JP2019112511A - Raw material composition for friction material, method for producing raw material composition for friction material, and method for producing friction material - Google Patents

Abstract

To provide a raw material composition for friction material that suppresses the occurrence of dust during compression molding and damage to an opponent part, and can improve frictional coefficients.SOLUTION: The composition contains a phenolic resin, a fiber, a friction modifier, water, and an oxidized cellulose nanofiber with an average fiber length 100 nm-1 μm and an average fiber diameter 2 nm-500 nm.SELECTED DRAWING: None

Description

  The present invention relates to a raw material composition for a friction material containing oxidized cellulose nanofibers, a method for producing the raw material composition, and a method for producing a friction material using the raw material composition.

Conventionally, friction materials used for automobile clutches etc. are friction materials made by mixing phenolic resin, fiber (organic / inorganic), filler (organic / inorganic), friction modifier, non-ferrous metal, etc. with a mixer The raw material of (1), as it is or after preforming, is introduced into a mold and compression molded. Alternatively, it is manufactured by preparing a sheet using a raw material for friction material to which water is added by papermaking, and compression-molding the sheet.
For example, Patent Document 1 discloses a friction material in which a thermosetting resin is impregnated and cured in a sheet made of fibers and fillers mixed in water.

JP, 2017-141875, A

When raw materials used only for mixing various materials with a mixer are used, a large amount of dust is generated during compression molding, and even when preformed, they are easily deformed even when they are preformed. Are difficult to obtain. On the other hand, when manufactured by papermaking, the resulting friction material is in the form of a sheet, and the shape is restricted. In addition, the contents flow with the water at the time of paper making, and the equipment is large.
In addition, when trying to increase the coefficient of friction of the conventional friction material, the life of the friction material itself becomes short. When the coefficient of friction is increased by increasing the amount of inorganic fibers and inorganic fillers, the mating part is used. There are problems such as attack and occurrence of abrasive wear.

  Therefore, the object of the present invention is to provide a raw material composition for a friction material which can suppress generation of dust at the time of compression molding and damage to a counterpart part, and improve the friction coefficient, and a method of manufacturing the same. Do. The present invention also provides a method for producing a friction material using the raw material composition for a friction material of the present invention.

The present invention provides the following.
(1) A raw material composition for a friction material, comprising phenolic resins, fibers, a friction modifier, water, and oxidized cellulose nanofibers having an average fiber length of 100 nm to 1 μm and an average fiber diameter of 2 nm to 500 nm.
(2) The composition for a friction material according to (1), further comprising a nonferrous metal.
(3) An aqueous dispersion of oxidized cellulose nanofibers having an average fiber length of 100 nm to 1 μm and an average fiber diameter of 2 nm to 500 nm is added after the step of mixing the phenolic resins, fibers and the friction modifier with a mixer A process for producing a raw material composition for friction materials, comprising the step of mixing
(4) A method for producing a friction material, comprising the step of compression molding the raw material composition for a friction material according to (1) or (2).

  ADVANTAGE OF THE INVENTION According to this invention, the raw material composition for friction materials which can suppress generation | occurrence | production of the dust at the time of compression molding, and the damage to a companion part, and can improve a coefficient of friction can be provided. Moreover, the manufacturing method of the friction material using the raw material composition for friction materials of this invention can be provided.

  Hereinafter, the present invention will be described in detail. In the present invention, "-" includes an end value. That is, “X to Y” includes the values X and Y at its both ends.

  The raw material composition for a friction material of the present invention comprises phenolic resins, fibers, a friction modifier, water, and oxidized cellulose nanofibers having an average fiber length of 100 nm to 1 μm and an average fiber diameter of 2 nm to 500 nm.

