Antistatic treatment agent for vehicle and antistatic treatment method for vehicle

Abstract

To provide an antistatic treatment agent for vehicles and a method for vehicle antistatic treatment that hardly cause disturbance of airflow and have no adverse influence on the vehicle appearance.SOLUTION: An antistatic treatment agent for vehicles comprises a primer composition containing colloidal silica, an alkyl silicate, an aqueous solvent, and an acid, and a clear coating containing an acrylic polymer having at least one of an alkoxysilyl group and a silanol group and having a hydrophilic group, and a solvent; and a method for antistatic treatment of vehicles using the antistatic treatment agent for vehicles.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an antistatic treatment agent for vehicles and a method for antistatic treatment of vehicles. [Background technology]

[0002] Vehicles such as automobiles become positively charged when they move. In addition, because air generally carries a positive charge, a repulsive force is generated between the positively charged vehicle and the airflow. This repulsive force causes the airflow to separate from the vicinity of the vehicle's outer surface, which can prevent the intended aerodynamic characteristics from being achieved, potentially resulting in a decrease in driving performance or handling stability. Patent Document 1 describes that by attaching conductive aluminum tape to a vehicle, the self-discharge of this conductive coating can be utilized to reduce the aforementioned repulsive force, thereby suppressing the separation of airflow from near the vehicle's outer surface. Patent Document 2 describes that anti-static measures for vehicles are taken using a film made of an anti-static composition for vehicles that contains nickel powder and an acid-modified polyolefin resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2015 / 064195 [Patent Document 2] Japanese Patent Application Publication No. 2018-154665 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the conductive aluminum tape described in Patent Document 1 requires a certain thickness, and when applied to a vehicle, it may disrupt the airflow on the vehicle surface. Furthermore, conductive aluminum tape has the problem of limiting the areas where it can be applied because it affects the vehicle's appearance. The antistatic composition for vehicles containing nickel powder and an acid-modified polyolefin resin described in Patent Document 2 may also have limitations on the areas where it can be applied due to factors such as coloring by the nickel powder and the thickness and weight of the coating film.

[0005] An object of the present invention is to provide an antistatic treatment agent for vehicles and an antistatic treatment method for vehicles that are less likely to disturb airflow and do not affect the appearance of the vehicle. [Means for solving the problem]

[0006] [1] a primer composition containing colloidal silica, an alkyl silicate, a water-based solvent, and an acid; a clear coating material containing an acrylic polymer having at least one of an alkoxysilyl group and a silanol group and a hydrophilic group, and a solvent; An antistatic treatment agent for vehicles comprising: [2] Any part of the vehicle, A primer composition containing colloidal silica, an alkyl silicate, a water-based solvent, and an acid is applied to form a primer coating film; On the primer coating film, A clear coating film is formed by applying a clear coating material containing an acrylic polymer having at least one of an alkoxysilyl group and a silanol group, and a hydrophilic group, and a solvent. Antistatic treatment method for vehicles. [3] The antistatic treatment method for a vehicle according to [2], wherein the clear coating has a thickness of 300 to 700 nm and a water contact angle on the surface of the clear coating is 20° or less. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an antistatic treatment agent for vehicles and an antistatic treatment method for vehicles that are less likely to disturb airflow and do not affect the appearance of the vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Anti-static treatment agent for vehicles] The antistatic treatment agent for vehicles of the present invention comprises: a primer composition containing colloidal silica, an alkyl silicate, a water-based solvent, and an acid; a clear coating material containing an acrylic polymer having at least one of an alkoxysilyl group and a silanol group and a hydrophilic group, and a solvent; It consists of:

[0009] In the present invention, a vehicle is antistatically treated using a coating film formed using a specific primer composition and a specific clear coating. The specific clear coating contains a hydrophilic acrylic polymer, which allows the formation of a highly hydrophilic coating film. The highly hydrophilic coating film captures moisture in the atmosphere. This moisture is believed to be a medium through which positive charges on the vehicle surface can be released, contributing to improved driving performance and handling stability. Furthermore, in the present invention, by reducing the thickness of the coating film, it is possible to make the air flow less likely to be disturbed. Furthermore, the paint film is a colorless, transparent clear paint film, so it does not affect the appearance of the vehicle.

