WO2014034642A1

WO2014034642A1 - Polyamide-imide resin composition for lubricating coating material

Info

Publication number: WO2014034642A1
Application number: PCT/JP2013/072817
Authority: WO
Inventors: 示野　勝也; 武久家根; 貴洋服部; 雅人谷川
Original assignee: 東洋紡株式会社
Priority date: 2012-08-30
Filing date: 2013-08-27
Publication date: 2014-03-06
Also published as: JP2014062223A; CN104471000A; JP6015551B2; CN104471000B

Abstract

Provided is a polyamide-imide resin composition for lubricating coating materials which retains the excellent heat resistance (i.e., high glass transition temperature) and mechanical strength (i.e., high modulus) inherent in polyamide-imide resins and in which the resin has excellent solubility in the solvents including γ-butyrolactone, which is a non-amide solvent, and the dissolved state can be maintained for a long time even when the solvents are in the state of being apt to easily absorb moisture. The polyamide-imide resin composition for lubricating coating materials is characterized by containing a polyamide-imide resin that contains the repeating unit represented by formula [I] in an amount of 50 mol% or more of all the repeating units contained in the structure of the polyamide-imide resin and by containing γ-butyrolactone and 1,3-dimethyl-2-imidazolidinone as solvents.

Description

Polyamideimide resin composition for lubricating paint

The present invention relates to a polyamide-imide resin composition for lubricating paint, a paint containing the same, and a sliding member coated with the paint.

Polyamideimide resin is a binder for electrical insulation paints, coating materials for various substrates, and sliding member paints (also referred to as “lubricant paints”) because of its good heat resistance, mechanical strength, solvent resistance and chemical resistance. Widely used as a resin.

As a lubricant paint used for a sliding member, a composition in which a solvent, a solid lubricant, an epoxy resin and a fluororesin are blended with a polyamideimide resin is known. For example, Patent Literature 1 and Patent Literature 2 disclose a resin composition for a lubricating paint using a polyamideimide resin as a binder. Further, Patent Document 3 discloses a resin composition for a lubricating paint using a silicone-modified polyamideimide resin as a binder.

The resin composition for lubricating paint is used to form a lubricating film by applying it to the surface of the sliding member, to prevent the sliding part from becoming familiar and scuffing, and to reduce the friction coefficient. In a sliding member for an automobile, improvement in wear resistance of the lubricating film and long-term sustainability of the effect are required from the viewpoint of reducing fuel consumption. In order to satisfy these requirements, it is necessary that the binder resin of the lubricating film exhibit high mechanical strength and high heat resistance. Polyamideimide resin is advantageous compared to other binder resins because of its excellent mechanical strength and heat resistance.

However, conventionally used polyamideimide resins have low solubility in non-amide solvents, and amide solvents such as N-methyl-2-pyrrolidone (NMP) and N, N-dimethylacetamidoamide (DMAc) alone Alternatively, it was soluble only in a mixed solvent with a non-amide solvent containing an amide solvent as a main component. Therefore, when a polyamideimide resin is used as a binder resin, it is necessary to use a solvent mainly composed of an amide solvent.

When a resin composition using a solvent mainly composed of an amide solvent is applied to the sliding member, the hygroscopicity of the solvent becomes a problem. That is, when a resin composition containing a large amount of an amide solvent is applied to a sliding member by a roll coat transfer method or an air spray method, if the solvent has high hygroscopicity, it easily absorbs moisture in the air during work, As a result, the moisture content in the resin composition increases. If it does so, the solution viscosity of a resin composition will raise remarkably and the change of coating conditions will be needed. In some cases, since the resin cannot be dissolved and precipitates, it is necessary to stop the equipment and perform cleaning each time, and the working efficiency is significantly reduced.

In order to overcome such a problem, Patent Document 4 proposes a method in which a polyamideimide resin is modified and dissolved in a non-amide solvent having low hygroscopicity. However, such modification tends to impair the excellent mechanical strength and heat resistance inherent in polyamideimide resins that can be polymerized with amide solvents. Therefore, the modified polyamideimide resin cannot be suitably used as a resin composition for a lubricating paint for a sliding member.

Also, attempts have been made to obtain a polyamideimide that is soluble in non-amide solvent gamma-butyrolactone and exhibits high mechanical strength (see Patent Document 5). Gamma-butyrolactone has a problem that the solubility of the polyamideimide resin is low, and further, the resin solubility is lowered when exposed to an environment where moisture absorption is likely assuming an actual coating environment of the paint. That is, when the resin composition is spread thinly without being hermetically sealed, the resin solubility is lowered due to moisture absorption by gamma-butyrolactone, and the resin is easily gelled or insolubilized. In Patent Document 5, these problems are considered to some extent, but the effect is not sufficient.

When using polyamideimide resin as a lubricant paint, methylethylketone, methylisobutylketone, cyclohexanone, cyclopentanone, toluene, xylene, etc. for the purpose of improving drying properties and improving dispersibility of additives such as curing agents and solid lubricants A low boiling dilution solvent such as dioxane may be added. These solvents are poor solvents for polyamide-imide resins, and when added, precipitates and smudges are generated, and there is a problem that the storage stability of the lubricating paint deteriorates.

JP 2005-30376 A JP 2003-306604 A JP-A-8-92528 JP 2003-289594 A JP 2008-285660 A

The present invention has been made in view of the above-described state of the prior art. Its purpose is to maintain excellent heat resistance (ie, high glass transition temperature) and mechanical strength (ie, high elastic modulus) of polyamide-imide resin, and excellent solubility in low hygroscopic solvents based on gamma-butyrolactone. Furthermore, there are provided a polyamide-imide resin composition for a lubricating paint capable of maintaining a dissolved state for a long time even in a state where the solvent easily absorbs moisture, a paint containing the same, and a sliding member coated with the paint. There is.
Another object of the present invention is to provide a polyamide-imide resin composition for lubricating coatings that does not cause deposits or scum even when the polyamide-imide resin composition for lubricating coatings is diluted with a poor solvent for polyamide-imide resin. To provide things.

