JP4651982B2 - Heat-shrinkable laminated film and packaging lightweight PET bottle - Google Patents

Description

  The present invention relates to a heat-shrinkable laminated film mainly composed of a polyolefin-based resin, particularly a specific polyethylene-based resin, and a lightweight PET bottle packaged with a label using the film.

Examples of films for packaging (individually) PET bottles include heat-shrinkable polyethylene terephthalate film (hereinafter referred to as PET film), heat-shrinkable polystyrene film (hereinafter referred to as PS film), and heat. A shrinkable polyolefin film (hereinafter referred to as PO film) is known.
The process up to packaging PET bottles and the like using these films is generally as follows.
First, a heat-shrinkable film (generally a laminated flat film) stretched by a predetermined amount mainly in the transverse direction is produced. Then, printing is performed on the inner surface of the film, perforations are formed, and both end surfaces are overlapped (polymerized) and bonded to form a tube shape (long). Then, it is cut into a tube-shaped label for one plastic bottle, which is inserted into the plastic bottle, heat-shrinked, and fastened / packaged.

By the way, a recent effort in the plastic bottle industry (particularly the manufacturer side) is to reduce the weight of the plastic bottle. This is also a result of the conservation of oil resources, which is being promoted as one of the national policies. Along with the weight reduction of this plastic bottle, the weight of the peripheral members is also being reduced. One of them is also a heat-shrinkable tube label.
These weight reductions are all about reducing the thickness (reducing the amount of raw materials used). For example, the target is about 20% for 500ml PET bottles and about 7% for 1.5L PET bottles. It is said that.

However, with regard to weight reduction of PET bottles, problems have arisen particularly on the side of existing labels (tubes) used for the bottles. This problem is mainly summarized in the following three points.
The first point is that if a beverage-filled PET bottle is accidentally dropped, the perforation is easy to break, leading to a drop in the attached label. The cause of this is that the thickness of the bottle has been reduced. For example, when the bottle is dropped, the internal pressure is concentrated on the barrel portion of the bottle due to the impact, and as a result, the barrel portion swells for a moment, and the bulge is perforated. However, this point is referred to as perforation breakage due to dropping, and the resistance is referred to as drop perforation breakage resistance. This rupture is the phenomenon that is most common in polystyrene labels among the existing labels and is often found in polyolefin labels.
The second point is the case of cooling (for example, −5 ° C.) and freezing (selling) a plastic bottle filled with an aqueous or sports beverage. In other words, since the contents are expanded even by this freezing, the body portion of the bottle is expanded. As a result, as in the first point, the perforation cannot endure, leading to breakage (hereinafter, this point is called perforation breakage due to freezing, and the resistance is called freezing perforation breakability). This rupture is the phenomenon that is most common in polystyrene labels among the existing labels and is often found in polyolefin labels.
The third point is the separation of the mounting label and the plastic bottle after the perforation (first performed after use). Although this perforation is performed manually, it is required to be more easily broken because it is manual. (Hereinafter, this characteristic of easily broken labels is called perforation breakability.) However, on the other hand, the ease of perforation is not good for such cases. In other words, there is a contradictory relationship. This is not a problem if there is a label that balances both easily and easily, but it does not exist in the existing label.

  The present invention has been finally found as a result of earnest studies so that the third problem can be solved in a balanced manner together with the first and second problems.

In addition, although the related prior art which tried to solve the above three points as a main problem cannot be found, the problem is that the cylindrical processing of the label can be performed with a solvent seal, and the separation between the PET bottle and the cylindrical label can be performed with water. The patent application that is said is seen.
For example, in this application, a polyethylene copolymer resin (for example, an LLDPE resin alone or a cyclic olefin copolymer resin having a Tg of 50 to 70 ° C. of 30% by weight or less) (further 30% by weight or less of petroleum oil) is used as the resin component used in the intermediate layer. Resin and further 20 wt% or less LDPE resin may be blended), and both surface layers have a cyclic olefin copolymer resin having a Tg of 50 to 75 ° C. (the resin alone, but 5 wt% or less). If there is, LLDPE resin may be blended), and a heat-shrinkable polyolefin film in which at least three layers are laminated (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2001-315260

That is, the present invention is characterized by a heat-shrinkable laminated film in which a film made of the following resin composition A is an intermediate layer (A) and a film made of the resin composition B is both outer surface layers (B).
<Resin composition A>,
Linear metallocene-catalyzed low-density polyethylene resin 45-65 wt%, low-density polyethylene resin 5-25 wt%, 10-15 wt% cyclic olefin-based resins and petroleum resins 5-25 wt%.
<Resin composition B>,
Cyclic olefin resin 70-90 mass% and linear low density polyethylene resin 10-30 mass%.

