JPH0824896B2 - Fluorine resin coating method - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for coating a surface of a substrate with a fluororesin.

[0002]

2. Description of the Related Art Conventionally, when a polyimide film is coated with a fluororesin, in order to improve the interlayer adhesion strength between the polyimide film and the fluororesin, the surface of the polyimide film is subjected to a primer treatment, an ultrasonic treatment, an etching treatment, etc. Wet treatment, dry treatment such as corona treatment, plasma treatment, ultraviolet (UV) treatment, electron beam treatment, laser treatment and the like are performed. Among the above treatments, the primer treatment is preferable from various viewpoints, and the polyamic acid solution is used as the primer. As the polyamic acid solution, it is preferable to use a solution having heat resistance equal to or higher than that of the fluororesin by imidization (JP-A-3-12268).

[0003]

However, the above primer treatment to improve the interlayer adhesive strength between the polyimide film and the fluororesin reduces the adhesive strength when continuously used in a high temperature atmosphere, There is a problem that the fluororesin layer is easily peeled off.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for coating a fluororesin having excellent durability at high temperatures.

[0005]

In order to achieve the above object, the method for coating a fluororesin of the present invention has a glass transition temperature of 220 ° C. or lower between the two when the surface of the substrate is coated with the fluororesin. The structure is such that a primer layer containing a polyimide resin as a main component is formed.

[0006]

That is, the inventors of the present invention have conducted a series of studies in order to obtain one having excellent adhesive strength without peeling of the fluororesin layer when continuously used in a high temperature atmosphere. As a result of repeated studies centering on the polyimide resin layer conventionally used as a primer between the two, it was found that there is a correlation between the adhesive strength and the glass transition temperature of the polyimide resin. From this, as a result of repeated studies on the relationship of the adhesive strength at the glass transition temperature of the polyimide resin, when the substrate is coated with the fluororesin, a polyimide resin layer having a glass transition temperature of 220 ° C. or less is formed between them. The inventors have found that the adhesive strength of the fluororesin layer is improved, and that it has excellent high-temperature durability can be obtained.

Next, the present invention will be described in detail.

The fluororesin coating method of the present invention forms a primer layer containing a specific polyimide resin as a main component on the surface of a substrate. In the present invention, the term “main component” is intended to include a case where the main component is included.

A polyamic acid solution is used as the primer layer forming material containing a polyimide resin as a main component formed on the surface of the substrate.

The polyamic acid solution is obtained by reacting an acid dianhydride or its derivative with a diamine component in an approximately equimolar amount in an organic polar solvent. Particularly preferably, a polyamic acid obtained by reacting an aromatic tetracarboxylic acid dianhydride with an aromatic diamine is used. Then, the acid dianhydride and the diamine component must be selected so that a polyimide resin having a glass transition temperature (Tg) of 220 ° C. or less can be obtained. Particularly, those having at least one meta-substituted phenyl group in the diamine component are preferable.

Specific examples of the acid dianhydride include pyromellitic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,3,3', 4 '. -Biphenyltetracarboxylic dianhydride, 2,3,6,7-
Naphthalenetetracarboxylic dianhydride, 1,4,5,8
-Naphthalene tetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride,
Examples thereof include bis (3,4-dicarboxyphenyl) sulfone dianhydride. These may be used alone or in combination of two or more.

As the above-mentioned diamine component, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane,
3,3'-dichlorobenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3'-dimethyl- 4,4'-biphenyldiamine, benzidine, 3,
3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 4,4'-diaminodiphenyl sulfide,
4,4'-diaminodiphenylpropane, 2,4-bis (β-amino-tert-butyl) toluene, bis (p-β-
Amino-tert-butylphenyl) ether, bis (p-β
-Methyl-δ-aminophenyl) benzene, bis-p-
(1,1-Dimethyl-5-amino-pentyl) benzene, 1-isopropyl-2,4-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, di (p-aminocyclohexyl) methane, hexa Methylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diaminopropyltetramethylene, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2. −
Bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethylhexamethylenediamine, 2,
5-dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 5-methylnonamethylenediamine, 2,17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10-
Diamino-1,10-dimethyldecane, 1,12-diaminooctadecane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, piperazine,

H ₂ N (CH ₂ ) ₃ O (CH ₂ ) ₂ O (C
H ₂ ) NH ₂ ,

H ₂ N (CH ₂ ) ₃ S (CH ₂ ) ₃ NH ₂ ,

H ₂ N (CH ₂ ) ₃ N (CH ₃ ) (CH ₂ ) ₃ NH _{2 and the} like can be mentioned. These may be used alone or in combination of two or more.

