Water reducing agent as well as preparation method and application thereof

Abstract

The invention provides a water reducing agent as well as a preparation method and application thereof. The water reducing agent is formed by polymerizing a double-terminated esterified functional monomer and an allyl monomer, the double-end-capped esterified functional monomer is prepared from a single-end-capped esterified functional monomer and dimethyl phthalate through a transesterification reaction; the single-terminated esterified functional monomer is prepared from polyethylene glycol and methacrylic acid through esterification reaction. The water reducing agent does not adopt a polyether macromonomer, so that introduction of a polyether long side chain which is easy to perform physical adsorption and chemical intercalation is avoided, and dimethyl phthalate containing a benzene ring rigid structure is introduced into the water reducing agent, so that chemical intercalation of the water reducing agent in layered clay mineral can be better avoided; the tolerance of the water reducing agent to clay is further improved, the water reducing agent has excellent water reducing and slump retaining performance, and the flowability of concrete containing LC3 cement can be well improved. Concrete prepared from the water reducing agent disclosed by the invention has excellent flowability and slump loss resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete building materials, and specifically relates to a water reducing agent and a preparation method and application thereof. Background Art

[0002] Water reducer is a chemical admixture used to improve the performance of concrete. Its main function is to disperse cement particles in concrete, reduce the amount of water used in concrete, and thus improve the fluidity, strength and durability of concrete. Calcined limestone clay cement (LC3 cement) is a low-carbon cementitious material whose main components include silicate cement, calcined clay, limestone and gypsum. LC3 cement is becoming a research hotspot in the field of building materials due to its significant environmental benefits and economic advantages. However, due to its high specific surface area and layered structure, the calcined clay in LC3 cement has significant interactions with polycarboxylate water reducers, which is mainly manifested in excessive adsorption and chemical intercalation of the long polyether side chains of polycarboxylate water reducers on the surface of calcined clay. This phenomenon will lead to a decrease in the fluidity and workability of concrete, which seriously hinders the widespread application and promotion of LC3 cement in the field of concrete.

[0003] Therefore, how to provide a water reducing agent with excellent water-reducing and slump-retaining properties and improve the fluidity of concrete containing LC3 cement is a technical problem to be solved urgently in the art. Summary of the invention

[0004] The invention provides a water reducing agent, wherein the water reducing agent does not introduce a polyether long side chain that is easy to generate physical adsorption and chemical intercalation with LC3 cement, has excellent water-reducing and slump-retaining properties, and can improve the fluidity of concrete containing LC3 cement.

[0005] The present invention also provides a method for preparing a water reducing agent. The water reducing agent prepared by the preparation method has excellent water-reducing and slump-retaining properties and can improve the fluidity of concrete containing LC3 cement.

[0006] The present invention also provides concrete, which adopts the water reducing agent and has excellent fluidity and slump retention.

[0007] In a first aspect, the present invention provides a water reducing agent, which is polymerized from a double-terminated esterification functional monomer and an olefin monomer;

[0008] The double-terminated esterification functional monomer is formed by a single-terminated esterification functional monomer and dimethyl phthalate through an ester exchange reaction;

[0009] The single-terminated esterification functional monomer is prepared by esterification reaction of polyethylene glycol and methacrylic acid.

[0010] The water reducing agent as described above, wherein the mass ratio of the double-terminated esterification functional monomer to the olefinic monomer is (8.5-13):1.

[0011] The water reducing agent as described above, wherein the mass ratio of the single-terminated esterified functional monomer to dimethyl phthalate is (4.9-8.8):1.

[0012] The water reducing agent as described above, wherein the mass ratio of the polyethylene glycol to methacrylic acid is (9-17.5):1.

[0013] The water reducing agent as described above, wherein the single-terminated esterification functional monomer comprises a compound as shown in Formula 1 below:

[0014] Formula 1;

[0015] In formula 1, n=16~35.

[0016] The water reducing agent as described above, wherein the dimethyl phthalate includes at least one of dimethyl terephthalate, dimethyl isophthalate or dimethyl phthalate.

[0017] The water reducing agent as described above, wherein the olefinic monomer comprises a compound as shown in Formula 2 below:

[0018] Formula 2;

[0019] In Formula 2, R1, R2, and R3 are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a carboxyl group having 1 to 5 carbon atoms.

[0020] The water reducer as described above, wherein the vinyl monomer comprises at least one of acrylic acid, crotonic acid, citraconic acid, maleic acid, methacrylic acid, itaconic acid or fumaric acid. The water reducer as described above, wherein the double-terminated esterification functional monomer comprises at least one of the compound represented by the following formula A, the compound represented by the following formula B or the compound represented by the following formula C:

[0021] Formula A;

[0022] Formula B;

[0023] Formula C;

[0024] In Formula A, Formula B, and Formula C, n=16~35.

