JP5603133B2 - Curing method - Google Patents

Description

The present invention relates to a curing method. The present invention relates to, for example, a method for curing an acrylic curable composition or a room temperature curable acrylic adhesive composition.

As a room temperature curable acrylic adhesive composition, a two-part acrylic adhesive is known. As a typical example, a second generation acrylic adhesive (SGA) is known.

SGA is classified into two types depending on the form of the two agents used. One is called one main agent, one auxiliary agent type (primer type). A curing initiator is added to the main agent mainly composed of an acrylic monomer, and this is used as one main agent, and a curing accelerator is dissolved or dispersed in a solvent or the like. Use the solution as a primer. The other is a two main agent type in which an acrylic monomer and a curing initiator are added to one of the two agents, and an acrylic monomer and a curing accelerator are added to the other.

Among these, although the two main agent type SGA is a two agent type, it does not require accurate measurement due to its high reaction propagation property, and is excellent in workability. In addition, oil surface adhesion is possible, and the balance of shear bond strength, peel bond strength, and impact bond strength is excellent. In addition, it is widely used because the cured portion is well cured.

The following patent documents 1-4 are mentioned as a technique of SGA. Patent Documents 1 and 2 are SGAs for speakers. Patent Documents 3 and 4 are SGAs for motor applications. In these patents, thiourea derivatives, β-diketone chelates, β-ketoesters, and transition metal salts are used as curing accelerators and reducing agents.

JP 2000-159835 A JP-A-11-71436 JP 2002-332320 A JP 2002-332319 A

As a curable composition, it is required to reduce the generation of formaldehyde and acetaldehyde harmful to the human body during curing. For example, suppression of aldehyde is required in speakers, motors, housings, and the like.

The present invention aims to provide a curing method.

The present invention, (a) (meth) acrylate, a curable composition containing (b) an organic peroxide and (c) a transition metal salt under inert gas atmosphere, subjected to aging, cure to A curable composition comprising (a) (meth) acrylate, (b) an organic peroxide and (c) a transition metal salt, which is bubbled with an inert gas and cured. It is a curing method, and (a) the amount of (b) organic peroxide used is 0.2 to 10 parts by mass, and (c) the amount of transition metal salt used is 100 parts by mass of (meth) acrylate. It is this hardening method which is 0.001-10 mass parts, (a) (meth) acrylate contains (a-1) alkyl (meth) acrylate and (a-2) hydroxyalkyl (meth) acrylate. And the composition ratio is mass ratio (a-1) :( a- 2) = 10 to 90: This curing method is 10 to 90, and (a-1) the alkyl (meth) acrylate is one or more members selected from the group consisting of methyl (meth) acrylate and ethyl (meth) acrylate. Yes, (a-2) hydroxyalkyl (meth) acrylate is 2-hydroxyethyl (meth) acrylate, and the curable composition is (d) acidic phosphorus with respect to 100 parts by weight of (a) (meth) acrylate. It is this hardening method formed by containing 0.05 to 10 parts by mass of an acid compound, and the transition metal salt is one or more selected from the group consisting of cobalt octylate, cobalt naphthenate, copper naphthenate and vanadyl acetylacetonate. The curing method, wherein the transition metal salt is vanadyl (IV) acetylacetonate, and the curable composition is an adhesive composition A curing method, a bonded body obtained by bonding an adherend using the curing method, a speaker formed using the curing method, and manufactured using the bonding method. A cured product of the curable composition, wherein the content of formaldehyde in the cured product of the curable composition is 30 ppm or less. In this curing method, the content of acetaldehyde in the cured product is 40 ppm or less.

The present invention provides the effect that the amount of formaldehyde and acetaldehyde generated is small.

It is sectional drawing of a speaker. It is a half sectional view showing the structure of the speaker three points.

(A) (Meth) acrylate refers to an acrylic compound selected from (meth) acrylic acid and / or (meth) acrylic acid ester.

