CS237475B1 - Zinc phosphate multi-phase anti-corrosion pigment - Google Patents

Abstract

A multiphase zinc phosphate anticorrosive pigment based on iron oxide and titanium dioxide pigments is prepared by adding zinc oxide in an amount corresponding to 5 to 30%, preferably 10 to 15% Zn3(PO4)2 · 2 H2O - 4 H2O, to an aqueous suspension of iron oxide or titanium dioxide under stirring and at elevated temperature. After homogenization of the suspension, an equivalent amount of dilute or concentrated phosphoric acid is added within 30 to 120 minutes and after a 60 to 120 minute delay, the suspension is filtered, washed, dried at a temperature of up to 160 °C and ground. Phosphoric acid can also be added all at once and after 60 to 120 minutes the suspension is filtered and further processed as described above. A reverse method of preparing anti-corrosion pigments is also possible by first adding phosphoric acid to a suspension of iron oxide or titanium dioxide and then adding an equivalent amount of zinc oxide over a period of 60 to 120 minutes.

Description

The invention relates to a zinc phosphate multiphase anti-corrosion pigment based on ferric oxide and titanium dioxide pigments.

This type of product is linked to MS. No. 235 770 Zinc phosphate core anticorrosive pigment, based on soluble zinc salt and alkaline phosphate or zinc oxide and phosphoric acid.

From the viewpoint of the production of the anticorrosive pigment, the second method is preferable, since it does not produce soluble salts, thereby saving a considerable amount of washing water and avoiding salinisation of the waste water.

Examination of the electron images of the anticorrosive pigment prepared from zinc oxide and phosphoric acid showed that the precipitation of Zn ₃ (PC> ₄ ) ₂ · 2 H 2 O - 4 f 4 O does not occur entirely on the iron oxide and titanium dioxide pigment particles.

A small amount of phosphoric acid of 0.1 to 0.3% is bound during the precipitation to iron oxide such as FePO4 and titanium dioxide as Ti4PO4. These poorly soluble salts hydrolyze more slowly than zinc phosphate, thereby prolonging the protective effect of the anticorrosive pigment, especially in the final corrosion phase. Theoretical considerations are under investigation and will be published later.

The present invention relates to a zinc phosphate multi-phase anti-corrosion pigment based on iron oxide or titanium dioxide, containing 5 to 30% Zn ₃ ( ₄ > _2. 2 H ₂ 0-4 H ₂ O and 0.1 to 0.3% FePO 4). or TijfPO4).

This type of anticorrosive pigment can be prepared in three ways:

1. A process for preparing a multi-phase anti-corrosion pigment with zinc phosphate based on ferric oxide and titanium dioxide is to add a calculated amount to an aqueous suspension of ferric pigment or titanium dioxide at a concentration of 150-300 g / l with stirring at 60-80 ° C. zinc oxide corresponding to 5 to 30%, preferably 10 to 15% Zn ₃ (P ® ₄ > _2. 2 H ₂ O. After homogenizing the suspension, an equivalent amount of dilute or concentrated phosphoric acid and 60 to 120 minutes is added over 60 to 120 minutes. while the suspension is filtered, washed, dried at a temperature of up to 160 ° C and ground.

2. The process for preparing a multi-phase anti-corrosion pigment according to item 1 except that phosphoric acid is added all at once and after 60 to 120 minutes the suspension is filtered, washed, dried and ground.

3. The process for preparing a multi-phase anti-corrosion pigment according to item 1, except that phosphoric acid is first added to the pigment suspension, and then a zinc oxide suspension is added over a period of 30 to 60 minutes, and after a 60 to 120 minute delay. .

In particular, the progress achieved by the invention is to obtain an effective multiphase anticorrosive pigment with a very good opacity, which cannot be achieved by zinc phosphate alone.

