Acrylic resin composition, adhesive composition, substrate for adhesive sheet, and adhesive sheet

Abstract

The invention relates to an acrylic resin composition, an adhesive composition, a substrate for an adhesive sheet, and an adhesive sheet. Provided is an acrylic resin composition having high chemical resistance and high oil resistance. The acrylic resin composition contains a polymer containing units derived from a predetermined monomer, and the proportion of the units derived from the predetermined monomer contained in the polymer is 40-99 mass% with respect to 100 mass% of all monomer units constituting the polymer. The tensile strength of the acrylic resin composition after being immersed in oleic acid for 24 hours is 50% or more of the tensile strength before being immersed in oleic acid.

Description

[0001] This application is a divisional application. The parent application was filed on June 22, 2017, with international application number PCT / JP2017 / 022966 and Chinese national phase application number 201780092223.7. The invention is entitled "Acrylic Resin Composition, Adhesive Composition, Substrate for Adhesive Sheet and Adhesive Sheet". Technical Field

[0002] This invention relates to acrylic resin compositions, adhesive compositions, substrates for adhesive sheets, and adhesive sheets. Background Technology

[0003] Acrylic resins possess excellent weather resistance, durability, and high transparency. Furthermore, the wide variety of monomers available allows for diverse applications. Alkyl (meth)acrylates, in particular, exhibit a low glass transition temperature (Tg), excellent rubber elasticity, and inherent viscous properties when formulated as homopolymers, making them ideal for use in acrylic rubbers, adhesives, and bonding agents. Alkyl (meth)acrylate polymers are primarily manufactured via solution polymerization. Consequently, their solubility parameters are close to those of common industrial organic solvents such as toluene, ethyl acetate, and methyl ethyl ketone, indicating their easy dissolution in these solvents.

[0004] In recent years, mobile devices, such as smartphones and tablets, have become increasingly widespread. These devices often utilize acrylic adhesives and double-sided bonding agents to bond the display panel and the housing. Additionally, these devices incorporate touch panels for operation via fingers or by touching the face during calls. When the touch panel comes into contact with fingers or the face, oily components such as sebum and fingerprints adhere to it. These oily components contain oleic acid, whose SP value is close to that of industrial organic solvents, dissolving common acrylic resins. While industrial organic solvents have low boiling points and vaporize quickly without causing serious damage to adhesives, oleic acid and other oily components have high boiling points and do not vaporize in the environment, remaining inside the electronic device and damaging the adhesives. This can cause components to lift or peel off, shortening the lifespan of the electronic device.

[0005] Furthermore, in structural bonding double-sided adhesive tapes used in industrial fields such as building materials, automobiles, home appliances, and large electronic equipment, acrylic foam with excellent flexibility and stress-following properties is mostly used as the base material. However, in the case of building materials, if chemical reagents such as floor cleaners and waxes adhere to the tape, the double-sided adhesive tape with the acrylic foam base material will be damaged. In the case of automotive exterior parts, detergents or waxes may adhere during car washes, or gasoline may adhere during refueling, which can cause the common acrylic resins to dissolve or swell. In the case of home appliances, washing machines may adhere to laundry detergents and fabric softeners, microwave ovens and refrigerators may adhere to cooking oils, and fingerprints may adhere due to human contact and operation. Thus, double-sided adhesive tapes with acrylic foam base materials made of common acrylic resins can be damaged by chemical reagents and oil components, resulting in product defects or shortened lifespan.

[0006] For example, Patent Document 1 describes a method for obtaining a coating with high chemical resistance by performing two curing reactions: a carbamate bond formation reaction between the acrylic polyol resin and the polyisocyanate compound, and a free radical polymerization reaction of the multifunctional photocurable compound based on a photoinitiator, on a photocurable coating composition comprising a specific acrylic polyol resin, a multifunctional photocurable compound, and a polyisocyanate compound in a specific ratio. Patent Documents 2 and 3 describe resin compositions comprising acrylic resins mainly composed of n-butyl acrylate units that are resistant to oleic acid and artificial sebum. Patent Document 4 describes an adhesive composition comprising acrylic resins mainly composed of alkyl (meth)acrylate units having 1 to 6 carbon atoms that are resistant to sebum and cosmetics.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2016-37609

[0010] Patent Document 2: Japanese Patent Application Publication No. 2009-215355

[0011] Patent Document 3: Japanese Patent Application Publication No. 2013-100485

[0012] Patent Document 4: Japanese Patent Application Publication No. 2017-57371 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] However, the chemical resistance and oil resistance of the technologies described in Patent Documents 1 to 4 are insufficient, and further improvements are desired.

