Polyoxyalkylene ether macromonomer, preparation method and application of polyoxyalkylene ether macromonomer in preparation of polycarboxylate superplasticizer

Abstract

The invention provides a polyoxyalkylene ether macromonomer, a preparation method and application of the polyoxyalkylene ether macromonomer in preparation of a polycarboxylate superplasticizer, the polyoxyalkylene ether macromonomer is obtained by performing ring-opening polymerization reaction on an initiator and an alkylene oxide monomer under the action of a deprotonation reagent, and the initiator is allyl mercaptan or methyl and phenyl substituted allyl mercaptan. The polycarboxylate superplasticizer is obtained by free radical copolymerization reaction of an acid monomer and the polyoxyalkylene ether macromonomer under the action of an initiator and a reducing agent. Allyl sulfide is easy to generate uniform cracking of carbon-sulfur bonds in the polymerization process, polyoxyalkylene ether sulfydryl free radicals are generated, chain transfer is achieved, in the chain transfer process of the polyoxyalkylene ether macromonomer, a transferred chain still retains terminal double bonds and can participate in polymerization again, and the polyoxyalkylene ether macromonomer has a good polymerization effect. Therefore, polycarboxylic acid synthesized by using the polyoxyalkylene ether macromonomer has a certain branched topological structure, and cement paste dispersed by the polyoxyalkylene ether macromonomer has better workability.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a polyoxyalkylene ether macromonomer, a preparation method and application thereof in preparing a polycarboxylic acid water reducer. Background Art

[0002] In recent years, with the rapid advancement of various infrastructure projects in my country, the demand for concrete admixtures has grown rapidly. Among admixtures, cement water reducers (dispersants) are used as admixtures to enhance the fluidity of cement and concrete, reduce water content, and improve strength. Their development and application technology has received much attention. Among them, high-performance water reducers represented by polycarboxylic acids have attracted extensive attention from academia and industry due to their high water-reducing performance, high slump retention at low content, and molecular designability.

[0003] Polycarboxylic acid water reducers are comb-shaped polymers composed of anionic main chains composed of monomers such as acrylic acid, methacrylic acid, and methacrylic acid, and side chains composed of polyethylene glycol (i.e., polyoxyethylene, polyethylene oxide). Its anionic main chain can be adsorbed on the surface of cement and its hydration products, and the steric hindrance effect of the side chain inhibits the mutual aggregation of cement particles and disperses the aggregates of particles, thereby greatly enhancing the fluidity of the cement paste. The polycarboxylic acid water reducers currently available on the market have the advantages of low dosage, high water reduction rate, simple preparation process, and low pollution. However, it still cannot meet the needs of high-standard construction and some special occasions. It is manifested in the following aspects:

[0004] The molecular weight of polymer is an important factor affecting the performance of polycarboxylic acid water reducer. The molecular weight control of current polycarboxylic acid water reducers mainly relies on chain transfer agents, which are mainly small molecular thiol compounds. Such compounds are often highly toxic and have irritating odors, posing potential risks to the safety of operators in the production process and the environmental performance of products. Therefore, seeking new chain transfer technologies to replace small molecular thiol compounds is a powerful breakthrough point for the green and sustainable development of the polycarboxylic acid industry.

[0005] Patent CN202111188698.0 reports a chain transfer agent for polycarboxylic acid water reducer, its use and preparation method, characterized in that the chain transfer agent is prepared by amidation reaction of aminobenzenesulfonate and functional thiol substances under catalyst catalysis. The chain transfer agent for polycarboxylic acid water reducer contains thiol and benzenesulfonic acid groups in its structure, which can improve its water solubility and chain transfer catalytic performance in polymerization reaction, and the molecular weight distribution of the obtained polycarboxylic acid is narrower. However, the chain transfer agent disclosed in the patent is still a small molecule compound containing thiol, and its environmental hazard cannot be ignored.

