A kind of polycarboxylic acid water-reducing agent with improved workability and preparation method thereof

Abstract

The present invention discloses a workability-improved polycarboxylate water-reducing agent and a preparation method thereof, and belongs to the technical field of building materials. The polycarboxylate water-reducing agent in the present invention is prepared from polyether macromonomers, unsaturated functional small monomers, workability-improving monomers, redox initiation systems, chain transfer agents, and crosslinking agents as raw materials through condensation polymerization and free radical copolymerization. The present invention grafts and crosslinks workability-improving monomers onto polyether macromonomers and acrylic acid, enriches the branching types of the polycarboxylate water-reducing agent, increases the branching length of the polycarboxylate water-reducing agent, optimizes the comb-like structure of the polycarboxylate water-reducing agent molecule, and improves the steric hindrance of the polycarboxylate water-reducing agent. The polycarboxylate water-reducing agent with longer side chains can better block the mutual aggregation of cementitious materials on the one hand, and can also better resist the adsorption of the porous structure of aggregates on the other hand, thereby reducing the adsorption loss of the polycarboxylate water-reducing agent.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to a workability-improved polycarboxylate water-reducing agent and a preparation method thereof. Background Art

[0002] In order to protect the ecological environment and reduce the production cost of concrete, there is a clear trend for concrete production companies to use machine-made sand to completely or partially replace natural sand as fine aggregate. However, compared with natural sand, machine-made sand has great differences in particle shape, particle grading, stone powder and mud content. The concrete prepared with machine-made sand has certain differences in working performance and strength compared with natural sand. Because the grading of machine-made sand is not as reasonable as river sand during the production process, it is easy to break the grading, and the production stability is poor, which causes concrete to be prone to segregation, bleeding, poor workability and other workability problems during the use of machine-made sand.

[0003] The workability of concrete is one of the important factors that determine the construction performance of concrete. The important indicators that determine the workability of concrete include water retention, cohesion and fluidity. At present, the workability of concrete can be improved in many ways, including optimizing the mix ratio of concrete, optimizing the grading and particle shape of concrete fine aggregate, increasing the air content of concrete, adding workability improvement components to concrete admixtures, changing the water-reducing components of concrete admixtures, etc. However, different methods of adjusting workability have negative effects or constraints on concrete: the mix ratio of concrete is often affected by the overall cost of concrete and construction requirements and cannot be adjusted significantly; currently, there is a shortage of high-quality concrete fine aggregate resources, and more and more concrete production uses machine-made sand as fine aggregate that is not conducive to workability; admixture plants often add dextrin or cellulose additives to concrete admixtures to improve the workability of concrete, but these additives significantly reduce the fluidity of concrete; the current mainstream concrete water-reducing component is polycarboxylate water-reducing agent (PCE), such as replacing it with naphthalene water-reducing agent or wood sulfonate water-reducing agent will increase the cost of concrete and it will be difficult to meet the performance requirements of water reduction rate. Therefore, under the premise of controlling the cost of concrete, comprehensively improving PCE's effects on concrete water retention, cohesion and fluidity is one of the issues that urgently need to be addressed in the current concrete industry. Summary of the invention

[0004] In view of the above-mentioned prior art, the present invention provides a workability-improved polycarboxylic acid water-reducing agent and a preparation method thereof, so that the prepared water-reducing agent can be widely adapted to machine-made sand of different qualities, significantly improve the workability of machine-made sand concrete, and improve the working performance of machine-made sand concrete.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is to provide a polycarboxylate water reducer with improved workability, the structure of which is shown in Formula I:

[0006]

[0007] Among them, the monomer of A is a polyether macromonomer structure, the monomer of B is a cross-linked monomer structure of acrylic acid and a workability improving monomer, C is an unsaturated functional small monomer structure, and D is a cross-linked monomer structure of a polyether macromonomer and a workability improving monomer; a is an integer of 0 to 100, b is an integer of 0 to 30, c is an integer of 0 to 50, d is an integer of 0 to 30, and m is an integer of 10 to 50.

[0008] Based on the above technical solution, the present invention can also be improved as follows.

[0009] Furthermore, the polyether macromonomer is at least one of 4-hydroxybutyl vinyl polyoxyethylene ether (VPEG), ethylene glycol monovinyl polyethylene glycol ether (EPEG), isopentanol polyoxyethylene ether (TPEG) and isobutylene alcohol polyoxyethylene ether (HPEG), and has a molecular weight of 2000 to 4000.

