CN115818681B - Method for preparing large-particle monocrystalline aluminum hydroxide by one-stage method - Google Patents
Method for preparing large-particle monocrystalline aluminum hydroxide by one-stage method Download PDFInfo
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- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 title claims abstract description 49
- 239000002245 particle Substances 0.000 title claims abstract description 34
- 238000000034 method Methods 0.000 title claims abstract description 23
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 47
- 229910001388 sodium aluminate Inorganic materials 0.000 claims abstract description 43
- ANBBXQWFNXMHLD-UHFFFAOYSA-N aluminum;sodium;oxygen(2-) Chemical compound [O-2].[O-2].[Na+].[Al+3] ANBBXQWFNXMHLD-UHFFFAOYSA-N 0.000 claims abstract description 42
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims abstract description 40
- 239000013078 crystal Substances 0.000 claims abstract description 33
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims abstract description 20
- 235000017557 sodium bicarbonate Nutrition 0.000 claims abstract description 20
- 239000002002 slurry Substances 0.000 claims abstract description 17
- 230000032683 aging Effects 0.000 claims abstract description 13
- 239000002270 dispersing agent Substances 0.000 claims abstract description 10
- 239000000243 solution Substances 0.000 claims description 47
- 239000007864 aqueous solution Substances 0.000 claims description 7
- 229920001495 poly(sodium acrylate) polymer Polymers 0.000 claims description 5
- NNMHYFLPFNGQFZ-UHFFFAOYSA-M sodium polyacrylate Chemical compound [Na+].[O-]C(=O)C=C NNMHYFLPFNGQFZ-UHFFFAOYSA-M 0.000 claims description 5
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 claims description 4
- 229940080264 sodium dodecylbenzenesulfonate Drugs 0.000 claims description 4
- 235000010482 polyoxyethylene sorbitan monooleate Nutrition 0.000 claims description 3
- 229920000053 polysorbate 80 Polymers 0.000 claims description 3
- 239000012295 chemical reaction liquid Substances 0.000 claims description 2
- 238000006243 chemical reaction Methods 0.000 abstract description 12
- 238000001035 drying Methods 0.000 abstract description 8
- 238000005406 washing Methods 0.000 abstract description 8
- 238000009826 distribution Methods 0.000 abstract description 5
- 239000000203 mixture Substances 0.000 abstract description 5
- 239000006185 dispersion Substances 0.000 abstract description 3
- 238000001816 cooling Methods 0.000 abstract 1
- 238000001914 filtration Methods 0.000 abstract 1
- 229940024545 aluminum hydroxide Drugs 0.000 description 45
- 238000003756 stirring Methods 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 16
- 238000005303 weighing Methods 0.000 description 14
- 238000005054 agglomeration Methods 0.000 description 10
- 230000002776 aggregation Effects 0.000 description 10
- 238000000635 electron micrograph Methods 0.000 description 9
- 239000007787 solid Substances 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 238000002360 preparation method Methods 0.000 description 6
- 229920002379 silicone rubber Polymers 0.000 description 6
- 210000000582 semen Anatomy 0.000 description 5
- 239000004945 silicone rubber Substances 0.000 description 5
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 description 3
- 229910021502 aluminium hydroxide Inorganic materials 0.000 description 3
- 239000003063 flame retardant Substances 0.000 description 3
- 239000011734 sodium Substances 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 239000003518 caustics Substances 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 238000001493 electron microscopy Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 1
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 1
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 150000004645 aluminates Chemical class 0.000 description 1
- 229940024546 aluminum hydroxide gel Drugs 0.000 description 1
- VXAUWWUXCIMFIM-UHFFFAOYSA-M aluminum;oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Al+3] VXAUWWUXCIMFIM-UHFFFAOYSA-M 0.000 description 1
- SMYKVLBUSSNXMV-UHFFFAOYSA-K aluminum;trihydroxide;hydrate Chemical compound O.[OH-].[OH-].[OH-].[Al+3] SMYKVLBUSSNXMV-UHFFFAOYSA-K 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- -1 filling Substances 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 230000002431 foraging effect Effects 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 238000010335 hydrothermal treatment Methods 0.000 description 1
- 239000012796 inorganic flame retardant Substances 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229920000620 organic polymer Polymers 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- ZFXYFBGIUFBOJW-UHFFFAOYSA-N theophylline Chemical compound O=C1N(C)C(=O)N(C)C2=C1NC=N2 ZFXYFBGIUFBOJW-UHFFFAOYSA-N 0.000 description 1
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- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The method comprises the steps of carrying out aging after sodium bicarbonate solution and sodium aluminate solution are reacted by a hypergravity rotating bed, adding a dispersing agent, carrying out reaction and dispersion for the second time by the hypergravity rotating bed, then taking the mixture as seed crystals, and adding the sodium aluminate solution for natural cooling and one-stage decomposition; filtering, washing, drying and depolymerizing the decomposed slurry to obtain the high-dispersion large-single-crystal aluminum hydroxide product with concentrated particle size distribution. The invention has simple process, high decomposition rate and low cost, and has industrial value.
