Filler of light calcium silicate cement board and preparation method of filler

Abstract

The invention belongs to the technical field of building materials, and particularly relates to filler of a light calcium silicate cement board and a preparation method of the filler. According to the invention, carboxyl modified activated carbon is used for impurity removal treatment, a mesoporous material is used for purification treatment, benzene ring-containing polyacrylamide is introduced, and a coaxial electrostatic spraying molding process is matched, so that the whiteness of the calcium silicate filler is effectively increased, the stacking density is reduced, and a relatively high specific surface area can be obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to a filler for a lightweight calcium silicate cement board and a preparation method thereof. Background Art

[0002] Calcium silicate cement board is a commonly used new type of building and industrial board, which has the characteristics of fire prevention, moisture prevention, sound insulation, and good durability. It is an ideal decorative board for ceiling and partition. The difference between calcium silicate board and cement board is that it uses silicon and calcium with low thermal conductivity as raw materials to replace cement, so that the thermal conductivity of the board is reduced, thus playing a role in heat preservation and insulation. The excellent performance of calcium silicate board mainly comes from calcium silicate filler, which has the following characteristics: good high-temperature stability, can be used as heat insulation material in high-temperature environment; chemically stable, not easy to react with other substances; friendly to human body and environment, and safe to use.

[0003] Chinese Patent (Publication No. CN118745088A) discloses a microporous calcium silicate lightweight aggregate, a lightweight calcium silicate board and a preparation method thereof. The microporous calcium silicate lightweight aggregate is prepared by using calcium hydroxide powder, ultrafine quartz powder, zirconium dioxide and sodium hydroxide as raw materials, stirring in an ultrasonic treatment environment, and then carrying out hydrothermal reaction. This microporous calcium silicate lightweight aggregate has a small density, is lighter and more portable, and is suitable for preparing a lighter calcium silicate board; it has excellent strength, high compressive and flexural properties, and the prepared calcium silicate board can meet the requirements of various complex building structures; it can also absorb free moisture in the air and play a role in regulating indoor humidity. However, this patent fails to solve the problems existing in the filler of the lightweight calcium silicate cement board in the prior art, such as high impurity content resulting in low whiteness, high bulk density, and small specific surface area, which seriously affect its actual use.

[0004] Therefore, there is an urgent need for a filler for a lightweight calcium silicate cement board, which can reduce the impurity content in calcium silicate, and at the same time, combined with other forming processes, increase the whiteness of calcium silicate filler, reduce the bulk density, and obtain a higher specific surface area. Summary of the Invention

[0005] The purpose of the present invention is to provide a filler for a lightweight calcium silicate cement board and a preparation method thereof. By using carboxyl-modified activated carbon for impurity removal treatment, mesoporous materials for purification treatment, introducing benzene ring-containing polyacrylamide, and at the same time, combined with coaxial electrostatic spraying forming process, the whiteness of calcium silicate filler can be effectively increased, the bulk density can be reduced, and a higher specific surface area can be obtained.

[0006] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0007] The first aspect of the present invention provides a preparation method of a filler for a lightweight calcium silicate cement board, comprising the following steps:

[0008] Step S1: By weight, add 26 - 30 parts of sodium metasilicate to 60 - 70 parts of deionized water, stir and mix evenly, then perform impurity removal treatment through activated carbon to obtain the impurity-removed solution. Add 2 - 4 parts of surfactant and 0.4 - 0.8 part of polyacrylamide to 60 - 70 parts of the impurity-removed solution, and stir for 50 - 60 min to obtain an aqueous sodium silicate solution after impurity removal.

[0009] Step S2: By weight, add 20 - 24 parts of calcium nitrate to 70 - 80 parts of deionized water, stir for 40 - 50 min, and then perform purification treatment through mesoporous materials to obtain a purified calcium nitrate solution.

[0010] Step S3: By weight, under the conditions of a temperature of 60 - 70 °C and a stirring speed of 100 - 200 r / min, add 70 - 80 parts of the purified calcium nitrate solution dropwise to 60 - 70 parts of the aqueous sodium silicate solution after impurity removal at a rate of 3 - 5 mL / h to obtain a calcium silicate mixture.

[0011] Step S4: Use the calcium silicate mixture as the cortical liquid and deionized water as the core liquid for coaxial electrospray, then perform static aging, filtration, water washing, and freeze-drying to obtain the filler for lightweight calcium silicate cement board.

[0012] As a preferred solution, the activated carbon is carboxyl-modified activated carbon; the preparation method of the carboxyl-modified activated carbon includes: by weight, disperse 6 - 10 parts of activated carbon in a mixed solution of 20 - 24 parts of sulfuric acid and 26 - 30 parts of nitric acid, perform ultrasonic dispersion for 60 - 80 min under the condition of a power of 800 - 1000 W, then perform heat treatment for 60 - 90 min under the condition of 150 - 160 °C, and filter to obtain an acidified intermediate; add 6 - 10 parts of the acidified intermediate to 80 - 100 parts of N,N-dimethylformamide, perform ultrasonic dispersion for 30 - 40 min, then add 4 - 6 parts of dicyclohexylcarbodiimide, 1 - 3 parts of 4-dimethylaminopyridine, and 6 - 8 parts of acrylic acid, place it under the protection of a nitrogen atmosphere, and react for 20 - 24 h under the condition of 82 - 88 °C, filter, wash with water, and dry to obtain carboxyl-modified activated carbon.

