CN111704725A - Preparation method of modified natural bio-based lignin sulfonate high-efficiency water reducing agent - Google Patents
Preparation method of modified natural bio-based lignin sulfonate high-efficiency water reducing agent Download PDFInfo
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Abstract
The invention provides a preparation method of a modified natural bio-based lignin sulfonate high-efficiency water reducing agent, which is used for extracting alkali lignin and carrying out fractional purification to obtain high-molecular-weight and low-molecular-weight alkali lignin. The condensation reaction of acetone and formaldehyde connects the hydroxymethyl acetone group to the molecular chain of high molecular weight alkali lignin; the methylolation reaction of formaldehyde introduces methylol groups on the low molecular weight alkali lignin molecules. Under the conditions of acidity and high temperature, the hydroxymethyl acetone group on the high molecular weight alkali lignin molecule is condensed with the hydroxymethyl group on the low molecular weight alkali lignin molecule to obtain the alkali lignin high polymer. Sodium bisulfite is used for sulfonating the alkali lignin high polymer at high temperature to introduce sulfonic acid groups. The modified lignosulfonate high-efficiency water reducing agent is prepared by using natural lignin, so that the negative influence of artificially synthesized chemicals on the environment in the production of the high-efficiency water reducing agent is avoided. The prepared modified lignosulfonate high-efficiency water reducing agent has higher water reducing rate, better concrete fluidity retentivity and mechanical property than the common lignosulfonate water reducing agent.
Description
Technical Field
The invention relates to the technical field of high-efficiency water reducing agent preparation, in particular to a preparation method of a modified natural bio-based lignin sulfonate high-efficiency water reducing agent.
Background
With the acceleration of village and town and civil engineering construction speed in China, the cement concrete material has been widely used in civil buildings, expressways, bridges, tunnels, docks, drilling platforms and other engineering constructions due to the characteristics of wide material sources and low cost, and is the building material with the largest use amount in the world at present. The cement concrete material mainly comprises a cementing material, coarse aggregate, fine aggregate, water, a high-efficiency water reducing agent and the like. The high-efficiency water reducing agent is an important component in concrete materials. The high-efficiency water reducing agent as an anionic surfactant can be adsorbed on the surface of cement particles to form an interfacial film with certain mechanical strength, and the interfacial film can reduce the resistance among the particles, play a role in lubrication and improve the rheological property of concrete mixture. Under the same slump, the addition of the high-efficiency water reducing agent reduces the mixing water consumption and the water-cement ratio in the concrete, and improves the compactness and the mechanical property of the concrete. The high-efficiency water reducing agent can also increase the frost resistance of concrete and reduce the segregation of the underwater concrete during pouring, so that the preparation of the self-compacting concrete with high fluidity and high strength becomes possible.
At present, water reducing agents commonly used at home and abroad are classified into common water reducing agents and high-efficiency water reducing agents (also called superplasticizers) according to the water reducing effect. The lignosulfonate water reducing agent is used as a common water reducing agent, the water reducing effect is low, the water reducing rate is only 8-12% under the mixing amount of 0.6%, the gas content of concrete doped with the lignosulfonate water reducing agent is large, the concrete is easy to generate a retardation phenomenon, the adaptability of cement is poor, and the lignosulfonate water reducing agent needs to be compounded with other high-efficiency water reducing agents for use, so that the application range of the lignosulfonate water reducing agent is limited. The high-efficiency water reducing agent is mainly represented by naphthalene sulfonate, sulfonated melamine, aliphatic, sulfamate and polycarboxylic acid high-efficiency water reducing agent. The high-efficiency water reducing agent has the advantages of simple production process, small mixing amount and the like, but raw materials for preparing the high-efficiency water reducing agent are artificial synthetic chemicals of industrial naphthalene, melamine, phenol, sulfanilic acid, olefin, unsaturated carboxylic acid copolymer, unsaturated polyether and graft polymer connected with sulfonic acid groups, the high-efficiency water reducing agent has higher price and certain toxicity, and the artificial synthetic chemicals can generate negative effects on the environment and public health in the production of the high-efficiency water reducing agent. The high-efficiency water reducing agent prepared from the modified natural biomass material not only widens the application field of natural biomass, but also has green and environment-friendly production process and good application and development prospect.
