JP2005178396A - Method for manufacturing heat-shrinkable polyester film roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a heat-shrinkable polyester film roll from which a film for covering a container excellent in stable processability and printability can be cut out at a high yield. <P>SOLUTION: The heat-shrinkable polyester film roll is manufactured by mixing a plurality of raw material polyesters with different compositions, melt-extruding the mixture, cooling it by a roll and drawing it. It is important that a chip with a shape within ±20% to a polyester chip with the maximum amount of use is used; as a final hopper just before or just above an extruder, a funnel-shaped hopper with an angle of inclination of ≥65° and with a volume of 15-120 mass% of the amount of extrusion per hour of the extruder is used; the film is brought into electrostatically close contact with a cooling roll by applying an electric voltage; and the width of fluctuation of a temperature on the film surface is made within an average temperature ±1°C in a preheating process for a drawing process, the drawing process and a heat-treatment process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a heat-shrinkable polyester film, and more particularly to a method for producing a heat-shrinkable polyester film suitable for label applications.

  Heat-shrinkable plastic films are widely used for applications such as shrink wrapping, shrinkage labels, cap seals, etc. 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. in use.

  However, the polyvinyl chloride film has problems such as low heat resistance, generation of hydrogen chloride gas during incineration, and dioxin. On the other hand, since a polystyrene film is inferior in solvent resistance, an ink having a special composition must be used for printing. Further, when the polyvinyl chloride film or polystyrene film is used as a shrinkable label for a PET container (PET bottle or the like), there is a problem that the container and the label must be separated when the container is recycled.

  Since the polyester film does not have the above-mentioned problem, it is highly expected as a shrinkable label to replace the polyvinyl chloride film or the polystyrene film, and the use amount tends to increase as the use amount of the PET container increases.

  However, the heat-shrinkable polyester film is also required to be further improved in shrinkage characteristics. In particular, shrinkage spots and wrinkles are likely to occur when coating and shrinking containers such as PET bottles, polyethylene bottles, glass bottles, etc., so characters and designs printed on the film before shrinkage may be distorted after coating shrinkage. There is a demand from the user side to make as small as possible. Further, the shrinkage stress is small and the adhesion of the film to the container may be inferior. Furthermore, the heat-shrinkable polyester film may be inferior in shrinkage at a low temperature as compared with a heat-shrinkable polystyrene film or the like, and may be shrunk at a high temperature to obtain a necessary shrinkage amount. However, when shrinking at a high temperature, the bottle may be deformed or whitened.

  When a bottle is coated with a heat-shrinkable film, conventionally, after the heat-shrinkable film is printed (printing process), the film can be attached to a container [label (tubular label), tube, bag Etc.]. After these processed films are mounted on the bottles, they are placed on a belt conveyor or the like, passed through a heating tunnel (shrinking tunnel), and thermally contracted to adhere to the container. As the shrinking tunnel, there are used a steam tunnel in which steam is blown to cause heat shrinkage, a hot air tunnel in which hot air is blown to cause heat shrinkage, and the like.

  When a steam tunnel is used, heat transfer efficiency is superior to that when a hot-air tunnel is used, and uniform heat-shrinking is possible, so that a good shrink-finished appearance can be obtained. However, even when a steam tunnel is used, a heat-shrinkable polyester film may not have a satisfactory shrink finish compared to a polyvinyl chloride film or a polystyrene film.

  Furthermore, the hot air tunnel has a characteristic that temperature spots are more likely to occur during thermal contraction than when a steam tunnel is used. For this reason, when a polyester film, which is inferior in shrink finish to a polyvinyl chloride film or polystyrene film, is subjected to heat shrinkage, shrinkage whitening, shrinkage spots, wrinkles, distortion, etc. are likely to occur. It is a problem.

  Furthermore, the heat-shrinkable film is also required to be excellent in stable processability and printability. In order to improve stable processability and printability, it is conceivable to make the film thickness substantially uniform. If the film thickness is made substantially uniform, wrinkles can be prevented from entering the film, and meandering is likely to occur during film running, so that workability can be improved. Further, it is possible to prevent partial printing from being lost during film printing. That is, in the heat shrinkable film, it is important to increase the uniformity of the film thickness.

As a method for making the film thickness uniform, a method is known in which when a melt-extruded film is cooled by a casting roll, the film and the roll are electrostatically adhered. In order to bring the film into electrostatic contact with the roll, it is important how many charge carriers are present on the surface of the molten film immediately after extrusion before contacting the roll. In order to increase the number of charge carriers, it is effective to modify the polyester to lower its specific resistance, and great efforts have been made. For example, in Patent Document 1, a magnesium compound, a sodium or potassium compound, and a phosphorus compound are added at the time of polyethylene terephthalate (PET) production, the Mg atom concentration is 30 to 400 ppm, and the Na atom or K atom concentration is 3.0. It is disclosed that the specific resistance value of the PET film is lowered by setting the atomic number ratio (Mg / P) between Mg and P to 1.2 to 20 and ˜50 ppm. In this publication, a magnesium compound is further added when the esterification rate is 20 to 80%, and a sodium or potassium compound is added until the intrinsic viscosity reaches 0.2, and the esterification rate is 90% or more. By adding a phosphorus compound during the period from the time of progress until the intrinsic viscosity reaches 0.2, the formation of insoluble foreign matter is suppressed, and the quality of the film is improved.
Japanese Examined Patent Publication No. 3-54129

  Therefore, the method developed in the PET (Patent Document 1: Japanese Patent Publication No. 3-54129) is applied to a heat-shrinkable polyester film, and Mg or P is added to the heat-shrinkable film to improve the melt adhesion. It is conceivable to increase the stability of the film and the printability by increasing the uniformity of the film thickness. However, since PET and heat-shrinkable polyester film have different polymer raw materials and properties, even if the method developed in PET is applied as it is, its effectiveness is doubtful. That is, heat-shrinkable polyester films (for example, polyester films copolymerized with CHDM) have significantly different thermal properties (melting point, crystallization temperature, glass transition temperature, etc.) and lower heat resistance than PET. . Therefore, in heat-shrinkable polyester film, it is normal to think that adding an additive will greatly change the thermal properties and further reduce the heat resistance, and the film will be colored and the viscosity will decrease (molecular weight). In general, it is generally considered that the same problem occurs when an additive such as Mg or P is added in order to lower the melting specific resistance value.

  In addition, in a long heat-shrinkable polyester film (film roll or the like), a plurality of container covering films are cut out from a single roll, so that stable processability and printability are excellent over the entire film roll. This is very important. However, when a film roll is produced according to the method of Patent Document 1 (Japanese Patent Publication No. 3-54129), a portion where the uniformity of thickness is insufficient may occur, and there is a portion where stable workability and printability deteriorate. May occur. Therefore, it is required to further increase the film yield.

  The present invention has been made paying attention to the above-mentioned circumstances, and the purpose thereof is a heat-shrinkable polyester film roll capable of cutting out a container coating film excellent in stable processability and printability with a high yield. It is in the point of providing a manufacturing method.

The manufacturing method of the heat-shrinkable polyester film roll of the present invention that can achieve the above object is to mix a plurality of raw material polyesters having different compositions, melt-press them, cool with a roll, and then directly or once wound on the roll. After that, it is assumed that the film is drawn again and then stretched. And
The shape of the most used polyester chip and the other polyester chip is an elliptical column shape with an elliptical cross section, and other polyester chips have an average length (mm) and an average short diameter ( mm), as well as using an average tip length (mm) within a range of ± 20% of those of the most used polyester tips,
As a final hopper immediately before or just above the extruder, a funnel-shaped hopper having a side wall inclination angle of 65 ° or more and a capacity in the range of 15 to 120% by mass of the discharge amount per hour of the extruder, Supplying the raw material chips from this final hopper to an extruder;
When the film melt-extruded from the extruder is cooled with a conductive cooling roll, an electrode is disposed between the extruder and the casting roll, and a voltage is applied between the electrode and the casting roll to electrostatically roll the film. The film is characterized in that, in the preheating step, the stretching step, and the heat treatment step after stretching, the fluctuation range of the temperature of the film surface is within an average temperature ± 1 ° C.

  It should be noted that the ratio of the fine powder of the raw material polyester chip is controlled within 1% by mass, and that the electrode is provided with a contaminated surface retracting means and a non-contaminated surface supplying means. This is a preferred embodiment.