[0013] As a preferred solution, the average particle size of the activated carbon is 80 - 120 mesh.

[0014] By introducing carboxyl groups through surface modification of the activated carbon, carboxyl groups, as a kind of strong polar groups, can combine with impurities through hydrogen bonding, electrostatic interaction, or chemical adsorption, etc., reduce the impurity content, and improve the whiteness of the filler.

[0015] As a preferred embodiment, the preparation method of the mesoporous material comprises: by weight, mixing 100-120 parts of absolute ethanol and 20-30 parts of deionized water, adding 0.2-0.6 part of ferric oxide and ultrasonically dispersing for 50-60 min, then adding 2-4 parts of tetraethyl orthosilicate and 3-5 parts of ammonia water, stirring at room temperature for 8 h, washing with deionized water, and drying in vacuum to obtain an intermediate product; mixing 80-90 parts of absolute ethanol, 10-20 parts of deionized water and 4-6 parts of ammonia water, stirring at 30-40 °C for 10-20 min, then adding 4-6 parts of the intermediate product and 0.2-0.4 part of (3-mercaptopropyl)triethoxysilane and stirring for reaction for 20-24 h, centrifuging to obtain a solid after the reaction is completed, washing the solid with absolute ethanol, and drying to obtain the mesoporous material.

[0016] The mesoporous material can reduce the iron content through multiple effects. Firstly, the large specific surface area and porous channels provided by the mesoporous structure enable metal ions to be adsorbed into the material interior through physical effects such as van der Waals forces. Secondly, the ferric oxide endows the material with magnetism, enabling effective adsorption of magnetic metal elements. Additionally, the presence of sulfhydryl groups increases the negative charge on the surface, which can combine with impurities through electrostatic attraction, coordination bonds, etc., adsorbing impurities through multiple levels, thereby improving the whiteness of the filler.

[0017] As a preferred embodiment, the polyacrylamide is benzene ring-containing polyacrylamide; the preparation method of the benzene ring-containing polyacrylamide comprises: by weight, mixing 26-28 parts of acrylonitrile, 22-24 parts of 2,4-diphenyl-4-methyl-1-pentene and 8-9 parts of diethyl ether tetrafluoroborate, reacting at 36-40 °C for 6-8 h, then standing for 24-30 h, washing with deionized water, and drying in vacuum at 45-50 °C for 4-5 h to obtain a modified monomer; adding 70-74 parts of commercially available acrylamide and 16-18 parts of 2-acrylamido-2-methylpropanesulfonic acid to 310-320 parts of deionized water, stirring for 1-2 h, then adjusting the pH to 8.4-8.6 with a sodium hydroxide solution with a mass concentration fraction of 20%, under a nitrogen atmosphere, adding 0.002-0.004 part of the modified monomer, 0.002-0.004 part of sodium dodecyl sulfonate, 0.004-0.006 part of azo initiator V50, 0.002-0.004 part of ammonium persulfate, 0.001-0.003 part of sodium bisulfite, 0.002-0.004 part of disodium ethylenediaminetetraacetate and 0.07-0.09 part of thiourea for reaction, the reaction initiation temperature is 20-24 °C, and the reaction time is 5-7 h; after the reaction is completed, drying the reaction product in vacuum at 45-55 °C for 6-8 h, then pulverizing and sieving to obtain the benzene ring-containing polyacrylamide.

[0018] In the present invention, surfactant monomer molecules will spontaneously aggregate into spherical micelles. A large number of positively charged groups are distributed on the outer part of the spherical micelles. The introduction of a benzene ring with a large steric hindrance in the polyacrylamide containing a benzene ring can restrict the movement of molecular chains and form a certain steric hindrance, thereby ensuring that the formed spherical micelles will not agglomerate and effectively increasing the specific surface area.

[0019] As a preferred embodiment, the surfactant is selected from any one or a combination of at least two of dodecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium chloride, and hexadecyl trimethyl ammonium chloride.

[0020] As a preferred embodiment, the conditions for coaxial electrospray include: the flow rate of the cortical liquid is 2.2 - 2.8 mL / h, the flow rate of the core liquid is 1.4 - 1.8 mL / h, the voltage is 14 - 20 kV, the receiving distance is 16 - 20 cm, and the time is 60 - 90 min.

[0021] By using coaxial electrostatic spraying for processing and forming, and cooperating with freeze-drying to obtain the filler of the calcium silicate lightweight cement board, wherein the cortical layer of the coaxial electrospinning is a calcium silicate emulsion, and the core layer is deionized water. During the process of coaxial electrospinning, the deionized water in the core layer will be wrapped by the cortical solution and removed during the subsequent freeze-drying process, thereby forming a "honeycomb-like" porous structure and effectively reducing the bulk density of the filler.

