Injection molding and coating integrated forming process for automobile large-size exterior trim covering part

Abstract

The invention discloses an injection molding and coating integrated forming process for an automobile large-size exterior trim covering part, which comprises the following steps: selecting modified polypropylene granules, and preparing an automobile exterior trim covering part framework through in-mold injection molding; opening the mold, rotating the mold, carrying out skeleton surface modification treatment by adopting flame or a PP treating agent, rotating the mold, closing the mold, controlling the mold temperature to be 50-90 DEG C, and controlling the time to be 1-30 minutes; and in-mold painting adopts equipment injection reaction to form polyester paint, a soft coating layer is formed on the surface of the exterior trim covering part through pressure maintaining and cooling, and in-mold coating of the exterior trim part is achieved. Injection molding and coating integrated forming of the large-size automobile exterior trim covering part is achieved through a one-step method, the problem of traditional paint spraying environment pollution is solved while manufacturing procedures are reduced, light-weight and customized green manufacturing of the automobile exterior trim covering part is achieved, and the high-beat and batch manufacturing requirements of automobiles are met.

Description

Technical Field

[0001] The invention relates to the technical field of automobile injection molding, and in particular to an integrated molding process of injection molding and painting of large-size automobile exterior covering parts. Background Art

[0002] As global climate change and environmental problems become increasingly severe, governments around the world are paying more and more attention to the sustainable development of a low-carbon economy. How to achieve energy conservation and emission reduction in the automotive industry is of great significance to the sustainable development of the automotive industry and economic construction.

[0003] In the transportation equipment manufacturing industry, which is mainly composed of automobile manufacturing, energy consumption in automobile paint shops accounts for about 70% of the total energy consumption of automobile production. The carbon-based emissions have a large base, and the task of green transformation is urgent. There is an urgent need to develop new short-process, high-quality and efficient painting technologies.

[0004] The key equipment technology and corresponding process technology of injection molding and painting integrated molding can not only improve the weight of parts and products and reduce manufacturing processes, but also save energy and reduce consumption, reduce environmental pollution and high-beat manufacturing, and has become a new trend leading the molding and manufacturing of automotive non-metallic parts. However, the injection molding and painting integrated molding process technology has not yet been applied in batches and on a large scale, especially the development of large-size automotive exterior panels is not mature.

[0005] For example, the patent CN116533436A discloses an integrated process for injection molding and painting of automotive interior parts, which uses ABS injection molding to form a skeleton and trim flash, and then sprays, injects PPT soft glue and sprays twice to form automotive interior parts. Although this process simplifies the process to a certain extent, it still requires secondary spraying and flash repair. The process is cumbersome and spraying is prone to environmental pollution, which does not meet the requirements of green manufacturing. Another example is the patent CN117774191A discloses an in-mold painting forming mold and an in-mold painting forming method, which forms a closed cavity for the painted product part inside it through the design of concave and convex molds, sealing plates, etc. After the product is first formed in the mold, the paint is injected into the cavity by a micro-opening method, and the parts are directly painted in the mold; although this method can save energy and reduce environmental pollution to a certain extent, the micro-opening precision requirements are high and the design is difficult, and it is very likely that defects such as flash will occur, resulting in a decrease in product quality.

[0006] Therefore, in view of the problems existing in the existing injection molding and painting integrated molding, realizing the integrated molding of large-size automobile exterior covering parts with complex structures is an urgent need for high-speed automobile manufacturing, and it is also a trend to promote the development of the automobile industry towards a low-carbon, green and sustainable economy. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides an integrated injection molding and painting process for large-size exterior covering parts for automobiles, which can simplify the process and achieve high-speed batch integrated injection molding and painting.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] The one-piece injection molding and painting process for large-size exterior covering parts of an automobile comprises the following steps:

[0010] S1. Select modified polypropylene pellets and prepare the framework of automobile exterior covering parts by in-mold injection molding;

[0011] S2, open the mold and rotate the mold, use flame or PP treatment agent to modify the skeleton surface, rotate the mold again, close the mold and control the mold temperature at 50-90℃ for 1-30min;

[0012] S3, in-mold painting uses equipment to inject reaction-molded polyester paint. After pressure maintenance and cooling, a soft coating layer is formed on the surface of the exterior covering part to achieve in-mold painting of the exterior covering part.

