A surface treatment composition for removing wax layers on a skid of an automobile painting line, and a preparation method and use thereof

Abstract

The application discloses a surface treatment composition for removing wax layer on a skid of an automobile coating line and a preparation method and application thereof. The surface treatment composition comprises, by weight, 30-40 parts of tea saponin-based dimer surfactant, 5-8 parts of tea saponin grafted polyamidoamine penetration aid, 0.5-1 part of composite solid builder, and 35-50 parts of deionized water. The application uses tea saponin as a basis for molecular design, and prepares tea saponin-based surfactant and tea saponin grafted polyamidoamine penetration aid through chemical modification, thereby improving the cleaning efficiency on the cavity wax film. Meanwhile, the composite solid builder is compounded in the product to assist in improving the cleaning on the gap and pore position of the skid. The technical problem that the skid body and the conveyor are slippery and the positioning accuracy of the skid is poor after the skid of the automobile coating workshop is polluted by the cavity wax is solved. Compared with the traditional solvent cleaning and physical cleaning mode, the technical scheme provided by the application has high cleaning efficiency, does not consume a large amount of solvent, and has low comprehensive cost.

Description

Technical Field

[0001] This invention belongs to the field of surface treatment compositions, and particularly relates to a surface treatment composition for removing wax layers from skids on automotive painting lines, its preparation method, and its application. Background Technology

[0002] Automobile exports are typically transported by sea, which necessitates superior corrosion resistance throughout the vehicle body. As a crucial component of the vehicle body's corrosion protection process, cavity wax injection technology effectively prevents rust and rust penetration during transportation and use.

[0003] On an automotive painting production line, skids are a crucial system for transporting and supporting the car body along the line. The skids carry the car body through pretreatment, electrophoresis, adhesive application, painting, and baking processes. After the overall paint coating is completed, a step is taken to improve the corrosion resistance of the car body's cavity structure: cavity wax injection. Cavity wax injection involves injecting liquid cavity wax into the gaps between the sheet metal layers using a spray gun. To ensure the cavity wax completely fills the gaps, it is usually allowed to fill the gaps before flowing out through the process holes. Therefore, the wax injection process causes wax to splash and solidify on the skid surface. When the wax dries and forms a film, it creates a highly adhesive residue. As production continues, the wax layer will accumulate. The polymer wax residue on the skid surface will seriously affect the connection and fit between the skid and the conveyor. This is because the wax material itself has excellent adhesion and interfacial lubrication. When the skid system is contaminated by residual cavity wax, the friction coefficient between the skid and the conveyor chain of the skid conveyor system will decrease, the positioning accuracy will drop significantly, and the conveyor will slip, which will lead to increased equipment wear, positioning deviation, and in severe cases, there is a risk of production line shutdown.

[0004] Based on the above technical issues, many OEM painting workshops have adopted various preventative measures to avoid cavity wax contamination of the painting line skids. These measures mainly include the following: ① Physical masking: This method typically involves placing a masking film on and around the skid to prevent wax contamination during the painting process. These films are usually transparent, and when enough wax accumulates on the masking film, it needs to be rearranged or replaced. The drawback of this method is that the installation of the masking film takes up a lot of time and can only be done when the line is stopped. When production is high, there is no time to replace the masking film; ② Mechanical physical removal: This involves using manual labor or a wax scraping device to remove cavity wax adhering to the production line. The disadvantage of this method is that, on the one hand, traditional manual scraping is inefficient, and on the other hand, neither manual nor mechanical scraping can remove the wax adhering to the surface and crevices of the skid. Even a very thin layer of wax can affect the skid's operation, so this method still requires frequent shutdowns for maintenance. ③ Solvent cleaning: This method is currently the most efficient way for OEMs to clean wax off skids. Using a brush and solvent, the skids are quite clean after cleaning, with almost no residue. However, its drawbacks are also very obvious. Volatile organic compounds (VOCs) in the painting workshop will evaporate into the air during the cleaning process, causing environmental pollution. Long-term exposure can damage the respiratory and nervous systems of operators, posing health risks. Secondly, there is the issue of cost. Organic solvents are expensive, and a large amount of solvent is consumed during the cleaning process. The recovery and disposal of solvents also require additional investment in equipment, personnel, and hazardous waste treatment costs.

[0005] Therefore, in order to solve the technical problem of slippage caused by wax contamination in the skid cavities of OEM painting workshops, it is an urgent technical problem to develop a surface treatment composition for cavity wax that can efficiently remove wax, is environmentally friendly and safe with low VOCs, has low overall usage costs, and is friendly to operators and the environment. Summary of the Invention

[0006] To address the above technical problems, this invention provides a surface treatment composition for removing wax from skids on automotive painting lines, its preparation method, and its application. The surface treatment composition for removing wax from skids on automotive painting lines solves the technical problems of low skid cleaning efficiency in OEM painting workshops, wax residue, poor cleaning effect, and the release of volatile organic compounds (VOCs) into the air and the resulting health risks when using solvents to clean skids.

[0007] The technical solution adopted in this invention is: a surface treatment composition for removing wax layer on skids in automotive painting lines, comprising the following components by weight: 30-40 parts of tea saponin-based dimer surfactant, 5-8 parts of tea saponin-grafted polyamide amine (PAMAM) penetration enhancer, 0.5-1 part of composite solid detergent, and 35-50 parts of deionized water.

[0008] The preparation method of the tea saponin-based dimer surfactant is as follows: under nitrogen atmosphere, tea saponin solution reacts with epichlorohydrin and catalyst, the pH of the solution is adjusted to neutral, the solvent is removed to obtain tea saponin glycidyl ether intermediate, solvent is added, stirring is performed, nitrogen is introduced, bridged amine and catalyst are added dropwise to react to obtain bridged reaction solution, water or ethanol aqueous solution is added to terminate the reaction, the pH is adjusted to alkaline, crystals are precipitated, and the solution is allowed to stand, filtered and dried to obtain tea saponin-based dimer surfactant.

