Polycarboxylate superplasticizer as well as preparation method and application thereof

Abstract

The invention belongs to the field of additives, and provides a polycarboxylate superplasticizer as well as a preparation method and application thereof. The preparation method of the polycarboxylic acid water reducer comprises the following steps: in the presence of water, an initiator and a chain transfer agent, comonomers including a polyether macromonomer, unsaturated carboxylic acid, unsaturated amide and a functional monomer are subjected to a polymerization reaction to form polycarboxylic acid, and the functional monomer is an esterification product of rhamnolipid and unsaturated alcohol. The polycarboxylate superplasticizer provided by the invention has improved workability while maintaining a relatively high water-reducing rate.

Description

Technical Field

[0001] The invention belongs to the field of admixtures, and specifically provides a polycarboxylate water reducer and a preparation method and application thereof. Background Art

[0002] With the continuous development of modern construction technology, the requirements for concrete performance in engineering are getting higher and higher. As an important component of high-performance concrete, water reducer has received increasing attention from the industry. Polycarboxylate water reducer has the advantages of low dosage, high water reduction rate, good collapse resistance, good dispersibility, good workability and durability, and is known as the third generation of concrete water reducer.

[0003] The total amount of cementing materials in high-strength concrete is large, and the water demand will increase. However, in order to improve the density and strength, the water-cement ratio must be reduced. The consequence of increasing the amount of cement and reducing the water-cement ratio is that the viscosity of the concrete increases and the rheology deteriorates. In the production and application of high-strength concrete, the polycarboxylic acid water reducer currently used faces the following major problems: (a) The water reduction rate of the water reducer is insufficient, which makes the high-strength concrete insufficiently fluid and difficult to construct; (b) High-strength concrete usually requires the addition of more water reducers, and it takes a certain amount of time for the water reducer molecules to disperse in the concrete, so it takes longer to stir, which affects production efficiency and is prone to water and other phenomena, resulting in poor workability; (c) The viscosity of high-strength concrete is relatively high, making it difficult to pump. Summary of the invention

[0004] In view of the above problems existing in the prior art, the object of the present invention is to provide a polycarboxylate water-reducing agent and a preparation method and application thereof. The polycarboxylate water-reducing agent of the present invention has improved workability while maintaining a high water reduction rate.

[0005] In a first aspect, the present invention provides a method for preparing a polycarboxylic acid water-reducing agent, the method comprising: in the presence of water, an initiator and a chain transfer agent, polymerizing a polyether macromonomer, an unsaturated carboxylic acid, an unsaturated amide and a functional monomer to form a polycarboxylic acid; wherein the functional monomer is an esterification product of a rhamnolipid and an unsaturated alcohol.

[0006] In the method of the present invention, rhamnolipid can be introduced into the molecular structure of polycarboxylic acid by using the functional monomer to participate in copolymerization. Rhamnolipid has low surface tension and shows good dispersibility in water. Rhamnolipid has a ring structure, which can improve steric hindrance, improve the dispersibility and stability of concrete slurry, and reduce the viscosity of slurry. Unsaturated amide monomer participates in the copolymerization of unsaturated carboxylic acid and polyether macromonomer, and amide group is introduced into the side chain of polycarboxylic acid molecular chain, which can improve the collapse retention performance of polycarboxylic acid water reducer. The functional monomer, unsaturated amide monomer, unsaturated carboxylic acid and polyether macromonomer are used as monomers for copolymerization, so that the prepared polycarboxylic acid water reducer maintains a high water reduction effect, promotes the rapid dispersion of fresh concrete, saves the mixing time of the production enterprise, improves the production efficiency, and can improve the phenomenon of reverse growth of concrete fluidity caused by low temperature.

[0007] In some embodiments of the present invention, the mass ratio of the polyether macromonomer, the unsaturated carboxylic acid, the unsaturated amide and the functional monomer is 200:(10-25):(0.2-2):(0.5-2).

[0008] In some embodiments of the present invention, the polymerization reaction temperature is 5 to 40° C., and the reaction time is 2 to 6 hours.

[0009] In some embodiments of the present invention, the unsaturated alcohol is selected from one or more of 2-methyl-3-butene-1-ol, 2-methyl-2-propene-1-ol and 2-methoxy-3-butene-1-ol.

[0010] In some embodiments of the present invention, in the preparation of the functional monomer, the molar ratio of the rhamnolipid to the unsaturated alcohol is 1:(1-2).

