A defoaming agent for cleaning steel and its preparation method

Abstract

This invention discloses a defoamer for steel cleaning, comprising the following components: 32-42% silicone grease, 4-9% fatty alcohol polyoxyethylene ether, 8-18% polyether-modified silicone oil, 1-5% triglyceride monostearate, 1-5% fatty acid polyoxyethylene ester, 1-5% sodium fatty alcohol polyoxyethylene ether sulfate, 0.1-0.2% bactericide, and the balance being deionized water. The silicone grease is prepared by mixing dimethyl silicone oil, methyl MQ silicone resin, and silica to obtain a premix. Hydrogen-containing silicone oil, vinyl silicone oil, and dimethyl silicone oil are then mixed, heated to 50-70°C, and a platinum catalyst is added. The mixture is stirred until the product viscosity reaches 30,000 mPa·s or higher. The premix is ​​then added, and the mixture is heated to 100-110°C and maintained at this temperature. Compared with existing organosilicon defoamers, this defoamer exhibits excellent temperature and alkali resistance, rapid defoaming speed, good emulsion stability, and low silicon precipitation rate under steel cleaning and degreasing conditions.

Description

Technical Field

[0001] This invention relates to a defoamer for steel cleaning and its preparation method, belonging to the field of defoamer technology. Background Technology

[0002] The steel cleaning and degreasing process is a crucial step in the surface treatment of cold-rolled and hot-rolled steel. Its working fluid is mainly composed of surfactants and caustic soda flakes, used to remove residual rolling oil and various oil stains from the surface of the rolled steel. During the cleaning and rinsing process of rolled steel parts, the working fluid easily generates a large amount of foam due to the strong mechanical agitation, residual rolling oil, and the synergistic effect of high concentrations of surfactants in the system. Excessive foam can cause a series of problems: on the one hand, it can easily lead to foam overflow and abnormal tank levels, resulting in a significant waste of raw materials such as surfactants and alkalis, while also reducing the effective volume of equipment and production cycle time, significantly impacting production capacity; on the other hand, foam coverage weakens the contact efficiency between the cleaning fluid and the steel surface, resulting in incomplete removal of rolling oil and other contaminants, and residual oil stains can seriously affect subsequent processing and product quality. Therefore, effective control of foam during the steel cleaning and degreasing process is a core prerequisite for ensuring production continuity and cleaning effectiveness.

[0003] With its advantages of fast defoaming speed, low dosage, strong chemical inertness, and wide applicability, silicone defoamer is currently the mainstream defoaming product in the steel cleaning industry, and its market application volume continues to grow. However, traditional silicone defoamers have the following technical defects in steel cleaning and degreasing conditions (strong alkali (pH 10-13), high temperature, high shear) and are difficult to meet application requirements: (1) They cannot effectively inhibit foam regeneration. Foam is repeatedly generated during the cleaning process, requiring frequent replenishment of defoamer, which increases the cost of use; (2) The instantaneous defoaming speed of the defoamer is slow, making it difficult to meet the application requirements and achieve long-term defoaming; (3) Steel degreasing systems are mostly high-alkali, high-ionic, and strongly emulsified environments. Conventional silicone defoamers are prone to stratification, demulsification, and silicone grease precipitation in this system. The precipitates will accumulate in large quantities in the cleaning tank, increasing the difficulty of equipment cleaning. At the same time, they are easy to adhere to the steel plate surface, forming silicone spots and oil film residues, which seriously interfere with subsequent processes and lead to product appearance defects and performance degradation. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an organosilicon defoamer suitable for steel cleaning and degreasing conditions. It has excellent temperature and alkali resistance, fast defoaming speed, good foam suppression performance, good emulsion stability, and low silicon precipitation rate under steel cleaning and degreasing conditions.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A defoamer for steel cleaning, based on 100% of the total mass of the defoamer, is composed of the following components in the following mass percentages: 32-42% silicone grease, 4-9% fatty alcohol polyoxyethylene ether, 8-18% polyether-modified silicone oil, 1-5% triglyceride monostearate, 1-5% fatty acid polyoxyethylene ester, 1-5% sodium fatty alcohol polyoxyethylene ether sulfate, 0.1-0.2% bactericide, and the balance being deionized water.

