CN101648979A - Preparation method for low air bleeding lignosulphonate high-efficiency water reducing agent - Google Patents

Abstract

The invention discloses a method for preparing a low air-entraining type lignosulfonate high-efficiency water reducer, which is prepared by the following steps: an aqueous solution of lignosulfonate is subjected to alkaline conditions and the presence of a defoamer and an activator , through the catalytic oxidation reaction, some molecular bonds are broken and recombined to increase the molecular weight, and then the sulfonation reaction is carried out to introduce sulfonic acid groups on the molecular chain to increase the degree of sulfonation. The invention has the advantages of mild reaction, simple operation, non-toxicity and pollution-free, safe to the environment, stable performance of the obtained product, small amount of entraining air, high water reducing rate and the like.

Description

Preparation method of low air-entraining lignosulfonate high-efficiency water reducer

technical field

The invention relates to a preparation method of a low air-entraining type lignosulfonate high-efficiency water reducer.

Background technique

As a concrete water reducer, lignosulfonate can improve the workability of fresh concrete, and it has a wide range of sources and low price, so it has been used in concrete for a long time. Defects such as low water rate seriously restrict its application. Lignosulfonate is an anionic surfactant composed of benzylpropane derivatives as hydrophobic groups and sulfonic acid groups, carboxyl groups, hydroxyl groups, etc. as hydrophilic groups. Its molecular structure and molecular weight distribution are extremely heterogeneous. Moreover, lignosulfonate contains a large amount of reducing sugar, and the increase in the amount of concrete will cause the phenomenon that the concrete does not condense for a long time, leading to engineering accidents. Lignosulfonate with small molecular weight has a large amount of air-entraining, and it is easy to reduce the strength of concrete in concrete applications, so it cannot be used in high-strength concrete. In addition, the water-reducing rate of lignosulfonate is low, and it is generally used as a common water-reducing agent. Increasing its water-reducing rate is of great significance for expanding its practical application in concrete. Lignosulfonate contains a variety of active groups, which are reactive and capable of oxidation, sulfonation, condensation and alkylation, etc., so it can improve its own problems through chemical modification.

Contents of the invention

The object of the present invention is to provide a method for preparing a low-air-entraining lignosulfonate high-efficiency water reducer with simple operation and high water reducing rate.

For realizing the above object, technical solution of the present invention is:

The invention provides a method for preparing a low-air-entraining lignosulfonate high-efficiency water reducer, which comprises the following steps:

In parts by mass, add 100 parts of lignosulfonate solids and 66.7 to 150 parts of water into the reaction kettle to prepare a solution with a certain concentration; add 0.5 to 0.8 parts of defoamer and 0.2 to 0.4 parts of activator, and use Adjust the pH to 8-10 with an appropriate amount of sulfuric acid, raise the temperature to 50-70°C, add 0.1-0.3 parts of catalyst and 1-5 parts of oxidant, and react for 0.5-1 hour, the retarding group in the molecular structure of lignosulfonate and the retarding group of reducing sugar in the system will be oxidized, and the content of low molecular weight lignosulfonate will be reduced due to the coupling reaction; add 12 to 20 parts of sulfonating agent and react for 1 to 2 hours. Lignosulfonate can introduce more sulfonic acid groups into the molecular structure, and after cooling, a low air-entraining lignosulfonate superplasticizer can be obtained.

The lignosulfonate is one of ammonium lignosulfonate, calcium lignosulfonate and sodium lignosulfonate.

The defoamer is one of tributyl phosphate, dimethyl polysiloxane, polyoxyethylene polyoxypropylene glyceryl ether.

The activator is one of sodium aminotrimethylene phosphonate and sodium hexamethylenediamine tetramethylene phosphonate.

The catalyst is one of vanum pentoxide, manganese dioxide and ammonium cerium nitrate.

The oxidizing agent is one of potassium permanganate, hydrogen peroxide and ammonium persulfate.

The sulfonating agent is one of sodium sulfite, sodium pyrosulfite, sulfamic acid and p-aminobenzenesulfonic acid.