[0006] Patent CN202010606122.0 discloses a method for preparing a star-shaped polycarboxylic acid water reducer using a tannic acid thiol compound as a chain transfer agent, which is characterized in that a tannic acid thiol compound is used as a chain transfer agent, and the chain transfer agent used is still a small molecule compound. Summary of the invention

[0007] In view of the fact that the polymer molecular weight control method in the prior art is limited to small molecule thiol compound chain transfer agents, resulting in a series of problems such as high toxicity, irritating odor and other potential environmental risks in the water reducer production process, and in order to avoid the use of volatile thiol compounds in polycarboxylic acid synthesis and enrich the topological structure of polycarboxylic acid water reducers, the present application provides a polyoxyalkylene ether macromonomer, a preparation method and its application in preparing polycarboxylic acid water reducers. First, small molecule thiol compounds are used in the synthesis of polyoxyalkylene ether macromonomers. According to the characteristics of the polyether synthesis reaction, the toxic effects caused by the residual small molecule thiol compounds are avoided. In the process of preparing polycarboxylic acid water reducers in the present application, problems such as high toxicity, flammability and explosion can be avoided, pollution to the environment and harm to the human body can be reduced, and the obtained polycarboxylic acid water reducer has excellent performance.

[0008] A polyoxyalkylene ether macromonomer, the structure of which is shown in the following formula (1):

[0009]

[0010] Among them, R1 is a hydrogen atom, a methyl group, or a phenyl group, p1 is a number from 0 to 10, p2 is a number from 20 to 100, and p1 / p2 is not higher than 1 / 8, p1+p2=20 to 100, and p1 or p2 can be arranged in blocks or randomly.

[0011] Preferably, p1 is a number from 0 to 8, p2 is a number from 25 to 95, and p1 / p2 is not higher than 1 / 8, and p1+p2=25 to 95.

[0012] A method for preparing a polyoxyalkylene ether macromonomer, wherein the polyoxyalkylene ether macromonomer is obtained by subjecting an initiator and an alkylene oxide monomer to a ring-opening polymerization reaction under the action of a deprotonating agent.

[0013] Specifically, the method comprises the following steps: adding an initiator and a deprotonating agent into a pressure-resistant, closed reactor, stirring evenly, sealing the container, and passing nitrogen to deoxygenate for 10 to 20 minutes; then, passing an alkylene oxide monomer in a molar amount 1.5 to 3 times that of the initiator, controlling the temperature at 40 to 60 degrees, and prepolymerizing for 30 to 60 minutes; then, heating to 70 to 95 degrees, starting to pass the remaining alkylene oxide monomer, and adjusting the temperature control device at the same time so that the system pressure is maintained at 0.5 to 1.0 MPa and the temperature is maintained at 90 to 120 degrees, until all the alkylene oxide monomers are passed in 2 to 8 hours; then, as the ring-opening polymerization reaction approaches the end, the system pressure decreases accordingly, and after the reactor pressure decreases to below 0.2 MPa, the temperature is raised to 110 to 130 degrees until the reactor pressure drops to within 0.05 MPa; discharging the material, neutralizing it with an appropriate amount of acid to pH 5 to 6, and obtaining a polyoxyalkylene ether macromonomer. The macromonomer can be stored in the form of a solid or a solution diluted with water to a concentration of 50% to 60% by mass.

[0014] In the preparation method of the polyoxyalkylene ether macromonomer, the process error range of the prepolymerization temperature is ±3 degrees Celsius, and the temperature error range after heating and starting to introduce the remaining alkylene oxide monomer is ±10 degrees Celsius.

[0015] The initiator is allyl mercaptan or allyl mercaptan substituted with methyl or phenyl, and its structural formula is shown in the following formula (2):

[0016] R1 is a hydrogen atom, a methyl group or a phenyl group.

[0017] The deprotonating agent is any one of sodium hydride, sodium methoxide and sodium ethoxide, and the amount of the deprotonating agent used is 5% to 20% of the molar amount of the initiator.

[0018] The alkylene oxide monomers are ethylene oxide, propylene oxide and mixtures thereof, and the total molar amount of the alkylene oxide monomers is 20 to 100 times that of the initiator. During the preparation process, different alkylene oxide monomers can be introduced in stages to obtain a block-arranged polyoxyalkylene ether structure.

[0019] The acid used for neutralization is any one of hydrochloric acid, phosphoric acid, and acetic acid.

[0020] A polycarboxylic acid water reducer is obtained by free radical copolymerization of an acid monomer and the above-mentioned polyoxyalkylene ether macromonomer under the action of an initiator and a reducing agent; the acid monomer is any one of acrylic acid or methacrylic acid; the molar ratio of the acid monomer to the polyoxyalkylene ether macromonomer is (3-8):1; and the weight average molecular weight of the polycarboxylic acid water reducer is 8000-50000 g / mol.

