JP2013214075A - Label for in-mold molding and injection-molded product with label - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a label for in-mold molding which is excellent in water resistance, detergent resistance, chemical resistance and durability and has an excellent adhesive strength even to an injection molded product composed of a nonpolar resin and a thermoplastic resin such as a polyethylene terephthalate resin and a styrene-acrylonitrile resin which is a polar resin, and to provide an injection molded product to which the label for in-mold molding is attached.SOLUTION: There is provided a label for in-mold molding composed of a laminated resin film including a base layer and a porous adhesive layer which has a surface aperture ratio of 6 to 30% and is subjected to plasma treatment under pressure close to the atmospheric pressure, wherein when the label is applied to an injection molded product made of an ester resin or a styrene resin to form an injection molded product with the label, the adhesive strength between the label after molding and the injection molded product is 200 to 800 gf/15 mm and the adhesive strength between the label obtained after the injection-molded product with the label is immersed in a surfactant solution for 24 hours and the injection-molded product is 150 to 600 gf/15 mm.

Description

  TECHNICAL FIELD The present invention relates to an in-mold molding label and an injection-molded body with a label using the same, and more specifically, an in-mold molding label comprising a laminated resin film including a base layer and a porous adhesive layer. However, by making the porous adhesive layer into a specific structure and performing a specific surface treatment, it is possible to achieve a uniform high adhesive force even on injection molded articles made from a wide variety of thermoplastic resin raw materials. The present invention relates to an in-mold molding label and an injection-molded body with a label using the same.

An injection molding technique for extruding a molten thermoplastic resin into a mold at a high pressure and shaping the resin into the shape of the mold is well known. At this time, a technique for obtaining a molded body in which the label is integrated by fixing a label or a blank in the mold and sticking the label to the resin together with the shaping of the molten resin is well known. Such a label used for in-mold sticking is called an “in-mold label” (IML) or an “in-mold label”.
In-mold molding labels that can be used for applications that require water resistance, chemical resistance, durability, etc. have been developed in the past, in addition to the characteristics of resin molded products such as water resistance, chemical resistance, and durability. Yes. For example, stretched or unstretched transparent film made of polyolefin resin, stretched or unstretched white film (synthetic paper) in which inorganic fine powder or organic filler is blended with polyolefin resin, and various types of heat on one side. Co-extruded heat seal layer made of sealing resin (Patent Document 1), bonded or laminated heat sealing resin film, heat sealing resin using various coating equipment A coating on the surface (Patent Document 2) and the like have been proposed, and some have been put to practical use.

  Separately, a white layer (synthetic paper) or the like is provided with a porous layer having fine openings on the surface, and this layer is used as an adhesive layer instead of a heat seal layer (Patent Document 3). ing. This can be used not only as a polyethylene resin having a suitable heat seal performance but also as a layer mainly composed of a polypropylene resin having a poor heat seal performance as an adhesive layer for an in-mold molding label. Furthermore, what coats this porous layer with heat-sealable resin (patent document 4) is also proposed. However, the methods of Patent Documents 1 to 3 are suitable for molded articles made of polyolefin resins such as polyethylene and polypropylene, which are nonpolar resins, but for molded articles made of polar resins such as polyethylene terephthalate. It was unsuitable and sufficient adhesive force was not obtained.

  In addition, since the method of Patent Document 4 can select a wide range of heat-sealable resins, it can be attached to various molded products including polar resins with sufficient adhesive force, but mainly coated with water-based heat-sealable resins. As a result, the molded product with a label is weak in water resistance, and the adhesive strength between the label and the molded product tends to decrease when the molded product is immersed in an aqueous liquid. There was a problem that the decrease in the adhesive strength when immersed in the activator solution was remarkable and easy to peel off. Therefore, it is suitable for the latter two that are polar resins among ester resins such as polyethylene, polypropylene, and polyethylene terephthalate, and styrene resins such as styrene-acrylonitrile resin, which are often used for daily goods such as food containers and detergent containers. There has not been proposed a label that can sufficiently withstand the use around water that touches the contents such as detergent.

The present inventor has provided a porous layer on the base layer by co-extrusion or lamination in the process of producing a resin film to be a label, and performs a process of chemically modifying the surface of the porous layer, thereby providing water resistance, Intensive research was conducted to obtain labels for in-mold molding that are excellent in detergent resistance, chemical resistance, and durability, and that can be applied not only to nonpolar resins but also to molded products of polar resins.
This inventor examined the usefulness of various plasma treatments as a method of chemically modifying the surface of these resin films. The plasma treatment is usually performed for the purpose of improving hydrophilicity and adhesion before coating on a film, before printing, and before lamination. For example, oxidation treatment by corona discharge is generally performed for the purpose of improving the wetting of a polyolefin-based film.

  Corona discharge treatment consists of a grounded roll and rod-like and plate-like applied electrodes. A sheet-like substrate to be treated is passed between the ground roll and the applied electrode, and the substrate to be treated is brought into contact with the grounding roll. In this method, the surface of the substrate to be treated is oxidized by applying a high voltage to the applied electrode. In order to use a high voltage, the substrate to be treated is located in a strong electric field. If the voltage is too high, a current partially flows and creeping discharge or arc discharge occurs on the surface of the substrate to be processed, which may cause scratches, pinholes, or processing unevenness on the substrate to be processed. For this reason, in this treatment, even after being immersed in the surfactant solution in the porous adhesive layer of the laminated resin film, it was not possible to carry out a treatment that was strong and effective enough to maintain the adhesive force.

For surface treatment other than the above corona discharge treatment, a minute amount of reactive gas is encapsulated under low pressure and plasma treatment is performed. A small amount of reactive gas is mixed in an expensive rare gas such as argon or helium under atmospheric pressure. And a method of treating with nitrogen gas mixed with water vapor (Patent Document 5) have been reported.
However, any of these methods cannot avoid the problem of complicated management of the processing environment pressure and the enclosed gas. Accordingly, the above-described methods for treating resin films are not so common, and the fact is that they are not so widespread that a person skilled in the art can easily try to accept or reject them.

