Paint remover and paint removing method of polyurethane wave-absorbing coating part

Abstract

The invention discloses a paint remover which comprises the following components in percentage by mass: 90-96% of a main solvent, 0-4% of a thickening agent, 0-5% of an accelerant and 0-4% of a corrosion inhibitor, and the thickening agent, the accelerant and the corrosion inhibitor are not zero at the same time; the main solvent comprises dichloromethane and benzyl alcohol; the mass ratio of dichloromethane to benzyl alcohol is (2-4): 1. Additives in the paint remover can be adjusted in a targeted mode according to soaking removal or brush coating removal to adapt to a construction mode, and a base material subjected to paint removal can be protected against the problem that the quality of secondary recoating is affected by pulverization, corrosion and the like. The main solvent in the paint remover is compounded, so that on one hand, a polyurethane polymer main chain can be solvated, and on the other hand, part of functional groups of the main chain can be permeated, so that volume swelling of the polymer main chain is replaced, and a coating is efficiently removed. The paint remover has great significance in airplane repair, airplane maintenance cost reduction and material utilization efficiency improvement, and is suitable for popularization and application.

Description

Technical Field

[0001] The present application relates to the field of coatings, and in particular to a paint stripper and a method for stripping polyurethane radar-absorbing coating products. Background Art

[0002] The radar absorbing coating applied to the aircraft effectively reduces the radar cross section of the equipment, but after years of service, the coating will be damaged by factors such as airflow impact and chemical corrosion, affecting the radar stealth function. If the coating applied to the core parts such as the air inlet and engine falls off, it will seriously affect flight safety. Therefore, it is necessary to remove the aged and damaged absorbing coating to lay a solid foundation for the secondary repair of the aircraft coating.

[0003] At present, radar absorbing coatings are generally formed by polyurethane resins. The main solvent is selected in a targeted manner. One part causes the polymer chain segments to undergo solvation, reducing the interaction between the polymer chain segments. The other part replaces certain blocks in the polymer chain, causing the volume of the cross-linked polymer chain to expand. The paint film swells and paint is removed, which is the current mainstream design direction of paint strippers. However, paint strippers disclosed in the prior art either cause corrosion or damage to the substrate metal, or do not completely remove the polyurethane resin, which will affect the performance of the secondary coating. Summary of the invention

[0004] In view of this, the present application provides a paint stripper and a method for stripping a polyurethane absorbing coating product. The paint stripper can efficiently remove the polyurethane-based absorbing coating at room temperature without causing damage or corrosion to the metal substrate.

[0005] The present application provides a paint stripper, which comprises, by mass percentage, 90% to 96% of a main solvent, 0% to 4% of a thickener, 0% to 5% of an accelerator and 0% to 4% of a corrosion inhibitor, wherein the thickener, the accelerator and the corrosion inhibitor are not zero at the same time; the main solvent comprises dichloromethane and benzyl alcohol; the mass ratio of dichloromethane to benzyl alcohol is (2-4):1.

[0006] The present application comprises, by mass percentage, 90% to 96% of a main solvent, 0% to 4% of a thickener, 0% to 5% of an accelerator and 0% to 4% of a corrosion inhibitor as raw materials to prepare a paint stripper, which can efficiently remove a polyurethane-based radar-absorbing coating.

[0007] The paint stripper provided in the present application comprises a main solvent, and the main solvent comprises dichloromethane and benzyl alcohol.

[0008] In some specific implementations, the mass percentage of the main solvent is 90% to 96%, which can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, and preferably 92% to 95%.

[0009] In some specific implementations, the mass ratio of dichloromethane to benzyl alcohol is (2-4):1, which can be 2:1, 2.5:1, 3:1, 3.5:1, 4:1, and preferably 3:1.

[0010] The paint stripper provided in the present application includes a thickener. In some specific implementations, the thickener includes but is not limited to one or more of aqueous methyl cellulose, carboxymethyl cellulose or ethyl cellulose, and the present application has no special requirements for the selection of the thickener.

[0011] In some specific implementations, the mass percentage of the thickener is 0% to 4%, which may be 0%, 1%, 2%, 3%, 4%, and preferably 1% to 3%.

[0012] The paint stripper provided in the present application includes an accelerator. In some specific implementations, the accelerator includes but is not limited to formic acid, acetic acid, p-toluenesulfonic acid or terephthalic acid. The present application has no special requirements for the selection of the accelerator.

