Heat-shrinkable polyester film roll

Abstract

To provide a heat-shrinkable polyester film roll for solving the problem of a film roll comprising a wound thinned heat-shrinkable polyester-based film having a longitudinal direction as a main shrinkage direction, and reduced in wrinkle generation of a winding core part.SOLUTION: A heat-shrinkable polyester-based film roll for printing processing is a film roll which is obtained by winding around a paper tube, which is a heat-shrinkable polyester-based film having a longitudinal direction as a main shrinkage direction, and a shrinkage ratio in the film main shrinkage direction after treatment in 90°C warm water for 10 seconds of 40% or more, and satisfies with respect to the heat-shrinkable polyester-based film and the film roll, the following requirements (1)-(7): (1) a film wound length is 1,000 m or more and 30,000 m or less; (2) a film width is 50 mm or more and 1,500 mm or less; (3) a film thickness is 5 μm or more and 30 μm or less; (4) thickness unevenness in a film width direction full width in a film roll front layer part is 20% or less; (5) the paper tube has an inner diameter of 3 inches, i.e., 76.2 mm, a gap difference of the paper tube in the width direction after the film is removed from the film roll is 0.5 mm or less, and flat pressure resistance strength of the paper tube after the film is removed is 1,700 N / 100 mm or more; (6) an average value of winding hardness in the width direction in the film roll front layer part is 500 or more and 850 or less; and (7) a natural shrinkage ratio in the longitudinal direction after the film is kept for 28 days in an atmosphere at 40°C and a relative humidity of 85% is 2.0% or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a heat-shrinkable polyester film roll obtained by winding up a heat-shrinkable polyester film. More specifically, the present invention relates to a heat-shrinkable polyester film roll in which the main shrinkage direction is the longitudinal direction, the film roll has a good winding core with little wrinkles, and has little loss during printing or processing. [Background technology]

[0002] In recent years, stretched films (so-called heat-shrinkable films) made of polyvinyl chloride resins, polystyrene resins, polyester resins, etc., have been widely used for label packaging, cap seals, and integrated packaging that serve to protect glass bottles, PET bottles, etc. and display products. Among such heat-shrinkable films, polyvinyl chloride films have problems such as low heat resistance, generating hydrogen chloride gas when incinerated, and causing dioxins. In addition, polystyrene films have poor solvent resistance, require the use of ink with a special composition when printing, and must be incinerated at high temperatures, resulting in the problem of generating a large amount of black smoke accompanied by an unpleasant odor when incinerated. Therefore, polyester-based heat-shrinkable films, which are highly heat-resistant, easy to incinerate, and excellent in solvent resistance, have been widely used as shrink labels, and their usage tends to increase with the increase in the distribution volume of PET containers.

[0003] In addition, as a typical heat-shrinkable polyester film, those that shrink significantly with the width direction as the main shrinkage direction are widely used. When used as a label film for a bottle or a strip label for a lunch box, the film must be made into a ring and attached to the bottle or lunch box and then heat-shrunk in the circumferential direction. Therefore, when attaching a heat-shrinkable film that heat-shrinks in the width direction, a ring body must be formed so that the width direction of the film is the circumferential direction, and the ring body must be cut at a predetermined length and attached to the beverage bottle or lunch box by hand-covering or the like. Therefore, it is difficult to attach a beverage label film or strip label made of a heat-shrinkable film that heat-shrinks in the width direction to a bottle or lunch box at high speed. Therefore, recently, there has been a demand for a film that heat-shrinks in the longitudinal direction, which can be directly wrapped around a bottle or lunch box after being unwound from a film roll and attached. This eliminates the need for a center seal process of forming and sealing a film ring body, which is essential for a film that mainly shrinks in the width direction, and processing such as cutting and hand-covering, and allows for high-speed attachment.

[0004] On the other hand, heat-shrinkable labels are often ultimately discarded as waste, and so there is a demand for them to be made thinner to be environmentally conscious. However, thinner labels tend to lose their stiffness and become more difficult to handle. Generally, after film production, a wide master roll is produced, and then the master roll is slit to the desired width and wound into a roll of the desired length to produce a film roll product. The film is then subjected to a printing process in roll form to give it a design or to display products. After printing, the film is slit again to the required width and wound into a roll. When the handling property of the film is deteriorated, problems are revealed in the film roll after slitting as a product and when re-slitting or printing is performed and the film is wound up. Heat-shrinkable films are difficult to handle because they have a lower stiffness than other general-purpose films, and according to the study by the present inventors, problems are particularly likely to occur in heat-shrinkable polyester films having a film thickness of 30 μm or less. Furthermore, the production speed of films is increasing year by year, and the slitting speed is also increasing accordingly, so that films that are difficult to handle are more likely to have problems. Problems occur when printing or processing the film roll and when using it as a label due to the problems. In particular, when wrinkles occur in the core part of the film roll, problems occur at that position during printing or processing, resulting in a large loss.

[0005] Furthermore, in the case of heat-shrinkable films in which the longitudinal direction is the primary shrinkage direction, the phenomenon in which the dimensions of the film decrease over time (so-called natural shrinkage) is likely to occur in the longitudinal direction, and so the degree of defects due to natural shrinkage is greater than that of films in which the transverse direction is the primary shrinkage direction, and tight winding and air leakage are likely to occur during storage and transportation in film rolls, and wrinkles are particularly likely to occur at the core, resulting in large losses. If the tight winding is particularly severe, the paper tube that is the roll core may deform, making it impossible to install it on the shaft during printing or processing, and the entire roll may be lost. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2003-266525 A [Patent Document 2] Patent No. 3678220 [Patent Document 3] JP 2014-73688 A [Non-patent literature]

[0007] [Non-Patent Document 1] Technical Guide to Slitters and Rewinders, published by Processing Technology Research Institute, Inc., 1998 Summary of the Invention [Problem to be solved by the invention]

[0008] Many technical documents have been published so far regarding the slitting conditions for making film rolls with fewer wrinkles. The above-mentioned Non-Patent Document 1 describes the tension and control of the slitter that winds up the film roll. However, it does not describe the paper tube or the physical properties of the film. In the above Patent Document 1, as a condition for slitting with less wrinkles and sagging of the film roll, it is desired that the winding hardness in the width direction of the film roll is uniform. The purpose is to prevent wrinkles and sagging of the film roll due to air escape. However, wrinkles due to air escape have a large effect near the surface layer of the film roll, and the effect of air escape is small on the winding core side, which is a position close to the paper tube of the film roll, so wrinkles may occur even if the winding hardness in the width direction is uniform. The above-mentioned Patent Document 2 describes a heat-shrinkable polyester film roll that has little variation in heat shrinkability and solvent adhesion within the roll and has good thickness uniformity, but does not mention wrinkles in the film roll. The above-mentioned Patent Document 3 describes a heat-shrinkable polyester film roll that is good for processing such as printing even after long-term storage. However, the difference in winding hardness in the width direction is larger than that of Patent Document 1. In addition, there is no description about wrinkles on the core side.