[0010] Furthermore, the unsaturated functional small monomer is at least one of acrylic acid, sodium acrylate, sodium propylene sulfonate, sodium methpropylene sulfonate, itaconic acid, hydroxyethyl acrylate and hydroxypropyl acrylate.

[0011] Furthermore, the workability improving monomer is at least one of dextrin, cellulose ether, polyethylene glycol, polyvinyl alcohol, weinlun gum and xanthan gum.

[0012] The present application also discloses a method for preparing a workability-improved polycarboxylate water-reducing agent, the preparation method comprising the following steps:

[0013] S1: Mix a polyether macromonomer, a crosslinking agent, a workability improving monomer and water in a mass ratio of 10:0.1-0.5:0.1-20:130-140, and stir at 20°C-50°C for 30-150 minutes to obtain a solution A;

[0014] S2: acrylic acid, a crosslinking agent, a workability improving monomer and water are mixed in a mass ratio of 10:0.1-0.5:0.1-20:130-140, and stirred at 20°C-50°C for 30min-150min to obtain a solution B;

[0015] S3: mixing the polyether macromonomer, the oxidant, the solution A and water in a mass ratio of 100:0.1-1:5-20:80-120, i.e., the solution C;

[0016] S4: Mix the unsaturated functional small monomer, solution B and water in a mass ratio of 5-10:10-30:10-20 to obtain solution D;

[0017] S5: mixing the reducing agent, the chain transfer agent and water in a mass ratio of 0.1-0.5:0.2-0.8:10-30 to obtain a solution E;

[0018] S6: under stirring, solution D and solution E are added dropwise to solution C, the starting temperature is 15°C to 35°C, the solution D is added dropwise for 60 to 120 min, and the solution E is added dropwise for 30 min longer than the solution D;

[0019] S7: After the dropwise addition is completed, the mixture is kept warm for reaction for 30 to 60 minutes under stirring; water is then added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0020] Furthermore, the crosslinking agent is diisocyanate.

[0021] Furthermore, the crosslinking agent is at least one of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI) and lysine diisocyanate (LDI).

[0022] Furthermore, the oxidant is at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate and potassium persulfate; the reducing agent is at least one of ascorbic acid, bleaching powder, sodium bisulfite, FeSO4, CuSO4, CoSO4, NiSO4 and ZnSO4.

[0023] Furthermore, the chain transfer agent is at least one of mercaptoethanol, thioglycolic acid, mercaptopropionic acid, aliphatic mercaptan and dodecyl mercaptan.

[0024] The beneficial effects of the present invention are:

[0025] 1. The polycarboxylate water-reducing agent in the present invention is made of polyether macromonomer, unsaturated functional small monomer, workability improving monomer, redox initiator system, chain transfer agent and crosslinking agent as raw materials, and is formed by condensation polymerization and free radical copolymerization. The present invention grafts and crosslinks the workability improving monomer onto the polyether macromonomer and acrylic acid, enriches the branching types of the polycarboxylate water-reducing agent, increases the branching length of the polycarboxylate water-reducing agent, optimizes the comb-like structure of the polycarboxylate water-reducing agent molecule, and improves the steric hindrance of the polycarboxylate water-reducing agent. The polycarboxylate water-reducing agent with longer branches can better prevent the cementitious materials from aggregating with each other on the one hand, and can also better resist the adsorption of the porous structure of the aggregate on the other hand, reducing the adsorption loss of the polycarboxylate water-reducing agent.

[0026] 2. Workability improvement: There are a variety of hydrophilic groups in the monomer, such as hydroxyl, amino, etc., which can easily associate with water, improve the affinity of the polycarboxylate water-reducing agent for water, and increase the water encapsulation of the concrete slurry; on the other hand, a large number of hydrophilic groups reduce the surface tension of the polycarboxylate water-reducing agent aqueous solution, making it easier for the present invention to generate tiny bubbles, which can effectively hinder the floating of free water in the concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the preparation process of workability-improved polycarboxylic acid water-reducing agent. DETAILED DESCRIPTION

[0028] The purpose of the present invention is to obtain a water reducing agent having a structure as shown in formula I,

[0029]

[0030] Among them, the monomer of A is a polyether macromonomer structure, the monomer of B is a cross-linked monomer structure of acrylic acid and a workability improving monomer, C is an unsaturated functional small monomer structure, and D is a cross-linked monomer structure of a polyether macromonomer and a workability improving monomer; a is an integer of 0 to 100, b is an integer of 0 to 30, c is an integer of 0 to 50, d is an integer of 0 to 30, and m is an integer of 10 to 50.