(A) As (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isodecyl ( (Meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, phenyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4 -Hydroxybutyl (meth) acrylate, diethylene glycol mono (meth) acrylate, polypropylene glycol (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 2-hydro Ci-3-phenoxypropyl (meth) acrylate, glycidyl (meth) acrylate, caprolactone-modified tetrahydrofurfuryl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) Acrylate, N, N-diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, ethoxycarbonylmethyl (meth) acrylate, phenol ethylene oxide modified (meth) acrylate, phenol (ethylene oxide 2 mol modified) (meta ) Acrylate, phenol (ethylene oxide 4 mol modified) (meth) acrylate, paracumylphenol ethylene oxide modified (meth) acrylate, nonylphenol ethylene oxide Modified (meth) acrylate, nonylphenol (modified with 4 mol of ethylene oxide) (meth) acrylate, nonylphenol (modified with 8 mol of ethylene oxide) (meth) acrylate, nonylphenol (modified with 2.5 mol of propylene oxide) (meth) acrylate, 2- Ethylhexyl carbitol (meth) acrylate, trifluoroethyl (meth) acrylate, β- (meth) acryloyloxyethyl hydrogen succinate, ω-carboxy-polycaprolactone mono (meth) acrylate, n- (meth) acryloyloxyalkyl Hexahydrophthalimide, (meth) acrylic acid, maleic acid, fumaric acid, ω-carboxy-polycaprolactone mono (meth) acrylate, monohydroxyethyl phthalate (meth) acrylate , (Meth) acrylic acid dimer, β- (meth) acryloyloxyethyl hydrogen succinate, 2-acryloyloxyethyl succinic acid, 2-methacryloyloxyethyl succinic acid, cyclohexyl (meth) acrylate, dicyclopentanyl ( (Meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, isobornyl (meth) acrylate, methoxylated cyclodecatriene (meth) acrylate, 1,2-polybutadiene terminated urethane (meth) acrylate (For example, “TE-2000”, “TEA-1000” manufactured by Nippon Soda Co., Ltd.), the hydrogenated product (for example, “TEAI-1000” manufactured by Nippon Soda Co., Ltd.), 1,4-polybutadiene-terminated urethane (meth) acrylate ( For example “BAC-45” manufactured by Osaka Organic Chemical Co., Ltd.), polyisoprene-terminated (meth) acrylate, polyester-based urethane (meth) acrylate, polyether-based urethane (meth) acrylate, polyester (meth) acrylate, bis-A type epoxy (meth) Acrylate (for example, “Biscoat # 540” manufactured by Osaka Organic Chemical Co., Ltd., “Biscoat VR-77” manufactured by Showa Polymer Co., Ltd.), 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) Acrylate, 1,6-hexadiol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, 2-ethyl-2 -Butyl-propanediol (meth) acrylate, neo Pentyl glycol modified trimethylolpropane di (meth) acrylate, stearic acid modified pentaerythritol diacrylate, polyethylene glycol modified bisphenol A di (meth) acrylate, polypropylene glycol modified bisphenol A di (meth) acrylate, polypropylene glycol di (meth) acrylate 2,2-bis (4- (meth) acryloxydiethoxyphenyl) propane, 2,2-bis (4- (meth) acryloxypropoxyphenyl) propane, 2,2-bis (4- (meth) acrylic Roxytetraethoxyphenyl) propane, trimethylolpropane tri (meth) acrylate, tris [(meth) acryloxyethyl] isocyanurate, dimethylolpropane tetra (meth) acrylate, pen Pentaerythritol tetra (meth) acrylate, pentaerythritol ethoxy tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate and dipentaerythritol hexa (meth) acrylate. These 1 type (s) or 2 or more types can be used.

Among (meth) acrylates, it is preferable that (a-1) alkyl (meth) acrylate and (a-2) hydroxyalkyl (meth) acrylate are contained because of their great effects.

(A-1) As the alkyl (meth) acrylate, (meth) acrylate represented by the general formula (A) is preferable.

Formula (A)
Z ₁ —O—R ₁ (wherein Z ₁ represents a (meth) acryloyl group and R ₁ represents an alkyl group).
)

Examples of the (meth) acrylate represented by the general formula (A) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isooctyl (meth) ) Acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and the like. These 1 type (s) or 2 or more types can be used. Among these, methyl (meth) acrylate is preferable because of its great effect.

R ₁ represents an alkyl group. R ₁ is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, and most preferably an alkyl group having 1 to 3 carbon atoms.