Japanese Patent Laid-Open No. 02-084319 Japanese Patent Laid-Open No. 02-122914 JP 2006-309175 A JP 2004-255864 A JP 2003-155364 A

  The present invention is excellent in water resistance, detergent resistance, chemical resistance, durability, and injection molded articles made of thermoplastic resins such as polyethylene terephthalate and styrene-acrylonitrile resin which are polar resins as well as nonpolar resins. However, it is an object of the present invention to provide an in-mold molding label having excellent adhesion and an injection-molded body with a label to which the in-mold molding label is attached.

  As a result of further earnest research, the present inventor performed plasma discharge treatment on the porous layer of the in-mold molding label made of a laminated resin film including a base layer and a porous adhesive layer under a pressure near atmospheric pressure. In-mold with excellent adhesion to injection molded products made of polar thermoplastic resins such as polyethylene terephthalate and styrene-acrylonitrile resin, and excellent water resistance, detergent resistance, chemical resistance and durability It has been found that a molding label can be provided, and the present invention has been completed.

That is, the present invention relates to an in-mold molding label and an injection-molded body with a label for in-mold molding having the following configurations.
(1) It consists of a laminated resin film including a base layer and a porous adhesive layer, the surface opening ratio of the porous adhesive layer is 6 to 30%, and the porous adhesive layer is under a pressure near atmospheric pressure. A label for in-mold molding that has been subjected to plasma treatment, wherein the treatment uses plasma generated by applying a high-frequency pulsed voltage of 0.5 to 100 kHz using an electrode covered with a solid dielectric. When the label is applied to an injection molded body made of an ester resin or a styrene resin to form an injection molded body with a label, the adhesive force between the molded label and the injection molded body is 200 to 800 gf / 15 mm, and the adhesive force between the label and the injection molded article after the labeled injection molded article is immersed in a surfactant solution for 24 hours is 150 to 600 gf / 15 mm. Labels for in-mold forming, characterized.

(2) The plasma treatment uses a pair of opposing electrodes covered with a solid dielectric, and a gas is filled between the electrodes under a pressure near atmospheric pressure, and then a high frequency pulse voltage is applied to the electrodes. In addition, in-mold molding as described in (1) above, wherein plasma is generated in the gas and the porous resin layer is activated by passing a laminated resin film between the electrodes. For labels.
(3) The plasma treatment uses opposing electrodes covered with a pair of solid dielectrics, and a gas is filled between the electrodes under a pressure near atmospheric pressure, and then a high frequency voltage is applied to the electrodes. (1) characterized in that plasma is generated in the gas, and the plasma gas is sprayed onto the porous adhesive layer of the laminated resin film located outside between the electrodes to perform the activation treatment of the porous layer. The label for in-mold molding as described.

(4) The in-mold forming label according to (2) or (3), wherein the gas used in the plasma treatment is nitrogen gas.
(5) The number of nitrogen atoms determined from the peak area of the 1S orbital spectrum using ESCA when the atomic composition ratio from the surface of the porous adhesive layer to the depth of 10 nm by performing plasma treatment under normal pressure nitrogen gas And the ratio of carbon atoms (N / C) is in the range of 0.015 to 0.070, and the label for in-mold molding according to (4) above.
(6) The above (1) to (5), wherein the porous adhesive layer constituting the in-mold molding label is a resin film containing a thermoplastic resin and at least one of an inorganic fine powder and an organic filler. ) In-mold molding label according to any one of the above.

(7) The in-mold molding label as described in (6) above, wherein the porous adhesive layer contains a polyolefin-based resin as the thermoplastic resin.
(8) The above (6) or (6), wherein the porous adhesive layer contains a polypropylene resin as the thermoplastic resin and contains 50 to 80% by weight of at least one of an inorganic fine powder and / or an organic filler. The label for in-mold formation as described in (7).
(9) The in-mold molding label according to any one of (1) to (8), wherein the porous adhesive layer is a resin film stretched in at least one axial direction.

The present invention also provides
(10) An injection-molded article with a label obtained by attaching the in-mold molding label according to any one of (1) to (8) above to an injection-molded article made of an ester resin or a styrene resin.
(11) The labeled injection-molded article as described in (10) above, wherein the ester resin is a resin containing one or more resins selected from the group consisting of polyethylene terephthalate and / or amorphous polyethylene terephthalate. .
(12) The label according to (10), wherein the styrenic resin is a resin containing one or more resins selected from the group consisting of styrene-acrylonitrile resin and / or acrylonitrile-butadiene-styrene resin. With injection molding.

  The label for in-mold molding of the present invention has an excellent adhesive force not only for molded products of nonpolar resins such as polyethylene and polypropylene, but also for molded products of polar resins such as polyethylene terephthalate and styrene-acrylonitrile resin. Thus, even if the labeled injection-molded article of the present invention is immersed in a surfactant solution, the label does not easily peel off.

Below, the label for in-mold shaping | molding of this invention and this injection molded body with a label are demonstrated in detail.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
(1) Porous adhesive layer In the laminated resin film constituting the in-mold molding label of the present invention, the porous adhesive layer functions as an adhesive that joins the label and the injection molded article. When molding an injection-molded body in a mold, the molten resin extruded at a high pressure is thrown into the surface opening of the porous adhesive layer of the label and joined to the injection-molded body to exert a strong adhesive force. It is possible. The porous adhesive layer is preferably a resin film made of a thermoplastic resin and containing at least one of inorganic fine powder and / or organic filler.

Thermoplastic resin constituting the porous adhesive layer (A)
Examples of the thermoplastic resin used in the porous adhesive layer of the present invention include polypropylene resins, high density polyethylene, medium density polyethylene, crystalline polyolefin resins such as linear linear low density polyethylene, ethylene-vinyl acetate copolymers, Ethylene-acrylic acid copolymer, ethylene-acrylic acid alkyl ester copolymer, ethylene-methacrylic acid alkyl ester copolymer (the alkyl group has 1 to 8 carbon atoms), ethylene-methacrylic acid copolymer metal salt ( Ionomers), poly 4-methyl-1-pentene, crystalline polyolefin resins such as ethylene-cycloolefin copolymers, polyethylene terephthalate resins, polyvinyl chloride resins, nylon-6, nylon-6,6, nylon-6, 10, polyamide resin such as nylon-6, 12, styrene-a Rironitoriru resin, acrylonitrile - butadiene - styrene resins and the like. Preferably, it is a thermoplastic resin having a melting point in the range of 130 to 280 ° C., such as polypropylene resin, high density polyethylene, polyethylene terephthalate resin, etc., and these resins can also be used in combination.

