Medical adhesive agent and medical adhesive sheet

Abstract

Provided is a medical adhesive agent. The adhesive agent comprises: a water-dispersible copolymer produced by the copolymerization of a monomer mixture comprising a (meth)acrylic acid alkyl ester, a carboxy-group-containing monomer, a nitrogen-atom-containing monomer, and a silane-based monomer; and an organic liquid component in which the number of hydroxyl groups per molecule is more than 1.

Description

Medical adhesives and medical adhesive sheets

[0001] The present invention relates to a medical adhesive and a medical adhesive sheet. This application claims priority to Japanese Patent Application No. 2023-117593, filed on July 19, 2023, the entire contents of which are incorporated herein by reference.

[0002] Various medical adhesives and medical adhesive sheets using such adhesives are widely used for the purposes of protecting affected skin areas, transdermal absorption of drugs, and fixing gauze, tubes, etc. to the skin. Such medical adhesives and medical adhesive sheets are used in the form of, for example, adhesive bandages, surgical tapes, first-aid adhesive plasters, large adhesive plasters, dressings, poultices, etc. Prior art documents disclosing this type of conventional technology include, for example, Patent Documents 1 and 2. Patent Documents 1 and 2 disclose adhesives that are used by adhering to the skin in medical applications.

[0003] Japanese Patent Application Publication No. 2002-315775 Japanese Patent Application Publication No. 2008-113763

[0004] Adhesives applied to the skin in medical applications are required to have good adhesion to the skin, while delaminating the skin without causing damage such as keratin abrasion, and desirably, being able to be removed without pain or irritation. Furthermore, it is desirable that no adhesive components migrate or remain on the skin after removal, preventing skin contamination by the adhesive components. For example, Patent Document 1 describes that skin irritation can be reduced by incorporating 60 parts by weight of a specific liquid carboxylic acid ester into an acrylic adhesive per 100 parts by weight of an acrylic copolymer. Patent Document 2 also studies a composition in which 30 parts by weight of sorbitan trioleate, sorbitan monolaurate, or sorbitan monooleate are incorporated into an acrylic adhesive per 100 parts by weight of an acrylic copolymer.

[0005] Furthermore, adhesives that are applied to the skin are required to have water resistance that enables them to maintain adhesion to the skin even when sweating, because sweating on the adherend can generate moisture at the adhesive interface of the adhesive, which can reduce adhesion and lead to peeling.

[0006] Recently, there has been a trend toward eliminating or reducing the use of organic solvents in adhesives, due to considerations of the environment and worker health. Regarding the above-mentioned prior art documents, adhesives using water-dispersible copolymers, such as those disclosed in Patent Document 2, are more desirable than adhesives prepared using organic solvents such as toluene, as disclosed in Patent Document 1. However, adhesives using water-dispersible copolymers typically tend to have lower water resistance than solvent-based adhesives prepared using organic solvents. Therefore, they are disadvantageous for applications such as those described above, where adhesives are applied to sweating skin. The inventors' investigations of the adhesive described in Patent Document 2 also revealed that there is room for improvement in terms of water resistance.

[0007] Therefore, the present inventors have conducted extensive research and have succeeded in creating a pressure-sensitive adhesive that has improved water resistance while maintaining the ability to cause little skin irritation when peeled off from the skin, thereby completing the present invention. That is, an object of the present invention is to provide a pressure-sensitive adhesive that causes little skin irritation when peeled off from the skin, has good water resistance, and is excellent in preventing skin contamination. Another related object is to provide a pressure-sensitive adhesive sheet comprising the above pressure-sensitive adhesive.

[0008] This specification provides a medical adhesive. This adhesive contains a water-dispersible copolymer obtained by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester, a carboxyl group-containing monomer, a nitrogen atom-containing monomer, and a silane-based monomer, and an organic liquid component having more than one hydroxyl group per molecule. An adhesive having the above composition causes minimal skin irritation upon peeling, has good water resistance, and can prevent skin contamination by the adhesive components. The adhesive described in Patent Document 2 does not have the water resistance of the technology disclosed therein, as shown in the results of Comparative Example 4 below. Attempting to improve the water resistance of such an adhesive by, for example, reducing the amount of organic liquid component used is likely to result in a decrease in the ability to suppress skin irritation upon peeling. Patent Document 2 does not suggest that the technology disclosed therein can be used to achieve both suppression of skin irritation upon peeling and good water resistance.

[0009] In some preferred embodiments, the amount of the nitrogen atom-containing monomer in 100 parts by mass of the monomer mixture is 0.1 to 10 parts by mass, i.e., the content of the nitrogen atom-containing monomer in the monomer mixture is 0.1 to 10% by mass. By using the nitrogen atom-containing monomer in the above range, it is possible to preferably achieve improved water resistance of the PSA.

[0010] In some preferred embodiments, the nitrogen atom-containing monomer has a structure in which no hydrogen atom is bonded to the nitrogen atom. By using a nitrogen atom-containing monomer having such a structure, it is possible to preferably achieve improved water resistance of the PSA.

[0011] In some preferred embodiments, the nitrogen atom-containing monomer has a cyclic structure containing a nitrogen atom in the ring. By using a nitrogen atom-containing monomer having such a structure, better water resistance is likely to be obtained.

[0012] In some preferred embodiments, the amount of the carboxyl group-containing monomer in 100 parts by mass of the monomer mixture is 0.1 to 10 parts by mass, i.e., the content of the carboxyl group-containing monomer in the monomer mixture is 0.1 to 10% by mass. By using the carboxyl group-containing monomer in the above range, good water resistance can be preferably obtained.

[0013] In some preferred embodiments, the HLB (Hydrophile-Lipophile Balance) of the organic liquid component is 3 to 16. By using an organic liquid component with an HLB in the range of 3 to 16, it is possible to better achieve both suppression of skin irritation during peeling and good water resistance. Furthermore, organic liquid components having the above HLB tend to provide excellent skin contamination prevention properties.

[0014] In some preferred embodiments, the organic liquid component is a fatty acid ester derivative of a polyhydric alcohol. The technology disclosed herein is preferably implemented in embodiments using an organic liquid component having the above structure. In particular, it is more preferable to use a fatty acid that forms the fatty acid ester derivative and has 8 to 18 carbon atoms.

[0015] In some preferred embodiments, the PSA contains 1 to 60 parts by mass of the organic liquid component per 100 parts by mass of the water-dispersible copolymer. By setting the blending amount of the organic liquid component within the above range, it is possible to preferably achieve both suppression of skin irritation during peeling and good water resistance.

[0016] This specification also provides a medical adhesive sheet. This adhesive sheet has any of the medical adhesives disclosed herein on at least one surface of a support. The adhesive sheet having the above configuration can be preferably used in the form of various medical adhesive sheets, such as adhesive bandages, surgical tapes, first aid adhesive plasters, large adhesive plasters, dressings, and poultices.

[0017] 1 is a cross-sectional view schematically illustrating the configuration of a pressure-sensitive adhesive sheet according to one embodiment.

[0018] Preferred embodiments of the present invention are described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. Furthermore, in the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic for the purpose of clearly explaining the present invention, and do not necessarily accurately represent the size or scale of the actual product provided.

[0019] In this specification, the term "adhesive" refers to a material that, as mentioned above, is in a soft solid (viscoelastic) state in the temperature range around room temperature and has the property of easily adhering to an adherend by pressure. The adhesive referred to here is generally a material having a complex tensile modulus E as defined in "CA Dahlquist, "Adhesion: Fundamentals and Practice", McLaren & Sons, (1966) p. 143". ＊ (1Hz) <10 ７ dyne / cm ２ The material may be a material having the properties satisfying the above (typically, a material having the above properties at 25°C).

[0020] In this specification, "weight" may be read as "mass." For example, "% by weight" may be read as "% by mass," and "parts by weight" may be read as "parts by mass."

[0021] <Pressure-Sensitive Adhesive Composition> (Water-Dispersible Copolymer) The pressure-sensitive adhesive composition disclosed herein contains a water-dispersible copolymer. Here, "water-dispersible copolymer" refers to a copolymer synthesized in a water-dispersed form, typically a copolymer synthesized by emulsion polymerization. Using a water-dispersible copolymer as a pressure-sensitive adhesive component enables the elimination of organic solvents and the reduction of organic solvent usage, resulting in the formation of a pressure-sensitive adhesive that is environmentally and worker-health-conscious. The water-dispersible copolymer is typically contained as a base polymer in the pressure-sensitive adhesive composition. Here, "base polymer" refers to the main component of the polymer contained in the pressure-sensitive adhesive composition (which may also be a pressure-sensitive adhesive), and is not intended to be limiting in any other sense. Furthermore, in this specification, the term "main component" refers to the component that accounts for the largest proportion of the components contained, by weight. Therefore, for example, when a pressure-sensitive adhesive composition is composed of three or more polymers, the content of the main component in the polymer may be 34 wt % or more, typically exceeding 50 wt %.

[0022] An acrylic copolymer is used as the aqueous dispersion copolymer. Acrylic adhesives containing an acrylic copolymer tend to provide good adhesion and are relatively less irritating to the skin than rubber-based adhesives, making them suitable as medical adhesives to be applied to the skin. In this specification, "acrylic copolymer" refers to a polymer derived from a monomer mixture containing more than 50% by weight of an acrylic monomer. The acrylic monomer refers to a monomer having at least one (meth)acryloyl group per molecule. In this specification, "(meth)acryloyl" refers to acryloyl and methacryloyl in a comprehensive sense. Similarly, "(meth)acrylate" refers to acrylate and methacrylate in a comprehensive sense, and "(meth)acrylic" refers to acrylic and methacrylic in a comprehensive sense.

