High-efficiency and all-purpose alkaline degreasing agent as well as preparation method and application of high-efficiency and all-purpose alkaline degreasing agent

Abstract

The invention belongs to the technical field of metal surface treatment, and discloses a high-efficiency all-purpose alkaline degreaser as well as a preparation method and application thereof. The alkaline degreasing agent comprises an alkaline component, a complexing agent, a surfactant and an auxiliary agent, the alkaline component comprises sodium silicate and alkaline organic amine, and the surfactant comprises a polyoxyethylene nonionic surfactant and a Gemini surfactant. The alkaline degreaser provided by the invention has the characteristics of high efficiency, low temperature, environmental protection and suitability for various metals, the oil stain removal rate is 96% or above at the low temperature of 25-35 DEG C, and the energy consumption is reduced; and meanwhile, excellent cleaning capacity and metal surface protection capacity are considered, aluminum alloy corrosion or stainless steel oxidation is prevented, the aluminum alloy corrosion rate can be controlled to be 0.007 g / m < 2 >. H or below, and the universality to metal such as aluminum, magnesium, steel and stainless steel is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal surface treatment, and particularly relates to a highly efficient all-round alkaline degreaser and its preparation method and application. Background Art

[0002] In the modern metal processing and surface treatment industries, degreasing and cleaning is a key step to ensure the quality of subsequent processes (such as electroplating, painting, anodizing). If the oil stains, dust, and oxides on the metal surface are not thoroughly removed, it will directly affect the adhesion and corrosion resistance of the coating or plating. The current degreasing technologies are mainly divided into the following two categories:

[0003] Acid degreasing: mainly composed of phosphoric acid, sulfuric acid, hydrochloric acid, etc., and is commonly used for the surface treatment of steel and stainless steel. Its advantages are that it has a significant effect on removing stubborn oil stains and scale, but its disadvantages are strong corrosiveness, large equipment loss, and the acidic waste liquid contains phosphates and fluorides, with high treatment costs and easy environmental pollution.

[0004] Alkaline degreasing: using sodium hydroxide, sodium carbonate, silicate, etc. as alkaline components, combined with surfactants and complexing agents, and is widely used in the cleaning of various metals such as aluminum, magnesium, and steel. Compared with acid degreasing, it has less corrosion to equipment and relatively environmentally friendly waste liquid treatment. However, traditional alkaline degreasers need to be used above 60°C, with low degreasing efficiency (below 80%) under low temperature (25 - 35°C) conditions, and there is a high corrosion risk for active metals (such as aluminum and magnesium).

[0005] With the increasingly strict environmental protection regulations, the industry's demand for degreasers has shifted towards phosphorus-free, heavy metal-free, low-corrosion, and high-efficiency directions. Therefore, there is an urgent need to develop an alkaline degreaser that is suitable for various metals, has high efficiency at low temperature, and is environmentally friendly. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. For this reason, the present invention provides a highly efficient all-round alkaline degreaser and its preparation method and application. The alkaline degreaser provided by the present invention can still maintain high-efficiency degreasing ability under low temperature conditions, and has low corrosiveness, and is suitable for cleaning oil stains, oxides, and organic pollutants on the surfaces of various metals such as aluminum, magnesium, steel, and stainless steel.

[0007] In the first aspect of the present invention, there is provided an alkaline degreaser, which includes an alkaline component, a complexing agent, a surfactant, and an auxiliary agent. The alkaline component includes sodium silicate and alkaline organic amine, and the surfactant includes polyoxyethylene non-ionic surfactant and Gemini surfactant.

[0008] In some embodiments of the present invention, by mass parts, the alkaline degreasing agent comprises 10 - 40 parts of an alkaline component, 3 - 10 parts of a complexing agent, 5 - 20 parts of a surfactant, and 4 - 10 parts of an auxiliary agent.

[0009] In some embodiments of the present invention, the complexing agent comprises at least one of sodium ethylenediaminetetraacetate, citric acid, and sorbic acid.

[0010] In some embodiments of the present invention, the auxiliary agent comprises at least one of a demulsifier, a dispersant, and a corrosion inhibitor.

[0011] In some embodiments of the present invention, the demulsifier comprises an EO - PO block copolymer.

[0012] In some embodiments of the present invention, the dispersant comprises sodium polyacrylate.

[0013] In some embodiments of the present invention, the corrosion inhibitor comprises benzotriazole.

[0014] In some embodiments of the present invention, the alkaline component further comprises an alkali metal carbonate.

[0015] In some embodiments of the present invention, the alkaline organic amine comprises triethanolamine and / or methyldiethanolamine.

