JPH10330779A - Engine lubricating oil and lubrication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lubricating oil which remarkably reduces the friction resistance inside an engine thereby to reduce the noise caused by engine rotation, to improve fuel consumption, and to extend the life of the engine and which itself has a long life by dispersing an effective amt. of a fine BN powder having a crystalline disordered layer structure in an oil. SOLUTION: An effective amt. of a fine BN powder having a crystalline disordered layer structure and pref. having an average primary particle size of 0.5 μm or lower is dispersed in an oil, pref. a petroleum-derived oil, or a synthetic oil, or a mixture of these oils. Alternatively, a fine BN powder of a crystalline disordered layer structure and a fine BN powder of a hexagonal system, both having an average primary particle size of 1 μm or lower, pref. 0.5 μm or lower, are dispersed in the oil, the amt. of the powder of a crystalline disordered layer structure accounting for at least 50 wt.% of the whole powder dispersed. The amt. of the whole powder dispersed is pref. 0.02-50 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine lubricating oil, an engine lubricant and an engine lubricating method used for lubricating various internal combustion engines. The invention further relates to bearings, gears, and other rotating or sliding members, especially general lubricants when subjected to high loads or high temperatures.

[0002]

2. Description of the Related Art There has been proposed an engine lubricating oil containing molybdenum disulfide powder as a solid lubricant. Engine lubricating oil to which molybdenum disulfide powder has been added has an effect of being added, but it is estimated that the reason why the use effect is not so large is that the effect of adding is not remarkable, and it is costly to obtain the effect obtained.

[0003] Boron nitride (BN) is a compound consisting of boron and nitrogen, and boron nitride has a polymorph having the same crystal structure as carbon. Examples of carbon include amorphous carbon, graphite such as hexagonal having a structure in which hexagonal mesh layers are stacked, and cubic diamond. Among these, graphite such as hexagonal system, which exhibits remarkable cleavage between layers having a structure in which hexagonal mesh layers are stacked, exhibits solid lubricity. In the case of boron nitride, amorphous boron nitride (hereinafter referred to as a-BN), hexagonal boron nitride (hereinafter referred to as h-BN) having a structure in which hexagonal mesh layers are laminated in a two-layer cycle, A rhombohedral boron nitride (hereinafter, referred to as r-BN) having a structure in which rectangular mesh layers are stacked in three layers, and a turbostratic boron nitride (hereinafter, referred to as t-BN) in which hexagonal mesh layers are randomly stacked. And high-pressure phase cubic boron nitride (hereinafter referred to as c-BN) are known.

[0004] It is known that h-BN crystals have cleavage properties similar to those of hexagonal graphite crystals and exhibit good solid lubricity. The origin of the lubricity of the h-BN crystal is the van der Waals bond, in which the bond between the two-dimensional hexagonal mesh layers is weak, as in the case of the graphite crystal. It is understood that this is because the crystal grains have a property of slipping easily with each other.

[0005] A sintered body of high purity h-BN powder is colorless or white, has excellent electrical insulation, has higher oxidation resistance than graphite,
Unlike graphite, carbon does not react with and melt into iron-based materials, and hardly reacts with iron-based materials. In this sense, hB
N is a lubricant suitable as a solid lubricant, particularly for lubricating steel-based materials.

[0006] As an example of an application utilizing the lubricity of h-BN, Japanese Patent Application Laid-Open No. 61-261397 discloses that boron nitride fine powder is dispersed in an ester fat or oil at 0.01 to 30% by weight with a homogenizer or the like. Added lubricating oils have been proposed. Japanese Patent Application Laid-Open No. 63-135496 discloses a lubricating oil having excellent heat resistance and friction reducing effect obtained by dispersing h-BN powder and polyetheretherketone powder each having an average particle size of 20 μm or less in a fluid oil or fat. An oil is disclosed.

[0007]

As the boron nitride powder to be added to the lubricating oil, a-BN powder is hygroscopic and unstable and unsuitable, so that only h-BN powder having no hygroscopicity is used. Have been. However, since the price of h-BN powder is not low, it is used only as a lubricating oil for a special purpose which is applicable even if the cost is considerably increased.
Further, r-BN and t-BN have only reached a laboratory prototype stage, and there is no known method for synthesizing them in good yield and at low cost. It is.

[0008] It is an object of the present invention to provide an engine lubricating oil or a lubricant for adding the same which is excellent in cost performance. Another object of the present invention is to provide a method of lubricating an engine using such an engine lubricating oil (or the same additive lubricant).

[0009]

According to a first aspect of the present invention, the engine lubricating oil of the present invention contains crystalline t-B in the oil.
It is characterized by containing an effective amount of N fine powder dispersed therein.
In a second aspect, the engine lubricating oil of the present invention comprises a crystalline t-BN fine powder having an average primary particle size of 1 μm or less and an h-BN fine powder having an average primary particle size of 1 μm or less in the oil. , Wherein at least 50% by weight of the fine boron nitride powder is crystalline t-BN fine powder. In a third aspect, the engine lubrication method of the present invention is characterized in that the engine is lubricated using an engine lubricant containing an effective amount of crystalline t-BN fine powder.

In the present invention, a crystal structure composed of a two-dimensional network layer develops, shows a sharp diffraction line at the [004] position, and indicates the existence of a regular laminated structure of the network layer unique to h-BN. Boron nitride having no or almost no diffraction line at the [102] position is referred to as crystalline t-BN.