(A-2) As a hydroxyalkyl (meth) acrylate, the (meth) acrylate shown by general formula (B) is preferable.

General formula (B)
Z ₂ —O— (R ₂ O) _p —H (wherein Z ₁ represents a (meth) acryloyl group, R ₂ represents an alkylene group, and p represents an integer of 1 to 10).

As the (meth) acrylate represented by the general formula (B), 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate , Diethylene glycol mono (meth) acrylate, polypropylene glycol (meth) acrylate, and the like. These 1 type (s) or 2 or more types can be used. Among these, 2-hydroxyethyl (meth) acrylate is preferable because of its great effect.

R ₂ represents an alkylene group. R ₂ is preferably —C ₂ H ₄ —, —C ₃ H ₆ —, —CH ₂ CH (CH ₃ ) —, —C ₄ H ₈ — or —C ₆ H ₁₂ —. p is preferably an integer of 1 to 10, and more preferably an integer of 1 to 4.

When (a-1) and (a-2) are used in combination, the composition ratio is preferably (a-1) :( a-2) = 10 to 90:10 to 90 by mass ratio, and 25 to 75:25. -70 are more preferable, and 40-60: 40-60 are the most preferable.

(B) As a polymerization initiator, an organic peroxide is preferable.

Examples of organic peroxides include cumene hydroperoxide, paramentane hydroperoxide, tertiary butyl hydroperoxide, diisopropylbenzene dihydroperoxide, methyl ethyl ketone peroxide, benzoyl peroxide, and tertiary butyl peroxybenzoate. . These 1 type (s) or 2 or more types can be used. Among these, cumene hydroperoxide and / or benzoyl peroxide are preferable in terms of reactivity, and cumene hydroperoxide is more preferable.

(B) As for the usage-amount of a polymerization initiator, 0.2-10 mass parts is preferable with respect to 100 mass parts of (a) (meth) acrylate, 0.5-5.0 mass parts is more preferable, 8-3.0 parts by mass is most preferred.

The (c) curing accelerator can be used, for example, as long as it reacts with the polymerization initiator (b) to generate radicals and accelerate the polymerization of the monomer. (C) The curing accelerator may be a known one.

Among the curing accelerators, one or two or more of the group consisting of a tertiary amine, a thiourea derivative and a transition metal salt are preferable because they are highly effective.

Examples of the tertiary amine include triethylamine, tripropylamine, tributylamine, N, N-dimethylparatoluidine, N, N-dimethylaniline, and the like. Examples of the thiourea derivative include 2-mercaptobenzimidazole, methylthiourea, dibutylthiourea, tetramethylthiourea, and ethylenethiourea. Examples of the transition metal salt include cobalt octylate, cobalt naphthenate, copper naphthenate, and vanadyl acetylacetonate. Among these, a transition metal salt is preferable and vanadyl acetylacetonate is more preferable because of its high effect.

(C) 0.001-10 mass parts is preferable with respect to 100 mass parts of (a) (meth) acrylate, 0.01-1.0 mass part is more preferable, and the usage-amount of a hardening accelerator is 0.1. 05-0.5 mass part is the most preferable, and 0.2-0.4 mass part is still more preferable.

The present invention is a curing method for curing a curable composition containing (a) (meth) acrylate, (b) a polymerization initiator, and (c) a curing accelerator in an inert gas atmosphere.

The present invention uses an inert gas when a curable composition is used for bonding and bonding.

An inert gas is a gas with low reactivity other than oxygen. As the inert gas, one or more of the group consisting of nitrogen, neon, argon, xenon and carbon dioxide is preferable.

Generation | occurrence | production of aldehydes can be suppressed by joining, couple | bonding in an inert gas atmosphere, and making it the state which does not touch oxygen.

Examples of the curing method for curing in an inert gas atmosphere include a curing method obtained by curing and curing a curable composition in an inert gas atmosphere. The curing time is preferably 0.25 to 10 days, preferably 0.5 to 7 days, and most preferably 1 to 5 days from the viewpoint of great effect.

Examples of a curing method for curing in an inert gas atmosphere include a curing method in which a curable composition is bubbled with an inert gas and cured. By bubbling the curable composition with an inert gas and replacing it with oxygen, aldehydes generated during bonding and bonding can be reduced.