The process for preparing the multi-phase anti-corrosion pigment is shown in the following examples

Example 1

150 g of anatase titanium dioxide are decanted with stirring and the addition of 0.2% monoethanolamine in desalinated water to a total volume of 750 ml. After heating the suspension to 70 ° C, 76.6 ml of 200 g / l zinc oxide are added. After stirring for 15 minutes, 10.8 ml of phosphoric acid is metered in over 90 minutes. After the dosing is complete, the suspension is stirred for a further 60 minutes, the product is filtered, washed, dried at a temperature of up to 160 ° C and ground.

The white, multi-phase anticorrosive pigment contains 14.8% Zn ₃ (PO ₄ ) ₂ · 2 H ₂ 0 - 4 H ₂ 0 and 0.15% τι ₃ (ρο ₄ ) ₄ .

Example 2

The procedure of Example 1, except that thermal iron red was used instead of titanium white.

The red, multiphase anticorrosive pigment contains 14.7 Z Zn ₃ (PO ₄ ) ₂ . 2 H, 0-4 H ₂ O and 0.18 i FePO ₄ .

Example 3

The procedure of Example 1 was followed except that phosphoric acid was added all at once and after a 120 minute residence time, the product was filtered, washed, dried at a temperature of up to 160 ° C and ground.

The white, multiphase anti-corrosion pigment contains 14.75% Zn ₃ (PO ₄ ) ₂ . 2 I ^ O - 4 I ^ O and 0.26 and Ti ₃ (PO _{4) 4).}

attaches

The procedure of Example 1 was followed, except that phosphoric acid was added to the titanium dioxide slurry at once, and then zinc oxide was metered in over 90 minutes. After a delay of 60 minutes, the suspension is filtered, washed, dried at a temperature of up to 160 ° C and ground.

The white, multiphase anticorrosive pigment contains 14.85% Zn (PC ₄ ) ₂ · 2 H ₂ O - 4 H ₂ O and 0.20% Ti ₃ (PO ₄ ) ₄ .

Corrosion tests were performed in an aqueous extract of a coating film with a pentaerythritic alkyd binder CHSP-L65, modified with 65% linseed oil at a concentration of 30% OKP for 10 days.

The test results are shown in the table in comparison with pure alkyd binder and water. As can be seen from the table, the multi-phase anti-corrosion pigments with zinc phosphate based on iron oxide or titanium dioxide have a very good inhibitory effect.

Claims (4)

ferric phosphate or titanium phosphate. 2. A process for the preparation of a multi-phase anticorrosive pigment according to claim 1, characterized in that a measured amount of zinc oxide suspension is added to the aqueous suspension of ferric pigment or titanium dioxide at a concentration of 150 to 300 g / l. corresponding to 5 to 30% zinc phosphate, preferably 10 to 15%, based on the pigment as a whole, and then dosed over 30 to 120 minutes with an amount of dilute or concentrated phosphoric acid molar equivalent to zinc oxide, after a 60 to 120 minute delay washed, dried at a temperature of up to 160 ° C and ground, 3. A process for the preparation of a multi-phase anticorrosive pigment according to claim 1, characterized in that a measured amount of zinc oxide suspension is added to the aqueous suspension of ferric pigment or titanium dioxide at a concentration of 150 to 300 g / l. corresponding to 5 to 30% of zinc phosphate, preferably 10 to 15%, based on the pigment as a whole, and then a quantity of dilute or concentrated phosphoric acid molar equivalent to zinc oxide is added all at once; after 60 to 120 minutes delay the treated product is filtered, washed, dried at 160 ° C and ground. 4. A process for the preparation of a multi-phase anticorrosive pigment according to claim 1, characterized in that phosphoric acid is added to the aqueous suspension of iron oxide or titanium dioxide at a concentration of 150 to 300 g / l with stirring at 60 to 80 [deg.] C. equivalent to zinc oxide and then an aqueous slurry of zinc oxide at a concentration of 100-200 g / l is metered in and after a residence time of 60-120 minutes, the treated product is filtered, washed and dried at 160 ° C and ground.