JP2003335979A - Method for producing titanium dioxide pigment and resin composition in which the pigment is formulated - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a titanium dioxide pigment, excel lent in balance of hydrophobicity, dispersibility and heat resistance and particu larly suitable for thin film processing of a plastic and to provide a resin composi tion in which titanium dioxide pigment obtained by the method is formulated. <P>SOLUTION: The method for producing the titanium dioxide pigment comprises dry-coating the surfaces of titanium dioxide pigment particles with hydrolyzate of a specific organosilane compound. As a result, the titanium dioxide pigment is useful in a field of thin film processing, particularly for films to which lacing resistance is required, as a coloring agent for plastics and the resin composition is nearly free from such processing defect as to protrude lacing, pinhole, etc., defective particles of dispersibility of titanium dioxide pigment on the surface and has excellent surface smoothness and gloss. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a titanium dioxide pigment having excellent processing characteristics and dispersibility in a plastic system, and a resin composition containing the titanium dioxide pigment obtained by the production method.

[0002]

2. Description of the Related Art Since a titanium dioxide pigment has hydrophilicity, it has a low affinity for organic resins and a low dispersibility and filling property in plastics. In particular, when processing a thin film, racing (foaming) and pinholes are likely to occur due to water content due to the titanium dioxide pigment. Therefore, a method is known in which the surface of the titanium dioxide pigment is coated with an organosilicon compound to impart affinity to a plastic resin and hydrophobicity.

Among the organosilicon compounds, the hydrolysis products of the hydrolyzable alkylsilane compounds react chemically with the hydroxyl groups on the surface of the titanium dioxide pigment to form a chemical bond with the hydrophobicity of the titanium dioxide pigment and the plastic resin. Can be highly improved, while the alkyl group of the hydrolysis product is inactive with respect to organic compounds and has excellent selectivity for plastic resin species, so it is widely used in such fields. ing. However, the hydrolysis product of a hydrolyzable alkylsilane compound, which is generally excellent in hydrophobicity, has low heat resistance, and the titanium dioxide pigment coated with this product is dried after coating and heated in the pulverization process to form a pigment powder. There is a problem in that it becomes yellowish, and by extension, a plastic molded product also becomes yellowish.

[0004]

DISCLOSURE OF THE INVENTION The present invention overcomes the above-mentioned problems of the prior art and is excellent in hydrophobicity (that is, affinity with resin), dispersibility, and heat resistance, and in particular, it is a plastic. The present invention has been made to provide a method for producing a titanium dioxide pigment suitable for the processing of a thin film, and a resin composition containing the titanium dioxide pigment obtained by the method.

[0005]

[Means for Solving the Problems] As a result of intensive studies to solve these problems, the present inventors have found that the hydrolysis product of a specific organic silane compound is treated with a titanium dioxide pigment particle by a dry treatment. It was found that when the surface is coated, excellent hydrophobicity and dispersibility are obtained, and heat resistance is also excellent, and the present invention has been completed.

That is, the present invention uses the formula (1)

[Chemical 2] [R is an alkyl group having 5 or less carbon atoms, R'is a hydrolyzable group, n is 1 to 3, m is 0 to 2, and is an integer satisfying n + m≤3. ] The method for producing a titanium dioxide pigment, characterized in that the surface of the titanium dioxide pigment particles is dry-coated with a hydrolysis product of an alkylsilane compound represented by the formula [1].

