JP2000001694A - Liquid lubricant and control of its lubricant properties - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant of which lubricant properties can be controlled according to the status of use and a controlling method of its lubricant properties. SOLUTION: An electroviscous fluid that includes disperse phase particles and a liquid dispersion medium and manifests reversible viscosity change by application of an electric field is used as a liquid lubricant. This liquid lubricant can be controlled its lubricant properties by application of electric fields according to its application situations. The application of electric fields to the liquid lubricant with the intensity in response to temperature change ensures the retention of an always constant viscosity, namely the maintenance of constant lubricant properties regardless of temperature fluctuation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid lubricant and a method for controlling its lubricating properties.

[0002]

2. Description of the Related Art A lubricant is present between two moving bodies (equipment) so as not to cause damage to the relative planes, and is used to maintain a smooth state of motion. is there. Lubricants include liquid, solid, and semi-solid lubricants, and among them, liquid lubricants are most often used. Generally, liquid lubricants are classified into mineral oil-based, synthetic oil-based, emulsion-based, water-based, and liquid metal-based lubricants.

The functions required of these lubricants include:
For example, cooling, reduced friction, reduced wear, reduced burn-in,
Examples include a sealing effect, rust prevention, and clean dispersion. However, it is rare that all of the above functions are required at the same time, and the role mainly required of the lubricant is determined each time depending on the place where the lubricant is used, the design condition of the machine, and the like.

[0004] For this reason, various additives are used in accordance with the place of use of the lubricant, the design condition of the machine, and the like, for example, to improve the lubrication characteristics of the lubricant. Examples of the additive include a viscosity index improver.

[0005] Generally, the viscosity of a lubricant changes, such as its kinematic viscosity and viscosity coefficient, due to changes in the external environment such as temperature and pressure. However, if the kinematic viscosity of the lubricant is reduced due to a change in the external environment, the lubrication characteristics are reduced, and problems such as deterioration of machine operation and increased wear occur. Therefore, a viscosity index improver is used to reduce the change in viscosity of the lubricant when the temperature changes.

[0006]

However, when the viscosity index improver is used, the change in viscosity of the lubricant at the time of temperature change can be reduced, but the change in viscosity cannot be completely prevented. It cannot respond completely to changes in the environment.

Further, depending on the application of the lubricant, for example, it is required to change the lubricating property only at a certain specific position in the mechanical device. However, when the viscosity index improver is used, Such a local change in lubrication characteristics cannot be expected.

Accordingly, a lubricant that can completely adapt to changes in the external environment such as temperature and pressure, and can change the lubrication characteristics as needed at a desired position in a mechanical device, There is a need for a lubricant that can control lubrication properties according to the situation. However, there is no known conventional lubricant having such a function.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a liquid lubricant capable of controlling lubricating characteristics according to a use condition and a method of controlling the lubricating characteristics. It is in.

[0010]

The inventors of the present invention have made intensive studies to solve the above-mentioned conventional problems. As a result, the inventors of the present invention consisted of an electrorheological fluid containing dispersed phase particles and a liquid dispersion medium. By applying an electric field according to the usage conditions, the liquid lubricant that exhibits a reversible change in viscosity can control the lubrication characteristics arbitrarily according to the usage conditions, and can control the external environment such as temperature and pressure. The present invention has been found to be able to completely adapt to the change in lubrication, and to be able to arbitrarily change the lubrication characteristics as required at a desired position in the mechanical device.

That is, in order to solve the above-mentioned problems, the liquid lubricant according to the first aspect of the present invention comprises an electrorheological fluid containing dispersed phase particles and a liquid dispersion medium, and is reversible with the application of an electric field. It is characterized by showing a great change in viscosity.

According to a second aspect of the present invention, there is provided a liquid lubricant according to the first aspect, wherein the average particle diameter of the dispersed phase particles is 0.001 μm.
-1 μm.

According to a third aspect of the present invention, there is provided a liquid lubricant according to the first or second aspect, wherein the dispersed phase particles are dielectric particles. I have.

According to the above configuration, since the liquid lubricant exhibits a reversible change in viscosity with the application of an electric field, the electric field is applied in accordance with changes in the external environment such as temperature and pressure. Thus, the viscosity can be reversibly and arbitrarily changed according to the external environment. As a result, the change in the viscosity of the fluid constituting the liquid lubricant due to the change in the external environment such as temperature and pressure can be offset by the application of an electric field. Therefore, constant lubrication characteristics can always be maintained. In addition, the above-mentioned liquid lubricant applies an electric field at a desired position in a mechanical device, for example, to arbitrarily change lubrication characteristics at a desired position in a mechanical device, or apply an electric field only when necessary. For example, required lubrication characteristics can be secured instantaneously. Therefore, according to the above configuration, it is possible to provide a liquid lubricant capable of controlling the lubrication characteristics according to the use situation.

According to a fourth aspect of the present invention, there is provided a method for controlling a lubricating characteristic of a liquid lubricant, which comprises an electrorheological fluid containing dispersed phase particles and a liquid dispersion medium, and is provided with the application of an electric field. It is characterized in that an electric field is applied to a liquid lubricant exhibiting a reversible viscosity change according to the use condition, thereby controlling the lubrication characteristics.

According to the above-described method, an electric field is applied to the liquid lubricant having the above-described structure in accordance with a change in an external environment such as a temperature and a pressure, a use position in a mechanical device, and the like, and Since the lubrication characteristics (viscosity) can be arbitrarily adjusted, for example, even if the external environment such as temperature and pressure changes, the viscosity is reversibly changed according to the change of the external environment, so that the constant Maintain the lubricating properties, or at the desired location in the mechanical device, if necessary,
Lubrication characteristics can be changed arbitrarily. Therefore, according to the method described above, it is possible to control the lubrication characteristics according to the use condition, and to easily and quickly change in the use condition,
It can be repeated and adapted.

Hereinafter, the present invention will be described in detail. The liquid lubricant according to the present invention is composed of an electrorheological fluid containing dispersed phase particles and a liquid dispersion medium, and the viscosity such as kinematic viscosity and viscosity coefficient reversibly changes with application of an electric field (application of an electric field). In other words, they exhibit the so-called ER effect.

