JPS6335575B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a novel granular titanium dioxide.
More specifically, the present invention relates to a novel composite granular titanium dioxide made of titanium dioxide powder and ultrafine silica particles. BACKGROUND OF THE INVENTION Titanium dioxide powder is widely used today in various fields as a white pigment that is harmless and has excellent hiding power. The primary particles of known titanium dioxide powders have a particle size of 0.2 to 1 μm, but usually have a particle size of 1 to 50 μm.
It exists as a secondary particle of m. Such known titanium dioxide powder has strong adhesion between particles, tends to aggregate, and has low fluidity, so it does not flow smoothly during transportation and handling, and is prone to so-called "spills" and "splatters". Powder materials are among the most difficult to handle, requiring dust-proofing measures and frequent cleaning, as they scatter and contaminate the work environment. One way to solve this problem is to granulate the powder into a size that is easy to handle. However, coarse particles caused by sintering have poor dispersibility in resins and paints, and granulation using a binder requires the particle strength, fluidity,
None of them have been successful due to problems such as the negative impact of the organic binder used on the end use. On the one hand, the particle size obtained by precisely controlling crystal formation by gas-phase hydrolysis of chlorinated silicon compounds or when neutralizing a sodium silicate solution with acid to precipitate silicate crystals. It is well known that ultrafine silica particles with a diameter of 0.2 μm or less have unique rheological and surface chemical properties. While attempting to mix titanium dioxide powder and ultrafine silica for the purpose of improving the fluidity of titanium dioxide powder, the present inventors discovered that titanium dioxide becomes granulated, and studied the granulation conditions. It was discovered that the bulk density could be increased approximately twice, and the present invention was completed. Structure of the invention According to the invention, titanium dioxide powder of 95 to 99.99% by weight and particle size of 0.01 to 5% by weight
Composite granular titanium dioxide is provided which is made of ultrafine silica particles of 0.002 to 0.2 μm and has a particle size of 10 μm to 2 mm. In the granular titanium dioxide of the present invention, particles of titanium dioxide and particles of silica are finely and uniformly mixed to form particles of the above-mentioned size. The composite granular titanium dioxide of the present invention is granular like pharmaceutical granules, does not generate dust, is easy to handle, and has excellent dispersibility, coloring power, hiding power, color tone, and gloss when mixed with resin or paint. The pigment properties, such as , are the same as the raw material titanium dioxide used. The titanium dioxide used in the production of the composite granular titanium dioxide of the present invention may be produced by either the sulfuric acid method or the chlorine method, and may be of either the rutile type or the anatase type. Usually, powder in the form of secondary particles with a particle size of 1 to 50 μm is used. The ultrafine silica used in the production of the composite granular titanium dioxide of the present invention may be produced by the above-mentioned precisely controlled wet method or by the gas phase hydrolysis method.
It is sufficient if the particle size is 0.2 μm or less (specific surface area is 25 m ² /g or more), but it is preferable to use a gas phase hydrolysis method. The composite granular titanium dioxide of the present invention can be produced by mixing the above-mentioned ultrafine particle silica and titanium dioxide in the above-mentioned amounts and stirring. The composite granular titanium dioxide of the present invention can be used in all conventional uses of titanium dioxide. The known uses of titanium dioxide (pigments, additives to glasses, etc.) are not hindered by the small amount of silica present. DETAILED DESCRIPTION OF THE INVENTION The attached FIG. 1 is a 100x microscopic photograph of the composite granular titanium dioxide of the present invention (product of Production Example 1 described later). The granules in this figure contain approximately 0.5% ultrafine silica and have a particle size of approximately 0.5 mm. FIG. 2 is an electron micrograph of the cross section of the granules shown in FIG. 1, magnified 600 times. Figure 3 is a photograph of the titanium concentration distribution in the cross section shown in Figure 2 taken using an X-ray microanalyzer, and Figure 4 shows the silicon distribution in the cross section shown in Figure 3 taken using an X-ray microanalyzer. This is the photo I researched. Judging from these photographs, some of the titanium dioxide particles return to primary particles and are bonded by ultrafine silica particles interposed between them to form composite granules. Although the mechanism of formation of such granules is not clearly understood, it is presumed to be due to hydrogen bonding by silanol groups present on the surface of ultrafine silica particles. Since hydrogen bonds are relatively weak bonds, the bonding of titanium dioxide particles is probably limited to a diameter of about 2 mm. It is imagined that one granule of the composite granular titanium dioxide of the present invention is composed of 10 ³ to ^{10 12} titanium dioxide primary particles. Hydrogen bonds are weak bonds, so if they are subjected to strong shearing force when mixed with resin or paint, they will easily break and return to the original titanium dioxide particles. The ultrafine silica used to produce the composite granular titanium dioxide particles of the present invention may be produced by the above-mentioned precision controlled wet method or by the gas phase hydrolysis method, but may be produced by the chlorinated silicon compound (silicon tetrachloride). , trichlorosilane, methyltrichlorosilane, etc.) in an oxyhydrogen flame (Japanese Patent Publication No. 47-46274). Such gas-phase hydrolyzed ultrafine silica particles are known under trade names such as "Aerosil", "CABOSIL", and "HDK". In any case, the particle size of the primary particles is
The particle size is 0.2 μm or less (specific surface area: 25 m ² /g or more), preferably 0.05 μm or less (specific surface area: 130 m ² /g or more). In the composite granular titanium dioxide of the present invention, the composite particles have a particle size of 10 μm or more. If it is less than that, dust will be generated and operability will be lowered when kneading into the resin, making it impossible to achieve the initial purpose. To increase the particle size of composite granules to 10μm or more, use ultrafine silica.
It must be contained at least 0.01%. On the other hand, if the amount of ultrafine particle silica added exceeds 5%, the effect on the properties of titanium dioxide will be significant, so 5% is the limit. When the amount of ultrafine silica is up to 5%, composite granules will become unstable when the particle size exceeds 2 mm, the strength of the granules will decrease, the particles will collapse during handling, and the particle size will naturally decrease. is limited. Note that even if the amount of ultrafine silica added exceeds 5% by weight, no further increase in the particle size of the composite granules can be expected. When mixing the above two powders, one of the powders may be introduced into the mixer first and the other may be added little by little, or a predetermined amount of both may be added at once. As mentioned above, titanium dioxide powder tends to aggregate easily and tends to stick to the inner wall of the mixer during mixing, reducing the yield. Therefore, add ultrafine silica powder first and add titanium dioxide powder later. It is desirable to add In this case, even if titanium dioxide is added later in small amounts, the distribution of ultrafine silica particles in the resulting composite granules is uniform. The reason for this is still not well understood. In this way, the composite granular titanium dioxide of the present invention can be fully specified as a product. Production example 1 Put 0.5 g of ultrafine silica (#200 manufactured by Nippon Aerosil Co., Ltd.) into a turbular mixer, and add 10 g of titanium dioxide powder (TCA-888 manufactured by Tohoku Kagaku Co., Ltd.).
The mixture was mixed for 5 minutes at 90 rpm, and then 10 g of titanium dioxide powder was added and mixed for 5 minutes, thus mixing a total of 100 g of titanium dioxide powder. Figure 5 is a 100x micrograph of the starting titanium dioxide powder. Figure 6 is after the first mixing, Figure 7 is after the second mixing, Figure 8 is after the third mixing, Figure 9 is after the fourth mixing, Figure 10 is after the fifth mixing.
FIG. 11 is a similar photograph after the 6th mixing, and FIG. 12 is a similar photograph after the 9th mixing. Figure 13 shows the broken particles found in the sample after the ninth mixing. Thereafter, 10 g of titanium dioxide powder was further added and mixed for 5 minutes (10th time), and the resulting particles are shown in FIG. As seen in these photos, the amount of silica is approx.
At 0.5%, the growth of composite particles stops after approximately 9 to 10 cycles, and destruction of the produced particles appears to occur from this stage. Particle size is 10μm~ as measured by micrograph
It was distributed in a range of 0.5 mm. Production example 2 Put 0.5 g of ultrafine silica (#200 manufactured by Nippon Aerosil Co., Ltd.) into a V-type blender, start the operation of the mixer, and add titanium dioxide powder (TCA manufactured by Tohoku Chemical Co., Ltd.).
-888) was added at once and mixed for 80 minutes.
The resulting composite granules were substantially identical to those shown in FIG. Production Examples 3 to 10 Next, using various titanium dioxide powders,
Composite granules were manufactured using various methods. The conditions and results are summarized in Table 1 below.

