Copolymer and adhesive resin composition

Abstract

To provide a copolymer having excellent adhesion even to an aluminum substrate, and excellent transparency and hardness. [Solution] The copolymer of the present invention contains 50 to 99 mol % of structural units derived from monomer (A) represented by the following general formula (1) and 1 to 50 mol % of structural units derived from monomer (B) copolymerizable with said monomer (A), and has a weight average molecular weight of 5,000 to 1,000,000. [Formula 1] TIFF2026043924000008.tif34119 (In general formula (1), R1 represents an alkyl group having 1 to 4 carbon atoms, and R2 represents a hydrogen atom or a carboxy group.)

Description

[Technical Field]

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

[0002] Copolymers containing cyclic monomers such as acid anhydride skeletons or maleimide skeletons as structural units are excellent in reactivity, dispersibility, and adhesion, and also have sufficient hardness and heat resistance. Therefore, they are used in applications such as coating and resin molding process improvers and dispersants, one example of which is adhesive resin compositions.

[0003] As an example of adhesive resin compositions made of copolymers containing structural units such as an acid anhydride skeleton or a maleimide skeleton, Patent Document 1 discloses an adhesive resin composition made of a maleic anhydride-modified polyolefin. Patent Document 2 also discloses an adhesive resin composition containing a polyimide resin, a maleimide compound, and a radical polymerization initiator. It is described that the adhesive composition becomes a cured product in which the polyimide resin and the maleimide resin are copolymerized by heating.

[0004] In addition, as an adhesive resin composition used for bonding a metal body and a resin film, for example, Patent Document 3 discloses an adhesive resin composition containing polyurethane and polyol as main components. Furthermore, as an adhesive resin composition with excellent transparency, for example, Patent Document 4 discloses an adhesive composition containing an epoxy group and a polymerizable unsaturated group-containing monomer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-008694 [Patent Document 2] Japanese Patent Application Publication No. 2023-147329 [Patent Document 3] Japanese Patent Application Laid-Open No. 2018-76436 [Patent Document 4] International Publication No. 2015 / 163216 Summary of the Invention [Problem to be solved by the invention]

[0006] Adhesive resin compositions containing a structure derived from a cyclic monomer, as shown in Patent Documents 1 and 2, both have excellent adhesion to substrates made of copper or plastic, and also have hardness sufficient to withstand denaturation after adhesion. However, the adhesive resin compositions described above have insufficient adhesion to aluminum substrates, making them difficult to use in environments involving aluminum substrates, such as the manufacture of RFID tags. Furthermore, because discoloration can occur over time, it has been necessary to avoid their use in applications requiring transparency, such as the RFID and resist fields.

[0007] On the other hand, the adhesive resin composition of Patent Document 3 is said to have excellent adhesion to aluminum substrates. Also, the adhesive resin composition of Patent Document 4 is said to have little coloration and excellent transparency. However, neither of these compositions achieves both adhesion to aluminum substrates and transparency, and in addition, they have problems such as insufficient hardness, leaving room for improvement.

[0008] Accordingly, an object of the present invention is to provide a copolymer that has excellent adhesion even to aluminum substrates and is excellent in transparency and hardness, and an adhesive resin composition containing the copolymer. [Means for solving the problem]

[0009] As a result of investigations aimed at solving the above problems, it was found that the above problems can be solved by using a copolymer containing a specific amount of a monomer with a specific structure. That is, the present invention relates to the following copolymer and an adhesive resin composition containing the copolymer:

[0010] [1] A copolymer comprising 50 to 99 mol % of a structural unit derived from a monomer (A) represented by the following general formula (1) and 1 to 50 mol % of a structural unit derived from a monomer (B) copolymerizable with the monomer (A), and having a weight average molecular weight of 5,000 to 1,000,000: [ka] (In formula (1), R1 represents an alkyl group having 1 to 4 carbon atoms, and R2 represents a hydrogen atom or a carboxy group.) [2] The copolymer according to [1], wherein the monomer (B) includes a (meth)acrylate monomer. [3] An adhesive resin composition comprising the copolymer described in [1] above. [4] The adhesive resin composition according to [3], further comprising a thermosetting resin. [5] The adhesive resin composition according to [4], which contains 1 to 100 parts by mass of the thermosetting resin and further contains 1 to 100 parts by mass of a solvent relative to 100 parts by mass of the copolymer. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a copolymer that has excellent adhesion even to aluminum substrates and is excellent in transparency and hardness, and an adhesive resin composition containing the copolymer. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described.