[0009] An object of the present invention is to provide a heat-shrinkable polyester film roll which solves the problems associated with the conventional thin-walled heat-shrinkable polyester film having a main shrinkage direction in the longitudinal direction and which is wound up, and which is less prone to wrinkles at the core portion. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems and have completed the present invention.

[0011] 1. A heat-shrinkable polyester film roll comprising a heat-shrinkable polyester film whose main shrinkage direction is the longitudinal direction and whose shrinkage rate in the main shrinkage direction after treatment in 90°C hot water for 10 seconds is 40% or more, wound around a paper tube, said heat-shrinkable polyester film and said film roll being characterized in that the following requirements (1) to (7) are satisfied: (1) The length of the film roll is between 1,000 m and 30,000 m. (2) Film width: 50 mm or more and 1,500 mm or less (3) Film thickness is 5 μm or more and 30 μm or less (4) Thickness unevenness in the entire width of the film in the film roll surface area is 20% or less (5) The cardboard tube has an inner diameter of 3 inches, the gap difference in the width direction of the cardboard tube after removing the film from the film roll is 0.5 mm or less, and the flattening pressure resistance of the cardboard tube after removing the film is 1700 N / 100 mm or more. (6) The average winding hardness in the width direction at the surface layer of the film roll is 500 or more and 850 or less. (7) After the film is left in an atmosphere of 40°C and 85% relative humidity for 28 days, the natural shrinkage rate in the longitudinal direction is 2.0% or less. 2. A heat-shrinkable polyester film roll according to 1., in which the thickness unevenness across the entire width of the film in the transverse direction of each sample sampled at 1000 m intervals along the length of the film roll from the surface layer of the film roll is 20% or less for all samples. 3. The heat-shrinkable polyester film roll according to claim 1 or 2, wherein the thickness unevenness in the longitudinal direction of the film roll over a length of 30 m is 20% or less. 4. A heat-shrinkable polyester film roll according to any one of 1. to 3., wherein the heat-shrinkable polyester film has a static friction coefficient and a dynamic friction coefficient both outside and inside the roll of 0.1 or more and 0.8 or less. 5. The heat-shrinkable polyester film roll according to any one of 1. to 4., wherein the heat-shrinkable polyester film has a shrinkage stress in the main shrinkage direction of 4 MPa or more and 16 MPa or less. Effect of the Invention

[0012] The heat-shrinkable polyester film roll of the present invention has little wrinkles on the core, and therefore can be used satisfactorily with few problems in post-processing such as printing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [Heat-shrinkable polyester film constituting the heat-shrinkable polyester film roll] The polyester used in the heat-shrinkable polyester film constituting the heat-shrinkable polyester film roll of the present invention is a polyester mainly composed of ethylene terephthalate. That is, the polyester contains 50 mol% or more, preferably 60 mol% or more, of ethylene terephthalate relative to 100 mol% of all the constituent components of the polyester. Examples of dicarboxylic acid components other than terephthalic acid constituting the polyester of the present invention include aromatic dicarboxylic acids such as isophthalic acid, naphthalene dicarboxylic acid, orthophthalic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, and alicyclic dicarboxylic acids.

[0014] When an aliphatic dicarboxylic acid (such as adipic acid, sebacic acid, decanedicarboxylic acid, etc.) is contained, the content is preferably less than 3 mol %. Heat-shrinkable polyester films obtained using polyesters containing 3 mol % or more of these aliphatic dicarboxylic acids are not preferred because they have insufficient film stiffness and cause problems during slitting and post-processing.

[0015] It is also preferable not to contain trivalent or higher polyvalent carboxylic acids (for example, trimellitic acid, pyromellitic acid, and anhydrides thereof, etc.) Heat-shrinkable polyester films obtained using polyesters containing these polyvalent carboxylic acids are difficult to achieve the required high shrinkage ratio.

[0016] Examples of diol components other than ethylene glycol that constitute the polyester used in the present invention include aliphatic diols such as 1-3 propanediol, 1-4 butanediol, neopentyl glycol, and hexanediol, alicyclic diols such as 1,4-cyclohexanedimethanol, and aromatic diols such as bisphenol A.

[0017] The polyester used in the heat-shrinkable polyester film of the present invention is preferably a polyester whose glass transition point (Tg) is adjusted to 60 to 80°C by containing one or more of cyclic diols such as 1,4-cyclohexanedimethanol and diols having 3 to 6 carbon atoms (for example, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, hexanediol, etc.).

[0018] In addition, the polyester used in the heat-shrinkable polyester film of the present invention has a total content of one or more monomer components capable of becoming amorphous components in 100 mol % of polyhydric alcohol components or 100 mol % of polybasic carboxylic acid components in the entire polyester resin of preferably 14 mol % or more, more preferably 16 mol % or more, and particularly preferably 18 mol % or more. Examples of monomers capable of becoming amorphous components include neopentyl glycol, 1,4-cyclohexanedimethanol, isophthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,2-diethyl 1,3-propanediol, 2-n-butyl 2-ethyl 1,3-propanediol, 2,2-isopropyl 1,3-propanediol, 2,2-di-n-butyl 1,3-propanediol, 1,4-butanediol, and hexanediol. Among them, neopentyl glycol, 1,4-cyclohexanedimethanol, and isophthalic acid are preferably used.

[0019] The polyester used in the heat-shrinkable polyester film of the present invention preferably does not contain a diol having 8 or more carbon atoms (e.g., octanediol, etc.) or a polyhydric alcohol having a valence of 3 or more (e.g., trimethylolpropane, trimethylolethane, glycerin, diglycerin, etc.). A heat-shrinkable polyester film obtained by using a polyester containing such a diol or polyhydric alcohol is difficult to achieve a required high shrinkage ratio.

[0020] In addition, various additives such as waxes, antioxidants, antistatic agents, crystal nucleating agents, viscosity reducing agents, heat stabilizers, coloring pigments, coloring inhibitors, ultraviolet absorbers, etc. can be added to the resin forming the heat-shrinkable polyester film of the present invention as necessary. It is preferable to add fine particles as a lubricant to the resin forming the heat-shrinkable polyester film of the present invention to improve the workability (slipperiness) of the polyethylene terephthalate resin film. Any fine particles can be selected, and examples of inorganic fine particles include silica, alumina, titanium dioxide, calcium carbonate, kaolin, barium sulfate, etc. In addition, examples of organic fine particles include acrylic resin particles, melamine resin particles, silicone resin particles, crosslinked polystyrene particles, etc. The average particle diameter of the fine particles can be appropriately selected as necessary within the range of 0.05 to 3.0 μm (measured with a Coulter counter). The amount of fine particles added is within the range of 300 to 1200 ppm in the film, and good slipperiness (friction) and transparency can be achieved at the same time.

