Environmentally friendly gypsum-based self-leveling powder and preparation method thereof

Abstract

The invention discloses an environment-friendly gypsum-based self-leveling powder and a preparation method thereof, belonging to the technical field of self-leveling powders. The invention comprises the following raw materials in parts by weight: 85-90 parts of beta-hemihydrate gypsum, 5 parts of silicate cement, 2-3 parts of fly ash, 3 parts of mineral powder, 2-3 parts of modified silica fume powder, 0.05 parts of hydroxypropyl methylcellulose, 0.01-0.02 parts of polyether defoamer, 0.3-0.4 parts of modified water reducer, 0.02 parts of retarder, 0.08-0.1 parts of sodium gluconate and 1-1.5 parts of redispersible latex powder. The raw materials of the gypsum-based self-leveling powder prepared by the invention are environment-friendly and pollution-free, the amount of each raw material is reasonably configured and the amount of admixture is reduced, so that the prepared environment-friendly gypsum-based self-leveling powder not only has low cost, but also has the excellent effects of high fluidity, high strength and smooth surface, and has broad market prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of self-leveling powders, and in particular relates to an environmentally friendly gypsum-based self-leveling powder and a preparation method thereof. Background Art

[0002] Gypsum-based self-leveling powder is a powder material specially used for floor leveling, floor heating pipeline backfilling and flooring pad leveling, which is evenly mixed with fine aggregate (fine stone powder, fine quartz sand, etc.), cementitious materials (gypsum, cement, mineral admixtures, etc.) and various building chemical admixtures in the factory. The floor constructed with self-leveling mortar can be leveled in a very short time, with small shrinkage, high levelness, smooth surface and high efficiency.

[0003] The sand-containing gypsum-based self-leveling materials currently widely used have large fluidity loss, low pumping construction efficiency, poor leveling during construction, and are prone to shrinkage and cracking, which have great limitations in actual construction engineering applications. Increasing the amount of admixtures, such as increasing the amount of water reducer and retarder to improve the fluidity of gypsum-based self-leveling slurry, will not only increase the cost of self-leveling materials and reduce product profits, but excessive and poorly applicable admixtures will also reduce the strength of gypsum-based self-leveling.

[0004] Therefore, developing an environmentally friendly gypsum-based self-leveling powder with high fluidity, high strength and smooth surface after leveling and curing is a technical problem that urgently needs to be solved. Summary of the invention

[0005] The object of the present invention is to provide an environmentally friendly gypsum-based self-leveling powder and a preparation method thereof, so as to solve the problems in the background technology.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] An environmentally friendly gypsum-based self-leveling powder comprises the following raw materials in parts by weight:

[0008] 85-90 parts of β-hemihydrate gypsum, 5 parts of silicate cement, 2-3 parts of fly ash, 3 parts of mineral powder, 2-3 parts of modified silica fume powder, 0.05 parts of hydroxypropyl methylcellulose, 0.01-0.02 parts of polyether defoamer, 0.3-0.4 parts of modified water reducer, 0.02 parts of retarder, 0.08-0.1 parts of sodium gluconate, 1-1.5 parts of redispersible latex powder; specifically, the retarder is a protein retarder. Fly ash can increase fluidity, but excessive use will affect the smoothness of the surface after hardening; the addition of mineral powder can increase fluidity and significantly improve the later strength.

[0009] Furthermore, the modified silica fume powder is prepared by the following method:

[0010] Add polyvinyl pyrrolidone into deionized water and stir magnetically for 2 hours at room temperature to fully dissolve it. Add sodium hydroxide solution dropwise to adjust the pH value of the solution to 10. Then add silica ash and heat the oil bath to 50-60°C and stir to react for 3-4 hours. After filtering, dry at 100-105°C for 2-4 hours to obtain modified silica ash powder.

[0011] Furthermore, the dosage ratio of polyvinyl pyrrolidone, deionized water and silica fume is 4-6 mg: 300 mL: 100 mg.

