A synthesis method and application of a quaternary ammonium salt catalyst, an environmentally friendly hydroxyalkyl acrylate that can be directly used in the synthesis of polycarboxylic acid concrete admixtures

Abstract

The invention provides a method and application for synthesizing a quaternary ammonium salt catalyst and an environmentally friendly hydroxyalkyl acrylate that can be directly used for synthesizing a polycarboxylic acid-based concrete admixture. The method adopts a quaternary ammonium salt synthesized from vinyl iodide and hexamethylenetetramine as a catalyst, mixes the catalyst with a polymerization inhibitor and acrylic acid, introduces alkylene oxide into the catalyst under heating and pressurizing conditions in a protective atmosphere, and heats and matures the catalyst to prepare the hydroxyalkyl acrylate. The hydroxyalkyl acrylate has a fast reaction speed and a high conversion rate, does not require subsequent purification treatment, and can be directly used for synthesizing the concrete admixture.

Description

Technical Field

[0001] The invention belongs to the field of material preparation, and particularly relates to a synthesis method and application of a quaternary ammonium salt catalyst and an environmentally friendly hydroxyalkyl acrylate that can be directly used in the synthesis of a polycarboxylic acid series concrete admixture. Background Art

[0002] Hydroxyalkyl acrylates are important organic compounds with extremely active properties and a wide range of applications, primarily in fiber processing, coatings, light-curing resins, adhesives, paper processing, and the rubber industry. Hydroxyalkyl acrylates also play a key role in the synthesis of polycarboxylic acid-based concrete admixtures.

[0003] Concrete admixtures, as important substances for improving concrete properties, are widely used in construction projects. The synthesis of hydroxyalkyl acrylates, a key raw material for polycarboxylic acid-based concrete admixtures, has been a hot topic of research. However, traditional synthesis methods often suffer from slow reaction rates, low conversion rates, and the need for subsequent purification. This not only increases production costs but also affects product performance and application effectiveness. Furthermore, these products may contain harmful substances such as chloride ions and heavy metal ions, causing environmental pollution.

[0004] At present, the routes for synthesizing hydroxyalkyl acrylates mainly include the ring-opening method (divided into direct method and indirect method), direct esterification method, transesterification method, reaction method of diols with acryloyl chloride, reaction method of diol carbonate with acrylic acid, chlorohydrin method, etc.

[0005] The indirect method of ring opening of alkylene oxide and the transesterification method for producing hydroxyalkyl acrylate have many steps, which increases production cost and is uneconomical. The reaction method of diol and acryloyl chloride has high reactivity and fast reaction speed, but the cost of acyl chloride is much higher than that of the corresponding carboxylic acid, so its industrial application has great limitations. The reaction time of diol carbonate and acrylic acid is long and the reaction temperature is high. The long-term high temperature will produce more side reactions, thereby reducing the yield. The chlorohydrin method has a long synthesis cycle, unstable product quality, and there are problems with filtering the byproduct NaCl and the disadvantages of high toxicity of chlorohydrin.

[0006] Considering factors such as cost and yield, the synthetic process of hydroxyalkyl acrylates using acrylic acid and alkylene oxide as raw materials is reasonable and feasible, and the research focus of this process is on the development of efficient catalysts. Yin Jiazi and Zhu Xinbao have experimentally verified catalysts such as chromium-based catalysts, iron-based catalysts, and organic amines in the literature. However, each catalyst has its own advantages and disadvantages. After studying the hydroxyalkyl acrylates synthesized using these catalysts, they found that when used in the synthesis of concrete admixtures, the hydroxyalkyl acrylates need to be purified, otherwise the residual catalyst will have a certain negative impact on the synthesis of the concrete admixture. Summary of the Invention

[0007] The invention aims to provide a quaternary ammonium salt catalyst, wherein the quaternary ammonium salt prepared by reacting hexamethylenetetramine and ethylene iodide is used as a catalyst for synthesizing hydroxyalkyl olefinate, and the preparation method is simple.

