JP2000071243A - Manufacture of oil-containing pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an oil-containing pellet for obtaining a plastic molding in which lubricating oil is continuously stably oozed out from a surface of the molding and to manufacture a retainer for a rolling bearing in which lubricating oil is oozed out at continuously stable speed from a surface of the retainer. SOLUTION: The method for manufacturing an oil-containing resin comprises the steps of previously melt kneading synthetic resin and lubricating oil in the case of melt kneading the resin such as polyamide resin or the like, fiber- like oil conductive material such as solid glass fiber or hollow polyester fiber and lubricating oil, then adding the fiber-like oil conductive material to the mixture, and melt kneading them. This melt kneading can adopt melt kneading using a biaxial extruder. A method for manufacturing a retainer for a rolling bearing comprises the step of injection molding an oil-containing pellet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing oil-impregnated pellets and a method for producing a cage for rolling bearings using the oil-impregnated pellets.

[0002]

2. Description of the Related Art Generally, raw materials for molding plastics are:
Because the form differs depending on the polymerization method and the post-treatment method after polymerization,
As it is, it cannot be applied to molding machines such as general injection molding machines. That is, beads, flakes, crumbs, powders, or plastic raw materials in various forms such as a solution are mixed with a stabilizer, a lubricant, a coloring agent, and other necessary additives according to applications and varieties, and dispersed. It is extruded and pelletized and used as a plastic molding material.

In order to mix various additives into a synthetic resin, it is general to apply a shearing force to the synthetic resin in a molten state to disperse the additive in the synthetic resin. Specifically, addition and mixing are performed by a twin-screw extruder, a kneader, and a mixer.However, when a synthetic resin is mixed with a fibrous filler such as glass fiber by a twin-screw extruder, first, in order to prevent fiber breakage. The synthetic resin is supplied to a melt-kneading extruder such as a twin-screw extruder, and the fibrous filler is forcibly injected into the molten synthetic resin from the middle of the extruder.

[0004] Further, when a sliding part such as a bearing is formed by imparting lubricity to a plastic, lubricating oil may be contained in the pellet.

[0005] In particular, in the case of small-diameter bearings (miniature bearings), agitation resistance of grease is a problem in order to reduce rotational torque. However, bearing materials that lubricate without using grease have been proposed.

For example, Japanese Patent Application Laid-Open No. 61-6429 discloses a bearing formed by impregnating a fluorinated oil into a polyamideimide resin made porous by compression molding. Further, Japanese Patent Application Laid-Open No. 1-93623 discloses a cage in which an oil-impregnated plastic cage is impregnated with lubricating oil. Further, Japanese Patent Application Laid-Open No. Hei 8-21450 discloses a mixture of a polyolefin resin and a lubricating oil, and molding the fat composition into a retainer shape.

The order of mixing the synthetic resin material and the lubricating oil is as follows:
Usually, it is determined by the position of the lubricating oil inlet in the melt-kneading extruder. Near the outlet where the synthetic resin material and the fiber are mixed first, and the strands of the fiber are disjointed (raised and converged). That is, it is common to arrange the lubricating oil inlet after the base resin and the glass fiber are melt-kneaded.

By the way, supplying a fibrous filler such as glass fiber to a melt-kneading extruder can be more efficiently mixed in a shorter time than supplying a composition mixed by a Henschel mixer to a melt-kneading extruder. It is also excellent in that the mixture volume does not increase extremely. In particular,
When glass fibers arranged in a bundle by a sizing agent are supplied to a melt-kneading extruder and kneaded, the mixture has good fluidity, and does not increase in volume (bulk) as compared with the case of using a Henschel mixer. It can be kneaded efficiently in a short time.

[0009]

However, when molding is carried out using the oil-containing pellets produced by the above-mentioned conventional method, there is a problem that the lubricating oil does not ooze continuously and at a stable rate from the surface of the obtained molded article. There is.

That is, the inventors of the present application expect the oil additive to conduct to the fibrous additive dispersed and held inside the molded article, and the lubricating oil is applied to the inside of the molded article along the fibrous additive. An attempt was made to produce an oil-containing resin composition that oozes out from the surface of the molded article, but the lubricating oil inside the molded article did not ooze on the surface of the molded article stably for a long time at a predetermined oil amount.

