Binder for iron powder production

Abstract

This application relates to the field of iron powder binder technology, specifically disclosing a binder for iron powder production. It is prepared by mixing raw materials comprising the following parts by weight: 50-70 parts of binder active component, 20-30 parts of water, 5-8 parts of ammonium dihydrogen phosphate, and 3-5 parts of sodium carboxymethyl cellulose; wherein the binder active component is obtained by grafting a composite product with acrylic acid and then polymerizing it. Cold-pressed iron powder pellets produced using the binder of this application exhibit a drop strength > 7.6 times, a green pellet compressive strength > 41.2 daN, and a calcined pellet compressive strength > 238.8 daN, meeting practical application requirements.

Description

Technical Field

[0001] This application relates to the field of iron powder binder technology, and more specifically, it relates to a binder for iron powder production. Background Technology

[0002] In the iron powder smelting process, in order to improve the physical properties of the raw materials and the efficiency of subsequent processing, the iron powder is usually subjected to cold pressing treatment. The loose iron powder particles are compressed into clumps by mechanical pressure, which creates favorable conditions for subsequent reduction or smelting processes.

[0003] In the cold pressing stage of iron powder processing, a binder needs to be added to firmly bond the iron powder particles together, forming a stable pellet structure. Industrially used iron powder binders are divided into organic and inorganic binders. Among inorganic binders, sodium silicate has significant advantages due to its high-temperature resistance and excellent wetting properties. During use, the sodium silicate solution spreads on the surface of the iron powder particles, forming a physical adsorption layer through van der Waals forces, thus achieving a bonding effect. However, this bonding effect relies on the hydrolytic cross-linking of sodium silicate. The cold pressing environment, to some extent, limits the cross-linking reaction of sodium silicate, resulting in generally low initial strength in cold-pressed pellets made using sodium silicate binders, making the pellets prone to cracking.

[0004] Chinese patent application CN105219956A discloses a method for preparing a composite binder for cold-pressed iron powder pellets. The method involves combining a silicate binder with organic components such as pregelatinized starch and adding additives to improve the bonding strength of the cold-pressed iron powder pellets through a combined effect. At the same time, due to the characteristic that the organic components can be removed in subsequent heat treatment, the grade of the pellets can be improved.

[0005] In the above scheme, although the bonding strength of the pellets can be improved by combining the components of the composite binder, the blending method is difficult to achieve a combined effect of improving the initial bonding strength of the pellets. Furthermore, since a large amount of inorganic components are introduced into the binder components, they will still have a significant impact on the pellet grade. Therefore, it is necessary to find an iron powder binder formulation that can improve the initial bonding strength of cold-pressed pellets while reducing the introduction of inorganic impurities. Summary of the Invention

[0006] To further improve the initial bonding strength of cold-pressed pellets and reduce the residual inorganic impurities in the binder, this application provides a binder for iron powder production, employing the following technical solution:

[0007] A binder for iron powder production is prepared by mixing raw materials comprising the following parts by weight: 50-70 parts of binder active component, 20-30 parts of water, 5-8 parts of ammonium dihydrogen phosphate, and 3-5 parts of sodium carboxymethyl cellulose; wherein the preparation steps of the binder active component include the following:

[0008] [S01] Take the pre-liquid, mix it with chitosan microspheres, degas under reduced pressure, then restore normal pressure, let it stand, take the solid part, disperse it with an oily sealing agent, then add acid and stir, let it stand again, centrifuge at low speed, take the bottom precipitate, wash and dry it to obtain the composite product;

[0009] [S02] Take the composite product, add a mixed solvent, disperse, heat and purge with nitrogen, then add acrylic monomer for the first time, add crosslinking agent, react, then add acrylic monomer to initiate treatment, then adjust the pH to 7, filter to take the precipitate, wash with water and dry to obtain the binding active component;

[0010] The pre-solution is obtained by dissolving sodium silicate, aluminum silicate, borax and sodium hydroxide in water and then treating them.

