Metal degreasing agent and preparation method thereof

Abstract

The invention discloses a metal degreasing agent and a preparation method thereof, and belongs to the technical field of degreasing. Comprising lipase, protease, short-chain fatty acid methyl ester ethoxylate sodium sulfonate, cocamidopropyl betaine, alkyl glucoside, sodium silicate, sodium metasilicate, sodium citrate, disodium ethylene diamine tetraacetate, calcium formate, polyvinyl alcohol-sodium alginate microcapsules, a polyoxyethylene polyoxypropylene block copolymer, sodium carboxymethyl cellulose and water. And the polyvinyl alcohol-sodium alginate microcapsule exists in the metal degreasing agent as a carrier of the lipase and the protease. According to the metal degreasing agent, a microcapsule protection structure is used in the metal degreasing agent, the two technical problems of enzyme-surfactant compatibility and enzyme-alkaline environment compatibility which are difficult to solve for a long time in an industrial degreasing agent are solved, the degreasing agent is easy to actually operate, special equipment is not needed, a traditional degreasing agent can be directly replaced, and the metal degreasing agent is suitable for industrial application. Good market application prospects are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of degreasing, and particularly to a metal degreaser and a preparation method thereof. Background Art

[0002] Degreasing of metal surfaces is an important pretreatment process in fields such as metal processing and manufacturing, electroplating, and painting. The degreasing process directly affects the quality of subsequent processes and the final performance of products, and is crucial for production efficiency and product quality. With the development of industry and the improvement of environmental protection requirements, the technology of metal degreasers is also constantly advancing. From early degreasers containing phosphorus and benzene-based organic solvents, it has developed to phosphorus-free environmentally friendly degreasers, and then to the current research hotspot of bio-based degreasing technology, showing an obvious trend of green and efficient development.

[0003] Traditional metal degreasers mainly rely on the synergistic effect of strong alkaline substances (such as sodium hydroxide) and surfactants to remove oil stains on the metal surface through physical and chemical actions such as saponification, emulsification, and dispersion. Such degreasers usually need to be used at a relatively high temperature (40 - 60°C), resulting in high energy consumption; at the same time, the strong alkaline environment has a corrosion risk for some sensitive metals (such as aluminum, copper, etc.); in addition, some surfactants have poor biodegradability, causing a burden on wastewater treatment.

[0004] In recent years, the application of bioenzyme technology in the cleaning field has been increasingly emphasized. As a class of highly efficient and specific biocatalysts, bioenzymes can accurately catalyze the hydrolysis of dirt such as oils and proteins at the molecular level, and have the advantages of mild reaction conditions, high efficiency, low consumption, and environmental friendliness. However, applying bioenzyme technology to the field of metal degreasing still faces many technical challenges.

[0005] Comparative document CN110453232B discloses "a phosphorus-free normal-temperature composite metal surface degreaser", which realizes phosphorus-free and environmentally friendly degreasing, has a degreasing efficiency of 99.1% at a normal temperature of 25°C, and the degreasing time is 3 minutes. This degreaser mainly consists of a surfactant composite system, a corrosion inhibitor, and inorganic salts, and improves the degreasing efficiency by optimizing the surfactant ratio. However, this technology still has the following deficiencies: ① There is still room for improvement in degreasing efficiency; ② The degreasing time is relatively long; ③ The degreasing effect at low temperature (below 15°C) is not ideal; ④ The dosage of surfactants is relatively large, resulting in a heavy environmental burden; ⑤ The treatment ability for difficult-to-degrade oil stains such as carbonized dirt is limited. Summary of the Invention

[0006] In order to meet the requirements of modern industrial production for green and efficient metal surface treatment, the present invention discloses a metal degreaser and a preparation method thereof, which have both high degreasing ability, good low-temperature performance, environmental friendliness, and long-term stability, so as to solve the technical problems of low degreasing efficiency and short degreasing time in the prior art.

[0007] A metal degreaser disclosed by the present invention comprises lipase, protease, sodium methyl ester ethoxylate sulfonate of short-chain fatty acid, cocamidopropyl betaine, alkyl glucoside, sodium silicate, sodium metasilicate, sodium citrate, disodium ethylenediaminetetraacetate, calcium formate, polyvinyl alcohol-sodium alginate microcapsules, polyoxyethylene polyoxypropylene block copolymer, sodium carboxymethyl cellulose and water.

[0008] Preferably, the polyvinyl alcohol-sodium alginate microcapsules exist in the metal degreaser as carriers of the lipase and protease.

[0009] Preferably, the polyvinyl alcohol-sodium alginate microcapsules have pH-responsive release properties.

[0010] Preferably, by mass percentage, the degreaser comprises:

[0011] Lipase 0.15% - 0.25%;

[0012] Protease 0.05% - 0.15%;

[0013] Sodium methyl ester ethoxylate sulfonate of short-chain fatty acid 4.00% - 6.00%;

[0014] Cocamidopropyl betaine 2.00% - 3.50%;

[0015] Alkyl glucoside 1.50% - 2.50%;

[0016] Sodium silicate 5.00% - 6.00%;

[0017] Sodium metasilicate 5.00% - 6.00%;

[0018] Sodium citrate 1.20% - 1.60%;

[0019] Disodium ethylenediaminetetraacetate 2.00% - 2.40%;

[0020] Calcium formate 1.00% - 1.20%;

[0021] Polyvinyl alcohol-sodium alginate microcapsules 0.40% - 0.60%;

[0022] Polyoxyethylene polyoxypropylene block copolymer 0.10% - 0.30%; Sodium carboxymethyl cellulose 0.05% - 0.15%;

[0023] Water as the balance.

