Mass-production four-coating two-baking finish paint spraying method and finish paint

Abstract

The invention provides a four-coating two-baking finish paint spraying method capable of realizing mass production and finish paint, belongs to the technical field of vehicle body spraying, and aims to solve the problem that a whole vehicle needs to be polished in a multi-layer varnish finish paint technological process, and the method comprises the following steps: sequentially spraying a water-based floating coat and colored paint on a vehicle body subjected to electrophoresis treatment, and carrying out flash drying treatment; single-component varnish or double-component varnish is sprayed to the automobile body, and drying treatment is carried out; thirdly, the defect point positions on the vehicle body are polished, the two-component varnish is sprayed, drying treatment is conducted again, and the vehicle body coated with the finish paint for four times and dried for two times is obtained; the single-component varnish is prepared from the following components in parts by weight: 35 to 45 parts of acrylic resin, 13 to 18 parts of first amino resin, 18 to 23 parts of anti-sagging resin, 5 to 8 parts of polyester resin, 1.5 to 2 parts of auxiliaries and 15 to 18 parts of solvent. The two-component varnish comprises a main agent and a curing agent; the main agent comprises 35-47 parts of acrylic resin, 14-24 parts of second amino resin, 16-25 parts of anti-sagging resin, 0.8-1.3 parts of an auxiliary agent and 15-38 parts of a solvent; the curing agent comprises a polyisocyanate curing agent.

Description

Technical Field

[0001] The invention relates to the technical field of vehicle body spraying, and in particular to a mass-producible four-coat and two-bake topcoat spraying method and topcoat. Background Art

[0002] At present, in order to ensure the quality of automobile paint, a multi-layer varnish topcoat process is often used to spray the automobile body.

[0003] However, the multi-layer clearcoat and topcoat process often requires the entire vehicle to be polished and refined, resulting in low efficiency of the entire process and failure to meet the needs of mass production of vehicles. Summary of the invention

[0004] In view of this, the present invention proposes a mass-producible four-coat and two-bake topcoat spraying method to solve the problem of needing to polish the entire vehicle during the multi-layer clear varnish topcoat process.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] In a first aspect, the present invention provides a mass-producible four-coat and two-bake topcoat spraying method, the method comprising:

[0007] Step S1, spraying a water-based intermediate coating and a color paint on the electrophoresis treated vehicle body in sequence to form a water-based intermediate coating layer and a color paint layer, and then performing a flash drying treatment;

[0008] Step S2, after the flash-drying treatment is completed, spraying a single-component varnish or a two-component varnish on the vehicle body to form a first varnish layer, and performing a drying treatment;

[0009] Step S3, after the drying process is completed, the defective points on the vehicle body are polished, the two-component varnish is sprayed to form a second varnish layer, and the drying process is performed again to obtain a four-coat and two-bake topcoat vehicle body;

[0010] Wherein, the one-component varnish comprises, by weight, 35 to 45 parts of acrylic resin, 13 to 18 parts of a first amino resin, 18 to 23 parts of an anti-sagging resin, 5 to 8 parts of a polyester resin, 1.5 to 2 parts of an auxiliary agent and 15 to 18 parts of a solvent;

[0011] The two-component varnish includes a main agent and a curing agent, wherein the main agent includes: 35 to 47 parts of the acrylic resin, 14 to 24 parts of the second amino resin, 16 to 25 parts of the anti-sagging resin, 0.8 to 1.3 parts of the auxiliary agent and 15 to 38 parts of the solvent; the curing agent includes a polyisocyanate curing agent.

[0012] Optionally, in the step S2, the main agent in the two-component varnish sprayed includes, by weight, 35 to 45 parts of the acrylic resin, 14 to 18 parts of the second amino resin, 16 to 23 parts of the anti-sagging resin, 0.8 to 1.2 parts of the auxiliary agent and 28 to 28 parts of the solvent;

[0013] In step S3, the main agent of the two-component varnish sprayed includes, by weight, 39 to 47 parts of the acrylic resin, 18 to 24 parts of the second amino resin, 19 to 25 parts of the anti-sagging resin, 1 to 1.3 parts of the auxiliary agent and 15 to 25 parts of the solvent.

[0014] Optionally, in step S2, the main agent and the curing agent are mixed according to a first preset ratio, and the first preset ratio is 3.5:1 to 4:1;

[0015] In the step S3, the main agent and the curing agent are mixed according to a second preset ratio, and the second preset ratio is 3:1 to 3.5:1.

[0016] Optionally, the acrylic resin includes one or a mixture of multiple types in any proportion of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, hexyl (meth)acrylate and lauryl methacrylate.

[0017] Optionally, the first amino resin includes one of butylated melamine resin, mixed etherified melamine resin, methylated melamine resin, and methylated hexamethylol melamine resin, or a mixture of multiple thereof in any proportion;

[0018] The second amino resin includes one of methyl etherified melamine resin and methyl etherified hexamethylol melamine resin or a mixture of two or more of them in any proportion.

[0019] Optionally, the anti-sagging resin includes one of modified acrylic resin and polyamide wax slurry or a mixture of multiple thereof in any proportion.