[0007] The method for preparing the silicone grease includes the following steps:

[0008] (1) Mix dimethyl silicone oil, methyl MQ silicone resin and silica evenly to obtain a premix;

[0009] (2) After stirring the hydrogen-containing silicone oil, vinyl silicone oil and dimethyl silicone oil evenly, heat the mixture to 50-70°C, add platinum catalyst, stir the reaction until the product viscosity reaches 30000 mPa·s or more, then add the premix from step (1), stir and heat to 100-110°C, keep warm and stir for 2-4 hours to obtain silicone grease.

[0010] In step (1), the amount of dimethyl silicone oil accounts for 16-25% of the total mass of the silicone grease; the M / Q molar ratio of the methyl MQ silicone resin is 0.6-0.8, and the amount of methyl MQ silicone resin accounts for 5-13% of the total mass of the silicone grease; the silica is hydrophobic silica with a specific surface area of ​​50-150 m² / g. 2 / g, the amount of silica used accounts for 2 to 7% of the total mass of silicone grease.

[0011] In step (2), the hydrogen-containing silicone oil is a side-hydrogen-containing silicone oil with a hydrogen content of 0.05-0.3%, and the amount of hydrogen-containing silicone oil accounts for 26-38% of the total mass of silicone grease; the vinyl silicone oil is a terminal vinyl silicone oil with a vinyl content of less than 0.3%, and the amount of vinyl silicone oil accounts for 10-16% of the total mass of silicone grease; the amount of dimethyl silicone oil accounts for 15-22% of the total mass of silicone grease.

[0012] In steps (1) and (2), the viscosity of the dimethyl silicone oil is 500 to 1500 mPa·s.

[0013] Furthermore, the fatty alcohol polyoxyethylene ether is a C12-14 alcohol polyoxyethylene ether.

[0014] Furthermore, the fatty acid polyoxyethylene ester is lauric acid polyoxyethylene ester.

[0015] Furthermore, the bactericide is selected from any one of hydroxyethyl hexahydrotriazine, 1,2-benzisothiazolin-3-one, or Kathon.

[0016] Further, the preparation method of the polyether-modified silicone oil is as follows: Hydrogen-containing silicone oil with a hydrogen content of 0.1% and vinyl silicone oil with a vinyl content of 0.18%–0.40% are stirred and mixed, heated to 55°C–65°C, a platinum catalyst is added, and then stirring and heating are continued to 90–100°C. Allyl polyether is then added, and the mixture is stirred until the system becomes transparent to obtain the polyether-modified silicone oil. The mass ratio of the hydrogen-containing silicone oil, vinyl silicone oil, and allyl polyether is 45:(10–15):(40–50). The allyl polyether is an EO / PO block polyether, and the mass ratio of EO / PO is (2–4):5.

[0017] The preparation method of the above-mentioned defoamer for steel cleaning includes the following steps:

[0018] S1. Add silicone grease, fatty alcohol polyoxyethylene ether, polyether modified silicone oil, triglyceride monostearate, fatty acid polyoxyethylene ester, and sodium fatty alcohol polyoxyethylene ether sulfate to the reaction vessel, stir and heat to 60-70℃, and keep warm and stir for 30-60 min.

[0019] S2. Add deionized water slowly in batches. After each addition of water, stir and emulsify at 80-100 rpm for 15-30 minutes at 35℃-40℃. After all the deionized water has been added, stir until the emulsion inverts, and then cool to room temperature.

[0020] S3. Add bactericide and mix well to obtain defoamer for steel cleaning.

[0021] The beneficial effects of the present invention are as follows: The present invention provides an organosilicon defoamer suitable for steel cleaning and degreasing conditions. It has excellent temperature and alkali resistance, fast defoaming speed and good foam suppression performance under steel cleaning and degreasing conditions, good emulsion stability and low silica precipitation rate. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments.

