Adhesive composition

Abstract

An adhesive composition according to the present invention comprises at least one adhesive component and at least one organic compound having a melting point of 95°C or less. The organic compound is selected from the group consisting of liquid crystalline compounds, fatty acids, alkanes, alkenes, fats and oils, and any combination thereof (However, the adhesive composition may not contain an adhesive when the organic compound can play the role or function as an adhesive.).

Description

adhesive composition

[0001] The present invention relates to a heat-removable adhesive composition.

[0002] Hot melt adhesives are examples of adhesives that can be attached and detached by heating. Hot melt adhesives have the advantages of being fast curing and not requiring solvents, and are widely used in industrial applications such as for fastening electronic components (see, for example, Patent Documents 1 and 2).

[0003] However, hot melt adhesives have problems such as the need to be careful of burns because they are used at high temperatures of around 100°C, they are prone to deterioration with prolonged heating, and they require a dedicated applicator (coating machine). Therefore, they are not suitable for applications where easy attachment and detachment is required.

[0004] Furthermore, as a product that can be easily attached and detached at room temperature, there is a product sold under the trade name Post-it, which is widely used daily, including for office use (see, for example, Patent Document 3.) Although this product is easy to use, its adhesive strength is weak and therefore it is not suitable for use in fields where strong adhesive strength is required.

[0005] Furthermore, to obtain an adhesive with strong adhesive strength, for example, one that adheres at around room temperature but changes from an adhered state to a detachable state when exposed to heat or light, it is generally necessary to synthesize (develop) new molecules (polymers), which requires a lot of time and effort.

[0006] JP 2023-028531 A JP 2023-000196 A US-A1-005194299

[0007] An object of the present invention is to provide a removable adhesive composition that allows for arbitrary selection of the heating temperature at which the adhesive becomes removable, without the need for newly synthesizing molecules.

[0008] The inventors conducted research aimed at solving the above problems, and focused on phase transition materials. They discovered that by mixing a phase transition material with an existing adhesive in a specific ratio, it was possible to control the desorption temperature and provide an adhesive that could be desorbed with a small temperature change, thereby completing the present invention.

[0009] That is, the present invention has the following configurations. [1] An adhesive composition containing at least one adhesive component and at least one organic compound having a melting point of 95°C or less, wherein the organic compound is selected from the group consisting of liquid crystalline compounds, fatty acids, alkanes, alkenes, oils and fats, and any combination thereof (however, when the organic compound can fulfill the role or function of an adhesive, the adhesive composition does not need to contain an adhesive). [2] The adhesive composition according to [1], wherein the adhesive component is at least one selected from the group consisting of solvent-based adhesives, water-dispersed or latex-based adhesives, and adhesive components of reactive adhesives. [3] The adhesive composition according to [1] or [2], further containing an organic solvent. [4] The adhesive composition according to any one of [1] to [3], which, when applied to an adherend, becomes detachable by heating to a temperature close to the melting point of the organic compound. [5] The adhesive composition according to any one of [1] to [4], wherein the ratio (weight ratio) of the contents of the adhesive component to the organic compound having a melting point of 95°C or lower in the adhesive composition is 0:10 to 9:1. [6] The adhesive composition according to [5], wherein the ratio (weight ratio) of the contents of the adhesive component to the organic compound having a melting point of 95°C or lower in the adhesive composition is 2:8 to 5:5. [7] An article comprising two adherends that are the same or different, and the adhesive composition according to any one of [1] to [6], disposed between the two adherends.

[0010] The present invention makes it possible to provide an adhesive composition whose desorption temperature can be controlled and which can be desorbed with a small temperature change, thereby making it possible to provide an adhesive composition which can be desorbed with heat from a common household hair dryer or the like, without requiring a dedicated applicator or the like.

[0011] The methods of the desorption tests carried out in the examples are shown. Photographs of samples after the desorption tests of Comparative Example 1 and Examples 1 to 4 are shown. Photographs of samples after the desorption test of Example 4A are shown. Photographs of samples after the desorption tests of Comparative Example 2 and Example 5 are shown. Photographs of samples after the desorption tests of Comparative Example 3 and Example 6 are shown. Photographs of samples after the desorption test of Example 7 are shown. Photographs of samples after the desorption tests of Example 8, Example 9, and Comparative Example 4 are shown.

[0012] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be practiced with various modifications within the scope of the gist. In this specification, when the expression "to" is used, it is used as an expression including the numerical values ​​or physical property values ​​before and after it.

[0013] One embodiment of the present invention is an adhesive composition (hereinafter also referred to as "adhesive composition of the present invention") that contains at least one adhesive component and at least one organic compound having a melting point of 95°C or less, wherein the organic compound is selected from a liquid crystalline compound, a fatty acid, an alkane, an alkene, or any combination thereof (however, if the organic compound can fulfill the role or function of an adhesive, the adhesive composition does not need to contain an adhesive). The details of each component of the adhesive composition of the present invention are described below.

[0014] 1. Adhesive Component The adhesive composition of the present invention contains at least one adhesive component. The adhesive component in the present invention may be any component that enables an adhesive layer formed using the adhesive composition of the present invention to exhibit the desired adhesive properties.

[0015] The adhesive component that can be used in the adhesive composition of the present invention includes a solution-based (solvent-based) adhesive, a water-dispersed or latex-based adhesive, and a reactive adhesive.

