JP2001341173A - Method for manufacturing exterior parts for car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacture an exterior part for a car being a molded article having uniform, smooth and good appearance on its surface at a low cost from ground matter of a used coated molded article by a simple process. SOLUTION: Ground matter of a coated polyolefin molded article is melted to be injected in the cavity, which has a heat insulating layer on its surface or has the heat insulating layer and a surface thin-walled metal layer on its surface in this order, of an injection mold to obtain the exterior part for the car such as a bamper or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an automobile exterior part. More specifically, the present invention relates to a method for manufacturing an exterior component for an automobile having a product appearance excellent in smoothness without conspicuous foreign matter on the surface.

[0002]

2. Description of the Related Art In recent years, automotive exterior parts such as bumpers, side moldings, garnishes, over fenders, etc.
2. Description of the Related Art Recycling is often performed in which used products and defective products are crushed, formed into exterior parts, and reused.

However, if the painted bumper or the like is crushed and reused as it is, the coating film does not melt at the time of molding and remains as a foreign substance. This causes a problem that appearance is impaired.

[0004] As a method for solving this problem, conventionally, a method in which a coating film is previously decomposed with an alkali or the like and kneaded, a method in which the coating film is pulverized and then removed with a mesh, and a method in which the coating film is removed by peeling with a roll or the like is used. A method of pulverizing, a method of using a laminated product sandwiched so that a regenerated product is on the inside, and the like have been generally adopted.

[0005] However, these methods have disadvantages in that the steps are complicated and costly. Therefore, there has been a demand for the development of a method for manufacturing a low-cost, good-looking exterior component for automobiles by using a recycled product by a simple process.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a simple process for preparing exterior parts for automobiles having a smooth and good appearance without irregularities on the surface of the molded product from a painted used molded product or a crushed defective product. It is an object of the present invention to provide a method for manufacturing the device at low cost.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have provided a heat insulating layer on the inner surface of a cavity of an injection mold, and performed molding using the mold.
The inventors have found that the above problems can be solved, and have completed the present invention.

[0008] That is, the present invention relates to a method for manufacturing an automobile exterior part including a step of molding a molten resin with an injection mold, wherein a pulverized melt obtained by melting a pulverized product of a coated polyolefin molded product is melted as the molten resin. The present invention provides a method for manufacturing an automotive exterior part, characterized by using a mold provided with a heat insulating layer on an inner surface of a cavity as the injection mold.

Further, the present invention provides the above-mentioned injection molding die,
A method for manufacturing an automotive exterior component, characterized in that a heat insulating layer is provided on an inner surface of a cavity and a thin metal layer is further provided outside the heat insulating layer.

[0010] The present invention also provides the method for producing an automobile exterior component, wherein the pulverized melt contains 10% by volume or less of a solid having a particle size of 3000 µm or less. Further, the present invention provides the method for producing any of the above automotive exterior parts, wherein the coated polyolefin molded article is selected from the group consisting of a bumper, a side molding, a garnish, and an over fender.

Further, the present invention provides a method for manufacturing any of the above-mentioned automotive exterior components, wherein the exterior component is selected from the group consisting of a bumper, a side molding, a garnish, and an over fender. The present invention also provides a method for producing any of the above-mentioned automotive exterior parts, wherein the molding method is selected from the group consisting of injection molding, injection compression molding, two-layer molding, and sandwich molding.

[0012] In order to recycle used polyolefin molded products such as used bumpers and defective products, when crushed, melted and molded again, solid impurities such as crushed paint film remaining in the molten resin are present on the surface of the molded product. Irregularities occur as foreign matter, and the appearance is poor even when painted.However, by molding using a mold having a specific structure having the heat insulating layer of the present invention, the molten resin filled in the cavity under the influence of the heat insulating layer Since the surface of the resin is gradually cooled and the speed of forming a solidified layer is reduced, irregularities due to solid foreign matter remaining in the molten resin are less likely to occur on the surface.

The unevenness slightly remaining on the surface of the molded product is further improved by painting or embossing the surface of the molded product. In addition, when the coating film appearing on the surface of the molded product can be visually observed, the coating and the embossing are similarly improved.

[0014]

Embodiments of the present invention will be described below. The production method of the present invention is based on molding a molten resin containing a pulverized melt of a coated polyolefin molded product using an injection molding die.

