JP7459865B2 - Method for dehydrating organic solvent and method for purifying organic solvent - Google Patents

Description

The present invention relates to a method for dehydrating an organic solvent and a method for purifying an organic solvent, and in particular to a method for dehydrating an organic solvent using gas-liquid contact and a method for purifying an organic solvent using said dehydration method.

Conventionally, as a method for removing moisture contained in liquids such as organic solvents, an inert gas that has been dried by contacting with a moisture adsorbent such as a molecular sieve is blown into the liquid to remove moisture from the liquid. A method is known in which the active gas is entrained and removed (for example, see Patent Document 1).

Special Publication No. 52-4269

Here, for example, organic solvents used for manufacturing and cleaning semiconductor devices are required to reduce impurities such as moisture and fine particles.

However, the conventional dehydration method described above, in which dried gas is simply blown into the liquid to remove moisture from the liquid, had the problem that the amount of fine particles contained in the liquid increased after dehydration.

Therefore, an object of the present invention is to provide a method for dehydrating an organic solvent while suppressing an increase in the number of fine particles.
Another object of the present invention is to provide a method for purifying an organic solvent, which can effectively reduce both the water content and the number of fine particles.

The present invention has an object to advantageously solve the above problems, and the method for dehydrating an organic solvent of the present invention comprises a step (A) of preparing a dehydration gas and a step (B) of contacting the dehydration gas with an organic solvent, characterized in that the step (A) comprises a step (a1) of passing a gas having a dew point of -30° C. or less through a gas filter to obtain a dehydration gas, or a step (a2) of adjusting the dew point of the gas passed through the gas filter to -30° C. or less to obtain a dehydration gas. In this way, by using a dehydration gas obtained by passing a gas having a dew point of -30° C. or less through a gas filter, or a dehydration gas obtained by adjusting the dew point of the gas passed through the gas filter to -30° C. or less, it is possible to dehydrate an organic solvent while suppressing an increase in the number of fine particles.
In the present invention, the "dew point" refers to the dew point under atmospheric pressure determined from the moisture content measured using Fourier transform infrared spectroscopy (FT-IR).

Here, the organic solvent is a group consisting of hydrocarbons, alcohols, ethers, ketones, amides, esters, nitriles, hydrofluorocarbons, hydrofluoroethers, perfluorocarbons, and hydrofluoroolefins. The solvent may contain at least one solvent selected from the following.

Among them, it is preferable that the organic solvent contains 1,1,2,2,3,3,4-heptafluorocyclopentane. Organic solvents containing 1,1,2,2,3,3,4-heptafluorocyclopentane can be advantageously used in the manufacture and cleaning of semiconductor devices.

The organic solvent may also be an azeotropic composition.

The organic solvent is preferably a mixture of 1,1,2,2,3,3,4-heptafluorocyclopentane and tert-amyl alcohol. A mixture of 1,1,2,2,3,3,4-heptafluorocyclopentane and tert-amyl alcohol can be advantageously used in the manufacture and cleaning of semiconductor devices.

Further, the gas is preferably at least one selected from the group consisting of hydrogen, air, oxygen, nitrogen, helium, neon, argon, krypton, xenon, carbon monoxide, and carbon dioxide. By using these gases, it is possible to effectively dehydrate the organic solvent while suppressing the occurrence of side reactions.

The present invention also aims to advantageously solve the above problems, and the method for purifying an organic solvent of the present invention is characterized by including a step (α) of filtering the organic solvent with a filter, and a step (β) of dehydrating the organic solvent using any of the above-mentioned methods for dehydrating an organic solvent. By carrying out steps (α) and (β), it is possible to obtain a purified product consisting of an organic solvent with a reduced amount of moisture and number of particles by effectively removing both water and fine particles from the organic solvent.

Here, in the method for purifying an organic solvent of the present invention, it is preferable to dehydrate the organic solvent filtered in the step (α) in the step (β). By carrying out the step (β) after the step (α), it is possible to prevent water from being mixed in during filtration. In the method for purifying an organic solvent of the present invention, since the organic solvent is dehydrated in the step (β) using the above-mentioned method for dehydrating an organic solvent of the present invention, it is possible to obtain a purified product with a sufficiently reduced number of fine particles even when the step (β) is carried out after the step (α).