  The heat-shrinkable laminated film has a perforated tube-shaped label that is a packaged lightweight PET bottle that is heat-shrink-fastened to a lightweight PET bottle.

  Since this invention is comprised as mentioned above, there exist the following effects.

  In particular, it is a heat-shrinkable film having a good balance of perforation breakability in addition to excellent fall perforation breakability and freeze perforation breakage resistance for reducing the weight of PET bottles.

  Of course, other necessary properties such as proper film hardness (appropriate stiffness), transparency, tube label processability (eg, tube-shaped molding can be done with organic solvents, printing, etc. It is a heat-shrinkable film excellent in natural shrinkage resistance and the like.

  By giving the above-mentioned characteristics, it became possible to use as a perforated tube-like label for a thinner plastic bottle.

First, the intermediate layer (A) will be described.
The resin composition A forming the layer is a linear low-density polyethylene resin (hereinafter referred to as m-LLDPE resin), a low-density polyethylene resin (hereinafter referred to as LDPE resin), and a cyclic structure selected from metallocene catalysts. A combination of four components of an olefin resin (hereinafter referred to as CO resin) and a petroleum resin is essential, and m-LLDPE resin is 45 to 65% by mass, preferably 50 to 60% by mass, and LDPE resin is 5 to 25% by mass. , Preferably 10-20% by mass, CO resin 5-15% by mass, preferably 7-12% by mass, petroleum resin 5-25% by mass, preferably 7-15% by mass, and blended uniformly Must be resin. Here, this blending ratio is the ratio of each component when the four component mixture is 100 mass%.
The blend resin newly created by the four components and the blending ratio thereof is present as the intermediate layer (A), and in particular, the fall perforation resistance, the freeze perforation resistance, and the perforation resistance ( Hereinafter, these and the like are collectively referred to as “three characteristics”).
Therefore, if one of these four components is missing or replaced with another component, and if the blending ratio is outside these specific ranges, these three properties as well as other necessary properties are expressed in a balanced manner. I can't do that.
In addition, this newly created blend resin impairs the film formability, film transparency, adhesion to the front and back layers (B), natural shrinkage resistance, proper waist strength, etc. It also has characteristics that can be expressed in a well-balanced manner.

  As described above, the intermediate layer (A) is a layer that performs the central action of the above-described three characteristics. From the viewpoint of the components used, the m-LLDPE resin plays a central role. The other three components act to impart other necessary characteristics while more smoothly supporting the action of the resin. Other necessary properties include, for example, higher transparency, and balance development of heat shrinkage rate (especially at the initial stage) with both outer surface layers (B). Wrinkles and reduced transparency), increased interlayer adhesion, suppression of natural shrinkage, expression of proper hardness of the film waist (hard, not soft and easy to handle), higher heat For example, expression of shrinkage rate.

Specifically, the m-LLDPE resin is as follows.
That is, unlike the conventionally known linear low density polyethylene obtained by polymerization with a Ziegler-Natta catalyst, it is a linear low density polyethylene polymerized with a metallocene catalyst. The distribution of sharp molecular weight and α-olefin (eg, propylene, butene 1, hexene 1, octene 1, etc.) that is copolymerized in a small amount are uniform and have excellent impact strength, tear resistance, transparency, etc. is doing. These excellent characteristics are considered to act as a base for the expression of the three characteristics.

The m-LLDPE resin has a density, a melt flow rate (MFR) (MFR) (depending on the molecular weight and the type and amount of α-olefin (eg, propylene, butene 1, hexene 1, octene 1) to be copolymerized in a small amount. JISK K7210) (g / 10 min) is different. Although it selects suitably in this, when a preferable thing is illustrated, it is as follows.
The density (g / cm ³ ) is about 0.900 to 0.935, preferably 0.915 to 0.930, and the MFR is 1.0 to 3.0, preferably 1.5 to 2.5.
The density here is less than 0.900, particularly in the direction of making it weaker in terms of film strength and waist strength. Conversely, if it exceeds 0.935, transparency is particularly improved. By acting in the direction of worsening. On the other hand, if it is MFR, if it is less than 1.0, it becomes difficult to form more smoothly. Conversely, if it exceeds 3.0, among the above three characteristics, in particular, drop perforation resistance and freeze perforation resistance It does not act favorably on the expression of sex.

  And even if it is m-LLDPE resin, unless the compounding ratio shall be 45-65 mass%, the new blend resin which can express the said 3 characteristic most effectively will not be created. That is, when it is less than 45% by mass, the perforation drop breakability is particularly deteriorated, and when it exceeds 65% by mass, the perforation is particularly deteriorated.

