An antifoaming agent based on ethoxylation reaction and its preparation method

Abstract

The present invention relates to an antifoaming agent based on ethoxylation reaction and a preparation method thereof, belonging to the technical field of antifoaming agents. The antifoaming agent of the present invention has a branched structure and contains multiple branched ethoxy chain segments. The core glycoluril group inside has good stability and hydrophilicity, which can reduce the surface viscosity of the liquid film, increase the drainage speed of the liquid film. The networked branched ethoxy chain segments can be effectively spread on the interface of the liquid film, reducing the surface tension at the spreading position, and causing the liquid inside the liquid film to move towards the position with high surface tension, prompting the liquid film to quickly become thinner and achieving defoaming. The spiroether bond and the bulky spiro structure near the networked branched ethoxy chain segments can form hydrogen bonds with hydrogen atoms in water, making the nearby glycoluril groups and ethoxy chain segments more likely to combine with water, promoting foam inhibition and defoaming. They can also prevent the networked branched ethoxy chain segments from approaching and entangling with each other, improving the dispersion uniformity of the networked branched ethoxy chain segments and increasing the foam inhibition and defoaming efficiency of the functional groups.

Description

Technical Field

[0001] The present invention relates to an antifoaming agent based on ethoxylation reaction and its preparation method, belonging to the technical field of antifoaming agents. Background Art

[0002] In industrial production in many fields such as chemical industry, food, textile, printing and dyeing, paper making, coating, oil extraction, medicine, and metal processing, a large amount of foam is often generated. The existence of foam will seriously affect the appearance and quality of products, and even cause the production to be unable to proceed normally. Using an antifoaming agent to remove foam is a simple and economical way. After adding a low-concentration antifoaming agent to the foaming system, it can effectively control the foam. Due to different foaming systems and production conditions, the antifoaming agents used are also different. To meet various needs, it is necessary to produce antifoaming agents with diverse varieties and different performances.

[0003] Among them, silicone-based antifoaming agents have many advantages such as high defoaming efficiency, low toxicity, antioxidant, non-toxic, odorless, and no side effects. However, their compatibility is slightly poor, emulsification problems are likely to occur, and the foam suppression ability is relatively poor. Polyether-based antifoaming agents are a type of antifoaming agent that has been widely studied at present. They are prepared by ring-opening polymerization reaction of ethylene oxide or propylene oxide and have good water solubility. However, the foam breaking rate of polyether-based antifoaming agents is relatively low, and a large amount of addition is required during use, which affects other properties of the foam system.

[0004] Chinese patent document CN104231258A discloses a polyether-based antifoaming agent and its preparation method. The polyether-based antifoaming agent is made from the following raw materials in parts by weight: 200 - 600 parts of an initiator, 1 - 5 parts of a catalyst, 760 - 1900 parts of propylene oxide, and 48 - 125 parts of stearic acid. The initiator is glycerol and / or propylene glycol. The preparation method is as follows: dissolve the initiator and the catalyst to a homogeneous phase, displace, raise the temperature, and dropwise add propylene oxide and stearic acid to react to obtain crude polyether; the crude polyether is washed, neutralized, adsorbed, dried, and filtered to obtain the finished polyether. The polyether disclosed in this patent document needs to have a relatively large addition amount to have a good defoaming effect during use, but its foam suppression effect is relatively poor. Summary of the Invention

[0005] The purpose of the present invention is to provide an antifoaming agent based on ethoxylation reaction and its preparation method to solve the problem that the existing polyether antifoaming agents have relatively poor foam suppression effect.

[0006] The present invention provides a preparation method of an antifoaming agent based on ethoxylation reaction, including the following steps:

[0007] (1) React 1,4-cyclohexanedione monoethylene ketal with vinylmagnesium bromide to obtain a spirocyclic alcohol olefin compound;

[0008] (2) Carry out an addition reaction on the spirocyclic alcohol olefin compound and the multi-mercapto compound under the action of an initiator to obtain a branched spirocyclic alcohol compound; the multi-mercapto compound is 1,3,4,6-tetra(mercaptomethyl)glycoluril, 1,3,4,6-tetra(2-mercaptoethyl)glycoluril or 1,3,4,6-tetra(3-mercaptopropyl)glycoluril; the molar ratio of the spirocyclic alcohol olefin compound to the multi-mercapto compound is 4.2-5:1;

[0009] (3) Carry out a ring-opening polymerization reaction on the branched spirocyclic alcohol compound and ethylene oxide under the action of a basic catalyst to obtain an ethoxylated product; the molar ratio of the branched spirocyclic alcohol compound to ethylene oxide is 1:35-40;

[0010] (4) Carry out an esterification reaction on the ethoxylated product and a fatty acid to obtain an antifoaming agent based on the ethoxylation reaction; the fatty acid is stearic acid, oleic acid, palmitic acid, arachidic acid or myristic acid.

