JP6934344B2 - Powder for spherical silica filler and its manufacturing method - Google Patents

Description

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

Generally, various fillers are used for the purpose of improving the physical properties and functions of plastics, rubbers and the like. Silica is an inorganic compound that is naturally produced as silica stone and is an easily available inorganic compound. When used as a filler, spherical silica is widely used because the fluidity and filling property of the resin composition deteriorate when mixed with the resin in the crushed form. Spherical silica is generally amorphous, has a coefficient of thermal expansion of 0.5 ppm / K, and has a thermal conductivity of 1.4 W / mK (Patent Document 1). On the other hand, crystalline silicas such as cristobalite, α-quartz, and tridimite have a high coefficient of thermal expansion, and in particular, the coefficient of thermal expansion of cristobalite is about 17 to 36 ppm / K (Patent Document 2). Further, it is known that the thermal conductivity of crystalline silica is as high as 10 W / mK (Patent Document 3). Therefore, spherical cristobalite is used to control the thermal conductivity, the coefficient of thermal expansion, and the like without impairing the fluidity and filling property when a plastic, rubber, or the like is blended.

Various methods have been disclosed as methods for synthesizing spherical cristobalite.

For example, Patent Document 4 discloses a method in which spherical fused silica is left at 1500 ° C. for 20 hours and then cooled at a rate of 100 ° C. per hour. However, this method deteriorates productivity because it takes a long time to crystallize.

In Patent Document 5, a solution of an aluminum, titanium or magnesium compound is sprayed onto high-purity amorphous silica, dried at 100 ° C. for 5 hours, crushed into primary particles, and crushed into primary particles over 6 hours at 1400 ° C. A method of raising the temperature, maintaining the temperature at 1400 ° C. for 6 hours, and then cooling from 1400 ° C. to 600 ° C. for 6 hours and from 600 ° C. to 200 ° C. for 4 hours is disclosed. However, in this method, since the silica particles are treated with a liquid treatment agent and then dried, agglomerates are likely to be formed, and it is necessary to crush the silica particles before firing.

In Patent Document 1, a method in which silica powder containing aluminum is sprayed to form a spherical shape, the temperature is raised at a temperature rising rate of 200 ° C./hour, the temperature is maintained at 1300 ° C. for 6 hours, and then the temperature is lowered at a temperature lowering rate of 200 ° C./hour. Is disclosed. In this method, it is necessary to use the spheroidized silica by spraying the raw material silica whose amount of aluminum is adjusted by adding an aluminum compound to the silica particles as a raw material, and the raw material of cristobalite is limited.

Patent Document 2 proposes a production method in which alumina fine powder is mixed with spherical amorphous silica particles and fired at 1450 ° C. for 10 hours. In addition to requiring firing at high temperatures, this method produces alumina and mullite phases with a smaller coefficient of thermal expansion than cristobalite. Further, if the amount of alumina fine powder added is reduced in order to reduce the amount of the produced cristobalite particles, there is a problem that the produced cristobalite particles are fused.

In the prior art, it is necessary to add an aluminum, titanium, magnesium source, etc. in order to efficiently synthesize spherical cristobalite, and in order to suppress the formation of alumina, mullite phase, etc. having a small coefficient of thermal expansion, Patent Document 1 In addition to the fact that the raw materials for cristobalite are greatly limited, it is necessary to control the amount of impurities other than aluminum.

WO2016 / 031823 A1 Japanese Patent Application Laid-Open No. 10-251042 JP-A-2010-059056 JP 2001-172472 Japanese Patent Application Laid-Open No. 2008-162846

An object of the present invention is to provide a powder for a spherical silica filler capable of preparing a resin composition having a low viscosity and a high filling property even when the resin is highly filled. Another object of the present invention is to provide a powder for spherical silica filler, which has a high cristobalite phase content and a large effect of controlling the coefficient of thermal expansion when filled in a resin, although it is a synthetic method having excellent productivity.

(1) For a spherical silica filler having an average circularity of 0.90 or more, a cristobalite phase of 95% by mass or more, aluminum of 1000 ppm to 10000 ppm, and an average particle size of 1 to 50 μm. Powder.
(2) Spherical amorphous silica having an average circularity of 0.90 or ^{more and alumina powder having a specific surface area of 40 m 2} / g or more and a bulk density of 0.1 g / cm ³ or less are 1000 ppm in terms of aluminum. The method for producing a powder for spherical silica filler according to (1), wherein the powder is mixed so as to have a concentration of 10000 ppm and heated at 1200 ° C. to 1350 ° C. for 1 to 8 hours.
(3) The powder for spherical silica filler according to (1), which is used by blending in a resin.