[0015] The object of this invention is to provide an acrylic resin composition with high chemical resistance and high oil resistance. Furthermore, the object of this invention is to provide an adhesive composition comprising the acrylic resin composition, a substrate for an adhesive sheet comprising the acrylic resin composition, and an adhesive sheet.

[0016] Solution for solving the problem

[0017] The acrylic resin compositions of the present invention comprise polymers containing units derived from monomers represented by formula (1) below.

[0018] [Chemistry 1]

[0019]

[0020] (In the above formula (1), R) 1 R represents a hydrogen atom or a methyl group. 2 R represents an alkylene group having 2 to 4 carbon atoms. 3 (Indicates an alkyl group with 1 to 10 carbon atoms, where n represents an integer from 1 to 20)

[0021] The proportion of units derived from the monomers shown in formula (1) in the polymer is 40% to 99% by mass relative to 100% of the total monomer units constituting the polymer.

[0022] The tensile strength of the above acrylic resin composition after being impregnated in oleic acid for 24 hours is more than 50% of the tensile strength value before impregnation in oleic acid.

[0023] The adhesive composition of the present invention comprises the acrylic resin composition of the present invention.

[0024] The substrate for the adhesive sheet of the present invention comprises the acrylic resin composition of the present invention.

[0025] The adhesive sheet of the present invention has the adhesive composition of the present invention and / or the substrate for the adhesive sheet of the present invention.

[0026] Invention Effects

[0027] According to the present invention, an acrylic resin composition having high chemical resistance and high oil resistance can be provided. Additionally, an adhesive composition comprising the acrylic resin composition, a substrate for adhesive sheets comprising the acrylic resin composition, and an adhesive sheet can be provided. Detailed Implementation

[0028] [Acrylic Resin Composition]

[0029] The acrylic resin composition of the present invention comprises a polymer containing units derived from the monomer shown in formula (1). Here, the proportion of units derived from the monomer shown in formula (1) contained in the polymer is 40 to 99% by mass relative to 100% by mass of all monomer units constituting the polymer. Furthermore, the tensile strength of the acrylic resin composition after immersion in oleic acid for 24 hours is 50% or more of the tensile strength value before immersion in oleic acid.

[0030] The inventors have discovered that by making the polymer contained in the acrylic resin composition mainly contain units from the monomer shown in formula (1), an acrylic resin composition with high chemical resistance and high oil resistance can be obtained. Specifically, it was found that by making the proportion of the units from the monomer shown in formula (1) contained in the polymer 40 to 99% by mass relative to 100% of all monomer units constituting the polymer, the tensile strength of the acrylic resin composition can be maintained at more than 50% of the tensile strength value before immersion in oleic acid, even when the acrylic resin composition is immersed in oleic acid for 24 hours. By making the polymer (acrylic resin) contained in the acrylic resin composition mainly contain units from the monomer shown in formula (1), the polarity of the acrylic resin is increased, and the difference between the solubility parameter of the acrylic resin and the solubility parameter of chemical reagents, oil components, etc., becomes larger. Therefore, it is speculated that the chemical resistance and oil resistance of the acrylic resin composition are improved.

[0031] Hereinafter, embodiments of the acrylic resin composition of the present invention will be described. It should be noted that "(meth)acrylic acid" refers to acrylic acid and methacrylic acid. In addition, the acrylic resin composition of the present invention preferably contains 70% by mass or more, more preferably 80% by mass or more, of a polymer containing units derived from the monomer shown in formula (1) as described above.

