EP2639332A1 - Method for metallising non-conductive plastic surfaces - Google Patents

Abstract

Metallizing (P1) electrically nonconductive plastic surfaces of articles involves (a) fastening the article to a rack, (b) etching the plastic surface with an etching solution; (c) treating the plastic surface with a solution of a metal colloid or of a compound of a metal, where the metal is selected from the metals of transition group I of the Periodic Table of the Elements and transition group VIII of the Periodic Table of the Elements, and (d) metallizing the plastic surface with a metallizing solution; where the rack is treated with a solution comprising iodate ions.

Description

Field of the invention

The present invention relates to a method of metallizing electrically non-conductive plastic surfaces of articles. During the process, the rack mounting the said objects is treated with an iodine-containing solution to prevent metallization of the rack. After treatment with the lodate-containing solution, the articles can be metallized by known methods. The frame remains free of metal.

Background of the invention

Articles made of electrically non-conductive plastic can be metallized with an electroless metallization process. In this process, the article is first cleaned and pickled, then treated with a precious metal and finally metallized. The pickling is typically carried out by means of chromic acid. The etching serves to make the surface of the object susceptible to the subsequent metallization, so that the surfaces of the objects in the subsequent treatment steps are well wetted with the respective solutions and the deposited metal finally adheres sufficiently firmly to the surface.

For etching, the surface of articles of, for example, acrylonitrile-butadiene-styrene copolymer (ABS copolymer) is etched using chromosulfuric acid, so that superficially microcaverns form, in which metal is deposited and subsequently adheres firmly there. After pickling, the plastic for electroless metallization by means of an activator containing a noble metal, activated and then electroless metallized. Subsequently, a thicker metal layer can be applied electrolytically.

However, pickling solutions based on chromosulfuric acid are toxic and should therefore be replaced as far as possible.

The literature describes attempts to replace pickling solutions based on chromosulfuric acid by those containing permanganate salts.

The use of permanganates in alkaline medium for the metallization of printed circuit boards as a carrier of electronic circuits has long been established. Since the hexavalent (manganate) formed in the oxidation is water-soluble and has sufficient stability in the alkaline state, the manganate can be electrolytically re-oxidized similarly to the trivalent chromium to the original oxidant, in this case the permanganate. In Scripture DE 196 11 137 A1 the use of permanganate is also described for the metallization of plastics other than printed circuit board material. For the metallization of ABS plastics, a solution of alkaline permanganate has not proved to be suitable, since in this way a reliable, sufficient adhesive strength between metal layer and plastic substrate could not be produced. This adhesive strength is determined in the peel test. It should have at least a value of 0.4 N / mm.

In EP 1 0010 52 is an acidic permanganate solution which is said to be suitable for use in plastic plating. EP 1 0010 52 does not report the bond strengths achievable with this pretreatment. Our own tests have shown that the adhesive strengths are below a value of 0.4 N / mm. In addition, the in EP 1 0010 52 not stable solutions described. A constant quality of the metallization can therefore not be achieved.

As an alternative to chromic acid are in WO 2009/023628 A2 strongly acidic solutions containing an alkali permanganate salt proposed. The solution contains about 20 g / l alkali permanganate salt in 40-85% by weight phosphoric acid. Such solutions form colloidal manganese (IV) species that are difficult to separate. According to the WO 2009/023628 A2 lead the colloids after a short time to a coating of sufficient quality is no longer possible. To solve the problem suggests the WO 2009/023628 A2 to use sources of manganese (VII) that contain no alkali or alkaline earth ions. However, the preparation of such manganese (VII) sources is expensive.

Therefore, the toxic chromosulfuric acid is still used for the etching treatment of plastics.

For large-scale application of the metallization of plastic surfaces, the objects are usually attached to racks. These are metal carrier systems that allow the simultaneous treatment of a large number of objects with the successive solutions of the individual process steps and last steps for the electrolytic deposition of one or more metal layers. The racks are usually self-coated with plastic. Therefore, the racks in principle also represent a substrate for metallization processes on plastic surfaces.

The additional metallization of the racks is undesirable because the metal layers must be removed from the racks after the articles have been coated. This means an additional expense for the removal associated with additional consumption of chemicals. In addition, the productivity of the metallization plant is lower in this case, since the racks must first be demetallised before re-loading with objects. If the demetallization has to take place with half-concentrated hydrochloric acid and / or with nitric acid, vapors and aerosols are produced, which lead to corrosion in the environment.

Another problem is that when rack metallization occurs, it is no longer possible to achieve a defined current density, because the extent of the rack occupancy is usually not known and the exact area of the rack also not. In most cases, the applied metal layer is too thin as a result on the galvanized plastic objects.

The use of chromic acid stains significantly reduces this problem. The chromic acid also penetrates during the pickling in the plastic coating of the racks and diffuses during the subsequent process steps out of this and thus prevents the metallization of the frame.

If you want to replace the toxic chromosulfuric acid for etching treatment of plastics by ecologically safe process steps, it is necessary to prevent the unwanted metallization of the racks.

patent DE 195 10 855 C2 describes a method for selective or partial electrolytic metallization of non-conductive materials. This is the simultaneous Metallization of the frames prevented by treatment steps with adsorption-promoting solutions, so-called conditioners, is dispensed with. However, it is emphasized that the metallization process of non-conductive materials in DE 195 10 855 C2 only suitable for direct metallization.

Description of the drawings

• FIG. 1 : Influence of the iodate treatment on the framework metallization
• FIG. 2A : Rack after metallization process without iodate treatment
• FIG. 2B : Rack after metallization with iodate treatment
• FIG. 3 : Influence of the treatment time of articles made of an ABS / PC mixture with glycol compounds on the adhesive strength
• FIG. 4 : Influence of the treatment time of objects made of ABS with glycol compounds on the adhesive strength

Description of the invention

The present invention is therefore based on the problem that it is not yet possible to avoid the metallization of the racks and at the same time to achieve a metallization of objects made of electrically non-conductive plastic with sufficient process reliability and adhesion of the subsequently applied metal layers.

It is therefore an object to prevent the metallization of the racks, while electrically non-conductive plastic surfaces of objects are metallized.

