Preparation method of lightweight plastering gypsum

Abstract

The invention discloses a preparation method of light plastering gypsum, and relates to the technical field of building materials. The preparation method of the light plastering gypsum comprises the following steps: pretreating mirabilite gypsum, and grading the pretreated mirabilite gypsum with desulfurized gypsum and phosphogypsum to obtain a gypsum base material; the preparation method comprises the following steps: swelling cellulose ether and starch ether together to form a cross-linked network colloid, doping a polyether monomer, a propenyl monomer and an initiator, and carrying out graft copolymerization to obtain a water-retaining and thickening component; the preparation method comprises the following steps: preparing a wall material from chitosan and sodium carboxymethyl cellulose, and coating 3, 4-dihydroxyphenylalanine to obtain a water-resistant slow-release component; stirring and mixing the gypsum base material, the lightweight aggregate and the sepiolite fiber to obtain a primary mixture; and stirring and mixing the primary mixture with a water-retaining thickening component, a water-resistant slow-release component and a water reducing agent to obtain the light plastering gypsum. The water-retaining property and the water resistance of the light plastering gypsum are greatly improved, the water use range of the light plastering gypsum during construction is widened, and the construction difficulty is reduced.

Description

Technical Field

[0001] This application relates to the technical field of building materials, and particularly relates to a preparation method of lightweight plastering gypsum. Background Art

[0002] According to the current development status of the building materials industry, lightweight plastering gypsum has the characteristics of light texture, good hygroscopicity, excellent volume stability, no hollowing or cracking, and good fire resistance compared with traditional cement plastering materials. Moreover, lightweight plastering gypsum is easier to operate and more environmentally friendly than heavy plastering gypsum, making it gradually widely used as a wall plastering and leveling material with good material properties, construction performance, and service functions. However, when the existing lightweight plastering gypsum is under construction, it is usually particularly sensitive to water usage. Slight miscontrol of the water consumption at the construction site will affect the performance of the lightweight plastering gypsum. For example, when the water consumption is slightly low, the water retention property of the lightweight plastering gypsum is poor. When it is applied to water-absorbing surfaces such as aerated concrete and porous insulation boards, the water in the lightweight plastering gypsum is absorbed, affecting its hydration process and prone to phenomena such as powder shedding, dry shrinkage, and cracking. When the water consumption is slightly high, the water resistance is insufficient, resulting in an excess of water in the lightweight plastering gypsum mortar. The excess water will evaporate during the setting and hardening process of the gypsum, causing a large number of capillary pores to appear in the hardened gypsum and making it difficult to achieve sufficient strength. Summary of the Invention

[0003] The main purpose of this application is to provide a preparation method of lightweight plastering gypsum, aiming to solve the technical problem of the narrow range of construction water consumption of the existing lightweight plastering gypsum.

[0004] To achieve the above purpose, this application proposes a preparation method of lightweight plastering gypsum, including the following steps:

[0005] After pre-treating mirabilite gypsum, grading it with desulfurized gypsum and phosphogypsum to obtain a gypsum base material;

[0006] Swelling cellulose ether and starch ether together to form a cross-linked network-like colloid, and incorporating polyether monomers, allyl-based monomers, and initiators to carry out graft copolymerization reaction to obtain a water retention and thickening component;

[0007] Preparing a wall material with chitosan and sodium carboxymethylcellulose, and coating 3,4-dihydroxyphenylalanine to obtain a water-resistant and slow-release component;

[0008] Stirring and mixing the gypsum base material with lightweight aggregate and sepiolite fiber to obtain a preliminary mixture;

[0009] Stirring and mixing the preliminary mixture with the water retention and thickening component, the water-resistant and slow-release component, and a water reducer to obtain lightweight plastering gypsum.

[0010] Optionally, the step of pre-treating mirabilite gypsum includes:

[0011] After pulverizing mirabilite gypsum, it is dried at 40°C - 60°C for 6h - 10h, then ground, and the specific surface area is controlled between 200 m 2 / kg - 250 m 2 / kg. Then it is calcined at 130°C - 180°C for 2h - 3h. After cooling to 50°C - 60°C, it is aged. The aging time is not less than 2 days, and the adsorbed water content is controlled to be less than 1.5%.

[0012] Optionally, in the step of grading pre-treated mirabilite gypsum with desulfurized gypsum and phosphogypsum after pre-treating mirabilite gypsum, the particle size range of pre-treated mirabilite gypsum is controlled at 100μm - 200μm, the particle size range of desulfurized gypsum is controlled at 50μm - 100μm, and the particle size range of phosphogypsum is controlled at 150μm - 300μm;

[0013] The mass ratio of pre-treated mirabilite gypsum, desulfurized gypsum and phosphogypsum is (1 - 2) : (5 - 7) : (1 - 2).

[0014] Optionally, the step of swelling cellulose ether and starch ether together to form a cross-linked network colloid includes:

[0015] After heating water to 50°C - 60°C, cellulose ether and starch ether are added, and stirred for 1h - 1.5h. After complete dissolution, a cross-linked network colloid is formed;

[0016] Among them, the mass ratio of the cellulose ether to the starch ether is (6 - 7) : (2 - 3).

