JP2023032553A - Laminate, heat sensitive label, in-mold label and resin container with label - Google Patents

Abstract

To provide a laminate comprising sufficient adhesive force to an adherend, capable of being easily peeled when peeled from the adherend, having a heat sensitive adhesion layer which does not damage transparency of the laminate itself when being applied for a transparent substrate and whose peeling trace is opaque, and allowing easy determination of peeling after being adhered, an in-mold label, a heat sensitive label, and a resin container with a label using the in-mold label.SOLUTION: There is provided a laminate comprising: a substrate layer; and a heat sensitive adhesion layer provided on one surface of the substrate layer. The heat sensitive adhesion layer comprises: an olefin resin whose melting point is 50-115°C; and a polyalkylene oxide. In the laminate, to a total content of the olefin resin and the polyalkylene oxide, a content of the polyalkylene oxide is 30-70 mass%.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a laminate, a thermal label, an in-mold label, and a labeled resin container.

In recent years, for the purpose of preventing forgery and reuse of labeled resin containers, a plurality of labels that are destroyed when peeled off have been proposed.
For example, in Patent Document 1, a release sheet includes an adhesive layer formed on the upper side of the release sheet, a second layer formed on the upper side of the adhesive layer, and a layer formed on the upper side of the second layer. A label for preventing re-sticking has been proposed in which a release agent layer and a first layer formed on the upper side of the release agent layer are laminated. This label has a low peel strength between the first layer and the release agent layer, so that when the label is peeled off after application, part of the second layer remains on the adherend.

Further, Patent Document 2 proposes an adhesive label in which a brittle resin layer formed of a mixture of an acrylic resin and an ethylene-vinyl acetate copolymer resin and an adhesive layer are sequentially laminated on a film substrate. In this label, since the brittle resin layer has releasability from the film substrate, when the adhesive label is peeled off after being attached, only the film substrate is peeled off, instead of the entire adhesive label. Part of the resin layer and adhesive layer remains.

Furthermore, Patent Document 3 proposes an adhesive label, which is an easily peelable laminated film obtained by laminating a peelable surface layer having a specific peel strength on a base layer and further providing an adhesive layer. When the laminate is stretched, the peelable surface layer becomes porous and brittle due to the action of the organic or inorganic filler, and cohesive failure occurs when the label is peeled off, leaving part of the peelable surface layer on the adherend. ing.

On the other hand, in-mold labels, in which a label is placed in a mold in advance and attached at the same time as molding, are widely used from the viewpoint of design, adhesion to adherends, production efficiency, and the like. In such an in-mold label, a label that is destroyed when peeled off has also been proposed. An easy-peelable label for in-mold molding has been proposed in which an adhesive layer that is stretched in a direction is laminated. This label has a strong adhesive strength due to the anchoring effect of the molded product resin entering the openings on the surface of the adhesive layer. In addition, when the laminate is stretched, the adhesive layer becomes porous and brittle due to the action of the organic or inorganic filler, and cohesive failure occurs when the label is peeled off, leaving part of the adhesive layer on the adherend.

JP-A-8-099377 JP-A-2002-278459 JP-A-2002-113817 JP 2012-215799 A

However, with the label described in Patent Document 1, it is difficult to control the peel strength between layers. If the layer is completely peeled off without leaving any residue, and conversely, if it is too weak, the first layer tends to peel off during processing such as printing or punching, resulting in a problem of difficulty in handling.
In addition, the labels described in Patent Documents 1 to 3 need to be provided with an adhesive layer in addition to the layer destroyed by peeling.
The labels described in Patent Documents 3 and 4 cannot be applied to transparent labels because the peelable surface layer and the adhesive layer are white. There is a problem that the appearance is different from that of the others.

For this reason, it has a heat-sensitive adhesive layer that has sufficient adhesive strength to the adherend, can be easily peeled when peeling the label, and does not impair the transparency of the label itself even when applied to a transparent substrate, There is a demand for a heat-sensitive label that can easily determine that the label has been peeled off after being attached.

An object of the present invention is to provide a laminate, a heat-sensitive label, an in-mold label, and a labeled resin container using the in-mold label that solve the above problems.

As a result of intensive studies by the present inventors to solve the above problems, the heat-sensitive adhesive layer that adheres to the adherend is composed of an olefin resin having a specific melting point and a polyalkylene that is incompatible with the olefin resin. The present inventors have found that the above problems can be solved by containing an oxide in a specific blending ratio, and completed the present invention.
That is, the present invention is as follows.

(1) A laminate having a substrate layer and a heat-sensitive adhesive layer provided on one surface of the substrate layer,
The heat-sensitive adhesive layer contains an olefin resin having a melting point of 50 to 115° C. and a polyalkylene oxide,
A laminate in which the content of the polyalkylene oxide is 30 to 70% by mass with respect to the total content of the olefin resin and the polyalkylene oxide.

(2) The laminate according to (1), wherein the olefinic resin contains an olefinic resin having a polar group.

(3) The laminate according to (2), wherein the olefin-based resin having a polar group is a resin having a (meth)acrylic acid ester structure.

(4) The laminate according to any one of (1) to (3), wherein the polyalkylene oxide is polyethylene oxide.

(5) The laminate according to any one of (1) to (4), wherein the polyalkylene oxide has a number average molecular weight of 30,000 to 150,000.

(6) The laminate according to any one of (1) to (5), wherein the heat-sensitive adhesive layer further contains a tackifier.