(1) Pulverized Melt The pulverized melt in the production method of the present invention is obtained by melting a pulverized product of a coated polyolefin molded article. Examples of the painted polyolefin molded article include interior and exterior parts for automobiles such as used or defective bumpers, side moldings, garnishes, and over fenders. One of the objects of the present invention is to provide a method for effectively recycling such used articles.

The polyolefin resin as a material of the molded article includes a crystalline resin such as a crystalline polyolefin resin. Crystalline polyolefin resin is
By molding with the injection molding die of the present invention, the thickness of the oriented layer (skin layer) of polymer molecules on the surface of the molded product is reduced and the surface hardness is improved, so that the effects of the present invention can be sufficiently exhibited. it can.

The molten resin may be a non-polyolefin resin (polystyrene, polyamide resin, ABS resin, P
VC resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc. may be mixed, but such non-polyolefin resin is preferably avoided as much as possible to maintain the quality of the final molded product. When contamination is apparent, a suitable compatibilizing agent (acid-modified polypropylene, SEBS, etc.) can be added to prevent deterioration of quality.

Specific examples of the polyolefin resin include:
Ethylene homopolymer such as low pressure polyethylene, medium pressure polyethylene, high pressure polyethylene, linear low density polyethylene or ethylene resin such as ethylene / propylene copolymer; polypropylene homopolymer such as stereoregular polypropylene, or propylene Propylene resins such as ethylene copolymers; and other α-olefin resins such as stereoregular poly-1-butene and stereoregular poly-4-methyl-1-pentene.

Among them, it is preferable to use an ethylene resin such as an ethylene homopolymer or an ethylene / propylene copolymer, and a propylene resin such as a propylene homopolymer or a propylene / ethylene copolymer.

The polyolefin resin may contain an inorganic filler or a rubber component. Specifically, examples of the inorganic filler include calcium oxide, magnesium oxide, silica, titanium oxide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, basic magnesium carbonate, calcium carbonate, barium sulfate, talc, clay, and mica. Whisker such as zeolite, zeolite, fibrous potassium titanate, fibrous magnesium oxalate, and fibrous aluminum borate; carbon fiber; glass fiber; As rubber components, ethylene-propylene copolymer rubber (EPM), ethylene / 1-butene copolymer rubber, ethylene / propylene / 1-butene copolymer rubber, ethylene / propylene / non-conjugated diene copolymer rubber (EPDM), ethylene • 1-butene / non-conjugated diene copolymer rubber, polyolefin-based rubber such as ethylene / propylene / 1-butene / non-conjugated diene copolymer rubber, and styrene-based rubber such as styrene / butadiene copolymer. In addition, pigments and pigment dispersants for normal coloring, antioxidants, antistatic agents, light stabilizers, ultraviolet absorbers, neutralizing agents, metal corrosion inhibitors, lubricants, flame retardants, nucleating agents, dispersants, A workability stabilizer, a fluidity improver and the like may be blended.

The coated portion of the coated polyolefin molded article of the present invention may be formed by various methods such as applying a paint to the surface of the molded article, or forming a coating film on the surface of the molded article by insert molding, in-mold molding or the like. Provided by the method. When a paint is applied, the paint is not particularly limited as long as it is a paint used for coating ordinary automobile exterior parts and other polyolefin molded products. Specific examples include urethane-based and acrylic melamine-based paints. When a coating film is formed by insert molding or the like, examples of a coating film material such as an insert film include polyethylene terephthalate and tetrafluoroethylene.

The molded article is mainly an injection molded article obtained by injection molding, but is not limited thereto, and may be an extruded molded article, a blow molded article, a press molded article, a hollow injection molded article, or the like. It may be a molded product.

The pulverization of the coated polyolefin molded article can be carried out by a conventionally known method. Specifically, a method such as mechanical pulverization is used. The coated polyolefin molded article may be pulverized after washing, or may be pulverized without washing.

In the present invention, the pulverized product of such a coated polyolefin molded product is melted to obtain a pulverized molten product, and a molten resin containing optional components to be added as required is provided for molding. In this case, after adding the necessary components to the pulverized product as needed, it can be directly introduced into a molding machine and subjected to molding without a molten resin. If necessary, the pulverized product may be blended with an additive component, melt-kneaded, pelletized once, and then subjected to injection molding. The method of melting the pulverized material is not particularly limited, and is performed by melt-kneading using a conventional kneading machine, for example, a single-screw or twin-screw extruder, a Banbury mixer, a super mixer, a roll, a Brabender plastograph, a kneader, or the like. .