The lignin is a natural biomass material with a plant skeleton, which is formed by the polymerization of units such as guaiacyl propane, syringyl propane, p-hydroxy phenyl propane and the like through C-C bonds and C-O-C bonds. The lignin molecule contains active functional groups such as hydroxyl, carbonyl, carboxyl, methoxyl and the like, the hydroxyl exists in two forms of alcoholic hydroxyl and phenolic hydroxyl, and the quantity of the phenolic hydroxyl reflects the lignin etherification and condensation degree. The alpha position and the gamma position of the side chain of the lignin have the molecular configuration of the hydroxy benzoic acid, the vanillic acid, the syringic acid, the p-hydroxy cinnamic acid and the ferulic acid ester, the alpha position has the ester molecular configuration and also presents C-C structures of ethers and biphenyls, and the side chain structure of the lignin molecule is directly related to the chemical activity of the lignin molecule. Lignin is the second largest biomass material in nature in quantities second only to cellulose, with a lignin yield of 600 trillion tons per year in nature. The lignin is mainly from the papermaking industry, the total amount of the lignin in the papermaking and pulping waste liquid reaches 5000 ten thousand tons every year, 95 percent of the lignin in the pulping waste liquid is directly discharged into rivers or is burnt after being concentrated as waste along with the waste water, and only about 1 percent of the lignin in the pulping waste liquid is used for preparing the lignosulfonate water reducing agent. The discharge of a large amount of paper-making waste liquid wastes lignin resources and seriously pollutes underground water, rivers and the environment around a paper mill, and the discharge of the paper-making waste liquid is the most important problem influencing the environment of modern cities. Along with the continuous and deep consciousness of recycling and reusing waste resources, the efficient utilization of natural lignin resources has been widely regarded by various countries in the world. The lignosulfonate water reducing agent prepared by the traditional method has a common water reducing effect, and the using amount is limited. The development of a modified lignosulfonate superplasticizer which has low cost, high water reduction, high retardation and environmental friendliness has become a hotspot in the research field.
Previous researches show that the lignosulfonate can be subjected to polycondensation reaction with formaldehyde and beta-naphthalene sulfonate or sulfonated melamine to prepare the modified lignosulfonate superplasticizer, and the water reducing rate and the durability of concrete can be obviously improved by doping the modified lignosulfonate superplasticizer into the concrete. Under alkaline condition, lignosulfonate can be subjected to condensation reaction with phenol and formaldehyde to generate a sulfonated lignin-phenol-formaldehyde condensate. The modified lignosulfonate water reducing agent prepared from the lignosulfonate-modified grafted carbonyl aliphatic compound can obviously improve the adaptability of the water reducing agent and cement, and overcomes the problem of chromatic aberration of concrete doped with the aliphatic high-efficiency water reducing agent. The air entraining type lignosulfonate superplasticizer can be prepared by modifying lignosulfonate with formaldehyde and sulfanilic acid. The novel polycarboxylate-lignosulfonate copolymer type high-efficiency water reducing agent can be prepared by copolymerizing the esterified macromonomer polyethylene glycol monomethyl ether methacrylate with methacrylic acid, lignosulfonate and sodium methallylsulfonate, the modified lignosulfonate high-efficiency water reducing agent has good plasticizing effect and reinforcing effect, and the dispersing effect of the lignosulfonate water reducing agent on cement particles can be obviously improved by condensation modification of the lignosulfonate water reducing agent. But the existing method for preparing the modified lignosulfonate water reducing agent does not completely solve the problem that artificially synthesized chemicals are used in the production process of the high-efficiency water reducing agent; the artificial chemicals as raw materials have the advantages of limited sources, high price, complex preparation process and serious pollution to the surrounding environment in the production process; the utilization rate of lignin is not obviously improved, and the problem of regeneration and utilization of lignin black liquor waste in the paper industry cannot be completely solved.
Disclosure of Invention
The invention provides a preparation method of a modified natural bio-based lignosulfonate high-efficiency water reducing agent based on the problems in the existing preparation method of the modified lignosulfonate water reducing agent. The method disclosed by the invention is mainly started from the two aspects of improving the molecular weight and the sulfonation degree of the water reducing agent, the performance of the lignosulfonate water reducing agent is improved, the prepared novel modified lignosulfonate high-efficiency water reducing agent has the advantages of good water reducing effect, low air entraining amount and the like, and the high-performance and multi-functionalization of the modified lignosulfonate water reducing agent is realized.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
a preparation method of a modified natural bio-based lignin sulfonate high-efficiency water reducing agent is characterized by comprising the following steps:
the method comprises the following steps: crushing pine chips, screening pine particles with proper particle size, mixing the pine particles with water, adding a sodium hydroxide solution, uniformly stirring, putting the mixture into a rotary digester, heating, cooling the cooked product to room temperature, taking out, centrifuging the product, filtering, washing the filtered precipitate with distilled water to neutrality to obtain cellulose, and mixing the filtrate with washing liquid to obtain alkali lignin papermaking black liquor;
