JPH11262981A - Film for heat shrinkable label and pet bottle attached with label made of it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To center-seal with solvent by using a film having a polyolefin resin layer as a core material and non-polyolefin resin layers laminated on both side surfaces via adhesive resin layers with specific gravity. SOLUTION: A polyolefin resin layer is used as a core material, and flat-like sheet is co-extruded from a T-die by laminating non-polyolefin resin layers on both side surfaces via adhesive resin layers. It is cooled, taken OFF, longitudinally and laterally oriented, annealed while relaxing it in a lateral direction, thereby manufacturing a film for a heat shrinkable label. As the resin layer, an acid modified ultra-low density polyethylene resin or the like is used. Then, one side surface of the film for the label is printed, center-sealed by using a THF/n-hexane or the like as a sealing solvent to a heat shrinkable labels 1, 1'. A PET bottle 5 is covered with it, and heat shrunk by using a wet heating type shrinkage tunnel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable label film which can be easily separated from a PET bottle in a recycling step of obtaining a recycled PET flake or a recycled PET pellet from a used PET bottle, and a PET to which the label is attached.
About bottles.

[0002]

2. Description of the Related Art Recycling of PET bottles has become active due to the enforcement of the Containers and Packaging Recycling Law. As a recycling method, a method of cleaning and sterilizing the collected PET bottle and reusing it is also conceivable.
Generally, a method of obtaining a recycled PET flake or a recycled PET pellet from the collected PET bottle is adopted. The outline of this step will be described below.

[0003] The recovered PET bottles (usually with aluminum caps or heat-shrinkable labels) are
Glass bottles by hand, weight separator, X-ray inspection, etc.
Sorted from other containers such as cans and PVC bottles. Then P
The ET bottle is ground to several mm to 10 mm square. Next, the heat-shrinkable crushed label having a specific gravity of less than 1 is removed by a specific gravity separator. Then, by a wind separator,
The heat-shrinkable crushed label having a specific gravity of 1 or more is removed. Next, the aluminum cap pulverized body is removed by the aluminum separator. The desired recycled PET flakes or pellets are obtained from the crushed PET bottle thus obtained.

The above-mentioned specific gravity separator is a device in which a pulverized body is put in water and floats on water (a heat-shrinkable label having a specific gravity of less than 1).
A wind separator is a device that spreads a crushed body and blows the wind from below to blow off the heat-shrinkable crushed label body. From each principle,
While the specific gravity separator has a large processing capacity per unit time, that of the wind separator is small. Therefore, a heat-shrinkable label that is removed by a specific gravity separator, that is, has a specific gravity of less than 1 is desired.

As heat-shrinkable labels having a specific gravity of less than 1, there are labels made of heat-shrinkable polyethylene resin films and polypropylene resin films. In addition, special fair 5
JP-A-43590 discloses a film comprising a mixture of a propylene-based polymer and a polyolefin block copolymer comprising a linear ethylene unit and at least one α-olefin unit having 4 to 10 carbon atoms. Have been.

[0006]

A general process for obtaining a heat-shrinkable label from a heat-shrinkable film such as polystyrene and polyester is as follows. That is, a heat-shrinkable film is manufactured, gravure printing is performed on one side, and several sheets are cut to a predetermined width by a slitter. Then, the width direction is set to be the circumferential direction around the longitudinal direction of the film so that the printing surface is on the inside, and the solvent is applied to one end of the film to form a tubular shape in an envelope pasting shape (this The process is called center sealing, and the processing speed is 120 to 140 m.
/ Min. 2 and 3). Next, the tubular film is cut into a predetermined length to obtain an intended label.

On the other hand, polyolefin films such as a polyethylene film, a polypropylene film, and a film made of a mixture of a propylene polymer and a polyolefin block polymer have good solvent resistance and cannot be center-sealed with a solvent. For this reason, a method of performing corona treatment on the surface opposite to the printing surface and sealing the center using an urethane-based adhesive or the like dissolved in the solvent instead of the solvent, or employing a method of center-sealing with ultrasonic waves is not adopted. Not get.