Description
Technical Field
The invention relates to the field of inorganic material preparation, in particular to a production method of monocrystalline aluminum hydroxide.
Background
In the alumina production industry, the growth of aluminum hydroxide is mainly realized by controlling the process conditions through two processes of agglomeration and growth of fine particle aluminum hydroxide. For example, CN200410037937, high strength large particle aluminium hydroxide seed crystal decomposing method, adopts self product circulation as seed crystal and achieves the aim of large particle aluminium hydroxide through agglomeration and growth. However, the aluminum hydroxide is an agglomerate, and the performance requirements of some special aluminum hydroxide cannot be met.
The super-gravity rotating bed is used for mainly producing nano or sub-nano aluminum hydroxide, for example, CN1258639A discloses a preparation method of superfine aluminum hydroxide, which comprises two working procedures of carbon decomposition and hydrothermal treatment under the super-gravity condition of the rotating bed, and the obtained aluminum hydroxide particles are fibrous, have an average particle size of 1-5 nm and an aspect ratio of 5-100. CN200510032296 (preparation method of superfine aluminum hydroxide) is that sodium aluminate NaAlO2 solution is contacted with gas containing carbon dioxide, carbonization reaction is carried out under the condition of supergravity to prepare aluminum hydroxide gel, then superfine aluminum hydroxide with different crystal forms is obtained, and granular aluminum hydroxide with the particle size of about 10nm can be used as a good inorganic flame retardant; the prepared nano fibrous pseudo-boehmite has the particle size of about 5nm and the length of 200-300 nm.
In the field of electric and electronic technology, due to the rapid development of integration technology and assembly technology, the volumes of electronic elements and logic circuits are smaller and smaller, the power density is larger and larger, the heat dissipation problem is more and more remarkable, and insulating materials with high heat conductivity are more needed. Aluminum hydroxide has flame retardant, filling, smoke suppression and certain heat conducting property. The high-crystallinity large single-crystal aluminum hydroxide has good compatibility with organic polymer materials, good processability and better heat conduction and flame retardance after being compounded with other high-heat conduction products.
In the silicone rubber formula, aluminum hydroxide has great influence on the mechanical property, electrical property, hydrophobicity and flame retardance of the product. The aluminum hydroxide filler can improve the performances of the silicone rubber, such as tracking resistance, electric corrosion resistance, arc resistance, flashover resistance and the like. When the granularity of the aluminum hydroxide is too small, the particles are difficult to uniformly disperse in a silicone rubber system, so that the mechanical property and the flame retardant property of the aluminum hydroxide are poor; when the particle size is too large, the specific surface area is smaller, the mechanical property is also lower, and the aluminum hydroxide with too large particle size has poor compatibility with a silicone rubber organic system, so that the flame retardance is also poor. The mechanical property and the flame retardant property are good only when the granularity is moderate. Therefore, the development of the large single crystal aluminum hydroxide with moderate grain size has positive practical significance.
Disclosure of Invention
The invention aims to provide a method for preparing monocrystalline large-particle aluminum hydroxide with high dispersion, moderate particle size and concentrated particle size distribution.
The method for preparing the large-particle aluminum hydroxide single crystal according to the present invention comprises the steps of:
1) Soda is prepared into aqueous solution according to the mass ratio of 1:6-1:10, and the aqueous solution and sodium aluminate solution are reacted through a super-gravity rotating bed according to the mass ratio of 1:1-1:2.
2) Adding a dispersing agent to age for 2-8 hours,
3) Then the reaction liquid is reacted and dispersed by the second super-gravity rotating bed,
4) And adding the obtained slurry into sodium aluminate solution for decomposition for 60-120h to obtain the large single crystal aluminum hydroxide.