Next, LDPE resin, CO resin, and petroleum resin, which are other components, will be described.
First of all, LDPE resin, among other necessary properties, mainly helps to develop a balance between higher transparency and heat shrinkage rate between both outer surface layers (B).
Specifically, the resin is a generally known high-pressure LDPE, and its density (g / cm ³ ) is in the range of about 0.900 to 0.925.
Unlike the medium- and low-pressure high-density polyethylene, the resin itself is soft and excellent in impact strength and tear strength. These three characteristics can be obtained in a well-balanced manner when the MFR (JIS K6750) (g / 10 min) is in the range of 0.3 to 2.5.

  And even if it is the said LDPE resin, it is necessary to make the compounding ratio into 5-25 mass%. If it is less than 5% by mass, the initial heat shrinkage rate (for example, within 5 seconds at 60 to 70 ° C.) in a low temperature range with respect to both the outer surface layer (B) and the direction of worsening the transparency is particularly imbalanced. The difference in shrinkage speed of the intermediate layer is widened, and the intermediate layer becomes faster. When the amount exceeds 25 masses, this also deteriorates the transparency, and in particular, decreases the film strength of the entire intermediate layer (A). Because it becomes.

In addition to the above-mentioned necessary properties, the CO resin mainly helps to increase the interlayer adhesion, suppress the spontaneous shrinkage, and develop the appropriate hardness of the film waist.
The resin is specifically as follows.
Resins obtained by hydrogenating saturated ring-opening polymers of cyclic olefins (for example, norbornene), random copolymer resins of α-olefins such as ethylene or propylene and cyclic olefins (for example, norbornene and its derivatives, tetracyclododecene and its derivatives) And resins obtained by hydrogenating a ring-opening polymer of a cyclic olefin and an α-olefin, and resins obtained by grafting a small amount of an unsaturated carboxylic acid and a derivative thereof onto these resins.

  When the CO resin is a copolymer polymer with an α-olefin, various physical properties such as film moldability change with Tg (secondary point transfer temperature) depending on the copolymerization ratio of the α-olefin. Here, the preferred one with Tg should be selected, which is about 60-90 ° C, preferably 65-80 ° C. Those having this Tg range are particularly effective for suppressing spontaneous shrinkage.

  And even if it is the said CO resin, the compounding ratio needs to be 5-15 mass%. If the amount is less than 5% by mass, the natural heat shrinkage rate is particularly increased. If the amount exceeds 15% by mass, the central action of the m-LLDPE is particularly suppressed and the transparency is deteriorated.

And it is a petroleum resin, which assists in the expression of higher heat shrinkage and the appropriate hardness of the waist of the film among the other necessary properties. Furthermore, it effectively acts to improve to a higher level, particularly in the perforation breakability during the central action. Here, regarding the appropriate hardness of the waist, since the most effective hardness cannot be adjusted with the CO resin, the petroleum resin also effectively assists the adjustment.
Specific examples of the resin include generally known aliphatic, aromatic, alicyclic and terpene petroleum resins which do not have an unsaturated group (by hydrogenation). Saturation). Either may be used, but selection of those having a softening point of 115 to 145 ° C. is preferred.

  And even if it is the said petroleum resin, it is necessary to make the compounding ratio into 5-25 mass%. If this is less than 5% by mass, it becomes difficult to suppress the ductility that is necessary for m-LLDPE, and it becomes difficult to achieve proper ductility. It will have an adverse effect on the breakability of each perforation of falling and freezing.

Next, both outer surface layers (B) will be described.
The resin composition B forming the layer essentially comprises two components of a selected cyclic olefin resin and a linear low density polyethylene resin, and the cyclic olefin resin is preferably 70 to 90% by mass, preferably It should be 75 to 85% by mass, and the linear low density polyethylene resin should be blended in an amount of 10 to 30% by mass, preferably 15 to 25% by mass.
Here, the cyclic olefin-based resin is the same as the CO-based resin exemplified above, and the linear low-density polyethylene resin is an m-LLDPE resin exemplified above or an LLDPE resin by a Ziegler-Natta catalyst (hereinafter t). -Referred to as LLDPE resin). Of these, an appropriate selection is made in consideration of the balance with the intermediate layer (A). The CO-based resin is preferably the same resin as that used for the intermediate layer (A), but any LLDPE resin may be used for both outer surface layers.
In addition, the mass% of this component is a ratio when both mixing is 100 mass%.

