Method for producing high aspect ratio water-soluble salt

Abstract

To provide a novel high aspect-ratio water-soluble salt suitable as a spacer material added to a raw material for sintered body when manufacturing a grind stone used for cutting or polishing a carbon fiber plastic (CFRP) or the like and its manufacturing method.SOLUTION: Provided is a high aspect ratio water-soluble salt having an aspect ratio of 2 or more. A manufacturing method of a high aspect ratio water-soluble salt comprises a step of adding an aqueous solution of a water-soluble salt of 5 to 350 g / l to a single-layer or multi-layer carbon nanotube and stirring to prepare an aqueous gel, and a step of precipitating the high aspect ratio water-soluble salt from the aqueous gel.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to water-soluble salts having high aspect ratios. [Background technology]

[0002] In composite materials, materials with high aspect ratios are added to the matrix material to give it mechanical and thermal properties, thereby improving its performance. For example, carbon fiber reinforced plastics (CFRP) are made by adding fibers as reinforcement to a plastic matrix. CFRP has excellent mechanical properties and is widely used in aircraft parts, automobile parts, sports parts, and more recently, machine parts. In addition, there is growing demand in the mobility field for composite materials that have been given anisotropy using high aspect ratio materials.

[0003] CFRP parts often require drilling and trimming of the outer periphery after molding. However, cutting processes such as drilling and trimming have issues such as residual stress in the CFRP parts and uncut fibers rubbing the tool flank and promoting wear. Grinding processes also have issues such as clogging of the grinding wheel when grinding the plastic parts that hold the carbon fibers. Therefore, there is a demand for a grinding wheel that can withstand high-load processing without causing problems such as clogging even when grinding CFRP parts. As a method for manufacturing such a grinding wheel, for example, a method is being considered in which a water-soluble salt is mixed with the sintering raw material, and the water-soluble salt component is washed away after sintering to produce a porous grinding wheel.

[0004] Non-Patent Document 1 discloses an example of crystallizing high aspect ratio crystals by leaving high-temperature saturated salt water, i.e., salt water with a high degree of supersaturation, to stand. According to Non-Patent Document 1, when the degree of supersaturation is low, each face of the primary crystal grows equally to form a crystal close to a cube, but when the degree of supersaturation is high, the crystal grows in only one direction to form a needle-like or columnar crystal.

[0005] Since water-soluble salts such as sodium chloride have mechanical and chemical properties such as heat resistance, hardness, and corrosion resistance, as well as functions such as electrical conductivity and charge storage, it is believed that by forming a water-soluble salt with an appropriately adjusted aspect ratio and adding it to a composite material, a composite material that meets various performance requirements can be obtained. In addition, since water-soluble salts are heat-resistant, they can be suitably used in high-temperature processes. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Environmental conditions for salt precipitation and crystal shape (1), Masayoshi Murakami, Journal of the Japan Society of Sea Water Science, 2000, Vol. 54, No. 2, pp. 151-154 Summary of the Invention [Problem to be solved by the invention]

[0007] Non-Patent Document 1 reports that sodium chloride with an aspect ratio of about 10 to 20 was obtained, but these needle-shaped sodium chloride crystals precipitated almost accidentally from brine under specific conditions, and does not disclose the conditions under which salt with a high aspect ratio is stably formed.

[0008] The present invention aims to provide a novel high aspect ratio water-soluble salt suitable as a spacer material to be added to a sintered raw material when producing a porous grinding wheel used for cutting or grinding carbon fiber plastics (CFRP) and the like, and a method for producing the same. [Means for solving the problem]

[0009] The high aspect ratio water-soluble salt of the present invention is characterized by having an aspect ratio of 2 or more. There have been no reports of water-soluble salts having the above dimensions. The water-soluble salt is a novel material suitable as a spacer material for porous grinding wheels for CFRP.

[0010] The method for producing a high aspect ratio water-soluble salt of the present invention is characterized by comprising the steps of: preparing an aqueous gel-like body by adding 5 to 350 g / l of an aqueous solution of a water-soluble salt to single-walled or multi-walled carbon nanotubes and stirring the solution; and precipitating the high aspect ratio water-soluble salt from the aqueous gel-like body. Effect of the Invention

[0011] The high aspect ratio water-soluble salt of the present invention has an aspect ratio of 2 to 1500. The high aspect ratio water-soluble salt of the present invention can be obtained easily in a short time with high purity.