[0013] [Copolymer] The copolymer of the present invention contains a structural unit derived from a monomer (A) represented by the following general formula (1) and a structural unit derived from a monomer (B) copolymerizable with the monomer (A). The copolymer of the present invention has a content of structural units derived from monomer (A) represented by the following general formula (1) of 50 to 99 mol %, a content of structural units derived from monomer (B) copolymerizable with monomer (A) of 1 to 50 mol %, and a weight average molecular weight of 5,000 to 1,000,000. The copolymer of the present invention makes it possible to obtain an adhesive resin composition which has excellent adhesion to aluminum substrates, is less colored, and has sufficient hardness.

[0014] <Monomer (A)> The monomer (A) is a monomer represented by the following general formula (1). [ka]

[0015] In the general formula (1), R1 represents an alkyl group having 1 to 4 carbon atoms, and R2 represents a hydrogen atom or a carboxy group.

[0016] Examples of the monomer represented by formula (1) include dihydro-3-methyl-5-methylene-2H-pyran-2,6(3H)-dione and dihydro-3-methyl-3-carboxy-5-methylene-2H-pyran-2,6(3H)-dione.

[0017] The content of the structural units derived from monomer (A) in the copolymer of the present invention is 50 to 99 mol%, preferably 50 to 95 mol%, more preferably 60 to 95 mol%, and even more preferably 75 to 90 mol%. By making the content of the structural units derived from monomer (A) 50 mol% or more, it is possible to obtain an adhesive resin composition that has good adhesive properties, as well as excellent hardness durability and transparency. By making the content of the structural units derived from monomer (A) 99 mol% or less, it is possible to make the content of the structural units derived from monomer (B) a predetermined amount or more, thereby improving the properties derived from monomer (B) (particularly adhesive properties).

[0018] In this specification, the monomers (A) and (B) are present in the copolymer as structural units constituting the copolymer obtained by polymerizing the respective monomers as raw materials. In this specification, the content of the structural units derived from the monomers in the copolymer means the content of the structural units derived from each monomer relative to the total amount of the structural units constituting the copolymer. The content of the structural units derived from the monomers (A) and (B) can be measured by NMR.

[0019] <Monomer (B)> Monomer (B) is not particularly limited as long as it is a monomer copolymerizable with monomer (A). Examples of such monomers include monomers having an ethylenically unsaturated double bond, such as monofunctional monomers such as alkyl vinyl ether monomers and (meth)acrylate monomers. In this specification, "(meth)acrylate" refers to acrylate or methacrylate.

[0020] Examples of alkyl vinyl ether monomers include n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, n-hexyl vinyl ether, and 2-ethylhexyl vinyl ether.

[0021] Examples of the (meth)acrylate monomer include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, benzyl (meth)acrylate, and phenylethyl (meth)acrylate.

[0022] Among these, monomer (B) is preferably a (meth)acrylate-based monomer, more preferably a (meth)alkyl acrylate having 1 to 12 carbon atoms, and even more preferably a (meth)alkyl acrylate having 1 to 4 carbon atoms. Of these, from the viewpoint of improving adhesion to the substrate, alkyl (meth)acrylates having 4 to 12 carbon atoms are preferred, and specifically, butyl (meth)acrylate is more preferred. Furthermore, from the viewpoint of improving hardness, alkyl (meth)acrylates having 1 to 3 carbon atoms are preferred, and specifically, methyl (meth)acrylate is preferred. Furthermore, if the number of carbon atoms is approximately the same, acrylates are preferred from the viewpoint of adhesion, and methacrylates are preferred from the viewpoint of hardness.

[0023] The monomer (B) may be used alone or in combination of two or more. For example, a methacrylate-based monomer and an acrylate-based monomer may be used in combination. Furthermore, from the viewpoint of improving adhesion and hardness in a well-balanced manner, it is preferable to use an alkyl (meth)acrylate having 4 to 12 carbon atoms in combination with an alkyl (meth)acrylate having 1 to 3 carbon atoms, and it is more preferable to use butyl (meth)acrylate in combination with methyl (meth)acrylate. In this case, the molar ratio of butyl (meth)acrylate to methyl (meth)acrylate is preferably 3 / 1 to 1 / 1.