[0021] The method of blending the above particles into the resin forming the heat-shrinkable polyester film can be, for example, addition at any stage of the production of the polyester resin, but it is preferable to add the particles as a slurry dispersed in ethylene glycol or the like at the stage of esterification or after the completion of the transesterification reaction and before the start of the polycondensation reaction, and proceed with the polycondensation reaction. It is also preferable to blend a slurry of the particles dispersed in ethylene glycol or water or the like with the polyester resin raw material using a vented kneading extruder, or to blend dried particles with the polyester resin raw material using a kneading extruder.

[0022] Furthermore, the heat-shrinkable polyester film of the present invention may be subjected to corona treatment, coating treatment, flame treatment, or the like in order to improve the adhesiveness of the film surface.

[0023] The heat-shrinkable polyester film of the present invention also includes a laminated multi-layer polyester film having at least one polyester resin layer. When two or more polyester resin layers are laminated, the polyester resin layers may be polyesters of the same composition or different compositions. In addition, the layer that can be laminated as the other layer is not particularly limited as long as it is a thermoplastic resin layer, but is preferably a polystyrene resin layer in terms of cost and heat shrinkage properties.

[0024] Furthermore, when the heat-shrinkable polyester film of the present invention is treated in 90°C hot water for 10 seconds under no load, it is necessary that the heat shrinkage rate in the main shrinkage direction of the film (i.e., the hot water heat shrinkage rate at 90°C) calculated from the lengths before and after shrinkage using the following formula 1 is 40% or more. Heat shrinkage rate = {(length before shrinkage - length after shrinkage) / length before shrinkage} x 100 (%) Formula 1

[0025] If the hot water heat shrinkage rate in the main shrinkage direction at 90°C is less than 40%, the shrinkage amount is so small that wrinkles or insufficient shrinkage occurs in the label after heat shrinkage, which is not preferable as a heat shrinkable film.

[0026] The thickness of the heat-shrinkable polyester film of the present invention is preferably 5 μm or more and 30 μm or less. Since the thickness confirmed in the present invention was up to 5 μm, it is set to 5 μm or more. Although a thicker film has a firmer feel and tends to have fewer wrinkles at the winding core, this goes against the environmental friendliness of reducing the thickness. In the present invention, the upper limit of the film thickness is 30 μm. As described above, the present invention solves the problem of wrinkles at the winding core that are likely to occur especially in heat-shrinkable polyester film rolls with a film thickness of 30 μm or less.

[0027] In addition, the heat-shrinkable polyester film of the present invention preferably has a natural shrinkage rate of 2.0% or less in the main shrinkage direction after aging for 28 days (672 hours) in an environment at a temperature of 40°C and a relative humidity of 85%. In general, it is ideal to store heat-shrinkable film rolls in a low-temperature environment and transport them using a transportation method (such as a truck or ship) that can maintain a low temperature during transportation, but it is not realistic from a physical and economical perspective to treat all rolls in this way, and in some cases (due to seasonal influences, etc.), they are often placed in an environment of 40°C or higher. If the natural shrinkage rate exceeds 2.0%, natural shrinkage occurs in the longitudinal direction of the film during storage or transportation, that is, in the direction in which the winding becomes tighter, which is undesirable because it causes wrinkles in the winding core and distortion of the paper tube. More preferably, it is 1.5% or less, and even more preferably 1.0%. The ideal and lower limit of the natural shrinkage rate is 0.0%.

[0028] The heat-shrinkable polyester film of the present invention preferably has a maximum shrinkage stress in the main shrinkage direction of 2 MPa to 16 MPa as measured under hot air at 90° C. The shrinkage stress is measured by the method described in the examples. If the maximum shrinkage stress at 90°C in the main shrinkage direction exceeds 16 MPa, the paper tube is likely to become distorted when the film roll is stored or transported due to the natural shrinkage rate, and wrinkles are likely to occur in the core part. In the worse case, the paper tube may be crushed by the stress from the film, making processing impossible, resulting in product loss for the entire film roll. The maximum shrinkage stress at 90°C is more preferably 16 MPa or less, and even more preferably 14 MPa or less. Also, if the maximum shrinkage stress at 90°C is less than 2 MPa, it is not preferable because the label may become loose and not adhere to the container when used as a label, etc. The maximum shrinkage stress at 90°C is more preferably 3 MPa or more, and even more preferably 4 MPa or more.

[0029] In addition, the coefficient of static friction and the coefficient of dynamic friction between the film surfaces of the outer and inner surfaces of the heat-shrinkable polyester film of the present invention are preferably 0.1 to 0.8. If it is lower than 0.1, there is a possibility that the end surfaces may slip too much and cause misalignment. If it is higher than 0.8, the amount of air entrained during slitting increases, and the film is prone to slackness and wrinkles due to air loss during film rolling, which is undesirable. It is preferably 0.13 to 0.77, more preferably 0.16 to 0.74.

[0030] [Characteristics of heat-shrinkable polyester film roll] In addition, the length of the heat-shrinkable polyester film roll of the present invention or the film wound up on the heat-shrinkable multilayer polyester film roll is preferably 1000 m or more and 30000 m or less. In processing such as printing, the longer the winding length, the less frequently the roll needs to be replaced and the better the work efficiency. It is preferably 2000 m or more, and more preferably 3000 m or more. There is no particular upper limit, and the longer the winding length, the more preferable it is, but since the inventors have only confirmed a winding length up to 30000 m, the winding length of 30000 m is set as the upper limit.

[0031] The width of the heat-shrinkable polyester film roll of the present invention is preferably 50 mm or more and 1500 mm or less. There is no particular upper limit, and a longer film roll width is preferable because there is less loss in the printing process, but the inventors have only confirmed a width up to 1500 mm, so the upper limit is set to 1500 mm. As described above, a wider film roll is more efficient in processing such as printing, so the wider the film roll, the more preferable it is. The preferred width is 100 mm or more, and more preferably 300 mm or more.

[0032] In addition, the thickness unevenness in the width direction of the film at the surface layer portion of the heat-shrinkable polyester film roll of the present invention is 20% or less as expressed by the following formula 2. Poor thickness unevenness in the width direction is undesirable because wrinkles are likely to occur during slitting. It is preferably 18% or less, and more preferably 15% or less. The smaller the thickness unevenness value, the better. In the present invention, the "surface layer of the film roll" or the "surface portion of the film roll" refers to a portion obtained by removing 1 m of the film from the surface of the film roll. {(maximum thickness – minimum thickness) ÷ average thickness} × 100 (%) Formula 2

[0033] In addition, the thickness unevenness in the longitudinal direction of the heat-shrinkable polyester film roll of the present invention is 20% or less as expressed by the following formula 2. If the thickness unevenness in the longitudinal direction is poor, the tension during slitting is unstable and wrinkles are likely to occur, which is not preferable. It is preferably 18% or less, and more preferably 15% or less. The smaller the thickness unevenness value, the more preferable it is.

