Organic phosphine-chitosan high-temperature-resistant slow-release retarding microcapsule as well as preparation method and application thereof

Abstract

The invention relates to the field of building materials and chemical synthesis, and particularly discloses an organic phosphine-chitosan high-temperature-resistant slow-release retarding microcapsule as well as a preparation method and application thereof. The delayed coagulation microcapsule is prepared by the following steps: modifying chitosan, dissolving the modified chitosan in an acetic acid solution, adjusting the pH value, adding sodium chloroacetate, reacting, and treating to obtain the modified carboxymethyl chitosan. The preparation method comprises the following steps: mixing an organic phosphine retarder with a modified carboxymethyl chitosan solution, then adding a sodium tripolyphosphate cross-linking agent solution, carrying out a cross-linking reaction under specific temperature and pH conditions to form microcapsules, and finally separating, washing and drying to obtain the product. Through unique material combination and process design, the retarder has good stability and continuous slow release performance in a high-temperature or alkaline environment, the problems that an existing retarder is unstable at high temperature, the release rate is difficult to control and the like are effectively solved, the retarder is suitable for high-temperature and large-volume concrete construction, the concrete retarding time can be remarkably prolonged, and the service life of the retarder is prolonged. The construction quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of building admixtures, and in particular to an organic phosphine-chitosan high temperature resistant slow-release and slow-setting microcapsule and a preparation method and application thereof. Background Art

[0002] In concrete construction, especially in large-volume and high-temperature environments, retarders are crucial to ensure concrete performance and construction quality. Traditional retarders such as carboxylates, organic phosphonic acids, and polymer-modified materials mainly achieve the retarding effect by complexing calcium ions or inhibiting hydration reactions. However, these retarders have many problems at high temperatures: on the one hand, many retarders will decompose or chemically fail, resulting in uneven release and unstable control effects; on the other hand, temperature changes will intensify the reaction between the retarder and the calcium ions in the cement, accelerating its decomposition and making the hydration reaction time difficult to predict, affecting the progress and quality of the project. At the same time, it is difficult to control the release rate of traditional retarders at high temperatures, and they are prone to problems such as early inactivation and insufficient or excessive retarding time.

[0003] The root of these problems lies in the single mechanism of action of existing retarders, that is, directly complexing hydrated calcium ions or surface adsorption to delay the hydration reaction. This method works well at room temperature, but in high temperature or large-volume concrete applications, the hydration reaction is accelerated, the activity of the retarder molecules quickly fails, and it is difficult to achieve slow and stable release. Although existing technical research has attempted to compound retarders with polymers, it is easy to cause the active groups to be blocked, weakening the retarding effect, and the release of polymer-modified retarders at high temperatures is difficult to control, which cannot meet the construction needs of large-volume concrete. Summary of the invention

[0004] The present invention aims to solve the problems of poor stability and inability to continuously release the retarding effect of existing retarders when used at high temperatures, and provides an organophosphine-chitosan high temperature resistant slow-release slow-setting microcapsule, comprising a retarder small molecule and a chitosan-sodium tripolyphosphate cross-linked structure, wherein the retarder small molecule is encapsulated in the chitosan-sodium tripolyphosphate cross-linked structure, and the chitosan-sodium tripolyphosphate cross-linked structure has the structural formula: .

[0005] On the basis of the above technical solution, further, the retarder is an organic phosphine retarder, and its structural formula is: ; Wherein, R is an organic group containing a hydrocarbon chain or a functional group.

[0006] On the basis of the above technical solution, further, the retarder includes at least one of HEDP, ATMP, or phosphite.

[0007] The present invention also provides a method for preparing an organophosphine-chitosan high temperature resistant sustained-release and slow-setting microcapsule, comprising the following preparation steps: S100, using sodium chloroacetate as a raw material to modify chitosan to obtain partially modified carboxymethyl chitosan; wherein the molar ratio of the sodium chloroacetate to the chitosan is (0.4-0.8):1; In this process, the amount of modifier used is less than that of chitosan in order to perform only partial modification, and the carboxymethyl substitution rate of chitosan is controlled between 20% and 50%. This range can ensure that the modified chitosan has appropriate water solubility, can be gradually dissolved under alkaline conditions, achieve long-term sustained release, and maintain sufficient structural strength.

[0008] S200, using an organic phosphine retarder, a crosslinking agent and the obtained partially modified carboxymethyl chitosan through an ion crosslinking reaction to form microcapsules; The molar ratio of the amount of the organic phosphine retarder to chitosan is (0.3-0.6):1; The molar ratio of the cross-linking agent to chitosan is (0.1-0.5):1; S300, separating, collecting and drying the obtained microcapsules to obtain organophosphine-chitosan high temperature resistant slow-release and slow-setting microcapsules.

