged and laminated on the laminated resin obtained by laminating the resin component M and the resin component N through a static mixer.

  In addition, it is also possible to use a plurality of feed blocks and lead the laminated resin laminated in three or more layers to a static mixer to further increase the number of layers. In this case, the number of elements of the static mixer can be reduced by the number of layers in the feed block, but there is a unique effect of the film (improvement of perforation opening, etc.) caused by the lamination in the static mixer. In order to reduce the number, the number of stacked layers by the feed block is preferably within 100 layers.

  As the temperature of the laminating apparatus (static mixer or the like), when the composition exhibits crystallinity, the melting point + (5 ° C. to 30 ° C.), and when amorphous, the softening temperature + (20 ° C. to 150 ° C.). C.), and most preferably, it is set to the same temperature as the melting temperature.

  This laminated body is extruded from a slit die such as a T-die, and is brought into close contact with a cooling roll having a surface temperature of 10 to 40 ° C. to obtain an unstretched sheet. When extruding the laminated body from the slit die onto the cooling roll, the time from when the laminated body is discharged from the laminating apparatus (or the apparatus that performs the last laminating when multiple laminating apparatuses are used) until it comes into close contact with the cooling roll (For example, in FIG. 1, the time from when the laminate is discharged from the static mixer 4 to when the laminate is pushed out from the T die 5 and closely contacts the cooling roll 6) is 45 seconds to 10 minutes, preferably 1 to 8 Minutes, more preferably 1.5 to 5 minutes. By making the time from when the laminated body is discharged from the laminating apparatus until it is in close contact with the cooling roll within the above range, damage to the label film due to peeling between the X layer and the Y layer can be prevented, The strength of the label adhesion portion is ensured. In addition, that a laminated body closely_contact | adheres to a cooling roll means that a laminated body surface-contacts a cooling roll in the whole width direction. For example, when the electrostatic contact method is adopted, the laminated body extruded from the die first comes into contact with the cooling roll in a line in the entire width direction, but comes into surface contact with the rotation of the cooling roll. . The starting point of the surface contact appears as a line formed by continuously arranging the contact points between the cooling roll and the laminate in the width direction. Therefore, the moment when this line appears may be regarded as the time when the line is in close contact with the cooling roll.

  Examples of the method for adjusting the time from when the laminate is discharged from the laminate device to the close contact with the cooling roll include increasing the flow path from the laminate device to the slit die, and retaining the laminate in the path. A method is mentioned.

  Next, after preheating the obtained unstretched sheet as necessary at 50 to 120 ° C., preferably 60 to 100 ° C., it is 3.0 times or more by a tenter in the lateral direction (direction perpendicular to the extrusion direction), Preferably, it is stretched 3.5 times or more and 15 times or less. The stretching temperature is 60 ° C. or higher and 120 ° C. or lower, preferably 70 ° C. or higher and 100 ° C. or lower. It is not always necessary to perform longitudinal stretching before and after lateral stretching, but longitudinal stretching may be performed as necessary.

  Furthermore, it heat-processes at the temperature of 70-100 degreeC if needed, and obtains a heat-shrinkable polyester-type film. The said film is good also as a film roll by winding up in accordance with a conventional method.

  In addition, the stretching method is not limited to lateral uniaxial stretching with a tenter, but can be additionally stretched in the longitudinal direction and biaxially stretched. Such biaxial stretching may be performed by any of a sequential biaxial stretching method and a simultaneous biaxial stretching method, and may be re-stretched in the longitudinal direction or the transverse direction as necessary.

  In addition, when the film is stretched, if the fluctuation range of the surface temperature of the film is reduced (soaking), the film can be stretched and heat treated at the same temperature over the entire length of the film, and the thickness distribution value and heat shrinkage behavior are uniform. Can be

  The fluctuation range of the surface temperature is preferably such that the temperature at each point when the surface temperature of the film is measured at an arbitrary point is, for example, within the average temperature of the film ± 1 ° C. or less, and the average temperature ± 0.6 It is more preferable that the temperature is within a temperature.

