Preparation method of high-performance polycarboxylic acid water reducer monomer

Abstract

The application discloses a preparation method of high-performance polycarboxylic water-reducing agent monomer. The method comprises the process of reacting unsaturated alcohol and ethylene oxide in the presence of a catalyst, and is characterized in that after the catalyst is added, and before 1 / 2 of the total amount of ethylene oxide is added, preferably between 1 / 3 and 1 / 2 of the total amount of ethylene oxide is added, a calcium salt is added into the reaction system. By introducing a certain amount of calcium element in the reaction process, the product's double bond retention rate and storage stability are improved.

Description

Technical Field

[0001] This invention relates to a method for preparing a high-performance polycarboxylate superplasticizer monomer, belonging to the field of superplasticizers. Background Technology

[0002] Polycarboxylate superplasticizer monomers are alkoxylated polymers obtained by polymerization of small-molecule starting alcohols containing double bonds with EO. They are typically copolymerized with acrylic acid to produce superplasticizers used for water reduction and slump retention in concrete. In 2022, China's consumption of polycarboxylate superplasticizer monomers exceeded 2 million tons. Currently, the main superplasticizer monomers on the market include methyl allyl alcohol polyoxyethylene ether, isopentenyl alcohol polyoxyethylene ether, vinyl glycol ether polyoxyethylene ether, vinyl diethylene glycol ether polyoxyethylene ether, and vinyl butanediol ether polyoxyethylene ether.

[0003] Although there are many grades of water-reducing agent monomers on the market, double bond retention rate is a key indicator of concern for downstream customers. The level of double bond retention rate largely determines the performance of the water-reducing agent monomer. Generally, the double bond retention rate should be >95% according to the requirements of downstream applications. To ensure a high double bond retention rate, it is necessary to strictly control the reaction temperature to prevent high-temperature breakage of double bonds, and also to strictly control the moisture content in the system to avoid the formation of by-product polyethylene glycol (PEGs). This undoubtedly places strict requirements on production control and reduces reaction efficiency. To solve these problems, it is urgent to develop novel preparation methods to obtain high-performance polycarboxylate water-reducing agent monomers. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing high-performance polycarboxylate superplasticizer monomers. By introducing a certain amount of calcium during the reaction process, this invention helps to improve the bismuth retention rate and storage stability of the product.

[0005] A method for preparing a high-performance polycarboxylate superplasticizer monomer includes a process of reacting an unsaturated alcohol and ethylene oxide in the presence of a catalyst, characterized in that a calcium salt is added to the reaction system after the catalyst is added and before 1 / 2 of the total amount of ethylene oxide is added, preferably between 1 / 3 and 1 / 2 of the total amount of ethylene oxide is added.

[0006] On the one hand, by controlling the timing and temperature of calcium addition, calcium ions can be coupled and synergistically dispersed with catalyst metal ions in the water-reducing agent monomer, thus achieving stable dispersion. On the other hand, the introduction of calcium can buffer the pH of the product and play a role in ion balance, avoiding the enrichment and precipitation of catalyst metal, which could lead to excessively high local concentrations and loss of double bonds in the product.

[0007] As a preferred embodiment of the present invention, the calcium salt is selected from organic calcium salts and / or inorganic calcium salts, preferably one or more of calcium chloride, calcium sulfate, calcium carbonate, calcium hydroxide, calcium phosphate, calcium bicarbonate, calcium silicate, calcium oxalate, calcium propionate, calcium acetate, calcium lactate, calcium gluconate, calcium citrate, calcium citrate, calcium threonate, and polyether calcium salts and surfactant complexes of calcium ions.

[0008] As a preferred embodiment of the present invention, the amount of calcium salt added is 5-500 ppm, preferably 30-200 ppm, based on the mass content of calcium relative to the product. When the calcium content is <5 ppm, it cannot play a buffering and ion balance role during polymerization, while when the calcium content is >500 ppm, calcium ions in the product are prone to precipitation, leading to system instability.

[0009] As a preferred embodiment of the present invention, the unsaturated alcohol is one or more of allyl alcohol, methyl allyl alcohol, isopentenyl alcohol, vinyl ethylene glycol, vinyl diethylene glycol, and vinyl butylene glycol.

[0010] As a preferred embodiment of the present invention, the catalyst is metallic sodium.

