JP2015169586A - Method of cutting porous member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a porous member to be cut at a normal temperature while maintaining a state of the porous member filled with an impregnant and to allow the impregnant to be easily removed from the porous member.SOLUTION: A method of cutting a porous member includes an impregnation step of heating a molten salt which is solidified at a normal temperature, to fuse it and impregnating the porous member with the molten salt being in a liquid state; a solidification step of cooling the porous member impregnated with the molten salt to solidify the molten salt; a cutting step of cutting the porous member solidified with the molten metal; and a removal step of heating the cut porous member to fuse the molten salt and removing the molten salt from the porous member.

Description

  The present invention relates to a method for cutting a porous member. In particular, the present invention relates to a porous member cutting method that can be filled with an impregnating agent in a porous member and can be cut at room temperature while maintaining the state of the porous member, and can easily remove the impregnating agent from the porous member.

  Porous members made of resin, metal, or glass are used for various purposes. For example, a positive electrode current collector such as a nickel metal hydride battery or a lithium ion battery is a porous metal body made of nickel or aluminum (eg, “Celmet (registered trademark)”), and a separator is polyethylene (PE) or polypropylene (PP). Porous membranes (nonwoven fabrics) made of polyolefin resins such as are used.

  In order to evaluate and inspect such a porous member, it is possible to analyze the internal structure (structure) by preparing a sample for cross-sectional observation and observing the cross-section using an optical microscope or an electron microscope. Has been done. In order to observe the internal structure of the porous member, the cross-section is maintained while maintaining the state of the porous member without breaking the internal structure such as the shape of the skeleton (fiber) constituting the porous member and the pores inside the porous member. It is important to form Therefore, in general, the cross-sectional observation sample is obtained by embedding and hardening a porous member in a resin and cutting it using a microtome, an ion beam, or the like.

  In addition, for example, Patent Documents 1 and 2 disclose a method of forming a cross section of a porous member. Patent Document 1 describes that, in order to observe the internal structure of a porous fiber in a wet state, the dried fiber is embedded in a resin, then processed in cross section, and then the embedded resin is removed from the fiber. Has been. Patent Document 2 describes that a porous member made of synthetic resin is impregnated with alcohol and frozen, and then the frozen porous member is broken.

JP2013-92420A JP 2010-85173 A

  In the conventional method of cutting the porous member by filling the porous member with an impregnating agent such as resin or alcohol, it is difficult to remove the resin, or it is necessary to cool to a low temperature in order to solidify the alcohol. There are problems such as.

  For example, when a porous member is embedded in a resin, when the sample is cut out and the cross section is observed, the depth direction near the cross section cannot be observed with the filled resin, and only the internal structure at the cutting position can be observed. . That is, it is almost impossible to observe a three-dimensional cross section. Therefore, it is conceivable to remove the resin from the sample, but it is not easy to remove the resin once crosslinked and solidified without causing deformation or alteration of the porous member. Patent Document 1 proposes a method of etching with plasma as a method of removing the embedding resin after cross-section processing of the sample. However, such a method takes time and increases the equipment cost.

  On the other hand, in Patent Document 2, as a typical example, a freezing treatment is performed by immersing a porous member impregnated with ethanol in liquid nitrogen, but the working environment is restricted because the freezing treatment is performed at a very low temperature. For example, in the evaluation and inspection of a porous member, depending on the use of the porous member, it is desired to carry out from preparation of the sample to observation in the absence of exposure to the atmosphere in order to avoid alteration due to contact with moisture or oxygen. Therefore, it is conceivable to proceed with the work in the glove box, but if a cryogenic coolant such as liquid nitrogen is used in the glove box, the glove box is also cooled to a very low temperature, and the glove box is damaged by the effect. Can happen. In addition, when introducing a sample into the glove box, in order to remove moisture as much as possible, the sample is put in a spare chamber connected to the glove box, and evacuation and inert gas (eg, Ar gas) in the spare chamber are replaced. Gas introduction may be repeated several times alternately. At that time, the liquid nitrogen may be volatilized and lost by evacuation.

  The present invention has been made in view of the above circumstances, and one of the objects of the present invention is that the porous member is filled with an impregnating agent and can be cut at room temperature while maintaining the state of the porous member. An object of the present invention is to provide a porous member cutting method that can easily remove the impregnating agent from the porous member.