[Table] Product Properties The properties of the composite granular titanium dioxide of the present invention are as follows. In the following description, composite granular titanium dioxide refers to the product of Example 1, and known titanium dioxide powder refers to the TCA used in Example 1.
It means -888. Bulk density composite granular composite titanium dioxide 0.75 g/cc Known titanium dioxide powder 0.37 g/cc Angle of repose The composite granular titanium dioxide of the present invention has an angle of repose of
It is less than 30°. That of known titanium dioxide powder is
It is reported to be 45-46°. Fluidity Fluidity was evaluated using a glass hourglass-shaped funnel (inner surface treated with silicone) with an inner diameter of 40 mm and a height of 95 mm. Composite granular titanium dioxide 2.5 mm Known titanium dioxide powder 18.0 mm or more Mixing into paint A known titanium dioxide powder for pigments and the product of Production Example 1 were mixed into paint. Blended titanium dioxide 10.00g Betsukosol P-470 ^* 32.97g Mineral terpene 5.76g 10% carbon black 1.00g *Oil-based alkyd resin manufactured by Nippon Reichhold Co., Ltd. The above composition was mixed with a paint conditioner (manufactured by Red Devil Co., Ltd.) as a dispersion medium. 30 g of glass beads with a diameter of 3 mm were mixed together for the hue test and 8 g for the dispersibility test. Samples were taken from the paint conditioner every 10 minutes, and the size of the whelks was observed with the naked eye to evaluate dispersibility. The prepared paint was applied with a film applicator, left to dry, and then L, a, b, Rb, Rw and gloss were measured with a colorimeter (Suga Test Instruments Color Computer) to determine the hue of the paint film. evaluated. Further, the viscosity of the prepared paint was measured using a B-type viscometer. The above results are shown in Table 2. Mixing into polychloride resin Composite granular composite titanium dioxide and known titanium dioxide powder were mixed into polyvinyl chloride resin. Formula White Gray PVC compound ^* 100 parts 100 parts Titanium dioxide 4 parts 1 part Carbon black ^** 0 parts 3 parts *PVC compound formulation Nippon Zeon 103EP-8 100 parts DOP (plasticizer) 48 parts dibutyltin maleate (stabilizer) ) 2 parts ** Mitsubishi Kasei MA-100 The above composition was kneaded with two rollers kept at 130±5°C, taken out as a sheet, and heated using a hot press at 160°C and a pressure of 130 kg/
Press for 10 minutes under ^cm2 condition and finally