[0024] The content of the structural units derived from monomer (B) in the copolymer of the present invention is 1 to 50 mol%, preferably 5 to 50 mol%, more preferably 5 to 40 mol%, and even more preferably 10 to 25 mol%. By making the content of the structural units derived from monomer (B) 1 mol% or more, it is possible to further improve adhesion and hardness (particularly adhesion). By making the content of the structural units derived from monomer (B) 50 mol% or less, the content ratio of the structural units derived from monomer (A) becomes a predetermined value or more, and therefore it is possible to obtain an adhesive resin composition that has higher transparency and hardness while maintaining excellent adhesion.

[0025] <Weight average molecular weight Mw of copolymer> The weight-average molecular weight Mw of the copolymer of the present invention is 5,000 to 1,000,000, preferably 5,000 to 500,000, and more preferably 7,000 to 100,000. When the weight-average molecular weight Mw of the copolymer is 5,000 or more, the copolymer can be endowed with sufficient adhesiveness. When the weight-average molecular weight Mw of the copolymer is 1,000,000 or less, the coatability and the like can be improved. The weight-average molecular weight Mw of the copolymer can be measured in terms of polystyrene by gel permeation chromatography (GPC). Specific measurement conditions are the same as those in the examples described below.

[0026] [Method of producing copolymer] The copolymer of the present invention can be obtained by polymerizing the above-mentioned monomer components containing the above-mentioned monomer (A) and monomer (B). In this case, the method for obtaining the copolymer is not particularly limited, but a solution polymerization method is preferred from the viewpoint of easy temperature control during the polymerization reaction.

[0027] In the solution polymerization method, the raw materials, the monomers (A) and (B), are polymerized in a solvent such as a solvent in the presence of a polymerization initiator.

[0028] <solvent> The solvent used in solution polymerization is not particularly limited as long as it does not inhibit polymerization or alter the raw materials, monomer (A) and monomer (B). Specific examples of solvents include ester solvents such as ethyl acetate and butyl acetate, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, amide solvents such as N,N-dimethylformamide, sulfoxide solvents such as dimethyl sulfoxide, aromatic hydrocarbon solvents such as benzene, toluene, and xylene, and ether solvents such as tetrahydrofuran, diethylene glycol monomethyl ether, diethylene glycol ethyl methyl ether, and propylene glycol monomethyl ether. These solvents may be used alone or in combination of two or more.

[0029] <Polymerization initiator> Polymerization initiators that can be used in the polymerization reaction include ordinary radical polymerization initiators. Specific examples include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-methylpropionate)dimethyl, and 2,2'-azobis(2,4-dimethylvaleronitrile), and organic peroxides such as di-t-butyl peroxide, benzoyl peroxide, t-butyl peroxypivalate, t-butyl peroxybenzoate, and methyl ethyl ketone peroxide. These may be used alone or in combination of two or more.

[0030] The amount of the initiator used in the polymerization reaction is preferably 0.001 to 15 mol %, more preferably 0.01 to 10 mol %, based on the total amount of monomers.

[0031] <Application> The copolymer of the present invention has excellent transparency and hardness while also having excellent adhesive properties. Therefore, the copolymer of the present invention can be used as an adhesive resin composition. In particular, the copolymer of the present invention exhibits good adhesive properties even to metal substrates, especially aluminum substrates, and is therefore suitable for bonding metal substrates such as aluminum substrates to each other or between a metal substrate and a resin substrate.

[0032] [Adhesive resin composition] The adhesive resin composition of the present invention contains the above-mentioned copolymer.

[0033] The content of the copolymer in the adhesive resin composition is not particularly limited, but from the viewpoint of obtaining sufficient adhesion and transparency, it is, for example, 50 to 100 mass %, preferably 75 to 100 mass %, relative to the total mass of the adhesive resin composition.

[0034] The adhesive resin composition of the present invention preferably further contains a thermosetting resin, which makes it possible to provide an adhesive resin composition that not only has excellent adhesiveness and transparency but also has thermosetting properties.

[0035] <Thermosetting resin> The thermosetting resin is used to impart thermosetting properties. There are no particular limitations on the thermosetting resin, and any known thermosetting resin that hardens when heated to exhibit adhesive properties can be used.

