A method for synthesizing a polyether macro-monomer for a polycarboxylate-based water reducing agent with high double bond retention rate

Abstract

This invention relates to a method for synthesizing polyether macromonomers for polycarboxylate superplasticizers with high double bond retention. The method uses methyl allyl alcohol as an initiator, potassium hydroxide as a catalyst, and propylene oxide (PO) and ethylene oxide (EO) as comonomers, synthesizing the polyether macromonomers for polycarboxylate superplasticizers via block copolymerization. The invention employs a zero-pressure + nitrogen-protected feeding process to effectively prevent EO molecules from colliding and self-polymerizing, thus reducing the double bond retention rate. The use of trace amounts of catalyst in the synthesis process avoids the damage to unsaturated double bonds caused by alkaline catalysts. Limiting the reaction pressure range reduces the number of EO molecules in the reactor per unit time, thereby reducing the probability of EO molecules colliding. Applying this polyether to superplasticizers can significantly improve their water reduction rate, improve the fluidity of cement paste, and enhance slump retention. The polyether macromonomers synthesized using this method have a double bond retention rate as high as 99%.

Description

Technical Field

[0001] This invention relates to a method for synthesizing polyether macromonomers with high double bond retention rates, which is applied in the field of polycarboxylate superplasticizers. Background Technology

[0002] my country only began researching and developing polycarboxylate superplasticizers in the mid-to-late 1990s. Although starting late, development has been rapid, and some major products have reached or are close to the advanced performance levels of foreign products. The construction of high-speed railways in 2007 spurred the rapid development of high-performance polycarboxylate superplasticizers. Since 2011, concrete mixing plants across the country have been accepting polycarboxylate superplasticizers and applying them extensively in low-to-medium strength pumped concrete, leading to a significant increase in polycarboxylate superplasticizer production. In 2017, my country's total consumption of polycarboxylate superplasticizers reached 6.34 million tons, a 6% increase compared to 2016 and a 14% increase compared to 2015. To date, polycarboxylate superplasticizers have become the most consumed type of superplasticizer in my country.

[0003] In the early stages of polycarboxylate superplasticizer development, the main polyether macromonomer was polyethylene glycol monomethyl ether (MPEG). Before synthesizing the superplasticizer, this monomer needed to undergo esterification with smaller monomers such as acrylic acid or methacrylic acid to generate unsaturated polyether esters, which were then used to synthesize the polycarboxylate superplasticizer. This unsaturated polyether ester (MPEG) had several drawbacks: the synthesis process was complex and demanding, primarily due to the dehydration step required. During high-temperature dehydration esterification, side reactions were prone to occur, generating numerous byproduct impurities and leading to unstable product quality. Furthermore, the esterification reaction was reversible, resulting in incomplete reactions and the presence of residual MPEG (without polymerizable groups) in the system, severely impacting the application performance for downstream customers. Given the series of application problems of polycarboxylate superplasticizers based on MPEG, unsaturated ether-type polyether monomers, represented by allyl alcohol polyoxyethylene ether (APEG), methyl allyl alcohol polyoxyethylene ether (HPEG), and isopentenol polyoxyethylene ether (TPEG), have been developed domestically. The synthesis process of this series of polyether monomers is relatively simple (no esterification reaction is required; they can directly react with small-molecule unsaturated carboxylic acids to synthesize superplasticizers), with stable chemical properties and good product quality, and they have gradually gained widespread market acceptance. Initially, allyl alcohol polyoxyethylene ether (APEG) was the main product on the market, but APEG has relatively low polymerization activity and high monomer residue, resulting in low conversion rates of the synthesized superplasticizers and affecting their application performance. Furthermore, the initiator raw materials (methyl allyl alcohol and isopentenol) for TPEG and HPEG both need to be imported from abroad, which is relatively expensive, thus limiting their application in the superplasticizer industry. With the continuous progress of society and the continuous development of science and technology, the synthesis of TPEG and HPEG initiator raw materials (isoprenol and methyl allyl alcohol) has been gradually localized, and the price has also dropped significantly. In addition, compared with APEG polyether, TPEG and HPEG polyether monomers have higher reactivity. Polycarboxylate superplasticizer products synthesized using these monomers have higher water reduction rate and slump retention performance. Therefore, these two types of polyether macromonomers have gradually become the mainstream varieties in the market for polycarboxylate superplasticizer synthesis raw materials.

