Process for producing a powder of aluminum titanate-based ceramics

TECHNICAL FIELD The present invention relates to a method for the production of an aluminum titanate-based ceramics powder, more particularly to a method for producing a aluminum titanate-based ceramics powder by firing a mixture of precursors comprising a titanium source powder, a powder source of aluminum and a silicon source powder and its grinding and sorting.

BACKGROUND OF THE INVENTION [0002] Aluminum titanate is known as a ceramic with excellent thermal resistance, and, for example, Reference to Patent 1 discloses a process comprising mixing powdered titanium source and powdered aluminum source, and firing the resulting precursor mixture. The aluminum titanate-based ceramics obtained using the method are usually solid and the powder can be obtained by fragmentation. The resulting aluminum titanate based ceramic powder can be a molded mass using a method such as extrusion after the addition of a liquid component, such as water, to give it a loamy consistency.

[0003] Japanese Patent Application No. JPH11060240 A discloses a process comprising the steps of forming a mixture comprising alumina and titanium oxide and firing the article at 1600-1700 ° C. Next, the aluminum titanate powder can be obtained by grinding the calcined molded mass.

REFERENCE TO THE STATE OF TECHNOLOGY

REFERENCE TO THE PATENT [0004] Patent reference 1: international publication brochure WO05 / 105704

DISCLOSURE OF THE INVENTION

PROBLEM THAT DEVELES THE INVENTION [0005] However, aluminum titanate-based ceramics are easily ground into fine particles during grinding, and therefore the aluminum titanate-based ceramics powder obtained by grinding contains a large amount of the fine particle component. Accordingly, after comminution, the aluminum titanate-based ceramics powder is usually used to form after removal of the finer component and the coarse grain component using a sorting operation, such as sieving.

[0006] It is known that the removed particulate component clogs the formed ceramic mass pores obtained during manufacture of the extrudate. The coarse particle component may clog the extruder and there is a problem in that of the ingredient

The coarse grained products can not be obtained with molded particles having a thin wall. Correspondingly, the removed particulate component and the coarse particle component of the aluminum titanate based powder powder can not be used directly to form as such, and under the present conditions all wasted.

The object of the invention is to provide a method by which the formation of the fine particle component and the coarse particle component is inhibited, and an aluminum titanate based powder having a very sharp grain size distribution can be produced efficiently and with good yield.

step (A) of shredding a kiln of aluminum titanate-burned ceramic mass using impact and sorting of the milled ceramics to obtain a aluminum titanate-based ceramics powder having the required grain diameter or smaller, and step (B) to regrind the remaining crumbled ceramic using impact and sorting obtained crushed ceramics to obtain a ceramic powder based on aluminum titanate having the required grain diameter or smaller. In the present invention, step (B) is preferably repeated two or more times. and step (B) again grinding the remaining milled ceramics by impacting and sorting the obtained milled ceramics to obtain a aluminum titanate based ceramics powder having the required grain diameter or smaller. In the present invention, step (B) is preferably repeated two or more times. and step (B) again grinding the remaining milled ceramics by impacting and sorting the obtained milled ceramics to obtain a aluminum titanate based ceramics powder having the required grain diameter or smaller. In the present invention, step (B) is preferably repeated two or more times.

[0009] When step (B) is repeated two or more times, the "residual milled ceramic" in step (B) of the second or subsequent cycle can be referred to as "residual particulate ceramics obtained by sorting in step (B) of the previous cycle".

In the method according to the invention, step (A) and step (B) are preferably carried out continuously by direct sorting and discharging alumina based aluminum powder having the desired grain diameter or smaller, obtained by fragmentation of the crushed area, and including at the same time, continuing the grinding of the remaining crumbled pottery located in the grinding area. The grinding and sorting step is preferably carried out using a grinding device with a built-in sorting device.

The aluminum titanate-based ceramics powder obtained in step (A) and step (B) having the required grain diameter or smaller is preferably an aluminum titanate-based ceramics powder having a maximum grain diameter of 100 μm or less. Preferably, the precursor mixture further comprises a magnesium source powder.

[0012] The amount of the titanium dioxide equivalent of the titanium source powder used is preferably 20 parts by weight or more and 60 parts by weight or less in relation to the titanium dioxide used.

