Method for improving binding force of surface coating of cementing piece

Abstract

The invention belongs to a surface treatment technology, and relates to a method for improving the binding force of a surface coating of a glued part. The method comprises the following steps: preparing a special cleaning solvent for the glued part before painting, wherein the cleaning solvent comprises the following components in volume ratio: 30-50 parts of ethylene glycol monoethyl ether, 15-20 parts of ethylene glycol monoethyl ether acetate, 25-40 parts of xylene and 10-15 parts of cyclohexanone; a release agent on the surface of the cementing piece and an organosilicon compound transferred by a 3M adhesive tape glue solution at a fixed position can be effectively removed, the binding force between the to-be-painted cementing piece and a coating is improved, and the defects of floating and the like of the appearance of a paint layer are avoided.

Description

Technical Field

[0001] The invention belongs to surface treatment technology and relates to a method for improving the bonding force of coating on the surface of an adhesive joint. Background Art

[0002] Helicopter metal or composite bonded parts are an important part of helicopter structures, including cabin floors, sliding doors, sliding fairings, tail boom barrels and other main load-bearing structures of helicopters. After the parts are formed, in order to improve the corrosion protection ability of the product, primer and topcoat need to be sprayed on the surface of the parts. The following problems exist in the spraying process:

[0003] During the molding process, parts need to be vacuumed and cured at high temperature. To facilitate demoulding, a release agent needs to be sprayed on the inner surface of the product molding mold. In order to achieve the anti-stick function, the main component of the release agent is an organic silicon compound. Such compounds have weak surface tension, small surface energy, and strong film-forming ability. The release agent is transferred to the part mold surface during the product molding process and cannot be completely removed by conventional surface cleaning methods, which affects the bonding strength between the part substrate and the coating, causing the parts to be reworked multiple times.

[0004] Before the parts are vacuumed, high-temperature resistant 3M tape is needed to be used to fix the parts that are prone to shifting during the vacuuming process. In addition, in order to prevent the glue in the glue filling holes from overflowing during the heating and pressurizing process, which increases the difficulty of subsequent part surface cleaning, high-temperature resistant 3M tape is needed to seal the glue filling holes. The high-temperature resistant 3M tape is put into the curing furnace with the parts for heating and pressurization. Although the 3M tape has high-temperature resistance, the glue on the bonding surface of the 3M tape will still transfer to the surface of the parts during the curing process. The high-temperature resistant 3M tape also contains silicone compounds, which cannot be completely removed by conventional surface cleaning methods, affecting the bonding strength between the part substrate and the coating, causing the parts to be sprayed and reworked many times. Summary of the invention

[0005] Purpose of the Invention

[0006] Based on the above problems, research work on process technology to improve the bonding strength of coatings on adhesive joints was carried out to solve the adverse effects of residual silicone compounds in release agents and high-temperature resistant tapes on the bonding strength between the substrate and the coating, and to increase the first-time inspection pass rate of adhesive joints, thereby ensuring the efficiency of scientific research and batch production and improving the coating quality and corrosion protection capabilities of adhesive joints.

[0007] Technical Solution

[0008] A method for improving the bonding strength of a coating on a surface of an adhesive joint, characterized in that it comprises the following steps:

[0009] Step 1 Preparation of cleaning solvent: The volume ratio of the cleaning solvent is as follows:

[0010] Ethylene glycol ether: 30-50, Ethylene glycol ether acetate: 15-20, Xylene: 25-40

[0011] , Cyclohexanone: 10-15;

[0012] Step 2 Solvent Usage:

[0013] 1) Cleaning

[0014] Use white cotton cloth dipped in cleaning solvent to wipe and clean the surface of the molded parts.

[0015] 2) Polishing

[0016] Use sandpaper or industrial scouring pad to lightly sand the surface to be painted;

[0017] 3) Cleaning

[0018] Use compressed air to blow away the grinding chips and wipe the surface of the polished parts with a white cotton cloth dipped in cleaning solvent.

