Adhesive agent composition, method for producing same, and adhesive agent

Abstract

An adhesive agent composition comprising: a hydroxyl group-terminated urethane prepolymer; a tackifying resin; and a polyisocyanate compound, wherein the hydroxyl group-terminated urethane prepolymer is a reaction product between a diisocyanate compound and an oxyalkylene polymer having a number average molecular weight of 3,000 or more.

Description

Pressure-sensitive adhesive composition, method for producing the same, and pressure-sensitive adhesive

[0001] The present invention relates to an adhesive composition for obtaining an adhesive that can be applied to the skin, a method for producing the same, an adhesive, an adhesive patch, a wearable device, and a wearable device kit.

[0002] Urethane-based adhesives are used as adhesives for skin adhesive materials such as bandages, surgical tapes, poultices, and plasters, as well as for attaching patch-type wearable devices to the skin for continuously acquiring biological information such as body temperature and electroencephalograms.

[0003] As an example of a urethane-based adhesive for application to the skin, Patent Document 1 describes a medical adhesive composition containing a urethane resin (A), a tackifier resin (B) having a softening point of 75°C or higher and containing a hydroxyl group, and an isocyanate curing agent (C), wherein the adhesive strength ratio [(X2) / (X1)] of adhesive strength (X1) after 20 minutes in an environment of 23°C and 50% RH (relative humidity) to adhesive strength (X2) after 24 hours in an environment of 23°C and 50% RH to a stainless steel plate is 0.8 to 1.5.

[0004] Japanese Patent Application Laid-Open No. 2020-81438

[0005] However, investigations by the present inventors have revealed that the adhesive composition described in Patent Document 1 does not have sufficient long-term water resistance, i.e., the property of maintaining an adhered state for a long period of time even in wet conditions. The present invention has been made in view of such circumstances, and aims to provide an adhesive composition and a method for producing the same, as well as an adhesive, a patch, a wearable device, and a wearable device kit, which are capable of obtaining an adhesive that has sufficient adhesive strength to a device and a sealant and also has sufficient long-term water resistance.

[0006] As a result of extensive research, the present inventors have found that the pressure-sensitive adhesive composition described in the examples of Patent Document 1 does not provide sufficient long-term water resistance when the number-average molecular weight of the raw material polyol for the urethane resin is as low as 2,000 or less. Furthermore, the present inventors have found that a pressure-sensitive adhesive composition containing a urethane resin synthesized using a polyol with a high number-average molecular weight and a tackifier resin can provide sufficient adhesion to devices and sealants, and also provide a pressure-sensitive adhesive with sufficient long-term water resistance. The present invention was completed based on these findings.

[0007] The present invention provides the following means: [1] A pressure-sensitive adhesive composition comprising a hydroxyl-terminated urethane prepolymer, a tackifying resin, and a polyisocyanate compound, wherein the hydroxyl-terminated urethane prepolymer is a reaction product of an oxyalkylene polymer having a number-average molecular weight of 3,000 or more and a diisocyanate compound. [2] The pressure-sensitive adhesive composition according to the above [1], wherein the hydroxyl-terminated urethane prepolymer is a reaction product of an oxyalkylene polymer having a number-average molecular weight of 3,000 or more and a diisocyanate compound in the presence of a tin-free catalyst.

[0008] [3] The pressure-sensitive adhesive composition according to [1] or [2] above, wherein the tackifier resin is a tackifier resin having a softening point of 70°C or higher. [4] The pressure-sensitive adhesive composition according to any one of [1] to [3] above, wherein the tackifier resin is a terpene-based tackifier resin or a styrene-based tackifier resin. [5] The pressure-sensitive adhesive composition according to any one of [1] to [4] above, wherein the hydroxyl-terminated urethane prepolymer has a content of structural units based on ethylene oxide of 8 to 55% by mass. [6] The pressure-sensitive adhesive composition according to any one of [1] to [5] above, wherein the oxyalkylene polymer comprises an oxyalkylene polymer A having two or more hydroxyl groups per molecule and an oxyalkylene polymer B having one hydroxyl group per molecule.

[0009] [7] The pressure-sensitive adhesive composition according to any one of [1] to [6] above, wherein the hydroxyl-terminated urethane prepolymer has a weight-average molecular weight of 50,000 or more. [8] A method for producing a pressure-sensitive adhesive composition, comprising reacting an oxyalkylene polymer having a number-average molecular weight of 3,000 or more with a diisocyanate compound to obtain a hydroxyl-terminated urethane prepolymer, and mixing the hydroxyl-terminated urethane prepolymer, a tackifying resin, and a polyisocyanate compound.

[0010] [9] The method for producing a pressure-sensitive adhesive composition according to the above-mentioned [8], wherein the hydroxyl-terminated urethane prepolymer is a reaction product of reacting an oxyalkylene polymer having a number average molecular weight of 3,000 or more with a diisocyanate compound in the presence of a tin-free catalyst.

[10] The method for producing a pressure-sensitive adhesive composition according to the above-mentioned [9], wherein the tin-free catalyst is more than 0.001 parts by mass and not more than 0.1 parts by mass per 100 parts by mass of the oxyalkylene polymer.

[11] A pressure-sensitive adhesive which is a cured product of the pressure-sensitive adhesive composition according to any one of the above-mentioned [1] to [7].

[12] A patch having a substrate and a pressure-sensitive adhesive layer provided on at least a part of the surface of the substrate, the pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive according to the above-mentioned

[11] .

[13] The patch according to the above-mentioned

[12] , which is a pressure-sensitive adhesive tape.

[0011]

[14] A wearable device having a wearable device main body and an adhesive layer, wherein the adhesive layer is provided on at least a part of the surface of the wearable device that faces the skin and includes the adhesive described in

[11] above.

[15] A wearable device kit including a wearable device main body and at least one of the adhesive described in

[11] above and the patch described in

[12] or

[13] above.

[0012] According to the present invention, it is possible to provide an adhesive composition and a method for producing the same, which are capable of obtaining an adhesive that can achieve sufficient adhesion to a device and a sealant and has sufficient long-term water resistance, as well as an adhesive, a patch, a wearable device, and a wearable device kit.

[0013] The definitions and meanings of terms and notations used in this specification are as follows. Skin refers to human skin. The number average molecular weight (Mn) and weight average molecular weight (Mw) are polystyrene-equivalent molecular weights determined by gel permeation chromatography (GPC) based on a calibration curve prepared using a standard polystyrene sample. The hydroxyl value is determined by measurement in accordance with JIS K 1557-1:2007. The degree of unsaturation is determined by measurement in accordance with JIS K 1557-3:2007. The isocyanate index is the equivalent ratio ([isocyanate group] / [active hydrogen-containing group]) of the isocyanate group to be reacted and the active hydrogen-containing group (e.g., hydroxyl group), and is expressed as a percentage.

[0014] [Adhesive Composition] The adhesive composition according to an embodiment of the present invention (hereinafter referred to as the present embodiment) is an adhesive composition comprising a hydroxyl-terminated urethane prepolymer, a tackifying resin, and a polyisocyanate compound, wherein the hydroxyl-terminated urethane prepolymer is a reaction product of an oxyalkylene polymer having a number average molecular weight of 3,000 or more and a diisocyanate compound. The adhesive composition according to the present embodiment makes it possible to obtain an adhesive having sufficient adhesive strength to devices and sealants and sufficient long-term water resistance.

[0015] (Hydroxyl-Terminated Urethane Prepolymer) The hydroxyl-terminated urethane prepolymer of this embodiment is a reaction product of an oxyalkylene polymer having a number average molecular weight of 3,000 or more and a diisocyanate compound, thereby making it possible to obtain a pressure-sensitive adhesive having sufficient adhesive strength to devices and sealants, and sufficient long-term water resistance.

[0016] The hydroxyl-terminated urethane prepolymer of this embodiment is preferably a reaction product of an oxyalkylene polymer having a number average molecular weight of 3,000 or more with a diisocyanate compound in the presence of a tin-free catalyst, thereby making it possible to obtain a pressure-sensitive adhesive that is gentle on the skin and does not contain a tin-containing catalyst that has a detrimental effect on the skin.

[0017] The weight average molecular weight of the hydroxyl group-terminated urethane prepolymer is preferably 50,000 or more, more preferably 100,000 or more, and even more preferably 200,000 or more, from the viewpoint of obtaining a PSA having sufficient adhesive strength to devices and sealants and sufficient long-term water resistance. From the viewpoint of obtaining a PSA having sufficient adhesive strength to devices and sealants and sufficient long-term water resistance and from the viewpoint of ease of production, the weight average molecular weight is preferably 50,000 to 500,000, more preferably 100,000 to 500,000, even more preferably 200,000 to 450,000, still more preferably 200,000 to 400,000, and even more preferably 250,000 to 300,000.

[0018] From the viewpoint of obtaining a PSA having sufficient adhesive strength to devices and sealants and sufficient long-term water resistance, the content of structural units based on ethylene oxide (hereinafter abbreviated as "EO units") in the hydroxyl group-terminated urethane prepolymer is preferably 8 to 55 mass%, more preferably 8 to 40 mass%, even more preferably 8 to 20 mass%, still more preferably 8 to 18 mass%, even more preferably 8 to 16 mass%, and still more preferably 8 to 13 mass%. The lower the EO unit content in the hydroxyl group-terminated urethane prepolymer, the lower the skin irritation, and by keeping the EO unit content within the above range, a PSA that is gentle on the skin, has sufficient adhesive strength to devices and sealants, and is sufficient long-term water resistance is likely to be obtained.