[0025] The water reducing agent as described above, wherein the water reducing agent comprises at least one of the compound represented by the following formula D, the compound represented by the following formula E, or the compound represented by the following formula F:

[0026] Formula D;

[0027] Formula E;

[0028] Formula F;

[0029] In Formula D, Formula E, and Formula F, n=16-35, m1=10-50, m2=20-60, and R1, R2, and R3 are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a carboxyl group having 1 to 5 carbon atoms.

[0030] The water reducing agent as described above, wherein the weight average molecular weight of the water reducing agent is 44,000-77,000.

[0031] The present invention provides in a second aspect a method for preparing the water reducing agent according to the first aspect, comprising the following steps:

[0032] 1) Mix 360-400 parts of polyethylene glycol, 22-56 parts of methacrylic acid, 10-22 parts of a catalyst, and 8-16 parts of a polymerization inhibitor by weight, and carry out an esterification reaction under an inert atmosphere to obtain a single-terminated esterification functional monomer;

[0033] 2) adding 52 to 78 parts of dimethyl phthalate to the single-terminated esterification functional monomer, and performing an ester exchange reaction under an inert atmosphere to obtain a double-terminated esterification functional monomer;

[0034] 3) Add 3.2-6.8 parts of initiator to the double-terminated esterified functional monomer, and dropwise add 1.5-7 parts of chain transfer agent, 0.6-1.5 parts of reducing agent and 36-46 parts of olefin monomer to carry out polymerization reaction to obtain the water reducing agent.

[0035] The preparation method as described above, wherein step 3) further comprises adding water to the double-capped esterification functional monomer.

[0036] In the preparation method as described above, in step 1), in the esterification reaction, the reaction temperature is 95-115° C. and the reaction time is 6-9 h.

[0037] In the preparation method as described above, in step 2), in the transesterification reaction, the reaction temperature is 75-85° C. and the reaction time is 3-5 h.

[0038] In the preparation method as described above, in step 3), in the polymerization reaction, the reaction temperature is 15-60° C. and the reaction time is 2-5 h.

[0039] The preparation method as described above, wherein in step 3), the dropping time is 1 to 3.5 hours.

[0040] The present invention provides a concrete in a third aspect, wherein the concrete comprises the water reducing agent described in the first aspect.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The water reducer of the present invention is polymerized by double-terminated esterification functional monomers and olefin monomers, and polyether macromonomers such as isobutylene polyethylene glycol ether, isopentenyl polyethylene glycol ether, vinyl polyoxyethylene ether, etc. are not used, thereby avoiding the introduction of polyether long side chains that are prone to physical adsorption and chemical intercalation; and the introduction of dimethyl phthalate containing a rigid benzene ring structure into the water reducer can better avoid chemical intercalation of the water reducer in layered clay minerals, further improve the tolerance of the water reducer to clay, and enable the water reducer to have excellent water-reducing and slump-retaining performance, and can well improve the fluidity of concrete containing LC3 cement. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. 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.

[0044] The present invention provides a water reducing agent in a first aspect. The water reducing agent is prepared by polymerizing a double-terminated esterification functional monomer and an olefin monomer; the double-terminated esterification functional monomer is prepared by an ester exchange reaction between a single-terminated esterification functional monomer and dimethyl phthalate; and the single-terminated esterification functional monomer is prepared by an esterification reaction between polyethylene glycol and methacrylic acid.

[0045] The water reducer of the present invention is formed by polymerizing a double-terminated esterification functional monomer and an olefin monomer, and does not use polyether macromonomers such as isobutylene polyethylene glycol ether, isopentenyl polyethylene glycol ether, and vinyl polyoxyethylene ether, thereby avoiding the introduction of polyether long side chains that are prone to physical adsorption and chemical intercalation; and the double-terminated esterification functional monomer is formed by an ester exchange reaction between a single-terminated esterification functional monomer and dimethyl phthalate, and dimethyl phthalate contains a rigid benzene ring structure, and through a steric hindrance effect, the water reducer is better prevented from being chemically intercalated in layered clay minerals, thereby further improving the tolerance of the water reducer to clay and enabling the water reducer to have excellent water-reducing and slump-retaining properties, and can improve the fluidity of concrete containing LC3 cement.

[0046] The present invention controls the mass ratio of the double-terminated esterified functional monomer and the olefin monomer, the mass ratio of the single-terminated esterified functional monomer and dimethyl phthalate, and the mass ratio of polyethylene glycol and methacrylic acid, so that the water reducer has more excellent water-reducing and slump-retaining properties, and further improves the fluidity of concrete containing LC3 cement.

[0047] In some embodiments, the mass ratio of the double-terminated esterification functional monomer to the olefinic monomer is (8.5-13):1.

