Low-foam cleaning agent and preparation method thereof

Abstract

The invention belongs to the technical field of metal cleaning agents, and particularly relates to a low-foam cleaning agent and a preparation method thereof. The low-foam cleaning agent comprises the following components in percentage by mass: 7-10% of polyoxyethylene ether, 5-10% of sucrose fatty acid ester, 4-6% of a rust remover, 15-20% of a corrosion inhibitor, 8-15% of a salt aid and the balance of water. And the polyoxyethylene ether comprises octanedioic acid dimonoethanolamide polyoxyethylene ether. The metal cleaning agent provided by the invention is high in cleaning rate, less in foam residual quantity and friendly to the ecological environment, and has excellent rust removal and corrosion resistance at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of metal cleaning agents, and in particular relates to a low-foam cleaning agent and a preparation method thereof. Background Art

[0002] Metal cleaner is a chemical specially designed to remove grease, dirt, rust and other contaminants from metal surfaces. It mainly removes stains on metal surfaces through physical and chemical effects while protecting the metal surface from damage.

[0003] Most of the metal cleaning agents on the market currently have the following problems: 1. Insufficient cleaning power: If the cleaning power is not strong enough, it may not be able to effectively remove dirt and oil stains on the metal surface, resulting in poor cleaning effect. 2. Poor foam stability: Foam height and stability are important indicators to measure whether the cleaning agent is easy to produce foam and whether the foam can last. If the foam is unstable, it may cause too much or too little foam during the cleaning process, affecting the cleaning efficiency. 3. Poor anti-rust performance: The cleaning agent has limited ability to protect metals under certain conditions. If the anti-rust performance is not good, the metal surface after cleaning may rust quickly, affecting the service life. 4. Insufficient corrosion inhibition: If the corrosion inhibition is not good, the cleaning agent may corrode the metal and damage the metal surface.

[0004] Cleaning agents in the prior art usually contain surfactants, alkaline or acidic components and other additives to improve the cleaning effect, improve cleaning efficiency and adapt to the needs of different metal materials. They are widely used in manufacturing, automobile maintenance, aerospace and electronic product production. However, the metal cleaning agents currently used in the market contain a large number of halogens and heavy metals and other harmful substances that are not easy to degrade, which is not conducive to the health of practitioners and has potential harm to the ecological environment. On the other hand, the surfactants and organic solvents commonly used in metal cleaning agents will produce a lot of foam when used, which is not conducive to cleaning and subsequent processes.

[0005] Therefore, there is an urgent need for a low-foam cleaning agent and a preparation method thereof. Summary of the invention

[0006] The present invention aims to provide a low-foam, environmentally friendly metal cleaning agent and a preparation method thereof. The metal cleaning agent provided by the present invention has a high cleaning rate, a small amount of foam residue, is friendly to the ecological environment, and has excellent rust removal and corrosion resistance.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A low-foaming, environmentally friendly metal cleaning agent, comprising the following components in percentage by weight: 7-10% polyoxyethylene ether, 5-10% sucrose fatty acid ester, 4-6% rust remover, 15-20% corrosion inhibitor, 8-15% salt additive, and the balance water; the polyoxyethylene ether comprises suberic acid dimonoethanolamide polyoxyethylene ether;

[0009] The preparation method of suberic acid dimonoethanolamide polyoxyethylene ether comprises the following steps:

[0010] Step 1, adding suberic acid into a four-necked bottle and heating to melt; adding monoethanolamine into the four-necked bottle, stirring and heating to react, condensing and separating water generated during the reaction until no water is generated, stopping the reaction, and obtaining suberic acid dimonoethanolamide;

[0011] Step 2, adding the suberic acid dimonoethanolamide prepared in step 1 and the catalyst into a reaction kettle, stirring and heating to react, and evacuating the reaction kettle to remove water and other low-boiling point substances;

[0012] Step three, filling nitrogen into the reactor of step two to replace the air in the reactor, adding ethylene oxide to react with the suberic acid dimonoethanolamide added in step two, and after the reaction is completed, filling nitrogen again to derive the reaction product, which is suberic acid dimonoethanolamide polyoxyethylene ether.