[0023] In some embodiments, the water-dispersible copolymer is a polymer of a monomer mixture containing a (meth)acrylic acid alkyl ester (m1) as a main component. For example, it is preferable to use a copolymer containing, as a base polymer, a copolymer composed of a monomer mixture containing a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester terminal. Hereinafter, a (meth)acrylic acid alkyl ester having an alkyl group having X to Y carbon atoms at the ester terminal will be referred to as "(meth)acrylic acid C Ｘ－Ｙ In some preferred embodiments, the proportion of the (meth)acrylic acid alkyl ester (m1) in the monomer mixture is more than 50% by weight, preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more, from the viewpoint of obtaining the desired adhesive properties (adhesive strength, cohesive strength, etc.), and may be, for example, 92% by weight or more, or may be 94% by weight or more. Furthermore, from the viewpoint of obtaining the effect based on the copolymerization of the carboxy group-containing monomer (m2) and the nitrogen atom-containing monomer (m3) described below, the proportion of the (meth)acrylic acid alkyl ester (m1) in the monomer mixture is, for example, 99.4% by weight or less, preferably 99% by weight or less, more preferably 98% by weight or less, and even more preferably 97% by weight or less. The (meth)acrylic acid alkyl ester (m1) may be used alone or in combination of two or more.

[0024] (Meth)acrylic acid C １－２０Non-limiting examples of alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isopropyl (meth)acrylate. Examples of the acrylate include isooctyl (meth)acrylate, nonyl (meth)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, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0025] In some embodiments, the (meth)acrylic acid C １－２０ Among alkyl esters, (meth)acrylic acid C ４－２０ It is preferable to use alkyl esters, and (meth)acrylic acid C ４－１８ It is more preferable to use alkyl esters, and (meth)acrylic acid C ４－１２ It is more preferable to use alkyl esters, and acrylic acid C ４－１０ It is particularly preferred to use alkyl esters. In some embodiments, in the above monomer mixture, (meth)acrylic acid C １－２０ (Meth)acrylic acid C in alkyl esters ４－１８ Alkyl ester (preferably (meth)acrylic acid C ４－１２ Alkyl esters, more preferably acrylic acid C ４－１０The proportion of the (meth)acrylic acid alkyl ester is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more, and may be 95% or more, or may be 98 to 100% by weight. By using the (meth)acrylic acid alkyl ester as the main component, good adhesive properties are likely to be obtained.

[0026] In some preferred embodiments, the (meth)acrylic acid C １－２０ As alkyl ester, acrylic acid C ７－９ Alkyl esters are used. Acrylic acid C ７－９ By using alkyl ester, it is possible to preferably obtain a pressure-sensitive adhesive having good adhesive strength and excellent flexibility. A highly flexible pressure-sensitive adhesive is likely to obtain high adhesion to skin having a complex surface shape that expands and contracts and deforms. In some preferred embodiments, in the above-mentioned monomer mixture, (meth)acrylic acid C １－２０ Acrylic acid C in alkyl esters ７－９ The proportion of alkyl ester is suitably, for example, 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more, and may be 95% by weight or more, or may be 98 to 100% by weight. For example, it is particularly preferable that the monomer mixture contains 2-ethylhexyl acrylate (2EHA). ７－９ Other examples of alkyl esters include heptyl acrylate, octyl acrylate, isooctyl acrylate, and isononyl acrylate.

[0027] The monomer mixture also contains a carboxyl group-containing monomer (m2) and a nitrogen atom-containing monomer (m3). The combined use of the monomers (m2) and (m3) can improve water resistance. Furthermore, the combined use can provide high adhesive strength, allowing compositions incorporating the organic liquid component described below to maintain good adhesion to skin. The coexistence of the carboxyl group-containing monomer (m2) and the nitrogen atom-containing monomer (m3) is thought to improve cohesive strength due to their acid-base interaction, which contributes to improved water resistance and adhesive strength. The technology disclosed herein is not limited to the above considerations. By utilizing the combined use of the carboxyl group-containing monomer (m2) and the nitrogen atom-containing monomer (m3), for example, a highly flexible material can be used as the (meth)acrylic acid alkyl ester (m1), achieving both flexibility, water resistance, and adhesive strength.

[0028] The carboxyl group-containing monomer (m2) is not particularly limited, and various monomers having a carboxyl group can be used. The carboxyl group-containing monomer (m2) can be used alone or in combination of two or more.

[0029] In some embodiments, the carboxyl group-containing monomer (m2) used in the monomer mixture includes acrylic acid (m2a). By using acrylic acid (m2a) as the carboxyl group-containing monomer (m2), in the synthesis of the aqueous dispersion copolymer, the relatively highly polar acrylic acid (m2a) is present on the surface side of the polymer particles in the dispersion, and is thought to contribute to the dispersion stability of the particles and the ease of preparing the dispersion while interacting with the nitrogen atom-containing monomer (m3). Note that the technology disclosed herein is not limited to the above considerations.

[0030] In embodiments using acrylic acid (m2a) as the carboxy group-containing monomer (m2), the amount of acrylic acid (m2a) used (in other words, the copolymerization ratio of acrylic acid (m2a) in the water-dispersible copolymer) is not particularly limited and may be, for example, 0.1 wt % or more in the monomer mixture, preferably 0.5 wt % or more, and more preferably 1.0 wt % or more (e.g., 1.5 wt % or more). By using a predetermined amount of acrylic acid (m2a) or more, adhesive properties (adhesion strength, cohesion strength, etc.), dispersion stability, dispersion preparation ease, etc. can be improved. Furthermore, in some embodiments, the amount of acrylic acid (m2a) used in the monomer mixture is, from the viewpoints of water resistance, flexibility, etc., suitably 10 wt % or less, preferably 8.0 wt % or less, more preferably 6.0 wt % or less, even more preferably 5.0 wt % or less, and particularly preferably 3.0 wt % or less.

[0031] In some preferred embodiments, the carboxyl group-containing monomer (m2) comprises acrylic acid (m2a) and a carboxyl group-containing monomer (m2b) that is more hydrophobic than acrylic acid (m2a). By using acrylic acid (m2a) and a relatively hydrophobic carboxyl group-containing monomer (m2b) in combination as the carboxyl group-containing monomer (m2), a PSA with excellent water resistance and adhesive strength can be preferably obtained. In the synthesis of the water-dispersible copolymer, the relatively polar acrylic acid (m2a) is present on the surface of the polymer particles in the dispersion, as described above, while the relatively hydrophobic carboxyl group-containing monomer (m2b) is present in large amounts inside the polymer particles due to its hydrophobicity. It is believed that this improves the cohesive strength inside the polymer particles through acid-base interactions with the nitrogen atom-containing monomer (m3). As a result, even after the polymer particles are fused together by subsequent drying to form a PSA, the PSA maintains high cohesive strength as a bulk and exhibits excellent water resistance and adhesive strength. It should be noted that the technology disclosed herein is not limited to the above considerations. Whether or not the carboxyl group-containing monomer (m2b) has higher hydrophobicity than the acrylic acid (m2a) can be determined from its chemical structure, and can also be determined from its water solubility at 20°C, which will be described later.

[0032] Examples of carboxy group-containing monomers (m2b) that are more hydrophobic than acrylic acid (m2a) include ethylenically unsaturated monocarboxylic acids such as methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, 2-(meth)acryloyloxyethyl maleic acid, carboxypolycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethyl tetrahydrophthalic acid, crotonic acid, and isocrotonic acid. The carboxy group-containing monomers (m2b) can be used alone or in combination of two or more. Among these, MAA is preferred from the viewpoint that it has a low molecular weight and is effective even in small amounts.

[0033] In some preferred embodiments, a monomer having a water solubility (solubility in water) of 15.0 g / 100 mL or less at 20°C is used as the carboxyl group-containing monomer (m2b), which is more hydrophobic than acrylic acid (m2a). By using a hydrophobic carboxyl group-containing monomer (m2b) having a water solubility of a predetermined value or less in combination with acrylic acid (m2a), the monomer (m2b) is thought to be present in an appropriate amount inside the polymer particles, contributing to improved cohesion within the particles. From the viewpoint of improving cohesion within the polymer particles, the water solubility of the carboxyl group-containing monomer (m2b) is preferably 12.0 g / 100 mL or less, and may be 10.0 g / 100 mL or less, 8.0 g / 100 mL or less, or 5.0 g / 100 mL or less. Furthermore, from the viewpoint of emulsion polymerization properties, the water solubility of the carboxy group-containing monomer (m2b) is preferably 2.0 g / 100 mL or more, and may be 6.0 g / 100 mL or more, or may be 8.0 g / 100 mL or more. A suitable example of the carboxy group-containing monomer (m2b) having the above water solubility is MAA (water solubility at 20°C: 9.7 g / 100 mL). The water solubility of the monomer material at 20°C can be measured based on Techniques of Chemistry 4th Ed. Vol. II Organic Solvents (1985): New York, NY. John Wiley and Sons, Inc. ICSC(J)1997.

