JP5133309B2 - Plate-like potassium titanate, method for producing the same, and friction material - Google Patents

Description

  The present invention relates to plate-like potassium tetratitanate, a method for producing the same, and a friction material.

Since potassium 6 titanate (K ₂ O · 6TiO ₂ ) and potassium 4 titanate (K ₂ O · 4TiO ₂ ) are usually obtained as fibrous compounds and have excellent crystal strength and high heat insulation properties, Widely used as a reinforcing agent for friction modifiers and resins.

  However, conventional potassium 6 titanate and potassium 4 titanate have a fiber shape and are bulky, inferior in fluidity, and adhere to the wall of the supply channel during production, thereby blocking the supply channel. have. Moreover, as a resin reinforcement agent, it has the fault that the reinforcement performance with respect to the force added to a twist direction is not enough. In addition, in the use of a friction agent, a plate-like one is required in order to ensure a high effect on the friction surface.

  However, since potassium 6 titanate and potassium 4 titanate have the property of crystal growth in the form of fibers, plate-like potassium 6 titanate and potassium 4 titanate have not been obtained so far.

  An object of the present invention is to provide a plate-like potassium tetratitanate, a production method thereof, and a friction material using the same.

  The plate-like potassium tetratitanate of the present invention is characterized by having an average major axis of 1 to 100 μm and an average aspect ratio of 3 to 500.

  The method for producing plate-like potassium titanate of the present invention is characterized in that plate-like titanate is immersed in a potassium hydroxide solution and then fired.

  As plate-like titanic acid, what is obtained by acid-treating the plate-like thing of potassium magnesium titanate or potassium lithium titanate can be used, for example.

  In the production method of the present invention, the firing temperature is preferably 700 to 800 ° C.

  The friction material of the present invention is characterized by containing plate-like potassium tetratitanate as a friction modifier. The content is preferably 3 to 50% by weight.

A scanning electron micrograph of the plate-like potassium titanate obtained in Reference Example 1 (5000 times magnification). 3 is an X-ray diffraction chart of plate-like potassium titanate obtained in Reference Example 1. FIG. 4 is an X-ray diffraction chart of plate-like potassium tetratitanate obtained in Example 2. FIG.

  The plate-like potassium tetratitanate of the present invention is a plate-like material having an average major axis of 1 to 100 μm, preferably 3 to 30 μm, an average aspect ratio of 3 to 500, preferably 3 to 100, and more preferably 5 to 20. Here, the average major axis means a so-called average particle diameter, and is, for example, a value measured as a median diameter by a laser diffraction type particle size distribution measuring apparatus. The aspect ratio is the ratio of the average major axis to the average minor axis (thickness) (average major axis / average minor axis). The average aspect ratio can be determined by measuring the average minor axis (thickness) with a scanning electron microscope and calculating the ratio with the average major axis. In this case, generally, about 20 samples whose thickness can be confirmed within the field of view of the scanning electron microscope are measured, and the average value of the average minor axis is obtained.

  The method for producing plate-like potassium titanate of the present invention is characterized in that plate-like titanate is dipped in a potassium hydroxide solution, intercalated with potassium ions, and then fired. Plate-like titanic acid can be obtained by acid treatment using a compound that can deintercalate cations between layers by acid treatment. Examples of such a compound include plate-like potassium magnesium titanate and plate-like potassium lithium titanate. These compounds can be produced, for example, according to the methods disclosed in Japanese Patent Application Laid-Open No. 5-22195 and Japanese Patent Application No. 11-158086 by the present applicant.

  The plate-like potassium magnesium titanate can be obtained by mixing a titanium source, a potassium source, and a magnesium source, adding a flux, sufficiently mixing, and then firing at 1000 to 1100 ° C. for 1 to 8 hours.

  The titanium source can be arbitrarily selected from compounds containing titanium oxide. Specific examples include titanium oxide, rutile ore, titanium hydroxide wet cake, and hydrous titania.

  As a potassium source, it can select from the compound which produces potassium oxide by heating, and a potassium oxide, potassium carbonate, potassium hydroxide, potassium nitrate etc. can be illustrated as a specific example. Of these, potassium carbonate is preferred.

