JPH07100770B2 - Method for producing carbon black paint - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a carbon black paint used for black coloring, a conductive paint, a back coat paint for a magnetic recording medium, and the like.

2. Description of the Related Art Conventionally, ball mills, sand mills, etc. have been used to produce coating materials by dispersing carbon black. However, in order to obtain a highly dispersed paint only with these, a kneading process with a high viscosity (2000 poise or more) for loosening particles with a high shearing force is indispensable as a pretreatment of the dispersion process, and it is a planetary equipment for paint production. A mixer, a kneader, a pressure kneader, a continuous kneader, a twin-screw kneading extruder, etc. are used.

Problems to be Solved by the Invention A kneading step with high viscosity is indispensable in order to obtain a highly dispersed coating material as described above, but in this kneading step, the dispersion becomes extremely high in temperature as a binder resin. It is necessary to consider the decomposition of commonly used nitrification cotton, polyvinyl chloride, etc. When these are thermally decomposed, denitrification and dehydrochlorination occur, the paint becomes acidic, and the disperser and the metal to be coated are corroded.Therefore, there is a problem that only binder resin with good thermal stability can be used. It was Furthermore, these clay-like kneaded products have a viscosity (20
To 15 poise), the process was very difficult and time consuming.

Another method of dispersing with high shearing force is to use a three-roll mill or a two-roll mill to disperse and paint, but this also causes the dispersion to become extremely hot, or the paint being dispersed and made into a paint dries. Therefore, it is not possible to use nitrified cotton (which has a self-ignition property by impact in a dry state) as a binder resin alone, which is good for dispersing carbon black, and it is necessary to consider the thermal decomposition of the binder resin. . These problems have an adverse effect on manufacturing cost as well as product quality.

The present invention is to solve the above problems, and to obtain a highly dispersed carbon black paint in a simple manufacturing process in a short time, to obtain a carbon black paint of stable quality and low manufacturing cost. An object of the present invention is to provide a method for producing a paint.

Means for Solving the Problems In order to solve the above problems, the present invention has found that, as a result of various studies, a wetting step, which is a pre-step of dispersing / painting, is very effective for dispersing carbon black. .

The wetting step is a step of mixing only carbon black and a solvent, so that the surface of the carbon black particles is well wetted with the solvent and the gas such as air adhering to the surface is extruded so that the binder resin is adsorbed on the surface of the carbon black particles. It facilitates and improves dispersibility. An apparatus that can be used for this wetting step is a planetary mixer, but it is not easy to remove the paint from it.

In the wetting process, the use of the ball mill, which is a feature of the present invention, has a good wetting effect, pre-mixing with the binder resin is possible in the ball mill, and it is easy to take out and is used for the sand mill which is the dispersion process of the next process. It can be taken out directly into the tank and can be quickly transferred to the dispersion process. Furthermore, the use of the sand mill can significantly reduce the time of the dispersion process as compared with the case of using the ball mill.

This method is very simple, but it has not been done so far because when the sand mill is used in the dispersion process, the dispersion medium must have a viscosity of 20 poise or more to cause abrasion and cracking of the dispersion medium (glass beads, etc.). The viscosity of the pre-mixed paint must be 20 poise or more, because it is not well mixed into the paint. When premixing with a ball mill, paints of 20 poise or more cannot be efficiently taken out from the ball mill, and most of the paint remains inside the ball mill. 6 of the contents even when sucked with a pump
I can only take out about a percentage.

However, as a result of the study, after the wetting process with the solvent and carbon black, the viscosity of the wet material which was in the form of a slurry dropped sharply by rotating the ball mill with the addition of binder resin for several revolutions. It was found that the viscosity increased sharply again after 3 minutes. Therefore, if the operation of the ball mill after adding the binder resin is within 1 minute and the paint is taken out in the state where the paint viscosity is the minimum, almost all the paint inside the ball mill can be taken out.

The carbon black paint in a highly dispersed state can be produced by a simple manufacturing process by configuring the carbon black paint manufacturing method of the present invention by a wetting process using a ball mill, a premixing process and a dispersion process using a sand mill. Provided is a carbon black paint which is obtained in a short time, has stable quality, and is low in manufacturing cost.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples.

(Example 1) In order to know the effect of the wetting step, a carbon black coating material A that was subjected to the wetting step and a carbon black coating material B that was not subjected to the wetting step were prepared using only a ball mill.

(Carbon black paint A) Paint manufacturing method Wetting process; Steel ball mill Dispersing process: Steel ball mill The following carbon black and organic solvent are charged into a steel ball mill with an internal volume of 100 liters, and the carbon black is moistened by operating at 40 rpm for 5 hours. It was

Carbon black 5.0 kg (Mitsubishi Chemical Co., Ltd., trade name MA-7B) Organic solvent cyclohexanone 6.5 kg Methyl ethyl ketone 4.5 kg Then, as a binder resin, nitrocellulose solution 4.5 kg (Asahi Kasei Co., Ltd. trade name BTH 1 / 16 methyl ethyl ketone solution (solid content 25% by weight) was added, and the mixture was operated and dispersed at 40 rpm for 25 hours to obtain carbon black paint A.

(Carbon black paint B) Paint manufacturing method Wetting step; None Dispersion step; Steel ball mill As a method for manufacturing a carbon black coating that omits the wetting step, the same ball mill as carbon black coating A was used, but with the same composition, but the following materials were used. It was put into a ball mill at once, and was operated and dispersed at 40 rpm for 30 hours to obtain a carbon black paint B.

