JP7075877B2 - Grease composition - Google Patents

Description

The present invention relates to a grease composition, and more particularly to a grease composition suitable for a sealed lubricated portion or the like.

Grease compositions used in industrial machinery and the like are lubricants in which fine solids called thickeners are dispersed in a lubricating oil base oil to make them semi-solid, and the thickeners include lithium salts and calcium salts. In addition to alkali metal soaps such as alkali metal soaps, urea resins, fluororesins and melamine resins, inorganic substances such as silica gel and Benton are known.

The thickener to be added to the lubricating oil base oil is used properly according to the use and environment of the grease composition.

For example, Japanese Patent Application Laid-Open No. 2014-194226 of Patent Document 1 describes a grease composition for a resin in which lithium soap and styrene isoprene resin are added to polyalphaolefin oil, and Japanese Patent Application Laid-Open No. 2007-297422 of Patent Document 2 describes. It is described that the wear resistance and fatigue resistance are improved by containing a fluorine-based surfactant and a styrene-based block copolymer in a grease composition containing a base oil and a thickener.

Further, in Japanese Patent Application Laid-Open No. 7-11276 of Patent Document 3, a grease composition obtained by adding a thickener and a hydrogenated styrene-isoprene block copolymer to a lubricating oil has good water resistance and adhesiveness, and is low. It is stated that it has good pump operability at temperature.

Further, Japanese Patent Application Laid-Open No. 2002-327188 of Patent Document 4 states that separation of the lubricating oil component of the grease composition can be prevented by using a styrene-based block copolymer having an isoprene block as an alkaziene as a thickener. Have been described.

Japanese Unexamined Patent Publication No. 2014-194276 Japanese Unexamined Patent Publication No. 2007-297422 Japanese Unexamined Patent Publication No. 7-11276 Japanese Unexamined Patent Publication No. 2002-327188

However, the lubricant composition described in Patent Document 4 has low weather resistance and heat aging resistance, and its consistency is liable to change. Therefore, it is softened by use and difficult to apply to a sealed lubricating portion or the like.

The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a grease composition in which the lubricating oil component is not separated and the consistency change is small over a long period of time. There is something in it.

As a result of diligent studies to achieve the above object, the present inventor has used only a chemically stable hydrogenated styrene-isoprene block copolymer as a thickener without using metal soap or the like. , The present invention has been completed by finding that the above object can be achieved.

That is, the above problem is solved by the following (1) to (3) of the present invention.
(1) Lubricating oil Containing base oil and thickener,
The thickener consists only of a block copolymer represented by the following structural formula.
A grease composition characterized in that the styrene content of the block copolymer is 35 to 36% by mass and the average molecular weight is 90,000 to 120,000.

但し、上記構造式中ｌ、ｍは、繰り返し数を表わす整数を表わす。
（２）上記増ちょう剤を１０～３０質量％含有することを特徴とする（１）に記載のグリース組成物。
（３）上記潤滑油基油の粘度指数（ＶＩ）が１０～１４０であることを特徴とする（１）又は（２）に記載のグリース組成物。

However, in the above structural formula, l and m represent integers representing the number of repetitions.
(2) The grease composition according to (1), which contains 10 to 30% by mass of the thickener.
(3) The grease composition according to (1) or (2), wherein the lubricating oil base oil has a viscosity index (VI) of 10 to 140.

According to the present invention, since only the hydrogenated styrene-isoprene block copolymer is used as the thickener, it is possible to provide a grease composition having a small change in consistency over a long period of time.

The grease composition of the present invention will be described in detail.
The grease composition contains a lubricating oil base oil and a thickener, and the thickener comprises only a hydrogenated styrene-isoprene block copolymer represented by the following structural formula.

但し、上記構造式中、ｌ、ｍは、繰り返し数を表わす整数を表わす。

However, in the above structural formula, l and m represent integers representing the number of repetitions.

The thickener holds the liquid lubricating oil base oil in a three-dimensional network structure and turns the lubricating oil base oil into a semi-solid gel.

The present invention uses a hydrogenated styrene-isoprene block copolymer having a hard segment polystyrene block and a soft segment hydrogenated polyisoprene block and having a styrene content of 35 to 36% by mass as a thickener. ..

The polystyrene block is rigid, has a high glass transition temperature (Tg), acts as a physical cross-linking point where molecular chains are entangled at Tg or less, and makes the structure of the entire thickener like a three-dimensional network structure to be a lubricating oil group. Holds oil.

In addition, the hydrogenated polyisoprene in the soft segment increases the molecular weight between the entanglement points of the entire thickener to improve the oil absorbency of the lubricating oil base oil, and the methyl group in the side chain causes the molecular movement of the soft segment itself. It is suppressed, and in combination with the above polystyrene block, the thickener exhibits appropriate flexibility and improves shear stability.

Further, since the soft segment has a very stable structure containing no unsaturated bond, it has excellent weather resistance and heat aging resistance, and the change in the consistency of the grease composition can be extremely reduced over a long period of time. ..

