JP2012082368A - Porous petaloid particle, method for producing the same and friction material for brake containing the porous petaloid particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder particle useful as an additive for friction materials, coating materials, cosmetics, etc., obtained by using a layered clay mineral as the raw material to improve fluidity and handleability; and to provide a method for producing the same.SOLUTION: The porous petaloid particle is obtained by firing at 300-900°C temperature an aggregate of a layered clay mineral obtained by intercalating 1-75 mass% of a metal oxide fine particle inside the thin layers. The method for producing the porous petaloid particle comprises disc-atomizing spray-drying an aqueous suspension liquid of the layered clay mineral including the metal oxide fine particle, and firing the spray-dried product at 300-900°C.

Description

  The present invention relates to porous petal-like particles having pores, a method for producing the same, and a brake friction material including the porous petal-like particles. More specifically, the present invention relates to porous petal-like particles useful as an additive for friction materials, paints, cosmetics, etc., an effective production method thereof, and a brake friction material containing the porous petal-like particles. .

  Many techniques are known for producing powder particles composed of layered clay minerals. For example, a method for producing a clay interlayer crosslinked porous material obtained by crosslinking between layers of smectite-type clay minerals with alumina (for example, see Patent Document 1), an ion-exchangeable clay-calcium silicate complex, or calcium silicate An ultraviolet protective agent characterized by intercalating metal ions between layers (for example, see Patent Document 2) is disclosed. In the technique of this Patent Document 2, an iron group, an aluminum group, a titanium group, a zinc group, a copper group, an alkaline earth metal, or a chromium group is used as a metal ion.

Japanese Patent Laid-Open No. 9-30813 JP-A-11-29760

However, in both of the techniques described in Patent Document 1 and Patent Document 2, it is possible to produce an interlayer crosslinked body, but the fluidity of the raw material cannot be improved, and the form of the raw material remains unchanged. However, there is a problem that the particle characteristics as a bulk cannot be changed.
If lamellar clay minerals remain in the form of flakes, they may be attached to the surroundings or clogged in the piping, and handling is poor.

  The present invention has been made under such circumstances, and is useful as an additive for friction materials, paints, cosmetics, etc., using layered clay mineral as a raw material, improving fluidity and improving handling. The object is to provide powder particles.

As a result of intensive studies to achieve the above object, the present inventors have obtained the following knowledge.
An aqueous suspension of a layered clay mineral containing metal oxide fine particles in a predetermined ratio is subjected to disk spray drying, and then this spray-dried product is baked at a temperature of 300 to 900 ° C. It has been found that the petal-like particles can be obtained, and that the porous petal-like particles have good fluidity and good handling, and are particularly useful as additives for friction materials.
The present invention has been completed based on such findings.

That is, the present invention
(1) A porous petal obtained by firing a laminar clay mineral aggregate obtained by inserting 1 to 75% by mass of metal oxide fine particles into a thin layer at a temperature of 300 to 900 ° C. Particles,
(2) The porous petal-like particles according to (1) above, wherein the average particle diameter (d ₅₀ ) is 1 to 300 μm,
(3) The porous petal-like particle according to (1) or (2), wherein the specific surface area is 5 to 500 m ² / g,
(4) Items (1) to (3) above, wherein the metal oxide fine particles are at least one selected from titania particles, zirconia particles, alumina particles and silica particles having an average particle diameter (d ₅₀ ) of 1 to ₅₀ nm. Porous petal-like particles according to any one of
(5) The porous petalous particles according to any one of (1) to (4) above, wherein the layered clay mineral is mica, kaolinite, smectite, vermiculite or chlorite.
(6) The method for producing porous petal-like particles according to any one of (1) to (5) above, wherein a water suspension of a lamellar clay mineral containing metal oxide fine particles is subjected to disk spray drying. Then, this spray-dried product is calcined at a temperature of 300 to 900 ° C., and a method for producing porous petal-like particles,
(7) The production method according to (6) above, wherein the disc spray drying is performed using a disc atomizer.
(8) The production method according to (6) or (7) above, wherein the solid content concentration in the aqueous suspension of the layered clay mineral containing metal oxide fine particles is 0.5 to 10% by mass, and (9) A brake friction material comprising the porous petal-like particles according to any one of (1) to (5) above,
Is to provide.

