JP2017179065A - Molding material for slide member and slide member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding material for slide member excellent in sliding characteristics at low speed, high load and dry environment, having enhanced friction stability by reducing initial torque and suppressed noise during sliding and a slide member.SOLUTION: There is provided a molding material for slide member containing a phenol resin, phosphoric acid ester and pitch-based carbon fiber. The content of the phosphoric acid ester is preferably 0.5 pts.mass to 10 pts.mass based on 100 pts.mass of the phenol resin. The phosphoric acid ester is preferably at least one of triphenyl phosphate and tricresyl phosphate. Average fiber length of the pitch-based carbon fiber is preferably 0.005 mm to 1 mm. The pitch-based carbon fiber is preferably a mesophase pitch-based carbon fiber.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a molding material for a sliding member and a sliding member.

  Conventionally, metal parts have been frequently used as sliding parts for industrial equipment, office equipment, transportation equipment, and the like. However, in recent years, in order to meet the needs of downsizing, cost reduction, and weight reduction, there is a tendency to be replaced with resin parts. Resin used for sliding parts includes thermoplastic resin, thermosetting resin, etc., but the thermoplastic resin melts under high load and high speed conditions that replace metal parts. The holding performance of the thermosetting resin is superior. Among them, phenol resin molding materials are widely used in various fields as materials excellent in balance between heat resistance, dimensional accuracy, cost, and weight reduction.

  The sliding member, including the mating member, has a rough surface no matter how smooth it looks, and this affects the wear. This wear shifts from the initial wear to the steady wear where the wear is constant, but the frictional force increases at the start of movement from the stationary state, so there is a problem that the amount of wear of the sliding member increases due to the increase of the initial torque. there were. Further, the increase in the initial torque may cause an overload on the device at the time of starting the device, which may lead to a start-up trouble.

  In order to reduce such initial torque, for example, in Patent Document 1, a coat layer is formed on the sliding contact surface with the mating member, and a hard and lubricious material is used in the coat layer in order to increase its durability. The technique which introduce | transduces the spherical particle which consists of and suppresses abrasion of the other member is proposed. However, in order to form the coat layer, a dedicated machine is required, which increases the number of manufacturing steps, resulting in inconveniences that cost, labor, and time are required for manufacturing.

  Patent Document 2 describes a sliding material composed of fluororesin particles (especially made of PTFE) having an average aspect ratio of 1.5 to 10 and a binder resin. The fluororesin particles are transferred to the mating member, and low friction is expressed by shearing between the film formed by the transfer and the base material. Since the fluororesin particles themselves have low friction, the initial familiarity is good. However, since the fluororesin particles are melted and deformed by frictional heat, the life of the sliding member is shortened when continuously used or under a high temperature environment. In particular, in an environment where a lubricating component such as oil cannot be used (hereinafter referred to as “dry environment”), there is an inconvenience that it is melted by frictional heat and seizure resistance is lowered.

JP-A-5-247667 JP 2005-187617 A

  The present invention has been made on the basis of the circumstances as described above, and its purpose is to improve the friction stability by reducing the initial torque by being excellent in sliding characteristics in a low speed, high load and dry environment. Another object of the present invention is to provide a molding material for a sliding member and a sliding member in which noise during sliding is suppressed.

  The invention made to solve the above problems is a molding material for a sliding member containing a phenol resin, a phosphate ester, and pitch-based carbon fibers.

  The molding material for a sliding member of the present invention contains a phosphate ester and pitch-based carbon fibers in addition to a phenol resin as a base material. Phenol resin is a thermosetting resin and is not easily deformed by a rapid temperature rise. Phosphate ester improves sliding characteristics in a low speed, high load and dry environment, and contributes to friction reduction by combination with pitch-based carbon fiber. The pitch-based carbon fiber contributes to a reduction in starting torque in a low load and dry environment, and improves the strength of the sliding member. Therefore, the molding material for sliding members is excellent in sliding characteristics in low speed, high load and dry environment by combining phenol resin, phosphate ester and pitch-based carbon fiber, and friction is reduced by reducing initial torque. Stability can be improved and noise during sliding can be suppressed.

  As for content of the said phosphate ester with respect to 100 mass parts of said phenol resins, 0.5 mass part or more and 10 mass parts or less are preferable. By setting the content of the phosphate ester within the above range, the sliding property of the molding material for the sliding member can be improved at low speed, high load, and dry environment.