A porous member cutting method according to an aspect of the present invention includes the following steps.
An impregnation step of heating and melting a molten salt that solidifies at room temperature, and impregnating the porous member with the molten salt in a liquid state.
A solidification step of cooling the porous member impregnated with the molten salt to solidify the molten salt;
A cutting step of cutting the porous member solidified with the molten salt.
A removal step of heating the cut porous member to melt the molten salt and removing the molten salt from the porous member.

  The porous member cutting method can fill the porous member with the impregnating agent and cut the porous member at room temperature while maintaining the state of the porous member, and can easily remove the impregnating agent from the porous member.

2 is a cross-sectional photomicrograph of Sample 1. It is a cross-sectional microscope picture of the sample 2-1. It is a cross-sectional photomicrograph of Sample 2-2.

  As a result of various trials and errors, the present inventors have found that the above problem can be solved by using a molten salt as an impregnating agent.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.

(1) The porous member cutting method according to the embodiment includes the following steps.
An impregnation step in which molten salt that is solidified at room temperature is heated and melted to impregnate a porous member with molten salt in a liquid state.
A solidification step of solidifying the molten salt by cooling the porous member impregnated with the molten salt.
A cutting step of cutting the porous member solidified with the molten salt.
A removal step of heating the cut porous member to melt the molten salt and removing the molten salt from the porous member.

  According to the method for cutting a porous member, the porous member is impregnated with a molten salt in a liquid state, cooled and solidified, so that the porous member can be cut at room temperature while maintaining the state of the porous member. In addition, after cutting, the molten salt can be easily removed from the porous member by heating to melt the molten salt.

  The molten salt used in the porous member cutting method solidifies at room temperature (20 ° C. ± 15 ° C.), is solid at room temperature, and melts into liquid when heated. Therefore, the porous member can be easily impregnated with the molten salt by heating the molten salt to a temperature equal to or higher than the melting point to melt the molten salt. Moreover, the porous member impregnated with the molten salt can be cooled at room temperature to solidify the molten salt, and the state of the porous member can be maintained. Therefore, by solidifying the porous member with molten salt, the porous member can be cut at normal temperature while maintaining the state of the porous member without destroying the internal structure of the porous member. Furthermore, if the porous member is heated to a temperature equal to or higher than the melting point of the molten salt after cutting, the molten salt melts into a liquid state, so that the molten salt can be easily removed from the porous member. In addition, if it is a molten salt, the porous member is less likely to be altered. The solidified molten salt is easily brittle because it is a brittle material, and it is easy to obtain a good cross section by cutting the porous member solidified with the molten salt.

  (2) As one form of the said porous member cutting processing method, it is mentioned that melting | fusing point of molten salt is 30 degreeC or more and 140 degrees C or less.

  Molten salt is a material that solidifies at room temperature (20 ° C. ± 15 ° C.). The melting point of the molten salt is preferably not less than room temperature and a temperature that does not cause alteration or damage of the porous member. Thereby, in the impregnation step, the molten salt is heated and melted, and when the porous member is impregnated with the molten salt in the liquid state or in the removal step, the porous member is heated to melt the molten salt, When removing the molten salt from the member, it is possible to prevent the porous member from being altered or damaged due to high temperatures. That is, in the impregnation step and the removal step, the temperature of the molten salt in the liquid state and the heating temperature of the porous member can be made lower than the temperature at which the porous member is altered or damaged. Specifically, the melting point of the molten salt is preferably 30 ° C. or higher and 140 ° C. or lower. The lower limit of the melting point of the molten salt is further 40 ° C. or higher and 50 ° C. or higher. On the other hand, the upper limit is 120 ° C. or lower, 90 ° C. or lower, and 70 ° C. or lower. The lower the melting point of the molten salt, the more effectively the deterioration and damage of the porous member can be prevented, and the heating temperature of the molten salt in the impregnation step and the heating temperature of the porous member in the removal step can be lowered.

  (3) As one form of the cutting method of the porous member, the molten salt contains one or more kinds selected from alkali metals and alkaline earth metals as cations, and FSA, TFSA or FTA as anions It may be a single salt or a mixed salt thereof.

