Curable resin composition and adhesive agent comprising said composition

Abstract

This curable resin composition comprises an α-methylene cyclic lactone compound. The α-methylene cyclic lactone compound optionally has a 5- to 6-membered lactone structure. This curable resin composition optionally further comprises a multifunctional monomer and a (meth)acryloyl-group-containing polymer. The composition can further contain a polyfunctional monomer and a (meth) acryloyl group-containing polymer.

Description

Curable resin composition and adhesive containing the composition

[0001] The present invention relates to a curable resin composition and an adhesive containing the composition.

[0002] The use of multiple different materials in combination, known as multi-materialization, is progressing, as exemplified by the weight reduction of vehicles, aircraft, and the like. In multi-materialization, different materials are joined together (hereinafter sometimes referred to as "joining of dissimilar materials"), such as iron and aluminum alloy, metal and resin, or metal and CFRP (Carbon Fiber Reinforced Plastics), making it possible to reduce weight and impart functions that are difficult to achieve with a single material. In some cases where welding is not applicable to joining dissimilar materials, adhesive technologies that can join a variety of materials are being investigated.

[0003] Patent Document 1 discloses a curable resin composition that contains a specific group of monomers and that is strongly bonded to the surfaces of various types of materials, a curable resin composition that is strongly bonded to various types of materials, a pressure-sensitive adhesive, and a surface coating agent.

[0004] Japanese Patent Application Laid-Open No. 2022-123808

[0005] However, in order to adjust the glass transition temperature (hereinafter referred to as "Tg") and adhesive properties of adhesives for various applications, there is a demand for the development of new adhesive materials that can replace existing adhesive materials or that can be used in combination with these.

[0006] In order to solve the above-mentioned problems, an object of the present invention is to provide a novel curable resin composition that can exhibit excellent adhesive properties to adherends made of a variety of materials, and an adhesive using the same.

[0007] <1> A curable resin composition comprising an α-methylene cyclic lactone compound. <2> The curable resin composition according to <1>, wherein the α-methylene cyclic lactone compound has a 5- or 6-membered ring lactone structure. <3> The curable resin composition according to <1> or <2>, further comprising a polyfunctional monomer and a (meth)acryloyl group-containing polymer. <4> The curable resin composition according to any one of <1> to <3>, further comprising a polymerization initiator. <5> A pressure-sensitive adhesive comprising the curable resin composition according to any one of <1> to <4>.

[0008] According to the present invention, it is possible to provide a curable resin composition that can exhibit excellent adhesive properties to adherends made of a variety of materials, and an adhesive using the same.

[0009] In this specification, specific examples of the "polymerizable group" include a (meth)acryloyl group, a methylene group, a hydroxyl group, an isocyanate group, a carbon-carbon double bond, an epoxy group, and a (meth)acrylamide group.

[0010] In this specification, the term "(meth)acryloyl group" includes a methacryloyl group and an acryloyl group, and the term "(meth)acrylamide group" includes a methacrylamide group and an acrylamide group.

[0011] In this specification, when a numerical range is indicated using "to," it is intended to include both ends of the range.

[0012] <<Curable Resin Composition>> The curable resin composition of this embodiment contains an α-methylene cyclic lactone compound. Furthermore, the curable resin composition of this embodiment is a composition that, upon curing, can exhibit adhesive properties to a substrate to be adhered (hereinafter, may be simply referred to as "substrate"). The curable resin composition of this embodiment can exhibit excellent adhesive properties to a variety of substrates.

[0013] Throughout this specification, the expression "exhibiting adhesive properties" means that when the curable resin composition becomes a cured product, it exhibits at least one of the properties of "tackiness," "adhesion," and "adhesion" to a substrate, and includes both an embodiment in which only one of these properties is exhibited and an embodiment in which two or more of these properties are exhibited. The curable resin composition of the present embodiment can exhibit excellent adhesive properties to adherends made of a variety of materials, and can therefore be suitably used as an adhesive, and further as an adhesive for joining dissimilar materials. Details of adhesives will be described later.

[0014] <α-Methylene Cyclic Lactone Compound> The curable resin composition of this embodiment contains an α-methylene cyclic lactone compound. The α-methylene cyclic lactone compound is a compound having a methylene group at the α-position relative to a cyclic lactone structure, and is a polymerizable compound. The α-methylene cyclic lactone compound is superior in reactivity to cyclic lactone compounds having a methylene group at a position other than the α-position, such as the β-position. Furthermore, the α-methylene cyclic lactone compound may be a compound having a polymerizable group at another position in addition to the methylene group at the α-position, but is preferably a monofunctional monomer containing only the methylene group at the α-position as the polymerizable group.

[0015] The lactone structure of the α-methylene cyclic lactone compound is a heterocyclic ring containing two or more carbon atoms and one oxygen atom, and has a carbonyl group on the carbon atom adjacent to the oxygen atom that forms the ring. The α-methylene cyclic lactone compound of this embodiment has a methylene group (CH ２ ). Although not particularly limited, the α-methylene cyclic lactone compound in this embodiment preferably has a 4- to 8-membered ring lactone structure, and more preferably a 5- or 6-membered ring lactone structure, from the viewpoints of easily exhibiting excellent adhesive properties, easily adjusting the glass transition temperature of the cured product within a desired range (details will be described later), and easily improving the handleability of the curable resin composition of this embodiment. Furthermore, the lactone structure of the α-methylene cyclic lactone compound may be a structure in which another ring structure (aromatic ring, non-aromatic ring, heterocyclic ring, etc.) is condensed.

