JP3153698B2 - Granular precipitated silicic acid and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel granular precipitated silica. In particular, the present invention has a relatively large particle size suitable for fillers such as rubber, plastics, resins, and toothpastes, has high strength, and is hardly powdered. It is intended to provide a manufacturing method.

[0002]

2. Description of the Related Art Methods for producing silicic acid using alkali silicates and mineral acids as raw materials can be roughly classified into a precipitation method in which alkali is reacted to precipitate silicic acid, and a gel method in which acid is reacted to produce a hydrogel as an intermediate. There is. Silicic acid obtained by the gel method is generally hard and is used as a desiccant, a separating agent, a matting agent for paints, and the like. On the other hand, precipitated silicic acid is generally a soft, surface-active, tasteless, odorless and highly white powder, and is used for various purposes such as rubber reinforcing fillers, pesticides, paints, resins, information papers, toothpastes, and food additives. Used in the field.

[0003]

However, diversification of applications and demands for new physical properties have led to a need for precipitated silica having a larger particle diameter. For example, in cosmetics, toothpastes, and the like, there is a demand for improving the feel and feel of the skin by using precipitated silica having a larger particle diameter than before. In the field of fillers such as rubber, plastics and resins, there is also a demand for improving the workability when adding precipitated silica to rubber or the like by using precipitated silica having a larger particle diameter than ever before. is there.

[0004] On the other hand, the particle size of commercially available precipitated silica is generally 1 to 50 µm in average particle size.
m. However, there is substantially no literature or the like which discloses a technique aimed at obtaining precipitated silica having a larger particle diameter. However, it is not originally intended to obtain precipitated silica having a large particle diameter.
It is known that according to the methods disclosed in JP-A-2-32129 and JP-A-62-153113, precipitated silica having a relatively large particle diameter can be produced. In these methods, a wet cake obtained by filtering off hydrated silicic acid is dispersed in water to form a slurry, a weakly alkaline compound such as sodium carbonate or sodium acetate is added to the slurry, and the slurry is dried by spray drying to form a basic precipitate. This is to obtain silicic acid.

Therefore, the present inventor aimed at obtaining precipitated silicic acid having a large particle size, and prepared the above-mentioned JP-B-62-32.
129 and JP-A-62-153113 were examined. As a result, it was found that precipitated silica having a somewhat large particle diameter was obtained by the above method. However, it has been found that, when the obtained precipitated silica is to be added to, for example, rubber or the like, particles tend to be broken and powdered during handling. It was also found that when used in the fields of cosmetics, toothpaste, etc., the touch and feel were insufficient. Furthermore, it has been found that impurities such as sodium carbonate and sodium acetate are mixed in these precipitated silicic acids, and that it is also a problem depending on the use.

Accordingly, an object of the present invention is to provide a granular precipitated silicic acid which has a relatively large particle size, does not powder during handling, and has an appropriate touch and feel, and a method for producing the same. is there.

[0007]

According to the present invention, there is provided a method for converting a weight of 6
The present invention relates to granular precipitated silica, wherein 0% or more of the particles have a particle size in the range of 75 to 250 μm and a particle strength in the range of 0.1 to 0.3 kgf / mm ² .

The present invention further provides a suspension of precipitated silicic acid by adding sodium hydroxide or sodium silicate to adjust the pH of the suspension to a range of 8.5 to 11.5. And a method for producing the granular precipitated silica described above, which comprises spray-drying the suspension. Hereinafter, the present invention will be described in more detail.

The precipitated silica of the present invention is 60% by weight.
The particle diameter of the above particles is in the range of 75 to 250 μm.
Precipitated silicic acid having a particle diameter of 75 μm or less has been used in fields where the surface condition of paints, special papers, films, and the like is required to be relatively smooth.
On the other hand, in the present invention, even if the particle size is
Precipitated silicic acid in which the particles of m are 60% or more is a thing which has not been known so far, for example, it can provide a new texture and touch to cosmetics and toothpastes,
Alternatively, the present invention has been found to improve workability as a filler such as rubber, plastic, and resin. In particular, precipitated silicic acid in which 70% or more of particles having a particle diameter of at least 75 μm is suitable for obtaining the above-described effects. On the other hand, precipitated silica in which 60% or more of the particles have a particle size of more than 250 μm has a problem that the roughness becomes severe. Incidentally, in the present invention, the particle diameter is 250, 2 using a low tap type standard sieve shaker as described later.
00, 150, 105, 75 μm mesh sieve is set,
After adding 50 g of a sample and shaking for 10 minutes, the weight of the sample on each sieve is measured.

