Heat shrinkable film and labels

Abstract

To enable circular recycling, label printing can cause discoloration after recycling. The present invention aims to provide a heat-shrinkable film with excellent deinking properties. [Solution] The film is characterized in that when a sample cut into a 10cm x 10cm square is immersed in 90°C hot water for 10 seconds and then removed, the shrinkage rate in the main shrinkage direction is 40% or more, and the film has a coating layer containing an acrylic water-soluble polymer on one side.

Description

[Technical Field]

[0001] The present invention relates to a heat-shrinkable film, and more particularly to a heat-shrinkable film and a label therefor that allows for easy removal of printed labels after printing and is suitable for recycling. [Background technology]

[0002] Heat-shrinkable plastic films are widely used for purposes such as outer packaging to improve the appearance of packaged goods, packaging to prevent direct impact to the contents, and label packaging that serves both to protect glass bottles or plastic bottles and to display product information. Stretched plastic materials used for these purposes include polyvinyl chloride films, polystyrene films, and polyester films, which are used for labels, cap seals, and bulk packaging in various containers such as polyethylene terephthalate (PET) containers, polyethylene containers, and glass containers.

[0003] In recent years, there has been a growing demand for environmental protection. For example, PET bottles are recycled and regenerated as recycled PET resin, which is then used in various plastic products. Due to this increased demand for environmental protection, the amount of recycled PET resin used has increased, and the recycling rate of PET bottles has also risen. Furthermore, plastic waste and marine pollution have become global social problems. Therefore, it is crucial to recycle plastic products and packaging materials that were previously discarded, transforming them into new resources and building a circular economy.

[0004] Labels on beverage PET bottles and toiletry products that use heat-shrinkable film are often used on their own, without lamination with other films. Therefore, labels made with heat-shrinkable film are easier to recycle than food packaging bags and other items made from different materials that are laminated.

[0005] However, labels on beverage PET bottles and toiletry products are printed to enhance their design and provide product information. Even if printed labels are recycled, the resulting recycled material will be colored due to the printing ink, making it unsuitable for recycling. Therefore, in order to improve the recyclability of labels using heat-shrinkable film, it is necessary to remove the printing ink from the label (so-called deinking). Patent document 1 describes that by applying corona treatment to the film, the peelability of the printing ink can be improved by immersing it in an alkaline aqueous solution even after printing. However, alkaline solutions pose a risk of blindness if they get into the eyes and can cause chemical burns if they come into contact with the skin. Therefore, using alkaline solutions for deinking requires equipment to prevent the alkaline solution from splashing, which incurs significant investment costs. Consequently, there is a demand for heat-shrinkable films and labels that can be deinked using less hazardous materials such as water or warm water, in a safer process. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2002-60518 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] This invention was made in view of the above circumstances, and its purpose is to provide a heat-shrinkable film and label that is suitable for recycling, has excellent antistatic properties, allows for easy removal of printing ink from the label, and has excellent transparency. Furthermore, it provides a heat-shrinkable film and label that also has good solvent adhesion properties. [Means for solving the problem]

[0008] As a result of diligent research into the above-mentioned problems, the inventors discovered that these problems could be solved by applying a specific type of compound, and thus completed the present invention. In other words, the present invention has the following configuration. 1. A heat-shrinkable film that satisfies the following requirements (1) to (3). (1) When immersed in 90°C hot water for 10 seconds and then removed, and then immersed in 25°C water for 10 seconds and removed, the thermal shrinkage rate in the maximum thermal shrinkage direction is 40% or more and 80% or less. (2) At least one side has a coating layer containing an acrylic water-soluble polymer. (3) The surface resistivity of at least one side is 1 × 10⁻¹⁰ at a temperature of 23°C and a relative humidity of 65%. 8 (Ω / □) is higher than 1 × 10 15 (Ω / □) or less. 2. A heat-shrinkable film as described in 1, with a thickness of 5 μm or more. 3. A heat-shrinkable film according to 1. or 2., characterized in that the haze at a film thickness of 30 μm is 2% or more and 10% or less. 4. A label having a printed portion on the coating layer described in any of 1. to 3. above. 5. The label described in 4. used in the recycling process. [Effects of the Invention]

