WO2022043241A1

WO2022043241A1 - Method for metallizing a non-metallic substrate and pre-treatment composition

Info

Publication number: WO2022043241A1
Application number: PCT/EP2021/073224
Authority: WO
Inventors: Brigitte Dyrbusch; Franziska Finn; Carl Christian Fels
Original assignee: Atotech Deutschland GmbH & Co. KG
Priority date: 2020-08-25
Filing date: 2021-08-23
Publication date: 2022-03-03
Also published as: JP2023539605A; US20230357932A1; CN116134175A; EP4204601A1; CA3190838A1; BR112023003111A2; KR20230054853A

Abstract

The present invention relates to a method for metallizing a non-metallic substrate, the method comprising the steps (A) to (C), wherein step (A) is a pre-treatment step for etching and step (C) the metallization step. In step (A) a pre-treatment composition is utilized comprising individual manganese (II), (III), and (IV) species. The present invention furthermore relates to a specific pre-treatment composition.

Description

M et h od fo r m eta l l iz i n g a n o n -m eta l l i c s u bstrate a n d p re-treat- m e nt co m p os it i o n

Field of the Invention

Background of the Invention

Metallizing non-metallic substrates such as plastic substrates has a long history in modern technology. Typical applications are found in automotive industry as well as for sanitary articles.

However, making a non-metallic/non-conductive substrate receptive for a metal layer is demanding. Typically, a respective method starts with a surface modification of the substrate’s surface, typically known as etching. Usually, a sensitive balance is required in order to ensure a sufficient surface roughening without causing too strong defects.

Many methods and etching compositions are known, including compositions comprising environmentally questionable chromium species, such as hexavalent chromium species. Although these compositions usually provide very strong and acceptable etching results, environmentally friendly alternatives are more and more demanded and to a certain extent already provided in the art.

For example, WO 2018/095998 A1 refers to a chrome free etch for plating on plastic processes, wherein plastic surfaces are contacted in a first step with an etching solution at least comprising Mn(IV)-ions and, in a second etching step, with a solution at least comprising Mn(lll)- and Mn(VII)-ions prior to the plating step.

EP 3 584 352 A1 refers to a pretreatment composition for electroless plating and a respective pretreatment method exhibiting high plating deposition performance without using harmful chromic acid and expensive palladium, while reducing the number of steps.

EP 0 913 498 A1 refers to a process combining surface treatment and metal deposition. A respective aqueous solution comprises a metal activator, such as an oxidized species of silver, cobalt, ruthenium, cerium, iron, manganese, nickel, rhodium, or vanadium. The activator can be suitably oxidized to a higher oxidation state electrochemically. EP 2 025 708 A1 refers to an etching solution comprising Mn(VII) ions.

EP 2 937 446 B1 refers to a composition for etching treatment of a resin material, the composition comprising permanganate ions.

US 2017/159183 A1 refers to a resin plating method using an etching bath containing manganese as an active ingredient.

US 8,603,352 B1 refers to a chrome-free composition of an acidic suspension of manganese compounds and manganese ions are applied to an organic polymer surface to etch the surface. The suspension comprises one or more undissolved Mn(ll) compounds, or one or more undissolved Mn(lll) compounds, or mixtures thereof, dissolved Mn(ll) ions and dissolved Mn(lll) ions, and one or more acids.

CN 110172684 A refers to the formulation and preparation of a chromium-free roughening solution for ABS plastics.

As seen above, in many cases, manganese species are utilized instead of chromium ions. However, certain manganese species inherently have specific disadvantages. For example, manganese (VII) species typically form difficult to handle manganese dioxide, which often adsorbs on the surface of the substrate and needs to be chemically reduced in order to dissolve it.

Furthermore, besides the issue of environmentally questionable chromium ions, the etching process additionally affects the overall quality of the subsequently deposited outermost metal layer, in particular in terms of glance/brightness and surface roughness. This is in particular observed if the outermost metal layer is a chromium layer. Since the optical appearance of the outermost metal layer is desired to be as perfect as possible, a suitable method for metallizing starts with a well-balanced etching step.

