JPH0457923A - Production of polycrystalline yarn of potassium hexatitanate - Google Patents

Abstract

PURPOSE:To obtain the title fiber having a sound state free from linear cracks by coagulating a heated melt of raw material in an orientating way to give fiber lump of K2Ti2O2 fiber and subjecting the fiber lump to potassium removal treatment and calcining treatment at two stages. CONSTITUTION:First, a mixture of (A) a Ti compound to become TiO2 by heating and (B) a K compound to become K2O by heating in a molar ratio of TiO2/K2O of 1.5-2.5 is heated and melted and the heated melt is coagulated in an orientating way to give fiber lump of K2Ti2O2 fiber. Then the fiber lump is treated with a cleaning solution, K<+> ion is eluted, the fibers are opened to give potassium titanate hydrate mixed phase fiber having a molar ratio of potassium tetratitanate composition phase/potassium hexatitanate composition phase of 0.05/0.95 to 0.45/0.55. The fiber is dried and calcined. Finally, the fiber is treated with a cleaning solution, K<+> is eluted from the potassium tetratitanate phase and the prepared potassium titanate hydrate of potassium hexatitanate composition is dried, calcined and converted in structure into potassium hexatitanate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing potassium hexatitanate polycrystalline fibers.

[Conventional technology]

Potassium hexatitanate fiber (K, Ti, O.) is a synthetic inorganic fiber that has abrasion resistance, fire and heat resistance, heat insulation, reinforcing properties, etc., and is seen as a promising substitute for asbestos in various fields. .

A method called a melting method is known as a typical manufacturing method for this fiber. Its manufacturing method involves combining a titanium compound that becomes titanium dioxide (TiO2) by heating and a potassium compound that becomes potassium oxide by heating into TfOz/K2O.
A process of heating and melting the starting materials by mixing them so that the molar ratio of
The process of obtaining a fiber mass in which Ti z Os) is aggregated into bundles, the process of eluting K+ ions by washing the fiber mass with water, and the process of disaggregating the fibers, and the hydrated titanium recovered through this process. The process consists of drying the potassium acid fibers and firing them.

In the above-mentioned water washing treatment of the primary phase fiber mass, the potassium nititanate fibers are removed by elution of K3 ions (depotassium removal).
Although it is converted into a chemical composition equivalent to the target potassium hexatitanate, the crystal structure of the recovered fiber is different from that of potassium hexatitanate, and the crystal structure of the potassium nititanate fiber, which is its precursor fiber, is different from that of potassium hexatitanate. The remains of the structure have been preserved.

In order to convert the crystal structure, a firing treatment is performed after the above water washing treatment, and the firing treatment turns into a structurally perfect potassium hexatitanate fiber.

The potassium hexatitanate fiber thus obtained has a diameter of approximately 2
It is a polycrystalline fiber having a size of 0-50 avx and a length of about 100-300 uIIO.

[Problem to be solved by the invention]

The potassium hexatitanate polycrystalline fiber obtained by the above-mentioned conventional manufacturing method has many streak-like wrinkles observed on its surface. As an example, FIG. 6 shows a cross section of a composite member formed by adding and mixing potassium hexatitanate polycrystalline fibers into a resin. (F゛) is potassium hexatitanate fiber (fiber diameter: approximately 20-50
μm), and there are many streak-like wrinkles in each fiber. These fiber wrinkles are linear cracks along grain boundaries.

If such linear cracks exist, for example, when the fibers are mixed with resin and bond-molded to be used as a sliding member such as a disc pad that constitutes an automobile brake system, the fibers existing on the sliding surface may be damaged. However, friction with the mating material causes the fibers to separate along the linear cracks and prevent the fibers from falling off the sliding surface.At the same time, it causes fine fiber fragments to get mixed into the wear dust on the sliding surface. This is undesirable.

Further, it is desirable that the above-mentioned fibers be free of linear cracks from the viewpoint of strength, flexibility, and the like. It goes without saying that fibers without linear cracks are advantageous in order to fully exhibit the dispersion reinforcing effect when used as reinforcing fibers for metals, plastics, etc., for example.

The present invention aims to provide an improved method for producing potassium hexatitanate fibers to solve the above problems.