100 parts by weight of the total amount of titanium dioxide equivalent of the powdery source being the titanium source, the amount of aluminum oxide equivalent of the powdery source being the source of aluminum and the amount of magnesium equivalent of the magnesium source powder used. Furthermore, the amount of alumina equivalent of the aluminum source powder used is preferably 30 parts by weight or more and 70 parts by weight or less based on 100 parts by weight of the total titanium dioxide equivalent of the titanium source powder used, the amount of aluminum oxide equivalent of the aluminum powder source used and the amount of magnesium equivalent of the magnesium source powder used. Also,

THE RESULT OF THE INVENTION [0013] It is possible in the invention to efficiently produce an aluminum titanate-based ceramics powder having a very narrow grain size distribution that does not contain either a finer component or a coarse particle component. In particular, by using the manufacturing method according to the invention, the formation of an unsuitable component as molding powder, such as a fine particle component and a coarse grain component, is inhibited and a aluminum titanate based powder powder can be produced as a powder for forming in good yield. the right grain size distribution.

BRIEF DESCRIPTION OF THE DRAWINGS [0014] [Figure 1] Fig. 1 is a cross-sectional sketch showing an example of a shredding apparatus used with the invention with a built-in sorting device.

[Figure 2] Fig. 2 shows the grain size distribution spectrum of magnesium aluminum titanate powder obtained in Example 1, Comparative Example 1 and Comparative Example 2.

A METHOD FOR CARRYING OUT THE INVENTION [0015] In the invention, the method for making a ceramic powder based on aluminum titanate comprises the following step.

(1) A step of maintaining a mixture of precursors comprising a titanium source powder, a source aluminum powder and a silicon source powder at a temperature ranging from 1100 ° C to 1350 ° C for 3 hours or longer (referred to as a holding stage).

(2) A heating step of the mixture of precursors to a temperature of 1400 ° C or more, and thereafter

It is possible to burn, at this temperature, a mixture of precursors after holding to obtain a kiln of aluminum titanate-burned ceramic (called a firing step).

(3) The stage of grinding and sorting of the burned clay based on aluminum titanate (called the grinding and sorting step).

(1) Holding step [0016] In this step, a mixture of precursors comprising titanium source powder, a source of aluminum powder and a silicon source powder, is maintained at a temperature ranging from 1100 ° C to 1350 ° C for 3 hours or more. . The mixture of precursors can be obtained by mixing a powder source of titanium, a source of aluminum powder and a silicon source powder. The mixture of precursors leads to aluminum titanate based ceramics by firing.

[0017] The powder mixture constituting the precursor mixture being the source of titanium is a powder of a material that converts into a titanium component forming a ceramic based on aluminum titanate. The material includes, for example, titanium oxide powder. The titanium oxide includes, for example, titanium (IV) oxide, titanium (III) oxide and titanium (II) oxide, and preferably titanium (IV) oxide is used. The titanium (IV) oxide may be crystalline or amorphous. When titanium (IV) oxide is crystalline, the type of its crystals includes anatase type, rutile type and brookite type, and anatase type and rutile type are preferred.

[0018] The titanium source powder used in the invention may be a powder of material that can be brought into titanium dioxide (titanium oxide) by burning in air. The material includes, for example, titanium salt, titanium alkoxide, titanium hydroxide, titanium nitride, titanium sulfide and titanium.

The titanium salt particularly includes titanium trichloride, titanium tetrachloride, titanium (IV) sulfate, titanium (VI) sulfate and titanium (IV) sulfate. The titanium alkoxide in particular includes titanium (IV) ethoxide, titanium (IV) methoxide, titanium (IV) tert-butoxide, titanium (IV) isobutoxide, titanium (IV) propoxide, titanium (IV) tetraisopropoxide and chelate compounds thereof.

[0020] Titanium oxide powder is preferably used as the titanium source powder, and titanium oxide powder is more preferred.

[0021] The aluminum source powder is a powder of material that converts into an aluminum-forming component based on aluminum titanate and includes, for example, aluminum oxide (aluminum trioxide). The aluminum oxide may be crystalline or amorphous. When the aluminum oxide is crystalline, its crystalline form includes the γ form, the δ form, the θ form and the α form, and preferably the α form.

[0022] The aluminum powder source used in the invention may be a powder of material that can be brought into alumina by burning in air. The material includes, for example, aluminum salt, aluminum alkoxide, aluminum hydroxide and metallic aluminum.

