EP1001052B1 - Method for metallizing a plastic surface - Google Patents

Abstract

Metallization of plastic surfaces involves (a) pickling the plastic surfaces under moderate pickling conditions; (b) treating the plastic surfaces with a metal salt solution which contains a salt from cobalt -, silver -, tin - and lead; (c) treating the plastic surfaces with a sulfide solution and (d) metallizing the plastic surfaces in a metallizing bath.

Description

The invention relates to a method for metallization a plastic surface. - Within the scope of the invention Process is the plastic surface of a plastic object or become plastic surfaces of several Metallized plastic objects.

Metallized plastics become decorative on the one hand Purposes, for example in the sanitary area or at Automotive manufacturing. On the other hand, one finds Metallization of plastics but also in the context of coating of electronic components for the purpose of electronic Shielding instead. For decorative purposes especially surfaces of plastics such as acrylonitrile-butadiene-styrene (ABS) and possibly ABS polycarbonate blends metallized.

In a method known from US 4 919 768, the Plastic surface first by vigorous pickling, for example with chromic acid or with sulfuric acid, roughened. After pickling, the plastic surface is covered with a tin salt solution and then with a sulfide solution treated. The procedure is based on a Metallization completed. With this procedure you can but only a few very specific plastics to some extent be metallized satisfactorily.

In a method known from practice, the Plastic surface first by vigorous pickling, for example with chromic acid or chromic acid, roughened. Roughening means in particular that through the strong stains in the plastic surface of micro caverns be generated. The micro caverns usually have Diameters in the order of 0.1 to 10 µm. In particular, these micro-caverns have a depth (i.e. H. an extension from the plastic surface into the Plastic interior), which are of the order of 0.1 to 10 µm. The pickling takes place here at relatively high Temperatures and usually over a relatively long time Periods. The concentration of one used in the pickling solution Oxidizer is usually relatively high. The roughening of the plastic surface serves that then an activation layer to be applied and / or metal layer as it were in the roughened Can anchor or hook plastic surface. The Adhesion of a metal layer to the roughened plastic surface becomes as it were in this known method achieved by a push button principle. After pickling or The surface becomes roughened first with colloidal palladium or ionogenic palladium activated. This activation follows in the case of the colloidal Process a detachment of a tin protection colloid or a reduction in the case of the ionogenic process elemental palladium. It then becomes chemical Copper or chemical nickel as a conductive layer on the Plastic surface deposited. Then the galvanic coating or metallization instead. This Direct metallization of the plastic surfaces works in practice only with certain plastics. When a sufficient roughening of a plastic or the Formation of suitable micro-caverns in the plastic surface when pickling is not possible, it is reliable Adhesion of the metal layer to the plastic surface not guaranteed. As a result, the known Process especially the number of coatable Plastics severely restricted. The direct metallization works according to this known method without problems, usually only with ABS plastic parts. Metallization is used for ABS polycarbonate blends and polypropylene only in compliance with very specific working conditions possible. So far this is known method improvement.

In another known method ("New methods of electroless plating and direct electroplating of plastics ", A. Vaskelis et al., Institute of Chemistry, A Gostauto 9, 2600 Vilnius, Lithuania, paper to be presented at the INTERFINISH 96 WORLD CONGRESS, International Convention Center, Birmingham, England, 10-12 September 1996) the plastic surface also by relatively strong or sharp pickling roughened. Here too, when pickling Micro caverns created in the plastic surface, in to which the metal layer to be applied is mechanically anchored or should be hooked. The pickling is also with this Process carried out at elevated temperature. The pickling solution usually has high concentrations of an oxidizing agent on. The one pre-treated in this way Plastic surface is then covered with a copper salt solution treated and then with a second solution treated that contains sulfide ions or polysulfide ions. In this way, an electronically conductive layer of non-stoichiometric copper sulfide on the plastic surface generated. After a first procedure this known method, the treatment of the plastic surface with the two solutions mentioned at room temperature for a maximum of 1 minute. Also In this first procedure, only very specific ones can be used Plastics reasonably reliable and satisfactory be metallized. - After a second Procedure of this known method is treatment with the two solutions mentioned at increased Temperature of 70 to 90 ° C and during a longer treatment period from 5 to 15 minutes. With these Working conditions should be achieved that both Sulfur as well as copper ions through the plastic surface penetrate into the plastic and also below the Plastic surface of non-stoichiometric copper sulfide is formed. This is intended to ensure particularly good adhesion of the subsequently applied metal layer can be achieved. However, the penetration described is very incomplete instead and therefore also leaves the adhesion of the metal layer to be desired. You can also use this procedure satisfactory only certain plastics be metallized.