  Among these, from the viewpoints of water resistance, chemical resistance, production cost, and the like, it is preferable to use a polyolefin resin, and it is more preferable to use a polypropylene resin and high density polyethylene. It is preferable to use a polyolefin resin having crystallinity and a filler such as an inorganic fine powder because pores (openings) are sufficiently formed on the surface of the porous adhesive layer by stretching. The crystallinity of the resin can be measured by methods such as X-ray diffraction and infrared spectrum analysis.

As the polypropylene resin, it is preferable to use an isotactic polymer or a syndiotactic polymer obtained by homopolymerizing propylene. Copolymers mainly composed of propylene having various stereoregularities obtained by copolymerizing propylene with α-olefins such as ethylene, 1-butene, 1-hexene, 1-heptene, 4-methyl-1-pentene. Polymers can also be used. The copolymer may be a binary system or a ternary or higher multi-element system, and may be a random copolymer or a block copolymer.
The content of the thermoplastic resin (A) in the resin film as the porous adhesive layer of the present invention is usually 20 to 50% by weight, preferably 25 to 50% by weight, particularly preferably 35 to 50% by weight.
It is. If the content of the thermoplastic resin (A) exceeds 50% by weight, the adhesiveness between the in-mold molded injection molded product and the label tends to be insufficient without obtaining a desired surface opening ratio. Conversely, if it is less than 20% by weight, the resin film tends to be difficult to stretch.

Inorganic fine powder (B), organic filler (B ')
The kind of inorganic fine powder and / or organic filler used for the porous adhesive layer of the present invention is not particularly limited.
Examples of the inorganic fine powder (B) include heavy calcium carbonate, light calcium carbonate, calcined clay, talc, barium sulfate, diatomaceous earth, magnesium oxide, zinc oxide, titanium oxide, and silicon oxide. These may be surface-treated with a fatty acid, a polymer surfactant, an antistatic agent or the like. Among these, heavy calcium carbonate, calcined clay, and talc are preferable because they have good hole moldability and are inexpensive.

Examples of the organic filler (B ′) include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyamide, polycarbonate, polyethylene sulfide, polyphenylene sulfide, polyimide, polyether ketone, polyether ether ketone, polymethyl methacrylate, poly 4- Methylpent-1-ene, a homopolymer of cyclic olefin, a copolymer of cyclic olefin and ethylene, a melamine resin, etc., which are incompatible with the thermoplastic resin (A) and have a melting point of 120 to 300 ° C., Or what has a glass transition temperature of 120-280 degreeC is mentioned.
One of these inorganic fine powders and / or organic fillers may be selected and used alone, or two or more may be used in combination.

The total content of the inorganic fine powder (B) and / or the organic filler (B ′) in the resin film as the porous adhesive layer of the present invention is usually 50 to 80% by weight, preferably 50 to 75% by weight, particularly Preferably it is 50 to 65% by weight.
When the total content of the inorganic fine powder (B) and / or the organic filler (B ′) exceeds 80% by weight, it tends to be difficult to stretch the resin film.
On the other hand, if it is less than 50% by weight, the desired surface opening ratio cannot be obtained, and the adhesiveness between the in-mold molded injection molded article and the label tends to be insufficient.

Dispersant (C)
If necessary, an inorganic fine powder and / or an organic filler dispersant can be optionally added to the porous adhesive layer of the present invention. Examples of the dispersant include acid-modified polyolefin and silanol-modified polyolefin. Among these, it is preferable to use acid-modified polyolefin. Examples of the acid-modified polyolefin include a carboxylic anhydride group-containing polyolefin obtained by random copolymerization or graft copolymerization of maleic anhydride, or a carboxylic acid group obtained by random copolymerization or graft copolymerization of an unsaturated carboxylic acid such as methacrylic acid or acrylic acid. And polyolefins containing epoxy group-containing polyolefins obtained by random copolymerization or graft copolymerization of glycidyl methacrylate. Specific examples include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, acrylic acid-modified polypropylene, ethylene-methacrylic acid random copolymer, ethylene-glycidyl methacrylate random copolymer, ethylene-glycidyl methacrylate graft copolymer, glycidyl. Examples include methacrylate-modified polypropylene. Among these, it is preferable to use maleic anhydride-modified polyethylene and maleic anhydride-modified polypropylene.

Optional Components Other known additives for resin can be optionally added to the porous adhesive layer of the present invention as long as the desired adhesiveness and the like are not impaired as optional components.
Examples of such additives include antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, slip agents such as fatty acid amides, antiblocking agents, dyes, pigments, plasticizers, crystal nucleating agents, mold release agents, flame retardants. Etc.

(2) Base layer In the laminated resin film constituting the in-mold molding label of the present invention, the base layer provides the label with strength, printability, water resistance, chemical resistance and, in some cases, opacity, etc. To do. In label molding, the porous adhesive layer is supported to facilitate molding.
The base layer is a resin film containing at least a thermoplastic resin. The material of the base layer is not particularly limited, and includes the thermoplastic resin (A), the inorganic fine powder (B) and / or the organic filler (B ′), the dispersant (C), etc. described above in the section of the porous adhesive layer. It can be arbitrarily blended to obtain a desired resin film.
In addition, a known additive for resin can be optionally added as an optional component in the same range as the porous adhesive layer as long as the intended printability and water resistance are not impaired.

(3) Manufacture of resin film The laminated resin film which comprises the label for in-mold shaping | molding of this invention can be manufactured by combining various well-known methods among those skilled in the art. Any resin film produced by any method is included within the scope of the present invention as long as it satisfies the constituent requirements of the present invention.
The laminated resin film is preferably stretched at least in a uniaxial direction from the viewpoints of weight reduction by forming surface openings, hole formation, and improving rigidity by molecular orientation. When the base layer is composed of a plurality of layers, it is preferable that at least one of the layers is stretched. When extending | stretching a several layer, you may extend | stretch separately before laminating | stacking each layer, and you may extend | stretch after laminating | stacking. Further, the stretched layer may be stretched again after being laminated. In order to provide an opening on the surface as the porous adhesive layer, a method of stretching the whole after forming a material for forming the porous adhesive layer on the base layer is particularly preferable.