[0023] The aluminum salt may be a salt with an inorganic acid (inorganic salt) or a salt with an organic acid (organic salt). The inorganic aluminum salt in particular includes, for example, nitrates such as aluminum nitrate, ammonium aluminum nitrate; and carbonates, such as ammonium aluminum carbonate. The organic aluminum salts include, for example, aluminum oxalate, aluminum acetate, aluminum stearate,

Aluminum lactate and aluminum laurate.

[0024] Aluminum alkoxide in particular includes, for example, aluminum isopropoxide, aluminum ethoxide, aluminum sec-butoxide and aluminum tert-butoxide.

[0025] Aluminum hydroxide may be crystalline or amorphous. When the aluminum hydroxide is crystalline, the type of its crystals includes, for example, a type of gibbsite, a type of bayerite, a type of norstrandite, a type of boarite and a type of pseudobemite. Amorphous aluminum hydroxide includes, for example, an aluminum hydrolyzate obtained by hydrolysis of an aqueous solution of a water-soluble aluminum compound such as aluminum salt and aluminum alkoxide.

[0026] Aluminum oxide is preferably used as the aluminum source powder, and α-alumina powder is more preferable.

The silicon source powder is a powder of a material contained in an aluminum titanate based ceramics as a silicon component, e.g. silicon oxide powder (silica) such as silicon dioxide and silicon monoxide.

[0028] The silicon source powder used in the invention may be a powder of material that can be fed to the silica by firing in air. The material includes, for example, silicic acid, silicon carbide, silicon nitride, silicon sulfide, silicon tetrachloride, silicon acetate, sodium silicate, sodium orthosilicate and glass frit, and for the ease of industrial availability, a glass frit is preferred.

[0029] Glass frit means flakes or powder glass obtained by melting a mixture of raw material consisting of quartz sand, feldspar, lime and the like, and rapid cooling of the melt.

[0030] As a silicon source powder, it is possible to use a material powder which serves as both a silicon source and a source of aluminum. The material includes, for example, feldspar such as alkaline feldspar.

[0031] Mixing the precursors may contain a magnesium source powder, in which case aluminum magnesium titanate may be obtained as the aluminum titanate-based ceramics. The magnesium source powder is a powder of material that converts into a magnesium-forming component based on aluminum titanate, and includes, for example, magnesia (magnesium oxide) powder.

[0032] The magnesium source powder may be a powder of material that can be fed to the magnesia by burning in air. The material includes, for example, magnesium salt, magnesium alcoholate, magnesium hydroxide, magnesium nitride and magnesium metal.

[0033] Magnesium salt, in particular, includes magnesium chloride, magnesium perchlorate, magnesium phosphate, magnesium pyrophosphate, magnesium oxalate, magnesium nitrate, magnesium carbonate, magnesium acetate, magnesium sulfate, magnesium citrate, magnesium lactate, magnesium stearate, magnesium salicylate, magnesium myristate, magnesium gluconate, magnesium dimethacrylate and magnesium benzoate.

[0034] Magnesium alcoholate, in particular, includes magnesium methoxide and magnesium ethanolates.

[0035] As the powder constituting the magnesium source, it is possible to use a material powder that serves

Both as a magnesium source and as a source of aluminum. The material includes, for example, magnesium spinel [MgAl2O4].

[0036] The amount of titanium source powder used, the amount of powder source being the source of aluminum, the amount of magnesium source powder used and the amount of silicon source powder used are determined based on the calculated result based on the amount of titanium dioxide [TiO2], amount of oxide aluminum [Al2O3], amount of magnesia [MgO] and amount of silica [SiO2], containing the same amount of Ti, Al, Mg and Si as the amount of Ti, Al, Mg and Si contained in individual powders. The amount of titanium dioxide equivalent of the titanium source powder used is usually from 20 parts by weight to 60 parts by weight based on 100 parts by weight of the total titanium dioxide equivalent amount of the titanium source powder used, the amount of alumina equivalent of the powdered source being the source of aluminum and the amount of magnesium equivalent of the magnesium source powder used (hereinafter referred to as total amount of hydroxybenzane troxide), and preferably 30 parts by weight to 50 parts by weight. The amount of alumina equivalent of the aluminum source powder used is usually from 30 parts by weight to 70 parts by weight based on 100 parts by weight of the total amount of magnesium aluminum titanulphide dioxide, and preferably from 40 parts by weight to 60 parts by weight. The amount of silica equivalent of the silicon source powder used is usually from 0.1 parts by weight to 20 parts by weight based on 100 parts by weight of the total amount of magnesium titanium aluminum oxide; and preferably from one part by weight to 10 parts by weight. The amount of magnesium equivalent of the magnesium source powder used is usually 0.1 parts by weight to 10 parts by weight based on 100 parts by weight of the total amount of dibenzoxide, and preferably from 0.5 parts by weight to 5 parts by weight.

