Low-molecular-weight oxidized sulfonated starch water reducing agent as well as preparation method and application thereof

Abstract

The invention discloses a low-molecular-weight oxidized sulfonated starch water reducing agent as well as a preparation method and application thereof, and belongs to the technical field of preparation of water reducing agents. The preparation method of the low-molecular-weight oxidized sulfonated starch water reducing agent comprises the following steps: pre-gelatinizing starch, performing oxidative degradation, and sulfonating to obtain the low-molecular-weight oxidized sulfonated starch water reducing agent. The prepared low-molecular-weight oxidized sulfonated starch water reducing agent can keep the fluidity of cement paste at 200 mm or above, and has good dispersity.

Description

Technical Field

[0001] The invention relates to the technical field of water reducing agent preparation, and in particular to a low molecular weight oxidized sulfonated starch water reducing agent and a preparation method and application thereof. Background Art

[0002] Water reducer is a commonly used concrete admixture that can significantly reduce the unit water consumption of concrete and improve the fluidity and workability of concrete. Naphthalene and polycarboxylic acid water reducers are the mainstream water reducers on the market, but their raw materials are mostly derived from petroleum and petrochemical products, which consume a large amount of petrochemical resources and have high carbon emissions. Therefore, it is urgent to develop new green, environmentally friendly, pollution-free and cost-effective water reducers. Summary of the invention

[0003] The purpose of the present invention is to provide a low molecular weight oxidized sulfonated starch water reducer and a preparation method and application thereof, so as to solve the problems existing in the above-mentioned prior art.

[0004] To achieve the above object, the present invention provides the following solutions: One of the technical solutions of the present invention: a method for preparing a low molecular weight oxidized sulfonated starch water reducer, comprising the following steps: The starch is pre-gelatinized, oxidized and degraded, and then sulfonated to obtain the low molecular weight oxidized sulfonated starch water reducer.

[0005] Furthermore, the pregelatinization method specifically comprises: Starch is added into water and heated to react to obtain a pregelatinized starch solution.

[0006] Furthermore, the temperature of the heating reaction is 75-95° C., and the time is 0.5-2 h; and / or the mass ratio of the starch to water is (10-30): (60-150).

[0007] Furthermore, the oxidation method specifically includes: adding an oxidant to the pregelatinized starch solution to carry out an oxidative degradation reaction to obtain an oxidized starch solution.

[0008] Furthermore, the mass ratio of the starch to the oxidant is (10-30): (1-30); And / or, the oxidant includes hydrogen peroxide and / or anhydrous copper sulfate; And / or, the temperature of the oxidative degradation reaction is 45-75° C., and the time is 0.5-2 h.

[0009] Low molecular weight oxidized sulfonated starch water reducers with different weight average molecular weights can be prepared by adjusting the oxidation reaction temperature and the mass ratio of starch to oxidant.

[0010] Furthermore, the sulfonation method specifically comprises: adding a sulfonating agent to an oxidized starch solution to carry out a sulfonation reaction to obtain the low molecular weight oxidized sulfonated starch water reducing agent.

[0011] Furthermore, the mass ratio of the starch to the sulfonating agent is (10-30): (1-100); and / or, the sulfonating agent (inorganic sulfonating agent) comprises sodium sulfite and / or sodium bisulfite; And / or, the temperature of the sulfonation reaction is 45-60° C., and the time is 0.5-4 h.

[0012] Furthermore, the weight average molecular weight of the low molecular weight oxidized sulfonated starch water reducer is 1000-8000.

[0013] Starch is a natural high molecular substance with abundant sources, low price and easy biodegradation. Carboxyl and sulfonate groups are introduced into the starch molecular structure through oxidation and sulfonation. These anionic groups can complex calcium ions on cement particles to form an electrostatic adsorption double layer, thereby preventing cement hydration and achieving water reduction effect. The oxidized sulfonated starch is a new type of water reducer that can replace naphthalene and polycarboxylic acid water reducers, providing a guarantee for the sustainable development of admixtures and opening up the application field for natural high molecular materials.

[0014] The second technical solution of the present invention: a low molecular weight oxidized sulfonated starch water reducer prepared by the above preparation method.

