Method for producing nitroxides and curable compositions

Abstract

To provide a highly safe method for producing nitroxides that does not use peroxides such as hydrogen peroxide, and to provide a curable composition with excellent curing temperature, curing speed, and wettability. [Solution] By simultaneously irradiating a reactive compound with atmospheric pressure low-temperature plasma and ultrasound, nitroxides are generated without using peroxides. By constructing a curable composition using the reactive compound containing these nitroxides, a curable composition with excellent curing temperature, curing speed, and wettability can be obtained.

Description

Technical Field

[0001] This invention relates to a method for producing nitroxide and a curable composition. More specifically, it relates to a method for producing nitroxide that can obtain nitroxide with excellent safety without using peroxides, and a curable composition containing nitroxide.

Background Art

[0002] Conventionally, radicals have been recognized as highly reactive and unstable intermediates. However, due to stabilization by electronic effects (delocalization of unpaired electrons possessed by radicals) and steric effects (inhibition of various reactions due to steric hindrance near the radical center or suppression of dimerization), stable radicals with kinetic and thermodynamic stability are known.

[0003] Among stable radicals, nitroxides are widely used in various industries due to their high versatility. Examples of nitroxides include 2,2,6,6-tetramethylpiperidine 1-oxyl (hereinafter referred to as "TEMPO") and 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (hereinafter referred to as "TEMPOL"). There are various methods for producing nitroxides, and in any case, they are nitroxidated by reacting via a nitroxide precursor such as an amine with a peroxide including hydrogen peroxide. For example, Patent Document 1 describes that by reacting a (meth)acrylic acid imine polymer with hydrogen peroxide in an amide solvent in the presence of a tungstic acid catalyst and phosphonic acids, the amount of hydrogen peroxide used for nitroxidation can be reduced while obtaining a (meth)acrylic acid nitroxide polymer safely and at low cost.

[0004] On the other hand, it is known that by bonding nitroxides such as TEMPO and TEMPOL to the side chains of polymers including acrylic, epoxy, urethane, etc., functions such as weather resistance, flame retardancy, and redox ability can be imparted to the polymers. For example, Patent Document 2 states that a curable composition containing an isocyanate group-containing compound having a nitroxide free radical exhibits excellent weather resistance. Patent Document 3 states that a curable composition containing a room-temperature curable resin that reacts with an active hydrogen-containing compound to crosslink and harden, and a compound having a nitroxide free radical with a number average molecular weight of 2,000 or more, exhibits excellent workability, stain resistance, weather resistance, and rubber properties. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-87256 [Patent Document 2] Japanese Patent Publication No. 2015-140383 [Patent Document 3] Japanese Patent Publication No. 2017-31399 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the invention described in Patent Document 1 has not been able to reduce the amount of hydrogen peroxide used to zero, even when using a tungstic acid catalyst. Furthermore, since the inventions described in Patent Documents 2 and 3 synthesize a curable composition using nitroxide as a starting material, the method for producing nitroxide itself is not described, nor are the curing temperature, curing rate, and wettability of the curable composition described. Therefore, there was a need for a highly safe nitroxide manufacturing method and a curable composition with excellent curing temperature, curing speed, and wettability.

[0007] This invention has been made in view of the above circumstances, and aims to provide a safe method for producing nitroxides that does not use peroxides, including hydrogen peroxide, and further aims to provide a curable composition with excellent curing temperature, curing speed, and wettability. [Means for solving the problem]

[0008] The present invention provides a method for producing nitroxide that solves the above problems, characterized by simultaneously irradiating a reactive compound with atmospheric pressure low-temperature plasma and ultrasound. Furthermore, the curable composition according to the present invention, which solves the above problems, is characterized by containing nitroxide produced by the nitroxide production method according to the present invention. The reactive compound can be selected from compounds having one or more vinyl or vinylidene groups in its molecule. The reactive compound preferably has a vapor pressure of 0.001 to 50 Pa at room temperature. The discharge gas of the atmospheric pressure low-temperature plasma is preferably nitrogen or a nitrogen-containing mixed gas. The ultrasonic frequency is preferably 28 to 120 kHz. [Effects of the Invention]