[Means and effects for solving the problem] The method for producing potassium hexatitanate polycrystalline fiber according to the present invention comprises: a titanium compound that becomes titanium dioxide (TiOz) when heated; and potassium that becomes potassium oxide (K2O) when heated. The compound has a TiO2/K2O molar ratio of 1.5 to 2.
．． 5, a step of directional solidification of the heated melt to obtain a fiber mass which is a bundle-like aggregate of potassium nititanate fibers, and a step of treating the fiber mass with a washing liquid. By eluting K + ions and fibrillating, the composition consists of two types of hydrated potassium titanate, potassium tetratitanate composition and potassium hexatitanate composition, and a potassium tetratitanate composition phase/potassium hexatitanate composition phase is formed. The quantitative ratio (molar ratio) is 0.0510.95 to 0.
A step of obtaining a hydrated potassium titanate mixed-phase fiber having the composition No. 4510.55, by drying the hydrated potassium titanate mixed-phase fiber and subjecting it to a firing treatment, a multi-phase fiber consisting of a potassium tetratitanate phase and a potassium hexatitanate phase is obtained. A step of treating the multiphase fiber with a washing liquid to elute K + ions from the potassium tetratitanate phase and converting the composition into hydrated potassium titanate having a potassium hexatitanate composition, and after drying,
It consists of a step of structurally converting the hydrated potassium titanate into potassium hexatitanate by subjecting it to a firing treatment.

The potassium hexatitanate fibers obtained according to the present invention are polycrystalline fibers having a fiber size of about 20 to 50 microns in diameter and about 100 to 300 microns in length.

In the present invention, as described above, in the treatment process of K + ion elution (depotassium) and fibrillation by washing the lumps of primary phase fibers (potassium titanate fibers), the potassium titanate fibers are completely converted into potassium hexatitanate fibers. Unlike the conventional production method in which potassium removal is continued until the composition is reached, the potassium tetratitanate composition and the potassium hexatitanate composition are changed by temporarily stopping the potassium removal process at an intermediate stage and keeping a portion of the potassium tetratitanate composition. A multiphase fiber consisting of two types of hydrated potassium titanate is prepared, and after firing, the potassium tetratitanate phase in the multiphase fiber is converted into a potassium hexatitanate phase by performing potassium removal treatment and firing treatment again. We are planning to convert it to .

The potassium hexatitanate polycrystalline fibers obtained by the method of the present invention, which involves the two-step depotassium treatment and firing treatment, have no wrinkles (linear cracks) and have a healthy fiber morphology, unlike those of the conventional method. have. Although the mechanism that causes this difference in fiber morphology has not yet been fully elucidated, potassium dititanate fibers (a layered structure in which Ties triangular bipyramidal chains are stacked), which is the primary phase fiber, undergo -stage depotassium and sintering. In the conventional manufacturing method, the final product, potassium hexatitanate fiber (T i O, a tunnel structure formed by a chain of octahedrons) undergoes compositional and structural changes through treatment. In the process of structural transformation of potassium titanate into a tunnel structure, fibers (
The fiber of the present invention undergoes two-step depotassium treatment and firing treatment, whereas axial strain due to structural changes acts greatly on the interface between the crystals forming the polycrystalline body. In the conversion process, a multiphase fiber of potassium hexatitanate crystals and potassium tetratitanate crystals (T i O, a layered structure in which chains that share the edges and corners of an octahedron are laminated) is passed through as an intermediate step. It is thought that the strain at the grain interface due to structural transformation is small, and the generation of linear cracks is avoided as a result of the strain relaxation effect.

Hereinafter, the method of the present invention will be explained in detail step by step.

Various titanium compounds such as purified titanium oxide, synthetic rutile, titanium slag, natural rutile sand, and natural anatase sand are used as the starting material, which becomes titanium dioxide upon heating.

The potassium compound blended into the titanium compound is typically potassium carbonate (K, CO,), but other potassium compounds that become O during the heating and melting process, such as hydroxides and nitrates, may also be used. can.

The mixing ratio of titanium compound and potassium compound is T i
oz/KtO molar ratio 1.5-2.5 (7)
The reason for limiting the range is to ensure efficient production and growth of primary phase potassium dititanate fibers during the cooling and solidification process of the heated melt. Further, the reason why potassium nititanate fibers were formed as the primary phase fibers is that the fiber mass can be depotassiumed and defibrated relatively easily due to its crystal structure. A more preferable molar ratio is 1.8 to 2.2.

A mixture of a titanium compound and a potassium compound is charged into a melting crucible, heated to a temperature above the melting point and melted, and then cooled to cause directional solidification in one or multiple directions.
Potassium nititanate fiber [K t T iz Os
] Obtain a bundled fiber mass.

Next, the above-mentioned fiber mass is subjected to treatment with a washing liquid to defibrate and K
By elution of + ions (depotassium removal), a multiphase fiber consisting of two types of hydrated potassium titanate, a potassium tetratitanate composition and a potassium hexatitanate composition, is recovered.