[0016] Specific examples of the α-methylene cyclic lactone compound include, but are not limited to, the following compounds: Among them, α-methylene-γ-butyrolactone (MBL) having a five-membered ring is preferably used as the α-methylene cyclic lactone compound in this embodiment.

[0017]

[0018] The method for obtaining the α-methylene cyclic lactone compound is not particularly limited, and commercially available products can be used. Furthermore, the α-methylene cyclic lactone compound may be a so-called biomass-derived α-methylene cyclic lactone compound derived from plants, etc., in addition to conventional petroleum-derived compounds. The curable resin composition of the present embodiment may use a petroleum-derived α-methylene cyclic lactone compound and a biomass-derived α-methylene cyclic lactone compound, either alone or in combination. When a petroleum-derived α-methylene cyclic lactone compound and a biomass-derived α-methylene cyclic lactone compound are used in combination, there are no particular limitations. However, from the viewpoint of promoting the use of biomass resources, the content of the biomass-derived α-methylene cyclic lactone compound relative to the total mass of the α-methylene cyclic lactone compounds is preferably 50 to 100% by mass, more preferably 80 to 100% by mass, and particularly preferably 95 to 100% by mass. These α-methylene cyclic lactone compounds may be used alone, or two or more types may be used in combination. The ratio of petroleum-derived α-methylene cyclic lactone compounds and the ratio of biomass-derived α-methylene cyclic lactone compounds contained in the curable resin composition of the present embodiment are １４ It can be identified by C (radiocarbon) / C (carbon). In petroleum-derived α-methylene cyclic lactone compounds, １４ C / C is 1.0 x 10 －１４ In contrast, from the viewpoint of promoting the use of biomass resources, the α-methylene cyclic lactone compound contained in the curable resin composition of the present embodiment is preferably １４ C / C is 1.0 x 10 －１４ More preferably, 1.0×10 －１３ More preferably, 1.0 × 10－１２ When almost 100% by mass of the α-methylene cyclic lactone compound is made from non-fossil raw materials, the upper limit is 1.2 × 10 －１２ is. １４ The C / C ratio can be measured by a known method, for example, isotope mass spectrometry.

[0019] The glass transition temperature (Tg) of the α-methylene cyclic lactone compound is preferably 80 to 300° C., more preferably 100 to 280° C., and particularly preferably 100 to 250° C., from the viewpoint of improving the heat resistance and brittleness of the cured product (hereinafter sometimes simply referred to as the cured product) obtained from the curable resin composition of this embodiment. The Tg of the α-methylene cyclic lactone compound refers to the Tg of a homopolymer of the α-methylene cyclic lactone compound. For the Tg of the α-methylene cyclic lactone compound, known literature values ​​(e.g., values ​​described in "Polymer Handbook" (4th Edition, John Wiley & Sons, Inc., 1999)) can be used when available. In other cases, for example, the α-methylene cyclic lactone compound can be bulk polymerized to form a homopolymer, as described below, and the Tg of the homopolymer of the α-methylene cyclic lactone compound measured, and the resulting value can be used as the Tg of the α-methylene cyclic lactone compound monomer. The same applies to the Tg of other monomers other than the α-methylene cyclic lactone compounds described below.

[0020] An α-methylene cyclic lactone compound (monomer) and a polymerization initiator were injected into a mold (two glass plates, each with a release film attached, with the release film surfaces facing each other, between which a 4 mm thick silicone spacer was placed to form an area 100 mm long and 100 mm wide, with the silicone spacer sandwiched between the two glass plates so that the gap was approximately 2 to 4 mm). The mold was irradiated with ultraviolet light (wavelength: 365 nm) using an LED exposure device for 1 hour to obtain a polymer.

[0021] 10 mg of the obtained polymer was weighed out and attached to a differential scanning calorimeter (DSC7000X, manufactured by Hitachi High-Tech Science Corporation). Measurement was performed at a heating rate of 10°C / min in a temperature range of -20 to 250°C. The temperature of the endothermic peak attributable to the polymer during the first heating process was taken as the glass transition temperature (Tg) of the polymer, and this was also taken as the Tg of the α-methylene cyclic lactone compound (monomer).

[0022] <Other Monomers> The curable resin composition of the present embodiment may be in an embodiment containing only the α-methylene cyclic lactone compound as a monomer component, or other monofunctional monomers or polyfunctional monomers may be used. The α-methylene cyclic lactone compound of the present embodiment can exhibit excellent adhesive properties, and therefore, by using it in combination with monomers that have conventionally been used in adhesive applications, the adhesive properties of the curable resin composition can be improved while exhibiting the existing performance of these monomers.

[0023] (Other Monofunctional Monomer) The other monofunctional monomer is not particularly limited, but as described above, examples thereof include monomers that can be used in adhesive applications.

[0024] Examples of other monofunctional monomers include (meth)acryloyl group-containing monofunctional monomers.

