阅读说明：本技术 一种环保节能型汽车低温一体化涂装工艺 (Environment-friendly energy-saving automobile low-temperature integrated coating process ) 是由 王德修 李新雄 张冬明 廖作为 于 2019-10-11 设计创作，主要内容包括：本发明公开了一种环保节能型汽车低温一体化涂装工艺,包括以下步骤：(1)车身前处理、电泳底漆处理、PVC车底喷涂及焊缝密封处理；(2)装配与车身颜色要求一致的外饰件；(3)电泳底漆点磨,再喷涂中涂漆,流平后在中涂漆上喷涂面漆,流平后闪干；再在面漆上喷涂清漆,流平；(4)烘干漆膜,烘烤温度为60-100℃,保温时间为30-40min。本发明采用低温烘烤型中涂漆与面漆进行湿碰湿的喷涂工艺,不仅能大大减少涂装过程中能源的消耗,还能实现汽车车身与外饰件的一体化喷涂,解决了汽车车身与外饰件对色难的问题。(The invention discloses an environment-friendly energy-saving automobile low-temperature integrated coating process, which comprises the following steps: (1) pretreatment of a vehicle body, treatment of electrophoretic primer, spraying of PVC vehicle bottom and sealing treatment of welding seams; (2) assembling exterior trimming parts with the color requirement consistent with that of the vehicle body; (3) point grinding the electrophoretic primer, spraying middle paint, spraying finish paint on the middle paint after leveling, and flashing after leveling; spraying varnish on the finish paint, and leveling; (4) drying the paint film at 60-100 deg.c for 30-40 min. The invention adopts the low-temperature baking type middle painting and finish paint to carry out wet-on-wet spraying process, thereby not only greatly reducing the energy consumption in the coating process, but also realizing the integrated spraying of the automobile body and the exterior trimming parts and solving the problem of difficult color matching of the automobile body and the exterior trimming parts.)

1. An environment-friendly energy-saving automobile low-temperature integrated coating process is characterized by comprising the following steps:

(1) pretreatment of a vehicle body, treatment of electrophoretic primer, spraying of PVC vehicle bottom and sealing treatment of welding seams;

(2) assembling exterior trimming parts with the color requirement consistent with that of the vehicle body;

(3) point grinding the electrophoretic primer, spraying middle paint, spraying finish paint on the middle paint after leveling, and flashing after leveling; spraying varnish on the finish paint, and leveling;

(4) drying the paint film at 60-100 deg.c for 30-40 min.

2. The environment-friendly energy-saving automobile low-temperature integrated coating process according to claim 1, wherein the intermediate coating comprises a component A and a component B, wherein the component A comprises the following raw materials in parts by weight:

the component B is a curing agent, and the weight ratio of the component A to the component B is (6-10): 1.

3. the environment-friendly energy-saving automobile low-temperature integrated coating process as claimed in claim 2, wherein the aqueous polyurethane dispersion comprises one or more of polyether type aqueous polyurethane dispersion, polycarbonate type aqueous polyurethane dispersion and polyester type aqueous polyurethane dispersion.

4. The environment-friendly energy-saving automobile low-temperature integrated coating process as claimed in claim 2, wherein the aqueous polyurethane dispersion is polycarbonate aqueous polyurethane with hydroxyl groups, and the amine ester bonds of the polycarbonate aqueous polyurethane with hydroxyl groups are more than 8%.

5. The environment-friendly energy-saving automobile low-temperature integrated coating process according to claim 1, wherein the finish paint comprises a component C and a component D, wherein the component C comprises the following raw materials in parts by weight:

the component D is a curing agent, and the weight ratio of the component C to the component D is (5-8): 1.

6. the environment-friendly energy-saving automobile low-temperature integrated coating process according to any one of claims 2 to 5, wherein the polyester resin is mainly formed by polymerizing polybasic acid and polyhydric alcohol, the polybasic acid is dimer acid with long chain, the molecular weight polydispersity index of the polyester resin is 20 to 40, and the acid value is less than 1 mgKOH/g.

