A method for preparing a lightweight plastering gypsum

Abstract

The application 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: after mirabilite gypsum is pretreated, the mirabilite gypsum is graded with desulfurization gypsum and phosphorite gypsum to obtain a gypsum base material; cellulose ether and starch ether are swelled together to form a cross-linked network colloidal, and polyether monomer, propylene-based monomer and an initiator are added to carry out graft copolymerization reaction to obtain a water-retaining and thickening component; a wall material is prepared from chitosan and sodium carboxymethyl cellulose, and 3,4-dihydroxyphenylalanine is coated to obtain a water-resistant and slow-release component; the gypsum base material is stirred and mixed with light aggregate and sepiolite fiber to obtain a primary mixture; and the primary mixture is stirred and mixed with the water-retaining and thickening component, the water-resistant and 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 range during construction is widened, and the construction difficulty is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a preparation method of light plastering gypsum. BACKGROUND

[0002] According to the current development status of the building material industry, the light plastering gypsum has the characteristics of light texture, good hygroscopicity, good volume stability, no hollowing and cracking, excellent fire resistance, etc. compared with the traditional cement plastering material. Moreover, the light plastering gypsum is more easily operated and more environmentally friendly than the heavy plastering gypsum, so that the light plastering gypsum is gradually widely used as a wall plastering and leveling material with good material performance, construction performance and use function. However, the existing light plastering gypsum is usually very sensitive to water during construction, and the water consumption at the construction site is slightly controlled, which will affect the performance of the light plastering gypsum. For example, when the water consumption is slightly low, the water retention of the light plastering gypsum is poor, and when the light plastering gypsum is applied to the water-absorbing surface of aerated concrete, porous insulation board, etc., the water in the light plastering gypsum is absorbed, which affects the hydration process of the light plastering gypsum, and the light plastering gypsum is prone to phenomena such as powdering, drying shrinkage and cracking. When the water consumption is slightly high, the water resistance is insufficient, which leads to excess water in the light plastering gypsum mortar, and the excess water will evaporate during the hardening process of the gypsum, so that a large number of capillary pores appear in the hardened gypsum, which is difficult to achieve sufficient strength. SUMMARY

[0003] The main purpose of the present application is to provide a preparation method of light plastering gypsum, which aims to solve the technical problem of narrow water consumption range of the existing light plastering gypsum during construction.

[0004] To achieve the above-mentioned purpose, the present application provides a preparation method of light plastering gypsum, which comprises the following steps:

[0005] After the mirabilite gypsum is pretreated, it is graded with desulfurized gypsum and phosphorite gypsum to obtain a gypsum base material;

[0006] The cellulose ether and the starch ether are swelled together to form a cross-linked network-shaped colloid, and the polyether monomer, the propylene-based monomer and the initiator are added for graft copolymerization reaction to obtain a water-retention and thickening component;

[0007] A wall material is prepared from chitosan and sodium carboxymethyl cellulose, and 3,4-dihydroxyphenylalanine is coated to obtain a water-resistant slow-release component;

[0008] The gypsum base material is stirred and mixed with light aggregate and sepiolite fiber to obtain a preliminary mixture;

[0009] The preliminary mixture is stirred and mixed with the water-retention and thickening component, the water-resistant slow-release component and the water-reducing agent to obtain the light plastering gypsum.

[0010] Optionally, the step of pretreating mirabilite gypsum comprises:

[0011] After the mirabilite gypsum is crushed, it is dried at 40-60°C for 6-10 hours, then ground, and the specific surface area is controlled to be between 200-250 m 2 2 / kg, then calcined at 130-180°C for 2-3 hours, cooled to 50-60°C, and aged for no less than 2 days, with the adsorbed water content controlled to be less than 1.5%.

[0012] Optionally, in the step of grading the pretreated mirabilite gypsum with desulfurization gypsum and phosphorite gypsum, the particle size of the pretreated mirabilite gypsum is controlled to be in the range of 100-200 μm, the particle size of the desulfurization gypsum is controlled to be in the range of 50-100 μm, and the particle size of the phosphorite gypsum is controlled to be in the range of 150-300 μm.

