JPH0575623B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for manufacturing labeled plastic containers using heat-adhesive film labels, and more specifically, the present invention relates to a method for manufacturing a labeled plastic container using a heat-adhesive film label. This invention relates to a method for efficiently manufacturing labeled plastic containers using a heat-adhesive film label that prevents sticking or blocking and has a slippery outer surface. (Prior art) Attaching a label that indicates the contents to a blow-molded container has an important meaning in terms of packaging technology because it increases the commercial value of the packaged product and stimulates consumers' desire to purchase. There is. It has been known for a long time to apply labels to blow-molded containers by in-mold label operation.The label to be affixed to the inner surface of the cavity of a molding die is held by means such as vacuum suction, and the label is applied inside the mold. A method of blow-molding a plastic parison is generally employed (for example, Japanese Patent Laid-Open No. 61-202818). It is also already known to use a laminate of a solid polymer layer, a foam layer, and a polymer solution layer as a plastic label (Japanese Patent Application Laid-Open No. 1983-1989-1).
123333, 60-183343 and 60-242490). As labels for in-mold label operations, labels based on plastic film are desirable because they have advantages such as being able to print on the back side, providing clear images, and having excellent stain resistance. It is advantageous to use heat-sensitive adhesives, especially hot melt adhesives, in that the heat of the plastic container wall being formed is used to effect the bonding. (Problems to be Solved by the Invention) However, with thermoadhesive film labels based on plastic film and using hot melt adhesive as an adhesive, it is difficult to accurately feed labels one by one during in-mold labeling operations. It is often difficult to do so, resulting in the trouble of being supplied with a plurality of labels stacked one on top of the other on the side wall of the container. The reason for this is that because the film is highly smooth, it is easy for the film labels to stick together, and the hot melt adhesive is sensitive to heat.
As a result, it tends to stick depending on environmental conditions and the like. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems that occur when manufacturing labeled plastic containers by in-mold labeling operations, and to reliably supply heat-adhesive film labels one by one in a separated state. and to form a strong adhesive bond with the side wall of a plastic container that is being formed, and to provide a method for performing this labeling operation efficiently and with good workability in a rotary blow molding machine. There is something to do. (Means for Solving the Problems) According to the present invention, a single layer or multilayer plastic is molded in a mold with a label pasted on the inner surface of the cavity, and a label is attached to the side wall surface of the container to be formed. In a method for producing a labeled plastic container, which involves joining together, a number of blow molds are arranged circumferentially and in a rotary manner, and along their circumferential movement path, a label sticking area, a parison extrusion area, and a parison extrusion area are formed. , a blow molding cooling area, a flash collection area, and a container removal area are arranged in this order, and the label includes a plastic film layer, a printing layer provided on the inner surface side of the film layer, and a plastic film layer provided on the inner surface of the film layer. A heat-adhesive film label consisting of a hot-melt adhesive layer and an overcoat layer of a releasable material having a coefficient of static friction on the film of 0.20 or less is used, and a large number of the labels are accommodated in the label application area. The labels are sucked and held one by one from the magazine, transferred into the mold, and affixed to the mold surface. (Function) The thermal adhesive label of the present invention comprises a plastic film layer, a printing layer provided on the inner surface of the film layer, a hot melt adhesive layer provided on the printing layer, and an outer surface of the film layer. and an overcoat layer provided on the top. In the present invention, this heat-adhesive label is used, and a large number of labels are stacked one on top of the other and stored in a magazine, and the magazine is taken out by suction, held and transferred into a mold, and is pasted on the mold surface. to produce labeled plastic containers. Plastic film is used as a base for labels because it has excellent smoothness, wet strength, and stain resistance. The purpose of providing a printing layer on the inner surface of the film is to allow the printed image to be seen through the transparent film layer, thereby reproducing a beautiful and clear printed image, as well as
