JP6755376B2 - Spherical calcium fluoride - Google Patents

Description

The present invention relates to spherical calcium fluoride. The present invention relates to spheroidized calcium fluoride for the purpose of improving fluidity and filling property when blended with a polymer material such as resin or plastic as a filler, for example. The present invention relates to, for example, a resin composition filled with spherical calcium fluoride.

Generally, various fillers are used for the purpose of improving the physical properties and functions of plastics, rubbers and the like. Calcium fluoride is an inorganic compound that is naturally produced as fluorite, and is an inorganic compound that can be easily obtained as synthetic calcium fluoride that supplements the fluorine-containing compound discharged in the chemical industry in the form of a calcium salt. is there. The refractive index of calcium fluoride is 1.43, the thermal conductivity is 10 W / mK, the coefficient of thermal expansion is 24 ppm / K, and the dielectric constant is 6.8, which is excellent for a wide range of light from vacuum ultraviolet to infrared. It has various characteristics such as low Mohs hardness (Mohs hardness 4) and less damage to the mold as compared with silica and alumina, which show high permeability. Therefore, it is expected to be used in many applications in order to control the refractive index, thermal conductivity, thermal expansion coefficient, etc. of plastics and rubbers.

However, it is not so common as a filler to be blended in a resin. For example, Patent Document 1 describes a filler in artificial marble, and Patent Document 2 describes a resin sliding member containing calcium fluoride. As described above, calcium fluoride as a resin filler is used only slightly for special purposes.

In order to use it more preferably as a filler, it is necessary to improve the filling property, processability, and melt fluidity in the resin. Calcium fluoride is also spherical, has an appropriate particle size distribution, and has less aggregation. Is required. For example, in Patent Document 3, 79% of crushed calcium fluoride is filled, but in addition to the need for surface treatment with a silane coupling agent, the resin is limited to a thermoplastic resin. In Patent Document 4, spherical or particle-shaped calcium fluoride is packed in a polymer, but the calcium fluoride exemplified therein has an aspect ratio of 1.8, which is hard to say spherical and has a filling rate. Was also inadequate.

Various methods have been disclosed as methods for spheroidizing calcium fluoride.

For example, Patent Document 5 specifies a method of making mineral fine particles having a Mohs hardness of 5 or less into a slurry, injecting them from both sides at an injection pressure of 100 to 200 MPa, and causing them to collide with each other to form spheroids by wet pulverization. In the wet treatment, in order to use it as a filler, a step of drying the obtained particles is required, and further, the cost is increased due to the use of the solvent. In Non-Patent Document 1, spherical calcium fluoride is synthesized by wet synthesis by the reaction of calcium chloride and ammonium fluoride. However, in addition to the above-mentioned disadvantages of the wet treatment, micron-order particles preferably used as a filler are synthesized. It is difficult to do.

Further, in Non-Patent Document 2, the mixture of barium fluoride and calcium fluoride is spheroidized by the gas atomizing method, but the effect on the filling property into the resin is not specified. Further, since the ratio of calcium fluoride is about 30% and the main component is barium fluoride, the solubility in water and the specific gravity are increased, and it is not suitable as a filler to be filled in a resin. Further, Patent Document 6 states that the atomizing method is possible, but in addition to not describing the details of the atomizing method and the particle size and average circularity of the particles obtained by the atomizing method, the particles are spheroidized. The effect of is not specified.

Japanese Patent No. 4491619 Japanese Patent No. 5465270 JP-A-2003-40619 Japanese Patent No. 5547644 Japanese Patent No. 4193913 JP-A-2002-188007

AsepBayu Dani Nandyantoet al., KonapowerandParticle Journal, No.29, 141-157, 2011 Malcolm K. Stanford, Tribology Transitions, 51, 829-834, 2008

An object of the present invention is to provide spherical calcium fluoride capable of preparing a resin composition having low viscosity and high fluidity even when the resin is highly filled.