(7) The laminate according to any one of (1) to (6), wherein the heat-sensitive adhesive layer is a non-stretchable layer.

(8) The base layer has a haze value of 30% or less.
The laminate according to any one of (1) to (7).

(9) A thermal label comprising the laminate according to any one of (1) to (8).

(10) An in-mold label comprising the thermal label according to (9).

(11) A labeled resin container, wherein the in-mold label according to (10) is adhered to the outer surface of the resin container via the heat-sensitive adhesive layer.

According to the present invention, the laminate has sufficient adhesion to the adherend, can be easily peeled off from the adherend, and does not impair the transparency of the laminate itself when applied to a transparent base material. Provided is a laminated body having a heat-sensitive adhesive layer that leaves an opaque peeling trace, and enabling easy determination of peeling after sticking, a heat-sensitive label, an in-mold label, and a labeled resin container using the in-mold label. can do.

1 is a cross-sectional view schematically showing the layer structure of a laminate as an embodiment of the present invention; FIG.

Although the laminate of the present invention will be described in detail below, the following description is an example (representative example) of the present invention, and the present invention is not limited thereto.

In the following description, the description of "(meth)acrylic" indicates both acrylic and methacrylic.

(Laminate)
FIG. 1 is a cross-sectional view schematically showing the layer structure of a laminate as one embodiment of the present invention. A laminate 10 of the present invention has a substrate layer 1 and a heat-sensitive adhesive layer 2 provided on one surface of the substrate layer 1 . A printed layer 5 may be provided on the other side of the base material layer 1 by printing.

In the present invention, the heat-sensitive adhesive layer contains an olefin resin having a melting point of 50 to 115° C. and polyalkylene oxide. The heat-sensitive adhesive layer contains an olefin resin having a melting point of 50 to 115° C. and a polyalkylene oxide that is incompatible with the olefin resin in a specific blending ratio, thereby reducing the blending ratio of these resins. A phase-separated structure (sea-island structure) forming a dispersed island-like structure is formed at a higher compounding ratio, while a sea-like structure is formed at a lower compounding ratio. By adopting such a phase separation structure, for example, when the laminate adhered to the adherend is peeled off, the heat-sensitive adhesive layer undergoes cohesive failure and changes from transparent to cloudy color, and Part of the cloudy heat-sensitive adhesive layer remains stuck.

Since the residue looks cloudy compared to the appearance of the adherend and the laminate, it is possible to easily determine with the naked eye that the laminate has been peeled off. Furthermore, since the heat-sensitive adhesive layer of the present invention has high transparency, a transparent laminate can be obtained by providing it on a transparent substrate layer. In this case, the laminate attached to the adherend is transparent, but the traces of peeling of the laminate remaining on the surface of the adherend become opaque, such as a cloudy color, making it easy to determine that the laminate has been peeled off. A laminate can be provided.

In the present invention, when the haze value of the heat-sensitive adhesive layer is 30% or less, it is "transparent", and when it exceeds 30%, it is "opaque". The haze value can be measured, for example, by the same method as in the examples for a film formed by press molding using the material of the heat-sensitive adhesive layer.
Each layer will be described below.

<Heat-sensitive adhesive layer>
The heat-sensitive adhesive layer has relatively lower breaking strength than the substrate layer, and is a layer that undergoes cohesive failure when the laminate adhered to the adherend is peeled off.
The heat-sensitive adhesive layer contains an olefin resin having a melting point of 50 to 115° C. and a polyalkylene oxide. As described above, the olefin resin having a melting point of 50 to 115° C. and the polyalkylene oxide are incompatible. In this specification, the term "incompatible" means that when a mixture of an olefin resin having a melting point of 50 to 115° C. and a polyalkylene oxide is observed with an electron microscope, it has a sea-island structure and an island phase. has an average diameter of 0.3 to 10 μm. The average diameter of island phases in the heat-sensitive adhesive layer can be obtained according to the method described in JP-A-2021-91860.

The content of polyalkylene oxide with respect to the total content of olefin resin and polyalkylene oxide is 30% by mass or more, preferably 35% by mass or more, and more preferably 40% by mass or more. On the other hand, the content is 70% by mass or less, preferably 65% by mass or less, and more preferably 60% by mass or less. If the content of the polyalkylene oxide is within the above range, it is easy to obtain a laminate having both sufficient adhesive strength and easy peelability.

<<Olefin resin>>
The olefin-based resin is melted by heat during, for example, in-mold molding when the laminate is adhered to the resin molded article, thereby increasing the adhesive strength of the laminate.

The melting point of the olefin resin is 50° C. or higher, preferably 60° C. or higher, more preferably 70° C. or higher, still more preferably 75° C. or higher, and particularly 80° C. or higher. preferable. This makes it difficult for blocking between the laminates to occur. Also, it preferably has a lower melting point than the thermoplastic resin used for the base material layer, which will be described later. On the other hand, the melting point of the olefin resin is 115° C. or lower, preferably 110° C. or lower, more preferably 105° C. or lower, even more preferably 100° C. or lower, and 95° C. or lower. is particularly preferred. As a result, the olefinic resin is easily melted during, for example, in-mold molding, and the adhesive strength is easily increased. When two or more olefinic resins are used in combination, it is sufficient that at least one of them has a melting point within the above range, and all of them preferably have a melting point within the above range.
The melting point can be measured by a differential scanning calorimeter (DSC).

