CN101089053A

CN101089053A - Ferrooxide pigment from mill cinder

Info

Publication number: CN101089053A
Application number: CN 200610087162
Authority: CN
Inventors: 刘兼安
Original assignee: IOP PROFESSIONAL CO Ltd
Current assignee: IOP PROFESSIONAL CO Ltd
Priority date: 2006-06-15
Filing date: 2006-06-15
Publication date: 2007-12-19
Anticipated expiration: 2026-06-15
Also published as: CN101089053B

Abstract

The present invention relates to process of producing iron oxide pigment with rolled scraps. Rolled scraps is mixed with exogenous iron oxide to obtain mixture, and the mixture is heated in oxidizing atmosphere at 200-900 deg.c to produce the iron oxide pigment, black, brown or red. Each of the exogenous iron oxide and the produced iron oxide pigment has Fe2O3 and/or Fe3O4 as the main components. The said iron oxide pigment may be further mixed with rolled scraps and heated in reducing atmosphere at 200-900 deg.c to obtain black iron oxide pigment. Some additive of chromium oxide, manganese oxide, magnesium oxide, carbon containing material or their mixture may be added into black iron oxide pigment for high quality. The black iron oxide pigment is cooled in reducing atmosphere to avoid re-oxidizing.

Description

Iron oxide pigments from mill scale

Technical Field

The present invention relates to the production of iron oxide pigments, and in particular to the production of iron oxide pigments derived from mill scale.

Background

Iron oxide pigments may be yellow, orange-red, brown or black depending on their chemical composition andcrystal structure. Iron oxide pigments are suitable for use as: paints, ceramics, rubbers and plastics, paint pigments, coloring materials for blanks, bricks, tiles, porcelain enamel, glazes, glass, pet foods, face powders, colorants for pharmaceutical capsules and toners for printing.

Synthetic iron oxide pigments are generally prepared by reacting iron salts with bases, as disclosed in U.S. patent 1,327,061 to Penniman et al. Many other improvements and further work have been made based on Penniman's work.

Another major method for the synthesis of iron oxides for pigments is the Laux process, which utilizes iron oxides derived from the so-called nitrobenzene process. There are many improvements to the Laux process, one of which is described in Westerhaus et al, us 4,966,641. Both of these main processes use acids and bases. When chemicals are involved, the synthesis process becomes expensive and relatively difficult to operate. This not only increases the cost of raw materials, but also the equipment and consumables are relatively expensive. This results in higher process costs and, ultimately, makes the wholesale price of the synthesized iron oxide pigment relatively expensive.

Another major production technique for the synthesis of iron oxides is based on spray pyrolysis of solutions of iron chloride or iron sulfate (spray pyrolysis). References to this work can be found in U.S. patents 5,911,967 and 5,200,159. The iron oxides produced by this process are known as iron oxides and are suitable as starting materials for orthoferrites. The iron oxide is red in color, but is not generally used as a coloring pigment. In fact, the main purpose of the technology described in said two us patents is to treat the acid waste, which is a by-product of the pickling (pickling) process involved in the steel industry.

From the above discussion of iron oxidesynthesis processes, it can be seen that these processes are all chemical processes that require relatively expensive raw materials and expensive equipment. In recent years, the industry has come to appreciate the importance of synthesizing iron oxide pigments using mill scale as a raw material. Mill scale is a rust scale which is usually obtained and produced from steel billets or steel structures in a steel mill or steel structure company under heat and via a so-called hot-forging process. Mill scale may also be obtained from other iron and steel mill sources.

The company pfeiffe (patent number GB 1,090,043) used a combination of mill scale and iron sulfate as raw materials to produce iron oxide pigments. The main disadvantage of this process is the use of a highly corrosive chemical, ferric sulfate, which is similar to those chemical processes discussed above.

In the early 1990's, Yang et al (patent No. CN1,049,169) have calcined mill scale along with carbonaceous material under non-oxidizing conditions to form black iron oxides. A related work has been reported in us patent 5,738,717, in which iron oxide pigment process mill scale is utilized directly without the use of expensive chemicals. In this work, the main process step involves the calcination of mill scale. It is described therein that red, brown and black iron oxides can be obtained. However, many industrial operational difficulties are involved, such as controllability of the color stabilization process. Meanwhile, the reaction rate of the process for obtaining iron oxide pigments cannot be practical because the direct oxidation process of mill scale is slow. And control of the oxidation process to form the red and black oxides is not fully disclosed.

