JP6945295B2 - Molding materials for sliding members, sliding members and manufacturing methods - Google Patents

Description

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

Conventionally, as a sliding member for industrial equipment, office equipment, transportation equipment, etc., it has excellent bending strength and sliding characteristics in a dry environment (for example, high wear resistance, low friction coefficient, etc.), and has excellent warpage and warpage. Metal sliding members that do not easily make noise when sliding are often used. However, in recent years, in order to meet the needs for miniaturization, cost reduction, and weight reduction of various devices, there is a tendency to replace metal sliding members with resin sliding members. Examples of the resin for the resin sliding member include thermoplastic resin and thermosetting resin, and the resin is made of a resin that replaces the conventional metal sliding member that has been used under high load conditions and high speed conditions. As the sliding member, a thermosetting resin that does not melt is more suitable from the viewpoint of shape retention, and a phenol resin having an excellent balance of heat resistance, dimensional accuracy, cost, and lightness is particularly preferable.

Further, by adding a fiber material such as glass fiber, organic fiber, or carbon fiber to the phenol resin, the sliding characteristics of the formed sliding member can be further improved. Examples of the molding material for a sliding member containing such a phenol resin and a fiber material include a molding material for a sliding member in which glass fiber and wax are mixed with a phenol resin (see Patent Document 1), a phenol resin, graphite, and the like. A molding material for a sliding member (see Patent Document 2) containing an aramid fiber having an average fiber length of 200 to 300 μm has been proposed.

However, the sliding member formed of the molding material for the sliding member containing the glass fiber described in Patent Document 1 is a component such as a pump for transporting air or liquid, and has a foreign substance such as sand or dust on the sliding surface. If it is used in a situation where it is easy to get caught, the surface will be finely scratched and wear will easily proceed. Further, the sliding member formed of the molding material for the sliding member containing the organic fiber described in Patent Document 2 has an effect of improving the mechanical strength and the sliding property by the aramid fiber, but the productivity is difficult. There is. Specifically, when injection molding is performed, the filling property of the thin-walled portion and the fine-walled portion tends to be low, and the aramid fiber tends to reduce the workability even when performing processing such as grinding. Further, when organic fibers or carbon fibers are used, another inconvenience that the cost performance of the sliding member is lowered may occur.

Therefore, it has been studied to use relatively inexpensive wood flour as a fiber material to be added to the phenol resin. As a molding material for a sliding member using wood powder, for example, a molding material for a sliding member containing 40 to 60% by mass of wood flour, 10 to 15% by mass of graphite, and 10 to 20% by mass of titanium oxide has been proposed. (See Patent Document 3).

However, the sliding member formed of the molding material for the sliding member of Patent Document 3 has insufficient bending strength and sliding characteristics in a dry environment as compared with the metal sliding member, and has insufficient warpage and warpage. The noise during sliding cannot be sufficiently suppressed. Therefore, it is difficult to completely replace the metal sliding member with the sliding member formed of the conventional molding material for the sliding member.

Japanese Unexamined Patent Publication No. 2006-328215 Japanese Unexamined Patent Publication No. 2004-24031 JP-A-4-320443

The present invention has been made based on the above circumstances, and an object of the present invention is to have excellent bending strength and sliding characteristics in a dry environment, and to prevent warping and noise during sliding. An object of the present invention is to provide a molding material for a sliding member capable of forming a member.

The invention made to solve the above problems is a molding material for a sliding member containing a phenol resin, graphite, and wood powder, and the wood powder contains wood powder derived from coniferous trees.

The molding material for the sliding member is made by adding graphite, which is a solid lubricant, and wood flour, which functions as a fiber material, to phenol resin, which is a base material, and at least a part of the wood flour is a wood derived from coniferous trees. We are using powder. Here, since about 90% by mass of the total tissue of coniferous trees is composed of wood fibers (temporary vessels), the tissue structure of coniferous trees is simpler than that of other trees such as broad-leaved trees. Therefore, the wood powder derived from softwood is a relatively homogeneous powder with less variation in elasticity, bulk density, etc. than the wood powder derived from other trees such as hardwood, and therefore functions as a fiber material. It can be demonstrated stably. Further, since the wood powder derived from softwood is a relatively homogeneous powder as described above, it is difficult to impair its function as a solid lubricant even when used in combination with graphite. As described above, the molding material for the sliding member contains wood powder derived from softwood that stably exhibits the function as a fiber material, so that the bending strength of the sliding member formed and the dry environment The sliding characteristics of the above can be improved, and warpage and squealing during sliding can be suppressed.

