Pressure-sensitive adhesive composition

Abstract

To improve the adhesive force of an adhesive composition.SOLUTION: A pressure-sensitive adhesive composition comprising: a (meth) acrylic polymer; nanocellulose; and a crosslinking agent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition. [Background technology]

[0002] Pressure sensitive adhesives are processed into the form of, for example, tapes, labels, etc., and are used to bond plastics, paper, metals, glass, ceramics, etc.

[0003] Patent Document 1 aims to "have high adhesiveness even under high temperature conditions, and also has good stress relaxation properties, thereby exhibiting excellent durability," and describes a decorative film having a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive composition containing a vinyl polymer (A) and an acrylic pressure-sensitive adhesive polymer (B), wherein the vinyl polymer (A) has a glass transition temperature (Tg) of 30°C or more and 200°C or less, a number average molecular weight of 500 to 10,000, and is contained in an amount of 0.5 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the acrylic pressure-sensitive adhesive polymer (B), and the pressure-sensitive adhesive layer has a first Tg, which is the glass transition temperature of the entire pressure-sensitive adhesive layer, of -80°C or more and 10°C or less, and a storage modulus (G') at 90°C of 6.0 × 10 4 The adhesive layer has a second Tg, which is a glass transition temperature calculated from a surface portion thereof obtained by X-ray photoelectron spectroscopy, that is, a temperature at which the adhesive layer is heated to a temperature at which the first Tg is heated, by 30°C or more.

[0004] Furthermore, pressure-sensitive adhesive compositions containing acrylic pressure-sensitive adhesive polymers are also disclosed in, for example, Patent Documents 2 and 3. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-112574 [Patent Document 2] Japanese Patent Application Publication No. 2019-112573 [Patent Document 3] International Publication No. 2017 / 043901 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to improve the adhesive strength of a pressure-sensitive adhesive composition. [Means for solving the problem]

[0007] Adhesion can be improved by using a combination of a polymer with a specific structure, nanocellulose, and a crosslinking agent.

[0008] The present invention includes the following embodiments. [1] a (meth)acrylic polymer; Nanocellulose and a cross-linking agent; Including, Pressure-sensitive adhesive composition. [2] The pressure-sensitive adhesive composition according to [1], wherein the (meth)acrylic polymer is a random copolymer. [3] The pressure-sensitive adhesive composition according to [1] or [2], further comprising a vinyl polymer. [4] The pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the nanocellulose has a modifying group. [5] The pressure-sensitive adhesive composition according to [4], wherein the modifying group is introduced to at least some of the hydroxyl groups of the nanocellulose via a covalent bond. [6] The hydroxyl group to which the modifying group has been introduced is represented by the following formula (2): RC(=O)-O- (2) wherein R is a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted cycloalkenyl group. The pressure-sensitive adhesive composition according to [5], [7] The pressure-sensitive adhesive composition according to [4], wherein the modifying group is introduced to at least some of the carboxy groups of the nanocellulose via an ionic bond. [8] The pressure-sensitive adhesive composition according to [7], wherein the modifying group has an amino group. [9] The pressure-sensitive adhesive composition according to any one of [1] to [8], wherein the nanocellulose contains an oxide of a cellulose-based raw material with hypochlorous acid or a salt thereof, and is substantially free of N-oxyl compounds.

[10] The pressure-sensitive adhesive composition according to any one of [1] to [9], wherein the nanocellulose has a structure in which the hydroxyl groups at the second and third positions of the glucopyranose ring are oxidized to introduce dicarboxy groups.

[11] The pressure-sensitive adhesive composition according to any one of [1] to

[10] , wherein the ratio of the storage modulus at 0°C of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition to the storage modulus at 0°C of a pressure-sensitive adhesive sheet formed from a control composition in which the nanocellulose is omitted from the pressure-sensitive adhesive composition is 1.3 or more.

[12] The pressure-sensitive adhesive composition according to any one of [1] to

[11] , wherein the ratio of the storage modulus at 23°C of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition to the storage modulus at 23°C of a pressure-sensitive adhesive sheet formed from a control composition in which the nanocellulose is omitted from the pressure-sensitive adhesive composition is 1.3 or more.

[13] The pressure-sensitive adhesive composition according to any one of [1] to

[12] , wherein the ratio of the storage modulus at 150°C of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition to the storage modulus at 150°C of a pressure-sensitive adhesive sheet formed from a control composition in which the nanocellulose is omitted from the pressure-sensitive adhesive composition is 1.1 or more.

[14] The pressure-sensitive adhesive composition according to any one of [1] to

[13] , wherein the ratio of the peel strength of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition to the peel strength of a pressure-sensitive adhesive sheet formed from a control composition in which the nanocellulose is omitted from the pressure-sensitive adhesive composition is 1.05 or more.

[15] The pressure-sensitive adhesive composition according to any one of [1] to

[14] , wherein the ratio of the glass transition temperature of the pressure-sensitive adhesive composition to the glass transition temperature of a control composition obtained by omitting the nanocellulose from the pressure-sensitive adhesive composition is 0.9 to 1.1.

[16] The pressure-sensitive adhesive composition according to any one of [1] to

[15] , wherein the amount of the nanocellulose is 0.1 to 5 mass % based on the mass of the (meth)acrylic polymer.

[17] A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive composition according to any one of [1] to

[16] . [Effects of the Invention]

[0009] The present invention can improve the adhesive strength of a pressure-sensitive adhesive composition. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these and various modifications are possible without departing from the gist of the present invention.

[0011] As used herein, "(meth)acrylate" refers to acrylate and methacrylate. As used herein, "(meth)acryloyl" means acryloyl and methacryloyl. In this specification, "(meth)acrylic" means acrylic and methacrylic.

[0012] <<Adhesive composition>> One embodiment of the present invention relates to a pressure-sensitive adhesive composition comprising a (meth)acrylic polymer, nanocellulose, and a crosslinking agent.

[0013] In the pressure-sensitive adhesive composition according to this embodiment, the adhesive strength (peel strength) can be improved by using a polymer having a predetermined structure, nanocellulose, and a crosslinking agent in combination. Furthermore, the pressure-sensitive adhesive composition according to this embodiment can also improve the storage modulus. Furthermore, the pressure-sensitive adhesive composition according to this embodiment can suppress changes in glass transition temperature due to the use of nanocellulose. If the glass transition temperature were to change significantly due to the addition of nanocellulose, this could cause problems such as changes in the temperature at which the pressure-sensitive adhesive composition is used, which would affect how it is handled.

[0014] [nature] The pressure-sensitive adhesive composition according to this embodiment or the pressure-sensitive adhesive sheet formed therefrom preferably has the following properties: The method for producing the pressure-sensitive adhesive sheet and the method for measuring various properties are as described in the Examples below. The control composition described below is a composition obtained by removing the modified nanocellulose from the PSA composition according to this embodiment. Therefore, the control composition can be prepared using the same types and amounts of components as the PSA composition according to this embodiment, except that the modified nanocellulose is not used.

[0015] (Storage modulus: 0℃) The storage modulus (0°C) at 0°C of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition is preferably 150 kPa or more, more preferably 175 kPa or more, and even more preferably 200 kPa or more. There are no particular limitations on the upper limit of the storage modulus (0°C), but it may be, for example, 30,000 kPa, 40,000 kPa, or 50,000 kPa. The range of the storage modulus (0°C) can be determined by appropriately combining the above-mentioned upper and lower limits. The range of the storage modulus (0°C) may be, for example, 150 to 30,000 kPa, 200 to 50,000 kPa, or 150 to 50,000 kPa.

