JP2977854B2 - Method for producing potassium hexatitanate fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is excellent in heat resistance, heat insulation, chemical resistance and reinforcement, and is used as a fire-resistant heat insulating material, a filter material, a reinforcing material for plastics and low melting point metals, etc. More specifically, the present invention relates to a method for producing a potassium titanate fiber, more specifically, a titanium oxide surface-treated with alumina and / or silica in advance,
The present invention relates to a method for producing potassium hexatitanate fiber having a smooth surface and a uniform fiber diameter and fiber length, using potassium bicarbonate and titanium powder and / or titanium hydride powder as starting materials.

[Prior Art] Various methods for producing potassium titanate fiber have already been proposed, but they are roughly classified into a calcination method, a flux method, a melting method, a hydrothermal method, and a melt method. Among these, as methods for industrially producing potassium titanate fibers, it is said that a firing method, a flux method, and a melt method are advantageous in terms of increasing the scale and continuity.

The firing method is a method in which a mixture of potassium carbonate and titanium dioxide is usually fired at 600 to 1200 ° C. for a certain period of time. To increase the yield of single fiber crystals, a small amount of a third component (such as KCl) is used as a flux. It is preferred to add. According to this firing method, the yield of single fiber crystals is good,
There are drawbacks in that the crystallinity of the fiber is not very good and that only short fibers of several microns can be obtained.

As a flux method, a method of hydrogenating potassium chloride or potassium fluoride as a flux to a mixture of potassium carbonate and titanium dioxide is generally known, and a method of using potassium molybdate or potassium tungstate as a flux has also been proposed. ing. According to this flux method, relatively long (several microns to several tens of microns) fiber crystals can be obtained, and the yield of single fiber crystals is good. However, potassium chloride or potassium fluoride as a flux is advantageous. Due to its use, a large amount of harmful and corrosive gases including chlorine and fluorine are generated, and furthermore, it is necessary to treat wastewater discharged in the defibration process and the washing process and to collect the flux.
There is a problem that manufacturing equipment is expensive.

Melt method is a mixture of potassium carbonate and titanium dioxide 1100
It is a method of quenching and solidifying what has been heated and melted at a temperature of at least ℃, and the resulting nodules will be extremely rich in fiber, but the fiber is potassium dititanate fiber (K ₂ Ti ₂ O ₅ ), When X-ray analysis is performed, it is amorphous, the fiber diameter is large, and the strength is low, so the field of use is limited.

In order to overcome such disadvantages of the conventional method, the present inventors disclosed in Japanese Patent Application Laid-open No. Sho 62-256799 that potassium hexatitanate fiber having excellent heat resistance and chemical resistance and high mechanical strength was industrially manufactured. A method for producing titanium oxide-containing ore, which is generally used as a raw material for refining titanium metal, as a starting material by a firing method, which is considered to be an advantageous method, has been proposed at a relatively low cost.

[Problems to be Solved by the Invention] However, potassium titanate fiber is, as described above,
Today, there is a demand for the future of plastics, light metals, etc. and their use as reinforcing materials, and there is a bias in emphasizing the characteristics solely on the fiber length and fiber diameter. In addition to familiarity with matrix materials and corrosion resistance under severe conditions, furthermore, the demands of the industry in recent years are increasingly high, such as workability such as formability, stability to withstand deformation after molding, etc. In application, even the gloss of the surface becomes an indispensable requirement for aesthetics. In order to satisfy such requirements, it is desirable that the surface of the fiber is smooth and the fiber length and fiber diameter are averaged.

However, the conventionally known potassium titanate fiber has a fiber length to fiber diameter ratio, that is, an aspect ratio is not constant, the fiber contains about 8 μm or less, and the specific surface area is 10 to 15 m ^2. / g, and the amount of oil absorption also increases, adversely affecting the tendency to thicken and flowability, and has the problem that the application to the matrix material is limited because it hinders familiarity with the matrix material and uniform dispersion. Was.

