Cement admixture and method of making

Abstract

The cement admixture of the present invention comprises a copolymer (A), an unsaturated (poly)alkylene glycol ether monomer (a), and an alkenyl-free (poly)ethylene glycol (B); the copolymer (A) comprises unit I and unit II, wherein unit I is an unsaturated (poly)alkylene glycol ether monomer (a), and unit II is an unsaturated carboxylic acid monomer (b). The viscosity-reducing polycarboxylic acid superplasticizer of the present invention incorporates a polyether monomer with a longer carbon chain during synthesis, resulting in a polycarboxylic acid superplasticizer with a longer side chain structure. This increases its steric hindrance, making the steric stabilization effect of the superplasticizer more significant, exhibiting a noticeable viscosity-reducing effect. When reacting with cement and other aggregates, it can better exert its steric hindrance effect. Furthermore, it is low in cost, low in energy consumption, easy to prepare, environmentally friendly, and easily degradable, with a huge future market prospect.

Description

Technical Field

[0001] This invention relates to the field of concrete admixtures, and more particularly to a cement admixture and its preparation method. Background Technology

[0002] With increasingly stringent technical requirements for sand and gravel in modern concrete and high-speed rail projects, and a shrinking supply of natural sand and gravel to meet these demands, manufactured sand has become the preferred choice in the construction market to satisfy the rigid demand. The gradual replacement of natural sand and gravel with manufactured sand has become a necessity driven by market trends. However, the quality of manufactured sand is difficult to guarantee, and its relatively high mud and stone powder content leads to significant adsorption, greatly impacting the workability and retention properties of concrete. Ordinary polycarboxylate superplasticizers are no longer sufficient to meet the evolving needs of the construction market. The changing landscape of sand and gravel materials necessitates the redesign and development of new structures for superplasticizers and their polymer monomers to improve their viscosity-reducing properties.

[0003] Patent CN109053974B discloses a method for preparing a viscosity-reducing polycarboxylate superplasticizer. This superplasticizer is mainly composed of isopentenyl alcohol polyoxyethylene ether monomer, unsaturated diacid monomer or its derivative monomer, and a viscosity-reducing agent, which are synthesized through free radical polymerization under the action of a reducing agent, an oxidizing agent, and a chain transfer agent. The viscosity-reducing agent is fumarate diethanolamide phosphate. The polar groups such as ethanol groups, amide groups, and phosphate groups contained in the molecular structure of fumarate diethanolamide phosphate can increase the proportion of polar hydrophilic groups on the isopentenyl alcohol polyoxyethylene ether molecular chain, thereby increasing the hydrophilic-lipophilic balance value of the superplasticizer and improving its viscosity-reducing effect.

[0004] CN103553413A describes a viscosity-adjusting polycarboxylate superplasticizer and its preparation method. This superplasticizer is mainly obtained by copolymerizing unsaturated alkyl esters, fluorinated esters, alkyl acrylamides or mixtures thereof, along with unsaturated polyoxyethylene monomers and unsaturated acid monomers, in an aqueous solution at 70–90°C. This superplasticizer effectively reduces the plastic viscosity of cement paste, but the production process requires high temperatures and consumes a large amount of energy; furthermore, some surfactants cannot be removed from the final product.

[0005] Patent CN109180876B discloses a method for preparing a viscosity-reducing polycarboxylate superplasticizer. The method involves copolymerizing a product obtained by esterification of allyl hydroxyethyl ether with 2-butane-1,2,4-tricarboxylic acid (where the carboxyl group is single-esterified) with a small amount of a blend of products containing double and triple esterified carboxyl groups from 2-butane-1,2,4-tricarboxylic acid, VPE, 2-methacryloyloxyethyl phosphocholine, and unsaturated acids to prepare the viscosity-reducing polycarboxylate superplasticizer. This viscosity-reducing polycarboxylate superplasticizer not only reduces viscosity but also reduces water content, maintains slump, and resists mud, thus solving the problems of high viscosity, poor workability, and rapid mud loss caused by high mud content in current concrete raw materials.

