JPS61111366A - Production of ultramarine composition - Google Patents

Abstract

PURPOSE:To produce an ultramarine compsn. which does not cause fading, by bringing active silica gel into contact with ultramarine particles to deposit silica on the surfaces of the ultramarine particles. CONSTITUTION:One equivalent of an alkali metal silicate (e.g. sodium silicate) and 0.2-0.4 equivalents of a 1-10% aq. soln. of an acid (e.g. sulfuric acid) are fed through feeding means 9, 10 to a subreactor 5. The pH of the mixture is adjusted to 7-10 and the mixture is reacted at 60-100 deg.C to form active silica sol The active silica sol is fed to a main reactor 1 which contains a slurry having a pH of 9-11 and contg. 5-30wt% ultramarine particles having an average particle size of 0.2-20mu suspended therein, in such as proportion as to give 5-25pts.wt. silica sol per 100pts.wt. ultramarine, and ultramarine is brought into contact with silica sol at 90-95 deg.C for 20sec or shorter to deposit silica on the surfaces of ultramarine particles. The reaction mixture is neutralized, and the product is recovered by filtration, washed with water and dried by heating at 100 deg.C or above.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a method for producing an improved amorphous porphyry coated ultramarine composition having excellent quality properties such as chemical resistance, weather resistance, heat resistance, etc.

Conventional technology Ultramarine is a non-polluting inorganic pigment with a unique and vivid hue.As a blue inorganic pigment with excellent light resistance and heat resistance, it has a wide range of uses such as synthetic resins, paints, printing inks, cement, and detergents. However, ordinary ultramarine blue has insufficient acid resistance and has a p
It has the disadvantage that it decomposes and fades under weak acidity of about i-15, and when it is used to color plastics that become acidic over time (for example, vinyl chloride resin), it also fades and becomes white over time.

Furthermore, although cement alkali has excellent alkali resistance, it tends to have limited uses because it may cause a substitution reaction with weak Ca ions, resulting in fading and whitening.

Therefore, at present, improving the blue power, acid resistance, and cemento-alkali resistance of ultramarine pigments are considered important issues, and the deposition coating technology of amorphous silica is effective for improving the latter two properties. U.S. Patent No. 2.8 discloses a technology for improving various resistances by depositing amorphous silica on the surface of inorganic pigment particles.
It originates from Ill No. 5,366.

This patent relies exclusively on amorphous silica obtained by reacting an aqueous sodium silicate solution with an inorganic acid as a technique for depositing and coating pigment particles with amorphous silica.

However, when this is applied to ultramarine blue, the acid resistance is extremely poor as described above, and the pigment will be attacked by inorganic acids and fade and turn white before it is coated with amorphous silica.

For this reason, a combination of a weak acidic agent and an aqueous sodium silicate solution may be considered as an improvement technique for ultramarine blue.

For example, in U.S. Pat. No. 3.437.502,
Application of COf aqueous solution to water-soluble silicate composition (Toho Pigment, Nippon Kagaku) in Japanese Patent Publication No. 55-34184 (Toho Pigment, Nippon Kagaku): Application of Shiro acidic gas;
The application of inorganic acid alkali metal salts and ammonium salts is known in JP-A-55-115.1!59 (Toho Pigment, Nihon Kagaku).

According to the above-mentioned improved technique, the purpose can be achieved without damaging the ultramarine particles themselves when amorphous silica is deposited and coated on the surface of the ultramarine particles.

However, in the above-mentioned technology, the water-soluble organic acids, phosphoric acid, ammonium salts, etc. used as acidic agents have the strong possibility of leaving a big problem in terms of wastewater treatment when implementing the technology on an industrial scale. It is difficult to think of this as a source material. C.O.
When using an acidic gas such as v-gas, the reaction with the alkali silicate tends to be slow and reaction control becomes complicated.

Therefore, in the active silica sol forming reaction, it is most preferable to use an inorganic acid, but the conventional method of using an inorganic acid involves directly stretching a silicate and an inorganic acid in an ultramarine slurry. Since an active silica sol was formed in this process, the ultramarine blue slurry and the inorganic acid partially came into contact with each other, causing the ultramarine blue to discolor as described above, and it has hardly been put into practical use industrially.

Problems to be Solved by the Invention The present invention provides a method for obtaining a silica-coated ultramarine composition that does not fade by using an inorganic acid that causes few pollution problems, undergoes a reaction relatively quickly, and is favorable in terms of production efficiency. do.

Means for Solving the Problems The present invention focuses on the fact that the reaction of producing activated silica sol when silicate is reacted with acid is relatively slow, and the activity of the produced activated silica sol is maintained for a relatively long time. In this method, the activated silica sol forming reaction and the coating forming reaction are carried out separately, thereby solving the problems of the above method using an inorganic acid.

That is, the present invention provides a silica-coated ultramarine composition characterized in that an alkali silicate and an acid are reacted in advance in an aqueous medium, and then the generated active silica sol is brought into contact with ultramarine particles to deposit silica on the surfaces of the ultramarine particles. Concerning the manufacturing method.