[0011] In some embodiments of the present invention, the functional monomer is prepared by subjecting the rhamnolipid and the unsaturated alcohol to an esterification reaction under the protection of an inert gas in the presence of a catalyst and an inhibitor.

[0012] Furthermore, the temperature of the esterification reaction is 70-90° C., and the reaction time is 3-8 hours.

[0013] In some embodiments of the present invention, the polyether macromonomer is selected from at least one of isopentanol polyoxyethylene ether, methyl allyl alcohol polyoxyethylene ether, ethylene glycol monovinyl polyethylene glycol ether and 4-hydroxybutyl vinyl polyoxyethylene ether.

[0014] In some embodiments of the present invention, the unsaturated carboxylic acid is acrylic acid and / or methacrylic acid.

[0015] In some embodiments of the present invention, the unsaturated amide is selected from at least one of acrylamide, methacrylamide, N-hydroxymethyl acrylamide and 2-acrylamide-2-methylpropane sulfonic acid.

[0016] In some embodiments of the present invention, the chain transfer agent is at least one of mercaptoethanol, thioglycolic acid, mercaptopropanol, mercaptopropionic acid, trisodium phosphate, sodium formate and sodium acetate.

[0017] In some embodiments of the present invention, the mass amount of the chain transfer agent is 0.2% to 2% of the mass of the polyether macromonomer.

[0018] In some embodiments of the present invention, the initiator is a redox initiator.

[0019] In some embodiments of the present invention, the mass amount of the initiator is 0.1% to 2% of the mass of the polyether macromonomer.

[0020] In some embodiments of the present invention, the preparation method comprises the following steps:

[0021] (1) dissolving the polyether macromonomer, functional monomer and oxidant in water to obtain a base liquid, and dripping solution A into the base liquid under stirring at a temperature of 5 to 40° C., and starting to drip solution B after dripping solution A for 1 to 10 minutes, and starting to drip solution C after dripping solution B for 1 to 10 minutes; wherein:

[0022] The A solution is an aqueous solution of the unsaturated carboxylic acid, and the dropwise addition time of the A solution is t1;

[0023] The B solution is a mixed aqueous solution of the reducing agent and the chain transfer agent, and the dropping time of the B solution is t2;

[0024] The C solution is an aqueous solution of the unsaturated amide, and the dropping time of the C solution is t3;

[0025] t1 is 1.0~2.5h, t2 is 1.5~3h, t3 is 1.0~2.5h;

[0026] (2) After the solution is added dropwise, the reaction is continued for 0.5 to 2 hours to form a polycarboxylic acid.

[0027] The present invention can achieve regulation of the sequence of polycarboxylic acid molecular structural units by controlling the dripping order and dripping time of solutions A, B and C, obtain a copolymer product (polycarboxylic acid) with obvious differentiation, and promote the dispersion of polycarboxylic acid on cement particles; compared with dripping the three solutions at the same time, the water reducer prepared by the aforementioned differentiated dripping method makes the expansion degree of concrete change less different within 2 minutes of stirring, avoids the phenomenon of too slow concrete flow rate, can effectively improve the dispersion speed and play an effective viscosity reduction effect.

[0028] Optionally, the preparation method further comprises: (3) adjusting the pH of the product obtained in step (2) to 6-7 by using a base.

[0029] In some embodiments of the present invention, the amount of water used is such that the solid content of the prepared polycarboxylate water-reducing agent is 40% to 60%.

[0030] In a second aspect, the present invention provides a polycarboxylate water-reducing agent prepared by the preparation method described in the first aspect of the present invention.

[0031] The polycarboxylate water reducer of the present invention belongs to a glycolipid modified polycarboxylate water reducer, which can be applied to high-strength concrete to achieve rapid dispersion of slurry, save stirring time, effectively reduce concrete viscosity, and improve workability. In addition, the polycarboxylate water reducer also has high storage stability, so that the polycarboxylate water reducer still has a good appearance after being placed for a long time.

[0032] In a third aspect, the present invention provides use of the polycarboxylate water-reducing agent described in the second aspect of the present invention in building materials.

[0033] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0035] The "range" disclosed in the present invention is defined in the form of a lower limit and / or an upper limit, and a given range is defined by selecting a lower limit and / or an upper limit. The range defined in this way can be inclusive or exclusive of the end value, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form an undefined range, and any lower limit can be combined with other lower limits to form an undefined range, and any upper limit can be combined with any other upper limit to form an undefined range. In addition, each separately disclosed point or single value itself can be combined with any other point or single value as a lower limit or upper limit or with other lower limits or upper limits to form an undefined range.