The heat-shrinkable polyester film roll obtained by the above production method is as follows: (1) The end of the film at the winding end in the steady region where the film physical properties are stable in the film flow direction, and the end of the winding start side The first sample cutout portion is provided within 2 m inside the start end, and the final cutout portion is provided within 2 m inside the end portion, and about 100 m from the first cutout portion. A sample cutout is provided for each sample, and the shape of the cut-out sample is a rectangular shape having a length of 20 cm in the maximum shrinkage direction and a width of 5 cm. When measured, the thickness distribution value represented by the following formula is 7% or less in the sample at each location.
Thickness distribution value = (maximum thickness−minimum thickness) / average thickness × 100
When the heat-shrinkable polyester film roll as described above is produced, a container covering film excellent in stable processability and printability can be cut out with a high yield.

  (2) Each sample cut into a 10 cm × 10 cm square shape from the cut-out portion specified in (1) above is dipped in hot water at 85 ° C. for 10 seconds and then dipped in water at 25 ° C. for 10 seconds. When the average value is obtained by measuring the heat shrinkage rate in the maximum shrinkage direction when pulled up, the measured value of the heat shrinkage rate of each sample can be within ± 3% of the average value. In this way, if the fluctuation of the heat shrinkage rate in one heat shrinkable film roll is reduced, the fluctuation of heat shrinkage of one container mounting body (label, bag, etc.) can be reduced. Defects can be reduced, and the defect rate of products can be drastically reduced.

The heat-shrinkable polyester film roll produced in the present invention is usually
The length is 1000-6000 m,
A sample cut into a 10 cm × 10 cm square shape is dipped in hot water at 85 ° C. for 10 seconds and then pulled up by dipping in water at 25 ° C. for 10 seconds and the heat shrinkage rate in the maximum shrinkage direction is 20% or more. And
The base unit is ethylene terephthalate, and further contains a 1,4-cyclohexanedimethanol component and / or a diol component having 3 to 6 carbon atoms as the second alcohol component,
The melting specific resistance value at a temperature of 275 ° C. is 0.70 × 10 ⁸ Ω · cm or less.

  In the present specification, the term “unstretched film” includes a film on which a tension necessary for film feeding is applied.

  According to the present invention, it is possible to increase the uniformity of thickness over the entire film wound in a roll shape (steady region), and to cut out a container coating film excellent in stable processability and printability with a high yield. Can do.

  The heat-shrinkable polyester film roll is obtained by winding a heat-shrinkable polyester film (hereinafter sometimes simply referred to as a film). The heat-shrinkable polyester film can be generally obtained as follows.

  (1) A polyester composed of a dicarboxylic acid component and a polyhydric alcohol component is melt-extruded from an extruder and cooled with a conductive cooling roll (such as a casting roll) to form a film (unstretched film).

  In the extrusion, the copolyester is extruded alone or a plurality of polyesters (copolyester, homopolyester, etc.) are mixed and extruded. For this reason, the film contains a second alcohol component that is different from a base unit (such as a crystalline unit such as polyethylene terephthalate) and a polyhydric alcohol component (such as an ethylene glycol component) that constitutes the base unit.

  (2) When a polyester film containing a second alcohol component is stretched, a heat-shrinkable polyester film can be obtained.

  The stretching is preferably uniaxial stretching, but may be biaxial stretching that extends in a direction different from the direction of the uniaxial stretching (main direction). The stretching direction (main direction) is not particularly limited, and may be a film flow direction or a direction perpendicular to the flow direction (hereinafter referred to as a width direction). Preferably, it extends | stretches in the width direction of a film from a viewpoint on production efficiency.

  The roll obtained from the heat-shrinkable polyester film is drawn out from the roll, printed, and cut into an appropriate shape to obtain a container covering film. This container covering film is processed into a form [label (tubular label), tube, bag] that can be attached to the container, and then this processed film is attached to the container, and heating means (steam tunnel, hot air) The container can be covered by heat-shrinking the film using a tunnel or the like.

  [Heat Shrinkage Rate] The heat-shrinkable polyester film produced in the present invention was pulled up by immersing a sample cut into a 10 cm × 10 cm square shape in 85 ° C. warm water for 10 seconds and immediately in 10 ° C. water at 10 ° C. The heat shrinkage rate in the maximum shrinkage direction when dipped for a second and pulled up is 20% or more. When the film has a heat shrinkage rate of less than 20%, the amount of heat shrinkage of the film is insufficient when the container is coated and shrunk, resulting in poor appearance. A more preferable heat shrinkage rate is 30% or more, and further preferably 40% or more. The upper limit of the heat shrinkage rate is preferably 80% (particularly 75%).

Here, the heat shrinkage rate in the maximum shrinkage direction means the heat shrinkage rate in the direction in which the sample has shrunk most, and the maximum shrinkage direction is the length of the square in the vertical direction or in the horizontal direction (or oblique direction). It is decided by. Further, the heat shrinkage rate (%) was 25 ° C. ± 0.5 after a sample of 10 cm × 10 cm was immersed in warm water at 85 ° C. ± 0.5 ° C. for 10 seconds under a no-load condition and then heat shrunk. It is a value obtained by measuring the length of the film in the vertical and horizontal directions (or diagonal directions) after being immersed in water at 0 ° C. for 10 seconds under no load, and according to the following formula.
Heat shrinkage rate = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)

  The means for setting the heat shrinkage ratio in the above range is not particularly limited. For example, a method of forming a film containing a suitable amount of the second alcohol component without stretching the film and stretching the unstretched film at a suitable magnification. Is mentioned.

  The second alcohol component may be a diol component or a trihydric or higher alcohol component. Diols forming the diol component include ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 2,2-diethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl- Alkylene glycols such as 1,5-pentanediol, 2-methyl-1,5-pentanediol, 1,9-nonanediol, 1,10-decanediol; cyclic alcohols such as 1,4-cyclohexanedimethanol; diethylene glycol; Ether glycols such as triethylene glycol, polyethylene glycol, polypropylene glycol, polyoxytetramethylene glycol, alkylene oxide adducts of bisphenol compounds or derivatives thereof; and dimer diols. Trivalent or higher alcohols include trimethylolpropane, glycerin, pentaerythritol and the like.

  The ratio of the second alcohol component is, for example, about 3 to 80 mol%, preferably about 5 to 75 mol%, more preferably about 10 to 70 mol% in 100 mol% of the polyhydric alcohol component.

  The preferred second alcohol component includes a cyclic alcohol component (1,4-cyclohexanedimethanol component), a diol component having about 3 to 6 carbon atoms (a propanediol component, a butanediol component, a hexanediol component, etc.), and the like. .

  If the cyclic alcohol component is used, the degree of amorphousness of the film can be increased, so that the thermal contraction rate can be further increased. Furthermore, shrinkage finish (suppression of shrinkage whitening, suppression of contraction spots, suppression of wrinkles, suppression of distortion, and / or suppression of vertical shrinkage, etc.) can also be improved. The coating film cut out from the heat-shrinkable film roll can be attached to the container by bonding with a solvent (tetrahydrofuran, 1,3-dioxolane, etc.) [label (tubular label), tube In many cases, a cyclic alcohol component (1,4-cyclohexanedimethanol component or the like) can be used to improve solvent adhesion.

  The ratio of the cyclic alcohol component is, for example, 5 mol% or more in 100 mol% of the polyhydric alcohol component.

  By the way, in the heat-shrinkable polyester film, when the film reaches a temperature at which the film is heated in the heat-shrinking process, the heat shrinkage rate is saturated depending on the composition of the polyester constituting the film, and the film is heated to a higher temperature. However, no further shrinkage may be obtained. Such a film has an advantage that it can be thermally shrunk at a relatively low temperature. However, when it is heat shrunk in the hot air tunnel or after being stored for a long time in an atmosphere of 30 ° C. or higher before heat shrinking, When contracted, the contraction whitening phenomenon tends to occur. The cause of this shrinkage whitening phenomenon is considered to be because the molecular chain of the polyester is partially crystallized, and the refractive index of light of the crystal part is different from that of the amorphous part.

  However, the present inventors can remarkably suppress the shrinkage whitening by setting the ratio of the cyclic alcohol component (1,4-cyclohexanedimethanol component, etc.) to 10 mol% or more in 100 mol% of the polyhydric alcohol component. I found out. Furthermore, shrinkage spots can be remarkably suppressed.

  The amount of the cyclic alcohol component (such as 1,4-cyclohexanedimethanol component) is more preferably 12 mol% or more, and further preferably 14 mol% or more.

  The amount of the cyclic alcohol component is desirably suppressed to 80 mol% or less in 100 mol% of the polyhydric alcohol component. If the cyclic alcohol component is too much, the shrinkage rate of the film becomes excessively high, and there is a risk of label displacement and pattern distortion in the heat shrinking process. Further, since the solvent resistance of the film is lowered, the film is whitened by an ink solvent (such as ethyl acetate) in the printing process, or the tear resistance of the film is lowered. Accordingly, the 1,4-cyclohexanedimethanol component is more preferably at most 70 mol%, further preferably at most 60 mol%, particularly preferably at most 30 mol%.