[0013] As a preferred technical solution of the present invention, in step 1, the mass ratio of suberic acid to monoethanolamine is 1:2-1:2.5, and the heating temperature is 120-130°C.

[0014] As a preferred technical solution of the present invention, in step 2, the stirring rate is 500-700 rpm, the reaction temperature is 100-130° C., and the reaction time is 2-4 h.

[0015] As a preferred technical solution of the present invention, the catalyst in step 2 is potassium hydroxide.

[0016] As a preferred technical solution of the present invention, the amount of catalyst added in step 2 is 0.3-0.6% of the total mass of suberic acid dimonoethanolamide and ethylene oxide.

[0017] As a preferred technical solution of the present invention, the molar ratio of suberic acid dimonoethanolamide to ethylene oxide in step 3 is 1:20-1:30. The reaction temperature is 100-120° C. and the reaction time is 4-6 hours.

[0018] Preferably, the number of structural units of ethylene oxide in the suberic acid dimonoethanolamide polyoxyethylene ether is 20-30.

[0019] The specific structure of suberic acid dimonoethanolamide polyoxyethylene ether is shown in formula (1).

[0020]

[0021] Wherein, x and y are positive integers, and the sum of x and y is 20-30.

[0022] Preferably, the polyoxyethylene ether further comprises an alkyl polyoxyethylene ether surfactant, and the alkyl polyoxyethylene ether surfactant is selected from any one of methyl dodecanoate polyoxyethylene ether, methyl hexadecanoate polyoxyethylene ether, methyl octadecanoate polyoxyethylene ether, and bislaurylamide ethyl polyoxyethylene ether amine.

[0023] Preferably, the mass ratio of the alkyl polyoxyethylene ether surfactant to the suberic acid dimonoethanolamide polyoxyethylene ether is 1:1-1:1.5.

[0024] The present invention can improve the cleaning effect of a low-foam cleaning agent by compounding the prepared suberic acid dimonoethanolamide polyoxyethylene ether with an alkyl polyoxyethylene ether surfactant. The suberic acid dimonoethanolamide polyoxyethylene ether prepared by the present invention has good wettability and dispersibility, and the amide group and the polyoxyethylene chain in its molecular structure can effectively reduce the surface tension of the aqueous solution, reduce the formation and stability time of the foam, and the compounding with the alkyl polyoxyethylene ether surfactant can work together at different levels to significantly reduce the foam stability of the cleaning agent. The compounding of suberic acid dimonoethanolamide polyoxyethylene ether and the alkyl polyoxyethylene ether surfactant can significantly improve the wetting and penetration ability of the cleaning agent, ensure that the cleaning liquid can evenly cover the metal surface, and penetrate into tiny pores and cracks to thoroughly remove dirt. This synergistic effect enables the cleaning agent to perform well when processing metal parts of complex shapes, and is particularly suitable for the cleaning of precision machinery parts. By reasonably selecting the ratio of suberic acid dimonoethanolamide polyoxyethylene ether to the alkyl polyoxyethylene ether surfactant, the wettability and decontamination ability of the cleaning agent can be improved, while reducing foam and enhancing rust resistance.

[0025] Preferably, the sucrose fatty acid ester is one or more of sucrose methyl laurate, sucrose methyl myristate and sucrose methyl hexadecanoate.

[0026] Adding sucrose fatty acid ester to the low-foam cleaning agent of the present invention can improve the cleaning and defoaming ability of the metal cleaning agent. In the system of the present invention, when sucrose fatty acid ester is compounded with suberic acid dimonoethanolamide polyoxyethylene ether and alkyl polyoxyethylene ether surfactants, the three can exert a synergistic effect to further improve the overall performance of the cleaning agent. The three can work together at different levels through compounding to significantly improve the wetting and penetration ability of the cleaning agent; through compounding, a complex interface layer can be formed to promote the cleaning liquid to penetrate deeper into the pores and cracks on the metal surface and thoroughly remove stubborn dirt. At the same time, the compounding of the three components can prevent the intrusion of corrosive media and extend the service life of metal parts. This synergistic effect allows the cleaning agent to not only have a good cleaning effect, but also provide long-term rust and corrosion protection.

