JPH07232059A - Silica gel for filter aid and its production - Google Patents

Abstract

PURPOSE:To provide silica gel for a filter aid whose filtering property is hardly deteriorated by one breakdown of particles with the elapse of time and to provide silica gel having excellent adsorbing properties and filtering properties. CONSTITUTION:Silica gel for a filter aid has particle hardness 10kgf/cm<2> or higher, preferably 100-500kgf/cm<2>. The average particle size is 1-50mum. Moreover, of the silica gel for a filter aid the specific surface area is 300-600m<2>/g, average diameter of the fine pores is 50-200Angstrom , and the volume of the fine pores is 0.5-2.0ml/g. the silica gel manufacturing method involves drying silica hydrogel, more specifically, the method involves drying silica hydrogel at an average drying rate of 15% per min (drying standard) or lower at least until the water content lowers to 20%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel silica gel for a filter aid and a method for producing the same. More specifically, the present invention relates to silica gel for a filter aid which is useful for brews such as sake, mirin and beer.

[0002]

BACKGROUND OF THE INVENTION It is known that brewed products such as sake, mirin, and beer produce colloidal substances by the association of certain proteins and enzymes derived from rice and barley as raw materials in the process of their production. . This colloidal substance causes turbidity, which significantly impairs the quality of the product. Further, when attempting to filter out this colloidal substance, the filtration resistance is significantly increased, which causes a problem that filtration becomes difficult. In order to solve this problem, adsorbents have been used to adsorb the causative agent of turbidity and this is centrifuged, or the filter material is pre-coated with an adsorbent or filter aid, and brewed products such as sake, mirin and beer are brewed. A method of separating and removing by filtration, or a method of decomposing a protein with an enzyme has been proposed.

Examples of adsorbents or filter aids include organic adsorbents such as tannin and polyvinylpolypyrrolidone (PVPP), inorganic adsorbents such as silica, filter aids such as diatomaceous earth, perlite and cellulose, Examples of proteolytic enzymes include papain. Among them, silica is widely used because it has little influence on the quality of the substance to be filtered, has excellent adsorption performance, and has excellent performance as a filter aid.

In general, silica can be produced by a neutralization reaction between an aqueous solution of an alkali metal silicate and a mineral acid, and its production method is called a wet method. The wet method is classified into a precipitation method in which a precipitated silicic acid is obtained by reacting under neutral or alkaline conditions and which is relatively easy to filter, and a gel method in which a silicic acid in a gel state is obtained by reacting under acidic conditions. As the precipitation method, for example, Japanese Patent Publication No. 39
No. -1207, etc., and precipitated silica obtained by growing primary particles so as to have a structure by a neutralization reaction is washed with water, dried and pulverized to be a product. The precipitated silica obtained by these methods is mainly used as a general-purpose rubber reinforcing agent, pesticide carrier, paint delusterant, and viscosity modifier.

As the gel method, for example, US Pat. No. 246 is used.
No. 6842 and the like, washing gel-like silicic acid (called silica hydrogel) obtained by acidic reaction with water,
After drying, it is pulverized to obtain gel silica. These gel-method silicas generally have higher structural properties than precipitation-method silicas and can retain their structural properties even under high shear, so synthetic leather, coating agents such as plastics, anti-blocking agents for resin films, adsorbents, Used as a separating agent and catalyst. Due to these characteristics, gel method silica (hereinafter referred to as silica gel) is generally widely used in the field of filter aids as compared with precipitated silica.

Regarding silica gel for filter aid, for example, British Patent No. 938153, British Patent No. 9817
No. 15 describes a method of using silica xerogel as silica gel as a filter aid. Japanese Examiner Sho 63
-38188 discloses the use of calcined silica xerogel as a filter aid. In addition, Japanese Patent Publication No. 3-27483 discloses a hydrous silica gel.
The use of silica gel of specified physical properties obtained by controlling the water content as a filter aid is disclosed. Further, JP-A-5-177132 also describes the use of silica gel, which is characterized by flaky, scaly, or rod-like shapes having specific physical properties, as a filter aid.

[0007]

However, when silica gel is industrially used as a filter aid, it is desired to provide a filter having further improved filtration characteristics such as filtration speed and strength as a filter as compared with conventional silica gel.
Further, it is required to have not only filtration characteristics but also excellent adsorption performance that removes only proteins and the like unnecessary for the product and does not remove necessary proteins. To date, silica gels with a range of surface areas, pore volumes and average pore diameters are known to have excellent adsorption performance. However, upon examination by the present inventors, the silica gel particles satisfying these three conditions were fragile. As a result, when it is brought into contact with sake, mirin, beer, etc., the particles disintegrate with time and the filtration characteristics deteriorate, and the disintegration also reduces the pore volume and average pore diameter, resulting in poor adsorption performance. Was found to occur.

