JP2002161265A - Xonotlite powder and frictional material composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide xonotlite powder which has a high flowability and a high jetting property and enables the profitable production of a frictional material composition excellent in homogeneity. SOLUTION: This xonotlite power is aggregate of porous spherical secondary particles composed of spherically aggregated fibrous xonotlite primary particles, characterized in that D50 and D10 of the porous spherical secondary particles are 25 to 80 μm, and >=15 μm, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material composition and a sheet-like friction material, and more particularly to a zonotolite powder which can be suitably used for the production thereof.

[0002]

2. Description of the Related Art As a material for a surface layer of a brake or a clutch used in an automobile or various industrial vehicles, a friction material having excellent friction characteristics and excellent heat resistance is used. In general, friction materials used for such purposes include steel fibers, synthetic resin fibers, fiber base materials such as inorganic material fibers, graphite, metal oxides, metal salts (eg,
It is composed of a friction modifier such as barium sulfate), an organic powder (eg, cashew dust, rubber dust), and a composition mainly composed of a binder. And the composition is usually
It is used alone as a sheet or formed as a coating layer on a brake substrate or a clutch substrate.

[0003] Asbestos has been widely used as a fiber base material for friction materials in the past, but the use of asbestos has been rejected due to environmental problems. Is formed. Therefore, in recent years, development of a new friction material as a substitute for asbestos has been promoted, and the following proposals have been made.

JP-A-3-255187 discloses that as a brake lining material, a phenolic resin, a spherical zonotolite-type synthetic hydrous calcium silicate having an internal open structure having an average particle diameter of 50 to 70 μm, and other fillers are used. There are proposals to use different compositions.

[0005] Japanese Patent Application Laid-Open No. Hei 4-318092 proposes to use zonotolite as a part of an additive to be filled in a friction material.

[0006]

The zonotolite powder used for the friction material has a fluidity and a jet property in view of workability in producing the friction material and dispersibility in mixing with other materials such as a fiber base material. Is preferred, but according to the study of the present inventor, it has been found that if the fine particles are excessively contained in the zonotolite powder, the fluidity and the jettability of the zonotolite powder tend to decrease. Also, it is desirable that the sheet-like friction material used for various vehicles such as automobiles, such as a brake lining material, exhibit a high degree of homogeneity throughout the friction material so that the friction characteristics do not change depending on the contact position of the friction system. When the fine particles are excessively contained in the zonotolite powder, the homogeneity of the friction material is impaired, which may affect the braking performance such as friction characteristics.
It has been clarified by the study of the present inventors.

Accordingly, it is a main object of the present invention to provide a zonotolite powder having high fluidity and jettability. Another object of the present invention is to provide a method for producing a zonotolite powder containing less fine particles. Another object of the present invention is to provide a friction material composition and a sheet-like friction material having a high degree of homogeneity.

[0008]

Means for Solving the Problems The present invention is an aggregate of porous spherical secondary particles xonotlite primary fibrous particles is by agglomerating spherical, the D ₅₀ of the porous spherical secondary particles in the range of 25～80Myuemu, in xonotlite powder wherein a D ₁₀ of at 15μm or more.

[0009] D ₅₀ of the porous spherical secondary particles in xonotlite powder of the present invention (xonotlite secondary particles) 25
It is preferably in the range of 47 μm,
It is particularly preferred that it is in the range of m. Further, D ₁₀ of porous spherical secondary particles (xonotlite secondary particles) 20μm
It is preferable that it is above.

The present invention also provides a zonotolite slurry in which fibrous zonotolite primary particles are dispersed by forming porous spherical secondary particles having a D ₅₀ of less than 60 μm to obtain a wet solid by filtering under reduced pressure. then, the wet solids in the range D ₅₀ is 25~47μm of porous spherical secondary particles, characterized by crushing the xonotlite aggregates obtained by drying, D
There is also a method for producing a zonotolite powder in which ₁₀ is 15 μm or more.

