Defoaming agent based on ethoxylation reaction and preparation method thereof

Abstract

The invention relates to a defoaming agent based on ethoxylation reaction and a preparation method thereof, and belongs to the technical field of defoaming agents. The defoaming agent is of a branched structure and contains multiple ethyoxyl chain segments, a glycoluril group of an internal core has good stability and hydrophilicity, the surface viscosity of a liquid film can be reduced, the liquid drainage speed of the liquid film can be increased, the net-shaped branched ethyoxyl chain segments can be effectively spread on an interface of the liquid film, the surface tension of the spread position is reduced, and the defoaming effect is good. And the liquid in the liquid film moves to a high surface tension position, so that the liquid film is rapidly thinned, and defoaming is realized. Spiro-ether bonds and large-steric-hindrance spiro structures near net-shaped branched-chain ethyoxyl chain segments can form hydrogen bonds with hydrogen atoms in water, so that glycoluril groups and ethyoxyl chain segments near the net-shaped branched-chain ethyoxyl chain segments can be combined with water more easily, foam inhibition and defoaming are promoted, the net-shaped branched-chain ethyoxyl chain segments can be prevented from getting close to each other and being wound, and the foam inhibition effect is improved. The dispersion uniformity of a net-shaped branched-chain ethyoxyl chain segment is improved, and the foam inhibition and defoaming efficiency of a functional group is improved.

Description

Technical Field

[0001] The invention relates to a defoamer based on ethoxylation reaction and a preparation method thereof, belonging to the technical field of defoamers. Background Art

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

[0003] Among them, silicone defoamers have many advantages such as high defoaming efficiency, low toxicity, anti-oxidation, non-toxicity, tastelessness, and no side effects, but their compatibility is slightly poor, prone to emulsification problems, and poor anti-foaming ability. Polyether defoamers are a type of defoamer that is currently widely studied. They are made by ring-opening polymerization of ethylene oxide or propylene oxide and have good water solubility. However, the foam breaking rate of polyether defoamers is low, and the amount added when used is large, which affects other properties of the foam system.

[0004] Chinese patent document CN104231258A discloses a polyether defoamer and a preparation method thereof, wherein the polyether defoamer is made of the following raw materials in parts by weight: 200-600 parts of initiator, 1-5 parts of catalyst, 760-1900 parts of propylene oxide, 48-125 parts of stearic acid, wherein the initiator is glycerol and / or propylene glycol, and the preparation method thereof is as follows: dissolving the initiator and the catalyst into a homogeneous phase, displacing, heating, dripping propylene oxide and stearic acid to react to obtain a crude polyether; the crude polyether is washed, neutralized, adsorbed, dried, and filtered to obtain a finished polyether. The polyether disclosed in the patent document needs to have a better defoaming effect when the addition amount is large during use, but its anti-foaming effect is biased. Summary of the invention

[0005] The object of the present invention is to provide a defoamer based on ethoxylation reaction and a preparation method thereof, so as to solve the problem that the current polyether defoamer has a deviation in the antifoaming effect.

[0006] The present invention provides a method for preparing a defoamer based on ethoxylation reaction, comprising the following steps: (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 to 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 to 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.

[0007] Preferably, in step (1), the molar ratio of 1,4-cyclohexanedione monoethylene glycol acetal to vinyl magnesium bromide is 3.2:3.3-3.6.

[0008] Preferably, in step (1), the reaction time of 1,4-cyclohexanedione monoethylene glycol acetal and vinyl magnesium bromide is 3 to 5 hours.

[0009] Preferably, in step (2), the initiator is azobisisobutyronitrile, and the molar ratio of the spirool olefin compound, the polythiol compound and azobisisobutyronitrile is 4.2-5:1:0.02-0.03.

[0010] Preferably, in step (2), the temperature of the addition reaction is 60-70° C. and the time is 6-8 h.

[0011] Preferably, 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 spiro alcohol compound.

[0012] Preferably, in step (3), the temperature of the ring-opening polymerization reaction is 100 to 110° C., and the time is 18 to 24 hours.

[0013] 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 mass of the ethoxylation product and the fatty acid.

[0014] Preferably, in step (4), the temperature of the esterification reaction is 150-160° C., and the molar ratio of the hydroxyl group in the ethoxylation product to the carboxyl group in the fatty acid is 1:1.

