CN1654407A - High efficiency straw pulp sulfonated alkali lignin water-reducing agent and method for preparing same - Google Patents

Abstract

The invention relates to a preparation method of a straw pulp sulfonated alkali lignin high-efficiency water reducer suitable for concrete or mortar in construction engineering, comprising: adding 200 parts by weight of water to 100 parts by weight of alkali lignin of straw pulp to adjust the pH value to 3 to 10, heated to 40 to 100°C, added 5 to 15 parts by weight of hydrogen peroxide, 0.1 to 2 parts by weight of transition metal ion salt, and carried out catalytic oxidation reaction for 0.5 to 1 hour; added 5 to 50 parts by weight of condensing agent, 5 ~50 parts by weight of sulfite, carry out sulfomethylation-condensation reaction for 1-5 hours; cool the reaction product to room temperature to obtain a liquid product; the obtained grass pulp sulfonated alkali lignin high-efficiency water reducer has reached the standard of GB8075-1997 The performance standard of high-efficiency superplasticizers has the advantages of high water reducing rate, moderate retardation, good slump retention, adaptability to cement and good compatibility with other high-efficiency superplasticizers.

Description

Straw pulp sulfonated alkali lignin high-efficiency water reducer and preparation method thereof

Technical field

The invention relates to a high-efficiency water reducer suitable for concrete or mortar in construction engineering and a preparation method thereof. Specifically, the by-product straw pulp alkali lignin recovered from alkaline pulping is used as raw material, and the high-efficiency water reducer for concrete is prepared through catalytic oxidation and high-efficiency sulfonation. The water reducing agent has the advantages of high water reducing rate, moderate retardation, good slump retention, adaptability to cement and good compatibility with other high-efficiency water reducing agents.

Background technique

With the rapid development of the construction industry, new requirements are constantly put forward for the performance of concrete in various aspects, such as improving the strength and wear resistance of concrete, improving the workability of fresh concrete, and reducing the slump loss during concrete transportation. Ordinary concrete has been difficult to meet the new construction technology requirements. Adding admixtures to concrete is an effective, convenient and economical method to increase concrete strength and improve various properties of concrete.

Water reducer is the most widely used admixture in concrete. Water reducers are divided into three categories: sulfonated coal tar-based water reducers, resin-based water reducers and lignin-based water reducers. The first two types of water-reducing agents have a high water-reducing rate, but the production process is complicated, the cost is high, and the slump loss is large when used in concrete. Lignosulfonate superplasticizer has the advantages of rich sources, low cost, and good concrete slump performance, but its water reducing rate is low. It is currently a hot research topic to modify it into a high-efficiency superplasticizer. Lignosulfonate can be directly derived from the by-products of acid pulping waste liquor recovery in the paper industry, but a larger amount of lignosulfonate can be obtained through the sulfonation of alkali lignin, a by-product of alkaline pulping with lower prices. Get it.

Alkali pulping (lime method, caustic soda method, caustic soda-anthraquinone method, sulfate method, etc.) is the main pulping method used in my country's paper industry, and the alkali lignin of straw pulp comes from the recycled waste liquid of alkaline pulping. Almost one ton of acid-analyzed lignin is produced for every ton of straw pulp produced. Unmodified alkali lignin has almost no utilization value. If it is chemically modified, it will be able to obtain low-cost and widely used fine chemical products (such as water reducers), which not only greatly reduces the direct discharge of papermaking black liquor. Serious pollution of the ecological environment, turning waste into treasure, and providing a renewable source of raw materials for fine chemical products.

Patent CN 1219921A provides an admixture to reduce water consumption for mixing concrete mixtures. The admixture is an alkaline solution of lignin in the form of sulfomethyl hydroxy complexation and needs to be used as a compound defoamer. Patent CN 1177617A discloses a cement dispersant, which is prepared by introducing carboxyl groups through electro-oxidation of lignin, followed by sulfomethylation reaction at 100-175°C. However, these methods have the disadvantages of complicated process and high cost.