  When stretching the film, some of these steps are used to stretch the film through various steps such as a preheating step before stretching, a stretching step, a heat treatment step after stretching, a relaxation treatment, and a re-stretching treatment step. In all, it is preferable to use equipment that can reduce (homogenize) the fluctuation range of the surface temperature of the film. In particular, in order to make the thickness distribution value uniform over the entire length of the film, the fluctuation range of the surface temperature of the film can be reduced in the preheating step and the stretching step (and in the heat treatment step after stretching if necessary). It is preferable to use equipment. In order to make the thermal contraction rate behavior uniform, it is preferable to use equipment that can reduce the fluctuation range of the surface temperature of the film in the stretching step.

Examples of the equipment that can reduce the fluctuation of the film surface temperature include, for example, equipment equipped with a wind speed control means (such as an inverter) for controlling the supply speed of hot air for heating the film, and stably heating the air. Examples include equipment equipped with heating means for preparing the hot air [heating means using low-pressure steam of 500 kPa or less (5 kgf / cm ² or less) as a heat source].

  In order to achieve the object of the present invention, the horizontal direction is practical as the main shrinkage direction. Therefore, the example of the film forming method in the case where the main shrinkage direction is the horizontal direction has been described above. Even when the shrinking direction is the longitudinal direction, a film can be formed in accordance with the operation of the above method except that the stretching direction in the above method is changed by 90 degrees.

  The heat-shrinkable polyester film thus obtained has the general characteristics of a heat-shrinkable polyester film such as heat-shrinkability and tensile strength, and has a perforation cut property and strength of an adhesive part at the time of labeling. And is suitable as a bottle label.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited to these Examples at all. First, the evaluation method of the film created in the Example and the comparative example is demonstrated.

(1) Heat shrinkage rate The film was cut into a 10 cm × 10 cm square and heat-shrinked by treatment for 10 seconds in warm water at 95 ° C. ± 0.5 ° C. or 70 ° C. ± 0.5 ° C. under no load. . The film was immediately immersed in water at 25 ° C. ± 0.5 ° C. for 10 seconds, then the vertical and horizontal dimensions of the film were measured, and the thermal shrinkage rate was determined according to the following formula (1). 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 (%) (1)

(2) Solvent adhesive strength 1,3-Dioxolane was applied in a width of 2 ± 1 mm from the edge of one surface of one end of the film in a width of 2 ± 1 mm (application amount: 3.0 ± 0.3 g / m ² ). Immediately after the film was rolled, the ends were superposed and bonded, and processed into a tube (processing speed: 10 mm / min). The tube was rolled up in a flattened state to form a roll.

  The tube-shaped sample cut out from the roll-shaped material was cut open so that the adhesion location was in the center, and used as a film-shaped sample. From this film-like sample, a film-like test piece (n = 10) having a length of 100 mm and a width of 15 mm was cut out, and this film-like test piece was set to a tensile tester (made by Baldwin, " STM-T ") is set so that the solvent adhesion part is located at the center of the chucks, a tensile test is performed at a temperature of 23 ° C and a tensile speed of 200 mm / min, and the peel strength of the adhesion part is measured. This was defined as solvent adhesive strength.

(3) Tear Propagation Strength Based on JIS K7128-2 (1998), a film preliminarily shrunk at 85 ° C. by 10% was cut into a length of 51 mm × width of 64 mm, and a light load tear tester manufactured by Toyo Seiki Seisakusho The value obtained was used as the tear propagation strength.

(4) Perforation cut test Three colors were printed on a heat-shrinkable film in advance with grass, gold, and white ink from Toyo Ink Mfg. Co., Ltd. A tube-shaped label was prepared by adhering both ends of the printed film with 1,3-dioxolane. The label size was a folding diameter of 109 mm and a label length of 90 mm.

