JP2572814B2 - Grease composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a grease composition having a long life at high temperatures and excellent low-temperature performance.

(Prior Art) In recent years, the miniaturization and high output of various industrial motors have been further advanced, and there has been an increasing demand for longer life of bearings and bearing greases used in those motors. .

Under these circumstances, the lubricating life of the conventionally used lithium grease based on mineral oil under high temperature conditions depends on the oxidative deterioration of the base oil and the structural destruction of the thickener. It softened and did not have a very long life. Accordingly, synthetic lubricating oils such as ester oils, polyalpha-olefin oils and silicone oils, which have good thermal stability, have been used as base oils in lubricating parts requiring long life at high temperatures. Recently, not only grease using only one kind of synthetic lubricating oil as a base oil, but also mineral oil and synthetic lubricating oil such as mineral oil of ester oil or polyalphaolefin oil, polyalphaolefin oil and mineral oil, etc. In many cases, grease is used as the base oil for grease, but these greases have not been able to achieve the long life characteristics required by the market.

In addition, urea grease, which has improved oxidation stability and heat resistance to extend the lubrication life of bearings, has recently been used, but has disadvantages such as higher thermosetting properties and higher price than metal soap grease. There is.

In some places, lithium grease using silicone oil as a base oil is also used, but the price is high and the lubricity between steel and steel is poor, so that satisfactory results have not always been obtained.

(Problems to be Solved by the Invention) In addition, bearings using conventional metallic soap grease such as lithium grease do not always have a sufficient lubrication life, so grease lubrication is required in a short period of time. The labor cost is also high. In addition, since the number of persons in charge of those equipment managements also tends to be reduced, a grease having a long lubrication life is required, and its development is desired.

(Means for Solving the Problems) The present inventors have conducted intensive studies to solve the problems of the conventional grease, and as a result, by using the following means, if the problems can be solved. It is a stiff one. That is, the present invention was synthesized from (A) a hydroxide of an alkali metal or an alkaline earth metal, and a higher fatty acid having 10 or more carbon atoms or a higher hydroxy fatty acid having 10 or more carbon atoms having at least one hydroxyl group. 5 to 30% by weight of an alkali metal salt or an alkaline earth metal salt, (B) an ether-based synthetic oil which is an alkyl diphenyl ether having a structure in which an aromatic ring which is a kind of synthetic lubricating oil is bonded by an oxygen atom, and (C) The following general formula R ₁ OCO (CH ₂ ) _n COOR ₂ (wherein R ₁ and R ₂ are an aliphatic hydrocarbon group having 3 to 18 carbon atoms, and n is 3 to 12)
The diester synthetic oil represented by the following general formula:
Triester synthetic oil represented by C ₂ H ₅ C (CH ₂ OCOR) ₃ (R in the formula represents an aliphatic hydrocarbon group having 3 to 10 carbon atoms), and the following general formula C (CH ₂ OCOR) ₄ (R in the formula is carbon number 3
10 of an aliphatic hydrocarbon group) in tetra-ester synthetic oils represented by the following general formula _{C (CH 2 OCOR) 3 2H} 2 OCH 2 C
(CH ₂ OCOR) ₃ (wherein R represents an aliphatic hydrocarbon group having 3 to 10 carbon atoms) selected from the group consisting of dipentaerythritol synthetic oils and other neopentyl polyol ester synthetic oils. A mixture of at least one ester synthetic oil and a mixture ratio of the ether synthetic oil of the component (B) / the ester synthetic oil of the component (C) of more than 0.2 and not more than 4.5 by weight. A grease composition comprising 70 to 95% by weight of a mixed base oil.