[0032] (The monomer shown in formula (1))

[0033] In the above formula (1), R 1 Represents a hydrogen atom or a methyl group. R 2 R represents an alkylene group having 2 to 4 carbon atoms, preferably an alkylene group having 2 or 3 carbon atoms, and more preferably an ethylene group. 3 The alkyl group represents an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. n represents an integer from 1 to 20, preferably an integer from 1 to 15, and more preferably an integer from 1 to 10.

[0034] Specific examples of the monomers shown in formula (1) above include: methoxyethyl acrylate, methoxypropyl acrylate, methoxybutyl acrylate, ethoxyethyl acrylate, ethoxypropyl acrylate, ethoxybutyl acrylate, and other alkoxyalkyl acrylates of methacrylate; methoxydiethylene glycol acrylate, methoxytriethylene glycol acrylate, and other methoxy(poly)ethylene glycol acrylate, ethoxydiethylene glycol acrylate, ethoxytriethylene glycol acrylate, ethoxy(poly)ethylene glycol acrylate, methoxydipropylene glycol acrylate, methoxytripropylene glycol acrylate, and other methoxy(poly)propylene glycol acrylate, ethoxydipropylene glycol acrylate, ethoxytripropylene glycol acrylate, and other methoxy(poly)propylene glycol acrylate, and other methoxy(poly)propylene glycol acrylate, and other methoxy(poly)propylene glycol esters, and other methoxy(poly)propylene glycol esters, and other methoxy(poly)propylene glycol esters, and other methoxy(poly)propylene glycol esters, and other methoxy(poly)propylene glycol esters, and other methoxy(poly)propylene glycol esters, and other methoxy(poly)propylene glycol esters, and other methoxy(poly)propylene glycol esters, and other methoxy(poly)propylene glycol monoalkyl ether esters, etc. Among these, from the viewpoint of superior chemical and oil resistance, methoxyethyl methacrylate, ethoxyethyl methacrylate, methoxy(poly)glycol methacrylate, and ethoxy(poly)glycol methacrylate are preferred, with methoxyethyl methacrylate being more preferred. In particular, regarding 2-methoxyethyl acrylate, its homopolymer has a Tg as low as -50°C, close to that of monomers commonly used in acrylic adhesives, thus making it useful as an adhesive or bonding agent. These monomers can be used individually or in combination.

[0035] Relative to 100% by mass of all monomer units constituting the polymer, the proportion of units from the monomers shown in formula (1) contained in the polymer is 40-99% by mass, preferably 45-95% by mass, more preferably 50-92% by mass, and even more preferably 55-90% by mass. When this proportion is less than 40% by mass, the chemical resistance and oil resistance decrease. In addition, if this proportion exceeds 99% by mass, the proportion of units from reactive monomers used for crosslinking purposes decreases relatively. It should be noted that this proportion represents the mass percentage of units from the monomers shown in formula (1) contained in the polymer, based on monomers, when the total mass of all monomer units constituting the polymer is set as 100% by mass. The same applies to the proportion of units from other monomers described later.

[0036] (alkyl methacrylate)

[0037] The polymers described above may further comprise units derived from alkyl (meth)acrylates. By including units derived from alkyl (meth)acrylates in the polymers described above, acrylic resin compositions capable of being extended to multiple applications can be obtained. Specific examples of alkyl (meth)acrylates include: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, isohexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, isododecyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, etc. One or more of these may be used.

[0038] The proportion of the units derived from (meth)acrylate in the polymer is preferably 0.1 to 40% by mass relative to 100% by mass of all monomer units constituting the polymer, more preferably 5 to 35% by mass, and even more preferably 10 to 30% by mass. By setting this proportion to 40% by mass or less, the proportion of units derived from the monomers shown in formula (1) can be increased, thereby improving the chemical resistance and oil resistance of the acrylic resin composition.

[0039] (Methyl)acrylic acid monomers containing carboxylic acids)

[0040] The polymer described above preferably further comprises units derived from (meth)acrylic acid monomers containing carboxylic acids. By including units derived from (meth)acrylic acid monomers containing carboxylic acids in the polymer, the strength of the acrylic resin composition can be further improved. Specific examples of (meth)acrylic acid monomers containing carboxylic acids include: (meth)acrylic acid, β-carboxyethyl (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, etc. Among these, (meth)acrylic acid is preferred from the viewpoint of higher strength of the acrylic resin composition. One of these may be used, or two or more may be used in combination.