On the other hand, Journal of Resources and Materials Vol. 105,
No2. a-BN is replaced with t-BN in p201, 1989, etc.
Is explained. However, the powder X-ray diffraction diagram of the boron nitride powder, which is referred to as t-BN in the same document by CuKα radiation, is adjacent to the position of the [002] diffraction line of h-BN [1
Only two broad diffraction lines are shown at positions [00] and [101] (in this specification, for convenience of explanation, the positions of the diffraction lines in the powder X-ray diffraction diagram of the boron nitride powder are indicated by the h-BN diffraction line index). The same applies to the following.) [004] No or almost no diffraction line is observed at the position of the diffraction line. The X-ray powder diffraction pattern of the a-BN is similar to the X-ray powder diffraction pattern of the a-BN shown in FIG. 1, and it is not appropriate to assume that the a-BN is t-BN.

[0012] Boron nitride is chemically stable as compared with other solid lubricants such as graphite, does not oxidize in air up to about 1000 ° C, and has a characteristic that it does not easily stick to steel materials. FIGS. 1, 2 and 3 show examples of powder X-ray diffraction patterns of a-BN powder, h-BN powder and crystalline t-BN fine powder, respectively. When boron nitride is synthesized at a low temperature of 900 ° C. or lower, as shown in FIG. 1, the position of [002] of h-BN and the adjacent [100] and [10]
1) Wide (broad) with the position corresponding to the position
An a-BN powder exhibiting two diffraction lines is obtained. This a-
When the BN powder is heat-treated at a temperature higher than 1050 ° C., crystallization starts. As the crystallization proceeds, the diffraction line corresponding to the [002] diffraction line of h-BN has a small half-value width and changes to a diffraction line having a strong peak. At this time, the [004] diffraction line also appears as a sharp diffraction line having a small half-value width.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present application, the description of a numerical range is intended to represent not only the upper and lower limits but also any value in between. In particular, at least an arbitrary value of 1/10 unit of the predetermined range is included. Crystalline tB
Specifically, the N fine powder is heated in a reaction vessel holding a mixed raw material containing boric anhydride, urea and an alkali borate such as sodium borate as an optional component in a non-oxidizing atmosphere,
The reaction is performed at a temperature of 00 ° C. or less (preferably
-BN, and then (in the presence of an alkali borate if necessary) at 1200 to 1500 ° C (preferably 1 to
200-1400 degreeC, More preferably, 1250-135.
(0 ° C.) and crystallize into crystalline t-BN to produce a high yield. The obtained reaction product is purified by washing with water (preferably with hot water) (including acid washing as necessary), and excluding soluble components such as alkali and boron oxide, the average particle size of primary particles is 1 μm or less. Can be produced in high yield and can be mass-produced at low cost. Note that 1450
° C or higher (particularly, if the temperature is raised to 1500 ° C or higher, h-B
N-Nation starts, and if the temperature is further increased, h-BN is generated at an arbitrary quantitative ratio. According to this synthesis method, the particle size of the primary particles can be changed by changing the temperature and time for crystallization, and fine boron nitride powder in which h-BN and crystalline t-BN coexist in various ratios Can be synthesized. This new synthesis method is disclosed in Japanese Patent Application No. 9-210
No. 21052, the details of which are incorporated by reference herein as necessary.

The crystalline t, synthesized and purified as described above,
-BN fine powder is usually a secondary particle in which fine primary particles having a particle size of 1 μm or less are aggregated. However, if forcedly dispersed, the crystalline t-BN fine powder is mostly primary particles. It can be a dispersion. If necessary, dispersion may be performed using an attrition mill, a ball mill, or a roll type (including two or three) shearing mill using ceramic beads or balls (such as zirconia) as grinding media. By wet grinding or dry grinding such as a jet mill,
For example, the average particle size is 1 μm or less (preferably, the average particle size is 0.5 μm or less, 0.3 μm or less, and more preferably 0.1 μm or less.
The following can be broken down into fine primary particles and dissociated.
This crystalline t-BN fine powder does not have hygroscopicity as seen in a-BN powder, is stable and has oxidation resistance. According to the above-described production method, it is possible to provide a fine powder having a similar particle size distribution for h-BN, and it is possible to provide a crystalline boron nitride fine powder mainly composed of crystalline t-BN partially containing h-BN. Powder can also be mass-produced. Crystallization to h-BN is carried out by further converting the crystalline t-BN to 1500 ° C. or more (preferably about 1 ° C.).
Up to about 850 ° C, 1600 to 1800 ° C, 1
(750 to 1800 ° C.) for a predetermined time, thereby realizing industrially. The primary particles of the h-BN fine powder and the crystalline t-BN fine powder obtained by this manufacturing method are both composed of fine crystals having cleavage properties,
N fine powder and crystalline t-BN fine powder, especially crystalline t-B
N fine powder shows better solid lubricity.

In the specific viewpoint of the present invention, the reason why the boron nitride fine powder dispersed in the engine lubricating oil is a fine powder having an average primary particle size of 1 μm or less is that the finer the boron nitride fine powder, the narrower the fine powder. This is because it is easy to enter into a natural space and easily exert its function as an engine lubricating oil. The average particle size of the primary particles of boron nitride fine powder dispersed in oil is excellent in lubricity, especially 0.5 μm or less, 0.3 μm or less, or 0.2 μm or less, further 0.1 μm or less. The following are preferred. Especially crystalline t-BN
Even if the fine primary particles form secondary particles, their cohesive force is not so large, and they gradually dissociate and disperse into primary particles or smaller secondary particles due to the shearing force when used as engine lubricating oil, If a primary particle having a small particle diameter is used, a good function as an engine lubricating oil can be exhibited. The standard of the particle size of the secondary particles may be determined in consideration of the mesh of the engine oil strainer if necessary, and may be generally 10 μm or less.

