JPH08176495A - Coating resin composition and method for curing the composition - Google Patents

Abstract

PURPOSE: To improve the water repellency and oil repellency without any special and complicate step of coating by using a polyamideimide or a polyamideamic acid, polytetrafluoroethylene and a particular solvent as indispensable components. CONSTITUTION: A 40 to 80wt.% polyamideimide or polyamideamic acid, which is a precursor of polyamideimide, is dissolved in a solvent which can homogeneously dissolve the above compd. at room temp. 20 to 60wt.% polytetrafluoroethylene having a softening temp. of 300 deg.C or below is added and homogeneously mixed with the solution to prepare a coating resin compsn. The resin compsn. is applied onto a metal or the like, and the coating is baked in the temp. range of from the softening temp. of polytertrafluoroethylene to 370 deg.C. If necessary, a dispersion stabilizer, a resin stabilizer, a pigment, and an abrasion resistance improving material are added to the resin compsn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating resin composition having excellent water repellency and a curing method thereof. The resin composition of the present invention is applied to a surface of a metal or the like by baking it at a high temperature. It is useful as a surface treatment material for sliding members, etc., because it can form a film having excellent water-based property.

[0002]

2. Description of the Related Art Electronic parts, automobiles, railway vehicles, aircraft,
Parts used in various industrial fields such as office machines are
It is used in various usage environments. Among them, there are those used in contact with water such as pure water, acid and alkali, and those used in contact with lubricating oil such as sliding parts such as engine or motor. In addition, even when used originally under dry conditions, moisture often adheres to the surface due to condensation of moisture in the air. Due to the liquid adhering to the surface in this way, it becomes inoperable due to the adhering of the liquid feeding valve, frictional resistance increases in sliding parts such as motors, and smooth rotation cannot be performed. It becomes a fatal defect. Conventionally, in a portion where such a situation is expected, a method of surface-coating polytetrafluoroethylene (hereinafter abbreviated as PTFE) having a small surface tension, excellent water repellency, and excellent heat resistance and sliding characteristics Has been taken.

In order to form a PTFE coating film on a metal surface, first, the metal part to be coated is air-baked at about 400 ° C., the metal surface is roughened by sandblasting, and then the metal surface is washed. , Apply primer coating,
Subsequently, a method of spraying PTFE enamel and firing at a temperature of about 400 ° C. for about 10 to 40 minutes is used. Further, such a treatment usually needs to be repeatedly performed until the coating film has a predetermined thickness, which is very complicated and requires a lot of labor.

Japanese Unexamined Patent Publication (Kokai) No. 4-7376, Japanese Patent Laid-Open No. 6-5
No. 01974 discloses a coating composition in which PTFE and polyamide imide or PTFE and polyether sulfone are combined.

[0005]

However, these are obtained by finely pulverizing PTFE and polyamideimide resin or polyethersulfone in advance by a method such as freeze pulverization and dispersing them in a solvent. After baking, it is baked at a high temperature near 400 ° C and used.
As the dispersion solvent, those having no ability to dissolve in polyamide-imide resin or polyester sulfone, such as water and alcohols, are used. In these resin compositions, PTFE and polyamide-imide resin or polyester sulfone are used. It is supplied in the form of a fine powder dispersion. Therefore, when baking these resin compositions, in order to ensure adhesion with the base material, it must be heated above the melting point of the polyamide-imide resin or polyester sulfone, the baking temperature is usually 400 ℃ Is required.

Therefore, the present inventor has found that a resin composition obtained by combining PTFE with polyamide imide or polyether sulfone has a softening temperature of 300 as PTFE.
A resin composition which can be baked at a relatively low temperature was sought by using a resin having a temperature of not higher than 0 ° C., mixing these in a predetermined amount, uniformly dissolving them in a solvent.

[0007]

The present inventor has conducted numerous tests in order to solve such problems, and as a result, (a)
Polyamidoimide or polyamidoamidic acid which is a precursor of polyamidoimide 40 to 80 parts by weight, (b) polytetrafluoroethylene 20 to 60% by weight having a softening temperature of 300 ° C or lower, (c) at room temperature A resin composition containing a solvent capable of being uniformly dissolved as an essential component or (a) 40 to 80 parts by weight of polyether sulfone, (b) having a softening temperature of 3
20-60% by weight of polytetrafluoroethylene below 00 ° C,
(c) A resin composition containing, as an essential component, a solvent capable of uniformly dissolving (a) at room temperature is applied to a metal surface or the like and baked at a temperature in the range from the softening temperature of PTFE to 370 ° C. It was confirmed that a film having excellent water-based property was formed, and the present invention was completed.

