Preparation method of silica-based porous flame-retardant particles

Abstract

The invention relates to a preparation method of silica-based porous flame-retardant particles, which comprises the following steps: firstly, mixing aluminum hydroxide powder and a phosphoric acid solution according to a certain proportion to form a binder, and then uniformly mixing and stirring the binder, silica-based hollow microspheres and deionized water; and then drying, pelleting and pressureless sintering are carried out to finally prepare the silicon dioxide porous flame-retardant particles. The silicon dioxide porous flame-retardant particle has the beneficial effects that the silicon dioxide porous flame-retardant particle can be prepared by pressureless sintering at a relatively low temperature, and the prepared silicon dioxide porous flame-retardant particle is high in porosity, small in stacking density, small in heat conductivity coefficient and proper in particle size, has certain compressive strength, and is an environment-friendly inorganic flame-retardant material with wide application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic flame-retardant materials, and particularly relates to a preparation method of silica-based porous flame-retardant particles. BACKGROUND

[0002] Lithium batteries and other flammable dangerous goods may cause heat and fire due to external environmental changes or internal reactions during transportation, which seriously threatens the safety of equipment, personnel and environment during transportation. In order to effectively prevent or alleviate the harm caused by the heat and fire of flammable dangerous goods, a porous lightweight insulating flame-retardant material is invented in combination with the characteristics of dangerous goods packaging, transportation operation requirements and economic applicability. The material can be used as a filler in the packaging, providing cushioning and shock protection for the goods while absorbing heat, controlling the fire range, preventing or slowing down the fire, and providing flame-retardant protection for the cargo hold.

[0003] The present application develops a porous inorganic flame-retardant material with high porosity, small bulk density, low thermal conductivity, and particle size of about 3-6mm, and has a certain compressive strength to cope with bumps, impacts or extrusion during transportation. Due to the light weight of the porous inorganic flame-retardant material, the transportation cost can be effectively reduced.

[0004] Inorganic flame-retardant materials are widely used in clothing, petroleum, chemical industry, metallurgy, shipbuilding, fire protection, national defense and other fields due to their own non-combustibility, ability to inhibit or delay combustion, and non-production of other harmful substances during combustion. Among them, porous ceramic materials have the characteristics of insulation, low density and low thermal conductivity, but the porosity of the porous ceramic prepared by the commonly used preparation method is generally between 30%-70%. Particle packing method is a commonly used method for preparing porous ceramics, although the porosity can be adjusted by changing the particle packing method and particle grading, but the porosity is generally not more than 50%. The porosity of silica aerogel material can be greater than 90%, but it is difficult to form microspheres with certain mechanical strength and specific size, which cannot provide cushioning and shock protection for goods.

[0005] The main chemical component of the raw material hollow microbeads of silicon dioxide used in the present application is soda lime borosilicate glass, which has the characteristics of light weight, heat insulation, stable chemical properties, etc. Meanwhile, the hollow microbeads contain thin N2 or CO2 gas inside, even if the microspheres are broken due to exceeding the pressure they can bear, or softened at high temperature, the N2 and CO2 inside the spheres will escape, which is helpful for fire extinguishing. At present, the hollow microbeads are used as raw materials to prepare flame-retardant and heat-insulating materials, mainly by directly sintering at high temperature, or by adding them as fillers to improve the density, thermal conductivity and other properties of organic systems. However, the method of directly combining the microbeads by high temperature sintering cannot guarantee good contact between the microbeads, and may cause damage to the microbeads when a large pressure is applied. The thermal insulation materials prepared by adding the hollow microbeads to the organic system have relatively high density and low compressive strength, and the high temperature resistance of the organic system is generally poor, so the service temperature is generally low. In comparison, it is of great significance to make full use of the characteristics of the hollow microbeads to prepare flame-retardant and heat-insulating materials with low bulk density, low thermal conductivity and high mechanical strength at a relatively low temperature.

[0006] The key to preparing the porous silica flame-retardant particles from the hollow microbeads lies in how to select a suitable binder to connect the microbeads, and how to make the prepared porous flame-retardant particles have good mechanical properties and flame-retardant properties at a relatively low sintering temperature without damaging the hollow structure of the microbeads. As an inorganic high-temperature binder, aluminum phosphate has the advantages of excellent high-temperature resistance, high bonding strength, excellent dielectric properties, small thermal expansion coefficient, small solidification shrinkage, excellent durability, low price, simple preparation process, short production cycle, etc., and is a binder with great development prospect, but it also has the disadvantages of poor acid and alkali resistance, poor water resistance, high brittleness and poor impact resistance.