[0041] Relative to 100% by mass of all monomer units constituting the polymer, the proportion of units derived from carboxylic acid-containing (meth)acrylic acid monomers in the polymer is preferably 0.5 to 20% by mass, more preferably 5 to 18% by mass, even more preferably 10 to 17% by mass, and particularly preferably 11 to 15% by mass. By making the proportion of carboxylic acid-containing (meth)acrylic acid monomers 0.5% by mass or more, the strength of the acrylic resin composition can be further improved, and reaction sites with crosslinking agents such as epoxy crosslinking agents can be imparted.

[0042] (Nitrogen-containing acrylic monomers)

[0043] The polymer described above preferably further comprises units derived from nitrogen-containing acrylic monomers. By including units derived from nitrogen-containing acrylic monomers in the polymer, the strength and heat resistance of the acrylic resin composition, as well as its chemical resistance and oil resistance, can be improved. Specific examples of nitrogen-containing acrylic monomers include: (meth)acrylamide, N-isopropyl(meth)acrylamide and other N-alkyl-substituted (meth)acrylamides, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide and other N,N-dialkyl-substituted (meth)acrylamides, acryloylmorpholine, vinylpyridine, N-vinylpyrrolidone, aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, etc. From the viewpoint of versatility and industrial production, (meth)acrylamide, N-alkyl-substituted (meth)acrylamide, N,N-dialkyl-substituted (meth)acrylamide, and acryloylmorpholine are preferred. One of these can be used, or two or more can be used in combination.

[0044] Relative to 100% by mass of all monomer units constituting the polymer, the proportion of units derived from nitrogen-containing acrylic monomers in the polymer is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and even more preferably 10 to 30% by mass. Setting this proportion to 1% by mass or more is effective in resin modification. Furthermore, setting this proportion to 50% by mass or less allows the acrylic resin composition to be applied to a wide variety of uses.

[0045] (Other monomers)

[0046] In addition to units derived from the monomers described above, the polymers may also contain units derived from hydroxyl-containing comonomers, such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, 2-hydroxyhexyl methacrylate, and monoesters of methacrylate with polyethylene glycol or polypropylene glycol.

[0047] (Aggregation method)

[0048] The polymerization method for the monomer composition containing the above-mentioned monomers is not particularly limited. For example, it can be carried out using various polymerization methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization, including photopolymerization or thermal polymerization. Furthermore, polymerization using radiation such as gamma rays or electron beam polymerization can also be used. Photopolymerization, for example, can be carried out by irradiating the monomer composition with UV rays in the presence of a photopolymerization initiator. Thermal polymerization, for example, can be carried out by heating the monomer composition to 50–200°C in the presence of a thermal polymerization initiator.

[0049] (Cross-linking agent)

[0050] From the viewpoint that a cross-linked structure can be formed, the acrylic resin composition of the present invention preferably further comprises a cross-linking agent. As a cross-linking agent, from the viewpoint of reactivity with the acrylic resin composition, at least one cross-linking agent selected from polyfunctional (meth)acrylic monomers, polyfunctional (meth)acrylic oligomers, compounds containing glycidyl groups with two or more functions, and compounds containing isocyanate groups with two or more functions are preferred.

[0051] Specific examples of multifunctional (meth)acrylate monomers include: trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, etc.

[0052] Specific examples of multifunctional (meth)acrylic acid oligomers include: urethane (meth)acrylic acid esters and epoxy (meth)acrylic acid esters obtained by reacting (meth)acrylic acid, (meth)acrylic acid esters containing hydroxyl groups with compounds having multiple isocyanate groups and glycidyl groups to oligomerize them.