[0034] In embodiments in which acrylic acid (m2a) and a carboxyl group-containing monomer (m2b) that is more hydrophobic than acrylic acid (m2a) are used in combination as the carboxyl group-containing monomer (m2), the ratio of the two is not particularly limited, and an appropriate ratio can be adopted depending on factors such as dispersion stability, polymer preparation ease, and the type of carboxyl group-containing monomer (m2b) used. In some embodiments, the weight ratio (m2a / m2b) of the amount of acrylic acid (m2a) used to the amount of the carboxyl group-containing monomer (m2b) that is more hydrophobic than acrylic acid (m2a) used may be, for example, 0.1 or more, 0.5 or more, 1 or more (e.g., greater than 1), 1.5 or more, or 1.8 or more, from the viewpoints of dispersion stability, dispersion preparation ease, and the like. Furthermore, in some embodiments, the ratio (m2a / m2b) may be, for example, 10 or less, 5 or less, 3 or less, or 2 or less, from the viewpoints of improving water resistance and adhesive strength.

[0035] In an embodiment in which a carboxyl group-containing monomer (m2b) that is more hydrophobic than acrylic acid (m2a) is used as the carboxyl group-containing monomer (m2), the amount of the carboxyl group-containing monomer (m2b) that is more hydrophobic than acrylic acid (m2a) used (in other words, the copolymerization ratio of the carboxyl group-containing monomer (m2b) in the water-dispersible copolymer) is not particularly limited, and may be, for example, 0.1 wt % or more, preferably 0.3 wt % or more, more preferably 0.7 wt % or more, or even 1.0 wt % or more in the monomer mixture. By increasing the amount of the carboxyl group-containing monomer (m2b) used within a predetermined range, it is possible to preferably improve the cohesive strength, water resistance, and adhesive strength. In some embodiments, the amount of the carboxy group-containing monomer (m2b) used is, from the viewpoints of water resistance, flexibility, and the like, suitably 10% by weight or less, preferably 8.0% by weight or less, more preferably 6.0% by weight or less, even more preferably 5.0% by weight or less, particularly preferably 3.0% by weight or less, and may be, for example, 1.5% by weight or less, in the monomer mixture.

[0036] The amount of the carboxy group-containing monomer (m2) used (in other words, the copolymerization ratio of the carboxy group-containing monomer (m2) in the water-dispersible copolymer) is not particularly limited, and may be, for example, 0.1 wt% or more in the monomer mixture, preferably 0.5 wt% or more, more preferably 1.0 wt% or more, even more preferably 2.0 wt% or more, particularly preferably 2.5 wt% or more, and may even be 3.0 wt% or more. By increasing the amount of the carboxy group-containing monomer (m2) used within a predetermined range, adhesive strength, cohesive strength, and water resistance can be preferably improved. Furthermore, in some embodiments, from the viewpoint of water resistance, flexibility, etc., the amount of the carboxy group-containing monomer (m2) used in the monomer mixture is, for example, 10 wt% or less, preferably 8.0 wt% or less, more preferably 6.0 wt% or less, even more preferably 5.0 wt% or less, and may be 4.5 wt% or less, or may be 3.5 wt% or less.

[0037] The nitrogen atom-containing monomer (m3) is not particularly limited, and various monomers having a nitrogen atom can be used. For example, a monomer having a nitrogen atom-containing ring, an amide group-containing monomer, or an amino group-containing monomer can be used. The nitrogen atom-containing monomer (m3) can be used alone or in combination of two or more.

[0038] Examples of the monomer having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone (NVP), N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylmorpholine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, and N-vinylpyridazine.Examples of the amide group-containing monomer include (meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide; N-alkyl(meth)acrylamides such as N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and N-n-butyl(meth)acrylamide; N-vinylcarboxylic acid amides such as N-vinylacetamide; and monomers having a hydroxyl group and an amide group, such as N-(2-hydroxyethyl)(meth)acrylamide. N-hydroxyalkyl(meth)acrylamides such as N-(2-hydroxypropyl)(meth)acrylamide, N-(1-hydroxypropyl)(meth)acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, N-(2-hydroxybutyl)(meth)acrylamide, N-(3-hydroxybutyl)(meth)acrylamide, and N-(4-hydroxybutyl)(meth)acrylamide; monomers having an alkoxy group and an amide group, for example, N-alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide, N-methoxyethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide; and others such as N,N-dimethylaminopropyl(meth)acrylamide. Examples of the amino group-containing monomer include N,N-dialkylaminoalkyl(meth)acrylates such as N,N-dimethylaminoethyl(meth)acrylate; N-alkyl(meth)acrylates such as aminoethyl(meth)acrylate; and t-butylaminoethyl(meth)acrylate.

[0039] In some preferred embodiments, a monomer having a structure in which no hydrogen atom is bonded to the nitrogen atom is used as the nitrogen atom-containing monomer (m3). Water resistance can be improved by using a nitrogen atom-containing monomer having the above structure in combination with a carboxy group-containing monomer (m2). Furthermore, since high adhesive strength can be obtained by the above combination, good adhesion to skin can be maintained in a composition containing an organic liquid component, as described below. A nitrogen atom-containing monomer having no hydrogen atom bonded to the nitrogen atom strengthens the acid-base interaction with carboxylic acid, improving cohesive strength based on this acid-base interaction, which is thought to result in improved water resistance and adhesive strength. The technology disclosed herein is not limited to the above considerations. Nitrogen atom-containing monomers having a structure in which no hydrogen atom is bonded to the nitrogen atom can be used alone or in combination of two or more.

[0040] Although not particularly limited, it is preferable to use a nitrogen atom-containing monomer (m3) having a small acid dissociation constant (pKa). It is believed that the smaller the pKa, the stronger the acid-base interaction with carboxylic acid, making it easier to obtain excellent cohesive strength. The pKa of the nitrogen atom-containing monomer (m3) may be, for example, 7 or less, 5 or less, or 3 or less. In some preferred embodiments, a nitrogen atom-containing monomer (m3) having a pKa of 1 or less is used from the viewpoint of obtaining better water resistance and adhesive strength. The pKa is more preferably 0.5 or less, even more preferably 0 or less (e.g., lower than 0), and may be −0.5 or less. The lower limit of the pKa of the nitrogen atom-containing monomer (m3) is −2 or more, or may be −1.5 or more, or may be −1 or more. It is believed that by using a nitrogen atom-containing monomer (m3) having a pKa within the above range, good acid-base interaction can be obtained due to its basicity. A suitable example of a nitrogen atom-containing monomer having the above pKa is NVP (pKa: -0.34). Note that the pKa can be calculated from the concentration of the substance to be measured and the hydrogen ion concentration measured using a pH meter.

[0041] In some preferred embodiments, a monomer having a cyclic structure containing a nitrogen atom within the ring (monomer having a nitrogen atom-containing ring) is used as the nitrogen atom-containing monomer (m3). By using a monomer having a nitrogen atom-containing ring, better water resistance and adhesive strength can be achieved. This is thought to be because the structure having a nitrogen atom-containing ring provides a distance that facilitates interaction between the acid and base, making it easier to achieve a better cohesive strength improvement effect. Suitable examples of monomers having a nitrogen atom-containing ring include NVP and N-(meth)acryloylmorpholine. Among these, NVP has good biocompatibility and is suitable for medical adhesives that are applied to the skin. The monomers having a nitrogen atom-containing ring can be used alone or in combination of two or more.

[0042] In embodiments in which a monomer having a nitrogen atom-containing ring is used as the nitrogen atom-containing monomer (m3), the proportion of the monomer having a nitrogen atom-containing ring in the entire nitrogen atom-containing monomer (m3) is not particularly limited. In some embodiments, from the viewpoint of effectively exerting the effects of using the monomer having a nitrogen atom-containing ring, the proportion of the monomer having a nitrogen atom-containing ring in the entire nitrogen atom-containing monomer (m3) may be, for example, 10% by weight or more, suitably 50% by weight or more, preferably 70% by weight or more, and may even be 90% by weight or more (e.g., 95 to 100% by weight).

[0043] The amount of the nitrogen atom-containing monomer (m3) used (in other words, the copolymerization ratio of the nitrogen atom-containing monomer (m3) in the water-dispersible copolymer) is not particularly limited, and may be, for example, 0.1 wt% or more in the monomer mixture, preferably 0.3 wt% or more, more preferably 0.5 wt% or more, even more preferably 0.8 wt% or more, and particularly preferably 1.0 wt% or more. By increasing the amount of the nitrogen atom-containing monomer (m3) used within a predetermined range, cohesive strength, water resistance, and adhesive strength can be preferably improved. Furthermore, in some embodiments, from the viewpoint of water resistance, flexibility, etc., the amount of the nitrogen atom-containing monomer (m3) used in the monomer mixture is suitably, for example, 10 wt% or less, preferably 8.0 wt% or less, more preferably 6.0 wt% or less, even more preferably 5.0 wt% or less, even more preferably 3.0 wt% or less, and particularly preferably 2.5 wt% or less, and may be 2.0 wt% or less, 1.5 wt% or less, or 1.2 wt% or less.

