A bio-based water reducer with a claw-shaped branched structure and its preparation method

Abstract

The present invention provides a bio-based water reducer with a claw-shaped branched structure and a preparation method thereof. The water reducer comprises the following raw materials in parts by weight: 50-150 parts of modified lignin, 60-235 parts of ether-based unsaturated macromonomer, 5-20 parts of carboxylic acid-based unsaturated small monomer, 3-7.5 parts of initiator, 1-3.5 parts of chain transfer agent, 0.4-0.8 parts of reducing agent, 1-5 parts of pH regulator, and 200-350 parts of deionized water. The water reducer provided by the present invention is modified by bio-based materials, grafted with a variety of active functional groups, and a novel modified lignin polycarboxylate water reducer with a claw-shaped branched structure is prepared with an ether-based macromonomer and an acrylic acid-based small monomer, achieving excellent net paste flow and relatively low yield stress, forming a thick adsorption layer on the cement surface, providing a steric hindrance effect, having excellent water reducing performance, and being green and environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of water reducers, and particularly relates to a bio-based water reducer with a claw-shaped branched structure and a preparation method thereof. Background Art

[0002] High-performance concrete has the advantages of high compressive strength, large density and small self-weight, and is one of the indispensable building materials in modern engineering construction. A water reducer is a concrete admixture that can reduce the mixing water consumption under the condition of maintaining the basic unchanged slump of concrete. Its excellent performance greatly improves the workability of concrete and provides continuous development space for the development of high-performance concrete.

[0003] In recent years, with the progress of science and technology and the improvement of engineering requirements, polycarboxylate water reducers have been increasingly widely used in high-performance concrete due to their unique advantages such as extremely high water reduction rate. However, with the gradual shortage of concrete raw material resources, the adaptability of existing polycarboxylate water reducers to deteriorated concrete will gradually become worse.

[0004] Therefore, it is very necessary to find a new type of polycarboxylate water reducer with a high water reduction rate and wide applicability, especially to conduct invention exploration in aspects such as reducing cement consumption and raw material costs and improving the strength of concrete. Summary of the Invention

[0005] Aiming at the defects of the prior art, the purpose of the present invention is to provide a bio-based water reducer with a claw-shaped branched structure and a preparation method thereof. The water reducer prepared by the present invention has a certain claw-shaped structure, can achieve excellent adsorption and dispersion effects at a low dosage, reach excellent net paste fluidity and low yield stress, and has excellent performance; at the same time, it is modified with bio-based materials, which is green and environmentally friendly.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present invention is as follows:

[0007] On the one hand, the present invention provides a bio-based water reducer with a claw-shaped branched structure, and the water reducer is composed of the following raw materials in parts by weight: 50-150 parts of modified lignin, 60-235 parts of ether-based unsaturated macromonomer, 5-20 parts of carboxylic acid-based unsaturated small monomer, 3-7.5 parts of initiator, 1-3.5 parts of chain transfer agent, 0.4-0.8 part of reducing agent, 1-5 parts of pH regulator and 200-350 parts of deionized water.

[0008] Preferably, the modified lignin is prepared from ether-based substance A and substance B;

[0009] Further preferably, the substance A is polyallyl glycidyl ether with a molecular weight of 1500-3000 Da; the substance B is epichlorobutane.

[0010] Preferably, the preparation steps of the modified lignin are as follows:

[0011] First, add substance A to a reaction flask and heat it to melt at 50 - 70 °C, then add a catalyst and substance B and react for 1.5 - 3 h, then add lignin and react for 2 - 4 h at 70 - 85 °C, and cool to obtain the modified lignin.

[0012] More preferably, the preparation steps of the modified lignin are as follows:

[0013] First, add 0.1 mol of substance A to a reaction flask, heat it to melt at 60 °C, then add a catalyst and substance B and react for 2 h, then add lignin and react for 3 h at 80 °C, and cool to obtain the modified lignin.

[0014] Preferably, the molar ratios of substance A, substance B to lignin are 1:(1 - 1.3):(0.5 - 0.7) respectively;

[0015] More preferably, the molar ratios of substance A, substance B to lignin are 1:1.1:0.6 respectively;

[0016] Preferably, the catalyst is boron trifluoride diethyl ether;

[0017] More preferably, the addition amount of the catalyst is 25% of the total mass of substance A.

