Microcapsule slow-release water reducing agent and preparation method thereof

Abstract

The invention discloses a microcapsule slow-release type water reducing agent which is prepared by the following steps: by taking isopentenyl polyglycol ether as a polyether monomer and acrylic acid and hydroxyethyl acrylate as functional monomers, introducing-COOR (ester group) into the structure of the water reducing agent, reducing the content of-COOH, hydrolyzing and breaking the-COOR group into-COO-in an alkaline environment, complexing with Ca < 2 + > on the surface of a cement particle, and then adding a water reducing agent, thereby obtaining the microcapsule slow-release type water reducing agent. The effect of slowly releasing-COO <-> is achieved; gelatin, Arabic gum and deionized water are heated and stirred to prepare a capsule wall solution, the capsule wall solution is mixed with the slow-release water reducing agent, then transglutaminase is added, and the gelatin and the Arabic gum are mutually crosslinked under the action of the transglutaminase, so that gel is separated out and wraps the slow-release water reducing agent, and the microcapsule slow-release water reducing agent is obtained. When in use, the wall of the microcapsule is gradually loosened and broken, so that the water reducing agent is slowly released, and a dual slow release effect is realized. The preparation method provided by the invention has the advantages of simple operation and mild process parameters, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the field of building material admixtures, and in particular to a microcapsule slow-release water reducing agent and a preparation method thereof. Background Art

[0002] With the continuous development of the construction industry, the requirements for concrete quality are getting higher and higher. The loss of concrete slump is the main factor affecting the performance of concrete. In actual engineering applications, the slump loss of concrete is relatively fast, which increases the difficulty of construction progress and quality control, and directly affects the construction effect. The improvement process of concrete performance is inseparable from admixtures. As one of the important admixtures for improving concrete performance, water reducer, while improving concrete performance, is also accompanied by rapid slump loss and rapid hardening. Therefore, reducing the slump loss of concrete has always been a difficult problem that plagues construction engineering.

[0003] In addition, with the continuous growth of energy demand and the increasing awareness of environmental protection in countries around the world, the promotion and application of environmentally friendly materials has become inevitable, making it possible to use high-efficiency water reducers in the preparation of high-performance concrete. As a new generation of concrete admixtures, polycarboxylic acid water reducers have greatly improved the performance of concrete. They are called the third generation of high-performance water reducers and are green and environmentally friendly materials.

[0004] At present, the developed slow-release water reducers have the characteristics of continuous and slow dispersion of cement particles within a certain period of time, but their slow-release rate is difficult to control and there are disadvantages such as too fast initial release rate. Therefore, there is an urgent need for a water reducer that can extend the slow-release time of the water reducer, control the slow-release rate and improve the slump retention capacity, which has become the key research direction of new polycarboxylate water reducers.

[0005] Microcapsules with inorganic or polymer wall materials are micro-containers or wrappings that wrap the core material. The core material wrapped in the microcapsule after microencapsulation is slowly released under certain conditions as the wall dissolves, and then gradually takes effect. However, the current research on microcapsules in the field of water reducing agents is far from meeting the needs of the construction field. Summary of the invention

[0006] In order to solve the problems existing in the prior art, one of the purposes of the present invention is to provide a method for preparing a microcapsule sustained-release water reducing agent, which has a simple and convenient preparation process, mild process parameters, is suitable for industrial processing and production, and can meet the needs of the construction field.

[0007] The second object of the present invention is to provide a microcapsule sustained-release water reducing agent, which has the advantages of strong slump retention performance, long sustained-release time, good adaptability, and can effectively reduce the slump loss of concrete.

[0008] The technical solution of the present invention is as follows:

[0009] The present invention provides a method for preparing a microcapsule sustained-release water reducing agent, comprising the following steps:

[0010] S1. Preparation of slow-release water reducing agent:

[0011] At a temperature of 40 to 70° C., a polyether monomer solution containing a functional monomer, an initiator and a molecular weight regulator is mixed for 3 to 6 hours, kept warm for 1 to 3 hours, and then water is added to prepare a slow-release water reducing agent with a mass fraction of 40%;

[0012] S2. Preparation of capsule wall solution:

[0013] At a temperature of 60-80°C, gelatin, gum arabic and deionized water are mixed in a mass ratio of 1:1:(10-20) for 2-4 hours;

[0014] S3. Preparation of microcapsule sustained-release water reducing agent:

[0015] At a temperature of 60-80°C, add the capsule wall solution of S2 to the sustained-release water reducer of S1 in a mass ratio of 1:4-8, mix for 0.5-1h, add the curing agent after the temperature drops to 25-30°C, mix for 2-5h, filter and dry to obtain the microcapsule sustained-release water reducer.

[0016] Preferably, the polyether monomer in S1 is isopentenyl polyethylene glycol ether;

[0017] The functional monomers include acrylic acid and hydroxyethyl acrylate.

[0018] Preferably, the mass ratio of the isopentenyl polyethylene glycol ether (TPEG), the acrylic acid (AA) and the hydroxyethyl acrylate (HEA) is TPEG:AA:HEA=(16-28):1-2:3.

