Preparation method of basic magnesium carbonate glass microspheres

Abstract

The invention provides a preparation method of basic magnesium carbonate glass microspheres, and belongs to the technical field of flame-retardant material preparation.The preparation method comprises the steps that a magnesium sulfate aqueous solution and a sodium carbonate aqueous solution are taken and added into a reactor at a certain temperature in an opposite double-dropwise mode, hydrophilic glass microspheres are added at the same time, and then heating crystal transformation, standing curing, filtering, washing and drying are conducted to obtain the basic magnesium carbonate glass microspheres. The basic magnesium carbonate glass microspheres are obtained. According to the basic magnesium carbonate glass microspheres provided by the invention, glass microspheres are used as seed crystals to produce a basic magnesium carbonate flame retardant with ultralow bulk density, and the bulk density of basic magnesium carbonate is less than or equal to 0.05 g / mL; according to the basic magnesium carbonate glass microspheres, the basic magnesium carbonate and the glass microspheres are synergistically flame-retardant, so that the weight of a filled product is reduced, the flame-retardant effect is improved, and the flame-retardant cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardant material preparation, and particularly relates to a method for preparing basic magnesium carbonate glass microspheres. Background Art

[0002] Flame retardants are classified into halogen, phosphorus, halogen-phosphorus, nitrogen, silicon, aluminum-magnesium, etc. according to the element type, and inorganic flame retardants, organic flame retardants, polymer flame retardants, etc. according to the chemical structure. Among them, halogen flame retardants and phosphorus flame retardants are gradually eliminated because of their large smoke production and the generation of harmful gases during the flame retardant process. Basic magnesium carbonate is a magnesium salt compound and also an inorganic environmentally friendly flame retardant. It has the advantages of good thermal stability, non-toxicity, no toxic or volatile gas production, and low price. Its thermal decomposition temperature range is between 220 and 550°C. Compared with other flame retardants such as magnesium hydroxide (thermal decomposition temperature 300 to 340°C) and aluminum hydroxide (thermal decomposition temperature 180 to 200°C), basic magnesium carbonate has a wider thermal decomposition temperature range.

[0003] However, there are two existing methods for producing basic magnesium carbonate. One is to use solid magnesium ore (such as dolomite, magnesia, magnesia, etc.) to calcine into light-burned magnesium oxide, and then hydrate, purify and carbonize it. The other method is to use brine as raw material to prepare magnesium carbonate through the carbon ammonium method, soda ash method or ammonia method-carbonization method. However, both methods have the disadvantages of complex process and high cost. And the flame retardant effect of the prepared basic magnesium carbonate needs to be further strengthened.

[0004] Therefore, providing a simple, efficient and environmentally friendly method for preparing a basic magnesium carbonate flame retardant, especially producing a basic magnesium carbonate flame retardant with ultra-low bulk density, has always been a research hotspot in this field. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for preparing basic magnesium carbonate glass microspheres.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A method for preparing basic magnesium carbonate glass microspheres comprises the following steps: taking a magnesium sulfate aqueous solution and a sodium carbonate aqueous solution, adding them dropwise to a reactor maintained at a certain temperature, adding hydrophilic glass microspheres at the same time, and then heating and crystallizing, standing and aging, filtering, washing and drying to obtain the basic magnesium carbonate glass microspheres.

[0008] Furthermore, the preparation method comprises the following specific steps:

[0009] S1, adding hydrophilic glass microspheres into the reactor;

[0010] S2, taking an aqueous solution of magnesium sulfate and an aqueous solution of sodium carbonate, and adding them dropwise to a reactor maintained at a certain temperature;

[0011] S3, after the double dropwise addition is completed, the obtained reaction solution is heated to crystallize and allowed to stand for aging to obtain an aged mixed solution;

[0012] S4. The matured mixed solution is filtered, washed and dried to obtain the basic magnesium carbonate glass microspheres.

[0013] Furthermore, in the process of adding the magnesium sulfate aqueous solution and the sodium carbonate aqueous solution dropwise to the reactor maintained at a certain temperature, the temperature in the reactor is 35-50° C. and the stirring speed is 200-300 r / min.

[0014] Furthermore, the dripping speed is adjusted according to the amount of liquid added in opposite directions to ensure that the stable opposite dripping time is 2 to 2.5 hours.

[0015] Furthermore, the concentration of the hydrophilic glass microspheres in the reaction solution is 0.1-0.5 wt %.