This is because the printing layer is prevented from being contaminated or damaged during storage or transportation. The hot-melt adhesive layer is provided on the printing layer so that the label can be thermally bonded to the side wall of the container using the heat of the side wall of the container that is being formed. In addition, the overcoat layer provided on the outer surface of the plastic film is provided to protect the film and improve the texture and appearance of the label surface. This function prevents blocking caused by the label and also makes the outer surface of the label slippery. That is, a remarkable feature of the present invention is that an overcoat layer of a release material having a coefficient of static friction of 0.20 or less, particularly 0.15 or less is provided on the outer surface of the above-mentioned film layer. To eliminate stickiness or blocking tendency in a stacked state without impairing inherent excellent thermal adhesion, smoothness, decorative effect, etc., and to reliably supply them in a separated state one by one. The reason for this is that by providing the above-mentioned release substance as an overcoat layer on the outer surface of the film layer, the surface of the heat-adhesive film label becomes more slippery, and the film slips more easily. Even if adhesive film labels have a tendency to stick or block, they can be fed one by one by suctioning the labels from the magazine with a vacuum. In the present invention, it is also important that the static friction coefficient of the releasing substance is less than the above value. If the static friction coefficient is larger than the above value, the surface of the hot melt adhesive layer in the heat adhesive film label may be damaged due to environmental changes. When the adhesiveness becomes somewhat strong, it becomes difficult to provide the outer surface of the label with enough lubricity to overcome this adhesiveness, and because of the adhesion between the labels, even if the label is sucked with a vacuum cleaner, it will not be accurate. This makes it difficult to supply labels one by one. According to the present invention, a large number of blow molds are arranged circumferentially and in a rotary manner, and along their circumferential movement path, a label sticking area, a parison extrusion area, a blow molding cooling area, and a flash molding area are arranged. A collection area and a container removal area are arranged in this order, and in this label sticking area, labels are sucked and held one by one from the above-mentioned magazine, transferred into the mold, and stuck to the mold surface. By using the above-mentioned label, it is possible to quickly and reliably feed and attach the label into the mold in accordance with the molding cycle of the container, and it is also possible to feed and attach one label to a large number of split molds. Since it is only necessary to attach the adhesive, it is efficient and has excellent operability. (Preferred Embodiment of the Invention) In FIG. 1 showing an example of a heat-adhesive film label used in the present invention, this label 1 includes a plastic film substrate 2, a printed layer 3 applied to the back side thereof, and a printed layer 3 applied to the surface of the printed layer. It consists of a hot melt adhesive layer 4. The plastic film substrate 2 is generally uniaxially or biaxially stretched and transparent, and the printing layer 3 is passed through the film layer.
You will see. The printing layer 3 is so-called back-printed with printing ink, and may be a multiple printing layer such as an image area and a background, or the background may be made of a metal vapor deposited layer. The hot melt adhesive layer 4 is mainly made of a thermoplastic resin that can be thermally bonded by the heat of the side wall of the plastic container that is being thermoformed. In the present invention, an overcoat layer 5 made of a release material is further formed on the outer surface of the plastic film substrate 2. Overcoat Layer In the present invention, the release material used as the overcoat layer includes fluorine resin, melamine resin, silicone, paraffin, chlorinated paraffin, higher alcohol such as stearyl alcohol and cetyl alcohol, stearic acid, oleic acid, etc. Examples include fatty acids and fatty acid salts, fatty acid esters, polypropylene, ethers such as glycol alkyl ethers, fatty acid amides, graphite, molybdenum sulfide, and generally from 0.01 to
It is also important to provide a thickness of 50 μm, especially 0.1 to 10 μm. Although it depends on the viscosity of the releasable material, if the thickness of the overcoat layer is smaller than the above range, it will be difficult to obtain the above-mentioned static friction coefficient, and if it is larger than the above range, it will be difficult to obtain a clear image from the outer surface. become unable. In the present invention, it is preferable that the overcoat layer is made of a releasable material in order to prevent a decrease in adhesive strength due to transfer of the releasable material on the label surface to another label adhesive layer.