The present inventors have made intensive studies to solve such problems, and as a result, have reached the present invention and propose the present invention.

[Means for Solving the Problems] That is, the present invention provides (a) titanium oxide (hereinafter sometimes simply referred to as component (a)) which has been previously surface-treated with alumina and / or silica, and (b) carbonic acid. Alkali hydrogen metal (hereinafter sometimes simply referred to as component (b)), and (c) titanium powder and / or titanium hydride powder (hereinafter sometimes simply referred to as component (c)).
And the resulting mixture is heated and fired in a temperature range of 800 to 1200 ° C., and then the fired material is treated with water or hot water to extract a water-soluble component and then defibrated. It is intended to provide a method for producing potassium acid fiber.

As the component (a) used in the present invention, a commercially available titanium oxide for a pigment, which has been subjected to a surface treatment with alumina and silica, and is preferably a rutile type grade.

As the component (b) used in the present invention, commercially available potassium bicarbonate is usually preferred.

The component (c) used in the present invention may be a commercially available fine particle, but an undermesh product (-20 mesh) as an extraordinary product obtained from the titanium sponge manufacturing process is used. Is advantageous in terms of price. It is also possible to use titanium powder and titanium alloy powder obtained by cutting a titanium ingot and then pulverizing it.

In the method of the present invention, the component (a) and the component (b) are represented by the general formula K ₂ O · n (Ti · M) O ₂ (where n is 2.5 to 3.
5, M represents a metal used for surface treatment), and 0.1 to 10 wt% of the component (c) is added to the mixture, and the mixture is added to a powder blender such as a V-type blender. To improve the reactivity of the raw materials, then 800 ° C
Firing at 1-3200 ° C., preferably 1100 ° C. for 1-3 hours to form a fibrous fired body. Next, the fibrous fired body is gradually cooled, transferred to another container and pulverized, and then is subjected to a stirring treatment in water or hot water by a stirrer for 5 to 10 hours, followed by defibration in a colloid mill. The obtained fibrous material is washed with neutralized water, filtered, dried at 100 to 250 ° C., and calcined at 800 ° C.

Impurities Al ₂ O ₃ and SiO ₂ in raw materials used in the present invention
Etc. remain as trace components in the resulting fiber crystals. The product thus obtained was analyzed by X-ray diffraction, and it was confirmed that the product was a potassium hexatitanate fiber.

[Operation] It is not clear what mechanism is used during the reaction between titanium oxide used in the present invention and surface-treated with alumina and / or silica and alkali metal bicarbonate represented by potassium bicarbonate. As a result, as will be described later, it has become possible to stably produce potassium hexatitanate fibers having an intended fiber shape and a smooth surface, which is the intended purpose.

Further, the titanium powder or titanium hydride powder added in the present invention acts as a reaction accelerator, promotes the reaction between titanium dioxide and the potassium component in the oxidation reaction of titanium, and contributes to the reaction itself. Further, by adding titanium powder or titanium hydride powder, n in the above general formula is 2.5
As described above, preferably, the ratio of the fiber length and the fiber diameter, that is, the aspect ratio is adjusted by sintering without melting the mixture of potassium carbonate and titanium dioxide as in the conventional melting method without melting the mixture of potassium carbonate and titanium dioxide. A potassium acid fiber could be obtained. In addition, in the case of a fibrous material obtained by firing a mixture of a titanium oxide-containing ore and a potassium component without adding conventional titanium powder or titanium hydride powder, the degree of fiber growth is low, and subsequent fibrillation is difficult, so that fiber recovery is performed. However, in the present invention, titanium powder or hydrogen mixed with a mixture of titanium oxide surface-treated in advance with alumina and / or silica and an alkali metal bicarbonate represented by potassium bicarbonate was used in the present invention. It was recognized that these points could be eliminated and improved by adding titanium oxide powder.

