A sheet boron acid and a method for preparing the same

Abstract

The present invention provides a flaky boric acid and a preparation method thereof. The morphology of the flaky boric acid is flaky, D 50 The particle size is not less than 3 mm. The boric acid flakes provided by the present invention have D 50 The characteristic of larger particle size.

Description

Technical Field

[0001] The invention relates to flaky boric acid, in particular to flaky boric acid and a preparation method thereof, and belongs to the field of inorganic materials. Background Art

[0002] Boric acid is an important chemical raw material with a wide range of applications in the chemical industry, metallurgy, pesticides, and pharmaceuticals. With the continuous development of my country's industry, boric acid has been widely used in many new energy fields, such as glass, optical sensors, and ceramics, due to the electron-deficient structure of the element boron.

[0003] In certain chemical reactions, boric acid flakes are needed as a reaction raw material to obtain a larger surface area for phase interface contact. However, at present, the boric acid flakes obtained from industrial production have 50 Defects of smaller particle size.

[0004] Therefore, a D 50 The current research direction is to use flake boric acid with larger particle size. Summary of the Invention

[0005] The present invention provides a flaky boric acid having D 50 The characteristic of larger particle size.

[0006] The present invention also provides a method for preparing flaky boric acid, by which the above-mentioned flaky boric acid can be prepared. The preparation method has the advantages of simple operation, low preparation cost, and the ability to produce a large D 50 Characteristics of particle size flake boric acid.

[0007] The present invention provides a flaky boric acid, wherein the morphology of the flaky boric acid is flaky, and the D 50 The particle size is not less than 3mm.

[0008] The flake boric acid as described above, wherein D 50 The particle size is not less than 5mm.

[0009] The present invention also provides a method for preparing flaky boric acid, which comprises the following steps:

[0010] 1) mixing an aqueous boric acid solution with a precipitating agent to obtain a first mixed solution;

[0011] 2) crystallizing the first mixed solution to obtain the flake boric acid;

[0012] The precipitation agent is an ionic liquid, an inorganic salt or an organic solvent.

[0013] The preparation method as described above, wherein the precipitation agent is an ionic liquid, and the cation of the ionic liquid is selected from at least one of Formula 1 to Formula 9:

[0014]

[0015] Among them, 1≤n≤8;

[0016] R1, R2, R3, and R4 are independently selected from substituted or unsubstituted C 1～8 Alkyl, substituted or unsubstituted C 1～8 At least one of the alkoxy groups;

[0017] The anion of the ionic liquid is selected from F － 、Cl － Br － 、HSO4 － 、NO3 － CF3SO3 － At least one of .

[0018] In the preparation method as described above, the precipitating agent is an inorganic salt, and the inorganic salt is sulfate.

[0019] In the preparation method as described above, the precipitating agent is an organic solvent, and the organic solvent is selected from at least one of acetone, ethyl acetate, diethyl ether, 2-methyl sulfoxide, N,N-dimethylformamide, tetrahydrofuran, trimethyl phosphate, and ethanol.

[0020] The preparation method as described above, wherein the precipitating agent is an ionic liquid or an inorganic salt, and the mass ratio of the precipitating agent to the boric acid aqueous solution is 1:5-1:100; the precipitating agent is an organic solvent, and the volume ratio of the boric acid aqueous solution to the precipitating agent is 1:1-1:3.

[0021] In the preparation method as described above, the crystallization treatment includes cooling the first mixed solution at a rate of 0.5-2°C / min to obtain the flaky boric acid.

[0022] In the preparation method as described above, the crystallization treatment further comprises filtering the first mixed solution cooled to 25-40° C. to obtain the flaky boric acid.

[0023] As described above, in the preparation method, the mass percentage of boric acid in the boric acid aqueous solution is not less than 20 wt%.

