JP7069604B2 - Manufacturing method of precipitated silica - Google Patents

Description

The present invention relates to a method for producing precipitated silica.

In recent years, there is concern about global warming due to the increase in carbon dioxide. Carbon dioxide emissions have begun to be regulated, and alternative energy sources for fossil fuels are being sought around the world. Biomass energy is attracting attention as one of them. An increasing number of companies in the world have factories that operate boilers using rice husks as fuel. Since the raw material of rice husks is rice grown by photosynthesis, burning rice husks does not mean that carbon dioxide has increased. Therefore, companies aiming to reduce the burden on the global environment are paying attention to this technology.

However, ash remains after burning rice husks, and companies are having a hard time disposing of this ash. Since rice husks contain a large amount of silicon dioxide, they are sometimes mixed with concrete and used as building materials, but because they are traded at a very low price, they are expensive to process.

On the other hand, a method for obtaining industrial precipitated silica from a so-called water glass aqueous solution of sodium silicate has been studied for a long time, and many industrial products are now available. Precipitated silica obtained from water glass is granular, easy to filter, and stable in quality, unlike silica gel. The particle size of the precipitated silica when dispersed is relatively small, and may be several μm or 1 μm or less. Precipitated silica is applied to a wide range of applications such as matting paints, tires, and abrasives for toothpaste, depending on its size, specific surface area, and the like. For example, Patent Document 1 describes a method for producing precipitated silica having a large specific surface area, which can be applied to an inkjet recording paper filler and an anti-blocking agent for a film. Further, Patent Documents 2 and 3 describe a method for producing highly dispersed silica for tire applications.

Precipitated silica is typically heated by dropping water glass and a mineral acid such as sulfuric acid into water at the same time while keeping the pH alkaline at 8-10 over a period of time, and finally adjusting to pH 3. It is well known that it can be obtained by returning to a stable state, filtering, washing with water, and heating (Non-Patent Document 1).

Further, in Patent Documents 2 and 3, water glass is diluted to a low concentration of 0.5 to 7% in terms of silica weight concentration, sodium cations are removed with a cation exchange resin, and the mixture is heated. We have succeeded in obtaining highly dispersed silica with a small particle size by preparing a so-called seed solution in which small silica particles of about nm are stably dispersed, and by simultaneously dropping water glass and sulfuric acid. ing. However, the cost increases when the ion exchange resin process is included.

Further, Patent Document 4 discloses a method for producing precipitated silica by dropping a diluted sodium silicate aqueous solution and concentrated sulfuric acid into a diluted sodium silicate aqueous solution.

The water glass used for producing precipitated silica is obtained by adding an alkali to silica sand and heating and melting it at about 1000 ° C., and petroleum energy is also used for this high temperature heating. Therefore, it can be said that a product using precipitated silica obtained from ordinary water glass is a product that increases carbon dioxide. The water glass used in Patent Documents 1 to 4, that is, sodium silicate is derived from a mineral, and a silica-alkali molar ratio SiO ₂ / Na ₂ O = 2 to 4 is used.

In Patent Document 5, precipitated silica is obtained by suspending rice husk ash or the like in an aqueous solution of sodium hydroxide, heating and stirring at around 100 ° C., and dropping an aqueous solution of silicate alkali obtained by dropping it into water at the same time as concentrated sulfuric acid. ing. However, this method can only obtain precipitated silica with a large particle size.

Further, in Patent Document 6, water glass obtained from rice husk ash is diluted and acid is added to obtain precipitated silica. However, since acid is directly added to water glass, the acid is added directly to the water glass in a short time and in a high concentration state. Since the pH changes in a large range of about 9 to 3, some gelation occurs. Further, with this method, only precipitated silica having a large particle size can be obtained.

Patent No. 4596998 JP-A-2011-157453 JP 2012-106911 US patent 4681750 WO2015 / 186045 Patent No. 5128040

Emily D. E. R. Hyde, Ahmad Seyfaee, Frances Neville, and Roberto Moreno-Atanasio, Industrial & Engineering Chemistry Research, 2016, 55, 8891-8913.

An object of the present invention is to provide a method for producing precipitated silica having good dispersibility and a large surface area.

As a result of various studies, the present inventors first extract rice husk ash with an alkali to prepare an alkaline silicate aqueous solution, and then dilute the alkaline silicate aqueous solution with water and adjust the pH to a predetermined pH to prepare a seed solution. Then, by simultaneously dropping an alkaline silicate aqueous solution and a mineral acid into the seed solution while maintaining the pH, it was found that precipitated silica having good dispersibility and a large surface area can be easily produced. Completed.

That is, the present invention includes the following.
[1]
It is a method for producing precipitated silica.
A method comprising the following steps A to C:
(A) A step of preparing alkaline silicate aqueous solutions S1 and S2 by heating the ash of a silica-containing plant body in an alkaline aqueous solution;
(B) A step of preparing a seed solution by adjusting the pH of the alkaline aqueous silicate solution S1 to 8 to 10.
(C) A step of preparing precipitated silica by dropping the alkaline aqueous silicate solution S2 and mineral acid into the seed solution.
[2]
The method, wherein the step B comprises diluting the alkaline aqueous silicate solution S1.
[3]
The method, wherein the dilution is performed prior to the pH adjustment.
[4]
The method according to the method, wherein the silica concentration in the diluted alkaline aqueous solution of silicate S1 is 0.03% (w / w) to 1.0% (w / w).
[5]
The method according to which the silica concentration in the seed solution is 0.03% (w / w) to 1.0% (w / w).
[6]
In the step B, the pH of the alkaline aqueous silicate solution S1 is adjusted to 8 to 10 by adding a mineral acid.
[7]
In the step B, the pH of the aqueous alkali silicate solution S1 is adjusted to 2 to 4 by adding a mineral acid, and then further adjusted to 8 to 10 by adding an alkali.
[8]
The alkali used for the pH adjustment is an aqueous alkali silicate solution S3.
The method A is the following step A1.
(A1) A step of preparing alkaline aqueous silicate solutions S1, S2, and S3 by heating the ash of a silica-containing plant in an alkaline aqueous solution.
[9]
The method according to the above method, wherein the mineral acid dropped in the step C is sulfuric acid of 0.1 mol / L to 2 mol / L.
[10]
The method in which the alkaline aqueous silicate solution S2 and the mineral acid are simultaneously added dropwise to the seed solution in the step C.
[11]
The method of step C, wherein the pH of the seed solution is maintained at 8-11 during the dropping.
[12]
The method, wherein the step C comprises dropping an additional mineral acid into the seed solution after the dropping.
[13]
The method according to the method, wherein the dropping amount of the alkaline aqueous silicate solution S2 is 40 to 50 times the amount of the seed liquid in terms of the amount of silica.
[14]
The method, wherein the ash used in step A or A1 is rice husk ash.
[15]
The method in which the alkaline aqueous silicate solutions S1 and S2 are collectively prepared in the step A.
[16]
The method, wherein the alkaline aqueous silicate solutions S1, S2, and S3 are collectively prepared in step A1.
[17]
The method according to the method, wherein the silica concentration in the alkaline aqueous silicate solution S1, S2, and / or S3 is 3 to 50% (w / w).
[18]
Further, the method comprising the following step D:
(D) A step of adjusting the average particle size of the precipitated silica to 1 μm or less by ultrasonically crushing the precipitated silica obtained in the step C.
[19]
The method according to which the ultrasonic crushing is carried out so that silica particles having a particle size of 1 μm or more do not remain.
[20]
The method according to which the BET specific surface area value of the precipitated silica is 100 m ² / g to 250 m ² / g.
[21]
Precipitated silica obtained by the above method.
[22]
Precipitated silica
Precipitated silica having a BET specific surface area value of 100 m ² / g to 250 m ² / g and an average particle size of 1 μm or less after ultrasonic crushing.
[23]
It is a method of producing an object using precipitated silica as a raw material.
The precipitated silica is the precipitated silica obtained by the method, or the precipitated silica.
A method in which the object is an inkjet recording paper filler, a paint matte, jogging shoes, or a tire.