[0009] On the basis of the above technical scheme, further, in S100, chitosan is dissolved in acetic acid solution, preferably chitosan is dissolved in 1000 mL of 0.1 M acetic acid, stirred at room temperature until completely dissolved, the pH of the solution is adjusted to 7-8, sodium chloroacetate is added, the reaction temperature is maintained at 35-55°C, and the reaction is stirred; after the reaction is completed, a pH regulator is added dropwise to adjust the pH value of the reaction solution to 8-9, so that the modified chitosan is precipitated and separated; the precipitated carboxymethyl chitosan is extracted, washed with deionized water and freeze-dried to obtain partially modified carboxymethyl chitosan.

[0010] On the basis of the above technical solution, further, in S200, the organic phosphine retarder solution is slowly added to the partially modified carboxymethyl chitosan solution and stirred evenly, and the crosslinker solution is slowly added to the mixed solution of the partially modified carboxymethyl chitosan and the organic phosphine retarder solution using a dropping device, while maintaining the solution temperature at 20-30° C., and controlling the total dropping time to be 30-60 min; the pH value is adjusted by adding NaOH solution dropwise to maintain 7-8, and after the crosslinking reaction is completed, the solution is allowed to stand to form microcapsules.

[0011] On the basis of the above technical solution, further, the chitosan is a chitosan with a medium-high molecular weight and a deacetylation degree of 80%-90%, and its general structural formula is:

[0012] Wherein m and n represent the degree of polymerization, and the molecular weight of chitosan is 100-300 kDa, preferably 150 kDa.

[0013] On the basis of the above technical solution, further, the general structural formula of the partially modified carboxymethyl chitosan obtained in S100 is:

[0014] Where p and q represent the degree of polymerization.

[0015] On the basis of the above technical solution, further, the organic phosphine retarder includes at least one of HEDP, ATMP, or phosphite; The cross-linking agent is sodium tripolyphosphate.

[0016] The mechanism of using sodium tripolyphosphate as a crosslinking agent is through its polyphosphate (P3O 10 5 ⁻) The ions generate electrostatic interactions with the amino (-NH2) and hydroxyl (-OH) groups in the chitosan molecules, forming a stable ion-crosslinked network structure The present invention also provides a use of any of the above-mentioned organophosphine-chitosan high temperature resistant slow-release and slow-setting microcapsules in concrete construction.

[0017] The technical solution of the present invention has the following principles and beneficial effects: The organophosphine-chitosan high temperature resistant slow-release and slow-setting microcapsules provided by the present invention combine modified chitosan with an organophosphine retarder to form a microcapsule structure with high temperature slow-release properties, and ensure the stability and sustained action (slow-release effect) of the slow-release agent in a high temperature environment through an ion cross-linking reaction. In the preparation process scheme of the present invention, the amino cationic characteristics of chitosan are partially retained through carboxymethylation treatment, so that the modified chitosan has good hydrophilicity and shell material stability, and the coating ability and sustained release effect of the microcapsule are enhanced; sodium tripolyphosphate is used as a cross-linking agent, and the modified chitosan and the organic phosphine retarder form a shell-core structure through ionic cross-linking, so as to ensure the sustained release and stability in a high temperature environment, prolong the action time, and avoid the premature failure of the traditional retarder under high temperature conditions.

[0018] The organophosphine-chitosan high temperature resistant slow-release slow-setting microcapsules provided by the invention realize the effective slow-setting of concrete in a high temperature construction environment, and meet the special requirements of concrete construction in a high temperature environment. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The present invention provides the following embodiments of organophosphine-chitosan high temperature resistant sustained-release slow-setting microcapsules: It includes a retarder small molecule and a chitosan-sodium tripolyphosphate cross-linked structure, wherein the retarder small molecule is encapsulated in the chitosan-sodium tripolyphosphate cross-linked structure, and the chitosan-sodium tripolyphosphate cross-linked structure has the structural formula: .

[0021] Wherein, the retarder is an organic phosphine retarder, and its structural formula is: ; Wherein, R is an organic group containing a hydrocarbon chain or a functional group.

[0022] More specifically, the retarder may be at least one of HEDP, ATMP, or phosphite. The present invention also provides the following embodiment of the preparation method of the organophosphine-chitosan high temperature resistant sustained-release slow-setting microcapsules: Example 1 Carboxylation modification of chitosan: Dissolve 100g of medium molecular weight chitosan (150kDa) in 1000mL of 0.1M acetic acid solution and stir at room temperature until completely dissolved. Adjust the pH of the solution to 7-8, add 50g of sodium chloroacetate, maintain the reaction temperature at 40°C, and stir for 1 hour. After the reaction is completed, add a pH regulator dropwise to adjust the pH value of the reaction solution to 8-9 to precipitate and separate the modified chitosan. Collect the precipitated product by vacuum filtration, wash with deionized water and freeze-dry to obtain partially modified carboxymethyl chitosan.