[0017] Optionally, the step of incorporating polyether monomers, allyl monomers and initiators to carry out graft copolymerization reaction to obtain a water retention and thickening component includes:

[0018] Polyether monomers, allyl monomers and initiators are added to the cross-linked network colloid. After stirring for 5min - 10min, it is left standing for 1.5h - 2.5h. Then water at 50°C - 60°C is added, and after stirring for 10min - 14min, it is swollen for 1.5h - 2.5h while maintaining the temperature at 50°C - 60°C. After the swelling is completed, it is stirred at 45°C - 50°C for 8h - 12h, and then sodium lignosulfonate is added. After stirring for 15min - 20min, a water retention and thickening component is obtained;

[0019] Among them, the addition amount of the polyether monomer in the cross-linked network colloid is 2.5wt% - 3.5wt%;

[0020] The addition amount of the allyl monomer in the cross-linked network colloid is 4.5wt% - 6wt%.

[0021] Optionally, the polyether monomer includes at least one of 2-methylprop-2-enyl polyethylene glycol ether, 3-methylbut-3-enyl polyethylene glycol ether, 4-hydroxybutyl vinyl polyethylene oxide ether, and isopentenol polyethylene oxide ether;

[0022] The propenyl monomer includes at least one of acrylamide, acrylic acid, methacrylic acid, hydroxypropyl methacrylate, and N,N-dimethylacrylamide;

[0023] The initiator includes one of ammonium persulfate, sodium persulfate, and potassium persulfate.

[0024] Optionally, the step of preparing the wall material with chitosan and sodium carboxymethyl cellulose and coating 3,4-dihydroxyphenylalanine to obtain the water-resistant sustained-release component includes:

[0025] Mix chitosan, sodium carboxymethyl cellulose, and absolute ethanol to obtain a wall material solution;

[0026] Mix 3,4-dihydroxyphenylalanine with microcrystalline cellulose, and then add them to a spheronizer for rolling treatment to form spherical particle cores;

[0027] Add the wall material solution to an atomizing sprayer, spray the spherical particle cores, and stir at a rotation speed of 20 r / min - 30 r / min. After spraying, dry at 80 °C - 100 °C for 5 h - 7 h to obtain the water-resistant sustained-release component.

[0028] Optionally, the step of mixing the gypsum base material with the light aggregate and sepiolite fiber to obtain a preliminary mixture includes:

[0029] Mix the gypsum base material with the light aggregate and sepiolite fiber according to a mass ratio of (6 - 7):(2 - 3):1, stir at a rotation speed of 400 r / min - 600 r / min for 6 min - 10 min to obtain a preliminary mixture.

[0030] Optionally, the light aggregate is obtained by mixing expanded vitrified microspheres and nano zirconium diboride aerogel according to a mass ratio of (3 - 4):2.

[0031] Optionally, the step of mixing the preliminary mixture with the water retention and thickening component, the water-resistant sustained-release component, and the water reducer to obtain the light plaster includes:

[0032] Mix the initial mixture with the water retention and thickening component, the water-resistant and slow-release component, and the water reducer according to the mass ratio of (6-8):(1-1.2):(0.8-1):(0.2-0.4), with a stirring speed of 600 r / min - 800 r / min and a stirring time of 4 min - 8 min to obtain lightweight plastering gypsum.

[0033] This application has at least the following beneficial effects:

[0034] This application first pre-treats mirabilite gypsum to increase the content of its active ingredient, hemihydrate gypsum, and then grades it with high-grade gypsums such as desulfurized gypsum and phosphogypsum, thereby ensuring the workability, strength, and durability of the gypsum slurry.

[0035] In this application, cellulose ether and starch ether are swollen together, and these two polymer materials are crosslinked to form a stable three-dimensional network structure colloid. The crosslinked structure contains hydrophilic groups such as hydroxyl groups and ether groups, which can interact with water molecules and attract water into the crosslinked structure to ensure that the plastering gypsum has sufficient water retention and avoid water loss during construction. At the same time, graft copolymerization reaction is carried out with polyether monomers and allyl monomers, and multiple side chains with a certain length and stiffness are connected to the main chain of the molecules in the crosslinked structure, enabling them to adsorb on the surface of gypsum particles. The formation of the crosslinked structure helps to increase the plastic viscosity of the gypsum paste, thereby improving the water retention of the lightweight plastering gypsum.

[0036] In this application, 3,4-dihydroxyphenylalanine is used as the water-resistant active ingredient, and chitosan and sodium carboxymethylcellulose are used to prepare the wall material to coat 3,4-dihydroxyphenylalanine. After the lightweight plastering gypsum mortar of this application hardens, 3,4-dihydroxyphenylalanine can be gradually released, and the catechol groups contained in 3,4-dihydroxyphenylalanine can form bidentate metal coordination bonds with metal ions, enabling it to bind more tightly to the hydrated calcium compounds in the gypsum matrix. When the lightweight plastering gypsum absorbs water, it reduces the direct penetration of water into the interior, thereby reducing the possibility of a large amount of water seeping into and dissolving the dihydrate gypsum in the hardened lightweight plastering gypsum mortar, enhancing the water resistance of the lightweight plastering gypsum, and avoiding the easy influence of excessive water on the gypsum setting and hardening process.

