Medical adhesive and medical adhesive sheet

Abstract

Provided is a medical adhesive comprising: a water-dispersible acrylic polymer obtained by polymerization of an alkyl (meth)acrylate; and an organic liquid component having a molecular weight of 1,500-7,000 and a hydrophobic ratio of 38-75%.

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. 2024-152731, filed on September 4, 2024, 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 used in medical applications by applying them to the skin are required to closely conform to the irregularities present on the skin surface when applied to the skin. One method for improving such conformability and adhesion to the irregularities of the skin surface is to add an organic liquid component to the adhesive to plasticize the adhesive. For example, Patent Document 1 describes a solvent-based acrylic adhesive in which 100 parts by weight of an acrylic copolymer is blended with 60 parts by weight of a carboxylic acid ester (specifically, triglycidyl caprylate) that is liquid at room temperature. Patent Document 2 also discusses a water-dispersible acrylic adhesive in which 100 parts by weight of an acrylic copolymer is blended with 30 parts by weight of an organic liquid component (specifically, sorbitan trioleate, sorbitan monolaurate, or sorbitan monooleate).

[0005] Furthermore, in recent years, there has been a trend toward eliminating or reducing the use of organic solvents in PSA formulations from the viewpoints of environmental considerations, worker health, etc. With regard to the above-mentioned prior art documents, PSA formulations using water-dispersible polymers as disclosed in Patent Document 2 are more desirable than PSA formulations prepared using organic solvents such as toluene as disclosed in Patent Document 1.

[0006] Some medical adhesives are used to fix repulsive materials, such as tubes, to the skin. It is desirable for such adhesives to have high adhesion to the skin and to maintain this adhesion against forces acting in the direction of peeling from the skin, such as the repulsion of a tube. Such adhesives that have excellent adhesion retention to the skin are also preferred because they are less likely to peel over time. However, when an organic liquid component, such as those described in Patent Documents 1 and 2, is added to an adhesive, the adhesive's ability to maintain adhesion to the skin tends to decrease. In adhesives containing such organic liquid components, there is a technical trade-off between the ability to conform to and adhere to the skin surface and the ability to maintain adhesion to the skin. It would be useful to provide a medical adhesive containing a water-dispersible acrylic polymer that can better balance the ability to conform to and adhere to the skin surface and the ability to maintain adhesion to the skin.

[0007] The present invention was made in view of the above circumstances, and aims to provide a medical adhesive that can achieve both conformal adhesion to the skin and the ability to maintain adhesion to the skin. Another related aim is to provide a medical adhesive sheet containing the medical adhesive.

[0008] According to this specification, a medical adhesive is provided that contains a water-dispersible acrylic polymer obtained by polymerizing a (meth)acrylic acid alkyl ester, and an organic liquid component having a molecular weight of 1500 to 7000 and a hydrophobicity of 38 to 75%. An adhesive having this composition can achieve both conformal adhesion to the skin and the ability to maintain adhesion to the skin.

[0009] In some preferred embodiments, the organic liquid component is used in an amount of 1 to 15 parts by weight per 100 parts by weight of the acrylic polymer. By using the organic liquid component in the above range, the technology disclosed herein can be preferably implemented.

[0010] 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.

[0011] 1 is a cross-sectional view schematically illustrating the configuration of a medical adhesive sheet according to one embodiment.

[0012] 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.

[0013] 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 ２The material may be a material having the properties satisfying the above (typically, a material having the above properties at 25°C).

[0014] 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."

[0015] <Adhesive> (Water-dispersible acrylic polymer) The adhesive disclosed herein contains a water-dispersible acrylic polymer. Here, "water-dispersible acrylic polymer" refers to an acrylic polymer synthesized in a form dispersed in water, typically an acrylic polymer synthesized by emulsion polymerization. By using a water-dispersible polymer as an adhesive-forming component, it is possible to eliminate organic solvents and reduce the amount of organic solvent used, thereby forming an adhesive that takes into consideration the environment, worker health, etc. Furthermore, acrylic adhesives containing an acrylic polymer tend to provide good adhesion. Furthermore, acrylic adhesives are relatively less irritating to the skin than rubber-based adhesives, making them suitable as medical adhesives to be applied to the skin.

[0016] In this specification, "acrylic polymer" refers to a polymer derived from a monomer component containing more than 50% by weight of an acrylic monomer. The acrylic monomer refers to a monomer having at least one (meth)acryloyl group in one 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.

[0017] The water-dispersible acrylic polymer is typically contained as a base polymer in the PSA. Here, "base polymer" refers to the main component of the polymer contained in the PSA, and is not intended to be interpreted in any other limiting sense. Furthermore, in this specification, "main component" refers to the component that is contained in the largest proportion of the components by weight. Therefore, for example, if the PSA is composed of three or more polymers, the content of the main component in the polymer may be 34 wt % or more, and typically, may be a component that is contained in more than 50 wt %.

[0018] As the water-dispersible acrylic polymer, a polymer obtained by polymerizing a (meth)acrylic acid alkyl ester is used. The (meth)acrylic acid alkyl ester is typically contained as a main component of the monomer component (also referred to as a monomer mixture when a plurality of monomers are contained) used to form the acrylic polymer. This makes it possible to preferably design a pressure-sensitive adhesive having good adhesive properties (adhesive strength, cohesive strength, etc.). As the (meth)acrylic acid alkyl ester, for example, a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having from 1 to 20 carbon atoms at the ester terminal is used. Hereinafter, a (meth)acrylic acid alkyl ester having an alkyl group having from X to Y carbon atoms at the ester terminal will be referred to as "(meth)acrylic acid C Ｘ－Ｙ The (meth)acrylic acid alkyl esters may be used alone or in combination of two or more.

[0019] (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.

[0020] 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, the monomer component may be (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.

[0021] In some 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 conformability and adhesion to skin having a complex surface shape that expands, contracts, and deforms. In some embodiments, in the above-mentioned monomer component, (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 to include 2-ethylhexyl acrylate (2EHA) as the monomer component. ７－９ Other examples of alkyl esters include heptyl acrylate, octyl acrylate, isooctyl acrylate, and isononyl acrylate.