[0008] The present invention aims to provide an environmentally friendly method for synthesizing hydroxyalkyl acrylates that can be directly used in the synthesis of polycarboxylic acid-based concrete admixtures. The method utilizes a quaternary ammonium salt prepared by the reaction of hexamethylenetetramine and vinyl iodide as a catalyst to prepare the hydroxyalkyl acrylates. The method exhibits high catalytic efficiency, good selectivity, and eliminates the need for material separation, resulting in environmental friendliness. Furthermore, the prepared hydroxyalkyl acrylates can be directly used in the synthesis of polycarboxylic acid-based concrete admixtures.

[0009] Another object of the present invention is to provide an environmentally friendly application of hydroxyalkyl acrylate that can be directly used in the synthesis of polycarboxylic acid concrete admixtures, for use in the synthesis of polycarboxylic acid concrete admixtures.

[0010] The specific technical solutions of the present invention are as follows:

[0011] The present invention provides a quaternary ammonium salt catalyst, the structural formula of which is

[0012] The preparation method of the quaternary ammonium salt catalyst is:

[0013] Weigh hexamethylenetetramine and dissolve it in chloroform. Add vinyl iodide under heating and pressurization conditions to react. Purify after the reaction is completed.

[0014] The mass ratio of hexamethylenetetramine to chloroform is 1:(2.0-5.0);

[0015] In the preparation method of the quaternary ammonium salt catalyst, the heating and pressurizing conditions refer to a reaction temperature of 40-80° C., a reaction pressure of 0.1-1.0 MPa, and a reaction time of 1.0-3.0 h.

[0016] The molar ratio of hexamethylenetetramine to ethylene iodide is 1:(1.0-1.2);

[0017] The synthesis of the quaternary ammonium salt catalyst of the present invention comprises the following steps: after the catalyst synthesis is completed, nitrogen is purged at 60° C. to remove chloroform to obtain quaternary ammonium salt catalyst crystals without further purification.

[0018] The purity of the hexamethylenetetramine is above 99%, the purity of the vinyl iodide is above 80%, and the purity of the chloroform is above 99%.

[0019] The reaction equation of the quaternary ammonium salt catalyst is:

[0020]

[0021] The present invention provides an environmentally friendly method for synthesizing hydroxyalkyl acrylate that can be directly used in the synthesis of polycarboxylic acid-based concrete admixtures, specifically comprising:

[0022] The quaternary ammonium salt catalyst, polymerization inhibitor and acrylic acid prepared above are mixed, and alkylene oxide is introduced into the mixture under heating and pressurizing conditions in a protective atmosphere for reaction. The mixture is kept warm for aging, and after the reaction is completed, the temperature is lowered and the material is discharged.

[0023] The amount of the quaternary ammonium salt catalyst is 5‰-20‰ of the mass of acrylic acid;

[0024] The amount of the polymerization inhibitor is 0.5‰-10‰ of the mass of acrylic acid;

[0025] The effective content of the quaternary ammonium salt catalyst is ≥90%;

[0026] The molar ratio of acrylic acid to alkylene oxide is 1:(1.0-2.0);

[0027] The acrylic acid has a purity of ≥99.5%;

[0028] The alkylene oxide has a water content of ≤1000ppm, a gas phase purity of ≥99%, and an aldehyde content of ≤100ppm, and the alkylene oxide includes one of ethylene oxide (abbreviated as EO) and propylene oxide (abbreviated as PO);

[0029] The polymerization inhibitor is one of hydroquinone, tert-butylcatechol, phenothiazine, diethylhydroxylamine, and 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical. Acrylic acid is an organic acid containing unsaturated double bonds, which has high activity and is easy to self-polymerize in the presence of a catalyst. A certain amount of polymerization inhibitor needs to be added, which can also prevent the self-polymerization of hydroxyalkyl acrylate.

[0030] The protective atmosphere is nitrogen;

[0031] The heating and pressurizing conditions refer to a reaction temperature of 50-150°C and a reaction pressure of 0.1-1.0 MPa;

[0032] The heat preservation and aging refers to the heat preservation reaction time of 1.0h after the addition of alkylene oxide is completed.

[0033] The synthesis of the cycloalkyl acrylate mainly refers to hydroxyethyl acrylate (HEA) and hydroxypropyl acrylate (HPA).