[0021] Since the polyoxyalkylene ether macromonomer itself has a chain transfer effect, under the premise of a given initiator system, the chain transfer effect during the reaction is mainly determined by the relative content of the polyoxyalkylene ether macromonomer, the reaction temperature, and the initiator system. Under the premise of satisfying the acid-ether ratio, reaction temperature, initiator type, and dosage range described above and below, increasing the temperature and reducing the initiator dosage will help reduce the molecular weight; reducing the temperature and increasing the initiator dosage will help increase the molecular weight.

[0022] The initiator is a water-soluble peroxide compound or persulfate, and the amount of the initiator is 1.5-3.0% of the total molar amount of the polyoxyalkylene ether macromonomer and the acid monomer; the reducing agent is ascorbic acid, Rongalite, sodium bisulfite, and the amount of the reducing agent is 25%-100% of the molar amount of the initiator. The reducing agent can also be a reducing compound that can react with the above-mentioned initiator in the range of 20-70 degrees to produce a free radical reaction. The mass concentration of the reducing agent solution should make the final mass concentration of the water reducer 30%-50%. Under the premise of controlling the molecular weight of the obtained polycarboxylic acid by temperature, the molecular weight of the polycarboxylic acid can be further finely controlled by the amount of initiator.

[0023] A preparation method of a polycarboxylate water reducer comprises the following steps: adding a polyoxyalkylene ether macromonomer solution and an initiator into a reactor, stirring and mixing them uniformly, adjusting the temperature of the reactor, and then simultaneously dripping an acid monomer and a reducing agent, and after the dripping is completed, keeping the temperature for 0.5 to 2 hours, and then neutralizing with an alkali, discharging the material, and obtaining the polycarboxylate water reducer.

[0024] The concentration of the polyoxyalkylene ether macromonomer solution is 40-55%, and the solvent is water.

[0025] The acid monomer solution is added dropwise for 60 to 240 minutes; the reducing agent solution is added dropwise for 15 to 45 minutes longer than the acid monomer.

[0026] In the preparation process, the stirring rate when the acid monomer and reducing agent solution are added dropwise should be between 120 and 480 rpm. If the stirring is too slow, the mass transfer of the system will be poor, and if the stirring is too fast, too much oxygen will be introduced to affect the polymerization.

[0027] The alkali is sodium or potassium hydroxide, which can be in the form of solid or solution. The amount used is 0 to 80% of the total molar amount of the acid monomers. The neutralization process needs to be stirred for 15 to 30 minutes.

[0028] The principle of controlling molecular weight of the polyoxyalkylene ether macromonomer is to utilize the carbon-sulfur bond homolysis of allyl sulfide during the polymerization process to generate polyoxyalkylene ether thiol free radicals to achieve chain transfer, thereby achieving the effect of controlling molecular weight. With acrylic acid as the acid monomer participating in the copolymerization, the chain transfer principle of the polyoxyalkylene ether macromonomer is shown in the following formula (3).

[0029]

[0030] At the same time, another product of the homolytic cleavage of the carbon-sulfur bond is a polycarboxylic acid chain containing a double bond at the end, which can participate in polymerization again to obtain a branched polycarboxylic acid.

[0031] Compared with the prior art, this application has the following advantages:

[0032] (1) The present invention avoids the use of volatile small molecule thiol compounds in the synthesis process of polycarboxylic acid water reducer, avoids the volatilization of small molecule thiol compounds in the usually poorly sealed polycarboxylic acid synthesis reactor, and avoids the toxic effects caused by the residue after the reaction. Due to the characteristics of the polyether synthesis reaction, the small molecule thiol compounds used in the polyether synthesis will basically not have any residue.

[0033] (2) During the chain transfer process of the polyoxyalkylene ether macromonomer, the transferred chain still retains the terminal double bond and can participate in polymerization again. This makes the polycarboxylic acid synthesized using the polyoxyalkylene ether macromonomer have a certain branched topological structure. Under the same molecular weight and similar dispersion effect, its solution viscosity is lower than that of the traditional linear main chain polycarboxylic acid dispersant, thereby making the cement paste dispersed by it more workable. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a relationship diagram between the initial fluidity and collapse time of the water reducing agent of each embodiment and comparative example in the benchmark cement concrete;

[0035] Figure 2 It is the relationship diagram between the initial fluidity and collapse time of the water reducing agent of each embodiment and comparative example in Onoda cement concrete;

[0036] Figure 3 It is a relationship diagram between the initial fluidity and collapse time of the water reducing agent of each embodiment and comparative example in Conch cement concrete;

[0037] Figure 4 It is a relationship diagram between the initial fluidity and collapse time of the water reducing agent of each embodiment and comparative example in China Resources cement concrete; DETAILED DESCRIPTION

[0038] The technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. In this application, unless otherwise specified, all percentage contents are mass percentages.

