Polycarboxylate superplasticizer as well as preparation method and application thereof

Abstract

The invention relates to a polycarboxylate superplasticizer as well as a preparation method and application thereof. Comprising the following steps: mixing and dissolving IPEG and water, heating to a certain temperature, and adding an oxidizing agent to prepare a solution A; mixing a reducing agent and a chain transfer agent, and adding water to prepare a solution B; mixing an unsaturated acid monomer and a phosphate group-containing monomer, and adding water to prepare a solution C; and adding the solution B and the solution C into the solution A, stirring at a constant temperature until the reaction is completed, and cooling to room temperature to obtain the polycarboxylate superplasticizer, thereby completing the reaction. Compared with the prior art, the method has the advantages that the adsorption of the polycarboxylic acid water reducer to the micro powder is reduced, and the dispersion effect of the polycarboxylic acid water reducer is improved, so that the working performance of the high-micro-powder regenerated masonry mortar is improved, and the like.

Description

Technical Field

[0001] The invention relates to the field of concrete admixture preparation, and in particular to a polycarboxylate water reducer and a preparation method and application thereof. Background Art

[0002] The scale of construction waste output in my country has increased, and its large accumulation has led to many environmental burdens. It has become an industry consensus to use construction waste to recycle building materials to protect the environment, save energy and reduce emissions. The broken concrete contained in construction waste can be converted into recycled aggregate for masonry mortar production after secondary crushing. In addition, construction waste also contains a large amount of micropowder, which can significantly improve the strength of mortar when added to mortar in an appropriate amount. The composite application of recycled aggregate and micropowder to prepare high-micropowder recycled masonry mortar can greatly improve the resource utilization rate of construction waste and alleviate its accumulation dilemma. However, due to characteristics such as high water absorption, recycled aggregate and micropowder will cause a significant decrease in the workability of mortar. In practice, polycarboxylic acid water reducer must be added to improve the workability of high-micropowder recycled masonry mortar. Nevertheless, due to the similar particle size of micropowder and cement, the two compete to adsorb water reducer molecules, resulting in a significant reduction in the dispersion effect of water reducer. The above situation has hindered the engineering and industrial application of high-micropowder recycled masonry mortar, and it is urgent to develop high-efficiency polycarboxylic acid water reducer specifically adapted to high-micropowder recycled masonry mortar.

[0003] Patent publication number CN117903378A discloses a polycarboxylate water reducer containing a phosphate group, and a preparation method and application thereof, comprising the following steps: adding isopentanol polyoxyethylene ether to a reactor, adding deionized water, stirring automatically at room temperature to completely dissolve it, adding an aqueous solution of an unsaturated carboxylic acid small monomer, a chain transfer agent, an aqueous solution of an initiator, and a small monomer containing a phosphate group, adjusting the temperature of the reactor to 65-70°C, reacting at this temperature for 2-2.5h; then raising the temperature to 70-75°C, keeping the temperature for 3-3.5h, cooling to room temperature, and obtaining a polycarboxylate water reducer containing a phosphate group. However, in the preparation process of the water reducer, the initiator containing an oxidant is added after the isopentanol polyoxyethylene ether, which is prone to problems such as uneven reaction rate, and the reaction process temperature is high, which has certain reaction uncontrollability and danger. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art that the polycarboxylate water-reducing agent has poor adaptability and poor dispersion effect in high-micropowder recycled mortar, and to provide a polycarboxylate water-reducing agent and its preparation method and application, reduce the adsorption of polycarboxylate water-reducing agent on micropowder, improve the dispersion effect of polycarboxylate water-reducing agent, thereby improving the working performance of high-micropowder recycled masonry mortar.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] One of the technical solutions of the present invention is to provide a method for preparing a polycarboxylate water-reducing agent, comprising the following steps:

[0007] Mix and dissolve isopentanol polyoxyethylene ether (IPEG) and water, heat to a certain temperature, add an oxidant, and prepare solution A;

[0008] Mix the reducing agent and the chain transfer agent, and add water to prepare solution B;

[0009] The unsaturated acid monomer and the phosphoric acid group-containing monomer are mixed, and water is added to prepare solution C;

[0010] Solution B and solution C are added to solution A, stirred at a constant temperature until the reaction is completed, cooled to room temperature to obtain a polycarboxylate water reducer, and the reaction is completed.