[0015] The third technical solution of the present invention: an application of the above-mentioned low molecular weight oxidized sulfonated starch water reducer in the preparation of concrete.

[0016] Furthermore, the addition amount of the low molecular weight oxidized sulfonated starch water reducer is 0.03-20% of the mass of the cementitious material in the concrete.

[0017] The present invention discloses the following technical effects: (1) The low molecular weight oxidized sulfonated starch water reducer prepared by the present invention can keep the fluidity of cement paste above 200 mm and has good dispersibility.

[0018] (2) The present invention pre-gelatinizes starch and then oxidatively degrades it in an aqueous solution to obtain degraded starch with controllable molecular weight. At the same time, carboxyl groups are introduced by oxidation. By adding an inorganic sulfonating agent, the technical effect of preparing sulfonated starch in an aqueous phase is achieved (obtaining low molecular weight oxidized sulfonated starch). The product can be used directly without purification, thus overcoming the problem that the existing sulfonating agent needs to be recovered and recycled. The preparation method is green and sustainable. DETAILED DESCRIPTION

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0020] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0021] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0022] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0023] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0024] Example 1 A preparation method of low molecular weight oxidized sulfonated starch water reducer: Add starch and water in a mass ratio of 30:100 into a four-necked flask with a stirring rod, heat to 80°C, pre-gelatinize for 1h to obtain pre-gelatinized starch; control the reaction temperature to 50°C, add 25% of the starch mass 30wt.% hydrogen peroxide solution, react for 1h to obtain degraded oxidized starch; then add 35% of the starch mass sodium sulfite into the four-necked flask, and continue to react for 2h at the same temperature (50°C). After the reaction is completed, add an appropriate amount of water and dilute to a solid content of 20% to obtain a low molecular weight oxidized sulfonated starch water reducer solution.

[0025] The reaction of pregelatinized starch oxidation is as follows: ; The sulfonation reaction of degraded oxidized starch is as follows: .

[0026] Example 2 A preparation method of low molecular weight oxidized sulfonated starch water reducer: Add starch and water in a mass ratio of 30:100 into a four-necked flask with a stirring rod, heat to 80°C, pre-gelatinize for 1h, and obtain pre-gelatinized starch; control the reaction temperature to 50°C, add 10% of the starch mass copper sulfate pentahydrate and 30wt.% hydrogen peroxide solution (the mass ratio of copper sulfate pentahydrate to hydrogen peroxide solution is 1:100), react for 1h, and obtain degraded oxidized starch; then add 35% of the starch mass sodium sulfite into the four-necked flask, and continue to react for 4h at the same temperature (50°C). After the reaction is completed, add an appropriate amount of water and dilute to a solid content of 20% to obtain a low molecular weight oxidized sulfonated starch water reducer solution.

[0027] Example 3 A preparation method of low molecular weight oxidized sulfonated starch water reducer: Add starch and water in a mass ratio of 30:100 into a four-necked flask with a stirring rod, heat to 80°C, pre-gelatinize for 1h to obtain pre-gelatinized starch; control the reaction temperature to 50°C, add 15% of the starch mass copper sulfate pentahydrate and 30wt.% hydrogen peroxide solution (the mass ratio of copper sulfate pentahydrate to hydrogen peroxide solution is 1:100), react for 1h to obtain degraded oxidized starch; then add 35% of the starch mass sodium sulfite into the four-necked flask, and continue to react for 4h at the same temperature (50°C). After the reaction is completed, add an appropriate amount of water to dilute to a solid content of 20% to obtain a low molecular weight oxidized sulfonated starch water reducer solution.

[0028] Example 4 A preparation method of low molecular weight oxidized sulfonated starch water reducer: Add starch and water in a mass ratio of 30:100 to a four-necked flask with a stirring rod, heat to 90°C, pre-gelatinize for 1h to obtain pre-gelatinized starch; control the reaction temperature to 50°C, add 10% of the starch mass copper sulfate pentahydrate and 30wt.% hydrogen peroxide solution (the mass ratio of copper sulfate pentahydrate to hydrogen peroxide solution is 1:100), react for 2h to obtain degraded oxidized starch. Then add 35% of the starch mass sodium bisulfite to the four-necked flask, and continue to react for 4h at the same temperature (50°C). After the reaction is completed, add an appropriate amount of water and dilute to a solid content of 20% to obtain a low molecular weight oxidized sulfonated starch water reducer solution.