(1) Spherical calcium fluoride having an average particle size of 1 to 50 μm and an average circularity of 0.90 or more.
(2) The method for producing spherical calcium fluoride according to (1), wherein the calcium fluoride raw material is produced by a powder melting method in which a raw material for calcium fluoride is passed through a high temperature region having a temperature equal to or higher than the melting point to be spherical.
(3) Manufactured by the atomization method in which calcium fluoride is dissolved and a fluid is sprayed onto the molten metal dropped through a nozzle to disperse and spray the molten metal, quench and solidify it, and spheroidize it. The method for producing spherical calcium fluoride according to the above.
(4) Calcium fluoride is dissolved, and the molten metal is dropped onto a rotating disk with respect to the molten metal dropped through the nozzle. The molten metal is dispersed and sprayed, rapidly cooled and solidified, and spheroidized. The method for producing spherical calcium fluoride according to (1).

According to the present inventor, it is possible to provide spherical calcium fluoride capable of preparing a resin composition having low viscosity and high fluidity even when the resin composition is highly filled.

FIG. 1 is a scanning electron micrograph of the spherical calcium fluoride obtained in Example 1. The white line is the dimension. FIG. 2 is a scanning electron micrograph of the raw material of Example 1 and the calcium fluoride used in Comparative Example 8. The white line is the dimension.

The spherical calcium fluoride of the present invention has an average particle size of 1 to 50 μm and an average circularity of 0.90 or more. When the average particle size of spherical calcium fluoride is less than 1 μm, the viscosity when mixed with the resin increases and the fluidity when the resin composition is injected into a mold or the like decreases, and when it becomes larger than 50 μm, the resin Poor filling property. The average circularity of spherical calcium fluoride is 0.90 or more, preferably 0.95 or more. When the average circularity is less than 0.90, the rolling resistance of the particles when mixed with the resin increases, and the fluidity decreases.

The calcium fluoride used as the raw material of the present invention is not particularly limited, and crushed natural fluorite may be used, or synthetic calcium fluoride may be used. As the synthetic calcium fluoride, hydrofluoric acid or fluoride ions discharged from a process such as a chemical industry or a semiconductor industry using a fluorine compound is reacted with calcium hydroxide or calcium carbonate and recovered as calcium fluoride. Calcium fluoride is also included.

The purity of calcium fluoride, which is the raw material of the present invention, is preferably 75% by mass or more, more preferably 90% by mass. If it is less than 75% by mass, the physical properties of calcium fluoride itself may be impaired and impurities may increase. The average particle size of calcium fluoride, which is the raw material of the present invention, is preferably 1 to 50 μm.

As the method for producing spherical calcium fluoride of the present invention, a powder melting method or an atomizing method is used.

The powder melting method is a method in which a raw material powder is passed through a high temperature region having a temperature equal to or higher than the melting point. For example, it is a method in which the raw material powder is put into a chemical flame or thermal plasma to be melted and spheroidized by its own surface tension. The powder melting method described here also includes a method of passing the raw material powder through a high temperature region having a temperature higher than the melting point without using a chemical flame or thermal plasma. For example, the raw material is put into a vertical tube furnace or a tower kiln. Also includes a method of melting and spheroidizing by its own surface tension.

Further, in the powder melting method, particles obtained by granulating a powdery raw material with a spray dryer or the like, particles obtained by crushing a bulk material and adjusting to a desired particle size distribution, or the like can be used, and these particles can be used. Is put into a chemical flame or thermal plasma, a vertical tubular furnace or the like while suppressing the aggregation of particles, and melted in the chemical flame or thermal plasma, a vertical tubular furnace or the like. Further, a dispersion liquid of a raw material dispersed in a solvent or the like is prepared, and the liquid raw material is sprayed into a chemical flame or thermal plasma, a vertical tube furnace, etc. using a nozzle or the like to evaporate the dispersion medium. It is done by melting.

