Iron oxide black, process for its preparation and use thereof

Abstract

The present application provides a kind of iron oxide black and its preparation method and use, the preparation method includes: in the suspension reaction liquid is passed into the oxygen-containing gas and carries out the glue, obtains thick black reaction liquid, the suspension reaction liquid is formed by ferrous salt and alkaline aqueous solution contact;Then, under the condition of not less than 85 DEG C with oxygen-containing gas contact to remove crystallization water, form iron oxide black.In the iron oxide black particle formed by using the method in this application as pigment, can effectively reduce the amount of pigment, reduce the user production cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical preparation, in particular to a kind of iron oxide black and its preparation method and use. BACKGROUND

[0002] Iron black pigment is mainly applied in the fields of building, paint, plastic, rubber, etc., and the iron black pigment produced by special process can be used in special fields such as medicine and food.

[0003] There are two production processes for traditional iron black pigment: ferrous hydroxide oxidation method and addition method.

[0004] The ferrous hydroxide oxidation method is to add liquid alkali to ferrous sulfate, and then a neutralization reaction occurs to form ferrous hydroxide precipitate. Then, air is introduced into the ferrous hydroxide slurry at 95-100℃ and pH 8-11 to produce iron black pigment by oxidation.

[0005] FeSO4+2NaOH→Fe(OH)2↓+Na2SO4

[0006] 4Fe(OH)2+O2+2H2O→4Fe(OH)3↓

[0007] Fe(OH)2+2Fe(OH)3→Fe3O4+4H2O

[0008] In this method, the particles grow while they are agglomerated during the reaction process, which causes uneven particle size, low product strength, and poor dispersibility.

[0009] The addition method is to mix iron oxide-containing materials with ferrous sulfate solution, adjust the pH value by adding liquid alkali under certain process conditions to obtain iron black pigment. If there is unoxidized ferrous hydroxide, appropriate air is introduced or an appropriate amount of ammonium nitrate is added to promote oxidation.

[0010] FeSO4+2NaOH→Fe(OH)2↓+Na2SO4

[0011] Fe(OH)2+Fe2O3→Fe3O4+H2O

[0012] Fe(OH)2+Fe2O3·H2O→Fe3O4+2H2O

[0013] In this method, both large particles of iron oxide materials continue to react and grow, and particles generated by the reaction of ferrous sulfate and liquid alkali increase, resulting in uneven particle size, low strength, and poor dispersibility. SUMMARY

[0014] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an iron oxide black, its preparation method and uses, to solve the problems of poor dispersibility and low coloring strength of iron oxide black in the prior art.

[0015] To achieve the above and other related objectives, the present invention is implemented by including the following technical solutions.

[0016] The first aspect of this invention provides a method for preparing iron oxide black, comprising:

[0017] Oxygen-containing gas is passed through a suspension reaction solution to produce hairspray, resulting in a thick black reaction solution. The suspension reaction solution is formed by contacting ferrous salt with an alkaline aqueous solution.

[0018] Next, it is brought into contact with oxygen-containing gas at a temperature not lower than 85°C to remove the water of crystallization, forming iron oxide black.

[0019] Preferably, the ferrous ion content in the suspension reaction solution, based on the total mass of the suspension reaction solution, is 1 wt% to 5 wt%. If the Fe content is less than 1 wt%, the production efficiency is too low; if the Fe content is greater than 5 wt%, the colloid is too thick, making gas dispersion difficult and resulting in uneven gelation. The ferrous ion content can be tested using GB / T664-2011.

[0020] Preferably, the oxygen-containing gas is air.

[0021] More preferably, the Fe content in the ferrous ion-containing reaction solution is 2wt% to 4wt% based on the total mass of the reaction solution.

[0022] More preferably, the ferrous salt is one or more selected from ferrous sulfate, ferrous chloride, and ferrous chloride.

[0023] Preferably, the method further includes a step of adding water to the system during the removal of water of crystallization, wherein the amount of water added is 0.75 to 1.25 times the mass of the suspension reaction solution.

[0024] More preferably, the amount of alkali added is sufficient to maintain the pH value of the system during the preparation process. An alkaline solution, such as sodium hydroxide or potassium hydroxide, can be used.

