JP7372517B2 - Composite materials, their manufacturing methods, and their uses - Google Patents

Description

The present invention relates to a composite material containing inorganic pigment particles and a carbon material, a method for producing the same, and a conductive material, coating composition, and coating film containing the composite material.

Carbon materials are materials that are composed of carbon atoms and have various shapes, and carbon black, carbon nanotubes, graphene, carbon nanocoils, carbon nanohorns, fullerenes, diamond-like carbon, and the like are well known. For example, carbon nanotubes (CNTs) are materials that have a structure in which graphite sheets in which carbon atoms are arranged in a hexagonal network are wound into a cylindrical shape. Generally, as carbon nanotubes, it is known that single-walled CNTs and double-walled CNTs, which have a small number of layers, have particularly high properties such as electrical conductivity because they have a highly graphite structure.

Attempts have been made to combine such carbon materials with inorganic particles to impart properties such as electrical conductivity and thermal conductivity possessed by carbon materials to the inorganic particles. For example, Patent Document 1 discloses a composite particle in which a plurality of carbon nanotubes form a network structure in which they are directly connected to each other, and the network structure is directly fixed to the surface of a base particle. As base particles, metal particles such as aluminum nitride, aluminum oxide, titanium nitride, silicon nitride, boron nitride, chromium oxide, nickel, nickel oxide, magnesium oxide, silicon, silicon carbide, silicon nitride, silicon dioxide, titanium, titanium oxide are used. , titanium carbide, tungsten, tungsten carbide, zinc, zinc oxide, tin oxide, tin, etc. To produce these composite particles, the base particles are immersed in a liquid in which carbon nanotubes are dispersed, and a reversible reaction state between the dispersed state and the agglomerated state of the carbon nanotubes is generated on the surface of the base particle. The nanotubes are fixed.

Further, Patent Document 2 describes a composite ceramic containing 0.001% by weight or more and 0.1% by weight or less of carbon nanotubes on the surface of ceramic raw material particles and having a volume resistivity of 1.0×10 ⁸ Ω・cm or less. Material particles are disclosed. Examples of the ceramic raw material particles include alumina, zirconia, silicon nitride, aluminum nitride, boron nitride, silicon carbide, ferrite, zinc oxide, titanium oxide, and the like. To produce these composite ceramic material particles, there is a step of preparing a mixed slurry containing at least ceramic raw material particles, carbon nanotubes, a synthetic polymer for dispersing the carbon nanotubes, a dispersant such as a surfactant, and a solvent. discloses a method using a carbon dioxide supply step of supplying the mixed slurry into a pressure-resistant container and then supplying carbon dioxide into the pressure-resistant container while stirring the mixed slurry.

Furthermore, Patent Document 3 discloses that untreated carbon nanotubes are dispersed in a nitrogen atom-containing polar solvent, and the surface of the dispersion is treated with a silane coupling agent having a polar functional group such as an amino group, a carboxyl group, or a hydroxyl group. discloses a method of coating carbon nanotubes on the surface of modified silica gel particles, titanium oxide particles, or zinc oxide particles by stirring the particles.

Japanese Patent Application Publication No. 2015-140276 Japanese Patent Application Publication No. 2014-34476 Patent No. 5686416

By combining a carbon material and inorganic pigment particles, it is expected that the so-called "color separation" phenomenon can be prevented when the carbon material is blended into a solvent such as a solvent dispersion or a paint composition. The "color separation" phenomenon refers to a phenomenon in which a carbon material such as a carbon nanotube and an inorganic pigment particle such as titanium dioxide are separated in a solvent due to a difference in specific gravity between the two. When the "color separation" phenomenon occurs, the distribution of both becomes uneven, resulting in uneven properties (pigment properties, electrical conductivity, thermal conductivity, etc.) when formed into a coating film.

However, in the method of Patent Document 1, the strength is not sufficient because the carbon material is directly fixed to the surface of the inorganic pigment particles by van der Waals force, and when mixed in a solvent, the two separate, resulting in the A color separation phenomenon occurs. Furthermore, in the method of Patent Document 2, the dispersant and solvent dissolve in carbon dioxide in a supercritical state, resulting in an unstable dispersion state of the carbon material, and a force mainly based on van der Waals forces causes the inorganic pigment particles to However, the adsorption force alone is not strong enough, and when mixed in a solvent, the two separate, resulting in a "color separation" phenomenon. Furthermore, in the method of Patent Document 3, carbon materials are immobilized using particles whose surfaces are modified with a silane coupling agent having a functional group, but when they are mixed in a solvent, the immobilization of both is insufficient. The problem of the "color separation" phenomenon occurring due to the separation of the two colors remains unsolved.

The present invention has been made in view of the above-mentioned problems, and aims to firmly fix inorganic pigment particles and carbon materials and suppress the "color separation" phenomenon when blended with a solvent.

As a result of intensive studies to solve the above problems, the present inventors found that by using polyurethane having silanol groups at both ends, inorganic pigment particles and carbon material can be firmly fixed, and the composite material obtained in this way The present invention was completed based on the discovery that the "color separation" phenomenon can be sufficiently suppressed when the compound is blended with a solvent.