The label was perforated in a direction perpendicular to the main shrinkage direction of the label. Two sheets of cardboard with a thickness of 1 mm are placed under the folded label, and a sewing machine blade (a blade with a total length of 100 mm with 1 mm pitch blades spaced at 1 mm intervals) is placed on a test sealer (made by Seibu Kikai Co., Ltd.). Attach, press the sewing machine blade to the label with a gauge pressure of 2 kg / cm ² , and put a perforation parallel to the label edge at a position 5 mm from the edge of the folded label. The label was provided with two perforations provided with holes of 1 mm in length at intervals of 1 mm over the entire length of the label, and the interval between the two perforations was 10 mm.

Using a steam tunnel (model: SH-1500-L) manufactured by Fuji Astec Inc., spraying steam with a steam pressure of 1 kg / cm ² (pressure gauge display: 98 kPa) at a passing temperature of 2.5 seconds and a zone temperature of 80 ° C. (display). The label was heat-shrinked and attached to a 500 mL PET bottle (round shape, trunk diameter 62 mm, minimum neck diameter 25 mm). At this time, a portion (shoulder portion) having a diameter of about 40 mm was set to one end of the label.

  After that, this bottle is filled with about 500 mL of water, refrigerated at 5 ° C. for 12 hours, tearing the perforation of the label on the bottle immediately after taking it out of the refrigerator with a fingertip, and tearing it off vertically to remove the label from the bottle The number of completed samples was counted and the ratio (%) to 50 samples was shown.

(5) Breaking at the time of dropping A plastic bottle that had been attached with the label under the condition (4) and refrigerated at 5 ° C. for 12 hours was free-dropped onto a glossy concrete surface with dust-proof coating from a height of 1 m. At this time, holding the PET bottle sideways and releasing it, the bottle dropped from its side surface onto the concrete surface. A test was performed on 10 PET bottles. If even one bonded part was removed, it was rated as x.

(6) Breaking strength A film label having a fold diameter of 87.5 mm and a label length of 120 mm is placed on a 250 mL steel can (outer diameter 53 mm, height 133 mm) and immersed in hot water at 80 ° C. for 10 seconds. The can was contracted and mounted (approximately 5% contraction). The steel can with the label attached was immediately transferred into warm water of 60 ° C. ± 1 ° C. and immersed for 30 minutes. A sample was cut out from the steel can label (the part without back attachment) and JIS-K-7127 (1999) (the test piece was type 2. However, the distance between chucks: 20 mm, the pulling speed: 200 mm / min) A tensile test was conducted in the direction orthogonal to the maximum shrinkage direction of the film before heat treatment. The test piece has a length of 100 mm (direction perpendicular to the maximum shrinkage direction of the film) and a width of 15 mm. Test conditions are a distance between chucks of 20 mm, a temperature of 23 ° C., and a tensile speed of 200 mm / min. The strength at the time of breaking during the test was defined as the breaking strength.

  The evaluation results of (1) to (6) are shown in Table 3.

(7) Thermal analysis of polyester component Thermal analysis of the polyester component was performed using a DSC apparatus (model: DSC220) manufactured by Seiko Denshi Kogyo Co., Ltd. Each 10 ± 1 mg of the chip synthesized in the synthesis example described later is used as a sample. This sample is heated at 300 ° C. for 2 minutes, immediately put in liquid nitrogen and rapidly cooled, and then the temperature is increased from −40 ° C. to 300 ° C. at a rate of 20 ° C. / The temperature was raised in minutes, and the heat flow rate curve (DSC curve) was measured. The intersection of tangent lines drawn before and after the endothermic start curve in the DSC curve was defined as the glass transition temperature (Tg). The temperature showing the maximum value of the endothermic peak in the DSC curve was defined as the melting temperature (Tm). The integrated value of the endothermic peak of the DSC curve was defined as the heat of fusion (Hm). The results are shown in Table 1.