[0011] Further, IPEG and water are mixed and dissolved, and heated to 25-35°C, preferably 29-31°C; the temperature of constant temperature stirring is 25-35°C, preferably 29-31°C.

[0012] Furthermore, in the solution A, the molar ratio of the IPEG, the unsaturated acid monomer, and the phosphoric acid group-containing monomer is 1:3-5:0.01-0.2, preferably 1-3.5-4.5:0.05-0.15;

[0013] The mass ratio of the oxidant, the reducing agent, the chain transfer agent and the total mass of IPEG, the unsaturated acid monomer and the phosphoric acid group-containing monomer is 1-1.2:0.15-0.2:0.35-0.4:100.

[0014] Furthermore, the mass concentration of IPEG in the solution A is 30% to 80%, preferably 40% to 60%;

[0015] The mass concentration of the reducing agent in solution B is 1% to 5%, preferably 1% to 3%;

[0016] The mass concentration of the unsaturated acid monomer in solution C is 30% to 80%, preferably 40% to 60%.

[0017] Further, the oxidant is ammonium persulfate (APS);

[0018] The reducing agent is ascorbic acid (VC);

[0019] The chain transfer agent is β-mercaptopropionic acid (MPA);

[0020] The unsaturated acid monomer is acrylic acid (AA);

[0021] The phosphoric acid group-containing monomer is 2-(methacryloyloxy)ethyl phosphate (MOEP).

[0022] Furthermore, the molecular weight of the IPEG is 4000-5000.

[0023] Furthermore, the solution B and solution C are added to the solution A through a peristaltic pump, the total duration of the adding process is 3 to 3.5 hours, and the duration of constant temperature stirring after the addition is 0.5 to 2 hours.

[0024] The second technical solution of the present invention is to provide a polycarboxylic acid water reducer, which is prepared by the preparation method.

[0025] Furthermore, the weight average molecular weight of the polycarboxylate water-reducing agent is 4,000 to 45,000.

[0026] The third technical solution of the present invention is to provide an application of a polycarboxylate water-reducing agent in the field of high-micronized powder recycled masonry mortar, characterized in that the polycarboxylate water-reducing agent is used to prepare high-micronized powder recycled masonry mortar.

[0027] Furthermore, the high-micro powder recycled masonry mortar includes micro powder, recycled aggregate, cement, polycarboxylic acid water reducer and water.

[0028] Furthermore, the mass content of the fine powder in the high-fine powder recycled masonry mortar is 10wt% to 20wt%.

[0029] Furthermore, the solid content of the polycarboxylate water-reducing agent in the high-micronized powder recycled masonry mortar is 0.1wt% to 0.5wt%, that is, the mass of the polycarboxylate water-reducing agent in all solids in the high-micronized powder recycled masonry mortar is 0.1wt% to 0.5wt%.

[0030] Furthermore, the mass ratio of the cement to the recycled aggregate is 1:2-3, preferably 1:2-2.5.

[0031] Furthermore, the mass ratio of water to cement (ie, water-cement ratio) is 0.4-0.45:1.

[0032] Furthermore, the particle size of the recycled aggregate is 1.18-4.75 mm.

[0033] Furthermore, the cement is silicate cement.

[0034] Furthermore, the particle size of the micro powder is less than 0.075 mm.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] (1) The polycarboxylate water-reducing agent provided by the present invention is synthesized by a one-step method using IPEG, unsaturated acid monomers, phosphoric acid group-containing monomer oxidants, reducing agents, and chain transfer agents as raw materials. The preparation process is simple, the reaction is mild, and the pollution is small.