[0027] Preferably, the rust remover is one or more of potassium hydrogen phthalate, sodium hydrogen phthalate, hydroxyethylidene diphosphonic acid, tartaric acid, succinic acid, and isocitric acid.

[0028] Preferably, the corrosion inhibitor is one or more of triethanolamine, dodecenylsuccinic acid carboxamide, dodecenylsuccinic acid acetamide, sulfadiazine, sulfathiazole, and toluenesulfonyl hydrazide.

[0029] Preferably, the salt auxiliary agent is one or more of tetrasodium EDTA, pentasodium TDPA, sodium dodecylbenzene sulfonate, sodium gluconate, and sodium citrate.

[0030] The invention provides a method for preparing the low-foam cleaning agent, which comprises the following steps: mixing components of the low-foam cleaning agent and stirring them evenly to obtain the low-foam cleaning agent.

[0031] Compared with the existing technology, the adopted technical solution has the following beneficial effects:

[0032] (1) The present invention uses suberic acid dimonoethanolamide as a raw material and synthesizes a non-ionic surfactant suberic acid dimonoethanolamide polyoxyethylene ether through an ethoxylation reaction. Compared with ionic surfactants, suberic acid dimonoethanolamide polyoxyethylene ether is not easily affected by acid-base environment, has good solubility and high biodegradability. Compared with fatty acid monoethanolamide polyoxyethylene ether, which is widely used in the market, suberic acid dimonoethanolamide polyoxyethylene ether synthesized from difunctional suberic acid has the advantages of good wetting performance, strong detergency and low foaming. More importantly, the present invention prepares a polyoxyethylene ether surfactant with a moderate length of hydrophilic group and hydrophobic group, the best wetting ability, the lowest foaming and the strongest detergency by controlling the number of ethylene oxide structural units.

[0033] (2) The sucrose fatty acid ester surfactant used in the low-foam cleaning agent prepared by the present invention is odorless, non-toxic, non-environmentally friendly, easily biodegradable, and has excellent wettability, emulsification and dispersibility. Compared with the halogen-containing and vanadium-containing surfactants commonly used in metal cleaning agents on the market, the low-foam cleaning agent prepared by the present invention is more beneficial to the health of practitioners and ecological safety.

[0034] (3) The weak acid rust inhibitor used in the low-foam cleaning agent prepared by the present invention can penetrate and diffuse into the rust scale, undergo a chemical reaction to generate metal salts, and form a stable complex with metal ions through the chelation effect of the salt additive, so that the rust layer falls off the metal surface, thereby achieving the purpose of rust removal.

[0035] (4) The amine corrosion inhibitor used in the low-foam cleaning agent prepared by the present invention can be adsorbed on the metal / solution interface through physical and chemical effects, effectively removing surface water molecules and forming a dense barrier film on the metal surface, thereby enhancing the shielding and corrosion inhibition effect of organic compounds on material corrosion. DETAILED DESCRIPTION

[0036] The low foam cleaning agent provided by the present invention is described in detail below in conjunction with embodiments. The described embodiments are only part of the embodiments of the present invention, but not all of the embodiments.

[0037] Example 1

[0038] This embodiment provides a suberic acid dimonoethanolamide polyoxyethylene ether, and its preparation method comprises the following steps:

[0039] Step 1: add suberic acid into a four-necked bottle and heat to melt at 120° C. Add monoethanolamine into the four-necked bottle, the mass ratio of suberic acid to monoethanolamine is 1:2, condense and separate the water produced during the reaction until no water is produced, stop the reaction, and obtain suberic acid dimonoethanolamide.

