JPH10204341A - Paint composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating compsn. that is excellent in dispersion of carbon black in vehicle and gives a coating film with improved gloss and blackness, by dispersing a carbon black obtd. by oxidizing a furnace black with ozone, etc., in the presence of water and having a specified total acid group content into a varnish. SOLUTION: An oxidized carbon black having a total acid group content of 3μequ/m<2> or higher is used as the carbon black. Though there is no limitation about a carbon black to be oxidized, a furnace black, obtd. by the furnace process, is pref. in terms of enhancing the blackness of ink or a coating compsn. Any oxidizing agent can be used for the oxidation without being specifically limited, though a liq.-phase oxidation with ozone in the presence of water is pref. in terms of obtaining a desired total acid group content and an excellent dispersion. A carbon black having a desired total acid group content is dispersed as a pigment into a water-soluble or solvent-type varnish to give the objective coating compsn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a coating composition obtained by mixing and dispersing oxidized carbon black having a specific all acidic group in a coating varnish.

[0002]

2. Description of the Related Art Garbon black is used as a black pigment for paints and resins because of its low cost and good weather resistance. However, furnace black produced by the furnace method, which is a carbon black which is currently generally distributed, has no surface functional group, and therefore, when used as it is as a pigment for coatings, it is insufficiently dispersed in varnish. Therefore, in order to improve dispersibility, the material is used after being oxidized with an oxidizing agent such as nitric acid or ozone.

[0003]

However, these oxidized carbon blacks have sufficient dispersibility, probably because of the poor compatibility between the surface functional groups and the functional groups of the varnish used in the paint. Therefore, the paint gloss is inferior. Therefore, an oxidized carbon black having better gloss and higher blackness has been demanded.

An object of the present invention is to solve the above-mentioned problems of the prior art, improve dispersibility, improve paint gloss, and further improve paint blackness.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above problems, and found that carbon black obtained by oxidizing all the acidic groups of carbon black to a specific amount is converted into various vehicles. It has been found that the dispersibility of the compound is extremely excellent, and the present invention has been achieved. That is, the present invention resides in a coating composition comprising carbon black having a total acidic group content of 3 μequ / m ² or more in a coating varnish.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is characterized in that carbon black having a specific all acidic group is used as a pigment component of a paint. This is obtained by oxidizing the carbon black until it has the desired total acidic groups. The carbon black to be subjected to the oxidation treatment is not particularly limited, and any carbon black conventionally used as an ink pigment can be used. The particle size of the carbon black to be subjected to the oxidation treatment is not limited,
When the coating material has a thickness of 0 nm or less, more preferably 30 nm or less, the gloss is good and optimal. Since the alkali metal and alkaline earth metal in the carbon black dissolve in water and reduce the efficiency of ozone oxidation in the liquid, the smaller the better, the better. However, the total amount is preferably 1% by weight or less, more preferably 0% by weight or less. 0.5% by weight or less, more preferably 0.1% by weight
The following is preferred.

[0007] Further, sulfur or sulfur compounds or chlorine compounds in carbon black are oxidized by ozone to become strong acids in solution, and have a function of preventing the functional groups formed on the surface of carbon black from becoming ions. For this reason, it is desired that the content be as small as possible. However, it is preferably 0.5% by weight or less, preferably 0.1% by weight or less in total sulfur analysis value or total chlorine analysis value. In order to reduce the sulfur content, it is possible to use an aromatic hydrocarbon used as a raw material for carbon black, a liquid hydrocarbon used as a fuel, or a low hydrocarbon content gaseous hydrocarbon as a gaseous hydrocarbon. In addition, the chlorine content can be reduced by using pure water as water used as cooling water in producing carbon black.

The particle size of the carbon black used in the coating material is preferably 20 nm or less when high blackness is required depending on the application, and 30 nm or more when high toning stability is required. The DBP oil absorption is widely used in the range of 40 to 200 cc / 100 g in consideration of paint viscosity, glossiness and conductivity. Without being limited to properties, carbon black manufacturing method, furnace method, channel method, acetylene method,
The present invention can be applied to carbon black produced by any production method without being limited to the thermal method. Particularly preferably, the furnace method, that is, in a furnace heated to 1300 ° C. or more,
Furnace black obtained by a method of obtaining a carbon black by spraying a raw material oil is exemplified. Furnace black is not only excellent in productivity such as high yield, but also can obtain its characteristics, especially those with small particle size and structure, and enhances the blackness of inks and paints and exhibits excellent performance. From now on, it occupies the mainstream of carbon black. However, although furnace black is presumed to be due to its small particle size, surface functional group state, amount of volatile components, etc., it generally tends to have poor dispersibility in various vehicles, particularly aqueous media. It is in. On the other hand, according to the present invention, it is possible to obtain furnace black having excellent dispersibility even in an aqueous medium as described below. Can be improved.