step two: placing the alkali lignin papermaking black liquor in a freeze dryer for freeze drying to obtain alkali lignin solid, and then crushing and ball-milling the alkali lignin solid to obtain alkali lignin powder;
step three: placing alkali lignin powder and an acetone solvent in a reaction container, stirring the mixture to form a uniform suspension solution, placing the suspension solution in a centrifuge to separate the suspension solution into layers and solid and liquid, obtaining a high molecular weight alkali lignin solution dissolved in the acetone solvent and a centrifugal precipitate, and placing the centrifugal precipitate in a freeze dryer to freeze and dry to obtain low molecular weight alkali lignin solid powder;
step four: raising the temperature of the high molecular weight alkali lignin solution to 40-50 ℃, adding a sodium hydroxide solution into the high molecular weight alkali lignin solution, adjusting the pH of the solution to 14-15, slowly dropwise adding a formaldehyde solution, finishing the addition in 45-60 minutes, and reacting at the temperature of 50-60 ℃ for 1-2 hours to obtain a high molecular weight alkali lignin clear solution connected with a hydroxymethyl acetone group;
step five: mixing low molecular weight alkali lignin solid powder and water, raising the temperature to 40-50 ℃, stirring the mixture to mix the low molecular weight alkali lignin powder and the water into a uniform solution, then adding a sodium hydroxide solution, adjusting the pH of the solution to 14-15, slowly dropwise adding a formaldehyde solution, finishing the adding within 25-30 minutes, and reacting for 0.5-1 hour at the temperature of 70-75 ℃ to obtain a low molecular weight alkali lignin solution connected with ortho-methylol;
step six: mixing and rapidly stirring a high molecular weight alkali lignin solution connected with a hydroxymethyl acetone group and a low molecular weight alkali lignin solution connected with an ortho-position hydroxymethyl group, adding an acetic acid solution, adjusting the pH value of the solution to 5-6, raising the temperature of the system to 160-180 ℃, continuously stirring for 3-4 hours at the temperature, and condensing high molecular weight alkali lignin molecules connected with the hydroxymethyl acetone group and low molecular weight alkali lignin molecules containing the hydroxymethyl group into an alkali lignin high polymer;
step seven: adding sodium bisulfite into the alkali lignin high polymer solution, adjusting the pH value of the solution to be 14-15 by using sodium hydroxide, raising the temperature of the solution to 180-200 ℃, reacting for 5-6 hours at the temperature, cooling the reaction product to room temperature, and curing for 2-3 hours in a reaction vessel to obtain the modified lignosulfonate superplasticizer.
In order to optimize the technical scheme, the specific measures adopted further comprise:
in the first step, the mixture put into the rotary digester is specifically configured as follows: 30-35kg of pine wood particles are added into 65-70kg of water, and 4kg of sodium hydroxide solution is added to be mixed and stirred uniformly; wherein, the weight percentage concentration of the sodium hydroxide solution is 40%.
In the second step, the crushing and ball milling specifically comprises the following steps: crushing the alkali lignin solid, passing through a 5mm square-hole sieve, taking alkali lignin particles with the particle size of less than 5mm, and putting the alkali lignin particles into a ball mill to perform ball milling for 40-50 minutes at the speed of 80 revolutions per minute to obtain alkali lignin powder; wherein the particle size of the alkali lignin powder is less than 0.6 mm.
In the third step, the mass ratio of the alkali lignin powder to the acetone solvent is 12 (24-26).
In the fourth step, the mass ratio of the high molecular weight alkali lignin solution to the sodium hydroxide solution to the formaldehyde solution is 25 (1.5-1.8) to (58-59); wherein, the weight percentage concentration of the sodium hydroxide solution is 40 percent, and the weight percentage concentration of the formaldehyde solution is 37 percent.
In the fifth step, the mass ratio of the low molecular weight alkali lignin solid powder to the water to the sodium hydroxide solution to the formaldehyde solution is (70-80): 300-310): 7.5-8): 1.7-1.8; wherein, the weight percentage concentration of the sodium hydroxide solution is 40 percent, and the weight percentage concentration of the formaldehyde solution is 37 percent.
In the sixth step, the mass ratio of the high molecular weight alkali lignin solution connected with the hydroxymethyl acetone group, the low molecular weight alkali lignin solution connected with the ortho-position hydroxymethyl group and the acetic acid solution is (20-25): (75-80): (10-12.5).
In the seventh step, 30-35kg of sodium bisulfite and 100-125kg of sodium hydroxide solution are added into 970-975kg of alkali lignin high polymer solution; wherein, the weight percentage concentration of the sodium hydroxide solution is 40%.
The pH value of the modified lignosulfonate superplasticizer prepared in the seventh step is 12-13, the solid content is 15-20%, the weight average molecular weight is 10535-14369, and the sulfonation degree is 1.384-1.427 mmol/g.
And seventhly, detecting the water reducing rate of the modified lignosulfonate high-efficiency water reducing agent and the performance of the concrete doped with the modified lignosulfonate high-efficiency water reducing agent under different doping amounts, and comparing the performance of the concrete doped with the conventional lignosulfonate water reducing agent under the same doping amount.
