CN111233012B - Electrical-grade magnesium oxide powder and preparation method thereof - Google Patents
Electrical-grade magnesium oxide powder and preparation method thereof Download PDFInfo
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Abstract
The application discloses electrician's level magnesium oxide powder, electrician's level magnesium oxide powder's inside is magnesium oxide, the outside of magnesium oxide powder is the silica coating. The electrical-grade magnesium oxide powder has excellent hydrophobicity and durability.
Description
Technical Field
The application relates to electrical-grade magnesium oxide powder and a preparation method thereof, belonging to the field of material preparation.
Background
The electric-grade magnesia powder has excellent insulativity and heat conductivity, and is mainly used for manufacturing electric appliance elements with heating function. The raw materials of the electric-grade magnesia powder mainly come from electric-melting magnesia, the electric-melting magnesia in the market has low magnesia content, large moisture absorption rate, high hydration rate and easy moisture absorption, can damage the electrical performance of an electric heating element after being used, is easy to leak electricity and even explode tubes, and has great potential safety hazard.
At present, patent US20080248263 discloses a method for loading a super-hydrophilic or super-hydrophobic membrane on a substrate, and mainly depends on a chemical vapor spraying mode to react on the particle surface to form films with different properties, so that the substrate achieves the super-hydrophobic or super-hydrophilic effect. Patent US4677026 discloses a method for preparing moisture-proof electrical magnesium oxide powder, wherein 600 ℃ organosilicon steam is introduced into a fluidized bed containing electric melting magnesium oxide, and the organosilicon is pyrolyzed and then covers the surface of electric melting magnesium oxide particles, thereby forming a moisture-proof insulating electrical magnesium oxide powder product. Patent US5254411 discloses a high temperature resistant magnesium oxide material with strong hydrophobicity and a preparation method thereof, which is characterized in that silazane and organosilicon polymer are used, and two silicon-containing coatings are formed on the outer surface of magnesium oxide under the roasting process for more than two times, so that the insulation purpose is finally achieved.
China has developed to become a manufacturing base of global household appliances, and simultaneously, the fields of the heavy industry and the aerospace production are gradually expanded, and simultaneously, China is also a production base of the electric heating insulating material. However, the prior art is backward, equipment is not too much, so that the electrical grade magnesium oxide produced in China is high in cost and low in product quality, and generally mainly comprises medium-low temperature magnesium oxide powder. Therefore, the research and development of the high-quality, high-temperature-resistant and good-moisture-resistance electrical magnesium oxide powder are urgent.
Disclosure of Invention
According to one aspect of the present application, there is provided an electrical grade magnesium oxide powder having superior hydrophobicity and durability.
The electrical-grade magnesium oxide powder is characterized in that magnesium oxide is arranged inside the magnesium oxide powder, and a silicon dioxide coating is arranged outside the magnesium oxide powder.
The magnesium oxide in the present application is high purity magnesium oxide. The high-purity magnesium oxide is covered with a silicon dioxide coating, so that the electrical-grade magnesium oxide powder can not only resist high temperature, but also has higher moisture-proof insulating property and longer duration.
Optionally, the purity of the magnesium oxide is 96-99.9%.
Optionally, the thickness of the silicon dioxide coating is 0.5-100 nm.
The upper limit of the thickness of the silica coating is 20nm, 21nm, 55nm, 100nm, and the lower limit of the thickness of the silica coating is 0.5nm, 20nm, 21nm, 55 nm.
Optionally, the mass ratio of the silicon dioxide coating to the magnesium oxide is 0.5-10: 100.
the upper limit of the mass ratio of the silica coating to the magnesium oxide is 1: 100. 2.2: 100. 4.7: 100. 10: 100, the lower limit of the mass ratio of silica coating to magnesium oxide is 0.5: 100. 1: 100. 2.2: 100. 4.7: 100.
according to another method of the application, the method for preparing any one of the electric-grade magnesium oxide powders is simple to operate, green and environment-friendly in raw materials and low in energy consumption.