In the curable composition of the present invention, it is preferable to use (e) a phosphoric ester compound in terms of improving adhesiveness.

(E) As a phosphoric acid ester compound, the phosphoric acid ester which has a vinyl group or a (meth) acryl group is mentioned. Examples of the phosphoric acid ester having a vinyl group or a (meth) acryl group include (2-hydroxyethyl) methacrylic acid phosphate, (meth) acryloyloxyethyl acid phosphate, dibutyl 2- (meth) acryloyloxyethyl acid phosphate, Dioctyl 2- (meth) acryloyloxyethyl phosphate, diphenyl 2- (meth) acryloyloxyethyl phosphate, (meth) acryloyloxyethyl polyethylene glycol acid phosphate and (meth) acryloyloxyethyl acid phosphate monoethanolamine half sole And so on. These 1 type (s) or 2 or more types can be used.

(E) The amount of the phosphate ester compound used is preferably 0.05 to 10 parts by mass, more preferably 0.5 to 5.0 parts by mass, with respect to 100 parts by mass of (a) (meth) acrylate. .8 to 3.0 parts by mass is most preferable.

If desired, known substances such as elastomers, silane coupling agents, polymerization inhibitors, antioxidants, paraffins, plasticizers, fillers, rust preventive pigments and colorants can also be used.

The curable composition of the present invention can be used as an adhesive composition. The adhesive composition curable composition of the present invention can be used for adhesion of motors, transformers, speakers, housings, and the like.

The structure of the present invention also refers to motors, transformers, and speakers that are electrical components.

Hereinafter, the present invention will be described in more detail based on examples. Unless otherwise specified, the unit of use amount of each substance is indicated in parts by mass.

[Examples 1-4 and Comparative Examples 1-2]
Adhesive compositions were prepared by mixing raw materials of the types shown in Table 1 with the compositions shown in Table 1. The adhesive composition was cured for a period shown in Table 1 under a predetermined atmosphere. Example 3 was bubbled with nitrogen. About the obtained curable composition, the tensile shear bond strength, the content of aldehydes after curing, and the aldehyde emission amount by the Tedlar bag method were measured. Various physical properties were measured as follows. These results are shown in Table 1. As the acidic phosphoric acid compound, (2-hydroxyethyl) methacrylic acid phosphate (JPA 514, Johoku Chemical Co., Ltd.) was used.

[Tensile shear bond strength (shear bond strength)]
In accordance with JIS K-6850, the adhesive composition was applied to one side of a test piece (100 mm × 25 mm × 1.6 mm, SPCC-D sandblasting), and the other test piece (100 mm × 25 mm × 1.6 mm, SPCC- D sandblasting), and the overlapped portion was pressed with a push-pull gauge (“model 1S” manufactured by KOMURA) under a load of 68.6 N (7 kgf) for 5 to 6 seconds and bonded. It was cured at room temperature (23 ° C.) for 24 hours, and this was used as a sample for measuring tensile shear bond strength. The tensile shear bond strength (unit: MPa) was measured under the conditions of a temperature of 23 ° C. and a humidity of 50% under a tensile speed of 10 mm / min.

[Content of aldehydes after curing]
A DNPH-hydrochloric acid aqueous solution was prepared. In a 300 cc Erlenmeyer flask, 0.3 g of 2,4-dinitrophenylhydrazine (DNPH) was weighed and dissolved in 300 mol of 2 mol / l hydrochloric acid. This solution was suction filtered with a Buchner funnel or the like. The filtrate was divided into 100 cc separatory funnels, 150 cc of hexane was added to each, and the mixture was shaken and stirred for 10 minutes. The aqueous phase solution was taken out to obtain a DNPH-hydrochloric acid aqueous solution.

A cured product made of 5 g of the adhesive composition was prepared in a rectangular polyethylene container having a size of 1 cm × 1 cm × 10 cm in a 23 ° C. atmosphere and allowed to stand at 23 ° C. for curing. When bubbling, nitrogen was blown into (meth) acrylate to perform bubbling. When bubbling, each component of (meth) acrylate was bubbled with nitrogen for 6 hours. Then, each component was mixed and the curable composition was produced. When curing in a nitrogen atmosphere, nitrogen was always supplied in a bag that did not allow oxygen to pass through.