In the present invention, the ER effect means that when an electric field is applied to a fluid, the apparent viscosity (viscosity) increases,
This shows the phenomenon that the viscosity returns to its original state when the electric field is removed.
The ER effect is an electrorheological effect (electrorheological effect, Electro-Rheological Effect, or Electro-Visc effect).
ous Effect).

The liquid lubricant according to the present invention comprises an electrorheological fluid containing dispersed phase particles and a liquid dispersion medium, and can be obtained by dispersing dispersed phase particles to be a dispersed phase in the liquid dispersion medium. The above-mentioned electrorheological fluid has a rheological property that changes from a Newtonian type (Newtonian viscosity) to a viscoplastic type (Bingham visc) by applying an electric field change.
a fluid that exhibits an ER effect in which the apparent viscosity (viscosity) increases when an electric field is applied and returns to the original viscosity when the electric field is removed. .

The above-mentioned dispersed phase particles are not particularly limited, but specifically, for example, metal oxide particles such as silica, alumina, zirconia, zeolite, smectite, molybdenum dioxide; aluminum, gold,
Metal particles such as silver and copper; carbon allotrope particles such as carbon black, mesophase carbon, carbonaceous powder, and graphite; polymer particles such as polystyrene, polyethylene, polypropylene, and polymethyl methacrylate; ion exchange resins, poly (meth) acrylic acid, Polymer particles having an ionic dissociating group such as a crosslinked metal salt; particles of metal oxide particles, metal particles, carbon allotropes, etc., whose surface is coated with an electrically insulating thin film; carbon black obtained by grafting a polymer to carbon black A graft polymer and the like can be mentioned, and only one kind or a mixture of two or more kinds can be used.

The dispersed phase particles that can be used in the present invention have an average particle size of 0.001 μm to 1 μm.
m is preferably in the range of 0.003 μm to
More preferably, it is within a range of 0.5 μm,
Those having a range of from 05 μm to 0.2 μm are particularly preferred. If the average particle size exceeds 1 μm, the desired dispersion stability for the dispersed phase in the prepared liquid lubricant cannot be obtained, and the lubricating properties are reduced. Problems such as deterioration and increased wear occur. On the other hand, the average particle diameter is 0.001 μm.
If it is less than m, a large change in viscosity may not be obtained even when an electric field is applied to the prepared liquid lubricant. For this reason,
Even if an electric field is applied according to the temperature change, the viscosity change due to the temperature change is larger than the viscosity change due to the application of the electric field, and the viscosity change due to the temperature change cannot be offset.
There is a possibility that the lubrication characteristics cannot be maintained constant or that the lubrication characteristics cannot be sufficiently controlled at a predetermined position in the mechanical device. The above-mentioned dispersion stability is a property that the electrorheological fluid can be maintained uniformly for a long time without causing the dispersed phase particles to settle or float in the liquid dispersion medium.

As the dispersed phase particles according to the present invention, dielectric particles are more preferably used because the obtained liquid lubricant has a long life, and the induced shear stress is large and the range in which the lubrication characteristics can be adjusted is wide. Used. As the dielectric particles, conventionally known fine particles can be used as dispersed phase particles of an electrorheological fluid. Among the dielectric particles, for example, fine particles of 1 μm or less such as carbon black graft polymer and smectite are more preferably used, and among them, carbon black graft polymer is particularly preferably used.

The above-mentioned carbon black graft polymer is not particularly limited. For example, JP-B-42-22047, JP-B-44-3826, JP-B-45-17248, and JP-B-46-220. 26
970, Japanese Patent Publication No. 24868/1990,
-224292, JP-A-8-337624, JP-A-8-337789, and Japanese Patent Application No. 8-334.
332, Japanese Patent Application No. 8-334334, and the like.

[0024] Among the carbon black graft polymers, the dielectric particles include a carbon black graft having a polymer portion and a carbon black portion, wherein the polymer portion is grafted to the carbon black portion. Polymers are particularly preferred.

The reason is that a carbon black graft polymer having a polymer portion and a carbon black portion, in which the polymer portion is grafted to the carbon black portion, has a wide usable temperature range and a wide range. Being able to fully adapt to changes in the environment,
The response speed to the applied voltage is very fast, and a quick response is possible, the induced shear stress is particularly large, and the adjustable range of the lubrication characteristics is wide.

The term "graft" as used in the present invention means "done"
nnet) et al., as defined in their book "Carbon Black", refers to the irreversible addition of a polymer to a substrate such as carbon black.

By performing the irreversible addition reaction, the polymer can be chemically bonded to the surface of the carbon black particles, whereby the two can be surely bonded. Addition reactions that can be used for "grafting" include electrophilic addition reactions, radical addition reactions, nucleophilic addition reactions, and cycloaddition reactions.

The polymer portion in the above carbon black graft polymer preferably has a carbon-carbon bond in the main chain. The carbon black graft polymer in which the polymer is chemically bonded to carbon black,
It can be manufactured at low cost.

The reason that the carbon black graft polymer can be produced at low cost is that the polymer has many carbon molecules and has a high affinity between the carbon black and the polymer. Can be grafted more effectively.

When, for example, a polymer consisting of only polysiloxane is used as a raw material of the polymer portion having no carbon-carbon bond in the main chain, grafting of the polymer to carbon black does not proceed effectively, and the dispersed phase A carbon black graft polymer suitable as particles may not be obtained.

The polymer portion preferably contains a main chain obtained by polymerization of a vinyl monomer among polymer portions having a carbon-carbon bond in the main chain. A polymer obtained by polymerization of a vinyl monomer has a main chain consisting only of carbon-carbon bonds and has a high affinity for the carbon black, so that grafting can be effectively performed. Further, many vinyl monomers having a reactive group for performing grafting are known.
When the polymer portion does not contain a main chain obtained by polymerization of a vinyl monomer, grafting may not proceed effectively.