According to the method for dehydrating an organic solvent of the present invention, an organic solvent can be dehydrated while suppressing an increase in the number of fine particles.
Furthermore, according to the method for purifying an organic solvent of the present invention, a purified product can be obtained in which both the water content and the number of fine particles are reduced satisfactorily.

FIG. 2A is a diagram showing a flow chart of an example of the method for purifying an organic solvent of the present invention, and FIG. 2B is a diagram showing a flow chart of another example of the method for purifying an organic solvent of the present invention. FIG. 1 is an explanatory diagram showing a schematic configuration of an example of a dehydrating device that can be used for dehydrating an organic solvent.

Embodiments of the present invention will be described in detail below.
Here, the method for dehydrating an organic solvent of the present invention can be used when dehydrating an organic solvent. Furthermore, the organic solvent purification method of the present invention includes a step of dehydrating the organic solvent using the organic solvent dehydration method of the present invention, and removes both water and fine particles from the organic solvent to reduce the water content and It can be used to obtain a purified product made of an organic solvent with a reduced number of fine particles.

(Method for purifying organic solvent)
The method for purifying an organic solvent of the present invention includes a step (α) of filtering the organic solvent through a filter, and a step (β) of dehydrating the organic solvent by using the method for dehydrating an organic solvent of the present invention, and may optionally further include a pretreatment step (γ) prior to the step (α).

In the method for purifying an organic solvent of the present invention, the organic solvent is filtered through a filter in step (α), so that fine particles can be removed from the organic solvent. In the method for purifying an organic solvent of the present invention, the organic solvent is dehydrated in step (β) using the method for dehydrating an organic solvent of the present invention, so that the organic solvent can be dehydrated while suppressing an increase in the number of fine particles caused by the dehydration operation, as will be described in detail later. Therefore, according to the method for purifying an organic solvent of the present invention, a purified product can be obtained that is made of an organic solvent in which the water content and the number of fine particles have been satisfactorily reduced.

While either step (α) or step (β) may be performed first, it is preferable to perform step (α) first. If step (β) is performed first as shown in FIG. 1(b), moisture may be mixed into the organic solvent from the surrounding atmosphere when the dehydrated organic solvent is filtered through a filter. However, if step (α) is performed first as shown in FIG. 1(a) and the organic solvent filtered in step (α) is dehydrated, the moisture content in the resulting purified product can be sufficiently reduced. In addition, in step (β), the organic solvent can be dehydrated while suppressing an increase in the number of fine particles, so that even if step (α) is performed first, a purified product consisting of an organic solvent with a sufficiently reduced moisture content and number of fine particles can be obtained.

<Organic solvent>
Here, the organic solvents purified by the organic solvent purification method of the present invention are not particularly limited, and include, for example, hydrocarbons such as hexane, cyclohexane, octane, and decane; butanol, isopropanol, 2-butanol, Aliphatic alcohols such as methylbutanol, propanol, heptanol, hexanol, decanol, nonanol, benzyl alcohol, methylbenzyl alcohol, ethylbenzyl alcohol, methoxybenzyl alcohol, ethoxybenzyl alcohol, hydroxybenzyl alcohol, 3-phenylpropanol, cumyl alcohol , alcohols such as aromatic alcohols such as furfuryl alcohol, phenethyl alcohol, methoxyphenethyl alcohol, and ethoxyphenethyl alcohol; ethers such as dibutyl ether and cyclopentyl methyl ether; methyl ethyl ketone, acetyl ketone, methyl isobutyl ketone, cyclohexanone, and cyclopenta Ketones such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone and other amides;butyl acetate, isopropyl acetate, butyl propionate, methyl caproate, butyl caproate, etc. Esters; Nitriles such as acrylonitrile, methacrylonitrile, acetonitrile; Formula: C _n H _m F _2n+2-m [wherein, n is an integer of 4 or more and 6 or less, m is an integer of 1 or more A compound (for example, 1,1,1,3,3-pentafluorobutane) represented by the formula: C _n H _m F _2n-m [where n is an integer of 4 to 6, m is an integer of 1 or more] (for example, 1,1,2,2,3-pentafluorocyclobutane, 1,1,2,2,3,3,4-heptafluorocyclopentane, Hydrofluorocarbons such as 1,1,2,2,3,3,4,4,5-nonafluorocyclocyclohexane); methyl perfluorobutyl ether, methyl perfluoroisobutyl ether, methyl perfluoropentyl ether, ethyl perfluorobutyl ether , hydrofluoroethers such as ethyl perfluoroisobutyl ether; perfluorocarbons such as perfluorocyclohexane and perfluoromethylcyclohexane; hydrofluoroolefins such as 1-chloro-3,3,3-trifluoropropene; propylene glycol monomethyl Glycol ethers such as ether, dipropylene glycol monobutyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, 3-methoxy-3-methylbutanol; 3-methoxy-3-methylbutyl acetate carbonate esters such as dimethyl carbonate, diethyl carbonate, propyl carbonate; and lactones such as γ-butyllactone.
Note that the above-mentioned organic solvents can be used alone or in a mixture of two or more.