[0016] Examples of adhesive components for solution-based adhesives that can be used in the adhesive composition of the present invention include adhesive components of thermoplastic resin adhesives such as vinyl acetate, vinyl chloride, styrene, acrylic, saturated polyester, and polyvinylpyrrolidone resin adhesives (i.e., vinyl acetate resin, vinyl chloride resin, styrene resin, acrylic resin, saturated polyester resin, polyvinylpyrrolidone resin, etc.); adhesive components of urethane resin solvent-based adhesives (i.e., isocyanate polyol); and synthetic rubber elastomers such as chloroprene rubber, nitrile rubber, butyl rubber, styrene-butadiene rubber (SBR), and chloroprene rubber. Additionally, adhesive components for solution-based adhesives such as proteins such as casein, soy protein, and synthetic protein; various starches such as starch and oxidized starch; and cellulose derivatives such as carboxymethyl cellulose, methyl cellulose, and nitrocellulose can also be used.

[0017] Examples of aqueous dispersion or latex adhesives include vinyl polymer latexes such as conjugated diene polymer latexes of methyl methacrylate-butadiene copolymers, acrylic polymer latexes, vinyl acetate resins, ethylene-vinyl acetate copolymers, and α-olefin (isobutene-maleic anhydride copolymer) resins; polyvinyl alcohols including modified polyvinyl alcohols such as polyvinyl alcohol, cationic polyvinyl alcohol, and silyl-modified polyvinyl alcohol; aqueous polyurethane resins; and aqueous polyester resins; and adhesive components of these adhesives can also be used.

[0018] Examples of reactive adhesives include ionizing radiation-curable adhesives such as thermosetting adhesives, anaerobic-curable adhesives, moisture-curable adhesives, and ultraviolet-curable adhesives. Examples of adhesive components of thermosetting adhesives include adhesive components of thermosetting resin adhesives such as epoxy-based, urethane-based, unsaturated polyester-based, acrylic-based, and silicone-based adhesives. Thermosetting adhesives can use compositions that undergo a chemical reaction and crosslink when heated. For example, a base agent and a curing agent that crosslinks the base agents can be used as adhesive components of a thermosetting adhesive. Examples of such combinations of base agent and curing agent include combinations of base agents such as polyester-based resins, polyether-based resins, polyurethane-based resins, epoxy resins, and polyol-based resins with curing agents such as isocyanate curing agents and polyamine curing agents. Examples of the polyol-based resins include polyols such as polyethylene glycol, acrylic polyols, polyester polyols, and polyether polyols, as described in JP 2015-193208 A. Examples of the isocyanate curing agent include aliphatic or alicyclic isocyanate compounds described in JP-A-2015-193208 and the like.

[0019] Anaerobic curing adhesives are adhesives that cure when exposed to oxygen and intrinsic metal ions, and examples of such adhesives include acrylic adhesives. Moisture curing adhesives are adhesives that cure due to moisture in the air, and examples of such adhesives include silicone, cyanoacrylate, and urethane adhesives.

[0020] Furthermore, as the adhesive component of the ionizing radiation-curable adhesive, for example, a compound having a radically polymerizable unsaturated group such as a vinyl group or a (meth)acrylate group, or a cationically polymerizable group such as an epoxy group, or a monomer or oligomer having an unsaturated double bond, as described in JP-A-11-170791, etc., can be used. When ultraviolet light or the like is used as the ionizing radiation, a photopolymerization initiator can also be used as the adhesive component. The ionizing radiation may be any radiation capable of crosslinking the above-mentioned monomer or oligomer, and examples thereof include ultraviolet light, electron beams, etc.

[0021] The adhesive component in the adhesive composition of the present invention can be any of a solution-based (solvent-based) adhesive, a water-dispersed or latex-based adhesive, and a reactive adhesive, but a solution-based adhesive, a water-dispersed or latex-based adhesive is preferred. As described below, the adhesive composition of the present invention can be applied to an adherend and detached by heating, and can also be re-adhered by heating again to a temperature above the melting point. However, a solution-based adhesive, a water-dispersed or latex-based adhesive that does not involve a chemical reaction (crosslinking) is preferred because it facilitates re-adhesion. Furthermore, a solution-based (solvent-based) adhesive is more preferred because the solvent easily evaporates when dried.

[0022] 2. At least one organic compound having a melting point of 95°C or less. It is important that the adhesive composition of the present invention contains at least one organic compound (hereinafter also referred to as the "organic compound used in the present invention") having a melting point of 95°C or less. While not intending to be bound by theory, when a conventional adhesive is applied to an adherend such as glass, the two are bonded due to interactions between the adherend and the adhesive (hydrogen bonding, van der Waals forces, etc.), whereas when the adhesive composition of the present invention is applied to an adherend and dried, the organic compound (also referred to herein as the "phase change material") dispersed in the adhesive components is believed to adhere to the adherend in a solid state. It is believed that when one or both sides of the adherend are heated to near their melting point, the phase change material becomes liquid, preventing it from maintaining its bonded state and allowing it to be detached. Furthermore, because phase change materials rapidly change from a solid to a liquid state near their melting point, they can be detached from their bonded state with a small temperature difference.

[0023] The organic compound used in the present invention has a melting point of 95°C or less, preferably from -80 to 95°C, and more preferably from -18 to 60°C.