[0009] The preparation method of the tea saponin-grafted polyamide amine (PAMAM) penetration enhancer is as follows: add dendritic polymer polyamide amine (PAMAM) and catalyst to the tea saponin solution, and then introduce nitrogen gas to react and obtain a tea saponin-grafted polyamide amine (PAMAM) penetration enhancer solution. Add acetone, let stand, filter, and freeze dry to obtain the tea saponin-grafted polyamide amine (PAMAM) penetration enhancer.

[0010] The above-mentioned surface treatment composition for removing wax layer from skids on automotive painting lines includes the following steps in the preparation method of the tea saponin-based dimer surfactant.

[0011] 1) Take tea saponin powder and dry it under vacuum to obtain dehydrated tea saponin powder.

[0012] 2) Take 30-40 parts of dehydrated tea saponin powder and 50-60 parts of mixed solvent, mix and stir, control the temperature at 45-60℃, stir and filter to obtain tea saponin solution.

[0013] 3) Take 80-100 parts of tea saponin solution, pass nitrogen gas through it, add 2-8 parts of epichlorohydrin dropwise, add 0.1-0.3 parts of catalyst, stir the reaction, adjust the pH of the system to 6.5-7.5, filter and remove the solvent to obtain tea saponin glycidyl ether intermediate.

[0014] 4) Take 80-100 parts of tea saponin glycidyl ether intermediate, add 50-60 parts of mixed solvent, start stirring and purge with nitrogen for protection, then add 0.5-3 parts of bridged amine and 0.1-0.5 parts of catalyst dropwise to the reaction vessel. After the addition is complete, keep the mixture warm and stir to obtain the bridged reaction solution. Add deionized water or ethanol aqueous solution to the bridged reaction solution to terminate the reaction, adjust the pH to 7-9, add ethyl acetate to precipitate, let stand and filter, and vacuum dry the obtained product to obtain tea saponin-based dimer surfactant.

[0015] The above-mentioned surface treatment composition for removing wax layer from skids on automotive painting lines, wherein the tea saponin powder is a light yellow powder with a purity of 95-98%; in step 2), the mixed solvent is a combination of dimethyl sulfoxide and N,N-dimethylformamide, with a mass ratio of dimethyl sulfoxide:N,N-dimethylformamide = 1-3:1; in step 4), the mixed solvent is a combination of dimethyl sulfoxide and N,N-dimethylformamide, with a mass ratio of dimethyl sulfoxide:N,N-dimethylformamide = 1-3:1.

[0016] Furthermore, by mass ratio, dimethyl sulfoxide: N,N-dimethylformamide = 2:1.

[0017] In the above-mentioned surface treatment composition for removing wax layer from skids on automotive painting lines, in step 3), the stirring reaction is carried out at 50-65°C for 3-6 hours under stirring conditions, and the catalyst is a combination of sodium hydroxide and tetrabutylammonium bromide, with a mass ratio of sodium hydroxide:tetrabutylammonium bromide = 5-10:1; in step 4), the heat preservation stirring reaction is carried out at 50-80°C for 6-12 hours.

[0018] The aforementioned surface treatment composition for removing wax layers from skids on automotive painting lines, wherein the bridging amine is one or two of piperazine, N,N-dimethyl-1,3-propanediamine, and 1,6-hexanediamine, and the catalyst in the bridging reaction stage is one or two of triethylamine or N,N-diisopropylethylamine.

[0019] The above-mentioned surface treatment composition for removing wax layer from skids on automotive painting lines, wherein the tea saponin-grafted polyamide amine (PAMAM) penetration enhancer is prepared by the following steps.

[0020] 1) Take 30-50 parts of dehydrated tea saponin powder and 40-60 parts of N,N-dimethylformamide, mix and stir, add 20-30 parts of dendritic polymer polyamide amine PAMAM, add 0.3-0.5 parts of catalyst, then introduce nitrogen gas and stir to react, to obtain a tea saponin grafted polyamide amine PAMAM penetration aid solution.

[0021] 2) Pour the tea saponin-grafted polyamide amine (PAMAM) penetration enhancer solution obtained in step 1) into acetone, let it stand, filter the precipitate in the solvent, freeze-dry the filtered product, and obtain the tea saponin-grafted polyamide amine (PAMAM) penetration enhancer.

[0022] The above-mentioned surface treatment composition for removing wax layer from skids on automotive painting lines, wherein the catalyst is a combination of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and hydroxybenzotriazole; by mass ratio, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride: hydroxybenzotriazole = 1: 2-3, the stirring is carried out at 20-25°C for 1-3 hours, and the stirring reaction is carried out at 40-50°C for 12-24 hours.

[0023] The above-mentioned surface treatment composition for removing wax layer from skids on automotive painting lines, wherein the composite solid cleaning agent is a combination of colloidal silica and quaternary ammonium salt modified montmorillonite, with a mass ratio of colloidal silica:quaternary ammonium salt modified montmorillonite = 1:1-2.

[0024] A method for preparing the above-mentioned surface treatment composition for removing wax layer from skids on automotive painting lines includes the following steps: mixing deionized water and composite solid detergent in a mass ratio of 5-10:1, stirring at room temperature until a viscous paste is formed, adding the remaining deionized water, stirring, adding tea saponin-based dimer surfactant, stirring, adding tea saponin-grafted polyamide amine (PAMAM) penetration enhancer, and continuing to stir to obtain the surface treatment composition for cleaning wax layer from skids on automotive painting lines.

[0025] The application of the above-mentioned surface treatment composition for removing wax from skids on automotive painting lines in the brushing of skids contaminated with cavity wax in automotive painting workshops.

[0026] Furthermore, in the above-mentioned applications, the surface treatment composition is mixed with water at a mass ratio of 1:1-3 before use.

[0027] The beneficial effects of this invention are as follows.