Among them, the organic solvent is selected from the group consisting of hydrocarbons, alcohols, ethers, ketones, amides, esters, nitriles, hydrofluorocarbons, hydrofluoroethers, perfluorocarbons, and hydrofluoroolefins. It is preferable to contain at least one solvent containing fluorine atoms, more preferably to contain a fluorine atom-containing solvent (fluorine-based solvent), even more preferably to contain hydrofluorocarbons, and preferably to contain cyclic hydrofluorocarbons. More preferably, it contains 1,1,2,2,3,3,4-heptafluorocyclopentane. This is because hydrofluorocarbons are nonflammable, have excellent stability in the presence of water, have low toxicity, and have zero ozone depletion potential. In addition, 1,1,2,2,3,3,4-heptafluorocyclopentane has an appropriate boiling point to be handled as a solvent and can be advantageously used in the manufacture and cleaning of semiconductor devices. It is.

The organic solvent may be an azeotropic composition.
From the viewpoints of being advantageously usable in the manufacture and cleaning of semiconductor devices and easily forming an azeotropic composition, the organic solvent is preferably a mixture of a fluorine-based solvent and an alcohol having 5 or less carbon atoms, more preferably a mixture of 1,1,2,2,3,3,4-heptafluorocyclopentane and at least one selected from the group consisting of tert-amyl alcohol, benzyl alcohol and phenethyl alcohol, and even more preferably a mixture of 1,1,2,2,3,3,4-heptafluorocyclopentane and tert-amyl alcohol.

Note that the organic solvent may contain additives such as a phenolic antioxidant and a surfactant.

[Phenolic antioxidant]
Here, the phenolic antioxidant that may be optionally contained in the organic solvent is not particularly limited, and examples thereof include phenol, 2,6-di-t-butylphenol, 2,6-di-t-butyl- Examples include p-cresol and butylhydroxylanisole. Among these, 2,6-di-t-butyl-p-cresol is preferred as the phenolic antioxidant from the viewpoint of imparting a high antioxidant effect to the purified product obtained by the organic solvent purification method of the present invention. preferable.
The above-mentioned phenolic antioxidants can be used alone or in combination of two or more.
The concentration of the phenolic antioxidant in the organic solvent can be, for example, 1% by mass or more and 5% by mass or less.

[Surfactant]
The surfactant that may be optionally contained in the organic solvent is not particularly limited, but a nonionic surfactant is preferred from the viewpoint of easily imparting excellent cleaning properties to the purified product obtained by the method for purifying an organic solvent of the present invention.
The concentration of the surfactant in the organic solvent may be, for example, 1% by mass or more and 5% by mass or less.

The proportions of the organic solvent and the optional phenolic antioxidant and surfactant can be appropriately set depending on the purpose of use of the purified product obtained by the organic solvent purification method of the present invention.

<Pretreatment process (γ)>
Here, in the pretreatment step (γ) which may be optionally carried out before the step (α), for example, coarse particles contained in the organic solvent filtered in the step (α) are removed. By carrying out the pretreatment step (γ) before the step (α), it is possible to prevent the filter used in the step (α) from being clogged by the coarse particles and to prevent the life of the filter from being shortened.

Here, the method for removing coarse particles in the organic solvent in the pretreatment step (γ) is not particularly limited, and examples thereof include a method of filtering the organic solvent using a filter material such as a pretreatment filter having any mesh size. In this case, pressure filtration or vacuum filtration may be performed under any pressure.