Here, the pulverized melt has a particle size of 3000.
The solid matter having a size of not more than 10 μm, preferably 0.0
It is contained in an amount of 1% by volume or more and 3% by volume or less. In other words, many of the painted portions in the painted polyolefin molded product remain in the pulverized melt as solid foreign matter without being melted even after the above-mentioned melt-kneading after the pulverization. The above-mentioned solid is mainly a pulverized coating film remaining in the pulverized melt as described above, but is not limited to this, and various other solid impurities remaining without being melted in the pulverized melt also apply. In the present invention, in particular, in the molding of a molten resin containing a pulverized melt containing a solid having such a particle size in the above ratio, the effect is sufficiently exerted, and irregularities due to the solid on the surface of the molded product are not noticeable. A smooth finish can be achieved. In addition, the solid matter referred to herein does not include a solid component derived from an additive such as an inorganic filler newly added to the molten resin and an inorganic filler added to the pulverized melt in the production method of the present invention. .

(2) Molten resin The molten resin used in the present invention includes a pulverized melt of the above-mentioned coated polyolefin molded article, to which a polyolefin resin and / or an additive is blended if necessary. It is.

Here, as the polyolefin resin to be blended as required, a resin selected from the above-mentioned polyolefin resins used for a painted polyolefin molded article can be mentioned. That is, the virgin molding material before being subjected to molding can be used by being mixed with the pulverized melt, which is a used or defective recycled resin material.
When such a virgin material is used, its mixing ratio is not particularly limited because it is also affected by economics and the like, but is preferably about 1 to 95% by weight based on the total amount of the molten resin.

[0028] The additives used as needed here include inorganic fillers and rubber components. Specifically, examples of the inorganic filler include calcium oxide, magnesium oxide, silica, titanium oxide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, basic magnesium carbonate, calcium carbonate, barium sulfate, talc, clay, and mica. Whisker, such as zeolite, zeolite, fibrous potassium titanate, fibrous magnesium oxalate, and fibrous aluminum borate; carbon fiber; glass fiber; When the inorganic filler is added, the total amount of the inorganic filler after addition, including the one already contained in the above-mentioned pulverized material, is the polyolefin resin 1
It is added so as to be generally 60 parts by weight or less, preferably 30 parts by weight or less based on 00 parts by weight. Within this range, the effects of the present invention can be remarkably exhibited.

As rubber components, ethylene-propylene copolymer rubber (EPM), ethylene / 1-butene copolymer rubber, ethylene / propylene / 1-butene copolymer rubber, ethylene / propylene / non-conjugated diene copolymer rubber (EPD)
M), polyolefin-based rubber such as ethylene / 1-butene / non-conjugated diene copolymer rubber, ethylene / propylene / 1-butene / non-conjugated diene copolymer rubber, and styrene-based rubber such as styrene / butadiene copolymer. Among them, it is preferable to use a polyolefin rubber such as EPM and EPDM. These rubber components
A Mooney viscosity (ML _{1 + 4} ) measured at 100 ° C. in the range of usually 10 to 200, preferably 30 to 150 is used. When the rubber component is added, the total amount of the rubber component after addition, including that already contained in the pulverized material, is generally 60 parts by weight or less, preferably 5 to 40 parts by weight, based on 100 parts by weight of the polyolefin resin. It should be less than weight parts. Within this range, the effects of the present invention can be remarkably exhibited.

As other additives, pigments and pigment dispersants for coloring are usually used in many cases. However, in order to further improve the performance, an antioxidant, an antistatic agent, and the like other than the above components may be used as necessary. Agents, light stabilizers, ultraviolet absorbers, neutralizing agents, metal corrosion inhibitors, lubricants, flame retardants, nucleating agents, dispersants, processability stabilizers, flow improvers and the like can also be added.