[0013] In some specific implementations, the mass percentage of the accelerator is 0% to 5%, which may be 0%, 1%, 2%, 3%, 4%, 5%, and preferably 1% to 4%.

[0014] The paint stripper provided in the present application includes a corrosion inhibitor. In some specific implementations, the corrosion inhibitor includes but is not limited to sodium benzoate, benzotriazole, or methyl benzotriazole. The present application has no special requirements for the selection of the corrosion inhibitor.

[0015] In some specific implementations, the mass percentage of the corrosion inhibitor is 0% to 4%, which can be 0%, 1%, 2%, 3%, 4%, and preferably 1% to 3%.

[0016] The main solvent in the paint stripper is mainly selected for the hard segment of the polyurethane resin, and the formula is iterated according to the simulation of different construction environments and construction methods, while avoiding the corrosion of the LY-12 substrate. The paint stripper has good fluidity, is suitable for immersion paint stripping, and has a good paint stripping effect on parts that can be placed in a container.

[0017] The present application also provides a method for removing paint from a polyurethane absorbing coating product, comprising:

[0018] The polyurethane absorbing coating product is stripped in the above-mentioned paint stripper.

[0019] The present application first soaks the polyurethane absorbing coating part in a paint stripper to strip the paint. In some specific implementations, the paint stripping temperature is 13°C to 33°C, preferably 20°C to 30°C. In some specific implementations, the paint stripping time is 10min to 120min, preferably 15min to 30min. In some specific implementations, the paint stripping needs to ensure that the paint stripper immerses the polyurethane absorbing coating part. In some specific implementations, the swelling phenomenon of the paint film is observed. If a large area of ​​the paint film is bitten, the residual area is less than 5% after the swollen paint film is peeled off, confirming the effect of the paint stripper, otherwise continue to soak. In some specific implementations, the polyurethane absorbing coating part includes a substrate and a polyurethane absorbing coating composited on the substrate; the polyurethane absorbing coating is formed by curing the compound shown in formula (1), the compound shown in formula (2) and the compound shown in formula (3):

[0020]

[0021] In some specific implementations, the main group of the compound shown in formula (3) is NCO~, and the main solvent is selected in a targeted manner. A part of it causes the polymer chain segments to be solvated, thereby reducing the interaction between the polymer chain segments, and the other part replaces certain blocks in the polymer chain, causing the volume of the cross-linked polymer chain to expand.

[0022] In some specific implementations, the substrate of the polyurethane absorbing coating product is an LY-12 aluminum substrate. In some specific implementations, the paint stripping environment is neutral or weakly acidic.

[0023] The present application then rinses the polyurethane absorbing coating article after paint removal with NaOH solution, and then polishes it. In some specific implementations, the concentration of the NaOH solution is 0.5% to 3%. In some specific implementations, the polishing includes polishing with sandpaper, and the mesh number of the sandpaper is 240 to 400 mesh, preferably 300 to 350 mesh. After polishing, the surface is free of rust and powdering. In some specific implementations, the purpose of polishing is to remove the low surface energy layer material on the surface.

[0024] The present application then wipes the polished polyurethane absorbing coating product. In some specific implementations, the wiping solvent includes but is not limited to acetone and / or butanol, and the present application has no special requirements for the wiping solvent.

[0025] After paint stripping, the low surface energy substances that are not removed from the residual part of the substrate surface, as well as the solid, liquid, oil, dust, etc. during the construction process will cause shrinkage holes and bottom biting of the paint during the secondary recoating, affecting the adhesion of the secondary recoating coating. Therefore, it is necessary to cooperate with the above-mentioned paint stripper to find an efficient and simple post-processing method. The development of a paint stripping method for efficiently removing polyurethane absorbing coatings has important economic and social value. The paint stripping method can quickly, effectively, and without residue remove the polyurethane absorbing coating on the surface of metal parts, reduce the difficulty of secondary spraying, and ensure flight safety.

[0026] The paint stripping method removes the low surface energy layer on the surface of the substrate, thereby ensuring the surface quality of the substrate after paint stripping.

