FR2555156A1 - PROCESS FOR THE PREPARATION OF MODIFIED TITANIC ACID COMPOUNDS - Google Patents

Abstract

THE INVENTION RELATES TO A PROCESS FOR THE PREPARATION OF MODIFIED TITANIC ACID COMPOUNDS. THIS PROCESS CONSISTS OF HEATING, IN A NON-OXIDIZING ATMOSPHERE, A MIXTURE OF ONE OR MORE COMPOUNDS OF TITANIC ACID AND ONE OR MORE CARBIDES. THE PROCESS IS SIMPLE AND SAFE AND THE MODIFIED TITANIC ACID COMPOUNDS OBTAINED SHOW GOOD CONDUCTIVITY AND MODIFIED COLOR. APPLICATION TO THE PRODUCTION OF CONDUCTIVE MOLDED ARTICLES.

Description

The present invention relates to a method of preparing

  of modified titanium acid compounds.

  Recently, alkaline titanate compounds and alkaline earth titanate compounds have gained attention as reinforcing materials for ceramics and composites, and have found applications as various industrial materials. However, it is still

  demand to develop composite materials function-

  using heat resistance and suitability

  strengthening of the titaniumic acid compounds, in order to

  conduct conductivity and to color these compounds of the acid

  titanic by subjecting them to a metamorphosis.

  Thus, it is an object of the present invention to provide a novel process for imparting a conductive character to the compounds of titanic acid and coloring these compounds in them.

  subject to a modification or "metamorphosis".

  The present invention provides a method of preparing

  modification of modified titanium acid compounds, which comprises heating, in a non-oxidizing atmosphere, a mixture of: (1) a titanic acid compound or a eutectic mixture of at least two titanic acid compounds selected from:

  (a) an alkali metal titanate compound

  felt by the formula: Ma2O. n TiO2. m H2O (I) wherein Ma is an alkali metal, n is an integer from 1 to 10, and m is 0 or an integer of 1 to 10, and (b) an alkali metal titanate compound -terrous represented by the formula: MbO. nTiO2. mH2O (II) wherein Mb is an alkaline earth metal, and n and m are as susmintened, and

  (2) a carbide or a mixture of at least two carbides

  characterized by the formula: C (M) z (III) wherein M is an element, with the exception of carbon, selected from Groups III, IV and V of the Periodic Table, and z is an integer corresponding to valence The method of the present invention has the following advantages:

  (1) The change of shade shade and / or the modification

  Conductivity conferring on the titanic acid compounds can be effectively achieved without causing alteration of other properties such as

  to the heat of the titanium oxide compounds.

  (2) The treatment for the modification is simple and very safe because there is no need for heating in a hydrogen atmosphere. (3) Any separation step of the carbide used as

  starting material and remaining in the titanium

  The modified nickname obtained is useless. Substances from this starting material have excellent heat resistance and their conductivity is not diminished, and thus the product containing these substances can be sintered

as is.

  The alkali metal titanate compounds represented by the aforementioned formula (I) include, for example, anhydrides and hydrates of lithium titanate, sodium titanate, potassium titanate, etc. Of these, potassium titanates, in particular K20.4TiO2, K20.6TiO2, K20.8TiO2 and their hydrates, which are in the form of fine fibrous crystals and have excellent resistance to oxidation, are preferred for industrial applications. heat and excellent buildability when used

for composite materials.

  The alkaline earth metal titanate compounds represented by the above-mentioned formula (II) include, for example, anhydrides and hydrates of calcium titanate, magnesium titanate, barium titanate, strontium titanate, and the like. According to the present invention, the compounds represented by the above-mentioned formula (I) or (II) may be used either individually or in the form of a mixture or a

  eutectic mixing of at least two of them.

  The carbides represented by formula (III) above

  which are used in the present invention include

  those which are well known such as boron carbide, silicon carbide, titanium carbide, germanium carbide, tin carbide, lead carbide, phosphorus carbide, etc. Of these, boron carbide, silicon carbide, titanium carbide and the like are preferred. They are used individually or in the form of a mixture of

least two of them.