The oxidizing agent used in the oxidizing treatment in the present invention is not particularly limited, and examples thereof include generally known oxidizing agents such as ozone, hypochlorous acid, and nitric acid. The method of oxidation treatment in the present invention is not limited, and can be oxidation by gas phase or liquid phase. Particularly, oxidation treatment with ozone in liquid phase in the presence of water makes it possible to easily obtain the desired total acidic group. Oxidation treatment can be carried out until the amount becomes sufficient, and thereby, the dispersibility in various dispersion media becomes particularly excellent. The method of oxidation with ozone in the liquid phase is not particularly limited, but preferably, the amount of water is the ratio (weight ratio) of carbon black to water.
95: 5 to 0.5: 99.5 is appropriate, more preferably 50:50 to 2:98, and still more preferably 20: 5 to 2:98.
The range of 80 to 5:95 is good. Thus, water and carbon black are mixed, and ozone is introduced into the mixture to oxidize the carbon black. Specifically, ozone and / or
Alternatively, the oxidation treatment of carbon black can be performed by passing an ozone-containing gas into water.

When ozone is used, carbon black can be oxidized in the presence of water by generating ozone with an ozone generator and introducing the ozone into a mixture of water and carbon black. An ozone generator generally generates ozone by discharging in air or oxygen, but it can also be generated by electrolyzing water. As the generator for generating ozone used in the present invention, any generator can be used irrespective of the system. However, a higher ozone generation concentration is preferable because the reaction efficiency of oxidation of carbon black is higher. Generally, generators for generating an ozone-containing gas having an ozone concentration of 1 to 20% by weight are commercially available, and these are sufficient.

As described above, the carbon black is oxidized with ozone in the presence of water, and the properties are extremely excellent by a simple operation of oxidizing all the acidic groups on the surface of the carbon black to a specific amount as described later. The mechanism by which the oxidized carbon black is easily obtained is not clear, but if water is present on the surface of the carbon black, the ozone does not directly react with the surface of the carbon black, but the ozone dissolves in the water and the oxidizing power is weakened. Is considered to be oxidized in the hot state. Furthermore, it is also conceivable that, by reacting in the presence of water, the functional groups generated also have good compatibility with water and exhibit dispersion stability.

[0012] For these reasons, even when compared with carbon black which has been oxidized by ozone oxidation in the gas phase to the extent that it has the same total acidic groups, the oxidation treatment has been greatly improved in dispersibility in water. In addition to the effect of being carbon black, it is presumed that a surprising effect is exhibited even with a solvent-based paint. In particular, the use of ozone as an oxidizing agent is particularly preferable because the treated carbon black aqueous dispersion can be directly mixed with various vehicles without contamination of foreign substances such as chlorine ions and sodium ions.

In the ozone oxidation reaction in the presence of such water, it is said that the pH of the obtained dispersion becomes low, and that the carbon black agglomerates normally when the pH in the liquid becomes low. The oxidized carbon black obtained in the present invention has a good dispersion stability even when the pH of the liquid is 2, and even when an alkali such as NaOH is added to the aqueous dispersion containing the oxidized carbon black obtained in the present invention. And the dispersion stability is extremely excellent up to pH 12. This aqueous dispersion can be directly added to a water-soluble paint varnish, or water can be removed from the aqueous dispersion to be added to a solvent-type paint varnish. The oxidized carbon black of the present invention has extremely good compatibility with the solvent-type varnish, and can disperse water without any problem even if about 10% by weight of water remains. It is sufficient to remove water from the aqueous carbon black dispersion by, for example, drying the carbon black obtained by filtration with a 0.1 micron millipore filter at 60 ° C. for 24 hours.

In the present invention, the degree of oxidation of the carbon black is determined by determining that the total amount of acidic groups on the surface of the carbon black is 3 μeq.
Oxidation treatment is performed until u / m ² or more. Thereby, the dispersibility in the solvent-based paint in addition to the water-based paint can be made extremely excellent. If all the acidic groups are less than 3 μequ / m ^2, it will be difficult to disperse in the paint, which is not desirable as a paint pigment. If it is more preferably at least 6 μequ / m ² , the dispersion in the coating medium will be very good. The amount of all acidic groups can be determined as the amount reacted with a strong alkali such as NaOH or KOH.

The method for determining the total acidic groups is as follows. The oxidized carbon black is filtered through a 0.1 micron membrane filter to separate it from water. The separated carbon black is dried all day and night with a dryer at 60 ° C., and then pulverized in an agate mortar. 0.2 to 0.5 g of the oxidized carbon black after drying.
The flask was placed in an Erlenmeyer flask containing 60 cc of 0.01 N NaOH, and nitrogen was flowed through the Erlenmeyer flask.
Stir for hours to react. The reaction product is filtered again using a 0.1 micron membrane filter to obtain a filtrate.

