Heat-shrinkable polyester film roll

Abstract

To provide a heat-shrinkable polyester film roll that reduces the generation of failures such as wrinkles or longitudinal shrink marks caused by the fluctuation of heat shrinkage within a film roll during the process of heat shrinkage, even though recycled raw material from PET bottles is contained.SOLUTION: A film roll comprises a heat-shrinkable polyester film composed of a polyester that contains 5 mass% or more and 50 mass% or less of recycled raw material from PET bottles and an isophthalic acid component. The film roll satisfies the following requirements (1) to (3): (1) an average value of a shrinkage in a main shrinkage direction of the film samples collected at every 100 m pitch in a longitudinal direction of the film roll is 40% or more when the film samples are soaked in hot water of 90°C for 10 seconds, and the shrinkage for all the film samples is within ±3% of the average value; (2) the isophthalic acid ratio in 100 mol% of total acid components contained in polyester constituting each of the film samples collected at every 100 m pitch in the longitudinal direction of the film roll is within ±0.3 mol% of the average value of isophthalic acid ratio of all the film samples; (3) the film roll satisfies a thickness unevenness of 20% or less in the longitudinal direction of the film roll.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a film roll obtained by winding up a heat-shrinkable polyester film. More specifically, the present invention relates to a heat-shrinkable polyester film roll which uses recycled PET bottles as a raw material and yet has high shrinkability, small variation in shrinkage properties in the longitudinal direction of the film roll, and little occurrence of defects such as insufficient shrinkage, uneven shrinkage, distortion, and longitudinal shrinkage in post-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, generation of hydrogen chloride gas when incinerated, and dioxin generation. In addition, polystyrene films have poor solvent resistance, require the use of ink with a special composition when printing, and need to be incinerated at high temperatures, resulting in the problem of 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 (PET bottles).

[0003] However, due to the dramatic increase in the use of PET bottles, waste problems and resource conservation have become social issues. As one of the countermeasures, there is a growing movement to collect used PET bottles and reuse them as resources (recycling). The main recycling technologies include mechanical recycling, chemical recycling, and thermal recycling, of which mechanical recycling is the most widespread. In this process, used containers are sorted, crushed, washed, and turned into resin chips again in an extruder. These are then processed into PET bottles or fibers or films for reuse.

[0004] By using some of the above-mentioned recycled PET bottle raw materials in heat-shrinkable polyester film labels, it is possible to contribute to the life cycle of PET, from production, use, to disposal, and thereby contribute to reducing the environmental impact.

[0005] In general, in order to obtain high shrinkability of heat-shrinkable polyester films, it is necessary to reduce the crystallinity of the polyester that constitutes the film. However, PET bottle recycled raw materials are highly crystalline raw materials. Therefore, when using PET bottle recycled raw materials, it is essential to mix at least two types of raw materials with a highly amorphous raw material.

[0006] After production, the heat-shrinkable film is once wound into a roll and sent in the form of a film roll to a printing process for various designs, and after printing is completed, it is slit according to the size of the label or the like to be used in the final product as necessary, and then the left and right ends of the film are overlapped and sealed by means of solvent bonding or the like to form a tube, which is then cut and processed into the form of labels, bags, etc. The label or bag is then attached to a container and passed on a belt conveyer or the like through the inside of a shrink tunnel (hot air tunnel) of the type that causes thermal shrinkage by blowing steam, whereby it is thermally shrunk and adhered to the container.

[0007] However, in this heat shrinking process, if the heat shrinkage rate of each label, bag, etc. varies, that is, if there is a large variation, because the heating conditions in the tunnel are the same, labels, bags, etc. that do not exhibit the appropriate heat shrinkage rate will be generated, and these will cause poor appearance due to insufficient shrinkage, uneven shrinkage, wrinkles, distortion of the design, vertical sink marks, etc., and will not be usable as a final product. Vertical sink marks here refer to the uneven length of the labels after shrinking, causing the upper edge of the label to draw a downward curved line or the lower edge to draw an upward curved line. The appearance is poor.

[0008] Such a change in the heat shrinkage rate is largely due to the effect that a change in the polyester composition constituting the film in the longitudinal direction of the roll has on the heat shrinkage rate. Typically, heat-shrinkable polyester films are made by feeding various raw material chips into an extruder, melting them, and extruding the molten resin through a die to obtain an unstretched raw film, which is then stretched. However, it is believed that variations in composition occur before the various raw material chips are fed into the extruder; in other words, the various raw material chips are not mixed uniformly and segregate, causing the composition to vary.

[0009] Segregation does not occur by using the components required for polyester film as raw material chips with a single composition (using only one type of raw material chips), but as mentioned above, when using recycled PET bottle raw materials, at least two types of raw material chips must be mixed and used, and there is a risk of segregation. In other words, as long as recycled PET bottle raw materials are used, there is a risk of fluctuations in the thermal shrinkage rate in the longitudinal direction. For example, in the PET bottle recycling process, it is not impossible to obtain raw material chips with a single composition that contain all the components required for film by adding amorphous polyester when crushing, washing, and re-chipping the bottles, but this is not realistic because recycled raw materials are also used for purposes other than film. Furthermore, the inventors of the present application have found that recycled PET bottle raw materials are often made by randomly mixing various PET bottles and recycling them, and that the molecular weight, etc. of the raw materials decreases due to repeated use, and that additives such as high crystallization nucleating agents are often used. Therefore, when used as a raw material for film, the inventors have found that this has the disadvantage that the impact of fluctuations in the blending amount due to segregation on fluctuations in the physical properties of the film is more pronounced than with other raw materials.

[0010] Patent Document 1 describes a heat-shrinkable polyester film made from recycled PET bottle materials, but makes no mention of the variation in the heat shrinkage rate in the longitudinal direction. Patent Document 2 describes a heat-shrinkable polyester film containing a high proportion of recycled PET bottle materials, but the method described makes it difficult to achieve a shrinkage rate of 45% or more at 90°C, and there is no description of the variation in heat shrinkage rate in the longitudinal direction. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Patent No. 5320737 [Patent Document 2] Patent No. 6402954 Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention aims to provide a heat-shrinkable polyester film roll that reduces the occurrence of defects such as wrinkles and vertical sink marks during a heat shrinkage process caused by fluctuations in the heat shrinkage rate within the film roll even when the film roll contains recycled PET bottle raw materials. [Means for solving the problem]

[0013] The present inventors have conducted extensive research to solve the above problems and have completed the present invention.