[0015] The present invention also provides an ethoxylation-based defoamer prepared by the above-mentioned method for preparing an ethoxylation-based defoamer.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The defoamer of the present invention is a branched structure containing multiple ethoxy segments. The internal core glycoluril group has good stability and hydrophilicity, which can reduce the surface viscosity of the liquid film and increase the liquid film drainage speed. The network branched ethoxy segments can effectively spread on the interface of the liquid film, reduce the surface tension at the spreading point, and move the liquid in the liquid film to the high surface tension point, so that the liquid film quickly becomes thinner and defoaming is achieved. The spirocyclic ether bond and large steric hindered spirocyclic structure near the network branched ethoxy segments can form hydrogen bonds with hydrogen atoms in water, making it easier for the glycoluril groups and ethoxy segments near them to combine with water, promoting foam suppression and defoaming; on the other hand, it can prevent the network branched ethoxy segments from approaching each other and entanglement, improve the dispersion uniformity of the network branched ethoxy segments, and increase the efficiency of the anti-foam and defoaming 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 network branched ethoxy segments easier to spread on the interface of the liquid film, and improve the anti-foam and defoaming effect.

[0017] (2) The defoamer prepared by the present invention has good defoaming performance and antifoaming performance. When the addition amount is 0.2%, the antifoaming time t1 is at least 18s, and the defoaming time t2 is at most 128s. When the addition amount is 0.05%, the antifoaming time t1 is at least 12s, and the defoaming time t2 is at most 153s. The present invention optimizes the performance of the defoamer by adjusting the molecular weight of the branched ethoxy chain segment. When the molecular weight of the branched ethoxy chain segment is too large, the large steric hindered spirocyclic structure cannot effectively hinder the interference caused by entanglement between the branches, resulting in a low degree of dispersion of the ethoxy sites on the branch chain and a poor defoaming effect. When the molecular weight of the branched ethoxy chain segment is too small, the number of ethoxy sites on the branch chain is also relatively small, resulting in insufficient antifoaming and defoaming performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the H NMR spectrum of the branched spirocyclic alcohol compound prepared in Example 1. DETAILED DESCRIPTION

[0019] The following examples are intended to further illustrate the present invention rather than to limit the scope of protection of the present invention.

[0020] The specific embodiments of the defoamer based on ethoxylation reaction and the preparation method thereof of the present invention are as follows: Example 1 The preparation method of the defoamer based on ethoxylation reaction in this embodiment comprises the following steps: (1) 3.2 mol of 1,4-cyclohexanedione monoethylene glycol acetal was added to a reactor, and nitrogen was injected for protection. Then 1500 mL of anhydrous tetrahydrofuran was added. At 0°C, 3.3 mol of vinyl magnesium bromide was added dropwise to the reactor. After the addition was completed, the materials in the reactor were stirred and reacted for 3 hours at room temperature. Then saturated sodium bicarbonate solution was added to the reactor, and ethyl acetate was added after stirring evenly to extract. The organic phase obtained by extraction was distilled under reduced pressure to remove the solvent to obtain a concentrate. The concentrate was purified by silica gel column chromatography (the eluent was composed of ethyl acetate and petroleum ether in a volume ratio of 6:1) to obtain a spirocyclic alcohol olefin compound. Among them, the structural formula of 1,4-cyclohexanedione monoethylene glycol acetal is as follows: ; The structural formula of the spirocyclic alcohol olefin compound is as follows: .

[0021] (2) Add the spiro alcohol olefin compound, the polythiol compound and tetrahydrofuran (the mass of tetrahydrofuran is 50% of the sum of the mass of the spiro alcohol olefin compound and the polythiol compound) into a reactor, then introduce nitrogen into the reactor and heat it to 60°C. Add azobisisobutyronitrile into the reactor under stirring. After adding, continue stirring and react for 6 hours. Distill under reduced pressure to remove the solvent, and purify the concentrate by silica gel column chromatography (the eluent is composed of ethyl acetate and petroleum ether in a volume ratio of 8:1) to obtain a branched spiro alcohol compound (the nuclear magnetic hydrogen spectrum of the branched spiro alcohol compound is shown in FIG. Figure 1 As shown). Among them, the polythiol compound is 1,3,4,6-tetrakis (mercaptomethyl) glycoluril, and the molar ratio of the spirocyclic alcohol olefin compound, the polythiol compound and azobisisobutyronitrile is 4.2:1:0.02. The structural formula of 1,3,4,6-tetrakis (mercaptomethyl) glycoluril is as follows: ; The structural formula of the branched spirocyclic alcohol compound is as follows: .