[0024] The organic compound used in the present invention is selected from the group consisting of liquid crystalline compounds, fatty acids, alkanes, alkenes, oils and fats, and any combination thereof, each having a melting point of 95° C. or less. Among these, fatty acids, liquid crystalline compounds, and oils and fats are preferred because of their high safety and low toxicity.

[0025] The liquid crystal compound that can be used in the present invention is not particularly limited as long as it has a melting point of 95° C. or less, and examples thereof include 4-cyano-4′-heptylbiphenyl (7CB), 4-cyano-4′-octyloxybiphenyl (8OCB), 4-cyano-4′-pentylbiphenyl, 4-cyano-4′-hexylbiphenyl, 4-cyano-4′-n-octylbiphenyl, 4-(trans-4-amylcyclohexyl)benzonitrile, 4-(trans-4-ethylcyclohexyl)benzonitrile, (S)-4-cyano-4′-(2-methylbutyl)biphenyl, 3,4,5-trifluoro-4′-(trans-4-propylcyclohexyl)biphenyl, 4′-ethoxybenzylidene-4-butylaniline, TK-LQ 3858, TK-LQ 2040, cholesterol linoleate, cholesterol oleyl carbonate, phospholipids, etc. Examples of phospholipids include phosphatidic acids (e.g., dimyristoylphosphatidylcholine, dipalmitoylphosphatidylcholine, distearylphosphatidylcholine, etc.) having a melting point of 95°C or less, phosphatidylethanolamine, phosphatidylcholine, phosphatidylserine, phosphatidylglycerol, etc. The liquid crystal compound may also be a mixture of two or more of these.

[0026] The fatty acid that can be used in the present invention is not particularly limited as long as it has a melting point of 95°C or less, and examples thereof include octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, linoleic acid, palmitic acid, behenic acid, melissic acid, hexadec-9-enoic acid, (9Z)-octadec-9-enoic acid, (9E)-9-octadecenoic acid, (9E,11E,13Z)-9,11,13-octadecatrienoic acid, (13Z)-13-docosenoic acid, (Z)-tetracos-15-enoic acid, and mixtures of two or more thereof.

[0027] The alkanes and alkenes that can be used in the present invention are not particularly limited as long as they have a melting point of 95°C or less. Examples of such alkanes and alkenes include linear alkanes, alkenes, paraffinic hydrocarbons, and branched alkanes. C8 to C50 alkanes are preferred, and C12 to C26 alkanes are more preferred.

[0028] The fats and oils that can be used in the present invention are not particularly limited as long as they have a melting point of 95°C or less, and examples thereof include palm oil, palm kernel oil, coconut oil, slightly hydrogenated horse oil, lard, beef tallow, cacao butter, palm butter, almond butter, macadamia butter, hemp seed butter, jojo butter, coffee butter, shea butter, soybean butter, macadamia nut butter, acai butter, avocado butter, argan butter, olive butter, orange butter, chamomile butter, cranberry butter, pomegranate butter, tangerine butter, horsetail butter, pumpkin seed butter, pistachio butter, and Brazil nut butter. , blueberry butter, monoi butter, lime butter, lavender butter, lemon butter, coconut butter, kokum butter, mango butter, sal butter, aloe butter, murumuru butter, tucuma butter, cupuacu butter, hardened castor oil, hardened coconut oil, hardened palm oil, hardened beef tallow oil, hardened lard oil, hardened soybean oil, hardened rapeseed oil, hardened jojoba oil, hardened rice oil, ostrich oil, extremely hardened palm oil (hydrogenated palm oil), extremely hardened rapeseed oil, hyercin extremely hardened rapeseed oil, extremely hardened soybean oil (hydrogenated soybean oil), extremely hardened beef tallow oil (hydrogenated beef tallow), extremely hardened lard oil (hydrogenated lard), and mixtures of two or more thereof. Among the above-mentioned oils and fats, palm oil, palm kernel oil, coconut oil, lard, beef tallow, cacao butter, palm butter, almond butter, macadamia butter, hemp seed butter, cheek butter, coffee butter, shea butter, soybean butter, hardened palm oil, hardened palm oil, hardened beef tallow oil, hardened lard oil, hardened soybean oil, hardened rapeseed oil, and mixtures of two or more thereof (for example, a mixture of hardened palm oil, palm kernel oil, and palm oil) are easily available and can be suitably used.

[0029] The organic compound may be any combination of a liquid crystal compound, a fatty acid, an alkane, an alkene, and an oil or fat. In this case, it may be two or more liquid crystal compounds, two or more fatty acids, two or more alkanes, two or more alkenes, or two or more oil or fats, or may be a combination of two or more selected from liquid crystal compounds, fatty acids, alkanes, alkenes, and oils (for example, a combination of one liquid crystal compound and one fatty acid, a combination of one liquid crystal compound and one oil or fat, etc.).

[0030] The organic compound may be in an encapsulated or non-encapsulated form, but is preferably in an non-encapsulated form. As described above, in the present invention, since the phase-change material transitions from a solid to a liquid by heating, enabling desorption, an non-encapsulated form is preferred for effective desorption. When two or more organic compounds are contained, some of the organic compounds may be in an encapsulated form, but it is preferred that all of the phase-change materials be in an non-encapsulated form.

[0031] 3. Other Components The adhesive composition of the present invention contains an adhesive component and a phase change material, but may also contain other components as needed. Such other components may include a solvent for dispersing or dissolving the adhesive component and the phase change material, a dispersant for improving the dispersibility of the phase change material, a color pigment, etc.