Incidentally, a number of methods are practical known in which after pickling the plastic surface under micro-cavern formation the plastic surface is treated with a copper salt solution. In connection this is followed by treatment with a sulfide solution. All these methods are characterized by the disadvantage from that to produce a reasonably satisfactory Metal layer the process steps mentioned must be carried out several times in succession. It understands themselves that this is complex and costly.

In contrast, the invention is based on the technical problem to specify a procedure of the type mentioned at the outset, with which a large number of plastics can be produced in a relatively inexpensive manner functionally reliable and reproducible metallized can be and the plastics with a metal layer provided that meets all requirements.

1.1) die Kunststoffoberfläche wird einer Beizbehandlung unter milden Beizbedingungen unterzogen, wobei diese milden Beizbedingungen so eingestellt werden, dass an der Kunststoffoberfläche lediglich kleine Öffnungen oder Kanäle erzeugt werden, die eine Tiefe < 0,09 µm aufweisen,

1.2) im Anschluss daran wird die Kunststoffoberfläche mit einer Metallsalzlösung behandelt, die zumindest ein Salz aus der Gruppe "Kobaltsalz, Silbersalz, Zinnsalz, Bleisalz" enthält,

1.3) die Kunststoffoberfläche wird mit einer Sulfidlösung behandelt,

1.4) letztendlich wird die Kunststoffoberfläche in einem Metallisierungsbad metallisiert.

To solve this technical problem, the invention teaches a method for metallizing a plastic surface, the following method steps being carried out in succession:

1.1) the plastic surface is subjected to a pickling treatment under mild pickling conditions, these mild pickling conditions being set such that only small openings or channels are created on the plastic surface that have a depth of <0.09 μm,

1.2) then the plastic surface is treated with a metal salt solution which contains at least one salt from the group "cobalt salt, silver salt, tin salt, lead salt",

1.3) the plastic surface is treated with a sulfide solution,

1.4) finally the plastic surface is metallized in a metallization bath.

The method steps according to the invention can be further Process steps, in particular rinsing steps, interposed his.

Mild pickling conditions means in the context of the invention in particular that the "pickling" or the corresponding treatment the plastic surface with a pickling solution low temperatures and / or during a short Treatment time and / or at low concentration of Pickling solution is carried out. Mild pickling conditions can in principle already be realized when one of the above three conditions is met. Low In the context of the invention, temperature means a temperature of a maximum of 40 ° C. If mild pickling conditions are caused by a low temperature, this is expediently at most 30 ° C., preferably between 15 ° C. and 25 ° C. At the above low The pretreatment takes place with the pickling solution especially over a period of 3 to 15 minutes, preferably from 5 to 15 minutes, preferably from 5 to 10 minutes. instead of. It is within the scope of the invention that Treatment time is shorter, the higher the temperature is. Mild pickling conditions can also be Temperatures above 40 ° C can be realized when the treatment time is chosen accordingly short. To In one embodiment of the invention, the pickling treatment takes place at temperatures from 40 ° C to 95 ° C, preferably 50 ° C to 70 ° C over a treatment period from 15 seconds to 5 minutes, preferably from 0.5 to 3 minutes. instead of. It is also within the scope of the invention that the Treatment time is shorter, the higher the treatment temperature is. The treatment temperature is expedient and / or the treatment time of the pickling treatment depending on the type of pickling solution used selected.