[0009] According to the present invention, by simultaneously irradiating a reactive compound with atmospheric pressure low-temperature plasma and ultrasound, a nitroxide is generated without using a peroxide. Furthermore, by constructing a curable composition with the stable radical-containing reactive compound, a curable composition with excellent curing temperature, curing speed, and wettability can be obtained. [Brief explanation of the drawing]

[0010] [Figure 1] This is an explanatory diagram of the main components showing an example of a manufacturing apparatus used in the nitroxide manufacturing method according to the present invention. [Figure 2] This is a graph of an electron spin resonance spectrum showing an example of a nitroxide produced by the nitroxide production method according to the present invention. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below. In the example below, a nitroxide is generated by simultaneously irradiating a reactive compound with atmospheric pressure low-temperature plasma and ultrasound, and a curable composition is obtained from the stable radical-containing reactive compound. The embodiments described herein represent only one aspect of the present invention, and the present invention is not limited to these configurations.

[0012] [Reactive compounds] Preferred reactive compounds are those having one or more reactive functional groups, such as vinyl groups or vinylidene groups, within their molecule. Examples include vinyl compounds and vinylidene compounds. The composition of the reactive compound may be a single compound or a mixture, but it is preferable that it be in a liquid state at room temperature. The vapor pressure of the reactive compound is preferably 100 Pa or less at room temperature, and particularly preferably in the range of 0.001 to 50 Pa. The molecular weight is preferably 100 or more, and particularly preferably in the range of 120 to 25,000.

[0013] Reactive compounds having one vinyl group or vinylidene group in their molecule include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, n-pentyl acrylate, n-pentyl methacrylate, and Isopentyl acrylate, isopentyl methacrylate, sec-pentyl acrylate, sec-pentyl methacrylate, neopentyl acrylate, neopentyl methacrylate, cyclopentyl acrylate, cyclopentyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, isohexyl acrylate, isohexyl methacrylate, sec-hexyl acrylate, sec-hexyl methacrylate, tert-hexyl acrylate, tert-hexyl methacrylate, neohexyl acrylate, neohexyl methacrylate, acrylic acid Cyclohexyl, cyclohexyl methacrylate, n-heptyl acrylate, n-heptyl methacrylate, isoheptyl acrylate, isoheptyl methacrylate, sec-heptyl acrylate, sec-heptyl methacrylate, cycloheptyl acrylate, cycloheptyl methacrylate, n-octyl acrylate, n-octyl methacrylate, isooctyl acrylate, isooctyl methacrylate, sec-octyl acrylate, sec-octyl methacrylate, cyclooctyl acrylate, cyclooctyl methacrylate, n-nonyl acrylate, methacrylate n-nonyl acrylate, isononyl acrylate, isononyl methacrylate, sec-nonyl acrylate, sec-nonyl methacrylate, n-decyl acrylate, n-decyl methacrylate, isodecyl acrylate, isodecyl methacrylate, sec-decyl acrylate, sec-decyl methacrylate, cyclodecyl acrylate, cyclodecyl methacrylate, undecyl acrylate, undecyl methacrylate, dodecyl acrylate, dodecyl methacrylate, cyclododecyl acrylate, cyclododecyl methacrylate, tridecyl acrylate, tridecyl methacrylate,Tetradecyl acrylate, tetradecyl methacrylate, pentadecyl acrylate, pentadecyl methacrylate, hexadecyl acrylate, hexadecyl methacrylate, heptadecyl acrylate, heptadecyl methacrylate, octadecyl acrylate, octadecyl methacrylate, nonadecyl acrylate, nonadecyl methacrylate, eicosyl acrylate, eicosyl methacrylate, phenyl acrylate, phenyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, methacrylate 2-Hydroxypropyl Acrylate, 3-Hydroxypropyl Acrylate, 3-Hydroxypropyl Methacrylate, 2-Hydroxybutyl Acrylate, 2-Hydroxybutyl Methacrylate, 3-Hydroxybutyl Acrylate, 3-Hydroxybutyl Methacrylate, 4-Hydroxybutyl Acrylate, 4-Hydroxybutyl Methacrylate, 6-Hydroxyhexyl Acrylate, 6-Hydroxyhexyl Methacrylate, 2-Methoxyethyl Acrylate, 2-Methoxyethyl Methacrylate, 3-Hydroxypropyl Acrylate, 3-Hydroxypropyl Methacrylate , acrylamide, methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-isopropylacrylamide, N-isopropylmethacrylamide, 2-aminoethyl acrylate, 2-aminoethyl methacrylate, 2-(dimethylamino)ethyl acrylate, 2-(dimethylamino)ethyl methacrylate, 2-(diethylamino)ethyl acrylate, 2-(diethylamino)ethyl methacrylate, tetrahydrofurfuryl acrylate, tetrahydrofuryl methacrylate, vinyltrimethoxysilane, vinyltriethoxysilane, p - Styryltrimethoxysilane, 3-acryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 2,2,2-trifluoroethyl acrylate, 2,2,2-trifluoroethyl methacrylate, 2-(perfluorobutyl)ethyl acrylate, 2-(perfluorobutyl)ethyl methacrylate, (perfluorocyclohexyl)methyl acrylate,Examples include methyl (perfluorocyclohexyl) methacrylate, glycidyl acrylate, glycidyl methacrylate, etc.