[0013] The mass ratio of the pretreated mirabilite gypsum, the desulfurization gypsum, and the phosphorite gypsum is (1-2) : (5-7) : (1-2).

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

[0015] After the water is heated to 50-60°C, the cellulose ether and the starch ether are added, stirred for 1-1.5 hours, and completely dissolved to form a cross-linked network gel.

[0016] The mass ratio of the cellulose ether and the starch ether is (6-7) : (2-3).

[0017] Optionally, the step of incorporating a polyether monomer, an acryl monomer, and an initiator to perform a graft copolymerization reaction to obtain a water-retaining thickening component comprises:

[0018] The polyether monomer, the acryl monomer, and the initiator are added to the cross-linked network gel, stirred for 5-10 minutes, and then left to stand for 1.5-2.5 hours, 50-60°C water is added, stirred for 10-14 minutes, and then swelled for 1.5-2.5 hours while the temperature is maintained at 50-60°C, after the swelling is completed, stirred at 45-50°C for 8-12 hours, and then sodium lignosulfonate is added, stirred for 15-20 minutes to obtain the water-retaining thickening component.

[0019] The amount of the polyether monomer added to the cross-linked network gel is 2.5-3.5 wt%.

[0020] The amount of the acryl monomer added to the cross-linked network gel is 4.5-6 wt%.​

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

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

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

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

[0025] The chitosan, sodium carboxymethyl cellulose and anhydrous ethanol are mixed to obtain a wall material solution;

[0026] The 3,4-dihydroxyphenylalanine is mixed with the microcrystalline cellulose and then added into a balling machine for rolling treatment to form a spherical granular core material;

[0027] The wall material solution is added into an atomizing sprayer to spray the spherical granular core material, while stirring at a speed of 20 r / min-30 r / min, and after the spraying is completed, drying at 80℃-100℃ for 5h-7h to obtain the water-resistant slow-release component.

[0028] Optionally, the step of obtaining the initial mixture by stirring and mixing the gypsum base material with lightweight aggregate and sepiolite fiber comprises:

[0029] The gypsum base material, lightweight aggregate and sepiolite fiber are stirred and mixed at 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 to obtain the initial mixture.

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

[0031] Optionally, the step of obtaining the lightweight plastering gypsum by stirring and mixing the initial mixture with the water-retention thickening component, the water-resistant slow-release component and the water-reducing agent comprises:

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

[0033] The present application at least includes the following beneficial effects:

[0034] The present application first pretreats mirabilite gypsum to increase the content of hemihydrate gypsum, and then performs grading with high-grade gypsum such as desulfurization gypsum and phosphorite gypsum, so as to ensure the workability, strength and durability of the gypsum slurry;

[0035] The present application swells cellulose ether and starch ether together, crosslinks the two high molecular materials to form a stable space network structure colloid, the crosslinked structure contains hydrophilic groups such as hydroxyl groups and ether groups, these groups can interact with water molecules, attract water into the crosslinked structure, to ensure that the plastering gypsum has sufficient water retention, and avoid water loss during construction, and then graft copolymerization with polyether monomer and propylene-based monomer, to connect multiple side chains with certain length and rigidity on the molecular backbone of the crosslinked structure, so that they can be adsorbed on the surface of the gypsum particles, and the formation of the crosslinked structure helps to increase the plastic viscosity of the gypsum slurry, thereby improving the water retention of the lightweight plastering gypsum;

[0036] The present application uses 3,4-dihydroxyphenylalanine as a water-resistant effective component, and uses chitosan and carboxymethyl cellulose sodium to prepare a wall material to coat 3,4-dihydroxyphenylalanine, so that after the hardening of the lightweight plastering gypsum mortar of the present application, 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, so that it can be more closely combined with the hydrated calcium compound 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 dissolution of dihydrate gypsum in the hardened lightweight plastering gypsum mortar after a large amount of water penetrates, and enhancing the water resistance of the lightweight plastering gypsum, avoiding the easy influence of excess water on the gypsum setting and hardening process;

[0037] The present application greatly improves the water retention and water resistance of the lightweight plastering gypsum by matching the gypsum base material with the water-retention thickening component and the water-resistant slow-release component, thereby widening the water range of the lightweight plastering gypsum of the present application during construction, even if the water quantity at the construction site is not well controlled, the performance of the lightweight plastering gypsum will not be easily affected, thereby reducing the construction difficulty. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below only illustrate some of the embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort based on the drawings shown.