  Examples of the magnesium source include magnesium hydroxide, magnesium carbonate, magnesium fluoride and the like.

The mixing ratio of the titanium source, potassium source, and magnesium source is basically a ratio of Ti: K: Mg = 4: 2: 1 (molar ratio). . If the ratio is greatly deviated, K ₂ MgTi ₇ O ₁₆ , which is a non-plate-like byproduct, may be precipitated, which is not preferable.

  Examples of the flux include potassium chloride, potassium fluoride, potassium molybdate, and potassium tungstate. Of these, potassium chloride is preferable.

  The addition ratio of the flux is 3: 1 to 3:15, preferably 3: 3.5 to 3:10, in terms of a molar ratio with the raw material (raw material: flux). The smaller the amount of flux added, the more economically advantageous. However, if the amount is too small, the plate crystals are broken, which is not preferable.

  Firing can be performed by any method such as an electric furnace or a muffle furnace, but when mass production is performed, the prepared raw material is press-molded into a shaped body such as a brick shape or a cylindrical shape, and then a tunnel kiln is used. Preferably.

  The firing temperature is preferably maintained by keeping the temperature between 1000 ° C. and 1100 ° C. for 1 to 24 hours. Although there are no particular restrictions on the temperature rise and temperature drop rates, it is usually preferably 3 to 7 ° C./min. As the firing temperature is higher, a large plate-like material is obtained, but if it exceeds 1100 ° C., the shape is impaired by melting, which is generally not preferable. Further, the longer the holding time, the larger the particle shape.

  After calcination, after performing coarse pulverization and fine pulverization using a jaw crusher, a bin mill or the like, wet crushing can be performed by dispersing in water and stirring as a slurry of about 5 to 10%. Further, classification, filtration, and drying are performed as necessary to obtain plate-like potassium magnesium titanate. Plate-like potassium magnesium titanate is suitable as a raw material for the relatively small plate-like potassium tetratitanate of the present invention having an average major axis of about 3 to 30 μm.

  Moreover, as a manufacturing method of potassium lithium titanate, the method of mixing a titanium source, a potassium source, and a lithium source, adding a flux, mixing sufficiently, and hold | maintaining at 825-1150 degreeC for 1 to 12 hours is illustrated, for example. it can.

  As the titanium source, potassium source, and flux, the same materials as those used in the production of the potassium magnesium titanate can be used.

  As a lithium source, it can select suitably from the compound which can produce | generate lithium oxide by heating, For example, lithium carbonate, lithium nitrate, etc. can be illustrated.

  The mixing ratio of the titanium source, the potassium source and the lithium source is basically a ratio of Ti: K: Li = 1.73: 0.8: 0.27 (molar ratio). There is no problem even if it is changed. Moreover, it is good to use the addition ratio of a flux with the ratio of 1-4 (molar ratio) with respect to the raw material 1. FIG. If the amount of the flux is too small, the product does not become plate-like, and if the amount of the flux is too large, it is economically disadvantageous, which is not preferable.

  The firing means can be carried out by the same means as in the production of potassium magnesium titanate, but the firing temperature is preferably between 825 and 1150 ° C., and is preferably maintained for 1 to 24 hours.

  The crushing, classification, filtration, and drying steps can be performed by the same means as in the production of the potassium magnesium titanate.

  Potassium lithium titanate is suitable as a raw material for a relatively large plate-like potassium tetratitanate of the present invention having an average major axis of about 10 to 100 μm.

  Examples of acids used for deintercalation by acid treatment of these compounds include mineral acids such as sulfuric acid, nitric acid and hydrochloric acid. The acid treatment is preferably performed by stirring in an aqueous solution of about 1 mol / liter (1N) of these acids until the cations between layers are almost completely eluted. Stirring is usually preferably performed over 5 to 8 hours.

  The obtained plate-like titanic acid is washed with water and used for the next potassium ion intercalation step. Note that whether the plate-like potassium titanate or the plate-like potassium titanate is produced is determined depending on the conditions of the steps after the intercalation step. Hereinafter, the case of producing plate-like potassium titanate and the case of producing plate-like potassium titanate 4 will be described separately.