[0025] Preferably, during the gelling process, oxygen-containing gas is aerated to form bubbles <500μm, which then contact the suspension reaction liquid. If the bubbles are too large, the gas mass transfer efficiency is poor, the residence time is short, and this is not conducive to thorough gelling.

[0026] Preferably, when using hairspray and the oxygen-containing gas is air, the air flow rate is 0.1–10 m³ / h. 3 / h.

[0027] Preferably, the temperature during gelling is not higher than 40°C. Excessive temperature will cause the material surface to oxidize too quickly, affecting the product color. More preferably, the temperature during gelling is 0–39°C, and even more preferably, the temperature during gelling is 0–35°C, such as 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, or 35°C.

[0028] Dehydration is difficult when the temperature is below 85°C. Preferably, the dehydration temperature is 88–100°C, such as 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, or 100°C. However, when the temperature is above 95°C, the steam evaporates too quickly, resulting in excessive energy consumption. Most preferably, the dehydration temperature is 90–95°C.

[0029] During the preparation process, the pH of the reaction system is controlled by alkali to ensure it is not lower than 6. When the pH of the reaction system is less than 6, the resulting product is prone to forming iron oxide yellow, affecting the color; however, when the pH is greater than 8.5, the alkali in the raw material solution is wasted. Preferably, the pH of the reaction system is 7.5-8.5.

[0030] Preferably, the process further includes a post-treatment step on the obtained iron oxide black particles. The post-treatment includes at least drying. It may also include washing prior to drying, wherein the washing is performed with water.

[0031] More preferably, the drying temperature is no more than 75°C. At this temperature, discoloration of the iron oxide black particles is prevented.

[0032] A second aspect of the present invention also provides iron oxide black prepared by the above-described preparation method.

[0033] Preferably, the fineness of the iron oxide black is 12-14 μm.

[0034] The present invention also discloses the use of iron oxide black as a pigment in paints, varnishes and printing inks as described above.

[0035] The beneficial effects of the technical solution of this invention are as follows:

[0036] The iron oxide black product prepared by the method of this invention exhibits higher tinting strength under the same dispersion conditions compared to iron oxide black products prepared by methods in the prior art. Therefore, when using iron oxide black particles prepared by the method of this application as pigments, the amount of pigment used can be effectively reduced, thereby lowering the user's production costs. Attached Figure Description

[0037] Figure 1 The image shown is an electron microscope image of the iron oxide black particles prepared in Example 1 of this invention.

[0038] Figure 2The image shown is an electron microscope image of the iron oxide black particles prepared in Example 2 of this invention. Detailed Implementation

[0039] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0040] It should be noted that, unless otherwise specified in the following embodiments, all process equipment or apparatuses used are conventional equipment or apparatuses in the art, such as aeration equipment, as long as it can form air bubbles <500μm. The reaction vessel can be any reaction vessel commonly used in the prior art, as long as it meets the conditions of the preparation method of this invention.

[0041] Furthermore, it should be understood that the one or more method steps mentioned in this invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not intended to limit the order of the method steps or to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0042] Huayi's iron oxide black product, model 380, is currently the commercially available iron oxide black pigment with the highest tinting strength, widely used in coloring various building materials, paints, coatings, plastics, paper, etc. In the embodiments and comparative examples of this application, product 380 is used as the standard sample, and its tinting strength is set to 100. The tinting strength of the products obtained in the following specific experiments is compared with that of product 380; a value greater than 100 indicates higher tinting strength, and a value less than 100 indicates lower tinting strength.

[0043] The LAB+ intensity was obtained using a datecolor600 colorimeter.

[0044] In the following examples and comparative examples, a fineness tester was used to test the fineness of the products according to GBT1724-2019. The smaller the fineness, the better the dispersion effect.

[0045] Example 1

[0046] The method for preparing iron oxide black particles in this embodiment includes:

[0047] Add 40g / 100ml of 3.5L ferrous sulfate aqueous solution to a 5L reactor, add sodium hydroxide solution to adjust the pH, stir to mix the materials evenly, maintain the pH at 7.5, and form a suspension. The ferrous salt content of the suspension was measured to be 3.98%.

[0048] Air is introduced through the aeration equipment at a flow rate of 0.1 m³ / s. 3 The reaction was carried out at a temperature of 15°C for approximately 4 hours, and the thickening and gelling process was observed to be complete.