Mild pickling also means within the scope of the invention that in contrast to the known methods explained at the outset a roughening of the plastic surface or a generation of micro-caverns in the plastic surface takes place. The state of the art generated during pickling Usually have micro-caverns or cavities Diameters or depths on the order of 0.1 to 10 microns. In contrast, it is within the scope of the invention that the Pickling conditions are set so that on the Plastic surface only small openings or pores are generated that have a diameter and in particular a Depth <0.09 µm, preferably <0.05 µm. Depth means the opening / pore extending from the plastic surface inside the plastic. So there is none here Pickling in the classic sense instead, as is the case with the known ones Procedure is carried out. It is within the Invention that the plastic surface by generating the small openings or pores just for the Diffusion of the metal ions of the metal salt solution opened becomes. In other words, the plastic surface as it were formed like a membrane or in the plastic surface a diffusion membrane is created. Mild pickling conditions in the context of the invention means that the pickling conditions are set with the proviso that only the small pores mentioned in the Plastic surface are generated and micro-caverns or internal voids in the plastic surface do not arise. According to the invention in the area of the plastic surface Created diffusion openings or diffusion channels, the depth <0.09 µm, preferably <0.05 µm exhibit.

The mild pickling treatment according to the invention can be carried out with a Pickling solution and / or basically also by plasma treatment or plasma etching can be realized.

A pickling solution used for pickling preferably contains at least one oxidizing agent. Mild pickling also means in the context of the invention that an oxidizing agent is used in a relatively low concentration. Permanganate and / or peroxodisulfate and / or periodate and / or peroxide can be used as the oxidizing agent. In one embodiment, pickling is carried out using an acidic pickling solution which contains at least one oxidizing agent. An acidic aqueous pickling solution which contains permanganate and phosphoric acid (H ₃ PO ₄ ) and / or sulfuric acid is preferably used. Potassium permanganate is expediently used as the permanganate. An acid pickling solution which contains only phosphoric acid or mainly contains phosphoric acid and only a little sulfuric acid is very preferably used. According to another embodiment of the invention, the pickling treatment is carried out with an alkaline aqueous solution containing permanganate. Here too, potassium permanganate is preferably used. The alkaline aqueous solution expediently contains sodium hydroxide solution. It is within the scope of the invention that the type of pickling solution used is selected depending on the type of plastic treated. - The oxidizing agent is preferably contained in the pickling solution in a concentration of 0.05 to 0.6 mol / l. The pickling solution expediently contains 0.05 to 0.6 mol / l permanganate or persulfate. It is also within the scope of the invention that the pickling solution contains 0.1 to 0.5 mol / l periodate or hydrogen peroxide. As already stated above, the pickling solution very preferably contains permanganate. The content of permanganate is preferably 1 g / l up to the solubility limit of the permanganate, preferably the potassium permanganate.

A permanganate solution expediently contains 2 to 15 g / l permanganate, preferably 2 to 15 g / l potassium permanganate. It is within the scope of the invention that the permanganate solution contains a wetting agent. - As above a mild pickling can also be demonstrated with a diluted one aqueous persulfate solution or periodate solution or one dilute aqueous peroxide solution. Preferably is the mild pickling treatment with a pickling solution carried out with stirring. - Following the mild The plastic surface is expediently pickled rinsed, for example 1 to 3 minutes in water.

According to a very preferred embodiment of the invention treatment with the metal salt solution according to 1.2) a temperature of at most 30 ° C, preferably at a Temperature between 15 and 25 ° C carried out. It is therefore within the scope of the invention, also the treatment with the Make metal salt solution in the room temperature range. The treatment with the metal salt solution is expedient without stirring instead. The treatment time is preferably 30 seconds to 15 minutes, preferably 3 to 12 minutes. A metal salt solution is preferably used, in which a pH between 7.5 and 12.5, preferably between 8 and 12 is set. According to a preferred embodiment the invention is with a metal salt solution worked that contains ammonia and / or at least one amine. The above pH adjustment can be done with Aid made of ammonia and in this case is in the frame the invention an ammoniacal metal salt solution used. Basically, however, it is also within the framework of the invention to use a metal salt solution which a or contains several amines. The metal salt solution can, for example Contain monoethanolamine and / or triethanolamine. Treatment with the metal salt solution means in the frame the invention in particular dipping the plastic surface into the metal salt solution.