[0039] The structures of the polyoxyalkylene ether macromonomers used in the various embodiments or comparative examples are shown in Table 1 below:

[0040] Table 1

[0041]

[0042] The specific preparation methods of A-1 to A-5 are as follows:

[0043] In a pressure-resistant, closed reactor, add 17.6 g of methyl allyl mercaptan as an initiator, add 0.48 g of sodium hydride (60% purity) by weight, stir evenly, seal the container, and pass nitrogen to deoxygenate for 10 minutes. Then, pass 17.6 g of ethylene oxide monomer, control the temperature at 50 degrees, and prepolymerize for 45 minutes. Then, raise the temperature to 80 degrees, start to pass the remaining 422.4 g of ethylene oxide monomer, and adjust the temperature control device at the same time so that the system pressure is maintained in the range of 0.5-1.0 MPa during the process of passing, and the temperature is maintained at 100-110 degrees until all the alkylene oxide monomers are passed in 4 hours. Afterwards, after the pressure of the reactor drops to below 0.2 MPa, the temperature is raised to 115-125 degrees until the pressure of the reactor drops to within 0.05 MPa. After that, the pressure is released, the reactor is opened, the material is discharged, neutralized with acetic acid to pH 5-6, and diluted with water to a mass concentration of 55% to obtain A-1.

[0044] In a pressure-resistant, closed reactor, add 22.2g of initiator allyl mercaptan, add 0.81g of sodium methoxide, stir evenly, close the container, and pass nitrogen to deoxygenate for 15min. Then, pass 19.8g of ethylene oxide monomer, control the temperature at 45 degrees, and prepolymerize for 30min. Then, heat up to 75 degrees, start to pass the remaining 310.2g of alkylene oxide monomer, and adjust the temperature control device at the same time to maintain the system pressure at 0.5-1.0MPa and the temperature at 90-100 degrees until all alkylene oxide monomers are passed in 2.5h. Then, after the reactor pressure drops to below 0.2MPa, heat up to 110-120 degrees until the reactor pressure drops to less than 0.05MPa, then release the pressure, open the reactor, discharge the material, neutralize to pH 5-6 with an appropriate amount of hydrochloric acid, and dilute with water to 60% mass concentration to obtain A-2.

[0045] In a pressure-resistant, closed reactor, add 22.5 g of initiator phenyl allyl mercaptan, add 0.72 g of sodium hydride (60% purity) by weight, stir evenly, close the container, and pass nitrogen to deoxygenate for 20 minutes. After that, pass 19.8 g of ethylene oxide monomer, control the temperature at 60 degrees, and prepolymerize for 60 minutes. After that, heat up to 95 degrees, start to pass the remaining 607.2 g of ethylene oxide monomer, and adjust the temperature control device at the same time to maintain the system pressure at 0.5-1.0 MPa and the temperature at 110-120 degrees until all the alkylene oxide monomers are passed in 7.5 hours. After that, after the reactor pressure drops to below 0.2 MPa, heat up to 120-130 degrees until the reactor pressure drops to within 0.05 MPa, then release the pressure, open the reactor, discharge the material, neutralize with an appropriate amount of acetic acid to pH 5-6, and dilute with water to 50% mass concentration to obtain A-3.

[0046] In a pressure-resistant, closed reactor, add 18.25 g of initiator allyl mercaptan, add 1.70 g of sodium ethoxide, stir evenly, close the container, and pass nitrogen to deoxygenate for 15 minutes. After that, pass 29.0 g of propylene oxide monomer, control the temperature at 50 degrees, and prepolymerize for 45 minutes. After that, raise the temperature to 90 degrees, start to pass the remaining 29.0 g of propylene oxide and 385.0 g of ethylene oxide monomer, and adjust the temperature control device at the same time to maintain the system pressure at 0.5-1.0 MPa and the temperature at 105-120 degrees until all the alkylene oxide monomers are passed in 5 hours. After that, after the reactor pressure drops to below 0.2 MPa, raise the temperature to 110-125 degrees until the reactor pressure drops to less than 0.05 MPa, then release the pressure, open the reactor, discharge the material, neutralize it to pH 5-6 with an appropriate amount of phosphoric acid, and store it in solid form to obtain A-4.

