JP2012188530A - Grease composition for resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grease composition excellent in abrasion resistance when being applied to a resin sliding part, and to provide the grease composition that can improve especially the abrasion resistance of a PTFE resin sliding part especially.SOLUTION: The grease composition used at a resin sliding part includes: at least one base oil chosen from mineral lubricant base oils and synthesis lubricant base oils having 1-2,000 mm/s of a kinematic viscosity at 40°C; a thickener; and 1-20 mass% of a calcium fluoride powder.

Description

  The present invention relates to a grease composition for a resin excellent in wear resistance that can be applied to a lubricated portion of a resin sliding portion such as a bearing or a gear using a resin.

  The grease composition applied to resin sliding parts such as bearings and gears using resin reacts with the metal surface even if an extreme pressure additive such as ZnDTP sulfur and phosphorus forming a lubricating film is added. For example, since a lubricating effect cannot be expected, a solid lubricant is usually blended. As a solid lubricant used in such a grease composition for a resin, polytetrafluoroethylene resin (hereinafter sometimes referred to as “PTFE resin” or “PTFE”) powder is most frequently used (Patent Documents). 1, see Patent Document 2.). In addition, a technique in which a solid lubricant such as boron nitride or graphite is blended has been developed (see Patent Document 3).

  By the way, although sliding characteristics differ depending on the type of resin, PTFE resin and high-density polyethylene resin (hereinafter sometimes referred to as “high-density PE resin”) are particularly excellent in low-friction properties. Is used for sliding parts. These resins have a mechanism showing a low friction property by taking a molecular orientation during friction and then peeling (wearing) the surface layer as small pieces. However, if the peeled wear powder increases too much, the grease may harden and the original performance may not be fully exhibited. Therefore, it is important to suppress the wear of the resin in a place where such a resin is used, and a grease composition for a resin having a further excellent effect of suppressing the wear of the resin is desired.

As such a resin grease, a resin grease composition (Patent Document 3) containing a compound powder having a layered structure such as boron nitride and graphite and a PTFE resin powder in a specific ratio has already been developed. The effect of improving the wear resistance in the PTFE resin and the high density PE resin sliding portion has been confirmed. However, this technique improves the friction characteristics of the PBT resin as well as the wear resistance of the PTFE resin and the high density PE resin, and improves the wear resistance of the resin such as the PTFE resin and the high density PE resin. When focusing only on, further improvement was desired.

JP 2001-89778 A JP 2005-247971 A JP 2009-221307 A

  An object of the present invention is to provide a grease composition having excellent wear resistance when applied to a resin sliding portion, and in particular, to improve the wear resistance of a PTFE resin sliding portion. An object of the present invention is to provide a grease composition that can be used.

As a result of intensive studies to achieve the above object, the present inventors have found that the wear resistance of the resin grease composition can be improved by containing 1 to 20% by mass of calcium fluoride powder. The headline and the present invention were completed.

That is, the present invention relates to at least one base oil selected from mineral oil base oils and synthetic base oils having a kinematic viscosity at 40 ° C. of 1 to 2000 mm ² / s, a thickener, and calcium fluoride. Provided is a resin grease composition for use in a resin sliding portion, which contains 1 to 20% by mass of a powder.

The present invention also provides a resin grease composition characterized in that the resin grease composition further contains 5 to 30% by mass of polytetrafluoroethylene resin powder.
The present invention also provides a resin grease composition characterized in that the thickener in the resin grease composition is a scaly particulate lithium soap thickener.
The present invention also provides the resin grease composition, wherein the base oil is a silicone oil.
The present invention also provides the resin grease composition, wherein the resin sliding portion is a sliding portion using a polytetrafluoroethylene resin or a high-density polyethylene resin.

  The grease composition for resin of the present invention is excellent in the abrasion resistance of the resin in the resin sliding portion. Therefore, the resin grease composition of the present invention is extremely useful in practice.