  The present invention can be achieved only when both the outer surface layers (B) having the two components and the blending ratio are laminated on both surfaces of the intermediate layer (A). The effect is mainly the expression of the center seal property by the organic solvent which is difficult to obtain in the layer (A). The center seal property is a property that allows both ends of a flat heat-shrinkable film to be polymerized at the center, an organic solvent is continuously applied to the polymerized portion, and the adhesive can be firmly bonded simply by pressure bonding. For the center seal, there are other methods such as adhesives and heat-sealing. However, these methods are limited in speeding up, uneven adhesion easily, and complicated in equipment. .

  The organic solvent is required to have a polymer film surface that dissolves or swells at an appropriate rate and is easy to evaporate. The proper speed is, for example, a speed at which the surface layer portion of the film dissolves or swells following the speed when polymerizing and bonding at a speed of 100 to 200 m / min. Therefore, the solvent that dissolves or swells at a rate faster than this rate will erode into the film, leading to whitening. Conversely, if it is slow, it will not be possible to bond. The control of the dissolution or swelling rate can be performed by the polymerization adhesion rate itself, but is preferably carried out by mixing two or three kinds of the solvents having different preferable dissolution or swelling ability. One example is a mixed solvent of a cyclic saturated hydrocarbon such as cyclohexane, a saturated hydrocarbon such as n-hexane and a fatty ketone such as acetone or a cyclic ketone such as tetrahydrofuran.

The (adhesion) seal action by the organic solvent is manifested by the CO-based resin component in the two components. However, with only this component, for example, when a finger or the like comes into contact with the film surface during handling, a fingerprint is likely to be attached to that portion. The attached fingerprint portion becomes whitish (it is considered to be due to the erosion of hand oil), and the appearance is of course deteriorated as well as the gloss. Further, with this component alone, the appropriate film waist hardness expressed by the intermediate layer (A) is easily shifted to a harder one.
A means found to solve these problems is, in particular, a blend of LLDPE resin to CO-based resin. An appropriate film waist hardness is maintained, whitening due to the fingerprint is eliminated, and both outer surface layers having excellent center seal properties can be obtained.
Of course, this two-component blend resin is extremely excellent in layer moldability and adhesion to the intermediate layer (A), and there is no need for an adhesive layer to intervene.

And although it is new resin by the blend of the said 2 component, it is necessary to keep the compounding ratio to 70-90 mass% for CO-type resin, and to suppress LLDPE resin to 10-30 mass%. If the CO-based resin is less than 70% by mass, the above-mentioned center seal property cannot be obtained most effectively. On the contrary, if it exceeds 90% by mass, whitening due to fingerprints cannot be completely eliminated and the most appropriate film can be obtained. It becomes impossible to maintain the stiffness of the waist (shifts in a direction that is hard and difficult to use).
As a blocking inhibitor, for example, a small amount of silica may be added.

In the heat shrinkability of the film by the three layers, there is no difference in heat shrinkage speed between the intermediate layer (A) and both outer surface layers (B), and in which direction (longitudinal and transverse directions) The heat shrinkage rate is something, but the direction in which the heat shrinkage rate is required is determined by the intended use of the film. The following is an example of a plastic bottle tubular label, which is cited as one preferred application of the present invention.
The label must first be able to suppress shrinkage in the vertical direction as much as possible, and can mainly shrink in the horizontal direction, and the shrinkage rate is 20 to 40%, preferably 28 to 38% in the horizontal direction. The direction is 5.0% or less, preferably 1.0 to 3.0%. Here, the maximum in the horizontal direction is 40% because when it exceeds this, it shrinks with an excessively strong contraction force, so when it is attached to a lightweight PET bottle (the bottle with a thinner wall thickness), the bottle This is because there is a risk of causing deformation. If the lower limit of 20% is smaller than this, the label is not fastened to the bottle, and the shrinkage (residual remaining force) is small, so that a gap is easily generated in the attached label.
Although it is better to suppress the vertical direction as much as possible, it is not good if it is less than 1%. This is because it is not preferable for more complete fastening of the label. This is because if the upper limit of 5.0% is larger than this, wrinkles and printed images are liable to occur. Such heat shrinkability can be obtained by adopting a stretching means described later.
In addition, the said shrinkage rate is a case where the shrinkage | contraction degree of the horizontal and vertical direction at the time of immersing the obtained three-layer extending | stretching film in 80 degreeC hot water for 10 second is shown by%. Therefore, if the heating medium, temperature, and time change, the shrinkage rate changes accordingly.