[0034] In addition, the heat-shrinkable polyester film roll of the present invention preferably has a gap difference in the width direction of the paper tube after the film is removed from the film roll of 0.5 mm or less. When the film is stored after being wound around the paper tube, the paper tube is deformed (distorted) due to distortion of the film or natural shrinkage. In this case, if the distortion difference of the paper tube in the width direction (gap difference in the width direction) is large, wrinkles will occur on the winding core side of the film roll, which is not preferable. Therefore, the gap difference in the paper tube after the film is removed from the film roll is preferably 0.4 mm or less, more preferably 0.3 mm or less. The gap difference in the width direction of the paper tube can be measured by the method described in the Examples below.

[0035] The core around which the film is wound can be a paper core, a plastic core, a metal core, etc., but in the present invention, a paper core with an inner diameter of 3 inches is used, which is inexpensive and versatile. The thickness of the cardboard core is preferably about 7 to 30 mm.

[0036] In addition, the heat-shrinkable polyester film roll of the present invention preferably has a flattened pressure resistance of 1700 N / 100 mm or more of a 3-inch core cardboard tube after the film is removed from the film roll. If the pressure resistance is lower than 1700 N / 100 mm, the cardboard tube may be distorted due to internal stress applied after the film is wound up or the natural shrinkage rate during storage, which is undesirable since wrinkles may occur in the core of the film roll. The pressure resistance is preferably 1800 N / 100 mm or more, and more preferably 1900 N / 100 mm or more. The higher the pressure resistance, the better. As a means for obtaining a high flattened pressure resistance of the cardboard tube, there may be mentioned a method of increasing the thickness of the cardboard tube, using a hard cardboard tube or an ultra-hard cardboard tube designed for high strength, and the like.

[0037] In the heat-shrinkable polyester film roll of the present invention, in order to make the gap difference of the paper tube after removing the film from the film roll 0.5 mm or less as described above, the gap difference in the width direction of the paper tube before winding the film used for winding is preferably 0.3 mm or less, more preferably 0.2 mm or less, and even more preferably 0.1 mm or less. Means for reducing the gap difference of the paper tube include using a paper tube that is hard and difficult to deform due to vibration during transportation, storing the paper tube in a moisture-proof bag until use so that it does not absorb moisture and deform, and storing the paper tube in a room with constant temperature and humidity so that it does not absorb moisture and deform.

[0038] The average winding hardness in the width direction of the heat-shrinkable polyester film roll surface layer of the present invention is preferably 500 or more and 850 or less. If it is less than 500, the winding state becomes soft and the winding core wrinkles are in a good direction, but the film roll end face is displaced, which is not preferable. If the winding hardness is higher than 850, the winding state becomes hard and wrinkles are likely to occur due to thickness unevenness, which is not preferable. The average winding hardness in the width direction of the film roll surface layer is preferably 550 or more and 800 or less, more preferably 600 or more and 750 or less. It is particularly preferably more than 650 and 750 or less. The winding hardness in the present invention refers to the winding hardness measured by the method described in the examples described later. A preferred winding method for setting the winding hardness within the above-mentioned predetermined range will be described later.

[0039] The heat-shrinkable polyester film roll of the present invention has as one of its objectives the reduction of core wrinkles. Core wrinkles occur when the film roll is slit, stored, or transported by truck, and may occur over several hundred meters from the core in long ones, which may result in a large loss when the film roll is processed, such as printed. It is preferable that no wrinkles are generated at a winding length position of 30 m or more from the paper tube of the heat-shrinkable polyester film roll of the present invention. If wrinkles are present at a position longer than 30 m from the paper tube, the wrinkles will be included in processed products such as printed products, resulting in a loss of the processed products, which is not preferable. In addition, the winding length with wrinkles from the paper tube is preferably 0 m, which is completely wrinkle-free. However, in processing such as printing, the winding length from the paper tube to about 30 m is often not used on the pass line of the printing machine, so the length is set to 30 m.

[0040] [Method of manufacturing heat-shrinkable polyester film roll] A preferred method for producing the heat-shrinkable polyester film roll of the present invention will now be described.

[0041] The heat-shrinkable polyester film of the present invention can be obtained by melt-extruding the above-mentioned polyester raw material with an extruder to form an unstretched film, and stretching and heat-treating the unstretched film by a predetermined method described below. In the case of lamination, a plurality of extruders, feed blocks, or multi-manifolds may be used. The polyester can be obtained by polycondensing the above-mentioned suitable dicarboxylic acid component and diol component by a known method. In addition, two or more kinds of chip-like polyesters are usually mixed and used as the raw material for the film.

[0042] When two or more kinds of raw materials are mixed, when they are fed into the extruder, there occurs variation in the raw material supply (so-called raw material segregation), which causes variation in the film composition and causes thickness unevenness in the width direction. In order to prevent this and to keep the thickness unevenness within the specified range in the present invention, it is preferable to install a mixer in the piping or hopper immediately above the extruder to uniformly mix the raw materials before melt extrusion.

[0043] As a specific method for producing the film and label, the raw material chips are dried using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer, and the raw materials are mixed uniformly in a hopper on an extruder using a stirrer, and the mixed raw materials are extruded into a film at a temperature of 200 to 280 ° C. Alternatively, the undried polyester raw materials mixed uniformly in the same manner as above are extruded into a film in a vent-type extruder while removing moisture. Any existing method such as the T-die method or the tubular method may be used for extrusion, but the T-die method is preferred to improve thickness unevenness. The temperature during extrusion should not exceed 280 ° C. If the melting temperature is too high, the intrinsic viscosity when made into a label decreases, and cracks are likely to occur, which is not preferable.

[0044] In addition, the shear rate at the die exit was calculated using the following formula 3. Shear rate γ=6Q / (W×H 2 ) ···expression 3 γ: Shear rate (sec -1 ) Q: Amount of raw material discharged from the extruder (cm 3 / sec) W: width of die outlet opening (cm) H: Die lip gap (cm)

[0045] A higher shear rate is preferable because it reduces thickness unevenness in the longitudinal and transverse directions of the film. In particular, it can reduce thickness unevenness measured on a 30 m long sample in the longitudinal direction. A higher shear rate stabilizes the pressure at the time of resin discharge at the T-die outlet. The preferred shear rate is 200 sec -1 More preferably, 250 sec -1 More than 270 sec, especially preferred -1 A higher draft ratio is preferable because it improves thickness uniformity in the longitudinal direction, but if the draft ratio is too high, resin residue and the like adheres to the resin discharge portion of the die, reducing productivity, so an excessively high draft ratio is not preferable.

[0046] After extrusion, the film is quenched to obtain an unstretched film. The term "unstretched film" includes films to which tension necessary for film feeding is applied. As a method for quenching the molten resin, a method in which the molten resin is cast from a die onto a rotating drum and rapidly cooled and solidified to obtain a substantially unoriented resin sheet can be suitably adopted.