[0037] (2) The polycarboxylic acid water reducer provided by the present invention has adsorption groups such as carboxyl and phosphate in the reaction polymer chain, which can reduce the adsorption of the water reducer on the fine powder and improve the dispersion effect of the water reducer.

[0038] (3) The present invention fully disperses IPEG and the oxidant before the reaction, which reduces the temperature required to maintain the reaction rate, improves the controllability of the reaction process, and reduces the risk of the reaction.

[0039] (4) The present invention adds the oxidant before the reaction and fully disperses it, thereby avoiding uneven generation of free radicals when the oxidant is added during the reaction and improving the purity of the product.

[0040] (5) The present invention ensures uniform concentration distribution of the reducing agent, chain transfer agent and unsaturated monomer in the system by slowly adding solutions B and C, thereby improving the reaction efficiency.

[0041] (6) When preparing high-micron powder recycled masonry mortar, adding a small amount of the polycarboxylic acid water-reducing agent provided by the present invention can significantly improve the working performance of the high-micron powder recycled masonry mortar. DETAILED DESCRIPTION

[0042] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments. Based on the given embodiments, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0043] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art.

[0044] In the following examples, CAS No. of VC is 50-81-7, Shanghai test; CAS No. of MPA is 107-96-0, Alfa-A13261, 99%; CAS No. of AA is 79-10-7, AR (Shanghai test), ≥99.0%; CAS No. of MOEP is 52628-03-2, 98% (Wokai); all of the above are purchased from Sinopharm Chemical Reagent Co., Ltd. Benchmark silicate cement (PO 42.5) was purchased from Tangshan Polar Bear Building Materials Co., Ltd. Recycled micropowder and recycled aggregate were collected from abandoned building demolition sites. Commercial water reducer is -I polycarboxylic acid high performance water reducer, purchased from Jiangsu Subote New Materials Co., Ltd.

[0045] Example 1

[0046] A method for preparing a polycarboxylate water-reducing agent comprises the following steps:

[0047] (1) 112.9 g of IPEG was placed in a flask, and an equal amount of water was added, followed by placing in a 30°C water bath with an external electric stirrer until the IPEG was dissolved. 0.12 g of APS (oxidant) was then added to the solution to form solution A.

[0048] (2) Add 0.18 g VC (reducing agent) and 0.42 g MPA (chain transfer agent) into a beaker, and add 29.4 g water. Stir with a glass rod to prepare a mixed solution B.

[0049] (3) Add 0.5 g AA (unsaturated acid monomer) and 6.6 g MOEP (monomer containing phosphoric acid group) into a beaker, and add 7.1 g water, and stir with a glass rod to prepare unsaturated monomer solution C.

[0050] (4) Using a peristaltic pump, solution B and unsaturated monomer solution C were slowly added to solution A at the same time. The pumping rates were 0.04 ml / min and 0.16 ml / min, respectively. The total duration of the addition process was 3.5 h. After the addition was completed, the solution was stirred at a constant temperature of 30° C. for 1 h. Then, the solution was poured out of the flask and cooled to room temperature to obtain the polycarboxylic acid water reducer.

[0051] According to the ratio of raw materials to water, the solid content of the polycarboxylate water-reducing agent is calculated to be 40%.

[0052] Sampling was performed and the weight average molecular weight of the water reducer was determined by GPC to be 42977 and the dispersion coefficient was 1.6.

[0053] The polycarboxylate water-reducing agent prepared in this example is used to prepare high-micronized recycled masonry mortar, as follows:

[0054] The high-micro powder recycled masonry mortar comprises micro powder, recycled aggregate, cement, polycarboxylic acid water reducer and water.