[0011] Preferably, in step (1), the molar ratio of 1,4-cyclohexanedione monoethylene ketal to vinylmagnesium bromide is 3.2:3.3-3.6.

[0012] Preferably, in step (1), the reaction time of 1,4-cyclohexanedione monoethylene ketal and vinylmagnesium bromide is 3-5 h.

[0013] Preferably, in step (2), the initiator is azobisisobutyronitrile, and the molar ratio of the spirocyclic alcohol olefin compound, the multi-mercapto compound and azobisisobutyronitrile is 4.2-5:1:0.02-0.03.

[0014] Preferably, in step (2), the temperature of the addition reaction is 60-70 °C, and the time is 6-8 h.

[0015] Preferably, in step (3), the basic catalyst is potassium hydroxide, and the mass of potassium hydroxide is 1.8-2% of the mass of the branched spirocyclic alcohol compound.

[0016] Preferably, in step (3), the temperature of the ring-opening polymerization reaction is 100-110 °C, and the time is 18-24 h.

[0017] Preferably, in step (4), the catalyst used in the esterification reaction is p-toluenesulfonic acid, and the mass of p-toluenesulfonic acid is 0.3-0.5% of the sum of the masses of the ethoxylated product and the fatty acid.

[0018] Preferably, in step (4), the temperature of the esterification reaction is 150-160 °C, and the molar ratio of the hydroxyl group in the ethoxylated product to the carboxyl group in the fatty acid is 1:1.

[0019] The present invention also provides an antifoaming agent based on ethoxylation reaction prepared by the preparation method of the antifoaming agent based on ethoxylation reaction as described above.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The antifoaming agent of the present invention has a branched structure and contains multiple branched ethoxy chain segments. The glycoluril group in the internal core has good stability and hydrophilicity. It can reduce the surface viscosity of the liquid film, increase the drainage rate of the liquid film. The networked branched ethoxy chain segments can be effectively spread on the interface of the liquid film, reducing the surface tension at the spreading position, and causing the liquid in the liquid film to move towards the area with high surface tension, promoting the rapid thinning of the liquid film and achieving defoaming. The spiroether bond and the large steric hindrance spiro structure near the networked branched ethoxy chain segments can, on the one hand, form hydrogen bonds with hydrogen atoms in water, making the nearby glycoluril group and ethoxy chain segments more likely to combine with water, promoting foam inhibition and defoaming; on the other hand, they can prevent the networked branched ethoxy chain segments from approaching and winding around each other, improving the dispersion uniformity of the networked branched ethoxy chain segments and increasing the efficiency of the foam inhibition and defoaming functional groups. The ester group at the end of the molecular chain can improve the hydrophobicity of the antifoaming agent, reduce the surface tension, make the networked branched ethoxy chain segments more likely to spread on the interface of the liquid film, and improve the foam inhibition and defoaming effects.

[0022] (2) The antifoaming agent prepared by the present invention has good defoaming performance and foam inhibition performance at the same time. When the addition amount is 0.2%, the minimum foam inhibition time t 1 is 18 s, and the maximum defoaming time t 2 is 128 s. When the addition amount is 0.05%, the minimum foam inhibition time t 1 is 12 s, and the maximum defoaming time t 2 is 153 s. The present invention optimizes the performance of the antifoaming agent by adjusting the molecular weight of the branched ethoxy chain segments. When the molecular weight of the branched ethoxy chain segments is too large, the large steric hindrance spiro structure cannot effectively prevent the interference caused by the winding between each branch, resulting in a low dispersion degree of the ethoxy sites on the branches and poor defoaming effect. When the molecular weight of the branched ethoxy chain segments is too small, the number of ethoxy sites on the branches is also relatively small, resulting in insufficient foam inhibition and defoaming performance. Description of the Drawings

[0023] Figure 1 1H NMR spectrum of the branched spiro alcohol compound prepared in Example 1. Detailed Embodiments

[0024] The following examples are intended to further illustrate the content of the present invention rather than limit the protection scope of the present invention.

