JPH0159215B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing rutile-pridelite-potassium hexatitanate composite fibers having excellent heat resistance, heat insulation properties, chemical resistance, and reinforcing properties. For more details, we use naturally produced rutile sand or anatase sand as is, and utilize the impurities contained therein as active ingredients to create rutile with excellent properties.
The present invention relates to a method for producing pridelite-potassium hexatitanate composite fiber.

Fibrous potassium hexatitanate K ₂ Ti ₆ O ₁₃ has been known as a heat-resistant and heat-insulating material. It is manufactured by the flux method, melt method, slow cooling and sintering method, etc., but in all of these methods, the raw material titanium dioxide is produced by treating ilmenite ore with a sulfuric acid method or a chlorine method. Highly purified products of over 99% purity have been used. Therefore, there was a drawback that the cost of raw materials was high.

An object of the present invention is to provide an inexpensive heat-resistant and heat-insulating material.

The present inventors investigated the composition of naturally produced rutile sand and anatase sand, and found that the main solid solution impurities contained therein were Fe ₂ O ₃ , Al ₂ O ₃ ,
CrO ₃ and these are pridelite K _x (M _x 〓
Ti _8-x ) O ₁₆ (M is Fe, Al, Cr, Ga,
It was found that this is a component that occupies the M〓 seat (x represents 1.5<x<2).

Therefore, these naturally produced impurity-containing materials were mixed with potassium carbonate without removing the impurities.
K ₂ O・n(Ti・M)O ₂ (where n is 1.5 to 2.5, M
represents the impurity metal contained), it harmonically melts like conventional high-purity titanium dioxide, and the melt crystallizes to form a fibrous material having a layered structure. It was found that a rutile-pridellite-potassium hexatitanate composite fiber can be obtained by heat-treating the fiber after extracting the K ₂ O component occupying the interlayer space. The present invention was completed based on this knowledge.

The gist of the present invention is to produce potassium oxide using naturally occurring rutile sand or anatase sand represented by the general formula (Ti, M)O ₂ (where M represents the impurity metal contained) and potassium oxide or by heating. or a mixture thereof, with the general formula K ₂ O.
n(Ti,M)O ₂ (where n is 1.5 to 2.5 and M is the same as above), the mixture is heated to form a melt, and potassium dititanate is extracted from the melt. (K ₂ O・2TiO ₂ ) is formed by cooling and solidifying a fibrous material consisting of crystals with the same layered structure.
This method is characterized in that a part of the K ₂ O component in the fibrous material is then extracted and then heat-treated at a temperature of 800° C. or higher and lower than the melting temperature.

The naturally occurring rutile sand used in the present invention is obtained in the form of sand from alluvial deposits, has a TiO ₂ grade of approximately 95%, and contains Fe ₂ O ₃ , Al ₂ O ₃ , and impurities.
Cr ₂ O ₃ , SiO ₂ , Nb ₂ O ₅ , ZrO ₂ , V ₂ O ₅ , etc. are included, and the content is, for example, Fe ₂ O ₃ 0.6%,
_ZrO2 0.7%, _SiO2 0.6%, _{Cr2O3 0.3} %, _{V2O5 0.7} %,
Nb ₂ O ₅ 0.3%, Al ₂ O ₃ 0.4%. These impurities, particularly Fe ₂ O ₃ , Al ₂ O ₃ , Cr ₂ O ₃ and the like, can be effectively utilized as constituents of priderite. Anatase Sand also has almost the same compositional components.

Since it is desirable that raw materials such as rutile sand react easily with potassium components, it is preferable to use them with fine particle size.

As the potassium component used in the present invention,
Examples include K ₂ O, and potassium compounds that produce K ₂ O upon heating, such as KOH, K ₂ CO ₃ , KHCO ₃ , etc. alone or in mixtures.

Naturally produced rutile sand and the above-mentioned potassium component are mixed at a ratio that produces the general formula K ₂ O・n(TiM)O ₂ (n, M are the same as above), and this is mixed with 1100
When heated and melted at ℃, and this melt is cooled and solidified,
A crystalline fibrous material having a layered structure is obtained.

If n is mixed in a ratio of less than 1.5, a layered structure will not be formed, and if n is 1, fibers will not form. Also, when n is larger than 2.5,
Not only does the melting point become high, but potassium titanate with a composition of K ₂ Ti ₄ O ₉ is produced, making it impossible to separate the fibers. Therefore, the value of n needs to be 1.5 to 2.5, preferably 2.