However, in the method using an adhesive,
In addition to the need for corona treatment, it is difficult to apply the adhesive stably. Therefore, reduce the processing speed to 50 to 70 m / min. Need to be. Also, to confirm whether the obtained center seal has a normal adhesion,
Since the solvent must be diffused into the polyolefin film and the adhesive must be hardened almost completely, there is a problem that it cannot be performed until 12 hours or more, usually about 24 hours after the center sealing. Furthermore, since the adhesive does not have heat shrinkage, the seal strength after the resulting label is heat shrunk and attached to a container is reduced. For this reason, the subsequent heating process, that is, hot filling of the contents,
There is a problem that the seal portion is easily peeled off in a heat treatment process such as a boiling process and a retort process. In addition, the method of center sealing by ultrasonic waves has a disadvantage that the processing speed is as slow as 30 to 50 m / min, and the seal portion is wavy, resulting in poor appearance.

The first problem to be solved by the present invention is as follows.
An object of the present invention is to provide a heat-shrinkable label film which has a specific gravity of less than 1 and can be center-sealed with a solvent and which is advantageous for recycling PET bottles.

The second problem is that PET is advantageous for recycling.
To provide a bottle.

[0011]

SUMMARY OF THE INVENTION In order to solve the problems, the present invention provides a polyolefin resin layer as a core material, a non-polyolefin resin layer laminated on both sides of the core layer with an adhesive resin layer interposed therebetween, and a specific gravity of 0.99 or less. Characterized in that it is a heat-shrinkable label film.

Further, the polyolefin resin layer is characterized in that it is a layer mainly composed of an ethylene-propylene random copolymer containing 0.2 to 10 mol% of ethylene. 100
It is a layer mainly composed of a resin system in which 2 to 50 parts by weight of a petroleum resin is mixed in parts by weight.

Further, the adhesive resin layer is a layer mainly composed of an acid-modified polyethylene resin, and the non-polyolefin resin layer is a layer mainly composed of a polystyrene resin or a polyester resin. I do.

Further, a P which is provided with a label comprising the above-mentioned heat-shrinkable label film and which is advantageous for recycling is provided.
It is an ET bottle.

[0015]

Embodiments of the present invention will be described in detail below.

The polyolefin resin of the present invention has a specific gravity of 0.96 or less, preferably 0.94 or less, more preferably 0.92 or less, and ethylene, propylene and C number of 4
To -12, a homopolymer of two or more of these olefins, or a mixture of these polymers. When the specific gravity exceeds 0.96, of the present invention,
In obtaining a heat-shrinkable label film having a specific gravity of 0.99 or less, the selection of the adhesive resin and the non-polyolefin resin and the restriction on the thickness constituting ratio of each layer are unfavorably increased. In addition, monomers other than olefins, for example, vinyl acetate, acrylic acid and its derivatives, methacrylic acid and its derivatives, copolymers of various vinyl compounds and the above-mentioned olefins, crosslinked structures of modified polyolefins, ionomers, etc. The body is also included in the present invention as long as the specific gravity satisfies the above.

From the viewpoints of heat shrinkage properties, transparency, stiffness of the film, and the like, preferred polyolefin resins include ethylene-propylene random copolymers. Above all,
0.2 to 10 mol% ethylene, specific gravity 0.88 to
A 0.92 ethylene-propylene random copolymer is preferred. Further, a resin system in which 2 to 50 parts by weight of a petroleum resin is mixed with 100 parts by weight of an ethylene-propylene random copolymer containing 0.2 to 10 mol% of ethylene is more preferable. Petroleum resins are aliphatic hydrocarbons, alicyclic hydrocarbons,
Made of hydrogenated hydrocarbon or the like, specific gravity of 0.91 to 1.0
0 resin.

The adhesive resin of the present invention refers to a resin for bonding a polyolefin resin layer and a non-polyolefin resin layer, and is not particularly limited as long as the required adhesive strength can be obtained. For example, modified polyolefin, ionomer, ethylene-ethyl acrylate and the like can be mentioned. The MFR of the adhesive resin is 0.2 to 60, preferably 1
To 30, more preferably 2 to 10. If the MFR is less than 0.2, extrusion molding tends to be difficult. If the MFR is more than 60, the film softens upon heating, so that the film is wrinkled during heat shrinkage or during heat treatment such as hot filling of contents, boil treatment, retort treatment, etc., which is not preferable.

From the viewpoint of stable adhesion to the non-polyolefin resin layer, preferred adhesive resins include acid-modified polyethylene resins modified with maleic acid, fumaric acid, other unsaturated carboxylic acids or anhydrides thereof. Above all, an acid-modified ultra-low density polyethylene resin having a specific gravity of 0.88 to 0.90 is more preferable from the viewpoint that the specific gravity is small as well as stable adhesive strength.