[0010] (Primer composition) The primer composition used in the present invention contains colloidal silica, an alkyl silicate, an aqueous solvent, and an acid. The primer composition is used to form a primer coating film. The primer coating film is preferably provided between a vehicle and a clear coating film (a coating film formed from a clear paint), and can improve adhesion between the vehicle and the clear coating film.

[0011] The primer composition used in the present invention is preferably colorless and transparent, so that when the primer composition is applied to a vehicle to form a primer coating film, the appearance of the vehicle is not affected. The primer coating film formed using the primer composition of the present invention and having a thickness of 300 to 700 nm is preferably colorless and transparent. The term "colorless and transparent" means that the visible light transmittance is 70% or more. The visible light transmittance of the primer coating film is preferably 70% to 95%.

[0012] <Colloidal silica> The primer composition contains colloidal silica. Colloidal silica is a colloidal dispersion consisting of spherical silica particles having a particle diameter of about 1 nm to 200 nm and a dispersion medium. In one embodiment, the dispersion medium in the colloidal silica is water or a hydrophilic organic solvent. Examples of hydrophilic organic solvents include, but are not limited to, lower alcohols such as methanol, ethanol, normal propyl alcohol, and isopropyl alcohol; glycols such as ethylene glycol and propylene glycol; and glycol ethers such as ethylene glycol monomethyl ether and propylene glycol monomethyl ether. Colloidal silica includes those in which spherical silica particles are dispersed (referred to as "spherical colloidal silica"), those in which multiple spherical silica particles are connected in a ring shape like a pearl necklace (referred to as "pearl necklace-shaped colloidal silica"), and those in which multiple spherical silica particles are connected in a chain (referred to as "chain colloidal silica"). Any of these can be used. Chain colloidal silica is preferred because it has a high hydrophilicity-imparting effect. Furthermore, using chain colloidal silica in combination with spherical colloidal silica is preferred because it can provide both the hydrophilicity-imparting effect and the strength of the primer coating film. Commercially available colloidal silica can be used. For example, commercially available colloidal silica is Organosilicasol (manufactured by Nissan Chemical Industries, Ltd.), which is dispersed in an organic solvent, and Snowtex (registered trademark) (manufactured by Nissan Chemical Industries, Ltd.), which is a dispersion medium in water stabilized with monovalent cations such as sodium or ammonium. Other commercially available products that can be used include Ludox (manufactured by DuPont) and Cataloid (manufactured by JGC Catalysts and Chemicals).

[0013] Colloidal silica has the effect of imparting hydrophilicity to the primer coating film. Furthermore, when the primer composition contains a compound that swells the organic substrate, colloidal silica penetrates the swollen organic substrate and forms a coating, thereby improving the adhesion between the organic substrate and the primer coating film.

[0014] The content of colloidal silica in the primer composition is preferably 0.20 to 10.00 mass% and more preferably 0.50 to 5.00 mass% in terms of silica solid content. When the content is 0.20 mass% or more, the hydrophilicity-imparting effect is enhanced, and when it is 10.00 mass% or less, cracks and cloudiness are less likely to occur in the primer coating film.

