JP6284443B2 - Method for producing colloidal silica containing core-shell type silica particles - Google Patents

Description

  The present invention relates to a method for producing colloidal silica containing core-shell type silica particles.

  Colloidal silica is a dispersion of silica particles in a medium such as water. In addition to being used as a physical property improver in the fields of paper, fiber, steel, etc., it is also used as an abrasive for electronic materials such as semiconductor wafers. Has been. The silica particles dispersed in colloidal silica used for such applications are required to have high purity and denseness, and various treatments such as modifying the surface of the silica particles are performed.

  As a method for producing colloidal silica capable of meeting the above requirements, for example, a method for producing modified colloidal silica in which colloidal silica obtained by hydrolyzing and condensing a hydrolyzable silicon compound is modified with a modifier is proposed. (For example, refer to Patent Document 1).

  According to the method described in Patent Document 1, the surface of silica particles dispersed in colloidal silica obtained by hydrolyzing and condensing a silicon compound is surface-modified with a silane coupling agent, which makes it stable. High purity colloidal silica has been produced.

  However, such a method for producing colloidal silica has a problem that the surface of the silica particles can be modified only with a limited thickness and cannot be sufficiently modified.

  Further, colloidal silica used in the field of abrasives or the like requires that silica particles exhibit an appropriate potential in order to impart stability. In the above-mentioned method, since the surface of the silica particles in the obtained colloidal silica is only modified, the potential that can be applied is limited, and the potential of the silica particles cannot be adjusted to an appropriate range. There is a problem.

  Furthermore, when a large amount of modifier is used to increase the thickness of the surface-modified portion of the silica particles, there is a problem that the colloidal silica causes gelation.

  Manufacture that contains silica particles with high purity and high density, can adjust the potential of the silica particles to an appropriate range, and can easily produce stable colloidal silica with suppressed gelation The method has not been developed yet.

JP 2005-162533 A

  The present invention contains core-shell type silica particles excellent in high purity and denseness, can adjust the potential of the silica particles to an appropriate range, and can easily produce stable colloidal silica in which gelation is suppressed. It aims at providing the manufacturing method of colloidal silica which can be manufactured.

As a result of intensive studies to achieve the above object, the present inventor has obtained a method for producing colloidal silica containing core-shell type silica particles. Step I for preparing a mother liquor containing particles and having a pH of 7 or more and 12 or less, and (II) the mother liquor is represented by the following general formula (1)
Si (OR ¹ ) ₄ (1)
(In the formula, R ¹ represents an alkyl group.)
And an alkoxysilane represented by the following general formula (2)
_{^{R 2 m Si (OR 3)}} n (R 4 -NH 2) p (2)
(In the formula, R ² is an alkyl group having 1 to 6 carbon atoms, R ³ is an alkyl group having 1 to 3 carbon atoms, and R ⁴ is a hydrocarbon group or amino group having 1 to 4 carbon atoms. And a hydrocarbon group having 1 to 4 carbon atoms, which is substituted with m, an integer of 0 to 2, p is 1 or 2, n is an integer of 1 to 3, and (m + n + p = 4)
According to the production method having the step II of forming a shell on the surface of the silica particles by adding the alkoxysilane represented by the formula, the inventors have found that the above object can be achieved and have completed the present invention.