[0049] After the gel has fully developed, add an equal volume of water to the reaction system as the ferrous sulfate solution was initially added. Raise the temperature to 90°C, continuously adding liquid alkali to maintain the pH at 8.0 and the air flow rate at 0.3 m³ / h during the reaction. 3 / h, until it is completely dehydrated.

[0050] The reaction is stopped once dehydration is complete.

[0051] Dry at 70℃ and package to obtain the finished product.

[0052] A strength comparison was made with the iron oxide black pigment of our own standard sample model 380.

[0053] Item Coloring strength Fineness Product in Example 1 111.72 12 μm

[0054] Example 2

[0055] The method for preparing iron oxide black particles in this embodiment includes:

[0056] 11L of ferrous sulfate solution (40g / 100ml) was added to a 15L reactor. Sodium hydroxide solution was added to adjust the pH. Stirring was started to mix the materials evenly and the pH was maintained at 8.0 to form a suspension. The ferrous salt content of the suspension was measured to be 3.75wt%.

[0057] Air is introduced into the suspension through an aeration device at a flow rate of 0.3 m³ / s. 3 / h, reaction temperature 20℃, reaction time about 3 hours, and it was observed that the thickening and gelling were complete;

[0058] After the gel has fully developed, add an equal volume of water to the reaction system as the ferrous sulfate solution was initially added. Raise the temperature to 95°C, continuously adding liquid alkali to maintain the pH at 8.5 and the air flow rate at 1.5 m³ / h during the reaction. 3 / h, until it is completely dehydrated;

[0059] The reaction is stopped once dehydration is complete.

[0060] Further processing: Dry at 70℃ and package to obtain the finished product.

[0061] The comparison results of the indicators are as follows, based on the comparison with the standard sample 380 iron oxide black pigment produced by our company.

[0062] Item Coloring strength Fineness Product in Example 2 111.7 14 μm

[0063] Example 3

[0064] The method for preparing iron oxide black particles in this embodiment includes:

[0065] Add 40g / 100ml of 35L ferrous sulfate solution to a 50L reactor, add sodium hydroxide solution to adjust the pH, turn on the stirrer to mix the materials evenly, maintain the pH at 8.0, and form a suspension. The ferrous salt content of the suspension was measured to be 3.90%.

[0066] Air is introduced through the aeration equipment at a flow rate of 1.0 m³ / h. 3 The reaction was carried out at a temperature of 20°C for approximately 3 hours, and the thickening and gelling process was observed to be complete.

[0067] After the gel has fully developed, add an equal volume of water (the same volume as the ferrous sulfate solution added during initial feeding) to the reaction system, raise the temperature to 93°C, and continuously add liquid alkali to maintain the pH at 8.5 and the air flow rate at 3.0 m³ / h during the reaction. 3 / h, until it is completely dehydrated.

[0068] The reaction is stopped once dehydration is complete.

[0069] Dry at 70℃ and package to obtain the finished product.

[0070] The finished product specifications are as follows: color data is compared with standard sample 380.

[0071] Compare with our own standard sample iron oxide black pigment, model 380.

[0072] Item Coloring strength Dispersion Product in Example 3 119.91 14 μm

[0073] Example 4

[0074] The method for preparing iron oxide black particles in this embodiment includes:

[0075] Add 40g / 100ml of 70L ferrous sulfate solution to a 100L reactor, add sodium hydroxide solution to adjust the pH, stir to mix the materials evenly, maintain the pH at 7.5, and form a suspension. The ferrous salt content of the suspension was measured to be 3.78wt%.

[0076] Air is introduced into the suspension through an aeration device at a flow rate of 2.0 m³ / s. 3 / h, reaction temperature 25℃, reaction time about 3 hours, and complete thickening and gelling were observed;

[0077] After the gel has fully developed, add an equal volume of water to the reaction system as the ferrous sulfate solution was initially added. Raise the temperature to 95°C, continuously adding liquid alkali to maintain the pH at 8.0 and the air flow rate at 6.0 m³ / h during the reaction.3 / h, until it is completely dehydrated;

[0078] The reaction is stopped once dehydration is complete.

[0079] Dry at 70℃.