[0020] Optionally, the auxiliary agent includes one of a leveling agent, a defoaming agent and a drying agent, or a plurality of the above-mentioned agents mixed in any proportion;

[0021] Among them, the leveling agent includes one of modified silicone, epoxy-modified polyacrylate and modified organic polysiloxane polyisocyanate or a combination of multiple thereof in any proportion; the defoaming agent includes one of polyamide hydrophobic particle polymer and propylene glycol methyl ether acetate or a combination of multiple thereof in any proportion; the drying agent includes one of dibutyltin dilaurate and p-toluenesulfonic acid amino salt solution or a combination of multiple thereof in any proportion.

[0022] Optionally, the solvent includes one of ethyl acetate, solvent oil, ethylene glycol butyl ether acetate, diethylene glycol butyl ether, dimethyl carbonate, isopropyl alcohol and diethyl carbonate, or a mixture of multiple thereof in any proportion.

[0023] Optionally, the flash drying treatment comprises: flash drying the vehicle body at 75 to 80° C. for 4 to 6 minutes;

[0024] The drying process comprises: baking at 130-150° C. for 20-30 minutes.

[0025] Optionally, in step S1, the water-based intermediate coating is sprayed to a thickness of 9 to 15 μm, and the color paint is sprayed to a thickness of 10 to 15 μm;

[0026] In the step S2, the thickness of spraying the one-component varnish or the two-component varnish is 25 to 35 μm;

[0027] In the step S3, the thickness of the two-component varnish sprayed is 35-50 μm.

[0028] Optionally, the thickness of the water-based mid-coat layer is 9-15 μm; the thickness of the color paint layer is 10-15 μm; the thickness of the first clear varnish layer is 25-35 μm; and the thickness of the second clear varnish layer is 45-60 μm.

[0029] In a second aspect, the present invention provides a topcoat comprising:

[0030] The water-based intermediate coating, the color paint layer, the first clear varnish layer and the second clear varnish layer are sequentially stacked on the surface of the vehicle body; wherein,

[0031] Counted in parts by weight, the first varnish layer is formed by spraying a single-component varnish or a two-component varnish, and the second varnish layer is formed by spraying a two-component varnish;

[0032] The one-component varnish comprises: 35 to 45 parts of acrylic resin, 13 to 18 parts of a first amino resin, 18 to 23 parts of an anti-sagging resin, 5 to 8 parts of a polyester resin, 1.5 to 2 parts of an auxiliary agent and 15 to 18 parts of a solvent;

[0033] The two-component varnish comprises a main agent and a curing agent, wherein the main agent comprises: 35 to 47 parts of the acrylic resin, 14 to 24 parts of the second amino resin, 16 to 25 parts of the anti-sagging resin, 0.8 to 1.3 parts of the auxiliary agent and 15 to 38 parts of the solvent; the curing agent comprises a polyisocyanate curing agent.

[0034] The present invention has the following advantages over the prior art:

[0035] The present invention proposes a special one-component varnish and a two-component varnish. By reducing the weight percentage of the additives in the one-component varnish and the two-component varnish, the surface roughness of the paint film formed after the one-component varnish or the two-component varnish is greatly improved, which is conducive to the formation of physical forces between the paint layers in the form of hydrogen bonds or mechanical riveting, and enhances the adhesion between the paint layers. Therefore, after the first drying treatment is completed, there is no need to polish the entire vehicle, and only the defective points on the vehicle body need to be polished; at the same time, the present invention also reduces the weight percentage of the first amino resin in the one-component varnish and reduces the weight percentage of the second amino resin in the two-component varnish. In this way, after the one-component varnish or the two-component varnish is sprayed, the crosslinking density can be reduced, leaving more active sites, so that when the vehicle body is subjected to the second drying treatment in step S3, a chemical reaction can further occur, greatly improving the adhesion between the paint layers, so that there is no need to polish the vehicle body, and a four-coat and two-bake topcoat vehicle body can be obtained. Therefore, the present invention reduces the polishing of the vehicle body during the entire spraying process, and even does not require polishing after the second drying treatment, which greatly saves the process beat, improves production efficiency, and meets the mass production needs of vehicles; secondly, since the present invention reduces the polishing of the vehicle body, it can avoid problems such as many paint particles and easy shrinkage defects after polishing; in addition, the present invention adopts a four-coat and two-bake topcoat process to improve the overall sensory feel, flatness, brightness, fullness, etc. of the paint surface, greatly improves the appearance of the paint surface, and surpasses the paint surface quality level of the traditional 3C2B (three-coat and two-bake) process. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0037] Figure 1 This is a flow chart of the steps of a mass-producible four-coat and two-bake topcoat spraying method shown in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of a four-coat, two-bake topcoat vehicle body shown in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the preferred embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that the following examples are provided only for the purpose of illustration and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0040] In the related art, the 3C2B (three coatings and two baking) process is often used to spray the vehicle body. In this process, after the first varnish spraying and baking, the varnish paint surface of the whole vehicle must be polished to solve the problem of interlayer adhesion. The whole process is inefficient and has high labor costs. After the varnish is sprayed and baked again, the paint film is prone to defects such as particles and shrinkage holes, and the whole vehicle still needs to be polished. In other words, after each baking, the body needs to be polished, which makes the entire spraying process time-consuming, and the beat cannot meet the mass production requirements of more than 30 vehicles per hour, and is only suitable for prototype trial production. In addition, after the body is polished, defects such as particles and shrinkage holes are prone to occur on the paint surface, affecting the quality of the paint surface.