(8-1) Number of layers inside film (part 1)
The number of layers inside the film was determined by observation using a transmission electron microscope. First, the film was embedded in an epoxy resin. As the epoxy resin used, a mixture of Luabeck 812, Luavec NMA (manufactured by Nacalai Tesque) and DMP30 (manufactured by TAAB) in a ratio of 100: 89: 3 was used. Next, after embedding the sample film in the above-described mixed resin, the sample film was left in an oven adjusted to a temperature of 60 ° C. for 16 hours to cure the resin and obtain an embedded block.

  The obtained embedding block was attached to an ultra cut N manufactured by Nissan Sangyo Co., Ltd., and an ultrathin section was prepared. First, trimming was performed using a glass knife until a cross section of a portion desired to be observed for the film appeared on the resin surface. Next, an ultrathin section was cut out using a diamond knife (Sumitomo Electric Sumiknife SK2045). The cut sections were collected on a mesh and then stained by standing in a ruthenium tetroxide vapor for 30 minutes at room temperature, followed by thin carbon deposition.

  The electron microscope observation was performed using JEM-2010 manufactured by JEOL under the condition of an acceleration voltage of 200 kV. The obtained image was recorded on an imaging plate (FDL UR-V manufactured by Fuji Photo Film). The signal recorded on the imaging plate is read out using digital luminography (Pixsys TEM manufactured by JEOL), recorded as digital image information on a Windows (registered trademark) personal computer, and confirmed from the difference in staining degree between the X and Y layers. Counted the number of layers to be played.

(8-2) Number of layers inside film (part 2)
The number of layers inside the film was determined by observation using a transmission electron microscope (TEM). First, the film was embedded in an epoxy resin. As the epoxy resin used, Luabeck 812, Luavec NMA (manufactured by Nacalai Tesque), and DMP30 (manufactured by TAAB) were mixed well at a ratio (mass) of 100: 89: 3, respectively. Next, after embedding the sample film in the above-described mixed resin, the sample film was left in an oven adjusted to a temperature of 60 ° C. for 16 hours to cure the resin and obtain an embedded block.

  The resin was cut with respect to the embedded block using a glass knife until the cross section of the film portion appeared on the block surface (surface exposure). The embedding block after the surface exposure was put in a vessel sealed with ruthenium chloride vapor for 3 days to carry out ruthenium staining. Ruthenium chloride vapor was replaced with fresh vapor every day.

  A number of ultrathin sections having a thickness of about 700 mm with a microtome were cut from the surface of the embedded block to about 1.5 μm from the surface of the embedded block. The ultra-thin slice with the clearest contrast was selected and subjected to carbon deposition to obtain a sample for TEM observation.

  The electron microscope observation was performed using JEM-2010 manufactured by JEOL Ltd. under the condition of an acceleration voltage of 200 kV. The obtained image was recorded on an imaging plate (“FDL UR-V” manufactured by Fuji Photo Film Co., Ltd.). The signal recorded on the imaging plate was read out using digital luminography (“Pixsys TEM” manufactured by JEOL Ltd.) and recorded as digital image information on a Windows (registered trademark) personal computer. The magnification was appropriately selected from 5000 to 20000 times.

  The image information was analyzed using image analysis software (Scion Image Alpha 4.0.3.2; manufactured by Scion Corporation). First, preliminary confirmation was performed before confirming the detailed number of layers. The preliminary confirmation was performed as follows.

1. The color density in the film thickness direction was quantified by a line profile. Specifically, the density of 100 pixels in width and 3000 pixels in length (the number of pixels can be changed arbitrarily) is read, and the curve is drawn with the horizontal axis as the pixel in the length direction and the vertical axis as the signal intensity (darkness). And graphed.

2. Since there are many peaks in the curve in the graph, for one peak, the number of pixels at the position where the maximum value exists and the number of pixels at the position where the minimum value exists are read, and the difference d (peak width) About half) was considered the thickness of the layer. About 30 peaks, d was calculated _| required and average value _dav was calculated.