[0037] The precursor mixture may be obtained, for example, by mixing a powder source of titanium, a source of aluminum powder, a silicon source powder and an optionally used magnesium source powder. The mixing can be carried out either in dry conditions or in wet conditions. The mixing order is not particularly limited and these powders of starting materials can be mixed at the same time.

[0038] During mixing, the starting powder powder is usually mixed by comminuting and mixing using grinding media in a grinding tank. As a grinding tank, a tank made of a metal material such as stainless steel is usually used, and its inner surface may be coated with a fluorinated resin, a silicone resin, a urethane resin and the like. Examples of disintegrating agents include alumina beads or zirconia beads having a grain diameter of 1 mm 100 mm, preferably 5 mm to 50 mm.

[0039] Mixing can be carried out, for example, by using vibrations or rotation of the refining tank, in which the powder of the starting material and the disintegrating means are placed. By using vibrations or rotational motion of the grinding tank, the powder of the starting material is mixed and mixed with the grinding media and is crushed. In order to vibrate or rotate the grinding tank, for example, a conventional grinding apparatus, such as a vibratory mill, a ball mill and a planetary mill, can be used, and from

In view of the ease of operation on an industrial scale, a vibratory mill is preferably used. The mixing can be carried out using a continuous process or a batch process, and from the point of view of the ease of operation on an industrial scale, a continuous process is preferred. The time for mixing and grinding is usually from one minute to 6 hours, preferably from 1.5 minutes to 2 hours.

[0040] Additives, such as a dispersing agent, a grinding aid and a flocculation prevention agent may be added during mixing and grinding. An auxiliary agent used for grinding includes, for example, monohydric alcohols, such as methanol, ethanol and propanol; dihydric alcohols, such as propylene glycol and ethylene glycol; amines, such as triethanolamine; higher fatty acids, such as palmitic acid, stearic acid and oleic acid; carbon materials such as carbon black and graphite. They can be used either singly or in combination with each other.

[0041] When additives are used, the total amount can usually be from 0.1 parts by weight to 10 parts by weight, preferably from 0.5 parts by weight to 5 parts by weight, more preferably from 0.75 parts by weight to 2 parts by weight, with respect to 100 parts by weight of the total amount of starting powder used, i.e. the total amount of powder source being a source of titanium, a source of aluminum powder, a silicon source powder and a magnesium source powder.

[0042] When additives are used, depending on the properties of the additives, additives can be removed from the precursor mixture after mixing. For example, additives can be removed by heating and burning in the air. The heating temperature is usually 500 ° C or less.

[0043] In the holding step, the aforementioned precursor mixture is maintained at a temperature range of 1100 ° C to 1350 ° C for 3 hours or more. By firing after the holding step, a compact burnt mass of aluminum titanate-based ceramics can be obtained, respectively, the formation of the fine particle component during the grinding of the kiln-burned aluminum-based ceramic mass can be inhibited.

[0044] The reason for maintaining the mixture of precursors in the temperature range from 1100 ° C to 1350 ° C is to produce an aluminum titanate-based ceramics having a low coefficient of thermal expansion at a firing temperature lower than 1500 ° C.

[0045] A mixture of precursors (a mixture of powder being the source of titanium, a source of aluminum, a silicon source powder and an optionally added magnesium source powder) can be heated to a temperature range of 1100 ° C to 1350 ° C and kept within a temperature range in powder form the formed mass obtained by forming a mixture of precursors can be maintained within a temperature range. The method of forming a mixture of precursors includes conventional methods, such as a pressing method in a shape-imparting mold using uniaxial pressing, tabletting and the like; a molding method in a granulator, extruder and the like, and drying after addition of a mixture of precursors of a liquid component, such as water.