In the present invention, the ultramarine particles to be coated with silica have an average particle diameter of 02 to 20μ, preferably 05 to 5μ), and silicate is a water-soluble silicate, generally sodium silicate. Aqueous solutions are suitable.

The content of these silicates is preferably 2 to 15% in terms of solid content so that a stable active silica sol can be obtained when reacted with an acid.

The acid used may be either an organic acid or an inorganic acid.

It is particularly suitable for the purposes of the invention to use inorganic acids. Examples of the inorganic acid include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, sulfamic acid, and sulfurous acid, with sulfuric acid being particularly preferred. The concentration of the acid used is preferably 1 to 10%, particularly 2 to 5%.

The equivalent ratio of silicate and acid is 1 equivalent of the former to 02~02 of the latter.
Guess 0.4 equivalent. The pH of the generated activated silica sol
It is preferable to select it so that it is in the range of 7 to 1O. If the active silica sol is lower than pl-1 or 5, the ultramarine blue particles themselves will decompose and discolor, which is not preferable.

Is it possible for the silicate and acid to extend into the reaction tank while maintaining the above equivalent ratio (quantitative proportional addition method)?

In addition, at the beginning of the reaction, 0 sulfuric acid was added to 1 equivalent of silicate.
Adding at a concentration and rate of 2 to 0.4 equivalents, active silica sol is generated in a relatively high pH range, and silica deposition coating is carried out while contacting this with ultramarine particles, until a coating amount of 7% or more is reached. After that, it is possible to gradually increase the rate of addition of sulfuric acid to cause the reaction. In this method, initially high p
In the al region, that is, under conditions where ultramarine is stable, the formation of nolica film on the surface of ultramarine is avoided and acid resistance is imparted, and then even if the acid addition rate is increased and local contact between acid and ultramarine occurs, ultramarine remains. The reaction can proceed without any further decomposition, and is an effective means for shortening the reaction time compared to the above-mentioned methods.

The reaction temperature of silicate and acid is 60~100℃, especially 70~9
It is preferable to maintain the temperature at 5°C; if the temperature is lower than 60°C, the activity of the produced silica sol will decrease. Also 95℃
At higher temperatures, 1
Since the activity of the activated silica sol disappears in a short time, contact with the ultramarine blue must be carried out quickly, which is unfavorable in terms of process control. If the activity of the activated silica sol is lost before contact with the ultramarine blue, a uniform silica coating will not be formed on the surface of the ultramarine, resulting in insufficient acid resistance, and silica powder will be mixed into the ultramarine as an impurity. , the ultramarine quality decreases.

The contact between the ultramarine particles and the activated silica sol depends on the temperature, pH 1 stirring conditions, etc., or is preferably carried out within 20 seconds, more preferably within 10 seconds after the contact between the silicate and the acid. . If the time is longer than 20 seconds, colloidal particles of silica sol will grow, making it difficult to form a uniform coating, and the acid resistance of the silica-coated ultramarine formed will be insufficient considering the thickness of the coating.

If the contact is delayed further, the activity of the silica sol will decrease.

The reaction between ultramarine blue and activated silica sol is preferably carried out in an aqueous medium, and the aqueous medium in which ultramarine blue is dispersed has a pto violet of 9 to II.
In particular, it is preferable to maintain the pH at 9.5 to 10.0, and if necessary, adjust the pH to 9.5 to 10 before contacting the activated silica sol.
．． You can adjust it to 0.

The temperature may be 90 to 95°C or higher. If the temperature is lower than 90°C, the inactivation by hydrolysis of the activated silica is delayed, and the ultramarine surface of the silica I. is insufficiently deposited, and the productivity is reduced.

The silica sol adhering to the ultramarine surface may be inactivated by contacting the ultramarine blue with the silica sol in an aqueous medium at a temperature lower than 90°C, and then heating and drying at 100°C or higher.

The concentration of the ultramarine aqueous slurry is 5 to 30% by weight, more preferably 10 to 15% by weight, and the amount of silica sol is 5 to 25 parts by weight, more preferably 10 to 15 parts by weight based on 100 parts by weight of ultramarine blue. is preferred.

The resulting silica-coated ultramarine slurry is neutralized, then filtered, washed with water, and dried.

Effects of the Invention According to the present invention, since an inorganic acid can be used, it is highly economical and easy to treat wastewater. Also, using strong inorganic acids will not cause the ultramarine blue to fade. The resulting ultramarine blue composition has excellent acid resistance, and can provide ultramarine blue that does not change in hue even when immersed in 5% hydrochloric acid for 1 hour, for example. Furthermore, good acid resistance can be obtained in the coated plate acid resistance test shown in Examples below. On the other hand, the treatment also provides good resistance to cement alkalis.

Ai 1 carp An apparatus as shown in FIG. 1 was used.

The main reaction tank (1) is equipped with a jacket and a high-speed stirrer (2
). This stirrer was a DeSilver type, the impeller diameter was 25 to 30% of the inner diameter of the reaction tank, and it was operated at a circumferential speed of 10 m/s or more.