[0009] The present invention provides a heat-shrinkable film with excellent antistatic properties and transparency. Furthermore, labels printed using this heat-shrinkable film can be easily cleaned of printing ink, thus providing a heat-shrinkable film and label with excellent recyclability after use. Moreover, the heat-shrinkable film can also be given good solvent adhesion properties. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present invention are a heat-shrinkable film and a label obtained by applying an antistatic agent having an acrylic-based water-soluble polymer on at least one side of a heat-shrinkable film. The heat-shrinkable film and the label on the surface coated with the acrylic-based water-soluble polymer have good antistatic properties and can easily remove printing ink.

[0011] The heat-shrinkable film of the present invention can be composed of polyester, polystyrene, or polyolefin, but is preferably a heat-shrinkable polyester-based film. Hereinafter, a heat-shrinkable polyester-based film will be taken as an example for detailed description. Although the manufacturing method of the heat-shrinkable polyester-based film will be described in detail later, the heat-shrinkable film is usually obtained by conveying an unstretched film obtained by cooling and solidifying a melt-extruded resin using a roll or the like and stretching it. At this time, the conveying direction (film-forming direction) of the film is referred to as the longitudinal direction, and the direction orthogonal to the longitudinal direction is referred to as the film width direction.

[0012] The polyester used for the heat-shrinkable polyester-based film of the present invention has ethylene terephthalate units as main constituent components. It is preferable that the ethylene terephthalate units be contained in an amount of 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more in 100 mol% of the constituent units of the polyester. Examples of other dicarboxylic acid components constituting the polyester of the present invention include aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid, and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid. Moreover, it is preferable not to contain a polyvalent carboxylic acid having a valence of 3 or more (for example, trimellitic acid, pyromellitic acid, and their anhydrides) in the polyester. In a heat-shrinkable polyester-based film obtained by using a polyester containing these polyvalent carboxylic acids, it becomes difficult to achieve the required high shrinkage rate.

[0013] Examples of diol components that make up polyester include ethylene glycol, as well as aliphatic diols such as 1,3-propanediol, 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, hexanediol, neopentyl glycol, hexanediol, alicyclic diols such as 1,4-cyclohexanedimethanol, and aromatic diols such as bisphenol A. Among these, it is preferable to use cyclic diols such as 1,4-cyclohexanedimethanol, or diols having 3 to 6 carbon atoms (for example, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, hexanediol, etc.). In particular, using 1,4-butanediol or neopentyl glycol makes it easier to obtain polyesters that satisfy the essential requirements of the present invention.

[0014] Furthermore, the polyester has a total amorphous component content of 17 mol% or more, preferably 18 mol% or more, more preferably 19 mol% or more, and particularly preferably 20 mol% or more, in 100 mol% of the polyhydric alcohol component and 100 mol% of the polyhydric carboxylic acid component (i.e., in a total of 200 mol%) in the total polyester resin. Among the monomer components mentioned above, examples of monomers that can become 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, and hexanediol. There is no particular upper limit to the total amorphous component content, but it is preferably 30 mol% or less. By adjusting the amount of amorphous components within the above range, a polyester with a glass transition temperature (Tg) of 60-80°C can be obtained.

[0015] Furthermore, it is preferable that the polyester does not contain diols with 8 or more carbon atoms (e.g., octanediol) or polyhydric alcohols with a valency of 3 or higher (e.g., trimethylolpropane, trimethylolethane, glycerin, diglycerin). Heat-shrinkable polyester films obtained using polyesters containing these diols or polyhydric alcohols are less likely to achieve the required high shrinkage rate. It is also preferable that the polyester contains as little diethylene glycol, triethylene glycol, and polyethylene glycol as possible.

[0016] The resin forming the heat-shrinkable polyester film of the present invention may contain various additives as needed, such as waxes, antioxidants, antistatic agents, nucleating agents, viscosity reducers, heat stabilizers, coloring pigments, color inhibitors, and ultraviolet absorbers.