[0016] In some embodiments of the present invention, the polyoxyethylene non - ionic surfactant comprises at least one of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether.

[0017] In some embodiments of the present invention, by mass parts, the alkaline degreasing agent comprises 5 - 15 parts of sodium silicate, 8 - 15 parts of an alkaline organic amine, 2 - 8 parts of an alkali metal carbonate, 3 - 10 parts of a complexing agent, 2 - 8 parts of fatty alcohol polyoxyethylene ether, 2 - 6 parts of alkylphenol polyoxyethylene ether, 1 - 3 parts of a Gemini surfactant, and 4 - 10 parts of an auxiliary agent.

[0018] In some embodiments of the present invention, the pH value of the alkaline degreasing agent is 10.5 - 12.5.

[0019] Specifically, among the alkaline components used in the present invention, sodium silicate provides an alkaline environment (pH 10.5 - 12.5), and at the same time forms a passivating silicate protective film to prevent the corrosion of active metals such as aluminum and magnesium; alkaline organic amines such as triethanolamine (TEA) have weak alkalinity (pKa≈7.8), can dissolve fatty acids in oil stains, and at the same time can form complexes with the metal surface to prevent secondary pollution. Alkali metal carbonates such as sodium carbonate can provide a buffered alkaline environment to prevent excessive pH fluctuations and at the same time assist in dissolving certain organic pollutants. Compared with the traditional sodium hydroxide system, the present invention uses a combination of sodium silicate and alkaline organic amines, avoiding the strong corrosiveness of sodium hydroxide, making it applicable to various metals such as aluminum, magnesium, and stainless steel; alkaline organic amines can provide both alkalinity and complexation protection, being applicable to various metal materials such as aluminum, steel, stainless steel, and magnesium alloy, expanding the scope of application of the alkaline degreasing agent.

[0020] Specifically, among the surfactants used in the present invention, the hydrophilic-lipophilic balance value (HLB value) of fatty alcohol polyoxyethylene ether such as AEO-9 is 13.5, which is suitable for emulsifying hydrophobic mineral oil; the HLB value of alkylphenol polyoxyethylene ether such as TX-10 is 14.5, which can effectively disperse the oil film attached to the metal surface. Compared with the traditional SDS (sodium dodecyl sulfate) system, the present invention preferably uses a dual-phase emulsification system of AEO-9 and TX-10, which has less foam and stronger detergency, and is particularly suitable for spray cleaning processes. By regulating the HLB value, the removal ability of different types of oil stains (polar & non-polar) is optimized to ensure a comprehensive cleaning of the metal surface. On this basis, Gemini surfactants are introduced. Compared with AEO-9 and TX-10, they have a lower critical micelle concentration (CMC), that is, a more efficient detergency effect can be achieved at a lower concentration, which can reduce the addition amount of surfactants and improve economic efficiency; at the same time, it enhances the low-temperature adaptability and improves the cleaning efficiency under the conditions of 25 - 35°C, making the alkaline degreasing agent of the present invention more energy-saving and environmentally friendly.

[0021] Specifically, compared with traditional phosphate complexing agents, the complexing agent of the present invention preferably uses sodium ethylenediaminetetraacetate, citric acid, and sorbic acid to ensure phosphorus-free environmental protection and meet the requirements of wastewater discharge; and it synergistically acts with the alkaline component TEA to improve the complexing efficiency, reduce the residue on the metal surface, and improve the adhesion of subsequent coatings and films.

[0022] Specifically, the demulsifier (EO-PO block copolymer) used in the present invention destroys the oil-water emulsion interface, causing the oil stains to form large particle aggregates, which are thus easy to separate, ensuring an efficient demulsification ability for various types of oil stains. Compared with the traditional emulsification system (OP-10, SDS), it can reduce the secondary deposition of oil stains, improve the cleaning stability, be applicable to the circulating cleaning system, reduce the frequency of waste liquid replacement, and improve the economic efficiency of industrial applications.

[0023] Specifically, the dispersant sodium polyacrylate (PAAS, molecular weight 2000 - 5000) used in the present invention is a water-soluble polymer dispersant with strong negative charges. It can effectively adsorb on the surface of oil stain particles, oxides or dust, preventing their agglomeration or deposition. It is compatible with the non-ionic surfactants (such as AEO-9, TX-10) and Gemini surfactants in the system of the present invention and does not interfere with the emulsification effect.

