JP2000104083A - Lubricant paste and lubricating film obtained therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lubricant paste which has a low viscosity and is easily applicable even when its solid content is high by mixing a lubricant powder into a varnish prepd. by dissolving, in an org. solvent, a polyimide precursor formed from a diamine and a tetracarboxylic acid and/or its ester. SOLUTION: A lubricant powder is mixed into a varnish which is prepd. by dissolving a polyimide precursor formed from (A) a diamine of formula I and (B) a tetracarboxylic acid and/or its ester of formula II in an org. solvent in a concn. of the precursor of 5-80 wt.%. In the formulas, R1 and R2 are selected from the groups represented by formula III, etc., and from the groups represented by formula IV, etc., respectively; R3 to R8 are each H or 1-5C alkyl; and m is an integer of 0-10. Pref., the wt. ratio of A/B is (20/80)-(99/1), and 0.5-200 pts.wt. lubricant powder is mixed into 100 pts.wt. polyimide precursor varnish.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricant paste comprising a varnish of a polyimide precursor and a lubricant powder, and a lubricating film obtained therefrom.

[0002]

2. Description of the Related Art Conventionally, lubricating films used for friction sliding members such as dynamic pressure bearings and piston rings are made of thermosetting materials such as epoxy resin, phenol / formaldehyde resin, melamine resin, and acrylic resin dissolved in an organic solvent. Solid lubricant powder and other additives are added to a binder resin made of a resin or a thermoplastic resin such as polyamideimide, mixed and dispersed to prepare a lubricant paste, and the lubricant paste is applied to a substrate and dried. And cured. In recent years, the demand for the durability of the solid lubricating layer has become more and more severe due to the high-speed rotation of bearings and the high operating temperature environment, and lubricant paste made of binder resin with better heat resistance and durability Is required. In response to such demands, polyimide resins are well known as resins excellent in various physical properties and durability at high temperatures. As a solution (varnish) of the polyimide precursor, a solution of a polyimide precursor composed of a polyamic acid using dimethylformamide or N-methylpyrrolidone as a solvent has been well known, and a varnish of such a polyimide precursor has been known. The dispersion of various fillers therein is also known from various documents. By applying this technology, it is considered possible to produce a lubricant paste in which lubricant powder is dispersed in a varnish of a polyimide precursor.

However, varnishes using a polyamic acid as a polyimide precursor are difficult to increase the solid content ratio in the varnish due to a high degree of polymerization and a low solubility. The lubricant paste manufactured using the varnish required complicated operations such as repeated printing and coating in order to obtain a thin film having a predetermined thickness. Furthermore, since the varnish using a polyamic acid as a polyimide precursor has a high viscosity even at a low solids concentration, the viscosity further increases when a lubricant paste is prepared by mixing a dielectric powder, and a predetermined viscosity. When the proportion of the lubricant is increased to obtain a solid lubricating film having friction and wear characteristics, there is a problem that printing and coating become difficult.

[0004]

In view of the above, it is an object of the present invention to provide a lubricant paste which has a low viscosity and is easy to apply even when a polyimide precursor and a lubricant powder are contained in an organic solvent at a high solid content ratio. And to provide a uniform lubricating film having a smooth surface obtained from the lubricant paste.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, a varnish prepared by dissolving a polyimide precursor comprising a specific diamine and a specific carboxylic acid in an organic solvent. And found that the lubricant paste made of lubricant powder has a low viscosity even if it has a high solid content ratio, and furthermore, it is made of polyimide and solid lubricant powder by coating and curing the lubricant paste It has been found that a uniform lubricating film can be obtained. That is, the gist of the present invention is that, first, a diamine represented by the following formula (1) and a tetracarboxylic acid and / or an ester thereof represented by the following formula (2) are dissolved in an organic solvent as a polyimide precursor, A lubricant paste comprising a varnish of a polyimide precursor in which the concentration of the diamine, tetracarboxylic acid and / or ester thereof is 5 to 80% by weight, and lubricant powder.

[0006]

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In the formula, R ₁ and R ₂ are each selected from structural formula groups 1 and 2, and R _{3 to} R ₈ are a hydrogen atom or a carbon atom having 1 to 5 carbon atoms.
And m represents an integer of 0 to 10.

Second, a lubricating film is characterized in that a polyimide comprising a repeating unit represented by the following formula (3) obtained by applying the lubricating paste to a substrate and heating is used as a binder.

[0009]

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In the formula, R ₁ and R ₂ are each selected from Structural Formula Group 1 and Structural Formula Group 2, and n is an integer of 10 to 5000.