  ADVANTAGE OF THE INVENTION According to this invention, the porous petal-like particle useful as additives, such as a friction material, a coating material, and cosmetics, the effective manufacturing method, and the friction material for brakes containing the said porous petal-like particle can be provided. .

It is a columnar graph which shows the specific surface area of the particle | grains obtained by the Example and the comparative example. It is a graph which shows the pore distribution of the particle | grains obtained by the Example and the comparative example. 4 is a TEM photograph showing the inside of porous petal-like particles obtained in Example 3. 4 is a TEM photograph showing the inside of porous petal-like particles obtained in Example 4. 6 is a TEM photograph showing the inside of porous petal-like particles obtained in Example 5. 4 is a TEM photograph showing the inside of powder particles obtained in Comparative Example 2. 6 is a TEM photograph showing the inside of porous petal-like particles obtained in Example 6. 4 is a SEM photograph showing the appearance of porous petal-like particles obtained in Example 3. 4 is a SEM photograph showing the appearance of porous petal-like particles obtained in Example 4. 4 is a SEM photograph showing a cross section of the powder particles obtained in Comparative Example 1.

First, the porous petal-like particles of the present invention will be described.
[Porous petal-like particles]
The porous petal-like particles of the present invention (hereinafter sometimes simply referred to as petal-like particles) are an aggregate of lamellar clay minerals formed by inserting 1 to 75% by mass of metal oxide fine particles into a thin layer, It is characterized by being fired at a temperature of 300 to 900 ° C.

The petal-like particles of the present invention preferably have an average particle diameter (d ₅₀ ) in the range of 1 to 300 μm. The reason why the range of the average particle diameter is 1 to 300 μm is that if it is less than 1 μm, the formation of the petal state is insufficient, and if it exceeds 300 μm, the particles become more spherical and the petal shape becomes difficult to obtain. On the other hand, when the thickness is 1 to 300 μm, the above-mentioned problems are not caused, and it can be preferably used for additives for friction materials, paints, cosmetics and the like. The average particle diameter (d ₅₀ ) of the petal-like particles of the present invention is preferably 5 to 200 μm, and more preferably 10 to 100 μm.

The average particle diameter (d ₅₀ ) of the petal-like particles is a value measured by a laser diffraction scattering method.

In the present invention, the specific surface area of petal-like particles, in the range of 5 to 500 m ² / g, preferably in the range of 7~425m ² / g, more preferably be controlled within the range of 9~350m ² / g Can do. This specific surface area can be controlled by the amount of metal oxide fine particles contained in the thin layer of the layered clay mineral, the firing conditions, and the like.

(Layered clay mineral)
Examples of the layered clay mineral constituting the petal-like particles of the present invention include natural clay minerals and synthetic clay minerals having a cation exchange ability. Examples of the natural clay mineral and the synthetic clay mineral include mica, brittle mica, kaolinite, smectite, vermiculite, chlorite and the like. Examples of the smectite include montmorillonite, saponite, beidellite, nontronite and the like. it can. In addition, synthetic fluorine mica obtained by treating mica with fluorine can be used, and this synthetic fluorine mica is suitable as a layered clay mineral because of small variations in quality. As the synthetic fluorine mica, sodium tetrasilicate fluorine mica is preferable. (NaMg _2.5 Si ₄ O ₁₀ F ₂ ) can be exemplified. These layered clay minerals may be used alone or in combination of two or more.

The average particle diameter (d ₅₀ ) of the layered clay mineral is preferably 0.5 to 200 μm, more preferably 1 to 100 μm, and particularly preferably 5 to 60 μm.

The average particle diameter (d ₅₀ ) of the layered clay mineral is a value measured by a laser diffraction scattering method.

(Metal oxide fine particles)
In the petal-like particles of the present invention, the metal oxide fine particles inserted into the thin layer of the layered clay mineral include at least one selected from titania particles, zirconia particles, alumina particles, and silica particles. it can.

The average particle diameter (d ₅₀ ) of these metal oxide fine particles is preferably 1 to 50 nm, more preferably 3 to 40 nm, and still more preferably 5 to 30 nm from the viewpoint of intercalation.