[0013] In step 1, the exterior covering frame injection molding method is as follows:

[0014] 1) Drying and heating the injection molding raw materials to melt;

[0015] 2) Injecting the melted injection molding material into the mold cavity through the injection molding equipment;

[0016] 3) Maintain pressure and cool the mold cavity.

[0017] 3. The process for injection molding and coating of large-size exterior covering parts for automobiles as claimed in claim 2, characterized in that: the injection molding raw material is EPDM, talcum powder or glass fiber modified polypropylene granules, wherein the glass fiber modified polypropylene granules are 0.2-0.6 mm short glass fiber reinforced polypropylene or 5-20 mm long glass fiber reinforced polypropylene, the fiber content is 10-60%, and the linear expansion coefficient is less than 35×10 -6 m / (m·K);

[0018] The heating and melting temperature range of injection molding pellets is 180-300℃; the injection pressure is 800-1000bar, the holding pressure is 300-500bar, and the cooling time is 10-20s.

[0019] In step S2, the mold is rotated 90 degrees, and a flame spray gun is controlled by a mechanical arm to flame treat the exterior frame. A mixture of methane and air is preferably used as a combustion source, the equivalent ratio is preferably 0.9-1.2, the total flow rate is preferably 100-150 L / min, the treatment distance is preferably 75-85 mm, and the flame treatment exposure time is 20-30 ms.

[0020] In step S3, the in-mold painting process is as follows:

[0021] 1) Place the two-component polyester paints A and B in vacuum storage tanks respectively, the temperature is preferably controlled at 40-70° C., and the stirring speed is preferably 500-800 r / min;

[0022] 2) Open the mixing head, and the A and B materials are metered into the mixing chamber by the high-pressure pump and evenly mixed, and then injected into the cavity containing the exterior component skeleton at a certain speed to form a paint surface on the surface of the component. After curing, pressure holding and cooling, the in-mold painting is completed;

[0023] 3) Lower the clamping force, open the mold and take out the injection molding and coating integrated product.

[0024] In step S3, material A is isocyanate, and component B is a composite of polyester polyol or polyether polyol, catalyst, diamine chain extender, auxiliary agent, and color paste, and the ratio of A to B is preferably 1:1-1:2.

[0025] In the step S3, the pumping pressure of material A and material B is 20-30 MPa, the pumping speed is 80-120 g / s, the curing time is 10-20 s, the curing temperature, i.e. the mold temperature, is 50-70° C., the holding pressure is 200-300 bar, and the cooling time is 10-20 s; the thickness of the in-mold paint film is 300-500 um.

[0026] Specifically, the molding process preferably includes the following steps:

[0027] Pretreatment of injection molding substrate: Place a certain amount of long glass fiber modified polypropylene pellets in a drying oven for drying, and set the temperature to 90-100℃;

[0028] Injection molding of the skeleton of automobile exterior cover: the pellets are accurately measured and evenly conveyed to the hopper of the injection molding machine by vacuum suction, and the pellets are conveyed to the barrel of the injection molding machine through the controller of the injection molding machine. The pellets are heated, melted, sheared, and mixed into a plastic melt with good fluidity in the injection molding machine. The four-stage temperature range of the injection molding machine barrel is set at 180-300℃; mold closing and filling injection molding, the clamping pressure is 500-2000T, the mold temperature is 25-90℃, and the injection pressure is 500-1000bar; pressure holding, shrinkage compensation and cooling and shaping, the pressure holding pressure is 100-500bar, and the cooling time is 5-40s;

