Adhesive composition and method of producing the same

Abstract

To provide an adhesive composition having excellent adhesive force and cooling-enhanced peelability, and to provide a method of producing the same.SOLUTION: Provided is an adhesive composition that satisfies the following characteristics (1) and (2) when an inclined ball tack test is performed under the conditions that the adhesive composition is molded into a plate shape having a length of 150 mm, a width of 20 mm, and a thickness of 0.2 mm to obtain a test piece, the test piece is attached to an upper portion of a slope whose inclination angle with respect to the ground and temperature can be controlled such that an inclination direction of the slope and a length direction of the test piece coincide with each other, the inclination angle is set to 20°, a portion from 0 mm to 50 mm in the length direction from the top of the slope of the test piece is set as an approach portion, and a portion from 50 mm to 150 mm from the top of the slope of the test piece in the length direction is set as measurement portion. (1) The ball number of the largest ball that stops for 5 seconds or more in the measurement unit when the temperature of the inclined surface is 36°C, is 7 or more. (2) The ball number of the largest ball that stops for 5 seconds or more in the measurement portion when the temperature of the inclined surface is 4°C, is less than 3.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition and a method for producing the same. [Background technology]

[0002] Pressure-sensitive adhesive compositions have various properties such as adhesion, conformability, cooling properties, water absorption, swelling properties, moisture retention properties, and electrical conductivity, and by utilizing these properties, they are used in a wide range of fields such as medicine, cosmetics, beauty, electricity, sports, and food.

[0003] In the medical field, attention has been focused on stimulus-easily peelable adhesive compositions that have the property of undergoing a rapid phase transition from an adhesive state to a non-adhesive state in response to an external stimulus, and these compositions are used in surgical tapes, dressing films, etc.

[0004] As a conventionally known irritation-sensitive peelable adhesive composition, for example, Patent Document 1 discloses a medical adhesive tape that can be peeled off by irradiation with ultraviolet light.

[0005] Patent Document 2 discloses a medical adhesive composition that can be peeled off by heating.

[0006] Patent Document 3 discloses a medical device including an electrically peelable pressure-sensitive adhesive for application to the skin, which comprises a conductive member and a pressure-sensitive adhesive layer in direct contact with the conductive member. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 1-240589 [Patent Document 2] Patent Publication No. 2023-045488 [Patent Document 3] WO-A1-2021 / 180809 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the stimuli-sensitive peelable adhesives disclosed in Patent Documents 1 to 3 peel off when stimulated by ultraviolet light, which is harmful to the skin, heat, which poses a risk of skin burns, or electricity, which poses a risk of electric shock, and therefore pose a problem of being dangerous, particularly when used on the skin or in medical applications.

[0009] There is a need for the development of a stimuli-sensitive adhesive that can undergo a phase transition to a non-adhesive state with mild stimulation without causing damage to the skin or other surfaces when peeled off.

[0010] The problem to be solved by the present invention is to provide a pressure-sensitive adhesive composition having excellent adhesive strength and easy peelability upon cooling, and a method for producing the same. [Means for solving the problem]

[0011] The present invention encompasses the embodiments described below. [1] An adhesive composition, The adhesive composition is formed into a plate having a length of 150 mm, a width of 20 mm, and a thickness of 0.2 mm to prepare a test piece, and the test piece is attached to the top of a slope whose inclination angle with respect to the ground and temperature can be controlled so that the inclination direction of the slope coincides with the length direction of the test piece.When an inclined ball tack test is performed under the conditions of setting the inclination angle to 20°, using a runway from 0 mm to 50 mm in the length direction from the top of the slope of the test piece, and a measurement area from 50 mm to 150 mm in the length direction from the top of the slope of the test piece, the adhesive composition satisfies the properties (1) and (2) below. (1) When the temperature of the slope is 36°C, the ball number of the largest ball that stops in the measuring section for 5 seconds or more is 7 or more. (2) When the temperature of the slope is 4°C, the ball number of the largest ball that stops in the measuring section for 5 seconds or more is less than 3. [2] An adhesive composition comprising a crystalline oil containing at least one selected from the group consisting of an ester represented by formula (1) and an ester represented by formula (2), and a polymer matrix, the storage modulus G'(35°C) of the pressure-sensitive adhesive composition at 35°C is 100,000 Pa or less; The pressure-sensitive adhesive composition has a storage modulus G'(0°C) of 200,000 Pa or more at 0°C, and The adhesive composition according to [1], wherein the value obtained by dividing G'(0°C) by G'(35°C) [G'(0°C) / G'(35°C)] is 10 or more. R 1 -COO-R 2 (1) [In formula (1), R 1 represents a linear or branched alkyl or alkenyl group having 1 to 22 carbon atoms, R 2 represents a linear, branched, or cyclic alkyl group, alkenyl group, or ether having 1 to 34 carbon atoms; R 2 may have a hydroxyl group.] (R 3 O)-CHCH(OR 4 )-CH2(OR 5 ) (2) [In formula (2), R 3 , R 4 and R 5 are each independently a hydrogen atom or a group represented by formula (2-1), R 3 , R 4 and R 5 At least one selected from the group consisting of is a group represented by formula (2-1). -CO-R 6 (2-1) [In formula (2-1), R 6 represents an alkyl or alkenyl group having 7 to 27 carbon atoms which may have a hydroxyl group. [3] The adhesive composition described in [2], wherein the content of the crystalline oil is 30 to 65 parts by mass when the total mass of the crystalline oil and the polymer matrix is ​​100 parts by mass. [4] The adhesive composition according to [2] or [3], wherein the polymerizable monomer constituting the polymer matrix contains a hydrophobic monomer. [5] The pressure-sensitive adhesive composition described in [4], wherein the hydrophobic monomer comprises at least one selected from the group consisting of an acrylic monomer, an acrylamide monomer, a urethane monomer, and an acrylic silicone monomer. [6] The pressure-sensitive adhesive composition according to [4], wherein the hydrophobic monomer comprises at least one selected from the group consisting of 4-tert-butylcyclohexyl acrylate (TBCHA) and isobornyl acrylate (IBXA). [7] The adhesive composition according to any one of [1] to [6], wherein the content of water is less than 5 mass % relative to 100 mass parts of the adhesive composition. [8] A medical adhesive composition comprising the adhesive composition according to any one of [1] to [7]. [9] A nail adhesive comprising the pressure-sensitive adhesive composition according to any one of [1] to [7].