The average particle size (d ₅₀ ) can be controlled by controlling the particle size of the metal oxide fine particles in the aggregate of the layered clay mineral before firing and the firing conditions.

The average particle size (d ₅₀ ) of the metal oxide fine particles in the petal-like particles is a value measured by the following method based on a transmission electron microscope (TEM) photograph.

First, after fixing the sample to the holder and coating with Pt, it was cut into a thickness of about 100 nm by FIB (focused ion beam device), and the metal in the petal-like particles was based on a transmission electron microscope (TEM) photograph of the cross section. The average particle diameter (d ₅₀ ) of the oxide fine particles is measured.

  From the viewpoint of the porous structure, the content of the metal oxide fine particles in the petal-like particles of the present invention needs to be 1 to 75% by mass, preferably 2 to 60% by mass, and more preferably 5 to 50%. % By mass. When the content is less than 1% by mass, the effect of the present invention is not sufficiently exerted. On the other hand, when the content exceeds 75% by mass, the intercalation does not occur and adhesion to the layered clay mineral ends increases.

Next, the manufacturing method of the petal-like particle | grains of this invention is demonstrated.
[Method for producing petal-like particles]
The method for producing petal-like particles of the present invention is the above-described method for producing porous petal-like particles, in which a layered clay mineral aqueous suspension containing metal oxide fine particles is subjected to disk spray drying, and then this spray-dried product. Is calcined at a temperature of 300 to 900 ° C.

(Preparation of aqueous suspension of layered clay mineral containing metal oxide fine particles)
In the method for producing petal-like particles of the present invention, first, an aqueous suspension of a lamellar clay mineral containing the metal oxide fine particles described above is prepared.
The aqueous suspension can be prepared, for example, by the following method.

  First, an aqueous medium and a lamellar clay mineral are mixed, and sufficient interstitial water is taken into the clay mineral to form a sol in which the layer gap is maximized.

  On the other hand, a hydrolyzable metal compound is added to an organic acid aqueous solution having an appropriate concentration, and the metal compound is hydrolyzed and condensed at a temperature of about 20 to 70 ° C. for about 5 to 240 minutes to obtain a metal oxide precursor. A sol is formed. In this case, the organic acid used is for stabilizing the metal oxide precursor sol, and examples thereof include carboxylic acids such as acetic acid, oxalic acid, and formic acid.

  Next, the layered clay mineral sol and the metal oxide precursor sol are mixed and maintained at a temperature of about room temperature to about 100 ° C. for about 10 to 300 minutes, thereby intercalating water taken into the clay mineral. And the metal oxide precursor sol are replaced, and the metal oxide precursor sol is intercalated by being sandwiched between clay mineral layers.

  In addition, as said hydrolysable metal compound, Ti compound, Zr compound, Al compound, and Si compound which have hydrolyzability can be mentioned preferably. Examples of the metal oxide precursor sol include titania precursor sol, zirconia precursor sol, alumina precursor sol, and silica precursor sol.

<Hydrolyzable metal compound>
Examples of the hydrolyzable metal compound used for forming the metal oxide precursor sol include, for example, the general formula (1)
R _n MX _m−n (1)
Wherein R is a non-hydrolyzable group, M is a metal atom, Ti, Zr, Al or Si, X is a hydrolyzable group or a hydroxyl group, m is the valence of the metal atom M, and m is In the case of 4, n is an integer of 0 to 3, and when m is 3, n is an integer of 0 to 2. When there are a plurality of R, the plurality of R may be the same or different, and X is When there are a plurality of Xs, the plurality of Xs may be the same or different.)
The compound represented by these can be used.

  In the general formula (1), examples of the non-hydrolyzable group represented by R include a hydrocarbon group which may have a functional group. Examples of the hydrocarbon group include linear or branched alkyl or alkenyl groups, cycloalkyl groups, aryl groups, and aralkyl groups.

  The alkyl group and alkenyl group preferably have 1 to 25 carbon atoms, particularly 1 to 3 carbon atoms, and the cycloalkyl group preferably has 3 to 25 carbon atoms, particularly 3 to 6 carbon atoms. The aryl group preferably has 6 to 25 carbon atoms, particularly 6 to 10 carbon atoms, and the aralkyl group preferably has 7 to 25 carbon atoms, particularly 7 to 10 carbon atoms.