[0039] Figure 1 The preparation method flow chart of the light plastering gypsum described in the embodiments of the present application.

[0040] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and drawings. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort belong to the scope of protection of 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 shown in Figure 1 The preparation method of light plastering gypsum comprises the following steps:

[0043] S10, after pretreatment of mirabilite gypsum, grading with desulfurization gypsum and phosphor gypsum to obtain a gypsum base material.

[0044] In the specific implementation process, when the mirabilite gypsum is pretreated, first, the mirabilite gypsum is crushed, dried at 40-60℃ for 6-10h, then ground, and the specific surface area is controlled between 200m 2 / kg-250m 2 / kg, then calcined at 130-180℃ for 2-3h, cooled to 50-60℃, aged for not less than 2 days, and the adsorbed water content is controlled to be less than 1.5%.

[0045] Since the mirabilite gypsum generally contains a lot of hydrated sodium sulfate (Na2SO4), the effective ingredient is low, and the clay impurity content is high, which significantly weakens the strength, so that it is difficult to be directly applied. Therefore, the mirabilite gypsum is calcined and aged in the present application to increase the content of the effective ingredient hemihydrate gypsum, so as to realize the rational utilization of mirabilite gypsum resources and avoid the waste of mirabilite gypsum.

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

[0047] To further improve the content of effective component hemihydrate gypsum in the gypsum raw material, the pretreated mirabilite gypsum is graded with desulfurization gypsum and phosphogypsum in the application. The mirabilite gypsum has good fluidity and lower water demand, and the crystallization is relatively coarse, which can provide higher early strength. The particle size of the mirabilite gypsum is controlled to be between 100 μm and 200 μm to ensure sufficient specific surface area for reaction, while avoiding excessive fine particle size which brings larger reaction heat. The desulfurization gypsum mainly comes from the desulfurization process of coal-fired power plants, contains more calcium components, has higher hydration degree and faster hardening speed, and is more active than the mirabilite gypsum. The particle size of the desulfurization gypsum is controlled to be between 50 μm and 100 μm to maintain appropriate fineness, so as to provide higher activity and reactivity, help to form a more uniform hardened structure, and the desulfurization gypsum as a finer component can increase the fluidity of the gypsum slurry and reduce the cement dosage. The phosphogypsum comes from the by-product in the phosphate fertilizer industry, contains higher calcium phosphate (Ca3(PO4)2), and is suitable for enhancing the comprehensive performance of gypsum, especially water resistance and crack resistance. However, the particle size of the phosphogypsum is relatively large, and it contains certain impurities, so the reactivity is not as good as that of the mirabilite gypsum and the desulfurization gypsum. Based on the characteristics of these different gypsums, the particle size ratio is reasonably controlled in the application, so as to ensure the workability, strength and durability of the gypsum slurry.

[0048] S20, the cellulose ether and the starch ether are swelled together to form a cross-linked network-like colloid, and the polyether monomer, the propylene-based monomer and the initiator are incorporated to carry out graft copolymerization reaction to obtain a water-retention and thickening component.

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

[0050] After the water is heated to 50-60℃, the cellulose ether and the starch ether are added and stirred for 1-1.5 h, and after complete dissolution, a cross-linked network-like colloid is formed.

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

[0052] Further, the polyether monomer, the propylene-based monomer and the initiator are added in the cross-linked network gel, stirred for 5-10 minutes, and then left for 1.5-2.5 hours. Then, water at 50-60°C is added, stirred for 10-14 minutes, and then swelled for 1.5-2.5 hours while the temperature is kept at 50-60°C. After the swelling is completed, stirring is performed at 45-50°C for 8-12 hours. Then, sodium lignosulfonate is added, stirred for 15-20 minutes, and then the water-retention and thickening component is obtained.

