PP exterior trimming part with improved adhesive force and good appearance, production method of PP exterior trimming part and vehicle

Abstract

The invention provides a PP exterior trimming part with improved adhesive force and good appearance, a production method of the PP exterior trimming part and a vehicle. The PP exterior trimming part is characterized in that a separation film containing a treatment layer is placed in a mold A, the separation film is tightly attached to a cavity through vacuum adsorption, the treatment layer is a surface, a base material is subjected to injection molding after the mold A is closed, and the separation film can be separated after the mold is opened; and then the paint film layer covers the surface of the treatment layer and is combined with the surface of the treatment layer in a mold B through an in-mold painting process, and finally the integrated structural part is formed. According to the invention, the base material plays a mechanical support role, the treatment layer is a treatment agent layer containing polar groups and is attached to the separation membrane, and the separation membrane not only can protect a treatment agent from being in contact with a mold, but also is very easy to peel off; and the paint film layer has a good appearance effect. Compared with the prior art, the production process provided by the invention has the advantages that rapid production can be met, the surface of a non-polar base material is not damaged, surface modification of a non-polar material can be realized, the product has good appearance, a mold is not corroded, and the production process is feasible.

Description

Technical Field

[0001] The present invention belongs to the field of automobile exterior decoration production, and particularly relates to a PP exterior decoration with improved adhesion and good appearance, a production method thereof, and a vehicle. Background Art

[0002] Common automotive exterior parts are primarily painted, and the appearance requirements are quite stringent, particularly regarding the orange peel index (Lw≤20; Sw≤25; DOI≥80). Orange peel parameters are related to numerous factors, such as substrate roughness, paint film thickness, and process. Therefore, fiber-reinforced substrates (such as PP-GF30 / PP-LGF30 and other materials) have exposed fibers and a low yield rate, making traditional spray coating impossible. Flame-treated surfaces, however, have more exposed glass fibers, making it even more difficult to meet the orange peel requirements for a good appearance for painted parts. Therefore, flame treatment requires the use of putty, adding multiple steps. Even with PP+EPDM-T30 materials, many exterior parts with poor paint finishes after flame treatment ultimately require rework and polishing.

[0003] In addition, although the in-mold painting process can obtain good-looking parts, they are all polar substrates. For the in-mold painting of non-polar substrates, this process cannot be used to obtain parts. In the prior art, such as the patent with publication number CN 119682111 A published on March 25, 2025, a large-scale automobile exterior cover injection molding and painting integrated molding process is disclosed. Although flame treatment or treatment agent is used to treat non-polar materials, the process is used to obtain parts. However, on the one hand, flame or plasma treatment has high investment costs, potential safety risks, and is not conducive to production rhythm; on the other hand, flame treatment will increase and damage the surface roughness, which is not conducive to obtaining a good appearance of the parts. Although the treatment agent can be coated on the PP surface to achieve good adhesion, the drying time is too long (tens of minutes), and the treatment agent on the substrate surface is uneven under the action of gravity, resulting in uneven adhesion. In addition, the treatment agent must be applied on the mold, which will corrode the mold and reduce the service life of the mold. The treatment agent application process generally requires manual handling, which will also have a significant impact on the production rhythm and cannot meet the actual production process and environmental protection requirements.

[0004] Therefore, it is very necessary to provide a production method that can not only improve adhesion and good appearance but also does not affect the production rhythm. Summary of the Invention

[0005] The purpose of the present invention is to provide a PP exterior decoration part with improved adhesion and good appearance and a production method thereof. The present invention places a separation membrane with a treatment layer on one side on the surface of the mold cavity, and injects PP after in-mold adsorption to achieve the addition of a treatment layer on the surface of the PP substrate; then, the in-mold painting process is used to form a paint film layer on the surface of the non-polar PP substrate, overcoming the shortcomings of flame treatment and treatment processes, not only improving adhesion and good appearance, but also not affecting the production rhythm, and meeting the process requirements of actual production.

[0006] Another object of the present invention is to provide a vehicle comprising the above-mentioned PP exterior parts with improved adhesion and good appearance.