[0040] Step 2: Add the suberic acid dimonoethanolamide and sodium hydroxide obtained in step 1 into the reaction kettle, stir at 600 rpm, heat at 110° C. for 2 hours, and then evacuate the reaction kettle to remove water and other low-boiling substances. The catalyst is sodium hydroxide, and the added amount is 0.5% of the total mass of suberic acid dimonoethanolamide and ethylene oxide.

[0041] Step three, filling nitrogen into the reactor of step two to replace the air in the reactor, introducing ethylene oxide at a molar ratio of 30:1 between ethylene oxide and suberic acid dimonoethanolamide to initiate the reaction, the reaction temperature is 110°C, the reaction time is 5 hours, and after the reaction is completed, nitrogen is filled again to extract the reaction product, suberic acid dimonoethanolamide polyoxyethylene ether.

[0042] The surfactant of suberic acid dimonoethanolamide polyoxyethylene ether (ethylene oxide connection number 30) prepared by the above steps has a wetting time of 30s, an initial foam volume of 17mL, a cloud point of 22°C, a critical surface tension of 16.2mN / m, and a relative detergency value of 92%.

[0043] Example 2

[0044] The difference between this embodiment and embodiment 1 is that in step 1, the mass ratio of suberic acid to monoethanolamine is 1:2.5, in step 3, ethylene oxide is introduced at a molar ratio of ethylene oxide to suberic acid dimonoethanolamide of 20:1 to initiate the reaction, and the remaining steps are consistent with embodiment 1.

[0045] The suberic acid dimonoethanolamide polyoxyethylene ether surfactant prepared by the above steps has a wetting time of 32s, an initial foam volume of 20mL, a cloud point of 20°C, a critical surface tension of 18.6mN / m, and a relative detergency value of 91%.

[0046] Example 3

[0047] The difference between this embodiment and embodiment 1 is that in step 3, ethylene oxide is introduced at a molar ratio of ethylene oxide to suberic acid dimonoethanolamide of 26:1 to initiate the reaction, and the remaining steps are consistent with embodiment 1.

[0048] The suberic acid dimonoethanolamide polyoxyethylene ether surfactant prepared by the above steps has a wetting time of 36 seconds, an initial foam volume of 25 mL, a cloud point of 21° C., a critical surface tension of 17.5 mN / m, and a relative detergency value of 90%.

[0049] Comparative Example 1

[0050] The difference between this comparative example and Example 1 is that in step 3, ethylene oxide is introduced at a molar ratio of ethylene oxide to suberic acid dimonoethanolamide of 10:1 to initiate the reaction, and the remaining steps are consistent with Example 1.

[0051] The suberic acid dimonoethanolamide polyoxyethylene ether surfactant prepared by the above steps has a wetting time of 70s, an initial foam volume of 65mL, a cloud point of 17°C, a critical surface tension of 60.3mN / m, and a relative detergency value of 73%.

[0052] Comparative Example 2

[0053] The difference between this comparative example and Example 1 is that in step 3, ethylene oxide is introduced at a molar ratio of ethylene oxide to suberic acid dimonoethanolamide of 50:1 to initiate the reaction, and the remaining steps are consistent with Example 1.

[0054] The suberic acid dimonoethanolamide polyoxyethylene ether surfactant prepared by the above steps has a wetting time of 78s, an initial foam volume of 72mL, a cloud point of 85°C, a critical surface tension of 82.5mN / m, and a relative detergency value of 69%.

[0055] Example 4

[0056] The present embodiment provides a low-foaming metal cleaning agent, comprising the following components in percentage by weight: 5% polyoxyethylene methyl dodecanoate, 5% polyoxyethylene suberyl dimonoethanolamide polyoxyethylene ether (the number of ethylene oxide repeating units is 30) prepared in Example 1, 10% sucrose methyl dodecanoate, 6% potassium hydrogen phthalate, 20% triethanolamine, 7% tetrasodium EDTA, 8% sodium dodecylbenzene sulfonate, and the balance water.

[0057] The preparation method of the low-foam cleaning agent comprises the following steps: mixing the components of the low-foam cleaning agent and stirring them evenly to obtain the low-foam cleaning agent.

