A method for preparing a biomass-based water reducing agent

Abstract

The invention relates to the technical field of water reducers, and in particular to a method for preparing a biomass-based water reducer. The raw materials include 20-40 parts of cassava starch, 40-60 parts of bagasse, 8-12 parts of ammonium acrylate, 5-10 parts of methyl allyl alcohol polyoxyethylene ether, 1-2 parts of ammonium persulfate, 6-9 parts of an oxidant, 3-5 parts of a sulfonating agent, and 3-5 parts of a preservative. The cassava starch and bagasse are thermally decomposed with anhydrous ethanol, separated and washed to obtain an organic phase and a solid mixture, the organic phase is sulfonated, hydrogen atoms in the solid mixture are electrophilically substituted by sulfonic acid groups, and active OH in a benzene ring is easily grafted under an initiator to form a water reducer. The method reduces the consumption of organic matter in the water reducer by bacterial rate, ensures the long-term use of the water reducer, and has a good water reducing effect. The water reducer adsorbs more cement particle surfaces, the steric hindrance effect is enhanced, the amount of water reducer entering concrete or cement particle gaps is reduced, invalid adsorption is reduced, the dispersed flow between particles is promoted, and the cement fluidity is increased.

Description

Technical Field

[0001] The invention relates to the technical field of water reducing agents, and in particular to a method for preparing a biomass-based water reducing agent. Background Art

[0002] Water reducers are commonly used additives in the modern cement concrete industry. They can reduce the amount of water used, better disperse cement, mortar and other cementitious materials, increase the plasticity of concrete, effectively reduce the water-cement ratio of concrete, and improve the durability of concrete. Currently, the commonly used high-efficiency water reducers mainly include naphthalene series, aminosulfonate series, aliphatic series, polycarboxylic acid series, etc. The raw materials of these water reducers are mostly non-renewable resources, the preparation process is relatively complicated, and a large amount of toxic or carcinogenic chemicals are used. Improper handling will cause intermediates or residues to exist in the water reducer, which will be slowly released in the water reducer, causing long-term harm to human health and environmental pollution.

[0003] With the increase of environmental awareness and the concept of sustainable development of resources, the use of renewable materials and environmentally degradable materials to replace traditional non-renewable resources has been deeply rooted in the hearts of the people in all walks of life. Starting from the raw materials, the use of renewable materials to prepare water reducers has a positive significance for saving resources. In addition, in the process of preparing water reducers, reducing the use of toxic, harmful or carcinogenic substances and reducing the amount of toxic substances in water reducers has a positive significance for green environmental protection and environmental protection. At present, many scholars and experts have begun to study the preparation of water reducers with biomass materials. However, there are still several problems in the current research on biomass-based water reducers, such as the source and cost of raw materials are not advantageous enough, the production process is complicated, the process is cumbersome, and the production cost is high. In addition, once the bio-based water reducer is affected by bacteria and fungi, the main components will be consumed, which will cause the water reduction effect to decrease, which is not conducive to long-term maintenance or use.

[0004] To this end, it is of positive significance to expand the source of bio-based water reducer raw materials, optimize the production process, and develop green, non-toxic and corrosion-resistant bio-based water reducers. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method of a biomass-based water-reducing agent, reduce the consumption of organic matter in the water-reducing agent by the bacterial rate, ensure the long-term use of the water-reducing agent, and achieve a good water-reducing effect. The prepared water-reducing agent is more adsorbed on the surface of cement particles, and the steric hindrance effect is enhanced during the adsorption process. The amount of water-reducing agent entering the gaps between concrete or cement particles is reduced, the amount of ineffective adsorption on cement particles is reduced, the dispersed flow between particles is promoted, and the fluidity of cement is increased.

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

[0007] A method for preparing a biomass-based water-reducing agent, comprising the following raw materials in parts by weight: 20 to 40 parts of cassava starch, 40 to 60 parts of bagasse, 8 to 12 parts of ammonium acrylate, 5 to 10 parts of methyl allyl alcohol polyoxyethylene ether, 1 to 2 parts of ammonium persulfate, 6 to 9 parts of an oxidant, 3 to 5 parts of a sulfonating agent, and 3 to 5 parts of a preservative;

[0008] The preparation method of the biomass-based water reducing agent comprises the following steps:

[0009] Step 1: Mix cassava starch and bagasse by mass, grind them, pass through a 100-mesh sieve to form a mixed powder, transfer them to a reactor, add 1 to 2 times the mass of the mixed powder, mix them evenly, evacuate the nitrogen, seal the reactor, react at 180 to 220° C. for 2 to 4 hours, separate the solid and the liquid, extract the liquid with ethyl acetate, wash the organic mixed liquid with a saturated sodium bicarbonate solution, separate the phases, and obtain an organic phase; wash the solid with anhydrous ethanol and dry it to obtain a solid mixture;