Various conventionally known methods can be applied to the stretching of the laminated resin film. For example, the resin material is melt-kneaded using a screw-type extruder, the molten resin is extruded into a sheet shape using a T die or I die connected to the extruder, and then the sheet is stretched and laminated. As a method for obtaining a resin film, a longitudinal stretching method between rolls utilizing a difference in peripheral speed between roll groups, a transverse stretching method utilizing a tenter oven, a sequential biaxial stretching method combining these, and the like can be used. Moreover, the simultaneous biaxial stretching method by the combination of a tenter oven and a pantograph, the simultaneous biaxial stretching method by the combination of a tenter oven and a linear motor, etc. can be used. Further, a simultaneous biaxial stretching (inflation molding) method in which air is blown into the molten resin after being extruded into a tube shape using a circular die connected to a screw type extruder can be used.
When the thermoplastic resin is an amorphous resin, the stretching temperature is set to be equal to or higher than the glass transition point of the resin to be used, and in the case of a crystalline resin, the temperature is set to be higher than the glass transition point of the non-crystalline portion and lower than the melting point of the crystalline portion. can do.
In particular, when a crystalline resin is used as the constituent resin component of the porous adhesive layer and the stretching temperature exceeds the melting point of the crystal part, the desired surface area ratio cannot be obtained, and the adhesion between the label and the injection molded article Tends to decrease.

In order to stably stretch the resin film, the stretching speed is preferably 20 to 350 m / min. Similarly, the draw ratio is preferably 2 to 80 times, more preferably 3 to 60 times, and particularly preferably 4 to 50 times as the area draw ratio. When the area stretch ratio is less than 2 times, a desired surface opening ratio cannot be obtained in the porous adhesive layer, and there is a tendency that sufficient adhesion between the label and the injection molded article cannot be obtained at the time of in-mold molding. On the contrary, if the area stretch ratio exceeds 80 times, the resin film is likely to break, and stable stretch molding is difficult.
The porous adhesive layer in the laminated resin film of the present invention produced by such a method has a surface opening ratio of 6 to 30%, preferably 7 to 29%, measured by the following method. If the surface opening ratio is less than 6%, a sufficient anchoring effect on the label of the injection-molded product cannot be obtained at the time of in-mold molding, and the adhesiveness between the molded product and the label tends to decrease. Also, if the surface area ratio exceeds 30%, the internal cohesive force of the porous adhesive layer decreases, and material destruction easily occurs in the same layer, resulting in high adhesion between the molded body and the label. However, it is likely to become a problem in practical use.

  The surface opening ratio in the present invention indicates an area ratio occupied by pores (openings) in the observation region when the surface of the laminated resin film on the porous adhesive layer side is observed with an electron microscope. Specifically, an arbitrary part of the resin film sample is cut out and attached to an observation sample stage, gold or gold-palladium is vapor-deposited on the observation surface, and an arbitrary magnification (500 times easy to observe with an electron microscope). Observe the surface vacancies at ~ 3000x magnification). Further, the observed region was taken in as image data, and the image was processed with an image analysis device, and the area ratio of the pores was determined to obtain the surface opening ratio of the porous adhesive layer.

(4) Plasma treatment under pressure near atmospheric pressure The following two types of methods can be applied to the plasma treatment under pressure near atmospheric pressure, which is carried out in the present invention. One is a method of performing treatment by passing a substrate to be treated through plasma generated between opposed electrodes, and is called a direct method or a planar method. In the present specification, this will be referred to as a direct method hereinafter.
The other is a method in which plasma generated between the electrodes is blown from the electrode toward the substrate to be processed by gas flow or electric field arrangement, such as a remote method, a downstream method, or a plasma jet method. It is what is called. In the present specification, it is hereinafter referred to as a remote method.

Here, under the pressure near atmospheric pressure refers to under a pressure in the range of 1.333 × 10 ^{4 to} 10.9797 × 10 ⁴ Pa. Among them, easy pressure adjustment range of the apparatus is simplified ^{9.331 × 10 4 ~10.397 × 10 4} Pa is preferred. The atmospheric pressure (1 atm) is 10.133 × 10 ⁴ Pa. Since the plasma treatment used in the present invention is performed under a pressure near atmospheric pressure, it is excellent in workability and safety as compared with the conventional plasma treatment.
In the direct plasma processing, a pair of opposing electrodes covered with a solid dielectric is used, and a gas having a pressure near atmospheric pressure is introduced between the opposing electrodes with a substrate to be processed disposed between the electrodes. In this method, a pulsed voltage is applied to one electrode and the other is grounded, thereby performing plasma discharge in the gas and bringing the plasma into contact with the substrate.
In this case, both of the pair of electrodes used in the present invention may be flat plate-shaped, the ground-side electrode may be a roll shape, the application-side electrode may be a curved plate shape along the roll curved surface, and the ground-side electrode is a flat plate The application side electrode may have a plurality of fine lines.

  As said electrode, what consists of single metals, such as copper and aluminum, alloys, such as stainless steel and brass, is mentioned, for example. Solid dielectric materials include plastics such as polytetrafluoroethylene and polyethylene terephthalate, glass, metal oxides such as silicon dioxide, aluminum oxide, zirconium dioxide and titanium dioxide, and complex oxides such as barium titanate (ceramics). ) And the like. The distance between the electrodes is preferably about 1 to 20 mm, although it depends on the magnitude of the applied voltage and the type of processing gas. If it is less than 1 mm, it becomes difficult to install the substrate to be treated within the interval, and if it is more than 20 mm, it is difficult to generate uniform discharge plasma.

In this plasma treatment, a pulse voltage is applied between the counter electrodes. The pulsed voltage waveform used may be any of an impulse waveform, a square waveform, and a modulation waveform. The rise time and fall time of the pulse voltage are preferably 100 μs or less, and particularly preferably 50 ns to 5 μs. If it exceeds 100 μs, it is easy to shift to arc discharge, and it becomes unstable, and it is difficult to realize less than 50 ns due to restrictions on the apparatus.
The rise time here refers to the time during which the voltage (absolute value) increases continuously, and the fall time refers to the time during which the voltage (absolute value) decreases continuously.