  Examples of the functional group that may be introduced into the hydrocarbon group include an ester bond, an ether bond, an epoxy group, an amino group, a carboxy group, a carbonyl group, an amide group, a mercapto group, a sulfonyl group, a sulfenyl group, and a cyano group. , Hydroxyl group, halogen atom and the like.

  In the general formula (1), examples of the hydrolyzable group in X include an alkoxy group, an alkenyloxy group, a ketoxime group, an acyloxy group, and a halogen atom. m represents the valence of the metal atom M, and is 4 when M is Ti, Zr and Si, and 3 when Al. When m is 4, n is an integer of 0 to 3, preferably an integer of 0 to 2, and more preferably 0 or 1. When m is 3, n is an integer of 0 to 2, and is preferably 0 or 1.

  Preferred examples of the hydrolyzable metal compound represented by the general formula (1) include tetraethoxy titanium, tetra-n-propoxy titanium, tetraisopropoxy titanium, tetra-n-butoxy titanium, tetraisobutoxy titanium, Tetra-sec-butoxy titanium, tetra-tert-butoxy titanium, tetraacetoxy titanium, methyl triethoxy titanium, vinyl triethoxy titanium, phenyl triethoxy titanium, methyl tri-n-propoxy titanium, vinyl tri-n-propoxy titanium, methyl triiso Titanium compounds such as propoxy titanium, vinyl triisopropoxy titanium, and phenyl triisopropoxy titanium, and zirconium compounds or silicon in which the titanium in the titanium compound is replaced with zirconium or silane. Compounds, further triethoxyaluminum, tri-n-propoxyaluminum, triisopropoxyaluminum, tri-n-butoxyaluminum, triisobutoxyaluminum, tri-sec-butoxyaluminum, vinyldiethoxyaluminum, phenyldiethoxyaluminum, Examples thereof include aluminum compounds such as methyldi-n-propoxyaluminum, vinyldi-n-propoxyaluminum, methyldiisopropoxyaluminum, vinyldiisopropoxyaluminum, and phenyldiisopropoxyaluminum. These hydrolyzable metal compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

(Disc spray drying process)
In the method for producing petal-like particles of the present invention, an aqueous suspension of a layered clay mineral containing the metal oxide precursor sol prepared as described above (the metal oxide precursor sol is intercalated between the clay mineral layers). The disc is spray-dried.

  The present inventors tried various devices such as a two-fluid nozzle spray dryer and a disk atomizer spray dryer as a spray drying device for the aqueous suspension of the layered clay mineral containing the metal oxide precursor sol. However, it has been found that petal-like particles can be obtained for the first time by disc spray drying using a disc atomizer spray dryer.

  In the method for producing petal-like particles of the present invention, the disc spray-drying treatment is preferably spray-dried by a disc atomizer that rotates an aqueous suspension of a layered clay mineral containing a metal oxide precursor sol. As the disk atomizer, it is preferable to use an M-type disk atomizer, a K-type disk atomizer, or an N-type disk atomizer manufactured by Okawara Chemical Industry Co., Ltd., and it is particularly preferable to use an M-type disk atomizer.

  In the method for producing petal-like particles of the present invention, the solid content concentration in the aqueous suspension is 0.5 to 10% by mass from the viewpoint of facilitating the disc spray drying process and the formation of petal-like particles. It is preferable that it is 0.75-8 mass%, It is more preferable that it is 1.0-7 mass%. If the solid content concentration is less than 0.5% by mass, the dry amount of water increases, resulting in poor production efficiency. On the other hand, if the solid content concentration exceeds 10% by mass, the viscosity of the aqueous suspension increases and an efficient apparatus is obtained. It becomes impossible to send liquid to

(Baking process)
In the method for producing petal-like particles of the present invention, the spray-dried product obtained as described above is fired at a temperature of 300 to 900 ° C. When the firing temperature is less than 300 ° C., firing is insufficient. On the other hand, when the firing temperature exceeds 900 ° C., the metal oxide particles in the petals grow, the particle size increases, and the specific surface area of the petal-like particles decreases greatly. Further, when the temperature is around 1100 ° C., the petals are fused.