[0031] The preparation process of the water reducing agent in the present invention is as follows Figure 1 As shown, the specific steps include:

[0032] S1: Mix a polyether macromonomer, a crosslinking agent, a workability improving monomer and water in a mass ratio of 10:0.1-0.5:0.1-20:130-140, and stir at 20°C-50°C for 30-150 minutes to obtain a solution A;

[0033] S2: acrylic acid, a crosslinking agent, a workability improving monomer and water are mixed in a mass ratio of 10:0.1-0.5:0.1-20:130-140, and stirred at 20°C-50°C for 30min-150min to obtain a solution B;

[0034] S3: mixing the polyether macromonomer, the oxidant, the solution A and water in a mass ratio of 100:0.1-1:5-20:80-120, i.e., the solution C;

[0035] S4: Mix the unsaturated functional small monomer, solution B and water in a mass ratio of 5-10:10-30:10-20 to obtain solution D;

[0036] S5: mixing the reducing agent, the chain transfer agent and water in a mass ratio of 0.1-0.5:0.2-0.8:10-30 to obtain a solution E;

[0037] S6: under stirring, solution D and solution E are added dropwise to solution C, the starting temperature is 15°C to 35°C, the solution D is added dropwise for 60 to 120 min, and the solution E is added dropwise for 30 min longer than the solution D;

[0038] S7: After the dropwise addition is completed, the mixture is kept warm for reaction for 30 to 60 minutes under stirring; water is then added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0039] The specific implementation modes of the present invention are described in detail below with reference to the embodiments.

[0040] Example 1

[0041] A workability-improved polycarboxylate water-reducing agent having a structure as shown in Formula I,

[0042]

[0043] Among them, the monomer of A is a polyether macromonomer structure, the monomer of B is a cross-linked monomer structure of acrylic acid and a workability-improving monomer, C is an unsaturated functional small monomer structure, and D is a cross-linked monomer structure of a polyether macromonomer and a workability-improving monomer.

[0044] The water reducing agent in this embodiment is prepared by the following steps:

[0045] (1) Under stirring, 10 parts of HPEG-2400, 0.1 parts of HDI, 5 parts of dextrin and 135 parts of water were mixed evenly and stirred at 25° C. for 60 minutes to obtain solution A;

[0046] (2) While stirring, 10 parts of acrylic acid, 0.2 parts of HDI, 5 parts of dextrin and 135 parts of water were mixed evenly and stirred at 30° C. for 60 minutes to obtain solution B;

[0047] (3) While stirring, mix 100 parts of HPEG-2400, 0.3 parts of hydrogen peroxide, 10 parts of solution A and 80 parts of water to obtain solution C;

[0048] (4) 6 parts of acrylic acid, 10 parts of solution B and 20 parts of water were mixed evenly to obtain solution D;

[0049] (5) 0.1 part of ascorbic acid, 0.3 part of thioglycolic acid and 30 parts of water were mixed to obtain solution E;

[0050] (6) Under stirring, solution D and solution E were added dropwise to solution C, the polymerization starting temperature was controlled to be 25°C, the addition time of solution D was 120 min, and the addition time of solution E was 150 min;

[0051] (7) After the addition is completed, the mixture is kept warm for 30 minutes under stirring; then water is added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0052] Example 2

[0053] A workability-improved polycarboxylate water-reducing agent having a structure as shown in Formula I,

[0054]

[0055] Among them, the monomer of A is a polyether macromonomer structure, the monomer of B is a cross-linked monomer structure of acrylic acid and a workability-improving monomer, C is an unsaturated functional small monomer structure, and D is a cross-linked monomer structure of a polyether macromonomer and a workability-improving monomer.

[0056] The water reducing agent in this embodiment is prepared by the following steps:

[0057] (1) Under stirring, 10 parts of HPEG-2400, 0.1 parts of HDI, 5 parts of water-soluble cellulose ether and 135 parts of water were mixed evenly, and stirred at 25° C. for 60 minutes to obtain solution A;

[0058] (2) While stirring, 10 parts of acrylic acid, 0.2 parts of HDI, 5 parts of water-soluble cellulose ether and 135 parts of water were mixed evenly and stirred at 30° C. for 60 minutes to obtain solution B;

[0059] (3) While stirring, mix 100 parts of HPEG-2400, 0.3 parts of hydrogen peroxide, 10 parts of solution A and 80 parts of water to obtain solution C;

[0060] (4) 6 parts of acrylic acid, 10 parts of solution B and 20 parts of water were mixed evenly to obtain solution D;