[0032] (1) Solvent Any solvent can be used in the adhesive composition of the present invention as long as it allows the adhesive components and the organic compound to be mixed with each other. Examples include organic solvents such as acetone, cyclohexane, methylcyclohexane, ethanol, isopropyl alcohol, ethyl acetate, isopropyl acetate, methyl ethyl ketone, methyl isobutyl ketone, toluene, normal hexane, normal heptane, and petroleum naphtha. These organic solvents can be used alone or in combination of two or more. Furthermore, water can be used as the solvent, or a mixture of an organic solvent and water can be used.

[0033] (2) Dispersant Any dispersant capable of improving the dispersibility of the phase-change material may be used, such as Triton X-100, sodium dodecyl sulfate, or TWEEN 20. The content of the dispersant may be any dispersant capable of improving the dispersibility of the phase-change material, and may be, for example, in the range of 1 to 1,000 parts by weight per 10 parts by weight of the phase-change material.

[0034] (3) Others In addition to the above components, other components may include known additives that can be used in adhesives, such as antioxidants, light stabilizers, antistatic agents, colorants, etc. The content of such additives may be within a range that does not impair the removability, adhesiveness, etc. of the adhesive layer formed using the adhesive composition.

[0035] 4. Adhesive Composition (1) Composition and Production Method of Adhesive Composition The method for producing the adhesive composition of the present invention may be any method that allows the above-mentioned components to be mixed with good dispersibility, and any known kneading method can be used. Specifically, the adhesive composition of the present invention can be produced by mixing an organic compound having a melting point of 95°C or less with a conventional adhesive (a commonly used solvent-based adhesive, water-dispersed or latex-based adhesive, or reactive adhesive, preferably a solvent-based adhesive, water-dispersed or latex-based adhesive) in any desired ratio to produce the adhesive composition.

[0036] The content of the adhesive component in the adhesive used may be any content that allows for the formation of an adhesive layer with the desired adhesiveness, and may be, for example, 10% by weight or more in the adhesive, preferably in the range of 25% to 55% by weight. By keeping the content within this range, the adhesive composition of the present invention can form an adhesive layer with excellent adhesiveness.

[0037] The organic compound having a melting point of 95°C or less may be mixed with the adhesive as is, or may be dissolved in advance in a solvent (at least one organic solvent, water, or a mixed solvent of water and an organic solvent) and the resulting solution may be mixed with the adhesive. Here, the solvent used to dissolve the organic compound may be any of the solvents exemplified in the previous section regarding other components.

[0038] In the adhesive composition of the present invention, the ratio (by weight) of the adhesive component to the organic compound having a melting point of 95°C or less is preferably 0:10 to 9:1, more preferably 1:9 to 6:4, even more preferably 1.5:8.5 to 6:4, and particularly preferably 2:8 to 5:5. This range is advantageous in that it controls the adhesive strength and enables debonding by heating to a temperature near the melting point. Here, if the organic compound used in the present invention can fulfill the role or function of an adhesive, the adhesive composition of the present invention does not need to contain an adhesive. Here, "being able to fulfill the role or function of an adhesive" means that two substances can be joined by the adhesive and the two substances can be debonded by heating. Examples of such organic compounds include, but are not limited to, lauric acid and decanoic acid.

[0039] The content of the organic compound having a melting point of 95°C or less in the adhesive composition of the present invention varies depending on the required degree of desorption, but can be in the range of 10 wt % to 100 wt %, preferably in the range of 40 wt % to 90 wt %, more preferably in the range of 40 wt % to 85 wt %, and even more preferably in the range of 50 wt % to 80 wt %, relative to the total weight of the solids content of the adhesive composition (the composition of the adhesive composition excluding the solvent).

[0040] The content of the adhesive component in the adhesive composition of the present invention may be any content that allows the formation of an adhesive layer with the desired adhesiveness, and may be, for example, from 0 to 90% by weight, preferably in the range of 10 to 60% by weight, more preferably in the range of 15 to 60% by weight, and even more preferably in the range of 20 to 50% by weight, relative to the total weight of the solid content of the adhesive composition. By keeping the content within the above range, the adhesive composition of the present invention can form an adhesive layer with excellent adhesiveness.

[0041] The content of the solvent in the adhesive composition of the present invention can be set to an appropriate amount, but the amount of solvent is greater than the ratio (weight ratio) of the solvent content to the solid content of 1:1.

[0042] The adhesive composition of the present invention may also be in a solvent-free form. Such an adhesive composition can be prepared, for example, by first preparing a solvent-containing adhesive composition and then removing the solvent using an evaporator and / or vacuum drying. When such an adhesive composition is in a solid state, the adhesive composition can be heated, preferably at a temperature equal to or higher than the melting point, to melt the composition and then applied to the adherend.

[0043] (2) Properties of the Adhesive Composition When the adhesive composition of the present invention is applied to an adherend (an article to be adhered), the adherend can be detached by heating the adhesive composition to a temperature near the melting point of the organic compound. Furthermore, after the adherend has been detached (debonded), the adherend can be reattached to the adherend by heating the adherend again to a temperature near or above the melting point of the organic compound. Furthermore, because phase-transition materials rapidly change from a solid to a liquid state at their melting point, they can be detached from a bonded state with a small temperature difference.