[10] A method for producing the pressure-sensitive adhesive composition according to any one of [1] to [7], comprising: A step of mixing at least one selected from the group consisting of an ester represented by formula (1) and an ester represented by formula (2), a hydrophobic monomer, and a crosslinkable monomer to obtain a polymerizable solution; and A step of curing the polymerizable solution by irradiating it with ultraviolet light. A method for producing a pressure-sensitive adhesive composition comprising: [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition having excellent adhesive strength and easy peelability upon cooling, and a method for producing the same. [Brief explanation of the drawings]

[0013] [Figure 1] A schematic diagram of the tilted ball tack test is shown. DETAILED DESCRIPTION OF THE INVENTION

[0014] As used herein, the singular forms "a," "an," and "the" are intended to include both the singular and the plural unless otherwise expressly stated herein or clearly contradicted by context.

[0015] In this specification, the term "comprise" is a concept that encompasses "consist essentially only of" and "consist only of."

[0016] In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example or a value that can be unambiguously derived from an example. Furthermore, in this specification, a numerical value connected with "~" means a numerical range that includes the numbers before and after "~" as the upper and lower limits.

[0017] According to one aspect of the present invention, there is provided an adhesive composition, which satisfies the following conditions (1) and (2) when an inclined ball tack test is performed under the conditions that the adhesive composition is formed into a plate of 150 mm in length, 20 mm in width, and 0.2 mm in thickness to form a test piece, the test piece is attached to the top of a slope whose inclination angle with respect to the ground and temperature can be controlled so that the inclination direction of the slope coincides with the length direction of the test piece, the inclination angle is 20°, the portion of the test piece from the top of the slope in the lengthwise direction is the runway, and the portion of the test piece from the top of the slope in the lengthwise direction is the 50 mm to 150 mm, the adhesive composition satisfies the following conditions (1) and (2): (1) When the temperature of the slope is 36°C, the largest ball that stops in the measuring area for 5 seconds or more has a ball number of 7 or more. (2) When the temperature of the slope is 4°C, the ball number of the largest ball that stops in the measuring area for 5 seconds or more is less than 3.

[0018] Inclined Ball Tack Test The ball tack test is a test that can measure the tack when an adhesive composition or the like comes into contact with an adherend, that is, the stickiness when it adheres, and is specified in JIS Z 0237:2009.

[0019] In the present invention, the inclined ball tack test can be carried out in accordance with JIS Z 0237:2009 by the following procedure (FIG. 1).

[0020] A temperature-controllable hot plate or cool plate 10 is tilted 20° relative to the horizontal plane 30 to create an inclined surface. An aluminum plate 12 measuring 150 mm long, 25 mm wide, and 0.5 mm thick is placed on this inclined surface with double-sided tape. This serves as the temperature-controlled inclined surface, and the test temperature is set as desired. A pressure-sensitive adhesive composition 14 is molded to a length of 150 mm, width of 20 mm, and thickness of 0.2 mm, and covered on both sides with PET film. The PET film on one side is peeled off and the test piece is attached to the temperature-controlled inclined surface. The PET film 16 is then left intact on the runway 18 50 mm above the inclined surface, and the PET film on the measurement section 20 100 mm below the inclined surface is peeled off to expose the adhesive surface. Next, 30 sizes of steel balls (22) were prepared, ranging in diameter from 3 / 32 to 1 / 10 in the "inch" series of nominal diameters specified in JIS B 1501:2009 (excluding 5 / 64, 7 / 64, 9 / 64, 11 / 64, 13 / 64, 15 / 64, 17 / 64, 19 / 64, 21 / 64, 23 / 64, 25 / 64, 27 / 64, 29 / 64, and 31 / 64). Each ball (22) was released from its starting position at the top of the slope of the test specimen (the ball's position indicated by the dotted line) so that its initial velocity was zero. The balls (22) fell along the runway (18) and measurement section (20) as indicated by the arrows. The diameter ball number (32 times the ball diameter) of the largest ball (22) that remained stationary within measurement section (20) for 5 seconds or more was recorded, and this was designated as the ball number at the desired test temperature (Figure 1). If no ball 22 of any size remains stationary within the measuring unit 20 for 5 seconds or more, the ball number is determined to be less than 3.

[0021] The inclined ball tack test can typically be carried out by the method described in the Examples.

[0022] As a result of extensive research, the inventors have found that it is possible to produce an adhesive composition that has excellent adhesive strength and easy peelability upon cooling, based on the measured values ​​of an inclined ball tack test in which the inclined surface temperature is 36°C and the measured values ​​of an inclined ball tack test in which the inclined surface temperature is 4°C.

[0023] The adhesive composition of the embodiment of the present invention satisfies the conditions that the ball number of the largest ball that stops in the measurement section for 5 seconds or more when the temperature of the inclined surface is 36° C. is 7 or more, and the ball number of the largest ball that stops in the measurement section for 5 seconds or more when the temperature of the inclined surface is 4° C. is less than 3. According to this configuration, an adhesive composition having excellent adhesive strength and easy peelability on cooling can be produced.

[0024] From the viewpoint of adhesive strength, the ball number of the largest ball that stops in the measurement section for 5 seconds or more when the temperature of the inclined surface is 36°C is preferably 7 or more, more preferably 20 or more, and even more preferably 30 or more.

[0025] If the ball number of the largest ball that stops in the measuring section for 5 seconds or more when the temperature of the slope is 36°C is less than 7, the adhesive strength will be weak, which is not preferable.

[0026] From the viewpoint of easy peeling during cooling, the ball number of the largest ball that stops in the measurement section for 5 seconds or more when the temperature of the inclined surface is 4°C is preferably 7 or less, more preferably 5 or less, and even more preferably 3 or less.

[0027] If the ball number of the largest ball that stops in the measurement section for 5 seconds or more when the temperature of the inclined surface is 3 or more, this is not preferable because the adhesive composition cannot be easily peeled off even after being attached to the adherend and cooled under mild cooling conditions.