The molten salt includes one or more selected from alkali metals and alkaline earth metals as cations, and includes FSA (bisfluorosulfonylamide; [(FSO ₂ ) ₂ N] ⁻ ), TFSA (bistrifluoromethylsulfonyl). An amide; [(CF ₃ SO ₂ ) ₂ N] ⁻ ) or FTA (fluorotrifluoromethylsulfonylamide; [(FSO ₂ ) (CF ₃ SO ₂ ) N] ⁻ ) as an anion or a mixed salt thereof It can be suitably used. Such a molten salt can have a low melting point and can realize a low melting point of 140 ° C. or lower. Furthermore, it is possible to lower melting | fusing point more by setting it as the mixed salt which mixed multiple types of single salt. For example, a mixed salt (NaFSA-KFSA) of NaFSA with Na as a cation and FSA as an anion and KFSA with K as a cation and FSA as an anion can be used as the molten salt.

  (4) As one form of the porous member cutting method, the viscosity of the molten salt in a liquid state is 3.5 Pa · s or less.

  When the viscosity of the molten salt in the liquid state is 3.5 Pa · s or less, the fluidity is high, and in the impregnation step, the molten salt easily penetrates and fills the pores inside the porous member, and in the removal step The molten salt can be efficiently removed from the porous member. The viscosity of the molten salt is a value measured at a temperature immediately before impregnation (at the start), for example, a value measured in a temperature range 10 ° C. to 20 ° C. higher than the melting point.

  (5) As one form of the method for cutting the porous member, in the impregnation step, the porous member is immersed in a molten salt in a liquid state in a vacuum atmosphere, and the porous member is impregnated with the molten salt. Can be mentioned.

  By immersing the porous member in a molten salt in a liquid state under a vacuum atmosphere, the molten salt penetrates into the fine pores inside the porous member, making it easy to densely fill the porous member. Can be impregnated well.

  (6) One form of the porous member cutting method includes cutting the porous member by cleaving in the cutting step.

  By cutting the porous member by cleaving, the internal structure of the porous member is not easily broken by the stress at the time of cutting, and it is easy to obtain a smooth and better cross section.

  (7) As one form of the cutting method of the porous member, in the removing step, after the molten salt is melted to remove the molten salt from the porous member, the porous member is further washed with a solvent. It is done.

  In addition to melting the molten salt to remove the molten salt from the porous member, it is easy to completely remove the molten salt from the porous member by washing the porous member with a solvent. For example, acetonitrile can be used as the solvent.

[Details of the embodiment of the present invention]
A specific example of the porous member cutting method according to the embodiment of the present invention will be described. In addition, this invention is not limited to these illustrations, is shown by the claim, and is intended that all the changes within the meaning and range equivalent to the claim are included.

<Cutting method of porous member>
The porous member cutting method according to the embodiment includes the following impregnation step, solidification step, cutting step, and removal step.
Impregnation step: The molten salt that is solidified at room temperature is heated and melted, and the porous member is impregnated with the molten salt in a liquid state.
Solidification step: The porous member impregnated with the molten salt is cooled to solidify the molten salt.
-Cutting process: The porous member solidified with molten salt is cut.
Removal step: The cut porous member is heated to melt the molten salt, and the molten salt is removed from the porous member.
First, the porous member to be cut and the molten salt used for the impregnating agent will be described, and then each step will be described in detail.

(Porous member)
The porous member is formed of a member or material having a porous structure (tissue) having a large number of pores (particularly, open pores) inside. Examples of the porous member include a foam having a spongy network skeleton, a particle aggregate in which particles are bonded, a woven or knitted fabric in which fibers are woven or knitted, and a nonwoven fabric in which fibers are entangled or bonded. Fiber aggregates. The material of the porous member is not particularly limited, such as resin, metal, glass, and ceramic. Examples of the porous member include a porous metal body made of nickel or aluminum (eg, “Celmet (registered trademark)”) used for a positive electrode current collector such as a nickel metal hydride battery or a lithium ion battery, or a separator. Examples thereof include a porous film (nonwoven fabric) made of a polyolefin-based resin. In addition, there are porous membranes made of carbon fibers used for electrodes of redox flow batteries, and porous membranes made of fluororesins such as polytetrafluoroethylene (PTFE) used for diaphragms (ion exchange membranes). Can be mentioned. Furthermore, the porous membrane which consists of glass fiber and PTFE currently used for the separator of a molten salt battery is mentioned. In addition, a porous membrane made of PTFE (eg, “PORFLON (registered trademark)”) used for a filtration membrane for water treatment can be mentioned.