The frequency of the pulse voltage is preferably 0.5 to 100 kHz (similar applied voltage is expressed as a high frequency pulse voltage in this specification). If the frequency is less than 0.5 kHz, the plasma density is lowered and processing takes time. Conversely, if the frequency exceeds 100 kHz, arc discharge tends to occur, resulting in an unstable state.
The pulse duration is preferably 1 to 1000 μs. If the time is less than 1 μs, the discharge becomes unstable, and if it exceeds 1000 μs, it tends to shift to arc discharge. More preferably, it is 3 to 200 μs. Here, one pulse continuation time refers to a continuous ON time of one pulse in a pulse voltage composed of repetition of ON and OFF.

The difference between the plasma treatment of the present invention and the conventional corona treatment is that a high-frequency pulse voltage is applied to the application electrode using an electrode covered with a solid dielectric.
In the conventional corona treatment, a corona is generated using a high-frequency alternating current (sine wave, sine wave) voltage. However, arc discharge is likely to occur, and the treatment strength that can treat the substrate to be treated uniformly, that is, the set voltage. The range of is narrow. For example, in order to obtain a sufficient treatment effect in the corona treatment, for example, to introduce nitrogen atoms into the substrate to be treated under a nitrogen gas atmosphere, even if the voltage is increased, a uniform and stable corona hardly occurs and arc discharge is often caused. The nitrogen atom introduction effect is low, and surface defects increase. In addition, many low molecular weight oxides (degraded products) are generated on the surface of the substrate to be treated, and this causes problems in adhesion, and the treatment life is short due to the migration of the substrate to be treated. . This plasma treatment can generate a stable plasma with a wide range of treatment intensities and enables uniform activation treatment to the substrate to be treated. For example, nitrogen atoms can be introduced with high efficiency in a nitrogen gas atmosphere. As a result, high adhesive strength to the molded body can be obtained during in-mold molding.

Although it is possible to use air as the gas introduced in the plasma treatment of the present invention, the adhesive force between the label and the molded body after immersing the molded body with a label for in-mold molding in a surfactant solution, That is, in order to further improve the detergent resistance, it is preferable for the purpose of the present invention to use nitrogen gas capable of positively introducing nitrogen atoms into the substrate to be treated. In addition, this treatment can continuously process a roll-shaped substrate, and when nitrogen gas is introduced, nitrogen is introduced by a small amount of oxygen in the entrained air on the surface of the substrate. Not only atoms but also oxygen atoms are introduced into the surface of the substrate to be treated.
In the present invention, by performing a plasma treatment using nitrogen gas, the atomic composition ratio from the surface of the porous adhesive layer to a depth of 10 nm is obtained from the number of nitrogen atoms determined from the peak area of the 1S orbital spectrum using ESCA and The ratio of carbon atoms (N / C) is preferably in the range of 0.015 to 0.070.

The remote type plasma treatment is characterized in that the substrate to be treated is located between a pair of opposed electrodes.
Since it exists outside between electrodes, the to-be-processed base material is not damaged by the influence of a strong electric field. Therefore, a high processing effect according to the applied energy can be obtained. As the apparatus shape and method, two parallel sides of plate-like electrodes arranged in parallel are sealed to form a substantially cylindrical shape, and gas is introduced from one end that is not sealed, and the substrate to be processed from the other end. The method of spraying plasma toward the surface, both the application side and ground side electrodes are cylindrical, one is positioned inside the other, gas is introduced between the cylinders from the end of the cylinder, and the object is processed from the other end A method of spraying plasma toward the substrate, or a plate-shaped solid dielectric that has a plate-like application side and ground side electrode embedded therein, and a plurality of through holes are opened in the plate, The treatment base material is located below the ground side electrode, and includes a method of introducing gas from the application side to make it plasma in the through hole and spraying it on the treatment base material. Among these, more preferably, the treatment Plate-shaped electrode with large area It is a method that was used.

  This remote type solid dielectric is only required to be coated on at least one, and the same materials as those of the former direct type are used for the electrodes and the solid dielectric. The distance between the electrodes is preferably 0.1 to 50 mm. If it is less than 0.1 mm, it is difficult to install electrodes at intervals, and if it exceeds 50 mm, uniform discharge plasma is difficult to be generated. Furthermore, although the space | interval of an electrode edge part and a to-be-processed base material is based also on an applied voltage and the flow rate of gas, 1-50 mm is preferable. If it is less than 1 mm, arc discharge tends to occur from the electrode end to the substrate to be treated. The voltage applied to the electrode is a high frequency voltage. The waveform may be an alternating wave having a sine waveform or a sine waveform, or may be pulsed having an impulse waveform, a square waveform or a modulated waveform.

  This remote method blows out the plasma generated between the electrodes to the outside of the electrode with the substrate to be processed, and applies a certain amount of pressure to the gas to be introduced to flow the plasma to the substrate to be processed. Alternatively, there is a method in which plasma is blown out by an electric field generated by a voltage applied between electrodes in order to generate plasma, or a method in which both are combined, but a method using a gas flow in which the applied voltage can be changed is preferable. Although air can also be used as the gas introduced in the plasma treatment, it is preferable for the purpose of the present invention to use nitrogen gas capable of introducing nitrogen atoms into the substrate to be treated.

In the present invention, a high frequency voltage or a high frequency pulsed voltage is applied to the plasma treatment. Since both of these waveform voltages are converted from a DC power source, the surface treatment on the substrate to be treated (porous adhesive layer) is performed. The strength is the processing intensity (kJ / m ² ) obtained from the value obtained by dividing the power (wattage) of the original DC power source by the processing area per unit time (processing speed × processing width) of the substrate to be processed. Can be sought. The optimum range of the treatment strength varies depending on each treatment method, the substrate to be treated, and the clearance (gap distance), but it is sufficient that the substrate to be treated does not have arc damage, thermal deformation, shrinkage, etc., 1 to 300 kJ / m ² is preferred.

Injection-molded body with label When the label for in-mold molding of the present invention is used for an injection-molded body made of a wide variety of thermoplastic resin raw materials, it can achieve a uniform high adhesive force.
In particular, the in-mold molding label of the present invention is characterized in that a high adhesive force can be realized even when applied to an injection-molded body made of an ester resin or a styrene resin, which could not be pasted with a high adhesive force. .
Here, the ester-based resin is from the group consisting of polyethylene terephthalate, amorphous polyethylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene succinate, amorphous polybutylene succinate, polylactic acid. It is a resin containing one or more selected resins.

