JP2007022033A - In-mold label molded form - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high quality in-mold label which can be well applied to either of a blow-molding process or an orientation blow-molding process and also an in-mold label molded form which has outstanding designability and adhesion as a container for a soft drink, an alcoholic drink, a soy sauce, an oil and a detergent, and label releasability. <P>SOLUTION: This in-mold label molded form (C) comprises an in-mold label (A) composed of a plastic resin film (a) as a base material, a printing ink receptive layer (b) formed on the face of the film (a) and a hot-melt heat sealing layer (c) formed on the back, and a molded form (B) to which the in-molded label is laminated. The hot-melt heat sealing layer (b) contains a polymer (1), a tackifier (2) and a wax (3). In addition, the softening point of the hot-melt heat sealing layer is 60 to 100°C, and the coefficient of dynamic friction of the in-mold label is 0.2 to 0.6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an in-mold label molded article characterized by having excellent in-mold suitability and printability, and further label peelability.
The in-mold label molded body of the present invention is useful as a container for soft drinks, sake, soy sauce, oil, detergents and the like.

Blow molded products made from non-olefin resins such as polyethylene, polypropylene, and olefin resins such as polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, polynaphthalene terephthalate, polyamide, and polystyrene are tough, lightweight and stable in strength. It has the advantage of having properties and is used in a wide range of fields as a packaging container.
In particular, in recent years, bottles made by blow molding of non-olefin resins such as polyethylene terephthalate are superior to olefin resins in terms of transparency, surface gloss, chemical resistance, internal pressure resistance, etc. as the price of non-olefin resins decreases. Therefore, the market is expanding rapidly in wide fields such as food and detergent.

For blow molded products of olefin resin, in-mold label molding is performed by attaching a label in the blow mold and blow molding the olefin resin parison in the blow mold simultaneously. The method is widely used in terms of reducing the bottle forming process and reducing the total bottle cost.
In addition, in recent years, in-mold label molding is also being performed for non-olefin resin bottles such as polyethylene terephthalate. In polyethylene terephthalate, a metal rod called a storage rod is used when molding large containers of 500 ml or more. The so-called stretch blow molding method, in which the molding resin is stretched in the longitudinal direction by insertion and stretched in the transverse direction at the blow pressure, is often carried out in large containers, and the conventional blow molding method and stretch blow molding are often performed. Development of in-mold labels adapted to both molding methods has been widely implemented as disclosed in Patent Document 1, for example.

Furthermore, in recent social circumstances, with the enactment of the law (container and packaging recycling law) concerning the separation and collection of containers and packaging and the promotion of re-commercialization, the container body and label are separated even in blow-molded containers. A method of recycling containers has been devised as disclosed in, for example, Patent Document 2.
However, since the label is not completely adhered to the bottle, the label is naturally peeled off, or the glue remains in the bottle, so that there is a drawback that it cannot be actually recycled.
This phenomenon occurs due to inappropriate selection of the heat seal layer of the in-mold label. In the selection of the heat seal layer of the in-mold label, particularly in the stretch blow molding method, the resin temperature during molding is 90%. Since the temperature is around 50 ° C. and lower by 50 ° C. than ordinary blow molding, it is necessary to lower the softening point of the heat sealant and further reduce the viscosity at the time of softening.

A hot-melt heat sealant can be considered as a low-softening point and low-viscosity heat sealant. However, with general hot heat sealants, it is common to add a tackifier because of poor adhesion to the substrate. is there.
However, if the viscosity of the heat sealant is decreased, the adhesion between the molded body and the label is reduced during blow molding, and the heat sealant protrudes at the boundary between the molded body and the label, so that when melted, There is a limit to viscosity reduction.
In addition, the softening point of the heat sealant and the decrease in viscosity during softening can be handled with various additives because of label blocking, label slipperiness, and ease of thermal decomposition during heat sealant coating. There is a need to.

However, when a lubricant such as silicone is easily added as a label blocking inhibitor in the heat seal layer that is the back surface layer or the amount of antioxidant is easily increased to prevent thermal decomposition, the printing ink that is the surface layer Lubricants and antioxidants are transferred to the receiving layer, causing adverse effects such as a decrease in printability such as adhesion to UV ink and a decrease in heat sealability.
Furthermore, in the case of a highly transparent bottle such as a polyethylene terephthalate bottle, transparency is also required for the in-mold label. However, in the case of a transparent in-mold label, a minute amount remaining between the label and the bottle that cannot be confirmed on an opaque substrate. The air reservoir can be easily seen, and therefore, it is necessary to develop an in-mold label having excellent adhesion and molding characteristics.

JP 2002-355886 A Japanese Utility Model Publication No. 06-55727

Therefore, the present invention has been made to solve the problems of these conventional techniques, and to provide an excellent in-mold label molded body that can be applied to any molding method of blow molding and stretch blow molding.
An object of the present invention is to provide an in-mold label molded body having excellent design and adhesiveness as containers for soft drinks, sake, soy sauce, oil, detergents, and the like, and capable of label separation.