[0028] 1. This invention provides a novel surface treatment composition for cleaning wax layers from skids on automotive painting lines. It is suitable for treating skids contaminated by wax drips from cavities in OEM painting workshops. Its advantages lie in the fact that when skids on the painting line are contaminated by wax from cavities, the surface treatment composition of this invention can efficiently remove the wax film adhering to the surface and crevices of the skid, thereby reducing slippage between the skid and the conveyor caused by wax residue, improving the stability and positioning accuracy of the skid operation, and reducing the risk of line stoppage due to conveyor slippage.

[0029] 2. The advantages of this invention compared to conventional wax removal methods in painting workshops are as follows: Compared to physical masking methods, using the surface treatment composition of this invention for wax removal reduces the time spent on masking film placement and replacement, eliminating the need to wait for line shutdown before addressing wax film contamination, thus improving maintenance efficiency on the production floor; Compared to mechanical physical removal methods, using the surface treatment composition of this invention improves cleaning efficiency and addresses the issue of wax film residue on skid surfaces and in crevices; Compared to simple organic solvent cleaning methods, this invention reduces the amount of organic solvent used while ensuring good wax removal results, thereby reducing the release of volatile organic compounds (VOCs) during the cleaning process, mitigating adverse effects on the operating environment and personnel health, and reducing waste solvent treatment costs and overall usage costs.

[0030] 3. This invention uses tea saponin, a natural bio-based surfactant, as the molecular design basis to prepare a tea saponin-based dimer surfactant specifically for removing cavity wax. It further combines this surfactant with a tea saponin-grafted polyamide amine (PAMAM) penetration enhancer and a composite solid cleaning agent. The beneficial effects are that the tea saponin-based dimer surfactant provides good wetting, emulsification, stripping, and dispersion of cavity wax films. To further improve cleaning efficiency, the addition of the tea saponin-grafted polyamide amine (PAMAM) penetration enhancer improves the penetration ability of the surface treatment composition into the gaps, pores, and small pits of the skid, thereby improving the removal and removal of localized residual wax films by the cleaning solution. Simultaneously, combined with the skid-washing application method used by OEMs, the composite solid cleaning agent further enhances the cleaning ability on the skid surface and in the gaps. Thus, the combined effects of surface activity, penetration enhancement, and solid cleaning agent achieve a better cleaning effect.

[0031] 4. This invention uses a tea saponin-based dimer surfactant as the main washing component. Its beneficial effect lies in the fact that, compared to native tea saponin or ordinary modified tea saponin surfactants, the tea saponin-based dimer surfactant, containing two tea saponin amphiphilic units, enhances its effect on the cavity wax film / cleaning fluid interface, improving its wetting, peeling, and dispersing ability on highly adhesive cavity wax films, thereby improving cleaning efficiency, especially suitable for removing cavity wax after drying and film formation.

[0032] 5. This invention uses high-purity tea saponin as a raw material. Its beneficial effects are that the high-purity tea saponin raw material has lower levels of impurities such as sugars, proteins, starches, and pectins, which helps reduce side reactions and impurity interference in subsequent reaction processes, improving the stability of the target product preparation process. At the same time, the increased purity of the raw material also helps improve the uniformity of the final surface-treated composition product's appearance and storage stability.

[0033] 6. In the preparation of tea saponin-based dimer surfactants, this invention uses a mixed solvent of dimethyl sulfoxide and N,N-dimethylformamide as the reaction medium. The beneficial effect is that this mixed solvent system can effectively disperse or dissolve tea saponin and its intermediates, improving the homogeneity of the reaction system and facilitating the introduction of epichlorohydrin and subsequent bridging reactions, thereby improving the preparation efficiency and process stability of the target product.

[0034] 7. This invention uses epichlorohydrin to intermediate tea saponin and further constructs tea saponin-based dimer surfactants through bridging amines. Its beneficial effect lies in the fact that by introducing an amine-containing hydroxypropyl bridging structure, two amphiphilic units of tea saponin are linked to the same molecule, which enhances the surfactant molecule's ability to interact with the wax film interface, thereby improving the cleaning effect on high-adhesion cavity wax films.

[0035] 8. In the preparation of tea saponin-based dimer surfactants, this invention employs a combined catalytic system of sodium hydroxide and tetrabutylammonium bromide, and uses triethylamine and / or N,N-diisopropylethylamine as catalysts in the bridging reaction stage. The beneficial effects are that the former facilitates the reaction between epichlorohydrin and tea saponin, while the latter promotes the reaction between the bridged amine and the intermediate, thereby improving the reaction efficiency and process controllability of the entire preparation process.

[0036] 9. This invention uses tea saponin-grafted polyamide amine (PAMAM) as a penetration enhancer. Its beneficial effect lies in the fact that PAMAM molecules have a dendritic structure and numerous active sites. Grafting with tea saponin improves its compatibility with the cleaning system and facilitates the penetration of the cleaning solution into the cavity wax film and the gaps in the skid, thereby improving the cleaning effect on localized residual wax film and further enhancing the overall wax removal capability.

[0037] 10. To further improve the cleaning effect, this invention introduces a composite solid cleaning aid into the product components. Its beneficial effects are that colloidal silica, during the brushing process, facilitates the shearing and breaking action on the wax film, while the layered structure of quaternary ammonium salt-modified montmorillonite is beneficial for adsorbing and removing desorbed wax. The combination of these two ingredients further enhances the removal capacity of dried, film-forming cavities of wax and improves the cleaning effect on skid gaps and pores. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the embodiments. All raw materials mentioned in the embodiments are commercially available.

[0039] Example 1: A surface treatment composition for removing wax from skids on automotive painting lines.

[0040] (a) The preparation method is as follows.

[0041] 1. Preparation of tea saponin-based dimer surfactant.

[0042] 1) Take 40 kg of light yellow tea saponin powder with a purity of 95% and put it into a vacuum drying oven at a temperature of 80℃ and a vacuum degree of -0.1MPa for 1 hour to obtain dehydrated tea saponin powder.

