JP3346964B2 - Hydrophobic silica - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel hydrophobic silica. Specifically, when added to non-polar organic compounds such as silicone oil, while showing a high viscosity,
It is a hydrophobic silica capable of maintaining the transparency of the non-polar organic compound.

[0002]

2. Description of the Related Art Dry process silica obtained by a dry process of pyrolyzing chlorosilane has a specific surface area of 50 to 500.
It is an ultrafine powder of m ² / g and is generally called fumed silica.

[0003] This dry silica is used as a filler or reinforcing material for liquids or high molecular compounds. When dry silica is used for these purposes, the surface of the dry silica usually has a silanol group. In many cases, it is necessary to make the surface hydrophobic by substituting the surface with a methyl group.

The effect of using dry-processed silica that has been subjected to a hydrophobic treatment is as follows. For example, when hydrophobic dry-processed silica is used for dimethylpolysiloxane or hexamethyldisiloxane whose ends are covered with trimethyl, the dispersion of silica particles is reduced. In order to enhance the properties, there is an effect of changing the strength and viscosity over time or improving the transparency. Conventionally, monomethyltrichlorosilane and / or dimethyldichlorosilane, or a mixture thereof has been widely and generally used as an alkylsilane for hydrophobizing dry silica. Also,
Usually, the value of carbon per unit surface area of the hydrophobic silica subjected to the hydrophobic treatment is 6.5 × 10 ^{−5 to} 10.0.
× 10 ^-5 g / m ² , and the amount of the obtained hydrophobic silica suspended in water is 0.5% or less.

[0005]

However, in the above-mentioned hydrophobic silica, the dispersibility of silica particles is too high in many non-polar organic compounds, and the effect of improving transparency can be obtained. The effect was extremely small.

[0006] For these reasons, it has been a major problem to develop a hydrophobic dry-processed silica which does not impair transparency and also exhibits a thickening effect among nonpolar organic compounds.

[0007]

Means for Solving the Problems The present inventor has continued intensive studies to solve the above-mentioned problems. As a result, they have found that hydrophobic silica obtained by hydrophobizing the surface of a dry-processed silica with an alkylsilane at a specific concentration can solve the above-mentioned problem extremely effectively, and have completed the present invention.

That is, according to the present invention, monomethylsilane is present on the dry silica surface so that the concentration per unit surface area is in the range of 3 × 10 ^{−5 to} 6 × 10 ⁻⁵ g / m ² in terms of carbon. It is a hydrophobic silica for a thickener, which is characterized by the following.

In the present invention, the hydrophobic silica can be obtained by using a known dry process silica. Such a fumed silica preferably has a specific surface area of 50 to 500 m ² / g, particularly preferably 90 to 300 m ² / g .

The hydrophobic silica for a thickener of the present invention is prepared by mixing monomethylsilane with a concentration per unit surface area of 3 × 10 ^{−5 to} 6 × 10 ⁻⁵ g / m ² in terms of carbon. It is characterized by having it exist. That is, when the carbon equivalent value per unit surface area exceeds 6 × 10 ⁻⁵ g / m ² , a high thickening effect cannot be obtained when added to a nonpolar organic compound such as silicone oil. Further, when the carbon conversion value per unit surface area is less than 3 × 10 ⁻⁵ g / m ² , when added to a non-polar organic compound, the transparency is significantly reduced, thereby achieving the object of the present invention. Can not.

[0011] Incidentally, in the hydrophobic silica, the concentration per unit surface area of the mono-methyl Shi <br/> run (carbon conversion value) is measured using a carbon analyzer the amount of carbon present on the surface of the hydrophobic silica And the amount of carbon obtained is BET
It is a value obtained by dividing by the specific surface area of the hydrophobic silica measured by a specific surface area meter.

The hydrophobic silica for a thickener according to the present invention satisfies the above-mentioned conditions, and has a property that when mixed with water, the amount of suspension in water is 0.7 to 70% by weight (wt)%. Are particularly preferred.