[0012] Furthermore, the polyvinyl pyrrolidone is PVP-K30, the molecular chain length of PVP-K30 is moderate and can be wrapped around the silica fume particles to wrap the silica fume particles into a film, and the silica fume particles are evenly dispersed to avoid agglomeration through the steric hindrance of polyvinyl pyrrolidone; at the same time, the PVP layer on the surface of the silica fume powder is easily combined with hydrogen bonds between water molecules, so that a lubricating film is formed on the surface of the silica fume particles, which is conducive to moving in the gaps of the β-gypsum hydration product.

[0013] Furthermore, the modified water reducing agent is prepared by the following steps:

[0014] Step S1, adding isopentanol polyoxyethylene ether to deionized water and stirring well, then adding 30wt% hydrogen peroxide and stirring for 5min, then dropping mixed aqueous solution A and mixed aqueous solution B respectively, the dropping time is 3h and 2.5h respectively, after the dropping is completed, keeping warm for 1h, then adding 30wt% sodium hydroxide solution to adjust the pH to neutral, to obtain a modified water reducer solution;

[0015] Step S2, adding the modified water-reducing agent solution into a centrifugal spray dryer, spraying and powdering in hot air at a temperature of 70-90° C., cooling and powdering to obtain the modified water-reducing agent.

[0016] Furthermore, the mass ratio of the isopentanol polyoxyethylene ether, deionized water, hydrogen peroxide, mixed aqueous solution A and mixed aqueous solution B is 60-70:60:0.5-0.6:20:42-43.

[0017] Furthermore, the mixed aqueous solution A is composed of mercaptopropionic acid, vitamin C and deionized water in a mass ratio of 0.22-0.25:0.15:20.

[0018] Furthermore, the mixed aqueous solution B is composed of acrylic acid, methacrylic acid monophosphate, acrylamide and deionized water in a mass ratio of 10:1-1.2:1-1.2:30.

[0019] A method for preparing an environmentally friendly gypsum-based self-leveling powder comprises the following steps:

[0020] Add β-hemihydrate gypsum, silicate cement, fly ash, mineral powder, modified silica fume powder, hydroxypropyl methylcellulose, defoamer, modified water reducing agent, retarder, sodium gluconate and redispersible latex powder into a V-type mixer, stir and mix for 5-10 minutes, and obtain an environmentally friendly gypsum-based self-leveling powder after discharging.

[0021] Beneficial effects:

[0022] The present invention physically blends polyvinyl pyrrolidone with silica fume to modify the mixture, so that the polyvinyl pyrrolidone is wrapped on the surface of silica fume particles, thereby obtaining modified silica fume powder with excellent dispersibility. Compared with unmodified silica fume, the modified silica fume powder of the present invention can not only reduce the negative impact on the fluidity of the self-leveling slurry, but also better fill the pores and micro-voids of the hardened structure, thereby improving the density of the hardened system and thus improving the hardness after hardening. The adhesiveness of polyvinyl pyrrolidone can improve the connection strength between silica fume and gypsum matrix, thereby further improving the strength of the gypsum-based self-leveling hardening system.

[0023] The invention uses hydrogen peroxide and vitamin C as initiators and mercaptopropionic acid as a chain transfer agent, and carries out free radical polymerization of reaction monomers consisting of isopentanol polyoxyethylene ether and acrylic acid, methacrylic acid monophosphate and acrylamide at room temperature, and prepares a water reducer having ether bond branches, carboxyl branches, phosphate ester branches and amide branches in a molecular structure by setting a reasonable amount of raw materials; the amino group generated by the hydrolysis of the amide group is conducive to the formation of the crystal nucleus of the hydration product, and the phosphate formed by the phosphate ester group covers the surface of the crystal nucleus, which slows down the growth of the crystal nucleus; the two act synergistically, so that the crystals in the hardening system are small and dense, which can not only reduce the amount of the retarder, but also improve the strength of the hardening system;