[0019] Preferably, the initiator in S1 is at least one selected from potassium persulfate, azobisisobutyronitrile, benzoyl peroxide, ammonium cerium nitrate and ammonium cerium sulfate.

[0020] Preferably, the initiator is at least one selected from a hydrogen peroxide-ascorbic acid redox system, a K2S2O8-NaHSO3 redox system and a K2S2O8-Na2S2O4 redox system.

[0021] Preferably, the amount of the initiator used is 0.5-1.5% of the sum of the mass of the polyether monomer and the functional monomer.

[0022] Preferably, the molecular weight regulator in S1 is at least one selected from mercaptopropionic acid, mercaptoethanol and sodium methacrylic acid.

[0023] Preferably, the molecular weight regulator is used in an amount of 0.25-1% of the sum of the mass of the polyether monomer and the functional monomer.

[0024] Preferably, the solidifying agent in S3 is transglutaminase.

[0025] Preferably, the amount of the transglutaminase used is 1.5-2% of the mass of the capsule wall solution.

[0026] The present invention further provides a concrete microcapsule sustained-release water reducing agent prepared by the preparation method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. Compared with naphthalene-based water reducers, the microcapsule sustained-release water reducer provided by the present invention has the advantages of low dosage, high water reduction rate, strong slump retention, good fluidity and adaptability of fresh concrete, and significant molecular structure designability.

[0029] 2. The present invention uses isopentenyl polyethylene glycol ether as a polyether monomer, acrylic acid and hydroxyethyl acrylate as functional monomers, and introduces -COOR (ester group) into the water reducer structure, thereby reducing the content of -COOH. After the slow-release water reducer is added to cement, the -COOR group is first hydrolyzed in an alkaline environment and breaks into -COO － After that, it reacts with Ca on the surface of cement particles. 2+ Complexation, thus achieving a slow release of -COO － Effect.

[0030] 3. The capsule wall solution is obtained by heating and stirring gelatin, gum arabic and deionized water, and after mixing with the slow-release water reducer, the temperature is lowered to 25-30°C, the solubility of the solute is reduced, and then transglutaminase is added. Under the action of transglutaminase, gelatin and gum arabic are cross-linked with each other, and the solubility is reduced again, thereby precipitating gel, which wraps the slow-release water reducer. After drying and cooling, the microcapsule slow-release water reducer is obtained. When added to cement, the microcapsule wall gradually loosens and breaks, and the slow-release water reducer is slowly released, thereby achieving a "double slow-release" effect.

[0031] 4. The present invention further provides a method for preparing a microcapsule sustained-release water-reducing agent, which adopts a preparation method integrating polymerization and esterification, which can not only eliminate the problem of incompatibility between polyether and carboxylic acid, but also effectively control the molecular weight of the polymer. At the same time, no formaldehyde is used in the production process, and no waste liquid or waste gas is discharged, which has green and environmentally friendly performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a flow chart for preparing the microcapsule sustained-release water reducing agent. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with specific embodiments, but the embodiments of the present invention are not limited thereto.

[0034] Examples 1-6 and Comparative Example 1

[0035] The object of the present invention is to provide a microcapsule sustained-release water reducing agent and a preparation method thereof, which is achieved by the following technical scheme:

[0036] The polyether monomer used in the embodiment of the present invention is: isopentenyl polyethylene glycol ether; functional monomer: acrylic acid and hydroxyethyl acrylate; initiator: at least one selected from potassium persulfate, azobisisobutyronitrile, benzoyl peroxide, ammonium cerium nitrate, ammonium cerium sulfate, hydrogen peroxide-ascorbic acid redox system, K2S2O8-NaHSO3 redox system and K2S2O8-Na2S2O4 redox system; molecular weight regulator: at least one selected from mercaptopropionic acid, mercaptoethanol and sodium methyl methacrylate sulfonate; curing agent: transglutaminase, all of which are commercially available products.

[0037] The dissolved polyether monomer solution is placed in a three-necked flask, and functional monomers, initiators and molecular weight regulators are added. The mixture is reacted at 40-70° C. for 3-6 hours. After the reaction is complete, the mixture is kept warm for 1-3 hours to obtain a sustained-release water reducer. Then, water is added until the mass of the sustained-release water reducer accounts for 40% of the mass of the total solution. The raw material ratios and synthesis conditions of the sustained-release water reducer of Examples 1-6 and Comparative Example 1 are shown in Table 1, wherein the initiator and the molecular weight regulator are added in an amount of 0.5-1.5% of the sum of the mass of the polyether monomer and the functional monomer, as shown in Table 1.

[0038] Gelatin, gum arabic and deionized water were heated and stirred to obtain a capsule wall solution. The raw material ratio and synthesis conditions of the capsule wall solution of Examples 1-6 are shown in Table 2. The capsule wall solution was then added to the sustained-release water reducer, and then stirred at 60-80°C for 0.5-1h. After being evenly dispersed, transglutaminase was added after cooling to 25-30°C and continued to stir for 2-5h to generate a gel, which was filtered and dried to obtain a microcapsule sustained-release water reducer. The raw material ratio and synthesis conditions of the microcapsule sustained-release water reducer of Examples 1-6 are shown in Table 3, wherein the amount of transglutaminase used is 1.5-2% of the mass of the capsule wall solution.

