JP2922389B2 - Preparation method of hydrophobic inorganic compound fine particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing hydrophobic inorganic compound fine particles useful as a reinforcing agent for synthetic resins and the like.

[0002]

2. Description of the Related Art Inorganic compound fine particles have various uses such as a reinforcing agent, a coloring agent, an anti-blocking agent, and a fluidity improver. Many synthetic resin molded articles, synthetic resin films,
Widely used in paints, cosmetics, electrophotographic toner, fire extinguisher powder, etc.

[0003] At the time of this compounding, improving the dispersibility in the substrate enables an increase in the amount of the compounding, and in turn, improves the reinforcing effect on the substrate. Further, in the case of a molding resin or the like, since scale-out can be prevented at the time of molding, smooth molding becomes possible, and effects such as improvement in workability can be expected. Also, imparting hydrophobicity to these inorganic compound fine particles has the advantage of improving the water resistance and fluidity of synthetic resins, oil paints, cosmetics, electrophotographic toners, fire extinguisher powders and the like in which they are blended.

Various silicone treatment methods have been proposed as a method for making the surface of the inorganic compound fine particles hydrophobic.
For example, a method in which fine particles of an inorganic compound coated on the surface with an oxide are dispersed in polydimethylsiloxane functional at one end and then heat-treated (JP-A-4-36370). There are known a method of coating (JP-A-3-281536) and a method of emulsion-condensation polymerization of polycondensable organopolysiloxane on colloidal silica. However, it is difficult to uniformly coat the surface of the inorganic compound by any of the methods, and thus the obtained hydrophobicity is not uniform. In addition, a method has been proposed in which an organopolysiloxane is directly coated on an inorganic compound powder and cured (Japanese Unexamined Patent Publication (Kokai) No. 2-243667). Further, JP-A-3-12460 proposes a method in which an organosilane and an inorganic compound powder are mixed and then hydrolyzed with ammonia water or the like, but it is difficult to set conditions for uniform coating.

When the inorganic compound powder is titanium oxide,
Some surface hydrophobizing methods other than the above, for example, titanium oxide fine particles, various alkyl polysiloxane, direct coating, emulsion coating, or solvent solution coating,
After drying, baking (JP-B-49-1769, JP-A-56-16404), a siloxane containing a hydrosilyl group is directly coated or coated with a solvent solution.
A method of baking (Japanese Patent Application Laid-Open No. 57-200306), a method of bringing a cyclic siloxane containing a hydrosilyl group into contact with titanium oxide powder in the form of vapor and supporting a silicone polymer on the surface of the powder (Japanese Patent Application Laid-Open No. JP-A-163172), a method in which an alkoxysilane is directly coated or coated with a solvent solution on titanium oxide fine particles, and then treated with water or steam to carry out hydrolytic condensation to form a film of a condensation product (Japanese Patent Application Laid-Open No. No. 57-200306). However, in any of these methods, it is difficult to impart sufficient hydrophobicity to the titanium oxide fine particles because the amount of silicone adhered to the surface is small and the chemical adhesion of the silicone film adhered to the surface is weak.

To provide sufficient hydrophobicity, a method has been proposed in which a large amount of silicone oil is blended with titanium oxide powder and mixed (Japanese Patent Laid-Open No. 54-14528).
However, in this method, although the hydrophobicity is sufficient, the obtained surface-treated powder particles are partially aggregated due to a large amount of silicone oil.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and to provide a method for preparing an inorganic compound powder having uniform and excellent hydrophobicity and good dispersibility.

[0008]

That is, according to the present invention,
(A) The inorganic compound fine particles contain at least one surfactant selected from the group consisting of anionic surfactants, cationic surfactants and amphoteric surfactants in an amount of 0.01 to 10%, and are contained in an aqueous solution having a pH of 8 to 13. An aqueous slurry dispersed in the aqueous slurry is prepared. (B) The aqueous slurry has the general formula (1): R ¹ Si (OR ² ) ₃ (1) (where R ¹ is a saturated carbon atom having 1 to 20 carbon atoms) Alternatively, an unsaturated monovalent hydrocarbon group, and R ² is a monovalent hydrocarbon group having 1 to 6 carbon atoms) is mixed with 5 to 500 parts by weight of inorganic compound fine particles per 100 parts by weight. , A method for preparing fine particles of a hydrophobic inorganic compound, comprising the steps of:

Following the step (B), a step of neutralizing the obtained aqueous slurry, further separating a solid content, and drying is optional. In this case, the hydrophobic inorganic compound powder can get.