[0046] The retention time of the precursor mixture at a temperature in the range of 1100 ° C to 1350 ° C is 3 hours or more, preferably 4 hours or more, and more preferably 6 hours.

EP 2 336 087 B1 or more. The holding time is usually 24 hours or less. While maintaining the temperature range from 1100 ° C to 1350 ° C, the precursor mixture can be kept at a constant temperature, or it can be heated gradually, or it can be cooled gradually, or it can be repeatedly alternately heated and cooled if the temperature does not go outside range. In the case of heating or cooling, the heating or cooling rate is usually 100 ° C / hour or less, preferably 80 ° C / hour or less, more preferably 50 ° C / hour, in view of the ease of maintaining the mixture of precursors in the temperature range.

[0047] The atmosphere in heating to a temperature range and maintaining in the temperature range is usually air. The atmosphere may be an inert gas, such as nitrogen gas and argon gas; or a reducing gas, such as carbon monoxide and hydrogen gas, depending on the type or the amount of starting powder used, i.e. the powder source of titanium, a source of aluminum powder, a silicon source powder and a magnesium source powder. Heating and maintaining can be carried out in an atmosphere in which the partial vapor pressure is reduced.

[0048] Heating and maintaining in the temperature range is usually carried out using a conventional heating furnace such as a tubular electric furnace, electric furnace, tunnel furnace, far infrared oven, microwave heat furnace, shaft furnace, flame furnace, rotary kiln and furnace. with a roller table.

(2) Firing step [0049] In this step, the precursor mixture after the holding step is heated to 1400 ° C or higher, and usually lower than 1500 ° C, and fired at this temperature to obtain a kiln of aluminum titanate-based ceramics. The firing is usually carried out by heating the mixture of precursors to the firing temperature after the holding step, and in the same atmosphere as that in the holding step, and using the same heating furnace as that in the holding step.

[0050] The time for firing may be a time sufficient to convert the precursor mixture after the holding step to aluminum titanate based ceramics, and is usually from 10 minutes to 24 hours, depending on the amount of the precursor mixture, the type of furnace and the firing atmosphere.

[0051] A burnt mass of aluminum titanate-based ceramics can be obtained in the steps described above. The burned ceramic mass based on aluminum titanate is usually solid when the precursor mixture is fired as a powder. When the formed mass of the precursor mixture is burned out, the shape of the formed mass is almost completely preserved immediately after forming.

(3) Grinding and sorting step [0052] In this step, the kiln-burned alumina-based ceramics are ground and sorted to give a aluminum titanate-based ceramic powder. In the method of the invention, the grinding and sorting step comprises the following steps. (A) the step of grinding the burned-out ceramic mass based on aluminum titanate using impact, and sorting the shredded ceramics

To obtain a ceramic powder based on aluminum titanate, having the required grain diameter or smaller, and step (B) to regrind the remaining grinded ceramic by impacting and sorting the obtained milled ceramics to obtain an aluminum titanate-based ceramics powder having the required size. COG diameter grains or less.

[0053] A mixture of aluminum titanate based ceramics powder having the required grain diameter or smaller obtained in steps (A) and (B) is an expected aluminum titanate based ceramic powder. By grinding and sorting, comprising steps (A) and (B), it is possible to sieve and collect only the component having the required grain diameter or smaller, and therefore an aluminum titanate based powder powder based on coarse particles can be obtained. Furthermore, by re-grinding and sorting in step (B), the coarse-grain component in step (A) is crushed in order to have the required grain diameter or smaller and collected, and therefore the formation of a coarse particle component may be significantly inhibited. , unsuitable as forming powder. In the present invention, it is preferred that step (B) be repeated two or more times. The higher the number of the repeats of step (B), the more the performance of the required aluminum titanate based powder increases, and the amount of the remaining remaining coarse particles may be more reduced.

[0054] When step (B) is repeated two or more times, the "remaining grinded ceramic" in step (B) of the second or subsequent cycle is referred to as "the remaining particulate ceramics obtained by sorting in step (B) of the previous cycle".

