JPS6113519B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel grease composition for brakes or clutches, and in particular to a grease composition suitably used for lubricating and rust-preventing the sliding parts of automobile brake or clutch systems. The sliding parts of automobile brake systems include the pistons and cylinder bodies in wheel cylinders, mass cylinders, and disc brakes, and the sliding parts of automobile clutch systems include the pistons and cylinder bodies of clutch master cylinders, clutch relay cylinders, etc. Cylinder body is available. Such sliding parts are usually placed in harsh environments and are required to operate accurately even in such harsh environments. This will be explained in more detail using a foil cylinder as an example. The wheel cylinder receives the hydraulic pressure of the brake fluid generated in the master cylinder and converts it into a force that pushes and expands the brake shoe, and is composed of a cylinder body, a piston, a piston cup, and a boot. Aluminum castings are generally used for cylinder bodies from the viewpoints of strength, friction characteristics, and weight reduction, but aluminum castings are easily damaged if the lubricity of grease deteriorates. Cast iron is also commonly used for large vehicles. Generally, pistons are made of SC material galvanized and then chromate treated, or made of SC material with a triiron tetroxide (Fe ₃ O ₄ ) film formed on it. The chromate treatment film peels off quickly due to incomplete application of grease that does not take into account the relationship between White rust occurs on plating, and red rust occurs on those that have formed a triiron tetroxide film. This rust becomes foreign matter and precipitates, causing abnormal wear on the cup and causing liquid leakage. Styrene-butadiene rubber is generally used as the material for the piston cup due to its resistance to brake fluid, but if heat resistance is required, ethylene-butadiene rubber is used.
A propylene-diene copolymer is used, and the shape of the piston cup has a large effect on the sealing effect. Styrene-butadiene rubber, chloroprene rubber, etc. are generally used for boots. Brake fluid must be chemically stable and do not undergo deterioration or precipitation during storage or use, pistons, cylinder bodies, and rubber products (piston cups).
It has a low freezing point, a high boiling point, does not corrode the piston cup (no corrosion, expansion, hardening, etc.), does not corrode metals, and has no hygroscopicity. Various conditions are required, such as being small and not causing separation or precipitation even if moisture enters. The composition of brake fluids generally consists of a non-mineral oil base, a solvent, and additives. Conventionally, castor oil has been used as a base agent, but polyglycols are now generally used from the viewpoints of heat resistance, cold resistance, and water resistance. The solvent adjusts the viscosity of the base agent, gives the brake fluid a desired boiling point, and at the same time maintains appropriate rubber swelling properties. Usually alcohols, glycols, and glycol ethers are used. Additives prevent brake fluid from oxidizing and provide anti-rust properties, including quinones,
Amines, phenols, etc. are mainly used, but some inorganic salts may also be used. Vapor lock is fatal to brake fluid, so its boiling point is of particular importance. In a wheel cylinder, the sliding part of the piston is located through one piston cup, one on the brake fluid side to receive hydraulic pressure, and the other in the atmosphere, and the piston slides inside the cylinder with a clearance of around 100μ. . Furthermore, most of the inner surface of the cylinder and the sliding surface of the piston are exposed to the atmosphere and are covered with only one rubber boot. However, the boots are made of rubber, and this member is exposed to extremely high temperatures due to the heat generated by friction during brake operation, which causes permanent deformation over time, which reduces the initial interference and reduces sealing performance. Moreover, since the suspension of the brake is a rotating body, it is structurally impossible to completely seal the inside of the brake, so rainwater, mud, dust, melted snow, melting snow salt, etc. cannot be avoided, and such intrusion water etc. The surface of the piston that is in contact with the boot corrodes due to moisture and moisture, further reducing the sealing performance. Also, when adjusting the shoe clearance using the adjuster screwdriver, it is possible to inadvertently puncture the boot with the tip of the screwdriver. As described above, the sealing performance of the boot is extremely unreliable, and if the sealing performance of the boot deteriorates, problems such as decreased lubricity and sticking of the piston will occur. Brake fluid leakage depends on the sealing performance of the lip of the piston cup, and many experiments have shown that if even a single hair gets caught, it will stop at low normal pressures (10 to 20 kg/kg).
^cm2 ) Causes liquid leakage. Furthermore, due to the reduced sealing performance of the boot, the foil cylinder becomes more susceptible to the unfavorable environment in which it is placed, which promotes the wear of sliding parts and the generation of rusting foreign matter.
