DE2414805A1 - Mfr. of yellow or yellow-brown iron oxide pigments - using iron turnings, ferrous chloride soln., nitrobenzene and sulphites - Google Patents

Abstract

Yellow to yellow-brown iron oxide-hydrate pigments are mfd. by the oxidn. of iron and the simultaneous redn. of aromatic nitro-cpds. in the presence of iron salt solns. The oxidn. of the iron is carried out in the presence of the oxyacids of sulphur or their alkali(ne earth) metal salts where the average oxidn. stage of the sulphur is =5. The oxidn. of the iron is pref. carried out in the presence of the Na, K, NH4, Mg and/or the Ca salts of sulphurous acid, thiosulphurous acid, thio-sulphuric acid, dithionous acid, dithionic acid and/or pyrosulphurous acid, using 2-20% S w.r.t. the wt. of nitrobenzene. The iron oxide pigments obtd. may be used for the prodn. of yellow and red pigments. No foreign hydrolysable metal ions are used in the process which might form oxide or oxide-hydrate impurities in the iron oxide pigments so the iron oxide content in the latter is increased by 2-7%. By subsequent heating of the pigments, various shades of red can be obtd. The colour brightness and purity is superior to that of conventional pigments and the colouring power is increased by =45%; only a very small amt. of the sulphur cpds. are occluded in the pigments.

Description

Process for the production of yellow to yellow-brown iron oxide pigments The present invention relates to a process for the production of yellow to yellow-brown iron oxide pigments by oxidation of iron with simultaneous reduction of aromatic nitro compounds in the presence of special sulfur compounds.

Processes are already known according to which yellow or brown iron oxide pigments by oxidation of iron with simultaneous reduction of nitrobenzene in the presence of dilute aluminum salt solutions, especially aluminum chloride (German patent 515 758) or in the presence of solutions hydrolyzable trivalent and tetravalent Metals (German Patent 516 999) or in the presence of aluminum chloride solution and addition of tin salts (German Patent 703 416).

The methods mentioned have various disadvantages. So is the addition strange metal salts necessary, those in the formed Iron oxide pigments in the form of the> corresponding foreign metal oxides or. Oxide hydrates as impurities appear.

There has now been a process for making yellow to tan Iron oxide hydrate pigments through oxidation of iron with simultaneous reduction of aromatic nitro compounds found in the presence of iron salt solutions, which is characterized in that the oxidation of iron in the presence of Oxygen acids of sulfur or their alkali and / or alkaline earth metal salts, which contain sulfur in the middle oxidation stage up to a maximum of 5, carried out will.

Examples of the sulfur compounds to be used according to the invention are in addition to the acids, especially sodium, potassium, ammonium, magnesium and / or Calcium salts of sulphurous acid, thiosulphurous acid, thiosulphuric acid, dithionic acid, dithionic acid, pyrosulphurous acid.

The sulfur compounds to be used according to the invention are in Quantities from 2 to 20 wt. S, preferably from 8 to 12 wt. S, based on nitrobenzene used.

The iron can, as in the known processes, for example in the form of cast chips, wire pins, granules, etc.

can be used.

Since in the method according to the invention any addition is strange If there are no hydrolyzable metal ions, no foreign metal oxides or Oxide hydrates as impurities in the iron oxides formed. This increases the iron oxide content in the pigment by 2 to 7%. Those produced by the new process yellow and yellow-brown iron oxide hydrate pigments can be removed by subsequent Convert glow into red pigments of various color nuances.

These pigments excel in full color paint and in Laek TiO lightening the previously known types considerably both in terms of color purity and color strength. The color strength is up to 45 f more intense. According to the method according to the invention The pigments obtained are also more finely crystalline than those obtained by known processes manufactured.

The sulfur compounds added according to the process according to the invention are only incorporated into the iron oxide pigments to a very low percentage.

In the following, the process according to the invention is carried out by various Examples explained in more detail: Example 1: To 250 g of cast iron filings, grain size 0.6-1.7 cm are added 210 ml iron (II) chloride solution, 6O g / l Fell2, 100 ml water, 20 ml nitrobenzene and 65 grams of sodium pyrosulfite. The mixture is brought with stirring and reflux to boiling temperature 100 ° C and then leaves 147 ml of nitrobenzene within 2 hours run up.

After the reduction is complete, the aniline formed is partly by decantation and partly separated from the resulting iron oxide hydrate by steam distillation. The aniline-free iron oxide hydrate slurry is washed salt-free and filtered.

If you dry the filter residue for 1/2 hour at 1800C, you get a yellow iron oxide pigment; by annealing this yellow iron oxide pigment for 1/2 h 8000C, a red iron oxide pigment is obtained, which has a more pure paint finish and a Blending with titanium white 45 ffi is stronger than the same pigments made after 4b and 5b.

Example 2: To 200 g of cast iron shavings, grain size 0.6-1.7 mm are added 210 ml iron (II) chloride solution, 360 g / l FeCl2, 100 ml water, 20 ml nitrobenzene and 60 g sodium hyposulfite. The mixture is brought with stirring and reflux to boiling temperature 1000 and then leaves 130 ml of nitrobenzene within 2 hours run up.

The reaction mass is as described in Example 1, Paragraph 2, worked up.

