JPWO2020149283A1 - Carbon nano brush antistatic paint - Google Patents

Abstract

An object of the present invention is to provide a coating film having high antistatic performance. The coating film of the present invention is characterized in that single-layer carbon nanohorns are radially aggregated and contain a conductive component containing a fibrous carbon nanohorn aggregate connected in a fibrous manner.

Description

The present invention relates to a coating film containing a fibrous carbon nanohorn aggregate and a method for producing an antistatic coating film.

Conductive paints that prevent the generation of static electricity have been developed. As a conductive component added to a paint, a carbon material having excellent conductivity such as carbon nanotubes is being studied. For example, Patent Document 1 discloses a coating composition containing carbon nanotubes.

International Publication No. 2012/060292

Since carbon nanotubes are inferior in dispersibility, there is a problem that a coating film having sufficient antistatic performance cannot be formed. An object of the present invention is to provide a coating film having high antistatic performance.

The coating film of the present invention is characterized in that single-layer carbon nanohorns are radially aggregated and contain a conductive component containing a fibrous carbon nanohorn aggregate connected in a fibrous manner.

According to the present invention, it is possible to provide a coating film having high antistatic performance.

<Aggregate of fibrous carbon nanohorns>
The coating film according to the present embodiment contains a fibrous carbon nanohorn aggregate. The fibrous carbon nanohorn aggregate is also called a carbon nanobrush (CNB), and has a structure in which single-layer carbon nanohorns are radially assembled and connected in a fibrous manner. The fibrous carbon nanohorn aggregate can maintain the fibrous shape even if an operation such as centrifugation or ultrasonic dispersion is performed, unlike a structure in which a plurality of single-layer carbon nanohorns are simply arranged to look fibrous. The single-layer carbon nanohorn is a conical carbon structure with a diameter of 1 nm to 5 nm and a length of 30 nm to 100 nm, with the tip of the structure wrapped with a graphene sheet pointed like a horn with a tip angle of about 20 °. Is. Here, the carbon structure is a structure mainly containing carbon, and may contain a light element or a catalyst metal. Fibrous carbon nanohorn aggregates are fibrous carbon structures, generally 30 nm to 200 nm in diameter and 1 μm to 100 μm in length, for example 2 μm to 30 μm. The aspect ratio (length / diameter) of the fibrous carbon nanohorn aggregate is generally 4 to 4000, for example 5 to 3500. The surface of the fibrous carbon nanohorn aggregate has protrusions of a single-layer carbon nanohorn having a diameter of 1 nm to 5 nm and a length of 30 nm to 100 nm. Since single-layer carbon nanohorns having high conductivity are connected in a fibrous form and characterized by a structure having a long conductive path, the aggregate of fibrous carbon nanohorns has high conductivity. Further, the fibrous carbon nanohorn aggregate also has high dispersibility, and is highly effective in imparting conductivity.

The fibrous carbon nanohorn aggregate is generally formed by connecting seed-type, bud-type, dahlia-type, petal-daria-type, and petal-type (graphene sheet structure) carbon nanohorn aggregates. That is, one or more of these carbon nanohorn aggregates are contained in the fibrous structure. The seed type has a shape with few or no square protrusions on the surface of the aggregate, the bud type has a shape with some square protrusions on the surface of the aggregate, and the dalia type has the surface of the aggregate. The petal type has a shape with many horn-shaped protrusions, and the petal type has a shape with petal-shaped protrusions on the surface of the aggregate. The petal structure is a graphene sheet structure having a width of 50 nm to 200 nm and a thickness of 0.34 nm to 10 nm and 2 to 30 sheets. The petal-dahlia type is an intermediate structure between the dahlia type and the petal type. The form and particle size of the carbon nanohorn aggregate to be produced change depending on the type and flow rate of the gas.

Fibrous carbon nanohorn aggregates are also described in detail in WO 2016/147909. FIGS. 1 and 2 of WO 2016/147909 disclose transmission micrographs of fibrous carbon nanohorn aggregates. In the fibrous carbon nanohorn aggregate shown in this transmissive micrograph, single-layer carbon nanohorns (carbon nanohorn aggregate) that are radially assembled are connected in a fibrous manner. All disclosures of WO 2016/147909 are incorporated herein by reference.

