JP6671866B2 - Heat shrinkable film - Google Patents

Description

  The present invention relates to a heat-shrinkable film used as a heat-shrinkable label for containers such as PET bottles.

  In recent years, a heat-shrinkable film has been attached to a container such as a PET bottle for the purpose of imparting designability. Such a heat-shrinkable film is required to have shrinkage characteristics and design suitable for use in a container.

  As such a heat-shrinkable film, for example, 5 to 30 parts by mass of an aliphatic ester compound and / or an aromatic ester compound is blended with 100 parts by mass of a polystyrene resin containing syndiotactic polystyrene. A heat-shrinkable film having at least one layer has been proposed (see Patent Document 1).

  However, Patent Literature 1 does not sufficiently study the wear resistance of the heat-shrinkable film. In the case of using a heat-shrinkable film, when a polystyrene resin is used, the heat shrinkage is excellent, but the abrasion resistance of the surface is inferior. There is a problem that the performance is reduced.

  Therefore, development of a heat-shrinkable film having excellent wear resistance is desired.

JP 2007-70545 A

  An object of the present invention is to provide a heat-shrinkable film having excellent wear resistance.

  The present inventor has conducted intensive studies to solve the above problems, and as a result, a heat shrinkable film having at least a layer containing a resin component containing a styrene-butadiene copolymer, as a resin component, by a specific method. It has been found that the above object can be achieved by using a structure having a measured softening point of 82 ° C. or lower, and the present invention has been completed.

That is, the present invention provides the following heat-shrinkable film.
1. A heat-shrinkable film having at least a layer containing a resin component containing a styrene-butadiene copolymer,
The resin component has a softening point of 82 ° C. or less as measured by the following measurement method.
A heat-shrinkable film;
[Softening point measurement method]
(1) A needle probe is placed on the pellet sample placed in the furnace.
(2) A load of 450 g is applied to the needle insertion probe, and the temperature is raised at a rate of 2 ° C./min.
(3) The softening point is defined as the temperature at which the probe enters the sample at 1000 μm.
2. The heat-shrinkable film according to claim 1, wherein the abrasion resistance measured by the following measurement method is 1,000 times or more;
[Abrasion resistance measurement method]
(1) A heat-shrinkable film is attached to a conical jig made of aluminum having a vertex R of R = 10 mm using a tape.
(2) A heat-shrinkable film is separately attached to an aluminum plate.
(3) The heat-shrinkable film at the top of the jig is brought into contact with the heat-shrinkable film attached to the aluminum plate, a load of 100 g is placed on the jig, and the temperature is 23 ° C ± 2 ° C. The jig is slid parallel to the aluminum plate under the conditions of a humidity of 65% ± 10% and a speed of 6000 mm / min and a moving distance of 45 mm.
(4) In the heat-shrinkable film attached to the aluminum plate, whether the heat-shrinkable film at the top of the jig was in contact with the heat-shrinkable film was permeated on a white paper by applying a permeating solution. Then, the occurrence of a pinhole is determined, and the number of sliding operations until the occurrence of the pinhole is measured with one reciprocation being one.

  The heat shrinkable film of the present invention can exhibit excellent wear resistance.

It is a schematic diagram which shows the abrasion resistance measuring method.

The heat-shrinkable film of the present invention has at least a layer containing a resin component containing a styrene-butadiene copolymer, and the resin component has a softening point of 82 ° C or lower as measured by the following measurement method.
[Softening point measurement method]
(1) A needle probe is placed on the pellet sample placed in the furnace.
(2) A load of 450 g is applied to the needle insertion probe, and the temperature is raised at a rate of 2 ° C./min.
(3) The softening point is defined as the temperature at which the probe enters the sample at 1000 μm.
Hereinafter, the heat shrinkable film of the present invention will be described in detail.

  The heat-shrinkable film of the present invention has at least a layer containing a resin component containing a styrene-butadiene copolymer, and the resin component has a softening point of 82 ° C or less. When the heat-shrinkable film has at least the above-mentioned layer, excellent wear resistance can be exhibited. When the softening point exceeds 82 ° C., the heat-shrinkable film cannot exhibit sufficient abrasion resistance. A preferred upper limit of the softening point is 80 ° C, and a more preferred upper limit is 78 ° C. The lower limit of the softening point is not particularly limited, but is preferably 70 ° C, and more preferably 75 ° C. The heat shrinkable film of the present invention may have at least one layer having a softening point of the resin component of 82 ° C. or lower, and may have a multilayer structure. When the heat-shrinkable film of the present invention has a multilayer structure, it is preferable that the heat-shrinkable film has a layer structure having the above layer on the outermost surface.

