JP2001097710A - Surface-modified silica fine particles for low viscosity slurry and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce surface-modified silica fine particles that can give a silica slurry of low viscosity even in the case of a high silica concentration, and a use thereof. SOLUTION: The surfaces of silica fine particles are treated with an amino group-bearing silane-coupling agent until the whole amount of the nitrogen reaches 0.3-1.0 wt.%. The resultant surface-modified silica fine particles are used in the low-viscosity silica slurry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a surface-modified silica fine powder which can obtain a slurry having a much lower viscosity and a good fluidity than conventional ones, even if the slurry concentration is relatively high, and its silica. For applications involving slurries.

[0002]

2. Description of the Related Art Silica fine powder is widely used as a thickener for liquids, and can significantly improve the viscosity of various liquids by adding a small amount thereof, and can be used for various kinds of cosmetics, adhesives, paints, printing inks and the like. Used in the field. In particular, silica produced by a gas phase method is suitable for a thickener because it has a large specific surface area and is fine.

[0003] The thickening effect of this silica fine powder increases with an increase in its specific surface area, and increases in proportion to the added amount. For example, the viscosity of a silica slurry containing fine silica powder having a BET specific surface area of 200 m ² / g produced by a gas phase method reaches about 2000 mPa · s at an addition amount of 12 wt%.
(Degussa-Huels AG Technical Bullelin Pigmente No.2
3). It is also known that silica fine powder exhibits the best thickening effect in the range of pH 4 to 9, and its viscosity is reduced to a maximum near pH 6 (Nippon Aerosil Co., Ltd., Cataloku No. 12 AER).
Behavior of OSIL in liquid).

[0004]

On the other hand, a silica slurry containing fine silica powder has a viscosity as low as possible while containing a high concentration of silica from the viewpoints of workability, production efficiency, application characteristics and the like in its use. May be required. For example, in the fields of abrasives, paper coating agents, inks, rubbers, plastics, and the like, a high-concentration but low-viscosity silica slurry may be required. However, the conventional silica fine powder has a problem that if the amount of addition is large, the viscosity of the slurry sharply increases, and a desired slurry cannot be obtained.

The present invention has solved such a conventional problem. A high-concentration slurry has a surface which can obtain a silica slurry having a significantly lower viscosity and excellent fluidity than conventional ones. An object of the present invention is to provide a modified silica fine powder and an improved printing material containing the low-viscosity silica slurry.

[0006]

That is, the present invention relates to the following surface-modified silica fine powder and use thereof. (1) Surface modification characterized by being a fine silica powder having a total nitrogen content of 0.3 to 1.0 wt%, which is surface-treated with an amino group-containing silane coupling agent, and which is used for a low-viscosity silica slurry. Silica fine powder. (2) Fine silica powder having a total nitrogen content of 0.3 to 1.0 wt% and a BET specific surface area of 200 to 400 m ² / g, which has been surface-treated with an amino group-containing silane coupling agent, A surface-modified fine silica powder having a viscosity of 50 mPa · s or less under a range of pH and silica concentration. (3) A silica fine powder having a BET specific surface area of 200 to 400 m ² / g was mixed with an amino group-containing silane coupling agent at 30 mmol / 100.
g or more and is a fine silica powder whose total nitrogen content is 0.3 to 1.0 wt% by surface treatment under dry condition. The surface of the above (1) or (2) used for a low-viscosity silica slurry. Modified silica fine powder. (4) A silica slurry composed of surface-modified silica fine powder, which has a pH and silica concentration within a standard range of 50%.
A low viscosity silica slurry having a viscosity of mPa · s or less. (5) A silica fine powder having a BET specific surface area of 200 to 400 m ² / g was mixed with an amino group-containing silane coupling agent at 30 mmol / 100.
g and a silica slurry composed of fine silica powder having a total nitrogen content of 0.3 to 1.0 wt% by surface treatment under a dry process, wherein the pH is 3 to 6 and 15 to 30 wt%.
Having a viscosity of 1 to 50 mPa · s under a silica concentration of
The low viscosity silica slurry of (4). (6) An ink receiving layer forming liquid, comprising a silica slurry containing 5 to 30% by weight of the surface-modified silica fine powder of (1), (2) or (3). (7) An ink-receiving layer forming liquid comprising the silica slurry of (4) or (5). (8) A printing material, wherein the ink receiving layer is formed by the silica slurry of (6) or (7).