[0041] In view of this, the embodiment of the present invention proposes a mass-producible four-coat and two-bake topcoat spraying method and topcoat, which improves the adhesion between paint layers and reduces or even eliminates the need for polishing the vehicle body, thereby saving process beats, improving production efficiency, and meeting the mass production needs of vehicles. The specific implementation contents are as follows:

[0042] In a first aspect, the present invention provides a four-coat and two-bake topcoat spraying method, Figure 1 FIG. 1 shows a flow chart of the steps of a mass-producible four-coat and two-bake topcoat spraying method according to an embodiment of the present invention, as shown in FIG. Figure 1 As shown, the method comprises the following steps:

[0043] Step S1, spraying a water-based intermediate coating and a color paint on the electrophoresis treated vehicle body in sequence to form a water-based intermediate coating layer and a color paint layer, and then performing a flash drying treatment;

[0044] Step S2, after the flash-drying treatment is completed, spraying a single-component varnish or a two-component varnish on the vehicle body to form a first varnish layer, and performing a drying treatment;

[0045] Step S3, after the drying process is completed, the defective points on the vehicle body are polished, the two-component varnish is sprayed to form a second varnish layer, and the drying process is performed again to obtain a four-coat and two-bake topcoat vehicle body;

[0046] Wherein, the one-component varnish comprises, by weight, 35 to 45 parts of acrylic resin, 13 to 18 parts of a first amino resin, 18 to 23 parts of an anti-sagging resin, 5 to 8 parts of a polyester resin, 1.5 to 2 parts of an auxiliary agent and 15 to 18 parts of a solvent;

[0047] The two-component varnish includes a main agent and a curing agent, wherein the main agent includes: 35 to 47 parts of the acrylic resin, 14 to 24 parts of the second amino resin, 16 to 25 parts of the anti-sagging resin, 0.8 to 1.3 parts of the auxiliary agent and 15 to 38 parts of the solvent; the curing agent includes a polyisocyanate curing agent.

[0048] In the embodiment of the present invention, a four-coat and two-bake topcoat process is used to spray the vehicle body. First, the vehicle body is subjected to electrophoresis treatment to obtain an electrophoresis vehicle body, and then a water-based intermediate coating and a color paint are sprayed on the electrophoresis vehicle body in sequence. The color paint can be a color paint of any color. After the color paint is sprayed, the vehicle body is flash-dried. Specifically, the vehicle is moved into a flash-drying oven for leveling and dehydration.

[0049] After the flash-drying treatment is completed, the vehicle body can be coated with a single-component varnish, which can be used directly after dilution, and the required drying time is short, which can improve production efficiency. In an embodiment of the present invention, in order to further shorten the process cycle and improve production efficiency, the composition of the single-component varnish includes: 35 to 45 parts of acrylic resin, 13 to 18 parts of the first amino resin, 18 to 23 parts of anti-sagging resin, 5 to 8 parts of polyester resin, 1.5 to 2 parts of additives and 15 to 18 parts of solvent.

[0050] The auxiliary agent includes one or more of leveling agent, defoamer and drying agent in any proportion. Leveling agent is used to reduce the surface tension between the single-component varnish and the vehicle body, so that the single-component varnish and the vehicle body have good wettability and do not form a surface tension gradient between the substances that cause shrinkage cavities; on the other hand, it is used to adjust the solvent evaporation rate, reduce viscosity, improve the fluidity of the single-component varnish, prolong the leveling time, and make the formed paint film more glossy; defoamer has a spontaneous defoaming effect, can prevent microbubbles, and can effectively improve the paint film surface without bubbling; drying agent can shorten the coating curing film forming time, increase the coating film strength and water resistance, and is also beneficial to the wetting and dispersion of pigments, and improves the viscoelasticity of the coating.

[0051] In the embodiment of the present invention, 1.5 to 2 parts of additives are used. In this way, the amount of additives, especially the amount of leveling agent, can be reduced, which can improve the surface roughness of the formed paint film, facilitate the formation of physical forces between layers in the form of hydrogen bonds or mechanical riveting, and enhance the adhesion between paint layers.

[0052] Therefore, after the basecoat of the single-component clearcoat is dried, there is no need to polish the entire vehicle, only the defective points on the vehicle body need to be polished. The drying process may include: moving the vehicle into a topcoat drying oven for leveling and curing. 2000-grit sandpaper may be used to polish the defective points on the vehicle body.

[0053] After polishing the defective points on the car body, two-component varnish can be applied on the surface. The composition of the two-component varnish includes a main agent and a curing agent. The main agent includes: 35-47 parts of acrylic resin, 14-24 parts of second amino resin, 16-25 parts of anti-sagging resin, 0.8-1.3 parts of auxiliary agent and 15-38 parts of solvent; the curing agent includes a polyisocyanate curing agent. Among them, the curing agent can accelerate the film-forming speed of the main agent and improve production efficiency.

[0054] In one example, the polyisocyanate curing agent may include aliphatic polyisocyanates and alicyclic polyisocyanates. Such curing agents do not contain aromatic groups, will not produce benzene ring conjugated quinone chromophores, will not produce yellowing, and are beneficial to the color stability of the paint film.

[0055] The aliphatic polyisocyanate includes one of hexamethylene diisocyanate and 2,2,4-trimethylhexane diisocyanate or a plurality of them mixed in any proportion; the alicyclic isocyanate includes one of dicyclohexylmethylene diisocyanate and isophorone diisocyanate or a plurality of them mixed in any proportion.