[0053] Examples of compounds containing glycidyl groups with two or more functions include: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidylm-phenylenediamine, N,N,N',N'-tetraglycidylaminophenylmethane, triglycidyl isocyanurate, m-N,N-diglycidylaminophenylglycidyl ether, N,N-diglycidyltoluidine, N,N-diglycidylaniline, pentaerythritol polyglycidyl ether, and 1,6-hexanediol diglycidyl ether.

[0054] Examples of isocyanate monomers containing two or more functional groups include: toluene diisocyanate (TDI), chlorophenyl diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and hydrogenated diphenylmethane diisocyanate; and isocyanate compounds, isocyanurates, biuret-type compounds, and urethane prepolymers obtained by adding these isocyanate monomers to trimethylolpropane, etc.

[0055] The amount of crosslinking agent in the acrylic resin composition is preferably 0.01 to 10 parts by mass relative to 100 parts by mass of the polymer (all monomers before polymerization), more preferably 0.03 to 1 part by mass, and even more preferably 0.05 to 0.5 parts by mass.

[0056] (Hollow microfiller)

[0057] From the viewpoint of imparting strength and lightweight, the acrylic resin composition of the present invention may include hollow microfillers as fillers. Examples of hollow microfillers include hollow glass beads and hollow resin spheres. Among these, hollow glass beads are preferred from the viewpoint of chemical resistance and oil resistance. The average particle size of the hollow microfiller is preferably 1 to 100 μm, more preferably 10 to 50 μm. The content of hollow microfiller in the acrylic resin composition is preferably 2 to 50 parts by weight relative to 100 parts by weight of the polymer, more preferably 5 to 30 parts by weight, and even more preferably 10 to 20 parts by weight. In addition, in order to improve the dispersibility in the acrylic resin composition, the hollow microfiller may be subjected to appropriate surface treatments such as coupling treatment or stearic acid treatment.

[0058] (Flame retardant)

[0059] The acrylic resin composition of the present invention may contain a flame retardant. Examples of flame retardants include: phosphorus-based flame retardants such as ammonium polyphosphate and phosphate esters; melamine-based flame retardants such as melamine sulfate and (polymerized) melamine phosphate; and metal hydroxides. Among these, ammonium polyphosphate is preferred. One of these flame retardants may be used, or two or more may be used in combination. These flame retardants may be coated with a thermosetting resin for improving water resistance, or surface treatments such as microencapsulation may be performed. In addition, to improve dispersibility in the acrylic resin composition, the flame retardant may be appropriately subjected to surface treatments such as coupling treatment or stearic acid treatment.

[0060] The flame retardant content in the acrylic resin composition varies depending on the required degree of flame retardancy; for example, it may be 20 to 200 parts by weight relative to 100 parts by weight of the polymer. It should be noted that adhesion decreases with increasing flame retardant content; therefore, it is preferable to use a flame retardant that exhibits flame retardancy in a smaller quantity.

[0061] (thermally conductive particles)

[0062] The acrylic resin composition of the present invention may contain thermally conductive particles. Examples of thermally conductive particles include metal powder, metal oxide, metal hydroxide, boron nitride, silicon nitride, and carbon nitride. One or more of these thermally conductive particles may be used. The average particle size of the thermally conductive particles is preferably 1 to 100 μm, more preferably 10 to 50 μm. To improve dispersibility in the acrylic resin composition, the thermally conductive particles may be subjected to appropriate surface treatments such as coupling treatment or stearic acid treatment.

[0063] (Other additives)

[0064] The acrylic resin composition of the present invention may contain various additives such as silane coupling agents as needed.

[0065] (Tensile strength of acrylic resin compositions)

[0066] The tensile strength of the acrylic resin composition of the present invention after immersion in oleic acid for 24 hours is 50% or more, preferably 60% or more, and more preferably 70% or more. By maintaining this ratio (hereinafter also referred to as the retention rate) at 50% or more, the acrylic resin composition exhibits high chemical resistance and oil resistance. There is no particular upper limit to the retention rate; a higher value is preferred. It should be noted that the acrylic resin composition of the present invention is solid at room temperature (15–25°C), and its tensile strength can be measured. This tensile strength is a value measured based on JIS K 7114, and specifically, it can be measured using the method described later. The acrylic resin composition of the present invention not only exhibits good resistance to oleic acid, but also, as shown in the examples described later, shows higher resistance to other industrial solvents such as toluene and other oils such as gasoline than conventional acrylic resin compositions.