[0019] 4) Apply chemical oxidizing liquid

[0020] When the bonded part is an aluminum alloy panel, use a chemical oxidizing liquid to brush the polished surface. After the film is formed on the aluminum alloy surface, use clean water to clean the surface to be painted, absorb the surface moisture with absorbent cotton, and then blow dry with compressed air.

[0021] 5) Paint

[0022] Spray the prepared paint on the surface of the joint according to the drawing requirements. After spraying a layer of paint crosswise, wait for 10-15 minutes, and then spray another layer of paint crosswise until the thickness reaches the specified thickness in the process documents.

[0023] Further, it also includes 6) curing

[0024] After the sprayed parts have been leveled at room temperature for at least 30 minutes, they should be dried at the specified temperature and for the specified time as required by the process documents.

[0025] Furthermore, it also includes 7) inspection

[0026] Carry out relevant tests according to the coating related process documents.

[0027] Furthermore, the inspection contents specifically include:

[0028] (4) Coating appearance

[0029] The coating appearance should be smooth, uniform and continuous, without defects such as sagging, orange peel, bubbling, cracks and blooming;

[0030] (5) The coating thickness meets the requirements of the corresponding process documents of the coating;

[0031] (6) Coating adhesion;

[0032] Furthermore, the cured coating is subjected to tape adhesion and wet adhesion tests, and the coating should not fall off or fall off at the adhesive tape attachment site.

[0033] Furthermore, the sandpaper in step 2 is specifically 180#-320#.

[0034] Furthermore, the 2) polishing specifically includes: polishing the composite material joint until the surface loses its gloss but does not hit the composite material fibers, and polishing the metal surface until the surface treatment layer is removed.

[0035] Furthermore, after the above 1) cleaning and 3) cleaning, the cleaning surface needs to be wiped with a clean white cotton cloth in time to prevent the special cleaning solvent from naturally volatilizing on the surface of the adhesive joint.

[0036] The beneficial effects of this application are:

[0037] By preparing a special cleaning solvent before painting the adhesive joints, the release agent on the surface of the adhesive joints and the silicone compounds transferred by the 3M tape adhesive at the fixed position can be effectively removed, thereby improving the bonding strength between the adhesive joints to be painted and the coating, and avoiding defects such as flowery appearance of the paint layer. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the implementation of the present invention clearer, the technical scheme in the embodiment of the present invention will be described in more detail in combination with the embodiment of the present invention. In the example, the same or similar reference numerals throughout represent the same or similar originals or elements with the same or similar functions. The described embodiments are part of the embodiments of the present invention, not all of them. The embodiments described below by reference are exemplary and intended to be used to explain the present invention, and should not be construed as limitations on the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present invention. The following is a detailed description in combination with the embodiments of the present invention.

[0039] The existing surface painting process of adhesive joints is as follows:

[0040] 1. Process flow

[0041] Cleaning - Sanding - Cleaning - Applying chemical oxidizing liquid (if necessary) - Painting -

[0042] —Curing —Repair (if necessary) —Inspection

[0043] 2. Description of main processes

[0044] 2.1 Cleaning

[0045] Use white cotton cloth dipped in ethanol, butanone and other organic solvents to wipe and clean the surface of the formed parts. And wipe and clean the surface with a clean white cotton cloth in time to prevent the organic solvent from volatilizing naturally on the surface of the bonded parts.

[0046] 2.2 Polishing

[0047] Use 180#-320# sandpaper or industrial scouring pad to lightly polish the painted surface. Polish the composite joints until the surface loses its gloss but do not hit the composite fibers. Polish the metal surface until the surface treatment layer is removed.

[0048] 2.3 Cleaning

[0049] Use compressed air to blow away the grinding debris, and wipe the surface of the polished parts with white cotton cloth dipped in organic solvents such as ethanol and butanone. And wipe the surface with a clean white cotton cloth in time to prevent the organic solvent from volatilizing naturally on the surface of the bonded parts.

[0050] 2.4 Brushing chemical oxidation liquid

[0051] When the bonded part is an aluminum alloy panel, you can use a chemical oxidizing liquid to brush the polished surface. After the film is formed on the aluminum alloy surface, use clean water to clean the surface to be painted, and use absorbent cotton to absorb the surface moisture and then blow it dry with compressed air.