The coniferous tree may be Sugi, Pine, Hinoki, Fir, Ichii, Ginkgo, Kaya, Tsuga, Podocarpus macrophylla, Sciadopity or a combination thereof. As described above, the coniferous tree is sugi, pine, cypress, fir, yew, ginkgo, torreya, hemlock, inumaki, sciadopity, or a combination thereof, that is, the wood flour contains wood flour derived from the coniferous tree. As a result, it is possible to more reliably improve the bending strength of the formed sliding member and the sliding characteristics in a dry environment, and suppress warpage and squealing during sliding.

The content ratio of lignin in the wood flour is preferably 20% by mass or more and 35% by mass or less. As described above, by setting the content ratio of lignin in the wood flour within the above range, that is, by making it relatively large, the wear resistance of the formed sliding member can be further improved.

The content of the wood flour with respect to 100 parts by mass of the phenol resin is preferably 15 parts by mass or more and 75 parts by mass or less. As described above, by setting the content of wood powder with respect to 100 parts by mass of the phenol resin in the above range, productivity and moldability at the time of injection molding or cutting can be improved.

The mass ratio of the wood flour to the graphite (wood powder / graphite) is preferably 0.4 or more and 4.5 or less. As described above, by setting the content of the wood powder to the content of the graphite in the above range, the sliding characteristics and moldability of the formed sliding member can be improved in a well-balanced manner.

The molding material for the sliding member may further contain an inorganic filler. When the molding material for the sliding member further contains an inorganic filler, the strength of the formed sliding member can be improved by the reinforcing effect, and as a result, the bending strength and the sliding property in a dry environment can be improved. Improvement and suppression of warpage can be achieved more reliably.

Another invention made to solve the above problems is a sliding member formed of the above-mentioned molding material for a sliding member.

Since the sliding member is formed of the above-mentioned molding material for the sliding member, it is excellent in bending strength and sliding characteristics in a dry environment, and is less likely to warp and make noise during sliding.

Yet another invention made to solve the above problems is a method for manufacturing a sliding member, which comprises a step of molding the above-mentioned molding material for a sliding member.

By using the above-mentioned molding material for sliding members, the sliding member is excellent in bending strength and sliding characteristics in a dry environment, and is less likely to warp and make noise during sliding. Members can be manufactured easily and reliably.

Here, the "conifer" refers to a tree of the gymnosperm coniferous phylum.

According to the molding material for a sliding member, the sliding member, and the manufacturing method of the present invention, a sliding member having excellent bending strength and sliding characteristics in a dry environment and which is less likely to warp and make noise during sliding can be obtained. Can be provided.

It is a schematic diagram which shows the abrasion resistance test performed in an Example.

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

<Molding material for sliding members>
The molding material for the sliding member contains phenol resin, graphite, and wood powder, and the wood powder contains wood powder derived from coniferous trees. The molding material for a sliding member may contain other optional components as long as the effects of the present invention are not impaired. Hereinafter, each component will be described.

[Phenol resin]
Phenol resin is an oligomer made from phenols and aldehydes, and is cured by a curing step described later to form a three-dimensional crosslinked structure, resulting in an insoluble and infusible state. Examples of the phenol resin include novolak type phenol resin and resol type phenol resin. Examples of the resole-type phenol resin include methylol-type phenol resins and dimethylene ether-type phenol resins. Among these, dimethylene ether-type phenol resins are preferable from the viewpoint of making it difficult for chips to occur during processing. Among these, the novolak type phenol resin is preferable as the phenol resin from the viewpoint of improving the wear resistance of the sliding member to be formed. The phenol resin can be used alone or in combination of two or more.

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

Examples of the aldehydes include formaldehyde and paraformaldehyde. Of these, paraformaldehyde is preferred. The above aldehydes can be used alone or in combination of two or more.