[0010] Step 2: Take the organic phase obtained in step 1 and add it to a reaction container, slowly add an equal amount of concentrated sulfuric acid while stirring, slowly heat to 70-80° C., and keep warm for 2-3 hours to obtain a sulfonated organic compound;

[0011] Step 3: Take the solid mixture obtained in step 1, add deionized water of 1 times the mass of the solid mixture and the mass fraction of the oxidant, stir evenly, slowly add the mass fraction of the sulfonating agent, stir at a speed of 60-80 r / min, heat in a water bath to 70-80° C., keep warm for 4-5 hours, and obtain an oxidized mixture;

[0012] Step 4: Add the sulfonated organic matter obtained in step 2 and the oxidation mixture obtained in step 3 to a reaction vessel with a condensation reflux device, slowly drop by weight portions of ammonium acrylate and methyl allyl alcohol polyoxyethylene ether, heat the water bath to 75-95°C, and keep warm for 3-6 hours. After the reaction is completed, after washing and drying, add by weight portions of preservatives, mix well to obtain a biomass water reducer.

[0013] The organic phase contains a large amount of biophenol, accounting for more than 60%. The solid mixture obtained is mainly composed of cellulose, lignin and carbon. In step 2, the biophenol in the organic phase undergoes sulfonation reaction under the action of concentrated sulfuric acid. Taking phenol as an example, the reaction is:

[0014] .

[0015] After the solid mixture is oxidized, the hydrogen atoms in the lignin are easily replaced by the sulfonic acid groups. Under the action of the initiator, the active -OH in the benzene ring is easy to undergo a grafting reaction. The reactions involved in step three are as follows:

[0016] .

[0017] More preferably, the oxidant is one of hydrogen peroxide and formaldehyde or a mixture of them in a mass ratio of 1:1.

[0018] More preferably, the sulfonating agent is one of concentrated sulfuric acid and sodium sulfite or a mixture of them in a mass ratio of 1:1.

[0019] More preferably, the preservative is one of sodium nitrite and bis(hydroxymethyl)imidazolidinyl urea or a mixture thereof in a mass ratio of 1:1.

[0020] Further preferably, in step 1 of the preparation method, the organic mixed solution obtained by extraction is washed 3 to 5 times with a saturated sodium bicarbonate solution, and then phase-separated into a static stratification drainage phase or centrifugal separation to obtain an aqueous phase and an organic phase, and the ethyl acetate in the organic phase is removed by distillation.

[0021] More preferably, in step 2 of the preparation method, the stirring speed of slowly adding concentrated sulfuric acid while stirring is 50-70 r / min, and the heating speed of slowly heating to 70-80° C. is 0.5-1° C. / min.

[0022] Further preferably, in step four of the preparation method, after insulation, washing is performed by soaking in isopropanol for 30 to 40 minutes, filtering to obtain a precipitate, and the precipitate is washed with anhydrous ethanol and methanol for 2 to 3 times, respectively, and then the washing is completed; drying is performed in a vacuum drying oven at a temperature set to 50 to 60° C. for 10 to 12 hours.

[0023] Beneficial effects of the present invention:

[0024] 1. Cassava starch and bagasse are used as biomass raw materials, which are pyrolyzed with anhydrous ethanol, and then separated and washed to obtain an organic phase and a solid mixture, wherein the main component of the organic phase is biophenol, and the solid mixture is mainly composed of cellulose, lignin and carbon. The biophenol in the organic phase will undergo sulfonation reaction under the action of concentrated sulfuric acid, and the hydrogen atoms in substances such as lignin in the solid mixture are easily electrophilically replaced by sulfonic acid groups. Under the action of an initiator, the active -OH in the benzene ring is easily grafted to form a water reducer rich in sulfonic acid groups and having ether bonds and amide bonds in the side chains, which has a good water-reducing effect. In addition, the introduction of side chains into the water reducer molecules increases the molecular weight and molecular structure, and increases the steric hindrance, which is beneficial to improve the dispersibility of particles when used in mortar.