Amorphous polyethylene terephthalate refers to ethylene glycol and terephthalic acid as raw materials, other dicarboxylic acids such as isophthalic acid, and other diols such as 1,4-cyclohexanedimethanol, neopentyl glycol and diethylene glycol. It is a ternary or higher copolymer obtained by mixing and copolymerization.
Amorphous polybutylene succinate is copolymerized by mixing 1,4-butanediol and succinic acid as raw materials with other dicarboxylic acids such as adipic acid and copolymerizable hydroxycarboxylic acids such as lactic acid. It is a copolymer of ternary system or more obtained as described above.
Among these, it is preferable to use either polyethylene terephthalate, amorphous polyethylene terephthalate, or a mixture of both because of the versatility often used in household goods such as food containers and detergent containers.

Here, the styrene resin is polystyrene, high impact polystyrene, styrene-acrylonitrile resin, acrylonitrile-butadiene-styrene resin, styrene-butadiene resin, acrylonitrile-styrene-acrylic ester resin, methacrylic ester-butadiene-styrene resin. It is resin containing 1 or more resin chosen from the group which consists of.
Among these, it is preferable to use either a styrene-acrylonitrile resin, an acrylonitrile-butadiene-styrene resin, or a mixture of both because of the versatility often used for daily goods such as food containers and detergent containers.

The porous adhesive layer of the present invention has an adhesive strength of 200 to 800 gf / 15 mm, preferably 250 to 800 gf / 15 mm, when the injection molded product with a label is formed by the above-described aperture ratio and plasma treatment. Especially preferably, it is configured to be 350 to 800 gf / 15 mm. If the adhesive strength is less than 200 gf / 15 mm, the label may be peeled off due to impact applied during transportation after filling the contents of the injection-molded article with label or when displaying the product.
In the present invention, the adhesive strength between the label and the injection molded article after the labeled injection molded article is immersed in a surfactant solution for 24 hours is 150 to 600 gf / 15 mm, and preferably 170 to 600 gf / 15 mm. . When the adhesive strength is less than 150 gf / 15 mm, when the molded body is, for example, a container and a surfactant such as a body soap or shampoo is used as the contents, the label may be peeled off due to a long-term use.
Details of tests and conditions in the present invention will be specifically described in the following test examples.

The features of the present invention will be described more specifically with reference to examples and comparative examples.
The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.
Example 1
<Manufacture of laminated resin film>
Propylene homopolymer (trade name “Novatech PPMA-8”, melting point 164 ° C., manufactured by Nippon Polypro Co., Ltd.) 67% by weight, high density polyethylene (trade name “Novatech HDHJ580”, melting point 134 ° C., manufactured by Nippon Polyethylene Co., Ltd.) ) A resin composition (a) comprising 10% by weight and 23% by weight of calcium carbonate powder having an average particle size of 1.5 μm was melt-kneaded at 260 ° C. using an extruder, and then extruded into a film form from a die. The film was cooled to a temperature of 50 ° C. This film was heated again to about 140 ° C. and then stretched 5 times in the longitudinal direction using the peripheral speed of the roll group to obtain a uniaxially stretched film to be a core layer.
On the other hand, propylene homopolymer (trade name “Novatech PPMA-3”, manufactured by Nippon Polypro Co., Ltd.) 51.5% by weight, high density polyethylene (trade name “Novatech HDHJ580”, manufactured by Nippon Polyethylene Co., Ltd.) 3.5 A resin composition (b) comprising 42% by weight of calcium carbonate powder having an average particle size of 1.5 μm and 3% by weight of titanium oxide powder having an average particle size of 0.8 μm was melted at 250 ° C. using another extruder. This was kneaded, extruded onto a single side of the uniaxially stretched film in a film form from a die, and laminated to obtain a surface layer / core layer (b / a) laminate.

Further, using different extruders, propylene homopolymer (trade name “Novatech PPMA-3”, manufactured by Nippon Polypro Co., Ltd.) 51.5% by weight, high density polyethylene (trade name “
Novatec HDHJ580 "(manufactured by Nippon Polyethylene Co., Ltd.) 3.5% by weight, 42% by weight of calcium carbonate powder having an average particle size of 1.5 μm and 3% by weight of titanium oxide powder having an average particle size of 0.8 μm ( c), propylene homopolymer (trade name “Novatech PPFY-4”, manufactured by Nippon Polypro Co., Ltd.) 39% by weight, maleic acid-modified polypropylene (trade name “Yumex1001”, manufactured by Sanyo Chemical Industries, Ltd.) 1 weight % And heavy calcium carbonate (trade name “Caltex 7”, manufactured by Maruo Calcium Co., Ltd.) 60% by weight of a resin composition (d) melt-kneaded at 250 ° C. and supplied to one coextrusion die Laminate in the die, extrude into a film from the die, and laminate so that the porous adhesive layer (d) is the outermost layer on the core layer (a) side surface of the laminate (b / a) Thus, a laminate (b / a / c / d) having a four-layer structure of surface layer / core layer / back surface layer / porous adhesive layer was obtained. Here, the laminate (b / a / c) having a three-layer structure of front surface layer / core layer / back surface layer corresponds to the base layer in the laminated resin film used in the present invention.
This four-layer laminate is guided to a tenter oven, heated to 155 ° C., stretched 5 times in the transverse direction using a tenter, then heat-set (annealed) at 164 ° C., and further cooled to 55 ° C. After slitting the ear part, it was wound up in a roll shape with a winder to obtain a laminated resin film of Example 1. The surface opening ratio of the porous adhesive layer of this laminated resin film was 15%.

