JP5465884B2 - Method for producing mixed powder containing silicon fine particles - Google Patents

Description

  The present invention relates to a method for producing a mixed powder containing silicon fine particles having ultraviolet absorption characteristics.

  A substance (referred to as a nanoparticle) miniaturized to a particle size of nanometer unit develops a unique electromagnetic effect as the electronic state changes. In addition, it is known that when a substance is made into nanoparticles, the surface area of the substance increases, thereby expressing different characteristics from those in the case where the substance is present in a lump.

  For example, a composite of silicon fine particles and silicon oxide fine particles (referred to as a mixed powder containing silicon fine particles) has ultraviolet absorption characteristics. A uniform dispersion of mixed powder containing silicon fine particles is used, for example, as an ultraviolet (UV) cut cosmetic.

JP-A-6-279015

  In the conventional method, since the mixed powder is agglomerated, it has been difficult to prepare a uniform dispersion of the mixed powder unless processing such as pulverization and classification is performed.

  An object of the present invention is to provide a method for producing a mixed powder of silicon fine particles that can be easily and easily produced in a large amount in a mixed powder of silicon fine particles that is easily dispersed in a solvent and has excellent dispersion stability. To do.

  In order to solve the above-described problems, the present invention has the following features. First, the first feature of the present invention is that a step (S1) of firing a mixture containing a silicon source and a carbon source in an inert atmosphere, and a gas generated in the firing step are extracted from the inert atmosphere and rapidly cooled. And a step (S2) of obtaining a mixed powder containing silicon fine particles and a step (S3) of pulverizing the mixed powder together with a predetermined solvent.

  According to a feature of the present invention, a mixed powder containing silicon fine particles is obtained by extracting a gas generated when a mixture containing a silicon source and a carbon source is fired in an inert atmosphere from the inert atmosphere and quenching. can get. Therefore, the manufacturing process becomes simpler and a large amount of silicon fine particles can be produced as compared with the conventional method of producing silicon fine particles by evaporating the silicon electrode with plasma.

  Further, according to the feature of the present invention, by mixing the mixed powder together with a predetermined solvent, it is possible to produce a mixed powder of silicon fine particles that is easily dispersed in the predetermined solvent and has excellent dispersion stability. .

  The second feature of the present invention relates to the first feature of the present invention, and further includes a step (S4) of separating silicon fine particles having a predetermined size or less from the predetermined solvent containing the pulverized mixed powder. This is the gist.

  The third feature of the present invention relates to the second feature of the present invention, and is summarized in that a centrifugal separation method is used in the separating step.

  A fourth feature of the present invention relates to the first feature of the present invention, and is summarized in that a pulverizing method using a ball mill is used in the pulverizing step.

  A fifth feature of the present invention relates to the fourth feature of the present invention, and is summarized in that the pulverizing step is wet pulverization.

  A sixth feature of the present invention relates to any one of the first to fifth features of the present invention, and is summarized in that the silicon source is ethyl silicate.

  A seventh feature of the present invention relates to any one of the first to sixth features of the present invention, and is summarized in that the carbon source is a phenol resin.

  An object of the present invention is to provide a method for producing a mixed powder containing silicon fine particles, which can easily produce a mixed powder of silicon fine particles which is easily dispersed in a solvent and has excellent dispersion stability in a large amount. And

It is a flowchart explaining the mixed powder containing the silicon fine particle which concerns on embodiment of this invention. It is a lineblock diagram explaining the manufacture device of the silicon particulates concerning the embodiment of the present invention. The transmission electron micrograph of the mixed powder containing silicon fine particles is shown. The transmission electron micrograph of the mixed powder containing silicon fine particles is shown.

  An embodiment of a mixed powder containing silicon fine particles according to the present invention will be described with reference to the drawings. Specifically, (1) mixed powder containing silicon fine particles, (2) silicon source and carbon source, (3) production apparatus for silicon fine particles, (4) examples, (5) evaluation of dispersibility of silicon fine particles , (6) Actions and effects, and (7) Other embodiments will be described.