Accordingly, an object of the present invention is to provide a method for producing oil-containing pellets, which solves the above-mentioned problems and provides a plastic molded product in which lubricating oil continuously oozes at a stable speed from the surface of the molded product. That is.

In addition, with respect to a cage for a rolling bearing, particularly a cage for a small-diameter bearing such as a miniature bearing, to manufacture a cage for a rolling bearing in which lubricating oil continuously oozes from the surface of the cage at a stable speed. Is an issue.

[0013]

In order to solve the above-mentioned problems, according to the present invention, a synthetic resin, a fibrous oil conducting material and a lubricating oil are melt-kneaded and granulated to produce oil-containing pellets. In the method, when the melt-kneading is performed, a synthetic resin and a lubricating oil are melt-kneaded in advance, and then a fibrous oil conducting material is added to the mixture, and the mixture is melt-kneaded to produce oil-containing pellets.

The fibrous oil conducting material may be an oil conducting material composed of solid or hollow fibers, and the melt kneading may be melt kneading using a twin screw extruder. Can be.

Further, in order to solve the problem of the cage for a rolling bearing, the present invention provides a method for manufacturing a cage for a rolling bearing by injection molding oil-containing pellets manufactured by the above-described method.

In the method for producing oil-containing pellets of the present invention constituted as described above, a synthetic resin and a lubricating oil are melt-kneaded in advance, and then a fibrous oil conducting material is added to the mixture and melt-kneaded. When using a melt-kneading device such as a twin-screw extruder, select a material charging location to the melt-kneading machine, pour lubricating oil into the molten resin, and then pour fibrous conductors into Is wetted with lubricating oil, and the fibrous oil conducting material in this state is dispersed and held in the synthetic resin.

When molding is performed using the oil-containing pellets produced by this method, the lubricating oil present inside the molded article is formed along the surface of the fibrous filler (the interface between the base resin and the fibrous filler) as the oil conducting material. As a result, the lubricant oozes out to the surface of the molded article stably for a long time due to the capillary phenomenon that the lubricant passes.
Therefore, when a sliding member such as a bearing retainer is formed using the oil-containing pellets, the surface of the formed body exhibits good lubrication characteristics such as low friction and wear resistance.

For example, when the molded article is used as a cage for a rolling bearing, since lubricating oil and a fibrous filler as a conductive material for the lubricating oil are present inside the cage, the lubricating oil present inside is not conductive. It passes through the interface between the fiber surface and the resin, and is stable for a long period of time.

The bearing incorporating the cage has a small torque required for rotation and a small fluctuation in torque.
Further, since good lubrication is performed for a long time, a rolling bearing having excellent durability can be obtained.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The synthetic resin used in the present invention may be of any type as long as it meets the required strength of the sliding member. Fon, polyether imide, polyamide imide, polyether ether ketone, thermoplastic polyimide, aliphatic polyketone, and the like. Among these, those having oil resistance to the impregnating lubricating oil, those having good heat resistance, and those which can be obtained at a low cost are preferable. For example, polyamide resins are preferable in these respects.

Polyamide resins are polyhexamethylene adipamide (6,6-nylon), polyhexamethylene azeramid (6,9-nylon), polyhexamethylene sebasamide (6,10-nylon), polyhexamethylene Decamide (6,12-nylon) polytetramethylene adipamide (4,6-nylon), polycaprolactam (6
-Nylon), polylaurin lactam (12-nylon), poly-11-aminoundecane (11-nylon), polymethaxylene adipamide (nylon MXD-
6) and other aliphatic polyamide resins, polymetaphenylene isophthalamide, polyparaphenylene terephthalamide, polymetaxylylene adipamide (nylon MXD-
6) and the like.
These can be used alone or as a mixture.

The solid or hollow fibrous filler used in the present invention includes glass fiber, pitch-based carbon fiber,
PAN-based carbon fiber, aramid fiber, alumina fiber, boron fiber, silicon carbide fiber, boron nitride fiber, silicon nitride fiber,
There are metal fibers and the like. In particular, glass fiber is suitable as a fibrous filler because the surface is smooth, oil is easily transmitted, and the unit price is low.