(3) Mold for Injection Molding The mold for injection molding used in the present invention is used for injection molding of ordinary thermoplastic resin, and has at least an upper mold so that the mold can be opened after molding. It is formed from a lower mold and a cavity is formed when these two molds are combined. Then, a product is formed by injection-filling the thermoplastic resin into the cavity. The upper mold and the lower mold are usually formed mainly of a metal material such as an alloy such as stainless steel containing iron or iron as a main component, an aluminum alloy, a nickel alloy, a zinc alloy, and a copper alloy.

The injection mold of the present invention is characterized in that a heat insulating layer is provided on the inner surface of the cavity of the mold in contact with the filled thermoplastic resin.

[Heat Insulation Layer] The heat insulation layer may be made of any material as long as it has a low thermal conductivity having a heat insulating effect and does not soften even when filled with a molten resin. Preferably, the thermal conductivity is 1 × 10
⁻⁴ to 30 × 10 ⁻⁴ cal / cm · sec · ° C., more preferably 1 × 10 ^{−4 to} 5 × 10 ⁻⁴ cal / cm ·
sec. ° C. is used. When the thermal conductivity is within the above range, even if the molten resin contains a solid substance, the surface of the molded article is unlikely to have irregularities and a smooth surface can be obtained. Also,
No flow marks, welds, silver streaks, uneven gloss, sink marks, swirl marks during foam molding, etc.
Good product appearance is obtained and surface hardness is also improved.

Examples of such a material include a heat-resistant plastic, a plastic composite material, a ceramic material having a low thermal conductivity such as zirconia, glass, and an enamel. Examples of heat-resistant plastics include epoxy resin, polyimide, polybenzimidazole, polyimidazopyrrolone, polyetheretherketone, polyphenylene sulfide, polyethylene terephthalate, polytetrafluoroethylene, polycarbonate, and nylon. And a reinforcing material. Of these, heat-resistant plastics are preferred, and epoxy resins are preferred.

When the material is a thermoplastic resin, its melting point or softening point is preferably 150 ° C. or more, more preferably 150 to 260 ° C. If the melting point or softening point is within the above range, a high appearance can be achieved.

The number of heat insulating layers is not limited to one, and a plurality of layers of different materials may be provided. The thickness of the entire heat insulating layer can be appropriately determined in consideration of the size of the molded product, required accuracy, productivity, and the like, and is specifically preferably from 5 to 2000 μm, particularly preferably from 50 to 1000 μm. If the thickness is less than the above range, high appearance may not be achieved, and if the thickness exceeds the range, cooling may take too much time and productivity may be reduced.

[Surface Thin Metal Layer] The injection mold used in the present invention may have only the above-mentioned heat insulating layer on the cavity surface, but more preferably, the outside of the above-mentioned heat insulating layer. And those further provided with a thin metal layer on the surface. That is, in this case, in order from the outside to the inside of the cavity inner surface of the mold, the configuration is such that the surface is a thin metal layer / a heat insulating layer / the mold body. Therefore,
The surface thin metal layer is formed on the mold surface on the side in contact with the thermoplastic resin. Examples of the material of the surface thin metal layer include steel, chromium, nickel, and copper.

The surface thin metal layer is not limited to one layer.
A plurality of layers of different materials may be provided. The thickness of the entire surface thin metal layer is preferably from 5 to 2000 μm, particularly preferably from 50 to 1000 μm. Within this range, it is preferable in terms of durability and grain workability. By providing the thin metal layer on the surface in this way, the durability of the mold is greatly improved.

In the injection mold used in the present invention, the entire inner surface of the cavity may be formed of a heat insulating layer or a heat insulating layer and a surface thin metal layer. It may have a nest of a predetermined structure provided with a surface layer composed of a heat insulating layer and a surface thin metal layer. The surface layer portion is provided on the nested base material so that the surface thin metal layer forms a surface in contact with the thermoplastic resin. Further, by making the thickness of the heat insulating layer of the insert into an inclined structure, there is no difference in transferability between the insert and the mold body, and the appearance of the product is further improved. In addition, in the molding step using such a mold, it is not necessary to lengthen the molding cycle and the industrial productivity is excellent, and the cost is excellent because no expensive mold is required.

[Other Layers] In addition to the above-mentioned thin metal layer and heat insulating layer, various layers may be further laminated on the inner surface of the cavity of the injection mold according to the present invention, if necessary. . Specifically, a nickel layer, an iron layer, and the like can be given.