[0016] Take 40 cc of this filtrate and add 0.025N
Titration with an automatic neutralization titrator using hydrochloric acid
Determine the OH concentration. The total acidic group of carbon black can be determined by the following calculation.

(Equation 1) Surprisingly, the oxidized carbon black of the present invention is easily dispersed in water only by dilution with water. Therefore, a particularly excellent water-based paint can be obtained. Preferably, if the carbon black concentration is adjusted to 20% by weight or less and diluted with water, the dispersion stability in an aqueous medium can be sufficiently maintained without addition of a dispersant or dispersion treatment using a bead mill or the like. It has a special effect.

When carbon foreign matter having a particle size of 1 μm or more is present in the carbon black, it may be removed by a method such as filtration or centrifugal sedimentation. The above-described specific amount of carbon black having all acidic groups is blended as a pigment in a paint varnish to prepare a paint composition. Here, the paint is generally a pigment that covers the object to be coated, an oil or resin that adheres to the object to form a film and binds the pigment, and a solvent or diluent that dissolves the oil or resin and the resin. It refers to a liquid applied for the purpose of beautifying or protecting an object to be coated, and can be prepared by a conventionally known component or method except that the above-mentioned specific oxidized carbon black is used as a pigment. Specifically, the oxidized carbon black is mixed with various water-soluble paint varnishes and solvent-based paint varnishes, mixed and dispersed to obtain a paint composition.

The solvent type paint varnish is prepared by dissolving a vehicle in a solvent. Oils and fats and synthetic resins are used as vehicles for solvent-type paints, and hemp oil and castor oil are used as oils and fats. And the like. Examples of the solvent include alcohols such as methanol, ketones such as acetone, esters such as methyl acetate, and aromatics such as toluene and xylene. As a vehicle for water-soluble paint,
Acrylic resin and other molecules in which COOH and OH groups that are easily compatible with water are introduced, those that are neutralized with amines, and those in which the resin is emulsified using a dispersant, etc. are used. It is common to disperse to form a water-soluble paint varnish. Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 Commercially available carbon black "# 4"
7 "(manufactured by Mitsubishi Chemical Corporation, sulfur content 0.5%, total content of alkali metal and alkaline earth metal 0.1%) 20g
Was placed in 500 cc of water containing 0.1 N acetic acid and dispersed with a household mixer for 5 minutes. The resulting dispersion was placed in a 3 liter glass vessel equipped with a stirrer. While stirring with a stirrer, 10 wt% of ozone gas was 3000 cc /
Oxidation treatment with ozone was performed by introducing the mixture for 2 hours. As the ozone generator at this time, a discharge type ozonizer using pure oxygen manufactured by PCI, USA was used.

Take out the liquid after the oxidation treatment with ozone and extract the pH
Was 2.1 when measured. (The pH was measured according to JIS K 6221.) When the particle size distribution of carbon black in this liquid was measured by “Microtrack UPA” manufactured by Nikkiso Co., Ltd., the average was 50 nm in diameter and 72 nm. The dispersion was observed at a magnification of 400 times using an optical microscope, and it was found that the dispersion was in a good dispersion state and the dispersion stability was good. Next, this solution was filtered through a micropore filter having a diameter of 0.1 micron to obtain an oxidized carbon black.

The oxidized carbon black is dried at 60 ° C., and 3.0 g of the carbon black is
140cc containing 90g of 3.5mm diameter glass beads
Into a glass bottle with a lid, and then add “Amirac Clear” (a varnish for solvent-based paint) manufactured by Kansai Paint Co., Ltd.
g and Amirac thinner (10 g) were placed in a paint shaker manufactured by Red Revil Co., Ltd., and dispersed for 60 minutes. After dispersing is completed, "Amirac Clear" 50g
Was added and diluted to obtain a paint. This paint was evaluated by applying the paint to a pet film using a # 22 bar coater, evaporating the solvent in the room for 20 minutes,
After baking for 0 minutes, the coating film was visually evaluated for blackness and gloss under a bright light source and indexed. Table 2 shows the results.
Shown in

Example 2 Commercially available carbon black "# 2"
600 "(manufactured by Mitsubishi Chemical Corporation, sulfur content 0.5%, total content of alkali metals and alkaline earth metals 0.3%) 20
g was placed in 500 cc of water containing 0.1N acetic acid and dispersed with a household mixer for 5 minutes. The resulting dispersion was placed in a 3 liter glass vessel equipped with a stirrer. While stirring with a stirrer, an ozone-containing gas having an ozone concentration of 10 wt% was introduced at 3000 cc / min for 3 hours to perform an ozone oxidation treatment. As the ozone generator at this time, a discharge type ozonizer using pure oxygen manufactured by PCI, USA was used.