[0014] Examples of the reactive compound having two vinyl groups or vinylidene groups in the molecule include ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, tripropylene glycol diacrylate, tripropylene glycol dimethacrylate, 1,3-butylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, allyl acrylate, allyl methacrylate, etc.

[0015] Examples of the reactive compound having three vinyl groups or vinylidene groups in the molecule include propoxylated (3) trimethylolpropane triacrylate, propoxylated (3) trimethylolpropane trimethacrylate, etc.

[0016] <Nitroxide production apparatus> The nitroxide production apparatus includes a plasma irradiation device 1 for irradiating a reactive compound with plasma and a ultrasonic irradiation device 2 for irradiating the reactive compound with ultrasonic waves.

[0017] [Plasma] As the plasma, it is preferable to use atmospheric pressure plasma (plasma stably generated in normal atmospheric pressure without performing decompression), and for example, it is particularly preferable to use non-equilibrium plasma jet or atmospheric pressure low-temperature plasma by AC pulse discharge (see, for example, JP-A-2020-140794).

[0018] The plasma irradiation device is a device that irradiates a reactive compound with plasma at a pressure equal to atmospheric pressure or approximately atmospheric pressure. The example shown here includes an electrode pair composed of a first electrode 4 and a second electrode (ground electrode) 5 connected to a power supply device, and a gas flow generation device 3 that supplies a discharge gas to a space (gas flow path) provided between the electrode pair to generate a gas flow directed toward the reactive compound.

[0019] The first electrode 4 and the second electrode 5 are arranged to face each other through a slit 7 having a uniform width that serves as a gas flow path. For example, as shown in FIG. 1, if a configuration is adopted in which a dielectric layer 6 is arranged between the electrode pair, the discharge current can be reduced and the temperature of the plasma can be lowered. The first electrode 4 and the second electrode 5 can be made of a conductive material such as tungsten, molybdenum, aluminum, copper, carbon, stainless steel, etc. The dielectric layer 6 can be made of a material having a relative permittivity of about 2.0 to 10.0 that is resistant to plasma. For example, a dielectric such as silicone resin (silicone rubber), polyethylene resin, polyester resin, nylon resin, natural rubber, neoprene, glass, or ceramics can be used.

[0020] [Discharge gas] As the discharge gas used for plasma generation, nitrogen, argon, helium, etc., or a mixed gas containing any of them can be used. The nitrogen concentration in the discharge gas is preferably 80 Vol% or more, and particularly preferably 99 Vol% or more. Considering the vapor pressure of the reactive compound, the discharge gas pressure is preferably 1.0 MPa or less, and particularly preferably 0.1 to 0.3 MPa. Considering the vapor pressure of the reactive compound, the gas flow rate is preferably 50 liters / minute or less, and particularly preferably 10 liters / minute or less. The gas flow generation device 3 is adopted to have the ability to form the above conditions and environment in a sealed reaction chamber.