According to a very preferred embodiment, which is of particular importance in the context of the invention, a cobalt salt solution is used as the metal salt solution. The cobalt salt solution preferably contains 0.1 to 15 g / l of Co (II) salt, preferably 5 to 12 g / l of Co (II) salt. The cobalt (II) solution expediently contains cobalt (II) sulfate and / or cobalt (II) chloride. The cobalt (II) solution preferably contains 0.1 to 15 g / l CoSO ₄ .7H ₂ O, very preferably 1 to 10 g / l CoSO ₄ .7H ₂ O. According to a very preferred embodiment of the invention, a metal salt solution, worked in particular cobalt salt solution that contains at least one oxidizing agent. The oxidizing agent can be, for example, hydrogen peroxide. The oxidizer can also be provided by blowing air into the metal salt solution. If, according to a preferred embodiment of the invention, the metal salt solution is a cobalt (II) salt solution, the oxidizing agent is preferably used with the proviso that at least part of the cobalt (II) is oxidized to cobalt (III). - After the treatment with the metal salt solution, the plastic surface is expediently rinsed.

According to a preferred embodiment of the invention takes place between process steps 1.2) and 1.3) diving the Plastic surface in aqueous alkaline solution instead.

The treatment time or diving time is preferably 10 Sec. To 3. Min., Very preferably 0.5 to 2 Min. Preferably is at a bath temperature of maximum 30 ° C, preferably 15 to 25 ° C, worked. The alkaline aqueous The solution expediently has a pH of 9 to 14 on. Diving in aqueous alkaline solution is very enjoyable preferably in dilute sodium hydroxide solution. It's in the frame of the invention for the preparation of the aqueous alkaline Solution of sodium hydroxide and / or potassium hydroxide and / or Use sodium carbonate. It very preferably contains aqueous alkaline solution 5 to 50 g / l sodium hydroxide or Potassium hydroxide. The concentration is preferred The higher the sodium hydroxide or potassium hydroxide, the higher is the metal salt concentration of the metal salt solution. Basically, the plastic surface can be used instead of aqueous alkaline solution also with an aqueous acidic Solution to be treated. - It is within the Invention, a rinse after the immersion treatment with water or distilled water.

According to a preferred embodiment of the invention, the plastic surface is treated according to process step 1.3) with an alkaline solution of an alkali metal sulfide. An ammonium sulfide can also be used. The sulfide can be, for example, a monosulfide, a disulfide, a trisulfide, a tetrasulfide or a polysulfide. According to a preferred embodiment, an alkali metal monosulfide (M ₂ S; M = alkali metal) is used, advantageously sodium sulfide (Na ₂ S). The concentration of the alkali metal monosulfide, preferably the sodium sulfide, is preferably 0.5 to 10 g / l, very preferably 2 to 8 g / l. The alkaline solution of the alkali metal sulfide expediently contains 5 to 25 g / l of sodium hydroxide, for example 10 g / l of sodium hydroxide. The treatment with the sulfide solution is preferably carried out over a period of 15 seconds to 5 minutes, very preferably 30 seconds to 2 minutes. The treatment with the sulfide solution according to process step 1.3) is preferably carried out at a temperature of at most 30 ° C. preferably carried out at a temperature between 15 and 25 ° C. - After the treatment with the sulfide solution, it is expedient to rinse, for example 1 to 3 minutes, with cold water.