In order to achieve the above-mentioned object, the present inventors diligently studied the structure of a repeating unit of a polyamide-imide resin that exhibits high solubility in a solvent containing gamma-butyrolactone. As a result, a specific structure that does not include an aliphatic or alicyclic structure that causes a decrease in heat resistance and mechanical strength and has a bent isocyanate component as a repeating unit of the polyamideimide resin exceeds a specific amount. It has been found that the above purpose can be achieved by inclusion. Furthermore, it has been found that by including a specific amount of 1,3-dimethyl-2-imidazolidinone as a solvent, no precipitate or smudge is produced even when diluted with a poor solvent for polyamideimide resin. The present invention has been completed based on these findings.

That is, the present invention has the following configurations (1) to (4).
(1) A polyamide-imide resin composition for lubricating coatings characterized by the following (i) to (iv):
(I) When the total amount of repeating units in the structure of the polyamideimide resin is 100 mol%, it contains a polyamideimide resin containing 50 mol% or more of repeating units of the following formula [I];

(Ii) containing gamma butyrolactone and 1,3-dimethyl-2-imidazolidinone as solvent;
(Iii) the proportion of gamma-butyrolactone in the total solvent is 60% by mass or more and 99.5% by mass or less; and (iv) the proportion of 1,3-dimethyl-2-imidazolidinone in the total solvent is 0.8. 5 mass% or more and 40 mass% or less.
(2) A lubricating paint comprising the polyamideimide resin composition for lubricating paint according to (1).
(3) One or more solvents selected from the group consisting of xylene, toluene, cyclohexanone, cyclopentanone, methyl ethyl ketone, and methyl isobutyl ketone are 5% by mass or more and 39.5% by mass or less in the total solvent of the lubricant paint. The lubricating paint according to (2), which is contained.
(4) A sliding member comprising a coating layer formed from the lubricating paint according to (2) or (3).

Since the polyamideimide resin used in the polyamideimide resin composition of the present invention contains a specific amount or more of the repeating unit represented by the formula [I], the polyamideimide resin has excellent heat resistance (that is, high glass transition). Temperature) and mechanical strength (that is, high elastic modulus) while maintaining solubility in a solvent containing gamma-butyrolactone with low hygroscopicity, and even if the solvent is easily hygroscopic, it will remain dissolved for a long time. The effect can be realized at the same time.
Further, since the polyamideimide resin composition of the present invention uses gamma-butyrolactone and 1,3-dimethyl-2-imidazolidinone in combination, it becomes soluble even when diluted with a poor solvent for polyamideimide resin. Excellent, no deposits or mist.
Furthermore, due to the effect of the polyamideimide resin of the present invention, the paint containing the polyamideimide resin composition of the present invention can simultaneously achieve the effects of excellent heat resistance, mechanical strength, and adhesion. Therefore, the sliding member obtained by applying the paint containing the polyamideimide resin composition of the present invention is extremely suitable for a piston for an automobile engine, a sliding member for a compressor of an air conditioner, and the like.

The polyamideimide resin composition of the present invention can be suitably used for a lubricant paint for sliding members. In addition, the polyamide-imide resin composition of the present invention means that the polyamide-imide resin is in a state dissolved in a solvent (particularly a polymerization solvent and a storage solvent).

The polyamideimide resin composition of the present invention includes a polyamideimide resin containing 50 mol% or more of repeating units of the following formula [I], when the total amount of repeating units in the structure of the polyamideimide resin is 100 mol%, and a solvent. And gamma-butyrolactone and 1,3-dimethyl-2-imidazolidinone.

The above formula [I] present in the repeating unit in the structure of the polyamideimide resin of the present invention does not include an aliphatic or alicyclic structure, so that heat resistance and mechanical strength are not reduced, In addition, the isocyanate component is bent. Therefore, it exhibits excellent solubility in a solvent containing gamma butyrolactone, and can maintain a dissolved state for a long period of time even in a state where the solvent easily absorbs moisture. Therefore, in order for the polyamide-imide resin of the present invention to sufficiently exhibit such an effect, it is necessary to contain 50 mol% or more of the repeating unit of the formula [I] when the total amount of repeating units is 100 mol%. . Preferably it is 55 mol% or more, More preferably, it is 60 mol% or more.

The polyamideimide resin of the present invention can be produced by a conventionally known method, for example, an isocyanate method produced from an acid component and an isocyanate component, an acid chloride method produced from an acid chloride component and an amine component, an acid component and an amine component. It can be manufactured by a direct method of manufacturing. Among these, the isocyanate method is preferable from the viewpoint of production cost.

Hereinafter, the isocyanate method will be described as a representative method for producing the polyamideimide resin, but the polyamideimide resin can also be produced by the above acid chloride method and direct method by using the corresponding amine and acid / acid chloride, respectively. be able to.

In the case of producing a polyamideimide resin by the isocyanate method, in order to obtain the structure of the formula [I], polymerization may be performed using trimellitic anhydride (TMA) as an acid component and tolylene diisocyanate (TDI) as an isocyanate component. . Here, although an isomer exists in TDI, it may be tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, or a mixture thereof. Tolylene-2,4-diisocyanate is preferable. Moreover, as long as the above-mentioned effects of the present invention are not impaired, components other than TMA may be included as the acid component, and components other than TDI may be included as the isocyanate component. The method for containing 50 mol% or more of the repeating units of the formula [I] is not particularly limited. For example, when the total amount of the acid component is only TMA, and the total amount of the isocyanate component is 100 mol%, the structure of the formula [I] is added to the polyamideimide resin obtained by using TDI in 50 mol% or more of the isocyanate component. 50 mol% or more can be introduced. When the total amount of the isocyanate component is only TDI and the total amount of the acid component is 100 mol%, the structure of the formula [I] is added to the polyamideimide resin obtained by using TMA for 50 mol% or more of the acid component. 50 mol% or more can be introduced. As another example, when the total amount of the acid component is 100 mol%, 80 mol% of the acid component is TMA, and when the total amount of the isocyanate component is 100 mol%, 80 mol% of the isocyanate component is TDI. The amount of the structure of formula [I] introduced into the imide resin is 64 mol%. In other cases, the introduction amount (mol%) of the structure of the formula [I] in the polyamideimide resin can be calculated by the same method.