[0025] 2. Cassava starch and bagasse are biomass raw materials with high yield, renewable resources, degradability and no pollution to the environment. After thermal decomposition with anhydrous ethanol, the organic phase is separated. The organic phase contains an extremely high proportion of biophenol. The hydrogen atoms at the para and ortho positions of the hydroxyl group in the biophenol are easily replaced by electrophilic sulfonic acid groups, among which the hydrogen atoms at the para position of the hydroxyl group are replaced mainly. When sulfuric acid is used, sulfonation reaction is easy to occur. The introduction of sulfonic acid groups into biophenol can increase the carbon chain and has strong hydrophilicity, which can improve the dispersibility and fluidity between cement particles and achieve a good water-reducing effect.

[0026] 3. The use of ammonium acrylate and methyl allyl alcohol polyoxyethylene ether, which undergo grafting reaction with phenolic hydroxyl groups, introduces new functional groups such as ether bonds and amide bonds into the water reducer molecules, causing changes in the molecular surface structure, increasing the molecular weight and molecular structure, and the steric hindrance of the side chains introduced by grafting modification improves the dispersion fluidity. In addition, the increase in molecular structure allows the modified water reducer to be more adsorbed on the surface of cement particles, and the steric hindrance is enhanced during the adsorption process, reducing the amount of water reducer entering the gaps between concrete or cement particles, reducing the amount of ineffective adsorption on cement particles, promoting the dispersion flow between particles, and increasing the fluidity of cement.

[0027] 4. Ammonium persulfate is used as an initiator, which is beneficial to the smooth grafting reaction of ammonium acrylate and methyl allyl alcohol polyoxyethylene ether with phenolic hydroxyl groups. The treatment of the solid mixture by the oxidant and the sulfonating agent makes the hydrogen atoms in the solid mixture more active and easy to be replaced by the sulfonating agent, thereby introducing hydrophilic sulfonic acid groups into the water reducer molecules and increasing the hydrophilicity of the hydroxyl groups, which is beneficial to improving the water reducing performance of the water reducer. The use of preservatives is beneficial to killing fungal substances in the water reducer, reducing the consumption of organic matter in the water reducer by the bacterial rate, and ensuring the long-term use of the water reducer.

[0028] 5. The biophenol in the liquid after the reaction is enriched by extraction with ethyl acetate. The organic mixture after extraction is washed with saturated sodium bicarbonate to remove the acid substances in the organic mixture and ensure the purity of the phenolic substances. The ethyl acetate is then removed by phase separation to obtain a relatively pure biophenol, which is conducive to the efficient and smooth progress of the subsequent biophenol sulfonation reaction. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be described clearly and completely below. 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. Example 1

[0030] A method for preparing a biomass-based water reducer comprises the following raw materials in parts by weight: 20 parts of cassava starch, 40 parts of bagasse, 8 parts of ammonium acrylate, 5 parts of methyl allyl alcohol polyoxyethylene ether, 1 part of ammonium persulfate, 6 parts of an oxidant, 3 parts of a sulfonating agent, and 3 parts of a preservative;

[0031] The oxidant is hydrogen peroxide; the sulfonating agent is concentrated sulfuric acid; the preservative is sodium nitrite;

[0032] The preparation method of the biomass-based water reducer comprises the following steps:

[0033] Step 1: Mix cassava starch and sugarcane by mass, grind them, pass through a 100-mesh sieve to form a mixed powder, transfer it to a reactor, add anhydrous ethanol in an amount of 1 times the mass of the mixed powder, mix them evenly, evacuate the nitrogen, seal the reactor, react at 180° C. for 2 hours, separate the solid and the liquid through solid-liquid separation, then extract the liquid through ethyl acetate, wash the organic mixed liquid obtained through extraction with a saturated sodium bicarbonate solution, separate the phases, and obtain an organic phase; wash the solid with anhydrous ethanol and dry it to obtain a solid mixture;

[0034] Step 2: Take the organic phase obtained in step 1 and add it to a reaction vessel, slowly add an equal amount of concentrated sulfuric acid while stirring, slowly heat to 70°C, and keep warm for 2 hours to obtain a sulfonated organic compound;

[0035] Step 3: Take the solid mixture obtained in step 1, add 1 times the mass of the solid mixture of deionized water and oxidant by mass, stir evenly, slowly add sulfonating agent by mass, stir at a speed of 60r / min, heat in a water bath to 70°C, keep warm for 4h, and obtain an oxidized mixture;

[0036] Step 4: Add the sulfonated organic matter obtained in step 2 and the oxidation mixture obtained in step 3 to a reaction vessel with a condensation reflux device, slowly drop by weight portions of ammonium acrylate and methyl allyl alcohol polyoxyethylene ether, heat to 75°C in a water bath, and keep warm for 3 hours. After the reaction is completed, after washing and drying, add by weight portions of preservatives, mix well, and obtain a biomass water reducer. Example 2