[0022] (3) Add the branched spiro alcohol compound, ethylene oxide and potassium hydroxide into a reactor, introduce nitrogen into the reactor, heat to 100°C, stir and react for 18 hours, then add dilute hydrochloric acid to the reactor to adjust the pH of the material to 7, add adsorbent magnesium silicate, stir evenly, filter, collect the filtrate, and remove water by reduced pressure distillation to obtain an ethoxylated product. The molar ratio of the branched spiro alcohol compound to ethylene oxide is 1:35, and the mass of potassium hydroxide is 1.8% of the mass of the branched spiro alcohol compound.

[0023] (4) Add the ethoxylated product, fatty acid and p-toluenesulfonic acid into a reactor, introduce nitrogen into the reactor, heat to 150°C, stir and react until the acid value no longer changes, and cool to room temperature to obtain a defoaming agent. 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 mass of the ethoxylated product and the fatty acid, and the fatty acid is stearic acid.

[0024] Example 2 The preparation method of the defoamer based on ethoxylation reaction in this embodiment comprises the following steps: (1) 3.2 mol of 1,4-cyclohexanedione monoethylene glycol acetal was added to a reaction kettle, and nitrogen was injected for protection. Then, 1800 mL of anhydrous tetrahydrofuran was added. At 0°C, 3.4 mol of vinyl magnesium bromide was added dropwise to the reaction kettle. After the addition was completed, the materials in the reaction kettle were stirred and reacted for 4 hours at room temperature. Then, saturated sodium bicarbonate solution was added to the reaction kettle, and ethyl acetate was added after stirring evenly to extract. The organic phase obtained by the extraction was distilled under reduced pressure to remove the solvent to obtain a concentrate. The concentrate was purified by silica gel column chromatography (the eluent was composed of ethyl acetate and petroleum ether in a volume ratio of 6:1) to obtain a spirocyclic alcohol olefin compound.

[0025] (2) Add the spiro alcohol olefin compound, the polythiol compound and tetrahydrofuran (the mass of tetrahydrofuran is 52% of the mass of the spiro alcohol olefin compound and the polythiol compound) into a reactor, then introduce nitrogen into the reactor, heat to 65°C, add azobisisobutyronitrile into the reactor under stirring, continue stirring and react for 7 hours, distill under reduced pressure to remove the solvent, and purify the concentrate by silica gel column chromatography (the eluent is composed of ethyl acetate and petroleum ether in a volume ratio of 8:1) to obtain a branched spiro alcohol compound. The polythiol compound is 1,3,4,6-tetrakis(mercaptomethyl)glycoluril, and the molar ratio of the spiro alcohol olefin compound, the polythiol compound and azobisisobutyronitrile is 4.7:1:0.025.

[0026] (3) Add the branched spiro alcohol compound, ethylene oxide and potassium hydroxide into a reactor, introduce nitrogen into the reactor, heat to 105°C, stir and react for 20 hours, then add dilute hydrochloric acid to the reactor 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 an ethoxylated product. The molar ratio of the branched spiro alcohol compound to ethylene oxide is 1:37, and the mass of potassium hydroxide is 1.9% of the mass of the branched spiro alcohol compound.

[0027] (4) Add the ethoxylated product, fatty acid and p-toluenesulfonic acid into a reaction kettle, introduce nitrogen into the reaction kettle, heat to 155°C, stir and react until the acid value no longer changes, and cool to room temperature to obtain a defoaming agent. 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 mass of the ethoxylated product and the fatty acid, and the fatty acid is stearic acid.

[0028] Example 3 The preparation method of the defoamer based on ethoxylation reaction in this embodiment comprises the following steps: (1) 3.2 mol of 1,4-cyclohexanedione monoethylene glycol acetal was added to a reaction kettle, and nitrogen was injected for protection. Then, 2000 mL of anhydrous tetrahydrofuran was added. At 0°C, 3.6 mol of vinyl magnesium bromide was added dropwise to the reaction kettle. After the addition was completed, the materials in the reaction kettle were stirred and reacted for 5 hours at room temperature. Then, saturated sodium bicarbonate solution was added to the reaction kettle, and ethyl acetate was added after stirring evenly to extract. The organic phase obtained by extraction was distilled under reduced pressure to remove the solvent to obtain a concentrate. The concentrate was purified by silica gel column chromatography (the eluent was composed of ethyl acetate and petroleum ether in a volume ratio of 6:1) to obtain a spirocyclic alcohol olefin compound.