[0048] Illustratively, the mass ratio of the double-terminated esterification functional monomer to the olefinic monomer is 8.5:1, 9:1, 9.5:1, 10:1, 10.5:1, 11:1, 11.5:1, 12:1, 12.5:1 or 13:1, etc.

[0049] In some embodiments, the mass ratio of the single-terminated esterification functional monomer to dimethyl phthalate is (4.9-8.8):1.

[0050] In some embodiments, the mass ratio of polyethylene glycol to methacrylic acid is (9-17.5):1.

[0051] Illustratively, the mass ratio of polyethylene glycol to methacrylic acid can be 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1 or 17.5:1, etc.

[0052] In the present invention, the single-terminated esterification functional monomer includes a compound as shown in Formula 1:

[0053] Formula 1;

[0054] In formula 1, n=16~35.

[0055] The single-terminal esterification functional monomer of the present invention has a zigzag chain structure, contains an unsaturated functional group, has copolymerization activity, and can participate in ester exchange reaction. n=16-35 can make the single-terminal esterification functional monomer have both excellent reactivity and dispersibility.

[0056] In some embodiments, the dimethyl phthalate includes at least one of dimethyl terephthalate, dimethyl isophthalate, or dimethyl phthalate.

[0057] In some embodiments, the olefinic monomer includes a compound shown in Formula 2:

[0058] Formula 2;

[0059] In Formula 2, R1, R2, and R3 are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a carboxyl group having 1 to 5 carbon atoms.

[0060] The olefin monomer of the present invention adopts the compound shown in Formula 2, which can enhance the interaction between the water reducer and the LC3 cement particles and improve the water-reducing and slump-preserving effect of the water reducer.

[0061] In some embodiments, considering the availability of raw materials, the vinyl monomer includes at least one of acrylic acid, crotonic acid, citraconic acid, maleic acid, methacrylic acid, itaconic acid, and fumaric acid.

[0062] According to the technical solution of the present invention, the double-terminated esterification functional monomer includes at least one of the compound represented by the following formula A, the compound represented by the following formula B, or the compound represented by the following formula C:

[0063] Formula A;

[0064] Formula B;

[0065] Formula C;

[0066] In Formula A, Formula B, and Formula C, n=16~35.

[0067] The double-terminated esterified functional monomer of the present invention is a zigzag chain structure, contains unsaturated functional groups, and has copolymerization activity. The introduced rigid end-capping structure (benzene ring) can protect the alkyl chain, avoid chemical intercalation of the alkyl chain of the water reducer in the layered clay mineral, enhance the dispersion effect of cement, and make the water reducer have excellent water-reducing and slump-retaining properties.

[0068] In some embodiments, the water reducing agent includes at least one of the compound represented by the following formula D, the compound represented by the following formula E, or the compound represented by the following formula F:

[0069] Formula D;

[0070] Formula E;

[0071] Formula F;

[0072] In Formula D, Formula E, and Formula F, n=16-35, m1=10-50, m2=20-60, and R1, R2, and R3 are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a carboxyl group having 1 to 5 carbon atoms.

[0073] In the present invention, the weight average molecular weight of the water reducer is 44,000-77,000, which helps to further improve the adsorption capacity and dispersion effect of the water reducer on the surface of LC3 cement particles.

[0074] The present invention provides in a second aspect a method for preparing the water reducing agent according to the first aspect, comprising the following steps:

[0075] 1) In parts by weight, 360-400 parts (such as 360 parts, 370 parts, 380 parts, 390 parts or 400 parts) of polyethylene glycol, 22-56 parts (such as 22 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts or 56 parts) of methacrylic acid, 10-22 parts (such as 10 parts, 12 parts, 15 parts, 17 parts, 20 parts or 22 parts) of a catalyst, and 8-16 parts (such as 8 parts, 10 parts, 12 parts, 14 parts or 16 parts) of a polymerization inhibitor are mixed, and an esterification reaction is carried out under an inert atmosphere to obtain a single-terminated esterification functional monomer;

[0076] 2) adding 52 to 78 parts (e.g., 52 parts, 58 parts, 64 parts, 70 parts or 78 parts, etc.) of dimethyl phthalate to the single-terminated esterification functional monomer, and conducting an ester exchange reaction under an inert atmosphere to obtain a double-terminated esterification functional monomer;

[0077] 3) adding 3.2-6.8 parts (such as 3.2 parts, 4 parts, 4.8 parts, 5.6 parts or 6.8 parts) of initiator to the double-terminated esterified functional monomer, and dropwise adding 1.5-7 parts (such as 1.5 parts, 2 parts, 4 parts, 5.6 parts or 7 parts) of chain transfer agent, 0.6-1.5 parts (such as 0.6 parts, 1 parts, 1.2 parts or 1.5 parts) of reducing agent and 36-46 parts (such as 36 parts, 38 parts, 40 parts, 44 parts or 46 parts) of olefin monomer to carry out polymerization reaction to obtain the water reducer.