<Oxidized cellulose nanofibers>
Oxidized cellulose nanofibers are fine fibers obtained by defibrillating oxidized cellulose obtained by oxidizing a cellulose raw material, and the average fiber length and the average fiber diameter of the fine fibers are oxidized or defibrated It can be adjusted.
In the present invention, it is important to include oxidized cellulose nanofibers having an average fiber length of 100 nm to 1 μm, preferably 100 nm to 400 nm, and an average fiber diameter of 2 nm to 500 nm, preferably 2 nm to 150 nm.

The average fiber length and the average fiber diameter of the oxidized cellulose nanofibers are obtained by averaging the fiber length and the fiber diameter obtained from the result of observing each fiber using a field emission scanning electron microscope (FE-SEM). You can get it.
The average aspect ratio of oxidized cellulose nanofibers is usually 50 or more. The upper limit is not particularly limited, but is usually 1000 or less. The average aspect ratio can be calculated by the following equation:
Aspect ratio = average fiber length / average fiber diameter

(1) Cellulose raw material The origin of the cellulose raw material which is a raw material of the oxidized cellulose nanofiber is not particularly limited. For example, plants (eg, wood, bamboo, hemp, jute, kenaf, farmland waste, cloth, pulp (conifers not Bleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP) , Thermomechanical pulp (TMP), regenerated pulp, used paper, etc., animals (eg, ascidians), algae, microorganisms (eg, acetic acid bacteria (acetobacter)), microbial products, etc. The cellulose raw material used in the present invention is , Any of these may be used or a combination of two or more Although it may be, it is preferably a cellulose raw material (for example, cellulose fiber) derived from a plant or a microorganism, and more preferably a cellulose raw material (for example, cellulose fiber) derived from a plant.

  The number average fiber diameter of the cellulose raw material is not particularly limited, but is about 30 to 60 μm in the case of softwood kraft pulp which is a general pulp and about 10 to 30 μm in the case of hardwood kraft pulp. In the case of other pulps, those after general refining are about 50 μm. For example, in the case where a chip or the like having a size of several centimeters is purified, it is preferable to perform mechanical processing with a disintegrator such as a refiner or a beater to adjust to about 50 μm.

(2) Oxidation The amount of carboxyl group based on the dry weight of oxidized cellulose or cellulose nanofibers obtained by modifying the cellulose raw material by oxidation is preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more. More preferably, it is 1.0 mmol / g or more. The upper limit is preferably 3.0 mmol / g or less, more preferably 2.5 mmol / g or less, and still more preferably 2.0 mmol / g or less. Therefore, 0.5 mmol / g to 3.0 mmol / g is preferable, 0.8 mmol / g to 2.5 mmol / g is more preferable, and 1.0 mmol / g to 2.0 mmol / g is more preferable.

  The method of oxidation is not particularly limited, but one example is cellulose in water using an oxidizing agent in the presence of an N-oxyl compound and a substance selected from the group consisting of bromide, iodide or a mixture thereof The method of oxidizing a raw material is mentioned. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring of the cellulose surface is selectively oxidized to form a group selected from the group consisting of an aldehyde group, a carboxyl group, and a carboxylate group. The concentration of the cellulose raw material at the time of reaction is not particularly limited, but is preferably 5% by weight or less.

The N-oxyl compound refers to a compound capable of generating a nitroxy radical. Examples of nitroxyl radicals include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO). As the N-oxyl compound, any compound can be used as long as it promotes the target oxidation reaction.
The amount of use of the N-oxyl compound is not particularly limited as long as it is a catalytic amount capable of oxidizing cellulose as a raw material. For example, 0.01 mmol or more is preferable with respect to 1 g of absolutely dried cellulose, and 0.02 mmol or more is more preferable. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and still more preferably 0.5 mmol or less. Therefore, the amount of the N-oxyl compound to be used is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and still more preferably 0.02 to 0.5 mmol relative to 1 g of cellulose completely dried.