[0017] The heat-shrinkable polyester film of the present invention preferably has a heat shrinkage rate in the width direction, which is the main shrinkage direction of the film, calculated by formula 1 below from the length before and after shrinkage when treated in 90°C hot water for 10 seconds under no load, which is 40% or more and 80% or less. Thermal shrinkage rate = {(length before shrinkage - length after shrinkage) / length before shrinkage} × 100 (%) · Equation 1

[0018] If the hot water shrinkage rate in the main shrinkage direction at 90°C is less than 40%, it is undesirable when used as a film for beverage labels or bento box packaging because the amount of shrinkage is too small, resulting in wrinkles and sagging of the label after heat shrinkage. A hot water shrinkage rate of 43% or more at 90°C is more preferable, 46% or more is particularly preferable, and 50% or more is most preferable. Although it is not a problem if the hot water shrinkage rate in the main shrinkage direction at 90°C is higher than 80%, in this invention, it was not possible to obtain a film with a hot water shrinkage rate higher than 80% at 90°C, so the upper limit was set at 80%.

[0019] The heat shrinkage rate in the orthogonal direction (longitudinal direction) at 90 °C is preferably not less than -3% and not more than 10%. If the hot water heat shrinkage rate in the longitudinal direction at 90 °C is less than -3%, when used as a film for beverage label applications or bento packaging, the elongation becomes large and the appearance deteriorates, which is not preferable. The hot water shrinkage rate in the longitudinal direction at 90 °C is more preferably not less than -2%, particularly preferably not less than -1%, and most preferably not less than 0%. If the hot water heat shrinkage rate in the longitudinal direction at 90 °C is higher than 10%, when used as a film for beverage label applications or bento packaging, the shrinkage in the non-shrinking direction becomes large and the appearance deteriorates, which is not preferable. The hot water shrinkage rate in the longitudinal direction at 90 °C is more preferably not more than 8%, particularly preferably not more than 6%, and most preferably not more than 5%.

[0020] The heat-shrinkable polyester-based film of the present invention preferably has a surface resistivity of at most 1 × 10 13 (Ω / sq) on at least one surface of the film under an atmosphere of 23 °C and 65% relative humidity. When the surface resistivity is high, various troubles due to electrostatic interference occur. For example, in the printing process, so-called printing whiskers occur, winding around rolls in the printing and tubing processes, adhesion of labels to each other after label cutting, particularly difficulties in workability due to adhesion when picking up and attaching labels one by one by hand after stacking the labels, troubles such as poor opening property of the cut labels, and adhesion of dirt such as dust to the surface occur. The surface resistivity is more preferably at most 1 × 10 12.5 (Ω / sq), particularly preferably at most 1 × 10 12 (Ω / sq), and most preferably at most 1 × 10 11.5 (Ω / sq). The surface resistivity under an atmosphere of 23 °C and 65% relative humidity may be at most 1 × 10 8 (Ω / sq), but in the present invention, a film having a lower surface resistivity than 1 × 10 8 (Ω / sq) could not be obtained, so the upper limit was set to 1 × 10 8 (Ω / sq).

[0021] The heat-shrinkable polyester film of the present invention preferably has a coating layer containing an acrylic water-soluble polymer on at least one side of the film. It is more preferable that the coating layer is made of the acrylic water-soluble polymer. By having this coating layer, the surface resistivity value described above can be obtained under an atmosphere of 23°C and 65% relative humidity. In this invention, Elecut C-031L manufactured by Takemoto Oil Co., Ltd. was used.

[0022] From the viewpoint of cost and environmental impact, it is preferable to make the thickness of the heat-shrinkable polyester film of the present invention as thin as possible. However, if it is too thin, the film may tear during the recycling process. Since the present invention has only been implemented up to a film thickness of 5 μm, the lower limit of the thickness has been set to 5 μm.

[0023] The labels obtained from the heat-shrinkable polyester film of the present invention preferably have printing applied to the coating layer of an acrylic water-soluble polymer applied to the film (i.e., have a printed area). By printing on top of the water-soluble coating layer, the printed area can be removed using a liquid such as water or hot water after use as a label.