[0047] Furthermore, the obtained unstretched film can be stretched in the longitudinal direction under predetermined conditions as described below, thereby obtaining the heat-shrinkable polyester film of the present invention.

[0048] A typical heat-shrinkable polyester film is produced by stretching an unstretched film in the direction in which it is desired to shrink. In the present invention, the film is uniaxially stretched in the longitudinal direction, which is the main shrinkage direction. Alternatively, the film is stretched in the width direction, and then stretched in the longitudinal direction to perform biaxial stretching. When uniaxially stretching in the longitudinal direction, the unstretched film is introduced into a longitudinal stretching machine in which a group of rolls is arranged in series, the film is heated to a predetermined temperature on a preheat roll (low-speed roll), and then a roll (high-speed roll) that is faster than the preheat roll is provided downstream of the preheat roll, and the film is stretched in the longitudinal direction due to the speed difference between the low-speed roll and the high-speed roll (longitudinal stretching).

[0049] The stretching ratio at this time is not particularly specified, but is preferably 2 times or more and 6 times or less. If the stretching ratio is less than 2 times, it is difficult to obtain a high shrinkage ratio in terms of material balance, and the thickness unevenness in the longitudinal direction becomes worse, which is not preferable. If the stretching ratio exceeds 6 times, the stretching stress becomes too high, and the shrinkage stress of the obtained film becomes high, which is not preferable because the paper tube is easily distorted and crushed due to tight winding in the film roll. More preferably, it is 3.5 times or more and 5.5 times or less, and even more preferably, it is about 4.0 times or more and 5.0 times or less.

[0050] The film temperature during longitudinal stretching is preferably Tg+5°C or more and 40°C or less. If the film temperature is less than Tg+5°C, breakage is likely to occur during stretching, which is not preferred. If the film temperature is higher than Tg+40°C, thermal crystallization of the film progresses and the shrinkage rate decreases, which is not preferred. More preferably, the film temperature is Tg+8°C or more and Tg+37°C or less, and even more preferably, the film temperature is Tg+11°C or more and Tg+34°C or less.

[0051] The distance between the low-speed roll and the high-speed roll during longitudinal stretching is preferably narrow, and specifically, the stretching distance is preferably 30 mm or more and 300 mm or less. If the stretching distance during longitudinal stretching exceeds 300 mm, necking is likely to occur during longitudinal stretching due to the long stretching distance. Necking is a phenomenon in which stress is also generated in the width direction due to Poisson's force accompanying the stretching stress during longitudinal stretching, causing the film width to narrow. Since necking occurs near the ends of the film (i.e., the film shrinks in the width direction near the ends), the thickness near the ends is greater than that of the center. Therefore, necking worsens the thickness unevenness in the width direction, and when the film is wound into a roll, wrinkles are likely to occur in the winding core, which is not preferable. Therefore, it is preferable that necking is as small as possible. The upper limit of the stretching distance is preferably 250 mm or less, and more preferably 200 mm or less. The stretching distance can be narrowed by arranging the low-speed roll and the high-speed roll just before stretching diagonally and setting the film as a cross pass line, but since the lower limit of the stretching distance is thought to be about 30 mm at most, 30 mm was set as the lower limit. In addition, film production after stretching usually includes a process of continuously cutting off the edges after stretching (to remove thick parts caused by necking during casting or to remove unstretched parts during transverse stretching), but in this process, it is also possible to reduce thickness unevenness in the width direction of the film roll by cutting off the thick parts at the edges caused by necking during longitudinal stretching. However, since the effective cutting width of the product is reduced and costs increase, it is not preferable to continuously remove the edges over a wide range, and it is preferable to minimize necking as described above.

[0052] In addition, transverse stretching may be performed using a tenter device before the longitudinal stretching step. By performing transverse stretching, it becomes easy to obtain a film with a uniform thickness in the width direction over a wide width. In addition, biaxial stretching increases the entanglement of polymer chains, and has the effect of reducing the natural shrinkage rate. However, there is a disadvantage that the installation of a transverse stretching device makes the entire film-forming machine longer and increases costs. When performing transverse stretching, it is preferable to heat the film to a temperature of Tg+5°C or more and Tg+40°C or less, and stretch the film at a stretch ratio of 3.0 times or more and 6.0 times or less.

[0053] After the longitudinal stretching, the film is preferably introduced into a tenter device capable of holding both ends of the film with clips and heating the film. By carrying out the heat treatment, the residual stress generated during the longitudinal stretching can be alleviated, thereby reducing the natural shrinkage rate and shrinkage stress in the longitudinal direction. The heat treatment temperature is preferably equal to or higher than the Tg of the film and equal to or lower than Tg+40°C. If the heating temperature is lower than Tg, the above effect cannot be obtained, and if it exceeds Tg+40°C, the shrinkage rate is significantly reduced, which is not preferable.

[0054] The obtained heat-shrinkable polyester film is wound up as a wide roll as an intermediate product, and then slit to a specified width and length using a slitter and wound up on a 3-inch paper tube for winding to obtain a heat-shrinkable polyester film roll. The preferred winding length and width of the film roll are as described above. In addition, it is preferable to reduce core wrinkles that occur during slitting by adopting the following slitting conditions. By adopting these slitting conditions, in a heat-shrinkable polyester film having a thickness of 30 μm or less and a longitudinal direction as the main shrinkage direction, which is prone to cause problems when made into a film roll, core wrinkles can be reduced, end surface misalignment can be suppressed as described below, and the average winding hardness of the surface layer part of the film roll can be kept within an appropriate range.

[0055] Specific slitting conditions are an initial tension of 70 to 140 N / m, preferably 80 to 130 N / m, and an initial surface pressure of 200 to 400 N / m, preferably 250 to 350 N / m, at which slitting is started. If the initial tension is higher than 140 N / m, the uneven thickness portion is slightly stretched by the tension during slitting, which causes wrinkles (wrinkles at the core) and slackness, which is not preferable. Furthermore, if the initial tension is higher than 140 N / m, the influence of slight curvature or distortion of the paper tube becomes large, which causes wrinkles at the core. Also, if the initial tension is 70 N / m or less, the tension is insufficient when the film is wound up by slitting, and wrinkles at the core are less likely to occur, but the end faces of the film roll become uneven (so-called end face misalignment) is generated, which is not preferable. It is desirable to constantly reduce the tension in correlation with the winding length so that the tension at 800 m before the end of slitting is 50 to 80%, preferably 60 to 70%, of the initial tension, and then wind the film at a constant tension until the end of winding. In addition, it is preferable that the surface pressure be within ±5% of the initial surface pressure as much as possible, and more preferably within ±3% of the initial surface pressure, over the entire winding length.