As the lower limit of the number average molecular weight (Mn) of the phenol resin, 350 is preferable, and 450 is more preferable. On the other hand, as the upper limit of Mn, 1,200 is preferable, and 900 is more preferable. If the Mn of the phenol resin is smaller than the above lower limit, the heat shock resistance of the formed sliding member may be insufficient. On the contrary, when the Mn of the phenol resin exceeds the upper limit, the workability in manufacturing the molding material for the sliding member may be lowered. The number average molecular weight of the phenol resin and the weight average molecular weight described later are values measured by the area method of the 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. On the other hand, the upper limit of the Mw is preferably 9,000, more preferably 5,000, and even more preferably 4,000. If the Mw of the phenol resin is smaller than the lower limit, it may be difficult to mold the sliding member. On the contrary, when the Mw of the upper limit phenol resin exceeds the above upper limit, the workability in manufacturing the molding material for the sliding member may be deteriorated.

The lower limit of the dispersion ratio (Mw / Mn) of the phenol resin is preferably 1.5, more preferably 3, and even more preferably 5. On the other hand, as the upper limit of the dispersion ratio, 20 is preferable, 15 is more preferable, and 10 is further preferable. By setting the dispersion ratio in the above range, the friction coefficient of the formed sliding member can be reduced, and as a result, the wear resistance can be further improved.

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 within the above range, the friction coefficient of the formed sliding member can be reduced. The total content of the phenolic monomer and the phenolic dimer is a value measured by the area method of the gel filtration chromatograph.

It is particularly preferable that the phenol resin has a dispersion ratio in the above range and a total content of the phenolic monomer and the phenolic dimer in the above range. By setting the dispersion ratio in the phenol resin and the total content of the phenol monomer and the phenol dimer within the above ranges, the friction coefficient of the formed sliding member can be further reduced, and as a result, wear resistance can be obtained. The sex can be further improved.

The lower limit of the content ratio of the phenol resin in the molding material for the sliding member is preferably 20% by mass, more preferably 30% by mass. On the other hand, the upper limit of the content ratio of the phenol resin is preferably 80% by mass, more preferably 70% by mass, and even more preferably 60% by mass. If the content ratio of the phenol resin is smaller than the lower limit, the moldability may be lowered. On the contrary, when the content ratio of the phenol resin exceeds the upper limit, other components such as graphite and wood powder may be insufficient, and the sliding characteristics of the formed sliding member may be deteriorated.

(Manufacturing method of phenol resin)
Examples of the method for producing the phenol resin include a step of preparing a mixed solution of phenols, aldehydes and a catalyst (preparation step), a step of condensing the prepared mixed solution at a reflux temperature (condensation reaction step), and the like. Examples thereof include a method including a step (removal step) of removing the monomer and the like from the mixed solution after the condensation reaction.

(Preparation process)
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, paratoluene sulfonic acid, benzene sulfonic acid and xylene sulfonic acid, and zinc oxide. Examples thereof include acid catalysts such as acidic inorganic salts such as zinc chloride, magnesium oxide and zinc acetate. Of these, inorganic acids are preferred, and phosphoric acid is more preferred. The molar ratio of aldehydes to phenols in the mixed solution is, for example, 0.75 or more and 0.95 or less.

When synthesizing a resole-type phenol resin, examples of the catalyst include an alkali catalyst such as an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, and lithium hydroxide. The molar ratio of aldehydes to phenols in the mixed solution is, for example, 1.1 or more and 4.0 or less.

The lower limit of the catalyst content in the mixed solution is, for example, 0.05 parts by mass, preferably 0.1 parts by mass, based on 100 parts by mass of the phenols. On the other hand, the upper limit of the content of the catalyst is, for example, 70 parts by mass and 50 parts by mass is preferable with respect to 100 parts by mass of phenols.

Additives such as ethylene glycol may be further added to the mixed solution. The content of the additive in the mixed solution is, for example, 40 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of phenols.

(Condensation reaction step)
The reaction time in the condensation reaction is, for example, 2 hours or more and 12 hours or less.

(Removal process)
As a method for removing the monomer and the like in the removing step, for example, a step of adding an organic solvent such as methyl isobutyl ketone to the mixed solution after the condensation reaction to phase-separate the organic solvent layer (upper layer) and the aqueous solution layer (lower layer). A method including 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 vacuum distillation or the like, a method of removing water and monomers by vacuum distillation from the mixed solution after the condensation reaction, etc. Can be mentioned.