[0024] Specifically, the corrosion inhibitor benzotriazole (BTA) used in the present invention forms a dense protective film on the surface of metals such as aluminum and magnesium. Collaborating with the silicate film of sodium silicate, it significantly reduces the corrosion rate and has a protective effect on the copper element in stainless steel and trace copper in aluminum alloy, avoiding surface damage caused by local electrochemical corrosion and improving the multi-metal adaptability of the system of the present invention.

[0025] The second aspect of the present invention provides a preparation method of the alkaline degreasing agent described in the first aspect of the present invention, including the following steps:

[0026] Mix and stir the alkaline component, complexing agent, surfactant and auxiliary agent to obtain the alkaline degreasing agent.

[0027] In some embodiments of the present invention, the rotation speed of the stirring is 100 - 300 rpm; and / or, the stirring time is 10 - 30 min.

[0028] The third aspect of the present invention provides an application of the alkaline degreasing agent described in the first aspect of the present invention in the pretreatment of metal surfaces.

[0029] In some embodiments of the present invention, the pretreatment of the metal surface is: using the alkaline degreasing agent described in the present invention to degrease the metal surface, including the following steps:

[0030] Mix and dilute the alkaline degreasing agent and water at a mass ratio of 1:(5 - 20) to obtain a cleaning solution;

[0031] Use the cleaning solution to clean the metal surface; after cleaning, rinse with clean water and dry.

[0032] In some embodiments of the present invention, the cleaning methods include spraying, soaking or ultrasonic cleaning. When spraying, the pressure is 0.1 - 0.5 MPa; soaking or ultrasonic cleaning does not require pressurization.

[0033] In some embodiments of the present invention, the cleaning temperature is 20 - 80 °C, preferably 25 - 35 °C; the cleaning time is 3 - 10 min, preferably 4 - 6 min.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] The alkaline degreasing agent provided by the present invention is characterized by high efficiency, low temperature, environmental protection and applicability to various metals. It can achieve an oil removal rate of more than 96% under the low-temperature condition of 25 - 35 °C, reducing energy consumption. At the same time, it takes into account excellent cleaning ability and metal surface protection ability, preventing the corrosion of aluminum alloy or the oxidation of stainless steel. The corrosion rate of aluminum alloy can be controlled below 0.007 g / m 2 ·h, ensuring the universality for metals such as aluminum, magnesium, steel, and stainless steel. It adopts a phosphorus-free and heavy-metal-free formula, reducing the COD value of the waste liquid by more than 30%, meeting the environmental protection requirements. The present invention further prevents the secondary deposition of oil stains through a demulsification and dispersion system, improving the stability of the cleaning solution diluted from the alkaline degreasing agent. Detailed implementation manners

[0036] The content of the present invention will be further described in detail through specific embodiments below. Unless otherwise specified, the raw materials, reagents or devices used in the embodiments can be obtained from conventional commercial channels or can be obtained by existing technical methods. Unless otherwise specified, the test or testing methods are all conventional methods in the art.

[0037] Example 1

[0038] An alkaline degreasing agent comprises the following components in parts by mass: 10 parts of sodium silicate, 10 parts of triethanolamine, 3 parts of sodium carbonate, 4 parts of AEO-9, 3 parts of TX-10, 1 part of Gemini surfactant, 3 parts of EDTA-4Na, 2 parts of citric acid, 4 parts of EO-PO block copolymer, 2 parts of sodium polyacrylate, 1 part of benzotriazole, and 57 parts of water.

[0039] The preparation method of the above-mentioned alkaline degreasing agent comprises the following steps:

[0040] 1) Add water to the reaction kettle and start stirring (rotation speed is 200 rpm);

[0041] 2) Add sodium silicate, triethanolamine, and sodium carbonate to the reaction kettle and stir for 15 min until completely dissolved;

[0042] 3) Add EDTA-4Na and citric acid to the reaction kettle and continue stirring for 12 min;

[0043] 4) Add AEO-9, TX-10, and Gemini surfactant to the reaction kettle and stir for 18 min until the solution is uniformly transparent;

[0044] 5) Add EO-PO block copolymer, sodium polyacrylate, and benzotriazole to the reaction kettle and stir for 25 min until the system is uniformly mixed to obtain the alkaline degreasing agent (pH value is 11).

[0045] Example 2

[0046] An alkaline degreaser, comprising the following components in parts by mass: 12 parts of sodium silicate, 8 parts of triethanolamine, 4 parts of methyldiethanolamine, 4 parts of sodium carbonate, 5 parts of AEO-9, 3 parts of TX-10, 2 parts of Gemini surfactant, 2 parts of EDTA-4Na, 2 parts of citric acid, 1 part of sorbic acid, 5 parts of EO-PO block copolymer, 2 parts of sodium polyacrylate, 1 part of benzotriazole, and 49 parts of water.