[0011] By adopting the above technical solution, the active binder component can exert a binding effect in both cold-pressing pelletizing and subsequent heat treatment stages. The active binder component is prepared by grafting a composite product with polyacrylic acid; wherein, the composite product is obtained by reacting chitosan with epichlorohydrin in a chitosan "water-in-oil" emulsion to obtain chitosan microspheres, and the microspheres are then subjected to vacuum encapsulation pre-liquidation and pore sealing treatment. The pre-liquid inside the chitosan microspheres is mainly composed of sodium silicate hydrate, which is used to maintain the stability of the pellets during the hot-melt stage. During use, the outer layer of polyacrylic acid in the binder's active component bonds with the oxide layer on the surface of iron powder through hydrogen and covalent bonds. Simultaneously, its growing chain structure can penetrate the gaps between iron powder particles, ultimately improving the stability of the initial structure of the cold-pressed pellets through chemical bonding and physical entanglement. During subsequent heat treatment of the cold-pressed pellets, the sealing structure of the binder's active component breaks down during the initial heating stage. The pre-liquid embedded in the chitosan microspheres rapidly leaks and overflows along the microsphere channels, quickly condensing into a network under heat, thus maintaining the structural stability of the cold-pressed pellets during the heat treatment stage. As heating continues, the organic matter in the binder's active component decomposes into carbon components, providing a carbon source for the pellet heat treatment. This carbon is also released with the hot melt exhaust gas during the process, reducing the influence of the binder component on the grade of the cold-pressed pellets.

[0012] Preferably, in step [S01], the preparation steps of chitosan microspheres include the following: taking a chitosan solution, treating it in a water bath, then adding n-hexane, treating it by high-speed shearing, then adding epichlorohydrin with a mass concentration of 10%, reacting, and then obtaining chitosan microspheres after leaching and low-temperature centrifugation.

[0013] The chitosan solution was obtained by mixing chitosan, deionized water and glacial acetic acid in a mass-volume ratio of (0.8-1) g: 100 ml: (0.5-0.7) ml.

[0014] The degree of deacetylation of the chitosan is 50%.

[0015] The volume ratio of the chitosan solution, n-hexane, and epichlorohydrin with a mass concentration of 10% is 100:(70-80):(10-12).

[0016] The high-speed shearing process is as follows: adjust the rotation speed to 5000-8000 rpm and process for 15-25 minutes;

[0017] The leaching and low-temperature centrifugation process is as follows: add five times the volume of chitosan solution to the solution of anhydrous ethanol, treat for 3-5 hours, then adjust the temperature to 3-4℃, adjust the centrifugation speed to 3000-5000 rpm, and treat for 10-20 minutes.

[0018] By adopting the above technical solution, chitosan solution is used as the aqueous phase and hexane as the oil phase. After high-speed shear emulsification, an oil-in-water emulsion can be obtained. Subsequently, epichlorohydrin diffuses through the oil phase and reacts with functional groups such as amino groups on the chitosan dispersed in the aqueous phase to form a cross-linked network, ultimately yielding spherical chitosan. The addition of anhydrous ethanol for leaching can remove the oil phase and unreacted impurities through solvent replacement. Subsequent low-temperature auxiliary treatment can further promote the formation of the cavity structure.

[0019] Preferably, in step [S01], the degassing treatment is performed by: reducing the pressure of the container to 0.1-0.3 MPa, adjusting the magnetic stirring speed to 75 rpm, and treating for 3-4 hours;

[0020] The oily sealing agent is obtained by mixing white mineral oil, n-hexanol and Tween-20 in a mass-volume ratio of (40-50) ml: 10 ml: (0.5-1) g;

[0021] The acid addition and stirring process is as follows: add 0.05 mol / L hydrochloric acid at a rate of 1-1.5 ml / min, adjust the magnetic stirring speed to 50 rpm, and stir for 40-60 min before stopping the stirring.

[0022] By employing the above technical solution, this section describes the pre-solvent embedding and post-sealing treatment of chitosan cavity structures. The pre-solvent is replenished into the cavity under reduced pressure and degassing conditions. Then, an oily sealing agent is temporarily dispersed around the chitosan microspheres to form an oily protective layer, preventing premature overflow of the pre-solvent from the cavity structure during treatment. Subsequently, a dilute acid solution is added for further treatment. The acid, permeating the oil layer, promotes the condensation and cross-linking of sodium silicate in the pre-solvent on the surface of the chitosan microspheres, sealing the exposed pores of the microspheres.