  The phosphate ester is preferably at least one of triphenyl phosphate and tricresyl phosphate. By using the above-mentioned specific phosphoric acid ester, it is possible to further improve the sliding characteristics of the molding material for the sliding member at low speed, high load, and dry environment.

  The average fiber length of the pitch-based carbon fibers is preferably 0.005 mm or more and 1 mm or less. By setting the average fiber length of the pitch-based carbon fibers in the specific range, both the strength and sliding characteristics of the sliding member can be improved.

  The pitch-based carbon fiber is preferably a mesophase pitch-based carbon fiber. By using the specific carbon fiber as the pitch-based carbon fiber, the strength of the sliding member can be improved.

  It is preferable that the molding material for the sliding member further contains graphite. The graphite contributes as a solid lubricant. The molding material for the sliding member can further have a stable coefficient of friction when it shifts to steady wear by further containing graphite.

  The ratio of the total mass of the pitch-based carbon fiber and the graphite to the mass of the phenol resin is preferably 1 or more and 2 or less. By setting the content ratio of the pitch-based carbon fiber and the graphite to the phenol resin within the specific range, the friction coefficient can be reduced and the strength can be maintained.

  The total content of the phenolic monomer and the phenolic dimer in the phenolic resin is preferably 20% by mass or less. Moreover, it is preferable that ratio (Mw / Mn) with respect to the number average molecular weight (Mn) of the weight average molecular weight (Mw) in the said phenol resin is 1.5-20. By setting the total content of the phenolic monomer and the phenolic dimer and / or the ratio (Mw / Mn) in the above range, the phenolic monomer and the phenolic dimer, which are low molecular components, affect the friction. Can be reduced.

  Therefore, the sliding member formed from the molding material for the sliding member can be suitably used as a sliding component for automobile parts, OA equipment and the like.

  According to the present invention, the molding for a sliding member is excellent in sliding characteristics in a low speed, high load and dry environment, the initial torque is reduced, the friction stability is improved, and the noise during sliding is suppressed. Materials and sliding members can be provided.

It is a schematic diagram which shows the measuring apparatus of a limit PV value. It is a graph which shows the friction stability of the molding material for sliding members of Example 9 and Comparative Example 4.

  Hereinafter, the molding material for a sliding member of the present invention and the manufacturing method thereof, the sliding member formed from the molding material for the sliding member, and the manufacturing method thereof will be described in detail.

<Sliding member molding material>
The molding material for the sliding member contains a phenol resin, a phosphate ester, and pitch-based carbon fibers. The molding material for sliding member may contain graphite as a suitable component, and may contain other optional components as long as the effects of the present invention are not impaired. Hereinafter, each component will be described.

[Phenolic resin]
The phenol resin is an oligomer using phenols and aldehydes as raw materials, and forms a three-dimensional cross-linked structure by being cured by a curing process described later, and becomes insoluble and infusible. Examples of the phenol resin include novolac type phenol resins and resol type phenol resins. Examples of the resol type phenol resin include methylol type phenol resin and dimethylene ether type phenol resin. Among these, dimethylene ether type phenol resin is preferred from the viewpoint of making it difficult to cause chipping during processing. Among these, a novolac type phenol resin is preferable from the viewpoint of easily suppressing wear of the sliding member and improving the limit PV value. A phenol resin can be used individually by 1 type or in combination of 2 or more types.

  Examples of phenols include cresol, ethylphenol, xylenol, pt-butylphenol, octylphenol, nonylphenol, alkylphenols such as dodecylphenol, p-phenylphenol, and phenol. Of these, phenol is preferred. Phenols can be used alone or in combination of two or more.

  Examples of aldehydes include formaldehyde and paraformaldehyde. Of these, paraformaldehyde is preferred. Aldehydes can be used singly or in combination of two or more.

  As a minimum of the number average molecular weight (Mn) of a phenol resin, 400 is preferable and 600 is more preferable. As an upper limit of the Mn, 1,200 is preferable, and 900 is more preferable. When Mn of a phenol resin is less than the said minimum, there exists a possibility that the heat shock resistance of a sliding member may become inadequate. On the other hand, when the Mn of the phenol resin exceeds the above upper limit, workability at the time of material production may be deteriorated. In addition, the number average molecular weight of a phenol resin and the below-mentioned weight average molecular weight are the values measured by the area method of a gel filtration chromatograph.