[0024] By using an acrylic water-soluble polymer, it is possible to impart antistatic properties and the aforementioned removal properties even when the coating layer is very thin. Furthermore, it does not impair the transparency of the film. If the coating layer is made from an acrylic water-soluble polymer, the thickness is very thin and cannot be measured using conventional measurement methods. However, acrylic water-soluble polymers have excellent antistatic properties, and if the coating layer is made from an acrylic water-soluble polymer, the surface resistivity under the above conditions of 23°C and 65% relative humidity will be low. 13 For coating thicknesses less than or equal to (Ω / □), removing the print is not a problem.

[0025] The solid content concentration (amount of adhesion) of the acrylic water-soluble polymer in the coating layer of the stretched heat-shrinkable film is 0.003 g / m². 2 If the value is above 1, the surface resistivity under conditions of 23°C and 65% relative humidity is 1 × 10⁻¹⁰. 13 (Ω / □) or less is preferable. The solid content concentration of the acrylic water-soluble polymer is 0.004 (g / m³). 2 It is more preferable that it be 0.005 (g / m³) or more. 2 It is particularly preferable that it be 0.006 (g / m³) or more, and 0.006 (g / m³) 2 ) or higher is most preferable. The upper limit of the solid content concentration of the acrylic water-soluble polymer in the coating layer of the stretched heat-shrinkable film is 2 (g / m²). 2 If the density is 2 (g / m²), printing is more likely to occur on the labels after printing, so 2 Preferably less than 1.9 g / m³. The solids content concentration of the acrylic water-soluble polymer is 1.9 g / m³. 2 It is more preferable that it be less than 1,8 (g / m³). 2 It is particularly preferable that it be less than 1.7 (g / m²). 2 It is most preferable if it is less than )

[0026] Furthermore, the heat-shrinkable film of the present invention preferably has a haze of 2% to 12% at a thickness of 30 μm. If the haze is higher than 12%, the transparency is poor when used as a film for beverage labels or bento box packaging, making it undesirable as the contents are not clearly visible. A haze of 11% or less at a thickness of 30 μm is more preferable, 10% or less is particularly preferable, and 9% or less is most preferable. A haze of less than 2% is acceptable for a thickness of 30 μm, but since we were unable to obtain a film with less than 2% haze in this invention, the lower limit was set at 2%.

[0027] Furthermore, the dynamic friction coefficient of the heat-shrinkable film of the present invention is preferably 0.06 or more and 0.7 or less. If the dynamic friction coefficient is less than 0.06, it is undesirable because the film will collapse when the labels are cut into sheets and stacked. Also, if the dynamic friction coefficient is higher than 0.7, it is undesirable because the slipperiness is poor and scratches may occur when the film comes into contact with the roll during printing. The dynamic friction coefficient is more preferably 0.08 or more and 0.68 or less, particularly preferably 0.1 or more and 0.66 or less, and most preferably 0.12 or more and 0.64 or less.

[0028] In addition, the heat-shrinkable film of the present invention preferably has a solvent adhesion strength of 2 N / 15 mm or more, as measured by the method described in the examples below. More preferably, the solvent adhesion strength is 2.5 N / 15 mm or more, and even more preferably 3 N / 15 mm or more. Note that the solvent adhesion strength may decrease due to the presence of a coating layer, so it is preferable to form a coating layer using the above-mentioned acrylic water-soluble polymer within a preferred coating amount range in order to ensure solvent adhesion strength.

[0029] The heat-shrinkable film of the present invention only needs to have a coated surface such that the coating layer containing an acrylic water-soluble polymer has a surface resistivity within the range described above. Therefore, the material of the heat-shrinkable film may be polyester, polystyrene, or polyolefin.

[0030] The heat-shrinkable polyester film of the present invention can be obtained by melt-extruding the above-mentioned polyester raw material using an extruder to form an unstretched film, and then stretching the unstretched film transversely uniaxially and heat-treating it using the predetermined method described below. When laminating, multiple extruders, feed blocks, and multi-manifolds may be used. The polyester can be obtained by polycondensing the above-mentioned suitable dicarboxylic acid component and diol component using a known method. In addition, usually, two or more types of chip-shaped polyester are mixed and used as the raw material for the film. When laminating, multiple extruders may be used. When melt-extruding the raw material resin, it is preferable to dry the polyester raw material using a dryer such as a hopper dryer or paddle dryer, or a vacuum dryer. After drying the polyester raw material in this way, it is melted at a temperature of 200-300°C using an extruder and extruded into a film. Any existing method such as the T-die method or the tubular method can be used for extrusion.