[0044] Examples of the (meth)acryloyl group-containing monofunctional monomer include the following monomers, and among them, from the viewpoint of exhibiting good adhesive properties, 4-hydroxybutyl (meth)acrylate (4-HB(M)A), tetrahydrofurfuryl (meth)acrylate (THF(M)A), γ-butyrolactone (meth)acrylate (GBL(M)A), isobornyl (meth)acrylate (IBX(M)A), (meth)acrylic acid ((M)MA), lauryl acrylate (LA), butyl (meth)acrylate (B(M)A), 2-methoxyethyl (meth)acrylate (2-MT(M)A), 1-adamantyl (meth)acrylate ((M)ADMA), benzyl (meth)acrylate (Bz(M)A), cyclohexyl (meth)acrylate (CH(M)A), and phenyl (meth)acrylate (PH(M)A) are preferred. Furthermore, from the viewpoint of increasing the ratio of biomass-derived raw materials in the curable resin composition and promoting the use of biomass resources, it is preferable to contain THF(M)A and IBX(M)A derived from biomass resources. These other monofunctional monomers may be used alone or in combination of two or more.

[0025]

[0026] (Polyfunctional Monomer) The curable resin composition of the present embodiment may contain a polyfunctional monomer as long as the object of the present disclosure is not impaired. When the curable resin composition of the present embodiment contains a polyfunctional monomer, the curing rate tends to be improved. The polyfunctional monomer is a monomer having at least two polymerizable functional groups.

[0027] Examples of the polyfunctional monomer include polyfunctional (meth)acrylamides having two or more (preferably two) (meth)acryloyl groups, such as methylenebisacrylamide and methylenebismethacrylamide; ethylene di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, trimethylol Examples of the polyfunctional (meth)acrylate include polyfunctional (meth)acrylates having two or more (preferably two or three) (meth)acryloyl groups, such as diolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; polyfunctional isocyanates having two or more (preferably two or three) isocyanate groups, such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane-4,4'-diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, lysine triisocyanate and methylidyne triphenylene triisocyanate; polyfunctional amines having two or more (preferably two or three) carbon-carbon double bonds, such as diallylamine and triallylamine; and polyfunctional monomers such as aromatic compounds having two or more (preferably two or three) carbon-carbon double bonds, such as divinylbenzene and diallylbenzene. These polyfunctional monomers may be used alone or in combination of two or more.

[0028] <Monomer Component> From the viewpoint of exhibiting good adhesive properties, the content of all monomers in the curable resin composition of the present embodiment is preferably 5 to 80 mass %, more preferably 15 to 70 mass %, and particularly preferably 25 to 65 mass %, relative to the total amount (mass) of the curable resin composition. When the curable resin composition of the present embodiment uses only an α-methylene cyclic lactone compound as a monomer, the content of all monomers in the curable resin composition is the content of the α-methylene cyclic lactone compound in the curable resin composition.

[0029] Furthermore, when other monomers are used in addition to the α-methylene cyclic lactone compound in the curable resin composition of this embodiment, the content and Tg of each monomer component can be adjusted appropriately depending on the purpose of the curable composition. Examples of purposes for the curable composition include pressure-sensitive adhesive applications, but it is also anticipated that the curable composition may be used as a relatively flexible "pressure-sensitive adhesive" or as an "adhesive" that requires relatively high hardness. For example, an "adhesive" with relatively high hardness may be an adhesive in which the Young's modulus of the curable resin after curing is 1,000 to 10,000 MPa. Examples of each embodiment are described below. However, the curable resin composition of this embodiment is not limited to the following description.

[0030] (Adhesive Use) For example, when the curable resin composition of the present embodiment is used as a "adhesive" and a monofunctional monomer other than the α-methylene cyclic lactone compound is used in combination, the glass transition temperature (Tg) of the other monofunctional monomer is preferably −100 to 300° C., more preferably −80 to 280° C., and particularly preferably −60 to 250° C., from the viewpoint of easily exhibiting good adhesive properties.

[0031] When an α-methylene cyclic lactone compound and another monofunctional monomer are used in combination, from the viewpoint that the Tg of the cured product falls within a range that makes it easy to handle as an adhesive, the total amount of the other monofunctional monomer is preferably more than 0 parts by mass and not more than 2000 parts by mass, more preferably more than 0 parts by mass and not more than 1500 parts by mass, and particularly preferably more than 0 parts by mass and not more than 1000 parts by mass, relative to 100 parts by mass of the total amount of the α-methylene cyclic lactone compounds.

[0032] When the curable resin composition of the present embodiment is used as a "tacky adhesive" and an α-methylene cyclic lactone compound and a polyfunctional monomer are used in combination, the glass transition temperature (Tg) of the polyfunctional monomer is preferably 10 to 200°C, more preferably 30 to 150°C, and particularly preferably 50 to 100°C, from the viewpoint of easily exhibiting good adhesive properties.

[0033] In this case, from the viewpoint of ensuring that the Tg of the cured product falls within a range that makes it easy to handle as a pressure-sensitive adhesive, the total amount of the polyfunctional monomers is preferably more than 0 parts by mass and not more than 200 parts by mass, more preferably more than 0 parts by mass and not more than 190 parts by mass, and particularly preferably more than 0 parts by mass and not more than 180 parts by mass, relative to 100 parts by mass of the total amount of the monofunctional monomers.