  The lower limit of the weight average molecular weight (Mw) of the phenol resin is preferably 400, more preferably 1,000, and even more preferably 1,500. The upper limit of the Mw is preferably 9,000, more preferably 5,000, and further preferably 4,000. When the Mw of the phenol resin is less than the above lower limit, it may be difficult to form the sliding member. On the other hand, when the Mw of the phenol resin exceeds the above upper limit, workability at the time of manufacturing the material may be deteriorated.

  As a minimum of ratio (Mw / Mn: dispersion ratio) of Mw of Mw of a phenol resin, 1.5 is preferred, 3 is more preferred, and 5 is still more preferred. The upper limit of the ratio is preferably 20, more preferably 15, and even more preferably 10. By setting the Mw / Mn in the above range, the friction coefficient can be further reduced, and as a result, the wear amount can be further reduced.

  The upper limit of the total content of the phenolic monomer and the phenolic dimer in the phenolic resin is preferably 20% by mass, more preferably 12% by mass, and even more preferably 6% by mass. The lower limit of the total content is, for example, 0.1% by mass. By setting the total content of the phenolic monomer and the phenolic dimer in the above range, the friction coefficient can be further reduced. The total content of phenolic monomers and phenolic dimers is a value measured by the area method of gel filtration chromatography.

  It is particularly preferable that Mw / Mn of the phenol resin is in the above range and that the total content of the phenolic monomer and the phenolic dimer in the phenol resin is in the above range. By setting the total content of Mw / Mn and phenolic monomer and phenolic dimer in the phenol resin within the above ranges, the friction coefficient can be further reduced, and as a result, the wear amount can be further reduced.

(Phenolic resin production method)
As a method for producing a phenol resin, for example, a step of preparing a mixed solution of phenols, aldehydes and a catalyst (preparation step), a step of condensing the prepared liquid mixture at a reflux temperature (condensation reaction step), a condensation A manufacturing method provided with the process (removal process) of removing a monomer etc. from the liquid mixture after reaction is mentioned.

  As a method for removing monomers and the like in the removal step, for example, a step of phase-separating into an organic solvent layer (upper layer) and an aqueous solution layer (lower layer) by addition to a mixed solution after the condensation reaction of an organic solvent such as methyl isobutyl ketone , A method comprising a step of washing the upper layer with water and a step of removing an organic solvent such as methyl isobutyl ketone from the upper layer by distillation under reduced pressure, and a step of removing water and monomers by vacuum distillation of the mixed solution after the condensation reaction Methods and the like.

  When synthesizing a novolak-type phenol resin, examples of the catalyst include inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, organic acids such as oxalic acid, paratoluenesulfonic acid, benzenesulfonic acid, and xylenesulfonic acid, zinc oxide, and zinc chloride. And acid catalysts such as acidic inorganic salts such as magnesium oxide and zinc acetate. Among these, inorganic acids are preferable, and phosphoric acid is more preferable. The lower limit of the molar ratio of aldehydes to phenols in the mixed solution is, for example, 0.75. The upper limit of the molar ratio is, for example, 0.95.

  When synthesizing a resol type phenol resin, examples of the catalyst include alkali catalysts such as alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide. The lower limit of the molar ratio of aldehydes to phenols in the mixed solution is, for example, 1.1. The upper limit of the molar ratio is, for example, 4.0.

  The lower limit of the content of the catalyst in the mixed solution is, for example, 0.05 part by mass with respect to 100 parts by mass of the phenols. As an upper limit of the said content, it is 70 mass parts, for example.

  You may add additives, such as ethylene glycol, to a liquid mixture further. As a minimum of content of an additive in a liquid mixture, it is 40 mass parts with respect to 100 mass parts of phenols, for example. As an upper limit of the said content, it is 60 mass parts, for example.

  The lower limit of the reaction time in the condensation reaction is, for example, 2 hours. The upper limit of the reaction time is, for example, 12 hours.

[Phosphate ester]
Examples of the phosphoric acid ester include phosphoric acid monoester, phosphoric acid diester, and phosphoric acid triester. Further, the phosphate ester may be a condensed phosphate ester. Of these, phosphate triesters are preferred. Examples of phosphoric acid triesters include tricresyl phosphate, triphenyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, cresyl di-2,6-xylenyl phosphate, and the like. Among these, triphenyl phosphate and tricresyl phosphate are preferable from the viewpoint of excellent sliding characteristics in a low speed, high load and dry environment. Phosphoric acid ester may be used individually by 1 type, and may use 2 or more types together.