[0016] Further, the molar ratio of magnesium sulfate in the magnesium sulfate aqueous solution to sodium carbonate in the sodium carbonate aqueous solution is 1:0.95-1.3;

[0017] The concentration of magnesium sulfate in the magnesium sulfate aqueous solution is 0.2-0.5 mol / L;

[0018] The concentration of sodium carbonate in the sodium carbonate aqueous solution is 0.2-0.5 mol / L.

[0019] Furthermore, the temperature-raising crystallization is that after the double dropwise addition is completed, the reaction temperature of the obtained reaction solution is raised to 60-90° C., the stirring speed is reduced to 100-200 r / min, and the reaction time is 2 h.

[0020] Furthermore, the temperature of the static aging is 60 to 90° C. and the time is more than 2 hours.

[0021] Furthermore, the reactor is a reactor, and two oppositely arranged feeding ports on the reactor are respectively connected to two dripping tubes that pass directly into the reactor. The outlets of the two dripping tubes are close to the bottom of the reactor, and the outlets of the two dripping tubes are arranged oppositely; a soda-water mixer is provided at the outlets of the two dripping tubes.

[0022] Furthermore, the reactor is provided with a two-blade pitched-blade paddle agitator, and the inclination angle θ of the two blades in the two-blade pitched-blade paddle agitator is 45°.

[0023] The beneficial effects of the preparation method of basic magnesium carbonate glass microspheres of the present invention are:

[0024] The basic magnesium carbonate glass microspheres provided by the present invention use glass microspheres as crystal seeds to produce an ultra-low bulk density basic magnesium carbonate flame retardant, and the bulk density of the basic magnesium carbonate is ≤0.05 g / mL;

[0025] The basic magnesium carbonate glass microspheres of the present invention are flame-retardant by synergistically combining basic magnesium carbonate and glass microspheres, thereby reducing the weight of the filled product, improving the flame-retardant effect, and reducing the flame-retardant cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic structural diagram of the reactor used in the present invention;

[0027] In the figure, 1. dripping tube; 2. CLP immersion soda mixer; 3. two-blade inclined blade paddle stirrer; 31. blade. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention are described clearly and completely below. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0029] A method for preparing basic magnesium carbonate glass microspheres of the present invention comprises the following steps:

[0030] S1, adding hydrophilic glass microspheres into the reactor, the amount of which is 0.1-0.5wt% of the total weight of the reaction solution;

[0031] Hydrophilic glass microspheres are purchased hollow glass microspheres with rich hydroxyl groups on the surface. The hydroxyl groups on the hydrophilic glass microspheres can absorb metal magnesium ions and make basic magnesium carbonate crystals grow;

[0032] S2. Under the conditions of maintaining the temperature in the reactor at 35-50°C and the stirring speed at 200-300 r / min, taking a magnesium sulfate aqueous solution with a concentration of 0.2-0.5 mol / L and a sodium carbonate aqueous solution with a concentration of 0.2-0.5 mol / L according to the molar ratio of magnesium sulfate to sodium carbonate of 1:0.95-1.3, add them to the bottom of the reactor in opposite directions, and adjust the drop speed according to the amount of liquid added in the opposite directions, so as to ensure that the time of the opposite directions double drop is controlled within 2-2.5 hours. Among them, if Figure 1As shown, the reactor adopts a conventional reactor, and the reactor is provided with a stirring device. Two dropping tubes 1 which pass directly into the reactor are respectively introduced into the feeding ports which are arranged oppositely on the reactor on both sides of the stirring device. The outlets of the two dropping tubes 1 are close to the bottom of the reactor, and the outlets of the two dropping tubes 1 are arranged oppositely. CLP immersion soda-water mixers 2 are arranged at the outlets of the two dropping tubes 1, that is, the outlets of the two CLP immersion soda-water mixers 2 are arranged oppositely; the magnesium sulfate aqueous solution and the sodium carbonate aqueous solution are respectively sprayed and dripped through the two dropping tubes 1 and the CLP immersion soda-water mixer 2, and the two streams of materials dripped into the reactor are sprayed and contacted in opposite directions, which can ensure that the whole reaction process is in a state of low concentration and low saturation, so that the product crystals grow and are easy to wash, thereby reducing the bulk density of the product.

