A kind of descaling degreasing agent for stainless steel plate after cold rolling and its preparation method

Abstract

The application discloses a kind of descaling degreasing agent for stainless steel plate after cold rolling and a preparation method thereof, the descaling degreasing agent is composed of the following components by weight percentage: alkali salt 15-20%, chelating agent 6-8%, small molecule dispersant 8-10%, high molecular dispersant 10-12%, surfactant 8-10%, solubilizer 3-4%, defoaming agent 0.1-0.5%, and the balance is water.The descaling degreasing agent is easy to rinse and has strong cleaning ability, with good descaling effect.

Description

Technical Field

[0001] This invention relates to a degreasing agent for use after cold rolling of stainless steel plates, and also to a method for preparing the above-mentioned degreasing agent. Technical Background

[0002] Cold-rolled stainless steel sheets are widely used in the automotive, home appliance, and construction industries. For further processing and surface treatment, the surface of stainless steel sheets after degreasing and annealing must have a relatively high surface quality. During the cold rolling process, the high temperatures generated on the sheet surface cause the rolling oil to undergo thermal decomposition. The high-temperature decomposition products of hydrocarbons, besides hydrogen, mainly include methane, ethylene, and propylene. Methane continues to decompose at high temperatures to form active carbon atoms, which are easily adsorbed onto the solid surface and combine to form molecular carbon deposits. Ethylene and propylene first polymerize at high temperatures and then decompose, releasing hydrogen gas that deposits carbon black or coke-like solid deposits on the steel sheet surface. Carbon elements in the steel matrix may also diffuse to the surface, forming amorphous carbon, graphite carbon, and other forms. These substances deposit on the sheet surface, forming black ash. If a large area of ​​black ash remains on the steel sheet surface after degreasing and annealing, it not only affects subsequent electroplating and coating but also, during leveling, the carbon will be pressed into the steel sheet, affecting the quality of subsequent surface treatment.

[0003] Currently, degreasing agents used after cold rolling mainly include acidic, alkaline, and solvent-based degreasing agents. Acidic degreasing agents have excellent degreasing effects, but they generate acid mist during the cleaning process, which can harm the health of workers, and they require high corrosion resistance from the materials used in the cleaning equipment. Alkaline degreasing agents, such as phosphate-based alkaline degreasing agents, have excellent emulsification and cleaning effects on oil stains and also have good dispersion effects on particulate matter. However, the waste liquid from these degreasing agents can cause eutrophication of water bodies, resulting in environmental pollution. Sodium silicate-based alkaline degreasing agents, while having good cleaning and dispersion effects, have strong adsorption on metal surfaces, making them difficult to remove with water washing. After annealing, they easily form a SiO2 film, affecting the quality of subsequent electroplating and coating processes. Solvent-based cleaning agents have excellent cleaning effects on oil stains due to their similar compatibility characteristics and, when combined with dispersants, have good degreasing effects. However, these cleaning agents have low flash points, which can easily cause fire accidents, and given the large volume of degreasing liquid used in steel mills, the likelihood of using solvent-based degreasing agents is low. Summary of the Invention

[0004] Objective of the invention: The present invention aims to provide a degreasing agent for stainless steel plates after cold rolling. This degreasing agent is easy to rinse and has strong cleaning ability, and has a good degreasing effect. Another objective of the present invention is to provide a method for preparing the above-mentioned degreasing agent.

[0005] Technical solution: The degreasing agent for stainless steel plates after cold rolling according to the present invention is composed of the following components by weight percentage: 15-20% alkali salt, 6-8% chelating agent, 8-10% small molecule dispersant, 10-12% high molecule dispersant, 8-10% surfactant, 3-4% solubilizer, 0.1-0.5% defoamer, and the balance being water.

[0006] The alkaline salt is composed of potassium hydroxide and potassium carbonate mixed in a mass ratio of 2:1.