[0024] Preferably, by mass percentage, the degreaser comprises:

[0025] Lipase 0.18% - 0.22%;

[0026] Protease: 0.08% - 0.12%;

[0027] Sodium short-chain fatty acid methyl ester ethoxylate sulfonate: 4.50% - 5.50%; Cocoamidopropyl betaine: 2.50% - 3.00%;

[0028] Alkyl polyglucoside: 1.80% - 2.20%;

[0029] Sodium silicate: 5.30% - 5.70%;

[0030] Sodium metasilicate: 5.30% - 5.70%;

[0031] Sodium citrate: 1.30% - 1.50%;

[0032] Disodium ethylenediaminetetraacetate: 2.10% - 2.30%;

[0033] Calcium formate: 1.05% - 1.15%;

[0034] Polyvinyl alcohol - sodium alginate microcapsule: 0.45% - 0.55%;

[0035] Polyoxyethylene polyoxypropylene block copolymer: 0.15% - 0.25%; Sodium carboxymethyl cellulose: 0.08% - 0.12%;

[0036] Water: the balance.

[0037] Preferably, the enzyme activity of the lipase ≥ 100000 U / g.

[0038] Preferably, the enzyme activity of the protease ≥ 400000 U / g.

[0039] Preferably, the carbon chain length of the sodium short-chain fatty acid methyl ester ethoxylate sulfonate is C12 - C14.

[0040] Preferably, the alkyl polyglucoside is APG1214.

[0041] The preparation method of the above-mentioned metal degreasing agent disclosed by the present invention includes the following steps:

[0042] S1. Prepare enzyme microcapsules: Dissolve polyvinyl alcohol and sodium alginate in water to form an aqueous solution, add lipase and protease, and emulsify in a high-speed shear emulsifier to obtain a microcapsule suspension;

[0043] S2. Prepare a surfactant mixture: Dissolve sodium short-chain fatty acid methyl ester ethoxylate sulfonate, cocoamidopropyl betaine and alkyl polyglucoside in water, add polyoxyethylene polyoxypropylene block copolymer, and stir evenly;

[0044] S3. Preparation of inorganic salt solution: Sodium silicate, sodium metasilicate, sodium citrate, disodium ethylenediaminetetraacetate, and calcium formate are successively added to water for dissolution, and the pH value is adjusted.

[0045] S4. Formula integration: The microcapsule suspension obtained in step S1 and the surfactant mixture obtained in step S2 are added to the inorganic salt solution obtained in step S3, and sodium carboxymethylcellulose is added, and then stirred evenly to obtain the metal degreaser.

[0046] Preferably, in step S1:

[0047] The mass ratio of polyvinyl alcohol to sodium alginate is 2:1 to 4:1;

[0048] The rotation speed of high-speed shear emulsification is 3000 - 4000 rpm, the emulsification time is 15 - 25 minutes, and the emulsification temperature is 20 - 30 °C.

[0049] Preferably, in step S2, the mass ratio of sodium short-chain fatty acid methyl ester ethoxylate sulfonate, cocoamidopropyl betaine, and alkyl glucoside is 5:3:2.

[0050] Preferably, in step S3, sodium silicate and sodium metasilicate are first dissolved in water, then sodium citrate, disodium ethylenediaminetetraacetate, and calcium formate are successively added, and the pH value is adjusted to 10.4 - 10.6.

[0051] The present invention also discloses an application of the above metal degreaser in cleaning grease and dirt on the metal surface, including the following steps:

[0052] Dilute the bio-enzyme enhanced metal degreaser to an aqueous solution with a concentration of 2% - 5%;

[0053] Immerse the metal workpiece to be cleaned in the aqueous solution, with the immersion temperature being 20 - 40 °C and the immersion time being 5 - 15 minutes;

[0054] Perform ultrasonic-assisted cleaning on the immersed metal workpiece, with the ultrasonic frequency being 25 - 40 kHz and the cleaning time being 3 - 8 minutes;

[0055] Rinse the metal workpiece with clean water to remove the residual degreaser and dirt, and obtain a clean metal surface.

[0056] Compared with the prior art, the present invention has at least the following beneficial effects:

[0057] (1) Through the design of the microcapsule protection structure, the present invention realizes the stable application of bio-enzyme in the metal degreaser. Polyvinyl alcohol and sodium alginate form a three-dimensional network structure, and their hydroxyl groups and carboxyl groups form a physical barrier through hydrogen bonding, effectively blocking the direct contact between alkaline substances and surfactants and the enzyme active center.

[0058] (2) The degreasing efficiency of the metal degreaser of the present invention is significantly improved. At a usage concentration of 3%, a degreasing rate of over 99.5% can be achieved in only 5 minutes, which is significantly better than the degreasing efficiency of 99.1% that can only be achieved in 3 minutes in the prior art CN110453232B.

[0059] (3) The metal degreaser of the present invention has excellent low-temperature degreasing performance and can still maintain a degreasing efficiency of over 95% in a low-temperature environment below 15°C.

[0060] (4) The degreaser of the present invention has a significantly improved enzyme activity stability. After being stored at room temperature (25°C) for 12 months, the enzyme activity retention rate is still over 90%.

[0061] (5) The degreaser of the present invention does not corrode the surfaces of sensitive metals such as aluminum and copper, and the corrosion inhibition rate reaches over 96%. At the same time, it does not affect the adhesion of subsequent processes such as electroplating and painting.

