JP5321211B2 - Biodegradable plastic machine parts and rolling bearings - Google Patents

Description

The present invention relates to an inner ring, an outer ring, a rolling element, a cage, and a seal member formed by molding a biodegradable resin . The present invention also relates to a rolling bearing provided with the inner ring , outer ring, rolling element, cage, and seal member.

  The biodegradable resin is gradually decomposed into carbon dioxide and water by bacteria and the like when left in the soil. Since the mechanical parts made of this biodegradable resin are naturally decomposed until they remain in their original form even when released into the natural environment, they are unlikely to have an adverse effect on the natural environment. Biomass plastics produced from renewable raw materials such as plants and other biological resources are also attracting attention as carbon neutral materials.

  These environmentally friendly plastics were mainly used for materials such as garbage bags, bottle containers, food trays, agricultural multi-films, etc. Recently, research and development as mechanical parts and structural parts materials have become active, Application to rolling bearing cages and seal members is also being studied. The present applicant has also proposed a rolling bearing including a cage and a seal made of a resin composition in which a reinforcing fiber material is blended with polyvinyl alcohol (see Patent Documents 1 to 4).

JP 2004-92732 A JP 2004-92769 A Japanese Patent No. 3791439 Japanese Patent No. 4117478

  However, although polyvinyl alcohol has a high melting point of 200 ° C. or higher, mechanical properties are greatly reduced at about 100 ° C. Further, since it has a large amount of hydroxyl groups in the molecule, it is inferior in water resistance, and water absorption proceeds even with moisture in the atmosphere, and mechanical properties are likely to deteriorate over time. For this reason, there may be a concern that the strength is insufficient for use in a wide range of applications as an inner ring, an outer ring, and a rolling element of a rolling bearing. Further, the cage and the seal member are required to further improve the strength.

Therefore, the present invention improves the heat resistance and mechanical properties of a molded product based on polyvinyl alcohol having excellent biodegradability, and further maintains high strength for a long period of time. The inner and outer rings of rolling bearings, rolling elements, It aims at making it fully usable as a cage and a seal member .

In order to achieve the above object, the present invention provides the following biodegradable resin mechanical parts and rolling bearings.
(1) At least one mechanical component of an inner ring, an outer ring, a rolling element, a cage, and a seal member of a rolling bearing, and 2 to 5 parts by mass of polyvinyl alcohol as a base resin with respect to 100 parts by mass of the base resin. A biodegradable resin mechanical part, wherein a resin composition containing an imide-based crosslinking agent is molded into the mechanical part, and then the molded product is heat-treated at 120 to 170 ° C. to advance a crosslinking reaction .
(2) The biodegradable resin mechanical part as described in (1) above, wherein the imide-based crosslinking agent is a carbodiimide compound.
(3) The raw material according to (1) or (2), wherein the polyvinyl alcohol has a saponification degree of 73 to 98 mol%, an oxyalkylene group amount of 0.1 to 5 mol%, and a polymerization degree of 500 to 1500. Degradable plastic machine parts.
(4) A rolling bearing having a seal member, which is rotatably held between a inner ring and an outer ring via a cage, and includes an inner ring, an outer ring, a rolling element, a cage, and a seal. A rolling bearing characterized in that at least one of the members is the biodegradable resin mechanical part according to any one of (1) to (3) above.

ADVANTAGE OF THE INVENTION According to this invention, while being excellent in biodegradability, it is excellent also in heat resistance and mechanical strength, and the long life inner ring and outer ring of a rolling bearing, a rolling element , a holder | retainer, and a sealing member are provided.

It is sectional drawing of the deep groove ball bearing which shows one Embodiment of the rolling bearing of this invention. It is a perspective view which shows the holder | retainer integrated in the deep groove ball bearing of FIG.

  Hereinafter, the present invention will be described in detail.

In the present invention, polyvinyl alcohol is used which is excellent in biodegradability as the base resin. As polyvinyl alcohol, what has the basic skeleton represented by the following general formula (I) is preferable.