[0053] The cellulose ether has good water solubility and water swelling property, and the starch ether is a compound formed by combining starch molecules with ether groups. In water, the starch ether can absorb water to swell and form a gel or a viscous solution. The cellulose ether and the starch ether have good thickening and water-retention effects on the plastering gypsum. However, in the prior art, the cellulose ether or the starch ether is directly mixed with the gypsum base material, so that the cellulose ether or the starch ether is first swelled and then dissolved in the stirring process. However, direct feeding can cause a large water demand of the plastering gypsum, and insufficient stirring time can also easily cause poor dissolution of the cellulose ether or the starch ether, thereby affecting the water-retention property of the plastering gypsum. Therefore, in the present application, the two high molecular materials are first cross-linked to form a stable space network structure gel. The cross-linked structure contains hydrophilic groups such as hydroxyl groups and ether groups. These groups can interact with water molecules to attract water into the cross-linked structure, so as to ensure that the plastering gypsum has sufficient water-retention property and avoid water loss during construction. Then, the polyether monomer and the propylene-based monomer are subjected to graft copolymerization reaction, so as to connect multiple side chains with certain length and rigidity to the molecular main chain of the cross-linked structure. The side chains can be adsorbed on the surface of the gypsum particles. The formation of the cross-linked structure helps to increase the plastic viscosity of the gypsum slurry, so as to achieve the effects of thickening and water-retention.

[0054] In the cross-linked network gel, the polyether monomer is added in an amount of 2.5wt%-3.5wt%. 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 isopentenyl alcohol polyoxyethylene ether.

[0055] In the present application, the polyether monomers such as 2-methylprop-2-enyl polyethylene glycol ether, 3-methylbut-3-enyl polyethylene glycol ether, 4-hydroxybutyl vinyl polyoxyethylene ether and isopentenyl alcohol polyoxyethylene ether are used for graft copolymerization reaction. In the polymerization process, the polyether monomers can react with the polymer chains to transfer the intermediate free radicals formed in the polymerization to themselves, so as to change the molecular chain length of the polymerization and adjust the rate of the polymerization. Meanwhile, the polyether monomers can introduce short side chains into the cross-linked network structure, so as to form a three-dimensional structure with the gypsum particles and further increase the viscosity and water-retention property of the gypsum.

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

[0057] Since the propenyl monomers such as acrylamide, acrylic acid, methacrylic acid, hydroxypropyl methacrylate and N,N-dimethyl acrylamide contain hydroxyl, carboxyl, ester, amide and other groups, by introducing the propenyl monomers for graft copolymerization, hydroxyl, carboxyl, ester, amide and other groups can be further introduced in the molecular side chain of the crosslinked network gel, and such groups are beneficial to the free water in the associated gypsum slurry, thereby improving the water retention of the plastering gypsum.

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

[0059] S30, a wall material is prepared from chitosan and sodium carboxymethyl cellulose, and 3,4-dihydroxyphenylalanine is coated to obtain a water-resistant slow-release component.

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

[0061] After 3,4-dihydroxyphenylalanine is mixed with microcrystalline cellulose, it is added into a balling machine for rolling treatment to form a spherical granular core material;

[0062] The wall material solution is added into an atomizing sprayer to spray the spherical granular core material, while stirring at a speed of 20r / min-30r / min, after the spraying is completed, drying at 80℃-100℃ for 5h-7h to obtain the water-resistant slow-release component.

[0063] The application takes 3,4-dihydroxyphenylalanine as a water-resistant effective component, and uses chitosan and sodium carboxymethyl cellulose to prepare a wall material to coat 3,4-dihydroxyphenylalanine, so that after the hardening of the light plastering gypsum mortar of the application, 3,4-dihydroxyphenylalanine can be gradually released. The catechol group contained in 3,4-dihydroxyphenylalanine can form a bidentate metal coordination bond, also called a metal coordination covalent bond, with metal ions. The strength of this covalent bond is much higher than that of a hydrogen bond, and it has higher binding capacity and stability than a hydrogen bond, so it can be more closely combined with the hydrated calcium compound (such as Ca(OH)2) in the gypsum matrix, thereby forming a more stable hydrate structure. In this way, when the light plastering gypsum absorbs water, water is not easy to penetrate directly 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 penetrates, thereby reducing the water swelling property of the hardened light plastering gypsum and enhancing the water resistance of the light plastering gypsum. Even if the actual water consumption is higher than the standard water consumption, the excess water will not easily affect the gypsum coagulation and hardening process.