Further, the polymer portion preferably has an affinity for the liquid dispersion medium. When the polymer portion has no affinity for the liquid dispersion medium, the obtained liquid lubricant may not be able to impart desired dispersion stability.

The ratio of the carbon black portion to the polymer portion in the carbon black graft polymer is from 10 parts by weight to 3.0 parts by weight with respect to 100 parts by weight of the former.
It is preferably in the range of 00 parts by weight, particularly preferably in the range of 50 parts by weight to 1,000 parts by weight. If the above ratio is less than 10 parts by weight, the density of current flowing when an electric field is applied may increase. When the above ratio exceeds 3,000 parts by weight, a large change in viscosity may not be obtained even when an electric field is applied to the prepared electrorheological fluid composition.

The carbon black used in the present invention preferably has conductivity. The term “conductivity” as used in the present invention refers to a property of low electric resistance to electric conduction. Carbon black is usually considered a semiconductor. In the present invention, in addition to semiconductive carbon black,
Conductive carbon black can be used.

The following method is a simple method for evaluating whether or not carbon black has conductivity. Carbon black itself or a mixture of 50 parts by weight to 300 parts by weight of polydimethylsiloxane (silicone oil), which is highly electrically insulating from carbon black, with respect to 100 parts by weight of the former, is filled between the electrodes at an interval of 1 mm. When a 3 kV electric field is applied between the electrodes, a current density of 300 mA / cm ² or more flows;
Alternatively, carbon black having electrical breakdown and incapable of applying an electric field of 3 kV is referred to as conductive carbon black.

The carbon black that can be used in the present invention preferably has an electric conductivity of 10 ⁻¹⁰ s · cm ⁻¹ or more. As the carbon black, conventionally known carbon blacks can be used, and examples thereof include thermal black, channel black, furnace black, acetylene black, and color black.

When carbon black having no conductivity is used, there is a problem that the obtained liquid lubricant does not induce a large change in viscosity when an electric field is applied.

The carbon black preferably has a functional group such as a carboxyl group or a hydroxyl group on its surface, and more preferably has a carboxyl group. Further, the carbon black has a pH of 6
It is preferred to use less than less carbon black. Those obtained by oxidizing neutral or basic carbon black can also be suitably used as a raw material of the carbon black graft polymer. When the carbon black does not have a functional group such as a carboxyl group or has a pH of 6 or more, grafting may not be performed effectively.

The carbon content in the carbon black is preferably at least 85% by weight. When the carbon content is less than 85% by weight, carbon black may not show conductivity.

The polymer having a reactive group in the present invention is not particularly limited as long as it is a polymer having a reactive group capable of reacting with the surface functional group of carbon black, and examples thereof include vinyl polymers, polyesters, and polyethers. And the like. Among them, a vinyl polymer containing a main chain obtained by polymerizing a vinyl monomer is preferable.

The vinyl polymer is preferable because the vinyl polymer has a carbon-carbon bond in the main chain and various monomers having a reactive group for grafting are known. It is in. Therefore, when a vinyl polymer is used as the polymer, grafting to conductive carbon black can be effectively performed.

The reactive group in the polymer having a reactive group is preferably at least one selected from the group consisting of an epoxy group, a thioepoxy group, an aziridine group, and an oxazoline group.

The reactive group capable of undergoing an addition reaction with the surface functional group of carbon black is not necessarily limited to only these reactive groups. However, when a polymer having a group other than these reactive groups is used, There may be restrictions on the types of carbon black that can be used.

In the grafting of the polymer having a reactive group, the reason why it is preferable to use the one having the reactive group is as follows. First, regardless of the type or state of the carbon black used, even under mild conditions, the carbon black and the polymer having a reactive group undergo an addition reaction with a very high grafting efficiency, and are suitable as the dispersed phase particles of the present invention. Where a high carbon black graft polymer can be obtained.

The molecular weight of the polymer having a reactive group is not particularly limited. However, considering the effect of grafting on conductive carbon black and the workability during the reaction with the carbon black, the molecular weight is Average molecular weight 5
It is preferably in the range of 00 to 1,000,000, and more preferably in the range of 1,000 to 100,000.

The grafting may be performed, for example, by subjecting a polymer having a reactive group to carbon black to a usual addition reaction with the carbon black, or by forming a polymer in the presence of carbon black. The above reaction may be carried out, and the production of the polymer and the reaction of the polymer with carbon black may be carried out simultaneously. However, in order to obtain a carbon black graft polymer with high grafting efficiency, it is preferable to use the former method.

In the reaction between the carbon black and the polymer having a reactive group, the polymer is added in an amount of 10 to 3,000 parts by weight based on 100 parts by weight of the carbon black.
It is preferable to use it in a proportion by weight. When the proportion of the polymer is less than 10 parts by weight, the density of current flowing when an electric field is applied may increase. When the ratio of the above polymer is 3,0
If the amount exceeds 00 parts by weight, a large change in viscosity may not be obtained even when an electric field is applied.

The reaction between the carbon black and the polymer having a reactive group is preferably carried out by stirring and mixing within a range of 0 to 350 ° C. If the temperature during the reaction exceeds 350 ° C., the above-mentioned polymer deteriorates and the current density flowing when an electric field is applied to the prepared liquid lubricant may increase.

The addition reaction of the conductive carbon black to the polymer can be carried out without using other components. According to this method, when the carbon black having a weak cohesive force is used, the coagulation is disintegrated along with the reaction, and the grafting proceeds efficiently. Therefore, the obtained dielectric particles are suitable for the present invention.

The above addition reaction can be performed even in the presence of other substances such as a polymer, a polymerizable monomer, and an organic solvent which do not correspond to the above polymer. In such a case, the affinity with the carbon black is high, and reacting in the coexistence of aromatic hydrocarbons that dissolve the polymer, the carbon black and the polymer are promptly mixed, It is preferable because it is stirred. As described above, the reaction between the carbon black and the polymer having a reactive group is desirably performed using various stirrers and kneaders.