[0034] Preferably, the synthesis method of the environmentally friendly hydroxyalkyl acrylate that can be directly used in the synthesis of polycarboxylic acid concrete admixtures is:

[0035] A quaternary ammonium salt catalyst, a polymerization inhibitor and acrylic acid are added to a reactor, the reactor is sealed and nitrogen replaced three times, the reactor is heated to a set temperature, and alkylene oxide is introduced into the reactor at 50-150° C. and a reaction pressure of 0.1-1.0 MPa. After the feeding is completed, the reactor is kept warm and aged. After the reaction is completed, the reactor is cooled to below 50° C. and discharged to obtain a reaction solution of hydroxyalkyl acrylate.

[0036] The environmentally friendly hydroxyalkyl acrylate prepared by the above method, which can be directly used in the synthesis of polycarboxylic acid concrete admixtures, has the following structural formula:

[0037] Wherein R is one of H or CH3.

[0038] The reaction equation for the synthesis of environmentally friendly hydroxyalkyl acrylate that can be directly used in the synthesis of polycarboxylic acid concrete admixtures is:

[0039] R is one of H or CH3.

[0040] The present invention provides an environmentally friendly hydroxyalkyl acrylate that can be directly used in the synthesis of polycarboxylic acid concrete admixtures without purification and can be directly used to prepare polycarboxylic acid concrete admixtures;

[0041] The structural formula of the polycarboxylic acid concrete admixture is:

[0042] Wherein R is one of H or CH3; a is a positive integer between 1 and 20; b is a positive integer between 20 and 80; c is a positive integer between 10 and 30; n is a positive integer between 50 and 70;

[0043] The preparation method of the polycarboxylic acid-based concrete admixture specifically comprises: using a polyether macromonomer, an oxidant, and water as a primer, preparing an aqueous solution of acrylic acid and an environmentally friendly hydroxyalkyl acrylate that can be directly used in the synthesis of the polycarboxylic acid-based concrete admixture as a dropwise addition material A, a reducing agent and a chain transfer agent as a dropwise addition material B, and preparing an alkaline solution as a dropwise addition material C; dropwise adding materials A, B, and C to the primer; and maintaining the temperature for reaction after the dropwise addition is completed.

[0044] The structural formula of the polyether macromonomer is:

[0045] wherein n is a positive integer between 50 and 70; the polyether macromonomer is selected from vinyl polyoxyethylene ether;

[0046] The preparation method of the polycarboxylic acid concrete admixture is carried out at room temperature and normal pressure.

[0047] The mass ratio of the polyether macromonomer, acrylic acid and environmentally friendly hydroxyalkyl acrylate that can be directly used in the synthesis of polycarboxylic acid concrete admixtures is 30: (0.6-3.0): (1.5-5);

[0048] In the preparation method of the polycarboxylic acid concrete admixture, the mass concentration of material A is 50%;

[0049] The addition time of material A was 1.0 h, the addition time of material B was 1.0 h, and the addition time of material C was 1.5 h. After the addition was completed, the heat preservation reaction time was 1.0 h.

[0050] The oxidant is one of hydrogen peroxide, sodium persulfate and ammonium persulfate, and the amount used is 0.1%-5% of the mass of the polyether macromonomer.

[0051] The reducing agent is one of L-ascorbic acid, Rongalite and sodium formaldehyde sulfoxylate, and its usage is 0.1%-1% of the mass of the polyether macromonomer.

[0052] The chain transfer agent is one of mercaptoethanol, mercaptopropanol, thioglycolic acid, mercaptopropionic acid, and sodium hypophosphite, and the amount used is 0.2%-1% of the mass of the polyether macromonomer;

[0053] The alkali solution is one of sodium hydroxide solution and potassium hydroxide solution, with a mass concentration of 10%; and the usage amount is 1%-5% of the mass of the polyether macromonomer.

[0054] The polycarboxylic acid concrete admixture of the present invention is prepared by polymerizing vinyl polyoxyethylene ether macromonomer, acrylic acid, and self-made hydroxyalkyl acrylate; the free radical polymerization method is an aqueous phase free radical polymerization method, and the initiation system includes an oxidant, a reducing agent, and a chain transfer agent.