(Characteristics of molten salt)
In the porous member cutting method according to the embodiment, preferable characteristics required for the impregnating agent are as follows. (1) A temperature that causes a phase change (state change) due to a temperature change, has a melting point of normal temperature (20 ° C. ± 15 ° C.) or more, and does not cause deterioration or damage of the porous member. (2) The porous member should not be altered. (3) It has fluidity in a liquid state (molten state) and can be easily impregnated and removed. (4) It is brittle in the solid state (solidified state) and has a cleavage property. As a material that satisfies all of the required characteristics, a molten salt can be cited.

By satisfying the characteristics of (1) above, the porous member is impregnated with molten salt melted by heating, and then cooled at room temperature to solidify the molten salt, and the porous member solidified with molten salt is cut at room temperature it can. Further, when the molten salt is heated and melted for impregnation / removal, the heating temperature can be made lower than the temperature at which the porous member is altered or damaged, and the porous member can be prevented from being altered or damaged due to high temperature. In addition, there is no need for freezing at a low temperature (for example, 0 ° C. or lower), and there are few restrictions on the working environment. By satisfy | filling the characteristic of said (2), a porous member does not react with molten salt and a quality change is not produced in a porous member. By satisfying the above property (3), the molten salt melted by heating penetrates and fills the pores inside the porous member, and is easily removed from the porous member efficiently. When the porous member solidified with the molten salt is cut by satisfying the above characteristic (4), the porous member is cleaved following the molten salt, and it is easy to obtain a good cross section with less sagging and deformation. . In addition, since the molten salt has a vapor pressure of almost 0 (less than 1 × 10 ⁻³ Pa) and is nonflammable, it has high safety.

(Melting point of molten salt)
It is preferable that melting | fusing point of molten salt is 30 degreeC or more and 140 degrees C or less. By satisfying such a melting point, the molten salt can be solidified by cooling at room temperature, and the heating temperature when impregnating / removing the molten salt by heating and melting is less than the temperature at which the porous member is altered or damaged. As a result, the porous member can be prevented from being altered or damaged by high temperatures. The lower limit of the melting point of the molten salt is further 40 ° C. or higher and 50 ° C. or higher. On the other hand, the upper limit is further preferably 120 ° C. or lower, 90 ° C. or lower, and 70 ° C. or lower. The lower the melting point of the molten salt, the more effectively the alteration and damage of the porous member can be prevented. Can be lowered.

(Viscosity of molten salt)
The viscosity of the molten salt in the liquid state is preferably 3.5 Pa · s or less. When the viscosity of the molten salt in the liquid state is 3.5 Pa · s or less, the fluidity is high, and when the porous member is impregnated with the molten salt, the molten salt penetrates and fills the pores inside the porous member. In addition, the molten salt can be efficiently removed from the porous member in the removing step. The viscosity of the molten salt is more preferably 2.5 Pa · s or less. Note that the viscosity of the molten salt is a value measured in a temperature range higher by 10 ° C. to 20 ° C. than the melting point.

(Composition of molten salt)
The molten salt includes one or more selected from alkali metals and alkaline earth metals as a cation, and FSA (bisfluorosulfonylamide), TFSA (bistrifluoromethylsulfonylamide) or FTA (fluorotrifluoromethylsulfonyl). A simple salt containing amide) as an anion or a mixed salt thereof can be suitably used. The molten salt has a melting point higher than room temperature, is in a solid state at room temperature, and melts into a liquid state at a temperature equal to or higher than the melting point. The molten salt can have a low melting point, can realize a low melting point of 140 ° C. or lower, and can also realize a viscosity in a liquid state of 3.5 Pa · s or lower.