The invention adopts the means of twice hypergravity field reaction and aging in the middle to prepare the seed crystal, and the seed crystal is used for separating sodium aluminate solution, so that the large aluminum hydroxide monocrystal with the grain size of 1-10 microns can be obtained, and the monocrystal is very suitable for the application of silicon rubber and circuit board materials.
Drawings
FIG. 1 is an electron micrograph of the single-crystal aluminum hydroxide obtained in example 1.
FIG. 2 is an electron micrograph of the single-crystal aluminum hydroxide obtained in example 2.
FIG. 3 is an electron micrograph of the single-crystal aluminum hydroxide obtained in example 3.
FIG. 4 is an electron micrograph of the single-crystal aluminum hydroxide obtained in example 4.
FIG. 5 is an electron micrograph of the aluminum hydroxide obtained in comparative example 1.
FIG. 6 is an electron micrograph of the aluminum hydroxide obtained in comparative example 2.
FIG. 7 is an electron micrograph of the aluminum hydroxide obtained in comparative example 3.
FIG. 8 is an electron micrograph of the aluminum hydroxide obtained in comparative example 4.
Detailed Description
N mentioned in the present disclosure k 、α k Having the general meaning of the art. Specifically, na of sodium aluminate solution 2 O content, including Na which reacts with alumina to form sodium aluminate 2 O and free Na in NaOH form 2 O, all of which are caustic and are designated N k The units are g/l. Caustic alkali Na in sodium aluminate solution 2 O and Al 2 O 3 The molar ratio of (a) is denoted as alpha k 。
In the present disclosure, "highly dispersed" means that the product obtained by the process of the present invention has a low degree of agglomeration, which exists substantially as single crystal formation. Even if agglomerates are present, they are not apparent in electron microscopy. In the present disclosure, "moderate particle size" refers to a size suitable for use in silicone rubber and circuit board materials and maintaining good mechanical properties, and thermal conductivity, with aluminum hydroxide crystals having a particle size substantially between 1.0-10.0 μm. "particle size distribution concentration" means that the D50 of the single crystal aluminum hydroxide obtained according to the scheme of the present invention is between 2.0 and 6.0, the D50 value obtained according to the preferred scheme is between 3.0 and 5.5. Mu.m, and the Span value of the particle size (calculated from (D90-D10)/D50) is usually between 1.0 and 2.0.
In the present invention, in order to prepare a suitable seed crystal, a two-stage supergravity rotating bed reaction is employed, and an aging process is performed between the two stages. By the first stage of supergravity field reaction, a large amount of nano-scale aluminum hydroxide crystal nuclei with uniform particle size are generated in a short time. Through the subsequent aging process, the nuclei grow gradually in spherical form and surface finishing is performed. Agglomeration of crystal nuclei is eliminated to a great extent by the second supergravity reaction, further homogenization of the decomposition particle size is also facilitated, and the obtained seed crystal is basically monocrystalline. The seeds obtained by the process of the invention have nanoscale seeds with low agglomeration and low aspect ratio (not more than 3, in particular not more than 2).
In a preferred embodiment, a dispersant is introduced during the aging process, which may further reduce seed agglomeration. The dispersing agent used in the exemplary embodiment of the invention is one or more of sodium polyacrylate, sodium dodecyl benzene sulfonate and tween 80, and the adding amount is 0.1-2g/L, preferably 0.2-1.5g/L, and more preferably 0.3-1g/L.
In a typical embodiment, sodium aluminate solution Al is used 2 O 3 The content is 80g/L-180g/L, the ak value is 1.2-2.0, and Al in sodium aluminate solution is preferred 2 O 3 The content is 120g/L-150g/L, ak is 1.3-1.5.
In the invention, baking soda is prepared into an aqueous solution according to a mass ratio of 1:6-1:10, and the aqueous solution and sodium aluminate solution pass through a super-gravity rotating bed according to a mass ratio of 1:1-1:2. Alternatively, the mass ratio of sodium bicarbonate solids to sodium aluminate solution may be controlled at 1:8-20, preferably 1: 8-12. In the range, the aging time of the prepared seed crystal is short, which is beneficial to reducing the cost.
In a preferred embodiment of the invention, the aqueous solution of sodium bicarbonate enters the reactor at a temperature of 30-40 ℃ and the sodium aluminate solution enters the reactor at a temperature of 40-60 ℃ which is advantageous in that the crystal nuclei phase formed is Bayer-stone type aluminium hydroxide, providing for a reduction of the next deagglomeration.