Step (A) In this step (A), an aqueous slurry is prepared by dispersing the inorganic compound fine particles in an aqueous solution of a surfactant whose pH has been adjusted to alkaline.

The inorganic compound fine particles used in the present invention include, for example, titanium oxide, silicon dioxide, zinc oxide,
Metal oxide compounds such as aluminum oxide and zirconium oxide, calcium carbonate, zinc carbonate, magnesium carbonate, lead carbonate, nickel carbonate, barium carbonate, metal carbonate compounds such as manganese carbonate, metal sulfate compounds such as calcium sulfate and barium sulfate, Examples include natural inorganic compounds such as kaolin clay, talc, sericite, pyroxene clay, mica, bentonite, calcium silicate, and aluminum silicate.

The particle size of these inorganic fine particles is not strictly limited, but when they are blended in synthetic resins, paints, cosmetics, electrophotographic toners, fire extinguisher powders, etc., they do not cause a decrease in the strength of these substrates. Is desirable, usually 100μ
m, preferably 20 μm or less. The shape of the inorganic fine particles is not particularly limited, and examples thereof include various shapes such as a spherical shape, an irregular shape, a needle shape, and a scale shape.

When the content of the inorganic compound fine particles in the alkaline aqueous solution is too small, the yield is low and it is economically disadvantageous. When the content is too large, the viscosity of the obtained aqueous slurry becomes too high, and The uniformity of the silicone resin layer coated on the surface is poor. Usually 1
~ 50% by weight is required, preferably 5-20% by weight.

The aqueous slurry in which the inorganic compound fine particles are dispersed may be newly prepared, or may be obtained in the form of a slurry and prepared as the aqueous slurry in the step (A).

In addition, when the obtained aqueous slurry of the fine particles of the inorganic compound is not at the prescribed pH or surfactant concentration,
An aqueous slurry that satisfies the requirement of the step (A) may be prepared by adding an alkaline compound, a surfactant, and / or dilution water as needed.

When the raw material inorganic compound fine particles are powder, they may be dispersed in an aqueous surfactant solution whose pH has been adjusted in advance to prepare an aqueous slurry satisfying the conditions of the step (A).

PH of aqueous solution in which inorganic compound fine particles are dispersed
Is set to 8 to 13, preferably 10 to 12.5. When the pH is lower than 8, the hydrolysis condensation of trialkoxysilane described below does not sufficiently proceed, and when the pH is higher than 13, the hydrolysis rate of the trialkoxysilane becomes too large, and the silicone resin coating of the inorganic compound fine particles may not be obtained. It becomes uneven.

The alkaline substance used for adjusting the pH of the alkaline aqueous solution may be any as long as it has a catalytic action for the hydrolysis-condensation reaction of trialkoxysilane.
Usually, for example, potassium hydroxide, sodium hydroxide, alkali metal hydroxides such as lithium hydroxide, calcium hydroxide, alkaline earth metal hydroxides such as barium hydroxide,
Potassium carbonate, alkali metal carbonate such as sodium carbonate, ammonia, monomethylamine, dimethylamine,
Amines such as monoethylamine, diethylamine and ethylenediamine, and quaternary ammonium hydroxides such as tetramethylammonium hydroxide are used.
Among them, ammonia is most preferable because it has excellent solubility in water and catalytic activity and can be easily removed from powder by volatilization. For example, a commercially available aqueous ammonia solution (concentration 28% by weight) may be used.

The surfactant used in the present invention is at least one so-called ionic surfactant selected from an anionic surfactant, a cationic surfactant and an amphoteric surfactant.