  The firing temperature is preferably in the range of 500 to 900 ° C, more preferably 700 to 900 ° C.

  The rate of temperature increase from room temperature to a predetermined temperature in the above range is preferably in the range of 10 to 500 ° C / h, more preferably in the range of 50 to 400 ° C / h, and 100 to 350 ° C / h. More preferably, it is in the range of h.

  The holding time after reaching the predetermined temperature is usually about 0.5 to 24 hours, preferably 1.0 to 16 hours, more preferably 2.0 to 12 hours. After the baking treatment, it is allowed to cool to room temperature.

By this firing treatment, porous petal-like particles having pores are obtained. The porous petal-like particles having pores have good fluidity and good handling, and the specific surface area is in the range of 5 to 500 m ² / g, preferably 7 to 425 m ² / g as described above. More preferably, it can be controlled within the range of 9 to 350 m ² / g.

  The porous petal-like particles of the present invention are useful as additives for friction materials, paints, cosmetics and the like, and are particularly suitably used as additives for friction materials.

Next, the brake friction material of the present invention will be described.
[Brake friction material]
The brake friction material of the present invention includes the above-described porous petal-like particles of the present invention.

  The brake friction material of the present invention can be obtained by molding in accordance with a conventional method using a friction material forming material including a binder resin, a solid lubricant, a fibrous reinforcing material, a friction modifier, and other fillers. .

  In the brake friction material of the present invention, the above-described porous petal-like particles of the present invention are used as other fillers such as a reinforcing material and a friction modifier in the friction material forming material. As a result, the brake friction material of the present invention has an effect of suppressing wear of the counterpart material.

  There is no restriction | limiting in particular as binder resin in the said friction material formation material, Conventionally known thermosetting resin known as binder resin in the friction material for brakes, for example, phenol resin, epoxy resin, polybenzoxazine resin Any one can be appropriately selected and used.

  As the solid lubricant in the friction material forming material, an arbitrary one can be appropriately selected and used in combination from known materials conventionally used as a lubricant for friction materials. Specific examples of this lubricant include graphite, fluorinated graphite, carbon black, metal sulfides such as tin sulfide and tungsten disulfide, and polytetrafluoroethylene (PTFE), boron nitride, and the like. These may be used individually by 1 type and may be used in combination of 2 or more type.

  As the fibrous reinforcing material in the friction material forming material, both organic fibers and inorganic fibers can be used. Examples of organic fibers include high-strength aromatic polyamide fibers (aramid fibers; manufactured by DuPont, trade name “Kevlar”, etc.), flame-resistant acrylic fibers, polyimide fibers, polyacrylate fibers, polyester fibers, and the like. On the other hand, as inorganic fibers, in addition to potassium titanate fibers, basalt fibers, silicon carbide fibers, glass fibers, carbon fibers, wollastonite, etc., ceramic fibers such as alumina silica fibers, stainless fibers, copper fibers, brass fibers, Examples thereof include metal fibers such as nickel fibers and iron fibers. These fibrous substances may be used alone or in combination of two or more.

  Moreover, there is no restriction | limiting in particular as a friction modifier in the said friction material formation material, Arbitrary things can be suitably selected from the well-known things used as a friction modifier in the conventional friction material. Specific examples of the friction modifier include metal oxides such as magnesia and iron oxide; zirconium silicate; silicon carbide; metal powders such as copper, brass, zinc and iron, and inorganic friction modifiers such as titanate powder. And organic friction modifiers such as rubber dust such as NBR, SBR, and tire tread, and organic dust such as cashew dust. These may be used individually by 1 type and may be used in combination of 2 or more type.

  In the friction material forming material, as other fillers such as a reinforcing material and a friction modifier, a swellable clay mineral can be contained in addition to the porous petal-like particles of the present invention. Examples of the swellable clay mineral include kaolin, talc, smectite, vermiculite, and mica.

  Further, calcium carbonate, barium sulfate, calcium hydroxide and the like can be contained.

  In the friction material forming material, among the lubricant, friction modifier and other fillers, the inorganic filler is treated with an organic compound in order to improve dispersibility in the material. Filled fillers can be used.

