CN117881817A - Decorative plastic part and method for producing such a part - Google Patents

Abstract

The invention relates to a decorative plastic part having a coating for producing a colored corrosion-resistant metal layer, comprising a substrate (a) made of plastic, on which a first layer (c) is deposited and a zinc, zinc-nickel or nickel layer (e) is applied. The surface is coloured and sealed (f). The invention also relates to a method for producing such a decorative plastic part.

Description

Decorative plastic part and method for producing such a part

The invention relates to a component produced by plastic injection molding, comprising a substrate made of plastic, with a coating for producing a coloured corrosion-resistant metal layer. Methods of producing such components are also described.

In the expression coating is understood to mean, in the sense of the present invention, the application of a firmly adhering layer of non-form material to a workpiece made of a substrate. The layer and the substrate here form an inseparable object made of different materials. The final coating, in particular the decorative layer, assumes the contact function, i.e. protection against chemical, corrosion and mechanical attacks. The decorative layer is used for visual or decorative purposes, while the substrate assumes a supporting function.

In the automotive industry, various decorated plastic parts are used to enhance visual effects. Traditional surface techniques for such surface-decorated components are plastic surface lacquering, plastic surface plating, coating using PVD or related techniques, decoration in injection molding molds by film decoration according to the IMD or FIM method, and post-injection molding of metal films.

In addition to all of these conventional surface techniques, the presentation of metallic surfaces is also particularly popular, as such surfaces represent an unparalleled high quality, corrosion resistant and strong impression.

In addition to parts decorated with real metal, i.e. parts veneered, joined or post-injection moulded with stainless steel or aluminium sheets, it is particularly preferred to use metal-coated plastic parts as decorative elements.

For example, one type of coating that may be used to achieve a visual metal surface is vapor deposition, which includes PVD (physical vapor deposition) and its modifications, such as CVD (chemical vapor deposition) and PeCVD (plasma enhanced chemical vapor deposition), among others. In this case, a thin metal layer is deposited onto a substrate in a vacuum chamber that is evacuated. The material to be deposited is in solid form. The evaporated material moves through the coating chamber and impinges on the component to be coated, thereby forming a layer by deposition. Although PVD methods are generally suitable for fabricating metal layers; however, it has proven problematic that very thin metal coatings do not have sufficient strength against wear and corrosion without an additional protective layer. For this reason, it is necessary to apply protective layers, such as varnish systems. In order to obtain sufficient basic adhesion on the plastic part to be deposited, it is often also necessary to apply an adhesion promoter or primer. However, an advantage of such a coating is the formation of an optionally coloured variant.

Another coating that is very important in industry is the electrodeposition of metals on plastic parts. In this case, the components are first produced by injection molding, for example from a platable butadiene-containing copolymer such as ABS or ABS/PC. After the injection molding operation, the part is first chemically pretreated to then autocatalytically deposit thereon a first thin conductive metal layer, typically a thin layer of nickel or copper. In a further electroplating process, the other metal layer is then electrodeposited until the end of the deposition of the chromium layer, which is usually the electroplating process.

In electrodeposition, a highly attractive impression, excellent resistance to mechanical damage and high dielectric resistance are achieved, and thus plated parts are often mounted on the outside and inside of automobiles.

In the electrodeposition described above, galvanization and passivation have hitherto been used in the case of components made of metal for functional reasons or requirements, i.e. in order to improve corrosion resistance. For this purpose, the zinc surface is treated by different passivation, depending on the corrosion protection required. The conversion layer is formed by immersing the workpiece in a corresponding electrolyte. The surface colour can also be changed by passivation. The color is generated by the metal compound itself in the passivation at the time of passivation. Thus, staining is a side effect of passivation. Passivation based on trivalent chromium protects the zinc coating and thus optimizes the corrosion resistance of the layer system. The different hues (black, blue, violet, iridescent) obtained after passivation enable color recognition of the coated component. This property is exploited in particular in order to be able to distinguish the components from each other, for example in terms of thread size, diameter, material thickness, etc.

A disadvantage of this type of surface coating that must be mentioned here is that there are fewer color variants. Conventional electrodeposited surface quality and color generally range from high gloss through various matts to pale gray and brown hues through modified electrolytes and processes. Depending on the method, the passivation layer may have a (light) blue, yellow, black, olive or transparent color. However, the color imparting is only a side effect of the organic and inorganic complex compounds in the passivation. The main purpose of passivation is to improve the corrosion resistance of components made of metal.