In addition, when step (β) is carried out before step (α) in the method for purifying an organic solvent of the present invention, the pretreatment step (γ) may be carried out before step (β) or between step (β) and step (α).

<Process (α)>
In step (α), the organic solvent is filtered using a filter. Note that the organic solvent may be filtered in air, for example, under an inert gas atmosphere such as an argon atmosphere or a nitrogen atmosphere. Furthermore, filtration may be performed using a general liquid filtration device, or may be performed by installing a filter at a location on an industrial line such as a chemical supply device where the organic solvent as a chemical solution passes. However, it is also possible to conduct the process in multiple stages by connecting units in which filters are packed in containers in series.

〔filter〕
The organic solvent filtered through the filter usually contains fine particles.
The filter used in step (α) is not particularly limited as long as it is capable of separating at least the fine particles from the organic solvent, and may be a filter made of an organic material or a filter made of an inorganic material, but a filter made of an organic material is preferable.

In particular, when the organic solvent contains a fluorine-based solvent, it is preferable to use a filter made of a material containing fluorine atoms in order to effectively separate fine particles.

The material containing fluorine atoms is not particularly limited, and is preferably, for example, a polymer containing at least one fluorine-containing monomer unit selected from the group consisting of a tetrafluoroethylene unit, a chlorotrifluoroethylene unit, a vinylidene fluoride unit, a perfluoroalkyl vinyl ether unit, and a hexafluoropropylene unit.
The polymer may contain, optionally, a non-fluorine-containing monomer unit. The non-fluorine-containing monomer unit is not particularly limited, and examples thereof include an ethylene unit and a propylene unit.
In this specification, "containing a monomer unit" means that "a polymer obtained by using the monomer contains a repeating unit derived from the monomer".

The proportion of fluorine-containing monomer units in the above polymer is preferably 80% by mass or more, more preferably 90% by mass or more, and 100% by mass, that is, the material containing fluorine atoms , a homopolymer of a fluorine-containing monomer is more preferable. Here, the content ratio of each monomer unit contained in the polymer can be determined, for example, by measuring ¹ H-NMR and ¹⁹ F-NMR.

The above-mentioned polymer is not particularly limited, and examples thereof include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, chlorotrifluoroethylene-ethylene copolymer, etc. Among these, the polymer is most preferably polytetrafluoroethylene.

The pore size of the filter is preferably 30 nm or less, more preferably 20 nm or less, even more preferably 15 nm or less, and preferably 0.1 nm or more, and 0.2 nm or more. It is more preferable that the particle size is at least 0.5 nm, and even more preferably 0.5 nm or more. When the pore size of the filter is 30 nm or less, fine particles with a particle size of 30 nm or more contained in the organic solvent are removed by the filter, so that a purified product with reduced fine particles can be obtained more effectively.

[Filtration conditions]
In step (α), the flow rate per effective filtration area of the filter when filtering the organic solvent is preferably less than 0.2 mL/min· ^cm2 , more preferably 0.15 mL/min· ^cm2 or less, even more preferably 0.1 mL/min· ^cm2 or less, and preferably 0.001 mL/min·cm2 or ^more , more preferably 0.002 mL/min· ^cm2 or more. By setting the flow rate of the organic solvent per effective filtration area of the filter to less than 0.2 mL/min· ^cm2 , it is possible to sufficiently reduce fine particles in the purified product. In addition, when filtering in multiple stages by connecting units each composed of a filter packed in a container in series, the effective filtration area of the filter is the effective filtration area of all the filters used.

The pressure in step (α) may be appropriately set in consideration of the pore size of the filter used, the filtration rate, etc., but from the viewpoint of improving the filtration efficiency, it is preferable to carry out the process under pressure. In this case, the pressure applied is usually 0.001 MPa or more, preferably 0.01 MPa or more, and usually 0.5 MPa or less, preferably 0.3 MPa or less.

Further, the temperature in step (α) may be appropriately set in consideration of the boiling point of the organic solvent to be filtered, but the upper limit of the temperature is usually at least 10°C lower than the boiling point of the organic solvent, and is preferably is a temperature lower by 15°C or more, more preferably a temperature lower by 20°C or more. Further, the lower limit of the temperature is not particularly limited, but is usually a temperature higher than the freezing point of the organic solvent by 1°C or more, preferably 2°C or more, and more preferably 5°C or more.