[0047] In a pressure-resistant, closed reactor, add 14.1 g of methyl allyl mercaptan as initiator, add 0.58 g of sodium hydride (60% purity) by weight, stir evenly, seal the container, and pass nitrogen to deoxygenate for 20 minutes. Then, pass 23.2 g of propylene oxide monomer, control the temperature at 55 degrees, and prepolymerize for 45 minutes. Then, raise the temperature to 85 degrees, start to pass the remaining 51.0 g of propylene oxide and 598.4 g of ethylene oxide monomer, and adjust the temperature control device at the same time to maintain the system pressure at 0.5-1.0 MPa and the temperature at 105-115 degrees until all the alkylene oxide monomers are passed in within 8 hours. Afterwards, after the pressure of the reactor drops to below 0.2MPa, the temperature is raised to 120-130 degrees until the pressure of the reactor drops to within 0.05MPa. After that, the pressure is released, the reactor is opened, the material is discharged, and the pH is neutralized to 5-6 with an appropriate amount of acetic acid, and water is added to dilute it to a mass concentration of 50% to obtain A-5.

[0048] The process of synthesizing polycarboxylic acid water-reducing agent using the above-mentioned embodiment as raw material is shown in the following examples. In the following examples, the weight average molecular weight and conversion rate of polycarboxylic acid are characterized by Shimazu LC-20AD aqueous gel permeation chromatograph. The specific parameters are as follows: chromatographic column: TSK-GELSW (TOSOH company), mobile phase: 0.1 mol / L NaNO3, flow rate: 1 mL / min, sampling volume: 20 μL 1% aqueous solution, detector: differential refractive index detector.

[0049] Example 1

[0050] In the reactor, add 240g of A-1, 24g of water and 0.66g of hydrogen peroxide solution (30%), heat to 35 degrees, then, under stirring at 240rpm, drop 17.42g of acrylic acid and 75g of a solution containing 0.26g of ascorbic acid, respectively, wherein the acrylic acid is added dropwise for 120min and the ascorbic acid solution is added dropwise for 150min. After the addition is completed, keep warm for 1h, then neutralize the product with 15.00g of 35% liquid alkali solution, stir for 20min and then discharge to obtain polycarboxylate water reducer P-1, whose weight average molecular weight is 26734 and the conversion rate is 93.7%.

[0051] Example 2

[0052] In the reactor, add 240g of A-1, 24g of water and 0.66g of hydrogen peroxide solution (30%), heat to 50 degrees, then, under stirring at 240rpm, drop 17.42g of acrylic acid and 75g of a solution containing 0.26g of ascorbic acid, wherein acrylic acid is added for 120min and ascorbic acid solution is added for 150min. After the addition is completed, keep warm for 1h, then neutralize the product with 15.00g of 35% liquid alkali solution, stir for 20min and discharge, and obtain polycarboxylate water reducer P-2, whose weight average molecular weight is 19343 and conversion rate is 92.3%.

[0053] Example 3

[0054] In the reactor, 220g of A-2, 20g of water and 1.65g of ammonium persulfate were added, and the temperature was raised to 55 degrees. Then, 26.71g of acrylic acid and 50g of a solution containing 0.75g of sodium bisulfite were added dropwise under stirring at 150rpm, wherein the acid monomer was added dropwise for 90min and the sodium bisulfite solution was added dropwise for 110min. After the addition was completed, the temperature was kept for 0.5h, and then the material was discharged to obtain a polycarboxylate water-reducing agent P-3, whose weight average molecular weight was 11342 and the conversion rate was 95.5%.

[0055] Example 4

[0056] In the reactor, 400g of A-3, 100g of water and 1.38g of hydrogen peroxide solution (30%) were added, and the temperature was raised to 40 degrees. Then, 30.99g of methacrylic acid and 132g of a solution containing 0.60g of ascorbic acid were added dropwise respectively under stirring at 450rpm, wherein methacrylic acid was added dropwise for 240min and ascorbic acid solution was added dropwise for 280min. After the addition was completed, the temperature was kept for 2h, and then the product was neutralized with 34.60g of 35% liquid alkali solution, and the material was discharged to obtain polycarboxylate water-reducing agent P-4, whose weight average molecular weight was 44563 and the conversion rate was 90.5%.