[0029] (2) Add the spiro alcohol olefin compound, the polythiol compound and tetrahydrofuran (the mass of tetrahydrofuran is 55% of the mass of the spiro alcohol olefin compound and the polythiol compound) into a reactor, then introduce nitrogen into the reactor, heat to 70°C, add azobisisobutyronitrile into the reactor under stirring, continue stirring and react for 8 hours, distill under reduced pressure to remove the solvent, and purify the concentrate by silica gel column chromatography (the eluent is composed of ethyl acetate and petroleum ether in a volume ratio of 8:1) to obtain a branched spiro alcohol compound. The polythiol compound is 1,3,4,6-tetrakis(mercaptomethyl)glycoluril, and the molar ratio of the spiro alcohol olefin compound, the polythiol compound and azobisisobutyronitrile is 5:1:0.03.

[0030] (3) Add the branched spiro alcohol compound, ethylene oxide and potassium hydroxide into a reactor, introduce nitrogen into the reactor, heat to 110°C, stir and react for 24 hours, then add dilute hydrochloric acid to the reactor 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 an ethoxylated product. The molar ratio of the branched spiro alcohol compound to ethylene oxide is 1:40, and the mass of potassium hydroxide is 2% of the mass of the branched spiro alcohol compound.

[0031] (4) Add the ethoxylated product, fatty acid and p-toluenesulfonic acid into a reactor, introduce nitrogen into the reactor, heat to 160°C, stir and react until the acid value no longer changes, and cool to room temperature to obtain a defoaming agent. 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 mass of the ethoxylated product and the fatty acid, and the fatty acid is stearic acid.

[0032] Example 4 The difference between the preparation method of the defoamer based on ethoxylation reaction in this embodiment and the preparation method of the defoamer based on ethoxylation reaction in Example 2 is that the polythiol compound in step (2) of the preparation method of the defoamer based on ethoxylation reaction in this embodiment 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: .

[0033] Example 5 The difference between the preparation method of the defoamer based on ethoxylation reaction in this embodiment and the preparation method of the defoamer based on ethoxylation reaction in Example 2 is that the polythiol compound in step (2) of the preparation method of the defoamer based on ethoxylation reaction in this embodiment 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: .

[0034] Example 6 The difference between the method for preparing a defoamer based on ethoxylation reaction in this embodiment and the method for preparing a defoamer based on ethoxylation reaction in Example 2 is that the fatty acid in step (4) of the method for preparing a defoamer based on ethoxylation reaction in this embodiment is oleic acid.

[0035] Example 7 The difference between the method for preparing a defoamer based on ethoxylation reaction in this embodiment and the method for preparing a defoamer based on ethoxylation reaction in Example 2 is that the fatty acid in step (4) of the method for preparing a defoamer based on ethoxylation reaction in this embodiment is palmitic acid.

[0036] Example 8 The difference between the method for preparing a defoamer based on ethoxylation reaction in this embodiment and the method for preparing a defoamer based on ethoxylation reaction in Example 2 is that the fatty acid in step (4) of the method for preparing a defoamer based on ethoxylation reaction in this embodiment is arachidic acid.

[0037] Example 9 The difference between the method for preparing a defoamer based on ethoxylation reaction in this embodiment and the method for preparing a defoamer based on ethoxylation reaction in Example 2 is that the fatty acid in step (4) of the method for preparing a defoamer based on ethoxylation reaction in this embodiment is myristic acid.

[0038] Comparative Example 1 The difference between the preparation method of the defoamer based on ethoxylation reaction in this comparative example and the preparation method of the defoamer based on ethoxylation reaction in Example 2 is that in step (3) of the preparation method of the defoamer based on ethoxylation reaction in this comparative example, the branched spirocyclic alcohol compound is replaced by sorbitol.

[0039] Comparative Example 2 The difference between the preparation method of the defoamer based on ethoxylation reaction in this comparative example and the preparation method of the defoamer based on ethoxylation reaction in Example 2 is that the molar ratio of the branched spiro 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.

[0040] Comparative Example 3 The difference between the preparation method of the defoamer based on ethoxylation reaction in this comparative example and the preparation method of the defoamer based on ethoxylation reaction in Example 2 is that the molar ratio of the branched spiro 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.

[0041] Effect example In order to investigate the defoaming and antifoaming effects of the defoaming agents prepared in various embodiments and comparative examples, a 2% mass fraction of sodium dodecyl sulfate solution and a defoaming agent (the mass of the defoaming agent 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 rose, and the time when the foam height reached 30 cm was recorded as t1. Then the stirring was stopped, the foam height gradually decreased, and the time required for all the foam to disappear was recorded as t2. Among them, time t1 is used to reflect the antifoaming effect of the defoaming agent. The larger its value, the better the antifoaming effect of the defoaming agent, and the less likely it is to foam; time t2 is used to reflect the defoaming effect of the defoaming agent. The smaller its value, the better the defoaming effect of the defoaming agent. The defoaming and antifoaming effects of the defoaming agents prepared in various embodiments and comparative examples are shown in Table 1.