According to the present invention, precipitated silica having good dispersibility and a large surface area can be produced at low cost.

<1> Method of the present invention The method of the present invention is a method for producing precipitated silica, which comprises the following steps A to C:
(A) A step of preparing alkaline silicate aqueous solutions S1 and S2 by heating the ash of a silica-containing plant body in an alkaline aqueous solution;
(B) A step of preparing a seed solution by adjusting the pH of the alkaline aqueous silicate solution S1 to 8 to 10.
(C) A step of preparing precipitated silica by dropping the alkaline aqueous silicate solution S2 and mineral acid into the seed solution.

<Process A>
In step A, the silica-containing alkaline aqueous solutions S1 and S2 can be prepared by heating the silica-containing plant ash in an alkaline aqueous solution.

In step A, an aqueous alkaline silicate solution S3 (described later) can also be prepared. That is, the step A may be the following step A1:
(A1) A step of preparing alkaline aqueous silicate solutions S1, S2, and S3 by heating the ash of a silica-containing plant in an alkaline aqueous solution.

Alkaline silicate aqueous solutions S1 and S2 are used in steps B and C, respectively. The alkaline aqueous silicate solution S3 may be used in step B.

The alkaline silicate aqueous solutions S1 to S3 may or may not be prepared individually. That is, a part or all of the alkaline silicate aqueous solutions S1 to S3 can be prepared together. For example, aqueous alkaline silicate solutions S1 and S2, S1 and S3, S2 and S3, or S1 to S3 can be collectively prepared.

Specifically, for example, by carrying out the step A individually for the alkaline silicate aqueous solutions S1 and S2, the silicate alkaline aqueous solutions S1 and S2 can be individually prepared. Further, specifically, for example, by carrying out the step A collectively for the alkaline silicate aqueous solutions S1 and S2, the silicate alkaline aqueous solutions S1 and S2 can be collectively prepared. In addition, "preparing the silicate alkaline aqueous solution S1 and S2 together" means preparing the silicate alkaline aqueous solution commonly used as the silicate alkaline aqueous solution S1 and S2. That is, when the alkaline silicate aqueous solutions S1 and S2 are collectively prepared, a part of the prepared alkaline silicate aqueous solution may be used as the silicate alkaline aqueous solution S1, and a part or all of the rest may be used as the silicate alkaline aqueous solution S2. can. The same applies to the cases of other combinations.

When a plurality of alkaline silicate aqueous solutions are individually prepared, the implementation conditions of step A (type of raw material, concentration of raw material, heating temperature, heating time, etc.) may or may not be the same for each. May be good. Further, when a plurality of aqueous alkali silicate solutions are individually prepared, their compositions (silica concentration, etc.) may or may not be the same.

As the alkaline silicate aqueous solutions S1 to S3, one kind of alkaline silicate aqueous solution may be used, or two or more kinds of alkaline silicate aqueous solutions may be used in combination.

In the method of the present invention, silica-containing plant ash is used as a raw material for precipitated silica. Hereinafter, the ash of the silica-containing plant body is also referred to as “raw material ash”. "Silica-containing plant" means the whole or a part of the silica-containing plant. The silica-containing plant is not particularly limited as long as it contains silica to a desired degree. Examples of the silica-containing plant include grasses such as rice, wheat, barley, crow wheat, rye, honeybee, millet, millet, Japanese millet, and corn. The part of the plant is not particularly limited as long as it contains silica to a desired degree. Examples of parts of the plant include rice husks and straw. Rice husks are particularly mentioned as a part of the plant body. That is, as the raw material ash, rice husk ash is particularly mentioned. The raw material ash is obtained by burning a silica-containing plant. Specifically, the raw material ash is obtained, for example, as a by-product generated when a silica-containing plant is burned in a biomass boiler as a fuel. The combustion temperature when producing the raw material ash is not particularly limited. The combustion temperature may be, for example, 400 ° C to 900 ° C. As the raw material ash, one kind of raw material ash may be used, or two or more kinds of raw material ash may be used in combination. In addition, the raw material ash is heated in mineral acid, then filtered and washed with water in order to remove impurities such as alkaline earth metals, heavy metals, and organic compounds contained in the raw material ash in a trace amount. You may use it. The mineral acid used in this case is not limited, and hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like may be used, and the mineral acid may be diluted with water before use.