In the step 2), the aging temperature is controlled between 40 ℃ and 50 ℃. The aging time may be controlled to be 2 to 8 hours, preferably 2 to 6 hours, and too long a time may result in increased agglomeration of the crystal nuclei. At this temperature and time, agglomeration of the nuclei can be well prevented, especially in combination with the above-mentioned amount of dispersant.
In step 4), the slurry containing seed crystals obtained in step 3) is added into a sodium aluminate solution at a seed ratio of 0.01-0.05, and decomposed for 60-120 hours at a temperature of 50-65 ℃. The preferable mode is that the initial decomposition temperature is 55-65 ℃ and the final decomposition temperature is not lower than 50 ℃.
Example 1:
(1) Weighing 1Kg of sodium bicarbonate solid, adding into 10Kg of warm water at 30 ℃, stirring to dissolve completely, and weighing 10Kg of sodium aluminate solution, wherein a k 1.5, al 2 O 3 The concentration is 152g/L, and the temperature is controlled at 50 ℃;
(2) The rotating speed of the super-gravity rotating bed is controlled at 1200rpm, the adding speed of the baking soda solution and the semen is 60L/h, and 0.5g/L sodium polyacrylate is added after the reaction, and the mixture is stirred and aged for 4h. The rotating bed speed is still 1000rpm, and then the rotating bed is still passed through the rotating bed for the second time at the feeding speed of 60L/h;
(3) Adding the slurry passing through the secondary rotating bed in the step (2) into about 300L of sodium aluminate solution according to the seed ratio of 0.01 for decomposition, wherein the components of the sodium aluminate solution are the same as those in the step (1), the initial decomposition temperature is 65 ℃, the decomposition is carried out for 65 hours under natural stirring, and the decomposition end temperature is 60 ℃, and the decomposition rate reaches 45%;
(4) And (3) separating, washing, drying and dispersing the decomposed slurry in the step (3) to obtain the single crystal large particle aluminum hydroxide, wherein an electron microscope is shown in the figure 1.
Example 2:
(5) Weighing 1Kg of sodium bicarbonate solid, adding into 6Kg of warm water at 40 ℃, stirring to dissolve as much as possible, and weighing 20Kg of sodium aluminate solution, a k 1.45, al 2 O 3 The concentration is 130g/L, and the temperature is controlled at 40 ℃;
(6) The rotating speed of the super-gravity rotating bed is controlled at 1000rpm, the adding speed of the baking soda solution and the semen is 80L/h, 1g/L of sodium dodecyl benzene sulfonate is added after the reaction, and the mixture is stirred and aged for 8h. The rotating bed speed is still 1000rpm, and then the rotating bed is still passed through the rotating bed for the second time at the feeding speed of 80L/h;
(7) Adding the slurry passing through the secondary rotating bed in the step (6) into about 380L of sodium aluminate solution according to the seed ratio of 0.02 for decomposition, wherein the components of the sodium aluminate solution are the same as those in the step (5), the initial decomposition temperature is 60 ℃, the decomposition is carried out for 80 hours under natural stirring, and the decomposition end temperature is 56 ℃, and the decomposition rate reaches 48%;
(8) And (3) separating, washing, drying and dispersing the decomposed slurry in the step (7) to obtain the single crystal large particle aluminum hydroxide, wherein an electron microscope is shown in the figure 2.
Example 3:
(9) Weighing 1Kg of sodium bicarbonate solid, adding into 8Kg of warm water at 30 ℃, stirring to dissolve, and weighing 8Kg of sodium aluminate solution, wherein a k 1.6, al 2 O 3 The concentration is 150g/L, and the temperature is controlled at 60 ℃;
(10) The rotating speed of the super-gravity rotating bed is controlled at 1400rpm, the adding speed of the baking soda solution and the semen is 100L/h, and sodium polyacrylate (molecular weight 4000) and sodium dodecyl sulfate are respectively added into the mixture after the reaction for stirring and ageing for 6h. The rotating bed speed is still 1000rpm, and then the rotating bed is still passed through the rotating bed for the second time at the feeding speed of 100L/h;
(11) Adding the slurry passing through the secondary rotating bed in the step (10) into about 50L of sodium aluminate solution according to the seed ratio of 0.05 for decomposition, wherein the components of the sodium aluminate solution are the same as those in the step (9), the initial decomposition temperature is 55 ℃, the natural stirring decomposition is carried out for 100 hours, the decomposition final temperature is 50 ℃, and the decomposition rate reaches 50%;
separating, washing, drying and dispersing the decomposed slurry in the step (11) to obtain the large-particle monocrystalline aluminum hydroxide, wherein an electron microscope is shown in the figure 3.