[0056] The winding hardness of the surface layer part of the film roll slit as described above is preferably from 500 to 850. The preferred range of the average winding hardness in the width direction of the surface layer part of the film roll is as described above. In the present invention, the end surface misalignment of the film roll refers to the end surface misalignment measured by the method described in the Examples below. The end surface misalignment of the film roll is preferably 2 mm or less. If the end surface misalignment is large, pitch misalignment is likely to occur in printing, particularly in multicolor printing, and may impair the design and commercial value of processed products such as labels.

[0057] In general, in industrially produced film rolls, a film that has been continuously produced is continuously wound up, and if the film production conditions are constant, the degree of thickness unevenness in the film width direction is almost constant over the entire length of the winding, but due to minute fluctuations in each process during film production, some fluctuations occur over the entire length of the winding. It is preferable that the thickness unevenness in the film width direction is controlled over the entire length of the winding. Whether the thickness unevenness is controlled over the entire length of the winding can be confirmed, for example, by taking samples from the surface layer of the film roll at regular intervals for each winding length and measuring the thickness unevenness of each sample. In the film roll of the present invention, the thickness unevenness can be measured by taking samples from the surface layer part of the film roll and using them as a representative value for the film roll. In the present invention, as described in the examples described later, a sample is taken from a part where 1 m of the film is removed from the surface layer of the film roll, and the representative value is obtained by measuring the thickness unevenness. The preferred range of thickness unevenness in the film width direction at the surface layer part of the film roll is as described above. In a preferred embodiment of the present invention, samples are taken from the surface layer of the film roll every 1000 m of the winding length, and the thickness unevenness of all the samples is within a predetermined range. The preferred range of thickness unevenness in the entire width of the film in the width direction over the entire length of the film roll is as described above. EXAMPLES

[0058] Next, the present invention will be specifically described using examples and comparative examples. However, the present invention is not limited to the aspects of such examples and can be appropriately modified without departing from the spirit of the present invention.

[0059] The evaluation methods used in the present invention are as follows: Unless otherwise specified, 1 m of the film was removed from the surface of the film roll, and the film or film roll of the surface portion after the removal was evaluated.

[0060] [Heat shrinkage rate in the main shrinkage direction] The film was cut into a 10 cm x 10 cm square and heat-shrunk by immersing it in hot water at 90°C ± 0.5°C for 10 seconds under no load. The dimension of the film in the longitudinal direction (main shrinkage direction) was then measured and the heat shrinkage rate was calculated according to the following formula (1). Heat shrinkage rate = ((length before shrinkage - length after shrinkage) / length before shrinkage) x 100 (%) Formula 1

[0061] [Thickness unevenness across the entire width] The roll was placed on a slitter, and after removing 1 m from the roll surface, the film roll was sampled across the entire width and 40 mm in the longitudinal direction, and the thickness in the width direction was continuously measured at 5 m / min using a continuous contact thickness meter manufactured by Micron Measurement Instruments Co., Ltd. The maximum thickness during measurement was Tmax., the minimum thickness was Tmin., and the average thickness was Tave., and the thickness unevenness in the film width direction was calculated using the following formula (2). Thickness unevenness = {(Tmax.-Tmin.) / Tave.} x 100 (%) Formula 2

[0062] [Thickness variation in the longitudinal direction] The film was sampled in the longitudinal direction into a long roll measuring 30 m in length and 40 mm in width, and measured at a speed of 5 m / min using a continuous contact type thickness meter manufactured by Micron Measurement Instruments Co., Ltd. The thickness unevenness in the longitudinal direction of the film was calculated from formula (2) in the same way as for the thickness unevenness in the width direction.

[0063] [Evaluation of wrinkles on the core] The film was rewound from the film roll to a winding length position of the indicated length -300m. After that, the film was slit at a speed of 30m / min to the paper tube position, and wrinkles were visually checked. Evaluation was performed based on the presence or absence of wrinkles at winding length positions of 30m to 300m from the paper tube. No wrinkles: Yes There is one or more wrinkles: ×

[0064] [Difference in widthwise gap of paper core before film is wound] The paper tube was placed on a horizontal stand, and the difference was measured at a total of five points in the width direction: 10 mm from both ends, at the center, and halfway between the center and 10 mm from the ends. The values ​​at each position were measured using a thickness gauge while the paper tube was rotated once on the horizontal stand. The maximum gap around one circumference of the paper tube was taken as the gap at that position. Then, the gaps were measured at five points in the width direction (three points at the center of the paper tube, and two points halfway between the center and both ends, for a total of five points), and the difference between the maximum gap and the minimum gap was taken as the distortion of the paper tube.

[0065] [Difference in gap between paper tubes after film removal] The film was rewound from the film roll and removed, and the paper tube remaining after removal was measured using the method described above.

[0066] [Paper tube flattening pressure resistance] The paper tube after removing the film was cut to a length of 100 mm in the width direction. The cut paper tube was compressed at a speed of 20 mm / min using a Shimadzu pressure tester (AGS-G) to perform measurements.

[0067] [Rolling hardness] Measurements were made across the width of the roll at intervals of 100 mm from the end using a hardness tester, Paro Tester 2, manufactured by Proseo AG, Switzerland. The average value of the values ​​measured across the width of the roll was used as the measured value.

[0068] [Natural shrinkage rate] The film was cut into a size of 200 mm × 30 mm (main shrinkage direction × perpendicular direction), and a 150 mm long marked line was drawn in the main shrinkage direction. After leaving the film in an atmosphere of 40°C and 85% RH for 28 days (672 hours), the length of the marked line was measured and the natural shrinkage rate was calculated by the following formula. Natural shrinkage rate = (length of the gauge line before aging (150 mm) - length of the gauge line after aging) ÷ (length of the gauge line before aging (150 mm) × 100 (%) Formula 4

[0069] [Friction coefficient] In accordance with JIS K-7125, a tensile tester (ORIENTEC Tensilon) was used to determine the static and dynamic friction coefficients when the front and back surfaces of the film were in contact at 23°C and 65% RH. The weight of the sled (weight) on which the upper film was wrapped was 1.5 kg, and the size of the base area of ​​the sled was 63 mm long x 63 mm wide. The tensile speed during friction measurement was 200 mm / min.

[0070] [Shrinkage stress] A strip-shaped film sample having a length of 150 mm in the main shrinkage direction and a width of 20 mm was cut out from the heat-shrinkable film, and the shrinkage stress was measured using a heating furnace-equipped strength and elongation measuring instrument Tesilon Universal Testing Instrument PTM-250 (registered trademark of Orientec Co., Ltd.) manufactured by Toyo Baldwin Co., Ltd. (currently Orientec Co., Ltd.). The heating furnace of the strength and elongation measuring instrument was heated to 90°C in advance, and the distance between the chucks for holding the film sample was 100 mm. When attaching the sample to the chuck of the strength and elongation measuring instrument, the air blowing of the heating furnace was stopped once, the door of the heating furnace was opened, and 25 mm each of both ends of the sample with a length of 150 mm was clamped between the chucks, the distance between the chucks was set to 100 mm, and the sample was fixed without loosening so that the distance between the chucks and the length direction of the sample coincided and the sample was horizontal. After attaching the sample to the chuck, the door of the heating furnace was quickly closed, and the air blowing was resumed. The point at which the door of the heating furnace was closed and air flow was resumed was regarded as the starting point for measuring the shrinkage stress, and the maximum value of the shrinkage stress measured from the starting point for measuring the shrinkage stress up to 30 seconds after the start of the measurement was regarded as the shrinkage stress (MPa).