[0036] Examples of thermosetting resins include epoxy resins, acrylic resins, silicone resins, phenolic resins, thermosetting polyimide resins, polyurethane resins, and melamine resins. Among these, epoxy resins are preferred. The thermosetting resins may be used alone or in combination of two or more.

[0037] Examples of epoxy resins that can be used include bifunctional epoxy resins such as bisphenol-type epoxy resins (e.g., bisphenol A-type epoxy resins), novolac-type epoxy resins such as phenol novolac-type epoxy resins and cresol novolac-type epoxy resins, etc. Other known epoxy resins that can be used include polyfunctional epoxy resins, glycidylamine-type epoxy resins, heterocycle-containing epoxy resins, and alicyclic epoxy resins.

[0038] The content of the thermosetting resin in the adhesive resin composition of the present invention is not particularly limited, but is preferably 1 to 100 parts by mass, more preferably 10 to 50 parts by mass, and even more preferably 15 to 30 parts by mass, relative to 100 parts by mass of the copolymer. By making the content of the thermosetting resin 1 part by mass or more, the thermosetting property of the adhesive resin composition is further improved, and the hardness of the cured product is further increased, which is preferable.

[0039] <Solvent> The adhesive resin composition of the present invention preferably further contains a solvent. Examples of the solvent include, but are not limited to, organic solvents such as esters such as ethyl acetate and n-butyl acetate; alcohols such as methanol, ethanol, propanol, and isopropanol; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. The above solvents may be used alone or in combination of two or more.

[0040] The content of the solvent in the adhesive resin composition of the present invention is not particularly limited, but is preferably 1 to 100 parts by mass, more preferably 20 to 50 parts by mass, relative to 100 parts by mass of the copolymer. By setting the content of the solvent to 1 part by mass or more, the viscosity of the adhesive resin composition can be more appropriately adjusted, and the coatability and the like can be further improved.

[0041] <Other ingredients> In addition to the copolymer and the thermosetting resin, the adhesive resin composition of the present invention may contain, as necessary, known additives such as curing accelerators, antioxidants, fillers, colorants, UV absorbers, antioxidants, crosslinking agents, plasticizers, surfactants, and antistatic agents, provided that the properties of the present invention are not impaired. The additives may be used alone or in combination of two or more. In particular, from the viewpoint of further enhancing thermosetting properties, it is preferred that the adhesive resin composition of the present invention further contains a curing accelerator.

[0042] Examples of the curing accelerator include phosphine compounds such as triphenylphosphine and tributylphosphine, imidazole compounds such as 2-phenyl-4-methyl-5-hydroxymethylimidazole, and tertiary amine compounds such as U-CAT (registered trademark) SA series (DBU salts, manufactured by San-Apro Co., Ltd.) The content of the curing accelerator is preferably 1 to 25 parts by mass, and more preferably 1 to 10 parts by mass, per 100 parts by mass of the thermosetting resin. [Example]

[0043] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0044] [Copolymer materials] The monomers used to prepare the copolymer are listed below.

[0045] <Monomer (A)> [Table 1] DMMPD: Dihydro-3-methyl-5-methylene-2H-pyran-2,6(3H)-dione (a compound of general formula (1) in which R1 is an alkyl group having one carbon atom and R2 is a hydrogen atom) DPCMPD: Dihydro-3-propyl-3-carboxy-5-methylene-2H-pyran-2,6(3H)-dione (a compound in which R1 is an alkyl group having 3 carbon atoms and R2 is a carboxy group in general formula (1))

[0046] The synthesis method is shown below. Synthesis of DMMPD: A 200 mL recovery flask was charged with 21 g of a 20 wt% sodium ethoxide solution and 40 mL of ethanol and immersed in an ice bath. 10.9 g of dimethyl methylmalonate was added dropwise with a dropper and stirred. A 500 mL round-bottom flask equipped with a thermometer, stirrer, and reflux condenser was charged with ethanol and ethyl 2-(bromomethyl)acrylate, followed by dropwise addition of 71 g of the ethanol solution containing dimethyl methylmalonate over 30 minutes and stirring at room temperature for 4 hours. After stirring, 300 mL of ion-exchanged water and 200 mL of ethyl acetate were added to recover the organic layer, which was then washed twice with 100 mL of saturated brine. The mixture was dehydrated using sodium sulfate, the solvent was concentrated under reduced pressure, and product (A) was recovered. 1.0 g of the resulting product (A) was added to a 500 mL round-bottom flask equipped with a thermometer, stirrer, and reflux condenser. A solution of 10 mL of tert-butyl alcohol, 10 mL of water, and 0.62 g of concentrated sulfuric acid was added, and the mixture was stirred at 75°C for 4 hours. After removing the tert-butyl alcohol and the by-product ethanol by concentration under reduced pressure, the mixture was reacted at 95°C for 1 hour, and then again by concentration under reduced pressure to remove water. The mixture was reacted at an external temperature of 160°C for 7 hours to obtain product (B). 0.5 g of the obtained product (B) and 3.54 g of acetic anhydride were added to a 50 mL recovery flask and stirred in a water bath at 60 °C. Then, 2 drops of concentrated sulfuric acid were added and the mixture was reacted for 2 hours, and the mixture was dried in vacuum at room temperature to obtain DMMPD.