[0078] The present invention firstly carries out an esterification reaction on methacrylic acid and polyethylene glycol to obtain a single-terminal esterification functional monomer, then uses dimethyl phthalate to carry out an ester exchange reaction on the single-terminal esterification functional monomer to obtain a double-terminal esterification functional monomer, and carries out a free radical polymerization reaction on the obtained double-terminal esterification functional monomer and an olefin monomer to prepare a water reducer. The water reducer has excellent water reduction and slump retention, and can improve the fluidity of concrete containing LC3 cement. At the same time, the preparation method is simple in process and convenient for industrial production.

[0079] In some embodiments, the inert atmosphere includes nitrogen, argon, etc. Nitrogen or argon is used as the inert atmosphere to prevent oxygen from entering the reaction system, thereby avoiding oxygen interference with esterification, transesterification and polymerization reactions or oxidation of the product.

[0080] In some embodiments, the catalyst may be an existing substance that can catalyze the esterification reaction, including but not limited to at least one of concentrated sulfuric acid, p-toluenesulfonic acid, dimethylaminopyridine or p-aminobenzenesulfonic acid, which helps to accelerate the esterification reaction.

[0081] In some embodiments, the inhibitor includes, but is not limited to, at least one of p-hydroxyanisole, hydroquinone, diphenol, or phenothiazine, which can prevent side reactions initiated by free radicals.

[0082] In some embodiments, the initiator includes at least one of hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate or azobisisobutyronitrile to better control the initiation and progress of the polymerization reaction.

[0083] In some embodiments, the average molecular weight of polyethylene glycol is 722-1558, which is beneficial to control the side chain length of the water reducer, helps to improve the adsorption capacity and dispersion effect of the water reducer on the surface of cement particles, and makes the water reducer have a better water-reducing and slump-preserving effect.

[0084] In some embodiments, the esterification reaction, transesterification reaction and polymerization reaction are all carried out under stirring and mixing conditions to improve the uniformity and efficiency of the reaction.

[0085] In some embodiments, the chain transfer agent includes at least one of isopropanol, phosphorous acid, hypophosphorous acid, phosphite, hypophosphorous acid, sulfurous acid, bisulfite, dithionite, dithionite, metabisulfite, mercaptoethanol, thioglycolic acid, mercaptopropionic acid, thiomalic acid, 2-mercaptoethanesulfonic acid, thioglycolate, mercaptopropionic acid, thiomalate or 2-mercaptoethanesulfonic acid, which can better control the molecular weight of the water reducer and terminate the chain growth by transferring the terminal free radicals of the active chain.

[0086] In some embodiments, the reducing agent includes at least one of vitamin C, ferrous sulfate, cuprous sulfate, oxalic acid, sodium bisulfite or sodium sulfite. The reducing agent can react with the initiator to generate free radicals to promote the polymerization reaction.

[0087] According to the technical solution of the present invention, the step 3) further comprises adding water to the double-terminated esterification functional monomer, so that the polymerization reaction can be carried out more efficiently and stably.

[0088] In some embodiments, in step 3), the amount of water added is 400-430 parts.

[0089] According to the technical solution of the present invention, in step 1), in the esterification reaction, the temperature is 95-115°C (such as 95°C, 100°C, 105°C, 110°C or 115°C, etc.), and the time is 6-9h (such as 6h, 7h, 8h or 9h, etc.).

[0090] In some embodiments, in step 2), during the transesterification reaction, the temperature is 75-85°C (such as 75°C, 78°C, 80°C or 85°C, etc.), and the time is 3-5h (such as 3h, 3.5h, 4h, 4.5h or 5h, etc.).

[0091] In some embodiments, in step 3), during the polymerization reaction, the temperature is 15-60°C (such as 15°C, 20°C, 30°C, 40°C, 50°C or 60°C, etc.), and the time is 2-5h (such as 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, etc.). The polymerization reaction time includes the dropwise addition time.

[0092] In the present invention, in step 3), the dripping time is 1 to 3.5 hours (such as 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours or 3.5 hours, etc.), and the dripping speed of the chain transfer agent, the reducing agent and the olefin monomer is controlled to ensure the stability and uniformity of the polymerization reaction and avoid local overheating or incomplete reaction. The dripping time refers to the time for dripping the chain transfer agent, the reducing agent and the olefin monomer into the double-terminated esterification functional monomer.

[0093] The present invention controls the temperature and time of the esterification reaction, the transesterification reaction and the polymerization reaction within the above range, which can ensure a high conversion rate and reduce the generation of by-products. The present invention provides a concrete in a third aspect, the concrete includes the water reducer described in the first aspect. The concrete adopts the water reducer and has excellent fluidity and slump retention.