[0027] The paint stripper described in the present application can be adjusted according to the additives in the paint stripper to adapt to the construction method according to the soaking removal or brushing removal, and can protect the substrate from powdering and rusting after paint stripping, which affects the quality problems of secondary recoating. The main solvent compound in the paint stripper can solvate the polyurethane polymer main chain on the one hand, and can penetrate the functional groups of the main chain to replace the volume swelling of the polymer main chain on the other hand, so as to efficiently remove the coating. This application is of great significance for aircraft repair, reducing aircraft maintenance costs and improving the utilization efficiency of materials, and is suitable for promotion and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A flow chart of a paint stripping method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] It should be understood that the expression "one or more of..." includes each of the items recited after the expression individually and in various different combinations of two or more of the recited items, unless otherwise understood from the context and usage. The expression "and / or" in combination with three or more recited items should be understood to have the same meaning, unless otherwise understood from the context.

[0030] The use of the terms "comprising", "having" or "containing", including their grammatical synonyms, should generally be understood as open and non-restrictive, for example not excluding other unrecited elements or steps, unless otherwise specifically stated or otherwise understood from the context.

[0031] It should be understood that the order of steps or the order in which certain actions are performed is not important as long as the application is still operable. In addition, two or more steps or actions can be performed simultaneously.

[0032] The use of any and all examples or exemplary language, such as "for example" or "including", herein is intended only to better illustrate the present application and does not limit the scope of the present application unless the claims are set forth. No language in this specification should be construed as indicating that any non-claimed element is essential to the practice of the present application.

[0033] In addition, the numerical ranges and parameters used to define the present application are approximate values, and the relevant values ​​in the specific embodiments have been presented as accurately as possible. However, any numerical value inherently inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise expressly stated, it should be understood that all ranges, quantities, values ​​and percentages used in this disclosure are modified by "about". Here, "about" generally means that the actual value is within plus or minus 10%, 5%, 1% or 0.5% of a specific value or range.

[0034] The present application is further described below in conjunction with the following embodiments. The protection scope of the present application is not limited by the following embodiments.

[0035] Example 1

[0036] A paint stripper includes, by weight percentage, 72% of dichloromethane, 24% of benzyl alcohol, 2% of acetic acid, and 2% of sodium benzoate. The paint stripper is prepared by mixing the above-mentioned weight proportions at room temperature. The paint stripper has good fluidity, is suitable for immersion paint stripping, and has a good paint stripping effect on workpieces that can be placed in a container.

[0037] A method for removing paint from a polyurethane absorbing coating product, the process is as follows Figure 1 As shown, S1 injects a pre-mixed paint stripper into a container and maintains the temperature of the paint stripper at 13°C to 33°C; S2 directly puts the polyurethane absorbing coating workpiece into the container and ensures that the paint stripper submerges the workpiece; S3 removes the polyurethane absorbing coating after soaking the workpiece for a period of time; S4 observes the swelling of the paint film. If a large area of ​​the paint surface is bitten, and the residual area is less than 5% after the swollen paint film is peeled off, the effect of the paint stripper is confirmed. Otherwise, continue soaking until the residual area of ​​the paint film is less than 5%; S5 uses sandpaper to remove the low surface energy layer material on the surface of the residual coating workpiece, and wipes it with a detergent.

[0038] Place the parts with polyurethane absorbing coating in a container, add paint stripper, and control the temperature in the container to 23℃. Place the parts with polyurethane absorbing coating in a container, making sure that the paint stripper submerges the parts. After soaking the parts for 30 minutes, the paint film is bitten up over a large area. After peeling off the paint film with tweezers, rinse the parts with 1% NaOH solution, and use 400-grit sandpaper to remove the low surface energy layer on the surface of the parts. There is no rust or powdering on the surface. Use butanone to wipe the surface of the parts, and perform a water film test on the surface of the parts. It is found that the water film is continuous and the polyurethane absorbing coating on the surface of the substrate of the parts is successfully removed.

[0039] Example 2

[0040] A paint stripper includes, by weight percentage, 70% dichloromethane, 24% benzyl alcohol, 1% acetic acid, 3% aqueous methyl cellulose, and 2% sodium benzoate. The paint stripper is prepared by mixing the above weight proportions at room temperature. The paint stripper has good fluidity, is suitable for immersion paint stripping, and has a good paint stripping effect on workpieces that can be placed in a container.

[0041] Place the parts with polyurethane absorbing coating in a container, add paint stripper, and control the temperature in the container to 23℃. Place the parts with polyurethane absorbing coating in a container, making sure that the paint stripper submerges the parts. After soaking the parts for 40 minutes, the paint film is bitten up over a large area. After peeling off the paint film with tweezers, rinse the parts with 1% NaOH solution, and use 240-grit sandpaper to remove the low surface energy layer on the surface of the parts. There is no rust or powdering on the surface. Use acetone to wipe the surface of the parts, and perform a water film test on the surface of the parts. It is found that the water film is continuous and the polyurethane absorbing coating on the surface of the substrate of the parts is successfully removed.