[0034] (Adhesive Application) For example, when the curable resin composition of the present embodiment is used as a relatively flexible "adhesive" and a monofunctional monomer other than the α-methylene cyclic lactone compound is used in combination, the glass transition temperature (Tg) of the other monofunctional monomer is preferably −100 to 150° C., more preferably −80 to 120° C., and particularly preferably −60 to 110° C., from the viewpoint of easily exhibiting good adhesiveness.

[0035] When an α-methylene cyclic lactone compound is used in combination with another monofunctional monomer, the total amount of the other monofunctional monomer is preferably 20 to 2,000 parts by mass, more preferably 30 to 1,500 parts by mass, and particularly preferably 40 to 1,000 parts by mass, per 100 parts by mass of the total amount of the α-methylene cyclic lactone compound, from the viewpoint of ensuring that the Tg of the cured product falls within a range that makes it easy to handle as a pressure-sensitive adhesive.

[0036] When the curable resin composition of the present embodiment is used as a relatively flexible "adhesive" and an α-methylene cyclic lactone compound and a polyfunctional monomer are used in combination, the glass transition temperature (Tg) of the polyfunctional monomer is preferably 10 to 120°C, more preferably 30 to 100°C, and particularly preferably 50 to 80°C, from the viewpoint of easily exhibiting good adhesiveness.

[0037] When an α-methylene cyclic lactone compound and a polyfunctional monomer are used in combination, from the viewpoint of ensuring that the Tg of the cured product falls within a range that makes it easy to handle as a pressure-sensitive adhesive, the total amount of the polyfunctional monomers is preferably more than 0 parts by mass and not more than 1 part by mass, more preferably more than 0 parts by mass and not more than 0.5 parts by mass, and particularly preferably more than 0 parts by mass and not more than 0.1 parts by mass, relative to 100 parts by mass of the total amount of the monofunctional monomers.

[0038] (Adhesive Use) For example, when the curable resin composition of the present embodiment is used as an "adhesive" that is required to have a relatively high hardness, and when a monofunctional monomer other than the α-methylene cyclic lactone compound is used in combination, the glass transition temperature (Tg) of the other monofunctional monomer is preferably 80 to 300°C, more preferably 100 to 280°C, and particularly preferably 120 to 250°C, from the viewpoint of easily exhibiting good adhesiveness.

[0039] When an α-methylene cyclic lactone compound is used in combination with another monofunctional monomer, the total amount of the other monofunctional monomer is preferably 10 to 40 parts by mass, more preferably 10 to 30 parts by mass, and particularly preferably 10 to 20 parts by mass, per 100 parts by mass of the total amount of the α-methylene cyclic lactone compound, from the viewpoint of ensuring that the Tg of the cured product falls within a range that makes it easy to handle as an adhesive.

[0040] When the curable resin composition of the present embodiment is used as an "adhesive" that is required to have a relatively high hardness, and an α-methylene cyclic lactone compound and a polyfunctional monomer are used in combination, the glass transition temperature (Tg) of the polyfunctional monomer is preferably 10 to 200°C, more preferably 30 to 150°C, and particularly preferably 50 to 100°C, from the viewpoint of easily exhibiting good adhesive properties.

[0041] When an α-methylene cyclic lactone compound and a polyfunctional monomer are used in combination, the total amount of the polyfunctional monomers is preferably 0 to 180 parts by mass, more preferably 1 to 160 parts by mass, and particularly preferably 5 to 140 parts by mass, per 100 parts by mass of the total amount of the monofunctional monomers, from the viewpoint of ensuring that the Tg of the cured product falls within a range that makes it easy to handle as an adhesive.

[0042] <Other Components> In addition to the above-described monomer components such as the α-methylene cyclic lactone compound, the curable resin composition of the present embodiment may further contain a polymer, a solvent, and additives that are generally added to pressure-sensitive adhesives or adhesives, within the scope of the present disclosure. Examples of such additives include a polymerization initiator, a silane coupling agent, a crosslinking agent, an ultraviolet absorber, a tackifier, an adhesion promoter, an antiaging agent, a plasticizer, a softener, a dye, a pigment, and a filler.

[0043] (Polymer) The curable resin composition of this embodiment may contain a polymer. When the curable resin composition of this embodiment contains a polymer, the heat resistance and brittleness of the cured product tend to be improved. Such a polymer may be used without particular limitation as long as it reacts with the α-methylene cyclic lactone compound contained in the curable resin composition of this embodiment or the other monomers described above to form a cured product, and examples thereof include (meth)acryloyl group-containing polymers. These polymers may be used alone or in combination of two or more types.

[0044] -(Meth)acryloyl Group-Containing Polymer- The curable resin composition of this embodiment may contain a (meth)acryloyl group-containing polymer, for example, an α-methylene cyclic lactone compound, a polyfunctional monomer, and a (meth)acryloyl group-containing polymer. The (meth)acryloyl group-containing polymer is not particularly limited as long as it is a polymer containing at least one (meth)acryloyl group at at least one end of the main chain and / or in a side chain. The (meth)acryloyl group-containing polymer may also be a (meth)acryloyl group-containing polymer having a urethane bond, an ester bond, an ether bond, a polyol bond, or the like, or a combination of two or more selected from these. Commercially available (meth)acryloyl group-containing polymers may be used, such as the ART RESIN series, such as "UN-9200A" manufactured by Negami Chemical Industrial Co., Ltd.

