Plastering gypsum and preparation method thereof

Abstract

The invention relates to plastering gypsum and a preparation method thereof, and relates to the technical field of building materials, the plastering gypsum comprises building gypsum powder, heavy calcium carbonate aggregate, a functional auxiliary agent, and a multi-component synergistic enhancement system; the functional auxiliary agent comprises hydroxypropyl methyl cellulose ether, starch ether, a protein retarder and an air entraining agent, and the multi-component synergistic enhancement system comprises silane modified nano, attapulgite, EVA latex powder and a polycarboxylic acid water reducing agent. The preparation method comprises the steps of screening, surface pre-wrapping, plastering gypsum preparation, primary mixing and final mixing. The plastering gypsum disclosed by the invention is excellent in flowability and easy to spray under high shear of stirring and pumping, once the plastering gypsum is sprayed out, the shear force disappears, a three-dimensional network is quickly recovered, water and particles are locked, vertical flow is prevented, and high strength and high mechanical spraying coexist.

Description

TECHNICAL FIELD

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

[0002] With the development of the building industry and the continuous rise in labor costs, the mechanized spraying method has become the mainstream method for plastering gypsum construction. The machine-sprayed plastering gypsum, which is excellent and highly practical, has become the mainstream material and process for plastering new wall materials due to its high construction efficiency and low labor intensity.

[0003] A kind of quick-setting jet modified gypsum mortar is disclosed in Chinese patent application with publication number CN111848076A and publication date October 30, 2020, wherein the raw materials include: gypsum retarder 4-7 parts, quartz sand 320-350 parts, latex powder 8-10 parts, hydroxypropyl methyl cellulose ether 2-4 parts, water reducing agent 1-2 parts, and defoaming agent 1-2 parts.

[0004] By adding various admixtures such as hydroxypropyl methyl cellulose ether, latex powder, and water reducing agent, each plays its role to achieve high strength and wear resistance of machine-sprayed gypsum. The addition of hydroxypropyl methyl cellulose ether provides high viscosity for thickening to play a water retention role. The latex powder enhances the cohesive strength and toughness.

[0005] For the above technical solution, the inventors found that the high viscosity brought by hydroxypropyl methyl cellulose ether appears stable when at rest, but under the continuous vibration and pressure of pumping, the particles will gradually separate, there is a risk of sediment accumulation, and the rheological properties and stability are defective, which can easily cause frequent blockage of the delivery pipeline and spray gun.

[0006] An ideal pumped slurry should have good fluidity and uniformity to facilitate pumping, while also having good plastic setting properties to avoid the problem of sagging when the slurry is sprayed onto the wall. Although reducing the amount of hydroxypropyl methyl cellulose ether can weaken the retarding effect and shorten the setting time, reducing the amount of hydroxypropyl methyl cellulose ether will cause the mortar to become loose, bleed water, and be prone to sedimentation. Therefore, there is an urgent need for a machine-sprayed gypsum that does not affect the plastic setting properties while meeting the rheological properties. SUMMARY

[0007] In order to meet the rheological properties without affecting the strength of machine-sprayed gypsum, the present application provides a plastering gypsum and a preparation method thereof.

[0008] In a first aspect, the present application provides a plastering gypsum, which adopts the following technical solution: The plastering gypsum is composed of 70-80 parts by mass of building gypsum powder, 15-25 parts by mass of heavy calcium carbonate aggregate, 0.2-0.43 parts by mass of functional additives, and 2.4-5.6 parts by mass of a multi-component synergistic reinforcing system; the functional additives include 0.15-0.25 parts by mass of hydroxypropyl methyl cellulose ether, 0.01-0.05 parts by mass of starch ether, 0.03-0.10 parts by mass of protein retarder, and 0.01-0.03 parts by mass of air entraining agent; and the multi-component synergistic reinforcing system includes 0.3-0.8 parts by mass of silane-modified nano , 0.5-1.5 parts by mass of attapulgite, 1.5-3 parts by mass of EVA latex powder, and 0.1-0.3 parts by mass of polycarboxylic acid water reducer.

[0009] By using the above technical solution, the silane-modified nano attapulgite + EVA latex powder + polycarboxylic acid water reducer synergistic reinforcing system is used to construct a three-dimensional network structure; under high shear of stirring and pumping, the attapulgite network is disintegrated, the system viscosity is reduced to the minimum, the fluidity is excellent, and the spraying is easy; once sprayed, the shear force disappears, the three-dimensional network of attapulgite is quickly restored, the water and particles are locked, and the vertical flow is prevented; at the same time, the silane-modified nano hydrophobicity is enhanced, and the agglomeration is reduced, thereby reducing the flow resistance caused by particle agglomeration; the polycarboxylic acid water reducer mainly serves the silane-modified nano and attapulgite, and ensures that they exist in the form of primary particles or small agglomerates; the EVA latex powder is emulsified after water, gradually forms a film in the gypsum hydration process, forms a continuous and flexible polymer network to wrap the gypsum crystals, and enhances the cohesion of the overall matrix; and the attapulgite precisely regulates the rheology and modified nano technology to obtain high strength and high spraying coexisting; The functional additives mainly have a trace amount of high-efficiency complex effect; the hydroxypropyl methyl cellulose ether focuses on the most core water retention and thickening effect; the starch ether mainly enhances the anti-vertical hanging property during spraying, has strong synergism with the hydroxypropyl methyl cellulose ether, and further enhances the cohesion and thixotropic structure of the mortar; the protein retarder mainly has a retarding effect, and prevents premature condensation and pipe blockage; and the air entraining agent can introduce a large number of uniform, stable and small bubbles in the mortar, reduces the surface tension of water, makes the mortar more smooth, reduces the pumping resistance, and reduces the labor intensity of the spraying gun operation.

[0010] Optionally, the attapulgite is modified attapulgite by ion exchange method using a cationic surfactant.

[0011] By using the above technical solution, the cationic surfactant is modified attapulgite by ion exchange method using a cationic surfactant. ​, equal charge exchange occurs, and the surface charge characteristics are accurately changed; in addition, the long-chain hydrophobic tail of the cationic surfactant extends vertically outward, forming a "three-dimensional hydrophobic barrier" on the surface of the attapulgite particles; when adjacent particles approach, the steric repulsion of the hydrophobic chains prevents the particles from agglomerating; the natural attapulgite modified by the cationic surfactant achieves the dual anti-agglomeration effect of "charge neutralization + steric hindrance", thereby allowing the formulation to still achieve excellent pumping stability even when a very low amount of hydroxypropyl methyl cellulose ether is used.

[0012] Optionally, the hydroxypropyl methyl cellulose ether is a low-viscosity hydroxypropyl methyl cellulose ether, wherein the viscosity of a 2% aqueous solution of the low-viscosity hydroxypropyl methyl cellulose ether is less than 100 mPa·s. .