[0042] Example 3

[0043] A paint stripper includes, by weight percentage, 72% of dichloromethane, 24% of benzyl alcohol, and 4% of aqueous methyl cellulose. The paint stripper is prepared by mixing the above-mentioned weight ratios at room temperature. The paint stripper has good fluidity, is suitable for immersion paint stripping, and has a good paint stripping effect on workpieces that can be placed in a container.

[0044] Place the workpiece with polyurethane absorbing coating in a container, add paint stripper, and control the temperature in the container to 33℃. Place the workpiece with polyurethane absorbing coating in a container, and make sure that the paint stripper submerges the workpiece. After soaking the workpiece for 1.5 hours, the paint film is bitten up over a large area. After peeling off the paint film with tweezers, rinse the workpiece with 0.5% NaOH solution, and use 400 mesh sandpaper to remove the low surface energy layer on the surface of the workpiece. There is no rust or powdering on the surface. Use acetone to wipe the surface of the workpiece, and perform a water film test on the surface of the workpiece. It is found that the water film is continuous and the polyurethane absorbing coating on the surface of the workpiece substrate is successfully removed.

[0045] Example 4

[0046] A paint stripper includes, by weight percentage, 72% of dichloromethane, 24% of benzyl alcohol, 2% of acetic acid, and 2% of sodium benzoate. The paint stripper is prepared by mixing the above-mentioned weight proportions at room temperature. The paint stripper has good fluidity, is suitable for immersion paint stripping, and has a good paint stripping effect on workpieces that can be placed in a container.

[0047] Place the parts with polyurethane absorbing coating in a container, add paint stripper, and control the temperature in the container to 13°C. Place the parts with polyurethane absorbing coating in a container, making sure that the paint stripper submerges the parts. After soaking the parts for 120 minutes, the paint film is bitten up over a large area. After peeling off the paint film with tweezers, rinse the parts with 1% NaOH solution, and use 400-grit sandpaper to remove the low surface energy layer on the surface of the parts. There is no rust or powdering on the surface. Use butanone to wipe the surface of the parts, and perform a water film test on the surface of the parts. It is found that the water film is continuous and the polyurethane absorbing coating on the surface of the substrate of the parts is successfully removed.

[0048] Example 5

[0049] A paint stripper includes, by weight percentage, 70% dichloromethane, 22% benzyl alcohol, 4% acetic acid, and 4% sodium benzoate. The paint stripper is prepared by mixing the above weight proportions at room temperature. The paint stripper has good fluidity, is suitable for immersion paint stripping, and has a good paint stripping effect on workpieces that can be placed in a container.

[0050] Place the parts with polyurethane absorbing coating in a container, add paint stripper, and control the temperature in the container to 23℃. Place the parts with polyurethane absorbing coating in a container, making sure that the paint stripper submerges the parts. After soaking the parts for 10 minutes, the paint film is bitten up over a large area. After peeling off the paint film with tweezers, rinse the parts with 2% NaOH solution for 3 times. After removing the low surface energy layer on the surface of the parts with 320-grit sandpaper, there is no rust or powdering on the surface. Use butanone to wipe the surface of the parts, and perform a water film test on the surface of the parts. It is found that the water film is continuous and the polyurethane absorbing coating on the surface of the substrate of the parts is successfully removed.

[0051] Comparative Example 1

[0052] A paint stripper includes, by weight percentage, 96% dichloromethane, 2% acetic acid, and 2% sodium benzoate. The paint stripper is prepared by mixing the above weight proportions at room temperature. The paint stripper has good fluidity, is suitable for immersion paint stripping, and has a good paint stripping effect on workpieces that can be placed in a container.

[0053] Place the parts with polyurethane absorbing coating in a container, add paint stripper, and control the temperature in the container to 23℃. Place the parts with polyurethane absorbing coating in a container, making sure that the paint stripper submerges the parts. After soaking the parts for 45 minutes, the paint film is bitten up over a large area. After peeling off the paint film with tweezers, rinse the parts with 1% NaOH solution, and use 400-grit sandpaper to remove the low surface energy layer on the surface of the parts. After polishing, rust and powder appear on the surface. Use acetone to wipe the surface of the parts, and perform a water film test on the surface of the parts. The water film is discontinuous.