Example 4:
(12) Weighing 1Kg of sodium bicarbonate solid, adding into 9Kg of warm water at 30 ℃, stirring to dissolve completely, and weighing 9Kg of sodium aluminate solution, wherein a k 1.5, al 2 O 3 The concentration is 160g/L, and the temperature is controlled at 62 ℃;
(13) The rotating speed of the super-gravity rotating bed is controlled at 1500rpm, the adding speed of the baking soda solution and the semen is 60L/h, and after the reaction, 1g/L of Tween 80 is added, and the stirring and the aging are carried out for 5h. The rotating bed speed is still 1000rpm, and then the rotating bed is still passed through the rotating bed for the second time at the feeding speed of 100L/h;
(14) Adding the slurry passing through the secondary rotating bed in the step (13) into about 50L of sodium aluminate solution according to the seed ratio of 0.05 for decomposition, wherein the components of the sodium aluminate solution are the same as those in the step (12), the initial decomposition temperature is 58 ℃, the decomposition is carried out for 95 hours under natural stirring, and the decomposition final temperature is 54 ℃, so that the decomposition rate reaches 49%;
separating, washing, drying and dispersing the decomposed slurry in the step (14) to obtain the large-particle monocrystalline aluminum hydroxide, wherein an electron microscope is shown in fig. 4.
Comparative example 1:
(1) Weighing 1Kg of sodium bicarbonate solid, adding into 10Kg of warm water at 30 ℃, stirring to dissolve completely, and weighing 10Kg of sodium aluminate solution, wherein a k 1.5, al 2 O 3 The concentration is 150g/L, and the temperature is controlled at 63 ℃;
(2) Adding sodium bicarbonate solution in the step (1) into sodium aluminate solution in the step (1), controlling the temperature to 63 ℃, and decomposing for 5 hours to obtain seed crystal liquid;
(3) Adding about 100L of sodium aluminate solution according to the seed ratio of 0.03 for decomposition, wherein the components of the sodium aluminate solution are the same as those in the step (1), the initial decomposition temperature is 65 ℃, the decomposition is carried out for 70 hours under natural stirring, the decomposition end temperature is 56 ℃, and the decomposition rate reaches 46%;
(4) And (3) separating, washing, drying and dispersing the discharged slurry in the step (2) to obtain aluminum hydroxide crystals, wherein an electron microscope photo is shown in fig. 5.
Comparative example 2:
(1) Weighing 1Kg of sodium bicarbonate solid, adding into 10Kg of warm water at 30 ℃, stirring to dissolve completely, and weighing 10KgSodium aluminate solution, a k 1.5, al 2 O 3 The concentration is 150g/L, and the temperature is controlled at 63 ℃;
(2) The sodium bicarbonate solution in (1) was added to the sodium aluminate solution in (1) at a stirring speed of 100rpm, and the addition speed was controlled at 80L/h. Then adding 1g/L sodium dodecyl benzene sulfonate for aging for 8 hours;
(3) Adding about 100L of sodium aluminate solution according to the seed ratio of 0.03 for decomposition, wherein the components of the sodium aluminate solution are the same as those in the step (1), the initial decomposition temperature is 65 ℃, the decomposition is carried out for 100 hours under natural stirring, the decomposition end temperature is 60 ℃, and the decomposition rate reaches 47%;
(4) And (3) separating, washing, drying and dispersing the decomposed slurry in the step (3) to obtain dry powder aluminum hydroxide, wherein an electron microscope is shown in figure 6.
Comparative example 3:
(1) Weighing 1Kg of sodium bicarbonate solid, adding into 10Kg of warm water at 30 ℃, stirring to dissolve completely, and weighing 10Kg of sodium aluminate solution, wherein a k 1.5, al 2 O 3 The concentration is 152g/L, and the temperature is controlled at 50 ℃;
(2) The rotating speed of the super-gravity rotating bed is controlled at 1200rpm, the adding speed of the baking soda solution and the semen is 60L/h, 0.5g/L sodium polyacrylate is added after the reaction, and the mixture is stirred and aged for 4h;
(3) Adding the slurry passing through the primary rotating bed in the step (2) into about 300L of sodium aluminate solution according to the seed ratio of 0.01 for decomposition, wherein the components of the sodium aluminate solution are the same as those in the step (1), the initial decomposition temperature is 65 ℃, the decomposition is carried out for 65 hours under natural stirring, and the decomposition end temperature is 60 ℃, and the decomposition rate reaches 45%;
(4) And (3) separating, washing, drying and dispersing the decomposed slurry in the step (3) to obtain an aluminum hydroxide product, wherein an electron microscope is shown in figure 7.
