Method of coating shaped polymer bodies and means of implementing a microstructured surface of the shaped polymer bodies

Abstract

The invention relates to the field of chemistry and relates to a method which, for example, coats the shaped polymer bodies with various metals and can be used in automobile construction. It is an object of the present invention to specify a method of coating shaped polymer bodies which is simpler and less expensive and achieves good adhesion and / or low surface roughness of the coating on the shaped polymer bodies. The object is achieved by a method in which the shaped polymer bodies consist at least partly of a thermoplastic with a filler level of at least 10 percent by mass and have been subjected to a pretreatment in a liquid composed of at least one acid and one oxidizing agent, and, directly after the pretreatment and prior to the coating, the pretreated shaped polymer articles are subjected to a treatment in at least one acid having a maximum of 5 millimoles of an oxidizing agent per litre of at least one acid for at least 1 min, and galvanically coated.

Description

[0001] Method for coating plastic moldings and means for realizing a microstructured surface of the plastic moldings

[0002] The invention relates to the fields of chemistry and mechanical engineering and relates to a method for coating plastic moldings which, for example, can be coated with various metals and used for various technical applications, such as in automobile construction, in the electronics industry, for example for high-frequency filters or high-frequency antennas, or in the jewelry industry, and a means for realizing a microstructured surface of the plastic moldings.

[0003] The metallization of plastic surfaces is usually carried out industrially electrochemically. After the molding process, the plastic molded part is immersed in a bath containing a salt solution of the metal to be applied. The bath also contains an anode made of the metal to be applied or an inert anode. The metal is oxidized at the anode and evaporates into solution. During electroplating, the metal ions are reduced on the plastic molded part to be coated, which is connected as the cathode. This deposits a metallic precipitate onto the plastic molded part to be coated. Typically, several layers of different or identical metals are applied. Reduction and oxidation reactions are enabled by the provision of an electric current.

[0004] However, the prerequisite for this process is that the plastic molded part is electrically conductive.

[0005] The state-of-the-art technology for making plastic molded parts electrically conductive for metallization is achieved after the molding process by applying metal salts, which are reduced to metal nuclei or metal colloids. A first metal layer is often applied to the surface, upon which metallization then takes place.

[0006] The metallization of plastic surfaces requires good adhesion of the nuclei and the first chemically applied metal layer to the surface of the plastic molded part in question. In the case of plastics, the hydrophobic surface of the plastic molded part must first be chemically modified to enable good wetting with the electrolyte.

[0007] Various methods are known for this.

[0008] For example, DE 39 01 029 A1 describes a process for metallizing molded articles made of polyarylene sulfides, in which a glass-based non-corrosive oxidizing agent is applied to the molded articles prior to activation. Polyarylene sulfides containing 3-40% polycarbonate or polyarylene ester, 2.5-15% polyamide or polyester, and 2-20% rubber elastomer are used as polyarylene sulfides, with the exception of TiO2 and MgCO3 as fillers for polycarbonates, polyarylene esters, polyamide, and polyester. The oxidizing agents used are bromine solutions, concentrated sulfuric acid or chromic sulfuric acid, or mixtures thereof with phosphoric acid, or organic peracids.

[0009] WO 2009 / 133751 A1 also discloses a metallized molded body and a method for its production. The metallized molded body comprises a coating layer of conductive polymer particles with a binder, which is applied to the surface of the molded body to be metallized, onto which a metal layer is formed by electroless plating through the adsorption of a catalyst metal.

[0010] Also known from EP 3 414 364 B1 is a method for pretreating the surfaces of plastic parts for electroplating, in which a plastic pretreatment dipping solution containing at least undissociated peroxomonosulfuric acid and undissociated sulfuric acid is prepared and the plastic parts to be coated are dipped into the plastic pretreatment dipping solution.

[0011] In all known pretreatments, the plastics are modified at least on the surface.

[0012] For example, the acids in the pretreatment agent cause ABS plastics to swell significantly, forming a layer of approximately 1 μm on the surface. The oxidizing agents in the pretreatment agent can then penetrate the swollen plastic and oxidize the butadiene contained therein. Due to the oxidation of the butadiene, the gas evolution causes the butadiene to foam, and the inorganic acid present in the pretreatment agent can penetrate the foamed surface. This creates a microstructured surface on the ABS plastics.