[0055] While existing catalysts used in ring-opening methods exhibit excellent catalytic activity and selectivity for the synthesis of hydroxyalkyl acrylates, they also present several challenges and shortcomings. Currently, the catalysts used in the industrialization of hydroxyalkyl acrylates are primarily chromium-based catalysts. The main drawbacks are the cumbersome subsequent purification process and the tendency for the hydroxyalkyl acrylate to self-polymerize during purification. Without purification, residual chromium can negatively impact the synthesis of polycarboxylic acid-based concrete admixtures. Furthermore, chromium ions are heavy metal ions, posing a hazard to the environment.

[0056] Compared with the prior art, the present invention adopts the quaternary ammonium salt synthesized by vinyl iodide and hexamethylenetetramine as catalyst, is used to prepare hydroxyalkyl acrylate, has fast reaction speed, high conversion rate, does not need subsequent purification process, can be directly used in the synthesis of concrete admixture. Due to the characteristics of environmental protection, high efficiency, can be directly used in the synthesis of concrete admixture, it is particularly suitable for industrialized production. Containing alkene group in the catalyst structure of the present invention, this not only has no influence on the ring opening of alkylene oxide. And owing to introducing a double bond to form quaternary ammonium salt catalyst on hexamethylenetetramine, when synthesizing polycarboxylic acid, the double bond in the catalyst can break and polyether macromonomer, acrylic acid, hydroxyalkyl acrylate etc. occur water-phase free radical polymerization, generate a kind of comb-shaped polycarboxylic acid structure, so not only do not have negative impact on the synthesis of polycarboxylic acid concrete admixture, but also become a kind of polycarboxylic acid on the contrary, the performance of polycarboxylic acid concrete admixture has been further improved. After introducing double bonds on hexamethylenetetramine, quaternary ammonium salt catalyst is formed. Due to containing double bonds in the catalyst, double bonds can be disconnected and aqueous phase free radical polymerization occurs with polyether macromonomers, acrylic acid, hydroxyalkyl acrylate, etc. to form a polycarboxylic acid structure. This structure is similar to the admixture structure and also has a promoting effect on concrete performance. In practical applications, this method can significantly reduce production costs, improve production efficiency, and simultaneously ensure the quality and performance of the product. The environment-friendly synthesis method of the present invention will be more popular in the market. By the implementation of the present invention, not only the progress of hydroxyalkyl acrylate synthesis technology can be promoted, but also the green development and sustainable development of the concrete admixture industry can be promoted. Therefore, the present invention has a wide range of industrial applicability in the fields of chemical synthesis, concrete admixture production, etc. The catalyst of the present invention does not contain toxic and harmful substances such as heavy metals, is a kind of environmentally friendly catalyst, and will not pollute the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is the GPC data of the product in Example 3;

[0058] Figure 2 This is the GPC data spectrum of the product in Example 6. DETAILED DESCRIPTION

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments 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, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0060] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0061] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0062] The number average molecular weight (Mn), weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), and polymer peak area ratio were determined using a Waters e 2695 gel permeation chromatograph. (Mobile phase: 0.1 mol / L NaNO3 aqueous solution; mobile phase velocity: 0.6 ml / min; injection volume: 30 μl; sample preparation concentration: 2% (g sample / g mobile phase);

[0063] The reaction solution of the hydroxyalkyl acrylate described in the present invention was tested using a Shimadzu 2030 gas chromatograph. The chromatographic column was an Agilent HP-5 chromatographic column (column length × column inner diameter × coating thickness: 30m × 0.32mm × 0.25um). The sample was injected and tested using an ethanol solution with a mass ratio of 1:10. The test conditions were: injection volume of 0.2 μL, split ratio of 20:1, injection port temperature set to 250°C, detector temperature set to 270°C, and the column oven set to a programmed temperature increase (initial 100°C, hold for 1 minute, increase to 160°C at 5°C / min, hold for 1 minute, increase to 200°C at 20°C / min, hold for 6 minutes, and increase to 260°C at 10°C / min, hold for 5 minutes).