In the present invention, the softening point is measured by the following measuring method.
(1) A needle probe is placed on the pellet sample placed in the furnace.
(2) A load of 450 g is applied to the needle insertion probe, and the temperature is raised at a rate of 2 ° C./min.
(3) The softening point is defined as the temperature at which the probe enters the sample at 1000 μm.
The softening point can be measured, for example, using a thermomechanical analyzer TMA-50 (model number) manufactured by Shimadzu Corporation in a measurement temperature range of 20 to 110 ° C. In the above-described measurement method, when the pellet sample set in the furnace starts to soften, the needle probe enters the sample, and the position of the needle probe is displaced downward. In the above-described measurement method, the temperature at the time when the penetration probe penetrates the sample by 1000 μm is defined as the softening point.

  The resin component contained in the layer constituting the heat shrinkable film of the present invention contains a styrene-butadiene copolymer. The styrene-butadiene copolymer preferably has a butadiene unit content of 15 to 30% by weight. When the resin component constituting the heat-shrinkable film contains a styrene-butadiene copolymer having a butadiene unit content of 15 to 30% by weight, the heat-shrinkable film exhibits excellent wear resistance. it can. The content of butadiene units in the styrene-butadiene copolymer is more preferably from 20 to 25% by weight, and still more preferably from 21 to 24% by weight.

  If the softening point of the resin component is 82 ° C. or lower, the styrene-butadiene copolymer may be used alone, or two or more styrene-butadiene copolymers may be used as a mixture.

  The styrene-butadiene copolymer has a melt flow rate (MFR) of preferably 4 to 9 g / 10 minutes, more preferably 5 to 8 g / 10 minutes. If the melt flow rate is too low, the fluidity of the styrene-butadiene copolymer may decrease during extrusion molding, and if it is too high, the uniformity of the thickness of the front and back layers may decrease. In this specification, the melt flow rate is a value measured under the conditions of a temperature of 200 ° C. and a load of 49.03 N.

  The number average molecular weight of the styrene-butadiene copolymer is preferably from 80,000 to 200,000, more preferably from 100,000 to 180,000. By setting the number average molecular weight within the above range, a heat-shrinkable film having more excellent heat-shrinkability and the like can be obtained. In addition, in this specification, a number average molecular weight is a value measured by gel permeation chromatography (GPC).

  The above layer may contain an anti-blocking agent. By containing the above anti-blocking agent, the heat-shrinkable film of the present invention can exhibit excellent anti-blocking properties.

  The antiblocking agent is not particularly limited, and includes, for example, impact-resistant polystyrene, organic fine particles, and the like.

  As the impact polystyrene, for example, styrene-butadiene graft copolymer obtained by graft polymerization of butadiene with styrene, polybutadiene rubber is dissolved in a styrene monomer, and this solution is subjected to bulk polymerization, solution polymerization or suspension polymerization, A resin or the like obtained by simply mechanically mixing can be used.

  The impact-resistant polystyrene has a so-called sea-island structure in which a rubber phase is dispersed in a polystyrene phase. In this case, the average particle diameter of the rubber phase dispersed in the polystyrene phase is preferably from 1 to 3 μm, more preferably from 2 to 2.5 μm. If the average particle size of the rubber phase is too small, the anti-blocking effect is not sufficient, and blocking may occur. If the average particle size is too large, ink flying may occur during printing, resulting in poor printing.

  The melt flow rate (MFR) of the impact-resistant polystyrene is preferably from 1.5 to 10 g / 10 minutes, more preferably from 2 to 8 g / 10 minutes. By setting the MFR within the above range, the heat-shrinkable film can exhibit an appropriate anti-blocking property.

  Examples of commercially available impact-resistant polystyrene include Toyostyrol E640 (manufactured by Toyo Styrene), PSJ-polystyrene H6872 (manufactured by PS Japan), and 475D (manufactured by PS Japan).