Fluororesin, melamine resin, etc. are preferably used. In addition, the release material may be nitrocellulose, vinyl chloride-vinyl acetate copolymer, acrylic resin,
It is preferable to use a mixture of polyester urethane, polyvinyl urethane, polyvinyl urethane chloride, polyamide, etc., generally in an amount of 0.1 to 50% by weight, particularly 1 to 30% by weight, as the mold release resin. The overcoat layer is formed by gravure coating, spray coating, comma coating, roll reverse coating, lip coating, or the like. The static friction coefficient of the overcoat layer was measured according to the friction coefficient test method for plastic films and sheets (JIS K 7125).
Measurement was made by contacting the Label Substrate In the present invention, plastics constituting the label substrate include, for example, crystalline polypropylene,
Crystalline propylene-ethylene copolymer, crystalline polybutene-1, crystalline poly-4-methylpentene-
1. Polyolefins such as low-, medium-, or high-density polyethylene; aromatic vinyl polymers such as polystyrene, styrene-butadiene copolymer; halogenated vinyl polymers such as polyvinyl chloride and vinylidene chloride resin; acrylonitrile- Nitrile polymers such as styrene copolymers and acrylonitrile-styrene-butadiene copolymers; polyamides such as nylon 6, nylon 6,6, para- or metaxylylene adipamide; polyesters such as polyethylene terephthalate, polytetramethylene terephthalate, etc. various polycarbonates; thermoplastic resins such as polyacetals such as polyoxymethylene; The thickness of the stretched film is generally 20 to 300 μm, particularly preferably 50 to 150 μm. Further, as the label base material, a plastic base material such as the one described above to which aluminum vapor deposition has been applied or a material laminated with aluminum foil may be used. Hot Melt Adhesive As the hot melt adhesive, any hot melt adhesive known per se can be used, but generally the vinyl acetate content is 5 to 5.
Ethylene-vinyl acetate copolymer (EVA) with a content of 40% by weight, ethylene-ethyl acrylate copolymer (EEA) with an acrylic acid content of 5 to 40% by weight
, low density polyethylene (LDPE), EVA, EEA
Ethylene resins such as ethylene resins, etc., and 5 to 30% by weight of tackifiers such as rosins, terpene resins, petroleum resins, and styrene resins are used in combination with these resins. The hot melt adhesive resin is generally applied on the base film with a thickness of 0.1 to 40 μm, especially 1 to 10 μm.
It is best to provide an average thickness of . Note that the printing layer can be formed by a method known per se,
For example, the overcoat layer can be formed by letterpress printing, intaglio printing, gravure printing, lithography or offset printing, silk screen printing, thermal transfer printing, electrophotographic printing, etc. The overcoat layer can be formed using acrylic resin, vinyl chloride resin, cellulose derivative, etc. This can be done using a resin solution with excellent transparency. The thermoadhesive film label of the present invention is particularly advantageously used in the production of labeled containers by in-mold labeling operations on plastic containers. In FIG. 2 for explaining the in-mold label operation, in step A, prior to blow molding the plastic parison, blow molds 11a and 11b are
are in an open state, and a label 1 is previously applied to the cavity surface 6 of at least one of these. That is, the cavity surface 6 has a portion that supports the label 1, a vacuum suction mechanism 7 is provided in this portion, and the label 1 is held on the cavity surface 6 by a suction. In this case, the label is positioned such that the plastic film base 2 is on the outside and the hot melt adhesive resin layer 4 is on the inside. The application and fixing of the label 1 to the cavity surface 6 is not limited to suction, but can also be carried out, for example, by electrostatic electricity. Next, in step B, the molten plastic parison 9 is extruded from the die 8, and the blow mold 11