By heating the raw material ash in an alkaline aqueous solution, an aqueous solution containing silicate ions (alkali silicate aqueous solution) can be prepared. In other words, the alkaline aqueous solution of silicate can be prepared by heating the alkaline aqueous solution containing the raw material ash. An alkaline aqueous solution containing raw material ash is also referred to as a "raw material mixed solution". The raw material mixture is obtained, for example, by mixing raw material ash, alkali, and water. The order of mixing is not particularly limited. Specifically, the raw material mixed solution is obtained by mixing, for example, raw material ash and an alkaline aqueous solution. Examples of the alkali include sodium hydroxide, potassium hydroxide and lithium hydroxide. Examples of the alkali include sodium hydroxide. As the alkali, one kind of alkali may be used, or two or more kinds of alkalis may be used in combination.

The usage amount ratio and the usage concentration of the raw material ash and the alkali are not particularly limited as long as an aqueous alkali silicate solution that can be used in the method of the present invention can be obtained. Hereinafter, the ratio of the amount of the raw material ash to the alkali used and the concentration to be used will be described on the assumption that the raw material ash and the alkaline aqueous solution are mixed to obtain the raw material mixed solution. Can also be applied mutatis mutandis when obtaining. The concentration of alkali used is, for example, 0.1 mol / L or more, 0.3 mol / L or more, 0.5 mol / L or more, 1 mol / L or more as the alkali concentration in the alkaline aqueous solution before mixing with the raw material ash. It may be L or more, 1.5 mol / L or more, 4 mol / L or less, 3 mol / L or less, or 2 mol / L or less, or a combination thereof. The concentration of the alkali used may be, for example, 1 mol / L to 4 mol / L as the alkali concentration in the alkaline aqueous solution before mixing with the raw material ash. The equivalent amount of alkali used may be, for example, 1 mmol or more, 5 mmol or more, 10 mmol or more, or 15 mmol or more, 100 mmol or less, 50 mmol or less, or 20 to 1 g of dry raw material ash. It may be less than or equal to millimole, or a combination thereof. The equivalent of the alkali used may be, for example, 10 mmol to 100 mmol, specifically, with respect to 1 g of the dry raw material ash. The alkali concentration and the raw material ash concentration in the raw material mixed solution are in the range calculated from the alkali concentration in the alkaline aqueous solution before mixing with the raw material ash exemplified above and the usage amount ratio of the raw material ash and the alkali exemplified above. May be.

The heating conditions are not particularly limited as long as an alkaline silicate aqueous solution that can be used in the method of the present invention can be obtained. The heating temperature may be, for example, 50 ° C. or higher, 60 ° C. or higher, or 80 ° C. or higher, 100 ° C. or lower, or a combination thereof. The heating may be carried out under static conditions or may be carried out with stirring, for example. Silica can be extracted with high extraction efficiency by stirring vigorously. The heating time may be, for example, 1 hour or more, 3 hours or more, 5 hours or more, or 10 hours or more, and may be 24 hours or less, 18 hours or less, 12 hours or less, or 6 hours or less. It may be a combination thereof. Specifically, the heating time may be, for example, 5 hours to 24 hours. The heated raw material mixture can be used as it is, or after being diluted, concentrated, purified, or the like, and then used in the subsequent steps. For example, after heating, carbon content can be removed from the raw material mixture. The carbon content can be removed by filtering the raw material mixture with, for example, a filter press or the like.

The silica concentration in the alkaline silicate aqueous solution is not particularly limited as long as the method of the present invention can be carried out using the alkaline silicate aqueous solution. The silica concentration in the alkaline silicate aqueous solution can be appropriately set according to various conditions such as the usage mode of the alkaline silicate aqueous solution. The silica concentration in the alkaline aqueous solution of silicate is, for example, 0.03% (w / w) or more, 0.1% (w / w) or more, 0.3% (w / w) or more, and 1% (w / w /). It may be w) or more, or 3% (w / w) or more, 50% (w / w) or less, 30% (w / w) or less, 15% (w / w) or less, and 10% (w). / W) or less, 5% (w / w) or less, 3% (w / w) or less, or 1% (w / w) or less, or a consistent combination thereof. Specifically, the silica concentration in the alkaline aqueous solution of silicate may be, for example, 0.03% (w / w) to 50% (w / w), and 0.03% (w / w) to 0.03% (w / w). It may be 1.0% (w / w) or 3% (w / w) to 50% (w / w). The silica concentration in the aqueous alkali silicate solution S1 may be 0.03% (w / w) to 1.0% (w / w), particularly when the dilution is not carried out in the step B. Further, the silica concentration in the aqueous alkali silicate solution S1 may be 3% (w / w) to 50% (w / w), particularly when the dilution is carried out in the step B. Further, the silica concentration in the aqueous alkali silicate solution S2 may be particularly 3% (w / w) to 50% (w / w). Further, the silica concentration in the aqueous alkali silicate solution S3 may be particularly 3% (w / w) to 50% (w / w). The silica concentration can be measured by a conventional method. The silica concentration can be measured using, for example, pack test silica (Kyoritsu Institute of Physical and Chemical Research).

<Process B>
In step B, the seed solution can be prepared by adjusting the pH of the alkaline aqueous silicate solution S1 to a predetermined range.

"Seed" refers to fine particles of silica. That is, in step B, specifically, the silicate ions in the silicate alkaline aqueous solution S1 are precipitated as silica fine particles. By preparing fine particles of silica in advance in step B, precipitated silica having good dispersibility can be obtained in subsequent step C.

Mineral acid or alkali can be used for pH adjustment. Examples of the mineral acid include sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid. Examples of the mineral acid include sulfuric acid. Examples of the alkali include sodium hydroxide, potassium hydroxide and lithium hydroxide. Examples of the alkali include sodium hydroxide. Further, as the alkali, in particular, the alkaline aqueous solution S3 silicate can be mentioned. As the mineral acid, one kind of mineral acid may be used, or two or more kinds of mineral acids may be used in combination. As the alkali, one kind of alkali may be used, or two or more kinds of alkalis may be used in combination. The concentration of mineral acid or alkali is not particularly limited. The concentrations of mineral acid and alkali are, for example, 0.1 mol / L or more, 0.3 mol / L or more, 0.5 mol / L or more, 1 mol / L or more, or 1.5 mol / L or more, respectively. It may be 4 mol / L or less, 3 mol / L or less, or 2 mol / L or less, or a combination thereof. Specifically, the concentration of the mineral acid may be, for example, 0.1 mol / L to 2 mol / L. Specifically, the concentration of alkali may be, for example, 1 mol / L to 4 mol / L. Each of the mineral acid and the alkali can be used, for example, as an aqueous solution having the above-exemplified concentrations.