The alkali metal to be a cation can be selected from Li, Na, K, Rb and Cs, and the alkaline earth metal can be selected from Mg, Ca, Sr and Ba. For example, as a single salt of a molten salt having FSA as an anion, LiFSA, NaFSA, KFSA, RbFSA, CsFSA, Mg (FSA) ₂ , Ca (FSA) ₂ , Sr (FSA) _2, and Ba (FSA) ₂ can be mentioned. It is done. Examples of the molten salt having TFSA as an anion include LiTFSA, NaTFSA, KTFSA, RbTFSA, CsTFSA, Mg (TFSA) ₂ , Ca (TFSA) ₂ , Sr (TFSA) ₂ and Ba (TFSA) _2. It is done. Examples of the single salt of the molten salt having FTA as an anion include LiFTA, NaFTA, KFTA, RbFTA, CsFTA, Mg (FTA) ₂ , Ca (FTA) ₂ , Sr (FTA) ₂ and Ba (FTA) ₂ . Moreover, it can also be set as the mixed salt which mixed these single salts, and it is possible to lower melting | fusing point more by using mixed salt. Furthermore, the molten salt may contain an organic cation. Examples of organic cations include alkylimidazole cations such as 1-ethyl-3-methylimidazolium cation, alkylpyrrolidinium cations such as N-ethyl-N-methylpyrrolidinium cation, and 1-methyl-pyridinium cation. And quaternary ammonium cations such as alkylpyridinium cations and trimethylhexylammonium cations.

  An example of the molten salt is a mixed salt (NaFSA-KFSA) of NaFSA with Na as a cation and FSA as an anion and KFSA with K as a cation and FSA as an anion. NaFSA-KFSA can change the melting point by changing the molar ratio of NaFSA and KFSA, and the melting point is 140 ° C. or less by setting NaFSA to 30 mol% to 60 mol% and KFSA to 40 mol% to 70 mol%. Further, it can be set to 120 ° C. or lower. In particular, when NaFSA is 40 mol% or more and 50 mol% or less and KFSA is 50 mol% or more and 60 mol% or less, the melting point can be 90 ° C. or less, which is preferable. For example, when NaFSA is 45 mol% and KFSA is 55 mol%, the melting point of NaFSA-KFSA is about 57 ° C.

<Impregnation process>
In the impregnation step, the molten salt that solidifies at room temperature is heated and melted to impregnate the porous member with the molten salt in a liquid state. The porous member can be easily impregnated with the molten salt by liquefying the molten salt by heating and melting the molten salt to a temperature equal to or higher than the melting point (for example, 30 ° C.). The heating temperature when the molten salt is melted by heating, that is, the temperature of the molten salt in a liquid state is set to a temperature range (for example, 140 ° C. or less) that does not cause the porous member to be altered or damaged. Here, if the viscosity of the molten salt in the liquid state is 3.5 Pa · s or less, the molten salt easily penetrates into and fills the pores inside the porous member. The impregnation includes, for example, putting a porous member into a mold, injecting a molten salt in a liquid state into the mold, and immersing the porous member in the molten salt.

  Furthermore, in the impregnation step, the porous member is preferably impregnated with the molten salt by immersing the porous member in a molten salt in a liquid state in a vacuum atmosphere. By immersing the porous member in a molten salt in a liquid state in a vacuum atmosphere, the molten salt penetrates into fine pores inside the porous member and becomes easy to be densely filled. The degree of vacuum in the vacuum atmosphere is, for example, 10 Pa or less, preferably 1 Pa or less. Since the molten salt has an extremely low vapor pressure (nearly 0), it does not vaporize and disappear even when used in a vacuum atmosphere.

<Solidification process>
In the solidification step, the porous member impregnated with the molten salt is cooled to solidify the molten salt. By cooling the porous member impregnated with the molten salt to solidify the molten salt, the porous member can be solidified with the molten salt. The porous member impregnated with the molten salt can be cooled at room temperature to solidify the molten salt. Cooling may be natural cooling by standing cooling, forced cooling by air cooling or water cooling, and the time required for solidification can be shortened by forced cooling.

<Cutting process>
In the cutting step, the porous member solidified with the molten salt is cut. By cutting the porous member solidified with the molten salt, the internal structure of the porous member is not easily destroyed, and the cross section can be formed while maintaining the state of the porous member, and a good cross section can be obtained. Cutting can be performed at room temperature. Examples of the cutting method include cleaving by cleaving the porous member by applying mechanical impact or bending stress, shearing by sandwiching the porous member with a pair of blades, and pulling by pressing a knife or saw blade against the porous member. Various methods such as cutting with a cutting blade can be adopted.

