JP7072220B2 - Method for manufacturing unfired silica solidified body - Google Patents

Description

The present invention relates to a method for producing a solidified unfired silica.

In Patent Document 1, an activated ceramic powder having a mechanochemically amorphized surface is treated with an alkaline aqueous solution to dissolve and reprecipitate the surface of the activated ceramic powder to solidify the ceramic. How to get is described. Patent Document 2 describes a method in which an alkali-containing mixed solution is used as a method for producing a composite material containing silica, and ethanol or the like is used as a solvent for the alkali-containing mixed solution. However, it is possible to produce a solidified body using two types of silica having different particle sizes, and for the produced solidified body, for example, the porosity and shrinkage rate, which indicate the characteristics of the solidified body, are adjusted according to the conditions of the manufacturing process. There was a problem that it was not possible to obtain knowledge about silica.

Japanese Unexamined Patent Publication No. 2008-239433 WO2015 / 050243

The problem of the present invention is to solve the above-mentioned conventional problems, to produce a strong solidified body through solid cross-linking using two types of silica having different particle sizes, and to show the characteristics of the silica solidified body. It is an object of the present invention to provide the knowledge of the manufacturing process capable of controlling the porosity and the shrinkage rate.

(1) A granulation compression step of granulating and uniaxially compressing a silica particle raw material contained in an alkaline solution in which the silica particles have an alkali concentration of 1 M to 5 M to obtain a first solid body, and the first solid body. Production of a non-fired silica solidified body comprising a curing step of bridging the silica particles to become a second solid body by curing and a drying step of drying the second solid body. The method.
(2) In the method for producing a non-firing silica solidified body according to (1), a compression step of compressing without granulation is included instead of the granulation compression step, and the fine silica particles are alkaline in the silica particle raw material. It further comprises a mixing step of mixing the fine silica particle raw materials contained in the alkaline solution having a concentration of 3 M, and is characterized by including cross-linking caused by the fine silica particles becoming a semi-solid semi-liquid during the curing step. This is a method for producing a solidified body of uncalcined silica.
(3) The method for producing a solidified unfired silica according to (2), wherein the ratio of the raw material of the fine silica particles to the voids formed by the silica particles is 40 vol% to 280 vol%.
(4) The method for producing a solidified unfired silica according to (1), further comprising an alcohol mixing step of mixing alcohol before the granulation compression step.
(5) The method for producing a solidified unfired silica according to (2) or (3), further comprising an alcohol mixing step of mixing alcohol before the compression step.
(6) The non-firing silica solidified body according to (1) to (5), wherein the curing temperature is 40 ° C. to 80 ° C. and the curing time is 40 hours or less as the curing conditions of the curing step. It is a manufacturing method.

The method for producing a non-firing silica solidified body according to the present invention can produce a strong solidified body using two types of silica having different particle sizes, and particularly exhibits the characteristics of the silica solidified body depending on the curing conditions of the curing step. It has the effect of being able to control the porosity and contraction rate.

It is a schematic diagram which shows the flow of the manufacturing method of the uncalcined silica solidified body which is one Embodiment of this invention. (A) Schematic diagram showing a second solid body produced in the process of manufacturing a solidified silica without calcining, (B) Schematic diagram showing an enlarged semi-solid semi-liquid region formed on the second solid body. It is a figure. It is a figure which shows the relationship between the Log differential pore volume distribution and the integrated pore volume which the uncalcined silica solidified body has when the amount of ethanol added in an alcohol mixing step is (A) 0.625 g, and (B) 1.06 g. be. It is a figure which shows the relationship between the porosity and the shrinkage rate of the uncalcined silica solidified body containing ethanol with respect to the curing temperature in a curing process. It is a figure (magnification 40,000 times) which shows the SEM photograph of the uncalcined silica solidified body containing ethanol with respect to the curing time (0, 1, 3, 5 and 20 hours). It is a figure which shows the relationship of the integrated pore volume cc / g of the uncalcined silica solidified body with respect to the curing time (0, 1, 3, 5 and 20 hours) with respect to a large void or a small void.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be made without departing from the scope of the invention.

As shown in FIG. 1, the uncalcined silica solidified body according to the embodiment of the present invention is obtained by mixing silica particles and an alkaline solution having an alkali concentration of 1 M to 5 M, and performing granulation uniaxial compression. A Granulation compression step to make the first solid body, a curing step to cure the first solid body to make it a second solid body, and a drying step to dry the second solid body. It is manufactured by a manufacturing method comprising a drying step of cross-linking silica to each other.

From the viewpoint of obtaining the fluidity and mixing uniformity of the slurry, the production method preferably further includes an alcohol mixing step of mixing alcohol before the granulation compression step and the compression step. The amount of alcohol to be mixed is preferably 1 wt% to 10 wt%, preferably 1 wt% to 6 wt%, with respect to the silica particle raw material mixed with the silica particle raw material or the fine silica particle raw material, from the viewpoint of obtaining the fluidity and mixing uniformity of the slurry. % Is more preferable. Further, as the alcohol, for example, ethanol (EtOH) is preferable from the viewpoint of safety and evaporation removal. However, the present invention is not limited to this as long as it can be removed by evaporation.

