JPH07102197A - Coating composition - Google Patents

Abstract

PURPOSE: To obtain a coating composition which gives a coating film excellent in conductivity and strength, and can be applied to concrete, metal, wood, etc. and useful for e.g. removal of static electricity and electromagnetic wave shielding, by mixing an organic polymer binder with a carbonaceous fibril material in a specified form and a solvent.

CONSTITUTION: The composition is obtained by mixing 100 pts.wt. organic polymer binder (A) comprising, e.g. an epoxy resin with 0.2-30 pts.wt., preferably 0.4-15 pts.wt., carbonaceous fibril material (B) comprising agglomerates of fine fibrous carbonaceous fibrils of a diameter of 3.5-75 nm entangled among one another, with a mean particle diameter of 0.1-50 μm, and a solvent (C). It is useful also for an anticorrosive coating and a black coating.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition, and more particularly to a coating composition having excellent conductivity which is preferably used for the purpose of preventing static electricity and shielding electromagnetic waves.

[0002]

2. Description of the Related Art Heretofore, as conductive coating compositions, carbon black type coatings, nickel, silver, aluminum,
Various metallic paints such as copper have been used.

[0003]

However, metal-based paints have problems such as expensive metal, high specific gravity and corrosion.
On the other hand, carbon black-based paints have few problems like metal-based paints, but have drawbacks such as insufficient conductivity. The present invention has been made in view of these problems, and provides a coating composition that is inexpensive and has excellent conductivity.

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention have studied new carbon-based materials as a method for improving the drawbacks of conventional conductive coating compositions, and as a result, have used carbon fibrils having a specific structure. Therefore, it has been found that the above-mentioned drawbacks can be improved.

That is, according to the present invention, 100 parts by weight of an organic polymer binder and fine thread-like carbon fibrils having a diameter of 3.5 to 75 nm are entangled with each other, and an average particle diameter of 0.1 to 50.
Carbon fibril material consisting mainly of agglomerates of μm.
Provided is a coating composition prepared by mixing 2 to 30 parts by weight and a solvent.

The carbon fibril material used in the present invention is
It is composed of fine thread-like carbon fibrils having a diameter of 3.5 to 75 nm and pill-like aggregates in which the carbon fibrils are entangled and having an average particle diameter of 0.1 to 50 μm. The average particle size of the aggregate is preferably 0.2 to 30 μm.

If the average particle size of the aggregate exceeds 50 μm,
The carbon fibril material in the coating film becomes poorly dispersed,
The tensile strength of the coating film is reduced, and the appearance of the coating film surface is impaired. It is difficult to produce aggregates having an average particle size of less than 0.1 μm. The proportion of aggregates in the carbon fibril material is preferably 30% or more, more preferably 50% or more.

In the description of the present invention, the phrase "90% diameter" is used. This is defined as follows. The particle size is d, and the distribution having the volume fraction Vd in the particle size as a random variable is called a particle size distribution D. In this particle size distribution D, a specific particle size such that the total sum of the volume fractions from the minimum particle size to a certain particle size is half of the total is defined as the average particle size dm. Similarly, a specific particle diameter is defined as 90% diameter so that the sum of the volume fractions from the minimum particle diameter to a certain particle diameter is 90% of the total.

The particle size distribution of the aggregate of carbon fibril material used in the present invention is as follows. That is, the 90% diameter defined above is usually 100 μm or less, preferably 80 μm or less, and more preferably 50 μm or less.
Further, this 90% diameter is also 7.5 times or less of the average particle diameter.

The carbon fibrils constituting the carbon fibril aggregate have a variation in diameter of preferably 15% or less of the average diameter of 10 samples, and an aspect ratio of usually 5 or more, preferably 100 or more, more preferably 1
It is in the form of a tube having at least 000 filaments and usually having a hollow core.

Furthermore, the carbon fibrils have a plurality of graphitic layers parallel to the fibril axis and preferably have no continuous thermal carbon coating. The percentage of surface area covered by this thermal carbon coating is usually less than 50%, preferably 25
% Or less, more preferably 5% or less.

Carbon fibrils whose surface has been modified can be used. For example, it can be modified by means of chemical reaction such as oxidation or coating with a polymer such as an epoxy resin.

The proportion of the carbon fibril material in the coating composition of the present invention is 0.2 to 30 parts by weight, preferably 0.3 to 20 parts by weight, particularly preferably 0.4, based on 100 parts by weight of the organic polymer binder. ~ 15 parts by weight. 0.2
If it is less than 10 parts by weight, the effect of the carbon fibril material is poor, and if it exceeds 30 parts by weight, the fluidity of the coating composition is deteriorated, and the strength of the coating film and the adhesiveness of the substrate are deteriorated.