[0067] [Adhesive compositions, substrates for adhesive sheets, and adhesive sheets]

[0068] The adhesive composition of the present invention comprises the acrylic resin composition of the present invention. The substrate for the adhesive sheet of the present invention comprises the acrylic resin composition of the present invention. The adhesive sheet of the present invention comprises the adhesive composition of the present invention and / or the substrate for the adhesive sheet of the present invention.

[0069] The adhesive sheet of the present invention may, for example, comprise: an adhesive sheet substrate serving as a support, and an adhesive layer (resin layer) formed of an adhesive composition disposed on the adhesive sheet substrate. The adhesive sheet substrate and / or the adhesive composition are the adhesive sheet substrate and / or adhesive composition of the present invention. The adhesive layer may be disposed on only one side of the adhesive sheet substrate, or on both sides. Furthermore, the adhesive layer may be directly bonded to the adhesive sheet substrate, or indirectly bonded via a primer coating or the like. Additionally, an adhesive sheet may be manufactured in which the adhesive sheet of the present invention is disposed on one side of a release liner, and the release liner is peeled off during use.

[0070] The adhesive sheet substrate of the present invention can contain the acrylic resin composition of the present invention in the form of acrylic foam. As a method for manufacturing acrylic foam, for example, Japanese Patent Application Publication No. 2012-153900 discloses a low-density acrylic foam adhesive with fine and uniformly dispersed bubbles and a method for manufacturing the same. Other methods include adding a foaming agent and foaming it during sheet formation, or adding the aforementioned hollow microfiller and forming it into a sheet. When using an adhesive sheet substrate other than the adhesive sheet substrate of the present invention, examples of such adhesive sheet substrates include: various films such as polyester, polyimide, and polyolefin; nonwoven fabrics such as rayon and Manila paper; metal foil and woven fabric.

[0071] The thickness of the adhesive layer formed by the adhesive composition of the present invention is not particularly limited, and can be, for example, 0.1 to 5 mm, preferably 0.1 to 1 mm.

[0072] The adhesive sheet of the present invention is suitable for bonding various components, such as electronic device parts, automotive parts, and building materials.

[0073] Example

[0074] [Evaluation Test Methods]

[0075] The following evaluation items are based on JIS K 7114 "Test method for determining the impregnation effect in plastics-liquid chemical reagents".

[0076] <Tensile Strength>

[0077] Initially: Resin sheets cut into 10mm×100mm pieces were stretched using STROGRAPH at a stretching speed of 300mm / min, and the strength at break was measured.

[0078] After impregnation with various chemical reagents (oil components): resin sheets cut into 10mm×100mm were impregnated in various chemical reagents (oleic acid, gasoline, toluene) at 23°C for 24 hours. After removal, they were immediately stretched with STROGRAPH at a tensile speed of 300mm / min, and the strength at break was measured.

[0079] <Rate of Dimensional Change>

[0080] Resin sheets cut into 10mm×100mm pieces were immersed in various chemical reagents (oleic acid, gasoline, toluene) at 23°C for 24 hours. Immediately after removal, the width of the test sample was measured, and the dimensional change rate was calculated using the following formula.

[0081] Dimensional change rate = [(width of the test sample after impregnation) - (width of the test sample before impregnation (10mm))] / width of the test sample before impregnation (10mm) × 100 (%).

[0082] <Rate of change in mass>

[0083] The mass of resin sheets cut into 10mm × 100mm pieces was measured. The test samples were then immersed in various chemical reagents (oleic acid, gasoline, toluene) at 23°C for 24 hours. After removal, the chemical reagents on the surface of the test samples were immediately wiped off, and the mass was measured. The rate of change of mass relative to the initial mass was calculated using the following formula.

[0084] Mass change rate = [(mass of the test sample after immersion) - (mass of the test sample before immersion)] / mass of the test sample before immersion × 100 (%).