Objective of the present Invention

It is therefore the objective of the present invention to overcome the above mentioned shortcomings of the prior art.

It is in particular an objective of the present invention to provide a method for metallizing a non-metallic substrate, wherein the obtained metallized substrate (in particular with a chromium layer) provides an even further improved quality. It is in particular demanded to obtain a metal layer (in particular a chromium layer), which is very smooth and has an improved metallic glance/brightness, but still being sufficiently adhered to the non-metallic substrate.

It is furthermore an objective of the present invention to provide a method including a single pre-treatment step, in particular without chemical reducing steps. It is another objective to provide a method that is less dependent on substrates with high manufacturing quality but rather also allows a homogeneous pre-treatment and metallization, respectively, of substrates of lower manufacturing quality, in particular substrates comprising polybutadiene.

Summary of the Invention

Above mentioned objectives are solved by a method for metallizing a non-metallic substrate, the method comprising the steps

(A) contacting the non-metallic substrate with a pre-treatment composition such that a pre-treated substrate is obtained, wherein the pre-treatment composition comprises

(A-a) individual manganese (II), (III), and (IV) species,

(B) contacting the pre-treated substrate with an activation composition such that an activated substrate is obtained, and

(C) contacting the activated substrate with one or more than one metalizing composition such that a metalized substrate is obtained, with the proviso that

- in the pre-treatment composition, the total concentration of manganese (IV) species is higher than the combined concentration of manganese (II) and (III) species,

- an electrical current is applied to the pre-treatment composition such that manganese (II) species are oxidized to manganese (III) species, and

- in step (A) contacting said substrate with manganese species is carried out in a single step.

The present invention is primarily based on a specifically designed pre-treatment composition utilized in step (A); most preferably in combination with a metalizing composition comprising nickel for nickel plating in step (C). Said specifically designed pre-treatment composition comprises individual manganese (II), (III), and (IV) species. This means that throughout the method, the pre-treatment composition comprises at least three distinct manganese species, which are different from each other. All three species are simultaneously present. In the context of the present invention, the term “manganese (II), (III), and (IV)” denotes the element manganese with the oxidation numbers +2, +3, and +4, respectively, in respective compounds and/or ions. Preferred is a method of the present invention, wherein the individual manganese (II), (III), and (IV) species are present in a steady state in the pre-treatment composition during step (A).

The method of the present invention results in a unique, fine sponge-like etch pattern/struc- ture leading to a sufficient roughening of the substrate without causing too deep or large cavities (i.e. soft etching). Although deep and/or large cavities are typically desired in order to obtain a strong adhesion to a metal layer, our own investigations show that such deep/strong cavities often negatively affect the optical appearance of the final decorative layer (e.g. a chromium layer), in particular in terms of brightness and uniformity. Such deep/strong cavities (which are undesired in the context of the present invention) are typically obtained if the substrate is contacted with a composition comprising suitable amounts of manganese (VII) species, in particular permanganate ions. In contrast, said fine spongelike etch pattern/structure, which is seemingly a disadvantage, is in fact a great advantage of the present invention. This is in particular the case if the substrates are of varying manufacturing quality; a problem sometimes observed for substrates comprising butadiene moi- eties, preferably polybutadiene. Often such defects are a result of varying manufacturing parameters during a casting process, typically leading to an inhomogeneous material distribution or other manufacturing defects. Such defects are not necessarily outwardly seen right from the beginning but often become obvious or at least pronounced during the pretreatment step. However, if the pre-treatment step pronounces such defects, the optical quality of a respective metallized substrate is in many cases deteriorated particularly at such areas of the substrate.

It was surprising that the method of the present invention did not only produced fine results with high quality substrates but still very acceptable results for substrates with manufacturing defects, i.e. lower manufacturing quality. In most cases a still very homogeneous optical appearance of the metallized substrate was obtained due to the less pronounced manufacturing defects. As a result, the method of the present invention allows a metallization of substrates that otherwise would be discarded.

