A preparation method of an environment-friendly iron zinc chromium brown pigment

Abstract

A preparation method of an environment-friendly iron-zinc-chromium brown pigment, comprising the following steps: (1) After dissolving a zinc source, an iron source and a chromium source in water, adding EDTA and a modified nano-graphene oxide powder, and performing a mixing treatment under ultrasonic conditions; (2) Adding an acidic aqueous solution to make it acidic, and at the same time adding a sol agent, and performing gelation under heating and stirring conditions; (3) First performing a pre-calcination treatment, and then subjecting the obtained precursor powder to a high-temperature calcination treatment; (4) After ball milling treatment, adding stearic acid and performing heating and stirring to obtain the iron-zinc-chromium brown pigment. The method of the present invention has simple technology, is environmentally friendly, green and low in energy consumption and cost, is suitable for industrial production, and the obtained iron-zinc-chromium brown pigment has small particle size, no particle feeling, uniform quality, no color difference and good dispersibility.

Description

Technical Field

[0001] The present invention relates to a preparation method of iron zinc chromium brown pigment, and particularly to a preparation method of an environment-friendly iron zinc chromium brown pigment. Background Art

[0002] Iron zinc chromium brown pigment is one of the commonly used brown pigments, and the color of the pigment has the characteristics of calmness, stability and simplicity. The brown pigments presented by iron zinc chromium brown have been widely used in glazed tiles and antique tiles since ancient times. It has excellent chemical resistance, outdoor light and weather resistance, and thermal stability, no bleeding, no migration, comprehensive performance, can meet the high requirements of modern coatings and plastics, is compatible with most thermoplastic and thermosetting resins, and is a non-toxic and environment-friendly pigment; its chromatogram ranges from yellowish red brown to deep red red brown, and it also has very excellent infrared reflection function, is suitable for reflective heat insulation coatings and camouflage coatings, etc., and can be made into camouflage coatings for many military fields.

[0003] At present, the preparation of iron zinc chromium brown pigment mainly adopts high-temperature solid-phase method and gel solid-phase method. The pigment products prepared by the high-temperature solid-phase method have problems such as large particle size and unstable color formation, and traditional high-temperature solid-phase has high energy consumption and poor environmental protection; while the gel solid-phase method uses heavy metal salt solutions for preparation, the heavy metal reaction yield is low, and there is a problem of heavy metal dissolution in the pigment. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the above-mentioned defects existing in the prior art, and provide a preparation method of an environment-friendly iron zinc chromium brown pigment with simple process, environmental friendliness, greenness, low energy consumption, low cost, suitable for industrial production, and the obtained iron zinc chromium brown pigment has small particle size, no particle feeling, uniform quality, no color difference and good dispersion.

[0005] The technical solution adopted by the present invention to solve its technical problems is as follows: A preparation method of an environment-friendly iron zinc chromium brown pigment, comprising the following steps:

[0006] (1) Add zinc source, iron source and chromium source into water and dissolve, then add EDTA and modified nano-graphene oxide powder, and perform mixing treatment under ultrasonic conditions to obtain a mixed suspension;

[0007] (2) Add an aqueous acid solution to acidity in the mixed suspension obtained in step (1), and at the same time add a sol agent, and perform gelation under heating and stirring conditions to obtain a gel;

[0008] (3) First perform pre-calcination treatment on the gel obtained in step (2), and then perform high-temperature calcination treatment on the obtained precursor powder to obtain iron zinc chromium brown powder;

[0009] (4) After ball-milling the iron-zinc-chromium brown powder obtained in step (3), stearic acid is added and heated with stirring to obtain an iron-zinc-chromium brown pigment.

[0010] The inventive concept of the method of the present invention is as follows: By step (1), the dispersibility of heavy metal ions in the mixed system is improved, and the uniformity of the mixture is enhanced, so as to facilitate the formation of a complex gel system with uniform distribution of heavy metal ions during gelation in step (2). Then, through step (3), a two-stage calcination treatment is carried out to obtain a mixed-phase crystal of zinc-iron-chromium oxide with impurities removed and a stable crystal lattice. Finally, through step (4), surface modification is carried out to improve the water resistance of the obtained pigment.