[0023] Preferably, in step [S02], the mixed solvent is obtained by mixing ethanol and acetic acid with a mass concentration of 0.5% at a volume ratio of (0.5-1):1;

[0024] The crosslinking agent is obtained by mixing cerium ammonium nitrate and ethylenediaminetetraacetic acid (EDTA) with a mass concentration of 3% at a mass-to-volume ratio of (0.2-0.3) g:(1-1.2) ml;

[0025] The mass ratio of the composite product, the initial addition of acrylic monomer to the supplementary addition of acrylic monomer is (10-15):1:(5-6).

[0026] By employing the above technical solution, a polyacrylic acid extended chain structure can be obtained on the surface of chitosan microspheres. Under the action of a crosslinking agent, the initial addition of a small amount of acrylic acid monomer can react with chitosan through an initiation reaction to achieve preliminary composite formation; subsequent addition of acrylic acid monomers continues the reaction, ultimately resulting in a polyacrylic acid extended chain on the chitosan microspheres.

[0027] In summary, this application has the following beneficial effects:

[0028] 1. In this application, the active component of the binder is preferably obtained by grafting the composite product with polyacrylic acid. During the cold pressing of iron powder into pellets, the outer polyacrylic acid of the composite product can improve the stability of the initial structure of the cold-pressed pellets through bonding and physical entanglement. During the heat treatment of the cold-pressed pellets, the organic components in the active component of the binder decompose into carbon-containing substances, providing a carbon source for the reduction of iron powder, and are released with the hot melt tail gas during the process, reducing the impact of the binder introduction on the grade of the cold-pressed pellets.

[0029] 2. This application obtains chitosan microspheres with a cavity structure through epichlorohydrin and chitosan emulsion polymerization reaction. Then, pre-liquid is embedded in the cavity through treatment. In the early stage of heat treatment of cold-pressed pellets, the pre-liquid inside the microspheres leaks out and rapidly condenses into a network to wrap the pellet powder under the action of heat, thus maintaining the overall structural stability of the cold-pressed pellets.

[0030] 3. Cold-pressed pellets prepared using the binder for iron powder production of this application have a drop strength > 7.6 times, a green pellet compressive strength > 41.2 daN, and a calcined pellet compressive strength > 238.8 daN, which meets the requirements of practical applications. Attached Figure Description

[0031] Figure 1 The results are SEM scans of chitosan microspheres from Example 2 of this application.

[0032] Figure 2 The results are the pellet drop strength test results of the test samples of Examples 1-5 and Comparative Examples 1-2 of this application.

[0033] Figure 3 The results are the compressive strength test results of raw / cooked balls for the test samples of Examples 1-5 and Comparative Examples 1-2 of this application. Detailed Implementation

[0034] Preparation Example 1

[0035] Take 100 ml of chitosan solution, adjust the magnetic stirring speed to 100 rpm, and treat it in a 40℃ water bath for 2 h. Then mix it with 70 ml of n-hexane, and treat it for 15 min using a high-speed emulsifier at 5000 rpm. Then slowly add 10 ml of 10% epichlorohydrin solution to the system at a rate of 2 ml / min, readjust the magnetic stirring speed to 50 rpm, and react for 5 h. Then add 500 ml of anhydrous ethanol and continue treatment for 3 h. Then lower the system temperature to 3℃, adjust the centrifugation speed to 3000 rpm and treat for 10 min. Then take the bottom precipitate, wash it three times with anhydrous ethanol, and dry it under vacuum at 35℃ to obtain chitosan microspheres.

[0036] Mix 60g sodium silicate, 15g aluminum silicate, 3g borax, 0.3g sodium hydroxide, and 22.5g deionized water. Adjust the magnetic stirring speed to 250 rpm and treat for 5 min. Then add 7.5g chitosan microspheres, reduce the container pressure to 0.1 MPa, adjust the magnetic stirring speed to 75 rpm, treat for 3 h, restore to normal pressure, and let stand for another 3 h. Then take the solid part and add it to 50 ml of oily sealing agent. Adjust the magnetic stirring speed to 100 rpm and stir for 5 min. Reduce the stirring speed to 50 rpm and add 10 ml of 0.05 mol / L hydrochloric acid to the system at a rate of 1 ml / min. Stir for 40 min and then stop stirring. Let stand for 30 min, then centrifuge at 1000 rpm. Take the bottom precipitate, wash twice with alcohol, and let stand overnight at room temperature. After drying, the composite product is obtained.

