JPH0747753B2 - Method for producing low noise urea grease composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a urea grease composition used for bearings that require low noise.

[Conventional technology and its problems] Due to the recent technological development and the high-class trend of users, in home electric appliances, OA equipment, and even automobile parts, the improvement of their original functions and the reduction of offensive noise have become issues. ing.

As one of the noise sources of such devices, there is a bearing that supports a rotating shaft of a rotating device such as a motor.
The sound generated from this bearing, together with the sound generated from other parts, raises the noise level of the entire equipment. The causes of this bearing noise include the problems of processing and assembling precision of the bearing, mounting precision, and the influence of foreign matter and thickener particles in grease used as a lubricant.
The problem is the noise caused by the lubricating grease. That is, when foreign matter or thickener particles in the lubricating grease that have entered the minute gaps between the rolling elements and the rolling surfaces of the bearing are rubbed or crushed, the bearing is vibrated, which appears as noise in the bearing.

Lithium soap grease manufactured by a strictly controlled manufacturing process is widely used for bearings that require low noise, but it is stable for a long time even at high temperatures due to severe operating conditions in recent years. Grease that exhibits excellent performance has been demanded.

In order to meet such requirements, it has been attempted to use urea grease having a gel structure that is stable even at high temperatures as compared with lithium soap grease, but urea grease has the property of thickening agent particles to reduce bearing noise. It is not widely used in bearings that are easy to generate and require low noise.

The inventors of the present invention first analyzed the commercially available urea grease in order to investigate the cause of bearing noise generation due to urea grease, and found that the major axis (or fiber length) of the unit particles (or unit fibers, hereinafter the same) of the urea compound in the grease was analyzed. ) Indicates that there are many aggregates of about 20 to 200 μm in which the unit particles are gathered, even though the aggregate is about 10 μm and most of them is 5 μm or less, and this aggregate causes the bearing noise. I found it.

Further, for each combination of amines, diisocyanates, and base oils shown below, the weight ratio of urea compound and base oil produced by the reaction of amine and diisocyanate is 10:90.
A mixture of amine base oil solution and diisocyanate base oil solution is mixed and reacted, heated and stirred at 170 ° C, allowed to cool to room temperature, and finished with a three-roll mill. As a result of trial manufacture using a general manufacturing method and analysis, 20
It was confirmed that many aggregates of about 200 μm existed.

Amines n-propylamine, isopropylamine n-butylamine, isobutylamine s-butylamine, n-pentylamine 3-methylbutylamine, n-heptylamine n-octylamine, n-tetradecylamine n-dodecylamine, 2-ethylhexyl Amine n-hexadecylamine, n-octadecylamine aniline, 4-biphenylamine p-phenetidine, p-anisidine p-dodecylaniline, cyclopentylamine cyclohexylamine, dihydroabietylamine, 3,5,5-trimethylhexylamine diisocyanates 1 , 5-Naphthylene diisocyanate 4,4'-Diphenylmethane diisocyanate 2,4'-Tolylene diisocyanate 3,3'-Dimethyl-4,4'-biphenylene diisocyanate Hexamethylene Isocyanate Base oil α-olefin oligomer (40 ° C kinematic viscosity 30cSt) Paraffin mineral oil (40 ° C kinematic viscosity 67cSt) Dimethyl silicone (25 ° C kinematic viscosity 200cSt) Pentaerythritol tetraester (40 ° C kinematic viscosity 31cSt) In addition, n-octylamine And 4,4'-diphenylmethane diisocyanate were mixed with paraffinic mineral oil (40 ° C kinematic viscosity 67
The grease, cyclohexylamine, and 4,4'-diphenylmethane diisocyanate reacted in cSt) were mixed with pentaerythritol tetraester (40 ° C kinematic viscosity 31 cSt).
As a result of investigating the change of aggregates during the manufacturing process for the two types of grease reacted in the inside, both types already have aggregates at the time of reaction, and although there is some increase or decrease with the transition of the process I confirmed that it would not disappear. It was found that the three-roll mill had the effect of reducing this agglomerate in the process, and it decreased about 50% after 20 passes. Even after passing 100 times, a slight decrease is recognized but it does not completely disappear, and such a method requires an excessive amount of time and labor and is difficult to put to practical use. As other finishing methods, a homogenizer treatment, a ball mill treatment and a colloid mill treatment were tried, but no remarkable effect was obtained.