[0016] The ratio of the storage modulus at 0°C of a PSA sheet formed from the PSA composition to the storage modulus at 0°C of a PSA sheet formed from a control composition in which nanocellulose is omitted from the PSA composition (hereinafter referred to as the "storage modulus ratio (0°C)") is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more. The upper limit of the storage modulus ratio (0°C) is not particularly limited, and may be, for example, 10.0, 12.5, or 15.0. The range of the storage modulus ratio (0°C) can be determined by appropriately combining the above-mentioned upper and lower limits. The range of the storage modulus ratio (0°C) may be, for example, 1.1 to 10.0, 1.3 to 15.0, or 1.1 to 15.0.

[0017] (Storage modulus: 23℃) The storage modulus (23°C) at 23°C of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition is preferably 50 kPa or more, more preferably 75 kPa or more, and even more preferably 100 kPa or more. The upper limit of the storage modulus (23°C) is not particularly limited, and may be, for example, 700 kPa, 800 kPa, or 900 kPa. The range of the storage modulus (23°C) can be determined by appropriately combining the above-mentioned upper and lower limits. The range of the storage modulus (23°C) may be, for example, 50 to 700 kPa, 75 to 900 kPa, or 50 to 900 kPa.

[0018] The ratio of the storage modulus at 23°C of a PSA sheet formed from the PSA composition to the storage modulus at 23°C of a PSA sheet formed from a control composition in which nanocellulose is omitted from the PSA composition (hereinafter referred to as the "storage modulus ratio (23°C)") is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more. The upper limit of the storage modulus ratio (23°C) is not particularly limited, and may be, for example, 2.2, 2.4, or 2.6. The range of the storage modulus ratio (23°C) can be determined by appropriately combining the above-mentioned upper and lower limits. The range of the storage modulus ratio (23°C) may be, for example, 1.1 to 2.2, 1.3 to 2.6, or 1.1 to 2.6.

[0019] (Storage modulus: 150℃) The storage modulus (150°C) at 150°C of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition is preferably 13 kPa or more, more preferably 14 kPa or more, and even more preferably 15 kPa or more. There are no particular limitations on the upper limit of the storage modulus (150°C), but it may be, for example, 90 kPa, 95 kPa, or 100 kPa. The range of the storage modulus (150°C) can be determined by appropriately combining the above-mentioned upper and lower limits. The range of the storage modulus (150°C) may be, for example, 13 to 90 kPa, 15 to 100 kPa, or 13 to 100 kPa.

[0020] The ratio of the storage modulus at 150°C of a PSA sheet formed from the PSA composition to the storage modulus at 150°C of a PSA sheet formed from a control composition in which nanocellulose is omitted from the PSA composition (hereinafter referred to as the "storage modulus ratio (150°C)") is preferably 1.05 or greater, more preferably 1.10 or greater, and even more preferably 1.15 or greater. The upper limit of the storage modulus ratio (150°C) is not particularly limited, but may be, for example, 2.20, 2.40, or 2.60. The range of the storage modulus ratio (150°C) can be determined by appropriately combining the above-mentioned upper and lower limits. The range of the storage modulus ratio (150°C) may be, for example, 1.05 to 2.20, 1.10 to 2.60, or 1.05 to 2.60.

[0021] The storage modulus can be adjusted, for example, by changing the amount of modified nanocellulose. For example, increasing the amount of modified nanocellulose tends to increase the storage modulus.

[0022] (peel strength) The peel strength of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition is preferably 15 N / 25 mm or more, more preferably 20 N / 25 mm or more, and even more preferably 25 N / 25 mm or more. There are no particular limitations on the upper limit of the peel strength, but it may be, for example, 40 N / 25 mm, 50 N / 25 mm, or 60 N / 25 mm. The range of the peel strength can be determined by appropriately combining the above-mentioned upper and lower limits. The range of the peel strength may be, for example, 15 to 60 N / 25 mm, 25 to 60 N / 25 mm, or 15 to 40 N / 25 mm.

[0023] The ratio of the peel strength of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition to the peel strength of a pressure-sensitive adhesive sheet formed from a control composition in which nanocellulose is omitted from the pressure-sensitive adhesive composition (hereinafter referred to as the "peel strength ratio") is preferably 1.02 or greater, more preferably 1.04 or greater, and even more preferably 1.06 or greater. The upper limit of the peel strength ratio is not particularly limited, but may be, for example, 1.35, 1.40, or 1.50. The range of the peel strength ratio can be determined by appropriately combining the above-mentioned upper and lower limits. The range of the peel strength ratio may be, for example, 1.02 to 1.35, 1.06 to 1.50, or 1.02 to 1.50.

[0024] The peel strength can be adjusted, for example, by changing the amount of modified nanocellulose, e.g., increasing the amount of modified nanocellulose tends to increase the storage modulus.

[0025] (glass transition temperature (Tg)) The pressure-sensitive adhesive composition has a glass transition temperature of preferably -80°C to 20°C, more preferably -60°C to 10°C, and even more preferably -40°C to 6°C.

[0026] The ratio of the glass transition temperature of the pressure-sensitive adhesive composition to the glass transition temperature of a control composition obtained by omitting nanocellulose from the pressure-sensitive adhesive composition (hereinafter referred to as the "glass transition temperature ratio") is preferably 0.90 to 1.10, more preferably 0.95 to 1.05, and even more preferably 0.98 to 1.02.

[0027] In the pressure-sensitive adhesive composition according to this embodiment, even when nanocellulose is used, the change in glass transition temperature can be suppressed.

[0028] <(Meth)acrylic polymer (A)> The pressure-sensitive adhesive composition according to this embodiment contains a (meth)acrylic polymer (A). The (meth)acrylic polymer is preferably a random copolymer.

[0029] The glass transition temperature of the (meth)acrylic polymer (A) is preferably -80°C or higher and 30°C or lower, more preferably -60°C or higher and 20°C or lower, and even more preferably -40°C or higher and 10°C or lower.

[0030] By adjusting the glass transition temperature of the (meth)acrylic polymer (A) to fall within the above range, the adhesive strength tends to be further improved.

[0031] The glass transition temperature of the (meth)acrylic polymer (A) can be adjusted by changing the type and amount of the monomers that constitute the polymer.

[0032] The method for measuring the glass transition temperature of the (meth)acrylic polymer (A) is as described in the Examples below.

[0033] The number average molecular weight (Mn) of the (meth)acrylic polymer (A) is preferably 40,000 or more and 500,000 or less, more preferably 60,000 or more and 400,000 or less, and even more preferably 80,000 or more and 300,000 or less.

[0034] The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is preferably 200,000 or more and 3,000,000 or less, more preferably 300,000 or more and 2,000,000 or less, and even more preferably 400,000 or more and 1,000,000 or less.

[0035] The molecular weight distribution (Mw / Mn) of the (meth)acrylic polymer (A) is preferably 1.0 or more and 9.0 or less, more preferably 2.0 or more and 8.0 or less, and even more preferably 3.0 or more and 7.0 or less.

[0036] By setting the Mn, Mw, and / or Mw / Mn of the (meth)acrylic polymer (A) within the above ranges, the adhesive strength tends to be further improved.

[0037] The Mn and Mw of the (meth)acrylic polymer (A) can be measured by converting the molecular weight measured by gel permeation chromatography (GPC) into polystyrene equivalents.

[0038] The amount of the (meth)acrylic polymer (A) is preferably 50 to 99 mass %, more preferably 70 to 97 mass %, and even more preferably 90 to 95 mass %, based on the mass of the solid content of the pressure-sensitive adhesive composition (i.e., components excluding the solvent).

[0039] Examples of monomers constituting the (meth)acrylic polymer (A) include alkyl (meth)acrylates (the alkyl group preferably has 1 to 12 carbon atoms), alkoxyalkyl (meth)acrylates (the alkoxyalkyl group preferably has 2 to 12 carbon atoms), hydroxyalkyl (meth)acrylates (the alkyl group preferably has 1 to 12 carbon atoms), and (meth)acrylic acid.