[0058] The cleaning effect of the prepared low-foam cleaning agent was tested to be 98%, the initial foam height of the circulating bubbler at 50°C was 1100mL, and the residual foam height was 0mL after closing the cycle for 2 hours. The rust removal test of cast iron chips with 5wt% dilution was qualified, and the corrosion test of TH300 cast iron sheets with 5wt% dilution was qualified.

[0059] Example 5

[0060] The present embodiment is different from the embodiment 4 in that the low foam cleaning agent comprises the following components in percentage by weight: 2.8% of polyoxyethylene methyl hexadecanoate, 4.2% of polyoxyethylene suberyl dimonoethanolamide polyoxyethylene ether (the number of ethylene oxide repeating units is 20) prepared in the embodiment 2, 5% of sucrose methyl tetradecanoate, 2% of sodium hydrogen phthalate, 2% of hydroxyethylidene diphosphoric acid, 10% of dodecenyl succinic acid formamide, 5% of dodecenyl succinic acid acetamide, 3% of sodium gluconate, 5% of sodium citrate, and the balance of water.

[0061] The cleaning effect of the prepared low-foam cleaning agent was tested to be 97%, the initial foam height of the circulating bubbler at 50°C was 1100mL, and the residual foam height was 0mL after the circulation was closed for 2 hours. The rust removal test of cast iron chips with 5wt% dilution was qualified, and the corrosion test of TH300 cast iron sheets with 5wt% dilution was qualified.

[0062] Example 6

[0063] The present embodiment is different from the embodiment 4 in that the low foam cleaning agent comprises the following components in percentage by weight: 4% of methyl octadecanoate polyoxyethylene ether, 6% of suberic acid dimonoethanolamide polyoxyethylene ether (the number of ethylene oxide repeating units is 26) prepared in the embodiment 3, 5% of sucrose methyl hexadecanoate, 1% of tartaric acid, 2% of succinic acid, 2% of isocitric acid, 5% of sulfadiazine, 5% of sulfathiazole, 8% of toluenesulfonyl hydrazide, 10% of pentasodium TDPA, and the balance of water.

[0064] The cleaning effect of the prepared low-foam cleaning agent was tested to be 98%, the initial foam height of the circulating bubbler at 50°C was 1150mL, and the residual foam height was 0mL after the circulation was closed for 2 hours. The rust removal test of cast iron chips with 5wt% dilution was qualified, and the corrosion test of TH300 cast iron sheets with 5wt% dilution was qualified.

[0065] Comparative Example 3

[0066] The difference between this comparative example and Example 4 is that the suberic acid dimonoethanolamide polyoxyethylene ether prepared in Example 1 is not added to the formula of the low-foam cleaning agent, and the remaining preparation steps are the same as those in Example 4.

[0067] The cleaning effect of the prepared low-foam cleaning agent was tested to be 75%, the initial foam height of the circulating bubbler at 50°C was 1900mL, the residual foam height after closing the cycle for 2 hours was 250mL, the 5wt% dilution passed the cast iron chips rust removal test, and the 5wt% dilution passed the TH300 cast iron sheet corrosion test.

[0068] Comparative Example 4

[0069] The difference between this comparative example and Example 4 is that the suberic acid dimonoethanolamide polyoxyethylene ether (the number of ethylene oxide repeating units is 10) prepared in Comparative Example 1 is added to the formula of the low-foaming detergent, and the remaining preparation steps are the same as those of Example 4.

[0070] The cleaning effect of the prepared low-foam cleaning agent was 80% after testing. The initial foam height of the circulating bubbler at 50°C was 1500mL, and the residual foam height was 180mL after closing the circulation for 2 hours. The rust removal test of cast iron chips with 5wt% dilution was qualified, and the corrosion test of TH300 cast iron sheets with 5wt% dilution was qualified.