[0023] Example 1

[0024] A defoamer for cleaning steel is composed of the following components: 36% silicone grease, 6% fatty alcohol polyoxyethylene ether, 14% polyether modified silicone oil, 2.1% triglyceride monostearate, 2.1% fatty acid polyoxyethylene ester, 1.6% sodium fatty alcohol polyoxyethylene ether sulfate, 0.1% bactericide, and 38.1% deionized water.

[0025] In this embodiment, the fatty alcohol polyoxyethylene ether is a C12-14 alcohol polyoxyethylene ether, the fatty acid polyoxyethylene ester is lauric acid polyoxyethylene ester, and the bactericide is hydroxyethyl hexahydrotriazine.

[0026] The method for preparing the silicone grease:

[0027] (1) Mix 82 kg of dimethyl silicone oil (viscosity 1000 mPa·s), 32 kg of methyl MQ silicone resin (M / Q molar ratio 0.68), and 16 kg of [unclear text - likely a specific surface area] with a specific surface area of ​​90 m². 2 / g of hydrophobic silica is mixed evenly to obtain a premix;

[0028] (2) Mix 110 kg of hydrogen-containing silicone oil with a hydrogen content of 0.18% (viscosity of 100 mPa·s), 55 kg of vinyl silicone oil with a vinyl content of 0.2% (viscosity of 10000 mPa·s) and 65 kg of dimethyl silicone oil (viscosity of 1000 mPa·s) evenly, heat to 60°C, add 7 ppm isopropanol chloroplatinic acid solution, stir and react until the product viscosity reaches more than 30000 mPa·s, then add the premix from step (1), stir and heat to 105°C, keep warm and stir for 3 hours to obtain silicone grease.

[0029] The preparation method of the polyether-modified silicone oil is as follows: Hydrogen-containing silicone oil with a hydrogen content of 0.1% and vinyl silicone oil with a vinyl content of 0.35% (viscosity 1000 mPa·s) are stirred and mixed, and heated to 60°C. 7 ppm of isopropanol chloroplatinic acid solution is added, and then stirring and heating are continued to 95°C. Allyl polyether (EO / PO block polyether, EO / PO mass ratio of 4:5) is added, and the mixture is stirred until the system becomes transparent to obtain the polyether-modified silicone oil. The mass ratio of the hydrogen-containing silicone oil, vinyl silicone oil, and allyl polyether is 45:11:44.

[0030] The preparation method of defoamer for steel cleaning includes the following steps:

[0031] S1. Add silicone grease, fatty alcohol polyoxyethylene ether, polyether modified silicone oil, triglyceride monostearate, fatty acid polyoxyethylene ester, and fatty alcohol polyoxyethylene ether sodium sulfate to the reaction vessel, stir and heat to 65°C, and keep warm and stir for 45 min.

[0032] S2. Add deionized water slowly in batches. After each addition of water, stir and emulsify at 90 rpm for 20 minutes at 35℃~40℃. After all the deionized water has been added, stir until the emulsion inverts, and then cool to room temperature.

[0033] S3. Add bactericide and mix well to obtain defoamer for steel cleaning.

[0034] Example 2

[0035] A defoamer for cleaning steel is composed of the following components: 36% silicone grease, 6.8% fatty alcohol polyoxyethylene ether, 13% polyether modified silicone oil, 2.8% triglyceride monostearate, 1.8% fatty acid polyoxyethylene ester, 1.4% sodium fatty alcohol polyoxyethylene ether sulfate, 0.1% bactericide, and 38.1% deionized water.

[0036] In this embodiment, the fatty alcohol polyoxyethylene ether is a C12-14 alcohol polyoxyethylene ether, the fatty acid polyoxyethylene ester is lauric acid polyoxyethylene ester, and the bactericide is hydroxyethyl hexahydrotriazine.

[0037] The preparation methods for silicone grease and polyether-modified silicone oil are the same as in Example 1.

[0038] The preparation method of the defoamer for steel cleaning is the same as in Example 1.

[0039] Example 3

[0040] A defoamer for cleaning steel is composed of the following components: 36% silicone grease, 5% fatty alcohol polyoxyethylene ether, 16% polyether modified silicone oil, 1.8% triglyceride monostearate, 1.5% fatty acid polyoxyethylene ester, 1.5% sodium fatty alcohol polyoxyethylene ether sulfate, 0.1% bactericide, and 38.1% deionized water.