As described above, the carbon black graft polymer as the dielectric particles is formed by grafting the polymer portion to the carbon black portion, so that the carbon black graft polymer is polymerized in a liquid dispersion medium, preferably an electric insulating oil. The coalesced portion can be made to extend from the surface of the carbon black portion into the liquid dispersion medium, and in the liquid dispersion medium, the polymer portion can be interposed between the easily aggregated carbon black portions.

As a result, aggregation of the dielectric particles in the liquid dispersion medium can be prevented, so that the obtained liquid lubricant can be provided with excellent dispersion stability. In addition, since the contact between the carbon black portions having conductivity can be avoided by the interposition of the polymer portions, the electrical insulation between the carbon black portions can be maintained, and the electrical dispersant of the liquid dispersant when an electric field is applied can be maintained. Dielectric breakdown can be prevented.

In particular, when the polymer portion has an affinity for the electric insulating oil, since the molecules of the electric insulating oil gather around the polymer portion, not only the polymer portion but also the electric insulating oil is used. Even with the insulating oil, the electrical insulation between the carbon black portions can be more effectively maintained.

The liquid dispersion medium used in the present invention is not particularly limited as long as it is a liquid substance (liquid), and water or a known oily substance can be used. The liquid substance may be water alone or oily substance alone, or may be a mixture of water and oily substance. In this case, the oily substance may be dissolved in water, or may be dispersed or emulsified. Conversely, water may be dissolved in the oily substance, or may be dispersed or emulsified. However, when the liquid dispersion medium contains water, the relative surfaces of the equipment moving through the obtained liquid lubricant, that is,
If the contact surface of the mechanical device with the liquid lubricant is metal, the liquid dispersion medium preferably contains a rust preventive.

The above oily substance that can be used in the present invention is not particularly limited. For example, “Petroleum, Lubricants and Petrochemicals Series II Lubricating Oil (2nd) Base Oil (1)” by Takashi Kishikawa Petrotech, Vol. 18, No. 6, 479-4
Page 85 (1995) "and" Petroleum, Lubricants and Petrochemicals Series II Lubricants (3rd) Base Oil (Bottom) "
No. 7, pp. 584-587 (1995) ".

Specifically, the above oily substances include, for example, paraffinic mineral oil refined from crude oil containing a large amount of paraffinic hydrocarbons; so-called mixed base mineral oil / mixed base mineral oil produced from intermediate base crude oil; Naphthenic mineral oil containing a large amount of paraffin; whale oil, tallow, lard, etc. alone or animal oil obtained by mixing these oils with petroleum oil; vegetable oil, such as rapeseed oil, soybean oil, coconut oil; diluted with a solvent, such as methyl ethyl ketone, Solvent dewaxed oil obtained by filtering and separating wax that is difficult to dissolve at low temperature; separation and disposal by selectively capturing long-molecule wax in the pores of the catalyst using a zeolite-based catalyst and cutting it. Instead, a catalytic dewaxing oil obtained by converting the structure into an active ingredient can be used.

Other oily substances include, for example, a solvent-refined oil obtained by extracting and removing a polycyclic aromatic or polycyclic naphthene component, a sulfur compound and the like into a solvent phase; sulfur and nitrogen which are highly reactive with hydrogen. Hydrogen finishing oil with improved dye stability, thermal stability, oxidation stability, etc. by removing compounds or modifying unsaturated components; hydrogenating at high temperature and pressure to remove sulfur and nitrogen compounds In addition, hydrocracked oils obtained by cycloparaffinization by polycyclic aromatic decomposition, ring opening, dealkylation of side chains, hydrogenation of aromatic nuclei, or isoparaffinization by isomerization of linear components are exemplified.

Further, other oily substances include, for example,
Poly-α-olefin obtained by polymerizing and hydrogenating an α-olefin having 6 to 14 carbon atoms having a double bond at a terminal by wax decomposition or ethylene polymerization in the presence of a Friedel-Crafts catalyst and distilling out low molecular weight; Naphtha C ₄ alkyl aromatics with alkylated benzene rings with olefins from dehydrogenation, wax pyrolysis, or ethylene polymerization
Butane of C ₄ component remaining after extracting butadiene from the fraction,
Polybutene obtained by polymerizing butylene using a Friedel-Crafts catalyst in the presence of a Friedel-Crafts catalyst, separating the catalyst by alkali washing and removing low molecules; petroleum-based alcohols such as tallow, soy oleic acid, coconut oil, and palm Esters such as diesters of dibasic organic acids and monohydric alcohols and polyol esters of monobasic organic acids and polyhydric alcohols, starting from animal and vegetable oil-based organic acids such as caprylic acid / capric acid contained in oils and the like. And synthetic oils.

Still another oily substance is, for example, an ester of a phosphoric acid compound, which is an inorganic acid, with an aromatic phenol derivative, for example, by reacting phosphorus oxychloride with phenols and neutralizing and washing to remove the catalyst. Removed, removed by hydrolysis and distillation by washing, phosphoric acid ester that is commercialized through purification such as decolorization and dehydration; ring-opening polymerization of lower alcohol and alkylene oxide such as ethylene oxide and propylene oxide, Polyglycols obtained by converting a monoether-type terminal hydroxyl group into an alkali metal and then reacting the resulting product with an alkyl halide are exemplified.

As another oily substance, an organochlorosilane represented by the general formula R ₃ SiCl or R ₂ SiCl ₂ is prepared as an intermediate by reacting a chlorinated hydrocarbon with silicon. (R ₃ Si) ₂ O, obtained by hydrolyzing chlorosilane, (R ₂
A silicone synthetic oil obtained by adjusting the ratio of SiO) _n and then polymerizing in the presence of an acid or alkali catalyst;
A polyphenol synthesized by a reaction between an aromatic halide and an alkali metal salt of a phenol with a copper-based catalyst is exemplified.

Still other oily substances include alkylphenyl ethers obtained by the Friedel-Crafts reaction of an α-olefin and phenyl ether with a catalyst such as aluminum chloride; low-polymerization of ethylene trifluoride chloride or polyglycol structure A fluorine-based polyether obtained by substituting hydrogen with fluorine.