[0047] Synthesis of DPCMPD: A 200 mL recovery flask was charged with 21 g of a 20 wt% sodium ethoxide solution and 40 mL of ethanol and immersed in an ice bath. 12.7 g of dimethyl propylmalonate was added dropwise with a dropper and stirred. A 500 mL round-bottom flask equipped with a thermometer, stirrer, and reflux condenser was charged with ethanol and ethyl 2-(bromomethyl)acrylate, followed by the dropwise addition of 71 g of the ethanol solution containing dimethyl propylmalonate over 30 minutes and stirring at room temperature for 4 hours. After stirring, 300 mL of ion-exchanged water and 200 mL of ethyl acetate were added to recover the organic layer, which was then washed twice with 100 mL of saturated brine. The mixture was dehydrated using sodium sulfate, the solvent was concentrated under reduced pressure, and product (C) was recovered. 1.1 g of the resulting product (C) was added to a 500 mL round-bottom flask equipped with a thermometer, stirrer, and reflux condenser. A mixture of 10 mL of tert-butyl alcohol, 10 mL of water, and 0.62 g of concentrated sulfuric acid was added, and the mixture was stirred at 75°C for 4 hours. After removing the tert-butyl alcohol and the by-product ethanol by concentration under reduced pressure, the mixture was reacted at 95°C for 1 hour, and the water was removed by concentration under reduced pressure again to obtain product (D). 0.9 g of the obtained product (D) and 3.54 g of acetic anhydride were added to a 50 mL recovery flask and stirred in a water bath at 60 °C. Then, 2 drops of concentrated sulfuric acid were added and the mixture was reacted for 2 hours, and the mixture was dried in vacuum at room temperature to obtain DPCMPD.

[0048] <Monomer (B)> Methyl methacrylate (MMA, Acryester M manufactured by Mitsubishi Chemical Corporation) Butyl acrylate (BA, manufactured by Mitsubishi Chemical Corporation)

[0049] <Monomer A'> (Other monomers) Maleic anhydride (Kishida Chemical Co., Ltd.) N-phenylmaleimide (Imilex-P, manufactured by Nippon Shokubai Co., Ltd.)

[0050] <Polymerization initiator> Azobisisobutyronitrile (Kishida Chemical Co., Ltd.)

[0051] [Materials for adhesive resin composition] <Thermosetting resin> Bisphenol A epoxy resin (jER 828 manufactured by Mitsubishi Chemical Corporation)

[0052] <Curing accelerator> U-CAT SA102 (manufactured by San-Apro Co., Ltd.)

[0053] 1. Copolymer Preparation and Evaluation [Preparation of copolymer] (Example 1-1) A 1 L separable flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 100 g of DMMPD, 72 g of methyl methacrylate, 258 g of dimethylformamide, and 8 g of azobisisobutyronitrile. After nitrogen flow, the mixture was stirred and mixed for 7 hours while maintaining the reaction temperature at 80°C. Subsequently, the obtained polymer solution was poured into a mixed solvent of 1320 g of methanol and 1320 g of ion-exchanged water to cause reprecipitation, and the reprecipitation was purified by decantation to obtain a copolymer P1.

[0054] (Example 1-2) A copolymer P2 was obtained in the same manner as in Example 1-1, except that the ingredients were changed to 100 g of DMMPD, 72 g of methyl methacrylate, 258 g of dimethylformamide, and 4 g of azobisisobutyronitrile.