[0011] The present invention further provides a friction material composition porous spherical secondary particles xonotlite primary fibrous particles is by agglomerating spherically are dispersed, D ₅₀ of the porous spherical secondary particles 15μm but the range of 25~80μm, D ₁₀ is
There is also a friction material composition characterized by the above, and a sheet-like friction material obtained by pressurizing the friction material composition.

[0012] The D50 of the porous spherical secondary particles (secondary zonotrite particles) dispersed in the friction material composition and the sheet-like friction material of the present invention is preferably in the range of 25 to 47 µm, and 30 to ₅₀ µm. It is particularly preferred that it is in the range of 47 μm. Further, it is preferable that D ₁₀ of the porous spherical secondary particles (xonotlite secondary particles) is 20μm or more.

In the present invention, D ₅₀ and D ₁₀ are values obtained from an integrated distribution curve of the volume-based particle size of secondary zonotrite particles, and D ₅₀ is 50% of the integrated distribution curve.
Mean particle size (ie, median size),
D ₁₀ represent respectively the particle diameters means a particle diameter corresponding to 10% towards the particle size of cumulative distribution curve is small. The particle size of the zonotolite secondary particles is a value measured by a laser diffraction method.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The zonotorite powder of the present invention is an aggregate of porous spherical zonotorite secondary particles formed by agglomeration of fibrous primary zonotorite particles in the same manner as conventionally known spherical zonotorite. although, in the range D ₅₀ of xonotlite secondary particles of 25～80Myuemu, and D ₁₀ of more than 15 [mu] m (preferably 20μm or more) it is characterized mainly in that a. That is, one of the features of the zonotolite powder of the present invention is that the content of fine particles having a volume-based particle size of 15 μm or less (preferably 20 μm or less) is 10% by volume or less.

In the present invention, the shape of the fibrous primary zonotolite particles forming the secondary zonotolite particles is not particularly limited, but usually the average fiber length is in the range of 1 to 5 μm and the average fiber diameter is 0.1. ０．５0.5 μm.

The zonotolite powder can be produced by pulverizing a zonotolite aggregate obtained by drying a zonotolite slurry in which zonotolite secondary particles are dispersed. During crushing, it was found that secondary zonotrite particles were broken and fine particles were easily generated. As a result of further research, the present inventor has found that as a method for producing a zonotolite powder with a small amount of fine particles mixed therein, a zonotolite slurry was filtered under reduced pressure to obtain a wet solid, and then the wet solid was dried. A method for producing zonotolite powder for crushing the obtained zonotolite aggregates was developed.

In the above production method, fine pores (through holes) are formed in the wet solid by filtering the zonotolite slurry under reduced pressure, and the wet solid is dried so as to maintain the fine pores. It is characterized by producing zonotolite aggregates. The zonotolite aggregate produced by this method is relatively small by a crushing machine such as a vibrating sieving machine or a crushing and sizing apparatus using a high-speed rotating plate stirring blade (eg, Power Mill, manufactured by Dalton Co., Ltd.). Since it can be crushed into a powder by impact, the secondary particles of zonotlite are less likely to be broken. The zonotolite aggregates are easier to disintegrate if they have many holes, but if they have too many holes, they become rather brittle and workability deteriorates. Therefore, the zonotolite aggregate has a bulk density of 0.15 to 0.25 g / c.
It is preferable that holes are formed so as to be within the range of m ³ .

According to the above-mentioned production method, the D ₅₀ of the zonotolite secondary particles dispersed in the zonotolite slurry is adjusted to 60 μm.
m, preferably 25 to 47 μm, particularly preferably 3 to
This is a particularly advantageous method when the thickness is 0 to 47 μm. Physical strength of xonotlite secondary particles tends to be weaker the particle size increases, the D ₅₀ is equal to or greater than 60 [mu] m, increasingly proportion of xonotlite secondary particles are broken upon crushing the xonotlite aggregates This is because the mixing amount of the fine particles increases. Adjustment of D ₅₀ of xonotlite secondary particles in the slurry, and the slurry stirred with a stirring blade, can be carried out by applying a shearing force to the xonotlite secondary particles.