It is within the scope of the invention that the metal salt solution, preferably cobalt salt solution and / or the sulfide solution Complexing agent to stabilize the corresponding solution is clogged. The metal salt solution can therefore the metal at least partially in the form of a metal complex. It is also within the scope of the invention that A wetting agent is added to the metal salt solution and / or sulfide solution is thus a better wetting of the plastic surface takes place.

Within the scope of the invention, a sulfide solution can be used be at least one substance from the group "Alcohol, diol, polyol, polyalkane glycol, polyalkylene glycol, gel / sol-forming substance such as silica gel or aluminum oxide gel " contains. It is within the scope of the invention Use mixtures of these substances in the sulfide solution. - It can in the context of the inventive method also with a metal salt solution, preferably cobalt salt solution to be worked on, at least one substance from the Group "alcohol, diol, polyol, polyalkane glycol, polyalkene glycol, gel / sol forming substance such as silica gel or alumina gel ". It is within the scope of Invention, mixtures of the substances mentioned in the Use metal salt solution.

According to a very preferred embodiment of the invention between process step 1.3) and process step 1.4) the plastic surface is dried. It is within the scope of the invention that Drying by heat treatment of the plastic surface (at elevated temperature) is realized. The plastic surface is preferably metallized only after drying. in principle can when performing the method according to the invention Treatment with the metal salt solution and / or the treatment can be repeated with the sulfide solution. It's in the frame the invention that in multiple treatment with the sulfide solution the plastic surface after each treatment is dried.

After process step 1.3), the plastic surface can be directly metallized. According to a very preferred embodiment, which is of particular importance in the context of the invention, the plastic surface is nickel-plated in a nickel bath in accordance with process step 1.4). In this respect, direct electrolytic metallization can be carried out. Electrochemical nickel plating preferably takes place in a Watts electrolyte. The treatment time is expediently 10 to 15 minutes and the electrolyte temperature is preferably 30 to 40 ° C. It is within the scope of the invention that an initial current density of 0.3 A / dm ² is used for the electrochemical nickel plating, wherein the current density is increased up to 3 A / dm ² later. A nickel layer can be applied to the plastic surface by electrolytic metallization.

The invention is based on the knowledge that by the mild pickling according to the invention the plastic surface is manipulated so that, ultimately, surprisingly a very firm adhesion of the applied metal layer is reached on the plastic surface. This firmly adhering metal layers have a high resistance to temperature changes accordingly and all pass accordingly usual temperature change shocks. The invention also lies based on the knowledge that with the invention Process achieved conditions in a relatively short time can be used for the subsequent application of the Metal layer or nickel layer are optimally suitable. Although it is basically within the scope of the invention, to repeat the method steps according to the invention and in particular to repeat process steps 1.2) and 1.3), surprisingly, optimal results are also achievable without repeating these process steps. in the Within the scope of the invention are made with little effort and high quality metal layers, especially nickel layers on the plastic surface receive. There is nothing special about this either apparatus expenditure required and in principle can conventional or conventional devices are used. To carry out the method according to the invention is in advantageously only a small amount of space is required. In addition, the time required to carry out the method according to the invention low, so that each other the known methods also save considerable time results. The method can also be simple How to functionally control what ultimately depends on affects the quality of the metal layers. Of special It is important in the context of the invention that when carried out of the measures according to the invention surprisingly one Variety of different plastics effective and reliable can be metallized. This is so far surprising than with the previously known methods only very certain few plastics are satisfactory could be metallized. First of all, let's get pure ABS easily and optimally with the method according to the invention metallized. This also applies to ABS / PC blends and especially for ABS / PC blends with a relatively high PC content (PC: polycarbonate). A pure PC is also no problem can be metallized using the method according to the invention. Such an effective and reliable Surprisingly, metallization is also common to many other plastics possible, in particular in particular also for the following plastics: POM (polyoxymethylene), PEEK (polyether ether ketone), PP (polypropylene).