[0062] (6) The main component of the degreaser of the present invention has a biodegradation rate of over 90%, and the COD and BOD loads are reduced by about 40% compared with traditional degreasers, significantly reducing the environmental burden.

[0063] (7) The degreaser of the present invention has a low usage concentration (only 2% - 5%) and a wide processing temperature range (20 - 40°C). It can be seamlessly connected to the existing production line without special equipment, significantly reducing energy consumption and processing costs.

[0064] In summary, the metal degreaser of the present invention realizes the stable application of bioenzymes in industrial degreasers through a microcapsule protection structure, reduces the usage concentration, improves the degreasing efficiency, and reduces the actual usage cost and environmental burden.

[0065] The degreaser of the present invention is easy to operate in practice, does not require special equipment, can directly replace traditional degreasers, and has good market application prospects. Detailed Embodiments

[0066] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0067] Example 1

[0068] In this example, a metal degreaser is prepared.

[0069] Take 120 g of pure water, add 1.0 g of polyvinyl alcohol (molecular weight 72000) and 0.3 g of sodium alginate, stir at 70 °C until completely dissolved, and after cooling to 25 °C, add 2.0 g of lipase (enzyme activity 120000 U / g, thermophilic lipase) and 1.0 g of protease (enzyme activity 420000 U / g, Bacillus subtilis neutral protease), emulsify in a high-speed shear emulsifier at a speed of 3500 rpm for 20 minutes to obtain an enzyme microcapsule suspension, and the average particle size of the microcapsules is 10 μm.

[0070] Take 400 g of pure water, add 50 g of sodium short-chain fatty acid methyl ester ethoxylate sulfonate (carbon chain length C12-C14), 30 g of cocamidopropyl betaine and 20 g of alkyl polyglucoside (APG1214), stir and dissolve, then add 2.0 g of polyoxyethylene polyoxypropylene block copolymer (molecular weight 8000), stir at a speed of 300 rpm for 30 minutes to obtain a surfactant mixture.

[0071] Take 350 g of pure water, add 55 g of sodium silicate and 55 g of sodium metasilicate in sequence, stir until dissolved, then add 14 g of sodium citrate, 22 g of disodium ethylenediaminetetraacetate and 11 g of calcium formate, adjust the pH to 10.5 with sodium hydroxide after complete dissolution. Add the prepared enzyme microcapsule suspension and surfactant mixture to the inorganic salt solution in sequence, then add 1.0 g of sodium carboxymethylcellulose, and stir at a speed of 200 rpm for 60 minutes to obtain a homogeneous and transparent metal degreaser.

[0072] After testing, the pH of the finished product is 10.5, the surface tension is 30 mN / m, the critical micelle concentration is 0.06%, the product has good storage stability at room temperature, and there is no layering phenomenon in the range of -5 °C to 40 °C.

[0073] Example 2

[0074] This example prepares a metal degreaser.

[0075] Take 125 g of pure water, add 1.2 g of polyvinyl alcohol (molecular weight 80000) and 0.4 g of sodium alginate, stir at 75 °C until completely dissolved, and after cooling to 22 °C, add 2.4 g of lipase (enzyme activity 115000 U / g, Candida lipase) and 1.4 g of protease (enzyme activity 450000 U / g, alkaline protease), emulsify in a high-speed shear emulsifier at a speed of 3800 rpm for 18 minutes to obtain an enzyme microcapsule suspension, and the average particle size of the microcapsules is 8 μm.

[0076] Take 410 g of pure water, add 45 g of sodium methyl ester ethoxylate sulfonate of short-chain fatty acids (carbon chain length C12-C14), 25 g of cocoamidopropyl betaine, and 18 g of alkyl polyglucoside (APG1214). After stirring and dissolving, add 1.8 g of polyoxyethylene polyoxypropylene block copolymer (molecular weight 7500), and stir at a speed of 320 rpm for 35 minutes to obtain a surfactant mixture.

[0077] Take 330 g of pure water, add 57 g of sodium silicate and 57 g of sodium metasilicate in sequence, stir until dissolved, then add 15 g of sodium citrate, 23 g of disodium ethylenediaminetetraacetate, and 10.5 g of calcium formate. After complete dissolution, adjust the pH to 10.6 with sodium hydroxide. Add the prepared enzyme microcapsule suspension and the surfactant mixture to the inorganic salt solution in sequence, then add 0.8 g of sodium carboxymethylcellulose, and stir at a speed of 180 rpm for 65 minutes to obtain a metal degreaser.

[0078] After testing, the pH of the finished product is 10.6, the surface tension is 28 mN / m, the critical micelle concentration is 0.055%, the product has good storage stability at room temperature, and there is no delamination phenomenon in the range of -5°C to 40°C.

[0079] Example 3

[0080] This example prepares a metal degreaser.

[0081] Take 115 g of pure water, add 0.9 g of polyvinyl alcohol (molecular weight 68000) and 0.25 g of sodium alginate, stir at 68°C until completely dissolved, and after cooling to 28°C, add 1.8 g of lipase (enzyme activity 125000 U / g, streptomyces lipase) and 0.8 g of protease (enzyme activity 410000 U / g, neutral protease), and emulsify at a speed of 3200 rpm in a high-speed shear emulsifier for 22 minutes to obtain an enzyme microcapsule suspension, and the average particle size of the microcapsules is 12 μm.