In the method of the present invention an electrical current is applied to the pre-treatment composition such that manganese (II) species are oxidized to manganese (III) species, preferably continually. By that, further procedural advantages are obtained.

First, in the method of the present invention, no strongly adhering particulate manganese dioxide is formed during step (A) which otherwise must be chemically reduced by contacting the substrate with a composition comprising a reducing agent. Instead, it is easily removed by a simple rinsing, which is typically anyways applied (preferably with water). Since it does not strongly adhere to the substrate (i.e. they are not incorporated onto the substrate), removal is quickly and easily accomplished.

Second, the electrical current allows to keep the individual manganese (II), (III), and (IV) species in individual and comparatively constant concentration ranges, which would be not achievable without an electrical current. Furthermore, some manganese species, in particular the manganese (III) species, would not be present without the applied electrical current. As a result, without wishing to be bound to any theory, the presence of the individual manganese (II), (III), and (IV) species in the pre-treatment composition, caused by the electrical current, are essential to achieve the advantages mentioned above. The manganese species primarily needed for the excellent pre-treating result is believed to be the manganese (IV) species.

In addition, the electrical current preferably decomposes water that typically accumulates in the pre-treatment composition, e.g. due to hygroscopic effects. Thus, the quality of the pretreatment composition maintains stable (e.g. in terms of density).

Detailed Description of the Invention

The method of the present invention primarily includes a contacting with a specific pretreatment composition in order to obtain a particularly pre-treated substrate.

Preferred is a method of the present invention, wherein in step (A) the pre-treatment composition is an etching-composition for etching the non-metallic substrate, preferably a non- metallic substrate as defined as being preferred throughout the present text.

Step (A):

The non-metallic substrate:

Preferred is a method of the present invention, wherein the non-metallic substrate comprises, preferably is, a non-conductive substrate.

Preferred is a method of the present invention, wherein the non-metallic substrate comprises, preferably is, a plastic substrate.

More preferred is a method of the present invention, wherein the non-metallic substrate (and the non-conductive substrate, respectively) comprises butadiene moieties, preferably polybutadiene.

Also preferred is a method of the present invention, wherein the non-metallic substrate (and the non-conductive substrate, respectively) comprises nitrile moieties.

Also preferred is a method of the present invention, wherein the non-metallic substrate (and the non-conductive substrate, respectively) comprises acryl moieties. Also preferred is a method of the present invention, wherein the non-metallic substrate (and the non-conductive substrate, respectively) comprises styrene moieties.

Most preferred is a method of the present invention, wherein the non-metallic substrate comprises, preferably is, acrylonitrile-butadiene-styrene (ABS) and/or acrylonitrile-butadi- ene-styrene-polycarbonate (ABS-PC).

The pre-treatment composition:

The pre-treatment composition utilized in the method of the present invention comprises water. Preferably, the pre-treatment composition comprises less than 50 wt.-% water, based on the total weight of the pre-treatment composition, preferably 45 wt.-% or less, more preferably 40 wt.-% or less, even more preferably 35 wt.-% or less, yet even more preferably 30 wt.-% or less, most preferably 25 wt.-% or less. Preferred is a method of the present invention, wherein the pre-treatment composition comprises water ranging from 0 wt.-% to 25 wt.-%, based on the total weight of the pre-treatment composition, preferably from 0.1 wt.-% to 21 wt.-%, more preferably from 1 wt.-% to 18 wt.-%, even more preferably from 2 wt.-% to 16 wt.-%, yet even more preferably from 5 wt.-% to 14 wt.-%, most preferably from 8 wt.-% to 12 wt.-%. Most preferably, water is the only solvent in the pre-treatment composition.

In the method of the present invention the pre-treatment composition comprise specific manganese species. Other manganese species are less preferred or are most preferably to be avoided entirely.