After adopting the above scheme, due to the catalytic oxidation reaction of lignosulfonate in the preparation process of the present invention, the retarding group (hydroxyl or ether group) in the molecular structure can be oxidized and oxidized into a small retarding group. The carboxyl group of the reducing sugar in the system will also be oxidized; the oxidation reaction can also break the lignosulfonate molecular chain, and the newly generated active free chain end can be coupled to form a long molecular chain under the action of the activator. chain, so as to increase the relative molecular weight of lignosulfonate; at the same time, adding a defoamer to the system can reduce the large amount of foam (small molecular weight lignosulfonate) suspended on the surface of the system during the oxidation reaction, Promote the participation of small molecular weight lignosulfonate in the reaction. The lignosulfonate after catalytic oxidation undergoes a sulfonation reaction to introduce sulfonic acid groups into the molecular chain to increase the degree of sulfonation, thereby increasing its water-reducing rate. Therefore, the present invention has the following advantages:

1. It can improve the problem of long retarding time of lignosulfonate.

2. It can reduce the air-entraining amount of lignosulfonate.

3. It can increase the water reducing rate of lignosulfonate.

4. The reaction conditions are mild and the operation is simple.

Detailed ways

Example 1

In terms of parts by mass, 100kg of solid sodium lignosulfonate and 100kg of water were added into a 500L reaction kettle to prepare a solution with a concentration of 50%. Add 0.5kg tributyl phosphate and 0.2kg sodium hexamethylenediamine tetramethylene phosphonate, adjust the pH to 8 with an appropriate amount of sulfuric acid, raise the temperature to 70°C, then add 0.2kg cerium ammonium nitrate and 5kg hydrogen peroxide, and react for 0.5 hours Finally, the retarding group in the molecular structure of sodium lignosulfonate and the retarding group of the reducing sugar in the system will be oxidized, and at the same time due to the coupling reaction, the content of low molecular weight lignosulfonate is reduced; add 12kg amino Sulfonic acid, reacted for 2 hours, lignosulfonate can introduce more sulfonic acid groups into the molecular structure, and after cooling, a low air-entraining type lignosulfonate high-efficiency water reducer is obtained, with a weight concentration of 53.95%.

Example 2

In terms of parts by mass, 100 kg of solid ammonium lignosulfonate and 100 kg of water were added into a 500 L reaction kettle to prepare a solution with a concentration of 50%. Add 0.7kg tributyl phosphate and 0.2kg sodium hexamethylenediamine tetramethylene phosphonate, adjust the pH to 9 with an appropriate amount of sulfuric acid, raise the temperature to 50°C, then add 0.3kg manganese dioxide and 2kg potassium permanganate, and react for 0.5 Hours later, the retarding group in the molecular structure of ammonium lignosulfonate and the retarding group of reducing sugar in the system will all be oxidized, and at the same time due to the coupling reaction, the content of low molecular weight lignosulfonate is reduced; add 16kg Sodium pyrosulfite, reacted for 1 hour, lignosulfonate can introduce more sulfonic acid groups into the molecular structure, and after cooling, a low air-entraining type lignosulfonate superplasticizer was obtained, with a weight concentration of 54.23%.

Example 3

In parts by mass, 100kg of solid calcium lignosulfonate and 100kg of water were added into a 500L reaction kettle to prepare a solution with a concentration of 50%. Add 0.8kg of dimethyl polysiloxane and 0.4kg of sodium hexamethylenediamine tetramethylene phosphonate, adjust the pH to 10 with an appropriate amount of sulfuric acid, raise the temperature to 55°C, and then add 0.2kg of vanum pentoxide and 4kg of ammonium persulfate , after reacting for 0.5 hours, the retarding group in the molecular structure of calcium lignosulfonate and the retarding group of the reducing sugar in the system will be oxidized, and the content of low molecular weight lignosulfonate will be reduced due to the coupling reaction Add 18kg of sodium sulfite and react for 2 hours. The lignosulfonate can introduce more sulfonic acid groups into the molecular structure. After cooling, a low-air-entraining lignosulfonate high-efficiency water reducer is obtained, with a weight concentration of 54.87%.

Example 4

In terms of parts by mass, 100kg of solid sodium lignosulfonate and 100kg of water were added into a 500L reaction kettle to prepare a solution with a concentration of 50%. Add 0.6kg of polyoxyethylene polyoxypropylene glyceryl ether and 0.3kg of sodium aminotrimethylene phosphonate, adjust the pH to 10 with an appropriate amount of sulfuric acid, raise the temperature to 60°C, then add 0.1kg of alum pentoxide and 1kg of potassium permanganate, After reacting for 1 hour, the retarding group in the molecular structure of sodium lignosulfonate and the retarding group of the reducing sugar in the system will be oxidized, and the content of low molecular weight lignosulfonate will be reduced due to the coupling reaction; Add 20kg of p-aminobenzenesulfonic acid and react for 2 hours. The lignosulfonate can introduce more sulfonic acid groups into the molecular structure. After cooling, a low air-entraining type lignosulfonate high-efficiency water reducer is obtained. The weight concentration is 54.10%.