In another embodiment of the method for producing a solidified uncalcined silica, fine silica particles having an average particle size smaller than the average particle size of the silica particles are mixed with a raw material for the fine silica particles contained in an alkaline liquid having an alkaline concentration of 3 M. The mixing step of mixing is further included, and the mixture is compressed without granulation. The ratio of the fine silica particle raw material is 30 vol% to 280 vol% from the viewpoint of forming a close-packed structure with respect to the voids formed by the silica particles. The voids are gaps between the powders formed when the silica particle powders are filled.

The alkaline liquid containing the fine silica particles is 3M from the viewpoint of not completely dissolving. That is, for example, the raw material for fine silica particles can be prepared by adding an alkaline solution to the fine silica particles and mixing them at a predetermined temperature and cycle using a shaking bath.

The silica (SiO ₂ ) particles preferably have an average particle size of 0.1 μm to 100 μm from the viewpoint of reaction and drying shrinkage, and the fine silica (SiO ₂ ) particles are considered to be between the above-mentioned silica particles. Therefore, one having a size of 1/10 to 1/10000 of large particle silica and an average particle size of about 1 nm to 500 nm is preferably used.

From the viewpoint of the packing density of the particles, the ratio of the fine silica particle raw material preferably mixed with the silica particle raw material is preferably 40 vol% to 280 vol%, more preferably 50 vol% to 250 vol% with respect to the voids formed by the silica particles. Here, the voids formed by the silica particles can be determined by the bulk density of the large particles.

As shown in FIG. 2A, the second solid body cures the first solid body, so that the silica particles (1) are bonded (crosslinked) to each other by the semi-solid semi-liquid region (2). Further, as shown in the same (B), the semi-solid semi-liquid region (2) is composed of a liquid micro region portion (2a) and a solid micro region portion (2b), and the solid micro region portion (2b) is composed of micro silica. However, the liquid micro-region portion (2a) may include a liquid in which fine silica is eluted with an alkaline liquid, and may include a liquid in which silica particles (1) are eluted.

Regarding the curing conditions, the curing temperature is preferably 100 ° C. or lower, more preferably 60 ° C. to 80 ° C. from the viewpoint of reaction promotion and evaporation. The curing time is preferably 1 hour or longer, more preferably 4 hours or longer, from the viewpoint of the amount of reaction.

(Examples 1 to 4)
Glass beads (SO-C1, soda-lime glass, average particle size of about 300 μm, manufactured by Unitika) were used as the silica particles. A solvent in which 3 M potassium hydroxide solution and ethanol prepared separately are added to 10 g of silica particles SO-C1 to 0.625 g of ethanol with 2.53 g of potassium hydroxide solution or 1.06 g of ethanol with 2.10 g of potassium hydroxide solution. Was added and kneaded. The former kneaded product was granulated, and 3 g thereof was uniaxially compressed using a commercially available metal mold (inner diameter 14 mm) and dried to obtain an uncalcined silica solidified body (Reference Example 1). 3 g of the latter kneaded product was also granulated, uniaxially compressed, cured (curing time 0, 1, 3, 5, 20 hr), and dried to obtain an uncalcined silica solidified body (Reference Example 2, Example). 1-4). The production conditions of Reference Examples 1 and 2 and Examples 1 to 4 are as shown in Table 1, and the size of the solidified unfired silica is φ13.9 to 13.5 mm × height 11.3 to 10.5 mm. there were. In Reference Example 1, when ethanol was not added, granulation was difficult and a solidified body could not be prepared by the above process (Comparative Example 1).

Curing conditions The curing temperature was 60 ° C., and the drying conditions were two-step. First, drying was performed at room temperature for 12 hours or more, and then vacuum drying was performed at 170 ° C. for 12 hours or more. Regarding the granulation conditions, the particle size was set to 0.5 mm to 1.7 mm by sieving. The uniaxial compression condition was 65 MPa.

Regarding the integrated pore volume of the uncalcined silica solidified body from FIG. 3, in Reference Example 1 (FIG. 3 (A)), the integrated pore volume was about 0.05 cc / g in the range of the pore diameter of 0.1 μm to 10 μm. rice field. On the other hand, in Reference Example 2 (FIG. 3 (B)), the integrated pore volume was approximately 0.0 cc / g or less in the range of 0.1 μm to 10 μm. Therefore, when Reference Example 1 and Reference Example 2 are compared, Reference Example It was found that 2 had less coarse voids. That is, it was found that when the amount of ethanol contained in the silica particle raw material increased, the coarse voids contained in the uncalcined silica solidified body decreased.

From the plots of Reference Example 2 and Examples 1 to 4 shown in FIG. 4, the porosity of the uncalcined silica solidified body tends to decrease and the shrinkage rate tends to increase as the curing time increases for the curing conditions. I understood. That is, it was found that the porosity and shrinkage of the uncalcined silica solidified body can be controlled by the curing time. In addition, granulation and pressing before curing are effective in reducing the porosity.