[0024] The raw materials of the gypsum-based self-leveling powder prepared by the present invention are environmentally friendly and pollution-free. The amount of each raw material is reasonably configured and the amount of admixture is reduced, so that the prepared environmentally friendly gypsum-based self-leveling powder is not only low in cost, but also has the excellent effects of high fluidity, high strength and smooth surface, and has broad market prospects. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1

[0027] This embodiment provides a modified silica fume powder, which is prepared by the following method:

[0028] 4 mg PVP-K30 was added into 300 mL deionized water, and magnetically stirred for 2 h at room temperature to fully dissolve, and sodium hydroxide solution was added dropwise to adjust the solution pH to 10. Then 100 mg silica ash was added, and the oil bath was heated to 50 °C and stirred for 4 h. After filtering, the mixture was dried at 100 °C for 4 h to obtain modified silica ash powder.

[0029] Example 2

[0030] This embodiment provides a modified silica fume powder, which is prepared by the following method:

[0031] 5 mg PVP-K30 was added into 300 mL deionized water, and magnetically stirred for 2 h at room temperature to fully dissolve, and sodium hydroxide solution was added dropwise to adjust the solution pH to 10. Then 100 mg silica ash was added, and the oil bath was heated to 55 °C and stirred for 3.5 h. After filtering, the mixture was dried at 100 °C for 3 h to obtain modified silica ash powder.

[0032] Example 3

[0033] This embodiment provides a modified silica fume powder, which is prepared by the following method:

[0034] 6 mg PVP-K30 was added into 300 mL deionized water, and magnetically stirred for 2 h at room temperature to fully dissolve, and sodium hydroxide solution was added dropwise to adjust the solution pH to 10. Then 100 mg silica ash was added, and the oil bath was heated to 60 ° C and stirred for 3 h. After filtering, it was dried at 105 ° C for 2 h to obtain modified silica ash powder.

[0035] Example 4

[0036] This embodiment provides a modified water reducing agent, which is prepared by the following steps:

[0037] Step S1, adding 60g of isopentanol polyoxyethylene ether to 60g of deionized water and stirring well, then adding 0.5g of 30wt% hydrogen peroxide and stirring for 5min, and then dripping 20g of mixed aqueous solution A and 42g of mixed aqueous solution B respectively, wherein the mixed aqueous solution A is a mixture of mercaptopropionic acid, vitamin C and deionized water in a mass ratio of 0.22:0.15:20, and the mixed aqueous solution B is a mixture of acrylic acid, methacrylic acid monophosphate, acrylamide and deionized water in a mass ratio of 10:1:1:30, and the dripping time is 3h and 2.5h respectively. After dripping, the reaction is kept warm for 1h, and then a 30wt% sodium hydroxide solution is added to adjust the pH to neutral to obtain a modified water reducer solution;

[0038] Step S2, adding the modified water-reducing agent solution into a centrifugal spray dryer, spraying and powdering in hot air at a temperature of 70° C., cooling and powdering to obtain the modified water-reducing agent.

[0039] Example 5

[0040] This embodiment provides a modified water reducing agent, which is prepared by the following steps:

[0041] Step S1, adding 65g of isopentanol polyoxyethylene ether to 60g of deionized water and stirring well, then adding 0.55g of 30wt% hydrogen peroxide and stirring for 5min, and then dropping 20g of mixed aqueous solution A and 42.5g of mixed aqueous solution B respectively, wherein the mixed aqueous solution A is a mixture of mercaptopropionic acid, vitamin C and deionized water in a mass ratio of 0.24:0.15:20, and the mixed aqueous solution B is a mixture of acrylic acid, methacrylic acid monophosphate, acrylamide and deionized water in a mass ratio of 10:1.1:1.1:30, the dropping time is 3h and 2.5h respectively, and the reaction is kept warm for 1h after the dropping is completed, and then a 30wt% sodium hydroxide solution is added to adjust the pH to neutral to obtain a modified water reducer solution;

[0042] Step S2, adding the modified water-reducing agent solution into a centrifugal spray dryer, spraying and powdering in hot air at a temperature of 80° C., cooling and powdering to obtain the modified water-reducing agent.