Among alkali metal salts, grease using lithium soap as a thickener is widely used for lubricating bearings of various steelmaking facilities, automobile parts, home electric appliances and the like. The motors used in these fields are also diversified, but a common requirement is miniaturization and high output. As seen in H-class motors and VVVF motors, many bearings have been exposed to high-temperature and high-speed lubrication conditions, and inevitably require a long life for grease, contributing to resource and energy savings. It is said. In response to these demands, recently many urea greases using urea compounds as thickeners have appeared,
There is also a problem that the grease is hardened by the heat generated during the operation of the motor, lubrication of the bearings is not smooth, and when the motor is restarted after being cooled to room temperature after the motor is stopped, the starting torque is increased. One of the important properties required for grease used for small-diameter bearings is low noise of grease, but urea grease is not always sufficient for this performance. Furthermore, when supplying grease to the bearings of various motors, grease using alkali metal salts such as lithium soap as a thickener has been the mainstream in the past, and grease using different thickeners such as urea grease has been used. Then, the grease is mixed with the past grease, and a change in the consistency may be observed, which is not always satisfactory. In addition, since most urea compounds, which are thickeners for urea grease, are not easily dissolved in grease base oil, it is difficult to remove contaminants using a filter such as lithium soap. There are still few urea greases with excellent properties, and greases using metal soaps, especially lithium soap, as a thickener are mainly used.

(Operation) The grease composition of the present invention comprises 5 to 30% by weight of an alkali metal salt or an alkaline earth metal salt of the component (A) and an ether synthetic oil of the component (B) and an ester synthetic oil of the component (C). And 70 to 95% by weight of a mixed base oil consisting of If the compounding amount of the alkali metal salt or alkaline earth metal salt of the component (A) is less than 5% by weight, the product is too soft to be greased and becomes almost liquid, while if it exceeds 30% by weight, it is too hard. Therefore, it is expected that the lubrication of bearings or the like may have a bad lubrication effect.

Next, the ratio of the ether-based synthetic oil (B) used as the base oil in the grease composition of the present invention and the ester-based synthetic oil (C) is more than 0.2 in weight ratio (B / C) to 4.5 or less,
Preferably 0.25 or more and 4.0 or less, more preferably
It is in the range of 0.5 or more and 2.0 or less. When the weight ratio of B / C is 0.2 or less, the amount of ester synthetic oil becomes excessive, which is not preferable. The reasons are as follows. The thermal stability of the base oil, for example, the magnitude of the evaporation loss of the base oil at high temperatures, is one of the factors governing grease deterioration. Comparing the thermal stability of the compounds, ether synthetic oils are superior. Therefore, when B / C is 0.2 or less, the thermal stability of the grease composition of the present invention is reduced, and the oxidation stability of the obtained grease composition is further reduced, so that the object cannot be achieved. If B / C is larger than 4.5, the amount of ether-based synthetic oil becomes excessive, which is not preferable. The reasons are as follows. Lithium soap which is a thickener of the grease composition of the present invention, and the compatibility of the ether-based synthetic oil used as the base oil are not always good, and only the ether-based synthetic oil is used as the base oil, and the lithium soap is used as a thickener. When grease is manufactured as above, the obtained grease does not always have good low-temperature performance (for example, low-temperature startability). The low-temperature performance of grease is one of the important performances required for grease used in bearings and the like, and it is necessary to have low torque.

The composition of the present invention may be blended with various antioxidants usually used, for example, phenyl-α (β) naphthylamine, dioctyldiphenylamine, phenothiazine, tertiary butylphenol, and various lubricating additives such as derivatives thereof and rust preventives. Almost no change is observed in the resulting lubrication performance.

The ether-based synthetic oil of the component (B) used in the present invention is:
A synthetic lubricating oil called alkyl diphenyl ether having a structure in which aromatic rings are bonded by oxygen atoms, and having a kinematic viscosity of 40
It has a temperature of 90 to 165 cSt and a flash point of 260 ° C or higher. This synthetic oil has extremely excellent heat stability and oxidation stability, and is used for rotary pump oil and the like. Although such ether-based synthetic oils are excellent in thermal stability and oxidative stability, they cannot always be said to have good low-temperature performance, and have not been widely used as grease base oils. The present inventors have conducted intensive studies to improve these drawbacks of ether-based synthetic oils, and as a base oil, obtained a mixed oil obtained by mixing with ester-based synthetic oils at a specific ratio, using lithium soap as a base oil. It has been found that the grease composition obtained as a thickener has a significantly longer lubricating life than conventional greases, and has a low-temperature performance that can sufficiently withstand practical use.

