KR20100010345A - Plastic complex materials with high weatherability and impact resistance - Google Patents

Abstract

PURPOSE: A plastic composite material having the excellent weathering performance and shock resistance is provided to use as an outer panel for a tail gate of a vehicle by using a multi-layer sheet by using a multi-layer sheet composed of a polymethyl methacrylate resin layer and an acrylonitrile-butadiene-styrene resin layer. CONSTITUTION: A plastic composite material having the excellent weathering performance and shock resistance contains polymethyl methacrylate resin of 3 ~ 8 weight%, polyvinylidene fluoride resin of 3 ~ 8 weight%, and acrylonitrile-butadiene-styrene resin of 84 ~ 94 weight%. The mixed resin layer of the polymethyl methacrylate resin and the polyvinylidene fluoride resin and the acrylonitrile-butadiene-styrene resin layer are laminated successively.

Description

Plastic complex materials with high weatherability and impact resistance}

The present invention relates to a plastic composite material excellent in weather resistance and impact resistance, which can replace a steel material.

Tailgate is a part that is located between the side outer panel and the bumper, and is used as an exterior part as well as a structural member among the automobile body shells, which are currently steel materials. The main roles that tailgates have to play include structural stiffness, maintaining constant gaps and gaps with surrounding components, and matching colors. The tailgate is divided into two parts, an outer panel and an inner panel, and in the case of a steel panel, the outer panel and the inner panel are integrated by welding. The outer panel is simple in shape, but the inner panel has a complex shape for rigidity, so it has to go through several molding processes.

Multi-layered sheets made of polymethyl methacrylate resin layer and acrylonitrile-butadiene-styrene resin layer are used for soundproof walls or canopies, which are weather-resistant to ultraviolet rays of the sun, scratch resistance to withstand scratches of external stimuli, and external Characteristics such as impact resistance against impact should be particularly good. Existing multilayer sheets are mostly transparent sheets, and there are no examples where the application field is applied to automobiles.

On the other hand, long-fiber reinforced polypropylene is used in parts requiring rigidity, and has recently been used in engine undercovers, bumper back beams, and the like instead of glass fiber matted thermoplastic (GMT) applied to existing parts.

The present invention is to provide a plastic composite material that can replace the steel material used in the manufacture of the vehicle body shell.

In particular, the present invention relates to a method for improving the physical properties of a multilayer sheet composed of a polymethyl methacrylate resin layer and an acrylonitrile-butadiene-styrene resin layer to be suitable as a vehicle tailgate outer panel material, and a vehicle tailgate using the multilayer sheet. Provided is a method of making an outer panel.

The present invention also provides an automotive tailgate assembly manufactured by using a plastic composite material using an inner panel made of long fiber reinforced polypropylene together with the automotive tailgate outer panel, and a method of manufacturing the same.

The multilayer sheet for exterior panel of the automotive tailgate of the present invention is 3 to 8% by weight of polymethyl methacrylate resin, 3 to 8% by weight of polyvinylidene fluoride resin and 84 to 94% by weight of acrylonitrile-butadiene And a styrene resin, wherein a mixed resin layer of the polymethyl methacrylate resin and the polyvinylidene fluoride resin and an acrylonitrile-butadiene-styrene resin layer are sequentially stacked.

In addition, the multilayer sheet for outer panel of the automotive tailgate of the present invention is characterized in that it further comprises a pigment in the acrylonitrile-butadiene-styrene resin layer.

In addition, the outer panel of the automotive tailgate of the present invention is characterized by being manufactured by molding the multilayer sheet.

In addition, the automotive tailgate assembly of the present invention is characterized in that the vehicle tailgate outer panel and the car tailgate inner panel manufactured by injection molding long fiber reinforced polypropylene are bonded with a urethane-based adhesive.

In addition, the method for manufacturing a vehicle tailgate exterior panel of the present invention is a polymethyl methacrylate resin and 3 to 8% by weight of polyvinylidene fluoride resin after mixing 3 to 8% by weight of the polymethyl methacrylate and Preparing a multilayer sheet by sequentially laminating a polyvinylidene fluoride mixed resin and 84 to 94% by weight of acrylonitrile-butadiene-styrene resin; And heating and softening the multi-layer sheet, fixing the mold on the mold having a plurality of holes for vacuum suction, and discharging the air inside the mold through the vacuum suction hole to form a vehicle tailgate outer panel due to a difference in pressure and atmospheric pressure in the mold. Forming to; characterized in that it comprises a.