Examples and Comparative Examples Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

<Example 1> Titanium oxide for pigment (as a result of composition analysis by the present inventors, Al
₂ O ₃ 2.2 wt% SiO ₂ 0.05 wt%, rutile type, surface-treated product) and potassium bicarbonate (powder) are mixed at a molar ratio of 3: 1 in terms of titanium oxide and potassium carbonate,
5 wt% of titanium powder (-20 ^# product) was added to the mixture, and mixed for about 15 minutes by a V-type blender. Next, 500 g of the mixture was placed in an electric furnace and baked at 1100 ° C. for 3 hours. After cooling, the fired product is taken out and divided into small pieces, immersed in cold water (3), stirred for 8 hours to form a slurry, and the slurry is defibrated by a disper mill (manufactured by Hosokawa Micron Corporation) to remove fibrous substances. separated.

The defibrated and separated slurry is sieved with a 100 ^# sieve into a residue and a fibrous material. The resulting 100 ^# under slurry is neutralized, and then filtered by a vacuum filtration method to obtain a cake-like material. The cake-like substance was dried while maintaining the temperature at 150 to 200 ° C., and was further heated to 800 ° C. and heat-treated for 30 minutes.

The fiber thus obtained had a smooth surface, a fiber diameter of 0.5 μm on average, and a fiber length of 50 μm on average, which was almost even.

FIG. 1 shows an electron micrograph of the shape and surface smoothness of the fiber.

<Comparative Example> Titanium oxide for a pigment was an anatase type surface-untreated product (alumina and silica were not found to be contained according to analysis by the present inventors), and potassium carbonate was used instead of potassium bicarbonate. An experiment was conducted in the same manner as in Example 1 except that no titanium powder was added.

The fiber diameter of the obtained fiber varied from 0.5 to 1.0 μm on average and the fiber length from 10 to 20 μm on average, and the fiber shape was angular and the surface was in the shape of a thorn.

FIG. 2 shows an electron micrograph of the surface state of the fiber.

[Effects of the Invention] According to the method of the present invention, the obtained potassium hexatitanate fiber has a uniform fiber length and fiber diameter ratio (aspect ratio), and its surface is extremely smooth as compared with conventionally known ones. Therefore, it exerts remarkable reinforcing performance on a fiber-reinforced metal or a plastic containing the same. Also,
Because the surface of the fiber is dense and smooth, its specific surface area is small, and when blended into a matrix material such as plastic or light metal, without impairing the fluidity, the tendency to thicken can be suppressed extremely low, Excellent workability. This can be used for large molded products, especially when blended in plastics, in order to reduce the coefficient of thermal expansion and reduce the deformation of the resulting composite.

Furthermore, since it is a firing method as compared with the conventional melting method, there is an advantage that the apparatus is simplified and the equipment cost is reduced. Further, since a tunnel furnace or the like can be used for firing, continuous firing can be performed. Considering these points, the potassium titanate fiber can be produced at low cost, so that the field of use has been limited in terms of cost, but according to the present invention, the field of use can be expanded.

[Brief description of the drawings]

FIG. 1 is an electron micrograph showing the shape of the potassium titanate fiber obtained by Example 1 of the present invention, and FIG. 2 is an electron micrograph showing the shape of the potassium titanate fiber obtained by the comparative example. is there.

Claims (2)

(57) [Claims] 1. A method comprising mixing (a) titanium oxide which has been previously surface-treated with alumina and / or silica, (b) an alkali metal hydrogencarbonate, and (c) titanium powder and / or titanium hydride powder. 800-120
A method for producing a potassium hexatitanate fiber, comprising heating and firing in a temperature range of 0 ° C., treating the fired product with water or warm water to extract a water-soluble component, and then defibrating. 2. The method for producing potassium hexatitanate fiber according to claim 1, wherein the alkali metal bicarbonate is potassium bicarbonate.