The method for producing the carbon fibril material used in the present invention is described in Japanese Patent Application Laid-Open No. 2-503334, and specific examples will be described below. Carbon fibrils are produced by introducing metal-containing catalyst particles into a carbon-containing gas stream by gravity or injecting a gas such as an inert gas in a vertical tubular reactor. Reaction temperature is 550
~ 1200 ° C. Catalyst particles may be formed in the reactor by decomposition of precursor compounds, such as ferrocene.
The reactor is equipped with a quartz tube with an internal plug of quartz wool that receives the catalyst particles and a thermocouple that monitors the temperature of the reactor. Further, an inlet port for introducing a catalyst, a reaction gas, and a purge gas such as argon, and an outlet port for degassing the reactor are provided.

Suitable carbon-containing gases are saturated hydrocarbons,
Examples are methane, ethane, propane, butane, hexane and cyclohexane, unsaturated hydrocarbons such as ethylene, propylene, benzene and toluene, oxygen-containing hydrocarbons such as acetone, methanol and tetrahydrofuran, and carbon monoxide. Preferred gases are ethylene and propane. Hydrogen gas is preferably added. Typically the ratio of carbon containing gas to hydrogen gas is in the range of 1:20 to 20: 1. Preferred catalysts are iron, molybdenum-iron, chromium-deposited on vapor-deposited alumina.
Iron, cerium-iron and manganese-iron particles.

Five reaction tubes were used to grow the fibrils.
Heat to 50-1200 ° C. and simultaneously purge with, for example, argon. When the reaction tube reaches a predetermined temperature, introduction of the hydrogen flow and the carbon-containing gas flow is started. For a 1 inch thick reaction tube, a hydrogen flow rate of about 100 milliliters / minute and a carbon-containing gas flow rate of about 200 milliliters / minute are suitable. After purging the reaction tube with the reaction gas at the above flow rate for 5 minutes or more, the catalyst is dropped on a quartz wool plug. next,
The reaction gas is passed through the reactor with a catalyst (typically 0.
5 to 1 hour). At the end of the reaction time, the flow of the reaction gas is stopped, a carbon-free gas such as argon is purged, the reactor is cooled to room temperature, and the fibrils are recovered from the reaction tube. The yield of fibrils is 30% of the iron content of the catalyst.
More than double.

The carbon fibril material used in the present invention is obtained by preparing the carbon fibrils produced as described above as they are or, in many cases, crushing them to a predetermined size. Examples of the crushing means include an airflow crusher (jet mill) and an impact crusher. Since these pulverizers can be continuously operated and the throughput per unit time is large as compared with a ball mill, a vibration mill, etc., the pulverization cost can be kept low. Further, it is preferable to provide a classifying mechanism in the crusher or to provide a classifier such as a cyclone in the line because a uniform carbon fibril aggregate having a narrow particle size distribution can be obtained.

The carbon fibril material of the present invention can be used as a mixture with other conductive powder. Examples of conductive powders are carbon-based materials such as acetylene black, Ketjen black, graphite powder, various carbon fibers, and metal fibers and powders such as silver, nickel and aluminum, and metal such as nickel. Glass fiber and the like.

The organic polymer binder used in the present invention is exemplified. Thermosetting resin such as phenol resin, alkyd resin, urea resin, melamine resin, furan resin, unsaturated polyester resin, epoxy resin, polyurethane resin, silicon resin, amino resin, polyimide resin, polyamide resin, polyurethane resin, vinyl chloride A resin, a thermoplastic resin such as an ethylene-vinyl acetate copolymer, an acrylic resin, a cellulose resin, a butyral resin, a rubber elastic body such as a silicone rubber, a polyurethane rubber, a styrene-butadiene rubber, a natural rubber, or a mixture thereof is used.

The organic polymer binder can be used as an emulsion or a latex, but it is preferably dissolved in a solvent and used as a solution. The solvent is not particularly limited as long as it dissolves or disperses the organic polymer binder.

For example, hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as dichloroethane and trichloroethane, alcohols such as isopropyl alcohol and butanol, ketones such as methyl ethyl ketone and methyl isobutyl ketone, ethyl acetate and ethyl propylate. Esters, ethers such as methyl ether of ethylene glycol and dimethyl ether of diethylene glycol, carbitol derivatives and water are used alone or in combination.

In the coating composition of the present invention, additives for improving coating properties can be used if necessary. For example, leveling agents, thickeners, antioxidants, pigments, coupling agents, plasticizers, crosslinking agents, fillers,
Examples include antifoaming agents.

The coating composition of the present invention can be usually produced by mixing an organic polymer binder solution and a carbon fibril material. As the mixing device, an ordinary device such as a three-roll mill, a liquor machine, or a ball mill can be used. Further, the coating composition of the present invention can be applied by a usual method such as brush coating, roller coating and spraying.

