JPH06306383A - Grease for prelubricated bearing - Google Patents

Abstract

PURPOSE:To obtain the title grease having durability at a high temperatures, having a suitably low degree of oil separation under no shear and showing a behavior of churning under shear. CONSTITUTION:The grease is prepared by adding about 5-20wt.% urea-type thickener to a base oil prepared by mixing a synthetic hydrocarbon oil with an ester-type synthetic oil in a weight ratio of (0.65-0.75):(0.35-0.25) and adding an antioxidant, a rust preventive, an extreme-pressure additive, an oiliness agent, etc., to the resulting mixture. This grease shows a behavior of churning under shear.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing-filling grease, and more particularly to a bearing-filling grease applied to a sealed bearing which is required to have heat resistance.

[0002]

2. Description of the Related Art Generally, as a typical example of a mechanical component using grease as a lubricant, there is a rolling sealed bearing in which grease is filled and sealed with a rubber seal or a metal shield, and its performance and life depend on the characteristics of the grease. Is known to do.

The grease filled in the bearing is mechanically sheared to be in a fluidized state and exhibits lubricity.
It is known to exhibit various behaviors depending on the degree of shearing.

For example, lithium charged in a ball bearing is
The 12-hydroxy stearate grease has a relationship in which the shear rate and the shear stress of the grease correspond to each other when the ball bearing is operated at a low speed, and is homogeneous and has a stable viscosity.

However, when such a bearing is rapidly accelerated from the start up to a steady rotation of 10,000 rpm, the filled grease is stratified and the separated oil flows in the gap between the layers. Then, a behavior called so-called channeling is exhibited.

Such channeling, as shown in the graph of FIG. 1 (a), sharply reduces the torque of the bearing, and is a phenomenon that occurs accidentally at many points in the bearing. Therefore, the bearing torque may recover (become higher) as a whole as shown in FIG. 1B, but it is extremely unstable and is not in a preferable state.

A bearing filled with, for example, lithium stearate grease instead of the above-mentioned lithium-12-hydroxystearate grease is agitated by shearing in the bearing even if it is accelerated and rotated under the same conditions. It is known that it is in a state and does not cause channeling.

In the above-mentioned churning state, since the grease is frequently supplied to the rolling surface of the bearing, the torque is recovered in small increments (indicated by the arrow in FIG. 2 (a)), and as shown in FIG. 2 (b). As shown, the bearing torque does not drop sharply and remains relatively stable over a long period of time.

[0009]

As described above, in order to operate the bearing with stable torque characteristics, it is desirable that the grease be made to function in the state of churn, but the conventional grease showing the churn behavior is required. Are all blended with a soap thickener. This grease shows good churning behavior when subjected to shearing at high temperatures, but its heat resistance is not sufficient, so the problem is that the life of the grease cannot be sufficiently satisfied under conditions of being used at relatively high temperatures. is there.

Further, since such a grease exhibits a high oil separation degree in a state where the shearing is stopped, there is a problem that it easily leaks from a housing such as a bearing.

In view of the above, the present invention solves the above-mentioned problems and provides a bearing-encapsulating grease that is durable at high temperatures and has an appropriately low oil separation when shearing is stopped. The challenge is to make the grease exhibit the behavior of churning when it is received.

[0012]

In order to solve the above-mentioned problems, in the present invention, the synthetic hydrocarbon oil and the ester synthetic oil have a weight of 0.65 to 0.75: 0.35 to 0.25. The grease was formed by adding a urea thickener to the base oil blended in a ratio.

The details will be described below.

Among the base oils used in the present invention, synthetic hydrocarbon oils include poly α-olefin oils, polybutenes and olefin copolymers, and have a viscosity (40 ° C.) of 20 to 40.
It is preferable to employ a material having a flash point of 100 ° C and a flash point of 220 ° C or higher.

These are structures in which α-olefin is low-polymerized to form an oligomer, and hydrogen is added to the terminal double bond, and the structure represented by the following chemical formula 1 can be exemplified. Polybutene is also a kind of poly α-olefin, and it can be produced by polymerizing a starting material mainly containing isobutylene with aluminum chloride as a catalyst. Polybutene may be used as it is or after hydrogenation.