The main reactor is further equipped with a pH meter (3) and a thermometer (4).

The side reaction tank (5) is equipped with a high-speed stirrer (6) and a pH meter (7).
), thermometer (8), alkali silicate aqueous solution supply means (9)
and acid supply means (IO). High speed stirring! !
! As for (6), although a desilver type was used in this embodiment, an ultrasonic horn may also be used.

The alkali silicate aqueous solution supply means and the acid supply means are equipped with metering pumps, which control the pH of the mixture from 7 to 1.
Control the supply amount of both liquids so that it is within the 0 range.

In the above-mentioned apparatus, ultramarine blue was added as a dry product in the main reaction tank.
00 gttl equivalent of press cake was taken, and water, a dispersant, and an aqueous sodium silicate solution were added to it to make a total volume of 151 gttl.
．． The ultramarine aqueous slurry was first stirred at high speed for 30 minutes to sufficiently crush it into particles close to primary particles.Then, the temperature was raised to 90-95°C.

While maintaining the conditions of the main reaction tank, the high-speed mixing device in the side reaction tank was operated, and 1220 g (StO*60 g) of 10% sodium silicate solution (492% SiOy) was supplied from the sodium silicate supply nozzle.
equivalent, 12% coating for ultramarine) at 5.1 per minute
2.5% from the Ikekata acid supply nozzle.
1227 g of sulfuric acid aqueous solution was proportionally fed at a rate of 4.3 g/min. At this time, the amount of sulfuric acid supplied was adjusted so that the pH of the activated silica sol flowing out from the side reaction tank was 7 or higher, preferably 9 or higher.

1゛ Retention of silica sol in the side reaction tank is 1 to 20 seconds, preferably 3 to 10 seconds.
Seconds are preferred. The residence time is controlled by an orifice at the bottom of the side reaction tank.

While the silica sol is flowing into the main reaction tank, the ultramarine aqueous slurry has a pH of 9.5 to +0.0. The temperature was maintained at 90-95°C. The total addition time was 240 minutes, sulfuric acid aqueous solution 4i 280 minutes. After the entire amounts of the sodium silicate aqueous solution and the sulfuric acid aqueous solution were introduced, I)H was adjusted to 6.5 to 7.5. After cooling,
The product was filtered, washed with water, washed with water until no salts were detected in the furnace solution, and then dried to obtain about 560 g of ultramarine coated with amorphous silica (100% of the theoretical yield).

During the reaction, the acid decomposition of ultramarine causes Go<H*5 (IifC hydrogen hydride)
No odor was detected, demonstrating the effectiveness of the method of the present invention.

The acid resistance color difference of the amorphous silica-coated ultramarine thus obtained was ΔE=2.4, and practical acid resistance was confirmed.

The acid resistance test method adopted in the above examples is as follows.

(1) Sample preparation: Treated (or untreated) ultramarine 1 part titanium oxide 1 part PVC clear (N, V
, 40 parts to 5 parts of a mill base and dispersion in a ball mill to obtain a paint having a dispersed particle size of 10 μm or less.

This paint was applied to a corrosion-resistant aluminum plate using an applicator to a thickness of 7 mils (175 μm).
Dry at 5°C for 60 minutes to obtain a test coat.

(2) fMl property test After first determining the colorimetric value of the test coated plate obtained as above, immersing it in a 5% sulfuric acid aqueous solution at 25°C for 10 hours, taking it out, washing with water and drying, and determining the colorimetric value again. .

(3) Sail”L Measured color values (L, a) before immersion using a rechargeable color difference meter.

b value) and the colorimetric values (L', ao, b° values) after immersion.

The color difference (ΔE
) and use it as the acid resistance color difference.

[Brief explanation of drawings]

FIG. 1 shows one version of an apparatus for carrying out the invention. (+) Main reaction tank (2) Stirrer (3) pH meter (4) Thermometer (5) Side reaction tank (6) Stirrer (7) pH meter (8) Thermometer (9) P stage for supplying aqueous alkali silicate solution (lO) Acid supply means

Claims (1)

[Claims] 1. A silica-coated ultramarine composition characterized in that an alkali silicate and an acid are reacted in advance in an aqueous medium, and the resulting active silica sol is brought into contact with ultramarine particles to deposit silica on the surfaces of the ultramarine particles. How things are manufactured. 2. The method for producing a silica-coated ultramarine composition according to item 1, wherein the pH of the activated silica sol is adjusted to 7 to 10. 3. The method for producing a silica-coated ultramarine composition according to item 1, wherein an active silica sol is added to the aqueous medium of the ultramarine particles. 4. The method for producing a silica-coated ultramarine composition according to item 1, wherein the ultramarine particles are brought into contact with an active silica sol while maintaining the pH of the aqueous medium at 9 to 11. 5. The method for producing a silica-coated ultramarine composition according to item 1, wherein the active silica sol is brought into contact with ultramarine particles within 20 seconds after formation. 6. Contact between activated silica sol and ultramarine particles at a temperature of 90-95
2. A method for producing a silica-coated ultramarine composition according to item 1, which is carried out in an aqueous medium at .degree.