Although the thickness structure of the heat-shrinkable film by the three layers also varies depending on the purpose of use of the film, at least the intermediate layer (A) has both outer surface layers (B) in order to increase the central function expression. It is better to set it thicker than
The following is an example of a tubular label for a plastic bottle, which is cited as one preferred application of the present invention.
First, the total thickness is 40 to 70 μm, the intermediate layer (A) is 30 to 50 μm, and the remaining 10 to 20 μm is both outer surface layers (B) (total), but each outer surface layer is the same. Thickness is good because there is no danger of curl deformation.

Next, means for producing the three-layer heat-shrinkable film (flat shape) will be described.
The film production means includes three-layer coextrusion molding with a round die and a T die, but since a T die is preferred, a method using a T die will be described below.
First, when the components and the mixing ratio are determined, they are sufficiently dispersed and mixed simply by dry blending or melt kneading to obtain a resin composition A and a resin composition B as new resins.
The resin composition A is supplied to one melt extruder, and the resin composition B is supplied to the other two melt extruders. Each composition is arranged from the extruder adjusted to a predetermined temperature toward a three-layer T die adjusted to the predetermined temperature, and the resin composition A is arranged in the middle and the resin composition B is arranged on both sides. Are extruded at the same time. The die is integrated into three layers and cooled and solidified by a cooling roll. The film is not substantially stretched until the roll is cooled.

Next, the substantially unstretched three-layer film obtained is sent to a stretching apparatus and stretched. In this stretching apparatus, at least two rolls for stretching in the longitudinal direction and tenters for stretching in the lateral direction are arranged in the flow direction with heating means. Depending on the purpose of use, stretching in the machine direction and / or the transverse direction is carried out.
For example, in the case of the above-mentioned preferable example for a tubular label of a PET bottle, first, in correspondence with the acquisition of the shrinkage rate, the temperature is 75 times or less, preferably 1.1 to 1.5 times in the vertical direction, and the temperature 75 Roll stretching is performed at about ˜90 ° C., followed by tenter stretching at a temperature of about 85 to 100 ° C. in the transverse direction to 3.0 to 7.5 times, preferably 4.5 to 7.0 times. Next, relaxation heat treatment is performed in the tenter. The thermal relaxation is performed at a relaxation rate of about 5 to 8% and a temperature of about 70 to 80 ° C.

The obtained stretched three-layer film is further subjected to the following treatment. These are corona discharge treatment and aging treatment.
Here, the corona discharge treatment strengthens printing ink loading and ink adhesion, and the aging treatment is removal of internal distortion.
The corona discharge treatment is performed in air at an output of 10 W / m ² / min or more, and the aging treatment is performed by leaving it in an aging chamber at about 30 to 40 ° C. for 10 to 29 hours.

Next, a series of steps when the three-layer heat-shrinkable film is used as a tube-like label for a PET bottle will be described.
First, color printing by gravure is performed on the surface subjected to the corona discharge treatment. The printing ink is a water-based or oil-based gravure ink generally used for an olefin-based film. This printing is performed by multiple sticking. When this printing is completed, the sheet is vertically slit with a width corresponding to one and wound up on a roll. This one portion will be described with reference to FIG. In the figure, 1 (diagonal line) is the actual printing part (the entire circumference of the PET bottle circumference), 2 is the non-printing part provided in the vertical direction, and 3 is the non-printing provided at the upper and lower ends when one label is used. The portion, that is, one portion, is composed of one actual printing portion, two longitudinal non-printing portions, and three upper and lower non-printing portions. Gradually printing is performed by making one unit layout as one unit layout, and adding this in the horizontal direction. When this multi-letter printing is completed, the positions 4a and 4 are slit in the vertical direction with the width shown by the left and right 4a-4, and the roll-wrapped printing film of the number of the multi-sticker is obtained.

The obtained roll winding printing film is formed into a tubular shape as follows.
First, the film is unwound toward the former part of the center sealing machine. At this time, a perforation 6 is formed. The perforation 6 may be a single vertical column or a double column. Both ends of the perforated film are in the center position, that is, in FIG. 1, the non-printing portion indicated by 2 on the right side is the top surface, and the end portion of the actual printing portion cut by the left side 4a is the bottom surface. It is polymerized to become. This polymerized film inserts a nozzle between the polymerized portions, and discharges an appropriate amount of the organic solvent described above. Immediately, the layer surfaces of the upper and lower joints are dissolved or swollen, and this is continuously pressed by a nip roll. The polymerized surface is tightly bonded and molded into a tube shape, so it is wound up (in a flat shape).

  The wound tube-shaped film is cut into one label (for one PET bottle), and this cut position is an intermediate position 5 of the non-printing portion indicated by 3 in FIG. . One label cut in the horizontal direction has non-printing portions at the upper and lower ends. The widths of the non-printing portions 2 and 3 in the above are appropriate, but generally the non-printing portion 2 is 3 to 5 mm and the non-printing portion 3 is 2 to 4 mm.

