JP3028398B2 - Method for producing sodium titanate fiber - 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 producing sodium titanate fiber useful as a base material for a sliding member, a reinforcing material for plastics, a filler for resin paint, and the like.

[0002]

2. Description of the Related Art Titanium represented by sodium hexatitanate
Sodium acid fiber (Na_TwoO ・ n H _TwoO, n = 1 to 1
6) is excellent in wear resistance, heat resistance, heat insulation, reinforcement, etc.
Synthetic inorganic compound fiber, recently replacing asbestos fiber
As a product, various engineering applications are being attempted. Six
Sodium titanate fiber is made of titanium oxide (TiO_Two)Also
Is a titanium compound that becomes titanium oxide when heated,
Thorium (Na_TwoO) or sodium oxide by heating
Using a mixture with the sodium compound
Built. Melting known as one of its industrial manufacturing methods
According to the method, the starting material is TiO _Two/ Na_TwoO molar ratio
Is adjusted to about 3 and melted by heating, and the melt is cooled.
And trisodium titanate fiber (Na_TwoTi_ThreeO₇) Or
After obtaining a fiber mass consisting of
By eluting some of the Na ions in the fiber with the solution
With a chemical composition equivalent to sodium hexatitanate
The process of converting the composition to sodium tanoate and then firing
Through the process, the desired sodium hexatitanate fiber was obtained.
It is.

[0003]

In the above production method, a high temperature of about 1300 ° C. is required for the heating and melting treatment of the starting material, so that the maintenance burden due to corrosion damage of the melting apparatus is large. In addition, it is difficult to defibrate the fiber mass obtained by cooling the melt, and a forced defibration treatment with a strong stirring action is required. For this reason, the fiber is liable to be broken or powdered during the defibrating treatment, the shape and size of the final product fiber vary greatly, and the fiber yield is low.
Moreover, a large amount of acid is required for the Na ion elution treatment, and it is somewhat difficult to control the Na ion elution amount. The present invention has been made for the purpose of solving the above-mentioned problems relating to the production process and fiber quality of sodium titanate fiber by a melting method.

[0004]

According to the present invention, there is provided a method for producing sodium titanate fiber comprising TiO ₂ or Ti by heating.
A titanium compound that produces O ₂ and a potassium compound that produces K ₂ O or K ₂ O by heating are combined with TiO ₂ / K ₂
The mixture blended in such a manner that the molar ratio of O becomes 1.5 to 2.5 is heated and melted, and the heated melt is cooled to obtain a fiber lump composed of potassium dititanate fiber. By immersing and fibrillating, and eluting the total amount of K ions in the fiber, a polycrystalline fiber of hydrated dititanic acid is obtained, and the hydrated dititanate fiber is treated with a solution containing Na ions. As a result, after adsorbing 8.5% by weight or more of Na ions between the layers of the hydrated dititanic acid crystal, the temperature was raised to 9%.
It is characterized by firing at 00 to 1250 ° C.

[0005]

[Action] The starting material in the production method of the present invention, a titanium compound and a potassium compound, since TiO ₂ / K ₂ O (molar ratio) is prepared by mixing the ratio to be 1.5 to 2.5 The heat melting process is achieved in a relatively low temperature range of about 1150 ° C. or less. The fibers in the fiber mass obtained by cooling the heated melt are potassium dititanate crystals, which have a layered structure and are immersed in water to cause an active hydration reaction. Is easily achieved, and does not require forced defibration treatment that causes breakage and powderization of the fiber. The sodium titanate fiber according to the present invention (general formula “Na ₂ O.
represented by n H ₂ O ". n = 1 to 6) have different crystal phases depending on the amount of adsorption in the Na ion adsorption treatment, and include sodium hexatitanate fiber (Na ₂ Ti ₆ O ₁₃ ) and tetrasodium pentatitanate fiber (Na ₂ Ti ₄ O). ₉ ), or sodium trititanate fiber (Na ₄ Ti ₅ O ₁₂ ), or a composite fiber thereof. The fibers are plate-like polycrystalline fibers with little variation in shape and size, and have a fiber diameter of about 10 to 60 μm, a length of about 80 to 400 μm, and an aspect ratio of about 2 to 10.