[0022] As a preferred embodiment, the conditions for static aging include: the temperature is 4 - 10 °C, and the time is 20 - 24 h.

[0023] As a preferred embodiment, the conditions for freeze-drying include: the temperature is -24 °C to -20 °C, the time is 24 - 48 h, and the vacuum degree is 0.12 - 0.16 MPa.

[0024] The second aspect of the present invention provides a filler for a calcium silicate lightweight cement board prepared by the method as described in the first aspect and its preparation method.

[0025] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0026] 1. By introducing carboxyl groups through surface modification of activated carbon in the present invention, carboxyl groups, as a kind of strongly polar groups, can combine with impurities through hydrogen bonding, electrostatic interaction or chemical adsorption, etc., reduce the impurity content, and improve the whiteness of the filler.

[0027] 2. The mesoporous material of the present invention can reduce the iron content through multiple effects. Firstly, the large specific surface area and porous channels provided by the mesoporous structure enable metal ions to be adsorbed into the material interior through physical actions such as van der Waals forces. Secondly, the magnetite endows the material with magnetism, enabling effective adsorption of magnetic metal elements. Additionally, the presence of mercapto groups increases the negative charge on the surface, which can combine with impurities through electrostatic attraction, coordination bonds, etc., thereby improving the whiteness of the filler.

[0028] 3. When the surfactant monomer molecules are added in the present invention, they will spontaneously aggregate into spherical micelles. A large number of positively charged groups are distributed on the outer part of the spherical micelles, and the introduction of benzene rings with large steric hindrance in the polyacrylamide containing benzene rings can restrict the movement of molecular chains, forming a certain steric hindrance, thereby ensuring that the formed spherical micelles will not agglomerate and effectively increasing the specific surface area.

[0029] 4. In the present invention, the filler of the lightweight calcium silicate cement board is obtained by using coaxial electrostatic spraying for processing and forming, in combination with freeze-drying. The skin layer of the coaxial electrospinning is a calcium silicate emulsion, while the core layer is deionized water. During the process of coaxial electrospinning, the deionized water in the core layer will be wrapped by the skin layer solution and removed during the subsequent freeze-drying process, thereby forming a "honeycomb-like" porous structure, effectively reducing the bulk density of the filler. Detailed implementation manners

[0030] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0031] The sources of some components in the examples and comparative examples are as follows:

[0032] Sodium metasilicate, CAS No. 13517-24-3, purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0033] Dodecyltrimethylammonium chloride, CAS No. 112-00-5, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0034] Tetradecyltrimethylammonium chloride, CAS No. 4574-04-3, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0035] Hexadecyltrimethylammonium chloride, CAS No. 112-02-7, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0036] Polyacrylamide, product number S31321, purchased from Shanghai Yuanye Bio-Technology Co., Ltd.;

[0037] Activated carbon Ⅰ, with the product number C299105, an average particle size of 100 mesh, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0038] Activated carbon Ⅱ, with the product number A768977, an average particle size of 200 mesh, was purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0039] Activated carbon Ⅲ, with the product number A805342, an average particle size of 12 mesh, was purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0040] Calcium nitrate, CAS number 13477-34-4, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0041] Dicyclohexylcarbodiimide, CAS number 538-75-0, was purchased from Zhongshan Dixin Chemical Industry Co., Ltd.;

[0042] 4-Dimethylaminopyridine, CAS number 1122-58-3, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0043] Acrylic acid, CAS number 79-10-7, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0044] Iron(II,III) oxide, CAS number 12227-89-3, was purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0045] Tetraethyl orthosilicate, CAS number 78-10-4, was purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0046] (3-Mercaptopropyl)triethoxysilane, CAS number 14814-09-6, was purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0047] Acrylonitrile, CAS number 107-13-1, was purchased from Beijing Innochem Science & Technology Co., Ltd.;

[0048] 2,4-Diphenyl-4-methyl-1-pentene, CAS number 6362-80-7, was purchased from Tokyo Chemical Industry Co., Ltd.;

[0049] Diethyl ether tetrafluoroborate, CAS number 67969-82-8, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0050] Acrylamide, CAS number 79-06-1, was purchased from Shandong Wanhua Tianhe New Materials Co., Ltd.;

[0051] 2-Acrylamido-2-methylpropanesulfonic acid, CAS number 15214-89-8, was purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0052] Sodium dodecyl sulfonate, CAS No. 2386-53-0, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0053] Azo initiator V50, CAS No. 2997-92-4, was purchased from Guangzhou Yuanda New Materials Co., Ltd.;

[0054] Ammonium persulfate, CAS No. 7727-54-0, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0055] Sodium bisulfite, CAS No. 7631-90-5, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0056] Disodium ethylenediaminetetraacetate, CAS No. 139-33-3, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0057] Thiourea, CAS No. 62-56-6, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0058] Example 1

[0059] This example provides a preparation method for the filler of a lightweight calcium silicate cement board, including the following steps:

[0060] Preparation of carboxyl-modified activated carbon: By weight, 10 parts of activated carbon I (product number C299105, average particle size 100 mesh) were dispersed in a mixed solution of 24 parts of sulfuric acid and 30 parts of nitric acid, ultrasonically dispersed for 80 min under the condition of a power of 1000 W, then heat-treated at 160 °C for 60 min, and the acidified intermediate was obtained after filtration; 10 parts of the acidified intermediate were added to 100 parts of N,N-dimethylformamide and ultrasonically dispersed for 40 min, then 6 parts of dicyclohexylcarbodiimide, 3 parts of 4-dimethylaminopyridine and 8 parts of acrylic acid were added, placed under nitrogen atmosphere protection, reacted at 88 °C for 20 h, filtered, washed with water, and dried to obtain carboxyl-modified activated carbon.

[0061] Preparation of mesoporous material: By weight, 120 parts of absolute ethanol and 30 parts of deionized water were mixed, 0.6 part of iron tetroxide was added and ultrasonically dispersed for 60 min, then 4 parts of tetraethyl orthosilicate and 5 parts of ammonia water were added, and stirred at room temperature for 8 h, washed with deionized water, and dried in vacuum to obtain an intermediate product; 90 parts of absolute ethanol, 20 parts of deionized water and 6 parts of ammonia water were mixed, stirred at 40 °C for 10 min, then 6 parts of the intermediate product and 0.4 part of (3-mercaptopropyl)triethoxysilane were added and stirred for reaction for 24 h. After the reaction was completed, the solid was obtained by centrifugation, and the solid was washed with absolute ethanol and dried to obtain the mesoporous material.

[0062] Preparation of polyacrylamide containing benzene ring: By weight, 28 parts of acrylonitrile, 24 parts of 2,4-diphenyl-4-methyl-1-pentene and 9 parts of diethyl ether tetrafluoroborate are mixed and reacted at 40 °C for 6 h, then left standing for 30 h, washed with deionized water, and vacuum dried at 50 °C for 4 h to obtain a modified monomer; 74 parts of commercially available acrylamide and 18 parts of 2-acrylamido-2-methylpropanesulfonic acid are added to 320 parts of deionized water, stirred for 2 h, and then the pH is adjusted to 8.6 with a sodium hydroxide solution with a mass concentration fraction of 20%. Under a nitrogen atmosphere, 0.004 parts of the modified monomer, 0.004 parts of sodium dodecyl sulfate, 0.006 parts of azo initiator V50, 0.004 parts of ammonium persulfate, 0.003 parts of sodium bisulfite, 0.004 parts of disodium ethylenediaminetetraacetate and 0.09 parts of thiourea are added for reaction. The reaction initiation temperature is 24 °C and the reaction time is 5 h; after the reaction is completed, the reaction product is vacuum dried at 55 °C for 6 h, then crushed and sieved to obtain polyacrylamide containing benzene ring.

[0063] Step S1: By weight, 30 parts of sodium metasilicate are added to 70 parts of deionized water and stirred and mixed evenly, and then impurity removal treatment is carried out through carboxyl-modified activated carbon to obtain a solution after impurity removal. 4 parts of surfactant dodecyltrimethylammonium chloride and 0.8 parts of polyacrylamide containing benzene ring are added to 70 parts of the solution after impurity removal, and stirred for 60 min to obtain an aqueous sodium silicate solution after impurity removal;

[0064] Step S2: By weight, 24 parts of calcium nitrate are added to 80 parts of deionized water and stirred for 50 min, and then purification treatment is carried out through a mesoporous material to obtain a purified calcium nitrate solution;

[0065] Step S3: By weight, at a temperature of 70 °C and a stirring speed of 200 r / min, 80 parts of the purified calcium nitrate solution are added dropwise to 70 parts of the aqueous sodium silicate solution after impurity removal at a rate of 5 mL / h to obtain a calcium silicate mixture;

[0066] Step S4: The calcium silicate mixture is used as the cortical liquid, and deionized water is used as the core liquid for coaxial electrospray, and then left standing for aging (temperature is 10 °C, time is 20 h), filtered, washed with water, and freeze-dried (temperature is -24 °C, time is 24 h, vacuum degree is 0.16 MPa) to obtain a filler for lightweight calcium silicate cement board;

[0067] The conditions for the coaxial electrospray include: the flow rate of the cortical liquid is 2.8 mL / h, the flow rate of the core liquid is 1.8 mL / h, the voltage is 20 kV, the receiving distance is 20 cm, and the time is 60 min.

[0068] Example 2

[0069] This embodiment provides a preparation method for a filler of a lightweight calcium silicate cement board, comprising the following steps:

[0070] Preparation of carboxyl-modified activated carbon: By weight, disperse 6 parts of activated carbon I (product number C299105, average particle size 100 mesh) in a mixed solution of 20 parts of sulfuric acid and 26 parts of nitric acid, ultrasonically disperse for 80 min under the condition of a power of 800 W, then perform heat treatment at 150 °C for 90 min, and obtain an acidified intermediate after filtration; add 6 parts of the acidified intermediate to 80 parts of N,N-dimethylformamide, ultrasonically disperse for 30 min, then add 4 parts of dicyclohexylcarbodiimide, 1 part of 4-dimethylaminopyridine, and 6 parts of acrylic acid, place it under the protection of a nitrogen atmosphere, react at 82 °C for 24 h, filter, wash with water, and dry to obtain carboxyl-modified activated carbon.