[0055] (Examples 1-3) A copolymer P3 was obtained in the same manner as in Example 1-1, except that the ingredients were changed to 159 g of DMMPD, 13 g of methyl methacrylate, 258 g of dimethylformamide, and 3 g of azobisisobutyronitrile.

[0056] (Examples 1-4) A copolymer P4 was obtained in the same manner as in Example 1-1, except that the ingredients were changed to 156 g of DMMPD, 16 g of butyl acrylate, 258 g of dimethylformamide, and 3 g of azobisisobutyronitrile.

[0057] (Examples 1-5) Copolymer P5 was obtained in the same manner as in Example 1-1, except that the ingredients were changed to 134 g of DMMPD, 13 g of methyl methacrylate, 25 g of butyl acrylate, 258 g of dimethylformamide, and 3 g of azobisisobutyronitrile.

[0058] (Examples 1 to 6) Copolymer P6 was obtained in the same manner as in Example 1-1, except that the ingredients were changed to 141 g of DMMPD, 6 g of methyl methacrylate, 25 g of butyl acrylate, 258 g of dimethylformamide, and 3 g of azobisisobutyronitrile.

[0059] (Examples 1-7) Copolymer P7 was obtained in the same manner as in Example 1-1, except that the ingredients were changed to 147 g of DPCMPD, 25 g of butyl acrylate, 258 g of dimethylformamide, and 2 g of azobisisobutyronitrile.

[0060] (Comparative Example 1-1) A copolymer P8 was obtained in the same manner as in Example 1, except that the ingredients were changed to 85 g of maleic anhydride, 87 g of methyl methacrylate, 258 g of dimethylformamide, and 4 g of azobisisobutyronitrile.

[0061] (Comparative Example 1-2) Copolymer P9 was obtained in the same manner as in Example 1-1, except that the ingredients were changed to 81 g of maleic anhydride, 49 g of methyl methacrylate, 42 g of butyl acrylate, 258 g of dimethylformamide, and 3 g of azobisisobutyronitrile.

[0062] (Comparative Examples 1-3) A copolymer P10 was obtained in the same manner as in Example 1-1, except that the ingredients were changed to 109 g of N-phenylmaleimide, 63 g of methyl methacrylate, 258 g of dimethylformamide, and 3 g of azobisisobutyronitrile.

[0063] [Evaluation of copolymers] The copolymers obtained in Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-3 were subjected to measurement of weight-average molecular weight and evaluation of coloration. The evaluation results are shown in Table 2. In Table 2, the content of the constituent units derived from each monomer in the copolymer is expressed in mol%.

[0064] (Measurement of weight average molecular weight) The weight average molecular weight (Mw) was measured by gel permeation chromatography (GPC) under the following conditions and was obtained as a polystyrene equivalent value. GPC device name: HLC-8320GPC (Tosoh Corporation) Column used: Shodex GPCKF-805 (Resonac) Column temperature: 40℃ Detection method: Differential refractive index method Mobile phase: tetrahydrofuran Sample concentration: 1% by mass Injection volume: 100μL Calibration curve: Prepared using standard polystyrene (manufactured by VARIAN, weight average molecular weight Mw = 1,090,000, 812,000, 427,000, 225,000, 110,000, 37,900, 18,500, 10,000, 5,430, 2,550, 1,120, 589).

[0065] (Color APHA measurement) Methyl ethyl ketone was added to the produced copolymer to prepare a 20 mass % solution, and the hue was measured using a petroleum product measuring device (OME-2000) manufactured by Nippon Denshoku Industries Co., Ltd.

[0066] [Table 2]

[0067] As shown in Table 2, it can be seen that the copolymers P1 to P7 obtained in Examples 1-1 to 1-7 all have little coloration and excellent transparency, while the copolymers P8 to P10 obtained in Comparative Examples 1-1 to 1-3 all have coloration and poor transparency.

[0068] 2. Preparation and Evaluation of Adhesive Resin Compositions [Preparation of adhesive resin composition] Example 2-1 100 parts by mass of the copolymer P1 was dissolved in 25 parts by mass of methyl ethyl ketone to prepare a methyl ethyl ketone solution, to which 25 parts by mass of bisphenol A type and 1 part by mass of a curing accelerator were added and stirred to prepare a thermosetting adhesive resin composition (solution).

[0069] (Examples 2-2 to 2-7) A thermosetting adhesive resin composition (solution) was prepared in the same manner as in Example 2-1, except that the type of copolymer was changed as shown in Table 3.