[graphite]
Graphite functions as a solid lubricant that reduces the friction coefficient of the sliding member formed in the molding material for the sliding member. Since the molding material for the sliding member contains graphite, the friction coefficient can be stabilized when the formed sliding member shifts to steady wear. Examples of the graphite include natural graphite such as scaly graphite, scaly graphite, and earthy graphite, and artificial graphite. Among these, natural graphite is preferable, and earth-like graphite is more preferable. Graphite can be used alone or in combination of two or more.

The lower limit of the graphite content in the molding material for the sliding member is preferably 10 parts by mass, more preferably 15 parts by mass, and even more preferably 20 parts by mass with respect to 100 parts by mass of the phenol resin. On the other hand, the upper limit of the graphite content is preferably 120 parts by mass, more preferably 90 parts by mass, further preferably 80 parts by mass, and particularly preferably 70 parts by mass with respect to 100 parts by mass of the phenol resin. By setting the graphite content in the above range, it is possible to reduce the amount of wear of the formed sliding member during sliding, and it is also possible to further suppress squealing. If the graphite content is less than the lower limit, the wear resistance of the formed sliding member may decrease. On the contrary, when the graphite content exceeds the above upper limit, the strength of the formed sliding member may decrease or the amount of wear during sliding may increase.

[Wood flour]
The wood powder in the molding material for the sliding member is obtained by processing a tree into fine particles and mainly functions as a fiber material. The wood flour used as the molding material for the sliding member contains at least wood flour derived from coniferous trees. Wood flour can be used alone or in combination of two or more.

By using a combination of graphite and wood powder as the molding material for the sliding member, the friction coefficient can be reduced without lowering the abrasion resistance of the sliding member to be formed, and carbon fiber, glass fiber, etc. are used. Physical strength can be maintained without it. Further, while a sliding member using carbon fiber or glass fiber as a fiber material is difficult to process such as cutting, the sliding member formed by the molding material for the sliding member uses wood powder. Therefore, cutting is very easy.

In addition, coniferous trees are characterized by a tissue structure that determines the performance of wood flour compared to other trees such as hardwoods. Specifically, the tissue structure is very simple and the wood fibers (temporary vessels) are arranged in an orderly manner. It is mainly composed of. This is because in coniferous trees, wood fibers, which are tissues that carry sap like the canals in broad-leaved trees, occupy 90% by mass or more of the total tissue. Therefore, the wood powder derived from coniferous trees is a relatively homogeneous powder mainly composed of finely dispersed wood fibers with little variation, and can stably exert its function as a fiber material. Since the molding material for the sliding member uses wood powder derived from softwood having such characteristics, it has excellent bending strength and sliding characteristics in a dry environment, and warps and squeals during sliding. It is possible to form a sliding member that is unlikely to occur. On the other hand, since other trees such as hardwoods have a complicated tissue structure formed by various types of cells, it is difficult to obtain the above-mentioned effects even if wood powder derived from hardwoods or the like is used. .. Furthermore, coniferous trees are also suitable in terms of being easy to procure domestically.

The wood flour derived from coniferous trees can be easily identified when observed with an electron microscope because it is characterized by being composed of wood fibers arranged in an orderly manner.

The lower limit of the content ratio of wood powder derived from softwood in the wood powder contained in the molding material for the sliding member is preferably 90% by volume, more preferably 95% by volume, still more preferably 98% by volume. In this way, by setting the content ratio to the above lower limit or more, a sliding member having excellent bending strength and sliding characteristics in a dry environment and which is less likely to warp and make noise during sliding is formed more reliably. can. The content ratio is most preferably 100% by volume.

Here, the "content ratio of wood flour derived from coniferous trees" is determined by observing the material for forming the sliding member or any 100 wood flour contained in the sliding member using an electron microscope, and the total area of the total wood flour. and S _a, can be calculated by the following equation based on the total area S _C of wood flour from softwood.
Content of wood flour from softwood _{(vol%) = 100 × S C /} S A

The coniferous tree is not particularly limited, but sugi, pine, cypress, fir, ichii, ginkgo, kaya, hemlock, inumaki and sciadopity are preferable, and sugi, pine and cypress are more preferable from the viewpoint of physical properties and availability. The type of tree that is the raw material for wood flour can be estimated by comparing it with each wood powder by observing with an electron microscope.