Drying the filter residue for 1/2 hour at 180 ° C. gives a yellow iron oxide pigment; by calcining the yellow iron oxide pigment for 1/2 hour at 80 ° C one is a yellow-red iron oxide pigment, which is purer in the full color shade and in the blend with titanium white 40 ffi is stronger in color than pigments produced according to the process 4b and 5b.

Example 3: Add to 250 g of cast iron filings, grain size 0.6-1.7 mm 210 ml iron (II) chloride solution, 360 g / l FeCl2, 100 ml water, 20 ml nitrobenzene and 70 g sodium sulfite. The reaction mixture is brought with stirring and cooling in the Runkfluss to boiling temperature 100 ° C and then leaves 147 ml of nitrobenzene within 2 hours run up.

The reaction mass is as described in Example 1, Paragraph 2, worked up.

The filter residue is dried at 180 ° C. for 1/2 hour; one receives a yellow iron oxide pigment, which by annealing for 1/2 h at 800 ° C, to a red iron oxide pigment is converted, which is darker, purer in the full color and in Waste 40 ffi stronger and more bluish than pigments according to 4b and 5b.

Example 4: a) 10.2 kg of cast iron chips, Grain 0, OT - 0.6 µm, with 8.4 l iron (II) chloride solution (360 g, l), 0.8 l nitrobenzene and 4.4 l of 40% sodium hydrogen sulfite solution are added together. While stirring and The reaction mixture is brought to boiling temperature under reflux cooling, then left a further 5.9 liters of nitrobenzene are run in over the course of 3 hours.

After the end of the reduction, the reaction mass, as in Example 1, Section 2 - 3 described, worked up, dried and glazed b) In one The second reaction vessel is 4.0 kg of cast iron filings, grain size 0.07-0.6 mm, 8 Add l aluminum chloride solution (170 g / l), 4.8 l water and 1 l nitrobenzene together and brought to boiling temperature with stirring and reflux cooling. Then one lets within 3 hours a further 5.7 1 nitrobenzene uril 6 kg cast iron shavings, grain size Taper 0.07-0.6 mm.

The work-up, drying and calcination also takes place here as in the example 1, section 2 - 3.

The red pigments obtained in both cases differ in Iron oxide content a) 96.6% Fe2O3 b) 90.7% Fe2O3 as well as in the pigment quality. That The pigment produced according to 4a is softer, purer in the full color shade and in the blend 40% stronger color with TiO2.

Example 5: a) 10 kg of cast iron filings are placed in a reaction vessel with grain size 0.6 - 1.7 mm, 8.4 1 iron IT chloride solution (360 g / l FeC12), 0.8. 1 nitrobenzene and 4.4 1 40 goat sodium hydrogen sulfite solution together and works as under example 4 a), an iron oxide pigment red with 97.6% Fe2O3 is obtained.

b) 4 kg of cast iron filings with grain size are added to a second reaction vessel 0.6 - 1.7 mm, with 8 1 aluminum chloride solution (170 g / 1), 4.8 1 water and 1 1 nitrobenzene together, heated with stirring and reflux cooling to boiling temperature and leaves then within 3 hours 5.7 1 nitrobenzene and 6 kg cast iron filings, grain size 0.6 - 1.7 mm taper, a red color is obtained after working up, drying and calcining Iron oxide pigment with 92.2% Fe2O3.

The two pigments differ in such a way that the one produced according to 5a The pigment is softer and the full color shade is purer.

A 40% higher color strength is achieved in the blend.

Example 6: To 2,800 kg of cast iron filings, grain size 0.6 - 1.7 mm 2,300 1 iron (II) chloride solution () 60 g / l), 250 1 nitrobenzene and 1,300 1 40 fiige Sodium hydrogen sulfite solution. A reaction takes place with stirring and reflux cooling, at which the heat of reaction released the aqueous reaction mixture very soon brings to boiling temperature. 1,800 liters of nitrobenzene are then added over 2 1/2 hours and towards the end of the reduction another 800 kg of cast iron filings, grain size 0.07-0.6 mm, within Added 1/4 h.

After work-up, drying and calcination, as in Example 1, section 2-3, an iron oxide yellow and iron oxide red pigment is obtained which In the full color of the lacquer, it is more yellow, pure and when blended with titanium white, it is more yellow and 50% stronger is produced as pigments according to Example 4b.

The red pigment contains 96.3% Fe2O3.

Claims (5)

Patent claims: 1) Process for the production of yellow to yellow-brown iron oxide hydrate pigments by oxidation of iron with simultaneous reduction of aromatic nitro compounds found in the presence of iron salt solutions, characterized in that the oxidation of iron in the presence of oxo acids of sulfur or their alkali and / or Alkaline earth metal salts, the sulfur in the middle oxidation level up to a maximum 5 included. 2) Method according to claim 1, characterized in that the oxidation of iron in the presence of sodium, potassium, ammonium, magnesium and / or calcium salts sulphurous acid, thiosulphurous acid, thiosulphuric acid, dithionic acid Acid, dithionic acid and / or pyrosulfuric acid is carried out. 3) Method according to claim 1 or 2, characterized in that the Oxygen acid of sulfur and / or alkali or alkaline earth metal salts in quantities from 2 to 20% by weight, based on nitrobenzene, is used. 4) Use of the iron oxide pigments, produced according to one of the claims 1 to 3, for the production of yellow and red pigments. 5) Dye compositions containing an iron oxide pigment prepared according to one of claims 1 to 4.