[0071] Preparation of mesoporous material: By weight, mix 100 parts of absolute ethanol and 20 parts of deionized water, add 0.2 parts of iron tetroxide and ultrasonically disperse for 50 min, then add 2 parts of tetraethyl orthosilicate and 3 parts of ammonia water, stir at room temperature for 8 h, wash with deionized water, and vacuum dry to obtain an intermediate product; mix 80 parts of absolute ethanol, 10 parts of deionized water, and 4 parts of ammonia water, stir at 30 °C for 20 min, then add 4 parts of the intermediate product and 0.2 parts of (3-mercaptopropyl)triethoxysilane and stir to react for 20 h. After the reaction is completed, centrifuge to obtain a solid, wash the solid with absolute ethanol, and dry to obtain the mesoporous material.

[0072] Preparation of polyacrylamide containing benzene ring: By weight, mix 26 parts of acrylonitrile, 22 parts of 2,4-diphenyl-4-methyl-1-pentene, and 8 parts of diethyl ether tetrafluoroborate, react at 36 °C for 8 h, then let it stand for 30 h, wash with deionized water, and vacuum dry at 45 °C for 5 h to obtain a modified monomer; add 70 parts of commercially available acrylamide and 16 parts of 2-acrylamido-2-methylpropanesulfonic acid to 310 parts of deionized water, stir for 1 h, then adjust the pH to 8.4 with a sodium hydroxide solution with a mass concentration of 20%. Under a nitrogen atmosphere, add 0.002 parts of the modified monomer, 0.002 parts of sodium dodecylsulfonate, 0.004 parts of azo initiator V50, 0.002 parts of ammonium persulfate, 0.001 parts of sodium bisulfite, 0.002 parts of disodium ethylenediaminetetraacetate, and 0.07 parts of thiourea to react. The reaction initiation temperature is 20 °C, and the reaction time is 7 h; after the reaction is completed, vacuum dry the reaction product at 45 °C for 8 h, then pulverize and sieve to obtain polyacrylamide containing benzene ring.

[0073] Step S1: By weight, 26 parts of sodium metasilicate are added to 60 parts of deionized water and stirred until evenly mixed, and then impurity removal treatment is carried out with carboxyl-modified activated carbon to obtain a solution after impurity removal. 2 parts of tetradecyltrimethylammonium chloride and 0.4 part of benzene ring-containing polyacrylamide are added to 60 parts of the solution after impurity removal, and stirred for 50 min to obtain an aqueous sodium silicate solution after impurity removal;

[0074] Step S2: By weight, 20 parts of calcium nitrate are added to 70 parts of deionized water and stirred for 40 min, and then purification treatment is carried out with mesoporous materials to obtain a purified calcium nitrate solution;

[0075] Step S3: By weight, at a temperature of 60 °C and a stirring speed of 100 r / min, 70 parts of the purified calcium nitrate solution are added dropwise to 60 parts of the aqueous sodium silicate solution after impurity removal at a rate of 3 mL / h to obtain a calcium silicate mixture;

[0076] Step S4: Using the calcium silicate mixture as the cortical liquid and deionized water as the core liquid, coaxial electrospray is carried out, and then standing aging (temperature 4 °C, time 24 h) is carried out, followed by filtration, washing with water, and freeze-drying (temperature -20 °C, time 48 h, vacuum degree 0.12 MPa) to obtain the filler for the lightweight calcium silicate cement board;

[0077] The conditions for the coaxial electrospray include: the flow rate of the cortical liquid is 2.2 mL / h, the flow rate of the core liquid is 1.4 mL / h, the voltage is 14 kV, the receiving distance is 16 cm, and the time is 90 min.

[0078] Example 3

[0079] This example provides a method for preparing a filler for a lightweight calcium silicate cement board, including the following steps:

[0080] Preparation of carboxyl-modified activated carbon: By weight, 8 parts of activated carbon I (product number C299105, average particle size 100 mesh) are dispersed in a mixed solution of 22 parts of sulfuric acid and 28 parts of nitric acid, ultrasonically dispersed for 70 min under the condition of a power of 900 W, and then heat-treated at 155 °C for 80 min. After filtration, an acidified intermediate is obtained; 8 parts of the acidified intermediate are added to 90 parts of N,N-dimethylformamide and ultrasonically dispersed for 35 min, then 5 parts of dicyclohexylcarbodiimide, 2 parts of 4-dimethylaminopyridine, and 6 - 8 parts of acrylic acid are added, placed under nitrogen atmosphere protection, and reacted at 86 °C for 22 h. After filtration, washing with water, and drying, carboxyl-modified activated carbon is obtained.