According to the present invention, it is possible to provide a powder for a spherical silica filler capable of preparing a resin composition having low viscosity and high filling property even when the resin composition is highly filled. In addition, since the cristobalite phase content is high despite the synthetic conditions with good productivity, the effect of controlling the coefficient of thermal expansion is great when the resin is filled.

FIG. 1 is a scanning electron micrograph of the powder for spherical silica filler obtained in Example 1.

The powder for spherical silica filler of the present invention has an average circularity of 0.90 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. Further, the powder for spherical silica filler of the present invention contains 95% by mass or more of the cristobalite phase. When the content of the cristobalite phase is less than 95% by mass, the coefficient of thermal expansion becomes small. Further, the powder for spherical silica filler of the present invention contains 1000 ppm to 10000 ppm of aluminum. If the amount of aluminum is less than 1000 ppm, the crystallization rate of cristobalite will decrease, and it will be necessary to heat and crystallize for a longer period of time at a high temperature, resulting in poor productivity. Further, when the amount of aluminum is more than 10,000 ppm, a phase other than cristobalite having a small coefficient of thermal expansion, for example, a mullite phase, is generated, and the coefficient of thermal expansion decreases.

The spherical amorphous silica particles used as the raw material of the present invention preferably have an average circularity of 0.90 or more. When the average circularity of the spherical amorphous silica particles is less than 0.90, the average circularity of the obtained silica filler powder is less than 0.90, the rolling resistance of the particles when mixed with the resin is increased, and the particles flow. The sex is reduced.

The average particle size of the powder for spherical silica filler of the present invention is preferably 1 to 50 μm. When the average particle size 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 is larger than 50 μm, the filling property into the resin becomes poor. Deteriorate.

As a method for producing a powder for silica filler of the present invention, a heat crystallization method is used.

The heat crystallization method is a method of heating a raw material powder at a high temperature to crystallize it. Any heating device may be used as long as a high temperature can be obtained, and for example, an electric furnace, a rotary kiln, a pusher furnace, or the like is used. The heating temperature is preferably 1200 to 1350 ° C. If the heating temperature is less than 1200 ° C., crystallization takes time, crystallization is insufficient, the ratio of the cristobalite phase is low, and the physical properties of cristobalite itself are impaired. If the heating temperature exceeds 1350 ° C., a crystal phase having a small coefficient of thermal expansion, for example, a mullite phase is formed, which is not desirable. In addition, the fusion of the particles becomes stronger due to heating, and the average circularity decreases, so that the viscosity when mixed with the resin increases. The heating time is preferably 1 to 8 hours. If the heating time is less than 1 hour, crystallization into cristobalite will be insufficient. Further, if the heating time exceeds 8 hours, it is not economical and the production capacity is lowered, which is not preferable.

As a method for mixing spherical amorphous silica and alumina, which are raw materials, dry mixing of powders is preferable. In the method of coating the surface of spherical amorphous silica with alumina sol or an aluminum-based coupling agent, the silica particles tend to aggregate, so that the average circularity decreases after heat crystallization and the crystallization rate also decreases. Examples of the mixing method for processing include crushers such as agate mortars, ball mills and vibration mills, and various mixers.

During heat crystallization, alumina powder is added as an auxiliary agent to promote crystallization into cristobalite. The alumina powder preferably has a specific surface area of 40 m ² / g or more and a bulk density of 0.1 g / cm ³ or less. If the specific surface area is ^{less than 40 m 2} / g, the contact and reaction of the raw material with the surface of the spherical amorphous silica particles will be insufficient, and the crystallization rate to cristobalite will decrease. In addition, since the particles are fused to each other after heating, the average circularity is lowered and the viscosity is increased when mixed with the resin. If the bulk density ^{exceeds 0.1 g / cm 3} , the silica particles tend to come into contact with each other, the silica particles tend to fuse with each other, and the crystallization rate also decreases, which is not preferable.

The amount of alumina added is preferably 1000 ppm to 10000 ppm in terms of metallic aluminum. If it is less than 1000 ppm, the crystallization rate to cristobalite is slow, crystallization takes a long time, and the proportion of cristobalite decreases. Further, since the silica particles are fused, the average circularity is lowered and the viscosity when mixed with the resin is increased. If it exceeds 10000 ppm, a phase other than cristobalite having a small coefficient of thermal expansion, for example, a mullite phase is formed, so that the coefficient of thermal expansion decreases.

Spherical amorphous silica, which is a raw material powder, is not particularly specified. For example, silica produced by the sol-gel method or water glass, or silica produced by the melting method can be used.

Since the silica filler powder obtained in the present invention has a high average circularity, it has a low viscosity, exhibits extremely good moldability when filled in a resin, and can increase the filling rate. If necessary, the obtained spherical particles are classified so as to obtain a desired filling rate, and then surface-treated 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.