Examples of the acid component other than TMA include polycarboxylic acid anhydrides and dicarboxylic acids having an aromatic ring.
Examples of acid anhydrides of polycarboxylic acids having an aromatic ring include pyromellitic dianhydride, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, 3,3', 4,4'- Biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, ethylene glycol bisanhydro trimellitate, propylene Glycol bisanhydro trimellitate, alkylene glycol bis anhydro trimellitate such as 1,4-butanediol bis anhydro trimellitate, 3,4,9,10-perylene tetracarboxylic dianhydride, 3, 3 ', 4,4'-Diphenylsulfonetetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride , 4,4'-oxydiphthalic dianhydride, 1,1,1,3,3,3-hexafluoro-2,2-bis (2,3- or 3,4-dicarboxyphenyl) propane dianhydride 2,2-bis (2,3- or 3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis [4- (2,3- or 3,4-dicarboxyphenoxy) phenyl] Examples thereof include propane dianhydride.
Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, and oxydibenzoic acid.
These may be used alone or in combination of two or more. These acid components other than TMA are 100 mol of the total acid component from the viewpoint of expressing solubility of the polyamide-imide resin in the solvent containing gamma-butyrolactone and maintaining the dissolved state for a long time even when the solvent absorbs moisture. %, It is preferably less than 50 mol%, more preferably less than 40 mol%.

As the acid component, aliphatic or alicyclic acid anhydrides and alicyclic or aliphatic dicarboxylic acids can be used in addition to those already having an aromatic ring. For example, an acid component obtained by hydrogenating any of the components listed in the previous section can be given. Also, meso-butane-1,2,3,4-tetracarboxylic dianhydride, pentane-1,2,4,5-tetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic Acid dianhydride, dicyclohexyl-3,3 ', 4,4'-tetracarboxylic dianhydride, hexahydrotrimellitic anhydride, cyclohexanedicarboxylic acid, succinic acid, glutaric acid, adipic acid, heptanedioic acid, octane Examples thereof include diacids, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, and the like, and those having a hydrocarbon substituent in the dicarboxylic acid such as 2-methylsuccinic acid. These may be used alone or in combination of two or more. From the viewpoint of maintaining the heat resistance and mechanical strength of the polyamideimide resin, these acid components other than TMA are preferably less than 50 mol%, more preferably less than 40 mol% when the total acid component is 100 mol%. .

Examples of isocyanate components other than TDI include diisocyanates having aromatic rings such as 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate and structural isomers thereof, 3,3'-diethyldiphenylmethane-4,4'- Diisocyanate and its structural isomers, diphenylmethane-4,4'-diisocyanate, diphenylmethane-3,3'-diisocyanate, diphenylmethane-3,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-2,2'- Diisocyanate, diphenyl ether-4,4'-diisocyanate, benzophenone-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, m-xylylene diisocyanate, p-xy Diisocyanate, naphthalene-2,6-diisocyanate, 3,3 'or 2,2'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'- or 2,2'-diethylbiphenyl-4,4'- Diisocyanate, 3,3′-dimethoxybiphenyl-4,4′-diisocyanate and the like can be mentioned. Diphenylmethane-4,4′-diisocyanate (MDI) and 3,3′-dimethylbiphenyl-4,4′-diisocyanate (ToDI) are preferable, and diphenylmethane-4,4′-diisocyanate (MDI) is particularly preferable. is there. These may be used alone or in combination of two or more. These isocyanate components other than TDI are 100 mol of all isocyanate components from the viewpoint of expressing solubility of the polyamideimide resin in a solvent containing gamma-butyrolactone and maintaining the dissolved state for a long time even if the solvent is easily hygroscopic. %, It is preferably less than 50 mol%, more preferably less than 40 mol%.

As the isocyanate component, in addition to those having the aromatic ring already mentioned, aliphatic or alicyclic ones can also be used, for example, diisocyanate obtained by hydrogenating any of the components mentioned in the previous section. Further, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, ethylene diisocyanate, propylene diisocyanate, hexamethylene diisocyanate and the like can be mentioned. These isocyanate components other than TDI are from the viewpoint of heat resistance and mechanical strength of polyamide-imide resin, expression of solubility in a solvent containing gamma-butyrolactone, and maintaining a dissolved state for a long time even when the solvent is easily hygroscopic. When the total isocyanate component is 100 mol%, it is preferably less than 50 mol%, more preferably 40 mol% or less.

The polyamideimide resin of the present invention can be copolymerized with a compound having three or more functional groups for the purpose of increasing the number of reaction points between the resulting resin and the curing agent. Examples of such compounds include polyfunctional carboxylic acids such as trimesic acid and trimellitic acid, dicarboxylic acids having a hydroxyl group such as 5-hydroxyisophthalic acid, dicarboxylic acids having an amino group such as 5-aminoisophthalic acid, trimethylolpropane, Examples thereof include those having 3 or more hydroxyl groups such as glycerin and polyglycerol, and those having 3 or more amino groups such as tris (2-aminoethyl) amine. Among these, those having 3 or more amino groups such as dicarboxylic acid having a hydroxyl group such as 5-hydroxyisophthalic acid and tris (2-aminoethyl) amine are preferable from the viewpoint of reactivity and solubility. When these compounds are copolymerized, when the total acid component and the total isocyanate component are each 100 mol%, it is preferably 20 mol% or less with respect to the total 200 mol%. If it exceeds 20 mol%, there will be a lot of branching during polyamideimide polymerization, which may cause gelation or insoluble matter.