[0007] The specific technical solutions of the present invention are as follows:

[0008] The present invention provides a method for producing a PP exterior trim with improved adhesion and good appearance, comprising the following steps:

[0009] 1) Place a separation membrane with a treated layer on one side on the surface of the mold cavity A, and place the other side of the separation membrane against the cavity. After vacuum adsorption, the other side of the separation membrane is in close contact with the surface of the mold cavity A;

[0010] 2) Close mold A and obtain the PP substrate by injection molding or hot pressing;

[0011] 3) Opening mold A, peeling off the separation film to obtain a substrate with a treated layer on the surface;

[0012] 4) placing the substrate with the treated layer on the surface prepared in step 4) into mold B and closing the mold, and obtaining a paint film layer on the surface of the treated layer through an in-mold painting process;

[0013] 5) Open the B mold to obtain PP exterior parts with improved adhesion and good appearance.

[0014] In step 1), the treated layer has a dyne value of ≥36 dyne / cm and a thickness of 0.010-0.500 mm, preferably 0.038-0.150 mm;

[0015] In step 1), the separation membrane with a treatment layer on one side means that the treatment agent is coated on one side of the separation membrane, and the other side of the separation membrane is not coated with the treatment layer; the other side not coated with the treatment layer is attached to the surface of the mold cavity A and will not corrode the mold.

[0016] The treatment agent is selected from any one or more of PP treatment agent, modified nano-SiO2 grafting treatment agent, siloxane coupling agent, silica gel treatment agent or silicone treatment agent, and contains a large number of polar groups such as hydroxyl, carboxyl, ester bond, carbonyl and the like.

[0017] Further preferably, silicone oil or silicone coating is first performed on one side of the separation membrane, and then the treatment agent is applied; this is more conducive to separation; the silicone oil or silicone used is a commercially available product and can be diluted with an organic solvent before coating.

[0018] The separation membrane in step 1) is selected from a paper substrate, a cloth substrate or a plastic film;

[0019] The paper substrate is selected from high-strength and tear-resistant kraft paper, tissue paper, grid paper, tin foil, and silicone oil paper; the cloth substrate is selected from wear-resistant and flexible non-woven fabric or cotton cloth; the plastic film is selected from high-temperature resistant polyimide PI film, PET film, or PTFE film;

[0020] The thickness of the separation membrane is 0.025 to 5 mm, preferably 0.5 to 1.5 mm.

[0021] More preferably, the preparation method of the separation membrane having a treatment layer on one side in step 1) is:

[0022] a. The nano-SiO2 was dispersed in mineral oil and ultrasonically treated for 30 minutes to obtain a mixture;

[0023] b. The resulting mixture is applied to one side of a PET film and cured;

[0024] In the above preparation method, nano-SiO2 is dispersed in mineral oil at a mass fraction of 0.05%-0.5%, preferably 0.1%-0.3%. The mineral oil is a saturated alkane or aromatic hydrocarbon, preferably a saturated alkane such as liquid paraffin. Curing is performed at 150°C for 30-60 minutes, during which the mineral oil evaporates, forming pores and a porous layer. The separation membrane prepared has a treatment layer on one side, which is a nano-SiO2-reinforced treatment layer. The nano-SiO2-reinforced treatment agent is used. When the PP lamination treatment agent is injection-molded, the nanoparticles are embedded in the PP surface, enhancing mechanical adhesion.

[0025] Alternatively, the preparation method of the separation membrane having a treatment layer on one side in step 1) is:

[0026] Add silane coupling agent to acrylic adhesive, apply it on PI film substrate, and dry it.

[0027] In the above preparation, the acrylic adhesive is selected from 3M models DP810NS, DP8825NS or DP8410NS, and the silane coupling agent is selected from siloxane coupling agent KH-550; the weight proportion of the silane coupling agent is 2%.

[0028] The separation membrane with a treatment layer on one side prepared above is a separation membrane with a siloxane coupling agent treatment layer on one side, and adopts a reactive silane coupling agent coating. When subsequently attached to a PP substrate, the silane reacts with the surface hydroxyl group to form a covalent bond.

[0029] Alternatively, the preparation method of the separation membrane having a treatment layer on one side in step 1) is:

[0030] First, a low-concentration PP treatment agent is coated on the surface of the separation membrane, and after solidification, a high-concentration PP treatment agent is coated on the surface of the separation membrane, and after solidification, the separation membrane is obtained;

[0031] In the above preparation, the PP treating agent is selected from model KY-P20-0004-1, KY-T21-1806K or QF301-81793-1; the solvents of the low-concentration and high-concentration PP treating agents are both organic solvents, such as butyl acetate or isopropyl alcohol; the mass concentration of the low-concentration PP treating agent is 5%, and the mass concentration of the high-concentration PP treating agent is 20%. The curing conditions of the low-concentration PP treating agent are: 30-100°C, preferably 60-80°C, and the curing time is 1min-30min, preferably 1-10min; the curing conditions of the high-concentration PP treating agent are: 30-100°C, preferably 60-80°C, and the curing time is 1min-30min, preferably 1-10min; the separation membrane with a treatment layer on one side prepared above is a separation membrane with a PP treating agent layer on one side; using the PP treating agent, when the injection-molded PP substrate is adhered to the treating agent, it is slowly released and diffused, and embedded in the surface and interior of the PP.