  As a minimum of content of phosphate ester, 0.5 mass part is preferred to 2 mass parts with respect to 100 mass parts of phenol resin, 2 mass parts are more preferred, and 3 mass parts are still more preferred. As an upper limit of the said content, 10 mass parts is preferable, 8 mass parts or less are more preferable, and 7 mass parts is further more preferable. By setting the content of the phosphate ester within the above range, the sliding property of the molding material for the sliding member can be improved at low speed, high load, and dry environment. When the phosphate ester content is less than the above lower limit, the wear amount increases, and the sliding characteristics such as the friction coefficient may be deteriorated. When the content of the phosphate ester exceeds the above upper limit, the workability during production may be reduced.

[Pitch-based carbon fiber]
Pitch-based carbon fibers are carbon fibers that use pitch as a raw material, and have a graphite crystal structure. By including the pitch-based carbon fiber, the sliding member molding material can reduce the initial dynamic friction coefficient at a low speed, a high load, and a dry environment.

  Pitch-based carbon fibers are classified into mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers depending on the crystal state of the pitch used for spinning. The mesophase pitch-based carbon fiber is oriented in a constituent liquid crystal state and optically anisotropic when observed with a polarizing microscope. On the other hand, the isotropic pitch-based carbon fiber is optically isotropic because the constituent molecules are randomly oriented. Among these, isotropic pitch-based carbon fibers are structurally lower in mechanical properties (strength, elastic modulus) than mesophase pitch-based carbon fibers, and therefore, as pitch-based carbon fibers, mesophase pitch-based carbon is used. Fiber is preferred.

  Further, pitch-based carbon fibers are classified into petroleum-based, coal-based, etc., for example, depending on the carbon source. Among these, in applications where a dry environment is required, a coal system with less oil is preferable.

  In the molding material for the sliding member, in order to improve the rigidity of the sliding member, a PAN-based carbon fiber may be used in combination with the pitch-based carbon fiber. In this case, the upper limit of the content of the PAN-based carbon fiber is preferably 50 parts by mass and more preferably 35 parts by mass with respect to 100 parts by mass of the pitch-based carbon fiber. As a minimum of the above-mentioned content, it is 1 mass part, for example.

  The average fiber length of the pitch-based carbon fibers is not particularly limited, but the lower limit of the average fiber length is preferably 0.005 mm, more preferably 0.01 mm, and even more preferably 0.05 mm. The upper limit of the average fiber length is preferably 1 mm, more preferably 0.8 mm, and even more preferably 0.5 mm. By setting the average fiber length of the pitch-based carbon fibers in the above range, both the strength and sliding characteristics of the sliding member can be improved. When the average fiber length of the pitch-based carbon fiber is less than the lower limit, the strength of the sliding member becomes insufficient, and the sliding characteristics may be deteriorated. Conversely, when the average fiber length of the pitch-based carbon fibers exceeds the above upper limit, the carbon fibers are easily peeled off from the sliding member, and as a result, the sliding characteristics may be deteriorated. In addition, pitch-based carbon fibers usually have a certain fiber length before adding the material, but when the molding material for the sliding member is obtained by kneading and pulverizing, the fibers break. The average fiber length is different from that before kneading. The average fiber length of the pitch-based carbon fiber in the present invention means an average fiber length in the molding material for sliding member after kneading and pulverizing the material.

  As a minimum of the average fiber diameter of pitch type carbon fiber, 1 micrometer is preferred, 3 micrometers is more preferred, and 6 micrometers is still more preferred. The upper limit of the average fiber diameter is preferably 18 μm, more preferably 15 μm, and still more preferably 12 μm. When the average fiber diameter of the pitch-based carbon fiber is less than the above lower limit, the strength of the sliding member becomes insufficient, and the sliding characteristics may be deteriorated. On the contrary, when the average fiber diameter of the pitch-based carbon fiber exceeds the above upper limit, there is a possibility that it will easily fall off as wear powder.

  As a minimum of content of pitch system carbon fiber, 50 mass parts is preferred to 100 mass parts of phenol resin, 80 mass parts is more preferred, and 100 mass parts is still more preferred. As an upper limit of the said content, 400 mass parts is preferable, 250 mass parts is more preferable, 200 mass parts is further more preferable. When content of pitch-type carbon fiber is less than the said minimum, there exists a possibility that the intensity | strength of a sliding member may become inadequate. On the contrary, when the content of the pitch-based carbon fiber exceeds the upper limit, it may be difficult to form the sliding member.