The color limitations of the electroplated chrome surfaces have long been tolerated in the case of plastic parts, although more individualization, freedom of design techniques, and color and structural design of the surfaces are always desirable. Just the automotive industry would like more color room, especially in the case of metal surfaces such as electroplated coatings.

There are many methods for presenting a surface that is colored and at the same time metallic in appearance. For example, DE 10233120A1 describes a technique in which a combination of lacquers, vapor-phase deposits, such as PVD coatings, and tinted, i.e. weakly colored, lacquers are used.

EP 2369032 A1 describes another technique in which a metal layer to be deposited is deposited in a coloured manner onto a substrate directly by means of a special metal alloy via PVD. However, there is also a need for primers and subsequent varnishes to promote adhesion.

DE 10201001713 A9 also describes vapor deposition using PVD and other techniques on plastics and metals in order to produce a surface which is coloured and at the same time has a metallic impression. In this application, the deposition surface would be and must be protected with a final coating.

For example, EP 1033416 A1 also describes a method in which at least one corrosion protection layer and an outer layer made of zirconium, nitrogen, carbon and/or hafnium are deposited on a substrate using PVD coating, wherein the outer layer forms a passivation layer under the action of air or water.

Against this background, it is an object of the present invention to propose a simple, effective and resource-saving and gentle technique for producing corrosion-resistant colored plastic parts of metal.

This object is achieved by the features of claim 1.

By means of the invention, a high-quality, corrosion-resistant and colored metal layer can be selectively formed on plastic parts, preferably on multicomponent plastic parts.

For this purpose, the component to be coated is first produced by injection molding of a plastic from a platable plastic, preferably from a polyamide, particularly preferably from a platable butadiene-containing copolymer, such as ABS or ABS/PC. After the injection molding operation, the component is chemically pretreated by direct metallization, particularly preferably by a conventional electroplating process, in order to subsequently autocatalytically deposit a first (especially conductive) thin metal layer, typically a nickel or copper thin layer, on the processed surface. In a further electroplating process, at least one other metal layer, preferably a glossy or matte copper layer, is then electrodeposited.

According to a particular embodiment of the invention, the first electrically conductive layer for further electrolytic deposition may also be carried out by vapor deposition, for example PVD, CVD or PeCVD. The advantage in this case is that, when such a precoat is used, special platable plastics and usual chemical pretreatments can be essentially dispensed with, and thus also non-platable plastics, such as polycarbonate or the like, can be used.

In one embodiment of the invention, decorative zinc, nickel zinc and chromium layers are applied to the further metal layers.

In a further embodiment of the invention, it is proposed that the decorative zinc, nickel zinc or chromium layer is also applied by vapor deposition, for example PVD, CVD or PeCVD, or that the decorative layer is post-injection molded as a metallic or metal-coated film insert from a plastic substrate.

By forming a matte and glossy decorative layer, the desired appearance of the final layer can also be directly affected.

In order to adjust the color of the decorative layer in addition to its own color of the metal, the metal layer may be colored and passivated by an organic or inorganic compound made of, for example, a carbon compound or a metal salt.

According to another embodiment of the invention, a further surface layer made of an inorganic, organic or even very thin translucent layer is finally applied to the decorative metal layer, which further surface layer is applied by lacquering, powder coating, printing, dipping or by vapor deposition.

The layer sequence of at least one metal layer and an organic or inorganic layer or the combination of the layer sequence of at least one inorganic layer and an organic layer with a decorative metal layer yields the desired color of the decorative plastic part.

Since the facing is in some cases highly worn, it must have a high mechanical resistance and a high resistance to media. The invention therefore proposes that organic or inorganic polymer compounds can be used as transparent ceramic hard material layers, in particular from AlSi _x O _y N _z 、AlO _x N _y 、Al ₂ O ₃ Or SiO ₂ Those produced are applied as a top layer to the decorative and pigmented metal layer. The hard material layer is a transparent scratch-resistant layer on the color-imparting decorative metal layer. It also acts as a barrier or diffusion protection layer, thereby again increasing the chemical resistance of the underlying metal layer.