In the powder melting method, the chemical flame means, for example, a flame generated by burning a flammable gas with a burner. As the source of the chemical flame, it is sufficient that a temperature equal to or higher than the melting point of calcium fluoride can be obtained. For example, natural gas, propane gas, acetylene gas, liquefied petroleum gas (LPG), hydrogen or the like is used as the flammable gas. Can be done. Air, oxygen, etc. are used in combination with the flammable gas as a flammable gas. The size of the chemical flame, the temperature, etc. can be adjusted by adjusting the size of the burner and the flow rates of the flammable gas and the combustible gas. The supply amount of calcium fluoride as a raw material is preferably 0.01 to 10 kg / Nm ^{3 and} more preferably 0.05 to 2 kg / Nm ³ with respect to the total amount of flammable gas and combustible gas. 0.01 kg / Nm ³ is reduced and productivity low volume than, for many consisting of calcium fluoride than 10 kg / Nm ³ are aggregated, it becomes difficult to control the particle size. Unless otherwise specified, flow rates are in normal notation. Further, as a source of thermal plasma, oxygen, nitrogen, argon, carbon dioxide gas and a mixed gas thereof are preferably used. Further, as a melting source, a vertical tube furnace or a tower kiln can also be used. It is preferable that the melting atmosphere of the furnace is such that heating can be performed above the melting point of calcium fluoride, the raw materials do not evaporate or decompose, and the inside of the furnace is not significantly consumed. Without the frame, the supply amount of calcium fluoride as a raw material, the atmospheric gas 1Nm per ^3, 0.01 to 10 is preferred. If the amount is less than 0.01 kg, the productivity is lowered, and if the amount is more than 10 kg, calcium fluoride aggregates, which makes it difficult to control the particle size.

In the atomizing method, for example, a calcium fluoride raw material is dissolved using a crucible or the like, and a fluid such as water or gas is sprayed onto the molten metal dropped through a nozzle at the bottom of the crucible, or the molten metal is poured onto a rotating disk. This is a method of obtaining spherical calcium fluoride by dispersing and spraying the molten metal by dropping it and quenching and solidifying it. As the atomizing method, any method such as a gas atomizing method, a centrifugal atomizing method, a hybrid atomizing method, a water atomizing method, and a high-speed combustion flame atomizing method can be preferably used depending on the method for dispersing the molten metal flow.

In the gas atomization method, the temperature of the molten metal (melting temperature) is preferably 1500 to 2000 ° C. The diameter of the nozzle at the bottom of the crucible is preferably 0.5 to 3.0 mm. Examples of the gas include argon gas and the like. The injection pressure of the fluid is preferably 0.8 to 10 MPa. In the centrifugal atomization method, the temperature of the molten metal (melting temperature) is preferably 1500 to 2000 ° C. The diameter of the nozzle at the bottom of the crucible is preferably 0.5 to 3.0 mm. The rotation speed of the disc is preferably 20000 rpm to 120,000 rpm. The diameter of the disc is preferably 20 mm to 100 mm. As the material of the disk, a material having a melting point higher than that of calcium fluoride and being resistant to thermal shock, for example, Mo, W, Pt, SiC, BN and the like is selected.

In the case of the atomizing method, the shape of the raw material may be either a powder or a bulk material, or a combination thereof may be used. These raw materials are placed in a crucible having a melting point higher than that of calcium fluoride, for example, a crucible made of carbon, Mo, W, Pt, etc., and then melted. The melting method may be any method as long as it can heat the raw material above its melting point, and for example, high frequency, plasma, laser, electron beam, light or infrared rays can be used. The melting of the raw material is preferably carried out in an atmosphere in which the raw material does not evaporate or decompose and the crucible is not significantly consumed. The optimum atmosphere is selected according to the heating temperature and the material of the crucible used, such as in the air, in an inert gas, or in a vacuum.

Since the spherical calcium fluoride obtained in the present invention has a high average circularity, it has extremely good fluidity, exhibits extremely good moldability when filled in a resin, and can increase the filling rate. The obtained spherical particles are classified so as to obtain a desired filling rate, and then surface-treated as necessary to further increase the filling rate. As the surface treatment agent, a silane coupling agent is generally used, but a titanate coupling agent and an aluminate-based coupling agent can also be used.

Next, the resin composition of the present invention will be described.

Examples of the resin used in the present invention include polyamides such as epoxy resin, silicone resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyimide, polyamideimide, and polyetherimide, polybutylene terephthalate, and polyethylene terephthalate. Polyphenylene sulfide, total aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber, styrene) resin, AES (acrylonitrile, ethylene, propylene, diene rubber) -Sterinic) Resin and the like can be mentioned.