The fine boron nitride powder dispersed in the engine lubricating oil is preferably a fine boron nitride powder containing 50% by weight or more of crystalline t-BN fine powder. The crystalline t-BN fine powder referred to in the present invention typically means that the crystallization of a two-dimensional network layer has progressed and the diffraction lines at the [002] position and the [004] position of the h-BN crystal. All of the corresponding diffraction lines have a small half-width (the half-width of the [004] diffraction line whose 2θ in the powder X-ray diffraction pattern obtained with CuKα ray is about ° is 0.6 ° or less) is a sharp diffraction line. While
Little or no [102] diffraction lines specific to h-BN crystals, which indicate that the laminated structure has regularity, are observed.
It is specifically intended that the diffraction lines corresponding to the [100] diffraction line of N and the “101” diffraction line are one diffraction line ([10] diffraction line of t-BN). [10] of this t-BN
The fact that the X-ray diffraction line has a pattern in which the high-angle side of the diffraction line gradually decreases indicates that although the two-dimensional crystallization is progressing, there is no regularity in the way the hexagonal mesh layers are stacked (lamination pattern). It means that it is a crystalline t-BN having a layer structure. In the present invention, being crystalline t-BN typically means that each diffraction line corresponding to the diffraction lines [100], [101] and [102] in the powder X-ray diffraction diagram of the h-BN crystal. Occupied by S102 / (S100 + S1) between S100, S101 and S102 (proportional to the intensity of each diffraction line)
01) It can be defined numerically as having a relationship of ≦ 0.02.

The fine powder of boron nitride to be dispersed in the oil of the engine lubricating oil has a secondary particle having a mean particle size of 5 μm, which is wet-dispersed with a medium such as alcohol having good dispersibility.
It is preferable to use a fine powder of m or less (further 3 μm or less, 2 μm or less, more preferably 1 μm or less). The secondary particles of boron nitride fine powder in engine lubricating oil gradually disintegrate during use to become fine secondary particles and even primary particles, and the proportion of primary particles gradually increases, resulting in better lubricity Will be demonstrated. Therefore, an engine lubricating oil in which boron nitride fine powder containing a large amount of secondary particles that are large to some extent in the beginning may be dispersed. The crystalline t-BN fine powder used in the engine lubricating oil of the present invention has an extremely fine and uniform primary particle having an average particle size of 0.5 μm or less, 0.2 μm or less, and even 0.1 μm or less (in the order of nanometers). Those having an appropriate particle size distribution (uniform particle size) are preferable.

The crystalline t-BN fine powder shows lubricity even when it is a dry fine powder. However, in the case of engine lubricating oil, boron nitride fine powder is mixed with oil so that it can be sent to a narrow local area to be lubricated. And disperse in oil. However, BN as powder
The fine powder can be stored and dispersed and mixed in oil as needed. As the oil for the engine lubricating oil, petroleum-based oils, synthetic oils of esters with good dispersibility, or mixed oils of petroleum-based oils and synthetic esters of esters can be used. The optimal combination may be selected according to the conditions.

Incidentally, as a practical storage form, it can be handled in a state of being dispersed at a high concentration as a lubricant for addition (or a master liquid). Engine lubrication can be performed. However, a predetermined BN fine powder may be dispersed and contained in the engine oil from the beginning. The dispersion state as the additive lubricant may be determined in consideration of easy dispersibility at the time of addition to the engine oil, no sedimentation and coagulation, and sufficient fluidity. There is no particular limitation. The amount of BN in the additive lubricant is not less than an effective amount and is up to about 70% by weight, preferably 0.1 to 50% by weight, 1 to 30% by weight, and the like. This range can be appropriately changed depending on the performance and the amount ratio, and the like.
The concentration of N can be selected according to the purpose of use.

Since crystalline t-BN to h-BN are stable, commercially available engine lubricating oils can be used as they are for the engine lubricating oil of the present invention. Non-ionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, oil-soluble surfactants are used as dispersants in engine lubricating oils to keep the boron nitride fine powder in a stable suspension state. It is preferable to add at least one selected from activators. Dispersants, detergents, antioxidants, and the like added to commercially available engine lubricating oils for the purpose of suppressing the generation and aggregation of combustion products generated in the lubricating oil during use, improving lubrication characteristics, etc. Includes various additives such as corrosion inhibitors, rust inhibitors, oil agents, extreme pressure additives, oil film strengthening agents, wear inhibitors, pour point depressants, viscosity index improvers, foam deodorants, etc.
As for the engine lubricating oil of the present invention, it is preferable to add at least one selected from an antioxidant, a viscosity index improver, an antiseptic, a rust preventive, an extreme pressure additive, and an antifoaming agent.

Boron nitride fine powder, especially fine crystalline t
-To uniformly disperse the BN fine powder in the oil, add the above-mentioned dispersant or surfactant, stir at high speed with a homogenizer, knead with a roll, or apply shearing force in a ball mill or attrition mill. It is preferred to mix and grind below. The engine lubricating oil is preferably prepared and stored in advance in the form of a suspension of dense boron nitride fine powder, and when diluted with oil to have the required concentration for use, it does not become bulky when transported or stored. So convenient. In the engine lubricating oil of the present invention, the finer the boron nitride fine powder, the finer the crystal powder, the more excellent the lubricating properties can be exhibited even with a small amount of addition.