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method for producing a titanium dioxide pigment, which comprises subjecting titanium dioxide pigment particle surfaces to dry coating treatment with a hydrolysis product of an alkylsilane compound represented by the formula (1). Characterize. When the alkylsilane compound has 7 or more carbon atoms in the alkyl group, the heat resistance is significantly reduced. For this reason, the hydrophobicity and the dispersibility were insufficient even when the wet treatment was performed using the one having 6 carbon atoms.
In the present invention, by the dry treatment, the chemical reaction between the hydrolysis product of the alkylsilane compound and the hydroxyl group of the titanium dioxide pigment on the surface, the bond easily occurs, and the surface of the hydrophilic titanium dioxide pigment has an alkylsilane compound. It is presumed that it is sufficiently covered with the hydrolysis product of. Therefore, as in the alkylsilane compound represented by the formula (1), at least one alkyl group has 6 carbon atoms.
As long as the number of carbon atoms of other alkyl groups is 5 or less, a titanium dioxide pigment having high hydrophobicity and high affinity with a plastic resin can be obtained. An alkylsilane compound in which all the alkyl groups have 5 or less carbon atoms (n in the formula (1)
= 0, m = 3), the hydrophobicity and the affinity with organic substances are low, and the desired characteristics cannot be obtained even if the dry treatment is applied.

The hydrolyzable group (R 'in the formula) is not particularly limited, such as a halogen group or a hydroxyl group, but it is an alkoxy group which is less likely to produce harmful secondary products and has excellent stability. It is preferable that the alkoxy group is a methoxy group or an ethoxy group because it has excellent hydrolyzability and is more preferable. Furthermore, it is desirable that n + m in the formula has a large number of reaction sites with hydroxyl groups on the surface of the titanium dioxide pigment, which is 1 or 2. Specific examples thereof include hexyltrimethoxysilane, hexyltriethoxysilane, hexylmethyldimethoxysilane, and hexylmethyldiethoxysilane, and these can be used alone or in combination of two or more.

The hydrolysis product in the present invention is a product in which a hydrolyzable group of an alkylsilane compound is hydrolyzed to form silanol, or silanols are polycondensed to form an oligomer or polymer having a siloxane bond. It may include a part of unreacted alkylsilane compound as long as the object of the present invention is not impaired. The dry coating treatment refers to a method in which a titanium dioxide pigment and an alkylsilane compound or a hydrolysis product thereof are brought into contact with each other in the gas phase to coat the surfaces of the titanium dioxide pigment particles with the hydrolysis product of the alkylsilane compound. As long as the coating treatment is carried out by contacting both in the gas phase, it corresponds to the dry coating treatment. That is, the titanium dioxide pigment, the alkylsilane compound and the hydrolysis product of the alkylsilane compound need not be in a dry state.

The hydrolysis product of the alkylsilane compound represented by the formula (1) is coated by a so-called wet treatment in which a titanium dioxide pigment is brought into contact with the alkylsilane compound in a liquid medium such as water or an organic solvent. If the pH of the slurry
In the alkaline region, the hydrolysis rate of the alkylsilane compound decreases, polycondensation of silanols preferentially progresses even after hydrolysis, and the reactivity of silanol with the hydroxyl group on the titanium dioxide pigment surface decreases. By doing
The coating of hydrolysis products becomes difficult. When the pH of the slurry is in the neutral to acidic range, the titanium dioxide pigment aggregates and precipitates, or the viscosity of the slurry increases,
On an industrial scale, it is difficult to sufficiently mix and stir and uniform coating is difficult.

The dry coating treatment may be carried out by mixing the titanium oxide pigment and the hydrolysis product of the alkylsilane compound using a high-speed stirrer or the like, but fluid energy grinding using a titanium dioxide pigment as a grinding medium. When adding the hydrolysis product of the alkylsilane compound adjusted in advance to the crusher when crushing using a machine, or when crushing using a fluid energy crusher with water vapor as the crushing medium When it is added to a pulverizer or the like, the pulverization of the pigment and the coating treatment can be performed at the same time, which is preferable. As the fluid energy pulverizer, it is preferable to use a swirl type one such as a jet mill because the pulverization efficiency is good and the mixing property is excellent. In the method (1), the gas serving as the grinding medium may be air, water vapor, or the like and is not particularly limited. Further, in the method (1), the alkylsilane compound is reacted with water vapor to form a hydrolysis product, which is coated on the titanium dioxide pigment. The amount of water vapor and the vapor pressure for effectively hydrolyzing the alkylsilane compound can be experimentally determined.