The polyamidoimide resin of the present invention has an acrylonitrile-butadiene rubber having a functional group at its terminal as a long chain component having a number average molecular weight of 500 or more for the purpose of imparting flexibility to the extent that the effects of the present invention are not impaired. And polyester, polyether, polycarbonate, dimer acid, polysiloxane, and the like can be copolymerized. In that case, if the amount of copolymerization to the polyamide-imide resin is large, the heat resistance and mechanical strength may be impaired. Therefore, when these components are each 100 mol% of the total acid component and the total isocyanate component, It is preferable that it is 20 mol% or less with respect to 200 mol% in total. If it exceeds 20 mol%, the heat resistance of the polyamideimide resin may be reduced.

The polymerization reaction of the polyamideimide resin of the present invention can be carried out by stirring the acid component and the isocyanate component while heating them in a solvent at 60 ° C. to 200 ° C. as conventionally known. At this time, the molar ratio of the acid component / isocyanate component is preferably in the range of 90/100 to 100/90. In general, the content of the acid component and the isocyanate component in the polyamideimide resin is the same as the ratio of each component during polymerization. In order to accelerate the reaction, alkali metals such as sodium fluoride, potassium fluoride, sodium methoxide, triethylenediamine, triethylamine, diethanolamine, 1,8-diazabicyclo [5,4,0] -7-undecene, An amine such as 1,5-diazabicyclo [4,3,0] -5-nonene or a catalyst such as dibutyltin dilaurate can be used. If these catalysts are too small, the catalytic effect cannot be obtained, and if they are too large, there is a possibility that side reactions occur. It is preferable to use 5 mol%, more preferably 0.1 to 3 mol%.

Since the polyamide-imide resin of the present invention does not require solvent substitution, it is preferably polymerized in a storage solvent described later, but can also be polymerized using a polymerization solvent other than the storage solvent. In this case, after polymerization, the polyamideimide resin composition has a suitable gamma butyrolactone concentration (60% by mass or more and 99.5% by mass or less in the total solvent) and a suitable 1,3-dimethyl-2-imidazolidinone concentration (0.5%). You may substitute the solvent in a polyamide-imide resin composition so that it may become mass% or more and 40 mass% or less. Here, the polymerization solvent is a solvent that can dissolve or disperse the raw material used for the polymerization of the polyamideimide resin and the resulting polymer, and a storage solvent for storing the polyamideimide resin composition described later. Is different from the stage of use.

As the polymerization solvent, one or a plurality of amide solvents and non-amide solvents can be selected and used. The amide solvent is a solvent having an amide group in the skeleton, and includes N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, 1,3-dimethyl-2-imidazolide. Non- and N-ethyl-2-pyrrolidone are exemplified. The non-amide solvent is a solvent having no amide group in the skeleton, and includes gamma-butyrolactone, cyclohexanone, cyclopentanone, tetrahydrofuran, isophorone, and other solvents other than amide solvents.

The polyamidoimide resin of the present invention preferably has a logarithmic viscosity of 0.2 dl / g or more. This range of logarithmic viscosity is for expressing the mechanical strength and adhesion necessary for using polyamideimide resin as a lubricant paint for sliding members.

The logarithmic viscosity is a value depending on the molecular weight of the polyamideimide resin, and a large value indicates that the polyamideimide resin has a high molecular weight. Here, when the logarithmic viscosity is less than 0.2 dl / g, the film as the lubricating film for the sliding member is brittle, and the film may be peeled off or broken during use of the sliding member. The higher the logarithmic viscosity, the less brittle the film. Therefore, in order to express the mechanical strength and adhesion of the lubricating coating film, a logarithmic viscosity of a certain level or higher is required as a polyamideimide resin. There is no particular upper limit to the value of the logarithmic viscosity, but if it is too high, the solution viscosity of the lubricating paint using the polyamideimide resin also increases, which may make the coating operation difficult. Accordingly, the logarithmic viscosity is preferably 2.0 dl / g or less, preferably 1.5 dl / g or less, more preferably 1.0 dl / g or less.

The glass transition temperature of the polyamide-imide resin of the present invention is preferably 200 ° C. or higher, more preferably 250 ° C. or higher, and further preferably 300 ° C. or higher. The upper limit is actually 400 ° C. The glass transition temperature is an index showing the heat resistance of the polyamide-imide resin and the lubricating coating film containing the same, and the higher the glass transition temperature, the higher the heat resistance of the resin.

The elastic modulus of the polyamide-imide resin of the present invention is preferably 2000 MPa or more, more preferably 2500 MPa or more, and further preferably 2700 MPa or more. The upper limit is practically 10,000 MPa. If the elastic modulus is low, there is a possibility that it is easily worn when used as a lubricating paint on the sliding member. The elastic modulus of the polyamideimide resin of the present invention can be adjusted by a combination of the aforementioned compositions.

The polyamide-imide resin composition for lubricating coatings of the present invention is in a state where the polyamide-imide resin of the present invention produced as described above is dissolved in a storage solvent. Conventional polyamide-imide resins have been polymerized and stored in a solvent mainly composed of an amide solvent having excellent solubility. However, the amide solvent easily absorbs moisture, and the solubility of the polyamide-imide resin is reduced by absorbing moisture. As a result, there has been a problem that the polyamideimide resin is easily insolubilized in the manufacturing, production, and processing steps of a paint using the polyamideimide resin composition. Here, when a non-amide solvent such as gamma-butyrolactone having a low hygroscopic property is used for polymerization and storage of the polyamideimide resin, the solubility of the polyamideimide resin is low, and the polymerization and storage are difficult. In addition, the non-amide solvent has low hygroscopicity, but gradually absorbs moisture in an unsealed environment, and when it absorbs moisture, the solubility of the resin further decreases. Therefore, it has been conventionally known that the polyamideimide resin exhibits excellent solubility in non-amide solvents without impairing the heat resistance and mechanical strength, and that the solvent remains in a dissolved state for a long time even in a state where it is likely to absorb moisture. It was difficult.