[0006] CN104262550A discloses a method for preparing a viscosity-reducing polycarboxylate superplasticizer. The method involves first synthesizing unsaturated primary amine monomers from unsaturated acid anhydrides and unsaturated primary amines at a certain temperature. These monomers are then reacted with small organic molecules containing epoxy and halogen groups to obtain quaternary ammonium salt unsaturated monomers. Finally, these unsaturated quaternary ammonium salts are introduced as a third monomer into the polycarboxylate molecule. The resulting product exhibits good properties such as reducing concrete viscosity and improving slump retention. However, this method has drawbacks such as cumbersome steps, high raw material costs, and significant pollution during production. Summary of the Invention

[0007] To address the technical problems of high energy consumption, unsatisfactory performance, and difficulty in ensuring product stability in the production of existing viscosity-reducing polycarboxylate superplasticizers, this invention provides a cement admixture and its preparation method.

[0008] The present invention provides a cement admixture comprising a copolymer (A), an unsaturated (poly)alkylene glycol ether monomer (a), and an alkenyl-free (poly)ethylene glycol (B);

[0009] The unsaturated (poly)alkylene glycol ether monomer (a) and the alkenyl-free (poly)ethylene glycol (B) account for 1-100% and 1-50% of the weight of the copolymer (A), respectively, preferably 1-50% and 1-10%.

[0010] The copolymer (A) comprises unit I and unit II, wherein unit I is an unsaturated (poly)alkylene glycol ether monomer (a) and unit II is an unsaturated carboxylic acid monomer (b); the weight of unit I and unit II each accounts for more than 1% of the total weight of the copolymer (A), preferably unit II accounts for 2-15% of the total weight of the copolymer (A);

[0011] The unsaturated (poly)alkylene glycol ether monomer (a) is represented by the general formula (1):

[0012] L 1 O(X1 ) m (R 2 O) n R 3 (1)

[0013] Among them, L 1 This refers to alkenes with 6-12 carbon atoms; X 1 -CH2-, -CH2CH2-, -CH2CH2O-, -CH2CH2CH2CH2O-, or -C=O, where m represents 0 or 1; R 2 O represents an alkoxy group with 2-18 carbon atoms, n represents the alkylene oxide addition number, where n is an integer from 1 to 500, and R 3 Indicates -H or C1 to C30 alkyl group;

[0014] The unsaturated carboxylic acid monomer (b) is represented by general formula (2):

[0015]

[0016] Among them, R 4 R 5 R 6 Each can be independently -H, -CH3, or -(CH2). p COOM; when the unsaturated carboxylic acid monomer (b) is an acid monomer of an unsaturated monocarboxylic acid, R 4 R 5 and R 6 Each is independently selected from -H or -CH3; the M group may be the same or different, representing -H, a monovalent metal atom, a divalent metal atom, an ammonium group or an organic amine group; p represents an integer from 0 to 2; when there are two -COOM groups, the two -COOM groups form a -COOCO- group.

[0017] According to one embodiment of the present invention, the copolymer (A) has a weight average molecular weight of 10,000 to 100,000, preferably 20,000 to 50,000.

[0018] According to another embodiment of the present invention, the initiator of the unsaturated (poly)ethylene glycol ether monomer (a) is selected from one or more of 5-hexen-1-ol, 3-methyl-5-hexen-3-ol, 7-octen-1-ol and 1-octen-3-ol.

[0019] According to another embodiment of the invention, the unsaturated (poly)alkylene glycol ether monomer (a) is the product of the reaction of the initiator with an epoxy compound.

[0020] According to another embodiment of the present invention, the alkenyl-free (poly)ethylene glycol (B) is a compound with active hydrogen other than an unsaturated alcohol generated by the reaction of the initiator with the epoxy compound.

[0021] According to another embodiment of the present invention, the unsaturated carboxylic acid monomer (b) is one or more of (meth)acrylic acid, maleic anhydride, maleic acid, itaconic acid, fumaric acid, and crotonic acid.

[0022] Another aspect of the present invention provides a method for preparing the above-mentioned cement admixture, comprising: S1, reacting an unsaturated alcohol having 6-8 carbon atoms with an epoxy compound as a starting agent; and S2, mixing the product from step S1 with deionized water, adding an initiator, an aqueous solution of the unsaturated carboxylic acid monomer (b), and an aqueous solution of a chain transfer agent to carry out a polymerization reaction, and after the polymerization reaction is completed, adding a sodium hydroxide solution to adjust the pH value to 6-7 to obtain the cement admixture.

[0023] According to one embodiment of the present invention, in step S1, the initiator is contained in an initiator system, the initiator system being composed of the initiator and water, and the water content in the initiator system being 0.01%-0.2%.

[0024] According to another embodiment of the present invention, the polymerization temperature in step S2 is 20-70°C and the polymerization time is 2-4 hours.