1. A) Befestigen des Gegenstands in einem Gestell,
2. B) Beizen der Kunststoffoberfläche mit einer Beizlösung,
3. C) Behandeln der Kunststoffoberfläche mit einer Lösung eines Metall-Kolloids oder einer Verbindung eines Metalls, wobei das Metall ausgewählt ist aus den Metallen der I. Nebengruppe des Periodensystems der Elemente und der VIII. Nebengruppe des Periodensystems der Elemente, und
4. D) Metallisieren der Kunststoffoberfläche mit einer Metallisierungslösung;

dadurch gekennzeichnet, dass das Gestell mit einer Lösung enthaltend eine Quelle für Iodationen behandelt wird.This object is achieved with the following method according to the invention: Method for metallizing electrically non-conductive plastic surfaces of objects, comprising the method steps:

1. A) securing the article in a rack,
2. B) pickling the plastic surface with a pickling solution,
3. C) treating the plastic surface with a solution of a metal colloid or a compound of a metal, wherein the metal is selected from the metals of the I subgroup of the Periodic Table of the Elements and the VIII. Subgroup of the Periodic Table of the Elements, and
4. D) metallizing the plastic surface with a metallizing solution;

characterized in that the rack is treated with a solution containing a source of iodate ions.

In the context of this invention, articles are understood to mean objects which are made of at least one electrically non-conductive plastic or which are covered with at least one layer of at least one electrically non-conductive plastic. The objects thus have surfaces of at least one electrically non-conductive plastic. In the context of this invention, plastic surfaces are understood as meaning said surfaces of the objects.

The process steps of the present invention are carried out in the order given, but not necessarily immediately consecutively. It is possible to carry out further process steps and, in each case, additional rinsing steps, preferably with water, between the steps.

By treating the rack according to the invention with a solution containing a source of iodate ions, the metallization of the rack is avoided, while the electrically non-conductive plastic surfaces of objects are coated with metal. The frame thus remains free of metal during the process according to the invention. With the method according to the invention, it is not necessary to free the racks of metal again after use, since the racks are not metallized by the treatment according to the invention with iodate ions and thus remain free of metal. Thus, after performing the metallization process and removing the metallized objects from the racks, the racks can be returned directly to the production cycle without further treatment and used to metallize further objects.

There are no additional cleaning and etching steps for demetallizing the racks necessary. This also reduces the effort for wastewater disposal. In addition, fewer chemicals are consumed. The productivity of the metallization is also increased because a given number of existing racks a larger number of objects to be metallized can be treated.

The plastic surfaces are made of at least one electrically non-conductive plastic. In one embodiment of the present invention, the at least one electrically nonconducting plastic is selected from the group comprising an acrylonitrile-butadiene-styrene copolymer (ABS copolymer), a polyamide (PA), a polycarbonate (PC) and a mixture of an ABS copolymer with at least one other polymer.
In a preferred embodiment of the invention, the electrically non-conductive plastic is an ABS copolymer or a mixture of an ABS copolymer with at least one further polymer. The at least one further polymer is particularly preferably polycarbonate (PC), that is to say particularly preferred are ABS / PC mixtures.

The treatment according to the invention of the rack with a solution containing a source of iodate ions is also referred to below as protecting the rack. The protection of the frame can take place at different times during the method according to the invention. In a preferred embodiment of the present invention, treating the rack with a solution containing a source of iodate ions takes place prior to step A).

At this time, the items are not yet mounted in the rack. Thus, the frame alone, without the objects, is treated with the solution containing a source of iodate ions.

Step A) of the method according to the invention is the attachment of the objects in racks, which allow the simultaneous treatment of a large number of objects with the successive solutions of the individual process steps as well as the electrical contacting during the last steps for the electrolytic deposition of one or more metal layers. The treatment of the articles according to the method of the invention is preferably carried out in a conventional dipping process by successively immersing the articles in solutions in containers in which the respective treatment takes place. In this case, the articles can either be attached to racks or filled with drums into the solutions. An attachment to racks is preferred. The racks are usually self-coated with plastic. The plastic is usually polyvinyl chloride (PVC).

• A i) Behandeln der Kunststoffoberfläche in einer wässrigen Lösung enthaltend mindestens eine Glykolverbindung.

In a further embodiment of the invention, the following further method step is carried out between method steps A) and B):

• A i) treating the plastic surface in an aqueous solution containing at least one glycol compound.

The further process step A i) is also referred to as a pretreatment step. By this pretreatment step, the adhesion strength between the plastic of the article and the metal layer is increased.

worin
n eine ganze Zahl zwischen 1 und 4 bedeutet; und
R1 und R2 unabhängig voneinander bedeuten -H, -CH₃, -CH₂-CH₃, -CH₂-CH₂-CH₃, -CH(CH₃)-CH₃, -CH₂-CH₂-CH₂-CH₃, -CH(CH₃)-CH₂-CH₃, -CH₂-CH(CH₃)-CH₃, -CH₂-CH₂-CH₂-CH₂-CH₃, -CH(CH₃)-CH₂-CH₂-CH₃, -CH₂-CH(CH₃)-CH₂-CH₃, -CH₂-CH₂-CH(CH₃)-CH₃, -CH(CH₂-CH₃)-CH₂-CH₃, -CH₂-CH(CH₂-CH₃)-CH₃, -CO-CH₃, -CO-CH₂-CH₃, -CO-CH₂-CH₂-CH₃, -CO-CH(CH₃)-CH₃, -CO-CH(CH₃)-CH₂-CH₃, -CO-CH₂-CH(CH₃)-CH_3, -CO-CH₂-CH₂-CH₂-CH₃.A glycol compound is understood as meaning compounds of the following general formula (I):

wherein
n is an integer between 1 and 4; and
R ₁ and R _2, independently of one another, denote -H, -CH ₃ , -CH ₂ -CH ₃ , -CH ₂ -CH ₂ -CH ₃ , -CH (CH ₃ ) -CH ₃ , -CH ₂ -CH ₂ -CH ₂ - CH ₃ , -CH (CH ₃ ) -CH ₂ -CH ₃ , -CH ₂ -CH (CH ₃ ) -CH ₃ , -CH ₂ -CH ₂ -CH ₂ -CH ₂ -CH ₃ , -CH (CH ₃ ) -CH ₂ -CH ₂ -CH ₃ , -CH ₂ -CH (CH ₃ ) -CH ₂ -CH ₃ , -CH ₂ -CH ₂ -CH (CH ₃ ) -CH ₃ , -CH (CH ₂ -CH ₃ ) -CH ₂ -CH ₃ , -CH ₂ -CH (CH ₂ -CH ₃ ) -CH ₃ , -CO-CH ₃ , -CO-CH ₂ -CH ₃ , -CO-CH ₂ -CH ₂ -CH ₃ , -CO-CH (CH ₃ ) -CH ₃ , -CO-CH (CH ₃ ) -CH ₂ -CH ₃ , -CO-CH ₂ -CH (CH ₃ ) -CH _3, -CO-CH ₂ - CH ₂ -CH ₂ -CH ₃ .

According to the general formula (I), the glycol compounds include the glycols themselves as well as glycol derivatives. The glycol derivatives, the glycol esters and the glycol ether esters are calculated as glycol derivatives. The glycol compounds are solvents.