[0033] The magnesium sulfate aqueous solution and the sodium carbonate aqueous solution are added to the reactor in a counter-double-drop manner, which means that the magnesium sulfate aqueous solution and the sodium carbonate aqueous solution enter the two dropping tubes 1 at the same flow rate, enter the bottom of the reactor through the two dropping tubes 1, and then pass through the CLP immersion soda mixer 2 to be sprayed into the reactor in counter-directions. The magnesium sulfate aqueous solution and the sodium carbonate aqueous solution sprayed into the reactor in counter-directions are contacted and mixed to produce basic magnesium carbonate.

[0034] Furthermore, in order to make the reaction more complete and controllable, the stirring device of the reactor adopts a two-blade inclined blade paddle stirrer 3, and the inclination angle θ of the two blades 31 in the two-blade inclined blade paddle stirrer 3 is 45°.

[0035] S3, after the double dropwise addition is completed, the reaction temperature of the obtained reaction solution is raised to 60-90°C, the stirring speed is reduced to 100-200r / min, the reaction time is more than 2h (i.e., temperature rise and crystallization), and then the two-blade inclined blade paddle stirrer 3 is turned off (i.e., stirring is stopped), and the temperature is maintained at 60-90°C for aging for more than 2h to obtain an aged mixed solution;

[0036] Since crystal formation can be completed within 2 hours of both the reaction time of temperature-increasing crystal transformation and the time of static aging, and prolonging the time will not lead to further growth or destruction of the crystal, the reaction time of temperature-increasing crystal transformation and the time of static aging can be any time above 2 hours. However, based on economic and practical considerations, the reaction time of temperature-increasing crystal transformation and the time of static aging can generally be 2 hours.

[0037] S4. The matured mixed solution is filtered, washed and dried to obtain basic magnesium carbonate glass microspheres. Basic magnesium carbonate glass microspheres are a basic magnesium carbonate flame retardant with ultra-low bulk density, wherein the chemical formula of basic magnesium carbonate is 4Mg(CO3)2·Mg(OH)2·4H2O.

[0038] The basic magnesium carbonate glass microspheres prepared by the present invention have synergistic flame retardancy between basic magnesium carbonate and glass microspheres, thereby reducing the amount of flame retardant added and reducing the flame retardancy cost.

[0039] Example 1 A method for preparing basic magnesium carbonate glass microspheres

[0040] This embodiment is a method for preparing basic magnesium carbonate glass microspheres, comprising the following steps:

[0041] S1, adding 0.3wt% of the total weight of the reaction solution of hydrophilic glass microspheres into the reactor;

[0042] S2, maintaining the stirring speed at 300r / min and the temperature at 48°C in the reactor, taking a 0.2mol / L magnesium sulfate aqueous solution and a 0.2mol / L sodium carbonate aqueous solution in a molar ratio of 1:1, and adding them dropwise to the bottom of the reactor in opposite directions for 2h;

[0043] S3, after the double dropwise addition is completed, the reaction temperature of the obtained reaction solution is raised to 60°C, the rotation speed is adjusted to 200r / min, the reaction time is 2h (i.e., temperature rise and crystallization), the two-blade inclined blade paddle stirrer 3 is turned off (i.e., stirring is stopped), and the mixture is kept at 60°C for 2h to obtain a matured mixed solution;

[0044] S4. The matured mixed solution is filtered, washed and dried to obtain basic magnesium carbonate glass microspheres, which are marked as T1 and have a bulk density of 0.05 g / mL.

[0045] Example 2 A method for preparing basic magnesium carbonate glass microspheres

[0046] This embodiment is a method for preparing basic magnesium carbonate glass microspheres, comprising the following steps:

[0047] S1, adding 0.2wt% of the total weight of the reaction solution of hydrophilic glass microspheres into the reactor;

[0048] S2, maintaining the stirring speed in the reactor at 250r / min and the temperature at 50°C, according to the molar ratio of magnesium sulfate to sodium carbonate of 1:0.95, take a 0.5mol / L magnesium sulfate aqueous solution and a 0.475mol / L sodium carbonate aqueous solution, and add them dropwise to the bottom of the reactor in opposite directions, and the time of the opposite double addition is 2.3h;

[0049] S3, after the double dropwise addition is completed, the reaction temperature of the obtained reaction solution is raised to 70°C, the rotation speed is adjusted to 150r / min, the reaction time is 2h (i.e., temperature rise and crystallization), the two-blade inclined blade paddle stirrer 3 is turned off (i.e., stirring is stopped), and the mixture is kept at 70°C for 2h to obtain a matured mixed solution;

[0050] S4. The matured mixed solution is filtered, washed and dried to obtain basic magnesium carbonate glass microspheres, which are marked as T2 and have a bulk density of 0.042 g / mL.