Preferred is a method of the present invention, wherein in step (A) the pre-treatment composition is substantially free of, preferably does not comprise, manganese (VII) species, or only up to a total concentration of 100 mg/L, based on the total volume of the pre-treatment composition and on the element manganese, preferably only up to a total concentration of 75 mg/L, more preferably only up to a total concentration of 50 mg/L, even more preferably only up to a total concentration of 35 mg/L, most preferably only up to a total concentration of 20 mg/L, even most preferably only up to a total concentration of 10 mg/L. Own experiments indicate that an insignificant low amount (e.g. as an impurity or unavoidable side reaction) of such manganese species is tolerable. However, preferred is a method of the present invention, wherein the pre-treatment composition comprises manganese (VII) species in a concentration from 0 mg/L to 10 mg/L, based on the total volume of the pre-treatment composition.

If present, manganese (VII) species are preferably formed (preferably only) in situ, most preferably up to a concentration range as defined above. This means that manganese (VII) species, are preferably not intentionally/purposely added to the pre-treatment composition. Preferred is a method of the present invention, wherein in step (A) the pre-treatment composition is substantially free of, preferably does not comprise, permanganate ions, or only up to a total concentration of 100 mg/L, based on the total volume of the pre-treatment composition and the element manganese, preferably only up to a total concentration of 75 mg/L, more preferably only up to a total concentration of 50 mg/L, even more preferably only up to a total concentration of 35 mg/L, most preferably only up to a total concentration of 20 mg/L, even most preferably only up to a total concentration of 10 mg/L. The aforementioned regarding manganese (VII) species preferably applies likewise.

If present at all, permanganate ions are preferably formed (preferably only) in situ, most preferably up to a concentration range as defined above. This means, that permanganate ions are preferably not intentionally/purposely added to the pre-treatment composition.

Preferred is a method of the present invention, wherein the pre-treatment composition is substantially free of, preferably does not comprise, a methane sulfonic acid and salts thereof, preferably is substantially free of, preferably does not comprise, a C1 to C4 alkyl sulfonic acid and salts thereof, most preferably is substantially free of, preferably does not comprise, a C1 to C4 sulfonic acid and salts thereof. It appears that such compounds negatively affect the water balance in a respective pre-treatment composition.

Preferred is a method of the present invention, wherein the pre-treatment composition is substantially free of, preferably does not comprise, bromide and iodide anions, preferably is substantially free of, preferably does not comprise, chloride, bromide, and iodide anions, most preferably is substantially free of, preferably does not comprise, halide anions.

Preferred is a method of the present invention, wherein the pre-treatment composition is substantially free of, preferably does not comprise, trivalent chromium ions and hexavalent chromium compounds, preferably is substantially free of, preferably does not comprise, any compounds and ions comprising chromium.

Preferred is a method of the present invention, wherein the pre-treatment composition is substantially free of, preferably does not comprise, manganese (V) species, or only up to a total concentration of 100 mg/L, based on the total volume of the pre-treatment composition and the element manganese, preferably only up to a total concentration of 75 mg/L, more preferably only up to a total concentration of 50 mg/L, even more preferably only up to a total concentration of 35 mg/L, most preferably only up to a total concentration of 20 mg/L, even most preferably only up to a total concentration of 10 mg/L. Most preferably, manganese (V) species are not detectable, preferably via UV/VIS spectroscopy. Preferably they are not intentionally/purposely added to the pre-treatment composition. Preferred is a method of the present invention, wherein the pre-treatment composition is substantially free of, preferably does not comprise, manganese (VI) species, or only up to a total concentration of 100 mg/L, based on the total volume of the pre-treatment composition and the element manganese, preferably only up to a total concentration of 75 mg/L, more preferably only up to a total concentration of 50 mg/L, even more preferably only up to a total concentration of 35 mg/L, most preferably only up to a total concentration of 20 mg/L, even most preferably only up to a total concentration of 10 mg/L. Most preferably, manganese (VI) species are not detectable, preferably via UV/VIS spectroscopy. Preferably they are not intentionally/purposely added to the pre-treatment composition.