[0029] Example 5 A preparation method of low molecular weight oxidized sulfonated starch water reducer: Add starch and water in a mass ratio of 30:100 to a four-necked flask with a stirring rod, heat to 90°C, pre-gelatinize for 2 hours to obtain pre-gelatinized starch; control the reaction temperature to 50°C, add 15% of the starch mass of copper sulfate pentahydrate and 30wt.% hydrogen peroxide solution (the mass ratio of copper sulfate pentahydrate to hydrogen peroxide solution is 1:100), react for 2 hours to obtain degraded oxidized starch. Then add 70% of the starch mass of sodium bisulfite to the four-necked flask, and continue to react for 4 hours at the same temperature (50°C). After the reaction is completed, add an appropriate amount of water and dilute to a solid content of 20% to obtain a low molecular weight oxidized sulfonated starch water reducer solution.

[0030] Example 6 A preparation method of low molecular weight oxidized sulfonated starch water reducer: Add starch and water in a mass ratio of 30:100 to a four-necked flask with a stirring rod, heat to 90°C, pre-gelatinize for 2 hours to obtain pre-gelatinized starch; control the reaction temperature to 60°C, add 10% of the starch mass copper sulfate pentahydrate and 30wt.% hydrogen peroxide solution (the mass ratio of copper sulfate pentahydrate to hydrogen peroxide solution is 1:100), react for 2 hours to obtain degraded oxidized starch. Then add 35% of the starch mass sodium sulfite to the four-necked flask, and continue to react for 4 hours at the same temperature (60°C). After the reaction is completed, add an appropriate amount of water and dilute to a solid content of 20% to obtain a low molecular weight oxidized sulfonated starch water reducer solution.

[0031] Example 7 A preparation method of low molecular weight oxidized sulfonated starch water reducer: Add starch and water in a mass ratio of 30:100 to a four-necked flask with a stirring rod, heat to 90°C, pre-gelatinize for 2 hours to obtain pre-gelatinized starch; control the reaction temperature to 60°C, add 15% of the starch mass of copper sulfate pentahydrate and 30wt.% hydrogen peroxide solution (the mass ratio of copper sulfate pentahydrate to hydrogen peroxide solution is 1:100), react for 2 hours to obtain degraded oxidized starch. Then add 35% of the starch mass of sodium bisulfite to the four-necked flask, and continue to react for 4 hours at the same temperature (60°C). After the reaction is completed, add an appropriate amount of water and dilute to a solid content of 20% to obtain a low molecular weight oxidized sulfonated starch water reducer solution.

[0032] Example 8 A preparation method of low molecular weight oxidized sulfonated starch water reducer: Add starch and water in a mass ratio of 30:100 to a four-necked flask with a stirring rod, heat to 90°C, pre-gelatinize for 2 hours to obtain pre-gelatinized starch; control the reaction temperature to 60°C, add 10% of the starch mass of copper sulfate pentahydrate and 30wt.% hydrogen peroxide solution (the mass ratio of copper sulfate pentahydrate to hydrogen peroxide solution is 1:100), react for 2 hours to obtain degraded oxidized starch. Then add 100% of the starch mass of sodium bisulfite to the four-necked flask, and continue to react for 4 hours at the same temperature (60°C). After the reaction is completed, add an appropriate amount of water and dilute to a solid content of 20% to obtain a low molecular weight oxidized sulfonated starch water reducer solution.

[0033] The weight average molecular weight of the low molecular weight oxidized sulfonated starch water reducer prepared in the measurement example is shown in Table 1.

[0034] Table 1 Weight average molecular weight Grouping Weight average molecular weight / Dalton starch 120000 Example 1 20260 Example 2 11230 Example 3 5600 Example 4 11100 Example 5 5500 Example 6 9120 Example 7 2800 Example 8 8800 It can be seen from Table 1 that the method of the present invention can effectively reduce the weight average molecular weight of starch to no more than 31,000 (the molecular weight of starch is not less than 100,000).

