JP2003190780A - Filter aid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new filter aid capable of obtaining a filtrate having high clarity for a short time. <P>SOLUTION: Primary particles comprise amorphous inorganic particles having pores of which the pore size is uniform. The filter aid comprises an aggregate of primary particles being a porous substance which comprises amorphous inorganic particles having pores of which the pore size is uniform and is characterized in that the mean particle size DL of particles measured by a dynamic light scattering method is 10-400 nm and the difference SB-SL between a converted specific surface area SL calculated from DL and a nitrogen adsorbing specific surface area SB of particles due to a BET method is 250 m<SP>2</SP>/g or more. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a filter aid, and more particularly to a filter aid containing a specific porous substance as a main component.

[0002]

2. Description of the Related Art A filter aid is obtained by adsorbing or incorporating solid or colloidal substances in a slurry.
It is used for the purpose of reducing filtration resistance, preventing clogging of the filter medium, and obtaining a filtrate with high clarity. And
A filter aid, for example, usually has a thickness of 1
Is used to form a cake layer of about 2 mm, and solids and the like in the slurry are separated in the cake layer. Conventionally, various types of filter aids such as silica gel, diatomaceous earth, perlite, and cellulose have been used. However, there are drawbacks such as difficulty in obtaining a high-clarity filtrate in a short time.

[0003]

DISCLOSURE OF THE INVENTION The present invention has a relatively large pore volume and a specific surface area unlike the above-mentioned conventional filter aids, has high safety and is easy to dispose of. The object of the present invention is to provide a novel filter aid which can form a stable cake layer and can obtain a high-clarity filtrate in a short time.

[0004]

SUMMARY OF THE INVENTION The above object of the present invention, however, is to measure by a dynamic light scattering method, in which the primary particles are composed of amorphous inorganic particles having fine pores having a uniform diameter. The average particle diameter D _{L of the} particles is 10 to 400 nm, and the difference S _B −S _L between the reduced specific surface area S _L obtained from D _L and the nitrogen adsorption specific surface area S _B of the particles by the BET method is 250.
It is easily achieved by a filter aid characterized by being a porous material with m ² / g or more.

The present invention will be described in detail below. The filter aid of the present invention is characterized by primary particles. That is,
The primary particles of the filter aid used in the present invention are composed of inorganic particles which are amorphous and have fine pores having a uniform diameter, and have an average particle diameter D _L measured by a dynamic light scattering method. 1
0 to 400 nm, converted specific surface area S obtained from D _L
It is characterized by being a porous substance having a difference S _B −S _L of 250 m ² / g or more between _L and the nitrogen adsorption specific surface area S _B of the particles by the BET method. The porous material having a relatively large specific surface area as described above is novel, and exhibits a comparable effect as a conventional filter aid, and its unique appearance shape forms a stable cake layer. It has a feature that it can. The average diameter of the aggregate of the present invention (the diameter may be simply referred to as the diameter) is not particularly limited, but 5
To 100 μm is preferable. If the average diameter of the agglomerates is less than 5 μm, the filtration resistance becomes large and the required filtration flow rate cannot be obtained. No filtering action can be obtained.

The porous material of the present invention will be described below. The present invention has an average particle diameter D _L, as measured by dynamic light scattering method 10 to 400 nm, the difference between the nitrogen adsorption specific surface area S _B according converted specific surface area S _L and the BET method obtained from D _L S _B - S _L is at 250 meters ² / g or more minerals, wherein the porous substance having a uniform pore amorphous. Amorphous in the present invention means that the atomic structure or pore structure of the porous material does not have a long-range regularity (that is, does not have long-range order) and has a clear peak in powder X-ray diffraction. Means not having. For example, in the case of an array of atoms, it has only regularity in the range of several nm. In the case of the arrangement of pores, it has regularity in the range of 10 or less at most.

The term "porosity" in the present invention means that the pores are measured by the nitrogen adsorption method, and the pore volume is
Preferably 0.1 mL / g or more, more preferably 0.5
It means at least mL / g. The average pore diameter of the porous substance (the diameter may be simply referred to as the diameter) is not particularly limited, but 6 nm or more is preferable, and 6 to
30 nm is more preferable. Although it depends on the substance to be filtered, a substance having a large pore size is preferable because a substance having a large size can easily enter the pores and can diffuse quickly. If the pores are small, water in the air may block the pores and block the flow of the substance into the pores, which is not preferable. Having a uniform pore diameter means that the pore diameter determined from the nitrogen adsorption isotherm and the total pore volume (pore amount measurable by the nitrogen adsorption method of 50 nm or less) is ± 50% of the average pore diameter. It refers to a porous material whose range contains 50% or more of the total pore volume. Further, it can be confirmed by TEM observation that the pores are uniform.