[0037] A method for preparing a biomass-based water reducer comprises the following raw materials in parts by weight: 40 parts of cassava starch, 60 parts of bagasse, 12 parts of ammonium acrylate, 10 parts of methyl allyl alcohol polyoxyethylene ether, 2 parts of ammonium persulfate, 9 parts of an oxidant, 5 parts of a sulfonating agent, and 5 parts of a preservative;

[0038] The oxidizing agent is formaldehyde; the sulfonating agent is sodium sulfite; the preservative is bis(hydroxymethyl)imidazolidinyl urea;

[0039] The preparation method of the biomass-based water reducer comprises the following steps:

[0040] Step 1: Mix cassava starch and sugarcane by mass, grind them, pass through a 100-mesh sieve to form a mixed powder, transfer it to a reactor, add anhydrous ethanol twice the mass of the mixed powder, mix them evenly, evacuate the nitrogen, seal the reactor, react at 220° C. for 4 hours, separate the solid and the liquid through solid-liquid separation, then extract the liquid through ethyl acetate, wash the organic mixed liquid obtained through saturated sodium bicarbonate solution, separate the phases, and obtain an organic phase; wash the solid with anhydrous ethanol and dry it to obtain a solid mixture;

[0041] Step 2: Take the organic phase obtained in step 1 and add it to a reaction vessel, slowly add an equal amount of concentrated sulfuric acid while stirring, slowly heat to 80°C, and keep warm for 3 hours to obtain a sulfonated organic matter;

[0042] Step 3: Take the solid mixture obtained in step 1, add 1 times the mass of the solid mixture of deionized water and oxidant by mass, stir evenly, slowly add sulfonating agent by mass, stir at a speed of 80r / min, heat in a water bath to 80°C, keep warm for 5h, and obtain an oxidized mixture;

[0043] Step 4: Add the sulfonated organic matter obtained in step 2 and the oxidation mixture obtained in step 3 to a reaction vessel with a condensation reflux device, slowly drop by weight portions of ammonium acrylate and methyl allyl alcohol polyoxyethylene ether, heat to 95°C in a water bath, and keep warm for 6 hours. After the reaction is completed, after washing and drying, add by weight portions of preservatives, mix well, and obtain a biomass water reducer. Example 3

[0044] A method for preparing a biomass-based water reducer comprises the following raw materials in parts by weight: 30 parts of cassava starch, 50 parts of bagasse, 10 parts of ammonium acrylate, 7 parts of methyl allyl alcohol polyoxyethylene ether, 2 parts of ammonium persulfate, 7 parts of an oxidant, 4 parts of a sulfonating agent, and 4 parts of a preservative;

[0045] The oxidant is a mixture of hydrogen peroxide and formaldehyde in a mass ratio of 1:1; the sulfonating agent is a mixture of concentrated sulfuric acid and sodium sulfite in a mass ratio of 1:1; the preservative is a mixture of sodium nitrite and bis(hydroxymethyl)imidazolidinyl urea in a mass ratio of 1:1;

[0046] The preparation method of the biomass-based water reducer comprises the following steps:

[0047] Step 1: Mix cassava starch and sugarcane by mass, grind them, pass through a 100-mesh sieve to form a mixed powder, transfer it to a reactor, add anhydrous ethanol twice the mass of the mixed powder, mix them evenly, evacuate the nitrogen, seal the reactor, react at 200° C. for 3 hours, separate the solid and the liquid through solid-liquid separation, then extract the liquid through ethyl acetate, wash the organic mixed liquid obtained through saturated sodium bicarbonate solution, separate the phases, and obtain an organic phase; wash the solid with anhydrous ethanol and dry it to obtain a solid mixture;

[0048] Step 2: Take the organic phase obtained in step 1 and add it to a reaction vessel, slowly add an equal amount of concentrated sulfuric acid while stirring, slowly heat to 75°C, and keep warm for 3 hours to obtain a sulfonated organic compound;

[0049] Step 3: Take the solid mixture obtained in step 1, add 1 times the mass of the solid mixture of deionized water and oxidant by mass, stir evenly, slowly add sulfonating agent by mass, stir at a speed of 70r / min, heat in a water bath to 75°C, keep warm for 5h, and obtain an oxidized mixture;

[0050] Step 4: Add the sulfonated organic matter obtained in step 2 and the oxidation mixture obtained in step 3 to a reaction vessel with a condensation reflux device, slowly drop by weight portions of ammonium acrylate and methyl allyl alcohol polyoxyethylene ether, heat to 85°C in a water bath, and keep warm for 4 hours. After the reaction is completed, after washing and drying, add by weight portions of preservatives, mix well to obtain a biomass water reducer.