[0025] According to another embodiment of the present invention, the initiator is a redox initiator composed of an oxidant and a reductant; the oxidant is selected from one or more of hydrogen peroxide, sodium formaldehyde sulfoxylate, vitamin C, ferrous sulfate, and persulfate, and the reductant is selected from sodium bisulfite; the chain transfer agent is selected from one or more of mercaptopropionic acid, mercaptoacetic acid, sodium hypophosphite, sodium aluminum phosphate, and sodium thiophosphate.

[0026] The present invention incorporates polyether monomers with longer carbon chains during the synthesis of the viscosity-reducing polycarboxylate superplasticizer, resulting in a polycarboxylate superplasticizer with longer side chain structures. This increases its steric hindrance, making the steric stabilization effect of the superplasticizer more significant and exhibiting a noticeable viscosity-reducing effect. When reacting with cement and other aggregates, it can better exert its steric hindrance effect. Furthermore, it is low in cost, low in energy consumption, easy to prepare, environmentally friendly, and easily degradable, with a huge future market prospect. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments, but is not limited thereto. Unless otherwise stated, all percentage contents in this patent are weight percentage contents.

[0028] The cement admixture of the present invention comprises copolymer (A), unsaturated (poly)alkylene glycol ether monomer (a), and alkenyl-free (poly)ethylene glycol (B).

[0029] The copolymer (A) comprises unit I and unit II, wherein unit I is an unsaturated (poly)alkylene glycol ether monomer (a) and unit II is an unsaturated carboxylic acid monomer (b).

[0030] The unsaturated (poly)alkylene glycol ether monomer (a) is represented by the general formula (1):

[0031] L 1 O(X 1 ) m (R 2 O) n R 3 (1)

[0032] Among them, L 1 This refers to alkenes with 6-12 carbon atoms; X 1 -CH2-, -CH2CH2-, -CH2CH2O-, -CH2CH2CH2CH2O-, or -C=O, where m represents 0 or 1; R 2 O represents an alkoxy group with 2-18 carbon atoms, n represents the alkylene oxide addition number, where n is an integer from 1 to 500, and R 3 It represents -H or C1 to C30 alkyl groups.

[0033] The initiator for the unsaturated (poly)alkenyl glycol ether monomer (a) is preferably an unsaturated alcohol having 6-8 carbon atoms, and is selected from one or more of 5-hexen-1-ol, 3-methyl-5-hexen-3-ol, 7-octen-1-ol, and 1-octen-3-ol. The initiator reacts with the epoxide compound to generate the unsaturated (poly)alkylene glycol ether monomer (a) and the byproduct alkenyl-free (poly)ethylene glycol (B). The byproduct alkenyl-free (poly)ethylene glycol (B) is a compound with active hydrogen other than the unsaturated alcohol generated by the reaction of the initiator with the epoxide compound.

[0034] The unsaturated carboxylic acid monomer (b) is represented by the general formula (2):

[0035]

[0036] Among them, R 4 R 5 R 6 Each can be independently -H, -CH3, or -(CH2). p COOM; when the unsaturated carboxylic acid monomer (b) is an acid monomer of an unsaturated monocarboxylic acid, R 4 R 5 and R 6Each is independently selected from -H or -CH3; the M group may be the same or different, representing -H, a monovalent metal atom, a divalent metal atom, an ammonium group or an organic amine group; p represents an integer from 0 to 2; when there are two -COOM groups, the two -COOM groups form a -COOCO- group.

[0037] In copolymer (A), the weight of unit I and unit II each accounts for more than 1% of the total weight of copolymer (A), preferably unit II accounts for 2-15% of the total weight of copolymer (A).

[0038] The method for preparing the cement admixture of the present invention includes: S1, reacting an unsaturated alcohol having 6-8 carbon atoms with an epoxy compound as a starting agent; and S2, mixing the product from step S1 with deionized water, adding an initiator, an aqueous solution of the unsaturated carboxylic acid monomer (b), and an aqueous solution of a chain transfer agent to carry out a polymerization reaction, and after the polymerization reaction is completed, adding sodium hydroxide solution to adjust the pH value to 6-7 to obtain the cement admixture.