[0044] Here, by applying the adhesive composition to adherends (articles to be bonded), an article consisting of adherend A / adhesive composition, or a layer (i.e., adhesive layer) made of the adhesive composition / adherend B is formed. Adherend A and adherend B may be the same or different. That is, another embodiment of the present invention is an article comprising two adherends, which may be the same or different, and the adhesive composition of the present invention disposed between the two adherends. Here, the adhesive composition of the present invention disposed between the two adherends may contain a solvent, or may be in a state in which the adhesive composition is disposed between the adherends and then dried to volatilize the solvent (an adhesive composition containing an adhesive component and an organic compound having a melting point of 95°C or less, or an adhesive composition substantially consisting of an adhesive component and an organic compound having a melting point of 95°C or less).

[0045] In the present invention, the application of the adhesive composition to the adherends includes: (1) sandwiching the adhesive composition between two adherends (such as, but not limited to, glass or plastic films) and drying to bond the two adherends; (2) applying the adhesive composition to one adherend, laminating another adherend on top of the coated adhesive composition, and drying to bond the two adherends; (3) applying the adhesive composition to one adherend and drying to form an adhesive layer, laminating another adherend on top of the adhesive layer, and optionally heating the adhesive layer and / or the other adherend to bond the two adherends; (4) applying the adhesive composition to a substrate such as a release film and drying to separately form a film consisting of an adhesive layer, sandwiching the adhesive layer film between two adherends, and optionally heating the adhesive layer film and / or one or two adherends to bond the two adherends; (5) Various embodiments are included, such as placing an adhesive layer film on one adherend, optionally heating the adhesive layer film and / or the adherend to bond the adherend and the adhesive layer, and then laminating another adherend on top of the adhesive layer, optionally heating the adhesive layer and / or the other adherend to bond the two adherends.

[0046] In this specification, the term "temperature near the melting point" refers to a temperature around the melting point of the organic compound, preferably a temperature between the melting point and the adhesive composition, and more preferably a temperature between the melting point and the adhesive composition. The term "heating to a temperature near the melting point of the organic compound" also includes heating an article in which an adhesive composition is sandwiched between two adherends (i.e., an article consisting of adherend A / adhesive composition or adhesive layer / adherend B) by applying heat to the vicinity of the surface of one or both of the adherends, and placing an article in which an adhesive composition is sandwiched between two adherends in a low-temperature environment (for example, but not limited to, inside a refrigerator, freezer, or low-temperature room), and then removing the article from the low-temperature environment and heating it to a temperature near the melting point of the organic compound, for example, room temperature (20°C ± 15°C (5 to 35°C)) or a temperature near room temperature. Examples of a method for applying heat near the surface of one or both adherends include, for example, heating with a hair dryer, heating with a heater, or heating by bringing a fire or lighter close by.

[0047] Examples of the substrate to be adhered include glass, plastic plates, plastic films or sheets, plastic molded products, paper, cloth, fibers, metals, alloys, ceramics, and polymeric materials.

[0048] In the present invention, known methods can be used to apply the adhesive composition to the adherends. For example, the adhesive composition can be directly applied to one or both of the adherends and then smoothed to the same thickness with a spatula or the like, thereby bonding the two adherends together. Various known and commonly used coating devices can be used to apply the adhesive composition to the adherends, such as a blade coater, air knife coater, roll coater, brush coater, champlex coater, bar coater, lip coater, gravure coater, curtain coater, slot die coater, slide coater, and sprayer. Various coating methods, such as a doctor blade, wire bar, die coater, comma coater, and gravure coater, can be used to form a film (adhesive layer) made of the adhesive composition. Alternatively, a method can be used in which two adherends are continuously fed with their bonding surfaces facing inward, and the adhesive composition is cast between them.

[0049] Before applying the adhesive composition, one or both of the bonding surfaces of the adherend may be subjected to an adhesion-improving treatment (surface activation treatment) such as saponification treatment, corona discharge treatment, plasma treatment, flame treatment, primer treatment, anchor coating treatment, or the like.

[0050] When an ionizing radiation-curable adhesive is used as the adhesive component, the adhesive composition layer is cured by irradiating it with active energy rays. The light source used to irradiate the active energy rays may be any light source capable of generating ultraviolet rays, electron beams, X-rays, etc. In particular, light sources having an emission distribution of wavelengths of 400 nm or less, such as low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps, are preferably used.

[0051] (3) Uses of the Adhesive Composition The temperature range in which the adhesive composition of the present invention can be used is from low temperatures of -20°C or lower to high temperatures of 100°C or higher, and can be, for example, from low temperatures such as those of a freezer (about -18°C or lower) to the boiling point of water (about 90°C). Furthermore, the adhesive composition of the present invention allows the temperature at which the adhesive is removed (desorption) to be controlled, and can be used repeatedly. Furthermore, the adhesive composition can be easily desorbed using a hair dryer or the like found in an ordinary household, and no dedicated applicator is required.