[0041] In this embodiment, the fatty alcohol polyoxyethylene ether is a C12-14 alcohol polyoxyethylene ether, the fatty acid polyoxyethylene ester is lauric acid polyoxyethylene ester, and the bactericide is hydroxyethyl hexahydrotriazine.

[0042] The preparation methods for silicone grease and polyether-modified silicone oil are the same as in Example 1.

[0043] The preparation method of the defoamer for steel cleaning is the same as in Example 1.

[0044] Comparative Example 1

[0045] A defoamer for cleaning steel is composed of the following components: 36% silicone grease, 7.8% fatty alcohol polyoxyethylene ether, 7% polyether modified silicone oil, 1.3% triglyceride monostearate, 5.2% fatty acid polyoxyethylene ester, 4.5% sodium fatty alcohol polyoxyethylene ether sulfate, 0.1% bactericide, and 38.1% deionized water.

[0046] In this comparative example, the fatty alcohol polyoxyethylene ether is a C12-14 alcohol polyoxyethylene ether, the fatty acid polyoxyethylene ester is lauric acid polyoxyethylene ester, and the bactericide is hydroxyethyl hexahydrotriazine.

[0047] The preparation methods for silicone grease and polyether-modified silicone oil are the same as in Example 1.

[0048] The preparation method of the defoamer for steel cleaning is the same as in Example 1.

[0049] Comparative Example 2

[0050] A defoamer for cleaning steel is composed of the following components: 36% silicone grease, 6% fatty alcohol polyoxyethylene ether, 14% polyether modified silicone oil, 2.1% triglyceride monostearate, 2.1% fatty acid polyoxyethylene ester, 1.6% sodium fatty alcohol polyoxyethylene ether sulfate, 0.1% bactericide, and 38.1% deionized water.

[0051] In this comparative example, the fatty alcohol polyoxyethylene ether is a C12-14 alcohol polyoxyethylene ether, the fatty acid polyoxyethylene ester is lauric acid polyoxyethylene ester, and the bactericide is hydroxyethyl hexahydrotriazine.

[0052] In this comparative example, the preparation method of the silicone grease is as follows:

[0053] (1) Mix 76 kg of dimethyl silicone oil (viscosity 1000 mPa·s), 28 kg of methyl MQ silicone resin (M / Q molar ratio 0.68), and 15 kg of [unclear text - likely a specific surface area] with a specific surface area of ​​90 m². 2 / g of hydrophobic silica is mixed evenly to obtain a premix;

[0054] (2) Mix 102 kg of hydrogen-containing silicone oil with a hydrogen content of 0.18% (viscosity of 100 mPa·s), 78 kg of vinyl silicone oil with a vinyl content of 0.2% (viscosity of 10000 mPa·s) and 61 kg of dimethyl silicone oil (viscosity of 1000 mPa·s) evenly, heat to 60°C, add 7 ppm isopropanol chloroplatinic acid solution, stir and react until the product viscosity reaches more than 30000 mPa·s, then add the premix from step (1), stir and heat to 105°C, keep warm and stir for 3 hours to obtain silicone grease.

[0055] The preparation method of polyether-modified silicone oil is the same as in Example 1.

[0056] The preparation method of the defoamer for steel cleaning is the same as in Example 1.

[0057] The defoamers prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests. The degreasing agent working solution used in the following test methods was prepared as follows: 30.0 g sodium hydroxide (analytical grade), 3.0 g solubilizer (anionic surfactant H-66, Solvay), 3.0 g nonylphenol polyoxyethylene ether (NP-10), 5.0 g sodium gluconate, and 2.0 g sodium oleate soap (16% content) were added to 1957.0 g deionized water and mixed evenly.

[0058] 1. Foam suppression and defoaming performance test

[0059] The samples were the defoamers of Examples 1-3, the defoamers of Comparative Examples 1-2, and imported silicone defoamer A. All samples were diluted to a solid content of 10% at room temperature and then tested using a circulating bubble apparatus.