[0013] A comparable microstructured surface can also be achieved with molded articles made of filled polyphenylene sulfide (PPS). In this case, the plastic matrix and, in some cases, the fillers are oxidized or displaced at different rates by the oxidizing agents.

[0014] It is also known that after treatment with sulfuric acid and surface normalization with water, a white, non-adherent film is present on the surface of polyetherimides (PEI). This film has a grainy texture and is composed of oxidized PEI (Bradley R. Karas et al.: J. of Adhesion Science and Technology, (1992), 6:7, 815-828). Good adhesion of the metal coating to such a microstructured surface containing the residues of oxidized polymers is also prevented by the fact that these residues are not completely removed by surface normalization or rinsing with water. In particular, the remaining, relatively irregularly sized and irregularly distributed residues are resolidified by the subsequent conventional rinsing treatments and are not completely removed from the surface even by subsequent cleaning treatments.

[0015] As a result, these residues often only detach together with the metal coating during the subsequent metallization, resulting in incomplete metallization of the surface.

[0016] In order to achieve improved adhesion and metallization of PPS surfaces in these cases too, EP 0 435 212 A1 discloses a process for pretreating the metal coating of a molded article made of a resin which contains, as its main components, a polyphenylene sulfide resin, reinforcing glass fillers, and optionally one or more other thermoplastic resins. In this process, the molded article made of the resin is first immersed in an oxidative acid solution, then in a liquid containing an organic polar solvent, and finally in a solvent which dissolves the reinforcing glass fillers and the thermoplastic resin. Hydrogen peroxide and sulfuric acid can be used as the oxidative acid solution, N-methylpyrrolidone or dimethylacetamide can be used as the organic polar solvent, and sulfuric acid and / or an aqueous alkali solution can be used as the solvent.

[0017] A disadvantage of the existing solutions remains that the adhesive strength of the coatings on plastic molded bodies is insufficient, or that numerous and / or complex process steps must be carried out before coating the plastic molded bodies to improve the adhesive strength. Another disadvantage is the high surface roughness of the plastic molded bodies after coating.

[0018] Another disadvantage is the use of organic solvents, which requires not only occupational safety measures but also extensive explosion protection in large immersion baths. The object of the present invention is to provide a process for coating plastic moldings that is simpler and more cost-effective and achieves good adhesion and / or low surface roughness of the coating on the plastic moldings. It is also to provide a means for creating a microstructured surface on the plastic moldings, which achieves a hydrophilic and microstructured surface on the plastic moldings prior to chemical and / or electroplating coating.

[0019] The problem is solved by the invention defined in the claims. Advantageous embodiments are the subject of the subclaims, which may individually, severally, or all together be advantageous embodiments of the main claim.

[0020] In the method according to the invention for coating plastic moldings, plastic moldings which consist at least partially of a thermoplastic filled to at least 10 percent by mass and which have been subjected to a pretreatment in a liquid comprising at least one acid and an oxidizing agent are subjected, and directly after the pretreatment of the plastic moldings and before the coating, the at least pretreated plastic moldings are subjected to a treatment in at least one acid which has a maximum of 5 millimoles of an oxidizing agent per liter of at least one acid for at least 1 minute, and then the plastic moldings treated in this way are rinsed and / or cleaned and chemically and / or galvanically coated.

[0021] Advantageously, plastic moldings are used which consist of one or more thermoplastics filled to 20 to 80% by mass.

[0022] Polyphenylene sulfide, polyoxymethylene or polyetheretherketone are also advantageously used as thermoplastics.

[0023] Furthermore, it is advantageous to use plastic moldings containing inorganic fillers, advantageously inorganic salts such as carbonates and / or sulfates and / or chlorides. It is also advantageous to use plastic moldings consisting at least partially of polyphenylene sulfide or polyoxymethylene or polyetheretherketone filled with calcium carbonate, calcium sulfate, magnesium carbonate, or dolomite.

[0024] It is also advantageous to use plastic molded bodies whose fillers are in the form of particles, fibers, spheres and / or geometrically shaped bodies.

[0025] It is also advantageous if a liquid consisting of concentrated sulfuric acid, water and peroxomonosulfuric acid as an oxidizing agent is used for the pretreatment of the plastic moldings.

[0026] It is also advantageous to use precursors that form an oxidizing agent in situ during the pretreatment of the plastic moldings.