[0022] The proportion of the (meth)acrylic acid alkyl ester among the above-mentioned monomer components is suitably 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, for example, 92% by weight or more, or even 94% by weight or more, from the viewpoint of obtaining the desired adhesive properties (adhesive strength, cohesive strength, etc.). In an embodiment using a monomer copolymerizable with the (meth)acrylic acid alkyl ester (copolymerizable monomer), such as a carboxy group-containing monomer described below, the proportion of the (meth)acrylic acid alkyl ester among the above-mentioned monomer components 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, from the viewpoint of obtaining the effect based on the copolymerizable monomer.

[0023] In some embodiments, the monomer component may contain, in addition to the (meth)acrylic acid alkyl ester, a monomer (copolymerizable monomer) copolymerizable with the (meth)acrylic acid alkyl ester. By selecting and using an appropriate copolymerizable monomer, it is possible to introduce crosslinking points into the water-dispersible acrylic polymer or increase the cohesive strength of the water-dispersible acrylic polymer. For example, the copolymerizable monomer may be a monomer (functional group-containing monomer) having a functional group such as a crosslinkable reactive group or a polar group. The copolymerizable monomer may be used alone or in combination of two or more.

[0024] In some embodiments, the monomer component includes a carboxyl group-containing monomer as the copolymerizable monomer. The use of a carboxyl group-containing monomer can increase cohesive strength, which tends to result in good adhesive strength and water resistance. Furthermore, a water-dispersible acrylic polymer in which an appropriate carboxyl group-containing monomer is polymerized has good dispersion stability in an aqueous dispersion and is advantageous in terms of productivity. The carboxyl group-containing monomer is not particularly limited, and various monomers having a carboxyl group can be used. The carboxyl group-containing monomer can be used alone or in combination of two or more.

[0025] In some embodiments, the carboxyl group-containing monomer includes acrylic acid. This can provide effects such as improved cohesive strength (e.g., action on the surface of polymer particles) based on acrylic acid copolymerization. In embodiments using acrylic acid, the amount of acrylic acid used (in other words, the copolymerization ratio of acrylic acid in the water-dispersible acrylic polymer) is not particularly limited and may be, for example, 0.1 wt% or more of the monomer components, preferably 0.5 wt% or more, and more preferably 1.0 wt% or more (e.g., 1.5 wt% or more). By using acrylic acid in a predetermined amount or more, adhesive properties (adhesive strength, cohesive strength, etc.), dispersion stability, dispersion preparation ease, etc. can be improved. In some embodiments, the amount of acrylic acid used is, from the viewpoint of water resistance, flexibility, etc., suitably, for example, 10 wt% or less of the monomer components, 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.

[0026] In some embodiments, the carboxyl group-containing monomer includes a carboxyl group-containing monomer other than acrylic acid. For example, a carboxyl group-containing monomer having a higher hydrophobicity than acrylic acid can be used as such a carboxyl group-containing monomer. The use of such a relatively hydrophobic carboxyl group-containing monomer can improve cohesion (e.g., cohesion within polymer particles). The carboxyl group-containing monomer other than acrylic acid can be used alone or in combination of two or more. Whether a carboxyl group-containing monomer has a higher hydrophobicity than acrylic acid can be determined from its chemical structure and also from its water solubility at 20°C, which will be described later.

[0027] Examples of carboxy group-containing monomers other than acrylic acid 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. All of these are carboxy group-containing monomers that are more hydrophobic than acrylic acid. Among these, MAA is preferred from the viewpoint of being effective in small amounts due to its low molecular weight.

[0028] As a carboxy group-containing monomer that is more hydrophobic than acrylic acid, for example, a monomer having a water solubility (solubility in water) of 15.0 g / 100 mL or less at 20°C can be used. From the viewpoint of improving the cohesion force inside the polymer particles, the water solubility of the carboxy group-containing monomer 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 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 a carboxy group-containing monomer 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 a value measured in accordance with Techniques of Chemistry 4th Ed. Vol. II Organic Solvents (1985): New York, NY. John Wiley and Sons, Inc. ICSC(J)1997.

[0029] In embodiments using a carboxy group-containing monomer other than acrylic acid (preferably a carboxy group-containing monomer more hydrophobic than acrylic acid), the amount of the carboxy group-containing monomer other than acrylic acid (in other words, the copolymerization ratio of the carboxy group-containing monomer other than acrylic acid in the water-dispersible acrylic polymer) 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 of the monomer components. Increasing the amount of the carboxy group-containing monomer within a predetermined range can favorably improve cohesive strength and adhesive strength. In addition, in some embodiments, the amount of the carboxy group-containing monomer other than acrylic acid used 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, particularly preferably 3.0 wt% or less, and may be, for example, 1.5 wt% or less of the monomer components.

[0030] In some embodiments, the carboxy group-containing monomer includes acrylic acid and a carboxy group-containing monomer that is more hydrophobic than acrylic acid. By using acrylic acid in combination with a relatively hydrophobic carboxy group-containing monomer as the carboxy group-containing monomer, a PSA having excellent adhesive strength and cohesive strength can be preferably obtained. Due to the cohesive strength, such PSA also tends to have excellent water resistance. In embodiments in which acrylic acid and a carboxy group-containing monomer that is more hydrophobic than acrylic acid are used in combination as the carboxy group-containing monomer, the ratio of the two monomers is not particularly limited, and an appropriate ratio can be adopted depending on factors such as dispersion stability, polymer preparation, and the type of carboxy group-containing monomer used. In some embodiments, the weight ratio (C1 / C2) of the amount of acrylic acid (C1) used to the amount of carboxy group-containing monomer (C2) used that is more hydrophobic than acrylic acid 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, and the like. In some embodiments, the ratio (C1 / C2) may be, for example, 10 or less, 5 or less, 3 or less, or 2 or less, from the viewpoint of improving adhesive strength and cohesive strength.