If the styrene content of the thickener is less than 35% by mass, the holding power of the lubricating oil base oil is lowered, and the lubricating oil base oil cannot be absorbed and is easily separated. If it exceeds 36% by mass, the grease composition The fluidity of the

The thickener has a mass average molecular weight of 90,000 to 120,000, preferably 90,000 to 110,000, and more preferably 90,000 to 100,000. When the mass average molecular weight is less than 90,000, even if the content is increased, a semi-solid gel state is not formed and thixotropic property is not exhibited. Further, when the mass average molecular weight exceeds 120,000, it becomes difficult to absorb the lubricating oil base oil, and even if the lubricating oil base oil is absorbed by heating, the shear stress required to cause the flow of the grease composition, That is, the yield stress increases and the fluidity decreases.

When the mass average molecular weight of the hydrogenated styrene-isoprene block copolymer is 90,000 to 100,000, it can be greased by mixing with the lubricating oil base oil without heating and stirring, and the lubricating oil group by heating can be obtained. It is preferable because it can prevent deterioration of oil. Further, when the hydrogenated styrene-isoprene block copolymer is in the form of powder, grease formation becomes easier.

Examples of the hydrogenated styrene-isoprene block copolymer that can be used as the thickener include Septon 1001 and Septon 1020 (both manufactured by Kuraray).

The grease composition of the present invention preferably contains the above-mentioned thickener in an amount of 10 to 30% by mass, more preferably 15% by mass to 25% by mass.
If the content of the thickener is less than 10% by mass, the thickening property required for a grease thickener cannot be obtained, and the viscosity of the lubricating oil base oil remains increased and the function is not sufficiently satisfied. If it exceeds 30% by mass, the grease composition becomes too hard, which causes problems in lubricity and commercialization.

As the lubricating oil base oil, vegetable oils and the like can be used in addition to conventionally known synthetic oils and mineral oils used as grease compositions.

Examples of the synthetic oil include poly-α-olefin, ethylene-α-olefin oligomer, diester, polyol ester, alkyldiphenyl ether, polyphenyl ether, liquid paraffin and the like, and examples of the vegetable oil include castor oil and rapeseed oil. Can be mentioned.

The lubricating oil base oil preferably has a viscosity index (VI) of 10 to 140. Specifically, when the lubricating oil base oil is a mineral oil, the kinematic viscosity at 40 ° C is 5 cst to 500 cst, when the kinematic viscosity at 100 ° C is 2 cst to 40 cst, and when it is a synthetic oil, the kinematic viscosity at 40 ° C. Is 30 cst to 1300 cst, and the kinematic viscosity at 100 ° C. is 5 cst to 130 cst.

The grease composition may be used as an antioxidant, a rust preventive, an extreme pressure agent, an anti-wear agent, a defoaming material, a cleaning dispersant, a viscosity index improver, an emulsifier, a pour point lowering agent, and a corrosion inhibitor, if necessary. Etc. may be contained.

The grease composition can be produced by a conventionally known method. Specifically, it can be produced by mixing a lubricating oil base oil and a thickener, and if necessary, heating the thickener to a temperature equal to or higher than the glass transition temperature of the thickener and stirring the mixture.

The above grease composition can be used for lubricating parts such as drive parts and bearing parts of all industrial machines such as automobile industry, steel industry, electric industry, robot industry, aviation industry, medical care, food industry, etc. Since there is no separation and the change in consistency is small over a long period of time, it can be particularly preferably used for sealed lubricated parts where maintenance is difficult.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

[Example 1]
As a thickener, a hydrogenated styrene-isoprene block copolymer (Septon 1020, manufactured by Claret: styrene content 36% by mass, average molecular weight 95000, JIS A hardness 70) represented by the following structural formula SEP in powder form is used. It was mixed with each of three types of lubricating oil base oils of mineral oil, polyα-olefin, and ester oil so as to have a molecular weight of 15% by mass, stirred and dispersed at room temperature, and then rolled to obtain three types of grease compositions.
Table 1 shows the viscosities and viscosity indexes of mineral oils, polyα-olefins and ester oils.

但し、上記構造式ＳＥＰ中、ｌ、ｍは、繰り返し数を表わす整数を表わす。

However, in the above structural formula SEP, l and m represent integers representing the number of repetitions.

[Example 2]
As a thickener, a pelletized hydrogenated styrene-isoprene block copolymer represented by the above structural formula SEP (Septon 1001, manufactured by Claret: styrene content 35% by mass, average molecular weight 114000, JIS A hardness 80) is used. Mix each with 3 types of lubricating oil base oils of mineral oil, poly α-olefin, and ester oil so as to be 15% by mass, heat to 80 ° C., stir and disperse, and then roll to obtain 3 types of grease compositions. Obtained.