Next, the manufacturing method of the present invention will be described in the order of steps. [Preparation of Starting Materials] Starting materials are TiO ₂ or a titanium compound that generates TiO ₂ by heating (for example, purified anatase, titanium oxide hydrate, natural rutile ore),
It is prepared by blending K ₂ O or a potassium compound that produces K ₂ O by heating (for example, potassium carbonate, potassium hydrogen carbonate, potassium hydroxide, etc.). TiO ₂ / K ₂ O of starting material (molar ratio), what is 1.5 to 2.5, in this composition range, can relatively achieved in a low temperature range of heating and melting, and an initiation phase fibers two This is because potassium titanate fibers can be efficiently generated.

[Heat melting and cooling and solidifying treatment of the melt]
The heating and melting treatment of the starting material is achieved by heating and maintaining the starting material in a temperature range higher than the melting point for an appropriate time (approximately 0.5 to 4 hours). The heating temperature varies depending on the composition ratio of the raw materials, but is about 950 to 1150 ° C, and high-temperature heating exceeding about 1150 ° C is not required. The heat-melted product is transferred to an appropriate container (for example, a vessel made of copper) and solidified by cooling to obtain a fiber mass in which fibrous potassium dititanate crystals are collected in a bundle as an initial phase.

[Fibrillation treatment] The fiber mass is immersed in water for an appropriate period of time (about one night) to cause separation and cleavage of the crystal layers due to the hydration swelling reaction of the potassium dititanate crystal, which results in high efficiency. Achieve defibration. If desired, agitation for accelerating defibration can be added, but mild agitation is sufficient.
There is no need for strong agitation to force the fibers to separate from each other under the action of shearing forces. For this reason, there is little fiber breakage and powdering, and a homogeneous polycrystalline fiber having a high aspect ratio and a uniform fiber size can be obtained.

[K-ion elution treatment] An aqueous acid solution, for example, a 0.8% or more aqueous sulfuric acid solution, 0.8% or more hydrochloric acid, or the like is used as a treatment solution, and the potassium dititanate fiber is immersed in the treatment solution. Elute the entire amount of K ions in. If desired, a mild agitated stream is added to facilitate elution. This K ion elution treatment does not require consumption of a large amount of acid as in the case of eluting Na ions from sodium dititanate fiber, and the elution amount is relatively easy to control. This is because potassium dititanate crystals (having a continuous layered structure of TiO ₅ ) tend to undergo a hydration reaction.

[Sodium adsorption treatment] The adsorption amount of Na ions to the hydrated titanate fiber from which K ions have been eluted (sodium content of the fiber) is set to 8.5% by weight or more when the adsorption amount is less than that. This is because, in the subsequent sintering step, titania crystals are precipitated, and it becomes impossible to obtain sodium titanate crystal single-phase fibers. N
a The amount of adsorbed ions is 8.5% by weight (TiO ₂ / Na ₂ O =
6.0), the final fiber obtained by baking this is sodium hexatitanate crystal (Na ₂ Ti).
₆ O ₁₃ ) fiber. If the amount of adsorption of Na ions is further increased, sodium titanate fibers other than sodium hexatitanate crystals are obtained. For example, when the amount of adsorption is about 15.2% by weight, sodium trititanate fiber (Na ₂ Ti ₃ O ₇ ) ,
When the amount of adsorption is about 17.6% by weight, tetrasodium pentatitanate fiber (Na ₄ Ti ₅ O ₁₂ ) is obtained, and when the amount of adsorption is adjusted to an intermediate region between them, a plurality of crystal phases are mixed. In the case of a composite fiber, for example, when the amount of adsorption is about 12% by weight, a fiber composed of sodium hexatitanate crystals and sodium trititanate crystals is obtained. The Na ion adsorption treatment is achieved by using an aqueous solution of sodium hydroxide, an aqueous solution of sodium carbonate, or the like as a treatment liquid and immersing the treatment liquid for an appropriate time.
The amount of Na ions adsorbed can be controlled by the concentration, amount, pH, treatment time, etc. of the treatment solution.