Crystalline tB with developed two-dimensional crystal structure
It is not clear why the engine lubricating oil in which the N fine powder is suspended exhibits better lubricating properties than the lubricating oil in which the h-BN fine powder is suspended, but at least the difference in the regularity of the lamination of the mesh layers (Basically random in crystalline t-BN) is considered to be the main cause. That is, in the crystalline t-BN, the bonding strength between the hexagonal mesh layers of the h-BN crystal is smaller than the bonding strength between the hexagonal mesh layers of the h-BN crystal, so that it is easy to slip between the layers or to be easily cleaved between the layers, in a direction parallel to the hexagonal mesh layer of the crystal. Since there is no directionality, it is considered that the cleavable scale-like crystals are liable to slide in any direction parallel to the mesh layer. Furthermore, in the crystalline t-BN fine powder synthesized by the above-described production method, the primary particles are fine (usually, the average particle diameter is 1 μm or less,
0.3 [mu] m or less, and further, 0.1 [mu] m or less, nanometer-order fine primary particles of 10 [mu] m in diameter.
This is considered to be because finer and more crystalline boron nitride particles are more likely to exhibit a function as a solid lubricant.

The crystalline boron nitride fine powder is aB synthesized at a low temperature of 1100 ° C. or less, preferably 950 ° C. or less.
Fine boron nitride powder having various degrees of crystallization can be obtained depending on the temperature and time when N is crystallized. Crystallization to t-BN is performed at 1200 to 1500 ° C., preferably 1200
で 1400 ° C., more preferably 1300 ± 50 ° C. If the temperature is further increased for crystallization, the boron nitride will eventually be converted to h-BN, which is stable at high temperatures. When the crystalline t-BN fine powder is heat-treated at 1450 ° C or more, h-
Conversion to BN starts, and a powder in which t-BN and h-BN are mixed is obtained. The finer the boron nitride fine powder dispersed in the engine lubricating oil, the higher the content of the crystalline t-BN fine powder, the better the lubricity. In order to demonstrate excellent lubricity,
Preferably 50% by weight or more of the boron nitride fine powder contained in the lubricating oil (70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, 99% by weight or more, substantially all) Is preferably a crystalline t-BN fine powder. The content ratio of the crystalline t-BN fine powder in the boron nitride fine powder is determined by comparing the intensity (area of the diffraction line) of the diffraction lines obtained by powder X-ray diffraction with the standard boron nitride mixed powder diagram whose mixing ratio is known. It can be measured by comparing the intensity of powder X-ray diffraction.

The finer h-BN and crystalline t-BN powder show a good lubricating effect even with a small amount of addition. For this reason, the average particle size of the secondary particles of the boron nitride fine powder in the lubricating oil is preferably 10 μm or less, 5 μm or less, more preferably 2 μm or less (particularly preferably 1 μm or less). If the fine powder of boron nitride is pulverized in a mill such as an attrition mill, the secondary particles can be relatively easily pulverized into fine powder mainly composed of primary particles. The particle size distribution of the fine boron nitride powder can be measured, for example, by a sedimentation method. In the present invention, the average particle size refers to the particle size at the position where the integrated weight of the weight integrated particle size distribution is 50% by weight. In order to determine the average particle size of the primary particles, an enlarged photograph of a fine powder taken by a scanning electron microscope (SEM) is taken and measured.

If the average particle diameter (secondary particle diameter) of the fine boron nitride powder is as small as 2 μm or less, and further 1 μm or less, most of the fine particles of the boron nitride fine powder are reduced to primary particles. The lubricity of the lubricating oil is further improved. Since fine boron nitride fine powder can enter into small recesses of the order of microns on the sliding surface, the average particle size of the secondary particles in the engine lubricating oil is 1 μm or less, and further 0.5 μm.
By dispersing fine powder as fine as not more than m, more favorable lubricity can be imparted.

The amount of the fine boron nitride powder dispersed in the engine lubricating oil is appropriate and economical depending on the conditions of use, but it can provide a good lubricating effect and can cover a wide range of conditions of use. The dispersion amount of the fine boron nitride powder in the engine lubricating oil is 0.02 to 50% by weight.
It is preferred that If the mixing amount is 0.02% by weight or less, the obtained lubricating effect is not clear, and if it exceeds 50% by weight, it may be difficult to form a uniform suspension. In order to exhibit lubricity with good cost performance, the mixing amount of the boron nitride fine powder is preferably 0.05 to 20% by weight, more preferably 0.1 to 10% by weight,
5% by weight or less, or 2% by weight or less, depending on the application
It may be 1% by weight or less.

Crystalline tB with developed two-dimensional crystal structure
The N fine powder has a substantially disk-shaped or substantially spherical primary particle shape as shown in the SEM enlarged photograph of FIG. 5, and has excellent lubrication performance. Since the addition of the crystalline t-BN fine powder can impart excellent lubricating properties to the engine lubricating oil,
In the lubricating oil of the present invention, preferably 50% by weight or more, more preferably 70% by weight or more (more preferably 80% by weight or more, 90% by weight or more, most preferably, of the primary particles of the boron nitride fine powder contained in the lubricating oil. (Substantially all) are substantially disk-shaped or substantially spherical. The shape of the primary particles of the fine boron nitride powder can be observed from an enlarged photograph of an SEM, and the particle diameter of the primary particles of the crystalline t-BN fine powder obtained by the above-described production method is usually as small as 1 μm or less. The primary particles of the crystalline t-BN fine powder do not have a hexagonal plate shape like the h-BN crystal particles because the crystalline t-BN has no regularity in the lamination relationship between the two-dimensional network layers. Is understood to be.