In this step, step (A) and step (B) are preferably carried out continuously by direct sorting and discharging of the aluminum titanate-based ceramics powder having the required grain diameter or smaller, obtained by grinding the shredded area, and thereby time, continuing the grinding of the remaining crumbled pottery located in the grinding area. When the fine powder produced using the grinding process remains in the grinding area, then the powder may have some negative effect on subsequent grinding; but in contrast, when the aluminum-based titanate-based powder made using the grinding process, having the required diameter or smaller, is discharged immediately from the grinding area,

The burnt aluminum-based ceramic mass obtained in the holding and firing steps and fed to the grinding-sorting step is a high density material, and therefore the fine particle component is difficult to mold, even if the burnt mass is crushed and sorted. Thus, in accordance with the method of producing the present invention, an aluminum titanate based powder powder can be obtained that does not contain either a finer component or a coarse particle component.

[0057] The aluminum titanate-based ceramics powder collected in steps (A) and (B) having the required grain diameter or smaller, preferably has a maximum grain diameter of 110 μm or less, considering the ease of forming the aluminum titanate based ceramics powder and the quality a molded article according to the invention.

[0058] As a comminution-sorting device for carrying out the above-mentioned steps (A) and (B), it is preferable to use a grinding device with a built-in device

The grinding apparatus shown in Fig. 1 comprises a main body 100, having an orifice 101 for introducing gas in its lower part and having an opening 102 for evacuating gas and powder in its upper part. The interior of the main body 100 is divided by the cylindrical body 103 into an outer grinding area 200 and an inner sorting area 300. The main body 100 is provided with an inlet opening 104 that is in communication with the grinding area 200 and through which the substance to be crushed and sorted is delivered.

[0059] The grinding area 200 is provided with a grinding roll 201, and on its edge the roll 201 is provided with grinding mills 202. More specifically, a plurality of grinding mills 202 is mounted to the outer peripheral portion of the grinding roll 201, away from the liner 203 formed on the shredder. the inner wall of the shredding area200. The chopping roll 201 rotates around its central axis. In its lower part, the shredding region 100 is communicated with an opening for gas introduction.

[0060] The gas stream from the gas injection hole 101 carries the powder powder in the crushing area 200 to the sorting area 300. In the 300 sorting area, the powder is sorted into a fine powder and a coarse powder, and only a fine powder can pass. The sorting area 300 is communicated with the drain opening 102. The sorting area 300 is provided with a sorting device that includes a sorting roller 301 rotating about a central axis, and a plurality of sorting fans 302 installed so as to be on the outer circumferential portion of the sorting roll 301, e.g., at an angle of about 6 degrees. The sorting device is arranged such that only the sorted fine powder can pass through the device and can be discharged through the draining hole102.

[0061] In the grinding and sorting of a kiln of aluminum titanate-burned ceramic mass using a grinding device, a kiln of aluminum titanate-based ceramics fired into the apparatus through the inlet opening 104 is firstly introduced into the grinding region 200 and comminuted. The grinding can be carried out by rotating the shredding roll 201 and supplying the impact using grinding mills 202. Through the gas entry opening 201, a gas, such as air or inert gas, is introduced into the main body 100, and the gas flows towards the drain opening 102 after passing through. from the bottom of the crushing area 200 to the top 300 sorting area and passes through the sorting fans 302. Or the gas flows towards the drain opening 102 after passing from the bottom of the crushing area 200 to the outside of the sorting area 300, then flows from the top to the bottom of the sorting area 300 and passes through the sorting fans 302. Accordingly, the particulate powder flows with the gas to the grinding area 300. In the 300 sorting area, the particulate powder is separated into fine powder and coarse powder using the difference between the gas current flowing from the sorting area 300 towards the discharge opening 102 and the centrifugal force provided by the sorting roller 301. In particular, the current is more effective for the fine powder and the fine powder is able to pass through the sorting fans 302, and is discharged from the opening 102 for draining and withdrawal.

EP 2 336 087 B1 passes through the sorting fans 302, but returns again to the grinding area 200 from the bottom of the cylindrical body 103. The coarse powder returned to the grinding area 200 is refined again and then sorted again in the sorting area 300. You can repeat shredding and sorting operations on this machine.

[0062] One example of the grinding device having the structure shown in Fig. 1 is the ACM Pulverizer produced by the company Hosokawa Micron (e.g. ACM Pulverizer ACM-10), which can be advantageously used in the invention.

