Starch-based gradient structure water reducer and its mathematized controllable preparation method

Abstract

The application discloses a starch-based gradient structure water reducing agent and a mathematized controllable preparation method thereof, and comprises the following steps: starch is gelatinized; a first monomer, a second monomer and a third monomer are sequentially added into the gelatinized starch liquid according to a preset program through a three-stage gradient grafting copolymerization reaction; the three-stage gradient grafting copolymerization reaction comprises the following steps: grafting the first monomer at a first temperature and for a first reaction time in a first stage; grafting the second monomer at a second temperature and for a second reaction time in a second stage; and grafting the third monomer at a third temperature and for a third reaction time in a third stage; the three-stage gradient grafting copolymerization reaction realizes the dominant grafting of different monomers by controlling the integral path of a reaction progress function; and the starch-based gradient structure water reducing agent is prepared through neutralization, precipitation and drying. The application solves the problems of the existing polycarboxylic acid water reducing agent, such as non-renewable raw materials, insufficient slump retention and poor mud resistance.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a starch-based gradient structure water-reducing agent and its mathematically controllable preparation method. Background Technology

[0002] High-performance concrete is the cornerstone of modern civil engineering, and water-reducing agents are one of its key components. A water-reducing agent is a concrete admixture that reduces the amount of mixing water while maintaining a relatively constant slump. Most water-reducing agents are anionic surfactants, including lignin sulfonates, naphthalene sulfonates, and formaldehyde polymers. When added to concrete mixtures, water-reducing agents disperse cement particles, improving workability, reducing unit water consumption, and improving the fluidity of the concrete mixture; or reducing unit cement consumption, thus saving cement. Existing polycarboxylate superplasticizers (PCEs) suffer from problems such as non-renewable raw materials, insufficient slump retention, and poor resistance to mud. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, a starch-based gradient structure water-reducing agent and its mathematically controllable preparation method are provided to solve the problems of non-renewable raw materials, insufficient slump retention and poor mud resistance of existing polycarboxylate superplasticizers (PCEs).

[0004] To achieve the above objectives, a mathematically controllable preparation method for a starch-based gradient structure water-reducing agent is provided, comprising the following steps:

[0005] Gelatinized starch is obtained by gelatinizing oxidatively degraded starch;

[0006] A three-stage gradient graft copolymerization reaction is employed, in which a first monomer containing a carboxyl group, a second monomer containing an ester group or an amide group, and a third monomer containing an amide group or a quaternary ammonium salt group are sequentially added to the gelatinized starch solution according to a preset procedure. The three-stage gradient graft copolymerization reaction includes:

[0007] The first monomer is grafted at the first temperature and the first reaction time in the first stage. The first temperature is 60-70℃ and the first reaction time is 1-2h.

[0008] The second monomer is grafted at the second temperature and during the second reaction time in the second stage. The second temperature is 50-58℃ and the second reaction time is 2-3h.

[0009] The third monomer is grafted at the third temperature and the third reaction time in the third stage, with the third temperature being 65℃~75℃ and the third reaction time being 1.5~2.5h.

[0010] The three-stage gradient graft copolymerization reaction achieves the advantageous grafting of different monomers by controlling the integral path of the reaction process function Φ_i=∫k_i(T(t))·[M_i(t)]dt, where k_i(T(t)) is the reaction rate constant of the i-th monomer under the temperature process T(t), and [M_i(t)] is the concentration of the i-th monomer at time t;

[0011] After the three-stage gradient graft copolymerization reaction, a starch-based gradient structure water-reducing agent is obtained through neutralization, precipitation, and drying.

[0012] Furthermore, the mass ratio of the oxidized degraded starch to the first monomer is 100:3-6, the mass ratio of the oxidized degraded starch to the second monomer is 100:2-5, and the mass ratio of the oxidized degraded starch to the third monomer is 100:1-3.

[0013] Furthermore, the first monomer is any one of acrylic acid, methacrylic acid, maleic acid, and itaconic acid.

[0014] Furthermore, the second monomer is any one of hydroxyethyl acrylate, hydroxypropyl acrylate, polyethylene glycol-400-methacrylate, and acrylamide.

[0015] Furthermore, the third monomer is any one of acrylamide, methacrylamide, and methacryloyloxyethyltrimethylammonium chloride.

[0016] Furthermore, the reducing sugar content of the oxidized and degraded starch is 8-15%.

[0017] Furthermore, the carboxyl content of the oxidized and degraded starch is 0.20–0.45 mmol / g.