Furthermore, the invention starts from the molecular design of the high-efficiency water reducing agent and the theory of leading functional groups, and firstly, improves the dispersing performance of the lignosulfonate water reducing agent from the aspects of improving the molecular weight and the sulfonation degree of the water reducing agent. Firstly, extracting alkali lignin in natural biomass materials by adopting a caustic soda high-temperature cooking method, and performing molecular weight classification on the alkali lignin by utilizing an acetone organic solvent, wherein the alkali lignin with high molecular weight is easily dissolved in the acetone solventThe low molecular weight alkali lignin precipitates in a precipitated manner. Then, the condensation reaction of acetone and formaldehyde in the high molecular weight alkali lignin solution is utilized to connect the hydroxymethyl acetone group to the molecular chain of the high molecular weight alkali lignin. C utilizing low molecular weight alkali lignin molecules9The condensation reaction is easy to occur near the phenol methyl on the chain, and the hydroxymethyl is introduced into the low molecular weight alkali lignin molecule through the formaldehyde hydroxymethylation reaction. Under the conditions of acidity and high temperature, the hydroxymethyl acetone group on the high molecular weight alkali lignin molecule and the hydroxymethyl group on the low molecular weight alkali lignin molecule are condensed to obtain the alkali lignin high polymer. Finally, the sodium bisulfite sulfonating agent is used for carrying out high-temperature sulfonation treatment on the alkali lignin high polymer to introduce sulfonic acid groups, and the-SO-containing lignin is prepared3H、-OH、-CH2OH and other groups of modified lignosulfonate superplasticizer.
Compared with the prior art, the invention has the beneficial effects that:
(1) in the invention, low molecular weight alkali lignin and high molecular weight alkali lignin are subjected to condensation reaction under acidic and high temperature conditions, so that the molecular weight of the modified lignin polymer is increased. And (3) carrying out sulfonation modification treatment on the lignin polymer to introduce a sulfonate group with negative charges into a lignin polymer molecular chain. The modified lignosulfonate superplasticizer is added into concrete, so that the electrostatic repulsion on the surface of cement particles is increased, the molecules of the modified lignosulfonate superplasticizer also have a certain comb-shaped structure, and the modified lignosulfonate superplasticizer is adsorbed on the surface of the cement particles to generate a certain steric hindrance effect. The novel modified lignosulfonate superplasticizer prepared has the advantages of good water reducing effect, low air entraining amount and the like, realizes high-performance and multi-functionalization of the modified lignosulfonate superplasticizer,
(2) under the same mixing amount, the modified natural bio-based lignosulfonate superplasticizer has a better water reducing effect than the traditional lignosulfonate superplasticizer. Under the same initial fluidity of concrete, the required mixing amount of the modified natural bio-based lignin sulfonate high-efficiency water reducing agent is smaller, and by using the modified natural bio-based lignin sulfonate high-efficiency water reducing agent, the cost of the water reducing agent can be saved by 0.452 yuan per formula of concrete.
(3) The papermaking black liquor has wide sources and a large amount of waste alkali lignin contained in the papermaking black liquor is not fully utilized. The high molecular weight alkali lignin and the low molecular weight alkali lignin are subjected to fractional purification, condensation and sulfonation instead of artificially synthesized chemicals to prepare the modified lignosulfonate superplasticizer, so that the natural lignin resources rich in resources are fully utilized, and the raw material cost for preparing the modified lignosulfonate superplasticizer is reduced. And 183.2 yuan can be saved in raw material consumption when one ton of the modified lignosulfonate superplasticizer is produced. The modified lignosulfonate superplasticizer prepared by using the alkali lignin in the papermaking industry black liquor also expands the application field of the alkali lignin-containing papermaking black liquor waste.
(4) The natural lignin replaces artificially synthesized chemicals to prepare the modified lignosulfonate superplasticizer, the pollution of the synthesized chemicals to the environment in the preparation process of the superplasticizer is avoided, and the green and environment-friendly production process of the modified lignosulfonate superplasticizer is realized. The preparation method also simplifies the production flow, shortens the production time and improves the production efficiency.
In conclusion, 8000 tons of the modified lignosulfonate superplasticizer is produced every year, the production cost is saved by 146.56 ten thousand yuan, the investment cost of production equipment is saved, the flow and production time cost is simplified, the environmental protection cost reaches 13.39 ten thousand yuan, and 2.90 × 10 can be prepared by 8000 tons of the superplasticizer6The cost of the modified lignosulfonate water reducing agent can be saved by 131.08 ten thousand yuan based on the square concrete. 8000 tons of modified lignosulfonate superplasticizer is produced every year, and the economic benefit of 291.03 ten thousand yuan can be generated in total.
Drawings
FIG. 1 is a flow chart of the preparation of the modified natural bio-based lignin sulfonate high efficiency water reducing agent of the present invention.
FIG. 2 is a graph comparing water reduction rates of a modified natural bio-based lignosulfonate superplasticizer blended with a commercially available lignosulfonate superplasticizer.
FIG. 3 is a schematic of concrete slump as a function of time with the modified natural bio-based lignosulfonate superplasticizer incorporated therein.
FIG. 4 is a graphical representation of concrete slump as a function of time with a commercial lignosulfonate water reducer.
FIG. 5 is a graph comparing the air content of concrete doped with a modified natural bio-based lignosulfonate superplasticizer and a commercially available lignosulfonate superplasticizer.
FIG. 6 is a schematic diagram of the compressive strength of concrete doped with the modified natural bio-based lignin sulfonate superplasticizer.
FIG. 7 is a graphical representation of the compressive strength of concrete blended with a commercial lignosulfonate water reducer.
Detailed Description
The invention is further illustrated by the following figures and examples.
Example 1
Referring to fig. 1, one ton of modified natural bio-based lignin sulfonate superplasticizer was produced according to the method described in the present invention for concrete application studies.