[graphite]
In the molding material for the sliding member, graphite functions as a solid lubricant that reduces the friction coefficient of the sliding member. The molding material for the sliding member can further have a stable coefficient of friction when it shifts to steady wear by further containing graphite. The graphite may be natural graphite such as flaky graphite, scaly graphite, earthy graphite, or artificial graphite. Among these, natural graphite is preferable and earth graphite is more preferable. Graphite can be used alone or in combination of two or more.

  As a minimum of content of graphite, 10 mass parts are preferred to 20 mass parts with respect to 100 mass parts of phenol resin, 20 mass parts are more preferred, and 30 mass parts are still more preferred. As an upper limit of the said content, 90 mass parts is preferable, 80 mass parts is more preferable, and 70 mass parts is further more preferable. When the graphite content is less than the above lower limit, the friction coefficient of the sliding member may increase. On the other hand, when the graphite content exceeds the above upper limit, the strength of the sliding member may be reduced, and it may be easily worn.

  Moreover, when the molding material for the sliding member contains graphite, since each of the pitch-based carbon fiber and graphite is a carbon-based filler, the mass of the phenol resin and the total mass of the pitch-based carbon fiber and graphite The ratio is preferably in a specific range. From the viewpoint of reducing the coefficient of friction and maintaining strength, the lower limit of the ratio of the total mass of the pitch-based carbon fiber and the graphite to the mass of the phenol resin is preferably 1, and more preferably 1.2. The upper limit of the ratio is preferably 2, and more preferably 1.8.

(Other optional ingredients)
Examples of other optional components that may be contained in the molding material for the sliding member include a curing agent, a filler, a release agent, a curing accelerator, a coupling agent, and a solvent.

  The curing agent accelerates the curing reaction of the phenol resin. When the phenolic resin is a novolac type phenolic resin, the molding material for the sliding member usually contains a curing agent. Examples of the curing agent include hexamethylenetetramine. When the said molding material for sliding members contains a hardening | curing agent, as a minimum of content of a hardening | curing agent, 5 mass parts is preferable with respect to 100 mass parts of phenol resins. As an upper limit of the said content, 20 mass parts is preferable.

  The filler improves the strength and durability of the sliding member. Examples of the filler include carbon materials other than the above carbon fibers and graphite, elastomers, calcium carbonate, clay, talc, silica, alumina, glass fibers, and aramid fibers.

  The release agent improves the releasability of the sliding member. Examples of the mold release agent include calcium stearate and zinc stearate.

  The curing accelerator further accelerates the curing reaction of the phenol resin. Examples of the curing accelerator include magnesium oxide and slaked lime.

<Method for producing molding material for sliding member>
As a method for producing the molding material for the sliding member, various known methods can be mentioned. Specifically, as a method for producing the molding material for the sliding member, for example, the above-mentioned various components are heated and melted with a pressure kneader, a mixing roll, a twin-screw extruder, and the like, and then kneaded. Examples include a method of forming into a sheet shape and further pulverizing the sheet-shaped product using a pelletizer, a power mill or the like.

<Sliding member>
The said sliding member is formed from the said molding material for said sliding members. Although it does not specifically limit as a shape of the said sliding member, For example, disk shape, square plate shape, column shape, prismatic shape, ring shape etc. are mentioned. Further, the use of the sliding member is not particularly limited, but preferable examples include a thrust washer, a pulley, a bearing, a gear, a gear, a bearing, a pump component, and a swash plate.

<Sliding member manufacturing method>
The sliding member manufacturing method includes a step of molding the sliding member molding material (molding step) and a step of curing the phenol resin contained in the sliding member molding material (curing step). The curing step is performed simultaneously with the molding step or after the molding step. In addition, you may further provide the process (melt-kneading process) of melt-kneading the said molding material for sliding members before the said formation process.

(Melting and kneading process)
In this step, the molding material for the sliding member is melt-kneaded. As a method for melt-kneading the molding material for the sliding member, for example, the above-mentioned various components are heated and melted with a pressure kneader, a mixing roll, a twin-screw extruder, etc., and then kneaded, and the resulting kneaded material is formed into a sheet. Examples thereof include a method by molding and further pulverizing the obtained sheet-like molded product using a pelletizer, a power mill or the like.