[0037] The chitosan solution was prepared by mixing chitosan (50% deacetylation), deionized water, and glacial acetic acid in a mass-to-volume ratio of 0.8g:100ml:0.5ml. The oily sealing agent was prepared by mixing white mineral oil, n-hexanol, and Tween-20 in a mass-to-volume ratio of 40ml:10ml:0.5g.

[0038] Preparation Example 2

[0039] Take 100 ml of chitosan solution, adjust the magnetic stirring speed to 100 rpm, and treat it in a 45℃ water bath for 2 h. Then mix it with 75 ml of n-hexane, and treat it for 15 min using a high-speed emulsifier at 8000 rpm. Then slowly add 10 ml of 10% epichlorohydrin solution to the system at a rate of 2 ml / min, readjust the magnetic stirring speed to 50 rpm, and react for 5 h. Then add 500 ml of anhydrous ethanol and continue treatment for 3 h. Then lower the system temperature to 4℃, adjust the centrifugation speed to 3000 rpm and treat for 15 min. Then take the bottom precipitate, wash it three times with anhydrous ethanol, and dry it under vacuum at 35℃ to obtain chitosan microspheres.

[0040] Mix 75g sodium silicate, 16g aluminum silicate, 4g borax, 0.4g sodium hydroxide, and 25g deionized water. Adjust the magnetic stirring speed to 300 rpm and treat for 15 min. Then add 8g chitosan microspheres, reduce the container pressure to 0.2 MPa, adjust the magnetic stirring speed to 75 rpm, treat for 4 h, restore to normal pressure, and let stand for 3 h. Then take the solid part and add it to 50 ml of oily sealing agent. Adjust the magnetic stirring speed to 100 rpm and stir for 10 min. Reduce the stirring speed to 50 rpm and add 10 ml of 0.05 mol / L hydrochloric acid to the system at a rate of 1.2 ml / min. Stir for 60 min and then stop stirring. Let stand for 30 min, then centrifuge at 1000 rpm. Take the bottom precipitate, wash it three times with alcohol, and let it stand overnight at room temperature. After drying, the composite product is obtained.

[0041] The chitosan solution was prepared by mixing chitosan (50% deacetylation), deionized water, and glacial acetic acid in a mass-volume ratio of 1g:100ml:0.6ml. The oily sealing agent was prepared by mixing white mineral oil, n-hexanol, and Tween-20 in a mass-volume ratio of 45ml:10ml:0.75g.

[0042] Preparation Example 3

[0043] Take 100 ml of chitosan solution, adjust the magnetic stirring speed to 100 rpm, and treat it in a 50℃ water bath for 3 h. Then mix it with 80 ml of n-hexane, and treat it for 25 min using a high-speed emulsifier at 8000 rpm. Then slowly add 12 ml of 10% epichlorohydrin solution to the system at a rate of 3 ml / min, readjust the magnetic stirring speed to 50 rpm, and react for 8 h. Then add 500 ml of anhydrous ethanol and continue treatment for 5 h. Then lower the system temperature to 4℃, adjust the centrifugation speed to 5000 rpm and treat for 20 min. Then take the bottom precipitate, wash it three times with anhydrous ethanol, and dry it under vacuum at 35℃ to obtain chitosan microspheres.

[0044] Mix 90g sodium silicate, 18g aluminum silicate, 4.5g borax, 0.45g sodium hydroxide, and 30g deionized water. Adjust the magnetic stirring speed to 300rpm and treat for 20min. Then add 8g chitosan microspheres, reduce the container pressure to 0.3MPa, adjust the magnetic stirring speed to 75rpm, treat for 4h, restore normal pressure, and let stand for another 4h. Then take the solid part and add it to 50ml of oily sealing agent. Adjust the magnetic stirring speed to 100rpm and stir for 10min. Reduce the stirring speed to 50rpm and add 10ml of 0.05mol / L hydrochloric acid to the system at a rate of 1.5ml / min. Stir for 60min and then stop stirring. Let stand for 30min, then centrifuge at 1000rpm. Take the bottom precipitate, wash it three times with alcohol, and let it stand overnight at room temperature. After drying, the composite product is obtained.