After curing, the cured product was freeze-pulverized, 0.25 g was placed in an Erlenmeyer flask, 40 cc of THF (tetrahydrofuran) was added, and a stir bar was added, followed by dissolution and stirring. 2 cc of DNPH-hydrochloric acid aqueous solution was added and stirred for 1 hour. One hour later, 8 cc of pure water was added, filtered through a membrane filter, and measured by HPLC (high performance liquid chromatography). As the HPLC column, Waters Symmetry C18φ3.9 × 150 cc was used. Liquid A and liquid B were used as eluents. As the liquid A, acetonitrile / pure water = 45/55 (volume ratio) was used. Liquid B used THF. As a gradient, the liquid A was kept at 100% for 10 minutes, and the liquid was switched to the liquid B at 100% in the next 1 minute. The sample was injected and held at 100% B for 10 minutes. Thereafter, the liquid A was switched to 100% in 1 minute. The flow rate was 1.3 cc / min, and the injection amount was 20 μL. UV (360 nm) was used as the detection method.

[Speaker production]
The speaker shown in FIG. 1 was assembled under the conditions of 23 ° C. and 50% humidity. The speaker is formed by laminating a bottom plate 1, a ring-shaped magnet 2, and a ring-shaped top plate 3, and a frame 4 is coupled to the bonded field portion. Edge) 7 is joined, voice coil 8 is joined to the central part of cone 6, the middle part of voice coil 8 is held by damper 9, and the lower part of voice coil 8 is fitted to the central part of bottom plate 1. It is configured to The speaker is configured by attaching a dust cap 10 to the upper center surface of the cone 6.

The adhesion of the three points of the speaker comprising the cone 6, the voice coil 8 and the damper 9 is as shown in FIG. The voice coil 8 is configured by winding a paper tape 11 around the outer periphery of the voice coil 8, and further winding a coil 12 around the outer periphery of the paper tape 11 (in the figure, the parts indicated by circles indicate the bonding points of the three points of the speaker). 3 points of the speaker are bonded by the adhesive composition 13).

Cotton was used as a material for the damper 9 (outer diameter 60 mm × inner diameter 20 mm × thickness 0.25 mm). This material was impregnated with a phenol-based thermosetting resin composition and heat-molded into the shape of the damper 9 shown in FIG. The material of the frame 4 was iron whose surface was chromated. The obtained damper 9 and the voice coil 8 (made of aluminum) around which the paper tape 11 and the coil 12 shown in FIG. 2 are wound, the location where the voice coil joint is paper (the location indicated by the circle in FIG. 2). The speaker 9 (paper tape 11 and adhesive composition 13 are not shown) shown in FIG. 1 was prepared by bonding the damper 9 and the frame 5 to prepare a sample. As a bonding method, a method of applying 0.2 g of the adhesive composition to the joint and curing it at room temperature for 24 hours was used.

[Aldehyde emissions by Tedlar bag method]
A silicon tube (manufactured by Tigers Polymer: φ5 × 9 mm) was connected to a 10 L tedlar bag (AA Science 10 manufactured by GL Science Co., Ltd. (sleeve outer diameter φ7)) with a one-sleeve sleeve, and two stop valves were attached. Thereafter, the Tedlar bag was filled with pure nitrogen gas. The filled pure nitrogen gas was extracted with an aspirator. The cleaning was completed by repeating the filling and exhausting of pure nitrogen gas three times. One end of the Tedlar bag was cut with scissors. The speaker was placed in a Tedlar bag and the Tedlar bag was sealed. The Tedlar bag was filled with pure nitrogen gas. Nitrogen gas was removed with an aspirator. A fixed amount (4 L) of pure nitrogen gas was filled into the Tedlar bag using a flow meter, and the two stop valves attached to the silicon tube were closed. A Tedlar bag was placed in a hot air dryer, and the silicon tube was taken out of the tank and fixed with a clip. In this state, it was heated at 65 ° C. for 2 hours.