[0015] <Alkyl silicate> The primer composition contains an alkyl silicate. In this specification, alkyl silicate refers to an alkyl silicate monomer represented by the general formula Si(OR)4 (R is an alkyl group) and an alkyl silicate oligomer formed by condensation polymerization of 2 to 10, preferably 3 to 5, alkyl silicate monomers. The alkyl group (R) preferably has 1 to 4 carbon atoms, and more preferably has 1 to 3 carbon atoms. Specific examples of alkyl silicates include, but are not limited to, tetramethoxysilane, methyl polysilicate, tetraethoxysilane, and ethyl polysilicate, of which tetraethoxysilane and ethyl polysilicate are preferred from the viewpoints of reactivity, stability, and safety. The alkyl silicate imparts hydrophilicity and also functions as a film-forming aid. The content of alkyl silicate in the primer composition is preferably 0.50 to 5.00% by mass, and more preferably 1.00 to 5.00% by mass. When the content of alkyl silicate is 0.50 to 5.00% by mass, the fixation of colloidal silica is improved and a film can be formed. When the content is 0.50% by mass or more, a sufficient film can be formed and the film is less likely to become brittle. On the other hand, when the content is 5.00% by mass or less, hydrophilicity is increased.

[0016] <Water-based solvent> The primer composition contains an aqueous solvent. The aqueous solvent is a solvent containing at least one of water and a hydrophilic organic solvent, and examples thereof include water, alcohol, and a mixture of water and alcohol, with water or a mixture of water and alcohol being preferred. The water content in the mixture of water and alcohol is preferably 50% by mass or more but less than 100%, and more preferably 70% by mass or more but less than 100%. Examples of alcohol include hydrophilic solvents such as lower alcohols such as methanol, ethanol, propanol, and isopropanol; glycols such as ethylene glycol and propylene glycol; and glycol ethers such as ethylene glycol monomethyl ether and propylene glycol monomethyl ether. The aqueous solvent may contain one type of solvent alone, or may contain two or more types of solvents.

[0017] The content of the aqueous solvent in the primer composition is preferably 60.00 to 99.00 mass%, more preferably 65.00 to 95.00 mass%, and even more preferably 65.00 to 90.00 mass%. Of these, the content of water is preferably 1.00 to 35.00 mass%, more preferably 2.00 to 30.00 mass%, and even more preferably 3.00 to 25.00 mass%. The content of alcohols is preferably 5.00 to 90.00 mass%, more preferably 20.00 to 85.00 mass%, and even more preferably 30.00 to 80.00 mass%. Furthermore, the content of glycols and glycol ethers is preferably 20.00 to 60.00 mass%, and even more preferably 40.00 to 60.00 mass%.

[0018] Methanol and ethanol swell or partially dissolve the surface of the organic substrate, thereby increasing the adhesive strength of the primer coating film of the primer composition to the organic substrate, and also function as a dispersing solvent for colloidal silica. Isopropyl alcohol, normal propyl alcohol, glycols, and glycol ethers swell or partially dissolve the surface of the organic substrate, thereby increasing the adhesive strength of the primer coating film of the primer composition to the organic substrate, and also function as a dispersing solvent for colloidal silica, and further adjust the drying rate when dried at room temperature after application.

[0019] <Acid> The primer composition contains an acid. The acid acts as a catalyst for the condensation polymerization reaction of alkyl silicate and promotes the formation of a coating of alkyl silicate. The type of acid is not particularly limited, and may be an organic acid or an inorganic acid. For example, formic acid, acetic acid, hydrochloric acid, sulfuric acid, nitric acid, etc. can be used, but is not limited to these. Among these, nitric acid is preferred from the viewpoints of reactivity and low corrosiveness. The content of the acid in the primer composition is preferably 0.01 to 0.10% by mass.

[0020] <Other ingredients> The primer composition may contain other components in addition to those described above. Examples of other components include tetrahydrofuran, boric acid, water glass (sodium silicate No. 3), organic resins (acrylic resins, methacrylic resins, acrylic urethane resins, urethane resins, etc.), and silane coupling agents. When other components are contained, the content of the other components is preferably 3.2 mass % or less.

[0021] Tetrahydrofuran swells or partially dissolves the surface of an organic substrate, thereby enhancing the adhesive strength of the primer coating film formed by the primer composition to the organic substrate. In particular, it can promote the swelling of the surfaces of polycarbonate resins and polyester resins, which are difficult to swell with lower alcohols or glycols alone. The content of tetrahydrofuran in the primer composition is preferably 0.10 to 3.00 mass%, more preferably 0.10 to 1.00 mass%.