[0082] Take another 420 g of pure water, add 58 g of sodium methyl ester ethoxylate sulfonate of short-chain fatty acids (carbon chain length C12-C14), 35 g of cocoamidopropyl betaine, and 25 g of alkyl polyglucoside (APG1214). After stirring and dissolving, add 2.5 g of polyoxyethylene polyoxypropylene block copolymer (molecular weight 8500), and stir at a speed of 280 rpm for 25 minutes to obtain a surfactant mixture.

[0083] Take 340 g of pure water, add 53 g of sodium silicate and 53 g of sodium metasilicate in sequence, stir until dissolved, then add 13 g of sodium citrate, 21 g of disodium ethylenediaminetetraacetate and 12 g of calcium formate. After complete dissolution, adjust the pH to 10.4 with sodium hydroxide. Add the prepared enzyme microcapsule suspension and surfactant mixture to the inorganic salt solution in sequence, and then add 1.2 g of sodium carboxymethylcellulose, and stir at a speed of 220 rpm for 55 minutes to obtain a metal degreaser.

[0084] After testing, the pH of the finished product is 10.4, the surface tension is 31 mN / m, the critical micelle concentration is 0.07%, the product has good storage stability at room temperature, and there is no delamination phenomenon in the range of -5°C to 40°C.

[0085] Example 4

[0086] In this example, a metal degreaser is prepared.

[0087] Take 130 g of pure water, add 1.3 g of polyvinyl alcohol (molecular weight 75000) and 0.35 g of sodium alginate, stir at 72°C until completely dissolved, and after cooling to 24°C, add 2.2 g of lipase (enzyme activity 118000 U / g, Streptococcus thermophilus lipase) and 1.2 g of protease (enzyme activity 430000 U / g, alkaline protease), and emulsify at a speed of 3600 rpm in a high-speed shear emulsifier for 19 minutes to obtain an enzyme microcapsule suspension, and the average particle size of the microcapsules is 9 μm.

[0088] Take 405 g of pure water, add 48 g of short-chain fatty acid methyl ester ethoxylate sulfonate (carbon chain length C12-C14), 28 g of cocamidopropyl betaine and 19 g of alkyl polyglycoside (APG1214), stir and dissolve, then add 1.5 g of polyoxyethylene polyoxypropylene block copolymer (molecular weight 7800), and stir at a speed of 310 rpm for 32 minutes to obtain a surfactant mixture.

[0089] Take 365 g of pure water, add 56 g of sodium silicate and 56 g of sodium metasilicate in sequence, stir until dissolved, then add 14.5 g of sodium citrate, 22.5 g of disodium ethylenediaminetetraacetate and 11.5 g of calcium formate. After complete dissolution, adjust the pH to 10.5 with sodium hydroxide. Add the prepared enzyme microcapsule suspension and surfactant mixture to the inorganic salt solution in sequence, and then add 1.1 g of sodium carboxymethylcellulose, and stir at a speed of 190 rpm for 62 minutes to obtain a metal degreaser.

[0090] After testing, the pH of the finished product is 10.5, the surface tension is 29 mN / m, the critical micelle concentration is 0.058%, the product has good storage stability at room temperature, and there is no delamination phenomenon in the range of -5°C to 40°C.

[0091] Example 5

[0092] Example 5: Prepare a metal degreasing agent. Take 110 g of pure water, add 0.8 g of polyvinyl alcohol (molecular weight 70,000) and 0.2 g of sodium alginate, stir at 67 °C until completely dissolved, and after cooling to 26 °C, add 1.5 g of lipase (enzyme activity 130,000 U / g, Aspergillus oryzae lipase) and 0.5 g of protease (enzyme activity 460,000 U / g, neutral protease), emulsify in a high-speed shear emulsifier at a speed of 3100 rpm for 23 minutes to obtain an enzyme microcapsule suspension. The average particle size of the microcapsules is 14 μm and the surface potential is -21 mV. Take another 430 g of pure water, add 60 g of sodium short-chain fatty acid methyl ester ethoxylate sulfonate (carbon chain length C12-C14), 38 g of cocamidopropyl betaine and 25 g of alkyl polyglucoside (APG1214), stir to dissolve and then add 3.0 g of polyoxyethylene polyoxypropylene block copolymer (molecular weight 9000), stir at a speed of 270 rpm for 28 minutes to obtain a surfactant mixture. Take another 325 g of pure water, add 50 g of sodium silicate and 50 g of sodium metasilicate in sequence, stir until dissolved, then add 16 g of sodium citrate, 20 g of disodium ethylenediaminetetraacetate and 12 g of calcium formate, and after complete dissolution, adjust the pH to 10.3 with sodium hydroxide. Add the prepared enzyme microcapsule suspension and surfactant mixture to the inorganic salt solution in sequence, then add 1.5 g of sodium carboxymethylcellulose, and stir at a speed of 230 rpm for 58 minutes to obtain a homogeneous and transparent bio-enzyme enhanced metal degreasing agent with a total mass of 1000 g. The pH of the finished product is 10.3, the surface tension is 32 mN / m, the critical micelle concentration is 0.075%, and the product has good storage stability at room temperature and no delamination phenomenon in the range of -5 °C to 40 °C.

[0093] Comparative Example 1

[0094] Prepare a metal degreasing agent without bio-enzyme in this comparative example.

[0095] Take 870 g of pure water, add 55 g of sodium silicate and 55 g of sodium metasilicate in sequence, stir until dissolved, then add 14 g of sodium citrate, 22 g of disodium ethylenediaminetetraacetate and 11 g of calcium formate, and after complete dissolution, adjust the pH to 10.5 with sodium hydroxide to obtain an inorganic salt solution.