In addition, the method of manufacturing a vehicle tailgate assembly of the present invention comprises the steps of manufacturing the vehicle tailgate outer panel; Car tailgate inner panel is molded by injection molding of long-fiber-reinforced polypropylene into a mold having a molding space in the shape of an inner panel of a car tailgate that protrudes a plurality of box-shaped structures having rib patterns and inner spaces to compensate for rigidity on the inner surface. Manufacturing step; And integrally adhering to the portions of the inner panel and the outer panel which are in contact with each other by using a urethane-based adhesive.

By using the multilayer sheet of the present invention, the vehicle tailgate inner panel, the vehicle tailgate assembly and a method of manufacturing the same, the following effects can be achieved.

(1) The effect of public relations can be seen by applying multi-layer sheets, which have not been used in the existing automobile field, to the body shell.

(2) By replacing both the interior and exterior panels of the automotive tailgate with plastic, it is possible to expect fuel efficiency improvement through weight reduction.

(3) In manufacturing the inner panel and the outer panel, it can save a lot of money through cheap mold cost and short production period.

(4) Since the multi-layered sheet itself implements color, the cost can be reduced by eliminating the painting process.

(5) It can be effectively applied to the vehicle models of small quantity production.

(6) It can be effectively applied to small quantity production models with unusual design.

Hereinafter, the present invention will be described in more detail with examples, but the present invention is not limited by the following examples.

The multilayer sheet for exterior panel of the automotive tailgate of the present invention is 3 to 8% by weight of polymethyl methacrylate resin, 3 to 8% by weight of polyvinylidene fluoride resin and 84 to 94% by weight of acrylonitrile-butadiene -Including styrene resin, when the amount of the polyvinylidene fluoride resin is less than 3% by weight does not appear to improve the weather resistance and impact resistance, and when it exceeds 8% by weight, the viscosity increases due to the increase in the molecular weight flow during sheet production Difficult to mold because of poor properties.

In addition, when the amount of the polymethyl methacrylate resin is less than 3% by weight, a flow mark may occur during extrusion, and when it exceeds 8% by weight, cracks may be formed.

When the amount of acrylonitrile-butadiene-styrene resin is less than 84% by weight, the impact strength of the multilayer sheet decreases, thereby decreasing physical properties. When the amount of acrylonitrile-butadiene-styrene resin is less than 84% by weight, a flow mark is applied to the surface layer polymethylmethacrylate resin. It is preferable to keep the above range because there is a risk of occurrence.

In order to confirm the effect of addition of polyvinylidene fluoride resin on polymethyl methacrylate resin, 50% by weight of a specimen prepared from polymethyl methacrylate resin (PMMA), polymethyl methacrylate and polyvinylidene fluoride The weather resistance of specimens (PMMA / PVDF) prepared from the mixed resin was compared.

Each prepared specimen was placed in a weather resistant chamber for 500 hours, 1000 hours, 1500 hours, and 2000 hours, and the change of ΔE was observed with a weather-o-meter, and the results are shown in Table 1. ΔE is an indicator for evaluating weather resistance. The smaller the value is, the better the weather resistance is.

time △ E PMMA PMMA / PVDF 500 0.393 1.452 1000 4.570 1.202 1500 3.068 1.949 2000 4.755 1.820

The results of Table 1 are shown graphically in FIG. From the above results, it can be seen that weather resistance is much improved by adding polyvinylidene fluoride to the polymethyl methacrylate resin. Specimen of polymethacrylate resin increases ΔE value with time, and after 1000 hours, △ E value of automobile exterior parts far exceeds 3, but △ E when polyvinylidene fluoride is added It can be seen that the value is less than the value of polymethylmethacrylate.

In the multilayer sheet of the present invention, a mixed resin layer of a polymethyl methacrylate resin and a polyvinylidene fluoride resin and an acrylonitrile-butadiene-styrene resin layer are sequentially stacked, and a polymethyl methacrylate resin and a polyvinylidene fluoride The mixed resin layer of the ride resin serves to complement impact resistance and weather resistance, and the acrylonitrile-butadiene-styrene resin layer imparts mechanical strength as a substrate. In addition, a pigment may be added to the acrylonitrile-butadiene-styrene resin layer, and in this case, a separate coating process may be deleted, thereby saving costs.