[0027] It is also advantageous if the inorganic acid or acid mixture used during the pretreatment is used for the treatment of the pretreated plastic moldings, whereby it is even more advantageous to use an inorganic acid for the pretreatment of the plastic moldings and the treatment with an acid, which is again advantageously a concentrated sulfuric acid.

[0028] It is also advantageous if the pretreated plastic molded bodies are subjected to treatment in at least one acid for between 1 and 30 minutes.

[0029] It is also advantageous if the plastic molded bodies are rinsed and / or cleaned in at least one acid one to five times after treatment.

[0030] It is also advantageous if the plastic molded bodies are chemically or electroplated after treatment in at least one acid, with or without rinsing and / or cleaning steps. It is also advantageous if, during the pretreatment of the plastic molded bodies, mechanical stress is applied to the pretreatment fluid, advantageously by means of ultrasound, stirring, creating a flow, turbulence, or by moving the plastic molded bodies in the pretreatment fluid.

[0031] It is also advantageous if, during the treatment of the plastic molded bodies in at least one acid, a mechanical stress on the acid is realized, advantageously by means of ultrasound, stirring, realization of a flow, swirling, or the plastic molded bodies are moved in the acid.

[0032] The agent according to the invention for realizing a microstructured surface of plastic moldings for the coating of plastic moldings after a pretreatment and a directly subsequent treatment before the coating of plastic moldings consists of at least one acid with the exclusion of oxidizing agents, wherein the exclusion of oxidizing agents means that a maximum of 5 millimoles of an oxidizing agent per liter of acid are present.

[0033] The present invention provides for the first time a simple and cost-effective method for coating plastic moldings, which realizes good adhesion and / or low surface roughness of the coating on the plastic moldings, as well as a means for realizing a microstructured surface of the plastic moldings, which realizes a hydrophilic and microstructured surface of the plastic moldings.

[0034] This is achieved by the process according to the invention for coating plastic moldings. This process allows the coating of plastic moldings that consist at least partially of a thermoplastic filled to at least 10% by mass.

[0035] Such plastic moldings can advantageously be made from one or more

[0036] 20 to 80 mass% filled thermoplastic material(s). Polyphenylene sulfide, polyoxymethylene, or polyetheretherketone are advantageously used as thermoplastic materials.

[0037] Thermoplastics can also be used that differ in the types of plastic or in the variants of identical plastic types from different manufacturers, which usually result from minor differences in the manufacturing processes.

[0038] Advantageously, thermoplastic molded articles are used which contain inorganic fillers, even more advantageously inorganic salts as fillers, such as carbonates and / or sulfates and / or chlorides.

[0039] Particularly advantageously, plastic moldings which consist at least partially of polyphenylene sulfide or polyoxymethylene or polyetheretherketone filled with calcium carbonate, calcium sulfate, magnesium carbonate or dolomite are used in the process according to the invention.

[0040] Advantageously, fillers are used in the thermoplastic molded bodies which are in the form of particles, fibers, spheres and / or geometrically shaped bodies.

[0041] The plastic molded bodies used according to the invention are subjected to a pretreatment in a liquid comprising at least one acid and at least one oxidizing agent, wherein the oxidizing agent must be capable of at least oxidizing the plastic on the surface and in the near-surface region and advantageously also of oxidizing the filler on the surface and in the near-surface region.

[0042] The pretreatment parameters for the plastic molded bodies used can also be adapted to different types of plastic or to the variants of different manufacturers for identical types of plastic.

[0043] The acid used in the pretreatment must also be capable of dissolving the oxidized plastic parts and, if applicable, the oxidized fillers at least from the surface. An inorganic acid is advantageously used as the acid. The fillers on the surface of the thermoplastics can be at least partially removed from the surface of the thermoplastics by the acid and / or the oxidizing agent, but also by other means, or by mechanical or thermal means.

[0044] Advantageously, the pretreatment of the plastic molded articles can be carried out in a liquid containing sulfuric acid as well as oxidizing agents, such as peroxomonosulfuric acid. Both the acid and the oxidizing agents can advantageously be used partially or completely in undissociated form.

[0045] Even more advantageously, a liquid consisting of concentrated sulfuric acid, water, and peroxy compounds as oxidizing agents is used for the pretreatment of the plastic moldings. Precursors of the peroxy compounds can also be used, and the formation of the peroxy compounds then occurs in situ during the pretreatment of the plastic moldings.