The preparation method of the electrical-grade magnesium oxide powder comprises the following steps:
(a) mixing the solution A containing the silicon source with cationic resin, and filtering to obtain a solution B;
(b) mixing the solution B with silica sol and an alcohol solvent, and aging to obtain a solution C;
(c) mixing the fused magnesia powder with the solution C, and drying to obtain treated fused magnesia powder I;
(d) repeating the step (c) on the treated fused magnesia powder I to obtain treated fused magnesia powder II;
(e) and roasting the treated electric melting magnesia powder II to obtain the electrical grade magnesia powder.
In the present application, the fused magnesia powder may be purchased commercially or may be manufactured by self-production. The method for preparing the fused magnesia powder can be any one of the methods in the prior art, such as: and (3) crushing the fused magnesia into 40-325 meshes to prepare the fused magnesia powder. In the fused magnesia powder, the content of magnesia is 95-98%.
In the step (a), the solution A containing the silicon source is mixed with the cation resin with the same volume (achieving the purpose of exchanging all cations in the silicon source), stirred for 30-120 min, and the cation resin is filtered to obtain the solution B.
The cation resin in this application may be 732 cation resin, 732 cation exchange resin is styrene-divinyl copolymer with 7% crosslinking having sulfonic acid group (-SO)3H) The cation exchange resin of (1).
Optionally, the solution a containing a silicon source in step (a) comprises an inorganic silicon solution and an organosilicon solution; the mass ratio of the inorganic silicon liquid to the organic silicon liquid is 1: 0.1 to 10.
Preferably, the inorganic silicon liquid is at least one selected from the group consisting of water glass, potassium silicate, sodium silicate, and lithium silicate.
Preferably, the organosilicon liquid is at least one selected from methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, butyl orthosilicate, sodium methyl silicate, potassium methyl silicate, sodium ethyl silicate and trimethoxymethyl silane.
Further preferably, the organosilicon is at least one selected from the group consisting of methyl orthosilicate, ethyl orthosilicate, potassium methylsilicate and trimethoxymethylsilane.
In the step (B), the solution B is mixed with silica sol and an alcohol solvent, stirred for 10min to 6h, and aged for 1 to 24h at the temperature of 25 to 80 ℃ to obtain a solution C.
Alternatively, the upper limit of the stirring time is selected from 2h, 4h, 5.5h, 6h, and the lower limit of the stirring time is selected from 10min, 2h, 4h, 5.5 h.
The upper limit of the aging temperature is selected from 55 deg.C, 70 deg.C, 75 deg.C, and 80 deg.C, and the lower limit of the aging temperature is selected from 25 deg.C, 55 deg.C, 70 deg.C, and 75 deg.C.
The upper limit of the aging time is selected from 3h, 5h, 10h and 24h, and the lower limit of the aging time is selected from 1h, 3h, 5h and 10 h.
Optionally, the alcohol in the alcoholic solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol and ethylene glycol.
Preferably, the alcohol in the alcohol solvent is selected from at least one of methanol, ethanol and isopropanol.
Optionally, the particle size of the silica sol in the step (b) is 5-1000 nm, and the mass percentage concentration of the silica sol is 1-50%.
The particle size and mass percentage concentration of the silica sol are not strictly limited, and those skilled in the art can select proper particle size and concentration according to actual production needs.
Preferably, the upper limit of the silica sol particle size is selected from 6.5nm, 10nm, 25nm, 1000nm, and the lower limit of the silica sol particle size is selected from 5nm, 6.5nm, 10nm, 25 nm.
Preferably, the upper limit of the mass percentage concentration of the silica sol is selected from 22%, 30%, 40%, 50%, and the lower limit of the mass percentage concentration of the silica sol is selected from 1%, 22%, 30%, 40%.
Optionally, the volume ratio of the solution B, the silica sol and the alcohol solvent in the step (B) is 1: 0.5-10: 0.1 to 5.
In the step (C), the fused magnesia powder is mixed with the solution C, dried for 2-72 hours at room temperature, and then dried for 5-24 hours in an oven at 50-90 ℃ to obtain the treated fused magnesia powder I.
Optionally, the mass ratio of the fused magnesia powder to the solution C is 1: 0.01 to 1.
In the step (d), the step (C) is repeated on the fused magnesia powder I, namely, the fused magnesia powder I is mixed with the solution C again, dried for 2-72 hours at room temperature, then placed in an oven for drying for 5-24 hours at 50-90 ℃, and repeated for 3-6 times, so as to obtain the treated fused magnesia powder II.