[0022] Boric acid acts to increase the adhesive strength of the primer coating film formed by the primer composition to the organic substrate. The content of boric acid in the primer composition is preferably 0.02 to 0.40 mass %, more preferably 0.03 to 0.10 mass %.

[0023] Water glass (No. 3 sodium silicate) functions as a film-forming aid. The content of water glass (No. 3 sodium silicate) in the primer composition is preferably 0.01 to 0.20% by mass, and more preferably 0.01 to 0.10% by mass.

[0024] The organic resin functions as an agent for improving adhesion of the primer coating film to the substrate. Examples of organic resins that can be used include, but are not limited to, acrylic resins, methacrylic resins, acrylic urethane resins, and urethane resins. Specifically, resins that dissolve or disperse even in polar solvents containing water are preferred. The content of the organic resin in the primer composition is preferably 0.01 to 1.00% by mass.

[0025] The silane coupling agent functions as an agent for improving adhesion of the primer coating film to the substrate, and the content of the silane coupling agent in the primer composition is preferably 0.10 to 1.00% by mass. In addition to the above, the primer composition may contain various additives that are commonly used in paints, such as a leveling agent, a viscosity modifier, and an antifoaming agent.

[0026] (clear paint) The clear coating used in the present invention contains an acrylic polymer having a hydrophilic group and at least one of an alkoxysilyl group and a silanol group, and a solvent. The clear coating used in the present invention is colorless and transparent. The clear coating film formed using the clear coating material used in the present invention and having a thickness of 100 to 600 nm is preferably colorless and transparent. The term "colorless and transparent" means that the visible light transmittance is 70% or more. The visible light transmittance of the clear coating film is preferably 70% to 95%.

[0027] <Acrylic polymer> The acrylic polymer contained in the clear coating is an acrylic polymer having at least one of an alkoxysilyl group and a silanol group, and a hydrophilic group. When the acrylic polymer is a linear polymer, at least one of an alkoxysilyl group and a silanol group may be present at at least one terminal of the acrylic polymer, or may be present on a side chain.

[0028] The alkoxysilyl group is preferably a group represented by the following formula (A).

[0029] [ka]

[0030] In formula (A), Rx and Ry each independently represent an alkyl group. When a plurality of Rx and Ry are present, they may be the same or different. n represents 1, 2, or 3. * represents the bonding position. The alkyl group represented by Rx and Ry may be linear or branched. The number of carbon atoms in the alkyl group represented by Rx and Ry is not particularly limited, and may be, for example, 1 to 10.

[0031] The acrylic polymer has a hydrophilic group, such as an alkoxysilyl group or a silanol group.

[0032] The acrylic polymer preferably contains a repeating unit represented by the following formula (1).

[0033] The viscosity average molecular weight of the acrylic polymer is preferably 100 or more, more preferably 500 or more, and from the viewpoint of enhancing the solubility of the acrylic polymer, is preferably 100,000 or less. The viscosity average molecular weight can be determined by gel permeation chromatography.

[0034] [ka]

[0035] In formula (1), R 1 and R 2 each independently represents a hydrogen atom or a substituent. R 1 and R 2 When represents a substituent, examples of the substituent include an alkyl group, a cycloalkyl group, and an aryl group, and the alkyl group, the cycloalkyl group, and the aryl group may be substituted with a substituent such as an alkoxysilyl group, a silanol group, or a hydrophilic group.

[0036] The content of the acrylic polymer in the clear coating is preferably adjusted to be 0.05 to 5.00 mass %, more preferably 1.00 to 3.00 mass %, and even more preferably 1.00 to 2.00 mass %.