On the other hand, when a diol having 3 to 6 carbon atoms (C _3-6 diol) is contained, the glass transition temperature (Tg) of the polyester film can be lowered, and the low temperature shrinkability of the film can be enhanced. When C _3-6 diol is contained, the glass transition temperature (Tg) of the film can be adjusted to about 60 to 75 ° C., for example.

The proportion of the C _3-6 diol component is, for example, about 2 to 40 mol%, preferably about 3 to 35 mol%, and more preferably about 5 to 30 mol% in 100 mol% of the polyhydric alcohol component.

The cyclic alcohol (such as 1,4-cyclohexanedimethanol) and C _3-6 diol are desirably used in combination. When used in combination, the total amount of the cyclic alcohol component and the C _3-6 diol component is, for example, about 10 to 80 mol%, preferably about 15 to 70 mol%, more preferably about 100 mol% of the polyhydric alcohol component. It is about 20-60 mol%. The ratio of the C _3-6 diol component is, for example, about 2.5 to 150 mol, preferably about 4 to 120 mol, and more preferably about 7 to 100 mol, per 100 mol of the cyclic alcohol component.

  As described above, the polyhydric alcohol component other than the second alcohol component is an alcohol component (ethylene glycol or the like) constituting a crystalline unit (ethylene terephthalate unit or the like). The more the alcohol component for the crystalline unit, the higher the tear resistance, strength, heat resistance, etc. of the film.

  As dicarboxylic acids forming the dicarboxylic acid component of the film, various dicarboxylic acids can be used in addition to dicarboxylic acids (terephthalic acid, ester-forming derivatives thereof, etc.) forming the base unit (crystalline unit). Aromatic dicarboxylic acids, ester-forming derivatives thereof, various aliphatic dicarboxylic acids and the like can be used. Examples of the aromatic dicarboxylic acid include, in addition to the terephthalic acid, isophthalic acid, naphthalene-1,4- or -2,6-dicarboxylic acid, 5-sodium sulfoisophthalic acid, and the like. Examples of ester derivatives include derivatives such as dialkyl esters and diaryl esters. Examples of the aliphatic dicarboxylic acid include dimer acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, oxalic acid, and succinic acid.

The draw ratio (stretch ratio in the main direction) of the film can be appropriately selected according to the type and ratio of the second alcohol component, and is, for example, about 3.0 to 5.5 times, preferably 3.2 to 5 times. About 4 times, more preferably about 3.4 to 5.3 times. When the second alcohol component is a cyclic alcohol component (1,4-cyclohexanedimethanol component), a C _3-6 diol component, or a combination thereof, the draw ratio is, for example, 2.3. About 7.3 times, preferably about 2.5 to 6.0 times.

[Melting resistivity]
The heat-shrinkable polyester film produced in the present invention has a melting specific resistance value of 0.70 × 10 ⁸ Ω · cm or less at a temperature of 275 ° C. 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.

[Thickness distribution value in the maximum shrinkage direction]
It should be noted that, as described above, even if the specific resistance of the film is lowered to increase the uniformity of the film thickness, it is not sufficient. That is, when forming a film roll, since the said film is long (for example, about 300-6000m), there exists a possibility that the uniformity of thickness may fall depending on a measurement location.

  However, in the film roll obtained by the present invention, the film thickness is uniformized at a high level in the film flow direction. Therefore, according to the film roll obtained by the present invention, there is no possibility that the yield of the container covering film cut out from the film roll is lowered.

  Usually, a plurality of the same kind of container mounting bodies (final product labels, bags, etc.) are manufactured from one heat-shrinkable film roll. The difference in thickness becomes large, and a difference in rigidity (waist) occurs when the container is mounted on the container, which may increase the product defect rate due to a mounting error. However, according to the present invention, since the samples from each cut-out portion are excellent in uniformity, the product defect rate can be reduced and the yield can be increased.

  The film thickness does not necessarily need to be uniform at a high level over the entire region of the heat-shrinkable film wound around the film roll, and at least the film physical properties are stable to some extent in the film flow direction. What is necessary is just to be uniform at a high level in the steady region. That is, the heat-shrinkable film is manufactured by extruding a molten plastic to form a film, and then stretching, but until the film forming process and the stretching process are stabilized (until a steady state is reached), the film The physical properties of fluctuate greatly. Further, even after the film forming process and the stretching process reach a steady state, the physical properties of the film greatly vary when the film forming conditions and the stretching conditions are changed. The present invention does not equalize the thickness of the film obtained when the film-forming process or stretching process does not reach a steady state, but is obtained when the film-forming process or stretching process is operated in a steady state. In the obtained film, the film thickness is made more uniform than the conventional level.

  Note that the number of the steady regions (steady operation) is not particularly limited, and there may be only one place (including the case of one place over the whole film roll) per one film roll. May be present. The steady region may be evaluated, for example, by measuring the heat shrinkage rate of the film. In the steady region, the heat shrinkage rate is stable within a range of, for example, about 20% (preferably about 16%).

  The uniformity of the film thickness in the steady region is that the end of the film at the winding end side of the steady region is the starting end, the end of the winding start side is the end, and the first location is within 2 m inside the starting end. The sample cutout portion is provided, the final cutout portion is provided within 2 m inside the end, the sample cutout portion is provided about every 100 m from the first cutout portion, and the film thickness of the sample cut out from each portion Can be evaluated by measuring. “About every 100 m” means that the sample may be cut out at about 100 m ± 1 m (hereinafter the same).

The uniformity of the thickness can be determined based on the thickness distribution value represented by the following formula.
Thickness distribution value = (maximum thickness−minimum thickness) / average thickness × 100

  The maximum thickness, the minimum thickness, and the average thickness are measured by cutting a test piece from a roll so that the length in the maximum shrinkage direction is 20 cm and the width is 5 cm, and the thickness is displaced with respect to the maximum shrinkage direction using a contact-type thickness meter. Can be determined by measuring.

  And according to the film roll obtained by the present invention, when the displacement of the thickness in the maximum shrinkage direction is measured for the sample at each location cut out from each cut-out portion, the thickness distribution value represented by the above formula in the sample at each location Is 7% or less, preferably 6% or less, and more preferably 5% or less.

  In order for the sample at each location to have the predetermined thickness distribution value, it is not sufficient that the film forming process and the stretching process reach a steady state, and when the molten polyester is extruded and cooled with a cooling roll, It is necessary to stabilize the electrostatic adhesion of the film from the beginning to the end of film production. Therefore, in the present invention, an electrode having an electrode contaminated surface retracting means and an electrode non-contaminated surface supplying means is used as the electrode used for the cooling. That is, when electricity is applied from an electrode during film formation of molten polyester and the film is electrostatically adhered, the polyester contains a plurality of types of polymers (homopolymers, copolymerized polymers, etc.) and monomers. Since it often contains a molecular weight component, the low molecular weight component volatilizes during melt extrusion and gradually contaminates the electrode. For this reason, if the production of the film is continued, the contamination of the electrode gradually becomes severe, and sufficient electricity cannot be applied to the film, so that there is a possibility that the electrostatic adhesion of the film is lowered. However, in the present invention, by using the specific electrode, the electrode-contaminated surface can be retracted, and a non-contaminated surface can be supplied instead, and the electrode surface can be maintained in a fresh state with little contamination. Therefore, even if the production of the film is continued, there is no possibility that the electrostatic adhesiveness is lowered, and the sample at each location can have the predetermined thickness distribution.

Examples of the specific electrode include the following electrodes (1) to (3).
(1) A wire-like electrode that can face the film surface, and is provided with a wire feeding device (supplying device) and a storage device (retracting device) such as a wire winding device. Electrode having rotating means for rotating the cylindrical electrode such as a motor (in this case, the rotating means serves as both the supplying means and the retracting means) (3) A plurality of electrode units (wires) Electrode means, brush-like electrode units, etc.), with proximity means (supply means) for bringing each electrode unit close to the film independently, and means (retracting means) for keeping each electrode unit independently from the film Electrode When using the electrode (1) and the electrode (2), the wire electrode is fed out from the feeding device and the cylindrical electrode is rotated by the rotating means continuously. At best, it may be performed intermittently, but is preferably carried out continuously.

  The material of the electrode is not particularly limited, but it is preferable to use a tungsten electrode from the viewpoint of the stability of electrostatic adhesion and the strength of the electrode.