Olefin-based resins suitable for use in the heat-sensitive adhesive layer include, for example, homopolymers and copolymers of olefins, and copolymers formed from olefins and other comonomers. Specific examples of olefins include ethylene and propylene. Among these, ethylene is preferable because it is easy to obtain an appropriate degree of crystallinity and easy to adjust adhesiveness. That is, ethylene-based resins, which are homopolymers or copolymers of ethylene, are preferable as olefin-based resins.

From the viewpoint of enhancing adhesiveness at low temperatures, the proportion of structural units derived from ethylene in the ethylene-based resin is preferably 80 mol% or more, more preferably 95 mol% or more, and even more preferably 97 mol% or more. In addition, the upper limit of the same ratio is less than 100 mol%. On the other hand, from the viewpoint of suppressing blocking, the ratio of structural units derived from monomers copolymerizable with ethylene in the polyethylene resin is preferably 5 mol % or less, more preferably 3 mol % or less. In addition, the lower limit of the same ratio exceeds 0 mol %.

When the olefin-based resin is an ethylene-based resin, for example, low or medium density polyethylene with a density of 0.900 to 0.940 g/cm ³ , linear low density with a density of 0.880 to 0.940 g/cm ³ polyethylene, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid alkyl ester copolymer (the alkyl group preferably has 1 to 8 carbon atoms), and ethylene- Ethylene-based resins having a melting point of 60 to 130° C., such as metal salts of (meth)acrylic acid copolymers such as Zn, Al, Li, K and Na, are preferred. The polyethylene has a crystallinity of 10 to 60% and a melt flow rate (190° C., 2.16 kg load) of 3 to 40 g/10 minutes as measured by an X-ray method, and has a low density, medium density, or straight chain Low density polyethylene is preferred.

From the viewpoint of enhancing adhesion and reducing blocking when stacking laminates, the olefin resin preferably has a polar group. That is, it is preferable to use a copolymer containing a structural unit having a polar group (hereinafter sometimes referred to as a polar structural unit).
Polar structural units include, for example, vinyl acetate structural units, (meth)acrylic acid structural units, (meth)acrylic acid ester structural units, maleic anhydride structural units, urethane structural units, and amide structural units. Among these, a vinyl acetate structural unit, a (meth)acrylic acid structural unit, a (meth)acrylic acid ester structural unit, or a maleic anhydride structural unit is preferable, and a (meth)acrylic acid ester structural unit is more preferable. That is, the olefin-based resin having a polar group is preferably a resin having a (meth)acrylic acid ester structure, more preferably an ethylene-(meth)acrylic acid ester copolymer, and particularly an ethylene-methacrylic acid ester copolymer. preferable.
For example, when the polar structural unit is copolymerized with ethylene, the melting point is lower than that of the ethylene homopolymer, making it easy to adjust the melting point within the range of the molding temperature for in-mold molding, for example, the stretching blow method.

In the heat-sensitive adhesive layer, one kind of thermoplastic resin may be used alone, or two or more kinds of thermoplastic resins may be mixed and used. It is preferable that the two or more resins to be mixed have high compatibility.

<<polyalkylene oxide>>
A polyalkylene oxide forms a phase-separated structure with the above olefinic resin. As a result, when the laminate adhered to the adherend is peeled off, peeling progresses due to cohesive failure of the heat-sensitive adhesive layer, and the heat-sensitive adhesive layer remaining on the adherend after peeling becomes cloudy.
Examples of polyalkylene oxides include polyethylene oxide, polypropylene oxide, polytetramethylene oxide, polyhexamethylene oxide, polyneopentylene oxide, and copolymers thereof. These may be used alone or in combination of two or more. Among these, polyethylene oxide is particularly preferable from the viewpoint of easy formation of a phase-separated structure.

Although the molecular weight of the polyalkylene oxide is not particularly limited, it preferably has a somewhat high melt viscosity from the viewpoint of moldability. On the other hand, even if the melt viscosity is too high, the moldability deteriorates, so the number average molecular weight is preferably 150,000 or less, more preferably 120,000 or less. By setting the number average molecular weight within the above range, the extrudability of the heat-sensitive adhesive layer is improved.

<<Tackifier>>
The heat-sensitive adhesive layer can contain a tackifier. By containing a tackifier, it is easy to obtain not only high adhesive strength with molded articles such as polyethylene or polypropylene, but also high adhesive strength with polyester molded articles, especially polar resin molded articles represented by polyethylene terephthalate resin. Become.

Examples of tackifiers include hydrogenated petroleum resins, aromatic hydrocarbon resins, and aliphatic hydrocarbon resins. Hydrogenated petroleum resins include, for example, partially hydrogenated petroleum resins. Examples of aromatic hydrocarbon resins include terpene-based resins, rosin-based resins, and styrene-based resins. A terpene-based tackifier is preferable from the viewpoint of improving the adhesive strength, particularly the adhesive strength to a polyester molded article.

The softening point of the tackifier is preferably 85°C or higher, more preferably 90°C or higher, and even more preferably 95°C or higher. The softening point is preferably 110°C or lower, more preferably 105°C or lower. When the softening point is at least the above lower limit, the tackiness of the remelted resin during the high-temperature alkali treatment is suppressed, and the associated decrease in recyclability is easily suppressed. Further, when the melting point is equal to or less than the above upper limit, sufficient adhesive strength to the molded article can be easily obtained with a small amount of heat.

The content of the tackifier in the heat-sensitive adhesive layer is usually about 0.3-5 mass %, preferably about 0.5-3 mass %.