[0028] In one embodiment, the water content is less than 5% by mass relative to 100 parts by mass of the adhesive composition. When the adhesive composition is an organogel, the water content is more preferably less than 5% by mass, even more preferably less than 3% by mass, relative to 100 parts by mass of the adhesive composition, and particularly preferably zero.

[0029] In one embodiment of the present invention, there is provided an adhesive composition comprising at least one crystalline oil selected from the group consisting of an ester represented by the following formula (1) and an ester represented by the following formula (2), and a polymer matrix, wherein the adhesive composition has a storage modulus G'(35°C) of 100,000 (Pa) or less at 35°C, a storage modulus G'(0°C) of 200,000 (Pa) or more at 0°C, and a value obtained by dividing G'(0°C) by G'(35°C) [G'(0°C) / G'(35°C)] of 10 or more. R 1 -COO-R 2 (1) [In formula (1), R 1 represents a linear or branched alkyl or alkenyl group having 1 to 22 carbon atoms, R 2 represents a linear, branched, or cyclic alkyl group, alkenyl group, or ether having 1 to 34 carbon atoms, R 2 may have a hydroxyl group.] (R 3 O)-CHCH(OR 4 )-CH2(OR 5 ) (2) [In formula (2), R 3 , R 4 and R 5 are each independently a hydrogen atom or a group represented by formula (2-1), R 3 , R 4 and R 5 At least one selected from the group consisting of is a group represented by formula (2-1). -CO-R 6 (2-1) [In formula (2-1), R 6 represents an alkyl or alkenyl group having 7 to 27 carbon atoms which may have a hydroxyl group. Such a configuration is preferable from the viewpoint of obtaining a pressure-sensitive adhesive composition having easy peelability upon cooling.

[0030] The crystalline fat or oil is not particularly limited as long as it has a melting point around room temperature.

[0031] In one embodiment of the present invention, the crystalline oil or fat comprises at least one type of crystalline oil or fat selected from the group consisting of the ester represented by the above formula (1) and the ester represented by the above formula (2), and from the viewpoint of being able to arbitrarily adjust the hardness and softening temperature of the gel, the crystalline oil or fat may comprise two or more types of crystalline oil or fat selected from the group consisting of the ester represented by the above formula (1) and the ester represented by the above formula (2).

[0032] Examples of the ester represented by the above formula (1) include myristyl 2-ethylhexanoate, cetyl 2-ethylhexanoate, stearyl 2-ethylhexanoate, isodecyl octanoate, isocetyl octanoate, isononyl isononanoate, isotridecyl isononanoate, cetearyl isononanoate, octyl propylheptanoate, methyl laurate, isopropyl myristate, octyldodecyl myristate, isopropyl palmitate, 2-ethylhexyl palmitate, isocetyl palmitate, 2-ethylhexyl stearate, isocetyl stearate, isotridecyl stearate, isopropyl isostearate, octyl isostearate, isostearyl and at least one selected from the group consisting of isocetyl palmitate, isostearyl isostearate, batyl isostearate, 2-ethylhexyl hydroxystearate, methyl oleate, oleyl oleate, isobutyl oleate, oleyl erucate, alkyl benzoate (alkyl having 12 to 15 carbon atoms), phytosteryl isostearate, and diethylhexyl naphthalenedicarboxylate. From the viewpoint of obtaining an adhesive composition that hardens within a temperature range that can be cooled with an ice pack or the like, it is preferable to use at least one selected from the group consisting of isopropyl palmitate, batyl isostearate, and phytosteryl isostearate.

[0033] Examples of the ester represented by the above formula (2) include at least one selected from the group consisting of glyceryl tri-2-ethylhexanoate, glyceryl tricaprylate, jojoba oil, shea oil, olive oil, sunflower oil, soybean oil, peanut oil, rapeseed oil, almond oil, palm oil, coconut oil, meadowhoo oil, castor oil, wheat germ oil, grape seed oil, thistle oil, evening primrose oil, macadamia nut oil, corn germ oil, and mango seed oil. From the viewpoint of obtaining an adhesive composition that hardens within a temperature range that can be cooled with an ice pack or the like, it is preferable to use at least one selected from the group consisting of jojoba oil, shea oil, coconut oil, meadowhoo oil, and mango seed oil.

[0034] The melting point of the crystalline oil or fat is preferably within the range of 5 to 40°C, more preferably within the range of 20 to 40°C, and even more preferably within the range of 20 to 38°C, from the viewpoint of obtaining an adhesive composition that hardens within a temperature range that can be cooled with an ice pack or the like.

[0035] The content of the crystalline oil is not particularly limited, but from the viewpoint of obtaining a pressure-sensitive adhesive composition having cooling curing properties and from the viewpoint of the shape retention of the gel, it is preferably in the range of 30 to 65 parts by mass, more preferably in the range of 40 to 60 parts by mass, and even more preferably in the range of 55 to 60 parts by mass, per 100 parts by mass of the total mass of the crystalline oil and the hydrophobic monomer.

[0036] The content of the crystalline oil is not particularly limited, but from the viewpoint of obtaining a pressure-sensitive adhesive composition having cooling curing properties and from the viewpoint of the shape retention of the gel, it is preferably in the range of 30 to 65 parts by mass, more preferably in the range of 40 to 60 parts by mass, and even more preferably in the range of 55 to 60 parts by mass, per 100 parts by mass of the total mass of the crystalline oil and polymer matrix.

[0037] The polymer matrix is ​​not particularly limited as long as it can form an adhesive composition.

[0038] The content of the polymer matrix is ​​not particularly limited, but from the viewpoint of obtaining an adhesive composition with appropriate elasticity, it is preferably in the range of 35 to 70 parts by mass, more preferably in the range of 35 to 60 parts by mass, and even more preferably in the range of 40 to 60 parts by mass, per 100 parts by mass of the total mass of the crystalline oil and the polymer matrix.

[0039] In one embodiment, the polymerizable monomer constituting the polymer matrix includes a hydrophobic monomer, which is preferable from the viewpoint of compatibility between the crystalline oil and the polymer matrix.