Examples of the anionic surfactant include, for example,
Sodium lauryl sulfate, ammonium lauryl sulfate,
Examples include sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium dialkylsulfosuccinate, potassium alkylphosphate, sodium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, sodium polyoxyethylene tridecyl ether sulfate, and the like. Examples of the cationic surfactant include cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, lauryltrimethylammonium chloride, stearylamine hydrochloride, coconutamine hydrochloride, coconutamine acetate , Stearylamine acetate, alkylbenzene dimethyl ammonium chloride and the like. As the amphoteric surfactant, for example,
N-acylamidopropyl-N, N-dimethylammoniobetaines, N-acylamidopropyl-N, N'-
Dimethyl-N'-β-hydroxypropylammoniobetaines, coconut betaines and the like.

When the concentration of the surfactant in the aqueous solution as a dispersion medium is less than 0.01% by weight, the silicone resin coating on the fine particles of the inorganic compound cannot be formed uniformly. The surfactant easily remains on the surface of the fine particles, and the hydrophobic property of the inorganic compound fine particles is inferior. Therefore, it is required to be in the range of 0.01% by weight to 10% by weight, more preferably 0.1% by weight.
２2% by weight.

(B) Step In the next step (B), a trialkoxysilane represented by the general formula (1) is mixed with the aqueous slurry prepared in the step (A), followed by hydrolysis and condensation. . As described above, as the trialkoxysilane, one represented by the general formula (1): R ¹ Si (OR ² ) ₃ (1) is used.

In the general formula (1), examples of the saturated or unsaturated monovalent hydrocarbon group having 1 to 20 carbon atoms represented by R ¹ include a methyl group, an ethyl group, a propyl group, a butyl group, C1-C20 alkyl groups such as pentyl group, hexyl group, heptyl group, octyl group, decyl group, dodecyl group, octadecyl group and eicosyl group; aryl groups such as phenyl group; alkenyl groups such as vinyl group and allyl group. And substituted hydrocarbon groups in which some or all of the hydrogen atoms of these groups are substituted with amino groups, epoxy groups, vinyl groups, halogen atoms, and the like. Examples of the monovalent hydrocarbon group having 1 to 6 carbon atoms represented by R ² include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group,
Examples thereof include an alkyl group having 1 to 6 carbon atoms such as a hexyl group.

Examples of the trialkoxysilane represented by the general formula (1) include, for example, methyltrimethoxysilane,
Methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, γ-amino Propyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,4,4,5,5, 6,6,6-nonafluorohexyltrimethoxysilane, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluoro There are decyltrimethoxysilane and the like, which can be used alone or in combination of two or more. Among them, the trialkoxysilane preferably contains trimethoxysilane in an amount of 50 mol% or more.

The trialkoxysilane is preferably mixed with the aqueous slurry so as to be in a range of 5 to 500 parts by weight based on 100 parts by weight of the inorganic compound fine particles. The proportion is more preferably 8 to 200 parts by weight. If the amount of trialkoxysilane is too small, sufficient hydrophobicity cannot be imparted to the inorganic compound fine particles, and if it is too large, particles composed only of the hydrolyzed condensate of the trialkoxysilane are formed during the hydrolytic condensation. This is because the coating on the surface of the inorganic compound fine particles lacks uniformity.

The amount of trialkoxysilane is not more than 30 parts by weight, especially 0.1 to 100 parts by weight of the aqueous slurry.
Preferably, it is 10 parts by weight. If the amount of the trialkoxysilane with respect to the aqueous slurry is too large, particles composed of only the hydrolysis-condensation product of the trialkoxysilane are likely to be generated.

The mixing of the trialkoxysilane and the aqueous slurry may be generally carried out by charging a required amount of the trialkoxysilane to the aqueous slurry and stirring. By this mixing, the hydrolysis and condensation reactions of the trialkoxysilane proceed, and a silicone resin coat is formed on the surface of the inorganic compound fine particles. The stirring needs to be performed to such an extent that the inorganic compound fine particles do not settle. In this case, if the stirring is too strong, particularly when the amount of trialkoxysilane used is relatively large, the aggregation or fusion of the inorganic compound fine particles coated with the silicone resin tends to occur. Is preferably performed. As the stirring device to be used, a device provided with a propeller blade or a flat plate blade is preferable.