  Examples of fillers treated with organic compounds include treatment with organic compounds such as swellable clay minerals, calcium carbonate, barium sulfate, magnesia, aluminum powder, copper powder, zinc powder, graphite, tin sulfide, and tungsten disulfide. You can list things.

  In order to produce the friction material of the present invention, the above-mentioned friction material forming material is filled in a mold or the like, preformed at room temperature and at a pressure of about 5 to 30 MPa, and then at a temperature of about 130 to 190 ° C. and a pressure of 10 After heating and pressure forming for about 5 to 35 minutes under about 100 MPa conditions, heat treatment is performed at a temperature of about 160 to 270 ° C. for about 1 to 10 hours as necessary to produce a desired friction material. be able to.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Various characteristics in each example were determined by the following methods.

<Porous petal-like particles obtained>
(1) Average particle diameter (d ₅₀ )
The average particle diameter (d ₅₀ ) was measured using a particle size distribution device [manufactured by Beckman Coulter, model name “LS13320”] by a laser diffraction scattering method.

(2) Specific surface area and pore distribution The specific surface area and pore distribution were measured using a gas adsorption specific surface area measuring apparatus [manufactured by Shimadzu Corporation, model name “Gemini”].

(3) Angle of repose The angle of repose was measured using an angle of repose measuring apparatus [manufactured by Hosokawa Micron Corporation, model name “Powder Tester”]. The smaller the angle of repose, the better the fluidity.

(4) Average particle diameter of titania particles in petal-like particles (d ₅₀ )
Based on a transmission electron microscope (TEM) [manufactured by Hitachi High-Tech, model name “STEM HD-2000”], the average particle diameter (d ₅₀ ) of titania particles was measured according to the following method.
First, after fixing the sample to the holder and coating with Pt, it was cut into a thickness of about 100 nm by FIB (focused ion beam device), and the average particle diameter of titania particles in the petal-like particles was cut based on the TEM photograph of the cross section. (D ₅₀ ) was measured.

(5) Content of titania particles in petal-like particles The following calculation formula Titania particle content (mass%) = [TiO ₂ equivalent mass of used alkoxy titanium / (use swellable synthetic mica mass + TiO _{2 of} used alkoxy titanium) Equivalent mass)] × 100
Calculate according to

Example 1
(1) Preparation of Swellable Synthetic Mica Suspension After adding 2925 g of ion-exchanged water to 75 g of swellable synthetic mica (ME-100 manufactured by Coop Chemical Co., Ltd.) which is a layered clay mineral, the mixture was stirred for 24 hours to synthesize. A synthetic mica suspension having a mica concentration of 2.5% by mass was prepared.

(2) Preparation of titania precursor sol Add 965 g of acetic acid to 645 g of ion-exchanged water to prepare an aqueous solution having a concentration of 60% by mass of acetic acid, add 160 g of tetrabutoxy titanium, and stir at 25 ° C. for 1 hour. A titania precursor sol was prepared.

(3) Intercalation of titania precursor sol between layers of swellable synthetic mica To titania precursor sol obtained in (2) above was added to the synthetic mica suspension obtained in (1) above. By stirring at room temperature for 2 hours, the titania precursor sol was intercalated between the layers of the swellable synthetic mica.
Next, this mixed solution was subjected to solid-liquid separation with a centrifuge, and then the solid content was sufficiently washed with water. The TiO ₂ content is 30% by mass.

(4) Disc spray drying treatment Ion-exchanged water is added to the solid content washed in (3) above to prepare a suspension with a solid content concentration of 2.5% by mass, and a disc atomizer spray dryer [Okawara Kako Co., Ltd. , Model name “CL-8 type”], and the disc spray drying process was performed under the conditions of a rotational speed of 20000 rpm, a liquid feed speed of 28 g / min, and a drying temperature of 180 ° C.

(5) Firing treatment The spray-dried product obtained in (4) was fired under the following conditions to obtain porous petal-like particles having pores.
<Baking conditions>
Room temperature → 500 ° C .: Temperature rising rate 250 ° C./h
500 ° C. holding time: 2 hours 500 ° C. → room temperature: allowed to cool

Table 1 shows the TiO ₂ content, specific surface area, angle of repose, average particle diameter (d ₅₀ ), drying method, firing conditions and the like in the obtained porous petal-like particles.
FIG. 1 shows the specific surface area as a columnar graph, and FIG. 2 shows the pore distribution as a graph.