(Molding process)
In this step, the molding material for the sliding member is molded. Although it does not specifically limit as a method of shape | molding the said molding material for sliding members, For example, injection molding, transfer molding, compression molding, etc. are mentioned. Of these, injection molding is preferred. When molding by injection molding, the lower limit of the temperature at the front of the cylinder is, for example, 70 ° C. The upper limit of the temperature is 120 ° C., for example. The lower limit of the temperature at the rear of the cylinder is, for example, 30 ° C. The upper limit of the temperature is, for example, 60 ° C.

(Curing process)
In this step, the phenol resin contained in the molding material for sliding member is cured. As a method of curing the phenol resin, a method of heating the phenol resin is usually mentioned. The lower limit of the heating temperature is, for example, 150 ° C. The upper limit of the temperature is, for example, 200 ° C. The lower limit of the heating time is, for example, 30 seconds. The upper limit of the time is, for example, 90 seconds.

  The molded product obtained after molding is preferably after-cured. By applying after cure, the sliding characteristics of the sliding member can be further improved. Examples of the after-curing method include a heating method. The lower limit of the heating temperature is, for example, 150 ° C. The upper limit of the temperature is 230 ° C., for example. The heating time is, for example, 3 hours. The upper limit of the time is, for example, 24 hours.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by a following example. In the examples, “parts” and “%” indicate “parts by mass” and “% by mass” unless otherwise specified. Further, in the present specification, when the blending amount is described using parts by mass, it is part by mass with respect to 100 parts by mass of the phenol resin unless otherwise specified.

<Manufacture of phenolic resin>
[Production Example 1] (Production of novolak-type phenolic resin (1))
In a reaction vessel equipped with a thermometer, a stirrer and a condenser, 193 parts of phenol, 57 parts of 92% paraformaldehyde (molar ratio of formaldehyde / phenol: 0.85), 116 parts of 89% phosphoric acid (mass ratio to phenol: 0.6) and 96.5 parts of ethylene glycol (mass ratio with respect to phenol: 0.5) were respectively added, followed by stirring and mixing. Next, under a cloudy state (two-phase mixture) formed by stirring and mixing, the temperature was gradually raised to the reflux temperature, and a condensation reaction was further performed at the same temperature for 10 hours. After the reaction was stopped, methyl isobutyl ketone was added to the reaction mixture with stirring and mixing to dissolve the condensation product. Then, stirring and mixing were stopped, and the contents were transferred to a separation flask and allowed to stand, and separated into a methyl isobutyl ketone solution layer (upper layer) and a phosphoric acid aqueous solution layer (lower layer). Next, the phosphoric acid aqueous solution layer is removed, and the methyl isobutyl ketone solution layer is washed several times with water to remove phosphoric acid. Then, the contents are returned to the reaction vessel again, and the methyl isobutyl ketone is completely removed by vacuum distillation. 213.5 parts of a novolac type phenol resin (1) was obtained. This novolac type phenol resin (1) had a number average molecular weight of 755 and a dispersion ratio of 1.63.

[Production Example 2] (Production of Novolac Type Phenolic Resin (2))
In a reaction vessel equipped with a thermometer, a stirrer and a condenser, 193 parts of phenol, 142 parts of 37% formalin (formaldehyde / phenol molar ratio: 0.85) and 0.97 parts of oxalic acid (0.5% relative to phenol) (Mass%) was charged, and then the temperature was gradually raised to the reflux temperature (98 to 102 ° C.), and a condensation reaction was performed at the same temperature for 6 hours. Subsequently, when vacuum concentration was performed, 199 parts (103 mass% with respect to the charged phenol) of novolac type phenol resin (2) was obtained. The number average molecular weight of this phenol resin was 512, and the dispersion ratio was 7.5.

[Production Example 3] (Production of resol-type phenol resin)
In a reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser, 100 parts of phenol, 52 parts of 92% paraformaldehyde (formaldehyde / phenol molar ratio: 1.50), 0.12 part of zinc chloride (based on phenol) 0.12% by mass), 0.28 parts of manganese acetate (0.28% by mass with respect to phenol) and 8 parts of water (8% by mass with respect to phenol) were respectively added, followed by stirring and mixing. Next, the temperature was gradually raised to the reflux temperature, and the reaction was further performed at the same temperature for 3.5 hours. Subsequently, dehydration condensation reaction was performed under reduced pressure for 3.5 hours, and after cooling, a solid resol type phenol resin was obtained. The number average molecular weight of this resol type phenol resin was 777, and the dispersion ratio was 11.47.