[0039] Table 1 Raw material ratio and synthesis conditions of slow-release water reducing agent Unit: part

[0040]

[0041] Table 2 Raw material ratio and synthesis conditions of capsule wall solution Unit: part

[0042]

[0043]

[0044] Table 3 Raw material ratio and synthesis conditions of microcapsule sustained-release water reducing agent Unit: part

[0045]

[0046] The microcapsule slow-release water reducer prepared in Examples 1-6 and the slow-release water reducer prepared in Comparative Example 1 were added to cement, and the fluidity test was carried out according to GB / T8077-2000 "Test Method for Homogeneity of Concrete Admixtures", using the fluidity of the pure paste, and the dosage was 0.2% (solid content) of the cement mass. For Comparative Example 2, a common commercially available polycarboxylate water reducer was added to cement to carry out the fluidity test.

[0047] Table 4 Test results of Examples 1-6 and Comparative Examples 1-2

[0048]

[0049] The experimental results show that the cement paste with microcapsule slow-release water reducer can reach a fluidity of more than 290 mm in 2 hours, still maintains good fluidity in 3 hours, and still has a certain fluidity in 4 hours; while the fluidity of ordinary polycarboxylate water reducer has been significantly reduced in 2 hours, the fluidity in 3 hours is only 100 mm, and the fluidity in 4 hours has been completely lost; the fluidity loss of slow-release water reducer in 3 hours is relatively obvious, and the fluidity in 4 hours has also been completely lost. It can be seen that the microcapsule slow-release water reducer prepared by the present invention has a more obvious slow-release effect and has an excellent collapse-preserving effect.

[0050] The above is only a preferred embodiment of the present invention. A person skilled in the art may make several improvements and changes without departing from the inventive concept of the present invention, and all of these belong to the protection scope of the present invention.

Claims

1. A method for preparing a microcapsule sustained-release water reducing agent, characterized in that: The method comprises the following steps: S1. Preparation of slow-release water reducing agent: At a temperature of 40 to 70° C., a polyether monomer solution containing a functional monomer, an initiator and a molecular weight regulator is mixed for 3 to 6 hours, kept warm for 1 to 3 hours, and then water is added to prepare a slow-release water reducing agent with a mass fraction of 40%; S2. Preparation of capsule wall solution: At a temperature of 60-80°C, gelatin, gum arabic and deionized water are mixed in a mass ratio of 1:1:(10-20) for 2-4 hours; S3. Preparation of microcapsule sustained-release water reducing agent: At a temperature of 60-80°C, add the capsule wall solution of S2 to the sustained-release water reducer of S1 in a mass ratio of 1:4-8, mix for 0.5-1h, add the curing agent after the temperature drops to 25-30°C, mix for 2-5h, filter and dry to obtain the microcapsule sustained-release water reducer.

2. The method for preparing the microcapsule sustained-release water reducing agent according to claim 1, characterized in that: In S1 The polyether monomer is isopentenyl polyethylene glycol ether; The functional monomers include acrylic acid and hydroxyethyl acrylate.

3. The method for preparing the microcapsule sustained-release water reducing agent according to claim 2, characterized in that: The mass ratio of the isopentenyl polyethylene glycol ether (TPEG), the acrylic acid (AA) and the hydroxyethyl acrylate (HEA) is TPEG:AA:HEA=(16-28):(1-2):

3.

4. The method for preparing the microcapsule sustained-release water reducing agent according to claim 1, characterized in that: The initiator in S1 is at least one selected from potassium persulfate, azobisisobutyronitrile, benzoyl peroxide, ammonium cerium nitrate and ammonium cerium sulfate.

5. The method for preparing the microcapsule sustained-release water reducing agent according to claim 1, characterized in that: The initiator is at least one selected from a hydrogen peroxide-ascorbic acid redox system, a K2S2O8-NaHSO3 redox system and a K2S2O8-Na2S2O4 redox system.

6. The method for preparing the microcapsule sustained-release water reducing agent according to claim 4 or 5, characterized in that: The amount of the initiator used is 0.5-1.5% of the sum of the mass of the polyether monomer and the functional monomer.

7. The method for preparing the microcapsule sustained-release water reducing agent according to claim 1, characterized in that: The molecular weight regulator in S1 is at least one selected from mercaptopropionic acid, mercaptoethanol and sodium methacrylic acid.

8. The method for preparing the microcapsule sustained-release water reducing agent according to claim 7, characterized in that: The amount of the molecular weight regulator is 0.25-1% of the sum of the mass of the polyether monomer and the functional monomer.

9. The method for preparing the microcapsule sustained-release water reducing agent according to claim 1, characterized in that: The solidifying agent in S3 is transglutaminase.

10. The method for preparing the microcapsule sustained-release water reducing agent according to claim 9, characterized in that: The amount of the transglutaminase used is 1.5-2% of the mass of the capsule wall solution.

11. A concrete microcapsule sustained-release water reducing agent prepared according to the preparation method according to any one of claims 1 to 5.

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