JPH0849119A - Production of sodium titanate fiber - Google Patents

Abstract

PURPOSE:To facilitate the opening treatment of especially a fibrous mass, prevent fibers from breaking and powdering and produce a sodium titanate fiber having a fiber size suitable as a reinforcing fiber, etc. CONSTITUTION:This method for producing a sodium titanate fiber comprises passing a starting raw material composition containing TiO2 and K2O (at 1.5-2.5 molar ratio of TiO2/K2O) through a step for thermally melting the starting raw material composition, a step for cooling the resultant melt, providing a fibrous mass of a potassium dititanate fiber, subsequently wet opening and simultaneously eluting the total amount of K ions in the fiber, then a step for adsorbing Na ions (in an amount adsorbed of >=8.5wt.%) in the fiber with an aqueous solution of caustic soda, etc., and a step for baking treatment of the resultant fiber (at 900-1250 deg.C) and providing the platy polycrystalline sodium titanate fiber.

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 which is useful as a base material for sliding members, a reinforcing material for plastics, a filler for resin paints and the like.

[0002]

2. Description of the Related Art Titanium typified by sodium hexatitanate
Sodium acid fiber (Na₂O ・ n H ₂O, n = 1
6) has excellent wear resistance, heat resistance, heat insulation, reinforcement, etc.
Synthetic inorganic compound fiber, recently replaced with asbestos fiber
As a product, various fields of engineering application have been tried. Six
Sodium tannate fiber is made of titanium oxide (TiO 2₂)Also
Is a titanium compound that becomes titanium oxide when heated, and
Thorium (Na₂O) or sodium oxide by heating
Made with a mixture of
Is built. Melting known as one of its industrial manufacturing methods
According to the method, the starting material is TiO 2. ₂/ Na₂O molar ratio
The composition is adjusted to about 3 and melted by heating, and the melt is cooled.
Sodium trititanate fiber (Na₂Ti₃O₇)
Fiber lump consisting of
By eluting part of the Na ions in the fiber with the solution
Is a hydrated titanium compound with a chemical composition equivalent to that of sodium hexatitanate.
A process in which the composition is converted to sodium titanate and then baked.
After that, the target sodium hexatitanate fiber was obtained.
Be done.

[0003]

In the above manufacturing method, since a high temperature of about 1300 ° C. is required for the heating and melting process of the starting material, the maintenance load due to the corrosion damage of the melting device is large. Further, 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 likely to be broken or pulverized during the defibration process, the variation in the shape and size of the final product fiber becomes large, and the fiber yield is low.
Moreover, a large amount of acid is required for the elution treatment of Na ions, and it is rather difficult to control the elution amount of Na ions. The present invention has been made for the purpose of solving the above-mentioned problems relating to the manufacturing process and fiber quality of sodium titanate fibers by the melting method.

[0004]

The method for producing sodium titanate fibers according to the present invention comprises: TiO ₂ or Ti by heating.
A titanium compound which produces O ₂ and a potassium compound which produces K ₂ O or K ₂ O by heating are mixed with TiO ₂ / K ₂
The mixture, which was mixed at a molar ratio of O of 1.5 to 2.5, was heated and melted, and the heated melt was cooled to obtain a fiber lump composed of potassium dititanate fiber. The fiber lump was placed in the liquid. By immersing and defibrating and eluting the total amount of K ions in the fiber, hydrated dititanic acid polycrystalline fibers are obtained, and the hydrated dititanate fibers are treated with a solution containing Na ions. Thus, after adsorbing 8.5% by weight or more of Na ions between the layers of the hydrated dititanic acid crystal,
It is characterized in that the baking treatment is performed at 00 to 1250 ° C.