3. The average value d _av was converted into nm units, and when the converted value was 100 nm or more, the number of layers was counted visually from the TEM image on the imaging plate. In the conversion, when the TEM image is 5000 times, one pixel is 5 nm, and when it is 20,000 times, one pixel is 1.25 nm.

4). When d _av (nm) after the above conversion was less than 100 nm, the following detailed layer number confirmation method was adopted to determine the number of layers.

A detailed method for confirming the number of layers was performed as follows.
1. About the said TEM observation image, the correction process with the noise and the unevenness of the shade of an image was performed. First, the image was captured using image analysis software (L Process ver. 1.96; manufactured by FUJIFILM Science Lab99) (FIG. 2). With the setting of the image selector tool set to 2 ⁿ , Fourier transform (FFT) was performed in the maximum image range (2048 × 2048 pixels, but can be arbitrarily specified) (FIG. 3). In FIG. 2, the center of the figure is determined, and the layer direction (stripe direction) is taken as the X axis, and the direction perpendicular to the direction is taken as the Y axis. In FIG. 3, the center of FIG. 2 and the center of FIG. 3 (zero pixel) are arranged so that the collection of white bright spots is along the Y-axis (in the figure, a horizontal line and a vertical line are visible, which is noise). In addition, the 5th pixel to the 1020th pixel on the Y axis were surrounded by a rectangle having a width of 200 pixels (from −100 pixel to + 100th pixel on the X axis). Similarly, the rectangle from the -5th pixel to the -1020th pixel was surrounded by a rectangle having a width of 200 pixels. The areas other than those enclosed are treated as noise. The numerical values of 5 to 1020 pixels and the width of 200 pixels are empirically derived values for removing noise. Only the enclosed part was subjected to inverse Fourier transform (IFFT), and the obtained image was saved in TIFF format (16 bits) (FIG. 4).

  2. The image after inverse Fourier transform was read into image analysis software (Scion Image Alpha 4.0.3.2; manufactured by Scion Corporation), and the density of the image was clarified by the Threshold function and changed to the BMP format (FIG. 5). (End of correction process)

  3. In this BMP format image, using the Profile Plot function, a line profile that is as long as possible (about 2000 to 2500 pixels) parallel to the Y axis is taken with a plot width of 1 pixel, so that the density of the film cross-sectional image is binarized. And saved in Plot Value format.

  4). This Plot Value format data was read into Microsoft Excel, and the average value (Av) of all the data for each pixel of the line parallel to the Y axis was obtained. Next, when the data of a certain pixel is larger than the average value (Av), the judgment value +1 is given to the pixel, and otherwise, the judgment value -1 is given to the pixel. When the judgment value of each pixel is plotted with respect to the pixel (horizontal axis), the obtained graph is a horizontal straight line connecting +1 and +1 (or -1 and -1), +1 and -1 (or vice versa). It became a line consisting of diagonal straight lines connecting The number of diagonal lines was determined as the number of layers.

The number of layers obtained by the above method may be smaller than the 2 ⁿ layer or 2 ^{n + 1} layer theoretically obtained from the number n of elements of the static mixer. The polyester resin component M constituting the X layer and the polyester resin component N constituting the Y layer have a different resin composition, but the transesterification occurs at the interface between adjacent layers during the lamination process, and the X layer and the Y layer. A polyester having the same composition may be formed in the vicinity of the interface. For example, if the number of layers is increased and the thickness of one layer is reduced to a level of several nanometers, it is identified that a part of the X layer and the Y layer are layers of the same polyester composition. It is considered to be smaller than the theoretical value when the confirmation method is adopted.