In the repeated process, the mass ratio of the fused magnesia powder I to the solution C is not specifically limited in the application, and a person skilled in the art can select a proper mass ratio according to the actual production requirement. Preferably, the mass ratio of the fused magnesia powder II to the solution C is 1: 0.01 to 1.
In the step (e), the treated electric melting magnesia powder II is roasted at the roasting temperature of 800-2000 ℃ for 2-10 hours to obtain the electrical grade magnesia powder.
The upper limit of the baking temperature is selected from 1000 deg.C, 1200 deg.C, 2000 deg.C, and the lower limit of the baking temperature is selected from 800 deg.C, 1000 deg.C, 1200 deg.C.
The upper limit of the roasting time is selected from 4h, 5h, 6h and 10h, and the lower limit of the roasting time is selected from 2h, 4h, 5h and 6 h.
The beneficial effects that this application can produce include:
1) the electric-grade magnesium oxide powder provided by the application can not only resist high temperature (obtained by roasting at 800-2000 ℃), but also has the moisture-proof insulating property of more than 1000M omega and the duration of more than 72 h.
2) The electric-grade magnesium oxide powder provided by the application can be widely applied to aerospace, nuclear power, military industry and daily-use electronic components
2) The preparation method of the electrical-grade magnesium oxide powder is simple to operate, low in energy consumption and low in raw material price.
3) The preparation method of the electrical grade magnesium oxide powder is easy to industrialize, does not have a complex pollutant post-treatment process, and greatly reduces the production cost.
Drawings
FIG. 1 is an SEM topography picture of sample # 3;
FIG. 2 is an SEM topography picture of sample # 3.
Detailed Description
The present application will be described in detail with reference to examples, but the present application is not limited to these examples.
Unless otherwise specified, the raw materials and catalysts in the examples of the present application were all purchased commercially.
Example 1
1) Crushing and screening the crude fused magnesia to 40-325 meshes to prepare fused magnesia powder;
2) taking 80.2g of potassium silicate, 5.7g of methyl potassium silicate and 50.9g of methyl orthosilicate, fully and uniformly stirring to prepare a solution A, taking 732 type cationic resin with the same volume as the solution A, fully stirring and mixing the solution A and the 732 type cationic resin with the same volume, stirring for 50min, filtering the mixture, carrying out solid-liquid separation, and recovering liquid to obtain a solution B;
3) taking 151ml of methanol, mixing 705ml of silica sol with the particle size of 25nm and the mass percentage concentration of 30% with the solution B, stirring for 2 hours, heating to 55 ℃, and aging for 10 hours to obtain a solution C;
4) adding 50.3g of the solution C into 532g of fused magnesia powder, uniformly mixing, and stirring for 30 minutes; after the mixing is finished, naturally drying for 60h, and then drying in an oven at 80 ℃ for 16h to obtain treated fused magnesia powder I;
5) repeating the operation in 4) for 2 times to obtain treated fused magnesia powder II;
6) and taking out the treated fused magnesia powder II, naturally cooling, and roasting in a kiln at 1200 ℃ for 6 hours to obtain the electrical-grade magnesia powder which is recorded as sample No. 1.
Example 2
1) Crushing and screening the crude fused magnesia to 40-325 meshes to prepare fused magnesia powder;
2) taking 10.7g of potassium silicate, 35.2g of water glass, 7g of trimethoxy methyl silane and 90.5g of ethyl orthosilicate, fully and uniformly stirring to prepare a solution A, taking 732 type cationic resin with the same volume as the solution A, fully stirring and mixing the solution A with the same volume, stirring for 30min, carrying out solid-liquid separation on the mixture, and recovering liquid to obtain a solution B;
3) taking 201ml of ethanol, mixing 525ml of silica sol with the particle size of 10nm and the concentration of 40% with the solution B, stirring for 4 hours, heating to 75 ℃, and aging for 5 hours to obtain a solution C;
4) adding 22.3g of the solution C into 600g of fused magnesia powder, uniformly mixing, and stirring for 30 minutes; after the mixing is finished, naturally drying for 52h, and then drying in an oven at 90 ℃ for 18h to obtain treated fused magnesia powder I;
5) repeating the operation in 4) for 5 times to obtain treated fused magnesia powder II;
6) and taking out the treated fused magnesia powder II, naturally cooling, and roasting in a kiln at 1000 ℃ for 4 hours to obtain the electrical-grade magnesia powder which is recorded as sample No. 2.
