Method for producing dialkylphosphinic acid and / or salt thereof

Abstract

To provide a method for producing a dialkylphosphinic acid and / or a salt thereof, which can produce a dialkylphosphinic acid and / or a salt thereof in an industrially advantageous manner.SOLUTION: There is provided a method for producing a dialkylphosphinic acid and / or a salt thereof, including: a first step of preparing a phosphorus compound raw material-containing carboxylic acid solution in which hypophosphorous acid and / or hypophosphite is dissolved or suspended in a carboxylic acid; and a second step of adding an olefin and a radical initiator to the phosphorus compound raw material-containing carboxylic acid solution and allowing the reaction to proceed at a reaction temperature of more than 100°C and 200°C or less, and at a reaction pressure of 0.20 MPa or less to obtain a dialkylphosphinic acid and / or a salt thereof.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a dialkylphosphinic acid and / or a salt thereof. [Background technology]

[0002] Dialkylphosphinic acids have been known to be useful substances as metal extractants, flame retardants, surfactants, and the like.

[0003] As a method for producing a dialkylphosphinic acid and / or a salt thereof, for example, a method has been proposed in which an organic carboxylic acid such as acetic acid is used as a reaction solvent, and an olefin is reacted with hypophosphorous acid and / or a hypophosphite in the presence of a radical initiator (e.g., Patent Document 1, Patent Document 2, and Patent Document 4).

[0004] By the way, rare metals are indispensable resources for advanced industries because they are the raw materials for various functional materials such as high-performance alloys, electronic and magnetic materials, optical glass, and phosphors. For example, rare metals such as lithium, nickel, cobalt, and manganese are used as components of the positive electrode active material of the lithium-ion secondary batteries installed in electric vehicles, which have been attracting attention in recent years from the viewpoint of reducing carbon dioxide emissions. Concerns about the supply of rare metals due to the rapid spread of electric vehicles have caused the market prices of rare metals to soar, and there has been an increase in the movement to recycle used lithium-ion secondary batteries, such as the adoption of a proposed battery regulation in Europe.

[0005] Among dialkylphosphinic acids, di(2,4,4-trimethylpentyl)phosphinic acid is known to be a metal extractant with excellent separation properties for cobalt ions and nickel ions (see, for example, Patent Document 3, etc.).

[0006] As a method for producing di(2,4,4-trimethylpentyl)phosphinic acid, for example, Patent Document 1 describes a reaction carried out under pressure at 135° C. for 30 hours using sodium hypophosphite monohydrate, diisobutylene, tert-butyl peroxide as a radical initiator, and acetic acid as a solvent. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special table 2008-517947 publication [Patent Document 2] Special table 2001-525328 publication [Patent Document 3] Japanese Patent Application Publication No. 57-73142 [Patent Document 4] Special table 2017-513817 publication Summary of the Invention [Problem to be solved by the invention]

[0008] However, the method of Patent Document 1 requires a special apparatus such as an autoclave to produce di(2,4,4-trimethylpentyl)phosphinic acid, and the reaction takes one day or more, so it is not industrially advantageous.

[0009] In addition, Patent Document 2 discloses a method for producing dialkylphosphinic acid and / or a salt thereof, in which a radical initiator is added in portions to sodium hypophosphite monohydrate and an olefin in the presence of a carboxylic acid and a reaction is carried out under normal pressure. However, even when the method disclosed in Patent Document 2 in which 1-octene is reacted at normal pressure and 95° C. is used, the reactivity of the olefin significantly decreases with an increase in the number of substituents of the C=C bond and the bulkiness of the substituents. Therefore, even when the method is applied to diisobutylene, which is a mixture of 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene, the reaction does not proceed at all, and di(2,4,4-trimethylpentyl)phosphinic acid and / or a salt thereof could not be produced (see Comparative Example 1).

[0010] Furthermore, Patent Document 4 discloses a method for producing a dialkylphosphinic acid and / or a salt thereof, in which a mixed solution of sodium hypophosphite monohydrate and a radical initiator is continuously added to an olefin to react with it, and describes that the reaction efficiency can be improved and the required reaction time can be significantly shortened by adding all of the sodium hypophosphite monohydrate at once and then carrying out the reaction. However, this method still requires a relatively high pressure reaction of about 0.3 to 0.6 MPa, which is disadvantageous for industrial production.

[0011] Therefore, an object of the present invention is to provide a method for producing a dialkylphosphinic acid and / or a salt thereof, which is capable of producing a dialkylphosphinic acid and / or a salt thereof in an industrially advantageous manner. [Means for solving the problem]

[0012] In view of the above-mentioned circumstances, the present inventors have conducted extensive research and found that in a method for producing dialkylphosphinic acid and / or its salt by reacting hypophosphorous acid and / or a hypophosphite with an olefin in a carboxylic acid solvent in the presence of a radical initiator, for example, at a low pressure of 0.20 MPa or less and a temperature range of 100°C or less, the thermal energy required for radical generation or hydrogen abstraction is insufficient, and the reaction of a bulky, low-boiling olefin such as diisobutylene does not proceed at a low pressure of 0.20 MPa or less. Then, by heating a raw material phosphorus compound-containing carboxylic acid liquid to a temperature exceeding 100°C, and then adding an olefin and a radical initiator to this liquid under heating, the reaction proceeds at a low pressure of 0.20 MPa or less, and the desired dialkylphosphinic acid and / or its salt can be obtained, and the present invention has been completed.

[0013] That is, the present invention relates to a method for producing a raw material phosphorus compound-containing carboxylic acid liquid by dissolving or suspending hypophosphorous acid and / or a hypophosphite in a carboxylic acid; a second step of reacting the raw material phosphorus compound-containing carboxylic acid liquid with an olefin and a radical initiator at a reaction temperature of more than 100° C. and not more than 200° C. and a reaction pressure of not more than 0.20 MPa to obtain a dialkylphosphinic acid and / or a salt thereof; having The present invention provides a method for producing a dialkylphosphinic acid and / or a salt thereof, characterized by the above. Effect of the Invention

[0014] According to the present invention, a dialkylphosphinic acid and / or a salt thereof can be produced in an industrially advantageous manner without using a special apparatus such as an autoclave. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the present invention will be described based on preferred embodiments. The method for producing a dialkylphosphinic acid and / or a salt thereof of the present invention includes a first step of preparing a raw material phosphorus compound-containing carboxylic acid liquid by dissolving or suspending hypophosphorous acid and / or a hypophosphite in a carboxylic acid; a second step of reacting the raw material phosphorus compound-containing carboxylic acid liquid with an olefin and a radical initiator at a reaction temperature of more than 100° C. and not more than 200° C. and a reaction pressure of not more than 0.20 MPa to obtain a dialkylphosphinic acid and / or a salt thereof; having The present invention relates to a method for producing a dialkylphosphinic acid and / or a salt thereof.

[0016] The first step is a step of preparing a raw carboxylic acid solution by dissolving or suspending hypophosphorous acid and / or a hypophosphite salt, which are raw phosphorus compounds, in a carboxylic acid.

[0017] The present inventors have discovered that at a low pressure of 0.20 MPa or less and a temperature range of 100°C or less, the input of thermal energy required for radical generation or hydrogen abstraction is insufficient, and that in conventional methods, a large amount of unreacted low-boiling-point olefins present in the reaction system prevents the reaction temperature from increasing or causes the reaction temperature to decrease, and that bulky, low-boiling-point olefins such as diisobutylene do not react at a pressure of 0.20 MPa or less. Therefore, the present inventors have discovered that by heating a raw material phosphorus compound-containing carboxylic acid liquid to a temperature exceeding 100°C, and then adding an olefin and a radical initiator to this liquid while heating, the reaction can proceed even with bulky, low-boiling-point olefins such as diisobutylene at a low pressure of 0.20 MPa or less, and the desired dialkylphosphinic acid and / or a salt thereof can be obtained. Furthermore, it has been found that in the first step of the present production method, the yield of the target dialkylphosphinic acid and / or its salt can be improved by using hypophosphorous acid and / or hypophosphite having a low water content and / or a carboxylic acid having a high boiling point, and performing the second step described below. In this production method, by using hypophosphorous acid and / or hypophosphite having a water content of 10 mass% or less, preferably 8 mass% and particularly preferably 4 mass% or less, and preparing a raw material phosphorus-compound-containing carboxylic acid liquid in which they are dissolved or suspended, for the reaction, reflux of water can be prevented and the temperature in the reaction system can be more easily raised to a temperature exceeding 100°C or higher, thereby further improving the yield of the target dialkylphosphinic acid and / or its salt, for example, compared to the case where the same carboxylic acid is used as the reaction solvent.

[0018] In the present invention, the water content of hypophosphorous acid and / or a hypophosphite is a value calculated from the following calculation formula (1) using a loss on drying test method. Water content (mass%)=(A / B)×100 (1) (In the formula, A is the mass (g) lost when the sample was heated at 0.02 MPa and 80°C for 1 hour using a rotary evaporator, and B is the mass (g) of the measurement target before heating.)

[0019] In the first step, hypophosphorous acid and / or hypophosphite having a water content of more than 10 mass% based on the anhydride equivalent of hypophosphorous acid and / or hypophosphite may be used as the raw phosphorus compound. In addition, the upper limit of the water content of the hypophosphorous acid and / or hypophosphite used as the raw phosphorus compound in the first step is not particularly limited, but the water content of the hypophosphorous acid and / or hypophosphite based on the anhydride equivalent is preferably 10 mass% or less.