[0094] Hereinafter, the present invention will be further described in detail through specific examples.

[0095] Example 1

[0096] The water reducing agent of this embodiment is prepared by the following steps:

[0097] (1) By weight, 365 parts of polyethylene glycol (average molecular weight of 1000), 32 parts of methacrylic acid, 11 parts of p-toluenesulfonic acid, and 11 parts of phenothiazine were mixed and subjected to esterification reaction at 110° C. under nitrogen protection for 7 hours to obtain a single-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 1058;

[0098] (2) cooling to 80° C., adding 70 parts of dimethyl terephthalate to the single-terminated esterification functional monomer obtained in step (1), and carrying out ester exchange reaction at 80° C. under nitrogen protection for 4 hours, and no methanol condensate appears, thereby obtaining a double-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC is 1210;

[0099] (3) To the double-terminated esterified functional monomer obtained in step (2), 430 parts of water were added, 4 parts of hydrogen peroxide (mass fraction 27%) were added at 25°C, and 5 parts of thioglycolic acid, 0.9 parts of vitamin C, and 46 parts of acrylic acid were added dropwise for 3.5 hours. After the above raw materials were added dropwise, the mixture was kept warm at 60°C for 1 hour to obtain a water reducing agent. The weight average molecular weight of the product measured by GPC was 52240.

[0100] Example 2

[0101] The water reducing agent of this embodiment is prepared by the following steps:

[0102] (1) By weight, 360 parts of polyethylene glycol (average molecular weight of 800), 38 parts of methacrylic acid, 14 parts of p-dimethylaminopyridine, and 11 parts of p-hydroxyanisole were mixed, and esterification reaction was carried out at 110° C. for 6.5 hours under nitrogen protection to obtain a single-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 880;

[0103] (2) Cooling to 80°C, adding 76 parts of dimethyl isophthalate to the single-terminated esterification functional monomer, and carrying out ester exchange reaction at 80°C under nitrogen protection for 4 hours, without the appearance of methanol condensate, to obtain a double-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 1052;

[0104] (3) To the double-terminated esterified functional monomer, 430 parts of water were added, 4.8 parts of hydrogen peroxide (mass fraction 27%) were added at 25°C, and 5.7 parts of mercaptopropionic acid, 0.9 parts of vitamin C, and 52 parts of crotonic acid were added dropwise for 3.5 hours. After the addition of the above raw materials, the mixture was kept warm at 60°C for 1 hour to obtain a water reducing agent. The weight average molecular weight of the product measured by GPC was 44160.

[0105] Example 3

[0106] The water reducing agent of this embodiment is prepared by the following steps:

[0107] (1) By weight, 380 parts of polyethylene glycol (average molecular weight of 1200), 27 parts of methacrylic acid, 10 parts of p-aminobenzenesulfonic acid, and 8 parts of p-aminobenzenesulfonic acid were mixed, and esterification reaction was carried out at 110° C. under nitrogen protection for 8 hours to obtain a single-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 1256;

[0108] (2) Cooling to 80°C, adding 62 parts of dimethyl terephthalate to the single-terminated esterification functional monomer, under nitrogen protection, ester exchange reaction was carried out at 80°C for 4 hours, and no methanol condensate appeared, thereby obtaining a double-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 1345;

[0109] (3) Add 420 parts of water to the double-terminated esterified functional monomer, add 5.5 parts of ammonium persulfate at 25°C, and dropwise add 6 parts of phosphorous acid, 0.7 parts of oxalic acid, and 54 parts of maleic acid. The dropping time is 3.5 hours. After dropping the above raw materials, keep warm at 60°C for 1 hour to prepare a water reducing agent. The weight average molecular weight of the product measured by GPC is 60320.

[0110] Example 4

[0111] The water reducing agent of this embodiment is prepared by the following steps:

[0112] (1) By weight, 370 parts of polyethylene glycol (average molecular weight of 1000), 31 parts of methacrylic acid, 15 parts of concentrated sulfuric acid, and 9 parts of diphenol were mixed and subjected to esterification reaction at 110° C. under nitrogen protection for 7 hours to obtain a single-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 1051;

[0113] (2) Cooling to 80°C, adding 62 parts of dimethyl terephthalate to the single-terminated esterification functional monomer, under nitrogen protection, ester exchange reaction was carried out at 80°C for 4 hours, and no methanol condensate appeared, thereby obtaining a double-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 1216;

[0114] (3) Add 420 parts of water to the double-terminated esterified functional monomer, add 6.5 parts of azobisisobutyronitrile at 25°C, and dropwise add 6 parts of 2-mercaptoethanesulfonic acid, 0.6 parts of sodium bisulfite, and 38 parts of methacrylic acid. The dropping time is 3.5 hours. After dropping the above raw materials, keep warm at 60°C for 1 hour to prepare a water reducing agent. The weight average molecular weight of the product measured by GPC is 51680.