<<<Antistatic agent>>>
The thermosensitive adhesive layer may contain an antistatic agent from the viewpoint of reducing adhesion of dust due to charging and transportation failure during printing.
From the viewpoint of reducing surface contamination due to bleeding out, the antistatic agent is preferably a polymer type antistatic agent. The polymer type antistatic agent is not particularly limited, and cationic, anionic, amphoteric or nonionic antistatic agents can be used. These can be used individually by 1 type or in combination of 2 or more types.

From the viewpoint of antistatic properties, the content of the antistatic agent in the heat-sensitive adhesive layer is preferably 0.01% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more. From the viewpoint of water resistance, the content of the antistatic agent in the heat-sensitive adhesive layer is preferably 85% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less.

<<Additives>>
The heat-sensitive adhesive layer can contain known additives as long as they do not significantly impair the heat-sensitive adhesive properties. Examples of additives include waxes and antiblocking agents.
Examples of waxes include paraffin wax, microcrystalline wax, carnauba wax and Fisher tops wax. The weight average molecular weight Mw of waxes is, for example, 5000 or less. Examples of antiblocking agents include inorganic powders such as silica, talc and zeolite.
The content of these additives in the heat-sensitive adhesive layer is usually 0.01 to 5% by weight independently for each type of additive.

In addition, it is preferable that the heat-sensitive adhesive layer does not substantially contain a filler. By substantially not containing a filler, it is possible to suppress the formation of voids inside and to increase the transparency of the heat-sensitive adhesive layer. In this specification, "substantially free of filler" means that the heat-sensitive adhesive layer does not contain any intentional filler. More specifically, the content of filler in the heat-sensitive adhesive layer is 0 to 3 mass. %, preferably 0 to 1 mass %, more preferably 0 to 0.5 mass %.

<<Layer thickness>>
The thickness of the heat-sensitive adhesive layer is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. The thickness is preferably 35 μm or less, more preferably 25 μm or less, even more preferably 15 μm or less. When the thickness is at least the above lower limit, the adhesive strength is likely to be improved. If the thickness is equal to or less than the above upper limit, workability during punching is good.
The thickness of the heat-sensitive adhesive layer can be measured by cross-sectional observation with a scanning electron microscope, as described in Examples below.

<Base material layer>
The base material layer has relatively higher breaking strength than the heat-sensitive adhesive layer, and does not break itself when the base material layer is held and peeled off.
The substrate layer may have a single-layer structure, or may have a multi-layer structure of two or more layers.

<<Thermoplastic Resin>>
The base layer contains a thermoplastic resin.
Examples of thermoplastic resins include olefin resins, ester resins, amide resins, polyvinyl chloride resins, polystyrene resins, and polycarbonate resins. From the viewpoint of mechanical strength, the base material layer preferably contains an olefin resin or an ester resin as a thermoplastic resin, and more preferably contains an olefin resin.

Examples of olefin-based resins include propylene-based resins and ethylene-based resins. Propylene-based resins are preferred from the viewpoint of moldability and mechanical strength.

The propylene-based resin is not particularly limited as long as propylene is used as the main monomer. Examples include isotactic and syndiotactic polymers obtained by homopolymerizing propylene. It is also a copolymer of propylene, which is the main component, and α-olefins such as ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. , propylene-α-olefin copolymers and the like can also be used. The copolymer may be a binary system or a multi-component system having three or more monomer components, and may be a random copolymer or a block copolymer. Also, a propylene homopolymer and a propylene copolymer may be used in combination. Among these, a propylene homopolymer is preferable as a main raw material for the base material layer because it is easy to handle.

Examples of ethylene-based resins include high density polyethylene with a density of 0.940 to 0.965 g/cm ³ , medium density polyethylene with a density of 0.920 to 0.934 g/cm ³ , and density of 0.900 to 0.920 g. / cm ³ linear low-density polyethylene, ethylene, etc. as the main component, propylene, butene, hexene, heptene, octene, 4-methylpentene-1, etc. α-olefin copolymer, ethylene-acrylic acid copolymers, ethylene-alkyl acrylate copolymers, ethylene-alkyl methacrylate copolymers, metal salts of ethylene-methacrylic acid copolymers (metals are zinc, aluminum, lithium, sodium, potassium, etc.), Examples include ethylene-cyclic olefin copolymers.

Examples of ester resins include polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate.
Examples of amide-based resins include nylon-6, nylon-6,6, nylon-6,10, and nylon-6,12.

The content of the thermoplastic resin in the substrate layer is preferably 50% by mass or more, more preferably 70% by mass or more. If the content is 50% by mass or more, the mechanical strength of the base material layer is likely to be improved. On the other hand, there is no particular upper limit for the content of the thermoplastic resin, and it may be 100% by mass, or less than 100% by mass with the addition of fillers, additives, etc. described later within a range that does not affect the strength or moldability. can be

<<Filler>>
The base material layer may or may not contain a filler. If the base material layer contains a filler, voids are likely to be formed inside, the whiteness or opacity of the base material layer can be increased, and the hiding property of the laminate can be increased. On the other hand, transparency can be enhanced if the substrate layer does not contain a filler. When a filler is contained, examples of the filler that can be used in the base material layer include inorganic fillers and organic fillers.