That is, this invention relates to the manufacturing method of the following colloidal silica.
1. A method for producing colloidal silica containing core-shell type silica particles,
(I) Step I of preparing a mother liquor containing silica particles as a core of the core-shell type silica particles in a solvent and having a pH of 7 or more and 12 or less, and (II) The following formula (1) )
Si (OR ¹ ) ₄ (1)
(In the formula, R ¹ represents an alkyl group.)
And an alkoxysilane represented by the following general formula (2)
_{^{R 2 m Si (OR 3)}} n (R 4 -NH 2) p (2)
(In the formula, R ² is an alkyl group having 1 to 6 carbon atoms, R ³ is an alkyl group having 1 to 3 carbon atoms, and R ⁴ is a hydrocarbon group or amino group having 1 to 4 carbon atoms. And a hydrocarbon group having 1 to 4 carbon atoms, which is substituted with m, an integer of 0 to 2, p is 1 or 2, n is an integer of 1 to 3, and (m + n + p = 4)
Step II of forming a shell on the surface of the silica particles by adding an alkoxysilane represented by formula II
A manufacturing method comprising:
2. The production method according to Item 1, wherein the alkoxysilane represented by the formula (1) is at least one selected from tetramethylorthosilicate and tetraethylorthosilicate.
3. Item 2. The production method according to Item 1, wherein the alkoxysilane represented by the formula (1) is tetramethylorthosilicate.
4). The alkoxysilane represented by the formula (2) is aminopropyltrimethoxysilane, (aminoethyl) aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, and aminobutyl. Item 4. The production method according to any one of Items 1 to 3, which is at least one selected from the group consisting of triethoxysilane.

  Hereinafter, the manufacturing method of the colloidal silica of this invention is demonstrated in detail.

  In the production method of the present invention, in step I, a mother liquor containing silica particles that are cores of core-shell type silica particles in a solvent and having a pH of 7 or more and 12 or less is prepared. A specific alkoxysilane having a group and a specific alkoxysilane having a specific hydrocarbon group and amino group are added to form a shell on the surface of the silica particles serving as the core.

  According to the production method of the present invention, a colloidal silkworm containing core-shell type silica particles in which a shell having a functional group having a specific hydrocarbon group and amino group is formed on the core silica particles is easily produced. can do. The core-shell type silica particle is suitable for use as a physical property improving agent in the field of paper, fiber, steel, etc., since a shell having a specific functional group is formed. In particular, an electronic material such as a semiconductor wafer It can be suitably used as a polishing agent.

  In addition, since the core-shell type silica particle has a shell having a specific functional group formed on the surface of the silica particle as the core, the polishing agent is more effective than the case where only the surface of the silica particle is modified with a modifier. For example, it is possible to exhibit more suitable performance.

  Further, the core-shell type silica particles have a shell having a specific functional group formed on the surface of the silica particles as a core, and the potential is adjusted by the shell, so that the potential of the core-shell type silica particles is kept in a desired range. It can be adjusted and stable colloidal silica can be obtained.

  Furthermore, according to the production method of the present invention, it is not necessary to use a large amount of modifier, and gelation of colloidal silica is suppressed.

1. Process I
Step I is a step of preparing a mother liquor having a pH of 7 or more and 12 or less, containing silica particles serving as cores of core-shell type silica particles in a solvent.

  It does not specifically limit as a silica particle used as the said core, A conventionally well-known thing can be used. Examples of such silica particles include silica particles prepared by a conventionally known method such as the Stöber method or the water glass method.

  Although the average particle diameter of the silica particle used as the said core is not specifically limited, About 5-200 nm is preferable and about 10-100 nm is more preferable. In addition, in this specification, the average particle diameter of the silica particle used as the said core represents the primary particle diameter converted by 2727 / specific surface area value.

  The content of the silica particles in the mother liquor is preferably 0.1 to 40% by mass, more preferably 1 to 20% by mass with the mother liquor as 100% by mass. If the content of silica particles in the mother liquor is too large, the efficiency in forming a shell with a desired thickness may be significantly reduced. If the content of silica particles is too small, the formation of the shell will proceed sufficiently. Therefore, there is a risk of causing the generation of new nuclei.

  The solvent used in Step I is not particularly limited as long as the silica particles can be dispersed, and examples thereof include water, an organic solvent, and an organic solvent containing water. Among these, it is preferable to use water. By using water, the core-shell type silica particles can be formed inexpensively and safely.

  When an organic solvent is used as the solvent, the organic solvent includes alcohols such as methanol, ethanol, isopropanol, n-butanol, t-butanol, pentanol, ethylene glycol, propylene glycol, 1,4-butanediol, It is preferable to use a hydrophilic organic solvent such as ketones such as acetone and methyl ethyl ketone, and it is more preferable to use alcohols such as methanol, ethanol and isopropanol.