The silica filler powder of the present invention is used, for example, by blending it in a resin. Examples of the resin used in the present invention include polyamide resins such as epoxy resins, silicone resins, phenol resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamideimides, and polyetherimides, and polybutylene terephthalates. Polyester such as 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-styrene) resin and the like can be mentioned.

The ratio of the powder for the spherical silica filler in the resin is appropriately selected according to the physical properties such as the target coefficient of thermal expansion. For example, the amount of the resin used is appropriately selected in the range of preferably 1 to 100 parts by mass, more preferably 10 to 50 parts by mass with respect to 100 parts by mass of the silica filler powder.

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]
As a starting material, spherical amorphous silica particles (“FB-5SDX” manufactured by Denka Co., Ltd., average particle diameter 5 μm, average circularity 0.95) were used. In addition, alumina particles (“AEROXIDE AluC” manufactured by Nippon Aerosil Co., Ltd., specific surface area 100 m ² / g, bulk density 0.05 g / cm ³ ) were used. Next, 98.5 parts by mass of the silica raw material and 1.5 parts by mass of the alumina raw material were sufficiently mixed with a mixer (“EL-1” manufactured by Nippon Eirich Co., Ltd.), and then heated at 1300 ° C. for 2 hours. The obtained fired product was in powder form.

The characteristics of the particle composition prepared in Example 1 were evaluated by the following method. The evaluation results are shown in Table 1.

[Identification and quantification of crystal phase]
The crystal phase was identified and quantified by powder X-ray diffraction measurement and Rietveld method. The equipment used was RINT-Ultima IV manufactured by Rigaku Co., Ltd., the X-ray source was CuKα, the tube voltage was 40 kV, the tube current was 40 mA, the scan speed was 5.0 / min, and the 2θ scan range was 10 ° to 80 °. For the quantitative analysis, Rietveld software (manufactured by Rigaku, integrated powder X-ray software PDXL) was used. As for the content of the crystal phase, 50% by mass of the standard sample α-alumina for X-ray diffraction manufactured by the National Institute of Standards and Technology (NIST) was added to the powder obtained in Example 1 as an internal standard substance, and the cristobalite phase was contained. The rate was measured.

[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 Christobalite particles moving in the cell were recorded as an image with an objective lens, and this recorded image and the following equation (1) were recorded. ), The average circularity was calculated. In the formula (1), S represents the area of the captured recorded image in the particle projection drawing, and L represents the perimeter of the particle projection drawing. The average value of 200 particles calculated in this way was taken as the average circularity of the particles obtained in Example 1.
Circularity = 4πS / L ² (1)

[Metallic aluminum content analysis]
To 0.5 g of the powder obtained in Example 1, 2 mL of nitric acid and 10 mL of hydrofluoric acid were added, dried on a hot plate at 140 ° C., 10 mL of nitric acid was added to the residue to dissolve it, and the volume was adjusted to 20 mL. The aluminum content was analyzed in.

[density]
5 g of the powder obtained in Example 1 was placed in a sample cell for measurement, and measured by a gas substitution method using a dry densitometer (“Accupic II 1340” manufactured by Shimadzu Corporation).

[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, 50 cc of pure water and 0.1 g of the powder obtained in Example 1 were added to a glass beaker, and the sample was dispersed with an ultrasonic homogenizer (“SFX250” manufactured by BRANSON) for 1 minute. The dispersion liquid of the powder for spherical silica filler 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 the measurement was performed 30 seconds after the predetermined amount was added. 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 in the laser diffraction type particle size distribution measuring device. 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%.

[viscosity]
Mix with bisphenol A type liquid epoxy resin (“JER828” manufactured by Mitsubishi Chemical Corporation) so that the powder obtained in Example 1 accounts for 50% by volume of the whole, and use a planetary stirrer (Shinky Co., Ltd. “Awatori Rentaro”). AR-250 ”, rotation speed 2000 rpm) was kneaded to prepare a resin composition. The viscosity of the obtained resin composition was measured under the following conditions using a rheometer (“MCR-300” manufactured by Nihon Shibel Hegner Co., Ltd.).
Plate shape: Circular flat plate 25 mmφ
Sample thickness: 1 mm
Temperature: 25 ± 1 ° C
Shear rate: 1s ^-1