[Means for Solving Problems] As described above, various methods were devised because of limitations in mechanical treatment, and as a result of trials, a mixture of a urea compound and a base oil having a melting point of 230 ° C. or less was heated. The urea compound was dissolved in base oil, and this solution was then cooled to room temperature at a rate of 5 ° C. or more per second, whereby it was possible to eliminate aggregates of 20 μm or more. By this method, a uniform dispersion system of fine urea compound crystals having a particle major axis (or fiber length) of 5 μm or less was obtained, and it was revealed that it has a low noise performance superior to that of a commercial lithium soap grease.

The urea compound used in the present invention is represented by the following general formula.

R1-NHCONH-R2-NHCONH-R3 [In the formula, R1 and R3 represent a saturated alkyl group having 8 to 18 carbon atoms, and R2 represents a tolylene group, a diphenylmethane group or a dimethylbiphenylene group. ] In this formula, urea compounds in which R1 and R3 have 7 or less carbon atoms and Clair compounds in which R1 and R3 contain a phenyl group and a cycloalkyl group have a melting point of more than 230 ° C and are heated above the flash point of the base oil. It is not suitable for the present invention because it may be necessary and may be dangerous, and it may not be dissolved in the base oil even if heated above the melting point. That is, the melting point of the urea compound having the above structure used in the present invention is 230 ° C. or lower. Further, a compound in which R1 and R3 have more than 18 carbon atoms is not suitable for practical use because it is difficult to obtain a long-chain monoamine as a raw material at an economical price. R2 is a hydrocarbon portion of the raw material diisocyanate, and the following four types of diisocyanates can be used in the present invention.

2,4-Tolylene diisocyanate 2,6-Tolylene diisocyanate 4,4'-Diphenylmethane diisocyanate 3,3'-Dimethyl-4,4'-biphenylene diisocyanate In the urea grease composition of the present invention, diurea which is a thickener is used. The content of the compound is 2 to 30% by weight, preferably 5
~ 25% by weight. Diurea compound content is 2% by weight
When the amount is less than the above, the thickening effect is small and the grease is not formed, and when it exceeds 30% by weight, the grease becomes too hard to obtain a sufficient lubricating effect.

The base oil used in the present invention is a generally known lubricating oil, such as mineral oil, α-olefin oligomer, silicone oil,
Examples thereof include diester oil, triester oil, tetraester oil, fluorine oil, phosphate ester oil, castor oil, phenyl ether oil, alkylnaphthalene and alkylene glycol.

To the urea grease of the present invention, various additives such as an antioxidant, a rust preventive and an extreme pressure agent are added in addition to the original components in order to further improve the performance thereof without impairing the intended properties. I can do things.

Further, in the present invention, the rate of cooling the solution comprising the urea compound and the base oil to room temperature is 5 ° C. or more per second, preferably 10 ° C. or more per second. If the temperature is 5 ° C. or more per second, the cooling rate may change midway. When cooled at a rate of less than 5 ° C. per second, aggregates of 20 μm or more are likely to be formed, which is not suitable for the present invention.

The cooling device used in the present invention is not particularly limited as long as it is a device that can obtain a desired cooling rate. For example, a desired cooling rate can be obtained by a method in which tap water is sprayed from the bottom to continuously pour the solution onto a cooling stainless plate.

The method for producing the grease used in the present invention is to rapidly agglomerate the crystals unique to urea grease by rapidly passing the temperature for crystallization by rapidly cooling the molecules of the Clare compound dispersed in the base oil at high temperature. To prevent. When the solution is cooled slowly, the crystallized urea compound and the urea compound dissolved in the base oil are mixed around the temperature at which the urea compound crystallizes, and the latter is entangled with the previously crystallized urea compound. Since it is easy to crystallize in, it is considered that huge aggregates are generated, and this can be prevented by rapidly and uniformly cooling the entire grease.

The manufacturing method of the present invention is to make a low noise urea grease obtained by melting and quenching a mixture of a low melting point urea compound and a base oil into a grease that maintains a stable gel structure even at high temperatures.
Grease using a low-melting urea compound as a thickener naturally drops at 230 ° C or lower in the dropping point test (JIS.K 2220 5.4). Also, when the temperature is raised little by little, it becomes almost liquid above 160 ° C, and in reality it is 150 ° C.
It can only be used at the following temperatures. As a result of repeated studies for the purpose of improving this point, the present inventors have found that the grease composition obtained by the method for producing the grease used in the present invention is
By mixing more than one kind, we found that the dropping point becomes higher, and we have completed the target low-noise urea grease that has a stable gel structure even when used at high temperatures of 150 ° C or higher.