[0025] Specific embodiments of the antifoaming agent based on ethoxylation reaction and its preparation method of the present invention are as follows:

[0026] Example 1

[0027] The preparation method of the defoamer based on ethoxylation reaction in this example includes the following steps:

[0028] (1) Add 3.2 mol of 1,4 - cyclohexanedione monoethylene ketal to the reaction kettle, inject nitrogen for protection, then add 1500 mL of anhydrous tetrahydrofuran. At 0 °C, drop 3.3 mol of vinylmagnesium bromide into the reaction kettle. After the dropping is completed, at room temperature, continue to stir the materials in the reaction kettle for 3 h. Then add saturated sodium bicarbonate solution to the reaction kettle, stir evenly and then add ethyl acetate for extraction. The obtained organic phase is distilled under reduced pressure to remove the solvent to obtain a concentrate. The concentrate is purified by silica gel column chromatography (the eluent consists of ethyl acetate and petroleum ether with a volume ratio of 6:1) to obtain a spirocyclic alcohol olefin compound. Among them, the structural formula of 1,4 - cyclohexanedione monoethylene ketal is as follows:

[0029] ;

[0030] The structural formula of the spirocyclic alcohol olefin compound is as follows:

[0031] .

[0032] (2) Add the spirocyclic alcohol olefin compound, the multi - mercapto compound and tetrahydrofuran (the mass of tetrahydrofuran is 50% of the sum of the masses of the spirocyclic alcohol olefin compound and the multi - mercapto compound) to the reaction kettle. Then introduce nitrogen into the reaction kettle and heat to 60 °C. Under stirring, add azobisisobutyronitrile to the reaction kettle. After adding, continue to stir and react for 6 h. Distill under reduced pressure to remove the solvent. The concentrate is purified by silica gel column chromatography (the eluent consists of ethyl acetate and petroleum ether with a volume ratio of 8:1) to obtain a branched spirocyclic alcohol compound (the proton nuclear magnetic resonance spectrum of the branched spirocyclic alcohol compound is as shown in Figure 1 ). Among them, the multi - mercapto compound is 1,3,4,6 - tetra(mercaptomethyl)glycoluril, and the molar ratio of the spirocyclic alcohol olefin compound, the multi - mercapto compound and azobisisobutyronitrile is 4.2:1:0.02. The structural formula of 1,3,4,6 - tetra(mercaptomethyl)glycoluril is as follows:

[0033] ;

[0034] The structural formula of the branched spirocyclic alcohol compound is as follows:

[0035] .

[0036] (3) Add the branched spiroalcohol compound, ethylene oxide, and potassium hydroxide into a reaction kettle. Introduce nitrogen into the reaction kettle, then heat to 100 °C, stir and react for 18 h. Then add dilute hydrochloric acid into the reaction kettle to adjust the pH of the material to 7. Add adsorbent magnesium silicate, stir evenly, filter, collect the filtrate, and remove water by vacuum distillation to obtain the ethoxylated product. Among them, the molar ratio of the branched spiroalcohol compound to ethylene oxide is 1:35, and the mass of potassium hydroxide is 1.8% of the mass of the branched spiroalcohol compound.

[0037] (4) Add the ethoxylated product, fatty acid, and p-toluenesulfonic acid into a reaction kettle. Introduce nitrogen into the reaction kettle, then heat to 150 °C, stir and react until the acid value no longer changes, and then cool to room temperature to obtain the defoamer. Among them, the molar ratio of the hydroxyl group in the ethoxylated product to the carboxyl group in the fatty acid is 1:1, the mass of p-toluenesulfonic acid is 0.3% of the sum of the masses of the ethoxylated product and the fatty acid, and the fatty acid is stearic acid.

[0038] Example 2

[0039] The preparation method of the defoamer based on the ethoxylation reaction in this example includes the following steps:

[0040] (1) Add 3.2 mol of 1,4-cyclohexanedione monoethylene ketal into a reaction kettle, inject nitrogen for protection, then add 1800 mL of anhydrous tetrahydrofuran. Under the condition of 0 °C, dropwise add 3.4 mol of vinylmagnesium bromide into the reaction kettle. After the dropping is completed, at room temperature, continue to stir the materials in the reaction kettle and react for 4 h. Then add saturated sodium bicarbonate solution into the reaction kettle, stir evenly, add ethyl acetate, perform extraction, and distill the obtained organic phase under reduced pressure to remove the solvent to obtain a concentrate. Purify the concentrate by silica gel column chromatography (the eluent consists of ethyl acetate and petroleum ether with a volume ratio of 6:1) to obtain the spiroalcohol olefin compound.