[0031] In embodiments using a carboxy group-containing monomer, the amount of the carboxy group-containing monomer used (in other words, the copolymerization ratio of the carboxy group-containing monomer in the water-dispersible acrylic polymer) is not particularly limited, and may be, for example, 0.1 wt% or more of the monomer components, 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, or even 3.0 wt% or more. By increasing the amount of the carboxy group-containing monomer used within a predetermined range, adhesive strength, cohesive strength, and the like can be favorably improved. Furthermore, in some embodiments, from the viewpoints of flexibility, water resistance, and the like, the amount of the carboxy group-containing monomer used is suitably, for example, 10 wt% or less of the monomer components, 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.

[0032] In some embodiments, the monomer component includes a nitrogen-atom-containing monomer as a copolymerizable monomer. The use of a nitrogen-atom-containing monomer can enhance cohesive strength, which tends to result in good adhesive strength and water resistance. The nitrogen-atom-containing monomer is not particularly limited, and various monomers containing nitrogen atoms 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 can be used alone or in combination of two or more.

[0033] 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.

[0034] In some embodiments, the nitrogen atom-containing monomer is used in combination with a carboxy group-containing monomer. That is, the monomer component of the water-dispersible acrylic polymer may contain a carboxy group-containing monomer and a nitrogen atom-containing monomer. The combined use of a carboxy group-containing monomer and a nitrogen atom-containing monomer can further improve adhesive strength and cohesion, which can contribute to achieving good adhesion in compositions containing an organic liquid component, as described below. This is thought to be because the coexistence of a carboxy group-containing monomer and a nitrogen atom-containing monomer improves cohesion due to their acid-base interaction. Note that the technology disclosed herein is not limited to the above considerations. By utilizing the effects based on the combined use of the above monomers, for example, a highly flexible material can be used as the (meth)acrylic acid alkyl ester, thereby achieving a favorable balance between flexibility, adhesive strength, and cohesion.

[0035] In some 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. For example, in an embodiment in which a monomer having a structure in which no hydrogen atom is bonded to the nitrogen atom is used in combination with a carboxy group-containing monomer, the acid-base interaction with the carboxylic acid is strengthened, and the cohesive strength and adhesive strength can be improved based on this acid-base interaction. The nitrogen atom-containing monomer 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.

[0036] Although not particularly limited, in some embodiments, a nitrogen atom-containing monomer having a small acid dissociation constant (pKa) is used as the nitrogen atom-containing monomer. For example, in embodiments in which a nitrogen atom-containing monomer and a carboxy group-containing monomer are used in combination, the smaller the pKa of the nitrogen atom-containing monomer, the stronger the acid-base interaction with the carboxylic acid, and the more likely it is that excellent cohesive strength will be obtained. The pKa of the nitrogen atom-containing monomer may be, for example, 7 or less, 5 or less, or 3 or less. From the viewpoint of obtaining better cohesive strength and adhesive strength, a nitrogen atom-containing monomer having a pKa of 1 or less may be used. 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 is -2 or more, or may be -1.5 or more, or may be -1 or more. A suitable example of a nitrogen atom-containing monomer having the above pKa is NVP (pKa: -0.34). The pKa can be calculated from the concentration of the substance to be measured and the hydrogen ion concentration by measuring the hydrogen ion concentration of the substance using a pH meter.

[0037] In some embodiments, a monomer having a cyclic structure containing a nitrogen atom within the ring (a monomer having a nitrogen atom-containing ring) is used as the nitrogen atom-containing monomer. By using a monomer having a nitrogen atom-containing ring, better cohesive strength and adhesive strength can be achieved. It is believed that the structure having a nitrogen atom-containing ring, for example, in an embodiment in which a nitrogen atom-containing monomer is used in combination with a carboxy group-containing monomer, provides a distance that facilitates interaction between an acid and a base, making it easier to achieve a better cohesive strength improvement effect. Suitable examples of a monomer 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 monomer having a nitrogen atom-containing ring can be used alone or in combination of two or more.

[0038] In embodiments in which a monomer having a nitrogen atom-containing ring is used as the nitrogen atom-containing monomer, the proportion of the monomer having a nitrogen atom-containing ring in the total nitrogen atom-containing monomers 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 total nitrogen atom-containing monomers may be, for example, 10% by weight or more, suitably 50% by weight or more, preferably 70% by weight or more, or even 90% by weight or more (e.g., 95 to 100% by weight).

[0039] In embodiments using a nitrogen atom-containing monomer, the amount of the nitrogen atom-containing monomer used (in other words, the copolymerization ratio of the nitrogen atom-containing monomer in the water-dispersible acrylic polymer) is not particularly limited and may be, for example, 0.1 wt% or more of the monomer components, 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. Increasing the amount of the nitrogen atom-containing monomer used within a predetermined range can favorably improve cohesive strength and adhesive strength. In addition, in some embodiments, from the viewpoint of flexibility, etc., the amount of the nitrogen atom-containing monomer used is suitably, for example, 10 wt% or less of the monomer components, 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.

[0040] In addition, in embodiments in which a nitrogen atom-containing monomer and a carboxy group-containing monomer are used in combination, the ratio of the carboxy group-containing monomer to the nitrogen atom-containing monomer is not particularly limited and is appropriately set so as to exhibit the desired adhesive properties (adhesive strength, cohesive strength, etc.). In some embodiments, the weight ratio (C / N) of the amount of the carboxy group-containing monomer (C) to the amount of the nitrogen atom-containing monomer (N) 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. In some embodiments, the ratio (C / N) 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.

[0041] In some embodiments, the monomer component may further comprise a silane-based monomer. A water-dispersible acrylic polymer having a monomer composition containing a silane-based monomer can introduce a crosslinked structure between polymer particles through a silanol group condensation reaction (silanol condensation). This crosslinking between polymer particles improves cohesion, water resistance, and adhesive strength. The silane-based monomer is also called a silane coupling agent.

[0042] As the silane-based monomer, for example, an alkoxysilyl group-containing monomer can be 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-based monomer include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane. The silane-based monomers can be used alone or in combination of two or more.

[0043] In an embodiment in which a silane-based monomer is used in the synthesis of a water-dispersible acrylic polymer, the proportion of the silane-based monomer in the monomer component 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 an adherend, the proportion of the silane-based monomer is, for example, suitably 0.5% by weight or less, preferably 0.2% by weight or less, or even 0.1% by weight or less, or 0.05% by weight or less.