That is, the present invention includes the following inventions (1) to (10).
(1) A composite material containing inorganic pigment particles, a carbon material, and a polyurethane having silanol groups at both ends.
(2) The composite material according to (1), wherein the inorganic pigment particles and the carbon material are fixed with polyurethane having silanol groups at both ends.
(3) The composite material according to (1) or (2), wherein the inorganic pigment particles are inorganic white pigment particles.
(4) The composite material according to (3), wherein the inorganic white pigment particles are titanium dioxide pigments.
(5) The composite material according to any one of (1) to (4), wherein the carbon material is a carbon nanotube.
(6) A conductive material containing the composite material according to any one of (1) to (5).
(7) A coating composition comprising the composite material according to any one of (1) to (5) or the conductive material according to (6), and a resin.
(8) A coating film comprising the composite material according to any one of (1) to (5) or the conductive material according to (6).
(9) A method for producing a composite material, including the step of mixing at least inorganic pigment particles, a carbon material, and a polyurethane having silanol groups at both ends in an aqueous dispersion medium.
(10) A composite material comprising a step of solid-liquid separation of the mixed liquid obtained in the mixing step described in (9), and a step of heating the obtained solid content at a temperature of 30°C or higher and 180°C or lower. Production method.

According to the present invention, since the inorganic pigment particles and the carbon material can be firmly fixed, the phenomenon of "color separation" when blended with a solvent can be suppressed, and stable coating film properties (pigment properties, conductivity, thermal conductivity, etc.).

1 is an electron micrograph of a composite material of Example 1 of the present invention.

The composite material of the present invention includes inorganic pigment particles, a carbon material, and a polyurethane having silanol groups at both ends. The adhesive action of polyurethane having silanol groups at both ends can fix the inorganic pigment particles and the carbon material. The mechanism is not clear, but the silanol group has some kind of bond with the surface of the inorganic pigment particle, and the other silanol group also has some kind of bond with the surface of the carbon material, and the adhesive action of polyurethane strengthens the bond between the two. It is thought that it is possible to increase the

The above-mentioned inorganic pigment particles refer to chemically inorganic pigment particles, and may be natural minerals or may be produced from compounds such as zinc, titanium, lead, iron, copper, and chromium. For example, white pigments (zinc oxide, titanium dioxide, lead white, etc.), red pigments (red, vermilion, cadmium red, etc.), yellow pigments (yellow, yellow ocher, cadmium yellow, etc.), green pigments (emerald green, etc.). , chromium oxide green, etc.), blue pigments (dark blue, cobalt blue, etc.), violet pigments (manganese violet, mars violet, etc.), black pigments (titanium black, iron black, etc.), transparent white pigments (also called extender pigments) (silica white, alumina white, white clay, calcium carbonate, etc.), but are not limited to these. Inorganic pigment particles also include transparent pigments such as titanium oxide fine particles and tin oxide fine particles, and metal pigments such as aluminum, gold, silver, and copper. In the present invention, white pigments (inorganic white pigment particles) are preferred, and titanium dioxide and zinc white (zinc oxide) are more preferred.

The average primary particle diameter of inorganic pigment particles can be measured by electron microscopy. Specifically, inorganic pigment particles were photographed using a transmission electron microscope (Hitachi H-7000), and image processing was performed using an automatic image processing and analysis device (Nireco Luzex (registered trademark) AP). The primary particle size of 2000 particles is measured, and the average value is defined as the average primary particle size.

The shape of the inorganic pigment particles is not particularly limited, and any shape such as spherical, rod-like, needle-like, spindle-like, or plate-like shape can be used. The above average primary particle diameter for shapes other than spherical is defined by the average length of the minor axis for rod-shaped, needle-shaped, and spindle-shaped particles, and the average diagonal length of the surface for plate-shaped particles. stipulated by.

The titanium dioxide white pigment is titanium dioxide particles with an average primary particle size of about 0.1 μm or more and 1.0 μm or less, and from the viewpoint of the whiteness and hiding property of the coating film, the average particle size is about 0.15 μm or more and 0.1 μm or more. It is preferably 6 μm or less, and preferably 0.2 μm or more and 0.4 μm or less. The crystal structure of the titanium dioxide white pigment is not particularly limited either, and anatase type, rutile type, brookite type, etc. can be used, but rutile type is preferable from the viewpoint of suppressing deterioration of paint resin.

As the titanium dioxide white pigment, those produced by either the so-called sulfuric acid method or the chlorine method can be used. Further, titanium dioxide white pigment whose particle surface is coated with various inorganic compounds or organic compounds may be used. Examples of the inorganic compound include metal oxides and/or metal hydrated oxides such as silicon, aluminum, titanium, zirconium, tin, and antimony. Examples of organic compounds include polyol-based, amine-based, and carboxylic acid-based organic compounds (specifically, trimethylolmethane, trimethylolethane, trimethylolpropane, pentaerythritol, dimethylethanolamine, triethanolamine, and stearin). acid, oleic acid, etc.). The particle surface of titanium dioxide may be coated with the above-mentioned inorganic compound and then further coated with the above-mentioned organic compound.

The above-mentioned carbon material is a material having various shapes composed of carbon atoms, and carbon black, carbon nanotubes, graphene, carbon nanocoils, carbon nanohorns, fullerenes, diamond-like carbon, etc. can be used. Carbon nanoparticles such as the following are preferred.

The carbon nanotubes are not particularly limited in their structure, and either single-wall carbon nanotubes or multi-wall carbon nanotubes such as double-wall carbon nanotubes can be used. It is preferable that the carbon nanotubes have an average length of 5 μm or more. By doing so, even with a small amount of compounding, a conductive path can be formed well on the surface of the composite material, and the conductivity of the composite material can be sufficiently increased. Moreover, it is preferable that the carbon nanotubes have an average diameter of 1 nm or more and 3 nm or less. By doing so, the conductivity of the composite material can be improved. The average length of carbon nanotubes means the average length of 100 particles when the particles are observed using a transmission electron microscope (TEM). The same applies to the average diameter.