[0014] 1. A heat-shrinkable polyester-based film roll comprising a heat-shrinkable polyester-based film made of a polyester containing 5% by mass or more and 50% by mass or less of recycled PET bottle raw materials and containing an isophthalic acid component, the heat-shrinkable polyester-based film roll being characterized in that it satisfies the following requirements (1) to (3): (1) Film samples taken at 100m intervals along the length of the roll are immersed in 90°C hot water for 10 seconds. The average shrinkage rate in the main shrinkage direction is 40% or more, and the average value for all samples is within ±3%. (2) In film samples taken at 100 m intervals along the length of the roll, the content of isophthalic acid in the polyester that constitutes the film is within the average value ±0.3 mol% of the total acid component (100 mol%). (3) Thickness variation in the longitudinal direction of the roll is 20% or less. 2. A heat-shrinkable polyester film roll according to 1., characterized in that the heat-shrinkable polyester film is formed from a mixture of at least recycled PET bottle materials and one or more types of polymer chips having different compositions. 3. A heat-shrinkable polyester film roll according to 1 or 2, characterized in that the polyester constituting the heat-shrinkable polyester film is mainly composed of ethylene terephthalate. 4. A heat-shrinkable polyester film roll according to any one of 1. to 3., characterized in that in film samples taken at 100 m intervals in the longitudinal direction of the roll, the polyester constituting the film has an average isophthalic acid content of 0.3 mol% or more and 3.0 mol% or less in 100 mol% of all acid components. 5. The heat-shrinkable polyester film roll according to any one of 1. to 4., wherein the heat-shrinkable polyester film roll has a winding length of 1000 m or more. 6. A heat-shrinkable polyester film roll according to any one of 1. to 5., characterized in that when film samples taken at 100 m intervals in the longitudinal direction of the roll are immersed in 90°C hot water for 10 seconds, the average shrinkage rate in a direction perpendicular to the main shrinkage direction is 0% or more and 15% or less, and the shrinkage rates of all samples are within the average value ±3%. Effect of the Invention

[0015] Even when the heat-shrinkable polyester film roll of the present invention is mixed with recycled PET bottle materials, the variation in the heat shrinkage rate within the film roll is small, and it is possible to extremely reduce the occurrence of defects such as wrinkles and vertical sink marks during the heat shrinkage process due to the small variation. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing an example of the relationship between an extruder 2 equipped with a hopper 1 and an inner pipe. [Diagram 2] FIG. 2 is an enlarged view showing a portion A in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The polyester used in the heat-shrinkable polyester film constituting the heat-shrinkable polyester film roll of the present invention (hereinafter, sometimes referred to as the heat-shrinkable polyester film of the present invention) is a polyester having ethylene terephthalate as a main component. That is, it contains 50 mol% or more, preferably 60 mol% or more, of ethylene terephthalate relative to 100 mol% of all components of the polyester. In addition, as described below, the polyester contains an isophthalic acid component. Examples of dicarboxylic acid components other than terephthalic acid and isophthalic acid constituting the polyester of the present invention include aromatic dicarboxylic acids such as naphthalenedicarboxylic acid and orthophthalic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid, and alicyclic dicarboxylic acids.

[0018] 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.

[0019] 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.

[0020] 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, aromatic diols such as bisphenol A, and diethylene glycol.

[0021] 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, diethylene glycol, etc.).

[0022] In addition, the polyester used in the heat-shrinkable polyester film of the present invention has a total of at least one monomer component that can be an amorphous component in 100 mol % of the polyhydric alcohol component or 100 mol % of the polyvalent carboxylic acid component in the entire polyester resin, preferably at least 14 mol %, more preferably at least 16 mol %, and particularly preferably at least 18 mol %. Examples of monomers that can be an amorphous component include neopentyl glycol, 1,4-cyclohexanedimethanol, 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, and among them, neopentyl glycol or 1,4-cyclohexanedimethanol is preferably used. The upper limit of the total monomer component that can be an amorphous component is preferably 40 mol % or less. It is more preferably 38 mol % or less, and further preferably 36 mol % or less.

[0023] 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.

[0024] The intrinsic viscosity of the heat-shrinkable polyester film of the present invention is preferably 0.55 dl / g or more and 1.50 dl / g or less. If the intrinsic viscosity is less than 0.55 dl / g, the strength of the film is significantly reduced and the film is easily broken during film formation and processing, which is not preferred. Also, if the intrinsic viscosity exceeds 1.50 dl / g, it is not preferred because stretching becomes difficult and this may cause breakage. More preferably, the intrinsic viscosity is 0.58 dl / g or more and 1.47 dl / g or less, and even more preferably, the intrinsic viscosity is 0.61 dl / g or more and 1.44 dl / g or less.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] The heat-shrinkable polyester film of the present invention contains 5% by mass or more and 50% by mass or less of recycled PET bottle raw materials. If it is less than 5% by mass, the contribution to reducing the environmental load is very small, and the effect of the present invention is not achieved. If it is used in an amount of more than 50% by mass, the amorphousness (amount of amorphous components) of the raw materials other than the recycled PET bottle raw materials must be extremely high, which is uneconomical because it increases the polymerization time of the raw materials. The content of the recycled PET bottle raw materials is more preferably 10% by mass or more and 45% by mass or less, and even more preferably 20% by mass or more and 40% by mass or less.

[0029] In the present invention, when the film is sampled at 100 m intervals in the longitudinal direction of the film roll and the shrinkage rate of each film sample is measured in 90°C hot water (90°C hot water shrinkage rate), the average shrinkage rate in the main shrinkage direction is 40% or more, and the shrinkage rates of all samples are within the average value ±3%. The hot water shrinkage rate is calculated from the length before and after shrinkage when treated in hot water at 90° C. for 10 seconds under no load, using the following formula 1. Heat shrinkage rate = {(length before shrinkage - length after shrinkage) / length before shrinkage} × 100 (%) (Formula 1) If the average shrinkage rate is less than 40%, the shrinkage amount is so small that the label after heat shrinkage will have wrinkles or will not shrink enough, making it undesirable as a heat shrinkable film. There is no particular upper limit for the shrinkage rate, but the upper limit is about 80%. Furthermore, if the shrinkage rate of the film sampled at 100 m intervals exceeds the range of the average value ±3%, the shrinkage rate of each label will vary greatly when processed into labels, and labels that have poor appearance such as wrinkles when finished in a shrink tunnel will be more likely to be produced. More preferably, it is the average value ±2.5%, even more preferably the average value ±2.0%, particularly preferably the average value ±1.5% or less, and most preferably the average value ±1.0% or less. In addition, in the present invention, when the film is sampled at 100 m intervals in the roll longitudinal direction and the shrinkage rate in 90 ° C. hot water (90 ° C. hot water shrinkage rate) is measured for each film sample, the shrinkage rate in the direction perpendicular to the main shrinkage direction of all samples is within the range of the average value ± 3%. If the shrinkage rate in the direction perpendicular to the main shrinkage direction of the film sampled at 100 m intervals exceeds the range of the average value ± 3%, when processed into labels, the shrinkage rate of each label will fluctuate greatly, and when finished in a shrink tunnel, the height of the labels will differ for each label, which is not preferable. More preferably, it is the average value ± 2.5%, even more preferably the average value ± 2.0%, particularly preferably the average value ± 1.5% or less, and most preferably the average value ± 1.0% or less. In addition, the upper limit of the average value of the shrinkage rate in the direction perpendicular to the main shrinkage direction of all samples is 20%. If the average value exceeds 20%, vertical sink marks will increase during shrink finishing, which is not preferable. More preferably, it is 17% or less, and even more preferably, it is 14% or less. The shrinkage rate in the direction perpendicular to the main shrinkage direction is preferably as low as possible.