Comparative example 4
The test of example 1 was repeated except that no dispersant was added during aging, and the results are shown in Table 1 and electron microscopy FIG. 8.
Table 1 example index
| Project | D50 | D10 | D90 | Span |
| Example 1 | 3.5 | 1.2 | 7.6 | 1.83 |
| Example 2 | 4.2 | 1.3 | 6.2 | 1.17 |
| Example 3 | 3.4 | 1.2 | 6.8 | 1.65 |
| Example 4 | 5.5 | 1.4 | 9.6 | 1.49 |
| Comparative example 1 | 5.0 | 1.0 | 16.2 | 3.04 |
| Comparative example 2 | 1.6 | 0.9 | 7.8 | 4.31 |
| Comparative example 3 | 3.6 | 1.1 | 9.8 | 2.42 |
| Comparative example 4 | 3.8 | 1.0 | 9.4 | 2.21 |
Referring to Table 1 and the electron micrographs in the drawings, in each of the above examples, examples 1 to 4 employed the scheme of the present invention, the particle size of the product was substantially between 1 and 10. Mu.m, and the Span value was less than 2. In comparative example 1, conventional seed crystals are used, the particle size of the product is larger, D10 reaches 5 μm, D90 reaches 16 μm, span value is as high as 3.04, comparative example 2 does not use a supergravity field reactor to prepare the seed crystals, but dispersing agents are added in the preparation process to age, the particle size of the product is smaller, D50 is smaller than 2 μm, but Span value is wider and reaches 4.31. Comparative example 3 differs from example 1 only in that the seed preparation process was not subjected to the second supergravity rotating bed reaction, and the resulting product showed a degree of agglomeration with a particle size D90 of 9.8 and a particle size distribution Span of 2.42. Comparative example 4 differs from example 1 only in that no dispersant was added during the aging process of the seed preparation, and the resulting product also showed a degree of agglomeration with a particle size D90 of 9.4 and a particle size distribution Span of 2.21.
The embodiments selected herein for the purposes of the present invention should be construed as illustrative, and not limiting the scope of the invention, which is defined in the claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made to the present invention without departing from its spirit or scope.
Claims (8)
1. The method for preparing the large-particle monocrystalline aluminum hydroxide by the one-stage method comprises the following steps of:
1) Sodium bicarbonate is prepared into aqueous solution according to the mass ratio of 1:6-1:10, and reacts with sodium aluminate solution according to the mass ratio of 1:1-1:2 through a hypergravity rotating bed,
2) Adding a dispersing agent to age the slurry,
3) Then the reaction liquid is reacted and dispersed by the second super-gravity rotating bed,
4) And adding the obtained slurry into sodium aluminate solution for decomposition for 60-120h to obtain the large single crystal aluminum hydroxide.
2. The process according to claim 1, wherein the sodium aluminate solution Al used in steps 1) and 4) 2 O 3 The content is 80g/L-180g/L, a k The value is 1.2-2.0.
3. The method of claim 1, wherein the temperature of the aqueous solution of step 1) of sodium bicarbonate is 30-40 ℃ and the temperature of the solution of sodium aluminate is 40-60 ℃.
4. The method of claim 1, wherein the aging temperature in step 2) is controlled between 40 ℃ and 50 ℃.
5. The method of claim 1, wherein the decomposition temperature of the sodium aluminate solution of step 4) is controlled between 55 ℃ and 65 ℃.
6. The method of claim 1, wherein the dispersing agent is one or more of sodium polyacrylate, sodium dodecyl benzene sulfonate and tween 80, and the adding amount is 0.5-2g/L.
7. The method of claim 1, wherein the seed ratio added in step 4) is 0.01-0.05.
8. The method according to claim 1, wherein the initial decomposition temperature in step 4) is 55 ℃ to 65 ℃, and the final decomposition temperature is not lower than 50 ℃ after 60 to 120 hours of natural decomposition.
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