The fact that, according to the invention, pickling the plastic surface is not required at high temperatures also achieved energy savings. Because only mild Pickling conditions required can be very variable Different pickling solutions are used, so that the method according to the invention also in this regard is not subject to any restrictions. Because of the invention mild pickling conditions to be set advantageously also on aggressive pickling solution components, for example, chromic acid can be dispensed with. - Because preferably at least the process steps 1.1), 1.2) and 1.3) at a maximum temperature 30 ° C, preferably at a temperature of 15 to 25 ° C, are carried out for the realization of the invention Overall, the procedure only mild conditions required, which among other things a considerable energy saving conditionally. Otherwise, the mild conditions unwanted side reactions largely avoided. With the method according to the invention, a very selective Metallization of the plastic surfaces can be achieved. It should be emphasized that a rack occupancy during implementation the method can be reliably avoided can.

The process sequence of the method according to the invention is explained below using an example: Depending on the type of plastic to be metallized, either an acidic pickling solution or an alkaline pickling solution is used. According to a preferred embodiment of the invention, an acidic pickling solution is used for the mild pickling, which contains 100 to 300 ml / l water, 700 to 900 ml / l concentrated phosphoric acid and 3 to 7 g / l potassium permanganate. According to one embodiment, the acidic pickling solution consists of 74% by weight phosphoric acid, 26% by weight water and 5 g potassium permanganate. According to another embodiment of the invention, an alkaline pickling solution is used for mild pickling, which advantageously contains 20 to 40 g / l sodium hydroxide and 5 to 15 g / l potassium permanganate. According to one embodiment, the alkaline aqueous pickling solution consists of 30 g / l sodium hydroxide and 10 g / l potassium permanganate. With the acidic pickling solution or the alkaline pickling solution explained above, pickling is preferably carried out at room temperature and over a treatment time of 10 minutes. Following the pickling treatment, the plastic surface is expediently rinsed with water. - Furthermore, according to a preferred embodiment of the invention, an ammoniacal metal salt solution is used which contains 0.1 to 12 g / l cobalt (II) sulfate and 10 to 50 ml / l 25% ammonia solution. The cobalt salt solution is preferably activated at room temperature for a treatment time of 5 to 10 minutes. The plastic surface is expediently rinsed with water after the activation with the cobalt salt solution. - For the aqueous alkaline solution, in which is preferably dipped after the treatment with the metal salt solution, 10 to 50 g / l sodium hydroxide are dissolved in water. According to one embodiment, an aqueous alkaline solution with 20 g / l sodium hydroxide is used. The immersion in the aqueous alkaline solution expediently takes place at room temperature and over a treatment period of 0.5 to 2 minutes. - An alkaline sulfide solution which contains 0.5 to 10 g / l sodium sulfide (Na ₂ S) and advantageously 5 to 25 g / l sodium hydroxide is preferably used as the sulfide solution. According to a preferred embodiment, an alkaline alkali sulfide solution is used which contains 5 g / l sodium sulfide (Na ₂ S) and 10 g / l sodium hydroxide. The sulfide treatment is preferably carried out at room temperature and for a treatment period of 0.5 to 5 minutes. The plastic surface is expediently rinsed with water after the sulfide treatment. It is within the scope of the invention that the plastic surface is dried before metallization, in particular nickel plating.

The invention is explained in more detail below on the basis of six exemplary embodiments. Exemplary embodiments 1 and 2 correspond to the prior art (comparative examples), while exemplary embodiments 3 to 6 illustrate the method according to the invention. In Examples 1, 3 and 5, discs made of ABS plastic with a surface area of 50 cm ^{2 were} used, while in Examples 2, 4 and 6, molded products made of impact-resistant polystyrene with a surface area of 70 cm ^{2 were} used. In the following, the specification "M" corresponds to the concentration specification "mol / l".