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. Surface modified silica fine powder of the present invention,
By subjecting the silica fine powder to a surface treatment using an amino group-containing silane coupling agent and introducing a certain amount or more of amino groups to the silica surface, a silica slurry having a low viscosity even at a high slurry concentration can be obtained. It is made possible. Specifically, preferably, fine silica powder having a BET specific surface area of 200 to 400 m ² / g is subjected to a surface treatment with an amino group-containing silane coupling agent to make the total nitrogen amount 0.3 to 1.0 wt%. Is a surface-modified silica fine powder characterized in that the silica slurry has a viscosity of 50 mPa · s or less under a standard range of pH and silica concentration in the silica slurry.

The silica fine powder of the present invention has a specific surface area (expressed as a BET specific surface area) of at least 200, preferably from 200 to 400 m ² / g, by the BET method. If the specific surface area is less than 200 m ² / g, the amount of amino groups introduced per unit surface area during surface modification using aminosilane is limited, and the nitrogen amount after the treatment becomes less than 0.3 wt%. is not. It should be noted that fumed silica fine powder having a specific surface area exceeding 400 m ² / g is difficult to obtain because it is not commercially produced at present, and even if the BET specific surface area is too large, the amount of amino groups introduced naturally increases. Since the particle size is limited, silica having a specific surface area in the above range is appropriate.

As the silica fine powder, a silica fine powder produced by a gas phase method is preferably used. Silica obtained by the wet method has large aggregated particles, and it is difficult to uniformly modify the particle surface under dry conditions. Further, when the ink receiving layer is formed, a transparent feeling cannot be obtained, which is not preferable. As a production example of the gas phase method, a flame hydrolysis method using silicon tetrachloride as a raw material is known. Examples of the silica produced by the gas phase method include products manufactured by Nippon Aerosil Co., Ltd. (trade names: Aerosil200, Aerosil200CF, Aerosil30).
0, Aerosil300CF, Aerosil380, Aerosil380S), Cabot products (trade name: Cabosil), Wacker products (trade name: HDK), Tokuyama products (trade name: Leolosil), and the like.

The fine silica powder produced by the gas phase method has a hydroxyl group on its surface and has an adsorption ability for anions, but its adsorption ability is low. Therefore, in the present invention, the total nitrogen amount on the surface of the silica particles is adjusted to a certain level or more by introducing an amino group which is a cationic substance on the silica surface. Specifically, this total nitrogen amount is 0.3
Increase to ~ 1.0 wt%. The amino group to be introduced may be one having at least one of a primary amine, a secondary amine, a tertiary amine and a quaternary ammonium salt. Examples of such an amino group-containing silane coupling agent include, for example, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ- (2aminoethyl) aminopropyltrimethoxysilane, γ- (2aminoethyl)
Aminopropyltriethoxysilane, N-phenyl-γ
Aminopropyltrimethoxysilane, N-phenyl-γ
Aminopropyl triethoxysilane, otakudecyldimethyl (3- (trimethoxysilyl) propyl) ammonium chloride and the like are used. One or more of these amino group-containing silane coupling agents can be used.

The amount of the amino group-containing silane coupling agent used is suitably not less than 30 mmol (ie. 30 mmol / 100 g) per 100 g of the silica fine powder having the above specific surface area. If the amount of the amino group-containing silane coupling agent is less than this, the nitrogen content of the surface-modified silica is less than 0.3% by weight. Even when the amount of the amino group-containing silane coupling agent used is 30 mmol / 100 g or more, the number of reacting silanols per unit area of the silica surface is almost constant, and the steric hindrance of the alkyl group to be coated is not affected. The amount of amino groups introduced for the purpose is limited. Incidentally, the amount of nitrogen after surface modification is about 1 wt% even if the specific surface area of silica is large.