[0040] Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, and lauryl (meth)acrylate.

[0041] Examples of alkoxyalkyl (meth)acrylates include methoxymethyl (meth)acrylate, ethoxytyl (meth)acrylate, butoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxybutyl (meth)acrylate, and butoxybutyl (meth)acrylate.

[0042] Examples of hydroxyalkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0043] From the viewpoint of obtaining excellent adhesive strength, the monomer constituting the (meth)acrylic polymer (A) preferably contains alkyl (meth)acrylate and / or alkoxyalkyl (meth)acrylate.

[0044] The total amount of structural units derived from alkyl (meth)acrylate and alkoxyalkyl (meth)acrylate is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, and particularly preferably 70% by mass or more, based on the mass of all structural units of the (meth)acrylic polymer (A). There is no particular upper limit on the total amount of structural units derived from alkyl (meth)acrylate and alkoxyalkyl (meth)acrylate, but it may be, for example, 100 mass %, 95 mass %, 90 mass %, or 80 mass %. The range of the total amount of structural units derived from alkyl (meth)acrylate and alkoxyalkyl (meth)acrylate may be determined by appropriately combining the above lower and upper limits, and the range may be, for example, 10 to 100 mass%, 30 to 95 mass%, 50 to 90 mass%, or 70 to 80 mass%.

[0045] <Vinyl polymer (B)> The pressure-sensitive adhesive composition according to this embodiment may contain a vinyl polymer (B). When the pressure-sensitive adhesive composition according to this embodiment contains a vinyl polymer (B), the (meth)acrylic polymer (A) and the vinyl polymer (B) are not the same.

[0046] It is preferable that the vinyl polymer (B) is not completely miscible with the (meth)acrylic polymer (A) and does not completely phase separate. The vinyl polymer (B) preferably has lower polarity than the (meth)acrylic polymer (A). By using such a vinyl polymer (B), when a pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive composition, the vinyl polymer (B) segregates on the surface of the pressure-sensitive adhesive layer, thereby exhibiting excellent adhesiveness.

[0047] The glass transition temperature of the vinyl polymer (B) is preferably 30°C or higher and 200°C or lower, more preferably 40°C or higher and 180°C or lower, and even more preferably 60°C or higher and 150°C or lower.

[0048] By adjusting the glass transition temperature of the vinyl polymer (B) to fall within the above range, the adhesive strength tends to be further improved.

[0049] The glass transition temperature of the vinyl polymer (B) can be adjusted by changing the type and amount of the monomers that constitute the polymer.

[0050] The glass transition temperature of the vinyl polymer (B) is measured by the method described later in the Examples.

[0051] The number average molecular weight (Mn) of the vinyl polymer (B) is preferably 500 or more and 10,000 or less, more preferably 1,000 or more and 7,000 or less, and even more preferably 1,500 or more and 5,000 or less.

[0052] The weight average molecular weight (Mw) of the vinyl polymer (B) is preferably 1,000 or more and 12,000 or less, more preferably 2,000 or more and 10,000 or less, and even more preferably 3,000 or more and 8,000 or less.

[0053] The molecular weight distribution (Mw / Mn) of the vinyl polymer (B) is preferably 1.0 or more and 3.0 or less, more preferably 1.1 or more and 2.5 or less, and even more preferably 1.2 or more and 2.0 or less.

[0054] By setting the Mn, Mw, and / or Mw / Mn of the vinyl polymer (B) within the above ranges, the degree of segregation of the vinyl polymer (B) on the surface of the pressure-sensitive adhesive layer is suitably controlled, and adhesiveness tends to be further improved.

[0055] The Mn and Mw of the vinyl polymer (B) can be measured by converting the molecular weight measured by gel permeation chromatography (GPC) into polystyrene equivalents.

[0056] The amount of the vinyl polymer (B) is preferably 0.5 to 30% by mass, more preferably 1 to 20% by mass, and even more preferably 3 to 10% by mass, based on the mass of the (meth)acrylic polymer (A).

[0057] If the amount of vinyl polymer (B) is too small, the segregation of the vinyl polymer (B) on the surface of the pressure-sensitive adhesive layer becomes insufficient. If the amount of vinyl polymer (B) is too large, phase separation from the (meth)acrylic polymer (A) tends to occur, resulting in a decrease in adhesiveness. By adjusting the amount of vinyl polymer (B) within the above range, the degree of segregation of the vinyl polymer (B) on the surface of the pressure-sensitive adhesive layer can be suitably adjusted, and adhesiveness tends to be further improved.

[0058] The vinyl polymer (B) preferably contains a structural unit derived from a radically polymerizable vinyl monomer. Examples of the radically polymerizable vinyl monomer include (meth)acrylic acid compounds, aromatic vinyl compounds, unsaturated carboxylic acids, unsaturated acid anhydrides, hydroxyl group-containing unsaturated compounds, amino group-containing unsaturated compounds, amide group-containing unsaturated compounds, alkoxyl group-containing unsaturated compounds, cyano group-containing unsaturated compounds, nitrile group-containing unsaturated compounds, and maleimide compounds.

[0059] Examples of (meth)acrylic acid compounds include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, ethylhexyl (meth)acrylate, n-dodecyl (meth)acrylate, n-octadecyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, phenyl (meth)acrylate, and benzyl (meth)acrylate.

[0060] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, vinyltoluene, β-methylstyrene, ethylstyrene, p-tert-butylstyrene, vinylxylene, and vinylnaphthalene.

[0061] Examples of unsaturated carboxylic acids include (meth)acrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, cinnamic acid, and monoalkyl esters of unsaturated dicarboxylic acids (maleic acid, fumaric acid, itaconic acid, citraconic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, etc.).

[0062] Unsaturated acid anhydrides include, for example, maleic anhydride, itaconic anhydride, and citraconic anhydride.

[0063] Examples of hydroxyl group-containing unsaturated compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, mono(meth)acrylic acid esters of polyalkylene glycols (polyethylene glycol, polypropylene glycol, etc.), p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, and o-isopropenylphenol.

[0064] Examples of amino group-containing unsaturated compounds include dimethylaminomethyl (meth)acrylate, diethylaminomethyl (meth)acrylate, 2-dimethylaminoethyl (meth)acrylate, 2-diethylaminoethyl (meth)acrylate, 2-(di-n-propylamino)ethyl (meth)acrylate, 2-dimethylaminopropyl (meth)acrylate, 2-diethylaminopropyl (meth)acrylate, 2-(di-n-propylamino)propyl (meth)acrylate, 3-dimethylaminopropyl (meth)acrylate, 3-diethylaminopropyl (meth)acrylate, and 3-(di-n-propylamino)propyl (meth)acrylate.

[0065] Examples of the amide group-containing unsaturated compound include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, and N-methylol(meth)acrylamide.

[0066] Examples of alkoxyl group-containing unsaturated compounds include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(n-propoxy)ethyl (meth)acrylate, 2-(n-butoxy)ethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 2-(n-propoxy)propyl (meth)acrylate, and 2-(n-butoxy)propyl (meth)acrylate.

[0067] Examples of cyano group-containing unsaturated compounds include cyanomethyl (meth)acrylate, 1-cyanoethyl (meth)acrylate, 2-cyanoethyl (meth)acrylate, 1-cyanopropyl (meth)acrylate, 2-cyanopropyl (meth)acrylate, 3-cyanopropyl (meth)acrylate, 4-cyanobutyl (meth)acrylate, 6-cyanohexyl (meth)acrylate, 2-ethyl-6-cyanohexyl (meth)acrylate, and 8-cyanooctyl (meth)acrylate.