[Properties of filtrate]
The filtrate obtained by filtering the organic solvent through a filter in step (α) (organic solvent after filtration) usually has a number of fine particles with a particle size of 30 nm or more of 100 particles/mL or less. Specifically, the number of fine particles with a particle size of 30 nm or more and less than 100 nm contained in the filtrate is usually 95 particles/mL or less. Further, the number of fine particles having a particle size of 100 nm or more contained in the filtrate is usually 5 particles/mL or less.
Note that the "number of fine particles" can be measured using the method described in Examples.

<Process (β)>
In step (β), the organic solvent is dehydrated using the organic solvent dehydration method of the present invention. Specifically, step (β) includes a step (A) of preparing a dehydration gas, and a step (B) of bringing the dehydration gas prepared in step (A) into contact with an organic solvent. Dehydrate the organic solvent using a dehydration method. Then, step (A) is a step (a1) of passing gas whose dew point is -30°C or lower through a gas filter to obtain dehydration gas, or reducing the dew point of the gas that has passed through the gas filter to -30°C or lower. It is necessary to include a step (a2) of adjusting and obtaining a dehydration gas. Note that step (β) may include steps other than step (A) and step (B). Further, step (A) may include steps other than step (a1) and step (a2).
In step (β), the dehydration gas obtained by passing gas with a dew point of -30°C or lower through a gas filter, or the dehydration gas obtained by adjusting the dew point of the gas passed through a gas filter to -30°C or lower. Since a dehydrating gas is used, the organic solvent can be dehydrated while suppressing an increase in the number of fine particles. Note that from the viewpoint of further suppressing the increase in the number of fine particles, it is preferable to use a dehydrating gas obtained by passing a gas having a dew point of −30° C. or lower through a gas filter in step (β). If gas whose dew point has been adjusted in advance to -30°C or less is passed through a gas filter to be used as a dehydration gas, it is possible to suppress fine particles mixed in during dew point adjustment from being brought into the dehydration gas.

〔gas〕
Here, the gas having a dew point of -30°C or lower that is passed through the gas filter in step (a1) and the gas that is passed through the gas filter in step (a2) are not particularly limited, and examples include hydrogen, air, etc. , oxygen, nitrogen, helium, neon, argon, krypton, xenon, carbon monoxide, and carbon dioxide. By using these gases, it is possible to effectively dehydrate the organic solvent while suppressing the occurrence of side reactions.
Among them, from the viewpoint of easy availability, the gases with a dew point of -30°C or lower that are passed through the gas filter in step (a1) and the gases that are passed through the gas filter in step (a2) are air, oxygen, nitrogen, and helium. Or argon is preferable.

In the steps (a1) and (a2), the gas having a dew point of −30° C. or lower can be prepared by using a known method such as cooling dehumidification or compression dehumidification.
From the viewpoint of effectively dehydrating the organic solvent, the dew point of the gas passed through the gas filter in step (a1) is preferably −60° C. or lower. In step (a2), the dew point of the gas passed through the gas filter is preferably adjusted to −60° C. or lower.

[Gas filter]
The gas filter is not particularly limited, and may be a resin filter such as a polypropylene (PP) gas filter or a polytetrafluoroethylene (PTFE) gas filter, or a metal filter such as a SUS filter or a nickel filter.

In the gas filter, the minimum particle diameter (captured particle diameter) at which the particle capture rate is 99.9% or more when particles are passed through is preferably 0.03 μm or less, and preferably 0.01 μm or less. It is more preferable that it is, and it is even more preferable that it is 0.003 μm or less. If the captured particle diameter is below the upper limit value, it is possible to obtain a dehydrating gas with a small number of fine particles, so that the organic solvent can be dehydrated while satisfactorily suppressing an increase in the number of fine particles.

[Ventilation conditions]
The temperature, pressure and flow rate at which the gas is passed through the gas filter in the steps (a1) and (a2) can be appropriately set.

〔contact〕
The contact of the dehydration gas with the organic solvent in step (B) is not particularly limited, and can be carried out, for example, by blowing (bubbling) the dehydration gas into the organic solvent or by spraying the organic solvent into the dehydration gas.