[0071] Comparative Example 5

[0072] The difference between this comparative example and Example 4 is that the suberic acid dimonoethanolamide polyoxyethylene ether (the number of ethylene oxide repeating units is 50) prepared in Comparative Example 2 is added to the formula of the low-foaming detergent, and the remaining preparation steps are the same as those of Example 4.

[0073] The cleaning effect of the prepared low-foam cleaning agent was tested to be 78%, the initial foam height of the circulating bubbler at 50°C was 1700mL, the residual foam height after closing the cycle for 2 hours was 200mL, the 5wt% dilution passed the cast iron chips rust removal test, and the 5wt% dilution passed the TH300 cast iron sheet corrosion test.

[0074] Comparative Example 6

[0075] The difference between this comparative example and Example 4 is that methyl sucrose dodecanoate is not added to the formula of the low-foam cleaning agent, and the remaining preparation steps are the same as those of Example 4.

[0076] The cleaning effect of the prepared low-foam cleaning agent was tested to be 79%, the initial foam height of the circulating bubbler at 50°C was 1450mL, and the residual foam height was 170mL after closing the cycle for 2 hours. The rust removal test of cast iron chips with 5wt% dilution was qualified, and the corrosion test of TH300 cast iron sheets with 5wt% dilution was qualified.

[0077] Comparative Example 7

[0078] The difference between this comparative example and Example 4 is that potassium hydrogen phthalate is not added to the formula of the low-foam cleaning agent, and the remaining preparation steps are the same as those of Example 4.

[0079] The cleaning effect of the prepared low-foam cleaning agent was tested to be 89%, the initial foam height of the circulating bubbler at 50°C was 1300mL, and the residual foam height was 150mL after the circulation was closed for 2 hours. The rust removal test of cast iron chips with 5wt% dilution failed, but the corrosion test of TH300 cast iron sheets with 5wt% dilution passed.

[0080] Comparative Example 8

[0081] The difference between this comparative example and Example 4 is that triethanolamine is not added to the formula of the low-foam cleaning agent, and the remaining preparation steps are the same as those of Example 4.

[0082] The cleaning effect of the prepared low-foam cleaning agent was tested to be 91%, the initial foam height of the circulating bubbler at 50°C was 1350mL, and the residual foam height was 145mL after closing the cycle for 2 hours. The rust removal test of cast iron chips with 5wt% dilution was qualified, but the corrosion test of TH300 cast iron sheets with 5wt% dilution was unqualified.

[0083] The performance test results of the suberic acid dimonoethanolamide polyoxyethylene ether surfactant prepared in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1. The performance test results of the low-foam cleaning agents prepared in Examples 4-6 and Comparative Examples 3-8 are shown in Table 2.

[0084] Table 1 Suberic acid dimonoethanolamide polyoxyethylene ether test results

[0085]

[0086] Table 2 Performance test results of low foam cleaning agent

[0087]

[0088]

[0089] As can be seen from Table 1, by controlling the number of structural units of ethylene oxide in suberic acid dimonoethanolamide polyoxyethylene ether, the suberic acid dimonoethanolamide polyoxyethylene ether synthesized by the present invention has the advantages of strong wetting ability, low foaming, moderate cloud point, low critical surface tension and strong detergency.

[0090] It can be seen from Table 2 that the low-foam cleaning agents prepared in Examples 4-6 have a cleaning rate of more than 95%, low foam and fast defoaming speed, and excellent anti-rust and corrosion effects. At the same time, the biodegradable surfactants used are beneficial to the protection of the ecological environment and the health of practitioners.

[0091] Comparative Examples 3-5 show that the absence of the synthesized suberic acid dimonoethanolamide polyoxyethylene ether of the present invention will cause the cleaning ability and defoaming ability of the metal cleaning agent to be greatly reduced. At the same time, too many or too few structural units of ethylene oxide in suberic acid dimonoethanolamide polyoxyethylene ether will cause the surfactant to be too hydrophilic / lipophilic, affecting wettability, surface tension and decontamination ability, and also reducing the cleaning ability and defoaming ability of the metal cleaning agent. Comparative Example 6 shows that sucrose fatty acid esters, as degradable surfactants, also have a positive effect on the cleaning and defoaming ability of metal cleaning agents. Comparative Examples 7-8 show the important role of rust inhibitors and corrosion inhibitors in reducing metal surface corrosion and delaying environmental corrosion.