  The organic fine particles are not particularly limited, and include, for example, polymethyl methacrylate, polystyrene, methyl methacrylate-styrene copolymer, and the like. Among these, a methyl methacrylate-styrene copolymer is preferred. These organic fine particles may be used alone or in combination of two or more.

  The organic fine particles may be crosslinked or non-crosslinked. Examples of commercially available organic fine particles include Gantz Pearl (trade name) manufactured by Gantz Kasei Co., Ltd. and Art Pearl (trade name) manufactured by Negami Corporation.

  The average particle diameter of the organic fine particles is about 0.5 to 5 μm, preferably about 1 to 4 μm. When the average particle diameter is 0.5 μm or more, the effect of improving lubricity and blocking resistance is excellent, and when the average particle diameter is 5 μm or less, ink skipping or the like hardly occurs during printing. As the organic fine particles, organic fine particles having different average particle diameters can be used in combination.

  The amount of the antiblocking agent in the above layer is preferably 0.2 to 1.2 parts by weight, more preferably 0.4 to 1.0 part by weight, based on 100 parts by weight of the styrene-butadiene copolymer contained. . If the amount of the anti-blocking agent is too small, the effect of suppressing blocking may be small, and if the amount is too large, the transparency of the film may be reduced.

  The above layer may contain a lubricant. When the layer contains a lubricant, the wear resistance of the heat-shrinkable film can be further improved.

  The lubricant is not particularly limited, and examples thereof include oleamide, stearamide, and erucamide.

  Commercially available lubricants include, for example, Armoslip CP powder (Lion), Armoslip HT powder (Lion), Armoslip E (Lion), fatty acid amide E (Kao), fatty acid amide S (manufactured by Kao Corporation) and the like.

  The heat shrinkable film of the present invention may be a multilayer. When the heat-shrinkable film of the present invention is a multilayer, the layer configuration is not particularly limited, and it is sufficient that the heat-shrinkable film has at least one layer having a softening point of the resin component of 82 ° C. or less. When the heat-shrinkable film of the present invention has a multilayer structure, for example, a surface layer (A), an intermediate layer (B) and a back layer (C) are laminated in this order, and the surface layer (A) The back layer (C) includes a resin component containing the above-mentioned styrene-butadiene copolymer, and the resin component has a softening point of 82 ° C. or lower. Hereinafter, the heat-shrinkable film having the layer configuration will be described.

<Surface layer (A) and back layer (C)>
In the heat-shrinkable film, the above-described layers can be used as the surface layer (A) and the back layer (C) (hereinafter, also referred to as “front and back layers”). The front and back layers may have the same composition, the same thickness, or may be different. The front and back layers preferably have the same composition and the same thickness in that the warp of the heat-shrinkable film can be suppressed.

<Intermediate layer (B)>
The intermediate layer (B) (hereinafter, also simply referred to as “intermediate layer”) of the heat shrinkable film preferably contains a styrene-butadiene copolymer having a butadiene unit content of 15 to 30% by weight. More preferably, it contains 20 to 25% by weight of a styrene-butadiene copolymer. Since the intermediate layer of the heat-shrinkable film contains the styrene-butadiene copolymer having the butadiene unit content in the above range, the heat-shrinkable film has excellent heat shrinkage and abrasion resistance, and has a high tensile elongation. Is shown.

  The melt flow rate (MFR) of the styrene-butadiene copolymer contained in the intermediate layer is preferably from 4 to 9 g / 10 minutes, more preferably from 5 to 8 g / 10 minutes. If the melt flow rate is too low, the fluidity of the styrene-butadiene copolymer may decrease during extrusion molding, and if it is too high, the uniformity of the thickness of the intermediate layer may decrease.

  The number average molecular weight of the styrene-butadiene copolymer contained in the intermediate layer is preferably from 80,000 to 200,000, more preferably from 100,000 to 180,000. By setting the number average molecular weight within the above range, a heat-shrinkable film having more excellent heat-shrinkability and the like can be obtained.

  The intermediate layer may contain a styrene homopolymer (GPPS). When the intermediate layer contains a styrene homopolymer, the abrasion resistance of the heat-shrinkable film can be further improved.