Example 1:

Disks made of ABS plastic with a surface area of 50 cm ² were pickled for 3 minutes at 70 ° C. in a pickling solution made of 4 M H ₂ SO ₄ and 3.5 M CrO ₃ . Then it was rinsed with water. The plastic objects were then treated for 30 seconds in an ammoniacal solution with 0.5 M CuSO ₄ .5H ₂ O, which had a pH of 9.5 and a temperature of 20 ° C. The plastic objects were then immersed in distilled water for 20 seconds and then treated with a sulfide solution containing 0.1 M Na ₂ S ₂ and having a temperature of 20 ° C. for 30 seconds. After this treatment, the plastic articles were washed again with cold water. This was followed by the electrochemical nickel plating. For this, treatment was carried out for 15 minutes in a Watts electrolyte which contained 1.2 M NiSO ₄ .7H ₂ O, 0.2 M NiCl ₂ .6H ₂ O and 0.5 MH ₃ BO ₃ . The initial current was 0.3 A / dm ² and the nickel plating was carried out at 40 ° C.

Example 2:

Molded objects made of impact-resistant polystyrene with a surface area of 70 cm ² were pickled for 30 seconds in a pickling solution which contained 15 MH ₂ SO ₄ and 0.1 M CrO ₃ and had a temperature of 20 ° C. It was then washed with water and then immersed in an emulsion of 0.2 g / l xylene and 0.2 g / l sintanol at 20 ° C. for 30 seconds. After the pickling treatment, the articles were washed with distilled water. The objects were then treated for 30 seconds in a metal salt solution which contained 0.5 M CuSO ₄ .5H ₂ O and in which the pH had been adjusted to 9.8 with monoethanolamine. The temperature of the solution was 20 ° C. The objects were then immersed in distilled water for 20 seconds and then treated for 30 seconds with a sulfide solution which contained 0.1 M Na ₂ S and which had a temperature of Had 20 ° C. Thereafter, the treatment in the metal salt solution and the subsequent treatment with the sulfide solution were repeated in the order described above. After this treatment, the objects were rinsed with distilled water and electrochemically nickel-plated in a Watts electrolyte according to embodiment 1.

Example 3:

The surface of the ABS plastic parts was pickled at room temperature in a solution containing 15 MH ₂ SO ₄ and 0.05 M KMnO ₄ . After pickling, the objects were rinsed with water and then treated for 10 minutes in an ammoniacal solution which contained 0.1 M CoSO ₄ and had a pH of 10 and a temperature of 20 ° C. The articles were then treated with water acidified to pH 1 with H ₂ SO ₄ . This was followed by treatment with a sulfide solution containing 0.01 M Na ₂ S ₂ for a period of 30 seconds. After this treatment, the objects were rinsed with distilled water, dried and then electrochemically nickel-plated in a Watts electrolyte according to embodiment 1.

Example 4:

The surface of the impact-resistant polystyrene articles was pickled for 10 minutes at room temperature with a solution containing 17 MH ₂ SO ₄ and 1 MH ₂ O ₂ . After pickling, the objects were rinsed with water and then treated for 10 minutes in a solution which contained 0.01 M CoF ₃ and monoethanolamine up to a pH of 8 at a temperature of 20 ° C. Then the articles were immersed for 20 seconds in an aqueous alkaline solution containing enough sodium hydroxide to have a pH of 14. The mixture was then treated for 30 seconds with a sulfide solution containing 0.05 MK ₂ S ₄ . The treated articles were then rinsed with distilled water, dried and then nickel-plated for 15 minutes in a Watts electrolyte according to Example 1.

Example 5:

The surfaces of the ABS plastic objects were pickled at room temperature with a solution containing 13 MH ₃ PO ₄ and 0.5 MK ₂ S ₂ O ₈ . After pickling, the items were rinsed with water. They were then treated for 10 min in a solution which contained 0.25 M CoSO ₄ and triethanolamine up to a pH of 9 at 20 ° C. Thereafter, the articles were immersed in an aqueous alkaline solution adjusted to pH 9 with sodium carbonate. Thereafter, treatment was carried out for 30 seconds in a sulfide solution containing 0.02 K ₂ S ₃ . After the treatment, the plastic objects were rinsed with distilled water, dried and then electrochemically nickel-plated in a Watts electrolyte according to working example 1 over a period of 15 minutes.