[0007] In the aluminum phosphate binder, by adjusting the amount of phosphoric acid, metal oxide and hydroxide, aluminum phosphate binders with different molar ratios of P to Al can be obtained. Among them, aluminum dihydrogen phosphate, which has a wide range of applications, is an aluminum phosphate salt with (AlH2P3O 10 ·2H2O) (type C), Al (H2PO4) 3·1.5H2O and Al (H2PO4) 3·3H2O three types, all of which are colorless transparent viscous solution. The aluminum phosphate binder can be used as a flame-retardant material for refractory materials, fibers, wood, etc. It can also be used to produce heat-resistant insulation products due to its electrical insulation property. In addition, it is also one of the coating materials with great potential in the field of high-temperature oxidation prevention. SUMMARY

[0008] In view of the above problems existing in the prior art, the main purpose of the present application is to provide a preparation method of porous flame-retardant particles based on silicon dioxide.

[0009] The technical scheme of the present application is as follows:

[0010] A preparation method of a silica-based porous fire-retardant particle, comprising the following steps:

[0011] S1: uniformly mixing silica-based hollow microbeads, an aluminum-based binder, and deionized water;

[0012] S2: then drying and agglomerating through an oven with a temperature of 65-105 DEG C, and obtaining spherical green bodies with a diameter of 3-6 mm through a pelletizer;

[0013] S3: placing the spherical green bodies in an oven with a temperature of 65-105 DEG C for 4.5-7 h for preliminary solidification;

[0014] S4: using a muffle furnace for pressureless sintering of the spherical green bodies after preliminary solidification, the temperature of the pressureless sintering being 500-800 DEG C, and the holding time being 1-3 h, to obtain fire-retardant silica porous ceramic microspheres.

[0015] The aluminum-based binder in the step S1 is prepared by the following method:

[0016] First, a certain proportion of phosphoric acid solution and aluminum hydroxide powder are mixed and reacted in batches, 650 r / min constant temperature stirring for 1-2 h until the solution is clear, then a certain amount of deionized water is added to dilute the clear solution, constant temperature stirring for more than 1 h, and finally a certain mass percentage of aluminum-based adhesive is obtained.

[0017] The mass percentage of the phosphoric acid solution is 50 wt%, and the specific preparation method is as follows:

[0018] The mass percentage of the phosphoric acid solution is 85 wt%, and the deionized water is mixed according to the mass percentage of 1:0.7 to prepare.

[0019] The aluminum hydroxide and the phosphoric acid solution are mixed according to the molar ratio of Al to P of 1:3, and constant temperature stirring is carried out at a temperature of 90 DEG C until the solution is clear, so that the two are fully reacted.

[0020] The composition of the aluminum-based binder is aluminum phosphate salt, and the aluminum phosphate salt is aluminum dihydrogen phosphate.

[0021] The aluminum-based binder is aluminum dihydrogen phosphate with a mass percentage of 15 wt%.

[0022] The raw material of the silica-based hollow microbeads is at least one of silica, sodium oxide, calcium oxide, and boron oxide, the particle size of the silica-based hollow microbeads is 10-250 mu m, the wall thickness is 1-2 mu m, and the inside is filled with thin N2 gas or CO2 gas.

[0023] The step S1 is uniformly mixing the silica-based hollow microbeads, the aluminum-based binder and the deionized water, wherein the mass percentage of the silica-based hollow microbeads is 60wt%-75wt%, and the mass percentage of the aluminum-based binder is 166.7wt%-266.7wt%.

[0024] The diameter of the silica-based porous fire-retardant particle is 3-6mm, and the silica-based porous fire-retardant particle is composed of 10-250um hollow microspheres.

[0025] The present application has the following advantages and beneficial effects: the preparation method of the silica-based porous fire-retardant particle provided by the embodiment of the present application, the prepared porous silica-based fire-retardant particle, the reasonable proportion of the aluminum-based binder, the realization of the pressureless sintering at a lower temperature, the plasticity and certain mechanical strength of the porous fire-retardant particle, the advantages of high porosity, low bulk density and good fire-retardant performance, the process suitable for industrial production, environmental protection, non-toxicity, environmental friendliness, wide application, and application in fire suppression, flammable dangerous goods transportation protection, building fireproofing and heat preservation, etc. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a macrograph of the porous silica-based fire-retardant particle prepared by the embodiment 2 of the present application.

[0027] Figure 2 is an SEM graph of the porous silica-based fire-retardant particle prepared by the embodiment 2 of the present application.

[0028] Figure 3 is a process flow chart of the aluminum-based binder aluminum phosphate solution prepared by the embodiment of the present application.