[0030] In the heat-shrinkable polyester film roll of the present invention, it is preferable that the content ratio of isophthalic acid in 100 mol % of the total acid components of the polyester is within the average value ±0.3 mol % in film samples taken at 100 m intervals in the longitudinal direction of the roll. The content ratio of isophthalic acid is measured and calculated by NMR measurement as described later. If the content of isophthalic acid varies beyond the range of the average value ±0.3 mol%, the variation in composition will cause a large variation in thermal shrinkage. As a result, when processed into labels, the shrinkage rate will vary from label to label, making them more likely to have poor appearance such as wrinkles, which is undesirable. The film roll of the present invention uses PET bottle recycled raw materials, which generally contain a small amount of isophthalic acid as an acid component, as described below. Fluctuations in the ratio of isophthalic acid mean that the PET bottle recycled raw material chips and other raw material chips are segregated. As described above, PET bottle recycled raw materials often contain additives such as high crystallization nucleating agents, and the molecular weight, etc., is reduced by repeated use, so that the impact of segregation on the physical property fluctuations in the film roll is greater than that of other raw materials. A method for reducing segregation will be described later. The isophthalic acid ratio is more preferably in a range of the average value ±0.2 mol %, and even more preferably in a range of the average value ±0.1 mol %.

[0031] The average content of the isophthalic acid is preferably 0.3 mol% or more and 3.0 mol% or less in 100 mol% of the total acid components of the polyester. The crystallinity of the polyester used in PET bottles is controlled in order to improve the appearance of the bottle, and as a result, polyester containing 10 mol% or less of isophthalic acid is generally used. In the present invention, since the PET bottle recycled raw material is contained in an amount of 50 mass% or less, the upper limit of the average content of isophthalic acid is preferably 3.0 mol% or less. More preferably, it is 2.8 mol% or less, even more preferably 2.6 mol% or less, and particularly preferably 2.4 mol% or less. The lower limit of the average value of the isophthalic acid content is preferably 0.3 mol %, more preferably 0.4 mol %, further preferably 0.5 mol %, and particularly preferably 0.6 mol %.

[0032] 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 thickness of each label will differ when processed into a label. If the label thickness differs, the way the heat is applied to the label inside the steam tunnel (hot air tunnel) differs, which is undesirable because it is likely to cause defects in appearance such as wrinkles. It is preferably 18% or less, and more preferably 15% or less. The smaller the thickness unevenness value, the more preferable it is. Thickness unevenness = {(maximum thickness – minimum thickness) ÷ average thickness} × 100 (%) (Formula 2)

[0033] The thickness of the heat-shrinkable polyester film of the present invention is preferably 5 μm or more and 40 μm or less. If the thickness is less than 5 μm, the risk of breakage during film production increases, and the stiffness of the film when made into a label decreases, which is undesirable. In addition, the thicker the film, the more stable the film production becomes, and the stiffness increases, so that problems such as wrinkles tend to be less likely to occur, but this is undesirable because it goes against the film of the present invention, which is intended to reduce environmental impact, in terms of volume reduction. More preferably, the film thickness is 8 μm or more and 37 μm or less, and even more preferably, 11 μm or more and 34 μm or less.

[0034] The width of the heat-shrinkable polyester film roll of the present invention is preferably 500 mm or more, more preferably 1000 mm or more, and particularly preferably 1500 mm or more, and the length of the film roll is preferably 2000 m or more, more preferably 4000 m or more, and particularly preferably 8000 m or more.

[0035] A preferred method for producing the heat-shrinkable polyester film roll of the present invention will now be described. The heat-shrinkable polyester film roll of the present invention is produced through the steps of storing and supplying a raw resin, extruding the resin while melting it, forming the extruded resin into an unstretched sheet, stretching the unstretched sheet, and winding up the obtained stretched film. In addition, in order to obtain a film roll having the characteristics of the present invention, it is important to suppress the variation in the film composition. Specific methods are described below.

[0036] Methods for suppressing variations in film composition Heat shrinkable films generally require amorphous components as raw materials, but the heat shrinkable polyester film of the present invention uses PET bottle recycled raw material chips, so it is necessary to use at least two types of raw material chips including PET bottle recycled raw material. The blending method is generally used, but the raw material chips are prone to segregation. Therefore, in the present invention, it is preferable to suppress the segregation of the raw material chips in the blending method by various methods and combinations of the methods shown below.

[0037] (a) Uniform chip shape In the blending method, multiple raw polyester chips with different compositions are usually blended in a hopper, melt-kneaded, and extruded into a film by an extruder. In the present invention, PET bottle recycled raw material chips and other amorphous raw material chips are continuously or intermittently fed and mixed in the hopper, and finally the mixed raw material chips are fed to a hopper (final hopper) directly above the extruder, where the raw materials are fed in accordance with the extrusion rate of the extruder to form a film. However, it has been found that depending on the capacity or shape of the hopper in which the raw materials are mixed and the final hopper, when the amount of chips in the hopper is large and when the total amount is small, the mixing ratio of the chips fed to the subsequent hopper or extruder is different. This problem is particularly evident when the shapes and specific gravities of various polyester raw material chips are different. As a result, the content of isophthalic acid in the present invention fluctuates. In order to obtain the film roll of the present invention having small fluctuations in the longitudinal shrinkage rate and the isophthalic acid content, it is preferable to match the shape of the raw material chips used as a means for reducing compositional fluctuations of the polyester constituting the film, thereby suppressing the raw material segregation phenomenon inside the hopper.