In the multilayer sheet of the present invention, the thickness of each layer is 0.2 to 1 mm, preferably 0.3 to 0.8 mm, and most preferably about 0, of the mixed resin layer of the polymethylmethacrylate resin and the polyvinylidene fluoride resin. 5 mm, and the acrylonitrile-butadiene-styrene resin layer has a thickness of 2 to 4 mm, preferably 2.2 to 3 mm, most preferably about 2.5 mm.

The manufacturing method of the multilayer sheet of this invention is shown in FIG. (a) Feed polymethyl methacrylate (PMMA) resin and acrylonitrile-butadiene-styrene (ABS) resin to which polyvinylidene fluoride was added to the extruders 11 and 12 maintained above the melting temperature of each resin. Supplying to the block (13) to sequentially laminate the polymethyl methacrylate resin layer and acrylonitrile-butadiene-styrene resin layer and (b) the polymethyl methacrylate resin layer and acryl Processing the ronitrile-butadiene-styrene resin layer onto a sheet in die 14 to produce a multilayer sheet.

When the temperature of the polymethylmethacrylate (PMMA) resin to which polyvinylidene fluoride is added in the process (a) is maintained below 255 ° C, the viscosity and flowability of the acrylonitrile-butadiene-styrene (ABS) resin Due to the difference in MI), there is a possibility that a flow mark or the like may occur during extrusion, and when the temperature exceeds 260 ° C., the resin may be decomposed in the extruder due to the high extrusion temperature. In addition, when the temperature of the acrylonitrile-butadiene-styrene (ABS) resin is lower than 230 ° C. when the polymethyl methacrylate (PMMA) resin and the acrylonitrile-butadiene-styrene (ABS) resin are combined, the polymethylmethacrylate (PMMA) resin is used. ) Because of the difference between resin and viscosity and flowability (MI), flow mark may be generated during extrusion and acrylonitrile-butadiene-styrene (ABS) resin may be decomposed in extruder if it exceeds 235 ℃. It is preferably maintained in the temperature range and combined with the polymethylmethacrylate (PMMA) resin through an extruder.

Meanwhile, in the present invention, the thickness control of each layer of the multilayer sheet can be controlled by the extrusion amount of the resin flowing into the feed block from each extruder, so that the amount of resin introduced is always uniform to maintain the thickness of each layer of the multilayer sheet. It must be introduced and the amount of extrusion precisely controlled.

In order to confirm that the multilayer sheet of the present invention is applicable to automotive tailgate exterior panels, 5% by weight of polymethylmethacrylate resin, 5% by weight of polyvinylidene fluoride resin and 90% by weight of acrylonitrile-butadiene The multi-layered sheet standard specimen consisting of styrene resin, the mixed resin layer of polymethylmethacrylate resin and polyvinylidene fluoride resin is 0.5 mm, and the acrylonitrile-butadiene-styrene resin layer is 2.5 mm. Prepared by the method described to measure the appearance quality, chipping resistance, gloss and weather resistance, and then compared with the target value of the steel material.

First, a photograph of a sample in which white, red and black pigments are appropriately added to the acrylonitrile-butadiene-styrene resin is shown in FIG. 3.

Tolerability evaluation is a visual evaluation method that checks the surface condition by imagining unpaved roads and sprays small grains on the surface. It is divided into 8 grades from 1st to 8th grade, and it means that the surface condition is superior to 8th grade. In the first grade, the surface has a lot of granules, so there are many dents. In the eighth grade, there are not many grains and the dents are not many. The evaluation standard of steel used for the exterior of the car body is now 7th grade and the multi-layer sheet is 8th grade, which is superior to steel.

Gloss was measured using a meter called a glossmeter, and the glossmeter may have a maximum value of 100 as a method of measuring the amount of reflected light by projecting light. The multilayer sheet of the present invention satisfied the criterion of 85 or more.

Appearance quality is measured by measuring instrument called Wave Scan DOI, and evaluation of surface brightness, turbidity, and roughness of surface is based on CF value expressed by composite index. Through the optical sensor, it is possible to measure the overall appearance quality by showing the surface quality of gloss, clarity and surface roughness as a numerical value by using the surface reflection of light of the coating film. Surface roughness refers to the degree of reflection of light in various directions on rough surfaces in the form of orange peels, and can be measured by averaging the spectrum represented by the intensity of light reflected at each point as the measuring device passes through the surface of the material. Sensitivity is the degree to which the clear mirror image of the surface fits, and the material with the finer texture, the higher the sharpness. Gloss is obtained by measuring the intensity at which light irradiated at a particular angle is reflected off the surface.