[0007] The chelating agent is a combination of at least two of the following: tetrasodium ethylenediaminetetraacetate, pentasodium diethylenetriaminepentaacetate, or tetrasodium iminodisuccinate. The surface of carbon black is similar to that of polycyclic aromatic hydrocarbon (PAH) derivatives. PAHs can form n-π interactions with elements carrying lone pairs of electrons, such as oxygen and nitrogen. Therefore, the compounded chelating agents simultaneously possess amino and carboxyl groups, resulting in a certain adsorption and dispersion effect on carbon black. Furthermore, the chelating agents can chelate heavy metal ions from polar additives in rolling oil, which aids in the cleaning of the rolling oil.

[0008] The small molecule dispersant is a combination of at least two of the following: sodium ethylenediamine di-o-phenylacetate, sodium methylene bis(naphthalene) sulfonate, sodium benzoate, or short-chain alkyl naphthalene sulfonate (C4-C8 alkyl naphthalene sulfonate). The role of the compounded small molecule dispersant in the system is as follows: through the anchoring groups such as benzene rings and naphthalene rings in the structure of the small molecule dispersant, it binds to the carbon black surface. Its dispersing effect is similar to that of polymeric dispersants, but its molecular weight is smaller, resulting in faster molecular migration compared to polymeric dispersants. Therefore, it exhibits a good synergistic effect with polymeric dispersants in dust removal.

[0009] The polymeric dispersant is a combination of at least two of the following: naphthalenesulfonic acid formaldehyde condensate, styrene-acrylic acid copolymer, sulfonated styrene copolymer, or polyvinylpyrrolidone. The molecular weight of the polymeric dispersant is 3000-6000. The role of the compounded polymeric dispersant in the system is as follows: Carbon black has a strong binding force with metal, and the polycyclic aromatic hydrocarbon surface of carbon black is weakly polar, resulting in poor wettability with polar water and difficulty in dispersing in water, thus making cleaning difficult. The hydrophobic end of the dispersant binds to the particles through acid-base interactions, hydrogen bonds, intermolecular van der Waals forces, and π-π interactions between planar molecules, forming a stable anchoring mechanism. The hydrophilic end provides polarity, enhancing the wetting and dispersion of carbon black in water and reducing the binding force between carbon black and the metal surface. With the mechanical force of the roller brush, carbon black is more easily removed from the metal surface. In addition, the hydrophilic end extends into the water to provide steric repulsion and electrostatic repulsion, preventing the aggregation of carbon black particles (in actual use, carbon black particles washed off in the bath solution cannot be effectively filtered out, so this property is also very important) and redeposition on the metal surface.

[0010] The surfactant is a combination of at least three of the following: alkylbenzyl polyoxyethylene ether, sodium dodecyl diphenyl ether disulfonate, sodium N-dodecyl ethylenediamine triacetate, or C8-10 alcohol polyoxyethylene polyoxypropylene ether. The above surfactant formulation principles all employ a combination of long-chain and short-chain surfactants, and a combination of nonionic and anionic surfactants, resulting in a synergistic effect on oil stain removal. Furthermore, the molecular structures of alkylbenzyl polyoxyethylene ether, sodium dodecyl diphenyl ether disulfonate, and sodium N-dodecyl ethylenediamine triacetate all contain groups that can bind to the carbon black surface, thereby effectively improving the cleaning effect on carbon black.

[0011] The solubilizer is isooctanoic acid or isononanoic acid.

[0012] The defoamer is ethylene oxide-propylene oxide block copolymer ether.

[0013] The preparation method of the above-mentioned degreasing agent includes the following steps:

[0014] (1) Under normal temperature stirring conditions, add the formulated amount of alkaline salt and chelating agent to pure water, stir evenly, and obtain a premixed solution;

[0015] (2) When the first premixed solution is cooled to 10-40℃ (the cloud point requirement of the degreaser is greater than 40℃. If it is not cooled to this temperature, the product may precipitate surfactants and separate into layers after the degreaser is produced due to the temperature being higher than the cloud point), add the formula amount of small molecule dispersant and high molecule dispersant to the first premixed solution, stir evenly, and obtain the second premixed solution.

