CS235770B1 - Anticorrosive core pigment and method of its production - Google Patents

Abstract

Anticorrosive core pigment consisting by weight of 70 to 95% titanium white-based core, iron pigments, zinc white, lithopone, barium sulfate, silicon dioxide, aluminum oxide, kaolin, mica, talc, alkaline earth carbonates and magnesium and 5 to 30% zinc phosphate-based filler, is more economically advantageous than zinc phosphate alone; possible savings are up to $90> of anticorrosive substances, it can be applied to all types of basic anticorrosive coatings.

Description

Corrosion is causing great damage to our economy and to the world economy. Iron losses are estimated to be up to 2% of annual production.

Corrosion due to weathering is electrochemical corrosion, which takes place in a homogeneous thin layer of moisture on the metal surface and is amplified according to the environment by various concentrations of gases contained in the atmosphere, such as carbon dioxide, sulfur and hydrogen sulfide, which increase acidity and thus aggressiveness .

The task of anticorrosive pigments is to stop these reactions or to slow them down to a minimum. passivation of metals with an anticorrosive or inhibitory pigment.

The most widely used anti-corrosive pigments are lead compounds - red lead Pb? O ^, lead suboxide PbgO further zinc and chromium compounds lead - zinc tetrahydroxichroman CrO4.ZnO.4Zni0H) ₂ and zinc trihydroxichroman ZnOodZniOH CrO ^ ^ with alkaline cnroman lead PbCrO ^ .pbo, strontium chromate SrCrO4 and zinc phosphate Zn2PO4 g.

In recent years, manufacturers and consumers have endeavored to replace the harmful pigments based on lead and chromium with zinc phosphate, which is completely harmless from the hygienic and environmental point of view. The use of zinc phosphate as an inhibitory pigment has recently been well established. Coatings based on this pigment offer a number of very real advantages for both the manufacturer and the customer. Its consumption is now increasing at a very high speed. A number of explanations have been provided for the effectiveness of zinc phosphate in preventing rust formation. They are also believed to reduce the rate of diffusion of ammonium ions across the coating film (which is very important for corrosion control) by slowly fossilizing the metal surface, creating a very stable film, making it passive against corrosion.

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Work is still ongoing to determine the iunnanism associated with the activity of this pigment. Workability in various binder systems as well as adhesion between the coating layers was also found to be excellent. Unlike most sulphurous primers that are formulated in slow drying oils, zinc phosphate can be used extensively in alkyd and urethane binders, which provide exceptional fast drying properties.

A number of professional publications and patents have been prepared for the preparation of zinc phosphate and its use in anticorrosive coatings. In all patents it is essentially a pure product with the chemical formula Zn ^ tPO ^ Jg · SHgO-4HpOO

A new effective anticorrosive pigment with a substantially lower zinc phosphate content in the form of a core pigment with good adhesion has been developed.

The subject of the invention is a core anticorrosive pigment based on inorganic pigments and fillers - titanium white, ferric pigments, zinc white, lithopone, barium sulfate, kaolin, silica, alumina, silica clays, mica, talc, calcium carbonate and magnesium carbonate, a layer of anticorrosive zinc phosphate in an amount of 5 to 30%, preferably 8 to 15%

The invention is relatively simple and is based only on the surface treatment of inorganic pigments and zinc phosphate fillers.

SUMMARY OF THE INVENTION Zinc phosphate is applied to a pigment or filler coating in an aqueous slurry at a concentration of 50 to 250 g / l at 50 to 70 ° C by precipitation of an equivalent amount of zinc salt and sodium phosphate or phosphoric acid at a constant pH of 7 to 3. Particularly good results are obtained when both components are dosed simultaneously at a constant pH of 7 to 3. If phosphoric acid is used instead of sodium phosphate, a measured amount of zinc salt solution is first introduced and then an equivalent amount of phosphoric acid is metered in at the same time; alkaline hydroxide or ammonia solution at a constant pH of 7 to 8. If, instead of the soluble zinc salt, zinc oxide is added to the pigment or filler suspension, zinc phosphate precipitates on the surface of these substances with dilute phosphoric acid at 70 to 90 ° C.