That is, among low noise urea greases obtained by melting and quenching a composition consisting of a low melting point urea compound having a melting point of 230 ° C. or lower and a base oil, two or more kinds having different urea compounds are mixed at an arbitrary ratio. A low melting urea grease having a high dropping point and a stable gel structure even at high temperatures can be obtained. As for the mixing ratio of grease, the dropping point can be increased even if the weight ratio of the thickeners of the two types of mixed grease is 1:99, but the grease having a dropping point of 250 ° C or higher In order to obtain a weight ratio of different thickeners from 5 to 95
A mixing ratio of 95 to 5 is desirable. The reason for increasing the dropping point by mixing in this way is considered that each urea compound mutually reinforces the gel structure, but it has not yet been elucidated theoretically.

[Examples] The present invention will be specifically described by the following examples and comparative examples. Abbreviations, terms, and test methods used in Examples and Comparative Examples are as follows.

TDI 2,4-Tolylene diisocyanate MDI 4,4'-Diphenylmethane diisocyanate TODI 3,3'-Dimethyl-4,4'-biphenylene diisocyanate Mineral oil Paraffin refined mineral oil 40 ° C Kinematic viscosity 67cSt ester pentaerythritol tetraester 40 ° C Kinematic viscosity 31cSt Solution temperature Temperature at which the solution in which the urea compound is completely dissolved in the base oil is transferred to the cooling process Average cooling temperature Average value of the cooling rate of the solution to around room temperature in the cooling process. For example, when cooling from 200 ° C to 20 ° C in 5 seconds, the average cooling rate is 36 ° C / sec.

 Consistency According to JIS K 2220 5.3.

 Drop point According to JIS K 2220 5.4.

Number of aggregates Applying the foreign matter test (JIS K 2220 5.9), apply grease to the slide glass, cover it with a cover glass to make the grease film thickness 30 μm, and observe with an optical microscope (magnification 100 ×). Count the aggregates with a size of 20 μm or more in a frame of mm × 0.64 mm.

Anderon value The Anderon meter is widely used as a vibration measuring device for rolling bearings, and it is a device that rotates the inner ring of the bearing and indicates the vibration of the outer ring under a thrust load in units called Anderon. In the present invention, the bearing was rotated for 1 minute under the test conditions of bearing 6200, grease filling amount 0.30g, bearing inner ring speed 1800r.pm, thrust load 2.0kg, and the indication value in High Band (1800 to 10000Hz) after 1 minute was changed. Read as the Anderon value.

Grease 1 to be used in the present invention by the following manufacturing method
Got 11. Add 70 to 10 parts of a solution of heat-dissolved isocyanate in 1/2 volume of base oil and a solution of amine dissolved in the rest of base oil.
Mix and react at a temperature of 0 ° C, heat while stirring, and when a uniform solution is obtained, pour tap water into the stainless steel container that is continuously spraying from the bottom to cool, and cool to around room temperature. Was passed twice through a three-roll mill. The temperature change during cooling was measured by connecting a thermocouple in a stainless steel container and connecting it to a recorder, and the average cooling rate was calculated from this temperature change record. The dropping points of the greases 1 to 11 are similar to those of commercial lithium soap grease, but there are no aggregates of 20 μm or more and the Anderon value is 11.0 to 14.0, and the commercial urea greases and commercial low noise shown in Comparative Examples 8 to 11 are obtained. It is clear that it has lower noise performance than lithium soap grease.

Greases 12 and 13 are produced with the same composition as Grease 7, but with different average cooling rates. Grease 12 is the average cooling rate
13 ℃ / sec, Grease 13 has an average cooling rate of 153 ℃ / sec,
It has almost the same low noise performance as Grease 7 with an average cooling rate of 54 ° C / sec. Therefore, it can be seen that changing the average cooling rate within this range does not affect the low noise performance.

In Example 1, the weight ratio of grease 1 and grease 4 was
It is a grease obtained by mixing so as to be 99: 1 and passing it through a three-roll mill twice. This grease has a dropping point of 230 ° C, 2
The number of aggregates of 0 μm or more was 0, and the Anderon value was 12.5.

In Example 2, the weight ratio of grease 1 and grease 4 was
It is a grease obtained by mixing so as to be 95: 5 and passing it through a three-roll mill twice. This grease has a dropping point of 254 ℃, 20
The number of aggregates having a size of μm or more was 0, and the Anderon value was 12.5.

In Example 3, the weight ratio of grease 1 and grease 4 is thickener.
It is a grease obtained by mixing so as to be 65:35 and passing it through a three-roll mill twice. This grease has a dropping point of 272 ° C, 2
The number of aggregates of 0 μm or more was 0, and the Anderon value was 12.5.