[0064] S40, the gypsum base is mixed with light aggregate and sepiolite fiber to obtain a preliminary mixture.

[0065] In the specific implementation process, the gypsum base, light aggregate and sepiolite fiber are mixed at 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 microbeads and nano-zirconium diboride aerogel at a mass ratio of (3-4):2.

[0067] The application uses expanded vitrified microsphere and nano-zirconium diboride aerogel as light aggregate, and sepiolite fiber to reinforce the toughness of light plastering gypsum. Both expanded vitrified microsphere and nano-zirconium diboride aerogel are low-density materials, which can help to significantly reduce the overall density of plastering gypsum when added to plastering gypsum. Nano-zirconium diboride aerogel has very low thermal conductivity, and expanded vitrified microsphere also has certain thermal insulation performance. When the two are compounded with plastering gypsum, the thermal insulation performance of plastering gypsum can be significantly improved, and the thermal insulation effect can be improved. Nano-zirconium diboride aerogel and expanded vitrified microsphere can enhance the toughness of 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 generally has low hydrophilicity. Especially in high humidity or humid environment, it can effectively reduce water penetration, so the addition of nano-zirconium diboride aerogel has a positive effect on improving the water resistance of light plastering gypsum. The porous structure of expanded vitrified microsphere can absorb and retain water to some extent, which helps to improve the water retention of plastering gypsum, prolong the construction time, and avoid rapid drying. The use of expanded vitrified microsphere and nano-zirconium diboride aerogel in light plastering gypsum can significantly improve the performance of light plastering gypsum.

[0068] S50, the initial mixture is mixed with the water-retaining thickening component, the water-resistant slow-release component and the water reducing agent to obtain light plastering gypsum.

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

[0070] Specifically, the water reducing agent is amino trimethylene phosphonic acid. Amino trimethylene phosphonic acid contains phosphonic acid groups, which can form a large number of negative ions after ionization, and can be quickly adsorbed on the surface of gypsum particles, so that the surface of the gypsum particles has a negative charge, thereby enhancing the negative electric effect at this position, forming a negative electric protection. Under the action of electric charge repulsion, the gypsum particles can be uniformly dispersed in the system, thereby achieving the effect of water reduction, so that the actual water consumption can be reduced.

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

[0072] Example 1

[0073] A preparation method of light plastering gypsum, comprising the following steps:

[0074] The mirabilite gypsum is crushed, dried at 50℃ for 8h, ground, and controlled to have a specific surface area of 200m 2 / kg-250m 2 / kg, calcined at 155℃ for 2.5h, cooled to 55℃, aged for not less than 2 days, and controlled to have an adsorbed water content of less than 1.5%, to obtain pretreated mirabilite gypsum;

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

[0076] 500g of water is heated to 55℃, then 2.4g of cellulose ether and 1.2g of starch ether are added, stirred for 1.2h, completely dissolved to form a cross-linked network colloidal, then 15g of 2-methylprop-2-enyl polyethylene glycol ether, 25g of acrylamide and 7g of ammonium persulfate are added, stirred for 7min, then placed for 2.0h, then 55℃ water is added, stirred for 12min, then swelled for 2.0h while keeping the temperature at 55℃, after swelling, stirred at 47℃ for 10h, then 8.5g of sodium lignosulfonate is added, stirred for 17min, to obtain a water-retention thickening component;

[0077] 30g of chitosan, 10g of sodium carboxymethyl cellulose and 15g of anhydrous ethanol are mixed to obtain a wall material solution;

[0078] 20g of 3,4-dihydroxyphenylalanine and 12g of microcrystalline cellulose are mixed, then added into a balling machine for rolling treatment to form a spherical particle core material;

[0079] The wall material solution is added into an atomizing sprayer to spray the spherical particle core material while stirring at a speed of 25r / min, after spraying, dried at 90℃ for 6h to obtain a water-resistant slow-release component;