  Although the mechanism of modification of the titaniumic acid compounds in the process of the present invention is not fully understood, it is believed that when a mixture of the titaniumic acid compound and the carbide of the formula (III) is heated in an atmosphere non-oxidizing, the carbide can act as a deoxidizer and cause a reductive modification of the compound

  of titanium acid and give a product with good

  and a modified color, so that the carbide can be

  also be dehydrogenated or oxidized without affecting the electro-

  conductivity of the titanium acid compound.

  With regard to the mixing ratio of the titaniumic acid compound and the carbide of formula (III), both

  components can be mixed in a ratio such as the name-

  number of carbon atoms in the carbide is from 0.01 to 10 times, preferably 0.1 to 3 times the number of oxygen atoms in the titanium acid compound with the exception of the at least one oxygen constituting any water of crystallization contained therein, although the ratio may vary depending on the type of titanium acid compound and the carbide used and also

  depending on the final application of the product obtained. When the quantity

  carbide is too low, difficulties are likely

  appear to achieve the purpose of this invention.

  tion. Moreover, when the proportion of carbide is too high, the mixture of starting materials becomes difficult and

  Heating requires a lot of energy.

  If it is necessary to separate excess carbide remaining after the modification of the titanium acid compound, the

  separation can be made using the difference in den-

  between the titanium acid compound and the carbide. However,

  the carbide remaining in the modified product does not generally limit

  not use the product.

  The non-oxidizing atmosphere used in the present invention means a non-oxidizing atmosphere substantially containing more than 90% by volume of one or more reducing gases such as carbon monoxide, or inert gases

  such as nitrogen, helium or carbon dioxide. We pre-

  in particular a nitrogen gas atmosphere or a

  atmosphere of gaseous carbon dioxide.

  The heat treatment according to the present invention is generally carried out between 500 and 15000C for 2 to 600 minutes, preferably between 800 and 1200 C for 5 to 180 minutes, although the treatment conditions may vary according to the

  type of starting materials and the use of the product

  sultant. No special oven is needed for the treatment

  temperature, and any heating oven can be used

usual fage.

  Although the heat treatment can be carried out by heating a simple mixture of the titanium acid compound and the carbide as it is, it is preferable to use a uniform mixture of the titanium acid compound and the carbide, both in the form of of fine powder, so that the titanium acid compound comes into suitable contact with the carbide. In addition, it is advantageous to eliminate the air contained in the

  mixture, in particular the mixture of titanium acid compound

  and carbide powder, or to replace the air with a

  non-oxidizing, as far as possible. The air contained in the mixture could consume the carbide before the end of the modification of the titanium acid compound, require a prolonged duration of the modification and an excess of the carbide, and

  be the cause of an incomplete or non-uniform change.

  Therefore, it is preferable, in this

  to remove air from the mixture of the titanium

  and 1) a process comprising first compressing the mixture under reduced pressure into a compact mass and then heating the mass, or 2) a method of incorporating a binder into the mixture.

  which is decomposed into non-oxidising gases by heating,

  sea the mixture into a compact mass, if necessary, then

  heat the mixture or the compact mass.

  The binder which is decomposed into non-oxidizing gases by heating means compounds which contain, as a main component, one or more elements selected from hydrogen, carbon and nitrogen, and are decomposed by heating to water vapor gaseous carbon dioxide, carbon monoxide or nitrogen gas. The binder can be arbitrarily selected from water, ammonia and amino compounds, nitrogen compounds, hydrocarbons, carbohydrates and various synthetic resins, or a mixture of at least one of them, provided it is in liquid form at room temperature or at the time of die casting and can exert the bonding action necessary for molding the mixture of the titanium acid compound and the carbide. However, for reasons of economy and from the point of view of the applications of the product, examples are water, hydrocarbon compounds, glycerol, ethylene glycol, carbohydrates such as starch, urea derivatives, a polyvinyl alcohol, a butyral resin, a polyvinyl acetate resin, a

  atactic polyethylene, a liquid polypropylene, a poly-

  butene, acrylic resin, etc. The amount of these binders to be used can vary without limitation according to the type of

  of titanium and carbide and the application of

  final cation. However, it is preferable to use the binder in an amount not exceeding 300 parts by weight (hereinafter "parts" refers to parts by weight), more preferably not more than 100 parts by weight.