Example 4 is a grease obtained by mixing Grease 1, Grease 4, and Grease 2 so that the weight ratio of the thickener was 37.7: 28.3: 34.0, and passing through a three-roll mill twice. This grease had a dropping point of 281 ° C., the number of aggregates of 20 μm or more was 0, and the Anderon value was 12.5.

Examples 2, 3 and 4 have a high dropping point and therefore can be used even at a temperature of 150 ° C. or higher that cannot be used with lithium soap grease, and have extremely low noise performance superior to commercially available urea grease and commercially available low noise lithium soap grease. It is grease.

Since Comparative Examples 1 and 2 use n-butylamine and n-heptylamine, respectively, R1 and R3 of the urea compound produced by the reaction with diisocyanate have 7 or less carbon atoms. These greases, which were obtained by the same manufacturing method as Greases 1 to 11, did not dissolve the thickening agent in the base oil at 230 ° C. Anderon values are as large as 38.0 and 27.0, respectively.

Since cyclohexylamine and p-phenetidine are used in Comparative Examples 3 and 4, respectively, R1 and R3 of the urea compound produced by the reaction with diisocyanate contain a cycloalkyl group or a phenyl group. Grease 1-11
Both greases obtained by the same manufacturing method as
At 230 ° C, the thickener does not dissolve in the base oil, and even if it is rapidly cooled at a rate of 5 ° C / sec or more, aggregates of 20 μm or more are present, and the Anderon values are as large as 26.0 and 46.0, respectively.

Comparative Example 5 is a grease obtained by a manufacturing method in which after reacting with the same composition as Grease 2, heating and stirring is stopped at 170 ° C., cooling is performed at a rate of 56 ° C./sec, and the mixture is passed through a three-roll mill twice. is there. Since this grease urea compound was not completely dissolved in the base oil, aggregates of 20 μm or more were present, and the Anderon value was as large as 33.0.

Comparative Examples 6 and 7 were reacted with the same composition as Grease 2, heated and stirred to completely dissolve the urea compound in the base oil at 223 ° C., and then at an average cooling rate of 2.4 ° C./sec and 4.1 ° C./sec, respectively. It is a grease obtained by a manufacturing method in which it is cooled and passed through a three-roll mill twice. Since this grease has an average cooling rate of less than 5 ° C./sec, aggregates having a size of 20 μm or more are present, and the Anderon values are both as large as 24.0.

Comparative Examples 8 and 9 are commercial urea greases, and Comparative Examples 10 and 11 are commercial low noise lithium soap greases.

The above results are tabulated below.

[Advantages of the Invention] By the method for producing a low noise urea grease composition according to the present invention, 20 μm or more aggregates of diurea compound particles as a thickener are present without impairing the high temperature stability that is a characteristic of urea grease. Without, particle major axis (or fiber length) 15μ
It has succeeded in obtaining a urea grease composition in which fine diurea compound crystals of m or less are uniformly dispersed.

Since the obtained low noise urea grease composition is a mixture of two or more kinds of greases containing different urea compounds,
It has higher heat resistance than one type of grease, and
It was confirmed that it has low noise performance and high temperature stability superior to commercial low noise lithium soap grease.

That is, the method for producing the low-noise urea grease composition according to the present invention has an effect of providing a low-noise urea grease having higher heat resistance and durability than conventional low-noise lithium soap grease.

Continuation of the front page (56) References JP-A-63-162790 (JP, A) JP-A-62-290797 (JP, A) JP-A-2-80493 (JP, A) Michio Hoshino and 2 others, " Tribology Monograph 8 Lubricating Greases and Synthetic Lubricants ", Koshobo Co., Ltd., Issued the first edition, December 25, 1983, first edition, p. 54-55 Hiroshi Horiguchi, "Lubricants and Greases", Sankyo Publishing Co., Ltd., published April 25, 1968, p. 410

Claims (1)

[Claims] 1. A general formula R1-NHCONH-R2-NHCONH-R3 [wherein R1 and R3 represent a saturated alkyl group having 8 to 18 carbon atoms, and R2 represents a tolylene group, a diphenylmethane group or a dimethylbiphenylene group. ] A mixture of 2 to 30% by weight of a urea compound and 98 to 70% by weight of a base oil is heated to 170 to 200 ° C to completely dissolve the urea compound, and 5 seconds per second after the first step. ℃
The second step of cooling to room temperature at the above rate, and the second step
Among the greases obtained by the process, the third step of mixing two or more kinds of greases composed of different urea compounds makes it possible to obtain a grease having higher heat resistance than that of one kind of grease. Method for producing low noise urea grease composition