JP2012241067A - Granule for friction material and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing granules for friction material, capable of producing a friction material having excellent mechanical strength without needing reinforcement with a fiber base material by a simplified process free from: aggregation of material; wall surface adhesion thereof in a manufacturing process; or generation of powder dust.SOLUTION: The method for producing granules for friction material includes: granulating a friction adjustment particle material in the presence of a solution containing a thermosetting resin composition including potassium titanate particles having an average particle size of 0.1-0.5 μm, uncrosslinked rubber and a thermosetting resin; and granulating the resulting granulates in the presence of a solution containing a water-soluble or water-dispersible binder.

Description

  The present invention relates to a friction material excellent in quality such as friction performance and a method for producing a granulated material for friction material that can be used for the friction material, and in particular, brake pads, brake linings, clutch facings, etc. for automobiles, railway vehicles, industrial machines, etc. It is related with the friction material used for.

Friction materials used for brakes such as disc brakes and drum brakes, or clutches, are made of a fiber base material that reinforces, a friction adjustment material that imparts friction and adjusts its friction performance, and these components. It is made of a material such as a binding material.
As materials for imparting a friction effect to the friction material and adjusting the friction performance, various solid powder materials called friction adjustment materials, solid lubricants, fillers and the like are generally used. These have their respective characteristics and are usually used in friction materials in combination of two or more types.

  Phenolic thermosetting resins (including various elastomer modifications) that are usually used as a binder for friction materials are excellent in heat resistance and durability, but such phenolic thermosetting resins can be used for aramid fibers, etc. Since the wettability with the fiber base material is not sufficient, a resin composition with improved wettability is disclosed in Patent Document 1 and Patent Document 2 includes fiber base materials such as aramid fiber, straight phenol resin and phenol aralkyl resin. , Under high load conditions to the disk pad friction material comprising the composition containing the filler, reducing the occurrence of squealing while maintaining the durability as a disk pad, and the friction material and back plate adhesion surface edge and the vicinity A disk pad that reduces cracks and peeling is disclosed.

  In addition, since these raw materials of friction materials are powder, environmental aspects and process reforms such as material aggregation, wall adhesion within the manufacturing process, generation of dust, and inhibition of process simplification due to blending of fiber materials, etc. It is a big problem on the top. As a countermeasure against this, there is a method of using these powder raw materials as a granulated product. Generally, the granulated product has a spherical shape with a strong surface. Residue of this is a major cause of a decrease in strength of the molded body. As a solution to this problem, Patent Document 3 discloses a method using a water-soluble or water-dispersible binder such as polyvinyl alcohol as a granulating binder.

JP 2004-231850 A JP 2006-275198 A JP 2008-189738 A

  Under such circumstances, aromatic polyamide fibers such as aramid fibers, when used for friction materials, are susceptible to segregation / separation of powder raw materials, or quality and environmental effects due to scattering. There is a demand for friction materials and the like that do not contain any of them. However, in the system including the conventional resin composition, since the adhesion between the raw materials is small, there is a problem that the performance deteriorates when the fiber is removed from the friction material and the like, and it is safer and has sufficient durability strength. The appearance of friction materials is desired.

  On the other hand, the conventional friction material, even when using a conventional granulated material, because these granulated products are molded using a phenolic thermosetting resin conventionally used as a binder for molding, In terms of using organic fibers such as aramid fibers, there are the same problems as described above, and further, there are problems such as inhibition of simplification of the process by blending fiber materials.

  On the other hand, in the technique of Patent Document 3, since a water-soluble or water-dispersible binder is used as a granulating binder, there is a problem in terms of heat resistance, and for molding for molding a granulated product. Since the binder is powder, it has environmental problems such as material aggregation, wall surface adhesion in the manufacturing process, and generation of dust.

This invention solves said subject and provides the friction material which is excellent in sufficient mechanical strength, without reinforcing with fiber base materials, such as an aramid fiber.
Furthermore, the present invention can simplify the process of a friction material that is excellent in mechanical strength without being reinforced with a fiber base material, without material aggregation, wall surface adhesion or dust generation in the manufacturing process. The manufacturing method of the excellent friction material manufactured by the method is provided.

  As a result of various studies, the present inventors have obtained a granulated product using a specific thermosetting resin composition-containing solution as a binder for granulation, and further granulated with a water-soluble or water-dispersible binder-containing solution. Thus, it was found that the above problem can be solved by obtaining a granulated product for a friction material and producing a friction material using this, and the present invention has been achieved as follows.