[0043] 2) Take 30 kg of dehydrated tea saponin powder, 25 kg of dimethyl sulfoxide and 25 kg of N,N-dimethylformamide and add them to the reaction vessel. Turn on the stirring and stir at 40 rpm. Control the temperature at 45℃ and stir for 1 hour. Then filter the resulting liquid through a 500-mesh filter to obtain a tea saponin solution.

[0044] 3) Add 80 kg of tea saponin solution to the reaction vessel, then introduce nitrogen gas into the reaction vessel and adjust the flow rate of nitrogen gas to 50 mL / min. Then add 2 kg of epichlorohydrin, 0.083 kg of sodium hydroxide and 0.017 kg of tetrabutylammonium bromide to the reaction vessel. Control the reaction temperature at 50℃ and stir the reaction for 3 h. Then adjust the pH of the system to 6.5 with 0.5 kg of 5% hydrochloric acid solution. Filter and remove the solvent to obtain the tea saponin glycidyl ether intermediate.

[0045] 4) Take 80 kg of tea saponin glycidyl ether intermediate, add 25 kg of dimethyl sulfoxide and 25 kg of N,N-dimethylformamide, start stirring, and purge with nitrogen gas for protection. Adjust the nitrogen flow rate to 20 mL / min, then add 0.5 kg of piperazine and 0.1 kg of triethylamine dropwise to the reaction vessel. After the addition is complete within 30 minutes, adjust the reaction temperature to 50℃, keep the temperature and stir for 6 h to obtain the bridging reaction solution. Finally, add 20 kg of deionized water to the bridging reaction solution to terminate the reaction, adjust the pH to 7, and then add 50 kg of ethyl acetate to the system for precipitation. After standing for 0.5 h, filter. The obtained product is vacuum dried at 40℃ for 6 h to obtain the tea saponin-based dimer surfactant.

[0046] 2. Preparation of tea saponin grafted with polyamide amine (PAMAM) penetration enhancer.

[0047] 1) Take 30 kg of dehydrated tea saponin powder and 40 kg of N,N-dimethylformamide, add them to the reaction vessel, start stirring, the stirring speed is 30 rpm, stir at 20℃ for 1 h, then add 20 kg of dendritic polymer polyamide amine PAMAM to the reaction vessel, then add 0.1 kg of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 0.2 kg of hydroxybenzotriazole, then introduce nitrogen into the reaction vessel, adjust the nitrogen flow rate to 20 mL / min, raise the temperature of the reaction system to 40℃, stir and react for 12 h, and the tea saponin grafted polyamide amine (PAMAM) penetration aid solution is obtained.

[0048] 2) Take 40 kg of tea saponin-grafted polyamide amine (PAMAM) penetration enhancer solution, pour it into 50 kg of acetone, let it stand for 1 hour, then filter the precipitate in the solvent through a 500-mesh filter, and freeze-dry the filtered product at -30°C for 24 hours to obtain tea saponin-grafted polyamide amine (PAMAM) penetration enhancer.

[0049] 3. Preparation of a surface treatment composition for removing wax layers from skids on automotive painting lines.

[0050] Add 5 kg of deionized water, 0.5 kg of colloidal silica, and 0.5 kg of quaternary ammonium salt modified montmorillonite to a high-speed dispersion reactor. Start stirring at 1000 rpm and stir at room temperature until a viscous paste is formed. Then add 30 kg of deionized water and stir for 0.5 h. Add 30 kg of tea saponin-based dimer surfactant and stir for 0.5 h. Add 5 kg of tea saponin-grafted polyamide amine (PAMAM) penetration enhancer and continue stirring for 0.5 h to obtain a surface treatment composition for removing wax layer from skids on automotive painting lines.

[0051] The surface treatment composition for removing wax from skids on automotive painting lines was mixed with water at a mass ratio of 1:1 to prepare a working solution. The product performance indicators are shown in Table 1.

[0052] Comparative Example 1: A surface treatment composition for removing wax layers from skids on automotive painting lines.

[0053] (a) The preparation method is as follows.

[0054] 1. Preparation of tea saponin-based dimer surfactant.

[0055] 1) Take 40 kg of yellow tea saponin powder with a purity of 80% and put it into a vacuum drying oven at a temperature of 80℃ and a vacuum degree of -0.1MPa for 1 hour to obtain dehydrated tea saponin powder.

[0056] 2) The subsequent preparation method of the tea saponin-based dimer surfactant is the same as in Example 1.

[0057] 2. Preparation of tea saponin grafted polyamide amine (PAMAM) penetration enhancer: Same as in Example 1.

[0058] 3. Preparation of the surface treatment composition for removing wax layer from skids on automotive painting lines: Same as in Example 1. The surface treatment composition for cleaning the cavities of wax on skids on automotive painting lines was mixed with water at a mass ratio of 1:1 to prepare a working solution. The performance indicators of the product were tested and are shown in Table 1.

[0059] Comparative Example 2: A surface treatment composition for removing wax layers from skids on automotive painting lines.

[0060] (a) The preparation method is as follows.

[0061] 1. Preparation of tea saponin-based dimer surfactant.

[0062] 1) Take 40 kg of light yellow tea saponin powder with a purity of 95% and put it into a vacuum drying oven at a temperature of 80℃ and a vacuum degree of -0.1MPa for 1 hour to obtain dehydrated tea saponin powder.

[0063] 2) Take 30 kg of dehydrated tea saponin powder, 25 kg of dimethyl sulfoxide and 25 kg of N,N-dimethylformamide and add them to the reaction vessel. Turn on the stirring and stir at 40 rpm. Control the temperature at 45℃ and stir for 1 hour. Then filter the resulting liquid through a 500-mesh filter to obtain a tea saponin solution.