[Characteristics of phenolic resin]
The characteristics of the various phenol resins obtained in Production Examples 1 to 3 were measured by the following test methods. The obtained results are shown in Table 1. In addition, the dispersion ratio of Table 1, content of a phenolic monomer, and content of a phenol dimer are the values obtained by the following measuring methods.

(Dispersion ratio)
Using a gel filtration chromatograph (“SC-8020 series build-up system” manufactured by Tosoh Corporation, column: “G2000Hxl” and “G4000Hxl”, detector: UV254 nm, carrier: tetrahydrofuran (1 mL / min), column temperature: 38 ° C.) Thus, the weight average molecular weight (Mw) and the number average molecular weight (Mn) in terms of standard polystyrene were determined, and the dispersion ratio (Mw / Mn) was calculated.

[Contents of phenolic monomers and phenolic dimers]
The total area of the phenolic monomer and the phenolic dimer with respect to the total area of the molecular weight distribution was measured by an area method displaying the percentage.

<Manufacture of molding materials for sliding members>
[Example 1]
As shown in Table 2 and Table 3 below, 100 parts by mass of novolak type phenol resin (1), 5 parts by mass of triphenyl phosphate (Tokyo Chemical Industry Co., Ltd.) as a phosphate ester, pitch-based carbon fiber (“Mitsubishi Resin's“ K6331T ", fiber length 3.0 mm, coal-based mesophase pitch-based carbon fiber) 50 parts by mass, graphite (graphite) (" Blue P "from Nippon Graphite Industry Co., Ltd.) 100 parts by mass, hexamethylenetetramine 11 parts by mass and calcium stearate 4 Part by mass was blended and mixed uniformly. Next, the obtained mixture was uniformly heated and kneaded with a hot roll to form a sheet, cooled, and then pulverized with a power mill to obtain a granulated molding material for a sliding member. The average fiber length of the pitch-based carbon fibers after kneading and pulverization is 0.1 mm.

The obtained molding material for sliding member was injection molded under the following molding conditions and cured to obtain a test piece.
(Molding condition)
Cylinder temperature: front 90 ° C, rear 40 ° C
Mold temperature: 170 ° C
Curing time: 60 seconds

[Examples 2 to 20 and Comparative Examples 1 to 7]
In Example 1, the molding material for sliding members was manufactured like Example 1 except having changed the kind and compounding quantity of each component like Table 2 and Table 3. FIG. In addition, it shows below about each component used in Examples 2-20 and Comparative Examples 1-7.
PAN-based carbon fiber: ("T-008A" manufactured by Toray Industries Inc., fiber length 3 mm), average fiber length 0.1 mm in molding material for sliding member after kneading and pulverization
Pitch-based carbon fiber: (Mitsubishi Resin “K6331T”, fiber length 3 mm, coal-based mesophase pitch-based carbon fiber), average fiber length 0.3 mm in molding material for sliding members after kneading and pulverization
Pitch-based carbon fiber: (Mitsubishi Resin “K6331T”, fiber length 3 mm, coal-based mesophase pitch-based carbon fiber), average fiber length 1.0 mm in molding material for sliding members after kneading and pulverization
Tricresyl phosphate: (Daihachi Chemical Industry Co., Ltd.)

<Evaluation>
Using the obtained test piece, according to the following method, each evaluation was made on the limit PV value, the maximum torque / starting torque / ratio, and the noise. The evaluation results are shown in Tables 2 and 3.

[Limit PV value]
The limit PV value was measured by the thrust friction wear measuring apparatus X1 shown in FIG. The thrust friction wear measuring device X1 includes a test piece X2 and a mating member X3 disposed on the upper surface of the test piece X2. The mating member X3 is a hollow cylinder having an outer diameter of 26.6 mm, an inner diameter of 20 mm, and a height of 15 mm, and is made of S45C carbon steel. There was no lubrication (dry environment) between the test piece X2 and the counterpart member X3. The mating member X3 was rotated at the test speed B while receiving the test surface pressure A from above. The test surface pressure A was 4.9 MPa at the start of the test, and was increased stepwise by 0.33 m / s every 20 minutes. The test surface pressure A × test speed B when the generation of abrasion powder due to abnormal wear and / or a friction coefficient increase of 2 times or more was observed was calculated, and this value was defined as the limit PV value (MPa · m / s). . The limit PV value (MPa · m / s) indicates that the larger the value, the better the sliding characteristics. When the value is 8 (MPa · m / s) or more, “good” and 4 (MPa · m / s) If it is less than 8 (MPa · m / s), it can be evaluated as “possible”, and if it is less than 4 (MPa · m / s), it can be evaluated as “insufficient”.