The average particle diameter (the diameter may be simply referred to as the diameter) of the porous material of the present invention measured by the dynamic light scattering method is preferably 10 to 400 nm, more preferably 10 to 300 nm, More preferably 10 to 2
00 nm. Reduced specific surface area S _L (m calculated from average particle size D _L (nm) measured by dynamic light scattering method
² / g), assuming that the particles of porous material are spherical,
S _L = 6 × 10 ³ / (density (g / cm ³ ) × D _L ). The fact that the difference S _B −S _L between this value and the nitrogen adsorption specific surface area S _B by the BET method is 250 m ² / g or more indicates that the particles of the porous substance are extremely porous. When this value is small, the ability to absorb the substance inside becomes small, and when this value is large, the filtration resistance may become large.

The method for producing the porous material of the present invention will be described. The method for producing the porous substance of the present invention is not particularly limited, but the following production method is mentioned as a preferable method. That is, a process including a step of mixing a metal source composed of a metal oxide and / or a precursor thereof, a template and water to manufacture a sol of a metal oxide / template composite, and a step of removing the template from the composite. Is the way. The above metal source is a metal oxide and / or a precursor thereof, and the metal species include silicon, alkaline earth metals such as magnesium and calcium of Group 2, zinc, and 3
Examples include aluminum, gallium, rare earths, etc., Group 4 titanium, zirconium, etc., Group 5 phosphorus, vanadium, Group 7 manganese, tellurium, etc., Group 8 iron, cobalt, etc. Examples of the precursor include nitrates of these metals, inorganic salts such as hydrochlorides, acetates, organic acid salts such as naphthenates, organic metal salts such as alkylaluminums, alkoxides, and hydroxides, which will be described later. It is not limited to this as long as it can be synthesized by the method. Of course, these may be used alone or in combination.

When silicon is selected as the metal, it is possible to use a precursor that repeats condensation and polymerization to finally give silica, preferably tetraethoxysilane, methyltriethoxysilane and dimethyltriethoxysilane. Alkoxides such as 1,2-bis (triethoxysilyl) ethane and activated silica can be used alone or in combination. Activated silica is particularly preferable because it is inexpensive and highly safe. The active silica used in the present invention can be prepared by extracting water glass with an organic solvent, or ion-exchange water glass. For example, when water glass is prepared by contacting it with an H ⁺ type cation exchanger, it is industrially preferable to use No. 3 water glass because it contains little Na and is inexpensive. As the cation exchanger, for example, a sulfonated polystyrene divinylbenzene-based strongly acidic exchange resin (for example, Amberlite IR-120B manufactured by Rohm & Haas) is preferable, but the cation exchanger is not particularly limited thereto.

As the template used in the present invention, cationic, anionic, nonionic, amphoteric surfactants such as quaternary ammonium type and amines and amines such as dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, etc. Any neutral template such as oxide may be used, but a triblock type such as Asahi Denka's Adeka Pluronic L / P / F / R series or polyethylene glycol such as Asahi Denka's Adeka PEG series or Adeka Pronic is preferred. Nonionic surfactants such as ethylenediamine based types such as TR series can be used.

As the nonionic surfactant, ethylene is used.
Triblock consisting of oxide and propylene oxide
It is possible to use a nonionic surfactant of the ku type. In particular,
Structural formula HO (C₂H_FourO)_a− (C₃H₆O)_b− (C
₂H_FourO)_cH (however, a and c are 10 to 110, b is
30 to 70), or a structural formula
R (OCH₂CH₂)_nOH (however, R has 12 to 12 carbon atoms
20 alkyl groups, and n represents 2 to 30)
Those are preferable. Specifically, Asahi Denka Pluronic P
103 (HO (C₂H_FourO)₁₇− (C₃H₆O)₆₀− (
C₂H_FourO)_{1 7}H), P123 (HO (C₂H_FourO)
₂₀− (C₃H₆O)₇₀− (C₂H_FourO) ₂₀H), P85
Etc. and polyoxyethylene lauryl ether, polyoxy
Ethylene cetyl ether, polyoxyethylene steari
Examples thereof include ruether and the like.