Preferred glycol compounds are ethylene glycol, diethylene glycol, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monopropyl ether acetate, butyl glycol, ethylene glycol monobutyl ether, ethylene glycol diacetate and mixtures thereof. Particularly preferred Diethylene glycol monoethyl ether acetate, ethylene glycol acetate, ethylene glycol diacetate, butyl glycol and mixtures thereof.

• CH₃-CO-O-CH₂CH₂-O-CH₂CH₂-O-CH₂CH₃ + H2O →
• CH₃-COOH + HO-CH₂CH₂-O-CH₂CH₂-O-CH₂CH₃

When using glycol esters and glycol ether esters, it is useful to keep the pH of the aqueous solution of the glycol compound in the neutral range by suitable measures in order to force back the hydrolysis to the alcohol and the carboxylic acid as much as possible. An example is the hydrolysis of diethylene glycol monoethyl ether acetate:

• CH ₃ -CO-O-CH ₂ CH ₂ -O-CH ₂ CH ₂ -O-CH ₂ CH ₃ + H ₂ O →
• CH ₃ -COOH + HO-CH ₂ CH ₂ -O-CH ₂ CH ₂ -O-CH ₂ CH ₃

The water concentration of the solution containing a glycol compound also has an influence on the hydrolysis of the glycol esters and glycol ether esters. However, the solution must contain water for two reasons: on the one hand to obtain a non-flammable treatment solution and on the other hand to adjust the strength of the attack on the plastic surface can. A pure solvent, ie 100% of a glycol compound, would dissolve most uncrosslinked polymers or leave at least one unacceptable surface. It has therefore been found to be very advantageous to buffer the solution of a glycol ester or glycol ether ester and thus to keep it in the neutral pH range, which means to trap the protons produced by hydrolysis of the solvent. A phosphate buffer mixture has proven to be sufficiently suitable for this purpose. The readily soluble potassium phosphates allow sufficiently high concentrations with good buffer capacity at solvent concentrations up to 40% vol.

The optimal treatment time of the plastic surface depends on the plastic used, the temperature and the type and concentration of the glycol compound. The treatment parameters have an influence on the adhesion between the treated plastic surface and the metal layer applied in subsequent process steps. Higher temperatures or concentrations of the glycol compounds also affect the texture of the plastic surface. In any case, it should be possible for the subsequent pickling step B) to remove the solvent from the plastic matrix again, because otherwise the subsequent steps of the process, in particular the activation according to process step C), will be disturbed.

Adhesive strengths of at least 0.8 N / mm are obtained with the method according to the invention, which is significantly above the required minimum value of 0.4 N / mm. The treatment duration in process step A i) is between 1 and 30 minutes, preferably between 5 and 20 minutes and more preferably between 7 and 15 minutes.

The treatment temperature is between 20 ° C and 70 ° C, depending on the type of solvent or solvent mixture used. Preferably, a treatment temperature between 20 ° C and 50 ° C, more preferably a treatment temperature between 20 ° C and 45 ° C.

The treatment of the plastic surfaces according to process step A i) can be carried out in an aqueous solution containing a glycol compound or in an aqueous solution containing two or more different glycol compounds. The total concentration of glycol compounds in the aqueous solution is 5% vol. -50% vol., Preferably 10% vol. - 40% vol., And more preferably 20% vol. - 40% vol. When said solution contains a glycol compound the total concentration of the concentration of this one glycol compound. When said solution contains two or more different glycol compounds, the total concentration equals the sum of the concentrations of all the glycol compounds contained. In connection with the solution containing at least one glycol compound, the concentration data for the glycol compound / glycol compounds in% always means a concentration in% vol.

Thus, for the pretreatment of ABS plastic surfaces, a solution of 15% by volume of diethylene glycol monoethyl ether acetate in a mixture with 10% by volume of butylglycol at 45 ° C. has proven advantageous (see Example 4). In this case, the first solvent serves to produce the adhesive strength, while the second solvent, as a nonionic surfactant, increases the wettability and helps to remove possibly existing contaminants from the plastic surface.

For the pretreatment of ABS / PC mixtures, for example Bayblend T45 or Bayblend T65PG, a solution of 40% by volume of diethylene glycol monoethyl ether acetate in water at room temperature has been found to be more advantageous proved because it allows a higher adhesion of the applied metal layers in these plastics (see Example 5).

In a further preferred embodiment of the present invention, treating the rack with a solution containing a source of iodate ions takes place between method steps A) and B). In this case, the treatment of the frame with a solution containing a source of iodate ions between the method steps A) and A i) take place or between the method steps A i) and B).

At these times, the items are already mounted in the rack. The frame is therefore treated together with the objects with the solution containing a source of iodate ions.
The terms "treating the rack with a solution containing a source of iodate ions" and "treating the rack with a solution containing a source of iodate ions" in the context of this invention mean that the guarding of the rack can take place alone, without the objects (e.g. when protecting the rack occurs prior to step A) or that the rack may be protected together with the items (for example, if the rack is protected at any time after step A)).
Regardless of whether the protection of the rack takes place on its own or together with the objects, it provides special protection of the plastic casing of the racks prior to metal deposition, while the objects which are mounted in the racks during process step A) are metallised. The protection of the frame ensures that the plastic coating of the frames in the later process steps C) to D) is not metallized, that is, the racks remain free of metal. This effect is particularly pronounced on a PVC sheathing of the racks.

The pickling treatment according to process step B) is carried out in a pickling solution. The pickling solution contains a source of permanganate ions. The source of permanganate ions is selected from the group of alkali metal permanganates containing potassium permanganate and sodium permanganate. The source of permanganate ions is present in the pickling solution at a concentration of between 30 g / l and 250 g / l, preferably between 30 g / l and 180 g / l, more preferably between 90 g / l and 180 g / l and more preferably 100 g / l. Potassium permanganate may be due to its Solubility in a concentration of up to 70 g / l contained in the pickling solution. Sodium permanganate can be contained in the pickling solution at a concentration of up to 250 g / l. The lower concentration limit of each of these two salts is typically 30 g / l. The content of sodium permanganate is preferably between 90 g / l and 180 g / l.

The pickling solution is preferably acidic, that is it preferably contains an acid. Surprisingly, alkaline permanganate solutions, which are routinely used in the printed circuit board industry as a pickling solution, are not suitable for the present invention because they do not provide sufficient adhesion between the plastic surface and the metal layer.