An appropriate oil for the engine lubricating oil can be selected according to the use conditions. Any oil having good dispersibility in boron nitride fine powder or an oil capable of imparting good dispersibility by adding a dispersing agent may be used. Examples of the oil include inexpensive petroleum oils and esters having good dispersibility. It is preferable to use synthetic oils of the above or mixed oils of petroleum-based oils and synthetic oils of esters. As an example, it is preferable to use a commercially available engine lubricating oil or an oil equivalent to a commercially available engine lubricating oil because commercially available products can be obtained at low cost.

The boron nitride fine powder itself does not always have good dispersibility in oil. Even if the boron nitride fine powder is fine, the fine powder that is agglomerated cannot exhibit good lubricity stably. In order to disperse the fine boron nitride powder in the oil to exhibit lubricity, it is preferable to add a dispersant to the engine lubricating oil. Comparison of various dispersants revealed that nonionic surfactants, anionic surfactants, amphoteric surfactants, and oil-soluble surfactants are particularly useful for dispersing fine boron nitride powder in oil. Admitted.
That is, as the dispersant for the engine lubricating oil of the present invention,
It is preferable to use one or more selected from nonionic surfactants, anionic surfactants, amphoteric surfactants, and oil-soluble surfactants. If a dispersant is added to the engine lubricating oil, redispersion is easy even if the boron nitride fine powder is settled and separated in the oil due to a difference in specific gravity from the oil. Among these dispersants, particularly preferred dispersants are amphoteric surfactants and oil-soluble surfactants.

The engine lubricating oil of the present invention is preferably mixed with various additives other than the dispersant according to the conditions used and the type of oil. Specific examples of additives include an antioxidant, a viscosity index improver, a pour point depressant, an antiseptic, a rust inhibitor, an extreme pressure additive and an antifoaming agent. As these additives, known additives added to commercially available engine lubricating oils can be preferably used.

[0031]

EXAMPLES Hereinafter, the engine lubricating oil of the present invention will be specifically described with reference to examples. However, the following example is an example of the present invention, and the engine lubricating oil of the present invention is not limited to the examples described below. Not limited. That is, the engine lubricating oil of the present invention provides the type of engine to be lubricated, the displacement, the number of revolutions, the torque,
It can be applied according to various viewpoints in accordance with various conditions such as temperature.

[Example 1] (Production of crystalline t-BN fine powder) [Example 1A] 3.5 kg of boric anhydride (B ₂ O ₃ ), 5.3 kg of urea ((NH ₂ ) ₂ CO), borax (Na ₂ B ₄ O _7.
10H ₂ O) A mixture consisting of 0.63 kg was used as a starting material. The mixture was placed in a stainless steel reaction vessel having a diameter of 530 mm and covered with a lid.
0-500 ° C; 500-600 ° C, 600-700 ° C,
700 to 800 ° C, 800 to 900 ° C each in 10 stages
The temperature was raised over a period of 10 minutes, and the reaction was carried out at 900 ± 10 ° C. for 10 minutes (total 1 hour). At about 100 ° C., steam began to erupt, and at 200 ° C., the components began to partially melt, the reaction proceeded, and the gas continued to be released as a bubble. Further 350
Mainly emits water vapor up to 400 ° C,
Holding for 0 minutes reduced the release of product gas. In this state, the reaction vessel was allowed to cool, the lid of the reaction vessel was opened, and the reaction product was taken out of the reaction vessel. At this time, the reactant in the reaction vessel is B ₂
The dried bamboo scallop carme was shown, indicating that the O ₃ was almost completely reacted. The reaction product was crushed in a reaction vessel, taken out by vacuum suction, and further crushed by a crusher (crusher) to obtain a 1-mm pass powder (the above is the primary step). This produced powder is hereinafter referred to as a starting material for the second step.

The container was transferred to a container with a lid made of ceramic (alumina) refractory (the lid was lightly closed), and the whole container with the lid was placed in an electric furnace. N ₂ or CO ₂ was introduced into the electric furnace to form a non-oxidizing atmosphere, the temperature was raised from room temperature to 1300 ° C. over 10 hours, and finally kept at about 1300 ° C. for 2 hours and allowed to cool.

The powder taken out of the container with the lid was
Neutralize at 5 ° C and wash with sufficient stirring and crushing with exchanged water (hot water) to remove alkali components, and finally acid (HCl)
And then neutralized, further washed with water and dried. After washing, about 0.6 to 0.6 per 10 kg of the starting material of the secondary process
5 kg of t-BN were obtained. This resulted in about 28.5% or more of t-BN based on the weight of the starting boron in the first step, and the yield was as high as 70% or more and high in purity. In addition, from the first process product to the heat treatment of the second process, 10 to 20
% Weight loss was observed.