[0045] An example of the weight average molecular weight, Tg, and content of the polymer in this embodiment will be described below, although the curable resin composition of this embodiment is not limited to the following description.

[0046] (Adhesive Use) For example, when the curable resin composition of the present embodiment is used as a "adhesive," the weight-average molecular weight (Mw) of the polymer in the present embodiment is preferably 3,000 to 5,0000, more preferably 5,000 to 30,000, and particularly preferably 10,000 to 20,000, from the viewpoints of easily exhibiting good adhesive properties, excellent applicability to the target object, and suppressing gelation of the curable resin composition. The weight-average molecular weight of the polymer can be measured in polystyrene equivalent terms using gel permeation chromatography (Tosoh Corporation, Product No.: HLC-8320GPC, Column: Tosoh Corporation, Product No.: TSKgel GMHH-R, Solvent: Tetrahydrofuran, Flow Rate: 0.6 mL / min).

[0047] In this case, the glass transition temperature (Tg) of the polymer in this embodiment is not particularly limited, but from the viewpoint of easily exhibiting good adhesive properties, it is preferably −100 to 30° C., more preferably −80 to 10° C., and particularly preferably −70 to −10° C. The glass transition temperature of the polymer in this embodiment can be determined by a differential scanning calorimeter (DSC). The measurement conditions for DSC are the same as those described above.

[0048] In the case of pressure-sensitive adhesive applications, from the viewpoint of easily exhibiting good pressure-sensitive adhesive properties, the content of the polymer in the curable resin composition of the present embodiment is preferably 35 to 170 parts by mass, more preferably 50 to 155 parts by mass, and particularly preferably 65 to 140 parts by mass, relative to 100 parts by mass of the total amount of the monomer components.

[0049] (Adhesive Use) For example, when the curable resin composition of this embodiment is used as a relatively flexible "adhesive," the weight average molecular weight (Mw) of the polymer in this embodiment is preferably 3,000 to 5,0000, more preferably 5,000 to 30,000, and particularly preferably 10,000 to 20,000, from the viewpoints of easily exhibiting good adhesive properties, excellent applicability to the target object, and suppressing gelation of the curable resin composition. The weight average molecular weight of the polymer can be measured in polystyrene equivalent terms using gel permeation chromatography (Tosoh Corporation, product number: HLC-8320GPC, column: Tosoh Corporation, product number: TSKgel GMHH-R, solvent: tetrahydrofuran, flow rate: 0.6 mL / min).

[0050] In this case, the glass transition temperature (Tg) of the polymer in this embodiment is not particularly limited, but from the viewpoint of easily exhibiting good adhesiveness, it is preferably −100 to 0° C., more preferably −80 to −20° C., and particularly preferably −60 to −25° C. The glass transition temperature of the polymer in this embodiment can be determined by differential scanning calorimetry (DSC). The measurement conditions for DSC are the same as those described above.

[0051] In the case of relatively soft pressure-sensitive adhesive applications, from the viewpoint of easily exhibiting good adhesiveness, the content of the polymer in the curable resin composition of the present embodiment is preferably 35 to 170 parts by mass, more preferably 50 to 155 parts by mass, and particularly preferably 65 to 140 parts by mass, relative to 100 parts by mass of the total amount of the monomer components.

[0052] (Adhesive Use) For example, when the curable resin composition of the present embodiment is used as an "adhesive" that is required to have a relatively high hardness, the weight average molecular weight (Mw) of the polymer of the present embodiment is preferably 3,000 to 50,000, more preferably 5,000 to 30,000, and particularly preferably 10,000 to 20,000, from the viewpoint of easily exhibiting good adhesive properties.

[0053] In this case, the glass transition temperature (Tg) of the polymer in this embodiment is not particularly limited, but from the viewpoint of easily exhibiting good adhesiveness, it is preferably −70 to 30° C., more preferably −50 to 10° C., and particularly preferably −30 to −10° C. The glass transition temperature of the polymer in this embodiment can be determined by differential scanning calorimetry (DSC). The measurement conditions for DSC are the same as those described above.

[0054] In the case of adhesive applications that require a relatively high hardness, from the viewpoint of easily exhibiting good adhesive properties, the content of the polymer in the curable resin composition of the present embodiment is preferably 35 to 170 parts by mass, more preferably 50 to 155 parts by mass, and particularly preferably 65 to 140 parts by mass, relative to 100 parts by mass of the total amount of the monomer components.

[0055] (Polymerization initiator) The curable resin composition of the present embodiment may contain a polymerization initiator, if necessary. Examples of the polymerization initiator include a photopolymerization initiator and a thermal polymerization initiator.

