JP2007308351A - Fluorine-containing nano diamond dispersion liquid and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorine-containing nano diamond dispersion liquid useful as a precision abrasive, a lubricating agent, a heat exchanging fluid medium and the like, and a method for producing the same. <P>SOLUTION: The fluorine-containing nano diamond dispersion liquid is prepared by mixing a dispersion medium and a fluorine-containing nano diamond, and classifying the mixture. The dispersion medium is at least one fluorine organic solvent selected from the group consisting of a hydrofluorocarbon, a hydrofluoroether, a hydrofluorochlorocarbon, and a fluoride of an alcohol. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fluorine-containing nanodiamond dispersion useful as a precision abrasive, a lubricant, a heat exchange fluid medium, and the like, and a method for producing the same.

  Diamonds obtained by the impact-pressure explosion method (impact method) using oxygen-deficient explosives such as trinitrotoluene (TNT) and hexogen (RDX) are nanodiamonds because the primary particles are as small as 3 to 20 nm. ND). However, since the surface of the ND fine particles is produced as a secondary or tertiary aggregate having a non-graphitic or graphite film fused and having a particle diameter of 50 to 7500 nm, it is also called cluster diamond (CD). (For example, Non-Patent Document 1, Non-Patent Document 2). Depending on the nanoparticle size, ND is a composite material with abrasive, lubricant, heat exchange fluid medium, resin, metal, etc., low dielectric constant film, electronic material such as emitter material, DNA carrier, virus capture carrier, etc. It is expected to be used in a wide range of applications other than normal diamond applications such as in the medical field. Thus, when ND is industrially used as a composite material or the like, it is required to provide a dispersion liquid in which ND is dispersed in liquid with nano-order fine particles. However, when handling nano-level to hundreds of nano-order particles dispersed in a solution, the smaller the particles, the more likely the particles will aggregate, and the aggregated particles will settle down to obtain a stable dispersion. Is very difficult. Therefore, in ND, various methods for stably dispersing CD in the liquid as ND of primary particles in an ultrasonic homogenizer, bead mill wet disintegrator, etc. have been studied (for example, Patent Document 1 and Patent Document 2). . However, it has not been able to meet market demands such as poor long-term stability and re-aggregation after drying.

On the other hand, a method of reacting CD with fluorine gas for the purpose of crushing secondary and tertiary aggregates of CD has been reported. For example, when CD is brought into contact with fluorine at a reaction temperature of 300 to 500 ° C., a fluorine gas pressure of 0.1 MPa, a reaction time of 5 to 10 days, the F / C molar ratio is maintained while maintaining the diamond structure. A fluorine-containing CD of about 0.2 (XPS, elemental analysis) is obtained (Non-patent Document 3). It has been observed by TEM that CD having a secondary particle diameter of about 40 μm is partially dissolved by the fluorine treatment to be about 200 nm. Further, it was confirmed that the friction coefficient of CD was remarkably lowered by a rotary friction test using a mixed powder with polytetrafluoroethylene (PTFE) (Non-patent Document 4). This is because the non-graphitic carbon on the ND surface is removed by the reaction at a high temperature because the ND lattice pattern by TEM observation is clear, and the CF group, CF ₂ group, CF ₃ group on the ND surface are further removed. It has been reported that the surface energy has decreased due to the formation of the above (Non-Patent Document 5). Moreover, the fluorine content is 5 to 8.6 at. By fluorine treatment of reaction temperature: 150, 310, 410, 470 ° C., F ₂ / H ₂ flow rate ratio: 3/1, reaction time: 48 hours. % (Analysis by EDX) has been reported to improve the solubility in polar solvents such as ethanol compared to the original ND (Non-Patent Document 6, Patent Document 3).

These NDs and fluorine-containing NDs can be dispersed in a dispersion medium such as ethanol having 3 or less carbon atoms such as ethanol or dimethyl sulfoxide to produce a dispersion containing ND or fluorine-containing ND at a high concentration. However, it does not disperse at all in hydrocarbons such as n-hexane, benzene, petroleum oil (mainly linear hydrocarbons having 10 or more carbon atoms), ketones, ethers, alcohols having 8 or more carbon atoms, etc. Also, the dispersibility is extremely low. Dispersions using ND or fluorine-containing ND for the above-mentioned abrasives, lubricants, etc. require the physicochemical properties of the dispersion medium such as viscosity, volatility, flammability, and electrical conductivity for each application. There are few types of dispersion media that can be dispersed, and the range of selection is extremely limited.
JP-A-2005-1983 JP 2005-97375 A US2005 / 0158549A1 Specification Eiji Osawa: Journal of Abrasive Technology, 47,414 (2003). Kotaro Hanada: Journal of the Japan Society for Abrasive Technology, 47,422 (2003). Satoshi Oi, Kyoko Yonemoto, Koji Kawasaki, Fujio Okino, Hidekazu Higashihara: Abstracts of the 26th Fluorine Chemistry Conference (November 2002) Yoko Yonemoto, Atsushi Ooi, Atsushi Kawasaki, Fujio Okino, Fumiaki Kataoka, Eiji Osawa, Hidekazu Higashihara: The 83rd Annual Meeting of the Chemical Society of Japan (March 2003) H. Touhara, K. Komatsu, T. Ohi, A. Yonemoto, S. Kawasaki, F. Okino and H. Kataura: Third French-Japanese Seminar on Fluorine in Inorganic Chemistry and Electrochemistry (April, 2003) Y. Liu, Z. Gu, JL Margrave, and V. Khahabashesku; Chem. Mater. 16, 3924 (2004).