As a result of these, and furthermore, the piston cup is damaged and fluid leaks due to the striations in the cylinder caused by the shifting of the piston during braking. Currently, there is no lubricant that can prevent the above-mentioned deterioration phenomena over time in foil cylinders, and we have no choice but to use various greases containing various thickening agents in fatty oil. , it is still far from being sufficient. For example, using castor oil, which has excellent rubber swelling properties, as a base oil,
Metallic soap greases containing other additives such as rust preventives and antioxidants are widely used.
This grease has poor water resistance and tends to generate crystalline foreign matter when it comes into contact with brake fluid.
In addition, the brakes may soften and leak under high temperatures during brake operation.
Due to lack of heat resistance, it cannot withstand high temperatures sufficiently and causes carbonization, which is one of the causes of trouble.
It's becoming one. In addition, this grease lacks stability due to the presence of carbon-carbon double bonds in the castor oil molecules used as the base oil.
There remains the problem of hardening over time during long-term storage or use. Furthermore, compatibility with brake fluid,
It has disadvantages such as poor compatibility. However, the present inventors have conducted intensive research to develop a brake or clutch grease that can overcome the drawbacks of the conventional brake grease and prevent the above-mentioned deterioration phenomenon over time in wheel cylinders, etc., and as a result, they have developed the present invention. I have completed my invention. That is, the present invention comprises a base oil, a thickening agent, a rust preventive agent, an antioxidant, and an antioxidant aid, and the base oil has the general formula: (In the formula, k is an integer of 1 to 5, m and n are 2 to
5 integer, x and y are positive integers, where -C _n
When the H _2n O- group and the -C _o H _2o O- group are the same,
one of x and y is zero), the polyoxyalkylene triol has an average molecular weight of 200 to 6000, and the thickening agent consists of lithium 12-oxystearate alone or mainly, The rust inhibitor is composed of at least one selected from the group consisting of calcium salts of sulfonic acids, calcium salts of lanophosphate, and calcium salts of oxidized waxes, and more preferably the antioxidant is phenyl-α-naphthylamine, phenyl-β-
Naphthylamine, 2,2'-4'-trialkyldiphenylamine, 4-octyldiphenylamine,
2,2,4-trimethyl-1,3-dihydroquinoline, 4,4'-dioctyldiphenylamine,
4,4'-Butylidene-bis(6-tert-butyl-
3-methylphenol), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxylpenzyl)benzene and 2,5-dimercapto-1,3, The present invention relates to a grease composition for brakes or clutches, comprising at least one member selected from the group consisting of 4-thiadiazole, and characterized in that the antioxidant auxiliary agent is methylphenyl polysiloxane. The grease composition of the present invention uses the above specific polyoxyalkylene triol alone as a base oil, uses lithium 12-oxystearate as a thickening agent, and uses the above specific calcium salt rust preventive agent as a rust preventive agent. More preferably, the specific compound is used as the antioxidant and silicone oil is used as the antioxidant aid. The present invention provides that the specific base oil has optimal rubber swelling properties, excellent low-temperature fluidity, heat resistance, and water resistance, does not react with brake fluid, and has high metal rust prevention properties. The lithium 12-oxystearate used as a thickening agent has an excellent effect of stabilizing the network structure, the specific base oil and the specific calcium salt-based rust inhibitor, and the specific antioxidant. It was discovered that excellent antirust properties can be achieved without impairing the other properties of a grease by combining it with an antioxidant aid, and this has been completed. That is, it is important to use the above-mentioned specific polyoxyalkylene triol as the base oil, and this can be prepared, for example, by the general formula: C _k H _2k+1 O-(C _n C _2n O _x C _o H _2o O-) _y H (formula polyoxyalkylene monoalkyl ether (with an average molecular weight of about 300 to 27,000) or the general formula: (In the formula, l is an integer of 2 to 5, and m, n, x and y are the same as above.) When polyoxyalkylene diol (having an average molecular weight of about 200 to 6000) is used alone, The quality performance of the grease will be poor, especially the compatibility with brake fluid, compatibility, and water resistance. In addition, in the present invention, it has been found that in the case of grease, the effect of adding additives, particularly rust preventives, is greatly influenced by the composition of the base oil. It was discovered that excellent rust prevention properties can only be achieved when a salt-based rust preventive agent is used. Various types of rust preventive agents are used for grease, but for example, barium salts, sodium salts of sulfonic acids, or amine rust preventive agents can be used in combination with the above-mentioned specific base oils to prevent rust. It has no effect at all,
It may cause the opposite effect. As described above, the grease composition of the present invention comprising the above-mentioned specific base oil, thickener, rust inhibitor, antioxidant, and antioxidant aid has excellent performance as a brake or clutch grease.