[0056] After spraying the above-mentioned two-component varnish, the formed paint film has excellent hardness, flexibility and fullness, which greatly improves the quality of the car body paint.

[0057] In addition, in the embodiment of the present invention, 0.8 to 1.3 parts of additives are used. In this way, reducing the amount of additives, especially reducing the amount of leveling agent, can improve the surface roughness of the formed paint film, which is conducive to the formation of physical forces between layers in the form of hydrogen bonds or mechanical riveting, thereby enhancing the adhesion between paint layers.

[0058] Next, the car body is dried. Since the weight proportion of the first amino resin in the one-component varnish is relatively small, 13 to 18 parts, the cross-linking density is relatively low when the addition polymerization reaction occurs during spraying in step S2, leaving more active sites, so that in step S3, when the car body is dried for the second time, a chemical reaction can further occur, further improving the adhesion between the paint layers.

[0059] Therefore, after the drying process is completed, the vehicle can be obtained without polishing. Figure 2 Four-coat, two-bake finish body shown.

[0060] In another example, after step S1 is completed, that is, after the flash-drying treatment is completed, a two-component varnish may be applied to the bottom of the vehicle body. The two-component varnish may make the formed paint film have excellent hardness, flexibility and fullness. In addition, in the embodiment of the present invention, 0.8 to 1.3 parts of additives are used. In this way, the amount of additives, especially the amount of leveling agent, is reduced, and the surface roughness of the formed paint film can be improved, which is conducive to the formation of physical forces between layers in the form of hydrogen bonds or mechanical riveting, and enhances the adhesion between paint layers.

[0061] Therefore, after applying the two-component varnish and drying the car body, there is no need to polish the entire car, only the defective points on the car body need to be polished.

[0062] After polishing the defective points on the car body, a two-component varnish is applied to the top layer, so that the formed paint film has excellent hardness, flexibility and fullness, greatly improving the quality of the car body paint.

[0063] In addition, in an embodiment of the present invention, the two-component varnish includes only 0.8 to 1.3 parts of additives. In this way, reducing the amount of additives, especially reducing the amount of leveling agent, can improve the surface roughness of the formed paint film, which is beneficial to the formation of physical forces between layers in the form of hydrogen bonds or mechanical riveting, thereby enhancing the adhesion between paint layers.

[0064] Next, the car body is dried. Since the weight proportion of the second amino resin in the two-component varnish is relatively small, 14 to 24 parts, the cross-linking density is relatively low when the addition polymerization reaction occurs during spraying in step S2, leaving more active sites, so that in step S3, when the car body is dried for the second time, a chemical reaction can further occur, further improving the adhesion between the paint layers.

[0065] Therefore, after the drying process is completed, there is no need to polish the entire vehicle, and a four-coat and two-bake topcoat body can be obtained.

[0066] Therefore, the embodiment of the present invention adopts a five-coat and two-bake topcoat process, which greatly improves the overall feel, flatness, brightness, and fullness of the paint surface. At the same time, a single-component varnish or a two-component varnish is used in the primer, and a two-component varnish is used in the topcoat. By reducing the weight of the additives in the single-component varnish and the two-component varnish, the surface roughness of the paint film formed after the primer is applied with the single-component varnish or the two-component varnish is greatly improved, which is conducive to the formation of physical forces between the paint layers in the form of hydrogen bonds or mechanical riveting, and enhances the adhesion between the paint layers. Therefore, after the first drying treatment is completed, there is no The whole vehicle needs to be polished, and only the defective points on the vehicle body need to be polished; at the same time, the embodiment of the present invention also reduces the weight percentage of the first amino resin in the single-component varnish, and reduces the weight percentage of the second amino resin in the two-component varnish. In this way, after spraying the single-component varnish or the two-component varnish, the cross-linking density can be reduced, leaving more active sites, so that when the vehicle body is dried for the second time in step S3, a chemical reaction can further occur, greatly improving the adhesion between the paint layers, so that there is no need to polish the vehicle body, and a four-coat and two-bake topcoat vehicle body can be obtained.

[0067] Therefore, the embodiment of the present invention reduces the polishing of the vehicle body during the entire spraying process, and even does not require polishing after the second drying treatment, which greatly saves the process flow, improves production efficiency, and meets the mass production needs of vehicles. At the same time, since the embodiment of the present invention reduces the polishing of the vehicle body, it can avoid problems such as a large number of paint particles after polishing and the occurrence of shrinkage defects.

[0068] In an optional embodiment, in the step S2, the main agent in the two-component varnish sprayed includes, by weight, 35 to 45 parts of the acrylic resin, 14 to 18 parts of the second amino resin, 16 to 23 parts of the anti-sagging resin, 0.8 to 1.2 parts of the auxiliary agent and 28 to 28 parts of the solvent;

[0069] In step S3, the main agent of the two-component varnish sprayed includes, by weight, 39 to 47 parts of the acrylic resin, 18 to 24 parts of the second amino resin, 19 to 25 parts of the anti-sagging resin, 1 to 1.3 parts of the auxiliary agent and 15 to 25 parts of the solvent.