<Plasma treatment>
The above-mentioned laminated resin film was subjected to direct plasma treatment under a pressure in the vicinity of atmospheric pressure under the following conditions.
Each of the pair of electrodes has a plate shape, and is made of stainless steel so as to have a length of 100 mm, a width of 150 mm, and a thickness of 20 mm, and is covered with a ceramic that is a solid dielectric. A cavity through which a cooling medium can flow is provided inside the electrode, and the cooling medium can be circulated and pumped to maintain a constant temperature during the discharge process. These pair of electrodes were fixed so as to maintain a distance of 20 mm.
The substrate to be treated (laminated resin film) was passed between these electrodes so that the porous adhesive layer side was directed to the application side electrode, and the distance between the application side electrode and the substrate was adjusted to 10 mm. Furthermore, nitrogen gas was introduced between the electrodes at 10.133 × 10 ⁴ Pa, 100 l / min, and the substrate roll was wound at a speed of 30 m / min, while the application side electrode had an AC frequency of 50 kHz and a pulse duration of 100 μs. A plasma discharge treatment was applied to the porous adhesive layer of the substrate to be treated by applying a pulse voltage. When the value obtained by dividing the amount of power of the DC power source before pulsing by the area of the substrate to be treated was taken as the treatment intensity, the intensity of the plasma treatment was 12 kJ / m ² .

<Punching>
The printed product thus obtained was once cut from a roll shape into a sheet shape, and then punched into a label shape having a length of 11 cm and a width of 9 cm using a Thomson blade to obtain a label for in-mold molding of the present invention.

<Adhesion 1>
Using an injection molding machine (trade name “NV50ST”, clamping force 50 tons, vertical arrangement type, manufactured by Niigata Steel Co., Ltd.), the size of the molded body is 130 mm wide, 150 mm long, and 1 mm thick. The split mold for injection molding was used. The in-mold molding label is fixed to the surface of the female mold attached to the lower fixed platen side so that the surface layer side of the label is in contact with the mold, and then the split mold is clamped and set to 230 ° C. The acrylonitrile-butadiene-styrene copolymer resin (trade name “Techno ABS110”, manufactured by Technopolymer Co., Ltd.) melted by the extruder was injected from the gate portion into the mold at a pressure of 129 kgf / cm ² . The mold was cooled to 80 ° C., and after the molten resin was cooled and solidified for about 10 seconds, the mold was opened to obtain a flat-plate-shaped ABS injection-molded article having a label attached thereto.

<Adhesion 2>
In sticking 1, polyethylene terephthalate (trade name “Unipet RA163C”, manufactured by Nihon Unipet Co., Ltd.) melted by an extruder set at 270 ° C. was cooled to 30 ° C. from the gate portion at a pressure of 100 kgf / cm ^2. A flat PET resin injection molded body was produced in the same manner as the sticking 1 except that it was injected into the mold.

(Example 2)
In Example 1, except that the processing speed was set to 60 m / min, which is twice that of Example 1, so that the plasma processing intensity was 6 kJ / m ² , the in-mold was manufactured. A molding label and an injection-molded article with a label were obtained.
(Example 3)
In Example 1, except that the processing speed was set to 120 m / min which is four times that of Example 1 so that the processing intensity of the plasma processing becomes ¼, 3 kJ / m ² , Thus, an in-mold label and an injection-molded body with a label were obtained.
Example 4
In Example 1, a label for in-mold molding and an injection-molded article with a label were obtained in the same manner as in Example 1 except that air was introduced instead of nitrogen gas for plasma treatment.

(Example 5)
In the first embodiment, in order to change the plasma treatment from the direct method to the remote method, the same electrode as in the first embodiment is used, the distance between the electrodes is fixed to 1 mm, and the two parallel sides of the electrode are sealed with an insulator. And arrange the roll of the laminated resin film, which is the substrate to be treated, outside the pair of electrodes, and arrange the porous substrate side of the substrate to be treated (laminated resin film) to face these electrodes, The distance between the electrode and the substrate to be treated was adjusted to 3 mm. Further, nitrogen gas was introduced between the electrodes so as to be blown toward the adhesive layer side of the roll at a flow rate of 10.133 × 10 ⁴ Pa and 300 l / min. Implemented except that the high-frequency voltage was applied to the electrode while the roll was wound at a speed of 5 m / min, so that the amount of power of the DC power supply before high-frequency conversion was 1 kw, and the plasma treatment was performed at a treatment intensity of 80 kJ / m ^2. In the same manner as in Example 1, a label for in-mold molding and an injection-molded article with a label were obtained.

(Example 6)
In Example 1, the blending ratio of the heavy calcium carbonate of the resin composition (d) is 75% by weight so that the surface opening ratio of the porous adhesive layer is 27%, and the blending ratio of the propylene homopolymer is 24%. Except for the weight percentage, the same production as in Example 1 was carried out to obtain a label for in-mold molding and an injection-molded article with a label.
(Example 7)
In Example 1, the blending ratio of the heavy calcium carbonate in the resin composition (d) was 50% by weight so that the surface opening ratio of the porous adhesive layer was 6.5%, and the blending ratio of the propylene homopolymer Was produced in the same manner as in Example 1 except that the content was changed to 49% by weight to obtain an in-mold molding label and an injection-molded body with a label.

(Comparative Example 1)
In Example 1, except that the porous adhesive layer was not subjected to plasma treatment, it was produced in the same manner as in Example 1 to obtain an in-mold label and an injection-molded body with a label.
(Comparative Example 2)
In Example 1, the blending ratio of the heavy calcium carbonate in the resin composition (d) is 85% by weight so that the surface opening ratio of the porous adhesive layer is 35%, and the blending ratio of the propylene homopolymer is 14%. Except for the weight percentage, the same production as in Example 1 was carried out to obtain a label for in-mold molding and an injection-molded article with a label.
(Comparative Example 3)
In Example 1, the resin composition (d) was prepared so that the surface opening ratio of the porous adhesive layer was 5%.
This was manufactured in the same manner as in Example 1 except that the blending ratio of the heavy calcium carbonate was 45% by weight and the blending ratio of the propylene homopolymer was 54% by weight to obtain an in-mold molding label and a labeled injection molded body. It was.

(Comparative Example 4)
In Example 1, corona discharge treatment was performed instead of plasma treatment. Surrounding the discharge electrode of the corona discharge treatment apparatus, introducing nitrogen gas into the enclosure at a flow rate of 10.133 × 10 ⁴ Pa and 80 l / min, winding the roll at a speed of 20 m / min, A high frequency voltage having a sine waveform was applied to the electrodes so that the treatment intensity obtained by dividing the amount of power of the DC power source before conversion into the area of the substrate to be treated was 3 kJ / m ² . A label for in-mold molding and an injection-molded article with a label were obtained in the same manner as in Example 1 except that the surface treatment was applied to the porous adhesive layer of the laminated resin film by corona discharge treatment in a nitrogen gas atmosphere.