[0044] The ratio of the carboxy group-containing monomer (m2) to the nitrogen atom-containing monomer (m3) is not particularly limited and is appropriately set so as to exhibit the desired water resistance, adhesive strength, etc. In some embodiments, the weight ratio (m2 / m3) of the amount of the carboxy group-containing monomer (m2) to the amount of the nitrogen atom-containing monomer (m3) may be, for example, 0.1 or more, suitably 0.5 or more, preferably 1 or more (e.g., greater than 1), more preferably 1.5 or more, even more preferably 2.0 or more, and may even be 2.5 or more. Furthermore, in some embodiments, the ratio (m2 / m3) may be, for example, 10 or less, suitably 7 or less, preferably 5 or less, more preferably 4 or less, and may even be 3 or less.

[0045] The monomer mixture further contains a silane-based monomer (m4). A water-dispersible copolymer having a monomer composition containing the silane-based monomer (m4) can introduce a crosslinked structure between polymer particles in the resulting adhesive through a silanol group condensation reaction (silanol condensation). This crosslinking between the polymer particles improves cohesive strength, thereby improving water resistance and adhesive strength. The silane-based monomer (m4) is also known as a silane coupling agent.

[0046] As the silane monomer (m4), an alkoxysilyl group-containing monomer is preferably used. The alkoxysilyl group-containing monomer is typically an ethylenically unsaturated monomer having at least one (preferably two or more, for example, two or three) alkoxysilyl group in one molecule. Examples of the silane monomer (m4) include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane. The silane monomer (m4) can be used alone or in combination of two or more.

[0047] The proportion of the silane monomer (m4) in the monomer mixture is, for example, suitably 0.001% by weight or more, preferably 0.01% by weight or more. In some embodiments, from the viewpoint of improving adhesion to the adherend, the proportion of the silane monomer (m4) is, for example, suitably 0.5% by weight or less, preferably 0.2% by weight or less, or may be 0.1% by weight or less, or may be 0.05% by weight or less.

[0048] The monomer mixture may optionally contain another monomer (another copolymerizable monomer) that is copolymerizable with any of the carboxy group-containing monomer (m2), nitrogen atom-containing monomer (m3), and silane-based monomer (m4). Suitable examples of the other copolymerizable monomer include monomers having a functional group such as a hydroxyl group and monomers whose homopolymer glass transition temperature is relatively high (e.g., 10°C or higher). The other copolymerizable monomers may be used alone or in combination of two or more.

[0049] Non-limiting examples of other copolymerizable monomers include acid anhydride group-containing monomers, hydroxyl group-containing monomers (e.g., 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate), sulfonic acid group- or phosphoric acid group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, isocyanate group-containing monomers, alkoxy group-containing monomers, vinyl esters, vinyl ethers, aromatic vinyl compounds, olefins, (meth)acrylic acid esters having an alicyclic hydrocarbon group, and (meth)acrylic acid esters having an aromatic hydrocarbon group. acid esters, and other examples include heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylates, silicon atom-containing (meth)acrylates such as silicone (meth)acrylate, (meth)acrylic acid esters obtained from terpene compound derivative alcohols, and polyfunctional monomers (monomers having at least two polymerizable functional groups with unsaturated double bonds such as (meth)acryloyl groups and vinyl groups).

[0050] The other copolymerizable monomers can be used in an appropriate amount as long as the effects of the invention are not impaired. When the monomer mixture contains the other copolymerizable monomers, the proportion of the other copolymerizable monomers in the monomer mixture is suitably about 30 wt% or less, and may be 10 wt% or less, 3 wt% or less, or 1 wt% or less (e.g., 0.1 wt% or less). The monomer mixture may be substantially free of other copolymerizable monomers. Furthermore, the PSA disclosed herein can achieve good water resistance based on high cohesive strength by using a combination of a carboxy group-containing monomer (m2) and a nitrogen atom-containing monomer (m3), and therefore does not need to rely on hydroxyl group-containing monomers used for crosslinking reactions or to improve cohesive strength. Therefore, the technology disclosed herein can be preferably practiced in an embodiment in which the content of the hydroxyl group-containing monomer in the monomer mixture is 3% by weight or less (e.g., 1% by weight or less, or even 0.1% by weight or less), or in an embodiment in which the monomer mixture is substantially free of the hydroxyl group-containing monomer.

[0051] The water-dispersible copolymer can be synthesized by emulsion polymerization. Emulsion polymerization allows the preparation of a polymerization solution in the form of an emulsion in which a polymer is dispersed in water (polymer emulsion, also referred to as an aqueous polymer dispersion). The emulsion polymerization method is not particularly limited, and various monomer supply methods, polymerization conditions, materials used, etc., similar to those of conventional emulsion polymerization, can be appropriately adopted. For example, the monomer supply method can be a batch feed method in which the entire monomer mixture is supplied at once, a continuous supply (dropping) method, or a divided supply (dropping) method. It is preferable that a portion or all of the monomer mixture be supplied as a dispersion (emulsion) emulsified in water. For example, when the monomer mixture is supplied by a dropwise method, it is preferable that the monomer mixture be added dropwise in the form of an emulsion. The polymerization temperature can be, for example, about 30°C or higher (usually 50°C or higher), and is suitably about 100°C or lower (usually 80°C or lower).

[0052] The initiator used in the polymerization can be appropriately selected from conventionally known polymerization initiators depending on the type of polymerization method. For example, azo-based polymerization initiators, peroxide-based initiators, redox-based initiators formed by combining peroxides with reducing agents, substituted ethane-based initiators, etc. can be used. In emulsion polymerization, it is preferable to use a water-soluble polymerization initiator. The polymerization initiator can be used alone or in appropriate combination of two or more types. The amount of polymerization initiator used can be selected, for example, from the range of approximately 0.005 to 1 part by weight (typically approximately 0.01 to 1 part by weight) per 100 parts by weight of the monomer mixture.

[0053] The emulsifier used in emulsion polymerization is not particularly limited, and known anionic surfactants, nonionic surfactants, etc. can be used. In some embodiments, from the viewpoint of improving water resistance, it is preferable to use a surfactant having a radical polymerizable functional group (reactive emulsifier). The emulsifier can be used alone or in combination of two or more.

[0054] As the reactive emulsifier, for example, one having a structure in which a radically polymerizable functional group is introduced into an anionic surfactant or a nonionic surfactant can be used. From the viewpoint of polymerization stability during emulsion polymerization, emulsifying properties, etc., it is preferable to use an anionic reactive emulsifier. Examples of the radically polymerizable functional group include a vinyl group, a propenyl group, an isopropenyl group, a vinyl ether group (vinyloxy group), an allyl ether group (allyloxy group), etc. The concept of a propenyl group here includes a 1-propenyl group (CH ３ -CH=CH-) and 2-propenyl group (CH ２ =CH-CH ２ -; sometimes referred to as an allyl group.

[0055] Examples of anionic reactive emulsifiers include polyoxyethylene (allyloxymethyl) alkyl ether sulfates (e.g., ammonium salts), polyoxyethylene nonylpropenyl phenyl ether sulfates (e.g., ammonium salts), alkyl allyl sulfosuccinates (e.g., sodium salts), methacryloxypolyoxypropylene sulfate ester salts (e.g., sodium salts), and polyoxyalkylene alkenyl ether sulfates (e.g., ammonium salts in which the alkenyl group terminates in an isopropenyl group). When the anionic reactive emulsifier forms a salt, the salt may be, for example, a metal salt such as a sodium salt, or a non-metal salt such as an ammonium salt or an amine salt. Examples of nonionic reactive emulsifiers include polyoxyethylene nonylpropenyl phenyl ether.

[0056] By emulsion polymerizing a monomer mixture in the presence of a reactive emulsifier having a radically polymerizable functional group, the reactive emulsifier can react and be incorporated into the polymer. The reactive emulsifier incorporated into the polymer is restricted in its movement within the pressure-sensitive adhesive layer, making it less likely to migrate to the surface of the pressure-sensitive adhesive layer. Therefore, the use of a reactive emulsifier can inhibit the emulsifier from migrating to the surface of the pressure-sensitive adhesive layer. This can be advantageous in terms of inhibiting a decrease in water-resistant adhesive strength when water is generated on the surface of the pressure-sensitive adhesive layer.

[0057] The amount of emulsifier used in emulsion polymerization may be, for example, 0.2 parts by weight or more, 0.5 parts by weight or more, 1.0 parts by weight or more, or 1.5 parts by weight or more, relative to 100 parts by weight of the monomer mixture. From the viewpoint of improving water resistance, in some embodiments, the amount of emulsifier used is suitably 10 parts by weight or less, preferably 5 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 2.5 parts by weight or less, relative to 100 parts by weight of the monomer mixture.

[0058] In the polymerization, various conventionally known chain transfer agents (which may also be understood as molecular weight regulators or polymerization degree regulators) can be used as needed. Examples of chain transfer agents that can be used include mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan (t-lauryl mercaptan), thioglycolic acid, and α-thioglycerol. Alternatively, a chain transfer agent that does not contain a sulfur atom (non-sulfur chain transfer agent) may be used. The chain transfer agents can be used alone or in combination of two or more. When a chain transfer agent is used, the amount used can be, for example, about 0.01 to 1 part by weight per 100 parts by weight of the monomer mixture.