Acids used in the pickling solution are preferably inorganic acids. The inorganic acid in the pickling solution according to process step B) is selected from the group comprising sulfuric acid, nitric acid and phosphoric acid. The acid concentration must not be too high, otherwise the pickling solution will not be stable. The acid concentration is between 0.02-0.6 mol / l based on a monobasic acid. It is preferably between 0.06 and 0.45 mol / l, more preferably between 0.07 and 0.30 mol / l in each case based on a monobasic acid. Sulfuric acid is preferably used in a concentration between 0.035 and 0.15 mol / l, which corresponds to an acid concentration between 0.07 and 0.30 mol / l based on a monobasic acid.

The pickling solution can be operated at temperatures between 30 ° C and 90 ° C, preferably between 55 ° C to 75 ° C. Although it has been found that sufficiently high bond strengths between metal layers and plastic surfaces can be achieved even at low temperatures between 30 ° C and 55 ° C. However, it can then not be ensured that all solvent of the treatment with glycol compound according to process step A i) is removed from the plastic surface. This is especially true for pure ABS. Thus, if step A i) is carried out in the process according to the invention, the temperatures in the subsequent process step B) are to be higher, namely in the range of 55 ° C to 90 ° C, preferably in the range of 55 ° C to 75 ° C. The optimal treatment time depends on the treated plastic surface and the selected temperature of the pickling solution. For ABS and ABS / PC plastic surfaces, the best adhesion is between Plastic surface and then applied metal layer at a treatment time of between 5 and 30 minutes achieved, preferably between 10 and 25 minutes and more preferably between 10 and 15 minutes. A longer treatment time than 30 minutes usually does not lead to an improvement in the adhesive strength.

An acidic permanganate solution is very reactive at elevated temperatures, for example at 70 ° C. It then form by the oxidation reaction with the plastic surface much manganese (IV) species, which precipitate out. These manganese (IV) species are predominantly manganese (IV) oxides or oxide hydrates and are referred to below simply as manganese dioxide.

The manganese dioxide precipitate interferes with the subsequent metallization when it remains on the plastic surface. During activation according to method step C), it ensures that areas of the plastic surface are not covered with metal colloid or generates unacceptable roughness of the metal layer to be applied in later method steps.

The pickling solution contains no chromium or chromium compounds; the pickling solution contains neither chromium (III) ions nor chromium (VI) ions. The pickling solution according to the invention is thus free of chromium or chromium compounds; the pickling solution is free of chromium (III) ions and chromium (VI) ions.
In a further embodiment, after the permanganate treatment according to method step B), the articles are cleaned by rinsing off excess permanganate solution. The rinsing takes place in one or more, preferably three, rinsing steps with water.

• B i) Behandeln der Kunststoffoberfläche in einer Lösung enthaltend ein Reduktionsmittel für Mangandioxid.

In a further embodiment of the invention, the following further method step is carried out between method steps B) and C):

• B i) treating the plastic surface in a solution containing a reducing agent for manganese dioxide.

The further process step B i) is also referred to as a reduction treatment. By means of this reduction treatment, manganese dioxide adhering to the plastic surfaces is reduced to water-soluble manganese (II) ions. The reduction treatment is carried out after the permanganate treatment according to process step B) and optionally after rinsing off. For this purpose, an acidic solution of a reducing agent is used. The reducing agent is selected from the group consisting of hydroxylammonium sulfate, hydroxylammonium chloride and hydrogen peroxide. Preferred is an acidic solution of hydrogen peroxide because hydrogen peroxide is neither toxic nor complexing. The content of hydrogen peroxide in the solution of reduction treatment (reduction solution) is between 25 ml / l and 35 ml / l of a 30% hydrogen peroxide solution (wt%), preferably 30 ml / l of a 30% hydrogen peroxide solution (wt. -%).

The acid used in the reduction solution is an inorganic acid, preferably sulfuric acid. The acid concentration is 0.5 mol / l to 5.0 mol / l, preferably 1.0 mol / l to 3.0 mol / l, particularly preferably 1.0 mol / l to 2.0 mol / l in each case based on a monobasic acid. When using sulfuric acid, concentrations of 50 g / l of 96% sulfuric acid to 100 g / l of 96% sulfuric acid are particularly preferred, resulting in an acid concentration of 1.0 mol / l to 2.0 mol / l based on a monobasic Acid corresponds.

The reduction treatment removes the manganese dioxide precipitate, which has a disruptive effect on the metallization of the objects. The reduction treatment of process step B i) thereby promotes the uniform continuous coverage of the articles with the desired metal layer and promotes the adhesion and smoothness of the metal layer applied to the articles.

The reduction treatment according to process step B i) also has an advantageous effect on the metallization of the plastic coating of the frame. The unwanted occupancy of the plastic coating with palladium during process step C) is suppressed. This effect is particularly pronounced when the reducing solution contains a strong inorganic acid, preferably sulfuric acid. Hydrogen peroxide is also preferred over hydroxylammonium sulfate or chloride in the reducing solution because it better suppresses framework metallization.

The reduction treatment according to process step B i) is carried out at a temperature between 30 ° C and 50 ° C, preferably at 40 ° C to 45 ° C. The Reduction treatment is carried out for a period of between 1 and 10 minutes, preferably between 3 to 6 minutes. In order to achieve sufficient protection of the racks prior to activation, it is advantageous to increase the treatment time in the reducing solution to 3 to 10 minutes, preferably to 3 to 6 minutes.

The reducing agent hydrogen peroxide used must be replenished from time to time. The consumption of hydrogen peroxide can be calculated from the amount of manganese dioxide bound on the plastic surfaces. In practice, it is sufficient to observe the evolution of gas in the reduction reaction during process step B i) and to meter the original amount of hydrogen peroxide, for example 30 ml / l of a 30% solution, as the gas evolution subsides. At elevated operating temperature of the reducing solution, for example at 40 ° C, the reaction is completed quickly and after one minute at the latest.

In a further preferred embodiment of the present invention, the treatment of the rack with a solution containing a source of iodate ions takes place between the method steps B) and C), particularly preferably between the method steps B i) and B ii).

Regardless of which of the times described in the method according to the invention takes place protecting the frame, it provides a special protection of the plastic coating of the frames before the metal deposition, while the objects which are fixed in the racks during step A), are metallized.

The effect of protecting the frame on the metallization of the frames is also in FIGS. 2A and 2B shown. FIG. 2A shows a part of a frame after a plastic surface of a plate-shaped object, which is fixed in the frame has been coppered. The method for applying the copper layer corresponded to the metallization method according to the invention with the deviation that the protection of the frame was not performed. The part of the frame that came into contact with the different treatment solutions of the metallization process is completely covered by a layer of copper. FIG. 2B shows a corresponding part of a frame after a plastic surface of a plate-shaped object which is mounted in the frame, including the protection of the frame was coppered. The plastic surface of the article carries a uniform copper layer, while the plastic sheath of the frame was not coppered. The plastic coating of the frame continues to bear the black-green color, which is caused by long use of the frame.