Further, the precipitated silica of the present invention has a particle strength in the range of 0.1 to 0.3 kgf / mm ² . If the particle strength is 0.1 kgf / mm ² or more, there is substantially no powdering during handling. In addition, the particle strength is 0.3
Precipitated silicic acid exceeding kgf / mm ² is harder to powder, but becomes too hard like stone powder or silica gel,
It cannot be used in the field of application aimed at by the present invention. Furthermore, if it is within the above range, it is possible to provide a new texture and a new touch to cosmetics and toothpaste, which is not known until now. In addition, the measurement of the particle strength of the precipitated silica in the present invention is performed by measuring the particle strength using a micro compression tester (for example, MCTM-2 manufactured by Shimadzu Corporation).

The precipitated silica of the present invention has a particle size of 75 to 2
More preferably, particles having a size in the range of 50 μm account for 60% or less of the whole and a bulk specific gravity in the range of 150 to 300 g / l. The bulk specific gravity defines, to some extent, the amount of particles having a particle size outside the range of 75 to 250 μm. When the bulk specific gravity is 150 g / l or more, the content of particles having a small particle diameter is suppressed, and the effect of increasing the particle diameter is more easily exerted. Further, precipitated silica having a bulk specific gravity of more than 300 g / l tends to be unsuitable for use in the above-mentioned applications, because the content of particles exceeding 250 μm becomes too large and the roughness becomes severe.

The precipitated silica of the present invention has an improved particle strength by adding sodium hydroxide or sodium silicate. Thus, more than a certain amount of sodium hydroxide or sodium silicate is present in the precipitated silica. As a guide, the pH of a 4% suspension can be used. If this pH is 8.5 or more, the particle strength in the above range can be obtained. If the amount of sodium hydroxide or sodium silicate added is too large, the precipitated silicic acid dissolves, causing a significant change in the physical properties of the precipitated silicic acid. Therefore, the pH of a 4% suspension is preferably 11.5 or less.

Hereinafter, the method for producing the granular precipitated silica of the present invention will be described. The granular precipitated silica of the present invention is prepared by adding sodium hydroxide or sodium silicate to a suspension of the precipitated silica to adjust the pH of the suspension to 8.5 to 11.5.
Can be produced by spray drying the resulting suspension. The precipitated silica used as a raw material is not particularly limited. Hereinafter, a general method for producing precipitated silica will be described. Sodium silicate is generally used as an alkali silicate as a reaction raw material, and the sodium silicate preferably has a SiO ₂ / Na ₂ O molar ratio of 2.0 to 4.0. Sulfuric acid or hydrochloric acid is preferably used as the mineral acid. Precipitated silicic acid hydrate is prepared by adding warm water and sodium silicate solution to a reaction tank, and then adding sulfuric acid and sodium silicate solution in a predetermined time while controlling the temperature and pH in the reaction tank to be constant. Obtain a slurry. The hydrated precipitated silica slurry is filtered and washed with water to obtain a wet cake.

By dispersing the wet cake obtained above in water to form a slurry, a suspension of precipitated silicic acid can be obtained. In the present invention, sodium silicate or sodium hydroxide is added to this suspension to adjust the pH of the suspension to 8.5.
Adjust to the range of ~ 11.5. p of suspension before pH adjustment
H varies depending on the amount of mineral acid used in the reaction of the above-mentioned hydrated precipitated silicic acid and the like. Therefore, in general, by adding a certain amount of sodium silicate or sodium hydroxide, the desired p
It is difficult to adjust to H. Therefore, while monitoring the pH of the suspension while stirring the suspension of precipitated silicic acid, sodium silicate or sodium hydroxide is added to obtain a suspension of the desired pH. The pH of the suspension can be adjusted to the above range by using sodium carbonate or sodium acetate instead of sodium silicate or sodium hydroxide. However, if a suspension set in a predetermined range using sodium carbonate or sodium acetate is used, the granular precipitated silica of the present invention cannot be obtained.

If the pH of the suspension due to the addition of sodium hydroxide or sodium silicate is less than 8.5, it is not possible to obtain a granular precipitated silicic acid having the desired particle strength. If the amount of addition is too large and the pH exceeds 11.5, dissolution of the precipitated silicic acid starts, and the granular precipitated silicic acid of the present invention cannot be obtained. In addition, when obtaining the hydrated precipitated silica slurry, the amount of the mineral acid for the reaction is reduced, and the pH of the slurry liquid is kept high at the end of the reaction, so that the pH of the suspension of the precipitated silica is 8. 5 or more
Both are possible. However, even when the precipitated silicic acid suspension having a pH in a predetermined range thus obtained is dried in the same manner as in the present invention, a suspension having the same particle strength as the granular precipitated silicic acid of the present invention is obtained. Absent.