[0018] In the present invention, the ether substances A and B are subjected to ring-opening condensation under the action of an acid catalyst to synthesize a long-chain olefin polyether, and then combined with the alcohol hydroxyl groups and phenolic hydroxyl groups on lignin, so that the modified lignin has a stronger dispersion ability than ordinary lignin.

[0019] Compared with the prior art, due to the introduction of more active branched structures, the modified lignin has more adsorption sites on the concrete surface, better compatibility, and excellent versatility; at the same time, its higher surface activity and air-entraining effect result in a significant water-reducing effect.

[0020] Preferably, the ether unsaturated macromonomer is at least one of isopentenol polyoxyethylene ether, methyl allyl polyoxyethylene ether, isobutene polyoxyethylene ether, and polyallyl glycidyl ether.

[0021] More preferably, the ether unsaturated macromonomer is polyallyl glycidyl ether, and the structural general formula of the polyallyl glycidyl ether is C3H5(OCH2CH(OH)CH2O) n H.

[0022] Preferably, the molecular weight of the ether unsaturated macromonomer is 1500 - 3000 Da;

[0023] Further preferably, the molecular weight of the ether unsaturated macromonomer is 2000-2300 Da.

[0024] The present invention does not make special limitations on the source of the polyallyl glycidyl ether, and it can be obtained by commercial purchase, including but not limited to being purchased from Shanghai Kaisai Chemical Co., Ltd.

[0025] Preferably, the carboxylic acid unsaturated small monomer is an acrylic acid monomer.

[0026] Preferably, the molar ratio of the modified lignin to the ether unsaturated macromonomer is 1:(2.2-5);

[0027] Further preferably, the molar ratio of the modified lignin to the ether unsaturated macromonomer is 1:3.

[0028] The applicant adjusts the proportions of the modified lignin, the ether unsaturated macromonomer, and the carboxylic acid unsaturated small monomer during the free radical polymerization process to improve the molecular weight and versatility of the synthesized product. At this time, due to the hydrophobic structure, the modified lignin is surrounded by hydrophilic polyethers in the molecular center, forming a claw-shaped branched structure, which increases the surface activity of the generated bio-based water reducer modified polyether lignin and improves the dispersion effect. At the same time, due to the addition of the short-chain branched structure, the entanglement effect between molecules during aggregation is weakened, and the degree of volume compression is smaller. Coupled with the strong supporting effect of the lignin molecule itself, the structure of the synthesized bio-based water reducer is more compact and three-dimensional, with higher steric hindrance, preventing the settlement of concrete particles and maintaining high fluidity.

[0029] Preferably, the initiator is at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate;

[0030] The chain transfer agent is at least one of sodium methallyl sulfonate, mercaptoacetic acid, 2-mercaptopropionic acid, and mercaptoethanol;

[0031] The reducing agent is at least one of sodium formaldehyde sulfoxylate, L-ascorbic acid, sodium hydrosulfite, and ferrous sulfate;

[0032] The pH regulator is at least one of hydroxides.

[0033] Further preferably, the initiator is sodium persulfate;

[0034] The chain transfer agent is sodium methallyl sulfonate;

[0035] The reducing agent is L-ascorbic acid;

[0036] The pH regulator is sodium hydroxide.

[0037] More preferably, the addition amount of the initiator is 3% of the total mass of the monomers;

[0038] The addition amount of the chain transfer agent is 1.3% of the total mass of the monomers;

[0039] The addition amount of the reducing agent is 0.6% of the total mass of the monomers;

[0040] The addition weight portion of the pH regulator is 3 parts.