[Firing] The fiber adsorbed with Na ions has a chemical composition equivalent to that of sodium titanate crystals, but has a crystal structure of potassium dititanate as a precursor. Remains of the structure remain. The firing treatment is a treatment for converting the structure into sodium titanate crystals. The sintering treatment is achieved by heating and holding in a temperature range of 900 to 1250 ° C. The lower limit of the treatment temperature is set to 900 ° C. at a lower temperature because the obtained composite fiber has poor crystallinity and is chemically unstable. This is for preventing melting of the sodium acid crystals. The conversion reaction of the crystal structure is achieved by maintaining the above-mentioned temperature range for several minutes. However, since the processing time is related to the sintering of the crystal grains and the fiber strength due to the sintering, several hours (for example, (1-5 Hr).

[0012]

【Example】

[1] The starting material prepared purified anatase powder (purity: 99%) of potassium carbonate powder (purity: 99%) and, TiO ₂ / K ₂ O (molar ratio) were blended in ratio to form 2 uniformly mixture. [2] Heat melting and cooling and solidification of the melt The starting material is put in a platinum crucible and heated and maintained at 1100 ° C. for 1 hour in a heating furnace. The melt is poured into a copper dish, cooled and solidified to obtain a fiber mass made of potassium dititanate fiber. .

[3] Wet defibration and K ion elution treatment Fiber lumps are immersed in water and left overnight to achieve defibration. Next, industrial sulfuric acid (62.5%) is added, and the entire amount of K ions in the fiber is eluted to obtain a hydrated titanate fiber. Fluid volume:
100 times the amount (weight) of the solid content, sulfuric acid addition amount: 80% by weight based on the solid content, treatment time: 4 hr.

[4] Na ion adsorption treatment After dehydrating and drying the hydrated titanate fiber (80 ° C., overnight),
Subject to adsorption treatment. Treatment liquid: water with industrial caustic soda (sodium hydroxide 48
% Aqueous solution). Liquid amount: 50 times (weight ratio to solid content, industrial caustic soda amount to solid content is 55% by weight) Processing time: 4Hr [5] Firing treatment Fiber recovered from the Na adsorption treatment liquid is dehydrated and dried (200
After firing at a temperature of 1050 ° C. (treatment time: 2 hours).

The fibers obtained are as follows. Na content: about 8.5% by weight Crystal structure: sodium hexatitanate (Na ₂ Ti
₆ O ₁₃ ) Single phase Shape size: plate-like polycrystalline fiber (diameter 25 μm, length 15
0 μm, aspect ratio 6, (average).

[0016]

According to the method of the present invention, the heating and melting of the starting material can be performed in a relatively low temperature range, the corrosion damage of the melting equipment is small, and the maintenance is reduced. Further, the fibrous mass obtained by cooling the melt is easily defibrated, breakage and powdering of the fiber during the defibration treatment are prevented, and the homogeneity of the fiber shape and size is enhanced. The obtained sodium titanate fiber is useful as, for example, a base fiber of a friction material, a plastic reinforcing material, a filler of a resin paint, and the like, and is a slightly larger plate-like polycrystalline fiber unlike an ultrafine single crystal fiber. Therefore, use problems such as whiskers (for example,
The problems of difficulties in uniform kneading into the resin and generation of ultrafine fiber fragments which are detrimental to environmental hygiene) are avoided, and the high aspect ratio provides an excellent reinforcing effect.

Claims (1)

(57) [Claims] 1. TiO_TwoOr TiO by heating_TwoRaw
A titanium compound to be formed and K_TwoO or K by heating_TwoO
Is formed from TiO_Two/ K _TwoMole of O
Heat the mixture blended at a ratio of 1.5-2.5
It is made of potassium dititanate fiber by melting and cooling the heated melt
A fiber mass is obtained, and the fiber mass is immersed in a liquid to defibrate,
By eluting the total amount of ions, hydrated dititanic acid
A polycrystalline fiber is obtained, and the hydrated dititanate fiber is treated with a solution containing Na ions.
7. between the layers of the hydrated dititanic acid crystal
After adsorbing 5% by weight or more of Na ions, calcination is performed at a temperature of 900 to 1250 ° C.
For producing polycrystalline sodium titanate fibers.