[0016]

[Chemical 1]

Examples of the ester synthetic oil used in the present invention include polyol ester oil, diester oil, polyester oil, phosphoric acid ester, silicic acid ester and complex ester oils thereof, and the viscosity (40
C.) is 10 to 245 cst and has a flash point of 220.degree.
It is preferable to adopt the above.

The above-mentioned polyol ester oil has 3 or 4 ester groups in the molecule, the β-carbon on the alcohol side is quaternary as shown in the following chemical formula 2, Representative examples include methylol propane ester.

[0019]

[Chemical 2]

Examples of the phosphoric acid ester include triaryl phosphoric acid ester and trialkyl phosphoric acid ester.

The composition of the base oil described above is 0.65 to 0.75: 0.35 of synthetic hydrocarbon oil and ester synthetic oil.
It is compounded in a weight ratio of ˜0.25. This is because if the synthetic hydrocarbon oil or ester synthetic oil in the base oil is out of the above range, the grease exhibits the behavior of channeling in the bearing, and the desired effect cannot be achieved.

The urea-based thickener used in the present invention may be a well-known urea compound represented by the following formula (3). This is a urea compound obtained by subjecting amine and diisocyanate to polyaddition reaction in a base oil and precipitating them, and as the diisocyanate forming R ₂ , 4,4′-diphenylmethane diisocyanate, Examples include tolylene diisocyanate. The amine forming R ₁ and R ₃ in the formula may be any combination of an alicyclic amine such as toluidine, cyclohexylamine and stearylamine, an aromatic amine, and an aliphatic amine. Good results have been obtained using an aliphatic amine as the amine.

[0023]

[Chemical 3]

The blending ratio of such urea thickener in the grease is preferably 5 to 20% by weight.

This is because if the amount is less than 5% by weight, it becomes a liquid having a poor viscosity and easily leaks, making it difficult to seal the bearing. On the other hand, if it exceeds 20% by weight, it solidifies to have a consistency of 200 or less, which makes it impractical as a grease for bearing encapsulation.

It is needless to say that antioxidants, rust preventives, extreme pressure agents, oiliness agents and the like can be added, if necessary, as long as the effects of the present invention are not impaired.

[0027]

The grease for bearing encapsulation of the present invention employs a synthetic hydrocarbon oil and an ester synthetic oil as specific base oil components, and these are formulated in a predetermined blending ratio, and a urea-based thickener is used as a thickener. Since the compound is used, the dropping point is 2
Although it is set to 50 ° C or higher and shows a churn that can withstand use at high temperatures, the oil separation degree becomes appropriate when the temperature is lowered, and the grease does not easily leak.

[0028]

[Examples] Table 1 shows materials and blending ratios of Examples and Comparative Examples.
Or shown in Table 2.

The abbreviations used in the table are shown below, and the base oil viscosity is measured at 40 ° C. according to JIS K2220.5.19.

(1) Poly α-olefin synthetic hydrocarbon oil (viscosity 40.6) [PAO-a] (2) Poly α-olefin synthetic hydrocarbon oil (viscosity 30.
5) [PAO-b] (3) Poly α-olefin synthetic hydrocarbon oil (viscosity 46.
0) [PAO-c] (4) complex ester oil [ester oil-1] (5) polyol ester oil [ester oil-2] (6) paraffinic mineral oil [mineral oil] [Examples 1 to 3 and Comparative Example 1] ~ 3, Comparative Example 5, Comparative Example 6]
The base oil was formed in the blending ratios shown in Table 1 and Table 2, the isocyanate was dissolved in half of the base oil, and the monoamine was dissolved in the other half, and these were mixed and stirred at 160 to 170 ° C. for 30 minutes to prepare the base oil. The urea compound was deposited on.
Then, after cooling, a mixture of an antioxidant, a rust preventive and an antiwear agent was added in an amount of 5% by weight and homogenized by a mixer to obtain a grease.

The grease obtained was subjected to the following tests, and the results are shown in Tables 1 and 3.

(A) Consistency: JIS K 2220.5.
3 was measured.

(B) Oil separation degree: JIS K 2220.
It was measured according to 5.7.

(C) Bearing torque: 1.79 to 1.81 g of the grease of the embodiment or the comparative example is filled in the bearing 6204, an iron non-contact seal is attached to the side surface of the bearing, and an axial load of 4 kgf is applied thereto every minute. Driving at 3600 rpm,
The bearing torque at room temperature was measured.