Excellent lubrication performance can be maintained for a long period of time even under severe conditions in the sliding parts of brakes and clutches, thereby preventing the above-mentioned deterioration phenomenon over time in wheel cylinders and the like. The base oil in the grease composition of the present invention is a polyoxyalkylene triol represented by the general formula (). In the general formula (),
Examples of the group represented by -C _n H _2n or -C _o H _2o - include ethylene, propylene, trimethylene, butylene, pentylene, tetramethylene, and pentamethylene. In the general formula (),

The group represented by [Formula] is propane-1,2,3
- Examples include triyl. Specific examples of the polyoxyalkylene triol represented by the general formula () include polyoxyethylene glycerin triol, polyoxypropylene glycerin triol, polyoxybutylene glycerin triol, polyoxypentylene glycerin triol, and polyoxyethylene oxypropylene glycerin triol. , polyoxyethylene oxybutylene glycerin triol, and the like. The polyoxyalkylene triol used in the present invention has a molecular weight of 200 to 6,000. In particular, polyoxyalkylene triol with a molecular weight of 2,000 to 6,000 has better water resistance and heat resistance, and the above-mentioned specific calcium salt-based protective The composition of the rust agent shows an excellent affinity for the metal base surface, and therefore the calcium salt-based rust preventive agent exhibits a remarkable rust preventive effect. In the grease composition of the present invention, lithium 12-oxystearate alone or a mixture of lithium salts of saturated or unsaturated fatty acids having 12 to 32 carbon atoms is used as the thickening agent.
Such thickeners form stable networks in combination with the specified base oils. 12
- Examples of lithium salts other than lithium oxystearate include lithium salts of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and the like. In the grease of the present invention, the ratio of the base oil to the thickening agent is preferably 97 to 70:3 to 30 (weight ratio, the same applies hereinafter). Grease compositions in which the proportion of base oil is less than the above range become too hard, while grease compositions in which the proportion of base oil is greater than the above range become too soft and cannot provide an appropriate degree of stiffness as a grease. In the grease composition of the present invention, a calcium salt of sulfonic acids, a calcium salt of lanophosphate, or a calcium salt of an oxidized wax is used as a rust preventive agent. Calcium salts of sulfonic acids include petroleum salts with an average molecular weight of 400 or more represented by the general formula R-SO ₃ H (wherein R is a 1- to 2-ring aromatic hydrocarbon having a paraffin side chain or naphthene ring in the molecule). Examples include calcium salts such as sulfonic acid, naphthalene sulfonic acid, and alkylbenzenesulfonic acid. Such calcium salt-based rust preventives may be used alone or in combination of two or more. The rust inhibitor is usually used in a ratio of 0.5 to 20 parts per 100 parts (by weight, same hereinafter) of base oil. If the proportion of the rust preventive agent is less than 0.5 part, the rust preventive effect of the combination with the above-mentioned specific base oil will not be sufficiently exhibited, while if it is more than 20 parts, the anti-rust properties, compatibility with brake fluid, heat resistance, Lubricity deteriorates. Antioxidants used in the grease composition of the present invention include phenyl-α-naphthylamine (hereinafter abbreviated as antioxidant A), phenyl-β-naphthylamine (B), 2, 2',4'-trialkyldiphenylamine (C), 4-octyldiphenylamine (D), 2,2,4-trimethyl-1,3-dihydroquinoline (E), 4,4'-dioctyldiphenylamine enylamine (F), 4,4'-butylidene-bis(6-tert-3-methylphenol) (G), 1,
3,5-trimethyl-2,4,6-tris (3,
5-di-tert-butyl-4-hydroxybenzyl)benzene (H), 2,5-dimethylcapto-
1,3,4-thiadiazole (I) is preferably used. Although these antioxidants may be used alone, heat resistance at higher temperatures and storage stability for a longer period of time can be obtained by using two or more kinds in combination. As combinations of such antioxidants, combinations such as C and E, C and F, and E and I are particularly preferred, followed by combinations such as A and G, E and G, and F and G. The amount of antioxidant is usually 0.3 to 8.0 parts, preferably 0.5 to 8.0 parts per 100 parts of base oil.