[0013] By adopting the above technical solution, on the one hand, the consistency can be reduced, and the probability of false adhesion occurring at rest can be reduced, because under the continuous vibration and pressure of pumping, the particles will gradually separate, and there is a risk of sediment accumulation; on the other hand, the molecular chain of the low-viscosity hydroxypropyl methyl cellulose ether is relatively short, and can form a "short-long chain entanglement structure" with the long molecular chain of the starch ether; at rest, the short-chain hydroxypropyl methyl cellulose ether and the long-chain starch ether form a weak gel through hydrogen bonds, providing sufficient viscosity; when shearing, the weak hydrogen bonds are broken, and the viscosity of the slurry decreases, ensuring easy extensibility; after shearing stops, the hydrogen bonds quickly recombine, and the viscosity returns to the resting state, avoiding sagging.

[0014] Optionally, the low-viscosity hydroxypropyl methyl cellulose ether is a modified low-viscosity hydroxypropyl methyl cellulose ether, wherein the content of hydroxypropoxy groups on the molecular chain of the modified low-viscosity hydroxypropyl methyl cellulose ether accounts for 23-32.0 wt% of the low-viscosity hydroxypropyl methyl cellulose ether.

[0015] By adopting the above technical solution, the low-viscosity modified hydroxypropyl methyl cellulose ether does not need to introduce complex functional groups, but only needs to optimize the content of hydroxypropoxy groups on the molecular chain; on the one hand, the higher content of hydroxypropoxy groups in the hydroxypropyl methyl cellulose ether makes the molecular chain polarity more uniform, and the adsorption force with the EVA latex powder is weakened, without hindering the fusion of EVA particles; on the other hand, hydroxypropylation modification only increases the content of hydroxypropoxy groups, without introducing cationic, hydrophobic, and other complex modified groups; the molecular chain is still neutral due to the electrostatic or steric antagonism with the polycarboxylic acid sodium salt, and can be adsorbed on the surface of the nano particles together with the branched chains of the polycarboxylic acid sodium salt through "hydrogen bonding + steric hindrance" dual action, avoiding the agglomeration of the nano particles; in addition, the three-dimensional network structure of the multi-component synergistic enhancement system is more compact, meeting the mechanical performance requirements of the plastering gypsum.

[0016] Optionally, the protein-based retarder is a protein-based retarder grafted with carboxyl groups.

[0017] By adopting the above technical solution, on the one hand, the introduction of carboxyl groups can adjust the rigidity of the protein molecular chain, inhibiting only the excessively rapid growth of gypsum crystals without hindering the hydration process; on the other hand, the grafted carboxyl groups can interact with attapulgite. It forms strong coordination bonds and forms dual-site adsorption with the original amino and hydroxyl groups of the protein, improving adsorption capacity; third, the carboxyl groups can interact with nanoparticles. The formation of "hydrogen bond bridging," rather than direct adsorption, neither hinders the dispersion of nanoparticles nor hinders their formation. When combined with a gypsum matrix, the density of the three-dimensional network nodes is increased, enhancing crack resistance; optimized retardation avoids "excessive retardation" that leads to a decrease in strength in the later stages.

[0018] Secondly, the present invention provides a method for preparing plaster, which adopts the following technical solution: A method for preparing plaster includes the following steps: Screening: The building gypsum powder is screened to obtain building gypsum powder with a mesh size of 80-120. Surface pre-coating: Hydroxypropyl methylcellulose solution is coated onto the screened building gypsum powder by atomization, with the film thickness controlled at 2-3 μm; then dried and cured at low temperature; Preparation of plaster: a. Masterbatch premixing stage: Silane-modified nano-silica, polycarboxylate superplasticizer and 10-20 wt% heavy calcium carbonate aggregate are premixed to prepare premixed masterbatch; b. Main mixing stage: The pre-coated building gypsum powder, the remaining heavy calcium carbonate aggregate, attapulgite clay, EVA latex powder, starch ether, protein retarder, and air-entraining agent are mixed with the premixed masterbatch obtained in step a to obtain the machine-sprayed plaster dry powder product.

[0019] By adopting the above technical solutions, the fineness and uniformity of the gypsum raw materials are ensured after screening of the plastering gypsum substrate; the masterbatch premixing allows silane-modified nano-silica to fully fill the micropores of the gypsum slurry, making the structure more compact; the atomized surface pre-coating step can greatly improve the utilization efficiency of additives, prevent local unevenness of additives, and make the retarding and water retention effects more stable. Silane modified nano-silica and polycarboxylic acid type water reducing agent are both functional additives with extremely small dosage but huge effect. They have small particle size and huge specific surface area, and are extremely easy to agglomerate. If they are directly put into main mixing, these agglomerates will be "submerged" by a large amount of gypsum and aggregates, and cannot be dispersed, which finally leads to uneven product performance, local over-strength or over-weakness. In the masterbatch premixing stage, the additives are first mixed with a small amount of heavy calcium carbonate aggregate. The heavy calcium carbonate aggregate particles collide and rub with each other under the action of mechanical force, which can effectively disperse the additive agglomerates and physically adsorb them on the surface. Each aggregate particle carries a large number of functional additive molecules, solving the problem of uniform dispersion of trace high-efficiency components in a large amount of main material, and achieving uniform coating. Too high or too low will damage the coating effect.

[0020] Optionally, in the surface pre-coating step, the added hydroxypropyl methyl cellulose is a low viscosity modified hydroxypropyl methyl cellulose, and the preparation method of the low viscosity modified hydroxypropyl methyl cellulose is specifically as follows: a. Dispersing and activating hydroxyl with alkali: under a nitrogen protection environment, add a volume ratio of 1:1 isopropyl alcohol-water solvent, add dry hydroxypropyl methyl cellulose under stirring, and disperse for 30 min until no particles are left; b. Hydroxypropylation reaction: under the environment of continuous nitrogen protection, warm up to 45-55℃, and drop propylene oxide, stir and keep warm for 4-6h; c. Termination and post-treatment: cool down to 30℃, drop 10% acetic acid to adjust pH to 6.5-7.0, and terminate the reaction; collect the filter cake by suction filtration, wash it with a volume ratio of 1:1 isopropyl alcohol-water for 3 times, finally dehydrate with anhydrous ethanol, and vacuum dry at 60-70℃ until the weight is constant, and then crush it through an 80 mesh sieve.

[0021] By adopting the above technical scheme, the low viscosity hydroxypropyl methyl cellulose ether solution can improve the uniformity of the atomized particles during high-pressure atomization; the deep modification of hydroxypropylation can significantly enhance the film adsorption firmness and increase the water retention by increasing the hydroxypropoxy density and forming a "bidentate coordination bond".