A typical polyamic acid which is a precursor of polyamide or polyamideimide used in the present invention is represented by the following formula.

[0009]

Embedded image (In the formula, m and n represent an integer of 1 or more)

[0010]

Embedded image (In the formula, m and n represent an integer of 1 or more)

These compounds are sold under the trade name of "Torlon" by Teijin Amoco. When the two types of compounds are compared, those having a polyamide-imide structure are chemically stable and have excellent storage stability, but very few solvents can be uniformly dissolved, and this solvent is highly polar and has a low permissible concentration. In addition, special equipment is required for the equipment and environment during painting. On the other hand, those having a polyamidoamidic acid structure have a slightly poorer storage stability, but can be uniformly dissolved even in a solvent having a relatively low polarity and a high allowable concentration, which makes the prepared resin composition easy to handle. Therefore, depending on the usage situation, you can choose the suitable one.

For the polyether sulfone used in the practice of the present invention, a usual injection molding grade can be used, but from the viewpoint of improving the ease of adjusting the viscosity of the resin composition and the properties of the coating film after curing. Therefore, it is preferable to use a grade for baking paint.

The solvent used in the present invention can be uniformly dissolved at room temperature, and any solvent can be used as long as it can uniformly dissolve the polyamide imide, polyamide amic acid, and polyether sulfone used. is there. This solvent may be used alone or in combination of a plurality of solvents as long as it can prepare a uniform resin solution at room temperature. Even if the solvent does not dissolve the resin easily at room temperature, a uniform resin solution is prepared by heating and dissolving it in advance, and when the temperature is returned to room temperature, the resin component does not precipitate and the uniformity is maintained. If so, it can be used. Examples of these solvents include:
An aprotic polar solvent such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N, N-dimethylimidazolidinone (DMI). , Ethers such as diethylene glycol dimethyl ether (DMDG) and diethylene glycol diethyl ether (DEDG), and chlorides of aliphatic hydrocarbons such as methylene chloride and ethane tetrachloride. In addition to such a solvent, it is possible to add a solvent such as an alcohol, a hydrocarbon, or a halogenated carbon within a range that does not reduce the solubility of the resin.

As the PTFE used in the present invention, a special grade having a softening temperature (melting point) superior to that of a normal product and having excellent fluidity when melted is used. P with such a low melting point
As an example of TFE, Teflon TFE (melting point: 255 to 280 ° C.) manufactured by Mitsui Fluorochemicals Co., Ltd. has —CF ₃ on the side chain.
The melting point is lowered by the introduction of C., Asflon COP (melting point: 255 to 270 ° C) of Asahi Glass Co., Ltd., the one whose ethylene group is introduced into a part of tetrafluoroethylene to lower the melting point, Central Examples thereof include Cefral lube (melting point: 180 to 280 ° C.) manufactured by Glass Co., Ltd., whose melting point is lowered by extremely lowering the average molecular weight. All of these special grades of PTFE have a softening temperature (melting point) of 300 ° C or lower. In order to uniformly mix these PTFEs with a liquid composition composed of a resin solution such as polyamideimide, the PTFE is used in a powder state having a specific particle size with good dispersibility.

The weight ratio of PTFE to polyamide-imide or polyether sulfone in the resin composition of the present invention is in the range of 20/80 to 60/40. If it is less than 20/80 out of this range, the predetermined slidability and water repellency cannot be obtained, and conversely, if it exceeds 60/40, the viscosity of the resin composition becomes high and the coating property deteriorates, and May cause poor adhesion with.

In preparing the resin composition of the present invention, it is possible to add a dispersion stabilizer, a resin stabilizer, a pigment, an abrasion resistance improver, etc., in addition to the above-mentioned resin, solvent and PTFE. The coating resin composition of the present invention can be used in various forms such as a spray coating material, a screen printing ink, a dipping coating material, a spin coating coating material and a brush coating coating material. This method of use can be performed according to a known method. PTFE to be used for baking
Above the melting point and below 400 ° C, preferably 280 to 340 ° C. Since melting of PTFE does not occur at a temperature lower than the melting point of PTFE, the PT on the coating surface
A coating film of FE cannot be formed, and when baking is performed at a temperature exceeding 400 ° C, the film characteristics are deteriorated due to thermal decomposition of PTFE.