[0011] As a preferred embodiment of the present invention, the amount of catalyst used is 00-2000 ppm, which is the mass content of metallic sodium relative to the product.

[0012] In this invention, the amounts of unsaturated alcohol and ethylene oxide added as raw materials for preparing polycarboxylate superplasticizer monomers are determined based on the molecular weight of the target product and the molecular weight of the unsaturated alcohol. Generally, the theoretical molecular weight of the target product, the polycarboxylate superplasticizer monomer, = molecular weight of the unsaturated alcohol + molecular weight of ethylene oxide × number of molecules. In specific embodiments, if the amount of the unsaturated alcohol used differs from its molecular weight, simply ensuring that the molecular weight × number of molecules of ethylene oxide increases or decreases by the same multiple will yield a target product with a yield that increases or decreases exponentially. As a preferred embodiment of this invention, after adding the calcium salt, the reaction is carried out at a temperature of 80-130℃, preferably 100-120℃.

[0013] As a preferred embodiment of the present invention, after the reaction is completed, the product is obtained by aging, demonstration, and neutralization.

[0014] The aging, demonolysis, and neutralization operations are routine operations for preparing polycarboxylate superplasticizer monomers, which are described in detail in patents such as CN106916291B, CN107057053B, and CN109384914B, and will not be repeated here.

[0015] The water-reducing agent monomers that can be prepared by the method of the present invention are, for example, allyl alcohol polyoxyethylene ether, methyl allyl alcohol polyoxyethylene ether, isopentenyl alcohol polyoxyethylene ether, vinyl glycol ether polyoxyethylene ether, vinyl diethylene glycol ether polyoxyethylene ether, vinyl butylene glycol ether polyoxyethylene ether, etc.

[0016] The molecular weight of the polycarboxylate superplasticizer monomer obtained by the above invention method is 1000-7000 g / mol, preferably 2000-4000 g / mol.

[0017] After long-term testing and verification, the dual-building retention rate of the water-reducing agent monomer provided by this invention is 2-3% higher than that of conventional products. After more than six months of storage, the dual-building retention rate does not decrease significantly, and the storage stability is good. Detailed Implementation

[0018] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0019] Unless otherwise specified, all raw materials and reagents used in this invention can be purchased commercially.

[0020] The main testing methods involved in the following embodiments of the present invention are as follows:

[0021] Hydroxyl value determination: The acetic anhydride method according to standard GB / T 7383-2007 was used.

[0022] Double bond retention rate: The iodine value was tested according to standard GB / T 13892, and then calculated according to the formula Double bond retention rate = Iodine value (g / 100g) * Mw (g / mol) / 25400.

[0023] Storage stability test: The sample was stored at 40℃ and 70% relative humidity for 3 months, and then the double bond retention rate was tested.

[0024] In the following examples, "parts" refers to parts by mass.

[0025]

Example 1

[0026] 100 parts of methyl allyl alcohol and 2 parts of metallic sodium were added to the reactor. The dissolution temperature of the metallic sodium was controlled at <60℃. After complete dissolution, the reactor was purged with nitrogen. Then the temperature was raised to 100℃, and 100 parts of ethylene oxide were continuously introduced. Then 30 ppm of calcium acetate (based on the mass content of calcium relative to the product) was added. The reaction temperature was controlled at 110℃. Finally, the remaining 3200 parts of ethylene oxide were introduced to react. After the reaction was completed, the product was deisolated and cooled to 80℃. 6 parts of acetic acid were introduced to neutralize the product, resulting in allyl alcohol polyoxyethylene ether with a target molecular weight of 2410 g / mol and a hydroxyl value of 23.27 mgKOH / g.

[0027]

Example 2-10

[0028] The water-reducing agent monomer was prepared using essentially the same method as in Example 1, with the only difference being that some of the reaction conditions are shown in Table 1.

[0029] Comparative Example 1

[0030] The water-reducing agent monomer was prepared using a method essentially the same as in Example 1, except that calcium acetate was not added and ethylene oxide was added all at once. The resulting product had a molecular weight of 2405 g / mol and a hydroxyl value of 23.33 mg KOH / g.