[0039] In step S1, unsaturated alcohols are used as initiators to synthesize unsaturated (poly)alkylene glycol ether monomers (a) and the byproduct alkenyl-free (poly)glycol (B). The initiator is included in the initiator system, which consists of the initiator and water, with a water content of 0.01%–0.2%. If the water content in the initiator system exceeds 0.2%, it will lead to an increase in the content of the byproduct alkenyl-free (poly)glycol (B) in the corresponding polyether synthesized from the unsaturated alcohol, thereby causing a decrease in concrete performance.

[0040] Subsequently, in step S2, the product from step S1, namely the unsaturated (poly)alkylene glycol ether monomer (a) and the byproduct non-alkenyl (poly) glycol (B), is mixed with deionized water. An initiator, an aqueous solution of unsaturated carboxylic acid monomer (b), and an aqueous solution of chain transfer agent are then added to initiate a polymerization reaction. After the polymerization reaction is complete, sodium hydroxide solution is added to adjust the pH to 6-7, yielding the cement admixture. The unsaturated (poly)alkylene glycol ether monomer (a) (i.e., monomer I) participating in the polymerization reaction accounts for more than 1% of the total copolymer (A). If the proportion of unsaturated polyoxyalkylene ether is too low (below 1%), the viscosity of copolymer (A) decreases. The residual unsaturated (poly)alkylene glycol ether monomer (a) after the polymerization reaction accounts for 1-100% of the total copolymer (A), preferably 1-50%. The unsaturated carboxylic acid monomer (b) (i.e., monomer II) participating in the polymerization reaction accounts for more than 1% of the total copolymer (A), preferably 2-15% by weight. If the content of unsaturated carboxylic acid monomer (b) is too low (below 1%), the synthesized copolymer (A) cannot be fully adsorbed onto cement particles, resulting in poor dispersion performance; if the content is too high (above 15%), the viscosity of the produced copolymer (A) will be too high, affecting the water reduction rate. Those skilled in the art can select appropriate values ​​for the content of residual unsaturated (poly)alkylene glycol ether monomer (a), monomer I, and monomer II according to specific needs. For example, but not limited to, the unsaturated (poly)alkylene glycol ether monomer (a) remaining after the reaction accounts for 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% of the total copolymer (A); the content of monomer I can be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%; the content of monomer II can be 1%, 5%, 10%, 15%, etc.

[0041] In step S2, the initiator can be one or more of hydrogen peroxide, sodium bisulfite, formaldehyde, vitamin C, ferrous sulfate, ammonium persulfate, sodium sulfite, and sodium bisulfite; the chain transfer agent can be one or more selected from mercaptopropionic acid, mercaptoacetic acid, sodium hypophosphite, sodium aluminum phosphate, and sodium thiophosphate. The polymerization temperature can be 20-70℃, and the time is 2-4 hours. The polymerization temperature is preferably 30-50℃, within which the formation of reaction products can be better controlled, allowing the polymerization reaction to proceed rapidly and smoothly, and minimizing the occurrence of side reactions.

[0042] The weight-average molecular weight of copolymer (A) in the cement admixture of the present invention is 10,000-100,000. If the molecular weight is below 10,000, the copolymer polymerization is insufficient, the reaction is incomplete, and the water reduction rate and dispersion performance are poor; if it is above 100,000, the viscosity of the reaction system increases, the side chain density increases, and the cement particles cannot be fully adsorbed, resulting in poor dispersion performance. Preferably, the weight-average molecular weight of copolymer (A) is 20,000-50,000. Any copolymer (A) with an appropriate weight-average molecular weight within the above range can be selected according to specific needs, such as, but not limited to, copolymers (A) with weight-average molecular weights of 10,000, 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, etc.

[0043] The present invention provides a simple, highly operable, energy-efficient, and inexpensive method for preparing a viscosity-reducing polycarboxylate superplasticizer. The resulting polycarboxylate superplasticizer exhibits stable performance, strong adaptability to cement, and is environmentally friendly. The following detailed description, in conjunction with specific embodiments, illustrates the viscosity-reducing polycarboxylate superplasticizer and its preparation method. The weight-average molecular weight of the viscosity-reducing polycarboxylate superplasticizer was measured using a Beckman Coulter multi-angle laser scattering instrument.

[0044] The method for determining the hydroxyl value of macromonomers in polycarboxylate superplasticizers refers to GB / T7383.

[0045] The method for determining the iodine value of macromonomers in polycarboxylate superplasticizers refers to GB / T13892.