Example 2
Except for changing the amount of tetrabutoxytitanium in Example 1 (2) from 160 g (TiO ₂ content 30 mass%) to 240 g (TiO ₂ content 45 mass%), the same operation as in Example 1 was performed, Porous petal-like particles having pores were obtained.

Table 1 shows the TiO ₂ content, specific surface area, angle of repose, average particle diameter (d ₅₀ ), drying method, firing conditions and the like in the obtained porous petal-like particles.
FIG. 1 shows the specific surface area as a columnar graph, and FIG. 2 shows the pore distribution as a graph.

Example 3
Except for changing the amount of tetrabutoxytitanium in Example 1 (2) from 160 g (TiO ₂ content 30 mass%) to 320 g (TiO ₂ content 60 mass%), the same operation as in Example 1 was performed, Porous petal-like particles having pores were obtained.

Table 1 shows the TiO ₂ content, specific surface area, angle of repose, average particle diameter (d ₅₀ ), drying method, firing conditions and the like in the obtained porous petal-like particles.
FIG. 1 shows the specific surface area as a columnar graph, and FIG. 2 shows the pore distribution as a graph. 3 is a transmission electron microscope (TEM) showing the inside of the porous petal-like particles [manufactured by Hitachi High-Tech, model name “STEM HD-2000”], and FIG. 8 is an external view of the porous petal-like particles. It is a scanning electron microscope (SEM) [manufactured by Hitachi High-Tech, model name “S-4800”].

Example 4
While changing the amount of tetrabutoxy titanium in Example 1 (2) from 160 g (TiO ₂ content 30 mass%) to 240 g (TiO ₂ content 45 mass%), the firing conditions in Example 1 (5) are as follows. Except for the change as described above, the same operation as in Example 1 was performed to obtain porous petal-like particles having pores.
<Baking conditions>
Room temperature → 700 ° C .: Temperature rising rate 250 ° C./h
700 ° C. holding time: 2 hours 700 ° C. → room temperature: allowed to cool

Table 1 shows the TiO ₂ content, specific surface area, angle of repose, average particle diameter (d ₅₀ ), drying method, firing conditions and the like in the obtained porous petal-like particles.
FIG. 1 shows the specific surface area as a columnar graph, and FIG. 2 shows the pore distribution as a graph. Further, FIG. 4 is a TEM photograph showing the inside of the porous petal-like particle, and FIG. 9 is an SEM photograph showing the appearance of the porous petal-like particle.

Example 5
While changing the amount of tetrabutoxy titanium in Example 1 (2) from 160 g (TiO ₂ content 30 mass%) to 240 g (TiO ₂ content 45 mass%), the firing conditions in Example 1 (5) are as follows. Except for the change as described above, the same operation as in Example 1 was performed to obtain porous petal-like particles having pores.
<Baking conditions>
Room temperature → 900 ° C .: Temperature rising rate 250 ° C./h
900 ° C. holding time: 2 hours 900 ° C. → room temperature: allowed to cool

Table 1 shows the TiO ₂ content, specific surface area, angle of repose, average particle diameter (d ₅₀ ), drying method, firing conditions and the like in the obtained porous petal-like particles.
FIG. 1 shows the specific surface area as a columnar graph, and FIG. 2 shows the pore distribution as a graph. FIG. 5 is a TEM photograph showing the inside of porous petal-like particles.

Example 6
In Example 1 (5), except having changed baking conditions as follows, operation similar to Example 1 was performed and the porous petal-like particle | grains which have a pore were obtained.
<Baking conditions>
Room temperature → 300 ° C .: Temperature rising rate 250 ° C./h
300 ° C. holding time: 2 hours 300 ° C. → room temperature: allowed to cool

Table 1 shows the TiO ₂ content, specific surface area, angle of repose, average particle diameter (d ₅₀ ), drying method, firing conditions and the like in the obtained porous petal-like particles. FIG. 1 shows the specific surface area as a columnar graph, and FIG. 2 shows the pore distribution as a graph. FIG. 7 is a TEM photograph showing the inside of the porous petal-like particles.