The above surface treatment is preferably performed in a dry manner.
Conventionally, there has been known a method of surface-treating by dropping aminosilane while dispersing silica in water.
5 [9] 630-636, 1986) In such a wet method, when silica produced by a gas phase method is used, its viscosity is extremely high, so that silica cannot be dispersed in water at a high concentration. May not be surface treated. Further, in the wet treatment, it is necessary to dry after the surface treatment, so that the treatment process is complicated. In addition, the silica particles tend to agglomerate due to capillary pressure during drying, which may require crushing or the like, which is not economical. In the treatment method using a hydrophobizing agent even in the dry treatment, the surface-treated silica cannot be dispersed in water due to its hydrophobicity, and is not suitable for an ink receiving layer made of an aqueous material.

By the surface modification treatment, hydrophilic silica fine powder is obtained. When the ink receiving layer applied to the surface of the printing paper is formed of an aqueous material such as a slurry of an alcohol solution, the hydrophilic silica can be uniformly dispersed in the aqueous material to form a good ink receiving layer. can do. If the silica is hydrophobic, the dispersibility in such an aqueous material is poor, and a favorable ink receiving layer cannot be formed.

The above surface-modified silica fine powder of the present invention comprises BE
T specific surface area 200-400m ² / g and total nitrogen 0.3-
It has a physical property of 1.0 wt%, and when it is used as an aqueous slurry, the isoelectric point of silica is pH 6 to 10, and the viscosity is 50 mPa · s or less at a pH and a silica concentration in a reference range. It becomes a highly fluid silica slurry of 1 to 50 mPa · s. The viscosity of the slurry varies depending on its pH and the concentration of silica.
6 and a silica concentration of 15 to 30 wt% are abbreviated as a reference range of pH and silica concentration for convenience. Here, if the nitrogen content is less than 0.3 wt%, the isoelectric point of silica is pH
Below 6, the viscosity of silica slurry in the reference range is 50 mP
The liquidity decreases beyond a · s. In addition, the above nitrogen amount is 0.1.
If the BET specific surface area is less than 200 m ² / g, the isoelectric point is lower than pH 6 due to the large particle diameter even if the BET specific surface area is 3 wt% or more, and the viscosity of the slurry also exceeds 50 mPa · s and the fluidity decreases. I do.

For preparing the silica slurry, a disk-type high-speed stirrer, a homogenizer, a wet jet mill or the like can be used. However, the present invention is not limited thereto. May be used. The timing of adjusting the pH of the silica dispersion may be before or after the silica is charged into the liquid, but preferably before the silica is charged, a pH adjusting reagent is previously charged so that the final pH after the silica mixing becomes 3 to 6. good. This is effective for improving the wettability with the surface-modified silica.

An ink receiving layer forming liquid can be obtained by mixing the above surface-modified silica fine powder with an alcohol solution or the like to form a silica slurry. The silica concentration of this solution is suitably from 5 to 30% by weight. 3 wt% of surface modified silica
When the amount is less than 30% by weight, the viscosity of the slurry becomes high, which is not suitable for uniformly applying the liquid. By applying this ink receiving layer to the surface of printing paper such as recording paper, a printing material suitable for inkjet can be obtained.