[0036] If not otherwise specified, all embodiments and optional embodiments of the present invention may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present invention.

[0037] The first aspect of the present invention provides a method for preparing a polycarboxylic acid water-reducing agent, the method comprising: in the presence of water, an initiator and a chain transfer agent, polymerizing comonomers including a polyether macromonomer, an unsaturated carboxylic acid, an unsaturated amide and a functional monomer to form a polycarboxylic acid.

[0038] In the present invention, the polyether macromonomer can be selected from various ether macromonomers having carbon-carbon double bonds. Preferably, the polyether macromonomer is selected from at least one of isopentanol polyoxyethylene ether (TPEG), methyl allyl alcohol polyoxyethylene ether (HPEG), ethylene glycol monovinyl polyethylene glycol ether (EPEG) and 4-hydroxybutyl vinyl polyoxyethylene ether (VPEG).

[0039] In some embodiments, the average molecular weight (Mw) of the polyether macromonomer is 2,000 to 4,000.

[0040] As some specific examples, the polyether macromonomer can be one or more of EPEG-2400, EPEG-3000, TPEG-2400, TPEG-2400, and HPEG-2400. The polyether macromonomer of the present invention can be prepared by methods well known in the art, or can be commercially obtained, such as polyether products selected from Aoke Chemical Co., Ltd., Fujian Zhongshan Chemical Co., Ltd., and Jiahua Chemical Quanzhou Co., Ltd.

[0041] In the present invention, the functional monomer is an esterification product of rhamnolipid and unsaturated alcohol, wherein the rhamnolipid can be one or more of monosaccharide monoester structure, monosaccharide diester structure, disaccharide monoester structure, and disaccharide diester structure rhamnolipid.

[0042] In some embodiments, the rhamnolipid has any structure shown in Formula 1-1 (monosaccharide monoester), Formula 1-2 (monosaccharide diester), Formula 1-3 (disaccharide monoester), or Formula 1-4 (disaccharide diester):

[0043]

[0044] wherein m is any integer from 1 to 10, specifically 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10; and n is any integer from 1 to 10, specifically 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0045] The present invention has no special requirements on the source of the rhamnolipid. It can be synthesized by fermentation methods or chemical methods well known in the art, or directly obtained from commercial sources, such as but not limited to rhamnolipid produced by Evonik Specialty Chemicals (Shanghai) Co., Ltd. (effective active content is 100%) and rhamnolipid produced by Shanghai Myrel Biochemical Technology Co., Ltd. (purity ≥95%).

[0046] In the present invention, the unsaturated alcohol may be an unsaturated monohydric alcohol having a double bond. According to some embodiments, the structure of the unsaturated alcohol is shown in Formula 2:

[0047]

[0048] Wherein, L represents a substituted or unsubstituted straight-chain alkylene group having 1 to 4 carbon atoms, and the substituent is a methoxy group (-OCH3) or a methyl group (-CH3). Specific examples of the straight-chain alkylene group having 1 to 4 carbon atoms include a methylene group (-CH2-), an ethylene group (-CH2CH2-), a n-propylene group (-CH2CH2-) or a n-butylene group (-CH2CH2CH2CH2-).

[0049] Preferably, the unsaturated alcohol is selected from one or more of 2-methyl-3-butene-1-ol, 2-methyl-2-propene-1-ol and 2-methoxy-3-butene-1-ol.

[0050] In the present invention, the rhamnolipid uses the carboxyl group (-COOH) provided by the rhamnolipid to undergo an esterification reaction with the hydroxyl group (-OH) provided by the unsaturated alcohol to remove small molecule water to form the functional monomer. Taking the rhamnolipid of Formula 1-1 as an example and the unsaturated alcohol shown in Formula 2 as an example, the functional monomer (esterification product) shown in structural formula a can be obtained:

[0051]

[0052] In some embodiments, the molar ratio of the rhamnolipid to the unsaturated alcohol can be 1:(1-2), for example, 1:1, 1:1.2, 1:1.5, 1:1.7, 1:1.8, 1:2, etc.

[0053] In some embodiments, the temperature of the esterification reaction can be 70-90°C, for example 80°C, 85°C, 90°C, etc.; the reaction time can be 3-8h, for example 3h, 4h, 5h, 6h, 7h, 8h, etc.

[0054] As some preferred embodiments, the functional monomer is obtained by subjecting the rhamnolipid and the unsaturated alcohol to an esterification reaction in the presence of a catalyst and an inhibitor, and the esterification reaction is carried out under the protection of an inert gas (eg, nitrogen).