[0052] The adhesive composition of the present invention, possessing the above-described properties, can be used in the following applications. It can be used in place of screws, enabling opening and closing without the need for screws, even when normally required for opening. It can also be used as a magnet replacement or as an adhesive for fixing televisions and other items (replacing earthquake-resistant gel). It can also be used for bonding in low-temperature environments such as refrigerators and freezers, but the adhesive will break at room temperature, or for the opening and closing of plastic cases that require heat (and cannot be opened with scissors). Other applications include lockable safes that cannot be opened unless heated with a hair dryer, packaging bags that open when placed in hot water, blind shutters (shutters that close automatically when hot), lids, bag closures, boxes, and windows that open automatically when heated, fans that rotate automatically when heated but stop when cold, and notebooks that can be separated. It can also open and close materials that would be damaged if heated too high, at moderate temperatures. Furthermore, the adhesive composition of the present invention can be used as an adhesive that can adhere at human body temperature of about 35 to 36°C, remains fixed at room temperature, and can be removed at human body temperature without the need for equipment such as a hair dryer. For example, by using an organic compound having a desired phase transition temperature, the adhesive composition of the present invention can control the adhesion / detachment temperature to 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, or 90°C. The adhesive strength can also be changed by changing the ratio of the organic compound to the adhesive.

[0053] The present invention will be described below based on examples, but the scope of the present invention is not limited to these examples.

[0054] [Materials and Equipment] (1) Adhesives Adhesive 1: Plastic adhesive (product name: Plastic Adhesive, manufactured by Daiso Industries Co., Ltd.) Ingredients: 45% by weight of styrene butadiene rubber, 55% by weight of organic solvent (acetone, methylcyclohexane) Adhesive 2: Tube glue (product name: Tube glue, manufactured by Daiso Industries Co., Ltd.) Main ingredient: Starch (contains water) Adhesive 3: Wood glue (product name: Wood glue, manufactured by Konishi Co., Ltd.) Ingredients: 41% by weight of vinyl acetate resin, 59% by weight of water Adhesive 4: Solution of styrene butadiene rubber dissolved in methylcyclohexane (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd.)

[0055] (2) Phase change materials: Fatty acids: Lauric acid (melting point: 44°C) (trade name: Lauric Acid, manufactured by Tokyo Chemical Industry Co., Ltd.), Decanoic acid (melting point: 29-33°C) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), Nonanoic acid (melting point: 10°C) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), Liquid crystal compound: 8OCB (4-cyano-4'-octylbiphenyl) (melting point: 55-80°C) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), Vegetable oils that are mixtures other than the above-mentioned pure substances: A mixture of extremely hardened palm oil (hydrogenated palm oil), palm kernel oil, and palm oil (melting point: 44-50°C); hereinafter also referred to as P1. A mixture of extremely hardened palm oil (hydrogenated palm oil) (melting point: 50-54°C); hereinafter also referred to as P2.

[0056] (3) Measuring equipment: Surface temperature measurement: Thermometer (product name: Infrared Thermography FLIRE4, manufactured by FLIR Systems) Tensile strength test (shear): A&D Tabletop Tensile Compression Tester (Force Tester) MCT-2150. The material was stretched 6 to 7.5 cm. ２ The upper and lower ends were fixed to the testing machine, and the upper end was pulled vertically until the bonded area peeled off.

[0057] Example 1 The following experiment was conducted using Adhesive 1 and lauric acid (melting point: 44°C) as a phase-change material. (1) 2.0 g of lauric acid was dissolved in 3.1 mL (2.44 g) of a mixed solvent of acetone and cyclohexane (1:1) to prepare a mixed solution (45 wt% lauric acid, 55 wt% organic solvent (acetone / cyclohexane)). (2) The mixed solution from (1) and Adhesive 1 were mixed in a ratio of 8:2 (by weight) and thoroughly stirred with a spatula to prepare Adhesive Composition A. (3) Two glass slides were bonded with Adhesive Composition A and thoroughly dried (at room temperature for at least two days) to obtain Sample 1. (4) For Sample 1, one tip of the bonded glass slide was fixed, a 100 g weight was attached to the tip of the other glass slide, and a hair dryer was applied to one side of the glass slide. The lauric acid in Adhesive Composition A dissolved, and the glass slide was removed (see Figure 1; the image on the right is an enlarged view). (5) The detached slide glass was heated again to a temperature above its melting point and reattached.

[0058] While the dryer was being applied in (4) above, the surface temperatures of both sides of the slide glass were measured with a thermometer. The temperatures at which the two slide glasses were detached (demounted) were approximately 62°C on the front side (the side exposed to the dryer) and approximately 40°C on the back side.

[0059] Example 2 Using decanoic acid (melting point: 29-33°C) as the phase change material, 20% by weight of adhesive 1 was mixed with 80% by weight of decanoic acid solution (45% by weight of decanoic acid, 55% by weight of organic solvent (acetone / cyclohexane)), to prepare adhesive composition B in the same steps as in (1) and (2) of Example 1, and sample 2 was obtained in the same step as in (3) of Example 1. Next, sample 2 was placed in a freezer, and remained adhered while in the freezer. When removed from the freezer and left at room temperature, the two glass slides separated. The temperature at which they separated was approximately 24°C.

[0060] [Example 3] Using nonanoic acid (melting point: 10°C) as the phase change material, 20 wt% of adhesive 1 was mixed with 80 wt% of nonanoic acid solution (45 wt% nonanoic acid, 55 wt% organic solvent (acetone / cyclohexane)), to prepare adhesive composition C in the same steps as in (1) and (2) of Example 1, and sample 3 was obtained in the same step as in (3) of Example 1. Next, sample 3 was placed in a freezer, and remained adhered while in the freezer. When removed from the freezer and left at room temperature, the two glass slides separated. The temperature at which they separated was approximately 10°C.