[0040] The hydrophobic monomer is not particularly limited as long as it is a polymerizable monomer that is incompatible with water and separates into two layers even when mixed with water. Examples of the hydrophobic monomer include ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isobornyl acrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 4-tert-butylcyclohexyl acrylate, benzyl acrylate, benzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenyldiethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and the like. acrylate, 2-hydroxy-3-phenoxypropyl methacrylate, methylphenoxyethyl acrylate, methylphenoxyethyl methacrylate, ethoxylated orthophenylphenol acrylate, 1,10-decanediol acrylate, 1,9-nonanediol acrylate, N-octylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, N-hydroxyethylacrylamide, acrylamide, hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, bis(isocyanatomethyl)benzene, 1,3-bis(isocyanatomethyl)cyclohexane, diphenylmethane diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate-based polyisocyanate, 1,At least one selected from the group consisting of 5-pentamethylene diisocyanate, isocyanatomethylethylbenzene, isophorone diisocyanate, methylenebis-(4-cyclohexylisocyanate), M-tetramethylene diisocyanate, meta-tetramethylene xylene diisocyanate, saturated methylene diphenyl diisocyanate, toluene diisocyanate, dilinol diol, hexamethylene diamine, glycerol, polyglycerol, pentaerythritol, pentaerythritol tetrakis(3-mercaptopropionate), trimethylolpropane, mercaptanized soybean oil, glycerol propoxylate, glyceryl poly(oxypropylene)triamine, melamine, and acrylic silicone monomers can be used. Examples of acrylic silicone monomers that can be used include Silaplane FM-0711 (product name, manufactured by JNC Corporation), Silaplane FM-0721 (product name, manufactured by JNC Corporation), Silaplane FM-0725 (product name, manufactured by JNC Corporation), Silaplane TM-0701 (product name, manufactured by JNC Corporation), Silaplane TM-0701T (product name, manufactured by JNC Corporation), X-22-174DX (product name, manufactured by Shin-Etsu Chemical Co., Ltd.), X-22-2426 (product name, manufactured by Shin-Etsu Chemical Co., Ltd.), X-22-2475 (product name, manufactured by Shin-Etsu Chemical Co., Ltd.), and 3-(meth)acryloxypropylmethyldimethoxysilane.

[0041] From the viewpoint of obtaining an adhesive composition having appropriate elasticity, the content of the hydrophobic monomer is preferably within the range of 35 to 70 parts by mass, more preferably within the range of 35 to 60 parts by mass, and even more preferably within the range of 40 to 60 parts by mass, per 100 parts by mass of the total mass of the crystalline oil and the hydrophobic monomer.

[0042] From the viewpoint of obtaining an adhesive composition with appropriate elasticity, the content of the hydrophobic monomer is preferably within the range of 35 to 70 parts by mass, more preferably within the range of 35 to 60 parts by mass, and even more preferably within the range of 40 to 60 parts by mass, per 100 parts by mass of the total mass of the crystalline oil and fat and the polymer matrix.

[0043] From the viewpoint of obtaining an adhesive composition with appropriate elasticity, the content of the hydrophobic monomer is preferably within the range of 80 to 100 parts by mass, more preferably within the range of 95 to 100 parts by mass, and even more preferably within the range of 95 to 98 parts by mass, per 100 parts by mass of the total mass of the polymer matrix.

[0044] From the viewpoint of compatibility between the crystalline oil and the polymer matrix, the hydrophobic monomer preferably includes at least one selected from the group consisting of acrylic monomers, acrylamide monomers, urethane monomers, and acrylic silicone monomers.

[0045] Examples of the acrylic monomer include ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isobornyl acrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 4-tert-butylcyclohexyl At least one selected from the group consisting of acrylate, benzyl acrylate, benzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenyl diethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxy-3-phenoxypropyl methacrylate, methylphenoxyethyl acrylate, methylphenoxyethyl methacrylate, ethoxylated orthophenylphenol acrylate, 1,10-decanediol acrylate, 1,9-nonanediol acrylate, and the like can be mentioned.

[0046] From the viewpoint of compatibility between the crystalline oil and the polymer matrix, the acrylic monomer preferably contains at least one selected from the group consisting of 4-tert-butylcyclohexyl acrylate (TBCHA) and isobornyl acrylate (IBXA).

[0047] Examples of the acrylamide monomer include at least one selected from the group consisting of N-octylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, N-hydroxyethylacrylamide, acrylamide, and the like. From the viewpoint of compatibility between the crystalline oil and the polymer matrix, N-octylacrylamide is preferably used.

[0048] The urethane-based polymer matrix refers to a material formed by reacting a polyisocyanate monomer and a polyol monomer. Examples of the polyisocyanate monomer include at least one selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, bis(isocyanatomethyl)benzene, 1,3-bis(isocyanatomethyl)cyclohexane, diphenylmethane diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate-based polyisocyanate, 1,5-pentamethylene diisocyanate, isocyanatomethylethylbenzene, isophorone diisocyanate, methylenebis(4-cyclohexylisocyanate), m-tetramethylene diisocyanate, meta-tetramethylene xylene diisocyanate, saturated methylene diphenyl diisocyanate, and toluene diisocyanate. From the viewpoint of compatibility between the crystalline oil and the polymer matrix, it is preferable to use at least one selected from the group consisting of hexamethylene diisocyanate and isophorone diisocyanate. Examples of the polyol monomer include at least one selected from the group consisting of dilinolediol, hexamethylenediamine, glycerol, polyglycerol, pentaerythritol, pentaerythritol tetrakis(3-mercaptopropionate), trimethylolpropane, mercaptanized soybean oil, glycerol propoxylate, glyceryl poly(oxypropylene)triamine, and melamine. From the viewpoint of compatibility between the crystalline oil and the polymer matrix, it is preferable to use at least one selected from the group consisting of dilinolediol and hexamethylenediamine.

[0049] Examples of the acrylic silicone monomer include at least one selected from the group consisting of Silaplane FM-0711 (product name, manufactured by JNC Corporation), Silaplane FM-0721 (product name, manufactured by JNC Corporation), Silaplane FM-0725 (product name, manufactured by JNC Corporation), Silaplane TM-0701 (product name, manufactured by JNC Corporation), Silaplane TM-0701T (product name, manufactured by JNC Corporation), X-22-174DX (product name, manufactured by Shin-Etsu Chemical Co., Ltd.), X-22-2426 (product name, manufactured by Shin-Etsu Chemical Co., Ltd.), X-22-2475 (product name, manufactured by Shin-Etsu Chemical Co., Ltd.), and 3-(meth)acryloxypropylmethyldimethoxysilane. From the viewpoint of compatibility between the crystalline oil and the polymer matrix, 3-(meth)acryloxypropylmethyldimethoxysilane can be preferably used.