The filling amount of the conductive material of oil composed of solid fibers is preferably 1 to 40 to 95% by weight of the synthetic resin.
-40% by weight, more preferably 5-35% by weight. If the amount is less than the predetermined amount, the oil passage is insufficient.
This is because if the amount of the oil supplied from the cage to the rolling elements is insufficient, and if the amount exceeds the predetermined amount, the moldability is impaired, which is not preferable.

Suitable hollow fibrous fillers for use in the present invention include polyester hollow fibers (Toyobo Co., Ltd .: Lubro) and polyester hollow fibers (Teijin Co., Ltd .: Aerocapsule Dry). Yes, these are appropriately cut and used. As the hollow fiber, a hollow fiber in which a hole penetrating in the longitudinal direction of the fiber is formed or a hollow fiber in which a large number of transmission holes are present may be cut into a short length for use.

The filling amount of the conductive material of oil consisting of hollow fibers is
For the same reason as for the solid fiber, the content is preferably 1 to 30% by weight, more preferably 5 to 25% by weight based on 50 to 95% by weight of the synthetic resin.

When the fibrous oil conducting material is a solid fiber, it has a fiber diameter of 3 to 25 μm and a fiber length of 10 μm.
It is preferable to employ an oil conducting material of 0 to 6000 μm.

Because, when the above-mentioned thin fiber having a fiber diameter of less than φ3 μm is employed, the fiber is easily broken during kneading and molding.
This is because the length of the fibers present in the product is considerably shortened, and the intended function as a conductor is not fulfilled. Also, if a thick fiber with a fiber diameter exceeding 25 μm is adopted,
Since the specific surface area of the fiber is smaller than that in the case of a predetermined fiber diameter, there is no effect as a conductor. From this trend,
A more preferable fiber diameter is φ5 to 20 μm. Further, if the fiber length is less than the predetermined range, the desired effect as a conductor is not obtained, which is not preferable. If a long fiber exceeding the predetermined range is employed, the moldability is deteriorated, which is not preferable. From this tendency, the more preferable fiber length is 10
0 to 5000 μm.

When the fibrous oil conducting material is a hollow fiber, it is preferable to employ an oil conducting material having a fiber diameter of 25 to 75 μm and a fiber length of 50 to 6000 μm.

This is because the use of thin fibers having a fiber diameter of less than φ25 μm reduces the volume of holes penetrating inside the fibers in the longitudinal direction, and the amount of retained oil is not sufficient. Is no longer effective. Further, when a thick fiber having a fiber diameter of more than 75 μm is employed, a longitudinal hole (oil passage) inside the hollow fiber becomes large. As a result, the retained oil easily comes out, and the oil runs out in the initial stage, so that the oil cannot be continuously supplied. From such a tendency, a more preferable fiber diameter is 30 to 70 µm. If the fiber length is less than the predetermined range, it is not preferable because the effect of the conductor is not provided, and if a long fiber exceeding the predetermined range is employed, the moldability deteriorates, which is not preferable. From such a tendency, a more preferable fiber length is 100 to 5000 μm.

As the lubricating oil used in the present invention, any lubricating oil that is generally used can be used without any particular limitation. However, heat resistance that can withstand the kneading temperature of the selected synthetic resin is a necessary property. is there. Such lubricating oils include spindle oil, refrigeration oil, turbine oil, machine oil, mineral oil such as dynamo oil, or hydrocarbon oil, ester oil, polyglycol oil, silicone oil, fluorinated oil,
And the like.

The viscosity of the lubricating oil is 40 ° C.
The kinematic viscosity of preferably 10 to 500 mm ² / s at, more preferably a kinematic viscosity at 40 ° C. in the range of 20 to 300 mm ² / s. When the kinematic viscosity at 40 ° C. of the lubricating oil is less than 10 mm ² / s, the molecules of the lubricating oil are short, and the molecules may break during melt-kneading with the resin, causing decomposition.
On the other hand, when the kinematic viscosity at 40 ° C. is larger than 500 mm ² / s, the fluidity is extremely poor, and the handleability during molding is extremely poor.