(1) Mixed powder containing silicon fine particles In the process of producing a silicon carbide sintered body, as an example of a method for producing silicon carbide powder, there is a method of firing a high-purity silicon carbide precursor (referred to as a high-purity precursor). is there. The high purity precursor is a mixture obtained by homogeneously mixing a silicon source, a carbon source, and a polymerization or crosslinking catalyst.

  In the process of producing silicon carbide powder from this high-purity precursor, the silicon source and the carbon source are mixed, and then the mixture is heated at a temperature of 1600 ° C. or higher in a non-oxidizing atmosphere, whereby silicon carbide (SiC) powder is obtained. can get.

  That is, in the process of producing silicon carbide powder from a high-purity precursor, it passes through silicon monoxide (SiO) gas by a chemical reaction represented by the formulas (1) and (2) in an inert atmosphere (non-oxidizing atmosphere). As a result, silicon carbide is produced. According to this method, silicon carbide is extracted as a powder.

SiO ₂ + C → SiO + CO (1)
SiO + 2C → SiC + CO (2)

When the present inventors rapidly cool the gas extracted from the inert atmosphere after the silicon carbide is generated to a temperature of less than 1600 ° C., the chemical reaction represented by the formula (3) occurs, so that silicon (Si) It has been found that mixed powders containing silicon dioxide (SiO ₂ ) can be obtained.

2SiO → Si + SiO ₂ (3)
As described above, the mixed powder containing silicon fine particles shown as an embodiment of the present invention is to separate silicon fine particles from the gas generated as a by-product in the step of firing a high purity precursor.

  FIG. 1 is a flowchart illustrating a mixed powder containing silicon fine particles. As shown in FIG. 1, the mixed powder containing silicon fine particles has a firing step S1, a rapid cooling step S2, and a pulverizing step S3.

  The firing step S1 is a mixture (referred to as a high-purity precursor) in which a silicon source containing at least one silicon compound, a carbon source containing at least one organic compound that generates carbon by heating, and a polymerization or crosslinking catalyst are mixed. ) In an inert atmosphere. The silicon source is, for example, ethyl silicate. The carbon source is, for example, a phenol resin. Details of the silicon source and the carbon source will be described later.

  The rapid cooling step S2 is a step in which the gas generated when the high-purity precursor is fired in the firing step is extracted from the inert atmosphere and rapidly cooled. That is, a gas which is a by-product of the reaction for generating silicon carbide by firing a high-purity precursor is taken out and cooled.

  When the gas as a by-product is cooled under the above conditions, a mixed powder containing silicon fine particles is obtained.

  In the pulverization step S3, the mixed powder obtained in the rapid cooling step S2 is pulverized together with a predetermined solvent. The solvent includes water or an organic solvent. The pulverization step S3 is wet pulverization using a planetary ball mill. In the pulverization step S3, the planetary ball mill and the suspension containing the mixed powder being pulverized are alternately pulverized and stopped in order to avoid a temperature rise.

  The mixed powder containing silicon fine particles further has a separation step S4. In the separation step S4, a dispersion medium containing silicon fine particles having a predetermined size or less is separated from the slurry containing the mixed powder pulverized in the pulverization step S3. In the separation step S4, a centrifugal separation method is used.

(2) Silicon source and carbon source (2-1) Silicon source The silicon source containing the silicon compound is at least one selected from the group comprising a liquid silicon compound and a silicon solid synthesized from a hydrolyzable silicon compound. A seed containing silicon. A liquid silicon source and a solid silicon source can be used in combination. When a plurality of types of silicon sources are used, at least one type is liquid.

  The liquid silicon source is a polymer of alkoxysilane (mono-, di-, tri-, tetra-) and tetraalkoxysilane. Among the alkoxysilanes, tetraalkoxysilane is preferably used. Specific examples include methoxysilane, ethoxysilane, propoxysilane, butoxysilane and the like. In view of easy handling of the raw material, ethoxysilane is preferably used.

  Examples of the tetraalkoxysilane polymer include a low molecular weight polymer (oligomer) having a polymerization degree of about 2 to 15 and a silicate polymer having a high polymerization degree and exhibiting a liquid state. Examples of the solid silicon source that can be used in combination with these include silicon oxide.