The obtained label is opened, and a plastic bottle is inserted.
Since this insertion is also performed automatically and continuously, it is first necessary that the bottle can be easily inserted around its body portion. For this purpose, a predetermined gap (this gap can be obtained by making the inner diameter of the label larger than the outer diameter of the bottle) is necessary. If the gap is large, the fastening will not be sufficient. It is desirable that this fastening is also performed with a certain amount of residual shrinkage. An example of the gap in which the fitting gap and the fastening are well balanced is about 5 to 8 mm.
The inserted bottle passes through a steam tunnel at about 75-95 ° C. for 5-15 seconds. The residual shrinkage force is maintained and tightened firmly.

Hereinafter, the present invention will be described in further detail with reference to examples and comparative examples.
In this example, the strength of the waist (hardness), heat shrinkage rate, whitening by fingerprint (referred to as fingerprint whitening), whitening by low-temperature initial heat shrinkage (hereinafter referred to as initial shrinkage whitening), and seal strength. The drop perforation break resistance, the freeze perforation break resistance, and the perforation breakability were measured under the following conditions.

● film waist hardness,
The longitudinal direction of the obtained heat shrinkable film was measured using LOOP STIFFNESS TESTER manufactured by Toyo Seiki Seisakusho Co., Ltd. (10-point average value), and the value was expressed in mN. 22-30 mN is appropriate.
In addition, regarding the waist hardness, the longitudinal direction is particularly measured because it is necessary to maintain the open state firmly in use as a tube label.

● Heat shrinkage,
Ten samples of 100 mm (longitudinal direction) × 100 mm (lateral direction) are cut out from the obtained heat-shrinkable film. When one of the samples is immersed in hot water at 80 ° C. for 10 seconds, it is immediately taken out and immersed in cold water. The horizontal length L (mm) and the vertical length La are measured. And 100-L and 100-La are calculated, respectively, and set as heat shrinkage percentage%.

● Fingerprint whitening,
A thin layer of oleic acid is applied to the fingerprint surface of the index finger, and after contact with the surface of the resulting heat-shrinkable film, it is exposed to hot air at 80 ° C. for 10 seconds under tension. “X” indicates a white fingerprint that is clearly attached, and “Yes” indicates that the fingerprint cannot be visually observed.

● Initial shrinkage whitening (whiteness seen in frosted glass),
The obtained heat-shrinkable film is immersed in 70 ° C. hot water for 3 seconds. The dried film is placed on a white paper printed with 10-point Mincho characters and seen through. The case where the character is clearly visible and legible is marked with ◯, and when the character is visible but blurred, it is marked with x.

Seal strength,
The tube film center-sealed with an organic solvent is opened from a portion other than the seal portion, and the seal portion is peeled 180 degrees using a PEELING TESTER HEIDON-17 type measuring machine manufactured by Shinto Kagaku Co., Ltd. The strength obtained is shown in N / cm. 3N / cm or more is effective.

● Fall perforation resistance,
The obtained plastic bottle of the label fastening packaging is filled with water, and dropped vertically from the height of 1 m onto the concrete surface (bottom side down). The bottle is visually checked for perforations. If there is at least one break at any position of the perforation, ×, and none for none.

● Freezing perforation resistance,
The obtained label fastening packaging PET bottle is filled with water and stored frozen at −5 ° C. for 24 hours. After confirming that it is frozen, visually check the perforation and check for breakage. X if there is a break, ○ if there is none.

● Perforation breaking,
A female (housewives in the home / random) is tested for the perforation of the plastic bottle that has passed the freeze perforation resistance test. In the tearing operation, a toe of a hand is put on the upper end of the perforation, and the woman breaks along the perforation. In this operation, when the toe of the hand is inserted and the label is raised to break, if that part stretches and does not lead to the perforation of the perforation, the perforation (without the extension of that part) Is broken along the perforation line, but when the part which is not perforated is broken in the middle, it is marked as x, and when it breaks smoothly without any case, it is marked as ◯.
The perforations in the measurement on the three perforations were performed at a pitch of 0.5 mm: 2.0 mm (hole length 0.5 mm, hole-to-hole spacing 2.0 mm).