The amount of these lubricating oils in the synthetic resin composition is preferably 1 to 30% by weight, more preferably 3 to 30% by weight.
It is in the range of 25% by weight. When the amount of the lubricating oil is less than 1% by weight, the amount of the lubricating oil of the oil is absolutely insufficient, and the amount of the oil supplied from the cage to the rolling elements is insufficient, thereby impairing the durability of the bearing. Further, it is not preferable because the dimensional accuracy of the retainer is lowered and the mechanical properties are lowered.

Further, the following fillers may be added for the purpose of reinforcing the mechanical strength of the lubricating composition and improving the moldability. For example, calcium carbonate, talc, silica,
Minerals such as clay and mica, inorganic whiskers such as aluminum borate whiskers, or inorganic fibers such as glass fiber, silicon nitride fiber, asbestos, quartz wool, and metal fibers; these woven into a cloth; or carbon black And various thermosetting resins such as graphite, carbon fiber, aramid fiber, polyester fiber, polyimide resin and polybenzimidazole. Further, polytetrafluoroethylene, boron nitride, molybdenum disulfide, tungsten disulfide, or the like may be added.
For the purpose of improving the thermal conductivity of the lubricating composition, carbon fibers, metal fibers, graphite powder, zinc oxide, etc. may be added.

It should be noted that additives that can be widely applied to general synthetic resins may be used in combination in amounts that do not impair the effects of the present invention. For example, industrial lubricants such as a release agent, a flame retardant, an antistatic agent, a weather resistance improver, an antioxidant, and a coloring agent may be appropriately added, and the method of adding these is not particularly limited.

As the method of mixing the resin composition in the present invention, a method using a known mixer such as a kneader, a mixer, a twin screw extruder or the like can be adopted. For example, when a kneader or a mixer is used, injection molding pellets are produced by mixing a base resin and a lubricating oil in advance, adding an oil conducting material, performing melt-kneading, and taking out and pulverizing the composition.

Further, using a melt extruder (for example, a twin screw extruder) having an inlet capable of separately introducing the base resin, the fibrous oil conducting material, and the lubricating oil, the lubricating oil is provided after the base resin. And finally, a fibrous oil conducting material. The twin screw extruder is 2
One screw may rotate in the same direction or another screw may rotate in a different direction, and may have a conical (oblique axis).

In the molded article formed by using the oil-containing pellets produced by these methods, since the fibrous filler exists as a conductive material for the lubricating oil inside the molded article, the lubricating oil present inside is the conductive material. Good lubricating properties such as low friction and abrasion resistance are ensured by the lubricant oozing on the surface of the molded product through the surface of the fibrous filler (the interface between the base resin and the fibrous filler) for a long period of time and stable. Show.

As a method for molding the oil-impregnated pellets produced according to the present invention, any of extrusion molding, injection molding, compression molding, vacuum molding, blow molding and foam molding may be used. Injection molding is a particularly preferred molding method in terms of good production efficiency.

As long as the desired lubricity of the molded article is not impaired, the form of the intermediate product or the final product is separately modified for property improvement by chemical or physical treatment such as annealing. Of course, it may be possible.

[0040]

Examples and Comparative Examples The materials used in the examples and the comparative examples are collectively shown below. Note that, in parentheses [], Table 2
The abbreviations used in the table are shown. (1) Polyamide resin (Toray Co., CM1001)
[PA6] (2) Glass fiber (Asahi Fiberglass Co., Ltd .: CS0)
3MA497, chopped strand, fiber length: 3m
m) [Fiber] (3) Polyester hollow fiber (Toyobo: Lubro, fiber diameter φ45 μm, length 1 mm) [Fiber] (4) Ester oil (Nippon Oil & Fat Co., Ltd .: H481R)
〔oil〕

[0041]

[Table 1]

[0042]

[Table 2]

Example 1 A polyamide resin (manufactured by Toray Industries, Inc., CM1001) was used as a heat and oil resistant resin, and glass fibers (manufactured by Asahi Fiber Glass Co., Ltd.) were used as a fibrous filler.
CS03MA497, chopped strand, fiber length:
3 mm) and ester oil (H481R, manufactured by NOF CORPORATION) as a lubricating oil at a ratio shown in Table 1 and Table 2
(Polyamide resin is described as PA6) and 2 shown in FIG.
Fiber and oil were fed from the feeding point of the shaft extruder. That is, a polyamide resin and a lubricating oil were charged and melt-kneaded, and an oil conducting material made of glass fiber was charged into the mixture and melt-kneaded.