The lower limit of the maximum particle size of the wood flour is preferably 100 μm, more preferably 120 μm. On the other hand, the upper limit of the maximum particle size of the wood powder is preferably 400 μm, more preferably 360 μm. If the maximum particle size of the wood powder is smaller than the lower limit, the strength of the formed sliding member may be insufficient and the wear resistance may be lowered. On the contrary, when the maximum particle size of the wood powder exceeds the upper limit, the wood powder may hinder the friction of the formed sliding member, which may reduce the wear resistance or the warp may not be sufficiently suppressed. be. Here, the "maximum particle size" means any 100 trees in the field of view when the molding material for forming the sliding member is observed with an electron microscope and the longest width of each wood powder is defined as the "particle size". Indicates the maximum particle size of the powder.

Wood flour having a maximum particle size in the above range can be easily obtained by, for example, sieving. For example, wood flour having a maximum particle size of 180 μm can be obtained by sieving wood flour as a raw material using a sieve having an opening of 180 μm. The maximum particle size of wood powder can also be measured by a laser diffraction type particle size distribution measuring device before it is added to the molding material for sliding members.

The lower limit of the lignin content in the wood flour is preferably 20% by mass, more preferably 23% by mass. On the other hand, the upper limit of the lignin content is preferably 35% by mass, more preferably 30% by mass. By setting the lignin content in the above range, that is, by making it relatively large, the wear resistance of the formed sliding member can be further improved. Since conifers tend to have a relatively high lignin content, the lignin content can be easily adjusted to the above range by using wood flour derived from conifers. On the other hand, since the lignin content of wood flour derived from hardwood tends to be smaller than the above lower limit, it is difficult to adjust the lignin content to the above range when only wood flour derived from hardwood is used. .. Here, the "lignin content" refers to a value measured by the Clarson method.

The lower limit of the content of the wood powder in the molding material for the sliding member is preferably 15 parts by mass, more preferably 25 parts by mass, and even more preferably 30 parts by mass with respect to 100 parts by mass of the phenol resin. On the other hand, as the upper limit of the content of the wood powder, 75 parts by mass is preferable, 60 parts by mass is more preferable, and 55 parts by mass is further preferable with respect to 100 parts by mass of the phenol resin. If the content of the wood powder is smaller than the lower limit, it may be difficult to mold the sliding member and the productivity may decrease. On the contrary, when the content of the wood powder exceeds the upper limit, the wood powder may hinder the friction of the formed sliding member, so that the wear resistance may be lowered. In addition, the warpage of the formed sliding member may not be sufficiently suppressed, or the sliding member may be difficult to mold and the productivity may decrease.

Further, the graphite content and the wood powder content in the molding material for the sliding member are constant from the viewpoints of improving the sliding characteristics, bending strength, etc. of the formed sliding member and suppressing warpage. It is preferably within the range of. Specifically, the lower limit of the mass ratio of wood powder to graphite in the molding material for sliding members is preferably 0.4, more preferably 0.5, and even more preferably 0.6. On the other hand, as the upper limit of the mass ratio of wood flour to graphite, 4.5 is preferable, 3.5 is more preferable, and 2.5 is further preferable.

[Inorganic filler]
The molding material for the sliding member preferably further contains an inorganic filler. When the molding material for the sliding member further contains an inorganic filler, the strength of the formed sliding member can be further improved by the reinforcing effect. The inorganic filler may be used alone or in combination of two or more.

The inorganic filler is not particularly limited, and an inorganic filler commonly used in conventional phenol resin molding materials may be appropriately used, and for example, a spherical filler, a plate-shaped filler, or the like can be used. Examples of the spherical filler include those derived from calcium carbonate, barium sulfate, calcium sulfate, aluminum hydroxide, clay, pearlite, silas balloon, silica soil, calcined alumina, calcium silicate and the like. Further, examples of the plate-shaped filler include talc, mica and the like. Of these, calcium carbonate, aluminum hydroxide, talc and mica are particularly preferable from the viewpoint of suppressing the influence on wear characteristics. In addition, in this specification, it is assumed that the inorganic filler does not contain a fiber filler.

When the molding material for the sliding member contains an inorganic filler, the lower limit of the content of the inorganic filler is preferably 30 parts by mass and more preferably 40 parts by mass with respect to 100 parts by mass of the phenol resin. On the other hand, as the upper limit of the content of the inorganic filler, 70 parts by mass is preferable, and 60 parts by mass is more preferable. If the content of the inorganic filler is less than the above lower limit, the wear resistance of the formed sliding member may decrease. On the contrary, when the content of the inorganic filler exceeds the upper limit, the friction coefficient of the formed sliding member may increase.