(Production of plate-like potassium titanate)
For intercalation of potassium ions, the plate-like titanic acid obtained above is made into 1-30%, preferably about 5-20% potassium hydroxide aqueous solution slurry, and the potassium hydroxide concentration in the slurry is the pH of the slurry. 13.5 or more, but less than 14, preferably about 13.75, by continuing stirring while adding and maintaining potassium hydroxide as necessary. Stirring is preferably performed for 1 hour or more, more preferably about 5 to 10 hours.

  A pH of 14 or more is not preferable because by-products of potassium tetratitanate and potassium dititanate increase in the next step, and a pH of less than 13.5 is not preferable because by-product of titanium oxide increases in the next step.

  After completion of potassium ion intercalation, plate-like potassium titanate can be obtained by baking at 600 to 800 ° C. after filtration, washing with water and drying. Firing can be performed by a tunnel kiln such as an electric furnace, a muffle furnace, a rotary kiln, a rotary kiln, or the like. The firing time is preferably 3 hours or longer.

  When the calcination temperature is below 600 ° C., the crystal structure does not change, and there are cases in which potassium hexatitanate cannot be obtained due to the formation of repidocrocite. On the other hand, when the firing temperature exceeds 800 ° C., the plate shape is impaired, and a columnar or fibrous crystal may be formed.

(Manufacture of plate-like potassium titanate)
For intercalation of potassium ions, the plate-like titanic acid obtained above is made into 1-30%, preferably about 5-20% potassium hydroxide aqueous solution slurry, and the potassium hydroxide concentration in the slurry is the pH of the slurry. 14.5 or more and less than 16.3, preferably about 15.0 to 15.5, by adding potassium hydroxide as necessary and maintaining the stirring. Stirring is preferably performed for 1 hour or more, more preferably about 5 to 10 hours.

  A pH of 16.3 or higher is not preferable because by-product of potassium dititanate increases in the next step, and a pH of less than 14.5 is not preferable because by-product of potassium hexatitanate increases in the next step.

  After completion of potassium ion intercalation, plate-like potassium titanate can be obtained by baking at 700 to 800 ° C. after filtration, washing with water and drying. Firing can be performed by a tunnel kiln such as an electric furnace, a muffle furnace, a rotary kiln, a rotary kiln, or the like. The firing time is preferably 3 hours or longer.

  If the calcination temperature is lower than 700 ° C., the crystal structure does not change, and it is not preferred because it may be reidocrocite and does not become potassium tetratitanate or potassium dititanate may precipitate. On the other hand, when the firing temperature exceeds 800 ° C., the plate shape is impaired, and a columnar or fibrous crystal may be formed.

  In addition, the potassium hydroxide in the said intercalation process can be used in aspects, such as a powder, a pellet, and aqueous solution, For example, use of 85 weight% pellet, 5-48 weight% aqueous solution, etc. can be illustrated. Whether potassium hydroxide is used in the form of powder, pellets, aqueous solution or the like is appropriately selected depending on the pH value of the aqueous solution to be set.

  For the convenience of the person skilled in the art, if an indication of the potassium hydroxide concentration required for setting to each predetermined pH in each intercalation step is given, pH 18 (1.46 g / l) at 18-20 ° C., pH 12.5 (3.09 g / l), pH 13.0 (8.0 g / l), pH 13.5 (30.57 g / l), pH 14 (65.97 g / l), pH 15 (400 g / l), pH 16 0.0 (480 g / l).

  In the intercalation step, if necessary, the pH of the slurry can be monitored, and potassium hydroxide (aqueous solution) or water can be added so as to be maintained within a predetermined range.

  The plate-like potassium titanate and plate-like potassium titanate thus obtained have the same physical properties as the fibrous potassium titanate and fibrous potassium titanate except for the properties derived from the shape and crystal system. It is a stable and non-toxic compound similar to fibrous potassium titanate and fibrous potassium titanate.