As the oily substance used in the present invention, a conventionally known organic solvent can be used in addition to the above-mentioned compounds. As the organic solvent,
For example, alcohols such as butanol and propanol;
Ketones such as methyl ethyl ketone and methyl butyl ketone; saturated aliphatic hydrocarbons such as octane and decane; aromatic hydrocarbons such as benzene, xylene and toluene; glycol derivatives such as ethyl glycol and butyl glycol; chloromethylene and chlorobenzene Organic chloride;
And the like. The above-mentioned oily substances may be used alone or as a mixture of two or more.

The liquid dispersion medium used in the present invention includes:
It is preferable to have electrical insulation properties, and among the above oily substances, electrical insulation oils are suitably used. Examples of the electric insulating oil include the above-described hydrocracked oils, ester-based synthetic oils, silicone-based synthetic oils, fluorine-based polyethers, aromatic hydrocarbons, and among others, silicone-based synthetic oils ( Silicone insulating oil) is particularly preferred.

The silicone-based synthetic oil (silicone-based insulating oil) is not particularly limited as long as it is mainly composed of silicone oil and is a substantially electrically insulating liquid. Silicone oil, which is the main component of silicone-based insulating oil, has a siloxane structure and is generally used as braking oil, air insulating oil, impregnating injection oil, lubricating oil, polishing agent, cosmetic component, release agent, defoaming agent, etc. Is what it is.

As described above, when the liquid dispersion medium has electric insulation, there is an advantage that the life as a liquid lubricant is prolonged.

The liquid lubricant of the present invention is prepared by mixing and dispersing the above-mentioned fine particles as dispersed phase particles constituting a dispersed phase in a liquid dispersion medium composed of the above-mentioned liquid substance.

In the present invention, the amount of the dispersed phase particles used for dispersing the dispersed phase particles in the liquid dispersion medium is not particularly limited, but may be from 0.1% by weight to the liquid dispersion medium.
It is preferably in the range of 80% by weight,
More preferably, it is in the range of 50% by weight. When the use amount of the fine particles is less than 0.1% by weight, a large viscosity change may not be obtained even when an electric field is applied to the prepared liquid lubricant, and even when the electric field is applied according to a temperature change. However, the change in viscosity due to temperature change is larger than the change in viscosity due to the application of an electric field, the change in viscosity due to temperature change cannot be offset, the lubrication characteristics cannot be maintained constant, or the There is a possibility that lubrication characteristics cannot be sufficiently controlled at a desired position. On the other hand, when the use amount of the dispersed phase particles exceeds 80% by weight, the amount of the liquid dispersion medium with respect to the dispersed phase particles is too small, the viscosity when no electric field is applied increases, the fluidity becomes poor, or the machine moves. There is a possibility that the abrasion becomes worse or the abrasion increases.

The liquid lubricant of the present invention, that is, the electrically insulating fluid used for the liquid lubricant contains additives such as a surfactant and a polymer thickener for adjusting the viscosity. And may further contain various conventionally known additives such as an antioxidant, a metal corrosion inhibitor, and a pour point depressant.

The liquid lubricant having the above structure can be manufactured at a low cost, and a large change in viscosity can be obtained by applying an electric field, and the usage conditions such as the external environment such as temperature and pressure and the usage position in a mechanical device can be obtained. The lubrication characteristics can be controlled according to the conditions.

In particular, when dielectric particles are used as the dispersed phase particles, the life as a liquid lubricant can be extended. In particular, when the above-described carbon black graft polymer is used, an electric field can be applied. As a result, a greater change in viscosity can be obtained, and a liquid lubricant having particularly excellent dispersion stability, fluidity, friction resistance, and abrasion resistance can be obtained.

Electro-rheological fluids have utilized the change in shear stress in response to the change in an external electric field to transmit stress in various devices such as engine mounts, clutches, dampers, brakes, shock absorbers, actuators, valves and cylinders. Attempts have been made to apply the ink to electrorheological fluid ink jets, but it has not been applied to lubricants.

The present invention uses a specific electrorheological fluid, which contains dispersed phase particles and a liquid dispersion medium and exhibits a reversible viscosity change with the application of an electric field, as a liquid lubricant, so that the lubrication characteristics can be arbitrarily determined. It is intended to provide a lubricant which can be controlled at a low speed.

It has been reported that when an electric field is applied to a liquid crystal known as a homogeneous electrorheological fluid, lubrication characteristics such as a friction coefficient of the liquid crystal itself change (Tribology Conference '94 Autumn Preprints (1994), 507). However, since the ER effect of the liquid crystal is very small, and the viscosity when no electric field is applied is high and the fluidity is poor, it is difficult to apply the liquid crystal to a lubricant. Moreover, the lubrication characteristics cannot be controlled arbitrarily and are expensive.

However, a heterogeneous electrorheological fluid containing dispersed phase particles and a liquid dispersion medium (dispersion electrorheological fluid)
By applying an electric field, a large change in viscosity can be obtained so that a change in viscosity due to a change in an external environment such as temperature or pressure can be obtained. Since the lubricating characteristics such as the above can be changed according to the use conditions and are inexpensive, they can be suitably used as a liquid lubricant.

In the present invention, the obtained liquid lubricant needs to contain both the dispersed phase particles and the liquid dispersion medium. When the liquid lubricant does not contain fine particles as dispersed phase particles, for example, even if an electric field is applied in accordance with a change in the external environment such as temperature or pressure, the change in the lubrication characteristics due to the change in the external environment is larger, This causes a problem that the lubrication characteristics cannot be maintained due to a change in the external environment or that the lubrication characteristics cannot be sufficiently controlled at a desired position in the mechanical device. Further, when the liquid material as a liquid dispersion medium is not contained, problems such as deterioration of lubricating properties, deterioration of machine operation, and increased wear are caused.

When the liquid lubricant is composed of an electrorheological fluid containing dispersed phase particles having a particle diameter on the order of nm, particularly an electrorheological fluid containing the above-described carbon black graft polymer as dispersed phase particles, dispersion stability is improved. The lubricating properties such as lubricity, dynamic friction coefficient, and abrasion resistance are improved, and it can be used in a wider range.