Example 1B A sample different from that of Example 1A, but having substantially the same crystallinity t as obtained in Example 1A.
-BN powder was examined by powder X-ray diffraction using CuKα radiation.
FIG. 3 shows an X-ray diffraction diagram of the obtained synthetic powder. When the X-ray diffraction pattern of the known h-BN shown in FIG. 2 is compared with the powder X-ray diffraction chart of FIG. 3, the boron nitride of the powder X-ray diffraction chart of FIG. [00] of h-BN in FIG.
Sharp diffraction lines are observed at about 26.6 ° and about 55 ° at positions corresponding to the diffraction line of [2] and the [004] diffraction line, respectively. However, it can be seen that no diffraction line is observed at a position corresponding to the [102] diffraction line of h-BN. Also, h-
The position corresponding to the [100] diffraction line of BN (41.55)
°) has a fairly sharp diffraction line. This [100]
The diffraction line overlaps with the lower [101] diffraction line at the high angle side where the sharp [101] diffraction line of h-BN is present, and the [101] diffraction line is slightly raised at the high angle side by pulling the tail. Painted background. This [10
1] The diffraction lines do not exist as sharp protrusions. This means that the synthetic boron nitride powder is a highly pure t-BN powder with advanced crystallization. The powder in FIG. 3 is an example of the crystalline t-BN powder according to the present invention.

The 2θ position and half width of each diffraction line in the powder X-ray diffraction diagram of FIG. 3 were examined.
At 6.58 °, the [004] diffraction line was at 55.0 ° and the half width was 0.47 °. From this, h-BN
[004] It can be seen that the half width of the equivalent diffraction line can be reduced to about 0.5 ° or less.

Example 1C An enlarged photograph (×) of a sample SEM of t-BN fine powder obtained in the same manner as in Example 1A
20,000 times and × 10,000 times) are shown in FIG. From the SEM photograph of FIG. 5, the average particle size of the primary particles of this t-BN synthetic powder is about 0.45 μm, and the particle size of the primary particles is substantially in the range of 0.3 to 0.75 μm. You can see that. The primary particles do not show the hexagonal plate-like crystal particle shape peculiar to the hexagonal system seen in the primary particles of h-BN, and are disc-shaped (large) which are considered to be peculiar to the crystalline t-BN crystal. Or a substantially spherical shape (small).

Example 1D Example 1A was prepared in the same manner as in Example 1A, except that 1% by weight of t-BN powder containing a large amount of dispersed primary particles was added to the raw material as a seed crystal. A t-BN powder was synthesized in the same manner as described above. In this example, the progress of the primary reaction was quick, and the final product tB
A further improvement in N yield was observed. Incidentally, the yield of the generated BN based on the charged boric anhydride reaches up to 80% or more.

Example 1E A dispersion of t-BN powder prepared under the same conditions as in Example 1A was prepared, and the particle size distribution was measured. The results are shown in FIG. The measurement is HORIBA LA
Performed using a -700 particle size analyzer. As a result, a cumulative 95.2 having a median diameter of 0.30 μm and a particle diameter of 1 μm or less was obtained.
%, 90% particle size was 0.75 μm. In this measurement, it is certain that the average particle size is 0.3 μm or less when walking at a point where the particles are not completely primary particles (measured with considerable aggregation). The specific surface area is 23.4.
m ² / cm ³ . FIG. 6 shows an SEM photograph of another sample obtained in the same manner. The particles are substantially disc-shaped or substantially spherical, the average primary particle diameter is about 0.3 μm, and the particle diameter of the primary particles is substantially within a very narrow range of 0.2 to 0.45 μm. I understand.

[Example 1F] The mixing ratio of boric anhydride and urea was changed to 4: 9 (weight ratio), the first step was heated for 1.5 hours without using borax, and the final temperature was 920 to 950.
BN was synthesized in the same manner as in Example 1A, except that the temperature was kept at 15 ° C. for 15 minutes, and that the inside of the closed vessel was sufficiently pressurized by squeezing the gas vent hole. The secondary process was performed under substantially the same conditions as in Example 1A, and the cleaning was performed similarly. Extremely pure t-BN was obtained. The SEM photograph is shown in FIG. The shape is substantially spherical, the average primary particle size is about 0.25 μm, and the primary particle size is mostly 0.2 to 0.3 μm and substantially 0.15 to 0.38 μm (ie, approximately 0.15 to 0.38 μm). ~ 0.4
μm). The mixing ratio (weight ratio) of boric anhydride and urea is preferably 4: 6 to 4: 9, but 4: 9 gave the best result.

Example 1G FIG. 8 shows an X-ray diffraction pattern of a sample t-BN prepared under the same conditions as in Example 1F.
Comparing the powder X-ray diffraction diagrams of FIG. 8 and FIG.
The boron nitride in the line diffraction diagram has undergone considerable t-BN crystallization, and sharp diffraction lines at positions corresponding to the [002] diffraction line and the [100] diffraction line of h-BN in FIG. 2 are 26.7, respectively.
°, 41.8 °. However, the position of the diffraction line of [002] is slightly shifted to a higher angle side than the corresponding diffraction line position of h-BN, and the diffraction line is diffracted to a position (50 °) corresponding to the [102] diffraction line of h-BN. It can be seen that no lines are observed. Further, there is a sharp diffraction line at a position (41.8 °) corresponding to the [100] diffraction line of h-BN, although not so high. This diffraction line has a slightly longer skirt extending through the shoulder to the high angle side of the [101] diffraction line of h-BN (hereinafter referred to as (10) diffraction line), but the [101] diffraction line is a clear projection. not exist. This means that the synthetic boron nitride powder is a single-phase t-BN powder of high purity with advanced crystallization as t-BN. The powder shown in FIG. 8 is an example of the high-purity crystalline t-BN powder according to the present invention (particularly, ultra-submicron particles of the order of 0.2 to 0.3 μm). It can be seen from the low background that the high purity and the t-BN single phase are sufficient. That is,
It should be noted that no peaks indicating B ₂ O ₃ appear at all in the diffraction lines in FIGS. 3 and 8.