As a result of diligent studies to solve these problems, the present inventors attach an in-mold label having a heat seal layer adjusted in a specific blending and melting point range by an in-mold molding method. Thus, it has been found that an in-mold label molded body having desired characteristics can be provided, and the present invention has been completed.
That is, the first invention of the present invention is an in-mold label comprising a plastic resin film (a) as a substrate, a printing ink receiving layer (b) on the front side, and a hot melt heat seal layer (c) on the back side. An in-mold label molded body (C) in which (A) is bonded to a molded body (B), wherein the hot-melt type heat seal layer (b) comprises a heat-adhesive polymer (1) and a tackifier (2). And a wax (3), and the softening point of the hot melt heat seal layer is 60 to 100 ° C.

2nd invention is an in-mold label molded object, wherein the acid value of a hot-melt type heat seal layer (b) is 10-200.
A third invention is the in-mold label molded body, wherein the printing ink receiving layer (b) has a surface resistivity of 1 × 10 ¹³ Ω or less.
4th invention is a base-material thickness of a thermoplastic resin film (a), and is an in-mold label molded object characterized by 30-200 micrometers.
5th invention is an in-mold label molded object characterized by the thermoplastic resin film (a) being comprised with polyolefin.

6th invention is a molded object by which the molded object (B) was comprised with the polymer chosen from polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, polynaphthalene terephthalate, polyamide, polystyrene, and polycarbonate. This is an in-mold label molded article.
A seventh invention is an in-mold label molded product, wherein the molded product (B) is a molded product composed of a polymer selected from polyethylene terephthalate, polyethylene naphthalate, polystyrene, and polycarbonate.
The eighth invention is an in-mold label molded body, wherein the in-mold label molded body (C) is a molded body formed by a stretch blow molding method.

The specific configuration of the present invention will be described below.
[Thermoplastic resin film (a)]
The thermoplastic resin film (a) of the present invention is a layer containing a thermoplastic resin and serves as a support as an in-mold label. By containing a thermoplastic resin, an in-mold label having excellent water resistance and shape followability to a container can be obtained.
The thermoplastic resin film (a) of the present invention may contain any thermoplastic resin as long as it has excellent water resistance and shape stability. Examples of the thermoplastic resin contained in the thermoplastic resin film (a) include polyolefin resins such as high density polyethylene, medium density polyethylene, low density polyethylene, propylene resin, polymethyl-1-pentene, ethylene / acetic acid, and the like. Functional group-containing polyolefin resins such as vinyl copolymers, ethylene / acrylic acid copolymers, maleic acid-modified polyethylene, maleic acid-modified polypropylene, polyamide resins such as nylon-6 and nylon-6,6, polyethylene terephthalate and the like Copolymers, thermoplastic polyester resins such as polybutylene terephthalate and aliphatic polyester, polycarbonate, atactic polystyrene, syndiotactic polystyrene and the like can be used. Among these thermoplastic resins, it is preferable to use a polyolefin-based resin because of excellent processability.

More specific examples of polyolefin resins include homopolymers of olefins such as ethylene, propylene, butylene, butadiene, isoprene, chloroprene, and methyl-1-pentene, and copolymers of two or more of these olefins. Examples thereof include polymers and copolymers with functional group-containing monomers such as styrene, α-methylstyrene, vinyl acetate, vinyl alcohol, acrylic acid derivatives, vinyl ethers, and the like.
Further, among these polyolefin resins, propylene resins are preferable from the viewpoint of chemical resistance, cost, ease of separation due to specific gravity difference at the time of label peeling, and the like. The propylene-based resin is a propylene homopolymer and is mainly composed of polypropylene, propylene having isotactic or syndiotactic and various degrees of stereoregularity, and ethylene, 1-butene, 1-hexane, It is desirable to use as a main component a copolymer obtained by copolymerization with an α-olefin such as 1-heptane or 4-methyl-1-pentene. This copolymer may be a binary system or a ternary system or may be a random copolymer or a block copolymer. The propylene resin is preferably used by blending 2 to 25% by weight of a resin having a melting point lower than that of the propylene homopolymer. Examples of such a resin having a low melting point include high-density or low-density polyethylene.

  To the thermoplastic resin film (a), inorganic fine powder, organic filler, stabilizer, light stabilizer, dispersant, lubricant, antistatic agent and the like can be added as necessary. When adding an inorganic fine powder, the particle size is usually 0.01 to 15 μm, preferably 0.01 to 5 μm. Specifically, calcium carbonate, calcined clay, silica, diatomaceous earth, white clay, talc, titanium oxide, barium sulfate, alumina, zeolite, mica, sericite, bentonite, sepiolite, vermiculite, dolomite, wollastonite, glass fiber Etc. can be used. Further, when an inorganic fine powder is used, it is desirable to subject the filler surface to a surface treatment such as a hydrophilic treatment and / or an oleophilic treatment in advance, and the surface treatment improves dispersibility, and a thermoplastic resin film ( Various performances such as printability, coating suitability, scratch resistance, labeling suitability, and secondary processing suitability can be imparted to a).