[0031] Then, an unstretched film can be obtained by rapidly cooling the sheet-like molten resin after extrusion. As a method for rapidly cooling the molten resin, a method of casting the molten resin from a die onto a rotating drum and rapidly cooling and solidifying it to obtain a substantially unoriented resin sheet can be suitably employed.

[0032] When employing the so-called in-line coating method, it is preferable to coat the resulting unstretched film with an acrylic water-soluble polymer using a gravure roll method. However, the method is not limited to this, and it is also possible to coat a heat-shrinkable polyester film with an acrylic water-soluble polymer after film formation.

[0033] Furthermore, as described later, an unstretched film coated with an acrylic water-soluble polymer can be stretched in the width direction under predetermined conditions to obtain the heat-shrinkable polyester film of the present invention. The following describes preferred stretching methods for obtaining the heat-shrinkable polyester film of the present invention.

[0034] Conventional heat-shrinkable polyester films are manufactured by stretching an unstretched film in the direction of desired shrinkage. Alternatively, there is a manufacturing method called biaxial stretching, which involves stretching longitudinally followed by transverse stretching, but biaxial stretching requires large-scale equipment. In this invention, uniaxial stretching is performed in the width direction, which is the primary shrinkage direction. Furthermore, the manufacturing method using uniaxial stretching in the width (transverse) direction has the advantage of being able to be manufactured with simple equipment because it does not require stretching equipment in the longitudinal direction.

[0035] For stretching in the width direction, the unstretched film is guided to a tenter device that can hold both ends of the film with clips and heat it. After heating the film to a predetermined temperature with hot air, it is stretched by increasing the distance between the clips while conveying it in the longitudinal direction. The preheating temperature for the unstretched film is preferably between Tg + 10°C and + 50°C. More preferably between Tg + 15°C and + 40°C. Preheating below Tg + 10°C is undesirable because the preheating temperature is insufficient, resulting in high stretching force and increased risk of breakage. Heating at temperatures higher than Tg + 50°C is also undesirable because it reduces the stretching force in the width direction of the unstretched sheet, resulting in poor thickness accuracy (uneven thickness) in the width direction. More preferably between Tg + 20°C and + 30°C.

[0036] The film temperature during widthwise stretching is preferably lower than the preheating temperature of the tenter device described above, and between -10°C and +20°C of the film Tg. When the stretching stress in the latter half of the stretching process is higher than that in the first half, the thickness accuracy (so-called uneven thickness) of the stretched film improves. Therefore, to increase the stretching stress in the latter half of the stretching process compared to the first half, it is preferable that the stretching temperature be lower than the preheating temperature. If the film temperature is below Tg -15°C, the stretching force becomes too high, making the film prone to breakage, which is undesirable. If the film temperature exceeds Tg +20°C, the stretching force is too low, resulting in a low thermal shrinkage rate in the widthwise direction measured at 90°C, as described above, which is undesirable. More preferably, the temperature is between Tg -5°C and +15°C, and even more preferably between Tg and +10°C.

[0037] The stretching ratio in the width direction is preferably between 3.5 and 6 times. If the stretching ratio is less than 3.5 times, the stretching force is insufficient, resulting in poor thickness accuracy in the width direction of the film. If the stretching ratio exceeds 6 times, the risk of breakage during film formation increases, and the equipment becomes long, which is undesirable. More preferably, it is between 3.7 and 5.5 times. While stretching is generally performed in a linear pattern, using an exponential stretching pattern results in higher stretching stress at the same stretching ratio, thus improving the thickness accuracy in the film width direction.

[0038] Furthermore, although not particularly limited, it is preferable to cool the film at a temperature lower than the film's Tg after stretching in the width direction. Applying heat treatment after stretching is undesirable because it causes a bowing phenomenon, resulting in differences in the film's physical properties in the width direction. The film is preferably cooled at a temperature of Tg-3°C or lower after stretching, and more preferably at Tg-6°C or lower. Reducing bowing also has the effect of preventing the dried coating layer from cracking. If the coating layer cracks, when printing on the resulting heat-shrinkable film, the printed areas where the coating layer cracked cannot be deinked, so it is desirable that the coating layer does not crack.