(Other optional ingredients)
The molding material for the sliding member may further contain other optional components. Examples of the other optional components include fiber materials other than the above wood flour, curing agents, fillers, mold release agents, curing accelerators, coupling agents, solvents and the like.

Examples of the other fiber materials include organic fibers such as aramid fibers, glass fibers, and carbon fibers. The upper limit of the content of the other fibers in the molding material for the sliding member is preferably 10 parts by mass and more preferably 1 part by mass with respect to 100 parts by mass of the phenol resin. If the content of the other fiber material exceeds the above upper limit, the processability of the molding material for the sliding member may decrease or the raw material cost may increase. In particular, for a relatively hard fiber material such as glass fiber, if the blending amount is too large, the amount of wear of the mating material may increase during sliding, so it is desirable to suppress the addition as much as possible.

The curing agent accelerates the curing reaction of the phenol resin. When the phenol resin is a novolak type phenol resin, the molding material for the sliding member usually contains a curing agent. Examples of the curing agent include hexamethylenetetramine and the like. When the molding material for a sliding member contains a curing agent, the lower limit of the content of the curing agent is preferably 5 parts by mass with respect to 100 parts by mass of the phenol resin. On the other hand, the upper limit of the content is preferably 20 parts by mass.

The filler improves the strength, durability, wear resistance, etc. of the sliding member to be formed. Examples of the filler include carbon materials other than graphite, elastomers, PTFE (polytetrafluoroethylene) and the like.

The release agent improves the releasability of the formed sliding member. Examples of the release agent include calcium stearate, zinc stearate and the like. The content of the mold release agent in the molding material for the sliding member can be, for example, 0.2 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the phenol resin.

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

[Manufacturing method of molding material for sliding members]
The method for producing the molding material for the sliding member is not particularly limited, and a known method for producing the molding material for the sliding member can be adopted. Specifically, for example, the above-mentioned various components are heated and melted by a pressure kneader, a mixing roll, a twin-screw extruder or the like and kneaded, and then the obtained kneaded product is molded into a sheet shape, and this sheet-shaped molded product is further obtained. Examples thereof include a method of crushing using a pelletizer, a power mill and the like. The kneaded product can be used as it is for molding as a molding material for the sliding member.

<Sliding member>
The sliding member is formed from the above-mentioned molding material for the sliding member. The shape of the sliding member is not particularly limited, and examples thereof include a disk shape, a square plate shape, a columnar shape, a prismatic shape, and a ring shape. The application of the sliding member is not particularly limited, but suitable ones include, for example, thrust washers, pulleys, bearings, gears, bearings, pump parts, swash plates, and the like.

<Manufacturing method of sliding member>
The method for manufacturing the sliding member includes a step (molding step) of molding the above-mentioned molding material for the sliding member. It is preferable that the method for manufacturing the sliding member further includes a step (curing step) of curing the phenol resin contained in the molding material for the sliding member at the same time as the molding step or after the molding step. The method for manufacturing the sliding member may further include a step of melt-kneading the molding material for the sliding member (melt-kneading step) before the molding step.

(Melting and kneading process)
The method of melt-kneading the molding material for a sliding member can be the same as the method of melt-kneading described in the above-mentioned method for producing a molding material for a sliding member, for example.

(Molding process)
In this step, the molding material for the sliding member is molded. The method for molding the molding material for the sliding member is not particularly limited, and examples thereof include injection molding, transfer molding, and compression molding. Of these, injection molding is preferred. When molding by injection molding, the temperature of the front part of the cylinder can be, for example, 70 ° C. or higher and 120 ° C. or lower. The temperature of the rear part of the cylinder can be, for example, 30 ° C. or higher and 60 ° C. or lower.

(Curing process)
In this step, the phenol resin contained in the molding material for the sliding member is cured. Examples of the method of curing the phenol resin include a method of heating a molded product obtained in a molding step. The heating temperature can be, for example, 150 ° C. or higher and 200 ° C. or lower. The heating time can be, for example, 30 seconds or more and 90 seconds or less.