Embodiments of the present invention are illustrated in the accompanying drawings and described in more detail below. In the accompanying drawings, like reference numerals refer to like layers. In which is shown:

FIG. 1 shows a method flow of an object according to the invention;

fig. 2 shows a section through a layer structure and method steps of a second object according to the invention;

fig. 3 shows a section through a layer structure and method steps of a third object according to the invention;

fig. 4 shows in a modified schematic view a section through a layer structure of an object according to the invention;

fig. 5 shows in another schematic representation a section through a layer structure of an object according to the invention.

The object shown in fig. 1 has a component (a) made of a plastic substrate (1) made by injection molding. By chemical pretreatment (2), the surface of the platable plastic material (b) is prepared for subsequent autocatalytically depositing a first conductive primer layer (3) in the form of a metal layer (c). In another embodiment of the invention, the first conductive metal layer (c) is applied by vapor deposition, for example by PVD, CVD or PeCVD methods.

The first (base) coating (3) preferably consists of an element or a compound of elements selected from zirconium, titanium, chromium, tin and zinc, copper or preferably nickel.

At least one further intermediate layer (d), preferably up to copper, is deposited, preferably electrolytically, on the first base layer (3), which has a leveling and bonding effect as a metallic intermediate layer (4). Copper deposition is achieved by cyanide or sulfuric acid electrolytes. The gloss of the surface can be adjusted from matte to glossy by adding substances.

A decorative layer (5), preferably made of nickel, is then applied electrolytically. The glossiness of the surface of the decorative layer (5) can be adjusted from matte to glossy by adding an organic substance. If the nickel layer is to be conditioned to matt, a specific matt nickel electrolyte with finely dispersed solution is used; in the case of bright nickel plating, a specific organic bright nickel species is used.

In a variant, the decorative layer (5) may be formed of an element or a compound of elements selected from zinc, zinc nickel or chromium. In the case of zinc, the adjustment from matte to glossy can be carried out electrolytically as an acidic electrolyte, an alkaline cyanide-free electrolyte and an alkaline cyanide-containing electrolyte. Alternatively, the decorative layer (5) (e) can also be applied electrolytically or physically directly, with the metal intermediate layer (4) omitted.

Treatment (f) with an organic or inorganic compound (6) then ensures surface passivation and, as adhesion promoter, coloration (g) of the metallic decorative coating on which it is finally also possible to form a preferably transparent or colored and translucent top layer (h) by means of a deposited or applied organic or inorganic polymer compound (7). Passivation in this context means the spontaneous formation or targeted generation of a nonmetallic protective layer on the metallic material to prevent or greatly slow down the oxygen corrosion of the base material.

The layer (6) is coloured by alternating current in a colouring electrolyte containing a metal salt, the metal ions of which penetrate into the layer (6). Alternatively, an immersion coloring method may also be used, in which the layer (6) is immersed in a coloring bath. The coloured particles are embedded in the pores by absorption.

According to the embodiment of the structure depicted in fig. 1, a metallic corrosion resistant, non-ferrous plastic component (i) can thus be produced.

The object shown in fig. 2 depicts the basic structure of a coating according to the invention, wherein a first metallic conductive primer layer (3) is deposited on a substrate (1) by means of a conventional plastic-plating pretreatment, by means of physical deposition or by means of direct metallization (2), on which an organic or metallic layer (4, 5) made of preferably copper is optionally applied in a thickened, leveling and joining manner, which carries a decorative zinc, zinc-nickel, nickel or chromium coating (6), which can be passivated and colored by means of treatment with an organic or inorganic compound (7). In order to protect the metallic decorative layer from environmental influences or from media attacks, it is also provided with a further coating (8) made of organic and inorganic polymer compounds.

The object shown in fig. 3 in turn comprises a substrate 1 made of plastic. A first metallic conductive primer layer (3) is deposited on the substrate by conventional plastic electroplating, by physical deposition or by direct metallization (2), on which an organic or metallic layer (4) made of preferably copper is optionally applied in a thickened, leveling and bonding manner. In this schematic illustration according to an embodiment of the invention, other metal deposits (5) made of preferably nickel or other metals are also applied, which carry a decorative zinc, zinc-nickel, nickel or chromium coating (6) which can be passivated and colored by treatment with an organic or inorganic compound (7), in contrast to the example according to fig. 2. In order to protect the metallic decorative layer from environmental influences or from media attacks, it is also provided with a further coating (8) made of organic and inorganic polymer compounds.