[Example 2] (Preparation of engine lubricating oil and practical test) [Example 2A] An engine lubricating oil was prepared as follows. That is, lubricating base oil (petroleum, flash point (co
c) Kinematic viscosity at about 218 ° C. and 40 ° C. about 27.8 mm
² / s (cSt) 64 parts by weight, polyoxyethylene coconut alkylamine derivative (Kao Amit 102) 6
The mixed solution consisting of parts by weight was put into a 7-liter alumina pot mill together with 7.6 kg of alumina balls having a diameter of 10 mm and mixed at 60 rpm for 1 hour. Next, 30 parts by weight of the crystalline t-BN fine powder were added into the same alumina pot mill container, and the mixture was mixed at 60 rpm for 24 hours, pulverized and uniformly dispersed, and about 30% by weight of borax was used in 1 liter. Crystalline t- with an average primary particle size of 0.3 μm
A suspension (master liquid) containing BN fine powder was obtained. This suspension was diluted about 30-fold with a commercially available engine lubricating oil A (Barbis Neo SJ15W-40 manufactured by Peter Lub International Co., Ltd.) to obtain an engine lubricating oil containing 1.0% by weight of t-BN fine powder. In addition, a small amount of an antioxidant, a viscosity index improver and a rust inhibitor are added as additives to the commercially available engine lubricating oil A.

The obtained engine lubricating oil containing the crystalline t-BN fine powder was used with a sedan (trade name: Legacy,
An EFI-MT engine with a displacement of 2,000 cc was put into the engine, and at the same time, the oil filter was replaced with a new one, and a running test was performed. A running test was performed on a commuting route of about 37 km one way including a 15 km highway running, and as a result, it was recognized that the engine rotational noise was clearly reduced during idling and running, particularly during high speed running. Also, it can be determined that the horsepower of the engine has improved due to the improvement in acceleration, and the average mileage per liter of regular gasoline has increased from 6.8 km (when using commercially available engine lubricating oil A) to 8.9 km. . Furthermore, as a result of the continued use of the same engine lubricant for lubricating the engine of the same sedan, the durability of the engine lubricant itself has been extended, and
It was judged that it could endure running over 10,000 km. Also,
When the engine oil was removed and the oil filter was checked, no abnormality was found.

Example 2B (Preparation of Engine Lubricating Oil and Practical Test) Using crystalline t-BN (primary particle diameter: about 0.25 μm) produced without using borax, this crystalline t-BN fine powder was used. 30 parts by weight of lubricating base oil 64 in the same manner as in Example 2A
Part by weight and 6 parts by weight of a polyoxyethylene coconut alkylamine derivative, and a suspension containing about 30% by weight of crystalline t-BN fine powder per liter (master liquid)
I got This suspension was mixed with a commercially available engine lubricating oil B (trade name: ZOA, SG, 10W-30, manufactured by Nippon Oil Co., Ltd.) to obtain an engine lubricating oil containing 1% by weight of t-BN fine powder. This engine lubricating oil was used with Mitsubishi Motors RV
Car (vehicle name Pajero, displacement 3,500cc ECI-A
(T car) and the oil filter was replaced with a new one at the same time, and a running test was performed. As a result of the running test performed in a running section where the highway is heavily used (about 45% is a highway), it was found that the engine rotational noise during idling and running, particularly during high speed running, was clearly reduced. In addition, the acceleration of the engine is improved due to the improvement in the horsepower of the engine, and the mileage per liter of regular gasoline when using commercially available engine lubricating oil B is 6.
When the engine lubricating oil containing the crystalline t-BN fine powder was used, the running distance was 7.8.
km.

[Example 2C] (Preparation and practical test of engine lubricating oil) 64 parts by weight of lubricating base oil (petroleum-based, flammable viscosity at about 218 ° C, 40 ° C, about 27.8 mm ² / s (cSt)) ,
A mixed solution composed of 6 parts by weight of a polyoxyethylene coconut alkylamine derivative (Kao Amit 102) was placed in a 7 liter alumina pot mill container having a diameter of 10 m.
60 rpm with 7.6 kg of alumina balls
m for 1 hour. Next, it was synthesized and purified by the same procedure as in Example 3, and 30% by weight of crystalline t-
A suspension (master liquid) in which the BN fine powder was uniformly dispersed in the oil was obtained.

This suspension was mixed with a commercially available diesel engine lubricating oil C (trade name ZOA Diesel R manufactured by Nippon Oil Co., Ltd.).
V, CF-SAE15W-40, and an additive such as an antioxidant, a viscosity index improver and a rust inhibitor) to obtain an engine lubricating oil containing 1% by weight of crystalline t-BN fine powder. The engine lubricating oil containing the crystalline t-BN fine powder is put into a diesel engine of a small truck (Hilux pickup, MT car with a displacement of 2,800 cc and equipped with a turbocharger) manufactured by Toyota Motor Corporation, and at the same time, an oil filter. Was replaced with a new one, and a running test was performed. As a result of the running test performed in a running section where the highway is frequently used (about 20% is a highway), it was found that the engine rotational noise during idling and running, particularly during high speed running, was clearly reduced. In addition to the improved acceleration, the mileage per liter of light oil when using commercially available diesel engine lubricating oil C was 9.5 km, whereas the crystalline t-BN fine powder of the present invention contained When the engine lubricating oil was used, the running distance increased to 10.9 km.