[0045] The chitosan solution was prepared by mixing chitosan (50% deacetylation), deionized water, and glacial acetic acid in a mass-volume ratio of 1g:100ml:0.7ml. The oily sealing agent was prepared by mixing white mineral oil, n-hexanol, and Tween-20 in a mass-volume ratio of 50ml:10ml:1g.

[0046] Example 1

[0047] In this embodiment, the preparation steps of the binder for iron powder production are as follows:

[0048] Take 50g of binder active component, 20g of deionized water, 5g of ammonium dihydrogen phosphate and 3g of sodium carboxymethyl cellulose, mix them, adjust the magnetic stirring speed to 100rpm, and process for 5min to obtain the final product.

[0049] In this embodiment, the preparation steps of the active component of the binder are as follows:

[0050] Take 5g of the composite product, add 50ml of mixed solvent, and immediately adjust the magnetic stirring speed to 100rpm. Treat for 5min, then raise the system temperature to 45℃, purge the air with nitrogen, add 0.5g of acrylic monomer and 0.2g of cerium ammonium nitrate to the system, and then add 1ml of 3% ethylenediaminetetraacetic acid dropwise at a rate of 1ml / min. Treat for 1h, then add 2.5g of acrylic monomer, 0.1g of methylenebisacrylamide and 0.1g of ammonium persulfate to the system, adjust the temperature to 50℃, and treat for 2h. Then adjust the pH to 7 with 0.1mol / L sodium hydroxide solution, filter the precipitate, wash twice with water, and dry in an oven at 35℃ for 3h to obtain the active component of the binder.

[0051] The composite product in this embodiment was prepared by Preparation Example 1.

[0052] The mixed solvent is obtained by mixing ethanol and acetic acid with a mass concentration of 0.5% at a volume ratio of 0.5:1.

[0053] Example 2

[0054] In this embodiment, the preparation steps of the binder for iron powder production are as follows:

[0055] Take 60g of binder active component, 25g of deionized water, 5g of ammonium dihydrogen phosphate and 4g of sodium carboxymethyl cellulose, mix them, adjust the magnetic stirring speed to 200rpm, and process for 10min to obtain the final product.

[0056] In this embodiment, the preparation steps of the active component of the binder are as follows:

[0057] Take 6g of the composite product, add 50ml of mixed solvent, and immediately adjust the magnetic stirring speed to 100rpm. Treat for 5min, then raise the system temperature to 45℃, purge the air with nitrogen, add 0.5g of acrylic monomer and 0.25g of cerium ammonium nitrate to the system, then add 1ml of 3% ethylenediaminetetraacetic acid dropwise at a rate of 1ml / min. Treat for 1.5h, then add 2.5g of acrylic monomer, 0.1g of methylenebisacrylamide and 0.1g of ammonium persulfate to the system, adjust the temperature to 50℃, and treat for 2h. Then adjust the pH to 7 with 0.1mol / L sodium hydroxide solution, filter the precipitate, wash twice with water, and dry in an oven at 35℃ for 3h to obtain the active component of the binder.

[0058] The composite product in this embodiment was prepared in Preparation Example 2.

[0059] The mixed solvent is obtained by mixing ethanol and acetic acid with a mass concentration of 0.5% at a volume ratio of 1:1.

[0060] Example 3

[0061] In this embodiment, the preparation steps of the binder for iron powder production are as follows:

[0062] Take 65g of binder active component, 30g of deionized water, 7g of ammonium dihydrogen phosphate and 5g of sodium carboxymethyl cellulose, mix them, adjust the magnetic stirring speed to 300rpm, and process for 15min to obtain the final product.