[0038] The raw polyester chips are taken out of the polymerization apparatus in a molten state after polymerization in the form of strands, immediately cooled with water, and then cut and molded with a strand cutter. In the case of recycled PET bottles, flake-like polyester obtained by sorting, crushing, and washing PET bottles is extruded again by an extruder, taken out in the form of strands, immediately cooled with water, and cut and molded with a strand cutter. For this reason, polyester chips usually have an elliptical cylindrical shape with an elliptical cross section. At this time, it is preferable that the average major axis (mm), average minor axis (mm), and average chip length (mm) of the cross-sectional ellipse of the polyester chips are each within a range of ±20%. Furthermore, it is more preferable that these average values ​​are each within a range of ±15%. The average major axis and average minor axis of the cross-sectional ellipse can be adjusted by adjusting the size of the nozzle hole of the die when extruding into a strand, and the length of the chips can be adjusted by adjusting the extrusion amount of the strand, the conveying speed of the strand, and the rotation speed of the strand cutter. When chips are different in size, the smaller chips tend to fall first as the chip mixture falls through the hopper. Therefore, when the amount of chips remaining in the hopper decreases, the ratio of larger chips increases, which can cause raw material segregation. However, by using raw material chips within the above range, it is possible to suppress this raw material segregation.

[0039] In addition, the angle of repose is an index of the granular fluidity of the raw material chips, that is, the ease of falling. The angle of repose is the angle between the horizontal plane and the slope of the mountain formed when a certain amount of raw material chips is dropped from a certain height. The angle of repose is determined by the shape and particle size of the chips, and the smaller the chips, the smaller the angle of repose tends to be, and the smaller the angle of repose of the resin, the easier it tends to fall. It is preferable that the difference in the angle of repose between the resin with the smallest angle of repose and the largest chip is 5 degrees or less. By using raw material chips within the above range, it is possible to suppress these raw material segregations, and it is more preferable that it is 4 degrees or less.

[0040] (b) Hopper shape optimization Optimizing the hopper shape as mentioned above is also a preferred measure to prevent raw material segregation. By using a funnel-shaped hopper for the mixed chips and setting its inclination angle to 65° or more, large chips can be dropped as easily as small chips, and the upper end of the contents descends while maintaining a horizontal plane, which is effective in reducing raw material segregation. A more preferred inclination angle is 70° or more. The inclination angle of the hopper is the angle between the hypotenuse of the funnel and the horizontal line.

[0041] (c) Optimization of hopper capacity As a means for reducing the segregation of raw material inside the hopper, it is also preferable to optimize the capacity of the hopper used. Here, the appropriate capacity of the hopper is within the range of 15 to 120 mass% of the hourly discharge amount of the extruder. If the hopper does not have a capacity of 15 mass% or more of this discharge amount, it is difficult to steadily supply raw material, and if the hopper is too large, the raw material chip mixture will remain in the hopper for a long time, during which time chip segregation may occur. These are the reasons for setting the hopper capacity within the above range. It is more preferable that the hopper capacity is within the range of 20 to 100 mass% of the hourly discharge amount of the extruder.

[0042] (d) Reduction of fine powder Reducing the ratio of fine powder generated by scraping of the raw material chips used is also a preferred means for suppressing raw material segregation. Fine powder gets between the chips, and the friction between the chips is reduced, which makes it easier for small chips to fall, promoting segregation. It is preferable to remove the fine powder generated during the process and reduce the ratio of fine powder contained in the hopper. The ratio of fine powder contained is preferably controlled to within 1% by mass throughout the entire process in which the raw material chips enter the extruder, and more preferably within 0.5% by mass. Specifically, fine powder can be removed by passing the chips through a sieve when forming the chips with a strand cutter, or by passing the raw chips through a cyclone air filter when air-transporting the raw chips.

[0043] (e) Use of uncrystallized raw materials Raw material segregation is also likely to occur when there is a large difference in specific gravity between the multiple raw material chips used. In other words, chips with a large specific gravity (heavy) tend to fall first when the chip mixture falls, promoting segregation. In the present invention, PET bottle recycled raw material chips and amorphous raw material chips are mixed and used, but since the PET bottle recycled raw material is a crystalline raw material, it has a higher specific gravity than the amorphous raw material, and there is a difference in specific gravity between the chips. Meanwhile, the raw chips are dried before being fed into the extruder to reduce the moisture content of the resin, or separately dried raw chips are fed into the hopper. PET bottle recycled raw material is dried by heating the chips to around 160°C to shorten the drying time, but at this time the polyester crystallizes and its specific gravity increases compared to the chips before drying. Therefore, the difference in specific gravity between the heated and dried PET bottle recycled raw chips and the amorphous raw chips increases further, promoting segregation. Therefore, the raw material chips used in the present invention are preferably dried without crystallization by vacuuming at room temperature to reduce the moisture content. Alternatively, it is preferable to use raw material chips without drying, that is, chips in a state where no crystallization has occurred, and use a twin-screw extruder with a vent to perform melt extrusion while removing moisture from the vent.

[0044] (f) Mixing inside the hopper It is also effective to reduce raw material segregation by stirring the inside of the hopper into which the mixture of raw material chips is placed. For example, by providing a stirring device with blades or a stirring device with a spiral ribbon in the hopper, the resins can be stirred and mixed while being fed to the next process (hopper or extruder), thereby reducing raw material segregation. The location of the hopper with a stirring function is not particularly limited, but it is more preferable that it is a hopper close to the extruder, and it is particularly preferable that the stirring be performed in the final hopper immediately above the extruder.

[0045] (g) Installation of cone baffles The falling of the raw material chips at the bottom of the hopper is affected by the pressure due to the weight of the raw material chips above it (so-called powder pressure). Films are usually produced continuously, but the supply of raw chips to the hopper is often intermittent. If the raw resin is supplied continuously, the chip transport device must be kept in operation at all times, which increases the frequency of breakdowns. In addition, the supply amount must be balanced with the consumption amount, and accurate measurement is difficult for resin chips with a small supply of raw material. Intermittent supply means that when the raw material in the hopper is consumed and falls below a certain capacity level, a certain amount of raw chips is supplied, and when the level is reached, the supply stops, and when the consumption progresses, the supply resumes. In this case, the capacity level of the hopper is constantly fluctuating, which means that the powder pressure at the bottom of the hopper also fluctuates. Fluctuations in powder pressure are undesirable because they promote raw material segregation. Therefore, it is preferable to install a cone baffle at the bottom of the hopper to cut the pressure from the raw material chips at the top of the hopper. By setting the minimum capacity level above the cone baffle, it becomes possible to keep constant the powder pressure applied to the raw material chips below the cone baffle at the bottom of the hopper, and to reduce raw material segregation. The shape of the cone baffle is not particularly limited, but it is preferably a cone or a triangular pyramid.