Among these, from the viewpoint of ease of operation, it is preferable to contact the dehydration gas with the organic solvent by blowing the dehydration gas into the organic solvent.
More specifically, in the step (β), for example, a dehydrating apparatus 10 as shown in FIG. 2 is used, and a gas having a dew point of −30° C. or less that has been passed through a gas filter 2 is diffused directly from an aeration tube 3 into the organic solvent stored in a vessel 1 to dehydrate the organic solvent.

[Contact conditions]
Here, the temperature at which the dehydration gas and the organic solvent are brought into contact is not particularly limited as long as it is above the freezing point of the organic solvent, but the organic solvent will solidify due to the heat of vaporization of the organic solvent, making bubbling impossible. From the viewpoint of preventing the freezing point, the temperature is preferably +5°C or higher, and from the viewpoint of preventing excessive vaporization of the organic solvent, the boiling point of the organic solvent is preferably -20°C or lower.
In addition, when blowing a dehydrating gas into an organic solvent, the volume of the gas that is brought into contact with the organic solvent is not particularly limited as long as it can be dehydrated, but from the perspective of obtaining a sufficient dehydrating effect, it should be at least 1 times the volume of the organic solvent. From the viewpoint of preventing excessive vaporization of the organic solvent, the volume is preferably 200 times or less relative to the volume of the organic solvent.

The water content in the dehydrated organic solvent is preferably 10 mass ppm or less, more preferably 5 mass ppm or less.
Note that the "moisture content" can be measured using the method described in Examples.

<Refined product>
The purified product obtained using the method for purifying an organic solvent of the present invention contains at least the organic solvent, and may optionally further contain other components such as a phenolic antioxidant and a surfactant.

The number of particles having a particle diameter of 30 nm or more in the purified product is preferably 100 particles/mL or less, more preferably 95 particles/mL or less, even more preferably 60 particles/mL or less, and particularly preferably 30 particles/mL or less. Specifically, the number of particles having a particle diameter of 30 nm or more and less than 100 nm in the purified product is preferably 95 particles/mL or less, more preferably 60 particles/mL or less, and even more preferably 30 particles/mL or less. The number of particles having a particle diameter of 100 nm or more in the purified product is preferably 5 particles or less, more preferably 4 particles or less, and even more preferably 3 particles or less.

In addition, the moisture content in the purified product is preferably 10 ppm by mass or less, and more preferably 5 ppm by mass or less.

The refined product has a reduced number of fine particles and a reduced amount of water, making it suitable for use as a solvent in the manufacture and cleaning of fine semiconductors.

EXAMPLES Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Note that the evaluation in this example was performed by the following method.
(1) Moisture content Measurement was performed three times using a Karl Fischer moisture meter (manufactured by Mitsubishi Analytic, CA-200), and the average value of the three measurements was taken as the water content in the organic solvent.
(2) Number of fine particles The number of fine particles with a particle size of 30 nm or more contained in the organic solvent was measured three times at a temperature of 23°C using a liquid particle counter (KS-19F, manufactured by RION). The average value of the measured values was taken as the number of fine particles in the organic solvent.

(Example 1)
<Production of filtration device>
As a filtration device, three units in which one filter was packed in one container were prepared, and a multistage filtration device was produced in which these units were connected in series in three stages.
As the filter packed in each unit, Filter A (manufactured by Entegris, PFFW15C3S, pore diameter: 15 nm, filtration area: 1300 cm ² ) made of polytetrafluoroethylene (PTFE) was used.
<Process (α)>
Organic solvent consisting of 1,1,2,2,3,3,4-heptafluorocyclopentane (number of particles with a particle size of 30 nm or more: 40,000 pieces/mL, water content: 50 mass ppm, boiling point: 82.5 ° C.) was placed in a pressurized container and heated to 30°C, and then the 1,1,2,2,3,3,4-heptafluorocyclopentane heated to 30°C in a high-purity argon atmosphere was heated to 30°C. Using a filtration device, the mixture was filtered at a filtration rate of 130 mL/min under a pressure of 0.02 MPa to obtain a filtrate (organic solvent after filtration).
The liquid passing rate per effective filtration area of the filter (=[filtration rate (mL/min)]/[filtration area (cm ² )]) was 0.1 mL/min·cm ² .
Then, the water content and the number of fine particles in the filtrate were measured. The results are shown in Table 1.
<Process (β)>
In a class 100 clean room, a pressure reducing valve, a float type flow meter, and a gas filter (manufactured by Entegris, WGMS02PRU, captured particle size: 0.003 μm) are connected from the upstream side with stainless steel piping, and 1/8 is connected to the end of the piping. A gas line was created by connecting inch PFA tubing. From the upstream side of this gas line, nitrogen gas with a dew point of -60°C generated by a cold evaporator was brought to a pressure of 0.08 MPa using a pressure reducing valve, and adjusted so that the measured value of the float type flow meter was 2 L/min. It was allowed to circulate for 30 minutes.
Next, 1.5 kg of the filtrate obtained in step (α) was placed in a brown bottle that had been dried after performing alkalization treatment and ultrapure water washing, and was heated to 30°C. Thereafter, a 1/8-inch PFA tube was inserted into the brown bottle, and nitrogen gas with a dew point of -60°C was bubbled from the bottom at a gas flow rate of 2 L/min for 30 minutes at a temperature of 30°C. After bubbling, 1,1,2,2,3,3,4-heptafluorocyclopentane as a purified product was sampled from the brown bottle, and the water content and the number of fine particles were measured. The results are shown in Table 1.