[0020] In the first step, it is preferable to prepare a raw phosphorus compound-containing carboxylic acid liquid using hypophosphorous acid and / or hypophosphite having a water content of 10% by mass or less, preferably 8% by mass or less, more preferably 4% by mass or less, based on the anhydride equivalent of hypophosphorous acid and / or hypophosphite, as the raw phosphorus compound. When the water content of the hypophosphorous acid and / or hypophosphite used in the first step is within the above range, water is difficult to reflux in the second step even if the reaction temperature is equal to or higher than the boiling point of water, so that the temperature of the reaction system, i.e., the reaction temperature, can be efficiently raised to a temperature required for radical generation or hydrogen abstraction, which is equal to or higher than the boiling point of water. If the water content of the hypophosphorous acid and / or hypophosphite used in the first step exceeds the above range, water reflux occurs when the reaction temperature is raised to a temperature required for radical generation or hydrogen abstraction above the boiling point of water in the second step, and as a result, the reaction temperature cannot be raised to a temperature above the boiling point of water or it takes time to raise the reaction temperature to a temperature above the boiling point of water, and the yield is also lower than when the same carboxylic acid is used as the reaction solvent. In the present invention, when either hypophosphorous acid or hypophosphite is used as the raw phosphorus compound in the first step, the water content refers to the percentage of the mass of water relative to the total mass of hypophosphorous acid or hypophosphite in anhydrous form, and when hypophosphorous acid and hypophosphite are used as the raw phosphorus compound, the water content refers to the percentage of the mass of water relative to the total mass of hypophosphorous acid and hypophosphite in anhydrous form. In the present invention, the "temperature above the boiling point of water" refers to the temperature at which water boils under the reaction pressure conditions in the second step.

[0021] In the first step, examples of a method for preparing a raw material phosphorus compound-containing carboxylic acid liquid by dissolving or suspending hypophosphorous acid and / or a hypophosphite in a carboxylic acid include the following methods. (1) A method of using hypophosphorous anhydride and / or hypophosphite anhydride and dissolving or suspending the hypophosphorous anhydride and / or hypophosphite anhydride directly in a carboxylic acid to prepare a raw material phosphorus compound-containing carboxylic acid liquid. (2) When using aqueous hypophosphorous acid and / or aqueous hypophosphite, a method in which aqueous hypophosphorous acid and / or aqueous hypophosphite in powder or solution form are heated and dehydrated by atmospheric diffusion, vacuum evacuation, and / or dry gas aeration, etc., until the water content is 10 mass% or less, preferably 8 mass% or less, more preferably 4 mass% or less, to reduce the water content, and the dehydrated hypophosphorous acid and / or hypophosphite are directly dissolved or suspended in a carboxylic acid to prepare a raw material phosphorus compound-containing carboxylic acid solution. (3) When a hydrous hypophosphite is used, the hydrous hypophosphite is dissolved in a carboxylic acid, refluxed under heating and the water is discharged from the system, and the hypophosphite (converted into anhydrous form) is dehydrated until the water content is 10% by mass or less, preferably 8% by mass or less, and more preferably 4% by mass or less, and the dehydrated hypophosphite is recovered, and the dehydrated hypophosphite is dissolved or suspended as it is in a carboxylic acid to prepare a raw material phosphorus compound-containing carboxylic acid solution. (4) When a hydrous hypophosphite is used, the hydrous hypophosphite is dissolved in a carboxylic acid, refluxed under heating, and the water is discharged from the system. The resulting hypophosphite-containing carboxylic acid liquid is dehydrated until the water content relative to the hypophosphite (converted into anhydrous form) is 10% by mass or less, preferably 8% by mass or less, and more preferably 4% by mass or less, and the resulting hypophosphite-containing carboxylic acid liquid is used as it is, or after adjusting the concentration if necessary, as a raw material phosphorus compound-containing carboxylic acid liquid.

[0022] As the raw phosphorus compound in the first step, either hypophosphorous acid or a hypophosphite, or hypophosphorous acid and a hypophosphite are used. Examples of hypophosphites include sodium hypophosphite, potassium hypophosphite, and ammonium hypophosphite, but sodium hypophosphite is preferred from the viewpoint of industrially being the cheapest and having excellent reactivity. In addition, the hypophosphite may be either hydrated or anhydrous.

[0023] In the above method (1), the anhydrous hypophosphorous acid and / or anhydrous hypophosphite used as the raw material phosphorus compound may be a commercially available product.

[0024] In the above methods (2), (3) and (4), the method of removing water by dehydrating the hydrated hypophosphorous acid and / or the hydrated hypophosphite by heating or the like does not necessarily require removing all water from the hydrated product to obtain an anhydrous product. For example, the water content of sodium hypophosphite monohydrate is approximately 17.0% by mass, and this sodium hypophosphite monohydrate may be dehydrated by heating at 60°C or higher, preferably 80 to 100°C, for 10 minutes or more, preferably 30 to 180 minutes under reduced pressure of 0.05 MPa or lower, preferably 0.02 to 0.001 MPa, to reduce the water content of the hypophosphorous acid and / or the hypophosphite to 10% by mass or lower, preferably 8% by mass or lower, more preferably 4% by mass or lower.

[0025] In the above methods (3) and (4), the carboxylic acid liquid containing the hydrous hypophosphite is heated at a temperature of 100°C or higher, preferably 100 to 180°C, to perform a dehydration treatment in which water is discharged outside the system, and the water content relative to the hypophosphite (in anhydrous form) can be reduced to 10% by mass or less, preferably 8% by mass or less, and more preferably 4% by mass or less.

[0026] Furthermore, when an aqueous solution of hypophosphorous acid and / or hypophosphite is used, the water in the solvent is removed by distillation or the like, and if necessary, dehydration treatment is performed according to the methods (2) to (4) above. After that, the dehydrated product of hypophosphorous acid and / or the dehydrated product of hypophosphite can be dissolved or suspended directly in a carboxylic acid to prepare a raw material phosphorus compound-containing carboxylic acid liquid.

[0027] In the method for producing a dialkylphosphinic acid and / or a salt thereof of the present invention, as the raw material phosphorus compound used in preparing the raw material phosphorus-compound-containing carboxylic acid liquid, sodium hypophosphite monohydrate is preferably used from the viewpoints of industrial ease of availability and low cost.

[0028] In the first step, the carboxylic acid used as the reaction solvent is represented by the following general formula (4):

[0029] [ka]

[0030] (In the formula, R 13 represents a hydrogen atom or a group selected from linear, branched or cyclic hydrocarbon groups having 1 to 16 carbon atoms, and the hydrocarbon group may be substituted with a halogen atom, an aryl group, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a cyano group, an ether bond functional group, a sulfide bond functional group or an ester bond functional group. In the present invention, the term "functional group having an ether bond" refers to a group having a substituent bonded to -OR via an ether bond, the term "functional group having a sulfide bond" refers to a group having a substituent bonded to -SR via a sulfide bond, and the term "functional group having an ester bond" refers to a group having a substituent bonded to -COO-R via an ester bond.

[0031] R in general formula (4) 13 is a hydrogen atom or a group selected from linear, branched, or cyclic hydrocarbon groups having 1 to 16 carbon atoms. Examples of linear, branched or cyclic hydrocarbon groups having 1 to 16 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, an isohexyl group, a neohexyl group, a 2-ethylbutyl group, an n-heptyl group, an n-octyl group, an isooctyl group, a 1-methylheptyl group, a 2-methylheptyl group, a 2-ethylhexyl group, a 2,4,4-trimethylpentyl group, an n-decyl group, an n-dodecyl group, an isododecyl group, an n-octadecyl group, an isooctadecyl group, a cyclopentyl group, a cyclohexyl group, a cyclohexylmethyl group, and an adamantyl group. The linear, branched or cyclic hydrocarbon group having 1 to 16 carbon atoms may be substituted with a halogen atom, an aryl group, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a cyano group, an ether bond functional group, a sulfide bond functional group, or an ester bond functional group.

[0032] Specific examples of the carboxylic acid compound represented by general formula (4) in the first step include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, cyclohexanecarboxylic acid, 2-ethylhexanoic acid, naphthenic acid, stearic acid, chloroacetic acid, 3-chloropropionic acid, benzoic acid, methoxyacetic acid, lactic acid, thioglycolic acid, and 3-mercaptopropionic acid. In particular, when a mixture of isomers of 2,4,4-trimethylpentene is used as the olefin, the reaction is desirably carried out at high temperatures from the viewpoint of activating the radical addition reaction. In terms of their high boiling points and facilitating reactions at high temperatures, acetic acid, propionic acid, butyric acid, and 2-ethylhexanoic acid are preferred, and carboxylic acids such as propionic acid, butyric acid, and 2-ethylhexanoic acid are particularly preferred.

[0033] In the preparation of the raw material phosphorus compound-containing carboxylic acid liquid in the first step, the water content of the carboxylic acid to which the hypophosphorous acid and / or hypophosphite is added is preferably low, for example, preferably 8% by mass or less, more preferably 4% by mass or less. The water content of commercially available carboxylic acids is usually 0.3% by mass or less, so that commercially available carboxylic acids can be used in the first step.

[0034] The water content of the raw phosphorus compound-containing carboxylic acid liquid prepared in the first step is preferably 8% by mass or less, more preferably 5% by mass or less, based on the mass of hypophosphorous acid and / or hypophosphite salt in terms of anhydride. When the water content of the raw phosphorus compound-containing carboxylic acid liquid is within the above range, water is difficult to reflux in the second step even if the reaction temperature is equal to or higher than the boiling point of water, and therefore the effect of being able to set the reaction temperature to a temperature equal to or higher than the boiling point of water and exceeding 100°C is enhanced.