Preparation of modified natural bio-based lignin sulfonate high-efficiency water reducing agent
1. Extraction of lignin
Jilin 29682and pine wood from spring forest farms are used as raw materials. Pine wood is sliced, sorted, cleaned, dried, crushed and sieved by a 5mm sieve, and impurities in pine wood chips are removed to obtain pine wood particles with certain particle size. 3000kg of pine wood particles are mixed with 6500kg of water, 400kg of sodium hydroxide solution (40% by weight) are added and stirred uniformly. The mixture was heated in a rotary cooker in a water bath, the temperature of the water bath was raised to 90 ℃ and cooked at this temperature for 3 hours. After the reaction is finished, the temperature of the system is reduced to room temperature and the system is taken out, the product is filtered after centrifugal treatment, the filtered precipitate is washed to be neutral by distilled water to obtain cellulose, and the main components of the filtrate and the washing liquid (papermaking black liquor) are alkali lignin. And (3) placing the papermaking black liquor in a freeze dryer for freeze drying for 30-60 minutes to obtain alkali lignin solid. And (3) crushing the alkali lignin solid, sieving the crushed alkali lignin solid through a 5mm square-hole sieve, taking alkali lignin particles with the particle size smaller than 5mm, and putting the alkali lignin particles into a ball mill to perform ball milling for 40-50 minutes at the speed of 80 revolutions per minute to obtain 1254kg of alkali lignin powder. The alkali lignin powder was tested to an average particle size of 0.525mm using a laser particle sizer.
2. Fractional purification of lignin
1200kg of alkali lignin powder and 2450kg of acetone are weighed into a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, and the mixture is stirred at a speed of 400 rpm for 45 minutes to form a uniform suspension solution. Then, the alkali lignin acetone suspension solution was placed in a centrifuge and treated at a centrifugation speed of 1500 rpm for 25 to 30 minutes to allow the suspension solution to be layered and subjected to solid-liquid separation, thereby obtaining 2850kg of a high molecular weight alkali lignin (H-FAL) acetone solution. And freeze-drying the precipitate in a freeze-drying machine for 30-50 min to obtain 765kg low-molecular-weight alkali lignin (L-FAL) solid powder.
3. Preparation of alkali lignin high polymer
2500kg of a high molecular weight alkali lignin acetone solution was placed in a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser. 160kg of sodium hydroxide solution with the weight percentage concentration of 40 percent is added into the high molecular weight alkali lignin acetone solution at the temperature of 45 ℃, the pH value of the solution is adjusted to be 14.46, 5850kg of formaldehyde solution with the concentration of 37 percent is slowly dripped, the addition is finished within 45 minutes, and the reaction is carried out for 1.5 hours at the temperature of 55 ℃ to obtain high molecular weight alkali lignin clear solution (DH-FAL) connected with hydroxymethyl acetone groups.
760kg of a low molecular weight alkali lignin solid powder and 3040kg of water were placed in a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser. The temperature was raised to 40 ℃ and the mixture was stirred at an accelerated rate to disperse the low molecular weight alkali lignin solid powder evenly into the water. 75kg of 40% strength by weight sodium hydroxide solution were added to adjust the pH of the solution to 14.89. Slowly adding 17kg of 37% formaldehyde solution dropwise, reacting at 70 deg.C for 1 hr, and adding into low molecular weight alkali lignin molecule C9Introducing hydroxymethyl to the chain to obtain low molecular weight alkali lignin solution (TL-FAL) with ortho-hydroxymethyl.
200kg of a high molecular weight alkali lignin solution (DH-FAL) having methylolacetone groups attached thereto and 750kg of a low molecular weight alkali lignin solution (TL-FAL) having ortho-methylol groups attached thereto were put into a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser tube, and rapidly stirred to obtain a uniform solution. Adding 100kg acetic acid solution, adjusting pH to 5.47, heating to 170 deg.C, stirring at the temperature for 4 hr, and condensing the high molecular weight alkali lignin with hydroxymethyl acetone group and low molecular weight alkali lignin containing hydroxymethyl group to obtain alkali lignin polymer.
4. Preparation of modified natural bio-based lignin sulfonate high-efficiency water reducing agent
Heating 970kg of alkali lignin high polymer solution to 200 ℃, adding 30kg of sodium bisulfite, adjusting the pH value of the solution to 14.21 by using 100kg of sodium hydroxide solution with the weight percentage concentration of 40%, reacting for 6 hours at 190 ℃, cooling the reaction product to room temperature, and curing for 2 hours in a reaction container to obtain the light black modified lignosulfonate high-efficiency water reducing agent with the pH value of 12.57, the solid content of 17.49%, the weight average molecular weight of 11562 and the sulfonation degree of 1.403 mmol/g.