[0041] On the other hand, the present invention provides a preparation method of a bio-based water reducer with a claw-shaped branched structure, comprising the following steps: under alkaline conditions, controlling the temperature at about 80 - 90 °C, adding modified lignin and ether-based unsaturated macromonomers, adding deionized water until it becomes a solution state, adding an initiator, then slowly dropping carboxylic acid-based unsaturated small monomers, adding a chain transfer agent and a reducing agent, reacting for 2 - 3 h, and after the reaction is completed, adding a pH regulator to adjust the pH to 6.5 - 7, finally synthesizing the bio-based water reducer with a claw-shaped branched structure.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] (1) The bio-based water reducer with a claw-shaped branched structure provided by the present invention modifies the commonly used lignin in the prior art by introducing more active branched structures, enabling it to have higher surface activity and air-entraining effect, and significantly improving the water-reducing effect.

[0044] (2) The bio-based water reducer with a claw-shaped branched structure provided by the present invention effectively maintains the strong supporting effect of the lignin molecules themselves by regulating the polymerization ratio of modified lignin and ether-based unsaturated macromonomers, making the synthesized water reducer more stable and more applicable.

[0045] (3) The bio-based water reducer with a claw-shaped branched structure provided by the present invention is different from the commonly used branched-structure water reducers. The synthesized water reducer of the present invention adds more short-chain branched structures, weakening the entanglement effect between molecules during agglomeration and reducing the degree of volume compression. Based on the strong supporting effect of the lignin molecules themselves, it can effectively prevent the settlement of concrete particles and maintain a large fluidity.

[0046] (4) The bio-based water reducer with a claw-shaped branched structure provided by the present invention is an excellent bio-based water reducer, which can achieve excellent fluidity of neat paste. By forming a thick adsorption layer on the surface of cement, it provides a steric hindrance effect, has excellent water-reducing performance, and is green and environmentally friendly. Specific Embodiments

[0047] The following will illustrate the present invention in combination with specific implementation schemes. It should be noted that the following examples are examples of the present invention, only used to illustrate the present invention, and not used to limit the present invention. Other combinations and various improvements within the concept of the present invention can be made without departing from the main idea or scope of the present invention.

[0048] The preparation steps of the following modified lignins A, B, C, D, and E are as follows:

[0049] The substance A is polyallyl glycidyl ether, the substance B is epichlorobutane, and the catalyst is boron trifluoride diethyl etherate.

[0050] 1. The preparation steps of modified lignin A are as follows: First, add 0.1 mol of substance A to a reaction flask, heat it to melt at 60 °C, then add the catalyst and 0.11 mol of substance B and react for 2 h, and then add 0.6 mol of lignin and react at 80 °C for 3 h to obtain modified lignin A.

[0051] 2. The preparation steps of modified lignin B are as follows: The preparation steps of modified lignin B are the same as those of modified lignin A, where the molar ratios of substance A, substance B, and lignin are 1:1:0.5, respectively.

[0052] 3. The preparation steps of modified lignin C are as follows: The preparation steps of modified lignin C are the same as those of modified lignin A, where the molar ratios of substance A, substance B, and lignin are 1:1.3:0.7, respectively.

[0053] 4. The preparation steps of modified lignin D are as follows: The preparation steps of modified lignin D are the same as those of modified lignin A, using substance A2 to replace substance A, and substance A2 is polyallyl glycidyl ether with a molecular weight < 1000.

[0054] 5. The preparation steps of modified lignin E are as follows: The preparation steps of modified lignin E are the same as those of modified lignin A, using substance A3 to replace substance A, and substance A3 is polyallyl glycidyl ether with a molecular weight > 3000.

[0055] In the following examples and comparative examples, unless otherwise specified, the ether unsaturated macromonomer is polyallyl glycidyl ether, the carboxylic acid unsaturated monomer is acrylic acid, the initiator is sodium persulfate, the chain transfer agent is sodium methallyl sulfonate, the reducing agent is L-ascorbic acid, and the pH regulator is 20 wt% sodium hydroxide solution.

[0056] Example 1

[0057] A bio-based water reducer with a claw-shaped branched structure, and the water reducer comprises the following raw materials in parts by weight: 100 parts of modified lignin A, 100 parts of ether unsaturated macromonomer, 15 parts of carboxylic acid unsaturated monomer, 6 parts of initiator, 2.8 parts of chain transfer agent, 0.7 part of reducing agent, 3 parts of pH regulator, and 270 parts of deionized water.