[0029] Surface treatment of the skeleton of automobile exterior covering parts: open the mold and rotate the mold table 90° counterclockwise, use a mechanical arm to flame treat the skeleton of automobile exterior covering parts, the fuel is a mixture of methane and air, the equivalent ratio is 0.5-1.5, the total flow rate is 60-200L / min, the treatment distance is preferably 60-120mm, and the flame treatment exposure time is 10-50ms;

[0030] In-mold painting of the skeleton of automobile exterior covering parts: the mold turntable rotates 90° counterclockwise, closes the mold and controls the mold temperature at 50-100℃, and the material A and material B are metered by the high-pressure pump and enter the mixing chamber. They are evenly mixed by high-speed collision in the mixing chamber and quickly injected into the mold cavity to complete the paint filling of the skeleton of the exterior covering parts. The injection pressure is 10-50MPa, the injection speed is 30-270g / s, the curing time is 5-60s, the holding pressure is 10-50MPa, the cooling time is 5-40s, and the paint film thickness is 100-500um.

[0031] The clamping force is lowered, the mold opens, the sample is ejected by the ejector and taken out by the robot arm.

[0032] The injection-molded and painted one-piece product has a Class A surface appearance.

[0033] The automobile exterior covering parts are front and rear bumpers, automobile roofs, doors, engine covers or A, B, C column cross beams.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] The integrated injection molding and painting process for large-size automobile exterior covering parts is reasonably designed. It realizes the integrated injection molding and painting of large-size automobile exterior covering parts through a one-step method. While reducing the manufacturing process, it solves the environmental pollution of traditional painting, realizes lightweight, customized and green manufacturing of automobile exterior covering parts, and meets the high-beat and mass production needs of automobiles. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The following is a brief description of the contents and symbols in the drawings of this specification:

[0037] Figure 1 It is a schematic diagram of the structure of a cover according to an embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram of the surface treatment of the skeleton of the present invention.

[0039] Figure 3 Schematic diagram of the in-mold painting system of the present invention.

[0040] Figure 4 This is a schematic diagram of the injection molding and coating integrated molding process of the present invention.

[0041] In the figure:

[0042] 1. Paint, 2. Injection molded frame middle panel, 3. Injection molded frame middle reinforcement rib structure,

[0043] 21. Methane gas, 22. Air, 23. Gas flow control valve, 24. Combustion chamber, 25. Flame, 26. Sample,

[0044] 31. Slurry A, 32. Slurry B, 33. Mixing head liquid system, 34. Metering pump controller, 35. Paint flow direction, 36. Mixing head. DETAILED DESCRIPTION

[0045] The specific implementation modes of the present invention will be further explained in detail below through the description of embodiments with reference to the accompanying drawings.

[0046] like Figures 1 to 4 As shown, the in-mold injection molding and painting integrated molding process of the large-size exterior covering parts of the automobile includes the following steps:

[0047] 1. Select modified polypropylene pellets and use in-mold injection molding to prepare the skeleton of automobile exterior covering parts;

[0048] 2. Open the mold and rotate the mold 90° counterclockwise, use flame or PP treatment agent to modify the skeleton surface, rotate the mold 90° counterclockwise, close the mold and control the mold temperature at 50-90℃ for 1-30min;

[0049] 3. In-mold painting uses RIM equipment to inject reaction-molded polyester paint. After pressure maintenance and cooling, a soft coating layer is formed on the surface of the exterior cover to achieve in-mold painting of the exterior parts.

[0050] Preferably, the exterior covering frame injection molding in step 1 is carried out in the following specific method:

[0051] 1) Drying and heating the injection molding raw materials to melt;

[0052] 2) Injecting the melted injection molding material into the mold cavity through the injection molding equipment;

[0053] 3) Maintain pressure and cool the mold cavity.