The treatment with iodate ions is particularly advantageous if the process step C ii) according to one embodiment of the invention consists of an electroless plating of the objects in a metallization solution.

The iodate ions are sufficiently stable in aqueous solution and are consumed only by extraction. In general, the effect of protecting the rack increases with increasing concentration of iodate ions and with increasing operating temperature. A determination of the optimum concentration will be described in Embodiment 1. The protection of the frame is carried out at a temperature of 20 ° C to 70 ° C, more preferably from 45 ° C to 55 ° C. Suitable sources of iodate ions are selected from the group of metal iodates containing sodium iodate, potassium iodate, magnesium iodate, calcium iodate and their hydrates. The concentration of the metal iodates is between 5 g / l and 50 g / l, preferably from 15 g / l to 25 g / l. The duration of treatment of the frame with iodate ions is between 1 to 20 minutes, preferably between 2 to 15 minutes and particularly preferably between 5 to 10 minutes.

The solution containing a source of iodate ions may further contain an acid. Preference is given to inorganic acids. The inorganic acids are selected from the group comprising sulfuric acid and phosphoric acid, preferably sulfuric acid. The acid concentration is 0.02 mol / l to 2.0 mol / l, preferably 0.06 mol / l to 1.5 mol / l, particularly preferably 0.1 mol / l to 1.0 mol / l in each case based on a monobasic acid. When sulfuric acid is used, concentrations of 5 g / l of 96% sulfuric acid to 50 g / l of 96% sulfuric acid are particularly preferred, resulting in an acid concentration of 0.1 mol / l to 1.0 mol / l based on a monobasic Acid corresponds.

The described composition of the solution containing a source of iodate ions and the temperature and duration of the treatment of the frame apply regardless of the time in the inventive process, takes place to protect the frame.

Further, treating the rack with a solution containing a source of iodate ions shows a storage effect. The effect of protecting the racks, namely, avoiding metal deposition on the racks, stops during one or more metallization cycles. In the context of this invention, a metallization cycle is understood as meaning a metallization process which contains the process steps A) to D) already described, but not the treatment of the framework with a solution containing a source of iodate ions. In each metallization cycle, non-metallized articles are mounted in the racks and metallized articles are produced therefrom. The inventive method comprising treating the rack with a solution containing a source of iodate ions is carried out and then one to four Metallisierungszyklen be performed. During the process of the invention and during the metallization cycles, objects are metallized. The rack is not metallized during the process of the invention nor during the subsequent metallization cycles, although the metallization cycles do not involve treating the rack with a solution containing a source of iodate ions. Treating the rack with a solution containing a source of iodate ions during the process of the invention is sufficient to avoid metalization of the rack during one to four subsequent metallization cycles.

The process of the present invention further includes process step C) wherein a plastic surface is treated with a solution of a metal colloid or a compound of a metal.

The metal of the metal colloid or of the metal compound is selected from the group comprising the metals of subgroup I of the Periodic Table of the Elements (PSE) and subgroup VIII of the PSE.

The VIII subgroup metal of the PSE is selected from the group consisting of palladium, platinum, iridium, rhodium and a mixture of two or more of these metals. The metal of the 1st subgroup of the PSE is selected from the group containing gold, silver and a mixture of these metals.

As the metal of the metal colloid, palladium is preferred. The metal colloid is stabilized with a protective colloid. The protective colloid is selected from the group comprising metallic protective colloids, organic protective colloids and other protective colloids. As the metallic protective colloid, tin ions are preferable. The organic protective colloid is selected from the group comprising polyvinyl alcohol, polyvinylpyrrolidone and gelatin, polyvinyl alcohol is preferred.

In a preferred embodiment of the invention, the solution of the metal colloid in process step C) is an activator solution with a palladium / tin colloid. This colloid solution is generated from a palladium salt, a stannous salt and an inorganic acid. As the palladium salt, palladium chloride is preferred. As stannous salt, tin (II) chloride is preferred. The inorganic acid may consist of hydrochloric acid or sulfuric acid, preferably hydrochloric acid. The colloid solution is formed by reduction of the palladium chloride to palladium with the aid of stannous chloride. The conversion of the palladium chloride into the colloid is complete, therefore the colloid solution no longer contains palladium chloride. The concentration of palladium is 5 mg / l-100 mg / l, preferably 20 mg / l-50 mg / l and particularly preferably 30 mg / l-45 mg / l, based on Pd ²⁺ . The concentration of tin (II) chloride 0.5 g / l - 10 g / l, preferably 1 g / L - 5 g / l, and most preferably 2 g / l - 4 g / l, based on Sn ^2+. The concentration of hydrochloric acid is 100 ml / l - 300 ml / l (37 wt% HCl). In addition, a palladium / tin colloidal solution additionally contains tin (IV) ions, which are formed by oxidation of tin (II) ions. The temperature of the colloid solution during process step C) is 20 ° C-50 ° C and preferably 35 ° C-45 ° C. The treatment time with the activator solution is 0.5 min-10 min, preferably 2 min-5 min and particularly preferably 3 min-5 min.

In a further embodiment of the invention, in method step C), the solution of a compound of a metal is used instead of the metal colloid. As a solution of a metal compound, a solution containing an acid and a metal salt is used. The metal of the metal salt consists of one or more of the above listed metals of the I. and VIII. Subgroup of the PSE. The metal salt may be a palladium salt, preferably palladium chloride, palladium sulfate or palladium acetate, or a silver salt, preferably silver acetate. The acid is preferably in hydrochloric acid. Alternatively, a metal complex can also be used, for example a palladium complex salt, such as a salt of a palladium-aminopyridine complex. The metal compound is present in process step C) in a concentration of 40 mg / l to 80 mg / l, based on the metal. The solution of the metal compound can be operated at a temperature of 25 ° C to 70 ° C, preferably at 25 ° C. The Treatment time with the solution of a metal compound is 0.5 min - 10 min, preferably 2 min - 6 min and more preferably 3 min - 5 min.

• B ii) Behandeln der Kunststoffoberfläche in einer wässrigen sauren Lösung.

Between method steps B) and C), the following further method step can be carried out:

• B ii) treating the plastic surface in an aqueous acidic solution.

Preferably, process step B ii) is carried out between process steps B i) and C). If in the method according to the invention at method step B i) the protection of the racks followed, method step B ii) is particularly preferably carried out between protecting the racks and method step C).