[0018] This invention provides a starch-based gradient structure water-reducing agent, which is prepared using a mathematically controllable preparation method for starch-based gradient structure water-reducing agents.

[0019] The beneficial effect of this invention is that the mathematically controllable preparation method of the starch-based gradient structure water-reducing agent of this invention achieves a "three-in-one" functional integration, and its comprehensive performance is superior to traditional starch-based water-reducing agents and most commercially available polycarboxylate-based water-reducing agents.

[0020] The mathematically controllable preparation method of starch-based gradient structure water-reducing agent of the present invention is advanced and controllable. The introduced reaction process control function elevates the synthesis process from empirical operation to a precise process guided by mathematical model, with good reproducibility.

[0021] The mathematically controllable preparation method of starch-based gradient structure water-reducing agent of the present invention uses renewable starch as raw material and achieves the unity of "green" and "high efficiency" through precise molecular engineering. Detailed Implementation

[0022] The present application will now be described in further detail with reference to the embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit the invention.

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0024] This invention provides a mathematically controllable preparation method for a starch-based gradient structure water-reducing agent, comprising the following steps:

[0025] S1. Gelatinize the oxidized and degraded starch to obtain a gelatinized starch solution.

[0026] The reducing sugar content of oxidatively degraded starch is 8-15%. The carboxyl content of oxidatively degraded starch is 0.20-0.45 mmol / g.

[0027] Specifically, oxidatively degraded starch is mixed with water and gelatinized to obtain a gelatinized starch solution.

[0028] S2. In the presence of an initiator, a three-stage gradient graft copolymerization reaction is adopted to add the first monomer containing a carboxyl group, the second monomer containing an ester group or an amide group, and the third monomer containing an amide group or a quaternary ammonium salt group to the gelatinized starch solution in sequence according to a preset program.

[0029] The first monomer is any one of acrylic acid, methacrylic acid, maleic acid, and itaconic acid. The mass ratio of oxidized degraded starch to the first monomer is 100:(3-6).

[0030] The second monomer is any one of hydroxyethyl acrylate, hydroxypropyl acrylate, polyethylene glycol-400-methacrylate, and acrylamide. The mass ratio of oxidized degraded starch to the second monomer is 100:(2-5).

[0031] The third monomer is any one of acrylamide, methacrylamide, or methacryloyloxyethyltrimethylammonium chloride. The mass ratio of oxidized degraded starch to the third monomer is 100:(1-3).

[0032] The initiator is either APS (ammonium persulfate) or KPS (potassium sulfate).

[0033] The three-stage gradient graft copolymerization reaction includes:

[0034] The first monomer is grafted within the first temperature T1 and the first reaction time t1 of the first stage, the first temperature is 60-70℃, the first reaction time is 1-2h, and some initiator is added.

[0035] The second monomer is grafted at the second temperature and during the second reaction time in the second stage. The second temperature is 50-58℃ and the second reaction time is 2-3h.

[0036] The third monomer is grafted at the third temperature and during the third reaction time in the third stage. The third temperature is 65℃~75℃ and the third reaction time is 1.5~2.5h.

[0037] The three-stage gradient graft copolymerization reaction achieves the advantageous grafting of different monomers by controlling the integral path of the reaction process function.

[0038] The reaction process control function is defined as: Φ_i=∫k_i(T(t))·[M_i(t)]dt,

[0039] Wherein, Φ_i: the overall grafting reaction process of the i-th monomer;

[0040] k_i(T(t)) is the reaction rate constant of the i-th monomer under the temperature process T(t), which follows the Arrhenius equation;

[0041] [M_i(t)] represents the concentration of the i-th monomer at time t, which is controlled by a preset feeding function.

[0042] The general process parameters and control objectives for the three-stage gradient graft copolymerization reaction are shown in Table 1 below.

[0043] Table 1. General process parameters and control targets for the three-stage gradient graft copolymerization reaction.

[0044]

[0045] S3. After the three-stage gradient graft copolymerization reaction, a starch-based gradient structure water-reducing agent is obtained by neutralization, precipitation and drying.

[0046] The mathematically controllable preparation method of the starch-based gradient structure water-reducing agent of the present invention achieves a "three-in-one" functional integration, and its comprehensive performance is superior to traditional starch-based water-reducing agents and most commercially available PCEs.

[0047] The mathematically controlled preparation method of starch-based gradient structure water-reducing agent of the present invention is advanced and controllable. The introduced reaction process control function Φ elevates the synthesis process from empirical operation to a precise process guided by mathematical model, with good reproducibility.