Further, the resin composition of the present invention may contain a low stress agent, a silane coupling agent, a surface treatment agent, a flame retardant, a flame retardant aid, a colorant, a mold release agent and the like, if necessary. .. Examples of the low stressing agent include silicone rubber, polysulfide rubber, acrylic rubber, butadiene rubber, rubber-like substances such as styrene block copolymers and saturated elastomers, various thermoplastic resins, silicone resins, and epoxy resins. Examples thereof include a resin obtained by modifying a part or all of the phenol resin with amino silicone, epoxy silicone, alkoxy silicone or the like. Examples of the silane coupling agent include epoxysilanes such as γ-glycidoxypropyltrimethoxysilane and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, aminopropyltriethoxysilane, ureidopropyltriethoxysilane, and N-. Examples thereof include aminosilanes such as phenylaminopropyltrimethoxysilane, hydrophobic silane compounds such as phenyltrimethoxysilane, methyltrimethoxysilane, and octadecyltrimethoxysilane, and mercaptosilane. Examples of the surface treatment agent include Zr chelate, titanate coupling agent, aluminum-based coupling agent and the like. Examples of the flame retardant include halogenated epoxy resins and phosphorus compounds. Examples of the flame retardant aid include Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O _{5, and the} like. Examples of the colorant include carbon black, iron oxide, dyes, pigments and the like. Examples of the release agent include natural waxes, synthetic waxes, metal salts of linear fatty acids, acid amides, esters, paraffin and the like.

In the resin composition of the present invention, the amount of the resin used is preferably 1 to 50 parts by mass, more preferably 10 to 30 parts by mass with respect to 100 parts by mass of spherical calcium fluoride.

The resin composition of the present invention can be produced by mixing the above materials with a blender or a mixer, melt-kneading them with a heating roll, a kneader, a single-screw or twin-screw extruder, a Banbury mixer, or the like, and cooling them.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the Examples.

Example 1-4, Comparative Example 1-4
The calcium fluoride raw material powder having the average particle size shown in Table 1 is put into a high-temperature flame formed by the amount of LPG shown in Table 1 and the amount of oxygen gas shown in Table 1 at the powder supply amount shown in Table 1. The spheroidizing treatment was carried out to prepare spheroidal calcium fluoride having an average particle size and an average circularity shown in Table 3. The purity of the calcium fluoride raw material powder used is 99.5%.

100 parts by mass of spherical calcium fluoride obtained by the above method, 25 parts by mass of bisphenol A type liquid epoxy resin ("JER828" manufactured by Mitsubishi Chemical Corporation), planetary stirrer (Sinky "Awatori Rentaro AR-250"" , 2000 rpm) to prepare a resin composition.

The characteristics of the particle composition and the resin composition prepared in Examples and Comparative Examples were evaluated by the following methods. The results are shown in FIGS. 1 and 4.

[Average particle size]
The measurement was performed using a "laser diffraction type particle size distribution measuring device LS 13 320" manufactured by Beckman Coulter. As a sample, 10 cc of pure water and 1 g of spherical calcium fluoride were added to a glass beaker, and dispersion treatment was performed for 1 minute with an ultrasonic cleaner. The dispersion of spherical calcium fluoride that had been subjected to the dispersion treatment was added drop by drop to the laser diffraction type particle size distribution measuring device with a dropper, and ultrasonic waves were irradiated again for 90 seconds. The measurement was performed 60 seconds after the irradiation. In the laser diffraction type particle size distribution measuring device, the particle size distribution was calculated from the data of the light intensity distribution of the diffracted / scattered light by the particles detected by the sensor. The average particle size was obtained by multiplying the measured particle size value by the relative particle amount (difference%) and dividing by the total relative particle amount (100%). The% here is the volume%.