The treatment of the plastic surfaces according to process step B ii) is also referred to as pretreatment and the aqueous acidic solution used as a pre-dip solution. The pre-dip solution has the same composition as the colloid solution in step C), without containing the metal of the colloid and its protective colloid. In the case of employing a palladium / tin colloid solution in process step C), the pre-dip solution contains exclusively hydrochloric acid if the colloid solution also contains hydrochloric acid. For pre-dipping a brief immersion in the pre-dipping solution at ambient temperature is sufficient. Without rinsing the plastic surfaces, they are further treated directly after treatment in the pre-dip solution with the colloid solution of process step C).

Process step B ii) is preferably carried out if process step C) consists of treating a plastic surface with a solution of a metal colloid. Process step B ii) can also be carried out if process step C) consists of treating a plastic surface with a solution of a compound of a metal.

• C i) Behandeln der Kunststoffoberfläche in einer wässrigen sauren Lösung und
• C ii) Stromloses Metallisieren der Kunststoffoberfläche in einer Metallisierungslösung.

After the treatment of the plastic surfaces with the metal colloid or the metal compound according to process step C), these can be rinsed.
In a further embodiment of the invention, the following further method steps are carried out between process steps C) and D):

• C i) treating the plastic surface in an aqueous acid solution and
• C ii) electroless plating of the plastic surface in a metallization solution.

The embodiment is shown schematically in Table 1. Table 1: Embodiment of plastic metallization step ingredients duration temperature A) Attach --- --- --- A i) Pretreatment Glycol compound as an organic solvent in water 2-15 min 35-50 ° C B) pickling 100 g / l sodium permanganate, 10 g / l 96% sulfuric acid 5-15 min 70 ° C B i) Reduce 100 g / l 96% sulfuric acid, 30 ml / l hydrogen peroxide, 30% by weight 1 min 45 ° C Protect the frame 20 g / l potassium iodate 2-5 min 40-60 ° C B ii) Prelude Hydrochloric acid, about 10% by weight 1 min 20 ° C C) Activate Hydrochloric acid palladium / tin colloid 3-6 min 20-45 ° C C i) Accelerate Sulfuric acid (5%) 2-6 min 40-50 ° C C ii) electrolessly deposit metal Chemically reductive nickel plating or copper plating 6-20 min 30-50 ° C D) metal deposit For example, electrochemical copper plating or nickel plating 15-70 min 20-35 ° C

These further method steps C i) and C ii) are used when the objects are to be metallized with an electroless metallization process, that is to say that a first metal layer is to be applied to the plastic surfaces by an electroless method.

When activation with a metal colloid has been carried out in method step C), in method step C i) the plastic surfaces are treated with an accelerator solution in order to remove constituents of the colloid of the colloid solution, for example a protective colloid, from the plastic surfaces. If the colloid of the colloid solution according to process step C) is a palladium / tin colloid, an aqueous solution of an acid is preferably used as accelerator solution. The acid is selected, for example, from the group comprising sulfuric acid, hydrochloric acid, citric acid and tetrafluoroboric acid. In the case of a palladium / tin colloid, the accelerator solution is used to remove the tin compounds which serve as a protective colloid.

Alternatively, in step C i) a reduction treatment is carried out if in step C) a solution of a metal compound has been used instead of a metal colloid for the activation. When the solution of the metal compound was in a hydrochloric acid solution of palladium chloride or an acid solution of a silver salt, the reducing agent solution used therefor contains hydrochloric acid and stannous chloride. The reductant solution may also contain another reducing agent, such as NaH ₂ PO ₂ or else a borane or borohydride, such as an alkali or alkaline earth borane or dimethylaminoborane. Preferably, NaH ₂ PO _{2 is} used in the reductor solution.

After the acceleration or treatment with the reducing agent solution according to process step C i), the plastic surfaces can first be rinsed.

Process step C i) and optionally one or more rinsing steps are followed by process step C ii), in which the plastic surfaces are electrolessly metallized. For electroless nickel plating, for example, a conventional nickel bath containing, among others, nickel sulfate, a hypophosphite, for example, sodium hypophosphite, as a reducing agent, and organic chelating agents and pH adjusting agents (for example, a buffer) is used. Dimethylaminoborane or a mixture of hypophosphite and dimethylaminoborane can likewise be used as the reducing agent.

Alternatively, electroless copper plating may be carried out using an electroless copper bath, typically a copper salt, for example, copper sulfate or copper hypophosphite, a reducing agent such as formaldehyde or a hypophosphite salt, for example an alkali or ammonium salt, or hypophosphorous acid, or one or more complexing agents such as tartaric acid and a pH adjusting agent such as sodium hydroxide.

The surface thus rendered conductive can then be metallized further electrolytically to obtain a functional or decorative surface.

Step D) of the process according to the invention is the metallization of the plastic surface with a metallization solution. The metallizing according to process step D) can be carried out electrolytically. For electrolytic metallization, any metal deposition baths can be used, for example for the deposition of nickel, copper, silver, gold, tin, zinc, iron, lead or their Alloys. Such deposition baths are familiar to the person skilled in the art. As a bright nickel bath typically a Watts nickel bath is used, which contains nickel sulfate, nickel chloride and boric acid and saccharin as an additive. As a bright copper bath, for example, a composition is used which contains copper sulfate, sulfuric acid, sodium chloride, and organic sulfur compounds in which the sulfur is in a low oxidation state, for example, organic sulfides or disulfides, as additives.

The metallization of the plastic surface in process step D) results in that the plastic surface is coated with metal, wherein the metal is selected from the above-mentioned metals for the electrodeposition baths. At the same time, protecting the frame means that the frame or racks are not covered with metal and thus remain free of metal.

• D i) Lagern der metallisierten Kunststoffoberfläche bei erhöhter Temperatur.

In a further embodiment of the invention, the following further method step is carried out after method step D):

• D i) storing the metallized plastic surface at elevated temperature.

As with all galvanic processes in which a non-conductor is wet-chemically coated with metal, the adhesion strength between metal and plastic substrate increases in the first time after the application of the metal layer. At room temperature, this process is completed in about three days. This can be significantly accelerated by storage at elevated temperature. The process is completed at 80 ° C after about an hour. It is believed that the initial low adhesion is caused by a thin layer of water located at the interface between metal and nonconductive substrate and hindering the formation of electrostatic forces.

The treatment of the metallized plastic surfaces at elevated temperature is therefore advantageous. Such a step may be to treat a copper-metallized ABS plastic article for a period of between 5 minutes and 60 minutes at elevated temperature in the range of 50 ° C to 80 ° C, preferably at a temperature of 70 ° C in a water bath, so that the water can be distributed at the boundary layer of metal - plastic in the plastic matrix. The treatment or storage of the metallized plastic surfaces at elevated temperature leads to a initial, lower adhesive strength is further enhanced, so that after the process step D i) an adhesive strength of the applied to the plastic surface metal layer is achieved, which is in the desired range of at least or greater than 0.8 N / mm.