Sulfonation is the most common method to improve the water solubility and dispersibility of alkali lignin. At present, there are mainly two kinds of sulfonation reactions of alkali lignin. One is a high-temperature sulfonation reaction at 100-170°C, using sodium sulfite to introduce a sulfonic acid group on the side chain of the benzene ring of alkali lignin:

One is to use the sulfomethylation reaction of formaldehyde and sodium sulfite below 100°C to introduce a sulfonic acid group on the benzene ring of alkali lignin:

The first modification method must be reacted under high temperature and pressure. The temperature usually needs to be 160-170°C, and it needs to be under a certain pressure. The operation process is complicated, the cost of product modification is high, and the reaction process is not suitable for large-scale production. . Although the sulfomethylation reaction at low temperature has mild reaction conditions, there are problems such as low sulfonation efficiency, low water solubility of sulfonated products, and unsatisfactory surface physical and chemical properties. The structure of alkali lignin is characterized by a high degree of condensation. The ortho and para positions of the guaiacyl and syringyl structures are occupied by methoxy groups and side chains. The methoxy group content is high and can be connected to sulfonic acid groups There are fewer positions and less activity. If the activity of alkali lignin can be improved, it will be beneficial to the sulfonation reaction and improve the efficiency of the sulfonation reaction, thereby improving the solubility and surface physical and chemical properties of the product.

Oxidation is an effective way to increase the reactivity of alkali lignin molecules. Through oxidation, the content of phenolic hydroxyl groups in lignin molecules increases, the network macromolecular structure is degraded, chemical bonds may be broken on the ether bonds, and the methoxy groups on the benzene rings may also be removed, thereby reducing the steric hindrance of the reaction. Increased reactivity points. Fenton's reagent is a strong inorganic oxidizing agent. It has the advantages of simple operation process, easy access to reactants, low cost, no need for complicated equipment, and environmental friendliness when used in oxidation reactions. It has been widely used in dyes, preservatives, and phase development. Toxic and refractory organics are treated in waste water treatment projects such as pesticides and pesticides, and there is no report on the application of Fenton reagent to the oxidation of alkali lignin.

Contents of Invention

The purpose of the present invention is to solve the problems existing in the prior art, to provide a preparation method of straw pulp sulfonated alkali lignin high-efficiency water reducer, through a simple chemical reaction process, directly modify the alkali lignin into concrete high-efficiency water reducer The water agent can give full play to the advantage of low price of alkali lignin and greatly increase the added value of alkali lignin.

The invention directly modifies extremely cheap grass pulp alkali lignin to prepare a high-efficiency water-reducing agent for concrete and mortar with high water-reducing rate, small slump loss and meeting the new requirements of the construction industry.

Another object of the present invention is to provide the straw pulp sulfonated alkali lignin superplasticizer prepared by the method.

The preparation method of straw pulp sulfonated alkali lignin superplasticizer of the present invention comprises the following steps:

(1) In 100 parts by weight of straw pulp alkali lignin, add 200 parts by weight of water, adjust the pH value to 3-10, heat to 40-100°C, add 5-15 parts by weight of hydrogen peroxide, 0.1-2 parts by weight of transition metal Ionic salt, carry out catalytic oxidation reaction for 0.5 to 1 hour;

(2) adding 5 to 50 parts by weight of condensing agent and 5 to 50 parts by weight of sulfite, and performing sulfomethylation-condensation reaction for 1 to 5 hours;

(3) the reaction product is cooled to room temperature to obtain a liquid product;

The straw pulp alkali lignin is the lignin obtained by acid precipitation of wheat straw pulp black liquor and/or rice straw pulp black liquor by alkaline process;

The transition metal ion salt adopts one or more mixtures of divalent iron ions, ferric ions, copper ions, nitrates, sulfates or hydrochlorides of manganese ions;

The condensing agent adopts terephthalenedimethanol, formaldehyde or a mixture thereof.

In step (1), acid or alkali can be used to adjust the pH value. In the present invention, NaOH or H ₂ SO ₄ is used to adjust the pH value.