[0029] Figure 4 is a process flow chart of the porous silica-based fire-retardant particle prepared by the embodiment of the present application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] like Figures 1 to 4 As shown: The method for preparing silica-based porous flame retardant particles according to an embodiment of the present invention comprises the following steps:

[0033] S1: uniformly mix silica-based hollow microspheres, aluminum-based binder and deionized water;

[0034] S2: The pellets are then dried in an oven at 65-105°C to form a mass, and pelletized into spherical green pieces with a diameter of 3-6 mm using a pelletizing machine;

[0035] S3: placing the spherical green body in an oven at a temperature of 65-105° C. for 4.5-7 hours for preliminary curing;

[0036] S4: The spherical green body after preliminary solidification is subjected to pressureless sintering in a muffle furnace. The pressureless sintering temperature is 500-800° C. and the holding time is 1-3 hours to obtain flame-retardant porous silica ceramic microspheres.

[0037] The aluminum-based binder in step S1 is prepared by the following method:

[0038] First, take a certain proportion of phosphoric acid solution and aluminum hydroxide powder, add the aluminum hydroxide powder into the phosphoric acid solution in batches for mixing and reaction, and stir at a constant temperature of 650r / min for 1-2 hours until the solution becomes clear. Then, add a certain amount of deionized water to dilute the clear solution, and stir at a constant temperature for more than 1 hour to finally obtain an aluminum-based adhesive with a certain mass percentage.

[0039] The mass percentage of the phosphoric acid solution is 50wt%, and the specific preparation method is as follows:

[0040] The method is prepared by mixing 85 wt % phosphoric acid solution and deionized water in a mass ratio of 1:0.7.

[0041] The aluminum hydroxide and phosphoric acid solution are mixed in a molar ratio of Al to P of 1:3, and are stirred at a constant temperature of 90° C. until the mixture becomes clear, so that the two react fully.

[0042] The component of the aluminum-based binder is aluminum phosphate, and the aluminum phosphate is aluminum dihydrogen phosphate.

[0043] The aluminum-based binder is aluminum dihydrogen phosphate with a mass percentage of 15 wt%.

[0044] The silica-based hollow microbeads, the aluminum-based binder and the deionized water are uniformly mixed in step S1, wherein the mass percentage of the silica-based hollow microbeads is 60wt%-75wt%, and the mass percentage of the aluminum-based binder is 166.7wt%-266.7wt%.

[0045] The diameter of the silica-based porous fireproof particles is 3-6mm, and the silica-based porous fireproof particles are composed of 10-250μm hollow microspheres which are stacked with each other and keep the structural integrity, and the surface of the microspheres is tightly covered and bonded by the aluminum-based binder.

[0046] In the embodiment of the present application, the bulk density of the porous silica-based fireproof particles is characterized by the following method: a part of the dried sample is taken, and first, the dry weight of the sample in the air is measured by using a densimeter and recorded as m1, then the sample is placed in a basket of solid density agent, and the floating weight of the sample in deionized water is measured and recorded as m2, and then the bulk density (D b ) can be calculated by the formula

[0047] .

[0048] In the embodiment of the present application, the bulk density of the porous silica-based fireproof particles is characterized by the following method: after the sample is washed and dried, the sample is placed in a 100mL beaker, and the sample is filled to the 100mL scale line, and then the mass of the filled product is measured and recorded as m3, and then the bulk density (ρ) can be calculated by the formula

[0049] .

[0050] In the embodiment of the present application, the true density of the porous silica-based fireproof particles is characterized by the following method: a part of the sample is taken and weighed and recorded as m4, and after being stirred and ground, the powder is placed in a tablet press, and a cake-shaped solid is obtained after being pressed at a pressure of 30MPa for 2min, and then the thickness and diameter of the cake-shaped solid are measured by using a screw micrometer, and the volume is calculated and recorded as v, and the influence of the internal fine pores on the true density is ignored, and then the true density (D r ) can be calculated by the formula .

[0051] In the embodiment of the present application, the porosity (P r ) of the porous silica-based fireproof particles can be calculated by the formula

[0052] .

[0053] The thermal conductivity of the porous silica-based flame-retardant particle is characterized by the following method: a sensor probe is placed in the middle of the porous silica-based flame-retardant particle, the sensor probe is covered by the porous silica-based flame-retardant particle sample, a known amount of power is transmitted to the sample through the probe, the sample temperature increases, the resistance of the probe changes accordingly, the temperature-time curve is obtained by recording the change of the probe voltage and current with time, and thus the thermal conductivity of the porous silica-based flame-retardant particle is calculated.