[0044] Furthermore, as the monomer component, one or more copolymerizable monomers may be used as needed, including monomers having functional groups different from the carboxy group-containing monomers, nitrogen atom-containing monomers, and silane-based monomers, and monomers having a relatively high glass transition temperature of the homopolymer (e.g., 10°C or higher). Non-limiting examples of such other copolymerizable monomers include acid anhydride group-containing monomers, hydroxyl group-containing monomers (e.g., 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate), monomers containing sulfonic acid groups or phosphoric acid groups, 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. Examples of suitable monomers include acrylic acid esters, 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).

[0045] The other copolymerizable monomers can be used in an appropriate amount as long as the effects of the invention are not impaired. In some embodiments, the monomer component may be substantially free of other copolymerizable monomers. For example, the content of hydroxyl group-containing monomers in the monomer component may be 3 wt % or less (e.g., 1 wt % or less, or even 0.1 wt % or less), and the monomer component may be substantially free of hydroxyl group-containing monomers.

[0046] In embodiments using a copolymerizable monomer, the amount of the copolymerizable monomer used (in other words, the copolymerization ratio of the copolymerizable monomer in the water-dispersible acrylic polymer) is not particularly limited, and may be, for example, 0.1% by weight or more, 1.0% by weight or more, or 2.0% by weight or more of the above-mentioned monomer components. In some embodiments, the ratio of the copolymerizable monomer in the above-mentioned monomer components is suitably, for example, about 30% by weight or less, and may be 10% by weight or less, or may be 5% by weight or less.

[0047] Water-dispersible acrylic polymers 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 conventionally known general emulsion polymerizations, can be appropriately adopted. For example, the monomer supply method can be a batch feed method in which all monomers are supplied at once, a continuous supply (dropping) method, or a divided supply (dropping) method. It is preferable that some or all of the monomer components are supplied as a dispersion (emulsion) emulsified in water. For example, when the monomer components are supplied by a dropwise method, they are preferably 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 preferably about 100°C or lower (usually 80°C or lower).

[0048] 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 component.

[0049] 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 adhesive properties such as adhesion, 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.

[0050] 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.

[0051] 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.

[0052] By emulsion polymerizing a monomer component 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 adhesion and retention of the adhesion state.

[0053] 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 component. From the viewpoint of adhesive properties such as adhesion, 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 component.

[0054] 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, 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. One chain transfer agent can be used alone, or two or more chain transfer agents can be used in combination. 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 component.

[0055] (Organic Liquid Component) The PSA 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). The organic liquid component has a molecular weight of 1500 to 7000 and a hydrophobicity of 38 to 75%. By incorporating an organic liquid component satisfying the above characteristics into a PSA containing a water-dispersible acrylic polymer, it is possible to achieve both conformal adhesion to the skin and the ability to maintain an intimate contact with the skin. An organic liquid component satisfying the above molecular weight and hydrophobicity satisfies the above-mentioned requirements, and due to its compatibility with the water-dispersible acrylic polymer, it moderately plasticizes the PSA, improving its ability to conform to the irregularities of the skin surface. This conformal ability improves adhesion to the skin (conformal adhesion). Furthermore, the organic liquid component has the above-mentioned molecular weight and hydrophobicity, so that its movement within the adhesive is restricted. For example, even when a force is applied in the direction of peeling from the adherend, or when the adhesive is left attached for a predetermined period of time while conforming to the unevenness of the adherend, the adhesive containing the organic liquid component undergoes little change in properties, and migration to the adhesive interface is also suppressed. Therefore, there is little change in adhesive properties, the adhesive maintains good adhesion to the skin, and peeling is unlikely to occur. 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.

[0056] In some preferred embodiments, the molecular weight of the organic liquid component may be 1600 or more, 1700 or more, 1800 or more, 1900 or more, or 2000 or more. By using an organic liquid component having a molecular weight of a certain level or higher, the movement of the organic liquid component within the PSA is likely to be restricted. Furthermore, from the viewpoint of plasticizing the PSA and improving its conformability and adhesion, in some embodiments, the molecular weight of the organic liquid component may be 6000 or less, or may be 5000 or less. In some preferred embodiments, the molecular weight of the organic liquid component is 4500 or less, more preferably 4000 or less, even more preferably 3500 or less, even more preferably 3000 or less, and particularly preferably 2500 or less. By using an organic liquid component having a lower molecular weight within the above range, the retention of the adhesion state can also be improved.

[0057] In this specification, the molecular weight of the organic liquid component is the weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) in terms of standard polystyrene. Specifically, the Mw of the organic liquid component is measured using an HPLC8020 (trade name, manufactured by Tosoh Corporation) with two TSKgel GMH-H (20) columns, using tetrahydrofuran as a solvent at a flow rate of approximately 0.5 mL / min.

[0058] In some embodiments, the hydrophobicity of the organic liquid component may be 40% or more, 42% or more, 44% or more, 46% or more, 48% or more, 50% or more, 52% or more, 54% or more, 56% or more, 58% or more, 60% or more, 62% or more, 64% or more, 66% or more, 68% or more, or 70% or more. In some embodiments, the hydrophobicity of the organic liquid component may be 73% or less, 70% or less, 67% or less, 64% or less, 60% or less, 57% or less, 54% or less, 52% or less, or 50% or less. For example, the desired effect can be achieved by selecting and using an organic liquid component having an appropriate hydrophobicity within the above range depending on the composition, molecular weight, etc. of the water-dispersible acrylic polymer used.