[0064] 3) Take 80 kg of tea saponin solution and add it to the reaction vessel. Do not add epichlorohydrin, sodium hydroxide and tetrabutylammonium bromide, or perform a bridging amine reaction. Directly turn on the vacuum pump and control the vacuum degree at -0.1 MPa. Remove the solvent to obtain undimerized tea saponin surfactant.

[0065] 2. Preparation of tea saponin grafted polyamide amine (PAMAM) penetration enhancer: Same as in Example 1.

[0066] 3. Preparation of the surface treatment composition for removing wax layer from skids on automotive painting lines: Replace the tea saponin-based dimer surfactant in Example 1 with the undimerized tea saponin surfactant prepared in this comparative example, and follow the same steps as in Example 1. After mixing the surface treatment composition for cleaning the cavity wax on skids on automotive painting lines with water at a mass ratio of 1:1 to prepare the working solution, the product performance indicators are tested as shown in Table 1.

[0067] Comparative Example 3: A surface treatment composition for removing wax layers from skids on automotive painting lines.

[0068] (a) The preparation method is as follows.

[0069] 1. Preparation of tea saponin-based dimer surfactant.

[0070] 1) Take 40 kg of light yellow tea saponin powder with a purity of 95% and put it into a vacuum drying oven at a temperature of 80℃ and a vacuum degree of -0.1MPa for 1 hour to obtain dehydrated tea saponin powder.

[0071] 2) Take 30 kg of dehydrated tea saponin powder, 25 kg of dimethyl sulfoxide and 25 kg of N,N-dimethylformamide and add them to the reaction vessel. Turn on the stirring and stir at 40 rpm. Control the temperature at 45℃ and stir for 1 hour. Then filter the resulting liquid through a 500-mesh filter to obtain a tea saponin solution.

[0072] 3) Add 80 kg of tea saponin solution to the reaction vessel, then introduce nitrogen gas into the reaction vessel and adjust the flow rate of nitrogen gas to 50 mL / min. Then add 2 kg of epichlorohydrin, 0.083 kg of sodium hydroxide and 0.017 kg of tetrabutylammonium bromide to the reaction vessel. Control the reaction temperature at 50℃ and stir the reaction for 3 h. Then adjust the pH of the system to 6.5 with 0.5 kg of 5% hydrochloric acid solution. Filter and remove the solvent to obtain the tea saponin glycidyl ether intermediate.

[0073] 4) Take 80 kg of tea saponin glycidyl ether intermediate, add 25 kg of dimethyl sulfoxide and 25 kg of N,N-dimethylformamide, start stirring and purge with nitrogen for protection, but do not add bridging amine dropwise, only add 0.1 kg of triethylamine, keep warm and stir at 50 °C for 6 h, then add 20 kg of deionized water to terminate the reaction, adjust the pH to 7, then add 50 kg of ethyl acetate to the system to precipitate, let stand for 0.5 h and filter, the obtained product is vacuum dried at 40 °C for 6 h to obtain unbridged tea saponin glycidyl ether surfactant.

[0074] 2. Preparation of tea saponin grafted polyamide amine (PAMAM) penetration enhancer: Same as in Example 1.

[0075] 3. Preparation of the surface treatment composition for removing wax layer from skids on automotive painting lines: The tea saponin-based dimer surfactant in Example 1 was replaced with the unbridged tea saponin glycidyl ether surfactant prepared in this comparative example, and the remaining steps were the same as in Example 1. After mixing the surface treatment composition for removing wax layer from skids on automotive painting lines with water at a mass ratio of 1:1 to prepare a working solution, the product performance indicators were tested as shown in Table 1.

[0076] Comparative Example 4: A surface treatment composition for removing wax layers from skids on automotive painting lines.

[0077] 1. Surfactant selection: Instead of preparing tea saponin-based dimer surfactants, fatty alcohol polyoxyethylene ether AEO-9 was directly used as the surfactant.

[0078] 2. Preparation of tea saponin grafted polyamide amine (PAMAM) penetration enhancer: Same as in Example 1.

[0079] 3. Preparation of the surface treatment composition for removing wax layer from skids on automotive painting lines: Replace 30 kg of tea saponin-based dimer surfactant in Example 1 with 30 kg of fatty alcohol polyoxyethylene ether AEO-9, and follow the same steps as in Example 1. After mixing the surface treatment composition for removing wax layer from skids on automotive painting lines with water at a mass ratio of 1:1 to prepare the working solution, the product performance indicators are shown in Table 1.

[0080] Comparative Example 5: A surface treatment composition for removing wax layers from skids on automotive painting lines.

[0081] (a) The preparation method is as follows.

[0082] 1. Preparation of tea saponin-based dimer surfactant: Same as in Example 1.

[0083] 2. Preparation of tea saponin grafted polyamide amine (PAMAM) penetration enhancer.

[0084] 1) Add 30 kg of dehydrated tea saponin powder to the reactor, start stirring, and then add 20 kg of dendritic polymer polyamide amine PAMAM to the reactor. Do not add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and hydroxybenzotriazole. Do not introduce nitrogen gas or carry out grafting reaction. Stir at 40°C for 12 h to obtain a physical mixture of tea saponin and polyamide amine PAMAM.

[0085] 3. Preparation of the surface treatment composition for removing wax layer from skids on automotive painting lines: The tea saponin-grafted polyamide amine (PAMAM) penetration enhancer in Example 1 was replaced with the physical mixture of tea saponin and polyamide amine PAMAM prepared in this comparative example. The remaining steps were the same as in Example 1. After mixing the surface treatment composition for removing wax layer from skids on automotive painting lines with water at a mass ratio of 1:1 to prepare the working solution, the product performance indicators were tested and are shown in Table 1.

[0086] Comparative Example 6: A surface treatment composition for removing wax layers from skids on automotive painting lines.

[0087] (a) The preparation method is as follows.

[0088] 1. Preparation of tea saponin-based dimer surfactant: Same as in Example 1.

[0089] 2. Preparation of tea saponin grafted polyamide amine (PAMAM) penetration enhancer: Same as in Example 1.