[0047] The preparation method of the alkaline degreaser in this example refers to Example 1.

[0048] Example 3

[0049] An alkaline degreaser, comprising the following components in parts by mass: 15 parts of sodium silicate, 12 parts of methyldiethanolamine, 2 parts of sodium carbonate, 3 parts of AEO-9, 2 parts of TX-10, 1.5 parts of Gemini surfactant, 3 parts of EDTA-4Na, 2 parts of sorbic acid, 3 parts of EO-PO block copolymer, 1 part of sodium polyacrylate, 0.5 part of benzotriazole, and 55 parts of water.

[0050] The preparation method of the alkaline degreaser in this example refers to Example 1.

[0051] Example 4

[0052] An alkaline degreaser, comprising the following components in parts by mass: 10 parts of sodium silicate, 10 parts of triethanolamine, 3 parts of sodium carbonate, 5 parts of TX-10, 3 parts of Gemini surfactant, 3 parts of EDTA-4Na, 2 parts of citric acid, 4 parts of EO-PO block copolymer, 2 parts of sodium polyacrylate, 1 part of benzotriazole, and 57 parts of water.

[0053] The preparation method of the alkaline degreaser in this example refers to Example 1.

[0054] Example 5

[0055] An alkaline degreaser, comprising the following components in parts by mass: 10 parts of sodium silicate, 10 parts of triethanolamine, 3 parts of sodium carbonate, 4 parts of AEO-9, 3 parts of TX-10, 1 part of Gemini surfactant, 5 parts of EDTA-4Na, 4 parts of EO-PO block copolymer, 2 parts of sodium polyacrylate, 1 part of benzotriazole, and 57 parts of water.

[0056] The preparation method of the alkaline degreaser in this example refers to Example 1.

[0057] Comparative Example 1 (Traditional Strong Alkaline Degreaser)

[0058] A strongly alkaline degreaser, comprising the following components in parts by mass: 15 parts of sodium hydroxide, 5 parts of sodium carbonate, 10 parts of trisodium phosphate, 5 parts of sodium dodecylbenzenesulfonate, 3 parts of EDTA-4Na, and 62 parts of water.

[0059] Comparative Example 2 (lacking triethanolamine compared to Example 1)

[0060] An alkaline degreaser, comprising the following components in parts by mass: 15 parts of sodium silicate, 8 parts of sodium carbonate, 4 parts of AEO-9, 3 parts of TX-10, 1 part of Gemini surfactant, 3 parts of EDTA-4Na, 2 parts of citric acid, 4 parts of EO-PO block copolymer, 2 parts of sodium polyacrylate, 1 part of benzotriazole, and 57 parts of water.

[0061] Comparative Example 3 (lacking methyldiethanolamine compared to Example 3)

[0062] An alkaline degreaser, comprising the following components in parts by mass: 20 parts of sodium silicate, 9 parts of sodium carbonate, 3 parts of AEO-9, 2 parts of TX-10, 1.5 parts of Gemini surfactant, 3 parts of EDTA-4Na, 2 parts of sorbic acid, 3 parts of EO-PO block copolymer, 1 part of sodium polyacrylate, 0.5 part of benzotriazole, and 55 parts of water.

[0063] Comparative Example 4 (lacking Gemini surfactant compared to Example 1)

[0064] An alkaline degreaser, comprising the following components in parts by mass: 10 parts of sodium silicate, 10 parts of triethanolamine, 3 parts of sodium carbonate, 4.5 parts of AEO-9, 3.5 parts of TX-10, 3 parts of EDTA-4Na, 2 parts of citric acid, 4 parts of EO-PO block copolymer, 2 parts of sodium polyacrylate, 1 part of benzotriazole, and 57 parts of water.

[0065] Performance Test

[0066] After mixing and diluting the alkaline degreasers provided in Examples 1-5 and Comparative Examples 1-4 with water to obtain cleaning solutions, a cleaning and degreasing test was carried out on the metal surface, and the test results are shown in Table 1.

[0067] Table 1

[0068]

[0069]

[0070] As can be seen from Table 1:

[0071] 1) Degreasing efficiency and time

[0072] Examples 1-5 can achieve an oil stain removal rate of 96%-99.2% in only 4-6 minutes at a relatively low temperature (25-35°C), showing high oil removal ability. Among them, Example 2 (preferred formulation) can reach a removal rate of 99.2% in only 4 minutes at 25°C, with the highest efficiency.