Sulfite is preferably used to refer to one or more of water-soluble sulfite or bisulfite.

The water-soluble sulfite is sodium sulfite, and the water-soluble bisulfite is sodium bisulfite.

The advantages and effects created by the present invention are as follows:

The invention uses Fenton reagent to effectively improve the reactivity of alkali lignin, so that it can be efficiently sulfonated at a temperature lower than 100°C to obtain products with excellent water solubility and dispersibility, and opens up a new way for the industrial development and application of alkali lignin .

The production process of the invention is carried out under normal pressure and low temperature, and is easy to operate and control. Compared with the current common sulfonation technology of alkali lignin, it has the advantages of simple process, high sulfonation efficiency and low production cost. The product has good water solubility and improved surface physical and chemical properties. The invention is applicable to the acid analysis of lignin in all industrial straw pulp black liquors, including the lignin obtained from the acid analysis of black liquor made from alkaline wheat straw pulp and rice straw pulp.

The high-efficiency water reducer of the present invention can be added to cement mortar or concrete mixture in the form of dry powder or aqueous solution, and its dosage is 0.2%-0.5% of the cement weight, and the optimal dosage is 0.25%-0.4%.

Compared with the lignosulfonate water reducer currently on the market, the high-efficiency water reducer of the present invention can increase the fluidity of cement mortar or concrete mixture more, have greater water reducing effect, and better dispersion effect, making cement slurry or Concrete has higher compressive strength and saves more cement. The water reducing agent of the present invention has a certain retarding and water-retaining effect, and its admixture makes the cement paste or concrete have good fluidity retention performance, has the advantages of small slump loss and good adaptability to cement. The retarding superplasticizer of the present invention can be used alone or in combination with other superplasticizers, and has good compatibility with naphthalene-based superplasticizers.

Detailed ways

Example 1

First, take 500g of acid-analyzed grass pulp alkali lignin, add 1000g of water, 2mL of concentrated H ₂ SO ₄ , adjust the pH value to 5, and heat to 70°C while stirring; then add 0.8g of FeCl ₂ and 50g of hydrogen peroxide to carry out catalytic oxidation reaction 0.5 hour; finally add 50g formaldehyde and 200g sodium sulfite to carry out sulfomethylation reaction and condensation reaction for 4 hours. After cooling, the liquid product of high-efficiency water reducer can be obtained, and then the powder product can be obtained after drying.

Example 2

First, take 500g of acid-analyzed straw alkali lignin, add 1000g of water and 10g of NaOH, adjust the pH to 8, and heat to 60°C while stirring; then add 0.8g of FeCl ₂ and 50g of hydrogen peroxide, and carry out catalytic oxidation reaction for 1 hour; finally add 50g of formaldehyde, 50g of terephthalenedimethanol, and 200g of sodium sulfite were subjected to sulfomethylation and condensation reactions for 3 hours. After cooling, the concrete high-efficiency water reducer liquid product can be obtained, and then the powder product can be obtained after drying.

Example 3

First, take 500g of acid-analyzed grass pulp alkali lignin, add 1000g of water, 20g of NaOH, adjust the pH value to 10, and heat to 80°C while stirring; then add 1g of FeCl ₂ , 1g of Cu(NO ₃ ) ₂ and 75g of hydrogen peroxide for catalytic oxidation React for 0.5 hours; finally add 25g of formaldehyde, 150g of terephthalenedimethanol, 100g of sodium sulfite, and 50g of sodium bisulfite to carry out the sulfomethylation reaction and condensation reaction for 2 hours. After cooling, the concrete high-efficiency water reducer liquid product can be obtained, and then the powder product can be obtained after drying.

