阅读说明：本技术 一种基于木质素的聚羧酸减水剂及其制备方法和应用 (Lignin-based polycarboxylate superplasticizer and preparation method and application thereof ) 是由 郑大锋 钟定明 李琼 杨东杰 姚日晖 于 2020-12-16 设计创作，主要内容包括：本发明属于混凝土高效减水剂技术领域,公开了一种木质素聚羧酸减水剂及其制备方法和在混凝土中的应用。本发明的基于木质素酯化物单体的聚羧酸减水剂由包括以下质量份的组分通过可逆加成-断裂链转移反应得到：1～20份不饱和的木质素酯化单体；99-70份的不饱和聚氧乙烯醚；10～18份不饱和羧酸；0.5～5份的引发剂；0.1～2份的链转移剂。所制备的木质素聚羧酸具有良好的分散性能,可以有效降低水泥浆的黏度,而且引气性良好,可以在混凝土中引入细小起泡增强砂浆的保温性能。(The invention belongs to the technical field of concrete high-efficiency water reducing agents, and discloses a lignin polycarboxylic acid water reducing agent, a preparation method thereof and application thereof in concrete. The polycarboxylate superplasticizer based on the lignin esterified monomer is prepared from the following components in parts by mass through a reversible addition-fragmentation chain transfer reaction: 1-20 parts of unsaturated lignin esterified monomer; 99-70 parts of unsaturated polyoxyethylene ether; 10-18 parts of unsaturated carboxylic acid; 0.5-5 parts of an initiator; 0.1-2 parts of chain transfer agent. The prepared lignin polycarboxylic acid has good dispersing performance, can effectively reduce the viscosity of cement paste, has good air entraining performance, and can introduce fine bubbles into concrete to enhance the heat insulation performance of mortar.)

1. A polycarboxylic acid water reducing agent based on lignin is characterized by comprising the following components in parts by mass: 1-20 parts of unsaturated lignin esterified monomer and 99-70 parts of unsaturated polyoxyethylene ether; 10-18 parts of unsaturated carboxylic acid; 0.5-5 parts of an initiator; 0.1-2 parts of chain transfer agent.

2. The lignin-based polycarboxylate water reducer of claim 1, characterized in that:

the unsaturated polyoxyethylene ether is at least one of vinyl butyl ether polyoxyethylene ether, methyl allyl polyoxyethylene ether, isopentenyl polyoxyethylene ether and allyl polyoxyether, and the unsaturated carboxylic acid is at least one of acrylic acid, methacrylic acid, maleic anhydride and carboxylate thereof.

3. The lignin-based polycarboxylate superplasticizer according to claim 1 or 2, wherein said unsaturated lignin esterified monomer is obtained by the following method steps: dissolving an acid-binding agent and lignin in an organic solvent, adding an unsaturated acylation reagent, and reacting to obtain an unsaturated lignin esterified substance.

4. The lignin-based polycarboxylate water reducer of claim 3, characterized in that:

the mass ratio of the acid-binding agent to the lignin to the unsaturated acylation reagent is 10-30: 100: 10 to 30.

5. The lignin-based polycarboxylate water reducer of claim 3, characterized in that:

the lignin is at least one of alkali lignin, enzymolysis lignin and lignosulfonate;

the acid-binding agent is at least one of triethylamine, pyridine, morpholine, diethylamine, triethylene diamine, N, N-diisopropylethylamine and isopropylamine;

the unsaturated acylating reagent is one of acryloyl chloride and maleic anhydride.

6. The lignin-based polycarboxylate water reducer of claim 5, characterized in that:

the reaction is carried out for 5-8 h at 30-50 ℃.

7. The lignin-based polycarboxylate water reducer of claim 1, characterized in that:

the initiator is at least one of azobisisoheptonitrile, dimethyl azobisisobutyrate, azobisisobutyronitrile, azoisobutyronitrile cyano formamide and azodicyclohexyl formonitrile;

the chain transfer agent is at least one of biscarboxymethyltrithiocarbonate, dithiobenzoic acid, dithioester and trithiocarbonate.