  Since the fluorine-containing ND is dispersed only in a part of the dispersion medium, it is difficult to select a dispersion medium suitable for the application.

  The present invention is to improve the situation in which physicochemical properties such as viscosity, volatility, solubility, flammability, and electrical conductivity of a dispersion liquid in which fluorine-containing ND particles are dispersed cannot be freely selected. It is another object of the present invention to provide a dispersion liquid in which fluorine-containing ND particles are dispersed with an average particle diameter of 300 nm or less and stable for a long period of 120 hours or more.

  As a result of intensive studies to achieve the above object, the present inventors made precipitation over a long period of 120 hours or more by using fluorine-containing ND as dispersed particles and using a fluorine-based organic solvent as a dispersion medium. The present invention has been found out that it exists stably without occurring.

  That is, the present invention is a fluorine-containing nanodiamond dispersion liquid characterized in that the dispersion medium is a fluorine-containing nanodiamond dispersion liquid, and the dispersion medium is a fluorine-based organic solvent. Fluorine-containing nanodiamond dispersion liquid comprising at least one of fluoroether, hydrochlorofluorocarbon, and fluorides of alcohols. Also, the suspension is obtained by mixing fluorine-containing nanodiamond particles and a fluorine-based organic solvent. The present invention provides a method for producing a fluorine-containing nanodiamond dispersion comprising a producing step and a step of classifying a suspension.

  The fluorine-containing nanodiamond dispersion liquid of the present invention can be stably dispersed and stored for a long period of 120 hours or more. In addition, the dispersion of the present invention can be used for useful applications such as precision abrasives, lubricants, and heat exchange fluid media.

  Hereinafter, the present invention will be described in further detail.

  As the fluorine-containing ND dispersed particles used in the present invention, fluorine-containing ND produced by direct reaction between ND and fluorine gas or fluorination by fluorine plasma is used. The fluorine content of the fluorine-containing ND is preferably 10 wt% or more. When the fluorine content is less than 10 wt%, the affinity with the fluorine-based organic solvent is lowered, and the concentration and stability of the dispersion are sufficient. It is difficult to obtain sex.

  In the present invention, the fluorinated organic solvent used is hydrofluorocarbon, hydrofluoroether, hydrochlorofluorocarbon, or fluoride of alcohols. Due to its structure, there are abundant substances with different viscosities, volatility, and chemical stability, and since it has high dispersibility with respect to fluorine-containing ND, it is suitable as a dispersion medium for achieving the above object.

As the fluorine-based organic solvents, _{specifically, HFC-365mfc (C 4 H} 5 F 5), HFC-43-10mee (C 5 H 2 F 10), HFC-52-13p (C 6 HF 13), or _{HFC-c-447ef (C 5} H 3 F 7) hydrofluorocarbons, such as (HFC), or _{HFE-449s1 (C 5 H 3} F 9 O), HFE-569sf2 (C 6 H 5 F 9 O), or HFE _{-347pc-f (C 4 H 3} F 7 O) hydrofluoroether such as _{(HFE), HCFC-225cb (} C 3 HCl 2 F 5), HCFC-141b (C 2 H 3 Cl 2 F) hydrochlorofluorocarbons such as fluorocarbons (HCFC), tetrafluoropropanol _{(TFP: C 3 H 4 F} 4 O), octafluoropentanol ( _{FP: C 5 H 4 F 8} O) and alcohols of fluoride such.

  Next, the method for producing the fluorine-containing ND dispersion of the present invention is such that the fluorine-containing ND and the fluorine-based organic solvent are mixed by ultrasonic irradiation, and the fluorine-containing ND particles are suspended in the fluorine-based organic solvent. By classifying the liquid by centrifugation, impurities and aggregated particles having a particle diameter exceeding 500 nm are removed, and a transparent dispersion liquid composed of fluorine-containing ND particles having an average particle diameter of 300 nm or less is prepared.

  The concentration of the resulting fluorine-containing ND dispersion is preferably 0.05 wt% or more. If the concentration of the dispersion is less than 0.05 wt%, the number of fluorine-containing ND particles contained in the dispersion is small, and the effect obtained when applied to an abrasive or the like is lowered, which is not preferable.

