JP4478423B2 - Method for producing granulated titanium dioxide pigment - Google Patents

Description

  The present invention relates to a granulated titanium dioxide pigment and a method for producing the same.

  Titanium dioxide has a high refractive index of visible light, is excellent in whiteness and hiding property, and is widely used as a white pigment by blending it into various compositions such as paints, inks, plastics and paper. However, the titanium dioxide pigment powder is not very good in fluidity. For example, titanium dioxide pigments that cause flow defects inside the equipment or are deposited due to flow defects during operations such as transportation, transfer, feed, premixing, packaging, etc. during storage or in the manufacturing process of the various compositions described above. Productivity may be significantly reduced, for example, the powder may adhere strongly to the inner wall of the device and cause the device to become clogged. In addition, some titanium dioxide pigment powders have a high dusting property and affect the working environment.

  As a method for improving the fluidity and workability of the powder, a technique for granulating the powder has been proposed. In general, mechanical methods such as pressure molding, stirring molding, extrusion molding, rolling molding, fluidized bed molding, spray drying, etc. are used for granulating powder, clay minerals such as bentonite and talc, water In addition, a solvent such as alcohol or a polymer compound such as polyvinyl alcohol is added as a binder during molding to increase the strength of the granulated product (see Non-Patent Document 1). In addition, a pigment powder such as titanium dioxide is known to be granulated using a dispersant such as a higher fatty acid or a metal salt thereof as a binder (see Patent Document 1).

“Granulation Handbook”, first edition, published by Ohmsha, March 10, 1991, p. 11, 203-204 Japanese Patent Publication No.54-7287 (pages 1 to 3)

  When the method described in Non-Patent Document 1 is applied to titanium dioxide pigment powder, for example, when a solvent is used as a binder, the titanium dioxide pigment powder aggregates strongly when the solvent evaporates, resulting in a decrease in dispersibility. did. Therefore, excessive energy was required to redisperse the titanium dioxide pigment to the primary particles. In addition, when clay minerals or polymer compounds are used as binders, optical properties such as whiteness and hiding property are deteriorated even though they can be adjusted to a granulated product having an appropriate hardness. On the other hand, in the method described in Patent Document 1, since the dispersant also acts as a binder, a granulated product having a balance between fluidity and workability and dispersibility can be obtained. It is necessary to select a dispersant suitable for components (resin components and additives) other than titanium oxide, and the application range is greatly limited. The present invention overcomes the above-described problems of the prior art, has excellent fluidity and workability, hardly causes a difference in dispersibility due to granulation, and has a highly versatile granulated titanium dioxide pigment and a method for producing the same. It is to provide.

  As a result of intensive studies to solve these problems, the present inventors have found a granulated titanium dioxide pigment that does not impair the dispersibility of the titanium dioxide pigment without using a binder, and a method for producing the same, and Completed.

  That is, the present invention is a granulated titanium dioxide pigment obtained by granulating a titanium dioxide pigment powder without containing a binder and having a dispersity of at least -1.5. Furthermore, this invention is a manufacturing method of the granulated titanium dioxide pigment characterized by carrying out the pressure granulation of the titanium dioxide pigment powder by the pressure of the range of 0.1-10 Mpa, without using a binder.

  When the granulated titanium dioxide pigment of the present invention is blended and used in various compositions such as paints, inks, plastics, paper, etc., (1) handling properties and measuring accuracy during transportation and packaging can be improved, and titanium dioxide due to adhesion Excellent fluidity, such as reduced pigment loss, (2) Excellent workability, such as reduced dust generation and improved working environment, (3) Dispersibility equivalent to powder And (4) versatility because no binder is used.

  The present invention is a granulated titanium dioxide pigment, characterized by granulating titanium dioxide pigment powder without containing a binder, and having a dispersity of at least -1.5. The granulated titanium dioxide pigment of the present invention is excellent in fluidity and workability, and is granulated without using a binder, so that it has high versatility and can be applied to a wide range of compositions. The binder in the present invention refers to one having an action of binding titanium dioxide particles during granulation, for example, clay minerals such as bentonite and talc, water, solvents such as alcohol, polymer compounds such as polyvinyl alcohol, and the like Examples thereof include dispersants such as fatty acids or metal salts thereof.