[0050] From the viewpoint of compatibility between the crystalline oil and the polymer matrix, the hydrophobic monomer preferably includes at least one selected from the group consisting of 4-tert-butylcyclohexyl acrylate (TBCHA) and isobornyl acrylate (IBXA).

[0051] The polymer matrix may or may not be crosslinked by a crosslinkable monomer having two or more double bonds in the molecule.

[0052] Examples of crosslinkable monomers include methylene bis(meth)acrylamide, ethylene bis(meth)acrylamide, polyalkylene glycol dimethacrylates such as (poly)ethylene glycol di(meth)acrylate and (poly)propylene glycol di(meth)acrylate, polyfunctional (meth)acrylamides or polyfunctional (meth)acrylic acid esters such as glycerin di(meth)acrylate and glycerin tri(meth)acrylate, polyfunctional (meth)acrylic acid esters such as polyglycerin poly(meth)acrylate, and tetraallyloxyethane, which may be used alone or in combination of two or more. In a particularly preferred embodiment, the crosslinkable monomer includes polyethylene glycol di(meth)acrylate. Polyethylene glycol di(meth)acrylate is preferred from the viewpoint of compatibility between the crystalline oil and the polymer matrix.

[0053] The amount of crosslinkable monomer to be blended is not particularly limited, but from the viewpoint of obtaining an adhesive composition with appropriate elasticity, it is preferably in the range of 0 to 5.0 mass % relative to 100 parts by mass of the total mass of the polymer matrix, and more preferably in the range of 1.0 to 2.5 mass %.

[0054] A polymerization initiator may be added to form the polymer matrix. The amount of the polymerization initiator is not particularly limited, but from the viewpoint of obtaining an adhesive composition with appropriate elasticity, it is preferably in the range of 0.50 to 5.0 mass%, more preferably 2.0 to 5.0 mass%, relative to 100 parts by mass of the total mass of the polymer matrix.

[0055] The type of polymerization initiator is not particularly limited, and may be a photopolymerization initiator or a thermal polymerization initiator. When the pressure-sensitive adhesive composition is formed into a sheet, a photopolymerization initiator is preferably used. Examples of the photopolymerization initiator include an acetophenone-based polymerization initiator and an azo-based polymerization initiator. More preferably, 2-hydroxy-2-methyl-1-phenylpropanone can be used.

[0056] The adhesive composition may further contain an organic solvent other than crystalline oils. Examples of organic solvents other than crystalline oils include, for example, hydrocarbons commonly known as organic solvents, such as heptane, hexane, octane, benzene, toluene, xylene, and cyclohexane; halogenated hydrocarbons, such as methyl chloride, dichloromethane, chloroform, and carbon tetrachloride; ethers, such as diethyl ether and dioxane; esters, such as ethyl acetate; ketones, such as acetone and 2-heptanone; alcohols, such as methanol, ethanol, isopropyl alcohol, benzyl alcohol, and glycerin; nitrogen compounds, such as pyridine and N,N-dimethylacetamide; and sulfur compounds, such as dimethyl sulfoxide. In addition to the above organic solvents, other examples include mineral oil, liquid paraffin, and synthetic hydrocarbon oils, such as poly-α-olefin (PAO) oil; polyalkylene glycols; phenyl ether oils, such as alkyl phenyl ether oils, dialkyl phenyl ether oils, and alkyl polyphenyl ether oils; cyclopentane oil, silicone oil, and perfluoropolyether oil. These may be used alone or in combination of two or more. In a specific preferred embodiment, the organic solvent other than the crystalline oil or fat comprises liquid paraffin. Liquid paraffin is preferred from the viewpoint of obtaining a gel having adhesiveness. When the adhesive composition comprises an organic solvent other than the crystalline oil or fat, its content is not particularly limited, but is preferably within the range of 0 to 50% by mass, more preferably within the range of 0 to 20% by mass, relative to 100 parts by mass of the total mass of the adhesive composition.

[0057] The adhesive composition may further contain components other than those described above. Examples of such components include conductivity imparting agents, thermoindicators, preservatives, disinfectants, mildew inhibitors, rust inhibitors, antioxidants, antifoaming agents, stabilizers, fragrances, surfactants, colorants, and medicinal ingredients (e.g., anti-inflammatory agents, vitamins, whitening agents, etc.). These may be used alone or in combination. These components may be added within a range that does not impair the effects of the present invention.

[0058] The storage modulus G'(35°C) of the adhesive composition at 35°C, the storage modulus G'(0°C) of the adhesive composition at 0°C, and the value obtained by dividing G'(0°C) by G'(35°C) [G'(0°C) / G'(35°C)] are indicators of the ease of peeling of the adhesive composition when cooled, and can be measured or calculated by the following method.

[0059] The adhesive composition was molded into a disk shape with a diameter of 25 mm (±1 mm) and a thickness of 1 mm (±0.1 mm) and used as a sample. The sample was sandwiched between the plates of a viscoelasticity measuring device, PHYSICA MCR301 (manufactured by Anton Paar), with the measurement start temperature set to ±0.50°C using the temperature control system CTD450, and adjusted to a measurement position where a normal force of 0.5 N was applied. After maintaining the measurement start temperature at ±0.50°C for 10 seconds, dynamic viscoelasticity measurements were performed in the range of -10°C to 50°C under constant conditions: strain of 0.01% to 1%, frequency of 1 Hz, heating rate of 2°C / min, measurement interval of 36.6 seconds, and normal force of 0.5 N. The storage modulus G' at 0°C was defined as the storage modulus G'(0°C), and the storage modulus G' at 35°C was defined as the storage modulus G'(35°C). Then, for each sample, G'(0°C) is divided by G'(35°C) to calculate the value [G'(0°C) / G'(35°C)].

[0060] The storage modulus G'(35°C) of the adhesive composition at 35°C, the storage modulus G'(0°C) of the adhesive composition at 0°C, and the value obtained by dividing G'(0°C) by G'(35°C) [G'(0°C) / G'(35°C)] can typically be measured or calculated by the method described in the Examples.