[0011] Preferably, in step (1), the mass ratio of the zinc source, iron source, and chromium source is 1:1.2 - 1.5:1.5 - 2.0.

[0012] Preferably, in step (1), the amount of water used is equivalent to 1.5 - 2.5 times the total mass of the zinc source, iron source, and chromium source. In the method of the present invention, if the amount of water is too small, it is not conducive to the dispersion of the gel during subsequent gelation, while excessive water is not conducive to the formation of a stable gel.

[0013] Preferably, in step (1), the addition amount of EDTA is equivalent to 0.3 - 2.4% (more preferably 0.5 - 2.0%) of the total mass of the zinc source, iron source, and chromium source. In the method of the present invention, the role of adding EDTA is that the amino and carboxyl groups in EDTA form stable complexes with heavy metal ions zinc, iron, and chromium, which can prevent the free dissolution of heavy metal ions, thereby improving the reaction yield of heavy metal ions during the preparation of the iron-zinc-chromium brown pigment.

[0014] Preferably, in step (1), the mixing treatment time is 30 - 40 min.

[0015] Preferably, in step (1), the zinc source includes zinc nitrate, etc. When using hydrates, the dosage is converted based on zinc nitrate.

[0016] Preferably, in step (1), the iron source includes iron nitrate, etc. When using hydrates, the dosage is converted based on iron nitrate.

[0017] Preferably, in step (1), the chromium source includes chromium nitrate, etc. When using hydrates, the dosage is converted based on chromium nitrate.

[0018] Preferably, in step (1), the addition amount of the modified nano-graphene oxide powder is equivalent to 2-5% (more preferably 2-4%) of the total mass of the zinc source, iron source and chromium source. In the method of the present invention, the function of adding the modified nano-graphene oxide powder is as follows: it has high thermal conductivity and a two-dimensional structure composed of single-layer carbon atoms, and the surface is rich in oxygen-containing functional groups such as hydroxyl groups and carboxyl groups, which can improve the dispersion of heavy metal ions in the mixed system, improve the uniformity of the mixture, and overcome the agglomeration caused by uneven dispersion, resulting in local overheating during subsequent calcination, leading to problems of color difference and uneven quality of the iron-zinc-chromium brown pigment; in addition, the oxygen-containing groups of the modified nano-graphene oxide powder assist in adsorbing heavy metal ions based on electrostatic interaction and cooperate with EDTA to further improve the reaction yield of heavy metal ions.

[0019] Preferably, in step (1), the modified nano-graphene oxide is obtained by blending polyvinylpyrrolidone and nano-graphene oxide. In the method of the present invention, covalent bond modification is carried out through polyvinylpyrrolidone to achieve covalent bond functionalization of the graphene surface. Compared with unmodified nano-graphene oxide, the dispersion of the modified nano-graphene oxide added in the method of the present invention in water has been significantly improved and the performance is more excellent; in addition, the modified nano-graphene oxide has excellent electrical conductivity and optical properties, which can enhance the light absorption and reflection capabilities of the iron-zinc-chromium brown pigment and effectively improve the color vividness of the pigment.

[0020] Preferably, the mass ratio of polyvinylpyrrolidone to nano-graphene oxide is 0.5-1.5:4-7. At this ratio, it is beneficial to play the role of polyvinylpyrrolidone and obtain a better dispersion effect.

[0021] Preferably, in step (1), the preparation method of the modified nano-graphene oxide is as follows: 1) Disperse the polyvinylpyrrolidone solution and nano-graphene oxide in water and mix them under ultrasonic conditions to obtain a uniformly dispersed colloidal solution; 2) First perform a primary stirring reaction on the uniformly dispersed colloidal solution obtained in step 1), then perform a secondary stirring reaction, and after washing the reaction-obtained colloid, dry it to obtain the product.

[0022] Preferably, in step 1), the amount of water used is equivalent to 1-2 times the total mass of the polyvinylpyrrolidone solution and nano-graphene oxide.

[0023] Preferably, in step 2), the temperature of the primary stirring reaction is 32-38 °C, the pH value is 7.6-8.0, and the time is 20-30 min. The main function of the primary stirring is to perform preliminary mixing.