[0055] In the present invention, the catalyst can be selected from various acid catalysts. Preferably, the catalyst is at least one of benzenesulfonic acid, p-toluenesulfonic acid and ethylsulfonic acid.

[0056] In the present invention, the amount of the catalyst can be selected according to the total amount of the reactants. Preferably, the mass amount of the catalyst is 0.5% to 5% of the total mass of the rhamnolipid and the unsaturated alcohol, such as 0.5%, 0.6%, 0.8%, 0.9%, 1.0%, 1.1%, 1.3%, 1.5%, 1.6%, 1.8%, 2%, 2.5%, 3%, 4%, etc.

[0057] In the present invention, the polymerization inhibitor can reduce the possibility of self-polymerization of unsaturated alcohols, and the specific types are well known in the art. As some preferred examples, the polymerization inhibitor is at least one of hydroquinone, phenothiazine and diphenylamine.

[0058] In the present invention, the amount of the polymerization inhibitor can be selected according to the total amount of the reactants. Preferably, the mass amount of the polymerization inhibitor is 0.3% to 3% of the total mass of the rhamnolipid and the unsaturated alcohol, such as 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.7%, 2%, 2.2%, 2.5%, etc.

[0059] In the present invention, the amount of the functional monomer can be selected according to the amount of the polyether macromonomer. According to some embodiments, the mass ratio of the polyether macromonomer to the functional monomer is 200:(0.5-2), such as 200:0.5, 200:0.8, 200:1, 200:1.2, 200:1.5, 200:1.6, 200:2, etc. In this way, the viscosity reduction effect can be further improved while promoting the rapid spreading of concrete.

[0060] In the present invention, the unsaturated amide can be selected from various aliphatic amide monomers having carbon-carbon double bonds. Preferably, the unsaturated amide is selected from at least one of acrylamide (AM), methacrylamide (MAM), N-hydroxymethyl acrylamide, and 2-acrylamide-2-methylpropanesulfonic acid (AMPS).

[0061] In the present invention, the amount of the unsaturated amide can be selected according to the amount of the polyether macromonomer. According to some embodiments, the mass ratio of the polyether macromonomer to the unsaturated amide is 200:(0.2-2), for example, 200:0.2, 200:0.4, 200:0.5, 200:0.6, 200:0.8, 200:1, 200:1.2, 200:1.5, etc. In this way, while improving the slump retention performance of the water reducer, the water reducer molecular chain maintains a higher number of carboxyl groups, and the adsorption capacity of the water reducer on the surface of cement particles is increased to improve the dispersibility.

[0062] In the present invention, the unsaturated carboxylic acid may be a carboxylic acid having a double bond and carbon atoms of 3 to 8. Preferably, the unsaturated carboxylic acid is acrylic acid (AA) and / or methacrylic acid (MAA).

[0063] In some embodiments, the mass ratio of the polyether macromonomer to the unsaturated carboxylic acid can be 200:(10-25), for example, 200:10, 200:11, 200:12, 200:13, 200:15, 200:18, 200:20, 200:22, 200:25, etc.

[0064] In the present invention, the polymerization temperature can be 5-40°C, such as 5°C, 7°C, 8°C, 10°C, 15°C, 25°C, 30°C, 33°C, 35°C, 40°C, etc. In some embodiments, the polymerization temperature can be controlled within any temperature range within the above range, such as between 10-40°C, between 13-25°C, between 15-30°C, etc.

[0065] In the present invention, the polymerization reaction time can be determined according to the conversion degree of the reactants, and can generally be 2 to 6 hours, such as 2 hours, 3.5 hours, 5 hours, 6 hours, etc.

[0066] In the present invention, the initiator can be selected from various water-soluble initiators, for example, it can be one or more of a redox initiator, a persulfate initiator (such as ammonium persulfate), a peroxide initiator (such as tert-butyl hydroperoxide), and preferably the initiator is a redox initiator. The redox initiator includes an oxidant and a reductant.

[0067] As some preferred examples, the oxidant is selected from at least one of hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, cumene hydroperoxide, dibenzoyl peroxide and tert-butyl peroxide. Among them, hydrogen peroxide can usually be used in the form of hydrogen peroxide, and the mass content of hydrogen peroxide in the hydrogen peroxide can be, for example, 27.5%.

[0068] As some preferred examples, the reducing agent is selected from at least one of L-ascorbic acid, azobisisopropylimidazoline hydrochloride, sodium bisulfite, sodium sulfite, sodium pyrosulfite, bleaching agent, ferrous sulfate, sodium hypophosphite, sodium phosphite and ammonium ferrous sulfate.