  In the formula, R1 is an oxyalkylene group, a polyether group, or a polyester group, and l, m, and n are integers. The degree of saponification is represented by m / (1 + m + n), preferably 73 to 98 mol%, more preferably 85 to 95 mol%. If the degree of saponification is less than 73 mol%, the mechanical parts become inferior in moisture resistance, and if it exceeds 98 mol%, the biodegradability becomes poor.

  Further, (l + m + n) represents the degree of polymerization, but is preferably 500 to 3000, and more preferably 500 to 1500. If the molecular weight is less than 500, the heat resistance of the machine part is not sufficient, and if it exceeds 3000, the fluidity at the time of molding is low, and the moldability is adversely affected.

  In the present invention, the polyvinyl alcohol is crosslinked with an imide-based crosslinking agent to improve mechanical properties. Among imide-based cross-linking agents, polyvinyl alcohol is highly reactive with active hydrogen, is stable at room temperature, has no self-reaction, can be melt-kneaded with polyvinyl alcohol, and is water and heat resistant. A carbodiimide compound having two or more carbodiimide groups in the molecule is preferable because it can impart sliding resistance.

  As the carbodiimide compound, those having a basic skeleton represented by the following general formula (II) are preferable.

  Specifically, 4,4′-dicyclohexylmethanecarbodiimide (wherein X is 4,4′-dicyclohexyl group, n = 2 to 20), tetramethylxylylene carbodiimide (wherein X is tetramethylxylyl). Len group, n = 2 to 20), N, N′-dimethylphenylcarbodiimide (wherein X is N, N′-dimethylphenyl group, n = 2 to 20), N, N′-di-2,6 -Diisopropylphenylcarbodiimide (X in the formula is N, N'-di-2,6-diisopropylphenyl group, n = 2 to 20) and the like.

  Among these, an aliphatic carbodiimide compound is preferable to an aromatic carbodiimide compound from the viewpoints of hue, safety, stability, hydrolysis resistance, weather resistance, and heat resistance. In addition, an aliphatic carbodiimide compound having a degree of polymerization of 5 or more is particularly preferred from the viewpoint of heat resistance in which the TG 5% weight loss rate temperature is 250 ° C. or higher. Furthermore, among aliphatic carbodiimide compounds, those having an isocyanate end are particularly preferred from the viewpoint of hydrolysis resistance,

The addition amount of an imide type crosslinking agent is 2-5 mass parts with respect to 100 mass parts of polyvinyl alcohol. When the addition amount of the imide-based crosslinking agent is less than 2 parts by mass, a sufficient crosslinking density cannot be obtained, and a machine part excellent in water resistance and mechanical strength cannot be obtained. On the other hand, when the amount of the imide-based crosslinking agent exceeds 5 parts by mass, the toughness of the machine parts is significantly reduced, and the cage tip (claw portion) is whitened particularly when used as a cage for a rolling bearing. In case of damage. Furthermore, there is a possibility that adverse effects such as deterioration of workability and difficulty in injection molding and deterioration of biodegradability may occur.

  Moreover, you may mix | blend a reinforcing material with polyvinyl alcohol for the purpose of the improvement of mechanical strength. Carbon fiber and glass fiber are generally used as the reinforcing material, and glass fiber is most suitable from the viewpoint of cost. However, since polyvinyl alcohol decomposes and remains in the soil, there is little impact on the environment. Light calcium carbonate (crystal form: calcite, argonite), natural hydrous aluminum silicate (kaolin, clay), talc, bentonite, fibrous magnesium hydroxide, wollastonite, sepiolite, mica, silicon dioxide, diatomaceous earth, etc. are suitable It is. The reinforcing material is suitably 15 to 40 parts by mass with respect to 100 parts by mass of polyvinyl alcohol, and if it is less than 15 parts by mass, the mechanical strength is insufficient. And the environmental load when it remains in the soil increases.

  Moreover, it is preferable that the reinforcing material is surfaced with the silane coupling agent which has an epoxy group with high reactivity with the hydroxyl group of polyvinyl alcohol.