[0070] In an embodiment of the present invention, the main agent in the two-component varnish used in the primer is different from the main agent composition in the two-component varnish used in the top coating. Specifically, in step S2, the main agent in the two-component varnish used in the primer includes: 35 to 45 parts of acrylic resin, 14 to 18 parts of the second amino resin, 16 to 23 parts of anti-sagging resin, 0.8 to 1.2 parts of auxiliary agents and 28 to 28 parts of solvents; in step S3, the main agent in the two-component varnish used in the top coating includes: 39 to 47 parts of acrylic resin, 18 to 24 parts of the second amino resin, 19 to 25 parts of anti-sagging resin, 1 to 1.3 parts of auxiliary agents and 15 to 25 parts of solvents.

[0071] In this way, when performing the primer coating, a two-component varnish with a lower second amino resin content is used, so that when the primer two-component varnish undergoes addition polymerization reaction, the crosslinking density is reduced, leaving more active sites, so that in step S3, when the car body is subjected to a second drying treatment, a chemical reaction can further occur, thereby improving the adhesion between the paint layers.

[0072] When applying the topcoat, a two-component varnish with a slightly higher content of the second amino resin is used to ensure the cross-linking density of the final paint film and improve the gloss of the paint film.

[0073] In addition, when applying the primer, a two-component varnish with a lower additive content is used to reduce the amount of additives, especially the amount of leveling agent, to improve the surface roughness of the paint film formed, which is conducive to the formation of physical forces between layers in the form of hydrogen bonds or mechanical riveting, thereby enhancing the adhesion between paint layers.

[0074] When applying the topcoat, a two-component varnish with a slightly higher additive content is used to ensure the strength and appearance quality of the final paint film.

[0075] Therefore, the embodiment of the present invention further optimizes the main agent components of the base coating two-component varnish and the top coating two-component varnish, while improving the adhesion between paint layers and ensuring the quality of the vehicle body paint surface.

[0076] In an optional embodiment, in the step S2, the main agent and the curing agent are mixed according to a first preset ratio, and the first preset ratio is 3.5:1 to 4:1;

[0077] In the step S3, the main agent and the curing agent are mixed according to a second preset ratio, and the second preset ratio is 3:1 to 3.5:1.

[0078] In an embodiment of the present invention, in step S2, the main agent and the curing agent in the two-component varnish used for the primer are mixed according to a first preset ratio, and the first preset ratio is 3.5:1 to 4:1. In this way, the amount of curing agent used is reduced, so that after the addition polymerization reaction, the acrylic resin in the main agent can leave a large number of unreacted active groups, and these active groups can combine with the active groups in the two-component varnish sprayed in step S3 to form chemical bonds, thereby greatly enhancing the interlayer adhesion. Therefore, it is ensured that after the second drying treatment is completed, there is no need to polish the entire vehicle, avoiding polishing operations, reducing the process flow rhythm, and meeting the mass production needs of vehicles.

[0079] In step S3, the main agent and the curing agent in the two-component varnish used for the top coating are mixed according to a second preset ratio, which is 3:1 to 3.5:1. In this way, the main agent in the two-component varnish is ensured to react completely and form a film quickly, thereby ensuring the quality of the top coating.

[0080] In an optional embodiment, the acrylic resin includes one or a mixture of multiple thereof in any proportion among methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, hexyl (meth)acrylate and lauryl methacrylate.

[0081] In the embodiments of the present invention, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, hexyl (meth)acrylate and lauryl methacrylate are all thermosetting resins. The above thermosetting resins have good gloss and color retention, water resistance and chemical resistance, so that the formed paint film has excellent fullness, gloss, hardness, solvent resistance, weather resistance, and does not change color or turn yellow when baked at high temperature.

[0082] In an optional embodiment, the first amino resin includes one or a mixture of any of butylated melamine resin, mixed etherified melamine resin, methylated melamine resin, and methylated hexamethylol melamine resin;

[0083] The second amino resin includes one of methyl etherified melamine resin and methyl etherified hexamethylol melamine resin or a mixture of two or more of them in any proportion.

[0084] In the embodiment of the present invention, the use of the first amino resin and the second amino resin can make the formed paint film have excellent gloss.

[0085] In an optional embodiment, the anti-sagging resin includes one of modified acrylic resin and polyamide wax slurry or a mixture of multiple thereof in any proportion.

[0086] In the embodiments of the present invention, the anti-sagging resin can be used to significantly improve the anti-sagging performance, high gloss and dust-proof effect of the paint film.

[0087] In an optional embodiment, the auxiliary agent includes one or a plurality of the following selected from the group consisting of a leveling agent, a defoaming agent and a drying agent in any proportion;

[0088] Among them, the leveling agent includes one of modified silicone, epoxy-modified polyacrylate and modified organic polysiloxane polyisocyanate or a combination of multiple thereof in any proportion; the defoaming agent includes one of polyamide hydrophobic particle polymer and propylene glycol methyl ether acetate or a combination of multiple thereof in any proportion; the drying agent includes one of dibutyltin dilaurate and p-toluenesulfonic acid amino salt solution or a combination of multiple thereof in any proportion.

[0089] In an optional embodiment, the solvent includes one or a mixture of multiple of ethyl acetate, solvent oil, ethylene glycol butyl ether acetate, diethylene glycol butyl ether, dimethyl carbonate, isopropyl alcohol and diethyl carbonate in any proportion.

[0090] In the embodiment of the present invention, the use of the above solvent is not only green and environmentally friendly, but also can significantly improve the deep surface quality and create a good product construction environment.

[0091] In an optional embodiment, the polyester resin includes one or a mixture of multiple types selected from the group consisting of oil-free alkyd resin, modified polyester resin and saturated polyester in any proportion.