[0024] The flaky boric acid provided by the present invention has D 50 The larger particle size provides a larger surface area for interfacial contact, which helps to increase the reaction rate of the chemical reactions in which it participates. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0026] Figure 1 This is the product appearance image of flaky boric acid A1-1;

[0027] Figure 2 This is the maximum size measurement image of flake boric acid A1-1;

[0028] Figure 3 This is a microscope observation image of flake boric acid A1-1;

[0029] Figure 4 This is the product appearance image of flake boric acid A1-5;

[0030] Figure 5 This is the maximum size measurement image of flake boric acid A1-5;

[0031] Figure 6 This is a microscope observation image of flake boric acid A1-5;

[0032] Figure 7 This is the product appearance image of flake boric acid A1-6;

[0033] Figure 8 This is the maximum size measurement image of flake boric acid A1-6;

[0034] Figure 9 This is a microscope observation image of flake boric acid A1-6;

[0035] Figure 10 This is the product appearance image of boric acid B1;

[0036] Figure 11 This is a microscope observation image of boric acid B1;

[0037] Figure 12 This is the product appearance image of boric acid B2;

[0038] Figure 13 This is a microscope observation image of boric acid B2. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific embodiments listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of the present invention.

[0040] The first aspect of the present invention provides a flake boric acid. Flake specifically refers to the boric acid solid having a morphological feature in which the maximum size is much larger than the thickness. The maximum size is the maximum distance between two points of the flake boric acid when observing the flake boric acid under a microscope. Furthermore, the D 50 Particle size not less than 3mm. 50 The particle size of not less than 3mm means that when the flake boric acid is screened using a dense sieve with a pore size of 3mm, the mass of the flake boric acid that cannot pass through the sieve and is retained by the dense sieve accounts for not less than 50% of the total mass of the flake boric acid involved in the screening operation. It can be understood that when the D 50 When the particle size is not less than 3 mm, at least 50% of the boric acid flakes have a maximum size of not less than 3 mm. The present invention does not impose any specific restrictions on the thickness of the boric acid flakes. Generally, the thickness of the boric acid flakes is 0.01-0.4 mm.

[0041] Furthermore, by selecting appropriate raw materials or defining a special preparation process, a product with a larger D 50 Specifically, the D 50 The particle size is not less than 5mm.

[0042] It is understood that since the boric acid flakes provided by the present invention are prepared from boric acid raw materials of relatively high purity, the boric acid flakes provided by the present invention also have relatively high purity, generally not less than 99%.

[0043] The boric acid flakes provided by the present invention have a large D 50 The particle size and maximum size, thus having a larger surface area for phase interface contact, help to increase the reaction rate of the chemical reaction in which it participates.

[0044] A second aspect of the present invention provides a method for preparing flaky boric acid, by which the above-mentioned flaky boric acid can be prepared. The method for preparing flaky boric acid comprises the following steps:

[0045] 1) mixing an aqueous boric acid solution with a precipitating agent to obtain a first mixed solution;

[0046] 2) crystallizing the first mixed solution to obtain boric acid flakes;

[0047] The precipitating agent is an ionic liquid, an inorganic salt or an organic solvent.

[0048] The aqueous boric acid solution refers to a mixture of water and boric acid. The present application does not specifically limit the concentration of the aqueous boric acid solution, which only needs to meet the requirement of obtaining the plate-like boric acid. It can be understood that, in order to facilitate the precipitation of the plate-like boric acid, the aqueous boric acid solution needs to have a relatively high concentration of boric acid. Generally, the percentage of boric acid in the aqueous boric acid solution is not less than 20wt% of the total mass of the aqueous boric acid solution; in an embodiment, the aqueous boric acid solution is a saturated aqueous boric acid solution.

[0049] The present application does not specifically limit the preparation method of the aqueous boric acid solution. In the preparation process, the solid boric acid can be mixed with deionized water to obtain the aqueous boric acid solution, or the solid boric acid can be added to a mixture containing water to obtain the aqueous boric acid solution. In order to increase the concentration of boric acid in the aqueous boric acid solution, heating and stirring can be used to make more boric acid dissolve in water when preparing the aqueous boric acid solution. When the aqueous boric acid solution is prepared by heating and stirring, the present application does not specifically limit the heating temperature, which can be determined according to the concentration of the aqueous boric acid solution required. In an embodiment, the heating temperature is 80-100℃.

[0050] The precipitating agent refers to a substance that can be mixed with the aqueous boric acid solution to obtain the plate-like boric acid described above. In the preparation method provided by the present application, the precipitating agent can be selected from an ionic liquid, an inorganic salt or an organic solvent.