[0069] In the present invention, the mass ratio of the oxidant to the initiator can be 1:(0.1-2), for example, 1:0.3, 1:0.4, 1:0.5, 1:0.7, 1:0.8, 1:1, 1:1.2, 1:1.3, 1:1.6, 1:1.8, etc.

[0070] In some embodiments, the mass amount of the initiator can be 0.1% to 2% of the mass of the polyether macromonomer, for example 0.1%, 0.2%, 0.3%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.5%, etc.

[0071] In the present invention, the chain transfer agent can be selected from various water-soluble chain transfer agents for free radical polymerization. As some preferred examples, the chain transfer agent is selected from at least one of mercaptoethanol, thioglycolic acid, mercaptopropanol, mercaptopropionic acid, trisodium phosphate, sodium formate and sodium acetate.

[0072] In some embodiments, the chain transfer agent is used in an amount of 0.2% to 2% by mass of the polyether macromonomer, such as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.5%, etc.

[0073] In the present invention, in order to improve the stability of the water reducer and its working performance on concrete, preferably, the preparation method of the polycarboxylate water reducer comprises the following steps (1) and (2).

[0074] Step (1): dissolving the polyether macromonomer, the functional monomer and the oxidant in water to obtain a base liquid, and dripping solution A into the base liquid under stirring at a temperature of 5 to 40° C., dripping solution B for 1 to 10 minutes after dripping solution A, and dripping solution C for 1 to 10 minutes after dripping solution B; wherein,

[0075] The A solution is an aqueous solution of the unsaturated carboxylic acid, and the dropwise addition time of the A solution is t1, where t1 is 1.0 to 2.5 h, for example, 1 h, 1.5 h, 2 h, etc.;

[0076] The B solution is a mixed aqueous solution of the reducing agent and the chain transfer agent, and the dropping time of the B solution is t2, and t2 is 1.5 to 3 hours, for example, 1.5 hours, 2 hours, etc.;

[0077] The C solution is an aqueous solution of the unsaturated amide, and the dropping time of the C solution is t3, and t3 is 1.0 to 2.5 hours, for example, 1 hour, 1.5 hours, etc.

[0078] In step (1), the order of connection of the structural units of the polycarboxylic acid molecular chain can be regulated by controlling the order and time of adding different materials, thereby promoting the formation of copolymer products with differentiated molecular structures.

[0079] Step (2): After the dropwise addition of the C solution is completed, the reaction is continued for 0.5 to 2 hours, for example, 0.5 hours, 1 hour, etc. In this way, the conversion rate of the comonomer can be further improved.

[0080] Optionally, the preparation method further comprises,

[0081] Step (3), neutralizing the product obtained in step (2) with a base to adjust the pH to 6 to 7. Specific examples of the base include, but are not limited to, sodium hydroxide. The base is preferably added in the form of alkaline solution.

[0082] In the present invention, the amount of water used can make the solid content of the prepared polycarboxylate water-reducing agent be 40% to 60%, for example, 45%, 48%, 49%, 50%, 55%, 56%, 58%, 60%, etc.

[0083] The second aspect of the present invention provides a polycarboxylate water-reducing agent prepared by the preparation method described in the first aspect of the present invention.

[0084] The third aspect of the present invention provides the use of the polycarboxylate water-reducing agent described in the second aspect of the present invention in building materials. The polycarboxylate water-reducing agent of the present invention has a high viscosity-reducing effect on building materials, especially concrete, and can promote the rapid dispersion of concrete and improve its workability.

[0085] The following are examples of the present invention. The following examples are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0086] The following preparation examples are used to illustrate the functional monomers and preparation methods used in the examples and comparative examples.

[0087] Preparation Example 1

[0088] Rhamnolipid (monosaccharide monoester, m=6), unsaturated alcohol (2-methyl-3-butene-1-ol), catalyst (benzenesulfonic acid) and inhibitor (hydroquinone) are added into a reactor, the molar ratio of rhamnolipid to unsaturated alcohol is 1:1.1, the amount of catalyst is 2.0% of the total mass of rhamnolipid and unsaturated alcohol, and the amount of inhibitor is 1.0% of the total mass of rhamnolipid and unsaturated alcohol. Under nitrogen protection and stirring, the temperature is raised to 85°C and the reaction is carried out at a constant temperature for 5 hours. During the reaction, water is removed by vacuuming. After the reaction is completed, it is naturally cooled to room temperature to obtain an esterification product (i.e., functional monomer), which is recorded as A1.