[0037] Through the cooperation of the gypsum base material with the water retention and thickening component and the water-resistant and slow-release component, this application greatly improves the water retention and water resistance of the lightweight plastering gypsum, broadens the water usage range of the lightweight plastering gypsum during construction, and even if the water consumption at the construction site is not well controlled, it will not easily affect the performance of the lightweight plastering gypsum, thereby reducing the construction difficulty. Description of the Drawings

[0038] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0039] Figure 1 It is a flowchart of the preparation method of the light plastering gypsum described in the embodiments of the present application.

[0040] The realization of the purpose of the present application, functional features and advantages will be further described in conjunction with the embodiments with reference to the accompanying drawings. Specific embodiments

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present application.

[0042] In view of the technical problems existing in the prior art, the embodiments of the present application provide a preparation method of light plastering gypsum, as Figure 1 shown, including the following steps:

[0043] S10. After pretreating mirabilite gypsum, perform grading with desulfurized gypsum and phosphogypsum to obtain a gypsum base material.

[0044] In the specific implementation process, when pretreating mirabilite gypsum, first crush the mirabilite gypsum, dry it at 40°C - 60°C for 6h - 10h, then perform grinding, and control the specific surface area between 200m 2 / kg - 250m 2 / kg, then calcine it at 130°C - 180°C for 2h - 3h, cool it to 50°C - 60°C, and then perform aging. The aging time is not less than 2 days, and control the adsorbed water content to be less than 1.5%.

[0045] Since mirabilite gypsum generally contains more hydrated sodium sulfate (Na 2 SO 4 ), has low effective components, and has a relatively high content of clay impurities, which significantly weakens the strength and makes it difficult to be directly applied. Therefore, the present application calcines and ages it to increase the content of the effective component hemihydrate gypsum, thereby realizing the rational utilization of mirabilite gypsum resources and avoiding the waste of mirabilite gypsum.

[0046] In the step of grading, the mass ratio of the pretreated mirabilite gypsum, desulfurized gypsum and phosphogypsum is (1 - 2):(5 - 7):(1 - 2); and the particle size range of the pretreated mirabilite gypsum is controlled at 100μm - 200μm, the particle size range of the desulfurized gypsum is controlled at 50μm - 100μm, and the particle size range of the phosphogypsum is controlled at 150μm - 300μm.

[0047] To further increase the content of the active ingredient hemihydrate gypsum in the gypsum raw material, the present application grades the pretreated mirabilite gypsum with desulfurized gypsum and phosphogypsum. Mirabilite gypsum has good fluidity and low water demand, and coarser crystals, which can provide higher early strength. Its particle size is controlled between 100μm - 200μm to ensure sufficient specific surface area for reaction, while avoiding excessive reaction heat caused by too fine particle size; while desulfurized gypsum mainly comes from the desulfurization process of coal-fired power plants, contains more calcium components, has a higher degree of hydration, a faster hardening speed, and is more reactive than mirabilite gypsum. Its particle size is controlled between 50μm - 100μm to maintain appropriate fineness, so as to provide higher activity and reactivity, help form a more uniform hardening structure, and as a finer component, desulfurized gypsum can increase the fluidity of the gypsum slurry and reduce the amount of cement used; phosphogypsum comes from the by-product in the phosphate fertilizer industry, contains a high content of calcium phosphate (Ca 3 (PO 4 ) 2 ), which is suitable for enhancing the comprehensive properties of gypsum, especially water resistance and crack resistance, but it has a larger particle size and contains certain impurities, and its reactivity is not as good as that of mirabilite gypsum and desulfurized gypsum. Based on the characteristics of these different gypsums, the present application ensures the workability, strength and durability of the gypsum slurry by reasonably controlling the particle size ratio.

[0048] S20. Swell cellulose ether and starch ether together to form a cross-linked network colloid, and incorporate polyether monomers, allyl monomers and initiators to carry out graft copolymerization reaction to obtain a water retention and thickening component.

[0049] In the specific implementation process, the step of swelling cellulose ether and starch ether together to form a cross-linked network colloid includes:

[0050] After heating water to 50℃ - 60℃, add cellulose ether and starch ether, stir for 1h - 1.5h, and after complete dissolution, form a cross-linked network colloid.

[0051] Among them, the mass ratio of the cellulose ether to the starch ether is (6 - 7):(2 - 3).

[0052] Further, a polyether monomer, an allyl monomer and an initiator are added to the cross-linked network colloid. After stirring for 5 min - 10 min, it is left standing for 1.5 h - 2.5 h, then water at 50°C - 60°C is added. After stirring for 10 min - 14 min, swelling is carried out for 1.5 h - 2.5 h while maintaining the temperature at 50°C - 60°C. After the swelling is completed, it is stirred at 45°C - 50°C for 8 h - 12 h, and then sodium lignosulfonate is added. After stirring for 15 min - 20 min, a water-retaining thickening component is obtained.

