JPH01246139A - Production of titania fiber - Google Patents

Abstract

PURPOSE:To obtain the fibers suitable for plastic filling and reinforcing purposes by forming potassium tetratitanate fibers using a mixture of an amorphous solid from a titanium compound and a potassium compound, and TiO2. CONSTITUTION:A mixture of a titanium compound which converts into TiO2 with heat and a potassium compound which converts into K2O with heat at a molar ratio of 1.5-2.5 TiO2/K2O is melted with heat and rapidly cooled to give an amorphous solid. The product is combined with TiO2 to form a homogeneously mixed powder at a molar ratio of 3-4 TiO2/K2O. Then, the powder is calcined to give potassium tetratitanate. Then, the product is treated to remove all of the potassium, then calcined at 400-1,100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing titania fibers useful as heat insulating materials, friction materials, reinforcing materials, and the like.

[Conventional technology]

As a method for producing titania (TiO2) fibers, a mixture of titanium dioxide (T iOz) and a potassium compound that becomes 2O when heated is used as a starting material, and this is heated and melted, and the melt is cooled to obtain initial After producing a fibrous material made of potassium nititanate crystals (K2O.2TiOz) as silk fibers, the fibrous material is depotassium treated with an acid aqueous solution to extract the entire amount of potassium, thereby producing crystalline titanate fibers. A method is known in which the titania fiber is then converted into titania fiber by performing a firing treatment. In addition, in order to reduce the manufacturing cost, it has been proposed to use naturally produced, inexpensive and easily available rutile sand or anatase sand as a source of titanium dioxide for the preparation of starting materials, instead of highly purified purified titanium dioxide. ing.

[Problem that the invention seeks to solve]

Titania fibers obtained by the above-mentioned conventional manufacturing method generally have a coarse fiber diameter of about 10 to 30 μm, and the fiber morphology (thickness and length) is also irregular and lacks homogeneity. this is,
Titanium oxide thermal fibers, which are primary silk fibers obtained by cooling a heated melt of the starting material, are generally coarse, and their fiber morphology may be affected by local differences in cooling rate during the cooling process (for example, cooling molds). This is because the morphology of the primary silk fiber has a strong influence on the morphology of the final product, the titania fiber. Therefore, in order to obtain titania fibers with fine fiber diameter and low homogeneity, the cooling rate must be precisely controlled in the cooling process of the heated melt to avoid coarsening of the primary silk fibers or variations in their morphology. It is necessary to do this. However, it is extremely difficult to carry out such precise control of the cooling rate in mass production and continuous production.

The present invention provides an improved method for producing titania fibers that solves the problems of the conventional methods described above.

[Means and effects for solving the problems] The method for producing titania fibers according to the present invention consists of a titanium compound that becomes titanium dioxide (T i O2) when heated and a potassium compound that becomes potassium oxide (K2O) when heated. , Ti
A mixture in which the molar ratio of O2/20 to Titanium, T
It is added to iO□/ so that the molar ratio of 0 is 3 to 4 to form a uniform powder mixture, which is fired to produce potassium tetratitanate fibers, and then subjected to a potassium removal treatment. Extract the entire amount of potassium, then add 400 to 1100
It is characterized by being fired at 'c.

Hereinafter, the method of the present invention will be explained in order of steps.

As the titanium dioxide source for preparing the starting material in the present invention, that is, the titanium compound that becomes titanium dioxide by heating, highly purified titanium oxide, synthetic rutile, titanium slag, naturally produced rutile sand, anatase sand, etc. are used. used. Naturally produced rutile sand and anatase sand are inexpensive titanium dioxide raw materials represented by the general formula (Ti, M)O□ [where M is an impurity element].

Its composition is approximately 95% TiO□, with Fe as an impurity.
zOz, S ioz, A/! zo:+, Zr0z, Cr
Contains small amounts of zOh and the like.

The potassium compound blended into the titanium compound is typically 2CO, and others include KOH.

Examples include KNO, 2CO, 2O, etc.

The mixing ratio of titanium compound and potassium compound is TiO2
/K2O molar ratio of 1.5 to 2.5 (potassium titanate equivalent composition) is suitable, and heating and melting is approximately 9
It can be carried out at a relatively low temperature range of 50 to 1100°C.