[0059] In this specification, the hydrophobicity of an organic liquid component refers to the ratio of hydrophobic moieties in a compound or a mixture of compounds that constitute the organic liquid component, and more specifically, is calculated using the following formula (A): (A) Hydrophobicity [%] = (1 - Molecular Weight of Hydrophilic Moiety / Molecular Weight of Organic Liquid Component) x 100 The hydrophilic moiety of the organic liquid component is composed of an oxygen atom in the organic liquid component, a carbon atom adjacent to the oxygen atom, and a hydrogen atom associated with the carbon atom. The molecular weight of the hydrophilic moiety of the organic liquid component is calculated from the sum of the products of the number of atoms that constitute the hydrophilic moiety and the atomic weight of the corresponding atom. The molecular weight of the organic liquid component is calculated from the chemical structure (chemical formula) of the organic liquid component. The portion of the organic liquid component other than the hydrophilic moiety is considered to be the hydrophobic moiety. Therefore, the hydrophobicity rate [%] of the organic liquid component can also be calculated by calculating the molecular weight of the hydrophobic portion from the sum of the products of the number of each atom constituting the hydrophobic portion of the organic liquid component and the atomic weight of the corresponding atom, and then using the following formula (B): (B) Hydrophobicity rate [%] = (molecular weight of hydrophobic portion / molecular weight of organic liquid component) × 100.

[0060] As the organic liquid component, various organic materials that are liquid at room temperature, have a molecular weight of 1500 to 7000, and a hydrophobicity of 38 to 75% can be used without particular limitation. In some embodiments, a fatty acid ester of a polyhydric alcohol is preferably used as the organic liquid component. The organic liquid component may also be a derivative of the fatty acid ester of the polyhydric alcohol.

[0061] The polyhydric alcohol may be a trivalent or higher polyhydric alcohol. The number of hydroxyl groups in the polyhydric alcohol (also referred to as the valence of the polyhydric alcohol) may be, for example, 5 or more, 7 or more, or 9 or more. The number of hydroxyl groups may be 20 or less, 15 or less, 12 or less, or 10 or less. Non-limiting examples of the polyhydric alcohol include glycerin, polyglycerol, trimethylolpropane, pentaerythritol, sorbitol, and sucrose. Among these, glycerin, polyglycerol, and sorbitol are preferred, with polyglycerol being particularly preferred.

[0062] The fatty acid forming the polyhydric alcohol fatty acid ester or its derivative is preferably one that imparts appropriate hydrophobicity to the organic liquid component. For example, fatty acid esters of saturated or unsaturated fatty acids having a carbon number of 4 to 22 or their derivatives 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 component is likely to be obtained. The carbon number of the fatty acid is preferably 8 or more, and may be 10 or more, 12 or more, 14 or more, or 16 or more. The higher the carbon number of the fatty acid, the higher the hydrophobicity of the organic liquid component tends to be. Furthermore, from the viewpoint of compatibility with the water-dispersible acrylic polymer, the carbon number of the fatty acid is preferably 18 or less, more preferably 15 or less, even more preferably 12 or less, even more preferably 10 or less, and particularly preferably 8 or less. Non-limiting examples of the fatty acid include ethylhexanoic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, and oleic acid. Among these, ethylhexanoic acid is preferred.

[0063] In embodiments where the organic liquid component is a fatty acid ester of a polyhydric alcohol or a derivative thereof, the number of fatty acids forming the organic liquid component is at least 1, and may be, for example, 3 or more, 5 or more, 7 or more, or 9 or more. The greater the number of fatty acids, the higher the hydrophobicity of the organic liquid component tends to be, and, for example, based on the structure of the fatty acids, the more likely it is that the organic liquid component will have good compatibility with the water-dispersible acrylic polymer. Furthermore, from the viewpoint of achieving a desired hydrophobicity, in some embodiments, the number of fatty acids may be 20 or less, 15 or less, 12 or less, or 10 or less.

[0064] Non-limiting examples of the organic liquid component include decaethylhexanoic acid polyglyceride, decastearic acid polyglyceride, pentaisostearic acid polyglyceride, decaisostearic acid polyglyceride, and the like.

[0065] In some other embodiments, the organic liquid component may be an acrylic oligomer having a molecular weight of 1500 to 7000 and a hydrophobicity of 38 to 75%. Such an acrylic oligomer may be a copolymer of a hydrophobic monomer and a hydrophilic monomer.

[0066] A typical example of the hydrophobic monomer constituting the acrylic oligomer is (meth)acrylic acid alkyl ester. As the (meth)acrylic acid alkyl ester, any of the (meth)acrylic acid alkyl esters exemplified as the monomer for the water-dispersible acrylic polymer can be used without any particular limitation. The (meth)acrylic acid alkyl ester is, for example, (meth)acrylic acid C １－２０ (Meth)acrylic acid C may be an alkyl ester. ４－２０ It may be an alkyl ester, and (meth)acrylic acid C ４－１８ It may be an alkyl ester, and (meth)acrylic acid C ４－１２ It may be an alkyl ester, and acrylic acid C ４－１０ It may be an alkyl ester, and acrylic acid C ７－９Alternatively, an alkyl ester (e.g., 2EHA) may be used. By using a monomer that is the same as or similar to the monomer of the water-dispersible acrylic polymer, compatibility with the water-dispersible acrylic polymer is easily achieved. The hydrophobic monomer (e.g., (meth)acrylic acid alkyl ester) may be used alone or in combination of two or more.

[0067] Examples of hydrophilic monomers constituting the acrylic oligomer include carboxy group-containing monomers, acid anhydride group-containing monomers, hydroxyl group-containing monomers, nitrogen atom-containing monomers, alkoxy group-containing monomers, and (poly)alkylene glycol-containing monomers. These hydrophilic monomers can be the same as those exemplified as monomers for water-dispersible acrylic polymers, and therefore redundant explanations will be omitted. The hydrophilic monomers can be used alone or in combination of two or more. In some embodiments, alkoxy group-containing monomers and (poly)alkylene glycol-containing monomers are used as the hydrophilic monomer. Examples of alkoxy group-containing monomers include alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and 2-ethoxyethyl (meth)acrylate. Examples of the (poly)alkylene glycol-containing monomer include (poly)alkylene glycol (meth)acrylates such as (poly)ethylene glycol (meth)acrylate, and alkoxy(poly)alkylene glycol (meth)acrylates having an alkoxy group such as a methoxy group at the (poly)alkylene glycol terminal of the (poly)alkylene glycol (meth)acrylate.