The molded product obtained by the molding step or the cured product obtained by the curing step can be used as it is as a sliding member, but it is preferable to use it as a sliding member after aftercuring. By applying aftercure, the sliding characteristics and dimensional accuracy can be improved. Examples of the aftercure method include a method of heating the molded product or the cured product. The heating temperature can be, for example, 150 ° C. or higher and 230 ° C. or lower. The heating time can be, for example, 3 hours or more and 24 hours or less.

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

First, the novolak-type phenol resin and wood powder used in this example will be described.

[Manufacturing of novolak type phenolic resin]
In a reaction vessel equipped with a thermometer, agitator and a condenser, 193 parts by mass of phenol, 142 parts by mass of 37 mass% formalin (formaldehyde / phenol molar ratio: 0.85) and 0.97 parts by mass of oxalic acid (of phenol). After charging 0.5% by mass with respect to the blending amount, the temperature was gradually raised to the reflux temperature (98 to 102 ° C.), and the condensation reaction was carried out at the same temperature for 6 hours. Then, when the mixture was concentrated under reduced pressure, 199 parts by mass (103% by mass with respect to the amount of phenol charged) of a novolak type phenol resin was obtained. This novolak type phenol resin had a number average molecular weight of 512, a weight average molecular weight of 3,842, and a dispersion ratio of 7.5.

[Wood flour]
Wood flour A (derived from coniferous trees): Made by Sanwa Cellulosin, a mixture of wood flour derived from sugi, wood flour derived from pine and wood flour derived from cypress, 80 mesh (maximum particle size 180 μm), lignin content 25 mass%
Wood flour B (derived from coniferous trees): Made by Sanwa Cellulosin, wood flour mainly composed of wood flour derived from sugi, 80 mesh (maximum particle size 180 μm), lignin content 30% by mass
Wood flour C (derived from coniferous trees): Made by Sanwa Cellulosin, wood flour mainly composed of wood flour derived from pine, 80 mesh (maximum particle size 180 μm), lignin content 28% by mass
Wood flour X (derived from hardwood): Made by Sanwa Cellulosin, wood flour mainly composed of wood flour derived from camphor tree, 80 mesh (maximum particle size 180 μm), lignin content 18% by mass
Wood flour Y (derived from hardwood): Made by Sanwa Cellulosin, wood flour mainly composed of beech-derived wood flour, 80 mesh (maximum particle size 180 μm), lignin content 19% by mass

<Manufacturing of molding materials for sliding members>
[Example 1]
As shown in Table 1 below, 100 parts by mass of novolak type phenol resin, 23 parts by mass of graphite (graphite) (“Blue PA” manufactured by Nippon Graphite Industry), 20 parts by mass of wood flour A (derived from coniferous tree), and inorganic 45 parts by mass of calcium carbonate (manufactured by Maruo Calcium) as a filler, 14 parts by mass of hexamethylenetetramine as a curing agent, and 1 part by mass of calcium stearate as a release agent were 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 granule-shaped molding material for a sliding member.

A plate-shaped test piece was obtained by injection molding and curing the obtained molding material for a sliding member of Example 1 under the following molding conditions.
(Molding condition)
Cylinder temperature: front 90 ° C, rear 40 ° C
Mold temperature: 170 ℃
Curing time: 60 seconds

[Examples 2 to 10 and Comparative Examples 1 to 3]
In Example 1, the same as in Example 1 except that the amount of the phenol resin, the type and amount of wood flour, the amount of graphite, and the amount of the inorganic filler were as shown in Table 1. By operating, molding materials and test pieces for sliding members of Examples 2 to 10 and Comparative Examples 1 to 3 were produced.

<Evaluation>
Using the obtained test piece, warpage, bending strength, wear resistance and squeal were evaluated according to the following method. The evaluation results are also shown in Table 1.

[warp]
A strip-shaped member of 10 mm × 150 mm × 3 mm was cut out from each test piece and placed on a flat test table with one surface facing down. In a state where the surface around one end of the strip-shaped member in the long side direction is fixed to the test table, the warp at the other end raised from the test table (lower part of the strip-shaped member at the other end). The distance between the surface on the side and the surface of the test stand) was measured with a feeler gauge. The warp was measured at n = 3, and the average value was evaluated as "A (particularly good)", "B (good)" or "C (not good)" according to the following criteria.
A: 0.04 mm or less B: More than 0.04 mm and less than 0.10 mm C: 0.10 mm or more

[Bending strength]
The bending strength of each test piece was measured according to JIS-K6911: 2006. The bending strength can be evaluated as "A (good)" when it is 80 MPa or more, and as "B (not good)" when it is less than 80 MPa.

[Abrasion resistance test]
The wear resistance of each test piece was measured with a thrust tester (“AFT-6A” manufactured by Azumahaka Precision Industries). Specifically, as shown in FIG. 1, a plate-shaped test piece X1 and a cylindrical mating member X2 arranged on the upper surface of the test piece X1 were arranged in a thrust tester (not shown). The mating member X2 is a hollow cylindrical carbon steel (S45C) having an outer diameter of 26.6 mm, an inner diameter of 20 mm, and a height of 15 mm. The space between the test piece X1 and the mating member X2 was unlubricated (dry environment). The mating member X2 was rotated in a certain direction B while applying a test surface pressure A from above. The test conditions were a test surface pressure A of 0.49 MPa, a test speed of 1.34 m / s, and a test time of 1 hour. After the test, the amount of wear (mm ³ ) was multiplied by the sliding distance (m) (the value obtained by multiplying the test speed by the test time) and the load (N) (test surface pressure A multiplied by the contact area of the test piece X1 and the mating member X2). The specific wear amount was calculated by dividing by (value). Abrasion resistance can be evaluated as "A (good)" or "B (not good)" based on the following criteria.
A: Specific wear amount is ^{less than 10 × 10-5} mm ³ / N ・ m B: Specific wear amount is 10 × ^10-5 mm ³ / N ・ m or more

[Sound]
In the test shown in FIG. 1, the generation of squealing when the speed and load were constant was measured with an acoustic vibration measuring machine (“NL-21” manufactured by Rion Co., Ltd.). The distance between the measurement position and the sliding part was 20 cm. The squeal was evaluated as "A (particularly good)", "B (good)" or "C (not good)" based on the following criteria.
A: No squeal was observed from beginning to end (70 dB or less, which is the driving sound of the test equipment).
B: A minute squeal was observed (more than 70 dB and less than 90 dB).
C: The occurrence of intense squealing was observed from beginning to end (90 dB or more).

As is clear from the results in Table 1 above, the molding material for sliding members of the examples containing phenol resin, graphite, and wood powder derived from coniferous trees is excellent in bending strength and sliding characteristics in a dry environment. In addition, it was possible to form a test piece in which warpage and squealing during sliding are unlikely to occur. On the other hand, the molding materials for sliding members of Comparative Examples 1 and 2 using wood powder derived from hardwood instead of wood powder derived from softwood are formed in comparison with the molding materials for sliding members of Examples. The bending strength and abrasion resistance of the test piece were low. Further, the molding materials for sliding members of Comparative Examples 3 to 4 in which graphite was not used have lower wear resistance of the test piece to be formed and squealing as compared with the molding materials for sliding members of Examples. It could not be suppressed sufficiently.

According to the molding material for a sliding member, the sliding member, and the manufacturing method of the present invention, a sliding member having excellent bending strength and sliding characteristics in a dry environment and which is less likely to warp and make noise during sliding can be obtained. Can be provided.

X1 test piece X2 mating member

Claims (5)

Contains phenolic resin, graphite and wood powder,
The wood flour, saw including a wood flour derived from coniferous trees,
The content of the graphite with respect to 100 parts by mass of the phenol resin is 10 parts by mass or more and 120 parts by mass or less.
The content of the wood flour with respect to 100 parts by mass of the phenol resin is 15 parts by mass or more and 75 parts by mass or less.
The mass ratio of the wood flour to the graphite is 0.4 or more and 4.5 or less.
A molding material for sliding members in which the content of lignin in the wood flour is 25% by mass or more. The molding material for a sliding member according to claim 1, wherein the conifer is sugi, pine, cypress, fir, yew, ginkgo, kaya, hemlock, inumaki, sciadopity, or a combination thereof. The molding material for a sliding member according to claim 1 or 2 , further containing an inorganic filler. A sliding member formed of the molding material for a sliding member according to claim 1, claim 2 or claim 3. A method for manufacturing a sliding member, comprising a step of molding the molding material for the sliding member according to any one of claims 1 to 4.

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