[0090] 3. Preparation of a surface treatment composition for cleaning the cavity wax on skids of an automotive painting line: Add 35 kg of deionized water to a high-speed dispersion reactor, start stirring at 1000 rpm, add 30 kg of tea saponin-based dimer surfactant, stir for 0.5 h, add 5 kg of tea saponin-grafted polyamide amine (PAMAM) penetration enhancer, and continue stirring for 0.5 h to obtain a surface treatment composition for cleaning the cavity wax on skids of an automotive painting line.

[0091] Colloidal silica and quaternary ammonium salt modified montmorillonite were not added in this comparative example. The surface treatment composition for removing wax layer from skids on automotive painting lines was mixed with water at a mass ratio of 1:1 to prepare a working solution, and the product performance indicators were tested as shown in Table 1.

[0092] Comparative Example 7: A surface treatment composition for removing wax layers from skids on automotive painting lines.

[0093] (a) The preparation method is as follows.

[0094] 1. Preparation of tea saponin-based dimer surfactant: Same as in Example 1.

[0095] 2. Preparation of tea saponin grafted polyamide amine (PAMAM) penetration enhancer: Same as in Example 1.

[0096] 3. Preparation of a surface treatment composition for removing wax layers from skids on automotive painting lines.

[0097] Add 5 kg of deionized water and 1 kg of colloidal silica to a high-speed dispersion reactor, start stirring at 1000 rpm, and stir at room temperature until a viscous paste is formed. Then add 30 kg of deionized water and stir for 0.5 h. Add 30 kg of tea saponin-based dimer surfactant and stir for 0.5 h. Add 5 kg of tea saponin-grafted polyamide amine (PAMAM) penetration enhancer and continue stirring for 0.5 h to obtain a surface treatment composition for removing wax layer from skids on automotive painting lines.

[0098] In this comparative example, only colloidal silica was used as a solid detergent additive, and no quaternary ammonium salt modified montmorillonite was added. The surface treatment composition used to remove wax from skids on automotive painting lines was mixed with water at a 1:1 mass ratio to prepare a working solution. The product performance indicators are shown in Table 1.

[0099] Comparative Example 8: A surface treatment composition for removing wax layers from skids on automotive painting lines.

[0100] (a) The preparation method is as follows.

[0101] 1. Preparation of tea saponin-based dimer surfactant: Same as in Example 1.

[0102] 2. Preparation of tea saponin grafted polyamide amine (PAMAM) penetration enhancer: Same as in Example 1.

[0103] 3. Preparation of a surface treatment composition for removing wax layers from skids on automotive painting lines.

[0104] Add 5 kg of deionized water and 1 kg of quaternary ammonium salt modified montmorillonite to a high-speed dispersion reactor, start stirring at 1000 rpm, and stir at room temperature until a viscous paste is formed. Then add 30 kg of deionized water and stir for 0.5 h. Add 30 kg of tea saponin-based dimer surfactant and stir for 0.5 h. Add 5 kg of tea saponin-grafted polyamide amine (PAMAM) penetration enhancer and continue stirring for 0.5 h to obtain a surface treatment composition for removing wax layer from skids on automotive painting lines.

[0105] In this comparative example, only quaternary ammonium salt modified montmorillonite was used as a solid detergent additive, and no colloidal silica was added. The surface treatment composition used to remove wax from skids on automotive painting lines was mixed with water at a 1:1 mass ratio to prepare a working solution. The product performance indicators are shown in Table 1.

[0106] Comparative Example 9: A surface treatment composition for removing wax layers from skids on automotive painting lines.

[0107] (a) The preparation method is as follows.

[0108] 1. Preparation of tea saponin-based dimer surfactant: Same as in Example 1.

[0109] 2. Preparation of a surface treatment composition for removing wax layer from skids on automotive painting lines: Add 5 kg of deionized water, 0.5 kg of colloidal silica, and 0.5 kg of quaternary ammonium salt modified montmorillonite to a high-speed dispersion reactor, start stirring at 1000 rpm, and stir at room temperature until a viscous paste is formed. Then add 35 kg of deionized water and stir for 0.5 h. Add 30 kg of tea saponin-based dimer surfactant and stir for 0.5 h to obtain a surface treatment composition for removing wax layer from skids on automotive painting lines.

[0110] This comparative example does not include tea saponin-grafted polyamide amine (PAMAM) penetration enhancer and is made up with deionized water. The surface treatment composition for removing wax from automotive paint line skids was mixed with water at a 1:1 mass ratio to prepare the working solution, and the product performance indicators are shown in Table 1.

[0111] Example 2 application.

[0112] 1. Method: The surface treatment compositions for removing wax layer on skids of automotive painting lines prepared in Example 1 and Comparative Examples 1-9 were placed in transparent sealed sample bottles and stored in a low temperature chamber at 5°C for 7 days, and then stored in a constant temperature incubator at 40°C for 7 days. This was one cycle, and a total of 6 cycles were performed. The appearance of the samples was then observed for whether there was layering or precipitation. The specific results are shown in Table 1.

[0113] 2. Metal corrosion test: The surface treatment compositions for removing wax layer on skids of automobile painting lines prepared in Example 1 and Comparative Examples 1-9 were formulated into working solutions. Copper, carbon steel and aluminum test pieces were placed in the working solution according to QB / T2117-1995 and immersed at 80°C for 2 hours. The corrosion level of the working solution on the metals was tested. The specific results are shown in Table 1.

[0114] 3. Cavity wax cleaning rate test: First, solvent-based, high-solids, and water-based cavity waxes with a dry film thickness of 100 μm were coated on the test plate and dried according to the actual drying conditions of each type of cavity wax. Then, the surface treatment compositions for removing wax layers on skids of automotive painting lines prepared in Example 1 and Comparative Examples 1-9 were formulated into working solutions. The test plate was placed in the working solution and the sample was brushed with a brush. The operation was repeated 5 times. The cavity wax cleaning rate was calculated based on the mass loss of the wax film before and after brushing. The specific results are shown in Table 1.