[0061] (5) 0.1 part of ascorbic acid, 0.3 part of thioglycolic acid and 30 parts of water were mixed to obtain solution E;

[0062] (6) Under stirring, solution D and solution E were added dropwise to solution C, the polymerization starting temperature was controlled to be 25°C, the addition time of solution D was 120 min, and the addition time of solution E was 150 min;

[0063] (7) After the addition is completed, the mixture is kept warm for 30 minutes under stirring; then water is added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0064] Example 3

[0065] A workability-improved polycarboxylate water-reducing agent having a structure as shown in Formula I,

[0066]

[0067] Among them, the monomer of A is a polyether macromonomer structure, the monomer of B is a cross-linked monomer structure of acrylic acid and a workability-improving monomer, C is an unsaturated functional small monomer structure, and D is a cross-linked monomer structure of a polyether macromonomer and a workability-improving monomer.

[0068] The water reducing agent in this embodiment is prepared by the following steps:

[0069] (1) Under stirring, 10 parts of HPEG-2400, 0.1 parts of HDI, 5 parts of polyethylene glycol and 135 parts of water were mixed evenly and stirred at 25° C. for 60 minutes to obtain solution A;

[0070] (2) Under stirring, 10 parts of acrylic acid, 0.2 parts of HDI, 5 parts of polyethylene glycol and 135 parts of water were mixed evenly and stirred at 30° C. for 60 minutes to obtain solution B;

[0071] (3) While stirring, mix 100 parts of HPEG-2400, 0.3 parts of hydrogen peroxide, 10 parts of solution A and 80 parts of water to obtain solution C;

[0072] (4) 6 parts of acrylic acid, 10 parts of solution B and 20 parts of water were mixed evenly to obtain solution D;

[0073] (5) 0.1 part of ascorbic acid, 0.3 part of thioglycolic acid and 30 parts of water were mixed to obtain solution E;

[0074] (6) Under stirring, solution D and solution E were added dropwise to solution C, the polymerization starting temperature was controlled to be 25°C, the addition time of solution D was 120 min, and the addition time of solution E was 150 min;

[0075] (7) After the addition is completed, the mixture is kept warm for 30 minutes under stirring; then water is added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0076] Example 4

[0077] A workability-improved polycarboxylate water-reducing agent having a structure as shown in Formula I,

[0078]

[0079] Among them, the monomer of A is a polyether macromonomer structure, the monomer of B is a cross-linked monomer structure of acrylic acid and a workability-improving monomer, C is an unsaturated functional small monomer structure, and D is a cross-linked monomer structure of a polyether macromonomer and a workability-improving monomer.

[0080] The water reducing agent in this embodiment is prepared by the following steps:

[0081] (1) Under stirring, 10 parts of HPEG-2400, 0.1 parts of HDI, 5 parts of polyvinyl alcohol and 135 parts of water were mixed evenly and stirred at 25° C. for 60 minutes to obtain solution A;

[0082] (2) Under stirring, 10 parts of acrylic acid, 0.2 parts of HDI, 5 parts of polyvinyl alcohol and 135 parts of water were mixed evenly and stirred at 30° C. for 60 minutes to obtain solution B;

[0083] (3) While stirring, mix 100 parts of HPEG-2400, 0.3 parts of hydrogen peroxide, 10 parts of solution A and 80 parts of water to obtain solution C;

[0084] (4) 6 parts of acrylic acid, 10 parts of solution B and 20 parts of water were mixed evenly to obtain solution D;

[0085] (5) 0.1 part of ascorbic acid, 0.3 part of thioglycolic acid and 30 parts of water were mixed to obtain solution E;

[0086] (6) Under stirring, solution D and solution E were added dropwise to solution C, the polymerization starting temperature was controlled to be 25°C, the addition time of solution D was 120 min, and the addition time of solution E was 150 min;

[0087] (7) After the addition is completed, the mixture is kept warm for 30 minutes under stirring; then water is added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0088] Example 5

[0089] A workability-improved polycarboxylate water-reducing agent having a structure as shown in Formula I,

[0090]

[0091] Among them, the monomer of A is a polyether macromonomer structure, the monomer of B is a cross-linked monomer structure of acrylic acid and a workability-improving monomer, C is an unsaturated functional small monomer structure, and D is a cross-linked monomer structure of a polyether macromonomer and a workability-improving monomer.