Therefore, as a result of intensive studies on the problem, the present inventors have determined that a certain amount of gamma-butyrolactone is used as a storage solvent by using a polyamideimide resin having a certain amount or more of the repeating unit of the formula [I] and at the same time as a storage solvent. It has been found that the above-mentioned problems can be solved by using the solvent contained above.

In addition, in the field of lubricating paints, for the purpose of improving the drying property and improving the dispersibility of additives, the polyamide-imide resin composition includes ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and cyclopentanone, toluene and xylene. In some cases, an aromatic hydrocarbon solvent such as tetrahydrofuran, dioxane or the like is added for dilution. These solvents are usually used in an amount of 50% by mass or less based on the total amount of solvents in the paint. However, for polyamide-imide resins, these solvents are poor solvents, and thus, when diluted, precipitates and smudges are likely to occur. Particularly for polyamideimide resins having a certain amount or more of the repeating unit of the formula [I], these solvents are poor solvents.

Accordingly, as a result of intensive studies on the problem, the present inventors have included 1,3-dimethyl-2-imidazolidinone in a specific amount in addition to gamma-butyrolactone as a solvent for the polyamideimide resin composition of the present invention. By this, it discovered that the dilution solubility at the time of adding a poor solvent can be improved.

In order to realize the low hygroscopicity of the solvent described above and the high solubility of the diluted solvent when a poor solvent is added, as a preservative solvent for the polyamideimide resin composition for lubricating paints of the present invention, Thus, it is necessary to add a specific amount of 1,3-dimethyl-2-imidazolidinone to a solvent containing gamma-butyrolactone as a main component.
The proportion of gamma butyrolactone in the total solvent of the polyamideimide resin composition may be 60% by mass or more and 99.5% by mass or less, preferably 80% by mass or more and 99.5% by mass or less, and more preferably 90% by mass. The content is 99.5% by mass or less.
The proportion of 1,3-dimethyl-2-imidazolidinone in the total solvent of the polyamideimide resin composition may be 0.5% by mass or more and 40% by mass or less, preferably 0.5% by mass or more and 20% by mass. % Or less, more preferably 0.5 mass% or more and 10 mass% or less.

If the amount is within the range that does not impair the above-mentioned effects, gamma-butyrolactone and 1,3-dimethyl-2-2 are used as storage solvents for the purpose of improving the stability of the dissolved state during storage of the polyamideimide resin composition. A solvent other than imidazolidinone may be used. For example, amide solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, and N-ethyl-2-pyrrolidone can be used. Among these, from the viewpoint of solubility of the polyamideimide resin, an amide solvent is preferable, and N-methyl-2-pyrrolidone is particularly preferable.

The concentration of the polyamideimide resin in the polyamideimide resin composition for lubricating coatings of the present invention is preferably 10 to 40% by mass, more preferably 15 to 30% by mass. When the concentration of the polyamideimide resin is low, the solution viscosity of the resin composition becomes too low, the workability is inferior, and it is difficult to obtain a coating film with little thickness unevenness. Moreover, when the density | concentration of a polyamideimide resin is high, the solution viscosity of a resin composition will become high and it will be inferior to workability | operativity.

Next, the lubricating paint of the present invention will be described. The polyamideimide resin composition of the present invention can be used as a lubricating coating as it is. In addition, the lubricating paint of the present invention includes a solid lubricant, an abrasion resistant material, an epoxy compound, an isocyanate compound, and / or a melamine compound added to the polyamideimide resin composition of the present invention, and a ball mill, a three-roll mill, a sand mill, etc. It can also be prepared by using and dispersing.

Solid lubricants include sulfides such as molybdenum disulfide and tungsten disulfide, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkylbutyl ether, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer Examples thereof include fluorine compounds such as coalesced polyvinylidene fluoride and trichlorotrifluoroethylene, and graphite. These may be used alone or in combination of two or more.

The blending amount of the solid lubricant is 5 to 500% by mass, preferably 10 to 200% by mass with respect to 100% by mass of the polyamideimide resin. If the solid lubricant is less than 5% by mass, the effect of reducing the friction coefficient and the seizure resistance may not be sufficiently exhibited. On the other hand, if it exceeds 500 mass%, the wear resistance may be insufficient.

Examples of the wear resistant material include silicon nitride, boron nitride, diamond, silica and the like, and these may be used alone or in combination of two or more. The particle size of the wear-resistant material is preferably 0.1 to 10 μm, and the blending amount is preferably 5 to 500% by mass with respect to 100% by mass of the polyamideimide resin. When the particle size of the wear-resistant material is less than 0.1 μm, the effect of improving the wear resistance is small, and when it exceeds 10 μm, the wear-resistant material tends to fall off the lubricating film. When the blending amount is less than 5% by mass, the effect of improving the wear resistance is not sufficiently exhibited. When the blending amount exceeds 500% by mass, the damage to the sliding partner is increased and the friction coefficient may be increased. There is.

Examples of the epoxy compound include bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, bisphenol F type epoxy resin, brominated bisphenol A type epoxy resin, phenol novolac type epoxy resin, o-cresol novolac type epoxy resin, Flexible epoxy resin, polyfunctional epoxy resin, amine type epoxy resin, heterocyclic ring-containing epoxy resin, alicyclic epoxy resin, bisphenol S type epoxy resin, triglycidyl isocyanurate, bixylenol type epoxy resin, bisphenol type epoxy resin, etc. These may be used alone or in combination of two or more.