The following principles apply to the preparation of the high performance anticorrosive pigment:

The particle size of the anticorrosive pigment should not exceed 0.5 µm. Prior to precipitation, the pigment or filler must be well melted at 50-70 ° C with stirring with 0.2-0.5% sodium phosphate. The precipitation should be selected such that the deposited zinc phosphate deposited on the surface and does not precipitate out of the particles. After drying, the pigment must be well ground in impact and pressure mills or steam micronisers. Grinding is necessary to disrupt the agglomerates formed by drying. The zinc phosphate coating on the particle surface is not broken by grinding and the efficiency of the anti-corrosion core pigment is not reduced »

The progress achieved by the invention is that the zinc phosphate core anticorrosion pigment is economically more advantageous than pure zinc phosphate alone, saving up to 90 anticorrosive agents is possible. By using the pigment as a base, an effective anti-corrosion core pigment is obtained with very good opacity, which cannot be achieved by zinc phosphate alone.

Example 1

130 g of titanium dioxide are decanted while stirring and adding 0.3% sodium phosphate to a volume of 600 ml in desalinated water, heated to 60 and then simultaneously dosed with 447 ml of solution over 60 minutes.

ZnSO. .7H _? 0 with a concentration of 100 g / l and 394 ml of a solution of .alpha

with a concentration of 100 g / l. Stirring is continued for 30 minutes after dosing is complete. The product is filtered, washed well with desalinated water, dried at 160 ° C and ground.

The white anticorrosive pigment contains 10% Zn2PO4. ₂ «

Example 2

130 g of thermal ferric red is melted with stirring and the addition of 0.3% sodium phosphate to a volume of 600 ml in desalinated water, heated to 60 ° C, 710 ml of 100 g ^ZnSO 4 ^· 7H ₂ O solution are added over 10 minutes / 1, then 59 ml 20%

- 4,235,770 over 60 minutes, and a 10% NaOH solution is added at the same time to maintain a pH of 7.5. Stirring is continued for 30 minutes after dosing is complete. The further procedure is the same as in Example 1. The colored anticorrosive pigment contains 15% ΖηβίΡΟ ^).

Example 3

The procedure of Example 1 differs in that barium sulfate is used instead of titanium white.

The white anticorrosive pigment contains 10% Zn-IPPO4.

Example 4

The procedure of Example 1 except that instead of titanium dioxide and kaolin is used when editing is added 710 ml solution of ZnSO ^ 7H ₂ O concentration of 100 g / 1 and 625 ml of Na ^ PO ^ .lSHgO a concentration of 100 g / 1. The further procedure is the same as in Example 1. The anticorrosive pigment contains 15% Zn2PO4.

Example 5

The procedure of Example 4, except that silica was used instead of kaolin.

White anticorrosive pigment contains 15% Ζη ^ (Ρ0 ^) ₂ ·

Example 6

The procedure of Example 4, except that alumina was used instead of kaolin.

White anticorrosive pigment contains 15% Znj (P0 ^) ₂ ·

EXAMPLE 7 kg of thermic ferric red is melted under stirring with the addition of 0.3% sodium phosphate to a volume of 300 l in water, heated to 80 DEG C. and 50 l of a 120 g / l ZnO slurry are added. Then 4.5 l of 40% H 2 PO 4 was metered in over 180 minutes and stirred for a further 30 minutes. The product is filtered, washed with desalinated water, dried and ground.

The colored anticorrosive pigment contains 15% Zn-PO4.

Example 8

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The procedure of Example 1 except that zinc white is used in place of titanium white »

The white anticorrosive pigment contains 10% ZnO2.

Example 9

The procedure of Example 1 except that lithopone was used instead of titanium white.