  One of these solvents can be used alone, or two or more organic solvents can be mixed and used.

  The mother liquor has a pH of 7 or more and 12 or less. When the pH of the mother liquor is less than 7, the shell formation reaction cannot be promoted. Moreover, when the pH of the mother liquor exceeds 12, dissolution of the core particles occurs. The pH of the mother liquor is preferably 7.5-12.

  The mother liquor may be added with an alkali catalyst not containing metal ions such as ammonia, urea, ethanolamine, tetramethylammonium hydroxide, etc., and the pH may be adjusted within the above range. More specific examples of the alkali catalyst include 3-ethoxypropylamine.

  It does not specifically limit as a method of preparing the said mother liquid, It can prepare by a conventionally well-known method. For example, it may be prepared by adding silica particles and, if necessary, an alkali catalyst to a solvent and stirring.

  By the process I demonstrated above, the mother liquor whose pH is 7-12 is prepared which contains the silica particle used as the core of the said core-shell type silica particle in a solvent.

2. Step II
In step II, the mother liquor is added to the following general formula (1).
Si (OR ¹ ) ₄ (1)
(In the formula, R ¹ represents an alkyl group.)
And an alkoxysilane represented by the following general formula (2)
_{^{R 2 m Si (OR 3)}} n (R 4 -NH 2) p (2)
(In the formula, R ² is an alkyl group having 1 to 6 carbon atoms, R ³ is an alkyl group having 1 to 3 carbon atoms, and R ⁴ is a hydrocarbon group or amino group having 1 to 4 carbon atoms. And a hydrocarbon group having 1 to 4 carbon atoms, which is substituted with m, an integer of 0 to 2, p is 1 or 2, n is an integer of 1 to 3, and (m + n + p = 4)
In which a shell is formed on the surface of the silica particles.

The following general formula (1)
Si (OR ¹ ) ₄ (1)
In the formula, R ¹ represents an alkyl group. R ¹ is not particularly limited as long as it is an alkyl group, but is preferably a lower alkyl group having 1 to 8 carbon atoms, and more preferably a lower alkyl group having 1 to 4 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, and a hexyl group. The alkoxysilane represented by the above general formula (1), tetramethoxysilane R ¹ is a methyl group (tetramethyl orthosilicate), tetraethoxysilane R ¹ is an ethyl group (tetraethyl orthosilicate), R ¹ Tetraisopropoxysilane in which is an isopropyl group is preferred, tetramethoxysilane in which R ¹ is a methyl group, tetraethoxysilane in which R ¹ is an ethyl group are more preferred, and tetramethoxysilane is still more preferred.

  The alkoxysilane represented by the general formula (1) may be a derivative. Examples of the alkoxysilane derivative include low-condensates obtained by partially hydrolyzing the alkoxysilane represented by the general formula (1).

  The alkoxysilane represented by the general formula (1) may be used alone or in combination of two or more.

  The addition amount of the alkoxysilane represented by the general formula (1) is not particularly limited, but is preferably 0.1 to 60 parts by mass with respect to 1 part by mass of the silica particles serving as the core of the core-shell type silica particles. 10 mass parts is more preferable. If the amount of the alkoxysilane represented by the general formula (1) is too small, the thickness of the shell may be too thin, and if it is too large, a side reaction (generation of new nuclei) other than shell formation may occur. .

The following general formula (2)
^{_{R 2 m Si (OR 3)}} n (R 4 -NH 2) p (2)
, M is an integer of 0 to 2, p is 1 or 2, n is an integer of 1 to 3, and m + n + p = 4.

R ² represents an alkyl group having 1 to 6 carbon atoms. Specific examples of R ² include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, pentyl group, isopentyl group, neopentyl group, hexyl group, and isohexyl group. And an alkyl group having 1 to 3 carbon atoms is preferable, and a methyl group and an ethyl group are more preferable.

R ³ represents an alkyl group having 1 to 3 carbon atoms. Specific examples of R ³ include a methyl group, an ethyl group, a propyl group, and an isopropyl group, and a methyl group and an ethyl group are preferable.