a and 11b are closed, and pressurized gas is blown into the closed parison 9. In step C, the parison expanding in the mold is held on the mold surface and pressed against the label 1 to bring them into close contact, and the expanded parison comes into contact with the mold surface and is cooled, forming the labeled container 10. becomes. Blow molding includes direct blow molding using horizontal rotary blow molding machines, vertical rotary blow molding machines, etc., as well as any blow molding methods such as injection blow molding, two-stage blow molding, sheet forming, and stretch blow molding. It can be done by injection molding, compression molding, or vacuum molding. In FIG. 3, which shows the schematic arrangement of an apparatus suitably used for manufacturing the labeled plastic container of the present invention, a large number of blow split molds 11a and 11b are arranged around the turret 12, with the axis of the turret 12 being centered. The labeling area A, the parison extrusion area B, the blow molding cooling area C, the flash collection area D, and the bottle removal area E are arranged in this order along the circumferential movement path. Placed. For ease of understanding, labeling area A,
In the parison extrusion area B, the flash recovery area D, and the bottle removal area E, one of the blow molds 11a
The split molds 11a, 11b are provided with a cavity surface 6 of a size and shape corresponding to the outer surface of the container (bottle) to be molded. The parting surfaces of the blow molds 11a and 11b are parallel to the plane of FIG. 3, and can be opened and closed by a cam 19 in a direction perpendicular to this surface. In label pasting area A, split molds 11a, 11b
is in the open position, and this area A is provided with a label magazine 13 and a labeling mechanism, generally designated 14. As shown in detail in FIG. 4, the label magazine 13 includes a cylindrical accommodating part 15 for accommodating the labels 1, a label take-out part 16 located at one end of the cylindrical accommodating part, and the other end of the cylindrical accommodating part. A spring member 17 for pressing the labels provided on the label 1 is provided in the storage portion 15, and a large number of labels 1 are stored in a stacked state. The label take-out section 16 is provided with a small claw (separation claw) 18 for making it possible to take out the labels one by one. In this specific example, label magazines are provided in pairs for the purpose of attaching labels to the front and back surfaces of containers. The label pasting mechanism 14 includes a suction cup 20 that suctions and holds the label 1 with a vacuum, an arm 21 that supports the suction cup 20, and an arm 21 that supports the suction cup 20.
It consists of a horizontal reciprocating mechanism 22 for horizontally reciprocating the arm, and a mechanism 24 for rotationally driving the arm around a shaft 23. To explain in more detail, the arm 21 supports the suction cup 20 on its radially distal end side, and its radially central end is pivotable on an annular sliding member 25 that is slidable along a shaft 23. It is connected to the. This annular sliding member 2
A mechanism 22 for horizontally reciprocating the cam 2
6 and a cam follower 27, and when the cam follower 27 moves toward the arm 21, the arm 21
swings to move the suction cup 20 to the opposite side (outside). In the specific example shown in FIG. 4, the arm 21 and the suction cup 20 are provided as a pair at 180 degrees with respect to the shaft 23, and are also provided in plane symmetry with respect to a plane perpendicular to the shaft 23. In addition, in FIG. 4, when the suction cup 20 in the upper position is aligned with the label magazines 13a, 13b, the suction cup 20 in the lower position is aligned with the split molds 11a, 13b.
It has a consistent relationship with 1b. In step 1 of Fig. 4, the upper suction cup 2
0 is in a state in which the label 1 is not held, while the lower suction cup 20 is in a state in which the label 1 is held. Moreover, these suction cups 20 are all attached to the label magazines 13a, 13b and the split mold 11.
It is in a position retreated from a and 11b. From this state, the horizontal reciprocating cam 26 is driven, and the suction cup 20 is driven forward toward the label magazines 13a, 13b and the split molds 11a, 11b.In step 2 in FIG. Contact with label 1 in 13a, 13b.