[0005]

The starting material in the production method of the present invention is prepared by mixing a titanium compound and a potassium compound in a ratio of TiO ₂ / K ₂ O (molar ratio) of 1.5 to 2.5. The heating and melting process is achieved in a relatively low temperature range of about 1150 ° C or lower. The fibers of the fiber mass obtained by cooling the heated melt are potassium dititanate crystals, which have a layered structure and undergo a vigorous hydration reaction when immersed in water, so the defibration treatment Is easily achieved and does not require a forced defibration process which causes breakage and pulverization of the fiber. Sodium titanate fibers according to the present invention (general formula “Na ₂ O.
n H ₂ O ”. n = 1 to 6) has a crystal phase that varies depending on the amount of Na ions adsorbed in the adsorption treatment, and sodium hexatitanate fiber (Na ₂ Ti ₆ O ₁₃ ), tetrasodium pentatitanate fiber (Na ₂ Ti ₄ O) ₉ ), or sodium trititanate fiber (Na ₄ Ti ₅ O ₁₂ ) or the like, or a composite fiber thereof. The fiber is a plate-like polycrystalline fiber having a small variation in shape size, and has 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 Material] The starting material is TiO ₂ or a titanium compound that produces TiO ₂ by heating (eg, purified anatase, titanium oxide hydrate, natural rutile ore, etc.),
It is prepared by blending K ₂ O or a potassium compound (eg, potassium carbonate, potassium hydrogen carbonate, potassium hydroxide, etc.) that produces K ₂ O by heating. The starting material TiO ₂ / K ₂ O (molar ratio) is set to 1.5 to 2.5, because in this composition range, heating and melting can be achieved in a relatively low temperature range, and it is a primary phase fiber. This is because potassium titanate fibers can be efficiently produced.

[Heat melting and cooling solidification treatment of the melt]
The heating and melting treatment of the starting material is achieved by heating and holding the material in the temperature range above the melting point for an appropriate time (generally 0.5 to 4 hours). The heating temperature varies depending on the blending 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, copper bethel) and cooled and solidified to obtain a fiber lump in which fibrous potassium dititanate crystals are gathered in a bundle as an initial phase.

[Defibration treatment] By immersing the fiber mass in water for an appropriate time (about one night), delamination / cleavage of the crystal layers due to the hydration swelling reaction of the potassium dititanate crystal occurs, and the fiber mass is efficiently generated. Achieve defibration. If desired, stirring can be added to promote defibration, but gentle stirring is sufficient,
Strong agitation that forces the fibers to separate by the action of shear forces is not required. Therefore, there is little breakage or pulverization of the fiber, and a homogeneous polycrystalline fiber having a high aspect ratio and uniform fiber size can be obtained.

[K ion elution treatment] An acid aqueous solution, for example, a 0.8% or more aqueous sulfuric acid solution, a 0.8% or more hydrochloric acid solution is used as a treatment liquid, and the potassium dititanate fiber is dipped in the treatment liquid to form a fiber. The total amount of K ions in the sample is eluted. If desired, a mild stirrer 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 elution of Na ions from sodium dititanate fiber, and the elution amount can be controlled relatively easily. This is because potassium dititanate crystals (having a continuous layered structure of TiO ₅ ) easily cause a hydration reaction.

[Sodium Adsorption Treatment] The adsorption amount of Na ions (sodium content of the fibers) to the hydrated titanic acid fiber from which K ions have been eluted (sodium content of the fiber) is not less than 8.5% by weight. And, in the subsequent firing step, the precipitation of the titania crystals is accompanied, and it becomes impossible to obtain the fibers of the sodium titanate crystal single phase. N
Adsorption amount of a ion is 8.5% by weight (TiO ₂ / Na ₂ O =
In the case of 6.0), the final fiber obtained by baking this is sodium hexatitanate crystal (Na ₂ Ti).
₆ O ₁₃ ) Fiber. If the amount of Na ions adsorbed is further increased, sodium titanate fibers other than sodium hexatitanate crystals are obtained. For example, when the amount adsorbed is about 15.2% by weight, sodium trititanate fibers (Na ₂ Ti ₃ O ₇ ) ,
When the adsorption amount is about 17.6% by weight, tetrasodium pentatitanate fiber (Na ₄ Ti ₅ O ₁₂ ) is obtained, and when the adsorption amount is adjusted to an intermediate region between them, a plurality of crystal phases are mixed. Composite fibers, for example, when the adsorption amount 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 it in the treatment liquid for an appropriate time.
The adsorption amount of Na ions can be controlled by the concentration of the treatment liquid, the liquid amount, pH, the treatment time, and the like.