[0073] For Comparative Example 1 (traditional strong base formulation) and the formulations of Comparative Examples 2-4, they respectively need to be under high temperature conditions of 60°C and 40°C, and the oil stain removal rate is about 95.0%, with significantly reduced efficiency.

[0074] It can be seen that the examples of the present invention can still maintain high oil removal ability under low temperature (25-35°C) conditions, showing excellent low temperature adaptability and having significant energy-saving advantages.

[0075] 2) Metal corrosion

[0076] Examples 1-5 have extremely low corrosion rates for aluminum alloy, only 0.004-0.007 g / m 2 ·h. Especially, the corrosion rate of Example 2 is the lowest (0.004 g / m 2 ·h), indicating its excellent protection performance for metals. Due to the use of strong base (sodium hydroxide), the corrosion rate of Comparative Example 1 is as high as 0.15 g / m 2 ·h, seriously damaging the surface of aluminum alloy.

[0077] In summary, the alkaline degreaser of the present invention adopts a composite mild alkaline system of sodium silicate and alkaline organic amine to replace the traditional strong base (NaOH) system. Among them, sodium silicate hydrolyzes in the solution to generate silicate ions, which can form a nanoscale silicate passivation film (with a thickness of 10-50 nm) on the surfaces of aluminum and magnesium, inhibiting the erosion of OH - through physical barriers and chemical adsorption; triethanolamine and methyldiethanolamine, as weak alkaline organic amines, can form coordination complexes (such as [Al(TEA)] 3+ ) with the metal surface, reducing the local OH - concentration, reducing corrosion, and significantly reducing the corrosion rate of active metals (such as the aluminum alloy corrosion rate drops from 0.15 g / m 2 ·h to 0.004-0.007 g / m 2 ·h), broadening the applicable range of metals (aluminum, magnesium, steel, stainless steel, copper).

[0078] In addition, the present invention introduces Gemini surfactants. Their unique amphiphilic molecular structure (two hydrophilic head groups and a hydrophobic tail chain connected by a bridging bond) significantly reduces the CMC, and can efficiently emulsify hydrophobic oil stains at 25-35°C. In cooperation with AEO-9 (HLB≈13.5) and TX-10 (HLB≈14.5), a multi-scale emulsification system (micelle particle size of 5-20 nm) is formed, thereby achieving the purpose of efficient oil removal at low temperature and reducing energy consumption. The present invention further adds a demulsifier (EO-PO block copolymer) to disrupt the oil-water interface, and PAAS disperses oil stain particles to prevent secondary deposition, enhancing the stability of the cleaning solution.

[0079] The preferred embodiments of the present invention have been specifically described above, but the present invention is not limited to the described embodiments. Those skilled in the art can make various equivalent variations or substitutions without departing from the spirit of the present invention, and these equivalent variations or substitutions are all included within the scope defined by the claims of this application.

Claims

1. An alkaline degreasing agent, characterized in that, The alkaline degreasing agent comprises an alkaline component, a complexing agent, a surfactant and an auxiliary agent. The alkaline component comprises sodium silicate and an alkaline organic amine. The surfactant comprises a polyoxyethylene nonionic surfactant and a Gemini surfactant.

2. The alkaline degreaser according to claim 1, wherein By mass, the alkaline degreasing agent comprises 10-40 parts of an alkaline component, 3-10 parts of a complexing agent, 5-20 parts of a surfactant and 4-10 parts of an auxiliary agent.

3. The alkaline degreaser according to claim 1, characterized in that, The complexing agent comprises at least one of sodium ethylenediaminetetraacetate, citric acid and sorbic acid.

4. The alkaline degreasing agent according to claim 1, characterized in that, The auxiliary agent comprises at least one of a demulsifier, a dispersant and a corrosion inhibitor.

5. The alkaline degreasing agent according to claim 1, characterized in that, The alkaline component further comprises an alkali metal carbonate.

6. The alkaline degreaser according to claim 1, wherein, The alkaline organic amine comprises triethanolamine and / or methyldiethanolamine.

7. The alkaline degreasing agent according to claim 1, wherein The polyoxyethylene nonionic surfactant comprises at least one of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether.

8. The preparation method of the alkaline degreasing agent according to any one of claims 1-7, characterized in that, It includes the following steps: Mix and stir the alkaline component, the complexing agent, the surfactant and the auxiliary agent to obtain the alkaline degreasing agent.

9. The preparation method according to claim 8, wherein The rotation speed of the stirring is 100-300 rpm; and / or, the stirring time is 10-30 min.

10. Application of the alkaline degreasing agent according to any one of claims 1-7 in the pretreatment of a metal surface.

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