Examples of the isocyanate compound include polyisocyanates of hexamethylene diisocyanate such as duranate, and polyisocyanates synthesized from 4,4′-diphenylmethane diisocyanate. The polyisocyanate preferably has a weight average molecular weight of 500 to 9000, more preferably 1000 to 5000.

The melamine compound is not particularly limited, and specific examples include a methylol group-containing compound obtained by reacting melamine with formaldehyde, paraformaldehyde or the like. The methylol group is preferably etherified with an alcohol having 1 to 6 carbon atoms.

Each compounding amount of the epoxy compound, isocyanate compound and melamine compound added to the polyamideimide resin composition is, for example, 1 to 40% by mass, preferably 5 to 30% by mass with respect to 100% by mass of the polyamideimide resin. It is preferable that If the blending amount is less than 1% by mass, the effect of improving the adhesion cannot be expected so much, and if it exceeds 40% by mass, the heat resistance and strength of the polyamideimide resin composition may not be maintained.

The polyamide-imide resin composition for lubricating coatings of the present invention contains a polyamide-imide resin containing a repeating unit of the formula [I] and contains gamma-butyrolactone and 1,3-dimethyl-2-imidazolidinone as a solvent. Therefore, the solubility in a hygroscopic state and the dilution solubility at the time of addition of the poor solvent with respect to a polyamide-imide resin are excellent. Therefore, the polyamideimide resin composition for lubricating coatings of the present invention contains repeating units of the formula [I] in an amount that does not impair the effects of the present invention for the purpose of improving drying properties and improving the dispersibility of additives. A poor solvent for the contained polyamideimide resin can be added to form a paint. For example, aromatic hydrocarbon solvents such as xylene and toluene, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and cyclopentanone may be added, or a mixture thereof. From the viewpoint of improving the drying property, it is preferable to use one or more selected from xylene, toluene, cyclohexanone, cyclopentanone, methyl ethyl ketone and methyl isobutyl ketone. The addition amount of these poor solvents is preferably 39.5% by mass or less, more preferably 35% by mass or less, and particularly preferably 30% by mass or less, based on the total amount of the solvent in the lubricating paint. If it is 39.5% by mass or less, the dilution solubility and the storage stability are particularly good without causing precipitates and smudges. Although there is no restriction | limiting in particular about a minimum, Preferably it is 5 mass% or more, More preferably, what is necessary is just 10 mass% or more. If it is 5 mass% or more, especially a drying improvement and the dispersibility improvement of an additive are obtained.

The polyamide-imide resin composition of the present invention may be further added with an antioxidant, a leveling agent, an antifoaming agent and the like for the purpose of improving workability and durability in an amount within a range that does not impair the characteristics.

The lubricating paint of the present invention can be adjusted to a viscosity suitable for use by dissolving in a preservative solvent. Examples of the method for applying the lubricating paint of the present invention to the sliding member include spraying, roll coating, dipping, screen printing, and the like, and the application method is selected depending on the shape of the sliding member and the thickness of the film. Can do. The sliding member coated with the lubricating paint of the present invention is heat-treated for drying the storage solvent and curing the paint.

After being applied to the surface of the sliding member, the lubricating paint of the present invention is heated to 150 ° C. or higher, preferably 150 to 380 ° C. for at least 10 minutes, for example, 10 to 120 minutes, to form a coating layer. . While being heated, volatile components such as a solvent contained in the lubricant paint are evaporated, and when a curing agent is blended, a curing reaction proceeds. By performing the heat treatment at such a temperature, the preservative solvent can be sufficiently removed, and the performance of protecting the coated substrate and the like can be sufficiently exhibited. In addition, when the heating time is 120 minutes or less, other additives added to the paint do not cause a side reaction or the applied paint does not deteriorate.

The sliding member of the present invention has a coating layer formed from the lubricating paint of the present invention. The coating layer can be formed by applying the lubricating paint of the present invention to at least a part of the surface of the sliding part of the member having the sliding part and then heat-treating it. Since the obtained coating layer is excellent in heat resistance, mechanical strength, and adhesion, the sliding member of the present invention is preferably used for, for example, a piston for an automobile engine or a sliding member for an air conditioner compressor. Can do.

Hereinafter, the effects of the present invention will be demonstrated by examples, but the present invention is not limited thereto. In addition, evaluation of the characteristic value in an Example was performed with the following method.

<Solvent solubility of polyamideimide resin>
After the production of the polyamideimide resin composition, it was visually confirmed whether or not the polyamideimide resin was insolubilized in a sealed state at room temperature for 1 day. Those in which the resin composition was turbid or precipitated were indicated by ×, and those in which the change was not observed and maintained in a transparent state were indicated by ◯.

<Logarithmic viscosity of polyamideimide resin>
A polyamideimide resin composition re-precipitated with water, filtered and dried (0.50 g) was dissolved in 100 ml of N-methyl-2-pyrrolidone, and the logarithmic viscosity of this solution was adjusted to 30 ° C. with an Ubbelohde viscosity tube. Measured with

<Preparation of polyamideimide resin coating film>
The polyamideimide resin composition was applied onto a copper foil so that the thickness after drying was 15 ± 5 μm, and dried with hot air at 100 ° C. for 5 minutes and at 250 ° C. for 60 minutes. Then, after immersing it at room temperature in a ferric chloride aqueous solution until the copper foil was completely removed by visual inspection, it was washed with water and dried at 50 ° C. for 60 minutes to obtain a polyamideimide resin coating film. . Using the obtained resin coating film, the following glass transition temperature and elastic modulus were measured.