To change the pore size, an aromatic hydrocarbon having 6 to 20 carbon atoms and 5 to 20 carbon atoms are used as an organic auxiliary agent.
Alicyclic hydrocarbons, aliphatic hydrocarbons having 3 to 16 carbon atoms and amines thereof, and halogen-substituted products thereof such as toluene, trimethylbenzene, triisopropylbenzene and the like can be added. The reaction between the metal source and the template can be performed, for example, after stirring and mixing a solution or dispersion of the metal source in a solvent and a solution or dispersion of the template in a solvent, but the reaction is not limited to this. Absent. Either water or a mixed solvent of water and an organic solvent may be used as the solvent, but alcohols are preferable as the organic solvent. As alcohols, lower alcohols such as ethanol and methanol are preferable. The composition used in these reactions varies depending on the template, the metal source, and the solvent, but it is necessary to select a range in which the particle size does not become large due to aggregation or precipitation. Further, an alkali such as NaOH or a stabilizer such as low molecular weight PVA may be added to prevent aggregation or precipitation of particles.

For example, activated silica is used as a metal source
Pluronic P103 (made by Asahi Denka) as a plate,
When using water as the solvent, use the following composition
be able to. P103 / SiO₂The weight ratio of
It is preferably 0.01 to 30, more preferably 0.1 to 5
Ranges are used. The weight ratio of organic auxiliary agent / P103 is good.
It is preferably 0.02 to 100, more preferably 0.05 to
35. The weight ratio of water / P103 during the reaction is
Preferably 10-1000, more preferably 20-50
A range of 0 is used. NaOH as N is used as a stabilizer.
aOH / SiO ₂1 × 10 as the weight ratio of^-Four~ 0.15
You may add in the range of. Use Pluronic P123
Also in this case, the same composition can be used. Metal sources and te
The mixing of the template and the solvent is preferably 0 to 80 ° C.
More preferably, the stirring is performed at 0 to 40 ° C. reaction
Easily progresses at room temperature, but if necessary
It can also be carried out under heating at. However, 100 ℃ or more
Conditions such as the hydrothermal reaction above are not needed. As reaction time
For 0.5 to 100 hours, preferably 3 to 50 hours.
A fence is used. The pH during the reaction is preferably 3-12.
, More preferably 4 to 12, and still more preferably 4 to
NaOH, ammonia for pH control in the range of 10
Such as alkali or hydrochloric acid, acetic acid, sulfuric acid
Good.

Next, a method of removing the template will be described. For example, a porous material is obtained by adding a solvent such as alcohol to the obtained reaction solution and removing the template from the complex. At this time, it is preferable to use an ultrafiltration device because the porous substance can be handled as a sol. As a material for the membrane for ultrafiltration, polysulfone, polyacrylonitrile, cellulose, etc. can be used, and the shape thereof may be any of hollow fiber type, flat membrane type, spiral type and the like. At this time, an alkali such as NaOH or a stabilizer such as low molecular weight PVA may be added to prevent aggregation of particles. The solvent used for the removal may be any solvent that dissolves the template, and water and alcohols having high dissolving power, which are easy to handle, are preferable. As alcohols, lower alcohols such as methanol and ethanol are preferable. The removal temperature varies depending on the solvent and template used, but is preferably 0 to 80 ° C., more preferably 20.
~ 80 ° C. The removed template can be reused by removing the solvent. In addition, the obtained complex is filtered by filtration or the like, washed with water, dried, and then the contained template is removed by a method such as contact with a solvent such as a supercritical fluid or alcohol, or firing. , A porous material may be obtained. The firing temperature is higher than the temperature at which the template disappears, generally 500 ° C. or higher. The firing time is appropriately set in relation to the temperature, but is 30 minutes to
It takes about 6 hours. As another removal method, a method of stirring and mixing the solvent and the complex, a method of packing the complex in a column or the like and circulating the solvent may be employed. As a method for removing the solvent from the sol to obtain the porous substance, methods such as heat drying, vacuum drying, spray drying, and supercritical drying can be used. The porous material of the present invention may be modified in various ways depending on the application. For example, the surface may be modified with a silane coupling agent or the like.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to Examples. Powder X-ray diffraction pattern is RINT25 manufactured by Rigaku
00 was used for the measurement. The pore distribution and the specific surface area were measured with nitrogen using AutoSorb-1 manufactured by Kantachrome Co., Ltd. The pore distribution was calculated by the BJH method.
The average pore diameter was calculated from the peak value in the mesopore region of the differential pore distribution curve obtained by the BJH method. Specific surface area is B
It was calculated by the ET method. The average particle diameter by the dynamic light scattering method was measured by a laser zeta potentiometer ELS-800 manufactured by Otsuka Electronics. The TEM photograph was taken using H-7100 manufactured by Hitachi.