[0068] Examples of the nitrile group-containing unsaturated compound include (meth)acrylonitrile, ethacrylonitrile, α-ethylacrylonitrile, α-isopropylacrylonitrile, α-chloroacrylonitrile, and α-fluoroacrylonitrile.

[0069] Examples of maleimide compounds include maleimide, N-methylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-dodecylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-(2-methylphenyl)maleimide, N-(4-methylphenyl)maleimide, N-(2,6-dimethylphenyl)maleimide, N-(2,6-diethylphenyl)maleimide, N-benzylmaleimide, and N-naphthylmaleimide.

[0070] From the viewpoint of obtaining suitable compatibility with the (meth)acrylic polymer (A), the radically polymerizable vinyl monomer preferably contains a (meth)acrylic acid compound.

[0071] The amount of structural units derived from (meth)acrylic acid compounds is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, and particularly preferably 70% by mass or more, based on the mass of all structural units in the vinyl polymer (B). The upper limit of the amount of structural units derived from (meth)acrylic acid compounds is not particularly limited, and may be, for example, 100%, 95%, 90%, or 80% by mass.

[0072] <Nanocellulose> The pressure-sensitive adhesive composition according to this embodiment contains nanocellulose. By using nanocellulose, adhesive strength can be improved.

[0073] The amount of nanocellulose is preferably 0.1 to 20 mass %, more preferably 0.5 to 10 mass %, and even more preferably 1 to 5 mass %, based on the mass of the (meth)acrylic polymer (A). By setting the amount of nanocellulose within the above range, the adhesive strength can be further improved.

[0074] The nanocellulose may be modified nanocellulose. Modified nanocellulose can be obtained, for example, by reacting nanocellulose with a modifying group-introducing compound described below. Nanocellulose is cellulose that has been nanosized. Nanocellulose can be obtained, for example, by oxidizing and nanoizing a cellulosic raw material. The order of oxidation and nanoization is not particularly limited, but it is preferable to oxidize the cellulosic raw material and then nanoize it. Nanoization tends to be easier by oxidizing the cellulosic raw material first.

[0075] Examples of oxidizing agents for oxidizing cellulosic raw materials include hypochlorous acid or its salts and N-oxyl compounds, such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO).

[0076] From the viewpoint of exerting excellent adhesive strength, it is preferable to use hypochlorous acid or its salt as the oxidizing agent. In other words, nanocellulose is preferably produced by oxidizing a cellulosic raw material with hypochlorous acid or its salt (without using an N-oxyl compound) and nano-sizing the resulting oxidized cellulose.

[0077] The following description focuses on the oxidation of cellulosic raw materials with hypochlorous acid or its salts, but nanocellulose is not limited to nanocellulose with hypochlorous acid or its salts.

[0078] [Oxidized cellulose] Unless otherwise specified, "oxidized cellulose" in this section below refers to an oxidation product of a cellulose-based raw material with hypochlorous acid or a salt thereof before defibration.

[0079] Examples of hypochlorous acid or salts thereof include hypochlorous acid water, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, and ammonium hypochlorite.

[0080] The amount of hypochlorous acid or its salt used is not particularly limited, but it is preferable to use it so that the available chlorine concentration in the reaction system is 6 to 43 mass %. The available chlorine concentration may be a low concentration of 6 to 14 mass %, or a high concentration of 14 to 43 mass %.

[0081] The definition of the effective chlorine concentration of hypochlorous acid or a salt thereof is as described in WO 2022 / 009979.

[0082] The cellulosic raw material is not particularly limited as long as it is a material primarily composed of cellulose, and examples thereof include pulp, natural cellulose, and fine cellulose obtained by depolymerizing cellulose through mechanical processing. The cellulosic raw material preferably has a type I crystal structure. As the cellulosic raw material, commercially available products such as crystalline cellulose made from pulp can be used as is. Alternatively, unused biomass containing a large amount of cellulose components, such as soybean pulp refuse or soybean hulls, may also be used as the raw material. Furthermore, the cellulosic raw material may be pre-treated with an alkali of an appropriate concentration in order to facilitate the penetration of the oxidizing agent used into the raw pulp. The main component of plants is cellulose, and bundles of cellulose molecules are called cellulose microfibrils. The cellulose in cellulosic raw materials is also contained in the form of cellulose microfibrils.

[0083] (N-oxyl compounds) Preferably, oxidized cellulose is substantially free of N-oxyl compounds. By being substantially free of N-oxyl compounds, the impact on the environment and human body is sufficiently reduced, resulting in a high level of safety. Examples of N-oxyl compounds include 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO).

[0084] As used herein, "substantially free of N-oxyl compounds" means that no N-oxyl compounds are used in the production of oxidized cellulose, that the oxidized cellulose contains no N-oxyl compounds at all, or that the content of N-oxyl compounds is 2.0 ppm by mass or less, and preferably 1.0 ppm by mass or less, relative to the total amount of oxidized cellulose. In addition, when the content of N-oxyl compounds is, as an increase from the cellulosic raw material, preferably 2.0 mass ppm or less, more preferably 1.0 mass ppm or less, it is also considered to be "substantially free of N-oxyl compounds."

[0085] The content of N-oxyl compounds can be measured by known means, such as a method using a trace total nitrogen analyzer (for example, TN-2100H manufactured by Nitto Seiko Analytech Co., Ltd.).

[0086] (carboxyl group amount) The amount of carboxy groups in the oxidized cellulose is preferably 0.1 to 3.0 mmol / g, more preferably 0.2 to 2.0 mmol / g, even more preferably 0.3 to 1.5 mmol / g, particularly preferably 0.4 to 1.2 mmol / g, and most preferably 0.5 to 0.9 mmol / g.

[0087] The amount of carboxy groups in oxidized cellulose can be measured by the method described in WO 2022 / 009979.

[0088] Oxidized cellulose preferably has a structure in which at least two of the hydroxyl groups on the glucopyranose ring that constitutes cellulose are oxidized, and more specifically, it preferably has a structure in which the hydroxyl groups at the second and third positions on the glucopyranose ring are oxidized and dicarboxyl groups are introduced. It is also preferable that the hydroxyl group at the sixth position on the glucopyranose ring is not oxidized and remains as a hydroxyl group. The position of the carboxyl group on the glucopyranose ring is determined by the solid 13 It can be analyzed by C-NMR spectroscopy.

[0089] Rayon has the same chemical structure as cellulose, and its oxide (rayon oxide) is water-soluble. 13 By C-NMR measurement, a carbon peak attributable to the carboxy group is observed at 165 to 185 ppm. In one embodiment of the oxidation of a cellulosic raw material with hypochlorous acid or its salt, two signals appear in this chemical shift range. Furthermore, by solution two-dimensional NMR measurement, it can be determined that the carboxy groups are introduced at the 2- and 3-positions.

[0090] Solid oxide of cellulosic raw materials with hypochlorous acid or its salts 13 In C-NMR, when the amount of carboxyl groups introduced is large, two signals appear at 165 to 185 ppm, and when the amount of carboxyl groups introduced is small, a very broad signal may appear. As can be seen from the results for oxidized rayon, the signals of the carboxyl group carbons introduced at the 2nd and 3rd positions are close to each other, and this is difficult to achieve with low-resolution solid state spectroscopy. 13 In C-NMR, the separation of the two signals is insufficient. Therefore, when the amount of carboxyl group introduced is small, a broad signal is observed. 13 In the C-NMR spectrum, the introduction of carboxy groups at the 2nd and 3rd positions can be confirmed by evaluating the broadening of the peaks appearing at 165 to 185 ppm.