[0012] When the high aspect ratio water-soluble salt is added as a spacer material to the raw material for sintered bodies in manufacturing porous grindstones for carbon fiber reinforced plastics (CFRP), interconnected pores are formed inside the grindstone after sintering. Since porous grindstones containing interconnected pores have excellent air permeability, even if chips are generated during grinding, they can be easily removed by supplying high-pressure air and are less likely to become clogged.

[0013] In addition, the inside of the grinding wheel is cooled by the air passing through the communication holes, which prevents the heat of the grinding wheel from adversely affecting the CFRP material. Depending on the object being ground, the inside of the grinding wheel can also be cooled by cutting oil instead of air.

[0014] In addition, when cubic sodium chloride crystals, for example, are added as a spacer material to the raw material for the sintered body in order to correct the continuous pores, the amount of high aspect ratio water-soluble salt added is smaller than that of cubic salt. In other words, the amount of high aspect ratio water-soluble salt added as a spacer material is small, which leads to improved strength. It can be easily removed by supplying high-pressure air, and the grinding wheel is less likely to become clogged. Therefore, such porous grinding wheels with excellent porosity can withstand high-load processing and have a long life.

[0015] Therefore, by using the water-soluble salt having a high aspect ratio of the present invention as a spacer material, it is possible to obtain a grinding wheel which can withstand high load processing and has a long life compared to the prior art. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a photograph showing the state of formation of high aspect ratio sodium chloride crystals in Example 1. [Diagram 2] Figure 2 is a photograph comparing high aspect ratio sodium chloride crystals with regular table salt cubic crystals. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The high aspect ratio water-soluble salt of the present invention will be described in detail below with reference to the photographs of the drawings. The high aspect ratio water-soluble salt of the present invention is characterized in that its aspect ratio is 2 or more. The water-soluble salt capable of forming a high aspect ratio water-soluble salt is not limited as long as it can be crystallized into a needle shape, and examples thereof include sodium chloride, potassium chloride, barium chloride, aluminum chloride, lithium benzoate, sodium benzoate, potassium benzoate, sodium acetate, and lithium tartrate. Of these, sodium chloride and potassium chloride are preferred because they are easy to crystallize and can form various shapes such as plate-like, columnar, or needle-like depending on the direction in which the crystals tend to grow. The aspect ratio of the high aspect ratio water-soluble salt is preferably 2 to 1500.

[0018] The high aspect ratio water-soluble salt of the present invention has needle-like crystals. FIG. 1 is a photograph of the production of high aspect ratio sodium chloride of the present invention. The high aspect ratio water-soluble salt has a length of 2 mm or more, preferably 5 to 60 mm, and a width (diameter) of 0.05 mm or more. The length of the high aspect ratio water-soluble salt can be adjusted by obtaining long needle-like crystals and then breaking them to reduce the aspect ratio. The upper limit of the width is about 0.2 mm or less. The aspect ratio, which is the ratio of these, is more preferably 10 to 100. FIG. 2 shows high aspect ratio sodium chloride crystals together with cubic sodium chloride for comparison. It can be seen that the length of high aspect ratio sodium chloride crystals is about 18 to 33 mm, and one side of cubic sodium chloride is about 0.6 mm.

[0019] The method for producing the high aspect ratio water-soluble salt of the present invention will be described below with an example. The water-soluble salt is dissolved in distilled water to prepare an aqueous solution. The concentration of the aqueous solution is not limited, and when the concentration of the aqueous solution is low, a small amount of needle-like crystals is obtained, and when the concentration of the aqueous solution is high, a large amount of needle-like crystals is obtained. In addition to distilled water, pure water, ion-exchanged water, ultrapure water, RO water, etc. may be used. Next, carbon nanotubes are added to the aqueous solution of the water-soluble salt and dispersed using an ultrasonic homogenizer, and the aqueous solution is permeated into the carbon nanotubes. In the method for producing a high aspect ratio water-soluble salt, the water-soluble salt, water and carbon nanotubes may be charged at once and dispersed with an ultrasonic homogenizer.

[0020] Carbon nanotubes include single-walled nanotubes, double-walled nanotubes and multi-walled nanotubes, and any of these can be used in the present invention, but multi-walled nanotubes, which are inexpensive and easily available, are usually used.

[0021] When carbon nanotubes penetrate into an aqueous solution of a water-soluble salt, their fluidity decreases compared to before penetration, and they become gel-like. This salt-containing carbon nanotube aqueous gel is placed in a container with an open top. Since the salt-containing carbon nanotube aqueous gel has a low degree of freedom of movement, the growth rate of the needle-like crystals is favored in the direction of the airflow. In other words, the needle-like crystals grow in a horizontal direction on the surface of the salt-containing carbon nanotube aqueous gel in the container. The needle-like crystals are then obtained by leaving it to stand at room temperature.