[0022] Optionally, the protein type retarder in the main mixing step is a plant protein retarder grafted with carboxyl groups, and the technical steps of grafting carboxyl groups on the plant protein type retarder are as follows: a. Prepare plant protein hydrolysate: take 3500 Da pretreated plant protein powder, add water at a ratio of 8-12wt%, and heat and stir to dissolve at 40-50℃; adjust pH to 7-8, filter, and collect the clear hydrolysate; b. Grafting carboxyl: the above clarified liquid is warmed to 60-80 DEG C, stirred at 300 r / min and passed nitrogen for 30 min; 2-4wt% of ammonium persulfate is added to the hydrolyzate protein, stirred until completely dissolved, then 10-30wt% of maleic anhydride is slowly added dropwise; warmed to 70-90 DEG C and kept for 3h, during which the pH is measured every 30 min, if <6.0, then adjusted to 7.0 with 1mol / L NaOH; c. Purification and drying: after reaction, cooled to room temperature, 2 times volume of 95% ethanol is added, stirred for 10 min, and then stand for 30 min; centrifuged at 4000 r / min for 15 min, the supernatant is discarded, and the precipitate is washed with 95% ethanol for 3 times; vacuum dried at 60 DEG C and -0.08MPa until the difference of consecutive two times weighing is <0.005g, then crushed and passed through 100 mesh sieve, to obtain white powder of grafting carboxyl soybean protein retarder.

[0023] By using the above technical scheme, the grafting carboxyl modification needs to go through high-temperature processes such as protein dissolution, carboxyl grafting, purification and drying, and the high heat resistance and low denaturation of the molecular structure characteristics of plant protein can ensure the modification efficiency and product stability, while animal protein is easy to be inactivated in the modification process.

[0024] In summary, the present application includes at least one of the following beneficial technical effects: 1. By using the synergistic system of "silane modified nano attapulgite + EVA latex powder + polycarboxylate superplasticizer", a three-dimensional network structure is constructed; under high shear of stirring and pumping, the fluidity is excellent, easy to spray, once sprayed, the three-dimensional network quickly recovers, locks water and particles, prevents vertical flow; through the precise regulation of rheology and modification of attapulgite by nanotechnology, high strength and high spraying coexist.

[0025] 2. The natural attapulgite modified by cationic surfactant realizes the effect of "charge neutralization + steric hindrance" dual anti-agglomeration, and then allows the formula to still obtain excellent pumping stability in the case of using extremely low amount of hydroxypropyl methyl cellulose ether.

[0026] 3. By using low viscosity modified hydroxypropyl methyl cellulose ether, sufficient viscosity can be provided when standing, when shearing, the weak hydrogen bond chain is broken, the slurry viscosity decreases, ensuring easy extension; after shearing stops, the hydrogen bond quickly recombines, the viscosity rises to the standing state, avoiding sagging; through the dual action of "hydrogen bond + steric hindrance", the nano agglomeration is avoided, and the three-dimensional network structure of the multi-component synergistic system is more dense, meeting the mechanical property requirements of plastering gypsum.

[0027] 4. The pre-coating step of the surface before the preparation of the plastering gypsum can greatly improve the utilization efficiency of the additive, prevent local unevenness of the additive, and make the retarding and water-retaining effects more stable; the additive is first mixed with a small amount of aggregate, which solves the problem of uniform dispersion of trace high-efficiency components in a large amount of main material, and can realize uniform coating. DETAILED DESCRIPTION

[0028] The application will be further described in detail below in combination with examples.

[0029] Example 1: This example discloses a plastering gypsum and a preparation method thereof.

[0030] The plastering gypsum comprises, in mass fraction: 80 parts of building gypsum powder, 15 parts of heavy calcium carbonate aggregate, 0.2 parts of functional additive, and 4.1 parts of multi-component synergistic reinforcing system; the functional additive comprises, in mass fraction: 0.15 parts of hydroxypropyl methyl cellulose ether, 0.01 parts of starch ether, 0.03 parts of protein retarder, and 0.01 parts of air entraining agent; and the multi-component synergistic reinforcing system comprises, in mass fraction: 0.3 parts of silane-modified nano , 0.5 parts of attapulgite, 3.0 parts of EVA latex powder, and 0.3 parts of polycarboxylic acid type water reducing agent.

[0031] The building gypsum powder can be selected from one or a combination of β-hemihydrate gypsum powder and α-hemihydrate gypsum powder, and β-hemihydrate gypsum powder is selected in this example; the heavy calcium carbonate aggregate raw material can be selected from one or a combination of calcite, marble or chalk, and is prepared by crushing, grinding and grading, and is preferably 70-140 mesh, and 100 mesh calcite is selected in this example; the starch ether can be selected from one or a combination of hydroxypropyl starch ether, carboxymethyl starch ether and cationic starch ether, and hydroxypropyl starch ether is selected in this example; the protein retarder can be selected from one or a combination of bone glue protein hydrolysate, casein and soybean protein hydrolysate, and bone glue protein hydrolysate is selected in this example; the air entraining agent can be selected from one or a combination of alkyl sulfonate, alkyl benzene sulfonate, rosin hot polymer and sodium fatty alcohol sulfate, and alkyl sulfonate is selected in this example; the silane in the silane-modified nano can be selected from one or a combination of γ-aminopropyl triethoxysilane, vinyl trimethoxysilane and methyl trimethoxysilane, and γ-aminopropyl triethoxysilane is selected in this example; the polycarboxylic acid type water reducing agent can be selected from one or a combination of methoxy polyethylene glycol methacrylate copolymer, olefin and unsaturated carboxylic acid and ester copolymer, and acrylic acid-hydroxyethyl acrylate copolymer, and methoxy polyethylene glycol methacrylate copolymer is selected in this example.

[0032] The preparation method is as follows: Screening: After the building gypsum powder is crushed, it is screened with a grading screen, with 80 mesh residue ≤0.3%, 120 mesh passing rate ≥99.5%, and coarse particles removed; Surface pre-wrapping: The screened building gypsum powder is added to a double-screw atomizing mixer, and 3wt% of a hydroxypropyl methyl cellulose ether aqueous solution is uniformly sprayed onto the surface of the gypsum powder through a high-pressure atomizing nozzle, with the atomizing amount controlled at 5mL / min, ensuring that 5kg of the hydroxypropyl methyl cellulose aqueous solution is sprayed for every 100kg of gypsum powder, so that the film thickness is controlled at 2.5±0.5μm; the mixer is kept running during the wrapping process, and the wrapping time is 20min; after the wrapping is completed, the material is transferred to a hot air circulating oven for low-temperature drying and curing, and the water content of the material after drying is ≤0.8%; Plaster preparation: a. Masterbatch premixing stage: Silane-modified nano-silicon dioxide, polycarboxylate superplasticizer, and 15wt% heavy calcium carbonate aggregate are added to a high-speed mixer to make a premixed masterbatch, with a uniformity variation coefficient ≤3%; b. Main mixing stage: The surface-pre-wrapped building gypsum powder, the remaining heavy calcium carbonate aggregate, attapulgite, EVA emulsion powder, starch ether, protein retarder, and air entraining agent are added to the mixer together with the premixed masterbatch obtained in step a, and the uniformity is detected every 5min during the mixing process to ensure that the uniformity variation coefficient of the final mixture is ≤2%, obtaining a machine-sprayed plaster gypsum dry powder product.