As the extruder, as shown in FIG. 1, a twin-screw extruder (L / D: 30) having the outer diameter of screws 47 and 47 mm rotating in the same direction was used.

The pellet molding conditions were as follows: cylinder temperature: 2
After extruding into water at 35 ° C. and a screw rotation speed of 180 rpm, and cooling the formed strand (φ3),
It was cut into a pellet having a length of 4 mm. The pellets are compression molded by heating at a mold temperature of 240 ° C.
A disk-shaped test piece having a thickness of 2 mm and a thickness of 2 mm was prepared.

The following test was performed on the obtained test piece, and the weight loss rate (%) of the test piece due to the oozing out of the lubricating oil.
Was examined.

(1) Amount of oozing of lubricating oil (weight reduction rate) The weight of the test piece after molding was measured, and the test piece was sandwiched with paraffin paper so that the lubricating oil could easily ooze out.
g in a constant temperature bath at 80 ° C. for 1 hour, and after taking out and weighing, again put in the constant temperature bath for 1 hour.
This was held for a time and this was repeated four times. The weight of the compact at each time was subtracted from the initial weight, the reduced weight was obtained, and the reduced weight was divided by the initial weight to obtain the following weight reduction rate (%).

Weight reduction rate (%) = (reduced weight / initial weight) × 100 Since the reduced weight is considered to be the amount of oozing of the lubricating oil, it can be said that the oozing of the lubricating oil increases as the weight reduction rate increases. FIG. 2 shows the thus measured weight loss rate after 4 hours.
FIG. 3 shows the change over time in weight loss every hour.

[Examples 2 to 6] In the same manner as in Example 1, fibers and oil were charged from the charging points shown in Table 2 at the mixing ratios shown in Table 1. That is, the polyamide resin and the lubricating oil were melt-kneaded, the mixture was mixed with an oil conducting material made of glass fiber, further melt-kneaded, and extruded into water under exactly the same conditions as in Example 1 to produce pellets. . Using the pellets, a test piece having a diameter of 100 mm and a thickness of 2 mm was subjected to heat compression molding at a mold temperature of 240 ° C. Example 1 for this test piece
The same test as in the above case was performed to examine the amount of oozing out of the lubricating oil. FIG. 2 shows the weight loss rate after 4 hours, and FIG. 3 shows the change over time in weight loss every hour.

[Examples 7 to 9] In the same manner as in Example 1, fibers and oil were charged from the charging points shown in Table 2 with the composition shown in Table 1, and the polyamide resin and lubricating oil were melt-kneaded. The oil conducting material composed of fibers was mixed and further melt-kneaded to produce pellets. As the fiber, a hollow fiber made of polyester (manufactured by Toyobo Co., Ltd .: Lubro, fiber diameter φ45 μm, length 1)
mm). Using this pellet, diameter φ100
A test piece having a thickness of 2 mm and a thickness of 2 mm was subjected to heat compression molding at a mold temperature of 240 ° C. The amount of oozing of the lubricating oil was examined for this test piece in the same manner as in Example 1, and the results are shown in FIGS. 2 and 3.

From the results shown in FIG. 2, the weight reduction rate after 4 hours in Examples 1 to 9 was 0.5% or more, and from the results shown in FIG.
It can be seen that the weight loss rate (oil bleeding speed) was stable during the test time of up to 4 hours, and the bleeding amount was also an appropriate amount.

As described above, the lubricating oil is supplied and melt-kneaded simultaneously with or after the base resin is charged, and the fibrous oil conduction is performed in relation to the material charging place or the charging sequence in the melt-kneading apparatus. In the manufacturing method of the example in which the material was charged and a molded body having a predetermined shape was manufactured, the fibrous filler exists as a conductive material for the lubricating oil inside the obtained molded body, and the lubricating oil present inside is electrically conductive. The lubricating oil passed through the surface of the fibrous filler (the interface between the base resin and the fibrous filler), which was a material, stably for a long period of time, and the lubricating oil bleed out onto the surface of the molded article.