[0051] Example 3 A method for preparing basic magnesium carbonate glass microspheres

[0052] This embodiment is a method for preparing basic magnesium carbonate glass microspheres, comprising the following steps:

[0053] S1, adding 0.5wt% of the total weight of the reaction solution of hydrophilic glass microspheres into the reactor;

[0054] S2, maintaining the reactor stirring speed at 300r / min, the temperature at 35°C, according to the molar ratio of magnesium sulfate to sodium carbonate of 1:1.3, take a 0.3mol / L magnesium sulfate aqueous solution and a 0.39mol / L sodium carbonate aqueous solution, and add them dropwise to the bottom of the reactor in opposite directions, and the time of the opposite double addition is 2.5h;

[0055] S3, after the double dropwise addition is completed, the reaction temperature of the obtained reaction solution is raised to 80°C, the rotation speed is adjusted to 100r / min, the reaction time is 2h (i.e., temperature rise and crystallization), the two-blade inclined blade paddle stirrer 3 is turned off (i.e., stirring is stopped), and the temperature is maintained at 80°C for 2h to obtain a mixed solution after aging;

[0056] S4. The matured mixed solution is filtered, washed and dried to obtain basic magnesium carbonate glass microspheres, which are marked as T3 and have a bulk density of 0.038 g / mL.

[0057] Example 4 A method for preparing basic magnesium carbonate glass microspheres

[0058] This embodiment is a method for preparing basic magnesium carbonate glass microspheres, comprising the following steps:

[0059] S1, adding 0.1wt% of the total weight of the reaction solution of hydrophilic glass microspheres into the reactor;

[0060] S2, maintaining the stirring speed in the reactor at 200r / min and the temperature at 40°C, taking a 0.5mol / L magnesium sulfate aqueous solution and a 0.5mol / L sodium carbonate aqueous solution in a molar ratio of magnesium sulfate to sodium carbonate of 1:1, and adding them dropwise to the bottom of the reactor in opposite directions for 2.5h;

[0061] S3, after the double dropwise addition is completed, the reaction temperature of the obtained reaction solution is raised to 90°C, the rotation speed is adjusted to 100r / min, the reaction time is 3h (i.e., temperature rise and crystallization), the two-blade inclined blade paddle stirrer 3 is turned off (i.e., stirring is stopped), and the 90°C is maintained for aging for 3h to obtain an aged mixed solution;

[0062] S4. The matured mixed solution is filtered, washed and dried to obtain basic magnesium carbonate glass microspheres, which are marked as T4 and have a bulk density of 0.03 g / mL.

[0063] Example 5 A method for preparing basic magnesium carbonate glass microspheres

[0064] This embodiment is a method for preparing basic magnesium carbonate glass microspheres, comprising the following steps:

[0065] S1, adding 0.1wt% of the total weight of the reaction solution of hydrophilic glass microspheres into the reactor;

[0066] S2, maintaining the stirring speed in the reactor at 300r / min and the temperature at 50°C, taking a 0.2mol / L magnesium sulfate aqueous solution and a 0.21mol / L sodium carbonate aqueous solution at a molar ratio of 1:1.05, and adding them dropwise to the bottom of the reactor in opposite directions for 2.5h;

[0067] S3, after the double dropwise addition is completed, the reaction temperature of the obtained reaction solution is raised to 90°C, the rotation speed is adjusted to 200r / min, the reaction time is 2h (i.e., temperature rise and crystallization), the two-blade inclined blade paddle stirrer 3 is turned off (i.e., stirring is stopped), and the 90°C is maintained for aging for 2h to obtain an aged mixed solution;

[0068] S4. The matured mixed solution is filtered, washed and dried to obtain basic magnesium carbonate glass microspheres, which are marked as T5 and have a bulk density of 0.02 g / mL.

[0069] Comparative Example 1 A method for preparing basic magnesium carbonate glass microspheres

[0070] Comparative Example 1 is a comparative experiment of the preparation process of a basic magnesium carbonate glass microsphere in Example 1. Its steps and process parameters are basically the same as those in Example 1, except that the stirring speed in step S2 is 500 r / min, and the basic magnesium carbonate glass microspheres finally prepared are marked as DT1, and their bulk density is 0.098 g / mL.