  The bromide is a compound containing bromine, and examples thereof include alkali metal bromides which can be dissociated and ionized in water, such as sodium bromide. In addition, iodide is a compound containing iodine, and examples thereof include alkali metal iodides. The amount of bromide or iodide used may be selected within the range capable of promoting the oxidation reaction. The total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, to 1 g of cellulose which is absolutely dry. The upper limit is preferably 100 mmol or less, more preferably 10 mmol or less, and still more preferably 5 mmol or less. Accordingly, the total amount of bromide and iodide is preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and still more preferably 0.5 to 5 mmol per 1 g of cellulose which is extremely dry.

  The oxidizing agent is not particularly limited, and examples thereof include halogens, hypohalous acids, subhalic acids, perhalogen acids, salts thereof, halogen oxides, peroxides and the like. Among them, hypohalous acid or a salt thereof is preferable, hypochlorous acid or a salt thereof is more preferable, and sodium hypochlorite is further preferable, because the cost and environmental load are small. The amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, and still more preferably 3 mmol or more, with respect to 1 g of absolutely dried cellulose. The upper limit is preferably 500 mmol or less, more preferably 50 mmol or less, and still more preferably 25 mmol or less. Therefore, the amount of the oxidizing agent used is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, still more preferably 1 to 25 mmol, and most preferably 3 to 25 mmol per 1 g of cellulose which is completely dried. When an N-oxyl compound is used, the amount of the oxidizing agent used is preferably 1 mol or more per 1 mol of the N-oxyl compound. The upper limit is preferably 40 mol. Therefore, the amount of the oxidizing agent used is preferably 1 to 40 mol with respect to 1 mol of the N-oxyl compound.

  The conditions such as pH and temperature at the time of the oxidation reaction are not particularly limited, and in general, the oxidation reaction proceeds efficiently even under relatively mild conditions. The reaction temperature is preferably 4 ° C. or more, more preferably 15 ° C. or more. The upper limit is preferably 40 ° C. or less, more preferably 30 ° C. or less. Therefore, the temperature is preferably 4 to 40 ° C., and may be about 15 to 30 ° C., that is, room temperature. The pH of the reaction solution is preferably 8 or more, more preferably 10 or more. The upper limit is preferably 12 or less, more preferably 11 or less. Therefore, the pH of the reaction solution is preferably about 8 to 12 and more preferably about 10 to 11. Generally, the pH of the reaction solution tends to decrease because carboxyl groups are formed in cellulose as the oxidation reaction proceeds. Therefore, in order to allow the oxidation reaction to proceed efficiently, it is preferable to add an alkaline solution such as an aqueous solution of sodium hydroxide to maintain the pH of the reaction solution in the above range. The reaction medium for oxidation is preferably water because of the ease of handling and the fact that side reactions are less likely to occur.

  The reaction time in the oxidation reaction can be appropriately set in accordance with the degree of progress of oxidation, and is usually 0.5 hours or more. The upper limit is usually 6 hours or less, preferably 4 hours or less. Therefore, the reaction time in the oxidation is usually about 0.5 to 6 hours, for example, about 0.5 to 4 hours.

  The oxidation may be carried out in two or more stages of reaction. For example, the oxidized cellulose obtained by filtering off after completion of the first stage reaction is oxidized again under the same or different reaction conditions, so that the reaction is not inhibited by the reaction by sodium chloride by-produced in the first stage reaction. It can be oxidized well.

  Another example of the carboxylation (oxidation) method is a method of oxidation by ozone treatment. This oxidation reaction oxidizes at least the 2- and 6-position hydroxyl groups of the glucopyranose ring constituting the cellulose and causes the decomposition of the cellulose chain. The ozone treatment is usually performed by contacting a gas containing ozone with a cellulose raw material.

The ozone concentration in the gas is preferably 50 g / m ³ or more. The upper limit is preferably 250 g / m ³ or less, more preferably 220 g / m ³ or less. Therefore, the ozone concentration in the gas is preferably 50 to 250 g / m ^3, more preferably 50~220g / m ^3. The amount of ozone added is preferably 0.1 parts by weight or more, and more preferably 5 parts by weight or more, with respect to 100 parts by weight of the solid content of the cellulose raw material. The upper limit is usually 30 parts by weight or less. Therefore, the addition amount of ozone is preferably 0.1 to 30 parts by weight, and more preferably 5 to 30 parts by weight with respect to 100 parts by weight of the solid content of the cellulose raw material.