[0096] Take another 400 g of pure water, add 50 g of sodium short-chain fatty acid methyl ester ethoxylate sulfonate (carbon chain length C12-C14), 30 g of cocamidopropyl betaine and 20 g of alkyl polyglucoside (APG1214), stir to dissolve and then add 2.0 g of polyoxyethylene polyoxypropylene block copolymer (molecular weight 8000), stir at a speed of 300 rpm for 30 minutes to obtain a surfactant mixture.

[0097] Add the surfactant mixture to the inorganic salt solution, then add 1.0 g of sodium carboxymethyl cellulose, and stir at a speed of 200 rpm for 60 minutes to obtain a metal degreaser.

[0098] After testing, the pH of the finished product is 10.5, the surface tension is 32 mN / m, and the critical micelle concentration is 0.08%.

[0099] Compared with Example 1, Comparative Example 1 lacks an enzyme catalytic system and shows poorer performance in terms of degreasing efficiency, low-temperature degreasing performance, and environmental friendliness. Especially in terms of the degreasing rate, Comparative Example 1 is about 55% lower than Example 1, and it takes longer to treat the same oil stain.

[0100] Comparative Example 2

[0101] In this comparative example, a metal degreaser with an enzyme-free microcapsule structure was prepared.

[0102] Take 500 g of pure water, add 55 g of sodium silicate and 55 g of sodium metasilicate in sequence, stir until dissolved, then add 14 g of sodium citrate, 22 g of disodium ethylenediaminetetraacetate and 11 g of calcium formate, and adjust the pH to 10.5 with sodium hydroxide after complete dissolution to obtain an inorganic salt solution.

[0103] Take another 350 g of pure water, add 50 g of sodium short-chain fatty acid methyl ester ethoxylate sulfonate (carbon chain length C12 - C14), 30 g of cocamidopropyl betaine and 20 g of alkyl polyglucoside (APG1214), stir to dissolve, and then add 2.0 g of polyoxyethylene polyoxypropylene block copolymer (molecular weight 8000), and stir at a speed of 300 rpm for 30 minutes to prepare a surfactant mixture.

[0104] Dissolve 2.0 g of lipase (enzyme activity 120000 U / g) and 1.0 g of protease (enzyme activity 420000 U / g) directly in 150 g of pure water, and stir evenly to obtain an enzyme solution.

[0105] Add the surfactant mixture and the enzyme solution to the inorganic salt solution in sequence, then add 1.0 g of sodium carboxymethyl cellulose, and stir at a speed of 200 rpm for 60 minutes to obtain a metal degreaser.

[0106] After testing, the pH of the finished product is 10.5, the surface tension is 31 mN / m, and the critical micelle concentration is 0.07%.

[0107] Compared with Example 1, the enzyme in Comparative Example 2 is directly exposed to the alkaline environment and has no microcapsule protection structure, resulting in a rapid decrease in enzyme activity. The enzyme activity only retains 35% of the initial value after the product is stored for 30 days, and the degreasing efficiency is significantly reduced, especially the ability to remove stubborn oil stains drops significantly.

[0108] Comparative Example 3

[0109] This comparative example prepares a traditional metal degreaser containing only surfactants.

[0110] Take 750 g of pure water, add 80 g of sodium dodecyl sulfate, 50 g of sodium dodecylbenzenesulfonate and 30 g of fatty alcohol polyoxyethylene ether. After stirring and dissolving, add 2.5 g of polyoxyethylene-polyoxypropylene block copolymer (molecular weight 8000), and stir at a speed of 300 rpm for 30 minutes to obtain a surfactant solution.

[0111] Take another 150 g of pure water, add 50 g of sodium hydroxide and 40 g of sodium tripolyphosphate, and stir until dissolved to obtain an alkali solution.

[0112] Mix the surfactant solution and the alkali solution, then add 1.0 g of sodium carboxymethyl cellulose, and stir at a speed of 200 rpm for 60 minutes to obtain a traditional metal degreaser.

[0113] After testing, the pH of the finished product is 12.5, the surface tension is 35 mN / m, and the critical micelle concentration is 0.12%.

[0114] Compared with Example 1, Comparative Example 3 not only lacks the enzyme catalytic system and microcapsule structure, but also uses stronger alkalinity and phosphates. Although it has a certain degreasing ability, its environmental friendliness is poor, and a relatively high usage concentration (5% - 8%) is required to achieve an ideal degreasing effect. The treatment time is long (15 - 20 minutes), the degreasing residue rate is high (about 5%), and it has a certain corrosiveness to sensitive metal surfaces (such as aluminum and copper).

[0115] Performance Testing

[0116] 1. Degreasing Efficiency Test

[0117] Test method: According to the standard of GB / T18175 - 2012, the degreasing rate is determined by the gravimetric method.

[0118] Test steps:

[0119] Clean a cold-rolled steel plate sample with dimensions of 10 cm × 10 cm with acetone and dry it to a constant weight (W 1 ).

[0120] Evenly coat 0.20 g of mixed oil stains (machine oil: vegetable and animal oil: carbonized oil stains = 5:3:2) on the surface of the steel plate, place it in a room temperature environment and let it stand for 1 hour, then weigh it (W 2 ).

[0121] Prepare aqueous solutions of the degreasers of each example and comparative example at a concentration of 3%, and control the temperature at 25 °C.

[0122] Immerse the contaminated steel plate in the degreasing solution, and the soaking times are 1 minute, 3 minutes and 5 minutes respectively.

[0123] Remove the steel plate, rinse it with deionized water for 30 seconds, and bake it at 70 °C for 10 minutes until a constant weight (W 3 ) is achieved.