[0091] That is, solid 13 A baseline is drawn around the peak in the range of 165 ppm to 185 ppm in the C-NMR spectrum to determine the overall area value, and then the area value is vertically divided at the peak top to determine the ratio of the two peak area values ​​(large area value / small area value). If the ratio of the peak area values ​​is 1.2 or more, the peak can be said to be broad. The presence or absence of the broad peak can be determined by the ratio of the length L of the baseline in the range of 165 ppm to 185 ppm to the length L' of the perpendicular line from the peak top to the baseline. That is, if the ratio L' / L is 0.1 or more, it can be determined that a broad peak is present. The ratio L' / L may be 0.2 or more, 0.3 or more, 0.4 or more, or even 0.5 or more. There is no particular upper limit to the ratio L' / L, but it is usually 3.0 or less, and may be 2.0 or less, or 1.0 or less.

[0092] The structure of the glucopyranose ring can also be determined by analysis according to the method described in Sustainable Chem. Eng. 2020, 8, 48, 17800-17806.

[0093] (Viscosity average degree of polymerization) The viscosity average degree of polymerization of the oxidized cellulose is preferably 30-500, more preferably 60-300, even more preferably 70-150, and particularly preferably 80-130.

[0094] The viscosity average degree of polymerization is the average degree of polymerization measured by a viscosity method. The viscosity average degree of polymerization can be measured by the method described in WO 2022 / 009979.

[0095] [Method of producing oxidized cellulose] Oxidized cellulose can be produced by oxidizing a cellulosic raw material with hypochlorous acid or a salt thereof. Specific production methods include those described in WO 2022 / 009979 and WO 2022 / 009980. Oxidized cellulose is also available commercially, such as Aronfibro (registered trademark) manufactured by Toagosei Co., Ltd.

[0096] [Nanocellulose] Unless otherwise specified, "nanocellulose" in this section hereinafter refers to an oxide of a cellulose-based raw material with hypochlorous acid or its salt, after defibration.

[0097] Nanocellulose is a general term for micronized cellulose, and includes micronized cellulose fibers and cellulose nanocrystals. Micronized cellulose fibers are also called cellulose nanofibers (also referred to as CNF).

[0098] Nanocellulose preferably has a carboxyl group. The carboxyl group may be in the H type (-COOH) or in the salt type. The type of salt is not particularly limited, but examples include alkali metal salts such as lithium salt, sodium salt, and potassium salt; alkaline earth metal salts such as calcium salt and barium salt; other metal salts such as magnesium salt and aluminum salt; ammonium salt; and organic amine salts.

[0099] Nanocellulose is a collection of individual fibers. When nanocellulose contains carboxylated nanocellulose, it is sufficient that it contains at least one carboxylated nanocellulose, and it is preferable that carboxylated nanocellulose is the main component. Here, carboxylated nanocellulose being the main component means that the proportion of carboxylated nanocellulose in the total amount of nanocellulose exceeds 50% by mass, preferably exceeds 70% by mass, and more preferably exceeds 80% by mass. The upper limit of the above proportion is 100% by mass, but it may also be 98% by mass or 95% by mass.

[0100] (N-oxyl compounds) It is preferable that nanocellulose is substantially free of N-oxyl compounds. The meaning of "substantially free of N-oxyl compounds" and the method for measuring the content of N-oxyl compounds are as described in the above [Oxidized Cellulose] (N-oxyl Compounds) section.

[0101] (carboxyl group amount) The amount of carboxyl groups in nanocellulose, the method for measuring them, and the position at which the carboxyl groups are introduced shall follow the description in the (Carboxy group amount) section of [Oxidized Cellulose] above.

[0102] (average fiber length) The average fiber length of nanocellulose is preferably 50 to 3000 nm, more preferably 50 to 700 nm, even more preferably 50 to 500 nm, still more preferably 60 to 300 nm, and particularly preferably 70 to 200 nm.

[0103] (average fiber width) The average fiber width of nanocellulose is preferably 1 to 20 nm, more preferably 1 to 15 nm, even more preferably 1 to 10 nm, and particularly preferably 1 to 5 nm.

[0104] The average fiber length and average fiber width of nanocellulose can be measured by the method described in WO 2022 / 009980.

[0105] (aspect ratio) The aspect ratio of nanocellulose (average fiber length / average fiber width) is preferably 20-1000, more preferably 20-200, even more preferably 30-190, and particularly preferably 40-180.

[0106] The average fiber length, average fiber width, and aspect ratio of the modified nanocellulose are preferably in the same range as those of the nanocellulose. The average fiber length, average fiber width, and aspect ratio of the modified nanocellulose can also be measured in accordance with the description of WO 2022 / 009980, as in the measurement of nanocellulose.

[0107] (zeta potential) The zeta potential of nanocellulose is preferably -30 mV or less, more preferably -90 mV or more and -30 mV or less, even more preferably -80 mV or more and -30 mV or less, even more preferably -70 mV or more and -30 mV or less, and particularly preferably -65 mV or more and -35 mV or less.

[0108] The zeta potential can be measured by the method described in WO 2022 / 009980.

[0109] (crystallinity) The crystallinity of the nanocellulose is preferably 10 to 70%, more preferably 20 to 70%, even more preferably 30 to 65%, particularly preferably 40 to 60%, and most preferably 50 to 55%.

[0110] The crystallinity can be measured by the method described in WO 2022 / 138759.

[0111] [Method of manufacturing nanocellulose] Nanocellulose can be produced by defibrating the above-mentioned oxidized cellulose. Specific production methods include those described in International Publication Nos. 2022 / 009979 and 2022 / 009980. Nanocellulose can also be obtained by defibrating commercially available oxidized cellulose (e.g., Aronfibro (registered trademark) manufactured by Toagosei Co., Ltd.).

[0112] [Modifying group] The nanocellulose may be modified nanocellulose in which a modifying group has been introduced into the nanocellulose. The modifying group may be of one type or of multiple types.

[0113] (First modifying group) The modified nanocellulose may have a first modifying group introduced into at least some of the hydroxyl groups of the nanocellulose. The hydroxyl groups to which the first modifying group has been introduced are preferably primary hydroxyl groups.

[0114] The bond between the first modifying group and nanocellulose is preferably a covalent bond, more preferably an ester bond. The ester bond is preferably composed of oxygen (O) derived from the hydroxyl group of nanocellulose and a carbonyl group (CO) derived from the first modifying group-introducing compound described below.

[0115] The hydroxyl group of nanocellulose into which the first modifying group has been introduced is preferably represented by the following formula (2). RC(=O)-O- (2)

[0116] In formula (1), R is a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted cycloalkenyl group. The alkyl group may be linear or branched. The alkenyl group may be linear or branched.

[0117] The alkyl group for R preferably has 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0118] The cycloalkyl group for R preferably has 3 to 14 carbon atoms, more preferably 4 to 10 carbon atoms, and even more preferably 5 to 6 carbon atoms.

[0119] The alkenyl group for R preferably has 2 to 8 carbon atoms, more preferably 2 to 5 carbon atoms, and even more preferably 2 to 3 carbon atoms.

[0120] The cycloalkenyl group for R preferably has 3 to 14 carbon atoms, more preferably 4 to 10 carbon atoms, and even more preferably 5 to 6 carbon atoms.

[0121] Examples of the substituents of the alkyl group, cycloalkyl group, alkenyl group, and cycloalkenyl group of R include a carboxy group.

[0122] (First modifying group-introducing compound) The first modifying group-introducing compound is a compound that is reacted with nanocellulose to introduce the first modifying group into the hydroxyl group of the nanocellulose. The first modifying group-introducing compound is preferably a carboxylic acid compound.