[0046] The formula for calculating the double bond retention rate of macromonomers in polycarboxylate superplasticizers is as follows:

[0047]

[0048] The following abbreviations are used in the embodiments:

[0049] a-1: L 1 =C6 olefin; X1=-CH2CH2O-, m=1,; R 2 O=-CH2CH2O-, n=15; R 3 =-H

[0050] a-2: L 1 =C6 olefin; m=0; R 2 O = -CH2CH2-, n = 50; R 3 =-H

[0051] a-3: L 1 =C7 olefin; X1=-CH2CH2O-, m=1; R 2 O = -CH2CH2-, n = 30; R 3 =-H

[0052] a-4: L 1 =C8 olefin; m=0; R 2 O = -CH2CH2-, n = 90; R 3 =-H

[0053] a-5: L 1 =C8 olefin; X1=-CH2CH2O-, m=1; R 2 O = -CH2CH2-, n = 80; R 3 =-H

[0054] a-6: L 1 =C8 olefin; m=0; R 2 O = -CH2CH2-, n = 115; R 3 =-H

[0055] b-1: Maleic anhydride

[0056] b-2: Acrylic acid

[0057] b-3: Methacrylic acid

[0058] Preparation Example 1

[0059] In an autoclave, 1 mol of ethylene glycol monohexene ether and 0.001 mol of metallic sodium were heated to 90°C and purged three times with nitrogen at a pressure of 5 bar. 15 mol of ethylene oxide was then added. The reaction temperature and pressure were controlled within the ranges of 120°C–130°C and 0.35–0.45 MPa, respectively. To complete the reaction, the mixture was post-treated at 120°C for 2 hours. The resulting reaction products included the byproducts of alkenyl-free polyethylene glycol (B) and hexene-free polyethylene glycol ether monomer (a-1). The yield of alkenyl-free polyethylene glycol relative to the hexene-free polyethylene glycol ether monomer (a-1) was 0.07%.

[0060] Preparation Example 2

[0061] In an autoclave, 1 mol of hexenol and 0.001 mol of metallic sodium were heated to 90°C and purged three times with nitrogen at a pressure of 5 bar. 50 mol of ethylene oxide and 5 mol of propylene oxide were then added. The reaction temperature and pressure were controlled within the ranges of 120°C–130°C and 0.35–0.45 MPa, respectively. To complete the reaction, the mixture was post-treated at 120°C for 2 hours. The resulting reaction products included the byproducts of alkenyl-free polyethylene glycol (B) and hexenyl alcohol ether monomer (a-2). The yield of alkenyl-free polyethylene glycol relative to the hexenyl alcohol ether monomer (a-2) was 0.08%.

[0062] Preparation Example 3

[0063] In an autoclave, 1 mol of ethylene glycol monoheptenyl ether and 0.001 mol of metallic sodium were heated to 90°C, purged three times with nitrogen, and the pressure was 5 bar. 30 mol of ethylene oxide was then added. The reaction temperature and pressure were controlled within the ranges of 120°C–130°C and 0.35–0.45 MPa, respectively. To complete the reaction, the mixture was post-treated at 120°C for 2 hours. The resulting reaction products included the byproducts of alkenyl-free polyethylene glycol (B) and heptenyl polyethylene glycol ether monomer (a-3). The yield of alkenyl-free polyethylene glycol relative to the heptenyl polyethylene glycol ether monomer (a-3) was 0.07%.

[0064] Preparation Example 4

[0065] In an autoclave, 1 mol of 7-octen-1-ol and 0.001 mol of metallic sodium were heated to 90°C and purged three times with nitrogen at a pressure of 5 bar. 90 mol of ethylene oxide was then added. The reaction temperature and pressure were controlled within the ranges of 120°C–130°C and 0.35–0.45 MPa, respectively. To complete the reaction, the mixture was post-treated at 120°C for 2 hours. The resulting reaction products included the byproducts of alkenyl-free polyethylene glycol (B) and octenyl alcohol ether monomer (a-4). The yield of alkenyl-free polyethylene glycol relative to the octenyl alcohol ether monomer (a-4) was 0.06%.

[0066] Preparation Example 5

[0067] In an autoclave, 1 mol of ethylene glycol monooctene ether and 0.001 mol of metallic sodium were heated to 90°C, purged three times with nitrogen, and the pressure was 5 bar. 80 mol of ethylene oxide was then added. The reaction temperature and pressure were controlled within the ranges of 120°C–130°C and 0.35–0.45 MPa, respectively. To complete the reaction, the mixture was post-treated at 120°C for 2 hours. The resulting reaction products included the byproducts of alkenyl polyethylene glycol (B) and octenyl polyethylene glycol ether monomer (a-5). The yield of alkenyl polyethylene glycol relative to the octenyl polyethylene glycol ether monomer (a-5) was 0.06%.