[0054] in,

[0055] The injection molding raw material in 1) is EPDM, talcum powder or glass fiber modified polypropylene granules, wherein the glass fiber modified polypropylene granules can be short glass fiber (0.2-0.6mm) reinforced polypropylene or long glass fiber (5-20mm) reinforced polypropylene, with a fiber content of 10-60% and a linear expansion coefficient of less than 35×10 -6m / (m·K). In order to ensure the rigidity and dimensional stability of the material, long fiber reinforced polypropylene pellets are preferred, with a fiber content of 20%-30%.

[0056] 2) The heating and melting temperature of the injection molding pellets is in the range of 180-300°C, preferably 200-280°C;

[0057] 3) The preferred injection pressure is 800-1000 bar, the holding pressure is 300-500 bar, and the cooling time is 10-20 s;

[0058] Preferably, the surface treatment of the exterior covering parts skeleton in step 2 is specifically as follows: the mold is rotated 90°, a flame spray gun is controlled by a robotic arm, and a flame treatment is performed on the exterior covering parts skeleton sample 26. Preferably, a mixed gas of methane gas 21 and air 22 is used as a combustion source, and the flow rate is controlled by a gas flow control valve 23. The flame 25 is mixed and controlled in a combustion chamber 24. The equivalent ratio is preferably 0.9-1.2, the total flow rate is preferably 100-150L / min, the treatment distance is preferably 75-85mm, and the flame treatment exposure time is 20-30ms.

[0059] Preferably, the in-mold painting process in step 3 is specifically performed as follows:

[0060] 1) Slurry A31 and slurry B32 two-component polyester paint are placed in vacuum storage tanks respectively, mixed by a mixing head liquid system 33, and the flow rate is controlled by a metering pump controller 34. The temperature is preferably controlled at 40-70° C., and the stirring speed is preferably 500-800 r / min;

[0061] 2) Open the mixing head 36, and the material A and the material B are metered into the mixing chamber by the high-pressure pump and are evenly mixed. They are injected into the cavity containing the exterior component skeleton through the mixing head at a certain speed according to the paint flow direction 35, forming a paint surface on the surface of the component. After curing, pressure holding and cooling, the in-mold painting is completed;

[0062] 3) Lower the clamping force, open the mold and take out the injection molding and coating integrated product.

[0063] Preferably, in step 3, 1) the material A is mainly isocyanate, and the component B is a compound of polyester polyol or polyether polyol, catalyst, diamine chain extender, additive, color paste, etc., and the ratio of A to B is preferably 1:1-1:2.

[0064] Preferably, in step 3 (2), the pumping pressure of material A and material B is preferably 20-30 MPa, the pumping speed is preferably 80-120 g / s, the curing time is preferably 10-20 s, the curing temperature, i.e., the mold temperature, is preferably 50-70°C, the holding pressure is preferably 200-300 bar, and the cooling time is preferably 10-20 s.

[0065] Preferably, in step 3) the in-mold painting film thickness is preferably 300-500um.

[0066] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0067] The use of in-mold injection molding and painting integrated molding process can greatly improve the design freedom and meet the functional diversity requirements of parts. By adjusting the injection molding material, surface modification and other methods, the panel tensile strength of 300-800MPa, the component modal of 25-50Hz, the bending stiffness of 45-110N / mm and other performance parameters can be controlled, and the weight is reduced by 20-50% compared with the raw materials.

[0068] The use of injection molding and painting integrated molding process can effectively solve the high equipment requirements, cumbersome processes and environmental pollution of traditional exterior parts preparation, and realize one-step molding of product structure and painting, smooth outer surface, low warping, continuous batch production and recyclability. Single-piece processing takes 3-10 minutes, production cycle efficiency is increased by 30%-60%, energy saving and consumption reduction is 30-50%, and large-size parts can be lightweight and green in one step.

[0069] The in-mold injection and painting integrated molding process can effectively solve the high energy consumption / high emission problems of traditional automobile painting, and realize in-mold painting of large-size parts, with a paint film thickness of 300-500um and A-level surface appearance.