[0023] Mixing and cross-linking reaction of reactant solutions: Dissolve 50g of HEDP retarder in 200ml of deionized water to form a uniform retarder solution. Dissolve the partially modified carboxymethyl chitosan obtained in the previous step in 800ml of deionized water to form a uniform shell material solution. Slowly add the retarder solution to the chitosan solution and stir evenly to ensure mixing. Dissolve 50g of sodium tripolyphosphate in 200mL of deionized water to generate a cross-linker solution. Use a dropper to slowly add the cross-linker solution to the mixed solution of chitosan and retarder at a certain speed, while keeping the solution temperature at 25°C, and control the total drop time to 30min. Adjust by adding 0.5M NaOH solution dropwise to keep the pH value at neutral (pH 7-8). Continue stirring the reaction for 1 hour, and let it stand after the cross-linking reaction is completed to form microcapsules.

[0024] Collection and drying of generated microcapsules: The generated microcapsule particles were separated by vacuum filtration. The unreacted crosslinking agent and shell material residues were washed three times with deionized water. The microcapsules were dried at 40°C to constant weight to obtain the final product.

[0025] Example 2 The molecular weight of chitosan is increased. Specifically, in the chitosan carboxylation modification step, chitosan is replaced with 100 g of chitosan with a molecular weight of 300 kDa. The rest is the same as Example 1.

[0026] Example 3 Increase the amount of modifier, specifically in the chitosan carboxylation modification step, the amount of sodium chloroacetate added is changed to 65g, and the rest is the same as Example 1 Example 4 increases the time for adding the crosslinking agent. Specifically, in the steps of mixing the reactant solution and crosslinking reaction, the time for adding the crosslinking agent solution is changed to 60 minutes. The rest is the same as in Example 1. In Example 5, the amount of crosslinking agent is increased, specifically in the steps of mixing the reactant solution and crosslinking reaction, specifically the amount of sodium tripolyphosphate added is changed to 69 g, and the rest is the same as in Example 1.

[0027] Example 6 increases the amount of retarder, specifically in the steps of mixing the reactant solution and cross-linking reaction, specifically the amount of HEDP retarder added is changed to 60 g, and the rest is the same as Example 1.

[0028] Mortar test verification The mortar test was conducted on the five examples of products in a 55 degree environment. Before mixing, the mortar raw materials were heated to 55 degrees Celsius; after mixing, the mortar was placed in a 55 degree Celsius oven for insulation, and the initial setting time test was conducted every 15 minutes from the third hour.

[0029] The formula of mortar is cement C: 400g, sand S: 800g, water W: 170g, admixture A: 2% of the total mass of the adhesive. The admixture used is Point-S pure water-reducing admixture (without slump retention or retarding effect) produced by Kezhijie New Materials Group Co., Ltd.

[0030] Wherein, comparative example 1 is a blank control; Comparative Example 2 is a comparison of adding organic phosphine HEDP as a retarder in mortar.

[0031] Comparative Example 3 is a comparison of directly adding a mixture of organic phosphine HEDP and chitosan (configured in a molar ratio of 0.5:0.1) into the mortar as a retarder.

[0032] Table 1 Fluidity and setting time of different retarders at high temperature

[0033] The above results show that the performance of the organophosphine-chitosan high temperature resistant slow-release slow-setting microcapsules prepared by the present invention was evaluated in a high temperature environment of 55 degrees through a mortar test experiment. The experimental results clearly show that compared with the HEDP molecule and other comparative samples, the organophosphine-chitosan high temperature resistant slow-release slow-setting microcapsules provided by the present invention exhibit excellent slow-setting performance, and can significantly prolong the initial setting time of the mortar under high temperature conditions with stable release.

[0034] The organophosphine-chitosan high temperature resistant slow-release slow-setting microcapsules provided by the present invention can stably form chelates with calcium ions, and still have a slow-setting effect at high temperatures. At the same time, chitosan and sodium tripolyphosphate are used to carry out a cross-linking reaction, and the organophosphine retarder is wrapped with chitosan. The chitosan structure and the network structure formed by cross-linking can enhance the high temperature stability of the molecule and provide a good slow-setting effect for high temperature cement slurry. In addition, the present invention achieves slow release by means of carboxymethylated chitosan and a three-dimensional cross-linked network structure. By adjusting the degree of carboxymethylation and the cross-linking density, the release rate of the retarder can be further controlled to achieve a medium- and long-term slow-release effect.