[0056] Examples of the photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,2'-bis(o-chlorophenyl)-4,4',5,5'-tetraphenyl-1,1'-biimidazole, 2,4,6-tris(trichloromethyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-(p-methoxyphenylvinyl)-1,3,5-triazine, diphenyliodonium tetrafluoroborate, diphenyliodonium hexafluorophosphate, 4,4'-di-tert-butyl ... t-butyldiphenyliodonium tetrafluoroborate, 4-diethylaminophenylbenzenediazonium hexafluorophosphate, benzoin, 2-hydroxy-2-methyl-1-phenylpropan-2-one, benzophenone, thioxanthone, 2,4,6-trimethylbenzoyldiphenylacylphosphine oxide (TPO), triphenylbutylborate tetraethylammonium, diphenyl-4-phenylthiophenylsulfonium hexafluorophosphate, 2,2-dimethoxy-1,2-diphenyl photoradical polymerization initiators such as phenylethan-1-one, phenylglyoxylic acid methyl ester, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 1,2-octanedione, 1-[4-(phenylthio)-2-(o-benzoyloxime)], and bis(η5-2,4-cyclopentadien-1-yl)bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyltitanium]; Examples of the photopolymerization initiator include cationic ring-opening photopolymerization initiators such as 2,4,6-tris(trichloromethyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-(p-methoxyphenylvinyl)-1,3,5-triazine, diphenyliodonium tetrafluoroborate, 4,4'-di-tert-butyldiphenyliodonium tetrafluoroborate, 4-diethylaminophenylbenzenediazonium hexafluorophosphate, and diphenyl-4-phenylthiophenylsulfonium hexafluorophosphate. These photopolymerization initiators may be used alone or in combination of two or more.

[0057] Examples of the thermal polymerization initiator include azo-based polymerization initiators such as dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobisisobutyronitrile (AIBN), dimethyl 2,2'-azobisisobutyrate, and azobisdimethylvaleronitrile; and peroxide-based polymerization initiators such as benzoyl peroxide, potassium persulfate, and ammonium persulfate. These thermal polymerization initiators may be used alone or in combination of two or more.

[0058] From the viewpoint of improving the curing rate, the content of the polymerization initiator in the curable resin composition of the present embodiment is preferably 1 to 10 mass %, more preferably 3 to 8 mass %, and particularly preferably 4 to 6 mass %, relative to the total amount (mass) of the curable resin composition.

[0059] (Solvent) The curable resin composition of the present embodiment may contain a solvent as needed. For example, when polymerizing the monomer components of the present embodiment, the polymerization method is not particularly limited, but examples thereof include bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization. Of these polymerization methods, from the viewpoints of manufacturability and handleability, bulk polymerization and solution polymerization are preferred, and bulk polymerization is more preferred. When using solution polymerization, a solvent can be used as appropriate.

[0060] As such a solvent, a non-aqueous organic solvent can be used from the viewpoints of manufacturability, handleability, etc. Examples of non-aqueous organic solvents include ether-based organic solvents such as dimethyl ether, diethyl ether, tetrahydrofuran, etc.; ketone-based organic solvents such as acetone and methyl ethyl ketone; ester-based organic solvents such as methyl acetate, ethyl acetate, butyl acetate, etc.; alcohol-based organic solvents such as ethanol and n-propanol; chloride-based organic solvents such as methylene chloride, chloroform, carbon tetrachloride, etc.; dimethylformamide, diethylformamide, dimethyl sulfoxide, dioxane, etc. These organic solvents may be used alone or in combination of two or more.

[0061] The content of the solvent in the curable resin composition of the embodiment is usually about 100 to 1000 parts by mass per 100 parts by mass of the monomer component, but is not limited to this range.

[0062] <Cured Product> As described above, the curable resin composition of the present embodiment, when cured, exhibits at least one of the properties of "tackiness," "adhesion," and "adhesion" to a substrate. The shape of the cured product is not particularly limited, and typical examples include a membrane or film shape.

[0063] The Tg of the cured product is preferably -80 to 300°C, more preferably -70 to 250°C, and particularly preferably -60 to 200°C, from the viewpoint of improving the heat resistance and brittleness of the cured product. Furthermore, when the cured product functions as a pressure-sensitive adhesive, the Tg of the cured product is preferably -80 to 0°C, more preferably -70 to -15°C, and particularly preferably -60 to -30°C, from the viewpoint of easily exhibiting good adhesive properties. Furthermore, when the cured product functions as an adhesive, the Tg of the cured product is preferably 50 to 300°C, more preferably 100 to 250°C, and particularly preferably 150 to 200°C, from the viewpoint of easily exhibiting good adhesive properties. Note that, when the curable resin composition that serves as the raw material for the cured product is available, the Tg of the cured product can be measured in the same manner as described above. Alternatively, the cured product itself may be analyzed and measured using the same analytical method as described above.

[0064] <Applications of Curable Resin Composition> The curable resin composition of the present embodiment can be used for applications such as pressure-sensitive adhesives and surface coating agents.

[0065] (Adhesive) The curable resin composition of the present embodiment can be suitably used as an adhesive. Here, the term "adhesive" refers to a material that intervenes between adherends, for example, by adhering one side to one substrate and the other side to the other substrate, thereby bonding to both the one substrate and preventing relative movement of the one substrate relative to the other substrate. "Preventing relative movement of one substrate relative to the other substrate" includes not only a case where one substrate is completely immobile relative to the other substrate, but also a case where one substrate is fixed so as to allow a certain range of movement relative to the other substrate. In other words, the adhesive according to an embodiment of the present disclosure does not need to be completely cured. The certain range may be determined depending on the location of the two substrates, the purpose of use, and the like. In other words, as described above, an "adhesive" may also be referred to as a "pressure-sensitive adhesive" or "adhesive" that has adhesive properties that are difficult to peel. Adhesives are sometimes used in places where strength is not required, such as for weight reduction and simplified work, instead of joining methods such as bolt fastening or welding. Furthermore, a soft adhesive is suitable for use in applications where vibration resistance and the like are required.