  When a wire electrode is used, the wire diameter is preferably in the range of about 0.15 to 0.35 mm from the viewpoint of the stability of electrostatic adhesion and the strength of the electrode.

  On the other hand, the cooling roll is not particularly limited as long as it has conductivity, but the surface is preferably coated with a metal, and the surface is particularly preferably chrome plated. Moreover, it is preferable that the surface temperature of the cooling roll is controlled in the range of 25 to 50 ° C.

  The applied voltage is, for example, 6.5 kV or more, preferably 7.5 kV or more, more preferably 8.5 kV or more, and usually 10 kV or less from the viewpoint of the stability of electrostatic adhesion.

  The current value is, for example, 3.0 mA or more, preferably 3.5 mA or more, more preferably 4.0 mA or more, and usually 5.0 mA or less.

  In order for the sample at each location to have the predetermined thickness distribution, (A) the polyester raw material during film production is homogenized together with the above method for stabilizing electrostatic adhesion from the beginning to the end of film production. It is desirable to employ a method, (B) a method for stabilizing a film forming step, and / or (C) a method for stabilizing a film stretching step.

(A) Method of homogenizing polyester raw material during film production In other words, in the present invention, when forming a polyester film as described above, a plurality of raw material polyesters having different compositions may be mixed (blended) and extruded. As the mixing and extrusion methods, specifically, the methods shown in the following (1) to (3) are often employed. (1) A plurality of polyesters (polyester chips) having different compositions are supplied continuously or intermittently to a plurality of hoppers for each polyester, and finally, a hopper just before or just above the extruder via a buffer hopper as necessary. (Final hopper) (2) Each polyester chip is mixed with this final hopper, and the mixed chip is quantitatively supplied to the extruder in accordance with the extrusion amount of the extruder to form a film.

  However, the material segregation (material uneven distribution) phenomenon that the composition of the mixed chips supplied from the final hopper to the extruder differs depending on whether the remaining amount of chips in the final hopper is large or small. The present inventors have found out. This phenomenon is likely to occur when the capacity and shape of the final hopper are inappropriate, particularly when various polyester chips have different shapes and specific gravity. As a result, the content of alkaline earth metal compound or phosphorus compound for improving electrostatic adhesion may vary during the production of the film, and the thickness distribution value may vary.

  As a method for obtaining a film with little variation in the content of alkaline earth metal compound or phosphorus compound, a method of suppressing raw material segregation (raw material uneven distribution) in the final hopper, for example, (1) matching the shape of each polyester chip A method, (2) a method of reducing finely powdered polyester chips, (3) a method of optimizing the shape of the final hopper, and (4) a method of optimizing the capacity of the final hopper.

(1) Method of matching the shape of each polyester chip When the shape of each polyester chip is matched, the raw material segregation can be reduced. In other words, if there is a difference in the size of the chips, when the mixed chips fall in the final hopper, small chips tend to fall first, so if the remaining amount of chips in the final hopper decreases, the ratio of large chips The segregation of raw materials appears. On the other hand, if the shape of each polyester chip is matched, it can prevent that a small chip | tip falls first and can reduce raw material segregation.

  Each polyester chip is usually formed in a molten state after polymerization in the form of a strand from the polymerization apparatus, immediately cooled with water, and then cut with a strand cutter. For this reason, the polyester chip usually has an elliptical column shape with an elliptical cross section. Therefore, when matching the shape of each polyester chip, it is desirable to match the average major axis (mm), average minor axis (mm), and average chip length (mm) of the cross-sectional ellipse of each polyester chip.

  Preferably, as other polyester chips to be mixed with the most used polyester chip (most polyester chip), the average major axis (mm) and average minor axis (mm) of the cross-sectional ellipse, and the average chip length (mm) Polyester chips having a range of ± 20% or less, preferably polyester chips having a range of ± 15% or less, are used with respect to those of the most polyester chips.

  The combination of the most polyester chips and other polyester chips is not particularly limited, but a copolymer polyester chip is used as the most polyester chip, and a homopolyester chip (polyethylene terephthalate chip, polybutylene terephthalate chip, etc.) is used as the other polyester chip. Is preferably used.

(2) Method of reducing finely powdered polyester chips Fine powder (fine powdered polyester chips) generated by scraping of raw material chips to be used promotes the occurrence of raw material segregation. Therefore, by reducing the ratio of the fine powders, Also, segregation of raw materials can be suppressed.

  The ratio of the fine powder in the polyester chip is preferably controlled within 1% by mass and more preferably within 0.5% by mass throughout the entire process until the raw material chip enters the extruder.

  As a method for reducing the fine powder, for example, a method for removing (classifying and removing) the fine powder generated in the process can be employed. For example, a method of passing a sieve at the time of chip formation by a strand cutter, a method of passing a cyclonic air filter when the raw material chips are fed by air, and the like can be adopted.

(3) Method of optimizing the shape of the final hopper For example, a method of using a funnel-shaped hopper as the final hopper and bringing its hypotenuse (side wall) closer to the vertical is mentioned. If the hypotenuse (side wall) is brought closer to the vertical, a large chip can be easily dropped like a small chip, and the upper end of the content descends while maintaining a horizontal plane, which is effective in reducing raw material segregation. is there.

  The inclination angle of the hypotenuse (side wall) is, for example, 65 ° or more, preferably 70 ° or more. Note that the inclination angle of the hypotenuse (side wall) is an angle between the funnel-like hypotenuse (side wall) and a horizontal line segment.

  When a plurality of hoppers (such as hoppers for supplying each chip) are used upstream of the final hopper, the inclination angle is preferably 65 ° or more, more preferably 70 ° or more in the plurality of hoppers.

(4) Method for optimizing the capacity of the final hopper When the mixed chips mixed in the final hopper are discharged from the final hopper to the extruder over time, segregation (uneven distribution) of the mixed chips may occur in the feed. is there.

  Therefore, if the existence time of the mixed chips in the hopper is shortened, that is, if the capacity of the hopper is reduced to such an extent that the mixed chips can be discharged in a relatively short time, the material segregation can be suppressed.

  The appropriate capacity of the hopper is, for example, in the range of 15 to 120% by mass of (discharge amount per hour of the extruder), preferably 20 to 100% by mass of (discharge amount per hour of the extruder). Within the range of.

  As a method of mixing two or more kinds of polyester chips having different compositions, a method of mixing while continuously feeding each raw material to the extruder with a hopper (final hopper) directly above the extruder is most preferable. In addition, a material whose chip size is controlled within the aforementioned range may be mixed in advance, and then supplied to the final hopper and the extruder via some intermediate (buffer) hoppers. When mixing multiple types of raw materials, use a method of mixing raw materials chips continuously while quantitatively supplying multiple types of raw materials into a hopper, or using a blender in advance. However, in the latter case, it is preferable to pay attention to the raw material chip size and the like so that the raw material segregation does not occur when the mixture is discharged.

(B) Method for Stabilizing Film Formation Step As a method for stabilizing the film formation step, a method for suppressing fluctuations in the discharge amount from an extruder, and a method for suppressing fluctuations in the rotation speed of a cooling roll (such as a casting roll). Etc.

  In order to suppress the discharge amount fluctuation, for example, it is preferable to stabilize the discharge amount in a range within ± 2% of the average discharge amount. In order to suppress the discharge amount fluctuation, for example, it is preferable to use a gear pump as the discharge means.

  In order to suppress the rotation speed fluctuation, for example, it is preferable to stabilize the rotation speed within a range of ± 2% of the average rotation speed. In order to suppress the rotational speed fluctuation, it is preferable to use, for example, means for controlling the rotation system of the roll drive system, for example, an inverter for controlling the rotational speed.

(C) Method for Stabilizing Film Stretching Process In order to impart heat shrinkability to the film, it is necessary to perform a stretching process on the unstretched film. When stabilizing the stretching process of the film, various devices for stabilization are applied to a general stretching method.

  First, the general stretching method will be described. The timing of the stretching process is not particularly limited. For example, after cooling with the cooling roll (casting roll or the like), the film is temporarily wound into a roll shape, and the film is drawn out from the roll. Alternatively, after the cooling, the film may be continuously stretched without being wound into a roll.

  The stretching direction (maximum shrinkage direction of the film) may be the transverse (width) direction of the film or the longitudinal direction (flow direction) of the film, but the stretching direction is the transverse (width) direction of the film. Since it is practical in terms of production efficiency, the following description will be made taking as an example a stretching method in which the stretching direction (maximum shrinkage direction) is the transverse direction. When the stretching direction (the maximum shrinkage direction of the film) is the film longitudinal (longitudinal) direction, the stretching may be performed according to a normal operation such as changing the stretching direction in the following method by 90 °.

