A chain transfer agent for polycarboxylate superplasticizer, its uses and preparation method

Abstract

This invention relates to the field of concrete admixtures, and particularly to a chain transfer agent for polycarboxylate superplasticizers, its uses, and a preparation method thereof. The chain transfer agent for polycarboxylate superplasticizers is prepared by an amidation reaction of aminobenzenesulfonate with a functional thiol group under catalysis. This chain transfer agent for polycarboxylate superplasticizers contains thiol and benzenesulfonic acid groups in its structure, which improves its water solubility and chain transfer catalytic performance in polymerization reactions. Using it as a chain transfer agent in the synthesis of polycarboxylate superplasticizers allows for better control of the molecular weight of the polycarboxylate superplasticizer, resulting in a narrower molecular weight distribution in the synthesized polycarboxylate superplasticizer. Furthermore, after the polycarboxylate superplasticizer is applied to concrete, it significantly improves the flowability, slump retention, and compressive strength of the concrete.

Description

Technical Field

[0001] This invention relates to the field of concrete admixtures, and in particular to a chain transfer agent for polycarboxylate superplasticizers, its uses, and preparation method. Background Technology

[0002] Polycarboxylate superplasticizers have continuously developed and evolved, from the initial aliphatic superplasticizers, aminosulfonate superplasticizers, and naphthalene-based superplasticizers to the current third-generation polycarboxylate superplasticizers. Currently, polycarboxylate superplasticizers on the market can be categorized by performance into water-reducing, slump-retaining, ultra-slow-release, early-strength, and viscosity-reducing types. Due to their mature production technology, relatively simple production process, economic applicability, diverse and controllable molecular structure, and the ability to achieve high water reduction rates in concrete even at low dosages, they have become one of the indispensable admixtures on the market.

[0003] Chain transfer agents are a crucial component in the production of polycarboxylate superplasticizers, playing a vital role in regulating the molecular weight of polycarboxylate. Properly utilizing chain transfer agents can not only adjust the molecular weight of polycarboxylate superplasticizers but also reduce production costs. Currently, the chain transfer agents used in polycarboxylate superplasticizers on the market are mercapto acids, thiols, and hypophosphites. However, mercapto acids, with their strong pungent odor and high volatility, pose significant challenges to polycarboxylate superplasticizer production and do not meet green and environmentally friendly production requirements. Hypophosphites, due to the continuously rising prices of raw materials such as yellow phosphorus in recent years, and their tendency to deliquesce and explode upon contact with strong oxidants, pose significant safety hazards in polycarboxylate superplasticizer production. Furthermore, according to reports, large amounts of thiols initially form many dead linear oligomers without dangling double bonds; in the later stages of the reaction, the concentration of thiols decreases, the chain transfer reaction decreases accordingly, and the resulting polymers have very high molecular weights, leading to a wide molecular weight distribution. In some reaction systems, direct cross-linking forms gels, causing quality accidents during production.

[0004] Chinese invention application CN201110334937.9, published on June 20, 2012, discloses a method for preparing polycarboxylate superplasticizer using sodium methacrylate as a chain transfer agent. The method is as follows: first, water, sodium methacrylate, and modified polyether are added to a reaction vessel; then, an acrylic acid solution is prepared by mixing sodium methacrylate, acrylic acid, and water; an ammonium persulfate solution is prepared by mixing water and ammonium persulfate; when the material reaches 60℃±2℃, the ammonium persulfate solution and acrylic acid solution are added dropwise simultaneously; the reaction is maintained at this temperature for 1 to 3 hours; when the temperature drops below 45℃, a 32% liquid alkali is added for neutralization, resulting in a polycarboxylate superplasticizer with a pH of 6 to 7 and a solid content of 40%. Because the preparation process of this polycarboxylate superplasticizer uses sodium methacrylate instead of mercaptoacetic acid or mercaptopropionic acid as a chain transfer agent, it can avoid the pollution to the environment and the toxic effects on the human body caused by the malodor and strong corrosiveness of mercaptopropionic acid or mercaptoacetic acid. Summary of the Invention

[0005] To address the series of problems associated with existing chain transfer agents in the synthesis of polycarboxylate superplasticizers mentioned in the background art—such as the volatility and low chain transfer catalytic efficiency of thiol-based chain transfer agents, and the deliquescent and explosive properties of hypophosphite-based chain transfer agents—this invention provides a chain transfer agent for polycarboxylate superplasticizers, with the following general structural formula:

[0006]

[0007] Where M is Na + or K + The substitution position of R is at least one of the ortho or para positions of the -SO3M group on the benzene ring, and the number of substitutions is 1 to 2. The general structural formula of R is:

[0008]

[0009] Where n is 2 to 3.