Example 5

In terms of parts by mass, 100kg of solid sodium lignosulfonate and 150kg of water were added into a 500L reaction kettle to prepare a solution with a concentration of 40%. Add 0.7kg of polyoxyethylene polyoxypropylene glyceryl ether and 0.3kg of sodium aminotrimethylene phosphonate, adjust the pH to 9 with an appropriate amount of sulfuric acid, raise the temperature to 60°C, then add 0.2kg of alum pentoxide and 3kg of potassium permanganate, After reacting for 0.7 hours, the retarding group in the molecular structure of sodium lignosulfonate and the retarding group of the reducing sugar in the system will be oxidized, and the content of low molecular weight lignosulfonate is reduced due to the coupling reaction; Add 15kg of p-aminobenzenesulfonic acid and react for 1.5 hours. The lignosulfonate can introduce more sulfonic acid groups into the molecular structure. After cooling, a low air-entraining type lignosulfonate high-efficiency water reducer is obtained. The weight concentration is 41.89%.

Example 6

In terms of parts by mass, 100kg of solid sodium lignosulfonate and 66.7kg of water were added into a 500L reaction kettle to prepare a solution with a concentration of 60%. Add 0.5kg of polyoxyethylene polyoxypropylene glyceryl ether and 0.2kg of sodium aminotrimethylene phosphonate, adjust the pH to 8 with an appropriate amount of sulfuric acid, raise the temperature to 50°C, then add 0.1kg of alum pentoxide and 2kg of potassium permanganate, After reacting for 0.5 hours, the retarding group in the molecular structure of sodium lignosulfonate and the retarding group of the reducing sugar in the system will be oxidized, and the content of low molecular weight lignosulfonate will be reduced due to the coupling reaction; Add 12kg of p-aminobenzenesulfonic acid, react for 1 hour, lignosulfonate can introduce more sulfonic acid groups in the molecular structure, and obtain low air-entraining type lignosulfonate high-efficiency water reducer after cooling, with a weight concentration of 61.34%.

The low-air-entraining lignosulfonate superplasticizers prepared in Examples 1 to 6 were tested.

The cement used is Jianfu P.O42.5R ordinary Portland cement, the sand is medium sand with a fineness modulus Mx=2.6, and the gravel is continuously graded crushed stone with a particle size of 5-31.5mm. The dosage of water reducer is 0.25% (calculated by converting into solid mass), and it is measured according to GB8076-1997.

The test results are listed in Table 1.

Table 1 performance test results

Claims (8)

1. A method for preparing a low-air-entraining lignosulfonate high-efficiency water reducer, characterized in that it comprises the following steps: adding 100 parts of lignosulfonate solids and 66.7 to 150 parts of water in parts by mass Put it into the reaction kettle and prepare a solution with a certain concentration; 0.2-0.4 parts of activator, adjust the pH to 8-10 with an appropriate amount of sulfuric acid, raise the temperature to 50-70 ° C, then add 0.1-0.3 parts of catalyst and 1-5 parts of oxidant, After reacting for 0.5 to 1 hour; add 12 to 20 parts of sulfonating agent and react for 1 to 2 hours. Lignosulfonate can introduce more sulfonic acid groups into the molecular structure and obtain low air-entraining lignosulfonate after cooling Salt superplasticizer. 2. The method for preparing a low-air-entraining lignosulfonate high-efficiency water reducer according to claim 1, characterized in that 0.5-0.8 parts of defoamer are added at the same time as the activator. 3. A method for preparing a low-air-entraining lignosulfonate high-efficiency water reducer according to claim 1, characterized in that: the lignosulfonate is ammonium lignosulfonate, lignosulfonate One of calcium acid and sodium lignosulfonate. 4. A method for preparing a low air-entraining lignosulfonate high-efficiency water reducer according to claim 2, characterized in that: the defoamer is tributyl phosphate, dimethylpolysiloxane One of alkanes, polyoxyethylene polyoxypropylene glyceryl ethers. 5. A method for preparing a low-air-entraining lignosulfonate high-efficiency water reducer according to claim 1, characterized in that: the activator is sodium aminotrimethylene phosphonate, hexamethylene diamine tetra One of the sodium methylene phosphonates. 6. A method for preparing a low-air-entraining lignosulfonate high-efficiency water reducer according to claim 1, characterized in that: the catalyst is a mixture of alum pentoxide, manganese dioxide, and ammonium cerium nitrate kind of. 7. A method for preparing a low-air-entraining lignosulfonate high-efficiency water reducer according to claim 1, characterized in that: the oxidant is potassium permanganate, hydrogen peroxide, ammonium persulfate kind of. 8. A method for preparing a low-air-entraining lignosulfonate high-efficiency water reducer according to claim 1, wherein the sulfonating agent is sodium sulfite, sodium pyrosulfite, sulfamic acid, p-amino One of the benzenesulfonic acid.