[0059] (Organic Liquid Component) The adhesive composition disclosed herein contains an organic liquid component. The organic liquid component is defined as an organic component that is liquid at room temperature (23°C). Furthermore, a compound having more than one hydroxyl group is used as the organic liquid component. An adhesive containing an organic liquid component having such a chemical structure exhibits low skin irritation upon peeling, good water resistance, and can prevent skin contamination by the adhesive components. Specifically, an organic liquid component having more than one hydroxyl group and moderate hydrophilicity is favorably distributed on the surface of polymer particles in the adhesive, appropriately plasticizing the adhesive overall and forming a weak boundary layer (WBL) on the surface of the adhesive layer, thereby suppressing skin irritation upon peeling. The action of the organic liquid component is believed to be exerted while maintaining the cohesive strength of the adhesive. Due to the cohesive strength of the water-dispersible copolymer, the adhesive exhibits good water resistance and prevents skin contamination by the adhesive components due to cohesive failure upon peeling. Furthermore, although the incorporation of the organic liquid component reduces the adhesive strength of the adhesive to a certain extent, the adhesive's adhesion to the skin is improved by the moderate plasticization as described above, so that it is possible to achieve both good adhesion to the skin and suppression of skin irritation upon peeling. Note that the technology disclosed herein is not limited to the above considerations. The organic liquid component can be used alone or in combination of two or more.

[0060] The number of hydroxyl groups in the molecule of the organic liquid component is more than 1, preferably 2 or more, more preferably 3 or more. The greater the number of hydroxyl groups in the organic liquid component, the better the affinity with the surface of the polymer particles in the PSA tends to be. The number of hydroxyl groups in the molecule of the organic liquid component is suitably set within an appropriate range based on the balance with the hydrophobic structure in the organic liquid component, and may be, for example, 20 or less, 15 or less, or 10 or less, and in some preferred embodiments, 5 or less, or 4 or less. When the organic liquid component is composed of two or more organic liquid components with different chemical structures, the number of hydroxyl groups in the molecule is determined as a weighted average value of the sum of the products of the number of hydroxyl groups in each component corresponding to the organic liquid component and the weight fraction of the corresponding component.

[0061] In some embodiments, a surfactant is preferably used as the organic liquid component. Examples of the organic liquid component that can be used include nonionic surfactants, anionic surfactants, and cationic surfactants. Among these, nonionic surfactants are preferred. By using an appropriate surfactant as the organic liquid component, it is possible to preferably achieve both suppression of skin irritation during peeling and good water resistance.

[0062] The HLB of the organic liquid component (typically a surfactant) is not particularly limited. In some embodiments, from the viewpoint of suppressing skin irritation, the HLB is preferably 3 or more, more preferably 5 or more, even more preferably 6 or more, even more preferably 7 or more, and particularly preferably 8 or more. Furthermore, by using an organic liquid component having an HLB within the above range in combination with the water-dispersible copolymer disclosed herein, an excellent skin irritation suppression effect can be achieved. Furthermore, an organic liquid component having the above HLB is likely to provide excellent skin contamination prevention. The upper limit of the HLB is 20 or less, and in some preferred embodiments, from the viewpoint of water resistance, it is 18 or less, more preferably 16 or less, and may be 14 or less, 12 or less, 10 or less, or 9 or less. By using an organic liquid component having an appropriate HLB within the above range, it is possible to better achieve both suppression of skin irritation during peeling and good water resistance. Furthermore, an organic liquid component having the above HLB is likely to provide excellent skin contamination prevention.

[0063] In this specification, HLB stands for Griffin's Hydrophile-Lipophile Balance, which is a value indicating the degree of affinity of a surfactant for water or oil, and is a ratio of hydrophilicity to lipophilicity expressed as a numerical value between 0 and 20. The definition of HLB is as described in W. C. Griffin: J. Soc. Cosmetic Chemists, 1,311 (1949), and in "Surfactant Handbook," 3rd Edition, Kogaku Toshosha Publishing, November 25, 1972, pp. 179-182, co-authored by Takahashi Etsutami, Namba Yoshiro, Koike Motoo, and Kobayashi Masao.

[0064] In some embodiments, a fatty acid ester derivative of a polyhydric alcohol (a concept encompassing fatty acid esters of polyhydric alcohols and their derivatives) is preferably used as the organic liquid component. Organic liquid components having the above structure have more than one hydroxyl group, tend to be liquid at room temperature, and tend to preferably exert the desired effect inside or on the surface of the PSA. The polyhydric alcohol may be a trivalent or higher polyhydric alcohol, such as a sugar alcohol. Non-limiting examples of the polyhydric alcohol include glycerin, polyglycerol, trimethylolpropane, pentaerythritol, sorbitol, and sucrose. Among these, preferred polyhydric alcohols forming the fatty acid ester derivative of the polyhydric alcohol are glycerin, polyglycerol, and sorbitol, with sorbitol being particularly preferred. Sorbitol has a considerable number of closely spaced hydroxyl groups within its molecule. It is believed that hydrogen bonding between these hydroxyl groups and carboxyl groups on the surface of the polymer particles allows the organic liquid component having a sorbitol-derived structure to be well positioned on the surface of the polymer particles in the PSA. It should be noted that the technology disclosed herein is not limited to the above considerations.

[0065] Fatty acids forming the fatty acid ester derivatives of polyhydric alcohols are preferably those that impart moderate hydrophobicity to the organic liquid component. For example, fatty acid ester derivatives of saturated or unsaturated fatty acids having a carbon number in the range of 8 to 18 are preferred. In the case of unsaturated fatty acids with a relatively low melting point, even if a fatty acid with a large carbon number is used, a liquid product is likely to be obtained. The carbon number of the fatty acid may be 9 or more, 10 or more, 11 or more, or 12 or more. Furthermore, from the viewpoint of achieving moderate hydrophilicity, the carbon number of the fatty acid is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less. Organic liquid components formed from fatty acids having a carbon number within the above range tend to produce adhesives that do not cause damage such as exfoliation of keratin when peeled from the skin and that cause less skin irritation. Non-limiting examples of the fatty acids include lauric acid, myristic acid, palmitic acid, and oleic acid. Among these, lauric acid is preferred.

[0066] In some embodiments, the organic liquid component also contains an oxyethylene unit (—CH ２ -CH ２ -O-), or may not contain the oxyethylene unit. An organic liquid component containing an oxyethylene unit can impart appropriate hydrophilicity to the pressure-sensitive adhesive surface and further reduce irritation to the skin. When an organic liquid component containing an oxyethylene unit is used, the number of oxyethylene units in the organic liquid component is 1 or more, and may be 3 or more. From the viewpoint of improving hydrophilicity, it is preferably 5 or more, more preferably 10 or more, even more preferably 15 or more, and may even be 18 or more. Furthermore, the upper limit of the number of oxyethylene units in the organic liquid component may be, for example, 50 or less, and from the viewpoint of water resistance, it is preferably 40 or less, more preferably 30 or less, and even more preferably 25 or less. Although not particularly limited, the oxyethylene unit may be contained in the organic liquid component in the form of a polyoxyethylene (POE) chain containing the oxyethylene unit (a chain structure in which two or more oxyethylene units are consecutive). For example, when the organic liquid component is a fatty acid ester derivative of a polyhydric alcohol, the oxyethylene unit or POE chain can be contained in the organic liquid component in a structure in which it is bonded to the polyhydric alcohol (ether bond).

[0067] Non-limiting examples of the organic liquid component include glycerol monooleate, polyglycerol laurate, polyglycerol oleate, polyglycerol myristylates, sorbitan monolaurate, sorbitan monooleate, POE sorbitan monolaurate, POE sorbitan monopalmitate, POE sorbitan monostearate, POE sorbitan monooleate, and the like.

[0068] The amount of the organic liquid component used is not particularly limited. In some embodiments, the amount of the organic liquid component used may be 1 part by weight or more, or may be 10 parts by weight or more, per 100 parts by weight of the water-dispersible copolymer. By using a predetermined amount or more of the organic liquid component, the effect of containing the organic liquid component can be favorably exhibited. In some preferred embodiments, the amount of the organic liquid component used per 100 parts by weight of the water-dispersible copolymer is 15 parts by weight or more, more preferably 20 parts by weight or more, even more preferably 25 parts by weight or more, or even 30 parts by weight or more. In some embodiments, the amount of the organic liquid component used per 100 parts by weight of the water-dispersible copolymer may be 100 parts by weight or less, or may be 80 parts by weight or less. By limiting the amount of the organic liquid component used, the organic liquid component is more likely to be well-compatible with the PSA and water resistance is also more likely to be improved. In some preferred embodiments, the amount of the organic liquid component used per 100 parts by weight of the water-dispersible copolymer is 60 parts by weight or less, more preferably 50 parts by weight or less, even more preferably 40 parts by weight or less, and particularly preferably 35 parts by weight or less.

[0069] (Crosslinking Agent) The pressure-sensitive adhesive composition disclosed herein may contain a crosslinking agent as needed. The type of crosslinking agent is not particularly limited, and can be appropriately selected from conventionally known crosslinking agents. Examples of such crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, and metal chelate-based crosslinking agents. The crosslinking agents can be used alone or in combination of two or more.

[0070] The amount of crosslinking agent used is not particularly limited and can be selected, for example, from the range of approximately 10 parts by weight or less (e.g., approximately 0.001 to 10 parts by weight, preferably approximately 0.01 to 5 parts by weight) per 100 parts by weight of the water-dispersible copolymer. In some embodiments, the amount of crosslinking agent used is 1 part by weight or less, or may be 0.5 parts by weight or less, or may be 0.1 parts by weight or less (e.g., 0.05 parts by weight or less) per 100 parts by weight of the water-dispersible copolymer. In some embodiments, the PSA composition may be substantially free of a crosslinking agent. According to the technology disclosed herein, by designing the monomer composition of the water-dispersible copolymer, high cohesive strength can be achieved with the use of a small amount of crosslinking agent, or even substantially no crosslinking agent.