[0085] [Example 1]

[0086] A monomer composition was prepared by adding 60.0 parts by weight of 2-methoxyethyl acrylate, 27.5 parts by weight of 2-ethylhexyl acrylate, 12.5 parts by weight of acrylic acid, 0.01 parts by weight of Irgacure 1173 (trade name, manufactured by BASF JAPAN) as a photopolymerization initiator, and 0.01 parts by weight of n-dodecyl mercaptan as a chain transfer agent to a reaction vessel equipped with a stirrer, reflux condenser, thermometer, UV lamp, and nitrogen inlet. A portion of the monomers were polymerized by irradiating the monomer composition with UV light under a nitrogen atmosphere, thereby preparing a syrupy composition. The polymer concentration in the syrupy composition was approximately 13% by weight, and the weight-average molecular weight of the polymer was approximately 850,000.

[0087] To 100 parts by weight of the above syrupy composition, 0.1 parts by weight of 1,6-hexanediol diacrylate (trade name: NK ESTER A-HD-N, manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) as a crosslinking agent and 0.5 parts by weight of Irgacure 1173 (trade name: manufactured by BASF JAPAN) as a photopolymerization initiator were added, and the mixture was stirred until homogeneous. Air bubbles introduced during mixing were removed by a degassing process to prepare the coating solution.

[0088] The above-mentioned coating liquid was applied to a 50 μm thick polyethylene terephthalate (PET) film whose surface had been treated with a release agent, such that the resulting resin layer thickness was 0.5 mm. A 50 μm thick PET film was then laminated onto the layer composed of the above-mentioned coating liquid, and then irradiated with ultraviolet light to produce a resin sheet having a resin layer formed from the acrylic resin composition of the present invention. The above-mentioned evaluation test was performed on the resin sheet. The results are shown in Table 1.

[0089] [Examples 2-8, Comparative Examples 1-5]

[0090] The types and amounts of monomers and crosslinking agents in the monomer composition were varied as shown in Table 1. Otherwise, resin sheets were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0091] It should be noted that in Examples 2 and 5, and Comparative Example 2, 15.0 parts by mass of glass beads (trade name: Sphericel 34P30, manufactured by Potters-Ballotini, average particle size: 35 μm) were added as fillers, relative to 100 parts by mass of the total monomers (the obtained polymer) used in preparing the syrup-like composition. It should also be noted that in the evaluation of the tensile strength after impregnation with gasoline and toluene in Comparative Examples 4 and 5, the resin sheet broke before being placed on the testing machine, therefore the test could not be performed.

[0092] [Example 9]

[0093] In a reaction vessel equipped with a condenser, stirrer, and thermometer, 60.0 parts by mass of 2-methoxyethyl acrylate, 27.5 parts by mass of 2-ethylhexyl acrylate, 12.5 parts by mass of acrylic acid, and 0.2 parts by mass of 2,2'-azobisisobutyronitrile (2,2'-azobisisobutyronitrile) as a polymerization initiator were dissolved in 100 parts by mass of ethyl acetate. After nitrogen purging, polymerization was carried out at 68°C for 4 hours, followed by the addition of 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and polymerization was carried out at 80°C for 2 hours. The resulting solution had a polymer concentration of approximately 50% by mass, and the polymer had a weight-average molecular weight of approximately 800,000. 0.08 parts by mass of a tetrafunctional glycidyl compound (trade name: Tetrad-X, manufactured by Mitsubishi Gas Chemical Co., Ltd.) as a crosslinking agent was added to this solution, and the mixture was stirred to prepare a coating solution.

[0094] The above-mentioned coating solution was applied to a 50 μm thick polyethylene terephthalate (PET) film with a surface treated with a release agent, such that the resulting resin layer thickness was 0.1 mm, and then dried using a dryer. This operation was repeated 5 times, and the layers were stacked until the resin layer thickness reached 0.5 mm, thereby producing a resin sheet having a resin layer formed from the acrylic resin composition of the present invention. The above-mentioned evaluation test was performed on the resin sheet. The results are shown in Table 1.