When the temperature of the dry coating treatment is 120 to 300 ° C., the reaction between the hydrolysis product of the alkylsilane compound and the hydroxyl group on the surface of the titanium dioxide pigment is further promoted, and the coating is more uniform, which is desirable. The temperature of the dry coating treatment can be performed within the above range by heating the inside of the pulverizer to a temperature within the above range or by heating the gas serving as the pulverizing medium to a temperature within the above range in advance.

In the above method, in order to prepare the hydrolysis product in advance, the alkylsilane compound and water may be mixed, and the concentration of the mixture is preferably in the range of 5 to 95% by weight, and 60 to The range of 95% by weight is more preferable. It is preferable to adjust the pH of the water or the mixed solution to a neutral to acidic range because hydrolysis easily proceeds. In the acidic region, it becomes difficult to form a polycondensate of a hydrophobic hydrolysis product, and it is easy to handle as an aqueous mixed solution, and its pH is 0.5.
It is preferable to adjust it in the range of 6 to 6, and the more preferable range is 1.5 to 4. Even in the neutral range, if a compatibilizer such as a lower alcohol is added, it becomes easy to handle as an aqueous mixed solution. The hydrolyzable organism may be used as it is, but when the water content is large, it is preferable to use it after reducing the water content.

The dry coating treatment amount of the hydrolysis product of the alkylsilane compound is preferably 0.01 to 3.0% by weight, more preferably 0.02 to 0.02% by weight based on the titanium dioxide pigment in terms of the alkylsilane compound. It is 1.0% by weight.
If it is less than this, it is difficult to obtain the desired effect, and if it is more than this, the effect corresponding to the addition amount of the alkylsilane compound is not recognized, which is economically disadvantageous.

In the present invention, titanium dioxide pigment particles are preliminarily formed on the surface thereof as an inorganic compound in accordance with desired characteristics such as imparting weather resistance and light resistance, improving productivity, etc. within a range not impairing the object of the present invention. It is preferable to use one having a coating layer of. Examples of such inorganic compounds include hydrated oxides of aluminum, silicon, tin, zirconium and the like, or phosphates thereof such as aluminum phosphate, which are known in the art. You may coat. The inorganic compound does not need to cover the entire surface of the titanium dioxide pigment, and may include a part that is not covered as long as desired characteristics are obtained. When the total coating amount of the inorganic compound is large, a porous coating layer is formed to easily absorb moisture. Above all, since the hydrated oxide contains bound water, the amount of water contained in the titanium dioxide pigment also increases. For this reason, when blended with a plastic resin and molded, particularly when molded into a thin film, processing defects due to these water contents are likely to occur. Therefore, it is preferable that the total coating amount is as small as possible. Although the specific upper limit of the total coating amount varies depending on the type of the inorganic compound, for example, in the case of the hydrated oxide of aluminum, Al ₂ O is used.
₃ , it is preferable that SiO ₂ is a hydrated oxide of silicon and Al ₂ PO ₄ is a phosphoric acid salt of aluminum, which is 1.0% by weight at the maximum with respect to the titanium dioxide pigment. Further, since the desired characteristics are easily obtained when the total coating amount of these inorganic compounds is at least 0.01% by weight, the range of 0.01 to 1.0% by weight is more preferable.

Since a titanium dioxide pigment having no inorganic compound coating layer generally has low light resistance, the plastic resin in which it is mixed discolors or discolors under ultraviolet light, or its decomposition is easily promoted. In the present invention, it is particularly preferable to use a titanium dioxide pigment having a coating layer containing a hydrated oxide of aluminum in advance. Coating with a hydrated oxide of aluminum facilitates operations such as dehydration, drying, and pulverization in the production process of the titanium dioxide pigment, and therefore this coating is industrially desirable.