Examples of inorganic fillers include heavy calcium carbonate, light calcium carbonate, calcined clay, silica, diatomaceous earth, clay, talc, titanium oxide such as rutile-type titanium dioxide, barium sulfate, aluminum sulfate, zinc oxide, magnesium oxide, mica, and celery. Inorganic particles such as site, bentonite, sepiolite, vermiculite, dolomite, wollastonite, and glass fibers. Among them, heavy calcium carbonate, clay or diatomaceous earth is preferable because it has good pore moldability and is inexpensive. For the purpose of improving dispersibility, etc., the surface of the inorganic filler may be surface-treated with a surface-treating agent such as fatty acid.

Examples of organic fillers include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyamide, polycarbonate, polystyrene, cyclic olefin homopolymer, ethylene-cyclic olefin copolymer, polyethylene sulfide, polyimide, poly Organic particles such as methacrylate, polyetheretherketone, polyphenylene sulfide, or melamine resin are included.
One of the above inorganic fillers or organic fillers can be used alone, or two or more thereof can be used in combination.

From the viewpoint of increasing the whiteness or opacity of the substrate layer, the content of the filler in the substrate layer is preferably 10% by mass or more, more preferably 15% by mass or more. In addition, from the viewpoint of improving the uniformity of molding of the base material layer, the content of the filler in the base material layer is preferably 70% by mass or less, more preferably 60% by mass or less, and 50% by mass or less. More preferred. On the other hand, the substrate layer is preferably transparent from the viewpoint of making the most of the transparency of the heat-sensitive adhesive layer. From the viewpoint of increasing the transparency of the substrate layer, the content of the filler in the substrate layer may be less than 10% by mass, or may be 0% by mass.

The average particle size of the inorganic filler or organic filler is preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.1 μm or more, from the viewpoint of ease of forming pores. From the viewpoint of imparting mechanical strength such as tear resistance, the average particle size of the inorganic filler or organic filler is preferably 15 μm or less, more preferably 5 μm or less, and even more preferably 2 μm or less.

The average particle diameter of the inorganic filler is the volume average particle diameter corresponding to 50% of the cumulative volume (cumulative 50% particle diameter) measured by a particle measuring device such as a laser diffraction particle size distribution measuring device (Microtrac, manufactured by Nikkiso Co., Ltd.). D50. Also, the average particle size of the organic filler is the average dispersed particle size when dispersed in the thermoplastic resin by melt-kneading and dispersion. The average dispersed particle size can be obtained by observing the cut surface of the thermoplastic resin film containing the organic filler with an electron microscope, measuring the maximum size of at least 10 particles, and calculating the average value.

<<Porosity>>
When the substrate layer has pores inside, the porosity, which indicates the ratio of pores in the layer, is preferably 10% or more, more preferably 20% or more, from the viewpoint of obtaining opacity. Preferably, it is more preferably 30% or more. From the viewpoint of maintaining mechanical strength, the porosity is preferably 70% or less, more preferably 55% or less, and even more preferably 40% or less. On the other hand, from the viewpoint of increasing the transparency of the substrate layer, the porosity may be less than 10% or may be 0%.
The porosity can be obtained from the ratio of the area occupied by pores in a certain region of the cross section of the sample observed with an electron microscope.

In general, the higher the filler content, the higher the porosity, and the higher the whiteness or opacity of the substrate layer. The filler content or porosity can be selected according to the transparency, whiteness, etc. required for the laminate.
The substrate layer of the laminate of the present invention may be transparent or opaque depending on its application, but the use of a transparent substrate layer effectively enhances the transparency of the heat-sensitive adhesive layer. It is preferable because it acts and a transparent and easily peelable laminate can be obtained. Here, the "transparent substrate layer" means a layer having a haze value of 30% or less.

Antioxidants such as sterically hindered phenols, phosphorus, amines, and sulfur; light stabilizers such as sterically hindered amines, benzotriazoles, and benzophenones; and dispersants. , or an antistatic agent. When the substrate layer contains these components, the content of each component is preferably 0.001 to 1% by mass relative to the total mass of each component constituting the substrate layer.

From the viewpoint of layer strength, the thickness of the substrate layer is preferably 20 μm or more, more preferably 40 μm or more. From the viewpoint of weight reduction of the laminate, the thickness of the substrate layer is preferably 200 μm or less, more preferably 150 μm or less.

The surface of the substrate layer opposite to the heat-sensitive adhesive layer may be surface-treated from the viewpoint of enhancing adhesion to the printed layer. Further, a print-receiving layer or the like having high adhesion to the print layer may be provided on the surface of the substrate layer opposite to the heat-sensitive adhesive layer.

(Laminate manufacturing method)
The laminate can be produced, for example, by laminating a heat-sensitive adhesive layer on one surface of the substrate layer.

<Film molding>
Methods of forming the substrate include extrusion molding (cast molding) with a T-die, inflation molding with an O-die, and film molding methods such as calendering with a rolling roll.

Examples of methods for laminating the heat-sensitive adhesive layer on the substrate layer include a coextrusion method, an extrusion lamination method, and a coating method.
In the co-extrusion method, a resin composition for the substrate layer and a resin composition for the heat-sensitive adhesive layer are supplied to a multilayer die, laminated in the multilayer die, and extruded. According to the co-extrusion method, lamination is performed in parallel with film formation.
In the extrusion lamination method, a base material layer is formed first, a melted resin composition for a heat-sensitive adhesive layer is laminated thereon, and the laminate is nipped with rolls while being cooled. According to the extrusion lamination method, film formation and lamination are performed in separate steps.

<Stretching>
The substrate layer and the heat-sensitive adhesive layer may each be a non-stretching layer or a stretched layer, but the heat-sensitive adhesive layer is preferably a non-stretching layer.