[0063] In this embodiment, the preparation steps of the active component of the binder are as follows:

[0064] Take 7.2g of the composite product, add 50ml of mixed solvent, and immediately adjust the magnetic stirring speed to 100rpm for 5min. Then raise the system temperature to 50℃, purge the air with nitrogen, add 0.5g of acrylic monomer and 0.3g of cerium ammonium nitrate to the system, and then add 1.1ml of 3% ethylenediaminetetraacetic acid dropwise at a rate of 1ml / min for 1.5h. Then add 3g of acrylic monomer, 0.1g of methylenebisacrylamide and 0.15g of ammonium persulfate to the system, adjust the temperature to 60℃, and treat for 2.5h. Then adjust the pH to 7 with 0.1mol / L sodium hydroxide solution, filter the precipitate, wash twice with water, and dry in an oven at 35℃ for 3h to obtain the active component of the binder.

[0065] The composite product in this embodiment was prepared by Preparation Example 3.

[0066] The mixed solvent is obtained by mixing ethanol and acetic acid with a mass concentration of 0.5% at a volume ratio of 0.5:1.

[0067] Example 4

[0068] In this embodiment, the preparation steps of the binder for iron powder production are as follows:

[0069] Take 70g of binder active component, 30g of deionized water, 8g of ammonium dihydrogen phosphate and 5g of sodium carboxymethyl cellulose, mix them, adjust the magnetic stirring speed to 300rpm, and process for 20min to obtain the final product.

[0070] In this embodiment, the preparation steps of the active component of the binder are as follows:

[0071] Take 7.5g of the composite product, add 50ml of mixed solvent, and immediately adjust the magnetic stirring speed to 100rpm for 5min. Then raise the system temperature to 50℃, purge the air with nitrogen, add 0.5g of acrylic monomer and 0.3g of cerium ammonium nitrate to the system, and then add 1.2ml of 3% ethylenediaminetetraacetic acid dropwise at a rate of 2ml / min for 2h. Then add 3g of acrylic monomer, 0.2g of methylenebisacrylamide and 0.15g of ammonium persulfate to the system, adjust the temperature to 60℃, and treat for 2.5h. Then adjust the pH to 7 with 0.1mol / L sodium hydroxide solution, filter the precipitate, wash it 3 times with water, and dry it in an oven at 35℃ for 3h to obtain the active component of the binder.

[0072] The composite product in this embodiment was prepared in Preparation Example 2.

[0073] The mixed solvent is obtained by mixing ethanol and acetic acid with a mass concentration of 0.5% at a volume ratio of 1:1.

[0074] Example 5

[0075] The only difference between this embodiment and Embodiment 1 is that the preparation steps of the active adhesive component are as follows:

[0076] Take 7.5g of the composite product, add 50ml of mixed solvent, and immediately adjust the magnetic stirring speed to 100rpm. Treat for 5min, then raise the system temperature to 50℃, purge the air with nitrogen, add 0.5g of acrylic monomer and 0.3g of cerium ammonium nitrate to the system, and then add 1.2ml of 3% ethylenediaminetetraacetic acid dropwise at a rate of 2ml / min. Treat for 2h, then add 3g of acrylic monomer, 0.2g of methylenebisacrylamide and 0.1g of ammonium persulfate to the system, adjust the temperature to 55℃, and treat for 2h. Then adjust the pH to 7 with 0.1mol / L sodium hydroxide solution, filter the precipitate, wash it 3 times with water, and dry it in an oven at 35℃ for 3h to obtain the active component of the binder.

[0077] The composite product in this embodiment was prepared by Preparation Example 3.

[0078] The mixed solvent is obtained by mixing ethanol and acetic acid with a mass concentration of 0.5% at a volume ratio of 1:1.

[0079] The remaining steps are the same as in Example 1.

[0080] Comparative Example 1

[0081] The only difference between this comparative example and Example 1 is that the preparation steps of the active adhesive component are as follows:

[0082] Take 7.5g of the composite product and mix it with 6g of polyacrylic acid to obtain the active component of the adhesive.

[0083] The polyacrylic acid (molecular weight 20,000) was supplied by Guangdong Wengjiang Chemical Reagent Co., Ltd.

[0084] The remaining steps are the same as in Example 1.