(1) Base oil The base oil used in the present invention includes various lubricating base oils such as mineral lubricating base oils, synthetic lubricating base oils, or mixtures thereof that are usually used in grease. While used, the value of kinematic viscosity at 40 ° C. is preferably 1~2000mm ² / s, more preferably 5~1500mm ² / s, more preferably 10~1500mm ² / s, still more preferably 110 to 1300mm was ² / s, particularly preferably 150~1200mm ² / s. If the kinematic viscosity is less than 1 mm ² / s, the wear resistance tends to be low. When the kinematic viscosity is larger than 2000 mm ² / s, the fluidity is deteriorated and the inherent performance of the grease tends to be difficult to be obtained.
Examples of the mineral oil base oil include those obtained by refining a lubricating oil fraction of crude oil by one of various purification methods such as solvent refining and hydrorefining, or by appropriately combining two or more.

  Examples of synthetic lubricating base oils include carbons such as α-olefin oligomers, polymers of α-olefins having 3 to 12 carbon atoms, sebacates such as 2-ethylhexyl sebacate, dioctyl sebacate, azelate, and adipate. Dialkyl diesters having 4 to 12 carbon atoms, 1-trimethylolpropane, polyols including esters obtained from pentaerythritol and monobasic acids having 3 to 12 carbon atoms, and alkylbenzenes having an alkyl group having 9 to 40 carbon atoms Polyglycols such as polyglycol obtained by condensing butyl alcohol with propylene oxide, phenyl ethers such as polyphenyl ether having about 2 to 5 ether chains and about 3 to 6 phenyl groups, dimethyl Polysiloxane, methyl ethyl policy Chain polysiloxane such as loxane, diethylpolysiloxane, methylphenylpolysiloxane, ethylphenylpolysiloxane, diphenylpolysiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexanesiloxane, tetradecamethylcycloheptasiloxane, etc. And a silicone oil such as a modified polysiloxane such as amino-modified polysiloxane, polyether-modified polysiloxane, alkyl-modified polysiloxane, and fluorine-modified polysiloxane. Of these, dimethylpolysiloxane (dimethylsilicone) is particularly preferable.

The mineral oil base oil and the synthetic base oil can be used alone or in combination of two or more, but depending on the type of resin of the sliding part using grease, the base oil Therefore, it is preferable to use an α-olefin oligomer or silicone oil as the resin grease. Moreover, it is particularly preferable to use silicone oil from the viewpoint of wear resistance and heat resistance.
The amount of the base oil can be appropriately selected according to the required characteristics, but is usually in the range of 55 to 98 mass%, preferably in the range of 60 to 95 mass% with respect to the total amount of the grease composition. is there.

(2) Calcium fluoride powder Any calcium fluoride powder may be used in the present invention, and fluorite powder whose main component is calcium fluoride may be used. When fluorite powder is used as the calcium fluoride powder, the calcium fluoride powder content is preferably 95% by mass or more, more preferably 98% by mass or more, and particularly preferably 99% by mass or more.

The average particle size of the calcium fluoride powder is preferably from 0.1 to 25 μm, more preferably from 2.1 to 20 μm, further preferably from 3.0 to 15 μm, particularly preferably from 4.0 to 10 μm.

The lower limit of the content of the calcium fluoride powder with respect to the total amount of the grease composition is 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more. The upper limit of the content of calcium fluoride powder is 20% by mass or less, preferably 15% by mass or less, and more preferably 7% by mass or less. If the blending amount is less than 1% by mass, the predetermined wear resistance cannot be obtained. If the blending amount exceeds 20% by mass, the grease itself becomes hard, resulting in an increase in torque and a shorter life, and relatively less oil content. There is a possibility that the lubricity is partially lowered by the decrease. In addition, the effect tends to be saturated.