The carbon nanotube preferably has an intensity ratio of G band to D band (G/D ratio) determined by Raman spectroscopy of 15 or more, more preferably 30 or more, and even more preferably 50 or more. The Raman shift seen around 1,590 cm ^-1 in the Raman spectrum obtained by Raman spectroscopy is called the G band derived from graphite, and the Raman shift seen around 1,350 cm ^-1 is caused by defects in amorphous carbon and graphite. It is called the D band derived from Carbon nanotubes with a higher intensity ratio of the G band and D band, that is, a higher G/D ratio, have a higher degree of graphitization and are of higher quality, indicating that they are highly crystalline and have high conductivity. There is.

Carbon nanotubes can be obtained by any method such as chemical vapor deposition (CVD), arc discharge, and laser deposition. Furthermore, various commercially available carbon nanotubes can also be used. For example, single-walled carbon nanotubes include TUBALL ^TM (manufactured by OCSiAl), ZEONANO (registered trademark) SG101 (manufactured by Nippon Zeon), NC1100 (manufactured by NANOCYL), MEIJO eDIPS (manufactured by Meijo Nano Carbon), and Hipco ^TM (manufactured by Meijo Nano Carbon). NanoIntegris), etc. can be used, and as the multi-walled carbon nanotube, VGCF (registered trademark)-H (manufactured by Showa Denko), etc. can be used.

The above-mentioned "polyurethane having silanol groups at both ends" is one in which silanol groups are introduced at both ends of polyurethane (a polymer having urethane bonds in the molecule) by any method. A silanol group means a group consisting of a silicon atom having at least one hydroxyl group, and may have a substituent such as an alkoxy group.

As a method for introducing silanol groups to both ends of polyurethane, a known method can be used, for example, a method described in JP-A No. 2009-235257 can be used. In this method, first, a polyol and a polyisocyanate are reacted to produce a polymer (urethane prepolymer) having isocyanate groups at both ends. By reacting this urethane prepolymer with an alkoxysilane compound (silylating agent) having a functional group that is reactive with isocyanate groups, a polyurethane having alkoxysilyl groups at both ends can be obtained. Furthermore, silanol groups can be introduced at both ends of the polyurethane by converting at least one of the alkoxysilyl groups at both ends into a silanol group (hydrogenization) by a hydrolysis reaction or the like. Hereinafter, the polymer compound obtained in this manner may be referred to as an aqueous silanated urethane polymer.

Polyurethane having silanol groups at both ends can be produced by various known methods, and commercially available products can also be used. For example, an aqueous silylated urethane resin composition (Aqualinker (registered trademark) SU500: manufactured by Konishi Co., Ltd.) can be used.

In the composite material of the present invention, the inorganic pigment particles and the carbon material are fixed to each other by the adhesive action of polyurethane having silanol groups at both ends so that they are difficult to separate when mixed in a solvent. Here, "fixed" in the present invention refers to a composite state in which it is difficult to separate when blended in a solvent, and it does not matter what kind of force may be applied. Although it is assumed that the inorganic pigment particles and the carbon material are bonded by chemical force, physical force, or both through polyurethane having silanol groups at both ends, the present invention is not limited thereto. An electron micrograph of the composite material of the present invention is shown in FIG.

In the composite material of the present invention, the fixation strength of the inorganic pigment particles and the carbon material in a solvent can be evaluated, for example, by the method below.

First, a coating composition is prepared using a chlorinated polyolefin resin as a binder resin, water as a solvent, and a pigment mass concentration (PWC) of the composite material of 60%. As the chlorinated polyolefin resin, for example, Superchron (registered trademark) E-480T manufactured by Nippon Paper Industries, Ltd., which is commercially available as a water-based chlorinated polyolefin resin, can be used. A portion of the coating composition immediately after being made into a coating material was collected and designated as Sample 1.

Next, the paint composition immediately after being made into a paint is centrifuged at 3000G for 10 minutes, and the paint composition near the liquid surface after centrifugation is collected and used as sample 2. "Near the liquid surface" usually means a range up to a depth of about 3 mm from the liquid surface, although it depends on the volume of the centrifuge tube used for centrifugation. The above-mentioned centrifugation operation is an operation for reproducing in a short time the situation when the coating composition is stored for a long period of time.

Subsequently, for each of Samples 1 and 2, values in the L ^* a ^* b ^* color system are measured using a spectrophotometer. As the spectrophotometer, X-Rite eXact manufactured by X-Rite, etc. can be used. Let L ^* value, a ^* value, b ^* value of sample ₁ be L1, _a1 , _b1, and let L ^* value, a ^* value, b ^* value of sample 2 be _L2 , _a2 , _b2 , ΔL from the difference between L ₁ and L ₂ (L ₁ - L ₂ ), Δa from the difference between a ₁ and a ₂ (a ₁ - a ₂ ), and Δa from the difference between b ₁ and b ₂ (b ₁ - b ₂ ) to calculate Δb.

Here, if the fixation strength between the inorganic pigment particles and the carbon material in the composite material is small, or if the inorganic pigment particles and the carbon material are not fixed and are simply in a mixed state, the inorganic pigment can be removed by the above centrifugation operation. The particles and the carbon material separate and most of the inorganic pigment particles (or composite material) settle, and free carbon material collects near the liquid surface. On the other hand, if the fixation strength between the inorganic pigment particles and the carbon material is high, the inorganic pigment particles and the carbon material will hardly be separated even by the above centrifugation operation, and most of the composite material will settle and remain near the liquid surface. There will be only a small amount of free carbon material present.

In this way, the amount of free carbon material present near the liquid surface after the centrifugation operation changes depending on the fixing strength between the inorganic pigment particles and the carbon material, and this changes at least one of the above-mentioned ΔL, Δa, and Δb. reflected in one. Therefore, at least one of ΔL, Δa, and Δb can be used as an indirect indicator of the fixing strength between the inorganic pigment particles and the carbon material. Which of ΔL, Δa, and Δb to use can be appropriately selected depending on the type (color) of the pigment.