7. The environment-friendly energy-saving automobile low-temperature integrated coating process according to any one of claims 2 to 5, wherein the acrylic modified polyurethane is an aliphatic urethane polyacrylate mixture.

8. The environment-friendly energy-saving automobile low-temperature integrated coating process according to any one of claims 2 to 5, wherein the acrylic emulsion is a functional aqueous acrylic emulsion with a core-shell structure, and mainly comprises aqueous acrylic resin, water and a neutralizer N, N-dimethylethanolamine, wherein the mass concentration of the aqueous acrylic resin is controlled to be 29-31%, and the dosage of N, N-dimethylethanolamine is controlled to be based on the pH value of the system to be 5.5-7.0.

9. The low-temperature integrated coating process for the environment-friendly energy-saving automobile according to any one of claims 2 to 5, wherein the curing agent comprises one or two of a water-based isocyanate curing agent or a water-based blocked isocyanate.

10. The environment-friendly energy-saving automobile low-temperature integrated coating process according to any one of claims 1 to 5, wherein the pretreatment of the automobile body sequentially comprises the following steps: pre-degreasing, primary washing, secondary washing, surface conditioning, phosphating, primary washing, secondary washing, pure washing, fresh pure washing and leaching; the electrophoretic primer treatment sequentially comprises the following steps: electrophoretic coating, ultrafiltrate UF rinsing, pure water rinsing, liquid leaching, electrophoretic drying and electrophoretic point grinding; and after the PVC vehicle bottom spraying and welding line sealing treatment, carrying out heat preservation at the temperature of 140 ℃ and 150 ℃ and then entering the next working procedure.

Technical Field

The invention belongs to the field of automobile production and manufacturing, and particularly relates to an automobile integrated coating process.

Background

With the increasing attention of our country to the environmental problems, a series of environmental policies and regulations are developed in various places, and environmental protection and energy conservation become the development trend of current automobile production. In the automobile manufacturing process, the energy consumption required by coating accounts for about 80% of the total energy consumption of the four processes of the whole automobile, the energy consumption of coating mainly comes from the spraying and baking processes of paint, and more automobile manufacturers begin to pay attention to environment-friendly and energy-saving coating processes.

In the traditional automobile production, automobile manufacturers adopt a 3C2B (three-coating two-baking) process to coat automobiles. The key process flow of the 3C2B is intermediate coating, drying, colored paint, flash drying, varnish and drying. Two times of high-temperature baking operation is required in the coating process, so that great energy consumption is caused, and a large amount of volatile solvent components are converted into gaseous state in the baking process and enter the air to form atmospheric pollutants. Therefore, the 3C2B coating process is very disadvantageous for environmental protection and resource saving.

In order to reduce the VOC emission, reduce the energy consumption in the production process and save the cost. A relatively environmentally friendly and energy efficient 3C1B painting process has been developed and is used in a number of factory and vehicle model instances. However, the existing 3C1B coating process is a high-temperature baking type process (as shown in fig. 2), and still has the defect of large energy consumption. Meanwhile, the high-temperature baking determines that the car body and the exterior trimming parts such as bumper bars must be coated separately, which also greatly increases the coating cost.

The existing 3C1B coating process can not well meet the requirements of energy conservation and environmental protection in the automobile coating process, and meanwhile, the automobile body and the exterior trimming parts are separately sprayed, so that the cost in the spraying process is increased, and the color matching difficulty of the automobile body and the exterior trimming parts is increased.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects and shortcomings in the background technology, and provide an environment-friendly and energy-saving automobile low-temperature integrated coating process, wherein the coating process can realize the integrated spraying of an automobile body and exterior trimming parts, and the drying process adopts low-temperature baking, so that the energy consumption is low. In order to solve the technical problems, the technical scheme provided by the invention is as follows:

an environment-friendly energy-saving automobile low-temperature integrated coating process comprises the following steps:

