JPH0517108A - Modified powder and method for producing modified powder - Google Patents

Abstract

PURPOSE:To give an excellent acid and alkali resistance and to improve the separation performance and the durability as a packing material for chromatography by coating the surface of raw material powder with a polysilazane, insolubilizing it and subsequently baking it for generation of silicon nitride. CONSTITUTION:A raw material powder (e.g. porous silica gel having <=1mm average particle size) is blended with a solution composed of a polysilazane (e.g. low-molecular inorganic polysilazane) dissolved in a solvent (e.g. benzene) and the resultant mixture is, after filtration, dried. The resultant dried material is heated at about 200 deg.C to insolubilize the polysilazane. Baking in the presence of nitrogen is then carried out at 1000-1100 deg.C for 8-20hr, thus obtaining the objective modified powder supporting silicon nitride on the surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modified powder obtained by coating the surface of various powders with a coating material and having excellent properties such as chemical resistance, acid resistance and alkali resistance. The present invention relates to a method for producing the same, and is used in the fields of, for example, fillers for liquid chromatography, cosmetics, paints, and inorganic zinc.

[0002]

2. Description of the Related Art For example, fillers for liquid chromatography are divided into organic ones based on styrene polymers and inorganic ones based on silica gel and alumina. Is also widely used as a packing material for adsorption and separation. Among them, organic fillers have a base material that is chemically stable against acids and alkalis, and therefore, the pH range of the eluent used is higher than that when inorganic fillers are used. It has a wide range of advantages, in particular, that it can be washed with an alkaline solution, and this is one of the factors that are frequently used when conducting analysis of polymer substances.

On the other hand, the most commonly used inorganic filler is a chemical bond type one in which silica gel is used as a base material and functional groups are introduced on the surface of the silica gel base material using various silane coupling agents. There is. Among them, particles having an octadecyl group, an octyl group or a phenyl group introduced therein are widely used as a packing material for reverse phase chromatography. Since the filler based on silica gel generally has high mechanical strength, the particles can be made finer, and as a result, high resolution can be obtained. Further, since swelling and shrinkage due to the organic solvent used does not occur, it has advantages that handling such as solvent exchange is easy and that the condition setting can be easily performed even when examining the analysis conditions.

By the way, the above-mentioned chemically-bonded inorganic filler can be obtained by improving the surface of a base material such as silica gel or alumina. However, it is not limited to a packing material for chromatography, and generally the surface properties of the base material are improved. As a technique for obtaining a modified powder by using a surface treatment agent such as a silane coupling agent or silicone oil, the surface treatment agent is reacted with the surface of the substrate, for example, silanol groups There is known a method of introducing an appropriate functional group into.

For example, in Japanese Patent Publication No. 41-9890, a powder of animal, vegetable or mineral powder is coated with a silicone resin coating material, which is dried and baked to give the powder. Techniques for imparting lubricity are described. Further, in Japanese Patent Publication No. 45-2915, a mineral powder such as talc and a silicone compound having a hydrogen atom having a hydrogen atom directly bonded to a silicon atom in a molecular chain are blended to obtain a mineral property. A technique is disclosed in which a silicone compound is simply attached to a powder and then baked by heating to impart a molecular chain to the powder. Further, in Japanese Patent Publication No. 45-18999, after dissolving dimethylpolysiloxane or methylhydrogenpolysiloxane in an organic solvent, the solution is contact-adhered to talc, and then, if necessary, cross-linking polymerization of methylhydrogenpolysiloxane. As a catalyst, for example, zinc octoate or the like is added, and a technique of imparting free flowability to the powder by baking is disclosed. In addition, in JP-B-49-1769, titanium dioxide is directly coated with various alkylpolysiloxanes, emulsion coating or solvent solution coating, and if necessary, an ester compound having a total carbon number of 6 or more is used in combination and dried and baked. By doing so, a technique for improving the dustiness and dispersibility of the powder is disclosed. In addition, JP-A-56-16404, JP-A-55-136213 and JP-A-56-2951
Each of Japanese Patent Laid-Open Publications No. 2 and No. 2 describes a method in which a silicone oil and an oil agent are added to powders, a mechanochemical reaction such as stirring and mixing or pulverization is performed to mix the powders, and then baking is performed.