(Example 2)
Fabrication and process of a filtration device were carried out in the same manner as in Example 1, except that in step (β), argon gas (dew point: -80°C) filled in an argon cylinder was used instead of nitrogen gas with a dew point of -60°C. (α) and step (β) were performed to obtain a purified product. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

Example 3
A filtration apparatus was prepared and steps (α) and (β) were carried out in the same manner as in Example 1, except that in step (β), compressed air controlled at a dew point of −30° C. was used instead of nitrogen gas with a dew point of −60° C., to obtain a purified product. Evaluation was then carried out in the same manner as in Example 1. The results are shown in Table 1.

(Example 4)
Fabrication and process of a filtration device were carried out in the same manner as in Example 1, except that in step (β), helium gas (dew point: -80°C) filled in a helium cylinder was used instead of nitrogen gas with a dew point of -60°C. (α) and step (β) were performed to obtain a purified product. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 5)
Fabrication and process of a filtration device were carried out in the same manner as in Example 1, except that in step (β), oxygen gas (dew point: -80°C) filled in an oxygen cylinder was used instead of nitrogen gas with a dew point of -60°C. (α) and step (β) were performed to obtain a purified product. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative example 1)
Fabrication of a filtration device, process ( α) and step (β) were performed to obtain a purified product. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative example 2)
Fabrication of a filtration device, process ( α) and step (β) were performed to obtain a purified product. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
A filtration device was prepared and steps (α) and (β) were carried out in the same manner as in Comparative Example 1, except that in step (β), compressed air controlled at a dew point of 0° C. was used instead of nitrogen gas with a dew point of −60° C., to obtain a purified product. Evaluation was then carried out in the same manner as in Example 1. The results are shown in Table 1.

(Comparative example 4)
Fabrication of a filtration device, and steps (α) and (β) were carried out in the same manner as in Example 1, except that in step (β), nitrogen gas with a dew point of 0°C was used instead of nitrogen gas with a dew point of -60°C. A purified product was obtained. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Reference example 1)
<Production of filtration device>
A multistage filtration device was produced in the same manner as in Example 1.
<Process (α)>
In the same manner as in Example 1, 1,1,2,2,3,3,4-heptafluorocyclopentane (number of fine particles with a particle size of 30 nm or more: 40,000 pieces/mL, water content: 50 mass ppm, boiling point: 82. 5° C.) was filtered to obtain a filtrate (organic solvent after filtration).
Then, when the water content and the number of fine particles of the filtrate were measured, the water content was 100 mass ppm, and the number of fine particles was 16 pieces/mL.
<Process (β')>
The filtrate obtained in step (α) and Molecular Sieve 5A as a dehydrating agent were added to the brown bottle, which had been dried after being dealkalized and washed with ultrapure water, in a class 100 clean room. The mixture was added so that the concentration was 10% by mass, and the mixture was shaken at a temperature of 25° C. for 24 hours. Thereafter, 1,1,2,2,3,3,4-heptafluorocyclopentane as a purified product was sampled from the brown bottle, and the water content and the number of fine particles were measured. The water content of the purified product was 1 mass ppm. In addition, the purified product was cloudy and the number of fine particles could not be measured (exceeded the upper limit of measurement).