The non-polyolefin resin of the present invention is not particularly limited as long as it is a resin different from the above-mentioned polyolefin resin, which has heat shrinkability and can be sealed with a solvent. For example, polystyrene resins, polyester resins, polyvinyl chloride resins, cyclic polyolefin resins, and the like can be exemplified.

As the solvent for the center seal, a mixed system of a solvent that dissolves the resin (film) and a solvent that does not dissolve is preferable from the viewpoint of the appearance of the seal portion. Because the solvent to dissolve the resin (film) alone is too strong to attack the resin (film), the seal part is wavy,
This is because it looks bad. Examples of such a mixed system include THF (tetrahydrofuran) / n-hexane for a polystyrene resin, methylene chloride / methyl acetate for a polyester resin, and THF (tetrahydrofuran) / n for a polyvinyl chloride resin. In the case of -hexane-based and cyclic polyolefin-based resins, cyclohexane / n-hexane-based resins can be exemplified.

Preferred non-polyolefin resins include polystyrene-based resins and polyester-based resins in that no harmful gas is emitted during incineration and the solvent sealing suitability is good. Polystyrene resin is a homopolymer composed of styrene and styrene derivatives such as α-methylstyrene,
It refers to a copolymer, a monomer copolymerizable therewith, for example, a copolymer with butadiene, isoprene, or the like, or a mixture of these polymers.

From the viewpoints of solvent sealability, heat shrinkage, film stiffness, specific gravity, etc., more preferred polystyrene resins include styrene butadiene block copolymers and styrene-isoprene block copolymers. Especially, butadiene or isoprene is 10 to 40% by weight.
Styrene butadiene block copolymer and styrene-isoprene block copolymer having a specific gravity of 1.02 to 1.08 are more preferable. A resin system in which 2 to 50 parts by weight of polystyrene is mixed with 100 parts by weight of the block copolymer is more preferable.

The polyester resin includes, for example, an aromatic dicarboxylic acid such as terephthalic acid and isophthalic acid; an aliphatic dicarboxylic acid such as adipic acid and sebacic acid;
Or a derivative thereof, wherein the diol component is ethylene glycol, propylene glycol, butanediol, an aliphatic diol such as neopentyl glycol,
Alicyclic diols such as 4-cyclohexanedimethanol,
Examples thereof include diethylene glycol and those comprising a substituted product thereof.

From the viewpoints of solvent sealing suitability, heat shrinkage characteristics, film stiffness, specific gravity, etc., preferred polyester resins include resins generally having a specific gravity of 1.20 to 1.39 and generally called copolymer polyester. Can be Above all, the dicarboxylic acid component is terephthalic acid, the diol component is ethylene glycol 60 to 98 mol% and cyclohexane dimethanol 40 to 2 mol%, and the specific gravity is 1.22 to
A 1.34 polyester resin is more preferred. Further, a small amount of a polyethylene terephthalate resin or the like may be mixed with the copolymerized polyester resin.

The specific gravity of the heat shrinkable label film of the present invention is 0.99 or less, preferably 0.97 or less, more preferably 0.95 or less. If it exceeds 0.99, the specific gravity of the solid content of the ink printed on the film is greater than 1, so that the specific gravity of the obtained heat-shrinkable label becomes 1 or more and cannot be separated by a specific gravity separator. The smaller the specific gravity is, the faster the separation speed is and the higher the processing capacity per unit time is, so that it is more advantageous for recycling PET bottles.

In order to achieve the above specific gravity, the thickness composition ratio of the polyolefin resin layer, the adhesive resin layer, and the non-polyolefin resin layer may be appropriately determined in consideration of heat shrinkage characteristics, film stiffness, and the like. The thickness of the heat shrinkable label film is not particularly limited, but is generally 20 to 100 μm.

Next, a method for producing a heat shrinkable label film will be described. The film is manufactured by a known co-extrusion technique or stretching technique. For example, a polyolefin resin layer is used as a core material, and a flat sheet is co-extruded from a T-die, cooled and taken off so that a non-polyolefin resin layer comes through an adhesive resin layer on both surfaces thereof, and is cooled in a longitudinal direction by 1.0 to 1.0 mm. A heat-shrinkable film can be obtained by stretching by 2.0 times roll, stretching by 10 to 10 times in the transverse direction, annealing while relaxing in the width direction by 0 to 10%, and then winding. Stretching may be performed by a known simultaneous biaxial stretching method.
Alternatively, a tubular sheet may be co-extruded from a round die and stretched in a tubular shape, or the sheet may be cut open to form a flat shape and stretched as described above. The step of obtaining a heat-shrinkable label from the obtained heat-shrinkable label film is as described above.