[0085] Comparative Example 2

[0086] The only difference between this comparative example and Example 1 is that the preparation steps of the binder for iron powder production are as follows:

[0087] Mix 15g of water glass, 10g of aluminum phosphate, 80g of deionized water, 2g of polyacrylamide and 5g of sodium carboxymethyl cellulose, adjust the magnetic stirring speed to 300rpm, and process for 20min to obtain the final product.

[0088] The remaining steps are the same as in Example 1.

[0089] Performance testing

[0090] 1. SEM testing

[0091] The chitosan microspheres prepared in Example 2 were subjected to SEM scanning tests, and the test results are as follows: Figure 1 As shown.

[0092] 2. Pellet strength test

[0093] Pretreatment: A briquetting machine was used, with the linear pressure ratio adjusted to 5t / cm, and the briquetting diameter to be 20±5mm. The raw material for briquetting was iron powder (average particle size of 20 micrometers). The binder for iron powder production from Examples 1-5 and Comparative Examples 1-2 was added to the briquetting machine at a liquid-to-material ratio of 1:75. The briquetting process was carried out for 10 minutes, and the resulting iron powder pellets were air-dried overnight under natural conditions to obtain the test samples.

[0094] 2.1 Drop Strength Test of Pellet

[0095] The test samples from Examples 1-5 and Comparative Examples 1-2 were placed on a test platform with a steel plate at the bottom and released from a height of 0.5m to allow the pellets to fall freely. If the pellets break after n drops, the drop strength of the pellets is (n-1) drops. The same group of test samples was tested 5 times, and the test data were recorded. The test results are as follows: Figure 2 As shown.

[0096] 2.2 Pellet compressive strength test

[0097] (1) Test of compressive strength of green pellets: According to the test method of GB / T14201-2018 "Determination of compressive strength of cold-pressed pellets for blast furnace and direct reduction", the compressive strength of the test samples of Examples 1-5 and Comparative Examples 1-2 was measured using a compressive strength tester. Each group of test samples was measured 5 times, and the compressive strength test data was recorded. The average value was taken as the final data.

[0098] (2) Test of compressive strength of cooked balls: The test samples of Examples 1-5 and Comparative Examples 1-2 were placed in a tube furnace, protected by nitrogen, and the temperature was controlled at 1250℃. The samples were roasted for 30 minutes, then cooled to room temperature and the heating was stopped. After overnight at room temperature, the compressive strength was tested using a compressive strength tester. Each group of test samples was tested 5 times, and the compressive strength test data were recorded. The average value was taken as the final data.

[0099] The test results of (1) and (2) are as follows Figure 3 As shown.

[0100] Analysis of Example 2 and in conjunction with Figure 1 It can be seen that by using hexane as the oil phase and chitosan dilute solution as the aqueous phase component, after epichlorohydrin crosslinking, leaching and low-temperature centrifugation, the obtained chitosan product has a spherical structure and has pores on the surface, which can provide a carrier for subsequent pre-liquid assembly.

[0101] Analysis of Examples 1-5 and Comparative Examples 1-2 in conjunction with Figure 2 and Figure 3 It can be seen that, in terms of strength properties, the embodiment scheme shows a significantly better effect than the comparative example scheme; in drop and green pellet compressive strength tests, the embodiment and comparative examples show the same trend; among them, the pellets of comparative example 2 have the worst impact and compressive strength; this is because, in the binder formulation used in comparative example 2, the bonding mainly relies on the gelation effect of sodium silicate initial hydrolysis and the capillary effect of the liquid phase film, and its force is relatively weak, so it does not bond the cold-pressed pellets firmly; while in the embodiment scheme, the polyacrylic acid chains are combined with the cold-pressed pellets through physical entanglement and bonding, resulting in better bonding of the cold-pressed pellets; comparative example 1 only uses a blending combination, and its effect is not as good as the embodiment scheme. In the compressive strength test of the cooked balls, Comparative Example 1 showed a reverse trend in strength, which is different from the trend of strength property changes in other test groups. This is because after the test samples were subjected to high-temperature heat treatment in a tube furnace, the organic components in the binder decomposed, thus losing their adhesive effect. Comparative Example 1, due to its high proportion of organic components, had the worst compressive strength after heat treatment. However, due to the combined effect of the active components of the binder in the early and late stages, the compressive strength of the cooked balls in the Example 2 was still better than that of Comparative Example 2, even after heat treatment.