R ⁴ represents a hydrocarbon group having 1 to 4 carbon atoms and a hydrocarbon group having 1 to 4 carbon atoms substituted with an amino group.

Among the above R ⁴ , specific examples of the hydrocarbon group having 1 to 4 carbon atoms include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, and the like. An alkylene group is preferable, and an ethylene group, a propylene group, and a butylene group are more preferable.

Of the above R ⁴ , specific examples of the hydrocarbon group having 1 to 4 carbon atoms substituted with an amino group include an aminomethylene group, an aminoethylene group, an aminopropylene group, an aminoisopropylene group, an aminobutylene group, and an aminoisobutylene. Group, etc., and an aminoethylene group and an aminopropylene group are preferable.

  Specific examples of the alkoxysilane represented by the general formula (2) include, for example, aminopropyltrimethoxysilane, (aminoethyl) aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropyl Examples thereof include methyldiethoxysilane and aminobutyltriethoxysilane.

  Although the addition amount of the alkoxysilane represented by the general formula (2) is not particularly limited, 0.005 to 1.6% by mass is preferable based on 100% by mass of the final product, colloidal silica, and 0.03 to 0.03%. 0.3 mass% is more preferable. If the amount of the alkoxysilane represented by the general formula (2) is too small, the number of amino groups introduced into the shell decreases, and a desired potential cannot be imparted to the core-shell type silica particles, resulting in stable dispersion over a long period of time. There is a possibility that a possible colloidal silica cannot be obtained. If the amount added is too large, there is a possibility that secondary particle size increases, aggregates are formed, and gelation occurs.

  The ratio of the addition amount of the alkoxysilane represented by the general formula (2) to the addition amount of the alkoxysilane represented by the general formula (1) is the addition amount of the alkoxysilane represented by the general formula (1). It is preferable that it is 0.05-3 mass parts with respect to 100 mass parts, and it is more preferable that it is 0.5-3 mass parts. When the proportion of the alkoxysilane represented by the general formula (2) is too small, the number of amino groups introduced into the shell decreases, and a desired potential cannot be applied to the core-shell type silica particles. There is a possibility that colloidal silica that can be stably dispersed for a period of time cannot be obtained. When the ratio of the addition amount of the alkoxysilane represented by the general formula (2) is too large, the secondary particle size may increase, aggregates may be formed, and gelation may occur.

  The temperature of the mother liquor in step II is not particularly limited, and may be any temperature from room temperature to the boiling point of the dispersion medium in which the colloidal silica is dispersed. Specifically, 0 to 100 ° C is preferable, and 70 to 90 ° C is more preferable. If the temperature of the mother liquor is too low, there is a risk of solidifying depending on the solvent, and there is a possibility that the reactivity of the alkoxysilane represented by the general formula (2) is lowered and the shell cannot be sufficiently formed. If the temperature of the mother liquor is too high, depending on the solvent, the boiling point of the solvent may be exceeded.

  The method of adding the alkoxysilane represented by the general formula (1) and the alkoxysilane represented by the general formula (2) to the mother liquor is not particularly limited, and these alkoxysilanes are added to the mother liquor by a conventionally known method. What is necessary is just to dripping. Although the dripping speed | velocity | rate of alkoxysilane is not specifically limited, It is preferable that it is 0.01-0.1 mol / h with respect to 1g of silica particles used as the core of the said core-shell type silica particle. If the addition rate is too high, the core-shell type silica particles may be formed in a state where the shell does not become dense (silanol groups remain). If the addition rate is too slow, the production efficiency may decrease.

  By the step II described above, colloidal silica containing core-shell type silica particles is produced.

  The colloidal silica preferably has a content of metal impurities such as sodium, potassium, iron, calcium, magnesium, titanium, nickel, chromium and copper of 10 ppm or less. When the content of metal impurities is 10 ppm or less, it can be suitably used for polishing electronic materials and the like.