[0006]

In the above-mentioned conventional surface modification techniques, silane coupling agents, silicone oils, alkyl silicates, etc. are used as the surface treatment agent, but all of these treatment agents are used. , Mainly composed of silicon oxide, is extremely unstable in its chemical properties under alkaline or strongly acidic conditions and is easily dissolved. Particularly, in the case of a chemical bond type filler in which various functional groups are introduced on the surface of a silica gel base material by using various silane coupling agents or silicone oil, the bond is a siloxane bond (Si- O-
Since it is Si), the usage conditions are limited, and for example, the packing conditions for liquid chromatography are limited to about pH 4 to 7. When the filler is used under alkaline or strongly acidic conditions beyond the range of use, not only erosion of the surface portion subjected to the surface treatment but also dissolution of the silica gel base material itself occurs, and as a filler for liquid chromatography. Will result in a decrease in the separability and durability.
Therefore, in the field of analysis using a packing material for liquid chromatography, there is a demand for a packing material that is chemically more stable and has excellent separation performance.

Therefore, an object of the present invention is to form a coating film of a silicon-containing compound containing no siloxane bond on the powder surface, which has problems of alkali resistance and acid resistance, which are structural defects in the prior art. Modified powder, which was solved by
Another object of the present invention is to provide a method for producing the modified powder.

[0008]

The gist of the present invention is to cover substantially the entire surface of a raw material powder, for example, a base material of a packing material for chromatography, with silicon nitride having acid resistance and alkali resistance. That is, the modified powder is formed.

As a method of producing the modified powder, after the surface of the raw material powder is coated with polysilazane, the surface of the raw material powder is covered with a polysilazane film, and the polysilazane is insolubilized on the surface of the raw material powder. The gist is that the silicon nitride is generated on the powder surface by firing it.

[0010]

The preferred embodiments of the present invention will be described below.

First, the powder used as the raw material of the modified powder according to the present invention is generally an inorganic substance having an average particle size of 10 mm or less, for example, a silicon oxide compound such as glass or silica gel, a zirconium oxide compound, a titanium oxide compound, or an oxide. It is formed from a substance such as an aluminum compound, a silicon nitride compound, or a silicon carbide compound. Moreover, the shape of the raw material powder is not particularly limited, and may be an aggregate or a granule. Further, the surface of the raw material powder may be smooth or rough, and may be porous. For example, when a packing material for chromatography is manufactured, porous glass, silica gel or alumina having an average particle size of 1 mm or less is used as the base material. In addition, zirconium oxide, titanium oxide, etc.
It can be used as a base material for a packing material for chromatography.

Further, the modified powder according to the present invention has substantially the entire surface coated with silicon nitride. The polysilazane used as a raw material for forming the silicon nitride coating is an organic polysilazane and an inorganic polysilazane. In this invention, it is desirable to use an inorganic polysilazane. The inorganic polysilazane is represented by the general formula shown in Chemical formula 1. Incidentally, n in the formula is an integer.

[0013]

[Chemical 1]

However, even when an organic polysilazane is used, the polysilazane obtained by its thermal decomposition is 800
It is possible to form a silicon nitride film by heating at a temperature of up to 2,000 ° C. However, in this case, in addition to silicon nitride, generation of silicon carbide or free carbon is observed.

Inorganic polysilazanes were described in 1921 by A. S
It has been synthesized by A. Stock (A. Stock a
nd K. Somieski, Ber. dt. Che
m. Ges. , 54, 740 (1921)),
In 1982, Seyferth et al. Proved that inorganic polysilazanes were useful as silicon nitride precursors (D. Seyferth and GH.
Wiseman, C.I. Prud 'Home, J.M. A
m. Ceram. Soc. , 66, C-13 (1983)). Further, in Japanese Patent Publication No. 63-16325, after forming an adduct of dichlorosilane and pyridine (a product of an addition reaction), the adduct is reacted with ammonia to give a compound represented by the general formula 1 The method for synthesizing the inorganic polysilazane is disclosed.