[Comparative Examples 1 to 6] In Comparative Examples 1 to 3, glass fibers and oil were charged from the charging points shown in Table 2 at the same compounding ratio as in Examples 4 to 6, and melted and mixed in an extruder to form pellets. Produced. That is, in Comparative Examples 1 to 3, the polyamide resin, the fiber, and the lubricating oil were mixed and melted together, or the polyamide resin and the fiber were mixed first, and the lubricating oil was melted and mixed. Diameter φ100m using the obtained pellet
m, a test piece having a thickness of 2 mm was heated and compression-molded at a mold temperature of 240 ° C., and the amount of oozing of the lubricating oil was examined for the test piece under the same conditions as in Example 1. This is shown in FIG. 2 and FIG.

In Comparative Examples 4 to 6, the same mixing ratio as in Example 7 was employed, and hollow fibers and oil were charged from the charging points shown in Table 2 in the extruder to produce pellets. Using these pellets, a test piece having a diameter of 100 mm and a thickness of 2 mm was 240
Heat compression molding was performed at a mold temperature of ° C. The amount of oozing of the lubricating oil was checked for this test piece in the same manner as in Example 1.
These results are shown in FIG. 2 and FIG.

As is clear from the results shown in FIG. 2, the weight reduction rates of Comparative Examples 1 to 6 after 4 hours were 0.1% or less. The results in FIG. 3 show that there was no continued weight loss and the amount of oil seeping out was insufficient. As described above, in each of the comparative examples, since the fiber was introduced before the lubricating oil, the base resin and the fiber were firmly bound, and there was no space where the oil was present at the interface between the resin and the fiber. Therefore, it is presumed that the oil dispersed in the resin could not use the fiber as a conductive material and could not seep out to the surface of the molded article.

[0056]

As described above, the present invention provides a method for producing oil-containing pellets in which a synthetic resin and a lubricating oil are melt-kneaded in advance, and then a fibrous oil conducting material is added to the mixture and melt-kneaded. Therefore, at the interface between the synthetic resin and the fibrous filler, there is an appropriate space through which the lubricating oil oozes out, and a plastic molded body is obtained in which the lubricating oil oozes out from the inside of the molded body to the surface continuously at a stable speed. There is an advantage that oil-containing pellets can be manufactured.

That is, a molded article produced from such an oil-containing pellet exhibits good lubricating properties such as a low coefficient of friction which is stable with time and excellent wear resistance.

By manufacturing a cage for rolling bearings, particularly a cage for small-diameter bearings such as miniature bearings, using the oil-impregnated pellets, the lubricating oil oozes from the surface of the cage continuously at a stable speed. There is an advantage that a cage for a rolling bearing can be manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a material input location of a twin-screw extrusion molding machine.

FIG. 2 is a table showing a weight loss rate of a test piece after 4 hours.

FIG. 3 is a table showing the relationship between the elapsed time of the test piece and the weight loss rate.

[Explanation of symbols]

 1, 2 screws

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F201 AB07 AC01 AD16 AH14 BA02 BC01 BC12 BC17 BC19 BC37 BD05 BK26 BL29 BL41 BL43 BL44

Claims (5)

[Claims] 1. A method for producing an oil-containing pellet by melt-kneading a synthetic resin, a fibrous oil conducting material and a lubricating oil, and granulating the mixture to produce oil-containing pellets. After kneading, a fibrous oil conducting material is added to the mixture and the mixture is melt-kneaded. 2. The method for producing an oil-containing pellet according to claim 1, wherein the fibrous oil conducting material is an oil conducting material composed of solid fibers. 3. The method for producing an oil-containing pellet according to claim 1, wherein the fibrous oil conducting material is an oil conducting material composed of hollow fibers. 4. The method for producing oil-containing pellets according to claim 1, wherein the melt-kneading is a melt-kneading using a twin-screw extruder. 5. A method for producing a rolling bearing retainer, comprising injection molding the oil-containing pellets produced in claim 1.