[0053] Cellulose ethers have good water solubility and water swelling properties. Starch ethers are compounds formed by the combination of starch molecules and ether groups, and can absorb water and swell in water to form gels or viscous solutions. Both cellulose ethers and starch ethers have good thickening and water-retaining effects on plastering gypsum. However, in the prior art, when applying cellulose ethers or starch ethers, they are directly mixed with gypsum base materials, so that they first swell and then dissolve during the stirring process. But direct feeding will lead to a large water demand for plastering gypsum, and insufficient stirring time is also very likely to cause poor dissolution, thus affecting the water retention of plastering gypsum. Therefore, in this application, these two polymer materials are first cross-linked to form a stable three-dimensional network structure colloid. The cross-linked structure contains hydrophilic groups such as hydroxyl groups and ether groups, and these groups can interact with water molecules to attract water into the cross-linked structure to ensure that the plastering gypsum has sufficient water retention and avoid the occurrence of water loss during the construction process. At the same time, a graft copolymerization reaction is carried out with a polyether monomer and an allyl monomer to connect multiple side chains with a certain length and stiffness on the main chain of the molecules of the cross-linked structure, so that it can adsorb on the surface of gypsum particles. The formation of the cross-linked structure helps to increase the plastic viscosity of the gypsum slurry to achieve the effect of thickening and water retention.

[0054] Among them, the addition amount of the polyether monomer in the cross-linked network colloid is 2.5 wt% - 3.5 wt%; the polyether monomer includes at least one of 2-methylprop-2-enyl polyethylene glycol ether, 3-methylbut-3-enyl polyethylene glycol ether, 4-hydroxybutyl vinyl polyoxyethylene ether and isopentenol polyoxyethylene ether.

[0055] In this application, polyether monomers such as 2-methylprop-2-enyl polyethylene glycol ether, 3-methylbut-3-enyl polyethylene glycol ether, 4-hydroxybutyl vinyl polyoxyethylene ether and isopentenol polyoxyethylene ether are used for graft copolymerization reaction. During the polymerization reaction process, this type of polyether monomer can transfer the intermediate free radicals formed in the polymerization reaction to itself by reacting with the polymer chain, thereby changing the molecular chain length of the polymerization, adjusting the polymerization reaction rate, and at the same time being able to introduce short side chains into the cross-linked network structure, and then forming a three-dimensional structure with gypsum particles to further increase the viscosity and water retention of gypsum.

[0056] Specifically, the addition amount of the allyl monomer in the crosslinked network colloid is 4.5 wt% - 6 wt%; the allyl monomer includes at least one of acrylamide, acrylic acid, methacrylic acid, hydroxypropyl methacrylate, and N,N-dimethylacrylamide.

[0057] Since allyl monomers such as acrylamide, acrylic acid, methacrylic acid, hydroxypropyl methacrylate, and N,N-dimethylacrylamide contain groups such as hydroxyl, carboxyl, ester, and amide groups, by introducing such allyl monomers for graft copolymerization reaction, hydroxyl, carboxyl, ester, amide and other groups can be further introduced into the molecular side chains of the crosslinked network colloid, and such groups are beneficial to associating the free water in the gypsum paste, thereby improving the water retention of the plastering gypsum.

[0058] The initiator includes one of ammonium persulfate, sodium persulfate, and potassium persulfate.

[0059] S30. Prepare a wall material from chitosan and sodium carboxymethylcellulose, and coat 3,4-dihydroxyphenylalanine to obtain a water-resistant slow-release component.

[0060] In the specific implementation process, chitosan, sodium carboxymethylcellulose, and absolute ethanol are mixed to obtain a wall material solution;

[0061] 3,4-Dihydroxyphenylalanine and microcrystalline cellulose are mixed and then added to a spheronizer for rolling treatment to form spherical particle cores;

[0062] The wall material solution is added to an atomizing sprayer to spray the spherical particle cores, and at the same time, it is stirred at a rotation speed of 20 r / min - 30 r / min. After spraying is completed, it is dried at 80 °C - 100 °C for 5 h - 7 h to obtain a water-resistant slow-release component.

[0063] In this application, 3,4-dihydroxyphenylalanine is used as the water-resistant active ingredient, and a wall material is prepared from chitosan and sodium carboxymethylcellulose to coat 3,4-dihydroxyphenylalanine, so that after the light plastering gypsum mortar of this application hardens, 3,4-dihydroxyphenylalanine can be gradually released, and the catechol group contained in 3,4-dihydroxyphenylalanine can form a bidentate metal coordination bond with metal ions, also called a metal coordination covalent bond. The strength of this covalent bond is much higher than that of a hydrogen bond, and it has higher binding ability and stability than a hydrogen bond, enabling it to react with the hydrated calcium compound in the gypsum matrix (such as Ca(OH) 2)A tighter combination is formed, thus creating a more stable hydrate structure. When the light plastering gypsum absorbs water, the water is not easily directly penetrated into the interior, thereby reducing the possibility of the dihydrate gypsum in the hardened light plastering gypsum mortar being dissolved after a large amount of water seeps in. Furthermore, the water swelling property of the hardened light plastering gypsum is reduced, and the water resistance of the light plastering gypsum is enhanced. Even when the actual water consumption is higher than the standard water consumption, the excess water will not easily affect the gypsum setting and hardening process.