[0051] The ionic liquid is a kind of liquid composed of ions, which is composed of cations and anions. In the present application, the ionic liquid specifically refers to a substance composed of free ions in a liquid state at room temperature or near room temperature. The present application does not specifically limit the composition of the ionic liquid, which only needs to meet the requirement of being in a liquid state at room temperature or near room temperature. In an embodiment, the cation of the ionic liquid is selected from at least one of quaternary ammonium salt ions, quaternary phosphonium salt ions, imidazole salt ions and pyrrole salt ions, and the anion of the ionic liquid is selected from at least one of halogen ions, tetrafluoroborate ions and hexafluorophosphate ions.

[0052] The inorganic salt refers to a salt in inorganic compounds, which can include non-metallic elements and / or metallic elements. The present application does not specifically limit the selection of the inorganic salt, which can be a commonly used inorganic salt in the field. For example, in an embodiment, the inorganic salt is selected from at least one of sodium sulfate, sodium chloride, ammonium nitrate and magnesium sulfate.

[0053] In the preparation method provided by the present application, the organic solvent refers to an organic compound in a liquid state at room temperature and soluble in water. The present application does not specifically limit the selection of the organic solvent, which only needs to meet the requirements of being in a liquid state at room temperature and being soluble in water. In an embodiment, the organic solvent can be selected from at least one of esters, ethers and ketones.

[0054] The inventors found that when using an ionic liquid as a precipitant, a flaky boron acid with a larger D 50 The inventors speculate that the reason may be that when the ionic liquid is used as a precipitant to mix with the aqueous solution of boron acid to obtain a first mixture, the ionic liquid can change the polarity and surface tension of the first mixture, so that the polarity and surface tension of the first mixture are reduced. When the polarity and surface tension of the first mixture are reduced, the boron acid solid crystallized from the first mixture tends to grow in a flaky direction. At the same time, the flaky boron acid surface can adsorb a part of the ionic liquid, and the adsorbed ionic liquid changes the surface properties of the flaky boron acid, so that the flaky boron acid crystal has a faster growth rate.

[0055] The inventors found that when using an organic solvent as a precipitant, a flaky boron acid with a larger D 50 The inventors speculate that the reason may be that when the ionic liquid is used as a precipitant to mix with the aqueous solution of boron acid to obtain a first mixture, the ionic liquid can change the polarity and surface tension of the first mixture, so that the polarity and surface tension of the first mixture are reduced. When the polarity and surface tension of the first mixture are reduced, the boron acid solid crystallized from the first mixture tends to grow in a flaky direction. At the same time, the flaky boron acid surface can adsorb a part of the ionic liquid, and the adsorbed ionic liquid changes the surface properties of the flaky boron acid, so that the flaky boron acid crystal has a faster growth rate.

[0056] The inventors further found that when using an inorganic salt as a precipitant, a flaky boron acid with a larger D 50 The inventors speculate that the reason may be that when the ionic liquid is used as a precipitant to mix with the aqueous solution of boron acid to obtain a first mixture, the ionic liquid can change the polarity and surface tension of the first mixture, so that the polarity and surface tension of the first mixture are reduced. When the polarity and surface tension of the first mixture are reduced, the boron acid solid crystallized from the first mixture tends to grow in a flaky direction. At the same time, the flaky boron acid surface can adsorb a part of the ionic liquid, and the adsorbed ionic liquid changes the surface properties of the flaky boron acid, so that the flaky boron acid crystal has a faster growth rate.

[0057] The crystallization treatment can crystallize the boron acid contained in the first mixture into a solid and separate it from the first mixture. The preparation method provided by the present application does not make specific limitations on the specific treatment methods adopted by the crystallization treatment, as long as the D 50 The crystallization treatment can be a common method for crystallizing a solid substance from a liquid in the art, for example, the crystallization treatment can be to heat the first mixture to evaporate the water, thereby obtaining the flaky boron acid, or the crystallization treatment can be to perform a temperature reduction treatment on the first mixture to reduce the temperature, so that the boron acid is crystallized due to the reduced solubility. In an embodiment, the crystallization treatment includes a temperature reduction treatment on the first mixture.

[0058] The preparation method of the flaky boron acid provided by the present application can prepare a flaky boron acid with a larger D 50 The preparation method has the characteristics of simple operation and low preparation cost.