[0115] 4. Calcium soap dispersing power test: The surface treatment compositions for removing wax layer on skids of automobile painting lines prepared in Example 1 and Comparative Examples 1-9 were formulated into working solutions. The dispersing power of the working solutions on calcium soap was then determined according to the national standard GB / T7463-1987. The specific results are shown in Table 1.

[0116] Table 1 Test Results.

[0117]

[0118] As shown in Table 1, the surface treatment composition prepared by this invention for removing wax layers from skids on automotive painting lines can achieve a brushing and cleaning rate of 95% or higher for solvent-based, high-solids, and water-based cavity waxes. 1g of the surface treatment composition can disperse calcium soap to 51.2g. Furthermore, the surface treatment composition does not corrode copper, carbon steel, or aluminum. The product has also passed six cycles of high and low temperature storage, demonstrating good stability.

[0119] The surface treatment composition prepared in Comparative Example 1 for removing wax layer from skids on automotive painting lines, due to the lack of sufficiently pure tea saponin as a raw material, impurities such as sugars, proteins, starches, and pectins in low-purity tea saponin will affect subsequent modification reactions, resulting in a decrease in the effective content of the target product. It will also cause the product to separate and precipitate, and the cleaning power will also decrease to a certain extent.

[0120] The surface treatment composition prepared in Comparative Example 2 for removing wax from skids on automotive painting lines, because it did not use epichlorohydrin to modify tea saponin with glycidyl etherification and did not undergo further bridging reaction, resulted in insufficient wetting, emulsifying and stripping ability of the undimerized tea saponin surfactant on the cavity wax film. Therefore, the cleaning rates of solvent-based, high-solids, and water-based cavity waxes were all significantly lower than those in Example 1.

[0121] The surface treatment composition prepared in Comparative Example 3 for removing wax layers from skids on automotive painting lines, although modified with epichlorohydrin, did not further form a tea saponin-based dimer structure through bridging amines. Consequently, the resulting surfactant molecules lacked sufficient interfacial bonding, penetration, stripping, and emulsification capabilities against the cavity wax film, and the cleaning effect failed to reach the level of Example 1. This indicates that the dimer structure formed with the participation of bridging amines plays a crucial role in enhancing the cleaning ability of cavity wax.

[0122] The surface treatment composition prepared in Comparative Example 4 for removing wax layers from skids on automotive painting lines used a conventional nonionic surfactant, AEO-9, instead of the tea saponin-based dimer surfactant. Since conventional nonionic surfactants are not molecularly designed for the high adhesion, high hydrophobicity, and drying film-forming properties of automotive cavity wax films, their wedging, peeling, and dispersing abilities are insufficient, resulting in a significantly lower cleaning efficiency than in Example 1.

[0123] The surface treatment composition prepared in Comparative Example 5 for removing wax from skids on automotive painting lines, because PAMAM and tea saponin were not linked through a grafting reaction, but only a physical mixture of tea saponin and PAMAM was used, the rigid dendritic PAMAM molecules were difficult to fully compatible with the tea saponin-based dimer surfactant system, resulting in poor product uniformity. Furthermore, the ability to penetrate the wax film in the small pits and crevices of the skid surface was insufficient, and the cleaning effect did not reach a good state.

[0124] The surface treatment composition prepared in Comparative Example 6 for removing wax from skids on automotive painting lines did not produce sufficient auxiliary shearing, adsorption, and transport effects on the wax film during the brushing process because no composite solid cleaning agent was added to the product. The wax that was removed was also prone to secondary adhesion on the skid surface, so the cleaning power did not reach the ideal state.

[0125] Comparative Examples 7 and 8 used either colloidal silica or quaternary ammonium salt-modified montmorillonite as solid detergent additives, respectively. Test results showed that while colloidal silica alone had some shearing effect on the wax film, its adsorption and transport capacity for detached wax was insufficient. Similarly, while quaternary ammonium salt-modified montmorillonite alone had some adsorption effect on oil and wax contaminants, its destructive shearing capacity against the dried wax film was insufficient. Therefore, the combination of colloidal silica and quaternary ammonium salt-modified montmorillonite can simultaneously exert both rigid shearing and lamellar adsorption and transport effects, thus improving the dewaxing effect of brushing.

[0126] The surface treatment composition prepared in Comparative Example 9 for removing wax from skids on automotive painting lines, due to the absence of tea saponin-grafted polyamide amine (PAMAM) penetration aid, had difficulty quickly penetrating into the cavity wax film and the interface between the wax film and the metal skid surface. As a result, although the wax film could be wetted and partially emulsified by the surface, the overall loosening and peeling efficiency was insufficient, especially for high-solids cavity wax, the cleaning effect was significantly reduced.

[0127] In summary, this invention achieves the wetting, penetration, emulsification, peeling, shearing, and dispersion suspension of the wax film in the cavities of the skid surface on an automotive painting line through the combined action of tea saponin-based dimer surfactant, tea saponin-grafted polyamide amine (PAMAM) penetration enhancer, and composite solid cleaning aid. This effectively improves the brushing and cleaning effect of wax on the skid surface and in the cavities of the gaps, while maintaining good product stability and a low risk of metal corrosion.