[0035] The content of the raw phosphorus compound in the raw phosphorus compound-containing carboxylic acid liquid in the first step is 1 to 99 mass %, preferably 10 to 50 mass %, calculated as an anhydride, from the viewpoints of uniformly mixing the raw phosphorus compound and the olefin and preventing damage to the synthesis apparatus. When the raw phosphorus compound-containing carboxylic acid liquid contains hypophosphorous acid and hypophosphite, the content of the raw phosphorus compound is the total content of hypophosphorous acid and hypophosphite.

[0036] The second step is a step in which an olefin and a radical initiator are added to the raw material phosphorus compound-containing carboxylic acid liquid prepared in the first step at a reaction temperature of more than 100°C and not more than 200°C and a reaction pressure of not more than 0.20 MPa, and the hypophosphorous acid and / or hypophosphite is reacted with the olefin.

[0037] The olefins used in the second step are preferably those represented by the following general formulas (1) to (3).

[0038] As the olefin in the second step, one preferred one is represented by the following general formula (1):

[0039] [ka]

[0040] (In the formula, R 1 ~R 4R represents a hydrogen atom or a group selected from linear, branched or cyclic alkyl groups having 1 to 18 carbon atoms, and the alkyl group may be substituted with a halogen atom, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a cyano group, an ether bond functional group, a sulfide bond functional group or an ester bond functional group. 1 ~R 4 may be different groups or the same group.) and substituted olefins substituted with functional groups.

[0041] In the general formula (1), R 1 ~R 4 is a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 18 carbon atoms.

[0042] In the general formula (1), examples of the chain alkyl group include linear or branched alkyl groups having 1 to 18 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, an isohexyl group, a neohexyl group, a 2-ethylbutyl group, an n-heptyl group, an n-octyl group, an isooctyl group, a 1-methylheptyl group, a 2-methylheptyl group, a 2-ethylhexyl group, a 2,4,4-trimethylpentyl group, an n-decyl group, an n-dodecyl group, an isododecyl group, an n-octadecyl group, and an isooctadecyl group.

[0043] In the general formula (1), examples of the cyclic alkyl group include a cyclopentyl group, a cyclohexyl group, a cyclohexylmethyl group, and an adamantyl group.

[0044] Examples of preferred compounds as the chain olefin represented by general formula (1) include compounds selected from ethylene, 1-butene, isobutylene, 1-hexene, neohexene, 2-ethyl-1-butene, methylenecyclopentane, 1-octene, cis-2-octene, 2-methyl-1-heptene, 2-ethyl-1-hexene, 2,4,4-trimethyl-1-pentene, vinylcyclohexane, allylcyclohexane, 1-decane, β-pinene, camphene, 1-octadecene, allylbenzene, cis-3-hexen-1-ol, and isopulegol, or mixtures containing isomers thereof.

[0045] In the general formula (1), the linear, branched or cyclic alkyl group may be substituted with a functional group, such as a halogen atom, an aryl group, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a cyano group, an ether bond functional group, a sulfide bond functional group, or an ester bond functional group.

[0046] Preferred examples of the substituted olefin compound substituted with a functional group represented by the general formula (1) include allyl chloride, allyl bromide, 1H,1H,2H-nonafluoro-1-hexene, 1H,1H,2H-tridecafluoro-1-octene, 1H,1H,2H-heptadecafluoro-1-decene, 1,1,1-trifluoro-2-(trifluoromethyl)-4-penten-2-ol, allyl pentafluorobenzene, allyl alcohol, 10-undecen-1-ol, ethylvinyl chloride, and the like. and mixtures containing a compound selected from the group consisting of allyl ether, allyl glycidyl ether, 2,5,8,11-tetraoxatetradec-13-ene allylbenzene, 10-undecenoic acid, allyl acetate, allylamine, allyl urea, 1-allylimidazole, allyl cyanide, 4-allylmorpholine, allyltrimethylsilane, diethyl allylphosphonate, allyltriphenylphosphonium bromide, allyl methyl sulfide, and S-allyl-L-cysteine, or isomers thereof.

[0047] More preferred compounds as the chain olefin represented by the general formula (1) and the substituted olefin substituted with a functional group include a compound selected from 2,4,4-trimethyl-1-pentene or a mixture containing its isomer 2,4,4-trimethyl-2-pentene (diisobutylene), and a compound selected from 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, allyl alcohol, and 10-undecenoic acid. In particular, a compound selected from 2,4,4-trimethyl-1-pentene or a mixture containing its isomer 2,4,4-trimethyl-2-pentene (diisobutylene) is industrially easily and inexpensively available, and furthermore, the derived di(2,4,4-trimethylpentyl)phosphinic acid is known to function as a metal extractant, and is therefore expected to be useful in recycling lithium ion secondary batteries. Therefore, it is even more preferred.

[0048] As the olefin in the second step, one preferred one is an olefin represented by the following general formula (2):

[0049] [ka]

[0050] (In the formula, R 5 represents a group selected from linear, branched or cyclic hydrocarbon groups having 2 to 6 carbon atoms, and the hydrocarbon group may be substituted with a halogen atom, an aryl group, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a cyano group, an ether bond functional group, a sulfide bond functional group or an ester bond functional group. and cyclic olefins represented by the following formula (I) or substituted olefins substituted with functional groups.

[0051] R in the general formula (2) 5 represents a group selected from linear, branched, or cyclic hydrocarbon groups having 2 to 6 carbon atoms. Examples of the linear, branched or cyclic hydrocarbon group having 2 to 6 carbon atoms include an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a methylethylene group, a 2-methyltetramethylene group, a 1,3-cyclopentylene group, and a 2-phenyltetramethylene group.

[0052] The linear, branched or cyclic hydrocarbon group having 2 to 6 carbon atoms in the general formula (2) may be substituted with a functional group, such as a halogen atom, an aryl group, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a cyano group, an ether bond functional group, a sulfide bond functional group, or an ester bond functional group.

[0053] Preferred compounds of the cyclic olefin represented by the general formula (2) or the substituted olefin substituted with a functional group include compounds selected from cyclopentene, cyclohexene, cycloheptene, cyclooctene, 4-methyl-1-cyclohexene, 2-norbornene, 4-phenyl-1-cyclohexene, 3-cyclohexene-1-methanol, 3-cyclopentene-1-carboxylic acid, 3-cyclohexene-1-carboxylic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylate bis(2-ethylhexyl), cis-1,2,3,6-tetrahydrophthalimide, and 4-cyano-1-cyclohexene, or mixtures containing isomers thereof.

[0054] As the olefin in the second step, one preferred one is an olefin represented by the following general formula (3):

[0055] [ka]

[0056] (In the formula, R 6 ~R 11R represents a hydrogen atom or a group selected from linear, branched or cyclic hydrocarbon groups having 1 to 6 carbon atoms, and the hydrocarbon group may be substituted with a halogen atom, an aryl group, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a cyano group, an ether bond functional group, a sulfide bond functional group or an ester bond functional group. 6 ~R 11 may be different groups or the same group, and two or more of these groups may be linked together. 12 represents a hydrocarbon group having 2 to 6 carbon atoms. Examples of the non-conjugated dienes include those represented by the following formula:

[0057] R in the general formula (3) 6 ~R 11 represents a hydrogen atom or a group selected from linear, branched or cyclic hydrocarbon groups having 1 to 6 carbon atoms. Examples of linear, branched, or cyclic hydrocarbon groups having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, an isohexyl group, a neohexyl group, a 2-ethylbutyl group, a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a methylethylene group, a 2-methyltetramethylene group, and a 1,3-cyclopentylene group.

[0058] The hydrocarbon group may be substituted with a functional group, such as a halogen atom, an aryl group, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a cyano group, an ether bond functional group, a sulfide bond functional group, or an ester bond functional group.

[0059] Examples of the non-conjugated diene represented by general formula (3) include compounds selected from 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene, 2,5-dimethyl-1,5-hexadiene, allyl ether, allyl sulfide, 4-vinyl-1-cyclohexene, 5-vinyl-2-norbornene, 1,4-cyclohexadiene, 2,5-norbornadiene, 1,5-cyclooctadiene, 3a,4,7,7a-tetrahydroindene, and dicyclopentadiene, and mixtures containing isomers thereof.

[0060] In the method for producing a dialkylphosphinic acid and / or a salt thereof of the present invention, a particularly preferred olefin is 2,4,4-trimethyl-1-pentene, or a mixture containing 2,4,4-trimethyl-1-pentene and its isomer 2,4,4-trimethyl-2-pentene (diisobutylene), from the viewpoint that the resulting dialkylphosphinic acid can also be used as a metal extractant.

[0061] In the method for producing a dialkylphosphinic acid and / or a salt thereof of the present invention, the amount of olefin added is, in terms of a molar ratio of olefin to the raw material phosphorus compound, 1.0 to 5.0, preferably 2.0 to 2.5, from the viewpoints of efficient reaction and green chemistry and atom economy.

[0062] Examples of the radical initiator in the second step include organic peroxides such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, benzoyl peroxide, acetyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, di-tert-butyl peroxide, tert-butyl peroxybenzoate, lauroyl peroxide, diisopropyl peroxydicarbonate, methyl ethyl ketone peroxide, and diacyl peroxides, hydrogen peroxide, ammonium peroxodisulfate, and peroxydicarbonates. Examples of radical initiators include inorganic peroxides such as potassium oxymonosulfate and calcium hypochlorite, and azo compounds such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], and 2,2'-azobis[N-butyl-2-methylpropionamide].