  Furthermore, other additives can be added depending on the purpose. For example, an antioxidant for preventing deterioration due to heat during formation or use, an ultraviolet absorber for preventing deterioration due to ultraviolet rays, a filler, and the like are suitable. It is preferable to select materials registered in the positive list (PL) of the Green Plastic Identification Display System operated by the Biodegradable Plastics Study Group (BPS).

  The polyvinyl alcohol and the imide-based crosslinking agent, and further, a reinforcing material and an additive are kneaded to obtain a resin composition, which is molded according to the shape of the machine part. For kneading, a kneader for resin or rubber can be used, for example, dry blending using a Henschel mixer or tumbler, etc., and melt kneading using a kneader such as a Banbury mixer, kneader, extruder, roll mill or the like. Also good. There is no limitation on the molding method, and a molding machine for resin or rubber can be used. From the viewpoint of productivity, injection molding is preferable. Moreover, you may cut after shaping | molding.

  In the present invention, the molded product is heat treated to increase the mechanical strength. The heat processing temperature is 120-170 degreeC, and 140-150 degreeC is more preferable. If the temperature is lower than 120 ° C, the crosslinking reaction does not proceed, and the physical properties such as mechanical strength are not sufficiently improved. If the temperature exceeds 170 ° C, the resin may be thermally deteriorated. The heat treatment is preferably performed in an inert gas atmosphere such as nitrogen gas or argon gas, and most preferably, the heat treatment is performed in a state of being fitted in a mold in order to prevent a dimensional change due to heat.

In the present invention as the type of machine parts can be applied the inner ring of the rolling bearing, the outer ring, rolling elements, the retainer, the seal member. Figure 1 is a sectional view of a deep groove ball bearing 10, between the inner ring 11 and outer ring 12 are incorporated in a state of being rollably held balls 13 are a plurality of rolling elements by the retainer 14, A seal member 15 seals a lubricant such as grease (not shown). Moreover, the holder | retainer 14 is a crown type holder | retainer as shown in FIG. The seal member 15 is fixed by fitting an engagement portion 15 a provided at one end thereof into the engaging grooves 12 a at both outer ends of the outer ring 12, and the lip portion 15 c at the other end is in sliding contact with the raceway surface of the inner ring 11. ing. Reference numeral 15b denotes a main body that connects the engaging portion 15a and the lip portion 15c.

  Even in Patent Documents 1 to 4, the cage 14 and the seal member 15 are made of a polyvinyl alcohol resin composition. However, in the present invention, since the mechanical strength is further improved, the cage 14 and the seal member 15 are also applied to the inner ring 11, the outer ring 12, and the balls 13. be able to.

  The lubricant is not limited, but is preferably biodegradable. For example, vegetable oil, biodegradable synthetic ester oil, or these oils may be increased with a thickener such as various metal soaps or urea compounds. The biodegradable grease made can be illustrated.

  Examples The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereby.

(Examples 1-3, Comparative Examples 1-3)
“Ecomaty AX-300” manufactured by Nippon Synthetic Chemical Industry Co., Ltd. (93% saponification degree, containing oxyalkylene group) as a polyvinyl alcohol resin, “ECS03” manufactured by Nittobo Material Co., Ltd. (treated with epoxy silane coupling agent) as glass fiber , “Carbodilite LA-1” (4,4′-dicyclohexylmethane carbodiimide, carboimide equivalent 248) manufactured by Nisshinbo Co., Ltd. as an imide-based cross-linking agent is added to the one blended with polyvinyl alcohol resin: glass fiber = 70: 30. It added in the ratio shown in Table 1, and melt-kneaded (200 degreeC, rotation speed 30rpm for 5 minutes) in the "Lab plast mill" by Toyo Seiki Seisakusho. In addition, the imide type crosslinking agent amount shown in Table 1 is an amount with respect to 100 parts by mass of polyvinyl alcohol.