[0064] S40. After stirring and mixing the gypsum base material with the light aggregate and sepiolite fiber, a preliminary mixture is obtained.

[0065] In the specific implementation process, the gypsum base material, the light aggregate and the sepiolite fiber are stirred and mixed according to a mass ratio of (6 - 7):(2 - 3):1, the stirring speed is 400 r / min - 600 r / min, and the stirring time is 6 min - 10 min.

[0066] Specifically, the light aggregate is obtained by mixing expanded vitrified microspheres and nano zirconium diboride aerogel according to a mass ratio of (3 - 4):2.

[0067] In this application, expanded vitrified microspheres and nano zirconium diboride aerogel are used as light aggregates, and sepiolite fiber is used to reinforce the toughness of light plastering gypsum. Both expanded vitrified microspheres and nano zirconium diboride aerogel are low - density materials. Adding them as light aggregates to the plastering gypsum helps to significantly reduce the overall density of the plastering gypsum; and nano zirconium diboride aerogel has a very low thermal conductivity, while expanded vitrified microspheres also have a certain heat - preservation performance. When these two are compounded with the plastering gypsum, it can significantly improve the thermal insulation performance of the plastering gypsum and improve its heat - preservation effect; and nano zirconium diboride aerogel and expanded vitrified microspheres can enhance the toughness of the plastering gypsum and reduce the generation of cracks caused by temperature changes or other environmental factors. At the same time, the structure of nano zirconium diboride aerogel is composed of very small nano - scale pores, and the surface of the aerogel usually has low hydrophilicity. Especially in a high - humidity or humid environment, it can effectively reduce water penetration. Therefore, the addition of nano zirconium diboride aerogel has a positive effect on improving the water resistance of light plastering gypsum, and the porous structure of expanded vitrified microspheres can adsorb and retain water to a certain extent, which helps to improve the water - retention property of the plastering gypsum, extend the construction time, and avoid rapid dry - setting. By compounding expanded vitrified microspheres and nano zirconium diboride aerogel for use in light plastering gypsum, the performance of light plastering gypsum can be significantly improved.

[0068] S50. After stirring and mixing the preliminary mixture with the water - retaining thickening component, the water - resistant slow - release component and the water - reducing agent, light plastering gypsum is obtained.

[0069] In the specific implementation process, the preliminary mixture is stirred and mixed with the water retention and thickening component, the water-resistant and slow-release component, and the water reducer according to a mass ratio of (6-8):(1-1.2):(0.8-1):(0.2-0.4), the stirring speed is 600 r / min - 800 r / min, and the stirring time is 4 min - 8 min to obtain lightweight plastering gypsum.

[0070] Specifically, the water reducer is aminotrimethylenephosphonic acid. Aminotrimethylenephosphonic acid contains phosphonic acid groups. After ionization, a large number of negative ions can be formed, which will be adsorbed on the surface of gypsum particles relatively quickly, making the surface of gypsum particles carry negative charges, thereby enhancing the negative charge effect at this place, forming a negative charge protection. Under the action of the charge repulsion force, the gypsum particles can be evenly dispersed in the system, and then the water reduction effect can be achieved, so the actual water consumption can be reduced.

[0071] The above technical solutions of the present application will be described in detail below with reference to specific embodiments.

[0072] Example 1

[0073] A preparation method of lightweight plastering gypsum includes the following steps:

[0074] After the mirabilite gypsum is crushed, it is dried at 50 °C for 8 h, then ground, and the specific surface area is controlled between 200 m 2 / kg - 250 m 2 / kg. Then it is calcined at 155 °C for 2.5 h. After cooling to 55 °C, it is aged. The aging time is not less than 2 days, and the adsorbed water content is controlled to be less than 1.5% to obtain pretreated mirabilite gypsum;

[0075] 1.5 kg of pretreated mirabilite gypsum, 6 kg of desulfurized gypsum, and 1.5 kg of phosphogypsum are graded. The particle size range of the pretreated mirabilite gypsum is controlled between 120 μm - 180 μm, the particle size range of the desulfurized gypsum is controlled between 70 μm - 90 μm, and the particle size range of the phosphogypsum is controlled between 170 μm - 250 μm to obtain a gypsum base material;

[0076] After heating 500 g of water to 55 °C, 2.4 g of cellulose ether and 1.2 g of starch ether are added, and stirred for 1.2 h. After complete dissolution, a cross-linked network-like colloid is formed. Then 15 g of 2-methylprop-2-enyl polyethylene glycol ether, 25 g of acrylamide, and 7 g of ammonium persulfate are added. After stirring for 7 min, it is left to stand for 2.0 h. Then 55 °C water is added, and after stirring for 12 min, it is swollen for 2.0 h while maintaining the temperature at 55 °C. After the swelling is completed, it is stirred at 47 °C for 10 h, and then 8.5 g of sodium lignosulfonate is added, and stirred for 17 min to obtain a water retention and thickening component;

[0077] After mixing 30 g of chitosan, 10 g of sodium carboxymethyl cellulose and 15 g of absolute ethanol, a wall material solution is obtained;

[0078] After mixing 20 g of 3,4-dihydroxyphenylalanine with 12 g of microcrystalline cellulose, the mixture is added to a spheronizer for rolling treatment to form spherical particle cores;