(Test example)
The following physical properties were measured and evaluated for the in-mold labels and the injection-molded articles with labels produced in Examples 1 to 7 and Comparative Examples 1 to 4.
[Surface opening ratio]
An arbitrary part is cut out from the laminated resin film sample, attached to the observation sample stage, gold is deposited on the observation surface (porous adhesive layer surface), and an electron microscope (device name “scanning electron microscope: SM-200” TOPCON Surface vacancies were observed at an arbitrary magnification (500 times to 3000 times) that can be easily observed using a product manufactured by KK. Further, the observed region is captured as image data, and the image is processed with an image analysis device (device name “small general-purpose image analysis device: Luzex AP”, manufactured by Nireco Corporation) to obtain the area ratio of the pores. The aperture ratio on the surface of the porous adhesive layer was used. The results are shown in Table-1.

[Atom composition ratio]
Using an ESCA spectrometer (device name “X-ray photoelectron spectrometer: ESCA3200 type”, manufactured by Shimadzu Corporation), incident X-ray: Mg—Kα ray (1250 eV), X-ray output: 8 kv × 30 mA (output) 240W), the measurement environment is a vacuum degree: about 10E-5Pa, the peak area obtained from the 1S orbital spectrum of the carbon of the surface layer portion from the surface of the porous adhesive layer of the label sample for in-mold molding to a depth of 10nm The peak area obtained from the 1S orbital spectrum of nitrogen obtained in the same manner was measured. Further, the ratio of the number of nitrogen atoms to the number of carbon atoms (N / C) was determined from the detected intensity of each element. The results are shown in Table-1.

[Label adhesiveness]
Cut 4 points of 15mm width and 120mm length of the label-attached part of the injection-molded body with label, peel off part of the attached label edge, about 10mm, and apply 120mm adhesive tape on the front and back of the peeled part wear. Using a tensile tester (trade name “Autograph AGS-D type”, manufactured by Shimadzu Corporation), the adhesive tape and the molded body part with the label end extended are peeled off by 60 mm at a tensile speed of 200 mm / min. The adhesion (peak value (gf) of peel strength) was measured, and the average value was obtained and determined according to the following criteria.
◎: 200 gf or more ○: 150 gf or more, less than 200 gf Δ: 100 gf or more, less than 150 gf ×: less than 100 gf

In addition, after the same sample cut into 15 mm width and 120 mm length was soaked in the following various liquids at room temperature for 24 hours, various liquids were wiped off so as not to hinder the evaluation, and adhesiveness (peel strength) was obtained in the same manner as described above. ) Was also confirmed, and evaluation was performed based on the same criteria as described above. The results are shown in Table-1.
In addition, the surfactant solution prescribed | regulated by this invention shows the following tableware detergents.
Dry: No pickling Water-resistant adhesion: Water (distilled water)
Oil-resistant adhesion: Edible oil (trade name “Nisshin beni flower oil”, manufactured by Nisshin Oilio Group)
Detergent-resistant adhesion: Detergent for tableware (trade name “Charmy Green”, manufactured by Lion Corporation)

The present invention relates to an in-mold molding label used in the in-mold molding technical field such as plastic bottles and containers, and an injection-molded body with a label using the same.

Claims (12)

A laminated resin film including a base layer and a porous adhesive layer, the surface opening ratio of the porous adhesive layer is 6 to 30%, and the porous adhesive layer is subjected to plasma treatment under a pressure near atmospheric pressure. A plasma treatment using a plasma generated by applying a high-frequency pulsed voltage of 0.5 to 100 kHz using an electrode covered with a solid dielectric, When the label is applied to an injection molded body made of an ester resin or a styrene resin to form an injection molded body with a label, the adhesive force between the molded label and the injection molded body is 200 to 800 gf / 15 mm, and the adhesive force between the label and the injection-molded product after dipping the labeled injection-molded product in a surfactant solution for 24 hours is 150 to 600 gf / 15 mm In-mold label for that.   The plasma treatment uses a pair of opposed electrodes covered with a solid dielectric, and a gas is filled between the electrodes under a pressure near atmospheric pressure, and then a high frequency pulse voltage is applied to the electrodes to form a gas. 2. The in-mold molding label according to claim 1, wherein the porous adhesive layer is activated by generating plasma therein and passing a laminated resin film between the electrodes.   The plasma treatment uses opposed electrodes covered with a pair of solid dielectrics, and a gas is filled between the electrodes under a pressure near atmospheric pressure, and then a high frequency voltage is applied to the electrodes to bring the gas into the gas. The porous layer is activated by generating plasma and spraying the plasma gas onto the porous adhesive layer of the laminated resin film located outside the space between the electrodes. Label for in-mold molding.   The in-mold molding label according to claim 2 or 3, wherein the gas used in the plasma treatment is nitrogen gas.   The atomic composition ratio from the surface of the porous adhesive layer to a depth of 10 nm is the ratio of the number of nitrogen atoms and the number of carbon atoms determined from the peak area of the 1S orbital spectrum using ESCA (N / C) is in the range of 0.015 to 0.070, and the label for in-mold molding according to claim 4.   The in-mold according to any one of claims 1 to 5, wherein the porous adhesive layer is a resin film containing a thermoplastic resin and at least one of an inorganic fine powder and / or an organic filler. Label for molding.   The in-mold molding label according to claim 6, wherein the porous adhesive layer contains a polyolefin resin as the thermoplastic resin.   The porous adhesive layer contains a polypropylene resin as a thermoplastic resin and contains at least one of inorganic fine powder and / or organic filler in an amount of 50 to 80% by weight. Label for in-mold molding.   The label for in-mold molding according to any one of claims 1 to 8, wherein the porous adhesive layer is a resin film stretched in at least one axial direction.   The injection-molded body with a label formed by sticking the label for in-mold molding as described in any one of Claims 1-9 to the injection-molded body which consists of ester resin or a styrene resin. The labeled injection-molded article according to claim 10, wherein the ester resin is a resin containing one or more resins selected from the group consisting of polyethylene terephthalate and / or amorphous polyethylene terephthalate.   11. The labeled injection-molded article according to claim 10, wherein the styrenic resin is a resin containing one or more resins selected from the group consisting of styrene-acrylonitrile resin and / or acrylonitrile-butadiene-styrene resin.