[0043] Example 6

[0044] This embodiment provides a modified water reducing agent, which is prepared by the following steps:

[0045] Step S1, adding 70g of isopentanol polyoxyethylene ether to 60g of deionized water and stirring well, then adding 0.6g of 30wt% hydrogen peroxide and stirring for 5min, and then dropping 20g of mixed aqueous solution A and 43g of mixed aqueous solution B respectively, wherein the mixed aqueous solution A is a mixture of mercaptopropionic acid, vitamin C and deionized water in a mass ratio of 0.25:0.15:20, and the mixed aqueous solution B is a mixture of acrylic acid, methacrylic acid monophosphate, acrylamide and deionized water in a mass ratio of 10:1.2:1.2:30, and the dropping time is 3h and 2.5h respectively. After the dropping is completed, the reaction is kept warm for 1h, and then a 30wt% sodium hydroxide solution is added to adjust the pH to neutral to obtain a modified water reducer solution;

[0046] Step S2, adding the modified water-reducing agent solution into a centrifugal spray dryer, spraying and powdering in hot air at a temperature of 90° C., cooling and powdering to obtain the modified water-reducing agent.

[0047] Comparative Example 1

[0048] Compared with Example 6, the mixed aqueous solution B in this comparative example does not contain methacrylic acid monophosphate, and the other raw materials and steps are the same.

[0049] Comparative Example 2

[0050] Compared with Example 6, the mixed aqueous solution B in this comparative example does not contain acrylamide, and the other raw materials and steps are the same.

[0051] Example 7

[0052] An environmentally friendly gypsum-based self-leveling powder comprises the following raw materials in parts by weight:

[0053] 85 parts of β-hemihydrate gypsum, 5 parts of silicate cement, 2 parts of fly ash, 3 parts of mineral powder, 2 parts of modified silica fume powder prepared in Example 1, 0.05 parts of hydroxypropyl methylcellulose, 0.01 parts of polyether defoamer, 0.3 parts of modified water reducing agent prepared in Example 4, 0.02 parts of protein retarder, 0.08 parts of sodium gluconate, 1 part of redispersible latex powder;

[0054] The method comprises the following steps:

[0055] The above raw materials in parts by weight were added into a V-type mixer, stirred and mixed for 5 minutes, and the environmentally friendly gypsum-based self-leveling powder was obtained after discharging.

[0056] Example 8

[0057] An environmentally friendly gypsum-based self-leveling powder comprises the following raw materials in parts by weight:

[0058] 88 parts of β-hemihydrate gypsum, 5 parts of Portland cement, 2.5 parts of fly ash, 3 parts of mineral powder, 2.5 parts of modified silica fume powder prepared in Example 2, 0.05 parts of hydroxypropyl methylcellulose, 0.02 parts of polyether defoamer, 0.4 parts of modified water reducing agent prepared in Example 5, 0.02 parts of protein retarder, 0.09 parts of sodium gluconate, and 1.2 parts of redispersible latex powder;

[0059] The method comprises the following steps:

[0060] The above raw materials in parts by weight were added into a V-type mixer, stirred and mixed for 8 minutes, and the environmentally friendly gypsum-based self-leveling powder was obtained after discharging.

[0061] Example 9

[0062] An environmentally friendly gypsum-based self-leveling powder comprises the following raw materials in parts by weight:

[0063] 90 parts of β-hemihydrate gypsum, 5 parts of silicate cement, 3 parts of fly ash, 3 parts of mineral powder, 3 parts of modified silica fume powder prepared in Example 3, 0.05 parts of hydroxypropyl methylcellulose, 0.02 parts of polyether defoamer, 0.4 parts of modified water reducing agent prepared in Example 6, 0.02 parts of protein retarder, 0.1 parts of sodium gluconate, and 1.5 parts of redispersible latex powder;

[0064] The method comprises the following steps:

[0065] The above raw materials in parts by weight were added into a V-type mixer, stirred and mixed for 10 minutes, and the environmentally friendly gypsum-based self-leveling powder was obtained after discharging.