[0024] Preferably, in step 2), the temperature of the secondary stirring reaction is 25 - 30 °C, the pH value is 6.8 - 7.2, and the time is 15 - 30 min. After reducing the temperature, continue secondary stirring to further remove bubbles and improve the homogenization effect.

[0025] Preferably, in step 2), wash 3 - 4 times successively with deionized water and ethanol. The purpose of washing the resulting colloid multiple times is to remove unreacted polyvinylpyrrolidone for subsequent drying.

[0026] Preferably, in step 2), the drying temperature is 50 - 70 °C.

[0027] The method of the present invention optimizes the conditions during the modified mixing and stirring reaction to ensure the full reaction of polyvinylpyrrolidone and nano-graphene oxide, making the particle size of the obtained modified nano-graphene oxide powder uniform and the properties stable.

[0028] Preferably, in step (2), add an aqueous acid solution until the pH value is 4 - 6. When the pH value is too low after adding the aqueous acid solution, adjust the pH value with an ammonia aqueous solution with a concentration of 0.5 mol / L.

[0029] Preferably, in step (2), the concentration of the aqueous acid solution is 1 - 2 mol / L.

[0030] Preferably, in step (2), the aqueous acid solution includes a citric acid aqueous solution, etc. In the method of the present invention, citric acid can coordinate with metal cations to form a gel.

[0031] Preferably, in step (2), the addition amount of the sol agent is equivalent to 0.5 - 1.0% of the volume of the mixed suspension. In the method of the present invention, the sol agent can reduce agglomeration, improve the stability of the gel, and contribute to obtaining a uniform and transparent gel.

[0032] Preferably, in step (2), the sol agent includes ethylene glycol, etc.

[0033] Preferably, in step (2), the temperature of gelation is 85 - 95 °C, the stirring speed is 200 - 400 r / min, and the time is 4 - 8 h. Citric acid coordinates with metal cations for gelation, and during the above process, slow stirring makes the reaction uniform.

[0034] The method step (3) of the present invention performs a two-stage calcination treatment including pre-calcination and high-temperature calcination, establishing a staged temperature-controlled calcination system to react and generate a spinel-structured zinc iron chromium oxide mixed-phase crystal, which can better control the crystal structure and properties of the iron zinc chromium brown pigment, and compared with direct high-temperature solid phase, the energy consumption is reduced and the environmental friendliness is improved. More preferably, the two-stage calcination treatment is carried out in a muffle furnace.

[0035] Preferably, in step (3), the conditions for the pre-calcination treatment are as follows: under a protective atmosphere, at a rate of 5-15 °C / min, heat up to 400-600 °C, and then keep the temperature for calcination for 1-3 h. The pre-calcination treatment in the method of the present invention is a low-temperature and slow calcination of the gel obtained in step (2), which can fully remove organic substances and is beneficial to the formation of the crystal structure of the powder.

[0036] Preferably, in step (3), the conditions for the high-temperature calcination treatment are as follows: under a protective atmosphere, at a rate of 50-150 °C / min, heat up to 1100-1300 °C, and then keep the temperature for calcination for 30-50 min. The high-temperature calcination treatment in the method of the present invention is a rapid high-temperature calcination of the precursor powder obtained by the pre-calcination treatment to achieve phase transformation, complete crystal reconstruction, and form a more stable structure.

[0037] Preferably, in step (3), the protective atmosphere includes nitrogen and / or argon, etc.

[0038] Preferably, in step (4), the diameter of the grinding balls used in the ball milling treatment is 20-40 mm, and the grinding balls are 40-50% of the mass of the iron-zinc-chromium brown powder. By optimizing the ball milling conditions, the particle size of the pigment particles is refined.

[0039] Preferably, in step (4), the rotation speed of the ball milling treatment is 60-80 r / min, and the time is 2-4 h. The method of the present invention refines the particle size of the pigment particles by optimizing the ball milling conditions, so that the obtained iron-zinc-chromium brown pigment has a small particle size, no particle feeling, uniform quality, no color difference, and good dispersibility. The ball milling treatment is carried out in a ball mill.