[0070] Through the above combined effects, the preparation process of integrally formed lightweight thermoplastic composite automotive load-bearing exterior parts is greatly shortened, equipment requirements are reduced, and no post-bonding is required. The product has high design freedom and strength. It can be used to prepare automotive front and rear bumpers, automotive roofs, doors, engine covers, or A, B, C column beams and other components to achieve lightweight and green manufacturing of parts.

[0071] like Figure 4 As shown, the molding process of the present invention is: mold closing a-injection molding of the automobile exterior cover frame b-flame modification treatment of the frame surface c-painting the frame in the mold d-opening the mold to take out the piece e; the corresponding cover structure includes paint 1, a panel 2 in the injection molded frame, and a reinforcing rib structure 3 in the injection molded frame; preferably, it specifically includes the following steps:

[0072] Pretreatment of injection molding substrate: Place a certain amount of long glass fiber modified polypropylene pellets in a drying oven for drying, and set the temperature to 90-100℃;

[0073] Injection molding of the skeleton of automobile exterior cover: the pellets are accurately measured and evenly conveyed to the hopper of the injection molding machine by vacuum suction, and the pellets are conveyed to the barrel of the injection molding machine through the controller of the injection molding machine. The pellets are heated, melted, sheared, and mixed into a plastic melt with good fluidity in the injection molding machine. The four-stage temperature range of the injection molding machine barrel is set at 180-300℃; mold closing and filling injection molding, the clamping pressure is 500-2000T, the mold temperature is 25-90℃, and the injection pressure is 500-1000bar; pressure holding, shrinkage compensation and cooling and shaping, the pressure holding pressure is 100-500bar, and the cooling time is 5-40s;

[0074] Surface treatment of the skeleton of automobile exterior covering parts: open the mold and rotate the mold table 90° counterclockwise, use a mechanical arm to flame treat the skeleton of automobile exterior covering parts, the fuel is a mixture of methane and air, the equivalent ratio is 0.5-1.5, the total flow rate is 60-200L / min, the treatment distance is preferably 60-120mm, and the flame treatment exposure time is 10-50ms;

[0075] In-mold painting of the skeleton of automobile exterior covering parts: the mold turntable rotates 90° counterclockwise, the mold is closed and the mold temperature is controlled at 50-100℃, material A and material B are metered by a high-pressure pump and then enter the mixing chamber, where they are evenly mixed by high-speed collision, and then quickly injected into the mold cavity to complete the painting of the skeleton of the exterior covering parts. The injection pressure is 10-50MPa, the injection speed is 30-270g / s, the curing time is 5-60s, the holding pressure is 10-50MPa, the cooling time is 5-40s, and the paint film thickness is 100-500um, which meets the requirements of automobile A-level surface.

[0076] The clamping force is lowered, the mold opens, the sample is ejected by the ejector and taken out by the robot arm.

[0077] Preferred embodiments of the present invention are:

[0078] The automobile exterior parts of the present invention include front and rear bumpers, automobile roofs, doors, engine covers, or A, B, C column beams and other components. This embodiment specifically prepares an engine cover for a new energy vehicle, and the specific steps include:

[0079] (1) Pretreatment of injection molding substrate: Place a certain amount of long glass fiber modified polypropylene pellets in a drying oven for drying at a temperature set at 90-100°C.

[0080] (2) Injection molding of the skeleton of automobile exterior cover parts: The pellets are accurately measured and evenly conveyed to the hopper of the injection molding machine by vacuum suction, and the pellets are conveyed to the barrel of the injection molding machine through the controller of the injection molding machine. The pellets are heated, melted, sheared, and mixed into a plastic melt with good fluidity in the injection molding machine. The four-stage temperature range of the injection molding machine barrel is set at 180-200℃; mold closing and filling injection molding, the clamping pressure is 800-1000T, the mold temperature is 30-50℃, and the injection pressure is 600-800bar; pressure holding, shrinkage compensation and cooling and shaping, the pressure holding pressure is 150-200bar, and the cooling time is 5-10s.