[0063] In the method for producing dialkylphosphinic acid and / or a salt thereof of the present invention, the radical initiator is preferably an organic peroxide that shows high initiator efficiency and generates highly reactive oxygen radicals, and in particular, tert-butyl peroxybenzoate is more preferred in that it shows a sustained decomposition rate in a temperature range of more than 100° C. and not more than 200° C. In addition, in the method for producing dialkylphosphinic acid and / or a salt thereof of the present invention, when the radical initiator is added intermittently or continuously in small amounts in two or more divided portions to the reaction system in a temperature range of more than 100° C. and not more than 200° C., a radical initiator such as an azo compound that shows a decomposition temperature of 100° C. or less also acts efficiently.

[0064] The amount of radical initiator added is, in terms of a molar ratio of the radical initiator to the raw material phosphorus compound, 0.005 to 0.5, preferably 0.02 to 0.2, which is preferable from the viewpoints of efficient reaction, green chemistry and atom economy.

[0065] In the second step, the raw material phosphorus compound-containing carboxylic acid liquid prepared in the first step is heated to a reaction temperature, and in this state, an olefin and a radical initiator are added to the raw material phosphorus compound-containing carboxylic acid liquid.

[0066] The reaction temperature in the second step, that is, the temperature in the reaction system when the olefin and the radical initiator are added to the raw material phosphorus compound-containing carboxylic acid liquid, may occur even at 20°C to 200°C depending on the type of olefin, but in consideration of the fact that the method for producing dialkylphosphinic acid and / or its salt of the present invention can advantageously carry out the reaction, particularly with bulky olefins, the reaction temperature in the second step is preferably a temperature exceeding 100°C and not exceeding 200°C and exceeding the boiling point of water. In addition, the reaction temperature in the second step is more preferably a temperature exceeding 100°C from the viewpoint of activating the radical addition reaction, more preferably a temperature exceeding 100°C and not exceeding 180°C, and even more preferably a temperature exceeding 100°C and not exceeding 160°C. In other words, in the second step, it is preferable to add the olefin and the radical initiator to the raw material phosphorus compound-containing carboxylic acid liquid while maintaining the reaction temperature (temperature in the reaction system) at a temperature exceeding the boiling point of water, in that the reaction can be advantageously carried out with bulky olefins. In the second step, from the viewpoint of activating the radical addition reaction, it is preferable to add the olefin and the radical initiator to the raw material phosphorus compound-containing carboxylic acid liquid while maintaining the reaction temperature (temperature in the reaction system) at a temperature exceeding 100°C, more preferably exceeding 100°C and not exceeding 180°C, and even more preferably exceeding 100°C and not exceeding 160°C. In the present invention, the "temperature exceeding the boiling point of water" refers to a temperature exceeding the temperature at which water boils under the reaction pressure conditions in the second step. In addition, the reaction pressure in the second step is 0.2 MPa or less, preferably 0.01 to 0.2 MPa.

[0067] In the second step, an olefin or a solution thereof and a radical initiator or a solution thereof may be added simultaneously to the raw material phosphorus compound-containing carboxylic acid liquid, or a mixture of an olefin and a radical initiator or a solution of both may be added.

[0068] As a solvent for dissolving the olefin and the radical initiator, the same carboxylic acid as that used in the first step can be used.

[0069] In the second step, the reaction proceeds by adding a radical initiator, and therefore, it is preferable to add the radical initiator simultaneously with the amount of olefin required for the reaction. In addition, in the second step, the olefin and the radical initiator may be added continuously in small amounts to the reaction system (raw material phosphorus compound-containing carboxylic acid liquid) while taking into consideration the prevention of accumulation of unreacted olefin in the reaction system and further the prevention of rapid thermal decomposition of the radical initiator, or the olefin and the radical initiator may be added intermittently to the reaction system (raw material phosphorus compound-containing carboxylic acid liquid) in two or more divided portions as required.

[0070] In the second step, regarding the addition of the radical initiator, when the addition of the necessary amount of the olefin and the radical initiator is completed, if unreacted hypophosphorous acid and / or hypophosphite or monoalkylphosphinic acid and / or salt thereof remains, an additional amount of the radical initiator can be added to continue the reaction.

[0071] In the second step, with regard to the addition of an olefin and a radical initiator, two PH bonds of hypophosphorous acid or a hypophosphite are added to two olefins in two steps, respectively. However, it is known that it is more difficult to generate a dialkylphosphinic acid and / or a salt thereof in the second step than to generate a monoalkylphosphinic acid and / or a salt thereof in the first step (Patent Document 4), and the reaction can also be carried out by appropriately adjusting the conditions for adding the olefin and the radical initiator in the first and second step reactions.

[0072] Hereinafter, an embodiment in which the olefin and the radical initiator are added in separate portions will be described. In the following, the reaction up to the production of monoalkylphosphinic acid and / or a salt thereof may be referred to as the "first reaction stage", and the reaction from monoalkylphosphine and / or a salt thereof to the production of dialkylphosphine and / or a salt thereof may be referred to as the "second reaction stage".

[0073] Regarding the addition of the olefin and the radical initiator in the first reaction stage, it is preferable to divide the necessary amounts of the olefin and the radical initiator into two or more portions and add them intermittently or continuously in small amounts to the reaction system, from the viewpoint of suppressing the accumulation of unreacted olefin in the reaction system and further suppressing the rapid thermal decomposition of the radical initiator. The amount of olefin added in the first reaction step is preferably 0.5 to 2.5, and more preferably 1.0 to 1.25, in terms of the molar ratio of olefin to the raw material phosphorus compound, from the viewpoints of efficient reaction, green chemistry and atom economy. Regarding the addition of the radical initiator in the first stage of the reaction, a radical initiator may be added in an amount sufficient to react with the olefin added in the first stage. The amount of the radical initiator added in the first stage is preferably 0.0025 to 0.25, and more preferably 0.01 to 0.1, in terms of the molar ratio of the radical initiator to the raw material phosphorus compound, in order to efficiently carry out the reaction and from the viewpoints of green chemistry and atom economy.

[0074] Regarding the addition of the olefin and the radical initiator in the second reaction stage, it is preferable to divide the necessary amounts of the olefin and the radical initiator into two or more portions and add them intermittently or continuously in small amounts to the reaction system, from the viewpoint of suppressing the accumulation of unreacted olefin in the reaction system and further suppressing the rapid thermal decomposition of the radical initiator. The amount of olefin added in the second reaction stage is preferably 0.5 to 2.5, and more preferably 1.0 to 1.25, in terms of the molar ratio of olefin to the raw material phosphorus compound, from the viewpoints of efficient reaction and green chemistry and atom economy. Regarding the addition of the radical initiator in the second stage of the reaction, a sufficient amount of the radical initiator may be added to react with the olefin added in the second stage. The amount of the radical initiator added in the second stage is preferably 0.0025 to 0.25, and more preferably 0.01 to 0.1, in terms of the molar ratio of the radical initiator to the raw material phosphorus compound, in order to efficiently carry out the reaction and from the viewpoints of green chemistry and atom economy.

[0075] After the entire amount of the required radical initiator is introduced into the reaction system, the reaction can be carried out at a temperature range of 20 to 200°C depending on the type of olefin. In view of the fact that the method for producing dialkylphosphinic acid and / or a salt thereof of the present invention can advantageously carry out the reaction particularly with bulky olefins, the reaction conditions, from the viewpoint of promoting the subsequent production of dialkylphosphinic acid and / or a salt thereof and the thermal decomposition of the radical initiator after the entire amount of the required radical initiator is introduced into the reaction system, are as follows: reaction temperature is higher than 100°C and lower than 200°C, preferably higher than 100°C and lower than 180°C, and more preferably higher than 100°C and lower than 160°C; reaction time is 1 hour or more, preferably 1 to 5 hours; and reaction pressure is 0.2 MPa or less, preferably 0.01 to 0.2 MPa.

[0076] In the method for producing a dialkylphosphinic acid and / or a salt thereof of the present invention, dialkylphosphinic acid and / or a dialkylphosphinic acid salt can be obtained by carrying out the second step. After carrying out the second step, for example, from the reaction liquid containing the dialkylphosphinic acid and / or the dialkylphosphinic acid salt obtained by carrying out the second step, unreacted olefin and carboxylic acid of the solvent are separated or removed, and then, when the reaction liquid contains a monoalkylphosphinic acid and / or a monoalkylphosphinic acid salt as a reaction intermediate, these reaction intermediates are removed, and then, when the reaction liquid contains a dialkylphosphinic acid salt, the reaction liquid is contacted with an aqueous acid solution to obtain a dialkylphosphinic acid.

[0077] In the method for producing a dialkylphosphinic acid and / or a salt thereof of the present invention, after carrying out the second step, a separation and recovery step can be carried out in which unreacted olefin and / or carboxylic acid of the solvent is separated and recovered from the reaction solution obtained. In the separation and recovery step, the reaction solution obtained by carrying out the second step can be distilled to separate a part or all of the olefin and / or carboxylic acid from the reaction system. Furthermore, the unreacted olefin and / or carboxylic acid separated and recovered in the separation and recovery step can be reused as the olefin in the second step and / or the carboxylic acid in the first step.