[0048] The mathematically controllable preparation method of starch-based gradient structure water-reducing agent of the present invention uses renewable starch as raw material and achieves the unity of "green" and "high efficiency" through precise molecular engineering.

[0049] This invention provides a starch-based gradient structure water-reducing agent, which is prepared using a mathematically controllable preparation method for starch-based gradient structure water-reducing agents.

[0050] The mathematically controllable preparation method of starch-based gradient structure water-reducing agent of the present invention uses natural starch as the backbone and prepares a starch-based graft copolymer water-reducing agent with a specific gradient molecular structure and high water reduction, high slump retention and high mud resistance through multi-stage precise control process.

[0051] To further illustrate the performance of the starch-based gradient structure water-reducing agent prepared by the mathematically controllable preparation method of the present invention, the following examples are provided for detailed explanation.

[0052] Example 1: Anti-slump gradient water-reducing agent (S-G1)

[0053] The starch-based gradient structure water-reducing agent in this embodiment is prepared using the following raw materials:

[0054] 100g of oxidized corn starch (reducing sugar 10.5%), 900g of water;

[0055] The first monomer is 4.0g of acrylic acid (pre-neutralized by 70%);

[0056] The second monomer is 3.0g of hydroxypropyl acrylate;

[0057] The third monomer is 1.8 g of DMC (80% aqueous solution) (Methacryloyloxyethyl Trimethyl Ammonium Chloride);

[0058] The initiator was 5.3g of APS.

[0059] The three-stage process of the mathematically controllable preparation method of starch-based gradient structure water-reducing agent in this embodiment is as follows:

[0060] Stage 1I: After starch gelatinization, the temperature is lowered to T1 of 68℃, 60% APS is added, and the reaction is carried out at a constant temperature for t1 of 1.5h.

[0061] Phase II: Cool down to T2 of 52°C, start adding the second monomer and the remaining 40% APS dropwise for 1.0 h. After the addition is complete, continue the reaction at 52°C for t2 of 1.5 h.

[0062] Phase III: Heat to 70°C (T3), add the third monomer, and react for 2.0 hours (t3).

[0063] Post-processing: neutralization, alcohol precipitation, and drying to obtain product S-G1.

[0064] Example 2: High slump retention gradient water-reducing agent (S-G2)

[0065] The starch-based gradient structure water-reducing agent in this embodiment is prepared using the following raw materials:

[0066] 100g of acid-hydrolyzed potato starch (15% reducing sugar), 900g of water.

[0067] First monomer: 3.5g of itaconic acid.

[0068] Second monomer: 5.0g of PEGMA500.

[0069] The third monomer: 1.5g of acrylamide.

[0070] The initiator was 5.0 g of KPS.

[0071] The three-stage process of the mathematically controllable preparation method of starch-based gradient structure water-reducing agent in this embodiment is as follows:

[0072] Phase I: T1 is 65℃, all KPS and the first monomer are added, and the reaction t1 is 2.0h.

[0073] Phase II: Cool down to T2 of 52°C, add the second monomer dropwise over 2.0 h, and maintain t2 at 1.0 h.

[0074] Phase III: The temperature is raised to T3 of 65°C, the third monomer is added, and the reaction time t3 is 2.5 h.

[0075] Example 3: High water-reducing gradient water-reducing agent (S-G3)

[0076] The starch-based gradient structure water-reducing agent in this embodiment is prepared using the following raw materials:

[0077] 100g of oxidized tapioca starch (12% reducing sugar), 900g of water.

[0078] First monomer: 5.0g of acrylic acid (pre-neutralized).

[0079] Second monomer: 2.0g of acrylamide.

[0080] Third monomer: 1.0g of AM.

[0081] The initiator was 5.5g of APS.

[0082] The three-stage process of the mathematically controllable preparation method of starch-based gradient structure water-reducing agent in this embodiment is as follows:

[0083] Phase I: T1 is 68℃, 70% APS and all of the first monomer are added, and the reaction t1 is 1.5h.

[0084] Phase II: Maintain T2 at 68°C, add the second monomer and the remaining APS dropwise for 1.0 h, and then react for another 1.0 h.

[0085] Phase III: Maintain T3 at 70°C, add the third monomer, and allow the reaction to proceed for t3 of 1.5 hours.