[0061] The storage modulus G'(35°C) of the pressure-sensitive adhesive composition at 35°C is preferably 100,000 Pa or less, more preferably 50,000 Pa or less, and even more preferably 15,000 Pa or less.

[0062] The storage modulus G'(0°C) of the pressure-sensitive adhesive composition at 0°C is preferably 200,000 Pa or more, more preferably 240,000 Pa or more, and even more preferably 700,000 Pa or more.

[0063] The value obtained by dividing G'(0°C) by G'(35°C) [G'(0°C) / G'(35°C)] is preferably 10 or more, more preferably 50 or more, and even more preferably 100 or more, from the viewpoint of obtaining an adhesive composition that has easy peelability upon cooling.

[0064] The content and composition of the polymer matrix in the adhesive composition can be appropriately adjusted so as to satisfy the numerical ranges of the ball number of the largest ball that stops for 5 seconds or more in the measurement section when the temperature of the inclined surface is 36°C, the ball number of the largest ball that stops for 5 seconds or more in the measurement section when the temperature of the inclined surface is 4°C, the storage modulus G'(35°C), the storage modulus G'(0°C), and the value obtained by dividing the storage modulus G'(0°C) by the storage modulus G'(35°C) [G'(0°C) / G'(35°C)].

[0065] The storage modulus G'(25°C) of the pressure-sensitive adhesive composition at 25°C can be measured by the following method.

[0066] The adhesive composition was molded into a disk shape with a diameter of 25 mm (±1 mm) and a thickness of 1 mm (±0.1 mm) and used as a sample. The sample was sandwiched between the plates of a viscoelasticity measuring device, PHYSICA MCR301 (manufactured by Anton Paar), with the measurement start temperature set to ±0.50°C using the temperature control system CTD450, and adjusted to a measurement position where a normal force was 0.5 N. After maintaining the measurement start temperature at ±0.50°C for 10 seconds, dynamic viscoelasticity measurements were performed in the range of -10°C to 50°C under constant conditions: strain 0.01% to 1%, frequency 1 Hz, heating rate 2°C / min, measurement interval 36.6 seconds, and normal force 0.5 N. The storage modulus G' at 25°C was taken as the storage modulus G' (25°C). The storage modulus G'(25°C) of the pressure-sensitive adhesive composition at 25°C is not particularly limited, but from the viewpoint of good compatibility with the skin even at room temperature and immediate adhesion after application, it is preferably within the range of 1,000 to 80,000 Pa, more preferably within the range of 3,000 to 40,000 Pa, and even more preferably within the range of 10,000 to 40,000 Pa.

[0067] In another aspect of the present invention, a method for producing a pressure-sensitive adhesive composition is provided.

[0068] The method includes the steps of dissolving and stirring a mixture containing at least one ester selected from the group consisting of an ester represented by formula (1) and an ester represented by formula (2), a hydrophobic monomer, and a crosslinkable monomer to obtain a polymerizable solution, and irradiating the polymerizable solution with ultraviolet light to cure the solution. These materials are as described above as components of the gel sheet.

[0069] The cumulative dose of ultraviolet light is not particularly limited, but from the viewpoint of obtaining an adhesive composition having appropriate elasticity, it is preferably 100 to 10,000 mJ / cm 2 2 It is preferable that the range is 500 to 7,500 mJ / cm 2 More preferably, it is in the range of 1,000 to 5,000 mJ / cm 2 It is particularly preferable that the range is:

[0070] According to the above method, it is possible to produce an adhesive composition that satisfies the following characteristics: (1) the ball number of the longest ball that stops for 5 seconds or more in the measurement section when the temperature of the slope is 36°C is 7 or more, and (2) the ball number of the longest ball that stops for 5 seconds or more in the measurement section when the temperature of the slope is 4°C is less than 3; when the temperature of the slope is 4°C, the ball number of the longest ball that stops for 5 seconds or more in the measurement section when the temperature of the slope is 4°C is less than 3; and when the slope temperature is 20°C, the ball number of the longest ball that stops for 5 seconds or more in the measurement section when the temperature of the slope is 36°C is 7 or more, the ball number of the longest ball that stops for 5 seconds or more in the measurement section when the temperature of the slope is 4°C is less than 3.

[0071] The adhesive composition of the present invention can also be used in combination with known materials.

[0072] The pressure-sensitive adhesive composition of the present invention has excellent adhesive strength and easy peelability upon cooling, and therefore can be used in a wide range of fields, including medicine, cosmetics, food, chemistry, bioengineering, sports, etc. More specifically, the pressure-sensitive adhesive composition of the present invention can be used, for example, for medical applications, nail adhesives, protective sheets for cosmetics, fixing materials, anti-fogging agents, temperature indicating materials, etc.

[0073] The present invention will be described in more detail using examples, but the present invention is not limited to these examples. [Example]

[0074] 1. Preparation of adhesive composition Example 1 4-tert-Butylcyclohexyl acrylate (TBCHA, manufactured by KJ Chemicals) as a hydrophobic monomer, polyethylene glycol dimethacrylate (trade name PDE-600, manufactured by NOF Corporation) as a cross-linking monomer, 2-hydroxy-2-methyl-1-phenylpropanone (trade name Omnirad1173, manufactured by IGM Resins BV) as a polymerization initiator, and phytosteryl isostearate (melting point: 20°C, manufactured by Tama Biochemical Co., Ltd.) as a crystalline oil were added to a plastic container, and the mixture was dissolved and stirred at 40°C to obtain a polymerizable solution.

[0075] Next, the composition was poured into a silicone rubber mold (70 mm x 100 mm, thickness 1.0 mm) on a 38 μm thick siliconized biaxially oriented polyester film placed on glass, and then a 38 μm siliconized biaxially oriented polyester film was placed on the mold to prevent air bubbles from forming, and then a quartz glass was placed on top to control the thickness. This was then subjected to a peak intensity of 95 mW / cm 2 The molded product was then irradiated with ultraviolet light from a UV lamp for 60 seconds, and taken out of the mold to be used as a sample.

[0076] (Examples 2 to 10 and Comparative Examples 1 to 5) Each sample of Examples 2 to 10 and Comparative Examples 1 to 5 was produced in the same manner as in Example 1, except that the composition was changed as shown in Table 1.