[0089] Preparation Examples 2 to 4

[0090] The functional monomers were prepared according to the method of Preparation Example 1, except that the types of reactants were replaced as shown in Table 1, and the prepared functional monomers were respectively recorded as A2, A3, and A4.

[0091] Table 1

[0092]

[0093] In the following examples and comparative examples, the concentration of H2O2 in hydrogen peroxide is 27.5%. Unless otherwise specified, parts are by weight, and the water used is deionized water. The interval between different solutions is the time between the first solution and the second solution.

[0094] Example 1

[0095] 200 parts of ethylene glycol monovinyl polyethylene glycol ether (EPEG-3000), 2 parts of functional monomer A1, 1.0 part of hydrogen peroxide and 120 parts of water were added into a reaction vessel and stirred evenly. The temperature was controlled at 15°C. Under this condition, solution A (12.0 parts of acrylic acid, 10.0 parts of water), solution B (0.5 parts of ascorbic acid, 1.5 parts of mercaptoethanol, 15.0 parts of water) and solution C (0.6 parts of N-hydroxymethyl acrylamide, 15.0 parts of water) were added into a reaction vessel and stirred evenly. The temperature was controlled at 15°C. The addition time of A solution is 1 hour, the addition time of B solution is 1.5 hours, and the addition time of C solution is 1 hour. After the addition of C solution is completed, the reaction is continued with stirring for 0.5 hour. Alkali is added to adjust the pH to 6-7, and water is used to adjust the solid content to obtain a polycarboxylate water-reducing agent with a solid content of 50%, which is recorded as PCE-1.

[0096] Example 2

[0097] 200 parts of isopentanol polyoxyethylene ether (TPEG-2400), 1 part of functional monomer A2, 1.0 part of hydrogen peroxide and 120 parts of water were added to a reaction container and stirred evenly. The temperature was controlled at 30°C. Under this condition, solution A (20.0 parts of methacrylic acid, 10.0 parts of water), solution B (1 part of sodium bisulfite, 0.8 parts of thioglycolic acid, 15.0 parts of water) and solution C (1 part of 2-acrylamide-2-methylpropanesulfonic acid, 15.0 parts of water) were sequentially dropped into the reaction container for reaction. The B solution and the A solution were added dropwise at an interval of 5 minutes, and the C solution and the B solution were added dropwise at an interval of 10 minutes. The dropping time of solution A was 1.5 hours, the dropping time of solution B was 1.5 hours, and the dropping time of solution C was 1 hour. After the dropping was completed, the reaction was continued for 1 hour, alkali was added to adjust the pH to 6-7, and the solid content was adjusted with water to obtain a polycarboxylic acid water reducer with a solid content of 50%, which was recorded as PCE-2.

[0098] Example 3

[0099] 200 parts of methyl allyl alcohol polyoxyethylene ether (HPEG-2400), 0.8 parts of functional monomer A3, 2.0 parts of hydrogen peroxide and 120 parts of water were added into a reaction container and stirred evenly. The temperature was controlled to be 20°C. Under this condition, solution A (12.0 parts of acrylic acid, 10.0 parts of water), solution B (0.5 parts of bleaching powder, 1.5 parts of mercaptopropionic acid, 15.0 parts of water) and solution C (0.6 parts of methacrylamide, 15.0 parts of water) were sequentially dropped into the reaction container for reaction. The B solution was dropped with an interval of 5 minutes between the A solution and the C solution was dropped with an interval of 10 minutes between the B solution. The dropping time of solution A was 1 hour, the dropping time of solution B was 1.5 hours, and the dropping time of solution C was 1 hour. After the dropping was completed, the reaction was continued to be kept warm for 1 hour. Alkali was added to adjust the pH to 6-7, and the solid content was adjusted with water to obtain a polycarboxylic acid water reducer with a solid content of 50%, which was recorded as PCE-3.

[0100] Example 4

[0101] 200 parts of TPEG-2400, 1.5 functional monomer A4, 1.0 part of hydrogen peroxide and 120 parts of water were added to a reaction container and stirred evenly. The temperature was controlled at 30°C. Under this condition, solution A (22.0 parts of acrylic acid, 10.0 parts of water), solution B (1 part of sodium bisulfite, 1 part of thioglycolic acid, 17.0 parts of water) and solution C (0.2 parts of acrylamide, 0.2 parts of methacrylamide, 15.0 parts of water) were sequentially dropped into the reaction container for reaction. The B solution was dropped with an interval of 5 minutes between the A solution and the C solution was dropped with an interval of 5 minutes between the B solution and the B solution. The dropping time of solution A was 1.5 hours, the dropping time of solution B was 1.5 hours, and the dropping time of solution C was 1 hour. After the dropping was completed, the reaction was continued for 1 hour. Alkali was added to adjust the pH to 6-7, and the solid content was adjusted with water to obtain a polycarboxylic acid water reducer with a solid content of 50%, which was recorded as PCE-4.