[0010] The present invention also provides a use of the chain transfer agent for polycarboxylate superplasticizer as described above: the chain transfer agent is used as a chain transfer agent in the synthesis reaction of polycarboxylate superplasticizer.

[0011] The present invention also provides a method for preparing the chain transfer agent for the polycarboxylate superplasticizer as described above, comprising the following steps:

[0012] S100. Add aminobenzenesulfonate and catalyst into the reactor and stir to mix. Then, introduce inert gas to fill the reactor until the amidation reaction is complete.

[0013] S200, raise the reaction temperature in the reactor to 60℃~75℃, and add functional thiol substances;

[0014] After S300 and functional thiol substances are added, the reaction temperature is raised to 85℃~105℃, and the amidation reaction is carried out at a constant temperature for a certain time to obtain the chain transfer agent for the polycarboxylate superplasticizer.

[0015] The general structural formula of the functional thiol group is as follows:

[0016]

[0017] Where R2 is -SO3H, and n is 2 to 3.

[0018] In one embodiment, the general structural formula of the aminobenzenesulfonate is:

[0019]

[0020] Where M is Na + K + R1 is -NH2 or -CH2NH2, and the substitution position of R1 is at least one of the ortho or para position of -SO3M on the benzene ring, with a substitution number of 1 to 2.

[0021] In one embodiment, by weight, the aminobenzenesulfonate is 5-15 parts, the functional thiol substance is 10-20 parts, and the catalyst is 0.01-0.1 parts;

[0022] In one embodiment, the aminobenzenesulfonate is one or more combinations of sodium 4-aminobenzenesulfonate, potassium 4-aminobenzenesulfonate, sodium 2,4-diaminobenzenesulfonate, potassium 2,4-diaminobenzenesulfonate, sodium 4-aminomethylbenzenesulfonate, potassium 4-aminomethylbenzenesulfonate, sodium 2,4-diaminomethylbenzenesulfonate, and potassium 2,4-diaminomethylbenzenesulfonate.

[0023] In one embodiment, the functional thiol substance is one or a combination of two of 2-mercaptoethanesulfonic acid and 2-mercaptopropanesulfonic acid.

[0024] In one embodiment, the catalyst is one or more combinations of metal chlorides and metal oxides.

[0025] In one embodiment, in S200, the functional thiol substance is slowly added dropwise to the reaction vessel for 1 to 3 hours; in S300, the amidation reaction at constant temperature takes 1 to 3 hours.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] The chain transfer agent for polycarboxylate superplasticizers provided by this invention contains mercapto and benzenesulfonic acid groups in its structure. Compared with the high volatility of mercapto acid chain transfer agents, its volatility is reduced, and its water solubility and chain transfer catalytic performance in polymerization reactions are improved. Using it as a chain transfer agent in the synthesis of polycarboxylate superplasticizers can better regulate the molecular weight of polycarboxylate superplasticizers. The molecular weight distribution of the polycarboxylate superplasticizers synthesized by this agent is narrower. Furthermore, after the polycarboxylate superplasticizer is applied to concrete, it can significantly improve the flowability, slump retention, and compressive strength of concrete, thus promoting the healthy development of the polycarboxylate superplasticizer industry. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 Gel permeation chromatogram of the polycarboxylate superplasticizer mother liquor prepared in Comparative Example 1 provided by the present invention;

[0030] Figure 2 Gel permeation chromatogram of the polycarboxylate superplasticizer mother liquor prepared in Example 1 of this invention;

[0031] Figure 3 Gel permeation chromatogram of the polycarboxylate superplasticizer mother liquor prepared in Example 2 of this invention. Detailed Implementation

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] This invention provides a method for preparing a chain transfer agent for polycarboxylate superplasticizers, comprising the following steps:

[0034] (1) Weigh out aminobenzenesulfonate, catalyst and functional thiol substances according to a certain weight ratio;

[0035] (2) Add aminobenzenesulfonate and catalyst into the reaction vessel and stir for 5 min to 15 min to make the raw materials evenly mixed. Then, introduce inert gas to fill the reaction vessel until the amidation reaction is completed.