  Furthermore, it is the same as fibrous potassium titanate and fibrous potassium potassium titanate in that it has the effect of improving mechanical strength such as tensile strength and bending strength when blended with resin, but it is a plate-like material. Further, it is possible to expect more remarkable effects in realizing high surface smoothness, sliding characteristics, securing strength against a force applied in the torsional direction, and improving Izod impact strength. Furthermore, as will be described below, a more remarkable effect can be expected as a brake friction material.

  The friction material of the present invention is characterized by containing the plate-like potassium tetratitanate of the present invention as a friction modifier.

  The compounding amount of the plate-like potassium tetratitanate in the friction material is preferably 3 to 50% by weight. If it is less than 3% by weight, the effect of improving the friction and wear characteristics may not be exhibited. If it exceeds 50% by weight, the effect of improving the friction and wear characteristics cannot be expected any more, which is economically disadvantageous. There is a case.

  As a specific example of the friction material of the present invention, for example, a friction material comprising a base fiber, a friction modifier and a binder can be exemplified. As a blending ratio of each component in the friction material, 1 to 60 parts by weight of a base fiber, 20 to 80 parts by weight of a friction modifier (including plate-like 6 potassium titanate and / or plate-like 4 potassium titanate), Examples include 10 to 40 parts by weight of a binder and 0 to 60 parts by weight of other components.

  Examples of the base fiber include resin fibers such as aramid fibers, metal fibers such as steel fibers and brass fibers, carbon fibers, glass fibers, ceramic fibers, rock wool, and wood pulp. These substrate fibers are treated with a surface treatment such as aminosilane, epoxysilane or vinylsilane, silane coupling agents, titanate coupling agents or phosphate esters to improve dispersibility and adhesion to the binder. May be used.

  As the friction modifier in the friction material of the present invention, in addition to the plate-like potassium titanate, other friction modifiers may be used in combination as long as the effects of the present invention are not impaired. For example, organic powder such as vulcanized or unvulcanized natural, synthetic rubber powder, cashew resin powder, resin dust, rubber dust, carbon black, graphite powder, molybdenum disulfide, barium sulfate, calcium carbonate, clay, mica, talc, Diatomaceous earth, antigolite, sepiolite, montmorillonite, zeolite, inorganic powders such as sodium trititanate, sodium pentatitanate and potassium titanate, metal powders such as copper, aluminum, zinc and iron, alumina, silica, chromium oxide And oxide powders such as titanium oxide and iron oxide.

  As binders, thermosetting resins such as phenol resin, formaldehyde resin, melamine resin, epoxy resin, acrylic resin, aromatic polyester resin, urea resin, natural rubber, nitrile rubber, butadiene rubber, styrene butadiene rubber, chloroprene rubber, Thermoplastics such as polyisoprene rubber, acrylic rubber, high styrene rubber, elastomers such as styrene propylene diene copolymer, polyamide resin, polyphenylene sulfide resin, polyether resin, polyimide resin, polyether ether ketone resin, thermoplastic liquid crystal polyester resin Examples thereof include organic binders such as resins and inorganic binders such as alumina sol, silica sol, and silicone resin.

  In addition to the above components, the friction material of the present invention may contain components such as a rust inhibitor, a lubricant, and an abrasive as necessary.

  There is no restriction | limiting in particular in the case of manufacture of the friction material of this invention, According to the manufacturing method of a conventionally well-known friction material, it can manufacture suitably.

  If an example of the manufacturing method of the friction material of this invention is given, a base material fiber will be disperse | distributed in binder, and it mix | blends combining a friction modifier and the other component mix | blended as needed, and mixes a friction material composition. An example is a method of preparing and then injecting the composition into a mold and pressurizing and heating to form a binder.

  As another example, the binder is melt-kneaded in a twin screw extruder, compounded from the side hopper in combination with the base fiber, the friction modifier and other components blended as necessary, and extruded. An example is a method of machining into a desired shape after molding.

  As another example, after the friction material composition is dispersed in water or the like and made on a paper making net, dehydrated and made into a sheet, it is heated and pressed with a press machine to form a binder, An example is a method of appropriately cutting and polishing the obtained friction material to obtain a desired shape.