Further, in addition to the above, as the combinations of the acid dianhydride and the diamine component, the following are listed. These combinations (1) to (3) have a glass transition temperature of 220 ° C. or lower in the resulting polyimide resin, and are particularly preferable from the viewpoint of high temperature durability.

3, which is represented by the following structural formula (1):
3 ', 4,4'-benzophenone tetracarboxylic acid dianhydride and 1,3-bis (3-aminophenoxy) benzene represented by the following structural formula (2).

[0018]

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[0019]

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4,4 'represented by the following structural formula (3)
-Oxydiphthalic dianhydride and bis [4- (3-aminophenoxy) phenyl] sulfone represented by the following structural formula (4).

[0021]

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[0022]

[Chemical 4]

3, which is represented by the following structural formula (1):
3 ', 4,4'-benzophenone tetracarboxylic dianhydride and bis [4- (3
-Aminophenoxy) phenol] sulfone.

[0024]

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[0025]

[Chemical 6]

4,4 'represented by the following structural formula (3)
-Oxydiphthalic dianhydride and 1,3-bis (3-aminophenoxy) benzene represented by the following structural formula (5).

[0027]

[Chemical 7]

[0028]

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The organic polar solvent used during the synthesis of the polyamic acid has a dipole whose functional group does not react with the acid dianhydride or diamine component. And
In addition to being inert to the system and acting as a solvent for the product polyamic acid, it must act as a solvent for at least one, preferably both, of the reaction components. In particular, as the organic polar solvent,
N, N-dialkylamides are useful, and examples thereof include N, N-dimethylformamide and N, N-dimethylacetamide, which are low molecular weight compounds. These can be easily removed from the polyamic acid and polyamic acid moldings by evaporation, displacement or diffusion.
In addition, as organic polar solvents other than the above, N, N-diethylformamide, N, N-diethylacetamide, N,
N-dimethylmethoxyacetamide, dimethylsulfoxide, hexamethylphosphortriamide, N-methyl-
2-pyrrolidone, pyridine, tetramethylene sulfone,
Examples thereof include dimethyltetramethylene sulfone. These may be used alone or in combination of two or more. Furthermore, cresol, phenol, phenols such as xylenol, benzonitrile, dioxane, butyrolactone, xylene, and
Cyclohexane, hexane, benzene, toluene and the like can be used alone or in combination of two or more,
The addition of water is not preferred. That is, the presence of water causes the polyamic acid to be hydrolyzed to lower its molecular weight, and therefore the polyamic acid must be synthesized under substantially anhydrous conditions.

A polyamic acid is obtained by reacting the acid dianhydride (a) with the diamine component (b) in an organic polar solvent. The monomer concentration [concentration of (a) + (b) in the solvent] at that time is set according to various conditions. However, it is usually 5 to 30% by weight (hereinafter abbreviated as "%"). The reaction temperature is preferably set to 80 ° C. or lower, particularly preferably 5 to 50 ° C., and the reaction time is about 0.5 to 10 hours.

It is also possible to use a mixture of polyimide resins having a glass transition temperature exceeding 220 ° C. within a range of 20% or less of the total amount of polyimide resins.

Examples of the fluororesin for coating according to the present invention include homopolymers of polytetrafluoroethylene and copolymers of tetrafluoroethylene and hexafluoropropylene, chlorotrifluoropropylene, perfluoroalkyl vinyl ether and the like. , Polychlorotrifluoroethylene or mixtures thereof. The form of applying the fluororesin is not particularly limited, and may be any form such as powder, granules, aqueous dispersion, organic dispersion, and emulsion of organosol in water.

Various fillers may be blended in order to impart functionality to the fluororesin. For example, glass powder, metal powder, metal oxide, carbon black, graphite and the like are used for coloring pigments, for improving the strength against compression, for improving abrasion resistance and for preventing static electricity.

The fluororesin coating method of the present invention is carried out, for example, as follows using the above-mentioned polyimide resin as a primer. That is, the polyamic acid solution is applied to the surface of the base material to form a polyimide resin layer including a non-imidized portion. Next, a fluororesin is applied on the polyimide resin layer to form an overcoat layer, and then the polyimide resin layer is baked at a predetermined temperature to accelerate imidization of the polyimide resin layer and sinter the fluororesin as the overcoat layer. This is done by simultaneously performing and.