The method according to the invention therefore makes it possible to avoid the metallization of the frames and at the same time to achieve metallization of electrically non-conductive plastic surfaces of objects with good process reliability and excellent adhesion of the subsequently applied metal layers. The adhesive strength of the metal layers applied to plastic surfaces reaches values of 0.8 N / mm and higher. Thus, the adhesive strengths achieved are also significantly higher than those which can be obtained according to the prior art. Moreover, the method of the invention is not only suitable for metallizing planar plastic surfaces but also for irregularly shaped plastic surfaces, such as e.g. Shower heads, whereby the metallization of the racks is successfully avoided.

The treatment of the plastic surfaces according to the method of the invention is preferably carried out in a conventional dipping process by immersing the articles successively in solutions in containers in which the respective treatment takes place. In this case, the articles can either be attached to racks or filled with drums into the solutions. An attachment to racks is preferred. Alternatively, the articles can also be treated in so-called continuous installations, for example by lying on trays and being conveyed continuously through the installations in a horizontal direction.

embodiments

The exemplary embodiments described below are intended to explain the invention in more detail.

Example 1 Example According to the Invention

An ABS molded part (shower head) was attached to a PVC coated support frame (step A)). For this example, an old support frame was selected which had a particularly strong tendency to frame metallization. The molded article was immersed with the holder for ten minutes in a solution of 15% 2- (2-ethoxyethoxy) ethyl acetate and 10% butoxyethanol adjusted to pH 7 with a potassium phosphate buffer and maintained in a thermostat at 45 ° C (Process step A i)). It was then rinsed under running water for one minute and then treated in a bath of 100 g / l sodium permanganate and 10 g / l 96% sulfuric acid kept at 70 ° C (step B)). After a treatment time of ten minutes, rinsing under water again and adhering manganese dioxide in a solution of 50 g / l 96% sulfuric acid and 30 ml / l 30% hydrogen peroxide was removed (step B i), see Table 2). Following this reduction, the rack with the ABS molded article in a solution with various concentrations of potassium iodate (0, 5, 10, 20, 40 g / l) in 50 g / l 96% sulfuric acid at 50 ° C ten Treated for minutes (protecting the frame).
After subsequent rinsing and brief immersion in a solution of 300 ml / l 36% hydrochloric acid (process step B ii)) was for three minutes in a colloidal activator based on a palladium colloid (Adhemax activator PL Fa. Atotech, 25 ppm palladium) activated (step C), see Table 2). After subsequent rinsing, the protective sheaths of the palladium particles were removed for five minutes at 50 ° C. (Adhemax ACC1 accelerator from Atotech, process step C i), see Table 2). The ABS molding was then electroless nickel-plated at 45 ° C for ten minutes (Adhemax LFS, Fa. Atotech, step C ii)) and then rinsed.
The ABS molded part was then completely and faultlessly covered with a light gray nickel layer. Depending on the concentration of potassium iodate in the above-described iodate solution, the PVC coating of the support rack was differently coated with nickel as shown in FIG FIG. 1 is illustrated. While without iodate treatment (0 g / l KlO ₃ in FIG. 1 ) an occupancy of the frame with nickel of 75% of the surface of the frame can be observed, the treatment of the frame with 40 g / l KlO ₃ already leads to a negligible occupancy of nickel of 2% of the surface of the frame.

The sequence of the process steps in Example 1 is summarized in Table 2. Table 2: Sequence of process steps in Example 1 step chemistry duration temperature A) Attach --- --- --- A i) Pretreatment 15% 2- (2-ethoxyethoxy) ethyl acetate and 10% butoxyethanol in water, potassium phosphate buffer, pH = 7 10 min 45 ° C B) pickling 100 g / l sodium permanganate, 10 g / l 96% sulfuric acid 10 min 70 ° C B i) Reduce 50 g / l 96% sulfuric acid, 30 ml / l hydrogen peroxide, 30% by weight 1 min 45 ° C Rack shooters 0, 5, 10, 20, 40 g / l potassium iodate in 50 g / l 96% sulfuric acid 10 min 50 ° C B ii) Prelude Hydrochloric acid, about 10% by weight 1 min 20 ° C C) Activate Palladium colloid, 25 ppm palladium 3 min 45 ° C C i) Accelerate Sulfuric acid 5% 5 min 50 ° C C ii) electrolessly deposit metal Chemically reductive nickel plating, Adhemax LFS, Atotech 10 min 45 ° C

Example 2 Example According to the Invention

Two so-called valve caps (round moldings about 7 cm in diameter) made of plastic Novodur P2MC (ABS) were attached to a support frame and treated as described in Example 1. Unlike in Example 1, a solution of 10% ethylene glycol diacetate and 10% ethylene glycol monobutyl ether was used in process step A i). This solution was held at 45 ° C, the valve caps were treated for five minutes. Subsequently, all the process steps of Example 1 were carried out. Following the reduction (step B i)), the rack was treated with the valve caps in a solution containing 20 g / l potassium iodate in 50 g / l 96% sulfuric acid at 50 ° C for ten minutes.
After electroless nickel plating, an additional 70 minutes of copper plating (Cupracid HT Fa. Atotech, 3.5 A / dm ² , room temperature, step D)). After rinsing, the valve caps were stored at 80 ° C for 30 minutes (step D i)). Subsequently, the metal layer was removed from the plastic with a tensile testing machine (Instron) ( ASTM B 533 1985 Reapproved 2009 ) and so determines the adhesion. Adhesive strengths of the metal layers to the plastic of the valve caps of 1.14 N / mm and 1.17 N / mm were determined.
The occupancy of the frame with metal was 4% of the frame surface and was therefore negligible.