[0017]

Examples and Comparative Examples Hereinafter, Examples of the present invention will be described together with Comparative Examples. The nitrogen content, hydrophilicity, isoelectric point, and slurry viscosity of the silica were measured by the following methods. (A) The amount of nitrogen in silica was oxidized at a high temperature, the generated NOx was further reacted with ozone to bring it into an excited state, and the light generated when the state changed from this excited state to the ground state was measured. The instrument used was a total nitrogen analyzer (manufactured by Mitsubishi Chemical Corporation: TN-10). (B) Evaluation of hydrophilicity The hydrophilicity is evaluated by the state in which the surface-modified silica is dispersed in water.
Specifically, about 2 g of surface-modified silica was added to a beaker (300 ml).
Volume), add about 100 ml of pure water and stir for 1 minute with a magnetic stirrer to make the silica powder floating in water hydrophilic. (C) Equipment that can measure even a slurry with a high isoelectric point concentration of silica (MATEC APPLIED S
It was measured after pH was adjusted using sodium hydroxide and hydrochloric acid using CIENCES ESA9800). (D) Viscosity of the slurry The viscosity was measured at a slurry temperature of 22 ° C. and a shear rate of 0.15 to 100 / sec (a rheometer manufactured by HAAKE: Lotbisco RT10, and a double gap DG41 as a sensor).

Example 1 A fumed silica having a BET specific surface area of 380 m ² / g (trade name: Aerosil
380S) was placed in a mixer, and 70 mmol / 100 g of γ- (2aminoethyl) aminopropyltrimethoxysilane (trade name: SH6020: manufactured by Toray Tow Corning Silicone Co., Ltd.) was added dropwise while stirring under a nitrogen atmosphere. C. for 1 hour while stirring, and after cooling to remove volatiles, the total nitrogen content was 0.95 wt.
% Of hydrophilic surface-modified silica fine powder was obtained. Disperse the silica fine powder in water using a wet jet mill disperser,
An aqueous slurry having a silica concentration of 20% by weight was obtained. The isoelectric point of this silica was pH 9.6. Furthermore, the slurry p
H was adjusted to 3.2 and the viscosity was measured.
It was 5 mPa · s.

Example 2 A fumed silica having a BET specific surface area of 200 m ² / g (trade name: Aerosil
200CF) using 100 g, and 32 mmol of γ-aminopropyltriethoxysilane (trade name: KBE903: product of Shin-Etsu Chemical Co., Ltd.)
/ 100 g was added dropwise, and the others were the same as in Example 1 to obtain a hydrophilic surface-modified silica fine powder. The total nitrogen content of this silica was 0.32% by weight. About this silica fine powder,
In the same manner as in Example 1, an aqueous slurry having a silica concentration of 20% by weight was prepared. The isoelectric point of this silica was pH 6.4. The pH of the slurry was adjusted to 3.6, and the viscosity was measured to be 1 to 30 mPa · s.

Example 3 A fumed silica having a BET specific surface area of 300 m ² / g (trade name: Aerosil
300) 100 g, and 20 mmol / 1 of γ-aminopropyltriethoxysilane (trade name KBE903: product of Shin-Etsu Chemical Co., Ltd.)
00g and γ- (2aminoethyl) aminopropyltrimethoxysilane (trade name: SH6020: a product of Toray Tow Corning Silicone Co., Ltd.)
20 mmol / 100 g was added dropwise, and in the same manner as in Example 1 except for this, a hydrophilic surface-modified silica fine powder was obtained. The total nitrogen content of this fine silica powder was 0.68 wt%. About this silica fine powder, the silica concentration 2
A 0 wt% aqueous slurry was prepared. The isoelectric point of this silica was pH 7.3. The pH of the slurry was adjusted to 5.6, and the viscosity was measured to be 1 to 45 mPa · s.

COMPARATIVE EXAMPLE 1 A fumed silica having a BET specific surface area of 380 m ² / g (trade name: Aerosil
380S), and the amount of γ- (2aminoethyl) aminopropyltrimethoxysilane (trade name: SH6020: product of Toray Tow Corning Silicone Co., Ltd.) was 28 mmol / 100 g, and the other conditions were the same as in Example 1. Thus, a hydrophilic surface-modified silica fine powder was obtained. The total nitrogen content of this silica is 0.28 wt%,
Lower than the level of the present invention. With respect to this silica fine powder, an aqueous slurry having a silica concentration of 20 wt% was prepared in the same manner as in Example 1. The pH of this slurry was adjusted to 3.8, and the viscosity was measured. The viscosity was 30 to 70 mPa · s, and the slurry had high viscosity and low fluidity.