In the present invention, unlike the prior art, zinc plating is not used as a functional layer but as a decorative layer. The main purpose of the passivation here is to achieve embedding of the coloring pigments, thus providing a broad color spectrum. By the method according to the invention, various different colors can be applied; from pink to purple, bronze to gold, etc. Here, a typical coloring solution or coloring pigment from aluminum coloring is used. Unlike in the case of anodized aluminum, the coloring pigment is not embedded as deeply into the zinc surface, but only near the surface.

In the case of aluminum and zinc, an oxide layer is formed in normal atmosphere. The oxide layer protects the metal. To increase corrosion resistance, an oxide layer may be further formed or treated. In the case of zinc, an oxide layer of a minimum of 20 to 300nm is formed only by chemical conversion using passivation, whereas in the case of aluminum an oxide layer of up to 30 μm can be formed electrolytically. This is not possible with zinc; in the case of zinc, the oxide layer can be formed only chemically, not electrolytically.

It has been demonstrated that the coloring pigment is located only very close to the zinc surface, due to the small formation of an oxide layer; it can be easily erased. Therefore, the passivation layer with embedded colored pigments is not scratch-proof. The surface is also not wear resistant. Thus, the coating (8) is protected from abrasion and scratches by applying it using organic and/or inorganic polymer compounds and/or ceramic coatings and/or nanoparticles.

In the trade-off between required expenditure and achieved outcome, the following process flows proved to be most convincing after a complex experimental series:

the layer structure according to the invention takes place on a component (a) made of a substrate (1) consisting of plastic. The component is subjected to a conventional plastic pretreatment (2) by roughening and activating with palladium or chromium-free coating (possibly also directly metallized) to copper, whereby a matt or glossy copper layer (4) is formed.

Then a nickel layer (5) is formed. It is applied electrolytically. The nickel layer has a thickness of 1 to 20 μm. It acts as a barrier to prevent zinc diffusion into copper and/or as a structured layer, for example to achieve different matte hues and at the same time create a diffusion barrier. The nickel layer (5) thus simultaneously acts as a diffusion barrier.

Zinc is then applied electrolytically and in a thickness of 5 to 30 μm. The zinc layer (6) can be deposited using a single-stage or multi-stage process. The coating time is 5 minutes to 2 hours at temperatures from RT up to 40 ℃.

Then brightening in 0.3 to 1% nitric acid at a temperature of RT to 30 ℃; the time is 5 seconds to 2 minutes. The brightening clarifies the surface of the zinc layer (6) so that a subsequent passivation solution can be deposited.

After the part is brightened, it is passivated. It is passivated in a trivalent chromium passivation solution. This may vary from thin layer passivation and/or thick layer passivation depending on the desired layer thickness and color embedding. Passivation can be used to passivate from transparent through blue to thick layers.

The part is then coloured (7) in an inorganic and/or organic and/or electrolyte compound and is at a temperature of RT to 40 ℃ for a period of 5 seconds to 60 minutes. The coloring pigments are deposited here only in the edge layer, the so-called conversion layer, which has a thickness of only 20nm to 300nm at maximum, near the surface. The coloration is preferably carried out in an immersion tank. In this case, the coloring is a separate method step.

These components are then provided with a protective layer (8) made of organic and/or inorganic polymer compounds and/or nanocoating compounds and/or ceramic hybrid compounds. The protective layer (8) is applied by dipping and/or spraying at a thickness of 0.5 to 40 [ mu ] m and is used for protection against ultraviolet rays in addition to abrasion.

Between the mentioned treatment steps, the component may be dried and/or thermally stored, so-called annealed.

By the above method, plastic parts with arbitrarily colored metal coatings can be produced. Furthermore, the component is galvanized in particular according to the invention, then passivated and colored. Galvanization is not used here for functional reasons as is the case for corrosion protection in the case of components made of metal, but for decorative reasons. This approach is unusual because the professional field typically uses galvanization as corrosion protection. However, since plastic parts do not corrode and galvanization also creates additional costs, there is no reason for the skilled person to galvanize plastic parts to date. By the invention, it is a sensible and advantageous application to galvanize plastic parts, i.e. to color metal coated plastic parts in all arbitrary colors of the color spectrum. This was not possible until the present invention emerged. In this case, according to the invention and in contrast to galvanising metal parts, the colouring is carried out in a separate processing step, preferably in an immersion tank.