Comparative Example 1
The raw material swellable synthetic mica (supra) was used as it was, and after drying in a hot air furnace, a baking treatment was performed under the same baking conditions as in Example 1 (5).

Table 1 shows the specific surface area, angle of repose, average particle diameter (d ₅₀ ), drying method, firing conditions and the like of the obtained powder particles.
FIG. 1 shows the specific surface area as a columnar graph, and FIG. 2 shows the pore distribution as a graph.

Comparative Example 2
Using swellable synthetic mica, the operations (5) and (6) in Example 1 were performed to obtain powder particles.

Table 1 shows the specific surface area, angle of repose, average particle diameter (d ₅₀ ), drying method, firing conditions and the like of the powder particles.
FIG. 1 shows the specific surface area as a columnar graph, and FIG. 2 shows the pore distribution as a graph. Further, FIG. 6 is a TEM photograph showing the inside of the powder particles, and no particles are observed between the sheets (between stripes).

  From Table 1, FIG. 1, FIG. 2 and each TEM photograph, in Comparative Examples 1 and 2 in which no tetrabutoxy titanium was added, in Examples 1 to 3, the specific surface area and pores (meso An increase in pores is observed.

From Examples 2, 4 and 5, a decrease in specific surface area is observed with an increase in the firing temperature. On the other hand, an increase in the size of the TiO ₂ particles inserted between the layers is recognized as the firing temperature rises.

From Example 6, even when the firing temperature was 300 ° C., an increase in specific surface area and growth of TiO ₂ particles were confirmed as compared with Comparative Example 2. From this, it is recognized that the firing temperature is required to be 300 ° C. or higher.
Further, in the examples, the angle of repose is decreased, and an improvement in fluidity is recognized.

From the above, it is possible to change the size of mesopores by producing a swellable synthetic mica in which TiO ₂ is inserted between thin layers by using this technology, and making it a petal-like particle, and as a bulk body of particles The fluidity can be improved, which is useful.

Example 7 and Comparative Example 3
The material for forming a friction material having the composition shown in Table 2 is preformed (20 MPa, held for 10 seconds), then charged into a thermoforming mold, heated and pressure-molded at 150 ° C. and 40 MPa for 6 minutes, and then molded. The body was heat treated at 250 ° C. for 3 hours and then processed into a predetermined size to produce a brake friction material.

  About this brake friction material, the friction performance test was implemented based on JASO-C406-82 using the friction tester (made by Sakai Engineer company). The results are shown in Table 2.

  The porous petal-like particles having pores of the present invention have good fluidity and good handling, are useful as additives for friction materials, paints, cosmetics and the like, and are particularly suitably used as additives for friction materials.

Claims (9)

  A porous petal-like particle obtained by firing a layered clay mineral aggregate obtained by inserting 1 to 75% by mass of metal oxide fine particles into a thin layer at a temperature of 300 to 900 ° C. 2. The porous petal-like particle according to claim 1, having an average particle diameter (d ₅₀ ) of 1 to 300 μm. The porous petal-like particle according to claim 1 or 2, having a specific surface area of 5 to 500 m ² / g. The metal oxide fine particles are at least one selected from titania particles, zirconia particles, alumina particles, and silica particles having an average particle size (d50) of 1 to ₅₀ nm. Porous petal-like particles.   The porous petal-like particle according to any one of claims 1 to 4, wherein the layered clay mineral is mica, kaolinite, smectite, vermiculite, or chlorite.   The method for producing porous petal-like particles according to any one of claims 1 to 5, wherein an aqueous suspension of a lamellar clay mineral containing metal oxide fine particles is disk spray-dried, and then the spray-dried product Is produced by firing at a temperature of 300 to 900 ° C.   The manufacturing method of Claim 6 which performs disk spray drying using a disk atomizer.   The production method according to claim 6 or 7, wherein the solid content concentration in the aqueous suspension of the layered clay mineral containing the metal oxide fine particles is 0.5 to 10% by mass.   A brake friction material comprising the porous petal-like particles according to any one of claims 1 to 5.