When using a white pigment such as titanium dioxide as the inorganic pigment particles, the above ΔL is used as an indirect index of the fixing strength between the inorganic white pigment particles and the carbon material. When the value of ΔL is less than 20, it can be evaluated that the fixing strength between the inorganic white pigment particles such as titanium dioxide and the carbon material is sufficiently secured. That is, when using a white pigment such as titanium dioxide as the inorganic pigment particles, the value of ΔL expressed by the following formula is preferably less than 20, more preferably 18 or less.
ΔL=L ₁ -L ₂
(L ₁ was obtained by preparing a paint composition containing the composite material, chlorinated polyolefin resin, and water and setting the pigment mass concentration of the composite material to 60%, and measuring the paint composition using a spectrophotometer. L ^* a ^* b ^* is the L ^* value in the color system, and L ₂ is the composition near the liquid surface after centrifuging the paint composition at 3000 G for 10 minutes using a spectrophotometer. (This is the L ^* value in the L ^* a ^* b ^* color system.)

In the composite material of the present invention, the mixing ratio of the inorganic pigment particles and the carbon material can be set as appropriate. For example, the lower limit of the content of the carbon material is 0.01% by mass with respect to the inorganic pigment particles. It is preferable because the effect of adding the carbon material can be obtained, more preferably 0.05% by mass, and even more preferably 0.1% by mass. On the other hand, the upper limit of the content of the carbon material can be appropriately set depending on the purpose, and is preferably 20% by mass, more preferably 10% by mass, and even more preferably 5% by mass based on the inorganic pigment particles. The content of carbon material in inorganic pigment particles can be determined by thermogravimetric analysis.

When using inorganic white pigment particles such as titanium dioxide, if the fixed amount of black carbon material is large, the composite material becomes darkish, but the content of carbon material is 0.02% by mass based on the inorganic white pigment particles. If the content is 0.5% by mass or less, the white state can be maintained, which is preferable. By doing so, good whiteness and conductivity can be achieved in the coating film containing the composite material.

Furthermore, in the composite material of the present invention, the mass ratio (M ₁ /M ₂ ) of the mass ( _M 1 ) of the polyurethane having silanol groups at both ends to the mass (M ₂ ) of the carbon material is 0.2 or more. It is preferable that it is, and 0.5 or more is more preferable. By doing so, the inorganic pigment particles and the carbon material can be more firmly fixed.

On the other hand, the greater the amount of polyurethane having silanol groups at both ends (the greater the value of M ₁ /M ₂ ), the greater the fixing strength between the inorganic pigment particles and the carbon material; Fixed strength has reached a plateau. Further, by keeping the amount of polyurethane having silanol groups at both ends to the minimum necessary, the influence on the conductivity of the composite material can be minimized. Taking this into consideration, the upper limit of the value of M ₁ /M ₂ is about 30, preferably 15 or less, more preferably 5 or less, and even more preferably 3 or less. The mass ratio of the polyurethane having silanol groups at both ends and the carbon material in the composite material can be determined by thermogravimetric analysis.

The composite material of the present invention can be produced, for example, by mixing at least inorganic pigment particles, a carbon material, and a polyurethane having silanol groups at both ends in an aqueous dispersion medium.

As the inorganic pigment particles, carbon material, and polyurethane having silanol groups at both ends, those described above can be used. Carbon materials are not limited to those in powder form, but also those in the form of dispersion of powder in various solvents (water, formic acid, methanol, ethanol, 1-propanol, 2-propanol, etc.) (dispersions). It can also be used.

The above-mentioned aqueous dispersion medium is one whose main component is water, that is, the water content is 50% by mass or more. The content of water in the aqueous dispersion medium is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass. Components other than water include formic acid and various organic solvents that dissolve in water (methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, tetrahydrofuran, etc.).

The above raw materials may be mixed in any order. That is, the inorganic pigment particles and the aqueous dispersion medium may be mixed in advance, and after adding the polyurethane having silanol groups at both ends, the carbon material may be added, or the carbon material and the aqueous dispersion medium may be mixed in advance. After mixing, the polyurethane having silanol groups at both ends may be added thereto, and then the inorganic pigment particles may be added. Alternatively, all ingredients may be added to the aqueous dispersion medium at once and mixed. The mixing ratio of the raw materials can be set as appropriate, and it is preferable to mix them within the above range. Additives such as a dispersant, an emulsifier, a pH adjuster, a thickener, an antifoaming agent, a surface conditioner, and an antisettling agent can be included as necessary.

In particular, it is preferable to add polyurethane having silanol groups at both ends to a dispersion of inorganic pigment particles and an aqueous dispersion medium, and finally add a carbon material. Moreover, it is more preferable to add the carbon material not in the form of powder but in the form of a dispersion liquid in which it is previously dispersed in a solvent. By doing so, the inorganic pigment particles and the carbon material can be more uniformly fixed.

For mixing the above raw materials, a known mixer such as a stirrer, mixer, homogenizer, or stirrer can be used.

When using inorganic white pigment particles such as titanium dioxide, the mixing ratio of the carbon material is preferably 0.02% by mass or more and 0.5% by mass or less based on the inorganic white pigment particles. By doing so, good whiteness and conductivity can be achieved in the coating film containing the composite material. Further, it is preferable that the mass ratio (M ₁ /M ₂ ) of the mass of the polyurethane having silanol groups at both ends ( _M 1 ) to the mass of the carbon material (M ₂ ) is 0.2 or more, and 0.2 or more. More preferably 5 or more. Further, the upper limit of the value of M ₁ /M ₂ is about 30, preferably 15 or less, more preferably 5 or less, and even more preferably 3 or less. By doing so, the influence of the polyurethane having silanol groups at both ends on the conductivity of the composite material can be minimized while ensuring sufficient fixing strength between the inorganic white pigment particles and the carbon material.