[0046] During this pretreatment of the plastic molded bodies, the presence of oxidizing agents causes the thermoplastic itself to be at least partially oxidized on the surface and in the near-surface area, usually to a depth of up to several micrometers.

[0047] The fillers can also be oxidized.

[0048] However, the fillers in the plastic molded part are and should always be dissolved out of the plastic composite at the surface and in the near-surface area, creating depressions in the plastic surface that form the microstructured surface of the plastic molded body and contribute to the realization and / or improvement of the adhesion of the metallization.

[0049] However, the oxidized and / or dissolved fillers and plastics are only partially removed from the surface during the pretreatment of the plastic molded parts. After the pretreatment of the plastic molded parts, relatively irregularly sized and irregularly distributed residues of oxidized plastic and filler remain on the surface of the plastic molded parts.

[0050] To remove these residues, according to the invention, the pretreatment of the plastic molded parts is immediately followed by treatment in at least one acid for at least 1 minute. According to the invention, this treatment must be carried out in at least one acid in the absence of an oxidizing agent.

[0051] After this treatment, cleaning and surface normalization steps or further process steps can be carried out before coating the plastic molded parts.

[0052] According to the invention, exclusion of an oxidizing agent in the context of the present invention means that the amount of oxidizing agent in the at least one acid is a maximum of 5 millimoles per liter.

[0053] Advantageously, the amount of oxidizing agents in the at least one acid is 0 to 3 millimoles per liter, particularly advantageously between 0 and 1 millimole per liter.

[0054] According to the invention, oxidizing agents are neither added to the at least one acid by oxidizing agents nor introduced into the at least one acid as precursors for an oxidizing agent, so that an oxidizing agent cannot form in situ in the at least one acid in concentrations higher than a maximum of 5 millimoles per liter of the at least one acid. However, oxidizing agents can be introduced due to technical implementation and / or by the introduction of oxidizing agents from previous treatment steps.

[0055] If acids which themselves have an oxidising effect are used in a treatment step prior to coating, these are either not used or used in small quantities, or acids which have only a slight oxidising effect on the plastic are used.

[0056] It is of particular importance for the present inventive method that the relatively irregularly large and irregularly distributed residues of oxidized plastic and optionally also oxidized filler on the surface of the plastic moldings are essentially completely removed by the treatment directly after the pretreatment and before the coating, and the thus cleaned and microstructured surface of the plastic moldings can be provided with a well-adhering coating.

[0057] To improve the oxidation of the thermoplastics and / or the fillers, it is advantageous if, during the pretreatment of the plastic moldings, a mechanical stress is applied to the pretreatment liquid, advantageously by means of ultrasound, stirring, realization of a flow, swirling, or the plastic moldings are moved in the pretreatment liquid.

[0058] It is particularly advantageous if, during the treatment of the plastic moldings in at least one acid with the exclusion of an oxidizing agent, a mechanical stress on the acid is realized, advantageously by means of ultrasound, stirring, realization of a flow, swirling, or the plastic moldings are moved in the acid with the exclusion of an oxidizing agent.

[0059] In the event that during a treatment step prior to coating, a renewed or further oxidation of the plastic occurs due to an oxidizing effect of the acids used, it is possible to repeat the treatment of the plastic moldings according to the invention in at least one acid with the exclusion of an oxidizing agent, whereby the oxidized plastics are in any case essentially completely removed from the surface of the plastic moldings.

[0060] Of particular importance for the present invention is that no process steps, in particular for cleaning, rinsing and / or surface normalization, are carried out between the pretreatment of the plastic moldings and the treatment according to the invention with at least one acid, excluding an oxidizing agent, since the existing irregularly large and irregularly distributed residues of oxidized plastic are thus essentially completely removed and the acids for the treatment according to the invention are also not contaminated.

[0061] Also according to the invention, the pretreatment and the treatment according to the invention take place in at least one acid, excluding an oxidizing agent, using the same acid, advantageously an inorganic acid. This further eliminates further contaminants.

[0062] Advantageously, the pretreated plastic molded bodies are subjected to treatment in at least one acid for between 1 minute and 30 minutes, excluding an oxidizing agent.

[0063] After the plastic moldings have been treated with at least one acid in the absence of an oxidizing agent, the plastic moldings treated in this way are rinsed and / or cleaned, can be activated with a catalyst, and chemically coated, i.e. without external current, and optionally also galvanically coated.