[0078] In the method for producing a dialkylphosphinic acid and / or a salt thereof of the present invention, water is added to the reaction liquid containing a dialkylphosphinic acid or a salt thereof obtained by carrying out the second step, or to the distillation residual liquid obtained by carrying out the separation and recovery step, to establish an aqueous phase and an organic phase, and the obtained organic phase is repeatedly extracted and washed with neutral or alkaline water until the monoalkylphosphinic acid and / or a salt thereof reaches a desired content, that is, repeatedly extracted and washed with water or an alkaline aqueous solution containing a base such as sodium hydroxide, potassium carbonate, or ammonia, and then the organic phase is separated, and then the obtained organic phase is acidified, that is, the organic phase is washed with an acid aqueous solution containing an acid such as hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid, and the organic phase is recovered, and filtration is carried out as necessary, and further a purification step can be carried out in which volatile substances such as unreacted olefins are removed from the organic phase by distillation to isolate and recover the dialkylphosphinic acid. The organic phase may be extracted and washed with water or an aqueous alkaline solution under heating, if necessary.

[0079] The method for producing a dialkylphosphinic acid and / or a salt thereof of the present invention includes a step A of separating and dehydrating a monoalkylphosphinic acid and / or a salt thereof from an aqueous phase containing a monoalkylphosphinic acid and / or a salt thereof obtained by carrying out a purification step, and then dissolving or suspending the obtained monoalkylphosphinic acid and / or a salt thereof in a carboxylic acid to prepare a carboxylic acid liquid containing a monoalkylphosphinic acid and / or a salt thereof; A step B of reacting the monoalkylphosphinic acid salt-containing carboxylic acid solution with an olefin and a radical initiator at a reaction temperature of more than 100° C. and not more than 200° C. and a reaction pressure of not more than 0.20 MPa to obtain a dialkylphosphinic acid and / or a salt thereof; may have the following structure:

[0080] The water content of the monoalkylphosphinic acid and / or its salt in step A is preferably 8% by mass or less, more preferably 4% by mass or less. The carboxylic acid in step A is the same as the carboxylic acid in step 1. The water content of the carboxylic acid solution containing the monoalkylphosphinic acid and / or its salt prepared in step A is preferably 8% by mass or less, more preferably 4% by mass or less, based on the mass of the monoalkylphosphinic acid salt in terms of anhydride.

[0081] The olefin and radical initiator in step B are the same as those in step 2. The reaction conditions in step B may be the same as those in the second step.

[0082] Furthermore, by carrying out the method for producing a dialkylphosphinic acid and / or a salt thereof of the present invention, the yield of the target dialkylphosphinic acid and / or a salt thereof may be lower than that of a monoalkylphosphinic acid and / or a salt thereof, but the target dialkylphosphinic acid and / or a salt thereof can be isolated by carrying out the above purification step.

[0083] As described above, in the method for producing a dialkylphosphinic acid and / or a salt thereof of the present invention, hypophosphorous acid and / or a hypophosphite can be reacted advantageously with an olefin, so that a dialkylphosphinic acid can be efficiently obtained. In particular, the reaction can be advantageously carried out with a bulky, low-boiling olefin that is difficult to react with hypophosphorous acid and / or a hypophosphite. EXAMPLES

[0084] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0085] (Water content measurement) In the following Examples, the water content of the hypophosphite used in the first step was calculated by the loss on drying test using the following calculation formula (1). In the examples, commercially available sodium hypophosphite monohydrate was used as the hypophosphite. Water content of hypophosphite (mass%) = (A / B) × 100 (1) A: The mass (g) lost when the sample was heated at 0.02 MPa and 80°C for 1 hour using a rotary evaporator B: Mass of the object before heating (g) (Carboxylic Acid) In the examples, the carboxylic acids used as the solvent were all commercially available products with a water content of 0.3% by mass or less.

[0086] Example 1: Use of sodium hypophosphite dehydrate, acetic acid and diisobutylene (Dehydration of sodium hypophosphite monohydrate) 4.24 g (0.0400 mol) of sodium hypophosphite monohydrate was weighed into a 100 mL eggplant-shaped flask, and the sodium hypophosphite monohydrate was dehydrated using a rotary evaporator at 0.01 MPa and 90° C. for 1 hour. From formula (1), it was estimated that 3.3 mass % of water remained in the sodium hypophosphite after the dehydration treatment. (1st step) The entire amount of sodium hypophosphite after dehydration was transferred to a 100mL four-neck flask equipped with a stirrer, thermometer, dropping funnel, and condenser, 4.34g of acetic acid was added, and the atmosphere inside the reaction vessel was replaced with nitrogen. The four-neck flask was immersed in a 130℃ oil bath, and the mixture of sodium hypophosphite monohydrate and acetic acid was heated while constantly stirring vigorously. The mixture dissolved and refluxed, and the temperature was constant at 116℃. (2nd process) The dropping funnel was filled with a solution of 1.59g (0.0040 mol) of lauroyl peroxide dissolved in 12.34g of diisobutylene (0.1100 mol of 2,4,4-trimethyl-1-pentene) and 1.00g of acetic acid, and the inside of the dropping funnel was replaced with a nitrogen atmosphere. The solution in the dropping funnel was added continuously to the reaction system in small amounts over a period of 4 hours, and the reaction was carried out while the reflux amount increased and the reaction liquid temperature decreased from 116°C to 110°C. After all the solution in the dropping funnel had been added, it was heated at the same temperature for another hour, then cooled to room temperature, 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 19.3 mol% Monoalkylphosphinate: 78.0 mol% Hypophosphite: 2.7 mol%

[0087] Comparative Example 1: Use of sodium hypophosphite monohydrate, acetic acid and diisobutylene In a 500 mL four-neck flask equipped with a stirrer, thermometer, dropping funnel, and condenser, 16.4 g (0.155 mol) of sodium hypophosphite monohydrate, 65.2 g of diisobutylene (0.581 mol of 2,4,4-trimethyl-1-pentene), and 388 g of acetic acid were added, and the mixture was stirred vigorously at a temperature of 95°C while a solution of 0.60 g (0.0031 mol) of 2,2'-azobis(2-methylbutyronitrile) dissolved in 19.4 g of acetic acid was added intermittently to the reaction system in equal portions over 16 times every hour to carry out the reaction. After the entire solution in the dropping funnel had been added, the mixture was heated at the same temperature for 1 hour, then cooled to room temperature, and the mixture was stirred vigorously at 95°C. 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 0 mol% Monoalkylphosphinate: 24.9 mol% Hypophosphite: 70.9 mol% Unknown component: 4.2 mol%

[0088] Comparative Example 2: Use of sodium hypophosphite monohydrate, acetic acid, and diisobutylene In a 500 mL four-neck flask equipped with a stirrer, a thermometer, a dropping funnel, and a condenser, 16.4 g (0.155 mol) of sodium hypophosphite monohydrate, 65.2 g of diisobutylene (0.581 mol of 2,4,4-trimethyl-1-pentene), and 388 g of acetic acid were added, and the mixture was stirred vigorously and heated to a temperature of 100°C or higher, but the temperature in the reaction system did not exceed 100°C. Therefore, the olefin and the radical initiator were not added.

[0089] [Table 1]

[0090] As is clear from Table 1, in the conventional method of JP2001-525328A, bulky and low boiling point diisobutylene does not react (Comparative Example 1), and it is difficult to raise the reaction temperature above 100°C (Comparative Example 2). It is also clear that the reaction of bulky and low boiling point diisobutylene does not proceed at all unless the temperature exceeds at least 100°C, as in Example 1.

[0091] Example 2: Use of sodium hypophosphite monohydrate, propionic acid and diisobutylene (Dehydration of sodium hypophosphite monohydrate) Sodium hypophosphite monohydrate was used as it was without dehydration treatment. Sodium hypophosphite monohydrate was estimated to contain 17.0 mass% water. (1st step) 10.60g (0.1000 moles) of sodium hypophosphite monohydrate and 14.82g of propionic acid were added to a 100mL four-neck flask equipped with a stirrer, thermometer, dropping funnel, and condenser, and the atmosphere in the reaction vessel was replaced with nitrogen. The four-neck flask was immersed in a 150°C oil bath, and the mixture of sodium hypophosphite monohydrate and propionic acid was heated with constant strong stirring. The mixture dissolved and refluxed, and the temperature was constant at 133°C. (2nd process) The dropping funnel was filled with a solution of 3.50 g (0.0180 mol) of tert-butyl peroxybenzoate dissolved in 30.86 g of diisobutylene (0.2200 mol of 2,4,4-trimethyl-1-pentene) and 5.56 g of propionic acid, and the atmosphere inside the dropping funnel was replaced with a nitrogen atmosphere. The solution in the dropping funnel was added continuously to the reaction system in small amounts over a period of 16 hours, and the reaction was carried out while the reflux amount increased and the reaction liquid temperature decreased from 133°C to 101°C. After the entire solution in the dropping funnel had been added, it was heated at the same temperature for another hour, then cooled to room temperature, and 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 41.7 mol% Monoalkylphosphinate: 52.2 mol% Hypophosphite: 0 mol% Unknown component: 6.1 mol%