The heat shrinkage rate of the heat shrinkable label film thus obtained is 20% or more in the horizontal direction and 5% or less in the vertical direction.
Usually, it is 30% or more in the horizontal direction and 3% or less in the vertical direction. The interlayer peel strength between the adhesive resin layer and the non-polyolefin resin layer is 200 g / cm or more, usually 300 g / cm or more (the polyolefin resin layer and the adhesive resin layer are well adhered and cannot be peeled off). ).

The method for obtaining a heat-shrinkable label from the film for a heat-shrinkable label is as described above, and the obtained heat-shrinkable label has a sealing strength of 450 g / cm or more.
It is 550 g / cm or more.

[0031]

EXAMPLES Next, typical examples of the present invention will be described.

The method for measuring physical properties used in the present invention is as follows.

The heat shrinkage of the heat shrinkable label film is as follows:
The following method is used. That is, vertical x horizontal 100mm x 100m
Cut the sample into m-squares. Next, this sample is immersed in a warm water bath at 80 ° C. for 5 seconds, immediately cooled with cold water, and then the length L (mm) in the vertical and horizontal directions is measured. And 10
Let 0-L be the heat shrinkage in the vertical and horizontal directions.

The delamination strength between the adhesive resin layer and the non-polyolefin resin layer was measured using HEIDON-17 manufactured by Shinto Kagaku Co., Ltd.
The measurement was performed using a mold peeling tester at a sample width of 1 cm, T-shaped peeling, and a peeling speed of 20 cm / min.

The sealing strength of the heat-shrinkable label is determined by the following method. That is, the cylindrical label is cut to a width of 1 cm in the circumferential direction. Next, the seal margin part of the seal part and the end of the other piece are each connected to HEIDON- manufactured by Shinto Kagaku Co., Ltd.
The sample was set in a 17-type peel tester and measured at a peel speed of 20 cm / min.

Example 1 A resin system in which 30 parts by weight of a petroleum resin was mixed with 100 parts by weight of an ethylene-propylene random copolymer containing 3.9 mol% of ethylene (A having a specific gravity of 0.92)
Layer), maleic anhydride-modified ultra-low density polyethylene (layer B having a specific gravity of 0.89), and a resin mixture obtained by mixing 18 parts by weight of polystyrene with 100 parts by weight of a styrene butadiene block copolymer containing 15% by weight of butadiene. (Specific gravity is 1.0
4) into separate extruders, and C / B
After being extruded from a T-die at 240 ° C. so as to form a laminate of / A / B / C, and cooled and solidified with a cooling roll at 30 ° C., 9
The film was stretched 6 times in the transverse direction at 0 ° C. and then annealed at 80 ° C. for 5 seconds while relaxing 8% in the width direction in the tenter to obtain a heat-shrinkable label film having a thickness of 50 μm (each layer). Is 4 μm / 2 μm / 38 μm / 2 μm
/ 4 μm). Table 1 shows the physical property values of the obtained heat shrinkable label film.

Example 2 The film obtained in Example 1 was slit to a width of 960 mm by a slitter. Next, five-color printing was performed on one side of the film using a gravure printing machine. The printed pattern used was a three-patterned one in the width direction of the film and a non-printed part intermittently with a width of 6 mm in the flow direction of the film. Next, three slits were made with a slitter. Next, center sealing was performed at a speed of 130 m / min using a THF / n-hexane system as a sealing solvent. Next, cut at the center of the non-printing part, the fold diameter is 57 mm,
A heat-shrinkable label having a length of 83 mm was obtained. Seal strength is 5
It was 90 g / cm. Then, as shown in FIG.
The ET bottle was covered with a heat-shrinkable label, and heat-shrinked at 80 ° C. for 5 seconds using a wet heat shrink tunnel (length: 3 m, vapor pressure: 0.3 kg / cm ² ). The label was tightly attached to the bottle, and there was no abnormality such as wrinkles, pock, vertical shrinkage, whitening of the film, and distortion of the design.

Example 3 100 PET bottles thus obtained were hot-filled with hot water at 98 ° C. and capped with aluminum. The state of the label after hot filling was completely the same as before filling. Also, there was no fusion between the labels.