(3) PTFE resin powder In the present invention, the abrasion resistance can be further improved by blending the PTFE resin powder. The PTFE resin powder used in the present invention is a typical fluorine-based resin powder. The PTFE resin has a band-like structure as a whole, and the band has a structure called a band structure in which plate-like crystal portions and amorphous portions are alternately arranged in a sandwich shape.

The average particle size of the PTFE resin powder is preferably from 0.1 to 25 μm, more preferably from 1.5 to 20 μm, particularly preferably from 1.9 to 15 μm.

The lower limit of the content of the PTFE resin powder with respect to the total amount of the grease composition is 5% by mass or more, preferably 10% by mass or more, and more preferably 12% by mass or more. The upper limit of the content of the PTFE resin powder is 30% by mass or less, preferably 20% by mass or less, and more preferably 15% by mass or less. Wear resistance can be improved by making a compounding quantity into 5 mass% or more. However, if the blending amount exceeds 30% by mass, the grease itself becomes hard, resulting in an increase in torque and a shortened life, and there is a possibility that the lubricity is partially lowered due to a relatively reduced oil content. . In addition, the effect tends to be saturated.

When PTFE resin powder is used in the present invention, the blending ratio of the calcium fluoride powder and PTFE resin powder is not particularly limited, but from the viewpoint of further improving the wear resistance, calcium fluoride powder and PTFE resin are used. The mass ratio of the powder is preferably 10:90 to 60:40, more preferably 20:80 to 50:50, and particularly preferably 20:80 to 40:60.

(4) Thickener The thickener used in the resin grease composition of the present invention is not particularly limited. For example, a metal soap-based thickener or a composite metal soap usually used as a thickener for grease. Examples of the thickener include polyurea and polyurea. Among these, it is preferable to use a lithium soap thickener.
Examples of the lithium soap-based thickener include aliphatic carboxylic acid lithium salts having a hydroxyl group such as lithium-12-hydroxystearate, aliphatic carboxylic acid lithium salts such as lithium stearate, and mixtures thereof. From the viewpoint of safety, lithium stearate is particularly preferable.

  Further, the lithium soap-based thickener is usually mixed with a scaly particulate lithium soap in a solvent composed of a base oil, heated to around 200 ° C., dissolved in the base oil, and then cooled. The lithium soap-based thickener itself is produced in a fibrous form by crystallization, so-called recrystallization. In the present invention, however, the fibrous lithium soap system is used from the viewpoint of improving friction characteristics. It is preferable to use a flaky particulate lithium soap thickener dispersed in a base oil at around 90 to 150 ° C., not a thickener. At this time, the temperature for stirring and dispersing the scaly particulate lithium soap in the base oil is preferably 90 to 150 ° C, more preferably 90 to 140 ° C, and still more preferably 95 to 130 ° C. It is. If the temperature is too low, the dispersibility of lithium soap in the base oil tends to be reduced. Further, if the temperature is too high, a part of the lithium soap may become fibrous, and there is a possibility that a predetermined scaly particulate lithium soap thickener cannot be formed.

The thickener used in the grease composition for resin of the present invention imparts consistency to the present invention, and the preferred blending amount is 5 to 50% by mass, more preferably 10%, based on the total amount of the grease composition. -40 mass%. When the blending amount is 5% by mass or more, the friction characteristics tend to be good. Moreover, it exists in the tendency for the lifetime of product grease to become favorable because a compounding quantity shall be 50 mass% or less.
The grease composition for resin of the present invention is produced by blending the above components, base oil and thickener, and various additives can be blended as necessary. .