[0058] The preparation method of the water reducer in this embodiment includes the following steps: under alkaline conditions, control the temperature at about 85 °C, add modified lignin A and ether unsaturated macromonomer, add deionized water until it becomes a solution state, add an initiator, then slowly dropwise add carboxylic acid unsaturated small monomer, add a chain transfer agent and a reducing agent, react for 2.5 h, after the reaction is completed, add a pH regulator to adjust the pH to 7, and finally synthesize the bio-based water reducer with a claw-shaped branched structure.

[0059] Example 2

[0060] A bio-based water reducer with a claw-shaped branched structure, the water reducer includes the following raw materials in parts by weight: 150 parts of modified lignin A, 100 parts of ether unsaturated macromonomer, 5 parts of carboxylic acid unsaturated small monomer, 7.5 parts of initiator, 3.3 parts of chain transfer agent, 0.8 part of reducing agent, 1 part of pH regulator and 200 parts of deionized water.

[0061] The preparation method of the water reducer in this embodiment includes the following steps: under alkaline conditions, control the temperature at about 80 °C, add modified lignin A and ether unsaturated macromonomer, add deionized water until it becomes a solution state, add an initiator, then slowly dropwise add carboxylic acid unsaturated small monomer, add a chain transfer agent and a reducing agent, react for 2 h, after the reaction is completed, add a pH regulator to adjust the pH to 6.5, and finally synthesize the bio-based water reducer with a claw-shaped branched structure.

[0062] Example 3

[0063] A bio-based water reducer with a claw-shaped branched structure, the water reducer includes the following raw materials in parts by weight: 50 parts of modified lignin A, 75 parts of ether unsaturated macromonomer, 20 parts of carboxylic acid unsaturated small monomer, 3.8 parts of initiator, 1.9 parts of chain transfer agent, 0.4 part of reducing agent, 5 parts of pH regulator and 350 parts of deionized water.

[0064] The preparation method of the water reducer in this embodiment includes the following steps: under alkaline conditions, control the temperature at about 90 °C, add modified lignin A and ether unsaturated macromonomer, add deionized water until it becomes a solution state, add an initiator, then slowly dropwise add carboxylic acid unsaturated small monomer, add a chain transfer agent and a reducing agent, react for 3 h, after the reaction is completed, add a pH regulator to adjust the pH to 7, and finally synthesize the bio-based water reducer with a claw-shaped branched structure.

[0065] Example 4

[0066] A bio-based water reducer with a claw-shaped branched structure, the water reducer includes the following raw materials in parts by weight: 100 parts of modified lignin B, 100 parts of ether unsaturated macromonomer, 15 parts of carboxylic acid unsaturated small monomer, 6 parts of initiator, 2.8 parts of chain transfer agent, 0.7 part of reducing agent, 3 parts of pH regulator and 270 parts of deionized water.

[0067] The preparation method of the water reducing agent in this example includes the following steps: Under alkaline conditions, control the temperature at about 85°C, add modified lignin B and ether unsaturated macromonomer, add deionized water until it becomes a solution state, add an initiator, then slowly dropwise add carboxylic acid unsaturated small monomer, add a chain transfer agent and a reducing agent, react for 2.5 h, after the reaction is completed, add a pH regulator to adjust the pH to 7, and finally synthesize the bio-based water reducing agent with a claw-shaped branched structure.

[0068] Example 5

[0069] A bio-based water reducing agent with a claw-shaped branched structure, the water reducing agent includes the following raw materials in parts by weight: 100 parts of modified lignin C, 100 parts of ether unsaturated macromonomer, 15 parts of carboxylic acid unsaturated small monomer, 6 parts of initiator, 2.8 parts of chain transfer agent, 0.7 part of reducing agent, 3 parts of pH regulator, and 270 parts of deionized water.

[0070] The preparation method of the water reducing agent in this example includes the following steps: Under alkaline conditions, control the temperature at about 85°C, add modified lignin C and ether unsaturated macromonomer, add deionized water until it becomes a solution state, add an initiator, then slowly dropwise add carboxylic acid unsaturated small monomer, add a chain transfer agent and a reducing agent, react for 2.5 h, after the reaction is completed, add a pH regulator to adjust the pH to 7, and finally synthesize the bio-based water reducing agent with a claw-shaped branched structure.