[0071] (Other Optional Components) The PSA composition disclosed herein may optionally contain a tackifier resin for purposes such as improving adhesive strength. The tackifier resin may be one or more selected from phenolic tackifier resins, terpene tackifier resins, modified terpene tackifier resins, rosin tackifier resins, hydrocarbon tackifier resins, epoxy tackifier resins, polyamide tackifier resins, elastomer tackifier resins, and ketone tackifier resins. When the PSA composition contains a tackifier resin, the amount of the tackifier resin used is suitably in the range of, for example, about 1 to 30 parts by weight, and may be 10 parts by weight or less, per 100 parts by weight of the water-dispersible copolymer. In some embodiments, the PSA composition is substantially free of a tackifier resin. According to the technology disclosed herein, the PSA composition (and thus the PSA) can exhibit good adhesion to skin without containing a tackifier resin.

[0072] The pressure-sensitive adhesive composition may contain, as necessary, various additives commonly used in the field of pressure-sensitive adhesive compositions, such as leveling agents, crosslinking aids, plasticizers, softeners, fillers, colorants (dyes, pigments), antistatic agents, antiaging agents, ultraviolet absorbers, antioxidants, light stabilizers, dispersants, etc. As for the various additives mentioned above, conventionally known ones can be used in the usual manner, and they do not particularly characterize the present invention, so detailed description thereof will be omitted.

[0073] In some embodiments, the PSA composition may have a limited amount of components other than the water-dispersible copolymer and the organic liquid component. A PSA containing fewer components other than the water-dispersible copolymer and the organic liquid component can prevent or reduce the effects of these components on the skin. For example, the PSA composition preferably contains less skin-irritating components. From this perspective, although not particularly limited, the amount of components other than the water-dispersible copolymer and the organic liquid component (specifically, non-volatile components) in the PSA composition (and thus the PSA) is suitably, for example, approximately 10 wt % or less, preferably approximately 5 wt % or less, more preferably approximately 3 wt % or less, and may even be 1.0 wt % or less. The technology disclosed herein can be preferably implemented with a composition in which the amount of components other than the water-dispersible copolymer and the organic liquid component is limited in this way.

[0074] (Water-Dispersed Pressure-Sensitive Adhesive Composition) The pressure-sensitive adhesive composition disclosed herein can be prepared using a water-dispersible copolymer and an organic liquid component as described above, thereby substantially eliminating the use of organic solvents or reducing the amount of organic solvent used. This is significant in terms of eliminating organic solvents, environmental considerations, worker health, and the like. The pressure-sensitive adhesive composition can be implemented in the form of a water-dispersed pressure-sensitive adhesive composition in which at least a portion of the pressure-sensitive adhesive-forming components are dispersed in an aqueous medium. The term "water-dispersed" also includes suspended and emulsified states. The term "aqueous medium" refers to a medium in which the solvent constituting the medium is water or a mixed solvent (aqueous solvent) primarily composed of water. The concept of the water-dispersed pressure-sensitive adhesive composition encompasses what are known as emulsion-type pressure-sensitive adhesive compositions. The pressure-sensitive adhesive composition disclosed herein typically has an emulsion form in which the water-dispersible copolymer is dispersed in water.

[0075] <Adhesive> The adhesive disclosed herein can be formed by a conventionally known method using, for example, the adhesive composition. For example, the adhesive composition can be applied to a releasable surface (release surface) and dried to form a layered adhesive (adhesive layer). In adhesive sheets having a support, for example, a method (direct method) can be used in which the adhesive composition is directly applied (typically coated) to the support and dried to form an adhesive layer. Alternatively, a method (transfer method) can be used in which the adhesive composition is applied to a releasable surface (release surface) and dried to form an adhesive layer on the surface, and the adhesive layer is then transferred to the support. For example, the surface of a release liner can be preferably used as the release surface. Note that the adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form. For example, the adhesive layer may be formed in a regular or random pattern, such as a dotted or striped pattern.

[0076] The pressure-sensitive adhesive composition can be applied using a conventional coater such as a gravure roll coater, a die coater, or a bar coater. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation or curtain coating. From the viewpoints of promoting the crosslinking reaction and improving production efficiency, the pressure-sensitive adhesive composition is preferably dried under heating. The drying temperature can be, for example, about 40 to 150°C, and preferably about 60 to 130°C. After drying the pressure-sensitive adhesive composition, aging may be performed for the purposes of adjusting component migration within the pressure-sensitive adhesive, promoting the crosslinking reaction, and alleviating distortion that may exist within the pressure-sensitive adhesive.

[0077] As described above, this specification provides a PSA containing components that can be contained in the PSA composition disclosed herein. Specifically, the PSA contains a water-dispersible copolymer and an organic liquid component, and may further contain the various optional components described above. The details described for the PSA composition also apply to PSA formed from the PSA composition, except for components that volatilize during PSA formation.

[0078] <Adhesive Sheet> (Configuration) The adhesive sheet disclosed herein is not particularly limited other than having an adhesive (layer) formed from the adhesive composition, and may be an adhesive sheet having the adhesive (layer) on one or both sides of a non-releasable support, or may be a support-less adhesive sheet (i.e., an adhesive sheet without a non-releasable support; typically, an adhesive sheet consisting of an adhesive layer) in which the adhesive (layer) is held by a release liner. The concept of adhesive sheet here may include what are called adhesive tapes, adhesive labels, adhesive films, etc. The adhesive sheet disclosed herein may be in the form of a roll or sheets. Alternatively, it may be an adhesive sheet processed into various shapes.

[0079] An example of the configuration of a pressure-sensitive adhesive sheet is shown in Fig. 1. The pressure-sensitive adhesive sheet 1 shown in Fig. 1 is configured as a single-sided pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer 10, one surface 10A of which serves as the surface to be attached to an adherend (skin), and a support 20 laminated on the other surface 10B of the pressure-sensitive adhesive layer 10. The pressure-sensitive adhesive layer 10 is fixedly bonded to one surface 20A of the support 20. Before use (before attachment to an adherend), the pressure-sensitive adhesive sheet 1 may be in the form of a release-liner-attached pressure-sensitive adhesive sheet 50, as shown in Fig. 1, in which the adhesive surface 10A is protected by a release liner 30, at least on the pressure-sensitive adhesive layer side, which serves as a release surface (release surface). Alternatively, the second surface 20B of the support 20 (the surface opposite to the first surface 20A, also referred to as the back surface) may serve as the release surface, and the adhesive surface 10A may be protected by being wound or laminated so that the adhesive surface 10A abuts against the second surface 20B of the support 20.

[0080] (Adhesive Layer) The thickness of the adhesive layer is not particularly limited. The thickness of the adhesive layer is usually about 300 μm or less, suitably about 100 μm or less, preferably about 80 μm or less, and may be 60 μm or less. The adhesive layer disclosed herein can be used as one having good adhesion to the skin with the above-mentioned limited thickness. Furthermore, an adhesive layer with a limited thickness can well meet the demand for thinner and lighter adhesive layers. The lower limit of the thickness of the adhesive layer is not particularly limited, and from the viewpoint of adhesive strength and conformability to the skin as an adherend, it is, for example, about 1 μm or more, suitably about 10 μm or more, preferably 20 μm or more, and may be, for example, 30 μm or more.

[0081] (Support) In some embodiments, the PSA sheet may be in the form of a PSA sheet having a PSA layer on one or both sides of the support. Examples of supports that support (back) the PSA layer include: polyolefin (polyethylene, polypropylene, ethylene-propylene copolymer, etc.) films, polyester (polyethylene terephthalate (PET), etc.) films, vinyl chloride resin films, vinyl acetate resin films, polyimide resin films, polyamide resin films, fluorine-based resin films, and other plastic films such as cellophane; papers such as Japanese paper, kraft paper, glassine paper, fine paper, synthetic paper, and top-coated paper; fabrics such as woven fabrics and nonwoven fabrics made from various fibrous materials, either alone or in a blend; rubber sheets made from natural rubber, butyl rubber, etc.; foam sheets made from foams such as polyurethane foam and polychloroprene rubber; metal foils such as aluminum foil and copper foil; composites thereof; and the like. The plastic films may be unstretched or stretched (uniaxially stretched or biaxially stretched). The support may have a single layer structure or a laminate structure.

[0082] In some embodiments, nonwoven fabrics, woven fabrics, other porous films, etc. are used as the support. When nonwoven fabrics or woven fabrics are used, the material thereof is not particularly limited, and materials made of one or more of the following can be used: natural fibers such as cotton, linen, and wool; cellulosic fibers such as rayon and acetate; polyamide fibers such as vinylon and nylon; polyolefin fibers such as polyethylene and polypropylene; polyester fibers such as polyethylene terephthalate; and synthetic fibers such as polyurethane fibers. Examples of porous films include resin porous films made of polypropylene, polyethylene, PET, polyurethane, etc. Among these, nonwoven fabrics are preferred, and nonwoven fabrics made of synthetic fibers such as polyester fibers are more preferred. These support materials have appropriate breathability and moisture permeability, and can also have appropriate stretchability / non-stretchability, so they are preferably used in applications where they are applied to the skin.