[0032] Alternatively, the preparation method of the separation membrane having a treatment layer on one side in step 1) is:

[0033] Apply silicone solution treatment agent on PI film substrate and cure at high temperature to form a stable coating;

[0034] In the above preparation method, the solvent of the silicone solution treating agent is an alkyl or aromatic hydrocarbon solvent, a ketone solvent, an ester solvent, or an epoxy resin diluent, preferably ethyl acetate; the concentration of the silicone solution is 5-20%, and the high temperature curing condition is 280°C for 2 hours;

[0035] The separation membrane having a treatment layer on one side prepared above uses a high temperature resistant treatment agent (silicone treatment agent).

[0036] In step 1), the vacuum adsorption and vacuum molding pressure are -0.08 to -0.1 MPa, so that the other side of the separation membrane is closely attached to the surface of the mold cavity A;

[0037] In step 2), the PP substrate is selected from modified PP materials, including one or more modified materials such as mineral powder reinforcement, rubber toughening, fiber reinforcement, and other resin reinforcement. More preferably, it is various modified materials containing PP, such as mineral powder reinforced PP-T20, rubber and mineral powder reinforced and toughened PP+EPDM-T30, glass fiber reinforced PP-GF30, straw reinforced PP, carbon fiber reinforced PP-CF10, PPO / PP alloy;

[0038] In step 2), the PP substrate can be formed into various structures according to design requirements through processes such as hot pressing and injection molding. The thickness of the PP substrate is 1.0-3.0 mm, and the thickness is preferably 2.0-2.8 mm depending on the actual part size.

[0039] In step 2), the injection molding parameters of the PP substrate are: injection molding temperature of 200-250°C, injection molding pressure of 80-130 MPa, and mold temperature of 30-65°C. The specific parameters vary slightly depending on the material.

[0040] In step 4), the in-mold painting process is mainly a reactive molding material, which can be one or more of polyurethane (PU), polydicyclopentadiene (PDCPD) or polyurea (PUa) materials;

[0041] The thickness of the paint film layer is 0.3mm-10mm. The larger the part, the thicker the paint film. The paint film color can be transparent or various colors as needed.

[0042] In step 3), when polyurethane (PU) is used, the injection pressure is 10-30 MPa; the injection flow rate is 1-200 g / s; the reaction time is 10 s-10 min, preferably 10 s-200 s; and the mold temperature is 40-80° C.;

[0043] Alternatively, in step 3), when polydicyclopentadiene (PDCPD) is used, the injection pressure is 3-15 MPa; the injection flow rate is 700-2200 g / s; the injection time is 0.5-100 s; and the mold temperature is 40-80° C.;

[0044] Alternatively, in step 3), when polyurea (PUa) is used, the injection pressure is 10-30 MPa; the mold temperature is 70-180° C., preferably 60-90° C.; the reaction time is 1 s-10 h, preferably 10 s-200 s; and the injection flow rate is 1-200 g / s.

[0045] The present invention provides a PP exterior decorative part with improved adhesion and good appearance, which is produced by adopting the above-mentioned production method.

[0046] The present invention provides a vehicle comprising the above-mentioned PP exterior trim with improved adhesion and good appearance.

[0047] The present invention requires at least two sets of molds: Mold A (mold with a surface treatment layer) + Mold B (mold for in-mold painting). First, a separation membrane containing a treatment layer is placed in Mold A. The separation membrane is tightly attached to the mold cavity through vacuum adsorption, with the treatment layer as the surface. After Mold A is closed, the substrate is injected, and the separation membrane can be removed after the mold is opened. Then, through the in-mold painting process, the paint film layer is covered and combined with the surface of the treatment layer in Mold B, ultimately forming an integrated structural part. In the present invention, the substrate serves as a mechanical support, and the treatment layer is a treatment agent layer containing polar groups, which is attached to the separation membrane. The separation membrane not only protects the treatment agent from contact with the mold but also is very easy to peel off. The paint film layer is used to achieve a good appearance.