[0059] Further, in one embodiment, the precipitation agent is an ionic liquid, and the cation of the ionic liquid is selected from at least one of Formula 1 to Formula 9:

[0060]

[0061] Among them, 1≤n≤8;

[0062] R1, R2, R3, and R4 are independently selected from substituted or unsubstituted C 1～8 Alkyl, substituted or unsubstituted C 1～8 At least one of the alkoxy groups;

[0063] The anion of the ionic liquid is selected from F － 、Cl － Br － 、HSO4 － 、NO3 － CF3SO3 － At least one of .

[0064] The inventors discovered that when the cations and anions of the ionic liquid are selected from the aforementioned ranges, the flake-shaped boric acid exhibits a faster growth rate. The inventors speculate that this may be because when the cations and anions of the ionic liquid are selected from the aforementioned ranges, the ionic liquid can more significantly reduce the surface tension of the first mixed liquid and bind to the surface of the precipitated flake-shaped boric acid, making the boric acid more likely to precipitate in a flake-like form and also achieving a faster precipitation rate.

[0065] The inventors also found that when n is greater than 8, the water solubility of the above ionic liquid will be significantly reduced. Therefore, controlling 1≤n≤8 can make the raw material saving feature of the preparation method provided by the present invention more prominent. In the present invention, R1, R2, R3, and R4 are independently selected from substituted or unsubstituted C 1～8 Alkyl, substituted or unsubstituted C 1～8 At least one of the alkoxy groups. When R1, R2, R3, and R4 include substituted C 1～8 When the alkyl or alkoxy group is present, the present invention does not impose any specific restrictions on the substituent. For example, in one embodiment, the substituent is at least one of a carbonyl group, a nitro group, and an amino group.

[0066] The inventors further discovered that when the cation is a pyridinium cation and the anion is selected from at least one of chloride ion and bromide ion, a larger D 50The inventors speculate that the reason may be that the pyridinium cations are larger in volume, while the chloride and bromide ions are smaller in volume. Since the cations are larger in volume and the anions are smaller in volume, the distance between the anions and cations is greater, the interaction force is weakened, resulting in a decrease in polarity and a decrease in the surface tension of the first mixed solution, which makes the boric acid more likely to precipitate in the form of flakes, thereby obtaining a larger D 50 At the same time, the ionic liquid composed of the above cations and anions can better combine with the surface of the boric acid crystal, which is beneficial to improving the precipitation rate of the flake boric acid.

[0067] Furthermore, when the precipitating agent is an ionic liquid, the mass ratio of the precipitating agent to the boric acid aqueous solution can be controlled to be 1:5-1:100. The reason is that when the mass ratio of the precipitating agent to the boric acid aqueous solution is in this range, the precipitating agent can more effectively regulate the surface tension and polarity of the first mixed liquid.

[0068] The inventors found that, in one embodiment, when the precipitation agent is sulfate, D 50 The inventors speculate that the reason may be that when sulfate is used as a precipitating agent, it can not only promote the crystallization of boric acid by increasing the saturation of boric acid in the first mixed solution, but also reduce the interfacial tension of the aqueous solution during the precipitation of boric acid by controlling the cooling rate and the cooling end temperature, thereby helping the boric acid crystals to grow in a flake form and obtaining a larger D 50 The preparation method provided herein does not impose any specific restrictions on the choice of sulfate, as long as the sulfate is readily soluble in water. For example, the sulfate can be selected from at least one of sodium sulfate, potassium sulfate, magnesium sulfate, and ammonium sulfate. The amount of sulfate added is also not specifically limited, as long as it can produce flaky boric acid.

[0069] Furthermore, when the precipitating agent is an inorganic salt, the mass ratio of the precipitating agent to the boric acid aqueous solution can be controlled to be 1:5-1:100. The reason is that when the mass ratio of the precipitating agent to the boric acid aqueous solution is within this range, the precipitating agent can effectively increase the saturation of boric acid in the first mixed solution. The small amount of precipitating agent used can also make the preparation method provided by the present invention more prominent in terms of saving reagents and having a lower preparation cost.