[0080] The expanded vitrified microsphere and nano-zirconium diboride aerogel are mixed according to a mass ratio of 3.5:2 to obtain lightweight aggregate;

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

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

[0083] Example 2

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

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

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

[0087] After water 500g is heated to 50℃, cellulose ether 2.7g and starch ether 0.9g are added, stirred for 1h, completely dissolved, and then a crosslinked network colloidal gel is formed, then 3-methylbut-3-enyl polyethylene glycol ether 14.5g, methacrylic acid 23g and sodium persulfate 7g are added, stirred for 5min, and then placed for 1.5h, then water at 50℃ is added, stirred for 10min, and then swelled for 1.5h while the temperature is kept at 50℃, after the swelling is completed, stirred at 45℃ for 12h, then sodium lignosulfonate 8.5g is added, stirred for 15min, to obtain a water-retention thickening component;

[0088] Chitosan 30g, sodium carboxymethyl cellulose 10g and anhydrous ethanol 15g are mixed to obtain a wall material solution;

[0089] 3,4-dihydroxyphenylalanine 20g and microcrystalline cellulose 12g are mixed, then added into a balling machine to perform rolling treatment, to form a spherical particle core material;

[0090] The wall material solution is added into an atomizing sprayer, and the spherical particle core material is sprayed, while stirring at a rotating speed of 20r / min, after the spraying is completed, dried at 80℃ for 7h, to obtain a water-resistant slow-release component;

[0091] Expanded vitrified microbeads and nano-zirconium diboride aerogel are mixed according to a mass ratio of 3:2, to obtain lightweight aggregates;

[0092] The gypsum base material 650g is mixed with the lightweight aggregates 200g and sepiolite fibers 100g, the stirring speed is 400r / min, and the stirring time is 10min, to obtain a preliminary mixture;

[0093] Mixing 700g of the initial mixture with 100g of the water-retention thickening component, 80g of the water-resistant slow-release component, and 20g of the water-reducing agent, the stirring speed is 600r / min, and the stirring time is 8min, to obtain the lightweight plastering gypsum.

[0094] Example 3

[0095] A method for preparing a lightweight plastering gypsum, comprising the following steps:

[0096] After crushing mirabilite gypsum, drying at 60℃ for 6h, then grinding, and controlling the specific surface area between 200m 2 / kg-250m 2 / kg, calcining at 180℃ for 2h, cooling to 60℃, then aging for not less than 2 days, and controlling the adsorbed water content to be less than 1.5%, to obtain pretreated mirabilite gypsum;

[0097] Grading 1.5kg of the pretreated mirabilite gypsum with 5kg of desulfurized gypsum and 2kg of phosphogypsum, the particle size range of the pretreated mirabilite gypsum is controlled to be 100μm-200μm, the particle size range of the desulfurized gypsum is controlled to be 50μm-100μm, and the particle size range of the phosphogypsum is controlled to be 150μm-300μm, to obtain the gypsum base material;

[0098] After heating 500g of water to 50℃, adding 3g of cellulose ether and 1g of starch ether, stirring for 1.5h, completely dissolving, forming a cross-linked network colloidal, then adding 15.5g of 4-hydroxybutyl vinyl polyoxyethylene ether, 30g of methacrylic acid, and 8g of potassium persulfate, stirring for 10min, standing for 2.5h, then adding 60℃ water, stirring for 14min, swelling for 2.5h while keeping the temperature at 60℃, after swelling, stirring at 50℃ for 8h, then adding 8.5g of sodium lignosulfonate, stirring for 20min, to obtain the water-retention thickening component;

[0099] Mixing 30g of chitosan, 10g of sodium carboxymethyl cellulose, and 15g of anhydrous ethanol to obtain the wall material solution;

[0100] Mixing 20g of 3,4-dihydroxyphenylalanine with 12g of microcrystalline cellulose, then adding into a balling machine for rolling treatment to form spherical particle core material;

[0101] Adding the wall material solution into an atomizing sprayer to spray the spherical particle core material while stirring at a speed of 30r / min, after spraying, drying at 100℃ for 5h, to obtain the water-resistant slow-release component;

[0102] Mixing expanded vitrified microsphere and nano-zirconium diboride aerogel according to a mass ratio of 2:1 to obtain lightweight aggregate;

[0103] The gypsum base 700 g is mixed with light aggregate 200 g and sepiolite fiber 100 g at a stirring speed of 600 r / min for 6 min to obtain a preliminary mixture;

[0104] The preliminary mixture 800 g is mixed with water-retention and thickening component 120 g, water-resistant and slow-release component 100 g, and water-reducing agent 20 g at a stirring speed of 800 r / min for 4 min to obtain light plastering gypsum.