[0060] Test method: Set the circulating water temperature of the circulating bubbler to 65℃ and the voltage to 14.0V. Take 500g of degreasing agent working solution and add it to the measuring cylinder of the circulating bubbler. Heat it to 65℃ and turn on the circulating pump. When the foam rises to 1300 mL, add 0.05mL of defoamer and start timing at the same time. Record the lowest foam height. When the foam rises to 1300 mL again, stop timing.

[0061] The test results are shown in Table 1:

[0062] Table 1 Results of foam suppression and defoaming performance tests

[0063]

[0064] According to the test data in Table 1, the defoamers of Examples 1-3 and Comparative Example 2 of the present invention have significantly longer foam suppression times at 65°C than Comparative Example 1 and imported silicone defoamer A, and their minimum foam height is lower than that of Comparative Example 1 and imported silicone defoamer A. This indicates that the defoamers of Examples 1-3 and Comparative Example 2 of the present invention have better defoaming and foam suppression performance.

[0065] 2. Foam instantaneous collapse time test

[0066] The samples were the defoamers of Examples 1-3, the defoamers of Comparative Examples 1-2, and imported silicone defoamer A. All samples were diluted to a solid content of 10% at room temperature before testing.

[0067] The defoaming and foam-inhibiting performance testing device from the patent with publication number CN216160385U was used for testing. The testing method was as follows:

[0068] 1) Take 100mL of degreasing agent working solution and add it to a 1L glass graduated cylinder, then place it in a constant temperature water bath at 65℃ and wait for it to reach a constant temperature.

[0069] 2) Turn on the air pump, place the stainless steel tube connected to the air stone in a container of clean water to clean it, and adjust the air flow rate to 300L / h.

[0070] 3) Place the cleaned air stones into the glass containers from step 1), and plug them with rubber stoppers. When the foam height reaches 1000mL, remove the air stones and add 0.05mL of the defoamer to be tested vertically. Record the defoaming time when the foam disappears and the liquid surface is visible. This is the instantaneous collapse time of the foam.

[0071] The test results are shown in Table 2:

[0072] Table 2 Results of foam instantaneous collapse time test

[0073]

[0074] As can be seen from the test data in Table 2, the foam collapse time of the defoamers in Examples 1-3 of the present invention and the defoamer in Comparative Example 2 at 65°C is significantly lower than that of Comparative Example 1 and imported silicone defoamer A. This indicates that the silicone defoamers in Examples 1-3 of the present invention have a faster defoaming speed.

[0075] 3. Defoamer silica exudation rate test

[0076] The samples were the defoamers of Examples 1-3, the defoamers of Comparative Examples 1-2, and imported silicone defoamer A. All samples were diluted to a solid content of 10% at room temperature before testing.

[0077] Test Method: Preheat the degreasing agent working solution to 65℃, and weigh 150 g into 500 mL transparent bottles. Add 5 g (mass m) of defoamer with 10% solid content (R) to each bottle, disperse evenly, fix on a vertical shaker, and shake the defoamer dispersion at 400 rpm and 5 cm amplitude for two minutes. Then filter the precipitate in the bottle with a 200-mesh filter cloth that has been pre-weighed to mass m0. Place the filtered filter cloth in a glass petri dish (mass m1) and dry it together in a 65℃ electric hot air drying oven for 30 minutes until constant weight. Weigh the dried product to mass m2, calculate and compare the mass of the precipitate from different defoamers, and thus calculate the silica precipitation rate X of the defoamer, X = ×100%, the test results are shown in Table 3:

[0078] Table 3. Silicon deposition rate test results

[0079]

[0080] As can be seen from the test results in Table 3, compared with the defoamers of Comparative Examples 1-2 and the imported silicone defoamer A, the silicone defoamers of Examples 1-3 of the present invention have a lower silicon precipitation rate at 65°C and in an alkaline environment, that is, they have better stability.