The liquid lubricant of the present invention can arbitrarily control the lubricating characteristics, and thus has the following effects, for example.

When the external environment such as temperature and pressure changes, the viscosity of the liquid lubricant is controlled by the ER effect, and the change in the viscosity accompanying the change of the external environment is canceled to maintain a constant lubrication characteristic.

When the shear rate increases, or
By applying an electric field only when necessary, such as when the pressure suddenly increases, the viscosity of the liquid lubricant is raised, and for example, the necessary lubricity is secured instantaneously.

Applying an electric field only at a particular location in a mechanical device changes the lubrication properties at that location.

For use in an environment where maintenance is difficult, such as use in a nuclear reactor or space, when the lubrication characteristics of the liquid lubricant are reduced, the lubrication characteristics of the lubricant are increased by the ER effect. Achieve equipment-free maintenance.

In addition, in the present invention, the lubrication characteristics under various conditions can be arbitrarily adjusted by controlling the presence or absence of the application of an electric field, that is, the presence or absence of the application of an electric field, as necessary. .

The control of the lubricating characteristics when the temperature changes as an example of the changes in the lubricating characteristics of the liquid lubricant and the external environment will be described below.

In the following description, a liquid lubricating oil prepared by dispersing a carbon black graft polymer having a silicone component in a polymer portion as dispersed phase particles in a silicone oil of 20 cs so that the concentration of the dispersed phase particles becomes 30% by weight. The case where an agent is used will be described. The viscosity of the liquid lubricant when no electric field is applied is 80 mPa · s (25 ° C.), and the particle size of the carbon black graft polymer is 30 nm to
The average particle size was 200 nm, and the average particle size was 81 nm.

For the measurement of the ER effect, a dynamic analyzer RDA-2 (Rheometric.
Scientific. (Manufactured by F.E.). A rotating double cylinder having an outer diameter of 26 mm, an inner diameter of 25 mm, and a height of 32 mm was used as an electrode.

The lubricating properties were evaluated by measuring the dynamic friction coefficient using a pendulum type oil-based friction tester (manufactured by Shinko Engineering Co., Ltd.) and measuring the load-bearing capacity using a Soda Class 4 tester.

As a result, the kinetic friction coefficient of the silicone oil as the dispersion medium is 0.23, whereas the kinetic friction coefficient of the liquid lubricant is 0.15, which is higher than that of the base liquid silicone oil. Friction was getting smaller. The load carrying capacity, which is a measure of abrasion resistance, was 3.5 kgf for the silicone oil and 3.5 kgf for the liquid lubricant. From this, it is considered that the liquid lubricant has at least as much abrasion resistance as silicone oil as its base oil (liquid dispersion medium).

The above-mentioned liquid lubricant was placed in a test tube,
The dispersion stability was evaluated by measuring the time-dependent change in the thickness of the supernatant layer when allowed to stand at 5 ° C., and as a result, the liquid lubricant did not precipitate over two months or more and showed excellent dispersion stability. . Further, the liquid lubricant was centrifuged by a centrifuge CF15.
Using D (manufactured by Hitachi, Ltd.), centrifugation was performed at 9,000 G and 25 ° C. for 1 hour to conduct a precipitation promotion test. As a result, no precipitation was observed, and almost semi-permanent dispersion stability was obtained. I found out. Therefore, the above liquid lubricant is
It was confirmed that the lubricating properties such as dynamic friction coefficient and abrasion resistance were excellent.

FIG. 1 shows, as an example of a change in the external environment, the electric field strength required to keep the viscosity of the liquid lubricant constant when the temperature changes, and the electric field strength used for the liquid lubricant. 4 is a graph showing a change in viscosity of a used silicone oil with a change in temperature. In this case, in order to obtain the electric field strength shown in FIG. 1, an AC voltage of 1,000 Hz was used here. In addition, the shear rate of the rotating double cylinder is 700 s
^{It was set to -1} .

As shown in FIG. 1, the viscosity of the silicone oil, which is the base liquid dispersion medium, decreases as the temperature increases, and the lubrication characteristics deteriorate. However, the above-described liquid lubricant can offset a change in viscosity due to a change in an external environment such as temperature and pressure by controlling the application of an electric field by applying an electric field having an intensity corresponding to the temperature. Regardless, it is possible to always maintain a constant viscosity (lubrication characteristics).

In the above description, the control of the lubrication characteristics when the temperature changes is described as an example of the change in the external environment. However, the liquid lubricant of the present invention is not limited to only the temperature,
It can respond to changes in the external environment such as pressure and shear rate, and control the lubrication characteristics by the ER effect as needed.

In other words, if a liquid lubricant that exhibits the ER effect when an electric field is applied is used, even if a change occurs in the external environment such as temperature and pressure, the change is offset by the application of the electric field, and the change is offset. Viscosity such as kinematic viscosity and viscosity coefficient of the liquid lubricant can be kept constant, and the lubrication characteristics of the liquid lubricant can be kept constant.

Further, if a liquid lubricant that exhibits the ER effect when an electric field is applied is used, the lubricating property of the liquid lubricant can be controlled at a desired position by applying the electric field at a desired position of the mechanical device. can do.

On the other hand, when the liquid lubricant does not exhibit the ER effect, there are problems that the change in lubricity due to the temperature change is large and the lubricity cannot be sufficiently controlled at a desired position in the mechanical device.

As described above, the lubricating properties of the liquid lubricant according to the present invention can be arbitrarily changed by applying an electric field according to the conditions of use. Therefore, according to the above-mentioned method, it is possible to control the lubricating characteristics according to the use condition, and it is possible to easily, quickly and repeatedly adapt to changes in the use condition.