[0081] Preparation of mesoporous material: By weight, 110 parts of absolute ethanol and 25 parts of deionized water are mixed, 0.4 part of iron tetroxide is added, and ultrasonic dispersion is carried out for 55 min. Then, 3 parts of tetraethyl orthosilicate and 4 parts of ammonia water are added, and stirring is carried out at room temperature for 8 h. Washing is carried out with deionized water, and vacuum drying is carried out to obtain an intermediate product; 85 parts of absolute ethanol, 15 parts of deionized water and 5 parts of ammonia water are mixed, stirring is carried out at 35 °C for 15 min, then 5 parts of the intermediate product and 0.3 part of (3-mercaptopropyl)triethoxysilane are added and stirring reaction is carried out for 22 h. After the reaction is completed, a solid substance is obtained by centrifugation. The solid substance is washed with absolute ethanol and dried to obtain the mesoporous material.

[0082] Preparation of benzene ring-containing polyacrylamide: By weight, 27 parts of acrylonitrile, 23 parts of 2,4-diphenyl-4-methyl-1-pentene and 8 parts of diethyl ether tetrafluoroborate are mixed, and reaction is carried out at 38 °C for 7 h. Then, standing is carried out for 26 h, washing is carried out with deionized water, and vacuum drying is carried out at 48 °C for 5 h to obtain a modified monomer; 72 parts of commercially available acrylamide and 17 parts of 2-acrylamido-2-methylpropanesulfonic acid are added to 315 parts of deionized water. After stirring for 1 h, the pH is adjusted to 8.5 with a sodium hydroxide solution with a mass concentration fraction of 20%. Under a nitrogen atmosphere, 0.003 part of the modified monomer, 0.003 part of sodium dodecylsulfonate, 0.005 part of azo initiator V50, 0.003 part of ammonium persulfate, 0.002 part of sodium bisulfite, 0.003 part of disodium ethylenediaminetetraacetate and 0.08 part of thiourea are added for reaction. The reaction initiation temperature is 22 °C, and the reaction time is 6 h; after the reaction is completed, the reaction product is vacuum dried at 50 °C for 7 h, and then crushed and sieved to obtain benzene ring-containing polyacrylamide.

[0083] Step S1: By weight, 28 parts of sodium metasilicate are added to 65 parts of deionized water and stirred and mixed evenly. Then, impurity removal treatment is carried out through carboxyl-modified activated carbon to obtain an impurity-removed solution. 3 parts of surfactant cetyltrimethylammonium chloride and 0.6 part of benzene ring-containing polyacrylamide are added to 65 parts of the impurity-removed solution, and stirring is carried out for 55 min to obtain an impurity-removed sodium silicate aqueous solution;

[0084] Step S2: By weight, 22 parts of calcium nitrate are added to 75 parts of deionized water and stirred for 45 min. Then, purification treatment is carried out through the mesoporous material to obtain a purified calcium nitrate solution;

[0085] Step S3: By weight, at a temperature of 65 °C and a stirring speed of 150 r / min, 75 parts of the purified calcium nitrate solution are added dropwise to 65 parts of the impurity-removed sodium silicate aqueous solution at a speed of 4 mL / h to obtain a calcium silicate mixture;

[0086] Step S4: Use the calcium silicate mixture as the cortical liquid and deionized water as the core liquid for coaxial electrospray, then let it stand for aging (temperature is 6°C, time is 22 h), filter, wash with water, and freeze-dry (temperature is -22°C, time is 36 h, vacuum degree is 0.14 MPa) to obtain the filler for the lightweight calcium silicate cement board;

[0087] The conditions for the coaxial electrospray include: the flow rate of the cortical liquid is 2.4 mL / h, the flow rate of the core liquid is 1.6 mL / h, the voltage is 16 kV, the receiving distance is 18 cm, and the time is 80 min.

[0088] Comparative Example 1

[0089] The difference between this comparative example and Example 1 is that activated carbon I is used to replace the carboxyl-modified activated carbon for impurity removal treatment.

[0090] Comparative Example 2

[0091] The difference between this comparative example and Example 1 is that activated carbon II is used to replace activated carbon I for the preparation of carboxyl-modified activated carbon.

[0092] Comparative Example 3

[0093] The difference between this comparative example and Example 1 is that activated carbon III is used to replace activated carbon I for the preparation of carboxyl-modified activated carbon.

[0094] Comparative Example 4

[0095] The difference between this comparative example and Example 1 is that no mesoporous material is used for purification treatment.

[0096] Comparative Example 5

[0097] The difference between this comparative example and Example 1 is that commercially available polycyclic acrylamide (product number S31321) is used to replace the polycyclic acrylamide containing benzene ring.

[0098] Comparative Example 6

[0099] The difference between this comparative example and Example 1 is that deionized water is not added as the core liquid for coaxial electrospray, but the calcium silicate mixture is directly electrosprayed.

[0100] Comparative Example 7

[0101] This comparative example is commercially available microporous calcium silicate, purchased from Tai'an Ping'an Thermal Insulation Materials Co., Ltd., and obtained by reacting a liquid phase component containing a certain alkalinity (80 - 90 g / L) and a certain silicon content (30 - 40 g / L) with lime milk at high temperature.