[0102] Analysis of Examples 1-5 and Comparative Examples 1-2 in conjunction with Figure 2 and Figure 3 It can be seen that among all test groups, the solution in Example 2 has the best effect and meets the needs of practical applications.

[0103] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A binder for iron powder production, characterized in that, It is prepared by mixing raw materials comprising the following parts by weight: 50-70 parts of binder active component, 20-30 parts of water, 5-8 parts of ammonium dihydrogen phosphate, and 3-5 parts of sodium carboxymethyl cellulose; wherein the preparation steps of the binder active component include the following: [S01] Take the pre-liquid, mix it with chitosan microspheres, degas under reduced pressure, then restore normal pressure, let it stand, take the solid part, disperse it with an oily sealing agent, then add acid and stir, let it stand again, centrifuge at low speed, take the bottom precipitate, wash and dry it to obtain the composite product; [S02] Take the composite product, add a mixed solvent, disperse, heat and purge with nitrogen, then add acrylic monomer for the first time, add crosslinking agent, react, then add acrylic monomer to initiate treatment, then adjust the pH to 7, filter to take the precipitate, wash with water and dry to obtain the binding active component; The pre-solution is obtained by dissolving sodium silicate, aluminum silicate, borax and sodium hydroxide in water and then treating them.

2. The binder for iron powder production according to claim 1, characterized in that, In step [S01], the preparation steps of chitosan microspheres include the following: taking chitosan solution, treating it in a water bath, then adding n-hexane, treating it by high-speed shearing, then adding epichlorohydrin with a mass concentration of 10%, reacting, and then obtaining chitosan microspheres after leaching and low-temperature centrifugation.

3. The binder for iron powder production according to claim 2, characterized in that, The chitosan solution was obtained by mixing chitosan, deionized water and glacial acetic acid in a mass-volume ratio of (0.8-1) g: 100 ml: (0.5-0.7) ml. The volume ratio of the chitosan solution, n-hexane, and epichlorohydrin with a mass concentration of 10% is 100:(70-80):(10-12). The high-speed shearing process is as follows: adjust the rotation speed to 5000-8000 rpm and process for 15-25 minutes.

4. The binder for iron powder production according to claim 2, characterized in that, The leaching and low-temperature centrifugation process is as follows: add five times the volume of chitosan solution to the solution of anhydrous ethanol, treat for 3-5 hours, then adjust the temperature to 3-4℃, adjust the centrifugation speed to 3000-5000 rpm, and treat for 10-20 minutes.

5. The binder for iron powder production according to claim 1, characterized in that, In step [S01], the degassing treatment is performed by reducing the pressure of the container to 0.1-0.3 MPa, adjusting the magnetic stirring speed to 75 rpm, and treating for 3-4 hours.

6. The binder for iron powder production according to claim 1, characterized in that, In step [S01], the oily sealing agent is obtained by mixing white mineral oil, n-hexanol and Tween-20 in a mass-volume ratio of (40-50) ml: 10 ml: (0.5-1) g.

7. The binder for iron powder production according to claim 1, characterized in that, In step [S01], the acid addition and stirring process is as follows: add 0.05mol / L hydrochloric acid at a rate of 1-1.5ml / min, adjust the magnetic stirring speed to 50rpm, and stop stirring after stirring for 40-60min.

8. The binder for iron powder production according to claim 1, characterized in that, In step [S02], the mixed solvent is obtained by mixing ethanol and acetic acid with a mass concentration of 0.5% in a volume ratio of (0.5-1):

1.

9. The binder for iron powder production according to claim 1, characterized in that, In step [S02], the crosslinking agent is obtained by mixing cerium ammonium nitrate and ethylenediaminetetraacetic acid with a mass concentration of 3% at a mass-volume ratio of (0.2-0.3) g: (1-1.2) ml.

10. The binder for iron powder production according to claim 1, characterized in that, In step [S02], the mass ratio of the composite product, the initially added acrylic monomer, and the supplemented acrylic monomer is (10-15):1:(5-6).

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