[0008] Therefore, a first object of the present invention is to provide a silica gel for a filter aid in which particles do not disintegrate over time and the filtration characteristics are not deteriorated.

Further, if only the particle hardness is increased with emphasis on the filtration characteristics, the problem that the performance as an adsorbent may be deteriorated due to the smaller pore volume and pore radius may occur. It became clear as a result of these studies. Therefore, a second object of the present invention is to provide a silica gel for a filter aid which has an excellent adsorption performance and an excellent filtration characteristic.

[0010]

The inventors of the present invention have conducted extensive studies to solve such a problem, and as a result, have a particle hardness of 100.
It has been found that the filtration characteristics are remarkably improved when it becomes more than kgf / cm ² , and the silica gel for filter aid of the present invention was completed. In particular, silica gel having an average particle diameter in the range of 1 to 50 μm and a particle hardness of 100 to 500 kgf / cm ² is excellent as a filter aid.

Further, in addition to the above physical properties, the surface area is 30.
0 to 600 m ² / g and average pore diameter of 50 to 20
It was also found that silica gel having a volume of 0Å and a pore volume of 0.5 to 2.0 ml / g was used as a filter aid and was excellent in not only filtration characteristics but also adsorption performance. It was also surprisingly found that by controlling the drying rate of silica hydrogel to silica gel, silica gel for a filter aid having excellent filtration properties and adsorption properties can be obtained.

That is, the present invention has a particle hardness of 100 kgf /
It relates to silica gel for a filter aid, which is characterized by having a size of not less than cm ² . Further, the present invention has an average particle size of 1 to 50.
μm and particle hardness of 100 to 500 kgf / c
m ² is silica gel for filter aid.

Further, according to the present invention, the particle hardness is 100 kgf.
/ Cm ² or more, or the average particle size is 1 to 50 μ
m and particle hardness of 100 to 500 kgf / cm
A silica gel is ^2, surface area 300 to 600
m ² / g, the average pore diameter is 50 to 200Å, and the pore volume is 0.5 to 2.0 ml / g.

Furthermore, the present invention is a method for producing silica gel by drying silica hydrogel, which is 15% / min (dry basis) until at least the water content reaches 20%.
The silica hydrogel is dried at the following average drying rate, the particle hardness is 100 kgf / cm ² or more, the surface area is 300 to 600 m ² / g, the average pore diameter is 50 to 200Å, and Pore volume is 0.5 ~
It relates to a method for producing silica gel which is 2.0 ml / g.

Further, the present invention is a method for producing silica gel by drying silica hydrogel, wherein the silica is dried at an average drying rate of 1 to 15% / min (drying standard) until the water content reaches 20%. The hydrogel is dried to obtain silica gel, and the obtained silica gel is then pulverized and classified to have an average particle diameter of 1 to 50 μm and a particle hardness of 100 kgf / cm ^{2 to} 500 kgf /
cm ² , the surface area is 300 to 600 m ² / g, the average pore diameter is 50 to 200 Å, and the pore volume is 0.5 to 2.0 ml / g. The present invention will be described in detail below.

The silica gel of the present invention is 100 kgf / c.
It has a particle hardness of m ² or more. Particle hardness is 100kgf
If it is above / cm ^2, it will be destroyed by contact with the substance to be filtered and pulverized, and as a result, the deterioration of the filtration characteristics will be significantly reduced. If only the filtration characteristics are taken into consideration, there is no particular upper limit on the particle hardness of silica gel. However, in view of easiness of production (especially easiness of pulverization) and influence on other physical properties, it is appropriate that the pressure is 500 kgf / cm ² or less. Preferably 100-300 kgf / cm ²
Range, more preferably 100-200 kgf /
It is in the range of cm ² .

The average particle size of the silica gel of the present invention is from 1 to
It is suitable to be in the range of 50 μm, preferably 5
˜30 μm, more preferably 7 to 20 μm. If the particle size is less than 1 μm, the cake density during filtration tends to be high even if no particle breakage occurs, and the filterability tends to deteriorate. If it exceeds 50 μm, the contact efficiency with the substance to be filtered tends to be low, and the adsorption performance per unit amount tends to be low. Silica gel in the range of 1 to 50 μm also has an advantage that a uniform precoat layer can be obtained when it is used by precoating the filter medium.