The substrate to be coated with the fluororesin is not particularly limited, and may be any material and shape such as metal, glass, pottery, and super heat resistant plastic. Further, in order to improve the adhesiveness with the polyimide resin layer formed by the polyamic acid solution, sandblasting, shot blasting, grip blasting, honing, paper scratching, wire scratching, in advance, on the polyamic acid solution coating surface of the base material, Surface treatment such as hairline treatment or chemical etching may be applied.

The method for forming the polyimide resin layer containing the non-imidized portion is as follows:
It is formed by drying at 0 ° C. for 5 to 20 minutes to remove the solvent in the polyamic acid solution.

Further, as the coating method of the polyamic acid solution and the fluororesin, there may be mentioned ordinary coating methods such as spraying method, dipping method, electrostatic coating and flow coating.

The firing temperature is appropriately set depending on the type of fluororesin used. For example, when polytetrafluoroethylene and a copolymer mainly composed of tetrafluoroethylene are used as the fluororesin, it is usually
The temperature is 340 to 420 ° C, preferably 360 to 400 ° C.

As described above, in the method for coating a fluororesin described above, a specific polyamic acid solution is applied to the surface of a base material to form a polyimide resin containing a portion not imidized,
A fluororesin is applied thereon to form an overcoat layer. Then, by firing, the imidization of the polyimide resin layer is promoted and the fluororesin layer of the overcoat layer is simultaneously sintered to coat the fluororesin. Therefore, by interposing a specific polyimide resin between the base material and the fluororesin, the fluororesin coating film obtained is firmly adhered to the base material and has excellent adhesive strength at high temperatures.

[0040]

As described above, according to the method for coating a fluororesin of the present invention, when the surface of the substrate is coated with the fluororesin, a polyimide resin having a glass transition temperature of 220.degree. To form a primer layer. For this reason, the obtained fluororesin coating film is firmly adhered to the substrate, and excellent adhesive strength is maintained even during continuous use in a high temperature atmosphere.

Next, examples will be described together with comparative examples.

[0042]

Example 1 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride (BTDA) and 1,3-bis (3
-Aminophenoxy) benzene (BAPB) was dissolved in N, N-dimethylacetamide (DMAc) shown in the same table in a flask in a substantially equimolar amount (monomer concentration 20%), and at a temperature of 20 ° C under a nitrogen gas atmosphere. The reaction was carried out while stirring for 5 hours to obtain a polyamic acid solution. The rotational viscosity of this polyamic acid solution was 30,000 poise. The rotational viscosity is a value measured with a B-type viscometer at a temperature of 20 ° C.

This polyamic acid solution was added with DMAc so as to be a 10% solution with respect to the polyimide solid content, diluted, and then heated to 50 ° C. to give a rotational viscosity of 19
A 0 centipoise polyamic acid solution was obtained.

This polyamic acid solution was applied to a 25 μm thick polyimide film by spraying so that the applied thickness would be 1 μm (after drying). Then, it was dried at 150 ° C. for 10 minutes under normal pressure.

Next, an aqueous dispersion (TE-334J manufactured by DuPont) having a concentration of 60% of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA) and a carbon black concentration of 16 were applied to the surface coated with the polyamic acid solution. A 5% aqueous dispersion (L-3, W-311N) mixed solution was applied to a coating thickness of 10 μm.
m (after firing) to apply by spraying, 150 ℃
It was dried for 10 minutes and baked at 400 ° C. for 10 minutes. In this way, a fluororesin coating film was formed. The ratio of PFA to carbon black in this mixed dispersion was 4 parts of carbon black to 100 parts of PFA.

This fluororesin coating film was uniform, and the pencil hardness at this time was 3H, and the pencil hardness after penciling after standing at 390 ° C. for 1 hour was H.

[0047]

Examples 2 to 4 The polyamic acid solution used as the primer for coating the fluororesin was replaced with the composition shown in Table 1 below. Other than that was produced like Example 1.

[0048]

Comparative Example 1 PFA was directly spray-coated on a polyimide film without using a fluororesin coating primer.
Other than that was produced like Example 1.