In the method for producing a fibrous carbon nanohorn aggregate, a catalyst-containing carbon is used as a target (referred to as a catalyst-containing carbon target), and the target is rotated in a container in which the catalyst-containing carbon target is placed to create a nitrogen atmosphere, an inert atmosphere, and hydrogen. The target is heated by laser ablation in a carbon dioxide or mixed atmosphere to evaporate the target. As the evaporated carbon and the catalyst cool, fibrous carbon nanohorn aggregates are obtained. In addition to the laser ablation method, an arc discharge method or a resistance heating method can be used. However, the laser ablation method is more preferable from the viewpoint of continuous generation at room temperature and atmospheric pressure.

In the laser ablation method applied in the present invention, the target is irradiated with laser light in a pulsed or continuous manner, and when the irradiation intensity exceeds the threshold value, the target converts energy, and as a result, a plume is generated and a product is produced. Is deposited on a substrate provided downstream of the target, or is generated in the space inside the apparatus and collected in the recovery chamber.

For laser ablation, a CO ₂ laser, a YAG laser, an excimer laser, a semiconductor laser, or the like can be used, and the CO ₂ laser, which can easily increase the output, is the most suitable. CO ₂ ^lasers, the output of 1kW / cm ² ~1000kW / cm 2 can be used, can be carried out by continuous irradiation and pulse irradiation. Continuous irradiation is preferable for the formation of fibrous carbon nanohorn aggregates. The laser beam is focused by a ZnSe lens or the like and irradiated. In addition, it can be continuously synthesized by rotating the target. The target rotation speed can be set arbitrarily, but 0.1 rpm to 6 rpm is particularly preferable. If it is 0.1 rpm or more, graphitization can be suppressed, and if it is 6 rpm or less, the increase of amorphous carbon can be suppressed. At this time, the laser output is ^{preferably 15 kW / cm 2} or more, and 30 kW / cm ^{2 to} 300 kW / cm ² is the most effective. When the laser output is 15 kW / cm ² or more, the target evaporates moderately, and the formation of fibrous carbon nanohorn aggregates becomes easy. Further, when the laser output is 300 kW / cm ² or less, the increase of amorphous carbon can be suppressed. The pressure in the container (chamber) can be used at 1333.2 hPa (10000 Torr) or less, but the closer the pressure is to vacuum, the easier it is for carbon nanotubes to be formed, and the fibrous carbon nanohorn aggregate cannot be obtained. The pressure in the container (chamber) is preferably 666.61 hPa (500 Torr) to 1266.56 hPa (950 Torr), and more preferably around normal pressure (1013 hPa (1 atm ≈ 760 Torr)) for mass synthesis and cost reduction. Also suitable for. The irradiation area may be controlled by the degree of condensing of the laser output and the lens, 0.005 cm ² 1 cm ² can be used.

As the catalyst, Fe, Ni, and Co can be used alone or in combination. The concentration of the catalyst can be appropriately selected, but is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass, based on carbon. When it is 0.1% by mass or more, the formation of fibrous carbon nanohorn aggregates is ensured. Further, when it is 10% by mass or less, an increase in the target cost can be suppressed.

The inside of the container can be used at any temperature, preferably 0 ° C to 100 ° C, and more preferably used at room temperature for mass synthesis and cost reduction.

The above atmosphere is created by introducing nitrogen gas, inert gas, hydrogen gas, CO ₂ gas, etc. into the container alone or in combination. From the viewpoint of cost, nitrogen gas and Ar gas are preferable. These gases circulate in the reaction vessel and the substances produced can be recovered by this gas flow. The atmospheric gas flow rate can be any amount, but is preferably in the range of 0.5 L / min to 100 L / min. In the process of evaporation of the target, the gas flow rate is controlled to be constant.