[0092] The water reducing agent in this embodiment is prepared by the following steps:

[0093] (1) Under stirring, 10 parts of HPEG-2400, 0.1 parts of HDI, 5 parts of Wenlun glue and 135 parts of water were mixed evenly and incubated at 25°C for 60 minutes to obtain solution A;

[0094] (2) Under stirring, 10 parts of acrylic acid, 0.2 parts of HDI, 5 parts of Wenlun glue and 135 parts of water were mixed evenly, and stirred at 30° C. for 60 minutes to obtain solution B;

[0095] (3) While stirring, mix 100 parts of HPEG-2400, 0.3 parts of hydrogen peroxide, 10 parts of solution A and 80 parts of water to obtain solution C;

[0096] (4) 6 parts of acrylic acid, 10 parts of solution B and 20 parts of water were mixed evenly to obtain solution D;

[0097] (5) 0.1 part of ascorbic acid, 0.3 part of thioglycolic acid and 30 parts of water were mixed to obtain solution E;

[0098] (6) Under stirring, solution D and solution E were added dropwise to solution C, the polymerization starting temperature was controlled to be 25°C, the addition time of solution D was 120 min, and the addition time of solution E was 150 min;

[0099] (7) After the addition is completed, the mixture is kept warm for 30 minutes under stirring; then water is added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0100] Example 6

[0101] A workability-improved polycarboxylate water-reducing agent having a structure as shown in Formula I,

[0102]

[0103] Among them, the monomer of A is a polyether macromonomer structure, the monomer of B is a cross-linked monomer structure of acrylic acid and a workability-improving monomer, C is an unsaturated functional small monomer structure, and D is a cross-linked monomer structure of a polyether macromonomer and a workability-improving monomer.

[0104] The water reducing agent in this embodiment is prepared by the following steps:

[0105] (1) Under stirring, 10 parts of HPEG-2400, 0.1 parts of HDI, 5 parts of xanthan gum and 135 parts of water were mixed evenly and stirred at 25° C. for 60 minutes to obtain solution A;

[0106] (2) Under stirring, 10 parts of acrylic acid, 0.2 parts of HDI, 5 parts of xanthan gum and 135 parts of water were mixed evenly and stirred at 30° C. for 60 minutes to obtain solution B;

[0107] (3) While stirring, mix 100 parts of HPEG-2400, 0.3 parts of hydrogen peroxide, 10 parts of solution A and 80 parts of water to obtain solution C;

[0108] (4) 6 parts of acrylic acid, 10 parts of solution B and 20 parts of water were mixed evenly to obtain solution D;

[0109] (5) 0.1 part of ascorbic acid, 0.3 part of thioglycolic acid and 30 parts of water were mixed to obtain solution E;

[0110] (6) Under stirring, solution D and solution E were added dropwise to solution C, the polymerization starting temperature was controlled to be 25°C, the addition time of solution D was 120 min, and the addition time of solution E was 150 min;

[0111] (7) After the addition is completed, the mixture is kept warm for 30 minutes under stirring; then water is added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0112] Example 7

[0113] A workability-improved polycarboxylate water-reducing agent having a structure as shown in Formula I,

[0114]

[0115] Among them, the monomer of A is a polyether macromonomer structure, the monomer of B is a cross-linked monomer structure of acrylic acid and a workability-improving monomer, C is an unsaturated functional small monomer structure, and D is a cross-linked monomer structure of a polyether macromonomer and a workability-improving monomer.

[0116] The water reducing agent in this embodiment is prepared by the following steps:

[0117] (1) Under stirring, 10 parts of VPEG, 0.5 parts of MDI, 0.1 parts of dextrin and 130 parts of water were mixed evenly and stirred at 20° C. for 150 minutes to obtain solution A;

[0118] (2) While stirring, 10 parts of acrylic acid, 0.5 parts of MDI, 0.1 parts of dextrin and 130 parts of water were mixed evenly and stirred at 20° C. for 150 minutes to obtain solution B;

[0119] (3) While stirring, 100 parts of VPEG, 0.5 parts of ammonium persulfate, 20 parts of solution A and 100 parts of water were mixed uniformly to obtain solution C;

[0120] (4) Mix 5 parts of hydroxypropyl acrylate, 30 parts of solution B and 20 parts of water to obtain solution D;

[0121] (5) 0.5 parts of sodium bisulfite, 0.5 parts of mercaptoethanol and 20 parts of water were mixed to obtain solution E;

[0122] (6) Under stirring, solution D and solution E were added dropwise to solution C, the polymerization starting temperature was controlled to be 35° C., the addition time of solution D was 60 min, and the addition time of solution E was 90 min;

[0123] (7) After the addition is completed, the mixture is kept warm for 60 minutes under stirring; then water is added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0124] Example 8

[0125] A workability-improved polycarboxylate water-reducing agent having a structure as shown in Formula I,

[0126]

[0127] Among them, the monomer of A is a polyether macromonomer structure, the monomer of B is a cross-linked monomer structure of acrylic acid and a workability-improving monomer, C is an unsaturated functional small monomer structure, and D is a cross-linked monomer structure of a polyether macromonomer and a workability-improving monomer.

