JP2002156360A - Method for discriminating hydrophilic film from hydrophobic coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for precisely and simply discriminating a coating film to be hydrophilic or hydrophobic. SOLUTION: This method for discriminating hydrophilic coating film and hydrophobic coating film includes a process electrifying a static electricity to the coating film surface, a process of measuring electrification rate on the coating film surface after the aforementioned process, and a process of identifying the coating film to be hydrophilic or hydrophobic, based on the measured electrification rate value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the surface characteristics of a coating film, and more particularly to a method for determining a hydrophilic coating film and a hydrophobic coating film.

[0002]

2. Description of the Related Art The surface of an article such as an automobile is usually coated with a paint for the purpose of protecting the surface, giving a desired color and aesthetic appearance. Coating is an operation in which a paint, which is a resin composition, is spread over the surface of an article and cured to form a continuous resin film having a substantially uniform thickness. The resin film formed on the surface of the article by painting is called a coating film.

In recent years, various functional paints have been developed, and coating films exhibiting excellent antifouling properties against pollutants peculiar to large cities such as smoke and exhaust gas have been known. For example, JP-A-10-
JP 140077 discloses an acid-epoxy-cured automotive topcoat coated with a low-condensate (silicate low-condensate) having a degree of condensation of 2 to 10 of tetramethyl silicate and / or tetraethyl silicate. In addition, JP-A-2
000-204312 describes an acid epoxy cured automotive topcoat having an alkoxysilyl group bonded to the polymer backbone.

[0004] In these coating films, the alkoxysilyl groups present in the vicinity of the coating film surface are hydrolyzed to hydroxyl groups by exposure or treatment with an acid, and exhibit high hydrophilicity due to the hydroxyl groups. As a result, there is an antifouling function in which lipophilic pollutants such as soot and exhaust gas hardly adhere, and even if they adhere, they are easily washed away by rain or the like.

[0005] By the way, if any malfunction of the paint, foaming, adhesion of dust, etc. occur during the coating process, the uniformity, continuity and surface smoothness of the formed coating film are hindered, and Defects such as cloudiness marks, dents and scratches occur on the surface of the film. Further, if the uniformity, continuity, and smoothness of the coating film are impaired by friction and collision of the vehicle body even after the formation of the coating film, defects occur on the coating film surface. If the surface of the coating film has defects, the aesthetic appearance of the vehicle body is impaired, and the commercial value of automobiles and the like is reduced.

Conventionally, the surface of a coating film is generally hydrophobic,
The repair method, material, etc. were also taken into consideration in terms of adhesion to the hydrophobic coating film, finish, and the like. However, in the case where the coating film to be repaired is hydrophilic, polishing, recoating, spot repair, and the like for the hydrophilic coating film are not performed, and the finished portion of the repaired portion and the antifouling function become insufficient. Accordingly, with the spread of hydrophilic paint having excellent antifouling properties, when repairing automotive coatings, it is necessary to determine whether the coating to be repaired is hydrophilic or hydrophobic.

[0007] In addition, even when a dedicated part is attached in the process of assembling an automobile or when the history of the vehicle body is unknown, it is necessary to determine whether the top coat of the vehicle body is hydrophilic or hydrophobic.

In general, methods for analyzing the surface characteristics of a coating film include an infrared absorption spectrum (IR), a nuclear magnetic resonance spectrum (NMR), and a mass spectrum (MS).
However, performing such an analysis is expensive because an expensive measuring device is required, and the operation is complicated because it is necessary to collect a coating film from a vehicle body and prepare a sample.

A method of actually applying water to the coating film and judging whether the surface is hydrophilic or hydrophobic based on the degree of wetting and the contact angle of the surface is also conceivable. However, in the manufacturing process of automobiles and the like, the coating film is not always flat, and the degree of hydrophilicity of the coating film, especially immediately after coating and before exposure, varies, and the degree of surface wetting and water contact angle are different. If is used as a criterion for determination, the determination will be inaccurate. Therefore, it is difficult to accurately determine whether a coating film is hydrophilic or hydrophobic by a method of applying water to the coating film.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a method for accurately and simply determining whether a coating film is hydrophilic or hydrophobic without destruction. Is to provide.