(1) pretreatment of a vehicle body, treatment of electrophoretic primer, spraying of PVC vehicle bottom and sealing treatment of welding seams;

(2) assembling exterior trimming parts with the color requirement consistent with that of the vehicle body;

(3) point grinding the electrophoretic primer, spraying middle paint, leveling (2-5min), spraying finish paint on the middle paint, leveling for 2-5min, and flash drying at 60-80 deg.C for 2-5 min; spraying varnish on the finish paint, leveling for 3-8min, and baking;

(4) drying the paint film at 60-100 deg.c for 30-40 min.

In the integrated coating process, preferably, the primer surfacer comprises a component A and a component B, wherein the component A comprises the following raw materials in parts by weight:

the component B is a curing agent, and the weight ratio of the component A to the component B is (6-10): 1.

in the above intermediate coating material, preferably, the aqueous polyurethane dispersion includes one or more of a polyether-type aqueous polyurethane dispersion, a polycarbonate-type aqueous polyurethane dispersion, and a polyester-type aqueous polyurethane dispersion. More preferably, the aqueous polyurethane dispersion includes a polycarbonate-type aqueous polyurethane dispersion or a polyester-type aqueous polyurethane dispersion. Further preferably, the aqueous polyurethane dispersion is a polycarbonate aqueous polyurethane with hydroxyl groups, and the amine ester bond of the polycarbonate aqueous polyurethane with hydroxyl groups is more than 8%. The existence of the aqueous polyurethane dispersion can enable the intermediate coating to have strong cohesive force and reduce the interaction with the finish, so that the aqueous polyurethane dispersion can cooperate with the polyester resin and the acrylic modified polyurethane in the formula to realize wet-on-wet coating, and can provide excellent adhesion, stone impact resistance, wear resistance, chemical resistance, oil resistance and other properties for the intermediate coating.

In the intermediate coating material, preferably, the polyester resin (hydroxyl group-containing polyester resin) is mainly obtained by polymerizing a polybasic acid and a polyhydric alcohol, the polybasic acid is a dimer acid having a long chain, and the polyester resin has a molecular weight polydispersity of 20 to 40 and an acid value of less than 1 mgKOH/g. The long-chain dimer acid is adopted as a dibasic acid structure, so that the resin has good thixotropy and good hydrophobicity, and the molecular structure design is adopted (mainly, the types, the number and the activity of functional groups on a polybasic acid chain and a polybasic alcohol chain are controlled, so that the polymerization reaction is selectively carried out), so that the resin has wide molecular weight distribution and low acid value, can provide good water resistance, flexibility, stone impact resistance and other properties for the middle coating, and can be well suitable for a wet-on-wet process.

In the primer coating, preferably, the acrylic modified polyurethane (self-crosslinking aqueous acrylic modified polyurethane emulsion) is an aliphatic urethane polyacrylate mixture. The special network structure of the aliphatic urethane polyacrylate mixture is beneficial to coating a middle coating on the surface of a workpiece to form a film, and meanwhile, the resin can limit the molecular structure motion of the middle coating and the surface coating in a wet film state, so that the surface effect of the middle coating and the surface coating in a wet-on-wet state is ensured.

In the primer surfacer, preferably, the acrylic emulsion is a functional aqueous acrylic emulsion with a core-shell structure, and mainly comprises aqueous acrylic resin, water and a neutralizer N, N-dimethylethanolamine which are physically mixed, wherein the mass concentration of the aqueous acrylic resin is controlled to be 29-31%, and the dosage of N, N-dimethylethanolamine is controlled according to the pH value of the system to be 5.5-7.0. The acrylic emulsion can improve the workability of the intermediate coating, so that the intermediate coating has good leveling and sagging properties, and the construction stability of the intermediate coating can be adjusted.