The "predetermined range" of pH in step B is 8-10. The "predetermined range" of pH in step B may be, for example, 8.5 or more, 9.5 or less, or 8.5 to 9.5.

In step B, the pH of the alkaline aqueous silicate solution S1 may or may not be adjusted to less than the predetermined range before being adjusted to the predetermined range. That is, the pH of the alkaline silicate aqueous solution S1 may be adjusted to a predetermined range without being adjusted to less than a predetermined range. Alternatively, the pH of the alkaline aqueous silicate solution S1 may be adjusted to less than a predetermined range and then further adjusted to a predetermined range. The amount less than the predetermined range may be, for example, 2 or more, less than 8.5, less than 8, or 4 or less, or a combination thereof. Specifically, the amount less than the predetermined range may be, for example, 2 to 4. That is, the pH of the alkaline aqueous silicate solution S1 may be adjusted to, for example, 2 to 4 and then further adjusted to 8 to 10. When the pH of the alkaline silicate aqueous solution S1 is adjusted to less than the predetermined range, the primary particle size tends to be smaller than when the pH of the alkaline silicate aqueous solution S1 is adjusted to less than the predetermined range. Is recognized. Therefore, the mode of pH adjustment can be changed according to the desired particle size of the precipitated silica.

Mineral acids and alkalis can be used alone or in combination as appropriate for pH adjustment. For example, pH adjustment may be carried out by the addition of mineral acid. That is, for example, mineral acid may be added to the alkaline aqueous solution S1 of silicate to adjust the pH within a predetermined range. Further, for example, the pH adjustment may be carried out by adding a mineral acid and an alkali. That is, for example, mineral acid is added to the silicate alkaline aqueous solution S1 to adjust the pH to less than a predetermined range, and further, an alkali such as silicate alkaline aqueous solution S3 or another alkali is added to adjust the pH to a predetermined range. You may. The increase / decrease in pH may be repeated a plurality of times.

Step C may be carried out immediately after adjusting the pH to a predetermined range, or step C may be carried out after a predetermined time has elapsed. When adjusting the pH to less than a predetermined range, the pH may be adjusted to a predetermined range immediately after the pH is adjusted to a value lower than the predetermined range, or the pH may be adjusted to a predetermined range after a predetermined time has elapsed. It may be adjusted to a range. The length of the predetermined time is not particularly limited. The length of the predetermined time after adjusting the pH to a predetermined range may be, for example, more than 0 hours, 1 hour or more, 3 hours or more, or 5 hours or more, 24 hours or less, 18 hours or less, It may be 12 hours or less, 8 hours or less, or a combination thereof. Specifically, the length of the predetermined time after adjusting the pH to a predetermined range may be, for example, more than 0 hours and 24 hours or less. The length of the predetermined time after adjusting the pH to less than the predetermined range may be, for example, more than 0 hours, 0.5 hours or more, or 1 hour or more, and 10 hours or less, 5 hours or less, Alternatively, it may be 3 hours or less, or a combination thereof. Specifically, the length of the predetermined time after adjusting the pH to less than the predetermined range may be, for example, more than 0 hours and 5 hours or less. The temperature when a predetermined time elapses is not particularly limited. The temperature over time may be, for example, room temperature or higher than room temperature. That is, the alkaline aqueous silicate solution S1 may be heated over time. The heating temperature may be, for example, 20 ° C. or higher, 40 ° C. or higher, or 60 ° C. or higher, 100 ° C. or lower, or a combination thereof. The pH adjustment and the passage of time may be carried out, for example, under static conditions or with stirring.

At the time of carrying out step B, the aqueous alkali silicate solution S1 may be diluted. That is, step B may include diluting the alkaline aqueous solution S1 of silicate. Dilution may be performed before the pH adjustment, during the pH adjustment, or after the pH adjustment. Dilution may be performed, in particular, prior to pH adjustment. Dilution and pH adjustment may be carried out in part or in whole at the same time. Simultaneous dilution and pH adjustment can be achieved, for example, by adding water and a pH adjusting component at the same time, or by performing dilution with a pH adjusting component. In other words, water or pH adjusting components can be used for dilution. These can be used alone or in combination as appropriate for dilution.

Dilution can be carried out, for example, so that the silica concentration in the alkaline aqueous silicate solution S1 is within a predetermined range. In other words, the dilution can be carried out, for example, when the silica concentration in the aqueous alkali silicate solution S1 is higher than a predetermined range.

Further, the dilution can be carried out, for example, so as to obtain a seed solution having a silica concentration in a predetermined range in step B.

The silica concentration in the diluted alkaline aqueous silicate solution S1 and the silica concentration in the seed solution are, for example, 0.03% (w / w) or more, 0.05% (w / w) or more, or 0. It may be 08% (w / w) or more, 1% (w / w) or less, 0.5% (w / w) or less, or 0.3% (w / w) or less. , They may be a combination thereof. Specifically, the silica concentration in the diluted alkaline aqueous silicate solution S1 and the silica concentration in the seed solution may be, for example, 0.03 to 1.0% (w / w), respectively. The silica concentration can be measured by a conventional method. The silica concentration can be measured using, for example, pack test silica (Kyoritsu Institute of Physical and Chemical Research). According to the pack test silica, only silica existing in the form of silicate ion is detected. Therefore, the silica concentration in a sample (seed solution, etc.) containing silica existing in a form other than silicate ions such as silica particles was determined by pretreating the sample (silica ionization) according to, for example, JIS K 0101 44.2 or 44.3. Later, it can be measured using pack test silica (Kyoritsu Institute of Physical and Chemical Research).

Unless otherwise specified, the "alkali silicate aqueous solution S1" referred to in step B is partially or completely carried out depending on the timing and progress of operations such as pH adjustment, heating and dilution. It may mean the aqueous alkali silicate solution S1 after being diluted. That is, for example, the "alkali silicate aqueous solution S1" diluted in step C and the "alkali silicate aqueous solution S1" heated in step C may be partially or completely converted into a seed solution. ..

<Process C>
In step C, precipitated silica can be prepared by dropping the alkaline aqueous silicate solution S2 and the mineral acid into the seed solution. The dropped mineral acid is also hereinafter referred to as "mineral acid M1".