[0024]

EXAMPLES The present invention will be described in more detail by way of examples, but the invention described in the claims is not limited by the examples in any sense.
The particle size of the carbon fibril aggregate is dispersed using an ultrasonic homogenizer in water containing a surfactant of carbon fibril material, and this aqueous dispersion is analyzed using a laser diffraction scattering particle size distribution analyzer. And measured.

Examples 1 to 4 As carbon fibril materials, fine filaments having an average diameter of 13 nm and tube-shaped graphite carbon fibrils are intertwined with each other, the average particle diameter is 3.5 μm, and the 90% diameter is 8. 2 μm aggregates were used.

Xylene / methyl amyl ketone = 2/1
Using a mixed solvent (weight ratio), a 50 wt% solution of an epoxy resin (Shell Chemical, Epicoat 1001) was prepared. A carbon fibril material was added to a part of this solution and mixed with a three-roll to prepare a dispersion containing the material in a relatively high concentration.

Next, a 50 wt% solution of the epoxy resin was further added to this dispersion to obtain a carbon fibril material dispersion having the concentration shown in Table 1. To this dispersion, 7 equivalents of an amine-sized epoxy curing agent (ACI Japan sales, Anchormin T) equivalent to epoxy equivalent 93 of the epoxy resin was added and stirred to obtain a coating composition.

This coating composition was applied onto a concrete block with a blade and set at room temperature for 2 hours.
Baking was carried out at 0 ° C. for 2 hours to obtain a black coating film. The coating film on the concrete was strong and did not come off at all in the cross-cut peeling test with cellophane tape. In order to judge the electroconductivity and the coating strength of the coating film, the coating materials were separately coated on a PET film with a blade, set at room temperature for 2 hours, and then at 80 ° C for 2 hours.
Burned for hours. The coating film was peeled off from PET, and the volume resistivity and the tensile strength were measured. The results are shown in Table 1. When this coating composition was applied to an iron plate, a wooden plate, and an ABS resin plate, a good black coating film was obtained.

Comparative Example 1 The procedure of Example 4 was repeated except that acetylene black was used instead of the carbon fibril material.

[0030]

[Table 1]

Example 5 A solution of polybutyl methacrylate (abbreviated as PBMA) in 15% by weight of an acrylic lacquer thinner was used, and the carbon fibril material used in Example 1 was added to the polymer in an amount of 12 parts by weight based on 88 parts by weight of the polymer. After mixing at room temperature for 3 days in a ball mill, 43.4 wt% acrylic lacquer thinner solution of PBMA was added to adjust the carbon fibril amount to 6 wt% in the total amount of polymer and carbon fibril. Thus, a coating composition was prepared. This composition was coated on a tin plate with a blade and dried at room temperature for 5 days to obtain a black coating film. The coating film on the tin plate was strong and did not come off at all in the cross-cut peeling test with cellophane tape. Separately, this composition was coated on a silicone rubber plate with a blade, dried at room temperature for 5 days, and then the coating film was peeled off from the silicone plate. The volume resistivity of this coating film is 3.6.
It was Ω · cm.

Example 6 Similar to Example 5, except that PBMA was changed to 1/2 ″ nitrocellulose, the solvent was changed to lacquer thinner, and the polymer solution concentration after ball mill mixing was changed to 20%. A coating composition was prepared in which the amount of carbon fibrils in the total amount of polymer and carbon fibrils was 6% by weight.
The coating film on a tin plate produced by using this composition in the same manner as in Example 5 was strong and was not peeled off at all in a cross-cut peeling test using cellophane tape. The coating film produced in the same manner as in Example 5 had a volume resistivity of 13.5 Ω · cm.

Comparative Example 2 A coating composition was prepared in exactly the same manner as in Example 6 except that acetylene black was used instead of the carbon fibril material of Example 6. The volume resistivity of the coating film is 10 ³ Ω
・ It was more than cm.

[0034]

In the coating composition of the present invention, the carbon fibril material is uniformly dispersed in the organic polymer binder, and the coating film has excellent conductivity and coating strength, so that it can be used for concrete, metal and wood. , Apply to a base such as plastic,
It can be suitably used for the purpose of removing static electricity and electromagnetic wave shielding, and as a corrosion-resistant paint and further as a black paint.

Claims (1)

[Claims] 1. A carbon fibril material 0.2 mainly consisting of 100 parts by weight of an organic polymer binder and fine thread-like carbon fibryl having a diameter of 3.5 to 75 nm intertwined with each other and having an average particle diameter of 0.1 to 50 μm. A coating composition obtained by mixing 30 parts by weight and a solvent.