(1) A friction adjusting particle material is prepared in the presence of a thermosetting resin composition-containing solution containing potassium titanate particles having an average particle size of 0.1 to 0.5 μm, uncrosslinked rubber, and a thermosetting resin. A method for producing a granulated product for a friction material, comprising granulating the resulting granulated product in the presence of a water-soluble or water-dispersible binder-containing solution.
(2) A method for producing a friction material, characterized in that a friction material is obtained by molding the granulated material for friction material obtained by the method described in (1) above.

(3) A friction adjusting particle material is prepared in the presence of a thermosetting resin composition-containing solution containing potassium titanate particles having an average particle size of 0.1 to 0.5 μm, uncrosslinked rubber, and a thermosetting resin. A friction material obtained by molding a granulated product for a friction material obtained by granulating the obtained granulated product in the presence of a water-soluble or water-dispersible binder-containing solution.

  The present inventors used a thermosetting resin composition-containing solution containing potassium titanate particles having an average particle size of 0.1 to 0.5 μm, uncrosslinked rubber and a thermosetting resin as a friction adjusting particle material (raw material). ), The raw material is firmly bonded, and it is found that a friction material having excellent mechanical properties can be obtained without reinforcing with a fiber substrate such as an aramid fiber. is there. Furthermore, in the present invention, a granulated product obtained by using the thermosetting resin composition-containing solution as a binder for granulation (hereinafter sometimes referred to as “primary granulated product”) is water-soluble or water-soluble. By granulating in the presence of a dispersible binder-containing solution (hereinafter, the resulting granulated product may be referred to as “secondary granulated product”), the mechanical properties are sufficiently maintained. It has been found that the wall surface adhesion and the generation of dust caused by the friction material material with insufficient particle growth can be effectively suppressed.

  Further, the granulated product of the present invention can be obtained by granulating the thermosetting resin composition coated on the surface of the friction-adjusting particle material (raw material) with the water-soluble or water-dispersible binder-containing solution. When fully cured and thermally cured, the raw materials are sufficiently bonded together to form a friction material. Therefore, molding binders such as phenolic resins that have been used in the past when molding these granules There is no need to use powder, and the movement due to softening of the molding binder during thermosetting is reduced, and the friction material reflecting the structure of the granulated product, that is, the arrangement of the raw materials can be obtained. .

  By using the granulated material for friction material of the present invention, a friction material having excellent mechanical strength without reinforcing with a fiber base such as aramid fiber can be used for material aggregation, wall surface adhesion, dust in the manufacturing process. Can be effectively produced without problems such as the occurrence of the above, and the inhibition of the simplification of the process due to the blending of the fiber material.

  The friction material of the present invention comprises a primary granulated product obtained by using a specific thermosetting resin composition-containing solution as a particle material for friction adjustment and a water-soluble or water-dispersible binder-containing solution. It is obtained by molding a secondary granulated product obtained by granulation. The friction material usually has a fiber base material that acts to reinforce the friction material, a binding material for integrating the materials contained in the friction material, and a friction effect on the friction material and adjusts its friction performance. Various solid powder materials are used, and these solid powder materials are sometimes referred to as friction modifiers, solid lubricants, fillers, and the like. In the present invention, solid powder materials that give a frictional action to the friction material and adjust its friction performance, other than the fiber base material and the binder, are collectively referred to as “friction adjusting particles” without particularly distinguishing them. “Material” or simply “friction modifier”.

  The friction material of the present invention uses a thermosetting resin composition-containing solution containing potassium titanate particles having an average particle size of 0.1 to 0.5 μm, uncrosslinked rubber, and a thermosetting resin as a binder for granulation. As a result, the particle material for friction adjustment is granulated, and the granulated materials are firmly bonded to each other, so that sufficient mechanical strength can be obtained without containing a fiber base material. . Furthermore, in the present invention, even when granulation is performed using a water-soluble or water-dispersible binder-containing solution, the function of the thermosetting resin composition can be sufficiently exerted, and further generation of dust in the production process It is possible to effectively solve such problems.