As a method for producing the zonotolite powder, a spray drying method in which the zonotolite slurry is directly sprayed and dried while being sprayed can be employed. However, in this case, the production cost increases, and thus the zonotolite slurry obtained from the zonotolite slurry is used. The method of crushing the aggregate is industrially advantageous.

Next, regarding the friction material composition of the present invention,
This will be described in detail below.

The friction material composition of the present invention, like the conventional friction material composition, fiber base material, friction modifier, and is a composition based on a binder, D ₅₀ in the composition Is 2
In the range of 5 to 80 m, D ₁₀ is characterized in that the 15μm or more xonotlite secondary particles are dispersed. The composition of these fiber base material, friction modifier, binder, and zonotolite secondary particles is not particularly limited, but usually,
The fiber base material is 5 to 40% by mass, the friction modifier is 10 to 50% by mass, the binder resin is 5 to 30% by mass, and the zonotrite secondary particles are 2 to 40% by mass.

The zonotolite secondary particles used in the friction material composition of the present invention may be used without any treatment. However, a resin material (binder) kneaded together by surface treatment with a silane coupling agent or the like. And the adhesion to the friction modifier.

Examples of the fiber base material used in the friction material composition of the present invention include metal fibers (eg, steel fibers, brass fibers, copper fibers), synthetic resin fibers (eg, aromatic polyamide fibers), and inorganic material fibers. (Examples include, but are not limited to, fibrous base materials such as (eg, rock wool, potassium titanate whisker, fibrous magnesium compound, and fibrous zonotolite).

Examples of the friction modifier used in the friction material composition of the present invention include graphite, powdered aluminum,
Friction modifiers such as powdered copper, metal oxides (eg, silica, aluminum oxide), metal salts (eg, barium sulfate, clay, calcium carbonate), and organic powders (eg, cashew dust, rubber dust) are given. It is possible, but not limited to these.

A typical example of the binder resin used in the friction material composition of the present invention is a phenol resin. Further, a melamine resin, an epoxy resin or the like can be used alone or in combination with a phenol resin.

The friction material composition of the present invention is produced by mixing a fibrous base material, a friction modifier, a binder, and zonotolite secondary particles with a mixer in the same manner as a normal friction material composition. The zonotorite secondary particles may be charged to the mixer in a powder state, or may be charged to the mixer in an aggregate state before being formed into a powder.

[0027]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but these do not limit the present invention.

[Example 1] (1) Production of zonotolite slurry Quick lime (CaO purity: 97.5% by mass) as a lime raw material
31 kg, silica powder as siliceous raw material (Brain specific surface area: 7000 cm ² / g, SiO ₂ purity 99.5% by mass)
33.2 kg and 650 liters of tap water with an internal volume of 1.
It was charged into a 0 m ³ SUS316 autoclave with a stirrer. Then, the temperature inside the autoclave was raised to 225 ° C. at a rate of 2 ° C./min while stirring at a rotation speed of a stirrer of 70 rpm, and the temperature was kept at 225 ° C. for 2 hours to perform a hydrothermal synthesis reaction. Then, it was allowed to cool to room temperature with stirring to obtain a zonotolite slurry. When the X-ray diffraction pattern of the particles in this slurry was measured, only the diffraction peak attributed to zonotolite was observed. When the volume-based particle diameter was measured by a laser diffraction method, the D ₅₀ of the particles was 43 μm. Met.

(2) Production of zonotolite aggregate The zonotolite slurry obtained in the above (1) is dehydrated with a vacuum filter (horizontal Honeyvis filter) to a wet solid (water content of 84% by mass), In a dryer (box-type dryer jumbo oven) at 150 ° C
And dried with zonotrite aggregate (water 0.1% by mass)
I got The apparent density of the obtained zonotolite aggregate,
A method similar to the method for measuring the apparent density of magnesia clinker by the Japan Society for the Promotion of Science (No. 124 Committee) (Refractory Handbook 197
It was 0.18 g / cm ^{3 as} measured by the 1-year edition, pages 292 to 295, Gakushin method 2, refractory technology association).