[0079] The wall material solution is added to an atomizing sprayer to spray the spherical particle cores, and at the same time, it is stirred at a rotation speed of 25 r / min. After spraying is completed, it is dried at 90 °C for 6 h to obtain a water-resistant slow-release component;

[0080] Expandable vitrified microspheres and nanozirconium diboride aerogel are mixed according to a mass ratio of 3.5:2 to obtain lightweight aggregate;

[0081] 650 g of gypsum base material, 250 g of lightweight aggregate and 100 g of sepiolite fiber are stirred and mixed at a stirring speed of 500 r / min for 8 min to obtain a preliminary mixture;

[0082] 700 g of the preliminary mixture, 110 g of water retention and thickening component, 90 g of water-resistant slow-release component and 30 g of water reducing agent are stirred and mixed at a stirring speed of 700 r / min for 6 min to obtain lightweight plastering gypsum.

[0083] Example 2

[0084] A preparation method of lightweight plastering gypsum, comprising the following steps:

[0085] After the mirabilite gypsum is crushed, it is dried at 40 °C for 10 h, then ground, and the specific surface area is controlled between 200 m 2 / kg - 250 m 2 / kg, and then calcined at 130 °C for 3 h. After cooling to 50 °C, it is aged, and the aging time is not less than 2 days, and the adsorbed water content is controlled to be less than 1.5% to obtain pretreated mirabilite gypsum;

[0086] 1.5 kg of pretreated mirabilite gypsum, 5 kg of desulfurized gypsum and 1 kg of phosphogypsum are graded. The particle size range of the pretreated mirabilite gypsum is controlled at 100 μm - 200 μm, the particle size range of the desulfurized gypsum is controlled at 50 μm - 100 μm, and the particle size range of the phosphogypsum is controlled at 150 μm - 300 μm to obtain a gypsum base material;

[0087] After heating 500 g of water to 50 °C, 2.7 g of cellulose ether and 0.9 g of starch ether were added, and stirred for 1 h. After complete dissolution, a cross-linked network colloid was formed. Then, 14.5 g of 3-methylbut-3-enyl polyethylene glycol ether, 23 g of methacrylic acid and 7 g of sodium persulfate were added. After stirring for 5 min, it was left standing for 1.5 h. Then, water at 50 °C was added, and after stirring for 10 min, swelling was carried out for 1.5 h while maintaining the temperature at 50 °C. After the swelling was completed, it was stirred at 45 °C for 12 h, and then 8.5 g of sodium lignosulfonate was added. After stirring for 15 min, a water-retaining and thickening component was obtained;

[0088] 30 g of chitosan, 10 g of sodium carboxymethyl cellulose and 15 g of absolute ethanol were mixed to obtain a wall material solution;

[0089] 20 g of 3,4-dihydroxyphenylalanine and 12 g of microcrystalline cellulose were mixed, and then added to a spheronizer for rolling treatment to form spherical particle cores;

[0090] The wall material solution was added to an atomizing sprayer to spray the spherical particle cores, and at the same time, it was stirred at a rotation speed of 20 r / min. After spraying was completed, it was dried at 80 °C for 7 h to obtain a water-resistant and slow-release component;

[0091] Expanded vitrified microspheres and nanozirconium diboride aerogel were mixed according to a mass ratio of 3:2 to obtain a lightweight aggregate;

[0092] 650 g of gypsum base material, 200 g of lightweight aggregate and 100 g of sepiolite fiber were stirred and mixed at a stirring speed of 400 r / min for 10 min to obtain a preliminary mixture;

[0093] 700 g of the preliminary mixture, 100 g of the water-retaining and thickening component, 80 g of the water-resistant and slow-release component and 20 g of water reducer were stirred and mixed at a stirring speed of 600 r / min for 8 min to obtain lightweight plastering gypsum.

[0094] Example 3

[0095] A preparation method of lightweight plastering gypsum, comprising the following steps:

[0096] After mirabilite gypsum was crushed, it was dried at 60 °C for 6 h, then ground, and the specific surface area was controlled between 200 m 2 / kg - 250 m 2 / kg. Then, it was calcined at 180 °C for 2 h. After cooling to 60 °C, aging was carried out, and the aging time was not less than 2 days, and the adsorbed water content was controlled to be less than 1.5%, to obtain pretreated mirabilite gypsum;

[0097] 1.5 kg of pretreated mirabilite gypsum, 5 kg of desulfurized gypsum, and 2 kg of phosphogypsum were proportioned. The particle size range of the pretreated mirabilite gypsum was controlled at 100 μm - 200 μm, the particle size range of the desulfurized gypsum was controlled at 50 μm - 100 μm, and the particle size range of the phosphogypsum was controlled at 150 μm - 300 μm to obtain a gypsum base material;

[0098] After heating 500 g of water to 50 °C, 3 g of cellulose ether and 1 g of starch ether were added, and stirred for 1.5 h. After complete dissolution, a cross-linked network-like colloid was formed. Then, 15.5 g of 4-hydroxybutyl vinyl polyoxyethylene ether, 30 g of methacrylic acid, and 8 g of potassium persulfate were added. After stirring for 10 min, it was left standing for 2.5 h. Then, water at 60 °C was added, stirred for 14 min, and then underwent swelling for 2.5 h while maintaining the temperature at 60 °C. After the swelling was completed, it was stirred at 50 °C for 8 h, and then 8.5 g of sodium lignosulfonate was added and stirred for 20 min to obtain a water-retaining thickening component;