[0033] The main tests include initial fluidity, initial setting time, final setting time, water retention rate, flexural strength, compressive strength, and tensile bonding strength, and the specific test methods are as follows: Initial fluidity: The diffusion diameter of the gypsum slurry is measured by a "flowing cone" to reflect the fluidity of the plaster gypsum after adding water.

[0034] a. The materials are weighed according to the water-cement ratio of the plaster, water: gypsum = 0.45; gypsum sample mass is (500±5)g, and water mass is calculated proportionally; pour the water into the stirring pot, slowly add the gypsum powder, and stir with an electric stirrer for 30±5s, stand for 15±5s, and then stir again for 30±5s, until a uniform and lump-free slurry is obtained; b. Pour the stirred slurry into the flowing cone at once to avoid overflow, and scrape it flat along the cone opening with a spatula to remove surface bubbles; quickly open the valve to let the slurry flow freely into the center of the glass flat, and start the stopwatch at the same time; when the slurry stops flowing completely, there is no obvious diffusion, and the timing is stopped; measure the diameters of the two perpendicular directions of the slurry diffusion circle on the flat, and take their average as the "initial fluidity"; parallel tests are not less than 2 times.

[0035] Initial setting time & final setting time: setting time reflects the time from the slurry to the hardened state of plaster, the initial setting needs to meet the workable time to avoid premature hardening, and the final setting needs to meet the strength development starting point. The detection uses the Vicat instrument method.

[0036] a. The same water-cement ratio and stirring method as the initial fluidity to prepare the slurry, pour it into the test mold at once, avoid air bubbles, and use a scraper to flatten the surface, immediately put it into a curing box at 20±2℃, relative humidity 60±5%; b. Initial setting time detection: start timing from the completion of slurry stirring, every 20 min, vertically lower the initial setting test needle of the Vicat instrument to the surface of the test mold, slowly release the test needle, and observe whether the test needle penetrates the slurry. If the penetration depth is ≥25mm, it is considered "not initial setting". When the penetration depth of the test needle is ≤2mm, record the time, and the difference between the initial time is the "initial setting time". Parallel test not less than 2 times, take the average value as the final result; c. Final setting time detection: immediately replace the final setting test needle after initial setting detection, continue to detect every 20 min; observe whether the annular attachment of the final setting test needle is completely free of slurry and the penetration depth of the test needle is ≤0.5mm; record the time, and the difference between the initial time is the "final setting time"; parallel test not less than 2 times, take the average value as the final result.

[0037] Water retention: water retention reflects the ability of plaster to retain water during construction, and measures the water loss of the slurry under pressure.

[0038] a. The same water-cement ratio and stirring method as the initial fluidity to prepare the slurry, pour it into the test mold, and flatten the surface; b. Clean the filter device of the water retention tester, and place 2 layers of dried filter paper on top of the filter screen as the initial mass m1. Turn the test mold upside down on the filter paper to ensure that the slurry is in complete contact with the filter paper; c. Cover the sealing cover, apply a pressure of 2.1kPa, and place it in a 20±2℃ environment for 20 min. After the time is up, immediately remove the test mold, place the filter paper soaked with water into a drying oven at 105℃ until it reaches a constant weight. After cooling, weigh it and record it as m2. Calculate the water retention rate according to the formula: water retention rate (%) = [1-(m2-m1) / m0]x100 (Note: m2-m1 is the water loss of the slurry, and m0 is the initial slurry mass). Parallel test not less than 3 times, take the average value as the final result.

[0039] Flexural strength & compressive strength: a. The water-cement ratio and stirring method of the initial fluidity are used to prepare the slurry, which is poured into the flexural test mold and the compressive test mold respectively, and the bubbles are removed. After the surface is scraped flat, it is placed in a curing box with a temperature of 20±2℃ and a relative humidity of ≥90%. After 24h of curing, it is demolded and placed in the curing box for curing until the 28d age. After demolding, the actual size of the sample is measured with a vernier caliper, which is used to correct the strength calculation results; b. Flexural strength detection: the 28d aged flexural sample is placed on the flexural support, ensuring that the sample axis is aligned with the center of the support span and the loading point is at the midpoint of the span. Start the pressure testing machine and load at a speed of 5mm / min until the sample breaks. Record the maximum load Fbreak at the time of fracture and calculate the flexural strength according to the formula: flexural strength (MPa) = 3xFbreakxL / (bxh2) (wherein: L is the span, b is the sample cross-sectional width, and h is the sample cross-sectional height). The parallel test is not less than 3 times, and the average value is taken as the final result. c. Compressive strength detection: the separately prepared compressive sample is placed in the center of the pressure plate of the pressure testing machine, ensuring that the upper and lower surfaces of the sample are in full contact with the pressure plate. If the surface is uneven, it needs to be leveled with plaster putty. Load at a speed of 2.4kN / s until the sample is crushed, and record the maximum load Fpress at the time of crushing. Calculate the compressive strength according to the formula: compressive strength (MPa) = Fpress / A (wherein: A is the sample pressure area, i.e. the square of the cross-sectional length); the parallel test is not less than 3 times, and the average value is taken as the final result.

[0040] Tensile bond strength: reflects the bonding ability of the plastering gypsum to the base layer, avoiding later hollowing and falling off, and simulates the vertical tensile force detection in actual use.

[0041] a. Base layer specimen treatment: the water-cement ratio and stirring method of the initial fluidity are used to prepare the slurry, and the base layer surface is cleaned and dried before being coated with a 1.5mm thick plastering gypsum slurry. The surface is scraped flat. The prepared "base layer-gypsum" specimen is placed in a curing box with a temperature of 20±2℃ and a relative humidity of 60±5% for curing until the 28d age. After the curing is completed, the epoxy resin adhesive is used to bond the pull head to the surface of the gypsum layer, and it is left to stand for 24h to allow the adhesive to fully cure. b. The specimen with the bonded pull head is installed on the pull testing machine, ensuring that the pull direction is perpendicular to the surface of the base layer. Load at a speed of 5±1mm / min until the gypsum layer separates from the base layer, and record the maximum tensile force Fstick. Measure the actual diameter of the pull head with a vernier caliper, calculate the pull area Astick (πx(diameter / 2)2), and calculate the tensile bond strength according to the formula: tensile bond strength fstick (MPa) = Fstick / Astick. Each group of tests is not less than 3 times, and the average value is taken as the final result.

[0042] Example 2: This example discloses a plastering gypsum and a preparation method thereof.

[0043] A plastering gypsum, which comprises by mass fraction: 70 parts of building gypsum powder, 25 parts of heavy calcium carbonate aggregate, 0.43 parts of functional additives, and 3.9 parts of a multi-component synergistic reinforcing system; the functional additives comprise by mass fraction: 0.25 parts of hydroxypropyl methyl cellulose ether, 0.05 parts of starch ether, 0.1 parts of a protein retarder, and 0.03 parts of an air entraining agent; and the multi-component synergistic reinforcing system comprises by mass fraction: 0.8 parts of silane-modified nano-silica, 1.5 parts of attapulgite, 1.5 parts of EVA latex powder, and 0.1 parts of a polycarboxylic acid type water reducing agent.