(3) Production of zonotolite powder The zonotolite aggregate obtained in the above (2) was converted to a power mill P-3 (2900 rpm, sieve opening 2 m, manufactured by Dalton Co., Ltd.).
m) to obtain a zonotlite powder. About the obtained zonotolite powder, surface observation with an electron microscope, particle size distribution, specific surface area, loose apparent specific gravity, solid apparent specific gravity, and compaction characteristics were measured, and fluidity and jetness were evaluated.

Example 2 Example 1 was repeated except that the rotation speed of the stirrer of the autoclave with stirrer was changed to 85 rpm.
The same operation as in (1) was performed to obtain a zonotolite slurry. When the X-ray diffraction pattern of the particles in this slurry was measured, only the diffraction peak attributed to zonotolite was recognized, and when the volume-based particle diameter was measured by a laser diffraction method, the D ₅₀ of the particles was 34 μm. there were. Subsequently, the same operation as in Example 1 (2) was performed to dehydrate and dry the zonotolite slurry to obtain a zonotolite aggregate. The apparent density of the obtained zonotolite aggregate was measured by a method similar to the method of measuring the apparent density of magnesia clinker by the Japan Society for the Promotion of Science (No. 124 Committee), and it was 0.17 g / cm ³ . Next, the same operation as in Example 1 (3) was performed to disintegrate the zonotolite aggregate to obtain a zonotolite powder.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the rotation speed of the stirrer of the autoclave with stirrer was changed to 50 rpm.
The same operation as in (1) was performed to obtain a zonotolite slurry. When the X-ray diffraction pattern of the particles in this slurry was measured, only the diffraction peak attributed to zonotolite was recognized, and when the volume-based particle diameter was measured by a laser diffraction method, the D ₅₀ of the particles was 60 μm. there were. Subsequently, the same operation as in Example 1 (2) was performed to dehydrate and dry the zonotolite slurry to obtain a zonotolite aggregate. The apparent density of the obtained zonotolite aggregate was measured by a method similar to the method of measuring the apparent density of magnesia clinker by the Japan Society for the Promotion of Science (Committee 124), and it was 0.18 g / cm ³ . Next, the same operation as in Example 1 (3) was performed to disintegrate the zonotolite aggregate to obtain a zonotolite powder.

[Comparative Example 2] A zonotolite slurry obtained by performing the same operation as in Example 1 (1) was dehydrated with a vacuum filter (horizontal Hanebis filter) to obtain a wet solid (moisture 8).
5% by mass), and the wet solid was dehydrated with a pressure dehydrator until the water content became 70% by mass, and then dried at 150 ° C. in a drier (box-type dryer jumbo oven). An aggregate (0.1% by mass of water) was obtained.
The bulk density of the obtained zonotolite aggregate was measured by a method for measuring bulk density of magnesia clinker by the Japan Society for the Promotion of Science (No. 124 Committee), and it was 0.40 g / cm ³ . Subsequently, the zonotolite aggregate was pulverized by an impact type pulverizer pulverizer to obtain a zonotolite powder.

Reference Example A commercially available spherical zonotorite powder (trade name: Promaxon) was prepared as a reference example.

[Evaluation of Zonotorite Powder] (1) Results of Surface Observation by Electron Microscope FIG. 1 shows an electron micrograph of the zonotorite powder produced in Example 1, and FIG. 2 shows an electron micrograph of the zonotorite powder produced in Example 2. Is shown. In the zonotolite powders of Examples 1 and 2, secondary spherical zonotolite particles having a uniform particle size were observed, and almost no fine particles were observed.
On the other hand, in the zonotolite powder produced in Comparative Examples 1 and 2, porous zonotolite secondary particles and fine particles were observed, and fine particles were also observed in the zonotolite powder of the reference example.