[0068] Preparation Example 6

[0069] In an autoclave, 1 mol of 7-octen-1-ol and 0.001 mol of metallic sodium were heated to 90 °C and purged three times with nitrogen at a pressure of 5 bar. 115 mol of ethylene oxide was then added. The reaction temperature and pressure were controlled within the ranges of 120 °C–130 °C and 0.35–0.45 MPa, respectively. To complete the reaction, the mixture was post-treated at 120 °C for 2 h. The resulting reaction products included the byproducts of alkenyl-free polyethylene glycol (B) and octenyl alcohol ether monomer (a-6). The yield of alkenyl-free polyethylene glycol relative to octenyl alcohol ether monomer (a-6) was 0.14%.

[0070] Table 1 Physicochemical properties of macromonomers in polycarboxylate superplasticizers

[0071]

[0072] Example 1

[0073] 20 parts of deionized water and 30 parts of the mixture obtained in Preparation Example 1 were placed in a glass reactor equipped with a thermometer, stirrer, dropping funnel, and reflux condenser, and heated to 65°C. 0.5 parts of ammonium persulfate were added. Then, 3 parts of a mixed aqueous solution of maleic anhydride monomer (b-1) and 5 parts of deionized water, and 0.1 parts of a mixed aqueous solution of mercaptopropionic acid and 10 parts of deionized water were added dropwise over 2 hours and 2.5 hours, respectively. The temperature was then maintained at 65°C for 2 hours to complete the polymerization reaction. The reaction mixture was then cooled to no higher than 50°C, and the pH was adjusted to 6-7 with 2.8 parts of 30% sodium hydroxide aqueous solution and 28.6 parts of deionized water to obtain the cement admixture copolymer (A-1) of the present invention, with a weight-average molecular weight of 23400.

[0074] Example 2

[0075] 25 parts of deionized water and 25 parts of the mixture obtained in Preparation Example 2 were placed in a glass reactor equipped with a thermometer, stirrer, dropping funnel, and reflux condenser, and heated to 65°C. 0.2 parts of hydrogen peroxide and 0.04 parts of vitamin C were added. Then, a mixed aqueous solution of 2.2 parts of maleic anhydride monomer (b-1) and 10 parts of deionized water was added dropwise, followed by a mixed aqueous solution of 0.03 parts of mercaptopropionic acid and 10 parts of deionized water, with addition times of 2 hours and 2.5 hours, respectively. The temperature was then maintained at 65°C for 2 hours to complete the polymerization reaction. The reaction mixture was then cooled to no higher than 50°C, and the pH was adjusted to 6-7 with 1.97 parts of 30% sodium hydroxide aqueous solution and 25.56 parts of deionized water to obtain the cement admixture copolymer (A-2) of this invention, with a weight-average molecular weight of 31,500.

[0076] Example 3

[0077] 22 parts of deionized water and 28 parts of the mixture obtained in Preparation Example 3 were placed in a glass reactor equipped with a thermometer, stirrer, dropping funnel, and reflux condenser, and heated to 70°C. 0.55 parts of ammonium persulfate were added. Then, a mixed aqueous solution of 3.68 parts of acrylic monomer (b-2) and 5 parts of deionized water, and a mixed aqueous solution of 0.03 parts of mercaptopropionic acid and 10 parts of deionized water were added dropwise over 2 hours and 2.5 hours, respectively. The temperature was then maintained at 70°C for 2 hours to complete the polymerization reaction. The reaction mixture was then cooled to no higher than 50°C, and the pH was adjusted to 6-7 with 3.4 parts of 30% sodium hydroxide aqueous solution and 27.34 parts of deionized water to obtain the invented cement admixture copolymer (A-3) with a weight-average molecular weight of 36,100.