Appearance quality evaluation results The multilayer sheet of the present invention satisfied the standard as 84.5.

The weather resistance evaluation measured ΔE values at 2000 hours in the same manner as described above, and the multilayer sheet of the present invention met the standard value of 1.6.

Evaluation item unit Target value (steel material) Measure 1. Chipping resistance - 7 or higher 8th grade 2. polished - 85 or more 85 3. Weather resistance △ E 3 or less 1.6 4. Appearance Quality CF 60 or more 84.5

Next, a method of manufacturing the automotive tailgate outer panel of the present invention using the multilayer sheet of the present invention will be described.

It is preferable to use a thermoforming method for producing the automotive tailgate outer panel from the multilayer sheet of the present invention. The thermoforming method has the advantages of low cost of equipment and mold, various materials of mold, especially short cycle time, initial cost is only 1/4 to 1/5 of injection molding, and much simpler than injection molding. Because of its structure, processing cost is low and processing time is also short. An example of such a thermoforming method is illustrated in FIG. 4.

In the present invention, the thermoforming method for forming a multilayer sheet into a vehicle tailgate outer panel is first softened by heating the multilayer sheet, and then fixing the sheet on the perforated mold for vacuum suction to move the mold or sheet to the sheet. After the mold is stamped, the air inside the mold is rapidly discharged through the vacuum hole, and the mold is formed at atmospheric pressure due to the internal pressure drop. The manufactured sheet is removed from the mold, and the edge is trimmed to obtain the final product.

FIG. 5 is a mold photograph for thermoforming an aluminum material manufactured for manufacturing a plastic tailgate outer panel according to an embodiment of the present invention, and FIG. 6 is thermoforming through a mold of FIG. 5 using a multilayer sheet of the present invention. This is a picture of the exterior panel of the car tailgate before trimming.

Next, a vehicle tailgate inner panel of the present invention will be described.

Long-fiber reinforced polypropylene used for forming the automotive tailgate inner panel of the present invention is applied to the pultrusion process to produce a pellet shape that is easy to injection molding by impregnating thermoplastic polypropylene with fibers of the same length in the pellets. After injection molding, the final product is reinforced with non-oriented fibers of the mesh structure and has excellent mechanical properties, dimensional stability, and heat resistance. In addition, when compared with the general short-fiber reinforced polypropylene and physical properties, glass fibers of 10 to 20 times the length of the impact strength and fracture strength is improved. In addition, the low anisotropy of the glass fiber can contribute to increase the impact strength and fracture strength. The specific components and composition ratios of the long fiber reinforced polypropylene composites are (a) 40 to 60% by weight (about 50% by weight) of glass fibers, (b) 35 to 50% by weight (about 43.5%) by weight of polypropylene, and (c) couples. 2 to 6% by weight of the ring agent (about 3% by weight), (d) 2 to 6% by weight (about 3.5% by weight) of antioxidants, carbon black, lubricants and the like.

Long-fiber reinforced polypropylene of the present invention has a weight reduction effect compared to glass fiber matted thermoplastic (GMT) and can be cheap in material costs, and also can adjust the glass fiber content to be impregnated and contains a general short fiber It has excellent physical properties such as better long-term durability, very low deformation, and very high impact strength.

In addition, automotive tailgate inner panel has a complicated structure of steel inner plate for rigidity, so product design for structural reinforcement is important for plastic design. To this end, it is preferable to form a rib pattern for stiffness supplementation on the inner surface or to protrude a plurality of box-shaped structures having an inner space. In this way, the thickness of the product is increased to 3.0 mm to reinforce the rigidity, and ribs are added to each part to further reinforce the rigidity.In order to compensate for the bending and torsional rigidity, a steel reinforce bracket is inserted into the rear window frame part. The model corresponding to one embodiment of the vehicle tailgate inner panel designed with the concept of molding is shown in FIG.

7 has a shape designed as shown in FIG. 7 to predict stiffness during molding through stiffness analysis. The stiffness analysis is conducted in two ways: bending stiffness and torsion stiffness. The bending stiffness gives a condition for fixing the mounting portion between the plastic tailgate and the actual vehicle, and when the lower portion is pressed in the same direction with 10Kg force, the bending stiffness is pressed, and pressing in different directions becomes a torsional rigidity measuring method. This is the actual tailgate stiffness measurement method and it is implemented through the constraint in the analysis. The results interpreted through the implemented conditions are shown in Table 3.