Diester synthetic oils represented by the general formula R ₁ OCO (CH ₂ ) _n COOR ₂ used in the present invention, general formula C ₂ H ₅ C (CH ₂ OCOR) ₃
A triester synthetic oil represented by the general formula C (CH ₂ O
Examples of the tetraester synthetic oils represented by COR) ₄ are as follows. Di-2-ethylhexyl sebacate, di-2-ethylhexyl azelate, di-2-ethylhexyl adipate, trimethylolpropane ester, pentoerythritol ester, dipentaerythritol ester and the like. In the diester synthetic oil, the value of n is preferably 3 to 12, and R ₁ and R ₂ are preferably an aliphatic hydrocarbon group having 3 to 18 carbon atoms. In the oil, R is preferably an aliphatic hydrocarbon group having 3 to 10 carbon atoms.

Among the various ester-based synthetic oils of the component (C) used in the present invention, neopentyl polyol ester-based synthetic oil is
The thermal stability and the oxidative stability are higher than the diester synthetic oil, and the thermal stability and the oxidative stability of the grease composition composed of the base oil obtained by mixing with the ether synthetic oil used in the present invention are also neo. More excellent curing is obtained when a pentyl polyol ester-based synthetic oil is used.

The grease composition of the present invention has excellent long-life characteristics with respect to the lubrication life of the bearing, and has low-temperature performance of a lithium soap grease based on a conventionally used ester synthetic oil or mineral oil as a base oil. The performance is maintained at a level that does not hinder practical use as compared to

Deterioration of grease, which is one of the factors governing the lubrication life of a bearing, is often caused by deterioration of a thickener, but many cases are also caused by deterioration of a base oil. On the other hand, the low-temperature performance of grease mostly depends on the low-temperature performance of the base oil itself. However, the grease composition of the present invention,
The heat stability and oxidation stability, which were not satisfied by the conventional greases based on ester-based synthetic oils or mineral oils, have been greatly improved by using ether-based synthetic oils. On the other hand, ether-based synthetic oils do not always have sufficient low-temperature performance because of their high pour points, and are greatly improved by using ester-based synthetic oils.
As described above, a technique for improving the performance of grease by using different types of base oils in combination is ester-based synthetic oil and mineral oil, ester-based synthetic oil and polyalpha-olefin oil, polyalpha-olefin oil and mineral oil. However, the grease composition obtained according to the present invention has a remarkably long life characteristic as compared with a conventional synthetic oil-based grease. Have.

(Examples and Comparative Examples) The present invention will be described more specifically by the following Examples and Comparative Examples.

 The base oils described in Table 1 are as follows.

B-1: kinematic viscosity at 40 ° C is 150 cSt, kinematic viscosity at 100 ° C is 18.0 cS
t, a viscosity index of 130, a dialkyl diphenyl ether oil with a flash point of 260 ° C or higher, B-2: a kinematic viscosity at 40 ° C of 104 cSt, and a kinematic viscosity at 100 ° C of 13.0 cS
t, a dialkyldiphenyl ether oil with a viscosity index of 120 and a flash point of 260 ° C or higher, C-1: kinematic viscosity at 40 ° C of 32.2 cSt, kinematic viscosity at 100 ° C of 5.84 cS
t, pentaerythritol tetraester oil with a viscosity index of 125 and a flash point of 260 ° C or higher, C-2: kinematic viscosity at 40 ° C is 11.6 cSt, kinematic viscosity at 100 ° C is 3.2 cS
t, a di-2-ethylhexyl sebacate oil having a viscosity index of 153 and a flash point of 210 ° C. or higher.