[0080] Compare with our own standard sample iron oxide black pigment, model 380.

[0081] Item Coloring strength Fineness Product in Example 4 122.98 12 μm

[0082] Example 5

[0083] The method for preparing iron oxide black particles in this embodiment includes:

[0084] 0.5m 3 Add 0.35m to the reactor 3 40g / 100ml of ferrous sulfate solution was mixed with sodium hydroxide solution to adjust the pH. The mixture was stirred to ensure uniform mixing and to maintain the pH at 7.5, forming a suspension. The ferrous salt content of the suspension was measured to be 3.85wt%.

[0085] Air is introduced into the suspension through an aeration device at a flow rate of 10 m³ / s. 3 / h, reaction temperature is 20℃, reaction time is about 3 hours, and its thickening and gelling are complete;

[0086] After the gel has fully developed, add water to the reaction system in an amount equal to the volume of ferrous sulfate solution used during initial feeding. Raise the temperature to 90°C, adding liquid alkali as needed to maintain the pH at 8.5 and the air flow rate at 25 m³ / h throughout the reaction. 3 / h, until it is completely dehydrated.

[0087] The reaction is stopped once dehydration is complete.

[0088] Dry at 60℃ and pulverize to obtain the finished product.

[0089] The results are as follows, compared with the iron oxide black pigment of our own standard sample model 380.

[0090] Item Coloring strength Dispersion Product in Example 5 112.13 14 μm

[0091] Comparative Example 1

[0092] This comparative example is the comparative example of Example 1.

[0093] This comparative example demonstrates a direct dehydration technique without gelling. The specific method for preparing iron oxide black particles includes:

[0094] Add 40g / 100ml of 3.5L ferrous sulfate solution to a 5L reactor, add sodium hydroxide solution to adjust the pH, turn on the stirrer to mix the materials evenly, maintain the pH at 7.5, and form a suspension. The ferrous salt content of the suspension was measured to be 4.05%.

[0095] Air is introduced through an aeration device at a flow rate of 0.3 m³ / h, the temperature is raised to 90°C, and the pH is maintained at 8.0 during the reaction process until the dehydration is complete.

[0096] The reaction is stopped once dehydration is complete.

[0097] Dry at 60℃ and then pulverize.

[0098] The results of the comparison with the standard sample iron oxide black pigment model 380 produced by our company are as follows.

[0099] Item Coloring strength Fineness Product in Comparative Example 1 86.11 24 μm

[0100] Comparative Example 2

[0101] Comparative Example 2 is a comparative example of Example 3.

[0102] This comparative example uses a technique where the pH is acidic during dehydration. The specific method for preparing iron oxide black particles includes:

[0103] Add 40g / 100ml of 35L ferrous sulfate solution to a 50L reactor, add sodium hydroxide solution to adjust the pH, turn on the stirrer to mix the materials evenly, maintain the pH at 8.0, and form a suspension. The ferrous salt content of the suspension was measured to be 3.94%.

[0104] Air is introduced through the aeration equipment at a flow rate of 1.0 m³ / h. 3 The reaction rate was 100 m / min, the reaction temperature was 20°C, and the reaction time was about 3 hours. It was observed that the thickening and gelling were complete.

[0105] After the gel has fully developed, add an equal volume of water (the same volume as the ferrous sulfate solution used during initial feeding) to the reaction system, raise the temperature to 93°C, maintain the pH at 5.5, and keep the air flow rate at 3.0 m³ / h during the reaction. 3 / h, until it is completely dehydrated.

[0106] The reaction is stopped once dehydration is complete.

[0107] Dry at 60℃ and then pulverize.

[0108] The results are as follows, compared with the iron oxide black pigment of our own standard sample model 380.

[0109] Item Coloring strength Fineness Product in Comparative Example 2 80.00 26 μm

[0110] Comparative Example 3

[0111] Comparative Example 3 is a comparative example of Example 3.

[0112] This comparative example uses a technique with a lower dehydration temperature. The specific method for preparing iron oxide black particles includes:

[0113] Add 40g / 100ml of 35L ferrous sulfate solution to a 50L glass reactor, add sodium hydroxide solution to adjust the pH, turn on the stirrer to mix the materials evenly, maintain the pH at 8.0, and form a suspension. The ferrous salt content of the suspension was measured to be 3.95wt%.