Carbon black 5.0kg (Mitsubishi Kasei Co., Ltd. trade name MA-7B) Organic solvent cyclohexanone 6.5kg Methyl ethyl ketone 4.5kg Binder resin nitrocellulose solution 4.5kg (Asahi Kasei Co. Ltd. trade name BTH 1/16 methyl ethyl ketone solution , Solid content 25% by weight) In order to observe the carbon black dispersion state of the above two types of carbon black paints A and B, the carbon black paint inside the ball mill was sampled at each dispersion time, and a gap of 25 μm was formed on the polyethylene terephthalate film. The coating was applied using the applicator of and the glossiness of the coating film was measured.

The results of carbon black paint A and carbon black paint B are compared and shown in FIG.

As is clear from these comparisons, the carbon black coating material A that has undergone the wetting process has a faster rise in glossiness, and the final glossiness is higher than that of the carbon black coating material B.
From the above, it can be seen that the wetting process in a ball mill is very effective.

However, if a sand mill is used in the dispersion step, a carbon black coating material in a more highly dispersed state can be obtained.

(Example 2) Two kinds of carbon black coating materials are produced by using a sand mill in the dispersion step.

(Carbon black paint C) Paint manufacturing method Wetting process; Steel ball mill Pre-mixing process; Steel ball mill Dispersion process; Sand mill The same carbon black and organic solvent as described in Example 1 are put into a steel ball mill having an internal volume of 100 liters, and 40 rpm.
The carbon black was wetted in the same manner as in the carbon black coating material A of Example 1 for 5 hours.

Carbon black 10.0 kg (Mitsubishi Chemical Co., Ltd., trade name MA-7B) Organic solvent cyclohexanone 13.0 kg Methyl ethyl ketone 9.0 kg After that, nitrocellulose solution 9.0 kg as a binder resin (Asahi Kasei Co., Ltd. trade name BTH 1/16 Of methyl ethyl ketone solution (solid content: 25% by weight) was added, and the mixture was operated at 40 rpm for 1 minute to premix the carbon black and the binder resin. Then, the paint was taken out from the ball mill and dispersed under the following sand mill equipment and conditions to obtain carbon black paint C.

Sand mill; Super mill made by Inoue Seisakusho Co., Ltd. Capacity 10 liter Disk peripheral speed 12 m / sec Paint flow rate; 1 liter / min Number of dispersion passes; 6 passes (Carbon black paint D) Paint manufacturing method Premixing process; Dissolver Dispersion process; Sand mill The following coating materials were put in a tank and mixed for 2 hours with a dissolver, and then dispersed by a sand mill in the same manner as the carbon black coating C to obtain a carbon black coating D.

Carbon black 10.0 kg (Mitsubishi Chemical Co., Ltd., trade name MA-7B) Organic solvent Cyclohexanone 13.0 kg Methyl ethyl ketone 9.0 kg Binder resin Nitrocellulose solution 9.0 kg (Asahi Kasei Co., Ltd. trade name BTH 1/16, methyl ethyl ketone solution) , Solid content 25% by weight) In order to observe the carbon black dispersion state of the above carbon black coatings C and D, the coating is sampled every dispersion pass,
The glossiness of the coating film applied on the polyethylene terephthalate film was measured using an applicator in the same manner as in Example 1.

The results of dispersion of carbon black paints C and D are compared and shown in FIG.

As is clear from these comparisons, the effect of wetting with a ball mill is good, the glossiness of the 6th pass is also about 20% higher, and a carbon black paint in a highly dispersed state is obtained.

Further, in the case of carbon black paint C, the yield of the paint when taken out naturally from the ball mill after the premixing process is 98
%, And most of the carbon black paint inside the ball mill could be taken out.

Further, in FIGS. 1 and 2, when the dispersion process is compared between the ball mill (carbon black paint A) and the sand mill (carbon black paint C), the final gloss is about 15% higher in the sand mill and the dispersion time is also longer. It was as short as about 5 hours (about 50 minutes per one pass of the sand mill), and it was able to be about 1/5 of the time when dispersed by the ball mill.

EFFECTS OF THE INVENTION As described above, according to the method for producing carbon black of the present invention, the highly dispersed state of carbon black can be formed into a coating material in a short time by a simple production process, and the production quality is stable and the production cost is stable. It is possible to provide a low carbon black paint, and its practical value is enormous.

[Brief description of drawings]

FIG. 1 is a characteristic diagram of ball mill operation / dispersion time vs. glossiness of carbon black paints A and B, and FIG. 2 is a characteristic diagram of sandmill dispersion pass times vs. glossiness of carbon black paints C and D. Carbon black paint A ... A paint that has a wetting process and is manufactured by performing a dispersion process in a steel ball mill, carbon black paint B ... A paint that is not equipped with a wetting process and is manufactured by performing a dispersion process in a steel ball mill, a carbon black paint C ... A coating having a wetting step and a dispersing step performed by a sand mill, carbon black coating D ... A coating having no wetting step and a dispersing step performed by a sand mill.

Claims (1)

[Claims] 1. A method for manufacturing a method of dispersing and coating carbon black using a binder resin, the method comprising: a wetting step of mixing carbon black and a solvent using a ball mill; and a solvent using the ball mill. A method for producing a carbon black paint comprising a premixing step of premixing the mixed carbon black and a binder resin, and a dispersing step of dispersing the carbon black premixed with the binder resin by using a sand mill.