[0063] The aluminum titanate based ceramics powder obtained using the method of the invention has a narrow grain size distribution that does not contain either a finer component or a coarse grain component. In particular, for example, the aluminum titanate-based ceramics powder obtained using the method of the invention has a content of fine particles having a particle diameter of 10 μm or less, 20% by volume or less, preferably 10% by volume or less, and content of coarse grain component having a grain diameter of 70 Pm or more, less than 10 vol.%, preferably less than 5 vol.%. Median grain diameter (median diameter) of aluminum titanate based ceramics powder obtained using the method of the invention,

[0064] The grain diameter characteristics (grain diameter distribution, median grain diameter and maximum grain diameter) of the aluminum titanate based ceramic powder can be controlled by adjusting the holding stage conditions (holding time, holding temperature and the like), the speed of the crushing roll and the sorting roller in a crushing apparatus with a built-in sorting device, and gas flow rates in the device and the like.

[0065] Since the aluminum titanate based powder obtained in the invention has a narrow grain size distribution, not containing either a fine particle component or a coarse particle component, it can advantageously be used as a material for a ceramic molded body. Examples of molded ceramic mass include tools for firing furnaces, such as crucibles, supports for ceramic products for the furnace, chamotte covers and refractories; filters and catalyst supports for use in the treatment of exhaust gases in internal combustion engines, such as diesel engines and gasoline engines; elements of electricity generating devices; electronic components, such as substrates and capacitors. EXAMPLES [0066] The invention is described in detail with reference to the following examples;

[Example 1] [0067] A mixture of precursors was obtained by mixing 38.1 parts by weight of titania (IV) powder [available from EI DuPont de Nemours and Company "R-900"], 52.5 parts by weight of α aluminum oxide powder [ available from Sumitomo Chemical Co., Ltd. "AES-12"], 5.7

Part F of the magnesia spinel powder and 3.7 parts by weight of feldspar powder [Fukushima Feldspar, SiO2-equivalent silicon content was 72% by weight, Al2O3-equivalent aluminum content was 15% by weight].

A mixture of precursors was placed in a crucible of alumina and fired by heating to 1100 ° C in air at a heating rate of 300 ° C / hour, maintained at from 1100 ° C to 1350 ° C for 5 hours, and then heated to 1430 ° C at a heating rate of 300 ° C / hour and maintained at this temperature for 3.75 hours to give a burnt mass of aluminum-magnesium titanate.

[0069] Next, the burnt mass of aluminum magnesium titanate was crushed and sorted using a crushing device with an in-line sorting device having the structure shown in Fig. 1 (ACM Pulverizer, available from Hosokawa Micron, "ACM-10"), under conditions, where the rotation speed of the crushing roll was 3,000 rpm, the sorter rotational speed was 2000 rpm, the gas (air) flow rate was 15 Nm³/ min, and aluminum-magnesium titanate powder was obtained. The grain diameter characteristics of the aluminum-magnesium titanate powder obtained are shown in Table 1. The grain size distribution spectrum is shown in Fig. 2. In addition, the grain diameter characteristics shown in Table 1 and the grain size distribution spectrum shown in Fig. 1 were measured using Sysmex's "Mastersizer2000. ".

(Example 2) [0070] Aluminum magnesium titanate powder was prepared in the same manner as in Example 1, except that the holding time at 1100 ° C to 1300 ° C was 6.7 hours. The grain diameter characteristics of the alumina-magnesium titanate powder obtained are shown in Table 1. (Example 3) Aluminum magnesium powder titanate was prepared in the same manner as in Example 2, except that the grinding roll speed was 6,800 revolutions per minute . The characteristics of the grain diameter of the alumina-magnesium titanate powder obtained are shown in Table 1.

(Comparative Example 1) [0072] First, in the same manner as in Example 2, a kiln mass of aluminum-magnesium titanate was obtained. Then, the burnt mass of aluminum-magnesium titanate was crushed using a quern (Premax "PR-200V", available from Chuo Kakohki Shoji) under conditions where the gap between stones was 90 μm and the number of rotations was 2000 rpm, and a powder was obtained. aluminum-magnesium titanate. The grain size distribution spectrum is shown in Fig. 2. (Comparative Example 2) [0073] First, the same mixture as used in Example 1 was placed in a crucible of alumina and fired by heating to 1100 ° C at 300 ° C / hour in the air was kept

At 1100 ° C to 1300 ° C for 2 hours, it was then heated to 1450 ° C at 300 ° C / hour and maintained at this temperature for 4 hours to give a kiln mass of aluminum magnesium titanate.