In the formula, R1 and R2 are each selected from Structural Formula Group 1 and Structural Formula Group 2, and n is an integer of 10 to 5000.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The lubricant paste of the present invention comprises a varnish obtained by dissolving a polyimide precursor in an organic solvent and containing a lubricant powder. The diamine represented by the above formula (1) and the above formula (2) are used as the polyimide precursor. And / or esters thereof. Then, the concentration of the polyimide precursor, that is, the diamine and the tetracarboxylic acid and / or its ester, that is, the solid content concentration is 5 to 8
It is dissolved in an organic solvent at 0% by weight. If this concentration is lower than 5% by weight, it may be difficult to obtain a predetermined lubricating film thickness only by adjusting the coating apparatus, and thus it may be necessary to repeatedly apply the coating, thereby deteriorating the advantage in terms of productivity. Easily. On the other hand, if the concentration is higher than 80% by weight, it becomes difficult to stably dissolve the polyimide precursor, and even if the polyimide precursor can be dissolved by selecting an organic solvent, the viscosity of the lubricant paste increases. As a result, the coating property may be reduced, and the productivity of the lubricating film may be reduced. In view of productivity, the preferred concentration range is from 20% by weight to 55% by weight. In this concentration range, a lubricant paste suitable for a conventionally known coating method such as screen printing used for forming a fine pattern or other spin coating method, bar coating method, spray coating method, dip coating method, or the like can be obtained.

The ratio between the diamine represented by the above formula (1) and the tetracarboxylic acid and / or ester thereof represented by the above formula (2) is such that the diamine represented by the formula (1) and the tetracarboxylic acid represented by the above formula (2) Sum 1 with acid and / or ester thereof
The diamine represented by the formula (1) is 20 to 100 parts by weight.
Preferably it is 99 parts by weight.

The organic solvent used in the lubricant paste of the present invention includes N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, hexamethylphosphoryltriamide, sulfolane, N, N
Polar solvents containing N, S, P atoms in molecules such as' -dimethylimidazolidinone, N-methylcaprolactam, etc., cellsolves such as cellsolve and phenylcellsolve, and cellsolve acetate such as ethylacetsolve and butylacetate Carbitols such as methyl carbitol and ethyl carbitol; carbitol acetates such as ethyl carbitol and butyl carbitol; carbitol diethers such as dimethyl carbitol (diglyme) and diethyl carbitol; Organic solvents having a boiling point of 150 ° C. or higher, such as alcohols such as hexanol and benzyl alcohol, ketones such as cyclohexanone and isophorone, and esters such as γ-butyrolactone, are preferred. This is because, when performing continuous production, if an organic solvent having a boiling point of less than 150 ° C. is used,
This is because the volatilization of the organic solvent is remarkable and the viscosity of the lubricant paste may not be stable. The type of the solvent can be appropriately selected depending on the desired evaporation rate and the viscosity of the paste. However, the use of a highly polar organic solvent containing N, S or P atoms in the molecule makes the solubility of the polyimide precursor higher. In order to increase the film thickness, it is preferable to use a strongly polar organic solvent in order to obtain a polyimide precursor varnish having a higher concentration.

The lubricant powder used in the present invention includes graphite, molybdenum disulfide, polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), and perfluoroethylene-6-fluoride. Powders of fluorine compounds such as propylene copolymer (FEP) and tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), boron nitride, and the like can be used. The particle size of the lubricant powder is not particularly limited, but is preferably in the range of 0.01 to 20 μm in consideration of the uniformity of the film. For the purpose of adjusting the film hardness, friction coefficient, viscosity and the like, inorganic particles can be added and dispersed. As the inorganic particles, silica, alumina, zinc white, iron oxide, ferrite, aluminum nitride, silicon nitride, silicon carbide, boron nitride and the like are used. The shape of the inorganic particles may be a true sphere, a needle, a flake, or the like.

The proportion of the lubricant powder is preferably 0.5 to 200 parts by weight based on 100 parts by weight of the varnish of the polyimide precursor.

When the lubricant paste is applied on a substrate such as stainless steel by screen printing, pre-coating or the like, and then heated to a temperature of 250 ° C. to 350 ° C.,
The polyimide precursor is imidized to form a lubricating film using polyimide as a binder on the substrate.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. Example 1 As a polyimide precursor, a diamine in which R ₁ is represented by the formula (4) and R ₂ is represented by the formula (5) in the above formula (1), R ₃ and R ₄ are hydrogen atoms and m is 3 And R ₂ in Formula (2) is represented by Formula (5), and R ₅ , R ₆ , R _7, and R ₈
A varnish was prepared by using a carboxylic acid having a hydrogen atom in a weight ratio of 85:15 and dissolving in dimethylacetamide so that the total concentration of the diamine and the carboxylic acid was 25% by weight. To 100 parts by weight of the varnish, 10 parts by weight of graphite powder having an average particle diameter of 2 μm and 1 part by weight of PTFE powder having an average particle diameter of 2 μm were added and kneaded to prepare a lubricant paste.