[0092] In the embodiments of the present invention, the use of the above-mentioned polyester resin can significantly improve the physical and mechanical properties of the paint film, especially toughness, wear resistance, impact resistance and scratch resistance, while also enhancing the gloss retention and color retention, and weather resistance of the paint film, without loss of gloss or yellowing after long-term exposure to sunlight.

[0093] In an optional implementation, in the step S3, after the defective points on the vehicle body are polished, the vehicle body is cleaned with alcohol or isopropyl alcohol.

[0094] After polishing the defective points on the car body, you can use alcohol or isopropyl alcohol to wipe the car body clean. This will not only wipe off the dust, foreign matter, etc. on the car body, but also keep the car body dry.

[0095] In an optional embodiment, the flash drying treatment comprises: flash drying the vehicle body at 75 to 80° C. for 4 to 6 minutes;

[0096] The drying process comprises: baking at 130-150° C. for 20-30 minutes.

[0097] In an embodiment of the present invention, the flash-drying treatment can achieve excellent leveling and dehydration of the sprayed water-based intermediate coating and color paint, thereby improving the spraying quality; the two drying treatments can achieve excellent leveling and curing of the sprayed single-component varnish or two-component varnish, thereby further improving the spraying quality.

[0098] In an optional embodiment, in the step S1, the thickness of the water-based intermediate coating sprayed is 9 to 15 μm, and the thickness of the color paint sprayed is 10 to 15 μm;

[0099] In the step S2, the thickness of spraying the one-component varnish or the two-component varnish is 25 to 35 μm;

[0100] In the step S3, the thickness of the two-component varnish sprayed is 35-50 μm.

[0101] In an embodiment of the present invention, the thickness of the water-based mid-coat is set to 9-15 μm, the thickness of the color paint is set to 10-15 μm, the thickness of the primer single-component varnish or two-component varnish is set to 25-35 μm, and the thickness of the top-coat two-component varnish is set to 35-50 μm, so as to ensure the best effect of car body orange peel at the lowest cost.

[0102] Based on the common knowledge in this field, the above-mentioned preferred conditions can be combined with each other to obtain a specific implementation method.

[0103] In a second aspect, the present invention provides a topcoat obtained by the mass-producible four-coat and two-bake topcoat spraying method provided in the first aspect above, Figure 2 A schematic diagram of a four-coat and two-bake topcoat vehicle body provided by an embodiment of the present invention is shown. Figure 2 As shown, including:

[0104] A water-based mid-coat layer, a color paint layer, a first varnish layer and a second varnish layer are sequentially stacked on the surface of a vehicle body; wherein, in parts by weight, the first varnish layer is formed by spraying a single-component varnish or a two-component varnish, and the second varnish layer is formed by spraying a two-component varnish; the composition of the single-component varnish includes: 35-45 parts of acrylic resin, 13-18 parts of a first amino resin, 18-23 parts of an anti-sagging resin, 5-8 parts of a polyester resin, 1.5-2 parts of an auxiliary agent and 15-18 parts of a solvent; the composition of the two-component varnish includes a main agent and a curing agent, the main agent includes: 35-47 parts of the acrylic resin, 14-24 parts of a second amino resin, 16-25 parts of the anti-sagging resin, 0.8-1.3 parts of the auxiliary agent and 15-38 parts of the solvent; the curing agent includes a polyisocyanate curing agent.

[0105] In order to enable those skilled in the art to better understand the present invention, the two-component varnish composition and the spraying method thereof provided by the present invention are described below through a plurality of specific embodiments.

[0106] Example 1

[0107] This embodiment 1 provides a primer one-component varnish, the composition of which is as follows:

[0108]

[0109] This embodiment 1 also provides a top-coating two-component varnish, including a main agent and a curing agent, the ratio of the main agent to the curing agent is 3:1, wherein the curing agent is hexamethylene diisocyanate, and the composition of the main agent is as follows:

[0110]

[0111] A four-coat and two-bake topcoat spraying method comprises the following steps:

[0112] Step S1, spraying a water-based intermediate coating on the electrophoresis treated vehicle body with a film thickness of 10 μm, and then spraying a black paint with a film thickness of 12 μm. After the spraying is completed, the vehicle is moved into a flash drying oven for leveling and dehydration. The flash drying condition is 80° C. for 5.5 minutes.

[0113] Step S2, after flash drying, spray the above-mentioned one-component varnish on the vehicle body with a film thickness of 30 μm. After spraying, move the vehicle into a topcoat drying oven for leveling and curing. The drying condition is baking at 140° C. for 20 minutes.

[0114] Step S3, after the drying is completed, use 2000 mesh sandpaper to polish the defective points on the car body, wipe the car body clean with alcohol, then spray the above-mentioned two-component varnish with a film thickness of 40μm, and then move the vehicle into the topcoat baking furnace again for leveling and curing. The drying condition is baking at 140℃ for 20min to obtain a four-coat and two-bake topcoat car body.

[0115] Example 2

[0116] This embodiment 2 provides a two-component base coating varnish, including a main agent and a curing agent, the ratio of the main agent to the curing agent is 4:1, wherein the curing agent is hexamethylene diisocyanate, and the composition of the main agent is as follows:

[0117]

[0118]

[0119] This embodiment 2 also provides a top-coating two-component varnish, including a main agent and a curing agent, the ratio of the main agent to the curing agent is 3:1, wherein the curing agent is hexamethylene diisocyanate, and the composition of the main agent is as follows:

[0120]

[0121] A four-coat and two-bake topcoat spraying method comprises the following steps:

[0122] Step S1, spraying a water-based intermediate coating on the electrophoresis treated vehicle body with a film thickness of 10 μm, and then spraying a black paint with a film thickness of 12 μm. After the spraying is completed, the vehicle is moved into a flash drying oven for leveling and dehydration. The flash drying condition is 80° C. for 5.5 minutes.