[0055] The high-micro powder recycled masonry mortar comprises a gel material, a polycarboxylate water reducer, and water, and the cementitious material comprises micro powder, recycled aggregate, and cement, wherein specifically 90wt% of standard silicate cement (PO 42.5), 10wt% of micro powder with a particle size less than 0.075mm, 33wt% of 1.18-2.36mm and 67wt% of 2.36-4.75mm recycled fine aggregate are used, the amount of the polycarboxylate water reducer is 0.1wt% of the cementitious material, the water-cement ratio is 0.45, the mass ratio of cement to recycled aggregate is 1:2, the mortar is mixed with reference to GB / T 17671-2021, and the fluidity of the mortar is measured with reference to GB / T 2419-2009 after mixing.

[0056] Example 2

[0057] Compared with Example 1, most of the contents are the same, except that during the preparation of high-micro-powder recycled masonry mortar, the dosage of micro-powder is adjusted to 15 wt %.

[0058] Example 3

[0059] Compared with Example 1, most of the contents are the same, except that during the preparation of high-micro-powder recycled masonry mortar, the dosage of micro-powder is adjusted to 20 wt%.

[0060] Example 4

[0061] Compared with Example 1, most of the contents are the same, except that in the preparation process of high-micronized powder recycled masonry mortar, the dosage of polycarboxylate water-reducing agent is adjusted to 0.3%.

[0062] Example 5

[0063] Compared with Example 2, most of the contents are the same, except that during the preparation of the high-micronized powder recycled masonry mortar, the dosage of the polycarboxylate water-reducing agent is adjusted to 0.3%.

[0064] Example 6

[0065] Compared with Example 3, most of the above are the same, except that in the preparation process of high-micro powder recycled masonry mortar, the dosage of polycarboxylate water-reducing agent is adjusted to 0.3%.

[0066] Example 7

[0067] Compared with Example 1, most of the above are the same, except that in the preparation process of high-micro powder recycled masonry mortar, the dosage of polycarboxylate water-reducing agent is adjusted to 0.5%.

[0068] Example 8

[0069] Compared with Example 2, most of the contents are the same, except that during the preparation of the high-micronized powder recycled masonry mortar, the dosage of the polycarboxylate water-reducing agent is adjusted to 0.5%.

[0070] Example 9

[0071] Compared with Example 3, most of the above are the same, except that during the preparation of the high-micronized powder recycled masonry mortar, the dosage of the polycarboxylate water-reducing agent is adjusted to 0.5%.

[0072] Comparative Example 1

[0073] Compared with Example 1, most of the steps are the same except that the polycarboxylate water-reducing agent is changed to a commercial water-reducing agent.

[0074] Comparative Example 2

[0075] Compared with Example 2, most of the steps are the same except that the polycarboxylate water-reducing agent is changed to a commercial water-reducing agent.

[0076] Comparative Example 3

[0077] Compared with Example 3, most of the steps are the same except that the polycarboxylate water-reducing agent is changed to a commercial water-reducing agent.

[0078] Comparative Example 4

[0079] Compared with Example 4, most of the steps are the same except that the polycarboxylate water-reducing agent is changed to a commercial water-reducing agent.

[0080] Comparative Example 5

[0081] Compared with Example 5, most of the steps are the same except that the polycarboxylate water-reducing agent is changed to a commercial water-reducing agent.

[0082] Comparative Example 6

[0083] Compared with Example 6, most of the steps are the same except that the polycarboxylate water-reducing agent is changed to a commercial water-reducing agent.

[0084] Comparative Example 7

[0085] Compared with Example 7, most of the steps are the same except that the polycarboxylate water-reducing agent is changed to a commercial water-reducing agent.

[0086] Comparative Example 8

[0087] Compared with Example 8, most of the steps are the same except that the polycarboxylate water-reducing agent is changed to a commercial water-reducing agent.