[0041] (2) Add the spiroalcohol olefin compound, multi-mercapto compound, and tetrahydrofuran (the mass of tetrahydrofuran is 52% of the sum of the masses of the spiroalcohol olefin compound and the multi-mercapto compound) into a reaction kettle. Then introduce nitrogen into the reaction kettle, heat to 65 °C, and under stirring, add azobisisobutyronitrile into the reaction kettle. After adding, continue to stir and react for 7 h, distill under reduced pressure to remove the solvent, and purify the concentrate by silica gel column chromatography (the eluent consists of ethyl acetate and petroleum ether with a volume ratio of 8:1) to obtain the branched spiroalcohol compound. Among them, the multi-mercapto compound is 1,3,4,6-tetra(mercaptomethyl)glycoluril, and the molar ratio of the spiroalcohol olefin compound, the multi-mercapto compound, and azobisisobutyronitrile is 4.7:1:0.025.

[0042] (3) Add the branched spiroalcohol compound, ethylene oxide, and potassium hydroxide to the reaction kettle. Introduce nitrogen into the reaction kettle, then heat to 105 °C and stir for reaction for 20 h. Then add dilute hydrochloric acid to the reaction kettle, adjust the pH of the material to 7, add the adsorbent magnesium silicate, stir evenly, filter, collect the filtrate, and remove water by vacuum distillation to obtain the ethoxylated product. Among them, the molar ratio of the branched spiroalcohol compound to ethylene oxide is 1:37, and the mass of potassium hydroxide is 1.9% of the mass of the branched spiroalcohol compound.

[0043] (4) Add the ethoxylated product, fatty acid, and p-toluenesulfonic acid to the reaction kettle. Introduce nitrogen into the reaction kettle, then heat to 155 °C and stir until the acid value no longer changes, and then cool to room temperature to obtain the defoamer. Among them, the molar ratio of the hydroxyl group in the ethoxylated product to the carboxyl group in the fatty acid is 1:1, the mass of p-toluenesulfonic acid is 0.4% of the sum of the masses of the ethoxylated product and the fatty acid, and the fatty acid is stearic acid.

[0044] Example 3

[0045] The preparation method of the defoamer based on the ethoxylation reaction in this example includes the following steps:

[0046] (1) Add 3.2 mol of 1,4-cyclohexanedione monoethylene ketal to the reaction kettle, inject nitrogen for protection, then add 2000 mL of anhydrous tetrahydrofuran. Under the condition of 0 °C, dropwise add 3.6 mol of vinylmagnesium bromide to the reaction kettle. After the dropwise addition, continue to stir the material in the reaction kettle at room temperature for 5 h. Then add saturated sodium bicarbonate solution to the reaction kettle, stir evenly and then add ethyl acetate for extraction. Distill the extracted organic phase under reduced pressure to remove the solvent to obtain a concentrate. Purify the concentrate by silica gel column chromatography (the eluent consists of ethyl acetate and petroleum ether with a volume ratio of 6:1) to obtain the spiroalcohol olefin compound.

[0047] (2) Add the spiroalcohol olefin compound, multi-mercapto compound, and tetrahydrofuran (the mass of tetrahydrofuran is 55% of the sum of the masses of the spiroalcohol olefin compound and the multi-mercapto compound) to the reaction kettle. Then introduce nitrogen into the reaction kettle, heat to 70 °C, and under stirring, add azobisisobutyronitrile to the reaction kettle. After adding, continue to stir and react for 8 h, distill under reduced pressure to remove the solvent, and purify the concentrate by silica gel column chromatography (the eluent consists of ethyl acetate and petroleum ether with a volume ratio of 8:1) to obtain the branched spiroalcohol compound. Among them, the multi-mercapto compound is 1,3,4,6-tetra(mercaptomethyl)glycoluril, and the molar ratio of the spiroalcohol olefin compound, multi-mercapto compound, and azobisisobutyronitrile is 5:1:0.03.