Next, the water in the 100 PET bottles was discarded, and the bottle was again covered with an aluminum cap. Then, these were pulverized to 7 to 10 mm square with a pulverizer and then subjected to a specific gravity separator. As a result, the heat-shrinkable label pulverized body quickly floated on water, and the pulverized body of the aluminum cap and the PET bottle sank into water.

(Example 4) The same resin as that used in Example 1 was used for the layer A resin and the layer B resin.
A polyester resin composed of terephthalic acid as a dicarboxylic acid component, 70 mol% of ethylene glycol as a diol component and 30 mol% of cyclohexanedimethanol (specific gravity of 1.2
8) and charged into separate extruders,
The mixture was extruded from a T-die at 250 ° C. so as to form a laminate of / B / A / B / C, solidified by cooling with a cooling roll at 40 ° C., and then stretched 1.3 times in the longitudinal direction at 80 ° C. The film was stretched by 6 times in the transverse direction at 10 ° C. and then annealed at 80 ° C. for 5 seconds while relaxing 4% in the width direction in the tenter to obtain a heat-shrinkable label film having a thickness of 50 μm (each layer was The thickness is 2 μm / 2 μm / 42 μm / 2 μm / 2
μm). Table 1 shows the physical property values of the obtained heat shrinkable label film. Next, gravure printing was performed on one surface of the film in the same manner as in Example 2. When the film piece was thrown into water, the film piece floated on the water.

Comparative Example 1 In Example 4, C / B /
The thickness of each layer of A / B / C is set to 8 μm / 2 μm / 30 μm /
A heat shrinkable label film was obtained in the same manner as in Example 4 except that the thickness was changed to 2 μm / 8 μm. The specific gravity of this film was 1.04. Next, a printed film was obtained in the same manner as in Example 4. When the film piece was thrown into water, the film piece sank.

[0042]

The present invention is embodied in the form described in detail above and has the following effects.

Since the heat-shrinkable label film of the present invention can be sealed at the center with a solvent, the sealing can be easily performed, the sealing speed is high, and the sealing strength is strong and stable. In addition, since the seal is not a seal made of an adhesive having no heat shrinkage, the seal strength does not decrease even if the obtained label is heat shrunk to a PET bottle. For this reason, the sealing portion does not peel off during the subsequent heating process such as hot filling of content items, boiling treatment, retorting treatment, and the like. In addition, since the film is manufactured by co-extrusion and co-stretching, not only can the film be obtained in one manufacturing step, but also the adhesive resin layer has heat shrinkability, so that heat shrinkage, hot filling, boiling, and retorting are performed. No wrinkles are formed during the heating process. Further, since the label has a specific gravity of less than 1, it can be separated by a specific gravity separator, which is advantageous for recycling PET bottles. A PET bottle to which a label obtained from the heat shrinkable label film of the present invention is attached is a bottle that is advantageous for recycling.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a heat-shrinkable label obtained from a film of the present invention and a PET bottle to which the label is attached.

FIG. 2 is a cross-sectional view illustrating a center sealing process.

FIG. 3 is a cross-sectional view of a heat-shrinkable label.

[Explanation of symbols]

 1, 1 'heat-shrinkable label 2 film for heat-shrinkable label 3 printing section 4 nozzle for applying sealing solvent 5 PET bottle

[Table 1]

Claims (6)

[Claims] 1. A heat-shrinkable label film having a specific gravity of 0.99 or less, wherein a polyolefin resin layer is used as a core material and a non-polyolefin resin layer is laminated on both surfaces thereof with an adhesive resin layer interposed therebetween. 2. The polyolefin resin layer according to claim 1, wherein said polyolefin resin layer contains ethylene in an amount of 0.1 to 0.2.
The heat-shrinkable label film according to claim 1, which is a layer mainly composed of 2 to 10 mol% of an ethylene-propylene random copolymer. 3. The polyolefin resin layer according to claim 1, wherein said polyolefin resin layer has a content of ethylene of 0.1%.
The heat-shrinkable label film according to claim 1, wherein the layer is a resin-based layer obtained by mixing 2 to 50 parts by weight of a petroleum resin with 100 parts by weight of a 2 to 10 mol% ethylene-propylene random copolymer. . 4. The heat-shrinkable label film according to claim 1, wherein the adhesive resin layer is a layer containing an acid-modified polyethylene resin as a main component. 5. The heat-shrinkable label film according to claim 1, wherein the non-polyolefin resin layer is a layer containing a polystyrene resin or a polyester resin as a main component. 6. A PE to which a label comprising the heat-shrinkable label film according to claim 1 is attached.
T bottle.