[0070] The inventors also found that, in one embodiment, when the precipitation agent is at least one of acetone, ethyl acetate, ether, 2-methyl sulfoxide, N,N-dimethylformamide, tetrahydrofuran, trimethyl phosphate, and ethanol, D 50 The inventors speculate that the reason may be that when the above substances are used as precipitating agents, a first mixed solution with a higher saturation of boric acid can be obtained. When the boric acid saturation in the first mixed solution is higher, it is more conducive to obtaining D50 Furthermore, when the precipitating agent is acetone, since acetone is highly volatile and easily soluble in water, under the premise of controlling the physical factors in the precipitation process, reducing the solubility of boric acid in aqueous solution is more conducive to the growth of boric acid into flakes, so the obtained flake boric acid has a larger D 50 Particle size.

[0071] Furthermore, when the precipitating agent is an organic solvent, the volume ratio of the boric acid aqueous solution to the precipitating agent can be controlled to be 1:1-1:3. The reason is that when the boric acid aqueous solution and the precipitating agent have the above-mentioned volume ratio, the precipitating agent can not only effectively increase the saturation of boric acid in the first mixed liquid, but also the preparation method provided by the present invention can save reagents and have a lower preparation cost due to the smaller amount of precipitating agent used. The characteristics are more prominent.

[0072] In one embodiment, the crystallization treatment includes cooling the first mixed solution at a rate of 0.5-2° C. / min to obtain flaky boric acid.

[0073] When the precipitating agent is mixed with the boric acid aqueous solution, the first mixed solution obtained is in a supersaturated state of boric acid. Therefore, cooling the first mixed solution is conducive to the precipitation of boric acid solids. The inventors found that when the cooling rate of the first mixed solution is 0.5-2℃ / min, a larger D 50 The inventors speculate that the reason may be that the cooling rate is positively correlated with the crystallization rate of boric acid solid. When the cooling rate is within the above range, the crystallization rate is moderate, which is conducive to a larger D 50 The formation of flake boric acid with different particle size.

[0074] Furthermore, the crystallization process also includes filtering the first mixed solution, which has been cooled to 25-40°C, to obtain flake boric acid. Filtering the first mixed solution at this temperature can further improve the purity of the boric acid while ensuring the boric acid yield. This is because if the temperature of the first mixed solution is too high during the filtration process, the first mixed solution still contains a large amount of dissolved boric acid. At this time, filtering will result in the loss of dissolved boric acid in the solution, reducing the yield of flake boric acid. If the temperature of the filtration process is too low, the inorganic salts contained in the first mixed solution are more likely to crystallize, resulting in a lower purity of the resulting flake boric acid.

[0075] In one embodiment, the process further includes drying the solid material obtained from the crystallization process to obtain boric acid flakes. This drying process removes impurities such as residual moisture on the surface of the solid material, thereby increasing the purity of the boric acid flakes. The present invention does not impose any specific limitations on the drying process temperature or time. In one embodiment, the drying process temperature is 30-50°C, and the drying process time is 6-18 hours.

[0076] Example 1-1

[0077] 1) Weigh 24 g of boric acid solid, mix with 100 g of deionized water, heat to 85°C to completely dissolve the boric acid solid, the solution is clear and transparent, keep stirring for 1 h to obtain a boric acid aqueous solution;

[0078] 2) Weigh 2 g of 1-methylpyridine chloride as a precipitating agent;

[0079] 3) Take 20 g of the boric acid aqueous solution and mix with 2 g of the precipitating agent to obtain a first mixed solution;

[0080] 4) After cooling the first mixed solution to 35°C at a rate of 1°C / min, filter treatment is performed, and the solid material obtained by the filter treatment is dried at 40°C for 12 h to prepare a sheet-shaped boric acid A1-1.

[0081] Example 1-2

[0082] This example is basically the same as Example 1-1, except that in step 2), 1-methyl-3-propanesulfonic acid imidazole hydrogen sulfate is used instead of 1-methylpyridine chloride.

[0083] A sheet-shaped boric acid A1-2 is prepared.

[0084] Example 1-3

[0085] This example is basically the same as Example 1-1, except that in step 2), tetramethylammonium bromide is used instead of 1-methylpyridine chloride.

[0086] A sheet-shaped boric acid A1-3 is prepared.