The dropping of the alkaline aqueous silicate solution S2 and the mineral acid M1 can be carried out at the same time, for example. That is, the alkaline aqueous solution S2 of silicate and the mineral acid M1 can be added dropwise to the seed solution at the same time. "Dripping of alkaline aqueous silicate solution S2 and M1 mineral acid is carried out simultaneously" means that dropping of alkaline aqueous silicate solution S2 and M1 mineral acid is carried out simultaneously during a part or all of the period during which they are dropped. It means to be done. "The dropping of the alkaline aqueous silicate solution S2 and the M1 mineral acid is carried out at the same time" means, for example, 80% (v / v) or more and 90% (v / v) of the total amount of the alkaline aqueous silicate solution S2 to be dropped. During the period in which the amount of the above or 95% (v / v) or more is dropped, the mineral acid M1 is dropped while dropping the alkaline aqueous silicate solution S2, and 80% of the total amount of the dropped mineral acid M1 ( During the period in which an amount of v / v) or more, 90% (v / v) or more, or 95% (v / v) or more is dropped, the alkali silicate aqueous solution S2 is dropped while dropping the mineral acid M1. It may be that.

The dropping of the alkaline aqueous silicate solution S2 and the mineral acid M1 can be carried out, for example, so that the pH of the seed solution is maintained in a predetermined range. That is, the pH of the seed solution may be maintained within a predetermined range during the dropping of the alkaline aqueous solution S2 silicate and the mineral acid M1. The "predetermined range" of pH in step C may be, for example, 8 or more, 8.5 or more, 11 or less, or 9.5 or less, or a combination thereof. .. Specifically, the “predetermined range” of pH in step C may be, for example, 8 to 11, preferably 8.5 to 9.5.

The dropping of the alkaline aqueous silicate solution S2 and the mineral acid M1 can be carried out simultaneously so that the pH of the seed solution is maintained in a predetermined range.

The amount of the alkaline silicate aqueous solution S2 dropped is not particularly limited as long as the desired precipitated silica can be obtained. The dropping amount of the alkaline aqueous silicate solution S2 may be, for example, 20 times or more, 30 times or more, or 40 times or more, 100 times or less, 70 times or less the amount of the seed liquid in terms of the amount of silica. , Or 50 times or less, or a combination thereof. The dropping amount of the alkaline aqueous silicate solution S2 may be, for example, 40 to 50 times the amount of the seed solution in terms of the amount of silica. The dropping amount of the alkaline aqueous silicate solution S2 can be appropriately set, for example, according to various conditions such as a desired BET value and a particle size distribution.

Examples of the mineral acid M1 include sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid. Examples of the mineral acid M1 include sulfuric acid. As the mineral acid M1, one kind of mineral acid may be used, or two or more kinds of mineral acids may be used in combination. The concentration of mineral acid M1 is not particularly limited. The lower the concentration of the mineral acid M1, the smaller the pH fluctuation and the easier it is to carry out the dropping. The concentration of the mineral acid M1 may be, for example, 0.1 mol / L or more, 0.3 mol / L or more, 0.5 mol / L or more, or 1 mol / L or more, and 4 mol / L or less. It may be 3 mol / L or less, 2 mol / L or less, or 1.5 mol / L or less, or a combination thereof. Specifically, the concentration of the mineral acid M1 may be, for example, 0.1 mol / L to 2 mol / L. The amount of the mineral acid M1 dropped is not particularly limited as long as the desired precipitated silica can be obtained. The dropping amount of the mineral acid M1 can be appropriately set according to various conditions such as, for example, the dropping amount of the alkaline aqueous silicate solution S2. The dropping amount of the mineral acid M1 can be set to, for example, an amount at which the pH of the seed solution is maintained within a predetermined range.

The dropping conditions of the alkaline aqueous silicate solution S2 and the mineral acid M1 are not particularly limited as long as the desired precipitated silica is obtained. The dropping time of the alkaline aqueous silicate solution S2 and the mineral acid M1 may be, for example, 15 minutes or more, 20 minutes or more, or 30 minutes or more, or 60 minutes or less, 50 minutes or less, or 40 minutes or less. Often, it may be a combination thereof. Specifically, the dropping time of the alkaline aqueous silicate solution S2 and the mineral acid M1 may be, for example, 15 minutes to 60 minutes, preferably 20 minutes to 50 minutes. The dropping speeds of the alkaline aqueous silicate solution S2 and the mineral acid M1 can be set, for example, so as to satisfy the above-exemplified dropping amount and dropping time. The temperature of the seed liquid at the time of dropping the aqueous alkaline silicate solution S2 and the mineral acid M1 may be, for example, 50 ° C. or higher, 60 ° C. or higher, or 70 ° C. or higher, and 100 ° C. or lower, 90 ° C. or lower, or 80 ° C. It may be the following, or it may be a combination thereof. Specifically, the temperature of the seed liquid at the time of dropping the aqueous alkali silicate solution S2 and the mineral acid M1 may be, for example, 50 ° C to 100 ° C, preferably 70 ° C to 90 ° C.

The usage mode (type, concentration, dropping conditions, etc.) of the alkaline aqueous silicate solution S2 and the mineral acid M1 may or may not be the same during the entire period of dropping.

After dropping the aqueous alkali silicate solution S2 and the mineral acid M1, additional mineral acid can be added dropwise to the seed solution. The added mineral acid to be dropped is also hereinafter referred to as "mineral acid M2". That is, the step C may include dropping the mineral acid M2 into the seed solution after dropping the silicate alkaline aqueous solution S2 and the mineral acid M1. In other words, step C may include dropping the mineral acid M2 into the seed solution after dropping the aqueous alkali silicate solution S2 and the mineral acid M1. As for the mineral acid M2, the description of the mineral acid M1 can be applied mutatis mutandis. The type and concentration of the mineral acid M2 may or may not be the same as the type and concentration of the mineral acid M1, respectively. The mineral acid M2 can be added dropwise, for example, until the pH of the seed solution becomes acidic. The pH of the seed solution after dropping the mineral acid M2 is not particularly limited as long as the silica does not gel and is stably present. The pH of the seed solution after dropping the mineral acid M2 may be, for example, 1.5 or more, or 2 or more, 6 or less, or 3.5 or less, or a combination thereof. good. Specifically, the pH of the seed solution after dropping the mineral acid M2 may be, for example, 1.5 to 6, preferably 2 to 3.5. The dropping of the mineral acid M2 can be carried out, for example, by continuing the dropping of the mineral acid M1 after the dropping of the alkaline aqueous solution S2 of silicate and the mineral acid M1. In other words, the mineral acid M1 can also be used as the mineral acid M2. Regarding the dropping rate of the mineral acid M2 and the temperature of the seed liquid at the time of dropping the mineral acid M2, the description of the dropping speed of the mineral acid M1 and the temperature of the seed liquid at the time of dropping the mineral acid M1 can be applied mutatis mutandis. The dropping rate of the mineral acid M2 and the temperature of the seed liquid at the time of dropping the mineral acid M2 may or may not be the same as the dropping speed of the mineral acid M1 and the temperature of the seed liquid at the time of dropping the mineral acid M1, respectively. May be good. The mode of use (type, concentration, dropping conditions, etc.) of the mineral acid M2 may or may not be the same during the entire period of dropping.