[0081] (3) Surface treatment of the skeleton of automobile exterior covering parts: open the mold and rotate the mold table 90° counterclockwise, use a robotic arm to perform flame treatment on the skeleton of automobile exterior covering parts, the fuel is a mixture of methane and air, the equivalent ratio is 0.5-1.0, the total flow rate is 100L / min, the treatment distance is preferably 60mm, and the flame treatment exposure time is 15ms.

[0082] (4) In-mold painting of the skeleton of automobile exterior covering parts: The mold turntable rotates 90° counterclockwise, the mold is closed and the mold temperature is controlled at 50-100℃, material A and material B are circulated separately before mixing, the mixing head is opened, and material A and material B are metered by high-pressure pumps and enter the mixing chamber. In the mixing chamber, they are evenly mixed by high-speed collision and quickly injected into the mold cavity to complete the painting of the skeleton of the exterior covering parts. The injection pressure is 10-50MPa, the injection speed is 30-270g / s, the curing time is 5-60s, the holding pressure is 10-50MPa, the cooling time is 5-40s, and the paint film thickness is 100-500um, which meets the requirements of automobile A-level surface.

[0083] The large-size automobile exterior covering part injection molding and coating integrated molding process of the present invention realizes the automobile exterior covering part products without shrinkage marks, warping, tensile strength of 300-800MPa, component mode of 25-50Hz, bending stiffness of 45-110N / mm and other performance parameters are controllable from four aspects of material and structural design, surface treatment and molding process, and the weight is reduced by 20-50% compared with the raw materials. It is an excellent choice for lightweight green manufacturing of automobile exterior covering parts.

[0084] The above is only an explanation of the preferred embodiments of the present invention, and the above technical features can be arbitrarily combined to form multiple embodiments of the present invention.

[0085] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A one-piece injection molding and painting process for large-size exterior covering parts of automobiles, characterized in that: The following steps are involved: S1. Select modified polypropylene pellets and prepare the framework of automobile exterior covering parts by in-mold injection molding; S2, open the mold and rotate the mold, use flame or PP treatment agent to modify the skeleton surface, rotate the mold again, close the mold and control the mold temperature at 50-90℃ for 1-30min; S3, in-mold painting uses equipment to inject reaction-molded polyester paint. After pressure maintenance and cooling, a soft coating layer is formed on the surface of the exterior covering part to achieve in-mold painting of the exterior covering part.

2. The process for integrated injection molding and painting of large-size exterior covering parts for automobiles as claimed in claim 1, characterized in that: In step 1, the exterior covering frame injection molding method is as follows: 1) Drying and heating the injection molding raw materials to melt; 2) Injecting the melted injection molding material into the mold cavity through the injection molding equipment; 3) Maintain pressure and cool the mold cavity.

3. The process for integrated injection molding and painting of large-size exterior covering parts for automobiles as claimed in claim 2, characterized in that: The injection molding raw material is EPDM, talcum powder or glass fiber modified polypropylene granules, wherein the glass fiber modified polypropylene granules are 0.2-0.6mm short glass fiber reinforced polypropylene or 5-20mm long glass fiber reinforced polypropylene, the fiber content is 10-60%, and the linear expansion coefficient is less than 35×10 -6 m / (m·K); The heating and melting temperature range of injection molding pellets is 180-300℃; the injection pressure is 800-1000bar, the holding pressure is 300-500bar, and the cooling time is 10-20s.

4. The process for integrated injection molding and painting of large-size exterior covering parts for automobiles as claimed in claim 1, characterized in that: In step S2, the mold is rotated 90 degrees, and a flame spray gun is controlled by a mechanical arm to flame treat the exterior frame. A mixture of methane and air is preferably used as a combustion source, the equivalent ratio is preferably 0.9-1.2, the total flow rate is preferably 100-150 L / min, the treatment distance is preferably 75-85 mm, and the flame treatment exposure time is 20-30 ms.