[0083] The support may contain various additives, such as fillers (inorganic fillers, organic fillers, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, and colorants (pigments, dyes, etc.), as needed. The surface of the support (particularly the surface on which the pressure-sensitive adhesive layer is to be formed) may be subjected to a known or conventional surface treatment, such as corona discharge treatment, plasma treatment, or application of a primer. Such a surface treatment may be, for example, a treatment to enhance the anchoring ability of the pressure-sensitive adhesive layer to the support.

[0084] The thickness of the support can be appropriately selected depending on the purpose, but is usually about 10 μm or more, for example, 20 μm or more, or 30 μm or more. Increasing the thickness of the support increases the strength of the support or pressure-sensitive adhesive sheet, making it easy to use and handle. The upper limit of the thickness of the support is not particularly limited, and in some embodiments, it is appropriate to set it to about 1 mm or less, for example, about 500 μm or less, about 300 μm or less, or 100 μm or less. Limiting the thickness of the support tends to improve the ability to follow the surface shape (steps, etc.) of the adherend.

[0085] (Release Liner) The release liner is not particularly limited, and for example, a release liner whose surface is a liner substrate such as a resin film or paper, or a release liner made of a low-adhesion material such as a fluorine-based polymer (such as polytetrafluoroethylene) or a polyolefin-based resin (such as polyethylene or polypropylene), can be used. For the release treatment, for example, a silicone-based or long-chain alkyl-based release treating agent can be used. In some embodiments, a release-treated resin film can be preferably used as the release liner.

[0086] (Adhesive Strength) Although not particularly limited, in some embodiments, the adhesive strength of the adhesive or adhesive sheet is preferably approximately 0.5 N / 10 mm or more, more preferably approximately 1.0 N / 10 mm or more, and even more preferably approximately 1.5 N / 10 mm or more. An adhesive or adhesive sheet having such adhesive strength adheres well to the skin and tends to be resistant to slippage and peeling while attached to the skin. In some embodiments, the adhesive strength is suitably, for example, 3.0 N / 10 mm or less, and may be 2.0 N / 10 mm or less. An adhesive sheet having an adhesive strength limited to a predetermined value or less reduces the peel load on the skin when peeled from the skin, allowing it to be peeled from the skin without damage such as keratin peeling. The adhesive strength is the 180-degree peel strength measured using a Bakelite plate as the adherend. The adhesive strength to the Bakelite plate (adhesive strength to Bakelite plate) can be specifically measured by the method described in the Examples below.

[0087] (Total Thickness) The total thickness of the PSA sheet disclosed herein (including the PSA layer and the support, but excluding the release liner) is not particularly limited. In some embodiments, the total thickness of the PSA sheet can be, for example, approximately 1 mm or less, and from the viewpoint of handleability, etc., it may be approximately 500 μm or less, approximately 300 μm or less, or approximately 100 μm or less. A PSA sheet with a limited thickness can make the product lighter and thinner. The lower limit of the thickness of the PSA sheet is not particularly limited, and from the viewpoint of adhesive properties (adhesive strength, etc.) and handleability, etc., in some embodiments, it is appropriate to set it to, for example, approximately 10 μm or more, preferably approximately 20 μm or more, more preferably approximately 30 μm or more, and may be approximately 50 μm or more.

[0088] <Applications> The adhesive compositions, adhesives, and adhesive sheets disclosed herein are suitable for medical applications in which they are applied to the skin, taking advantage of their features of causing little irritation to the skin when removed, having good water resistance, and preventing skin contamination by the adhesive components. For example, they can be used as various medical adhesives and medical adhesive sheets for the purposes of protecting affected skin areas, transdermal drug absorption, and fixing gauze, tubes, etc. to the skin. Although not particularly limited, the medical adhesives and medical adhesive sheets disclosed herein can be preferably used in the form of, for example, adhesive bandages, surgical tapes, first-aid adhesive plasters, large adhesive plasters, dressings, poultices, etc.

[0089] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

[0090] <Preparation of Water-Dispersible Acrylic Copolymer> (Preparation Example A1) Into a flask equipped with a reflux condenser, a thermometer, and a dropping funnel, 85 g of water and 10 g of a reactive emulsifier (product name "Aqualon KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., solids concentration 25%) were added. Separately, 350 g of 2-ethylhexyl acrylate (hereinafter abbreviated as 2EHA), 7.3 g of acrylic acid (AA), 3.7 g of N-vinylpyrrolidone (NVP), and 3.7 g of methacrylic acid (MAA) were added as monomers, and 0.18 g of a silane monomer (product name "KBM-503", manufactured by Shin-Etsu Chemical Co., Ltd., 3-methacryloxypropyltrimethoxysilane), 0.18 g of t-lauryl mercaptan as a chain transfer agent, 25 g of a reactive emulsifier (product name "Aqualon KH-1025"), and 140 g of water were added and emulsified using a high-pressure homogenizer to obtain an emulsion (emulsion of monomer mixture). 40 g of this emulsion was added to the flask and nitrogen substitution was performed for 1 hour. The temperature was then raised to 60°C, and 0.1 g of a water-soluble polymerization initiator (product name "VA-057", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate polymerization. After 1 hour, 0.1 g of a water-soluble polymerization initiator (product name "VA-057") was added, and a predetermined amount of the emulsion obtained above was added dropwise over 3 hours to carry out an emulsion polymerization reaction. Thereafter, the temperature was raised to 70°C and maintained for an additional 3 hours. After cooling to room temperature, 10% aqueous ammonia was added to the aqueous dispersion after the polymerization reaction to adjust the pH to 5.0, and the aggregates were filtered using a Teflon (registered trademark) mesh to obtain an aqueous dispersion A1 of an acrylic copolymer (solid concentration 54%).

[0091] (Preparation Example A2) The composition of the emulsion of the monomer mixture other than water was changed to 304 g of 2EHA, 6.8 g of AA, 27.1 g of methyl methacrylate (MMA), 0.07 g of the above silane-based monomer, 0.04 g of t-lauryl mercaptan, and 1.6 g of a non-reactive emulsifier (product name "Hitenol LA16", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., polyoxyethylene lauryl alkyl ether ammonium sulfate). Aqueous dispersion A2 of the acrylic copolymer was obtained using the same formulation as in Preparation Example A1.

[0092] Example 1 Sorbitan monolaurate (product name "Rheodol SP-L10", manufactured by Kao Corporation, liquid at room temperature, 3 hydroxyl groups per molecule, HLB 8.6) serving as an organic liquid component was blended into an aqueous dispersion A1 of an acrylic copolymer in an amount of 30 parts per 100 parts of the solids content of the aqueous dispersion A1, and the mixture was stirred for 10 minutes at 2000 rpm using a Thinky Mixer (product name: Awatori Rentaro), followed by degassing for 2 minutes at 2200 rpm to obtain a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition was applied to the release-treated surface of a 38 μm-thick release liner (product name: "MRF38", manufactured by Mitsubishi Chemical Corporation), one side of which had been treated with a silicone release agent, and then dried at 130°C for 3 minutes to form a 50 μm-thick pressure-sensitive adhesive layer. The exposed adhesive surface of the pressure-sensitive adhesive layer was protected by covering it with a 38 μm-thick release liner (manufactured by Mitsubishi Chemical Corporation, product name "MRE38"), which was a PET film with one side treated with a silicone release agent. In this way, a pressure-sensitive adhesive sheet was obtained, which consisted of a pressure-sensitive adhesive layer protected on each side with a release liner.

[0093] (Examples 2 to 6, Comparative Examples 1 to 5) Pressure-sensitive adhesive sheets according to each example were obtained in the same manner as in Example 1, except that the components and amounts used were changed as shown in Table 1. In Table 1, the product name "Rheodol SP-O10V" (manufactured by Kao Corporation, liquid at room temperature, 3 hydroxyl groups per molecule, HLB 4.3) was used for sorbitan monooleate, the product name "Tween 20" (manufactured by Tokyo Chemical Industry Co., Ltd., liquid at room temperature, 3 hydroxyl groups per molecule, HLB 16.7) was used for polyoxyethylene sorbitan monolaurate, and the product name "Tween 80" (manufactured by Tokyo Chemical Industry Co., Ltd., liquid at room temperature, 3 hydroxyl groups per molecule, HLB 16.7) was used for polyoxyethylene sorbitan monooleate. The sorbitan trioleate used was "Rheodol SP-O30V" (manufactured by Kao Corporation, liquid at room temperature, 1 hydroxyl group per molecule, HLB 1.8), the sorbitan tristearate used was "Rheodol SP-S30V" (manufactured by Kao Corporation, 1 hydroxyl group per molecule, HLB 2.1), and the dimer acid used was dimer acid (HLB 14) manufactured by Tokyo Chemical Industry Co., Ltd.