[0049]

Comparative Examples 2 to 7 The polyamic acid solution used as the fluororesin coating primer was replaced with the composition shown in Table 1 below. Other than that was produced like Example 1.

The glass transition temperature of the obtained polyimide resin is also shown in Table 1 below. In Table 1, BPDA is 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, PMDA is pyromellitic dianhydride, and BTDA is 3,3', 4,4'-benzophenonetetracarboxylic acid. Acid dianhydride, ODPA is 4,4′-oxydiphthalic dianhydride, 3BAPB is 1,3-bis (3-aminophenoxy) benzene, 4BAPB is 1,
3-bis (4-aminophenoxy) benzene, DDE is 4,4'-diaminodiphenyl ether, BAPF is 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, and 4BAPS is bis [4-.
(4-Aminophenoxy) phenyl] sulfone, 3BA
PS is bis [4- (3-aminophenoxy) phenyl]
Sulfone, BAPP is 2,2-bis [4- (4-aminophenoxy) phenyl] propane, DDS is 3,3'-
Diaminodiphenyl sulfone, NMP is N-methyl-2
-Pyrrolidone, DMAc is N, N-dimethylacetamide, and DMF is N, N-dimethylformamide.

[0051]

[Table 1]

A pencil hardness test was performed on the fluororesin coating film formed as described above. That is, since the coating film obtained by the fluororesin coating is often used with a coating thickness of 5 to 30 μm, it is impossible to measure the coating hardness with a general indentation type hardness meter. is there.
Therefore, the pencil scratch tester for coating film (JIS K5
401) was used and the measurement was carried out by the method described below.
In the test of the fluororesin coating film in this case, two measurements were performed after firing and after standing for 1 hour in a high temperature atmosphere of 390 ° C. The results are shown in Table 2 below.

[Pencil hardness test] First, J
A high-grade product specified by IS S6006 (pencil) was inspected and selected by the "Japan Paint Inspection Association" for each lot according to hardness symbols, and a series of hardness symbols was prepared as one set. For the pencil, first remove only the wood part, and the core is made into a cylindrical shape about 3
mm exposed and then placed on a hard, flat surface
Place the core at 0 at a right angle and gently grind while drawing a circle,
The tip was flat and the corners were sharp.

The pencil prepared as described above was attached to the tester, the tip of the core of the test piece placed on the tester was brought into contact,
The weight load is applied to the tip. Then, the test piece was moved at a constant speed in the direction opposite to the direction of the core by about 3 mm, the coating surface was scratched by the core, and it was examined whether or not the coating was broken.
The standard moving speed at this time was about 0.5 mm / sec.
This operation is repeated 5 times by changing the position of the test, and when two or more out of 5 breaks of the coating film reaching the base material are observed, the pencil is replaced by a pencil whose hardness symbol is one step lower and the same. The test was repeated. Then, the hardness code of the pencil when the breakage was once or less was recorded and expressed as the pencil hardness. Also, if the tear is less than 1 after 5 scratches,
The same test was repeated by sequentially replacing the pencil with a hardness symbol one step higher, and the pencil hardness was recorded one step below the hardness symbol of the pencil when the number of breaks was two or more (JIS K.
5400, JIS K5401, JIS K6894 and JIS S6006).

[0055]

[Table 2]

From the results shown in Table 2 above, all of the products of Comparative Examples 1 to 6 had low pencil hardness values and were soft. Further, in the product of Comparative Example 7, the pencil hardness was as high as H after firing, but the pencil hardness was as low as B after being left in a high temperature atmosphere. On the other hand, the example products do not decrease in the pencil hardness value after firing and after being left in a high temperature atmosphere,
The fluororesin coating film was excellent in high temperature durability.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masao Nakamura 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation (72) Inventor Tokio Fujita 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Issue Nitto Denko Corporation (72) Inventor Toshihiko Tomita 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Electric Works Ltd. (72) Inventor Hiroshi Ukai 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Nitto Electric Works Co., Ltd.

Claims (2)

[Claims] 1. A method for coating a fluororesin, which comprises forming a primer layer containing a polyimide resin having a glass transition temperature of 220 ° C. or lower as a main component between the two when the surface of the substrate is coated with the fluororesin. . 2. The polyimide resin comprises a polyamic acid obtained by reacting a tetracarboxylic dianhydride or its derivative with a diamine component, and has at least one meta-substituted phenyl group in the diamine component. The method for coating a fluororesin according to claim 1.