The porosity was determined by the formula (1). Here, the theoretical silica density was 2.21 g / cm ³ , and the bulk density was obtained from the dimensions measured with a caliper and the measurement results of the dry weight of the solidified unfired silica.

On the other hand, the shrinkage rate was determined by (inner diameter of mold-diameter of solidified body) / inner diameter of mold × 100.

From the above results, granulation and pressing before curing are effective in reducing the porosity, and by using ethanol, the viscosity is adjusted (decreased) and the solidification rate is adjusted (so that it does not solidify during granulation). It was presumed that lowering the viscosity was effective in lowering the porosity because the powder was easily filled. In addition, it was presumed that preventing the solidification during granulation makes it easier for the powder to be filled when pressed thereafter, and is more effective in lowering the porosity.

From the surface states of Reference Example 2 and Examples 1 to 4 shown in FIG. 5, it was observed that the gaps between the silica particles were filled in the unfired silica solidified body as the curing time became longer under the curing conditions. This is consistent with the fact that, in FIG. 4, the porosity of the uncalcined silica solidified body tended to decrease and the shrinkage rate tended to increase as the curing time became longer.

From the plots of Reference Example 2 and Examples 1 to 4 shown in FIG. 6, the cumulative pore volume of the small voids of the uncalcined silica solidified body tended to decrease as the curing time became longer for the curing conditions. The large voids of the uncalcined silica solidified material were almost constant.
The small voids were pores smaller than the particle size of the silica particles of 250 nm (including the gaps between the particles), and the large voids were pores larger than the particle size of the silica particles. From these facts, it was found that the volume of small pores can be controlled by the curing time. That is, it was found that the neck growth between particles can be controlled.

(Preparation of raw material for fine silica particles)
AEROSIL OX50 (average particle size of about 50 nm, manufactured by Nippon Aerosil Co., Ltd.) was used as fine silica particles, 80 g of 3M potassium hydroxide was added to 20 g of AEROSIL OX50, and the mixture was mixed using a shaking bath.

(Preparation of mixed raw materials)
As shown in Table 2, the glass beads (silica particles) and the fine silica particle raw materials contained in the separately prepared 3M potassium hydroxide solution were mixed to prepare mixed raw materials 1 to 5. Table 2 also shows the ratio of the raw material of the fine silica particles to the voids at that time. For Example 5 (mixed raw material 1), the ratio of the fine silica particle raw material to the voids was calculated to be 50.5 (= 0.356 / {(4.09 / 2.5)) based on the formula (2). ) × 0.301 / (1-0.301)}).

Using the mixed raw materials 1 to 5, 3 g of them were uniaxially compressed without granulation, cured (curing time 5 hr), and dried to obtain an uncalcined silica solidified body (Examples 5 to 9). ..

From Examples 5 to 9, it was found that when the ratio of the fine silica particle raw material to the voids was 50%, the degree of compression of the solidified body showed a maximum value of 70 MPa. The compressive strength decreased as the ratio of the raw material of the fine silica particles to the voids increased, and was 5 MPa at 250%.

It is possible to provide a strong non-firing silica solidified body and a non-firing silica solidified body having a controlled porosity and shrinkage rate.

1: Silica particles 2: Semi-solid semi-liquid region 2a: Liquid micro-region part 2b: Solid micro-region part 3: Second solid body

Claims (5)

A granulation compression step of granulating and uniaxially compressing a silica particle raw material contained in an alkaline solution having an alkali concentration of 1 M to 5 M to obtain a first solid body, and curing the first solid body. A curing step in which the silica particles are crosslinked to form a second solid body, a drying step of drying the second solid body, and an alcohol mixing step of mixing alcohol before the granulation compression step are performed. A method for producing a solidified non-firing silica, which comprises further preparation. By the compression step of compressing the silica particle raw material contained in the alkaline solution in which the silica particles have an alkali concentration of 1 to 5 M into a first solid body without granulating, and by curing the first solid body. An alkaline solution comprising a curing step in which the silica particles are crosslinked to form a second solid body and a drying step in which the second solid body is dried, and the silica particle raw material has a fine silica having an alkali concentration of 3 M. The unfired silica solidified body further comprises a mixing step of mixing the fine silica particle raw materials contained in the above, and comprises a cross-linking caused by the fine silica particles becoming a semi-solid semi-liquid during the curing step. Manufacturing method. The method for producing a solidified unfired silica according to claim 2, wherein the ratio of the raw material for fine silica particles to the voids formed by the silica particles is 40 vol% to 280 vol%. The method for producing a solidified unfired silica according to claim 2 or 3, further comprising an alcohol mixing step of mixing alcohol before the compression step. The method for producing a solidified unfired silica according to claims 1 to 4 , wherein the curing temperature is 40 ° C. to 80 ° C. and the curing time is 40 hours or less as the curing conditions of the curing step.

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