  When extending | stretching to a horizontal direction, it can extend | stretch using conventional extending | stretching means, such as a tenter.

  The draw ratio is the degree described in the column of [Heat Shrinkage] (for example, about 2.3 to 7.3 times, preferably about 2.5 to 6.0 times).

  In addition, when extending | stretching to a horizontal direction, it is not limited only to the uniaxial extension to the horizontal direction by a tenter etc., You may perform the biaxial extension extended | stretched also to a vertical direction. The draw ratio in the longitudinal direction is not more than the draw ratio in the transverse direction, for example, about 1.0 to 4.0 times, preferably about 1.1 to 2.0 times. If the stretching ratio in the machine direction is too large, the heat shrinkage in the direction perpendicular to the maximum shrinkage when measured according to the method for measuring heat shrinkage is too large (for example, exceeds 10%), It is not preferable. The biaxial stretching timing is not particularly limited, and for example, either sequential biaxial stretching or simultaneous biaxial stretching may be used, and restretching may be performed as necessary. In addition, when performing sequential biaxial stretching, the stretching order is not particularly limited, and stretching may be performed in any order such as vertical and horizontal, horizontal and vertical, vertical and horizontal, and horizontal and vertical.

  After the stretching treatment, heat treatment is performed at a predetermined temperature in the range of 50 ° C. to 110 ° C. while stretching 0-15% or relaxing 0-15%, and if necessary, in the range of 40 ° C. to 100 ° C. It is desirable to perform a further heat treatment at a predetermined temperature.

  Prior to the stretching treatment, the film may be preheated.

  And when stabilizing the extending | stretching process of a film, various devices for stabilization are given with respect to the said general extending | stretching method. For example, (1) control of stretching temperature, (2) suppression of internal heat generation due to stretching, (3) control of preheating (preheating) conditions, (4) soaking of film surface temperature during stretching, etc. It is done.

(1) Control of stretching temperature When the stretching temperature is controlled, the stretching temperature is controlled so as not to become too high. If the stretching temperature is too high, the film thickness distribution value may become too large. If the stretching temperature is too high, the strength of the film may be insufficient when the obtained heat-shrinkable film is mounted on a container (such as a bottle) at high speed.

  The stretching temperature is desirably controlled to, for example, glass transition temperature (Tg) + 40 ° C. or lower (preferably Tg + 15 ° C. or lower).

  Although the relevance to the thickness distribution value is small, the stretching temperature is set to glass transition temperature (Tg) -20 ° C. or higher (preferably Tg-5 ° C. or higher), Tg + 40 ° C. or lower (preferably lower than Tg + 15 ° C.). Is desirable. If the stretching temperature is too low, the thermal shrinkage rate of the film may be insufficient, and further the transparency of the film may be reduced.

(2) Suppression of internal heat generation due to stretching If internal heat generation of the film accompanying stretching is suppressed, film temperature spots in the stretching direction (width direction, etc.) can be reduced, and the thickness of the stretched film (heat-shrinkable film) is uniform. Can increase the sex.

  In order to suppress the internal heat generation, it is desirable that the film is easily heated by appropriately controlling the heating conditions (for example, by increasing the supply speed of hot air). When there is an insufficiently heated portion, internal heat generation due to stretching orientation occurs. On the other hand, when the film is sufficiently heated, the molecular chain becomes slippery during stretching, so that internal heat generation hardly occurs.

The heating condition is expressed in terms of a heat transfer coefficient. For example, the heat transfer coefficient is 0.0038 J / cm ² · sec · ° C. (0.0009 calories / cm ² · sec · ° C.) or more, preferably 0.0046 to 0.00. It is about 0071 J / cm ² · sec · ° C. (0.0011 to 0.0017 calories / cm ² · sec · ° C.).

(3) Control of preheating (preheating) conditions When controlling preheating conditions, it is desirable to control so that a film may be heated gradually. When the film is gradually heated in the preheating step, the temperature distribution of the film can be made substantially uniform, so that the uniformity of the thickness of the stretched film (heat-shrinkable film) can be enhanced.

The heating condition is, for example, about 0.00544 J / cm ² · sec · ° C. (0.0013 calories / cm ² · sec · ° C.) or less in terms of heat transfer coefficient. Moreover, in preheating, it is preferable to heat until a film surface temperature becomes the temperature in the range of Tg + 0 degreeC-Tg + 60 degreeC, and it is preferable that the temperature of a hot air is about Tg + 10 degreeC-Tg + 90 degreeC.

  Examples of the method for achieving the heat transfer coefficient include a method of slowing the hot air supply rate.

(4) Soaking the film surface temperature during stretching When the film is stretched, if the fluctuation range of the surface temperature of the film is reduced (soaking), stretching or heat treatment is performed at the same temperature over the entire length of the film. The thickness distribution value and heat shrinkage behavior can be made uniform.

  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 ± 1 ° C. of the film, and the average temperature ± 0.5 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].

[Thickness distribution value in the film flow direction]
The maximum shrinkage direction substantially coincides with the stretching direction (main stretching direction) of the film, and the stretching direction (main stretching direction) may be the longitudinal direction (flow direction) of the film as described above, and the width It may be a direction. Therefore, the thickness distribution value in the maximum shrinkage direction may mean a thickness distribution value in the film flow direction, or may mean a thickness distribution value in the film width direction.

  When the thickness distribution value in the maximum shrinkage direction means the thickness distribution value in the width direction of the film, the thickness distribution value in the film flow direction can be defined separately from the thickness distribution value in the maximum shrinkage direction (width direction). In this case, the thickness distribution value is preferably as follows.

  When the end of the winding end of the film in the steady region where the film physical properties are stable in the flow direction of the film is the starting end and the end of the winding starting side is the end, the first position is within 2 m inside the starting end. Sample cut-out portions, a final cut-out portion within 2 m inside the end, a sample cut-out portion provided approximately every 100 m from the first cut-out portion, and the length of the film flowing direction from each cut-out portion When a sample having a length of 50 m and a width of 5 cm was cut out and the displacement of the thickness in the film flow direction was measured for each sample, the thickness distribution value represented by the above formula in each sample was preferably 10% or less, preferably Is 9% or less, more preferably 8% or less.

  If the thickness distribution value in the flow direction is reduced, it is possible to prevent wrinkles from entering the film when printing the film and when performing solvent bonding with a center seal or the like. In addition, when the film is printed and then processed into a form that can be attached to the container, fluctuations in the tension of the film can be prevented, and printing failure and breakage trouble can be prevented.

  As a method for uniformizing the thickness distribution value in the flow direction at each location, the same method as that for uniforming the thickness distribution value in the maximum shrinkage direction at each location described above, that is, a method for lowering the melt resistivity value, a specific method Examples thereof include a method using an electrode, a method for homogenizing a polyester raw material during film production (a method for reducing raw material segregation), a method for stabilizing a film forming step, and a method for stabilizing a film stretching step.

[Heat shrinkage fluctuation]
When the heat-shrinkable polyester film roll of the present invention has an end on the winding end side of the film in a steady region where the film physical properties are stable in the flow direction of the film, and an end on the winding start side as the end, A first sample cutout is provided within 2 m inside the starting end, a final cutout is provided within 2 m inside the end, and a sample cutout is provided approximately every 100 m from the first cutout. The maximum shrinkage direction when each sample cut into a 10 cm × 10 cm square shape from the cut-out portion was dipped in hot water at 85 ° C. for 10 seconds and then dipped in water at 25 ° C. for 10 seconds. When the average value of the heat shrinkage is measured (average heat shrinkage), the measured value of the heat shrinkage of each sample is within ± 3% of the average value (average heat shrinkage) (preferably Preferably, it is within the range of ± 2%.

  That is, the absolute value (| X−Yn |) of the difference between the heat shrinkage rate Yn (%) of each sample cut out from the cutout portion and the average heat shrinkage rate X (%) of all the samples is 3 (%) or less [ Preferably it is 2 (%) or less]. In other words, if both the difference between the maximum values Ymax and X of Yn and the difference between the minimum values Ymin and X are within ± 3% (or within ± 2%), the above requirement is satisfied.

  As described above, when the fluctuation of the heat shrinkage rate in one heat-shrinkable film roll is reduced, the heat shrinkage fluctuation of one container mounting body (label, bag, etc.) can be reduced. Defects can be reduced, and the product defect rate can be drastically reduced.