[0114] Air is introduced through the aeration equipment at a flow rate of 1.0 m³ / h. 3 The reaction time is 1000 m / min, the reaction temperature is 20°C, and the reaction time is about 3 hours, during which the thickening and gelling are complete.

[0115] After the gel has fully developed, add an equal volume of water (the same volume as the ferrous sulfate solution used during initial feeding) to the reaction system, raise the temperature to 80°C, maintain the pH at 8.0, and keep the air flow rate at 3.0 m³ / h during the reaction. 3 / h, until it is completely dehydrated.

[0116] The reaction is stopped once dehydration is complete.

[0117] Dry at 60℃ and pulverize to obtain the finished product.

[0118] The results are as follows, compared with the iron oxide black pigment of our own standard sample model 380.

[0119] Item Coloring strength Fineness Product in Comparative Example 3 94.32 20 μm

[0120] Comparative Example 4

[0121] The preparation method of the iron oxide black particles in this comparative example includes:

[0122] Add ferrous sulfate solution to a 15L reactor, add sodium hydroxide solution to adjust the pH, turn on the stirrer to mix the materials evenly, maintain the pH at 8.0 to form a suspension, and adjust the ferrous salt content of the suspension to 6.00 wt%.

[0123] Air is introduced into the suspension through an aeration device at a flow rate of 0.3 m³ / s. 3 / h, reaction temperature is 20℃, reaction time is about 4 hours, and it was observed that the thickening and gelling were complete;

[0124] After the gel has fully developed, add an equal volume of water to the reaction system as the ferrous sulfate solution was initially added. Raise the temperature to 95°C, continuously adding liquid alkali to maintain the pH at 8.5 and the air flow rate at 1.5 m³ / h during the reaction. 3 / h, until it is completely dehydrated;

[0125] The reaction is stopped once dehydration is complete.

[0126] Further processing: Dry at 70℃ and package to obtain the finished product.

[0127] The comparison results of the indicators are as follows, based on the comparison with the standard sample 380 iron oxide black pigment produced by our company.

[0128] Item Coloring strength Fineness Product in Comparative Example 4 85.12 23 μm

[0129] The above embodiments are for illustrating the implementation schemes disclosed in this invention and should not be construed as limiting the invention. Furthermore, various modifications listed herein, as well as variations in the methods and compositions of the invention, will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been specifically described in conjunction with various specific preferred embodiments, it should be understood that the invention should not be limited to these specific embodiments. In fact, various modifications as described above that are obvious to those skilled in the art to obtain the invention should be included within the scope of this invention.

Claims

1. A method for preparing iron oxide black, characterized in that, include: Oxygen-containing gas is introduced into a suspension reaction solution to produce a thick black reaction solution. The suspension reaction solution is formed by contacting ferrous salt with an alkaline aqueous solution. Then, it is contacted with oxygen-containing gas at a temperature not lower than 85°C to remove the water of crystallization, forming iron oxide black. During the preparation process, the pH value of the reaction system is adjusted by alkali to ensure that it is not lower than 6. The content of ferrous ions in the suspension reaction solution is 1wt%~5wt% based on the total mass of the suspension reaction solution. The temperature during gelation is not higher than 40°C.

2. The preparation method according to claim 1, characterized in that, The oxygen-containing gas is air.

3. The preparation method according to claim 1, characterized in that, It also includes the step of adding water to the system during the removal of water of crystallization, with the amount of water added being 0.75 to 1.25 times the mass of the suspension reaction solution.

4. The preparation method according to claim 1, characterized in that, It also includes a post-treatment step for the obtained iron oxide black particles, the post-treatment including at least drying, the drying temperature being no more than 75°C.

5. The preparation method according to claim 1, characterized in that, During the gel-making process, oxygen-containing gas is aerated to form bubbles of <500μm, which then come into contact with the suspension reaction liquid.

6. An iron oxide black obtained by the preparation method according to any one of claims 1 to 5.

7. The iron oxide black according to claim 6, characterized in that, The fineness of the iron oxide black is 12~14μm.

8. Use of iron oxide black as a pigment as described in any one of claims 6 or 7 in paints, varnishes and printing inks.

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