[0061] Example 4 Using 8OCB (4-cyano-4'-octylbiphenyl) (melting point: 55-80°C) as the phase change material, 20 wt% of Adhesive 1 was mixed with 80 wt% of 8OCB solution (45 wt% 8OCB, 55 wt% organic solvent (acetone / cyclohexane)), to prepare Adhesive Composition D in the same manner as in (1) and (2) of Example 1, and Sample 4 was obtained in the same manner as in (3) of Example 1. When Sample 4 was used in the same manner as in (4) of Example 1, the two glass slides were separated (detached). The temperatures at which the glass slides separated were approximately 55°C on the front and approximately 48°C on the back.

[0062] [Example 4A] Sample 5 was obtained under the same conditions as in Example 4, except that 50 wt% of Adhesive 1 and 50 wt% of 8OCB solution were mixed. When Sample 5 was subjected to the same process as in (4) of Example 1, the two slide glasses were removed (detached). The temperatures at which the slide glasses were removed were 57°C on the front and 47°C on the back.

[0063] Comparative Example 1: The same steps as in (3) and (4) of Example 1 were carried out using only Adhesive 1 (100% by weight of Adhesive 1) without adding a phase transition material. As a result, the slide glass did not come off even when a hair dryer was applied to one side of the slide glass. The maximum temperature on the front side was 87°C, and the maximum temperature on the back side was 64°C.

[0064] FIG. 2 shows photographs of the samples of Comparative Example 1 and Examples 1 to 4 after the desorption tests. The explanation for each photograph is as follows. Example 1: For Sample 1, a hair dryer was applied to one side of the glass slide, and after the slide was detached, the detached glass slide was heated again to a temperature above the melting point and re-adhered. Example 2: For Sample 2, a photograph was taken of the glass slide left at room temperature, after the slide was detached, the detached glass slide was re-attached. Example 3: For Sample 3, a photograph was taken of the glass slide left at room temperature, after the slide was detached, the detached glass slide was re-attached. Example 4: For Sample 4, a photograph was taken of the glass slide left at room temperature, after the slide was detached, the detached glass slide was re-attached. Comparative Example 1: A photograph in which the adhesive did not come off despite continued application of the hair dryer. Furthermore, FIG. 3 shows a photograph of the sample after the desorption test of Example 4A was performed.

[0065] Example 5 Using Adhesive 2 as the adhesive and lauric acid as the phase change material, 20 wt% of Adhesive 2 was mixed with 80 wt% of a lauric acid solution (45 wt% lauric acid, 55 wt% organic solvent (acetone / cyclohexane)), to prepare adhesive composition E in the same steps as in (1) and (2) of Example 1, and sample 6 was obtained in the same step as in (3) of Example 1. When sample 6 was subjected to the same step as in (4) of Example 1, the two glass slides were separated. The temperatures at which the glass slides separated were approximately 48°C on the front and approximately 41°C on the back.

[0066] Comparative Example 2: The same steps as in (3) and (4) of Example 1 were carried out using only Adhesive 2 (100% by weight of Adhesive 2) without adding a phase-change material. As a result, the slide glass did not come off even when a hair dryer was applied to one side of the slide glass. The maximum temperature on the front side was 85°C, and the maximum temperature on the back side was 66°C.

[0067] Figure 4 shows photographs of the samples after the desorption tests of Comparative Example 2 and Example 5. The explanation for each photograph is as follows. Example 5: This photograph shows Sample 6, where a hair dryer was applied to one side of the slide glass, the slide glass was removed, and then the removed slide glass was heated again to a temperature above the melting point and re-adhered. Comparative Example 2: This photograph shows that the adhesive did not come off despite continued application of the hair dryer.

[0068] Example 6 Using Adhesive 3 as the adhesive and lauric acid as the phase change material, 20 wt% of Adhesive 3 was mixed with 80 wt% of a lauric acid solution (41 wt% lauric acid, 59 wt% organic solvent (ethanol / ethyl acetate)). Adhesive composition F was prepared by the same steps as in (1) below and (2) of Example 1, and sample 7 was obtained by the same step as in (3) of Example 1. When sample 7 was used in the same step as in (4) of Example 1, the two glass slides were removed. The temperatures at which the glass slides were removed were approximately 55°C on the front and approximately 45°C on the back. (1) 1.0 g of lauric acid was dissolved in 1.7 mL (1.44 g) of a mixed solvent of ethanol and ethyl acetate (1:1) to prepare a mixed solution (41 wt% lauric acid, 59 wt% organic solvent (ethanol / ethyl acetate)).

[0069] Comparative Example 3: The same steps as in (3) and (4) of Example 1 were carried out using only Adhesive 3 (100% by weight of Adhesive 3) without adding a phase transition material. As a result, the slide glass did not come off even when a hair dryer was applied to one side of the slide glass. The maximum temperature on the front side was 75°C, and the maximum temperature on the back side was 65°C.

[0070] 5 shows photographs of the samples after the desorption tests of Comparative Example 3 and Example 6. The explanation for each photograph is as follows. Example 6: This photograph shows Sample 7, where a hair dryer was applied to one side of the slide glass, the slide glass was removed, and then the removed slide glass was heated again to a temperature above the melting point and re-adhered. Comparative Example 3: This photograph shows that the adhesive did not come off despite continued application of the hair dryer.