[0128] The water reducing agent in this embodiment is prepared by the following steps:

[0129] (1) Under stirring, 10 parts of EPEG, 0.3 parts of TDI, 10 parts of polyethylene glycol and 140 parts of water were mixed evenly and stirred at 50° C. for 30 minutes to obtain solution A;

[0130] (2) Under stirring, 10 parts of acrylic acid, 0.3 parts of TDI, 10 parts of polyethylene glycol and 140 parts of water were mixed evenly and stirred at 50° C. for 30 minutes to obtain solution B;

[0131] (3) While stirring, mix 100 parts of EPEG, 1 part of sodium persulfate, 5 parts of solution A and 80 parts of water to obtain solution C;

[0132] (4) Mix 10 parts of itaconic acid, 20 parts of solution B and 20 parts of water to obtain solution D;

[0133] (5) 0.3 parts of diatomaceous earth, 0.8 parts of mercaptopropionic acid and 30 parts of water were mixed evenly to obtain solution E;

[0134] (6) Under stirring, solution D and solution E were added dropwise to solution C, the polymerization starting temperature was controlled to be 15°C, the addition time of solution D was 120 min, and the addition time of solution E was 150 min;

[0135] (7) After the addition is completed, the mixture is kept warm for 60 minutes under stirring; then water is added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0136] Example 9

[0137] A workability-improved polycarboxylate water-reducing agent having a structure as shown in Formula I,

[0138]

[0139] Among them, the monomer of A is a polyether macromonomer structure, the monomer of B is a cross-linked monomer structure of acrylic acid and a workability-improving monomer, C is an unsaturated functional small monomer structure, and D is a cross-linked monomer structure of a polyether macromonomer and a workability-improving monomer.

[0140] The water reducing agent in this embodiment is prepared by the following steps:

[0141] (1) Under stirring, 10 parts of TPEG, 0.5 parts of LDI, 20 parts of polyvinyl alcohol and 140 parts of water were mixed evenly and stirred at 30° C. for 90 minutes to obtain solution A;

[0142] (2) Under stirring, 10 parts of acrylic acid, 0.5 parts of LDI, 20 parts of polyvinyl alcohol and 140 parts of water were mixed evenly and stirred at 30° C. for 90 minutes to obtain solution B;

[0143] (3) While stirring, 100 parts of TPEG, 0.5 parts of potassium persulfate, 20 parts of solution A and 120 parts of water were mixed uniformly to obtain solution C;

[0144] (4) Mix 10 parts of sodium propylene sulfonate, 30 parts of solution B and 20 parts of water to obtain solution D;

[0145] (5) 0.1 part of FeSO4, 0.2 part of dodecyl mercaptan and 10 parts of water were mixed evenly to obtain solution E;

[0146] (6) Under stirring, solution D and solution E were added dropwise to solution C, the polymerization starting temperature was controlled to be 20° C., the addition time of solution D was 90 min, and the addition time of solution E was 120 min;

[0147] (7) After the addition is completed, the mixture is kept warm for 60 minutes under stirring; then water is added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0148] Comparative Example 1

[0149] A polycarboxylic acid water reducer is prepared based on Example 1 without using a workability improving monomer. The preparation process of the water reducer in this comparative example is as follows:

[0150] (1) Under stirring, 10 parts of HPEG-2400, 0.1 parts of HDI and 135 parts of water were mixed evenly and stirred at 25°C for 60 minutes to obtain solution A;

[0151] (2) While stirring, 10 parts of acrylic acid, 0.2 parts of HDI and 135 parts of water were mixed evenly and stirred at 30° C. for 60 minutes to obtain solution B;

[0152] (3) While stirring, mix 100 parts of HPEG-2400, 0.3 parts of hydrogen peroxide, 10 parts of solution A and 80 parts of water to obtain solution C;

[0153] (4) 6 parts of acrylic acid, 10 parts of solution B and 20 parts of water were mixed evenly to obtain solution D;

[0154] (5) 0.1 part of ascorbic acid, 0.3 part of thioglycolic acid and 30 parts of water were mixed to obtain solution E;