Unless otherwise specified, the "seed liquid" referred to in step C refers to the "seed liquid" according to the timing and progress of operations such as dropping of the alkaline aqueous solution S2 of silicate and the dropping of the mineral acid M1 and dropping of the mineral acid M2. It can mean the seed solution after the operation has been partially or completely performed. That is, for example, the "pH of the seed solution" in step C is the pH of the seed solution, the pH of the mixture of the alkaline silicate aqueous solution S2 and the mineral acid M1 after the start of dropping of the alkaline silicate aqueous solution S2 and the mineral acid M1. This means the pH of the mixture of the seed solution, the alkaline aqueous solution of silicate S2, the mineral acid M1 and the mineral acid M2 after the start of the dropping of the mineral acid M2.

By carrying out steps A to C in this way, precipitated silica is produced.

The produced precipitated silica can be recovered as appropriate. Precipitated silica can be recovered, for example, by filtering the seed liquid (the one after forming the precipitated silica) with a filter press or the like. The collected material can then be washed with a washing medium such as water. The washed precipitated silica can then be dried. Drying can be carried out by heating and drying at a temperature of 80 ° C. or higher using, for example, a normal dryer. Drying may be carried out, for example, until the water content of the precipitated silica reaches 5 to 10% (w / w).

The precipitated silica thus obtained is excellent in dispersibility. The particle size of the precipitated silica thus obtained can be adjusted, for example, by ultrasonically crushing the silica. The method of the present invention may include a step of adjusting the particle size by ultrasonically crushing the precipitated silica thus obtained. By ultrasonic crushing, for example, the average particle size of the precipitated silica can be adjusted to 1 μm or less. Further, ultrasonic crushing can be carried out, for example, so that silica particles having a particle size of 1 μm or more do not remain. Ultrasonic crushing can be performed, for example, in water. Examples of the ultrasonic crushing conditions include normal conditions for dispersing aggregates such as precipitated silica. The "average particle size" means the arithmetic average particle size (volume-based distribution) in the particle size distribution obtained by the laser diffraction / scattering method.

Further, the precipitated silica thus obtained has a high specific surface area. The specific surface area can usually be measured as a BET (Brunauer-Emmett-Teller method) specific surface area. The BET specific surface area of the precipitated silica thus obtained may be, for example, 100 m ² / g or more, 250 m ² / g or less, or a combination thereof. Specifically, the BET specific surface area of the precipitated silica thus obtained may be, for example, 100 m ² / g to 250 m ² / g. The specific surface area of the precipitated silica can be adjusted, for example, by adjusting the silica concentration, pH, and heating time in step B, the dropping amount of the alkaline silicate aqueous solution S2 in step C, and the like.

<2> Precipitated silica of the present invention The precipitated silica of the present invention is a precipitated silica having predetermined properties. As for the properties of the precipitated silica of the present invention, the description of the properties of the precipitated silica obtained by the method of the present invention can be applied mutatis mutandis. That is, the precipitated silica of the present invention may have one or more properties selected from the properties of the precipitated silica obtained by the method of the present invention. The precipitated silica of the present invention may have, for example, one or more properties selected from the following properties (1) to (3):
(1) The BET specific surface area value is 100 m ² / g to 250 m ² / g;
(2) The average particle size after ultrasonic crushing is 1 μm or less;
(3) After ultrasonic crushing, it does not contain silica particles having a particle size of 1 μm or more.

"The average particle size after ultrasonic crushing is 1 μm or less" means that the average particle size after ultrasonic crushing is 1 μm or less by subjecting the precipitated silica to ultrasonic crushing, and the average particle size before ultrasonic crushing is sufficient. It doesn't matter. Therefore, even if the precipitated silica has an average particle size of more than 1 μm, it corresponds to the precipitated silica having the above-mentioned property (2) as long as the average particle size becomes 1 μm or less by being subjected to ultrasonic crushing.

"Does not contain silica particles with a particle size of 1 μm or more after ultrasonic crushing" means that the silica particles with a particle size of 1 μm or more are eliminated by subjecting the precipitated silica to ultrasonic crushing, and the particle size before ultrasonic crushing is sufficient. It does not matter whether or not it contains silica particles of 1 μm or more. Therefore, even if the precipitated silica contains silica particles having a particle size of 1 μm or more, if the silica particles having a particle size of 1 μm or more disappear by being subjected to ultrasonic crushing, the precipitated silica having the above property (3) can be obtained. Applicable.

The precipitated silica of the present invention may have, for example, at least the above-mentioned property (1), or may have (1) and (2).

The method for producing the precipitated silica of the present invention is not particularly limited. The precipitated silica of the present invention can be produced, for example, by the method of the present invention. That is, one aspect of the precipitated silica of the present invention is the precipitated silica obtained by the method of the present invention.

<3> Utilization of Precipitated Silica of the Present Invention The use of the precipitated silica of the present invention is not particularly limited. The precipitated silica of the present invention can be used, for example, as a raw material in the production of an object. That is, the present invention provides, for example, a method for producing an object using the precipitated silica of the present invention as a raw material. Examples of the target product include those that can be generally produced from precipitated silica as a raw material. Specific examples of the object include an inkjet recording paper filler, a paint matting agent, jogging shoes, and a tire. The object is, in particular, a tire. The target product can be produced, for example, by a normal method using the usual raw material of the target product, except that the precipitated silica of the present invention is used as a raw material.

Hereinafter, the present invention will be described in more detail with reference to Examples.