[0071] As the stirring speed decreases, the collision between particles can be reduced, the crystal nucleation is reduced, and it is beneficial to the crystal growth. However, as the stirring speed increases, the collision between particles increases, the crystal nucleation increases, and it is not beneficial to the crystal growth. Therefore, the packing density of the basic magnesium carbonate glass microspheres DT1 prepared in Comparative Example 1 is greater than that of the basic magnesium carbonate glass microspheres T1 to T5 prepared in Examples 1 to 5.

[0072] Comparative Example 2 A method for preparing basic magnesium carbonate glass microspheres

[0073] Comparative Example 2 is a comparative experiment of the preparation process of a basic magnesium carbonate glass microsphere in Example 1. Its steps and process parameters are basically the same as those in Example 1, except that the time of the opposite double dropwise addition in step S2 is 0.5 h, and the basic magnesium carbonate glass microspheres finally prepared are marked as DT2, and their bulk density is 0.12 g / mL.

[0074] Since the time of the counter-double-dropping is reduced, the saturation of the reaction solution will increase, the crystal nucleation rate will increase, which is not conducive to crystal growth. Therefore, the packing density of the basic magnesium carbonate glass microspheres DT2 prepared in Comparative Example 2 is greater than that of the basic magnesium carbonate glass microspheres T1 to T5 prepared in Examples 1 to 5.

[0075] Comparative Example 3: A method for preparing basic magnesium carbonate

[0076] Comparative Example 3 is a method for preparing basic magnesium carbonate, which is prepared by the method in Chinese invention patent application CN 116969490A, and specifically comprises the following steps:

[0077] S1, add ammonia water with a concentration of 4 mol / L to the magnesium sulfate solution, adjust the pH value to 7.5 for impurity removal, filter and dilute the suspension after impurity removal to obtain a refined magnesium sulfate solution, at which the concentration of magnesium ions in the refined magnesium sulfate solution is 7 g / L;

[0078] S2. Under the conditions of stirring speed of 5r / min and temperature of 90°C, inject ammonia water and CO2 with a concentration of 1.7mol / L into the refined magnesium sulfate solution, and the introduction rate ratio of ammonia water to CO2 is 2:1;

[0079] After injection until the pH value reaches 9.4, a suspension I containing basic magnesium carbonate is obtained;

[0080] S3, cooling the suspension I to 35° C. and aging for 8 h to obtain a suspension II containing basic magnesium carbonate;

[0081] S4. Filter the suspension II to obtain a filtrate and a filter residue, recycle the filtrate, and dry and disperse the filter residue to obtain basic magnesium carbonate, which is marked as DT3 and has a bulk density of 0.09 g / mL.

[0082] Experimental Example 1 Flame retardant material performance verification experiment

[0083] The flame retardant material PVC is prepared using the basic magnesium carbonate glass microspheres T1-T5, DT1-DT2 prepared in Examples 1-5 and Comparative Examples 1-2 and the basic magnesium carbonate DT3 prepared in Comparative Example 3 as flame retardant raw materials. The specific preparation process is as follows: PVC and the flame retardant raw materials in a weight ratio of 7:3 are mixed on a high-speed mixer, the mixed materials are poured into a rubber mixer for mixing, the mixed mixture is then added to a flat vulcanizer for hot pressing, pressed into shape, cooled, and then cut to obtain the corresponding flame retardant material PVC. Among them, the flame retardant material PVC made of basic magnesium carbonate glass microspheres T1 to T5 are marked as PVCT1 to PVCT5 respectively (that is, the flame retardant material PVC made of basic magnesium carbonate glass microspheres T1 is marked as PVCT1, the flame retardant material PVC made of basic magnesium carbonate glass microspheres T2 is marked as PVCT2, and so on), the flame retardant material PVC made of basic magnesium carbonate glass microspheres DT1 to DT2 are marked as PVCDT1 to PVCDT2 respectively (that is, the flame retardant material PVC made of basic magnesium carbonate glass microspheres DT1 is marked as PVCDT1, and the flame retardant material PVC made of basic magnesium carbonate glass microspheres DT2 is marked as PVCDT2), and the flame retardant material PVC made of basic magnesium carbonate DT3 is marked as PVCDT3; at the same time, the flame retardant material PVC made by the above process without adding flame retardant raw materials and directly using PVP is marked as PVCDK as a blank control.