[0021] [Ultrasonic wave] The frequency of the ultrasonic wave is preferably in the range of 28 to 1000 kHz, and particularly preferably in the range of 28 to 120 kHz. The ultrasonic irradiation device 2 consists of an oscillating means 8 and a processing tank 9 that receives ultrasonic vibrations generated by the oscillating means 8. The oscillation means 8 comprises a vibrator 10 that vibrates in response to the application of voltage, and is a means for transmitting the vibration of the vibrator 10 to the processing tank 9. The processing tank 9 transmits the vibration to a vibrating medium (liquid) stored inside, and the vibrating medium transmits the vibration to the object to be processed immersed in the processing tank 9. Since the reactive compound to be processed is a liquid or gel-like fluid at room temperature, it is placed in a plasma-resistant, open-topped processing container 11 and positioned in the processing tank 9 facing the outlet of the slit 7, which is the gas flow path for the discharge gas.

[0022] [Operation of the nitroxide production device] The plasma irradiation device 1 of the nitroxide production apparatus generates plasma by applying a voltage of several kilovolts to tens of kilovolts between a pair of electrodes facing each other via a dielectric layer 6 and a slit 7. The gas flow generator 3 supplies discharge gas into the generated plasma and injects the plasma-like gas toward the reactive compound. This remote plasma method has the advantage that, because voltage is not directly applied to the reactive compound, it does not cause electrical damage to the reactive compound and the heat (plasma temperature) can be kept low. The plasma temperature is preferably 100°C or less, and particularly preferably 0 to 100°C, taking into account the vapor pressure of the reactive compound. The plasma irradiation distance is preferably 100 mm or less, and particularly preferably 60 mm or less.

[0023] The ultrasonic irradiation device 2 of the nitroxide production apparatus operates almost simultaneously with the plasma irradiation device 1, and generates ultrasonic waves by applying an electrical signal to the transducer 10, causing the transducer 10 to vibrate. The transducer 10 transmits ultrasonic waves to the reactive compound in the processing container 11 via the processing tank 9, the liquid (water) in the processing tank 9, and the processing container 11. In this way, irradiating a reactive compound with ultrasound provides a stirring effect on the reactive compound in the processing container 11, as well as a sonochemical effect depending on the selection of the frequency band. By adjusting the frequency within the preferred range described above, the cavitation effect on the reactive compound can be adjusted according to the desired function.

[0024] [Curable composition] The curable composition is composed of a stable radical-containing reactive compound obtained by irradiating the reactive compound with atmospheric pressure low-temperature plasma and ultrasound. The concentration of the stable radical-containing reactive compound in the curable composition is preferably 5% by mass or more, and particularly preferably 20% by mass or more. The composition of the curable composition may be a single compound or a mixture.

[0025] In addition to the components mentioned above, the curable composition of the present invention may contain monomers, oligomers, polymers, various solvents, polymerization initiators, polymerization inhibitors, curing accelerators, gelling agents, dispersants, surfactants, fillers, plasticizers, adhesion promoters, tackifiers, property modifiers, dehydrating agents, UV absorbers, antioxidants, flame retardants, colorants, friction inhibitors, and the like.

[0026] [Uses of curable compositions] The curable composition can be used in adhesives, sealants, paints, coatings, batteries, spin labels, inks, and the like, depending on the components it contains. [Examples]

[0027] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0028] Manufacturing Example 1 [Production of stable radical-containing reactive compound A] Ten g of the reactive compound 2-hydroxyethyl methacrylate (hereinafter referred to as "HEMA") was placed in a beaker. While maintaining the temperature of HEMA at 60°C, the HEMA was simultaneously irradiated for 15 minutes with atmospheric pressure low-temperature plasma (using nitrogen as the discharge gas, a discharge gas pressure of 0.28 MPa, a discharge gas flow rate of 8 liters / minute, a discharge voltage of 8.5 kV, and an irradiation distance of 55 mm) and ultrasound at a frequency of 40 kHz to obtain stable radical-containing reactive compound A. The radicals generated by simultaneous irradiation with atmospheric pressure low-temperature plasma and ultrasound were confirmed to be nitroxides based on electron spin resonance (ESR) results of stable radical-containing reactive compound A. Figure 2 shows the ESR spectrum of stable radical-containing reactive compound A.