  The friction material of the present invention has an excellent and stable friction coefficient and wear resistance over a wide temperature range from low temperature to high temperature. Therefore, by using it as a brake member material used in automobiles, railway vehicles, aircraft, various industrial equipment, etc., for example, a clutch facing material and a brake material such as a brake lining and a disk pad, the braking function is improved. Stabilization and service life improvement effect can be obtained.

  The friction material of this invention has the following effects by containing plate-like potassium titanate and / or plate-like potassium tetratitanate as a friction modifier.

  1) Since the friction modifier has a plate shape, stable friction and wear characteristics can be obtained.

  2) Since the aspect ratio of the friction modifier is large, it contributes to improving the strength of the friction material itself.

  3) The fluidity of the friction modifier is high and the adjustment of the raw material mixture is easy.

  4) High heat resistance and stable coefficient of friction in a wide temperature range from low to high.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(Reference Example 1)
1. Synthesis of plate-like potassium magnesium titanate (K _0.8 Mg _0.4 Ti _1.6 O ₄ ) 14.73 kg of anatase titanium oxide powder, 6.38 kg of potassium carbonate, 2.79 kg of magnesium hydroxide, 10.03 kg of potassium chloride, 2 liters of water and Henschel After sufficiently mixing using a mixer, it was press-pressed at a pressure of 19.6 MPa (200 kgf / cm ² ) to obtain a brick-like molded product of about 3 kg.

  This was placed on a carriage and fired with a tunnel kiln. Firing was performed by raising the temperature to 1050 ° C. at a rate of 5 ° C./min, holding for 3 hours, and then lowering the temperature to room temperature at a rate of 5 ° C./min.

The obtained fired product is coarsely pulverized using a jaw crusher and then finely pulverized to a few millimeters or less using a pin mill, then dispersed in water to form a 10% slurry solution, and stirred with a propeller blade for 1 hour. Wet crushing was performed. Next, the slurry was passed through a 200 mesh (aperture 75 μm) sieve and classified. The powder on the sieve was classified again by wet crushing. After centrifugal filtration, it was dried to obtain 17.80 kg of plate-like potassium magnesium titanate (K _0.8 Mg _0.4 Ti _1.6 O ₄ , average major axis 4.6 μm, average aspect ratio about 10). The shape was confirmed by observation with a scanning electron microscope (SEM), and the identification was performed by X-ray diffraction and fluorescent X-ray analysis. The average major axis (median diameter) was measured with a laser diffraction particle size distribution analyzer.

2. Deintercalation by acid treatment A solution in which 36.1 kg of 35% sulfuric acid is dissolved in 141.9 liters of water of the total amount of plate-like potassium magnesium titanate (K _0.8 Mg _0.4 Ti _1.6 O ₄ ) obtained in the previous step. To give a 10% slurry. Stirring was continued for about 5 hours with a stirring blade, followed by filtration, washing with water and drying to obtain 12.03 kg of plate-like titanic acid (H ₂ Ti ₂ O ₅ ). The obtained plate-like titanic acid had substantially the same shape as the plate-like potassium magnesium titanate. The shape was confirmed by SEM observation, and the identification was performed by X-ray diffraction and fluorescent X-ray analysis. The average major axis (median diameter) was measured with a laser diffraction particle size distribution analyzer.

3. Intercalation of potassium ions by alkali treatment The total amount of plate-like titanic acid obtained in the previous step was dispersed in 114.4 liters of water to make a 10% slurry, and the pH was maintained at around 13.75 throughout. Stirring was continued with a stirring blade for about 5 hours while adding% potassium hydroxide, followed by filtration, washing with water and drying at 110 ° C. for 2 hours. The total amount of 85% potassium hydroxide added was 6.99 kg.