[0092] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A low foam cleaning agent, characterized in that: The composition comprises the following components in percentage by weight: 7-10% polyoxyethylene ether, 5-10% sucrose fatty acid ester, 4-6% rust remover, 15-20% corrosion inhibitor, 8-15% salt additive, and the balance water; The polyoxyethylene ether includes suberic acid dimonoethanolamide polyoxyethylene ether; the preparation method of the suberic acid dimonoethanolamide polyoxyethylene ether includes the following steps: Step 1, adding suberic acid into a four-necked bottle and heating to melt; adding monoethanolamine into the four-necked bottle, stirring and heating to react, condensing and separating water generated during the reaction until no water is generated, stopping the reaction, and obtaining suberic acid dimonoethanolamide; Step 2, adding the suberic acid dimonoethanolamide and the catalyst obtained in step 1 into a reaction kettle, stirring and heating to react, and evacuating the reaction kettle to remove water and other low-boiling point substances; Step three, filling nitrogen into the reactor of step two to replace the air in the reactor, adding ethylene oxide to react with the suberic acid dimonoethanolamide added in step two, and after the reaction is completed, filling nitrogen again to derive the reaction product, which is suberic acid dimonoethanolamide polyoxyethylene ether.

2. The low foam cleaning agent according to claim 1, characterized in that: In step 1, the mass ratio of suberic acid to monoethanolamine is 1:2-1:2.5, and the heating temperature is 120-130°C.

3. The low foam cleaning agent according to claim 1, characterized in that: In step 2, the stirring rate is 500-700 rpm, the reaction temperature is 100-130° C., and the reaction time is 2-4 hours; the catalyst is sodium hydroxide, and the amount of the catalyst added is 0.3-0.6% of the total mass of suberic acid dimonoethanolamide and ethylene oxide.

4. The low foam cleaning agent according to claim 1, characterized in that: In step 3, the molar ratio of suberic acid dimonoethanolamide to ethylene oxide is 1:20-1:30; the reaction temperature is 100-120° C., and the reaction time is 4-6 hours.

5. The low foam cleaning agent according to claim 1, characterized in that: The number of structural units of ethylene oxide in the suberic acid dimonoethanolamide polyoxyethylene ether is 20-30.

6. The low foam cleaning agent according to claim 1, characterized in that: The polyoxyethylene ether also includes alkyl polyoxyethylene ether surfactants; the alkyl polyoxyethylene ether surfactants are selected from any one of methyl dodecanoate polyoxyethylene ether, methyl hexadecanoate polyoxyethylene ether, methyl octadecanoate polyoxyethylene ether, and bislaurylamide ethyl polyoxyethylene ether amine.

7. The low foam cleaning agent according to claim 6, characterized in that: The mass ratio of the alkyl polyoxyethylene ether surfactant to the suberic acid dimonoethanolamide polyoxyethylene ether is 1:1-1:1.

5.

8. The low foam cleaning agent according to claim 1, characterized in that: The rust remover is one or more of potassium hydrogen phthalate, sodium hydrogen phthalate, hydroxyethylidene diphosphonic acid, tartaric acid, succinic acid and isocitric acid.

9. The low foam cleaning agent according to claim 1, characterized in that: The corrosion inhibitor is one or more of triethanolamine, dodecenylsuccinic acid formamide, dodecenylsuccinic acid acetamide, sulfadiazine, sulfathiazole, and toluenesulfonyl hydrazide; the salt auxiliary agent is one or more of EDTA tetrasodium, TDPA pentasodium, sodium dodecylbenzene sulfonate, sodium gluconate, and sodium citrate.

10. A method for preparing the low-foam cleaning agent according to any one of claims 1 to 9, characterized in that: The following steps are involved: Mix the components of the low-foaming detergent and stir well to obtain it.

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