[0155] (6) Under stirring, solution D and solution E were added dropwise to solution C, the polymerization starting temperature was controlled to be 25°C, the addition time of solution D was 120 min, and the addition time of solution E was 150 min;

[0156] (7) After the addition is completed, the mixture is kept warm for 30 minutes under stirring; then water is added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0157] Comparative Example 2

[0158] A polycarboxylate water reducer is prepared based on Example 1 without pre-crosslinking the polyether macromonomer and the workability improving monomer. The preparation process of the water reducer in this comparative example is as follows:

[0159] (1) Under stirring, 10 parts of HPEG-2400, 5 parts of dextrin and 135 parts of water were mixed evenly and stirred at 25° C. for 60 minutes to obtain solution A;

[0160] (2) While stirring, 10 parts of acrylic acid, 0.2 parts of HDI, 5 parts of dextrin and 135 parts of water were mixed evenly and stirred at 30° C. for 60 minutes to obtain solution B;

[0161] (3) While stirring, mix 100 parts of HPEG-2400, 0.3 parts of hydrogen peroxide, 10 parts of solution A and 80 parts of water to obtain solution C;

[0162] (4) 6 parts of acrylic acid, 10 parts of solution B and 20 parts of water were mixed evenly to obtain solution D;

[0163] (5) 0.1 part of ascorbic acid, 0.3 part of thioglycolic acid and 30 parts of water were mixed to obtain solution E;

[0164] (6) Under stirring, solution D and solution E were added dropwise to solution C, the polymerization starting temperature was controlled to be 25°C, the addition time of solution D was 120 min, and the addition time of solution E was 150 min;

[0165] (7) After the addition is completed, the mixture is kept warm for 30 minutes under stirring; then water is added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0166] Comparative Example 3

[0167] A polycarboxylic acid water reducer, based on Example 1, without pre-crosslinking of acrylic acid and workability improving monomer. The preparation process of the water reducer in this comparative example is as follows:

[0168] (1) Under stirring, 10 parts of HPEG-2400, 0.1 parts of HDI, 5 parts of dextrin and 135 parts of water were mixed evenly and stirred at 25° C. for 60 minutes to obtain solution A;

[0169] (2) While stirring, 10 parts of acrylic acid, 5 parts of dextrin and 135 parts of water were mixed evenly and stirred at 30° C. for 60 minutes to obtain solution B;

[0170] (3) While stirring, mix 100 parts of HPEG-2400, 0.3 parts of hydrogen peroxide, 10 parts of solution A and 80 parts of water to obtain solution C;

[0171] (4) 6 parts of acrylic acid, 10 parts of solution B and 20 parts of water were mixed evenly to obtain solution D;

[0172] (5) 0.1 part of ascorbic acid, 0.3 part of thioglycolic acid and 30 parts of water were mixed to obtain solution E;

[0173] (6) Under stirring, solution D and solution E were added dropwise to solution C, the polymerization starting temperature was controlled to be 25°C, the addition time of solution D was 120 min, and the addition time of solution E was 150 min;

[0174] (7) After the addition is completed, the mixture is kept warm for 30 minutes under stirring; then water is added to adjust the mass concentration to 40%, thereby obtaining a polycarboxylic acid water-reducing agent.

[0175] Results Analysis

[0176] Since the performance of the water reducer prepared in Examples 7 to 9 is similar to that of the water reducer in Examples 1 to 6, the performance of the water reducer in the present application will be described in detail by taking the water reducer in Examples 1 to 6 as an example.

[0177] The examples 1 to 6 and comparative examples 1 to 3 of the present application were compared with commercially available samples to test their molecular weight, monomer conversion rate, surface tension, concrete fluidity over time, concrete air content, concrete pressure water bleeding rate, and concrete strength. Among them, high performance liquid chromatography was used to test the monomer conversion rate, number average molecular weight, and polydispersity index of the synthesized polycarboxylate water-reducing agent; a surface tension meter was used to test the surface tension of a 2% polycarboxylate water-reducing agent aqueous solution; and concrete-related data were tested with reference to GB8076-2016 "Specification for Concrete Admixtures", GB8077-2012 "Test Method for Homogeneity of Concrete Admixtures" and GB / T50080-2016 "Standard for Test Methods for Performance of Ordinary Concrete Mixtures". The same compound formula was used and applied to C30 concrete, and the concrete fluidity over time, concrete air content, concrete pressure water bleeding rate, and concrete strength were compared under room temperature. The cement is Esheng P.O42.5, the fineness modulus of machine-made sand is 2.6, the crushed stone is a continuously graded crushed stone with a particle size of 5-25 mm, and the dosage of 10% polycarboxylate water reducer is 2.0wt%. The test results are shown in Tables 1 and 2.