Used at a rate of 6.0 parts. As the antioxidant aid, silicone oil (methylphenyl polysiloxane type) is preferably used.
By incorporating this, the duration of the antioxidant effect of the antioxidant is greatly extended. The antioxidant aid is usually used in a ratio of 5 to 50 parts per 100 parts of the antioxidant. In addition to the above-mentioned components, the grease composition of the present invention further includes a structural stabilizer, an extreme pressure agent, a corrosion inhibitor,
Additives such as colorants may be added. The grease composition of the present invention is prepared in a conventional manner, for example with a desired amount of some base oil and 12-
Oxystearic acid or hydrogenated castor oil,
After adding a desired amount of lithium hydroxide aqueous solution to the mixture with other fatty acid esters or fatty acids and saponifying and dehydrating the mixture, the remaining base oil, antioxidant,
Add antioxidant aids and other additives if necessary,
It is prepared by kneading with a roll mill or the like. Next, the grease composition of the present invention will be explained with reference to Examples and Comparative Examples. Example 1 6.0 parts of 12-oxystearic acid, hydrogenated castor oil
6.0 parts of oleic acid, 1.0 parts of aluminum stearate, and 20.0 parts of polyoxypropylene glycerol triol having an average molecular weight of 3000 were charged into a saponification pot and uniformly dissolved and dispersed. A 20% aqueous solution of 2.0 parts of lithium hydroxide monohydrate was added to this, and the mixture was saponified and dehydrated. After completion of the reaction, add the same polyoxypropylene glycerol triol as above 50.0
of the mixture, the temperature was raised to 160°C, and the mixture was sufficiently stirred and mixed. After cooling this to 120℃, the average molecular weight
8.0 parts of calcium petroleum sulfonate of 1000, 1.0 parts of antioxidant C, 1.5 parts of antioxidant E, and 1.0 part of methylphenyl polysiloxane with an average molecular weight of 2200 were added and mixed thoroughly with stirring, cooled to room temperature, and milled on a roll mill. A grease composition was obtained by kneading the mixture homogeneously. Examples 2-3 and Comparative Examples 1-5 Base oil, rust inhibitor and antioxidant
A grease composition was prepared in the same manner as in Example 1 except that the composition was changed as shown in the table.

[Table] The following tests were conducted on the grease compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 4. A similar test was also conducted on a commercially available castor oil-based rubber grease (Comparative Example 5). (1) Temperature: Conducted in accordance with JISK2560 (A method). (2) Dropping point This was done in accordance with JISK2561. (3) Oil separation The oil separation was conducted at 100°C for 30 hours in accordance with JISK2570. (4) Water resistance Washing was conducted at 79°C for 1 hour in accordance with JISK2572. (5) Rubber swelling property Tested in accordance with Society of Automotive Engineers of Japan standard JASO7011 (rubber lubricant for brakes) 7.12. However, SBR (styrene-butadiene rubber) was used as the rubber test piece, and the test was conducted at 120°C for 70 hours. (6) Rust prevention (6-1) Wet (mild steel plate): Society of Automotive Engineers of Japan standard
JASO7011 (rubber lubricant for brakes) 7.11
This was done in accordance with the. (6-2) Wet (cast iron plate): The test piece in (6-1) above was tested according to JIS G 5501 (gray cast iron product).
A similar test was conducted using the three types (F _c -20) specified in . (6-3) Salt spray: Conducted in accordance with JIS Z 0236 (Rust preventive oil - General test methods) 6.2.2 (3). (7) Heat Resistance After thoroughly cleaning the cylinder body and piston of the foil cylinder and drying them with dry air, each grease composition was applied thinly and uniformly to the cylinder body and piston, and then the foil cylinder was assembled.
This foil cylinder was placed horizontally in a constant temperature air solution at 140±2°C and heated at 140±2°C for 2 hours, then taken out, left to cool at room temperature for more than 3 hours, and the sliding resistance (pulling force) was measured using a spring meter. The condition of the grease was observed visually and by touch. However, the following two types of combinations of the cylinder body and piston in the foil cylinder were used.