  In particular, it is preferable to cut the porous member by cleaving. Cutting by cleaving is smooth because there are few occurrences of chips, the adhesion of chips to the cross section is suppressed, the cross section is hardly deformed by the stress at the time of cutting, and the internal structure of the porous member is difficult to be destroyed. It is easy to obtain a better cross section. As the cleaving method, for example, a knife blade is pressed against the porous member to give an impact or bending stress, or a scribe line is formed on the porous member to give the impact or bending stress along the scribe line. It is done.

<Removal process>
In the removing step, the cut porous member is heated to melt the molten salt, and the molten salt is removed from the porous member. The molten salt can be easily removed from the porous member by liquefying the molten salt by heating and melting the porous member to a temperature equal to or higher than the melting point (for example, 30 ° C.) of the molten salt. The heating temperature of the porous member when the molten salt is melted and removed from the porous member is set to a temperature range (for example, 140 ° C. or less) that does not cause the porous member to be altered or damaged. Here, if the viscosity of the molten salt in a liquid state is 3.5 Pa · s or less, the molten salt can be efficiently removed from the porous member.

  Furthermore, it is preferable to wash the porous member with a solvent after melting the molten salt to remove the molten salt from the porous member. Thereby, it is easy to completely remove the molten salt from the porous member. As the solvent, for example, organic solvents such as acetonitrile, methanol, ethanol, and isopropyl alcohol can be suitably used.

[Test Example 1]
Sample for cross-sectional observation using NaFSA-KFSA (NaFSA: KFSA = 45 mol%: 55 mol%, melting point: about 57 ° C.) as the molten salt, and cutting the porous member by the porous member cutting method of the above-described embodiment. Was made. And the cut surface of the sample was observed and evaluated. When the viscosity of NaFSA-KFSA was measured using a rotational viscometer (DVH-E II type, manufactured by Tokyo Keiki Co., Ltd.), it was 5.919 Pa · s (5919 cp) at 60 ° C and 2.105 Pa · s (70 ° C). 2105 cp).

(Sample 1)
A PPS porous member formed of polyphenylene sulfide (PPS) resin fibers was prepared. Specifically, the PPS porous member is a sheet-like member having a thickness of about 60 μm, which is formed by entanglement with a large number of PPS resin fibers having a diameter of about 10 μm. Moreover, NaFSA-KFSA was heated to 70 ° C. and melted to prepare NaFSA-KFSA in a liquid state. A PPS porous member is placed in a mold, liquid NaFSA-KFSA is injected into the mold, and the PPS porous member is immersed in the liquid NaFSA-KFSA, thereby allowing NaFSA-KFSA to pass through the PPS. The material was impregnated. Then, the PPS porous member impregnated with NaFSA-KFSA was cooled by leaving the PPS porous member immersed in NaFSA-KFSA at room temperature to solidify NaFSA-KFSA. Next, the PPS porous member solidified with NaFSA-KFSA is taken out from the mold, and is cut by applying an impact by pressing a knife blade against the porous member, whereby the porous member of PPS solidified with NaFSA-KFSA Was cut off. The cut PPS porous member was heated to 70 ° C. to melt the impregnated NaFSA-KFSA, and the NaFSA-KFSA was removed from the PPS porous member. As described above, a sample for observing the cross section of Sample 1 was produced. And the cut surface of the produced sample 1 was observed with the scanning electron microscope (SEM). FIG. 1 shows a cross-sectional micrograph of Sample 1 (upper: 200 times magnification, lower: 1000 times magnification).

  As shown in FIG. 1, the cut surface of the sample 1 has a smooth cross section without sagging or deformation, and the state of the fiber and pores of the sample is maintained, so that the state of the sample can be clearly observed. I understand. Further, FIG. 1 shows that the state in the depth direction can be clearly observed on the cut surface. That is, according to the porous member cutting method of the embodiment, the cross-section can be formed while maintaining the state of the porous member without destroying the internal structure of the porous member. Can be observed clearly.

[Test Example 2]
In Test Example 2, a porous member made of an aramid resin was prepared as a cutting object. This porous member of aramid is a sheet-like member (aramid foam sheet) having a sponge-like network structure. And while cut | disconnecting the aramid foam sheet with the cutting method of the porous member of embodiment mentioned above and producing the sample for cross-section observation, the cut surface of the sample is observed by SEM like Test Example 1. evaluated.