[0004] Currently, the industry consensus is that the performance of polyether macromonomers used in water-reducing agents is primarily judged by the double bond retention rate. This value reflects the content of olefin bonds (unsaturated double bonds) in the polyether macromonomer. All olefin bonds are provided by the raw materials used to synthesize the polyether (such as methyl allyl alcohol). During the synthesis of polyether macromonomers, we strive to ensure that the olefin bonds are not damaged for subsequent applications; therefore, a higher double bond retention rate is better. According to the Chinese industry standard JC / T2033-2010, "Polyethers and their Derivatives for Concrete Admixtures," the qualified standard for the double bond retention rate, a key indicator for this type of polyether macromonomer, is clearly stipulated as 85%. Currently, the double bond retention rate of this type of polyether macromonomer in the industry is around 90%. For example, Chinese patent CN101928392A discloses the preparation of isopentenol polyoxyethylene ether by condensation of isopentenol with ethylene oxide in the presence of traditional alkaline catalysts sodium hydroxide, potassium hydroxide, sodium methoxide, sodium isopentenol, and sodium isopentenol.

[0005] Therefore, to address the issue of double bond retention, this invention provides a method for synthesizing polyether macromonomers with high double bond retention. The synthesized monomer polyether exhibits a double bond retention rate of up to 99% (unsaturated double bonds are almost completely destroyed), further enhancing the performance of polyether macromonomers for water-reducing agents. Summary of the Invention

[0006] The purpose of this invention is to provide a method for synthesizing polyether macromonomers with high double bond retention rates, addressing the aforementioned problems, comprising the following steps:

[0007] (1) Add methyl allyl alcohol to the reactor, add KOH catalyst, remove air from the reactor by vacuuming, add nitrogen to make the pressure inside the reactor 0, heat to 145-155℃, introduce ethylene oxide (EO), control the pressure to 0.5-0.15MPa, after the reaction is complete, remove gas by vacuuming, cool down and discharge to obtain the intermediate.

[0008] (2) The intermediate from step (1) is put back into the reactor of step (1), KOH catalyst is added, the air inside the reactor is removed by vacuuming, nitrogen is added to make the pressure inside the reactor 0, the temperature is raised to 135-150℃, ethylene oxide (EO) is introduced, the pressure is controlled at 0.5-0.15MPa, and the reaction is completed by vacuuming to remove gas.

[0009] (3) After step (2) is completed, propylene oxide (PO) is continuously introduced, and the temperature is controlled at 125-135℃ and the pressure at 0.5-0.15MPa. After the reaction is complete, vacuum degassing is performed, the material is cooled and discharged to obtain the final product.

[0010] In step (1), the amount of KOH used is the mass percentage of methyl allyl alcohol + EO, which is 0.05% to 0.08%, preferably 0.06%.

[0011] The amount of KOH used in step (2) is the mass percentage of intermediate + EO + PO in step (3), and its value is 0.05% to 0.1%, preferably 0.08%;

[0012] The molar ratio of methyl allyl alcohol to ethylene oxide involved in step (1) is 1:4.0 to 7.9.

[0013] The molar ratio of the intermediate to ethylene oxide involved in step (2) is 1:32.5 to 37.8.

[0014] The molar ratio of the intermediate involved in step (2) to the propylene oxide in step (3) is 1:1.5 to 4.1.

[0015] The technical solution disclosed and proposed in this invention is to provide a method for synthesizing polyether macromonomers with high double bond retention rate, filling the gap in the industry for high-quality polyether macromonomers.