In the present invention, potassium titanate particles are used as a reinforcing material for a thermosetting resin. In order to disperse the potassium titanate particles in the thermosetting resin, the particles are preferably smaller than the uncrosslinked rubber and other raw materials for the friction material.
Therefore, the average particle diameter of the potassium titanate particles in the present invention is preferably 0.1 to 0.5 μm, more preferably 0.1 to 0.3 μm. By using the potassium titanate particles in this range, it is possible to improve the mechanical strength in a high temperature range of 300 ° C. or higher. In addition, the measuring method of an average particle diameter is a value measured with a laser diffraction type or a dynamic light scattering type particle size distribution meter. The same applies to other powders of the thermosetting resin composition.

  By using the thermosetting resin composition of the present invention together with the friction modifier, the adhesion between the friction modifiers can be improved by the polymer blend of the thermosetting resin and the uncrosslinked rubber. Moreover, the potassium titanate particles in the thermosetting resin improve the mechanical strength of the thermosetting resin composition after thermosetting due to the anchor effect. Due to these combined effects, it is presumed that the thermosetting resin composition of the present invention functions as a binder for the friction modifier and becomes a friction material having high mechanical strength even at high temperatures. Hereinafter, the thermosetting resin composition of the present invention will be described in more detail.

The potassium titanate particles used in the present invention are not particularly limited as long as they have a predetermined average particle diameter, but those that are in circulation usually have a large average particle diameter and are subjected to wet pulverization treatment. Preferably, potassium titanate particles are used.
Examples of the wet pulverizer include a jet mill and a bead mill, and a bead mill is particularly preferable. Any dispersion medium can be used without particular limitation as long as it does not adversely affect the structure and dispersibility of the potassium titanate particles by treatment, and isopropyl alcohol, ethanol and the like are preferable.
Moreover, zirconia, an alumina, etc. are mentioned as a bead used for a bead mill, It is preferable to select bead diameter from 0.05-0.3 mm. In this case, potassium titanate particles having a predetermined average particle diameter can be obtained by combining the filling rate of beads, processing time, and the like.

The pulverized potassium titanate particles can be used for the preparation of a thermosetting resin composition by drying to form a powder or as a slurry as it is.
The potassium titanate particles are preferably 5 to 25% by mass, more preferably 10 to 20% by mass with respect to the entire thermosetting resin composition (solid content), and can effectively exhibit the effects of the present invention. If it is less than 5% by mass, the effect of addition is small, and if it exceeds 25% by mass, no further improvement effect is exhibited.

Uncrosslinked rubber has a function of strengthening the adhesiveness at the interface with the friction adjusting particle material used together with the thermosetting resin composition.
Examples of uncrosslinked rubbers used include NBR (acrylonitrile butadiene rubber), SBR (styrene butadiene rubber), IIR (butyl rubber), NR (natural rubber), IR (synthetic natural rubber), BR (butadiene rubber), ACM ( Acrylic rubber), EPDM (ethylene propylene rubber), and modified products thereof (introduced with functional groups such as amino groups and carboxyl groups), etc., and those having the desired characteristics (monomer compounding ratio) are appropriately selected. And it uses individually or in combination of 2 or more types. In this case, the same type or different types may be used. For example, NBR is preferably a high nitrile type or a medium / high nitrile type. Here, the high nitrile type means that the bound acrylonitrile content is 36 to 42% by mass relative to NBR, and the medium and high nitrile type is that the bound acrylonitrile content is 31 to 35% by mass relative to NBR. Means things.

  3-35 mass% is preferable with respect to the whole thermosetting resin composition (solid content), and uncrosslinked rubber | gum has more preferable 10-30 mass%. In this range, a sufficient addition effect can be obtained while maintaining a sufficient mechanical strength of the friction material, and the effects of the present invention can be effectively exhibited.

Examples of thermosetting resins include phenol resins (including straight phenol resins, various modified phenol resins such as compounds (excluding the uncrosslinked rubber)), melamine resins, epoxy resins, polyimide resins, polyamide resins, and the like. Or two or more types are used in combination.
The thermosetting resin is preferably 40 to 92% by mass, more preferably 50 to 80% by mass with respect to the thermosetting resin composition (solid content), and in this range, the effect of the present invention is effectively exhibited. Can do.

  The thermosetting resin composition of the present invention may contain only potassium titanate particles, uncrosslinked rubber, and thermosetting resin, or other components (excluding organic solvents). There is no restriction | limiting in particular in these other components, An organic substance or an inorganic substance may be sufficient, and 0-30 mass% is used with respect to a thermosetting resin composition (solid content).