<Glass transition temperature (Tg) of polyamideimide resin>
Using the dynamic viscoelasticity measuring apparatus DVA-220 manufactured by IT Measurement Control Co., Ltd., the viscoelasticity was measured at a frequency of 110 Hz and a heating rate of 4 ° C./min. The glass transition temperature (Tg) of the polyamideimide resin was determined from the inflection point of the storage elastic modulus. Specifically, tangent lines were drawn for the charts before and after the inflection point, and the temperature at the intersection was taken as the glass transition temperature.

<Elastic modulus of polyamideimide resin>
The coating film obtained as described above was adjusted to a width of 10 mm and a measurement length of 40 mm, and the modulus of elasticity of the polyamide-imide resin was measured at a room temperature of 25 ° C. and a tensile speed of 20 mm / min using a Tensilon manufactured by Toyo Baldwin. .

<Adhesiveness of polyamide-imide resin coating>
A polyamideimide resin composition was applied to a steel plate (SPCC-SB manufactured by Partec Co., Ltd.) so that the thickness after drying was 15 ± 5 μm, and dried in hot air at 100 ° C. for 5 minutes and at 250 ° C. for 60 minutes to obtain a laminate. . In accordance with a cross-cut test using cellophane tape (JIS K5600-5-6: 1999), the adhesion of the polyamideimide resin composition was evaluated.
Under the conditions of temperature (23 ± 2) ° C. and relative humidity (50 ± 5)%, a total of 100 squares of 10 squares × 10 squares are formed on the coating layer made of the polyamide-imide resin composition of the above laminate at intervals of 1 mm. A cross cut was formed, and the state of the coating film remaining after peeling of the cellophane tape was visually observed. In addition, Nichiban Co., Ltd. product was used for the peeling tape.
○: When the number of grids remains completely △: When the number of grids is less than 100 and 80 or more remain ×: When the number of grids is less than 80

<Solubility of Polyamideimide Resin Composition in Moisture Absorption>
The polyamideimide resin composition was applied on a PET film so that the thickness in a state containing a solvent was 100 μm, and the time until an insoluble material was formed in an environment of 25 ° C. and 70% humidity was measured. Judgment criteria were as follows.
◎: When the transparent state is maintained visually after 10 minutes and no insoluble matter is formed. ○: When the resin composition becomes cloudy and insoluble matter is visually observed in 5 minutes or more and less than 10 minutes ×: Less than 5 minutes When the resin composition becomes cloudy by visual inspection and produces insoluble matter

<Dilution solubility in poor solvent of polyamideimide resin composition (xylene dilution solubility)>
About 50 g of xylene is added to 100 g of polyamideimide resin composition (solid content concentration: 20% by weight), and it is about 3 in a glass bottle until uniform using a glass rod in an environment of 25 ° C. and a relative humidity of 65%. Stir for minutes. After stirring, the glass bottle was sealed, allowed to stand in a 5 ° C. incubator for 24 hours, the appearance of the polyamideimide resin composition was visually observed, and judged according to the following criteria.
◯: When the transparent state was maintained after 24 hours and no insoluble matter was produced. Δ: When the resin composition became cloudy and insoluble matter was produced immediately after stirring to less than 24 hours. X: Resin composition immediately after the end of stirring. When turbidity or insoluble matter occurs

<Content (mol%) of repeating unit of formula [I] contained in polyamideimide resin>
The content (mol%) of the repeating unit of the formula [I] contained in the polyamideimide resin was measured by the following method. A sample was prepared by dissolving 100 mg of polyamideimide resin in 0.6 ml of DMSO-d. The prepared sample was subjected to ¹ H-NMR analysis using an NMR apparatus 400MR manufactured by VARIAN, and the content (mol%) of the repeating unit of the formula [I] contained in the polyamideimide resin was determined.

(Example 1)
In a four-necked flask equipped with a nitrogen introduction tube and a cooling device, 192.1 g (1 mol) of trimellitic anhydride as an acid component and 165.5 g (0.95) of tolylene-2,4-diisocyanate as an isocyanate component Mol), a solvent prepared by adjusting the mass ratio of gamma-butyrolactone and 1,3-dimethyl-2-imidazolidinone to 99/1 as a polymerization solvent (hereinafter referred to as “adjusted solvent”) having a solid content concentration of 25 It added so that it might become the mass% (solid content concentration calculated from solid content (resin content) and solvent amount in the state which the raw material reacted and decarboxylated). Then, it was made to react at 130 degreeC for 5 hours, stirring in nitrogen atmosphere, and polyamidoimide resin was polymerized. Thereafter, the solution of the polyamideimide resin was cooled and diluted with the above-mentioned adjusting solvent so that the solid content concentration of the polyamideimide resin was 20% by weight, and the polyamideimide resin composition of Example 1 was obtained. Details of the polyamideimide resin composition of Example 1 are shown in Table 1, and the evaluation results are shown in Table 2.

(Examples 2 to 8)
The solid content concentration / atmosphere was the same as in Example 1 except that the total acid component was 1 mol, the total isocyanate component was 0.95 mol, and the acid component, isocyanate component and adjusting solvent were changed to the compositions shown in Table 1. -Polyamideimide resin compositions of Examples 2 to 8 were prepared respectively under the same conditions such as reaction time. Details of the polyamideimide resin compositions of Examples 2 to 8 are shown in Table 1, and the evaluation results are shown in Table 2.