That is, when the amount of suspension in water is 0.7 wt% or more, when added to a non-polar organic compound,
It is possible to exhibit a higher thickening effect, and it is possible to further improve the transparency when added to a non-polar organic compound by setting the amount of suspension in water to 70 wt% or less.

The above-mentioned suspension amount in water indicates the ratio of a substance which can be suspended in water when hydrophobic silica is mixed with water.

The method for obtaining the hydrophobic silica for a thickener of the present invention is not particularly limited. To illustrate a typical method,
It is as follows.

[0016] First, a method of hydrophobicized dry method silica monomethyl silane, a method of contacting the vapor of monomethyl silane dry silica is generally used. At this time, the reaction temperature can be in the range of 300 to 650 ° C., and particularly preferably in the range of 400 to 500 ° C. in the case of performing the hydrophobic treatment with monomethyltrichlorosilane.

[0017] In addition, methyl meth-
The method of the amount of silanes include, but are not particularly limited, in the above method, a method of diluting the monomethyl silane with an inert gas such as nitrogen is employed. In particular,
A method of introducing and diluting water vapor together with the above-mentioned inert gas is preferable.

[0018]

As will be understood from the above description , the hydrophobic dry process silica of the present invention for a thickener exhibits an excellent thickening effect by being added to a non-polar organic compound, and is transparent. It does not impair the sex.

In particular, when mixed with dimethylpolysiloxane or the like whose end is covered with trimethyl, it is possible to obtain an excellent thickening effect without impairing the transparency.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, various physical property measurement in an Example is based on the following method.

(1) Silicone Oil Viscosity 5.2 weight% of silica is added to 1000 cs dimethylpolysiloxane covered with trimethyl, and mixed at 10,000 rpm using a homomixer (TK homomixer model M manufactured by Tokushu Kika Co., Ltd.). Disperse for 2 minutes, 25 in a water bath
After adjusting the temperature to ° C., a BL type rotational viscosity type (manufactured by Tokyo Keiki), rotor No. Using No. 4, the viscosity at 60 rpm was measured.

(2) Silicone Torque 40 g of 10,000 cs dimethylpolysiloxane having a terminal covered with trimethyl was put into a Labo Plastomill torque measuring device (manufactured by Toyo Seiki Co., Ltd.), and 23.1% by weight of silica was put therein. The torque value was measured.

(3) Dispersion (dispersion index n) The liquid after the completion of the measurement of the viscosity of the silicone oil is defoamed, and the absorbance at a wavelength (λ) of 700 nm and 460 nm is measured using a spectrophotometer (manufactured by JASCO Corporation). (Τ), and
The dispersion index (n) was calculated from the equation τ = αλ- ⁿ .

(4) Measurement of Amount of Suspension in Water (Measurement of Amount of Hydrophilic Silica) 3 g of a sample was mixed with a mixer (MK-51M, manufactured by Matsushita Electric Industrial Co., Ltd.) for 30 minutes.
Disintegrate in seconds and weigh 1.000 g of the disintegrated sample. 50 ml of water was put into a 100 ml separatory funnel, and a precisely weighed sample was put in the shaker (shaking width 40 mm, 200 times /
) For 2 minutes. After standing for 30 minutes, only the liquid layer is collected in a 100 ml container, 10 ml of a 5N aqueous solution of sodium hydroxide is added, and the mixture is boiled for 20 minutes. 1 boiled liquid
After transferring to a 00 ml volumetric flask and adjusting the temperature to 25 ° C,
Make up to 100 ml with pure water. Thereafter, the amount of silica suspended in water is measured by sodium silicate titration.

(5) Transparency (light transmittance τ) After diluting and defoaming the sample after measuring the silicone torque, the light transmittance (τ) at a wavelength of 700 nm is measured using a spectrophotometer (manufactured by JASCO Corporation). did.