[0102] Comparative Example 1

[0103] A polycarboxylate water reducer was prepared according to the method of Example 1, except that the functional monomer A1 was not added. By adjusting the amount of water, a polycarboxylate water reducer with a solid content of 50% was obtained, which was recorded as PCE-D1.

[0104] Comparative Example 2

[0105] A polycarboxylate water reducer was prepared according to the method of Example 1, except that acrylamide was not added. By adjusting the amount of water, a polycarboxylate water reducer with a solid content of 50% was obtained, which was recorded as PCE-D2.

[0106] Comparative Example 3

[0107] A polycarboxylate water reducer was prepared according to the method of Example 1, except that the functional monomer A1 and C solution were not added. By adjusting the amount of water, a polycarboxylate water reducer with a solid content of 50% was prepared, which was recorded as PCE-D3.

[0108] Test Case

[0109] 1. Storage stability analysis

[0110] The water reducer was stored at room temperature for 6 months, during which the odor and appearance of the water reducer were observed. If there was neither mold nor odor, the result was recorded as "no". If there was odor and / or mold, the result was recorded as "yes". The test results are shown in Table 2.

[0111] Table 2

[0112]

[0113]

[0114] It can be seen from Table 2 that, compared with Comparative Examples 1 to 3, the polycarboxylate water-reducing agents prepared in Examples 1 to 4 have higher storage stability.

[0115] 2. Application performance testing

[0116] Runfeng cement (P·O42.5) was used to test the water reduction rate and its effect on fresh high-strength concrete according to the method specified in GB 8076-2008 "Concrete Admixtures":

[0117] Test the slump and expansion of freshly mixed high-strength concrete at 30s, 60s and 120s;

[0118] The test was conducted by measuring the emptying time of the inverted slump cone after mixing for 60s and 120s to quantify the viscosity of the concrete. The shorter the emptying time, the lower the viscosity of the concrete.

[0119] Observe the state of concrete during mixing. When the concrete exhibits fast flow rate, no water seepage, no slurry leakage, and no stone leakage when standing, it is considered to have "good workability". When the concrete has a slow flow rate or exhibits at least one of the following phenomena: water seepage, slurry leakage, black cap, accumulation, or stone leakage, it indicates poor workability.

[0120] Concrete mix ratio: cement 430kg / m 3 、Fly ash 30kg / m 3 、Mineral powder 90kg / m 3 , sand 700kg / m 3 、Stone 1050kg / m 3 , water 155kg / m 3 .

[0121] The experimental environment temperature is 5°C. The test results are shown in Table 3.

[0122] Table 3

[0123]

[0124]

[0125] It can be seen from the data in Table 3 that the polycarboxylate water-reducing agents prepared in Examples 1 to 4 have small changes in expansion when stirred for 30s, 60s and 120s each time, indicating that the water-reducing agents prepared in Examples 1 to 4 can achieve rapid dispersion and short slump emptying time, which shows that the viscosity of concrete can be effectively reduced and the workability of concrete is good.

[0126] Combining the data in Tables 2 and 3, it can be seen from Example 1 that when the functional monomer is not used (Comparative Example 1), the storage stability of the water reducer prepared without glycolipid modification will be poor, and its dispersion speed is slow in a low temperature environment, and the concrete is prone to hysteresis amplification, separation of water bleeding state and hysteresis water bleeding phenomenon; when the unsaturated amide monomer is not used (Comparative Example 2), the slump retention performance of the water reducer is affected. When only the polyether macromonomer and acrylic acid are copolymerized (Comparative Example 3), the dispersion efficiency of the water reducer formed on the concrete is not high, and water bleeding is serious.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for preparing a polycarboxylate water-reducing agent, characterized in that: The preparation method comprises: in the presence of water, an initiator and a chain transfer agent, polymerizing copolymer monomers including a polyether macromonomer, an unsaturated carboxylic acid, an unsaturated amide and a functional monomer to form a polycarboxylic acid; wherein the functional monomer is an esterification product of rhamnolipid and an unsaturated alcohol.