Example 9
In a four-necked flask equipped with a nitrogen introduction tube and a cooling device, 192.1 g (1 mol) of trimellitic anhydride as an acid component and 165.5 g (0.95) of tolylene-2,4-diisocyanate as an isocyanate component Mol), 821 g of N-methyl-2-pyrrolidone as a polymerization solvent was added so as to have a solid content concentration of 25% by weight, and the mixture was reacted at 130 ° C. for 5 hours with stirring in a nitrogen atmosphere to polymerize the polyamideimide resin. did. The solid content concentration was calculated from the solid content (resin content) and the amount of solvent in a state where the raw material reacted and decarboxylated. Thereafter, the polyamideimide resin solution was cooled and diluted with N-methyl-2-pyrrolidone so that the solid content concentration of the polyamideimide resin was 20% by weight. The polyamideimide resin in the obtained polyamideimide resin composition was precipitated / precipitated with acetone and the solvent was removed. Then, gamma-butyrolactone and 1,3-3- A polyamideimide resin composition of Example 9 was obtained by dissolving in a solvent adjusted so that the mass ratio of dimethyl-2-imidazolidinone was 95/5. Details of the polyamideimide resin composition of Example 9 are shown in Table 1, and the evaluation results are shown in Table 2.

(Comparative Examples 1 to 7)
The solid content concentration / atmosphere was the same as in Example 1 except that the total acid component was 1 mol, the total isocyanate component was 0.95 mol, and the acid component, isocyanate component and adjusting solvent were changed to the compositions shown in Table 1. -Polyamideimide resin compositions of Comparative Examples 1 to 7 were respectively prepared under the same conditions such as reaction time. Details of the polyamideimide resin compositions of Comparative Examples 1 to 7 are shown in Table 1, and the evaluation results are shown in Table 2.
In Comparative Example 7, polymerization could be performed, but when diluted and returned to room temperature, the resin changed from a transparent state to a cloudy state, and insolubilization was confirmed. For this reason, no other characteristics were analyzed. In Table 2, items that were not analyzed were indicated as [-].

The meanings of the abbreviations in the table are described below.
TMA: trimellitic anhydride TMEG: ethylene glycol bisanhydro trimellitate 2,4-TDI: tolylene-2,4-diisocyanate MDI: diphenylmethane-4,4′-diisocyanate 2,6-TDI: tolylene-2 6-diisocyanate GBL: gamma butyrolactone DMI: 1,3-dimethyl-2-imidazolidinone NMP: N-methyl-2-pyrrolidone

As is apparent from the results in Table 2, the resin compositions of Examples 1 to 8 in which the polyamideimide resin has a repeating unit of the formula [I] of 50 mol% or more have excellent heat resistance (that is, high glass transition temperature) and mechanical properties. While maintaining strength (that is, high elastic modulus), it exhibits solubility in solvents containing gamma-butyrolactone, and at the same time realizes the effect of maintaining the dissolved state for a long time even when the solvent is easy to absorb moisture. . Further, by containing 1,3-dimethyl-2-imidazolidinone in a certain range, dilution solubility when xylene as a poor solvent is added is improved.
In Example 9, N-methyl-2-pyrrolidone, which is an amide solvent, is used as the polymerization solvent, but the mass ratio of gamma-butyrolactone and 1,3-dimethyl-2-imidazolidinone is 95 as the storage solvent. By using the solvent adjusted to be / 5, the same effect as in Example 2 is exhibited.

On the other hand, the resin composition of Comparative Example 1 which does not contain gamma butyrolactone and 1,3-dimethyl-2-imidazolidinone is inferior in solubility in a moisture-absorbed state. The resin composition of Comparative Example 2, which does not contain 1,3-dimethyl-2-imidazolidinone, dissolves in a solvent containing gamma butyrolactone and exhibits sufficient characteristics such as heat resistance, elastic modulus, and adhesion, but xylene It is inferior in dilution solubility.

Further, the resin composition of Comparative Example 3 in which the repeating unit of the formula [I] in the polyamide-imide resin is less than 50 mol% has poor dilution solubility of xylene, which is a poor solvent, and similarly repeats the formula [I]. The resin composition of Comparative Example 6 having a unit of less than 50 mol% has poor solubility in a hygroscopic state. Furthermore, the resin composition of Comparative Example 7 that does not contain the repeating unit of the formula [I] does not dissolve in a solvent containing gamma butyrolactone and 1,3-dimethyl-2-imidazolidinone.

Comparative Example 5 in which the content of gamma-butyrolactone is less than 60% by mass in the total solvent has poor solubility in the moisture-absorbed state, and the content of 1,3-dimethyl-2-imidazolidinone exceeds 40% by mass. Comparative Example 4 also has poor solubility in the moisture-absorbed state.

From the above results, by dissolving a polyamideimide resin having 50 mol% or more of the repeating unit of the formula [I] in a solvent containing a certain amount of gamma butyrolactone and 1,3-dimethyl-2-imidazolidinone as a solvent, A polyamideimide composition having sufficient characteristics as a resin for lubricating coatings and excellent in dilution solubility of a poor solvent can be obtained.

Lubricating paints using the polyamideimide resin composition of the present invention are excellent in heat resistance, mechanical strength, and adhesiveness, and are suitable for application to sliding members. Is done.

Claims

Polyamideimide resin composition for lubricating coatings characterized by the following (i) to (iv):
(I) When the total amount of repeating units in the structure of the polyamideimide resin is 100 mol%, it contains a polyamideimide resin containing 50 mol% or more of repeating units of the following formula [I];

(Ii) containing gamma butyrolactone and 1,3-dimethyl-2-imidazolidinone as solvent;
(Iii) the proportion of gamma-butyrolactone in the total solvent is 60% by mass or more and 99.5% by mass or less; and (iv) the proportion of 1,3-dimethyl-2-imidazolidinone in the total solvent is 0.8. 5 mass% or more and 40 mass% or less.
A lubricating paint comprising the polyamideimide resin composition for lubricating paint according to claim 1.
One or more solvents selected from the group consisting of xylene, toluene, cyclohexanone, cyclopentanone, methyl ethyl ketone, and methyl isobutyl ketone are included in all the solvents of the lubricant paint in an amount of 5 mass% to 39.5 mass%. The lubricating paint according to claim 2.
A sliding member comprising a coating layer formed from the lubricating paint according to claim 2 or 3.