[0011]

SUMMARY OF THE INVENTION The present invention comprises a step of charging a coating film surface with static electricity; a step of measuring the charging rate of the coating film surface after the above-mentioned step; A method of distinguishing between a hydrophilic coating film and a hydrophobic coating film, which comprises a step of determining whether the coating film is hydrophilic or hydrophobic, thereby achieving the above object.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An electrostatic charging characteristic is different between a hydrophilic surface and a hydrophobic surface. Generally, the order of a substance based on the ease of emitting or accepting electrons is referred to as a charged series.
A substance that easily charges positively (+) has a higher charging sequence, and a substance that easily charges negatively (-) has a lower charging series. Thus, the hydrophilic coating has a lower charging sequence than the hydrophobic coating, and the hydrophobic coating has a higher charging sequence than the hydrophilic coating.

In the method of the present invention, the step of charging the coating film surface with static electricity can be performed, for example, by rubbing the coating film surface with a specific mediating material. According to this aspect, the surface of the coating film can be easily and reliably charged with static electricity using a simple friction device or human power.

[0014] As the above-mentioned mediating material, one having a charging sequence higher than the hydrophilic coating film and lower than the hydrophobic coating film, that is, a medium positioned between the hydrophilic coating film and the hydrophobic coating film in the charging sequence. Substances must be used.

Specifically, fibers or natural substances included in the range of asbestos (positive polarity) to hemp (negative polarity) in the charging sequence table are exemplified. When the hydrophilic coating film is rubbed with such an intermediate material, the surface of the hydrophilic coating film becomes negatively charged, and when the hydrophobic coating film is rubbed, the surface of the hydrophobic coating film becomes positively charged.

That is, the surface of the coating film is rubbed with the above mediating material, and if the value of the charge rate on the surface of the coating film is a negative number, it is determined to be hydrophilic. If the value of the charge rate is a positive number, it is hydrophobic. Can be determined. Table 1 shows an example of the charging sequence table.

[0017]

[Table 1]

In the method of the present invention, first, the surface of the coating film is rubbed with a fiber or a natural substance. This is for charging the coating film with static electricity by friction. Preferably, the rubbing is performed with a fibrous material such as cloth, nonwovens, and buffs. If the fiber material is deformed freely, it can follow the shape of the coating film surface, and it is flexible and the coating film is hardly damaged. When such conditions are satisfied, natural substances such as asbestos, human hair, and fur may be used.

As a specific example of the fiber or the natural substance, those in the range of asbestos (positive polarity) to hemp (negative polarity) in the charging line are preferable. This is because the coating film is appropriately charged. In other words, when the surface of the coating film is rubbed with these fiber materials, the film is properly charged negatively if the coating film is hydrophilic, and positively charged if the coating film is hydrophobic.

Specific examples of fibers or natural substances included in the range of asbestos (positive polarity) to hemp (negative polarity) in the charging line include asbestos, human hair, fur, glass, mica, wool, nylon, rayon, silk , Cotton, cotton and hemp. Preferred as fibers or natural substances are human hair, fur, wool, nylon, rayon, silk and cotton. Particularly preferred are nylon, rayon and silk. It is easy to obtain and excellent in flexibility.

The method of friction may be performed at a pressure rate sufficient to charge static electricity. Usually, the operation of rubbing with a human hand is preferable. For example, the fiber material is held in a hand and rubbed so as not to damage the surface of the coating film. Excessive rubbing is not preferred because it damages the coating. The number of times of rubbing is not particularly limited, but is generally about 5 to 10 reciprocations.

As another embodiment of the present invention, the step of charging the surface of the coating film with static electricity may be performed by spraying a gas ionized into positive ions or negative ions onto the coating film surface. According to this aspect, since there is no contact with the coating film, damage to the coating film is avoided. In addition, since no human work is required, the determination can be easily automated.