[0071] Example 7 The following experiment was conducted using lauric acid (melting point: 44°C) as a phase-change material without using an adhesive. (1) 2.0 g of lauric acid was dissolved in 3.1 mL (2.44 g) of a mixed solvent of acetone and cyclohexane (1:1) to prepare a mixed solution (45 wt% lauric acid, 55 wt% organic solvent (acetone / cyclohexane)). (2) Two glass slides were bonded together using the mixed solution (1) and thoroughly dried (at room temperature for at least two days) to obtain Sample 8. (3) For Sample 8, one end of the bonded glass slide was fixed, a 100 g weight was attached to the end of the other glass slide, and a hair dryer was applied to one side of the glass slide. The lauric acid dissolved, and the glass slide was detached. (4) The detached glass slide was again heated to a temperature above its melting point and reattached. While the hair dryer was applied in (3) above, the surface temperatures of both sides of the glass slide were measured with a thermometer. The temperatures at which the two slide glasses came off (detached) were about 46°C on the front side (the side exposed to the dryer) and about 40°C on the back side.

[0072] Figure 6 shows a photograph of the sample after the desorption test of Example 7. The explanation for the photograph is as follows: Example 7: For Sample 8, a hair dryer was applied to one side of the slide glass to remove it, and then the removed slide glass was heated again to a temperature above the melting point and re-adhered.

[0073] Example 8: 120 g of P1 (melting point: 44-50°C) as a phase change material was added to 348 g of a methylcyclohexane solution in which 40 g of styrene-butadiene rubber (Adhesive 4) was dissolved, and the mixture was heated to 60°C and thoroughly mixed with a medicine spoon to prepare Adhesive Composition G (the ratio of styrene-butadiene rubber to P1 was 1:3). Sample 9 was obtained using the same process as in (3) of Example 1. When Sample 9 was used in the same process as in (4) of Example 1, the two glass slides were separated. The temperatures at which the glass slides separated were approximately 53°C on the front and approximately 45°C on the back.

[0074] Example 9 3.0 g of P2 (melting point: 50-54°C) as a phase change material was added to 4 g of a methylcyclohexane solution in which 1.0 g of styrene-butadiene rubber (Adhesive 4) was dissolved, and the mixture was heated to 80°C and thoroughly mixed with a medicine spoon to prepare Adhesive Composition H (the ratio of styrene-butadiene rubber to P2 was 1:3). Sample 10 was obtained using the same process as in (3) of Example 1. When Sample 10 was used in the same process as in (4) of Example 1, the two glass slides were separated. The temperatures at which the glass slides separated were approximately 56°C on the front and approximately 46°C on the back.

[0075] Comparative Example 4: The same steps as in (3) to (4) of Example 1 were carried out using only Adhesive 4 (100% by weight of Adhesive 4) without adding a phase transition material. As a result, the slide glass did not come off even when a hair dryer was applied to one side of the slide glass. The maximum temperature on the front side was 83°C, and the maximum temperature on the back side was 60°C.

[0076] [Example 10] The solvent (methylcyclohexane) in the recovery flask was removed from Adhesive Composition G using an evaporator and vacuum drying. The layer of adhesive composition adhering to the recovery flask was heated to 60°C (above the melting point) and melted, and the following material was attached. After leaving it at room temperature for at least one hour, the strength was measured using a tensile strength test (shear). The results are shown in Table 1 below.

[0077]

[0078] Figure 7 shows photographs of the samples of Example 8, Example 9, and Comparative Example 4 after the desorption tests. The explanation for each photograph is as follows. Example 8: This photograph shows Sample 9, where a hair dryer was applied to one side of the glass slide, the slide was detached, and then the detached glass slide was heated again to a temperature above its melting point and re-adhered. Example 9: This photograph shows Sample 10, where a hair dryer was applied to one side of the glass slide, the slide was detached, and then the detached glass slide was heated again to a temperature above its melting point and re-adhered. Comparative Example 4: This photograph shows that the adhesive did not come off despite continued application of the hair dryer.

[0079] [Example 11] The relationship between the weight ratio of styrene butadiene rubber (S) and P2 (oil) in adhesive 4 and the strength was qualitatively investigated, and the following results were obtained. Increasing the ratio of S increased the adhesive strength. Furthermore, when heated with a hair dryer, all of the adhesive came off.

[0080]

Claims

1. An adhesive composition comprising at least one adhesive component and at least one organic compound having a melting point of 95°C or less, wherein the organic compound is selected from the group consisting of liquid crystal compounds, fatty acids, alkanes, alkenes, oils and fats, and any combination thereof (however, if the organic compound can fulfill the role or function of an adhesive, the adhesive composition does not need to contain an adhesive).

2. The adhesive composition according to claim 1, wherein the adhesive component is at least one selected from the group consisting of adhesive components of solvent-based adhesives, water-dispersed or latex-based adhesives, and reactive adhesives.

3. The adhesive composition according to claim 1, further comprising an organic solvent.

4. The adhesive composition according to claim 1, which, when applied to an object to be adhered, can be removed by heating to a temperature close to the melting point of the organic compound.

5. The adhesive composition according to claim 1, wherein the weight ratio of the adhesive component to the organic compound having a melting point of 95°C or less in the adhesive composition is 0:10 to 9:

1.

6. The adhesive composition according to claim 5, wherein the weight ratio of the adhesive component to the organic compound having a melting point of 95°C or less in the adhesive composition is 2:8 to 5:

5.

7. An article comprising two identical or different adherends, and the adhesive composition according to any one of claims 1 to 6, disposed between the two adherends.

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