[0016] This invention employs a zero-pressure + nitrogen-protected feeding process to effectively prevent EO molecules from colliding and self-polymerizing, thus reducing double bond retention. It utilizes a trace amount of catalyst to complete product synthesis, avoiding the damage to unsaturated double bonds caused by alkaline catalysts. Limiting the reaction pressure range reduces the number of EO molecules in the reactor per unit time, thereby lowering the probability of EO molecule collisions. The polyether macromonomer synthesized using this method can achieve a double bond retention rate of over 99%. Detailed Implementation

[0017] Example 1

[0018] (1) Weigh 200g of methyl allyl alcohol and put it into the reactor. Add 0.5g of KOH (0.053%), replace with nitrogen three times, and replenish nitrogen to make the pressure inside the reactor 0. Heat the reactor to 145℃ and continuously introduce 730.0g of ethylene oxide (EO) to carry out the ring-opening reaction. Control the pressure at 0.1MPa until the reaction is over. Then, degas under vacuum, cool down and discharge to obtain the intermediate.

[0019] (2) Weigh 200g of intermediate into the reactor, add 1.20g (0.1%) of KOH, replace with nitrogen three times, replenish nitrogen to make the pressure inside the reactor 0, heat the reactor to 140℃, continuously introduce 900.0g of ethylene oxide (EO) to carry out the ring-opening reaction, control the pressure at 0.1MPa, and after the reaction is complete, evacuate the vacuum to remove gas.

[0020] (3) Under negative pressure, 100.4g of propylene oxide (PO) was continuously introduced into the reactor to carry out the ring-opening reaction. The temperature was controlled at 130℃ and the pressure at 0.1MPa. After the reaction was complete, the gas was degassed by vacuuming and the product was discharged after cooling. The final product, polyether, was obtained. The double bond retention rate was 99.5%.

[0021] Example 2

[0022] (1) Weigh 200g of methyl allyl alcohol and put it into the reactor. Add 0.35g (0.05%) of KOH, replace with nitrogen three times, and replenish nitrogen to make the pressure inside the reactor 0. Heat the reactor to 150°C and continuously introduce 497.6g of ethylene oxide (EO) to carry out the ring-opening reaction. Control the pressure at 0.05MPa until the reaction is over. Then, degas under vacuum, cool down and discharge to obtain the intermediate.

[0023] (2) Weigh 200g of intermediate into the reactor, add 0.96g (0.06%) of KOH, replace with nitrogen three times, replenish nitrogen to make the pressure inside the reactor 0, heat the reactor to 145℃, continuously introduce 1330.0g of ethylene oxide (EO) to carry out the ring-opening reaction, control the pressure at 0.05MPa, and after the reaction is complete, evacuate the vacuum to remove gas.

[0024] (3) Under negative pressure, 70.0g of propylene oxide (PO) was continuously introduced into the reactor to carry out the ring-opening reaction. The temperature was controlled at 125℃ and the pressure at 0.05MPa. After the reaction was complete, the reactor was degassed under vacuum and cooled down to obtain the final product, polyether. The double bond retention rate was 96.2%.

[0025] Example 3

[0026] (1) Weigh 200g of methyl allyl alcohol and put it into the reactor. Add 0.93g (0.08%) of KOH, replace with nitrogen three times, and replenish nitrogen to make the pressure inside the reactor 0. Heat the reactor to 155℃ and continuously introduce 962.7g of ethylene oxide (EO) to carry out the ring-opening reaction. Control the pressure at 0.15MPa until the reaction is over. Then, degas under vacuum, cool down and discharge to obtain the intermediate.

[0027] (2) Weigh 200g of intermediate into the reactor, add 0.50g (0.05%) of KOH, replace with nitrogen three times, replenish nitrogen to make the pressure inside the reactor 0, heat the reactor to 150℃, continuously introduce 684.0g of ethylene oxide (EO) to carry out the ring-opening reaction, control the pressure at 0.15MPa, and after the reaction is complete, evacuate the vacuum to remove gas.