[0084] The performance of each flame retardant material PVC (including PVCT1~PVCT5, PVCDT1~PVCDT3 and PVCDK) was tested respectively, wherein the performance indicators included oxygen index test, tensile strength test and elongation at break test. The specific test results are shown in Table 1.

[0085] Among them, the oxygen index is tested according to the "Plastic Combustion Performance Test Method Oxygen Index Method" GB / T 2406;

[0086] The tensile strength and elongation at break are tested according to “Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber” GB / T 528-2009.

[0087] Table 1 List of test results of various flame retardant materials PVC

[0088]

[0089]

[0090] It can be seen from Table 1 that the basic magnesium carbonate glass microspheres prepared by the present invention have good flame retardancy, tensile strength and elongation at break. However, the flame retardant material PVC made from the basic magnesium carbonate glass microspheres of Comparative Examples 1-2 and the basic magnesium carbonate of Comparative Example 3 has relatively poor performance.

[0091] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing basic magnesium carbonate glass microspheres, characterized in that: The preparation method comprises taking a magnesium sulfate aqueous solution and a sodium carbonate aqueous solution, adding them dropwise into a reactor in opposite directions, adding hydrophilic glass microspheres at the same time, and then heating and crystallizing, standing and aging, filtering, washing and drying to obtain the basic magnesium carbonate glass microspheres.

2. The method for preparing basic magnesium carbonate glass microspheres according to claim 1, characterized in that: The preparation method comprises the following specific steps: S1, adding hydrophilic glass microspheres into the reactor; S2, taking an aqueous solution of magnesium sulfate and an aqueous solution of sodium carbonate, and adding them dropwise to the reactor in opposite directions; S3, after the double dropwise addition is completed, the obtained reaction solution is heated to crystallize and allowed to stand for aging to obtain an aged mixed solution; S4. The matured mixed solution is filtered, washed and dried to obtain the basic magnesium carbonate glass microspheres.

3. The method for preparing basic magnesium carbonate glass microspheres according to claim 1 or 2, characterized in that: During the process of adding the magnesium sulfate aqueous solution and the sodium carbonate aqueous solution into the reactor dropwise in opposite directions, the temperature in the reactor is 35 to 50° C. and the stirring speed is 200 to 300 r / min.

4. The method for preparing basic magnesium carbonate glass microspheres according to claim 1 or 2, characterized in that: The time for the double dropwise addition is 2 to 2.5 hours.

5. The method for preparing basic magnesium carbonate glass microspheres according to claim 1 or 2, characterized in that: The concentration of the hydrophilic glass microspheres in the reaction solution is 0.1-0.5 wt %.

6. The method for preparing basic magnesium carbonate glass microspheres according to claim 1 or 2, characterized in that: The molar ratio of magnesium sulfate in the magnesium sulfate aqueous solution to sodium carbonate in the sodium carbonate aqueous solution is 1:0.95-1.3; The concentration of magnesium sulfate in the magnesium sulfate aqueous solution is 0.2-0.5 mol / L; The concentration of sodium carbonate in the sodium carbonate aqueous solution is 0.2-0.5 mol / L.

7. The method for preparing basic magnesium carbonate glass microspheres according to claim 1 or 2, characterized in that: The temperature-raising crystallization is that after the double dropwise addition is completed, the reaction temperature of the obtained reaction solution is raised to 60-90° C., the stirring speed is reduced to 100-200 r / min, and the reaction time is more than 2 hours.

8. The method for preparing basic magnesium carbonate glass microspheres according to claim 1 or 2, characterized in that: The temperature for standing and aging is 60 to 90°C and the time is more than 2 hours.

9. The method for preparing basic magnesium carbonate glass microspheres according to claim 1 or 2, characterized in that: The reactor is a reaction kettle, and two oppositely arranged feeding ports on the reaction kettle are respectively connected to two dropping tubes that pass directly into the reaction kettle. The outlets of the two dropping tubes are close to the bottom of the reaction kettle, and the outlets of the two dropping tubes are oppositely arranged; and a soda-water mixer is arranged at the outlets of the two dropping tubes.

10. The method for preparing basic magnesium carbonate glass microspheres according to claim 1 or 2, characterized in that: The reactor is provided with a two-blade pitched-blade paddle agitator, and the inclination angle θ of the two blades in the two-blade pitched-blade paddle agitator is 45°.

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