In the production method of the present invention, the precipitated silica used is preferably adjusted at the reaction stage so that the BET specific surface area is in the range of 150 to 400 m ² / g.
By setting the BET specific surface area to 150 m ² / g or more, granular precipitated silica having a desired particle strength can be obtained with a relatively small amount of sodium hydroxide or sodium silicate. On the other hand, when the BET specific surface area increases, it tends to be difficult to obtain a high concentration precipitated silica suspension. Therefore, the BET specific surface area is preferably set to 400 m ² / g or less.

The precipitated silicic acid suspension adjusted to the above-mentioned pH is spray-dried to obtain granular precipitated silicic acid. In order to obtain granular precipitated silicic acid, a method of spray drying is more suitable than a method of drying slowly such as standing drying. For the spray drying, a known spray dryer can be used. As the spray, a nozzle type, a disk type and the like can be mentioned, and it is particularly preferable to use a nozzle type spray dryer. In the case of a nozzle type spray dryer, the particle size can be controlled by controlling the spray nozzle diameter. Therefore, in order to obtain the granular precipitated silica of the present invention, it is desirable to use one having a relatively large nozzle diameter. Further, the particle size of the granular precipitated silica can be changed depending on the slurry concentration of the suspension to be spray-dried. In order to obtain a granular precipitated silicic acid having a desired particle size, for example, a slurry concentration of 150 to 250 g / l is appropriate. In particular, the BET specific surface area is 150 to 400 m ²
/ G of precipitated silica is spray-dried using a suspension having a slurry concentration of 150 to 250 g / l, whereby a granular precipitated silica having a desired particle size can be obtained. it can.

[0018]

EXAMPLES Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples. In addition, the measurement of the bulk specific gravity, the particle diameter, the pH, and the particle strength in Examples and Comparative Examples was performed by the following method.

(I) Measurement of Bulk Specific Gravity The bulk specific gravity was measured according to the bulk test method specified in 18 of JIS K5101 (pigment test method). (II) Measurement of Particle Diameter 250, 200, 150, 10 using a low tap type standard sieve shaker (manufactured by Tsutsui Physical and Chemical Instruments Co., Ltd.)
5. Set a sieve with a mesh size of 75 μm, put 50 g of sample,
After shaking for 0 minutes, the sample weight on each sieve was measured and
The percentage in the 250 μm range was represented.

(III) Measurement of pH a) pH of slurry liquid 100 ml of the slurry was placed in a beaker, and the concentration was measured with a glass electrode pH meter. b) Product pH 2 g of a sample was added to 50 ml of pH 7 adjusted water, mixed for 5 minutes, and measured with a glass electrode pH meter. (IV) Measurement of Particle Strength Particle strength was measured using a micro compression tester (MCTM-2, manufactured by Shimadzu Corporation). (V) Degree of powdering Rub the precipitated silica sample between thumb and forefinger,
The degree of powdering was evaluated according to the following criteria. ：: Rolling property is maintained and powdering is not performed. ：: Some particles were broken, but felt granular. X: Particles are destroyed and no particles are observed.

Examples 1 to 3 and Comparative Example 1 No. 3 sodium silicate solution (about 7% of Na ₂ O, about 22% of SiO ₂ ) in 17,200 ml of warm water heated to 90 ° C.
637 ml was added and stirred, and then 5,970 ml of No. 3 sodium silicate solution (same concentration as above) and 48%
About 1,200 ml of sulfuric acid was simultaneously added for 60 minutes so that the pH of the reaction solution was kept at 9 to 11. Further, 48% sulfuric acid was added to acidify the reaction solution. The pH at the end of the acidification was about 3.0. The obtained precipitate was separated by filtration and sufficiently washed with warm water to obtain a wet cake. The wet cake was dispersed in water to prepare a slurry liquid such that the slurry liquid concentration was about 180 g / l. Next, a No. 3 sodium silicate solution (about 4% of Na ₂ O, about 13% of SiO ₂ ) was poured into the slurry. The amount added was 1.3%, 1.6% in terms of the amount of Na ₂ O in the sodium silicate solution, based on the solid content in the slurry liquid.
% And 1.9%, respectively, and stirred for 2 hours.
After measuring H, drying was performed using a nozzle type spray drier to obtain granular precipitated silicic acid. Comparative Example 1 does not contain sodium silicate. Table 1 shows the measurement results of this product.

Examples 4 to 6 and Comparative Example 2 No. 3 sodium silicate solution (about 7% of Na ₂ O, about 22% of SiO ₂ ) in 17,900 ml of warm water heated to 60 ° C.
130 ml of sodium silicate solution (the same concentration as above) was added to the mixture while stirring, and then 5,770 ml and 48%
About 1,200 ml of sulfuric acid was simultaneously added for 60 minutes so that the pH of the reaction solution was kept at 9 to 11. Further, 48% sulfuric acid was added to acidify the reaction solution. The pH at the end of the acidification was about 3.0. The obtained precipitate was separated by filtration and sufficiently washed with warm water to obtain a wet cake. The wet cake was dispersed in water to prepare a slurry liquid such that the slurry liquid concentration was about 150 g / l. Next, an aqueous sodium hydroxide solution was poured into the slurry liquid. The injection amount was 0.6%, 1.1% and 1.6% of Na ₂ O in the sodium hydroxide solution with respect to the solid content in the slurry, respectively, and the mixture was stirred for 2 hours. After measuring the pH of the solution, drying was performed using a nozzle type spray dryer to obtain granular precipitated silicic acid. Comparative Example 2 does not contain sodium silicate. Table 1 shows the measurement results of this product.