[0074] Next, the calcined mass of aluminum magnesium titanate was crushed and sorted using the above-mentioned grinding device with an in-line sorting device under conditions such that the grinding roll speed was 6,800 rpm, the sorter rotational speed was 2,000 rpm, and the gas (air) flow rate was 15 N / m³/ min, and aluminum-magnesium titanate powder was obtained. The characteristics of the grain diameter of the alumina-magnesium titanate powder obtained are shown in

Table 1. The grain size distribution spectrum is shown in Fig. 2.

(Comparative Example 3) [0075] Aluminum magnesium titanate powder was prepared in the same manner as in Comparative Example 2, except that the speed of the sorting roller was 500 rpm. The grain diameter characteristics of the aluminum-magnesium titanate powder obtained is shown in Table 1.

(Comparative Example 4) [0076] Aluminum magnesium titanate powder was prepared in the same manner as in Comparative Example 2, except that the rotational speed of the disintegrating roller was 4000 rpm. The grain diameter characteristics of the aluminum-magnesium titanate powder obtained is shown in Table 1.

(Comparative Example 5) [0077] Aluminum magnesium titanate powder was prepared in the same manner as in Comparative Example 2, except that the speed of the crushing roll was 300 rpm. The grain diameter characteristics of the aluminum-magnesium titanate powder obtained is shown in Table 1.

[Table 1]

<td></td><td>Median diameter grains (Μτ)</td><td>The component being fine particles, having grain diameter 10 μιτι or less (% by volume)</td><td>A component consisting of coarse particles having a grain diameter of 70 μτ or less (volume%)</td><td>Presence or absence component being coarse particles having a grain diameter of more than 110 μτ</td>

<td>Example 1</td><td>31.5</td><td>8.3</td><td>4.0</td><td>absent</td>

<td>Example 2</td><td>29.7</td><td>8.7</td><td>2.2</td><td>absent</td>

<td>Example 3</td><td>20.1</td><td>17.2</td><td>0</td><td>absent</td>

<td>Comparative Example 1</td><td>26.4</td><td>18.5</td><td>11.9</td><td>present</td>

<td>Comparative Example 2</td><td>13.4</td><td>33.4</td><td>0</td><td>absent</td>

EP 2 336 087 B1

<td></td><td>Median diameter grains (Μτ)</td><td>The component being fine particles, having diameter of 10 μιτ or less (% by volume)</td><td>Constituent component coarse particles having a grain diameter of 70 μτ or less (volume%)</td><td>Presence or absence of ingredient being coarse particles having a grain diameter of more than 110 μτ</td>

<td>Comparative Example 3</td><td>14.1</td><td>31.2</td><td>0.4</td><td>absent</td>

<td>Comparative Example 4</td><td>17.4</td><td>26.0</td><td>0</td><td>absent</td>

<td>Comparative Example 5</td><td>17.3</td><td>28.9</td><td>1.0</td><td>absent</td>

[0078] In Examples 1 to 3, all aspects of the invention were satisfactory, the formation of the finest component and the coarse particle component of the resulting aluminum magnesium titanate powder was inhibited. In addition, a tendency has been observed that the amount of the fine particle component increases with the increase in the speed of the crushing roll.

[0079] Meanwhile, Comparative Examples 1 to 5 were examples in which none of the elements of the invention were satisfactory. In Comparative Example 1, the amount of the finer component and the coarse grain component increased because sorting was not performed although the holding step was properly controlled. In Comparative Example 2, the amount of the fine particle component increased because the holding time was short.

[0080] The method and Examples of carrying out the invention disclosed at that time are illustrative in all respects, and should not be considered as limiting. The scope of the invention is indicated by the claims, and not by the above description, and is intended to cover all variations in the sense and scope of the equivalents of the claims.

EXPLANATION OF THE REFERENCES [0081]

100 main body

101 gas inlet

102 a hole for evacuating gas

103 cylindrical body

104 inlet opening

200 grinding area

201 shredding roller

202 shredding hammer

203 lining

300 sorting area

301 sorting roller

302 sorting fan

EP 2 336 087 B1