<1> Preparation of precipitated silica 1
<1-1> Preparation of sodium silicate aqueous solution from rice husk ash 50 g of rice husk ash was added to 335 mL of a 2 mol / L sodium hydroxide aqueous solution, and the mixture was stirred with a stirring rod (250 rpm). The mixture was heated and stirred at 80 ° C. for 6 hours, then returned to room temperature, centrifuged (Hitachi Koki Co., Ltd. CF16RX II, 8000 × g, 10 minutes) to precipitate carbon, and the supernatant was filtered through a Kiriyama funnel (). Filter paper No. 5B). Then, water was added to the precipitate, and the mixture was stirred and then centrifuged again (8000 g, 10 minutes), and the supernatant was filtered through a Kiriyama funnel and mixed with the above filtrate. Then, the filtrate was diluted with water so as to have a total weight of 400 g to obtain 400 g of an aqueous sodium silicate solution. 0.1 g of this sodium silicate aqueous solution was taken, diluted 4000-fold with water, and then quantified by "Packtest Silica" (Kyoritsu Rikagaku Kenkyusho Co., Ltd.). As a result, the silica concentration in the sodium silicate aqueous solution was 10.2% (W / W).

<1-2> Preparation of seed solution The pH of 2 g of the sodium silicate aqueous solution obtained in <1-1> above was adjusted to 2.7 by diluting it with 196 g of water and adding 2 g of 1 mol / L sulfuric acid. This was heated at 80 ° C. for 3 hours. Then, the pH was adjusted to 9.2 by adding 1 g of the sodium silicate aqueous solution obtained in <1-1> above, and the mixture was further heated at 80 ° C. for 6 hours. This solution was diluted with water to 200 g to obtain a seed solution.

<1-3> Preparation of Precipitated Silica 100 g of the seed solution obtained in <1-2> above was taken, heated to 80 ° C., and stirred. Stirring was continued while simultaneously dropping 60 g of the sodium silicate aqueous solution obtained in <1-1> and 1 mol / L sulfuric acid on the seed solution over 24 minutes (253 rpm). At this time, the pH was kept in the range of 8.5 to 9.5. After the addition of the sodium silicate aqueous solution was completed, only 1 mol / L sulfuric acid was continued to be added dropwise at the same rate, and the addition was completed when the pH reached 2.9. The amount of 1 mol / L sulfuric acid dropped was 49 g. The resulting white precipitate was filtered through a Kiriyama funnel (filter paper No. 5B), and the filtrate was washed with 100 g of water. This was repeated once more, and the filtrate was heated in a dryer (ADVANTEC FV-430) at 80 ° C. for 3 hours to obtain 4.6 g of white floc-like precipitated silica. This was called Precipitated Silica No. It was set to 1.

<2> Preparation of precipitated silica 2
<2-1> Preparation of seed solution Adjust the pH to 9.4 by diluting 3 g of the sodium silicate aqueous solution obtained in <1-1> above to 194.9 g of water and adding 2.1 g of 1 mol / L sulfuric acid. bottom. This was heated at 80 ° C. for 9 hours. After heating, this solution was diluted with water to 200 g to obtain a seed solution.

<2-2> Preparation of Precipitated Silica 100 g of the seed solution obtained in <2-1> above was taken, heated to 80 ° C., and stirred. Stirring was continued while simultaneously dropping 60 g of the sodium silicate aqueous solution obtained in <1-1> and 1 mol / L sulfuric acid onto the seed solution over 26 minutes (269 rpm). At this time, the pH was kept in the range of 8.5 to 9.5. After the addition of the sodium silicate aqueous solution was completed, only 1 mol / L sulfuric acid was continued to be added dropwise at the same rate, and when the pH reached 3.2, the addition was completed. The amount of 1 mol / L sulfuric acid dropped was 45 g. The resulting white precipitate was filtered through a Kiriyama funnel (filter paper No. 5B), and the filtrate was washed with 100 g of water. This was repeated once more, and the filtrate was heated in a dryer (ADVANTEC FV-430) at 90 ° C. for 2 hours to obtain 4.8 g of white floc-like precipitated silica. This was called Precipitated Silica No. It was set to 2.

<3> Preparation of precipitated silica 3
<3-1> Preparation of seed solution Adjust the pH to 8.7 by diluting 3 g of the sodium silicate aqueous solution obtained in <1-1> above to 194.8 g of water and adding 2.2 g of 1 mol / L sulfuric acid. bottom.

<3-2> Preparation of Precipitated Silica 100 g of the seed solution obtained in <3-1> above was taken, heated to 80 ° C., and stirred. Stirring was continued while simultaneously dropping 75 g of the sodium silicate aqueous solution obtained in <1-1> and 1 mol / L sulfuric acid with respect to the seed solution over 36 minutes (256 rpm). At this time, the pH was kept in the range of 8.5 to 9.5. After the addition of the sodium silicate aqueous solution was completed, only 1 mol / L sulfuric acid was continued to be added dropwise at the same rate, and when the pH reached 3.1, the addition was completed. The amount of 1 mol / L sulfuric acid dropped was 54 g. The resulting white precipitate was filtered through a Kiriyama funnel (filter paper No. 5B), and the filtrate was washed with 100 g of water. This was repeated once more, and the filtrate was heated in a dryer (ADVANTEC FV-430) at 90 ° C. for 2 hours to obtain 5.3 g of white floc-like precipitated silica. This was called Precipitated Silica No. It was set to 3.

<4> Preparation of precipitated silica 4
100 g of water was heated to 80 ° C. and stirred. Stirring was continued while adding 75 g of the sodium silicate aqueous solution obtained in <1-1> and 1 mol / L sulfuric acid to this water at the same time for 33 minutes (253 rpm). At this time, the pH was kept in the range of 8.5 to 9.5. After the addition of the sodium silicate aqueous solution was completed, only 1 mol / L sulfuric acid was continued to be added dropwise at the same rate, and when the pH reached 3.1, the addition was completed. The resulting white slurry was filtered through a Kiriyama funnel (filter paper No. 5B), and the filtrate was washed with 100 g of water. This was repeated once more, and the filtrate was heated in a dryer (ADVANTEC FV-430) at 80 ° C. for 3 hours to obtain 4.5 g of white floc-like silica. This was called Precipitated Silica No. It was set to 4.