[0044] The other aspects are completely identical to those of Embodiment 1.

[0045] Embodiment 3 discloses a plastering gypsum and a preparation method thereof.

[0046] A plastering gypsum, which comprises by mass fraction: 75 parts of building gypsum powder, 20 parts of heavy calcium carbonate aggregate, 0.32 parts of functional additives, and 4.1 parts of a multi-component synergistic reinforcing system; the functional additives comprise by mass fraction: 0.2 parts of hydroxypropyl methyl cellulose ether, 0.03 parts of starch ether, 0.07 parts of a protein retarder, and 0.02 parts of an air entraining agent; and the multi-component synergistic reinforcing system comprises by mass fraction: 0.6 parts of silane-modified nano-silica, 1 parts of attapulgite, 2.3 parts of EVA latex powder, and 0.2 parts of a polycarboxylic acid type water reducing agent.

[0047] The other aspects are completely identical to those of Embodiment 1.

[0048] The plastering gypsums prepared in Embodiments 1, 2 and 3 are detected, and the detection results are shown in Table 1. Table 1

[0049] The initial fluidity reflects the fluidity and construction performance of the gypsum in the initial state, and the stronger the fluidity, the easier the construction, and the poorer the fluidity, the greater the risk of plugging the machine spray pipeline.

[0050] The setting time reflects the time from the slurry to the hardening of the plastering gypsum, the initial setting needs to meet the construction time, and if the initial setting time is too short, the gypsum will harden too early and cannot be operated subsequently, and if the initial setting time is too long, the gypsum will have the risk of sagging, and generally, the time from the slurry to the completion of the construction is 30-40 min, and 45 min is a preferable initial setting time; the final setting needs to meet the strength development starting point, and if the final setting is too fast, the hydration reaction is intense and concentrated, a large amount of heat is released in a short time, the temperature difference between the inside and outside of the concrete is too large, temperature cracks are caused, the durability is affected, and if the final setting time is too long, the subsequent working hours are delayed.

[0051] ​​Water retention rate is an index of keeping water from being absorbed too fast by the base or evaporated too fast due to environmental factors. A too low water retention rate will cause a series of problems. The higher the water retention rate is under the condition of <98% during construction, the better.

[0052] The bending strength, compressive strength and tensile bonding strength reflect the strength of the gypsum, which is higher the better to a certain extent. Of course, other indicators also need to be considered comprehensively.

[0053] Therefore, it is required to have both high strength and rheological property, and it is necessary to find a balance between initial fluidity, setting time and strength. It is necessary to maintain high fluidity to meet the requirements of machine spraying, and it is also necessary to have a not too long final setting time, and to maintain a high strength after setting.

[0054] As can be seen from the data of Example 1, Example 2 and Example 3, the three examples can meet the construction window requirements of mechanical spraying. Specifically, the fluidity of Example 1 is the lowest, which is the worst among the three groups. The fluidity of Example 2 is the best, which is stronger than Example 1 and Example 3. Overall, Example 3 performs the most balanced and has the best construction performance.

[0055] Example 4 discloses a plastering gypsum and a preparation method thereof.

[0056] A plastering gypsum, which comprises, by mass fraction: 75 parts of building gypsum powder, 20 parts of heavy calcium carbonate aggregate, 0.32 parts of functional additive, and 4.1 parts of multi-component synergistic reinforcing system. The functional additive comprises, by mass fraction: 0.2 parts of hydroxypropyl methyl cellulose ether, 0.03 parts of starch ether, 0.07 parts of protein retarder, and 0.02 parts of air entraining agent. The multi-component synergistic reinforcing system comprises, by mass fraction: 0.6 parts of silane modified nano , 1 part of attapulgite, 2.3 parts of EVA latex powder, and 0.2 parts of polycarboxylic acid type water reducing agent.

[0057] The preparation method of the attapulgite modified by the cationic surfactant is as follows: a. crushing and acidification: crush the attapulgite, grind the particle size to be not more than 80 microns, add deionized water, ultrasonic treatment for 40 minutes, dropwise add hydrochloric acid, heat to 70 DEG C, and perform acidification reaction for 2 hours. After the reaction is completed, filter the product, dry the filtered product at 70 DEG C, and weigh until the mass difference of two consecutive weighings is less than the set error of 0.005 g, to obtain the acidified attapulgite powder; b. sodium treatment: add the acidified attapulgite powder into deionized water, add sodium carbonate, heat to 55 DEG C, and ultrasonic treatment for 0.8 hours. Collect the filtered product; heat the product to 280 DEG C under the protection of nitrogen atmosphere, and dry for 1.5 hours to obtain the sodium attapulgite; c. Modification reaction: disperse the sodiumized attapulgite in ultrapure water, ultrasonic dispersion for 20 minutes, add cationic surfactant, the mass ratio of sodiumized attapulgite to cetyltrimethylammonium bromide is 1:0.065, heat to 70℃, react for 7 hours, collect and filter the product; d. Dry the finished product: heat the filtered product to 180℃ under the protection of nitrogen atmosphere, dry for 0.8 hours, and obtain the modified attapulgite.

[0058] The cationic surfactant is mainly a quaternary ammonium salt, which can be selected from one or a combination of cetyltrimethylammonium bromide, bromohexadecylpyridine, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, dodecyl dimethyl benzyl bromide, and dodecyl dimethyl benzyl ammonium chloride. In this embodiment, cetyltrimethylammonium bromide is used.

[0059] The other steps are the same as those in Example 3.

[0060] Example 5: This embodiment discloses a plastering gypsum and a preparation method thereof.

[0061] The plastering gypsum comprises, by mass fraction: 75 parts of building gypsum powder, 20 parts of heavy calcium carbonate aggregate, 0.32 parts of functional additive, and 4.1 parts of multi-component synergistic reinforcing system. The functional additive comprises, by mass fraction: 0.2 parts of low-viscosity hydroxypropyl methyl cellulose ether, 0.03 parts of starch ether, 0.07 parts of protein retarder, and 0.02 parts of air entraining agent. The multi-component synergistic reinforcing system comprises, by mass fraction: 0.6 parts of silane-modified nano-silica, 1 part of attapulgite, 2.3 parts of EVA latex powder, and 0.2 parts of polycarboxylic acid water reducer.

[0062] The low-viscosity hydroxypropyl methyl cellulose ether has a viscosity of 2% hydroxypropyl methyl cellulose ether aqueous solution of less than 20 mPa·s. The low-viscosity hydroxypropyl methyl cellulose ether has a viscosity of 2% hydroxypropyl methyl cellulose ether aqueous solution of less than 20 mPa·s.