[0123] Examples of the carboxylic acid compound include saturated monocarboxylic acid compounds, saturated dicarboxylic acid compounds, monocarboxylic acid compounds having an unsaturated bond (hereinafter simply referred to as "unsaturated monocarboxylic acid compounds"), and dicarboxylic acid compounds having an unsaturated bond (hereinafter simply referred to as "unsaturated dicarboxylic acid compounds"). In this specification, the carboxylic acid compound also includes its acid anhydride.

[0124] Saturated monocarboxylic acid compounds include, for example, formic acid, acetic acid, propionic acid, and butyric acid.

[0125] Examples of saturated dicarboxylic acid compounds include succinic acid, glutaric acid, adipic acid, suberic acid, and sebacic acid.

[0126] Examples of unsaturated monocarboxylic acid compounds include (meth)acrylic acid, 2-ethylacrylic acid, 2-propylacrylic acid, and 2-isopropylacrylic acid.

[0127] Examples of unsaturated dicarboxylic acid compounds include maleic acid, fumaric acid, itaconic acid, and alkenyl-substituted succinic acid.

[0128] The first modifying group is preferably a group derived from a carboxylic acid compound, specifically the residue of a carboxylic acid compound that is attached to the nanocellulose as a result of reaction of the carboxylic acid compound with the nanocellulose.

[0129] (Second modifying group) The modified nanocellulose may have a second modifying group introduced into at least some of the carboxy groups of the nanocellulose, and the bond between the second modifying group and the nanocellulose is preferably an ionic bond.

[0130] The second modifying group preferably has an amino group. Preferably, an ionic bond is formed between the amino group of the second modifying group and a carboxyl group of the nanocellulose. The amino group of the second modifying group may be in the form of an ammonium ion.

[0131] The second modifying group can be introduced by reacting nanocellulose having a carboxy group with a second modifying group-introducing compound having an amino group. The second modifying group can also be expressed as a second modifying group-introducing compound that is ionically bonded to the carboxy group of nanocellulose. The second modifying group-introducing compound will be described below, but the second modifying group may have the same structure as the second modifying group-introducing compound, except for the ionic bond with nanocellulose.

[0132] (Second modifying group-introducing compound) The second modifying group-introducing compound is a compound that is reacted with nanocellulose to introduce a second modifying group into the carboxyl group of the nanocellulose. The second modifying group-introducing compound preferably has an amino group.

[0133] The number of amino groups per molecule is, for example, 1 to 4, 1 to 3, 1 or 2, or 1.

[0134] The second modifying group-introducing compound preferably has a long-chain linear or long-chain branched structure. The amino group is preferably located at the terminal of the molecule. The amino group may be located at only one terminal of the molecule, at multiple terminals of the molecule, or at all terminals of the molecule.

[0135] The second modifying group-introducing compound preferably has an oxyalkylene group, more preferably has multiple oxyalkylene groups (polyoxyalkylene groups). In this specification, a compound having an amino group and a polyoxyalkylene group is referred to as a polyetheramine.

[0136] The oxyalkylene group is preferably an oxyalkylene group having 1 to 6 carbon atoms, more preferably an oxyalkylene group having 2 to 4 carbon atoms, and even more preferably an oxyalkylene group having 2 or 3 carbon atoms.

[0137] The oxyalkylene group preferably contains at least one selected from the group consisting of an oxyethylene group, an oxypropylene group, and an oxybutylene group, and more preferably contains an oxyethylene group and / or an oxypropylene group.

[0138] The number of repeating units of the oxyalkylene group is preferably 5-70, more preferably 10-50, and even more preferably 20-45.

[0139] The weight-average molecular weight of the second modifying group-introducing compound is preferably 200 to 5000, more preferably 300 to 4000, and even more preferably 400 to 2500. The weight-average molecular weight can be measured by gel permeation chromatography (GPC).

[0140] <Crosslinking agent> The pressure-sensitive adhesive composition according to the present embodiment contains a crosslinking agent, which can improve adhesive strength by forming chemical crosslinks between components contained in the composition.

[0141] Examples of the crosslinking agent include an epoxy compound having two or more epoxy groups, an isocyanate compound having two or more isocyanate groups, an aziridine compound having two or more aziridinyl groups, an oxazoline compound having an oxazoline group, a metal chelate compound, and a butylated melamine compound.

[0142] The crosslinking agent preferably contains at least one selected from the group consisting of epoxy compounds, isocyanate compounds, and aziridine compounds.

[0143] Examples of epoxy compounds include bisphenol A epichlorohydrin-type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, diglycidylaniline, tetraglycidylxylenediamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, and sorbitol polyglycidyl ether.

[0144] Examples of the isocyanate compound include: Aromatic isocyanates such as diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate, tolylene diisocyanate, naphthalene diisocyanate (NDI), p-phenylene diisocyanate (PPDI), xylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI); Aliphatic isocyanates such as hexamethylene diisocyanate (HDI), lysine diisocyanate (LDI), and lysine triisocyanate (LTI); Alicyclic isocyanates such as isophorone diisocyanate (IPDI), cyclohexyl diisocyanate (CHDI), hydrogenated XDI (H6XDI), and hydrogenated MDI (H12MDI); and Modified isocyanates such as urethane-modified, dimer, trimer, carbodiimide-modified, allophanate-modified, biuret-modified, urea-modified, isocyanurate-modified, oxazolidone-modified, and isocyanate-terminated prepolymers of the above isocyanate compounds; Examples include:

[0145] Examples of the aziridine compound include 1,6-bis(1-aziridinylcarbonylamino)hexane, 1,1'-(methylene-di-p-phenylene)bis-3,3-aziridyl urea, 1,1'-(hexamethylene)bis-3,3-aziridyl urea, ethylene bis-(2-aziridinyl propionate), tris(1-aziridinyl)phosphine oxide, 2,4,6-triaziridinyl-1,3,5-triazine, and trimethylolpropane-tris-(2-aziridinyl propionate).

[0146] The amount of the crosslinking agent is preferably 0.01 to 10% by mass, more preferably 0.03 to 5% by mass, and even more preferably 0.05 to 2% by mass, based on the mass of the (meth)acrylic polymer (A).

[0147] <Optional ingredients> The pressure-sensitive adhesive composition according to the present embodiment may contain any additives, such as an antioxidant, an ultraviolet absorber, an antiaging agent, a flame retardant, an antifungal agent, a silane coupling agent, a filler, a colorant, and a solvent.

[0148] <Application> The pressure-sensitive adhesive composition according to the present embodiment is preferably used for bonding objects, for example, in a lamination method in which a decorative film is attached to a resin or metal molded body to obtain a decorated molded body.

[0149] <<Adhesive sheet>> One embodiment of the present invention relates to a pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive composition described above.

[0150] The PSA sheet preferably includes a PSA composition and a substrate. The PSA composition is preferably disposed on the surface of the substrate. When the substrate is porous, the PSA composition may be disposed on the surface of the substrate, inside the substrate, or both.

[0151] Examples of the substrate include a resin film, paper, cloth, and metal foil. Examples of the material for the resin film include a polyester resin, a polyethersulfone resin, an acetate resin, a polycarbonate resin, and a polyolefin resin.

[0152] The pressure-sensitive adhesive sheet may be the pressure-sensitive adhesive composition itself processed into a sheet shape. [Example]

[0153] The present invention will be described in more detail below using examples and comparative examples, but the technical scope of the present invention is not limited to these.

[0154] Various values ​​in the examples may be used as preferred lower or upper limits in the embodiments of the present invention. Two values ​​of the same type in the examples may be appropriately combined to form a preferred numerical range.