[0017]

According to the resin composition of the present invention, polyamide imide or polyether sulfone is homogeneously dissolved in a solvent before use. Therefore, the baking temperature of these resins must be above the glass transition temperature (200 to 260 ° C). Is enough. Further, by preliminarily dissolving these resins in a solvent, the coating film obtained becomes more homogeneous than when fine particles of the resin are dispersed. Further, by using a PTFE having a softening temperature lower than that of a normal PTFE, it is possible to form a coating film having predetermined characteristics by baking at 370 ° C. or lower.

[0018]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. The raw materials used in Examples and Comparative Examples are as follows, and the used parts are all parts by weight. Polyamideimide resin A-1): Torlon 4000T [manufactured by Teijin Amoco Co., Ltd.] Powder resin A-2): Torlon AI-10 [manufactured by Teijin Amoco Co., Ltd.] Powder Polyether sulfone resin S): VICTREX 5003P [Sumitomo Chemical Co., Ltd.] Powdered polytetrafluoroethylene (PTFE) Teflon FEP [Mitsui Fluorochemical Co., Ltd.] Aflon COP Z-8820 [Asahi Glass Co., Ltd.] Copolymer type average particle size 20 μm (melting point: 260-270 ° C.) Cefuralube-VH [Central Glass Co., Ltd.]
Low molecular weight PTFE (melting point: 250 to 270 ° C.) KTL-500F [manufactured by Kitamura Co., Ltd.] (melting point: 350 to
360 ° C.) Alumina AO-502 [manufactured by Tatsumori Co., Ltd.] True spherical alumina Average particle size 0.7 μm Solvent NMP: N-methyl-2-pyrrolidone DMDG: Diethylene glycol dimethyl ether Toluene: OFE: Ethyl orthoformate

The method of measuring the contact angle in the water repellency effect test is the tilt method, which is a smooth aluminum plate.
A film is applied on (100 × 100 mm) so that the film thickness is in the range of 7 to 11 μm, and half of this test piece is dipped in water and gradually inclined so that the liquid surface in contact with the test piece becomes horizontal (θ ) Is measured.

(Example 1) 340 parts of N-methyl-2-pyrrolidone (NMP), 100 parts of diethylene glycol dimethyl ether (DMDG), 25 parts of toluene, and 25 parts of ethyl orthoformate (OFE) were homogeneously mixed and mixed. 100 parts of powdery Torlon 4000T is sequentially dissolved.
After homogeneously dissolving, 30 parts of powdered Teflon FEP and 20 parts of alumina are added and mixed, and this is passed through a three-roll mill three times to mix uniformly. The resin composition thus prepared is applied onto an aluminum plate and placed in a hot air dryer to 1) 100 ° C / 30 minutes, 2) 150 ° C / 20 minutes, 3) 200 ° C / 20
Min., 4) 250 ° C./30 min, 5) 295 ° C./30 min, and the temperature was raised and cooled to form a milky white film on the aluminum plate. The results of measuring the water repellency of the coating film are shown in Table 1.

Comparative Example 1 In Example 1, PTFE was used.
Was changed to KTL-500F, and the same treatment was performed to form a film on the aluminum plate. The results of measuring the water repellency of the coating film are shown in Table 1.

(Example 2) The same procedure as in Example 1 was carried out except that the amount of solvent added and the type of resin were changed to form a film on the aluminum plate. The results of measuring the water repellency of the coating film are shown in Table 1.

(Embodiment 3) In the second embodiment, PTFE is used.
Was changed to AFLON COP, Z-8820 to form a coating on an aluminum plate.
The results of measuring the water repellency of the coating film are shown in Table 1.

(Comparative Example 2) A resin composition prepared in the same manner as in Example 3 was applied onto an aluminum plate and then in a hot air dryer, 1) 100 ° C / 30 minutes, 2) 150 ° C / 20 minutes. ,
When the temperature was raised in the order of 3) 200 ° C / 20 minutes and 4) 250 ° C / 30 minutes, respectively, and cooled, a milky white film could be formed on the aluminum plate. The results of measuring the water repellency of the coating film are shown in Table 1.

(Embodiment 4) In the second embodiment, the PTFE
Was changed to Cefuralube-VH to form a coating on an aluminum plate. The results of measuring the water repellency of the coating film are shown in Table 2.

Comparative Example 3 A resin composition prepared in the same manner as in Example 4 was coated on an aluminum plate and then in a hot air dryer, 1) 100 ° C./30 minutes, 2) 150 ° C./20 minutes, 3) 200
C./20 minutes, 4) The temperature was raised in the order of 250.degree. C./30 minutes and then cooled to form a milky white film on the aluminum plate. The results of measuring the water repellency of the coating film are shown in Table 2.