[0071] Comparative Example 1

[0072] A bio-based water reducing agent with a claw-shaped branched structure, the water reducing agent includes the following raw materials in parts by weight: 100 parts of lignin, 100 parts of ether unsaturated macromonomer, 15 parts of carboxylic acid unsaturated small monomer, 6 parts of initiator, 2.8 parts of chain transfer agent, 0.7 part of reducing agent, 3 parts of pH regulator, and 270 parts of deionized water.

[0073] The preparation method of the water reducing agent in this comparative example is the same as that in Example 1.

[0074] Example 6

[0075] A bio-based water reducing agent with a claw-shaped branched structure, the water reducing agent includes the following raw materials in parts by weight: 140 parts of modified lignin A, 60 parts of ether unsaturated macromonomer, 20 parts of carboxylic acid unsaturated small monomer, 6 parts of initiator, 2.9 parts of chain transfer agent, 0.7 part of reducing agent, 3 parts of pH regulator, and 270 parts of deionized water.

[0076] The preparation method of the water reducing agent in this example is the same as that in Example 1.

[0077] Example 7

[0078] A bio-based water reducer with a claw-shaped branched structure, the water reducer comprising the following raw materials in parts by weight: 100 parts of modified lignin A, 235 parts of ether-based unsaturated macromonomer, 7 parts of carboxylic acid-based unsaturated small monomer, 10.1 parts of initiator, 4.4 parts of chain transfer agent, 1 part of reducing agent, 5 parts of pH regulator, and 350 parts of deionized water.

[0079] The preparation method of the water reducer in this example is the same as that in Example 1.

[0080] Example 8

[0081] A bio-based water reducer with a claw-shaped branched structure, the water reducer comprising the following raw materials in parts by weight: 100 parts of modified lignin D, 100 parts of ether-based unsaturated macromonomer, 15 parts of carboxylic acid-based unsaturated small monomer, 6 parts of initiator, 2.8 parts of chain transfer agent, 0.7 part of reducing agent, 3 parts of pH regulator, and 270 parts of deionized water.

[0082] The preparation method of the water reducer in this example comprises the following steps: under alkaline conditions, control the temperature at about 85°C, add modified lignin D and ether-based unsaturated macromonomer, add deionized water until it becomes a solution state, add the initiator, then slowly drop in the carboxylic acid-based unsaturated small monomer, add the chain transfer agent and the reducing agent, react for 2.5 h, after the reaction is completed, add the pH regulator to adjust the pH to 7, and finally synthesize the bio-based water reducer with the claw-shaped branched structure.

[0083] Example 9

[0084] A bio-based water reducer with a claw-shaped branched structure, the water reducer comprising the following raw materials in parts by weight: 100 parts of modified lignin E, 100 parts of ether-based unsaturated macromonomer, 15 parts of carboxylic acid-based unsaturated small monomer, 6 parts of initiator, 2.8 parts of chain transfer agent, 0.7 part of reducing agent, 3 parts of pH regulator, and 270 parts of deionized water.

[0085] The preparation method of the water reducer in this example comprises the following steps: under alkaline conditions, control the temperature at about 85°C, add modified lignin E and ether-based unsaturated macromonomer, add deionized water until it becomes a solution state, add the initiator, then slowly drop in the carboxylic acid-based unsaturated small monomer, add the chain transfer agent and the reducing agent, react for 2.5 h, after the reaction is completed, add the pH regulator to adjust the pH to 7, and finally synthesize the bio-based water reducer with the claw-shaped branched structure.

[0086] Performance test:

[0087] Mix the water reducer obtained in each example with concrete according to a dosage of 1 wt%.

[0088] (1) Net paste fluidity: Test according to the standard GB / T 8077-2012;

[0089] (2) Concrete performance test: The water reduction rate, slump, and compressive strength were tested according to the standard GB / T 8076-2008;

[0090] The specific test results are shown in Tables 1 and 2.