Further, the lower suction cup 20 adheres the label 1 it holds to the cavity surface 6 of the split molds 11a, 11b. In the specific example shown in FIG. 4, the split molds 11a and 11b have their cam mechanisms 19
The label 1 is moved to close by a small distance, and the label 1 is smoothly attached to the cavity surface 6. In step 2 of Figure 4,
A vacuum acts on the upper suction cup 20 to hold the label 1. Vacuum is blocked from the lower suction cup 20, and the label 1 is released and held by the suction mechanism (suction mechanism 7 in FIG. 2) in the split molds 11a and 11b. Next, the horizontal reciprocating cam 26 is driven, and each suction cup 20
is retreated to the position shown in step 3 of FIG. Step 3
Then, the shaft 23 rotates 180 degrees, and the suction cup 20 holding the label 1 reaches the stroke 1 in FIG. 4, after which the same stroke as described above is repeated. Returning again to FIG. 3, in the parison extrusion zone B, the molten plastic parison 9 is passed from the die 8.
extrude. This parison 9 is divided into molds 11a and 11b.
is closed, a bottom is formed by pinch-off, and fluid is blown into the blow molding cooling area C.
Then, a plastic container 10 with a label is formed.
In the flash collection area D, open the split molds 11a and 11b and transfer the flash to the flash collection chute 28.
In the bottle removal area E, the labeled bottle 10 is removed from the mold 11 by the bottle gripper 29.
is taken out and discharged to the transport mechanism 30. In the present invention, the thermoplastic resin exemplified for the film substrate for labels is used as the thermoplastic resin constituting the plastic container. Plastic containers can have a single layer or multilayer construction, such as containers made of a single layer of polyolefin or polyethylene terephthalate,
Examples include multilayer containers in which polyolefin or polyethylene terephthalate are used as inner and outer layers, and a gas barrier thermoplastic resin is provided between these layers as an intermediate layer. Gas barrier resins include ethylene-vinyl alcohol copolymers with an ethylene content of 50 to 20 mol%; polyamides containing xylylene groups; gas barrier polyesters; polymers containing high nitrile groups; vinylidene chloride resins, etc. Gas barrier resins known per se can be used. When there is no adhesiveness between the inner and outer layers and the intermediate layer, adhesive resins such as acid-modified olefin resins, various copolyamides, and various copolyesters may be contained between them. Hot melt adhesives used for labels include:
It goes without saying that a material that exhibits thermal adhesion at or slightly lower than the melting temperature or stretching temperature of the plastic to be molded is selected depending on the type of plastic and the processing temperature. (Effects of the Invention) According to the present invention, the film layer of a thermally adhesive film label is composed of a plastic film layer, a printing layer provided on the inner surface of the film, and a hot melt adhesive layer provided on the printing layer. By providing an overcoat layer made of a releasable material with a coefficient of static friction of 0.2 or less on the outer surface of the heat-adhesive film label, the surface lubricity of the heat-adhesive film label is improved, and the hot-melt adhesive makes the label sticky. , even if they exhibit a blocking tendency, the presence of the overcoat layer allows the labels to slide against each other, making it possible to reliably supply and attach labels one by one to the split mold cavity surface during in-mold label operation. The mold label operation has excellent integrity between the label and the container, and because the coefficient of friction on the label surface is small, it has been possible to manufacture labeled plastic containers with excellent transportability and scratch resistance with high productivity. Additionally, this label had excellent adhesion to the side wall of the plastic container, and was prevented from coming off even under severe conditions. Further, by performing the labeling operation according to the above method in the first stage of the molding cycle using the rotary blow molding machine, labeled containers could be manufactured efficiently and with good workability. (Example) Example 1 One side of a 100 μm thick biaxially stretched film made of an ethylene-propylene random copolymer with a melting point of 137°C was printed, and ethylene-vinyl acetate copolymer and an ethylene-vinyl acetate copolymer were further printed on it. A solvent-based hot melt adhesive made of rosin resin was applied, and polyester urethane containing 20% silicone was applied to the other side to form an overcoat layer. The static friction coefficient of the surface of this overcoat layer was 0.12. Next, square labels with a length of 90 mm and a width of 60 mm are punched out from the obtained label base material, approximately 500 labels are stacked, and loaded into the magazine of an in-mold label pasting device, resulting in labels with a suction cup attached to the tip. The labels were taken out one by one from the magazine using the applicator head and placed in the blow mold shown in FIG. In this way, in the operation of taking out labels one by one from the magazine using the suction cup, no double labels were taken at all. At this time, the temperature around the label magazine was 26°C. Next, by the process shown in FIG. 4, it was attached to the surface of a bottle made of an ethylene-propylene copolymer having a molding shrinkage rate of 1.2% and a melting point of 157°C.