  The ozone treatment temperature is usually 0 ° C. or more, preferably 20 ° C. or more. The upper limit is usually 50 ° C. or less. Therefore, the ozone treatment temperature is usually 0 to 50 ° C, preferably 20 to 50 ° C. The ozone treatment time is usually 1 minute or more, preferably 30 minutes or more. The upper limit is usually 360 minutes or less. Accordingly, the ozone treatment time is usually about 1 to 360 minutes, preferably about 30 to 360 minutes. When the conditions of the ozone treatment are within the above-mentioned range, excessive oxidation and decomposition of cellulose can be prevented, and the yield of oxidized cellulose becomes good.

  The resulting product obtained after the ozone treatment may be further subjected to an additional oxidation treatment using an oxidizing agent. The oxidizing agent used for the additional oxidation treatment is not particularly limited, and examples thereof include chlorine based compounds such as chlorine dioxide and sodium chlorite; oxygen, hydrogen peroxide, persulfuric acid, peracetic acid and the like. Examples of the method of the additional oxidation treatment include a method of dissolving these oxidizing agents in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and immersing a cellulose raw material in the oxidizing agent solution.

The amount of the carboxyl group, the carboxylate group and the aldehyde group contained in the oxidized cellulose nanofibers can be adjusted by controlling the oxidation conditions such as the addition amount of the oxidizing agent and the reaction time.
An example of the method of measuring the amount of carboxyl groups is described below. After preparing 60 mL of 0.5 wt% slurry (water dispersion liquid) of oxidized cellulose and adding 0.1 M hydrochloric acid aqueous solution to adjust to pH 2.5, 0.05 N aqueous sodium hydroxide solution is dropped to pH 11 Measure the conductivity until The change in electrical conductivity can be calculated using the following equation from the amount of sodium hydroxide (a) consumed in the neutralization stage of a weak acid with moderate change:
Amount of carboxyl group [mmol / g oxidized cellulose or oxidized cellulose nanofiber] = a [mL] x 0.05 / weight of oxidized cellulose or oxidized cellulose nanofiber [g]

(3) Pulverization Pulverization of the oxidized cellulose raw material may be performed before or after the cellulose raw material is subjected to a modification treatment. The defibration may be carried out at one time or several times. In the case of multiple times, the timing of each disintegration may be any time.
The apparatus used for disintegration is not particularly limited, and examples thereof include high-speed rotation type, colloid mill type, high pressure type, roll mill type, ultrasonic type and the like, high pressure or ultra high pressure homogenizer is preferable, and wet high pressure Or the ultrahigh pressure homogenizer is more preferable. Preferably, the device is capable of applying strong shear to the cellulosic raw material or modified cellulose (usually a dispersion). The pressure to which the device can be applied is preferably 50 MPa or more, more preferably 100 MPa or more, and still more preferably 140 MPa or more. The apparatus is preferably a wet high pressure or ultra high pressure homogenizer capable of applying the above pressure to the cellulose raw material or the modified cellulose (usually a dispersion) and applying a strong shear force. Thereby, disintegration can be performed efficiently.

When disaggregating a dispersion of a cellulose material, the solid content concentration of the cellulose material in the dispersion is usually 0.1% by weight or more, preferably 0.2% by weight or more, and more preferably 0.3 % By weight or more. As a result, the amount of liquid relative to the amount of cellulose fiber raw material becomes appropriate and efficient. The upper limit is usually 10% by weight or less, preferably 6% by weight or less. This allows the liquidity to be maintained.
Prior to disintegration (preferably disintegration with a high-pressure homogenizer) or, if necessary, dispersion treatment prior to disintegration, pretreatment may be performed as necessary. The pretreatment may be performed using a mixing, stirring, emulsification, or dispersing device such as a high-speed shear mixer.

