CS249395B1 - Method of iron trioxide and titanium dioxide pigments' resistivity increase by means of barium compounds - Google Patents

Abstract

Method of increasing specific resistivity of pigments iron oxide and titanium dioxide by means of barium compounds in which the aqueous a suspension of ferric oxide or oxide pigments titanium dioxide at a concentration of 100 to 500 g / l, preferably 300 g / k, sufficiently washed from SO4 ions, with a resistivity of from 500 to 5,000 < " 1000 to 3000 < cm > cm, added with stirring and at room temperature 40 to 80 ° C aqueous barium sulphide solution, or barium hydroxide or aluminate barium or an aqueous suspension of carbonate barium at a concentration of 20 to 100 g / l in an amount based on pigment of 0.05 to 3% %, preferably 0.1 to 0.3 wt. After 30 to The treated product is filtered for 60 minutes. washed, dried and ground

Description

The invention relates to a method for increasing the resistivity of pigments of ferric oxide and titanium dioxide with barium compounds.

Specific resistivity is a very important property of pigments since it greatly affects their processing and inhibitory properties.

Pigments with low resistivity are less dispersible, especially in aqueous dispersion paints and cannot be applied in the coating by advanced progressive electrostatic and electrophoretic methods and greatly reduce the inhibitory efficiency of the coating.

Increasing the resistivity of ferric pigments and especially of treated titanium dioxide above 2000 to 3000fL / cm requires considerable financial costs for their further washing with desalinated water. The minimum resistivity should not fall below 6,000A.cm for normal commercial products. For high-quality pigments, the resistivity is about 10,000 IU / cm and above. The cause of the low resistivity of both thermal and precipitated ferric pigments is the residual amount of free and bound sulfuric acid on Fe @ ⁺ , Na @ ⁺ , NH @ ⁺ ions. For modified titanium + + 2+ * white, these are small, non-eluted amounts of Na, K and Zn sulphates

This serious problem can be solved according to the invention in a simple and inexpensive manner by precipitating SO4 ions with barium salts onto insoluble BaSO4. Water-soluble BaS, Ba (OH) ₂ , Ba ₃ (AlO ₃ ) ₂ and powdered BaCO ₃ have been found to be the most suitable barium salts. The barium salts of organic acids are less suitable because they leave a residue of organic acid upon precipitation, which must then be separated from the pigment during drying. The barium salts of inorganic acids also cannot be used.

The use of this method is particularly advantageous for pigments washed to a resistivity of 500 to 5,000 ohms / cm, with a small addition of 0.05 to 0.5 wt. barium salts can increase the resistivity of pigments to a desired value. Thus, small amounts of precipitated BaSO4 do not affect the quality of the pigment.

The amount of barium salt added should be chosen so that excess 2+ soluble Ba ions remain in the pigment. In the case of a small excess of barium salts, further partial washing of the pigment can be carried out. If BaS is used, it will again become insoluble BaSO4 during drying due to oxidation with air oxygen.

Method for increasing resistivity of the iron oxide pigment and carbon titatiničitého according to the invention is characterized in that the aqueous pigment ..suspenzi TiOj Ρθ2 ° or 3 ° ≤ ^valuation tration 100-500 g / 1, preferably 300 g / 1, sufficiently washed by SO of ions having a resistivity of 500 to 5,000 SLC are added with stirring at a temperature of 40 to 70 ° C in a small amount of 0.05 to 3 wt%, preferably 0.1 to 0.3 wt%, based on pigment, an aqueous solution of barium salt, preferably BaS, or Ba (OH) 2 #, or Ba 2 / AlO 4, or a suspension of BaCO 3, at a concentration of 50 to 100 g / l. After a residence time of 30 to 60 minutes, the treated pigment slurry is filtered, optionally washed, dried and ground.

The process of the invention is a simple technology with ease of application in technology practice, since it consists solely in the dosing of barium salt in conventional operations.

The progress achieved by the invention is that in this way high quality pigments of ferric and titanium dioxide with high resistivity can be prepared without increasing the cost.

The field of application of these products is then considerably broader and can advantageously be used in almost all fields, both in aqueous and non-aqueous paints and in organic plastics. of

The following examples are provided to illustrate the workflow:

Example 1

Κ 1 liter of a 350 g / l thermal resistivity ferric pigment suspension of 2 800 µlcin is added with stirring and at 60 ° C 17.5 ml of a 60 g / l aqueous BaS solution. After a 30 ml delay, the suspension is filtered, dried at 190 ° C and ground. A ferric pigment having a resistivity of 9 85θΑ is obtained. cm.

Example 2

See Example 1 except that Ba (OH) ₂ is used instead of BaS. A pigment with a resistivity of 10 250 µm is obtained.

Example 3

See Example 1 except that BaCO 4 is used instead of BaS. A pigment with a resistivity of 9,790Ώ is obtained. .cm.

Example 4

See Example 1 except that precipitated ferric yellow with a resistivity of 3 100.TL.cm is used instead of the thermal ferric pigment. A pigment having a resistivity of 10 [mu] L.cm is obtained.

Example 5

See Example 1 except that Ba ₃ (AlO ₃ ) ₂ is used instead of BaS. A pigment with a resistivity of 9 900 n is obtained. cm.

Example 6

Κ 1 liter dioxide rutile treated with 2% of Al ₂ O-0.5% _SiO2 resistivity 100JÍL.cm 3 was added with stirring and at 65 ° C, 17.5 ml of an aqueous solution of BaS a concentration of 60 g / 1 . After a 40 minute delay, the suspension is filtered, washed, dried at 160 ° C and ground. A pigment with a high resistivity of 12,200 Λ is obtained. cm.

Claims (1)

Method for increasing the resistivity of pigments of ferric oxide and titanium dioxide with barium compounds, characterized in that to an aqueous suspension of ferric oxide or titanium dioxide having a resistivity of 500-500A / cm, preferably 1000-3000. 500 g / l, preferably 200 to 300 g / l, are added, with stirring and at a temperature of 40 to 80 ° C, an aqueous solution of barium sulphide or barium hydroxide or barium aluminate or an aqueous suspension of barium carbonate at a concentration of 20 to 100 g / l. an amount based on pigment of 0.05 to 3% by weight, preferably 0.1 to 0.3%, after a 30 to 60 minute delay, the treated product is filtered, washed, dried and ground.