  parts of the total amount of the tita-

  and carbide. Too much binder is undesirable because it requires excessive heating during

  the modification and elimination of decomposition products

from the remaining binder.

  By heating in a non-oxidizing atmosphere, the aforementioned binder produces carbides remaining as ash, most of which, however, are harmless to the electroconductivity modification, although they are colored black. Therefore, it is unnecessary to specifically separate and remove the binder decomposition products prior to practical use of the binder.

  product, provided that the binder is used in one

appropriate portion.

  According to the present invention, it is also possible

  sible to use a combination sinter binder, which

  frit and serves as a binder of the mixture of titanium

  and carbide during heating.

  Moreover, it is possible, according to the present invention

  to obtain a modified molded or compact

  seducing a conductive character, by molding a mixture of

  of titaniumic acid, carbide, a binder of fried

  and, if necessary, a binder required for molding and then heating the molded article in a non-oxidizing atmosphere

  in order to simultaneously perform the modification of the

  titanium acid and modification and molding by

the sinter binder.

  For the molding of the mixture of acid compound

  tane, carbide and binder, any

  conventional molding method in which a uniform mixture, prepared by a conventional method and heated to the temperature

  ambient temperature or at a temperature that does not cause

  breakdown or decomposition of the binder, is subject to

  following molding processes:

  (1) a method using a compression molding machine;

  in which the mixture is introduced into a mold and then compressed,

  (2) a method using a granular molding machine

  wherein the mixture is placed in a granulator to obtain granules or flakes, (3) a method using a pelletizer, wherein the mixture is pellet, and (4) a method using pressure rollers, wherein

  the mixture passes between the rolls giving a sheet.

  However, it is preferable, from the point of uniformity and heating efficiency during the modification, to perform

  molding in such a way that the resulting molded part

  feels a larger contact area. In general, the temperature gradient of the molded part is greater as the molded part is thicker. It is necessary

  to adjust the thickness of the molded parts to avoid

  regularity of the heating, that is to say an irregularity of the metamorphosis. The invention is further illustrated by the following Examples. However, these examples are not indicated

  that illustrative and in no way limiting the invention.

Example 1

  3 g of potassium titanate (Otsuka Chemical Co., Ltd., Japan, Tismo D) and 1 g of powdered silicon carbide are mixed well in a mortar. We place the mixture in a

  30 ml crucible in the shape of a nacelle made of very pure alumina.

  The air in the crucible is displaced by nitrogen gas. The crucible is placed in a very pure alumina tubular electric furnace (internal diameter of the tube: 50 mm, length: 1 meter) maintained at 1100 C, heated for 2 hours under current

  50 ml / min of nitrogen, cooled to room temperature

  under a stream of nitrogen then removed. We obtain tita-

  Modified potassium nate whose color has turned pale blue.

  For comparison, without the addition of silicon carbide powder, the potassium titanate is heated and modified under the same conditions as above. Titanate

  resulting potassium is white and does not change

of color.

  Examples 2 to 6 and Comparative Example 1: A mixture of potassium titanate and powdered silicon carbide, prepared by the same, was compressed using a 15 MPa pressure pellet machine for 30 minutes under vacuum. method as in Example 1, to obtain tablets with a diameter of 10 mm and a thickness of 1 mm

  consisting of potassium titanate and silicon carbide.