[0115] Example 5

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

[0117] (1) By weight, 400 parts of polyethylene glycol (average molecular weight of 1500), 23 parts of methacrylic acid, 10 parts of p-aminobenzenesulfonic acid, and 8 parts of phenothiazine were mixed and subjected to esterification reaction at 110° C. under nitrogen protection for 9 hours to obtain a single-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 1549;

[0118] (2) Cooling to 80°C, adding 48 parts of dimethyl terephthalate to the single-terminated esterification functional monomer, and carrying out ester exchange reaction at 80°C under nitrogen protection for 4 hours, without the appearance of methanol condensate, to obtain a double-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 1710;

[0119] (3) Add 420 parts of water to the double-terminated esterified functional monomer, add 5.7 parts of ammonium persulfate at 25°C, and dropwise add 2 parts of mercaptoethanol, 0.4 parts of ferrous sulfate, and 56 parts of fumaric acid. The dropping time is 3.5 hours. After dropping the above raw materials, keep warm at 60°C for 1 hour to prepare a water reducing agent. The weight average molecular weight of the product measured by GPC is 77550.

[0120] Comparative Example 1

[0121] This comparative example uses the commercially available polycarboxylate water reducer of model MR802 produced by Hunan Zhongyan Building Materials Technology Co., Ltd.

[0122] Comparative Example 2

[0123] This comparative example uses the commercially available polycarboxylate water reducer of model LVP4511 produced by Lianhong New Materials Co., Ltd.

[0124] Comparative Example 3

[0125] The preparation method of the water reducing agent provided in this comparative example is basically the same as that of Example 1, except that dimethyl terephthalate is not used.

[0126] The specific preparation method comprises the following steps:

[0127] (1) By weight, 365 parts of polyethylene glycol (average molecular weight of 1000), 32 parts of methacrylic acid, 11 parts of p-toluenesulfonic acid, and 11 parts of phenothiazine were mixed and subjected to esterification reaction at 110° C. under nitrogen protection to obtain a single-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 1058;

[0128] (2) Add 430 parts of water to the single-terminated esterified functional monomer, add 4 parts of hydrogen peroxide (mass fraction 27%) at 25°C, and add 5 parts of thioglycolic acid, 0.9 parts of vitamin C, and 46 parts of acrylic acid dropwise for 3.5 hours. After adding the above raw materials, keep warm at 60°C for 1 hour to prepare a water reducer. The weight average molecular weight of the product measured by GPC is 51910.

[0129] Comparative Example 4

[0130] The preparation method of the water reducer provided in this comparative example is basically the same as that of Example 1, except that in step (3), 1 / 3 of the mass of the double-terminated esterified functional monomer is replaced by isobutylene polyethylene glycol ether (HPEG-2400) with an average molecular weight of 2400.

[0131] The specific preparation method comprises the following steps:

[0132] (1) By weight, 365 parts of polyethylene glycol (average molecular weight of 1000), 32 parts of methacrylic acid, 11 parts of p-toluenesulfonic acid, and 11 parts of phenothiazine were mixed and subjected to esterification reaction at 110° C. under nitrogen protection for 7 hours to obtain a single-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 1058;

[0133] (2) cooling to 80° C., adding 70 parts of dimethyl terephthalate to the single-terminated esterification functional monomer obtained in step (1), under nitrogen protection, carrying out ester exchange reaction at 80° C. for 4 hours, and no methanol condensate appears, to obtain a double-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC is 1210;

[0134] (3) Take 320 parts of the double-terminated esterified functional monomer obtained in step (2), 160 parts of isobutylene polyethylene glycol ether (HPEG-2400), add 430 parts of water, add 4 parts of hydrogen peroxide (mass fraction 27%) at 25°C, and add 5 parts of thioglycolic acid, 0.9 parts of vitamin C, and 46 parts of acrylic acid dropwise for 3.5 hours. After adding the above raw materials dropwise, keep warm at 60°C for 1 hour to prepare a water reducing agent. The weight average molecular weight of the product measured by GPC is 60550.

[0135] Comparative Example 5

[0136] The preparation method of the water reducer provided in this comparative example is basically the same as that of Example 1, except that in step (3), 1 / 3 of the mass of the double-terminated esterified functional monomer is replaced by isopentenyl polyethylene glycol ether (TPEG-2400) with an average molecular weight of 2400.