[0029] Manufacturing Example 2 [Production of stable radical-containing reactive compound B] Ten g of the reactive compound 4-hydroxybutyl acrylate (hereinafter referred to as "4-HBA") was placed in a beaker. While maintaining the temperature of the 4-HBA at 60°C, the 4-HBA was simultaneously irradiated for 15 minutes with atmospheric pressure low-temperature plasma (using nitrogen as the discharge gas, a discharge gas pressure of 0.28 MPa, a discharge gas flow rate of 8 liters / minute, a discharge voltage of 8.5 kV, and an irradiation distance of 55 mm) and ultrasound at a frequency of 40 kHz to obtain stable radical-containing reactive compound B. The radicals generated by simultaneous irradiation with atmospheric pressure low-temperature plasma and ultrasound were confirmed to be nitroxides based on ESR results of stable radical-containing reactive compound B.

[0030] Manufacturing Example 3 [Production of stable radical-containing reactive compound C] Ten g of the reactive compound 2-hydroxypropyl methacrylate (hereinafter referred to as "HPMA") was placed in a beaker. While maintaining the temperature of the HPMA at 60°C, the HPMA was simultaneously irradiated for 15 minutes with atmospheric pressure low-temperature plasma (using nitrogen as the discharge gas, a discharge gas pressure of 0.28 MPa, a discharge gas flow rate of 8 liters / minute, a discharge voltage of 8.5 kV, and an irradiation distance of 55 mm) and ultrasound at a frequency of 40 kHz to obtain a stable radical-containing reactive compound C. The radicals generated by simultaneous irradiation with atmospheric pressure low-temperature plasma and ultrasound were confirmed to be nitroxides based on ESR results of a stable radical-containing reactive compound C.

[0031] Manufacturing Example 4 [Production of stable radical-containing reactive compound D] Ten g of the reactive compound tripylene glycol diacrylate (hereinafter referred to as "TPGDA") was placed in a beaker. While maintaining the temperature of the TPGDA at 60°C, the TPGDA was simultaneously irradiated for 15 minutes with atmospheric pressure low-temperature plasma (using nitrogen as the discharge gas, a discharge gas pressure of 0.28 MPa, a discharge gas flow rate of 8 liters / minute, a discharge voltage of 8.5 kV, and an irradiation distance of 55 mm) and ultrasound at a frequency of 40 kHz to obtain a stable radical-containing reactive compound D. The radicals generated by simultaneous irradiation with atmospheric pressure low-temperature plasma and ultrasound were confirmed to be nitroxides based on ESR results of stable radical-containing reactive compound D.

[0032] Manufacturing Example 5 [Production of stable radical-containing reactive compound E] 10 g of the reactive compound trimethylolpropane triacrylate (3) (hereinafter referred to as "PTMPTA") was placed in a beaker. While maintaining the temperature of the PTMPTA at 60°C, the PTMPTA was simultaneously irradiated for 15 minutes with atmospheric pressure low-temperature plasma (using nitrogen as the discharge gas, a discharge gas pressure of 0.28 MPa, a discharge gas flow rate of 8 liters / minute, a discharge voltage of 8.5 kV, and an irradiation distance of 55 mm) and ultrasound at a frequency of 40 kHz to obtain a stable radical-containing reactive compound E. The radicals generated by simultaneous irradiation with atmospheric pressure low-temperature plasma and ultrasound were confirmed to be nitroxides based on ESR results of a stable radical-containing reactive compound E.

[0033] Examples 1-7 [Manufacturing of curable compositions] The stable radical-containing reactive compounds obtained in the above manufacturing example were mixed according to the formulations shown in Table 1 to obtain curable compositions. The curing temperature of the obtained curable compositions was evaluated by the method described below. The results are shown in Table 1.

[0034] [Evaluation of curing temperature] One g of the prepared curable composition was placed in a high-pressure reaction vessel made of polytetrafluoroethylene under a nitrogen atmosphere, and a thermal polymerization reaction was carried out in an electric furnace at 25-200°C for 100 minutes. The degree of curing of the resulting thermal polymerization product was checked according to the evaluation criteria below, and the curing temperature was evaluated. The results are shown in Table 1. (Evaluation Criteria) ◎: It hardened uniformly and changed into a solid. ○: Part of it gelled. ×: No change from liquid state.