[0019] The EO units in the hydroxyl group-terminated urethane prepolymer are derived from the EO units that constitute the oxyalkylene chain of the oxyalkylene polymer. １３ The content of EO units in the hydroxyl-terminated urethane prepolymer can be determined by analyzing the monomer composition of the oxyalkylene chain in the hydroxyl-terminated urethane prepolymer by C-NMR (nuclear magnetic resonance) measurement.

[0020] In the hydroxyl group-terminated urethane prepolymer, the total amount of the structure derived from the oxyalkylene polymer having a number average molecular weight of 3,000 or more and the structure derived from the diisocyanate compound is preferably 80 to 100 mass%, more preferably 90 to 100 mass%, and even more preferably 95 to 100 mass%.

[0021] <Oxyalkylene Polymer> The number-average molecular weight of the oxyalkylene polymer according to this embodiment is 3,000 or more. When a hydroxyl-terminated urethane prepolymer is obtained using an oxyalkylene polymer with a low molecular weight, it is difficult to increase the molecular weight of the hydroxyl-terminated urethane prepolymer, resulting in poor water resistance. Because the oxyalkylene polymer according to this embodiment has a number-average molecular weight of 3,000 or more, a high-molecular-weight hydroxyl-terminated urethane prepolymer can be obtained, thereby enabling the production of a pressure-sensitive adhesive having sufficient adhesive strength to devices and sealants and sufficient long-term water resistance. Furthermore, the number-average molecular weight of the oxyalkylene polymer according to this embodiment is preferably 50,000 or less. A number-average molecular weight of 50,000 or less prevents the molecular weight of the resulting hydroxyl-terminated urethane prepolymer from becoming too large, thereby preventing the viscosity of the pressure-sensitive adhesive composition from becoming too high, resulting in a pressure-sensitive adhesive composition with excellent handleability. From these viewpoints, the number average molecular weight of the oxyalkylene polymer is preferably 3,000 to 50,000, more preferably 5,500 to 45,000, even more preferably 6,000 to 40,000, still more preferably 7,000 to 30,000, and even more preferably 8,000 to 25,000.

[0022] The oxyalkylene polymer may be one type of oxyalkylene polymer or two or more types of oxyalkylene polymers. When a plurality of oxyalkylene polymers are used in the synthesis of the hydroxyl-terminated urethane prepolymer, the number average molecular weight of the oxyalkylene polymer means a weighted average value based on the blend amounts of the plurality of oxyalkylene polymers used in the synthesis of the hydroxyl-terminated urethane prepolymer. When a plurality of oxyalkylene polymers are used in the synthesis of the hydroxyl-terminated urethane prepolymer, the number average molecular weight of at least one of these plurality of types must be 3,000 or more, but the number average molecular weight of all of these plurality of types may also be 3,000 or more. For example, when the oxyalkylene polymers used in the synthesis of the hydroxyl-terminated urethane prepolymer are three types, namely, oxyalkylene polymer (1), oxyalkylene polymer (2), and oxyalkylene polymer (3), the number average molecular weight of at least one of these three types (e.g., oxyalkylene polymer (1)) must be 3,000 or more, but the number average molecular weight of two of these three types (e.g., oxyalkylene polymers (1) and (2)) may be 3,000 or more, or all three types (i.e., all of oxyalkylene polymers (1), (2), and (3)) may be 3,000 or more. However, the weighted average of the number average molecular weights of all three types (oxyalkylene polymers (1), (2), and (3)) based on the blending amounts must be 3,000 or more. The content of species having a number average molecular weight of 3,000 or more in the total amount (100% by mass) of the multiple oxyalkylene polymers used in the synthesis of the hydroxyl group-terminated urethane prepolymer is preferably 60 to 100% by mass, more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass, and may be, for example, 100% by mass.

[0023] The average content of EO units in the oxyalkylene polymer is preferably 8 to 55% by mass. When the average content of EO units in the oxyalkylene polymer is within this range, a PSA having good adhesive strength that is low in load on the skin and exhibits good fixation of circuits and the like is easily obtained. From this viewpoint, the average content of EO units in the oxyalkylene polymer is more preferably 8 to 40% by mass, even more preferably 8 to 20% by mass, even more preferably 8 to 18% by mass, even more preferably 8 to 16% by mass, and even more preferably 8 to 13% by mass. The average content of EO units in the oxyalkylene polymer refers to the weighted average value of the EO unit contents in each oxyalkylene polymer based on the blend amounts of multiple oxyalkylene polymers used in the synthesis of the hydroxyl-terminated urethane prepolymer. The EO unit content in each oxyalkylene polymer is a value calculated based on the EO blend amount of the raw material used in the synthesis of the oxyalkylene polymer. The EO unit content in the oxyalkylene polymer, like the EO unit content in the hydroxyl-terminated urethane prepolymer, is also １３ The average content of EO units in the oxyalkylene polymer can also be determined by C-NMR measurement. The smaller the average content of EO units in the oxyalkylene polymer, the less irritating it is to the skin, and by having the average content of EO units in the above range, it is easy to obtain a PSA that is gentle to the skin, has sufficient adhesive strength to devices and sealants, and has sufficient long-term water resistance.

[0024] From the viewpoint of obtaining a pressure-sensitive adhesive having sufficient adhesive strength to devices and sealants and sufficient long-term water resistance, the oxyalkylene polymer preferably has an average number of hydroxyl groups per molecule of the oxyalkylene polymer of 1.5 to 3.0, more preferably 1.7 to 2.8, and even more preferably 1.9 to 2.6. The average number of hydroxyl groups per molecule of the oxyalkylene polymer refers to a weighted average value based on the blend amounts of multiple oxyalkylene polymers used in the synthesis of the hydroxyl-terminated urethane prepolymer. The oxyalkylene polymer may be one type of oxyalkylene polymer or two or more types of oxyalkylene polymers.

[0025] The oxyalkylene polymer preferably comprises an oxyalkylene polymer A (hereinafter also simply referred to as "polymer A") having two or more hydroxyl groups per molecule, and an oxyalkylene polymer B (hereinafter also simply referred to as "polymer B") having one hydroxyl group per molecule. It is preferred that the hydroxyl groups of polymer A and polymer B react with the isocyanate groups of the diisocyanate compound to form urethane bonds, and that the unreacted hydroxyl groups are terminal hydroxyl groups of the molecular chain of the hydroxyl-terminated urethane prepolymer.

[0026] The total content of polymer A and polymer B in the oxyalkylene polymer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and still more preferably 100% by mass. From the viewpoint of obtaining a pressure-sensitive adhesive having sufficient adhesive strength to devices and sealants and sufficient long-term water resistance, the content ratio of polymer A to polymer B in the oxyalkylene polymer is preferably 10 / 90 to 95 / 5, more preferably 30 / 70 to 90 / 10, even more preferably 50 / 50 to 85 / 15, and still more preferably 60 / 40 to 85 / 15 by mass.

[0027] [Oxyalkylene Polymer A] Polymer A has two or more hydroxyl groups per molecule, preferably two to six. Polymer A may be one type of oxyalkylene polymer, or two or more types of oxyalkylene polymers. When polymer A is composed of two or more types of oxyalkylene polymers, it is easy to adjust the adhesive strength of the adhesive. When polymer A is composed of two or more types of oxyalkylene polymers, the average number of hydroxyl groups per molecule of polymer A is preferably 2.1 to 3.0, more preferably 2.2 to 2.9, and even more preferably 2.3 to 2.8. When the average number of hydroxyl groups of polymer A is within the above range, stress on the skin to which the device is fixed is reduced, and an adhesive that is less likely to leave adhesive residue on the skin is easily obtained. The average number of hydroxyl groups per molecule of polymer A can be calculated from the measured hydroxyl value and Mn of polymer A using the formula: hydroxyl value × Mn / 56,100.

[0028] When polymer A is composed of two or more types of oxyalkylene polymers, examples of polymer A include an oxyalkylene polymer A1 (hereinafter simply referred to as "polymer A1") having three hydroxyl groups per molecule, and an oxyalkylene polymer A2 (hereinafter simply referred to as "polymer A2") having two hydroxyl groups per molecule. Polymer A1 may be a single type or two or more types. Similarly, polymer A2 may be a single type or two or more types. Polymer A may contain an oxyalkylene polymer having four or more hydroxyl groups per molecule. When polymer A is composed of polymer A1 and polymer A2, the weighted average value based on the composition ratio (blending amount) of polymer A1 and polymer A2, where polymer A1 has three hydroxyl groups per molecule and polymer A2 has two hydroxyl groups per molecule, can be considered to be the average number of hydroxyl groups of polymer A.

[0029] From the viewpoint of ease of adjusting the adhesive strength of the PSA, the total amount of polymer A1 and polymer A2 in 100 parts by mass of polymer A is preferably 85 parts by mass or more, more preferably 90 parts by mass or more, and even more preferably 95 parts by mass or more. It is particularly preferable that the total amount of polymer A1 and polymer A2 in 100 parts by mass of polymer A is 100 parts by mass, i.e., polymer A consists of polymer A1 and polymer A2.

[0030] From the viewpoint of obtaining a pressure-sensitive adhesive having sufficient adhesive strength to devices and sealants and sufficient long-term water resistance, the amount of polymer A1 is preferably 20 parts by mass or more, more preferably 25 to 95 parts by mass, and even more preferably 30 to 90 parts by mass, per 100 parts by mass of the total of polymer A1 and polymer A2. From the same viewpoint, the amount of polymer A2 is preferably 80 parts by mass or less, more preferably 5 to 75 parts by mass, and even more preferably 10 to 70 parts by mass, per 100 parts by mass of the total of polymer A1 and polymer A2.