8. A method for preparing the lignin-based polycarboxylate superplasticizer according to any one of claims 1 to 7, which is characterized by comprising the following steps:

dissolving unsaturated polyoxyethylene ether in an organic solvent, carrying out stirring reaction under the action of an initiator and a chain transfer agent, then adding unsaturated carboxylic acid, supplementing the initiator, continuing stirring reaction, supplementing the initiator, adding an unsaturated lignin esterified monomer, and continuing stirring reaction to obtain the lignin polycarboxylic acid product.

9. The method of claim 8, wherein:

the first stirring reaction condition is that the reaction is carried out for 6-10 h at 70-90 ℃; the second stirring reaction is carried out for 4-8 h at the temperature of 70-90 ℃; the first stirring reaction condition is that the reaction lasts for 8-12 h at 70-90 ℃;

the organic solvent is at least one of dimethyl amide, N, N-dimethyl acetamide, N, N-dimethyl propionamide and dimethyl sulfoxide.

10. Use of a lignin-based polycarboxylate superplasticizer according to any one of claims 1 to 7 in thermal mortar.

Technical Field

The invention belongs to the technical field of high-efficiency water reducing agents in concrete, and particularly relates to a lignin-based polycarboxylic acid water reducing agent and a preparation method and application thereof.

Background

With the increasing shortage of natural resources, our country strongly pursues energy-saving and emission-reducing policies, and begins to pay attention to the problem of energy consumption in buildings, so that green buildings are actively popularized. Generally, the heat insulation of the building materials is realized by continuously improving the production process on the basis of the prior art and improving the heat insulation quality of the building materials, so that a large amount of building heat insulation materials appear. The polycarboxylate superplasticizer is the most common additive of building thermal insulation materials at present, and has high water reducing rate, strong dispersing performance, better cement adaptability and other excellent performances. Thus, water reducers based on polycarboxylic acids have been widely used in engineering during the last decade. However, polycarboxylic acid type high efficiency water reducing agents have some disadvantages. For example, it is difficult to solve the problem of excessive viscosity of concrete at low water-cement ratio and the air-entraining property is poor. The concrete prepared under the condition of low water cement ratio has larger viscosity, is difficult to construct and pump, and cannot achieve good heat preservation effect.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention mainly aims to provide a lignin-based polycarboxylate water reducer.

The water reducing agent can successfully introduce a lignin structure into a molecular structure of polycarboxylic acid, and changes the structure and properties of the polycarboxylic acid water reducing agent. The obtained water reducing agent has good dispersibility and excellent water retention property, has a certain effect of reducing the viscosity of a cement system, and increases the consumption of lignin, which is beneficial to obviously reducing the viscosity of cement paste and reducing the energy consumption of mortar in the stirring and pumping processes.

The invention also aims to provide a preparation method of the lignin-based polycarboxylate superplasticizer. The method combines the hydrophobicity of lignin with the high dispersibility of the polycarboxylic acid high-efficiency water reducing agent, and adjusts the hydrophilic and hydrophobic values of the whole molecule, and specifically, the lignin and the unsaturated acylate undergo esterification reaction to obtain an unsaturated lignin esterified monomer containing double bonds; and then carrying out certain block polymerization reaction on short-chain unsaturated polyether and unsaturated carboxylic acid, and finally adding the prepared unsaturated lignin esterified monomer to carry out block grafting reaction to obtain the lignin polycarboxylic acid water reducing agent.

The invention further aims to provide application of the lignin-based polycarboxylate superplasticizer in thermal mortar.

The purpose of the invention is realized by the following scheme:

a polycarboxylic acid water reducing agent based on lignin is specifically composed of the following components in parts by mass: 1-20 parts of unsaturated lignin esterified monomer and 99-70 parts of unsaturated polyoxyethylene ether; 10-18 parts of unsaturated carboxylic acid; 0.5-5 parts of an initiator; 0.1-2 parts of chain transfer agent.

Further, the unsaturated polyoxyethylene ether is at least one of vinyl butyl ether polyoxyethylene ether, methyl allyl polyoxyethylene ether, isopentene polyoxyethylene ether and allyl polyoxyether, and the molecular weight of the unsaturated polyoxyethylene ether is 400-5000;

further, the unsaturated carboxylic acid is at least one of acrylic acid, methacrylic acid, maleic anhydride and carboxylate thereof.