[0022] The concentration of carbon nanotubes in the aqueous solution is usually 1 to 20 g / l, preferably 4 to 8 g / l. The concentration of carbon nanotubes can be adjusted according to the desired thickness of the needle-like crystals. For example, when the concentration of carbon nanotubes is high, the carbon nanotubes are sparsely dispersed in the aqueous solution due to the percolation phenomenon, and needle-like crystals with a small diameter are obtained. On the other hand, when the concentration of carbon nanotubes is low, needle-like crystals with a large diameter are obtained. In addition to the concentration of carbon nanotubes, the crystal shape (thickness and length) can be adjusted by heating or applying an electric current.

[0023] A typical method for producing crystals of a water-soluble compound is to evaporate water from a concentrated aqueous solution of the water-soluble compound to cause crystallization. However, this method only produces crystals with a small aspect ratio, such as a rock salt structure.

[0024] The high aspect ratio water-soluble salt of the present invention is suitable as a spacer material to be added to the sintered body raw material when manufacturing grindstones for carbon fiber reinforced plastics (CFRP). When the high aspect ratio water-soluble salt is added, communicating holes are formed inside the grindstone after sintering, improving the breathability of the grindstone. If a grindstone with high breathability is used to grind CFRP parts, even if chips are generated during grinding, they can be easily removed by supplying high-pressure air, and the grindstone is less likely to become clogged. Therefore, such a porous grindstone with excellent porosity can withstand high-load processing and has a long life.

[0025] In addition, the amount of the high aspect ratio water-soluble salt added is more likely to form continuous pores than when a cubic salt is added to the raw material for the sintered body. Therefore, when the high aspect ratio water-soluble salt of the present invention is used, a porous grinding wheel that is excellent in air permeability and does not easily clog can be obtained with a small amount of the salt added. EXAMPLES

[0026] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to the following examples. [Example 1] 25 g of sodium chloride (Kanto Chemical) was dissolved in 500 ml of distilled water to prepare a 50 g / l saline solution. 4 g of multi-walled carbon nanotubes (CNT) (product name: NC7000; Nanocyl) was placed in a 500 ml polyethylene wide-mouth bottle, 500 ml of 50 g / l saline was added, and an ultrasonic homogenizer (model number UP400S, output 400 W; Hielscher) was used to irradiate ultrasonic waves with a frequency of 24 kHz for 3 minutes twice to prepare a salt-containing CNT aqueous gel (first step). The first step is the same as the operation described in Japanese Patent No. 5754001, except that "500 ml of distilled water" in the embodiment of the CNT aqueous gel preparation in Japanese Patent No. 5754001 was changed to "500 ml of 50 g / l saline".

[0027] 150 g of the salt-containing CNT aqueous gel was placed in a polycarbonate square container with a long side of 100 mm, a short side of 75 mm, and a depth of 60 mm, and a voltage of 1.5 V was applied for 8 hours, after which it was left to stand overnight at room temperature. The resulting needle-shaped crystals of sodium chloride were collected with tweezers (second step). The resulting needle-like crystals of sodium chloride were observed under a digital microscope and were found to have a length of 42 mm, a width of 33 μm, and an aspect ratio of 1273.

[0028] [Comparative Example 1] Cesium iodide crystals were formed in the same manner as in Example 1, except that cesium iodide (manufactured by Kanto Chemical Co., Ltd.) was used instead of sodium chloride (manufactured by Kanto Chemical Co., Ltd.) in Example 1. Observation of the resulting cesium iodide crystals under an electron microscope revealed that they had a length of 40 μm, a width of 50 μm, and an aspect ratio of 1.25, and no needle-shaped crystals were obtained.

Claims

[Claim 1] A step of adding 5 to 350 g / l of an aqueous solution of at least one water-soluble salt selected from the group consisting of sodium chloride, potassium chloride, barium chloride, aluminum chloride, lithium benzoate, sodium benzoate, potassium benzoate, sodium acetate, and lithium tartrate to single-walled or multi-walled carbon nanotubes and stirring the solution to prepare a salt-containing carbon nanotube aqueous gel; a step of passing an electric current through the salt-containing carbon nanotube aqueous gel and then leaving it to stand, thereby precipitating needle-like crystals of the water-soluble salt; A method for producing a high aspect ratio water-soluble salt having the above structure.

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