Example 3: Influence of glycol treatment on the adhesion of the deposited metals

Bayblend T45 plates were treated at 45 ° C. for a varying time in a 15% solution of 2- (2-ethoxyethoxy) ethyl acetate and 10% butoxyethanol adjusted to pH 7 with a potassium phosphate buffer. The plates were then rinsed under running water for about one minute and then placed in a bath of 100 g / l sodium permanganate and 10 g / l 96% sulfuric acid kept at 70 ° C. After a treatment period of ten minutes, rinsing again under water for one minute and then cleaning the dark brown plates in a solution of 50 g / l 96% sulfuric acid and 30 ml / l of 30% hydrogen peroxide from deposited manganese dioxide. After subsequent rinsing and brief immersion in a solution of 300 ml / l 36% hydrochloric acid, the plates were three minutes in a colloidal activator based on a palladium colloid (Adhemax activator PL Fa. Atotech, 25 ppm palladium) at 45 ° C. activated.
After subsequent rinsing, the protective sheaths of the palladium particles were removed for five minutes at 50 ° C. (Adhemax Accelerator ACC1 from Atotech). The plates were then electroless nickel-plated for 10 minutes (Adhemax LFS, Atotech.) At 45 ° C, rinsed and copper-plated at 3.5 A / dm ^{2 for} 70 minutes at room temperature (Cupracid HT, Fa. Atotech). After rinsing, the plates were stored at 80 ° C for 1 hour. Subsequently, a strip about 1 cm wide of the respective metallized plastic plate was cut out with a knife and the metal layer was removed from the plastic using a tensile testing machine (Instron) ( ASTM B 533 1985 Reapproved 2009 ).
The adhesive strengths of the metal layers are in FIG. 3 shown. The residence time of the plastic surfaces in the solution of the glycol compounds (process step A i)) has an influence on the adhesive strength of the applied metal layers. Without treatment with glycol compounds (residence time 0 min in FIG. 3 ) only an adhesive strength of 0.25 N / mm was obtained. After only 5 minutes of treatment with glycol compounds, on the other hand, a good adhesive strength of 0.9 N / mm was already achieved, which continues to increase with longer treatment time.

Example 4: Influence of glycol treatment on the adhesion of the deposited metals

Sheets of ABS plastic (Novodur P2MC), as described in Example 3, variously treated with a 15% solution of 2- (2-ethoxyethoxy) ethyl acetate and 10% butoxyethanol, subjected to the further metallization process and the adhesive strengths of the applied Metal layer determined.
The adhesive strengths of the metal layer as a function of the treatment time with the solution of the glycol compounds are in FIG. 4 shown. Again, the influence of treatment duration (in FIG. 4 referred to as residence time in the Vorbeizlösung) on the adhesion of the deposited metal layers clearly visible. Without treatment with glycol compounds (residence time 0 min in FIG. 4 ) only an adhesive strength of 0.25 N / mm was obtained. After only 5 minutes of treatment with glycol compounds, on the other hand, a very good adhesive strength of 1.4 N / mm was already achieved, which continues to increase with longer treatment time.

Example 5: Influence of glycol treatment on the adhesion of the deposited metals

Two plates of Bayblend T45 (5.2 x 14.9 x 0.3 cm, ABS / PC blend) were treated in a 40% solution of 2- (2-ethoxyethoxy) ethyl acetate for ten minutes at room temperature. The plates, after rinsing as described in Example 3, were subjected to the further metallization process and the adhesive strengths of the applied metal layer were determined. The following bond strengths were found: Plate 1 Front: 1.09 N / mm. Back: 1.27 N / mm Plate 2 Front: 1.30 N / mm. Rear: 1.32 N / mm

Claims (13)

Method for metallizing electrically non-conductive plastic surfaces of objects, comprising the method steps: A) securing the article in a rack, B) pickling the plastic surface with a pickling solution, C) treating the plastic surface with a solution of a metal colloid or a compound of a metal, wherein the metal is selected from the metals of the I subgroup of the Periodic Table of the Elements and the VIII. Subgroup of the Periodic Table of the Elements, and D) metallizing the plastic surface with a metallizing solution;
characterized in that the rack is treated with a solution containing a source of iodate ions. A method according to claim 1, characterized in that treating the rack with a solution containing a source of iodate ions
takes place before process step A) or
takes place between process steps A) and B) or
takes place between process steps B) and C). Method according to one of the preceding claims, characterized in that the following further method step is carried out between method steps A) and B): A i) treating the plastic surface in an aqueous solution containing at least one glycol compound. A method according to claim 3, characterized in that the at least one glycol compound is selected from compounds according to general formula (I)

wherein
n is an integer between 1 and 4; and
R ¹ and R ² independently represent -H, -CH ₃ , -CH ₂ -CH ₃ , -CH ₂ -CH ₂ -CH ₃ , -CH (CH ₃ ) -CH ₃ , -CH ₂ -CH ₂ -CH ₂ -CH ₃ , -CH (CH ₃ ) -CH ₂ -CH ₃ , -CH ₂ -CH (CH ₃ ) -CH ₃ , -CH ₂ -CH ₂ -CH ₂ -CH ₂ -CH ₃ , -CH (CH ₃ ) -CH ₂ -CH ₂ -CH ₃ , -CH ₂ -CH (CH ₃ ) -CH ₂ -CH ₃ , -CH ₂ -CH ₂ -CH (CH ₃ ) -CH ₃ , -CH (CH ₂ -CH ₃ ) -CH ₂ -CH ₃ , -CH ₂ -CH (CH ₂ -CH ₃ ) -CH ₃ , -CO-CH ₃ , -CO-CH ₂ -CH ₃ , -CO-CH ₂ -CH ₂ -CH ₃ , -CO-CH (CH ₃ ) -CH ₃ , -CO-CH (CH ₃ ) -CH ₂ -CH ₃ , -CO-CH ₂ -CH (CH ₃ ) -CH ₃ , CO-CH ₂ -CH ₂ -CH ₂ -CH ₃ . Method according to one of the preceding claims, characterized in that the plastic surface is made of at least one electrically non-conductive plastic and the at least one electrically non-conductive plastic is selected from the group comprising an acrylonitrile-butadiene-styrene copolymer, a polyamide, a polycarbonate and a Mixture of an acrylonitrile-butadiene-styrene copolymer with at least one further polymer. Method according to one of the preceding claims, characterized in that the following further method step is carried out between method steps B) and C): B i) treating the plastic surface in a solution containing a reducing agent for manganese dioxide. A method according to claim 6, characterized in that the reducing agent for manganese dioxide is selected from the group comprising hydroxylammonium sulfate, hydroxylammonium chloride and hydrogen peroxide. Method according to one of the preceding claims, characterized in that the source of iodate ions is selected from the group of metal iodates containing sodium iodate, potassium iodate, magnesium iodate, calcium iodate and their hydrates. A method according to claim 8, characterized in that the concentration of the metal iodates is between 5 g / l and 50 g / l. Method according to one of the preceding claims, characterized in that the solution containing a source of iodate ions further contains an inorganic acid. Method according to one of the preceding claims, characterized in that the treatment of the rack with a solution containing a source of iodate ions lasts between 1 and 20 minutes. Method according to one of the preceding claims, characterized in that the treatment of the frame with a solution containing a source of iodate ions at a temperature between 20 ° C and 70 ° C is performed. Method according to one of the preceding claims, characterized in that the following further method steps are carried out between method steps C) and D): C i) treating the plastic surface in an aqueous acid solution and C ii) electroless plating of the plastic surface in a metallization solution.

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