Incidentally, phenyl-alpha-naphthylamine was added as an antioxidant to the respective target compositions shown in Examples and Comparative Examples.

Example 1 200 g of dialkyl diphenyl ether oil and 600 g of pentaerythritol tetraester oil were mixed, and 120 g of lithium 12-hydroxystearate was added thereto, followed by heating to 230 ° C. while stirring. This was poured into a stainless steel container to a thickness of 3 to 5 mm, cooled, and then milled once with three rolls. The one obtained so far was used as a base grease. In a separate container, 17.5 g of dialkyl diphenyl ether oil and 52.5 g of pentaerythritol oil were mixed, and 10 g of phenyl-α-naphthylamine was added thereto.
The mixture was heated to 00 ° C. and dissolved. Add this to the base grease,
Milling was performed twice with three rolls to obtain the composition of the present invention. In addition, dialkyl diphenyl ether oil (B-
1) the weight ratio of pentaerythritol oil (C-1) to
That is, B / C is 0.33.

Example 2 400 g of dialkyldiphenyl ether oil and 400 g of pentaerythritol tetraester oil were mixed, and 120 g of lithium 12-hydroxystearate was added thereto, followed by heating to 230 ° C. while stirring. This was poured into a stainless steel container to a thickness of 3 to 5 mm, cooled, and then milled once with three rolls. The one obtained so far was used as a base grease. In a separate container, mix 35 g of dialkyl diphenyl ether oil and 35 g of pentaerythritol oil,
Add 10 g of phenyl-α-naphthylamine to this, and add
Until heated to dissolve. This was added to the base grease and milled twice with a three-roll mill to obtain the composition of the present invention. In addition, dialkyl diphenyl ether oil (B-1)
And the weight ratio of pentaerythritol oil (C-1), that is, B / C is 1.0.

Example 3 550 g of dialkyl diphenyl ether oil and 250 g of pentaerythritol tetraester oil were mixed, and 120 g of lithium 12-hydroxystearate was added thereto, followed by heating to 230 ° C. while stirring. This was poured into a stainless steel container to a thickness of 3 to 5 mm, cooled, and then milled once with three rolls. The one obtained so far was used as a base grease. In a separate container, mix 30 g of dialkyl diphenyl ether oil and 40 g of pentaerythritol oil,
Add 10 g of phenyl-α-naphthylamine to this, and add
Until heated to dissolve. This was added to the base grease and milled twice with a three-roll mill to obtain the composition of the present invention. In addition, dialkyl diphenyl ether oil (B-1)
And the weight ratio of pentaerythritol oil (C-1), that is, B / C is 2.0.

Example 4 630 g of dialkyl diphenyl ether oil and 170 g of pentaerythritol tetraester oil were mixed, and 120 g of lithium 12-hydroxystearate was added thereto, followed by heating to 230 ° C. while stirring. This was poured into a stainless steel container to a thickness of 3 to 5 mm, cooled, and then milled once with three rolls. The one obtained so far was used as a base grease. In a separate container, 225 g of dialkyl diphenyl ether oil and 47.5 g of pentaerythritol oil were mixed, and 10 g of phenyl-α-naphthylamine was added thereto.
The mixture was heated to 00 ° C. and dissolved. Add this to the base grease,
Milling was performed twice with three rolls to obtain the composition of the present invention. In addition, dialkyl diphenyl ether oil (B-
1) the weight ratio of penterythritol oil (C-1),
That is, B / C is 3.0.

Example 5 400 g of dialkyl diphenyl ether oil and 400 g of di-2-ethylhexyl sebacate oil were mixed, and 120 g of lithium 12-hydroxystearate was added. The mixture was heated to 230 ° C. while stirring. This was poured into a stainless steel container to a thickness of 3 to 5 mm, cooled, and then milled once with three rolls. The one obtained so far was used as a base grease. In a separate container, dialkyl diphenyl ether oil 35 g, di-2-ethylhexyl sebacate oil 3
5 g, and phenyl-α-naphthylamine 10 g was added thereto.
And heated to 100 ° C. to dissolve. This was added to the base grease and milled twice with a three-roll mill to obtain the composition of the present invention. In addition, dialkyl diphenyl ether oil (B-1) and 2-ethylhexyl sebacate oil (C
The weight ratio of -2, that is, B / C is 1.0.