The coating amount of hydrated oxide of aluminum is preferably in the range of 0.01 to 1.0% by weight in terms of Al ₂ O ₃ with respect to titanium dioxide, and 0.05 to 0.5% by weight. It is more preferable if it is within the range. If it is less than 0.01% by weight, it is difficult to obtain the desired light resistance, and if it is more than 1.0% by weight, the titanium dioxide pigment is mixed with the plastic resin due to the bound water contained in the hydrated oxide. When thin film processing is performed by using a thin film, processing defects due to moisture are likely to occur during plastic molding.

The hydrated oxide of aluminum may be coated by a known method. For example, (1) an aqueous solution of an aluminum compound is added to an aqueous slurry in which a titanium dioxide pigment is dispersed to prepare an acidic compound or a basic compound. The pH is adjusted to 4 to 9 using an aqueous solution of the compound. (2) An aqueous solution of the titanium dioxide pigment is added to the aqueous solution of the acidic compound or the basic compound to maintain the pH in the above range while maintaining the pH of the aluminum compound. Adding an aqueous solution into the slurry,
Any method may be used. After coating,
If necessary, filtration, washing and drying are performed.

The solid content concentration of the titanium dioxide pigment in the aqueous slurry is in the range of 50 to 800 g / liter, preferably in the range of 100 to 500 g / liter. 8
If the concentration is higher than 00 g / liter, the viscosity of the aqueous slurry becomes too high, which makes it difficult to uniformly coat the hydrated oxide of aluminum on the surface of the titanium dioxide pigment particles. When it is lower than 50 g / liter, industrial operability is deteriorated.

Examples of the aluminum compound used include sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum chloride and the like. Further, for adjusting the pH, an inorganic acid such as sulfuric acid or hydrochloric acid or an organic acid such as acetic acid or formic acid, or an inorganic basic compound such as sodium hydroxide, potassium hydroxide or ammonia can be used.

The titanium dioxide pigment obtained by the present invention is
It has an average particle diameter (electron micrograph) of 0.1 to 0.4 μm, and more preferably 0.1 to 0.25 μm. The crystal form may be either anatase type or rutile type, or a mixture of both. The method for producing the titanium dioxide pigment particles to be used is not particularly limited, and may be obtained, for example, by a so-called sulfuric acid method of hydrolyzing a titanium sulfate solution, or by a so-called chlorine method of vapor-phase oxidation of titanium halide.

The titanium dioxide pigment obtained according to the present invention comprises 2
It has a dispersibility of 0 kg / cm ² or less. The dispersibility in the present invention is measured by the following method.

(Method of evaluating dispersibility) Titanium dioxide pigment 50
0 g, 500 g of freeze-pulverized polyethylene resin [Sumikasen L-705 manufactured by Sumitomo Chemical Co., Ltd.] and 20 g of zinc stearate are mixed with a juice mixer for 5 minutes. The resin temperature of this product was set to 280 ° C. using a Labo Plastomill twin screw extruder manufactured by Toyo Seiki, and 145 was set on the discharge side.
Set 0 mesh screen and melt extrude over 1 hour. The resin pressures at the start of extrusion and after extrusion for 1 hour are measured, and the difference is taken as the value of dispersibility.

Next, the present invention is a resin composition, which is characterized by containing the above-mentioned titanium dioxide pigment and a plastic resin. This resin composition has excellent surface smoothness and luster, with almost no processing defects such as racing, pinholes, and particles with poor dispersibility of titanium dioxide pigment protruding to the surface.

The plastic resin used is a thermoplastic resin such as a polyolefin resin, a vinyl chloride resin, a polystyrene resin, an ABS resin or an engineering plastic,
Examples thereof include thermosetting resins such as phenol resins, urethane resins, unsaturated polyester resins and the like, and various resins can be used without particular limitation.