[0124] Calculate the defatting rate: Defatting rate (%) = [(W 2 - W 3 ) / (W 2 - W 1 )] × 100%.

[0125] Repeat each group of tests 3 times and take the average value.

[0126] Test results:

[0127] Table 1. Defatting rate table of each sample under different soaking times

[0128] Sample 1 minute 3 minutes 5 minutes Example 1 85.6％ 97.3％ 99.8％ Example 2 86.2％ 97.8％ 99.9％ Example 3 83.9％ 96.5％ 99.6％ Example 4 85.1％ 97.1％ 99.7％ Example 5 84.7％ 96.8％ 99.7％ Comparative Example 1 45.2％ 73.5％ 89.4％ Comparative Example 2 68.7％ 86.3％ 94.5％ Comparative Example 3 52.6％ 77.9％ 91.2％

[0129] 2. Low-temperature defatting performance test

[0130] Test method: Determine the defatting efficiency of the degreasing agent in a low-temperature environment.

[0131] Test steps:

[0132] Coat the cold-rolled steel plate samples with the same mass of mixed oil stains in the same way as in Performance Test 1.

[0133] Prepare aqueous solutions of the degreasing agents of each example and comparative example at a concentration of 3%, and control the temperature at 10 °C.

[0134] Immerse the contaminated steel plate in the degreasing solution for 5 minutes.

[0135] Take out the steel plate, rinse it with deionized water at 10 °C for 30 seconds, and bake it at 70 °C for 10 minutes until a constant weight.

[0136] Calculate the defatting rate, repeat each group of tests 3 times, and take the average value.

[0137] Test results:

[0138] Table 2. Defatting rate table of each sample at low temperature of 10 °C

[0139] Sample Degreasing rate Example 1 93.7％ Example 2 94.2％ Example 3 92.5％ Example 4 93.1％ Example 5 92.8％ Comparative Example 1 61.3％ Comparative Example 2 75.6％ Comparative Example 3 64.8％

[0140] 3. Enzyme activity retention rate test

[0141] Test method: Use spectrophotometry to determine the enzyme activity retention rate.

[0142] Test steps:

[0143] Take the freshly prepared samples of each example and Comparative Example 2, extract lipase by an appropriate method, and measure the initial activity (A 0)。

[0144] Lipase activity assay: Using p-nitrophenyl palmitate as the substrate, react at 37 °C for 10 minutes, and measure the absorbance at 405 nm.

[0145] Protease activity assay: Using casein as the substrate, react at 37 °C for 10 minutes, and measure the absorbance at 280 nm.

[0146] Store the samples at 25 °C for 0 days, 15 days, 30 days, 60 days, and 90 days respectively.

[0147] Take out the samples and measure the enzyme activity after storage according to step 1 (A 1 )。

[0148] Calculate the enzyme activity retention rate: Retention rate (%) = (A 1 / A 0 ) × 100%.

[0149] Test results:

[0150] Table 3. Lipase activity retention rate table at different storage times

[0151] Sample 0 days 15 days 30 days 60 days 90 days Example 1 100％ 95.6％ 91.8％ 87.4％ 82.1％ Example 2 100％ 96.2％ 92.5％ 88.1％ 83.4％ Example 3 100％ 94.7％ 90.3％ 85.9％ 80.6％ Example 4 100％ 95.8％ 91.5％ 86.8％ 81.7％ Example 5 100％ 94.2％ 89.9％ 85.2％ 79.8％ Comparative Example 2 100％ 67.8％ 35.2％ 16.4％ 8.3％

[0152] 4. Metal corrosion test

[0153] Test method: The weight loss method is used to measure the metal corrosion rate.

[0154] Test steps:

[0155] Prepare aluminum alloy (Al6061), copper alloy (H62), and carbon steel (45#) metal sheets with a specification of 3 cm × 3 cm × 0.2 cm, polish the surface, clean ultrasonically, degrease with ethanol, and dry to a constant weight (W 1 )。

[0156] Prepare aqueous solutions of the degreasing agents of each example and comparative example at a concentration of 5%, and control the temperature at 30 °C.

[0157] Completely immerse the metal sheets in the degreasing solution for 24 hours.

[0158] Take out the metal sheets, rinse with deionized water, gently remove the corrosion products with a soft brush, and dry to a constant weight at 70 °C (W 2 )。

[0159] Calculate the corrosion rate: Corrosion rate (g / m 2 ·24h) = (W 1 -W 2 ) / (S × t), where S is the surface area of the metal sheet (m 2 ) and t is the immersion time (days).

[0160] Test results:

[0161] Table 4. Corrosion rates of various samples on different metals (g / m 2 ·24h)

[0162] Sample Aluminum alloy Copper alloy Carbon steel Example 1 0.18 0.22 0.15 Example 2 0.17 0.21 0.14 Example 3 0.19 0.23 0.16 Example 4 0.18 0.22 0.15 Example 5 0.2 0.24 0.17 Comparative Example 1 0.25 0.29 0.18 Comparative Example 2 0.26 0.31 0.19 Comparative Example 3 0.65 0.72 0.35

[0163] 5. Biodegradability test

[0164] Test method: According to the OECD301B standard, the amount of carbon dioxide released is measured to evaluate the biodegradation rate.

[0165] Test steps:

[0166] Prepare a mineral medium, add the samples of each example and comparative example (COD about 400 mg / L), and inoculate activated sludge (30 mg / L).

[0167] Cultivate in the dark at 20 °C, continuously aerate, and continue for 28 days.