[0092] Example 3: Use of sodium hypophosphite dehydrate, propionic acid and diisobutylene (Dehydration of sodium hypophosphite monohydrate) 10.60 g (0.1000 mol) of sodium hypophosphite monohydrate was weighed into a 100 mL eggplant-shaped flask, and the sodium hypophosphite monohydrate was dehydrated for 2 hours using a rotary evaporator at 0.002 MPa and 80° C. From formula (1), it was estimated that 3.9 mass % of water remained in the sodium hypophosphite after the dehydration treatment. (1st step) The entire amount of sodium hypophosphite after dehydration was transferred to a 100mL four-neck flask equipped with a stirrer, thermometer, dropping funnel, and condenser, 14.82g of propionic acid was added, and the atmosphere inside the reaction vessel was replaced with nitrogen. The four-neck flask was immersed in a 150℃ oil bath, and the mixture of sodium hypophosphite and propionic acid was heated while constantly stirring vigorously. The mixture dissolved and refluxed, and the temperature became constant at 142℃. (2nd process) The dropping funnel was filled with a solution of 3.50 g (0.0180 mol) of tert-butyl peroxybenzoate dissolved in 30.86 g of diisobutylene (0.2200 mol of 2,4,4-trimethyl-1-pentene) and 5.56 g of propionic acid, and the atmosphere inside the dropping funnel was replaced with a nitrogen atmosphere. The solution in the dropping funnel was added continuously to the reaction system in small amounts over a period of 16 hours, and the reaction was carried out while the reflux amount increased and the reaction liquid temperature decreased from 142°C to 113°C. After the entire solution in the dropping funnel had been added, it was heated at the same temperature for another hour, then cooled to room temperature, and 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 62.8 mol% Monoalkylphosphinate: 7.89 mol% Hypophosphite: 0 mol% Unknown component: 29.3 mol%

[0093] Example 4: Use of sodium hypophosphite dehydrated product, propionic acid and diisobutylene, two-step reaction (Dehydration of sodium hypophosphite monohydrate) 12.72 g (0.1200 mol) of sodium hypophosphite monohydrate was weighed into a 100 mL eggplant-shaped flask, and the sodium hypophosphite monohydrate was dehydrated for 2 hours using a rotary evaporator at 0.002 MPa and 80° C. From formula (1), it was estimated that 3.1 mass % of water remained in the sodium hypophosphite after the dehydration treatment. (1st step) The entire amount of sodium hypophosphite after dehydration was transferred to a 100mL four-neck flask equipped with a stirrer, thermometer, dropping funnel, and condenser, 17.80g of propionic acid was added, and the atmosphere inside the reaction vessel was replaced with nitrogen. The four-neck flask was immersed in a 115℃ oil bath, and the mixture of sodium hypophosphite and propionic acid was heated while constantly stirring vigorously. The mixture dissolved and became constant at 109℃. (2nd process) In the first stage of the reaction, a solution of 0.47g (0.0024 mol) of tert-butyl peroxybenzoate dissolved in 18.52g of diisobutylene (0.1650 mol of 2,4,4-trimethyl-1-pentene) was filled into the dropping funnel, and the inside of the dropping funnel was replaced with a nitrogen atmosphere. The solution in the dropping funnel was continuously added to the reaction system in small amounts over 10 minutes, and after all the solution was added, the reaction was continued for 3.5 hours at the same oil bath temperature, and the reaction was carried out while the reaction liquid temperature increased from 109°C to 115°C. Next, the oil bath temperature was increased to 135°C, and the reaction mixture was heated for 30 minutes while constantly stirring vigorously, and the reaction was carried out while the reaction liquid temperature increased from 115°C to 131°C. In the second stage of the reaction, the dropping funnel was filled with a solution in which 1.86 g (0.0096 mol) of tert-butyl peroxybenzoate was dissolved in 18.52 g of diisobutylene (0.1650 mol of 2,4,4-trimethyl-1-pentene), and the inside of the dropping funnel was replaced with a nitrogen atmosphere. The solution in the dropping funnel was continuously added to the reaction system in small amounts over 3.5 hours, and after all of the solution had been added, the reaction was continued for 3.5 hours while heating at the same temperature, and the reaction was carried out while the reflux amount increased and the reaction liquid temperature decreased from 131 ° C to 115 ° C. Furthermore, after all of the solution in the dropping funnel had been added, the dropping funnel was filled with a solution in which 1.86 g (0.0096 mol) of tert-butyl peroxybenzoate was dissolved in 6.67 g of propionic acid, and the inside of the dropping funnel was replaced with a nitrogen atmosphere. The oil bath temperature was raised to 140°C, and the solution in the dropping funnel was divided equally and added intermittently to the reaction system five times every hour, and the reaction was carried out while the reflux amount decreased and the reaction liquid temperature rose from 115°C to 123°C. After the entire solution in the dropping funnel was added, the oil bath temperature was raised to 150°C, and the mixture was heated for 5 hours and then cooled to room temperature. 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 84.2 mol% Monoalkylphosphinate: 9.5 mol% Hypophosphite: 0 mol% Unknown component: 6.3 mol%

[0094] Example 5: Use of sodium hypophosphite dehydrate, butyric acid and diisobutylene (Dehydration of sodium hypophosphite monohydrate) 4.24 g (0.0400 mol) of sodium hypophosphite monohydrate was weighed into a 100 mL eggplant-shaped flask, and the sodium hypophosphite monohydrate was dehydrated for 1 hour using a rotary evaporator at 0.01 MPa and 90° C. From formula (1), it was estimated that 3.8% by mass of water remained in the sodium hypophosphite monohydrate after the dehydration treatment. (1st step) The entire amount of sodium hypophosphite after dehydration was transferred to a 100mL four-neck flask equipped with a stirrer, thermometer, dropping funnel, and condenser, 10.78g of butyric acid was added, and the atmosphere inside the reaction vessel was replaced with nitrogen. The four-neck flask was immersed in a 180℃ oil bath, and the mixture of sodium hypophosphite and butyric acid was heated while constantly stirring vigorously. The mixture dissolved and refluxed, and the temperature was constant at 164℃. (2nd process) The dropping funnel was filled with a solution of 0.78 g (0.0040 mol) of tert-butyl peroxybenzoate dissolved in 12.34 g of diisobutylene (0.1100 mol of 2,4,4-trimethyl-1-pentene), and the atmosphere inside the dropping funnel was replaced with a nitrogen atmosphere. The solution in the dropping funnel was added continuously to the reaction system in small amounts over a period of 3 hours, and the reaction was carried out while the reflux amount increased and the reaction liquid temperature decreased from 164°C to 128°C. After the entire solution in the dropping funnel had been added, it was heated at the same temperature for 2.5 hours and then cooled to room temperature. 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 73.4 mol% Monoalkylphosphinate: 20.5 mol% Hypophosphite: 0 mol% Unknown component: 6.1 mol%

[0095] (Example 6) Use of sodium hypophosphite dehydrated product, 2-ethylhexanoic acid and diisobutylene (Dehydration of sodium hypophosphite monohydrate) 4.24 g (0.0400 mol) of sodium hypophosphite monohydrate was weighed into a 100 mL eggplant-shaped flask, and the sodium hypophosphite monohydrate was dehydrated for 1 hour using a rotary evaporator at 0.002 MPa and 90° C. From formula (1), it was estimated that 3.3 mass % of water remained in the sodium hypophosphite after the dehydration treatment. (1st step) The entire amount of sodium hypophosphite after dehydration was transferred to a 100mL four-neck flask equipped with a stirrer, thermometer, dropping funnel, and condenser, 17.31g of 2-ethylhexanoic acid was added, and the atmosphere inside the reaction vessel was replaced with nitrogen. The four-neck flask was immersed in a 170℃ oil bath, and the mixture of sodium hypophosphite and 2-ethylhexanoic acid was heated while constantly stirring vigorously. The mixture became constant at 164℃. At this time, sodium hypophosphite did not dissolve. (2nd process) The dropping funnel was filled with a solution of 0.77 g (0.0040 mol) of 2,2'-azobis(2-methylbutyronitrile) dissolved in 12.34 g of diisobutylene (0.1100 mol of 2,4,4-trimethyl-1-pentene), and the atmosphere inside the dropping funnel was replaced with a nitrogen atmosphere. The solution in the dropping funnel was added continuously to the reaction system in small amounts over a period of 3.5 hours, and the reaction was carried out while the reflux amount increased and the reaction liquid temperature decreased from 164°C to 138°C. After all the solution in the dropping funnel had been added, it was heated at the same temperature for another hour, then cooled to room temperature, 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 44.8 mol% Monoalkylphosphinate: 53.4 mol% Hypophosphite: 0 mol% Unknown component: 1.8 mol%

[0096] (Example 7) Use of sodium hypophosphite dehydrate, propionic acid and 1H,1H,2H-nonafluoro-1-hexene (Dehydration of sodium hypophosphite monohydrate) 4.24 g (0.0400 mol) of sodium hypophosphite monohydrate was weighed into a 100 mL eggplant-shaped flask, and the sodium hypophosphite monohydrate was dehydrated for 1 hour using a rotary evaporator at 0.003 MPa and 90° C. From formula (1), it was estimated that 3.0 mass % of water remained in the sodium hypophosphite after the dehydration treatment. (1st step) The entire amount of sodium hypophosphite after dehydration was transferred to a 100mL four-neck flask equipped with a stirrer, thermometer, dropping funnel, and condenser, 8.90g of propionic acid was added, and the atmosphere inside the reaction vessel was replaced with nitrogen. The four-neck flask was immersed in a 150℃ oil bath, and the mixture of sodium hypophosphite and propionic acid was heated while constantly stirring vigorously. The mixture dissolved and refluxed, and the temperature became constant at 139℃. (2nd process) The dropping funnel was filled with a solution of 0.85 g (0.0044 mol) of 2,2'-azobis(2-methylbutyronitrile) dissolved in 21.66 g (0.0880 mol) of 1H,1H,2H-nonafluoro-1-hexene, and the atmosphere inside the dropping funnel was replaced with a nitrogen atmosphere. The solution in the dropping funnel was added continuously to the reaction system in small amounts over a period of 4 hours, and the reaction was carried out while the reflux amount increased and the reaction liquid temperature decreased from 139°C to 136°C. After all the solution in the dropping funnel had been added, it was heated at the same temperature for 1 hour and then cooled to room temperature. 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 89.6 mol% Monoalkylphosphinate: 7.2 mol% Hypophosphite: 0 mol% Unknown component: 3.2 mol%