(Reference example 2)
<Production of filtration device>
A multistage filtration device was produced in the same manner as in Example 1.
<Process (α)>
In the same manner as in Example 1, 1,1,2,2,3,3,4-heptafluorocyclopentane (number of fine particles with a particle size of 30 nm or more: 40,000 pieces/mL, water content: 50 mass ppm, boiling point: 82. 5° C.) was filtered to obtain a filtrate (organic solvent after filtration).
Then, when the water content and the number of fine particles of the filtrate were measured, the water content was 60 mass ppm, and the number of fine particles was 16 pieces/mL.
<Process (β')>
The filtrate obtained in step (α) is passed through a packed tower filled with molecular sieve 5A as a dehydrating agent in a class 100 clean room at a temperature of 25°C and a liquid hourly space velocity (LHSV) of 5 h ^-1 . 1,1,2,2,3,3,4-heptafluorocyclopentane was obtained as a purified product. Then, the water content and the number of fine particles of the purified product were measured. The water content of the purified product was 1 mass ppm, and the number of fine particles was unmeasurable (exceeded the upper limit of measurement).

From Table 1, it can be seen that in Examples 1 to 5, purified products were obtained in which both the water content and the number of fine particles were favorably reduced.
On the other hand, Table 1 shows that in Comparative Examples 1 to 3 in which no gas filter was used, it was not possible to suppress the increase in the number of fine particles during dehydration, and the number of fine particles in the purified product increased. Furthermore, it can be seen that in Comparative Examples 3 and 4 in which a gas with a dew point of 0° C. was used, the organic solvent could not be sufficiently dehydrated.
In addition, from Reference Examples 1 and 2, even when dehydration is performed by bringing a solid dehydrating agent such as molecular sieve into direct contact with an organic solvent, it is not possible to suppress the increase in the number of fine particles during dehydration, and the purification It can be seen that the number of fine particles in the object increases.

According to the method for dehydrating an organic solvent of the present invention, an organic solvent can be dehydrated while suppressing an increase in the number of fine particles.
Furthermore, according to the method for purifying an organic solvent of the present invention, a purified product can be obtained in which both the water content and the number of fine particles are reduced satisfactorily.

1 Container 2 Gas filter 3 Air diffuser 10 Dehydrator

Claims (8)

A step (A) of preparing a dehydration gas;
(B) contacting the dehydration gas with an organic solvent;
Including,
The step (A) includes a step (a1) of passing a gas having a dew point of −30° C. or less through a gas filter to obtain a gas for dehydration, or a step (a2) of adjusting the dew point of the gas passed through the gas filter to −30° C. or less to obtain a gas for dehydration,
The gas filter has a particle size of 0.03 μm or less, which results in a particle capture rate of 99.9% or more when particles pass through the gas filter. The organic solvent is selected from the group consisting of hydrocarbons, alcohols, ethers, ketones, amides, esters, nitriles, hydrofluorocarbons, hydrofluoroethers, perfluorocarbons, and hydrofluoroolefins. The method for dehydrating an organic solvent according to claim 1, comprising at least one type of solvent. A method for dehydrating an organic solvent according to claim 1 or 2, wherein the organic solvent comprises 1,1,2,2,3,3,4-heptafluorocyclopentane. A method for dehydrating an organic solvent according to any one of claims 1 to 3, wherein the organic solvent is an azeotropic composition. A method for dehydrating an organic solvent described in any one of claims 1 to 4, wherein the organic solvent is a mixture of 1,1,2,2,3,3,4-heptafluorocyclopentane and tert-amyl alcohol. A method for dehydrating an organic solvent according to any one of claims 1 to 5, wherein the gas is at least one selected from the group consisting of hydrogen, air, oxygen, nitrogen, helium, neon, argon, krypton, xenon, carbon monoxide and carbon dioxide. a step (α) of filtering the organic solvent;
a step (β) of dehydrating the organic solvent using the method for dehydrating an organic solvent according to any one of claims 1 to 6;
A method for purifying an organic solvent, including: The method for purifying an organic solvent according to claim 7, wherein in the step (β), the organic solvent filtered in the step (α) is dehydrated.

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