[0052] 2.5 Painting

[0053] Spray the prepared paint on the surface of the joint according to the drawing requirements. After spraying a layer of paint crosswise, wait for 10-15 minutes, and then spray another layer of paint crosswise until the thickness specified in the process documents is reached.

[0054] 2.6 Curing

[0055] After the sprayed parts have been leveled at room temperature for at least 30 minutes, they should be dried at the specified temperature and for the specified time as required by the process documents.

[0056] 2.7 Rework

[0057] 2.7.1 Repair of uncured coating

[0058] When appearance defects such as flow and blooming occur, they can be repaired according to the following procedures:

[0059] a) Use a clean white cotton cloth dipped in paint thinner or organic solvent to wipe off the paint layer on the part to be repaired, and the repaired part can be appropriately enlarged;

[0060] b) Wipe dry with a clean white cotton cloth or blow dry with compressed air;

[0061] c) If the coating appearance defect is caused by substrate problems, it is necessary to eliminate the substrate problems and re-spray;

[0062] d) Use appropriate paint for repair, and apply it thinly and evenly.

[0063] e) Cure the coating as required.

[0064] 2.7.2 Repair of Cured Coating

[0065] a) Remove the unqualified coating by grinding. According to the principle of coarse grinding first and fine grinding later, first use 180 mesh to remove the coating that does not meet the appearance requirements, and then use 240 mesh or finer sandpaper (without silicone adhesion) to grind and clean the area to be repaired to expose a uniform and fresh paint layer, and make the repair edge have a feather-like smooth transition, but do not grind to the substrate; then use clean compressed air and white cotton cloth to wipe to remove the grinding residue, and wipe with organic solvent if necessary, and change the white cotton cloth to wipe until there is no visible pollution or discoloration on the white cotton cloth;

[0066] b) Pay attention to isolation protection, repaint according to the requirements of relevant documents, and cure as required.

[0067] 2.8 Inspection

[0068] According to the relevant tests of coating related process documents,

[0069] (7) Coating appearance

[0070] The coating appearance should be smooth, uniform and continuous, without defects such as sagging, orange peel, bubbling, cracks and blooming;

[0071] (8) The coating thickness meets the requirements of the corresponding process documents of the coating.

[0072] (9) Coating adhesion

[0073] After curing, the coating is subjected to tape adhesion and wet adhesion tests. There should be no peeling of the coating or peeling of the coating where the adhesive tape is applied.

[0074] 3. Comparative analysis of the present invention patent and the current situation

[0075] 3.1 The present invention uses ethylene glycol ethyl ether, ethylene glycol ethyl ether acetate, xylene and cyclohexanone as main components to prepare solvents in proportion, which replace the original organic solvents such as ethanol and butanone to clean the surface of the product to be painted, effectively remove the residual organic silicon compounds on the surface of the adhesive joint to be painted, ensure the cleanliness of the surface of the adhesive joint to be painted, and improve the bonding strength between the coating and the substrate.

[0076] 3.2 The existing surface cleaning of adhesive joints before painting has the following problems:

[0077] (1) Grinding is not effective in removing residual silicone compounds from the surface to be painted.

[0078] (2) Using organic solvents such as butanone and ethanol to wipe and remove the residual organosilicon compounds on the surface to be painted is not effective.

[0079] The method for improving the bonding strength of the coating on the adhesive surface comprises the following steps:

[0080] 1. Preparation of cleaning solvent

[0081] In order to solve the problem that the residual organic silicon compounds on the surface of the adhesive joints after molding affect the bonding strength of the subsequent coating, a special cleaning agent preparation study was carried out. By searching for relevant information and conducting cleaning tests, the effects of the following organic solvents on removing organic silicon compounds were compared while other operating procedures remained unchanged.