Claims

1. A defoamer for steel cleaning, characterized in that, Based on the total mass of the defoamer (100%), it consists of the following components in the following mass percentages: silicone grease 32-42%, fatty alcohol polyoxyethylene ether 4-9%, polyether-modified silicone oil 8-18%, triglyceride monostearate 1-5%, fatty acid polyoxyethylene ester 1-5%, sodium fatty alcohol polyoxyethylene ether sulfate 1-5%, bactericide 0.1-0.2%, and the balance being deionized water; The method for preparing the silicone grease includes the following steps: (1) Mix dimethyl silicone oil, methyl MQ silicone resin and silica evenly to obtain a premix; (2) After stirring the hydrogen-containing silicone oil, vinyl silicone oil and dimethyl silicone oil evenly, heat the mixture to 50-70°C, add platinum catalyst, stir the reaction until the product viscosity reaches 30000 mPa·s or more, then add the premix from step (1), stir and heat to 100-110°C, keep warm and stir for 2-4 hours to obtain silicone grease. In step (1), the amount of dimethyl silicone oil accounts for 16-25% of the total mass of the silicone grease; the M / Q molar ratio of the methyl MQ silicone resin is 0.6-0.8, and the amount of the methyl MQ silicone resin accounts for 5-13% of the total mass of the silicone grease; the amount of silica accounts for 2-7% of the total mass of the silicone grease. In step (2), the hydrogen-containing silicone oil is a side-hydrogen-containing silicone oil with a hydrogen content of 0.05-0.3%, and the amount of hydrogen-containing silicone oil accounts for 26-38% of the total mass of silicone grease; the vinyl silicone oil is a terminal vinyl silicone oil with a vinyl content of less than 0.3%, and the amount of vinyl silicone oil accounts for 10-16% of the total mass of silicone grease; the amount of dimethyl silicone oil accounts for 15-22% of the total mass of silicone grease.

2. The defoamer for steel cleaning as described in claim 1, characterized in that, In steps (1) and (2), the viscosity of the dimethyl silicone oil is 500 to 1500 mPa·s.

3. The defoamer for steel cleaning as described in claim 1, characterized in that, In step (1), the silica is hydrophobic silica with a specific surface area of ​​50–150 m². 2 / g.

4. The defoamer for steel cleaning as described in claim 1, characterized in that, The fatty alcohol polyoxyethylene ether is a C12-14 alcohol polyoxyethylene ether.

5. The defoamer for steel cleaning as described in claim 1, characterized in that, The fatty acid polyoxyethylene ester is lauric acid polyoxyethylene ester.

6. The defoamer for steel cleaning as described in claim 1, characterized in that, The bactericide is selected from any one of hydroxyethyl hexahydrotriazine, 1,2-benzisothiazolin-3-one, or Kathon.

7. The defoamer for steel cleaning as described in any one of claims 1 to 6, characterized in that, The preparation method of the polyether-modified silicone oil is as follows: Hydrogen-containing silicone oil with a hydrogen content of 0.1% and vinyl silicone oil with a vinyl content of 0.18%–0.40% are stirred and mixed, and the temperature is raised to 55°C–65°C. A platinum catalyst is added, and then the mixture is stirred and heated to 90–100°C. Allyl polyether is then added, and the mixture is stirred until the system becomes transparent to obtain the polyether-modified silicone oil. The mass ratio of the hydrogen-containing silicone oil, vinyl silicone oil, and allyl polyether is 45:(10–15):(40–50). The allyl polyether is an EO / PO block polyether, and the mass ratio of EO / PO is (2–4):

5.

8. A method for preparing the defoamer for steel cleaning according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Add silicone grease, fatty alcohol polyoxyethylene ether, polyether modified silicone oil, triglyceride monostearate, fatty acid polyoxyethylene ester, and sodium fatty alcohol polyoxyethylene ether sulfate to the reaction vessel, stir and heat to 60-70℃, and keep warm and stir for 30-60 minutes. S2. Add deionized water slowly in batches. After each addition of water, stir and emulsify at 80-100 rpm for 15-30 minutes at 35℃-40℃. After all the deionized water has been added, stir until the emulsion inverts, and then cool to room temperature. S3. Add bactericide and mix well to obtain defoamer for steel cleaning.

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