<Phenolic resins>
In the present invention, phenolic resins are thermosetting resins used as a binder for friction materials. Specifically, various elastomer-dispersed phenolic resins such as phenolic resin, acrylic elastomer-dispersed phenolic resin and silicone elastomer-dispersed phenolic resin, various modified phenolic resins such as acrylic-modified phenolic resin, silicone-modified phenolic resin, cashew-modified phenolic resin and the like can be mentioned. It is preferable to use a phenol resin. These can be used alone or in combination of two or more.

  The weight average molecular weight of the phenol resin used in the present invention is not particularly limited, but is preferably 3,000 to 10,000, more preferably 4,000 to 10,000, from the viewpoint of suppressing molding defects and a decrease in product yield. .

<Fiber>
In the present invention, the fibers indicate the reinforcing action in the friction material. Specific examples thereof include cellulose fibers, natural fibers such as wood pulp, carbon fibers, aramid fibers, synthetic fibers such as acrylic fibers, glass fibers, rock wool and the like, but are not limited thereto. . Moreover, these fibers can be used individually or in combination of 2 or more types. The fibers in the present invention do not contain non-ferrous metal fibers.

<Friction modifier>
In the present invention, the friction modifier is intended to improve the sound vibration performance and the wear resistance of the friction material and to prevent the deterioration of the heat resistance. Specifically, as an inorganic friction modifier, diatomaceous earth, silica, alumina, barium sulfate, calcium carbonate, zinc oxide, etc. As an organic friction modifier, acrylonitrile-butadiene rubber (NBR), cashew dust, carbon particles, graphite And the like can be exemplified, but not limited thereto. Moreover, these friction modifiers can be used individually or in combination of 2 or more types. In the present invention, the friction modifier also has a function as a filler.

  In order to increase the coefficient of friction of the resulting friction material, silica, alumina or the like, which is a material having high aggressiveness to the other party, may be blended as a friction modifier in the raw material composition for friction material. The raw material composition for friction materials of this invention can raise the friction coefficient of the friction material obtained by containing an oxidized cellulose nanofiber by a fixed ratio. Therefore, in the raw material composition for a friction material of the present invention, it is possible to reduce the compounding amount of the material having a high attacking property to the other.

<Non-ferrous metal>
The raw material composition for a friction material of the present invention may contain a non-ferrous metal as needed together with the above-mentioned phenolic resins, fibers, friction modifiers, water and oxidized cellulose nanofibers.
In the present invention, the nonferrous metal is for obtaining the damping force of the friction material to improve the heat dissipation. Specific examples include fibers and particles of non-ferrous metals such as aluminum, copper, zinc and tin, fibers and particles of non-ferrous alloys such as bronze and brass (brass), but are not limited thereto. . In addition, these fibers and particles can be used alone or in combination of two or more.

<Compounding ratio of raw material composition for friction material>
In the present invention, the compounding amount of water and oxidized cellulose nanofibers is 30 to 40 with respect to the mixture 100 of the phenolic resin, the fiber, the friction modifier, and the nonferrous metal used as needed. And from the viewpoint of water removal time. More specifically, the blending ratio of phenolic resins, fibers, friction modifiers, nonferrous metals, water, and oxidized cellulose nanofibers is phenolic resins: fibers: friction modifiers: nonferrous metals: water: oxidized cellulose nanofibers ( The solid content) is preferably 8 to 20: 5 to 30: 35 to 70: 0 to 10: 25 to 30: 0.5 to 1.0.