The quantitative ratio of the two phases of the multiphase fiber [molar ratio of potassium tetratitanate composition phase/potassium hexatitanate composition phase] is 0.051
It needs to be 0.95 to 0.4510.55.

The lower limit of the two-phase quantity ratio was set at 0.0510.95 because if the proportion of the potassium tetratitanate composition phase is less than that, the effect of preventing linear cracks by mixing potassium tetratitanate will be insufficient. On the other hand, the reason why the upper limit of the two-phase ratio was set to 0.4510.55 is that if it exceeds this, fine linear cracks will occur in the potassium tetratitanate phase.
This is because the cracks remain as they are in the final fiber, and in this case too, linear cracks cannot be prevented.

The washing liquid for defibrating and depotassium may be water (room temperature), hot water (e.g. 50-80°C), or acid solution (e.g. 0.05-0.3% sulfuric acid aqueous solution, .05~0
．． 3% hydrochloric acid, 0.1-1% acetic acid aqueous solution), etc. are used, but water is usually sufficient. By adjusting the amount of washing liquid used and processing time in the washing liquid treatment, and controlling the amount of K ions eluted, it is possible to adjust the amount ratio of the two phases of the obtained multiphase fiber to a desired value. For example, when water is used as the washing liquid, the fiber mass is immersed in approximately 60 to 150 times the volume (weight ratio) of water, and is stirred for a predetermined period of time (for example, 3 to 10 hours).
By the treatment, the multiphase fiber having the predetermined two-phase ratio can be recovered.

The potassium tetratitanate composition phase and the potassium hexatitanate composition phase that constitute the multiphase fibers recovered through the treatment with the washing solution are structurally the crystal structures of the primary phase potassium dititanate, which is its precursor. The traces remain. Therefore, by drying it (for example, air drying) and firing it at an appropriate temperature, preferably about 800 to 1050 "C, it becomes structurally composed of two phases: potassium tetratitanate phase and potassium hexatitanate phase. Convert it into a multiphase fiber.

FIG. 2 shows the X-ray diffraction results of the multiphase fiber obtained through the treatment with the washing liquid and the firing treatment (for the sample fiber, see (I[) in Example 1 below). In the figure, 4T indicates a potassium tetratitanate phase, and 6T indicates a potassium hexatitanate phase. The quantitative ratio (molar ratio) of the potassium tetratitanate phase/potassium hexatitanate phase that constitutes this multiphase fiber is approximately 0.310.
7 (based on chemical analysis).

The fired multiphase fibers are further treated with a washing liquid (
The potassium tetratitanate phase is then subjected to K+
By eluting the ions, the potassium tetratitanate phase is converted into hydrated potassium titanate having a composition of potassium hexatitanate (structurally, the traces of the layered structure of potassium tetratitanate are retained). The washing liquid for this secondary elution treatment is water,
Although hot water or the like may be used, it is preferable to use an acid solution to promote depotassium. In that case, the acid solution is, for example, about 0.02-0.2% sulfuric acid aqueous solution, about 0.0%
．． A 1-1% acetic acid aqueous solution is suitable.

After the secondary elution treatment, the defibrated fibers collected from the washing liquid are dried (for example, air-dried) and then calcined (secondary firing) at a temperature of 00 to 1000°C, preferably around 800°C to obtain hexatitanic acid. The hydrated potassium titanate phase of potassium composition is converted from a layered structure of potassium tetratitanate to a tunnel structure of potassium hexatitanate.

In the above-mentioned secondary elution treatment and secondary firing treatment process of the multiphase fiber, there is no compositional or structural change in the phase existing as potassium hexatitanate in the multiphase fiber (only the potassium tetratitanate phase remains unchanged). A compositional and structural transformation to the potassium titanate phase takes place, resulting in a potassium hexatitanate single-phase polycrystalline fiber as the final fiber.

Figure 5 shows the potassium hexatitanate polycrystalline fiber of the present invention obtained through the above steps (the sample fiber is based on Example 1 described later).
This shows a composite material made by blending with resin and bond-molding (
magnification x100). Fibers mixed in the matrix resin (
F) has no linear cracks as observed in the conventional fiber (F") shown in FIG.

〔Example〕

The titanium compound used in each example was natural rutile sand (
Produced in Australia, purity 95.6%), and the potassium compound is potassium carbonate CKtCO2, purity 99.5%).
It is.