[0039] Furthermore, although not particularly limited, heat treatment may be performed after stretching in the width direction to adjust the shrinkage rate. Preferably, the film temperature during heat setting is above the film stretching temperature in the width direction and below the film stretching temperature in the width direction + 30°C. If the film heat setting temperature is below the film stretching temperature in the width direction, molecular relaxation in the width direction will be insufficient, and the heat setting effect will be lost, which is undesirable. If the film heat setting temperature exceeds the film stretching temperature in the width direction + 30°C, the film will crystallize and the shrinkage rate will be low, which is undesirable. More preferably, the film temperature is above the film stretching temperature in the width direction + 1°C and below the film stretching temperature in the width direction + 25°C, and even more preferably above the film stretching temperature in the width direction + 2°C and below the film stretching temperature in the width direction + 20°C.

[0040] The resulting heat-shrinkable polyester film can be printed on a film surface coated with an alkaline aqueous solution using conventionally known methods. The printed film can then be labeled using conventionally known methods. For example, a heat-shrinkable polyester film is cut to a desired width, printed appropriately, and the left and right ends of the film are joined together by solvent bonding or the like to produce a tube film. This tube film is then cut to an appropriate length to form a tube-shaped label. As the organic solvent for bonding, cyclic ethers such as 1,3-dioxolane or tetrahydrofuran are preferred. Other usable solvents include aromatic hydrocarbons such as benzene, toluene, xylene, and trimethylbenzene, halogenated hydrocarbons such as methylene chloride and chloroform, phenols such as phenol, or mixtures thereof. After forming perforations on the label using a known method, the label is placed over a PET bottle, and the PET bottle is placed on a conveyor belt or the like and passed through a shrinkage tunnel that uses steam (steam tunnel) or a shrinkage tunnel that uses hot air (hot air tunnel). As the label passes through these tunnels, it shrinks due to heat, and the label is attached to the bottle container such as a PET bottle. [Examples]

[0041] Next, the content and effects of the present invention will be described by example, but the present invention is not limited to the following examples without departing from its gist. The method for measuring characteristic values ​​in this specification is as follows.

[0042] (Thermal shrinkage rate) The stretched film was cut into 10cm x 10cm squares, with one side parallel to the film's direction of growth. These squares were then immersed in a 90°C water bath for 10 seconds. After 10 seconds, they were immediately immersed in a separate 25°C water bath for another 10 seconds before being removed. The length in the main shrinkage direction of the film was measured, and the thermal shrinkage rate was determined. The direction of greatest shrinkage was defined as the direction of maximum shrinkage. Shrinkage rate (%) = (Dimensions before heating - Dimensions after heating) / Dimensions before heating × 100

[0043] (Surface resistivity) The surface resistivity of the film was measured using a resistivity meter manufactured by Takeda Riken Co., Ltd., under conditions of an applied voltage of 500V, 23°C, and a 65RH atmosphere.

[0044] (Coefficient of friction) The coefficient of dynamic friction μd was measured in accordance with JIS K-7125, under conditions of 23°C and 65%RH, by overlapping a film with a coated surface and an uncoated surface.

[0045] (Solvent bonding strength) A film was coated with 1,3-dioxolane, and the two films were sealed by bonding the uncoated side of the film to the coated side. The sealed portion was cut to a width of 15 mm in the main stretching direction of the film, and this was set in a Baldwin Corporation STM-50 universal tensile testing machine and measured in a 180° peel test at a tensile speed of 200 mm / min.

[0046] (transparency) Haze was measured in accordance with JIS K7105.

[0047] (Film thickness) Measurements were taken using a dial gauge in accordance with JIS K7130-1999 Method A.

[0048] (printing) The print was created using three colors of inks from Toyo Ink Manufacturing Co., Ltd.: green, gold, and white.