[0054] The compressive strength of the porous silica-based flame-retardant particle is characterized by the following method: 10 silica-based porous flame-retardant particles are taken, the maximum compressive strength before cracking of a single particle is measured using a multifunctional material surface performance tester, which is the single-particle compressive strength, and then the average value of 10 silica-based porous flame-retardant particles is taken as the single-particle compressive strength.

[0055] Example 1

[0056] The preparation method of the aluminum-based adhesive in Example 1 of the present application is as follows: aluminum hydroxide powder and a 85wt% phosphoric acid solution are taken according to a molar ratio of Al to P of 1:3.1; deionized water is added to dilute the phosphoric acid solution to 50wt%, the aluminum hydroxide powder is added to the phosphoric acid solution in batches for mixing and reaction, constant temperature stirring is carried out at 650r / min and 90℃ for 2h until the solution is clear, then a certain amount of deionized water is added to the clear solution to dilute the binder to 15wt% of aluminum dihydrogen phosphate, and constant temperature stirring is carried out for more than 1h to obtain the aluminum-based adhesive.

[0057] The preparation method of the porous silica-based flame-retardant particle in the example of the present application is as follows: the raw material components are weighed according to the following mass percentages: 65wt% of silica hollow glass microspheres, 233.3wt% of aluminum-based binder, and here the effective component of the aluminum-based binder is 15wt% of aluminum dihydrogen phosphate, which accounts for 35wt% of the final product.

[0058] First, the silica-based hollow microspheres, the aluminum-based binder and deionized water are mixed uniformly, dried into a lump in an 80℃ oven, then a spherical green body with a diameter of 5mm is obtained through a pill-making machine, and then the spherical green body is placed in an 80℃ oven for 6h for preliminary solidification. Finally, the spherical green body is placed in a muffle furnace, heated to 650℃ at a heating rate of 5℃ / min, pressureless sintering is carried out, the temperature is kept for 2h, and then cooled to room temperature to obtain the porous silica-based flame-retardant particle.

[0059] Example 2

[0060] The difference between the embodiment 2 and the embodiment 1 of the present application is that the preparation method of the porous silica-based flame-retardant particle is as follows: the raw material components are weighed according to the following mass percentage: 70wt% of the hollow glass microbeads of silica, 200wt% of the aluminum-based binder, wherein the effective component of the aluminum-based binder is 15wt% of aluminum dihydrogen phosphate, and the mass percentage of the aluminum dihydrogen phosphate in the final product is 30wt%, and the other conditions are the same.

[0061] Embodiment 3

[0062] The difference between the embodiment 3 and the embodiment 1 of the present application is that the preparation method of the porous silica-based flame-retardant particle is as follows: the raw material components are weighed according to the following mass percentage: 75wt% of the hollow glass microbeads of silica, 166.7wt% of the aluminum-based binder, wherein the effective component of the aluminum-based binder is 15wt% of aluminum dihydrogen phosphate, and the mass percentage of the aluminum dihydrogen phosphate in the final product is 25wt%, and the other conditions are the same.

[0063] Embodiment 4

[0064] The difference between the embodiment 4 and the embodiment 1 of the present application is that the preparation method of the porous silica-based flame-retardant particle is as follows: the raw material components are weighed according to the following mass percentage: 80wt% of the hollow glass microbeads of silica, 133.3wt% of the aluminum-based binder, wherein the effective component of the aluminum-based binder is 15wt% of aluminum dihydrogen phosphate, and the mass percentage of the aluminum dihydrogen phosphate in the final product is 20wt%, and the other conditions are the same.

[0065] Embodiment 5

[0066] The difference between the embodiment 5 and the embodiment 2 of the present application is that the sintering temperature of the porous silica-based flame-retardant particle is 700℃, and the other conditions are the same.

[0067] Embodiment 6

[0068] The difference between the embodiment 6 and the embodiment 2 of the present application is that the sintering temperature of the porous silica-based flame-retardant particle is 600℃, and the other conditions are the same.

[0069] Embodiment 7

[0070] The difference between the embodiment 7 and the embodiment 2 of the present application is that the sintering temperature of the porous silica-based flame-retardant particle is 550℃, and the other conditions are the same.

[0071] Embodiment 8

[0072] The difference between Example 8 of the present invention and Example 1 is that the preparation method of porous silica-based flame retardant particles is as follows: the raw material components are weighed according to the following mass percentages: 60wt% of silica hollow glass microspheres, 15wt% of aluminum-based binder 266.7wt%, where the effective ingredient of the aluminum-based binder is 15wt% of aluminum dihydrogen phosphate by mass, which accounts for 40wt% of the mass percentage of the final product, and the other conditions are the same.