[0057] Example 5

[0058] In the reactor, 400g of A-3, 100g of water and 0.91g of hydrogen peroxide solution (30%) were added, and the temperature was raised to 40 degrees. Then, 30.99g of methacrylic acid and 50g of a solution containing 0.40g of ascorbic acid were added dropwise under stirring at 450rpm, wherein methacrylic acid was added dropwise for 240min and ascorbic acid solution was added dropwise for 280min. After the addition was completed, the temperature was kept for 2h, and then the product was neutralized with 34.60g of 35% liquid alkali solution, and the material was discharged to obtain polycarboxylate water-reducing agent P-5, whose weight average molecular weight was 38576 and the conversion rate was 92.1%.

[0059] Example 6

[0060] In the reactor, 120g of A-4, 120g of water and 2.45g of ammonium persulfate were added, and the temperature was raised to 65 degrees. Then, 25.85g of acrylic acid and 40g of a solution containing 1.13g of sodium bisulfite were added dropwise under stirring at 360rpm, wherein methacrylic acid was added dropwise for 60min and ascorbic acid solution was added dropwise for 75min. After the addition was completed, the temperature was kept for 0.5h, and then the product was neutralized with 12.06g of potassium hydroxide (stirred for 30min), and the material was discharged to obtain polycarboxylate water reducer P-6, whose weight average molecular weight was 22543 and the conversion rate was 93.6%.

[0061] Example 7

[0062] In the reactor, 450g of A-5, 50g of water and 1.42g of hydrogen peroxide solution (30%) were added, and the temperature was raised to 45 degrees. Then, 33.94g of methacrylic acid and 95g of a solution containing 0.71g of ascorbic acid were added dropwise respectively under stirring at 450rpm, wherein methacrylic acid was added dropwise for 150min and ascorbic acid solution was added dropwise for 180min. After the addition was completed, the temperature was kept for 1h, and then the product was neutralized with 16.58g of potassium hydroxide (stirred for 30min), and the material was discharged to obtain polycarboxylate water-reducing agent P-7, whose weight average molecular weight was 41420 and the conversion rate was 89.3%.

[0063] Comparative Example 1

[0064] In a pressure-resistant, closed reactor, add 14.4 g of methyl allyl alcohol as the initiator, add 0.48 g of sodium hydride (60% purity) by weight, stir evenly, close the container, and pass nitrogen to deoxygenate for 10 minutes. After that, pass 17.6 g of ethylene oxide monomer, control the temperature at 50 degrees, and prepolymerize for 45 minutes. After that, raise the temperature to 80 degrees, start to pass the remaining 422.4 g of ethylene oxide monomer, and adjust the temperature control device at the same time so that the system pressure is maintained in the range of 0.5-1.0 MPa during the process of passing, and the temperature is maintained at 100-110 degrees until all the alkylene oxide monomers are passed in 4 hours. After that, after the pressure of the reactor is reduced to below 0.2 MPa, raise the temperature to 115-125 degrees until the pressure of the reactor drops to less than 0.05 MPa, then release the pressure, open the reactor, discharge the material, neutralize it with acetic acid to pH 5-6, and dilute it with water to 55% mass concentration to obtain A-R1.

[0065] Comparative Example 2

[0066] In the reactor, add 240g of A-R1, 24g of water and 0.66g of hydrogen peroxide solution (30%), heat to 35 degrees, then, under stirring at 240rpm, drop 17.42g of acrylic acid and 75g of a solution containing 0.26g of ascorbic acid, wherein acrylic acid is added for 120min and ascorbic acid solution is added for 150min. After the addition is completed, keep warm for 1h, then neutralize the product with 15.00g of 35% liquid alkali solution, stir for 20min and then discharge to obtain polycarboxylate water reducer P-R1, whose molecular weight is 78635 and conversion rate is 93.1%.

[0067] A-R1 is a polyether prepared by replacing unsaturated mercaptans with unsaturated alcohols in equal moles during the preparation of A-1, and is used in the subsequent preparation of polycarboxylic acid water reducer P-R1 to illustrate the necessity of using thioether-containing polyethers.

[0068] The results show that the use of traditional polyether alone will lead to uncontrolled molecular weight of the final polycarboxylate water-reducing agent. Too high a molecular weight will produce a flocculation effect, which will greatly weaken the water-reducing efficiency.