[0049] (Deinking) The printed label was peeled off to create a 100mm x 150mm test specimen, which was then immersed in 50°C water for 10 minutes. The printed surface was then fixed to the specimen stand of a JSPS-type abrasion tester (Yasuda Seiki Co., Ltd.). Under a test environment of 23°C x 65%RH, a friction element with a load of 1.96N was subjected to a 50-reciprocation cycle (1 reciprocation = 20mm, total 10,000mm) at a speed of 30 reciprocations / minute to remove the ink. The remaining print on the abrasion test area was then visually inspected. ○: No printing △: There are some areas where the printing remains slightly visible. ×: The area where the printing remains is 20% or more of the total area.

[0050] The properties and composition of the polyester raw materials used in the examples and comparative examples, as well as the film manufacturing conditions (stretching, heat treatment conditions, etc.) in the examples and comparative examples, are shown in Tables 1 and 2, respectively.

[0051] The polyester used in the examples is as follows: Raw materials a, b: Polyethylene terephthalate. Intrinsic viscosity: 0.75 dl / g Raw material c: Polyester composed of 30 mol% neopentyl glycol, 70 mol% ethylene glycol, and terephthalic acid. Intrinsic viscosity: 0.78 dl / g

[0052] [Table 1]

[0053] The coating solution used in the examples is as follows: (1) Coating solution A: Coating solution of acrylic water-soluble polymer An aqueous solution containing 15% of an acrylic polymer-based mixture (Elecut C-031L, manufactured by Takemoto Oil & Fat Co., Ltd.) was diluted with water (weight ratio 50 / 50) to prepare the coating solution. (2) Coating solution B: Anionic surfactant A coating solution containing 15% anion (sodium paraffin sulfonate) was diluted with an isopropyl alcohol / water = 50 / 50 (by weight) solution to prepare the coating solution. (3) Coating solution C Nonionic surfactant A coating solution containing 15% nonionic surfactant was diluted with an isopropyl alcohol / water = 50 / 50 (by weight) solution to prepare the coating solution.

[0054] (Example 1) (1) Manufacturing of heat-shrinkable polyester film The raw materials a, b, and c described above were mixed in a weight ratio of 5:30:65 and fed into an extruder. The mixed resin was then melted at 280°C and extruded through a T-die. It was then wrapped around a rotating metal roll cooled to a surface temperature of 30°C and rapidly cooled to obtain an unstretched film with a thickness of 150 μm. The take-up speed (rotation speed of the metal roll) of the unstretched film at this time was approximately 40 m / min. The Tg of the unstretched film was 75°C. On one side of the obtained unstretched film, coating solution A was applied using a bar coater, resulting in a solid content coating of 0.080 g / m². 2 It was applied in this manner. The coated, unstretched film was held at both ends in the width direction by clips in a tenter device and heated at 95°C (Tg +20°C), with an airflow of 12 m / s for 12 seconds. It was then stretched five times in the width direction at 80°C (Tg +5°C), with an airflow of 18 m / s for 10 seconds. The stretched film was subjected to primary cooling at 50°C (Tg -25°C), with an airflow of 6 m / s for 3 seconds, followed by heat treatment at 82°C (Tg +7°C), with an airflow of 8 m / s for 10 seconds. After secondary cooling at 50°C (Tg -25°C), with an airflow of 8 m / s for 5 seconds, both edges were cut off and the film was wound into a roll, continuously producing a uniaxially oriented film with a width of 500 mm and a thickness of approximately 30 μm. The properties of the obtained film were evaluated using the method described above. The evaluation results are shown in Table 3. A heat-shrinkable film with good properties was obtained.

[0055] (2) Creating labels A stretched film coated with coating solution A was then printed in three colors using Toyo Ink Manufacturing Co., Ltd.'s green, gold, and white inks. Labels were created by applying 1,3-dioxolane longitudinally to the non-printed side of a printed film and then laminating the two films together, with the non-coated side (printed side) of the film being coated with 1,3-dioxolane. The printed labels were evaluated for threshing using the method described above. The evaluation results are shown in Table 3. No printing remained, indicating a good result.

[0056] (Example 2) The solid content coating amount of coating solution A is 0.160 g / m². 2 Except for applying it in the manner described above, A heat-shrinkable film and label were obtained using the same method as in Example 1. Compared to Example 1, better results were obtained, except for a decrease in surface resistance.