Further, the silica gel of the present invention has a surface area of 3
It is suitable that the range is from 00 to 600 m ² / g.
If it is less than 300 m ² / g, the adsorption performance tends to decrease. On the other hand, if it exceeds 600 m ² / g, the adsorptivity becomes too strong, and effective proteins other than the substance causing turbidity may be adsorbed. Moreover, the surface area is 300 to 600.
By being in the range of m ² / g, the particles are appropriately aggregated,
Dispersion is also relatively easy.

The average pore diameter is suitably in the range of 50 to 200Å. If it is less than 50Å, adsorption of the substance causing turbidity is less likely to occur, and the adsorption performance tends to be poor.
On the other hand, if it exceeds 200Å, active ingredients other than the causative substance of turbidity may be adsorbed.

The pore volume is suitably in the range of 0.5 to 2.0 ml / g. If it is less than 0.5 ml / g, the capacity for adsorbing the substance causing turbidity is insufficient and the adsorption performance tends to be poor. If it exceeds 2.0 ml / g, voids inside the particles or between the particles become large and the particle hardness is lowered, and the particles tend to be broken during filtration to deteriorate the filtration characteristics. When the pore volume is within the above range, it is possible to prevent the destruction of particles and prevent the deterioration of the adsorption performance due to the decrease of the pore volume and the average pore diameter.

The method for producing silica gel of the present invention will be described. The production method of the present invention is a method for producing silica gel by drying silica hydrogel, and is characterized in that silica gel having desired physical properties is obtained by controlling the drying rate. First, the silica hydrogel used in the production method of the present invention may be one obtained by a conventional method. That is, a uniform silica hydrosol is obtained by reacting an aqueous solution of an alkali metal silicate such as sodium silicate, potassium silicate or lithium silicate with a mineral acid such as sulfuric acid, hydrochloric acid or nitric acid in the presence of excess acid. Then, after gelling, it is crushed and washed with water. In the water washing step, hydrothermal treatment may be carried out by adding sodium hydroxide or an aqueous ammonia solution and heating for the purpose of removing by-product salts and, if necessary, reducing the specific surface area.

The silica hydrogel thus obtained generally has a water content of 65 to 75%. In the present invention,
Such a silica hydrogel has a water content of at least 20%.
Up to 15% / min (drying standard), the average drying rate is less than or equal to 15. As a result of examination by the present inventors, 15% / mi
The silica gel obtained by rapid drying exceeding n had a large pore volume, a large average pore diameter, and a low particle hardness. Furthermore, if this silica gel is used for filtration,
It was found that the particles were significantly destroyed during filtration, the filtration characteristics were deteriorated, and the adsorption performance was also deteriorated. However, if the average drying rate is too slow, the manufacturing time also becomes long. Therefore, it is appropriate that the average drying rate is 1% / min (drying standard) or more.

For drying, a static dryer, a band dryer, a paddle dryer, a fluid dryer, etc. are generally used, but the dryer is not limited thereto. The drying temperature is not particularly limited, but when uniform drying is performed at an average drying rate within the above range, it is suitable to perform the drying at 100 to 300 ° C. Water content of silica gel after drying is 3-10%
It is suitable to be in the range of (wet amount standard). The drying rate when further drying the water content from 20% is also preferably within the above range, but the physical properties of the silica gel do not change significantly even if the drying is carried out at a rapid rate exceeding 15% / min.

The silica gel thus obtained can be pulverized and classified for the purpose of adjusting the average particle size. The pulverization can be performed by a known method, for example, a method using a roll mill, a ball mill, a hammer mill, a pin mill, a jet mill or the like. Furthermore, classification is performed using a wind force classifier such as a micron separator, a centrifugal force classifier, or the like to obtain silica gel having a desired average particle size within the above range.

[0025]

EXAMPLES The present invention will be described in more detail below with reference to examples. Examples 1 to 3, Comparative Examples 1 to 3 and Reference Examples 1 to 2 20 wt% sodium silicate aqueous solution and 35 wt% sulfuric acid aqueous solution were reacted using a mixing nozzle to obtain SiO ₂ of 17.0 w.
t%, Na ₂ SO ₄ 1.6 wt%, moisture 74%, pH
A silica hydrogel of 0.8 was obtained. Samples of silica gel (Examples 1 to 3 and Comparative Examples 1 to 3) were crushed and washed with water sufficient to remove the by-product salt, dried under different drying conditions as shown in the table below, and then pulverized. Got The powder physical properties of the sample are shown in Table 1. Further, powder properties of commercially available silica gel are also shown in Table 1 as Reference Examples 1 and 2.