[0069] Comparative Example 3

[0070] In the reactor, add 240g of A-R1, 24g of water and 0.66g of hydrogen peroxide solution (30%), heat to 35 degrees, then, under stirring at 240rpm, drop 17.42g of acrylic acid and 75g of a solution containing 0.26g of ascorbic acid and 0.77g of mercaptopropionic acid, wherein acrylic acid is added for 120min, and ascorbic acid and mercaptopropionic acid solution are added for 150min. After the addition is completed, keep warm for 1h, then neutralize the product with 15.00g of 35% liquid alkali solution, stir for 20min and discharge, and obtain polycarboxylate water reducer P-R2, whose molecular weight is 24452 and conversion rate is 94.0%.

[0071] This comparative example is based on Example 1, and its purpose is to demonstrate the superiority of the technology disclosed in the present invention by using the polycarboxylic acid prepared by the technology disclosed in the present invention and the traditional technology.

[0072] Test Example 1: Working Performance Test

[0073] The application effects of the above embodiments and comparative examples were tested with various cements and sands. In addition to testing the embodiments and comparative examples, PCA-VIII polycarboxylate water reducer produced by Jiangsu Subote New Materials Co., Ltd. was used as a current commercial polycarboxylate control sample.

[0074] The determination method is carried out according to the relevant procedures of GB8077-2000 and GB8076-2008.

[0075] Firstly, the performance of the water reducing agent in the embodiment was tested. Four types of cement were selected and tested based on the C50 concrete mix ratio.

[0076] The mineral phase composition of each selected cement is shown in Table 2 below (based on the results of Rietveld semi-quantitative analysis of XRD):

[0077] Table 2

[0078]

[0079]

[0080] The concrete mix ratio used for the test is shown in Table 3 below. In the application example, the cement used is P II 52.5 Onoda cement, the sand is medium sand with a fineness modulus of M=2.6, and the gravel is continuously graded crushed stone with a particle size of 5-20 mm:

[0081] Table 3

[0082] Material cement sand Xiaoshi Zhongshi water <![CDATA[Dosage (kg / m 3 )]]> 480 728 328 764 150

[0083] The initial fluidity (slump / expansion, mm) results of the modified concrete in each embodiment are shown in Table 4 below:

[0084] Table 4

[0085]

[0086] As can be seen from Table 4 above, each embodiment has a good water-reducing effect on the four selected cements, and the initial expansion basically reaches or exceeds the commercial water-reducing agent PCA-VIII used as a comparison, and is significantly better than Comparative Example 2, which uses only traditional polyether and causes uncontrolled molecular weight. The overall water-reducing performance of each embodiment is also better than Comparative Example 3 using traditional chain transfer technology. In addition, the cements of each embodiment have good adaptability, and the performance behaviors in the four selected cements are close to each other. Although the commercial PCA-VIII has good performance in most of the tested cements, it has a phenomenon of excessive loss of fluidity in China Resources Cement.

[0087] While measuring the fluidity, collapse tests were also performed. The collapse time of the above samples and their correlation with the initial expansion are shown in Figure 1-Figure 4 As shown, Figure 1-Figure 4 In the figure, the expansion values ​​corresponding to each point are the values ​​in Table 4.

[0088] from Figure 1-Figure 4 As shown, the collapse time of PCA-VIII and Comparative Example 3 at the same fluidity is significantly higher than that of each embodiment, which indicates that the viscosity of the concrete dispersed by the two is greater and the workability is worse. At the same time, the fluidity-collapse time relationship of each embodiment is on the same trend line, which indicates that the concrete dispersed by the water reducer based on the technology of the present invention has good workability, confirming the effectiveness of the technology of the present invention within the scope of the embodiment. The workability advantage of each embodiment should come from the branched structure formed in the chain transfer process of the sulfur-containing polyether (3).

[0089] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A polyoxyalkylene ether macromonomer, characterized in that: The structure of the polyoxyalkylene ether macromonomer is shown in the following formula (1): Among them, R1 is a hydrogen atom, a methyl group, or a phenyl group, p1 is a number from 0 to 10, p2 is a number from 20 to 100, and p1 / p2 is not higher than 1 / 8, p1+p2=20 to 100, and p1 or p2 can be arranged in blocks or randomly.

2. A polyoxyalkylene ether macromonomer according to claim 1, characterized in that: The p1 is a number between 0 and 8, p2 is a number between 25 and 95, and p1 / p2 is not higher than 1 / 8, and p1+p2=25-95.