[0031] For example, when polymer A consists of polymer A1 and polymer A2, the content of polymer A1 is preferably 10 to 60 parts by mass, more preferably 20 to 50 parts by mass, and even more preferably 30 to 50 parts by mass, per 100 parts by mass of polymer A1, polymer A2, and polymer B in the oxyalkylene polymer, from the viewpoint of obtaining a pressure-sensitive adhesive having sufficient adhesive strength to devices and sealants and sufficient long-term water resistance. From the same viewpoint, the content of polymer A2 is preferably 15 to 50 parts by mass, more preferably 30 to 50 parts by mass, and even more preferably 30 to 40 parts by mass, per 100 parts by mass of polymer A1, polymer A2, and polymer B in the oxyalkylene polymer. From the same viewpoint, the content of polymer B is preferably 5 to 40 parts by mass, more preferably 10 to 35 parts by mass, and even more preferably 10 to 20 parts by mass, per 100 parts by mass of polymer A1, polymer A2, and polymer B in the oxyalkylene polymer.

[0032] The average content of EO units in polymer A is preferably 0 to 80% by mass, more preferably 1 to 50% by mass, even more preferably 5 to 30% by mass, and still more preferably 8 to 25% by mass. １３ The monomer composition of the oxyalkylene chain in polymer A can be analyzed and determined by C-NMR measurement. For example, when the oxyalkylene chain in polymer A is composed of EO units and PO units, the EO unit content can be calculated based on the area of ​​the peak representing the methylene group of the EO unit and the area of ​​the peak representing the methyl group of the PO unit. When polymer A is composed of, for example, polymer A1 and polymer A2, the EO unit contents of polymer A1 and polymer A2 are similar. The average EO unit content in polymer A can be considered to be a value calculated from the amount of EO blended in the synthetic raw materials for polymer A. When polymer A is composed of, for example, polymer A1 and polymer A2, the EO unit content of polymer A can be considered to be the weighted average of the EO unit content of polymer A1 and the EO unit content of polymer A2 based on the compositional proportions (blending amounts) of polymer A1 and polymer A2.

[0033] From the viewpoints of achieving good adhesive strength of the PSA, suppressing adhesive residue, and forming a PSA layer with good flexibility, the Mn of polymer A is preferably 1,000 to 50,000, more preferably 5,000 to 30,000, and even more preferably 8,000 to 25,000. The Mw / Mn (molecular weight distribution) of polymer A is close to 1. A narrower molecular weight distribution prevents the hydroxyl-terminated urethane prepolymer from becoming highly viscous and improves synthesis efficiency, so the Mw / Mn is preferably 1.25 or less, more preferably 1.22 or less, and even more preferably 1.20 or less. Furthermore, from the viewpoints of achieving good curing of the hydroxyl-terminated urethane prepolymer and suppressing adhesive residue of the PSA, the closer the unsaturation level of polymer A is to 0 meq / g, the more preferable it is, and preferably 0.020 meq / g or less, more preferably 0.018 meq / g or less, and even more preferably 0.015 meq / g or less. When polymer A is composed of two or more kinds of oxyalkylene polymers, it is preferable that each of the oxyalkylene polymers has Mn, Mw / Mn and degree of unsaturation within the above ranges.

[0034] The synthesis method of polymer A is not particularly limited, but can be obtained, for example, by ring-opening addition polymerization of a compound having a cyclic ether structure, preferably an alkylene oxide, with an initiator having two or more active hydrogens in the presence of a catalyst. When polymer A consists of polymer A1 and polymer A2, a method can also be used in which an initiator having three active hydrogens and an initiator having two active hydrogens are used in combination to perform ring-opening addition polymerization of a compound having a cyclic ether structure, thereby simultaneously producing polymer A1 and polymer A2. From the viewpoint of more accurately adjusting the blending amounts of polymer A1 and polymer A2, a method in which polymer A obtained by ring-opening addition polymerization of a compound having a cyclic ether structure with an initiator having three active hydrogens and polymer B obtained by ring-opening addition polymerization of a compound having a cyclic ether structure with an initiator having two active hydrogens are separately synthesized and then mixed is preferred.

[0035] The compound having a cyclic ether structure is preferably linear or branched and has 2 to 14 carbon atoms, more preferably 2 to 10 carbon atoms, and even more preferably 2 to 4 carbon atoms. The compound having a cyclic ether structure may be one type alone or two or more types. Examples of compounds having a cyclic ether structure include ethylene oxide (EO), propylene oxide (PO), 1,2-butylene oxide, 2,3-butylene oxide, methyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, lauryl glycidyl ether, hexyl glycidyl ether, and tetrahydrofuran. Of these, EO and PO are preferred.

[0036] When two or more compounds having a cyclic ether structure are used in combination, the arrangement of the oxyalkylene groups derived from each compound in the polymer A may be random or block.

[0037] Examples of groups having active hydrogen in the initiator include a hydroxyl group, a carboxyl group, and an amino group having a hydrogen atom bonded to a nitrogen atom. Of these, a hydroxyl group is preferred, and an alcoholic hydroxyl group is more preferred. Examples of initiators having three hydroxyl groups include glycerin, trimethylolethane, trimethylolpropane, and 1,2,6-hexanetriol. Of these, one type may be used alone, or two or more types may be used in combination. Examples of initiators having two hydroxyl groups include ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol. Of these, one type may be used alone, or two or more types may be used in combination.

[0038] The number of active hydrogens in the initiator usually corresponds to the number of hydroxyl groups per molecule of the oxyalkylene polymer. Polymer A1 can be synthesized, for example, using glycerin as an initiator. Polymer A2 can be synthesized, for example, using propylene glycol as an initiator. The initiators used as raw materials for synthesizing the oxyalkylene polymer are: １３ When polymer A is composed of polymer A1 and polymer A2, the type and amount of polymer A can be identified by C-NMR measurement. １３The ratio of polymer A1 to polymer A2 is determined by determining the content of oxyalkylene groups such as EO units and PO units bound to each initiator from information on the type and amount of the initiator obtained by C-NMR measurement.

[0039] Ring-opening addition polymerization can be carried out using known catalysts, such as alkali catalysts such as potassium hydroxide, transition metal compound-porphyrin complex catalysts such as complexes obtained by reacting an organoaluminum compound with porphyrin, composite metal cyanide complex catalysts, and catalysts made of phosphazene compounds. Among these catalysts, composite metal cyanide complex (DMC) catalysts are preferred because they tend to produce oxyalkylene polymers with narrow molecular weight distributions and relatively low viscosity. Known compounds can be used as composite metal cyanide complexes, such as zinc hexacyanocobaltate complexes with tert-butanol as a ligand. Synthesis of oxyalkylene polymers by ring-opening addition polymerization using a DMC catalyst can be carried out by known methods, for example, production methods described in WO 2003 / 062301, WO 2004 / 067633, JP 2004-269776 A, JP 2005-15786 A, WO 2013 / 065802, JP 2015-10162 A, etc. can be applied.

[0040] [Oxyalkylene Polymer B] The oxyalkylene polymer B has one hydroxyl group per molecule. The polymer B may be one type of oxyalkylene polymer or two or more types of oxyalkylene polymers. The number of hydroxyl groups of the polymer B is, like the polymer A, １３ This can be confirmed by identifying the type and amount of the initiator used in the synthesis by C-NMR measurement.

[0041] From the viewpoints of forming a pressure-sensitive adhesive layer with good flexibility, achieving good adhesive strength of the pressure-sensitive adhesive, and suppressing adhesive residue, the Mn of polymer B is preferably 4,000 to 30,000, more preferably 4,500 to 25,000, and even more preferably 5,000 to 20,000. The Mw / Mn of polymer B is preferably less than 1.20, more preferably less than 1.13, and even more preferably less than 1.10, because the closer to 1 and the narrower the molecular weight distribution, the less likely the hydroxyl-terminated urethane prepolymer will become highly viscous and the more efficient the synthesis. Furthermore, from the viewpoints of achieving good curing of the hydroxyl-terminated urethane prepolymer and suppressing adhesive residue in the pressure-sensitive adhesive layer, the degree of unsaturation of polymer B is preferably 0.015 meq / g or less, more preferably 0.013 meq / g or less, and even more preferably 0.010 meq / g or less, with the degree of unsaturation being closer to 0 meq / g being preferable.

[0042] The synthesis method of polymer B is not particularly limited, but it can be obtained, for example, by ring-opening addition polymerization of a compound having a cyclic ether structure, preferably an alkylene oxide, to an initiator having one active hydrogen in the presence of a catalyst. The compound having a cyclic ether structure is the same as that described for polymer A. Preferably, PO is used alone, or EO and PO are used in combination.

[0043] From the viewpoint of obtaining a pressure-sensitive adhesive having a good balance between adhesive strength to skin and adhesive strength to a device and having suppressed crystallinity, the average content of EO units in Polymer B is preferably 0 to 80 mass%, more preferably 0 to 60 mass%, and even more preferably 0 to 50 mass%. The average content of EO units in Polymer B is determined in the same manner as in the case of Polymer A.