In this case, since the hydrophilic surface and the hydrophobic surface have different ease of emitting or accepting electrons, the amount of charge accumulated on the surface after spraying an ionic gas also differs. . Specifically, when a predetermined amount of negatively ionized air is blown onto the coating film, the charge rate on the surface of the hydrophilic coating film becomes larger than the charge rate on the surface of the hydrophobic coating film. Conversely, when a certain amount of positively ionized air is blown onto the coating film, the charge rate of the hydrophilic film surface becomes smaller than the charge rate of the hydrophobic film surface.

That is, after spraying an ionic gas onto the surface of the coating film, it is possible to determine whether the coating film is a hydrophilic coating film or a hydrophobic coating film by comparing the magnitude of the charge ratio on the surface of the coating film.

The ionic gas is generated by, for example, a corona discharge method (voltage application method). The corona discharge method is a method in which a high voltage is applied to a discharge needle of a conductor to generate an electric discharge in the vicinity of the surface of the conductor to ionize air. If an air flow is created around the discharge needle, ionized air can be continuously blown. By controlling the air flow and the applied voltage, a certain amount of ionized air can be blown at a certain time.

When a negative voltage is applied to the discharge needle, the air is negatively ionized, and when a positive voltage is applied to the discharge needle, the air is positively ionized. The voltage applied to the discharge needle may be determined as appropriate, but the negative voltage is from -5000V to -15000.
V, preferably -10000 V to -15000 V, and 5,000 V to 15000 V, preferably 1 for positive voltage.
0000V to 15000V.

The speed of the air flow blown to the coating film may be determined as appropriate, but is preferably 1 to 350 m ³ / min, preferably 5 m ³ / min.
２０20 m ³ / min.

After the surface of the coating film is charged with static electricity by the friction method or the ion spraying method, the charge ratio of the coating film surface is measured. This is for quantifying the amount of static electricity charged on the coating film. The measurement of the charging rate can be performed using an electrostatic potential measuring device. Electrostatic potential meters are commercially available. For example, "KSD-0103" manufactured by Kasuga Electric Co., Ltd.
6110 ”and“ FMX-00 ”manufactured by Simco Japan
2 "may be used.

Since the static electricity charge ratio is different between the hydrophilic surface and the hydrophobic surface, it is possible to determine whether the coating film is hydrophilic or hydrophobic based on the value of the charge ratio. The value of the charge ratio at the boundary between hydrophilicity and hydrophobicity can be determined empirically.

The coating to be determined is generally a top coating of the article. Particularly high discrimination necessity and effectiveness are top coats of automobile bodies.

The hydrophilic coating film means a coating film having excellent wettability with water on its surface. In the case of a hydrophilic coating film having excellent wettability, when a water droplet is dropped on the surface, the contact angle of the water with the coating film becomes 70 degrees or less.

The hydrophilic coating has a predetermined amount of hydrophilic functional groups such as hydroxyl groups and carboxyl groups on the surface of the coating. It may have a predetermined amount of a functional group that is hydrolyzed by moisture in the air to give a hydrophilic functional group, for example, an alkoxysilyl group. The hydrophilic functional group or the functional group that is hydrolyzed to give a hydrophilic functional group may be one bonded to the polymer skeleton or one derived from a component mixed in the coating composition.

As the hydrophilic coating film, for example, JP-A-200
0-178501, JP-A-2000-204312
And Japanese Patent Application Laid-Open No. 10-140077.

The hydrophobic coating film means a coating film whose surface has poor wettability with water. When a water droplet is dropped on the surface of the hydrophobic coating film, the contact angle of the water with the coating film exceeds 70 degrees.

Examples of the hydrophobic coating film include, for example, those described in
45577, JP-A-3-287650, JP-A-4-363374, or JP-A-8-25
No. 9667 and the like.