[Table] Grease condition was evaluated based on the following criteria. A: Adhesiveness and hardness were almost unchanged, but slightly brownish. B: The stickiness and hardness remained almost the same, but the color became dark brown. C: It became quite hard and turned dark brown. D: It became very hard and turned blackish brown. E: Almost solidified and almost black. (8) Oxidation stability Tested at 98.9°C in accordance with JIS K 2569. (9) Metal corrosion Conducted in accordance with Society of Automotive Engineers of Japan standard JASO 7011 (rubber lubricants for brakes) 7.13. The results of the above tests are shown in Table 2.

[Table] As is clear from the test results in Table 2, Examples 1 to 1 in which calcium salt-based rust inhibitors such as calcium sulfonate, calcium lanophosphate, and calcium salt of oxidized wax were blended with specific base oils.
The rust prevention property of the grease composition No. 3 is extremely good.
On the other hand, in the case of the grease compositions of Comparative Examples 1 to 4 using rust preventives outside the scope of the present invention, such as barium sulfonate and amine type, the specifications of other components including the base oil were the same as those of Examples 1 to 3. The rust prevention properties are extremely poor, including the cases where it is exactly the same as that of the other products (Comparative Examples 1 and 2). Furthermore, as is clear from Comparative Example 4, when polyoxyalkylene diol is used alone as the base oil, water resistance decreases.
Furthermore, as is clear from Comparative Example 5, the conventional castor oil-based product has extremely poor heat resistance; the foil cylinder completely sticks to the product after heating, making it inoperable; furthermore, the product has poor water resistance. Since the grease compositions of Examples 1 to 3 and Comparative Examples 1 to 4 each use a suitable combination of antioxidants, they all have good heat resistance. It is clear that the grease compositions of Examples 1 to 3 according to the present invention had good properties and well-balanced overall performance. Since the grease composition of the present invention has a well-balanced overall performance, it can be applied not only to the sliding surfaces of automobile brake and clutch systems, but also to the sliding surfaces of auxiliary parts such as metal, rubber, and plastic. It goes without saying that the present invention can be applied to sliding surfaces and lip portions of oil seals in various combinations.

Claims (1)

[Claims] 1 Consists of a base oil, a thickener, a rust preventive, an antioxidant, and an antioxidant aid, and the base oil has the general formula: (In the formula, k is an integer of 1 to 5, m and n are 2 to
5 integer, x and y are positive integers, where -C _n
When the H _2n O- group and the -C _o H _2o O- group are the same, x
and y is zero) with an average molecular weight of 200 to 6000, and the thickening agent is composed of lithium 12-oxystearate alone or mainly composed of lithium 12-oxystearate, and A grease composition for brakes or clutches, wherein the rusting agent is at least one selected from the group consisting of calcium salts of sulfonic acids, calcium salts of lanophosphate, and calcium salts of oxidized waxes. 2. The composition according to claim 1, wherein the polyoxyalkylene triol has an average molecular weight of 2,000 to 6,000. 3 The antioxidant is phenyl-α-naphthylamine, phenyl-β-naphthylamine, 2,2′,
4'-trialkyldiphenylamine, 4-octyldiphenylamine, 2,2,4-trimethyl-
1,3-dihydroquinoline, 4,4'-dioctyldiphenylamine, 4,4'-butylidene-bis(6-tert-butyl-3-methylphenol),
1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene and 2,5-dimercapto-
The composition according to claim 1 or 2, which is at least one selected from the group consisting of 1,3,4-thiadiazole. 4 The antioxidants are 2,2',4'-trialkyldiphenylamine and 2,2,4-trimethyl-1,3
- mixture with dihydroquinoline, mixture with 2,2',4'-trialkyldiphenylamine and 4,4'-dioctyldiphenylamine, mixture with 2,2,4-trimethyl-1,3-dihydroquinoline ,5-
mixture with dimercapto-1,3,4-thiadiazole, phenyl-α-naphthylamine and 4,
4'-Butylidene-bis(6-tert-butyl-3-
2,2,4-trimethyl-1,3-dihydroquinoline and 4,4'-
mixtures of butylidene-bis(6-tert-butyl-3-methylphenol) and 4,4'-dioctyldiphenylamine and 4,4'-butylidene-bis(6-tert-butyl-3-methylphenol);
The composition according to claim 3, which is a mixture selected from the group consisting of mixtures with bis(6-tert-butyl-3-methylphenol). 5. The composition according to claim 1, 2, 3 or 4, wherein the antioxidant aid is methylphenylpolysiloxane.