[0036] (3) Raise the reaction temperature in the reactor to 60℃~75℃ and add functional thiol substances;

[0037] (4) After the functional mercapto substances are added, the reaction temperature is raised to 85℃~105℃ and the amidation reaction is carried out at a constant temperature for 1h~3h to obtain the chain transfer agent for the polycarboxylate superplasticizer.

[0038] The constant temperature reaction temperature of 85℃~105℃ is set to allow water to be removed from the chain transfer agent, which is beneficial to the forward equilibrium shift of the reaction and improves the conversion rate of the chain transfer agent in polycarboxylate superplasticizer.

[0039] Preferably, the functional thiol substance is slowly added dropwise to the reaction vessel over a period of 1 to 3 hours, allowing for a more complete reaction.

[0040] Preferably, the inert gas is nitrogen (N2). The present invention also provides the following embodiments and comparative examples:

[0041] Example 1

[0042] By weight, 8 parts of potassium 4-aminobenzenesulfonate and 0.04 parts of zinc chloride were added to a reaction vessel and stirred for 8 minutes. N2 was then introduced to fill the entire reaction vessel until the reaction was completed. The system in the reaction vessel was heated to 65°C, and 13 parts by weight of 2-mercaptoethanesulfonic acid were added dropwise. After 1 hour of dropwise addition, the temperature was raised to 95°C and the reaction was kept at a constant temperature for 2 hours to obtain the chain transfer agent for polycarboxylate superplasticizer.

[0043] Example 2

[0044] By weight, 15 parts of sodium 2,4-diaminomethylbenzenesulfonate and 0.1 parts of ferrous chloride were added to a reaction vessel and stirred for 15 minutes. N2 was then introduced to fill the entire reaction vessel until the reaction was completed. The system in the reaction vessel was heated to 75°C, and 20 parts of 2-mercaptopropanesulfonic acid were added dropwise. After 1 hour of dropwise addition, the temperature was raised to 105°C and the reaction was kept at a constant temperature for 3 hours to obtain a chain transfer agent for polycarboxylate superplasticizer.

[0045] Comparative Example 1

[0046] Commercially available thioglycolic acid chain transfer agents are available.

[0047] The chain transfer agents provided in the examples and comparative examples were used to synthesize polycarboxylate superplasticizer mother liquor under the same dosage conditions. The method for synthesizing the polycarboxylate superplasticizer mother liquor is as follows:

[0048] 195g of modified polyether HPEG, 2g of 27.5% hydrogen peroxide solution, and 100g of water were added to a reactor equipped with a stirrer. The temperature inside the reactor was raised to 40°C, and the mixture was stirred until the solution inside the reactor became colorless and transparent. A mixture of acrylic acid, ascorbic acid, and water (16.5g, 0.3g, and 20g respectively) was added dropwise, followed by a mixture of chain transfer agent and water (0.75g and 20g respectively). After the addition was complete, the mixture was kept at 40°C for 2 hours. 5g of solid sodium hydroxide was added to neutralize the reaction, and then 75g of water was added to obtain a 50% solid content polycarboxylate superplasticizer mother liquor. The modified polyether HPEG used was HPEG-LA888-01, manufactured by Hubei Ling'an Technology Co., Ltd., with a molecular weight of 2400.

[0049] The polycarboxylate superplasticizer mother liquors prepared in Examples 1-2 and Comparative Example 1 were all subjected to molecular weight determination according to GB / T27843-2011 "Determination of Low Molecular Weight Components in Chemical Polymers - Gel Permeation Chromatography (GPC)". The determination results are shown in Table 1 below. Figure 1-3 As shown:

[0050] Table 1 GPC Data

[0051] Sample number Number average molecular weight Mn Weight-average molecular weight Mw Peak molecular weight Mp Polydispersity Mw / Mn Comparative Example 1 29861 59901 43833 2.00 Example 1 33477 63263 47188 1.89 Example 2 24334 43463 35136 1.78

[0052] As shown in Table 1, the weight-average molecular weight of the polycarboxylate superplasticizer mother liquor prepared in Comparative Example 1 is 59901, and its polydispersity is 2.00, indicating a wide molecular weight distribution. The molecular weight polydispersity of Examples 1 and 2 is all below 2.00. In summary, the chain transfer agent provided by this invention can better regulate the molecular weight of the polycarboxylate superplasticizer, and the molecular weight distribution of the polycarboxylate superplasticizer it participates in the synthesis is narrower.