[0046] (h) Mixing directly above the extruder A method of inserting a pipe into the hopper (final hopper) directly above the extruder and mixing the chips just before extrusion is also a preferred method. Since the raw chips that cause segregation are mixed just before the extruder, the chances of actual segregation occurring are extremely low, making this method effective in reducing segregation. However, it is necessary to use equipment that satisfies at least the following formula 3. An example of a specific mixing procedure is shown in Figure 1. Figure 1 is a schematic diagram showing an example of the relationship between an extruder 2 equipped with a hopper 1 and an inner pipe, and Figure 2 is an enlarged view of part A in Figure 1. As shown in Figures 1 and 2, raw chips to be mixed are supplied from the inner pipe 3, and other raw chips are supplied from the top of the hopper 1. And since the outlet 4 of the inner pipe 3 is directly above the extruder (more precisely, directly above the raw chip supply port 5 of the extruder 2), the mixing ratio of the raw chip mixture can be kept constant. The height (H2) of the outlet 4 of the inner pipe 3 preferably satisfies the relationship of the following formula 3, and more preferably satisfies the relationships of both formulas 3 and 4. H2 < H1 ···(Formula 3) (In the formula, H1 represents the height of the portion where the inner wall of the hopper is vertical (see Figure 2)) 0.5 × L / tanθ < H2 ···(Formula 4) (In the formula, L represents the inner diameter of the outlet 4 of the inner pipe 3 (see Figure 2). θ is the angle of repose of the raw material chips that have entered the hopper before mixing.) By satisfying Formula 3, the position (H3) where the raw material chips are mixed can be made above the extruder, and it is possible to prevent air from entering the extruder and generating bubbles. The height H3 (= H2 - 0.5 × L / tanθ) of the mixing position of the raw material chips is preferably higher than 0 m and less than 2 m. Making it higher than 0 m is preferable because it can prevent air from entering the extruder. Also, making it less than 2 m can shorten the distance to the extruder and prevent raw material segregation. The height H3 is preferably 0.3 m or more and 1.7 m or less, and more preferably 0.6 m or more and 1.4 m or less.

[0047] In order to obtain a film roll with small variations in the longitudinal thermal shrinkage rate and variations in the isophthalic acid ratio of the present invention by adopting the blending method, it is preferable to perform all of the above (a) to (d). However, even if all of (a) to (d) are implemented, it is insufficient to reduce raw material segregation, and it is preferable to adopt one or more of the four means of (e) to (h), and more preferably to adopt two or more. Alternatively, without adopting the above blending method, the following means (i) can be adopted.

[0048] (i) Use of a twin-screw extruder and a side feeder In addition to the above method, as a method of using the raw material chips without blending, a method using a twin-screw extruder and a side feeder can be preferably used. Specifically, when using two types of raw material chips, amorphous raw material chips and recycled PET bottle raw material chips, it is preferable to supply the amorphous raw material chips to twin-screw extruder 1 and melt them inside the extruder, and then supply the recycled PET bottle raw material chips to another twin-screw extruder (hereinafter, this other twin-screw extruder will be referred to as twin-screw extruder 2), where they are melted and directly introduced into the middle of the twin-screw extruder 1 via piping using a side feed method, and then mix the two types of raw materials inside twin-screw extruder 1. Since there is no process of mixing the raw materials in chip form, the above-mentioned concern about segregation of the raw material chips is essentially eliminated. The mixing ratio of the raw materials can be accurately adjusted by adjusting the rotation speed of the screw feeder, etc., of the raw material chips fed into the twin-screw extruder 2 (side feeder). Therefore, it is possible to minimize the variation in composition in the longitudinal direction of the film.

[0049] The twin-screw extruder 1 preferably has a vent function. In order to prevent air bubbles from being mixed in when the raw materials are introduced by the side feeder, it is preferable to provide a vent at the starting position where the raw materials start to mix together for deaeration. It is preferable that the raw material chips fed to each of the twin screw extruders 1 and 2 must be a single material, in order to eliminate the process of mixing the raw material chips before feeding them to the extruders, and to essentially eliminate segregation of the raw material chips. When three or more kinds of raw materials are used, it is preferable to further provide another twin-screw extruder 3 and introduce the raw materials directly into the twin-screw extruder 1 by a side feed method.

[0050] The manufacturing process of the heat shrinkable polyester film of the present invention includes (1) melt extrusion and casting of an unstretched sheet, (2) transverse stretching, and (3) final heat treatment. Each of these steps will be described below.

[0051] (1) Melt extrusion and casting of undrawn sheets The raw materials are mixed and fed with the above-mentioned measures against segregation, and extruded into a sheet at a temperature of 220-280°C using an extruder by using existing methods such as the T-die method and the tubular method. If the temperature during extrusion exceeds 280°C, the intrinsic viscosity of the polyester resin decreases, making it easier for breakage to occur during the film-making process and making it difficult to obtain a steady-state film, which is not preferable. If the temperature falls below 220°C, some of the raw materials will not melt, causing an overload on the machine, and the unmelted resin will become the starting point for breakage during film-making, which is also not preferable. Thereafter, the film melted by extrusion is quenched to obtain an unstretched film. 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 quenched and solidified to obtain a substantially unoriented resin sheet can be suitably adopted. Furthermore, the shear rate when the molten resin is discharged from the mouth of the die is preferably 100 sec-1 or more, more preferably 150 sec-1 or more. The higher the shear rate, the more the shrinkage rate fluctuation and thickness unevenness in the longitudinal direction of the film can be suppressed. This is because the resin discharge pressure at the die mouth (exit) becomes stable as the shear rate increases. If the shear rate is less than 100 sec-1, the resin discharge pressure at the die outlet becomes unstable, and pulsation (thickness fluctuation of the unstretched film in the longitudinal direction) is likely to occur. As a result, the stretching in the longitudinal direction, which will be described later, is not uniform, and the thermal shrinkage rate fluctuation and thickness unevenness in the longitudinal direction become large. On the other hand, if the shear rate is higher than 600 sec-1, not only will the polyester molecular chains be cut (decomposed) to reduce the intrinsic viscosity, but also resin residue will adhere to the discharge portion of the die, reducing productivity, which is undesirable.

[0052] The shear rate at the die exit was calculated using the following equation 5. γ=6Q / (W×H2) (Formula 5) γ: Shear rate (sec -1 ) Q: Amount of raw material discharged from the extruder (cm 3 / sec) W: width of die opening (cm) H: Die lip gap (cm)

[0053] (2) Lateral stretching process The film is preferably stretched in a uniaxial transverse stretching manner in which the film is stretched only in the width direction. Although it is possible to use a method in which longitudinal stretching is performed in a process prior to the transverse stretching, this is not preferred because the production machine becomes long. The unstretched sheet obtained as described above is introduced into a tenter device capable of holding both ends of the sheet with clips and heating it, and after heating the film to a predetermined temperature with hot air in a preheating process, the film is stretched by conveying it in the longitudinal direction while widening the distance between the clips in the stretching process. The film temperature during width direction stretching is preferably Tg+5° C. or more, Tg+40° C. If the film temperature is less than Tg+5° C., the stretching force becomes too high, increasing the risk of breakage, which is not preferred. If the film temperature exceeds Tg+40° C., the stretching force is too low, making it difficult to impart sufficient shrinkability to the film, which is not preferred.