Examples of the above-mentioned hydrophobic coating film include general coating materials for top coats containing a film-forming resin, a curing agent and, if necessary, a pigment. The film-forming resin is not particularly limited, and an acrylic resin, a polyester resin, an epoxy resin, a urethane resin or the like can be used, and these are combined with a curing agent such as an amino resin and / or a blocked isocyanate resin. Used. For example, a combination of an acrylic resin and / or a polyester resin and an amino resin, or a combination of an acrylic resin and / or a polyester resin having a carboxylic acid / epoxy curing system, from the viewpoint of transparency or acid etching resistance.

[0037]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. As used herein, "parts" and "%" are based on weight unless otherwise specified.

Production Example 1 Preparation of Hydrophilic Coating Film (Acid-Epoxy Curing Clear) (1) Synthesis of Acrylic Copolymer Containing Half-Ester Acid Group A thermometer, stirrer, cooling tube, nitrogen inlet tube and dropping funnel were used. 330 parts of xylene and 110 parts of propylene glycol monomethyl ether acetate were charged into the provided 3 L reaction tank, and the temperature was increased to 127 ° C. Using a dropping funnel, 300 parts of styrene, 360 parts of 2-ethylhexyl methacrylate, 112 parts of isobutyl acrylate, 26 parts of acrylic acid, 202 parts of maleic anhydride, 300 parts of propylene glycol monomethyl ether acetate and 300 parts of t- Butyl peroxy-2-ethylhexanoate 90
And a solution consisting of 100 parts of xylene was added dropwise over 3 hours.

After maintaining at 127 ° C. for 30 minutes after the completion of the dropwise addition, a solution comprising 10 parts of t-butylperoxy-2-ethylhexanoate and 50 parts of xylene was added dropwise over 30 minutes. After the completion of the dropwise addition, 127 ° C. for another hour.
The reaction was continued to obtain a varnish containing 53% of nonvolatile matter containing acrylic polyanhydride having a number average molecular weight (Mn) of 3000.

To 1990 parts of the varnish obtained, 100 parts of methanol was added and reacted at 70 ° C. for 23 hours to obtain an acid value of 12
A varnish containing 7 mg KOH / g (in terms of solid content) of a half ester acid group-containing acrylic copolymer was obtained. The half-ester acid group-containing acrylic copolymer was measured for its infrared absorption spectrum to determine the absorption of acid anhydride groups (1785).
cm ^-1 ) disappeared.

(2) Synthesis of carboxyl group-containing polyester resin In a reaction vessel equipped with a thermometer, a stirrer, a cooling pipe, a nitrogen introduction pipe, a water separator and a rectification tower, 136 parts of Pentol, 456 parts of ε-caprolactone, 0.1 part of dibutyltin oxide was charged, heated to 170 ° C., and kept at 170 ° C. for 3 hours.

Thereafter, 539 parts of phthalic anhydride at the mouth of hexahydric acid dissolved by heating were added, and the mixture was kept at 150 ° C. for 1 hour. Then, 464 parts of ethyl 3-hydroxypropionate was added.
Number average molecular weight (Mn) 1700, weight average molecular weight (M
w) / number average molecular weight (Mn) = 1.28, acid value 174 m
gKOH / g (solid content conversion), hydroxyl value 25 mgKOH
/ G (as solid content) of a varnish with a nonvolatile content of 71% containing a carboxyl group-containing polyester resin.

(3) Synthesis of Polyoxy Group-Containing Acrylic Copolymer 500 parts of xylene was charged into a 2 L reaction tank equipped with a thermometer, a stirrer, a cooling pipe, a nitrogen introduction pipe, and a dropping funnel.
The temperature was raised to 5 ° C. Using a dropping funnel in this reactor, 380 parts of glycidyl methacrylate, 200 parts of styrene, 292 parts of 2-ethylhexyl methacrylate, and acrylic acid
128 parts of 4-hydroxybutyl and 100 parts of t-butylperoxy-2-ethylhexanoate and xylene 10
0 parts of the solution was added dropwise over 3 hours.