  When an organic filler is added, it is preferable to select a different type of resin from the thermoplastic resin that is the main component. For example, when the thermoplastic resin film is a polyolefin resin film, examples of the organic filler include polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon-6, nylon-6,6, cyclic olefin, polystyrene, and polymethacrylate. It is possible to use a polymer having a melting point higher than the melting point of the polyolefin resin (for example, 170 to 300 ° C.) or a glass transition temperature (for example, 170 to 280 ° C.) and made of an incompatible resin. it can.

"Molding resin film"
As a specific example of the method for forming the thermoplastic resin film (a), cast molding or circular die for extruding molten resin into a sheet using a single layer or multilayer T die or I die connected to a screw type extruder Inflation molding in which a molten resin is extruded into a tube shape using air pressure and expanded by air pressure inside, calender molding in which a kneaded material is rolled with a plurality of hot rolls and processed into a sheet shape, rolling molding, and the like.
"Lamination"
The thermoplastic resin film (a) can be laminated by various known methods. Specific examples include a multilayer die method using a feed block and a multi-manifold, and an extrusion lamination method using a plurality of dies. Etc. It is also possible to use a combination of multilayer dies and extrusion lamination.

"Stretching"
The thermoplastic resin film (a) can be stretched by any one of various methods usually used. The stretching temperature can be carried out within a known temperature range suitable for stretching a thermoplastic resin having a temperature not lower than the glass transition temperature of the thermoplastic resin mainly used for the thermoplastic resin film (a) and not higher than the melting point of the crystal part. . Specifically, when the thermoplastic resin of the thermoplastic resin film (a) is a propylene homopolymer (melting point 155 to 167 ° C.), it is 100 to 166 ° C., and when the thermoplastic resin is a high-density polyethylene (melting point 121 to 136 ° C.). It is -135 degreeC and is 1-70 degreeC temperature lower than melting | fusing point. The stretching speed is preferably 20 to 350 m / min.

As the stretching method, when stretching a cast film, longitudinal stretching using the difference in the peripheral speed of the roll group, lateral stretching using a tenter oven, rolling, simultaneous biaxial stretching using a combination of a tenter oven and a linear motor, etc. Can be mentioned. In addition, examples of the method for stretching the inflation film include simultaneous biaxial stretching by a tubular method.
The draw ratio is not particularly limited, and is appropriately determined in consideration of the characteristics of the thermoplastic resin used for the thermoplastic resin film (a). For example, when a propylene homopolymer or a copolymer thereof is used as a thermoplastic resin, it is about 1.2 to 12 times, preferably 2 to 10 times when stretched in one direction, and biaxially stretched. Is an area magnification of 1.5 to 60 times, preferably 4 to 50 times. When using other thermoplastic resins, it is 1.2 to 10 times, preferably 2 to 5 times in the case of stretching in one direction, and 1.5 to 20 times in area magnification in the case of biaxial stretching. Preferably it is 4 to 12 times.

The thickness of the thermoplastic resin film (a) is in the range of 30 to 200 μm, preferably 60 to 150 μm. If it is less than 30 μm, it is difficult to process because it is too weak at the time of printing or processing into a label, and the labeling suitability as a label is inferior, and the desired performance of the present invention cannot be exhibited. On the other hand, if the thickness exceeds 200 μm, the thickness of the entire in-mold label (A) becomes too thick, which affects the shape of the in-mold label molded body (C).
The thermoplastic resin film (a) is preferably stretched at least uniaxially, and may have a two-layer structure, a multilayer structure of three or more layers, and the number of stretch axes of this multilayer structure is one axis / 1. Axis, 1 axis / 2 axis, 2 axis / 1 axis, 1 axis / 1 axis / 2 axis, 1 axis / 2 axis / 1 axis, 2 axis / 1 axis / 1 axis, 1 axis / 2 axis / 2 axis, Two axes / 2 axes / 1 axis, 2 axes / 2 axes / 2 axes may be used. The multilayering of the thermoplastic resin film (a) makes it possible to add various functions such as printability, coating suitability, scratch resistance, labeling suitability, and secondary processing suitability.

[Printing ink receiving layer (b)]
The label for in-mold (A) of the present invention needs to be provided with a printing ink receiving layer (b) containing a polymer binder and an antistatic polymer on the surface of the substrate in order to improve designability by printing. Become.
The label printing can be performed by using known methods such as offset printing, gravure printing, flexographic printing, letter press printing, ink jet recording method, thermal recording method, thermal transfer recording method, and electrophotographic recording method. Offset printing, letter press printing, and flexographic printing are preferred from the standpoint of appearance of the printing surface and the ability to handle small lots. Furthermore, oil-based inks and UV inks can be used as printing inks, but UV inks are preferred from the viewpoint of abrasion resistance.
From the above, the printing ink receiving layer is provided with a coating layer containing a polymer binder and an antistatic agent, so that it has antistatic properties and can improve UV ink adhesion.