Example 4

First, take 500g of acid-analyzed straw alkali lignin, add 1000g of water, 4mL of concentrated H ₂ SO ₄ , adjust the pH value to 3, and heat to 90°C while stirring; then add 0.5g of FeCl ₃ , 1g of Mn(NO ₃ ) ₂ and 30g hydrogen peroxide, carry out catalytic oxidation reaction for 1 hour; finally add 100g formaldehyde, 100g sodium bisulfite, carry out sulfomethylation reaction and condensation reaction for 5 hours. After cooling, the concrete high-efficiency water reducer liquid product can be obtained, and then the powder product can be obtained after drying.

Example 5

First, take 500g of acid-analyzed grass pulp alkali lignin, add 1000g of water, 20g of NaOH, adjust the pH value to 10, and heat to 80°C while stirring; then add 0.5g of FeCl ₃ , 1g of CuSO ₄ , 1.5g of Mn(NO ₃ ) ₂ and 60g Hydrogen peroxide, carry out catalytic oxidation reaction for 0.5 hours; finally add 175g of terephthalenedimethanol, 100g of sodium bisulfite, carry out sulfomethylation reaction and condensation reaction for 5 hours. After cooling, the concrete high-efficiency water reducer liquid product can be obtained, and then the powder product can be obtained after drying.

The application properties of the high-efficiency water reducer powder product obtained in embodiment 3 are as follows:

1. When the retarding high-efficiency superplasticizer of the present invention is mixed at 0.25% to 0.4%, the water reducing rate of concrete can reach 12% to 16%, the 3-day compressive strength ratio reaches 126%, and the 7-day compressive strength ratio reaches 126%. It reached 131%, and the 28-day compressive strength ratio reached 127%.

2. When the retarding high-efficiency superplasticizer of the present invention is mixed at 0.25% to 0.4%, the water reducing rate of the mortar can reach 12% to 18%, the 3-day compressive strength ratio reaches 133%, and the 7-day compressive strength The ratio reaches 130%, and the 28-day compressive strength ratio reaches 126%.

3. The slow-setting high-efficiency superplasticizer of the present invention can prolong the initial setting time of mortar by 1 hour and 30 minutes and the final setting time by 3 hours and 30 minutes when the dosage is 0.25% to 0.4%.

The above tests were carried out in accordance with the national standard GB8075-1997 and the test methods for cement and concrete. The cement used was Jinyang Brand No. 32.5 ordinary Portland cement produced by Guangzhou Cement Factory.

Claims (5)

1, a kind of preparation method of high efficiency straw pulp sulfonated alkali lignin water-reducing agent is characterized in that may further comprise the steps:

(1) in 100 weight part straw pulp alkali lignins, add 200 weight parts waters, regulate pH value to 3～10, be heated to 40～100 ℃, add 5～15 weight part hydrogen peroxide, 0.1～2 weight part transition metal ion salt, carried out catalytic oxidation 0.5～1 hour;

(2) add 5～50 weight part condensing agents, 5～50 weight part sulphite, carried out sulfomethylation-condensation reaction 1～5 hour;

(3) the reaction product cool to room temperature is obtained liquid product;

Described straw pulp alkali lignin is the lignin that is obtained by alkaline process wheat straw black liquor and/or rice straw black liquor acid out;

One or more mixtures in nitrate, vitriol or the hydrochloride of the iron ion of described transition metal ion salt employing divalence, ferric ion, cupric ion, mn ion;

Described condensing agent adopts terephthalyl alcohol, formaldehyde or its mixture.

2, the preparation method of high efficiency straw pulp sulfonated alkali lignin water-reducing agent according to claim 1 is characterized in that adopting in the step (1) NaOH or H ₂SO ₄Regulate the pH value.

3, the preparation method of high efficiency straw pulp sulfonated alkali lignin water-reducing agent according to claim 1 and 2 is characterized in that sulphite is meant one or more in water miscible sulphite or the hydrosulphite.

4, the preparation method of high efficiency straw pulp sulfonated alkali lignin water-reducing agent according to claim 1 and 2 is characterized in that water miscible sulphite is S-WAT, and water miscible hydrosulphite is a sodium bisulfite.

5, the high efficiency straw pulp sulfonated alkali lignin water-reducing agent of the described method preparation of claim 1.