  The melt flow rate (MFR) of the styrene homopolymer is preferably from 4 to 12 g / 10 min, more preferably from 6 to 10 g / min. By setting the MFR of the styrene homopolymer within the above range, the thickness accuracy of the heat-shrinkable film can be further improved.

  The content of the styrene homopolymer in the intermediate layer is preferably from 5 to 35% by weight, more preferably from 10 to 30% by weight, based on 100% by weight of the resin component contained in the intermediate layer. By setting the content of the styrene homopolymer contained in the intermediate layer within the above range, the heat-shrinkable film is more excellent in abrasion resistance.

  Commercially available styrene homopolymers include, for example, CR3500 (manufactured by DIC), HF77 (manufactured by PS Japan), and the like.

  It is preferable that the ratio of the thickness of each layer of the heat-shrinkable film, that is, the ratio of the surface layer (A): the intermediate layer (B): the back layer (C) is 1: 4: 1 to 1: 14: 1. By setting the ratio of the thickness of each layer of the heat-shrinkable film to the above-described range, an appropriate tensile elongation can be imparted to the heat-shrinkable film.

  The heat-shrinkable film of the present invention preferably has an abrasion resistance of at least 1,000 times as measured by the following method. When the abrasion resistance of the heat-shrinkable film of the present invention is 1,000 times or more, the heat-shrinkable film can exhibit sufficient wear resistance to be used as a heat-shrinkable label for containers such as PET bottles. The wear resistance is more preferably 1200 times or more, and further preferably 1500 times or more.

[Abrasion resistance measurement method]
(1) A heat-shrinkable film is attached to a conical jig made of aluminum having a vertex R of R = 10 mm using a tape.
(2) A heat-shrinkable film is separately attached to an aluminum plate.
(3) The heat-shrinkable film at the top point, which is mounted on the jig, is brought into contact with the heat-shrinkable film attached to the aluminum plate, a load of 100 g is placed on the jig, and the temperature is 23 ° C ± 2 ° C. The jig is slid parallel to the aluminum plate at a speed of 6000 mm / min and a moving distance of 45 mm under the conditions of a humidity of 65% ± 10%.
(4) Depending on whether the penetrating liquid is applied to the heat-shrinkable film affixed to the aluminum plate at the top of the jig and where the heat-shrinkable film was in contact with the heat-shrinkable film on white paper or not. Then, the occurrence of a pinhole is determined, and the number of sliding operations until the occurrence of the pinhole is measured with one reciprocation being one.
The wear resistance can be measured, for example, by sliding a jig in parallel with the MD direction (flow direction) of the heat-shrinkable film using HEIDON Tribogear TYPE14FW (model number) manufactured by Shinto Kagaku Co., Ltd.

  The method for measuring wear resistance will be described with reference to the drawings. FIG. 1 is a schematic view showing the method for measuring wear resistance. In FIG. 1, the wear resistance measuring device 1 includes a conical jig 2 and a heat shrinkable film 3 attached to an aluminum plate. A heat-shrinkable film 5 is mounted on the conical jig 2 using a tape 4. The conical jig 2 is an aluminum jig, and R at the apex 21 is R = 10 mm. The heat-shrinkable film 5 is attached to the conical jig 2 so as to cover the apex 21. The heat-shrinkable film 5 at the apex 21 and the heat-shrinkable film 3 attached to the aluminum plate Are in contact with each other, and the conical jig 2 slides parallel to the aluminum plate (in the left-right direction with respect to the paper surface).

  If necessary, additives such as an antioxidant, a heat stabilizer, and an antistatic agent may be added to the heat-shrinkable film of the present invention. In particular, generation of gel can be suppressed by adding a heat stabilizer or an antioxidant.

  The heat shrinkage of the heat shrinkable film of the present invention is preferably 5 to 30%, more preferably 10 to 25% when immersed in a 70 ° C warm water bath for 10 seconds. The heat shrinkage of the heat shrinkable film of the present invention is preferably 30 to 50%, more preferably 35 to 45% when immersed in a hot water bath at 80 ° C for 10 seconds. The heat shrinkage of the heat shrinkable film of the present invention is preferably 55 to 75%, more preferably 60 to 70% when immersed in a warm water bath at 90 ° C for 10 seconds. If the heat shrinkage is too small, a large amount of heat is required when the container is attached to a PET bottle or the like, which may cause deformation of the container.If the heat shrinkage is too large, the container shrinks sharply due to heating. There is a possibility that it will easily occur.