[0016] (3) Add the formulated amount of surfactant and solubilizer to the secondary premixed solution, stir evenly, and obtain the tertiary premixed solution;

[0017] (4) Add the prescribed amount of defoamer to the three-stage premixed solution and stir evenly to obtain the descaling agent.

[0018] The purpose of adding components in batches in the preparation method is to facilitate production control. The primary, secondary, and tertiary premixed solutions are all transparent liquids. When problems occur in production, it is possible to quickly identify which part of the raw material is the problem, and it can avoid uneven mixing caused by adding materials all at once, which has little impact on the product performance.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant improvements: (1) The degreasing agent of the present invention has strong cleaning ability (strong degreasing ability). It uses a compound surfactant, which has excellent emulsification and dispersion effect on rolling oil. At the same time, it uses a compound chelating agent, which can better chelate heavy metal ions in rolling oil, thereby effectively improving the cleaning efficiency of the degreasing agent; (2) The degreasing agent of the present invention has good degreasing effect. It uses a compound small molecule dispersant and a compound high molecule dispersant, which has a good dispersion effect on carbon black and metal particles, thereby enhancing the wetting and dispersion of carbon black in water, reducing the bonding force between carbon black and metal surface, and with the mechanical force of the roller brush, carbon black is more easily removed from the metal surface; preventing the aggregation of carbon black particles and redeposition on the metal surface; (3) The degreasing agent of the present invention is easy to rinse. The system does not contain silicates, and the residue on the steel plate surface after water washing is low; (4) The system does not contain phosphates, so the waste liquid has little environmental pollution. Attached Figure Description

[0020] Figure 1 Samples were taken from the steel plate before processing;

[0021] Figure 2 Samples were taken from the steel plate after processing in Example 1.

[0022] Figure 3 Samples were taken from the steel plate after the treatment of Comparative Example 1. Detailed Implementation

[0023] Example 1

[0024] This invention relates to a degreasing agent for stainless steel plates after cold rolling, comprising the following components by weight percentage: potassium hydroxide 10%; potassium carbonate 5%; tetrasodium ethylenediaminetetraacetate 3%; tetrasodium iminodisuccinate 3%; sodium ethylenediamine di-o-phenylacetate 4%; sodium methylene bis(naphthalene)sulfonate 4%; naphthalenesulfonic acid formaldehyde condensate 6%; styrene-acrylic acid copolymer 4%; alkyl benzyl polyoxyethylene ether 2%; sodium dodecyl diphenyl ether disulfonate 2%; C8-10 alcohol polyoxyethylene polyoxypropylene ether 4%; isooctanoic acid 4%; ethylene oxide and propylene oxide block copolymer 0.5%; and deionized water as the balance.

[0025] Example 2

[0026] This invention relates to a degreasing agent for stainless steel plates after cold rolling, comprising the following components by weight percentage: 10% potassium hydroxide; 5% potassium carbonate; 3% pentasodium diethylenetriaminepentaacetate; 3% tetrasodium iminodisuccinate; 4% sodium benzoate; 4% sodium short-chain alkylnaphthalene sulfonate; 6% sulfonated styrene copolymer; 4% polyvinylpyrrolidone; 2% alkylbenzyl polyoxyethylene ether; 2% sodium N-dodecyl ethylenediaminetriacetate; 4% C8-10 alcohol polyoxyethylene polyoxypropylene ether; 3% isononanoic acid; 0.5% ethylene oxide and propylene oxide block copolymer ether; and the balance being deionized water.