The fibrous carbon nanohorn aggregate obtained as described above is usually obtained together with the spherical carbon nanohorn aggregate. Hereinafter, the mixture of the fibrous carbon nanohorn aggregate and the spherical carbon nanohorn aggregate is also simply referred to as a carbon nanohorn aggregate. The spherical carbon nanohorn aggregate is a spherical carbon structure in which single-layer carbon nanohorns are radially assembled. The spherical carbon nanohorn aggregate has a diameter of about 30 nm to 200 nm and has a substantially uniform size. Further, in the obtained fibrous carbon nanohorn aggregate and spherical carbon nanohorn aggregate, a part of the carbon skeleton may be replaced with a catalyst metal element, a nitrogen atom or the like. Fibrous carbon nanohorn aggregates may be isolated and used. Fibrous carbon nanohorn aggregates may be used with other carbon materials such as spherical carbon nanohorn aggregates. The fibrous carbon nanohorn aggregate and the spherical carbon nanohorn aggregate can be separated by the difference in size. Further, when impurities other than carbon nanohorn aggregates are contained, they can be removed by a centrifugal separation method, a difference in sedimentation speed, separation by size, or the like. Further, by changing the production conditions, it is possible to change the ratio of the fibrous carbon nanohorn aggregate and the spherical carbon nanohorn aggregate.

When making fine holes (opening) in the carbon nanohorn aggregate, it can be performed by an oxidation treatment. By this oxidation treatment, a surface functional group containing oxygen is formed in the opened portion. In addition, a gas phase process and a liquid phase process can be used for the oxidation treatment. In the case of a gas phase process, heat treatment is performed in an atmospheric gas containing oxygen such as air, oxygen, and carbon dioxide. Above all, air is suitable from the viewpoint of cost. Further, the temperature can be used in the range of 300 ° C. to 650 ° C., and 400 ° C. to 550 ° C. is more suitable. If the temperature is 300 ° C. or higher, carbon burns and pores can be reliably formed. Further, at 650 ° C. or lower, it is possible to suppress the entire combustion of the carbon nanohorn aggregate. In the case of a liquid phase process, it is carried out in a liquid containing an oxidizing substance such as nitric acid, sulfuric acid and hydrogen peroxide. In the case of nitric acid, it can be used in the temperature range of room temperature to 120 ° C. If the temperature is 120 ° C. or lower, it will not be oxidized more than necessary. In the case of hydrogen peroxide, it can be used in a temperature range of room temperature to 100 ° C, and 40 ° C or higher is more preferable. Oxidizing power acts efficiently in the temperature range of 40 ° C to 100 ° C, and pores can be efficiently formed. In addition, it is more effective to use light irradiation together in the liquid phase process.

The catalytic metal contained in the formation of the carbon nanohorn aggregate can be removed as needed. The catalyst metal can be removed because it dissolves in nitric acid, sulfuric acid, and hydrochloric acid. Hydrochloric acid is suitable from the viewpoint of ease of use. The temperature at which the catalyst is melted can be appropriately selected, but when the catalyst is sufficiently removed, it is desirable to heat the catalyst to 70 ° C. or higher. When nitric acid or sulfuric acid is used, the catalyst can be removed and the pores can be formed simultaneously or continuously. In addition, since the catalyst may be covered with a carbon film when the carbon nanohorn aggregate is formed, it is desirable to perform pretreatment to remove the carbon film. The pretreatment is preferably heated in air at about 250 ° C to 450 ° C. At 300 ° C. or higher, some openings may be formed as described above. Carbon nanohorn aggregates are easier to remove catalytic metals than carbon nanotubes. In the present embodiment, by using the carbon nanohorn aggregate from which the catalyst metal has been removed, it is possible to form a coating film that is substantially free of metal and does not elute metal. This makes it possible to prevent metal elution from the coating film.