Example 6:

The surface of the impact-resistant polystyrene articles was pickled at room temperature with a solution containing 17 M H ₂ SO ₄ and 0.5 M KJO ₄ . After pickling, the objects were rinsed with water and then treated for 10 minutes in a solution which contained 0.01 M CoF ₃ and in which a pH of 12 had been set with ammonia and which had a temperature of 20 ° C. , Then the objects were immersed for 20 seconds in an acidic solution in which a pH of 5 was set using acetic acid. The articles were then treated in a sulfide solution containing 0.01 M Na ₂ S for 30 seconds. After this treatment, the objects were rinsed with distilled water, dried and then electrochemically nickel-plated in a Watts electrolyte according to Example 1 for 15 minutes.

The data on the processes carried out according to working examples 1 to 6 and the properties of the metal coatings obtained can be found in the table below.

Claims (16)

1. Method of metallisation of a plastic surface, in which the following method steps are carried out successively:

   1.1) the plastic surface is subjected to an etching treatment under mild etching conditions, these mild etching conditions being set to that only small openings or channels with a depth < 0.09 µm are produced on the plastic surface,

   1.2) following this, the plastic surface is treated with a metal salt solution containing at least one salt from the group including cobalt salt, silver salt, tin salt and lead salt,

   1.3) the plastic surface is treated with a sulphide solution,

   1.4) finally, the plastic surface is metallised in a metallisation bath.
2. Method as claimed in Claim 1, in which the etching treatment is carried out at a maximum temperature of 40°C, preferably a maximum of 30°C, during a treatment time of 3 to 15 minutes, preferably 5 to 10 minutes.
3. Method as claimed in Claim 1, in which the etching treatment is carried out at temperatures of over 40°C to 95°C, preferably from over 30°C to 90°C, during a treatment time of 15 seconds to 5 minutes, preferably 0.5 to 3 minutes.
4. Method as claimed in one of Claims 1 to 3, in which etching is carried out using an acidic etching solution containing at least one oxidising agent.
5. Method as claimed in one of Claims 1 to 4, in which an acidic aqueous etching solution is used which contains permanganate and phosphoric acid and/or sulphuric acid.
6. Method as claimed in one of Claims 1 to 5, in which the etching treatment is carried out with an alkaline aqueous solution containing permanganate.
7. Method as claimed in one of Claims 1 to 6, in which the treatment with the metal solution is carried out at a temperature of at most 30°C, preferably at a temperature between 15 and 25°C.
8. Method as claimed in one of Claims 1 to 7, in which a metal salt solution is used in which a pH value between 7.5 and 12.5, preferably between 8 and 12, is set.
9. Method as claimed in one of Claims 1 to 8, in which a metal salt solution is used which contains ammonia and/or at least one amine.
10. Method as claimed in one of Claims 1 to 9, in which a cobalt salt solution is used as the metal solution, and the cobalt salt solution contains 0.1 to 15 g/l cobalt(II) salt, preferably 0.5 to 12 g/l cobalt(II) salt.
11. Method as claimed in one of Claims 1 to 10, in which a metal salt solution, particularly a cobalt salt solution, is used which contains at least one oxidising agent.
12. Method as claimed in one of Claims 1 to 11, in which between the method steps 1.2) and 1.3) an immersion of the plastic surface in an aqueous alkaline solution is carried out.
13. Method as claimed in one of Claims 1 to 12, in which in the method step 1.3) the plastic surface is treated with an alkaline solution of an alkali metal sulphide.
14. Method as claimed in one of Claims 1 to 13, in which the treatment with the sulphide solution is carried out according to the method step 1.3) at a temperature of at most 30°C, preferably at a temperature between 15 and 25°C.
15. Method as claimed in one of Claims 1 to 14, in which between the method step 1.3) and the method step 1.4) drying of the plastic surface is carried out.
16. Method as claimed in one of Claims 1 to 15, in which the plastic surface is nickel-plated in a nickel bath according to the method step 1.4).