[0063] The surface pre-coating step of the preparation method is different from that of Example 4, and the surface pre-coating step of this embodiment is as follows: Surface pre-coating: add the screened building gypsum powder into a double-screw atomizing mixer, uniformly spray 2wt% hydroxypropyl methyl cellulose ether aqueous solution to the surface of the gypsum powder through a high-pressure atomizing nozzle, control the atomizing amount to be 5 mL / min, ensure that 5 kg of hydroxypropyl methyl cellulose aqueous solution is sprayed for every 100 kg of gypsum powder, and control the film thickness to be 2.5±0.5 μm; keep the mixer running during the coating process, and the coating time is 20 min; after the coating is completed, transfer the material to a hot air circulating oven for low-temperature drying and curing, and the water content of the material after drying is ≤0.8%; The other steps are the same as those in Example 4.​

[0064] Embodiment 6: The embodiment discloses a plastering gypsum and a preparation method thereof.

[0065] The plastering gypsum is prepared from the following components in parts by mass: 75 parts of building gypsum powder, 20 parts of heavy calcium carbonate aggregate, 0.32 parts of functional additives, and 4.1 parts of a multi-component synergistic reinforcing system; the functional additives include 0.2 parts of modified low-viscosity hydroxypropyl methyl cellulose ether, 0.03 parts of starch ether, 0.07 parts of protein retarder, and 0.02 parts of air entraining agent; and the multi-component synergistic reinforcing system includes 0.6 parts of silane-modified nano-silica, 1 part of attapulgite, 2.3 parts of EVA latex powder, and 0.2 parts of polycarboxylic acid water reducing agent.

[0066] The hydroxypropoxy content in the molecular chain of the modified low-viscosity hydroxypropyl methyl cellulose ether is 23-32.0 wt% of the low-viscosity hydroxypropyl methyl cellulose ether, and the preparation method is as follows: a. dispersion and alkali activation of hydroxyl group: under the protection of nitrogen, 1:1 isopropyl alcohol-water solvent is added, and dry hydroxypropyl methyl cellulose is added under stirring, and is dispersed for 30 min until no particles are present; b. hydroxypropylation reaction: under the protection of nitrogen, the temperature is raised to 50 DEG C, and propylene oxide is added dropwise, and stirring and heat preservation reaction are performed for 5 h; c. termination and post-treatment: the temperature is lowered to 30 DEG C, 10% acetic acid is added dropwise to adjust the pH to 6.8, and the reaction is terminated; the filter cake is collected by suction filtration, washed with 1:1 isopropyl alcohol-water three times, finally dehydrated with anhydrous ethanol, and dried at 65 DEG C under vacuum until the mass difference of two consecutive weighings is less than the set error of 0.005 g, and then crushed to pass through an 80-mesh sieve.

[0067] In the surface pre-wrapping step of the preparation method of the embodiment, 2 wt% of modified hydroxypropyl methyl cellulose ether is used, and the other steps are the same as those of embodiment 5.

[0068] Embodiment 7: The embodiment discloses a plastering gypsum and a preparation method thereof.

[0069] The plastering gypsum is prepared from the following components in parts by mass: 75 parts of building gypsum powder, 20 parts of heavy calcium carbonate aggregate, 0.32 parts of functional additives, and 4.1 parts of a multi-component synergistic reinforcing system; the functional additives include 0.2 parts of modified low-viscosity hydroxypropyl methyl cellulose ether, 0.03 parts of starch ether, 0.07 parts of protein retarder, and 0.02 parts of air entraining agent; and the multi-component synergistic reinforcing system includes 0.6 parts of silane-modified nano-silica, 1 part of attapulgite, 2.3 parts of EVA latex powder, and 0.2 parts of polycarboxylic acid water reducing agent. , 1 part of attapulgite, 2.3 parts of EVA latex powder, and 0.2 parts of polycarboxylic acid water reducing agent.​

[0070] The preparation method of the grafting carboxyl protein retarder is as follows: a. Bone glue protein hydrolysis: add deionized water to dissolve bone glue to 25wt%, form a uniform bone glue solution; adjust the pH of the bone glue solution to 7.5 with NaOH, add 1.5wt% of alkaline protease based on the bone glue protein, hydrolyze at 50℃ for 3 hours, and inactivate at 80℃ for 15 minutes; adjust the pH of the system to 6.5 with NaOH, collect the filtrate, and obtain a bone glue protein hydrolysate; b. Grafting carboxyl: dilute the bone glue protein hydrolysate to 20wt% with deionized water, heat to 65℃, and slowly drop the initiator solution into the reaction bottle through a constant pressure dropping funnel, drop for 30 minutes, and stir for 10 minutes; then slowly drop the maleic anhydride monomer solution, drop for 1 hour, maintain the temperature at 65℃, and rotate at 400r / min during the dropping process; after the dropping is completed, heat to 80℃, continue to react for 3 hours, and generate a grafting product containing carboxyl groups; The carboxyl group source can be one or both of acrylic acid and maleic anhydride, and maleic anhydride is selected in this embodiment.

[0071] The preparation method in this embodiment uses a grafting carboxyl protein retarder, and the rest is completely the same as in embodiment 6.

[0072] Embodiment 8: This embodiment discloses a plastering gypsum and a preparation method thereof.

[0073] A plastering gypsum, which comprises, in mass fraction: 75 parts of building gypsum powder, 20 parts of heavy calcium carbonate aggregate, 0.32 parts of functional additive, and 4.1 parts of multi-component synergistic reinforcing system; the functional additive comprises, in mass fraction: 0.2 parts of modified low-viscosity hydroxypropyl methyl cellulose ether, 0.03 parts of starch ether, 0.07 parts of grafting carboxyl protein retarder, and 0.02 parts of air entraining agent; and the multi-component synergistic reinforcing system comprises, in mass fraction: 0.6 parts of silane modified nano-silica, 1 part of attapulgite, 2.3 parts of EVA latex powder, and 0.2 parts of polycarboxylic acid type water reducing agent.

[0074] The grafting carboxyl protein retarder is a grafting carboxyl soybean protein retarder, and the preparation method of the grafting carboxyl group is as follows: a. Preparation of soybean protein hydrolysate: add pretreated soybean protein powder with a molecular weight of 3500Da into water, so that the protein powder accounts for 10wt% of the water solution, heat and stir at 45℃ until dissolved; add sodium hydroxide to adjust the pH to 7.5, filter through a 0.45μm filter membrane, and collect the clear hydrolysate; ​b. Grafting carboxyl: The above clear soybean protein hydrolysate was heated to 70℃, the stirring rate was adjusted to 300 r / min, and nitrogen was passed for 30 min; ammonium persulfate was first added at 3 wt% of the protein in the hydrolysate, and stirring was performed until complete dissolution; maleic anhydride was slowly added dropwise, and the carboxyl monomer accounted for 20 wt% of the protein in the hydrolysate, and the dropwise addition time was controlled within 30 min; after the dropwise addition was completed, the temperature was raised to 80℃, and the reaction was maintained for 3 h; during the reaction, the pH was measured every 30 min, and if the pH dropped to below 6.0, a small amount of 1 mol / L NaOH was added to adjust the pH to 7.0; c. Purification and drying: After the reaction was completed, the system was cooled to room temperature, 2 volumes of 95% ethanol were slowly added, stirred for 10 min, and allowed to stand for 30 min to precipitate the grafting product; the mixture was placed in a high-speed centrifuge, centrifuged at 4000 r / min for 15 min, the supernatant was discarded, and the lower layer of the precipitate was collected and washed with 95% ethanol for 3 times to completely remove the residual maleic anhydride; the washed precipitate was placed in a vacuum drying oven, dried at 60℃ and -0.08 MPa, and the mass difference of two consecutive weighings was less than the set error of 0.005 g to end the drying; the dried product was crushed and sieved through a 100-mesh sieve to obtain a white powder of the grafting carboxyl soybean protein retarder.