  The tablets thus prepared are placed on a platinum boat and then in the same electric furnace as in Example 1. The air contained in the nacelle-shaped crucible is displaced by nitrogen gas for 30 minutes, and then the tablets are heated at temperatures and for times indicated in Table I under a stream of nitrogen. The properties of the resulting tablets which consist of mixtures of metamorphosed potassium titanate and silicum carbide are shown in Table 1. By comparison, the results obtained with titanate of

  potassium without silicon carbide are indicated under the heading

  Brick of "Comparative Example 1" in Table I.

Table I

  Condition of metamorphosis Color Conductivity ExemleTemp- Duration Before After Before After

  erature (min meta-meta-

N (min) mt is

Ngo (1C mormor- mor-

  (OC), phose phose Iphose phose 2 1000 30 White Violet greyish bluish no or 3 1050 20 White Violet - no yes greyish blackish i 4 1050 30 White Violet no yes greyish blackish 1100 15 White Violet no yes greyish blackish 6 1150 10 White Violet no yes grayish blackish

Example

  1050 White White non-tif greyish grayish

1

Note 1).

  In Table I, conductivity is evaluated with a "Digital Multimeter TR 6841" apparatus (manufactured by Takeda Riken Co., Ltd., Japan). The term "no" refers to the case where the resistance value was not lower than 106 when the electrodes were contacted on both sides of the tablet. The term "yes" refers to the case where the resistance value does not

was greater than 103 _.

Example 7

  4 g of potassium titanate (same as in Example 1) are mixed well in a mortar, 1 g of

  silicon and 0.5 g of liquid paraffin as binder,

  duit the mixture into a mold, compress it under pressure

  2 MPa for 3 minutes to obtain a cylindrical molded article.

  than 10 mm in diameter and 40 mm in length.

  The resulting molded article is placed in a platinum crucible in the form of a nacelle. The boat is deaerated for 30

  minutes, the air is replaced by nitrogen gas, and

  at 1150 ° C. for 30 minutes under a stream of nitrogen of 50 ml / min to obtain a cylindrical product of blackish violet color.

  presenting some gaps. The weight loss is 15%

  port to the weight of the original material.

  Both sides of this cylindrical product are coated with a silver paste, and the conductivity is measured by the same method as in Example 2 and found to be 2.8 × 10 -3. Resistivity volume is 5.50 x 1025 cm, calculated by the following equation: Resistivity Measured resistance (I) x electrode surface (cm2) volume distance between electrodes (cm) For comparison, the operations of the Example are repeated 7 without silicon carbide and a greyish white product is obtained

  which is the same color as the starting material before heating.

  wise. When no binder is used, no article is obtained.

  compression molded wrench at 2.0 MPa for 3 minutes

  and the product sags very easily.

  Examples 8 to 17 Molded parts were prepared by the same method as in Example 7, except that the types of titanium acid compounds, the

  silicon, the types and quantities of binders, the temperatures

  erations and heating times, as shown in Tables II and III. The results of these modifications are

shown in Table III.

  Examples 16 and 17 are repeated except that silicon carbide and liquid paraffin are omitted. These are the comparison examples 2 and 3 whose results

  are given in Tables II and III.

Table II

  EaaMJe Cmpos Titanium Binder Acid! Ca bre | Lnt Type2rtity | 2ope ntit6 Type Quantity ______g_ T1 (,, (-) _____ 8 Titanate of potas- 4 Carbide of 0.5 Paraffin 1.0 sium (Tismo D) liquid silicon

9 I. 4. 1 "1.0

  4 "1 Ethylene 1.0 Glycol 11 4" 1 Water 1.2 12 4 Carbstone of 2 Paraffin 1, 3 Liquid Titanium 1.3 13 Potato Titrate Carbide d - Polybutene 0.6 Si (Triso L) Silicon 14 4 Carbide of 2 Resin 0.3 14. Titanium Acrylic Titanate 4 Carbide 1 Paraffin 0.8 Barium. liquid silicon