[0035] [Table 1]

[0036] Comparative Examples 1-7 [Manufacturing of comparative compositions] The comparative compositions were prepared by mixing reactive compounds that had not been irradiated with atmospheric pressure low-temperature plasma or ultrasound, according to the formulations shown in Table 2.

[0037] [Evaluation of curing temperature] The curing temperature was evaluated using the same method as in Examples 1-7. The results are shown in Table 2.

[0038] [Table 2]

[0039] Tables 1 and 2 show that the curable compositions of the examples had lower curing temperatures and superior curability in the thermal polymerization reaction compared to the comparative examples.

[0040] Examples 8-9 [Manufacturing of curable compositions] The stable radical-containing reactive compounds obtained in the above manufacturing example were mixed with the photopolymerization initiator 1-hydroxycyclohexylphenyl ketone (hereinafter referred to as "HCPK") in the formulations shown in Table 3 to obtain curable compositions. The curing rate of the obtained curable compositions was evaluated by the following method. The results are shown in Table 3.

[0041] [Evaluation of curing speed] 1.5 g of the prepared curable composition was placed in a glass bottle and irradiated with 365 nm light from a UV lamp for 50 to 350 seconds under a nitrogen atmosphere to carry out a photopolymerization reaction. The results are shown in Table 3. The degree of curing of the obtained photopolymerized product was checked and the curing rate was evaluated according to the evaluation criteria below. The results are shown in Table 3. (Evaluation Criteria) ○: Part of it gelled. ×: No change from liquid state.

[0042] [Table 3]

[0043] Comparative Examples 8-10 [Manufacturing of comparative compositions] The comparative compositions were prepared by mixing reactive compounds that had not been irradiated with atmospheric pressure low-temperature plasma or ultrasound, according to the formulations shown in Table 4.

[0044] [Evaluation of curing speed] The curing speed was evaluated using the same method as in Examples 8-10. The results are shown in Table 4.

[0045] [Table 4]

[0046] Tables 3 and 4 show that the curable compositions of the examples exhibited superior curing rates in the photopolymerization reaction compared to the comparative examples.

[0047] Examples 11-13 [Manufacturing of curable compositions] The stable radical-containing reactive compounds obtained in the above manufacturing example were prepared according to the formulations shown in Table 5, and their wettability was evaluated by the following method. The results are shown in Table 5.

[0048] [Evaluation of wettability] The prepared curable composition was dropped onto a polytetrafluoroethylene substrate using a contact angle meter, and the contact angle at room temperature was measured. The results are shown in Table 5.

[0049] [Table 5]

[0050] Comparative Examples 11-13 [Manufacturing of comparative compositions] Comparative compositions were prepared using reactive compounds that had not been irradiated with atmospheric pressure low-temperature plasma or ultrasound, according to the formulations shown in Table 6.

[0051] [Evaluation of wettability] The wettability was evaluated using the same method as in Examples 11-13. The results are shown in Table 6.

[0052] [Table 6]

[0053] Tables 5 and 6 show that the curable compositions of the examples had a smaller contact angle and superior wettability compared to the comparative examples. [Explanation of Symbols]

[0054] 1. Plasma irradiation device, 2. Ultrasonic irradiation device, 3. Gas flow generator, 4 First electrode, 5 Second electrode, 6 Dielectric layer, 7 Slit, 8 Oscillation means, 9 Processing tank, 10 Vibrator, 11 Processing container

Claims

1. A method for producing nitroxides by simultaneously irradiating a reactive compound with atmospheric pressure low-temperature plasma and ultrasound.

2. The method for producing a nitroxide according to claim 1, characterized in that the reactive compound is a compound having one or more vinyl groups or vinylidene groups in its molecule.

3. The method for producing a nitroxide according to claim 1, characterized in that the reactive compound has a vapor pressure of 0.001 to 50 Pa at room temperature.

4. The method for producing nitroxide according to claim 1, characterized in that the discharge gas of the atmospheric pressure low-temperature plasma is nitrogen or a nitrogen-containing mixed gas.

5. The method for producing nitroxide according to claim 1, characterized in that the frequency of the ultrasonic waves is 28 to 120 kHz.

6. A curable composition containing a nitroxide produced by the nitroxide production method described in claim 1, claim 2, claim 3, claim 4, or claim 5.

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