(Sample 2-1)
NaFSA-KFSA used in Sample 1 was melted by heating to 70 ° C. to prepare NaFSA-KFSA in a liquid state. The aramid foam sheet was placed in a mold, liquid NaFSA-KFSA was poured into the mold, and the aramid foam sheet was immersed in liquid NaFSA-KFSA. Thereafter, the aramid foamed sheet was cooled at room temperature while being immersed in NaFSA-KFSA to solidify NaFSA-KFSA. Next, the aramid foamed sheet solidified with NaFSA-KFSA was taken out of the mold, pressed against it with a knife blade, and was cut by cleaving with impact. The cut aramid foam sheet was heated to 70 ° C. to melt NaFSA-KFSA, and the molten salt was removed from the aramid foam sheet. As described above, a sample for cross-sectional observation of Sample 2-1 was produced. FIG. 2 shows a cross-sectional photo of the sample 2-1 (upper: 5,000 times magnification, middle: 10000 times magnification, lower: 20,000 times magnification).

(Sample 2-2)
As a comparison, the same aramid foam sheet as that of Sample 2-1 was cut by a conventional freeze cleaving method to prepare a sample for cross-sectional observation, and the cut surface of the sample was observed with an SEM and evaluated. The aramid foam sheet was placed in a resin capsule, ethanol was sealed in the capsule, and the aramid foam sheet was impregnated with ethanol. Then, this capsule was immersed in liquid nitrogen and cooled, and ethanol was frozen. Next, a knife blade was pressed against the frozen capsule to give an impact, and the aramid foam sheet was cut. The cut aramid foam sheet was allowed to stand at room temperature to dissolve ethanol, and the ethanol was removed from the aramid foam sheet. As described above, a cross-sectional observation sample of Sample 2-2 was produced. FIG. 3 shows a cross-sectional micrograph of Sample 2-2 (upper: 5,000 times magnification, middle: 10000 times magnification, lower: 20,000 times magnification).

  As shown in FIG. 2 and FIG. 3, it can be seen that all the samples have a smooth cross section without sagging or deformation on the cut surface, and the state of the fibers and holes of the sample is maintained. In addition, it can be seen from FIGS. 2 and 3 that the cut surface of either sample can clearly observe the state in the depth direction. That is, according to the porous member cutting method of the embodiment, it is possible to obtain a good cross section equal to or better than that of the conventional freeze cutting method.

  In the test examples described above, the example of using the porous member cutting method of the embodiment for the preparation of the cross-sectional observation sample of the porous member is taken as an example, but the porous member cutting method of the embodiment is described below. It can also be used when a porous member is cut into a predetermined size and processed into a part. According to the porous member cutting method of the embodiment, the cutting surface is free from sagging and deformation, can be cut while maintaining the state of the porous member, and the impregnated molten salt can also be easily removed. The machined parts are less affected.

  The method for cutting a porous member of the present invention can be suitably used for cutting a porous member.

Claims (7)

An impregnation step of heating and melting the molten salt solidified at room temperature, and impregnating the porous member with the molten salt in a liquid state;
Cooling the porous member impregnated with the molten salt to solidify the molten salt;
A cutting step of cutting the porous member solidified with the molten salt;
Removing the molten salt by heating the cut porous member to melt the molten salt, and removing the molten salt from the porous member;
A method for cutting a porous member.   The porous member cutting method according to claim 1, wherein the molten salt has a melting point of 30 ° C. or higher and 140 ° C. or lower.   The molten salt is a single salt or a mixed salt thereof containing one or more kinds selected from alkali metals and alkaline earth metals as cations and containing FSA, TFSA or FTA as anions. The cutting method of the porous member as described in 2.   The method for cutting a porous member according to any one of claims 1 to 3, wherein a viscosity of the molten salt in a liquid state is 3.5 Pa · s or less.   The said impregnation process WHEREIN: The said porous member is immersed in the said molten salt in a liquid state in a vacuum atmosphere, The said molten salt is impregnated with the said molten salt in any one of Claims 1-4. A method for cutting a porous member.   The method for cutting a porous member according to any one of claims 1 to 5, wherein the porous member is cut by cleaving in the cutting step.   The said removal process WHEREIN: After melting the said molten salt and removing the said molten salt from the said porous member, the said porous member is further wash | cleaned with a solvent. A method for cutting a porous member.