The mixing ratio of the titanium dioxide pigment and the plastic resin is not particularly limited, but the plastic resin 10
The titanium dioxide pigment is 0.01 to 900 relative to 0 part by weight.
The range is parts by weight, more preferably 0.1 to 200 parts by weight. Further, depending on the application, to the resin composition, it is possible to add various additives such as stabilizers, dispersants, lubricants, antioxidants, ultraviolet absorbers, reinforcing agents, fillers and the like known to those skilled in the art, fillers and the like. it can.

The resin composition of the present invention can be obtained by blending a plastic resin obtained by melting a titanium dioxide pigment with a kneader. The kneader may be a commonly used one, and examples thereof include a single screw extruder, a twin screw extruder, an intensible mixer such as a Banbury mixer, and a roll forming machine.

[0028]

The present invention will be described in more detail with reference to the following examples. The following examples are provided for illustration only and the scope of the invention is not limited thereby.

Example 1 (Coating with hydrated oxide of aluminum) The average particle size was 0.
20μm rutile titanium dioxide pigment is mixed with water,
An aqueous slurry having a weight of titanium dioxide of 300 g / liter was prepared. While maintaining the slurry at 60 ° C., 0.30% of sodium aluminate as Al ₂ O ₃ was added to the weight of the titanium dioxide pigment while stirring,
Then, the pH was neutralized to 5.0 with sulfuric acid to coat a hydrated oxide of aluminum, followed by filtration, washing and drying at 120 ° C. for 10 hours.

(Coating of Hydrolysis Product of Alkylsilane Compound) The above titanium dioxide pigment was heated to 250 ° C. with steam (2.2 times the weight of the titanium dioxide pigment on a weight basis, steam pressure 1.4 MPa). Grinding with a fluid energy grinder used as a grinding medium, in which case 1.0% by weight of hexyltriethoxysilane with respect to the titanium dioxide pigment was added into the grinder to generate hydrolysis of hexyltriethoxysilane. The product was dry-coated on the surface of titanium dioxide pigment particles. The obtained titanium dioxide pigment is designated as sample A.

Example 2 In the same manner as in Example 1 except that 1.0% by weight of hexyltriethoxysilane as a hydrolysis product of hexyltriethoxysilane was added to the pulverizer with respect to the titanium dioxide pigment. The hydrolyzate of hexyltriethoxysilane was dry-coated on the surface of titanium dioxide pigment particles. The obtained titanium dioxide pigment is designated as sample B. still,
The hydrolysis product of hexyltriethoxysilane was adjusted to pH with sulfuric acid based on 9 parts by weight of hexyltriethoxysilane.
It was prepared by adding 1 part by weight of water designated as 2 and stirring for 1 hour, and used as it was.

Example 3 A hexyltrimethoxysilane hydrolysis product was dry-coated on the surface of titanium dioxide pigment particles in the same manner as in Example 1 except that hexyltrimethoxysilane was used instead of hexyltriethoxysilane. did. The obtained titanium dioxide pigment is designated as sample C.

Example 4 A hydrolysis product of hexyltrimethoxysilane was prepared in the same manner as in Example 2 except that the hydrolysis product of hexyltrimethoxysilane was used in place of the hydrolysis product of hexyltriethoxysilane. The surface of the titanium dioxide pigment particles was dry-coated. The obtained titanium dioxide pigment is designated as Sample D.

Example 5 The surface of titanium dioxide pigment particles was dry-coated with the hydrolysis product of hexylmethyldiethoxysilane in the same manner as in Example 1 except that hexylmethyldiethoxysilane was used instead of hexyltriethoxysilane. Processed. The obtained titanium dioxide pigment is designated as sample E.

Example 6 Hydrolysis production of hexylmethyldiethoxysilane was carried out in the same manner as in Example 2 except that the hydrolysis product of hexylmethyldiethoxysilane was used in place of the hydrolysis product of hexyltriethoxysilane. The product was dry-coated on the surface of titanium dioxide pigment particles. The obtained titanium dioxide pigment is designated as sample F.