In the method for producing the modified powder according to the present invention, the method for producing polysilazane is not particularly limited,
It is necessary to select the molecular weight of polysilazane depending on the shape of the raw material powder whose surface is to be improved. For example, if the raw material powder has a fine structure such as porous,
It is preferable to form a low molecular weight polysilazane on the surface of the raw material powder, and specifically, it is desirable to form an oligomer of about 10-mer. On the other hand, for raw material powders having a relatively simple surface shape, it is preferable to synthesize polysilazane of a tens of decomer.

In the method according to the present invention, the method of coating the surface of the raw material powder with polysilazane is not particularly limited, but after polysilazane is dissolved in a solvent such as benzene and mixed with the raw material powder, The raw material powder surface can be coated with the polysilazane film by a method such as filtering the powder and then drying it, or evaporating all the solvent.

Following the step of coating the surface of the raw material powder with polysilazane, the polysilazane is insolubilized. The insolubilization of the polysilazane carried on the surface of the raw material powder is usually about 20.
It is performed by heating at 0 ° C., but it also proceeds by leaving it at room temperature. The processing time in this case is
Depending on the method of synthesizing polysilazane, A. Stoc
k and other methods (A. Stock and K. Somie)
ski, Ber. dt. Chem. Ges. 54, p. 740 (1921)), polysilazane becomes insoluble when left alone for 3 to 5 days at room temperature when polysilazane is used alone. On the other hand, in the method disclosed in Japanese Patent Publication No. 63-16325, it is insolubilized at room temperature in several hours. Also in the method of the present invention, polysilazane can be insolubilized on the surface of the raw material powder as in these methods. Also,
The insolubilization time can be shortened by heating.

After the polysilazane is insolubilized, it is fired, and the firing treatment is carried out by heating the powder treated as described above in the presence of nitrogen. In the presence of nitrogen referred to here, ammonia alone, nitrogen alone, a mixed gas of nitrogen and an inert gas, for example, nitrogen and hydrogen, nitrogen and ammonia, each mixed gas of nitrogen and argon, or nitrogen-containing decomposition gas, For example, it means that it is present in the presence of an ammonia decomposition gas, and thus the firing treatment is performed in an atmosphere containing a nitrogen element. When a mixed gas is used, the mixing ratio of nitrogen and other component gas is not particularly limited, but it is desirable that the mixed gas contains an excess of nitrogen element.

The heat treatment temperature for calcination needs to be somewhat changed depending on the method of synthesizing polysilazane. For example, when polysilazane is synthesized by the method described in Japanese Patent Publication No. 63-16325, it is preferable. Is 1,000 to 1,100 ° C. Here, when the heat treatment temperature is an extremely low temperature such as 500 ° C. or lower, the removal of unreacted chlorine and hydrogen becomes incomplete, and the obtained silicon nitride contains chlorine and hydrogen. Become. On the other hand, when the heat treatment temperature exceeds 1,900 ° C., the generated silicon nitride is dissociated, which is also not preferable. Even when the heat treatment temperature is not extremely low or too high as described above, when polysilazane is treated at a temperature of 700 ° C. to less than 1,000 ° C., mainly amorphous silicon nitride and silicon A mixture is obtained, and when it is treated at a temperature of more than 1,100 ° C. and not more than 1,900 ° C., mainly β-type silicon nitride is obtained.

Regarding the heat treatment time, the time when the production of hydrogen by-produced by heating is stopped is a tentative guideline for the end of the heat treatment, but the heat treatment time is not particularly limited and is generally At high temperatures, it is relatively short, at low temperatures it is relatively long, and to age the crystals, it is relatively long. A preferable heat treatment time is 8 to 20 hours,
More preferably, it is 10 to 16 hours.

When polysilazane is heat-treated and baked in a heating furnace under a nitrogen atmosphere, a non-oxide material,
For example, it is preferable to use a furnace agent made of silicon nitride, silicon carbide, tantalum, molybdenum or the like.

As described above, the surface of the raw material powder is coated with the polysilazane film, the polysilazane is insolubilized, and then fired to obtain a modified powder having silicon nitride supported on the surface, for example, high resolution. It is possible to obtain a chromatographic packing material which has excellent acid resistance and alkali resistance and is extremely stable chemically.