  The “dispersion degree” in the present invention is evaluated by the following method.

(Dispersion evaluation method)
Using an air-flow type pulverizer (200AF type: manufactured by Fuji Sangyo Co., Ltd.), using compressed air as a pulverizing medium, 500g of granulated titanium dioxide pigment is added to the pulverizer at a rate of 200g / min to pulverize the granulated product. And redispersed to the original primary particles. That is, an operation of returning to the state of the titanium dioxide pigment powder before granulation is performed. Each of the samples before and after pulverization in Formula 1 shown in Table 1 below was placed in a 130 cc glass container and dispersed for 20 minutes using a paint conditioner (manufactured by Red Devil). In Table 2 shown in Table 2, the coating composition is 1 part by weight of titanium dioxide pigment and 46% solids volume concentration with respect to 1 part by weight of the resin component. The paints prepared using the samples before and after pulverization are each applied to a glass plate with a 4 mil applicator and allowed to stand for 30 minutes, and then baked at 120 ° C. for 30 minutes to form a coating film. The 20 ° glossiness of the obtained coating film is measured using a gloss meter (GM-26D type / Murakami Color Materials Laboratory). (20 ° gloss before pulverization) − (20 ° gloss after pulverization) is calculated, and this is defined as “dispersion”.

  In the present invention, this dispersity is at least -1.5. That is, the excellent dispersibility of the titanium dioxide pigment powder before granulation is retained after granulation. Although there is no particular upper limit for the degree of dispersion, in the present invention, there is usually no significant difference in the 20 ° gloss before and after pulverization, so the upper limit is less than +2.0. Therefore, the granulated titanium dioxide pigment of the present invention can be made into a primary particle by applying a shearing force by a dispersing machine commonly used in industry in the production of compositions such as paints, inks, plastics and paper. It can be easily dispersed.

  In the present invention, the granulated titanium dioxide pigment has a hardness in the range of 1 to 20 g. Since the granulated titanium dioxide pigment of the present invention has a hardness in the above range, the granulated product is hardly broken during transportation, transfer, storage and the like. In the present invention, the hardness is a value calculated by the following method.

(Measurement method of hardness)
Place one granulated titanium dioxide pigment on the electronic balance, compress this with a spatula from the top, and read the indicated value of the balance when crushed. This operation is repeated at least 20 times per sample, and the average value of the indicated values is calculated to obtain the hardness of the granulated titanium dioxide pigment.

  In addition, the angle of repose and the bulk density were used as physical property values for evaluating fluidity and workability. For the angle of repose, a sample passed through a 24-mesh sieve was poured in a mountain shape on a circular table of 80 mmφ using a funnel, the sample crest, table and ground contact angle were measured at three locations, and the average value was used. . The smaller the angle of repose, the better the fluidity. The angle of repose of the granulated titanium dioxide pigment of the present invention is as small as 45 ° at the maximum, and shows good fluidity compared with the titanium dioxide pigment powder. In addition, since the titanium dioxide pigment powder has small particles, air is easily involved in the manufacturing process, and there is a problem in workability that the bulk density is large and difficult to handle in addition to fluidity. The granulated titanium dioxide pigment of the present invention can increase the bulk density to 0.8 g / cc or more, and the workability is further improved as compared with the titanium dioxide pigment powder. The bulk density is measured based on JIS K5101.

  The shape of the granulated titanium dioxide pigment of the present invention is not particularly limited, such as flakes, granules, agglomerates, and irregular shapes, and includes ungranulated titanium dioxide pigment powder as long as the effects of the present invention are not impaired. Also good. The size of the granulated product is not particularly limited, and may be set as appropriate by the granulation conditions described later, and operations such as classification, crushing and sizing within a range where desired effects such as fluidity and workability can be obtained. Can do.