[0105] Comparative Example 1

[0106] Compared with Example 1, the water-retention and thickening component is replaced with cellulose ether and starch ether of the same weight and without any treatment, and the remaining steps remain unchanged.

[0107] Comparative Example 2

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

[0109] Experimental Example

[0110] The light plastering gypsum in the examples and comparative examples is subjected to performance detection. The standard diffusion water consumption of each is measured according to the test method in “Plastering Gypsum” GB / T28627-2012, and the base plastering gypsum mortar of the corresponding standard diffusion (165±5 mm) is prepared according to the specified method, and the water retention, sag resistance and tensile adhesion strength are detected. Meanwhile, 4% more water than the standard diffusion water consumption is used, and the water retention, sag resistance and tensile adhesion strength are tested according to the same method, and the water consumption sensitivity is represented by comparison. The test results are shown in Tables 1 and 2.

[0111] Table 1 Performance test under standard diffusion water consumption

[0112]

[0113] Table 2 Performance test under 4% more standard diffusion water consumption

[0114] Group Water retention rate (%) Anti-sagging drop value (mm) Tensile adhesive 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 Table 1 and Table 2, the light plastering gypsum prepared in the embodiments of the present application can reach a water retention rate of more than 90% under the standard diffusion water amount, and can effectively resist sagging, and has a high tensile bonding strength. Even in the case of an over-standard diffusion water amount of 4%, the water retention rate can still reach more than 84%, effectively resists sagging (it is generally considered that when the sagging drop value is greater than 10 mm, it is difficult to meet the use requirements of the surface plastering gypsum), and the tensile bonding strength does not decrease obviously, meeting the requirements of the surface plastering gypsum. It is indicated that the water range of the light plastering gypsum of the present application is wider. In the comparative example 1, the cellulose ether and starch ether are directly used as the water-retaining and thickening components. Since the dissolution process of the cellulose ether and starch ether is easily affected by the stirring time and feeding time, the water retention performance of the light plastering gypsum prepared finally is decreased. In the comparative example 2, the conventional sodium silicate is selected as the water-resistant component. Although the sodium silicate can combine with the dihydrate gypsum crystal to form a calcium silicate layer, the 3,4-dihydroxyphenylalanine of the present application can form a bidentate metal coordination bond with the calcium ion, has a higher combination ability and stability, and thus forms a more compact hydrate structure layer, further improving the water resistance of the light plastering gypsum.

[0116] The above-mentioned only optional embodiments of the present application, and do not limit the patent scope of the present application, any equivalent structural transformation made under the inventive concept of the present application, using the content of the present application specification and drawings, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A process for the preparation of a lightweight plastering gypsum, characterized in that, The method comprises the following steps: The mirabilite gypsum is pretreated, and then graded with desulfurization gypsum and phosphor gypsum to obtain a gypsum base; The cellulose ether and starch ether are swelled together to form a cross-linked network gelatin, and then polyether monomer, acryl monomer and initiator are added to perform graft copolymerization to obtain a water-retaining thickening component; The wall material is prepared from chitosan and sodium carboxymethyl cellulose, and 3,4-dihydroxyphenylalanine is coated to obtain a water-resistant slow-release component; The gypsum base, lightweight aggregate and sepiolite fiber are stirred and mixed to obtain a primary mixture; The primary mixture, the water-retaining thickening component, the water-resistant slow-release component and water reducing agent are stirred and mixed to obtain a lightweight plastering gypsum. The step of swelling the cellulose ether and starch ether together to form a cross-linked network gelatin comprises: The water is heated to 50-60℃, and then the cellulose ether and starch ether are added and stirred for 1-1.5 hours until completely dissolved to form a cross-linked network gelatin. The mass ratio of the cellulose ether to the starch ether is (6-7):(2-3). The lightweight aggregate is a mixture of expanded vitrified microbeads and nano zirconium diboride aerogel in a mass ratio of 3-4:

2.