Claims (26)

1. A method of producing a decorative plastic part comprising the method steps of:

-injection moulding of the component (1)

-applying a first metallic conductive primer layer (3)

-applying a leveling joint intermediate layer (4, 5)

-applying a decorative zinc, zinc nickel, nickel or chromium coating (6)

-depositing or applying a surface layer (7)

-applying a protective layer (8).

2. A method according to claim 1, characterized in that the first primer layer (3) is autocatalytically deposited.

3. A method according to claim 2, characterized in that the component (1) is chemically pretreated before the deposition of the primer layer (3).

4. A method according to claim 1, characterized in that the first primer layer (3) is physically deposited.

5. Method according to any one of the preceding claims, characterized in that the intermediate layer (4, 5) is applied in a thickened manner.

6. Method according to any of the preceding claims, characterized in that a metal layer is applied as an intermediate layer (4, 5).

7. Method according to any of the preceding claims, characterized in that a copper layer is applied as an intermediate layer (4).

8. A method according to any one of the preceding claims, characterized in that a further metal deposit (5) is applied to the intermediate layer (4).

9. Method according to claim 8, characterized in that other metal deposits (5) made of nickel are applied.

10. Method according to claim 9, characterized in that the further metal deposit (5) made of nickel is applied in a thickness of 1 to 20 μm.

11. The method according to any of the preceding claims, characterized in that the coating (6) made of electrolytic zinc is applied at a thickness of 5 to 30 μm by a coating time of 5 minutes to 2 hours at a temperature of RT up to 40 ℃.

12. The method of claim 11, wherein the brightening is performed in 0.3 to 1% nitric acid at a temperature of RT to 30 ℃ for a period of 5 seconds to 2 minutes.

13. A method according to any of the preceding claims, characterized in that the decorative zinc, nickel or chromium layer is applied by vapor deposition, such as PVD, CVD or PeCVD.

14. A method according to any of the preceding claims, characterized in that the part is coloured by treatment with an inorganic or organic or electrolytic compound at a temperature of RT to 40 ℃ for a time of 5 seconds to 60 minutes.

15. The method according to any one of the preceding claims, characterized in that the coating (8) is formed from an organic or inorganic polymer compound.

16. Method according to claim 15, characterized in that the coating (8) is applied as a transparent ceramic hard material layer, in particular of AlSi _x O _y N _z 、AlO _x N _y 、Al ₂ O ₃ Or SiO ₂ Is prepared.

17. Method according to claim 15 or 16, characterized in that the protective layer (8) is applied in a thickness of 0.5 μm to 40 μm by dipping and/or spraying.

18. Decorative plastic part with a coating for presenting a coloured corrosion resistant metal layer, comprising a substrate (1) (a) consisting of plastic, onto which a first layer (c) is deposited and onto which a zinc, zinc nickel or nickel layer (6) (e) is applied, the surface of which is coloured and sealed (f).

19. Decorative plastic part according to claim 17, characterized in that the substrate (1) is chemically pretreated.

20. Decorative plastic part according to claim 18 or 19, characterized in that the first layer is autocatalytically deposited.

21. Decorative plastic part according to claim 18 or 19, characterized in that the first layer is physically deposited.

22. Decorative plastic part according to any of the preceding claims, wherein the second metal layer is electrodeposited (d).

23. Decorative plastic part according to any of the preceding claims, characterized in that a protective layer (8) (g) is applied to the surface.

24. Decorative plastic part according to any of the preceding claims, characterized in that the first layer is formed as an organic layer (2), a metal layer (3) or as a layer sequence of at least one organic layer (2) and at least one metal layer (3).

25. Decorative plastic part according to any of the preceding claims, characterized in that the metal layer (3) consists of an element or a compound of elements selected from zirconium, titanium, chromium, tin and zinc.

26. Decorative plastic part according to any of the preceding claims, characterized in that the protective layer (8) is formed as an inorganic layer (5), as a further metal layer, as an organic layer (6), as a layer sequence of at least one inorganic layer and organic layer, or as a layer sequence of at least one further metal layer and organic layer.