Comparative Example 1 A titanium dioxide pigment (Sample G) was obtained in the same manner as in Example 1 except that hexyltriethoxysilane was not used.

Comparative Example 2 A titanium dioxide pigment (Sample H) was obtained in the same manner as in Example 1 except that octyltriethoxysilane was used instead of hexyltriethoxysilane.

Comparative Example 3 A titanium dioxide pigment (Sample I) was obtained in the same manner as in Example 1 except that butyltriethoxysilane was used instead of hexyltriethoxysilane.

Comparative Example 4 After coating with a hydrated oxide of aluminum in Example 1,
After adjusting the pH of the aqueous slurry to 9 with sodium hydroxide, 1.0% by weight of hexyltriethoxysilane based on the titanium dioxide pigment was added to the aqueous slurry and stirred for 2 hours. Then, the pH was adjusted to 5 with sulfuric acid, filtered, washed, dried at 120 ° C. for 10 hours, and then pulverized with a fluid energy pulverizer to obtain a titanium dioxide pigment (Sample J).

Comparative Example 5 A titanium dioxide pigment (Sample K) was obtained in the same manner as in Comparative Example 4 except that hexyltriethoxysilane was replaced by the hydrolysis product of hexyltriethoxylane used in Example 2.

Comparative Example 6 A titanium dioxide pigment (Sample L) was obtained in the same manner as in Example 1 except that decyltriethoxysilane was used instead of hexyltriethoxysilane.

Evaluation 1 (Karl Fischer water content) Samples A to K obtained in Examples 1 to 6 and Comparative Examples 1 to 5
24 at a temperature of 25 ° C and a constant humidity of 55% relative humidity.
After allowing to stand for an hour to reach an equilibrium state, 1 g of the sample is used at 100 ° C. and 30 ° C. using a Karl Fischer moisture measuring device and a moisture vaporizer attached to it (both are manufactured by Mitsubishi Chemical).
Karl Fischer moisture at 0 ° C was measured.

Evaluation 2 (Dispersibility) Samples A to L obtained in Examples 1 to 6 and Comparative Examples 1 to 5
According to the method described above as the method for evaluating dispersibility, the increase in resin pressure was measured to evaluate the dispersibility.

Evaluation 3 (Racing resistance) At the time of the above-mentioned dispersibility test, a strand die was attached to the discharge side of the Labo Plastomill, and the melt coming out from the strand was visually observed to judge the superiority or inferiority from the foamed state. did. The judgment criteria are as follows. Judgment A: No foaming is observed at all. Judgment O: Foaming is slightly observed. Judgment Δ: Foaming is partially observed. Judgment x: Foaming is recognized on the whole.

Evaluation 4 (heat resistance) Samples A to K4 obtained in Examples 1 to 6 and Comparative Examples 1 to 5
g was filled in an aluminum ring having an outer diameter of 38 mmφ, an inner diameter of 33φmm, and a thickness of 5 mm, and 147MP with a press machine.
After compression molding at a pressure of 5 seconds for 5 seconds,
Heated at 0 ° C for 10 minutes. The Hunter color system (L, a, b) before and after heating the molded product is changed to a color computer (SM-5).
Type: manufactured by Suga Test Instruments Co., Ltd., and measured by ΔE [= {(ΔL)
2+ (Δa) 2+ (Δb) 2} 1/2] was calculated. ΔE
The larger the value, the greater the discoloration and the poorer the heat resistance.

Table 1 shows the evaluation results of water content, racing resistance, dispersibility and heat resistance. It can be seen that the titanium dioxide pigment obtained by the production method of the present invention has excellent hydrophobicity, dispersibility and processing characteristics. Further, it can be seen that the resin composition of the present invention has an excellent appearance with almost no racing.