[0044] Examples of the group having an active hydrogen in the initiator include the same as those in the case of polymer A, with a hydroxyl group being preferred and an alcoholic hydroxyl group being more preferred. As the initiator having one hydroxyl group, from the viewpoint of availability and the like, a monohydric alcohol having 2 to 4 carbon atoms is preferred, for example, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, and tert-butanol are mentioned, and among these, n-butanol, sec-butanol, isobutanol, and tert-butanol are preferred. The initiator may be used alone or in combination of two or more types. The ring-opening addition polymerization can be carried out by a known method, as in the case of polymer A.

[0045] <Diisocyanate Compound> The diisocyanate compound used in the synthesis of the hydroxyl group-terminated urethane prepolymer is an organic compound having two isocyanate groups per molecule. The diisocyanate compound may be any of an aliphatic diisocyanate compound, an alicyclic diisocyanate compound, and an aromatic diisocyanate compound. The diisocyanate compound may be used alone or in combination of two or more types.

[0046] The aliphatic diisocyanate compound may be either linear or branched, and examples thereof include tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate. Examples of alicyclic diisocyanate compounds include isophorone diisocyanate (IPDI), hydrogenated xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate (HMDI), 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane. Examples of diisocyanate compounds having an aromatic ring structure include tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate (TMXDI). Of these, HDI, IPDI, HMDI, and TMXDI are preferred, with HDI being more preferred, from the viewpoints of obtaining a pressure-sensitive adhesive layer having good curing properties of the hydroxyl group-terminated urethane prepolymer and good flexibility.

[0047] Furthermore, as the diisocyanate compound, a bifunctional isocyanate-terminated urethane prepolymer obtained by previously reacting the above-mentioned diisocyanate compound with a diol (for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, etc.) can also be used.

[0048] <Tin-free catalyst> The tin-free catalyst is a urethane-forming catalyst that does not contain tin. In this embodiment, it is preferable not to use a tin-containing catalyst as the urethane-forming catalyst. From the viewpoint of obtaining a pressure-sensitive adhesive that is low in irritation and gentle on the skin, it is preferable that the pressure-sensitive adhesive of this embodiment does not contain tin or tin compounds.

[0049] Examples of tin-free catalysts include tertiary amine catalysts and organometallic catalysts containing metals other than tin. The catalysts may be used alone or in combination of two or more. The tin-free catalyst is preferably an organometallic catalyst from the viewpoint of better reaction promotion. Examples of metals contained in organometallic catalysts containing metals other than tin include zinc, bismuth, titanium, lead, iron, cobalt, and zirconium. Among these, zinc and bismuth are preferred, and zinc is more preferred from the viewpoints of low skin irritation and ease of handling.

[0050] Examples of tertiary amine catalysts include triethylamine, triethylenediamine, 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), etc. Examples of organometallic catalysts containing a metal other than tin include organometallic catalysts containing zinc, bismuth, titanium, lead, iron, cobalt, and zirconium, and organometallic catalysts containing bismuth or zinc are preferred. Examples of organometallic catalysts containing zinc, bismuth, titanium, lead, iron, cobalt, or zirconium include zinc compounds such as zinc carboxylates (e.g., zinc naphthenate and zinc 2-ethylhexanoate), and zinc acetylacetonate; bismuth compounds such as bismuth 2-ethylhexanoate and bismuth neodecanoate; titanium compounds such as dibutyltitanium dichloride, tetrabutyltitanium, and butoxytitanium trichloride; lead compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate; iron compounds such as iron 2-ethylhexanoate and iron acetylacetonate; cobalt compounds such as cobalt benzoate and cobalt 2-ethylhexanoate; and zirconium compounds such as zirconium naphthenate, with bismuth neodecanoate or zinc carboxylate being preferred.

[0051] The amount of the tin-free catalyst used in the reaction of an oxyalkylene polymer with a diisocyanate compound is, from the viewpoint of a good reaction-accelerating effect and a reduction in the amount of residual metal components, preferably more than 0.001 part by mass and not more than 0.1 part by mass, more preferably 0.005 or more and less than 0.05 part by mass, and even more preferably 0.01 to 0.04 part by mass, relative to 100 parts by mass of the oxyalkylene polymer.

[0052] (Tackifier Resin) The tackifier resin according to the present embodiment is not particularly limited, and may contain one or both of a tackifier resin having a softening point of 70° C. or higher and a tackifier resin having a softening point of less than 70° C. However, it is preferable to contain a tackifier resin having a softening point of 70° C. or higher, and it is also preferable to use a tackifier resin having a softening point of 70° C. or higher. By containing a tackifier resin having a softening point of 70° C. or higher, it is easy to obtain a PSA that has sufficient adhesive strength and is suppressed from remaining on the skin when peeled from the skin.

[0053] Examples of tackifier resins include rosin-based tackifier resins, terpene-based tackifier resins, alicyclic saturated hydrocarbon-based tackifier resins, styrene-based tackifier resins, and acrylic tackifier resins. From the viewpoint of improving adhesive strength to skin and SUS steel sheets, terpene-based tackifier resins or styrene-based tackifier resins are preferred. Terpene-based tackifier resins are more preferred from the viewpoint of good adhesive strength to phenolic resins. Furthermore, styrene-based tackifier resins are more preferred from the viewpoint of reducing coloration of the adhesive. The adhesive composition according to this embodiment can suitably contain either a tackifier resin having a hydroxyl group or a tackifier resin not having a hydroxyl group. However, from the viewpoint of appropriately suppressing adhesive strength to skin and further improving water resistance, a tackifier resin not having a hydroxyl group is preferably used. The adhesive composition according to this embodiment does not necessarily need to contain a tackifier resin not having a hydroxyl group.

[0054] Specific examples of rosin-based tackifying resins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by modifying these unmodified rosins through hydrogenation, disproportionation, polymerization, etc. (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc.; the same applies hereinafter); and various other rosin derivatives. Examples of the rosin derivatives include rosin esters such as those obtained by esterifying unmodified rosin with alcohols (i.e., esterified rosin products) and those obtained by esterifying modified rosin with alcohols (i.e., esterified rosin products); unsaturated fatty acid-modified rosins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty acid; unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acid; rosin alcohols obtained by reducing the carboxy groups of unmodified rosin, modified rosin, unsaturated fatty acid-modified rosin, or unsaturated fatty acid-modified rosin esters; metal salts of rosins (particularly rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives; and rosin phenolic resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) using an acid catalyst and then thermally polymerizing the resulting mixture; and rosin ester-based tackifying resins are preferred.

[0055] As the rosin-based tackifying resin, commercially available products can be used. For example, "HARIESTER TF", "HARIESTER S", "NEOTALL G2", "NEOTALL 101N", "NEOTALL 125HK", "HARITACK 8LJA", "HARITACK ER95", "HARITACK SE10", "HARITACK PH", "HARITACK F85", "HARITACK F105", "HARITACK FK100", "HARITACK FK125", and "HARITACK PCJ" manufactured by Harima Chemicals Co., Ltd.; "Foral 105-E", "Foral 85-E", and "Foral AX-E" manufactured by Eastman Chemical Co.; and "Superester A-75" and "Superester A-100," "Super Ester A-115," "Super Ester A-125," "Pensel A," "Pensel AZ," "Pensel C," "Pensel D-125," "Pine Crystal KE-100," "Pine Crystal KE-311," "Pine Crystal KE-359," "Pine Crystal KE-604," and "Pine Crystal KR-140" manufactured by GUANGDONG KOMO; "KF382S," "KF392S," "KF364," "KF384S," "KF394S," "KF398S," "KF399S," "KF452S," "KF462S," "KF454S," "KF464S," "KP120," "KP130," "KP140," "KP150," "K107," and "K108" manufactured by GUANGDONG KOMO.

[0056] Examples of terpene-based tackifying resins include terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers; and modified terpene resins obtained by modifying these terpene resins (e.g., phenol-modified, aromatic-modified, hydrogenated, hydrocarbon-modified, etc.). Examples of the modified terpene resins include terpene-modified phenolic resins, aromatic-modified terpene resins (e.g., styrene-modified terpene resins), and hydrogenated terpene resins. Among these, aromatic-modified terpene resins are preferred. Among the above-mentioned terpene-based tackifying resins (e.g., aromatic-modified terpene resins), one or more different types and properties (e.g., softening points) may be used in combination. Commercially available terpene-based tackifying resins can be used. Examples include YS Resin TO125 (manufactured by Yasuhara Chemical Co., Ltd.), YS Resin TH130 (manufactured by Yasuhara Chemical Co., Ltd.), and Alcon M115 (manufactured by Arakawa Chemical Industries, Ltd.).

[0057] Examples of hydrocarbon-based tackifying resins include various hydrocarbon resins such as aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic / aromatic copolymer (C5 / C9) petroleum resins, hydrogenated products thereof (for example, alicyclic petroleum resins (alicyclic saturated hydrocarbon resins) obtained by hydrogenating aromatic petroleum resins), various modified products thereof (for example, maleic anhydride modified products), coumarone resins, and coumarone-indene resins, with alicyclic saturated hydrocarbon resins being preferred. The hydrocarbon-based tackifying resins may be used alone or in combination of two or more.

[0058] Examples of styrene-based tackifying resins include styrene homopolymers, α-methylstyrene homopolymers, α-methylstyrene / styrene copolymers, styrene / aliphatic copolymers, α-methylstyrene / styrene / aliphatic copolymers, C9 petroleum resins, C5 / C9 petroleum resins, phenol-modified styrene resins, and hydrogenated products thereof. The styrene-based tackifying resins may be used alone or in combination of two or more.