White anticorrosive pigment contains 10% Zn ~ (P0 ^)

Example 10

The procedure of Example 1 except that mica was used instead of titanium white.

The anticorrosive pigment contains 10% Zn (P0) ₉ .

Example 11

180 g of talc is decanted with stirring and the addition of 0.3% sodium phosphate to a volume of 600 ml in desalinated water, heated to 80 ° C, then a suspension containing 20 g of zinc oxide is added. The suspension is heated to 80 ° C and stirred for 15 minutes. Subsequently, 32 ml of 40% phosphoric acid are metered in uniformly over 120 minutes. After the addition was complete, the suspension was stirred for a further 15 minutes, adjusted to pH 7 with alkaline hydroxide, filtered, washed well with desalinated water, dried at a temperature of up to 160 ° C and ground.

The anticorrosive pigment contains 15% Zn (CPO4).

Example 12

The process of Example 1 except that calcium carbonate was used instead of titanium white.

The anticorrosive pigment contains 10% Ζη ^ <Ρ0 ^ ₁₂ .

The same result is obtained when magnesium carbonate is used instead of calcium carbonate.

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The corrosion tests were carried out in an aqueous extract of the paint film with a pentaeritrite alkyd binder CHSP - L65, modified with 65% linseed oil with a volume concentration of 30% OKP, for 10 days.

The test results are shown in the table in comparison with pure zinc phosphate, alkyd binder used and water.

As shown in the table, the zinc phosphate-sealed pigments and fillers have a very good inhibitory effect.

Example Pigment - filler ZnJPO.) _ 3 4 2 % Corrosive decreases * · um / year Inhibic effect % 1 titanium white I. ⁰ 1.40 96.40 2 ferric red 15 Dec 1.80 95.37 3 barium sulphate 10 2.50 93.57 4 kaolin 15 Dec 2.36 93.93 5 silica 15 Dec 2.16 94.45 6 aluminum oxide 15 Dec 1.70 95.63 7 iron red 15- 2, JO 94.86 8 zinc white 10 1.20 96.91 9 litopon 10 1.60 95.38 10 mica 10 1.20 96.91 11 talc 15 Dec 2.36 93.90 12 calcium carbonate 10 2.50 93.54

in

Claims (4)

1. Anticorrosive pigment core based on inorganic pigments and fillers * characterized in that it comprises by weight 70 to 95% of the nuclei selected from the group consisting of titanium white, that ^R Lies pigments, zinc white, lithopone, barium sulphate, silica, alumina, kaolin, mica, talc, alkaline earth and magnesium carbonates and from 5 to 30% zinc phosphate coating » 2. A process according to claim 1, wherein an aqueous solution of zinc salt of 50-100 g / l and equivalent is introduced into the aqueous core suspension at a concentration of 50-300 g / l over 60-90 minutes with stirring. amount of an aqueous solution of alkaline or ammonium phosphate at a concentration of 50 to 100 g / l at a temperature of 50 to 70 ° C, after which the suspension is filtered, the product is washed, dried at a temperature of up to 160 ° C and milled » 3. A method according to claim 1, wherein an aqueous solution of zinc salt at a concentration of 50-100 g / l and an equivalent amount of 40 to 50 g / l is introduced over a period of 60 to 90 minutes. ^! % phosphoric acid while maintaining a constant pH of 6.5-7.5 by adding 20-40% alkaline hydroxide or ammonia at 50-70 ° C, after which the suspension is filtered, the product is washed and dried at a temperature of up to 160% ° G and ground. 4 »A process for producing an anticorrosive core pigment according to claim 1, characterized in that to the aqueous suspension of the core at a concentration of 50-300 g / 1 introducing an aqueous suspension of zinc oxide at a concentration of 50 to 300 g / 1 and within 90 to 180 minutes _T dosed equivalent amount of 40% phosphoric acid at 70 to 90 ° C, then the suspension is filtered, the product is washed, dried at a temperature of up to 160 ° C and milled.