[Table] A sheet with a thickness of 1 mm was prepared, and undispersed whelks on the sheet were visually determined. The results are summarized in Table 3. Comprehensive evaluation shows that the granular titanium dioxide powder of the present invention has the same performance as known untreated titanium dioxide powder in applications, and is far superior in flowability and dispersibility.

【table】

【table】 [Brief explanation of the drawing]

Each figure from FIG. 1 to FIG. 13 is a micrograph showing the particle structure of titanium dioxide, and in each figure, FIG. This is a microscopic photograph. Second
The figure is a 600x electron micrograph of the cross section of the granules shown in Figure 1. Figure 3 is a photograph of the titanium concentration distribution in the cross section shown in Figure 2 taken using an X-ray microanalyzer, and Figure 4 shows the silicon distribution in the cross section shown in Figure 3 taken using an X-ray microanalyzer. This is the photo I researched. Figure 5 is a 100x micrograph of the starting titanium dioxide powder. 6th
The figure shows after the first mixing in Production Example 1, Fig. 7 after the second mixing, Fig. 8 after the third mixing, Fig. 9 after the fourth mixing, and Fig. 10 after the fifth mixing. After that, FIG. 11 is a similar photograph after the 6th mixing, and FIG. 12 is a similar photograph after the 9th mixing. Figure 13 shows the broken particles found in the sample after the ninth mixing.

Claims (1)

[Claims] 1 95 to 99.99% by weight titanium dioxide powder,
Composite granular titanium dioxide comprising 0.01 to 5% by weight of ultrafine silica particles with a particle size of 0.002 to 0.2 μm and having a particle size of 10 μm to 2 mm.