[0040] Preferably, in step (4), the addition amount of stearic acid is 1-3% of the mass of the iron-zinc-chromium brown powder. Stearic acid can react with the surface of metal oxides through carboxyl groups. In the method of the present invention, the surface of the pigment is coated with stearic acid to reduce the surface energy of the iron-zinc-chromium brown pigment, form a hydrophobic protective layer, and thus improve the hydrophobicity; while enhancing the water resistance of the iron-zinc-chromium brown pigment, it also improves the dispersibility of the pigment particles, avoids particle agglomeration, and further enhances the coloring power and covering power of the iron-zinc-chromium brown pigment; at the same time, for the iron-zinc-chromium brown pigment treated with stearic acid, metal ions are stabilized in the crystal structure, reducing heavy metal exposure and the risk of dissolution.

[0041] Preferably, in step (4), the temperature of the heating and stirring is 80-100 °C, the stirring speed is 200-600 r / min, and the time is 1-2 h. Heating and stirring is beneficial to the melting of stearic acid and the formation of a hydrophobic layer on the surface of the iron-zinc-chromium brown powder.

[0042] The beneficial effects of the method of the present invention are as follows:

[0043] (1) The method of the present invention can avoid the free dissolution of heavy metal ions and improve the reaction yield of heavy metal ions during the preparation of iron-zinc-chromium brown pigment;

[0044] (2) The method of the present invention improves the dispersion of heavy metal ions in the mixed system, enhances the uniformity of the mixed materials, overcomes the agglomeration caused by uneven dispersion, and prevents local overheating during subsequent calcination, thus avoiding the problems of color difference and non-uniform quality of the iron-zinc-chromium brown pigment;

[0045] (3) The method of the present invention establishes a staged temperature-controlled calcination system to react and generate a spinel-structured zinc-iron-chromium oxide mixed-phase crystal, which can better control the crystal structure and properties of the iron-zinc-chromium brown pigment. Compared with direct high-temperature solid phase, the energy consumption is reduced and the environmental friendliness is improved;

[0046] (4) The method of the present invention has simple process, is environmentally friendly, green, has low energy consumption and low cost, is suitable for industrial production, and the obtained iron-zinc-chromium brown pigment has small particle size, no particle feeling, uniform quality, no color difference and good dispersion. Specific Embodiments

[0047] The present invention will be further described below in conjunction with embodiments.

[0048] The raw materials or chemical reagents used in the embodiments and comparative examples of the present invention are all obtained through conventional commercial channels unless otherwise specified.

[0049] Example 1

[0050] (1) 60 g of zinc nitrate, 72 g of iron nitrate and 90 g of chromium nitrate were added to 500 mL of water and dissolved, then 2.0 g of EDTA and 4.5 g of modified nano-graphene oxide powder were added, and the mixture was treated under ultrasonic conditions for 30 min to obtain a mixed suspension;

[0051] The preparation method of the modified nano-graphene oxide is as follows: 1) Polyvinylpyrrolidone solution and nano-graphene oxide are dispersed in water with a mass ratio of 0.7:4 and a total mass 1.5 times that of the polyvinylpyrrolidone solution and nano-graphene oxide, and mixed under ultrasonic conditions to obtain a uniformly dispersed colloidal solution; 2) The uniformly dispersed colloidal solution obtained in step 1) is first subjected to a first stirring reaction for 25 min at 35 °C and a pH value of 7.8, and then a second stirring reaction for 20 min at 28 °C and a pH value of 7.0. The resulting colloid is washed 3 times successively with deionized water and ethanol, and then dried at 60 °C to obtain the product. In the examples of the present invention, by optimizing the conditions during the modified mixing and stirring reaction, it is ensured that polyvinylpyrrolidone and nano-graphene oxide react fully, so that the particle size of the obtained modified nano-graphene oxide powder is uniform and its properties are stable; covalent modification is carried out through polyvinylpyrrolidone to achieve covalent functionalization of the graphene surface. Compared with unmodified nano-graphene oxide, the dispersibility of the modified nano-graphene oxide added in the examples of the present invention in water has been significantly improved and its performance is more excellent; in addition, the modified nano-graphene oxide has excellent electrical conductivity and optical properties, can enhance the light absorption and reflection capabilities of the iron-zinc-chromium brown pigment, and effectively improve the color brightness of the pigment;