[0099] 30 g of chitosan, 10 g of sodium carboxymethyl cellulose, and 15 g of absolute ethanol were mixed to obtain a wall material solution;

[0100] 20 g of 3,4-dihydroxyphenylalanine and 12 g of microcrystalline cellulose were mixed and then added to a spheronizer for rolling treatment to form spherical particle core materials;

[0101] The wall material solution was added to an atomizing sprayer to spray the spherical particle core materials, while stirring at a rotation speed of 30 r / min. After spraying was completed, it was dried at 100 °C for 5 h to obtain a water-resistant slow-release component;

[0102] Expanded vitrified microspheres and nanozirconium diboride aerogel were mixed in a mass ratio of 2:1 to obtain lightweight aggregate;

[0103] 700 g of the gypsum base material, 200 g of the lightweight aggregate, and 100 g of sepiolite fiber were stirred and mixed at a stirring speed of 600 r / min for 6 min to obtain a preliminary mixture;

[0104] 800 g of the preliminary mixture, 120 g of the water-retaining thickening component, 100 g of the water-resistant slow-release component, and 20 g of a water-reducing agent were stirred and mixed at a stirring speed of 800 r / min for 4 min to obtain lightweight plastering gypsum.

[0105] Comparative Example 1

[0106] Compared with Example 1, the water-retaining thickening component was replaced with cellulose ether and starch ether of equal weight and without any treatment, and the remaining steps remained unchanged.

[0107] Comparative Example 2

[0108] Compared with Example 1, 3,4-dihydroxyphenylalanine in the water-resistant and slow-release component was replaced with an equal weight of sodium silicate.

[0109] Experimental Example

[0110] The light plastering gypsum in the examples and comparative examples of this application was subjected to performance testing. The water consumption for standard fluidity was measured according to the test method in "Plastering Gypsum" GB / T 28627-2012, and the bottom-layer plastering gypsum mortar with a corresponding standard fluidity (165±5mm) was prepared according to the specified method, and the water retention rate, anti-sagging value, and tensile bond strength were tested. At the same time, 4% more water was used based on the water consumption for standard fluidity, and the water retention rate, anti-sagging value, and tensile bond strength were tested in the same way, and the water consumption sensitivity was characterized by comparison. The test results are shown in Tables 1 and 2 below.

[0111] Table 1 Performance Testing at the Water Consumption for Standard Fluidity

[0112]

[0113] Table 2 Performance Testing at 4% More Water than the Standard Fluidity

[0114] Group Water retention rate (%) Anti-sagging value (mm) Tensile adhesion strength (MPa) Example 1 90 4.3 1.01 Example 2 84 4.5 0.90 Example 3 88 4.5 0.92 Comparative Example 1 62 7.5 0.67 Comparative Example 2 65 7.3 0.69

[0115] As can be seen from Tables 1 and 2, the light plastering gypsum prepared in the examples of this application can achieve a water retention rate of over 90% at the water consumption for standard fluidity, and can effectively resist sagging, with a relatively high tensile bond strength. Even when the water consumption is 4% more than the standard fluidity, its water retention rate can still reach over 84%, and it can effectively resist sagging (generally, it is considered difficult to meet the use requirements of the surface-layer plastering gypsum when the anti-sagging value is greater than 10mm), and the decrease in tensile bond strength is not obvious, meeting the requirements of the surface-layer plastering gypsum, indicating that the water usage range of the light plastering gypsum of this application is wider; in Comparative Example 1, cellulose ether and starch ether were directly used as the water retention and thickening components. Since the dissolution process of cellulose ether and starch ether is easily affected by the stirring time and feeding time, the water retention performance of the finally prepared light plastering gypsum decreased; in Comparative Example 2, the conventional sodium silicate was selected as the water-resistant component. Although sodium silicate can combine with the dihydrate gypsum crystals to form a calcium silicate layer, 3,4-dihydroxyphenylalanine in this application can form a bidentate metal coordination bond with calcium ions, which has higher binding ability and stability, thus forming a more compact hydrate structure layer and further improving the water resistance of the light plastering gypsum.

[0116] The above are only alternative embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structural transformation made by using the content of the specification and drawings of the present application under the inventive concept of the present application, or any direct / indirect application in other related technical fields, is included in the patent protection scope of the present application.

Claims

1. A method for preparing a lightweight plaster, characterized in that: The following steps are involved: After pre-treatment, the mirabilite gypsum is graded with desulfurized gypsum and phosphogypsum to obtain a gypsum base material; The cellulose ether and the starch ether are swollen together to form a cross-linked network colloid, and polyether monomers, acrylic monomers and initiators are added to carry out graft copolymerization to obtain a water-retaining and thickening component; The wall material is prepared by using chitosan and sodium carboxymethyl cellulose, and 3,4-dihydroxyphenylalanine is coated to obtain a water-resistant sustained-release component; The gypsum base material is mixed with lightweight aggregate and sepiolite fiber to obtain a primary mixture; The primary mixture is stirred and mixed with the water-retaining thickening component, the water-resistant slow-release component and the water reducing agent to obtain a lightweight plaster.