[0048] Because the surface of the substrate material, especially the fiber-reinforced substrate surface, will increase in roughness extremely rapidly after flame treatment, destroying the original smooth surface, and then directly combining with the paint layer, it will affect the surface state, especially the thinner the paint film layer, the greater the impact. The treated layer of the present invention is only a thin layer adhered to the surface of the substrate, so it will not have much impact on the surface of the paint film. In addition, whether the paint film is transparent or has color, it will not affect the surface state. And good polar groups can deepen the combination with PU and enhance adhesion. Compared with the traditional surface treatment agent on the solid PP surface, which requires a long time to penetrate, react, and corrode the non-polar substrate surface, the surface treatment agent of the present invention is in direct contact with the flowing non-polar substrate (such as PP) at high temperature, and has better bonding performance (mechanical bite, chemical bonding, molecular penetration, etc. are better).

[0049] Compared with the prior art, the present invention provides a method for producing PP exterior parts with improved adhesion and good appearance, which is mainly used to replace various non-metallic spray-painted electroplated parts and is mainly used for the production of exterior parts. It addresses the shortcomings of ordinary plastic parts spray-painted parts and in-mold painted parts in the prior art, especially the surface deterioration of fiber-reinforced materials after flame treatment, which makes it impossible to obtain parts with good appearance (orange peel), and the treatment with treatment agents destroys the production rhythm, which cannot meet the process requirements of actual use. The present invention provides a method that can meet the requirements of rapid production without damaging the surface of non-polar substrates, and can also achieve surface modification of non-polar materials. The product has a good appearance and is a practical production process. The present invention utilizes in-mold adsorption and post-injection molding of PP to add a treatment layer on the surface of various PP substrates; and then utilizes the in-mold painting process to form a paint film layer on the surface of the non-polar PP substrate, thereby overcoming the shortcomings of the above-mentioned process and meeting the process requirements of actual production. The actual orange peel test of the sample was verified, indicating that this part design and manufacturing method can meet the appearance requirements of various PP substrates, and the adhesion effect is better than that of flame treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of the preparation process of the present invention;

[0051] Figure 2 The appearance of the substrate after surface treatment in Example 1. The treatment agent in Example 1 is better than the flame treatment. (a-a1) untreated; (b-b1) flame treatment; (c-c1) treatment agent treatment (Example 1);

[0052] Figure 3 The contact angles of the substrates before and after surface treatment in Example 1 are shown. The surface treatment agent in Example 1 is more effective than the flame treatment. (a) Untreated PP + EPDM-T30; (b) PP + EPDM-T30 flame-treated; (c) PP + EPDM-T30 treated with the treatment agent in Example 1.

[0053] Figure 4 The interface between PP+EPDM-T30 and PU on the surface of Example 1 shows that the treatment agent effect in Example 1 is better than that in flame treatment; (a, a1, a2) PP+EPDM-T30 interface after flame treatment; (b, b1, b2) PP+EPDM-T30 interface after treatment with the treatment agent in Example 1;

[0054] Figure 5 The actual adhesion of the surface of PP+EPDM-T30 combined with PU in Example 1 is shown in the cross-sectional surface states: (a) the effect after flame treatment; (b) the effect of treatment with a treatment agent. DETAILED DESCRIPTION

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0056] Example 1

[0057] A method for producing PP exterior parts with improved adhesion and good appearance, taking PP+EPDM-T30 as an injection molding substrate and a PU paint film as an example, the production method comprises the following steps:

[0058] 1) Using PP treating agent KY-P20-0004-1 as the solute and butyl acetate as the solvent, 5% and 20% PP treating agents were prepared. A 1 mm thick PI film was first coated with 5% PP treating agent and cured at 70°C for 10 minutes to a thickness of 0.05 mm. Then, 20% PP treating agent was applied and cured at 80°C for 15 minutes to a total thickness of 0.1 mm. The resulting 1 mm thick PI separation membrane with a 0.1 mm thick treatment layer (PP treating agent layer) on one side was placed in mold A. A vacuum forming pressure of -0.09 MPa was applied to ensure that the other side of the separation membrane completely fit into the mold cavity of mold A.