[0123] Step S2, after flash drying, spray the above-mentioned base coat two-component varnish on the vehicle body, with a film thickness of 30 μm. After spraying, move the vehicle into a topcoat baking oven for leveling and curing, and the drying condition is baking at 140° C. for 20 minutes;

[0124] Step S3, after the drying is completed, the defective points on the car body are polished with 2000 mesh sandpaper, and the car body is wiped clean with isopropyl alcohol, and then the above-mentioned topcoat two-component varnish is sprayed with a film thickness of 40 μm. Then, the vehicle is moved into the topcoat baking furnace again for leveling and curing. The drying condition is baking at 140°C for 20 minutes to obtain a four-coat and two-bake topcoat car body.

[0125] Comparative Example 1

[0126] The varnish used for the base coating of this comparative example 1 is BASF UniGloss 1K varnish, and the varnish used for the top coating is BASF ProGloss 2K varnish.

[0127] A four-coat and two-bake topcoat spraying method comprises the following steps:

[0128] Step S1, spraying a water-based intermediate coating on the electrophoresis treated vehicle body with a film thickness of 10 μm, and then spraying a black paint with a film thickness of 12 μm. After the spraying is completed, the vehicle is moved into a flash drying oven for leveling and dehydration. The flash drying condition is 80° C. for 5.5 minutes.

[0129] Step S2, after flash drying, spray the above-mentioned BASF UniGloss 1K varnish on the vehicle body, with a film thickness of 30 μm. After spraying, move the vehicle into a topcoat baking oven for leveling and curing, and the baking condition is 140° C. for 20 minutes;

[0130] Step S3, after the drying is completed, the whole vehicle is polished with 2000 mesh sandpaper, and then the above-mentioned top-coating BASF ProGloss 2K varnish is sprayed with a film thickness of 40 μm. Then, the vehicle is moved into the topcoat baking oven again for leveling and curing, and the drying condition is baking at 140° C. for 20 minutes to obtain a four-coat and two-bake topcoat vehicle body.

[0131] In this comparative example 1, conventional BASF UniGloss 1K varnish is used for primer coating, and conventional BASF ProGloss 2K varnish is used for top coating. After drying, the whole vehicle needs to be polished, which takes about 3-4 hours.

[0132] Comparative Example 2

[0133] The varnish used for the base coating of this comparative example 2 is BASF EverGloss 2K varnish, and the varnish used for the top coating is BASF ProGloss 2K varnish.

[0134] A four-coat and two-bake topcoat spraying method comprises the following steps:

[0135] Step S1, spraying a water-based intermediate coating on the electrophoresis treated vehicle body with a film thickness of 10 μm, and then spraying a black paint with a film thickness of 12 μm. After the spraying is completed, the vehicle is moved into a flash drying oven for leveling and dehydration. The flash drying condition is 80° C. for 5.5 minutes.

[0136] Step S2, after flash drying, spray the above-mentioned base coat BASF EverGloss 2K varnish on the vehicle body, with a film thickness of 30 μm. After spraying, move the vehicle into a topcoat baking oven for leveling and curing, and the drying condition is baking at 140° C. for 20 minutes;

[0137] Step S3, after the drying is completed, the whole vehicle is polished with 2000 mesh sandpaper, and then the above-mentioned top-coating BASF ProGloss 2K varnish is sprayed with a film thickness of 40 μm. Then, the vehicle is moved into the topcoat baking oven again for leveling and curing, and the drying condition is baking at 140° C. for 20 minutes to obtain a four-coat and two-bake topcoat vehicle body.

[0138] In this comparative example 2, conventional BASF EverGloss 2K varnish was used for primer coating, and conventional BASF ProGloss 2K varnish was used for top coating. After drying, the whole vehicle needed to be polished, which took about 3-4 hours.

[0139] Next, the performance boards were manufactured and tested according to the conditions of Example 1, Example 2, Comparative Example 1 and Comparative Example 2, respectively. The results are shown in Table 1 below:

[0140] Table 1. Performance test results of Example 1, Example 2, Comparative Example 1 and Comparative Example 2

[0141]

[0142]

[0143] As shown in Table 1 above, Example 1 and Example 2 can significantly improve their appearance data such as DOI and orange peel, as well as physical and chemical properties such as adhesion, impact resistance, and moisture and heat resistance while ensuring the construction performance, which are all higher than Comparative Example 1 and Comparative Example 2.

[0144] Each embodiment in this specification focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referenced to each other.