Further, the initiator is at least one of azobisisoheptonitrile, dimethyl azobisisobutyrate, azobisisobutyronitrile, azoisobutyronitrile, azodicyclohexyl carbonitrile;

further, the chain transfer agent is at least one of biscarboxymethyltrithiocarbonate, dithiobenzoic acid, dithioester and trithiocarbonate.

Further, the unsaturated lignin esterified monomer is obtained by the following method steps: dissolving an acid-binding agent and lignin in an organic solvent, adding an unsaturated acylation reagent, and reacting to obtain an unsaturated lignin esterified substance;

further, the mass ratio of the acid-binding agent to the lignin to the unsaturated acylation reagent is 10-30: 100: 10-30;

further, the reaction is carried out for 5-8 h at 30-50 ℃.

Further, the lignin is at least one of alkali lignin, enzymatic hydrolysis lignin and lignosulfonate;

further, the acid-binding agent is at least one of triethylamine, pyridine, morpholine, diethylamine, triethylene diamine, N, N-diisopropylethylamine and isopropylamine;

further, the organic solvent is at least one of dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, dimethylformamide and dioxane;

further, after the reaction is finished, precipitating with an alkaline solution to obtain a product; further, the alkaline aqueous solution is NaHCO₃Solution, Na₂CO₃Solution and KHCO₃At least one of the solutions.

Further, the unsaturated acylating reagent is one of acryloyl chloride and maleic anhydride.

The invention relates to a preparation method of a lignin polycarboxylate superplasticizer, which comprises the following steps:

dissolving unsaturated polyoxyethylene ether in an organic solvent, carrying out stirring reaction under the action of an initiator and a chain transfer agent, then adding unsaturated carboxylic acid, supplementing the initiator, continuing stirring reaction, then supplementing the initiator, adding an unsaturated lignin esterified monomer, and continuing stirring reaction to obtain the lignin polycarboxylic acid product.

The first stirring reaction condition is that the reaction is carried out for 6-10 h at 70-90 ℃; the second stirring reaction is carried out for 4-8 h at the temperature of 70-90 ℃; the first stirring reaction condition is that the reaction lasts for 8-12 hours at 70-90 ℃.

The organic solvent is at least one of dimethyl amide, N, N-dimethylacetamide, N, N-dimethylpropionamide and dimethyl sulfoxide.

The application of the lignin-based polycarboxylate superplasticizer in thermal mortar is provided.

The innovation of the invention is as follows: firstly, block unsaturated polyoxyethylene ether and unsaturated carboxylic acid are polymerized and then grafted to unsaturated lignin esterified substance, so that a novel lignin polycarboxylic acid polymerization method is provided; and secondly, the lignin polycarboxylic acid is applied to a heat-insulating concrete system.

The mechanism of the invention is as follows: the invention improves the molecular structure of the polycarboxylic acid water reducing agent by using the three-dimensional molecular structure and good biocompatibility of the lignin, so that the surface activity of the polycarboxylic acid is obviously improved, and the air entraining capability is enhanced. The mortar is fluffy by introducing tiny and compact bubbles into the concrete, and the air is a poor conductor for heat transfer, so that the bubbles in the mortar are more, the heat conductivity of the mortar is poor, the heat conductivity coefficient of the mortar is reduced, and the purpose of ensuring that the mortar has a good heat insulation effect is achieved.

The invention has the beneficial effects that: the characteristics of different molecules can be fully exerted by combining the block unsaturated polyoxyethylene ether, the unsaturated carboxylic acid and the unsaturated lignin esterified substance, the mixing amount range is large, the workability of cement is good, and the performance of the water reducing agent is improved; the product belongs to a functional polycarboxylate superplasticizer, has good compatibility with concrete, has no layered segregation phenomenon, and improves the heat-insulating capacity of the concrete to a certain extent.

Drawings

FIG. 1 is an infrared spectrum of lignin polycarboxylic acid prepared in example 1, example 2 and comparative example 1 of the present invention.

FIG. 2 is a graph showing the surface tension test of lignin polycarboxylic acids prepared in example 1, example 2 and comparative example 1.