[0066] The adhesive containing the curable resin composition of this embodiment has excellent adhesive properties for substrates made of a variety of materials. Examples of substrate materials that can be bonded with the adhesive of this embodiment include inorganic materials such as glass, hydroxyapatite, titanium oxide, zinc oxide, iron oxide, indium tin oxide (ITO), and molybdenum-aluminum-molybdenum laminate structures (MAM); metal materials such as aluminum (Al), copper (Cu), iron (Fe), gold (Pt), silver (Ag), zinc (Zn), tin (Sn), titanium (Ti), and alloys thereof; and organic materials such as PVC (polyvinyl chloride), PC (polycarbonate), polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene copolymer resin (ABS), polytetrafluoroethylene (PTFE), polyimide (PI), and fiber-reinforced plastic (FRP). Furthermore, the adhesive of this embodiment has good adhesive properties for substrates made of a variety of materials, making it suitable as an adhesive for bonding substrates made of different materials. Of course, the pressure-sensitive adhesive of the present embodiment may be used to bond substrates made of the same material to each other.

[0067] Furthermore, the pressure-sensitive adhesive of the present embodiment is also intended to be used for the purpose of bonding a surface coating agent such as a paint, such as a so-called undercoat paint, intermediate paint, or primer, to a substrate.

[0068] The shape of the substrates to be fixed together by the pressure-sensitive adhesive of the present embodiment is not particularly limited. Examples of the shape of the substrates include a shape where one and the other have any one selected from a plate shape, a sheet shape, a rod shape, and the like.

[0069] (Surface Coating Agent) As described above, the curable resin composition of the present embodiment can be used as a surface coating agent. A "surface coating agent" refers to a material that bonds to a substrate, cures, and protects the surface of the substrate. An example of a surface coating agent is a paint. In addition to the above-mentioned materials, the substrate also includes an undercoat paint, an intermediate paint, a primer, and the like.

[0070] The pressure-sensitive adhesive of the present embodiment described above is thought to bond more firmly to a substrate by exhibiting at least one of adhesion, tackiness, and adhesiveness to a variety of materials. The adhesion, tackiness, and adhesiveness can generally be evaluated by the test methods described in the examples below depending on the application and purpose of the pressure-sensitive adhesive. Therefore, each of these performances is a performance that evaluates the strength of bonding of the pressure-sensitive adhesive of the present embodiment to a substrate.

[0071] Adhesion (magnitude of adhesive force) indicates the adhesive force between the substrate and the interface of the adhesive or cured surface coating agent (paint), and generally, intermolecular forces, ionic bonds, and hydrogen bonds are involved in the magnitude of the adhesive force between the substrate and the adhesive. In addition, the anchoring effect between the unevenness of the substrate and the adhesive resin also contributes to improving adhesion. Therefore, improving adhesion can, for example, prevent peeling between the paint and the substrate.

[0072] Adhesion (magnitude of adhesive force) refers to, for example, the force required to peel two substrates attached by an adhesive, and is a combined force of the adhesion between the substrate and the adhesive, and the viscoelasticity and toughness of the adhesive itself. The magnitude of the viscoelasticity and toughness of a resin adhesive generally depend on the molecular weight and three-dimensional structure of the resin, as well as on intermolecular forces, ionic bonds, and hydrogen bonds, just like adhesion. For example, if an adhesive has reduced adhesion but excellent viscoelasticity and toughness, a releasable adhesive tape can be produced. Furthermore, improving the adhesion, viscoelasticity, and toughness of an adhesive can produce, for example, an adhesive tape that can guarantee a relatively long-term bond.

[0073] Adhesion (magnitude of adhesive force) refers to, for example, the combined force of the interfacial peeling (adhesion) between the adhesive and the substrate and the force (toughness) required to cause the destruction of the adhesive resin, for example, when two substrates are bonded together with an adhesive. Generally, when measuring adhesion, the adhesive breaks or the bond between the substrate and the adhesive is severed, resulting in the bond between the two substrates collapsing. The difference between adhesion and tackiness is that tackiness is generally an indicator of ease of adhesion or peeling, while adhesion is an indicator of the strength of the bond between the two substrates. Tackifiers capable of strong bonding can be used as adhesives in fields requiring strength, such as the construction and automotive fields, where durability and heat resistance are required. Furthermore, adhesives with viscoelasticity can be used to bond substrates to interior materials in the construction and automotive fields.

[0074] The reason why the pressure-sensitive adhesive of the present embodiment bonds more firmly to a wider variety of substrates is not entirely clear, but is thought to be as follows. When one substrate is bonded to another substrate with a pressure-sensitive adhesive, the pressure-sensitive adhesive is interposed between the substrates, and typically, a cured product of the pressure-sensitive adhesive is formed between the substrates. Similarly, a surface coating agent can be said to be a cured product formed by bonding a curable resin composition to a substrate after curing. Depending on the installation location and application of the substrate, stress such as vibration or impact may be applied directly or indirectly to these cured products, which may destroy the cured product or the bond between the surface of the substrate and the surface of the cured product. In other words, the pressure-sensitive adhesive may not be able to maintain the bond between the substrates (i.e., the relative positional relationship between the substrates). The pressure-sensitive adhesive of the present embodiment has excellent pressure-sensitive adhesive properties (at least one of adhesion, tackiness, and adhesiveness), and is therefore thought to be able to maintain its bond with the substrate even when stress is applied directly or indirectly to the cured product.