  The method for reducing the fluctuation of the thermal shrinkage rate between the samples is the same as the method for reducing the fluctuation of the thickness distribution value in the maximum shrinkage direction between the samples, that is, the method for lowering the melting specific resistance value, The method of using this electrode, the method of homogenizing the polyester raw material during film production (method of reducing raw material segregation), the method of stabilizing the film forming step, the method of stabilizing the film stretching step, and the like.

[Intrinsic viscosity]
As for the film roll manufactured by this invention, it is desirable that intrinsic viscosity is 0.66 dl / g or more. If the intrinsic viscosity of the heat-shrinkable film is too small, the molecular weight of the polyester constituting the film will be low, so the durability of the shrinkage stress during heat shrinkage will decrease, and defects such as shrinkage whitening and shrinkage spots will easily occur. It becomes inferior to shrink finish and appearance. Moreover, if the molecular weight of polyester falls, the mechanical strength and tear resistance of a film will be reduced.

  The intrinsic viscosity is preferably 0.67 dl / g or more, more preferably 0.68 dl / g or more. The intrinsic viscosity is usually about 1.30 dl / g.

  As a method for increasing the intrinsic viscosity of the film, for example, (1) a method of using a high molecular weight polyester as the polyester that is a raw material of the film (for example, the intrinsic viscosity is 0.7 dl / g or more, preferably 0.76 dl / g Above, more preferably a method using a polyester of 0.80 dl / g or more), (2) a method of suppressing thermal decomposition and hydrolysis when the polyester is extruded to form a film (for example, preliminary drying of the raw polyester) (3) A method of using a hydrolysis-resistant polyester as the polyester (for example, a polyester having an acid value of 25 eq / ton or less) (4) polyester containing an antioxidant (for example, 0.01 to 1) A scheme of amount% of content) are and the like.

[Heat shrinkage stress value]
The heat-shrinkable polyester film roll of the present invention preferably has a higher heat-shrinkage stress value (maximum heat-shrinkage stress value) in the maximum shrinkage direction. When the heat shrinkage stress value is high, the film (label or the like) can be prevented from loosening after the container is coated, and deterioration of tear resistance due to insufficient mechanical strength of the film can be prevented.

  The maximum heat shrinkage stress value of the heat shrinkable polyester film roll of the present invention is usually 3 MPa or more when a heat shrink test is performed in hot air at 90 ° C. under conditions of a test piece width of 20 mm and a distance between chucks of 100 mm. Preferably it is 3.5 MPa or more, More preferably, it is 4 MPa or more.

The maximum heat shrinkage stress value is measured as follows.
(1) From a heat-shrinkable film roll, a test piece having a length in the maximum shrinkage direction of 200 mm and a width of 20 mm is cut out. (2) A tensile tester equipped with a hot air heating furnace (for example, “Tensilon” manufactured by Toyo Seiki) In the heating furnace, hot air (wind speed = 5 m / sec) is supplied from each of the rear, left, and right directions, and the heating furnace is heated to 90 ° C. (3) Air blowing is stopped, and a test piece is placed in the heating furnace. set. The distance between chucks is set to 100 mm (constant). (4) Close the heating furnace door quickly and restart the air blowing as in (2) above to detect and measure the heat shrinkage stress. (5) Maximum value from the chart Is taken as the maximum heat shrinkage stress value (MPa)

  When the maximum heat shrinkage stress value is controlled within the predetermined range, it is effective to adjust the composition of the polyester film. For example, as the polyhydric alcohol component, the preferred second alcohol component described in the column of [Heat Shrinkage], that is, a cyclic alcohol component (1,4-cyclohexanedimethanol component), a diol having about 3 to 6 carbon atoms Components such as a propanediol component, a butanediol component, and a hexanediol component may be contained in the film. The ratio of these preferable second alcohol components may be as described in the column of [Heat Shrinkage].

  The polyester used in the present invention can be obtained by a melt polymerization method or other polymerization methods. Examples of the melt polymerization method include a method in which an oligomer obtained from a direct reaction between a dicarboxylic acid and a glycol is polycondensed (direct polymerization method), a dimethyl ester of dicarboxylic acid and a glycol are subjected to a transesterification reaction, and then the polymerization is performed. A condensation method (a transesterification method) or any other production method can be applied. The degree of polymerization of the polyester is preferably about 0.5 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.

  There is no particular limitation on the timing of addition of the above-mentioned compounds for reducing the specific resistance value (alkali metal compounds, alkaline earth metal compounds, phosphorus-containing compounds, etc.), and polymerization is performed before esterification, during esterification, and after completion of esterification. It may be at any stage during the polymerization until the start of the process and after the polymerization. It is preferably at any stage after the esterification step, more preferably from the end of 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.

  If necessary, fine particles such as silica, titanium dioxide, kaolin, calcium carbonate, etc. may be added to the film raw material, and antioxidants, ultraviolet absorbers, antistatic agents, coloring agents, antibacterial agents, etc. are added. You can also

  The heat-shrinkable polyester film can be produced according to a conventional method. Particularly in a heat-shrinkable polyester film, when the second alcohol component is prepared in a specific range, the preparation method includes a method of using a copolymerized polyester (copolyester) alone, a method of blending a plurality of polyesters [ For example, a method of blending a plurality of different homopolyesters; a method of blending a homopolyester (polyethylene terephthalate, etc.) and a copolymerized polyester; a method of blending a plurality of different copolyesters, etc.

  In the system in which the copolyester is used alone, a copolyester containing a polyhydric alcohol component (such as the second alcohol component) having a specific composition may be used. On the other hand, a method of blending a plurality of polyesters can be preferably adopted because the characteristics of the film can be easily changed only by changing the blend ratio and it can be used for industrial production of various types of films.

  Specifically, as a method for producing the film, the raw material polyester chips are dried using a dryer (such as a hopper dryer, paddle dryer, or vacuum dryer), and then formed into a film at a temperature of 200 to 300 ° C. using an extruder. The method of extruding is mentioned. Or the method of extruding an undried polyester raw material chip | tip into a film form similarly may be sufficient, removing a water | moisture content in a vent type extruder. For extrusion, various existing methods such as a T-die method and a tubular method can be employed. After extrusion, it is desirable to obtain an unstretched film by quenching with a cooling roll such as a casting roll.

  The thickness of the heat-shrinkable polyester film is not particularly limited. For example, when used for labeling, it is about 10 to 200 μm, preferably about 20 to 100 μm.

  The heat-shrinkable polyester film roll of the present invention is obtained by winding the heat-shrinkable polyester film on a winding core (core). The film wound around the film roll is preferably 200 mm or more in width and 300 m or more in length. The reason why the width is 200 mm or more is to increase the industrial utility value of the film roll. The length of 300 m or more is because the thickness distribution value over the entire length of the film tends to fluctuate as the winding length of the film becomes longer. The invention can increase the effectiveness.

  The width of the heat-shrinkable film wound around the roll is preferably 300 mm or more, more preferably 400 mm or more. Moreover, the length of the heat-shrinkable film wound around the roll is preferably 400 m or more, more preferably 500 m or more.

  The upper limit of the width of the film is not particularly limited, but is generally 1500 mm or less because of ease of handling. The upper limit of the length of the film is not particularly limited, but may be determined depending on the film thickness from the viewpoint of ease of handling. For example, when the film thickness is 45 μm, the film length is preferably 6000 m or less.

  As the winding core, a plastic core or a metal core can be usually used. The diameter of these cores is, for example, about 2 to 10 inches (for example, 3 inches, 6 inches, and 8 inches).

  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, the polyester used in an Example and a comparative example, the composition of the film obtained by the Example and the comparative example, and the measuring method of a physical property are as follows.

(1) Composition (i) Dicarboxylic acid component, polyhydric alcohol component Sample (chip or film) is mixed with chloroform D (manufactured by Yurisopp) and trifluoroacetic acid D1 (manufactured by Yurisop) at a ratio of 10: 1 (volume ratio). The sample solution was prepared by dissolving in the solvent, and the NMR of the proton in the sample solution was measured using NMR (“GEMINI-200”; manufactured by Varian) under the measurement conditions of a temperature of 23 ° C. and a total of 64 times. . Based on the peak intensity of protons measured by NMR measurement, the composition ratio of monomers constituting the sample was calculated.

(Ii) Metal component The contents of Na, Mg, and P contained in the sample (chip or film) were measured according to the following method.

[Na]
2 g of a sample was put in a platinum crucible and incinerated and decomposed at a temperature of 500 to 800 ° C., 5 ml of hydrochloric acid (concentration: 6 mol / L) was added and evaporated to dryness. The residue was dissolved in 10 ml of 1.2 mol / L hydrochloric acid, and the Na concentration was measured (calibration curve method) using an atomic absorption spectrometer [“AA-640-12”; manufactured by Shimadzu Corporation).