[Polymer binder (4)]
The polymer binder is selected for the purpose of improving adhesiveness with an ink such as UV ink and having adhesiveness with a thermoplastic resin film as a base material.
Specific examples of the polymer binder include polyethyleneimine, polyalkyleneimine having 1 to 12 carbon atoms, polyimethyleneimine adducts of poly (ethyleneimine-urea) and polyaminepolyamide, and epichlorohydrin adduct of polyaminepolyamide. Acrylic ester heavy polymers such as polymers, acrylic amide-acrylic ester copolymers, acrylic amide-acrylic ester-methacrylic ester copolymers, polyacrylamide derivatives, oxazoline group-containing acrylic ester polymers, etc. Polymer, polyvinylpyrrolidone, polyethylene glycol, etc., plus polyvinyl acetate, polyurethane, ethylene-vinyl acetate copolymer, polyvinylidene chloride, chlorinated polypropylene, acrylonitrile-butadiene copolymer , An organic solvent can be used diluted resin or a water-diluted resin such as polyester. Among these, polyethyleneimine polymers, polyurethane resins, polyacrylate copolymers, and the like are preferable.

[Antistatic agent (5)]
It is preferable to add an antistatic agent to the ink receiving layer in order to impart antistatic properties in addition to UV ink suitability.
General antistatic agents described in detail in "Introduction to New Surfactants" (published by Sanyo Kasei Kogyo Co., Ltd.) and "Introduction to Polymeric Drugs (published by Sanyo Kasei Kogyo Co., Ltd.)" The agent can be used. In terms of molecular weight, either a low molecular weight type or a high molecular weight polymer type can be used, but from the viewpoint of safety, a low molecular weight type and a high molecular weight polymer type are preferable from the viewpoint of stability of antistatic performance, and depending on the purpose of use. Selection of an antistatic agent is necessary.

When the low molecular weight type is classified by ionicity, a cation type, an anion type, an amphoteric type, a nonionic type and the like can be used. As the cationic type, a quaternary ammonium salt type cationic surfactant is used. As the anionic type, aliphatic sulfonate, higher alcohol ethylene oxide addition sulfate ester salt, higher alcohol phosphate ester salt, higher alcohol ethylene oxide adduct phosphorus is used. Examples of the acid ester salts include betaine-type amphoteric surfactants as amphoteric types and higher alcohol ethylene oxide adducts, polyethylene glycol fatty acid esters, polyhydric alcohol fatty acid esters and the like as nonionic types.
Further, when the polymer type is classified by ionicity, a cation type, an anion type, an amphoteric type, a nonionic type and the like can be used. Examples of the cationic type include those having an ammonium salt structure or a phosphonium salt structure. Anionic types include alkali metal salts such as sulfonic acid, phosphoric acid and carboxylic acid, for example, alkali metal salts such as acrylic acid, methacrylic acid and (anhydrous) maleic acid (for example, lithium salt, sodium salt, potassium salt, etc. ) Having a structure in the molecular structure.

The amphoteric type contains both the cation type and the anion type structures in the same molecule, and examples thereof include a betaine type. Examples of the nonionic type include an ethylene oxide polymer having an alkylene oxide structure and a polymer having an ethylene oxide polymerization component in a molecular chain. In addition, a polymer having boron in the molecular structure can be given as an example.
Among these, nitrogen-containing polymers are preferable, and tertiary nitrogen or quaternary nitrogen-containing acrylic polymers are more preferable. By adding an antistatic polymer to the above-mentioned polymer binder, troubles due to dust adhesion and charging during printing can be reduced. The addition amount of the antistatic polymer is usually in the range of 1 to 200 parts by weight with respect to 100 parts by weight of the polymer binder.

(Additive)
Furthermore, coating film strength and water resistance can be further improved by adding a crosslinking agent as an additive to the polymer binder. Examples of the crosslinking agent include epoxy compounds such as glycidyl ether and glycidyl ester, water-dispersed resins such as epoxy resins, isocyanate, oxazoline, formalin, hydrazide, and carbodiimide. The addition amount of the crosslinking agent is usually in the range of 1 to 200 parts by weight with respect to 100 parts by weight of the polymer binder.
A pigment component can be added to improve the fixing property of the UV ink component and prevent blocking between the ink receiving layer and the heat seal layer. As the pigment component, one type or two or more types selected from the inorganic fillers or organic fillers described in the section of the base material can be used. Furthermore, a surfactant, an antifoaming agent, a wetting agent, a water-soluble metal salt and other auxiliary agents can be included.
(Surface resistivity)
The printing ink receiving layer preferably has a surface resistivity of 1 × 10 ¹³ Ω or less from the viewpoint of preventing troubles in paper feeding and discharging due to static electricity during offset printing and preventing dust adhesion. It should be noted that an excessive addition of an antistatic polymer to reduce the surface resistivity also leads to a decrease in adhesion to printing ink, and therefore it is necessary to select an optimum value in a timely manner.