Since the thermosetting resin composition of the present invention is used as a binder for granulation, it is preferably used as a solution. Moreover, although there is no restriction | limiting in the manufacturing method of the thermosetting resin composition containing solution of this invention, For example, manufacturing with the following manufacturing methods is preferable.
The organic solvent is not particularly limited as long as it can uniformly dissolve the thermosetting resin and the uncrosslinked rubber. For example, an aromatic compound such as benzene, toluene and xylene, an alcohol type such as methanol, ethanol and isopropyl alcohol. Examples thereof include ketone compounds such as compounds, acetone, methyl ethyl ketone, and methyl isobutyl ketone. Among these, ketone compounds are preferable, and acetone, methyl ethyl ketone, and methyl isobutyl ketone are more preferable. Uncrosslinked rubber, thermosetting resin, and pulverized potassium titanate or slurry thereof are added to these alone or in a mixed solvent to dissolve uncrosslinked rubber and thermosetting resin, and pulverized titanic acid. A thermosetting resin composition-containing solution in which potassium particles are dispersed can be prepared. At this time, it is preferable to perform ultrasonic irradiation treatment for 5 to 15 minutes each in the initial stage and the end stage in which the above-described material is added to the organic solvent. Thereby, aggregation of potassium titanate particles can be effectively prevented.

  In the present invention, various friction modifiers can be used depending on the purpose as a friction modifier for imparting a frictional action and adjusting the friction performance, and usually used for friction materials, abrasives, fillers, Various solid particle materials called solid lubricants can be used.

  As the particle material for friction adjustment used in the present invention, those conventionally used as friction adjustment materials for friction materials can be used. Examples of such friction modifiers include abrasives, lubricants, organic dust, metals, fillers, and the like. These can be blended singly or in combination of two or more depending on the friction characteristics required for the product, for example, the friction coefficient, wear resistance, vibration characteristics, squeal characteristics, and the like.

  There is no restriction | limiting in particular as an abrasive material, Arbitrary things can be suitably selected from the well-known things used as an abrasive material for the friction material conventionally. Specific examples of the abrasive include iron oxide, aluminum oxide, silicon carbide, zirconium oxide, zirconium silicate, magnesium oxide, and silicon dioxide. These may be used alone. You may use combining more than a seed. The blending amount is usually about 0 to 30% by mass, preferably 5 to 15% by mass, based on the total amount of the raw material mixture, from the viewpoint of ensuring the friction coefficient and suppressing the aggressiveness.

  There is no restriction | limiting in particular as a lubricating material, Arbitrary things can be suitably selected from the well-known things currently used as a lubricating material for a friction material. Specific examples of the lubricant include graphite, metal sulfides such as molybdenum disulfide and antimony trisulfide, and these may be used alone or in combination of two or more. May be. The blending amount is usually about 0 to 30% by mass, preferably 0 to 15% by mass, based on the total amount of the raw material mixture, from the viewpoint of securing the lubricating force and the friction coefficient.

  There is no restriction | limiting in particular as organic dust, Arbitrary things can be suitably selected from the well-known thing currently used as organic dust for the friction material. Specific examples of the organic dust include rubber dust such as NBR and SBR, cashew dust, and the like. These may be used alone or in combination of two or more. The blending amount is usually about 0 to 30% by mass, preferably 0 to 15% by mass based on the total amount of the raw material mixture from the viewpoint of suppressing gas generation during fading and maintaining the effect of pores.

  There is no restriction | limiting in particular as metals, Arbitrary things can be suitably selected from the well-known things conventionally used as metals in a friction material. Specific examples of these metals include copper, brass, zinc, iron and the like, and these may be used alone or in combination of two or more. The blending amount is usually about 0 to 50% by mass, preferably 0 to 25% by mass, based on the total amount of the raw material mixture, from the viewpoint of suppressing segregation in the friction material due to an increase in the specific gravity of the granulated product.

  As fillers, inorganic fillers such as calcium carbonate, barium sulfate, or scaly inorganic substances such as vermiculite and mica, and further organic fillers can be contained. These fillers may be used individually by 1 type, and may be used in combination of 2 or more type. The blending amount is usually about 0 to 70% by mass, preferably 0, based on the total amount of the raw material mixture, from the viewpoint of sufficiently spreading the resin binder and maintaining the binding force and suppressing abnormal wear of the friction material. -50 mass%.