[Mg]
2 g of a sample was put in a platinum crucible and incinerated and decomposed at a temperature of 500 to 800 ° C., 5 ml of hydrochloric acid (concentration: 6 mol / L) was added and evaporated to dryness. The residue was dissolved in 10 ml of 1.2 mol / L hydrochloric acid, and the Mg concentration was measured (calibration curve method) using an ICP emission spectrometer [“ICPS-200”; manufactured by Shimadzu Corporation).

[P]
Using the sample, the phosphorus component in the sample was converted to normal phosphoric acid by any of the following methods (A) to (C). This orthophosphoric acid and molybdate were reacted in sulfuric acid (concentration: 1 mol / L) to obtain phosphomolybdic acid, and then reduced by adding hydrazine sulfate. The density | concentration of the produced heteropoly blue was calculated | required by measuring the light absorbency of 830 nm using the absorptiometer ["UV-150-02"; Shimadzu Corporation make] (calibration curve method).
(A) A sample and sodium carbonate are put into a platinum crucible and subjected to dry ashing decomposition.
(B) Wet decomposition in sulfuric acid / nitric acid / perchloric acid system (C) Wet decomposition in sulfuric acid / perchloric acid system

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

η _sp : Specific viscosity t ₀ : Dropping time of solvent using Ostwald viscometer t: Falling time of sample solution using Ostwald viscometer C: Concentration of sample solution.

  In the actual measurement, the intrinsic viscosity was calculated by the following approximate equation where k = 0.375 in the Huggins equation.

η _r : relative viscosity

(3) Residual amount of solid matter (foreign matter) 2 g of sample (chip or film) was dissolved in a mixed solution of phenol and tetrachloroethane [capacity 100 ml; phenol / tetrachloroethane = 3/2 (mass ratio)], By filtering with a membrane filter (pore size 0.1 μm) made of Teflon (registered trademark), solids were collected, and the solids remaining amount was evaluated based on the following criteria.
None: The foreign matter remaining on the membrane filter after filtration cannot be visually confirmed Micro: The foreign matter remaining locally on the membrane filter after filtration is found to be localized. Multi: The membrane filter after filtration When visually checking the relics remaining on the top, foreign matter is found on the entire filter surface.

(4) Melting specific resistance value A pair of electrode plates was inserted into a sample (chip or film) melted at a temperature of 275 ° C., and a voltage of 120 V was applied. The current was measured, and the melt specific resistance value (Si; unit Ω · cm) was determined based on the following formula.
Si (Ω · cm) = (A / I) × (V / io)
[In the formula, A represents the electrode area (cm ² ), I represents the interelectrode distance (cm), V represents the voltage (V), and io represents the current (A)]

(5) Castability A tungsten wire electrode is placed between the extruder T-die and the casting roll whose surface temperature is controlled at 30 ° C., and a voltage of 7 to 10 kV is applied between the electrode and the casting roll. did. After the resin was melt-extruded from the T-die at a temperature of 280 ° C., it was cooled by a casting roll to produce a film having a thickness of 180 μm (casting speed = 30 m / min). Pinner bubbles generated on the surface of the obtained film were visually observed and evaluated according to the following criteria.
○: No pinner bubble occurred △: Partial pinner bubble occurrence ×: Large pinner bubble occurrence

(6) Heat Shrinkage The film rolls obtained in the present experimental examples and comparative examples were operated in a steady state in the film forming process and the stretching process over the entire region from the beginning to the end of winding of the film. Therefore, the entire film corresponds to the steady region.

  Then, the first sample is cut out from the end of winding of the film (0 m from the end of winding), and the second and subsequent samples are cut out every about 100 m from the first cut out portion, and from the winding start portion (0 m from the start of winding) of the film. The final sample was cut out. The shape of each sample is a 10 cm × 10 cm square. Since the length of the film is 1000 m as will be described later, the number of samples is 11 in total.

Each sample was immersed in warm water of 85 ° C. ± 0.5 ° C. for 10 seconds under no load and thermally contracted, and then immersed in water of 25 ° C. ± 0.5 ° C. for 10 seconds. The length in the horizontal direction is measured and determined according to the following formula.
Heat shrinkage rate (%) = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)

  In Table 2 to be described later, the average value (X) is the average value of all the heat shrinkage rates of the 11 samples measured, the maximum value (Ymax) is the maximum value of the heat shrinkage rates of the 11 samples, and the minimum value (Ymin ) Shows the minimum heat shrinkage among the 11 samples, and also shows the difference from the average value.

(7) Tear resistance (breakage rate)
According to JIS K 7127, a tensile test is performed in a direction orthogonal to the maximum shrink direction of the film before heat shrink. The number of test pieces is 20. The test piece length is 200 mm, the distance between chucks is 100 mm, the test piece width is 15 mm, the temperature is 23 ° C., and the tensile speed is 200 mm / min. The number of test pieces fractured at an elongation of 5% or less is counted, and the percentage with respect to the total number of test pieces (20 pieces) is obtained to obtain the breaking rate (%).

(8) Maximum heat shrinkage stress value Using a tensile tester with a heating furnace (“Tensilon” manufactured by Toyo Seiki Co., Ltd.), a sample having a length of 200 mm in the maximum shrinkage direction and a width of 20 mm was cut out from the heat shrinkable film roll. Stop the air blowing in the heating furnace heated to 90 ° C in advance, attach the sample to the chuck at a position of 50 mm from each end of the sample so that the distance between chucks becomes 100 mm, and then quickly close the heating furnace door, The contraction stress detected by restarting the air flow (wind speed = 5 m / sec) from the three directions of the back, left, and right was measured, and the maximum value obtained from the chart was defined as the maximum heat contraction stress value (MPa).

(9) Thickness Distribution Value in Maximum Shrinkage Direction Sample 1 having a length of 20 cm and a width of 5 cm in the width direction of the film (corresponding to the maximum shrinkage direction in the following examples and comparative examples) was cut out from the film roll.

  When cutting out the sample 1, the first sample is cut out from the winding end portion (0 m from the winding end) of the film, and the second and subsequent samples are cut out from the first cutting portion about every 100 m, A sample at the final point is cut out from the winding start portion (0 m from the winding start) of the film. As will be described later, since the length of the film is 1000 m, the number of cutout portions of Sample 1 is 11 in total, and 10 pieces of Sample 1 were cut out for each cutout portion.

Measure the thickness in the longitudinal direction of the sample (ie, the maximum shrinkage direction) using a contact-type thickness meter [“KG60 / A”; manufactured by Anritsu Co., Ltd.] for each sample, and calculate the thickness distribution value based on the following formula: The average value was determined as the thickness distribution value at that location.
Thickness distribution = (maximum thickness−minimum thickness) / average thickness × 100

(10) Thickness distribution value in the flow direction In place of the sample 1, the thickness distribution value in the maximum shrinkage direction is measured except that the sample 2 having a length in the flow direction of the film of 20 cm and a width of 5 cm is cut out from the film roll. The same was done.

(11) Printing processability After drawing the film from the heat-shrinkable film roll and solidly printing grass-colored ink manufactured by Toyo Ink Co., Ltd., using a gravure plate with a lattice pattern (1 cm square lattice), printing was performed in the order of gold and white. The number of wrinkles generated when printing a 1000 m film was counted and evaluated according to the following criteria.
○: Less than 2 wrinkle occurrences (good printability)
Δ: 3 to 6 wrinkle occurrence locations ×: 7 or more wrinkle occurrence locations

(12) Shrinkage finishing property A film was drawn from a film roll, and this film was bonded with a solvent to produce a tube. In addition, about what could not be solvent-bonded, heat sealing was performed and the tube was manufactured. The tube was cut to produce a heat-shrinkable polyester film label. In addition, the tube-shaped label was created from the same film roll.

  Next, after attaching the label to a glass bottle having a capacity of 300 ml, the label was shrunk by passing through a hot air heat shrink tunnel of 160 ° C. (wind speed 10 m / sec) for 13 seconds. The degree of shrinkage whitening and shrinkage spots was judged visually, and the shrinkage finish was evaluated in five stages. Standards are 5: Best finish, 4: Good finish, 3: Shrinkage whiteness or slight shrinkage spots (within 2 places), 2: Shrinkage whitening or shrinkage spots (3-5 places), 1: Shrinkage whitening or As the number of shrinkage spots (6 or more), 4 or more was judged as acceptable, and 3 or less was judged as defective.