(2) Particle Size Distribution Measurement Results The particle size distribution is measured by using a laser diffraction / scattering type particle size distribution analyzer (Laser Micron Sizer LMS-30,
(Manufactured by Seishin Enterprise Co., Ltd.). The particle size distribution was measured using water as the dispersion medium, and the addition of the dispersant and the dispersion treatment of the zonotolite powder by ultrasonic dispersion were not performed. Table 1 shows D ₁₀ , D ₅₀ and D ₉₀ (particle diameters corresponding to 90% from the smaller particle diameter of the cumulative distribution curve) obtained from the cumulative distribution curve. Xonotlite powders of Examples 1-2 from Table 1 are D ₁₀ of xonotlite secondary particles 20μm or more, respectively, it can be seen that incorporation of Bifunko small.

(3) Specific surface area measurement result The specific surface area was measured by the BET method using nitrogen adsorption. Table 1 shows the results.

(4) Measurement results of loose apparent specific gravity and solid apparent specific gravity Measurement of loose apparent specific gravity and solid apparent specific gravity was carried out by a predetermined method using a powder tester manufactured by Hosokawa Micron Corporation. Table 1 shows the results.

(5) Measurement Results of Consolidation Characteristics The consolidation characteristics were evaluated by calculating the relative density of a compact (pellet) obtained by pressing zonotlite powder with a uniaxial molding machine. The molding pressure was 20 kg / cm ² and 2000 kg / cm ² . The calculation of the relative density was performed by the following equation (1). Table 1 shows the results.

Equation (1) Relative density = density of molded article (g / cm ³ ) / density of zonotolite (g / cm ³ ) × 100 [however, the density of zonotolite is 2.48 (g / cm ³ )]
And ]

From the results shown in Table 1, it can be seen that the zonotrite powders of Examples 1 and 2 and the relative densities of the molded articles molded at a molding pressure of 20 kg / cm ² and the comparative examples 1 and 2 were as follows. Although there is a difference between the zonotolite powder and the zonotolite powder of the reference example, a molding pressure of 2,000
In the relative density of the molded body molded at kg / cm ² ,
It can be seen that there is no significant difference between the zonotolite powders of Examples 1 and 2, the zonotolite powders of Comparative Examples 1 and 2, and the zonotolite powder of the reference example. This is the molding pressure 2000kg /
It is considered that the compact obtained by molding at ² cm ² was compacted in a state where the secondary particles of zonotolite were broken down to the primary particle level.

[0042]

[Table 1] Table 1 試 料 Sample Particle size distribution Specific surface area Looseness Hardening Apparent relative density (μm) (m ² / g) Multiplied specific gravity Specific gravity ───────── ──────── (g / cm ³ ) (g / cm ³ ) Molding pressure (kg / cm ² ) D ₁₀ D ₅₀ D ₉₀ ───────── 20 2000 ───────────────────────────── ─────── Example 1 30 42 63 49.1 0.095 0.145 10.5 54.8 Example 2 24 35 51 53.1 0.093 0.143 9.6 54.0 ───────────────────── ─────────────── Comparative Example 1 12 32 59 47.0 0.080 0.136 11.6 55.6 Comparative Example 2 3 7 17 43.8 0.097 0.186 21.2 54.4 ───────────── ─────────────────────── Reference example 8 33 131 34.2 0.081 0.157 11.9 53.6 ────────────── ─────────────────────

(6) Results of Evaluation of Fluidity and Jetability The evaluation of fluidity and jettability was carried out by using a powder tester manufactured by Hosokawa Micron Corp., and the angle of repose of zonotrite powder,
The collapse angle, the difference angle (the difference between the angle of repose and the collapse angle), the degree of compression, the degree of cohesion, the spatula angle, and the degree of dispersion are measured, and from these measured values, the fluidity index and jetness index proposed by Carr (Particle Handbook No. 2 Printing, Asakura Shoten, published in 1996, pp. 219). Table 2 shows the measurement results of the angle of repose, collapse angle, difference angle, compression degree, cohesion degree, spatula angle and dispersity of the zonotolite powder, and Table 4 shows the fluidity index and the jetness index. From the results shown in Table 3, it can be seen that the zonotolite powders of Examples 1 and 2 have high fluidity and jettability, and are excellent in workability (handling).