[0087] Example 1-4

[0088] This example is basically the same as Example 1-1, except that in step 2), 1 g of 1-methylpyridine chloride, 1 g of 1-methyl-3-propanesulfonic acid imidazole hydrogen sulfate, and 1 g of tetramethylammonium bromide are mixed as a precipitating agent.

[0089] A sheet-shaped boric acid A1-4 is prepared.

[0090] Example 1-5

[0091] 1) Weigh 5 g of anhydrous sodium sulfate as a precipitating agent, dissolve in 50 g of deionized water to obtain a sodium sulfate solution;

[0092] 2) Add 24 g of boric acid and 50 g of deionized water to the above sodium sulfate solution, heat and stir to 85°C until the solution is clear and transparent, then continue stirring for 0.5-2 h to obtain a first mixed solution;

[0093] 3) The first mixed solution was cooled to 35° C. at a rate of 1° C. / min and then filtered. The solid obtained by filtration was dried at 40° C. to obtain flaky boric acid A1-5.

[0094] Examples 1-6

[0095] This embodiment is basically the same as embodiment 1-1, except that:

[0096] In step 2), 10 mL of acetone was measured and used as a precipitation agent;

[0097] In step 3), 10 mL of boric acid aqueous solution was mixed with 10 mL of precipitating agent to obtain a first mixed solution;

[0098] The obtained boric acid A1-6 is in the form of flakes.

[0099] Examples 1-7

[0100] This embodiment is basically the same as embodiment 1-6, except that:

[0101] In step 2), 10 mL of tetrahydrofuran was measured as a precipitating agent;

[0102] The obtained boric acid A1-7 is in the form of flakes.

[0103] Examples 1-8

[0104] This embodiment is basically the same as embodiment 1-6, except that:

[0105] In step 2), 5 mL of ether and 5 mL of 2-methyl sulfoxide were mixed as a precipitation agent;

[0106] The obtained boric acid A1-8 is in the form of flakes.

[0107] Examples 1-9

[0108] This embodiment is basically the same as embodiment 1-6, except that:

[0109] In step 2), 10 mL of N,N-dimethylformamide was measured and used as a precipitation agent;

[0110] The obtained boric acid A1-9 is in the form of flakes.

[0111] Example 2-1

[0112] This embodiment is substantially the same as 1-1, except that, in step 3), 100 g of aqueous boric acid solution is mixed with 0.5 g of a precipitating agent to obtain a first mixed solution;

[0113] Obtained flaky boric acid A2-1.

[0114] Example 2-2

[0115] This embodiment is substantially the same as 1-1, except that, in step 3), 10 g of aqueous boric acid solution is mixed with 20 g of a precipitating agent to obtain a first mixed solution;

[0116] Obtained flaky boric acid A2-2.

[0117] Example 2-3

[0118] This embodiment is basically the same as 1-5, except that in step 1), the mass of anhydrous sodium sulfate is 1g;

[0119] Obtained flaky boric acid A2-3.

[0120] Examples 2-4

[0121] This embodiment is substantially the same as 1-5, except that anhydrous magnesium sulfate is used instead of anhydrous sodium sulfate as the precipitation agent.

[0122] The obtained boric acid A2-4 is in the form of flakes.

[0123] Examples 2-5

[0124] This embodiment is substantially the same as 1-6, except that, in step 3), 1 mL of boric acid aqueous solution is mixed with 10 mL of a precipitating agent to obtain a first mixed solution;

[0125] The obtained boric acid A2-5 is in the form of flakes.

[0126] Examples 2-6

[0127] This embodiment is substantially the same as 1-6, except that, in step 3), 10 mL of boric acid aqueous solution is mixed with 5 mL of a precipitating agent to obtain a first mixed solution;

[0128] The obtained boric acid A2-6 is in the form of flakes.

[0129] Examples 2-7

[0130] This embodiment is basically the same as 1-1, except that in step 4), the first mixed liquid is cooled at a rate of 10°C / min.

[0131] The obtained boric acid A2-7 is in the form of flakes.

[0132] Examples 2-8

[0133] This embodiment is basically the same as 1-5, except that in step 4), the first mixed liquid is cooled at a rate of 10° C. / min.

[0134] The obtained boric acid A2-8 is in the form of flakes.

[0135] Examples 2-9

[0136] This embodiment is basically the same as 1-6, except that in step 4), the first mixed liquid is cooled at a rate of 10° C. / min.