The particle size distribution in the liquid was measured using Nikkiso's "Microtrac UPA".
% Of the dispersion was 50 nm, and this liquid was taken and observed under an optical microscope at a magnification of 400 times. As a result, the entire dispersion had a micro-Brownian motion in a good dispersion state, and did not aggregate over time, and the dispersion stability was high. Was found to be good. Next, this solution was filtered through a micropore filter having a diameter of 0.1 micron to obtain an oxidized carbon black.
This oxidized carbon black was dried at 60 ° C. and evaluated in the same manner as in Example 1. Table 2 shows the results.

(Example 3) Using the oxidized carbon black obtained in Example 1, "Aqua No.", a varnish for water-soluble paint manufactured by NOF Corporation instead of "Amirac Clear" manufactured by Kansai Paint Co., Ltd. .8000T ". The formulation is as follows. Put 3.0 g of the dried carbon black into a 140 cc glass bottle with a lid containing 90 g of glass beads having a diameter of 2.5 to 3.5 mm,
Next, 16 g of “Aqua No. 8000T” and 10 g of water
g was set in a paint shaker manufactured by Red Revil Co., Ltd. and dispersed for 60 minutes. Table 2 shows the results.

Example 4 The oxidized carbon black obtained in Example 2 was replaced with "Aqua N" manufactured by NOF Corporation instead of "Amirac Clear" manufactured by Kansai Paint Co., Ltd.
o. 8000T "was dispersed in the same manner as in Example 3, and the coating film was evaluated. Table 2 shows the results.

Comparative Example 1 Commercially available carbon black "# 4
7 "was placed in a glass container having a diameter of 5 cm and a height of 20 cm, and an oxidation treatment was carried out by introducing an ozone-containing gas having an ozone concentration of 10 wt% at 3000 cc / min for 1 hour from below. The ozone generator used here was a discharge type ozonizer using pure oxygen, manufactured by PCI, USA. The liquid after the oxidation treatment was taken out, and the pH was measured. Further, this carbon black was put into water so as to have a concentration of 10% by weight, dispersed for 1 hour by an ultrasonic disperser, and the particle size distribution was measured on a “Microtrack UPA” manufactured by JGC Corporation.
The solution was taken at a magnification of 400 times using an optical microscope, and a large number of aggregates were observed, indicating that the dispersion was not good. Evaluation was performed in the same manner as in Example 1 using this oxidized carbon black.
Table 2 shows the results.

Comparative Example 2 Commercially available carbon black “# 2”
600 "(manufactured by Mitsubishi Chemical Corporation) with a diameter of 5 cm
Then, an oxidation treatment was performed by placing an ozone-containing gas having an ozone concentration of 10 wt% at 3000 cc / min for 1.5 hours from below in a glass container having a height of 20 cm. The ozone generator used here was a discharge type ozonizer using pure oxygen, manufactured by PCI, USA. This liquid was taken out and its pH was measured to be 2.0. Further, the carbon black in the liquid is taken out, put into water so as to have a concentration of 10% by weight, dispersed by an ultrasonic dispersing machine for 1 hour, and the particle size distribution is measured by Microtrac S manufactured by Nikkiso Co., Ltd.
When measured by PA, the average was 50 nm in diameter at a diameter of 250 nm, and this liquid was taken and confirmed under a 400-fold magnification using an optical microscope. As a result, it was found that many aggregates were observed and the dispersion was not good. Evaluation was performed in the same manner as in Example 1 using this oxidized carbon black. Table 2 shows the results.

Comparative Example 3 Using the oxidized carbon black obtained in Comparative Example 1, carbon black was dispersed in the same manner as in Example 3 and the coating film was evaluated. Table 2 shows the results. (Comparative Example 4) The same evaluation as in Example 4 was performed using the oxidized carbon black obtained in Comparative Example 2. Table 2 shows the results.

[0029]

[Table 1]

[0030]

[Table 2] As described above, in each of the examples, the gloss and the blackness of the paint were remarkably improved as compared with the comparative examples, and it can be seen that an extremely excellent paint composition can be obtained by the present invention.

[0031]

According to the present invention, a very excellent coating composition can be obtained.

Claims (5)

[Claims] 1. A coating composition comprising carbon black having a total acidic group content of 3 μequ / m ² or more in a coating varnish. 2. The coating composition according to claim 1, wherein the coating varnish is a solvent type coating varnish. 3. The coating composition according to claim 1, wherein the coating varnish is a water-soluble coating varnish. 4. The coating composition according to claim 1, wherein the carbon black has been oxidized by ozone in the presence of water. 5. The coating composition according to claim 1, wherein the carbon black is a furnace black obtained by a furnace method.