  In addition, the friction material of the present invention has various additive components, for example, an antioxidant, a heat stabilizer, an ultraviolet absorber, a light stabilizer, a mold release agent, and a coloring agent, as long as the object of the present invention is not impaired. An agent, a curing agent, and the like can be appropriately contained together with the friction adjusting particle material.

In the present invention, a granulated product (primary granulated product) is produced by using the thermosetting resin composition as a binding solution for granulation of a friction modifier, and further a water-soluble or water-dispersible binder-containing solution is produced. A granulated product (secondary granulated product) is produced by granulation in the presence, and a friction material is produced by molding the secondary granulated product.
Preferred examples of the water-soluble or water-dispersible binder include water-soluble or water-dispersible polymer compounds. Specifically, polyvinyl alcohol, polyvinyl acetal, polyvinyl pyrrolidone, hydroxymethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyvinyl acetate, polyethylene oxide, soluble starch, Examples include casein, gelatin, sodium alginate and the like. These may be used individually by 1 type and may be used in combination of 2 or more type.

  This polyvinyl alcohol has different solubility in water depending on the degree of polymerization and the degree of saponification, and in the present invention, a partially saponified polyvinyl alcohol is preferable, and the degree of polymerization is about 500 to 3500, and the degree of caking is about 85 to 92%. Are preferred.

  The binder-containing liquid may be either an aqueous solution or an aqueous emulsion. The concentration of the water-soluble or water-dispersible binder varies depending on the type of binder used, but is usually about 1 to 10% by mass, preferably 2 to 8% by mass when polyvinyl alcohol is used. In particular, by using a partially saponified polyvinyl alcohol and using a polyvinyl alcohol aqueous solution having a solid content concentration of 4 to 8% by mass in the aqueous solution, fine powders of less than 150 μm can be suppressed in a short time, which is preferable.

  In the present invention, the thermosetting resin composition-containing solution is used as a granulating binder to produce a granulated product containing the above-described friction adjusting particle material and other components used as desired. The granules are further granulated using a water-soluble or water-dispersible binder-containing solution as a binder for granulation, and then mixed using a normal mixer such as a Henschel mixer or a tumbler blender. A friction material can be manufactured by performing treatments such as hot pressing, after-curing, and polishing.

  In the granulated product obtained by growing the particle material for friction material using the thermosetting resin composition-containing solution of the present invention as a binder for granulation, the surface of the particle material for friction adjustment is coated with the thermosetting resin composition. Therefore, it has excellent adhesion of raw materials during thermosetting in the subsequent molding process. In addition, since it is not necessary to use a molding binder powder such as phenol resin in molding, the movement due to softening of the molding binder during thermosetting is small and reflects the structure of the granulated product, that is, friction material particles A friction material in which the arrangement structure of materials and the like is controlled can be obtained. In addition, by granulating using a water-soluble or water-dispersible binder-containing solution, without inhibiting the advantages of using the above thermosetting resin composition-containing solution as a binder for granulation, The friction material can be manufactured without causing problems such as wall surface adhesion in the manufacturing process, generation of dust, and inhibition of simplification of the process due to blending of the fiber material.

The granulation method of the primary granulated product and the secondary granulated product is not limited as long as it is a method capable of producing a granulated product including the above-mentioned components. For example, fluidized bed granulation method, stirring, kneading It can be produced by a granulation method or the like, or a composite granulation method combining these.
When the friction material granulated product of the present invention is granulated in a fluidized bed, the raw material mixture prepared as described above and a thermosetting resin composition-containing solution are used, and the raw material mixture is used as the thermosetting resin. A primary granulated product is obtained by granulation in a fluidized bed in the presence of a composition-containing solution, and then the primary granulated product is granulated in a fluidized bed in the presence of a water-soluble or water-dispersible binder. Thus, a granulated product for a friction material (secondary granulated product) can be produced.
The fluidized bed granulator used for this granulation is not particularly limited as long as it is a granulator capable of forming a fluidized bed by the gas blown from below, and various conventionally known fluidized bed granulators, For example, a normal fluidized bed granulator, a circulating fluidized bed granulator, a forced circulating fluidized bed granulator, a spouted bed granulator, or the like can be used.

  As a specific granulation method in the case of using the composite granulation method (stirring rolling fluidized bed type), the raw material mixture powder is placed in a container having a fluidized plate rotor at the bottom and added from the fluidized plate rotor. By feeding warm air, the powder is made into a fluidized bed state, and the powder is further stirred by a stirring blade, and a granulating binder solution (the solution containing the thermosetting resin composition) is sprayed onto the powder. The primary granulated product can be formed by bonding the powders in a porous state by spraying from the above. The same can be done when forming a secondary granulated product.