[0037] <Solvent> The clear coating contains a solvent, which is not particularly limited, and examples thereof include water, lower alcohols such as methanol, ethanol, normal propyl alcohol, and isopropyl alcohol, glycols such as ethylene glycol and propylene glycol, ketones such as acetone and methyl ethyl ketone, ethers such as diethyl ether and tetrahydrofuran, aromatic hydrocarbon compounds such as benzene, toluene, and xylene, aliphatic hydrocarbon compounds such as n-hexane, alicyclic hydrocarbon compounds such as cyclohexane, and acetates such as methyl acetate and ethyl acetate, which can be used alone or in combination of two or more.

[0038] The content of the solvent in the clear coating is not particularly limited, but it is preferable to adjust the content of the acrylic polymer in the clear coating so that it falls within the above-mentioned range.

[0039] <Other ingredients> The clear coating may contain other components in addition to those described above. Examples of other components include acids, alkalis, and additives commonly used in paints.

[0040] The clear coating may contain an acid or alkali. It is preferable to add an acid or alkali, particularly when using an acrylic polymer having an alkoxysilyl group at the terminal. Adding an acid or alkali promotes hydrolysis of the alkoxysilyl group, converting it to a silanol group. The type of acid is not particularly limited, and may be an organic acid or an inorganic acid, such as formic acid, acetic acid, hydrochloric acid, sulfuric acid, or nitric acid. Among these, nitric acid is preferred from the viewpoints of reactivity and low corrosiveness. The type of alkali is also not particularly limited, and sodium hydroxide, potassium hydroxide, ammonia, or the like may be used.

[0041] In addition to the above, the clear coating may contain various additives commonly used in coatings. For example, it may contain salts such as sodium sulfate, sodium chloride, potassium chloride, and ammonium sulfate in an amount of about 0.01 to 0.05% by mass. These salts play a role in improving the dissolution stability of the acrylic polymer.

[0042] [Anti-static treatment method for vehicles] The antistatic treatment method for a vehicle of the present invention comprises: A primer composition containing colloidal silica, an alkyl silicate, an aqueous solvent, and an acid is applied to form a primer coating film, and The antistatic treatment method for a vehicle involves applying a clear coating containing an acrylic polymer having at least one of an alkoxysilyl group and a silanol group, and a hydrophilic group, and a solvent to form a clear coating film.

[0043] The primer composition and the clear coating are the same as those described above.

[0044] The method for applying the primer composition and the clear coating is not particularly limited, and known methods can be used, such as spray coating, brush coating, bar coating, roller coating, and sponge coating. Sponge coating is preferred from the viewpoint of controlling the amount of coating and the appearance of the coating film. Drying the coating film at room temperature is not a problem, but forced drying at, for example, about 80°C is also possible, and the forced drying time may be about 30 minutes.

[0045] The thickness of the primer coating is preferably 300 to 600 nm, and more preferably 400 to 500 nm.

[0046] The thickness of the clear coating film is preferably 50 to 400 nm, more preferably 50 to 300 nm.

[0047] The total thickness of the primer coating film and the clear coating film is preferably 350 to 1000 nm, and the water contact angle on the surface of the clear coating film is preferably 20° or less, more preferably 10° or less. The water contact angle is measured as follows. 3 μl of pure water is dropped onto the coating film to be measured, and the contact angle is measured 10 seconds after dropping at a measurement temperature of 20°C by looking at the monitor of a CA-X model (Kyowa Interface Science Co., Ltd.). The average value of five measurements is taken as the water contact angle on the surface of the coating film to be measured.

[0048] In a vehicle, the portion to be antistatically treated (the portion where a coating film is formed using an antistatic treatment agent for vehicles) is not particularly limited. For example, when applied to an automobile, any of the parts described in Patent Document 1 (WO 2015 / 064195) may be treated. Examples of parts to be treated include bumpers (bumper covers), door mirrors, headlamps, door handles, tail lamps, antenna fins, plastic side doors, plastic back doors, steering column covers, window glass, intake systems, and exhaust systems. Plastic parts that are highly charged by airflow are preferred, and bumpers are particularly preferred. The portion to be antistatically treated may be the outer surface or the inner surface of these parts. [Example]

[0049] The present invention will be described in more detail below with reference to examples, but it goes without saying that the present invention is not limited to the following examples.