Stretching methods include, for example, a longitudinal stretching method using a difference in circumferential speed between rolls, a transverse stretching method using a tenter oven, a sequential biaxial stretching method combining these methods, a rolling method, and a simultaneous two-stretching method using a combination of a tenter oven and a pantograph. An axial stretching method and a simultaneous biaxial stretching method using a combination of a tenter oven and a linear motor can be used. A simultaneous biaxial stretching (inflation molding) method can also be used, in which a circular die connected to a screw extruder is used to extrude a molten resin into a tubular shape, and then air is blown into the tubular shape.

The base material layer and the heat-sensitive adhesive layer may be stretched individually before laminating each layer, or may be stretched collectively after lamination. Further, the stretched layer may be stretched again after lamination.

When the thermoplastic resin used for each layer is an amorphous resin, the stretching temperature when stretching is preferably in the range of the glass transition point of the thermoplastic resin or higher. Also, when the thermoplastic resin is a crystalline resin, the stretching temperature should be above the glass transition point of the non-crystalline portion of the thermoplastic resin and below the melting point of the crystalline portion of the thermoplastic resin. is preferred, and specifically, a temperature lower than the melting point of the thermoplastic resin by 2 to 60°C is preferred.

The stretching speed is not particularly limited, but from the viewpoint of stable stretching molding, it is preferably in the range of 20 to 350 m/min.
In addition, the draw ratio can also be appropriately determined in consideration of the properties of the thermoplastic resin to be used. For example, when a thermoplastic resin film containing a propylene homopolymer or a copolymer thereof is stretched in one direction, the draw ratio is usually about 1.2 times or more, preferably about 2 times or more. , is usually 12 times or less, preferably 10 times or less. In the case of biaxial stretching, the draw ratio in area draw ratio is usually 1.5 times or more, preferably 10 times or more, while it is usually 60 times or less, preferably 50 times or less. .
If the draw ratio is within the above range, the desired porosity can be obtained and the opacity tends to be improved. In addition, the film tends to be less likely to break and can be stretched stably.

<Surface treatment>
It is preferable that the substrate layer or the heat-sensitive adhesive layer is surface-treated to activate the surface in order to enhance the adhesion to the adjacent layer.
Surface treatments include corona discharge treatment, flame treatment, plasma treatment, glow discharge treatment, ozone treatment, and the like, and these treatments can be combined. Among them, corona discharge treatment or flame treatment is preferable, and corona discharge treatment is more preferable.

<Formation of printed layer>
A printed layer can be provided by printing on the surface of the laminate opposite to the heat-sensitive adhesive layer. Examples of printed information include, for example, when used as a label, product name, product display such as logo, manufacturer, sales company name, method of use, bar code, etc. When used as a decorative material, which will be described later, there are various printed information. color patterns, images, and the like.
Examples of printing methods include gravure printing, offset printing, flexographic printing, seal printing, and screen printing.

<Label processing>
The laminate of the present invention can be used for decorating molded products (adherends) by vacuum forming, air pressure forming, vacuum pressure forming (TOM molding), or insert molding, utilizing heat-sensitive adhesive properties, sealants, It can be used for packaging materials, labels and the like. Among them, it is preferable to use it as a heat-sensitive label from the viewpoint of taking advantage of the characteristics of the present invention.
The heat-sensitive label of the present invention can be processed into a required shape and size by cutting or punching the laminate having the substrate layer and the heat-sensitive adhesive layer obtained by the above steps. Although cutting or punching can be performed before printing, it is preferable to perform cutting or punching after printing in terms of ease of work.

(thermal label)
The thermal label of the present invention comprises the laminate of the present invention described above. The heat-sensitive label of the present invention can be adhered to a resin-made adherend via the heat-sensitive adhesive layer that is heated and melted.

(in-mold label)
The in-mold label of the present invention comprises the heat-sensitive label of the present invention described above. An in-mold label is a label attached to a container at the same time as the container is molded.
The in-mold label of the present invention can also be printed on the heat-sensitive adhesive layer side surface. When the substrate layer is transparent, the printed information of the heat-sensitive adhesive layer is not present in the outermost layer of the resin container with a label, and thus the durability is excellent. Further, if the base layer is opaque, when the base layer is peeled off, information such as patterns and characters under the heat-sensitive adhesive layer can be recognized from the resin molded article or label. The printing applied to the heat-sensitive adhesive layer can be visually confirmed using ordinary process 4-color ink, special color ink, metallic ink, etc., or fluorescent ink that can be visually confirmed only when it emits light under a black light. may be used. The latter allows better anti-counterfeiting protection.

<In-mold molding>
In the in-mold label of the present invention, the method of in-mold molding, that is, the method of attaching the in-mold label is not limited.
The in-mold label of the present invention is suitable for direct blow molding in which a molten resin parison is pressed against the inner wall of a mold by compressed air, or for stretch blow molding using a preform. It can also be suitably used as an in-mold label for injection molding in which the is injected and solidified by cooling.
Furthermore, as a label for differential pressure molding, after installing the label so that the printed surface of the label is in contact with the inner surface of the lower female mold of the differential pressure molding mold, it is fixed to the inner wall of the mold by suction. It is also possible to guide the melt of the resin sheet above the lower female mold and to integrally fuse the label to the outer wall of the molded product by differential pressure. Either vacuum forming or air pressure forming can be used for the differential pressure forming, but in general, differential pressure forming using both of them and using a plug assist is preferred.
In the resin molded product to which the in-mold label of the present invention is attached and integrated, the label and the resin molded product are integrally molded after the label is fixed in the mold. The label has an appropriate adhesive strength, no blisters, and a molded product decorated with the label and having a good appearance can be obtained.