[0054] (3) Final heat treatment process After the transverse stretching, the film is preferably finally heat-treated in a tenter with both ends in the width direction held by clips at a temperature of the transverse stretching temperature +5°C or more and 45°C or less for a time of 5 seconds or more and 10 seconds or less. If the temperature is higher than the transverse stretching temperature + 45°C, the shrinkage rate in the transverse direction decreases and the required shrinkage characteristics cannot be obtained, which is not preferable. Also, if the temperature is lower than the transverse stretching temperature + 5°C, when the final product is stored at room temperature, the shrinkage in the transverse direction (so-called natural shrinkage rate) increases over time, which is not preferable. Also, the longer the heat treatment time, the better, but if it is too long, the equipment will become large, so a time of 10 seconds or less is preferable. From the viewpoint of reducing the variation in the thermal shrinkage rate, it is preferable to control the fluctuation range of the film surface temperature measured at any point in each of the steps of preheating, stretching, and final heat treatment in the transverse stretching step and the final heat treatment step to within the average temperature ±1°C, and more preferably within the average temperature ±0.5°C. EXAMPLES

[0055] 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.

[0056] [Sampling method for evaluation samples] A 1m length of film was removed from the film roll to form the surface layer, and the first sample was cut out from the center in the width direction. After that, while the film roll was unwound using a winding machine, samples were cut out from the center in the width direction every 100m. When the remaining length of the film roll became less than 100m, sampling was stopped and the samples taken up to that point were evaluated.

[0057] [Heat shrinkage rate] 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. After that, the dimensions of the film in the longitudinal direction (direction perpendicular to the main shrinkage direction) and width direction (main shrinkage direction) were measured and the heat shrinkage rate was calculated according to the following formula (1). Regarding the fluctuation (variation) of the shrinkage rate, the heat shrinkage rate was measured for the samples sampled by the above-mentioned method, and the average, maximum and minimum values ​​were calculated. Heat shrinkage rate = ((length before shrinkage - length after shrinkage) / length before shrinkage) x 100 (%) Formula (1)

[0058] [Composition analysis] Each sample was dissolved in a solvent made by mixing chloroform D (manufactured by Eurisop) and trifluoroacetic acid D1 (manufactured by Eurisop) in a 10:1 (volume ratio) mixture to prepare a sample solution, and the NMR of the protons in the sample solution was measured using an NMR "GEMINI-200" (manufactured by Varian) at a temperature of 23°C and an accumulation number of 64 times. In the NMR measurement, the peak intensity of a specified proton was calculated to measure the amount of the component in 100 mol % of the diacid component. The average, maximum, and minimum values ​​of the component ratio (mol %) of isophthalic acid were calculated for the samples sampled every 100 m in the longitudinal direction as described above.

[0059] [Thickness variation in the longitudinal direction] A long roll measuring 100 m in length and 40 mm in width in the longitudinal direction of the film was sampled and measured at a speed of 5 (m / min) using a continuous contact type thickness meter manufactured by Micron Measurement Instruments Co., Ltd. The maximum thickness during measurement was defined as Tmax., the minimum thickness as Tmin., and the average thickness as Tave., and the thickness unevenness in the film width direction was calculated using the following formula (2). Thickness unevenness = {(Tmax.-Tmin.) / Tave.} × 100 (%) Formula (2)

[0060] [Tg (glass transition temperature)] Using a differential scanning calorimeter (DSC220, manufactured by Seiko Electric Industries Co., Ltd.), 5 mg of the unstretched film was placed in a sample pan, the pan was covered, and the temperature was increased from -40°C to 120°C at a heating rate of 10°C / min in a nitrogen gas atmosphere. Tg (°C) was determined based on JIS-K7121-1987.

[0061] [Intrinsic viscosity (IV)] 0.2 g of polyester was dissolved in 50 ml of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (60 / 40 (weight ratio)), and the viscosity was measured using an Ostwald viscometer at 30° C. The unit is dl / g.

[0062] [Evaluation of shrinkage finish] Both ends of the film were bonded with dioxolane to produce a cylindrical label (a label with the main shrinkage direction of the heat-shrinkable film as the circumferential direction), which was then cut to produce 3,000 labels. The diameter of the label in the shrinkage direction was 70 mm. The label was then attached to a 500 ml PET bottle (body diameter 62 mm, minimum diameter of neck 25 mm) by heat shrinking it using a steam tunnel (model: SH-1500-L) manufactured by Fuji Astec Inc., with a passage time of 4 seconds and a zone temperature of 90°C. During attachment, the neck was adjusted so that the 30 mm diameter was at one end of the label. The finish after shrinkage was evaluated visually, with the following criteria: 5: Best finish 4: Good finish 3: Slight defects (up to 2 places) 2: Defects present (3-5 places) 1: Many defects (6 or more) The defects here are wrinkles, folded label edges, uneven shrinkage, and insufficient shrinkage. An evaluation result of 4 or more was considered pass, and 3 or less was considered fail. 3,000 samples were evaluated. The shrinkage finish defect rate (%) was calculated according to the following formula: Shrinkage finish defect rate (%) = number of defective samples / total number of samples x 100

[0063] <Measurement of angle of repose> A stainless steel funnel with an inner diameter of 18 mm at the tip outlet was placed directly above a horizontal stainless steel plate so that the distance (height) from the tip to the plate was 200 mm. 3 kg of raw chips were poured into the funnel and dropped from the tip of the funnel onto the stainless steel plate. The chips were allowed to fall at a rate of approximately 50 g / min. The dropped raw chips formed a conical mountain and stabilized. The angle between the slope of the mountain and the stainless steel plate was measured with a protractor and taken as the angle of repose.