[0035] In an alkaline concrete environment, traditional slow-release materials will fail due to high pH values. However, the organophosphine-chitosan high-temperature resistant slow-release and slow-setting microcapsules provided by the present invention can stably and slowly release the slow-setting components under alkaline conditions, ensuring the fluidity and delayed setting time required for long-term construction, and are suitable for large-scale concrete projects or long-term construction under high temperature conditions.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An organophosphine-chitosan high temperature resistant sustained-release slow-setting microcapsule, characterized in that: It includes a retarder small molecule and a chitosan-sodium tripolyphosphate cross-linked structure, wherein the retarder small molecule is encapsulated in the chitosan-sodium tripolyphosphate cross-linked structure, and the chitosan-sodium tripolyphosphate cross-linked structure has the structural formula: 。 2. The organophosphine-chitosan high temperature resistant sustained-release slow-setting microcapsules according to claim 1, characterized in that: The retarder is an organic phosphine retarder, and its structural formula is: ； Wherein, R is an organic group containing a hydrocarbon chain or a functional group.

3. The organophosphine-chitosan high temperature resistant sustained-release slow-setting microcapsules according to claim 1, characterized in that: The retarder includes at least one of HEDP, ATMP, or phosphite.

4. A method for preparing organophosphine-chitosan high temperature resistant sustained-release slow-setting microcapsules, characterized in that: The method comprises the following preparation steps: S100, using sodium chloroacetate as a raw material to modify chitosan to obtain partially modified carboxymethyl chitosan; wherein the molar ratio of the sodium chloroacetate to the chitosan is (0.4-0.8):1; S200, forming microcapsules by subjecting the organic phosphine retarder solution, the crosslinking agent solution and the obtained partially modified carboxymethyl chitosan to ion crosslinking reaction; The molar ratio of the amount of the organic phosphine retarder to chitosan is (0.3-0.6):1; The molar ratio of the cross-linking agent to chitosan is (0.1-0.5):1; S300, separating, collecting and drying the obtained microcapsules to obtain organophosphine-chitosan high temperature resistant slow-release and slow-setting microcapsules.

5. The method for preparing the organophosphine-chitosan high temperature resistant sustained-release and slow-setting microcapsules according to claim 4, characterized in that: In S100, chitosan is dissolved in an acetic acid solution and stirred at room temperature until it is completely dissolved, the pH of the solution is adjusted to 7-8, sodium chloroacetate is added, the reaction temperature is maintained at 35-55°C, and the reaction is stirred; after the reaction is completed, a pH regulator is added dropwise to adjust the pH value of the reaction solution to 8-9, so that the modified chitosan is precipitated and separated; the precipitated carboxymethyl chitosan is extracted, washed with deionized water and freeze-dried to obtain partially modified carboxymethyl chitosan.

6. The method for preparing the high temperature resistant sustained-release and slow-setting organophosphine-chitosan microcapsules according to claim 4, characterized in that: In S200, the organic phosphine retarder solution is slowly added to the partially modified carboxymethyl chitosan solution and stirred evenly, and the crosslinker solution is slowly added to the mixed solution of the partially modified carboxymethyl chitosan and the organic phosphine retarder solution using a dropping device, while maintaining the solution temperature at 20-30° C., and controlling the total dropping time to be 30-60 min; the pH value is adjusted by adding NaOH solution dropwise to maintain 7-8, and after the crosslinking reaction is completed, the solution is allowed to stand to form microcapsules.

7. The method for preparing the high temperature resistant sustained-release and slow-setting microcapsules of organophosphine-chitosan according to claim 4, characterized in that: The chitosan is a chitosan with a medium-high molecular weight and a deacetylation degree of 80%-90%, and its general structural formula is: Wherein m and n represent the degree of polymerization, and the molecular weight of chitosan is 100-300 kDa, preferably 150 kDa.

8. The method for preparing the organophosphine-chitosan high temperature resistant sustained-release and slow-setting microcapsules according to claim 4, characterized in that: The general structural formula of the partially modified carboxymethyl chitosan obtained in S100 is: Where p and q represent the degree of polymerization.

9. The method for preparing the high temperature resistant sustained-release and slow-setting microcapsules of organophosphine-chitosan according to claim 4, characterized in that: The organic phosphine retarder includes at least one of HEDP, ATMP, or phosphite; The cross-linking agent is sodium tripolyphosphate.

10. Use of the organophosphine-chitosan high temperature resistant slow-release and slow-setting microcapsules according to any one of claims 1 to 9 in concrete construction.

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