[Average circularity]
The measurement was performed using a powder image analyzer (PITA-1) manufactured by Seishin Enterprise Co., Ltd. The sample was dispersed in pure water, this liquid was flowed into a planar stretch flow cell, and 200 spherical calcium fluoride particles moving in the cell were recorded as an image with an objective lens, and this recorded image and the next The average circularity was calculated from the formula (1). In the formula (1), S represents the area of the captured recorded image in the particle projection drawing, and L represents the peripheral length of the particle projection drawing. The average value of 200 particles calculated in this way was taken as the average circularity of the spherical calcium fluoride particles.
Average circularity = 4πS / L ² (1)

[viscosity]
The viscosity of the obtained resin composition was measured under the following conditions using a rheometer (“MCR-300” manufactured by Siber Hegner, Japan).
Plate shape: Circular flat plate 25 mmφ
Sample thickness: 1 mm
Temperature: 25 ± 1 ° C
Shear rate: 0.1s ^-1

Example 5-8, Comparative Example 5-6
The calcium fluoride raw material powder having the average particle size shown in Table 1 was put into a vertical tube furnace set at 1600 ° C. at the powder supply amount in Table 1 to perform spheroidizing treatment, and the average particle size shown in Table 3 was obtained. And spherical calcium fluoride having an average circularity was prepared. No LPG and oxygen gas were used. Other than that, the same procedure as in Example 1 was performed. The results are shown in Table 4.

Example 9-13, Comparative Example 7-9
The calcium fluoride raw material powder having the average particle size shown in Table 2 is melted in a carbon chamber at the melting temperature shown in Table 2, and is dropped through a nozzle having the diameter shown in Table 2 while injecting pressure shown in Table 2. The molten metal was dispersed and sprayed by injecting the argon gas of No. 3 to perform a spheroidizing treatment to prepare spheroidal calcium fluoride having an average particle size and an average circularity shown in Table 3. Other than that, the same procedure as in Example 1 was performed. The results are shown in Table 4.

Examples 16-17, Comparative Example 10-12
The calcium fluoride raw material powder shown in Table 3 is melted in a carbon chamber at the melting temperature shown in Table 3 and dropped through a nozzle having the diameter shown in Table 3 at the disc diameter and rotation speed shown in Table 3. The molten metal was dispersed and sprayed to perform spheroidizing treatment to prepare spheroidal calcium fluoride having an average particle size and an average circularity shown in Table 3. Other than that, the same procedure as in Example 1 was performed.
The results are shown in Table 4.

Comparative Example 8
The same procedure as in Example 1 was carried out except that the calcium fluoride raw material powder itself, which had not been spheroidized, used in Example 1 was used. The results are shown in Table 4.

As a result, the resin composition containing spherical calcium fluoride of the present invention has a lower viscosity and can be filled more highly than the resin composition containing a calcium fluoride filler having a small average circularity. A scanning electron micrograph showing the shape of the spherical calcium fluoride obtained in Example 1 is shown in FIG. A scanning electron micrograph showing the shape of the calcium fluoride raw material powder of Example 1 (that is, the calcium fluoride used in Comparative Example 8) is shown in FIG.

It goes without saying that the present invention is not limited to the above examples, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. ..

Since the resin composition using spherical calcium fluoride of the present invention has low viscosity and can be highly filled, it can be used as a filler for controlling the refractive index, thermal conductivity, thermal expansion coefficient, etc. of plastics, rubbers, and the like.

Claims (4)

Spherical calcium fluoride having an average particle size of 3 to 41 μm and an average circularity of 0.93 or more. The method for producing spherical calcium fluoride according to claim 1, wherein the calcium fluoride raw material is produced by a powder melting method in which a calcium fluoride raw material is passed through a high temperature region having a temperature equal to or higher than the melting point and spheroidized. The spherical shape according to claim 1, which is produced by an atomizing method in which calcium fluoride is dissolved and a fluid is sprayed onto the molten metal dropped through a nozzle to disperse and spray the molten metal and quench and solidify it to make it spheroidal. Method for producing calcium fluoride. Claim 1 is manufactured by an atomizing method in which calcium fluoride is dissolved and the molten metal is dropped onto a rotating disk with respect to the molten metal dropped through a nozzle to disperse and spray the molten metal, quench and solidify it, and spheroidize it. The method for producing spherical calcium fluoride according to.