By heating and melting the above mixture in a melting furnace and subjecting the melt to a rapid cooling process (for example, at a cooling rate of 10"C/sec or more), the formation of potassium nititanate crystals is prevented and the amorphous solidified product is The quenching treatment is carried out, for example, by the twin roll method. While rotating the metal twin rolls at high speed,
By flowing the melt into the gap between the twin rolls, a flaky amorphous solidified material can be efficiently obtained.

The amorphous solidified product obtained by the above quenching treatment is mixed with titanium dioxide (e.g. rutile sand, highly purified titanium oxide powder, etc.), and the molar ratio of TiO,/20 is 3 to 4 (potassium tetratitanate). This is ground into a homogeneous powder mixture using a disk mill or the like, and then subjected to a firing process. Although the particle size of the powder is not particularly limited, the finer the particle, the better in order to increase the yield of fibers and grow thin and long fibers. The preferred particle size is 10 μm or less. The calcination treatment is achieved by maintaining the temperature at 800 to 1200°C for an appropriate period of time (for example, 30 minutes). In this firing process, titanium dioxide is solid-dissolved in the amorphous solidified particles, and potassium tetratitanate fibers (K2O.4TiOz) are produced from the solid solution as primary silk fibers. The fibers are thin and have a uniform fiber morphology. The potassium tetratitanate fiber obtained in this way is
As it is, it appears in a bundle-like aggregated state with some fibers attached to each other, but if this is defibrated, for example by suspending it in water and stirring it with a mixer, the fibers are separated into individual fibers. will be collected as.

In addition, the molar ratio of TiO2/K2O of the starting material was adjusted to a high value of 3 to 4, and the melt was cooled to form an amorphous fK solidified product (composition equivalent to potassium tetratitanate), which was heat-treated. Although it is possible to produce potassium tetratitanate fibers by
Due to the extremely high carbon content, the melting furnace material may be eroded and its durability may be reduced.
In addition, the quality of titania fibers deteriorates due to the contamination of melted furnace materials, and the variation in the morphology of the obtained titania fibers increases due to a decrease in the amorphization rate of the melt (formation of crystalline phase). Therefore, it cannot be adopted.

The potassium tetratitanate fiber obtained through the above firing treatment is subjected to a potassium removal treatment to extract the entire potassium content, thereby converting the fiber composition to a titania-equivalent composition. The depotassium treatment can be carried out using water or an acid aqueous solution, preferably an acid aqueous solution (for example, a 2-10% sulfuric acid aqueous solution) as a washing liquid.

In addition, in the above process, the step of adding titanium dioxide to the amorphous assimilate and firing the mixture to generate potassium tetratitanate fibers is omitted, and for example, the amorphous solidified product is directly subjected to dealkalization treatment. After converting it to a composition equivalent to titania, heat treatment is applied to convert it to the crystal structure of titania, or
Alternatively, by reversing the order of the depotassium treatment and heat treatment, the amorphous solidified material (composition equivalent to potassium titanate) is converted into crystalline potassium dititanate fiber, and then the entire potassium content is extracted and the composition is equivalent to titania. If the composition is converted, the process will be simplified, but in the former case, the amorphous solidified material does not have the layered structure of potassium nititanate or potassium tetratitanate, so water washing and acid treatment are necessary. In the latter case, the rate of fiberization from amorphous assimilates was extremely low, so the yield of titania fibers was also extremely low, and the fibers were coarse and lacked homogeneity. Therefore, neither of them can be adopted.

As mentioned above, the chemical composition of the fiber obtained by depotassium treatment of potassium tetratitanate fiber corresponds to the titania composition, but the crystal structure is a trace of the original layered structure of potassium tetratitanate. This is dehydrated and
After drying, it is subjected to a firing treatment to convert the crystal structure of potassium tetratitanate to that of titania. The firing treatment is preferably achieved by heating and holding at 400 to 1100°C for an appropriate time (for example, 30 minutes). In this case, if the firing process is performed at a temperature of 800'C or less, titania fibers having an anatase phase can be obtained, and if the firing process is performed at a temperature exceeding 800°C, chiknia fibers having a rutile phase can be obtained.