Disclosure of Invention

The present invention relates to a method for producing iron oxide pigments from mill scale. The mill scale is mixed with exogenous iron oxide and the resulting mixture is heated in an oxidizing atmosphere to a temperature of 200 ℃ to 900 ℃ to produce an iron oxide pigment, which may be black, brown or red. The exogenous iron oxide used and the iron oxide pigment produced may be predominantly Fe₂O₃Or Fe₃O₄Or a mixture of both. Iron oxide pigments produced as above or obtained from any other source can be converted to black by mixing them with mill scale and heating the resulting mixture to a temperature of 200 ℃ to 900 ℃ in a non-oxidizing or reducing atmosphere to produce an iron oxide black pigment. Additives may be added in order to improve the quality of the iron oxide black pigment produced. The additive can beTo be chromium oxide or manganese oxide or magnesium oxide or any carbonaceous material or mixture thereof. In a non-oxidizing or reducing atmosphereThe iron oxide black pigment produced as above is cooled to ensure that it is not reoxidized.

Mill scale and iron oxides (mainly Fe)₂O₃Or Fe₃O₄Or a mixture of both) from an external source (hereinafter referred to as exogenous iron oxide). The mixture is heated in the presence of oxygen to a temperature between 200 ℃ and 900 ℃. The presence of exogenous iron oxide accelerates the oxidation reaction of the mill scale. The amount of exogenous iron oxide required and the time for which the mixture is heated depend on the type, quality and fineness of the mill scale used, and also on the degree of oxidation desired. The higher the fineness of the mill scale, the larger the contact surface between mill scale and iron oxide, the less amount of exogenous iron oxide is required and the shorter the heating time. The higher the degree of oxidation desired, the greater the amount of exogenous iron oxide required, and the longer the heating time. Depending on the degree of oxidation, iron oxide pigments (mainly Fe) are produced₂O₃Or Fe₃O₄Or a mixture of the two) may be black, brown or red. When complete oxidation occurs, a red iron oxide pigment is produced. On the other hand, when the oxidation process is incomplete, iron oxide black pigments are generated. To achieve a higher degree of oxidation, the exposed surface area of the mixture must be large. Any method that increases the exposed area may be used, such as using a stirring device while heating the mixture.

Iron oxide pigments (mainly Fe) obtained from reaction (i) or any other source₂O₃Or Fe₃O₄Or a mixture of the two) can be converted to a black pigment by mixing it with mill scale and reducing the mixture. The mixture is heated to a temperature between 200 ℃ and 900 ℃ in a non-oxidizing or reducing atmosphere. The mill scale acts as a reducing agent and the end product produced is an iron oxide black pigment (mainly Fe)₃O₄). The amount of mill scale required and the heating time of the mixture depend on the type, quality and fineness of the iron oxide pigment and mill scale used. The darker the red color of the iron oxide pigment used, the more amount of mill scale is required and the longer the heating time. The finer the iron oxide pigment and mill scale used, the larger the contact area between the iron oxide pigment and mill scale, the less mill scale amount is required and the shorter the heating time.

In order to obtain a better quality of the produced iron oxide black pigment, additives may be added in reaction (ii). The additive may be chromium oxide or manganese oxide or magnesium oxide or any carbonaceous material or mixtures thereof. The amount of additive required depends on the type, quality and fineness of the additive used, the iron oxide pigment and the mill scale. The finer the additive, iron oxide pigment and mill scale used, the larger the contact area between the additive, iron oxide pigment and mill scale, and the smaller the amount of additive required. (iii) allowing the iron oxide black pigment resulting from reaction (ii) to cool while still in a non-oxidizing or reducing atmosphere to ensure that it is not re-oxidized.

Detailed Description

The following examples are provided by way of illustration and should not be construed as limiting the invention.

Example 1

Spray-baked (spray baked) red iron oxide (3kg) was mixed with powdered mill scale (6kg) having a fineness of less than 50 microns. The mixture was heated to 450 ℃ for 3 hours in a cylindrical rotary furnace (rotating furnace) having a hole in a door to allow free flow of air. To achieve the desired degree of oxidation. Black iron oxide is obtained as brown color and ball milled to obtain the desired pigment quality with good tinctorial strength.

Example 2

Substantially the same results were obtained by repeating the procedure of example 1, in which the spray-calcined red iron oxide was replaced with the brown-colored black iron oxide obtained from example 1.