2. The preparation method according to claim 1, characterized in that: The rhamnolipid has any one of the structures of Formula 1-1 to Formula 1-4: Wherein, m and n are independently any integer from 1 to 10; Preferably, the structure of the unsaturated alcohol is as shown in Formula 2: In Formula 2, L represents a substituted or unsubstituted straight-chain alkylene group having 1 to 4 carbon atoms, and the substituent is a methoxy group or a methyl group; Preferably, the unsaturated alcohol is selected from one or more of 2-methyl-3-butene-1-ol, 2-methyl-2-propene-1-ol and 2-methoxy-3-butene-1-ol.

3. The preparation method according to claim 1 or 2, characterized in that: The functional monomer is prepared by subjecting the rhamnolipid and the unsaturated alcohol to an esterification reaction under the protection of an inert gas in the presence of a catalyst and an inhibitor; Preferably, the molar ratio of the rhamnolipid to the unsaturated alcohol is 1:(1-2); Preferably, the catalyst is at least one of benzenesulfonic acid, p-toluenesulfonic acid and ethylsulfonic acid; Preferably, the mass amount of the catalyst is 0.5% to 5% of the total mass of the rhamnolipid and the unsaturated alcohol; Preferably, the polymerization inhibitor is at least one of hydroquinone, phenothiazine and diphenylamine; Preferably, the mass dosage of the polymerization inhibitor is 0.3% to 3% of the total mass of the rhamnolipid and the unsaturated alcohol; Preferably, the temperature of the esterification reaction is 70-90° C., and the reaction time is 3-8 hours.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The mass ratio of the polyether macromonomer, unsaturated carboxylic acid, unsaturated amide and functional monomer is 200:(10-25):(0.2-2):(0.5-2); Preferably, the polymerization reaction temperature is 5 to 40° C., and the reaction time is 2 to 6 hours.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The polyether macromonomer is selected from at least one of isopentanol polyoxyethylene ether, methyl allyl alcohol polyoxyethylene ether, ethylene glycol monovinyl polyethylene glycol ether and 4-hydroxybutyl vinyl polyoxyethylene ether; Preferably, the unsaturated carboxylic acid is acrylic acid and / or methacrylic acid.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The unsaturated amide is at least one selected from acrylamide, methacrylamide, N-hydroxymethyl acrylamide and 2-acrylamide-2-methylpropane sulfonic acid.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The chain transfer agent is at least one of mercaptoethanol, thioglycolic acid, mercaptopropanol, mercaptopropionic acid, trisodium phosphate, sodium formate and sodium acetate; Preferably, the mass amount of the chain transfer agent is 0.2% to 2% of the mass of the polyether macromonomer; Preferably, the initiator is a redox initiator; Preferably, the oxidant in the redox initiator is at least one selected from hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, cumene hydroperoxide, dibenzoyl peroxide and tert-butyl peroxide; Preferably, the reducing agent in the redox initiator is selected from at least one of L-ascorbic acid, azodiisopropylimidazoline hydrochloride, sodium bisulfite, sodium sulfite, sodium pyrosulfite, bleaching powder, ferrous sulfate, sodium hypophosphite, sodium phosphite and ammonium ferrous sulfate; Preferably, the mass ratio of the oxidizing agent to the reducing agent is 1:(0.1-2); Preferably, the mass amount of the initiator is 0.1% to 2% of the mass of the polyether macromonomer.

8. The preparation method according to claim 7, characterized in that: The preparation method comprises the following steps: (1) dissolving the polyether macromonomer, functional monomer and oxidant in water to obtain a base liquid, and dripping solution A into the base liquid under stirring at a temperature of 5 to 40° C., and starting to drip solution B 1 to 10 minutes after dripping solution A, and starting to drip solution C 1 to 10 minutes after dripping solution B; wherein: The A solution is an aqueous solution of the unsaturated carboxylic acid, and the dropwise addition time of the A solution is t1; The B solution is a mixed aqueous solution of the reducing agent and the chain transfer agent, and the dropping time of the B solution is t2; The C solution is an aqueous solution of the unsaturated amide, and the dropping time of the C solution is t3; t1 is 1.0~2.5h, t2 is 1.5~3h, t3 is 1.0~2.5h, (2) After all the solutions have been added, continue the reaction for 0.5 to 2 hours; Optionally, the preparation method further comprises: (3) adjusting the pH of the product obtained in step (2) to 6-7 by using a base; Preferably, the amount of water used is such that the solid content of the prepared polycarboxylate water-reducing agent is 40% to 60%.

9. A polycarboxylate water-reducing agent prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the polycarboxylate water-reducing agent according to claim 9 in building materials.

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