[0068] In the acrylic oligomer, the copolymerization ratio of the hydrophobic monomer to the hydrophilic monomer is set so as to obtain a predetermined hydrophobicity. Although not particularly limited, the copolymerization ratio (M1 / M2) of the hydrophobic monomer M1 to the hydrophilic monomer M2 by weight may be 1 / 1 or more, 3 / 1 or more, 5 / 1 or more, or 99 / 1 or less, 30 / 1 or less, or 9 / 1 or less.

[0069] The acrylic oligomer can be formed by polymerizing its constituent monomer components. The polymerization method and polymerization mode are not particularly limited, and various conventionally known polymerization methods (e.g., solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be used in an appropriate mode. As the polymerization initiator, various polymerization initiators such as azo-based polymerization initiators can be used depending on the polymerization method, etc. The amount of the polymerization initiator and the amount of an optionally used chain transfer agent such as n-dodecyl mercaptan or thioglycerol are appropriately set based on common technical knowledge so as to achieve the desired molecular weight, and therefore detailed explanations thereof will be omitted here.

[0070] The amount of the organic liquid component used is not particularly limited. For example, the amount of the organic liquid component used may be 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more, relative to 100 parts by weight of the water-dispersible acrylic polymer. By using a predetermined amount or more of the organic liquid component, the effect of containing the organic liquid component can be effectively exerted. From the viewpoint of conformability and adhesion to the skin, in some preferred embodiments, the amount of the organic liquid component relative to 100 parts by weight of the acrylic polymer is approximately 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, or 5 parts by weight or more. A pressure-sensitive adhesive containing an organic liquid component in the above range has sufficient initial tack, good adhesion to the skin, and can be preferably used for medical applications. In some embodiments, the amount of the organic liquid component used is preferably about 15 parts by weight or less, or may be 12 parts by weight or less, 10 parts by weight or less (e.g., less than 10 parts by weight), 8 parts by weight or less, or 6 parts by weight or less, relative to 100 parts by weight of the acrylic polymer. By limiting the amount of the organic liquid component used within the above range, the organic liquid component is more likely to be well miscible in the PSA, and both conformal adhesion to the skin and retention of adhesion to the skin can be better achieved.

[0071] (Crosslinking Agent) The pressure-sensitive adhesive 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.

[0072] 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) relative to 100 parts by weight of the water-dispersible acrylic polymer. 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) relative to 100 parts by weight of the acrylic polymer. In some embodiments, the PSA may be substantially free of a crosslinking agent. According to the technology disclosed herein, by designing the monomer composition of the water-dispersible acrylic polymer, sufficient cohesive strength can be achieved with the use of a small amount of crosslinking agent or substantially no crosslinking agent.

[0073] (Other Optional Components) The PSA 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 contains a tackifier resin, the amount of the tackifier resin used is suitably in the range of, for example, 1 to 30 parts by weight, and may be 10 parts by weight or less, per 100 parts by weight of the water-dispersible acrylic polymer. In some embodiments, the PSA is substantially free of a tackifier resin. According to the technology disclosed herein, the PSA can exhibit high adhesion to skin without containing a tackifier resin.

[0074] The adhesive may contain various additives commonly used in the field of adhesives, such as leveling agents, thickeners, pH adjusters, crosslinking aids, plasticizers, softeners, fillers, colorants (dyes, pigments), antibacterial agents, antifungal agents, preservatives, antistatic agents, antioxidants, UV absorbers, antioxidants, light stabilizers, and dispersants, as needed. Furthermore, the adhesive may optionally contain a skin irritation-reducing component, such as a carboxylic acid ester or a fatty acid ester, that does not fall under the category of organic liquid components disclosed herein, within the scope of the invention. As for the various additives mentioned above, conventionally known ones can be used in the usual manner, and as they do not particularly characterize the present invention, detailed description thereof will be omitted.

[0075] (Method for Forming a Pressure-Sensitive Adhesive) The pressure-sensitive adhesive disclosed herein can be formed from a water-dispersed pressure-sensitive adhesive composition. The term "water-dispersed pressure-sensitive adhesive composition" refers to a pressure-sensitive adhesive composition in which at least a portion of the pressure-sensitive adhesive-forming components are dispersed in an aqueous medium. The pressure-sensitive adhesive disclosed herein can be prepared using a water-dispersed pressure-sensitive adhesive composition containing a water-dispersed acrylic polymer and an organic liquid component, 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 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 also encompasses what are known as emulsion-type pressure-sensitive adhesive compositions. The pressure-sensitive adhesive compositions disclosed herein typically have an emulsion form in which an acrylic polymer is dispersed in water.

[0076] The PSA disclosed herein can be formed by a conventionally known method using, for example, the adhesive composition. For example, a layered PSA (adhesive layer) can be formed by applying the PSA composition to a releasable surface (release surface) and drying it. For PSA sheets having a support, a method (direct method) can be used in which the PSA composition is directly applied (typically coated) to the support and dried to form a PSA layer. Alternatively, a method (transfer method) can be used in which the PSA composition is applied to a releasable surface (release surface) and dried to form a PSA layer on the surface, and the PSA layer is then transferred to the support. The release surface can preferably be, for example, the surface of a release liner. While the PSA layer disclosed herein is typically formed continuously, it is not limited to this form and may be formed in a regular or random pattern, such as dots or stripes.

[0077] 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.

[0078]

[0013] As described above, this specification provides a pressure-sensitive adhesive composition comprising the above-mentioned water-dispersible acrylic polymer and an organic liquid component. The pressure-sensitive adhesive composition may further comprise the various optional components described above. The matters described above regarding the pressure-sensitive adhesive are also applicable to the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive, except for components that volatilize during the formation of the pressure-sensitive adhesive.

[0079] <Adhesive Sheet> (Configuration) The adhesive sheet disclosed herein is not particularly limited other than having the above-mentioned adhesive (layer), and may be an adhesive sheet having the above-mentioned 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 above-mentioned 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.

[0080] 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.

[0081] (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.

[0082] (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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] (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.