[0059] 2) Close the mold and use an injection molding machine to form a PP+EPDM-T30 substrate at an injection temperature of 220°C, an injection pressure of 120 MPa, a mold temperature of 30°C, and a substrate thickness of 2.0 mm;

[0060] 3) Opening mold A, obtaining the substrate with the treated layer on the surface, and transferring it to mold B;

[0061] 3) Mold B was closed and a PU in-mold painting process was performed with an injection pressure of 20 MPa, an injection flow rate of 70 g / s, a reaction time of 120 s, and a mold temperature of 70° C. to obtain a 0.7 mm thick paint film layer on the surface of the treated layer.

[0062] 4) Finally, the mold is opened to obtain the structural parts.

[0063] In addition, an untreated substrate was prepared as a comparison by following the same method and parameters as in Example 1, except that step 1) in Example 1 was not performed.

[0064] A flame-treated substrate was prepared for comparison by following the same method and parameters as in Example 1, except that step 1) in Example 1 was not performed; and after step 2), a methane and air mixture was used as the combustion source, with an equivalent ratio of 1.0, a total flow rate of 110 L / min, a treatment distance of 80 mm, and a flame treatment exposure time of 20 ms; and subsequent steps were performed as in Example 1.

[0065] Figure 2 The surface appearance of the substrate after surface treatment in Example 1 is superior to that of flame treatment. (a-a1) is untreated; (b-b1) is flame treated; and (c-c1) is treated with a treatment agent (Example 1). The surface roughness of the flame-treated substrate deteriorates, making it difficult to produce high-quality parts using spray painting or in-mold painting. The roughness of the substrate treated with the treatment agent in Example 1 shows little change, making it more suitable for producing high-quality parts using spray painting or in-mold painting.

[0066] Figure 3: The contact angles of the substrate before and after surface treatment in Example 1; (a) untreated PP+EPDM-T30; (b) PP+EPDM-T30 flame-treated; (c) PP+EPDM-T30 treated with the treatment agent in Example 1; the increased surface polarity after treatment with the treatment agent in Example 1 is beneficial to the subsequent combination with PU, and the surface treatment agent treatment effect of the method in Example 1 is better than that of flame treatment.

[0067] Figure 4 The interface between PP+EPDM-T30 and PU on the surface of Example 1, (a, a1, a2) PP+EPDM-T30 interface after flame treatment; (b, b1, b2) PP+EPDM-T30 interface after treatment with the treatment agent of Example 1; Figure 4 It can be seen that the surface treatment agent has good bonding performance with both PP and PU, and the treatment effect of the treatment agent provided by the method of Example 1 is better than that of the flame treatment;

[0068] Figure 5 The actual adhesion of the surface of PP+EPDM-T30 combined with PU in Example 1 is shown in the cross-sectional surface state, (a) the effect after flame treatment; (b) the effect of treatment with the treatment agent in Example 1. It can be seen that the effect of the treatment agent in Example 1 is better than the flame effect.

[0069] The product of Example 1 and the flame-treated product were subjected to an orange peel test, and the results are shown in Table 1;

[0070] The product of Example 1, the flame-treated product and the untreated product were subjected to group tests, and the results are shown in Table 2 (tested using XPS-x-ray electron spectroscopy).

[0071] Table 1 Orange peel test results of the surface of PP reinforced material combined with PU after flame treatment and treatment in Example 1

[0072]

[0073]

[0074] As can be seen from Table 1, the present invention can solve the problem of poor appearance due to flame treatment and the like, and can enhance adhesion, with better bonding and smaller peeling areas.

[0075] Table 2 Polar group ratio after PP+EPDM-T30 treatment

[0076]

[0077] As can be seen from Table 2, the changes in surface polar groups after treatment in Example 1 show that the treatment agent has more polar groups.

[0078] Example 2

[0079] A method for producing PP exterior parts with improved adhesion and good appearance, taking a PP+EPDM-T30 unidirectional tape with a thickness of 2 mm and a PU paint film with a thickness of 0.5 mm as an example, the production method comprises the following steps:

[0080] 1) Using PP treating agent KY-T21-1806K as the solute and butyl acetate as the solvent, a 5% PP treating agent and a 20% PP treating agent were prepared; 5% PP treating agent was first applied to one surface of a 1 mm thick PI film and cured at 65°C for 8 minutes to a thickness of 0.04 mm; then 20% PP treating agent was applied and cured at 85°C for 18 minutes to a total PP treating agent layer thickness of 0.12 mm; the resulting 1.2 mm thick PI separation membrane containing a 0.12 mm thick treatment layer (PP treating agent layer) on one side was placed in a hot pressing mold with a vacuum forming pressure of -0.1 MPa, ensuring that the other side of the separation membrane completely fits into the hot pressing mold cavity.