[Reference Example 1]
15 mass of hydrogenated styrene-isoprene-styrene block copolymer (Septon 2004, manufactured by Claret: styrene content 18% by mass, average molecular weight 80,000, JIS A hardness 67) represented by the following structural formula SEPS in pellet form. It was mixed with three types of lubricating oil base oils, mineral oil, poly α-olefin, and ester oil so as to be%, heated to 50 ° C., and stirred, but lubricated with the hydrogenated styrene-isoprene-styrene block copolymer. It was separated from the oil-based oil and could not be rolled, and none of the three types of lubricating oil-based oil could be greased.

但し、上記構造式ＳＥＰＳ中、ｌ、ｍ、ｎは、繰り返し数を表わす整数を表わす。

However, in the structural formula SEPS, l, m, and n represent integers representing the number of repetitions.

[Reference Example 2]
15 mass of pellet-shaped hydrogenated styrene-isoprene-styrene block copolymer (Septon 2104, manufactured by Claret: styrene content 65% by mass, average molecular weight 70,000, JIS A hardness 98) represented by the above structural formula SEPS. It was mixed with three types of lubricating oil base oils, mineral oil, poly α-olefin, and ester oil so as to be%, heated to 50 ° C., and stirred, but lubricated with the hydrogenated styrene-isoprene-styrene block copolymer. It was separated from the oil-based oil and could not be rolled, and none of the three types of lubricating oil-based oil could be greased.

[Reference Example 3]
Hydrogenated styrene-poly (ethylene isoprene) block-styrene block copolymer represented by the following structural formula SEEPS in powder form (Septon 4033, manufactured by Claret: styrene content 30% by mass, average molecular weight 70,000, JIS A hardness 76) was mixed with three types of lubricating oil base oils, mineral oil, poly α-olefin, and ester oil so as to be 15% by mass, heated to 50 ° C., and stirred, but hydrogenated styrene-poly (ethylene isoprene) was added. ) The block-styrene block copolymer and the lubricating oil base oil were separated and could not be rolled, and none of the three types of lubricating oil base oil could be greased.

但し、上記構造式ＳＥＥＰＳ中、ｉ、ｋ、ｌ、ｍ、ｎは、繰り返し数を表わす整数を表わす。

However, in the structural formula SEEPS, i, k, l, m, and n represent integers representing the number of repetitions.

[Reference example 4]
Hydrogenated styrene-poly (ethylenebutylene) block-styrene block copolymer represented by the following structural formula SEBS in powder form (Septon 8004, manufactured by Kuraray Co., Ltd .: styrene content 31% by mass, average molecular weight 90,000, JIS A hardness 80) was mixed with three types of lubricating oil base oils, mineral oil, poly α-olefin, and ester oil so as to be 15% by mass, heated to 50 ° C., and stirred, but hydrogenated styrene-poly (ethylene butylene) was added. ) The block-styrene block copolymer and the lubricating oil base oil were separated and could not be rolled, and none of the three types of lubricating oil base oil could be greased.

但し、上記構造式ＳＥＢＳ中、ｉ、ｋ、ｌ、ｍ、ｎは、繰り返し数を表わす整数を表わす。

However, in the structural formula SEBS, i, k, l, m, and n represent integers representing the number of repetitions.

[Comparative Example 1]
As a thickener, the lithium soap is mixed with three types of lubricating oil base oils, mineral oil, poly-α-olefin, and ester oil so as to be 15% by mass, heated and stirred at 200 ° C., cooled, and then rolled. The treatment gave three kinds of grease compositions.

[Comparative Example 2]
After reacting the primary amine and diisocyanate with each of the three types of lubricating oil base oils, mineral oil, polyα-olefin, and ester oil, heat-dispersed and cooled so that the urea-based thickener becomes 15% by mass. , Roll treatment to obtain three kinds of grease compositions.

<Evaluation>
The change in immiscible consistency of the grease compositions of Examples 1 and 2 and Comparative Examples 1 and 2 at room temperature (25 ° C.) was measured by the shell roll method of ASTM D 1831 standard.
For Example 1, the change in consistency when 30% of water was mixed was also measured.
The evaluation results are shown in Table 2.

The grease composition of the present invention showed adhesiveness and stickiness even after 100 hours.
Further, from Table 1, the grease composition of the present invention has a small change in consistency over a long period of time and is highly durable as compared with a grease composition using a metal soap or the like as a thickener. It can be seen that it can be suitably used for.

Claims (3)

Lubricating oil Contains base oil and thickener,
The thickener consists only of a block copolymer represented by the following structural formula.
A grease composition characterized in that the styrene content of the block copolymer is 35 to 36% by mass and the average molecular weight is 90,000 to 120,000.

However, in the above structural formula, l and m represent integers representing the number of repetitions. The grease composition according to claim 1, wherein the grease composition contains 10 to 30% by mass of the thickener. The grease composition according to claim 1 or 2, wherein the lubricating oil base oil has a viscosity index (VI) of 10 to 140.