[0087] (Adhesive Strength) Although not particularly limited, in some embodiments, the adhesive strength of the adhesive or adhesive sheet is preferably approximately 2.0 N / 10 mm or more, more preferably approximately 3.0 N / 10 mm or more, even more preferably approximately 4.0 N / 10 mm or more, and may be approximately 4.5 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. Furthermore, in some embodiments, the adhesive strength is suitably, for example, 8.0 N / 10 mm or less, and may be 6.0 N / 10 mm or less. An adhesive sheet whose adhesive strength is limited to a predetermined value or less reduces the peel load on the skin when peeled from the skin, making it easier to peel 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.

[0088] (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.

[0089] <Applications> The adhesives and adhesive sheets disclosed herein are suitable for medical applications in which they are applied to the skin. Adhesives applied to the skin in medical applications are required to have good adhesion to the skin. Furthermore, adhesives applied to the skin desirably have water resistance so that they can maintain adhesion to the skin even when sweating. The adhesives and adhesive sheets disclosed herein preferably exhibit the performance required of medical adhesives as described above, and furthermore, are capable of conforming well to the skin and adhering to it well and maintaining good adhesion to the skin. The adhesives and adhesive sheets disclosed herein can be used as various medical adhesives and medical adhesive sheets for the purposes of, for example, protecting affected skin areas, transdermal drug absorption, and securing gauze, tubes, etc. to the skin. For example, they can be preferably used to secure tubes, etc., which require higher adhesion and the ability to maintain that adhesion. 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. The medical applications mentioned above include the fields of health care and preventive medicine.

[0090] 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.

[0091] <Preparation of Water-Dispersed Acrylic Polymer> (Preparation Example A1) Into a flask equipped with a reflux condenser, a thermometer, and a dropping funnel, 161 g of water and 1 g of a reactive emulsifier (product name "Aqualon KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., solids concentration 25%) were placed. Separately, 312 g of 2-ethylhexyl acrylate (hereinafter abbreviated as 2EHA), 6.5 g of acrylic acid (AA), 3.25 g of N-vinylpyrrolidone (NVP), and 3.25 g of methacrylic acid (MAA) were added as monomers, and 0.16 g of a silane monomer (product name "KBM-503", manufactured by Shin-Etsu Chemical Co., Ltd., 3-methacryloxypropyltrimethoxysilane), 0.16 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 polymer (solids concentration approximately 50%).

[0092] <Synthesis of Organic Liquid Component> (Preparation Example B1) A flask equipped with a reflux condenser, a thermometer, and a dropping funnel was charged with 145 g of toluene, 5 g of isopropyl alcohol, 50 g of 2EHA as a monomer component, 10 g of methoxyethyl acrylate (hereinafter abbreviated as MEA), and 3 g of thioglycerol as a chain transfer agent, followed by nitrogen substitution for 1 hour. The temperature was then raised to 60 ° C, and 0.18 g of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and the polymerization reaction was carried out for 3 hours. The temperature was then raised to 70 ° C, and the reaction was carried out for another 3 hours. After cooling to room temperature, the mixture was transferred to a tray and dried in a dryer at 80 ° C for 5 hours to remove the solvent, yielding organic liquid component B1. The weight average molecular weight (Mw) of this organic liquid component B1 measured by gel permeation chromatography (GPC) was approximately 2000, and the hydrophobicity was approximately 58%.

[0093] (Preparation Example B2) Organic liquid component B2 was obtained in the same manner as in Preparation Example B1, except that the amount of the chain transfer agent was changed to 1.8 g. The Mw of this organic liquid component B2 by GPC was about 3,000.

[0094] (Preparation Example B3) Organic liquid component B3 was obtained in the same manner as in Preparation Example B1, except that the amount of the chain transfer agent was changed to 1.2 g. The Mw of this organic liquid component B3 measured by GPC was about 5,000.

[0095] (Preparation Example B4) Organic liquid component B4 was obtained in the same manner as in Preparation Example B1, except that the amount of the chain transfer agent was changed to 0.6 g. The Mw of this organic liquid component B4 measured by GPC was about 8,000.

[0096] (Preparation Example B5) The monomer composition in Preparation Example B2 was changed to 20 g of 2EHA and 40 g of MEA. Organic liquid component B5 was obtained in the same manner as Preparation Example B2. The Mw of this organic liquid component B5 measured by GPC was about 3000, and the hydrophobicity was about 33%.

[0097] (Preparation Example B6) The monomer composition in Preparation Example B2 was changed to 56 g of 2EHA and 4 g of polyethylene glycol monoacrylate (product name "Blemmer AE-200", manufactured by NOF Corporation). Organic liquid component B6 was obtained by the same method as Preparation Example B2 except for the above. The Mw of this organic liquid component B6 measured by GPC was approximately 3000, and the hydrophobicity was approximately 66%.

[0098] (Preparation Example B7) The monomer composition in Preparation Example B2 was changed to 50 g of 2EHA and 10 g of polyethylene glycol monoacrylate (product name "Blemmer AE-200", manufactured by NOF Corporation). Organic liquid component B7 was obtained by the same method as Preparation Example B2 except for the above. The Mw of this organic liquid component B7 measured by GPC was approximately 3000, and the hydrophobicity was approximately 61%.

[0099] Example 1 Organic liquid component B1 was blended with the aqueous acrylic polymer dispersion A1 in an amount of 5 parts per 100 parts of the solids content of the aqueous acrylic polymer dispersion A1, and 28% aqueous ammonia was added to adjust the pH to approximately 8. Next, a thickener (product name "Primal ASE-60" manufactured by Dow Chemical Company) was added to adjust the viscosity to 30 to 55 cP. The aqueous dispersion-type PSA composition thus obtained was applied to the release-treated surface of a 38 μm-thick release liner (product name "MRF38" manufactured by Mitsubishi Chemical Corporation) with one side of the PET film treated with a silicone release agent, and dried at 130°C for 3 minutes to form a 50 μm-thick PSA layer. The exposed adhesive surface of the PSA layer was protected by covering it with a 38 μm-thick release liner (product name "MRE38" manufactured by Mitsubishi Chemical Corporation) with one side of the PET film 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 by a release liner.