[0082] Table 1 Comparison of solvent cleaning effects

[0083]

[0084] According to the above coating appearance and bonding strength test results, it was determined that ethylene glycol ethyl ether, ethylene glycol ethyl ether acetate, xylene, and cyclohexanone were used to prepare cleaning solvents to remove organic silicon compound residues and improve the bonding strength of the adhesive coating. By adjusting the proportion of each solvent, the effects of cleaning agents with different preparation ratios on removing organic silicon compounds were compared while other operating procedures remained unchanged.

[0085] Table 2 Comparison of cleaning effects of different ratios

[0086]

[0087]

[0088] Based on the above cleaning results of different solvent ratios, the proportion of cleaning solvent (volume ratio) is determined as follows:

[0089] Ethylene glycol ether: 30-50

[0090] Ethylene glycol ether acetate: 15-20

[0091] Xylene: 25-40

[0092] Cyclohexanone: 10-15

[0093] 2. How to use the solvent

[0094] 2.1 Cleaning

[0095] Use white cotton cloth dipped in special cleaning agent to wipe and clean the surface of the formed parts. And wipe and clean the surface with clean white cotton cloth in time to prevent the special cleaning agent from volatilizing naturally on the surface of the bonded parts.

[0096] 2.2 Polishing

[0097] Use 180#-320# sandpaper or industrial scouring pad to lightly polish the painted surface. Polish the composite joints until the surface loses its gloss but do not hit the composite fibers. Polish the metal surface until the surface treatment layer is removed.

[0098] 2.3 Cleaning

[0099] Use compressed air to blow away the grinding debris, and wipe the surface of the polished parts with a white cotton cloth dipped in a special cleaning agent. And wipe the surface with a clean white cotton cloth in time to prevent the special cleaning agent from evaporating naturally on the surface of the adhesive joint.

[0100] 2.4 Brushing chemical oxidation liquid

[0101] When the bonded part is an aluminum alloy panel, you can use a chemical oxidizing liquid to brush the polished surface. After the film is formed on the aluminum alloy surface, use clean water to clean the surface to be painted, and use absorbent cotton to absorb the surface moisture and then blow it dry with compressed air.

[0102] 2.5 Painting

[0103] Spray the prepared paint on the surface of the joint according to the drawing requirements. After spraying a layer of paint crosswise, wait for 10-15 minutes, and then spray another layer of paint crosswise until the thickness specified in the process documents is reached.

[0104] 2.6 Curing

[0105] After the sprayed parts have been leveled at room temperature for at least 30 minutes, they should be dried at the specified temperature and for the specified time as required by the process documents.

[0106] 2.7 Inspection

[0107] According to the relevant tests of coating related process documents,

[0108] (10) Coating appearance

[0109] The coating appearance should be smooth, uniform and continuous, without defects such as sagging, orange peel, bubbling, cracks and blooming;

[0110] (11) The coating thickness meets the requirements of the corresponding process documents of the coating.

[0111] (12) Coating adhesion

[0112] After curing, the coating is subjected to tape adhesion and wet adhesion tests. There should be no peeling of the coating or peeling of the coating where the adhesive tape is applied.

[0113] Embodiment 1:

[0114] Surface painting of helicopter metal floor joints

[0115] (1) Use white cotton cloth dipped in a special cleaning agent to clean the surface of the metal floor joints as a whole, and wipe the surface with a clean white cotton cloth in time to prevent the special cleaning agent from evaporating naturally on the surface of the joints.

[0116] (2) Use masking film, isolation tape, etc. to protect the areas on the surface of the floor joints that do not need to be painted.

[0117] (3) Use 320# sandpaper to gently sand the isolated floor joint surface to remove the surface release agent, particles and 3M tape transfer glue.

[0118] (4) Use a white cotton cloth dipped in a special cleaning agent to wipe the polished surface, and use another clean white cotton cloth to wipe the surface of the part before the special cleaning agent dries to prevent the special cleaning agent from evaporating naturally on the surface of the part.

[0119] (5) Spray H06-27 primer according to the part drawing requirements. The coating has no oil defects and the bonding strength reaches level 0.