Fiber forming methods include (1) melt spinning methods, such as methods similar to various methods for forming glass fibers;
(2) A method of draining the molten material into a separate container. (3) A method of rapidly cooling the bottom of a melting crucible. (4) A method of spraying high-pressure steam onto the molten material flowing out from the pushing using the steam spraying method.

When formed into a fiber by cooling and solidifying, it becomes a crystalline potassium titanate fiber having a crystallographic layered structure. When this is treated with water, hot water, or boiling water, the potassium component occupying between the layers is extracted. This treatment is preferably carried out using boiling water for 2 to 3 hours. After extracting a portion of the calcium component, heating to 800°C or higher transforms the layered structure into a tunnel structure, resulting in a rutile-pridelite-potassium hexatitanate composite fiber with good crystallinity.
The heating temperature must be 800℃ or higher,
Melting temperature (rutile: 1840℃, pridelite: approx.
1500℃, potassium hexatitanate: 1370℃) or less,
Preferably it is about 1000°C.

Example 1 Naturally produced rutile sand (Australian
Associated Minerals Consolidated Limited)
NS−grade ( _TiO2 95.9%, main impurities:
_{Fe2O3 0.6} %, _ZrO2 0.7%, _SiO2 0.6%, _{Cr2O3 0.3}
%, V ₂ O ₅ 0.7%, Nb ₂ O ₅ 0.3%, and Al ₂ O ₃ 0.4%. ) with a particle size of 100 to 60 μm was used.

The molar ratio of the rutile sand and K ₂ CO ₃ powder is 2:
They were mixed at a ratio of 1:1. 6 g of this mixture was heated in a 30 ml platinum crucible at 1100° C. for 30 minutes to melt it. The crucible containing this melt was placed on a water-cooled iron plate, and the bottom portion was rapidly cooled and solidified to form fibers. This fiber is K ₂ O.2 (Ti, M) O ₂
(However, M is a metal such as Fe).

The fibers were separated by soaking the crucible in 1 part of cold water for 2 hours, and the fibers were further washed with 1 part of water. Next, it was immersed in boiling water (1) for 30 minutes to remove potassium, washed well with water, and dried at 120°C.
The dried product was heat-treated at 1000°C for 1 hour.

The obtained fibers are 2-5 mm long and 0.01 mm in diameter.
It was ~0.2mm. When this was subjected to X-ray powder diffraction, it was found to be a mixed phase of well-crystalline rutile pridellite and potassium hexatitanate.

The thermal conductivity of each mixed phase at room temperature is rutile.
0.104 (W・cm ^-1・K ^-1 ), pridelite e.g.
The K ₂ Al ₂ Ti ₆ O ₁₆ composition shows a small value of 0.029 (W cm ^-1 K ^-1 ) and potassium hexatitanate 0.037 (W cm ^-1 K ^-1 ), indicating that it is not a composite phase. Even after aging, the thermal conductivity is as low as 0.020 (W·cm ^-1 ·K ^-1 ), and it has excellent heat insulating properties.

The ratio of each phase in this mixed phase changes depending on the amount of potassium and the amount of impurities, and if the raw materials are the same, the ratio can be kept constant by controlling the potassium removal treatment.

Incidentally, a composite fiber can be obtained from naturally produced anatase in the same manner.

According to the method of the present invention, unlike the conventional production of fibrous potassium dititanate, high-purity titanium raw materials are not used, and naturally produced rutile sand or anatase is used as is, so the raw material cost is approximately 1/1/2. 10, it is inexpensive, and the impurities contained in the natural raw materials are reacted to form the pridelite phase, resulting in a composite fiber with good crystallinity of rutile-pridelite-potassium hexatitanate that has excellent heat resistance. It has a good effect.

Claims (1)

[Claims] 1 Naturally produced rutile sand or anatase sand represented by the general formula (Ti, M)O ₂ (where M represents the impurity metal contained) and potassium oxide or a potassium compound that produces potassium oxide by heating, or these and the general formula
K ₂ O・n (Ti, M) O ₂ (where n is 1.5 to 2.5, M
are the same as above), the mixture is heated to form a melt, and from the melt a fiber consisting of a crystalline substance with the same layered structure as potassium dititanate (K ₂ O 2TiO ₂ ) is produced. rutile-pridellite-potassium hexatitanate, which is characterized in that a fibrous material is formed by cooling and solidifying, and then a part of the K ₂ O component in the fibrous material is extracted, and then heat-treated at a temperature of 800°C or higher and lower than the melting temperature. Method for manufacturing composite fibers.