(Resin molded product)
The laminate, thermosensitive label and in-mold label of the present invention are applicable to moldings made of a wide variety of thermoplastic resins. Examples of applicable thermoplastic resins include polypropylene resins, polyethylene resins, polystyrene resins, polyethylene terephthalate resins, and the like. These may be used alone, or may be used in combination.
The color of the resin molded product may be transparent, or may be a natural color that does not contain a colorant such as a pigment or dye, or may be an opaque color due to a colorant or coloring.
When the resin molded product is a container, the cross-sectional shape of the body of the container may be a perfect circle, an ellipse, or a rectangle. If the cross-sectional shape of the fuselage is rectangular, it is preferred that the corners have curvature. From the viewpoint of strength, the cross section of the body is preferably a perfect circle or an ellipse close to a perfect circle, more preferably a perfect circle.

(labeled resin container)
The resin container with a label of the present invention is a resin container in which the in-mold label of the present invention is adhered to the outer surface of the above-described resin molded article via a heat-sensitive adhesive layer. The labeled resin container of the present invention can be used, for example, for household detergents, bathtub detergents, toilet bowl detergents, car wash detergents, facial cleansers, liquid soaps, shampoos, rinses, deodorants, liquid bath salts, iron pastes, Chemical containers (bottles) used for sterilizing alcohol, polishing wax, pesticides, etc.; food containers (bottles) used for soft drinks, sake, soy sauce, oil, sauces, sauces, dressings, etc.; jam, margarine, peanuts It can be used as a squeeze container for spreading butter, ketchup, mayonnaise, etc.; a container for ice cream, yogurt, etc.; a container for laundry detergent, dishwashing detergent, wet wipes, etc.

<Adhesion strength>
The adhesive strength between the resin container and the in-mold label is measured according to JIS K6854-2: 1999 "Adhesive-Peeling adhesive strength test method-Part 2: 180 degree peeling". Under conditions where blisters (bubbles) do not occur, the adhesive strength is preferably 150 gf/15 mm or more, more preferably 200 gf/15 mm or more, and even more preferably 250 gf/15 mm or more. On the other hand, the upper limit of the adhesive strength is preferably 600 gf/15 mm or less for ease of manual peeling.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples. Descriptions of "parts", "%", etc. in the examples are based on mass unless otherwise specified.

Table 1 shows a list of materials used to manufacture the thermal labels of Examples and Comparative Examples.

(Example 1)
As a material for the substrate layer, 100 parts by mass of propylene homopolymer (MA) (trade name: Novatec PP MA4, manufactured by Japan Polypropylene Corporation, melting point (JIS-K7121): 167° C.) was prepared. This was melt-kneaded using an extruder heated to 210° C. and supplied to a two-layer coextrusion die.

As materials for the heat-sensitive adhesive layer, ethylene-methyl methacrylate copolymer (trade name: Aclift WH401-F, manufactured by Sumitomo Chemical Co., melting point: 86° C.): 40% by mass, polyethylene oxide (trade name: Alcox L-11 , Meisei Chemical Industry Co., Ltd., melting point: 65° C.) 40 parts by mass, and terpene resin (YS) (trade name: YS Resin PX1000, Yasuhara Chemical Co., Ltd., softening point: 100° C.) 20 parts by mass. These materials were melt-kneaded using an extruder heated to 150° C. and supplied to the two-layer coextrusion die.

A melt-kneaded product of each material was laminated in a two-layer co-extrusion die and extruded through a T-die to obtain a laminate having a two-layer structure of base material layer/heat-sensitive adhesive layer. The substrate layer side of this laminate was placed along a metal roll temperature-controlled with cooling water at 40°C, and a Teflon (registered trademark) roll temperature-controlled with cooling water at 35°C was placed on the heat-sensitive adhesive layer side. A two-layer laminate was obtained as a thermal label of Example 1 by pressing and conveying under a pressure of 2 MPa and cooling.

In the heat-sensitive label of Example 1, the thickness of the base layer was 67 μm, and the thickness of the heat-sensitive adhesive layer was 13 μm.

(Examples 2 and 3, Comparative Examples 1 and 2)
Thermal labels of Examples 2 and 3 and Comparative Examples 1 and 2 were produced in the same manner as in Example 1, except that the composition of the thermal adhesive layer was changed as shown in Table 2.

Various physical properties of the heat-sensitive label were measured as follows.

<Thickness>
The thickness (total thickness) of the thermal label was measured in accordance with JIS K7130:1999 using a constant pressure thickness gauge (product name: PG-01J, manufactured by Teclock). Also, the thickness of each layer in the thermal label was determined as follows. The sample to be measured is cooled to a temperature of -60 ° C or less with liquid nitrogen, and a razor blade (trade name: Proline blade, manufactured by Sick Japan) is applied at right angles to the sample placed on the glass plate and cut. , a sample for cross-sectional observation was prepared. The cross section of the obtained sample was observed using a scanning electron microscope (product name: JSM-6490, manufactured by JEOL Ltd.), and the boundary line for each thermoplastic resin composition in each layer was determined from the appearance. It was obtained by multiplying the measured total thickness of the thermal label by the observed thickness ratio of each layer.