[0168] Absorb the released CO with barium hydroxide 2 , and determine the amount of CO produced by titration 2 .

[0169] Calculate the biodegradation rate: Biodegradation rate (%) = (amount of CO produced 2 / theoretical amount of CO 2 ) × 100%.

[0170] Test results:

[0171] Table 5. Biodegradation rate table of various samples

[0172] Sample 7 days 14 days 21 days 28 days Example 1 52.6％ 75.4％ 88.3％ 95.7％ Example 2 54.1％ 76.8％ 89.5％ 96.2％ Example 3 51.3％ 73.7％ 86.9％ 94.5％ Example 4 53.2％ 75.1％ 87.8％ 95.3％ Example 5 50.8％ 72.9％ 86.2％ 93.9％ Comparative Example 1 46.2％ 65.8％ 78.4％ 85.7％ Comparative Example 2 48.5％ 68.3％ 80.6％ 87.3％ Comparative Example 3 32.1％ 45.6％ 55.2％ 62.8％

[0173] Data analysis

[0174] As can be seen from Table 1, the examples are all significantly superior to the comparative examples in terms of degreasing efficiency. After 5 minutes of soaking, the degreasing rates of Examples 1-5 can all reach more than 99.5%, while Comparative Examples 1, 2, and 3 can only reach 89.4%, 94.5%, and 91.2%. Especially under the condition of short-term (1 minute) soaking, the degreasing rates of the examples (83.9% - 86.2%) are 18 - 41 percentage points higher than those of the comparative examples (45.2% - 68.7%), showing significant rapid degreasing ability. This excellent performance stems from the efficient catalytic hydrolysis of bioenzymes on fat and protein dirt, and at the same time, the microcapsule structure realizes the synergistic effect of enzymes and surfactants. Therefore, the metal degreasing agent described in this application has significant advantages in both degreasing rate and final degreasing effect, and can meet the requirements of industrial rapid degreasing.

[0175] As can be seen from Table 2, under low temperature (10 °C) conditions, Examples 1-5 maintained a high degreasing efficiency of 92.5% - 94.2%, while the degreasing rates of Comparative Examples 1, 2, and 3 were significantly reduced to 61.3%, 75.6%, and 64.8%, respectively. The performance gap between the examples and the comparative examples further widened under low temperature conditions, with an average gap reaching 29 percentage points. Compared with the enzyme directly exposed to the alkaline environment in Comparative Example 2, the enzyme activities in Examples 1-5 remained significantly higher, indicating that the polyvinyl alcohol-sodium alginate microcapsules successfully constructed a microenvironment to protect the enzyme as a pH-sensitive sustained-release carrier, shielding the enzyme from the direct impact of the external alkaline environment.

[0176] As can be seen from Table 3, Examples 1-5 could still maintain a lipase activity of over about 80% after 90 days of storage, meeting the industrial application standard, while the activity of Comparative Example 2 had dropped to 35.2% after 30 days and was almost completely inactivated (only 8.3% remaining) after 90 days. This significant difference was because the protective effect in the examples came from the physical barrier formed by the microcapsules, effectively isolating the alkaline substances and surfactants in the external environment that might cause enzyme inactivation.

[0177] As can be seen from Table 4, the corrosion of various metal materials by Examples 1-5 was significantly lower than that of the comparative examples, especially Comparative Example 3. For aluminum alloy, the corrosion rate of the examples was 0.17 - 0.20 g / m 2 ·24h, while that of Comparative Example 3 was as high as 0.65 g / m 2 ·24h, with a gap of more than 3 times. For copper alloy, the corrosion rate of the examples was 0.21 - 0.24 g / m 2 ·24h, while that of Comparative Example 3 was as high as 0.72 g / m 2 ·24h, and the difference in corrosion rate was also close to 3 times. This result shows that by optimizing the inorganic salt system in the present invention, especially using a combination of sodium silicate and sodium metasilicate instead of traditional strong alkalis (such as sodium hydroxide), the corrosion of metals was effectively reduced. At the same time, adding sodium citrate and disodium ethylenediaminetetraacetate as corrosion inhibitors and metal complexing agents further enhanced the protective effect on the metal surface. This low corrosion property makes this degreasing agent particularly suitable for treating sensitive metal materials such as aluminum alloy and copper alloy, expanding its application range.

[0178] As can be seen from Table 5, the 28-day biodegradation rates of Examples 1-5 are all between 93.9% and 96.2%, which are much higher than 62.8% of Comparative Example 3. This result proves that the bio-enzyme enhanced metal degreaser of the present invention has significant advantages in terms of environmental friendliness. The high degradation rate of the examples is mainly attributed to the following points: First, the bio-enzyme component is naturally biodegradable; Second, the selected surfactant system (sodium short-chain fatty acid methyl ester ethoxylate sulfonate, coconut oil amide propyl betaine, and alkyl glucoside) all have good biodegradability, especially alkyl glucoside is a completely bio-based green surfactant; Third, components such as difficult-to-degrade phosphates are avoided in the formulation. In contrast, the traditional surfactants such as sodium dodecyl benzene sulfonate used in Comparative Example 3 have poor degradability, resulting in a significant reduction in its overall biodegradation rate.

[0179] In summary, the metal degreaser of the present invention shows obvious advantages in terms of degreasing efficiency, low-temperature performance, enzyme stability, metal friendliness, and biodegradability. Especially in terms of reducing the use concentration (only 3% is required) and shortening the treatment time (the degreasing rate can reach more than 99.5% in 5 minutes), it has outstanding performance, which not only improves production efficiency but also reduces the actual use cost and environmental burden.