In the intermediate coating, the titanium dioxide with stable structure, small optical activity and excellent weather resistance is preferably selected, and rutile titanium dioxide is preferably selected, and R-960 titanium dioxide of the American DuPont company is more preferably selected. The dispersing aid, which is selected to facilitate dispersion of the pigment during the refining process, is suitable for use with binder-containing and binder-free pigment concentrates that can be used to grind binder-free pigment concentrates, more preferably BYK2012, by peck corporation. The wetting and leveling agent can effectively reduce the surface tension of the coating, and is preferably an organosilane substrate wetting agent, and further preferably TEGO Twin 4100. The defoaming agent is used for eliminating bubbles generated in the processes of grinding and preparing the paint, and simultaneously ensuring that the interlayer adhesive force of the coating is not influenced, and the defoaming agent is a non-organic silicon defoaming agent, preferably BYK 011. The organic amine is used as a neutralizer as a coating pH regulator, preferably an organic amine neutralizer with a boiling point not higher than 150 ℃, and more preferably N, N-dimethylethanolamine. The film-forming assistant is alcohol ether film-forming assistant with hydrophilic-lipophilic balance and capable of exerting different film-forming effects on different resins, preferably dipropylene glycol methyl ether. The compatilizer can improve the compatibility of the coating components, and the solvent is one or more of alcohol ether, preferably propylene glycol butyl ether and propylene glycol methyl ether acetate. The water used in the intermediate coating is preferably deionized water, and the stability of the waterborne resin is affected due to the existence of multivalent ions such as calcium and magnesium in tap water, so that the stability of the final coating is poor.

The invention also provides a preparation method of the primer surfacer, wherein the component A of the primer surfacer comprises the following steps:

(1) adding 15-25 parts by weight of titanium dioxide, 0.5-0.9 part by weight of dispersing aid, 0.01-0.03 part by weight of wetting and leveling agent, 0.05-0.1 part by weight of defoaming agent, 0.1-0.2 part by weight of organic amine, 1-2 parts by weight of compatilizer and 3-5 parts by weight of deionized water into 5-8 parts by weight of acrylic resin under the stirring condition (400 revolutions per minute), continuing stirring after the addition is finished (stirring for 30min under the condition of 600 revolutions per minute of 400 revolutions per minute), and then grinding until the fineness is less than 10 mu m to obtain a premix;

(2) adding 10-20 parts by weight of aqueous polyurethane dispersoid, 12-23 parts by weight of polyester resin, 5-15 parts by weight of acrylic acid modified polyurethane, 2-8 parts by weight of acrylic acid emulsion, 0.04-0.17 part by weight of wetting and leveling agent, 0.15-0.4 part by weight of defoaming agent, 1-3 parts by weight of film forming additive, 0.3-0.6 part by weight of organic amine, 2-6 parts by weight of compatilizer and 1-3 parts by weight of deionized water into the premix obtained in the step (1) under the stirring condition (200 plus 400 r/min), adjusting the viscosity to 80-90s (25 ℃, Ford 4 cup), and filtering with 200-mesh filter cloth to obtain the component A of the intermediate coating.

In the integrated coating process, preferably, the finish paint comprises a component C and a component D, wherein the component C comprises the following raw materials in parts by weight:

the component D is a curing agent, and the weight ratio of the component C to the component D is (5-8): 1.

in the above finish paint, preferably, the polyester resin (hydroxyl-containing polyester resin) is mainly formed by polymerizing polybasic acid and polyhydric alcohol, the polybasic acid is dimer acid with long chain, and the polyester resin has a molecular weight polydispersity index of 20-40 and an acid value less than 1. The long-chain dimer acid is adopted as a dibasic acid structure, so that the resin has good thixotropy and good hydrophobicity, and molecular structure design is carried out (mainly by controlling the type, the number and the activity of functional groups on a polybasic acid chain and a polyhydric alcohol chain, so that the polymerization reaction is selectively carried out), so that the resin has wide molecular weight distribution and low acid value, can provide good water resistance and flexibility for finish paint, can be well adapted to a wet-on-wet process, and can effectively improve the arrangement of aluminum powder in the paint.