The crystallinity of the carbon nanohorn aggregate can be improved by heat treatment in a non-oxidizing atmosphere such as an inert gas, hydrogen, or vacuum. The heat treatment temperature can be 800 ° C. to 2000 ° C., but is preferably 1000 ° C. to 1500 ° C. Further, after the pore opening treatment, a surface functional group containing oxygen is formed in the pore opening portion, but it can also be removed by heat treatment. The heat treatment temperature can be 150 ° C to 2000 ° C. 150 ° C to 600 ° C is desirable for removing carboxyl groups, hydroxyl groups, etc., which are surface functional groups. In order to remove the carbonyl group which is a surface functional group, 600 ° C. or higher is desirable. In addition, surface functional groups can be removed by reduction in a gas or liquid atmosphere. Hydrogen can be used for reduction in a gaseous atmosphere, and can be used in combination with the above-mentioned improvement in crystallinity. Hydrazine and the like can be used in a liquid atmosphere.

<Paint>
The paint according to the present embodiment contains a conductive component containing a fibrous carbon nanohorn aggregate. Examples of the conductive component other than the fibrous carbon nanohorn aggregate include carbon materials such as spherical carbon nanohorn aggregate, carbon nanotube, and graphite. The conductive component is a component composed of a conductive material, and may include various other conductive materials. The conductive component may include, for example, conductive metal particles, a conductive polymer, or the like in addition to the carbon material. In one embodiment, the conductive material is a material having a volume resistivity (20 ° C.) of ^{about 10 -3 Ω · cm or less.}

The base material of the coating material is not particularly limited, and may be a material generally used for coating materials such as a resin and a polymerizable monomer that can form a coating film on a base material. Examples of the resin include alkyd resin, unsaturated polyester resin, melamine resin, phenol resin, epoxy resin, vinyl chloride resin, acrylic resin, acrylic urethane resin, urethane resin, silicone resin, acrylic silicone resin, fluororesin and the like. .. Examples of the polymerizable monomer include styrene, methylmethacrylate, 2-hydroxyethylacrylate, methacrylic acid, maleic acid, itaconic acid, 2-acrylamide-2-methylpropanesulfonic acid, o- and p-styrene sulfonate, and divinylbenzene. Examples thereof include ethylene diacrylate, N, N-methylenebisacrylamide and the like.

The paint may contain water and / or an organic solvent. Examples of the organic solvent include alcohols such as methanol, ethanol and isopropanol, glycols such as ethylene glycol, ketones and ethers.

The paint may contain a curing agent suitable for the base material (particularly the polymerizable monomer). Further, conventionally known additives such as leveling agents, slip agents, plasticizers, thickeners, desiccants, defoaming agents, pigments and dyes can be arbitrarily blended in the paint.

<Coating film>
A coating film can be formed by applying the paint to the substrate. If necessary, the coating film may be further dried to remove volatile components such as water and organic solvents. If necessary, the coating film may be further cured. The curing method of the coating film is appropriately determined depending on the type of the base material, particularly the polymerizable monomer. For example, thermosetting, photocuring, or the like can be adopted. The thickness of the coating film is not particularly limited, but is, for example, in the range of 1 μm to 50 μm.

The amount of the fibrous carbon nanohorn aggregate contained in the coating film is preferably 0.001% by mass or more, more preferably 0.002% by mass or more, and further preferably 0.003% by mass or more. When the amount of the fibrous carbon nanohorn aggregate is within this range, the conductivity of the coating film can be enhanced. The amount of the fibrous carbon nanohorn aggregate contained in the coating film is preferably 1% by mass or less, more preferably 0.1% by mass or less, still more preferably 0.01% by mass or less, and particularly preferably 0.005% by mass. It is as follows. When the amount of the fibrous carbon nanohorn aggregate is within this range, the fibrous carbon nanohorn aggregate does not easily affect the color of the coating film, and a transparent coating film can be formed. The total amount of the conductive component or the carbon material contained in the coating film is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, and further preferably 0.01% by mass or more. The total amount of the conductive component or the carbon material contained in the coating film is preferably 1% by mass or less, more preferably 0.1% by mass or less, and further preferably 0.08% by mass or less.

In order to further increase the conductivity of the coating film, a release sheet may be attached to the surface of the formed coating film. The surface of the coating film can be fluffed by peeling the release sheet from the coating film. On the surface of the fluffy coating film, the tip of the fibrous carbon nanohorn aggregate is exposed, and the conductivity of the coating film is enhanced.