[0047]

[Table 1]

Evaluation 5 (powder color) Samples A, G and L obtained in Example 1 and Comparative Examples 1 and 6
Was compression molded in the same manner as in Evaluation 4, and the powder color of the molded product in the Hunter color system (L, a, b) was measured using a color computer (SM-5 type: manufactured by Suga Test Instruments). did. The lower the L value, the lower the whiteness, and the larger the b value, the more yellowish the color tone.

The evaluation results of the powder color are shown in Table 2. The titanium dioxide pigment (Sample A) obtained by the production method of the present invention has almost the same whiteness and color tone as those when the compound treated with alkylsilane is not treated (Sample G). It is considered that this is because the heat resistance is excellent, and thus the discoloration is unlikely to occur even when heated during drying or crushing.

[0050]

[Table 2]

[0051]

The manufacturing method of the present invention has the following properties: hydrophobicity, dispersibility,
The present invention provides a titanium dioxide pigment having excellent heat resistance, and the titanium dioxide pigment is useful as a coloring agent for plastics, particularly in the field of thin film processing such as films for which racing resistance is required. Furthermore, the resin composition of the present invention,
It has excellent surface smoothness and gloss, with almost no processing defects such as racing, pinholes, and particles with poor dispersibility of titanium dioxide pigment protruding to the surface.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09C 3/12 C09C 3/12 F term (reference) 4G047 CA05 CB08 CB09 CC01 CD03 4J002 BB011 BC021 BD031 BN151 CC041 CF211 CK021 DE136 FB096 4J037 AA22 CA12 CB23 EE03 EE04 EE29 EE44 EE47 FF15

Claims (12)

[Claims] 1. A formula (1): [R is an alkyl group having 5 or less carbon atoms, R'is a hydrolyzable group, n is 1 to 3, m is 0 to 2, and is an integer satisfying n + m≤3. ] The manufacturing method of the titanium dioxide pigment including the process of carrying out the dry-coating process of the hydrolysis product of the alkylsilane compound represented by this. 2. The method for producing a titanium dioxide pigment according to claim 1, wherein R'is a methoxy group or an ethoxy group. 3. The method for producing a titanium dioxide pigment according to claim 1, wherein the titanium dioxide pigment particles are obtained by pulverizing the titanium dioxide pigment with a fluid energy pulverizer. 4. A pulverizing medium of a fluid energy pulverizer is a gas, and when pulverizing a titanium dioxide pigment, a hydrolysis product of an alkylsilane compound represented by the formula (1) is added to the pulverizer. The method for producing the titanium dioxide pigment according to claim 1. 5. The pulverizing medium of the fluid energy pulverizer is water vapor, and when the titanium dioxide pigment is pulverized, the alkylsilane compound represented by the formula (1) is added to the pulverizer. Method for producing titanium dioxide pigment. 6. The method for producing a titanium dioxide pigment according to claim 4, wherein the temperature of the dry coating treatment is 120 to 300 ° C. 7. The titanium dioxide according to claim 1, wherein the amount of the dry coating treatment of the hydrolysis product of the alkylsilane compound is in the range of 0.01 to 3.0% by weight based on the titanium dioxide pigment in terms of the alkylsilane compound. Method for producing pigment. 8. The method for producing a titanium dioxide pigment according to claim 1, wherein the titanium dioxide pigment particles are previously coated with an inorganic compound. 9. The method for producing a titanium dioxide pigment according to claim 8, wherein the inorganic compound is a hydrated oxide of aluminum. 10. The coating amount of hydrated aluminum oxide is A.
0.01 to 1. 1 with respect to the titanium dioxide pigment in terms of l ₂ O ₃ .
The method for producing a titanium dioxide pigment according to claim 9, wherein the amount is in the range of 0% by weight. 11. The method for producing a titanium dioxide pigment according to claim 1, wherein the dispersibility is 20 kg / cm ² or less. 12. A resin composition comprising the titanium dioxide pigment obtained by the production method according to claim 1 and a plastic resin.