FIG. 3 is a graph showing the foaming properties of lignin polycarboxylic acids prepared in example 1, example 2 and comparative example 1.

FIG. 4 is a graph showing the net pulp fluidity of lignin polycarboxylic acids prepared in example 1, example 2 and comparative example 1.

FIG. 5 is a graph showing the results of the net flow time test of lignin polycarboxylic acids prepared in example 1, example 2 and comparative example 1.

Detailed Description

In order to make the present invention more easily understood, the present invention will be further described with reference to the following examples and drawings, but the embodiments are not limited thereto.

The lignin esters in the examples were prepared by the following method

50g of alkali lignin (KL) and 300g of dimethyl sulfoxide are mixed and mechanically stirred to completely dissolve the alkali lignin. An ice bath was performed under nitrogen and 40g of triethylamine, an acid-binding agent, was added and the reaction mixture was stirred for 1 h. Then 36g of acryloyl chloride was added dropwise to the above mixture over a period of 1 hour. The reaction was further carried out at 40 ℃ for 5 hours. The product was then purified with saturated NaHCO₃The solution was precipitated, filtered, and washed repeatedly with distilled water. The precipitate was dried under vacuum to constant weight to obtain unsaturated lignin esterified product (ACL).

Example 1: preparation of lignin polycarboxylic acid water reducing agent

98g of TPEG-2400 was dissolved in 300ml of dimethylformamide, and N was passed through₂And (2) performing protection, adding 0.98g of initiator azobisisobutyronitrile and 1g of chain transfer agent bis (carboxymethyl trithiocarbonate), stirring and reacting for 8 hours at 80 ℃, then adding 10g of acrylic acid, supplementing 0.1g of initiator, continuing to stir and react for 4 hours, finally adding 2g of unsaturated lignin esterified monomer, supplementing 0.02g of initiator azobisisobutyronitrile, after reacting for 8 hours, performing rotary evaporation to remove the solvent, washing with isopropanol for multiple times, collecting the product, and drying in a vacuum oven at 50 ℃ to obtain the lignin polycarboxylic acid product.

Example 2: preparation of lignin polycarboxylic acid water reducing agent

95g of TPEG-2400 was dissolved in 300ml of dimethylformamide, and N was passed through₂Protecting, adding 0.95g of initiator azobisisobutyronitrile and 1g of chain transfer agent bis (carboxymethyl trithiocarbonate), stirring and reacting for 8 hours at 80 ℃, then adding 10g of acrylic acid, supplementing 0.1g of initiator, continuing to stir and react for 4 hours, finally adding 5g of unsaturated lignin esterified monomer, supplementing 0.05g of initiator azobisisobutyronitrile, after reacting for 8 hours, performing rotary evaporation to remove solvent, washing with isopropanol for multiple times, collecting the product, and drying in a vacuum oven at 50 ℃ to obtain the product, namely the woodAn aliphatic polycarboxylic acid.

Example 3: preparation of lignin polycarboxylic acid water reducing agent

90g of TPEG-2400 was dissolved in 300ml of dimethylformamide, and N was passed through₂And (2) protecting, adding 0.9g of initiator azobisisobutyronitrile and 1g of chain transfer agent bis (carboxymethyl trithiocarbonate), stirring and reacting for 8 hours at 80 ℃, then adding 10g of acrylic acid, supplementing 0.1g of initiator, continuing to stir and react for 4 hours, finally adding 10g of unsaturated lignin esterified monomer, supplementing 0.1g of initiator azobisisobutyronitrile, after reacting for 8 hours, performing rotary evaporation to remove solvent, washing with isopropanol for multiple times, collecting a product, and drying in a vacuum oven at 50 ℃ to obtain the lignin polycarboxylic acid product.