[0059] Among these, styrene homopolymers, α-methylstyrene homopolymers, α-methylstyrene / styrene copolymers, styrene / aliphatic polymers, α-methylstyrene / styrene / aliphatic copolymers, phenol-modified styrene resins, and partially hydrogenated products thereof are preferred, and styrene homopolymers, α-methylstyrene homopolymers, α-methylstyrene / styrene copolymers, and partially hydrogenated products thereof are more preferred. These have excellent compatibility with (meth)acrylic block copolymers. Styrene homopolymers are particularly preferred.

[0060] As the styrene-based tackifying resin, commercially available products can be used. For example, "SYLVARES SA-85," "SYLVARES SA-100," "SYLVARES SA-120," "SYLVARES SA-140," and "SYLVARES 520" manufactured by Arizona Chemical Company; "ESCOLETZ ECR-213" and "ESCOLETZ ECR-807" manufactured by ExxonMobil Corporation; "YS Resin SX100" manufactured by Yasuhara Chemical Co.; "FTR0100," "FTR2120," "FTR2140," "FTR6100," "FTR6110," "FTR6125," "FTR7100," "FTR8100," "FTR8120," and "FMR0150" manufactured by Mitsui Chemicals, Inc.; and "Kristalex" manufactured by Eastman Chemical Company. Examples of such acrylic resins include "Kristalex F85", "Kristalex F100", "Kristalex F115", "Kristalex 1120", "Kristalex 3070", "Kristalex 3085", "Kristalex 3100", and "Kristalex 5140".

[0061] Examples of acrylic tackifying resins include acrylic tackifying resins based on acrylic polymers (homopolymers or copolymers) that use one or more (meth)acrylic acid alkyl esters as monomer components. Specific examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and butyl (meth)acrylate. Examples of (meth)acrylic acid C1-20 alkyl esters include nonyl acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. Of these, (meth)acrylic acid alkyl esters having a linear or branched alkyl group having 4 to 18 carbon atoms can be preferably used.

[0062] The acrylic polymer may contain, as necessary, units corresponding to other monomer components copolymerizable with the alkyl (meth)acrylate.

[0063] The amount of tackifier resin used per 100 parts by mass of hydroxyl group-terminated urethane prepolymer is not particularly limited, but from the viewpoint of obtaining a PSA that has sufficient adhesive strength to devices and sealants and also has sufficient long-term water resistance, it is preferably 0.5 to 150 parts by mass, more preferably 1.0 to 100 parts by mass, even more preferably 3.0 to 50 parts by mass, and even more preferably 5.0 to 40 parts by mass.

[0064] (Polyisocyanate Compound) The polyisocyanate compound is a curing agent for the hydroxyl group-terminated urethane prepolymer. The polyisocyanate compound is a compound having two or more isocyanate groups in one molecule, and may be used alone or in combination of two or more. As the polyisocyanate compound, a diisocyanate compound is preferred from the viewpoints of availability and reactivity. Furthermore, from the viewpoints of good adhesive strength of the adhesive and suppression of adhesive residue, a polyisocyanate compound having three or more isocyanate groups in one molecule is preferred.

[0065] Specific examples of the diisocyanate compound include the same as the specific examples of the diisocyanate compound constituting the hydroxyl group-terminated urethane prepolymer described above. Examples of the polyisocyanate compound having three or more isocyanate groups per molecule include isocyanurate-modified compounds, biuret-modified compounds, and allophanate-modified compounds, which are derivatives of the diisocyanate compounds described above, and trifunctional or higher isocyanate group-terminated urethane prepolymers (adducts), which are reaction products of diisocyanate compounds with polyols having three or more hydroxyl groups per molecule (e.g., trimethylolpropane).

[0066] The amount of polyisocyanate compound used relative to 100 parts by mass of the total of the hydroxyl group-terminated urethane prepolymer and the tackifier resin is not particularly limited, but from the viewpoint of obtaining a PSA that has sufficient adhesive strength to devices and sealants and also has sufficient long-term water resistance, it is preferably 0.5 to 100 parts by mass, more preferably 1.0 to 50 parts by mass, even more preferably 1.0 to 30 parts by mass, and still more preferably 1.0 to 10 parts by mass.

[0067] (Other Components) The pressure-sensitive adhesive composition may contain other components in addition to the hydroxyl-terminated urethane prepolymer, tackifying resin, and polyisocyanate compound. Examples of other components include various additives such as plasticizers, antioxidants, antistatic agents, fillers, UV absorbers, light stabilizers, conductivity-imparting agents, leveling agents, and polyols. A solvent may also be contained. These other components may be used alone or in combination of two or more, and may be blended in a content range that does not impair the effects of the present invention. In order to fully exhibit the effects of the present invention, the total content of the hydroxyl-terminated urethane prepolymer, tackifying resin, and polyisocyanate compound in the pressure-sensitive adhesive composition (excluding the solvent) is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even preferably 100% by mass.

[0068] The plasticizer can be selected from the viewpoints of compatibility with other components and wettability of the pressure-sensitive adhesive layer to the adherend, and examples thereof include fatty acid esters having 8 to 30 carbon atoms and phosphate esters. The antioxidant contributes to suppressing thermal degradation of the pressure-sensitive adhesive layer, and examples thereof include phenolic, amine, sulfur, and phosphorus antioxidants. Of these, phenolic antioxidants are preferred from the viewpoint of low irritation to the skin. The antistatic agent contributes to suppressing damage to the circuit pattern due to electrostatic discharge, and examples thereof include inorganic salts; ionic liquids containing imidazolium ions, pyridinium ions, ammonium ions, etc.; and surfactants. Examples of fillers include talc, calcium carbonate, and titanium oxide. Examples of UV absorbers include benzophenone-based, benzotriazole-based, salicylic acid-based, oxalic acid anilide-based, cyanoacrylate-based, and triazine-based UV absorbers. Examples of light stabilizers include hindered amine-based light stabilizers and UV stabilizers. Examples of conductivity-imparting agents include metal fine particles such as silver nanoparticles. Examples of the leveling agent include polymer leveling agents such as acrylic, vinyl, silicone, and fluorine-based leveling agents.

[0069] The PSA composition of the present embodiment may or may not further contain a polyol as an additional component. From the viewpoint of improving the adhesive strength of the PSA, the number-average molecular weight of the polyol is preferably 5,000 or less, more preferably 600 to 3,000. However, the PSA composition of the present embodiment is likely to produce a PSA with sufficient adhesive strength even without containing a polyol with a number-average molecular weight of 5,000 or less. From the viewpoint of suppressing damage to the skin due to excessive adhesive strength, the content of the polyol with a number-average molecular weight of 5,000 or less in the PSA composition is preferably less than 2.5 parts by mass, more preferably 0 to 2.0 parts by mass, and even more preferably 0 to 1.0 part by mass, per 100 parts by mass of the hydroxyl-terminated urethane prepolymer. Similarly, the content of the polyol other than the hydroxyl-terminated urethane prepolymer in the PSA composition is preferably less than 2.5 parts by mass, more preferably 0 to 2.0 parts by mass, and even more preferably 0 to 1.0 part by mass, per 100 parts by mass of the hydroxyl-terminated urethane prepolymer.

[0070] [Method for producing pressure-sensitive adhesive composition] The method for producing a pressure-sensitive adhesive composition of this embodiment involves reacting an oxyalkylene polymer having a number-average molecular weight of 3,000 or more with a diisocyanate compound to obtain a hydroxyl-terminated urethane prepolymer, and then mixing the hydroxyl-terminated urethane prepolymer, a tackifier resin, and a polyisocyanate compound. The pressure-sensitive adhesive composition of this embodiment described above can be suitably obtained by reacting the hydroxyl-terminated prepolymer thus obtained with a polyisocyanate compound. Note that when mixing the hydroxyl-terminated urethane prepolymer, the tackifier resin, and the polyisocyanate compound, other components that may be contained in the pressure-sensitive adhesive composition described above may also be mixed.

[0071] The hydroxyl-terminated urethane prepolymer is preferably obtained by reacting an oxyalkylene polymer having a number-average molecular weight of 3,000 or more with a diisocyanate compound in the presence of a tin-free catalyst. The oxyalkylene polymer having a number-average molecular weight of 3,000 or more, the diisocyanate compound, and the tin-free catalyst are the same as those described above. The hydroxyl-terminated urethane prepolymer can be produced, for example, by a method in which the oxyalkylene polymer, the diisocyanate compound, the tackifier resin, the catalyst, and the solvent are all charged into a reaction vessel at once, or by a method in which the diisocyanate compound is added dropwise or the like to a reaction vessel charged with the oxyalkylene polymer, the tackifier resin, the catalyst, and the solvent.

[0072] Examples of the solvent include ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; and aromatic hydrocarbons such as toluene and xylene. The solvent may be used alone or in combination of two or more. When a solvent is used, the amount used is preferably 50 to 500 parts by mass, more preferably 70 to 400 parts by mass, and even more preferably 80 to 300 parts by mass per 100 parts by mass of the oxyalkylene polymer in terms of the uniformity of the reaction system and synthesis efficiency.

[0073] Furthermore, from the viewpoint of efficiently obtaining a hydroxyl group-terminated urethane prepolymer having an appropriate molecular chain length, it is preferable to react the oxyalkylene polymer with the diisocyanate compound at an isocyanate index of less than 100, preferably 30 to 95, and more preferably 50 to 95.

[0074] From the viewpoint of promoting the urethanization reaction and suppressing side reactions, the reaction temperature is preferably less than 100° C., more preferably 70 to 95° C., and even more preferably 75 to 90° C. After completion of the reaction, a reaction terminator such as acetylacetone may be added to deactivate the catalyst.