[0048] (3) Add the branched spiroalcohol compound, ethylene oxide, and potassium hydroxide into a reaction kettle. Introduce nitrogen into the reaction kettle, then heat to 110 °C, stir and react for 24 h. Then add dilute hydrochloric acid into the reaction kettle, adjust the pH of the material to 7, add the adsorbent magnesium silicate, stir evenly, filter, collect the filtrate, and remove water by vacuum distillation to obtain the ethoxylated product. Among them, the molar ratio of the branched spiroalcohol compound to ethylene oxide is 1:40, and the mass of potassium hydroxide is 2% of the mass of the branched spiroalcohol compound.

[0049] (4) Add the ethoxylated product, fatty acid, and p-toluenesulfonic acid into a reaction kettle. Introduce nitrogen into the reaction kettle, then heat to 160 °C, stir and react until the acid value no longer changes, and then cool to room temperature to obtain the defoamer. Among them, the molar ratio of the hydroxyl group in the ethoxylated product to the carboxyl group in the fatty acid is 1:1, the mass of p-toluenesulfonic acid is 0.5% of the sum of the masses of the ethoxylated product and the fatty acid, and the fatty acid is stearic acid.

[0050] Example 4

[0051] The difference between the preparation method of the defoamer based on ethoxylation reaction in this example and the preparation method of the defoamer based on ethoxylation reaction in Example 2 is only that the multi-mercapto compound in step (2) of the preparation method of the defoamer based on ethoxylation reaction in this example is 1,3,4,6-tetrakis(2-mercaptoethyl)glycoluril, and the structural formula of 1,3,4,6-tetrakis(2-mercaptoethyl)glycoluril is as follows:

[0052] .

[0053] Example 5

[0054] The difference between the preparation method of the defoamer based on ethoxylation reaction in this example and the preparation method of the defoamer based on ethoxylation reaction in Example 2 is only that the multi-mercapto compound in step (2) of the preparation method of the defoamer based on ethoxylation reaction in this example is 1,3,4,6-tetrakis(3-mercaptopropyl)glycoluril, and the structural formula of 1,3,4,6-tetrakis(3-mercaptopropyl)glycoluril is as follows:

[0055] .

[0056] Example 6

[0057] The difference between the preparation method of the defoamer based on ethoxylation reaction in this example and the preparation method of the defoamer based on ethoxylation reaction in Example 2 is only that the fatty acid in step (4) of the preparation method of the defoamer based on ethoxylation reaction in this example is oleic acid.

[0058] Example 7

[0059] The preparation method of the defoamer based on ethoxylation reaction in this example is only different from the preparation method of the defoamer based on ethoxylation reaction in Example 2 in that the fatty acid in step (4) of the preparation method of the defoamer based on ethoxylation reaction in this example is palmitic acid.

[0060] Example 8

[0061] The preparation method of the defoamer based on ethoxylation reaction in this example is only different from the preparation method of the defoamer based on ethoxylation reaction in Example 2 in that the fatty acid in step (4) of the preparation method of the defoamer based on ethoxylation reaction in this example is arachidic acid.

[0062] Example 9

[0063] The preparation method of the defoamer based on ethoxylation reaction in this example is only different from the preparation method of the defoamer based on ethoxylation reaction in Example 2 in that the fatty acid in step (4) of the preparation method of the defoamer based on ethoxylation reaction in this example is myristic acid.

[0064] Comparative Example 1

[0065] The preparation method of the defoamer based on ethoxylation reaction in this comparative example is only different from the preparation method of the defoamer based on ethoxylation reaction in Example 2 in that the branched spirocyclic alcohol compound is replaced by sorbitol in step (3) of the preparation method of the defoamer based on ethoxylation reaction in this comparative example.

[0066] Comparative Example 2

[0067] The preparation method of the defoamer based on ethoxylation reaction in this comparative example is only different from the preparation method of the defoamer based on ethoxylation reaction in Example 2 in that the molar ratio of the branched spirocyclic alcohol compound to ethylene oxide in step (3) of the preparation method of the defoamer based on ethoxylation reaction in this comparative example is 1:30.

[0068] Comparative Example 3

[0069] The preparation method of the defoamer based on ethoxylation reaction in this comparative example is only different from the preparation method of the defoamer based on ethoxylation reaction in Example 2 in that the molar ratio of the branched spirocyclic alcohol compound to ethylene oxide in step (3) of the preparation method of the defoamer based on ethoxylation reaction in this comparative example is 1:45.