Synthesis Example 1 (Synthesis of polyester)
In an esterification reactor, 57036 parts by mass of terephthalic acid (TPA), 33244 parts by mass of ethylene glycol (EG), 15733 parts by mass of neopentyl glycol (NPG), 23.2 parts by mass of antimony trioxide (polymerization catalyst) , 5.0 parts by weight of sodium acetate (alkali metal compound) and 46.1 parts by weight of trimethyl phosphate (phosphorus compound), adjusted to 0.25 MPa, and stirred at a temperature of 220 to 240 ° C. for 120 minutes to form an ester The reaction was carried out. The reaction vessel was returned to normal pressure, and 3.0 parts by mass of cobalt acetate tetrahydrate and 124.1 parts by mass of magnesium acetate tetrahydrate (alkaline earth metal compound) were added. After stirring for 5 minutes, the pressure was reduced to 0.5 hPa over 75 minutes and the temperature was raised to 280 ° C. Stirring was continued until the melt viscosity reached 4500 poise at a temperature of 280 ° C. (about 70 minutes), and then discharged into water in the form of a strand. A polyester chip A was obtained by cutting the discharged material with a strand cutter. The intrinsic viscosity of the polyester chip A was 0.75 dl / g.

Synthesis Examples 2-4
Polyester raw material chips B to D having the chip compositions shown in Table 1 were obtained in the same manner as in Synthesis Example 1. In the table, PD is an abbreviation for 1,3-propanediol, CHDM is 1,4-cyclohexanedimethanol, BD is 1,4-butanediol, and DEG is diethylene glycol. The intrinsic viscosity of each polyester was 0.92 dl / g for chip B, 0.72 dl / g for chip C, and 1.20 dl / g for chip D.

  The intrinsic viscosity was precisely weighed with 0.1 g of a chip, dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane = 3/2 (mass ratio), and then measured with an Ostwald viscometer at 30 ± 0.1 ° C. . The intrinsic viscosity [η] is obtained by the following formula (Huggins formula).

Here, η _sp : specific viscosity, t ₀ : solvent dropping time using Ostwald viscometer, t: chip solution dropping time using Ostwald viscometer, and C: concentration of chip solution. In the actual measurement, the intrinsic viscosity was calculated by the following approximate equation where k = 0.375 in the Huggins equation.

Here, η _{r is the} relative viscosity.

Example 1
Each chip obtained in the above synthesis example was separately pre-dried, and as shown in Table 2, 80 kg of chip A and 20 kg of chip B were sufficiently mixed using a super mixer (manufactured by Kawada Seisakusho), and then the mixed pellet was extruded. I (uniaxial 60 mm φ, L / D = 25) was charged to the hopper of, melted at 275 ℃ ± 2 ℃. Similarly, after 5 kg of chip A and 20 kg of chip B are sufficiently mixed using a super mixer, melt at 255 ° C. ± 2 ° C. with an extruder II (a twin screw extruder, 22.5 mm × 2, L / D = 25). did.

  The resin melted by both extruders is led to a feed block of 265 ° C. ± 2 ° C. so that I / II = 8/2 (discharge mass ratio), and further a static mixer of 275 ° C. ± 2 ° C. (Noritake Company) And 12 elements, an inner diameter of 38.4 mm, L / D of one element = 1.5, a twist angle of a plate of one element of 180 degrees, and a twist gradient of 46 degrees). Subsequently, it led to a T-die at 275 ° C. ± 2 ° C. and melt extruded. The extruded resin was electrostatically adhered onto a cooling roll having a surface temperature of 20 ° C. ± 2 ° C. to obtain an unstretched sheet. Note that the time from when the resin laminate was discharged from the exit of the static mixer at the end of lamination to the close contact with the cooling roll was about 2 minutes. Further, the discharge amount of the extruders I and II was 40 kg per hour.

  The unstretched sheet was preheated in a tenter at 82 ° C. for 24 seconds, subsequently stretched 4.8 times at 77 ° C. in the transverse direction, and subsequently heat treated at 70 ° C. for 24 seconds to obtain a thickness of 45 μm. A heat-shrinkable polyester film was obtained.