Example 6 400 g of dialkyl diphenyl ether oil and 400 g of pentaerythritol tetraester oil were mixed, and 120 g of lithium 12-hydroxystearate was added thereto, followed by heating to 230 ° C. while stirring. This was poured into a stainless steel container to a thickness of 3 to 5 mm, cooled, and then milled once with three rolls. The one obtained so far was used as a base grease. In a separate container, mix 35 g of dialkyl diphenyl ether oil and 35 g of pentaerythritol oil,
Add 10 g of phenyl-α-naphthylamine to this, and add
Until heated to dissolve. This was added to the base grease and milled twice with a three-roll mill to obtain the composition of the present invention. In addition, dialkyl diphenyl ether oil (B-2)
And the weight ratio of pentaerythritol oil (C-1), that is, B / C is 1.0.

Comparative Example 1 120 g of lithium 12-hydroxystearate was added to 800 g of pentaerythritol tetraester oil and heated to 230 ° C. while stirring. This was poured into a stainless steel container to a thickness of 3 to 5 mm, cooled, and then milled once with three rolls. What was obtained so far was used as the base grease. Pentaerythritol oil in a separate container
70 g was taken, 10 g of phenyl-α-naphthylamine was added thereto, and the mixture was heated to 100 ° C. and dissolved. This was added to the base grease, and milling was performed twice with a three-roll mill to obtain a target composition. The weight ratio of dialkyl diphenyl ether oil (B-1) to pentaerythritol oil (C-1), that is, B / C is 0.

Comparative Example 2 120 g of dialkyl diphenyl ether oil and 680 g of pentaerythritol tetraester oil were mixed, and 120 g of lithium 12-hydroxystearate was added thereto, followed by heating to 230 ° C. while stirring. This was poured into a stainless steel container to a thickness of 3 to 5 mm, cooled, and then milled once with three rolls. The one obtained so far was used as a base grease. In a separate container, mix 25 g of dialkyl diphenyl ether oil and 45 g of pentaerythritol oil,
Add 10 g of phenyl-α-naphthylamine to this, and add
Until heated to dissolve. This was added to the base grease, and milling was performed twice with a three-roll mill to obtain a target composition. The weight ratio of dialkyl diphenyl ether oil (B-1) and pentaerythritol oil (C-1), that is,
B / C is 0.2.

Comparative Example 3 700 g of dialkyldiphenyl ether oil and 100 g of pentaerythritol tetraester oil were mixed, and 120 g of lithium 12-hydroxystearate was added thereto, followed by heating to 230 ° C. while stirring. This was poured into a stainless steel container to a thickness of 3 to 5 mm, cooled, and then milled once with three rolls. The one obtained so far was used as a base grease. In a separate container, mix 20 g of dialkyl diphenyl ether oil and 50 g of pentaerythritol oil,
Add 10 g of phenyl-α-naphthylamine to this, and add
Until heated to dissolve. This was added to the base grease, and milling was performed twice with a three-roll mill to obtain a target composition. The weight ratio of dialkyl diphenyl ether oil (B-1) and pentaerythritol oil (C-1), that is,
B / C is 4.8.

Comparative Example 4 120 g of lithium 12-hydroxystearate was added to 800 g of dialkyldiphenyl ether oil, and the mixture was heated to 230 ° C. while stirring. This is poured into a stainless steel container to a thickness of 3 to 5 mm and cooled.
Milling was performed twice. The one obtained so far was used as a base grease. In a separate container, take 70 g of dialkyl diphenyl ether oil, and add phenyl-α-naphthylamine 1
0 g was added and heated to 100 ° C. This was added to the base grease, and milling was performed twice with a three-roll mill to obtain a target composition. In addition, it is out of the range because the ester synthetic oil is not used.