[0044]

[Table 2] Table 2 ─────────────────────────────────── Sample Repose angle Collapse angle Difference angle Compression Degree Cohesion degree Suphatula angle Dispersion degree ─────────────────────────────────── Example 1 44 29 15 36 2 45 70 Example 2 44 29 15 35 2.9 40.5 69.5 ─────────────────────────────────── Comparative Example 1 45 37 8 41 48.9 60 55 Comparative Example 2 43 33 10 48 53.5 59 28.2 ───────────────────────────────── ── Reference example 53 41 12 49 68.8 58.5 42.2 ───────────────────────────────────

[0045]

[Table 3] Table 3 試 料 Sample fluidity index Jetability index ────────────── << Example 1 56 82 Example 2 56 82 >> Comparative Example 1 39 64 Comparative Example 2 39 58 ─────────────────────── Reference example 30 56 ─────────────────────── ──

Example 3 25 parts by mass of the zonotolite powder produced in Example 1 above, steel fiber (1.5 m in length)
m) 25 parts by mass, 10 parts by mass of cashew dust, 20 parts by mass of barium sulfate, 10 parts by mass of graphite, and 10 parts by mass of phenol resin were mixed, and pressure was applied to produce a friction material sheet having a thickness of 10 mm.

Example 4 A friction material having a thickness of 10 mm was produced in the same manner as in Example 3 except that the same amount of the zonotolite powder produced in Example 2 was used instead of the zonotolite powder produced in Example 1. A sheet was manufactured.

Comparative Example 3 A friction material having a thickness of 10 mm was produced in the same manner as in Example 3 except that the same amount of the zonotolite powder produced in Comparative Example 1 was used instead of the zonotolite powder produced in Example 1. A sheet was manufactured.

[Evaluation of Friction Material Sheets] The cross sections of the friction material sheets of Example 3 and Example 4 and the friction material sheet of Comparative Example 3 were observed with a microscope, and the friction materials of Examples 3 and 4 were observed. In the sheet, the zonotolite particles were homogeneously dispersed, but in the friction material sheet of Comparative Example 3, the dispersion of the zonotolite particles was uneven.

[0050]

The zonotolite powder of the present invention exhibits excellent fluidity and jet properties, so that a friction material composition having excellent homogeneity can be industrially advantageously produced. Further, by using the method for producing a zonotolite powder of the present invention, a zonotolite powder having excellent fluidity and jettability can be produced industrially at low cost. In the friction material composition of the present invention, since the zonotorite secondary particles are uniformly dispersed, a friction material sheet having high strength and excellent in braking characteristics such as friction characteristics can be manufactured. Therefore, the sheet-like friction material of the present invention can be advantageously used as a material for brake linings and clutch facings.

[Brief description of the drawings]

FIG. 1 is an electron micrograph of the zonotolite powder produced in Example 1.

FIG. 2 is an electron micrograph of the zonotolite powder produced in Example 2.

Claims (6)

[Claims] 1. A collection of porous spherical secondary particles xonotlite primary particles formed by agglomerating the spherical fibrous range D ₅₀ of the porous spherical secondary particles of 25～80Myuemu,
Xonotlite powder wherein a D ₁₀ of at 15μm or more. 2. A xonotlite powder according to claim 1 in which D ₅₀ is characterized in that in the range of 25～47Myuemu. 3. The fibrous zonotolite primary particles are D ₅₀
Forms a porous spherical secondary particle having a diameter of less than 60 μm, and disperses the zonotolite slurry dispersed therein under reduced pressure to obtain a wet solid, and then dissolves the zonotolite aggregate obtained by drying the wet solid. The method for producing a zonotolite powder according to claim 2, wherein 4. A friction material composition porous spherical secondary particles xonotlite primary fibrous particles is by agglomerating spherically are dispersed, D ₅₀ of the porous spherical secondary particles 2
In the range of 5 to 80 m, the friction material composition, characterized in that D ₁₀ of at 15μm or more. 5. The friction material composition according to claim 4, wherein D ₅₀ is in the range of 25 to 47 μm. 6. A sheet-like friction material obtained by pressing the friction material composition according to claim 4 or 5.