Next, concrete manufacturing examples and comparative examples will be described.

[Synthesis Example 1 of Polysilazane]

Dichlorosilane was mixed with dehydrated pentane, nitrogen-ammonia gas was blown into the solution with stirring, and the mixture was reacted for 3 hours to obtain colorless oily polysilazane. The molecular weight of the polysilazane at this time was 750 (according to the VPO method).

The above polysilazane was dissolved in chloroform, and this solution was used as a coating solvent. The solution concentration at this time was adjusted to 15 wt%.

[Synthesis Example 2 of Polysilazane]

By gradually mixing dichlorosilane and pyridine under cooling, white solid SiH _{2 was obtained.}
Cl ₂ .2Py was obtained. Nitrogen-ammonia gas was blown into this solution while stirring to cause a reaction, and after the completion of the reaction, a solid product was removed to obtain a high-viscosity polysilazane. At this time, the polysilazane has a molecular weight of 1,500 (VPO
According to the law).

The above polysilazane was dissolved in chloroform, and this solution was used as a coating solution. The solution concentration at this time was adjusted to 15 wt%.

[Example of Surface Modification of Porous Silica Gel Powder]

Porous silica gel powder (particle size 10 μm,
10 ml of a 15 wt% solution of polysilazane obtained by the method of Synthesis Example 1 was added to 10 g of a pore size of 250 liter / g), and they were sufficiently mixed, and then the solvent was removed under reduced pressure. Then, the obtained silica gel powder coated with polysilazane was heated in a silicon nitride tubular furnace in a nitrogen-ammonia mixed gas atmosphere at a rate of 100 ° C./h to 80 ° C.
The temperature was raised to 0 ° C. and 1,000 ° C., and the temperature was maintained for 10 hours and then allowed to cool to room temperature to obtain a brown powder.

The powder has a pore size of 200 ° C. and a pore size of 200.
Å, the nitrogen content was 2.5%, the 1,000 ° C. fired powder had a pore size of 170Å, and the nitrogen content was 2.3%.

[Example of Surface Modification of Titanium Oxide Powder]

Modification was carried out in the same manner as in the above surface modification example of the porous silica gel powder, except that titanium oxide powder was used in place of the porous silica gel powder and the polysilazane solution concentration was diluted 10 times. By doing so, a modified powder having a surface improved with silicon nitride was obtained. The nitrogen content of the modified powder was 0.3%.

[Example of Surface Modification of Aluminum Oxide Powder]

A silicon nitride modified powder was obtained by carrying out modification in the same manner as in the surface modification example of titanium oxide powder described above except that aluminum oxide powder was used instead of titanium oxide powder. The nitrogen content of the modified powder was 0.4%.

[Example of Surface Modification of Zirconium Oxide Powder]

Zirconium oxide powder (particle size 100 μm)
To 10 g, 10 ml of a 15 wt% solution of polysilazane obtained by the method of Synthesis Example 1 was added, and they were sufficiently mixed, filtered, and vacuum dried. Then, the obtained polysilazane-coated zirconium oxide powder was treated at 100 ° C./h under a nitrogen-ammonia mixed gas atmosphere.
The temperature was raised to 1,000 ° C. at a rate of, the temperature was maintained for 5 hours, and then allowed to cool to room temperature to obtain a modified powder having a nitrogen content of 0.03%.

[Comparative Test 1]

Porous silica gel calcined modified powder of 800 ° C. (modified powder 1) and porous silica gel calcined modified powder of 1,000 ° C. (modified powder 2) obtained by the above-mentioned methods. , Titanium oxide modified powder (modified powder 3), aluminum oxide modified powder (modified powder 4) and zirconium oxide modified powder (modified powder 5), and respective raw materials The powder was subjected to an acid resistance test and an alkali resistance test according to the following procedures.

A) Acid resistance test

The test powder was mixed and stirred in a 1N HCl solution for 24 hours, and after the stirring was completed, the powder was filtered off, and the amount of Si-eluting component in the solution was measured and the raw material powder was analyzed.