[0064] Example 1

[0065] A method for preparing a quaternary ammonium salt catalyst comprises: dissolving 100 g of hexamethylenetetramine in 200 g of chloroform, pumping the mixture into a reactor under vacuum, and then reacting the mixture with vinyl iodide at a molar ratio of 1:1 at 80°C and 0.5 MPa for 2 hours to produce the hexamethylenetetramine salt. After the reaction, the chloroform is purged with nitrogen at 60°C to obtain quaternary ammonium salt catalyst crystals, which do not require further purification.

[0066] Example 2

[0067] A method for synthesizing an environmentally friendly hydroxyalkyl acrylate that can be directly used in the synthesis of polycarboxylic acid-based concrete admixtures comprises the following steps: 600 g of acrylic acid, 5.0 g of the quaternary ammonium salt catalyst prepared in Example 1, and 0.5 g of a polymerization inhibitor, phenothiazine, are weighed and added to a reactor. The reactor is sealed and nitrogen purged three times. The reactor is heated to 100° C., 400 g of ethylene oxide (EO) is fed, and the feeding time is controlled to be approximately 2 hours. The reaction temperature is controlled to be 100±5° C., and the maximum reaction pressure is 0.5 MPa. After the feeding is completed, the reaction is kept warm for 1.0 hour to obtain a brownish-yellow hydroxyethyl acrylate reaction solution. A sample is taken for GC analysis (area normalization method / %): ethylene oxide 2.26%, acrylic acid 0.42%, diethylene glycol monoacrylate 5.74%, ethylene glycol diacrylate 0.03%, hydroxyethyl acrylate 91.27%, and other unknown components 0.28%.

[0068] Example 3

[0069] The environmentally friendly hydroxyalkyl acrylate prepared in Example 2, which can be directly used in the synthesis of polycarboxylic acid concrete admixtures, is used in the synthesis of polycarboxylic acid concrete admixtures:

[0070] Weigh 360g of vinyl polyoxyethylene ether with a molecular weight of 2400, add water to prepare a 60% aqueous solution, and add 2.0g of hydrogen peroxide; weigh 30.0g of acrylic acid and 20.0g of prepared hydroxyethyl acrylate to prepare a 50% aqueous solution as material A; weigh 1.5g of reducing agent Rongalite and 3.0g of chain transfer agent mercaptopropionic acid to prepare a 10% aqueous solution as material B; prepare 40g of 10% sodium hydroxide lye as material C for dripping. The above materials A, B, and C are added to the base material at the same time according to the time of 1h, 1h, and 1.5h respectively. After the addition is completed, mature for 1h. The structural formula of polycarboxylic acid water reducer is:

[0071]

[0072] Detection of GPC data of polycarboxylate water reducer, such as Figure 1 The GPC conversion rate was 96.18%, Mn = 22591, Mw = 39400, and Mw:Mn = 1.744.

[0073] According to the standard GB / T8077-2000 experimental method, the difference in the fluidity of the slurry is measured: △FL0=5mm, △FL 60 =7mm, △FL 120 =6mm.

[0074] Example 4

[0075] Weigh 150g of hexamethylenetetramine and dissolve it in 300g of chloroform. This solution is then pumped into a reactor under vacuum. The mixture is then reacted with vinyl iodide at a molar ratio of 1:1.1 at 60°C and a reaction pressure of 0.6 MPa for 1.5 hours to produce a quaternary ammonium catalyst (hexamethylenetetramine salt). After the reaction is complete, the chloroform solvent is removed under a nitrogen atmosphere. The hexamethylenetetramine salt precipitates as a crystalline salt, eliminating the need for further purification.

[0076] Example 5

[0077] Weigh 500g of acrylic acid, 8.0g of the catalyst prepared in Example 4, and 0.8g of hydroquinone into a reactor, seal the reactor, and replace the atmosphere with nitrogen three times. The reactor is heated to 80°C. The feed amount of propylene oxide (PO) is 400g, the feed time is controlled to about 2h, the reaction temperature is controlled to 80±5°C, and the maximum reaction pressure is 0.4MPa. After the feed is completed, the reaction is kept warm for 1.0h to obtain a brown-yellow hydroxyethyl acrylate reaction solution, which is sampled for GC analysis (area normalization method / %): 1.44% propylene oxide, 0.65% acrylic acid, 6.52% 1,3-propylene glycol monoacrylate, 0.06% 1,3-propylene glycol diacrylate, 90.82% hydroxypropyl acrylate, and 0.51% other unknown components.