The heat shrinkage of the heat shrinkable film is a value measured by the following measuring method. That is, a test piece having a size of 100 mm in the MD direction × 100 mm in the TD direction is cut out from an arbitrary position on the heat-shrinkable film. In the case of a heat-shrinkable film, the TD direction is the direction in which the shrinkage is large. A hot water bath at each of 70 ° C., 80 ° C., and 100 ° C. is prepared, and the test piece is immersed for 10 seconds to perform heat treatment. The length L1 (mm) of one side in the TD direction of the heat-shrinkable film after the heat treatment is measured, and the heat shrinkage is calculated based on the following equation.
[Thermal shrinkage] (%) = [(100−L1) / 100] × 100

<Production method of heat shrinkable film>
The method for producing the heat-shrinkable film of the present invention is not particularly limited, and includes a conventionally known production method for forming a film. For example, when the heat-shrinkable film of the present invention has a layer configuration in which the surface layer (A), the intermediate layer (B) and the back layer (C) are laminated in this order as described above, the front and back layers and the A method in which the intermediate layer is simultaneously formed and laminated is used. In the co-extrusion method using a T-die, any of a feed block method, a multi-manifold method, and a method using a combination thereof may be used. Specifically, for example, a resin composition for forming the front and back layers, and a resin composition for forming the intermediate layer are each put into an extruder and extruded from a three-type three-layer die into a sheet. After laminating and solidifying by cooling using a take-off roll, there is a method of stretching uniaxially or biaxially.

  A heat-shrinkable label can be prepared by using the heat-shrinkable film of the present invention as a base film. The heat-shrinkable label may have the heat-shrinkable film of the present invention as a base film, and may be laminated with another layer such as a print layer, if necessary.

  The method for attaching the heat-shrinkable label to a container such as a PET bottle is not particularly limited. For example, a so-called center seal process in which the ends of the heat-shrinkable film are adhered to each other using a solvent to form a tube. After that, a heat-shrinkable label is applied, and then the label is attached by a method of shrinking by heating while covering the container.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1
According to the composition shown in Table 1, a resin composition for forming the front layer (A) and the back layer (C) and a resin composition for forming the intermediate layer (B) were prepared. Each of these resin compositions is supplied to a three-layer three-layer extruder at 150 to 200 ° C. so that a three-layer structure of a surface layer (A) / intermediate layer (B) / back layer (C) is obtained. The film was extruded from a 200 ° C. T-die into a sheet and taken out while being cooled and solidified by a take-off roll having a surface temperature of 40 ° C. to prepare a film.
Next, the obtained film is heated by a heating roll at a set temperature of 90 ° C. to longitudinally stretch the film to a stretch ratio of 1.5 times, and then horizontally stretched to a stretch ratio of 5.5 times in a tenter having a preheating zone of 115 ° C. and a stretching zone of 95 ° C. Stretched. Finally, heat treatment was performed at 90 ° C. in the tenter, and the film was wound by a winder to prepare a heat-shrinkable film. The thickness of the obtained heat-shrinkable film was 50 μm. In addition, the obtained heat-shrinkable film was substantially a single-layer film because the same resin was used for the front and back layers and the intermediate layer.

Example 2
According to the composition shown in Table 1, a resin composition for forming the front layer (A) and the back layer (C) and a resin composition for forming the intermediate layer (B) were prepared. Each of these resin compositions is supplied to a three-layer three-layer extruder at 150 to 200 ° C. so that a three-layer structure of a surface layer (A) / intermediate layer (B) / back layer (C) is obtained. The film was extruded from a 200 ° C. T-die into a sheet and taken out while being cooled and solidified by a take-off roll having a surface temperature of 40 ° C. to prepare a film.
Next, the obtained film is heated with a heating roll at a set temperature of 90 ° C. to longitudinally stretch the film to a stretch ratio of 1.5 times, and then horizontally stretched to a stretch ratio of 5.5 times in a tenter having a preheating zone of 115 ° C. and a stretching zone of 95 ° C. Stretched. Finally, heat treatment was performed at 90 ° C. in the tenter, and the film was wound by a winder to prepare a heat-shrinkable film. The thickness of the obtained heat-shrinkable film was 50 μm. The ratio of the thickness of each layer of the heat-shrinkable film, that is, the ratio of the surface layer (A): the intermediate layer (B): the back layer (C) was 1: 9: 1.