Example 3
1) Crushing and screening the crude fused magnesia to 40-325 meshes to prepare fused magnesia powder;
2) taking 17g of sodium silicate, 50.2g of lithium silicate and 55.3g of ethyl orthosilicate, fully and uniformly stirring to prepare a solution A, taking 732 type cationic resin with the same volume as the solution A, fully stirring and mixing the solution A, stirring for 30min, filtering the mixture for solid-liquid separation, and recovering liquid to obtain a solution B;
3) mixing 101ml of isopropanol, 50ml of ethanol, 305ml of 22% silica sol with the particle size of 6.5nm and the concentration of the silica sol with the solution B, stirring for 5.5 hours, heating to 70 ℃, and aging for 3 hours to obtain a solution C;
4) adding 35.6g of the solution C into 312g of fused magnesia powder, uniformly mixing, and stirring for 30 minutes; after the mixing is finished, naturally drying for 17h, and then drying in an oven at 85 ℃ for 18h to obtain treated fused magnesia powder I;
5) repeating the operation in the step 4) for 6 times to obtain treated fused magnesia powder II;
6) and taking out the treated fused magnesia powder II, naturally cooling, and roasting in a kiln at 1000 ℃ for 5 hours to obtain the electrical-grade magnesia powder which is recorded as a sample No. 3.
EXAMPLE 4 topography testing of samples
SEM morphology analysis was performed for samples # 1 to # 3, respectively, and Table 1 shows the silica coating thickness for samples # 1 to # 3.
TABLE 1 silica coating thickness for different samples
Taking sample 3# as a typical example, FIGS. 1 and 2 are SEM morphology pictures of sample 3#, and it can be seen from FIGS. 1 and 2 that the MgO particles are coated with SiO2Covered by a coating.
Comparative example 1 uncoated Electrical grade magnesium oxide powder
Uncoated samples of electrical grade magnesium oxide powder were purchased from jaboticaba scientific limited.
Example 5 analysis of composition content
After samples No. 1 to No. 3 and comparative example 1 were each prepared as a standard electric heating element, the component content was measured by a Maxix 2424X-ray fluorescence analyzer (XRF) from Philips.
The contents of the components are shown in Table 3, which is typical of sample # 3 and comparative example # 1.
In the present example, the component content means the mass ratio of each component to the whole composition.
TABLE 3 component contents (%)
| Sample (I) | MgO | CaO | Fe2O3 | SiO2 | Al2O3 | L.O.I |
| Sample No. 3 | 94.91 | 0.56 | 0.36 | 3.96 | 0.26 | 0.01 |
| Comparative example 1 | 97.02 | 0.82 | 0.4 | 1.46 | 0.26 | 0.04 |
From Table 3, it can be seen that SiO2The content is obviously increased.
The test results for the other samples were similar to sample # 3.
Example 6 mass ratio of silica coating to magnesium oxide testing of samples
The test method comprises the following steps: the mass ratio of the silica coating to the magnesium oxide was measured for samples 1# to 3# respectively, and the specific method was the same as the method for analyzing the content of the components in example 5. The test results are shown in table 2.
TABLE 2 Mass ratios of silica coating to magnesia for different samples
| Sample (I) | 1# | 2# | 3# |
| SiO2Coating to MgO mass ratio | 1：100 | 4.7：100 | 2.2：100 |
The original SiO in the fused magnesia powder should be removed in the calculation of the mass ratio of the silicon dioxide coating to the magnesia2The content of (a).
EXAMPLE 7 mesh number analysis of samples
Samples 1# to 3# and comparative example 1 were made into standard electric heating elements, respectively, and then mesh analysis was performed.
The particle size distribution at different mesh sizes from comparative example 1, represented by sample # 3, is shown in table 4.
TABLE 4
As can be seen from table 4, the increased number of small particles and the reduced porosity promote overall thermal conductivity.