[0051] Test: PO42.5 cement was used as cement, ISO standard sand as fine aggregate, crushed natural stone as coarse aggregate, the mass ratio of cement, fine aggregate and coarse aggregate was 1:2:2, the water-cement ratio (W / C) was 0.29, and the amount of water reducer was 1% based on the mass of cement. Compressive strength test of concrete specimens: referring to the standard concrete specimens with a molding size of 150mm×150mm×150mm in GB / T50081-2016, the compressive strength of the concrete specimens was tested by a YAW-300B testing machine after curing in batches for 7d and 28d under standard curing conditions; water reduction rate test: referring to GB 8076-2008, the water reduction rate of the water reducer samples prepared in Examples 1-3 was tested; the test results are as follows:

[0052]

[0053] As shown in the above table, the water reducing agent prepared by the method of the present invention has a good water reducing effect. When used in concrete, the compressive strength of the concrete standard parts is high, which can ensure that the concrete has good strength performance.

[0054] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a biomass-based water reducer, characterized in that: The invention comprises the following raw materials in parts by weight: 20 to 40 parts of cassava starch, 40 to 60 parts of bagasse, 8 to 12 parts of ammonium acrylate, 5 to 10 parts of methyl allyl alcohol polyoxyethylene ether, 1 to 2 parts of ammonium persulfate, 6 to 9 parts of oxidant, 3 to 5 parts of sulfonating agent, and 3 to 5 parts of preservative; The oxidant is hydrogen peroxide; the sulfonating agent is a mixture of concentrated sulfuric acid and sodium sulfite in a mass ratio of 1:1; the preservative is a mixture of sodium nitrite and bis(hydroxymethyl)imidazolidinyl urea in a mass ratio of 1:1; The preparation method of the biomass-based water reducer comprises the following steps: Step 1: Mix cassava starch and bagasse by mass, grind them, pass through a 100-mesh sieve to form a mixed powder, transfer them to a reactor, add 1 to 2 times the mass of the mixed powder, mix them evenly, evacuate the nitrogen, seal the reactor, react at 180 to 220° C. for 2 to 4 hours, separate the solid and the liquid, extract the liquid with ethyl acetate, wash the organic mixed liquid with a saturated sodium bicarbonate solution, separate the phases, and obtain an organic phase; wash the solid with anhydrous ethanol and dry it to obtain a solid mixture; Step 2: Take the organic phase obtained in step 1 and add it to a reaction vessel, slowly add an equal amount of concentrated sulfuric acid while stirring, slowly heat to 70-80°C, and keep warm for 2-3 hours to obtain a sulfonated organic matter; Step 3: Take the solid mixture obtained in step 1, add deionized water of 1 times the mass of the solid mixture and the mass fraction of the oxidant, stir evenly, slowly add the mass fraction of the sulfonating agent, stir at a speed of 60-80 r / min, heat in a water bath to 70-80° C., keep warm for 4-5 hours, and obtain an oxidized mixture; Step 4: Add the sulfonated organic matter obtained in step 2 and the oxidation mixture obtained in step 3 to a reaction vessel with a condensation reflux device, slowly drop by weight portions of ammonium acrylate and methyl allyl alcohol polyoxyethylene ether, heat the water bath to 75-95°C, and keep warm for 3-6 hours. After the reaction is completed, after washing and drying, add by weight portions of preservatives, mix well to obtain a biomass water reducer.

2. The method for preparing a biomass-based water reducing agent according to claim 1, characterized in that: In step 1 of the preparation method, the organic mixed solution obtained by extraction is washed with a saturated sodium bicarbonate solution for 3 to 5 times, and then phase-separated into a static stratification drainage phase or centrifugal separation to obtain an aqueous phase and an organic phase, and the ethyl acetate in the organic phase is removed by distillation.

3. The method for preparing a biomass-based water reducing agent according to claim 1, characterized in that: In step 2 of the preparation method, the stirring speed of slowly adding concentrated sulfuric acid while stirring is 50-70 r / min, and the heating speed of slowly heating to 70-80° C. is 0.5-1° C. / min.

4. The method for preparing a biomass-based water reducing agent according to claim 1, characterized in that: In step 4 of the preparation method, after heat preservation, washing is performed by soaking in isopropanol for 30 to 40 minutes, filtering to obtain a precipitate, and the precipitate is washed with anhydrous ethanol and methanol for 2 to 3 times, respectively, and then the washing is completed; drying is performed in a vacuum drying oven at a temperature set to 50 to 60° C. for 10 to 12 hours.

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