[0042] Table 1 Defoaming and antifoaming effects of the defoamers prepared in various embodiments and comparative examples

[0043] As can be seen from Table 1, the defoamer prepared by the present invention has good defoaming performance and anti-foaming performance. When the addition amount is 0.2%, the minimum anti-foaming time t1 is 18s, and the maximum anti-foaming time t2 is 128s. When the addition amount is 0.05%, the minimum anti-foaming time t1 is 12s, and the maximum anti-foaming time t2 is 153s. The above results show that the defoamer of the present invention is a branched structure, containing multiple ethoxy segments, and the internal core glycoluril group has good stability and hydrophilicity, which can reduce the surface viscosity of the liquid film and increase the drainage speed of the liquid film. The network branched ethoxy segments can be effectively spread on the interface of the liquid film, so that the surface tension at the spreading place is reduced, and the liquid in the liquid film moves to the high surface tension place, prompting the liquid film to become thinner rapidly, and achieving defoaming. On the one hand, the spiro ether bond and large sterically hindered spiro ring structure near the network branched ethoxy chain segment can form hydrogen bonds with hydrogen atoms in water, making it easier for the nearby glycoluril groups and ethoxy chain segments to combine with water, promoting foam suppression and defoaming; on the other hand, it can prevent the network branched ethoxy chain segments from approaching and entangled with each other, improve the dispersion uniformity of the network branched ethoxy chain segments, and improve the foam suppression 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 network branched ethoxy chain segments easier to spread on the interface of the liquid film, and improve the foam suppression and defoaming effect.

[0044] It can be seen from Examples 2 and 4-5 that when the structure of the polythiol compound is changed, the distance between the glycoluril group and the large steric spirocyclic structure changes, and the length of the hydrophobic carbon chain also changes at the same time, and the antifoaming and defoaming properties of the prepared defoamer also change. As the length of the hydrophobic carbon chain increases, it shows a trend of first increasing and then decreasing. This may be due to the fact that the length of the hydrophobic carbon chain is too long, which makes the branched ethoxy chain segments easy to entangle and then interfere with each other, thereby reducing the degree of dispersion of the action site. 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 antifoaming and defoaming properties.

[0045] As shown in Example 2 and Example 6-9, the ester carbon chain length at the end of the molecule also has a certain influence on the foam suppression and defoaming performance of the defoamer. As the ester carbon chain length increases, when it increases from 14 carbon atoms to 20 carbon atoms, the foam suppression and defoaming performance of the defoamer present a trend of first increasing and then decreasing, and the foam suppression and defoaming performance of the defoamer prepared by oleic acid containing unsaturated bonds are slightly poor. This may be due to the increase of carbon chains, hydrophobicity increases, surface tension decreases, and the network branched ethoxy chain segment is easier to spread on the interface of the liquid film, thereby improving and suppressing foam and defoaming performance, but when the carbon chain is too much, its hydrophobicity is too strong, which is not conducive to the contact between the defoamer and the aqueous foam system, resulting in the deterioration of the affinity of the two, and it is impossible to effectively spread on the interface of the liquid film.

[0046] It can be seen from Example 2 and Comparative Example 1 that when the branched spiro alcohol compound is replaced with sorbitol, although both are tetrahydric alcohols, sorbitol is too hydrophobic and lacks hydrophilic glycoluril groups and large sterically hindered spiro ring structures, resulting in poor antifoaming and defoaming properties of the defoamer.

[0047] It can be seen from Example 2 and Comparative Examples 2-3 that when the molecular weight or length of the branched ethoxy chain segment is adjusted by changing the molar ratio of the branched spirocyclic alcohol compound and ethylene oxide, the antifoaming and defoaming properties of the defoamer will also change significantly. When the molecular weight of the branched ethoxy chain segment is too large, the large steric hindered spirocyclic structure cannot effectively hinder the interference caused by entanglement between the branches, resulting in a low degree of dispersion of the ethoxy sites on the branches and poor defoaming effect. When the molecular weight of the branched ethoxy chain segment is too small, the number of ethoxy sites on the branches is small, resulting in insufficient antifoaming 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 preparation method of a defoamer based on ethoxylation reaction according to any one of claims 1 to 9.

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