B) Alkali resistance test 1

The powder to be tested is diluted with 0.1N NaOH solution to 24
After mixing and stirring for a period of time, the powder was filtered off after the stirring was completed, and the amount of Si-eluted components in the solution and the component analysis of the raw material powder were performed.

C) Alkali resistance test 2

1NNaO instead of 0.1N NaOH solution
The same procedure as in the alkali resistance test 1 was performed except that the H solution was used.

The results of these tests are shown in Table 1. The judgment in the table was based on the following criteria. That is, good: 0.01% or less of the total amount of Si eluted components, good: 0.1% or less of the total amount of Si eluted components, and poor: 0.1% or more of the total amount of Si eluted components.

[0049]

[Table 1]

As is clear from Table 1, all the modified powders have improved acid resistance and alkali resistance.

[Example 1 of Production Method of Silicon Nitride Modified Silica Gel Filler]

5 g of silica gel (particle size 5 μm, average pore size 150 Å) sufficiently deaerated under vacuum was suspended in 5 ml of a 15 wt% solution of polysilazane obtained by the method of [Synthesis example 1 of polysilazane] described above. After turbidity, a nitrogen-ammonia mixed gas was introduced into the suspension. It was placed under vacuum again and the solvent removed under reduced pressure. Then, the silica gel adsorbing the polysilazane was heated to a temperature of 800 ° C. at a rate of 100 ° C./h in a nitrogen-ammonia mixed gas atmosphere in a silicon nitride tubular furnace and kept at that temperature for 10 hours. After the firing was completed, the mixture was allowed to cool to room temperature to obtain a brown powder.

The obtained silicon nitride modified silica gel had a particle size of 5 μm, an average pore size of 110Å, and a nitrogen content of 3.2%.

[Production Example 2 of Silicon Nitride Modified Silica Gel Filler]

Silica gel (particle size 10 μm, average pore size 2
50 Å) 5 g, except that the polysilazane solution obtained by the above-mentioned method of [Polysilazane Synthesis Example 2] is used instead of the polysilazane obtained by the method of [Polysilazane Synthesis Example 1]. By the same method as in Example 1, a silicon nitride modified silica gel was obtained. This silicon nitride-modified silica gel had an average pore diameter of 250Å and a nitrogen content of 2.9%.

[Comparative Test 2]

Silicon Nitride Modified Silica Gel (Reformed Silica Gel 1) Obtained by Manufacturing Example 1 and Manufacturing Example 2
The silicon nitride modified silica gel (modified silica gel 2) obtained by the above and two commercially available water-based silica gel fillers (commercial product 1 and commercial product 2) were respectively subjected to a liquid chromatography column ( 7.8 mm x 30
cm).

Samples containing 10 μg / ml bovine serum albumin, 10 μg / ml egg albumin and 10 μg / ml lysozyme in eluent buffer were prepared and used. This sample was injected into each column and 0.2
M (NH ₄ ) ₂ SO ₄ /0.05M Tris buffer (pH
It was eluted by 9.0). This elution treatment was repeated, and the durability was evaluated by the number of times of sample injection in which the elution capacity of each protein was within 5% of the initial value and the separation could be performed without problems in terms of separation performance. The results of these tests are shown in Table 2.

[0059]

[Table 2]

From the results shown in Table 2, it can be seen that the silicon nitride-modified silica gel filler according to the present invention is much more stable than a commercially available silica-based filler and can process a large number of samples. It was also found that the filler according to the present invention exhibits excellent performance in a wide pH range.

[0061]

Since the present invention is constructed and operates as described above, according to the present invention, alkali resistance,
A modified powder having excellent acid resistance can be obtained. When the present invention is applied to a packing material for liquid chromatography, for example, a packing material that is chemically stable and has outstanding durability and is excellent in terms of separation performance can be obtained.

Claims (3)

[Claims] 1. A modified powder obtained by coating substantially the entire surface of a raw material powder with silicon nitride. 2. The modified powder according to claim 1, wherein the raw material powder is a base material of a packing material for chromatography. 3. A step of depositing polysilazane on the surface of the raw material powder to coat the surface of the raw material powder with a polysilazane film; and a step of insolubilizing the polysilazane on the surface of the raw material powder and then firing to generate silicon nitride. A method for producing a modified powder comprising the steps of: