Molded body and resin gear

Abstract

A molded body containing a fiber base material and a polyaminoamide resin, wherein the fiber base material includes aramid fibers and graphite.

Description

Molded body and resin gear

[0001] This disclosure relates to molded articles and resin gears.

[0002] Resin molded articles, composed of a fiber base material and resin, are used in a variety of fields due to their excellent lightweight properties and mechanical characteristics. For example, resin gears formed from resin molded articles are lighter and quieter than metal gears, and are therefore used as components in machine tools, industrial machinery, automobile engines, and drive units for electric motorcycles (see, for example, Patent Document 1 below).

[0003] Japanese Patent Application Publication No. 11-227061

[0004] One aspect of this disclosure aims to provide a molded article with a low coefficient of friction.

[0005] This disclosure includes the following aspects: [1] A molded article comprising a fiber base material and a polyaminoamide resin, wherein the fiber base material comprises aramid fibers and graphite. [2] The molded article according to [1], wherein the polyaminoamide resin comprises structural units derived from a bis(2-oxazoline) compound. [3] The molded article according to [2], wherein the polyaminoamide resin further comprises structural units derived from an aromatic diamine compound. [4] The molded article according to any one of [1] to [3], wherein the graphite content is 1% by mass or more and 13% by mass or less based on the total amount of the fiber base material. [5] The molded article according to any one of [1] to [4], wherein the average particle size of the graphite is 1 μm or more and 50 μm or less. [6] A resin gear comprising the molded article according to any one of [1] to [5]. [7] The resin gear according to [6], used together with a lubricant.

[0006] According to one aspect of this disclosure, it is possible to provide a molded article with a low coefficient of friction.

[0007] This is a schematic perspective view showing one embodiment of a resin gear.

[0008] The embodiments of this disclosure will be described in detail below. However, this disclosure is not limited to the embodiments described below.

[0009] One embodiment of the present disclosure is a molded article containing a fibrous substrate and a polyaminoamide resin. The fibrous substrate is a base material for maintaining the shape of the molded article. The fibrous substrate contains aramid fibers and graphite. The fibrous substrate may be a substrate (papered article) molded by papermaking from a mixture containing aramid fibers and graphite.

[0010] The aramid fiber may include para-aramid fiber and may include meta-aramid fiber. Preferably, the aramid fiber includes para-aramid fiber and meta-aramid fiber. Para-aramid fiber refers to an aramid fiber having a molecular structure that includes an aromatic ring in which the amide bond is located at the para position (position 1 and position 4). Meta-aramid fiber refers to an aramid fiber having a molecular structure that includes an aromatic ring in which the amide bond is located at the meta position (position 1 and position 3).

[0011] Para-aramid fibers may include fibers having a molecular structure represented by the following formula (1) (excluding fibers having a molecular structure represented by the following formula (2); hereinafter also referred to as "formula (1) fibers") and may also include fibers having a molecular structure represented by the following formula (2) (hereinafter also referred to as "formula (2) fibers"). Para-aramid fibers may include both formula (1) fibers and formula (2) fibers. In equations (1) and (2), a, b, and c each independently represent an integer greater than or equal to 2.

[0012] The content of the (1) fiber may be 1% by mass or more, 2% by mass or more, or 3% by mass or more, based on the total amount of aramid fibers, from the viewpoint of reducing the hygroscopicity of the molded article. The content of the (1) fiber may be 20% by mass or less, 10% by mass or less, or 8% by mass or less, based on the total amount of aramid fibers, from the viewpoint of further improving the durability (durability of the resin gear) when the molded article is used in a resin gear.

[0013] From the viewpoint of reducing the hygroscopicity of the molded article, the content of the formula (2) fiber may be 20% by mass or more, 30% by mass or more, 35% by mass or more, or 40% by mass or more, based on the total amount of aramid fiber. From the viewpoint of further improving the durability of the resin gear, the content of the formula (2) fiber may be 70% by mass or less, 60% by mass or less, 55% by mass or less, 50% by mass or less, or 45% by mass or less, based on the total amount of aramid fiber.

[0014] From the viewpoint of reducing the hygroscopicity of the molded article, the content of para-aramid fibers may be 20% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, or 45% by mass or more, based on the total amount of aramid fibers. From the viewpoint of further improving the durability of the resin gear, the content of para-aramid fibers may be 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, or 50% by mass or less, based on the total amount of aramid fibers.

[0015] Meta-aramid fibers may include fibers having a molecular structure represented by the following formula (3) (excluding fibers having a molecular structure represented by the above formula (1) or (2); hereinafter also referred to as "formula (3) fibers"). In equation (3), d represents an integer greater than or equal to 2.

[0016] The content of meta-aramid fibers (formula (3) fibers) may be 20% by mass or more, 30% by mass or more, 40% by mass or more, 45% by mass or more, or 50% by mass or more, based on the total amount of aramid fibers, from the viewpoint of further improving the durability of the resin gear. The content of meta-aramid fibers (formula (3) fibers) may be 80% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, or 55% by mass or less, based on the total amount of aramid fibers, from the viewpoint of reducing the hygroscopicity of the molded article.

[0017] The aramid fiber content may be 60% by mass or more, 70% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, or 92% by mass or more, based on the total amount of the fiber base material, and may be 99% by mass or less, 97% by mass or less, 95% by mass or less, or 91% by mass or less.

[0018] The fiber length of the aramid fiber may be 1 mm or more and 10 mm or less. The fiber diameter of the aramid fiber may be 8 μm or more and 12 μm or less.

[0019] The fiber base material may further contain fibers other than aramid fibers. Examples of fibers other than aramid fibers include thermoplastic resin fibers such as polyphenylene sulfide fibers, polyamide (aliphatic polyamide, aromatic polyamide) fibers, polyethylene fibers, and polypropylene fibers, inorganic fibers such as basalt fibers, alumina fibers, glass fibers, and carbon fibers, and metal fibers such as stainless steel fibers and aluminum fibers. The fiber base material may further contain two or more types of fibers other than aramid fibers. The content of fibers other than aramid fibers may be 1% by mass or more and 5% by mass or less, based on the total amount of the fiber base material.

[0020] Graphite is mainly composed of carbon atoms, has a layered crystalline structure, and belongs to the hexagonal crystal system. By including graphite in the fibrous substrate, a molded body with a low coefficient of friction can be obtained. The graphite may be artificial graphite or natural graphite.

[0021] From the viewpoint of further lowering the coefficient of friction of the molded body, the graphite content may be 1% by mass or more, 2% by mass or more, 3% by mass or more, 4% by mass or more, 5% by mass or more, 6% by mass or more, 7% by mass or more, 8% by mass or more, or 9% by mass or more, based on the total amount of the fiber base material. From the viewpoint of further improving the durability of the resin gear, the graphite content may be 13% by mass or less, 11% by mass or less, 10% by mass or less, or 9% by mass or less, based on the total amount of the fiber base material.

[0022] Graphite may be in particulate form. The shape of the graphite particles may be spherical or flaky.

[0023] The average particle size of graphite may be 1 μm or more, 2 μm or more, 3 μm or more, or 4 μm or more, preferably 10 μm or more, 15 μm or more, 18 μm or more, 20 μm or more, 23 μm or more, 25 μm or more, 28 μm or more, 30 μm or more, 33 μm or more, or 35 μm or more, from the viewpoint of further improving the durability of the resin gear and from the viewpoint of usability even under conditions where there are restrictions on nanomaterials. The average particle size of graphite may be 60 μm or less, 50 μm or less, 45 μm or less, 40 μm or less, 37 μm or less, 35 μm or less, 32 μm or less, 30 μm or less, 15 μm or less, 10 μm or less, or 7 μm or less, from the viewpoint of improving dispersibility during papermaking.

[0024] The average particle size of graphite can be measured by the following procedure: Cut the molded body so that the graphite inside is exposed. Next, polish the cut surface until the maximum particle size (length) of the graphite can be determined. Then, observe the cut surface using a scanning electron microscope (SEM) and measure the maximum particle size (length) of the graphite. Perform this particle size measurement for 20 pieces of graphite and take the average of the measured particle sizes as the average particle size.

[0025] The fiber base material content may be 10% by volume or more, 20% by volume or more, 30% by volume or more, 35% by volume or more, or 38% by volume or more, based on the total volume of the molded article, and may be 70% by volume or less, 60% by volume or less, 55% by volume or less, 50% by volume or less, 45% by volume or less, or 42% by volume or less.

[0026] The polyaminoamide resin may contain structural units derived from bis(2-oxazoline) compounds (hereinafter also referred to as "structural unit A"). A bis(2-oxazoline) compound is a compound having two oxazoline skeletons in one molecule. The two oxazoline skeletons may be directly bonded or bonded via organic groups. The polyaminoamide resin may contain two or more types of structural unit A. The bis(2-oxazoline) compound may be a compound represented by the following formula (4). In formula (4), R １ R represents a linear or branched alkylene group, a phenylene group, or a pyridinediyl group. ２ ~R ５Each of these independently represents a hydrogen atom, an alkyl group, or a phenyl group. １ The phenylene group and pyridinediyl group in R may be substituted with an alkyl group or with a methyl group. １ The number of carbon atoms in the alkylene group in R may be 1 or more, and may be 4 or less. ２ ~R ５ The number of carbon atoms in each alkyl group may be 1 or more, or 4 or less, independently of each other.

[0027] Examples of bis(2-oxazoline) compounds constituting structural unit A include 2,2'-(1,3-phenylene)bis(2-oxazoline), 2,2'-(1,4-phenylene)bis(2-oxazoline), 2,2'-(1,2-ethylene)bis(2-oxazoline), 2,2'-(1,4-butylene)bis(2-oxazoline), 2,2'-(1,3-phenylene)bis(5-methyl-2-oxazoline), (S,S)-2,6-bis(4-isopropyl-2-oxazoline-2-yl)pyridine, and (S,S)-2,2'-(dimethylmethylene)bis(4-phenyl-2-oxazoline). From the viewpoint of further lowering the coefficient of friction of the molded article, the polyaminoamide resin preferably contains a structural unit derived from 2,2'-(1,3-phenylene)bis(2-oxazoline).

[0028] The content of structural unit A may be 30% by mass or more, 40% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, or 67% by mass or more, based on the total amount of polyaminoamide resin, and may be 90% by mass or less, 80% by mass or less, 75% by mass or less, 72% by mass or less, or 70% by mass or less.

[0029] The content of structural unit A may be 40 mol% or more, 50 mol% or more, 60 mol% or more, or 64 mol% or more, based on the total amount of polyaminoamide resin, and may be 90 mol% or less, 80 mol% or less, 75 mol% or less, 72 mol% or less, or 70 mol% or less.

[0030] The polyaminoamide resin may contain a structural unit derived from an aromatic diamine compound (hereinafter also referred to as "structural unit B"). The polyaminoamide resin may contain two or more kinds of structural units B.

[0031] The aromatic diamine compound may be a compound represented by the following formula (5). In formula (5), R ６ represents a linear or branched alkylene group, or a 4,4'-(propan-2,2-diyl)diphenoxy group. R ７ ~R １４ each independently represents a hydrogen atom, an alkyl group, or a halogenated group. Examples of the halogenated group include a fluoro group, a chloro group, a bromo group, an iodo group, etc. The number of carbon atoms of the alkylene group in R ６ may be 1 or more and may be 10 or less. The number of carbon atoms of the alkyl group in R ７ ~R １４ may each independently be 1 or more and may be 4 or less.

[0032] As the alkylene group in R ６ , examples include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, etc. R ６ is preferably a methylene group.

[0033] Examples of the aromatic diamine compound constituting the structural unit B include 4,4'-diaminodiphenylmethane, 3,3'-dichloro-4,4'-diaminodiphenylmethane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-methylenebis(2-ethyl-6-methylaniline), and 4,4'-methylenebis(2-ethylaniline). From the viewpoint of further lowering the friction coefficient of the molded body, the polyaminoamide resin preferably contains a structural unit derived from 4,4'-diaminodiphenylmethane.

[0034] The content of structural unit B may be 10% by mass or more, 20% by mass or more, 25% by mass or more, or 28% by mass or more, and may be 60% by mass or less, 50% by mass or less, 40% by mass or less, 35% by mass or less, or 33% by mass or less, based on the total amount of the polyaminoamide resin.

[0035] The content of structural unit B may be 10 mol% or more, 20 mol% or more, 25 mol% or more, or 28 mol% or more, and may be 60 mol% or less, 50 mol% or less, 45 mol% or less, 40 mol% or less, or 35 mol% or less, based on the total amount of the polyaminoamide resin.

[0036] The molar ratio of structural unit B to structural unit A may be 0.1 or more, 0.3 or more, or 0.4 or more, and may be 0.9 or less, 0.7 or less, or 0.6 or less.

[0037] The polyaminoamide resin is obtained by thermally curing a thermosetting composition containing the above bis(2-oxazoline) compound and the above aromatic diamine compound. The polyaminoamide resin may also be obtained by thermally curing the thermosetting composition in a state where it is injected (impregnated) into a fiber substrate. From the viewpoint of promoting the curing reaction between the bis(2-oxazoline) compound and the aromatic diamine compound, the thermosetting composition may further contain a curing accelerator. Examples of the curing accelerator include p-toluenesulfonic acid esters such as n-octyl bromide and ethyl p-toluenesulfonate. The curing accelerator may be 0.1 part by mass or more, 0.5 part by mass or more, or 0.7 part by mass or more, and may be 2 parts by mass or less, 1.5 parts by mass or less, or 1 part by mass or less, based on 100 parts by mass in total of the bis(2-oxazoline) compound and the aromatic diamine compound.

[0038] The molded body or the thermosetting composition may further contain a resin other than the polyaminoamide resin. Examples of the resin other than the polyaminoamide resin include polyamide resin, epoxy resin, phenolic resin, melamine resin, urea resin, polyimide resin, polyester resin, and the like.

[0039] The molded article or thermosetting composition may further contain organic lubricants such as polyethylene glycol, and shock absorbers such as silicone rubber, fluororubber, or nitrile rubber.

[0040] Next, a method for manufacturing the molded article described above will be explained. One embodiment of the present disclosure is a method for manufacturing a molded article comprising: a first step of papermaking a mixture containing aramid fibers and graphite to obtain a fibrous base material; a second step of injecting (impregnating) the above-mentioned thermosetting composition into the fibrous base material; and a third step of curing the thermosetting composition. Details of the fibrous base material, aramid fibers, graphite, and polyaminoamide resin are the same as those described in the molded article described above.

[0041] The mixture used in the first step further contains water. Aramid fibers and graphite are dispersed in the water. The fiber base material may be formed into a shape corresponding to the shape of the final molded article by, for example, filling this mixture into a papermaking die and dewatering under pressure. The first step may also include a drying step after papermaking.

[0042] In the second step, the thermosetting composition may be injected (impregnated) into the fibrous substrate in a molten state. Alternatively, in the second step, the fibrous substrate may be preheated before injecting (impregnating) the thermosetting composition.

[0043] In the third step, the temperature at which the thermosetting composition is cured (curing temperature) may be 100°C or higher, 150°C or higher, 170°C or higher, or 180°C or higher, and may be 300°C or lower, 250°C or lower, 220°C or lower, or 200°C or lower. In the third step, the time at which the thermosetting composition is cured (curing time) may be 1 minute or more, and may be 30 minutes or less.

[0044] The molded body described above is suitably used in resin gears. One embodiment of the present disclosure is a resin gear including the above-described molded body. Figure 1 is a perspective view showing one embodiment of the resin gear. As shown in Figure 1, the resin gear 1 according to one embodiment comprises a substantially cylindrical body portion 2, teeth portion 3 provided on the outer circumferential surface of the body portion 2, and an axial hole 4 that penetrates the center of the body portion 2.

[0045] The gear teeth 3 have multiple tooth tips 31 and multiple tooth roots 32 so as to mesh with other gears. The tooth tips 31 and tooth roots 32 are arranged alternately so as to be arranged helically at predetermined intervals. The shaft hole 4 is formed so as to be able to be directly attached to the rotating shaft or to be attached to the rotating shaft via a metal bush or the like. The inner circumferential surface (side surface on the shaft hole 4 side) of the main body 2 has irregularities 5 to facilitate attachment to the rotating shaft.

[0046] Resin gears may be used with a lubricant to further improve their durability. Examples of lubricants include grease and engine oil.

[0047] In the above embodiment, the case where the resin gear 1 is a helical gear was described, but the resin gear may be a spur gear, a bevel gear, or the like. In the above embodiment, the case where the resin gear 1 has a shaft hole 4 was described, but the resin gear does not have to have a shaft hole, may be integrated with the rotating shaft, or may be integrated with other rotating bodies.

[0048] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to these examples.

[0049] (Example 1) A molded article was produced by the following method. 69 parts by mass of 2,2'-(1,3-phenylene)bis(2-oxazoline) (manufactured by Mikuni Pharmaceutical Co., Ltd., hereinafter also referred to as "PBO") and 31 parts by mass of 4,4'-diaminodiphenylmethane (manufactured by Manka Chemical Japan Co., Ltd., hereinafter also referred to as "MDA") were mixed and heated to dissolve into a liquid. To this liquid, n-octyl bromide (manufactured by Manac Co., Ltd.) was mixed as a curing accelerator at a ratio of 0.9 parts by mass per 100 parts by mass of the total of PBO and MDA to obtain a thermosetting composition.

[0050] A mixture was prepared by dispersing 5 parts by mass of para-aramid fibers (fibers obtained by dispersing Toray DuPont's product name "Kevlar Pulp," corresponding to "Formula (1) fiber" above), 42 parts by mass of cut para-aramid fibers (Teijin Limited's product name "Technora," corresponding to "Formula (2) fiber" above) (fiber length 3 mm), and 53 parts by mass of cut meta-aramid fibers (Teijin Limited's product name "Conex," corresponding to "Formula (3) fiber" above) (fiber length 3 mm) in water. Graphite (Ito Graphite Industry Co., Ltd., product name "RP99-150," average particle size: 36 μm, flaky) was added to the total amount of the fiber base material to make a mixture of 10% by mass. The mixture was then compressed in the thickness direction by pressurized dewatering in a papermaking die so that the fiber base material accounted for 40% by volume in the molded body, obtaining a rectangular parallelepiped fiber base material.

[0051] Next, the rectangular fibrous substrate obtained above was placed in the molding die and clamped, the thermosetting composition prepared above was further injected, and the molding die was heated at 190°C for 4 minutes to cure the thermosetting composition, thereby obtaining a rectangular molded body measuring 120 mm in length, 60 mm in width, and 14 mm in thickness. This molded body was then machined to obtain a cylindrical molded body measuring 5 mm in diameter and 13 mm in height.

[0052] (Comparative Example 1) A molded article was obtained in the same manner as in Example 1, except that graphite was not added.

[0053] (Comparative Example 2) A molded article was obtained in the same manner as in Example 1, except that molybdenum disulfide (manufactured by Daizo Co., Ltd., product name "A Powder", average particle size: 0.63 μm, flaky) was added in the same manner as in Example 1, in an amount of 10% by mass based on the total amount of the fiber base material, instead of graphite.

[0054] <Coefficient of Friction> The bottom surfaces of the molded bodies in Example 1 and Comparative Examples 1 and 2 were placed in contact with an S45C disk (Ra: 0.8 μm), and a load of 100 N was applied to the molded bodies. The disk was then rotated at a speed of 0.8 m / s, and the coefficient of friction was measured. At this time, the PV value was 4.0 MPa·m / s, the sliding distance was 9.0 km, the ambient temperature was 25°C, and the test time was 187.5 minutes. No lubricant was used in this test. The results are shown in Table 1.

[0055]

[0056] (Example 2) A molded body was obtained in the same manner as in Example 1, except that graphite (manufactured by Resonaq Corporation, product name "UFG-5", average particle size: 5 μm) was added in an amount of 7% by mass based on the total amount of the fiber base material, and a disc-shaped molded body was obtained by using a molding die for disc-shaped molded bodies.

[0057] (Example 3) A molded article was obtained in the same manner as in Example 2, except that graphite (manufactured by Resonaq Corporation, product name "UFG-30", average particle size: 30 μm) was added in an amount of 7% by mass based on the total amount of the fiber base material.

[0058] (Comparative Example 3) A molded article was obtained in the same manner as in Example 2, except that graphite was not added.

[0059] <Motoring Durability Test> Teeth were formed on the disc-shaped molded bodies of Examples 2 and 3 and Comparative Example 3 by machining, and these were made into resin gears. The obtained resin gears were continuously rotated under the test conditions shown below, and the time until the resin gear broke (durability time) was measured. The test was also performed in conjunction with the tooth root stress as shown below. For Examples 3 and Comparative Example 3, tests were performed both with and without grease. For Example 2, the test was performed without grease. The results are shown in Table 2. [Test Conditions] Test temperature: Room temperature Rotation speed (rpm): 250 Tooth root stress (MPa): Approximately 336

[0060]

[0061] 1... Resin gear, 2... Main body, 3... Teeth, 31... Tooth tip, 32... Tooth root, 4... Shaft hole, 5... Concave and concave.

Claims

1. A molded article comprising a fibrous base material and a polyaminoamide resin, wherein the fibrous base material contains aramid fibers and graphite.

2. The molded article according to claim 1, wherein the polyaminoamide resin contains structural units derived from a bis(2-oxazoline) compound.

3. The molded article according to claim 2, wherein the polyaminoamide resin further comprises structural units derived from an aromatic diamine compound.

4. The molded article according to claim 1, wherein the graphite content is 1% by mass or more and 13% by mass or less, based on the total amount of the fiber base material.

5. The molded article according to claim 1, wherein the average particle size of the graphite is 1 μm or more and 50 μm or less.

6. A resin gear comprising a molded body according to any one of claims 1 to 5.

7. The resin gear according to claim 6, used together with a lubricant.

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