  Silicon oxide includes SiO, silica gel (colloidal ultrafine silica-containing liquid, hydroxyl group, alkoxyl group, etc. inside), silicon dioxide (fine silica, quartz powder, etc.) and the like.

  In addition, as a silicon-containing raw material, a group of polymers obtained by trimethylation of a hydrolyzable silicic acid compound, an ester of a hydrolyzable silicon compound and a monovalent or polyhydric alcohol (for example, diol, triol) (for example, four Ethyl silicate synthesized by the reaction of silicon chloride and ethanol), reaction products other than esters obtained by the reaction of hydrolyzable silicon compounds and organic compounds (for example, tetramethylsilane, dimethyldiphenylsilane, polydimethylsilane) ) And the like.

  The silicon solid synthesized from the hydrolyzable silicon compound may be any substance that reacts with carbon to form silicon carbide in a high-temperature non-oxidizing atmosphere (in an inert atmosphere). A preferred example of the siliceous solid is amorphous silica fine powder obtained by hydrolysis of silicon tetrachloride.

  A silicon source may be used independently and may be used together 2 or more types. Among these silicon sources, from the viewpoint of good homogeneity and handling properties, it is preferable to use a tetraethoxysilane oligomer or a mixture of tetraethoxysilane oligomer and fine powder silica.

  The silicon source is preferably a substance containing silicon with high purity. Here, high purity indicates that the impurity content of the silicon compound before the formation of the mixture is 20 ppm or less. More preferably, the impurity content is 5 ppm or less.

  The silicon source is preferably one that generates silicon monoxide by heating. Specifically, it is preferable to use ethyl silicate as the silicon source.

(2-2) Carbon source The carbon-containing raw material used as the carbon source is preferably a high-purity organic compound containing oxygen in the molecule and carbon remaining by heating. The carbon source is a monomer, oligomer, or polymer composed of any one or two or more organic compounds that can be polymerized or crosslinked by heat, a catalyst, or a crosslinking agent.

  Preferable specific examples of the carbon source include phenol resins, furan resins, urea resins, epoxy resins, unsaturated polyester resins, curable resins such as polyimide resins and polyurethane resins, phenoxy resins, monosaccharides such as glucose, sucrose, etc. And various saccharides such as polysaccharides such as cellulose and starch. In particular, a resol type or novolac type phenol resin having a high residual carbon ratio and excellent workability is preferable.

  The resol type phenolic resin useful in the present embodiment includes monovalent or divalent phenols such as phenol, cresol, xylenol, resorcin, and bisphenol A in the presence of a catalyst (specifically, ammonia or organic amine). It is produced by reacting aldehydes such as formaldehyde, acetaldehyde and benzaldehyde.

  The carbon source is liquid at room temperature. The carbon source has solubility in a solvent. The carbon source has thermoplasticity or heat melting property and becomes soft or liquid by heating. Thus, the liquid or softening carbon source can be homogeneously mixed with the silicon source. A resol type phenol resin, a novolac type phenol resin, or the like can be suitably used as a carbon source. In particular, a resol type phenol resin is preferably used.

(2-3) Catalyst The polymerization and crosslinking catalyst used for the production of high-purity silicon carbide powder can be appropriately selected according to the carbon source. For example, when the carbon source is a phenol resin or a furan resin, acids such as maleic acid, toluenesulfonic acid, toluenecarboxylic acid, acetic acid, oxalic acid, sulfuric acid and the like can be mentioned. Among these, toluenesulfonic acid is preferably used.

(3) Silicon Fine Particle Manufacturing Device (3-1) Configuration of Manufacturing Device FIG. 2 shows a schematic diagram of a manufacturing device 1 used for manufacturing silicon fine particles. The manufacturing apparatus 1 includes a heating container 2 and a stage 8 that holds the heating container 2. The heating container 2 accommodates a mixture (high purity precursor) W in which a silicon source, a carbon source, and a polymerization or crosslinking catalyst are mixed.