[0178] Table 1 Water reducing agent performance

[0179]

[0180] As can be seen from Table 1, by comparing the water reducers in Examples 1 to 6 and Comparative Examples 1 to 3, it can be seen that the water reducer prepared by the method of the present invention has a larger molecular weight, a wider molecular weight distribution and a lower surface tension, indicating that the water reducer prepared by the method of the present invention has a longer branched structure.

[0181] Table 2 Water reducing properties of water reducing agent

[0182]

[0183]

[0184] It can be seen from Table 2 that the polycarboxylate water-reducing agent synthesized by the method of the present invention has the characteristics of high water reduction rate, good slump retention and good water retention.

[0185] Although the specific implementation of the present invention is described in detail in conjunction with the embodiments, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A workability-improved polycarboxylate water-reducing agent, characterized in that: The structure of the water reducing agent is shown in Formula I: Wherein, the monomer of A is a polyether macromonomer structure, the monomer of B is a cross-linked monomer structure of acrylic acid and a workability-improving monomer, C is an unsaturated functional small monomer structure, D is a cross-linked monomer structure of a polyether macromonomer and a workability-improving monomer, and the workability-improving monomer is at least one of dextrin, cellulose ether, polyethylene glycol, polyvinyl alcohol, Wenlun gum and xanthan gum; a is an integer of 0 to 100, b is an integer of 0 to 30, c is an integer of 0 to 50, d is an integer of 0 to 30, and m is an integer of 10 to 50; the workability-improving polycarboxylate water-reducing agent is prepared by the following steps: S1: Mix the polyether macromonomer, the crosslinking agent, the workability improving monomer and water in a mass ratio of 10:0.1-0.5:0.1-20:130-140, and stir at 20°C-50°C for 30 min-150 min to obtain solution A; S2: acrylic acid, a cross-linking agent, a workability improving monomer and water are mixed in a mass ratio of 10:0.1-0.5:0.1-20:130-140, and stirred at 20°C-50°C for 30 min-150 min to obtain a solution B; S3: Mix the polyether macromonomer, oxidant, solution A and water in a mass ratio of 100:0.1~1:5~20:80~120, i.e., solution C; S4: Mix the unsaturated functional small monomer, solution B and water in a mass ratio of 5-10:10-30:10-20, i.e. solution D; S5: mixing the reducing agent, the chain transfer agent and water in a mass ratio of 0.1-0.5:0.2-0.8:10-30 to obtain a solution E; S6: Under stirring, solution D and solution E are added dropwise to solution C, the starting temperature is 15°C~35°C, the solution D is added dropwise for 60~120 min, and the solution E is added dropwise for 30 min longer than the solution D; S7: After the addition is completed, keep the mixture warm for 30 to 60 minutes under stirring; then add water to adjust the mass concentration to 40% to obtain a polycarboxylic acid water reducer.

2. The workability-improved polycarboxylate water-reducing agent according to claim 1, characterized in that: The polyether macromonomer is at least one of 4-hydroxybutyl vinyl polyoxyethylene ether, ethylene glycol monovinyl polyethylene glycol ether, isopentanol polyoxyethylene ether and isobutylene alcohol polyoxyethylene ether, and has a molecular weight of 2000-4000.

3. The workability-improved polycarboxylate water-reducing agent according to claim 1, characterized in that: The unsaturated functional small monomer is at least one of acrylic acid, sodium acrylate, sodium propylene sulfonate, sodium methpropylene sulfonate, itaconic acid, hydroxyethyl acrylate and hydroxypropyl acrylate.

4. The workability-improved polycarboxylate water-reducing agent according to claim 1, characterized in that: The crosslinking agent is diisocyanate.

5. The workability-improved polycarboxylate water-reducing agent according to claim 4, characterized in that: The cross-linking agent is at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate and lysine diisocyanate.

6. The workability-improved polycarboxylate water-reducing agent according to claim 4, characterized in that: The oxidant is at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate and potassium persulfate; the reducing agent is at least one of ascorbic acid, bleaching powder, sodium bisulfite and FeSO4.

7. The workability-improved polycarboxylate water-reducing agent according to claim 4, characterized in that: The chain transfer agent is at least one of mercaptoethanol, thioglycolic acid, mercaptopropionic acid and aliphatic mercaptan.

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