16 4 1 0.8

17 4 2 1 _

Titmarate 4eC r ued aafn

4

Ex3 s lq 4 i d e

255515 6

Table III

  Conditions Resistance of Color of the article Example metamorphosis m3le n ,, - JL Tuérar ur eDr Before After

(Ca) npmetasrmetamor

  phose phose 8 900 30 White Violet 6.9 x 106 pale greyish 9 | 1100 30. Violet 2.4 x 104 bluish. 1150 20 "violet 4.7 x 103 intense il 1 1100 S0 Purple 7.1 x 104 blueish 12 1150 30 Purple- Violet 1.4 x 100 black black

____ ____ __ .. _. __ _ _ _

  13 1GO 30 Violet 3.7 x 104 bluish 14 1150 20 Purple 1.9 x 10 blackish '1000 30 "Gray 9,1x 10 16 1200 30 Brown 4.2 x 105 dark 17 I 1200 30 3, x 10

Example |

comparative 120030 White

gray-tre -

3,100 30

Claims (12)

  Process for the preparation of modified titanium acid compounds, characterized in that it consists in heating, in a non-oxidizing atmosphere, a mixture of (1) a titanic acid compound or an eutectic mixture or mixture of at least two titanium acid compounds selected from: (a) an alkali metal titanate compound represented by the formula: Ma2O. nTiO2. mH2O (I) wherein Ma is an alkali metal, n is an integer from 1 to 10, and m is 0 or an integer of 1 to, and   (b) an alkaline earth metal titanate compound   felt by the formula: MbO. nTiO2. mH2O (II) wherein Mb is an alkaline earth metal and n and m are as mentioned above, and   (2) a carbide or a mixture of at least two carbides sensed by the formula: -   C (M) z (III) wherein M is an element, with the exception of carbon, selected from Groups III, IV and V of the Periodic Table, and z is a number corresponding to the value of M. 2. Method according to claim 1, characterized in that the titanium acid compound and the carbide constituting the mixture are mixed in a ratio such that the number of carbon atoms in the carbide is from 0.01 to 10 times the number of atoms of oxygen of the titaniumic acid compound, except   oxygen atom (s) constituting any crystal water contained in it.   3. Method according to claim 2, characterized in that the titanium acid compound and the carbide mixture are mixed in a ratio such that the number of carbon atoms in the carbide is 0.1 to 3 times the number of oxygen atoms of the titanium acid compound, with the exception of   oxygen atoms constituting any water of crystalliza- contained in it.   4. Method according to claim 1, characterized in   the fact that the non-oxidizing atmosphere is an atmosphere containing   substantially more than 90% by volume of one or more reducing gases (with the exception of hydrogen gas) such as carbon monoxide, or inert gases such as   nitrogen, helium or carbon dioxide.   5. Method according to claim 1, characterized in that the heating is carried out between 500 and 1500 C during 2 to 600 minutes.   6. Method according to claim 5, characterized in that the heating is carried out between 800 and 1200 C for 180 minutes. 7. Method according to claim 1, characterized in that the mixture is compressed into a compact mass under   reduced pressure before heating.   8. Process according to claim 1 or 7, characterized   in that the mixture contains a binder which is decomposed in non-oxidizing gases by heating.   9. Process according to claim 8, characterized in that the binder consists of compounds containing, as main component, one or more selected elements.   among hydrogen, carbon and nitrogen, which are decomposed   placed by heating water vapor, carbon dioxide   gaseous, carbon monoxide or nitrogen gas.   The method of claim 1, 8 or 9, characterized   in that the mixture further contains a sintering binder. 11. Process according to claim 1, characterized in that the alkali metal titanate compound is potassium titanate, sodium titanate or lithium titanate.   the alkaline earth metal titanate compound is the titanium   calcium nate, magnesium titanate, barium titanate or strontium titanate, and the carbide is boron carbide, silicon carbide or titanium carbide. 12. Process according to claim 8, characterized in that the binder is a liquid paraffin, ethylene glycol,   acrylic resin, polybutene or water.