  When the solvent of the colloidal silica produced according to the above method contains a solvent other than water, the solvent can be replaced with water as necessary in order to enhance the long-term storage stability of the colloidal silica. The method for replacing the solvent with water is not particularly limited, and examples thereof include a method in which water is dropped in a constant amount while heating colloidal silica. Further, as another method, a method in which colloidal silica is separated from a solvent by precipitation / separation, centrifugation, or the like and then redispersed in water can be exemplified.

  The colloidal silica produced by the production method of the present invention is excellent in long-term dispersion stability in a wide pH range. The stability of colloidal silica can be evaluated by measuring the zeta potential of colloidal silica. The zeta potential is the potential difference that occurs at the interface between the solid and the liquid that are in contact with each other when they move relative to each other. If the absolute value of the zeta potential increases, the repulsion between particles is strong. Stability increases and the closer the absolute value of the zeta potential is to zero, the more likely the particles will aggregate.

  In particular, the modified colloidal silica according to the present invention has high stability in the acidic region. The alkoxysilane represented by the general formula (2) has a cationic group. Since the zeta potential of the solvent when the pH of the solvent is 1 to 5 is a positive potential, high dispersion stability can be exhibited even if the solvent is acidic. It also has an equipotential point at which the zeta potential is 0 when the solvent is at pH 5-7. When the dispersion medium is pH 7 or higher, the zeta potential is a negative potential.

  The colloidal silica produced by the production method of the present invention can be used for various applications such as abrasives and paper coating agents, but can be stably dispersed over a wide pH range for a long period of time, and metal such as sodium. Since the impurity content can be as high as 10 ppm or less, it can be suitably used as an abrasive for chemical mechanical polishing of semiconductor wafers.

  According to the production method of the present invention, the core-shell type silica particles excellent in high purity and denseness are contained, the potential of the silica particles can be adjusted to an appropriate range, and the gelation is suppressed stably. Colloidal silica can be easily produced.

It is a figure which shows the measurement result of zeta potential and pH of the colloidal silica prepared by the Example and the comparative example.

  The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples.

Example 1
(Production of colloidal silica containing core-shell type silica particles)
[Step I]: 5882 g of pure water as a solvent and 2604 g of BS-1H (silica concentration 10.5 mass%, secondary particle diameter 35 nm) as a silica particle as a solvent are placed in a flask, and 3-ethoxy as an alkali catalyst. Propylamine was added to adjust the pH to 10 to obtain a mother liquor.
[Step II]: After the mother liquor is heated to an internal temperature of 80 ° C., a mixed liquid of 1872.3 g of tetramethylorthosilicate and 16.3 g of 3-aminopropyltrimethoxysilane is adjusted to the mother liquor so as not to fluctuate the internal temperature. The solution was dropped at a constant rate over 180 minutes to obtain a colloidal silica dispersion containing core-shell type silica particles.

  The obtained dispersion was heated and concentrated to 4600 mL under normal pressure. Subsequently, in order to distill off methanol generated as a by-product during the reaction, the dispersion medium is replaced with 3000 mL of pure water while keeping the volume constant, and the colloidal contains core-shell type silica particles having aminosilane in the shell. Silica was prepared.

Example 2
(Production of colloidal silica containing core-shell type silica particles)
In Step II, colloidal silica containing core-shell type silica particles having an aminosilane in the shell was prepared in the same manner as in Example 1 except that the amount of 3-aminopropyltrimethoxysilane to be added was changed to 28.3 g.

Comparative Example 1
(Production of colloidal silica containing silica particles whose surface is modified with aminosilane)
[Step I]: A mother liquor was prepared in the same manner as in Example 1.
[Step II]: After heating the mother liquor to an internal temperature of 80 ° C., 1872.3 g of tetramethyl orthosilicate was added dropwise to the mother liquor at a constant rate over 180 minutes while controlling the temperature so as not to fluctuate the internal temperature. A liquid was obtained.

  The obtained dispersion was heated and concentrated to 4600 mL under normal pressure to obtain a concentrated solution. To this concentrate, a mixed solution of 16.3 g of 3-aminopropyltrimethoxysilane and 1614.5 g of methanol was added. Thereafter, colloidal silica containing silica particles whose surface was modified with aminosilane was prepared by replacing the dispersion medium with 5000 mL of pure water while keeping the volume constant.