The above raw materials are mixed in the manner described above to obtain a dispersion containing the composite material of the present invention. After this mixing, heating or pH adjustment may be performed as necessary.Furthermore, as necessary, the dispersion may be evaporated to dryness or the dispersion may be separated into solid and liquid. A powder may be obtained by drying the solid content. A known filtration method can be used for solid-liquid separation, for example, a filtration device using pressure filtration such as a rotary press or a filter press, which is usually used industrially, or a vacuum filtration device such as a Nutsche or Moore filter. Can be used. At that time, washing may be performed with pure water or the like, if necessary.

Further, the method may include a step of heating the dispersion liquid or the solid content obtained from the dispersion liquid by solid-liquid separation at a temperature of 30°C or higher and 180°C or lower, preferably 30°C or higher and 160°C or lower. This heating step can further increase the fixing strength between the inorganic pigment particles and the carbon material by the polyurethane having silanol groups at both ends. The temperature in the heating step is more preferably 60°C or more and 100°C or less. By doing so, the fixing strength between the inorganic pigment particles and the carbon material can be further increased.

It is more preferable that the heating step is performed on the solid content obtained from the solid-liquid separation of the dispersion. By doing so, the inorganic pigment particles and the carbon material can be more uniformly fixed.

Further, the heating time at the above temperature can be set arbitrarily, but it is preferably about 0.5 to 5 hours. In the heating step, heating equipment such as a dryer, an oven, an electric furnace, etc. can be used.

The composite material of the present invention produced by the above method may be appropriately adjusted in particle size using a known pulverizer, classifier, or the like.

The composite material of the present invention can be used as a pigment material by utilizing its pigment properties. Furthermore, it can be used as a conductive material by utilizing its conductivity. Furthermore, the composite material of the present invention can be used as a thermally conductive material by utilizing its thermal conductivity. In order to use these materials, additives used for the purpose can be mixed as appropriate.

The composite material of the present invention can be mixed with a solvent to form a dispersion or suspension. Furthermore, by mixing it with a paint resin or the like, it can be made into a paint composition. Further, the composite material and the above-mentioned conductive material can be mixed with a paint resin or the like to form a conductive paint composition. Examples of the conductive paint composition include primer paints used in electrostatic coating methods and antistatic paints used in clean rooms and the like.

Solvents used for dispersions and suspensions include aqueous solvents, alcohols (methanol, butanol, ethylene glycol, etc.), esters (ethyl acetate, etc.), ethers, ketones (acetone, methyl ethyl ketone, etc.), aromatics (toluene, (xylene, mineral spirit), non-aqueous solvents such as aliphatic hydrocarbons, or mixed solvents thereof. The dispersion or suspension may contain additives such as a dispersant, an emulsifier, an antifreeze agent, a pH adjuster, a thickener, and an antifoaming agent, if necessary.

The resin used in the coating composition is not particularly limited as long as it is commonly used in coating applications, and examples include phenol resins, alkyd resins, acrylic alkyd resins, acrylic resins, acrylic emulsion resins, polyester resins, and polyester urethane resins. , polyether resin, polyolefin resin, polyurethane resin, acrylic urethane resin, epoxy resin, modified epoxy resin, silicone resin, acrylic silicone resin, fluororesin, ethylene vinyl acetate copolymer, acrylic-styrene copolymer, amino resin, methacrylic Various coating resins such as resin, polycarbonate resin, and polyvinyl chloride resin can be used.

Among conductive paint compositions, especially when used as a conductive primer paint (a paint that imparts conductivity to a plastic base material, etc. when electrostatically painting the base material), adhesion to a non-polar base material is particularly important. From this point of view, it is preferable to use a chlorinated polyolefin resin, which is a type of polyolefin resin. The above-mentioned polyolefin resin is not particularly limited, and includes, for example, polymers of one or more olefins such as ethylene, propylene, butene, and these olefins together with vinyl acetate, butadiene, acrylic ester, and methacrylic ester. Examples include radical copolymers with the like. Furthermore, as the above-mentioned chlorinated polyolefin, one modified with maleic acid, maleic anhydride, etc. may be used. Preferred examples of the chlorinated polyolefin resin include chlorinated polyethylene, chlorinated polypropylene, chlorinated ethylene-propylene copolymer, and chlorinated ethylene-vinyl acetate copolymer. Furthermore, a chlorinated polyolefin graft-polymerized with a polymerizable monomer can also be used.

The coating composition can contain various additives, solvents, etc. as necessary. Examples of additives include various commonly used dispersants, emulsifiers, antifreeze agents, pH adjusters, thickeners, antifoaming agents, and the like. Examples of solvents include aqueous solvents, alcohols (methanol, butanol, ethylene glycol, etc.), esters (ethyl acetate, etc.), ethers, ketones (acetone, methyl ethyl ketone, etc.), aromatics (toluene, xylene, mineral spirits), carbonized aliphatics. Examples include non-aqueous solvents such as hydrogen, and mixed solvents thereof.

In addition, in paint compositions, since the composite material itself has coloring power and hiding power, there is no need to separately add colorants such as pigments. can be set. As the colorant, for example, the above-mentioned inorganic pigment particles can be used.