3. A method for preparing a polyoxyalkylene ether macromonomer according to any one of claims 1 to 2, characterized in that: The polyoxyalkylene ether macromonomer is obtained by a ring-opening polymerization reaction between an initiator and an alkylene oxide monomer under the action of a deprotonating agent.

4. The method for preparing a polyoxyalkylene ether macromonomer according to claim 3, characterized in that: The specific steps include: In a pressure-resistant, closed reactor, add an initiator and a deprotonating agent, stir evenly, seal the container, and pass nitrogen to deoxygenate for 10 to 20 minutes; then, pass an alkylene oxide monomer with a molar amount of 1.5 to 3 times that of the initiator, control the temperature at 40 to 60 degrees, and prepolymerize for 30 to 60 minutes; then, raise the temperature to 70 to 95 degrees, start to pass the remaining alkylene oxide monomer, and at the same time adjust the temperature control device to maintain the system pressure at 0.5 to 1.0 MPa and the temperature at 90 to 120 degrees until all the alkylene oxide monomers are passed within 2 to 8 hours; after the reactor pressure drops to below 0.2 MPa, raise the temperature to 110 to 130 degrees until the reactor pressure drops to within 0.05 MPa; discharge the material, neutralize it with an appropriate amount of acid to pH 5 to 6, and obtain a polyoxyalkylene ether macromonomer.

5. The method for preparing a polyoxyalkylene ether macromonomer according to claim 3, characterized in that: The initiator is allyl mercaptan or allyl mercaptan substituted with methyl or phenyl, and its structural formula is shown in the following formula (2): R1 is a hydrogen atom, a methyl group or a phenyl group.

6. The method for preparing a polyoxyalkylene ether macromonomer according to claim 3, characterized in that: The deprotonating agent is any one of sodium hydride, sodium methoxide and sodium ethoxide, and the amount of the deprotonating agent is 5% to 20% of the molar amount of the initiator.

7. The method for preparing a polyoxyalkylene ether macromonomer according to claim 3, characterized in that: The alkylene oxide monomers are ethylene oxide, propylene oxide and a mixture thereof, and the total molar amount of the alkylene oxide monomers is 20 to 100 times that of the initiator.

8. The method for preparing a polyoxyalkylene ether macromonomer according to claim 3, characterized in that: The acid used for neutralization is any one of hydrochloric acid, phosphoric acid, and acetic acid.

9. A polycarboxylate water reducer, characterized in that: The polycarboxylic acid water reducer is obtained by free radical copolymerization of an acid monomer and a polyoxyalkylene ether macromonomer under the action of an initiator and a reducing agent; the polyoxyalkylene ether macromonomer is the polyoxyalkylene ether macromonomer described in claim 1 or the polyoxyalkylene ether macromonomer obtained by the preparation method described in claim 3; the acid monomer is any one of acrylic acid and methacrylic acid; the molar ratio of the acid monomer to the polyoxyalkylene ether macromonomer is (3-8):1; and the weight average molecular weight of the polycarboxylic acid water reducer is 8000-50000 g / mol.

10. A polycarboxylate water-reducing agent according to claim 9, characterized in that: The initiator is a water-soluble peroxide compound or persulfate, and the amount of the initiator is 1.5-3.0% of the total molar amount of the polyoxyalkylene ether macromonomer and the acid monomer; the reducing agent is ascorbic acid, Rongalite, sodium bisulfite, and the amount of the reducing agent is 25%-100% of the molar amount of the initiator.

11. The method for preparing a polycarboxylate water-reducing agent according to claim 9, characterized in that: In the reactor, add the polyoxyalkylene ether macromonomer solution and the initiator, stir and mix evenly, adjust the reactor temperature, and then start to drop the acid monomer and the reducing agent at the same time. After the dropwise addition is completed, keep warm for 0.5 to 2 hours, then neutralize with alkali, and discharge the material to obtain the polycarboxylic acid water reducer.

12. The method for preparing a polycarboxylate water-reducing agent according to claim 11, characterized in that: The concentration of the polyoxyalkylene ether macromonomer solution is 40-55%.

13. The method for preparing a polycarboxylate water-reducing agent according to claim 11, characterized in that: The acid monomer solution is added dropwise for 60 to 240 minutes; the reducing agent solution is added dropwise for 15 to 45 minutes longer than the acid monomer.

14. The method for preparing a polycarboxylate water-reducing agent according to claim 11, characterized in that: The alkali is sodium or potassium hydroxide, and its usage is 0 to 80% of the total molar amount of the acid monomer.

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