<Method of producing raw material composition for friction material>
It is preferable to add and mix a mixture of water and an aqueous dispersion of oxidized cellulose nanofibers after mixing of phenolic resins, fibers, friction modifiers, and nonferrous metals used as needed with a mixer. The raw material composition for the friction material manufactured by this method is uniformly mixed with oxidized cellulose nanofibers. Further, the raw material composition for this friction material contains water, so that separation of fibers and powder is difficult to occur, and the obtained friction material has a uniform friction surface and less generation of dust and is easy to handle. further. Since the preform is difficult to be deformed and easy to handle, the mold can be easily put in at the time of compression molding.

<Method of manufacturing friction material>
The method of producing a friction material using the raw material composition for a friction material of the present invention is not particularly limited, but the raw material composition for a friction material is preformed into a predetermined shape and remains. It is preferable to carry out compression molding after removing moisture with a drying furnace or the like.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. In addition, when the measurement / calculation method of each numerical value in each Example is not described in particular, it is measured / calculated by the method described in the specification.

[Measurement method of static friction coefficient]
The friction material obtained in each Example and Comparative Example was processed into 1 cm square to prepare a test piece. Apply a load of 3 kg to the test piece and press the test piece against the disc surface for measurement, then move the disc position by 45 degrees, measure each time you move it, and make a round of the disc to the first measured location After measurement, the measurement was repeated again, and a minimum value was obtained from among the measurement values obtained by measuring a total of nine times, and the static friction coefficient was obtained. In addition, the measurement was performed on the conditions of room temperature 23 degreeC.

[Measurement method of dynamic friction coefficient]
The friction material obtained in each Example and Comparative Example was processed into 1 cm square to prepare a test piece. Using a constant-speed friction tester (pin-on-disk method), a test piece in which a 3 kg load was applied to a disk rotated at 3000 rpm was desorbed (ON / OFF) every second. In the first, 25th, 50th, (omitted), and 3000th cycles, the dynamic friction coefficient at each time was obtained. In addition, SPHC was used as a mating material. Moreover, the measurement was performed on the conditions of room temperature 23 degreeC.

[Production of oxidized cellulose nanofibers]
Softwood bleached unbeaten kraft pulp (whiteness 85%) 5.00 g (absolutely dry), TEMPO (Sigma Aldrich) 39 mg (0.05 mmol relative to 1 gram of absolute dry cellulose) and sodium bromide 514 mg (absolutely dry) The solution was added to 500 mL of an aqueous solution of 1.0 mmol) dissolved in 1 g of cellulose and stirred until the pulp was uniformly dispersed. An aqueous solution of sodium hypochlorite was added to the reaction system so that the concentration of sodium hypochlorite was 5.5 mmol / g, and an oxidation reaction was initiated at room temperature. During the reaction, the pH in the system decreased, but 3M aqueous sodium hydroxide solution was sequentially added to adjust to pH 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system did not change. The mixture after reaction was filtered through a glass filter to separate the pulp, and the pulp was thoroughly washed with water to obtain oxidized pulp (carboxylated cellulose). The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g. This was adjusted to 0.55% (w / v) with water and treated 10 times with an ultrahigh pressure homogenizer (20 ° C., 150 Mpa) to obtain an aqueous dispersion of oxidized cellulose nanofibers. The average fiber diameter of the obtained oxidized cellulose nanofibers was 3 nm, and the average fiber length was 300 nm.

Example 1
300 g of high molecular weight phenolic resin, 160 g of aramid fiber as fiber, 100 g of glass fiber, 240 g of rock wool, 200 g of barium sulfate as a friction modifier, 200 g of calcium carbonate, 70 g of silica, 70 g of alumina, 160 g of zinc oxide, 100 g of cashew dust, 100 g of NBR, 100 g of graphite, 100 g of aluminum powder as nonferrous metal and 40 g of brass were thoroughly mixed using a 20 L Henschel mixer. Furthermore, a dispersion of 120 g of water and 600 g of water is added to the above aqueous dispersion of oxidized cellulose nanofibers adjusted to 0.17% by weight, and the mixture is stirred (rotational speed 1500 rpm, stirring time 15 minutes) to prepare a raw material composition for friction material I got Also, a friction material was obtained by performing thermal compression molding using this raw material composition. The static friction coefficient and the dynamic friction coefficient of the obtained friction material were measured. Table 1 shows the measurement results of the static friction coefficient, and Table 2 shows the measurement results of the dynamic friction coefficient.