[0031] Comparative Example 2

[0032] The water-reducing agent monomer was prepared using a method essentially the same as in Example 1, except that the timing of calcium acetate addition was changed to simultaneous addition with the sodium metal catalyst. The resulting product had a molecular weight of 2390 g / mol and a hydroxyl value of 23.47 mg KOH / g.

[0033] Comparative Example 3

[0034] The water-reducing agent monomer was prepared using a method essentially the same as in Example 1, except that 2435 parts of ethylene oxide (3 / 4 of the total amount) were first introduced, followed by the addition of calcium acetate, and finally the remaining ethylene oxide was added. The resulting product had a molecular weight of 2420 g / mol and a hydroxyl value of 23.18 mg KOH / g.

[0035] The double bond retention rate and storage stability of the water-reducing agent monomers prepared in Examples 2-10 and Comparative Examples 1-3 were tested, and the results are shown in Table 2.

[0036] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

[0037] Table 1. Different reaction conditions in Examples 1-10

[0038]

[0039] Table 2. Performance test results of water-reducing agent monomers

[0040] Double bond retention rate Storage stability Example 1 99.1％ 99.0％ Example 2 99.2％ 99.1％ Example 3 98.5％ 98.1％ Example 4 98.3％ 98.1％ Example 5 97.3％ 96.9％ Example 6 97.0％ 96.8％ Example 7 99.2％ 99.0％ Example 8 98.9％ 98.7％ Example 9 99.0％ 98.7％ Example 10 99.3％ 99.0％ Comparative Example 1 96.2％ 95.0％ Comparative Example 2 96.4％ 94.5％ Comparative Example 3 98.0％ 94.0％

Claims

1. A method for preparing a high-performance polycarboxylate superplasticizer monomer, comprising a process of reacting an unsaturated alcohol and ethylene oxide in the presence of a catalyst, characterized in that, After the catalyst is added and before half of the total amount of ethylene oxide is added, calcium salt is added to the reaction system; after adding calcium salt, the reaction is carried out at a temperature of 80-130℃. The amount of calcium salt added is 5-500 ppm, based on the calcium content relative to the mass of the product.

2. The method for preparing the high-performance polycarboxylate superplasticizer monomer according to claim 1, characterized in that, After the catalyst is added, and ethylene oxide is added in amounts between 1 / 3 and 1 / 2 of the total amount, calcium salt is added to the reaction system.

3. The method for preparing the high-performance polycarboxylate superplasticizer monomer according to claim 1, characterized in that, The calcium salt is selected from organic calcium salts and / or inorganic calcium salts.

4. The method for preparing the high-performance polycarboxylate superplasticizer monomer according to claim 3, characterized in that, The calcium salt is selected from one or more of the following: calcium chloride, calcium sulfate, calcium carbonate, calcium hydroxide, calcium phosphate, calcium bicarbonate, calcium silicate, calcium oxalate, calcium propionate, calcium acetate, calcium lactate, calcium gluconate, calcium citrate, calcium citrate, calcium threonate, and polyether calcium salts and surfactant complexes of calcium ions.

5. The method for preparing the high-performance polycarboxylate superplasticizer monomer according to any one of claims 1-4, characterized in that, The amount of calcium salt added is 30-200 ppm, based on the calcium content relative to the mass of the product.

6. The method for preparing the high-performance polycarboxylate superplasticizer monomer according to any one of claims 1-4, characterized in that, The unsaturated alcohol is one or more of allyl alcohol, methyl allyl alcohol, isopentenyl alcohol, vinyl ethylene glycol, vinyl diethylene glycol, and vinyl butylene glycol.

7. The method for preparing the high-performance polycarboxylate superplasticizer monomer according to claim 6, characterized in that, The catalyst is metallic sodium.

8. The method for preparing the high-performance polycarboxylate superplasticizer monomer according to claim 7, characterized in that, The catalyst is used in an amount of 200-2000 ppm, based on the mass content of metallic sodium relative to the product.

9. The method for preparing the high-performance polycarboxylate superplasticizer monomer according to any one of claims 1-4, characterized in that, After adding calcium salt, the reaction is carried out at a temperature of 100-120℃.

10. The method for preparing the high-performance polycarboxylate superplasticizer monomer according to any one of claims 1-4, characterized in that, After the reaction is complete, the product is obtained through aging, de-monotropic treatment, and neutralization.

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