[0064] <Preparation of amorphous polyester raw material (polyester A) chips> In a stainless steel autoclave equipped with a stirrer, thermometer and partial reflux condenser, 100 mol% dimethyl terephthalate (DMT) as a dicarboxylic acid component, 55 mol% ethylene glycol (EG), 30 mol% neopentyl glycol (NPG) and 15 mol% diethylene glycol as polyhydric alcohol components were charged so that the polyhydric alcohol was 2.2 times that of dimethyl terephthalate in molar ratio, 0.05 mol% (relative to the acid component) zinc acetate as an ester exchange catalyst and 0.225 mol% (relative to the acid component) 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 under reduced pressure conditions of 280°C and 26.7 Pa to obtain polyester 1 with an intrinsic viscosity of 0.77 dl / g. The resin size of polyester A was calculated as an average value from 100 pieces of resin. The resin was assumed to be an elliptical cylinder, and the major axis, minor axis and length (cut length of the strand) of the elliptical cross section were measured using a vernier caliper. The results were 3.1 mm in major axis, 2.1 mm in minor axis, 3.3 mm in height, and 37 degrees in angle of repose. The composition, chip size, and angle of repose are shown in Table 1.

[0065] <Recycled PET bottle material (polyester B)> Polyester B is made from recycled PET bottles, and recycled chips from Utsumi Recycle Systems Co., Ltd. are used. It contains 2 mol% isophthalic acid relative to the total dicarboxylic acid components that make up the polyester. The resin size was measured in the same manner as above, and the results were a major axis of 2.9 mm, a minor axis of 2.0 mm, a length of 3.4 mm, and an angle of repose of 36 degrees. The major axis was -6% compared to Polyester A, the minor axis was -5% compared to Polyester A, and the length was +3% compared to Polyester A. The intrinsic viscosity of Polyester B was 0.68 dl / g.

[0066] <Preparation of amorphous polyester raw material (polyester C) chips> Polyester C was polymerized in the same way as Polyester A, and the resin size was changed by changing the die hole size when forming the strands and the cutter speed. The average resin size of Polyester C was calculated from 100 pieces of resin, and the results were a long diameter of 3.8 mm, a short diameter of 2.5 mm, a height of 4.3 mm, and an angle of repose of 43 degrees. The major axis was ±31% relative to polyester B, the minor axis was +25% relative to polyester B, and the length was +26% relative to polyester B. The intrinsic viscosity of Polyester C was 0.77 dl / g.

[0067] [Table 1]

[0068] <Method of manufacturing heat shrinkable film> [Example 1] The polyester A raw chips were dried at room temperature by vacuuming to a moisture content of less than 100 ppm. On the other hand, the polyester B raw chips were heated at 150°C and vacuumed to a moisture content of less than 100 ppm. The raw chips were mixed while being separately fed from the hopper in which they were stored to the final hopper directly above the extruder by a fixed-volume screw feeder. The feeding was carried out by air, and fine powder was removed by a cyclone air filter. The mixing ratio of the raw materials was polyester A: polyester B = 70:30. The raw chips were mixed together in the final hopper. The stirring device used a system in which a spiral ribbon rotates to stir the raw chips. The capacity of the final hopper was 190 kg, and the amount of feed to the extruder was 500 kg per hour. The inclination angle of the hopper was 70°. The mixed raw material chips were then fed from the final hopper to the extruder, melt-extruded using a single-screw extruder at an extrusion temperature of 280°C, and the molten resin was extruded from a T-die, after which it was quenched to obtain an unstretched film with a thickness of 135μm. The shear rate at this time was 180sec -1 The glass transition temperature of the unstretched film was 65°C. This unstretched film was introduced into a tenter and preheated until the film temperature reached 90° C. Then, the clip distance was widened to stretch the film 4.5 times in the width direction at a film temperature of 90° C. The film was then introduced into the final heat treatment zone and heat-treated at a film temperature of 100° C. for 6 seconds. The film temperature fluctuations were within the range of the average temperature ±0.5°C in the preheating, stretching, and final heat treatment steps. The heat-treated film was cooled, and both ends were cut continuously and wound into a roll to obtain a master roll. The thickness of the stretched film was 30 μm. The master roll obtained above was slit into a slit roll having a width of 800 mm and a wound length of 4000 m using a slitter to obtain a heat-shrinkable polyester film roll. The production method is shown in Table 2, and the film evaluation results are shown in Table 3. As a result of the evaluation, the film roll was made from a film having sufficient shrinkability in the width direction, small variations in the shrinkage rate and isophthalic acid ratio in the length direction, good shrink finish, and an extremely small defective rate.

[0069] [Example 2] A heat-shrinkable polyester film roll was produced in the same manner as in Example 1, except that stirring was not performed in the final hopper and a cone-shaped baffle was provided. The production method is shown in Table 2, and the film evaluation results are shown in Table 3. As a result of the evaluation, the film roll was made from a film having sufficient shrinkability in the width direction, small variations in the shrinkage rate and isophthalic acid ratio in the length direction, good shrink finish, and an extremely small defective rate.

[0070] [Example 3] A heat-shrinkable polyester film roll was produced in the same manner as in Example 1, except that no stirring was performed in the final hopper, and the raw material chips of Polyester A and Polyester B were mixed immediately before the extruder through the inner pipe. At this time, the raw material chips of Polyester A were supplied from the top of the final hopper, and the raw material chips of Polyester B were supplied through the inner pipe. At this time, the inner diameter of the inner pipe was 0.2 m, the height H1 in Figures 1 and 2 was 5 m, the height H2 was 1.5 m, and the height H3 was 1.37 m. The production method is shown in Table 2, and the film evaluation results are shown in Table 3. As a result of the evaluation, the film roll was made from a film having sufficient shrinkability in the width direction, small variations in the shrinkage rate and isophthalic acid ratio in the length direction, good shrink finish, and an extremely small defective rate.

[0071] [Example 4] After being chipped, polyester raw material A and polyester raw material B were charged into respective hoppers without drying. Then, they were fed into an extruder in the same manner as in Example 2. A vented twin-screw extruder was used as the extruder, and melt extrusion was carried out while degassing through the vent to remove moisture contained in the raw material chips from the extruder, to produce a film roll in the same manner as in Example 2. The production method is shown in Table 2, and the film evaluation results are shown in Table 3. As a result of the evaluation, the film roll was made from a film having sufficient shrinkability in the width direction, small variations in the shrinkage rate and isophthalic acid ratio in the length direction, good shrink finish, and an extremely small defective rate.

[0072] [Example 5] The raw material chips were dried and put into each hopper in the same manner as in Example 1. Thereafter, the raw material chips were not mixed in the hopper, and the polyester A raw material chips were put into a twin-screw extruder 1 with a vent. On the other hand, the polyester B raw material chips were put into another twin-screw extruder 2, and the molten resin of polyester B discharged from the tip of the twin-screw extruder 2 was side-fed into the twin-screw extruder 1. Each raw material chip was fed into the extruder while being quantified from the hopper by a screw feeder, and the rotation speed of the feeder was adjusted so that the mixing ratio of the raw materials was polyester A: polyester B = 70: 30. The twin-screw extruder 1 was designed to have a vent at the joining point of the resin from the twin-screw extruder 2, and degassing was performed. Polyester A and polyester B were melt-extruded while being mixed inside the twin-screw extruder 1, then extruded from a T-die, and then quenched to obtain an unstretched sheet. The subsequent manufacturing method was the same as in Example 1. The production method is shown in Table 2, and the film evaluation results are shown in Table 3. As a result of the evaluation, the film roll was made from a film having sufficient shrinkability in the width direction, small variations in the shrinkage rate and isophthalic acid ratio in the length direction, good shrink finish, and an extremely small defective rate.