The aldehyde was collected using a DNPH cartridge (Water-Sep-Pak Long). The upstream side of the DNPH cartridge was connected to a silicon tube, and the downstream side of the DNPH cartridge was connected to a pump (MP-Σ100H manufactured by Shibata Kagaku) and a rotary flow meter (Shinagawa DC-1C). Two stop valves were opened, and all the gas in the Tedlar bag was sampled at a sampling rate of 0.4 to 0.5 L / min.

A constant amount (3-6 ml) of acetonitrile was taken into a syringe and connected to one end of a DNPH cartridge, and acetonitrile was injected and extracted slowly. A test tube was used as a receiver. After the solvent came out, a small amount of air was taken into the syringe and all the solvent remaining in the DNPH cartridge was distilled off. The extracted acetonitrile was analyzed using a high performance liquid chromatograph. As an analyzer, HPLC VP manufactured by Shimadzu Corporation, detector UV 360 nm, and INTERSIL ODS-80 manufactured by Column GL Science were used. As the developing solution, a solution composed of 55% acetonitrile-45% water was used. The column temperature was 40 ° C.

Table 1 shows the following. Curing in a nitrogen atmosphere reduced the content and emission of formaldehyde and acetaldehyde. Nitrogen bubbling reduced the content and emission of aldehydes.

According to the present invention, the content of formaldehyde after curing can be reduced to 30 ppm or less, more preferably 20 ppm or less. According to the present invention, the content of acetaldehyde after curing can be reduced to 40 ppm or less, more preferably 30 ppm or less.

Generation | occurrence | production of formaldehyde and acetaldehyde can be suppressed with the hardening method using the curable resin composition of this invention. According to the present invention, a structure (speaker, motor, housing, or the like) in which generation of formaldehyde or acetaldehyde is suppressed can be manufactured. According to the present invention, it is possible to provide a structure that suppresses substances harmful to the human body and a method for producing the structure.

1 Bottom plate 2 Magnet 3 Top plate 4 Frame 5 Frame peripheral edge 6 Cone 7 Cone peripheral edge (cone edge)
8 Voice coil 9 Damper 10 Dust cap 11 Paper tape 12 Coil 13 Adhesive composition

Claims (14)

A curing method comprising curing and curing a curable composition containing (a) (meth) acrylate, (b) an organic peroxide, and (c) a transition metal salt in an inert gas atmosphere. A curing method obtained by bubbling an curable composition containing (a) (meth) acrylate, (b) an organic peroxide, and (c) a transition metal salt with an inert gas and curing. (A) With respect to 100 parts by mass of (meth) acrylate, the amount of (b) organic peroxide used is 0.2 to 10 parts by mass, and (c) the amount of transition metal salt used is 0.001 to 10 parts. The curing method according to claim 1, wherein the curing method is part by mass. (A) (meth) acrylate contains (a-1) alkyl (meth) acrylate and (a-2) hydroxyalkyl (meth) acrylate, and the composition ratio is (a-1) by mass ratio. : (a-2) = 10~90 : 10~90 a process, as claimed one of claims 1 to 3 is. (A-1) The alkyl (meth) acrylate is at least one member selected from the group consisting of methyl (meth) acrylate and ethyl (meth) acrylate, and (a-2) hydroxyalkyl (meth) acrylate is 2-hydroxyethyl. It is (meth) acrylate, and a curable composition contains 0.05-10 mass parts of (d) acidic phosphoric acid compounds with respect to 100 mass parts of (a) (meth) acrylate. The curing method according to 1 of 4 . Transition metal salts, cobalt octylate, cobalt naphthenate, curing method according one of claims 1 to 5 is one or more of the group consisting of copper naphthenate and vanadyl acetylacetonate. Transition metal salts, curing method according one of claims 1 to 6 is vanadyl (IV) acetylacetonate. The curing method according to claim 1, wherein the curable composition is an adhesive composition. A joined body formed by adhering an adherend using the curing method according to claim 8 . A speaker produced by using the curing method according to claim 8 . A motor produced by using the curing method according to claim 8 . A housing formed by using the curing method according to claim 8 . Curing method according one of of the cured product of formaldehyde claims 1-8 content is 30ppm or less of the curable composition. Curing method according one of of the cured product of acetaldehydes claims 1-8 content is 40ppm or less of the curable composition.