Actual lid ■ Soil CI) Starting material blend TiO2/K2O molar ratio: 2.0° (I [) Heat melting and cooling solidification treatment The starting material mixture was placed in a platinum crucible and heated to
After being heated and melted over a period of time, the melted material is poured into a metal cooling dish, and by unidirectional directional solidification from the bottom of the cooling dish upward, it becomes a bundle-like aggregate of primary phase potassium dititanate fibers. A certain fiber mass was obtained.

(I[[)-Next washing liquid treatment and baking treatment The above fiber mass is
The fibers were immersed in 20 times the amount of water to undergo defibration and depotassium treatment for about 6 hours.

After drying, the fibers recovered from the washing liquid were fired at 1000°C for 3 hours.

The obtained fiber has a diameter of about 20 to 50 μm and a length of about 100 μm.
It has a polycrystalline morphology of ~300 μ-, which is a two-phase multiphase fiber consisting of potassium tetratitanate phase and potassium hexatitanate phase by X-ray diffraction (Fig. 2), and Ti by chemical analysis. From the ratio of Ot and Kg, the molar ratio of potassium tetratitanate phase/potassium hexatitanate phase is 0.3010.7
It is 0.

[V] Secondary washing treatment and firing treatment The above multiphase fiber was treated with 50 times the amount of sulfuric acid aqueous solution (concentration 0.1%)
After being immersed in water for 1 hour to remove potassium, it was recovered from the washing liquid, dried at 120°C, and then fired at 800°C for 1 hour.

The morphology of the obtained fibers is shown in FIG. 1 (magnification: x100).

This fiber has a diameter of about 20-50 μ steel and a length of about 100-3
00 μm polycrystalline fibers, and X-ray diffraction shows that they are potassium hexatitanate single-phase fibers (Figure 3). No linear cracks are observed in the fibers.

Actual W (I) Starting raw material formulation Same as Example 1 (II) Heating melting and cooling solidification treatment Same as Example 1 [I [1] - Next elution treatment and firing treatment The fibrillation ring was
Soaked in 0 times the amount of water, treated for 7 hours, collected from the washing solution,
After drying (120°C), it was fired at 1050°C for 1 hour.

The obtained fibers were two-phase mixed phase fibers with a molar ratio of potassium tetratitanate phase/potassium hexatitanate phase of 0.1010.90 (
(by X-ray diffraction and chemical analysis).

The fiber diameter is about 20-50μm, and the length is about 100-300μm.

(IV) Secondary elution treatment and firing treatment
) for 1 hour to elute K+ ions,
It was dried and subjected to firing treatment (850°C x 1 hour).

The obtained fibers are potassium hexatitanate single-phase polycrystalline fibers similar to those of Example 1, and there are no linear cracks.The fiber size is approximately 20 to 50 μm in diameter and approximately 10 μm in length.
It is 0 to 300 μ-.

(1) Starting raw material composition Same as Example 1 [■] Heating melting and cooling solidification treatment Same as Example 1 (I[[)-Next elution treatment and firing treatment
It was immersed in twice the amount of water, treated for 7 hours, recovered from the washing liquid, dried (120°C), and then fired at 950°C for 3 hours.

The obtained fibers were two-phase mixed phase fibers with a molar ratio of potassium tetratitanate phase/potassium hexatitanate phase of 0.4210.58 (
X-ray diffraction and chemical analysis). Fiber diameter approximately 20-50
μ garden, about ioo to 300 μm in length.

(IV) Secondary elution treatment and firing treatment
) for 1 hour to elute the ions,
It was dried and subjected to firing treatment (800°C x 1 hour).

The obtained fibers were single-phase polycrystalline fibers of potassium hexatitanate, similar to those of Example 1, and there were no linear cracks. The fiber size is approximately 20 to 50 μ in diameter and approximately 1 in length.
00 to 300 μ-.

[Comparative example]

CI) Starting raw material formulation Same as Example 1 [■] Heat melting and cooling solidification treatment Same as Example 1 (I [) Treatment with washing liquid and firing treated fiber mass, 17
It was immersed in 0 times the amount of water, treated for 24 hours, collected from the washing solution, dried (110°C x 4 hours), and then heated at 1000°C for 4 hours.
The firing process took a long time.

The obtained fibers are polycrystalline fibers having a single phase of potassium hexatitanate. Fiber diameter: approx. 20~50〃■, length approx. 100~3
00μm. Many linear cracks are observed in this product.

[Reference example]

A disk pad (Bud A) was manufactured using the potassium hexatitanate polycrystalline fiber obtained in Example 1 as a base fiber, and the results of friction property measurement by Dynamotist were compared with the conventional potassium hexatitanate polycrystalline fiber. A disc pad (Pad B) using crystal fiber (manufactured according to the comparative example) and a disc pad (Pad C) using asbestos fiber were compared.