[0120] Embodiment 2:

[0121] Transport aircraft fuel tank glued wall panel painting process

[0122] (1) Use white cotton cloth dipped in a special cleaning agent to clean the surface of the tank wall panel joint as a whole, and wipe the surface with a clean white cotton cloth in time to prevent the special cleaning agent from evaporating naturally on the surface of the joint.

[0123] (2) Use masking film, isolation tape, etc. to protect the areas on the surface of the floor joints that do not need to be painted.

[0124] (3) Use 320# sandpaper to gently sand the isolated floor joint surface to remove the surface release agent, particles and 3M tape transfer glue.

[0125] (4) Use a white cotton cloth dipped in a special cleaning agent to wipe the polished surface, and use another clean white cotton cloth to wipe the surface of the part before the special cleaning agent dries to prevent the special cleaning agent from evaporating naturally on the surface of the part.

[0126] (5) Spray S06-0215 ​​primer according to the part drawing requirements. The coating has no oil defects and the bonding strength reaches level 1.

[0127] It is understood by those skilled in the art that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of ordinary technicians in the field to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and unless defined as here, will not be interpreted with idealized or overly formal meanings. The specific implementation methods described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Within the spirit and principle of the present invention, any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment of equivalent changes for application in other fields, but any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the technical solution content of the present invention, any modification, equivalent replacement, improvement, etc., made according to the technical essence of the present invention, should be included in the protection scope of the present invention.

Claims

1. A method for improving the bonding strength of a coating on a surface of an adhesive joint, characterized in that: The following steps are involved: Step 1: Preparation of cleaning solvent: The volume ratio of the cleaning solvent is as follows: ethylene glycol ethyl ether: 30-50, ethylene glycol ethyl ether acetate: 15-20, xylene: 25-40, cyclohexanone: 10-15; Step 2 Solvent Usage: 1) Cleaning Use white cotton cloth dipped in cleaning solvent to wipe and clean the surface of the molded parts; 2) Polishing Use sandpaper or industrial scouring pad to lightly sand the surface to be painted; 3) Cleaning Use compressed air to blow away the grinding debris, and wipe and clean the surface of the polished parts with a white cotton cloth dipped in a cleaning solvent; 4) Apply chemical oxidizing liquid When the adhesive joint is an aluminum alloy panel, use chemical oxidizing liquid to brush the polished surface. After the aluminum alloy surface is film-formed, use clean water to clean the painted surface, absorb the surface moisture with absorbent cotton, and then blow it dry with compressed air; 5) Paint Spray the prepared paint on the surface of the joint according to the drawing requirements. After spraying a layer of paint crosswise, wait for 10-15 minutes, and then spray another layer of paint crosswise until the thickness reaches the specified thickness in the process documents.

2. The method according to claim 1, characterized in that Also includes 6) curing After the sprayed parts have been leveled at room temperature for at least 30 minutes, they should be dried at the specified temperature and for the specified time as required by the process documents.

3. The method according to claim 2, characterized in that Also includes 7) inspection Carry out relevant tests according to the coating process documents.

4. The method according to claim 3, characterized in that The inspection contents include: (1) Coating appearance The coating appearance should be smooth, uniform and continuous, without sagging, orange peel, bubbling, cracks and blooming defects; (2) The coating thickness meets the requirements of the corresponding process documents of the coating; (3) Coating adhesion.

5. The method according to claim 4, characterized in that After curing, the coating is subjected to tape adhesion and wet adhesion tests. There should be no peeling of the coating or peeling of the coating where the adhesive tape is applied.

6. The method according to claim 5, characterized in that The sandpaper in step 2 is specifically 180#-320#.

7. The method according to claim 6, characterized in that The 2) grinding specifically includes: grinding the composite material joint until the surface loses its gloss but the composite material fibers are not hit, and grinding the metal surface until the surface treatment layer is removed.

8. The method according to claim 7, characterized in that After the above 1) cleaning and 3) cleaning, the cleaning surface needs to be wiped with a clean white cotton cloth in time to prevent the cleaning solvent from volatilizing naturally on the surface of the adhesive joint.

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