Comparative Example 5 626 g of pentaerythritol tetraester oil, di-2
-Mix 174 g of ethylhexyl sebacate oil, add 12
-Lithium hydroxystearate 120g was added and heated to 230 ° C with stirring. This was poured into a stainless steel container to a thickness of 3 to 5 mm, cooled, and then milled once with three rolls. The one obtained so far was used as a base grease. In a separate container, take 70 g of pentaerythritol oil, and add phenyl-α-naphthylamine 1
0 g was added and heated to 100 ° C. to dissolve. This was added to the base grease and milled twice with three rolls.
The desired composition was obtained. In addition, since a dialkyl diphenyl ether oil was not used, it is out of the range.

The performance of the greases of Examples 1 to 6 and Comparative Examples 1 to 5 was evaluated by the following measurement method, and the obtained results are also shown in Table 1.

Measurement method (a) Consistency Measure in accordance with JIS K 2220 5.3.

(B) Dropping point Measure according to JIS K 2220 5.4.

(C) Grease life test The ASTM D1741 grease life test method shown below is used.

Fill a 6 g grease into a deep groove ball bearing (6306) with an inner diameter of 30 mm, rotate at 3,500 rpm, and load radially 11.3 kg f (25 Lb
f), Thrust load 18.1kg f (40Lbf), 20 at specified temperature
Cycle operation with time operation and 4 hours pause is performed. The life is judged when the motor is overloaded, when the bearing temperature exceeds the set temperature by 10 ° C or more, or when abnormal noise continues for 10 minutes or more, the life is judged and the test is terminated.

(D) Low temperature torque test Measure in accordance with JIS K 2220 5.14.

(Effect of the Invention) The grease composition of the present invention comprises 5 to 30% by weight of an alkali metal salt or an alkaline earth metal salt of the component (A), an ether synthetic oil of the component (B) and an ester of the component (C). As can be seen from the results shown in Table 1, the mixed base oil composed of 70 to 95% by weight of the mixed base oil composed of the base synthetic oil and It was confirmed that it has a long life and also has excellent low-temperature performance.

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Claims (1)

(57) [Claims] (A) An alkali metal or alkaline earth metal hydroxide synthesized from a higher fatty acid having 10 or more carbon atoms or a higher hydroxy fatty acid having 10 or more carbon atoms having at least one hydroxyl group. 5 to 30% by weight of an alkali metal salt or an alkaline earth metal salt, and (B) an ether synthetic oil called an alkyl diphenyl ether having a structure in which an aromatic ring, which is a kind of synthetic lubricating oil, is bonded by an oxygen atom; A diester-based synthesis represented by the following general formula: R ₁ OCO (CH ₂ ) _n COOR ₂ (wherein R ₁ and R ₂ represent an aliphatic hydrocarbon group having 3 to 18 carbon atoms, and n represents 3 to 12) oil, the general formula _{C 2 H 5 C (CH 2} OCOR) 3 ( R in formula represents an aliphatic hydrocarbon group having 3 to 10 carbon atoms)
A triester synthetic oil represented by the following general formula C (CH ₂ OCOR) ₄ (R in the formula represents an aliphatic hydrocarbon group having 3 to 10 carbon atoms)
The following general formula C (CH ₂ OCOR) ₃ CH ₂ OCH ₂ C (CH ₂ OCOR) ₃ (wherein R represents an aliphatic hydrocarbon group having 3 to 10 carbon atoms) )
And a mixture with at least one ester synthetic oil selected from the group consisting of dipentaerythritol synthetic oils and other neopentyl polyol ester synthetic oils represented by the formula: A grease composition comprising 70 to 95% by weight of a mixed base oil in which a mixing ratio of an ester synthetic oil of component (C) is more than 0.2 and not more than 4.5 by weight.