<5> Preparation of precipitated silica 5
1.5 g of the sodium silicate aqueous solution obtained in <1-1> above was added to 98.5 g of water, and the mixture was heated to 80 ° C. and stirred. The pH of the agitated product was 10.6. Stirring was continued while simultaneously dropping 75 g of the sodium silicate aqueous solution obtained in <1-1> and 1 mol / L sulfuric acid over 32 minutes (261 rpm). At this time, the pH was kept in the range of 8.5 to 9.5. After the addition of the sodium silicate aqueous solution was completed, only 1 mol / L sulfuric acid was continued to be added dropwise at the same rate, and when the pH reached 3.1, the addition was completed. The resulting white slurry was filtered through a Kiriyama funnel (filter paper No. 5B), and the filtrate was washed with 100 g of water. This was repeated once more, and the filtrate was heated in a dryer (ADVANTEC FV-430) at 90 ° C. for 2 hours to obtain 7.7 g of white floc-like silica. This was called Precipitated Silica No. It was set to 5.

<6> Analysis of Precipitated Silica The obtained Precipitated Silica No. Water was added to 1 to 5, and each was pulverized at 60 W for 20 minutes using an ultrasonic crusher. The average particle size of the crushed material was immediately measured with a particle size distribution meter (LA-920, HORIBA, Ltd.). The results are shown in Table 1.

Precipitated silica No. The BET specific surface areas of 1 to 4 were measured, respectively (Microtrac Bell Co., Ltd. BELSORP-mini, adsorbent nitrogen, adsorption temperature 77K). The results are shown in Table 2.

From Tables 1 and 2, mineral acid is added to prepare a seed solution having a predetermined pH, and an aqueous sodium silicate solution is added dropwise to the mineral acid at the same time while maintaining the pH, so that the particle size distribution is small and the BET ratio is small. Precipitated silica having a large surface surface was obtained (Nos. 1 to 3). On the other hand, the precipitated silica produced by simultaneously dropping an aqueous solution of sodium silicate with water or a diluted solution of sodium silicate without adjusting the pH was silica having a large particle size distribution and poor dispersibility (s). No. 4-5).

According to the present invention, precipitated silica having good dispersibility and a large surface area can be produced at low cost.

Claims (20)

It is a method for producing precipitated silica.
Including the following steps A to C:
(A) A step of preparing alkaline silicate aqueous solutions S1 and S2 by heating the ash of a silica-containing plant body in an alkaline aqueous solution;
(B) A step of preparing a seed solution by adjusting the pH of the alkaline aqueous silicate solution S1 to 8 to 10.
(C) A step of preparing precipitated silica by dropping the alkaline aqueous silicate solution S2 and mineral acid into the seed solution ;
In the step A, the alkaline aqueous silicate solutions S1 and S2 are prepared individually, or a part or all of the alkaline aqueous silicate solutions S1 and S2 are prepared together.
The silica concentration in the seed solution prepared in the step B is 0.08% (w / w) to 0.3% (w / w).
The method in which the temperature of the seed liquid at the time of dropping the alkaline aqueous silicate solution S2 and the mineral acid in the step C is 80 ° C. or lower . The method according to claim 1, wherein the step B comprises diluting the alkaline aqueous silicate solution S1. The method of claim 2, wherein the dilution is performed prior to the pH adjustment. The method according to claim 2 or 3, wherein the silica concentration in the diluted alkaline aqueous silicate solution S1 is 0.03% (w / w) to 1.0% (w / w). The method according to any one of claims 1 to 4 , wherein in the step B, the pH of the alkaline aqueous silicate solution S1 is adjusted to 8 to 10 by adding a mineral acid. Any one of claims 1 to 4 , wherein in the step B, the pH of the aqueous alkali silicate solution S1 is adjusted to 2 to 4 by adding a mineral acid, and then further adjusted to 8 to 10 by adding an alkali. The method according to item 1. The alkali used for the pH adjustment is an aqueous alkali silicate solution S3.
The step A is the following step A1:
(A1) A step of preparing alkaline silicate aqueous solutions S1, S2, and S3 by heating the ash of a silica-containing plant body in an alkaline aqueous solution ;
The sixth aspect of the invention, wherein in the step A1, the alkaline aqueous silicate solutions S1, S2 and S3 are individually prepared, or a part or all of the alkaline aqueous silicate solutions S1, S2 and S3 are prepared together. The method described . The method according to any one of claims 1 to 7 , wherein the mineral acid dropped in the step C is sulfuric acid of 0.1 mol / L to 2 mol / L. The method according to any one of claims 1 to 8 , wherein in the step C, the alkaline aqueous silicate solution S2 and the mineral acid are simultaneously added dropwise to the seed solution. The method according to any one of claims 1 to 9 , wherein in the step C, the pH of the seed solution is maintained at 8 to 11 during the dropping. The method according to any one of claims 1 to 10 , wherein the step C comprises dropping an additional mineral acid into the seed liquid after the dropping. The method according to any one of claims 1 to 11 , wherein the dropping amount of the alkaline aqueous silicate solution S2 is 40 to 50 times the amount of the seed liquid in terms of the amount of silica. The method according to any one of claims 1 to 12 , wherein the ash used in the step A or A1 is rice husk ash. The method according to any one of claims 1 to 13 , wherein the alkaline aqueous silicate solutions S1 and S2 are collectively prepared in the step A. The method according to any one of claims 7 to 14 , wherein the alkaline aqueous silicate solutions S1, S2, and S3 are collectively prepared in the step A1. The method according to any one of claims 7 to 15 , wherein the silica concentration in the alkaline aqueous silicate solution S1, S2, and / or S3 is 3 to 50% (w / w). The method according to any one of claims 1 to 16 , further comprising the following step D:
(D) A step of adjusting the average particle size of the precipitated silica to 1 μm or less by ultrasonically crushing the precipitated silica obtained in the step C. The method according to claim 17 , wherein the ultrasonic crushing is carried out so that silica particles having a particle size of 1 μm or more do not remain. The method according to any one of claims 1 to 18 , wherein the BET specific surface area value of the precipitated silica is 100 m ² / g to 250 m ² / g. A method of manufacturing inkjet recording paper fillers, paint matting agents, jogging shoes, or tires using precipitated silica as a raw material.
The method, wherein the precipitated silica is the precipitated silica obtained by the method according to any one of claims 1 to 19 .