[0137] The specific preparation method comprises the following steps:

[0138] (1) By weight, 365 parts of polyethylene glycol (average molecular weight of 1000), 32 parts of methacrylic acid, 11 parts of p-toluenesulfonic acid, and 11 parts of phenothiazine were mixed, and esterification reaction was carried out at 110° C. for 7 hours under nitrogen protection to obtain a single-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 1058;

[0139] (2) cooling to 80° C., adding 70 parts of dimethyl terephthalate to the single-terminated esterification functional monomer obtained in step (1), under nitrogen protection, carrying out ester exchange reaction at 80° C. for 4 hours, and no methanol condensate appears, to obtain a double-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC is 1210;

[0140] (3) Take 320 parts of the double-terminated esterified functional monomer obtained in step (2), 160 parts of isopentyl polyethylene glycol ether (TPEG-2400), add 430 parts of water, add 4 parts of hydrogen peroxide (mass fraction 27%) at 25°C, and add 5 parts of thioglycolic acid, 0.9 parts of vitamin C, and 46 parts of acrylic acid dropwise for 3.5 hours. After adding the above raw materials, keep warm at 60°C for 1 hour to prepare a water reducing agent. The weight average molecular weight of the product measured by GPC is 61570.

[0141] Comparative Example 6

[0142] The preparation method of the water reducer provided in this comparative example is basically the same as that of Example 1, except that in step (3), 1 / 3 of the mass of the double-terminated esterified functional monomer is replaced by vinyl polyoxyethylene ether (VPEG-3000) with an average molecular weight of 3000.

[0143] The specific preparation method comprises the following steps:

[0144] (1) By weight, 365 parts of polyethylene glycol (average molecular weight of 1000), 32 parts of methacrylic acid, 11 parts of p-toluenesulfonic acid, and 11 parts of phenothiazine were mixed and subjected to esterification reaction at 110° C. under nitrogen protection for 7 hours to obtain a single-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC was 1058;

[0145] (2) cooling to 80° C., adding 70 parts of dimethyl terephthalate to the single-terminated esterification functional monomer obtained in step (1), under nitrogen protection, carrying out ester exchange reaction at 80° C. for 4 hours, and no methanol condensate appears, to obtain a double-terminated esterification functional monomer. The weight average molecular weight of the product measured by GPC is 1210;

[0146] (3) Take 320 parts of the double-terminated esterified functional monomer obtained in step (2), 160 parts of vinyl polyoxyethylene ether (VPEG-3000) with an average molecular weight of 3000, add 430 parts of water, add 4 parts of hydrogen peroxide (mass fraction 27%) at 25°C, and add 5 parts of thioglycolic acid, 0.9 parts of vitamin C, and 46 parts of acrylic acid dropwise for 3.5 hours. After adding the above raw materials, keep warm at 60°C for 1 hour to prepare a water reducing agent. The weight average molecular weight of the product measured by GPC is 68470.

[0147] Application Examples

[0148] LC3 cement prepared by Liaoning Beize Energy Co., Ltd. was used. The LC3 cement included 50wt% of silicate cement, 30wt% of calcined clay, 15wt% of limestone and 5wt% of gypsum. Machine-made mountain sand with a fineness modulus of 2.8, crushed stone 1 with a nominal particle size of 5mm-10mm and crushed stone 2 with a nominal particle size of 10mm-20mm were used as raw materials. The water reducer in the embodiment and the comparative example was added. The amount of the water reducer was 0.35% of the mass of the cement (solid content). According to the detection method provided in GB8076-2008 "Concrete Admixtures", the initial expansion of the concrete and the expansion of the concrete after standing for 1h and 2h were tested to determine the changes in the collapse retention and fluidity of the concrete over time. The results are shown in Table 2.

[0149] The concrete raw materials and mix ratio are shown in Table 1:

[0150] Table 1

[0151]

[0152] Table 2

[0153]

[0154] It can be seen from Table 2 that under the same water-reducing agent dosage in each embodiment and comparative example, after adding the water-reducing agent prepared in Examples 1 to 5, the expansion of the concrete mixed with LC3 cement was stably maintained at 455 to 475 mm within 120 min, indicating that the concrete has excellent water reduction and slump retention properties, and the tolerance to LC3 cement is significantly improved. However, Comparative Examples 1 to 2 are affected by LC3 cement, and the initial fluidity is small and the loss over time is large, which is not conducive to construction.

[0155] In Comparative Example 3, dimethyl terephthalate is not used, which will result in poor tolerance to LC3 cement and poor loss over time. The functional monomer lacks ester exchange reaction with dimethyl terephthalate, and the long side chain of the water reducer polymer lacks the rigid end capping of the ester group. The long side chain of the polycarboxylic acid molecule cannot be prevented from chemically intercalating in the layered clay mineral through the steric hindrance effect of the rigid end capping, and cannot effectively act on the surface of cement particles to improve the dispersion performance. Therefore, the tolerance to LC3 cement is poor and the loss over time is relatively large.