  The manufacturing apparatus 1 includes heating elements 10a and 10b. The heating elements 10a and 10b heat the mixture W inside the heating container 2. The manufacturing apparatus 1 includes a heat insulating material 12 that covers the heating container 2 and the heating elements 10a and 10b.

  The manufacturing apparatus 1 includes a suction tube 21 and a dust collector 22. The suction tube 21 is connected to the inside of the heating container 2. The suction pipe 21 sucks the gas generated when the mixture W is baked from the inside of the heating container 2 and guides it to the dust collector 22. The dust collector 22 collects mixed powder obtained from the sucked gas.

  The manufacturing apparatus 1 includes a blower 23 and a supply pipe 24 connected to the heating container 2. The blower 23 supplies argon gas to the supply pipe 24. The supply pipe 24 supplies argon gas into the heating container 2. That is, the argon gas circulates in the order of the supply pipe 24, the heating container 2, and the suction pipe 21 of the manufacturing apparatus 1. The gas generated from the mixture W is collected by the dust collector 22 on an argon gas stream.

  The manufacturing apparatus 1 has a solenoid valve 25. The electromagnetic valve 25 is provided in the suction pipe 21, and the electromagnetic valve 25 is automatically opened and closed according to the pressure set for the internal pressure of the heating container 2.

(3-2) Operation of Manufacturing Device The manufacturing device 1 causes the heating elements 10a and 10b to generate heat and heats the heating container 2 under a predetermined temperature condition. At this time, the inside of the heating container 2 is maintained in a nitrogen atmosphere or an argon atmosphere. The above corresponds to the firing step S1.

Subsequently, the manufacturing apparatus 1 operates the blower 23. At this time, when the blower 23 is activated, the gas generated from the mixture W is extracted from the inside of the heating container 2 to the dust collector 22 via the suction pipe 21 along the air flow of the argon gas supplied from the blower 23. Since the outside of the heat insulating material 12 is at room temperature, the gas guided to the outside of the heating container 2 by riding on an argon gas stream is rapidly cooled to room temperature. At this time, a composite of silicon (Si) and silicon dioxide (SiO ₂ ) is obtained from the gas. The obtained composite is collected by the dust collector 22. The above corresponds to the rapid cooling step S2.

  The composite powder (referred to as mixed powder) collected by the dust collector 22 is wet-pulverized with an organic solvent by a planetary ball mill (not shown in FIG. 2).

(4) Examples Hereinafter, production examples of silicon fine particles will be shown. A mixture composed of 620 g of ethyl silicate as a silicon source, 288 g of phenol resin as a carbon source, and 92 g (35 wt%) of an aqueous maleic acid solution as a polymerization catalyst was placed in the heating container 2 of FIG. Subsequently, the mixture was heated at 150 ° C. to solidify.

  The mixture was then carbonized for 1 hour at 90 ° C. under a nitrogen atmosphere. The carbonized mixture was heated at 1600 ° C. under an argon atmosphere. During this heating, a gas as a by-product generated from the mixture in the heating container 2 was sent out to the dust collector 22 by an argon gas poured from the blower 23. The gas was cooled in the suction tube 21 during the conveyance and collected as powder.

  The obtained powder was subjected to transmission electron microscope (TEM) photo analysis. 3 and 4 show photographs. This powder has a fine chain structure. It was confirmed that the powder was a mixed powder in which silicon fine particles were wrapped in chain silicon oxide.

  The obtained mixed powder was subjected to a pulverization step. That is, 2 g of mixed powder containing silicon fine particles was put into a tungsten carbide container together with 20 ml of ethanol and 48 g of tungsten carbide spheres having a diameter of 3 mm, and wet pulverized by a planetary ball mill.

  The grinding conditions were a revolution diameter of 141 mm, a revolution ratio of 1: -2.0, and a revolution speed of 600 rpm. The total time required for the pulverization was 21 hours. During this period, in order to prevent the temperature of the sample during the pulverization from being increased, the operation was stopped for 10 minutes every time it was operated for 5 minutes. Therefore, of the 21 hours of pulverization process, the substantial pulverization time by the planetary ball mill was 7 hours.