4). Synthesis of plate-like potassium titanate Next, this was fired at 700 ° C. for 3 hours in an electric furnace to obtain 13.87 kg of plate-like potassium titanate (average major axis 4.2 μm, average aspect ratio about 10). . The shape was confirmed by SEM observation, and the identification was performed by X-ray diffraction and fluorescent X-ray analysis. The average major axis (median diameter) was measured with a laser diffraction particle size distribution analyzer, and the average minor axis was measured by SEM observation. FIG. 1 is an SEM photograph of the obtained plate-like potassium titanate. FIG. 2 is an X-ray diffraction chart of the obtained plate-like potassium titanate.

(Example 2)
Plate-like potassium titanate was produced using the plate-like titanic acid obtained in Step 2 of Reference Example 1 above. Specifically, 50 g of plate-like titanic acid was dispersed in 800 ml of a 40% potassium hydroxide aqueous solution and stirred with a propeller blade at 500 rpm for 24 hours. During this time, the pH was maintained at about 15 throughout. The slurry was filtered with a suction filter, and the filter cake was dried at 110 ° C. and then baked in an electric furnace at 800 ° C. for 2 hours. The rate of temperature increase was 5 ° C./min. When the obtained powder was identified by X-ray diffraction method and fluorescent X-ray analysis, it was potassium tetratitanate. The average major axis (median diameter) was measured with a laser diffraction particle size distribution analyzer, and the average minor axis was observed with SEM. As a result, the average major axis of the obtained powder was 3.5 μm, and the average aspect ratio was about 15. FIG. 3 is an X-ray diffraction chart of the obtained plate-like potassium tetratitanate.

(Reference Example 3)
20 parts by weight of plate-like potassium titanate obtained in Reference Example 1, 10 parts by weight of aramid fiber (trade name “Kevlar pulp”, average length 3 mm, manufactured by Toray Industries, Inc.), 20 parts by weight of binder (phenol resin), A raw material mixture in which 50 parts by weight of barium sulfate was mixed was preformed at a pressure of 300 kgf / cm ² at room temperature for 1 minute, and then subjected to binder molding (pressure 150 kgf / cm ² , temperature 170 ° C., time 5 minutes). ) And after the molding, heat treatment (held at 180 ° C. for 3 hours). After removal from the mold, polishing was performed to obtain a test disk pad A (JIS D 4411 test piece).

  The fluidity of the friction modifier was good, and preparation of the raw material mixture was easy.

Example 4
20 parts by weight of plate-like potassium titanate obtained in Example 2, 10 parts by weight of aramid fiber (trade name “Kevlar Pulp”, average length 3 mm, manufactured by Toray Industries, Inc.), 20 parts by weight of binder (phenol resin), A raw material mixture in which 50 parts by weight of barium sulfate was mixed was preformed at a pressure of 300 kgf / cm ² at room temperature for 1 minute, and then subjected to binder molding (pressure 150 kgf / cm ² , temperature of 170 ° C., time of 5 minutes) ) And after the molding, heat treatment (held at 180 ° C. for 3 hours). After removal from the mold, polishing was performed to obtain a test disk pad A (JIS D 4411 test piece).

  The fluidity of the friction modifier was good, and preparation of the raw material mixture was easy.

Claims (7)

Plate-like potassium titanate having an average major axis of 1 to 100 μm and an average aspect ratio of 3 to 500, obtained by immersing the plate-like titanic acid in a potassium hydroxide solution having a pH of 14.5 or more and less than pH 16.3, followed by firing. .   A method for producing plate-like potassium titanate, comprising immersing plate-like titanic acid in a potassium hydroxide solution having a pH of 14.5 or more and less than pH 16.3, followed by firing.   3. The method for producing plate-like potassium titanate according to claim 2, wherein the plate-like titanic acid is obtained by acid-treating a plate-like material of potassium magnesium titanate or lithium potassium titanate.   The method for producing plate-like potassium titanate 4 according to claim 2 or 3, wherein the firing temperature is 700 to 800 ° C. A friction material comprising the plate-like potassium tetratitanate according to claim 1 as a friction modifier.   6. The friction material according to claim 5, comprising 3 to 50% by weight of plate-like potassium titanate. Friction according potassium the plate 4 titanate, to claim 5 or 6, characterized in that a plate-like 4 potassium titanate produced by the process of any one of 請 Motomeko 2-4 Wood.