[0070] (Examples 2-8) A thermosetting adhesive resin composition (solution) was prepared by mixing 10 parts by mass of bisphenol A type and 1 part by mass of a curing accelerator into a methyl ethyl ketone solution in which 100 parts by mass of copolymer P1 obtained in Example 2-1 was dissolved, and stirring the mixture.

[0071] (Examples 2-9) A thermosetting adhesive resin composition (solution) was prepared by mixing 50 parts by mass of bisphenol A type and 1 part by mass of a curing accelerator into a methyl ethyl ketone solution in which 100 parts by mass of copolymer P1 obtained in Example 2-1 was dissolved, and stirring the mixture.

[0072] (Comparative Examples 2-1 to 2-3) A thermosetting adhesive resin composition (solution) was prepared in the same manner as in Example 2-1, except that the type of copolymer was changed as shown in Table 4.

[0073] [evaluation] The thermosetting adhesive resin compositions prepared in Examples 2-1 to 2-9 and Comparative Examples 2-1 to 2-3 were evaluated for adhesion and hardness. The results are shown in Tables 3 and 4.

[0074] (Adhesion evaluation) Methyl ethyl ketone was added to the prepared thermosetting adhesive resin composition to prepare a 20% solution, which was then applied to an aluminum plate (Standard Test Piece A1070, 1 mm thick x 50 mm long x 50 mm wide) using a bar coater No. 75. The resulting solution was then dried on a hot plate at 140°C for 10 minutes to form a 7 μm thick cured film, which served as a test substrate. The resulting test substrate was subjected to a cross-cut test in accordance with JIS K 5600-5-6:1999. In the cross-cut test, grid-shaped cuts were made in the coating film of the test substrate to form a grid of 100 squares, and cellophane tape was applied to the surface and peeled off at a 60° angle. When the cellophane tape was peeled off, the number of squares where the cured film remained on the substrate was rated as ⊚ if it was 95 or more, ◯ if it was 90 or more but less than 95, △ if it was 85 or more but less than 90, and × if it was less than 85.

[0075] (Hardness evaluation) A test substrate was prepared in the same manner as in the adhesiveness evaluation, and a pencil hardness test was carried out in accordance with JIS K 5600-5-4:1999.

[0076] [Table 3]

[0077] [Table 4]

[0078] As shown in Table 3, in Examples 2-1 to 2-8, a copolymer incorporating DMMPD was used, and in Example 2-9, a copolymer incorporating DPCMPD was used, thereby obtaining adhesive resin compositions that not only had excellent adhesion to aluminum plates and sufficient hardness, but also suppressed discoloration.

[0079] On the other hand, as shown in Table 4, in Comparative Examples 2-1 and 2-2, sufficient hardness was obtained by using a copolymer into which an acid anhydride skeleton was introduced, but adhesion to the aluminum plate was poor and coloration suppression was insufficient. In Comparative Example 2-3, a copolymer having a maleimide skeleton introduced therein was used, and although sufficient hardness was obtained, adhesion to the aluminum plate was poor and suppression of coloration was insufficient. [Industrial Applicability]

[0080] The copolymer of the present invention has excellent adhesion to aluminum substrates and is also excellent in transparency and hardness, and therefore adhesive resin compositions containing the copolymer are particularly suitable for use in applications requiring transparency, such as the fields of RFID and resists.

Claims

1. The copolymer contains 50 to 99 mol % of a structural unit derived from a monomer (A) represented by the following general formula (1), and 1 to 50 mol % of a structural unit derived from a monomer (B) copolymerizable with the monomer (A), The weight average molecular weight is 5,000 to 1,000,000. Copolymer. 【Chemistry 1】 (In formula (1), R １ represents an alkyl group having 1 to 4 carbon atoms, R ２ represents a hydrogen atom or a carboxy group.)

2. The monomer (B) includes a (meth)acrylate monomer. The copolymer of claim 1.

3. The copolymer of claim 1 , Adhesive resin composition.

4. further comprising a thermosetting resin; The adhesive resin composition according to claim 3 .

5. Relative to 100 parts by mass of the copolymer, The thermosetting resin is contained in an amount of 1 to 100 parts by mass, Further containing 1 to 100 parts by weight of a solvent; The adhesive resin composition according to claim 4.

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