[Baking Treatment] The fibers adsorbing Na ions have a chemical composition equivalent to that of sodium titanate crystals, but the crystal structure is that of the precursor potassium dititanate crystal. It retains the remnants of the structure. The firing treatment is a treatment for converting the structure of this into a crystal of sodium titanate. The firing treatment is achieved by heating and holding in the temperature range of 900 to 1250 ° C. The lower limit of the treatment temperature is 900 ° C., because the crystallinity of the obtained conjugate fiber is poor and chemically unstable at lower temperatures, and the upper limit of 1250 ° C. is hexatitanium. This is to prevent the sodium acid crystal from melting. The conversion reaction of the crystal structure is achieved by holding in the above temperature range for several minutes, but since the treatment time is related to the sintering of the crystal grains and the fiber strength due to the sintering, a few hours (for example, from the point of increasing the fiber strength) It is desirable to perform the treatment for 1 to 5 hours.

[0012]

【Example】

[1] Preparation of Starting Material Purified anatase powder (purity: 99%) and potassium carbonate powder (purity: 99%) were mixed at a ratio of TiO ₂ / K ₂ O (molar ratio) of 2 and uniformly mixed. mixture. [2] Heat melting and cooling solidification of melt Put the starting material in a platinum crucible and heat and hold 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 composed of potassium dititanate fibers. .

[3] Wet disentanglement and K ion elution treatment Fiber mass was immersed in water and left overnight to achieve disentanglement. Then, industrial sulfuric acid (62.5%) is added to elute all the K ions in the fiber to obtain a hydrated titanate fiber. Liquid volume:
100 times amount (weight) with respect to solid content, addition amount of sulfuric acid: 80% by weight with respect to solid content, treatment time: 4 hr.

[4] Adsorption treatment of Na ions After dehydrating and drying the hydrated titanic acid 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) Treatment time: 4Hr [5] Firing treatment Fibers recovered from Na adsorption treatment liquid are dehydrated and dried (200
After ℃ -1Hr), baked at a temperature of 1050C (treatment time: 2Hr).

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-shaped 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. In addition, the fiber mass obtained by cooling the melt can be easily disentangled, the breakage and pulverization of the fiber in the disentanglement treatment can be prevented, and the homogeneity of the shape and size of the fiber can be 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 coating, and the like, and is a plate-like polycrystalline fiber of a slightly larger size, unlike ultrafine single crystal fiber. So, there is a problem in use such as whiskers (for example,
It is possible to avoid the problems of uniform kneading into the resin and the generation of extra fine fiber pieces which are harmful to the environment hygiene. Also, the high aspect ratio provides an excellent reinforcing effect.

Claims (1)

[Claims] 1. TiO₂Or TiO by heating₂Live
Titanium compound and K₂O or K by heating₂O
The potassium compound that produces₂/ K ₂O mole
Heat the mixture blended in a ratio of 1.5 to 2.5
Melts and heats the melt to cool and consists of potassium dititanate fibers
A fiber lump is obtained, and the fiber lump is immersed in a liquid to be defibrated and K in the fiber
By eluting the total amount of ions, the hydrated dititanic acid
Polycrystalline fiber was obtained, and the hydrated dititanate fiber was treated with a solution containing Na ions.
As a result, the hydrated dititanic acid crystals were separated between layers of 8.
After adsorbing 5% by weight or more of Na ions, a baking treatment is performed at a temperature of 900 to 1250 ° C.
Method for producing sodium titanate polycrystalline fiber.