In the above finish, preferably, the acrylic modified polyurethane (self-crosslinking aqueous acrylic modified polyurethane emulsion) is an aliphatic urethane polyacrylate mixture. The special network structure of the aliphatic carbamate polyacrylate mixture is beneficial to reducing the molecular motion capability of the finish paint, meets the spraying requirement of wet-on-wet, and can improve the orientation of aluminum powder, thereby providing the performances of quick drying, quick hardness development, good durability and weather resistance, good flowing smoothness, good stability, good scratch resistance and the like for the coating.

In the finish paint, preferably, the acrylic emulsion is a functional aqueous acrylic emulsion with a core-shell structure, and is mainly formed by physically mixing aqueous acrylic resin, water and a neutralizing agent N, N-dimethylethanolamine, wherein the mass concentration of the aqueous acrylic resin is controlled to be 29-31%, and the dosage of N, N-dimethylethanolamine is based on the control of the pH value of the system to be 5.5-7.0. The neutralizing agent is used for neutralizing the emulsion to obviously increase the viscosity of the emulsion and have the effect of shear thinning, but when the pH value of the emulsion is stabilized at 8.0-9.0, the viscosity of the emulsion is not changed greatly, and at the moment, obvious thixotropy can be generated after the alcohol ether compatilizer is added. By utilizing the characteristic, the aluminum powder paint can be used for providing excellent aluminum powder orientation in water-based aluminum powder paint on one hand, and the stability and the application property of the paint can be improved on the other hand.

In the finish paint, the types and the functions of the dispersing auxiliary agent, the compatilizer, the wetting agent, the defoaming agent, the organic amine and the deionized water are similar to those of the intermediate paint, and the details are not repeated here.

The invention also provides a preparation method of the component C of the finish paint, which comprises the following steps:

(1) adding 5-8 parts by weight of pigment, 0.01-1.2 parts by weight of dispersing aid, 0.01-0.02 part by weight of wetting and leveling agent, 0.05-0.08 part by weight of defoaming agent, 0.1-0.15 part by weight of organic amine, 1-1.5 parts by weight of compatilizer and 4-6 parts by weight of deionized water into 5-12 parts by weight of acrylic resin under the stirring condition (400 revolutions per minute), continuing stirring (stirring for 30min under the condition of 600 revolutions per minute of 400 revolutions per minute), and then grinding until the fineness is less than 10 mu m to obtain a premix;

(2) adding 40-60 parts by weight of acrylic emulsion, 30-50 parts by weight of polyester resin, 8-12 parts by weight of acrylic modified polyurethane, 0.04-0.06 part by weight of wetting and leveling agent, 0.05-0.12 part by weight of defoaming agent, 0.2-0.45 part by weight of organic amine, 9-12.5 parts by weight of compatilizer and 4-7 parts by weight of deionized water into the premix obtained in the step (1) under the stirring condition (200 plus 400 revolutions per minute), adjusting the viscosity to 80-90s (25 ℃, Ford 4 cup), and filtering through 200-mesh filter cloth to obtain the C component of the finish paint.

In the above-mentioned integrated coating process, preferably, the curing agent includes one or two of a water-based isocyanate curing agent (e.g. koste 2655, 401-60, wawa Aquolin268, etc.) or a water-based blocked isocyanate (Bayhydur BL5335, etc.).

After the intermediate coating and the finish coating are applied to integrated coating, the intermediate coating and the finish coating have a synergistic effect on the performance of the whole composite coating. The intermediate coating is used as a coating between the electrophoresis and the finish coat, has the advantages of improving the adhesion between the finish coat and the electrophoresis layer, simultaneously is beneficial to improving the covering, and is beneficial to the embodiment of the color effect of the finish coat. Meanwhile, the physical and chemical properties of the composite coating are also completed through the cooperation of the intermediate coating and the finish, and the performance of any coating can affect the performance of the whole composite coating when the performance of any coating can not meet the requirement. Only if good synergistic effect can be achieved between the intermediate coating and the finish paint, the composite coating can be ensured to play good protection on the coated workpiece, and meanwhile, the composite coating can also play a good decorative role.