[0100] Examples 2 to 12 and Comparative Examples 1 to 4 A water-dispersed PSA composition according to each example was prepared and a PSA sheet was obtained using the water-dispersed PSA composition in the same manner as in Example 1, except that the type and amount of the organic liquid component were changed as shown in Table 1. In Table 1, the organic liquid components other than organic liquid components B1 to B7 are as follows: Decaethylhexanoic acid polyglyceride-10: product name "S Face KEH-1010" (manufactured by Sakamoto Pharmaceutical Co., Ltd., Mw by GPC: approximately 2000, hydrophobicity: approximately 49%) Decastearic acid polyglyceride-10: product name "SY Glystar DAS-7S" (manufactured by Sakamoto Pharmaceutical Co., Ltd., Mw by GPC: approximately 3400, hydrophobicity: approximately 70%) Pentaisostearic acid polyglyceride-10: product name "S Face IS-1005P" (manufactured by Sakamoto Pharmaceutical Co., Ltd., Mw by GPC: approximately 2200, hydrophobicity: approximately 55%) Decaisostearic acid polyglyceride-10: product name "S Face IS-1009P" (manufactured by Sakamoto Pharmaceutical Co., Ltd., Mw by GPC: approximately 3400, hydrophobicity: approximately 70%) Caprylic acid triglyceride: Product name "Coconard RK" (Kao Corporation, molecular weight: approximately 470, hydrophobicity: approximately 63%) Sorbitan trioleate: Product name "Rheodol SP-O30V" (Kao Corporation, molecular weight: approximately 956, hydrophobicity: approximately 74%)

[0101] <Evaluation> (Adhesion Strength to Bakelite Plate) For each PSA sheet according to the present invention, the release liner covering one adhesive surface was peeled off, 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 roll of a 2 kg roller for pressure bonding. Under the same conditions, a tensile tester (product name "Autograph AG-Xplus HS 6000 mm / min high-speed model (AG-50NX plus)", manufactured by Shimadzu Corporation) was used to measure the load when the PSA sheet was peeled from the adherend at a peel angle of 180° 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.

[0102] (Skin Adhesion) The PSA sheet according to each example was cut into a size of 5 cm x 5 cm, and the release liner covering one adhesive surface was peeled off. 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.

[0103] (Adhesion Retention) The pressure-sensitive adhesive sheet according to each example was cut into a size of 10 cm long and 1 cm wide, and the release liner covering one adhesive surface was peeled off. This was then attached to an aluminum plate having a thickness of 0.3 mm, a length of 10 cm, and a width of 1 cm to obtain a test piece. The longitudinal direction of the test piece was bent into an arc along the side R of a cylindrical 100 mL Labolan screw cap (cross-sectional diameter 39 mm) (the aluminum plate side was the inside), and then the release liner covering the other adhesive layer of the test piece was peeled off. Using a laminator, the test piece was pressed against a 3 mm thick polymethyl methacrylate (PMMA) plate by rolling it back and forth with a 2 kg roller while returning the bent shape to its original state. The lift height [mm] of both ends after 0.5 hours and 2 hours was measured. Each measurement was carried out three times (i.e., n = 3), and the average value of these six measurements was calculated to evaluate the adhesion retention (adhesion retention) to the adherend.

[0104] The outline of each example and the evaluation results are shown in Table 1.

[0105]

[0106] As shown in Table 1, the adhesives of Examples 1 to 12, in which an organic liquid component having a molecular weight of 1500 to 7000 and a hydrophobicity of 38 to 75% was added to an adhesive containing a water-dispersible acrylic polymer, exhibited a skin adhesive strength of 7 N / 50 mm or more, and the evaluation results for adhesion retention showed that the lift height after 2 hours was kept to 10 mm or less, achieving both skin adhesive strength and adhesion retention. Furthermore, although not shown in the table, in Examples 10 to 12, in which the amount of organic liquid component used was changed, it was confirmed that the tack tended to decrease as the amount of organic liquid component used decreased.

[0107] On the other hand, Comparative Examples 1 to 4, which used organic liquid components that did not satisfy at least one of the requirements of a molecular weight of 1500 to 7000 and a hydrophobicity of 38 to 75%, showed poor evaluations of adhesion retention. In particular, Comparative Example 1, which used an organic liquid component with a molecular weight exceeding 7000, and Comparative Example 2, which used an organic liquid component with a hydrophobicity of less than 38%, showed poor results in both skin adhesion and adhesion retention. Comparing Examples 1 to 12 with Comparative Examples 1 to 4, it can be seen that Examples 1 to 12 not only had high skin adhesion, but also had skin adhesion that was approximately twice or more the adhesion to the Bakelite plate. This suggests that in addition to high adhesion to the adherend, they also exhibited excellent skin adhesion by adhering well to the unevenness of the skin surface. Examples 1 to 12 thus exhibited good skin-adjusting adhesion and good skin adhesion retention. In this regard, for example, Comparative Example 3 showed similar skin adhesion to the Examples, but significantly reduced adhesion retention. One possible reason for this is that, during the evaluation of adhesion retention, the pressure-sensitive adhesive was subjected to a force that caused the aluminum plate to return to its original shape, causing the low-molecular-weight organic liquid component to migrate to the surface of the pressure-sensitive adhesive, resulting in a decrease in adhesion retention.It is thought that the same phenomenon also caused the decrease in adhesion retention in Comparative Example 4.

[0108] The above results show that a pressure-sensitive adhesive comprising a water-dispersible acrylic polymer obtained by polymerizing a (meth)acrylic acid alkyl ester and an organic liquid component having a molecular weight of 1500 to 7000 and a hydrophobicity of 38 to 75% can achieve both conformal adhesion to the skin and the ability to maintain an adhesive state to the skin.

[0109] 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.

[0110] 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 acrylic polymer in which a (meth)acrylic acid alkyl ester is polymerized; and an organic liquid component having a molecular weight of 1500 to 7000 and a hydrophobicity rate of 38 to 75%.

2. The medical adhesive according to claim 1, wherein the organic liquid component is contained in an amount of 1 to 15 parts by weight per 100 parts by weight of the acrylic polymer.

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

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