[0096]

The present invention will be described below in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

The lubricating properties of the liquid lubricant were evaluated by apparent viscosity. First, about the obtained liquid lubricant,
The viscosity at a temperature of 20 ° C. without applying an electric field was measured. Further, the temperature is controlled to −10 ° C. while controlling the applied electric field intensity so that the apparent viscosity does not change even when the temperature changes.
To obtain the viscosity or apparent viscosity (cSt: 10 ^-2 · cm ² · s ^-1 ) and the electric field strength (kV / mm) at this time, ie, the above viscosity or apparent viscosity. Was measured. For the measurement, a double cylindrical rotary viscometer capable of applying an electric field (a gap between the inner cylinder and the outer cylinder of 0.5 mm, and a shear rate of 700 / s) was used.

Example 1 A stirrer, an inert gas introduction pipe,
Toluene 2 was placed in a flask equipped with a reflux condenser and a thermometer.
00 parts by weight were charged. There, methacryloyl group-containing polydimethylsiloxane (manufactured by Chisso Corporation; trade name
Thyraplane FM0721; molecular weight about 5,000)
130 parts by weight, 60 parts by weight of styrene, and 10 parts by weight of azobisisobutyronitrile dissolved in a monomer mixture consisting of 10 parts by weight of glycidyl methacrylate, and charged.
The contents in the flask were stirred to form a uniform solution.

Next, the above solution was heated to 70 ° C. while blowing nitrogen gas, and stirring was continued for 4 hours to carry out a polymerization reaction. Thereafter, toluene in the obtained polymer solution was distilled off under reduced pressure to obtain a polymer (1) having an epoxy group as a reactive group in the molecule. The average molecular weight of this polymer (1) was Mn = 15,000 as measured by GPC (Gel Permeation Chromatography).

Next, 15 parts by weight of a polymer (1) having an epoxy group as a reactive group in a molecule and carbon black MA-100R (Mitsubishi Corporation) were placed in a separable flask equipped with a thermometer, a stirring blade, and a condenser. Charge 15 parts by weight of carbon black manufactured by Kasei Co., Ltd., 70 parts by weight of silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .; trade name: KF96-20CS), and 1,000 parts by weight of SUS beads.
The carbon black was grafted by stirring and reacting at 20 ° C. and 600 rpm for 6 hours. After the reaction, the reaction contents are separated from the beads, whereby the contents obtained by dispersing the carbon black graft polymer (dispersed phase particles) in silicone oil (liquid dispersion medium), that is, the liquid lubricant according to the present invention ( 1) was obtained.

The average particle diameter of the carbon black graft polymer in the liquid lubricant (1) was 0.075 μm, as measured using a dynamic light scattering meter (TM370 manufactured by Particle Sizing Co., Ltd.). Further, the lubricating properties of the liquid lubricant (1) were evaluated by the method described above. Table 1 shows the results.

Example 2 A stirrer, an inert gas introduction pipe,
Toluene 2 was placed in a flask equipped with a reflux condenser and a thermometer.
00 parts by weight were charged. There, methacryloyl group-containing polydimethylsiloxane (manufactured by Chisso Corporation; trade name
Thyraplane FM0711; molecular weight about 1,000)
A monomer mixture consisting of 140 parts by weight, 40 parts by weight of styrene, and 20 parts by weight of glycidyl methacrylate was charged by dissolving 10 parts by weight of benzoyl peroxide, and the contents in the flask were stirred to form a uniform solution.

Next, the above solution was heated to 70 ° C. while blowing nitrogen gas, and stirring was continued for 4 hours to carry out a polymerization reaction. Thereafter, toluene in the obtained polymer solution was distilled off under reduced pressure to obtain a polymer (2) having an epoxy group as a reactive group in the molecule. The average molecular weight of this polymer (2) was Mn = 7,000 by GPC measurement.

Next, in Example 1, the polymer (1) 1
Instead of 5 parts by weight, 20 parts by weight of the polymer (2) having an epoxy group as a reactive group in the molecule was used, and the amount of carbon black MA-100R was changed from 15 parts by weight to 10 parts by weight. Except for the above, the same reaction and operation as in Example 1 were carried out to obtain a content in which the carbon black graft polymer (dispersed phase particles) was dispersed in silicone oil (liquid dispersion medium), that is, the liquid lubricant according to the present invention. (2) was obtained.

The average particle diameter of the carbon black graft polymer in the liquid lubricant (2) measured by the same method as in Example 1 was 0.92 μm. Further, the lubricating properties of the liquid lubricant (2) were evaluated by the method described above. Table 1 shows the results.

Example 3 A stirrer, an inert gas introduction pipe,
Toluene 2 was placed in a flask equipped with a reflux condenser and a thermometer.
00 parts by weight were charged. There, methacryloyl group-containing polydimethylsiloxane (manufactured by Chisso Corporation; trade name
Thyraplane FM0721; molecular weight about 5,000)
A monomer mixture consisting of 130 parts by weight, 60 parts by weight of styrene, and 10 parts by weight of isopropenyloxazoline was charged by dissolving 10 parts by weight of benzoyl peroxide, and the contents in the flask were stirred to form a uniform solution. .

Next, the above solution was heated to 90 ° C. while blowing nitrogen gas, and stirring was continued for 4 hours to carry out a polymerization reaction. Thereafter, toluene in the obtained polymer solution was distilled off under reduced pressure to obtain a polymer (3) having an oxazoline group as a reactive group in the molecule. The average molecular weight of this polymer (3) was Mn = 22,000 by GPC measurement.

Next, in a separable flask equipped with a thermometer, a stirring blade, and a cooling tube, 20 parts by weight of the polymer (3) having an oxazoline group as a reactive group in the molecule and carbon black MA-100R (Mitsubishi Corporation) 10 parts by weight of carbon black manufactured by Kasei Co., Ltd., silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .; trade name: KF96-20CS) 70
By weight, SUS beads (1,000 parts by weight) were charged, and the mixture was stirred and reacted at 100 ° C. and 600 rpm for 3 hours to perform carbon black grafting. After the reaction, the reaction contents are separated from the beads, whereby the contents obtained by dispersing the carbon black graft polymer (dispersed phase particles) in silicone oil (liquid dispersion medium), that is, the liquid lubricant according to the present invention ( 3) was obtained.