  In this case, the temperature in the container that is the fluidized bed, the pressure in the container (the state of the fluidized bed), the concentration and amount of the binder-containing liquid to be sprayed, the type of the binder, and the spraying pressure of the binder-containing liquid The porosity, particle diameter, etc. of the friction material granule can be adjusted by controlling the rotation speed of the fluidized plate rotor and the stirring blade. For example, in order to increase the porosity, it is only necessary to relatively increase the temperature in the container, increase the binder concentration, decrease the spray amount, increase the spray pressure, and relatively increase the particle diameter. The container temperature may be lowered, the binder concentration increased, the spray amount increased, and the spray pressure decreased.

  The friction material of the present invention comprises 75 to 95% by mass of a friction adjusting particle material, 5 to 20% by mass of a thermosetting resin composition (solid content), and a water-soluble or water-dispersible binder (based on the entire friction material). It is preferable to contain 0.1 to 5% by mass of the solid content), and 80 to 90% by mass of the particle material for friction adjustment, 5 to 15% by mass of the thermosetting resin composition (solid content), and the entire friction material More preferably, it contains 0.1 to 3% by mass of a water-soluble or water-dispersible binder (solid content). By setting it as this range, the effect of this invention can be exhibited effectively. In particular, the content of the water-soluble or water-dispersible binder is preferably less than 2% by mass. Within this range, the influence of secondary granulation is small, and the mechanical strength of the friction material can be sufficiently ensured. It is possible and preferable.

  The granulated product for friction material of the present invention is preferably a granulated product for friction material having the following physical properties. That is, the particle diameter is 100 to 2000 μm from the viewpoint of fluidity, and the average particle diameter D50 is about 300 to 900 μm. The particle diameter and the average particle diameter are measured with a laser diffraction / scattering particle size distribution analyzer (SALD-2000A manufactured by Shimadzu Corporation), and the average particle diameter D50 means a volume-based integrated 50% diameter. Moreover, the angle of repose measured based on JISR9301-2-2 is 40 degrees or less. When the angle of repose exceeds 40 °, the fluidity is insufficient, and the lower limit is usually about 15 °. A preferable angle of repose is 20 to 40 °, and more preferably 20 to 35 °. Furthermore, the compressive fracture strength is 10 MPa or less. When this compressive fracture strength exceeds 10 MPa, when the granulated product is put into a thermoforming mold and subjected to heat and pressure molding, the granulated product is not easily broken, and the granulated product interface remains in the molded product. It causes a decrease in strength. On the other hand, if the compressive fracture strength is too low, problems such as breakage occur during conveyance of the granulated product or mixing of the granulated product with other components. Therefore, the lower limit of the compressive fracture strength is usually about 1 MPa. A preferable compressive fracture strength is 1 to 10 MPa, and more preferably 1 to 5 MPa. In addition, this compressive fracture strength was measured with the micro compression tester (Shimadzu MCTM-500).

  The friction material of the present invention can be produced by heat-pressing the friction material granule obtained as described above to obtain a thermoformed product, followed by heat treatment. That is, the granulated material for friction material obtained as described above is put into a thermoforming mold, heated and pressed to produce a thermoformed body, and then the thermoformed body is further heat treated to obtain a desired friction. Produce material.

  In the present invention, when the granulated material for friction material is put into a thermoforming die and subjected to heat and pressure molding, the mixture of the granulated material for friction material and the fiber base material may be put into the thermoforming die. it can. In this case, the fibrous base material has a function of forming a skeleton in the friction material and maintaining the skeleton so that pores formed in the friction material are not crushed.

  As the fiber substrate, 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, inorganic fibers include inorganic whiskers such as potassium titanate whiskers and silicon carbide whiskers; glass fibers; carbon fibers; mineral fibers such as wollastonite, sepiolite, attapulgite, halloysite, mordenite, rock wool; alumina silica-based fibers, etc. Ceramic fibers; metal fibers such as aluminum fibers, stainless fibers, copper fibers, brass fibers, nickel fibers, and the like. These fibrous substances may be used alone or in combination of two or more.