As mentioned, the pre-treatment composition comprises individual manganese (II), (III), and (IV) species. Preferred is a method of the present invention, wherein during step (A) in the pre-treatment composition the total amount of all manganese species is more than 5.0 g/L, based on the total volume of the pre-treatment composition and the element manganese, preferably is 5.4 g/L or more, even more preferably is 5.8 g/L or more, most preferably is 6.0 g/L or more. A preferred maximum concentration is up to 7.5 g/L, based on the total volume of the pre-treatment composition and the element manganese, preferably up to 7.2 g/L, more preferably up to 7.0 g/L, even more preferably up to 6.8 g/L, yet even more preferably up to 6.6 g/L, most preferably up to 6.3 g/L.

Preferred is a method of the present invention, wherein in the pre-treatment composition manganese (III) species disproportionate to manganese species comprising manganese (IV) species.

Preferred is a method of the present invention, wherein the manganese (II) species comprise, preferably are, Mn(ll) ions.

Preferred is a method of the present invention, wherein during step (A) in the pre-treatment composition the manganese (II) species have a total concentration in a range from 0.1 g/L to 0.8 g/L, based on the total volume of the pre-treatment composition and the element manganese, preferably from 0.15 g/L to 0.7 g/L, more preferably from 0.2 g/L to 0.6 g/L, most preferably from 0.25 g/L to 0.5 g/L. This preferably includes all manganese species as long as the element manganese has the oxidation number +2.

A preferred source of manganese (II) species is manganese (II) sulfate.

Preferred is a method of the present invention, wherein the manganese (III) species comprise, preferably are, Mn(lll) ions.

Preferred is a method of the present invention, wherein during step (A) in the pre-treatment composition the manganese (III) species have a total concentration in a range from 0.2 g/L to 1.9 g/L, based on the total volume of the pre-treatment composition and the element manganese, preferably from 0.3 g/L to 1.5 g/L, more preferably from 0.4 g/L to 1.2 g/L, even more preferably from 0.5 g/L to 1.0 g/L, most preferably from 0.6 g/L to 0.8 g/L.

Preferred is a method of the present invention, wherein in the pre-treatment composition during step (A) the manganese (III) species have a higher total concentration than the manganese (II) species. Preferably, based on the element manganese, more preferably this applies to concentrations in g/L, based on the total volume of the pre-treatment composition and the element manganese in these manganese species.

Preferred is a method of the present invention, wherein the manganese (IV) species comprise colloidal manganese (IV) species, preferably comprise a mixture of colloidal manganese (IV) species and manganese (IV) ions.

Preferred is a method of the present invention, wherein during step (A) in the pre-treatment composition the manganese (IV) species have a total concentration in a range from 1.5 g/L to 5.0 g/L, based on the total volume of the pre-treatment composition and the element manganese, preferably from 1.8 g/L to 4.5 g/L, more preferably from 2.0 g/L to 4.0 g/L, even more preferably from 2.2 g/L to 3.5 g/L, most preferably from 2.4 g/L to 3.0 g/L.

Preferred is a method of the present invention, wherein in the pre-treatment composition more than 50 wt.-% of the manganese (IV) species, based on the total weight of all manganese (IV) species and based on the element manganese, comprise colloidal manganese (IV) species, preferably 60 wt.-% or more, more preferably 65 wt.-% or more, most preferably 70 wt.-% or more. Preferably, the colloidal manganese (IV) species comprises manganese dioxide.

In the pre-treatment composition utilized in the method of the present invention, the total concentration of manganese (IV) species is higher than the combined concentration of manganese (II) and (III) species. Preferably, based on the element manganese, this applies to concentrations in g/L, based on the total volume of the pre-treatment composition and the element manganese in each individual manganese species.

Preferred is a method of the present invention, wherein during step (A) in the pre-treatment composition 55 wt.-% or more are manganese (IV) species, based on the total weight of all manganese species and the element manganese, preferably 59 wt.-% or more, more preferably 63 wt.-% or more, even more preferably 67 wt.-% or more, most preferably 70 wt.-% or more.