[0064] The number and length of the rinsing and cleaning steps correspond to those of the known state of the art.

[0065] Chemical and galvanic coating are also carried out using state-of-the-art processes.

[0066] The process according to the invention essentially completely removes the relatively irregularly sized and irregularly distributed residues of oxidized material that were formed and remained during the pretreatment of the plastic moldings and that adhere more or less firmly to the plastic surface. For the subsequent chemical and / or electroplating coating, this means that a completely and well-adhering metallization of the plastic molding surface and a smooth metallization surface are achieved.

[0067] Furthermore, the object is achieved by a means for creating a microstructured surface on plastic moldings, which creates a microstructured surface on the plastic moldings before coating. This is achieved by a means for creating a microstructured surface on the plastic moldings for coating plastic moldings after a pretreatment and a directly subsequent treatment before coating the surfaces of the plastic moldings, which consists of at least one acid with the exclusion of oxidizing agents, wherein the exclusion of oxidizing agents means that a maximum of 5 millimoles of an oxidizing agent are present per liter of acid.

[0068] Advantageously, at least one inorganic acid is present.

[0069] For the agent according to the invention, the exclusion of oxidizing agents also means that the amount of oxidizing agents in the at least one acid is a maximum of 5 millimoles per liter, advantageously between 0 and 3 millimoles per liter, particularly advantageously between 0 and 1 millimole per liter.

[0070] According to the invention, the agent may contain a maximum of 5 millimoles per liter due to the technical implementation of the process and / or due to the introduction of oxidizing agents from previous treatment steps.

[0071] The inventive means for creating a microstructured surface on pretreated plastic moldings prior to coating removes irregularly sized and irregularly distributed residues of oxidized material on the surface and in the near-surface region of pretreated plastic moldings after pretreatment and prior to coating. At the same time, the filler still present on the surface and in the near-surface region of the plastic moldings is at least partially dissolved out and can also be at least partially oxidized and / or removed. The at least partial removal of the fillers from the plastic composite creates a microstructured surface that significantly improves the adhesion of the subsequently applied coating.

[0072] The invention is explained in more detail below using several exemplary embodiments. Reference Example 1

[0073] Coating of plastic moldings without treatment in at least one acid and excluding an oxidizing agent

[0074] The coating was applied to three injection-molded sheets made of PPS from Toray (Torelina A310MB6), a thermoplastic with a filler content of 65 wt.% glass fibers and mineral particles. The sheets measured 80 mm by 80 mm and had a thickness of 3 mm.

[0075] For pretreatment, the panels were first cleaned and degreased, then dried. A mixture of sulfuric acid and hydrogen peroxide was used as the oxidizing agent for the pretreatment, resulting in a 78% sulfuric acid solution with a total oxidizing agent content of 35 mM (millimoles). The panels were exposed to the etching solution for 2.5 minutes.

[0076] The plates thus pretreated were immediately subjected to a chemical galvanic coating in various immersion baths, with a triple rinsing in water between each immersion bath according to the state of the art for chemical galvanic processes:

[0077] Immersion bath:

[0078] 1 4 min exposure in the activator UDIQUE 879 (MacDermid Enthone) at 32°C

[0079] 2 4 min exposure in the accelerator UDIQUE 8810 (MacDermid Enthone) at 45°C

[0080] 3 7.5 min exposure in electroless nickel UDIQUE 891 (MacDermid Enthone) at 32°C and pH 8.9.

[0081] After this treatment, a continuous conductive nickel layer was present on the entire surface of the plates, which was then treated with the copper bath Cuprostar (MacDermid Enthone) for 45 minutes at room temperature and a current density of 4.0 A / dm 2was supplemented with a copper layer with a thickness of 40 pm. The plates were then pre-dried in a hot air stream and stored in a dry place for 24 hours for final drying.

[0082] To measure the adhesion strength, after drying, the copper layer on the plates was cut with a saw at a distance of one centimeter. The resulting copper strip was detached from the component over a length of 1 cm and clamped into a Mecmesin Multitest 2.5i material testing machine to measure peel strength in accordance with DIN EN 1464. The strip was peeled off at a speed of 50 mm / s at an angle of 90°.

[0083] The measurements showed values ​​between 2.9 N / cm and 3.7 N / cm for the peel force of the plates.