[0052] In the examples of the present invention, the function of adding EDTA is as follows: The amino and carboxyl groups in EDTA form stable complexes with heavy metal ions zinc, iron, and chromium, which can prevent the free dissolution of heavy metal ions, thereby improving the reaction yield of heavy metal ions during the preparation of the iron-zinc-chromium brown pigment;

[0053] In the examples of the present invention, the function of adding the modified nano-graphene oxide powder is as follows: It improves the dispersibility of heavy metal ions in the mixed system, enhances the uniformity of the mixture, overcomes the agglomeration caused by uneven dispersion, which may lead to local overheating during subsequent calcination, resulting in color difference and non-uniform quality of the iron-zinc-chromium brown pigment; in addition, the oxygen-containing groups of the modified nano-graphene oxide powder assist in adsorbing heavy metal ions based on electrostatic interaction, and cooperate with EDTA to further improve the reaction yield of heavy metal ions;

[0054] (2) In the mixed suspension obtained in step (1), 1 mol / L citric acid aqueous solution is added until the pH value reaches 5.0, and at the same time, ethylene glycol equivalent to 1% of the volume of the mixed suspension is added. The mixture is heated and stirred in a water bath at 90 °C with a stirring speed of 300 r / min for 6 h for gelation to obtain a gel. When the pH value is lower than 5.0 after adding the citric acid aqueous solution, the pH value is adjusted with 0.5 mol / L ammonia aqueous solution;

[0055] In the embodiments of the present invention, citric acid can coordinate with metal cations to form a gel; ethylene glycol, as a sol agent, can reduce agglomeration, improve the stability of the gel, and contribute to obtaining a uniform and transparent gel;

[0056] (3) Place the gel obtained in step (2) in a muffle furnace and first perform a pre-calcination treatment: under an argon atmosphere, heat it at a rate of 10 °C / min until the temperature reaches 400 °C, then keep it calcined for 3 h. Then, perform a high-temperature calcination treatment on the obtained precursor powder: under an argon atmosphere, heat it at a rate of 100 °C / min until the temperature reaches 1100 °C, and keep it calcined for 50 min to obtain iron-zinc-chromium brown powder;

[0057] In the embodiments of the present invention, a staged temperature-controlled calcination system is established to react and generate a spinel-structured zinc-iron-chromium oxide mixed-phase crystal, which can better control the crystal structure and properties of the iron-zinc-chromium brown pigment. Compared with direct high-temperature solid phase, the energy consumption is reduced and the environmental protection is improved; the pre-calcination treatment is a low-temperature and slow calcination of the gel obtained in step (2), which can fully remove organic substances and is beneficial to the formation of the crystal structure of the powder; the high-temperature calcination treatment is a rapid high-temperature calcination of the precursor powder obtained by the pre-calcination treatment to achieve phase transformation, complete crystal reconstruction, and form a more stable structure;

[0058] (4) Place the iron-zinc-chromium brown powder obtained in step (3) in a ball mill, where the diameter of the grinding balls is 20 mm, and the grinding balls are equivalent to 40% of the mass of the iron-zinc-chromium brown powder. Perform ball milling for 4 h at a rotation speed of 60 r / min, then add stearic acid equivalent to 1% of the mass of the iron-zinc-chromium brown powder, and then transfer them all to a blender and heat and stir at 80 °C and a stirring speed of 200 r / min for 2 h to obtain 1# iron-zinc-chromium brown pigment;

[0059] In the embodiments of the present invention, by optimizing the ball milling conditions, the particle size of the pigment particles is refined, so that the obtained iron-zinc-chromium brown pigment has a small particle size, no particle feeling, uniform quality, no color difference, and good dispersibility; by adding stearic acid to perform surface coating treatment on the pigment to reduce the surface energy of the iron-zinc-chromium brown pigment, a hydrophobic protective layer is formed to improve the hydrophobicity; while enhancing the water resistance of the iron-zinc-chromium brown pigment, the dispersibility of the pigment particles is also improved, avoiding particle agglomeration, and further enhancing the coloring power and covering power of the iron-zinc-chromium brown pigment; at the same time, for the iron-zinc-chromium brown pigment treated with stearic acid, metal ions are stabilized in the crystal structure, reducing heavy metal exposure and lowering the dissolution risk.