Unlike the conventional method in which potassium nititanate fibers are immediately produced as primary silk fibers from a molten material obtained by heating and melting a starting material, the present invention rapidly cools the molten material to once amorphize it, and then solidifies the amorphous material. In addition to producing potassium tetratitanate fibers as primary silk fibers from a mixed powder of titanium dioxide and titanium dioxide, the composition was changed by dealkalization and the crystal structure was changed by firing.The resulting titania fibers had a diameter of approximately The diameter is significantly smaller and longer at 0.1 to 1 μm compared to conventional ones (10 to 30 μm), and the variation is small, and the yield is about 60% or more.

〔Example〕

"Fuzashi" Raw (1) Raw material preparation (1) Titanium compound: Natural rutile sand (produced in Australia) T t Oz: 95.6%, FezOz
: 0.6%, p: o, ox%, S: 0.02%, Zr0
z: 0.1%.

cr, o,: 0.3%, 5io2: o, 6%, VzQ5
:0.7%, Nb2O5:0.3%, Affi20
．． :0.4%.

MnO: 0.01%, CaO: 0.03%, MgO: 0
．． 03%, the remainder being trace amounts of Co, Ga, etc.

(2) Potassium compound: K2CO2 (purity 99.5%)
(3) TiO2/K2O (molar ratio): 2.0[11
)Put the heated molten raw material mixed powder into a platinum crucible,
Heat for a minute.

(III) Quenching process The melt is allowed to flow down onto twin metal rolls rotating at high speed to obtain a solidified product in the form of flakes.

The solidified product was confirmed to be amorphous by X-ray diffraction.

[■] Firing treatment Rutile sand (same as that used for raw material preparation) was added to the above amorphous solidified material as titanium dioxide powder, and Ti0z/
Mix so that the molar ratio of KzO is 3.0, and grind with a disk mill to obtain a uniform powder mixture (average particle size: 5 μm)
Then, the powder mixture was placed in an aluminum crucible and heated and held at 1000° C. for 0.5 hour.

The above fired product was poured into 10 (amount (weight ratio)) of water, defibrated in a mixer for 15 minutes, dehydrated and
It was dried to obtain potassium tetratitanate fibers.

Its diameter is 0.2-1 μm and length is 5-20 μrn.

(V) Depotassium treatment A sulfuric acid aqueous solution (5%) is used as a washing liquid, and the potassium tetratitanate fibers obtained above are immersed in this, 1 g of fiber/10 cc of washing liquid.
), it took about 60 minutes to elute the ° ions, and then it was washed with water and dried.

(Vl) Put the depotassium-treated fibers into an aluminum crucible,
It was charged into a furnace set at 0°C, and the firing process was completed in about 0.5 hours.

X-ray diffraction shows that the obtained fibers are titania fibers (anatase phase). The yield from the starting material (weight of fiber obtained/weight of raw material x 100) is 61%.

Fiber form: diameter 0.1-1 μm, length = 5-20 μm
Titania fibers (rutile phase) were obtained according to the same steps and conditions as in Example 1, except that the test was carried out for 0.5 hours.

Fiber morphology: diameter 0.1-1 μm, length 5-20 μm, yield: 60%.

〔Effect of the invention〕

Compared to conventional titania fibers, titania fibers produced by the method of the present invention have smaller diameters, longer dimensions, and greater homogeneity, so they can be used in a variety of applications, such as heat-resistant materials, insulation materials, friction materials, etc. It is suitable as a filling material, a filter material, a reinforcing material, etc., especially as a filling reinforcing material for plastics.

Claims (1)

[Claims] 1. A mixture of a titanium compound that becomes titanium dioxide (TiO_2) when heated and a potassium compound that becomes potassium oxide (K_2O) when heated so that the molar ratio of TiO_2/K_2O is 1.5 to 2.5. Melt by heating, rapidly cool the melt to obtain an amorphous solidified product, and add titanium dioxide to the amorphous solidified product so that the molar ratio of TiO_2/K_2O is 3 to 4 to form a uniform powder mixture. titania, which is fired to produce potassium tetratitanate fibers, subjected to depotassium treatment to extract the entire potassium content, and then fired at 400 to 1100°C. Fiber manufacturing method.