In this case, the molten resin temperature of the ethylene-propylene copolymer parison is 210℃, and the blow mold temperature is 8℃.
It was hot. The appearance of the in-mold label bottle thus obtained was very good, and no wrinkles on the label or deformation of the bottle were observed. Furthermore, the adhesive strength between the label and the bottle was measured and found to be 420 g/15 mm width. Comparative Example 1 In Example 1, using a label without an overcoat layer, in the operation of taking out the label from the magazine with a suction cup, the frequency of 2 times was 4%.
A piece-off occurred. The static friction coefficient of this label is
It was 0.35. At this time, the temperature around the label magazine was 26°C. Example 2, Comparative Examples 2 and 3 The coefficient of static friction of the outer surface of the label and the ink were obtained using a label with an overcoat layer formed using a releasable resin as shown in Table 1, and when various films were used as the label base material. Table 1 shows the ease with which labels can be taken out when molded label bottles are formed. Example 3 Using the same label as used in Example 1, when the ambient temperature of the label magazine reached 40°C, Example 1
When molding was carried out in the same manner as above, the occurrence rate of two pieces was
It was 0.1%. Comparative Example 4 Using the same label as used in Comparative Example 1, when the ambient temperature of the label magazine reached 40℃, Comparative Example 1
When molding was carried out in the same manner as above, the occurrence rate of two pieces was
It reached 24%. 【table】

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the cross-sectional structure of the label of the present invention, FIG. 2 is a diagram illustrating the in-mold label operation, and FIG. 3 is a diagram showing the production of the labeled plastic container of the present invention. FIG. 4 is a schematic layout diagram of a device used in the present invention, and FIG. 4 is a schematic layout diagram showing a label pasting mechanism. Reference number 1 is the label, 2 is the plastic film substrate, 3 is the printing ink layer, 4 is the adhesive layer, 5 is the overcoat layer, 6 is the cavity surface, 7 is the vacuum suction mechanism, 8 is the die, 9 is the parison, 10 11 is a container with a label, 11 is a blow mold, 12 is a turret, 13 is a label magazine, 17 is a spring member, 19 is a cam mechanism, 20 is a suction cup, 21
24 is an arm, 24 is a rotational drive mechanism, 25 is an annular sliding member, 28 is a flash collection sheet, 29 is a bottle gripper, and 30 is a conveyance mechanism.

Claims (1)

[Claims] 1. A plastic container with a label, which is formed by molding a single layer or multilayer plastic in a mold with a label affixed to the inner surface of the cavity, and bonding the label to the side wall surface of the formed container. In the manufacturing method, a large number of blow molds are arranged circumferentially and in a rotary manner, and along their circumferential movement path, there are a label sticking area, a parison extrusion area, a blow molding cooling area, and a flash recovery area. and the container removal area are arranged in this order, and the label includes a plastic film layer, a printing layer provided on the inner surface side of the film layer, a hot melt adhesive layer provided on the printing layer, and a label on the film. A heat-adhesive film label consisting of an overcoat layer of a releasable material with a coefficient of static friction of 0.20 or less is used, and in the label application area, each label is removed one by one from a magazine containing a large number of labels. A method for manufacturing a plastic container with a label, which is characterized by suction-holding, transferring into a mold, and pasting it on the mold surface.