2. Process for the production of a lightweight plaster according to claim 1, characterized in that The step of pretreating the mirabilite gypsum comprises: After the mirabilite gypsum is crushed, it is dried at 40-60°C for 6-10 hours, then ground and controlled to have a specific surface area of 200-250 m 2 / kg, then calcined at 130-180°C for 2-3 hours, cooled to 50-60°C, aged for not less than 2 days, and controlled to have an adsorbed water content of less than 1.5%. 2 ​ 3. The method of preparing a lightweight plaster according to claim 1, characterized in that, In the step of grading the pretreated mirabilite gypsum with desulfurization gypsum and phosphor gypsum, the particle size of the pretreated mirabilite gypsum is controlled in the range of 100-200 μm, the particle size of the desulfurization gypsum is controlled in the range of 50-100 μm, and the particle size of the phosphor gypsum is controlled in the range of 150-300 μm. The mass ratio of the pretreated mirabilite gypsum, desulfurization gypsum and phosphor gypsum is (1-2):(5-7):(1-2).

4. The process for the preparation of a lightweight plaster according to claim 1, characterized in that, The step of adding polyether monomer, acryl monomer and initiator to the cross-linked network gelatin to perform graft copolymerization to obtain a water-retaining thickening component comprises: The polyether monomer, acryl monomer and initiator are added to the cross-linked network gelatin, stirred for 5-10 minutes, and then left for 1.5-2.5 hours. Then, water at 50-60℃ is added, stirred for 10-14 minutes, and then swelled for 1.5-2.5 hours while keeping the temperature at 50-60℃. After swelling, the mixture is stirred at 45-50℃ for 8-12 hours, and then sodium lignosulfonate is added, stirred for 15-20 minutes to obtain the water-retaining thickening component. The addition amount of the polyether monomer in the cross-linked network gelatin is 2.5wt%-3.5wt%. The addition amount of the acryl monomer in the cross-linked network gelatin is 4.5wt%-6wt%.

5. The method of preparing a lightweight plaster according to claim 1, characterized in that, The polyether monomer comprises at least one of 2-methylprop-2-enyl polyethylene glycol ether, 3-methylbut-3-enyl polyethylene glycol ether, 4-hydroxybutyl vinyl polyoxyethylene ether and isopentenyl alcohol polyoxyethylene ether. The acryl monomer comprises at least one of acrylamide, acrylic acid, methacrylic acid, hydroxypropyl methacrylate and N,N-dimethyl acrylamide. The initiator comprises one of ammonium persulfate, sodium persulfate and potassium persulfate.

6. The process for the preparation of a lightweight plaster according to claim 1, characterized in that, The step of preparing the wall material from chitosan and sodium carboxymethyl cellulose and coating 3,4-dihydroxyphenylalanine to obtain the water-resistant slow-release component comprises: After mixing chitosan, sodium carboxymethyl cellulose and anhydrous ethanol, a wall material solution is obtained; After mixing 3,4-dihydroxyphenylalanine and microcrystalline cellulose, the mixture is added to a balling machine for rolling treatment to form a spherical particle core material; The wall material solution is added to 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, the mixture is dried at 80℃-100℃ for 5h-7h to obtain the water-resistant slow-release component.

7. The method of preparing a lightweight plaster according to claim 1, characterized in that, The step of mixing the gypsum base material with lightweight aggregate and sepiolite fiber to obtain a preliminary mixture comprises: The gypsum base material, lightweight aggregate and sepiolite fiber are mixed at 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 to obtain the preliminary mixture.

8. The method of preparing a lightweight plaster according to claim 1, characterized in that, The step of mixing the preliminary mixture with the water-retention thickening component, the water-resistant slow-release component and the water-reducing agent to obtain the lightweight plastering gypsum comprises: The preliminary mixture, the water-retention thickening component, the water-resistant slow-release component and the water-reducing agent are mixed at 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 the lightweight plastering gypsum.

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