2. The method for preparing the lightweight plaster according to claim 1, characterized in that: The step of pre-treating the mirabilite gypsum comprises: After the mirabilite gypsum is crushed, it is dried at 40℃-60℃ for 6h-10h, and then ground to control the specific surface area to 200m 2 / kg-250m 2 / kg, and then calcined at 130℃-180℃ for 2h-3h, cooled to 50℃-60℃, and then aged. The aging time is not less than 2 days, and the adsorbed water content is controlled to be less than 1.5%.

3. The method for preparing the lightweight plaster according to claim 1, characterized in that: In the step of pre-treating the mirabilite gypsum and then grading it with the desulfurized gypsum and phosphogypsum, the particle size range of the pre-treated mirabilite gypsum is controlled to be 100 μm-200 μm, the particle size range of the desulfurized gypsum is controlled to be 50 μm-100 μm, and the particle size range of the phosphogypsum is controlled to be 150 μm-300 μm; The mass ratio of the pretreated mirabilite gypsum, desulfurized gypsum and phosphogypsum is (1-2):(5-7):(1-2).

4. The method for preparing the lightweight plaster according to claim 1, characterized in that: The step of swelling the cellulose ether and the starch ether together to form a cross-linked network colloid comprises: After heating water to 50-60°C, add cellulose ether and starch ether, stir for 1h-1.5h, and after complete dissolution, form a cross-linked network colloid; Wherein, the mass ratio of the cellulose ether to the starch ether is (6-7): (2-3).

5. The method for preparing the lightweight plaster according to claim 1, characterized in that: The step of adding polyether monomer, acrylic monomer and initiator to carry out graft copolymerization to obtain water-retaining and thickening component comprises: Adding polyether monomer, acrylic monomer and initiator to the cross-linked network colloid, stirring for 5-10 minutes, standing for 1.5-2.5 hours, adding water at 50-60°C, stirring for 10-14 minutes, swelling for 1.5-2.5 hours, while maintaining the temperature at 50-60°C, stirring at 45-50°C for 8-12 hours after swelling, adding sodium lignin sulfonate, stirring for 15-20 minutes, and obtaining a water-retaining thickening component; Wherein, the amount of the polyether monomer added to the cross-linked network colloid is 2.5wt%-3.5wt%; The amount of the acrylic monomer added to the cross-linked network colloid is 4.5 wt % to 6 wt %.

6. The method for preparing the lightweight plaster according to claim 1, characterized in that: The polyether monomer includes at least one of 2-methylprop-2-enyl polyethylene glycol ether, 3-methylbut-3-enyl polyethylene glycol ether, 4-hydroxybutyl vinyl polyoxyethylene ether and isopentanol polyoxyethylene ether; The acrylic monomer includes at least one of acrylamide, acrylic acid, methacrylic acid, hydroxypropyl methacrylate and N,N-dimethylacrylamide; The initiator includes one of ammonium persulfate, sodium persulfate and potassium persulfate.

7. The method for preparing the lightweight plaster according to claim 1, characterized in that: The step of preparing the wall material with chitosan and sodium carboxymethyl cellulose and coating 3,4-dihydroxyphenylalanine to obtain the water-resistant sustained-release component comprises: Mixing chitosan, sodium carboxymethyl cellulose and anhydrous ethanol to obtain a wall material solution; After mixing 3,4-dihydroxyphenylalanine and microcrystalline cellulose, the mixture is added into a spheronizer for rolling to form a spherical particle core material; The wall material solution is added into an atomizing sprayer, and the spherical particle core material is sprayed while being stirred at a speed of 20 r / min-30 r / min. After spraying, it is dried at 80° C.-100° C. for 5 h-7 h to obtain a water-resistant slow-release component.

8. The method for preparing the lightweight plaster according to claim 1, characterized in that: The step of mixing the gypsum base material with the lightweight aggregate and the sepiolite fiber to obtain a primary mixture comprises: The gypsum base material, lightweight aggregate and sepiolite fiber are stirred and mixed in a mass ratio of (6-7):(2-3):1, with a stirring speed of 400r / min-600r / min and a stirring time of 6min-10min to obtain a primary mixture.

9. The method for preparing the lightweight plaster according to claim 1, characterized in that: The lightweight aggregate is obtained by mixing expanded vitrified microspheres and nano zirconium diboride aerogel in a mass ratio of (3-4):

2.

10. The method for preparing the lightweight plaster according to claim 1, characterized in that: The step of mixing the primary mixture with the water-retaining thickening component, the water-resistant slow-release component and the water reducing agent to obtain a lightweight plaster comprises: The primary mixture is stirred and mixed with the water-retaining thickening component, the water-resistant slow-release component and the water reducer in a mass ratio of (6-8):(1-1.2):(0.8-1):(0.2-0.4), with a stirring speed of 600r / min-800r / min and a stirring time of 4min-8min to obtain a lightweight plaster.

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