  The average fiber diameter of the fiber base is usually about 0.1 to 500 μm, preferably 0.1 to 300 μm from the viewpoint of strength, and the average length is usually 5 to 1000 μm, preferably from the viewpoint of reinforcement. 10 to 300 μm.

  The ratio of the granulated material for friction material of the present invention to the fiber base material is such that the fibrous base material forms a skeleton in the friction material, and the pores formed in the friction material are prevented from collapsing. Based on the total amount, the fiber base material is preferably 3 to 50% by mass, and more preferably 10 to 45% by mass.

  In the present invention, the friction material granule or the mixture of the friction material granule and the fiber base material is put into a thermoforming mold, and the conditions for heat-press molding are usually set to a temperature of 100. ˜250 ° C., pressure 10-70 MPa, preferably temperature 140-190 ° C., pressure 30-50 MPa.

  In the present invention, by further heat-treating the thermoformed body, a friction material having the desired raw material arrangement and porosity can be produced. This heat treatment is usually performed at a temperature of about 150 to 350 ° C. for about 0.5 to 12 hours, preferably at a temperature of 200 to 300 ° C. for 0.5 to 6 hours.

  For example, when manufacturing a brake pad for a disc brake, a pressure plate formed into a predetermined shape by a sheet metal press, subjected to a degreasing treatment and a primer treatment, and coated with an adhesive, and the above-mentioned granulated material for friction material or A mixture of them and the fiber base material can be manufactured by a process of thermoforming at a predetermined temperature and pressure in a thermoforming process, fixing both members together, performing after-cure, and finally applying a finishing treatment. it can.

According to the present invention, by forming the friction material using the granulated material for friction material of the present invention, the following effects can be obtained.
(1) Since the primary granulated product has a structure whose surface is coated with the thermosetting resin composition of the present invention, it has excellent adhesion between the granulated products at the time of thermosetting, and uses a fiber base material. A friction material having a sufficient strength can be obtained. In addition, since a molding binder powder such as phenol resin is not required, movement due to softening of the molding binder during thermosetting is small, and a friction material reflecting the structure of the granulated product can be obtained. Moreover, separation / segregation of each raw material can be suppressed, and each component can be uniformly dispersed.
(2) Further, since secondary granulation is performed using a water-soluble or water-dispersible binder-containing solution, even if there are fine particles that could not be sufficiently grown in the primary granulation, the particles were sufficiently grown. The next granulated product can be obtained, dust generation and the like can be suppressed, and the above advantages are not impaired.

  Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Preparation Example 1 (Preparation of thermosetting resin composition-containing solution)
1) Preparation of potassium titanate fine particles Dispersion of potassium titanate particles having an average particle size of 117 nm in 2-propanol by dynamic light scattering particle size distribution measurement (Nanotrack UPA manufactured by Nikkiso Co., Ltd.) by wet grinding with a bead mill. A slurry was obtained.

2) Preparation of thermosetting resin composition containing solution The thermosetting resin composition of the mixing | blending as shown in Table 1 was prepared in the following procedure.
The NBR used was a high nitrile type, the phenol resin was a novolak type, and 10% by mass of hexamethylenetetramine was added as a curing agent. First, NBR and phenol resin are dissolved in 2-butanone, and then the potassium titanate fine particles dispersed in 2-propanol prepared above are mixed, followed by ultrasonic irradiation to disperse the potassium titanate fine particles. A thermosetting resin composition was obtained. In this case, the solid content of the thermosetting resin composition in 2-butanone was adjusted to 30% by mass and used as a binder solution for granulation of the composite fluidized bed.

Preparation Example 2 (Preparation of water-soluble binder-containing solution)
Using partially saponified polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., GH-20), an aqueous polyvinyl alcohol solution prepared in a solid content concentration of 6% by mass in ion-exchanged water was prepared.

Example 1
1) Production of primary granulated material Using a composite fluidized bed (SFC-MINI manufactured by Freund Sangyo Co., Ltd.), the friction modifier shown in the column of primary granulated material in Table 2 is flowed in the amount shown in the same column. Injected into the layer and sprayed the thermosetting resin composition-containing solution having a solid content of 30% by mass prepared as described above so that the solid content addition ratio to the friction material was 10% by mass, The raw material was granulated and dried to produce a primary granulated product, and the particle size distribution was measured by a sieving method.