Examples 3 to 12 and Comparative Examples 1 to 8
According to the formulations shown in Tables 1 and 2, a heat-shrinkable film was prepared in the same manner as in Example 2.

  The following evaluation was performed using the heat-shrinkable films of Examples and Comparative Examples prepared as described above.

<Softening point>
The softening point of the heat-shrinkable film was measured according to the procedures described in (1) to (3) below. The measurement was performed using a thermomechanical analyzer TMA-50 (model number) manufactured by Shimadzu Corporation at a measurement temperature range of 20 to 110 ° C.
(1) A needle probe is placed on the pellet sample placed in the furnace.
(2) A load of 450 g is applied to the needle insertion probe, and the temperature is raised at a rate of 2 ° C./min.
(3) The softening point is defined as the temperature at which the probe enters the sample at 1000 μm.

<Wear resistance>
The abrasion resistance of the heat-shrinkable film was evaluated according to the procedures described in the following (1) to (4). The measurement was performed by using a HEIDON Tribogear TYPE14FW (model number) manufactured by Shinto Kagaku Co., Ltd. and sliding the jig parallel to the MD direction (flow direction) of the heat-shrinkable film.
(1) A heat-shrinkable film was mounted on a conical jig made of aluminum having a vertex R of R = 10 mm using a tape.
(2) A heat-shrinkable film was separately attached to an aluminum plate.
(3) The heat-shrinkable film at the apex, which is mounted on the jig, is brought into contact with the heat-shrinkable film attached to the aluminum plate, a load of 100 g is placed on the jig, and the temperature is 23 ° C and the humidity is 65. %, The jig was slid parallel to the aluminum plate at a speed of 6000 mm / min and a moving distance of 45 mm.
(4) Depending on whether the penetrating liquid is applied to the heat-shrinkable film affixed to the aluminum plate at the top of the jig and where the heat-shrinkable film was in contact with the heat-shrinkable film on white paper or not. The occurrence of pinholes was determined, and the number of sliding operations until the occurrence of pinholes was measured with one reciprocation as one. Based on the measurement results, evaluation was performed according to the following evaluation criteria.
：: No pinhole occurs even if the number of times of sliding is 1000 times or more ×: Pinhole occurs when the number of times of sliding is 999 times or less

  The results are shown in Tables 1 and 2.

1. 1. Wear resistance measuring device Conical jig
21. 2. Vertex of conical jig 3. heat-shrinkable film attached to an aluminum plate Tape5. Heat shrinkable film

Claims (1)

A heat-shrinkable film having at least a layer containing a resin component containing a styrene-butadiene copolymer,
The resin component has a softening point measured by the following measurement method of 75 ° C. or more and 82 ° C. or less,
The abrasion resistance measured by the following measurement method is 1000 times or more,
A multilayer structure having the layer on the outermost surface,
A heat-shrinkable film;
[Softening point measurement method]
(1) A needle probe is placed on the pellet sample placed in the furnace.
(2) A load of 450 g is applied to the needle insertion probe, and the temperature is raised at a rate of 2 ° C./min.
(3) The softening point is defined as the temperature at which the probe enters the sample at 1000 μm.
[Abrasion resistance measurement method]
(1) A heat-shrinkable film is attached to a conical jig made of aluminum having a vertex R of R = 10 mm using a tape.
(2) A heat-shrinkable film is separately attached to an aluminum plate.
(3) The heat-shrinkable film at the top of the jig is brought into contact with the heat-shrinkable film attached to the aluminum plate, a load of 100 g is placed on the jig, and the temperature is 23 ° C ± 2 ° C. The jig is slid parallel to the aluminum plate at a speed of 6000 mm / min and a moving distance of 45 mm under conditions of 65% ± 10% humidity.
(4) Depending on whether the penetrating liquid is applied to the heat-shrinkable film affixed to the aluminum plate at the top of the jig and where the heat-shrinkable film was in contact with the heat-shrinkable film on white paper or not. Then, the occurrence of a pinhole is determined, and the number of sliding operations until the occurrence of the pinhole is measured with one reciprocation being one.