The average particle diameter of the carbon black graft polymer in the liquid lubricant (3) measured by the same method as in Example 1 was 0.082 μm. Further, the lubricating properties of the liquid lubricant (3) were evaluated by the method described above. Table 1 shows the results.

Example 4 Synthetic smectite was allowed to react with an equivalent aqueous solution of dimethyldialkyl (a mixture of octadecyl and hexadecyl) ammonium chloride (manufactured by Lion Akzo; trade name: Arquad2HT-75). The ions were exchanged for dimethyldialkylammonium ions. Further, 1.9% by weight of water was added to a clay-organic composite (manufactured by Coop Chemical Co .; trade name: SAN) obtained by drying and pulverizing the obtained synthetic smectite. Next, 10 parts by weight of this clay-organic composite was put into 90 parts by weight of silicone oil, and heated at 110 ° C. while stirring, and then about 200 g.
Content obtained by dispersing the clay-organic composite (dispersed phase particles) in silicone oil (liquid dispersion medium) by centrifugation at a gravitational acceleration of 20 minutes, that is, the liquid lubricant (4) according to the present invention. I got

The average particle size of the synthetic smectite in the liquid lubricant (4) measured by the same method as in Example 1 was 0.38 μm. Further, the lubricating properties of the liquid lubricant (4) were evaluated by the method described above. Table 1 shows the results.

Comparative Example 1 Polybutene “LV-25”
Liquid lubricant (1) for comparison with Nippon Petrochemical Co., Ltd.
And The lubricating properties of the comparative liquid lubricant (1) were evaluated by the method described above. Table 1 shows the results.

[Comparative Example 2] Silicone oil "KF96"
-100CS "(manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a comparative liquid lubricant (2). The lubricating properties of the comparative liquid lubricant (2) were evaluated by the method described above. Table 1 shows the results.

[0114]

[Table 1]

The liquid lubricant obtained in this example was compared with the viscosity at 20 ° C. when no electric field (electric field) was applied and the apparent viscosity at 20 ° C. when the electric field was applied. Since the apparent viscosity at 20 ° C. is higher than the viscosity at 20 ° C. when no electric field is applied, the liquid lubricant obtained in this example changes in viscosity by application of an electric field, that is, It can be seen that the ER effect is exhibited. Further, it can be seen that the liquid lubricant obtained in the present example can maintain a constant viscosity even when the temperature changes, by appropriately changing the electric field strength according to the change in the temperature.
Therefore, it can be seen that the liquid lubricant obtained in the present example can control the lubricating properties, and can always exhibit excellent lubricating properties even when used in environments with different temperature conditions.

On the other hand, the liquid lubricant for comparison obtained in the comparative example was compared with the viscosity at 20 ° C. when no electric field was applied and the viscosity at 20 ° C. when the electric field was applied. It can be seen that the viscosity does not change, and that the viscosity changes with a change in temperature.

[0117]

As described above, the liquid lubricant according to the first aspect of the present invention comprises an electrorheological fluid containing dispersed phase particles and a liquid dispersion medium, and undergoes a reversible viscosity change with the application of an electric field. This is the configuration shown.

As described above, the liquid lubricant according to the second aspect of the present invention is the liquid lubricant according to the first aspect, wherein the average particle diameter of the dispersed phase particles is in the range of 0.001 μm to 1 μm. It is.

As described above, the liquid lubricant according to the third aspect of the present invention has a structure in which the dispersed phase particles are dielectric particles in the liquid lubricant according to the first or second aspect.

Since the liquid lubricant having the above-described structure shows a reversible viscosity change with the application of an electric field, it depends on the use conditions such as changes in the external environment such as temperature and pressure and the position in the mechanical device. Instead, it is possible to always maintain a constant lubrication characteristic, or to arbitrarily change the lubrication characteristic as needed at a desired position in the mechanical device. Therefore, according to the above configuration, there is an effect that it is possible to provide a liquid lubricant capable of controlling the lubrication characteristics according to the use situation.

The method for controlling the lubricating properties of a liquid lubricant according to the present invention as described above comprises an electrorheological fluid containing dispersed phase particles and a liquid dispersion medium, and is reversible with the application of an electric field. This is a method of controlling the lubrication characteristics by applying an electric field to a liquid lubricant exhibiting a change in viscosity in accordance with the state of use.

According to the above configuration, the liquid lubricant is applied, for example, at a temperature or pressure by applying an electric field in accordance with a use condition such as a change in an external environment such as temperature and pressure and a position in a mechanical device. Even if the external environment such as pressure changes, the ER effect controls viscosity such as kinematic viscosity and viscosity to maintain constant lubrication characteristics,
Alternatively, the lubrication characteristics can be arbitrarily changed at a desired position in the mechanical device as needed.

[Brief description of the drawings]

FIG. 1 shows the electric field strength required to keep the viscosity of the liquid lubricant according to the present invention constant when the temperature changes,
4 is a graph showing a change in viscosity of a silicone oil used in the liquid lubricant with a change in temperature.

Continued on the front page F-term (reference) 4H104 AA01A AA04C AA08C AA13C AA22C BB34A BB44A BH03A CA02C CA03C CA07C CB07C CB08C CB14A CD04A CJ02A CJ04A CJ13A DA02A DA06A EA08A EA09 FA EA09A04

Claims (4)

[Claims] 1. A liquid lubricant comprising an electrorheological fluid containing dispersed phase particles and a liquid dispersion medium, and exhibiting a reversible change in viscosity with application of an electric field. 2. The dispersed phase particles having an average particle diameter of 0.001.
2. The method according to claim 1, wherein the distance is in the range of μm to 1 μm.
A liquid lubricant as described. 3. The liquid lubricant according to claim 1, wherein the dispersed phase particles are dielectric particles. 4. An electric field is applied to a liquid lubricant comprising an electrorheological fluid containing dispersed phase particles and a liquid dispersion medium, which exhibits a reversible change in viscosity with the application of an electric field, according to the use condition. And controlling the lubrication characteristics of the liquid lubricant.