[0019]

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[0020]

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Example 2 As a polyimide precursor, R ₁ in the above formula (1) is represented by the above formula (4), R ₂ is represented by the formula (6), R ₃ and R ₄ are hydrogen atoms, m is 3 A certain diamine, R ₂ in the above formula (2) is represented by the formula (6), R ₅ and R ₇ are methyl groups,
A varnish was prepared by dissolving in dimethylacetamide so that the total concentration of diamine and carboxylic acid was 25% by weight, using a carboxylic acid in which R ₆ and R ₈ were hydrogen atoms in a weight ratio of 93: 7. . To 100 parts by weight of the varnish, 25 parts by weight of a molybdenum disulfide powder having an average particle diameter of 0.3 μm were added and kneaded to prepare a lubricant paste.

[0022]

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Example 3 As a polyimide precursor, R ₁ in the above formula (1) is represented by the above formula (4), R ₂ is represented by the formula (6), R ₃ and R ₄ are hydrogen atoms, m is 3 A certain diamine, R ₂ in the above formula (2) is represented by the formula (6), R ₅ and R ₇ are methyl groups,
A varnish was prepared by dissolving in dimethylacetamide so that the total concentration of diamine and carboxylic acid was 25% by weight, using a carboxylic acid in which R ₆ and R ₈ were hydrogen atoms in a weight ratio of 93: 7. . To 100 parts by weight of the varnish, 4 parts by weight of graphite powder having an average particle diameter of 2 μm and 1.3 parts by weight of PTFE powder having an average particle diameter of 3 μm were added and kneaded to prepare a lubricant paste.

Example 4 To 100 parts by weight of the same varnish as in Example 3, 25 parts by weight of boron nitride powder having an average particle diameter of 0.5 μm was added and kneaded to prepare a lubricant paste.

Using the lubricant paste obtained in Examples 1 to 4, the paste was screen-printed on the outer periphery of a SUS rotary shaft (diameter: 4 mm) of the dynamic pressure bearing, and then dried and then heated to 300 ° C.
For 2 hours to form a lubricating film.

Example 5 The paste obtained in Example 1 was diluted with dimethylacetamide to adjust the viscosity to 0.5 poise. The paste was spray-coated on the rotating shaft of a dynamic pressure bearing, dried, dried and then heated at 300 ° C. for 2 hours to form a lubricating film.

Table 1 shows the viscosities of the lubricant pastes prepared in Examples 1 to 5 and the evaluation results of the obtained lubricating films.
As is clear from Table 1, it was found that each of the films had a uniform surface, did not peel off from the substrate, and had excellent adhesion.

[0028]

[Table 1]

As described above, the lubricant paste of the present invention has a low viscosity and can be easily applied even if the polyimide precursor and the lubricant powder are contained in the solvent at a high solid content ratio.
Accordingly, a lubricating film could be produced with high productivity from this lubricant paste, and the resulting lubricating film had a smooth surface and excellent adhesion to the substrate.

[0030]

The lubricating oil paste of the present invention has a low viscosity and is easy to apply even if the organic solvent contains the polyimide precursor and the lubricant powder at a high solid content ratio. The lubricating film obtained from this lubricant paste has a smooth and uniform surface.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C10M 133/06 C10M 133/06 // C10N 40:02 F term (reference) 4H104 AA04A AA19A AA26A BB23R BB33R BC07R BC09R BD07R BE07R BE11A BF01R BF03A BG05R CD02A EB03 FA06 LA20 QA13 QA19

Claims (5)

[Claims] 1. A diamine represented by the following formula (1) and a tetracarboxylic acid and / or an ester thereof represented by the following formula (2) are dissolved in an organic solvent as a polyimide precursor,
A lubricant paste comprising a varnish of a polyimide precursor having a concentration of the diamine, tetracarboxylic acid and / or ester thereof of 5 to 80% by weight, containing lubricant powder. Embedded image In the formula, R ₁ and R ₂ are each selected from Structural Formula Groups 1 and 2, R _{3 to} R ₈ represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and m represents an integer of 0 to 10. 2. A sum of a diamine represented by the formula (1) and a tetracarboxylic acid and / or an ester thereof represented by the formula (2):
The diamine represented by the formula (1) is 20 to 9 parts by weight based on 0 parts by weight.
2. The lubricant paste according to claim 1, wherein the amount is 9 parts by weight. 3. The lubricant paste according to claim 1, wherein the amount of the lubricant powder is 0.5 to 200 parts by weight based on 100 parts by weight of the varnish of the polyimide precursor. 4. The lubricant paste according to claim 1, wherein the lubricant powder is at least one powder selected from molybdenum disulfide, polytetrafluoroethylene, graphite, and boron nitride. 5. A lubricating film, characterized in that a polyimide comprising a repeating unit represented by the following formula (3) obtained by applying the lubricating paste according to claim 1 to a substrate and heating is used as a binder. Embedded image In the formula, R ₁ and R ₂ are each selected from Structural Formula Group 1 and Structural Formula Group 2, and n is an integer of 10 to 5000.