[0155] <Synthesis of (meth)acrylic polymer> [Synthesis Example A1] (Synthesis of Polymer A-1) A 3-liter four-neck flask was charged with 2-methoxyethyl acrylate (hereinafter also referred to as "MEA") (78 parts by mass), n-butyl acrylate (hereinafter also referred to as "BA") (17 parts by mass), 2-hydroxyethyl acrylate (hereinafter also referred to as "HEA") (5 parts by mass), and ethyl acetate (150 parts by mass). The mixture was thoroughly degassed by bubbling nitrogen gas through it, and the internal temperature of the mixture was raised to 60°C. 2,2'-azobis(2,4-dimethylvaleronitrile) (V-65, Fujifilm Wako Pure Chemical Industries, Ltd.) (0.02 parts by mass) was then charged to initiate polymerization. After 2 hours, the temperature was raised to 75°C and the reaction was continued for 5 hours to obtain Polymer A-1. The resulting Polymer A-1 had an Mw of 820,000, an Mn of 130,000, and an Mw / Mn of 6.3. The Tg was -25°C. The polymer composition and analytical results of Polymer A-1 are shown in Table 1.

[0156] [Synthesis Examples A2 to A6] (Synthesis of Polymers A-2 to A-6) The same procedure as in Synthesis Example A1 was carried out except that the types and amounts of raw materials charged into the flask were changed as shown in Table 1, to obtain polymers A-2 to A-6.

[0157] [Table 1]

[0158] <Synthesis of vinyl copolymer> [Synthesis Example B1] (Synthesis of vinyl polymer B-1) A 1-liter four-neck flask was charged with a mixture of butyl acetate (200 parts by mass) and dimethyl 2,2'-azobis(2-methylpropionate) (manufactured by Wako Pure Chemical Industries, Ltd., trade name "V-601") (0.9 parts by mass). The mixture was thoroughly degassed by bubbling nitrogen gas through it, and the internal temperature of the mixture was raised to 90°C. Separately, a mixture of methyl methacrylate (hereinafter referred to as "MMA") (165 parts by mass), isobornyl methacrylate (hereinafter referred to as "IBXMA") (44 parts by mass), V-601 (17 parts by mass), and butyl acetate (90 parts by mass) was added dropwise from a dropping funnel to the flask over 5 hours to carry out polymerization. After completion of the dropwise addition, the polymerization solution was added dropwise to a mixture of methanol (4800 parts by mass) and distilled water (1200 parts by mass). The vinyl polymer in the polymerization solution was isolated to obtain vinyl polymer B-1. The polymer composition of the obtained vinyl polymer B-1 was calculated from the charged amounts and the monomer consumption amounts measured by GC, and was found to consist of 80% by mass of MMA and 20% by mass of IBXMA, with Mw of 6700, Mn of 4370, and Mw / Mn of 1.53. Tg was 108°C. The composition and analytical results of vinyl polymer B-1 are shown in Table 2.

[0159] [Synthesis Examples B2 and B3] (Synthesis of Polymers B-2 and B-3) The same procedure as in Synthesis Example B1 was carried out except that the ratio of the raw materials charged into the flask was changed as shown in Table 2, to obtain vinyl polymers B-2 and B-3.

[0160] [Table 2]

[0161] <Production of modified nanocellulose> [Production Example 1] (Acetic acid-modified (acetylated) nanocellulose [N-1]) (oxidation process) A jacketed glass vessel was charged with 500 g of sodium hypochlorite solution with a pH of 12.7 and an available chlorine concentration of 12.5% ​​by mass, and the mixture was heated to 35°C while stirring at 200 rpm using a Shinto Scientific mixer (Three-One Motor, BL600) with three swept-back blades. Then, 47 g of powdered pulp (KC Flock W-100GK) from Nippon Paper Industries Co., Ltd. was added as a cellulosic raw material. After the cellulosic raw material was added, the mixture was stirred at 35°C until the pH dropped to 10.5. Then, a 25% by mass aqueous sodium hydroxide solution was added to maintain the pH at 10.5 during the reaction. The mixture was stirred under the same conditions for a total of 520 minutes after the cellulosic raw material was added. After the reaction was completed, the remaining sodium hypochlorite was inactivated by adding aqueous hydrogen peroxide, and then hydrochloric acid was added to convert the carboxyl groups of the oxidized cellulose from the salt form (-COO-Na) to the proton form (-COO-H), yielding an aqueous dispersion with a pH of 2.5. The solid-liquid separation was carried out by pressure filtration at 0.2 MPa, and then the dispersion was washed with an aqueous hydrochloric acid solution at pH 2.5. Sodium hydroxide was added to the resulting proton-type oxidized cellulose to convert the carboxylic acid groups from the proton-type (-COO-H) back to the salt-type (-COO-Na), yielding an aqueous dispersion of Na-type oxidized cellulose at pH 7.4. The amount of carboxyl groups in the oxidized cellulose was measured to be 0.78 mmol / g. The nitrogen content derived from N-oxyl compounds in the oxidized cellulose was measured as nitrogen using a trace total nitrogen analyzer (TN-2100H, manufactured by Nitto Seiko Analytech Co., Ltd.), and the increase from the raw pulp was calculated to be less than 1 ppm.

[0162] (defibration process) An aqueous dispersion of Na-type oxidized cellulose (7.5% solids by mass) was processed in a homomixer (Primix, Robomix) at 10,000 rpm with 440 g of liquid for 33 minutes to defibrate the oxidized cellulose into nanocellulose, yielding an aqueous nanocellulose dispersion. The resulting aqueous dispersion was adjusted to a pH of 2.0-2.1 by adding 1N hydrochloric acid solution, and then washed twice with pure water using a tabletop multi-rack centrifuge (KOKUSAN, H-40α). The mixture was then washed (substituted) four times with acetone, followed by concentration by suction filtration using a vacuum pump to obtain acetone-substituted H-type nanocellulose.

[0163] (acetylated denaturation) To the acetone-substituted H-type nanocellulose (1 part by mass) obtained in the above defibration process, acetic anhydride (1.5 parts by mass), 70% perchloric acid (0.05 parts by mass), acetone (6.0 parts by mass), and toluene (14.4 parts by mass) were added and stirred at room temperature for 1 hour. Methanol was added to the reaction solution, and the mixture was stirred to stop the reaction. After that, the mixture was washed (substituted) with methanol seven times using a tabletop multi-rack centrifuge (KOKUSAN, H-40α) to obtain acetylated modified H-type nanocellulose N-1.

[0164] [Production Example 2] (Methacrylic acid modified nanocellulose [N-2]) Methacrylic acid-modified H-type nanocellulose N-2 was obtained in the same manner as in Production Example 1, except that acetic anhydride was changed to methacrylic anhydride and the reaction temperature was changed to 50°C.

[0165] [Production Example 3] (Amine-modified nanocellulose [N-3]) To the acetone-substituted H-type nanocellulose obtained by the defibration step in Production Example 1, an amount of JEFFAMINE M-2005 (weight average molecular weight: 2,000, manufactured by Tomoe Engineering Co., Ltd.) equivalent to the acid value was added and stirred. Toluene was added to this, and the solids concentration was adjusted to 5% by mass. The residue was removed by filtration using a filter cloth, and the acetone was distilled off using an evaporator to obtain amine-modified nanocellulose N-3.

[0166] [Production Example 4] (Succinic acid modified nanocellulose [N-4]) To the amine-modified nanocellulose N-3 (1 part by mass) obtained in Production Example 3, succinic anhydride (20 parts by mass) and toluene (42 parts by mass) were added and stirred for 1.5 hours at 90°C. Methanol was added to the reaction solution, and the mixture was stirred to stop the reaction. After that, the mixture was washed (substituted) with methanol seven times using a tabletop multi-rack centrifuge (KOKUSAN, H-40α) to obtain succinic acid-modified H-type nanocellulose N-4.