[0075] In the preparation method of this example, the protein-based retarder used is a grafting carboxyl soybean protein retarder, and the other steps are the same as in Example 7.

[0076] The plastering gypsum prepared in Examples 4-8 was detected, and the detection results are shown in Table 2: Table 2: Index name Example 4 Example 5 Example 6 Example 7 Example 8 Initial fluidity (mm) 185 194 194 193 198 Initial setting time (min) 45 46 48 47 45 Final setting time (h) 1.79 2.08 2.01 2.05 2.02 Water retention rate (%) 90.5 93.8 96.5 95.8 96.6 Flexural strength (MPa) 3.6 3.9 4.3 4.6 4.7 Compressive strength (MPa) 7.8 8.3 9.3 9.6 9.8 Tensile bond strength (MPa) 0.41 0.48 0.52 0.57 0.59 By comparing Example 4 with Example 3, it can be seen that the initial fluidity, initial setting time, and final setting time are significantly improved, and the other indicators have little difference. The analysis shows that the cationic surfactant modified natural attapulgite achieves "charge neutralization + steric hindrance" dual anti-agglomeration, and obtains better pumping stability.

[0077] By comparing Example 5 with Example 4, the initial fluidity and water retention rate are slightly improved, the initial setting time has no obvious difference, but the final setting time is prolonged; at the same time, low-viscosity hydroxypropyl methyl cellulose ether is used, and the short molecular chain of the hydroxypropyl methyl cellulose ether is used to form a weak gel with long-chain starch ether through hydrogen bonding to provide sufficient viscosity when standing; when shearing, the weak hydrogen bonds are broken, the slurry viscosity decreases, and the extension is ensured; after the shearing stops, the hydrogen bonds quickly recombine, the viscosity rises to the standing state, and the sagging is avoided, so the strength is improved to a certain extent.

[0078] By comparing Example 6 with Example 5, it can be seen that there is no obvious difference in initial fluidity and setting time, but the bending strength, compressive strength and tensile bonding strength are all obviously improved. The hydroxypropylated modified hydroxypropyl methyl cellulose ether can be adsorbed on the surface of the branched polycarboxylic acid sodium salt through "hydrogen bond + steric hindrance" dual action, avoiding the agglomeration of the nano particles; it can make the three-dimensional network structure more compact to meet the mechanical performance requirements of the plastering gypsum.

[0079] By comparing Example 7 with Example 6, it can be seen that there is no obvious change in initial fluidity, setting time and water retention, but the bending strength, compressive strength and tensile bonding strength are all obviously improved; the introduction of carboxyl groups adjusts the rigidity of the protein molecular chain, only inhibits the too fast growth of the gypsum crystal, and does not hinder the hydration process; at the same time, it can form a "strong coordination bond" with the attapulgite and form a "hydrogen bond bridge" with the nano particles, the density of the three-dimensional network nodes is improved, and the strength is improved.

[0080] By comparing Example 8 with Example 7, it can be seen that the initial fluidity is significantly improved, the influence on the setting time and water retention is limited, but the strength and other indicators are all slightly improved, which shows that the use of plant protein retarder can further ensure the modification efficiency and product stability, and this adjustment reflects the balance design consideration of fluidity and setting time.

[0081] Comparative Example 1: The present comparative example discloses a plastering gypsum and a preparation method thereof.

[0082] A plastering gypsum, the mass fraction of its composition includes: 75 parts of building gypsum powder, 20 parts of heavy calcium carbonate aggregate, 0.32 parts of functional additives, 3 parts of EVA latex powder, and 1 part of polycarboxylic acid water reducing agent; the functional additives include 0.2 parts of modified low-viscosity hydroxypropyl methyl cellulose ether, 0.03 parts of starch ether, 0.07 parts of protein retarding agent grafted with carboxyl groups, and 0.02 parts of air entraining agent.

[0083] The preparation method is as follows: Screening: after crushing the building gypsum powder, it is screened by a grading screen, the 80-mesh residue is ≤0.3%, the 120-mesh passing rate is ≥99.5%, and the coarse particles are removed; ​​Surface pre-wrapping: the screened building gypsum powder is added to a double-screw atomizing mixer, and 3wt% of a hydroxypropyl methyl cellulose ether aqueous solution is uniformly sprayed onto the surface of the gypsum powder through a high-pressure atomizing nozzle, the atomizing amount is controlled to be 5 mL / min, and it is ensured that 5 kg of the hydroxypropyl methyl cellulose ether aqueous solution is sprayed for every 100 kg of the gypsum powder, so that the film thickness is controlled to be 2.5 pm ± 0.5 pm; the mixer is kept running during the wrapping process, and the wrapping time is 20 min; after the wrapping is completed, the material is transferred to a hot air circulating oven for low-temperature drying and curing, and the water content of the material after drying is ≤0.8%; Plaster preparation: a. Masterbatch premixing stage: the polycarboxylic acid type water reducing agent and 15wt% heavy calcium carbonate aggregate are added to a high-speed mixer to prepare a premixed masterbatch, and the uniformity variation coefficient is ≤3%; b. Main mixing stage: the surface pre-wrapped building gypsum powder, the remaining heavy calcium carbonate aggregate, the EVA latex powder, the starch ether, the protein type retarder, and the air entraining agent are added to the mixer together with the premixed masterbatch obtained in step a, and the uniformity is detected every 5 min during the mixing process to ensure that the uniformity variation coefficient of the final mixture is ≤2%, thereby obtaining the machine-sprayed plaster gypsum dry powder product.

[0084] The detection method is the same as that in Example 1.

[0085] Comparative Example 2: The comparative example discloses a plaster and a preparation method thereof.

[0086] The preparation method is as follows: Screening: after the building gypsum powder is crushed, the powder is screened by a grading screen, the 80-mesh residue is ≤0.3%, and the 120-mesh passing rate is ≥99.5%, and the coarse particles are removed. Plaster preparation: a. Masterbatch premixing stage: the silane-modified nano-silicon dioxide, the polycarboxylic acid type water reducing agent, and 15wt% heavy calcium carbonate aggregate are added to a high-speed mixer to prepare a premixed masterbatch, and the uniformity variation coefficient is ≤3%; b. Main mixing stage: the surface pre-wrapped building gypsum powder, the remaining heavy calcium carbonate aggregate, the attapulgite, the EVA latex powder, the modified low-viscosity hydroxypropyl methyl cellulose ether, the starch ether, the protein type retarder, and the air entraining agent are added to the mixer together with the premixed masterbatch obtained in step a, and the uniformity is detected every 5 min during the mixing process to ensure that the uniformity variation coefficient of the final mixture is ≤2%, thereby obtaining the machine-sprayed plaster gypsum dry powder product.