[0097] Example 8: Use of sodium hypophosphite dehydrate, propionic acid and allyl alcohol (Dehydration of sodium hypophosphite monohydrate) 9.54 g (0.0900 mol) of sodium hypophosphite monohydrate was weighed into a 100 mL eggplant-shaped flask, and the sodium hypophosphite monohydrate was dehydrated for 1 hour using a rotary evaporator at 0.004 MPa and 90° C. From formula (1), it was estimated that 3.3 mass % of water remained in the sodium hypophosphite after the dehydration treatment. (1st step) The entire amount of sodium hypophosphite after dehydration was transferred to a 100mL four-neck flask equipped with a stirrer, thermometer, dropping funnel, and condenser, 21.60g of propionic acid was added, and the atmosphere inside the reaction vessel was replaced with nitrogen. The four-neck flask was immersed in a 150℃ oil bath, and the mixture of sodium hypophosphite and propionic acid was heated while constantly stirring vigorously. The mixture dissolved and refluxed, and the temperature became constant at 139℃. (2nd process) The dropping funnel was filled with a solution of 1.90g (0.0099 mol) of 2,2'-azobis(2-methylbutyronitrile) dissolved in 11.50g (0.1980 mol) of allyl alcohol and 0.99g of propionic acid, and the atmosphere inside the dropping funnel was replaced with nitrogen. The solution in the dropping funnel was added continuously to the reaction system in small amounts over a period of 1.7 hours, and the reaction was carried out while the reflux amount increased and the reaction liquid temperature rose from 139°C to 148°C and then fell to 139°C. After all the solution in the dropping funnel had been added, it was heated at the same temperature for 1 hour and then cooled to room temperature. 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 87.8 mol% Monoalkylphosphinate: 5.9 mol% Hypophosphite: 0 mol% Unknown component: 6.3 mol%

[0098] (Example 9) Use of sodium hypophosphite dehydrate, propionic acid and 10-undecenoic acid (Dehydration of sodium hypophosphite monohydrate) 4.24 g (0.0400 mol) of sodium hypophosphite monohydrate was weighed into a 100 mL eggplant-shaped flask, and the sodium hypophosphite monohydrate was dehydrated for 1 hour using a rotary evaporator at 0.002 MPa and 90° C. From formula (1), it was estimated that 3.3 mass % of water remained in the sodium hypophosphite after the dehydration treatment. (1st step) The entire amount of sodium hypophosphite after dehydration was transferred to a 100mL four-neck flask equipped with a stirrer, thermometer, dropping funnel, and condenser, 8.90g of propionic acid was added, and the atmosphere inside the reaction vessel was replaced with nitrogen. The four-neck flask was immersed in a 150℃ oil bath, and the mixture of sodium hypophosphite and propionic acid was heated while constantly stirring vigorously. The mixture dissolved and refluxed, and the temperature was constant at 140℃. (2nd process) The dropping funnel was filled with a solution of 0.42 g (0.0022 mol) of 2,2'-azobis(2-methylbutyronitrile) dissolved in 16.22 g (0.0880 mol) of 10-undecenoic acid and 3.61 g of propionic acid, and the inside of the dropping funnel was replaced with a nitrogen atmosphere. The solution in the dropping funnel was added continuously to the reaction system in small amounts over a period of 2 hours, and the reaction was carried out while the reflux amount increased and the reaction liquid temperature rose from 140°C to 147°C and then fell to 144°C. After all the solution in the dropping funnel had been added, it was heated at the same temperature for 1.5 hours and then cooled to room temperature. 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 82.2 mol% Monoalkylphosphinate: 15.1 mol% Hypophosphite: 0 mol% Unknown component: 2.7 mol%

[0099] Example 10: Use of sodium hypophosphite dehydrate, propionic acid and cyclohexene (Dehydration of sodium hypophosphite monohydrate) 5.30 g (0.0500 mol) of sodium hypophosphite monohydrate was weighed into a 100 mL eggplant-shaped flask, and the sodium hypophosphite monohydrate was dehydrated for 1 hour using a rotary evaporator at 0.003 MPa and 90° C. From formula (1), it was estimated that 3.9 mass % of water remained in the sodium hypophosphite after the dehydration treatment. (1st step) The entire amount of sodium hypophosphite after dehydration was transferred to a 100mL four-neck flask equipped with a stirrer, thermometer, dropping funnel, and condenser, 10.19g of propionic acid was added, and the atmosphere inside the reaction vessel was replaced with nitrogen. The four-neck flask was immersed in a 150℃ oil bath, and the mixture of sodium hypophosphite and propionic acid was heated while constantly stirring vigorously. The mixture dissolved and refluxed, and the temperature was constant at 135℃. (2nd process) The dropping funnel was filled with a solution of 0.96 g (0.0050 mol) of 2,2'-azobis(2-methylbutyronitrile) dissolved in 9.04 g (0.1100 mol) of cyclohexene, and the inside of the dropping funnel was replaced with a nitrogen atmosphere. The solution in the dropping funnel was added continuously to the reaction system in small amounts over a period of 2 hours, and the reaction was carried out while the reflux amount increased and the reaction liquid temperature rose from 135°C to 140°C and then fell to 131°C. After all the solution in the dropping funnel had been added, it was heated at the same temperature for another hour, then cooled to room temperature, 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 62.9 mol% Monoalkylphosphinate: 35.1 mol% Hypophosphite: 0 mol% Unknown component: 2.0 mol% The four-neck flask was then again immersed in a 150°C oil bath, and the reaction mixture was heated with constant and vigorous stirring. The mixture refluxed and reached a constant temperature of 134°C. The dropping funnel was filled with 0.49g (0.0025 mol) of tert-butyl peroxybenzoate, and the atmosphere in the dropping funnel was replaced with a nitrogen atmosphere. The tert-butyl peroxybenzoate in the dropping funnel was evenly divided and added intermittently to the reaction system five times every hour, and the reaction was carried out while the reflux amount decreased and the reaction liquid temperature rose from 134°C to 141°C. After the entire solution in the dropping funnel had been added, the mixture was heated at the same temperature for 4.5 hours, then cooled to room temperature, and 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 88.7 mol% Monoalkylphosphinate: 5.4 mol% Hypophosphite: 0 mol% Unknown component: 5.9 mol%

[0100] (Example 11) Use of sodium hypophosphite dehydrate, propionic acid and cyclooctadiene (Dehydration of sodium hypophosphite monohydrate) 4.24 g (0.0400 mol) of sodium hypophosphite monohydrate was weighed into a 100 mL eggplant-shaped flask, and the sodium hypophosphite monohydrate was dehydrated for 1 hour using a rotary evaporator at 0.01 MPa and 90°C. From formula (1), it was estimated that 3.6% by mass of water remained in the sodium hypophosphite after the dehydration treatment. (1st step) The entire amount of sodium hypophosphite after dehydration was transferred to a 100mL four-neck flask equipped with a stirrer, thermometer, dropping funnel, and condenser, 8.89g of propionic acid was added, and the atmosphere inside the reaction vessel was replaced with nitrogen. The four-neck flask was immersed in a 150℃ oil bath, and the mixture of sodium hypophosphite and propionic acid was heated while constantly stirring vigorously. The mixture dissolved and refluxed, and the temperature was constant at 140℃. (2nd process) The dropping funnel was filled with a solution of 0.77 g (0.0040 mol) of 2,2'-azobis(2-methylbutyronitrile) dissolved in 4.76 g (0.0440 mol) of cyclooctadiene, and the atmosphere inside the dropping funnel was replaced with a nitrogen atmosphere. The solution in the dropping funnel was added continuously to the reaction system in small amounts over a period of one hour, and the reaction was carried out while the temperature of the reaction liquid rose from 140°C to 151°C and then fell to 141°C. After all the solution in the dropping funnel had been added, it was heated at the same temperature for another hour, then cooled to room temperature, 31 The composition of the phosphorus compounds in the reaction solution was analyzed by P NMR measurement. Dialkylphosphinate: 24.1 mol% Monoalkylphosphinate: 67.0 mol% Hypophosphite: 1.7 mol% Unknown component: 7.2 mol%

[0101] [Table 2]

[0102] Comparing Examples 2 to 4 in Table 2, it can be seen that the yield is improved by using sodium hypophosphite with a low water content. Also, comparing Example 1 in Table 1 with Examples 3 and 4 in Table 2, it can be seen that the yield is improved by using propionic acid (boiling point 141°C), a carboxylic acid with a higher boiling point than acetic acid (boiling point 118°C), as a reaction solvent.