(Formation of printing ink receiving layer)
The printing ink receiving layer is laminated on the thermoplastic resin film (a) by various coating methods. Coating methods include roll coaters, blade coaters, bar coaters, air knife coaters, size press coaters, gravure coaters, reverse coaters, die coaters, lip coaters, spray coaters, etc. Excess water and organic solvent are removed through the process. For the reason of improving the adhesiveness with the thermoplastic resin film, it is possible to perform an easy adhesion surface treatment such as corona treatment or frame treatment before coating.
Moreover, it is also possible to coat during the manufacturing process of a thermoplastic resin film for the reason of productivity improvement. In particular, when the thermoplastic resin film is a stretched film, the productivity is improved and the adhesion between the ink receiving layer and the thermoplastic resin film is improved by performing the coating process before or after the transverse stretching.
Coating amount is 0.005~10g / m ² as solid content after drying is preferably more preferably ^{0.01~1g / m 2 0.01~0.6g / m 2} .

[Hot melt heat seal layer (c)]
The hot melt heat seal layer (c) in the present invention contains the polymer (1), tackifier (2), and wax (3) components, and has a softening point in the range of 60 to 100 ° C. It is characterized by this.
If even one of the essential three components is insufficient, in-mold suitability or printing suitability is lowered, which is not preferable. Moreover, when the softening point of the said hot-melt type heat seal layer is less than 60 degreeC, the blocking property with the printing ink receiving layer which is a surface deteriorates, and when a softening point exceeds 100 degreeC, a molded object (B ).

(Thermo-adhesive polymer (1))
The heat-adhesive polymer (1) contained in the heat seal layer of the present invention is used as an essential component for improving the flexibility of hot melt and imparting cohesive force. The heat seal layer without the addition of polymer has high rigidity, and becomes hard and brittle.
Specific examples of the heat-adhesive polymer include polyethylene (PE), ethylene-vinyl acetate copolymer, ethylene-methacrylic acid ester copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer, ethylene -Acrylate ester copolymer, styrene-butadiene-styrene block polymer (SBS), styrene-ethylene-butylene-styrene block polymer (SEBS), styrene-ethylene-propylene-styrene block polymer (SEPS), styrene-isoprene- Examples thereof include styrene block polymer (SIS), atactic polypropylene resin (APP), polyamide resin, polyester resin, and derivatives thereof. In addition, from the viewpoint of adhesiveness to the molded body (B), an ethylene-vinyl acetate copolymer, an ethylene-methacrylic acid ester copolymer, an ethylene-acrylic acid ester copolymer, and an ethylene-methacrylic acid copolymer are preferable. An ethylene-acrylic acid ester copolymer is preferred.

(Tackifier (2))
In the present invention, the tackifier (2) is used as an essential component for improving the adhesion between the heat seal layer and the molded body. If the tackifier (2) is not used for the heat seal layer, the adhesive strength with the molded product is greatly reduced.
Specific examples of tackifiers include rosin, rosin derivatives (hydrogenated rosin, disproportionated rosin, polymerized rosin, rosin ester (such as esterified rosin such as alcohol, glycerin and pentaerythritol)), terpene resin (α-pinene, β-pinene), terpene phenol resin, aromatic modified terpene resin, hydrogenated terpene resin, aliphatic petroleum resin, aromatic petroleum resin, copolymer petroleum resin, alicyclic petroleum resin, coumarone-indene resin, styrene Resin, phenol resin and the like.

(Wax (3))
In the present invention, the wax (3) is added as an essential component for the purpose of improving workability by lowering the melt viscosity of the hot melt, as well as preventing blocking and preventing slipping. Furthermore, when wax is not added at the time of coating the hot melt heat seal layer, the viscosity of the coating solution is high, the workability is deteriorated, and the appearance of the coating layer is also deteriorated.
Specific examples of the wax include carnauba wax, canderia wax, montan wax, polyethylene wax, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polypropylene wax, and wax obtained by oxidizing these.

(Additive)
In the present invention, the heat seal layer may contain additives such as a stabilizer, a light stabilizer, a dispersant, and a lubricant in order to prevent thermal degradation, thermal decomposition and improve weather resistance. Stabilizers such as sterically hindered phenols, phosphorus, and amines are 0.001 to 1% by weight, and light stabilizers are sterically hindered amines, benzotriazoles, and benzophenones that are 0.001 to 1% by weight. May be added. However, excessive addition of additives to the heat seal layer will cause the additive to bleed out from the heat seal layer, and the bleed out component will be transferred to the printing ink receiving layer on the opposite side, reducing the adhesion to the printing ink. Therefore, the selection of additives and the optimization of the addition amount must be performed with great care.
(Coating method)
Examples of the coating method of the hot melt type heat heel agent label of the present invention include a roll coater method using a direct roll or a gravure roll, an extrusion coater method, and a slit orifice coater method. However, the solvent may be removed after dissolving and coating in a solvent.