Comparative Example 2 Vapor phase silica having a BET specific surface area of 200 m ² / g (trade name: Aerosil
200CF) using 100 g, the drop amount of γ-aminopropyltriethoxysilane (trade name KBE903: Shin-Etsu Chemical Co., Ltd.) was 28
The yield was changed to mmol / 100 g, and in the same manner as in Example 2, a hydrophilic surface-modified silica fine powder was obtained. The total nitrogen content of this silica was 0.18 wt%, which was lower than the level of the present invention. An aqueous slurry having a silica concentration of 20% by weight was prepared for the fine silica powder in the same manner as in Example 2. The pH of this slurry was adjusted to 4.3, and the viscosity was measured. The viscosity was 25 to 60 mPa · s, and the viscosity was high and the fluidity was low.

Comparative Example 3 A fumed silica having a BET specific surface area of 300 m ² / g (trade name: Aerosil
300) 100 g, and the drop amount of γ-aminopropyltriethoxysilane (trade name KBE903: Shin-Etsu Chemical Co., Ltd.) is 12 mm.
ol / 100 g, and the amount of γ- (2aminoethyl) aminopropyltrimethoxysilane (trade name: SH6020: manufactured by Toray-Tow Corning Silicone Co., Ltd.) was 12 mmol / 100 g.
In the same manner as in the above, a hydrophilic surface-modified silica fine powder was obtained. The total nitrogen content of this silica fine powder was 0.23% by weight, which was lower than the level of the present invention. An aqueous slurry having a silica concentration of 20% by weight was prepared in the same manner as in Example 3 for this silica fine powder. The pH of this slurry was adjusted to 5.0,
The viscosity was measured and found to be 40 to 80 mPa · s. The viscosity was high and the fluidity was low.

Example 4 25 parts of the surface-modified silica fine powder prepared in Example 1 was used and polyvinyl alcohol (PVA: 220: a product of Kuraray Co., Ltd.)
It was dispersed in a solution of 10 parts, 70 parts of water and 5 parts of acetic acid by a wet jet mill to prepare a silica slurry solution. The pH of this solution was 4.5. The viscosity was 1 to 15 mPa · s. For this silica slurry solution, a silica concentration of 1
Water and polyvinyl alcohol were added so that the concentration became 3 wt% and the polyvinyl alcohol concentration became 10 wt%, and the mixture was dispersed with a homogenizer to prepare an ink receiving layer forming liquid. This forming solution was applied to an uncoated paper for inkjet (I
JL Mitsubishi Paper Mills Co., Ltd.) so that the film thickness after drying was 8 μm. When printing was performed on this paper using a color inkjet printer (BJF-600, product of Canon Inc.), there was no cracking of the coating film and no bleeding of the ink.

Comparative Example 4 A silica slurry solution was prepared in the same manner as in Example 4 except that 25 parts of the surface-modified silica part powder prepared in Comparative Example 3 was used. The pH of this solution was 3.9, and the viscosity was measured in the same manner as in Example 4.
High with s. Further, a silica concentration of 13 w
Water and polyvinyl alcohol were added so that the concentration became 10% by weight and the polyvinyl alcohol concentration was 10% by weight, and the mixture was dispersed with a homogenizer to produce a liquid for forming an ink receiving layer. When a printing test similar to that of Example 4 was performed on paper coated with this forming liquid in the same manner as in Example 4, there was no crack in the coating film, but bleeding of the ink was observed.