[0027] Comparative Example 1 - No Small Molecule Dispersant

[0028] A degreasing agent for stainless steel plates after cold rolling comprises the following components by weight percentage: 10% potassium hydroxide; 5% potassium carbonate; 3% tetrasodium ethylenediaminetetraacetate; 3% tetrasodium iminodisuccinate; 6% naphthalenesulfonic acid formaldehyde condensate; 4% styrene-acrylic acid copolymer; 2% alkylbenzyl polyoxyethylene ether; 2% sodium dodecyl diphenyl ether disulfonate; 4% C8-10 alcohol polyoxyethylene polyoxypropylene ether; 4% isooctanoic acid; 0.5% ethylene oxide-propylene oxide block copolymer ether; and the balance being deionized water.

[0029] Comparative Example 2 - No Polymer Dispersant

[0030] A degreasing agent for stainless steel plates after cold rolling comprises the following components by weight percentage: 10% potassium hydroxide; 5% potassium carbonate; 3% tetrasodium ethylenediaminetetraacetate; 3% tetrasodium iminodisuccinate; 4% sodium ethylenediamine di-o-phenylacetate; 4% sodium methylene bis(naphthalene)sulfonate; 2% alkylbenzyl polyoxyethylene ether; 2% sodium dodecyl diphenyl ether disulfonate; 4% C8-10 alcohol polyoxyethylene polyoxypropylene ether; 4% isooctanoic acid; 0.5% ethylene oxide and propylene oxide block copolymer ether; and the balance being deionized water.

[0031] Comparative Example 3 - Changes in the types of surfactants in the compound formulation

[0032] A degreasing agent for stainless steel plates after cold rolling comprises the following components by weight percentage: 10% potassium hydroxide; 5% potassium carbonate; 3% tetrasodium ethylenediaminetetraacetate; 3% tetrasodium iminodisuccinate; 4% sodium ethylenediamine di-o-phenylacetate; 4% sodium methylene bis(naphthalene)sulfonate; 6% naphthalenesulfonic acid formaldehyde condensate; 4% styrene-acrylic acid copolymer; 2% isomeric alcohol polyoxyethylene ether; 2% secondary alcohol polyoxyethylene ether; 4% C8-10 alcohol polyoxyethylene polyoxypropylene ether; 4% isooctanoic acid; 0.5% ethylene oxide-propylene oxide block copolymer; and the balance being deionized water.

[0033] Comparative Example 4

[0034] This invention relates to a degreasing agent for stainless steel plates after cold rolling, comprising the following components by weight percentage: 10% potassium hydroxide; 5% potassium carbonate; 3% tetrasodium ethylenediaminetetraacetate; 3% tetrasodium iminodisuccinate; 4% sodium ethylenediamine di-o-phenylacetate; 4% sodium methylene bis(naphthalene)sulfonate; 10% sodium polyacrylate; 2% alkylbenzyl polyoxyethylene ether; 2% sodium dodecyl diphenyl ether disulfonate; 4% C8-10 alcohol polyoxyethylene polyoxypropylene ether; 4% isooctanoic acid; 0.5% ethylene oxide and propylene oxide block copolymer ether; and the balance being deionized water.

[0035] Comparative Example 5

[0036] This invention relates to a degreasing agent for stainless steel plates after cold rolling, comprising the following components by weight percentage: 10% potassium hydroxide; 5% potassium carbonate; 6% diethylenetriaminepentaacetic acid pentasodium; 8% sodium benzoate; 10% sulfonated styrene copolymer; 8% alkyl benzyl polyoxyethylene ether; 3% isononanoic acid; 0.5% ethylene oxide and propylene oxide block copolymer ether; and the balance being deionized water.

[0037] The ash removal effect of the ash removal agents in Examples 1-2 and Comparative Examples 1-5 was evaluated using reflectivity. Each sample was tested in parallel with three steel plates taken from steel strips rolled on-site in the industrial field.