[Production of Mold] The heat insulating layer is formed on the injection molding mold body of the present invention by, for example, spraying the resin onto the inner surface of the mold when the material is resin. It can be performed by a method such as sticking to the inner surface of the mold.

As a method for providing a thin metal layer on the surface of the heat insulating layer, for example, electroforming, machining, plating and the like can be mentioned.

(4) Production of Exterior Parts for Automobiles In the method for producing exterior parts for automobiles of the present invention, a pulverized product of the above-mentioned coated polyolefin molded product is used as a raw material, and the above-described present invention is applied using a molten resin obtained by melting this. Is molded using the injection molding die described above.

[Preparation of Raw Materials] The raw materials are prepared by adding the above-mentioned virgin materials, additives and the like to the pulverized product of the above-mentioned coated polyolefin molded product as required and sufficiently kneading. After melt-kneading, it may be directly used for molding, or may be once pelletized and then subjected to molding.

When performing foam molding, a foaming agent is further added. Examples of the foaming agent include inorganic compounds such as ammonium carbonate and sodium bicarbonate, and organic compounds such as azo compounds, sulfohydrazide compounds, nitroso compounds, and azide compounds.

The melt kneading is preferably carried out by kneading using an ordinary kneader, for example, a single-screw or twin-screw extruder, a Banbury mixer, a super mixer, a roll, a Brabender plastograph, a kneader, etc., and more preferably. Is kneaded using an extruder, particularly a twin-screw extruder.
The kneading conditions can be appropriately selected depending on the resin used, but are generally 180 to 260 ° C. under normal pressure, preferably 190 to 260 ° C.
Performed at 230 ° C.

[Molding] A molding method using the above-mentioned injection mold can be appropriately selected from injection molding, injection compression molding, two-layer molding, sandwich molding and the like, depending on a desired product.

In the case of injection molding, an injection molding machine is used, and the resin temperature is generally 180 to 250 ° C., and 300 to 1,300.
The injection is performed under the conditions of an injection pressure of kg / cm ^{2 and} a mold temperature of 20 to 60 ° C., and these conditions can be appropriately adjusted according to the size of the molded product.

In injection compression (injection press) molding, the mold is opened to a desired thickness of the molded product or more, and after the molten resin is injected, the mold is closed to the desired thickness of the molded product (clamping). It is a molding method. The mold clamping force is generally about 5 to 4500 t.

The two-layer molding is a method in which a thermoplastic resin having different properties is injection-molded into two layers to form a composite. For example, a material constituting a core material is first injected from an injection unit on the primary side to form a composite. After molding the core material by the injection molding method, the mold on the moving side is inverted and moved to the secondary side, and then the material constituting the skin is injected from the secondary side injection unit to form the core material. There is a method of injection molding a skin on the surface. As a result, the production process of the composite can be streamlined, and the composite can be rapidly molded.

In the sandwich molding, the material constituting the surface layer is first injected through the same sprue by using two injection units such as a multicolor molding machine, and a solidified film is formed by cooling on the mold surface. This is a method of injecting constituent materials from another cylinder to obtain a molded article having a sandwich structure in which an inner layer is sandwiched between surface layers. Thereby, for example, when a foamed molded product is to be obtained, a foamed molded product having an improved surface smoothness and the like and having a good appearance can be obtained by using a foamed material as the inner layer and a non-foamed material having a gloss or the like for the surface layer. Can be

(5) Automotive Exterior Parts The automobile exterior parts of the present invention obtained as described above are not particularly limited, but are preferably bumpers,
It is selected from the group consisting of side moldings, garnishes, and over fenders. If the method of the present invention is applied to such an exterior component, a product having a smooth and good appearance without irregularities due to foreign matter can be obtained even after the molded product is coated.