After maintaining at 125 ° C. for 30 minutes after the completion of the dropwise addition, a solution comprising 10 parts of t-butylperoxy-2-ethylhexanoate and 10 parts of xylene was added dropwise over 30 minutes. After completion of the dropping, the temperature is further increased to 125 ° C. for 1 hour.
To continue the reaction, number average molecular weight (Mn) 3700,
Polyoxy equivalent 400 (solid content equivalent), hydroxyl value 47 mg
A varnish having a nonvolatile content of 62% and containing an acrylic resin having an engineered oxy group of KOH / g (as solid content) was obtained.

(4) Synthesis of Silicate Graft Polymer Methyl silicate “MS-56” (trade name) manufactured by Mitsubishi Chemical Corporation is subjected to an alcohol exchange reaction with isopropyl alcohol to obtain a 100% nonvolatile content containing an alcohol-modified silicate compound. A composition was obtained. Alcohol exchange reaction conditions were as follows: 74 g of “MS-56” was mixed with 21 g of isopropyl alcohol and 0.2 g of triethylamine, reacted at a temperature of 80 ° C. for 12 hours, and distilled methanol generated under reduced pressure. I left.

The inside of a 1 L reaction vessel equipped with a thermometer, a condenser, a cooling pipe, and a nitrogen introduction pipe was replaced with nitrogen gas, and 100 parts of the above alcohol-modified silicate compound and the above-mentioned acrylic copolymer 270 containing a modified oxy group. And 2 parts of trimethyl orthoacetate were added thereto, and a graft reaction was carried out at 90 ° C. for 12 hours to obtain a varnish having a nonvolatile content of 72% containing a silicate graft polymer which is an epoxy group-containing acrylic copolymer grafted with a silicate compound. Obtained.

(5) Preparation of Coating Film The components and additives prepared in (1) to (4) were blended at the ratios shown in Table 2 while dispersing them together to obtain a clear coating for automotive top coating. Then, the paint was diluted to a coating viscosity with a thinner consisting of butyl acetate / xylene = 1/1.

[0048]

[Table 2]

Nippon Paint Co., Ltd. cationic electrodeposition paint "Powertop V-20" and polyester melamine type gray intermediate paint "Olga TO H-87"
0 "(both are trade names), each having a dry film thickness of 25
μm and 40μm to paint and heat cured,
A test plate was used.

A silver metallic base paint of “Olga TO H-300” (trade name) manufactured by Nippon Paint Co., Ltd. was applied to the test plate. On top of this, a clear paint for automotive top coating adjusted to a diluted viscosity was applied by wet-on-wet.

Thereafter, baking and drying were performed at 140 ° C. for 30 minutes to prepare a coating test plate having two coats and one bake (2CIB) as a coating method. In addition, the cured coating film of the base coating material and the clear coating material was applied such that the dry film thickness became 15 μm and 40 μm, respectively.

Preparation Example 2 Preparation of hydrophilic coating film (acid-epoxy cured system clear) Except for using the components shown in Table 3, a clear paint for automobile top coating was obtained in the same manner as in Preparation Example 1, and a coating test plate (2C
1B) was prepared.

[0053]

[Table 3]

Production Example 3 Preparation of Hydrophobic Coating Film (Acid-Epoxy Curing Clear) Methyl silicate “MS” manufactured by Mitsubishi Chemical Corporation having the components shown in Table 3
Except for preparing and using a paint without "-56", a clear paint for automobile top coating was obtained and a paint test plate (2C1B) was prepared in the same manner as in Production Example 1.

Production Example 4 Preparation of Hydrophobic Coating Film (Acryl-Melamine Curing Clear) Acrylic-melamine curing system “Olga TO-563 Clear” manufactured by Nippon Paint Co., Ltd. A painted test plate (2C1B) was prepared.

Preparation Example 5 Preparation of Hydrophobic Coating Film (Solid White of Acid-Epoxy Curing System)
In the same manner as in Production Example 1, except that 30 parts of a titanium dioxide pigment “CR-97” manufactured by Ishihara Sangyo Co., Ltd. is added, the pigment is dispersed until the particle size becomes 5 μm or less, and a paint is prepared. A solid white paint for top coating was obtained, and a coating test plate (1C1B) was prepared.