[0102] Performance Test

[0103] The fillers of the calcium silicate lightweight cement boards prepared in the above examples and comparative examples were subjected to the following tests:

[0104] (1) Whiteness test

[0105] The whiteness was tested according to the requirements of the TAPPI standard "T534 Brightness of clay and other mineral pigments".

[0106] (2) Bulk density test

[0107] The bulk density was tested according to the requirements of "GB / T 17431.2-2010 Lightweight aggregates and their test methods - Part 2: Test methods for lightweight aggregates".

[0108] (3) Specific surface area test

[0109] The specific surface area was tested according to the requirements of "GB / T 19587-2017 Determination of specific surface area of solid materials by gas adsorption BET method".

[0110] The performance test results are shown in Table 1.

[0111] Table 1 Performance test results

[0112] Whiteness (%) <![CDATA[Bulk density (g / cm 3 )]]> <![CDATA[Specific surface area (m 2 / g)]]> Example 1 89.6 0.201 121.32 Example 2 88.9 0.208 120.56 Example 3 89.3 0.205 120.94 Comparative Example 1 83.2 0.219 118.75 Comparative Example 2 85.8 0.214 119.24 Comparative Example 3 86.1 0.217 119.41 Comparative Example 4 83.4 0.221 118.37 Comparative Example 5 88.1 0.215 102.65 Comparative Example 6 87.9 0.263 117.16 Comparative Example 7 88.2 0.213 117.38

[0113] From the above performance test results, it can be seen that the fillers of the calcium silicate lightweight cement boards in Examples 1-3 have the best comprehensive performance, with a whiteness of 88.9-89.6%, a bulk density of 0.201-0.201 g / cm 3 , and a specific surface area of 120.56-121.32 m 2 / g; this is mainly because through the use of carboxyl-modified activated carbon for impurity removal treatment, mesoporous materials for purification treatment, and the introduction of benzene ring-containing polyacrylamide, combined with the coaxial electrostatic spraying forming process, it effectively increases the whiteness of the calcium silicate filler, reduces the bulk density, and can obtain a relatively high specific surface area.

[0114] In the comparative examples, since the necessary technical solutions were not adopted, their corresponding performance tests were significantly worse than those of the examples. Compared with Example 1, in Comparative Example 1, activated carbon I was used to replace carboxyl-modified activated carbon for impurity removal treatment, resulting in a decrease in whiteness; compared with Example 1, in Comparative Example 2, activated carbon II was used to replace activated carbon I for the preparation of carboxyl-modified activated carbon. Due to the too large mesh number of activated carbon II, the modification effect was poor, resulting in a decrease in whiteness; compared with Example 1, in Comparative Example 3, activated carbon III was used to replace activated carbon I for the preparation of carboxyl-modified activated carbon. Due to the too small mesh number of activated carbon III, the modification effect was poor, resulting in a decrease in whiteness; compared with Example 1, in Comparative Example 4, no mesoporous material was used for purification treatment, resulting in a decrease in whiteness; compared with Example 1, in Comparative Example 5, commercially available polyacrylamide (product number S31321) was used to replace polyacrylamide containing benzene rings, resulting in a decrease in specific surface area; compared with Example 1, in Comparative Example 6, deionized water was not added as the core layer liquid for coaxial electrospray, but the calcium silicate mixture was directly electrosprayed, resulting in an increase in bulk density. The above experimental results further prove the importance of the technical solutions defined in the present invention for its technical effects.

[0115] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle described in the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a filler for a lightweight calcium silicate cement board, characterized in that: The following steps are involved: Step S1: adding 26 to 30 parts of sodium metasilicate to 60 to 70 parts of deionized water by weight, stirring and mixing evenly, and then removing impurities through activated carbon to obtain a de-impurified solution, adding 2 to 4 parts of a surfactant and 0.4 to 0.8 parts of polyacrylamide to 60 to 70 parts of the de-impurified solution, stirring for 50 to 60 minutes, and obtaining a de-impurified sodium silicate aqueous solution; Step S2: adding 20 to 24 parts of calcium nitrate to 70 to 80 parts of deionized water by weight and stirring for 40 to 50 minutes, and then purifying the solution by a mesoporous material to obtain a purified calcium nitrate solution; Step S3: adding 70 to 80 parts of the purified calcium nitrate solution dropwise to 60 to 70 parts of the sodium silicate aqueous solution after impurity removal at a rate of 3 to 5 mL / h at a temperature of 60 to 70° C. and a stirring speed of 100 to 200 r / min, to obtain a calcium silicate mixed solution; Step S4: Using the calcium silicate mixed liquid as the skin layer liquid and deionized water as the core layer liquid, coaxial electrostatic spraying is performed, and then standing and aging, filtering, washing, and freeze-drying are performed to obtain a filler for a lightweight calcium silicate cement board.