Example 4: preparation of lignin polycarboxylic acid water reducing agent

85g of TPEG-2400 was dissolved in 300ml of dimethylformamide, and N was passed through₂And (2) protecting, adding 0.85g of initiator azobisisobutyronitrile and 1g of chain transfer agent bis (carboxymethyl trithiocarbonate), stirring and reacting for 8 hours at 80 ℃, then adding 10g of acrylic acid, supplementing 0.1g of initiator, continuing to stir and react for 4 hours, finally adding 15g of unsaturated lignin esterified monomer, supplementing 0.15g of initiator azobisisobutyronitrile, after reacting for 8 hours, performing rotary evaporation to remove solvent, washing with isopropanol for multiple times, collecting a product, and drying in a vacuum oven at 50 ℃ to obtain the lignin polycarboxylic acid product.

Example 5: preparation of lignin polycarboxylic acid water reducing agent

80g of TPEG-2400 was dissolved in 300ml of dimethylformamide, and N was passed through₂And (2) protecting, adding 0.8g of initiator azobisisobutyronitrile and 1g of chain transfer agent bis (carboxymethyl trithiocarbonate), stirring and reacting for 8 hours at 80 ℃, then adding 10g of acrylic acid, supplementing 0.1g of initiator, continuing to stir and react for 4 hours, finally adding 20g of unsaturated lignin esterified monomer, supplementing 0.2g of initiator azobisisobutyronitrile, after reacting for 8 hours, performing rotary evaporation to remove solvent, washing with isopropanol for multiple times, collecting a product, and drying in a vacuum oven at 50 ℃ to obtain the lignin polycarboxylic acid product.

Comparative example 1: 100g of TPEG-2400 was dissolved in 300ml of dimethylformamide, and N was passed through₂Go on to protectAnd (2) adding 1g of initiator azobisisobutyronitrile and 1g of chain transfer agent bis (carboxymethyl trithiocarbonate), stirring and reacting for 8 hours at the temperature of 80 ℃, then adding 10g of acrylic acid, supplementing 0.1g of initiator, continuing stirring and reacting for 4 hours, washing with isopropanol for multiple times after rotary evaporation and dissolution removal, collecting a product, and drying in a vacuum oven at the temperature of 50 ℃ to obtain the lignin polycarboxylic acid product.

In order to determine the structure, FTIR test was performed on the lignin polycarboxylic acid synthesized by the present invention, and the results are shown in FIG. 1, and a series of tests such as surface tension, foaming height, net slurry fluidity, net slurry flow time, thermal mortar performance, etc. were performed on the prepared lignin polycarboxylic acid, and the results are shown in FIGS. 2 to 5 and Table 1

As can be seen from the absorption peaks in the IR spectrum of FIG. 1, the lignin polycarboxylic acids synthesized in example 1, example 2 and example 3 were at 650cm^-1～900cm^-1And 1500cm^-1The absorption peak near the position is the absorption peak of a benzene ring, which indicates that the lignin is successfully introduced into the polycarboxylic acid.

As can be seen from the surface tension test results in FIG. 2, as the lignin content increases, the surface tension of the prepared lignin polycarboxylic acid at the same concentration becomes lower and lower, the surface activity increases, and the surface activity is greatly improved compared with that of comparative example 1.

As can be seen from the foaming height in FIG. 3, the foaming performance of the prepared lignin polycarboxylic acid is better and better with the increase of the lignin dosage, compared with the comparative example 1, the foaming performance is greatly improved, and the air entraining performance is stronger, so that the heat insulation performance of the mortar can be increased to a certain extent.

As seen from the net slurry fluidity test chart of fig. 4, the lignin polycarboxylic acids prepared in examples 1 and 2 have good dispersing properties at a water-cement ratio of 0.29, which is substantially superior to the polycarboxylic acid prepared in comparative example 1.

From the emptying time test results of the neat paste of fig. 5, the cement paste of lignin polycarboxylic acid prepared in example 1 and example 2 has lower viscosity, which is beneficial to reducing energy consumption during the stirring and pumping process of concrete.

From the performance test results of the thermal insulation mortar in table 1, the lignin polycarboxylic acids prepared in examples 1 and 2 have lower compressive strength, lower dry density and smaller thermal conductivity, because the lignin polycarboxylic acids have better air-entraining performance and more fine bubbles are formed in the mortar, so that the thermal conductivity of the mortar is reduced and the thermal insulation effect is improved.

Table 1 shows the results of the performance tests of the thermal mortar prepared in examples 1 and 2 and comparative example 1.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.