[0053] To further verify the effect of the chain transfer agent in Examples 1-2 and Comparative Example 1 on the polycarboxylate superplasticizer mother liquor, concrete experiments were conducted using the polycarboxylate superplasticizer mother liquors prepared in Examples 1-2 and Comparative Example 1. The specific experimental materials are as follows:

[0054] Cement: Conch Cement PO 42.5; Manufactured sand: Manufactured sand produced locally in Guizhou; Crushed stone: Crushed stone produced locally in Guizhou; Water-reducing agent: The polycarboxylate water-reducing agent mother liquor prepared in Examples 1-2 and Comparative Example 1 was diluted to a solid content of 15%.

[0055] The detailed information on the manufactured sand used is shown in Table 2 below:

[0056] Table 2. Detailed information on manufactured sand.

[0057] Appearance MB value Fineness modulus / % <![CDATA[Apparent density kg / m 3 > source White 2.8 3.2 2490 Locally produced in Guizhou

[0058] The details of the crushed stone used are shown in Table 3 below:

[0059] Table 3. Detailed Information on Crushed Stone

[0060] Appearance Particle size / mm MB value Crushing value / % source White 5～35 1.2 12.6 Locally produced in Guizhou

[0061] Concrete performance tests were conducted according to standard GB 8076-2008 "Concrete Admixtures". Three samples were tested using C30 concrete to compare their flowability and compressive strength. The concrete mix proportions (unit: kg / m³) were also specified. 3 As shown in Table 4:

[0062] Table 4 Experimental concrete mix proportions

[0063] Sample Name water cement Machine-made white sand gravel Water reducing agent Comparative Example 1 165 340 1020 850 4.08 Example 1 165 340 1020 850 4.08 Example 2 165 340 1020 850 4.08

[0064] Concrete was tested and evaluated according to the national standard GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" and tested according to GB 8076-2008 "Concrete Admixtures". The measured data are shown in Table 5.

[0065] Table 5 Concrete Performance Tests

[0066]

[0067] The test data in Table 5 shows that:

[0068] In Comparative Example 1, the initial slump of the concrete was 210 mm and the spread was 550 mm. After 2 hours, the slump was 185 mm and the spread was 380 mm. After 2 hours of time loss, the spread of the concrete decreased by 170 mm, which is a relatively large loss over time.

[0069] In Example 1, after 2 hours of time loss, the concrete spread decreased by 135 mm; in Example 2, after 2 hours of time loss, the concrete spread decreased by 140 mm.

[0070] Compared with Comparative Example 1, the concrete spread loss over time in Examples 1 and 2 was smaller, its slump retention performance was better, and the slump retention performance and compressive strength of the concrete were improved.

[0071] Analysis of the data in Tables 3 and 5 shows that the polycarboxylate superplasticizer with a wider molecular weight distribution provided in Comparative Example 1 has a faster loss of expansion; while the polycarboxylate superplasticizer with a narrower molecular weight distribution provided in Examples 1-2 has better initial flowability, better slump retention, and higher compressive strength in concrete.

[0072] It should be noted that:

[0073] In addition to the specific choices embodied in the above embodiments, the aminobenzenesulfonate can be selected with the following general structural formula:

[0074]

[0075] Where M is Na + K + R1 is -NH2 or -CH2NH2, and the substitution position of R1 is at least one of the ortho or para positions of -SO3M on the benzene ring. The number of substitutions is 1 to 2, including but not limited to the actual selections shown in the above embodiments. Specifically, the phrase "the number of substitutions is 1 to 2" in this document indicates that the number of substitution positions of R1 is 1 to 2, as shown in the following structural formula:

[0076]

[0077] Preferably, the aminobenzenesulfonate is one or more combinations of sodium 4-aminobenzenesulfonate, potassium 4-aminobenzenesulfonate, sodium 2,4-diaminobenzenesulfonate, potassium 2,4-diaminobenzenesulfonate, sodium 4-aminomethylbenzenesulfonate, potassium 4-aminomethylbenzenesulfonate, sodium 2,4-diaminomethylbenzenesulfonate, and potassium 2,4-diaminomethylbenzenesulfonate.