[0077] Details of each component listed in Table 1 are shown below. IBXA (Osaka Organic Chemical Industry Ltd.) Shea oil (melting point: 30-38°C, manufactured by IMCD) Palm oil (melting point: 19-25°C, Fujifilm Wako Pure Chemical Industries, Ltd.) Batyl isostearate (melting point: 20°C, manufactured by Nippon Surfactant Kogyo Co., Ltd., product name GM-18ISV) Meadowhof oil (melting point: <10°C, manufactured by Nippon Surfactant Industries Co., Ltd.) Hydrogenated palm oil (melting point: 50-54°C, manufactured by Nippon Surfactant Industries Co., Ltd., trade name TRIFAT P-52) Avocado oil (melting point: -4°C, manufactured by Nippon Surfactant Kogyo Co., Ltd.) Liquid paraffin (Fujifilm Wako Pure Chemical Industries, Ltd.)

[0078] 2. Measurement or evaluation methods and evaluation criteria (1) Evaluation of gelling properties The gelling property was evaluated by peeling off the biaxially stretched polyester film from each of the samples of Examples 1 to 10 and Comparative Examples 1 to 5, and then touching the test piece with a finger to confirm whether or not it had hardened. ○: Hardened (liquid does not stick to hands) ×: Not cured (liquid sticks to hands) (2) Ball tack test: Measurement of ball number at 36°C The ball numbers of each sample in Examples 1 to 10 and Comparative Examples 1 and 3 to 5 were measured according to the following method in accordance with JIS Z 0237:2009. A 150 mm x 25 mm x 0.5 mm aluminum plate (manufactured by TP Giken) was placed with double-sided tape on a 20° inclined surface created by tilting a hot plate (manufactured by AS ONE Corporation). This served as a temperature-controlled inclined surface, which was set to 36°C. A 150 mm x 20 mm x 0.2 mm test specimen was prepared, and the PET film on one side was peeled off, attached to the temperature-controlled inclined surface, and allowed to stand for 5 minutes. The PET film was then peeled off from a measurement section 100 mm below the inclined surface, leaving a 50 mm runway above the inclined surface of the test specimen, exposing the adhesive surface. Next, 30 steel ball sizes, ranging from 3 / 32 to 1 / 10 in diameter in the "inch" series of nominal diameters specified in JIS B 1501:2009 (excluding 5 / 64, 7 / 64, 9 / 64, 11 / 64, 13 / 64, 15 / 64, 17 / 64, 19 / 64, 21 / 64, 23 / 64, 25 / 64, 27 / 64, 29 / 64, and 31 / 64), were prepared. Each ball was released from the starting position at the top end of the inclined surface of the test piece so that its initial velocity was zero. The diameter ball number (32 times the ball diameter) of the largest ball that remained stationary within the measurement section for 5 seconds or more was recorded and used as the ball number at 36°C. If no steel ball of any size remained stationary within the measurement section for 5 seconds or more, the ball number was considered to be less than 3.

[0079] (3) Ball tack test: Measurement of ball number at 4°C The ball numbers of each sample in Examples 1 to 10 and Comparative Examples 1 and 3 to 5 were measured according to the following method in accordance with JIS Z 0237:2009. A 150 mm x 25 mm x 0.5 mm aluminum plate (manufactured by TP Giken) was placed with double-sided tape on a 20° inclined surface created by tilting a cool plate (manufactured by AS ONE Corporation). This served as a temperature-controlled inclined surface, which was set at 4°C. A 150 mm x 20 mm x 0.2 mm test specimen was prepared, and the PET film on one side was peeled off, attached to the temperature-controlled inclined surface, and allowed to stand for 5 minutes. The PET film was then peeled off from a measurement section 100 mm below the inclined surface, leaving a 50 mm runway above the inclined surface of the test specimen, exposing the adhesive surface. Next, 30 steel ball sizes, ranging from 3 / 32 to 1 / 10 in diameter in the "inch" series of nominal diameters specified in JIS B 1501:2009 (excluding 5 / 64, 7 / 64, 9 / 64, 11 / 64, 13 / 64, 15 / 64, 17 / 64, 19 / 64, 21 / 64, 23 / 64, 25 / 64, 27 / 64, 29 / 64, and 31 / 64), were prepared. Each ball was released from the starting position at the top end of the inclined surface of the test piece so that its initial velocity was zero. The diameter ball number (32 times the ball diameter) of the largest ball that remained stationary within the measurement section for 5 seconds or more was recorded and used as the ball number at 4°C. If no steel ball of any size remained stationary within the measurement section for 5 seconds or more, the ball number was considered to be less than 3.

[0080] (4) Measurement of storage modulus (G') For the adhesive compositions of Examples 1 to 10 and Comparative Examples 1 and 3 to 5, the storage modulus G'(35°C) of the adhesive composition at 35°C, the storage modulus G'(25°C) of the adhesive composition at 25°C, the storage modulus G'(0°C) of the adhesive composition at 0°C, and the value obtained by dividing G'(0°C) by G'(35°C) [G'(0°C) / G'(35°C)] were measured or calculated by the following method.

[0081] Each sample prepared in Examples 1 to 10 and Comparative Examples 1 and 3 to 5 was molded into a disk shape with a diameter of 25 mm (±1 mm) and a thickness of 1 mm (±0.1 mm) to prepare a test specimen. The test specimen was clamped between the plates of a viscoelasticity measuring device (PHYSICA MCR301, manufactured by Anton Paar) with a measurement start temperature of ±0.50°C set using a temperature control system CTD450, and adjusted to a measurement position with a normal force of 0.5 N. After maintaining the measurement start temperature at ±0.50°C for 10 seconds, dynamic viscoelasticity measurements were performed in the range of -10°C to 50°C under constant conditions: strain of 0.01% to 1%, frequency of 1 Hz, heating rate of 2°C / min, measurement interval of 36.6 seconds, and normal force of 0.5 N. The storage modulus G' at 35°C was recorded as the storage modulus G'(35°C), the storage modulus G' at 25°C was recorded as the storage modulus G'(25°C), and the storage modulus G' at 0°C was recorded as the storage modulus G'(0°C). Disposable φ25 mm parallel disks and disposable dishes were used as plates.