  After the pulverization step by the planetary ball mill, the tungsten carbide spheres were taken out from the pulverized composite powder and centrifuged into ethanol containing the mixed powder.

  The temperature of the centrifuged sample was set at 10 ° C. The relative centrifugal acceleration was set at 22000 × g. Centrifugation processing time was 1 hour and a half. Thereafter, the precipitate produced by centrifugation was removed, and the fine particles maintained in a dispersed state in ethanol were collected together with ethanol.

  The collected fine particles were observed with a transmission electron microscope (TEM). It was confirmed that the collected fine particles were silicon oxide fine particles having a diameter of about 200 nm or less, and contained silicon fine particles having a particle diameter of several nm inside.

(5) Evaluation of dispersibility of silicon fine particles The dispersion characteristics of the collected silicon fine particles were evaluated. Fine particles collected together with ethanol, that is, a dispersion solution in which a mixed powder containing silicon fine particles was dispersed in ethanol showed no turbidity and good dispersibility. Specifically, no precipitation appeared even after a year or more.

(6) Action / Effect According to the above-described method for producing a mixed powder containing silicon fine particles, the gas generated when the mixture containing the silicon source and the carbon source is baked in the inert atmosphere. A mixed powder containing silicon fine particles can be obtained by extracting from and quenching.

  This mixed powder has a fine chain structure and is pulverized very finely by the pulverization step. Therefore, a mixed powder of silicon fine particles that is easily dispersed in a solvent and excellent in dispersion stability can be easily produced in large quantities.

  According to the method for producing a mixed powder containing silicon fine particles as described above, the silicon fine particles are easily dispersed in a solvent by using a ball mill and wet pulverizing the mixed powder together with a predetermined solvent, and have excellent dispersion stability. The mixed powder can be easily produced in large quantities.

  The method for producing a mixed powder containing silicon fine particles includes a step (S4) of separating a mixed powder containing silicon fine particles having a predetermined size or less from a predetermined solvent containing a pulverized mixed powder. Thereby, the particle size of the mixed powder containing silicon fine particles is made uniform. Therefore, the dispersibility of the mixed powder can be improved.

  Moreover, in the manufacturing method of the mixed powder containing silicon fine particles, a pulverizing method using a ball mill is used for the pulverizing step. Thereby, the average particle diameter of the mixed powder containing silicon fine particles can be reduced. In addition, the concentration of the mixed powder containing silicon fine particles can be increased. Therefore, the dispersibility of the mixed powder containing silicon fine particles can be further improved.

(7) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the embodiment, it has been described that the centrifugal separation method is used when the silicon oxide fine particles are separated after wet pulverization with a ball mill. However, for example, liquid phase chromatography may be used.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  DESCRIPTION OF SYMBOLS 1 ... Heating device, 2 ... Heating container, W ... Mixture, 8 ... Stage, 10a, 10b ... Heating element, 12 ... Heat insulating material, 21 ... Suction pipe, 22 ... Dust collector, 23 ... Blower, 24 ... Supply pipe

Claims (5)

Firing a mixture containing a silicon source and a carbon source under an inert atmosphere;
Extracting the gas generated in the firing step from the inert atmosphere and quenching to obtain a mixed powder containing silicon fine particles; and
Crushing the mixed powder with ethanol ;
Separating silicon fine particles of a predetermined size or less from the ethanol containing the pulverized mixed powder;
In the separating step, a method for producing a mixed powder containing silicon fine particles using a centrifugal separation method.   The method for producing a mixed powder containing silicon fine particles according to claim 1, wherein a pulverizing method using a ball mill is used in the pulverizing step. The method for manufacturing a powder mixture containing silicon fine particles according to claim 1 which is a wet grinding to the grinding. The method for producing a mixed powder containing silicon fine particles according to any one of claims 1 to 3 , wherein the silicon source is ethyl silicate. The method for producing a mixed powder containing silicon fine particles according to any one of claims 1 to 4 , wherein the carbon source is a phenol resin.