[0087] The other aspects are completely the same as those in Example 3.

[0088] The plaster prepared in Comparative Examples 1 and 2 is detected, and the detection results are shown in Table 3: Table 3: Index name Comparative Example 1 Comparative Example 2 Initial fluidity (mm) 163 165 Initial setting time (min) 31 33 Final setting time (h) 0.89 1.13 Water retention rate (%) 82.3 85.6 Flexural strength (MPa) 2.8 3.1 Compressive strength (MPa) 6.5 6.9 Tensile bond strength (MPa) 0.31 0.34 By comparing the comparative example 1 with the example 3, it can be seen that the comparative example 1 has no nano filling voids, poor slurry fluidity; no attapulgite synergistic retarding, coagulation too fast, final setting time is short only 0.89h, subsequent polishing difficulty; no stable three-dimensional dense network, water loss easily, low water retention rate, and the strength is also low, in dry environment, easy to appear shrinkage crack due to surface water loss too fast, affect the stability of the later use; it is shown that attapulgite and nano synergistic effect on the whole system.

[0089] By comparing the comparative example 2 with the example 3, it can be seen that the water retention rate of the comparative example 2 is low, which may cause shrinkage cracks and other problems in the plaster layer, and all indicators are worse than the example 3, it is shown that the pre-wrapping step in the example 3 can greatly improve the utilization efficiency of the additive, improve the dispersibility of the additive, make the retarding and water retention effect more stable; at the same time, the pre-wrapping step can make the additive more uniform locally, and enhance the strength index of the bonding interface.

[0090] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, therefore: any equivalent changes made on the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A plastering gypsum, characterized in that, The mass parts of the components include: 70-80 parts of building gypsum powder, 15-25 parts of heavy calcium carbonate aggregate, 0.2-0.43 parts of functional additive, and 2.4-5.6 parts of multi-component synergistic reinforcing system; the functional additive includes 0.15-0.25 parts of hydroxypropyl methyl cellulose ether, 0.01-0.05 parts of starch ether, 0.03-0.10 parts of protein retarder, and 0.01-0.03 parts of air entraining agent; the multi-component synergistic reinforcing system includes 0.3-0.8 parts of silane modified nano , 0.5-1.5 parts of attapulgite, 1.5-3 parts of EVA latex powder, and 0.1-0.3 parts of polycarboxylic acid water reducer.

2. A plastering gypsum according to claim 1, characterized in that The attapulgite is attapulgite modified by ion exchange method using cationic surfactant.

3. A plastering gypsum according to claim 1 or 2, characterized in that The hydroxypropyl methylcellulose ether is a low viscosity hydroxypropyl methylcellulose ether, wherein the viscosity of a 2% aqueous solution of the low viscosity hydroxypropyl methylcellulose ether is < 100 mPa-s .

4. A plastering gypsum according to claim 3, characterized in that The low viscosity hydroxypropyl methyl cellulose ether is modified low viscosity hydroxypropyl methyl cellulose ether, wherein the content of hydroxypropoxy group in the molecular chain of the modified low viscosity hydroxypropyl methyl cellulose ether accounts for 23-32.0wt% of the low viscosity hydroxypropyl methyl cellulose ether.

5. A plastering gypsum according to claim 1 or 2, characterised in that The protein type retarder is a protein type retarder grafted with carboxyl.

6. A process for the production of the plastering gypsum according to any one of claims 1 to 5, characterized in that The method comprises the following steps: Screening: screening the building gypsum powder to obtain building gypsum powder with a mesh size of 80-120; Surface pre-wrapping: wrapping the building gypsum powder screened above with a hydroxypropyl methyl cellulose solution by atomization method, and controlling the film thickness to be 2-3μm; low-temperature drying and solidification; Plaster preparation: a. Masterbatch premixing stage: premixing silane modified nano silicon dioxide, polycarboxylic acid type water reducing agent and 10-20wt% heavy calcium carbonate aggregate to prepare a premixed masterbatch; b. Main mixing stage: mixing the building gypsum powder pre-wrapped on the surface, the remaining heavy calcium carbonate aggregate, attapulgite, EVA latex powder, starch ether, protein type retarder, air entraining agent and the premixed masterbatch obtained in step a to obtain the machine spraying plastering gypsum dry powder product.

7. A method of preparing a plaster according to claim 6, characterized in that, In the surface pre-wrapping step, the added hydroxypropyl methyl cellulose is low viscosity modified hydroxypropyl methyl cellulose, and the preparation method of the low viscosity modified hydroxypropyl methyl cellulose is as follows: a. Dispersing and activating hydroxyl with alkali: under a nitrogen protection environment, adding a volume ratio of 1:1 isopropyl alcohol-water solvent, and adding dry hydroxypropyl methyl cellulose under stirring to disperse for 30min until no particles are present; b. Hydroxypropylation reaction: under a nitrogen protection environment, increasing the temperature to 45-55℃, and adding propylene oxide dropwise, stirring and reacting for 4-6h; c. Termination and post-treatment: decreasing the temperature to 30℃, adding 10% acetic acid dropwise to adjust the pH to 6.5-7.0, terminating the reaction, collecting the filter cake by suction filtration, washing the filter cake with a volume ratio of 1:1 isopropyl alcohol-water for 3 times, finally dehydrating with anhydrous ethanol, and vacuum drying at 60-70℃ until the weight is constant, and crushing through an 80 mesh sieve.

8. A method of preparing a plaster according to claim 6 or 7, characterised in that, The protein type retarder in the main mixing step is a plant protein retarder grafted with carboxyl, and the technical steps of grafting carboxyl of the plant protein type retarder are as follows: a. Preparing a plant protein hydrolysate: taking 3500Da pretreated plant protein powder, adding water at a ratio of 8-12wt%, and heating and stirring to dissolve at 40-50℃; adjusting the pH to 7-8, filtering, and collecting the clear hydrolysate; b. Grafting carboxyl: increasing the temperature of the clear liquid to 60-80℃, stirring at 300r / min and passing nitrogen for 30min; adding 2-4wt% of ammonium persulfate based on the protein of the hydrolysate, stirring until completely dissolved, and then slowly adding 10-30wt% of maleic anhydride based on the protein of the hydrolysate; increasing the temperature to 70-90℃ for reaction for 3h, and measuring the pH every 30min during the reaction, and if the pH is <6.0, adjusting the pH to 7.0 with 1mol / L NaOH; c. Purification and drying: after reaction, cool to room temperature, add 2 times volume of 95% ethanol, stir for 10 min, stand for 30 min; centrifuge at 4000 r / min for 15 min, discard supernatant, and wash the precipitate with 95% ethanol for 3 times; dry at 60°C under -0.08 MPa vacuum until the difference of consecutive two times weighing is less than 0.005 g, crush and pass through 100 mesh sieve to obtain white powder of grafted carboxyl soybean protein retarder.

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