[0028] (3) Under negative pressure, 114.0 g of propylene oxide (PO) was continuously introduced into the reactor to carry out the ring-opening reaction. The temperature was controlled at 135℃ and the pressure at 0.15 MPa. After the reaction was complete, the gas was degassed by vacuuming and the product was discharged after cooling. The final product, polyether, was obtained. The double bond retention rate was 96.5%.

[0029] Example 4

[0030] (1) Weigh 200g of methyl allyl alcohol and put it into the reactor. Add 0.63g (0.06%) of KOH, replace with nitrogen three times, and replenish nitrogen to make the pressure inside the reactor 0. Heat the reactor to 149°C and continuously introduce 846.4g of ethylene oxide (EO) to carry out the ring-opening reaction. Control the pressure at 0.08MPa until the reaction is over. Then, degas under vacuum, cool down and discharge to obtain the intermediate.

[0031] (2) Weigh 200g of intermediate into the reactor, add 0.85g (0.08%) of KOH, replace with nitrogen three times, replenish nitrogen to make the pressure inside the reactor 0, heat the reactor to 135℃, continuously introduce 762.7g of ethylene oxide (EO) to carry out the ring-opening reaction, control the pressure at 0.08MPa, and after the reaction is complete, evacuate the vacuum to remove gas.

[0032] (3) Under negative pressure, 104.0g of propylene oxide (PO) was continuously introduced into the reactor to carry out the ring-opening reaction. The temperature was controlled at 128℃ and the pressure at 0.08MPa. After the reaction was complete, the gas was degassed by vacuuming and the product was discharged after cooling. The final product, polyether, was obtained. The double bond retention rate was 99.7%.

[0033] Those skilled in the art can implement the methods and procedures by appropriately modifying the conditions and routes described herein, even though the methods and preparation techniques of this invention have been described through preferred embodiments. It is evident that those skilled in the art can modify or recombine the methods and technical routes described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technique. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention. Matters not covered in this invention are considered public knowledge.

Claims

1. A method for synthesizing a polyether macromonomer for a polycarboxylate-type water reducing agent with high double bond retention, characterized by, Includes the following steps: (1) Add methyl allyl alcohol to the reactor, add 0.05%~0.08% KOH catalyst, remove air from the reactor by vacuuming, then add nitrogen to make the pressure inside the reactor 0, raise the temperature to 145~155℃, introduce ethylene oxide, and control the pressure to 0.05MPa, 0.08MPa, 0.1MPa or 0.15MPa. After the reaction is complete, remove gas by vacuuming, cool down and discharge the material to obtain the intermediate. (2) Put the intermediate from step (1) back into the reactor of step (1), add 0.05%~0.1% KOH catalyst, remove the air from the reactor by vacuuming, then add nitrogen to make the pressure inside the reactor 0, raise the temperature to 135~145℃, introduce ethylene oxide, and control the pressure to 0.05MPa, 0.08MPa, 0.1MPa or 0.15MPa. After the reaction is complete, remove the gas by vacuuming. (3) After step (2) is completed, propylene oxide is introduced, and the temperature is controlled at 125-135℃ and the pressure is 0.05MPa, 0.08MPa, 0.1MPa or 0.15MPa. After the reaction is complete, vacuum degassing is performed, the material is cooled and discharged to obtain the final product. In step (1), the amount of KOH used is the mass percentage of methyl allyl alcohol + ethylene oxide; The amount of KOH used in step (2) is the mass percentage of the intermediate + ethylene oxide + propylene oxide in step (3).

2. The synthesis method according to claim 1, characterized in that: In step (1), the amount of KOH used is 0.06%.

3. The synthesis method according to claim 1, characterized in that: In step (2), the amount of KOH used is 0.08%.

4. The synthesis method according to claim 1, characterized in that: In step (1), the molar ratio of methyl allyl alcohol to ethylene oxide is 1:4.0~7.

9.

5. The synthesis method according to claim 1, characterized in that: In step (2), the molar ratio of the intermediate to ethylene oxide is 1:32.5~37.

8.

6. The synthesis method according to claim 1, characterized in that: The molar ratio of the intermediate in step (2) to the propylene oxide in step (3) is 1:1.5~4.1.