The test results for the other samples were similar to sample # 3.
Example 8 Electrical insulation Performance test
After the samples 1# to 3# and the comparative example 1 were respectively manufactured into standard electric heating elements, electric insulation performance tests were performed. Specifically, the durability and hydrophobicity test of the sample is completed in an SU304 stainless steel tube with the diameter of 6.6mm and the length of 500mm
The heating power of the electric heating furnace wire is 110V/500W. The hydrophobicity test was conducted under conditions of 35% humidity, 90% humidity, and 30 ℃ temperature, respectively. Typically represented by sample # 3, the test results are shown in table 5,
TABLE 5
As can be seen from table 5, the moisture proof insulating property of sample # 3 is >1000M Ω and the duration is >72h at a humidity of 90%.
The test results for the other samples were similar to sample # 3.
Although the present application has been described with reference to a few embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.
Claims (8)
1. A preparation method of electrical-grade magnesium oxide powder is characterized by comprising the following steps:
(a) mixing the solution A containing the silicon source with cationic resin, and filtering to obtain a solution B;
(b) mixing the solution B with silica sol and an alcohol solvent, and aging to obtain a solution C;
(c) mixing the fused magnesia powder with the solution C, and drying to obtain treated fused magnesia powder I;
(d) repeating the step (c) on the treated fused magnesia powder I to obtain treated fused magnesia powder II;
(e) and roasting the treated electric melting magnesia powder II to obtain the electrical grade magnesia powder.
2. The method according to claim 1, wherein the solution a containing a silicon source in the step (a) comprises an inorganic silicon solution and an organic silicon solution;
the mass ratio of the inorganic silicon solution to the organic silicon solution is 1: 0.1 to 10.
3. The method according to claim 2, wherein the inorganic silicon solution is at least one selected from the group consisting of potassium silicate, sodium silicate, and lithium silicate.
4. The method according to claim 2, wherein the organosilicon solution is at least one selected from the group consisting of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, butyl orthosilicate, sodium methyl silicate, potassium methyl silicate, sodium ethyl silicate, trimethoxymethyl silane.
5. The method according to claim 1, wherein the alcohol in the alcoholic solvent in (b) is at least one selected from methanol, ethanol, n-propanol, isopropanol and ethylene glycol.
6. The method according to claim 1, wherein the silica sol in the step (b) has a particle size of 5 to 1000nm and a mass percentage concentration of 1 to 50%.
7. The method according to claim 1, wherein the volume ratio of the solution B, the silica sol and the alcohol solvent in (B) is 1: 0.5-10: 0.1 to 5.
8. The method according to claim 1, wherein the mass ratio of the electrofused magnesia powder to the solution C is 1: 0.01 to 1.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1288859A (en) * | 2000-11-03 | 2001-03-28 | 清华大学 | Preparation of high temperature resisting electrothermal insulating magnesia material |
| CN1923750A (en) * | 2006-09-28 | 2007-03-07 | 庄伟� | Preparation method of high temperature resisting electrothermal insulating magnesia material |
| CN104903239A (en) * | 2013-01-15 | 2015-09-09 | 达泰豪化学工业株式会社 | Coated magnesium oxide powder, and method for producing same |
| CN108341607A (en) * | 2018-03-13 | 2018-07-31 | 武汉理工大学 | A kind of silica modified magnesia and its preparation method and application |
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| US20090214858A1 (en) * | 2008-02-25 | 2009-08-27 | Pilkington North America, Inc. | Magnesium oxide coated glass article and a method for depositing magnesium oxide coatings on flat glass |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1288859A (en) * | 2000-11-03 | 2001-03-28 | 清华大学 | Preparation of high temperature resisting electrothermal insulating magnesia material |
| CN1923750A (en) * | 2006-09-28 | 2007-03-07 | 庄伟� | Preparation method of high temperature resisting electrothermal insulating magnesia material |
| CN104903239A (en) * | 2013-01-15 | 2015-09-09 | 达泰豪化学工业株式会社 | Coated magnesium oxide powder, and method for producing same |
| CN108341607A (en) * | 2018-03-13 | 2018-07-31 | 武汉理工大学 | A kind of silica modified magnesia and its preparation method and application |
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