Example 3

The black iron oxide brown in colour (6kg) obtained from example 2 was mixed with pulverulent mill scale (300g) having a fineness of less than 50 μm. The mixture was heated to a temperature of 550 ℃ for 2 hours in a chamber (chamber) with a purge of nitrogen gas. Subsequently, the mixture was cooled in a non-oxidizing atmosphere for 15 hours. Black iron oxide is obtained, which is ball milled to obtain the desired pigment quality with good tinctorial strength. The color intensity value measured with a Minolta colorimeter CR-210 is typically L-32.46, a-1.38 and b-2.54.

Example 4

Spray-calcined red iron oxide (1.5kg) was mixed with coarser mill scale (9kg) having a fineness between 250 and 600 microns. The coarser mill scale is selected here to help separate the excess mill scale from the final product (black iron oxide) to make the final product more pure. The mixture was heated to a temperature of 550 ℃ for 2 hours in a box furnace with internal stirring (internal stirring) under nitrogen purge. The mixture was then cooled in a non-oxidizing atmosphere for 15 hours. The resulting mixture was screened to separate excess mill scale and obtain the desired black iron oxide. The obtained black iron oxide was ball milled to obtain the desired pigment quality with good tinctorial strength.

Example 5

The procedure of example 4 is repeated, replacing the spray-calcined red iron oxide with red iron oxide, which is TiO₂A by-product of the production process. Substantially the same results were obtained.

Example 6

The procedure of example 4 was repeated, replacing the spray-calcined red iron oxide with the brown-colored black iron oxide obtained from example 2. Substantially the same results were obtained.

Example 7

The black iron oxide (6kg) obtained from example 3 wasmixed with manganese oxide (180g) and powdered charcoal (180 g). The mixture was heated to 500 ℃ for 2 hours in a chamber with a nitrogen purge. Subsequently, the mixture was cooled for 15 hours under a non-oxidizing atmosphere. A darker black oxide can be obtained. No mill scale was added here, since the black iron pigment obtained from example 3 already contained an excess of mill scale. The color intensity value measured with the Minolta colorimeter CR-210 is typically L-31.35, a-1.30 and b-2.56.

Example 8

The brown black iron oxide (6kg) obtained from example 2 was heated to 550 ℃ for 2 hours in a chamber with nitrogen purge. Subsequently, the mixture was cooled for 15 hours under a non-oxidizing atmosphere. Black iron oxides can be obtained which are ball milled to obtain the desired pigment quality with good tinctorial strength. No mill scale was added here because the brown black iron oxide obtained from example 2 already contained an excess of mill scale. The color intensity value measured with the Minolta colorimeter CR-210 is typically L-32.53, a-1.89 and b-2.63.

Claims

1. A method for producing iron oxide pigments from mill scale comprising the steps of:

(i) mixing iron oxide with mill scale;

(ii) (ii) heating the mixture obtained from (i) to a temperature of 200 ℃ to 900 ℃;

(iii) (iii) cooling the mixture obtained from (ii).

2. The method for producing iron oxide pigments according to claim 1, wherein the process of heating and cooling the mixture is performed in the following atmosphere:

a) oxidizing atmosphere to produce iron oxide pigment in black, brown or red color, or

b) Non-oxidizing or reducing atmosphere to produce iron oxide black pigment.

3. The method for producing an iron oxide pigment according to claim 1, wherein the iron oxide is mainly Fe₂O₃Or Fe₃O₄Or a mixture of both.

4. The method for producing an iron oxide pigment according to claim 2, wherein the oxidizing atmosphere comprises ordinary air or oxygen.

5. The method for producing an iron oxide pigment of claim 2, wherein the non-oxidizing or reducing atmosphere comprises steam, nitrogen, argon, carbon monoxide, carbon dioxide or other inert or reducing gas.

6. The method for producing an iron oxide pigment according to claim 2, wherein the iron oxide pigment produced is mainly Fe₂O₃Or Fe₃O₄Or a mixture of both.

7. The method for producing iron oxide pigments according to claim 2, characterized in that the iron oxide black pigments produced are mainly Fe₃O₄。

8. The method for producing an iron oxide pigment according to claim 2, wherein at least one or more additives selected from the group consisting of:

(i) chromium oxide

(ii) Manganese oxide

(iii) Magnesium oxide

(iv) A carbonaceous material.

9. An iron oxide pigment produced according to the process of any one of claims 1 to 8.