[Maximum torque / starting torque / ratio]
In the thrust frictional wear measuring apparatus X1 shown in FIG. 1, the frictional force was measured by a test with constant speed and load. Torque is a frictional force calculated by the following equation.
Torque value = frictional force (kgf) x 9.81 x radius of mating member X3 (m)
The definition of the maximum torque and the definition of the starting torque are as follows.
Maximum torque: Maximum torque value obtained within 5 minutes after the start of the test Starting torque: Torque value 5 seconds after the start of the test As the maximum torque / starting torque ratio is closer to 1, the friction stability is higher In the case of 3 or less, it can be evaluated as “good” and in the case of exceeding 3, it can be evaluated as “insufficient”.

[Sound]
In the thrust friction wear measuring apparatus X1 shown in FIG. 1, when measuring the frictional force in a test with a constant speed and load, ten panelists evaluated the squealing condition according to the following criteria, Superiority or inferiority was evaluated.
Sound (○): No sound was generated all the time. Sound (△): A small sound was generated. Sound (×): Violent sound was observed from time to time.

  From the result of the limit PV value shown in Table 2, with respect to the molding materials for sliding members of Comparative Examples 1 to 3 that did not contain either phosphate ester or pitch-based carbon fiber, Examples 1 to 8 It can be seen that the molding material for the sliding member has a high limit PV value. Therefore, it is judged that the molding materials for sliding members of Examples 1 to 8 are excellent in sliding characteristics at low speed, high load, and dry environment.

  When only the PAN-based carbon fiber shown in Table 4 is used, the starting torque is obtained under any conditions of low speed and low load (Comparative Example 4), low speed and high load (Comparative Example 5), and high speed and low load (Comparative Example 6). However, since the maximum torque is increased, the index of friction stability is deviated from 1, and a loud noise is generated during sliding. On the other hand, when only the pitch-based carbon fibers shown in Table 3 are used (Examples 9 to 11), the starting torque and the friction stability are improved under any condition, and the generated noise is remarkably suppressed. I understand that As a representative example, a comparison graph for the friction stability between Comparative Example 4 and Example 9 is shown in FIG. FIG. 2 also shows that there is a great difference in friction stability. This is presumably because pitch-based carbon fibers have better lubricating performance than PAN-based carbon fibers and act as solid lubricants.

  Since the molding material for sliding members of the present invention has excellent processability and sliding properties, it can be suitably used as a molding material for sliding members. Moreover, since the sliding member formed from the said molding material for sliding members has the outstanding sliding characteristic, it can be used suitably as sliding components for motor vehicles, OA equipment, etc.

X1 limit PV value measuring device X2 test piece X3 mating member A test surface pressure B test speed

Claims (10)

  A molding material for a sliding member containing a phenol resin, a phosphate ester, and pitch-based carbon fibers.   2. The molding material for a sliding member according to claim 1, wherein a content of the phosphoric ester with respect to 100 parts by mass of the phenol resin is 0.5 parts by mass or more and 10 parts by mass or less.   The molding material for a sliding member according to claim 1, wherein the phosphate ester is at least one of triphenyl phosphate and tricresyl phosphate.   The molding material for sliding members according to claim 1, wherein the pitch-based carbon fibers have an average fiber length of 0.005 mm or more and 1 mm or less.   The molding material for a sliding member according to any one of claims 1 to 4, wherein the pitch-based carbon fiber is a mesophase pitch-based carbon fiber.   The molding material for a sliding member according to any one of claims 1 to 5, further containing graphite.   The molding material for sliding members according to claim 6, wherein a ratio of a total mass of the pitch-based carbon fiber and the graphite to a mass of the phenol resin is 1 or more and 2 or less.   The molding material for sliding members according to any one of claims 1 to 7, wherein a total content of the phenolic monomer and the phenolic dimer in the phenolic resin is 20% by mass or less.   The sliding according to any one of claims 1 to 8, wherein a ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in the phenol resin is 1.5 or more and 20 or less. Molding material for parts. The sliding member formed from the molding material for sliding members of any one of Claims 1-9.

Images