The intermediate coating has excellent physical and chemical properties such as adhesive force, stone impact resistance, wear resistance and chemical resistance. The finish paint disclosed by the invention has excellent aluminum powder orientation performance, and the color spread of the color paste in the finish paint is good, so that the effect display of various complex colors can be met. Meanwhile, the finish paint also has excellent physicochemical properties of stone impact resistance, water resistance, chemical resistance and the like. The intermediate paint and the finish paint have some common functions such as: the coating has the advantages that the coating has the performances of adhesion, stone impact resistance, wear resistance and the like, and can play a role in protecting a coated workpiece, so that main resin with the same components can appear in the formula of the coating, and based on the same components, the intermediate coating and the finish paint are well matched with each other, and the intermediate coating and the finish paint are matched for use, so that the requirements of the 3C1B coating process in the invention can be met, and the requirements of a wet-on-wet construction process and a low-temperature (60-100 ℃) baking and curing process are met.

The intermediate coating and the finish coating are both double-component coatings, and the used curing agent can release isocyanate (-NCO) groups at the temperature of 60-80 ℃ to react with hydroxyl, carboxyl, amino and other groups on a molecular chain of the water-based resin to form a cross-linked structure, so that the complete polymerization of polyurethane, acrylic resin, polyester and the like in the coatings is completed. The curing agent and other components act together, so that the intermediate coating and the finish paint can meet the requirements of a wet-on-wet construction process and a low-temperature (60-100 ℃) baking curing process.

In the integrated coating process, preferably, the pretreatment of the vehicle body sequentially includes the following steps: pre-degreasing, primary washing, secondary washing, surface conditioning, phosphating, primary washing, secondary washing, pure washing, fresh pure washing and leaching; the electrophoretic primer treatment sequentially comprises the following steps: electrophoretic coating, ultrafiltrate UF rinsing, pure water rinsing, liquid leaching, electrophoretic drying and electrophoretic point grinding; and during electrophoresis drying, the drying temperature is 160-fold and 180 ℃, the heat preservation time is about 20min, and the PVC vehicle bottom is subjected to heat preservation for 20min at the temperature of 140-fold and 150 ℃ after the PVC vehicle bottom spraying and welding line sealing treatment, and then the next procedure is carried out.

In the integrated coating process, preferably, when the electrophoresis primer is used for spot grinding, the electrophoresis primer is manually used for spot grinding, the indoor air speed requirement of grinding is 0.2-0.3m/s, the indoor illumination intensity is 600Lx, the granularity of grinding abrasive paper is 400-; when wet hair polishing is adopted, deionized water is required to be used, and the surface of a workpiece is ensured to be dry when the workpiece enters the next procedure; and removing floating dust on the surface of the workpiece by using adhesive dust-free wiping cloth.

Compared with the prior art, the invention has the advantages that:

1. the invention adopts a brand new intermediate coat and finish coat system, can meet the characteristics of wet-on-wet construction process and baking and curing of a coating film at low temperature (60-100 ℃), and realizes the optimization of the coating process in the aspect of environmental protection on the premise of ensuring the quality of the coating film.

2. The invention adopts the low-temperature baking type middle painting and finish paint to carry out wet-on-wet spraying process, thereby not only greatly reducing the energy consumption in the coating process, but also realizing the integrated spraying of the automobile body and the exterior trimming parts and solving the problem of difficult color matching of the automobile body and the exterior trimming parts.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a flow chart of the low-temperature integrated coating process of the present invention.

Fig. 2 is a flow chart of a conventional 3C1B automobile body coating process.

Detailed Description

In order to facilitate an understanding of the invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.