(Acid value)
The heat sealant used for the hot melt heat seal layer preferably has an acid value of 10 to 200. When the acid value is less than 10, the labeling property of the label and the molded product is lowered, and when it exceeds 200, the water resistance of the label is lowered.
(Dynamic friction coefficient)
The in-mold label used in the present invention preferably has a dynamic friction coefficient between labels of 0.2 to 0.6. If the dynamic friction coefficient is 0.2 or less, there is a risk of paper feeding problems due to excessive slipping of labels during offset printing. If the dynamic friction coefficient is 0.6 or more, paper feeding troubles due to poor label slipping occur. To do.

[Molding of In-Mold Label Molded Body (C)]
The in-mold label (A) according to the present invention can be used in combination with various molded articles (B). For example, it can be used for containers made of high density polyethylene, low density polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polynaphthalene terephthalate, polyamide, polystyrene, polyvinyl chloride, polycarbonate, etc., among which polyethylene terephthalate whose specific gravity is heavier than water, When it is used in combination with polybutylene terephthalate, polyethylene naphthalate, polystyrene, or polycarbonate, separation due to the specific gravity difference between the label and the container is easy and particularly suitable.

Known methods are used to form these containers. For example, injection molding in which molten resin is poured into a mold, direct blow molding in which the molten resin is extruded from a circular die into a tube shape and expanded in a molten state inside the mold, and preforms formed by injection molding (small containers Examples include injection blow molding in which the shape preform is appropriately adjusted to the temperature and then expanded into a container shape, and stretch blow molding in which the molded preform is expanded into a container shape with a stretching rod and air pressure at a temperature lower than the melting point of the resin. It is done.
The present invention can be applied to any of these molding methods, and particularly has an advantage that it can cope with stretch blow molding, which has a low molding temperature and it has been difficult to obtain sufficient adhesion with conventional in-mold labels.

[Separation of in-mold label (A)]
The in-mold label (A) and molded body (B) of the present invention can be separated by water by regulating the acid value of the hot-melt heat seal layer (c) within the above range of 10 to 200. Separation of this label is manifested by immersion in water or warm water. Such warm water is preferably 70 to 100 ° C., more preferably 75 to 100 ° C., and still more preferably 80 to 95 ° C., and may be normal warm water or alkaline water. When alkaline water is used, 1.5% alkaline water as described in the voluntary design guidelines of the PET bottle recycling promotion council is desirable.

Hereinafter, the present invention will be described more specifically with reference to Examples, Formulation Examples, Comparative Examples, and Test Examples of the present invention.
The materials, amounts used, ratios, operations, and the like shown below can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited in any way by specific examples such as the following examples.
The% described below is% by weight unless otherwise specified. Table 1 summarizes the thermoplastic resin compositions used in the production examples of the present invention.

(Formulation example 1)
Polymer binder (1): Modified ethyleneimine polymer Polyethyleneimine “Epomin P-1000 (degree of polymerization 1600)” in a four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen gas inlet (Japan) 100 parts of a 25% by weight aqueous solution of a catalyst (trade name), 10 parts of glycidol and 10 parts of propylene glycol monomethyl ether were added and stirred under a nitrogen stream, and a denaturation reaction was performed at a temperature of 80 ° C. for 16 hours. A glycidol-modified polyethyleneimine aqueous solution was obtained. After drying this, the epoxy group of glycidol was converted to polyethylene by infrared spectroscopy, ¹ H-nuclear magnetic resonance spectroscopy ( ¹ H-NMR), and ¹³ C-nuclear magnetic resonance spectroscopy ( ¹³ C-NMR). It was confirmed that the structure formed by adding to imine nitrogen and that 23% of polyethyleneimine nitrogen reacted with glycidol.

(Formulation example 2)
Antistatic agent (1): Acrylic acid ester type antistatic polymer 35 parts of dimethylaminoethyl methacrylate and ethyl methacrylate in a 4-neck flask equipped with a reflux condenser, thermometer, glass tube for nitrogen substitution, and stirrer 20 parts, 20 parts of cyclohexyl methacrylate, 25 parts of stearyl methacrylate, 150 parts of ethyl alcohol and 1 part of azobisisobutyronitrile were added, and a polymerization reaction was carried out at a temperature of 80 ° C. for 6 hours in a nitrogen stream.
Next, 70 parts of a 60% solution of 3-chloro-2-hydroxypropylammonium chloride was added, and the mixture was further reacted at a temperature of 80 ° C. for 15 hours. Then, ethyl alcohol was distilled off while adding water dropwise to obtain a final solid content. 30% of a quaternary ammonium salt type copolymer was obtained. This is an acrylic acid alkyl ester polymer containing a group represented by the following general formula in the molecular chain.