[0070] Effect Example

[0071] To investigate the defoaming and foam inhibition effects of the defoamers prepared in each example and comparative example, a sodium dodecyl sulfate solution with a mass fraction of 2% and a defoamer (the mass of the defoamer is 0.2% or 0.05% of the mass of the sodium dodecyl sulfate solution) were added to a beaker and stirred with a stirrer. During the stirring process, the foam height gradually increased. The time when the foam height reached 30 cm was recorded as t 1 , and then the stirring was stopped. The foam height gradually decreased, and the time required for all the foam to disappear was recorded as t 2 . Among them, the time t 1 is used to reflect the foam inhibition effect of the defoamer. The larger the value, the better the foam inhibition effect of the defoamer and the less likely it is to form foam; the time t 2 is used to reflect the defoaming effect of the defoamer. The smaller the value, the better the defoaming effect of the defoamer. The defoaming and foam inhibition effects of the defoamers prepared in each example and comparative example are shown in Table 1.

[0072] Table 1 Defoaming and foam inhibition effects of the defoamers prepared in each example and comparative example

[0073]

[0074] As can be seen from Table 1, the defoamer prepared by the present invention has both good defoaming performance and foam inhibition performance. When the addition amount is 0.2%, the minimum foam inhibition time t 1 is 18 s, and the maximum defoaming time t 2 is 128 s. When the addition amount is 0.05%, the minimum foam inhibition time t 1 is 12 s, and the maximum defoaming time t 2 is 153 s. The above results show that: the defoamer of the present invention has a branched structure and contains multiple branched ethoxy chain segments. The glycoluril group in the internal core has good stability and hydrophilicity. It can reduce the surface viscosity of the liquid film, increase the drainage speed of the liquid film. The networked branched ethoxy chain segments can be effectively spread on the interface of the liquid film, reducing the surface tension at the spreading site. The liquid in the liquid film moves towards the area with high surface tension, prompting the liquid film to quickly become thinner and achieving defoaming. The spiro ether bond and the large steric hindrance spiro structure near the networked branched ethoxy chain segments can, on the one hand, form hydrogen bonds with hydrogen atoms in water, making the nearby glycoluril group and ethoxy chain segments more likely to combine with water, promoting foam inhibition and defoaming; on the other hand, they can prevent the networked branched ethoxy chain segments from approaching and entangling with each other, improving the dispersion uniformity of the networked branched ethoxy chain segments and enhancing the foam inhibition and defoaming efficiency of the functional groups. The ester group at the end of the molecular chain can improve the hydrophobicity of the defoamer, reduce the surface tension, make the networked branched ethoxy chain segments more likely to spread on the interface of the liquid film, and improve the foam inhibition and defoaming effects.

[0075] As can be seen from Example 2 and Examples 4-5, when the structure of the multi-mercapto compound is changed, the distance between the glycoluril group and the large steric hindrance spiro ring structure changes, and the length of the hydrophobic carbon chain also changes simultaneously. The foam inhibition and defoaming properties of the prepared defoamer also change. With the increase in the length of the hydrophobic carbon chain, it shows a trend of first increasing and then decreasing. This may be because when the length of the hydrophobic carbon chain is too long, the branched ethoxy chain segments are prone to entanglement, which in turn interferes with each other, and then reduces the dispersion degree of the action sites. When the length of the hydrophobic carbon chain is too short, its hydrophobicity is slightly poor, and it is not easy to reduce the surface tension, resulting in slightly poor foam inhibition and defoaming properties.

[0076] As can be seen from Example 2 and Examples 6-9, the length of the ester group carbon chain at the molecular end also has a certain influence on the foam inhibition and defoaming properties of the defoamer. With the increase in the length of the ester group carbon chain from 14 carbon atoms to 20 carbon atoms, the foam inhibition and defoaming properties of the defoamer show a trend of first increasing and then decreasing. And the foam inhibition and defoaming properties of the defoamer prepared from oleic acid containing unsaturated bonds are slightly poor. This may be because with the increase in the number of carbon chains, the hydrophobicity increases, the surface tension decreases, and the network branched ethoxy chain segments are more likely to spread on the interface of the liquid film, thereby improving the foam inhibition and defoaming properties. However, when the number of carbon chains is too large, its hydrophobicity is too strong, which is not conducive to the contact between the defoamer and the aqueous foam system, resulting in poor affinity between the two and unable to spread effectively on the interface of the liquid film.