[0071] [Film roll edge misalignment] The maximum and minimum difference in unevenness on the end surface was determined using a metal ruler. The evaluation was made according to the following method. 2mm or less: ○ More than 2mm: ×

[0072] <Preparation of polyester raw materials> [Synthesis Example 1] In a stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux condenser, 100 mol% of dimethyl terephthalate (DMT) as a dicarboxylic acid component and 100 mol% of ethylene glycol (EG) as a polyhydric alcohol component were charged so that the molar ratio of ethylene glycol was 2.2 times that of dimethyl terephthalate, 0.05 mol% (relative to the acid component) of zinc acetate as an ester exchange catalyst and 0.225 mol% (relative to the acid component) of antimony trioxide as a polycondensation catalyst were added, and an ester exchange reaction was carried out while distilling off the produced methanol outside the system. Thereafter, a polycondensation reaction was carried out at 280°C under reduced pressure of 26.7 Pa to obtain polyester 1 with an intrinsic viscosity of 0.75 dl / g. The composition is shown in Table 1.

[0073] [Synthesis Examples 2 to 5] Polyesters 2 to 4 shown in Table 1 were obtained by the same method as in Synthesis Example 1. When producing polyester 2, SiO2 (Silysia 266 manufactured by Fuji Silysia Corporation; average particle size 1.5 μm) was added as a lubricant at a ratio of 7200 ppm to the polyester. In the table, NPG stands for neopentyl glycol and BD stands for 1,4-butanediol. The intrinsic viscosities of the polyesters were 2:0.75 dl / g, 3:0.75 dl / g, and 4:1.20 dl / g, respectively. Each polyester was appropriately cut into chips. The composition of each polyester is shown in Table 1.

[0074] [Table 1]

[0075] <Method of manufacturing heat shrinkable film> Hereinafter, Examples 1 to 5 will be read as Reference Examples 1 to 5, and Examples 7 and 8 will be read as Reference Examples 7 and 8. [Example 1] The above polyester 1, polyester 2, polyester 3 and polyester 4 were dried separately, then mixed in a mass ratio of 23:7:60:10 and fed into an extruder. At this time, the four raw materials were fed into the extruder while being stirred using a mixer just above the extruder. The mixed resin was melted at 260°C and extruded through a T-die at a shear rate of 440 sec -1 The extrusion was performed under conditions of 100° C., ...

[0076] The unstretched film was introduced into a longitudinal stretching machine. After heating in a preheated roll to a film temperature of 90°C (Tg+21°C), the film was longitudinally stretched by a roll stretching method to a longitudinal stretch ratio of 4.5 times and a thickness of the stretched film of 15μm. After longitudinal stretching, the film was cooled with a cooling roll set at a surface temperature of 25°C. The stretching distance at this time was 150mm. The stretched film was introduced into a tenter, and the ends of the film were held with clips and heated to a film temperature of 80°C while maintaining a constant width, thereby subjecting the film to heat treatment. After cooling, 50mm was cut and removed from both ends of the film, and the film was wound into a roll with a width of 1200mm, thereby continuously producing a stretched film of 15μm in thickness over a predetermined length.

[0077] The stretched film obtained above was slit by a slitter into a size of 1100 mm width and a roll length of 12000 m. The slitting conditions at this time were as follows: initial tension was 110N / m, initial surface pressure was 350N / m when slitting started, the tension was reduced at a rate of 0.374N / m from 500m to 11200m of winding length, and the tension was set to 70N / m (64% of the initial tension) from 11200m to 12000m. The surface pressure was kept constant at 350N / m during slitting.

[0078] The properties of the obtained film roll and film were evaluated by the above-mentioned methods. The manufacturing conditions for the film and film roll are shown in Table 2, and the evaluation results are shown in Table 3. A film with the target characteristics was obtained, and the film roll had good results with no wrinkles on the core or misalignment on the ends.

[0079] [Example 2] The above polyester 1, polyester 2, polyester 3 and polyester 4 were dried separately, mixed in a mass ratio of 3:7:66:24, and fed into an extruder, and a film roll was obtained in the same manner as in Example 1, except that the longitudinal stretching temperature was changed to 85°C. At this time, the Tg of the unstretched film was 62°C. The production conditions are shown in Table 2, and the evaluation results are shown in Table 3. A film with the target characteristics was obtained, and the film roll had good results with no wrinkles in the core or misalignment at the end faces.

[0080] [Example 3] The above polyester 1, polyester 2, polyester 3 and polyester 4 were dried separately, then mixed in a mass ratio of 20:7:53:20 and fed into an extruder, and a film roll was obtained in the same manner as in Example 1, except that the longitudinal stretching temperature was changed to 87°C. At this time, the Tg of the unstretched film was 63°C. The production conditions are shown in Table 2, and the evaluation results are shown in Table 3. A film with the target characteristics was obtained, and the film roll had good results with no wrinkles in the core or misalignment at the end faces.

[0081] [Example 4] The melted mixed resin is passed through a T-die at a shear rate of 290 sec -1 A film roll was obtained by the same method as in Example 1, except that the extrusion was performed under the conditions described above. The production conditions are shown in Table 2, and the evaluation results are shown in Table 3. A film with the target properties was obtained, and the film roll had good results with no wrinkles on the core or misalignment on the end faces.

[0082] [Example 5] A film roll was obtained by the same production method as in Example 1, except that the stretching gap during longitudinal stretching was changed to 250 mm. The production conditions are shown in Table 2, and the evaluation results are shown in Table 3. A film with the target properties was obtained, and the film roll had good results with no wrinkles on the winding core or misalignment on the end faces.

[0083] [Example 6] After obtaining an unstretched film (thickness 150 μm) in the same manner as in the above-mentioned Example, the unstretched film was introduced into a tenter (transverse stretching machine), and while both ends of the film were held by clips, the film was preheated to a film temperature of 92 ° C. (Tg + 23 ° C.) and stretched 4.0 times in the transverse direction. Thereafter, the film after the transverse stretching was introduced into a longitudinal stretching machine, heated in a preheated roll form until the film temperature reached 90 ° C. (Tg + 21 ° C.), and then longitudinally stretched by a roll stretching method to a longitudinal stretching ratio of 2.5 times and a thickness of the stretched film of 15 μm. Thereafter, the film was introduced into the tenter again in the same manner as in Example 1 and heat-treated at 80 ° C. The stretched film obtained above was slit with a slitter into widths of 2200 mm, 1100 mm, and 200 mm so as to have a roll length of 12000 m. The specific slitting conditions were the same as those in Example 1. The properties of the obtained film roll and film were evaluated by the above-mentioned methods. The manufacturing conditions for the film and film roll are shown in Table 2, and the evaluation results are shown in Table 3. A film with the target characteristics was obtained, and the film roll had good results with no wrinkles on the core or misalignment on the ends.