[0091] Table 1

[0092] Net paste fluidity (mm) Water reducing rate (%) Example 1 286 29.1 Example 2 278 28.4 Example 3 280 28.6 Example 4 261 27.2 Example 5 266 27.5 Comparative Example 1 230 25.4 Example 6 247 27.8 Example 7 242 27.6 Example 8 220 26.5 Example 9 224 26.9

[0093] Table 2

[0094]

[0095] As can be seen from the above Tables 1 and 2, the water reducer provided by the present invention as a whole has an excellent water reduction effect on concrete. In Table 1, by comparing Examples 1-5 with Comparative Example 1, it can be seen that the water reducer synthesized from modified lignin provided by the present invention has better dispersion performance, excellent fluidity of neat cement, and a higher water reduction rate, while the dispersibility of Comparative Example 1 is relatively low; by comparing Examples 1-5 with Examples 8 and 9, it can be seen that when the molecular weight of the grafted monomer in the modified lignin is moderate, it is beneficial for the modified lignin to play a strong dispersion role in the water reducer, and the fluidity of neat cement is better. In Table 2, by comparing Examples 1-5 with Comparative Example 1, it can be seen that the water reducer provided by the present invention has an obvious enhancing effect on the strength of concrete; by comparing Examples 1-5 with Examples 6 and 7, it can be seen that the concrete dispersed by the water reducer prepared according to the preferred ratio provided by the present invention has a larger slump, and the slump after 1 h is better, and the water reduction performance is excellent.

[0096] The above is only a preferred embodiment of the present invention, and does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to be equivalent embodiments without departing from the technical solution of the present invention. However, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A preparation method of a bio-based water reducer with a claw-shaped branched structure, characterized in that, It includes the following steps: Under alkaline conditions, control the temperature at 80 - 90 °C. Add modified lignin and ether-based unsaturated macromonomers into the reactor, add deionized water until it becomes a solution state, add an initiator, then slowly dropwise add carboxylic acid-based unsaturated small monomers, add a chain transfer agent and a reducing agent, react for 2 - 3 h. After the reaction is completed, add a pH regulator to adjust the pH to 6.5 - 7, and finally synthesize the bio-based water reducer with a claw-shaped branched structure; The water reducer includes the following raw materials in parts by weight: 50 - 150 parts of modified lignin, 60 - 235 parts of ether-based unsaturated macromonomers, 5 - 20 parts of carboxylic acid-based unsaturated small monomers, 3 - 7.5 parts of initiator, 1 - 3.5 parts of chain transfer agent, 0.4 - 0.8 parts of reducing agent, 1 - 5 parts of pH regulator, and 200 - 350 parts of deionized water; The modified lignin is prepared by modifying lignin with substance A and substance B; The preparation steps of the modified lignin are as follows: First, add substance A into a reaction flask and heat it to melt at 50 - 70 °C, then add a catalyst and substance B and react for 1.5 - 3 h, then add lignin and react at 70 - 85 °C for 2 - 4 h, and cool to obtain the modified lignin; The molar ratio of substance A, substance B to lignin is 1:(1 - 1.3):(0.5 - 0.7); Substance A is polyallyl glycidyl ether with a molecular weight of 1500 - 3000 Da; Substance B is epichlorobutane; The ether-based unsaturated macromonomer is polyallyl glycidyl ether; The molecular weight of the ether-based unsaturated macromonomer is 1500 - 3000 Da; The carboxylic acid-based unsaturated small monomer is acrylic acid monomer; The molar ratio of the modified lignin, ether-based unsaturated macromonomer, and carboxylic acid-based unsaturated small monomer is 1:(2 - 3.5):(9.6 - 10).

2. The preparation method of the bio-based water reducing agent with a claw-shaped branched structure according to claim 1, characterized in that, The initiator is at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate; The chain transfer agent is at least one of sodium methallyl sulfonate, mercaptoacetic acid, 2-mercaptopropionic acid, and mercaptoethanol; The reducing agent is at least one of sodium formaldehyde sulfoxylate, L-ascorbic acid, sodium hydrosulfite, and ferrous sulfate; The pH regulator is at least one of hydroxides.

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