[0035] Comparative Example 1 Starch and water in a mass ratio of 30:100 were added to a four-necked flask with a stirring rod, heated to 90°C, and pre-gelatinized for 2 hours to obtain pre-gelatinized starch; the reaction temperature was controlled to 60°C, and copper sulfate pentahydrate with a mass ratio of 10% of the starch mass and 30wt.% hydrogen peroxide solution (the mass ratio of copper sulfate pentahydrate to hydrogen peroxide solution was 1:100) were added, and the reaction was continued for 2 hours. After the reaction was completed, an appropriate amount of water was added to dilute the solution to a solid content of 20% to obtain a degraded oxidized starch solution.

[0036] Comparative Example 2 Add starch and water in a mass ratio of 30:100 into a four-necked flask with a stirring rod, heat to 90°C, and pre-gelatinize for 2 hours to obtain pre-gelatinized starch. Add sodium bisulfite with a mass ratio of 100% of the starch into the four-necked flask and react at 60°C for 4 hours. After the reaction is completed, add an appropriate amount of water and dilute to a solid content of 20% to obtain a sulfonated starch solution.

[0037] Effect Example 1 The low molecular weight oxidized sulfonated starch water reducer prepared in the embodiment and the comparative example was added with a low molecular weight oxidized sulfonated starch water reducer solution having a solid content of 20% (the mass of the low molecular weight oxidized sulfonated starch water reducer in the low molecular weight oxidized sulfonated starch water reducer solution was 0.5% of the mass of cement) according to the method in the standard GB / T8077-2002 "Test method for homogeneity of concrete admixtures". The water-cement ratio was controlled to be 0.29, and its dispersion performance on cement was tested. The results are shown in Table 2.

[0038] Table 2 Cement paste fluidity Grouping Cement paste fluidity / mm Example 1 200 Example 2 210 Example 3 240 Example 4 225 Example 5 245 Example 6 215 Example 7 200 Example 8 240 Comparative Example 1 80 Comparative Example 2 60 It can be seen from Table 2 that the low molecular weight oxidized sulfonated starch water reducer prepared by the present invention can keep the cement paste fluidity above 200 mm, indicating that the low molecular weight oxidized sulfonated starch water reducer prepared by the present invention has good dispersibility.

[0039] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a low molecular weight oxidized sulfonated starch water reducer, characterized in that: The following steps are involved: The starch is pre-gelatinized, oxidized and degraded, and then sulfonated to obtain the low molecular weight oxidized sulfonated starch water reducer.

2. The preparation method according to claim 1, characterized in that: The pregelatinization method specifically comprises: Starch is added into water and heated to react to obtain a pregelatinized starch solution.

3. The preparation method according to claim 2, characterized in that: The temperature of the heating reaction is 75-95° C., and the time is 0.5-2 h; and / or the mass ratio of the starch to water is (10-30): (60-150).

4. The preparation method according to claim 2, characterized in that: The oxidation method specifically comprises: adding an oxidant to a pregelatinized starch solution to carry out an oxidative degradation reaction to obtain an oxidized starch solution.

5. The preparation method according to claim 4, characterized in that: The mass ratio of the starch to the oxidant is (10-30): (1-30); And / or, the oxidant includes hydrogen peroxide and / or anhydrous copper sulfate; And / or, the temperature of the oxidative degradation reaction is 45-75° C., and the time is 0.5-2 h.

6. The preparation method according to claim 4, characterized in that: The sulfonation method specifically comprises: adding a sulfonating agent to an oxidized starch solution to carry out a sulfonation reaction to obtain the low molecular weight oxidized sulfonated starch water reducing agent.

7. The preparation method according to claim 6, characterized in that: The mass ratio of the starch to the sulfonating agent is (10-30): (1-100); and / or, the sulfonating agent comprises sodium sulfite and / or sodium bisulfite; And / or, the temperature of the sulfonation reaction is 45-60° C., and the time is 0.5-4 h.

8. A low molecular weight oxidized sulfonated starch water reducer prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the low molecular weight oxidized sulfonated starch water reducer according to claim 8 in the preparation of concrete.

10. The use according to claim 9, characterized in that: The addition amount of the low molecular weight oxidized sulfonated starch water reducer is 0.03-20% of the mass of the cementitious material in the concrete.