(D) Bearing temperature rise: 1.79 to 1.81 g of the grease of the embodiment or the comparative example was filled in the bearing 6204, a non-contact iron seal was attached to the side surface of the bearing, and a radial load was set to 6.8 kgf. Thrust load is 6.8kgf
In addition, the temperature rise of the end face of the bearing outer ring was measured when the bearing was operated at room temperature at 10,000 rpm for 24 hours.

(E) Flow behavior test: 1.79 to 1.81 g of the grease of Example or Comparative Example was sealed in a bearing 6204 having an iron non-contact seal attached to the side surface of the bearing, and
1 at 3600 rpm with an axial load of 4 kgf
The bearing torque value was measured by operating for 0 to 15 minutes. Then, the judgment as to whether or not the grease has entered the bearing raceway was evaluated from the graph pattern of the bearing torque, and the charting was marked with ◯ and the channeling was marked with x in the table.

(F) Grease life measurement test: bearing 620
No. 4 is the grease of Examples or Comparative Examples 1.79 to 1.8.
Enclose 1g, attach a non-contact iron seal to the side surface of the bearing, set radial load to 6.8kgf and thrust load to 6.
8 kgf was added, and the inner ring was rotated at a speed of 10,000 rotations per minute in an atmosphere of 150 ° C. The grease life (number of hours) was defined as the time when the rotational torque of the bearing became excessive due to deterioration of grease or leakage to the outside of the bearing, and the input current of the electric motor driving the spindle exceeded the limit current.

Comparative Example 4 A grease was produced in exactly the same manner as in Comparative Example 1, except that lithium stearate was used as the lithium soap thickener instead of the urea thickener.

That is, stearic acid was added to half of the base oil and heated, and lithium hydroxide was added thereto to saponify. After the saponification was completed, the heat-dehydrated lithium soap was dispersed in the remaining half of the base oil and cooled.

Regarding the obtained grease, the above (a)
The tests (f) to (f) were performed, and the results are also shown in Table 3.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

As is clear from the results of Tables 1 and 3, Examples 1 to 3 satisfying all the conditions are stable in bearing torque and are suitable in the range of 170 to 180 gf · cm, and the oil separation It was confirmed that the degree was 0.7 to 0.8, the flow behavior thereof showed chuning, and the life of the grease was a long life of 3800 hours or more.

On the other hand, in Comparative Examples 1 to 4 in which the types of base oils were not predetermined combinations, channeling was exhibited, the life of grease was less than 2700 hours, and most of them had high oil separation. In Comparative Examples 5 and 6 in which the mixing ratio of the base oil was outside the predetermined range, the oil separation was low, but the bearing torque was abnormally low, channeling occurred, and the grease life was as short as 2100 hours or less.

[0046]

As described above, the present invention employs a synthetic hydrocarbon oil and an ester synthetic oil as specific base oil components, forms them at a predetermined mixing ratio, and further uses urea as a thickener. Since a system compound is used, it is durable at high temperature, and the oil separation degree is low when shearing is stopped, and when it is sheared, it shows the behavior of churning and leaks from the bearing. It has the advantage of becoming a difficult and high-performance grease for bearing encapsulation.

[Brief description of drawings]

FIG. 1A is a graph showing a relationship between a channeling time (minutes) and a bearing torque change amount. (B) A graph showing a relationship between a channeling time and a bearing torque.

FIG. 2 (a) is a graph showing the relationship between the time (minutes) in the charging state and the amount of change in the bearing torque. (B) A graph showing the relationship between the time in the learning state and the bearing torque.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication C10N 30:08 40:02 50:10 (72) Inventor Hideyuki Hasegawa 1 Koderamachi, Suma-ku, Kobe 1-13 13 Japan Grease Co., Ltd. (72) Inventor Takaro Yoshimatsu 1-1-13 Koderacho, Suma-ku, Kobe City Japan Grease Co., Ltd.

Claims (1)

[Claims] 1. A urea base thickener is added to a base oil in which a synthetic hydrocarbon oil and an ester synthetic oil are blended in a weight ratio of 0.65 to 0.75: 0.35 to 0.25. Grease for bearings.