[0066] Comparative Example 3

[0067] Compared with Example 9, this comparative example uses an equal amount of silica fume to replace the modified silica fume powder prepared in Example 3, and the other raw materials and steps are the same.

[0068] Comparative Example 4

[0069] Compared with Example 9, this comparative example uses an equal amount of the modified water-reducing agent prepared in Comparative Example 1 to replace the modified water-reducing agent prepared in Example 6, and the other raw materials and steps are the same.

[0070] Comparative Example 5

[0071] Compared with Example 9, this comparative example uses an equal amount of the modified water-reducing agent prepared in Comparative Example 2 to replace the modified water-reducing agent prepared in Example 6, and the other raw materials and steps are the same.

[0072] The self-leveling powders prepared in Examples 7 to 9 and Comparative Examples 3 to 5 were tested for relevant performance indicators according to the requirements of "Gypsum-based Self-leveling Mortar" JC / T 1023-2021. The results are shown in Table 1:

[0073] Table 1

[0074]

[0075] It can be seen from the data in Table 1 that the environmentally friendly gypsum-based self-leveling powders prepared in Examples 7 to 9 of the present invention have excellent flow properties and strength, and can fully meet the use requirements of existing standards.

[0076] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0077] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly gypsum-based self-leveling powder, characterized in that: It includes the following raw materials in parts by weight: 85-90 parts of β-hemihydrate gypsum, 5 parts of Portland cement, 2-3 parts of fly ash, 3 parts of mineral powder, 2-3 parts of modified silica fume, 0.05 parts of hydroxypropyl methylcellulose, 0.01-0.02 parts of polyether defoamer, 0.3-0.4 parts of modified water reducer, 0.02 parts of retarder, 0.08-0.1 parts of sodium gluconate, 1-1.5 parts of redispersible latex powder; The modified silica fume powder is prepared by the following method: Add polyvinyl pyrrolidone to deionized water, stir and dissolve at room temperature, add sodium hydroxide solution dropwise to adjust the solution pH to 10, then add silica fume, heat to 50-60°C and stir to react for 3-4 hours, filter and dry to obtain modified silica fume powder; the dosage ratio of polyvinyl pyrrolidone, deionized water and silica fume is 4-6mg:300mL:100mg; The modified water reducing agent is prepared by the following steps: Step S1, adding isopentanol polyoxyethylene ether to deionized water and stirring evenly, then adding hydrogen peroxide and stirring and mixing evenly, then dripping the mixed aqueous solution A and the mixed aqueous solution B respectively, the dripping time is 3h and 2.5h respectively, after the dripping is completed, the reaction is kept warm for 1h, and then adding a sodium hydroxide solution with a concentration of 30wt% to adjust the pH to neutral, to obtain a modified water reducing agent solution; The mass ratio of the isopentanol polyoxyethylene ether, deionized water, hydrogen peroxide, mixed aqueous solution A and mixed aqueous solution B is 60-70:60:0.5-0.6:20:42-43; the mixed aqueous solution A is composed of mercaptopropionic acid, vitamin C and deionized water in a mass ratio of 0.22-0.25:0.15:20; the mixed aqueous solution B is composed of acrylic acid, methacrylic acid monophosphate, acrylamide and deionized water in a mass ratio of 10:1-1.2:1-1.2:30; Step S2, adding the modified water-reducing agent solution into a centrifugal spray dryer for spraying and powdering, cooling, and collecting the powder to obtain the modified water-reducing agent.

2. The environmentally friendly gypsum-based self-leveling powder according to claim 1, characterized in that: The polyvinyl pyrrolidone is PVP-K30.

3. The method for preparing an environmentally friendly gypsum-based self-leveling powder according to claim 1, characterized in that: The following steps are involved: Add β-semihydrate gypsum, silicate cement, fly ash, mineral powder, modified silica fume powder, hydroxypropyl methylcellulose, defoamer, modified water reducing agent, retarder, sodium gluconate and redispersible latex powder into a V-type mixer, stir and mix evenly, and obtain environmentally friendly gypsum-based self-leveling powder after discharging.

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