  Here, in Example 1, the fluctuation range of the surface temperature of the film when the film was continuously produced was the average temperature ± 0.6 ° C. in the preheating process of the tenter, the average temperature ± 0.5 ° C. in the stretching process, and the heat treatment process. The average temperature was in the range of ± 0.5 ° C.

Examples 2-3
In Example 2, the chip A was changed to the chip C. In Example 3, the chip B was changed to the chip D, and the heat-shrinkability was the same as in Example 1 except that the preheating temperature during transverse stretching was changed to 79.degree. A polyester film was obtained.

Comparative Example 1
Polyester chip A and polyester chip B are charged into a single extruder I so that the resin ratio is A / B = 80/20 (mass ratio) and melted (temperature: 275 ° C. ± 2 ° C.), A heat-shrinkable polyester film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that an unstretched sheet was obtained by using a T-die temperature of 275 ° C. ± 2 ° C. without using a static mixer. .

  Table 1 shows the evaluation results of the films obtained in Examples 1 to 3 and Comparative Example 1. The number of layers in each example was determined by adopting the detailed method for confirming the number of layers in (8-2) above.

  The heat-shrinkable polyester film of the present invention is suitable for a bottle label.

It is the schematic which shows an example of the manufacturing line of the heat-shrinkable polyester film of this invention. It is the TEM photograph of the film taken in into image analysis software. FIG. 3 is an image after Fourier transform of FIG. 2. FIG. 4 is an image after the inverse Fourier transform of FIG. 3. It is an image after clarifying the shading of FIG.

Explanation of symbols

1 Extruder E
2 Extruder F
3 Feed block 4 Static mixer 5 T-die 6 Cooling roll

Claims (4)

A heat-shrinkable polyester film having a structure in which an X layer containing a polyester component M and a Y layer containing a polyester component N have a structure in which a total of 500 layers or more are alternately laminated,
The polyester component M contained in the X layer is 70 to 99% by mass of polyester A, which is polytrimethylene terephthalate or polybutylene terephthalate, based on a polyester composed of terephthalic acid as an acid component and ethylene glycol as a glycol component. 1-100 mass% of polyester B copolymerized with 5 mol% or more and less than 40 mol% of neopentyl glycol or 1,4-cyclohexanedimethanol in 100 mol%, and the polyester component N contained in the Y layer is the polyester 70 to 99% by mass of B and 1 to 30% by mass of the polyester A,
Tear propagation strength is 2.0 N or less,
The thermal shrinkage rate in the main shrinkage direction after being immersed in warm water of 95 ° C. ± 0.5 ° C. for 10 seconds is 50% or more,
1,3-dioxolane is coated slightly inside from one edge of one side of the film, the film is rolled up and the ends are overlapped to form a tubular film label,
Cover the 500 mL PET bottle with the film label and heat it at 80 ° C. for 2.5 seconds,
When the ten PET bottles are dropped from a height of 1 m, the film label is not damaged due to the peeling between the X layer and the Y layer for all the ten PET bottles. Shrinkable polyester film. Solvent adhesive strength is at 2.0 N / 15 mm or more, the breaking strength after immersion for 30 minutes in a 6 0 ° C. ± 1 ° C. warm water is not less than 20 MPa, according to claim 1 a thickness of 5~100μm Heat-shrinkable polyester film. A method for producing a heat-shrinkable polyester film according to claim 1 or 2,
The polyester component M and the polyester component N are respectively charged into separate extruders E and F and melted,
The molten polyester components M and N are charged into a laminating apparatus to obtain a laminate of an X layer containing the polyester component M and a Y layer containing the polyester component N ,
As the time until the laminate is brought into close contact with the cooling roll from being discharged from the stacking unit is 45 seconds to 10 minutes, lead to laminate from the laminating device slit die, undrawn extruded into cold 却Ro Lumpur Get the sheet,
A method for producing a heat-shrinkable polyester film, wherein the unstretched sheet is stretched at least uniaxially. Bottle label using a heat-shrinkable polyester film according to claim 1 or 2.