The mixing temperature is 0 to 60 ° C., especially 5
A range of -20 ° C is preferred. If the temperature is too low, the liquid may be coagulated. If the temperature is too high, the hydrolyzed condensate does not efficiently adhere to the surface of the inorganic compound fine particles, and the intended hydrophobic treatment is not effectively performed. In addition, the particles may aggregate or fuse together.

When a large amount of trialkoxysilane is added to the aqueous slurry, if it is added all at once, the particles may aggregate or fuse together. It is desirable to add it little by little. In this case, by appropriately selecting the type of the trialkoxysilane to be added last, it is possible to provide a functional group on the film formed by adhering to the surface of the inorganic compound fine particles. After the trialkoxysilane addition is completed, stirring is preferably continued for a while until the hydrolysis-condensation reaction is completed, but heating may be performed to complete the hydrolysis-condensation reaction. If necessary, an acidic substance may be added for neutralization.

By the treatment in the step (B) described above, the surface of the inorganic compound fine particles dispersed in the aqueous slurry becomes hydrophobic. The aqueous slurry in which the hydrophobic inorganic compound fine particles thus obtained are dispersed may be directly added to an aqueous medium such as an aqueous paint or a synthetic resin latex.

Further, after the aqueous slurry obtained in the step (B) is subjected to solid-liquid separation treatment, the separated solid is dried to obtain hydrophobic inorganic compound fine particles as a dry powder. Specifically, for example, filtration, centrifugal dehydration,
After solid-liquid separation such as liquid layer decantation separation after sedimentation, wash with water if necessary, spray dry,
A method such as fluidized drying under hot air or stirring and drying under reduced pressure may be used.

In the case where the obtained hydrophobic inorganic fine particles are partially agglomerated, they may be pulverized by using a pulverizer such as a jet mill, a ball mill, a hammer mill or the like as appropriate.

The obtained hydrophobic inorganic compound fine particles have a film of a trialkoxysilane hydrolyzed condensate having a strong chemical adhesion on the surface thereof and having a thickness sufficient to exhibit excellent hydrophobicity. Therefore, the obtained hydrophobicity is uniform and the dispersibility in an organic resin or the like is good.

Use Since the hydrophobic inorganic compound powder of the present invention is excellent in dispersibility in organic resin materials as described above, it is used as a reinforcing material, a coloring agent, an anti-blocking agent, a surface smoothness improving agent, and a water-resistant material. As an improver and a fluidity improver, it can be widely used in synthetic resin molded articles, paints, cosmetics, electrophotographic toners, fire extinguisher powders, and the like.

By blending the hydrophobic inorganic compound fine particles with an aqueous paint, a synthetic resin emulsion polymer or the like in the form of an aqueous slurry, it is possible to reinforce an oil paint or a synthetic resin molded product.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited only to these. In the following description,% means% by weight.

[0037]

EXAMPLE 1 A 25% aqueous slurry of titanium oxide (spherical, average particle size 0.05-0.15 .mu.m) was placed in a 2-liter glass flask equipped with an anchor-type stirring blade, a dropping funnel and a condenser provided in the center. 480g,
1296 g of deionized water, 42 g of 28% ammonia water and 20 g of 10% aqueous sodium lauryl sulfonate solution were added, the water temperature was adjusted to 8 ° C., and stirring was performed at a blade rotation speed of 200 rpm. The pH of the aqueous slurry thus obtained was 11.4.

Then, 162 g of methyltrimethoxysilane was added dropwise to the obtained aqueous slurry from a dropping funnel over 1 hour and 30 minutes. The liquid temperature during dropping was 10 ° C to 15 ° C. After completion of the dropwise addition, stirring was continued for 1 hour at room temperature, followed by heating with a hot water bath, and further stirring for 1 hour at 50 to 60 ° C.