[0078] In addition to the specific choices embodied in the above embodiments, the selection of the functional thiol group can be: its general structural formula is:

[0079]

[0080] Wherein, R2 is -SO3H, and n is 2 to 3, including but not limited to the actual selections embodied in the above embodiments;

[0081] Preferably, the functional thiol substance is one or more combinations of 2-mercaptoethanesulfonic acid and 2-mercaptopropanesulfonic acid.

[0082] In addition to the actual selections shown in the specific embodiments above, the catalyst is one or more combinations of metal chlorides and metal oxides, including but not limited to the actual selections shown in the embodiments above.

[0083] Preferably, the catalyst is one or a combination of zinc oxide, zinc chloride, ferrous chloride, and aluminum trichloride.

[0084] In addition to the actual selections shown in the specific embodiments above, the reaction raw materials include 5 to 15 parts of aminobenzenesulfonate, 10 to 20 parts of functional thiol substances and 0.01 to 0.1 parts of catalyst; the raw material components within the above weight ratio range are all acceptable, including but not limited to the actual selections shown in the above embodiments.

[0085] Apart from the actual selection of the synthesis process of polycarboxylate superplasticizer as shown in the specific embodiments above, the synthesis method of polycarboxylate superplasticizer is existing technology, and the addition of chain transfer agent to control the molecular weight of polycarboxylate during the synthesis reaction of polycarboxylate superplasticizer is also existing technology. Therefore, based on the use of the chain transfer agent for polycarboxylate superplasticizer provided by the present invention as the chain transfer agent, the specific selection of the specific preparation process parameters of polycarboxylate superplasticizer (reaction temperature and reaction time, etc.), the types of polyether macromonomers and unsaturated carboxylic acids, and the amount of polyether macromonomers, unsaturated carboxylic acids and chain transfer agents used in the synthesis process can be adjusted by those in the art according to the above design concept, including but not limited to the schemes shown in the embodiments.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A chain transfer agent for polycarboxylate superplasticizers, characterized in that: Its general structural formula is: Where M is Na + or K + The substitution position of R is at least one of the ortho or para positions of the -SO3M group on the benzene ring, and the number of substitutions is 1 to 2. The general structural formula of R is: Where n is 2 to 3.

2. The use of the chain transfer agent for the polycarboxylate superplasticizer as described in claim 1, characterized in that: It is used as a chain transfer agent in the synthesis reaction of polycarboxylate superplasticizers.

3. A method for preparing a chain transfer agent for a polycarboxylate superplasticizer as described in claim 1, characterized in that, Includes the following steps: S100. Add aminobenzenesulfonate and catalyst into the reactor and stir to mix. Then, introduce inert gas to fill the reactor until the amidation reaction is complete. S200, raise the reaction temperature in the reactor to 60℃~75℃, and add functional thiol substances; After S300 and functional thiol substances are added, the reaction temperature is raised to 85℃~105℃, and the amidation reaction is carried out at a constant temperature for a certain time to obtain the chain transfer agent for the polycarboxylate superplasticizer. The general structural formula of the functional thiol group is as follows: Wherein, R2 is -SO3H, and n is 2 to 3; The catalyst is one or a combination of zinc oxide, zinc chloride, ferrous chloride, and aluminum trichloride.

4. The method for preparing the chain transfer agent for polycarboxylate superplasticizer according to claim 3, characterized in that: The general structural formula of the aminobenzenesulfonate is: Where M is Na + K + R1 is -NH2, and R1 is substituted at least one of the ortho or para positions of -SO3M on the benzene ring, with 1 to 2 substitutions.

5. The method for preparing the chain transfer agent for the polycarboxylate superplasticizer according to claim 3, characterized in that: The aminobenzenesulfonate is one or more combinations of sodium 4-aminobenzenesulfonate, potassium 4-aminobenzenesulfonate, sodium 2,4-diaminobenzenesulfonate, and potassium 2,4-diaminobenzenesulfonate.

6. The method for preparing the chain transfer agent for polycarboxylate superplasticizer according to claim 3, characterized in that: The functional thiol substance is 2-mercaptoethanesulfonic acid.

7. The method for preparing the chain transfer agent for polycarboxylate superplasticizer according to claim 3, characterized in that: In S200, the functional thiol substance is slowly added dropwise to the reaction vessel for 1 to 3 hours; in S300, the amidation reaction at constant temperature takes 1 to 3 hours.

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