[0167] [Production Example 5] (Maleic acid-modified nanocellulose [N-5] and itaconic acid-modified nanocellulose [N-6]) Maleic acid-modified H-type nanocellulose [N-5] and itaconic acid-modified H-type nanocellulose [N-6] were obtained in the same manner as in Production Example 4, except that succinic anhydride in Production Example 4 was changed to itaconic anhydride or itaconic anhydride.

[0168] <Preparation of Pressure-Sensitive Adhesive Composition> [Examples 1 to 8] To the (meth)acrylic polymer, an ethyl acetate solution of a vinyl polymer with a solid content concentration of 30%, an ethyl acetate dispersion of modified nanocellulose with a solid content concentration of 1 to 3%, and additives were added so as to obtain the composition ratio (parts by mass) shown in Table 3, and the mixture was diluted with ethyl acetate as necessary to give an overall solid content concentration of 25%, and a crosslinking agent was mixed in to obtain each pressure-sensitive adhesive composition. The additive used was KBE-9007N manufactured by Shin-Etsu Silicone Co., Ltd. The crosslinking agents used were as follows: D-110N: Mitsui Chemicals Takenate D-110N D-101E: Mitsui Chemicals Takenate D-101E Tetrad-C: Mitsubishi Gas Chemical Company, Inc. Tetrad-X: TETRAD-C manufactured by Mitsubishi Gas Chemical Company, Ltd.

[0169] The "peel strength increase rate" in Table 3 is the ratio of the peel strength of the Examples to the peel strength of the Comparative Examples. Specifically, Examples 1, 7, and 8 are compared with Comparative Example 1. Examples 2 to 6 are compared with Comparative Examples 2 to 6, respectively.

[0170] [Comparative Examples 1 to 6] An ethyl acetate solution of a vinyl polymer with a solid content of 30% and additives were added to the (meth)acrylic polymer so as to obtain the composition ratio (ratio of parts by mass) shown in Table 4, and the mixture was diluted with ethyl acetate as necessary so that the overall solid content became 25%, and a crosslinking agent was mixed in to obtain each pressure-sensitive adhesive composition. Comparative Examples 1 to 6 are the same as Examples 1 to 6 except that modified nanocellulose is not used.

[0171] <Preparation of adhesive film samples> The pressure-sensitive adhesive compositions described in the Examples and Comparative Examples were applied to a 50 μm thick polyethylene terephthalate (hereinafter, "PET") separator so that the thickness after drying would be 50 μm. The pressure-sensitive adhesive composition was dried at 80°C for 4 minutes to remove ethyl acetate and cause a crosslinking reaction. A 38 μm thick PET separator with a different peel strength from the separator was then attached, and the resulting film was left to stand at 40°C for 5 days for aging, thereby obtaining various pressure-sensitive adhesive film samples with double-sided separators.

[0172] <Peel strength measurement> The adhesive film sample was transferred to a 100 μm PET film treated for easy adhesion to obtain a pressure-sensitive adhesive sheet for evaluation. The adhesive sheet for evaluation was then laminated to an ABS plate (TP Giken, 2 mm thick) and pressed at 2.0 kN and 120°C for 20 seconds using a precision heating and pressing device CYPM-10 (Shinto Kogyo Co., Ltd.) to obtain a test specimen for peel testing. The 180° peel strength of the adhesive sheet was measured using an electromechanical universal testing machine, the 5965 (Instron), at a temperature of 23°C and a peel rate of 300 mm / min, in accordance with JIS Z-0237 "Test Methods for Adhesive Tapes and Sheets." This was taken as the peel strength.

[0173] <Measurement of storage modulus> 50 μm thick adhesive film samples were laminated to a thickness of 1.0 mm to obtain various evaluation adhesive sheets. This was punched out into 8 mm diameter circles, and the dynamic viscoelasticity was measured using a dynamic shear viscoelasticity analyzer (TA Instruments, Discovery HR20) at a frequency of 1 Hz and a strain of 0.1% while heating from -40 ° C to 200 ° C at a rate of 2 ° C / min, and the storage modulus was read at 23 ° C, 50 ° C, 100 ° C, and 150 ° C. Parallel plates with an 8 mm diameter were used for the measurement.

[0174] <Glass transition temperature Tg> The glass transition temperature Tg of the (meth)acrylic polymer and the pressure-sensitive adhesive composition was determined by reading the maximum value of tan δ in dynamic shear viscoelasticity measurement.

[0175] The vinyl polymer was measured by DSC under the following conditions. DSC: TA Instrument (Q-100) Temperature rise: 10°C / min Measurement atmosphere: Nitrogen

[0176] [Table 3]

[0177] [Table 4]

Claims

1. a (meth)acrylic polymer; Nanocellulose and a cross-linking agent; Including, Pressure-sensitive adhesive composition.

2. The (meth)acrylic polymer is a random copolymer. The pressure-sensitive adhesive composition according to claim 1 .

3. Further comprising a vinyl polymer, The pressure-sensitive adhesive composition according to claim 1 .

4. The nanocellulose has a modifying group; The pressure-sensitive adhesive composition according to claim 1 .

5. The modifying group is introduced into at least some of the hydroxyl groups of the nanocellulose via a covalent bond; The pressure-sensitive adhesive composition according to claim 4.

6. The hydroxyl group to which the modifying group has been introduced is represented by the following formula (2): RC(=O)-O- (2) wherein R is a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted cycloalkenyl group. is expressed as The pressure-sensitive adhesive composition according to claim 5 .

7. The modifying group is introduced into at least some of the carboxy groups of the nanocellulose via ionic bonding; The pressure-sensitive adhesive composition according to claim 4.

8. the modifying group has an amino group; The pressure-sensitive adhesive composition according to claim 7.

9. The nanocellulose comprises an oxide of a cellulosic raw material with hypochlorous acid or a salt thereof, and is substantially free of N-oxyl compounds; The pressure-sensitive adhesive composition according to claim 1 .

10. The nanocellulose has a structure in which the second and third hydroxyl groups of the glucopyranose ring are oxidized and dicarboxyl groups are introduced, The pressure-sensitive adhesive composition according to claim 1 .

11. The ratio of the storage modulus at 0 ° C. of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition to the storage modulus at 0 ° C. of a pressure-sensitive adhesive sheet formed from a control composition in which the nanocellulose is omitted from the pressure-sensitive adhesive composition is 1.3 or more. The pressure-sensitive adhesive composition according to claim 1 .

12. The ratio of the storage modulus at 23°C of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition to the storage modulus at 23°C of a pressure-sensitive adhesive sheet formed from a control composition in which the nanocellulose is omitted from the pressure-sensitive adhesive composition is 1.3 or more. The pressure-sensitive adhesive composition according to claim 1 .

13. The ratio of the storage modulus at 150 ° C of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition to the storage modulus at 150 ° C of a pressure-sensitive adhesive sheet formed from a control composition in which the nanocellulose is omitted from the pressure-sensitive adhesive composition is 1.1 or more; The pressure-sensitive adhesive composition according to claim 1 .

14. The ratio of the peel strength of a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition to the peel strength of a pressure-sensitive adhesive sheet formed from a control composition in which the nanocellulose is omitted from the pressure-sensitive adhesive composition is 1.05 or more; The pressure-sensitive adhesive composition according to claim 1 .

15. The ratio of the glass transition temperature of the pressure-sensitive adhesive composition to the glass transition temperature of a control composition obtained by excluding the nanocellulose from the pressure-sensitive adhesive composition is 0.9 to 1.1; The pressure-sensitive adhesive composition according to claim 1 .

16. The amount of the nanocellulose is 0.1 to 5% by mass based on the mass of the (meth)acrylic polymer. The pressure-sensitive adhesive composition according to claim 1 .

17. A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive composition according to any one of claims 1 to 16.

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