[0053]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

The molding machine, mold, molding conditions, and evaluation method used in this example are as follows. (1) Molding machine “IS170” manufactured by Toshiba Corporation

(2) Die (test piece for evaluating unevenness) 350 × 100 × 3 mm, surface thin metal layer; chrome plating treatment [Layer structure of die] Dies (heat insulating layer used in Examples 1 to 5) Heat insulation type): steel / epoxy resin layer (thickness 500μ)
m) / nickel-chromium layer / Fe grain layer (total thickness of nickel-chromium layer and Fe grain layer = 300 μm) Mold used in Comparative Examples 1 to 5: steel material

(3) Molding conditions Cylinder temperature: 220 ° C. Mold temperature: 40 ° C. Injection time: 3-5 seconds Cooling time: 20 seconds Injection pressure: 600 kg / cm ² Clamping force: 170 t (injection molding)

(4) Evaluation Method A test piece for evaluating unevenness was injection-molded with the above-mentioned evaluation die, and the state of unevenness on the surface was visually evaluated according to the following criteria. ◎: No irregularities (product-producible level) ○: Inconspicuous irregularities (product-producible level) △: irregularities ×: marked irregularities

[0058]

Examples 1 to 5 Propylene block copolymer (copolymer of propylene and ethylene, MFR = 30 g / 10
Minutes: abbreviated as “PP”, a rubber component (ethylene-propylene copolymer rubber, for later addition: Mooney viscosity (ML1 +
4) = 60) and an inorganic filler (talc) were blended, and a test piece for coating was molded using the raw material as a raw material, and was coated with an acrylic melamine-based paint. Next, the coated test piece is mechanically pulverized, and the coated material A (the maximum particle size of the coating film is 1000 μm or less; 0.6% by volume) and B (the maximum particle size of the coating film is 300 μm)
(The amount of solids having a particle size of 3000 μm or less at the time of melting is 1.6% by volume).

The obtained materials A and B and the PP were blended in the proportions shown in Table 1, and a test piece for evaluating unevenness was formed by the above-mentioned molding machine, mold (insulation mold having a heat insulation layer) and molding conditions. Then, the appearance was evaluated. Further, the test piece is painted (acryl melamine-based paint, thickness 5
0 μm), and the coating appearance was evaluated.

[0060]

Comparative Examples 1 to 5 Test pieces for evaluating unevenness were molded in the same manner as in Examples 1 to 5 except that a conventional mold having no heat insulating layer was used as a molding die, and evaluation before and after coating was performed. Table 2 shows the mixing ratios of the raw materials A and B and PP, and the evaluation results.

[0061]

[Table 1]

[0062]

[Table 2]

[0063]

According to the present invention, even when a coated polyolefin molded article such as a used bumper is pulverized and reused, it is formed by solid impurities such as a pulverized coating film remaining in the molten resin. It is possible to manufacture an automobile exterior part having no unevenness on the product surface and having a smooth and good appearance, and it is possible to efficiently and efficiently recycle an automobile part by a simple process at a low cost. .

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 31:30 B29L 31:30 (72) Inventor Masaaki Isoi 1 Toho-cho, Yokkaichi-shi, Mie Japan Nippon Polychem F-term in the Material Development Center Co., Ltd. (Reference) 4F202 AA03 AA50 AC01 AH23 AH24 AJ02 AJ09 AJ13 AR12 CA11 CB01 CB22 CD21 CK11 4F206 AA03 AA50 AC01 AH23 AH24 AJ02 AJ09 AJ13 AR12 JA03 JA07 JB22 JF01 JL02 JM01

Claims (6)

[Claims] 1. A method for manufacturing an automotive exterior part including a step of molding a molten resin with an injection molding die, wherein the molten resin includes a pulverized melt obtained by melting a pulverized product of a coated polyolefin molded product. And a method of manufacturing an exterior part for an automobile, wherein a mold provided with a heat insulating layer on the inner surface of a cavity is used as the injection mold. 2. The injection mold according to claim 1, wherein a heat insulating layer is provided on an inner surface of the cavity, and a thin metal layer is further provided outside the heat insulating layer. Manufacturing method of automotive exterior parts. 3. The method for manufacturing an exterior part for an automobile according to claim 1, wherein the pulverized melt contains 10% by volume or less of a solid having a particle size of 3000 μm or less. 4. The method for producing an exterior component for an automobile according to claim 1, wherein said coated polyolefin molded product is selected from the group consisting of a bumper, a side molding, a garnish, and an over fender. 5. The method of manufacturing an automotive exterior component according to claim 1, wherein the exterior component is selected from the group consisting of a bumper, a side molding, a garnish, and an over fender. 6. The method of manufacturing an automotive exterior component according to claim 1, wherein the molding method is selected from the group consisting of injection molding, injection compression molding, two-layer molding, and sandwich molding.