[0026]

[Table 1]

Each powder physical property test was measured according to the following methods. (Particle hardness) A sample of 1.5 g of silica gel was placed in a cell with a cross-sectional area of 1.0 cm ² , deaerated in vacuum, and then the load was 5
Take a minute. The load applied at this time is changed to examine the change in pore volume. Here, when the pore volume of the sample before applying a load was 100, the load when the pore volume decreased to 90 was defined as the particle hardness of the sample. (Average particle diameter) It was measured by a Coulter counter method (Multisizer II: manufactured by Coulter Counter).

(Surface area) It was measured by the multipoint method of BET method. (ASAP2400: manufactured by Shimadzu Corporation) (pore volume, average pore diameter) Measured by a nitrogen adsorption method. The average pore diameter is B.V. J. It was measured by the H method. (ASAP2400: manufactured by Shimadzu Corporation) Next, a stabilization treatment test of beer was performed using 8 points of silica gel having the above physical properties. As the beer, a commercially available product was used, and as a test method, 0.4 g of silica gel was added to 500 ml of beer, and the mixture was contacted for 5 minutes with stirring and then filtered with a filter. The treated beer after filtration was measured for transmittance and foam retention according to the following methods. The results are shown in Table 2.

(Permeability) Stabilization treatment and untreated beer (blank) were stored in a constant temperature bath at 50 ° C. for 5 days,
Then, after cooling in a constant temperature bath at 0 ° C for 1 day, a spectrophotometer (U
V2400: Shimadzu Corp.) is used and 380-780n
The average transmittance at m was measured. The cell was 1 cm wide and made of quartz. (Foam lasting) Beer after stabilization treatment and untreated (BL
ANK), the Sigma method of ASBC (METHOD OF AN
ALYSIS OF THE AMERICAN SOCIETY OF BREWING CHEMISTS
The sigma value was measured according to BEER-22). The larger the sigma value is, the better the foam retention of beer is.

[0030]

[Table 2]

Further, a filtration test was carried out using 8 points of the above silica gel to measure the filterability. The filtration test was performed according to the following method. The measurement results are shown in Table 3. (Filtration test) The above silica gel was added to a commercially available beer without bubbles at a rate of 50 g / 1 liter of beer, and the mixture was stirred with a high speed mixer at 1500 rpm for 10 minutes. 5C (diameter 11cm) filter paper, suction pressure 50
It was filtered at 0 mmHg. At this time, the filterability was judged from the time required for filtration, and the cake density after filtration was measured and shown in Table 3. In addition, the filterability is such that the filtration rate is 200 liters / m ^2.
-Those with an amount of at least hr were evaluated as O, and those with less than were evaluated as X.

[0032]

[Table 3]

From the results shown in Table 2, the silica gel of the present invention removes only unnecessary proteins (high permeability (cloudiness) without removing useful proteins (foaming property is equivalent to conventional). It can be seen that it has an excellent adsorption performance that can be obtained). Furthermore, from the results shown in Table 3,
It can be seen that the silica gel of the present invention has excellent filtration characteristics.

[0034]

The silica gel for use as a filter aid of the present invention is excellent in filtration characteristics and further adsorption performance. Further, by the production method of the present invention in which drying from silica hydrogel is controlled, it is possible to provide silica gel for a filter aid having excellent adsorption performance and filtration characteristics.

Claims (5)

[Claims] 1. A silica gel for a filter aid having a particle hardness of 100 kgf / cm ² or more. ^2. The silica gel according to claim 1, which has an average particle size of 1 to 50 μm and a particle hardness of 100 to 500 kgf / cm ² . 3. A surface area of 300 to 600 m ² / g, an average pore diameter of 50 to 200 Å, and a pore volume of 0.5 to 2.0 ml / g. silica gel. 4. A method for producing silica gel by drying silica hydrogel, which comprises drying silica hydrogel at an average drying rate of 15% / min (dry basis) or less until the water content reaches 20%. The particle hardness is 100 kgf / cm ² or more, and the surface area is 3
0 to 600 m ² / g, and the average pore diameter is 50 to 2
00Å and the pore volume is 0.5 to 2.0 ml / g
Which is a method for producing silica gel. 5. A method for producing silica gel by drying silica hydrogel, which comprises drying silica hydrogel at an average drying rate of 1 to 15% / min (dry basis) until at least the water content becomes 20%. Silica gel is obtained by crushing and classifying the obtained silica gel, the average particle size is 1 to 50 μm, and the particle hardness is 1
00 kgf / cm ^{2 to} 500 kgf / cm ² , the surface area is 300 to 600 m ² / g, the average pore diameter is 50 to 200 Å, and the pore volume is 0.5 to 2.0.
A method for producing silica gel which is ml / g.