[0145] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0146] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0147] The present invention has been introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A mass-producible four-coat and two-bake topcoat spraying method, characterized in that: The method comprises: Step S1, spraying a water-based intermediate coating and a color paint on the electrophoresis treated vehicle body in sequence to form a water-based intermediate coating layer and a color paint layer, and then performing a flash drying treatment; Step S2, after the flash-drying treatment is completed, spraying a single-component varnish or a two-component varnish on the vehicle body to form a first varnish layer, and performing a drying treatment; Step S3, after the drying process is completed, the defective points on the vehicle body are polished, the two-component varnish is sprayed to form a second varnish layer, and the drying process is performed again to obtain a four-coat and two-bake topcoat vehicle body; Wherein, the composition of the one-component varnish includes, by weight, 35 to 45 parts of acrylic resin, 13 to 18 parts of first amino resin, 18 to 23 parts of anti-sagging resin, 5 to 8 parts of polyester resin, 1.5 to 2 parts of auxiliary agent and 15 to 18 parts of solvent; The two-component varnish comprises a main agent and a curing agent, wherein the main agent comprises: 35 to 47 parts of the acrylic resin, 14 to 24 parts of the second amino resin, 16 to 25 parts of the anti-sagging resin, 0.8 to 1.3 parts of the auxiliary agent and 15 to 38 parts of the solvent; the curing agent comprises a polyisocyanate curing agent.

2. A mass-producible four-coat and two-bake topcoat spraying method according to claim 1, characterized in that: In the step S2, the main agent in the two-component varnish sprayed includes, by weight, 35 to 45 parts of the acrylic resin, 14 to 18 parts of the second amino resin, 16 to 23 parts of the anti-sagging resin, 0.8 to 1.2 parts of the auxiliary agent and 28 to 28 parts of the solvent; In step S3, the main agent of the two-component varnish sprayed includes, by weight, 39 to 47 parts of the acrylic resin, 18 to 24 parts of the second amino resin, 19 to 25 parts of the anti-sagging resin, 1 to 1.3 parts of the auxiliary agent and 15 to 25 parts of the solvent.

3. A mass-producible four-coat and two-bake topcoat spraying method according to claim 1 or 2, characterized in that: In the step S2, the main agent and the curing agent are mixed according to a first preset ratio, and the first preset ratio is 3.5:1 to 4:1; In the step S3, the main agent and the curing agent are mixed according to a second preset ratio, and the second preset ratio is 3:1 to 3.5:

1.

4. A mass-producible four-coat and two-bake topcoat spraying method according to claim 1, characterized in that: The acrylic resin includes one or a mixture of any proportion of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, hexyl (meth)acrylate and lauryl methacrylate; The first amino resin comprises one of butylated melamine resin, mixed etherified melamine resin, methylated melamine resin or methylated hexamethylol melamine resin or a mixture of multiple thereof in any proportion; The second amino resin includes one of methyl etherified melamine resin and methyl etherified hexamethylol melamine resin or a mixture of two or more of them in any proportion.

5. A mass-producible four-coat and two-bake topcoat spraying method according to claim 1, characterized in that: The anti-sagging resin includes one of modified acrylic resin and polyamide wax slurry or a mixture of multiple types in any proportion.

6. A mass-producible four-coat and two-bake topcoat spraying method according to claim 1, characterized in that: The auxiliary agent includes one or a mixture of multiple agents selected from the group consisting of a leveling agent, a defoaming agent and a drying agent in any proportion; Among them, the leveling agent includes one of modified silicone, epoxy-modified polyacrylate and modified organic polysiloxane polyisocyanate or a combination of multiple thereof in any proportion; the defoaming agent includes one of polyamide hydrophobic particle polymer and propylene glycol methyl ether acetate or a combination of multiple thereof in any proportion; the drying agent includes one of dibutyltin dilaurate and p-toluenesulfonic acid amino salt solution or a combination of multiple thereof in any proportion.

7. A mass-producible four-coat and two-bake topcoat spraying method according to claim 1, characterized in that: The solvent includes one of ethyl acetate, solvent oil, ethylene glycol butyl ether acetate, diethylene glycol butyl ether, dimethyl carbonate, isopropyl alcohol and diethyl carbonate, or a plurality of the solvents mixed in any proportion.

8. The mass-producible four-coat and two-bake topcoat spraying method according to claim 1, characterized in that: The flash drying treatment comprises: flash drying the vehicle body at 75 to 80° C. for 4 to 6 minutes; The drying process comprises: baking at 130-150° C. for 20-30 minutes.

9. A mass-producible four-coat and two-bake topcoat spraying method according to claim 1, characterized in that: The thickness of the water-based mid-coat layer is 9-15 μm; the thickness of the color paint layer is 10-15 μm; the thickness of the first clear varnish layer is 25-35 μm; and the thickness of the second clear varnish layer is 45-60 μm.

10. A topcoat, characterized in that: include: The water-based intermediate coating, the color paint layer, the first clear varnish layer and the second clear varnish layer are sequentially stacked on the surface of the vehicle body; wherein, Counted in parts by weight, the first varnish layer is formed by spraying a single-component varnish or a two-component varnish, and the second varnish layer is formed by spraying a two-component varnish; The one-component varnish comprises: 35 to 45 parts of acrylic resin, 13 to 18 parts of a first amino resin, 18 to 23 parts of an anti-sagging resin, 5 to 8 parts of a polyester resin, 1.5 to 2 parts of an auxiliary agent and 15 to 18 parts of a solvent; The two-component varnish comprises a main agent and a curing agent, wherein the main agent comprises: 35 to 47 parts of the acrylic resin, 14 to 24 parts of the second amino resin, 16 to 25 parts of the anti-sagging resin, 0.8 to 1.3 parts of the auxiliary agent and 15 to 38 parts of the solvent; the curing agent comprises a polyisocyanate curing agent.

Images