Examples 5 to 7 and Comparative Examples 5 to 7 Using silica fine particles (100 g) produced by a gas phase method and amino group-containing silane, amino group-containing silane was added dropwise to the silica fine particles, and the mixture was added at 20 ° C. for 1 hour. After heating and stirring to remove volatile components, the mixture was cooled to obtain a surface-modified fine silica powder. Table 1 shows the specific surface area of the silica fine particles, the type and amount of the amino group-containing silane, and the total nitrogen amount of the surface-modified silica fine particles.
It was shown to. Next, the silica fine powder was dispersed in water using a wet jet mill disperser to obtain an aqueous silica slurry. The isoelectric point of this silica is shown in Table 1. Further, the pH of the slurry was adjusted, and the viscosity was measured. The results are shown in Table 1.

[0027]

[Table 1]

Example 8 and Comparative Example 8 Silica slurries were prepared in the same manner as in Example 4 using the surface-modified silica fine powders of Examples 5 and 7 respectively.
Table 2 shows the pH and viscosity of this slurry. Using this slurry, an ink receiving layer forming liquid produced in the same manner as in Example 4 was applied to printing paper, and a printing test was performed using an ink jet printer. In Example 8, there was no cracking of the coating film and no bleeding of the ink, but in Comparative Example 8, bleeding of the ink was observed.

[0029]

[Table 2]

[0030]

The surface-modified silica fine powder according to the present invention comprises:
In a high-concentration slurry, it is possible to obtain a silica slurry having significantly lower viscosity and excellent fluidity than conventional ones. In addition, by using this low-viscosity silica slurry, it is possible to form an ink-receiving layer free of ink bleeding and cracking of the coating film, whereby an excellent printing material can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuki Amano 3 Mitacho, Yokkaichi-shi, Mie Japan F-term in Yokkaichi Plant of Aerosil Co., Ltd. (Reference) 4G066 AA10D AA22B AB13B AB18D AC12D BA26 DA07 DA20 FA14 FA37 4G072 AA28 AA41 BB05 CC18 EE01 GG01 GG02 HH17 HH29 JJ11 JJ33 LL06 MM02 PP17 QQ06 TT06 UU25 4L055 AG05 AG35 AG64 AG98 AH02 AH37 AH50 AJ04 BE08 BE09 EA17 EA25 EA29 EA31 EA32 FA30 GA09 GA15

Claims (8)

[Claims] 1. A silica fine powder having a total nitrogen content of 0.3 to 1.0 wt%, which is surface-treated with an amino group-containing silane coupling agent, and is used for a low-viscosity silica slurry. Modified silica fine powder. 2. A total nitrogen content of 0.3 to 1.0 wt% surface-treated with an amino group-containing silane coupling agent and BE
T is a fine silica powder having a specific surface area of 200 to 400 m ² / g, wherein the silica slurry has a viscosity of 50 mPa · s or less under a standard range of pH and silica concentration. Powder. 3. A silica fine powder having a BET specific surface area of 200 to 400 m ² / g is mixed with an amino group-containing silane coupling agent of 30 mm.
ol / 100 g or more, which is a fine silica powder having a total nitrogen content of 0.3 to 1.0 wt% by surface treatment under a dry condition, and used for a low-viscosity silica slurry. Silica fine powder. 4. A low-viscosity silica slurry comprising a surface-modified silica fine powder, which has a viscosity of 50 mPa · s or less under a standard range of pH and silica concentration. 5. A silica fine powder having a BET specific surface area of 200 to 400 m ² / g is mixed with an amino group-containing silane coupling agent of 30 mm.
ol / 100 g or more and a silica slurry composed of fine silica powder having a total nitrogen content of 0.3 to 1.0 wt% by surface treatment under a dry condition, and having a pH of 3 to 6 and 15 to 3
The low viscosity silica slurry according to claim 4, which has a viscosity of 1 to 50 mPa · s at a silica concentration of 0 wt%. 6. An ink-receiving layer forming liquid comprising a silica slurry containing 5 to 30% by weight of the surface-modified silica fine powder according to claim 1, 2 or 3. 7. An ink-receiving layer forming liquid comprising the silica slurry of claim 4 or 5. 8. A printing material comprising an ink receiving layer formed by the silica slurry according to claim 6.