  As the titanium dioxide pigment powder used for granulation, those having an average particle diameter (50% particle diameter of primary particles by electron microscopy) in the range of 0.1 to 0.5 μm have high concealment properties. A more preferable range is 0.1 to 0.4 μm. The crystal form may be either a rutile type or an anatase type, or a mixture thereof or partially containing amorphous titanium dioxide. The titanium dioxide pigment powder may be obtained by, for example, a so-called sulfuric acid method for hydrolyzing a titanium sulfate solution, or may be obtained by a so-called chlorine method for vapor-phase oxidation of titanium halide. Is not particularly limited.

  In general, a titanium dioxide pigment whose surface is coated with an inorganic compound is further improved in weather resistance and light resistance, and an organic compound coating is further improved in affinity with a resin component. For this reason, the titanium dioxide pigment powder in the present invention is preferably one whose surface is previously coated with at least one of these. The coating amount of the inorganic compound varies depending on the application, but it is preferably in the range of 0.1 to 10% by weight when used in paints and ink compositions, and 0.05 to 5% by weight in the case of plastics compositions. A preferable coating amount of the organic compound is usually in the range of 0.01 to 5% by weight, and a more preferable range is 0.05 to 2% by weight.

  Examples of the inorganic compound used for the surface coating of the titanium dioxide pigment powder in the present invention include oxides such as aluminum, silicon, zirconium, tin, titanium, and antimony, hydroxides, hydrated oxides, and phosphates. Of these, compounds of aluminum, silicon, zirconium and tin are preferred. These may be a single layer, a laminate of two or more types of coatings, a mixture of two or more types of inorganic compounds, and a dense layer even when coated as a porous layer. There is no particular limitation.

  As the organic compound used for the surface coating of the titanium dioxide pigment powder in the present invention, polyhydric alcohol, alkanolamine or a derivative thereof, organosilicon compound, higher aliphatic hydrocarbon, etc. can be used, among which polyhydric alcohol, alkanol. Amines and organosilicon compounds are preferred. Specifically, for example, trimethylolethane, trimethylolpropane, pentaerythritol, etc. as polyhydric alcohol, triethylamine, trimethylamine, etc. as alkanolamine, dimethylpolysiloxane, methylhydrogenpolysiloxane, etc. as organosilicon compounds Polysiloxanes, silane coupling agents such as amino silane and vinyl silane, alkyl silanes, phenyl silanes, fluoroalkyl silanes and the like, and higher aliphatic hydrocarbons include paraffin wax, polyethylene wax and the like. Even what was seed-coated may be coated with a combination of two or more.

  Next, this invention is a manufacturing method of a granulated titanium dioxide pigment, Comprising: It pressurizes and granulates the titanium dioxide pigment powder by the pressure of the range of 0.1-10 Mpa, without using a binder. In the production method of the present invention, by subjecting the titanium dioxide pigment powder to pressure granulation at a pressure in the above range, there is almost no decrease in dispersibility due to granulation and excellent fluidity and workability without using a binder. A granulated titanium dioxide pigment is obtained. When the pressure is lower than the above range, sufficient fluidity and workability cannot be obtained, and when the pressure is higher, the dispersibility is lowered. A more preferable pressure range is 0.1 to 5 MPa.

  For pressure granulation, a known pressure molding machine such as a roll molding machine, a press molding machine, a tableting molding machine or the like can be used, and among them, the roll molding machine can continuously granulate a large amount of titanium dioxide pigment powder. Industrially preferable. In order to control the pressure at the time of granulation within the above range, when using a roll forming machine, the clearance of the roll, the number of rotations, the supply amount of titanium dioxide pigment powder, etc. are adjusted, or the roll surface material is made of metal, , By appropriately selecting from rubber or the like. Examples of the roll forming machine include an open roll and a briquetting roll. The roll surface may be smooth or corrugated and provided with a concave pocket or a convex briquette. There are no particular restrictions. The number of rolls and the roll diameter can be appropriately selected according to the production amount, but two rolls are generally used.