[0075] The average number of hydroxyl groups per molecule of the hydroxyl-terminated urethane prepolymer is preferably less than 3.0, more preferably 1.7 to 2.9, and even more preferably 1.8 to 2.5, from the viewpoint of obtaining a pressure-sensitive adhesive having a good balance between adhesive strength to skin and adhesive strength to a device.

[0076] The isocyanate index of the polyisocyanate compound to be reacted with the hydroxyl-terminated urethane prepolymer is preferably greater than 100, more preferably from 101 to 1,500, and even more preferably from 105 to 1,000.

[0077] [Adhesive] The adhesive of this embodiment is a cured product of the adhesive composition of this embodiment described above. The adhesive is obtained by reacting and curing the hydroxyl group-terminated urethane prepolymer and the polyisocyanate compound in the adhesive composition. As described below, for example, the adhesive composition can be applied to a substrate and cured to form an adhesive layer.

[0078] In the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound, a catalyst and a solvent may be used as necessary. The solvents described in the above "Method for Producing a Pressure-Sensitive Adhesive Composition" section can be suitably used. These solvents may be the same or different, but are preferably the same. When a catalyst is used, the above-mentioned tin-free urethane catalyst can be used. The catalyst may be the same as or different from the catalyst used in the synthesis of the hydroxyl-terminated urethane prepolymer. If the catalyst used in the synthesis of the hydroxyl-terminated urethane prepolymer remains, the remaining catalyst can also exert a catalytic effect in the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound. When a catalyst is added during the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound, the amount added is preferably more than 0.001 part by mass and not more than 0.1 part by mass, preferably 0.005 to 0.05 parts by mass, and more preferably 0.01 to 0.04 parts by mass, per 100 parts by mass of the combined total of the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound. When a catalyst is added, it is preferable to add a reaction terminator after the reaction to deactivate the catalyst.

[0079] The solvent used in the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound may be the same as that used in the synthesis of the hydroxyl-terminated urethane prepolymer described above. The solvent may be the same as or different from that used in the synthesis of the hydroxyl-terminated urethane prepolymer. If any solvent remains from the synthesis of the hydroxyl-terminated urethane prepolymer, it may be used as is. When a solvent is used, the amount used is preferably 50 to 500 parts by mass, more preferably 70 to 400 parts by mass, and even more preferably 80 to 300 parts by mass per 100 parts by mass of the total of the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound.

[0080] The reaction temperature between the hydroxyl group-terminated urethane prepolymer and the polyisocyanate compound is preferably less than 120°C, more preferably 40 to 110°C, and even more preferably 50 to 100°C, from the viewpoint of promoting the urethane reaction and suppressing side reactions.

[0081] [Patch] The patch of the present embodiment has a substrate and a pressure-sensitive adhesive layer provided on at least a part of the surface of the substrate, and the pressure-sensitive adhesive layer contains the pressure-sensitive adhesive of the present embodiment described above. A patch having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of the present embodiment can provide a pressure-sensitive adhesive that can achieve sufficient adhesion to a device and a sealant and has sufficient long-term water resistance.

[0082] The patch may be in the form of a sheet of a desired size depending on the mode of use, or may be cut to a desired size for use. From the viewpoint of convenience, the patch is preferably an adhesive tape.

[0083] The pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer may be a one-component type in which a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound as a curing agent are pre-mixed, depending on the mode of use of the patch, or may be a two-component type consisting of a first part containing a hydroxyl-terminated urethane prepolymer and a second part containing a polyisocyanate compound as a curing agent.

[0084] The thickness of the adhesive layer is preferably 5 to 100 μm, more preferably 10 to 80 μm, and even more preferably 20 to 50 μm, from the viewpoint of ensuring good adhesive strength to the skin.

[0085] The substrate is preferably made of a material that has good conformability to the skin of the patch or the shape of the device and is not easily broken during use of the patch, and examples thereof include resin films, cloths, paper, etc. The substrate may be made of one type alone or two or more types in combination, or may be a composite material formed by lamination or the like. Examples of materials for the resin film include polyurethane, polyamide, acrylic resin, polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer, and polyester, with polyester film being preferred. Examples of cloth include woven fabrics, nonwoven fabrics, knitted fabrics, and nets, and examples of materials include the resins used for the resin films described above, as well as natural fibers such as cotton, silk, and wool.

[0086] The thickness of the substrate is not particularly limited as long as it can ensure conformability to the shape of the skin and the device and is not easily broken when the patch is used, but is preferably 10 to 500 μm, more preferably 20 to 400 μm.

[0087] The surface of the adhesive layer of the patch is preferably covered with a release liner to protect the surface of the adhesive layer before use. The release liner is appropriately peeled off from the surface of the adhesive layer when the patch is used. Release liners used in known adhesive tapes for skin can be applied. Examples of release liners include high-quality paper, glassine paper, and parchment paper coated with a release agent such as silicone resin or fluororesin, as well as resin anchor coated or polyethylene-laminated high-quality paper coated with a release agent such as silicone resin or fluororesin. Transparent resin films can also be used as release liners, such as polyester films. The thickness of the release liner is not particularly limited as long as it can protect the adhesive layer and is easy to peel off during use, and is, for example, 15 to 200 μm.

[0088] The pressure-sensitive adhesive layer may be provided, for example, in one or more locations on a portion of the surface of the resin film substrate, on only a portion of one side, or on the entire surface of one side, or on both sides of the surface of the substrate.

[0089] When the pressure-sensitive adhesive layer is adhered to a sealing material or the like of a device, the adhesive strength to, for example, phenolic resin, which is a common material for sealing materials, is preferably 2.5 N / 15 mm or more, more preferably 3.0 N / 15 mm or more, from the viewpoint of well fixing the device.

[0090] Similarly, from the viewpoint of favorably fixing the device, the adhesive strength to the phenolic resin after the adhesive layer is attached to the phenolic resin and then immersed in a container of tap water at 23°C for 7 days is preferably 1.0 N / 15 mm or more, more preferably 2.5 N / 15 mm or more, and even more preferably 3.0 N / 15 mm or more.

[0091] When the pressure-sensitive adhesive layer is adhered to a sealant or the like for a device, the adhesive strength to, for example, SUS steel plate, which is a common material for devices, is preferably 2.0 N / 15 mm or more, more preferably 2.5 N / 15 mm or more, and even more preferably 3.0 N / 15 mm or more, from the viewpoint of favorable fixation of the device. The adhesive strength referred to here is a value measured according to a method in accordance with JIS Z 0237:2009, and specifically, is measured by the method described in the examples.

[0092] The adhesive patch can be produced using known methods, such as a method of applying a pressure-sensitive adhesive composition to a release liner, curing the composition to form a pressure-sensitive adhesive layer, and laminating a substrate. Another example is a method of applying a pressure-sensitive adhesive composition to a substrate, curing the composition to form a pressure-sensitive adhesive layer, and laminating a release liner. The method for applying the pressure-sensitive adhesive composition is not particularly limited, and known methods such as bar coating, knife coating, roll coating, blade coating, die coating, microgravure coating, comma coating, slot die coating, lip coating, and cast coating can be used. After application, the pressure-sensitive adhesive composition is preferably cured by, for example, hot air drying at 40 to 80°C to sufficiently volatilize the solvent contained in the pressure-sensitive adhesive composition, thereby forming a pressure-sensitive adhesive layer.

[0093] [Wearable Device] The wearable device of the present embodiment is a wearable device having a wearable device main body and an adhesive layer, the adhesive layer being provided on at least a portion of the surface of the wearable device facing the skin and containing the adhesive of the present embodiment. By using the adhesive composition of the present embodiment described above, an adhesive layer is formed that has a good balance of adhesive strength to the skin and adhesive strength to the device, and is gentle on the skin. For this reason, the adhesive of the present embodiment is suitable for application to wearable devices that are attached to the skin.

[0094] The adhesive layer can be formed in the form of the adhesive patch described above, for example. Alternatively, the adhesive layer can be formed in a form sandwiched between release liners on both sides, and the wearable device body can be adhered to the skin via the adhesive layer alone, without using a substrate.

[0095] Examples of wearable devices that are attached to the skin include biosensors and environmental sensors, which can detect, for example, cardiac potential, pulse wave, body temperature, acceleration, heart rate, pulse rate, respiratory rate, electrocardiogram, electromyogram, activity level, blood pressure, and electroencephalogram.

[0096] [Wearable Device Kit] The wearable device kit of this embodiment includes a wearable device main body and at least one of the adhesive of this embodiment and the patch of this embodiment. In this way, the wearable device main body does not have to have an adhesive layer in advance, but may include the adhesive or the patch as a separate component so that the adhesive layer can be formed during use. The adhesive and the patch may be used alone or in combination.

[0097] The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples, and various modifications are possible within the scope of the gist of the present invention.

[0098] [Measurement Methods] The methods for measuring various physical properties in the following synthesis examples are as follows.