[0060] Example 2

[0061] (1) Add 60 g of zinc nitrate, 78 g of iron nitrate, and 96 g of chromium nitrate to 500 mL of water and dissolve them, then add 2.0 g of EDTA and 7.02 g of modified nano-graphene oxide powder, and perform a mixing treatment under ultrasonic conditions for 30 min to obtain a mixed suspension;

[0062] The preparation method of the modified nano-graphene oxide is as follows: 1) Polyvinylpyrrolidone solution and nano-graphene oxide are dispersed in water with a mass ratio of 0.8:5 and 1.5 times the total mass of the polyvinylpyrrolidone solution and nano-graphene oxide, and mixed under ultrasonic conditions to obtain a uniformly dispersed colloidal solution; 2) The same as step 2) of the preparation method of the modified nano-graphene oxide in Example 1;

[0063] (2) The same as step (2) of Example 1;

[0064] (3) The gel obtained in step (2) is placed in a muffle furnace for pre-calcination treatment: under an argon atmosphere, it is heated at a rate of 10 °C / min to 450 °C, held for calcination for 2.5 h, and then the obtained precursor powder is subjected to high-temperature calcination treatment: under an argon atmosphere, it is heated at a rate of 90 °C / min to 1200 °C, held for calcination for 40 min to obtain iron-zinc-chromium brown powder;

[0065] (4) The iron-zinc-chromium brown powder obtained in step (3) is placed in a ball mill, where the diameter of the grinding balls is 30 mm, and the grinding balls are 45% of the mass of the iron-zinc-chromium brown powder. It is ball-milled for 3 h at a rotation speed of 70 r / min, then stearic acid equivalent to 2% of the mass of the iron-zinc-chromium brown powder is added, and then transferred to a stirrer together. It is heated and stirred at 90 °C and a stirring speed of 400 r / min for 1.5 h to obtain 2# iron-zinc-chromium brown pigment.

[0066] Example 3

[0067] (1) 60 g of zinc nitrate, 84 g of iron nitrate and 102 g of chromium nitrate are added to 500 mL of water and dissolved, then 3.9 g of EDTA and 9.8 g of modified nano-graphene oxide powder are added, and mixed under ultrasonic conditions for 35 min to obtain a mixed suspension;

[0068] The preparation method of the modified nano-graphene oxide is as follows: 1) Polyvinylpyrrolidone solution and nano-graphene oxide are dispersed in water with a mass ratio of 1:4 and 2 times the total mass of the polyvinylpyrrolidone solution and nano-graphene oxide, and mixed under ultrasonic conditions to obtain a uniformly dispersed colloidal solution; 2) The same as step 2) of the preparation method of the modified nano-graphene oxide in Example 1;

[0069] (2) The same as step (2) of Example 1;

[0070] (3) The same as step (3) of Example 2;

[0071] (4) The same as step (4) of Example 2.

[0072] Example 4

[0073] (1) Dissolve 60 g of zinc nitrate, 90 g of iron nitrate, and 108 g of chromium nitrate in 500 mL of water. Then add 2.5 g of EDTA and 9.0 g of modified nano-graphene oxide powder, and mix and process under ultrasonic conditions for 35 min to obtain a mixed suspension;

[0074] The preparation method of the modified nano-graphene oxide is as follows: 1) Disperse polyvinylpyrrolidone solution and nano-graphene oxide in water with a mass ratio of 1.4:7 and a volume equivalent to 2 times the total mass of the polyvinylpyrrolidone solution and nano-graphene oxide, and mix under ultrasonic conditions to obtain a uniformly dispersed colloidal solution; 2) First, carry out a primary stirring reaction for 20 min on the uniformly dispersed colloidal solution obtained in step 1) under the conditions of 38 °C and a pH value of 7.6, and then carry out a secondary stirring reaction for 25 min under the conditions of 30 °C and a pH value of 6.8. After washing the reacted colloid 4 times successively with deionized water and ethanol, dry it at 70 °C to obtain the product;