[0094] <Evaluation> [180-degree peel strength (adhesive strength)] For each PSA sheet according to the present invention, the release liner covering one adhesive surface was removed, and a 25 μm thick PET film (product name "Lumirror S10", manufactured by Toray Industries, Inc.) was attached to the backing to obtain a measurement sample. The measurement sample was cut to a size of 5 cm x 1 cm, and at room temperature (23°C), the other adhesive surface was exposed and the sample was attached to a Bakelite plate as an adherend, followed by one reciprocal press-bonding with a 2 kg roller. Under the same conditions, a tensile tester (manufactured by Shimadzu Corporation, trade name "Autograph AG-Xplus HS 6000 mm / min high-speed model (AG-50NX plus)") was used to measure the load when the PSA sheet was peeled from the adherend at a peel angle of 180 degrees and a tensile speed of 300 mm / min, and the peel strength (adhesion strength to Bakelite plate) [N / 10 mm] against the Bakelite plate was determined. The Bakelite plate used was a phenolic laminate (paper phenol) manufactured by Standard Test Piece Co., Ltd. Note that, for those that broke anchor from the backing PET film during peel strength measurement, the adhesive composition was directly applied to a 25 μm thick PET film (product name "Lumirror S10", manufactured by Toray Industries, Inc.) to form an adhesive layer with a thickness of 50 μm, and evaluation was performed using this.

[0095] [Skin Adhesion] The PSA sheet according to each example was cut into a size of 5 cm x 5 cm, after which the release liner covering one adhesive surface was peeled off, and a polyester spunlace nonwoven fabric (product name "Sontara #8010", manufactured by Nissei Corporation, basis weight 44 g / m) was cut into a size of 5 cm x 25 cm. ２ ) to obtain a measurement sample. The release liner covering the other adhesive surface was peeled off from the measurement sample, and the exposed adhesive surface of the measurement sample was attached to the inner arm of a test subject at room temperature and lightly pressed with the other hand for 10 seconds. Then, using the above-mentioned tensile tester under the same conditions, the load when the PSA sheet was peeled from the arm was measured at a peel angle of 180° and a tensile speed of 300 mm / min, and the peel strength (adhesion to skin) [N / 50 mm] was determined. Note that for samples that broke anchor from the nonwoven fabric during peel strength measurement, the PSA composition was applied to a release liner, and then the above-mentioned nonwoven fabric was attached thereto before drying, and dried at 130°C for 3 minutes to obtain a measurement sample, which was then used for evaluation.

[0096] [Skin irritation] A measurement sample was obtained using a pressure-sensitive adhesive sheet and a polyester spunlace nonwoven fabric according to the method described above for skin adhesion. The exposed adhesive surface of the measurement sample was attached to the inner arm of a subject, and after 2 hours, the pain felt when the measurement sample was peeled off from the inner arm was evaluated and rated according to the following criteria: AA: No pain felt at all. A: There was a strange feeling on the skin, but almost no pain felt. B: The skin was pulled, but not much pain felt. C: It was painful. An evaluation result of B or higher was judged as passing, and a result of C was judged as failing.

[0097] [Water Resistance] A measurement sample was obtained by backing the pressure-sensitive adhesive sheet with a PET film (product name "Lumirror S10", manufactured by Toray Industries, Inc., thickness 25 μm) or by directly coating the pressure-sensitive adhesive composition on the PET film. This measurement sample was cut to 2 cm × 6 cm and attached to a glass slide (product number "S1111", manufactured by Matsunami Glass Industry Co., Ltd.). The measurement sample was placed in a plastic container, and water was added to the container until the measurement sample was completely immersed. The container was then treated in an ultrasonic cleaner for 1 hour. The degree of water penetration into the pressure-sensitive adhesive layer was visually confirmed and rated according to the following criteria: A: No change was observed in the pressure-sensitive adhesive layer. B: Clouding was observed only in the peripheral portion (outer edge) of the pressure-sensitive adhesive layer. C: Clouding was observed even inside the pressure-sensitive adhesive layer, or the pressure-sensitive adhesive layer was peeled off from the PET film.

[0098] [Skin staining] The adhesive sheet was applied to a polyester spunlace nonwoven fabric (product name "Sontara #8010", manufactured by Nissei Corporation, basis weight 44 g / m ２ ) and cut into 2 cm x 5 cm pieces to obtain a measurement sample. The adhesive side of the measurement sample was attached to the outside of the subject's right arm near the wrist, and after 1 hour it was quickly peeled off from the skin. After peeling off the measurement sample, the presence or absence of adhesive contamination on the skin was visually observed and rated according to the following criteria: A: No adhesive contamination was observed. B: A faint residue was observed, but there was no tackiness when touched. C: Residue was observed, and there was tackiness when touched. An evaluation result of A was judged to be pass, and a result of B or lower was judged to be fail.

[0099] The outline of each example and the evaluation results are shown in Table 1.

[0100]

[0101] As shown in Table 1, Examples 1 to 6, which used PSA containing an aqueous dispersion copolymer obtained by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester, a carboxyl group-containing monomer, a nitrogen atom-containing monomer, and a silane-based monomer, and an organic liquid component having more than one hydroxyl group per molecule, passed the skin irritation evaluation, had good water resistance, and no skin staining was observed. On the other hand, Comparative Examples 1 to 3 and 5, which used an organic component having one hydroxyl group per molecule, failed the skin irritation evaluation and also showed poor skin staining evaluation results. In Examples 1 to 6, the organic liquid component containing more than one hydroxyl group and having moderate hydrophilicity was well distributed on the surface of the polymer particles in the PSA, moderately plasticizing the PSA overall and forming a WBL (Weak Boundary Layer) on the surface of the PSA layer, which is thought to suppress skin irritation during peeling. This observation is also supported by the adhesive strength measurement results of Examples 1 to 6. Although the adhesive strength of Examples 1 to 6 was lower than that of the comparative examples, the adhesiveness to the skin was improved by the moderate plasticization described above, resulting in good adhesion to the skin. In contrast, in Comparative Examples 1 to 3, organic components with one or fewer hydroxyl groups in the molecule are thought to have penetrated the interior of the polymer particles in the adhesive, causing peeling in a mode similar to cohesive failure. This is thought to be reflected in the skin irritation and skin staining evaluation results and the adhesive strength measurement results. The results of Comparative Example 3 confirm that the number of hydroxyl groups, rather than the HLB of the organic liquid component, has a greater impact on skin irritation, water resistance, and skin staining results. Furthermore, when sorbitan trioleate was used as the organic liquid component, a comparison of Comparative Examples 1 and 5 showed that increasing the amount of sorbitan trioleate did not improve skin irritation; rather, increasing the amount tended to worsen skin staining. Furthermore, in Comparative Example 4, which used a water-dispersible copolymer prepared without using a nitrogen-containing monomer, the use of the organic liquid component resulted in a passing skin irritation evaluation result, but good water resistance was not achieved. Comparative Example 4 has an adhesive composition corresponding to Example 4 of Patent Document 2, and the results of Comparative Example 4 show that the adhesives of Examples 1 to 6 have better water resistance than the adhesive described in Patent Document 2.The water-dispersible copolymer A2 used in Comparative Example 4 had lower adhesive strength than the water-dispersible copolymer A1 used in Example 1, but after blending with an organic liquid component (sorbitan monolaurate), the adhesive strength was higher than that of Example 1, and a difference in the degree of skin irritation was also observed. This result is thought to indicate that a better skin irritation suppression effect can be obtained by using a water-dispersible copolymer synthesized using a nitrogen atom-containing monomer in addition to a (meth)acrylic acid alkyl ester, a carboxy group-containing monomer, and a silane-based monomer in combination with an organic liquid component having more than one hydroxyl group.

[0102] The above results show that an adhesive containing a water-dispersible copolymer obtained by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester, a carboxy group-containing monomer, a nitrogen atom-containing monomer, and a silane-based monomer, and an organic liquid component having more than one hydroxyl group in the molecule, causes less irritation to the skin when peeled off from the skin, has good water resistance, and can prevent skin contamination by the adhesive components.

[0103] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0104] REFERENCE SIGNS LIST 1 adhesive sheet 10 adhesive layer 10A one surface (adhesive surface) 10B other surface 20 support 20A first surface 20B second surface (rear surface) 30 release liner 50 adhesive sheet with release liner

Claims

1. A medical adhesive comprising: a water-dispersible copolymer obtained by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester, a carboxyl group-containing monomer, a nitrogen atom-containing monomer, and a silane-based monomer; and an organic liquid component having more than one hydroxyl group in the molecule.

2. The medical adhesive according to claim 1, comprising 0.1 to 10 parts by mass of the nitrogen atom-containing monomer per 100 parts by mass of the monomer mixture.

3. The medical adhesive according to claim 1 or 2, wherein the nitrogen atom-containing monomer has a structure in which no hydrogen atom is bonded to the nitrogen atom.

4. The medical adhesive according to claim 1 or 2, wherein the nitrogen atom-containing monomer has a cyclic structure containing a nitrogen atom within the ring.

5. The medical adhesive according to claim 1 or 2, comprising 0.1 to 10 parts by mass of the carboxy group-containing monomer per 100 parts by mass of the monomer mixture.

6. The medical adhesive according to claim 1 or 2, wherein the HLB (hydrophile-lipophile balance) of the organic liquid component is 3-16.

7. The medical adhesive according to claim 1 or 2, wherein the organic liquid component is a fatty acid ester derivative of a polyhydric alcohol.

8. The medical adhesive according to claim 7, wherein the fatty acid forming the fatty acid ester derivative of the polyhydric alcohol is a fatty acid having 8 to 18 carbon atoms.

9. The medical adhesive according to claim 1 or 2, comprising 1 to 60 parts by mass of the organic liquid component per 100 parts by mass of the water-dispersible copolymer.

10. A medical adhesive sheet having the medical adhesive according to claim 1 or 2 on at least one surface of a support.

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