A mixture (fiber/phenolic resin/
Barium sulfate = 30/20150. Weight ratio) was preformed (temperature: room temperature, pressurized crab 300 kgf/d, pressurized time: 1 minute), and then bond molded using a mold (temperature: 170°C).
, pressurizing force of 150 kgf/d, pressurizing time: 5 minutes), and heat treated at 180°C for 3 hours after molding.

Hoshitoyo Lazyun disc Friction surface: Fe12 gray cast iron, Surface pressure: 10kg
f/C4,11! Friction speed near m/sec.

Figure 4 [! ] shows the friction coefficient measurement results, and [■] shows the wear rate (cd/kgm). In each figure, a is sample bud A
, b is the measurement result of the test pad B, and c is the measurement result of the test pad C. Test pad A using the fiber of the invention example has a lower wear rate and excellent durability compared to test pad B using conventional potassium titanate fiber and test pad C using asbestos fiber. I understand that.

B: Fiber-reinforced plastic board (sample board A) in which the potassium hexatitanate polycrystalline fiber obtained in Example 1 was used as a reinforcing material, and the conventional potassium hexatitanate polycrystalline fiber obtained in the comparative example. A fiber-reinforced plastic board (sample board B) using the material as a reinforcing material was manufactured and subjected to a bending test, and the results shown in Table 1 were obtained.

゛ -S ・Mixture of fiber and phenolic resin (fiber/resin-90/1
0. weight ratio) using a mold (temperature: 170°C,
Pressurized crab 150kgf/c4. The plate-shaped molded product obtained by heat treatment (180°C x 3 hours) after molding (pressurization time: 5 minutes) was conducted in accordance with the bending test method of JIS D 4311 r Automotive Clutch Facing. Test piece width: 15+g
a.

Span distance: 40mm, crosshead speed: 0.5
tumor/min.

Table 1 Bending strength test plate A (invention example) 6kgf/m" test plate B
(Comparative Example) 4 kgf/kaku2 The above test results show that the reinforced plastic using the fiber according to the present invention has significantly higher bending strength than that using the conventional fiber.

〔Effect of the invention〕

According to the present invention, potassium hexatitanate fibers can be produced as polycrystalline fibers having a sound morphology without linear cracks unlike conventional fibers.

The potassium hexatitanate polycrystalline fiber produced by the present invention is useful as a constituent material for friction materials, heat-resistant materials, heat-insulating materials, corrosion-resistant materials, and various other structural members, such as sliding members of braking devices for automobiles, etc. When used as constituent fibers, the fiber morphology is stable and does not easily cause fragmentation or peeling, resulting in improved friction properties on the sliding surface, and the fine fibers in the dust generated from the sliding surface. Effects such as less inclusion of fragments can be obtained, and by using the fibers of the present invention as reinforcing fibers for metals, plastics, etc., a dispersion reinforcing effect superior to that of conventional fibers can be exhibited.

[Brief explanation of drawings]

Figure 1 is a photomicrograph (magnification: 5 and 6 are micrographs (magnification: X 100) showing the cross section of conventional fibers.

Claims (1)

[Claims] (1) A titanium compound that becomes titanium dioxide (TiO_2) when heated and a potassium compound that becomes potassium oxide (K_2O) when heated were mixed so that the molar ratio of TiO_2/K_2O was 1.5 to 2.5. a step of heating and melting the mixture; a step of directional solidification of the heated melt to obtain a fiber mass which is a bundle-like aggregate of potassium dititanate fibers; and a step of treating the fiber mass with a washing liquid to remove K^+ ions. By elution and fibrillation, two types of hydrated potassium titanate, potassium tetratitanate composition and potassium hexatitanate composition, are formed, and the quantity ratio (mole) of potassium tetratitanate composition phase/potassium hexatitanate composition phase is ratio) is 0.05/0.95~0
．． A step of obtaining a hydrated potassium titanate mixed phase fiber having a ratio of 45/0.55, a mixed phase consisting of a potassium tetratitanate phase and a potassium hexatitanate phase by drying and firing the hydrated potassium titanate mixed phase fiber. Step of obtaining fibers: The multiphase fibers are treated with a washing liquid to elute K^+ ions from the potassium tetratitanate phase to convert the composition into hydrated potassium titanate having a potassium hexatitanate composition, and after drying, firing. A method for producing polycrystalline potassium hexatitanate fibers, which comprises the step of structurally converting the hydrated potassium titanate into potassium hexatitanate through treatment.