Example 2
Preparation of modified natural bio-based lignin sulfonate high-efficiency water reducing agent
1. Extraction of lignin
Jilin 29682and pine wood from spring forest farms are used as raw materials. Pine wood is sliced, sorted, cleaned, dried, crushed and sieved by a 5mm sieve, and impurities in the pine wood chips are removed to obtain pine wood particles with certain particle size. 3500kg of pine wood particles are mixed with 7000kg of water, 400kg of sodium hydroxide (40% strength by weight) solution is added and stirred uniformly. The mixture was heated in a rotary cooker in a water bath, the temperature of the water bath was raised to 90 ℃ and cooked at this temperature for 2 hours. After the reaction is finished, the temperature of the system is reduced to room temperature and the system is taken out, the product is filtered after centrifugal treatment, the filtered precipitate is washed to be neutral by distilled water to obtain cellulose, and the main components of the filtrate and the washing liquid (papermaking black liquor) are alkali lignin. And (3) placing the papermaking black liquor in a freeze dryer for freeze drying for 30-60 minutes to obtain alkali lignin solid. And (3) crushing the alkali lignin solid, sieving the crushed alkali lignin solid through a 5mm square-hole sieve, taking alkali lignin particles with the particle size smaller than 5mm, and putting the alkali lignin particles into a ball mill to perform ball milling for 40-50 minutes at the speed of 80 revolutions per minute to obtain 1268kg of alkali lignin powder. The average particle size of the alkali lignin powder was measured to be 0.577mm using a laser particle sizer.
2. Fractional purification of lignin
1200kg of alkali lignin powder and 2600kg of acetone were weighed into a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, and the mixture was stirred at 400 rpm for 45 minutes to form a uniform suspension solution. Then, the alkali lignin acetone suspension solution was placed in a centrifuge and treated at a centrifugation speed of 1500 rpm for 25-30 minutes to allow the suspension solution to separate layers and solid-liquid separation, and 2778kg of a high molecular weight alkali lignin (H-FAL) acetone solution was obtained. And (3) putting the precipitate after the centrifugal treatment into a freeze dryer for freeze drying for 30-50 minutes to obtain 769kg of low molecular weight alkali lignin (L-FAL) solid powder.
3. Preparation of alkali lignin high polymer
2500kg of a high molecular weight alkali lignin acetone solution was placed in a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser. Adding 165kg of sodium hydroxide solution with the weight percentage concentration of 40% into a high molecular weight alkali lignin acetone solution at the temperature of 45 ℃, adjusting the pH of the solution to be 15.49, slowly dropwise adding 5900kg of formaldehyde solution with the concentration of 37%, finishing the addition within 60 minutes, and reacting for 2 hours at the temperature of 60 ℃ to obtain a high molecular weight alkali lignin clear solution (DH-FAL) connected with hydroxymethyl acetone groups.
760kg of a low molecular weight alkali lignin solid powder and 3040kg of water were placed in a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser. The temperature was raised to 45 ℃ and the mixture was stirred at an accelerated rate to disperse the low molecular weight alkali lignin solid powder evenly into the water. 80kg of 40% strength by weight sodium hydroxide solution were added to adjust the pH of the solution to 14.25. Slowly adding 18kg of 37% formaldehyde solution dropwise, reacting at 75 deg.C for 1 hr, and adding into low molecular weight alkali lignin molecule C9Introducing hydroxymethyl to the chain to obtain low molecular weight alkali lignin solution (TL-FAL) with ortho-hydroxymethyl.
250kg of high molecular weight alkali lignin solution (DH-FAL) connected with hydroxymethyl acetone groups and 800kg of low molecular weight alkali lignin solution (TL-FAL) connected with ortho-hydroxymethyl groups are put into a reaction vessel provided with a stirrer, a thermometer, a dropping funnel and a reflux condenser tube and are rapidly stirred into uniform solution. Adding 125kg acetic acid solution, adjusting pH to 6.17, heating to 170 deg.C, stirring at the temperature for 4 hr, and condensing the high molecular weight alkali lignin with hydroxymethyl acetone group and low molecular weight alkali lignin containing hydroxymethyl group to obtain alkali lignin polymer.
4. Preparation of modified natural bio-based lignin sulfonate high-efficiency water reducing agent
975kg of alkali lignin high polymer solution is heated to 200 ℃, 35kg of sodium bisulfite is added, 125kg of sodium hydroxide solution with the weight percentage concentration of 40% is used for adjusting the pH value of the solution to 15.21, the reaction is carried out for 6 hours at the temperature of 190 ℃, the reaction product is cooled to room temperature and is aged in a reaction container for 3 hours, and the light black modified lignosulfonate high-efficiency water reducing agent with the pH value of 12.92, the solid content of 18.12 percent, the weight average molecular weight of 13694 and the sulfonation degree of 1.389mmol/g is obtained.
Examples of the experiments
The water reducing rate and the concrete performance of the modified natural bio-based lignin sulfonate high-efficiency water reducing agent.
1. Homogeneity of modified natural bio-based lignosulfonate high-efficiency water reducing agent and commercial lignosulfonate water reducing agent
Homogeneity analyses were carried out on the modified lignosulfonate superplasticizer (GCL-M) prepared in example 1 and a commercially available lignosulfonate superplasticizer (GCL-L, manufactured by Yanbian white foot paper industries, Ltd.). As shown in table 1.