[0047]

According to the conventional boron nitride synthesizing technique, there is no mass production method which can provide not only crystalline t-BN fine powder but also h-BN powder with good yield and low cost. For this reason, the price of h-BN powder is also high, and its application as a lubricating oil has been limited to only extremely limited applications. However, since the above-mentioned synthesis technology was established, h-BN
In addition to powder, crystalline t-BN fine powder having particularly excellent solid lubricity can be mass-produced at low cost and provided. The present invention is a development of the t-BN fine powder, which has not heretofore been known, a new use with the establishment of the above-mentioned synthesis technology. The present invention is applied to an engine lubricating oil, and a crystalline t-BN fine powder is applied to an engine lubricating oil. It was confirmed that a remarkable effect was obtained by the addition of. That is, when the engine lubricating oil of the present invention is used for lubricating the engine, the rotational noise of the engine is obviously reduced, and at the same time, the mileage per liter of fuel (fuel consumption).
It was confirmed that the service life of the engine lubricating oil itself was prolonged, and that there was no problem with the engine cooling effect of the engine lubricating oil. Based on the results of these tests, the durability of the engine body should naturally be extended. Therefore, by using the engine lubricating oil containing the crystalline t-BN fine powder of the present invention for lubricating the engine, the frictional resistance inside the engine can be remarkably reduced. Furthermore, the quietness of the cabin during high-speed running can be significantly improved, and the fuel efficiency and the durability of the engine can be significantly improved. Thus, the industrial utility value of the engine lubricant of the present invention is enormous. Furthermore, it goes without saying that the lubricating oil of the present invention exhibits excellent performance as a general lubricating oil for bearings, gears and other rotating or sliding members.

[Brief description of the drawings]

FIG. 1 is a powder X-ray diffraction diagram of an example of a conventional a-BN fine powder.

FIG. 2 is a powder X-ray diffraction diagram of an example of a conventional h-BN powder.

FIG. 3 shows the crystalline t added to the engine lubricating oil of the present invention.
It is a powder X-ray diffraction diagram of an example of -BN fine powder.

FIG. 4 shows the crystalline t added to the engine lubricating oil of the present invention.
-It is a particle size distribution graph of an example of BN fine powder.

FIG. 5 shows the crystalline t added to the engine lubricating oil of the present invention.
It is an enlarged photograph by a scanning electron microscope (SEM) of an example of -BN fine powder.

FIG. 6 shows the crystalline t added to the engine lubricating oil of the present invention.
-Scanning electron microscope (SEM) of another example of BN fine powder
It is an enlarged photograph by.

FIG. 7 shows the crystalline t added to the engine lubricating oil of the present invention.
-Scanning electron microscope (SEM) of another example of BN fine powder
It is an enlarged photograph by.

FIG. 8 shows the crystalline t added to the engine lubricating oil of the present invention.
It is a powder X-ray diffraction diagram of another example of -BN fine powder.

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Claims (11)

[Claims] 1. An engine lubricating oil comprising an effective amount of a finely divided boron nitride powder having a crystalline turbostratic structure dispersed therein. 2. A finely dispersed boron nitride fine powder having an average primary particle diameter of 1 μm or less and a hexagonal boron nitride fine powder having an average primary particle diameter of 1 μm or less are dispersed in oil. An engine lubricating oil characterized in that 50% by weight or more of the boron nitride fine powder is a boron nitride fine powder having a crystalline turbostratic structure. 3. The average particle size of primary particles of boron nitride fine powder dispersed in oil is 0.5 μm or less.
The engine lubricating oil according to the above. 4. The engine lubricating oil according to claim 1, wherein the amount of the fine boron nitride powder dispersed in the oil is 0.02 to 50% by weight. 5. The engine according to claim 1, wherein 50% by weight or more of the primary particles of the boron nitride fine powder observed by an electron microscope have a substantially spherical shape or a substantially disk shape. Lubricant. 6. The engine lubricating oil according to claim 1, wherein the oil is a petroleum-based oil, a synthetic oil of esters, or a mixed oil of a petroleum-based oil and a synthetic oil of esters. 7. As a dispersant for the boron nitride fine powder in oil, at least one selected from nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants and oil-soluble surfactants. The engine lubricating oil according to any one of claims 1 to 6, further comprising: 8. The oil according to claim 1, wherein at least one selected from the group consisting of an antioxidant, a viscosity index improver, a pour point depressant, an antiseptic, a rust preventive, an extreme pressure additive and a defoamer. Items 1 to 7
Engine lubricating oil according to any one of the above. 9. A method for lubricating an engine, comprising using the engine lubricating oil according to claim 1. 10. A method for producing an engine lubricating oil containing an effective amount of finely divided boron nitride having a crystalline turbostratic structure by mixing with a commercially available engine lubricating oil. An engine lubricant characterized by being dispersed in a high concentration. 11. A method for lubricating an engine, comprising: dispersing an effective amount of a fine powder of crystalline turbostratic boron nitride in oil to perform lubrication.