Production Example 6 Preparation of hydrophobic coating film (alkyd-melamine-cured solid white) Preparation of hydrophobic film (alkyd-melamine-cured solid white) "Olga TO-648PT White" manufactured by Nippon Paint Co., Ltd. Thus, a coating test plate (1C1B) was prepared.

Production Example 7 Preparation of hydrophobic coating film (alkyd-melamine-cured solid black) Preparation of hydrophobic coating film (alkyd-melamine-cured solid black "Olga TO-650PZ Black" manufactured by Nippon Paint Co., Ltd.) Thus, a coating test plate (1C1B) was prepared.

Example 1 A coated test plate was left at room temperature for 10 minutes. Ion-exchanged water was dropped on the coating test plate before friction in an atmosphere of 20 ° C., and the contact angle of water after 30 seconds of standing was measured. Next, a nylon glove was attached to the hand and the surface of the coating film was rubbed back and forth for 5 times. The charge ratio of the coating film surface was measured using an electrostatic potential meter “FMX-002” manufactured by Simco Japan. Table 4 shows the results.

Example 2 The paint test plate of Example 1 was neutralized with a ground rod. Next, the cotton flannel cloth was held in hand and the surface of the coating film was rubbed back and forth for 5 times. Simco Japan Electrostatic Potential Meter “FMX-00”
The charge ratio on the surface of the coating film was measured using "2." Table 4 shows the results.

[0061]

[Table 4]

Example 3 A painted test plate was left at room temperature for 3 weeks. Next, a nylon glove was attached to the hand and the surface of the coating film was rubbed back and forth for 5 times. The charge rate of the surface of the coating film was measured using an electrostatic potential meter “FMX-002” manufactured by Simco Japan. Table 5 shows the results.
Ion-exchanged water was also dropped on the left coated test plate in an atmosphere of 20 ° C. before rubbing, and the contact angle of water after 30 seconds was measured.

Example 4 The paint test plate of Example 3 was neutralized with a ground rod. Next, the cotton flannel cloth was held in hand and the surface of the coating film was rubbed back and forth for 5 times. Simco Japan Electrostatic Potential Meter “FMX-00”
The charge ratio on the surface of the coating film was measured using "2." Table 5 shows the results.

[0064]

[Table 5]

In Tables 4 and 5, when comparing the hydrophilic coating film and the hydrophobic coating film, the charge ratio was negative for the hydrophilic coating film and positive for the hydrophobic coating film. I was able to determine.

Example 5 A coating film type judging device having the structure shown in FIG. 1 was produced. This device has an ionized air blowing nozzle 3 housed in a housing 8 and a charge rate measuring sensor 9. The discharge needle 1 and the air supply pipe 2 are housed inside the ionized air blowing nozzle 3. The discharge needle 1 is electrically connected to the high voltage generator 4 by a cable 5. The air supply pipe 2 is connected to a compressed air tank 6. The air discharged from the tip of the air supply pipe 2 is ionized by a discharge needle to which a high voltage is applied, and is blown from the ionized air blowing nozzle 3 onto the surface of the coating film 7. The charge remaining on the surface of the coating film 7 is detected by the charge rate measuring sensor 9, amplified by the amplifier 10, and the amount is indicated on the voltmeter 11.

Next, a coated test plate having a hydrophilic coating film was prepared in the same manner as in Production Example 1. The coated test plate was allowed to stand at room temperature for 10 minutes, and the coated test plate was placed below the coating film type determination device with the coated surface facing up. The distance between the ionized air blowing nozzle and the coating film surface and the distance between the charge rate measuring sensor and the coating film surface were both adjusted to 50 mm.

A voltage of -15 kV was applied to the discharge needle of the coating type determining apparatus, and the air flow rate was adjusted to 50 m ³ / min.
When the value of the voltmeter became stable, the charging rate (kV) was recorded. Table 6 shows the results.