(evaluation)
Labeled containers were produced using the heat-sensitive labels of each example and comparative example in the following manner, and the adhesive strength and haze value of each heat-sensitive label were evaluated.

<Production of resin containers with labels>
Immediately after production, the thermal label was cut into sheets and punched into a rectangle with a long side of 8 cm and a short side of 6 cm to prepare a sample for evaluation.
The sample was charged using an electrostatic charging device, placed inside a molding die of a stretch blow molding machine (manufactured by Nissei ASB, machine name: ASB-70DPH), and clamped. Installation was performed so that the base material layer was in contact with the mold. The heat-sensitive label was placed in the mold such that the long side of the label was parallel to the circumferential direction of the body of the square prism-shaped resin container. The mold was controlled so that the surface temperature on the cavity side was within the range of 20 to 45°C.

On the other hand, a preform of polyethylene terephthalate resin was preheated to 100°C. This preform was introduced into a mold and stretch blow molded for 1 second under a blow pressure of 5 to 40 kg/cm ² . After cooling to 50° C. for 15 seconds, the mold was opened to obtain a PET container with a heat-sensitive label having a rectangular body portion with a height of 12 cm and a side of about 7 cm.

<Adhesion strength>
The obtained labeled PET container was stored for 2 days under an environment of a temperature of 23° C. and a relative humidity of 50%. Next, the labeled portion of the PET container with the label and the container body are cut together with a cutter, and the length is 12 cm with the circumferential direction of the container body as the longitudinal direction (8 cm for the label-attached portion, non-labeled). Samples of 4 cm pasted area) and 1.5 cm wide (full width label pasted) were taken.

The label-attached portion of the obtained sample was carefully peeled off from the label-unattached portion, and about 1 cm was peeled off to form a grasping margin. Next, a gripping margin and a PET film (thickness: 50 μm) with a width of 1.5 cm were overlapped and adhered with an adhesive to form a gripping margin portion on the label side, and a sample for adhesion strength measurement was produced.

Based on JIS K6854-2: 1999, using a tensile tester (manufactured by Shimadzu Corporation, model name: Autograph AGS-5kNJ), a 180 degree peel test between the container body and the label at a peel rate of 300 mm / min. carried out. The average value of the peel force over a peel length of 25 to 75 mm was measured, and the value obtained by averaging the measured values of 6 samples was taken as the adhesive strength. The unit of adhesive strength was gf/15 mm. An adhesive strength of 150 gf/15 mm or more can be evaluated as a practical level.

<Haze value>
The labeled portion of the PET container with the label and the container body were integrally cut with a cutter to obtain a sample of 3 cm×3 cm. The label of the obtained sample was manually peeled off at a peeling speed of 300 mm/min, and the sample after peeling the label was measured in accordance with JIS-K-7136:2000 with a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name: NDH2000). was measured using For comparison, the same measurement was performed on the portion of the container not provided with the label, and the difference from the measured value of the sample after peeling off the label was calculated. The same measurement was performed for two samples, and the average value of the differences was taken as the haze value after peeling off the label. A haze value of 50% or more after peeling off the label is a practical level.

Table 2 below shows the composition and evaluation results of the heat-sensitive adhesive layer in each heat-sensitive label.
The haze value of the PET container was 2.3%, and the haze value of the labeled portion before peeling off the label was 10%. Each heat-sensitive label was transparent, and visual observation did not impair the transparency of the container.

As shown in Table 2, the thermal labels of Examples 1 to 3 are compatible with sufficient adhesive strength and easy peelability. In addition, the heat-sensitive labels of Examples 1 to 3 have a high haze value of peeling traces, and since the difference from the haze value of the PET container is large, the visibility of the peeling traces is high. On the other hand, the thermal label of Comparative Example 1 has both sufficient adhesive strength and easy peelability, but the haze value of the peeling marks is low, and the difference from the haze value of the PET container is small, so the visibility of the peeling marks is low. is low. In Comparative Example 2, the visibility of peeling traces was better than in Comparative Example 1, but the adhesive strength was remarkably low.

DESCRIPTION OF SYMBOLS 10... Laminate, 1... Base material layer, 2... Thermal adhesive layer

Claims (11)

A laminate having a substrate layer and a heat-sensitive adhesive layer provided on one surface of the substrate layer,
The heat-sensitive adhesive layer contains an olefin resin having a melting point of 50 to 115° C. and a polyalkylene oxide,
A laminate in which the content of the polyalkylene oxide is 30 to 70% by mass with respect to the total content of the olefin resin and the polyalkylene oxide. The laminate according to claim 1, wherein the olefinic resin contains an olefinic resin having a polar group. The laminate according to claim 2, wherein the olefin resin having a polar group is a resin having a (meth)acrylic acid ester structure. The laminate according to any one of claims 1 to 3, wherein the polyalkylene oxide is polyethylene oxide. The laminate according to any one of claims 1 to 4, wherein the polyalkylene oxide has a number average molecular weight of 30,000 to 150,000. The laminate according to any one of claims 1 to 5, wherein the heat-sensitive adhesive layer further contains a tackifier. The laminate according to any one of claims 1 to 6, wherein the heat-sensitive adhesive layer is a non-stretchable layer. The base layer has a haze value of 30% or less,
The laminate according to any one of claims 1-7. A thermosensitive label comprising the laminate according to any one of claims 1 to 8. An in-mold label comprising the thermal label according to claim 9. A resin container with a label, wherein the in-mold label according to claim 10 is adhered to the outer surface of the resin container via the heat-sensitive adhesive layer.

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