The release sheet is preferably an easily release adhesive sheet having an adhesive layer containing an adhesive component. Examples of the adhesive component used for the adhesive layer of the easily peelable adhesive sheet include rubber-based resin, acrylic resin, silicone resin, urethane resin, vinyl ether resin and the like. In particular, as the easily peelable adhesive sheet, commercially available dicing tape or masking tape can be preferably used.

The adhesive surface of the easily peelable adhesive sheet preferably has a portion having a high adhesive strength (adhesive portion) and a portion having a low adhesive strength (non-adhesive portion). By providing the adhesive portion and the non-adhesive portion, when the easily peelable adhesive sheet is peeled off, the easily peelable adhesive sheet expands and contracts, and the number of fibrous carbon nanohorn aggregates exposed from the surface of the coating film can be increased. can. A peeling component such as a silicone stripping agent or a long-chain alkyl stripping agent can be used for the non-adhesive portion. Adhesive components such as rubber-based resin, acrylic resin, silicone resin, urethane resin, and vinyl ether resin can be used for the adhesive portion. A release agent layer may be provided on the base material, and an adhesive layer may be provided on a part thereof to form an adhesive portion and a non-adhesive portion. Alternatively, a pressure-sensitive adhesive layer may be provided on the base material, and a release agent layer may be provided on a part thereof to form a pressure-sensitive adhesive portion and a non-adhesive portion. The shape of the adhesive portion or the non-adhesive portion is not particularly limited, and examples thereof include a grid shape, a dot shape, a perforated shape, a striped shape, and the like. The area ratio of the adhesive portion to the non-adhesive portion on the adhesive surface of the easily peelable adhesive sheet may be, for example, 1:10 to 10: 1, preferably 1: 3 to 3: 1.

In order to expose the fibrous carbon nanohorn aggregate to the surface of the coating film, it is preferable that the peeling adhesive force between the coating film and the release sheet is within a predetermined range. The peeling adhesive strength between the coating film and the release sheet is preferably 0.1 N / cm or more, more preferably 1 N / cm or more, and further preferably 2 N / cm or more. The peeling adhesive force between the coating film and the release sheet is preferably 10 N / cm or less, more preferably 8 N / cm or less, and further preferably 4 N / cm or less. The peeling adhesive force is measured by JIS Z 0237 (a test method of peeling the release liner at 180 ° with respect to the adhesive surface of the tape and the sheet). In JIS Z 0237, the peeling adhesive force is measured by a tensile tester, and the peeling speed of the tensile tester is 5.0 ± 0.2 mm / s.

As described above, the coating film according to the present embodiment has high conductivity even when the content of the conductive component is small. The surface resistivity of the coating film is generally 1 × 10 ¹⁴ Ω / □ or less, preferably 1 × 10 ¹¹ Ω / □ or less, more preferably 1 × 10 ¹⁰ Ω / □ or less, and further preferably 1 × 10 ^{It is 9} Ω / □ or less. The surface resistivity of the coating film is generally 1 × 10 ⁵ Ω / □ or more. The surface resistivity can be measured according to JIS K6911. In one embodiment, the amount of the conductive material other than the carbon material (excluding the catalyst-derived metal for producing the fibrous carbon nanohorn aggregate) in the conductive component is preferably 1% by mass or less, more preferably 0. It is 1% by mass or less, more preferably 0.001% by mass or less. In one embodiment, the coating film does not contain a conductive material other than the carbon material (excluding the catalyst-derived metal for producing the fibrous carbon nanohorn aggregate) other than the conductive component. In one embodiment, the amount of the carbon material in the conductive component is preferably 50% by mass or more, more preferably 80% by mass or more, and may be 100% by mass.

<CNB product>
A carbon material mixture containing fibrous carbon nanohorn aggregates (hereinafter referred to as CNB product) was prepared by _{CO 2} laser ablation of a carbon target containing iron in a chamber under a nitrogen atmosphere. Specifically, a carbon target containing 1% by weight of iron was rotated at ₂ rpm and continuously irradiated with a CO 2 laser. The energy density of the CO ₂ laser was 50 kW / cm ² . The temperature inside the chamber was set to room temperature, and the flow rate of nitrogen supplied into the chamber was adjusted to 10 L / min. The pressure in the chamber was controlled to 933.254 hPa to 1266.559 hPa (700 Torr to 950 Torr).