TABLE 1 homogeneity of modified natural bio-based lignosulfonate superplasticizer and commercial lignosulfonate superplasticizer
| Name (R) | Appearance of the product | Solid content (%) | Molecular weight | Alkali content (%) | Na2SO4Content (%) | Cl-Content (%) |
| GCL-M | Light black liquid | 18.94 | 11562 | 18.97 | 3.28 | 0.0352 |
| GCL-L | Black solid powder | 98.47 | 6415 | 10.64 | 6.71 | 0.1064 |
2. Water reducing rate and concrete performance of modified natural bio-based lignosulfonate high-efficiency water reducing agent and commercial lignosulfonate water reducing agent
The water reducing rate and concrete performance of the modified natural bio-based lignosulfonate high-efficiency water reducing agent (GCL-M) and the commercial lignosulfonate water reducing agent (GCL-L) are measured under the mixing amount of 0-0.5% (by solid). The cement is P II grade 52.5 Portland cement, the coarse aggregate is crushed stone of 5-20mm and 20-40mm, wherein the crushed stone of 5-20mm accounts for 40%,20-40mm of crushed stone accounts for 60 percent. The fine aggregate is river sand, and the fineness modulus of the river sand fine aggregate is 2.12. The cement consumption in each concrete sample is 330kg/m3The sand ratio was 39%. The initial slump of the concrete doped with the natural bio-based lignosulfonate high-efficiency water reducing agent (GCL-M) and the commercial lignosulfonate water reducing agent is controlled to be 7.5-8.5cm, and the compounding ratio of the test concrete is shown in Table 2.
TABLE 2 concrete experiment mix proportion
3. Performance testing
FIG. 2 is a comparison graph of water reducing rates of two lignosulfonate water reducing agents GCL-M, GCL-L at different blending amounts, and it can be seen that the GCL-M modified natural bio-based lignosulfonate high-efficiency water reducing agent has a higher water reducing rate than the commercially available GCL-L lignosulfonate water reducing agent at the same blending amount.
FIGS. 3 and 4 are graphs comparing the slump of concrete doped with two lignosulfonate water-reducing agents GCL-M, GCL-L with time, and it can be seen that the concrete doped with GCL-M modified natural bio-based lignosulfonate high-efficiency water-reducing agent has higher slump flow retention than the concrete doped with a commercially available GCL-L lignosulfonate water-reducing agent.
As shown in FIG. 5, which is a graph comparing the gas contents of two types of GCL-M, GCL-L lignosulfonate water-reducing agent concrete, it can be seen that, under the same blending amount, the GCL-M-doped modified natural bio-based lignosulfonate superplasticizer concrete has a lower gas content than the commercially available GCL-L lignosulfonate water-reducing agent concrete.
FIG. 6 and FIG. 7 are comparative graphs showing the compressive strength of concrete doped with two lignosulfonate water-reducing agents GCL-M, GCL-L, respectively, and it can be seen from these graphs that the concrete doped with the GCL-M modified natural bio-based lignosulfonate high-efficiency water-reducing agent has higher compressive strength than the concrete doped with the commercially available GCL-L lignosulfonate water-reducing agent at different curing ages.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept of the present invention, and these changes and modifications are all within the scope of the present invention.
Claims (10)
1. A preparation method of a modified natural bio-based lignin sulfonate high-efficiency water reducing agent is characterized by comprising the following steps:
the method comprises the following steps: crushing pine chips, screening pine particles with proper particle size, mixing the pine particles with water, adding a sodium hydroxide solution, uniformly stirring, putting the mixture into a rotary digester, heating, cooling the cooked product to room temperature, taking out, centrifuging the product, filtering, washing the filtered precipitate with distilled water to neutrality to obtain cellulose, and mixing the filtrate with washing liquid to obtain alkali lignin papermaking black liquor;
step two: placing the alkali lignin papermaking black liquor in a freeze dryer for freeze drying to obtain alkali lignin solid, and then crushing and ball-milling the alkali lignin solid to obtain alkali lignin powder;
step three: placing alkali lignin powder and an acetone solvent in a reaction container, stirring the mixture to form a uniform suspension solution, placing the suspension solution in a centrifuge to separate the suspension solution into layers and solid and liquid, obtaining a high molecular weight alkali lignin solution dissolved in the acetone solvent and a centrifugal precipitate, and placing the centrifugal precipitate in a freeze dryer to freeze and dry to obtain low molecular weight alkali lignin solid powder;
step four: raising the temperature of the high molecular weight alkali lignin solution to 40-50 ℃, adding a sodium hydroxide solution into the high molecular weight alkali lignin solution, adjusting the pH of the solution to 14-15, slowly dropwise adding a formaldehyde solution, finishing the addition in 45-60 minutes, and reacting at the temperature of 50-60 ℃ for 1-2 hours to obtain a high molecular weight alkali lignin clear solution connected with a hydroxymethyl acetone group;
step five: mixing low molecular weight alkali lignin solid powder and water, raising the temperature to 40-50 ℃, stirring the mixture to mix the low molecular weight alkali lignin powder and the water into a uniform solution, then adding a sodium hydroxide solution, adjusting the pH of the solution to 14-15, slowly dropwise adding a formaldehyde solution, finishing the adding within 25-30 minutes, and reacting for 0.5-1 hour at the temperature of 70-75 ℃ to obtain a low molecular weight alkali lignin solution connected with ortho-methylol;
step six: mixing and rapidly stirring a high molecular weight alkali lignin solution connected with a hydroxymethyl acetone group and a low molecular weight alkali lignin solution connected with an ortho-position hydroxymethyl group, adding an acetic acid solution, adjusting the pH value of the solution to 5-6, raising the temperature of the system to 160-180 ℃, continuously stirring for 3-4 hours at the temperature, and condensing high molecular weight alkali lignin molecules connected with the hydroxymethyl acetone group and low molecular weight alkali lignin molecules containing the hydroxymethyl group into an alkali lignin high polymer;
step seven: adding sodium bisulfite into the alkali lignin high polymer solution, adjusting the pH value of the solution to be 14-15 by using sodium hydroxide, raising the temperature of the solution to 180-200 ℃, reacting for 5-6 hours at the temperature, cooling the reaction product to room temperature, and curing for 2-3 hours in a reaction vessel to obtain the modified lignosulfonate superplasticizer.