[0084] The nickel and copper-coated plates already exhibit macroscopically visible roughness in various places. A surface roughness measurement using a step-by-step device (Surface Roughness Tester YRT100) with a measuring length of 0.8 mm was performed before and after the treatment and yielded the following values: The values ​​show that the initial surface roughness of the plastic sheets has increased significantly as a result of the treatment.

[0085] Example 2

[0086] The process, up to and including pretreatment, was carried out as in Example 1 on three plastic molded bodies in the form of injection-molded sheets made of PPS from Toray (Torelina A310MB6), a thermoplastic with a filler content of 65 wt.% glass fibers and mineral particles. The dimensions of the sheets were again 80 mm by 80 mm and 3 mm thick.

[0087] The panels were first cleaned and degreased, then dried. A mixture of sulfuric acid and hydrogen peroxide was used as the oxidizing agent for the pretreatment, resulting in a 78% sulfuric acid solution with a total oxidizing agent content of 35 mM. The panels were exposed to the etching solution for 2.5 minutes.

[0088] While the injection-molded PPS sheets were very water-repellent before pretreatment with a contact angle of 120°, their surface was already hydrophilic after pretreatment with a contact angle close to 0°.

[0089] However, residues of oxidized material were still visually visible on the plastic surface.

[0090] Therefore, the injection-molded PPS sheets as plastic molded bodies were completely immersed in a solution as acid under exclusion of an oxidizing agent, which consisted of a 78% sulfuric acid with an addition of 0.1 g / l of the surfactant sodium lauryl sulfate (SDS), directly after the pretreatment.

[0091] The total content of oxidizing agents in the solution was determined by oxidizing an iron stock solution. For this purpose, an iron stock solution containing 19 g of iron(II) sulfate and 1.5 g of ammonium iron(II) sulfate was dissolved in 45 ml of deionized water, and the concentration was then determined by titration with potassium permanganate. 2 ml of this iron stock solution were added to a mixture of 50 ml of deionized water and 1 ml of the solution to be determined, and the concentration was again determined by a potassium permanganate titration. With this procedure, the decrease in Fe2+ ions due to the addition of the solution to be analyzed corresponds to twice the value of the oxidizing agents present.

[0092] The measurement resulted in a value of 0.8 millimoles per liter of oxidizing agents.

[0093] To mechanically enhance the surface cleaning, the solution containing the plates was placed in a water-filled laboratory ultrasonicator (Bandelin Sonorex RK100) and exposed to 80 watts of sonication during the exposure. The samples were then rinsed with water at room temperature (20 °C).

[0094] Immediately after this treatment with an acid in the absence of an oxidizing agent, the plastic molded bodies remained hydrophilic and exhibited a microstructured surface. The residues of oxidized material adhering to the plastic surface after the pretreatment step were now removed and no longer visually visible.

[0095] The further process steps for metal coating were carried out according to Example 1.

[0096] The measurement of the adhesion strength of the layer according to Example 1 resulted in values ​​between 3.5 N / cm and 4.5 N / cm.

[0097] The coated panels already exhibited a more homogeneous appearance across the entire surface and very low roughness. Surface roughness measurements were taken before and after treatment using the procedure described in Example 1 and yielded the following values:

[0098]

[0099] The values ​​show that, in contrast to the reference example, the initial surface roughness of the plastic sheets has been reduced by the treatment.

[0100] Example 3

[0101] The coating was applied to three injection-molded sheets made of polyphenylene sulfide (PPS) from DSM (Xytron M5710T black), a thermoplastic with a filler content of 57 wt.% glass fibers and mineral particles. The sheets measured 80 mm by 80 mm and had a thickness of 3 mm.

[0102] The panels were first cleaned and degreased, then dried. A mixture of sulfuric acid and hydrogen peroxide was used as the oxidizing agent for the pretreatment. The etching solution was prepared as a 79.5% sulfuric acid solution with a total oxidizing agent content of 50 mM. The etching solution was heated to 40°C, and the panels were fully immersed in the etching solution for 1.5 minutes.

[0103] While the injection-molded PPS sheets were very water-repellent before pretreatment with a contact angle of 120°, their surface was already hydrophilic after pretreatment with a contact angle close to 0°.

[0104] However, residues of oxidized material were still visually visible on the plastic surface.

[0105] Immediately afterwards, the plates were completely immersed in a bath consisting of 80% sulfuric acid at a temperature of 40°C for acid treatment, excluding any oxidizing agent.