[0075] (2) Add 2 mol / L citric acid aqueous solution to the mixed suspension obtained in step (1) until the pH value reaches 4.5. At the same time, add ethylene glycol equivalent to 0.8% of the volume of the mixed suspension, and carry out water bath heating and stirring at 85 °C and a stirring speed of 400 r / min for 5 h for gelation to obtain a gel; when the pH value is lower than 4.5 after adding the citric acid aqueous solution, adjust the pH value with 0.5 mol / L ammonia aqueous solution;

[0076] (3) Place the gel obtained in step (2) in a muffle furnace and first carry out pre-calcination treatment: under an argon atmosphere, heat and raise the temperature to 600 °C at a rate of 10 °C / min, then keep the temperature for calcination for 1 h. Then carry out high-temperature calcination treatment on the obtained precursor powder: under an argon atmosphere, heat and raise the temperature to 1300 °C at a rate of 80 °C / min, and then keep the temperature for calcination for 30 min to obtain iron zinc chromium brown powder;

[0077] (4) Place the iron zinc chromium brown powder obtained in step (3) in a ball mill, where the diameter of the grinding balls is 40 mm and the grinding balls are equivalent to 50% of the mass of the iron zinc chromium brown powder. Carry out ball milling treatment at a rotation speed of 80 r / min for 2 h, then add stearic acid equivalent to 3% of the mass of the iron zinc chromium brown powder, and then transfer them to a blender together. Heat and stir at 100 °C and a stirring speed of 600 r / min for 1 h to obtain 4# iron zinc chromium brown pigment.

[0078] Comparative Example 1

[0079] The difference between this comparative example and Example 3 is only that: in step (1), EDTA is not added. The rest is the same as in Example 3 to obtain 5# iron zinc chromium brown pigment.

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 3 is only that: in step (1), the modified nano-graphene oxide powder is not added. The rest is the same as in Example 3, and 6# iron-zinc-chromium brown pigment is obtained.

[0082] Comparative Example 3

[0083] The difference between this comparative example and Example 3 is only that: in step (4), stearic acid is not added for surface modification. The rest is the same as in Example 3, and 7# iron-zinc-chromium brown pigment is obtained.

[0084] Below, the commercially available Ranbar Brown I3660 iron-zinc-chromium brown pigment is used as the control group (labeled 0#), and the iron-zinc-chromium brown pigments obtained in Examples 1-4 and Comparative Examples 1-3 of the present invention (labeled 1#-7#) are used to conduct water resistance tests based on the regulations of GB / T5211.5-1985 "Method for Determining Water Resistance of Pigments"; based on the method of EPA3060A, dissolution solutions dissolved from pigments 0#-7# are respectively prepared, and whether there is heavy metal dissolution in the dissolution solution is determined by the diphenylcarbazide spectrophotometry method; the average particle size of the tested pigments and appearance observation are determined based on the microscopy method; the results are shown in Table 1.

[0085] Table 1 Performance comparison table of 0-7# iron-zinc-chromium brown pigments obtained from the control group, examples and comparative examples of the present invention

[0086]

[0087] Note: In the table, the higher the grade from 1 to 5 for water resistance, the better the water resistance.

[0088] As can be seen from Table 1, by comparing Example 3 of the present invention with Comparative Examples 1-3, it can be known that the method of the present invention can avoid the dissolution of heavy metal ions in the pigment by adding EDTA, thereby avoiding heavy metal pollution; by adding the modified nano-graphene oxide powder, a pigment product with uniform particle size, no color difference and no particle feeling can be obtained; by surface modification with stearic acid, the water resistance of the pigment can be significantly improved; in addition, since the modified nano-graphene oxide powder was not introduced in Comparative Example 2, trace heavy metal ions were detected in the dissolution test of the obtained pigment (6#), indicating that graphene has a synergistic effect of inhibiting the precipitation of heavy metals.