2. The method for preparing a filler for a lightweight calcium silicate cement board according to claim 1, characterized in that: The activated carbon is carboxyl-modified activated carbon; The preparation method of the carboxyl modified activated carbon comprises: dispersing 6 to 10 parts of activated carbon in a mixed solution of 20 to 24 parts of sulfuric acid and 26 to 30 parts of nitric acid by weight, ultrasonically dispersing the mixture at a power of 800 to 1000 W for 60 to 80 minutes, then heat treating the mixture at 150 to 160° C. for 60 to 90 minutes, and filtering to obtain an acidified intermediate; adding 6 to 10 parts of the acidified intermediate to 80 to 100 parts of N,N-dimethylformamide for ultrasonic dispersion for 30 to 40 minutes, then adding 4 to 6 parts of dicyclohexylcarbodiimide, 1 to 3 parts of 4-dimethylaminopyridine and 6 to 8 parts of acrylic acid, placing the mixture under nitrogen atmosphere protection, reacting the mixture at 82 to 88° C. for 20 to 24 hours, filtering, washing with water, and drying to obtain the carboxyl modified activated carbon.

3. The method for preparing a filler for a lightweight calcium silicate cement board according to claim 2, characterized in that: The average particle size of the activated carbon is 80-120 meshes.

4. The method for preparing a filler for a lightweight calcium silicate cement board according to claim 1, characterized in that: The preparation method of the mesoporous material comprises: mixing 100 to 120 parts of anhydrous ethanol and 20 to 30 parts of deionized water by weight, adding 0.2 to 0.6 parts of ferroferric oxide and ultrasonically dispersing for 50 to 60 minutes, then adding 2 to 4 parts of tetraethyl silicate and 3 to 5 parts of ammonia water, stirring at room temperature for 8 hours, washing with deionized water, and vacuum drying to obtain an intermediate product; mixing 80 to 90 parts of anhydrous ethanol, 10 to 20 parts of deionized water and 4 to 6 parts of ammonia water, stirring at 30 to 40° C. for 10 to 20 minutes, then adding 4 to 6 parts of the intermediate product and 0.2 to 0.4 parts of (3-mercaptopropyl) triethoxysilane and stirring for 20 to 24 hours, centrifuging to obtain a solid after the reaction is completed, washing the solid with anhydrous ethanol, and drying to obtain the mesoporous material.

5. The method for preparing a filler for a lightweight calcium silicate cement board according to claim 1, characterized in that: The polyacrylamide is a benzene ring-containing polyacrylamide; The preparation method of the benzene ring-containing polyacrylamide comprises: mixing 26 to 28 parts of acrylonitrile, 22 to 24 parts of 2,4-diphenyl-4-methyl-1-pentene and 8 to 9 parts of diethyl tetrafluoroborate by weight, reacting at 36 to 40° C. for 6 to 8 hours, then standing for 24 to 30 hours, washing with deionized water, and vacuum drying at 45 to 50° C. for 4 to 5 hours to obtain a modified monomer; adding 70 to 74 parts of commercially available acrylamide and 16 to 18 parts of 2-acrylamido-2-methylpropanesulfonic acid to 310 to 320 parts of deionized water, stirring for 1 to 2 hours, and adjusting the pH to 8 with a sodium hydroxide solution with a mass concentration of 20%. 4-8.6, under a nitrogen atmosphere, adding 0.002-0.004 parts of the modified monomer, 0.002-0.004 parts of sodium dodecyl sulfate, 0.004-0.006 parts of azo initiator V50, 0.002-0.004 parts of ammonium persulfate, 0.001-0.003 parts of sodium bisulfite, 0.002-0.004 parts of disodium ethylenediaminetetraacetate and 0.07-0.09 parts of thiourea for reaction, the reaction initiation temperature is 20-24° C., and the reaction time is 5-7 hours; after the reaction is completed, the reaction product is vacuum dried at 45-55° C. for 6-8 hours, and then crushed and sieved to obtain benzene ring-containing polyacrylamide.

6. The method for preparing a filler for a lightweight calcium silicate cement board according to claim 1, characterized in that: The surfactant is selected from any one of dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, and hexadecyltrimethylammonium chloride, or a combination of at least two thereof.

7. The method for preparing a filler for a lightweight calcium silicate cement board according to claim 1, characterized in that: The conditions of the coaxial electrostatic spray include: the flow rate of the skin layer liquid is 2.2-2.8 mL / h, the flow rate of the core layer liquid is 1.4-1.8 mL / h, the voltage is 14-20 kV, the receiving distance is 16-20 cm, and the time is 60-90 min.

8. The method for preparing a filler for a lightweight calcium silicate cement board according to claim 1, characterized in that: The conditions for the static aging include: a temperature of 4 to 10° C. and a time of 20 to 24 hours.

9. The method for preparing a filler for a lightweight calcium silicate cement board according to claim 1, characterized in that: The freeze-drying conditions include: temperature of -24°C to -20°C, time of 24 to 48 hours, and vacuum degree of 0.12 to 0.16 MPa.

10. A filler for a lightweight calcium silicate cement board, characterized in that: Prepared according to the method according to any one of claims 1 to 9.