[0081] 2) Preheat the PP+EPDM-T30 unidirectional strip to 130°C for 30 seconds, then place it in a hot pressing mold and heat press it in a hot pressing machine. The hot pressing mold temperature is 80°C; the PP+EPDM-T30 unidirectional strip has a thickness of 2mm.

[0082] 3) opening the hot pressing mold, obtaining the substrate with the surface treated layer, and transferring it to the in-mold painting mold;

[0083] 4) The in-mold painting mold was closed, and a PU in-mold painting process was performed with an injection pressure of 20 MPa, an injection flow rate of 50 g / s, a reaction time of 110 s, and a mold temperature of 70° C. to obtain a reaction-molded 0.5 mm thick paint film layer on the surface of the treated layer.

[0084] 5) Finally, the mold is opened to obtain the structural parts.

[0085] A flame-treated substrate was prepared for comparison by following the same method and parameters as in Example 2, except that step 1) in Example 1 was not performed; and after step 2), a methane and air mixture was used as the combustion source, with an equivalent ratio of 1.1, a total flow rate of 120 L / min, a treatment distance of 75 mm, and a flame treatment exposure time of 25 ms; and subsequent steps were performed according to Example 1.

[0086] The product of Example 2 and the flame-treated product were subjected to an orange peel test, and the results are shown in Table 3;

[0087] Table 3 Orange peel test results of the surface of PP reinforced material combined with PU after flame treatment and treatment in Example 2

[0088]

[0089] In summary, compared with general spray-painted exterior parts, the present invention has a simple product process, high manufacturing efficiency, no environmental pollution, and meets the actual production rhythm requirements; compared with in-mold painting and traditional spray-painted parts, when the substrate does not need flame treatment, it can meet the good appearance manufacturing of various non-polar materials (especially fiber reinforcement) without the need for various polishing post-processing processes; compared with substrate flame treatment, it has better adhesion effect and does not affect the continuity of the production process. The present invention can overcome the shortcomings of the prior art in overcoming the low efficiency surface modification of the in-mold painting process, the inability to meet the actual production needs, the increase in investment space and costs, the damage to the product surface state, the large carbon emissions, the mold deformation and corrosion, and the product surface adhesion, and has broad application prospects.

[0090] The above embodiments are described to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for producing PP exterior parts with improved adhesion and good appearance, characterized in that: The production method comprises the following steps: 1) Place a separation membrane with a treated layer on one side on the surface of the mold cavity A, and place the other side of the separation membrane against the cavity. After vacuum adsorption, the other side of the separation membrane is in close contact with the surface of the mold cavity A; 2) Close mold A and obtain the PP substrate by injection molding or hot pressing; 3) Opening mold A, peeling off the separation film to obtain a substrate with a treated layer on the surface; 4) placing the substrate with the treated layer on the surface prepared in step 4) into mold B and closing the mold, and obtaining a paint film layer on the surface of the treated layer through an in-mold painting process; 5) Open the B mold to obtain PP exterior parts with improved adhesion and good appearance.

2. The production method according to claim 1, characterized in that In step 1), the treated layer has a dyne value of ≥36 dyne / cm and a thickness of 0.010-0.500 mm.

3. The production method according to claim 1 or 2, characterized in that In step 1), the separation membrane having a treatment layer on one side means that the treatment agent is coated on one side of the separation membrane.

4. The production method according to claim 3, characterized in that The treatment agent is selected from any one or more of a PPP treatment agent, a modified nano-SiO2 grafting treatment agent, a siloxane coupling agent, a silica gel treatment agent or a silicone treatment agent.

5. The production method according to claim 1, characterized in that The separation membrane in step 1) is selected from a paper substrate, a cloth substrate or a plastic film.

6. The production method according to claim 1 or 5, characterized in that The thickness of the separation membrane is 0.025 to 5 mm.

7. The production method according to claim 1, characterized in that In step 2), the thickness of the PP substrate is 1.0-3.0 mm.

8. The production method according to claim 1, characterized in that In step 3), the thickness of the paint film layer is 0.3 mm to 10 mm.

9. A PP exterior part with improved adhesion and good appearance, characterized in that: The product is obtained by the production method according to any one of claims 1 to 8.

10. A vehicle, characterized in that: The vehicle includes the PP exterior part with improved adhesion and good appearance as claimed in claim 9.

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