(Examples 1-4)
In the following examples, MFR indicates a discharge amount g for 10 minutes at 200 ° C. and a load of 49.03 N (JIS K7210).
<Resin composition A>,
The resins used in Examples 1 to 4 are the following four components, and the blending ratio of each component is shown in Table 1.
The mixing of these four components was performed by dry blending each of the chip-like components.
◎ m-LLDPE resin ·· MFR 2.0 of hexene 1 copolymer and resin of density 0.926.
◎ LDPE resin ·· MFR 0.5, density 0.992 resin.
CO resin (Examples 1 to 3) A random copolymer resin of ethylene and tetracyclododecene having a Tg of 70 ° C.
(Example 4) A random copolymer resin composed of an ethylene unit and a cyclopentane unit having a Tg of 70 ° C.
◎ Petroleum resin: Hydrogenated product of alicyclic resin (cyclopentadiene) with a softening point of 137 ° C.
<Resin composition B>,
The mixing of these three components was performed by dry blending each of the chip-like components.
CO resin (Examples 1 to 3) A random copolymer resin of ethylene and tetracyclododecene having a Tg of 70 ° C.
(Example 4) A random copolymer resin composed of an ethylene unit and a cyclopentane unit having a Tg of 70 ° C.
LLDPE resin (Example 1) A hexene 1 copolymerized MFR 2.3 and a density of 0.914 t-LLDPE resin.
(Examples 2 to 4) MFR 2.0 of hexene 1 copolymer, m-LLDPE resin having a density of 0.926.
◎ Anti-blocking agent ·· Synthetic silica (EAZ-10 manufactured by Mitsui Chemicals, Inc.).

Then, using the resin compositions A and B in each of the above examples, each of the examples was coextruded with a three-layer T die under the same conditions as described below.
First, the composition A is supplied to one melt extruder, the composition B is supplied separately to two melt extruders, the composition A is in the middle, and the composition B is on both sides. Melt coextrusion was simultaneously performed from a 200 ° C. three-layer T-die, and this was cooled and solidified while being drawn on a 25 ° C. cooling roll to obtain a three-layer film.
The film was passed through a roll stretching machine and stretched 1.2 times at 85 ° C. in the machine direction, and then passed through a tenter stretching machine and stretched 6.7 times at 90 ° C. in the transverse direction. Next, it was heated to 75 ° C. using the tenter-stretching machine, heat-fixed while relaxing mainly by 7% in the transverse direction, and once cooled to room temperature, one side of the relaxed film was 12.5 W / m ² / Corona discharge treatment (in air) with a treatment strength of minutes was wound in a roll shape. Finally, the wound film was aged at 35 ° C. for 16 hours.
The total thickness of the obtained heat-shrinkable film was 50.0 μm in each example, and in particular, the intermediate layer (A) was 33.4 μm, both outer surface layers (B) were 8.3 μm, and each film stiffness The thermal shrinkage rate, fingerprint whitening, and initial shrinkage whitening were measured, and the results are shown in Table 2.

Next, each heat-shrinkable film obtained in each of the above examples was subjected to three-color gravure printing on the corona discharge treated surface with a single unit design of the next one.
In FIG. 1, the actual printing portion 1 is composed of (vertical) 146 mm × (horizontal) 235 mm, 2 (vertical direction) non-printing portion width 5 mm, 3 (corresponding to the upper and lower ends of the label) non-printing portion width 3 mm. Printing uses oil-based urethane gravure ink. All of the four examples could be printed beautifully without problems and wound up with a roll.

The heat-shrinkable film printed in each of the above examples was slit in the vertical direction at the positions 4a and 4 (shown in FIG. 1) to obtain a long roll wound with a width of 240 mm. Next, while feeding this long roll film at a speed of 150 m / min, perforation is first perforated under the following conditions, and then both ends are polymerized at the center (polymerization is the width of the non-printed portion of 2 above the top surface). Subsequently, the polymerized portion was bonded with an organic solvent, formed into a tube-like heat-shrinkable film, and wound up in a flat shape.
● Perforation perforation ・ ・ The hole length is 0.5mm at the position of 10mm on both ends of the actual printing part. Holes are opened with a rotary perforation at intervals of 2 mm.
● Adhesion with organic solvents ・ ・ Use a mixed solvent consisting of cyclohexane, n-hexane and acetone (mixed in almost the same amount), insert a nozzle into the polymerization area, discharge from this, and press-bond with a nip roller (room temperature) .
In addition, the discharge of the mixed solvent from the nozzle follows the speed, and the discharge is also performed mainly at the central position of the polymerization portion, and the amount thereof is adjusted so as to get wet (if more than necessary, the polymerization portion It ’s not good because it ’s leaking to others).
A part of the film in each of the obtained examples was cut out, and the seal strength of the polymerization adhesion part was measured. The results are shown in Table 2.