[Coefficient of thermal expansion]
Bisphenol F type liquid epoxy resin (“JER807” manufactured by Mitsubishi Chemical Corporation) 25.6 parts by mass, 4,4'-diaminophenylmethane (manufactured by Tokyo Kasei Co., Ltd.) 6.4 parts by mass were mixed while being melted at 95 ° C. The powder obtained in Example 1 was added so as to be 50% in terms of volume%, and mixed with a planetary stirrer (Shinky's "Awatori Rentaro AR-250", rotation speed 2000 rpm). The above mixture was poured into a preheated silicone mold (3 cm square x 5 mm thick), allowed to stand at 80 ° C. for 20 minutes, and vacuum-heated press machine ("IMC-1674-A type" manufactured by Imoto Seisakusho Co., Ltd.). ), Press-heat-cured in the order of 80 ° C./1 hour / 1.5 MPa, 150 ° C./1 hour / 2.5 MPa, and 200 ° C./0.5 hour / 5 MPa. The cured sample was processed to a sample size for measurement (4 × 4 × 15 mm), and the coefficient of thermal expansion was evaluated by TMA (“TMA4000SA” manufactured by Bruker). The temperature rise conditions were 5 ° C./min, the measurement temperature was -10 ° C to 250 ° C, and the atmosphere was a nitrogen atmosphere. From the obtained TMA measurement chart, 0 ° C to 100 ° C (α1) and 150 ° C to 200 ° C. The coefficient of thermal expansion of (α2) was calculated.

Example 2-5, Comparative Example 1-5
Tests and evaluations were carried out in the same manner as in Example 1 except that the amount of alumina powder added, the heating time, and the heating temperature were changed as shown in Tables 1 and 2. The results of the examples are shown in Table 1, and the results of the comparative examples are shown in Table 2.

Example 6
Tests and evaluations were carried out in the same manner as in Example 1 except that alumina powder (“Alu 65” manufactured by Nippon Aerosil Co., Ltd., specific surface area 65 m ² / g, bulk density 0.05 g / cm ^{3) was used.} The results are shown in Table 2.

Example 7
Tests and evaluations were carried out in the same manner as in Example 1 except that alumina powder (“Alu 130” manufactured by Nippon Aerosil Co., Ltd., specific surface area 130 m ² / g, bulk density 0.04 g / cm ^{3) was used.} The results are shown in Table 2.

Comparative Example 6
Tests and evaluations were carried out in the same manner as in Example 1 except that alumina powder (“AA-05” manufactured by Sumitomo Chemical Co., Ltd., specific surface area 10 m ² / g, bulk density 0.6 g / cm ^{3) was used.} The results are shown in Table 2.

Comparative Example 7
Tests and evaluations were carried out in the same manner as in Example 1 except that alumina powder (“AKP-G15” manufactured by Sumitomo Chemical Co., Ltd., specific surface area 156 m ² / g, bulk density 0.2 g / cm ^{3) was used.} The results are shown in Table 2.

Comparative Example 8
Al (C ₅ H ₇ O ₂ ) (C ₆ H ₉ O ₃ ) ₂ (“AL-3200” manufactured by Matsumoto Fine Chemicals Co., Ltd.) 14.9 parts by mass was dissolved in 50 parts by mass of isopropyl alcohol to prepare a spray liquid. Next, 98.5 parts by mass of spherical amorphous silica particles (“FB-5SDX” manufactured by Denka Co., Ltd., average particle diameter 5 μm, average circularity 0.95) were added to a mixer (manufactured by Nippon Eirich Co., Ltd., EL-1). ) Was stirred. The spray liquid was sprayed onto the silica particles being stirred, stirred for 1 hour, the powder was recovered, dried at 120 ° C. for 5 hours, and then heated and evaluated in the same manner as in Example 1.

As a result, the resin composition containing the powder for spherical silica filler of the present invention has a lower viscosity and can be filled more highly than the resin composition containing cristobalite having a small average circularity. In addition, since the cristobalite phase content is high in spite of the synthetic conditions with good productivity, the result is that the effect of controlling the coefficient of thermal expansion is large.

Since the resin composition using the powder for spherical silica filler of the present invention has a high average circularity and low viscosity, it can be highly filled. Therefore, the powder for spherical silica filler of the present invention has a thermal expansion rate of plastic, rubber, etc. It can be used as a filler to control.

Claims (3)

And an average circularity of 0.90 or more, cristobalite phase comprises 95 wt% or more, aluminum 6100 ppm to 9500 pp m seen including, wherein the average particle size of 1 to 50 [mu] m, for spherical silica filler Powder. Spherical amorphous silica with an average circularity of 0.90 or ^{more and alumina powder with a specific surface area of 40 m 2} / g or more and a bulk density of 0.1 g / cm ³ or less are 6100 ppm to 9500 in terms of aluminum. The method for producing a powder for a spherical silica filler according to claim 1, wherein the powder is mixed so as to be ppm and heated at 1200 ° C to 1350 ° C for 1 to 8 hours. The powder for spherical silica filler according to claim 1, wherein the powder is blended in a resin and used.

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