  After pulverizing the obtained kneaded material, a cage for deep groove ball bearing “6203” manufactured by NSK Ltd. (see FIG. 2) at a molding temperature of 190 to 210 ° C., a mold temperature of 50 ° C., and a cooling time of 50 seconds; The seal member was injection molded. Then, after performing a thermal crosslinking treatment at 145 ° C. for 24 hours, mechanical strength (ring strength), biodegradability, and water resistance were evaluated according to the following.

(1) Biodegradability evaluation The cage is crushed and put into the reaction cylinder part (completely composted + sea sand) of the microbial oxidative degradation measuring device "MODA" (corresponding to JIS K6953 and ISO 14855) manufactured by Ryosan Shoji Co., Ltd. for biodegradation The amount of carbon dioxide generated was measured and the progress of biodegradation was measured. The results are shown in Table 1. The degree of biodegradation is the degree of progress of biodegradation after 6 months, and the biodegradation rate is a relative value where the number of days required until biodegradation of Comparative Example 1 to 50% is 1. .

(2) Mechanical strength (ring strength)
The annular strength of the cage was measured at room temperature (23 ° C.) or 120 ° C. The results are shown in Table 1, and are relative values to the measured values of Comparative Example 1.

(3) Tensile elongation at break A tensile test was performed according to JIS K7113, and the elongation when the specimen was broken was measured. The results are shown in Table 1.

(4) Moisture resistance test The cage and the seal member were suspended in a constant temperature and humidity chamber of 60 ° C and 90% relative humidity and allowed to stand for 100 hours, and then the annular strength was measured. And the annular strength before a test was set to 1, and the relative ratio with the annular strength after leaving for 100 hours was calculated | required. The results are shown in Table 1.

(5) Bearing rotation test 6203 ball bearings (both inner ring, outer ring, and balls are all made by SUJ2) using cage and seal member, lithium soap-ester oil based biodegradable grease (mixing degree 250) Was encapsulated so as to be 20% of the bearing space volume to obtain a test bearing. The normal amount of grease filled is about 35% of the bearing space, but in this test it was set to 20% for acceleration. Then, the rotation time until the rotation was hindered due to continuous rotation under the following conditions and deformation of the cage was measured. The rotation was performed for 2000 hours, and the test was stopped when there was no problem with the rotation after 2000 hours. The results are shown in Table 1. “◯” indicates a case where there is no trouble in rotation after 2000 hours.
・ Atmosphere temperature: 120 ℃
・ Rotation speed: 10,000 min ^-1 (inner ring rotation)
・ Load: radial load 98N, axial load 245N

  From Table 1, in addition to being excellent in biodegradability, the cage and the seal member obtained by adding 2 to 5 parts by mass of an imide-based crosslinking agent to 100 parts by mass of polyvinyl alcohol according to the present invention are mechanically It can be seen that the strength and durability are excellent.

DESCRIPTION OF SYMBOLS 10 Deep groove ball bearing 11 Inner ring 12 Outer ring 13 Ball 14 Cage 15 Seal member

Claims (4)

Roller bearing inner ring, outer ring, rolling element, retainer, and seal member, and at least one mechanical part. Polyvinyl alcohol is used as a base resin, and 2 to 5 parts by mass of imide-based cross-linking with respect to 100 parts by mass of the base resin. A biodegradable resin mechanical part obtained by molding a resin composition containing an agent into the mechanical part and then heat-treating the molded product at 120 to 170 ° C. to advance a crosslinking reaction .   The biodegradable resin mechanical part according to claim 1, wherein the imide-based crosslinking agent is a carbodiimide compound.   The biodegradable resin mechanical part according to claim 1 or 2, wherein the polyvinyl alcohol has a saponification degree of 73 to 98 mol%, an oxyalkylene group amount of 0.1 to 5 mol%, and a polymerization degree of 500 to 1500. . A rolling bearing comprising a seal member and a plurality of rolling elements that are rotatably held between a inner ring and an outer ring via a cage,
A rolling bearing, wherein at least one of an inner ring, an outer ring, a rolling element, a cage, and a seal member is the biodegradable resin mechanical part according to any one of claims 1 to 3.

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