[0156] In Comparative Example 4, isobutylene polyethylene glycol ether (HPEG-2400) is used to replace 1 / 3 of the mass of the double-terminated esterified functional monomer, in Comparative Example 5, isopentenyl polyethylene glycol ether (TPEG-2400) is used to replace 1 / 3 of the mass of the double-terminated esterified functional monomer, and in Comparative Example 6, vinyl polyoxyethylene ether (VPEG-3000) is used to replace 1 / 3 of the mass of the double-terminated esterified functional monomer. Comparative Examples 4 to 6 all introduce long polyether side chains that are prone to physical adsorption and chemical intercalation. The water reducer polymer is severely adsorbed by the calcined clay in the LC3 cement, so the initial fluidity and time loss are relatively large.

[0157] In summary, the water reducing agent prepared in the embodiment of the present invention can be used as a special water reducing agent for concrete mixed with LC3 cement, and has excellent water reducing effect and collapse prevention effect.

[0158] Among them, it should be explained at the end that the above embodiments are only used to illustrate the technical solution 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 the technical solutions described in the aforementioned embodiments can still be modified, or part or all of the technical features can be replaced by equivalents. These modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the present invention.

Claims

1. A water reducing agent, characterized in that: The water reducing agent is polymerized from a double-terminated esterified functional monomer and an olefin monomer; The double-terminated esterification functional monomer is formed by a single-terminated esterification functional monomer and dimethyl phthalate through an ester exchange reaction; The single-terminated esterification functional monomer is prepared by esterification reaction of polyethylene glycol and methacrylic acid.

2. The water reducing agent according to claim 1, characterized in that The mass ratio of the double-terminated esterification functional monomer to the olefinic monomer is (8.5-13):1; and / or, The mass ratio of the single-terminated esterification functional monomer to dimethyl phthalate is (4.9-8.8): 1; and / or, The mass ratio of the polyethylene glycol to methacrylic acid is (9-17.5):

1.

3. The water reducing agent according to claim 1, characterized in that: The single-terminated esterification functional monomer includes a compound shown in the following formula 1: Formula 1; In formula 1, n=16~35.

4. The water reducing agent according to claim 1, characterized in that The dimethyl phthalate includes at least one of dimethyl terephthalate, dimethyl isophthalate or dimethyl phthalate; and / or, The olefin monomer includes a compound shown in Formula 2: Formula 2; In Formula 2, R1, R2, and R3 are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a carboxyl group having 1 to 5 carbon atoms.

5. The water reducing agent according to claim 4, characterized in that The double-terminated esterification functional monomer includes at least one of the compound represented by the following formula A, the compound represented by the following formula B, or the compound represented by the following formula C: Formula A; Formula B; Formula C; In Formula A, Formula B, and Formula C, n=16~35.

6. The water reducing agent according to claim 1, characterized in that: The water reducing agent includes at least one of the compound represented by the following formula D, the compound represented by the following formula E, or the compound represented by the following formula F: Formula D; Formula E; Formula F; In Formula D, Formula E, and Formula F, n=16-35, m1=10-50, m2=20-60, and R1, R2, and R3 are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a carboxyl group having 1 to 5 carbon atoms.

7. The water reducing agent according to any one of claims 1 to 6, characterized in that The weight average molecular weight of the water reducer is 44,000-77,000.

8. A method for preparing a water reducing agent according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) Mix 360-400 parts of polyethylene glycol, 22-56 parts of methacrylic acid, 10-22 parts of a catalyst, and 8-16 parts of a polymerization inhibitor by weight, and carry out an esterification reaction under an inert atmosphere to obtain a single-terminated esterification functional monomer; 2) adding 52 to 78 parts of dimethyl phthalate to the single-terminated esterification functional monomer, and performing an ester exchange reaction under an inert atmosphere to obtain a double-terminated esterification functional monomer; 3) Add 3.2-6.8 parts of initiator to the double-terminated esterified functional monomer, and dropwise add 1.5-7 parts of chain transfer agent, 0.6-1.5 parts of reducing agent and 36-46 parts of olefin monomer to carry out polymerization reaction to obtain the water reducing agent.

9. The preparation method according to claim 8, characterized in that: In step 1), in the esterification reaction, the reaction temperature is 95-115° C. and the reaction time is 6-9 h; and / or, In step 2), in the transesterification reaction, the reaction temperature is 75-85°C and the reaction time is 3-5h; and / or, In step 3), in the polymerization reaction, the reaction temperature is 15-60° C. and the reaction time is 2-5 h; and / or, In step 3), the dropping time is 1 to 3.5 hours.

10. A concrete, characterized in that: The concrete comprises the water reducing agent according to any one of claims 1 to 7.

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