[0086] Comparative Example 1: One-step mixing method (C-1)

[0087] This comparative example uses the exact same raw materials and total amount as Example 1. All monomers and all initiators are added at once to a starch gelatinization solution at 68°C and reacted for 4.5 hours.

[0088] Comparative Example 2: Commercially available polycarboxylate superplasticizer (PC-1)

[0089] This comparative example uses commercially available polycarboxylate superplasticizer (PC-1) with a solid content of 20%, a water reduction rate of over 25%, and a concrete slump loss of 0 mm over time.

[0090] VII. Technical Effects

[0091] The above products underwent a cement paste fluidity test (300g of reference cement, 87g of water, and 0.15% water-reducing agent). A mud resistance test was conducted by adding 5% bentonite to the cement. The test methods for cement paste fluidity and mud resistance are detailed in GB / T 8077-2012, "Test Method for Homogeneity of Concrete Admixtures". The performance test results of the products in Examples 1 to 3, and Comparative Examples 1 and 2 are shown in Table 2 below.

[0092] Table 2. Quantitative Comparison of Product Performance Test Results

[0093]

[0094] The mathematically controllable preparation method of starch-based gradient structure water-reducing agents of the present invention successfully prepared high-performance starch-based water-reducing agents through an innovative "mathematical gradient grafting process." As shown in Table 2, the products of the embodiments of the present invention significantly outperform the comparative examples and commercially available products in terms of slump retention and mud resistance, demonstrating the inventiveness and practicality of the process.

[0095] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A mathematically controllable preparation method for a starch-based gradient structure water-reducing agent, characterized in that, Includes the following steps: Gelatinized starch is obtained by gelatinizing oxidatively degraded starch; A three-stage gradient graft copolymerization reaction is employed, in which a first monomer containing a carboxyl group, a second monomer containing an ester group or an amide group, and a third monomer containing an amide group or a quaternary ammonium salt group are sequentially added to the gelatinized starch solution according to a preset procedure. The three-stage gradient graft copolymerization reaction includes: The first monomer is grafted at the first temperature and the first reaction time in the first stage. The first temperature is 60-70℃ and the first reaction time is 1-2h. The second monomer is grafted at the second temperature and during the second reaction time in the second stage. The second temperature is 50-58℃ and the second reaction time is 2-3h. The third monomer is grafted at the third temperature and the third reaction time in the third stage, with the third temperature being 65℃~75℃ and the third reaction time being 1.5~2.5h. The three-stage gradient graft copolymerization reaction achieves the advantageous grafting of different monomers by controlling the integral path of the reaction process function Φ_i=∫k_i(T(t))·[M_i(t)]dt, where k_i(T(t)) is the reaction rate constant of the i-th monomer under the temperature process T(t), and [M_i(t)] is the concentration of the i-th monomer at time t; After the three-stage gradient graft copolymerization reaction, a starch-based gradient structure water-reducing agent is obtained through neutralization, precipitation, and drying.

2. The mathematically controllable preparation method of the starch-based gradient structure water-reducing agent according to claim 1, characterized in that, The mass ratio of the oxidized degraded starch to the first monomer is 100:3-6, the mass ratio of the oxidized degraded starch to the second monomer is 100:2-5, and the mass ratio of the oxidized degraded starch to the third monomer is 100:1-3.

3. The mathematically controllable preparation method of the starch-based gradient structure water-reducing agent according to claim 1, characterized in that, The first monomer is any one of acrylic acid, methacrylic acid, maleic acid, and itaconic acid.

4. The mathematically controllable preparation method of the starch-based gradient structure water-reducing agent according to claim 3, characterized in that, The second monomer is any one of hydroxyethyl acrylate, hydroxypropyl acrylate, polyethylene glycol-400-methacrylate, and acrylamide.

5. The mathematically controllable preparation method of the starch-based gradient structure water-reducing agent according to claim 4, characterized in that, The third monomer is any one of acrylamide, methacrylamide, or methacryloyloxyethyltrimethylammonium chloride.

6. The mathematically controllable preparation method of the starch-based gradient structure water-reducing agent according to claim 1, characterized in that, The reducing sugar content of the oxidized and degraded starch is 8-15%.

7. The mathematically controllable preparation method of the starch-based gradient structure water-reducing agent according to claim 6, characterized in that, The oxidatively degraded starch has a carboxyl content of 0.20–0.45 mmol / g.

8. A starch-based gradient structure water-reducing agent, characterized in that, It is prepared by a mathematically controllable preparation method of starch-based gradient structure water-reducing agent as described in any one of claims 1 to 7.

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