[0095] [Table 1]

[0096]

[0097] 2-MEA: 2-Methoxyethyl Acrylate

[0098] AM-90G: Methoxylated (poly)ethylene glycol (n=9) acrylate

[0099] 2-EHA: 2-Ethylhexyl acrylate

[0100] n-BA: n-Butyl acrylate

[0101] AA: Acrylic acid

[0102] ACMO: Acryloylmorpholine

[0103] HDDA: 1,6-Hexanediol diacrylate

[0104] Tetrad-X: Trade name, manufactured by Mitsubishi Gas Chemical Co., Ltd., N,N,N',N'-tetraglycidyl-m-phenylenediamine.

Claims

1. An acrylic resin composition comprising: a polymer containing units derived from monomers of formula (1) below, and a crosslinking agent, In the above formula (1), R 1 R represents a hydrogen atom or a methyl group. 2 R represents an alkylene group having 2 to 4 carbon atoms. 3 Indicates an alkyl group having 1 to 10 carbon atoms, where n represents an integer from 1 to 20. The proportion of units derived from the monomers of formula (1) in the polymer is 40% to 78.0% by mass relative to 100% by mass of all monomer units constituting the polymer. The amount of the crosslinking agent is 0.01 to 0.1 parts by weight relative to 100 parts by weight of the polymer. The polymer does not contain units from (meth)acrylic acid monomers containing carboxylic acids, or the polymer contains 10% to 20% of the units from (meth)acrylic acid monomers containing carboxylic acids relative to 100% by mass of all monomer units constituting the polymer. The polymer also contains units derived from alkyl (meth)acrylates. The proportion of the units derived from (meth)acrylate in the polymer is 22.0% to 40% by mass relative to 100% by mass of all monomer units constituting the polymer. The tensile strength of the acrylic resin composition after being impregnated in oleic acid for 24 hours is more than 50% of the tensile strength before impregnation in oleic acid.

2. The acrylic resin composition according to claim 1, wherein, The crosslinking agent is at least one selected from polyfunctional (meth)acrylic acid monomers, polyfunctional (meth)acrylic acid oligomers, compounds with two or more functional groups containing glycidyl groups, and compounds with two or more functional groups containing isocyanate groups.

3. The acrylic resin composition according to claim 1 or 2, wherein, The polymer comprises units derived from (meth)acrylic acid monomers containing carboxylic acids.

4. The acrylic resin composition according to claim 1 or 2, wherein, The polymer comprises units derived from (meth)acrylic acid monomers containing carboxylic acids. The polymer contains 12.5% ​​to 20% by mass of units derived from (meth)acrylic acid monomers containing carboxylic acids.

5. The acrylic resin composition according to claim 3, wherein, The (meth)acrylic acid monomer containing carboxylic acid is (meth)acrylic acid.

6. The acrylic resin composition according to claim 1 or 2, wherein, The monomer represented by formula (1) is at least one monomer selected from (meth)acrylate, (meth)acrylate, (meth)acrylate, (poly)acrylate and (meth)acrylate.

7. The acrylic resin composition according to claim 1 or 2, wherein, The polymer also comprises units derived from nitrogen-containing acrylic monomers. The proportion of the units derived from nitrogen-containing acrylic monomers contained in the polymer is 1% to 50% by mass relative to 100% by mass of all monomer units constituting the polymer.

8. The acrylic resin composition according to claim 7, wherein, The nitrogen-containing acrylic monomer is at least one monomer selected from (meth)acrylamide, N-alkyl-substituted (meth)acrylamide, N,N-dialkyl-substituted (meth)acrylamide, and acryloylmorpholine.

9. The acrylic resin composition according to claim 1 or 2, further comprising hollow microfillers.

10. The acrylic resin composition according to claim 9, wherein, The hollow microfiller is a hollow glass bead, and the content of the hollow microfiller is 2 to 50 parts by mass relative to 100 parts by mass of the polymer.

11. An adhesive composition comprising the acrylic resin composition according to any one of claims 1 to 10.

12. A substrate for an adhesive sheet comprising the acrylic resin composition according to any one of claims 1 to 10.

13. An adhesive sheet having the adhesive composition of claim 11 and / or the substrate for adhesive sheets of claim 12.

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