A solvent dispersion can be prepared by mixing the composite material, a solvent, and, if necessary, the above-mentioned additives, colorants, solvents, etc., in a mixer, and defoaming if necessary. Further, a coating composition can be prepared by mixing the composite material, a resin, and, if necessary, the above-mentioned additives, colorants, solvents, etc., in a mixer, and defoaming if necessary. Examples of the mixer include a twin-screw mixer, a three-roll mixer, a sand mill, etc. which are usually used industrially, and a homogenizer, a paint shaker, etc. can be used in the case of a laboratory scale. At that time, grinding media containing glass, alumina, zirconia, zirconium silicate, etc. may be used as necessary.

As described above, in the composite material of the present invention, the inorganic pigment particles and the carbon material are firmly fixed. Therefore, even under conditions where external force (for example, shearing force during paint preparation) is applied to the composite material, the inorganic pigment particles and the carbon material do not separate and can maintain a highly composite state. As a result, in solvent dispersions and coating compositions, the phenomenon of "color separation" during long-term storage can be effectively suppressed.

A coating film can be formed by applying the above-mentioned solvent dispersion or coating composition to a substrate and curing it. Moreover, when the composite material has electrical conductivity, an electrically conductive coating film can be obtained. Further, when the composite material has thermal conductivity, a thermally conductive coating film can be obtained, and a coating film having the characteristics of the composite material can be produced.

Methods for applying the above-mentioned solvent dispersion and coating composition include spin coating, spray coating, roller coating, dip coating, flow coating, knife coating, electrostatic coating, bar coating, die coating, brush coating, and dropping droplets. General methods such as methods can be used without limitation. The equipment used for applying the solvent dispersion or coating composition can be appropriately selected from known equipment such as a spray gun, roller, brush, bar coater, and doctor blade. A coating film can be obtained by drying and curing after application. Furthermore, baking may be performed after drying. The baking conditions can be set as appropriate, and for example, the baking time can be set in a drying oven atmosphere at a temperature range of 40° C. or more and 150° C. or less for about 1 to 120 minutes. With these setting conditions, sufficient baking is possible in the drying oven of the coil coating line.

Furthermore, examples of the substrate to which the solvent dispersion or coating composition is applied include ceramic products, glass products, metal products, plastic products, paper products, and the like.

The coating film described above can retain the pigment properties of the composite material. Further, the conductive properties of the composite material can be maintained. For example, in a paint film made using a composite material using inorganic white pigment particles such as titanium dioxide and a paint composition containing a chlorinated polyolefin resin as a paint resin, the L value of the paint film in the Lab color system is 75. It can be more than 80, preferably 80 or more.

When measuring the L value, a value, and b value of the above-mentioned coating film, for example, prepare a paint composition with a pigment mass concentration (PWC) of 60%, and apply the dry coating using a 4 mil film applicator. A coating film is formed by applying it to black and white chart paper so that the film thickness is about 13 μm. The L value, a value, and b value of the coating film formed on the black surface of black and white chart paper are measured using a colorimeter (Color Computer SM-5: manufactured by Suga Test Instruments Co., Ltd.).

Further, the coating film described above can exhibit sufficient electrical conductivity. For example, the surface resistivity as a sheet resistance (unit: Ω/□) can be less than 1×10 ⁹ , preferably less than 1×10 ⁸ . Specifically, sheet resistance (unit: Ω/□ ) can be less than 1×10 ⁹ , preferably less than 1×10 ⁸ , more preferably less than 1×10 ⁷ .

When measuring the surface resistivity of a paint film, for example, a paint composition with a pigment mass concentration (PWC) of 60% is prepared, and a dry paint film thickness of approximately 13 μm is applied using a 4 mil film applicator. Coat it on black and white chart paper to form a coating film. The surface resistivity of the coating film formed on the black and white chart paper is measured using a surface resistivity meter (Hiresta (registered trademark)-UP MCP-HT450, manufactured by Mitsubishi Chemical Corporation) under the condition of an applied voltage of 10V.

Examples of the present invention are shown below, but the present invention is not limited to these Examples.

<Preparation of composite material>
(Example 1)
20 g of titanium dioxide pigment (CR-95, manufactured by Ishihara Sangyo Co., Ltd.) as inorganic white pigment particles and 150 ml of pure water were placed in a beaker and mixed by stirring at room temperature. To this liquid mixture, 0.04% by mass of an aqueous silanated urethane polymer based on the titanium dioxide pigment was added and further mixed. Specifically, an aqueous silylated urethane resin composition (Aqualincar (registered trademark) SU500, manufactured by Konishi Corporation) containing 40% by mass of an aqueous silanated urethane polymer as an active ingredient was diluted 100 times with pure water. 2.0 g of this diluted solution was added to the above mixed solution and mixed by stirring at room temperature for 10 minutes. Further, 0.04% by mass of carbon nanotubes (indicated as CNT in Tables 3 and 4) based on the titanium dioxide pigment was added to this liquid mixture, and the mixture was further mixed. Specifically, 4.0 g of a 0.2% by mass aqueous dispersion of carbon nanotubes (TUBALL ^TM COAT_E H ₂ O DBD: manufactured by OCSiAl) was added and mixed by stirring at room temperature for 10 minutes.
The mixture was suction filtered using a Buchner funnel to obtain solid content. This solid content was used as the sample of Example 1.

(Example 2)
The solid content obtained by filtration in Example 1 was dried at 150° C. for 3 hours using a dryer (Inert Oven DN411I: manufactured by Yamato Scientific Co., Ltd.) to obtain a sample of Example 2.

(Example 3)
A sample of Example 3 was obtained in the same manner as in Example 2, except that the amount of the aqueous silanated urethane polymer added was changed to 0.01% by mass based on the titanium dioxide pigment.