Next, the tube-shaped heat-shrinkable film obtained in each of the above examples is cut out as a single label at a position of 3 mm in the non-printing portion (position 5 in FIG. 1). Cut horizontally. The size of the obtained label was a folding diameter of 114 mm and a vertical length of 152 mm (the total length of the actual printed portion was 146 mm long and the non-printed portion was 3 mm at each of the upper and lower ends). Then, this label was inserted into a lightweight PET bottle under the following conditions, and heat-shrinked through a steam tunnel for fastening packaging.
● Lightweight PET bottle ・ 500g with 25g weight (previously 30g), body diameter 65mm (label diameter 70mm),
● Steam temperature and heating time-7 seconds at 80 ° C.
In each case, a lightweight PET bottle beautifully labeled and packaged could be obtained without problems.

  Finally, the light weight PET bottle of the obtained label packaging was filled with water and capped to measure the fall perforation resistance, the freeze perforation resistance, and the perforation resistance. The results are shown in Table 2.

(Comparative Examples 1-5) (Due to the difference in blending ratio)
<Resin composition A>,
The resins used in Comparative Examples 1 to 5 are the following four components, and the blending ratio of each component is shown in Table 1.
In addition, mixing of each component was based on the same dry blend as an Example.
◎ m-LLDPE resin. Same as the previous example.
◎ LDPE resin ... Same as the previous example.
◎ CO resin ・ Random copolymer resin of ethylene and tetracyclododecene with Tg of 70 ° C.
◎ Petroleum resin ... Same as the previous example.
<Resin composition B>,
The mixing of these three components was performed by dry blending each of the chip-like components.
◎ CO resin ... Same as the previous example.
◎ LLDPE resin ·· MFR2.0 of hexene 1 copolymerization, m-LLDPE resin with a density of 0.926.
◎ Anti-blocking agent. Same as in the previous example.

And using the said resin composition A and B, it coextruded with the 3 layer T die on the same conditions as Example 1, and performed extending | stretching, relaxation | loosening heat fixation, a corona discharge process, and aging.
The total thickness of the obtained heat-shrinkable film was the same in each example, 50.0 μm, in particular, the intermediate layer (A) 33.4 μm, both outer surface layers (B) were 8.3 μm, and each film Table 2 shows waist hardness, heat shrinkage, fingerprint whitening, and initial shrinkage whitening.

Then, using the heat-shrinkable film of each example obtained above, the process from printing to one label was obtained under the same conditions as in the example, and finally the label in each example was heat-shrinked into a lightweight PET bottle. And fastened and packed. The bottle was also filled and capped with water in the same manner as in Example 1 and similarly tested for perforations.
Similarly, the seal strength, drop perforation break resistance, freeze perforation break resistance, and perforation breakability of the polymerized bonded portion were measured, and the results are shown in Table 2.

(Comparative Example 6) (When t-LLDPE resin is used for the intermediate layer A)
In Example 1, in place of the m-LLDPE resin used in the resin composition A, heat shrinkage was performed under the same conditions except that a hexene 1 copolymerized MFR 2.3 and a density of 0.914 t-LLDPE resin were used. I got a film. The thickness structure of the film was the same as in the example, and the film stiffness, heat shrinkage rate, fingerprint whitening, and initial shrinkage whitening were measured and shown in Table 2.

And also about the said heat shrinkable film, on the same conditions as an Example, the process from printing to one label was obtained, and this label was heat-shrinked to the lightweight PET bottle, and was fastened and packaged finally. The bottle was filled and capped with water in the same manner as in Example 1, and a test for perforations was performed in the same manner.
Similarly, the seal strength, drop perforation break resistance, freeze perforation break resistance, and perforation breakability of the polymerized bonded portion were measured, and the results are shown in Table 2.

These are layout drawings (planes) for one (print).

Explanation of symbols

1 ・ ・ Actual printing part 2、3 ・ ・ Non-printing part 4a, 4, 5 ・ ・ Cut position 6 ・

Claims (2)

A heat-shrinkable laminated film, wherein a film made of the following resin composition A is used as an intermediate layer (A) and a film made of the resin composition B is used as both outer surface layers (B).
<Resin composition A>
Linear low density polyethylene resin 45 to 65 mass%, low density polyethylene resin 5 to 25 mass%, cyclic olefin resin 10 to 15 mass% by metallocene catalyst having a density (g / cm3) of 0.915 to 0.930. % And petroleum resin 5-25% by mass.
<Resin composition B>
Cyclic olefin resin 70-90 mass% and linear low density polyethylene resin 10-30 mass%. A packaged lightweight PET bottle in which a perforated tubular film made of the heat-shrinkable laminated film is heat-shrink fastened to a lightweight PET bottle as a label.

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