Claims

1. A surface treatment composition for removing wax layers from skids on automotive painting lines, characterized in that, The formula, by weight, includes the following components: 30-40 parts tea saponin-based dimer surfactant, 5-8 parts tea saponin-grafted polyamide amine (PAMAM) penetration enhancer, 0.5-1 part composite solid detergent builder, and 35-50 parts deionized water. The preparation method of the tea saponin-based dimer surfactant is as follows: under nitrogen atmosphere, tea saponin solution reacts with epichlorohydrin and catalyst, the pH of the solution is adjusted to neutral, the solvent is removed to obtain tea saponin glycidyl ether intermediate, solvent is added, stirring is performed, nitrogen is introduced, bridged amine and catalyst are added dropwise to react to obtain bridged reaction solution, water or ethanol aqueous solution is added to terminate the reaction, the pH is adjusted to alkaline, crystals are precipitated, and the solution is allowed to stand, filtered and dried to obtain tea saponin-based dimer surfactant; The preparation method of the tea saponin-grafted polyamide amine (PAMAM) penetration enhancer is as follows: add dendritic polymer polyamide amine (PAMAM) and catalyst to the tea saponin solution, and then introduce nitrogen gas to react and obtain a tea saponin-grafted polyamide amine (PAMAM) penetration enhancer solution. Add acetone, let stand, filter, and freeze dry to obtain the tea saponin-grafted polyamide amine (PAMAM) penetration enhancer.

2. The surface treatment composition for removing wax layer from skids on an automotive painting line according to claim 1, characterized in that, The preparation method of the tea saponin-based dimer surfactant includes the following steps: 1) Vacuum drying of tea saponin powder to obtain dehydrated tea saponin powder; 2) Mixing 30-40 parts of dehydrated tea saponin powder and 50-60 parts of mixed solvent, stirring, controlling the temperature at 45-60℃, stirring, filtering, and obtaining tea saponin solution; 3) Taking 80-100 parts of tea saponin solution, purging with nitrogen gas, adding 2-8 parts of epichlorohydrin, adding 0.1-0.3 parts of catalyst, stirring the reaction, adjusting the pH of the system to 6.5-7.5, filtering and removing the solvent to obtain tea saponin-based dimer surfactant. 4) Take 80-100 parts of tea saponin glycidyl ether intermediate, add 50-60 parts of mixed solvent, start stirring and purge with nitrogen for protection, then add 0.5-3 parts of bridged amine and 0.1-0.5 parts of catalyst dropwise to the reaction vessel. After the addition is complete, keep the mixture warm and stir to obtain the bridged reaction solution; add deionized water or ethanol aqueous solution to the bridged reaction solution to terminate the reaction, adjust the pH to 7-9, add ethyl acetate to precipitate, let stand and filter, and vacuum dry the obtained product to obtain tea saponin-based dimer surfactant.

3. The surface treatment composition for removing wax layer from skids on an automotive painting line according to claim 2, characterized in that, The tea saponin powder is a light yellow powder with a purity of 95-98%; in step 2), the mixed solvent is a combination of dimethyl sulfoxide and N,N-dimethylformamide, with a mass ratio of dimethyl sulfoxide:N,N-dimethylformamide = 1-3:1; in step 4), the mixed solvent is a combination of dimethyl sulfoxide and N,N-dimethylformamide, with a mass ratio of dimethyl sulfoxide:N,N-dimethylformamide = 1-3:

1.

4. The surface treatment composition for removing wax layer from skids on an automotive painting line according to claim 2, characterized in that, In step 3), the stirring reaction is carried out at 50-65℃ for 3-6 hours under stirring conditions, and the catalyst is a combination of sodium hydroxide and tetrabutylammonium bromide, with a mass ratio of sodium hydroxide:tetrabutylammonium bromide = 5-10:1; In step 4), the heat preservation stirring reaction is carried out at 50-80℃ for 6-12 hours.

5. The surface treatment composition for removing wax layer from skids on an automotive painting line according to claim 2, characterized in that, The bridging amine is one or two of piperazine, N,N-dimethyl-1,3-propanediamine, and 1,6-hexanediamine, and the catalyst in the bridging reaction stage is one or two of triethylamine or N,N-diisopropylethylamine.

6. The surface treatment composition for removing wax layer from skids on an automotive painting line according to claim 1, characterized in that, The preparation method of the tea saponin-grafted polyamide amine (PAMAM) penetration enhancer includes the following steps: 1) Take 30-50 parts of dehydrated tea saponin powder and 40-60 parts of N,N-dimethylformamide, mix and stir, add 20-30 parts of dendritic polymer polyamide amine (PAMAM), add 0.3-0.5 parts of catalyst, then introduce nitrogen gas and stir to react, to obtain a tea saponin-grafted polyamide amine (PAMAM) penetration enhancer solution; 2) Take the tea saponin-grafted polyamide amine (PAMAM) penetration enhancer solution obtained in step 1) and pour it into acetone, let it stand, filter the precipitate in the solvent, freeze-dry the filtered product, and obtain the tea saponin-grafted polyamide amine (PAMAM) penetration enhancer.

7. The surface treatment composition for removing wax layer from skids on an automotive painting line according to claim 6, characterized in that, The catalyst is a combination of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and hydroxybenzotriazole; by mass ratio, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride: hydroxybenzotriazole = 1: 2-3; the stirring is carried out at 20-25℃ for 1-3 hours; and the stirring reaction is carried out at 40-50℃ for 12-24 hours.

8. The surface treatment composition for removing wax layer from skids on an automotive painting line according to claim 1, characterized in that, The composite solid detergent additive is a combination of colloidal silica and quaternary ammonium salt modified montmorillonite, with a mass ratio of colloidal silica:quaternary ammonium salt modified montmorillonite = 1:1-2.

9. A method for preparing a surface treatment composition for removing wax layer from skids on an automotive painting line, as described in any one of claims 1-8, characterized in that, The process includes the following steps: mixing deionized water and composite solid detergent in a mass ratio of 5-10:1, stirring at room temperature until a viscous paste is formed, adding the remaining deionized water, stirring, adding tea saponin-based dimer surfactant, stirring, adding tea saponin-grafted polyamide amine (PAMAM) penetration enhancer, and continuing to stir to obtain a surface treatment composition for cleaning wax layers on skids in automotive painting lines.

10. The use of the surface treatment composition according to any one of claims 1-8 for removing wax from skis on an automotive painting line in the process of scrubbing skis contaminated with cavity wax in an automotive painting workshop.

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