When the CNB product was observed by SEM, a fibrous substance (fibrous carbon nanohorn aggregate), a spherical substance (spherical carbon nanohorn aggregate), and graphite were observed. The fibrous carbon nanohorn aggregate had a diameter of about 30 nm to 100 nm and a length of several μm to several tens of μm. Most of the spherical carbon nanohorn aggregates had a diameter in the range of about 30 nm to 200 nm and had a substantially uniform size. Graphite was 1 μm to several tens of μm in size.

From thermogravimetric analysis and particle size distribution measurement by dynamic light scattering, the CNB products were 4% by mass of fibrous carbon nanohorn aggregates, 62% by mass of spherical carbon nanohorn aggregates, 21% by mass of graphite, and 13% by mass of iron oxide. It was confirmed that it contained.

<Example 1>
0.05 parts by mass of CNB product was added to 100 parts by mass of a silicone resin emulsion (Asahi Kasei SILRES (registered trademark), containing 60% by mass of a non-volatile component), and the mixture was kneaded with a three-roll mill. The paint diluted with water was applied to the substrate with a roller and cured at 200 ° C. for 1 hour. When the surface resistivity of this coating film was measured by a four-probe method using a semiconductor parameter analyzer (trade name: Agilent 4155C, manufactured by Agilent Technologies) under the condition of 25 ° C., the surface resistivity of the coating film was measured. It was 2 × 10 ¹⁰ Ω / □.

<Example 2>
A dicing tape (Hitachi Kasei HAE-1503L) was attached to the surface of the coating film obtained in Example 1 and peeled off. The surface resistivity of the coating film was 3 × 10 ⁸ Ω / □.

<Comparative Example 1>
0.05 parts by mass of carbon nanotubes were added to 100 parts by mass of a silicone resin emulsion (Asahi Kasei SILRES (registered trademark), containing 60% by mass of a non-volatile component), and the mixture was kneaded with a three-roll mill. The paint diluted with water was applied to the substrate with a roller and cured at 200 ° C. for 1 hour. The surface resistivity of the coating film was 5 × 10 ¹² Ω / □.

<Comparative Example 2>
A dicing tape was attached to the surface of the coating film obtained in Comparative Example 1 and peeled off. The surface resistivity of the coating film was 2 × 10 ¹² Ω / □, and the effect of the surface treatment was smaller than that of the coating film to which the CNB product was added. Since the fibrous carbon nanohorn aggregate has an uneven shape, there are many parts that adhere to the dicing tape, and it is considered that the effect of the surface treatment is increased.

This application claims priority on the basis of Japanese Application Japanese Patent Application No. 2019-005018 filed on 16 January 2019 and incorporates all of its disclosures herein.

Although the present invention has been described above with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples. Various changes that can be understood by those skilled in the art can be made within the scope of the present invention in terms of the configuration and details of the present invention.

Claims (4)

A coating film containing a conductive component containing a fibrous carbon nanohorn aggregate in which single-layer carbon nanohorns are radially aggregated and connected in a fibrous manner. The coating film according to claim 1, wherein the amount of the fibrous carbon nanohorn aggregate is 0.001% by mass or more and 0.1% by mass or less. The coating film according to claim 1 or 2, wherein the amount of the conductive component is 0.1% by mass or less and the surface resistivity is 1 × 10 ^{10 Ω / □ or less.} A method for producing an antistatic coating film containing a conductive component containing a fibrous carbon nanohorn aggregate.
A process of applying a paint containing a conductive component containing a fibrous carbon nanohorn aggregate to a base material to form a coating film.
A method for producing an antistatic coating film, which comprises a step of attaching an easily peelable pressure-sensitive adhesive sheet to the coating film and a step of peeling the easily peelable pressure-sensitive adhesive sheet from the coating film.