[0073] Example 9

[0074] The difference between Example 9 of the present invention and Example 3 is that the sintering temperature of the porous silica-based flame retardant particles is 750° C., and the other conditions are the same.

[0075] The properties of the porous silica-based flame retardant particles prepared in different embodiments are shown in Table 1.

[0076] Table 1 Properties of porous silica-based flame retardant particles prepared in Examples 1-9

[0077]

[0078] Comparing the performance of the porous silica-based flame retardant particles prepared in different embodiments, in some embodiments, the pressureless sintering temperature of the flame retardant particles is 500-800°C, and the optimal temperature is 550-700°C; in some embodiments, the amount of aluminum-based binder added is 166.7wt%-266.7wt%, and the optimal addition amount is 166.7wt%-233.3wt.

[0079] In summary, the porous silica-based flame retardant particles prepared by the present invention have the characteristics of low bulk density, high porosity, good thermal insulation performance, etc., while also having a certain compressive strength, achieving a good balance between density, thermal conductivity and compressive strength.

[0080] Figure 1 This is a macroscopic image of the porous silica-based flame retardant particles prepared in Example 2 of the present invention; Figure 2 This is an SEM image of the porous silica-based flame retardant particles prepared in Example 2 of the present invention; Figure 3 The process flow chart of the aluminum-based adhesive prepared by the present invention; Figure 4 The process flow chart of the porous silica-based flame retardant particles prepared by the present invention. Figure 1 It can be seen that the porous silica flame retardant particles are not damaged and the particle size is relatively uniform. Figure 2 It can be seen that the porous silica flame retardant particles are composed of hollow microbeads of about 100 μm stacked together. The hollow microbeads maintain structural integrity as a whole, with only a small amount of breakage. The necks of the hollow microbeads are tightly bonded together by an aluminum-based adhesive.

[0081] Finally, it should be noted that the above-described embodiments are merely used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be replaced equivalently; and these modifications or replacements do not cause the essential nature of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of making a porous silica-based flame retardant particle, characterized by: The method comprises the following steps: S1: uniformly mixing silica-based hollow microspheres, aluminum-based binder and deionized water; S2: then drying and agglomerating through an oven with a temperature of 65-105 DEG C, and obtaining spherical green bodies with a diameter of 3-6 mm through a pill-making machine; S3: placing the spherical green bodies in an oven with a temperature of 65-105 DEG C for 4.5-7 h for preliminary solidification; S4: using a muffle furnace for pressureless sintering of the preliminary solidified spherical green bodies, the pressureless sintering temperature is 500-800 DEG C, and the holding time is 1-3 h, to obtain the flame-retardant silica-based porous ceramic microspheres.

2. The method of preparing silica-based porous flame retardant particles according to claim 1, characterized in that, The aluminum-based binder in step S1 is prepared by the following method: First, a certain proportion of phosphoric acid solution and aluminum hydroxide powder are mixed, the aluminum hydroxide powder is added into the phosphoric acid solution in batches, mixed and reacted, stirred at 650 r / min for 1-2 h, until the solution is clear, then a certain amount of deionized water is added to dilute the clear solution, and stirred at constant temperature for more than 1 h, finally a certain mass percentage of aluminum-based binder is obtained.

3. The method of preparing silica-based porous flame retardant particles according to claim 2, characterized in that, The mass percentage of the phosphoric acid solution is 50wt%, and the specific preparation method is as follows: The mass percentage of the phosphoric acid solution is 50wt%, and the specific preparation method is as follows:

4. The method of making silica-based porous flame retardant particles according to claim 2, wherein, The aluminum hydroxide and the phosphoric acid solution are mixed according to the molar ratio of Al to P of 1:3, and stirred at a temperature of 90 DEG C until clear, so that the two are fully reacted.

5. The method of making silica-based porous flame retardant particles according to claim 1, wherein, The aluminum-based binder is an aluminum phosphate salt.

6. The method of making silica-based porous flame retardant particles according to claim 1, wherein, The particle size of the silica-based hollow microspheres is 10-250 μm, and the wall thickness is 1-2 μm.

7. The method of making silica-based porous flame retardant particles according to claim 1, wherein, In step S1, the silica-based hollow microspheres, aluminum-based binder and deionized water are uniformly mixed, wherein the mass percentage of the silica-based hollow microspheres is 60wt%-75wt%, and the mass percentage of the aluminum-based binder is 166.7wt%-266.7wt%.

8. The method of making silica-based porous flame retardant particles according to claim 1, wherein, The diameter of the silica-based porous flame-retardant particles is 3-6 mm, and the silica-based porous flame-retardant particles are composed of 10-250 μm hollow microspheres stacked together.

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