Example 6 In the same manner as in Production Example 4, a coated test plate having a hydrophobic coating film was prepared. The charge rate of the surface of the coated test plate was measured in the same manner as in Example 5 except that the obtained coated test plate was used. Table 6 shows the results.

Example 7 A coated test plate was prepared in the same manner as in Production Example 1 except that an acid-epoxy-curable acrylic clear "Macflow 0-600 Clear" manufactured by Nippon Paint Co., Ltd. was used as the clear paint. The charge rate of the surface of the coated test plate was measured in the same manner as in Example 5 except that the obtained coated test plate was used. Table 6 shows the results.

Example 8 The coating test plate used in Example 5 was neutralized with a ground rod. This painted test plate was placed under the paint film type judging device with the painted surface facing up. The distance between the ionized air blowing nozzle and the coating film surface and the distance between the charge rate measuring sensor and the coating film surface were both adjusted to 50 mm.

A voltage of +15 kV was applied to the discharge needle of the coating type determining apparatus, and the air flow rate was adjusted to 50 m ³ / min.
When the value of the voltmeter became stable, the charging rate was recorded. Table 6 shows the results.

Example 9 The coating test plate used in Example 6 was neutralized with a ground rod. Except for using this painted test plate, the charge rate of the surface of the painted test plate was measured in the same manner as in Example 8. Table 6 shows the results.

Example 10 The coating test plate used in Example 7 was neutralized with a ground rod. Except for using this painted test plate, the charge rate of the surface of the painted test plate was measured in the same manner as in Example 8. Table 6 shows the results.

[0075]

[Table 6]

When comparing the hydrophilic coating film and the hydrophobic coating film in Table 6 and Examples 5 to 7, the charge ratio of the hydrophilic coating film was larger than that of the hydrophobic coating film, and both were easily discriminated. Also,
Comparing the hydrophilic coating film and the hydrophobic coating film in Examples 8 to 10, the charge ratio of the hydrophilic coating film was smaller than that of the hydrophobic coating film, and both were easily discriminated.

[0077]

According to the present invention, there has been provided a method for non-destructively, accurately and simply discriminating whether a coating film is hydrophilic or hydrophobic.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a coating film type determination device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Discharge needle, 2 ... Air supply pipe, 3 ... Ionized air blowing nozzle, 4 ... High voltage generator, 5 ... Cable, 6 ... Compressed air tank, 7 ... Coating film, 8 ... Housing, 9 ... Charge rate measurement sensor, 10: amplifier, 11: voltmeter.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Kubota 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (72) Takakazu Yamane 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Stock In company

Claims (9)

[Claims] 1. a step of charging the surface of the coating film with static electricity; a step of measuring the charging rate of the coating film surface after the above-mentioned step; and a coating film being hydrophilic or hydrophobic according to the value of the measured charging rate. Determining a hydrophilic coating film and a hydrophobic coating film. 2. The method according to claim 1, wherein the step of charging the coating film surface with static electricity is performed by rubbing the coating film surface with a fiber or a natural substance. 3. The method according to claim 1, wherein the fibers or natural substances are in a range of asbestos (positive polarity) to hemp (negative polarity) in a charged column,
3. The method according to claim 2, wherein if the value of the charge ratio is a negative number, the surface is determined to be hydrophilic, and if the value of the charge ratio is a positive number, the surface is determined to be hydrophobic. 4. The method according to claim 1, wherein the fiber or the natural substance is charged with human hair,
3. The method according to claim 2, wherein the range is from fur (positive polarity) to cotton (negative polarity). 5. The method according to claim 2, wherein said fiber or natural substance is nylon, rayon or silk. 6. The method according to claim 1, wherein the step of charging the surface of the coating film with static electricity is performed by spraying a gas ionized into positive ions or negative ions onto the coating film surface. 7. The method according to claim 1, wherein the step of charging the surface of the coating film with static electricity is performed by spraying a gas ionized into negative ions onto the coating film surface. 8. The method of claim 1, wherein said coating is a topcoat of an article. 9. The article of claim 8, wherein said article is a car body.
The described method.