[0082] Then, for each sample, G'(0°C) was divided by G'(35°C) to calculate the value [G'(0°C) / G'(35°C)].

[0083] (5) Sensory evaluation of adhesiveness Each sample prepared in Examples 1 to 10 and Comparative Examples 1 and 3 to 5 was cut into a 20 mm x 20 mm piece, the PET film on one side was peeled off, and the piece was attached to a Bioskin plate (manufactured by Viewlux, product number P002-001 (Smooth surface)). The sample was then left to stand for 5 minutes on a cool plate (manufactured by AS ONE Corporation) set to room temperature (25°C), and the adhesiveness when the sample was peeled off using tweezers was evaluated sensorily according to the following criteria. As a comparative control, ST-gel (registered trademark) SR grade (Sekisui Plastics Co., Ltd.) of the same dimensions was used instead of the sample. Note that ST-gel SR grade is a hydrogel containing water, and exhibits excellent adhesiveness at room temperature (25°C), but does not have easy peelability when cooled. ◎: More adhesive than ST-gel SR grade 〇: Same level of adhesiveness as ST-gel SR grade △: Inferior to ST-gel SR grade, but still sticky ×: No adhesiveness

[0084] (6) Sensory evaluation of peelability during cooling Each sample prepared in Examples 1 to 10 and Comparative Examples 1 and 3 to 5 was cut into a 20 mm x 20 mm piece, the PET film on one side was peeled off, and the piece was attached to a Bioskin plate (manufactured by Viewlux, product number P002-001 (Smooth surface)). The piece was then left to stand for 5 minutes on a cool plate (manufactured by AS ONE Corporation) set at -10°C, and the adhesiveness was evaluated sensorily when the sample was peeled off using tweezers. Easy to peel off after cooling: No adhesive No easy peeling when cooled: Inferior to ST-gel SR grade but still sticky, has the same level of stickiness as ST-gel SR grade or is more sticky than ST-gel SR grade

[0085] 3.Results The results are shown in Table 1. From the above results, it was shown that the pressure-sensitive adhesive compositions of this example, in which the ball number of the largest ball that stopped in the measurement area for 5 seconds or more when the inclined surface temperature was 36°C was 7 or more and the ball number of the largest ball that stopped in the measurement area for 5 seconds or more when the inclined surface temperature was 4°C was less than 3, had excellent adhesive strength and easy peelability on cooling.

[0086] [Table 1]

Claims

1. An adhesive composition, The adhesive composition is formed into a plate having a length of 150 mm, a width of 20 mm, and a thickness of 0.2 mm to prepare a test piece, and the test piece is attached to the top of a slope whose inclination angle with respect to the ground and temperature can be controlled so that the inclination direction of the slope coincides with the length direction of the test piece. When an inclined ball tack test is performed under the conditions that the inclination angle is 20°, the portion of the test piece from the top of the slope in the length direction is used as a runway, and the portion of the test piece from the top of the slope in the length direction is used as a measurement area, the adhesive composition satisfies the following properties (1) and (2): (1) When the temperature of the inclined surface is 36°C, the ball number of the largest ball that stops in the measuring section for 5 seconds or more is 7 or more. (2) When the temperature of the inclined surface is 4°C, the ball number of the largest ball that stops in the measuring section for 5 seconds or more is less than 3.

2. An adhesive composition comprising a crystalline oil containing at least one selected from the group consisting of an ester represented by formula (1) and an ester represented by formula (2), and a polymer matrix, the pressure-sensitive adhesive composition has a storage modulus G'(35°C) of 100,000 Pa or less at 35°C; The pressure-sensitive adhesive composition has a storage modulus G'(0°C) of 200,000 Pa or more at 0°C, and The adhesive composition according to claim 1, wherein the value obtained by dividing G'(0°C) by G'(35°C) [G'(0°C) / G'(35°C)] is 10 or more. R １ -COO-R ２ (1) [In formula (1), R １ represents a linear or branched alkyl or alkenyl group having from 1 to 22 carbon atoms, R ２ represents a linear, branched, or cyclic alkyl group, alkenyl group, or ether having 1 to 34 carbon atoms; R ２ may have a hydroxyl group. (R ３ O)-CH 2 CH(OR ４ )-CH 2 (OR ５ ) (2) [In formula (2), R ３ , R ４ and R ５ are each independently a hydrogen atom or a group represented by formula (2-1), R ３ , R ４ and R ５ At least one selected from the group consisting of is a group represented by formula (2-1). -CO-R ６ (2-1) [In formula (2-1), R ６ represents an alkyl or alkenyl group having 7 to 27 carbon atoms which may have a hydroxyl group.

3. The adhesive composition according to claim 2, wherein the content of the crystalline oil is 30 to 65 parts by mass when the total mass of the crystalline oil and the polymer matrix is ​​100 parts by mass.

4. The pressure-sensitive adhesive composition according to claim 2 , wherein the polymerizable monomer constituting the polymer matrix includes a hydrophobic monomer.

5. The pressure-sensitive adhesive composition according to claim 4, wherein the hydrophobic monomer comprises at least one selected from the group consisting of an acrylic monomer, an acrylamide monomer, a urethane monomer, and an acrylic silicone monomer.

6. The pressure-sensitive adhesive composition according to claim 4, wherein the hydrophobic monomer comprises at least one selected from the group consisting of 4-tert-butylcyclohexyl acrylate (TBCHA) and isobornyl acrylate (IBXA).

7. The adhesive composition according to claim 1 , wherein the water content is less than 5% by mass relative to 100 parts by mass of the adhesive composition.

8. A medical adhesive composition comprising the adhesive composition according to any one of claims 1 to 7.

9. A nail adhesive comprising the pressure-sensitive adhesive composition according to any one of claims 1 to 7.

10. A method for producing the pressure-sensitive adhesive composition according to any one of claims 1 to 7, A step of mixing at least one selected from the group consisting of an ester represented by formula (1) and an ester represented by formula (2), a hydrophobic monomer, and a crosslinkable monomer to obtain a polymerizable solution; and A step of curing the polymerizable solution by irradiating it with ultraviolet light. A method for producing a pressure-sensitive adhesive composition comprising:

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