[0050] (Creating test specimens) Using the antistatic composition for vehicles shown in Table 1, a 3 x 3 cm coating film was formed on a 4 x 4 cm polypropylene substrate (hereinafter referred to as PP plate). In Example 1, a first layer and a second layer were formed on the substrate in this order. Both the first and second layers were applied with a sponge, with a film thickness of 500 nm for the first layer and 300 nm for the second layer. The drying conditions were baking at 80°C for 30 minutes after application. In Comparative Example 1, a 4 × 4 cm PP plate similar to that in Example 1 was used without coating. In Comparative Example 2, a film was formed by hot melt application. The film was heated to 160°C and extruded onto the substrate, then allowed to cool and harden at room temperature, resulting in a film thickness of 270 μm (2.7 × 10 5 nm).

[0051] [Table 1]

[0052] The composition used in Example 1 is shown below. The primer composition (first liquid) used was Excelpure BP-05 (manufactured by Chuo Jidosha Kogyo Co., Ltd.) Excelpure BP-05 contains colloidal silica, alkyl silicate, a water-based solvent, and an acid. Furthermore, as the clear coating (second liquid), an aqueous solution of an acrylic polymer having an alkoxysilyl group and a betaine group as a hydrophilic group (LAMBIC-771W manufactured by Osaka Organic Chemical Industry Ltd., solid content concentration 10% by mass) was diluted five times with ion-exchanged water and used.

[0053] The composition used in Comparative Example 2 is shown in Table 2 below.

[0054] [Table 2]

[0055] (Measurement of hydrophilicity) <Measurement method (initial contact angle)> According to JIS R 3257, 3 μl of pure water was dropped onto each test plate, and the contact angle was measured 10 seconds after the drop at a measurement temperature of 25°C using a CA-X monitor (Kyowa Interface Science Co., Ltd.). The results are shown in Table 3. The values ​​in Table 3 are the average of five measurements.

[0056] [Table 3]

[0057] (Measuring half-life) Measurements were made using a static charge decay meter (Static Honest Meter H-0110-S4 manufactured by Shishido Electrostatic Corporation) in accordance with the electrostatic charge test method of JIS L 1094 (1997). An applied voltage of 8 kV was used. Measurements were made at 20°C and a relative humidity of 80%. The half-life is the time it takes for the initial potential to decrease to half. A shorter half-life time indicates a higher charge release effect and superior antistatic properties. The evaluation criteria and results are listed below.

[0058] [Evaluation of half-life] Half-life time≦0.5 seconds: ◎ 0.5 seconds < half time ≦ 1 second: Yes Not halved: ×

[0059] [Transparency evaluation] The transparency was evaluated visually. Transparency: Yes No transparency: ×

[0060] Table 4 shows the results of the initial charging voltage, half-life, and transparency.

[0061] [Table 4]

Claims

1. a primer composition containing colloidal silica, an alkyl silicate, a water-based solvent, and an acid; a clear coating material containing an acrylic polymer having at least one of an alkoxysilyl group and a silanol group and a hydrophilic group, and a solvent; An antistatic treatment agent for vehicles comprising:

2. Any part of the vehicle, A primer composition containing colloidal silica, an alkyl silicate, a water-based solvent, and an acid is applied to form a primer coating film; On the primer coating film, A clear coating film is formed by applying a clear coating material containing an acrylic polymer having at least one of an alkoxysilyl group and a silanol group, and a hydrophilic group, and a solvent. Antistatic treatment method for vehicles.

3. 3. The antistatic treatment method for a vehicle according to claim 2, wherein the clear coating has a thickness of 300 to 700 nm and a water contact angle on the surface of the clear coating is 20° or less.

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