Although bending and torsional stiffness analysis shows a slight decrease in performance compared to steel, it is expected that there is no abnormality because the analysis value is included in the steel tailgate stiffness reference value (HMC spec). Specified values of the steel tailgate stiffness test are bending stiffness 2.0 mm ↓ and torsional stiffness 3.5 mm ↓.

Next, the molding analysis was performed through an injection molding analysis program called "Mold Flow" in order to set the optimum mold structure and molding conditions before the mold design of the plasticized designed tailgate. Through the molding analysis, the optimal number and location of gates were determined and reflected in the mold design and fabrication. The shape of the injection mold thus produced is shown in FIG. 8.

In the injection process of the long fiber-reinforced polypropylene, which is a material of the inner panel of the automobile tailgate of the present invention, the shear force of the long fiber is received from the molten resin flowing during the injection molding process, and the breakage due to mutual collision between the fibers in the flow path. As a result, the length of the fiber is shortened. This is a factor that halves the advantages of long fiber-reinforced polypropylene, and the most important factor is the method of preserving the fiber length as much as possible in the injection molding process. In order to minimize breakage of the long fiber reinforced polypropylene, a dedicated screw was manufactured and molded. The shape of the manufactured screw is shown in FIG. 9, and the differences from the general injection screw are summarized in Table 4.

LFT Injection Screw General injection molding screw Screw length ratio 2: 4: 4 2: 2: 6 L / D 21 18 to 22 Compression Ratio 2: 3 2: 5 Pitch 150-250 75 Metering depth 10.7 2 ~ 3 Front radius R3 R3 ~ R5 Rear radius R12 R3 ~ R5 Screw diameter φ150 Incorrect according to the injection machine specification

The table shows the difference between the specification of the general injection molding screw and the specification of the screw for injection of the long fiber composite, at least to prevent breakage of the long fiber. In detail, the ratio of the screw length is reduced to prevent the long fiber breakage by reducing the rapid change, and the larger the L / D dimension is, the more the plasticization is advantageous, but the lower the fiber length is set in order to reduce the glass fiber breakage. If the pitch is small, a large number of threads are made, which is advantageous for plasticization but is set large because long fiber breakage occurs. Rear Radius is better to prevent long fiber breakage during plasticization, but if it is too large, high pressure is required to feed the raw material, and long fiber breakage may occur. Steel rayforce brackets are injected with the inner panel using the insert molding method. The insert molding method has the advantage that the bracket can be fixed to the mold before injection, and the bracket is covered by molten resin and fixed inside the injection molding before the injection. Therefore, the bracket can be fixed without additional bonding process. . The shape of the insert molded steel rain force bracket molded article with the inner panel is shown in the left figure of FIG. 10, and the shape of the insert molded steel rain force bracket only is shown in the right figure of FIG. 10.

The final plastic tailgate assembly can be fabricated through assembly work using the outer panels, inner panels and other components fabricated in this way. The adhesive strength can be increased by performing plasma treatment on the adhesive surface of the inner panel before bonding the inner panel and the outer panel.

The general assembly sequence is to join the various steel brackets to the inner panel using an adhesive, and to assemble the outer panel to the completed inner panel structure using an adhesive. In this case, it is preferable to use a two-component polyurethane-based structural adhesive when bonding brackets to the inner panel because elastic polyurethane is advantageous in consideration of vibration during driving, etc. It is advantageous to shorten the curing time.

The lower panel of the jig has an inner panel, and the upper panel holds the outer panel through the air, and the upper panel is lowered while matching the outer surface of the inner panel with the outer panel. After aligning the outer surface of the outer panel with the inner panel, use the weight of the top plate to maintain the adhesion surface and increase the adhesive strength. After maintaining the adhesive surface for about one day in the assembly jig can be obtained car tailgate assembly of the present invention (see Figure 11)

The vehicle tailgate assembly of the present invention manufactured as described above was mounted on a click vehicle of Hyundai Motor, and actual vehicle evaluation was performed.