Comparative Example 1
A friction material was obtained in the same manner as Example 1, except that water was used instead of the aqueous dispersion of oxidized cellulose nanofibers. The static friction coefficient and the dynamic friction coefficient of the obtained friction material were measured. Table 1 shows the measurement results of the static friction coefficient, and Table 2 shows the measurement results of the dynamic friction coefficient.

Example 2
300 g of high molecular weight phenolic resin, 160 g of aramid fibers as fibers, 60 g of acrylic fibers, 100 g of glass fibers, 240 g of rock wool, 360 g of barium sulfate as a friction modifier, 60 g of silica, 60 g of alumina, 160 g of zinc oxide, 100 g of cashew dust, 100 g of NBR, 160 g of graphite, 80 g of aluminum powder as non-ferrous metal and 60 g of brass were thoroughly mixed using a 20 L Henschel mixer. Furthermore, a dispersion of 120 g of water and 600 g of water is added to the above aqueous dispersion of oxidized cellulose nanofibers adjusted to 0.17% by weight, and the mixture is stirred (rotational speed 1500 rpm, stirring time 15 minutes) to prepare a raw material composition for friction material I got Also, a friction material was obtained by performing thermal compression molding using this raw material composition. The static friction coefficient and the dynamic friction coefficient of the obtained friction material were measured. Table 3 shows the measurement results of the static friction coefficient, and Table 4 shows the measurement results of the dynamic friction coefficient.

Comparative Example 2
A friction material was obtained in the same manner as Example 2, except that water was used instead of the aqueous dispersion of oxidized cellulose nanofibers, the amount of silica was changed to 140 g, and the amount of alumina was changed to 140 g. The static friction coefficient and the dynamic friction coefficient of the obtained friction material were measured. Table 3 shows the measurement results of the static friction coefficient, and Table 4 shows the measurement results of the dynamic friction coefficient.

  As shown in Tables 1 and 2, the friction material obtained using the raw material composition for the friction material containing the phenolic resin, fiber, friction modifier, water, and oxidized cellulose nanofiber of Example 1 is oxidized The coefficient of static friction and the coefficient of dynamic friction were higher than those of the friction material obtained using the raw material composition for the friction material of Comparative Example 1 containing no cellulose nanofibers.

  As shown in Tables 3 and 4, the raw material composition for the friction material containing the oxidized cellulose nanofibers of Example 2 reduced the amount of silica and alumina affecting the coefficient of friction from Comparative Example 2, but Example 2 As compared with the friction material obtained in Comparative Example 2, the friction material obtained in Comparative Example 2 did not show a drop in the coefficient of static friction and the coefficient of dynamic friction, and was equal to or more than that.

  From the above, when using a raw material composition for friction material containing phenolic resins, fibers, friction modifiers, water, and oxidized cellulose nanofibers having a specific fiber length and a specific fiber diameter, a friction material having a high friction coefficient can be obtained. You can get it.

Claims (4)

  What is claimed is: 1. A raw material composition for a friction material, comprising phenolic resins, fibers, a friction modifier, water, and oxidized cellulose nanofibers having an average fiber length of 100 nm to 1 μm and an average fiber diameter of 2 nm to 500 nm.   The composition for a friction material according to claim 1, further comprising a non-ferrous metal.   After mixing the phenolic resins, fibers, and friction modifier with a mixer, add an aqueous dispersion of oxidized cellulose nanofibers with an average fiber length of 100 nm to 1 μm and an average fiber diameter of 2 nm to 500 nm, and mix with a mixer A manufacturing method of a raw material composition for friction materials characterized by including a process.   A method for producing a friction material, comprising the step of compression molding the raw material composition for a friction material according to claim 1 or 2.