[0054] Comparative Example 2

[0055] A paint stripper includes, by weight percentage, 96% benzyl alcohol, 2% acetic acid, and 2% sodium benzoate. The paint stripper is prepared by mixing the above weight proportions at room temperature. The paint stripper has good fluidity, is suitable for immersion paint stripping, and has a good paint stripping effect on workpieces that can be placed in a container.

[0056] Place the part with polyurethane absorbing coating in a container, add paint stripper, and control the temperature in the container to 23°C. Place the part with polyurethane absorbing coating in a container, making sure that the paint stripper submerges the part. After soaking the part for 1440 minutes, the paint film is bitten off over a large area. After peeling off the paint film with tweezers, the part is rinsed with 1% NaOH solution, and some paint film remains on the surface. Wipe the surface of the part with acetone, and perform a water film test on the surface of the part. The water film is discontinuous.

[0057] Comparative Example 3

[0058] A paint stripper includes, by weight percentage, 96% DMF (N,N-dimethylformamide), 2% acetic acid, and 2% sodium benzoate. The paint stripper is prepared by mixing the above weight ratios at room temperature. The paint stripper has good fluidity and is suitable for immersion paint stripping, and has a good paint stripping effect on workpieces that can be placed in a container.

[0059] Place the parts with polyurethane absorbing coating in a container, add paint stripper, and control the temperature in the container to 60℃. Place the parts with polyurethane absorbing coating in a container, and make sure that the paint stripper submerges the parts. After soaking the parts for 60 minutes, the paint film is bitten up on a large area. After peeling off the paint film with tweezers, rinse the parts with 1% NaOH solution, and use 400 mesh sandpaper to remove the low surface energy layer on the surface of the parts. After polishing, there is no rust or powder on the surface. Use butanone to wipe the surface of the parts, and perform a water film test on the surface of the parts. If the water film is continuous, it is determined that the polyurethane absorbing coating on the surface of the substrate of the parts has been successfully removed.

[0060] The coating removal effects of the paint strippers obtained in Examples 1-5 and Comparative Examples 1-3 under corresponding paint stripping conditions are shown in Table 1.

[0061] Table 1

[0062]

[0063]

[0064] The above is only a preferred specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can make equivalent substitutions or changes within the technical scope disclosed in the present application according to the technical solution and application concept of the present application, which should be covered by the protection scope of the present application.

Claims

1. A paint stripper, characterized in that: The content by mass percentage includes: 90% to 96% of main solvent, 0% to 4% of thickener, 0% to 5% of accelerator and 0% to 4% of corrosion inhibitor. If thickener, accelerator and corrosion inhibitor are not simultaneously present, the content is zero. The main solvent includes dichloromethane and benzyl alcohol; the mass ratio of dichloromethane to benzyl alcohol is (2-4):

1.

2. The paint stripper according to claim 1, characterized in that The thickener includes one or more of aqueous methyl cellulose, carboxymethyl cellulose or ethyl cellulose.

3. The paint stripper according to claim 1, characterized in that The promoter includes one or more of formic acid, acetic acid, p-toluenesulfonic acid or terephthalic acid.

4. The paint stripper according to claim 1, characterized in that The corrosion inhibitor includes one or more of sodium benzoate, benzotriazole or methyl benzotriazole.

5. A method for removing paint from a polyurethane absorbing coating, characterized in that: include: The polyurethane absorbing coating product is subjected to paint stripping treatment in the paint stripper according to any one of claims 1 to 4.

6. The paint stripping method according to claim 5, characterized in that: The polyurethane absorbing coating product comprises a substrate and a polyurethane absorbing coating composited on the substrate; the polyurethane absorbing coating is formed by curing a compound represented by formula (1), a compound represented by formula (2) and a compound represented by formula (3):

7. The paint stripping method according to claim 6, characterized in that: The substrate of the polyurethane wave-absorbing coating product is an LY-12 aluminum substrate.

8. The paint stripping method according to claim 5, characterized in that: The paint stripping temperature is 13° C. to 33° C.; the paint stripping time is 10 min to 120 min.

9. The paint stripping method according to claim 5, characterized in that: The method also includes grinding and wiping the polyurethane absorbing coating parts after the paint is stripped.

10. The paint stripping method according to claim 9, characterized in that: The polishing includes polishing with sandpaper, wherein the mesh number of the sandpaper is 240 to 400; The wiping solvent includes acetone and / or butanol.

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