[0106] To ensure the best possible treatment, the process was interrupted three times for a few seconds after two minutes, and the plates were removed from the bath. After another four minutes of exposure, the plates were rinsed in water at 60°C for 10 minutes.

[0107] Immediately after this treatment with an acid in the absence of an oxidizing agent, the plastic molded bodies remained hydrophilic and exhibited a microstructured surface. The residues of oxidized material adhering to the plastic surface after the pretreatment step were removed and no longer visually visible.

[0108] The further process steps for metal coating were carried out again according to Example 1, but in step 3, with the same exposure time of 7.5 minutes, a particularly active nickel bath Enplate Ni-817 (MacDermid Enthone) at pH 4.7 and a temperature of 85°C was used.

[0109] The measurement of the adhesion strength of the layer according to Example 1 resulted in values ​​between 3.5 N / cm and 4.0 N / cm.

[0110] The nickel and copper-coated plates exhibited a macroscopically homogeneous appearance across the entire surface and very low roughness. A measurement of the surface roughness according to the method in Example 1 was carried out before and after treatment of the plates and yielded the following values:

[0111] The values ​​show that the initial surface roughness of the plastic sheets has been reduced by the treatment.

Claims

Patent claims 1. A process for coating plastic moldings, in which the plastic moldings consist at least partially of a thermoplastic filled to at least 10% by mass, which have been subjected to a pretreatment in a liquid comprising at least one acid and an oxidizing agent, and directly after the pretreatment of the plastic moldings and before coating, the at least pretreated plastic moldings are subjected to a treatment in at least one acid containing a maximum of 5 millimoles of an oxidizing agent per liter of at least one acid for at least 1 minute, and then the plastic moldings treated in this way are rinsed and / or cleaned and chemically and / or galvanically coated.

2. A process according to claim 1, wherein plastic moldings are used which consist of one or more thermoplastics filled to 20 to 80% by mass.

3. A process according to claim 1, wherein the thermoplastics used are polyphenylene sulfide, polyoxymethylene or polyetheretherketone.

4. A process according to claim 1, in which plastic moldings are used which contain inorganic fillers, advantageously inorganic salts such as carbonates and / or sulfates and / or chlorides.

5. A process according to claim 1, wherein plastic moldings are used which consist at least partially of polyphenylene sulfide or polyoxymethylene or polyetheretherketone filled with calcium carbonate, calcium sulfate, magnesium carbonate or dolomite.

6. A process according to claim 1, in which plastic moldings are used whose fillers are in the form of particles, fibers, spheres and / or geometrically shaped bodies.

7. A process according to claim 1, wherein a liquid consisting of concentrated sulfuric acid, water and peroxomonosulfuric acid as oxidizing agent is used for the pretreatment of the plastic moldings.

8. A process according to claim 1, wherein precursors are used which form an oxidizing agent in situ during the pretreatment of the plastic moldings.

9. A process according to claim 1, wherein the inorganic acid or acid mixture used during the pretreatment is used for the treatment of the pretreated plastic moldings.

10. The method according to claim 9, wherein an inorganic acid, advantageously concentrated sulfuric acid, is used for the pretreatment of the plastic moldings and the treatment with an acid.

11. The method according to claim 1, wherein the pretreated plastic molded bodies are subjected to treatment in at least one acid for between 1 and 30 minutes.

12. The method according to claim 1, wherein the plastic molded bodies are rinsed and / or cleaned one to five times after treatment in at least one acid.

13. A process according to claim 1, wherein the plastic molded bodies are chemically or galvanically coated after treatment in at least one acid with or without rinsing and / or cleaning steps.

14. The method according to claim 1, wherein during the pretreatment of the plastic moldings, a mechanical stress is applied to the pretreatment liquid, advantageously by means of ultrasound, stirring, realization of a flow, swirling, or the plastic moldings are moved in the pretreatment liquid.

15. A method according to claim 1, wherein during the treatment of the plastic molded body in at least one acid a mechanical stress the acid is realized, advantageously by means of ultrasound, stirring, realization of a flow, swirling, or the plastic moldings are moved in the acid.

16. Agent for realising a microstructured surface of plastic mouldings for the coating of plastic mouldings after a pre-treatment and a directly subsequent treatment before the coating of plastic mouldings, consisting at least of an acid with exclusion of oxidising agents, wherein the exclusion of oxidising agents means that a maximum of 5 millimoles of an oxidising agent are present per litre of acid.

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