[0088] Comparative Example 9

[0089] Compared with Example 9, most of the steps are the same except that the polycarboxylate water-reducing agent is changed to a commercial water-reducing agent.

[0090] The fluidity test results of the high-micropowder recycled masonry mortar prepared in Examples 1 to 9 and Comparative Examples 1 to 9 are shown in Tables 1 and 2.

[0091] Table 1 Test results of fluidity of high-micro powder recycled masonry mortar prepared in Examples 1 to 9

[0092]

[0093] Table 2 Test results of fluidity of high-micro powder recycled masonry mortar prepared in Examples 1 to 9

[0094]

[0095] It can be seen from the results in Tables 1 and 2 that the high-micronized recycled masonry mortar prepared by the present invention has good adaptability, and the low-dosage carboxylic acid water reducer can effectively improve the fluidity of the recycled masonry mortar. In addition, compared with commercial water reducers, the carboxylic acid water reducer prepared by the present invention significantly improves the fluidity of the recycled masonry mortar.

[0096] Although the present invention has been described in detail above by means of general description, specific implementation methods and tests, it is obvious to those skilled in the art that some modifications or improvements may be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a polycarboxylate water-reducing agent, characterized in that: The following steps are involved: IPEG and water are mixed and dissolved, heated to a certain temperature, and an oxidant is added to prepare solution A; Mix the reducing agent and the chain transfer agent, and add water to prepare solution B; The unsaturated acid monomer and the phosphoric acid group-containing monomer are mixed, and water is added to prepare solution C; Solution B and solution C are added to solution A, stirred at a constant temperature until the reaction is completed, cooled to room temperature to obtain a polycarboxylate water reducer, and the reaction is completed.

2. The method for preparing a polycarboxylate water-reducing agent according to claim 1, characterized in that: Mix and dissolve IPEG and water, and heat to 25-35°C; the temperature for constant temperature stirring is 25-35°C.

3. The method for preparing a polycarboxylate water-reducing agent according to claim 1, characterized in that: In the solution A, the molar ratio of the IPEG, the unsaturated acid monomer, and the phosphoric acid group-containing monomer is 1:3-5:0.01-0.2; The mass ratio of the oxidant, the reducing agent, the chain transfer agent and the total mass of IPEG, the unsaturated acid monomer and the phosphoric acid group-containing monomer is 1-1.2:0.15-0.2:0.35-0.4:

100.

4. The method for preparing a polycarboxylate water-reducing agent according to claim 1, characterized in that: The mass concentration of IPEG in the solution A is 30% to 80%; The mass concentration of the reducing agent in solution B is 1% to 5%; The mass concentration of the unsaturated acid monomer in solution C is 30% to 80%.

5. The method for preparing a polycarboxylate water-reducing agent according to claim 1, characterized in that: The oxidant is APS; The reducing agent is VC; The chain transfer agent is MPA; The unsaturated acid monomer is A; The phosphoric acid group-containing monomer is MOE.

6. The method for preparing a polycarboxylate water-reducing agent according to claim 1, characterized in that: The solution B and solution C are added to the solution A through a peristaltic pump. The total duration of the adding process is 3 to 3.5 hours. After the adding, the constant temperature stirring duration is 0.5 to 2 hours.

7. A polycarboxylate water-reducing agent, prepared by the preparation method according to any one of claims 1 to 6.

8. A polycarboxylate water reducer according to claim 7, characterized in that: The weight average molecular weight of the polycarboxylate water reducer is 4,000 to 45,000.

9. The use of a polycarboxylate water-reducing agent as claimed in claim 7 in the field of high-micronized powder recycled masonry mortar, characterized in that: The polycarboxylate water reducer is used for preparing high-micro powder recycled masonry mortar.

10. The use of a polycarboxylate water reducer according to claim 9, characterized in that: The high-micro powder recycled masonry mortar comprises micro powder, recycled aggregate, cement, polycarboxylic acid water reducing agent and water.

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