  It is particularly preferable to repeat the pressure granulation at least twice because the fluidity, workability and dispersibility of the resulting granulated titanium dioxide pigment can be easily adjusted. The method can be performed by collecting the pressure-granulated pigment once and further pressure-granulating, so-called batch-type pressure granulation is repeated, but pressure molding corresponding to the desired number of granulations It is preferable to prepare a machine and repeat pressure granulation continuously to improve productivity. After granulation, it is preferable to classify using a dry classifier such as a vibration sieve or a cyclone. If necessary, the particles may be classified after being crushed and sized so as to be easily classified.

  Examples of the present invention are shown below, but the present invention is not limited thereto.

Examples 1-6
As a titanium dioxide pigment powder, Taipei (registered trademark) CR-50 (Ishihara Sangyo: aluminum oxide coating), Taipei (registered trademark) CR-50-2 (Ishihara Sangyo: aluminum oxide, polyhydric alcohol coating), Taipei (registered) (Trademark) CR-90 (Ishihara Sangyo Co., Ltd .: Aluminum oxide, silicon oxide coating) was used for 20 kg each, continuously granulated under pressure at 1.4 MPa using two two-roll molding machines, and then opened. Was classified with a 3 mm vibrating sieve to obtain the granulated titanium dioxide pigment of the present invention. These are referred to as Examples 1 to 3 (Samples A to C). Moreover, the granulated titanium dioxide pigment was obtained like Example 1-3 except having changed the pressurization pressure into 3.4 MPa. These are designated as Examples 4 to 6 (Samples D to F).

Comparative Example 1
After CR-50 is dispersed in water to form an aqueous slurry of 200 g / liter, spray drying is performed using a spray dryer (FL-12 type: manufactured by Ogawara Processing Machine Co., Ltd.) at an inlet temperature of 230 ° C. and an outlet temperature of 120 ° C. at 3 ml / min. And granulated. This is designated as Comparative Example 1 (Sample G).

Comparative Example 2
14.4 kg of CR-50 was granulated by stirring for 3 minutes at 3000 rpm using a proshear mixer (WB-75 type / manufactured by Taiheiyo Kiko). This is designated as Comparative Example 2 (Sample H).

Comparative Example 3
A granulated titanium oxide pigment as a comparative sample was obtained in the same manner as in Example 1 except that the pressure was changed to 15 MPa. This is designated as Comparative Example 3 (Sample I).

Comparative Examples 4-6
The titanium dioxide pigment powder used in Examples 1 to 6 is referred to as Comparative Examples 4 to 6 (Samples J to L).
It was.

  The dispersity and hardness of each sample (A to I) obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were measured. Moreover, about each sample (AH, JL) of Examples 1-6 and Comparative Examples 1, 2, 4-6, the angle of repose and the bulk density were also measured.

  The results are shown in Table 3. The granulated titanium dioxide pigment of the present invention has such a hardness that the granulated product is hardly broken during transportation, transfer, storage, etc., and there is almost no decrease in dispersibility due to granulation, and before granulation. It can be seen that the dispersibility of the titanium dioxide pigment powder is maintained. Moreover, since the angle of repose is smaller than that of the titanium dioxide pigment powder, it is found that the fluidity is excellent, the bulk density is large, and the workability is also excellent. It can be seen that even if spray-drying or stirring molding can granulate a granulated product having high hardness, the dispersibility is lower than before granulation.

The granulated titanium dioxide pigment of the present invention is excellent in all of dispersibility, fluidity, and workability, and is used by blending it with various compositions such as paints, inks, plastics, and papers. Useful for.

Claims (3)

Pressure granulation of titanium dioxide pigment powder is repeated at least twice at a pressure in the range of 0.1 to 10 MPa without using a binder, and the degree of dispersion after pressure granulation is set to at least −1.5. A method for producing a granulated titanium dioxide pigment. Granulation method for manufacturing a titanium dioxide pigment according to claim 1, characterized in that the pressure-heading particle by using a roll molding machine. Pressurized heading after particle, the method for producing a granulated titanium dioxide pigment according to claim 1, wherein the classifying.