(5) Other additives Examples of additives include metal detergents such as alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates; alkenyl succinimides and alkenyl succinimide boronation modifications Various types of anti-wear agents such as zinc, sulfur, phosphorus, amine and ester; polymethacrylate, ethylene propylene copolymer, styrene-isoprene copolymer, styrene-isoprene copolymer Viscosity index improvers such as hydrides of poly and polyisobutylene; alkylphenols such as 2,6-di-tert-butyl-p-cresol, 4,4′-methylenebis- (2,6-di-t-butylphenol) Bisphenols such as n-octadecyl-3- (4′-hydroxy-3 ′, 5′-di tert-butylphenol) various antioxidants such as phenolic compounds such as propionate, aromatic amine compounds such as naphthylamines and dialkyldiphenylamines; extreme pressure agents such as sulfurized olefins and sulfurized fats and oils; carboxylic acids such as stearic acid, dicarboxylic acids And various rust inhibitors such as metal soaps, carboxylic acid amine salts, heavy sulfonic acid metal salts, carboxylic acid partial esters of polyhydric alcohols; and various corrosion inhibitors such as benzotriazole and benzimidazole. An additive can be used individually by 1 type or in combination of 2 or more types.

(6) Applications The grease composition for resins of the present invention can be used for sliding parts using various resins, but after the molecular orientation is taken during friction, the surface layer is peeled off as small pieces (wear). By doing so, it can be preferably applied to a resin having properties exhibiting low friction, and can be suitably used particularly for a sliding portion of PTFE resin or high-density PE resin.

  Next, the present invention will be specifically described with reference to examples. In addition, this invention is not limited at all by these Examples.

(Examples 1-7 and Comparative Examples 1-6)
In Examples and Comparative Examples, grease compositions containing the following * 1 to * 7 components in the proportions (mass) shown in Table 1 were prepared. The grease composition was prepared by appropriately mixing each component of * 1 to * 7 and milling to uniformly disperse the thickener in the grease. Specifically, the base oil, solid lubricant and other additives and lithium-stearate in the table are simultaneously charged into a heat-resistant container, and the lithium-stearate is sufficiently stirred and dispersed at about 100 ° C. By performing the treatment, a grease composition was prepared by mixing and dispersing scaly particles of lithium stearate in the base oil.
Each of the obtained grease compositions was evaluated for abrasion resistance of the resin.

* 1: Lithium stearate (“S-7000” manufactured by Sakai Chemical Co., Ltd.)
* 2: Silicone oil (40 ° C. kinematic viscosity: 380 mm ² / s dimethyl silicone (dimethylpolysiloxane))
* 3: Calcium fluoride powder (fluorite powder, Sankyo Seimitsu Co., Ltd., “HO- # 100”, average particle size 6.5 μm, calcium fluoride powder content 99 mass% or more)
* 4: Boron nitride powder (manufactured by Denki Kagaku Kogyo Co., Ltd., “GP”, average particle size 1.5 μm)
* 5: PTFE resin powder with an average particle size of 2.0 μm * 6: Antioxidant (amine antioxidant)

(Measuring method)
Abrasion resistance test It was carried out using a Falex friction tester. In the test, 0.5 g of grease was applied to the PTFE resin sliding part using a steel pin and a PTFE resin block, and the test was run for 5 minutes at a pinning speed of 500 rpm and a temperature of steadily with a tightening load of 50 N. Then, this operation was performed at 100 N for 55 minutes. Evaluation was made by measuring the weight loss (wear amount) of the block before and after the test.

Claims (5)

1 to 20 masses of at least one base oil selected from mineral oil base oils and synthetic base oils having a kinematic viscosity at 40 ° C. of 1 to 2000 mm ² / s, and a thickener and calcium fluoride powder. %. Grease composition for resin used in resin sliding part, characterized by comprising:   The resin grease composition according to claim 1, comprising 5 to 30% by mass of polytetrafluoroethylene resin powder. The resin grease composition according to claim 1 or 2, wherein the thickener in the resin grease composition is a scaly particulate lithium soap thickener. The grease composition for resin according to any one of claims 1 to 3, wherein the base oil is silicone oil. The resin grease composition according to any one of claims 1 to 4, wherein the resin sliding portion is a sliding portion using a polytetrafluoroethylene resin or a high-density polyethylene resin.