Example 5 A resin composition prepared in the same manner as in Example 4 was applied onto an aluminum plate and then 1) 100 ° C./30 minutes, 2) 150 ° C./20 minutes using a hot air dryer. , 3) 200 ℃
/ 20 minutes, 4) 250 ° C./30 minutes, 5) 330 ° C./30 minutes in that order, and cooled to form a milky white film on the aluminum plate. The result of measuring the water repellency of the coating is
It was as shown in Table 2.

(Comparative Example 4) In Example 2, PTFE was used.
Was changed to KTL-500F, and the same treatment was performed to form a film on the aluminum plate. The results of measuring the water repellency of the coating film are shown in Table 2.

(Example 6) 80 parts of N-methyl-2-pyrrolidone (NMP), 150 parts of diethylene glycol dimethyl ether (DMDG), 15 parts of toluene and 30 parts of ethyl orthoformate (OFE) were homogeneously mixed and mixed. 100 parts of powdery VICTREX 5003P was sequentially dissolved and homogeneously dissolved, and then powdery sepular lube-
30 parts of VH and 20 parts of alumina were added and mixed, and this was passed through a three-roll mill three times to mix uniformly. The resin composition thus prepared is applied onto an aluminum plate and put in a hot air drier, 1) 100 ° C / 30 minutes, 2) 150 ° C / 20
Min, 3) 200 ° C./20 min, 4) 250 ° C./30 min, 5) 295 ° C./30 min, and then cooled to form a white film on the aluminum plate. The results of measuring the water repellency of the coating film are shown in Table 3.

(Comparative Example 5) A resin composition prepared in the same manner as in Example 6 was applied onto an aluminum plate and then in a hot air dryer, 1) 100 ° C / 30 minutes, 2) 150 ° C / 20 minutes. ,
When the temperature was raised in the order of 3) 200 ° C / 20 minutes and 4) 250 ° C / 30 minutes, respectively, and cooled, a milky white film could be formed on the aluminum plate. The results of measuring the water repellency of the coating film are shown in Table 3.

(Example 7) A resin composition prepared in the same manner as in Example 6 was applied onto an aluminum plate, and then 1) 100 ° C / 30 minutes, 2) 150 ° C / 20 minutes in a hot air dryer. ,
When the temperature was raised in the order of 3) 200 ° C./20 minutes, 4) 250 ° C./30 minutes, 5) 330 ° C./30 minutes and then cooled, a milky white film could be formed on the aluminum plate. The results of measuring the water repellency of the coating film are shown in Table 3.

(Comparative Example 6) In Example 6, PTFE was used.
Was changed to KTL-500F, and the same treatment was performed to form a film on the aluminum plate. The results of measuring the water repellency of the coating film are shown in Table 3.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

According to the present invention, a coating film having excellent water and oil repellency can be formed on a metal surface by a printing process and baking similar to those of conventional paints and inks without requiring a special and complicated coating process. can do.

Claims (4)

[Claims] 1. A polyamidoimide or a polyamidoamic acid which is a precursor of a polyamidoimide 40 to 80 parts by weight, (b) 20 to 60% by weight of polytetrafluoroethylene having a softening temperature of 300 ° C. or lower, (c) ) A resin composition for coating, which contains a solvent capable of uniformly dissolving (a) at room temperature as an essential component. 2. (a) 40 to 80 parts by weight of polyether sulfone, (b) 20 to 60% by weight of polytetrafluoroethylene having a softening temperature of 300 ° C. or lower, (c) the above (a) is homogeneous at room temperature. A resin composition for coating, which comprises as an essential component a solvent to be dissolved in. 3. Polyamideimide or a polyamidoamic acid which is a precursor of polyamideimide (a) 40 to 80 parts by weight, (b) 20 to 60% by weight of polytetrafluoroethylene having a softening temperature of 300 ° C. or lower, (c) ) A resin composition containing, as an essential component, a solvent capable of uniformly dissolving (a) at room temperature is applied, and then baked at a temperature in the range from the softening temperature of the polytetrafluoroethylene to 370 ° C. A method for curing a coating resin composition. 4. (a) 40 to 80 parts by weight of polyether sulfone, (b) 20 to 60% by weight of polytetrafluoroethylene having a softening temperature of 300 ° C. or lower, (c) the above (a) is homogeneous at room temperature. A method for curing a coating resin composition, which comprises applying a resin composition containing as an essential component a solvent to be dissolved in, and baking at a temperature in the range from the softening temperature of the polytetrafluoroethylene to 370 ° C.