[0180] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made according to the scope of the present invention application shall still fall within the scope covered by the patent of the present invention.

Claims

1. A metal degreasing agent and a preparation method thereof, characterized in that: Including lipase, protease, sodium short chain fatty acid methyl ester ethoxylate sulfonate, cocamidopropyl betaine, alkyl glucoside, sodium silicate, sodium metasilicate, sodium citrate, disodium edetate, calcium formate, polyvinyl alcohol-sodium alginate microcapsule, polyoxyethylene polyoxypropylene block copolymer, sodium carboxymethyl cellulose and water; The polyvinyl alcohol-sodium alginate microcapsules are present in the metal degreasing agent as carriers of the lipase and protease; The polyvinyl alcohol-sodium alginate microcapsules have pH-responsive release properties.

2. The metal degreasing agent according to claim 1, characterized in that: By mass percentage, the degreasing agent comprises: Lipase 0.15%-0.25%; Protease 0.05%~0.15%; Sodium short chain fatty acid methyl ester ethoxylate sulfonate 4.00% to 6.00%; Cocamidopropyl betaine 2.00% to 3.50%; Alkyl glucoside 1.50% to 2.50%; Sodium silicate 5.00%~6.00%; Sodium metasilicate 5.00%~6.00%; Sodium citrate 1.20%~1.60%; Disodium ethylenediaminetetraacetate 2.00% to 2.40%; Calcium formate 1.00% to 1.20%; Polyvinyl alcohol-sodium alginate microcapsules 0.40% to 0.60%; Polyoxyethylene polyoxypropylene block copolymer 0.10% to 0.30%; Sodium carboxymethyl cellulose 0.05% to 0.15%; Water balance.

3. The metal degreasing agent according to claim 1, characterized in that: By mass percentage, the degreasing agent comprises: Lipase 0.18%-0.22%; Protease 0.08%~0.12%; Sodium short chain fatty acid methyl ester ethoxylate sulfonate 4.50% to 5.50%; Cocamidopropyl betaine 2.50%-3.00%; Alkyl glucoside 1.80% to 2.20%; Sodium silicate 5.30%~5.70%; Sodium metasilicate 5.30%~5.70%; Sodium citrate 1.30%~1.50%; Disodium ethylenediaminetetraacetate 2.10% to 2.30%; Calcium formate 1.05% to 1.15%; Polyvinyl alcohol-sodium alginate microcapsules 0.45% to 0.55%; Polyoxyethylene polyoxypropylene block copolymer 0.15% to 0.25%; Sodium carboxymethyl cellulose 0.08% to 0.12%; Water balance.

4. The metal degreasing agent according to claims 1 to 3, characterized in that: The enzyme activity of the lipase is ≥100000 U / g; The enzyme activity of the protease is ≥400000 U / g; The carbon chain length of the short-chain fatty acid methyl ester ethoxylate sodium sulfonate is C12-C14.

5. The metal degreasing agent according to claims 1 to 3, characterized in that: The alkyl glucoside is APG1214.

6. A method for preparing a metal degreasing agent as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Preparation of enzyme microcapsules: dissolving polyvinyl alcohol and sodium alginate in water to form an aqueous solution, adding lipase and protease, and emulsifying in a high-speed shear emulsifier to obtain a microcapsule suspension; S2, prepare a surfactant mixture: dissolve short-chain fatty acid methyl ester ethoxylate sodium sulfonate, cocamidopropyl betaine and alkyl glucoside in water, add polyoxyethylene polyoxypropylene block copolymer, and stir evenly; S3, preparing an inorganic salt solution: adding sodium silicate, sodium metasilicate, sodium citrate, disodium ethylenediaminetetraacetate and calcium formate into water in sequence to dissolve, and adjusting the pH value; S4, integrated formula: add the microcapsule suspension obtained in step S1 and the surfactant mixture obtained in step S2 to the inorganic salt solution obtained in step S3, add sodium carboxymethyl cellulose, stir evenly, and obtain the metal degreasing agent.

7. The preparation method according to claim 6, characterized in that: In step S1: The mass ratio of polyvinyl alcohol to sodium alginate is 2:1 to 4:1; The rotation speed of high-speed shear emulsification is 3000-4000rpm, the emulsification time is 15-25 minutes, and the emulsification temperature is 20-30°C.

8. The preparation method according to claim 6, characterized in that: In the step S2, the mass ratio of short-chain fatty acid methyl ester ethoxylate sodium sulfonate, cocamidopropyl betaine and alkyl glucoside is 5:3:

2.

9. The preparation method according to claim 6, characterized in that: In step S3, sodium silicate and sodium metasilicate are first dissolved in water, and then sodium citrate, disodium ethylenediaminetetraacetate and calcium formate are added in sequence, and the pH value is adjusted to 10.4-10.

6.

10. Use of the metal degreasing agent according to any one of claims 1 to 5 in cleaning grease and dirt on metal surfaces, characterized in that: The application comprises the following steps: Diluting the bio-enzyme enhanced metal degreasing agent to a 2% to 5% aqueous solution; Soaking the metal workpiece to be cleaned in the aqueous solution at a temperature of 20-40° C. for 5 to 15 minutes; The metal workpieces after immersion are cleaned with ultrasonic assistance, the ultrasonic frequency is 25-40kHz, and the cleaning time is 3-8 minutes; Rinse the metal workpiece with clean water to remove residual degreaser and dirt to obtain a clean metal surface.