[0137] The obtained boric acid A2-9 is in the form of flakes.

[0138] Example 2-10

[0139] This embodiment is basically the same as 1-5, except that, in step 4), the first mixed solution is cooled to 5° C. at a rate of 1° C. / min and then filtered.

[0140] The obtained boric acid A2-10 is in the form of flakes.

[0141] Comparative Example 1

[0142] In this comparative example, only steps 1) and 4) of Example 1-1 were performed, namely, the obtained boric acid aqueous solution was cooled to 35°C at a rate of 1°C / min and then filtered, and the solid matter obtained by filtration was dried at 40°C.

[0143] Boric acid B1 is obtained.

[0144] Comparative Example 2

[0145] This comparative example is substantially the same as Example 1-1, except that sodium acetate is used instead of 1-methylpyridine chloride as the precipitation agent.

[0146] Boric acid B2 is obtained.

[0147] Test Example 1

[0148] Observe the appearance of the product of flaky boric acid A1-1 and obtain Figure 1 ;

[0149] The maximum size of the boric acid flakes A1-1 was measured to obtain Figure 2 ;

[0150] Observe the morphology of boric acid A1-1 and obtain Figure 3 ;

[0151] Observe the appearance of the product of flaky boric acid A1-5 and obtain Figure 4 ;

[0152] The maximum size of the boric acid flakes A1-5 was measured to obtain Figure 5 ;

[0153] Observe the morphology of boric acid flakes A1-5 and obtain Figure 6 ;

[0154] Observe the appearance of the product of flaky boric acid A1-6 and obtain Figure 7 ;

[0155] The maximum size of the flaky borate A1-6 was measured to be Figure 8 ;

[0156] The morphology of the flaky borate A1-6 was observed to be Figure 9 ;

[0157] The product appearance of the borate B1 was observed to be Figure 10 ;

[0158] The morphology of the borate B1 was observed to be Figure 11 ;

[0159] The product appearance of the borate B2 was observed to be Figure 12 ;

[0160] The morphology of the borate B2 was observed to be Figure 13 .

[0161] wherein, Figure 2 , Figure 3 , Figure 5 , Figure 6 , Figure 8 , Figure 9 , Figure 11 , Figure 13 was measured or observed by randomly selecting the smallest unit sample in the corresponding sample.

[0162] It can be seen from the observation Figures 1 to 9 that the flaky borates A1-1, A1-5 and A1-6 are all flaky, and have the morphology characteristic that the maximum size of the plane is much larger than the thickness. It can be seen from the observation Figure 2 , Figure 4 , Figure 6 respectively that the maximum size of the flaky borate A1-1 is about 8.8 mm, the maximum size of the flaky borate A1-5 is about 13.1 mm, and the maximum size of the flaky borate A1-6 is about 13 mm.

[0163] It can be seen from the observation Figure 10-13 that the borates B1 and B2 are granular rather than flaky, and do not have the morphology characteristic that the maximum size of the plane is much larger than the thickness.

[0164] Test Example 2

[0165] A plurality of dense sieves with different pore sizes were used to sieve the flaky borates A1-1 to A1-9, A2-1 to A2-10, and the borates B1 and B2 as samples, and the D 50 particle sizes of the above samples were measured. It can be understood that, since the pore sizes of the dense sieves are not continuously changed, the ratio of the sample mass retained by the dense sieves to the total sample mass cannot be accurately controlled to be 50%. Therefore, the closest two sieve pore sizes on both sides of the ratio of the sample mass retained by the dense sieves to the total sample mass were used as the D 50 particle size range of the sample, and thus the measured D50 The particle size is an interval value.

[0166] For example, the D 50 When the particle size is 11-12 mm, the sample mass retained by the 11 mm aperture sieve is 52% of the total sample mass, and the sample mass retained by the 12 mm aperture sieve is 49% of the total sample mass, it can be determined that the D 50 The particle size is 11-12 mm.

[0167] Correspondingly, the mass percentage of boric acid in the above samples is measured, and the results are filled in Table 1.