[0078] Example 4

[0079] 20 parts of deionized water and 30 parts of the mixture obtained in Preparation Example 4 were placed in a glass reactor equipped with a thermometer, stirrer, dropping funnel, and reflux condenser, and heated to 70°C. 0.5 parts of ammonium persulfate were added. Then, a mixed aqueous solution of 3.6 parts of acrylic monomer (b-2) and 5 parts of deionized water, and a mixed aqueous solution of 0.06 parts of mercaptoacetic acid and 10 parts of deionized water were added dropwise over 2 hours and 3 hours, respectively. The temperature was then maintained at 70°C for 1 hour to complete the polymerization reaction. The reaction mixture was then cooled to no higher than 50°C, and the pH was adjusted to 6-7 with 3 parts of 30% sodium hydroxide aqueous solution and 27.84 parts of deionized water to obtain the cement admixture copolymer (A-4) of this invention, with a weight-average molecular weight of 39200.

[0080] Example 5

[0081] The mixture of 21 parts deionized water and 29 parts prepared in Example 5 was placed in a glass reactor equipped with a thermometer, stirrer, dropping funnel, and reflux condenser, and heated to 70°C. 0.45 parts ammonium persulfate were added. Then, a mixed aqueous solution of 2.38 parts methacrylic acid (b-3) and 5 parts deionized water, and a mixed aqueous solution of 0.05 parts mercaptoacetic acid and 10 parts deionized water were added dropwise over 2 hours and 2.5 hours, respectively. The temperature was then maintained at 70°C for 2 hours to complete the polymerization reaction. The reaction mixture was cooled to no higher than 50°C, and the pH was adjusted to 6-7 with 2.2 parts 30% sodium hydroxide aqueous solution and 29.92 parts deionized water to obtain the cement admixture copolymer (A-5) of the present invention, with a weight-average molecular weight of 28,000.

[0082] Comparative Example 1

[0083] A mixture of 20 parts deionized water and 30 parts prepared in Example 6 was placed in a glass reactor equipped with a thermometer, stirrer, dropping funnel, and reflux condenser, and heated to 70°C. 0.5 parts ammonium persulfate were added. Then, a mixed aqueous solution of 3.6 parts acrylic monomer (b-2) and 5 parts deionized water, and a mixed aqueous solution of 0.06 parts mercaptoacetic acid and 10 parts deionized water were added dropwise over 2 hours and 3 hours, respectively. The temperature was then maintained at 70°C for 1 hour to complete the polymerization reaction. The reaction mixture was then cooled to no higher than 50°C, and the pH was adjusted to 6-7 with 3 parts 30% sodium hydroxide aqueous solution and 27.84 parts deionized water to obtain the cement admixture copolymer (A-6) of this invention, with a weight-average molecular weight of 22300.

[0084] Table 2 Detection of Reaction Indicators in Examples

[0085]

[0086] Comparative Example 2

[0087] The mixture was prepared using 22 parts deionized water and 35.7 parts isopentenyl alcohol polyoxyethylene ether, and then heated to 70°C. 0.25 parts ammonium persulfate were added. Then, a mixed aqueous solution of 3.85 parts maleic anhydride monomer (b-1) and 5 parts deionized water was added dropwise, followed by a mixed aqueous solution of 0.1 parts mercaptoacetic acid and 10 parts deionized water, with addition times of 2 hours and 3.5 hours, respectively. The temperature was then maintained at 70°C for 2 hours to complete the polymerization reaction. The reaction mixture was then cooled to no higher than 50°C, and the pH was adjusted to 6-7 with 4.6 parts of 30% sodium hydroxide aqueous solution and 18.75 parts of deionized water to obtain the cement admixture copolymer (DB-1) of this invention, with a weight-average molecular weight of 32,500.

[0088] The admixtures synthesized in Examples 1 to 5 and Comparative Examples 1 and 2 were designed with sand, gravel, cement, water, etc., according to the mix proportions in JGJ55. The admixtures were then introduced into a concrete mixer and thoroughly mixed. After the concrete was poured out of the pot, the slump cone was inverted, the bottom was sealed, and the cone was quickly filled with concrete and smoothed with a shovel. The bottom cover was then quickly slid open. At this time, a stopwatch was started to measure the time taken for the concrete to flow out of the container, which was recorded as the backflow time of the concrete. For other data acquisition methods or detailed instructions, please refer to GB / 8076-2008.

[0089] The experimental results are shown in the table below:

[0090] Table 3. Experimental Results for Concrete Performance Evaluation

[0091]

[0092] Experimental results show that, under conditions of similar concrete slump, when comparing Comparative Example 1 with the cement admixture copolymer (A) of the present invention (Examples 1-5), the lower the content of alkenyl (poly)ethylene glycol (B) in copolymer (A), the significantly earlier the concrete backflow time. Compared with Comparative Example 2, which is a conventionally synthesized ultra-high performance polycarboxylate superplasticizer, Examples 1-5 of the cement admixture copolymer (A) of the present invention have similar dosages, comparable air content, good slump, and significantly earlier concrete backflow time; indicating that the cement admixture copolymer (A) of the present invention has a good viscosity-reducing effect on concrete.