(Example 4)
A sample of Example 4 was obtained in the same manner as in Example 2, except that the amount of the aqueous silanated urethane polymer added was changed to 0.5% by mass based on the titanium dioxide pigment.

(Example 5)
In Example 2, the amount of the aqueous silanated urethane polymer added was changed to 0.1% by mass relative to the titanium dioxide pigment, and the amount of carbon nanotubes added was changed to 0.1% by mass relative to the titanium dioxide pigment. A sample of Example 5 was obtained in the same manner as Example 2 except for the following changes.

(Comparative example 1)
Example 2 was the same as Example 2 except that 3-aminopropyltrimethoxysilane (KBM-903: manufactured by Shin-Etsu Silicone Co., Ltd.), a commercially available silane coupling agent, was used instead of the aqueous silanated urethane polymer. A sample of Comparative Example 1 was obtained. This silane coupling agent has a hydrolyzable alkoxysilyl group only at one end of the molecule.

(Comparative example 2)
In Example 2, except that 1,6-bis(trimethoxysilyl)hexane (KBM-3066: manufactured by Shin-Etsu Silicone Co., Ltd.), a commercially available silane coupling agent, was used instead of the aqueous silanated urethane polymer. A sample of Comparative Example 2 was obtained in the same manner as Example 2. This silane coupling agent has hydrolyzable alkoxysilyl groups at both ends of the molecule, and has a basic skeleton (hexane) different from polyurethane between the alkoxysilyl groups.

(Comparative example 3)
Comparative Example 3 was carried out in the same manner as in Example 2, except that a commercially available silane coupling agent, aminosilane (KBP-90, manufactured by Shin-Etsu Silicone Co., Ltd.) was used in place of the aqueous silanated urethane polymer. samples were obtained. This silane coupling agent has a plurality of silanol groups in its molecule, but does not have a polyurethane urethane skeleton between the silanol groups.

<Preparation of coating composition>
Using the samples of Examples 1 to 5 and Comparative Examples 1 to 3 above, coating compositions were prepared at a pigment mass concentration (PWC) of 60%. Specifically, raw materials were prepared with the composition shown in Table 1 below, and they were placed in a 70 ml mayonnaise bottle, 25 g of glass beads were added, and the mixture was mixed using a stirrer (paint shaker: manufactured by Red Devil). Mixed for 20 minutes. After filtering the glass beads, they were degassed by stirring at 2000 rpm for 1 minute using a defoaming machine (Awatori Rentaro (registered trademark) AR-250: manufactured by THINKY), and Examples 1 to 5 and Comparative Examples A coating composition containing samples 1 to 3 was obtained.

Further, raw materials were prepared with the compositions shown in Table 2, and a coating composition of Comparative Example 4 was obtained in the same manner as above. The coating composition of Comparative Example 4 contains the same amount of titanium dioxide pigment and carbon nanotubes as the coating composition of Example 1 in the form of a mixture.

<Evaluation of color separation of paint composition>
4 ml of each of the coating compositions of Examples and Comparative Examples immediately after being made into coatings was taken from near the liquid surface and designated as Sample 1. In addition, the coating compositions of the Examples and Comparative Examples immediately after being made into coatings were put into a centrifuge tube (50PA: manufactured by Hitachi Koki Co., Ltd.), and heated to 25°C using a centrifuge (CR21GII: manufactured by Hitachi Koki Co., Ltd.). Centrifugation was performed at 3000G for 10 minutes under temperature conditions. After centrifugation, 4 ml of the paint composition was taken from near the liquid surface and designated as Sample 2.

Each of Sample 1 and Sample 2 of each Example and Comparative Example was placed in a polystyrene disposable cell (#1937: manufactured by Kartell, optical path length 10 mm, optical path width 10 mm), and a spectrophotometer (X-Rite eXact: The L ^* value was measured in the single L ^* a ^* b ^* mode using the L*A*B* (manufactured by Wright Co., Ltd.). The L ^* value of Sample 1 was set as L ₁ and the L ^* value of Sample 2 was set as L ₂ , and the value (ΔL) of the difference (L ₁ −L ₂ ) between L ₁ and L ₂ was calculated. The results are shown in Table 3.

As is clear from Table 3, the value of ΔL is 20 or more in the coating composition (Comparative Example 4) in which only carbon nanotubes and titanium dioxide pigments are mixed. In the coating composition of Comparative Example 4, even in visual observation of the coating composition after centrifugation, suspended matter of carbon nanotubes was observed near the liquid surface, and the vicinity of the liquid surface appeared darkened. This is considered to be the reason why the value of ΔL of the coating composition becomes large.

In addition, in the cases in which carbon nanotubes and titanium dioxide pigments were tried to be fixed using various silane coupling agents (Comparative Examples 1 to 3), the ΔL value was almost the same as that in Comparative Example 4, and the visual A similar trend was observed in observations. From this result, in the samples of Comparative Examples 1 to 3, the titanium dioxide pigment and carbon nanotubes are not fixed in the first place, or even if they are fixed once, the carbon nanotubes and titanium dioxide are bonded together due to the shearing force during the coating process. It is thought that the "color separation" phenomenon occurs because the pigments are easily separated. That is, in Comparative Examples 1 to 3, the fixing strength between the carbon nanotubes and the titanium dioxide pigment was insufficient.

On the other hand, the coating compositions of Examples 1 to 5 have relatively low ΔL values of less than 20, and the "color separation" phenomenon is suppressed. This shows that in the samples (composite materials) of Examples 1 to 5, the carbon nanotubes and the titanium dioxide pigment were firmly fixed by the aqueous silanated urethane polymer.