[0017]

Example 1 100 g of a cation exchange resin (Amberlite, IR-120B) which had been made into H ⁺ type in advance was dispersed in 100 g of water, and No. 3 water glass (SiO ₂
= 29% by weight, Na ₂ O = 9.5% by weight), and a solution of 33.3 g diluted with 66.7 g of water is added. After sufficiently stirring this, the cation exchange resin was filtered off to obtain 200 g of an active silica aqueous solution. The SiO ₂ concentration of this activated silica aqueous solution was 5.0% by weight. 5 g of Asahi Denka Co., Ltd. Pluronic P103 was dissolved in 1360 g of water, and 60 g of the active silica aqueous solution was added while stirring in a 35 ° C water bath. Furthermore, 20 mL of 0.015 mol / L NaOH aqueous solution is added. The pH of this mixture was 7.5.
At this time, the weight ratio of water / P103 was 289.1.
The 103 / SiO ₂ weight ratio is 1.67. This mixture was stirred at 35 ° C. for 15 minutes, then left standing at 80 ° C. and reacted for 24 hours. A predetermined amount of ethanol was added to this solution and the nonionic surfactant was removed by using an ultrafiltration device.
A transparent porous sol having a concentration of about 4% by weight was obtained. The sample in this solution had an average particle diameter of 60 nm as measured by the dynamic light scattering method and a reduced specific surface area of 45 m ² / g. The sol was dried at 105 ° C to obtain a porous material. No clear peak was found in the X-ray diffraction pattern of this sample. The average pore diameter of this sample was 8 nm, and the pore volume was 1.
It was 21 mL / g. The nitrogen adsorption specific surface area by the BET method was 720 m ² / g, and the difference from the converted specific surface area was 67.
It was 5 m ² / g. The obtained aggregate of the porous material,
From observation with a transmission electron microscope, the average diameter was 20 μm.
Then using the aggregate of this porous material as a filter aid,
A filtration test was performed.

[0018]

Example 2 About 0.1% by weight of the filter aid obtained in Example 1
A vertical element filter was pre-coated with the contained water. The precoat flow rate was 3 kiloliters / m ² · hr and the precoat amount was 300 g / m ² . Separately, water containing 50 ppm of particles of 3 μm was prepared as a model liquid for filtration, and this water was passed through the vertical element filter at a flow rate of 0.5 kiloliter / m ² · hr. As a result, the number of particles in the filtrate after passing for 60 minutes was zero, and the pressure loss applied to the vertical element filter was ΔP = 0.025 kg / cm ² .

Comparative Example 1 Commercially available silica gel (average particle size 13 μm,
Example 2 using a surface area of 600 m ² / g, shape: crushed)
A filtration test was conducted in the same manner. As a result, a few particles were observed in the filtrate after passing through the solution for 60 minutes, and the pressure loss applied to the vertical element filter was as large as ΔP = 0.05 kg / cm ² .

[0019]

The filter aid of the present invention contains a porous substance having special physical properties as an active ingredient. Therefore, it has excellent filtration performance.

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Claims (4)

[Claims] 1. A filter aid comprising an agglomerate of primary particles, wherein the primary particles are inorganic particles that are amorphous and have pores of uniform diameter, and are measured by a dynamic light scattering method. The average particle diameter D _{L of the} particles is 10 to 400 nm, and the difference S _B −S _L between the converted specific surface area S _L obtained from D _L and the nitrogen adsorption specific surface area S _B of the particles by the BET method is 250.
A filter aid which is a porous substance having a m ² / g or more. 2. The filter aid according to claim 1, wherein the average diameter of the pores is 6 nm or more. 3. The filter aid according to claim 1, wherein the inorganic substance is silicon oxide. 4. The filter aid according to claim 1, wherein the aggregate has an average diameter of 5 to 100 μm.