The complete vehicle tailgate assembly was mounted on a vehicle to evaluate the mounting performance of measuring gaps and steps with peripheral components. The results are shown in Table 5, and the target values for gaps and flushes were achieved.

 location Gap (mm) Flush (mm) goal Measure goal Measure One 5.5 2.5 3.5 2.5 2 2.5 3.0 3 2.8 2.8 4 2.5 3.2 Average 5.5 2.6 3.5 2.9

In addition, the torsional and bending stiffness were measured while the vehicle was mounted on the vehicle, and 20,000 evaluations of the opening and closing durability, which is the HMC test criterion, were performed and the evaluation results are shown in Table 6.

division goal result Deformation amount ( mm ) ( LH Of RH  Average) flex 3.5 2.2 torsion 12 10.5 Opening and closing 20,000 times clear

As a result of the evaluation of the actual vehicle, the plastic tailgate assembly of the present invention had no problem when mounted on an automobile, and it is likely to be used as one of the good methods for producing a small quantity of various kinds of vehicles.

FIG. 1 compares the weather resistance of specimens prepared from polymethyl methacrylate resin (PMMA) and specimens prepared from resin containing 50% by weight of polymethyl methacrylate and polyvinylidene fluoride (PMMA / PVDF). It is a graph.

Figure 2 shows a method of manufacturing a multilayer sheet of the present invention.

Figure 3 shows a photograph of the multi-layered sheet of the present invention prepared by putting a proper amount of white, red, and black pigment in acetonitrile-butadiene-styrene resin, respectively.

Figure 4 shows the process of forming the automotive tailgate outer panel using the thermoforming method from the multilayer sheet of the present invention.

FIG. 5 is a mold photograph for thermoforming an aluminum material manufactured for manufacturing a plastic tailgate outer panel according to one embodiment of the present invention.

FIG. 6 is a photograph of a vehicle tailgate outer panel before trimming manufactured by thermoforming through the mold of FIG. 5 using the multilayer sheet of the present invention.

Figure 7 shows a model corresponding to one embodiment of the vehicle tailgate inner panel of the present invention.

FIG. 8 is an injection mold corresponding to an embodiment of the present invention in which a molding analysis is performed through an injection molding analysis program called mold flow to determine an optimal number of gates and positions. .

Figure 9 illustrates one embodiment of an injection-only screw used to minimize breaks in the long fiber reinforced polypropylene of the present invention.

10 is a form of the insert-shaped steel rain force bracket molded article with the inner panel of an embodiment of the present invention, the right view is a form of insert-molded steel rain force bracket only.

Figure 11 illustrates one embodiment of an automotive tailgate assembly of the present invention.

Claims (6)

3 to 8 weight percent polymethylmethacrylate resin, 3 to 8 weight percent polyvinylidene fluoride resin and 84 to 94 weight percent acrylonitrile-butadiene-styrene resin, A multilayer sheet for exterior panels of automotive tailgates, in which a mixed resin layer of the polymethyl methacrylate resin and a polyvinylidene fluoride resin and an acrylonitrile-butadiene-styrene resin layer are sequentially stacked. The multilayer sheet for exterior panel of an automotive tailgate according to claim 1, further comprising a pigment in the acrylonitrile-butadiene-styrene resin layer. An outer panel of an automotive tailgate manufactured by molding the multilayer sheet of claim 1. The vehicle tailgate assembly of claim 3, wherein the vehicle tailgate inner panel manufactured by injection molding long-fiber reinforced polypropylene is bonded with a urethane-based adhesive. After mixing 3 to 8% by weight of polymethyl methacrylate resin and 3 to 8% by weight of polyvinylidene fluoride resin, the polymethyl methacrylate and polyvinylidene fluoride mixed resin and 84 to 94% by weight Sequentially laminating acrylonitrile-butadiene-styrene resin to prepare a multilayer sheet; And After heating and softening the multilayer sheet, it is fixed on a mold having a plurality of holes for vacuum suction, and the air inside the mold is discharged through the vacuum suction hole to form a vehicle tailgate outer panel due to a difference in pressure and atmospheric pressure in the mold. Molding; Method for manufacturing a car tailgate outer panel comprising a. Manufacturing an automotive tailgate exterior panel of claim 5; Manufacturing an automotive tailgate inner panel by injection molding a long fiber-reinforced polypropylene into a mold having a molding space of an automotive tailgate inner panel shape having a rib pattern for stiffness supplementation on an inner side thereof; And Integrally bonding a portion of the inner panel and the outer panel to each other by using a urethane-based adhesive; Method of manufacturing a car tailgate assembly comprising a.

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