[0168] Table 1 Product D 50 Particle size and purity record table

[0169] serial number <![CDATA[D 50 Particle size (mm) Boric acid content (%) A1-1 10-11 99.9 A1-2 10-11 99.7 A1-3 11-12 99.8 A1-4 10-11 99.9 A1-5 13-14 99.5 A1-6 11-12 99.9 A1-7 10-11 99.9 A1-8 10-11 99.9 A1-9 10-11 99.9 A2-1 6-7 99.9 A2-2 4-5 99.3 A2-3 11-12 99.5 A2-4 8-9 99.5 A2-5 5-6 99.9 A2-6 4-5 99.9 A2-7 4-5 99.9 A2-8 8-9 99.5 A2-9 6-7 99.9 A2-10 10-11 99.0 B1 1-2 99.9 B2 Less than 1 99.5

[0170] From Table 1, we can see that:

[0171] 1) The D 50 The particle size is smaller than that of flaky boric acid A1-1, which may be due to the excessive or insufficient mass ratio of ionic liquid to boric acid aqueous solution during preparation.

[0172] 2) The D 50 The particle size is smaller than that of flaky boric acid A1-5, which may be due to the excessive or insufficient mass ratio of inorganic salt to boric acid aqueous solution during preparation.

[0173] 3) The D 50 The particle size is smaller than that of flaky boric acid A1-6, which may be due to the excessive or insufficient volume ratio of boric acid aqueous solution to organic solvent during preparation.

[0174] 4) The D 50 The particle size is smaller than that of flaky boric acid A1-1, A1-5, A1-6, respectively, which may be due to the excessive cooling rate of the first mixed solution during preparation.

[0175] 5) The purity of flaky A2-10 is low, which may be due to the low filtration temperature, causing the precipitant to co-crystallize with boric acid.

[0176] 6) The D 50 The particle size is less than 3 mm, and it is not flaky. This may be due to the fact that no precipitant was used during preparation, which prevented the boric acid from growing in the flaky direction and resulted in a small particle size.

[0177] 7) Boric acid B2 is similar to boric acid B1, the D 50The particle size is less than 3 mm and is not flaky, which may be because sodium acetate cannot reduce the interfacial tension of the solution, so that the boric acid crystals cannot grow in a flaky form.

[0178] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the comparative examples of the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing flaky boric acid, characterized in that: The following steps are involved: 1) mixing an aqueous boric acid solution with a precipitating agent to obtain a first mixed solution; 2) crystallizing the first mixed solution to obtain the flake boric acid; The precipitation agent is an ionic liquid; The cation of the ionic liquid is selected from at least one of Formula 1 to Formula 9: Among them, 1≤n≤8; R1, R2, R3, and R4 are independently selected from substituted or unsubstituted C 1~8 Alkyl, substituted or unsubstituted C 1~8 At least one of the alkoxy groups; The anion of the ionic liquid is selected from F － 、Cl － Br － 、HSO4 － 、NO3 － CF3SO3 － At least one of .

2. The preparation method according to claim 1, characterized in that The mass ratio of the precipitating agent to the boric acid aqueous solution is 1:5-1:

100.

3. The preparation method according to claim 1, characterized in that The crystallization treatment includes cooling the first mixed solution at a rate of 0.5-2 °C / min to obtain the flaky boric acid.

4. The preparation method according to claim 2, characterized in that The crystallization treatment includes cooling the first mixed solution at a rate of 0.5-2 °C / min to obtain the flaky boric acid.

5. The preparation method according to claim 1, characterized in that The crystallization process further includes filtering the first mixed solution cooled to 25-40° C. to obtain the flaky boric acid.

6. The preparation method according to claim 2, characterized in that The crystallization process further includes filtering the first mixed solution cooled to 25-40° C. to obtain the flaky boric acid.

7. The preparation method according to claim 3, characterized in that The crystallization process further includes filtering the first mixed solution cooled to 25-40° C. to obtain the flaky boric acid.

8. The preparation method according to claim 5, characterized in that The crystallization process further includes filtering the first mixed solution cooled to 25-40° C. to obtain the flaky boric acid.

9. The preparation method according to claim 1, characterized in that In the boric acid aqueous solution, the mass percentage of boric acid is not less than 20 wt %.

10. The preparation method according to claim 8, characterized in that In the boric acid aqueous solution, the mass percentage of boric acid is not less than 20 wt %.

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