[0099] <Number average molecular weight (Mn) and weight average molecular weight (Mw)> Mn and Mw were measured by gel permeation chromatography (GPC) under the following measurement conditions (polystyrene equivalent), and the molecular weight distribution (Mw / Mn) was calculated from these values. [Measurement conditions] - Instrument used: "HLC-8320GPC", manufactured by Tosoh Corporation - Column used: "TSKgel (registered trademark) SuperMultiporeHZ-M", manufactured by Tosoh Corporation - Detector: Refractive index (RI) detector - Detection temperature: 40°C - Eluent: Tetrahydrofuran - Flow rate: 0.350 mL / min - Sample concentration: 0.5% by mass - Sample injection amount: 10 μL - Standard sample: Polystyrene

[0100] <Ethylene oxide (EO) unit content> The EO unit content of each oxyalkylene polymer was determined based on the amounts of propylene oxide (PO) and EO used in the synthesis, and the amount of EO charged was considered to be the EO unit content in the oxyalkylene polymer. The EO unit content of the hydroxyl group-terminated urethane prepolymer was determined as the weighted average of the EO unit contents in each of the raw material components.

[0101] <Hydroxyl Value> The hydroxyl value was determined in accordance with Method B (automatic potentiometric titration) of JIS K 1557-1:2007.

[0102] <Degree of Unsaturation> The degree of unsaturation was measured in accordance with JIS K 1557-3:2007.

[0103] <Average number of hydroxyl groups per molecule of oxyalkylene polymer A> The average number of hydroxyl groups per molecule of oxyalkylene polymer A was determined by calculating the weighted average of the numbers of hydroxyl groups per molecule of oxyalkylene polymers A1 and A2 used as oxyalkylene polymer A (the number of hydroxyl groups per molecule of the initiator used in the synthesis of each oxyalkylene polymer) based on the blending amount of each oxyalkylene polymer.

[0104] <Average Number of Hydroxyl Groups per Molecule of Hydroxyl-Terminated Urethane Prepolymer> The number of hydroxyl groups per molecule of each oxyalkylene polymer and each diisocyanate compound used in the synthesis of the hydroxyl-terminated urethane prepolymer was weighted and averaged based on the blending amount of each oxyalkylene polymer and each diisocyanate compound, and this value was regarded as the average number of hydroxyl groups per molecule.

[0105] [Materials Used] Details of the materials used in the following synthesis examples and examples are shown below. (1) Initiator TBA-DMC catalyst: zinc hexacyanocobaltate complex with tert-butanol as a ligand (2) Adsorbent Adsorbent: synthetic magnesium silicate; "Kyoward (registered trademark) 600S", manufactured by Kyowa Chemical Industry Co., Ltd. (3) Polyisocyanate compound 50M-HDI: hexamethylene diisocyanate (HDI); "Duranate (registered trademark) 50M-HDI", manufactured by Asahi Kasei Corporation D201: HDI-based bifunctional isocyanate-terminated prepolymer; "Duranate (registered trademark) D201", manufactured by Asahi Kasei Corporation (4) Urethane catalyst Bismuth neodecanoate; bismuth (Bi)-containing urethane catalyst; manufactured by Sigma-Aldrich Corporation XK627: zinc carboxylate; zinc (Zn)-containing urethane catalyst; "K-KAT XK627", manufactured by KING INDUSTRIES (5) Curing agent Curing agent (polyisocyanate compound): HDI-based polyisocyanate; "Duranate (registered trademark) E402-80B", manufactured by Asahi Kasei Corporation; solid content 80% by mass (6) Tackifying resin Styrene resin: "YS Resin (registered trademark) SX100", manufactured by Yasuhara Chemical Co., Ltd., softening point 100 ° C. Terpene phenol resin: "YS Resin (registered trademark) TH130", manufactured by Yasuhara Chemical Co., Ltd., softening point 130 ° C. Alpha methyl styrene resin: "SYLVARES SA140", manufactured by Kraton Polymer Japan Co., Ltd., softening point 137 ° C. Phenol-modified alpha methyl styrene resin: "SYLVARES 520", manufactured by Kraton Polymer Japan Co., Ltd., softening point 75 ° C. (7) Oxyalkylene polymer A1: Oxyalkylene polymer synthesized in Synthesis Example 1-1 A2: Oxyalkylene polymer synthesized in Synthesis Example 1-2 B1: Oxyalkylene polymer synthesized in Synthesis Example 1-3 A3: Oxyalkylene polymer synthesized in Synthesis Example 1-4 A'1: "EXENOL903", manufactured by AGC Inc. A'2: "EXENOL2026T", manufactured by AGC Inc. B'1: "PREMINOL1002", manufactured by AGC Inc.

[0106] [Synthesis of Oxyalkylene Polymer] (Synthesis Example 1-1) 1000 g of glycerin as an initiator and a TBA-DMC catalyst (metal concentration 46 ppm by mass) were placed in a pressure vessel, and the vessel was purged with nitrogen. The reaction solution was heated to 135°C while stirring, and 120 g of propylene oxide (PO) was added and reacted. After the temperature rise of the reaction solution stopped, it was cooled to 135°C, and while stirring the reaction solution, 3782.4 g of PO and 945.6 g of ethylene oxide (EO) were added to the vessel. After confirming that the internal pressure had stopped changing, an adsorbent was added, and neutralization and catalyst removal were performed to obtain an oxyalkylene polymer A1.

[0107] Synthesis Example 1-2 Oxyalkylene polymer A2 was synthesized in the same manner as in Synthesis Example 1-1, except that the initiator in Synthesis Example 1-1 was changed from glycerin to propylene glycol.

[0108] Synthesis Example 1-3 Oxyalkylene polymer B1 was synthesized in the same manner as in Synthesis Example 1-1, except that the initiator in Synthesis Example 1-1 was changed from glycerin to n-butanol, and after cooling the reaction solution, 2364 g of PO was added instead of EO.

[0109] Synthesis Example 1-4 Oxyalkylene polymer A3 was synthesized in the same manner as in Synthesis Example 1-1, except that the initiator in Synthesis Example 1-1 was changed from glycerin to propylene glycol and EO was not added after cooling the reaction solution.

[0110] Table 1 shows various physical properties of the oxyalkylene polymers A1 to A3 and B1 synthesized as described above, and the commercially available oxyalkylene polymers A'1, A'2 and B'1.

[0111]

[0112] [Synthesis of Hydroxyl-Terminated Urethane Prepolymer] (Synthesis Example 2-1) A reaction vessel equipped with a thermometer, a stirrer, and a cooling tube was charged with 45 parts by mass of oxyalkylene polymer A1, 35 parts by mass of oxyalkylene polymer A3, 20 parts by mass of oxyalkylene polymer B1, 50.6 parts by mass of toluene, and 50.6 parts by mass of ethyl acetate, and 0.038 parts by mass of K-KAT XK-627 was added and mixed at 40 ° C. After which 1.7 parts by mass of HDI (isocyanate index 85) was added and reacted at 80 ° C. While appropriately diluting with ethyl acetate, the temperature was maintained at 80 ° C. and the reaction was carried out for 7 hours to obtain a 50% by mass solution of a transparent hydroxyl-terminated urethane prepolymer (urethane prepolymer U1; average number of hydroxyl groups 2.2, EO unit content 9% by mass).

[0113] Synthesis Example 2-2 A 50% by mass solution of a hydroxyl group-terminated urethane prepolymer (also referred to as "urethane prepolymer U2") was produced in the same manner as in Synthesis Example 2-1, except that the diisocyanate compound HDI was changed to D-201 (isocyanate index 85) and the amount added was changed as shown in Table 2.

[0114] Synthesis Example 2-3 A 50% by mass solution of a hydroxyl group-terminated urethane prepolymer (also referred to as "urethane prepolymer U3") was produced in the same manner as in Synthesis Example 2-1, except that the catalyst K-KAT XK-627 was changed to bismuth neodecanoate and the amount of bismuth neodecanoate added was changed as shown in Table 2.

[0115] Synthesis Example 2-4 A 50% by mass solution of a hydroxyl group-terminated urethane prepolymer (also referred to as "urethane prepolymer U4") was produced in the same manner as in Synthesis Example 2-2, except that the catalyst K-KAT XK-627 was changed to bismuth neodecanoate and the amount of bismuth neodecanoate added was changed as shown in Table 2.

[0116] Synthesis Example 2-5 A 50% by mass solution of a hydroxyl group-terminated urethane prepolymer (also referred to as "urethane prepolymer U5") was produced in the same manner as in Synthesis Example 2-1, except that the type and amount of the oxyalkylene polymer were changed as shown in Table 2.

[0117] Synthesis Example 2-6 A 50% by mass solution of a hydroxyl group-terminated urethane prepolymer (also referred to as "urethane prepolymer U6") was produced in the same manner as in Synthesis Example 2-1, except that the type and amount of the oxyalkylene polymer were changed as shown in Table 2.

[0118] Table 2 shows the blending compositions of the oxyalkylene polymer, diisocyanate compound and catalyst in Synthesis Examples 2-1 to 2-6.

[0119]

[0120] [Production of Adhesive Material] (Example 1) 180 parts by mass of a 50% by mass solution of hydroxyl-terminated urethane prepolymer U1 (equivalent to 90 parts by mass of hydroxyl-terminated urethane prepolymer U1), 10 parts by mass of tackifier resin YS Resin SX100, and 5 parts by mass of curing agent were mixed to obtain a pressure-sensitive adhesive composition. After degassing the pressure-sensitive adhesive composition, it was applied to a polyester film (thickness 38 μm) serving as a release liner using a knife coater and dried at 100°C for 2 minutes to form a 25 μm thick adhesive (adhesive layer). A polyester film (thickness 75 μm) serving as a substrate was bonded to this pressure-sensitive adhesive layer, and the layer was cured in a hot air dryer at 40°C for 3 days to produce a patch.

[0121] Examples 2 to 14 Patches were prepared in the same manner as in Example 1, except that the formulation was changed as shown in Table 3.