[Production of substrate layer (a)]
(Production Example 1)
The thermoplastic resin composition a was kneaded in an extruder set at 230 ° C., then supplied to an extrusion die set at 250 ° C. and extruded into a sheet shape, which was cooled by a cooling device to obtain an unstretched sheet. This unstretched sheet was heated to 140 ° C. and stretched 4 times in the longitudinal direction.
Separately, the plastic resin composition c was kneaded with an extruder set at 250 ° C., then extruded into a sheet and laminated on the back surface of the 4 × stretched film prepared above, and the plastic resin composition d was further set at 250 ° C. After kneading with an extruder, the film was extruded on a sheet and laminated on the surface of the 4 × stretched film prepared above to obtain a laminated film having a three-layer structure. Next, this three-layer laminated film is cooled to 60 ° C., heated to about 140 ° C. again using a tenter oven and stretched 10.0 times in the transverse direction, and then heat-treated in a heat setting zone adjusted to 160 ° C. Went. Thereafter, it is cooled to 60 ° C., slits at the ears, and has a three-layer [(d / a / c) = (30/40/30) μm: stretched layer structure (1 axis / 2 axis / 1 axis)] structure A white laminated film having a thickness of 100 μm and a density of 0.86 g / cm ³ was obtained.

(Production Example 2)
A thermoplastic resin composition a and a thermoplastic resin composition b are kneaded in an extruder set at 230 ° C., then supplied to a single coextrusion die set at 250 ° C., and laminated in the die Was extruded into a sheet shape and cooled by a cooling device to obtain a three-layer unstretched sheet. This unstretched sheet was heated to 150 ° C. and stretched 5 times in the longitudinal direction. Next, after cooling to a temperature of 60 ° C., it is heated again to a temperature of 150 ° C., stretched 8 times in the transverse direction with a tenter, annealed at a temperature of 160 ° C., and cooled to a temperature of 60 ° C. Corona discharge treatment, then slitting the ear, and the thickness of the three layers [(b / a / b) = (10/60/10) μm: stretched layer structure (2 axis / 2 axis / 2 axis)] structure A white laminated film having a thickness of 80 μm and a density of 0.76 g / cm ³ was obtained.

(Production Example 3)
The thermoplastic resin composition e was kneaded in an extruder set at 230 ° C., then supplied to an extrusion die set at 250 ° C. and extruded into a sheet shape, which was cooled by a cooling device to obtain an unstretched sheet. This unstretched sheet was subjected to corona discharge treatment, then the ears were slit, and the wall thickness was 100 μm.
The density was 0.89 g / cm ³ , and a transparent film was obtained.
(Production Example 4)
The thermoplastic resin composition e was kneaded in an extruder set at 230 ° C., then supplied to an extrusion die set at 250 ° C. and extruded into a sheet shape, which was cooled by a cooling device to obtain an unstretched sheet. This unstretched sheet was heated to 150 ° C. and stretched 5 times in the longitudinal direction. The longitudinally stretched film was cooled to 60 ° C., heated again to about 150 ° C. using a tenter oven and stretched 8.0 times in the transverse direction, and then heat-treated in a heat setting zone adjusted to 160 ° C. After cooling to 60 ° C., the ears were slit to obtain a transparent film having a thickness of 80 μm and a density of 0.91 g / cm ³ .

[Examples 1-7, Comparative Examples 1-5]
(1) Printing ink receptive layer coating A coating material containing the polymer binder and antistatic agent described in Table 3 and having the printing ink receptive layer coating composition shown in Table 5 was mixed so that the solid content concentration was 10%. An aqueous coating agent was prepared. The aqueous coating agent was applied to the front side of the thermoplastic resin films (a) of Production Examples 1 to 4 at a line speed of 20 m / min so that the dry coating amount was 0.5 g / m ² with a Mayer bar coater, It air-dried in the oven of length 10m set to 80 degreeC.

(2) Hot melt type heat seal layer coating The ingredients shown in Table 4 were formulated in the hot melt type heat seal layer of Table 5, and the wax and tackifier were heated and dissolved at 180 ° C. and then stirred with a stirrer. After slowly adding the polymer and mixing the heat sealant uniformly, the mixture is cooled to 150 ° C.
A 150 ° C. heat sealant is put into a roll coater paint pan, and applied to the back surface of the ink-receiving layer coating film with a roll coater so that the coating amount is 10 g / m ^2. ).

[Test example]
(Acid value)
1 g of a sample was dissolved by heating in 50 ml of xylene, added with 30 ml of ethanol, and titrated with an aqueous potassium hydroxide solution using a phenolphthalein solution as an indicator.
(Softening point)
A test piece is placed on a metal frame in the heating bath and the tip is flattened in the center, 1mm in diameter.
The temperature was raised at a rate of 50 ° C./hr with a 1 kg load applied to the top of the needle, and the temperature when the needle entered 1 mm was taken as the softening point.
(Dynamic friction coefficient)
A friction measuring machine (trade name: TR-2) manufactured by Toyo Seiki Seisakusho Co., Ltd. was used, and the friction between in-mold labels was measured using a load cell: 1 kgf, a moving speed: 150 mm / min, and a 200 g thread.