5. The process for integrated injection molding and painting of large-size exterior covering parts for automobiles as claimed in claim 1, characterized in that: In step S3, the in-mold painting process is as follows: 1) Place the two-component polyester paints A and B in vacuum storage tanks respectively, the temperature is preferably controlled at 40-70° C., and the stirring speed is preferably 500-800 r / min; 2) Open the mixing head, and the A and B materials are metered into the mixing chamber by the high-pressure pump and evenly mixed, and then injected into the cavity containing the exterior component skeleton at a certain speed to form a paint surface on the surface of the component. After curing, pressure holding and cooling, the in-mold painting is completed; 3) Lower the clamping force, open the mold and take out the injection molding and coating integrated product.

6. The process for integrated injection molding and painting of large-size exterior covering parts for automobiles as claimed in claim 5, characterized in that: In step S3, material A is isocyanate, and component B is a composite of polyester polyol or polyether polyol, catalyst, diamine chain extender, auxiliary agent, and color paste, and the ratio of A to B is preferably 1:1-1:

2.

7. The process for integrated injection molding and painting of large-size exterior covering parts for automobiles as claimed in claim 6, characterized in that: In the step S3, the pumping pressure of material A and material B is 20-30 MPa, the pumping speed is 80-120 g / s, the curing time is 10-20 s, the curing temperature, i.e. the mold temperature, is 50-70° C., the holding pressure is 200-300 bar, and the cooling time is 10-20 s; the thickness of the in-mold paint film is 300-500 um.

8. The process for integrated injection molding and painting of large-size exterior covering parts for automobiles as claimed in claim 1, characterized in that: The molding process comprises the following steps: Pretreatment of injection molding substrate: Place a certain amount of long glass fiber modified polypropylene pellets in a drying oven for drying, and set the temperature to 90-100℃; Injection molding of the skeleton of automobile exterior cover: the pellets are accurately measured and evenly conveyed to the hopper of the injection molding machine by vacuum suction, and the pellets are conveyed to the barrel of the injection molding machine through the controller of the injection molding machine. The pellets are heated, melted, sheared, and mixed into a plastic melt with good fluidity in the injection molding machine. The four-stage temperature range of the injection molding machine barrel is set at 180-300℃; mold closing and filling injection molding, the clamping pressure is 500-2000T, the mold temperature is 25-90℃, and the injection pressure is 500-1000bar; pressure holding, shrinkage compensation and cooling and shaping, the pressure holding pressure is 100-500bar, and the cooling time is 5-40s; Surface treatment of the skeleton of automobile exterior covering parts: open the mold and rotate the mold table 90° counterclockwise, use a mechanical arm to flame treat the skeleton of automobile exterior covering parts, the fuel is a mixture of methane and air, the equivalent ratio is 0.5-1.5, the total flow rate is 60-200L / min, the treatment distance is preferably 60-120mm, and the flame treatment exposure time is 10-50ms; In-mold painting of the skeleton of automobile exterior covering parts: the mold turntable rotates 90° counterclockwise, closes the mold and controls the mold temperature at 50-100℃, and the material A and material B are metered by the high-pressure pump and enter the mixing chamber. They are evenly mixed by high-speed collision in the mixing chamber and quickly injected into the mold cavity to complete the paint filling of the skeleton of the exterior covering parts. The injection pressure is 10-50MPa, the injection speed is 30-270g / s, the curing time is 5-60s, the holding pressure is 10-50MPa, the cooling time is 5-40s, and the paint film thickness is 100-500um. The clamping force is lowered, the mold opens, the sample is ejected by the ejector and taken out by the robot arm.

9. The process for integrated injection molding and painting of large-size exterior covering parts for automobiles as claimed in claim 8, characterized in that: The injection-molded and painted one-piece product has a Class A surface appearance.

10. The process for integrated injection molding and painting of large-size exterior covering parts for automobiles as claimed in claim 9, characterized in that: The automobile exterior covering parts are front and rear bumpers, automobile roofs, doors, engine covers or A, B, C column cross beams.

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