In addition, when comparing Example 1 and Example 2 with a focus on the presence or absence of a heating process in the production of the composite material, ΔL is a lower value in the case where there is a heating process (Example 2), The fixing strength between the titanium dioxide pigment and the carbon nanotubes can be increased by heating.

Furthermore, when comparing Examples 2, 3, and 4 focusing on the mass ratio of the fixed component (aqueous silanated urethane polymer) to the carbon nanotubes, it is found that when the mass ratio is the smallest (Example 3: mass Even if the ratio is 0.25), the value of ΔL is a sufficiently low value (less than 20), and sufficient fixing strength between the titanium dioxide pigment and the carbon nanotubes can be ensured.

<Evaluation of physical properties of paint film>
For the coating compositions of Examples 1 to 5 in which the "color separation" phenomenon was sufficiently suppressed, coating films were prepared by the following method, and the surface resistivity and whiteness of the coatings were measured.

(Preparation of coating film)
The coating compositions of Examples 1 to 5 were applied to black and white chart paper (Form 5C Opacify Chart, manufactured by LENETA) using a 4 mil film applicator (AP100, manufactured by Taiyu Kizai Co., Ltd.). This was dried at 80° C. for 5 minutes using a dryer (SPHH-202: manufactured by Espec) to produce a coating film with a dry coating thickness of about 13 μm.

(Measurement of surface resistivity of coating film)
The surface resistivity (Ω/□) of the above coating film was measured using a surface resistivity meter (Hiresta (registered trademark)-UP MCP-HT450: manufactured by Mitsubishi Chemical Corporation). A J-box U type was used as the electrode during measurement. Further, the applied voltage was 10V.

(Measurement of whiteness of paint film)
Regarding the above coating film, the L value (L value on black ground) in the Lab color system was measured using a colorimeter (Color Computer SM-5: manufactured by Suga Test Instruments Co., Ltd.).

As is clear from Table 4, in all of Examples 1 to 5, the L value of the coating film was 75 or more, indicating that the whiteness generally required for a white coating film was sufficiently achieved.

It can be seen that in any of Examples 1 to 5, the surface resistivity of the coating film was less than 1×10 ⁹ Ω/□, achieving the conductivity generally required for a conductive coating film.

In addition, when comparing Example 2 and Example 5 with a focus on the content of carbon nanotubes relative to the titanium dioxide pigment, the surface resistivity of the coating film is smaller and higher when the content is larger (Example 5). Conductivity can be achieved.

Furthermore, when comparing Examples 2, 3, and 4 with a focus on the mass ratio of the fixed component to the carbon nanotubes, the smaller the mass ratio, the lower the surface resistivity of the coating film, and the higher the conductivity. It can be realized. This is because by keeping the amount of fixing component used to the minimum amount necessary to fix the titanium dioxide pigment and carbon nanotubes, the effect of the fixing component on the conductivity of the coating film can be minimized. it is conceivable that.

According to the composite material of the present invention, it is possible to suppress the "color separation" phenomenon when blended into a solvent dispersion or a coating composition, and to obtain stable coating film properties (pigment properties, electrical conductivity, thermal conductivity, etc.). Can be done. Therefore, the composite material of the present invention is useful for various conductive paint compositions, such as primer paints used in electrostatic coating methods and antistatic paints used in clean rooms and the like.

Claims (10)

It contains inorganic white pigment particles, carbon nanotubes , and polyurethane having silanol groups at both ends, and the content of the carbon nanotubes is 0.02% by mass or more and 0.5% by mass or less based on the inorganic white pigment particles. , a composite material in which the inorganic white pigment particles and the carbon nanotubes are fixed with polyurethane having silanol groups at both ends . A composite material according to claim 1 , wherein the inorganic white pigment particles are titanium dioxide pigments. It contains inorganic white pigment particles, a carbon material, and a polyurethane having silanol groups at both ends, and the content of the carbon material is 0.02% by mass or more and 0.5% by mass or less based on the inorganic white pigment particles. A conductive material comprising a composite material in which the inorganic white pigment particles and the carbon material are fixed with polyurethane having silanol groups at both ends . 4. The conductive material according to claim 3, wherein the inorganic white pigment particles are titanium dioxide pigments. The conductive material according to claim 3 or 4, wherein the carbon material is a carbon nanotube. A coating composition comprising the composite material according to claim 1 or 2 or the conductive material according to claims 3 to 5 , and a resin. A coating film comprising the composite material according to claim 1 or 2 or the conductive material according to claim 3 to claim 5 . It includes a step of mixing at least inorganic white pigment particles, carbon nanotubes , and polyurethane having silanol groups at both ends in an aqueous dispersion medium, and the content of the carbon nanotubes is 0.02% by mass with respect to the inorganic white pigment particles. A method for producing a composite material in which inorganic white pigment particles and carbon nanotubes are fixed with polyurethane having silanol groups at both ends, the amount of which is 0.5% by mass or less. Inorganic white pigment particles and carbon , comprising a step of solid-liquid separation of the mixed liquid obtained in the mixing step according to claim 8 , and a step of heating the obtained solid content at a temperature of 30 ° C. or higher and 180 ° C. or lower. A method for producing a composite material in which nanotubes are fixed with polyurethane having silanol groups at both ends . It includes a step of mixing at least inorganic white pigment particles, a carbon material, and a polyurethane having silanol groups at both ends in an aqueous dispersion medium, and then a step of heating the obtained solid content at a temperature of 30°C or higher and 180°C or lower. , the content of the carbon material is 0.02% by mass or more and 0.5% by mass or less with respect to the inorganic white pigment particles, the inorganic white pigment particles and the carbon material are polyurethane having silanol groups at both ends. Method of manufacturing fixed composite materials.

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