Examples 1-4 Monomethyltrichlorosilane prepared by diluting dry silica having a specific surface area of 140 m ² / g with nitrogen and water vapor was mixed with 50 ml of dry silica.
Contact was made at 0 ° C. to produce a hydrophobically treated hydrophobic silica in a range of 3.5 to 6.0 × 10 ⁻⁵ g / m ² in terms of carbon per unit surface area.

The amount of the obtained hydrophobic silica suspended in water, silicone oil viscosity-transparency (dispersion index n) and silicone torque-transparency (light transmittance τ) were measured. The results are shown in Table 1.

Comparative Example 1 Hydrophobizing treatment of dry process silica having a specific surface area of 140 m ² / g such that monomethyltrichlorosilane has a carbon equivalent of 7.9 × 10 ⁻⁵ g / m ² per unit surface area (known product) For the hydrophobic hydrophobic dry silica, the amount of suspension in water,
Silicone oil viscosity-transparency (dispersion index n) and silicone torque-transparency (light transmittance τ) were measured. The results are shown in Table 1.

Comparative Example 2 Silicone oil viscosity-transparency (dispersion index n) and silicone torque-transparency (light transmittance τ) of a dry process silica having a specific surface area of 140 m ² / g without hydrophobizing treatment were measured. . The results are shown in Table 1.

COMPARATIVE EXAMPLE 3 A dry silica having a specific surface area of 140 m ² / g was treated with monomethyltrichlorosilane in the same manner as in Example 1 to obtain a specific surface area in terms of carbon of 1.5 × 10 ⁻⁵ g / m ² per unit surface area.
To produce hydrophobic silica.

The suspension amount of the obtained hydrophobic silica in water, silicone oil viscosity-transparency (dispersion index n), and silicone torque-transparency (light transmittance τ) were measured. The results are shown in Table 1.

Comparative Example 4 7.9 × 10 ⁻⁵ g / carbon equivalent value per unit surface area
A suspension of water in which water was prepared by mixing m ² of hydrophobic dry silica with non-hydrophobized dry silica and adjusting the carbon equivalent per unit surface area to 3.0 × 10 ⁻⁵ g / m ^2. The turbidity, silicone oil viscosity-transparency (dispersion index n) and silicone torque-transparency (light transmittance τ) were measured. The results are shown in Table 1.

Comparative Example 5 Carbon conversion value per unit surface area 7.9 × 10 ⁻⁵ g /
A suspension of water in which water was adjusted to 6.0 × 10 ⁻⁵ g / m ² in terms of carbon per unit surface area by mixing dry-processed silica that had not been subjected to a hydrophobizing treatment to m ² hydrophobic dry-process silica was mixed. The turbidity, silicone oil viscosity-transparency (dispersion index n) and silicone torque-transparency (light transmittance τ) were measured. The results are shown in Table 1.

[0034]

[Table 1]

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-58-181715 (JP, A) JP-A-7-10524 (JP, A) Misato Kaga, et al., Application technology of high-purity silica, Japan, Inc. CMC, March 1, 1991, 258-275 Kobayashi Hideki, et al., Characteristic of Silazane-treated Silica and Fluidity of Filling System with Polydimethylsiloxane, Collection of Polymers, The Society of Polymer Science, Japan, 1987 September 25, Vol. 44, No. 9, p. 675-679 (58) Field surveyed (Int. Cl. ⁷ , DB name) C01B 33/18

Claims (3)

(57) [Claims] (1) monomethylsilane on the surface of a dry silica;
The concentration per unit surface area is 3 × 10 ^{−5 in} terms of carbon.
A hydrophobic silica for a thickener, wherein the hydrophobic silica is present so as to be in a range of up to 6 × 10 ⁻⁵ g / m ² . 2. The amount of suspension in water when mixed with water is 0.7.
The hydrophobic silica for a thickener according to claim 1, wherein the amount is from 70 to 70% by weight. 3. A thickener comprising the hydrophobic silica according to claim 1.