In the aqueous slurry thus obtained, when the stirring was stopped, the titanium oxide fine particles settled out slowly. After allowing to cool to 30 ° C., the mixture was filtered through filter paper to obtain a wet cake of titanium oxide fine particles. The wet cake was allowed to stand in a hot-air circulating thermostat adjusted to 105 ° C. for 20 hours to obtain a dry powder.

The obtained titanium oxide powder was slightly pulverized in a mortar because slight aggregation was observed during drying. When the water repellency of the titanium oxide powder thus obtained was evaluated by the water repellency test method shown below, immediately after dispersion, and after standing for 24 hours, no precipitation of the titanium oxide powder in water was observed at all, It was found to have good water repellency.

[Test Method for Water Repellency] A 200 ml hard glass beaker is charged with 80 g of deionized water, and 2 g of a powder sample is further charged. Immediately after the powder sample is introduced and after standing at room temperature for 24 hours, the sedimentation of the powder material in water is visually observed.

Comparative Example 1 Surface treatment of titanium oxide fine particles was performed in exactly the same manner as in Example 1 except that a 10% aqueous solution of sodium lauryl sulfonate was not added to the preparation of the aqueous slurry. The water repellency of the obtained titanium oxide powder was evaluated in the same manner as in Example 1. Immediately after the dispersion, about 1/3 of the titanium oxide powder settled out.
After 24 hours, about 1/2 volume of sedimentation was observed.

Examples 2 to 3 and Comparative Example 2 As an aqueous slurry of titanium oxide, a major axis of 4 to 12 μm and a minor axis of
A hydrophobic titanium oxide slurry was obtained in the same manner as in Example 1, except that a 9.5% slurry of 0.05 to 0.15 μm titanium oxide needle-shaped fine particles was used, and the trialkoxysilane shown in Table 1 was used. .

When the water repellency of the obtained titanium oxide powder was evaluated in the same manner as in Example 1, the results shown in Table 1 were obtained.

Examples 4 to 9 and Comparative Examples 3 to 5 Calcium carbonate was treated in the same manner as in Example 1 in place of titanium oxide. The calcium carbonate used was an amorphous, powder having an average particle size of 1.2 μm and a specific surface area of 1.85 m ² / g (trade name “Whiteton SSB”, manufactured by Shiraishi Calcium Co., Ltd.). Details of the used ammonia water, surfactant aqueous solution and deionized water are as shown in Table 2. The hydrophobicity-treated calcium carbonate powder was evaluated for water repellency in the same manner as in Example 1, and the results shown in Table 2 were obtained.

[0046]

[Table 1]

[0047]

[Table 2]

Notes on Table 2: * 1 Product name: "Perex SSL" manufactured by Kao Corporation * 2 〃: "Perex TR" 〃 * 3 〃: "Amphitol 24B" 〃 * 4 〃: "Coatamine 24P" 〃 * 5 〃: "Emulgen 905" 〃

[0049]

According to the method of the present invention, the surface of the inorganic compound powder can be uniformly coated with silicone,
The obtained hydrophobic inorganic compound fine particles have uniform and excellent hydrophobicity. This method is a method in which the steps are simple, and the adjustment of the surface coating amount is easy.

Claims (1)

(57) [Claims] (A) The inorganic compound fine particles contain at least one surfactant selected from the group consisting of an anionic surfactant, a cationic surfactant and an amphoteric surfactant.
An aqueous slurry containing 0.01 to 10% and dispersed in an aqueous solution having a pH of 8 to 13 is prepared. (B) The aqueous slurry is mixed with the general formula (1): R ¹ Si (OR ² ) ₃ (1) Wherein R ¹ is a saturated or unsaturated monovalent hydrocarbon group having 1 to 20 carbon atoms, and R ² is a monovalent hydrocarbon group having 1 to 6 carbon atoms. A method for preparing hydrophobic inorganic compound fine particles comprising a step of mixing 5 to 500 parts by weight with respect to 100 parts by weight of fine particles.