Evaluate the shrinkage finish for all labels obtained from the same film roll, count the number of acceptable level tubular labels and the number of defective level tubular labels, and shrinkage finish based on the following formula Evaluated.
Shrinkage finish = (number of defective tubular labels) ÷ (number of all tubular labels) × 100 (%)

Synthesis Example 1 (Synthesis of polyester)
An esterification can was charged with 57036 parts by mass of terephthalic acid (TPA), 35801 parts by mass of ethylene glycol (EG), and 15843 parts by mass of 1,4-cyclohexanedimethanol (CHDM), and the pressure was adjusted to 0.25 MPa. The esterification reaction was performed by stirring at a temperature of 220 to 240 ° C. for 120 minutes. The reaction vessel was returned to normal pressure, 6.34 parts by mass of cobalt acetate tetrahydrate (polymerization catalyst), 8 parts by mass of titanium tetrabutoxide (polymerization catalyst), and 132.39 parts by mass of magnesium acetate.4 water. After adding a salt (alkaline earth metal compound), 5.35 parts by mass of sodium acetate (alkali metal compound) and 61.5 parts by mass of trimethyl phosphate (phosphorus compound) and stirring at 240 ° C. for 10 minutes, 75 While reducing the pressure to 0.5 hPa over a period of time, the temperature was raised to 280 ° C. Stirring was continued until the melt viscosity became 7000 poise at a temperature of 280 ° C. (about 40 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.

Synthesis Examples 2-6
Polyester chips B to F shown in Table 1 were obtained in the same manner as in Synthesis Example 1.
Table 1 shows the composition and physical properties of each polyester chip.

In the table, the content of inorganic components (Na, Mg, P, Ti, Co, Sb) is indicated by the concentration of each atom (unit: ppm; mass basis). The origin of each inorganic component is as follows.
Na: Mainly derived from sodium acetate Mg: Mainly derived from magnesium acetate tetrahydrate P: Mainly derived from trimethyl phosphate Ti: Mainly derived from titanium tetrabutoxide Co: Mainly cobalt acetate, four water Sb derived from salt: mainly derived from antimony trioxide In the table, the meanings of the abbreviations are as follows.
TPA: terephthalic acid EG: ethylene glycol CHDM: 1,4-cyclohexanedimethanol BD: 1,4-butanediol DEG: diethylene glycol

Example 1
Each chip obtained in the above synthesis example was separately pre-dried. Chip A, chip D, and chip E were mixed in this hopper while supplying them separately separately to the hopper directly above the extruder using a quantitative screw feeder (chip A: 52 mass%, chip D: 38 mass) %, Chip E: 10% by mass). This mixed chip was melt-extruded at a temperature of 280 ° C. using an extruder and quenched with a casting roll (chrome plating roll) whose surface temperature was controlled at 30 ° C. ± 1 ° C. to obtain an unstretched film having a thickness of 180 μm. .

  At the time of the extrusion, a tungsten wire (diameter 0.25 mm) is disposed so as to face the extruded unsolidified film, and electricity is applied from the wire to the film (applied voltage 9.5 kV, current) The value was 4 mmA), and the film was electrostatically adhered to the casting roll. The wire was continuously supplied from one side at a speed of 1.8 m / hr and wound up on the other side.

  The hopper used above has a capacity of 150 kg of chips, and the discharge rate of the extruder is 450 kg per hour. The inclination angle of the hopper side wall is 70 °.

  This unstretched film was continuously stretched over 1000 m or more. For stretching, after preheating at 91 ° C. for 10 seconds, using a tenter, the film is stretched 4.0 times in the transverse direction at a temperature of 72 ° C., and then heat-treated at a temperature of 79 ° C. for 10 seconds, resulting in a thermal shrinkage of 45 μm in thickness. A conductive polyester film was obtained. The fluctuation range of the film surface temperature when the heat-shrinkable film is continuously produced 1000 m is the average temperature ± 0.8 ° C. in the preheating step, the average temperature ± 0.6 ° C. in the stretching step, and the average temperature ± 0.5 in the heat treatment step It was within the range of ° C. The obtained film was slit into a width of 400 mm and a length of 1000 m, and wound on a 3-inch paper tube to obtain a heat-shrinkable film roll. Table 2 shows the composition and physical property values of the obtained film roll.

Example 2
As a mixed chip, a chip consisting of chip A (71% by mass), chip D (4% by mass), and chip E (25% by mass) was used. After preheating the unstretched film at a temperature of 78 ° C. for 10 seconds, a tenter was used. A heat-shrinkable film roll was obtained in the same manner as in Example 1 except that the film was stretched 4.0 times in the transverse direction at a temperature of 73 ° C., and subsequently heat-treated at a temperature of 80 ° C. for 10 seconds. Table 2 shows the composition and physical property values of the obtained film roll.

Comparative Example 1
A heat-shrinkable film roll was obtained in the same manner as in Example 2 except that a chip consisting of chip B (71 mass%), chip D (4 mass%), and chip E (25 mass%) was used as the mixed chip. . Table 2 shows the composition and physical property values of the obtained film roll.

Comparative Example 2
A heat-shrinkable film roll was obtained in the same manner as in Example 2 except that a chip consisting of chip C (71 mass%), chip D (4 mass%), and chip E (25 mass%) was used as the mixed chip. . Table 2 shows the composition and physical property values of the obtained film roll.

Example 3
As a mixed chip, a chip consisting of chip A (10 mass%), chip D (64 mass%), and chip E (26 mass%) was used. After preheating the unstretched film at a temperature of 78 ° C. for 10 seconds, a tenter was used. A heat-shrinkable film roll was obtained in the same manner as in Example 2 except that the film was stretched 4.0 times in the transverse direction at a temperature of 73 ° C., and subsequently heat-treated at a temperature of 80 ° C. for 10 seconds. Table 2 shows the composition and physical property values of the obtained film roll.

Comparative Example 3
Each chip obtained in the above synthesis example was separately pre-dried. Chip F, chip D, and chip E were mixed in this hopper while supplying them separately to the hopper directly above the extruder using a quantitative screw feeder (chip F: 71 mass%, chip D: 4 mass). %, Chip E: 25% by mass). This mixed chip was melt-extruded at a temperature of 280 ° C. using an extruder and quenched with a casting roll to obtain an unstretched film having a thickness of 180 μm. The hopper used above has a capacity of 400 kg of chips, and the discharge amount of the extruder is 450 kg per hour. The inclination angle of the hopper side wall is 60 °.

  This unstretched film was continuously stretched over 1000 m or more. In stretching, after preheating at 78 ° C. for 10 seconds, using a tenter, the film is stretched 4.0 times in the transverse direction at a temperature of 73 ° C., followed by heat treatment at a temperature of 80 ° C. for 10 seconds, thereby heat shrinkage of 45 μm in thickness. A conductive polyester film was obtained. The fluctuation range of the film surface temperature when the heat-shrinkable film is continuously produced 1000 m is the average temperature ± 1.0 ° C. in the preheating step, the average temperature ± 2.5 ° C. in the stretching step, and the average temperature ± 2.0 in the heat treatment step. It was within the range of ° C. The obtained film was slit into a width of 400 mm and a length of 1000 m, and wound on a 3-inch paper tube to obtain a heat-shrinkable film roll. Table 2 shows the composition and physical property values of the obtained film roll.

Claims (3)

A method of manufacturing a heat-shrinkable polyester film roll in which a plurality of raw material polyester chips having different compositions are mixed and melt-extruded, cooled with a roll, directly or once wound on a roll and then drawn out again. There,
The shape of the most used polyester chip and the other polyester chip is an elliptical cylinder with an elliptical cross section, and other polyester chips have an average length (mm) and an average minor diameter ( mm), as well as using an average tip length (mm) within a range of ± 20% of those of the most used polyester tips,
As a final hopper immediately before or just above the extruder, a funnel-shaped hopper having a side wall inclination angle of 65 ° or more and a capacity in the range of 15 to 120% by mass of the discharge amount per hour of the extruder, Supplying the raw material chips from this final hopper to an extruder;
When the film melt-extruded from the extruder is cooled with a conductive cooling roll, an electrode is disposed between the extruder and the casting roll, and a voltage is applied between the electrode and the casting roll to electrostatically roll the film. And in the preheating step, the stretching step, and the heat treatment step after stretching, the fluctuation range of the temperature of the film surface is within an average temperature ± 1 ° C. A method for producing a polyester film roll.   The manufacturing method of the heat-shrinkable polyester film roll of Claim 1 which controls the ratio of the fine powder of a raw material polyester chip within 1 mass%.   The method for producing a heat-shrinkable polyester film roll according to claim 1 or 2, wherein the electrode comprises a contaminated surface retracting means and a non-contaminated surface supplying means.