2. The preparation method of the modified natural bio-based lignin sulfonate high-efficiency water reducing agent according to claim 1, characterized in that: in the first step, the mixture put into the rotary digester is specifically configured as follows: 30-35kg of pine wood particles are added into 65-70kg of water, and 4kg of sodium hydroxide solution is added to be mixed and stirred uniformly; wherein, the weight percentage concentration of the sodium hydroxide solution is 40%.
3. The preparation method of the modified natural bio-based lignin sulfonate high-efficiency water reducing agent according to claim 1, characterized in that: in the second step, the crushing and ball milling specifically comprises the following steps: crushing the alkali lignin solid, passing through a 5mm square-hole sieve, taking alkali lignin particles with the particle size of less than 5mm, and putting the alkali lignin particles into a ball mill to perform ball milling for 40-50 minutes at the speed of 80 revolutions per minute to obtain alkali lignin powder; wherein the particle size of the alkali lignin powder is less than 0.6 mm.
4. The preparation method of the modified natural bio-based lignin sulfonate high-efficiency water reducing agent according to claim 1, characterized in that: in the third step, the mass ratio of the alkali lignin powder to the acetone solvent is 12 (24-26).
5. The preparation method of the modified natural bio-based lignin sulfonate high-efficiency water reducing agent according to claim 1, characterized in that: in the fourth step, the mass ratio of the high molecular weight alkali lignin solution to the sodium hydroxide solution to the formaldehyde solution is 25 (1.5-1.8) to (58-59); wherein, the weight percentage concentration of the sodium hydroxide solution is 40 percent, and the weight percentage concentration of the formaldehyde solution is 37 percent.
6. The preparation method of the modified natural bio-based lignin sulfonate high-efficiency water reducing agent according to claim 1, characterized in that: in the fifth step, the mass ratio of the low molecular weight alkali lignin solid powder to the water to the sodium hydroxide solution to the formaldehyde solution is (70-80): 300-310): 7.5-8): 1.7-1.8; wherein, the weight percentage concentration of the sodium hydroxide solution is 40 percent, and the weight percentage concentration of the formaldehyde solution is 37 percent.
7. The preparation method of the modified natural bio-based lignin sulfonate high-efficiency water reducing agent according to claim 1, characterized in that: in the sixth step, the mass ratio of the high molecular weight alkali lignin solution connected with the hydroxymethyl acetone group, the low molecular weight alkali lignin solution connected with the ortho-position hydroxymethyl group and the acetic acid solution is (20-25): 75-80): 10-12.5.
8. The preparation method of the modified natural bio-based lignin sulfonate high-efficiency water reducing agent according to claim 1, characterized in that: in the seventh step, 30-35kg of sodium bisulfite and 100-125kg of sodium hydroxide solution are added into each 970-975kg of alkali lignin high polymer solution; wherein, the weight percentage concentration of the sodium hydroxide solution is 40%.
9. The preparation method of the modified natural bio-based lignin sulfonate high-efficiency water reducing agent according to claim 1, characterized in that: the pH value of the modified lignosulfonate superplasticizer prepared in the seventh step is 12-13, the solid content is 15-20%, the weight average molecular weight is 10535-14369, and the sulfonation degree is 1.384-1.427 mmol/g.
10. The preparation method of the modified natural bio-based lignin sulfonate high-efficiency water reducing agent according to claim 1, characterized in that: and seventhly, detecting the water reducing rate of the modified lignosulfonate high-efficiency water reducing agent and the performance of the concrete doped with the modified lignosulfonate high-efficiency water reducing agent under different doping amounts, and comparing the performance with the performance of the concrete doped with the conventional lignosulfonate water reducing agent under the same doping amount.
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