[0057] (Example 3) The solid content coating amount of coating solution A is 0.040 g / m². 2 A heat-shrinkable film and label were obtained in the same manner as in Example 1, except that they were applied in the same manner as in Example 1. The surface resistance was higher than in Example 1. Aside from that, we obtained good results.

[0058] (Example 4) A heat-shrinkable film and label were obtained in the same manner as in Example 1, except that the weight ratio of raw materials a, b, and c was 2:33:65. Compared to Example 1, better results were obtained, except that the haze was reduced.

[0059] (Example 5) A heat-shrinkable film and label were obtained in the same manner as in Example 1, except that the thickness of the unstretched film was set to 30 μm. Better results were obtained compared to Example 1, except that the film thickness was thinner.

[0060] (Comparative Example 1) The heat-shrinkable film and label were prepared in the same manner as in Example 1, except that coating solution A was replaced with coating solution B. The result was obtained. The heat-shrinkable film was equivalent to that of Example 1, but the deinking of the resulting labels was poor. It was the result.

[0061] (Comparative Example 2) A heat-shrinkable film and label were obtained in the same manner as in Example 1, except that coating solution A was replaced with coating solution C. The heat-shrinkable film was equivalent to that of Example 1, but the deinking of the obtained label was poor. It was the result.

[0062] (Comparative Example 3) Coating solution A was changed to coating solution B, and the solid content coating amount was increased to 0.160 g / m². 2 A heat-shrinkable film and label were obtained in the same manner as in Example 1, except that the coating was applied in the same way. The surface resistance of the film was lower than in Example 1. Also, similar to Comparative Example 1, the deinking results were poor.

[0063] (Comparative Example 4) Coating solution A was changed to coating solution B, and the solid content coating amount was reduced to 0.040 g / m². 2 A heat-shrinkable film and label were obtained in the same manner as in Example 1, except that the coating was applied in the same way. The surface resistance of the film was higher than in Example 1. Also, similar to Comparative Example 1, the deinking results were poor.

[0064] (Comparative Example 5) Coating solution A was changed to coating solution C, and the solid content coating amount was increased to 0.160 g / m². 2 A heat-shrinkable film and label were obtained in the same manner as in Example 1, except that the coating was applied in the same way. The surface resistance of the film was lower than in Example 1. Also, similar to Comparative Example 2, the deinking results were poor.

[0065] (Comparative Example 6) Coating solution A was changed to coating solution C, and the solid content coating amount was reduced to 0.040 g / m². 2 A heat-shrinkable film and label were obtained in the same manner as in Example 1, except that the coating was applied in the same way. The surface resistance of the film was higher than in Example 1. Also, similar to Comparative Example 2, the deinking result was poor.

[0066] (Comparative Example 7) A heat-shrinkable film and label were obtained in the same manner as in Example 1, except that the coating solution was not applied. The surface resistance of the film was higher than in Example 1. Also, similar to Comparative Example 2, the deinking results were poor.

[0067] [Table 2]

[0068] [Table 3] [Industrial applicability]

[0069] The heat-shrinkable film of the present invention exhibits excellent deinking properties for printing and is easy to recycle after use as a label.

Claims

1. A heat-shrinkable film that satisfies the following requirements (1) to (3). (1) When immersed in 90°C hot water for 10 seconds and then removed, and then immersed in 25°C water for 10 seconds and removed, the thermal shrinkage rate in the direction of maximum thermal shrinkage is 40% or more and 80% or less. (2) At least one side has a coating layer containing an acrylic water-soluble polymer. (3) The surface resistivity of at least one side is 1 × 10⁻¹⁰ at a temperature of 23°C and a relative humidity of 65%. ８ (Ω / □) is higher than 1 × 10 １３ (Ω / □) or less.

2. The heat-shrinkable film according to claim 1, wherein the thickness is 5 μm or more.

3. The heat-shrinkable film according to claim 1, characterized in that the haze at a film thickness of 30 μm is 2% or more and 12% or less.

4. A label having a printed portion on the coating layer of a heat-shrinkable film according to any one of claims 1 to 3.

5. A label according to claim 4, used in a recycling process.

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