Comparative Example 2
(Production of colloidal silica containing silica particles whose surface is modified with aminosilane)
In the same manner as in Comparative Example 1, a colloidal silica dispersion was obtained.

  The obtained dispersion was heated and concentrated to 4600 mL under normal pressure to obtain a concentrated solution. To this concentrated liquid, a mixed liquid of 28.2 g of 3-aminopropyltrimethoxysilane and 2794.6 g of methanol was added. After the addition, silica aggregates were observed in the mixture.

Comparative Example 3
(Production of colloidal silica containing silica particles not modified with aminosilane)
[Step I]: A mother liquor was prepared in the same manner as in Example 1.
[Step II]: After heating the mother liquor to an internal temperature of 80 ° C., 1872.3 g of tetramethyl orthosilicate was added dropwise to the mother liquor at a constant rate over 180 minutes while controlling the temperature so as not to fluctuate the internal temperature. A liquid was obtained.

  The obtained dispersion was heated and concentrated to 4600 mL under normal pressure. Subsequently, colloidal silica was prepared by replacing the dispersion medium with 3000 mL of pure water while keeping the volume constant in order to distill off methanol produced as a by-product during the reaction.

  The following characteristics were evaluated about the colloidal silica of the obtained Example and the comparative example.

(BET specific surface area)
The colloidal silica was pre-dried on a hot plate and then heat treated at 800 ° C. for 1 hour to prepare a measurement sample. The BET specific surface area was measured using the prepared measurement sample.

(Primary particle size)
With the true specific gravity of silica being 2.2, the value of 2727 / specific surface area (m ² / g) was converted to the primary particle diameter (nm) of colloidal silica.

(Secondary particle size)
A sample obtained by adding colloidal silica to a 0.3 wt% aqueous citric acid solution as a measurement sample for the dynamic light scattering method was prepared. The secondary particle diameter was measured by the dynamic light scattering method (“ELS8000” manufactured by Otsuka Electronics Co., Ltd.) using the measurement sample.

(Zeta potential)
Using ELS-Z manufactured by Otsuka Electronics Co., Ltd., measurement was performed in a 10 mM sodium chloride aqueous solution under conditions of a silica concentration of 1 wt%.

  The association ratio is a value calculated from secondary particle size / primary particle size.

  The results are shown in the following table and figure.

  In Table 1, since the aggregate was produced | generated in the comparative example 2, it has not measured.

Claims (4)

A method for producing colloidal silica containing core-shell type silica particles,
(I) Step I of preparing a mother liquor containing silica particles as a core of the core-shell type silica particles in a solvent and having a pH of 7 or more and 12 or less, and (II) The following formula (1) )
Si (OR ¹ ) ₄ (1)
(In the formula, R ¹ represents an alkyl group.)
And an alkoxysilane represented by the following general formula (2)
_{^{R 2 m Si (OR 3)}} n (R 4 -NH 2) p (2)
(In the formula, R ² is an alkyl group having 1 to 6 carbon atoms, R ³ is an alkyl group having 1 to 3 carbon atoms, and R ⁴ is a hydrocarbon group or amino group having 1 to 4 carbon atoms. And a hydrocarbon group having 1 to 4 carbon atoms, which is substituted with m, an integer of 0 to 2, p is 1 or 2, n is an integer of 1 to 3, and (m + n + p = 4)
Step II of forming a shell on the surface of the silica particles by adding an alkoxysilane represented by formula II
Yes, and manufacturing method of the solvent is Ru water der contains no alcohol.   The production method according to claim 1, wherein the alkoxysilane represented by the formula (1) is at least one selected from tetramethylorthosilicate and tetraethylorthosilicate.   The production method according to claim 1, wherein the alkoxysilane represented by the formula (1) is tetramethyl orthosilicate.   The alkoxysilane represented by the formula (2) is aminopropyltrimethoxysilane, (aminoethyl) aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, and aminobutyl. The manufacturing method in any one of Claims 1-3 which is at least 1 sort (s) selected from the group which consists of triethoxysilane.