  In order to obtain the dispersion liquid having a fluorine-containing ND dispersion concentration of 0.05 wt% or more, the fluorine-containing ND particles are mixed with a fluorine-based organic solvent, and the ultrasonic wave irradiation is performed with an output of 400 W or more and 0.5 hours or more. A suspension is obtained by suspending fluorine-containing ND particles in a fluorine-based organic solvent. As a method for obtaining a suspension, there is stirring by a stirrer or the like other than ultrasonic irradiation. In this case, it is difficult to obtain a dispersion having a concentration of 0.05 wt% or more.

  Furthermore, the average particle size in the fluorine-containing ND dispersion is preferably 300 nm or less. When the average particle size in the dispersion exceeds 300 nm, precipitation occurs, and stability during storage and use decreases.

  In order to obtain a dispersion liquid of fluorine-containing ND having an average particle size of 300 nm or less, it is preferable to classify the suspension after ultrasonic irradiation by centrifugation at a relative centrifugal acceleration of 1800 G or more and 0.5 hours or more. . When the relative centrifugal acceleration is less than 1800 G or less than 0.5 hour, particles having a particle diameter of 500 nm or more cannot be completely removed, and a good dispersion cannot be obtained. As another classification method, there is a method of filtering using a filter or the like, but in this method, particles having a particle size of 500 nm or less are also removed by the filter, and it is difficult to obtain a dispersion having a concentration of 0.05 wt% or more. .

  Hereinafter, the present invention will be described specifically by way of examples.

Examples 1-6
In advance, the ND was heated to 400 ° C. under a pressure of 1 kPa or less for 3 hours to remove moisture contained in the ND. 20 g of the ND that had been subjected to the drying treatment was placed in a nickel reaction tube, and fluorine gas was supplied at a flow rate of 20 ml / min and argon gas at a flow rate of 380 ml / min. Then, the sample was heated to 400 ° C., and the circulation of the argon-diluted fluorine gas was continued for 140 hours, whereby ND and fluorine gas were reacted to produce a fluorine-containing ND. The fluorine content of the produced fluorine-containing ND was 12 wt% by elemental analysis.

  100 mg of each of the obtained fluorine-containing NDs was put into 10 ml of each dispersion medium described in Table 1, and ultrasonic irradiation with an output of 400 W was performed for 0.5 hour with an ultrasonic homogenizer (VCX-750, manufactured by Sonics & materials), A suspension in which fluorine-containing ND was dispersed was prepared.

  Next, the obtained suspension was treated with a centrifuge (CN-2060, manufactured by HSIANGTAI) at a rotational speed of 4300 rpm (relative centrifugal acceleration 2000 G) for 1 hour, and the supernatant liquid after centrifugation was collected and dispersed. A liquid was obtained.

  The dispersion thus obtained was allowed to stand for 120 hours, and then the weight-converted particle size distribution was measured with a particle size distribution analyzer (FPAR1000, manufactured by Otsuka Electronics Co., Ltd.) by a dynamic light scattering method, and the average particle size of the dispersion was calculated. . The dispersion particle concentration of the dispersion was measured by weighing 10 g of the dispersion, removing the dispersion medium by drying at 50 ° C., and then weighing the remaining particles to calculate the dispersion particle concentration. Table 1 shows the respective calculation results.

Comparative Example 1
100 mg of fluorine-containing ND prepared by the same method as in Examples 1 to 6 above was added to 10 ml of the dispersion medium 1-octanol (C ₈ H ₁₈ O) described in Table 1, and the same method as in Examples 1 to 6 above. Then, ultrasonic irradiation, centrifugal separation, particle size distribution measurement and dispersion particle concentration measurement are performed to calculate the average particle diameter and dispersion particle concentration of the dispersion, and the results are shown in Table 1.

Comparative Examples 2 and 3
100 mg of fluorine-containing ND prepared by the same method as in Examples 1 to 6 above was added to each 10 ml of benzene (C ₆ H ₆ ) and liquid paraffin as a dispersion medium, and the same method as in Examples 1 to 6 above. Sonication, centrifugation, particle size distribution measurement, and dispersion particle concentration measurement were performed, but none of the particles in the dispersion medium could be confirmed.

Comparative Example 4
ND was dispersed particles, HFC-43-10mee was used as a dispersion medium, and ultrasonic irradiation was performed in the same manner as in Examples 1 to 6, but the particles precipitated within 0.1 hour, and the suspension was Could not be produced.

Claims (3)

A fluorine-containing nanodiamond dispersion, wherein the dispersion medium is a fluorine-containing nanodiamond dispersion, and the dispersion medium is a fluorine-based organic solvent. 2. The fluorine-containing nanodiamond dispersion liquid according to claim 1, wherein the fluorine-based organic solvent comprises at least one of hydrofluorocarbon, hydrofluoroether, hydrochlorofluorocarbon, and alcohol fluorides. The method for producing a fluorine-containing nanodiamond dispersion liquid according to claim 1 or 2, comprising a step of preparing a suspension by mixing fluorine-containing nanodiamond particles and a fluorine-based organic solvent, and a step of classifying the suspension. .