[0084] [Example 7] The same procedure was followed as in Example 1, except that the discharge amount was adjusted so that the thickness of the stretched film was 25 μm. The properties of the obtained film roll and film were evaluated by the methods described above. The production conditions of the film and film roll are shown in Table 2, and the evaluation results are shown in Table 3. A film with the target properties was obtained, and the film roll had good results with no wrinkles on the winding core or misalignment on the end faces.

[0085] [Example 8] The same procedure was followed as in Example 1, except that the length of the film roll was 24,000 m. The properties of the obtained film roll and film were evaluated by the methods described above. The production conditions of the film and film roll are shown in Table 2, and the evaluation results are shown in Table 3. A film with the target properties was obtained, and the film roll had good results with no wrinkles on the winding core or misalignment on the end faces.

[0086] [Comparative Example 1] A film and a film roll were obtained in the same manner as in Example 1, except that the flattening pressure resistance of the paper tube before slitting was 1490 N / 100 mm. The manufacturing conditions for the film and film roll are shown in Table 2, and the evaluation results are shown in Table 3. The obtained film and film roll had a large gap difference in the width direction of the paper tube after the film was removed, and the film roll had poor wrinkles in the winding core and misalignment of the end faces.

[0087] [Comparative Example 2] A film and a film roll were obtained in the same manner as in Example 1, except that the difference in the gap in the width direction of the paper tube before slitting was large. The manufacturing conditions for the film and film roll are shown in Table 2, and the evaluation results are shown in Table 3. The obtained film and film roll had a large gap difference in the width direction of the paper tube after the film was removed, and the film roll had poor wrinkles in the winding core and misalignment of the end faces.

[0088] [Comparative Example 3] A film and a film roll were obtained in the same manner as in Example 1, except that no heat treatment was carried out after the longitudinal stretching. The manufacturing conditions for the film and film roll are shown in Table 2, and the evaluation results are shown in Table 3. The obtained film had a high natural shrinkage rate and shrinkage stress, and the film roll had a large gap difference in the width direction of the paper tube after the film was removed, and the film roll had poor wrinkles at the core.

[0089] [Comparative Example 4] The melted mixed resin is passed through a T-die at a shear rate of 180 sec -1 A film and a film roll were obtained by the same method as in Example 1, except that the extrusion was performed under the conditions above. The production conditions are shown in Table 2, and the evaluation results are shown in Table 3. The obtained film had poor thickness unevenness in the width direction and length direction, and the film roll had poor wrinkles at the core.

[0090] [Comparative Example 5] A film and a film roll were obtained in the same manner as in Example 1, except that the stretching gap for longitudinal stretching was set to 500 mm. The production conditions are shown in Table 2, and the evaluation results are shown in Table 3. The obtained film had poor thickness unevenness in the width direction, and the film roll had poor wrinkles at the core.

[0091] [Comparative Example 6] The stretched membrane and intermediate product roll were produced in the same manner as in Example 1, and the slitting conditions were as follows: initial tension was 60 N / m, initial surface pressure was 200 N / m, and the tension was reduced at a rate of 0.140 N / m from 500 m to 11200 m of winding length, and the tension was 45 N / m (75% of the initial tension) from 11200 m to 12000 m. The slitting was performed so that the surface pressure was constant at 200 N / m. The production conditions are shown in Table 2, and the evaluation results are shown in Table 3. The obtained film roll had low winding hardness in the surface layer, poor wrinkles in the winding core, and poor end misalignment.

[0092] [Comparative Example 7] The stretched membrane and intermediate product roll were produced in the same manner as in Example 1, and the slitting conditions were as follows: initial tension was 80 N / m, initial surface pressure was 180 N / m, and the tension was reduced at a rate of 0.003 N / m until the end of winding, so that the tension at the end of winding was 44 N / m (55% of the initial tension). The surface pressure was increased at a rate of 0.017 N / m, so that the surface pressure at the end of winding was 380 N / m (211% of the initial surface pressure). The manufacturing conditions are shown in Table 2, and the evaluation results are shown in Table 3. The obtained film roll had a large gap difference in the paper core, and the wrinkles in the core part were poor.

[0093] [Table 2]

[0094] [Table 3] [Industrial Applicability]

[0095] The heat-shrinkable polyester film roll of the present invention is favorable for use in processing such as printing because it has good resistance to core wrinkles and end surface misalignment as described above.

Claims

1. A heat-shrinkable biaxially stretched polyethylene terephthalate film having a main shrinkage direction in the longitudinal direction and a shrinkage rate in the main shrinkage direction of 40% or more after treatment in hot water at 90° C. for 10 seconds, wound around a paper tube, is a film roll characterized by satisfying the following requirements (1) to (7). (1) The length of the film roll is between 1,000 m and 30,000 m. (2) Film width: 50 mm or more and 1,500 mm or less (3) Film thickness is 5 μm or more and 30 μm or less (4) Thickness unevenness in the entire width of the film in the film width direction at the surface layer part of the film roll is 20% or less (5) The cardboard tube has an inner diameter of 3 inches, i.e., 76.2 mm, and the gap difference in the width direction of the cardboard tube after removing the film from the film roll is 0.5 mm or less, and the flattened pressure resistance of the cardboard tube after removing the film is 1700 N / 100 mm or more. (6) The average winding hardness in the width direction at the surface layer of the film roll is 500 or more and 850 or less. (7) After the film is left in an atmosphere of 40° C. and 85% relative humidity for 28 days, the natural shrinkage rate in the longitudinal direction is 2.0% or less.

2. 2. The heat-shrinkable polyethylene terephthalate film roll according to claim 1, wherein the thickness unevenness across the entire width of the film in the width direction of each sample sampled at intervals of 1000 m along the length of the film roll from the surface layer portion is 20% or less for all samples.

3. 3. The heat-shrinkable polyethylene terephthalate film roll according to claim 1 or 2, wherein the thickness unevenness of the film roll over a length of 30 m in the longitudinal direction is 20% or less.

4. The heat-shrinkable polyethylene terephthalate film roll according to any one of claims 1 to 3, wherein the heat-shrinkable polyethylene terephthalate film has a static friction coefficient and a dynamic friction coefficient between the outside and inside of the roll of 0.1 or more and 0.8 or less.

5. The heat-shrinkable polyethylene terephthalate film roll according to any one of claims 1 to 4, wherein the heat-shrinkable biaxially stretched polyethylene terephthalate film has a shrinkage stress in the main shrinkage direction of 4 MPa or more and 16 MPa or less.

Images