[0093] It should be noted that the above embodiments are merely some preferred embodiments of the present invention and are not intended to limit the present invention. Various other substitutions, changes, and improvements made within the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A cement admixture, characterized in that, It includes copolymer (A), unsaturated polyalkylene glycol ether monomer (a), and alkenyl-free polyethylene glycol (B); The unsaturated polyalkylene glycol ether monomer (a) and the alkenyl-free polyethylene glycol (B) account for 1-100% and 3.9-4.4% of the weight of the copolymer (A), respectively. The copolymer (A) comprises unit I and unit II, wherein unit I is an unsaturated polyalkylene glycol ether monomer (a) and unit II is an unsaturated carboxylic acid monomer (b); the weight of unit I and unit II each accounts for more than 1% of the total weight of the copolymer (A); The unsaturated polyalkylene glycol ether monomer (a) is represented by general formula (1): L 1 O(X 1 ) m (R 2 O) n R 3 (1) Among them, L 1 This refers to alkenes with 6-12 carbon atoms; X 1 -CH2-, -CH2CH2-, -CH2CH2O-, -CH2CH2CH2CH2O-, or -C=O, where m represents 0 or 1; R 2 O represents an alkoxy group with 2-18 carbon atoms, n represents the alkylene oxide addition number, where n is an integer from 1 to 500, and R 3 Indicates -H or C1 to C30 alkyl group; The unsaturated carboxylic acid monomer (b) is represented by general formula (2): Among them, R 4 R 5 R 6 Each can be independently -H, -CH3, or -(CH2). p COOM; M groups may be the same or different, representing -H, a monovalent metal atom, a divalent metal atom, an ammonium group or an organic amine group; p represents an integer from 0 to 2; and the unsaturated carboxylic acid monomer (b) has two -COOM groups, which form a -COOCO- group.

2. The cement admixture according to claim 1, characterized in that, The unsaturated polyalkylene glycol ether monomer (a) accounts for 1-50% of the weight of the copolymer (A).

3. The cement admixture according to claim 1, characterized in that, The weight of Unit II accounts for 2-15% of the total weight of the copolymer (A).

4. The cement admixture according to claim 1, characterized in that, The copolymer (A) has a weight average molecular weight of 10,000 to 100,000.

5. The cement admixture according to claim 4, characterized in that, The copolymer (A) has a weight average molecular weight of 20,000-50,000.

6. The cement admixture according to claim 1, characterized in that, The initiator for the unsaturated polyalkylene glycol ether monomer (a) is selected from one or more of 5-hexen-1-ol, 3-methyl-5-hexen-3-ol, 7-octen-1-ol and 1-octen-3-ol.

7. The cement admixture according to claim 6, characterized in that, The unsaturated polyalkylene glycol ether monomer (a) is the product of the reaction between the initiator and the epoxy compound.

8. The cement admixture according to claim 7, characterized in that, The alkenyl-free polyethylene glycol (B) is a compound with active hydrogen other than an unsaturated alcohol generated by the reaction of the initiator and the epoxy compound.

9. The cement admixture according to claim 1, characterized in that, The unsaturated carboxylic acid monomer (b) is maleic anhydride.

10. A method for preparing a cement admixture according to any one of claims 1-9, characterized in that, include: S1, using an unsaturated alcohol with 6-8 carbon atoms as a starting agent, reacts with an epoxide compound; and S2, after mixing the product from step S1 with deionized water, an initiator, an aqueous solution of the unsaturated carboxylic acid monomer (b), and an aqueous solution of the chain transfer agent are added to carry out a polymerization reaction. After the polymerization reaction is completed, sodium hydroxide solution is added to adjust the pH value to 6-7 to obtain the cement admixture.

11. The preparation method according to claim 10, characterized in that, In step S1, the initiator is contained in an initiator system, which is composed of the initiator and water, and the water content in the initiator system is 0.01%-0.2%.

12. The preparation method according to claim 10, characterized in that, The polymerization temperature in step S2 is 20-70℃, and the polymerization time is 2-4 hours.

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