[0075] The present invention will be described in more detail below using examples and comparative examples. However, the present invention is not limited to the following examples. The names of compounds shown in the following examples and comparative examples do not necessarily conform to the IUPAC nomenclature.

[0076] In the examples, the following abbreviations may be used in the tables below: <Monofunctional Monomer>

[0077] <Polyfunctional Monomer> TMP3A: Trimethylolpropane triacrylate (trade name: TMP3A, manufactured by Osaka Organic Chemical Industry Ltd.)

[0078] <(Meth)acryloyl group-containing polymer> 9200A: polycarbonate-based urethane acrylate (product name: UN-9200A, manufactured by Negami Chemical Industrial Co., Ltd.)

[0079] <Polymerization initiator> TPO: 2,4,6-trimethylbenzoyldiphenylacylphosphine oxide (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0080] <Base material> PVC: Polyvinyl chloride PC: Polycarbonate PET: Polyethylene terephthalate ABS: Acrylonitrile butadiene styrene copolymer resin FRP: Glass fiber reinforced epoxy resin Glass: Glass plate Cu: Copper Al: Aluminum ITO: Indium tin oxide (coated on glass) PPS: Polyphenylene sulfide

[0081] [Examples and Comparative Examples] According to the compositions in the above tables, TPO was added as a polymerization initiator to a mixture of monofunctional monomers and polyfunctional monomers, and the mixture was thoroughly mixed to prepare curable resin compositions corresponding to the respective Examples and Comparative Examples.

[0082] <Adhesion Test> <Preparation of Test Pieces> Next, each of the prepared curable resin compositions was applied onto a test plate formed of each material listed in the table using a bar coater No. 10 (manufactured by Daiichi Rika Co., Ltd., wet film thickness: approximately 22.90 μm). Next, using a UV exposure machine, the applied composition was exposed to an exposure dose of 2000 mJ / cm. ２ The coating was completely cured by irradiating it with UV rays to prepare test pieces, which were then left to stand at room temperature for 24 hours (film thickness: approximately 20 μm).

[0083] Test Method: The adhesion test was conducted in accordance with JIS K 5600-5-6:1999 "General Test Methods for Paints - Part 5: Mechanical Properties of Coatings - Section 6: Adhesion (Cross-Cut Method)." The coating film of the test piece was cross-cut into 2 x 2 mm grids (25 squares) using a utility knife. Next, 24 mm wide cellophane tape manufactured by Nichiban Co., Ltd. was applied to the grids, and the cellophane tape was pressed by the tester's hand for 2 minutes. The cellophane tape was then peeled off at a 45° angle to the substrate within 0.5 seconds and evaluated according to the following criteria. Each test piece was evaluated twice, and the average value was used. The evaluation criteria indicated that the smaller the numerical value, the better the adhesion to the substrate, and a rating of 3 or less indicated favorable use.

[0084] [Evaluation criteria] 0: The cut lines are completely smooth and there is no peeling at any of the grid squares. 1: Small peeling at the intersections of the cuts. Less than 5% of the cross-cut areas are affected. 2: The coating has peeled along the edges of the cuts and / or at the intersections. 5-15% of the cross-cut areas are affected. 3: The coating has peeled partially or completely to a large extent along the edges of the cuts and / or various parts of the squares have peeled partially or completely. 15-35% of the cross-cut areas are affected. 4: The coating has peeled partially or completely to a large extent along the edges of the cuts and / or several squares have peeled partially or completely. Less than 35% of the cross-cut areas are affected. 5: Large peeling that cannot be classified as level 4 above.

[0085]

[0086]

[0087]

[0088] As shown in each example and comparative example. Comparison of Example 1 with Comparative Examples 1-1 to 1-9 reveals that the curable resin compositions of the examples using α-methylene-γ-butyrolactone (MBL) alone exhibited better adhesion to more materials than the comparative examples using other monofunctional monomers, with particularly high adhesion to FRP, glass, and copper. Furthermore, comparison of Example 2-1 with Comparative Examples 2-1 to 2-5 reveals that when the content of monofunctional monomer was increased compared to Example 1, the number of materials exhibiting even better adhesion increased, including PET, ABS, Al, ITO, and PPS, in addition to FRP, glass, and copper. Furthermore, comparison of Examples 2-2 to 2-9 with Comparative Examples 2-2, 2-4, and 2-5 confirms that adding MBL to THFA, IBXA, and MMA, which are monofunctional monomers used in existing pressure-sensitive adhesives, resulted in materials with better adhesion.

Claims

1. A curable resin composition comprising an α-methylene cyclic lactone compound.

2. The curable resin composition according to claim 1, wherein the α-methylene cyclic lactone compound has a lactone structure having a 5- to 6-membered ring.

3. The curable resin composition according to claim 1, further comprising a polyfunctional monomer and a (meth)acryloyl group-containing polymer.

4. The curable resin composition according to claim 1, further comprising a polymerization initiator.

5. A pressure-sensitive adhesive comprising the curable resin composition according to any one of claims 1 to 4.

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