Claims

1. A preparation method of an environment-friendly iron zinc chromium brown pigment, characterized in that, It includes the following steps: (1) After adding a zinc source, an iron source, and a chromium source into water and dissolving them, add EDTA and modified nano-graphene oxide powder, and perform a mixing treatment under ultrasonic conditions to obtain a mixed suspension; the addition amount of the EDTA is equivalent to 0.3-2.4% of the total mass of the zinc source, the iron source, and the chromium source; the addition amount of the modified nano-graphene oxide powder is equivalent to 2-5% of the total mass of the zinc source, the iron source, and the chromium source; the modified nano-graphene oxide is obtained by blending polyvinylpyrrolidone and nano-graphene oxide; the mass ratio of the polyvinylpyrrolidone to the nano-graphene oxide is 0.5-1.5:4-7; The preparation method of the modified nano-graphene oxide is as follows: 1) Disperse the polyvinylpyrrolidone solution and nano-graphene oxide in water, and mix them under ultrasonic conditions to obtain a uniformly dispersed colloidal solution; 2) First perform a first stirring reaction on the uniformly dispersed colloidal solution obtained in step 1), then perform a second stirring reaction, wash the reacted colloid, and dry it to obtain the product; (2) In the mixed suspension obtained in step (1), add an aqueous acid solution until it is acidic, and at the same time add a sol agent, and perform gelation under heating and stirring conditions to obtain a gel; (3) First perform a pre-calcination treatment on the gel obtained in step (2), and then perform a high-temperature calcination treatment on the obtained precursor powder to obtain an iron-zinc-chromium brown powder; (4) After performing a ball milling treatment on the iron-zinc-chromium brown powder obtained in step (3), add stearic acid and perform heating and stirring to obtain an iron-zinc-chromium brown pigment; the addition amount of the stearic acid is equivalent to 1-3% of the mass of the iron-zinc-chromium brown powder.

2. The preparation method of the environment-friendly iron zinc chromium brown pigment according to claim 1, wherein: In step (1), the mass ratio of the zinc source, the iron source, and the chromium source is 1:1.2-1.5:1.5-2.0; the usage amount of the water is equivalent to 1.5-2.5 times the total mass of the zinc source, the iron source, and the chromium source; the mixing treatment time is 30-40 min; the zinc source includes zinc nitrate; the iron source includes iron nitrate; the chromium source includes chromium nitrate.

3. The preparation method of the environment-friendly iron zinc chromium brown pigment according to claim 1, characterized in that: In the preparation method of the modified nano-graphene oxide, in step 1), the usage amount of the water is equivalent to 1-2 times the total mass of the polyvinylpyrrolidone solution and nano-graphene oxide; in step 2), the temperature of the first stirring reaction is 32-38 °C, the pH value is 7.6-8.0, and the time is 20-30 min; the temperature of the second stirring reaction is 25-30 °C, the pH value is 6.8-7.2, and the time is 15-30 min; wash it 3-4 times with deionized water and ethanol successively; the drying temperature is 50-70 °C.

4. The preparation method of the environment-friendly iron zinc chromium brown pigment according to claim 1 or 2, characterized in that: In step (2), add an aqueous acid solution until the pH value is 4-6; the concentration of the aqueous acid solution is 1-2 mol / L; the aqueous acid solution includes a citric acid aqueous solution; the addition amount of the sol agent is equivalent to 0.5-1.0% of the volume of the mixed suspension; the sol agent includes ethylene glycol; the gelation temperature is 85-95 °C, the stirring speed is 200-400 r / min, and the time is 4-8 h.

5. The preparation method of the environment-friendly iron zinc chromium brown pigment according to claim 1 or 2, characterized in that: In step (3), the conditions for the pre-calcination treatment are as follows: under a protective atmosphere, at a rate of 5-15 °C / min, heat up to 400-600 °C, and then hold for calcination for 1-3 h; the conditions for the high-temperature calcination treatment are as follows: under a protective atmosphere, at a rate of 50-150 °C / min, heat up to 1100-1300 °C, and then hold for calcination for 30-50 min; the protective atmosphere includes nitrogen and / or argon.

6. The preparation method of the environment-friendly iron zinc chromium brown pigment according to claim 1 or 2, characterized in that: In step (4), the diameter of the grinding balls used in the ball milling treatment is 20-40 mm, and the grinding balls are equivalent to 40-50% of the mass of the iron-zinc-chromium brown powder; the rotation speed of the ball milling treatment is 60-80 r / min, and the time is 2-4 h; the temperature of the heating and stirring is 80-100 °C, the stirring speed is 200-600 r / min, and the time is 1-2 h.

Images