Comparative Examples 3 and 4 The wet cake obtained by the same reaction method as in Examples 1 to 3 was dispersed in water to prepare a slurry liquid so that the slurry liquid concentration was about 180 g / l. A 10% aqueous solution of sodium carbonate was added to the slurry solution with respect to the solid content in the slurry solution.
₂ % and 6% were added in ₂ CO ₃ amount, and after stirring for 2 hours, the pH of the slurry was measured and dried using a nozzle type spray drier to obtain granular precipitated silicic acid. Table 1 shows the measurement results of this product.

Comparative Example 5 No. 3 sodium silicate solution (about 7% of Na ₂ O, about 22% of SiO ₂ ) was added to 16,000 ml of warm water heated to 90 ° C.
After adding 355 ml and stirring, 7,100 ml of No. 3 sodium silicate solution (same concentration as above) and 48%
About 1,400 ml of sulfuric acid was simultaneously added over 60 minutes so that the pH of the reaction solution was maintained at 9 to 11. After completion of the simultaneous pouring, the precipitate was separated by filtration without adding sulfuric acid, and sufficiently washed with warm water to obtain a wet cake. The wet cake was dispersed in water to prepare a slurry liquid such that the slurry liquid concentration was about 150 g / l. After measuring the pH of the slurry liquid, it was dried using a nozzle type spray drier to obtain granular precipitated silica. Table 1 shows the measurement results of this product.

Comparative Example 6 To 19,600 ml of warm water heated to 60 ° C., 48% sulfuric acid was added to adjust the pH to about 3.0, and then a sodium silicate solution No. 3 (about 7% of Na ₂ O, about 22% of SiO ₂ ) 4,460m
and about 940 ml of 48% sulfuric acid, and the pH of the reaction solution is 2.5
Co-poured over 60 minutes to keep ~ 3.5. Then 2
A 3% aqueous sodium hydroxide solution was added until the pH of the reaction solution became about 9.0, the temperature of the reaction solution was raised to 90 ° C., and heat treatment was carried out for 4 hours. 3.0. The obtained precipitate was filtered and washed with water to obtain a wet cake. The wet cake was dispersed in water to prepare a slurry liquid so that the slurry liquid concentration was about 100 g / l, and the slurry was dried using a nozzle type spray dryer to obtain granular precipitated silica. Table 1 shows the measurement results of this product.

[0026]

[Table 1]

[0027]

According to the present invention, it is possible to obtain granular precipitated silicic acid which has a relatively large particle size, does not powder during handling, and has an appropriate touch and feel. According to the production method of the present invention, it is possible to easily and freely control the particle strength of granular precipitated silica to obtain granular precipitated silica having a desired particle strength. The granular precipitated silicic acid of the present invention is particularly effective in the industry where a large amount of the silicic acid is handled because it has good flowability and is less likely to be powdered during the handling. When used as a rubber filler, it has good bite during kneading and has a remarkable effect in shortening the working time. Of course, it is also effective as a filler for plastics, resins and the like. When used as a toothpaste filler, the granules can be maintained at an appropriate viscosity until use without breaking the granules during toothpaste production or storage and without impairing the tactile sensation in the mouth.

Claims (6)

(57) [Claims] 1. A particle having a particle size of 60% or more in terms of weight in a range of 75 to 250 μm and a particle strength of 0.1 to 0.1%.
A granular precipitated silicic acid characterized by being in the range of 0.3 kgf / mm ² . 2. The pH of the suspension as a 4% suspension
Is from 8.5 to 11.5. 3. The granular precipitated silicic acid according to claim 1, wherein the bulk specific gravity is in the range of 150 to 300 g / l. 4. The pH of the suspension is adjusted to 8.5 to 11.5 by adding sodium hydroxide or sodium silicate to the suspension of the precipitated silicic acid. The method for producing granular precipitated silicic acid according to claim 1, wherein the liquid is spray-dried. 5. A BET specific surface area of 150 to 400 m ² /
5. The method according to claim 4, wherein a precipitated silica in the range of g is used. 6. The slurry according to claim 4, wherein the slurry concentration of the suspension of the precipitated silica to be spray-dried is 150 to 250 g / l.
The manufacturing method as described.