[0038] Test method: Cut steel plates to the same size, prepare working solutions of the desiccant in Examples 1-2 and Comparative Examples 1-5 (the mass fraction of the desiccant in the working solution is 5%, which is obtained by diluting with pure water), spray the steel plates with the working solution at 55℃ and a pressure of 0.5MPa for 5 minutes, rinse the steel plates with pure water after cleaning, dry them with hot air from a blower, and cool them to room temperature to obtain the test plates.

[0039] Scotch tape was used to attach samples to the test plates, and then a NOVO-SHADE reflectance meter was used for measurement. The average reflectance of three parallel samples was taken for each sample. The higher the reflectance value, the cleaner the steel plate surface, and vice versa. The experimental results are shown in Table 1.

[0040] Table 1

[0041]

[0042]

[0043] As shown in Table 1, the desiccant degreasing agents of Examples 1-2 have significantly better desiccant removal effects than those of Comparative Examples 1-5. In Comparative Example 1, the reflectivity decreased after the removal of the small molecule dispersant, indicating a decline in desiccant removal effect. In Comparative Example 2, the reflectivity decreased significantly after the removal of the polymeric dispersant, indicating a significant reduction in surface desiccant removal effect. In Comparative Example 3, the reflectivity decreased after the surfactant was changed, indicating a decline in desiccant removal effect. In Comparative Example 4, the reflectivity decreased after the polymeric dispersant type was changed, indicating that the selection of polymeric dispersant has a significant impact on desiccant removal effect. In Comparative Example 5, the small molecule dispersant, polymeric dispersant, and surfactant were not compounded, and the reflectivity decreased, indicating a lack of synergistic effect from the compounding, resulting in a lower desiccant removal effect than that of Example 1.

[0044] pass Figures 1-3 The comparison shows that the black ash was heavier before treatment. Both Example 1 and Comparative Example 1 can remove the black ash to a certain extent, but the ash removal effect of Example 1 is significantly better than that of Comparative Example 1.

Claims

1. A degreasing agent for stainless steel plates after cold rolling, characterized in that, It is composed of the following components by weight percentage: potassium hydroxide 10%; potassium carbonate 5%; tetrasodium ethylenediaminetetraacetate 3%; tetrasodium iminodisuccinate 3%; sodium ethylenediamine di-o-phenylacetate 4%; sodium methylene bis(naphthalene)sulfonate 4%; naphthalenesulfonic acid formaldehyde condensate 6%; styrene-acrylic acid copolymer 4%; alkyl benzyl polyoxyethylene ether 2%; sodium dodecyl diphenyl ether disulfonate 2%; C8-10 alcohol polyoxyethylene polyoxypropylene ether 4%; isooctanoic acid 4%; ethylene oxide and propylene oxide block copolymer 0.5%; and deionized water as the balance.

2. The method for preparing the degreasing agent according to claim 1, characterized in that, Includes the following steps: (1) At room temperature, add the prescribed amounts of potassium hydroxide, potassium carbonate, tetrasodium ethylenediaminetetraacetate and tetrasodium iminodisuccinate to pure water and stir until homogeneous to obtain a premixed solution. (2) When the first premixed solution is cooled to 10~40℃, add the formulated amount of sodium ethylenediamine di-o-phenylacetate, sodium methylene bis(naphthalene) sulfonate, naphthalene sulfonic acid formaldehyde condensate and styrene-acrylic acid copolymer to the first premixed solution and stir evenly to obtain the second premixed solution. (3) Add the formulated amounts of alkyl benzyl polyoxyethylene ether, sodium dodecyl diphenyl ether disulfonate, C8-10 alcohol polyoxyethylene polyoxypropylene ether and isooctanoic acid to the secondary premixed solution, stir evenly, and obtain the tertiary premixed solution. (4) Add the formulated amount of ethylene oxide and propylene oxide block copolymer ether to the three-stage premixed solution and stir evenly to obtain the descaling agent.

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