[0078] Example 6

[0079] Weigh 360g of vinyl polyoxyethylene ether with a molecular weight of 2400 and prepare it into a 60% aqueous solution, add 2.8g of hydrogen peroxide; weigh 36.0g of acrylic acid and 26.0g of the prepared hydroxypropyl acrylate and prepare it into a 50% aqueous solution as material A; weigh 2.0g of reducing agent Rongalite and 2.8g of chain transfer agent mercaptoethanol and prepare it into a 10% aqueous solution as material B; prepare 45g of 10% sodium hydroxide lye as material C. Add the above materials A, B, and C to the base material at the same time according to the time of 1h, 1h, and 1.5h respectively. After the addition is completed, mature for 1h. The structural formula of the obtained polycarboxylic acid water reducer is:

[0080]

[0081] The GPC data of polycarboxylate water reducer was tested. The GPC conversion rate was 96.28%, Mn = 23961, Mw = 45225, Mw:Mn = 1.887. The GPC data spectrum is as follows Figure 2 .

[0082] According to the standard GB / T8077-2000 experimental method, the difference in the fluidity of the slurry is measured: △FL0 = -4mm, △FL 60 =8mm, △FL 120=8mm.

[0083] The above embodiments are described to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A quaternary ammonium salt catalyst, characterized in that The structural formula of the quaternary ammonium salt catalyst is .

2. quaternary ammonium salt catalyst according to claim 1, is characterized in that, The preparation method of the quaternary ammonium salt catalyst is: Weigh hexamethylenetetramine and dissolve it in chloroform. Add vinyl iodide under heating and pressurization conditions to react. Purify after the reaction is completed.

3. quaternary ammonium salt catalyst according to claim 2, is characterized in that, In the preparation method of the quaternary ammonium salt catalyst, the heating and pressurizing conditions refer to a reaction temperature of 40-80° C., a reaction pressure of 0.1-1.0 MPa, and a reaction time of 1.0-3.0 h.

4. quaternary ammonium salt catalyst according to claim 2, is characterized in that, The molar ratio of hexamethylenetetramine to ethylene iodide is 1:(1.0-1.2).

5. A method for synthesizing an environmentally friendly hydroxyalkyl acrylate that can be directly used in the synthesis of polycarboxylic acid concrete admixtures, characterized in that: The synthesis method uses the quaternary ammonium salt catalyst according to claim 1 as a catalyst. The synthesis method comprises the following steps: mixing the quaternary ammonium salt catalyst, a polymerization inhibitor and acrylic acid, introducing alkylene oxide into the mixture under a protective atmosphere and under heating and pressurizing conditions, heating and aging the mixture, cooling the mixture and discharging the mixture after the reaction is completed.

6. The synthesis method according to claim 5, characterized in that The amount of the quaternary ammonium salt catalyst is 5‰-20‰ of the mass of acrylic acid.

7. The synthesis method according to claim 5, characterized in that The molar ratio of acrylic acid to alkylene oxide is 1:(1.0-2.0).

8. The synthesis method according to claim 5, characterized in that The dosage of the polymerization inhibitor is 0.5‰-10‰ of the mass of acrylic acid.

9. The synthesis method according to claim 5 or 8, characterized in that The polymerization inhibitor is one of hydroquinone, tert-butylcatechol, phenothiazine, diethylhydroxylamine, and 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical.

10. The synthesis method according to claim 5 or 8, characterized in that The heating and pressurizing conditions refer to a reaction temperature of 50-150° C. and a reaction pressure of 0.1-1.0 MPa.

11. An application of the synthesis method according to any one of claims 5 to 10 to synthesize an environmentally friendly hydroxyalkyl acrylate that can be directly used in the synthesis of polycarboxylic acid concrete admixtures, characterized in that: It can be directly used to prepare polycarboxylic acid concrete admixtures without purification.

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