[0103] Example 12 (Unreacted olefin and carboxylic acid solvent recovery process) After completion of the reaction in the second step of Example 2, the reaction solution was distilled under 0.003 MPa and 100°C to obtain 14.2 g of a distillate. Tetramethylsilane was used as an internal standard. 1 The composition was analyzed by 1 H NMR measurement. 2,4,4-trimethyl-1-pentene: 22.8% by mass 2,4,4-trimethyl-2-pentene: 50.2% by mass Propionic acid: 14.5% by mass Next, the reaction liquid was heated to 140° C. under the same pressure and distilled to obtain 20.0 g of a distillate. 1 H NMR measurement revealed that almost the entire amount was propionic acid. (purification process) The reaction solution concentrated by distillation was heated to 70°C, 20g of pure water was added to remove the resulting aqueous phase, and the remaining organic phase was extracted and washed six times with 10g of pure water. The organic phase was then acidified with 12.5g of concentrated hydrochloric acid, washed with water at the same temperature, and further concentrated by vacuum distillation to obtain 30.9g of a colorless, transparent liquid. 31 P NMR measurement revealed that the product was the desired dialkylphosphinic acid with a purity of 92.8% and a yield of 88.1%. Dialkylphosphinic acid: 92.8 mol% Monoalkylphosphinic acid: 2.9 mol% Hypophosphorous acid: 0 mol% Unknown component: 4.3 mol%

Claims

1. A first step of preparing a raw material phosphorus compound-containing carboxylic acid liquid by dissolving or suspending hypophosphorous acid and / or a hypophosphite in a carboxylic acid; a second step of reacting the raw material phosphorus compound-containing carboxylic acid liquid with an olefin and a radical initiator at a reaction temperature of more than 100° C. and not more than 200° C. and a reaction pressure of not more than 0.20 MPa to obtain a dialkylphosphinic acid and / or a salt thereof; having A method for producing a dialkylphosphinic acid and / or a salt thereof, comprising the steps of:

2. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1, characterized in that the first step is carried out by dehydrating hydrated hypophosphorous acid and / or hydrated hypophosphite until the water content is 10 mass% or less, and dissolving or suspending the resulting dehydrated hypophosphorous acid and / or dehydrated hypophosphite in the carboxylic acid to prepare the raw material phosphorus compound-containing carboxylic acid liquid.

3. 3. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that in the second step, the olefin and the radical initiator in amounts necessary for the reaction are added to the reaction system in two or more portions.

4. The olefin is represented by the following general formula (1): 【Chemistry 1】 (In the formula, R １ ~R ４ R represents a hydrogen atom or a group selected from linear, branched or cyclic alkyl groups having 1 to 18 carbon atoms, and the alkyl group may be substituted with a halogen atom, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a cyano group, an ether bond functional group, a sulfide bond functional group or an ester bond functional group. １ ~R ４ may be different groups or the same group.) The dialkylphosphinic acid and / or the method for producing the same according to claim 1 or 2, characterized in that the dialkylphosphinic acid is a chain olefin represented by the following formula (I) or a substituted olefin substituted with a functional group:

5. 3. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the chain olefin represented by the general formula (1) is a compound selected from ethylene, 1-butene, isobutylene, 1-hexene, neohexene, 2-ethyl-1-butene, methylenecyclopentane, 1-octene, cis-2-octene, 2-methyl-1-heptene, 2-ethyl-1-hexene, 2,4,4-trimethyl-1-pentene, vinylcyclohexane, allylcyclohexane, 1-decane, β-pinene, camphene, 1-octadecene, allylbenzene, cis-3-hexen-1-ol and isopulegol, or a mixture containing an isomer thereof.

6. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the chain olefin represented by the general formula (1) is a compound selected from 2,4,4-trimethyl-1-pentene or a mixture containing its isomer 2,4,4-trimethyl-2-pentene (diisobutylene).

7. The substituted olefin substituted with the functional group represented by the general formula (1) is allyl chloride, allyl bromide, 1H,1H,2H-nonafluoro-1-hexene, 1H,1H,2H-tridecafluoro-1-octene, 1H,1H,2H-heptadecafluoro-1-decene, 1,1,1-trifluoro-2-(trifluoromethyl)-4-penten-2-ol, allyl pentafluorobenzene, allyl alcohol, 10-undecen-1-ol, ethyl vinyl ether, allyl glycidyl ether, 2,5,8,1 3. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the dialkylphosphinic acid and / or a salt thereof is a mixture containing a compound selected from the group consisting of 1-tetraoxatetradec-13-ene allylbenzene, 10-undecenoic acid, allyl acetate, allylamine, allyl urea, 1-allylimidazole, allyl cyanide, 4-allylmorpholine, allyltrimethylsilane, diethyl allylphosphonate, allyltriphenylphosphonium bromide, allyl methyl sulfide and S-allyl-L-cysteine, or an isomer thereof.

8. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the substituted olefin substituted with the functional group represented by the general formula (1) is a compound selected from 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, allyl alcohol, and 10-undecenoic acid.

9. The olefin is represented by the following general formula (2): 【Chemistry 2】 (In the formula, R ５ represents a group selected from linear, branched or cyclic hydrocarbon groups having 2 to 6 carbon atoms, and the hydrocarbon group may be substituted with a halogen atom, an aryl group, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a cyano group, an ether bond functional group, a sulfide bond functional group or an ester bond functional group.

3. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, wherein the dialkylphosphinic acid and / or a salt thereof is a cyclic olefin represented by the formula:

10. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the cyclic olefin represented by the general formula (2) or the substituted olefin substituted with a functional group is a compound selected from cyclopentene, cyclohexene, cycloheptene, cyclooctene, 4-methyl-1-cyclohexene, 2-norbornene, 4-phenyl-1-cyclohexene, 3-cyclohexene-1-methanol, 3-cyclopentene-1-carboxylic acid, 3-cyclohexene-1-carboxylic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylate bis(2-ethylhexyl), cis-1,2,3,6-tetrahydrophthalimide, and 4-cyano-1-cyclohexene, or a mixture containing an isomer thereof.

11. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the cyclic olefin represented by the general formula (2) or the substituted olefin substituted with a functional group is cyclohexene.

12. The olefin is represented by the following general formula (3): 【Chemistry 3】 (In the formula, R ６ ~R １１ represents a hydrogen atom or a group selected from linear, branched or cyclic hydrocarbon groups having 1 to 6 carbon atoms, and the hydrocarbon group may be substituted with a halogen atom, an aryl group, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a cyano group, an ether bond functional group, a sulfide bond functional group or an ester bond functional group. ６ ~R １１ may be different groups or the same group, and two or more of these groups may be linked together. １２ represents a hydrocarbon group having 2 to 6 carbon atoms.) The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the dialkylphosphinic acid and / or a salt thereof is a non-conjugated diene represented by the formula:

13. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the non-conjugated diene represented by the general formula (3) is a compound selected from 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene, 2,5-dimethyl-1,5-hexadiene, allyl ether, allyl sulfide, 4-vinyl-1-cyclohexene, 5-vinyl-2-norbornene, 1,4-cyclohexadiene, 2,5-norbornadiene, 1,5-cyclooctadiene, 3a,4,7,7a-tetrahydroindene and dicyclopentadiene, or a mixture containing an isomer thereof.

14. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the non-conjugated diene represented by the general formula (3) is 1,5-cyclooctadiene.

15. The carboxylic acid is represented by the following general formula (4): 【Chemistry 4】 (In the formula, R １３ represents a hydrogen atom or a group selected from linear, branched or cyclic hydrocarbon groups having 1 to 16 carbon atoms, and the hydrocarbon group may be substituted with a halogen atom, an aryl group, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a cyano group, an ether bond functional group, a sulfide bond functional group or an ester bond functional group. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the dialkylphosphinic acid and / or a salt thereof is a carboxylic acid represented by the formula:

16. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the carboxylic acid represented by the general formula (4) is a compound selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, cyclohexanecarboxylic acid, 2-ethylhexanoic acid, naphthenic acid, stearic acid, chloroacetic acid, 3-chloropropionic acid, benzoic acid, methoxyacetic acid, lactic acid, thioglycolic acid and 3-mercaptopropionic acid.

17. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the carboxylic acid represented by the general formula (4) is a compound selected from acetic acid, propionic acid, butyric acid and 2-ethylhexanoic acid.

18. 3. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that in the second step, the olefin and the radical initiator are added while maintaining the reaction temperature at a temperature exceeding the boiling point of water.

19. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the reaction temperature in the second step is higher than 100°C and not higher than 180°C.

20. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, characterized in that the reaction pressure in the second step is 0.01 to 0.20 MPa.

21. 3. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 2, further comprising a separation and recovery step of distilling a reaction liquid containing a dialkylphosphinic acid or a salt thereof obtained by carrying out the second step, to separate and recover unreacted olefin and / or carboxylic acid of the solvent.

22. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 1 or 21, further comprising a purification step of adding water to a reaction liquid containing a dialkylphosphinic acid or a salt thereof obtained by carrying out the second step, or to a distillation residual liquid obtained by carrying out the separation and recovery step to establish an aqueous phase and an organic phase, repeatedly extracting and washing the obtained organic phase with neutral or alkaline water until the monoalkylphosphinic acid and / or a salt thereof reaches a desired content, and then acidifying the organic phase to recover the dialkylphosphinic acid.

23. The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 21, characterized in that the olefin and / or the carboxylic acid obtained by carrying out the separation and recovery step is reused as the olefin in the second step and / or the carboxylic acid in the first step.

24. A step A of separating and dehydrating the monoalkylphosphinic acid and / or a salt thereof from the aqueous phase containing the monoalkylphosphinic acid and / or a salt thereof obtained by carrying out the purification step, and then dissolving or suspending the obtained monoalkylphosphinic acid and / or a salt thereof in a carboxylic acid to prepare a carboxylic acid liquid containing the monoalkylphosphinic acid and / or a salt thereof; A step B of reacting the monoalkylphosphinic acid-containing carboxylic acid solution and / or the monoalkylphosphinic acid and / or a salt thereof-containing carboxylate solution with an olefin and a radical initiator at a reaction temperature of more than 100° C. and not more than 200° C. and a reaction pressure of not more than 0.20 MPa to obtain a dialkylphosphinic acid and / or a salt thereof; having The method for producing a dialkylphosphinic acid and / or a salt thereof according to claim 22,

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