2) Preparation of secondary granulated product The above-mentioned polyvinyl alcohol aqueous solution is sprayed on the primary granulated product so that the polyvinyl alcohol solid content added to the granulated product is 0.7% by mass, and granulated. Then, drying was performed to produce a secondary granulated product, and the particle size distribution was measured in the same manner as described above.

3) Production of friction material The obtained secondary granulated product (granulated material for friction material) was directly put into a thermoforming mold and subjected to heat and pressure molding at 150 ° C. and 40 MPa for 5 minutes, at 220 ° C. A friction material was produced by heat treatment for 3 hours.

Example 2
In Example 1, the production of the secondary granulated product was the same as Example 1 except that the polyvinyl alcohol aqueous solution was sprayed so that the added amount of polyvinyl alcohol solid content was 1.3% by mass with respect to the primary granulated product. Thus, a friction material was produced.

Example 3
In Example 1, the production of the secondary granulated product was the same as Example 1 except that the polyvinyl alcohol aqueous solution was sprayed so that the added amount of polyvinyl alcohol solid content was 1.7% by mass with respect to the primary granulated product. Thus, a friction material was produced.

Comparative Example 1
Without using a thermosetting resin composition, use a phenol resin as a binder for friction material, and granulate using the above water-soluble binder-containing solution as a binder for granulation to produce a granulated product for friction material A friction material was produced in the same manner as in Example 1 except that it was produced.
That is, using a composite fluidized bed (SFC-MINI manufactured by Freund Sangyo Co., Ltd.) similar to the above, the friction modifier shown in the column of Comparative Example 1 in Table 2 is contained in the fluidized bed in the amount shown in the column. The polyvinyl alcohol aqueous solution with a solid content of 6% by mass obtained by the above-mentioned preparation is sprayed so that the addition ratio to the friction material is 1.3% by mass, and the raw material is granulated and dried. Thus, a granulated product for a friction material was prepared, and this was directly put into a thermoforming mold in the same manner as in Example 1 to perform heat and pressure molding and heat treatment to prepare a friction material.

<Measurement of mechanical strength of friction material>
Table 2 shows the measurement results for the maximum stress of each friction material obtained in Examples 1 to 3 and Comparative Example 1. Here, the maximum stress is processed into a test piece size of 8 × 8 × 10 mm (molding and pressing direction is 10 mm) using a universal testing machine (Shimadzu AG-X, 10 kN), and this is performed at 300 ° C. Compressed under the condition of holding for 30 minutes and determined the maximum stress until it breaks.

In the primary granulated product, fine particles of less than 150 μm were present at 11.0% by mass, whereas the secondary granulated product of Examples 1 to 3 obtained by granulating the primary granulated product with an aqueous polyvinyl alcohol solution was In both cases, particles less than 150 μm are reduced to 1% by mass or less, and dust from the granulated material is effectively suppressed, and a sufficient mechanical strength improving effect can be obtained by using the thermosetting resin composition. I understand that.
Further, from the results of Examples 2 and 3, it is presumed that the polyvinyl alcohol does not function as a molding binder because the mechanical strength of the friction material decreases due to an increase in the amount of polyvinyl alcohol added. The frictional material (Comparative Example 1) prepared using a phenolic resin used as a binder for a friction material as a binder and a water-soluble binder as a binder for granulation is sufficiently higher than the present invention. It turns out that the mechanical strength improvement effect of the molded object by the thermosetting resin composition of invention is fully expressed.

  The friction material of the present invention has excellent mechanical strength and easy control of friction performance, and is suitable for disk pads, brake linings, clutch facings, etc. for automobiles, large trucks, railway vehicles, various industrial machines, etc. Can be used.

Claims (3)

  The friction adjusting particle material is granulated in the presence of a thermosetting resin composition-containing solution containing potassium titanate particles having an average particle size of 0.1 to 0.5 μm, uncrosslinked rubber and a thermosetting resin, A method for producing a granulated product for a friction material, comprising granulating the obtained granulated product in the presence of a water-soluble or water-dispersible binder-containing solution.   A method for producing a friction material, wherein the friction material is obtained by molding the friction material granule obtained by the method according to claim 1.   The friction adjusting particle material is granulated in the presence of a thermosetting resin composition-containing solution containing potassium titanate particles having an average particle size of 0.1 to 0.5 μm, uncrosslinked rubber and a thermosetting resin, A friction material obtained by molding a granulated product for friction material obtained by granulating the obtained granulated product in the presence of a water-soluble or water-dispersible binder-containing solution.