[0073] [Example 6] The mixing ratio of the polyester raw materials was polyester A:polyester B = 80:20. The same conditions as in Example 5 were used except that the transverse stretching temperature in the tenter was 87°C and the final heat treatment temperature was 96°C. At this time, the Tg of the unstretched film was 62°C, the thickness of the unstretched film was 135 μm, and the thickness of the film after stretching was 30 μm. The production method is shown in Table 2, and the film evaluation results are shown in Table 3. As a result of the evaluation, the film roll was made from a film having sufficient shrinkability in the width direction, small variations in the shrinkage rate and isophthalic acid ratio in the length direction, good shrink finish, and an extremely small defective rate.

[0074] [Example 7] The mixing ratio of the polyester raw materials was polyester A:polyester B = 60:40. The same conditions as in Example 5 were used except that the transverse stretching temperature in the tenter was 94°C and the final heat treatment temperature was 103°C. At this time, the Tg of the unstretched film was 69°C, the thickness of the unstretched film was 135 μm, and the thickness of the film after stretching was 30 μm. The production method is shown in Table 2, and the film evaluation results are shown in Table 3. As a result of the evaluation, the film roll was made from a film having sufficient shrinkability in the width direction, small variations in the shrinkage rate and isophthalic acid ratio in the length direction, good shrink finish, and an extremely small defective rate.

[0075] [Comparative Example 1] The raw material chips of polyester B and polyester C were mixed in the final hopper at a mixing ratio of polyester B:polyester C=30:70. The other conditions were the same as those in Example 2. The production method is shown in Table 2, and the film evaluation results are shown in Table 3. As a result of the evaluation, it was found that although the film roll had sufficient shrinkage in the width direction, the difference in size of the raw material chips was large, and the difference in the angle of repose was large, causing raw material segregation, and the shrinkage rate and the isophthalic acid ratio in the width direction and length direction varied greatly, so that although the shrinkage finish was good in some cases, the film roll had a high defect rate.

[0076] [Comparative Example 2] The same procedure was followed as in Example 2, except that the amount of material fed to the extruder was changed to 120 kg per hour. The production method is shown in Table 2, and the film evaluation results are shown in Table 3. As a result of the evaluation, it was found that although the film roll had sufficient shrinkability in the width direction, the residence time in the final hopper was too long, which caused raw material segregation, and the shrinkage rate and the isophthalic acid ratio in the width and length directions varied greatly, so that although the shrinkage finish was sometimes good, the film roll had a high defect rate.

[0077] [Example 3] The same procedure as in Example 2 was carried out except that the inclination angle of the final hopper was changed to 50°. The production method is shown in Table 2, and the film evaluation results are shown in Table 3. As a result of the evaluation, although the film roll had sufficient shrinkage in the width direction, raw material segregation occurred due to the small inclination angle of the hopper, and the shrinkage rate and the isophthalic acid ratio in the width direction and length direction varied greatly, so that although the shrinkage finish was sometimes good, the film roll had a high defect rate.

[0078] [Example 4] The same procedure was followed as in Example 3, except that the height H2 of the inner pipe was changed to 7 m. In this case, the height H3 was 6.87 m. The production method is shown in Table 2, and the film evaluation results are shown in Table 3. As a result of the evaluation, although the film roll had sufficient shrinkage in the width direction, raw material segregation occurred because formulas 3 and 4 of the inner pipe were not satisfied, and the shrinkage rate and the isophthalic acid ratio in the width direction and length direction varied widely, so that the shrinkage finish was sometimes good, but the defective rate was high.

[0079] [Table 2]

[0080] [Table 3] [Industrial Applicability]

[0081] The heat-shrinkable polyester film roll of the present invention contains a predetermined amount of recycled PET bottle raw materials as described above, and has high shrinkability in the width direction. In addition, since the composition of the film varies little in the longitudinal direction of the roll, the variation in shrinkability in the width direction and longitudinal direction is extremely small. When the film roll is continuously processed into beverage labels, etc., and then shrunk and finished for use, the rate of occurrence of defects such as wrinkles and distortion is extremely small.

Claims

1. The polyester contains 5% by mass or more and 45% by mass or less of recycled PET bottle raw materials and contains an isophthalic acid component, and the polyester contains 50 mol% or more of ethylene terephthalate relative to 100 mol% of all constituent components, and is also composed of neopentyl glycol, 1,4-cyclohexanedimethanol, 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, a heat-shrinkable polyester film roll having a width of 500 mm or more, the heat-shrinkable polyester film roll comprising one or more monomer components selected from the group consisting of 1,2-di-n-butyl 1,3-propanediol, 1,4-butanediol, and hexanediol in an amount such that the total amount of the monomer components is 14 mol % or more in 100 mol % of a polyhydric alcohol component or 100 mol % of a polyvalent carboxylic acid component, and containing no trivalent or higher polyvalent carboxylic acid component, and the heat-shrinkable polyester film roll is characterized in that it satisfies the following requirements (1) to (3): (1) Film samples taken at 100 m intervals along the length of the roll are immersed in 90°C hot water for 10 seconds. The average shrinkage rate in the main shrinkage direction is 40% or more, and is within ±3% of the average value for all samples. (2) In film samples taken at 100 m intervals in the longitudinal direction of the roll, the content of isophthalic acid in the polyester constituting the film is within the average value ±0.3 mol% of the total acid components (100 mol%). (3) The thickness variation in the longitudinal direction of the roll is 20% or less.

2. 2. The heat-shrinkable polyester film roll according to claim 1, characterized in that the heat-shrinkable polyester film is formed from a mixture of at least recycled PET bottle material and one or more types of polymer chips having different compositions.

3. 3. The heat-shrinkable polyester film roll according to claim 1, wherein the polyester constituting the heat-shrinkable polyester film is mainly composed of ethylene terephthalate.

4. 4. The heat-shrinkable polyester film roll according to any one of claims 1 to 3, characterized in that in film samples taken at 100 m intervals in the longitudinal direction of the roll, the polyester constituting the film has an average isophthalic acid content of 0.3 mol% or more and 3.0 mol% or less in 100 mol% of all acid components.

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