[0122] Example 15 An adhesive patch was prepared in the same manner as in Example 1, except that the substrate was changed from polyester film (thickness 75 μm) to nonwoven fabric (thickness 200 μm).

[0123] Examples 16 to 28 Patches were prepared in the same manner as in Examples 2 to 14, except that the substrate was changed from polyester film (thickness 75 μm) to nonwoven fabric (thickness 200 μm).

[0124] [Evaluation of Patches] The following various evaluations were carried out for each of the patches produced in Examples 1 to 28 above. Table 3 shows the evaluation results for Examples 1 to 14. Examples 1 to 10 are working examples, and Examples 11 to 14 are comparative examples. In Examples 15 to 28, in which the substrate was changed from polyester film (thickness 75 μm) to nonwoven fabric (thickness 200 μm), evaluation results similar to those of Examples 1 to 14 were obtained. Examples 15 to 24 are working examples, and Examples 25 to 28 are comparative examples.

[0125] <Adhesive Strength> (Against Phenol Resin (Leaved to Stand for 20 Minutes)) The adhesive layer side of a patch (100 mm long, 15 mm wide) from which the release liner had been peeled off was placed on a phenolic resin plate ("SUMILITE (registered trademark) PL-1102", manufactured by Sumitomo Bakelite Co., Ltd.; 125 mm long, 30 mm wide, 2 mm thick), and a rubber roller was rolled back and forth from the substrate side of the patch at a load of 2 kg and a speed of 300 mm / min, thereby pressing the adhesive layer against the phenolic resin plate. After leaving to stand for 20 minutes, the patch was peeled off at a peel angle of 90° and a speed of 300 mm / min, and the adhesive strength when the adherend was a phenolic resin (against phenolic resin) was measured using a method in accordance with JIS Z 0237:2009.

[0126] Table 3 shows the average of three measurements. The measured adhesive strength was evaluated according to the following criteria: [Evaluation criteria (against phenolic resin)] A: 3.0 N / 15 mm or more B: 2.5 N / 15 mm or more and less than 3.0 N / 15 mm C: 2.0 N / 15 mm or more and less than 2.5 N / 15 mm D: Less than 2.0 N / 15 mm

[0127] In the case of grade A, it can be said that the adhesive strength to phenolic resin, which is a typical material for sealing circuit patterns in wearable devices, is sufficient. On the other hand, in the cases of grades B to D, the adhesive strength to phenolic resin was insufficient.

[0128] (Against phenolic resin (23°C, 100%, after 7 days)) In the same manner as in "Against phenolic resin (left standing for 20 minutes)" above, a pressure-sensitive adhesive layer was pressure-bonded to a phenolic resin plate. The phenolic resin plate with the pressure-sensitive adhesive layer pressure-bonded was immersed in a container filled with tap water at 23°C. After 7 days, the phenolic resin plate was removed from the container, lightly wiped to remove any moisture, and then within 30 minutes the pressure-sensitive adhesive layer was peeled off at a peel angle of 90° and a speed of 300 mm / min to measure the adhesive strength. Table 3 shows the average of three measured values. The measured adhesive strength was also evaluated according to the following evaluation criteria. In this test, pressure-sensitive adhesives rated B or higher have excellent long-term water resistance and can be used without any problems in practical use. Pressure-sensitive adhesives rated A have particularly excellent long-term water resistance. [Evaluation criteria (phenolic resin board, 23°C, 100% humidity, after 7 days)] A: 2.0 N / 15 mm or more B: 1.0 N / 15 mm or more but less than 2.0 N / 15 mm C: Less than 1.0 N / 15 mm

[0129] (Against SUS) The adhesive layer side of each adhesive sheet (100 mm long, 25 mm wide) from which the release liner had been peeled was placed on a SUS steel plate (manufactured by Standard Test Piece Co., Ltd.; 125 mm long, 30 mm wide, 2 mm thick), and a rubber roller was rolled back and forth from the substrate side of the adhesive sheet at a load of 2 kg and a speed of 600 mm / min to press the adhesive layer onto the SUS steel plate. After leaving to stand for 20 minutes, the adhesive sheet was peeled off at a peel angle of 90° and a speed of 300 mm / min, and the adhesive strength was measured according to a method in accordance with JIS Z 0237:2009. Table 3 shows the average of three measured values. The measured adhesive strength was also evaluated according to the following evaluation criteria. [Evaluation criteria (SUS)] A: 3.0 N / 15 mm or more B: 2.5 N / 15 mm or more and less than 3.0 N / 15 mm C: Less than 2.5 N / 15 mm Evaluations of A and B indicate good adhesive strength to SUS steel plates, which is the standard of JIS Z 0237:2009.

[0130] (Against Skin) When the adherend was the skin of the forearm of a human (three subjects), the adhesive strength was measured in the same manner as when the adherend was a phenolic resin.

[0131] The average values ​​of the measured values ​​are shown in Table 3. The measured adhesive strength was evaluated according to the following evaluation criteria: [Evaluation criteria (against skin)] A: 1.0 N / 15 mm or more and 3.0 N / 15 mm or less B: More than 3.0 N / 15 mm and 5.0 N / 15 mm or less C: Less than 1.0 N / 15 mm D: More than 5.0 N / 15 mm

[0132] In the case of rating A, it can be said that the adhesive strength to the skin is appropriate. In the case of rating B, the adhesive strength is sufficient, but is somewhat strong, and resistance is felt when peeling compared to the case of rating A. In the case of rating C, the adhesive strength is too weak and it peels easily. In the case of rating D, the adhesive strength is strong and it is difficult to peel. Ratings A and B have adhesive strength suitable for practical use.

[0133] <Skin Observation> In an atmosphere of 23°C and 50% RH, a test piece of the patch (20 mm long, 15 mm wide) was applied to the skin of the forearm of humans (3 subjects). After 1 hour, the test piece was peeled off the skin and the condition of the skin was visually observed. The observation results were evaluated according to the following evaluation criteria. In this test, adhesives rated B or higher are safe for application to the skin and can be used without any practical problems. Adhesives rated A are particularly safe for application to the skin. [Evaluation Criteria] A: No change from before application of the test piece. B: Some subjects noticed redness on the skin. C: Some subjects noticed residual glue (adhesive residue).

[0134]

[0135] The adhesives of Examples 1 to 10 combine low adhesion to the skin with high adhesion to the substrate, have good long-term water resistance, and ensure safe application to the skin. In contrast, the adhesives of Examples 11 and 12 did not contain a tackifier resin, and therefore did not adhere well to SUS interfaces and had poor adhesion to SUS steel plates. The adhesives of Examples 13 and 14 used hydroxyl-terminated urethane prepolymer U6, which uses an oxyalkylene polymer with a small number average molecular weight. Therefore, regardless of the presence or absence of a tackifier resin, they did not have excellent long-term water resistance and did not have enough cohesive strength to SUS steel plates, making it impossible to achieve sufficient adhesion.

Claims

1. A pressure-sensitive adhesive composition comprising a hydroxyl-terminated urethane prepolymer, a tackifier resin and a polyisocyanate compound, wherein the hydroxyl-terminated urethane prepolymer is a reaction product of an oxyalkylene polymer having a number average molecular weight of 3,000 or more and a diisocyanate compound.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the hydroxyl-terminated urethane prepolymer is a reaction product of an oxyalkylene polymer having a number average molecular weight of 3,000 or more with a diisocyanate compound in the presence of a tin-free catalyst.

3. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the tackifier resin has a softening point of 70° C. or higher.

4. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the tackifier resin is a terpene-based tackifier resin or a styrene-based tackifier resin.

5. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the hydroxyl-terminated urethane prepolymer has a content of structural units based on ethylene oxide of 8 to 55 mass %.

6. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the oxyalkylene polymer comprises an oxyalkylene polymer A having two or more hydroxyl groups per molecule, and an oxyalkylene polymer B having one hydroxyl group per molecule.

7. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the weight-average molecular weight of the hydroxyl-terminated urethane prepolymer is 50,000 or more.

8. A method for producing a pressure-sensitive adhesive composition, comprising reacting an oxyalkylene polymer having a number average molecular weight of 3,000 or more with a diisocyanate compound to obtain a hydroxyl-terminated urethane prepolymer, and mixing the hydroxyl-terminated urethane prepolymer, a tackifier resin, and a polyisocyanate compound.

9. The method for producing a pressure-sensitive adhesive composition described in claim 8, wherein the hydroxyl-terminated urethane prepolymer is a reaction product of an oxyalkylene polymer having a number average molecular weight of 3,000 or more and a diisocyanate compound in the presence of a tin-free catalyst.

10. The method for producing a pressure-sensitive adhesive composition according to claim 9, wherein the amount of the tin-free catalyst is more than 0.001 part by mass and not more than 0.1 part by mass per 100 parts by mass of the oxyalkylene polymer.

11. A pressure-sensitive adhesive which is a cured product of the pressure-sensitive adhesive composition according to claim 1.

12. A patch comprising a substrate and an adhesive layer provided on at least a portion of the surface of the substrate, the adhesive layer comprising the adhesive according to claim 11.

13. The adhesive material according to claim 12, which is an adhesive tape.

14. A wearable device having a wearable device body and an adhesive layer, the adhesive layer being provided on at least a portion of a surface of the wearable device that faces the skin, and comprising the adhesive described in claim 11.

15. A wearable device kit comprising a wearable device body and at least one of the adhesive according to claim 11 and the patch according to claim 13.