(Molding of in-mold label molded body)
The in-mold labels (A) of Examples 1 to 7 and Comparative Examples 1 to 4 are cut out to a height of 70 mm and a width of 90 mm, and the in-mold labels (A) as shown in FIG. 1 are as shown in FIG. A mold in which the surface of the printing ink receiving layer (b) opposite to the heat seal layer (c) is set to 25 ° C. of a stretch blow molding machine (manufactured by Yoki Sangyo Co., Ltd .: “trade name PET-2W type”) The inner wall (2-a) of 2) was attached and fixed by suction under reduced pressure from the vacuum suction hole (5).
Thereafter, polyethylene terephthalate (manufactured by Nippon Unipet Co., Ltd .: trade name “Unipet RT543”) previously molded into a preform (small container shape) (2) with an injection molding machine is heated to 95 ° C. with an infrared heater. Then, it was stretched and hollow-molded with a mold holding time of 10 seconds to obtain a cylindrical in-mold label molded body (C) having a height of 200 mm and a waist of 210 mm.

(Adhesion)
The in-mold label molded body was deformed by hand, and the followability of the label to the molded body was observed and evaluated according to the following evaluation criteria.
Very good (（) Does not peel off following the deformation of the molded product.
Good (O) The label peels off partially.
Slightly good (△) More than half of the area peels off.
Defective (x) Label peels off.

(Water resistant adhesion)
The in-mold label molded body was immersed in 40 ° C. warm water for 4 days, and the followability of the label to the molded body was observed and evaluated according to the following evaluation criteria.
Very good (（) Follows the deformation of the molded body and does not peel off.
Good (O) The label peels off partially.
Slightly good (△) More than half of the area peels off.
Defective (x) Label peels off.

(Delabeling property)
The in-mold label molded body is immersed in 80 ° C. warm water in which 1.5% by weight of sodium hydroxide (manufactured by Wako Pure Chemicals: reagent grade 1) is dissolved for 15 minutes, and the degree of peeling of the label is observed. It was evaluated with.
Very good (（) The label peels off within 10 minutes, and no heat seal layer remains on the molded product.
Good (O) The label peels off within 15 minutes, and no heat seal layer remains on the molded product.
Slightly good (△) Although peeled off, the heat seal layer remains on the molded product.
Defect (x) Does not peel completely.
The above results are summarized in Table 5.

  According to the present invention, after use as a container for soft drinks, sake, soy sauce, oil, detergent, etc., the label and the container can be easily separated, and the in-mold molded container excellent in recyclability can be easily produced.

It is a schematic sectional drawing of the label for in-mold (A). It is sectional drawing of the molding machine used for shaping | molding the in-mold label molded object of PET bottle. It is sectional drawing of the molding machine used for shaping | molding of the in-mold label molded object of PP bottle.

Explanation of symbols

1: In-mold label (A)
a: Thermoplastic resin film (a)
b: Printing ink receiving layer (b)
c: Heat seal layer (c)
2: Mold a: Mold inner wall 3: Preform 4: Suction hole 5: Stretching rod / air-injecting nozzle 6: Die 7: Parison 8: Air blowing nozzle

Claims (8)

  The in-mold label (A) composed of a plastic resin film (a) as a substrate, a printing ink receiving layer (b) on the front side, and a hot melt heat seal layer (c) on the back side is formed on the molded body (B). A bonded in-mold label molded body (C), wherein the hot-melt heat seal layer (b) contains a polymer (1), a tackifier (2), a wax (3), and a hot-melt heat An in-mold label molded article, wherein the softening point of the sealing layer is 60 to 100 ° C, and the dynamic friction coefficient of the in-mold label is 0.2 to 0.6.   The in-mold label molded article according to claim 1, wherein the acid value of the hot-melt heat seal layer (c) is 10 to 200. The printing ink receiving layer (b) contains a polymer binder (4) and an antistatic agent (5), and has a surface resistivity of 1 × 10 ¹³ Ω or less. The in-mold label molded article as described.   The in-mold label molded article according to any one of claims 1 to 3, wherein the thermoplastic resin film (a) has a thickness of 30 to 200 µm.   The in-mold label molded article according to any one of claims 1 to 4, wherein the thermoplastic resin film (a) is composed of polyolefin.   The molded body (B) is a molded body composed of a polymer selected from polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, polynaphthalene terephthalate, polyamide, polystyrene, and polycarbonate. Item 6. An in-mold label molded article according to any one of Items 1 to 5.   The molded body (B) is a molded body composed of a polymer selected from polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, and polycarbonate, according to any one of claims 1 to 5. In-mold label molded body.   The in-mold label molded body according to any one of claims 1 to 7, wherein the in-mold label molded body (C) is a molded body molded by stretch blow molding.

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