[0077] As can be seen from Example 2 and Comparative Example 1, when the branched spiro alcohol compound is replaced with sorbitol, although both are quaternary alcohols, sorbitol has too strong hydrophobicity and lacks the hydrophilic glycoluril group and the large steric hindrance spiro ring structure, resulting in poor foam inhibition and defoaming properties of the defoamer.

[0078] As can be seen from Example 2 and Comparative Examples 2-3, when adjusting the molecular weight or length of the branched ethoxy chain segments by changing the molar ratio of the branched spiro alcohol compound and ethylene oxide, the foam inhibition and defoaming properties of the defoamer will also change greatly. When the molecular weight of the branched ethoxy chain segments is too large, the large steric hindrance spiro ring structure cannot effectively prevent the interference caused by the entanglement between the branched chains, resulting in a low dispersion degree of the ethoxy sites on the branched chains and poor defoaming effect. When the molecular weight of the branched ethoxy chain segments is too small, the number of ethoxy sites on the branched chains is small, resulting in insufficient foam inhibition and defoaming properties.

Claims

1. A method for preparing a defoamer based on ethoxylation reaction, characterized in that: The following steps are involved: (1) reacting 1,4-cyclohexanedione monoethylene glycol acetal with vinyl magnesium bromide to obtain a spirocyclic alcohol olefin compound; (2) subjecting a spiro alcohol olefin compound and a polythiol compound to an addition reaction under the action of an initiator to obtain a branched spiro alcohol compound; the polythiol compound is 1,3,4,6-tetrakis(mercaptomethyl)glycoluril, 1,3,4,6-tetrakis(2-mercaptoethyl)glycoluril or 1,3,4,6-tetrakis(3-mercaptopropyl)glycoluril; and the molar ratio of the spiro alcohol olefin compound to the polythiol compound is 4.2-5:1; (3) subjecting the branched spiro alcohol compound and ethylene oxide to a ring-opening polymerization reaction under the action of an alkaline catalyst to obtain an ethoxylated product; the molar ratio of the branched spiro alcohol compound to the ethylene oxide is 1:35-40; (4) subjecting the ethoxylated product to an esterification reaction with a fatty acid to obtain a defoaming agent based on an ethoxylation reaction; the fatty acid is stearic acid, oleic acid, palmitic acid, arachidic acid or myristic acid.

2. The method for preparing a defoamer based on ethoxylation reaction according to claim 1, characterized in that: In step (1), the molar ratio of 1,4-cyclohexanedione monoethylene glycol acetal to vinyl magnesium bromide is 3.2:3.3-3.

6.

3. The method for preparing a defoamer based on ethoxylation reaction according to claim 1 or 2, characterized in that: In step (1), the reaction time of 1,4-cyclohexanedione monoethylene glycol acetal and vinyl magnesium bromide is 3 to 5 hours.

4. The method for preparing a defoamer based on ethoxylation reaction according to claim 1, wherein: In step (2), the initiator is azobisisobutyronitrile, and the molar ratio of the spirocyclic alcohol olefin compound, the polythiol compound and azobisisobutyronitrile is 4.2-5:1:0.02-0.

03.

5. The method for preparing a defoamer based on ethoxylation reaction according to claim 1 or 4, characterized in that: In step (2), the temperature of the addition reaction is 60-70°C and the time is 6-8 hours.

6. The method for preparing a defoamer based on ethoxylation reaction according to claim 1, characterized in that: In step (3), the alkaline catalyst is potassium hydroxide, and the mass of potassium hydroxide is 1.8-2% of the mass of the branched spirocyclic alcohol compound.

7. The method for preparing a defoamer based on ethoxylation reaction according to claim 1 or 6, characterized in that: In step (3), the temperature of the ring-opening polymerization reaction is 100-110° C. and the time is 18-24 hours.

8. The method for preparing a defoamer based on ethoxylation reaction according to claim 1, wherein: In step (4), the catalyst used in the esterification reaction is p-toluenesulfonic acid, and the mass of p-toluenesulfonic acid is 0.3-0.5% of the sum of the mass of the ethoxylation product and the fatty acid.

9. The method for preparing a defoamer based on ethoxylation reaction according to claim 1 or 8, characterized in that: In step (4), the temperature of the esterification reaction is 150-160° C., and the molar ratio of the hydroxyl group in the ethoxylated product to the carboxyl group in the fatty acid is 1:

1.

10. A defoamer based on ethoxylation reaction prepared by the method for preparing a defoamer based on ethoxylation reaction according to any one of claims 1 to 9.

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