Preferred is a method of the present invention, wherein the pre-treatment composition is acidic, preferably has a pH of 3.0 or below, more preferably of 2.1 or below, even more preferably of 1.5 or below, most preferably of 1.0 or below, even most preferably of 0.7 or below. Preferably, the strong acidic condition is a result of acids being present in the pretreatment composition.

Preferred is a method of the present invention, wherein the pre-treatment composition additionally comprises

(A-b) one, two or more than two (preferably two) acids, preferably inorganic acids, most preferably at least a combination of sulfuric acid and phosphoric acid.

Preferred is a method of the present invention, wherein the pre-treatment composition comprises sulfuric acid in a total concentration of 10 mol/L or less, based on the total volume of the pre-treatment composition, preferably of 9.6 mol/L or less, more preferably of 9.1 mol/L or less, most preferably of 8.6 mol/L or less.

Preferred is a method of the present invention, wherein the pre-treatment composition comprises sulfuric acid in a total concentration of at least 3.0 mol/L, based on the total volume of the pre-treatment composition, preferably of at last 3.5 mol/L, more preferably of at least 4.0 mol/L, most preferably of at least 4.5 mol/L.

Preferred is a method of the present invention, wherein in the pre-treatment composition the sulfuric acid has a concentration in a range from 3 mol/L to below 10 mol/L, based on the total volume of the pre-treatment composition, preferably from 3.5 mol/L to 8 mol/L, more preferably from 4 mol/L to 6 mol/L, most preferably from 4.5 mol/L to 5.5 mol/L.

Preferred is a method of the present invention, wherein the pre-treatment composition comprises at least a combination of sulfuric acid and phosphoric acid, wherein the phosphoric acid has a higher concentration than the sulfuric acid, preferably the molar ratio of phosphoric acid to sulfuric acid is in a range from 1.1 : 1 to 3 : 1 , more preferably is in a range from 1.3 : 1 to 2.6 : 1 , even more preferably is in a range from 1.4 : 1 to 2.4 : 1 , yet even more preferably is in a range from 1.5 : 1 to 2.1 : 1 , most preferably is in a range from 1.6 : 1 to 2.0 : 1.

In the context of the present invention it is most preferable that the phosphoric acid has a higher concentration than sulfuric acid. Typically, sulfuric acid incorporates a comparatively high amount of water due to hygroscopic effects. This leads to an undesired dilution of the pre-treatment composition. If the concentration of sulfuric acid is minimized to the best extent possible, such a dilution is minimized too. Own experiments have shown that the concentrations and molar ratios as defined above for sulfuric acid result in an excellent balance between water accumulation on the one hand and water decomposition by means of the electrical current on the other hand. This allows to keep the pre-treatment composition under stable condition (stable water-balance).

Preferred is a method of the present invention, wherein the pre-treatment composition has an absorbance of more than 1 .0, referenced to a wavelength of 400 nm and preferably a path length of 1 cm, preferably in a range from 1.1 to 2.1 , more preferably from 1.2 to 2.0, most preferably from 1.3 to 1.7. If the absorbance is significantly below 1.0, typically an undesired low adhesion between the non-metallic substrate and the metal layers applied in step (C) is often observed (e.g. <0.5 N/cm). In contrast, if the absorbance is above 1.0, more particularly in the preferred ranges as mentioned above, typically a good adhesion (e.g. >1.0 N/cm) is even observed. This parameter is a preferred quality parameter to evaluate whether the three manganese species are properly present in the pre-treatment composition.

Preferably, the absorbance (also named extinction) is determined via LIV/VIS spectroscopy with a path length of 1 cm at 400 nm (Beer-Lambert law).

(A-c) one or more than one species of additional transition metal ions different from manganese.

Preferred is a method of the present invention, wherein in the pre-treatment composition the one or more than one species of additional transition metal ions different from manganese has a total concentration in a range from 1 mmol/L to 50 mmol/L, based on the total volume of the pre-treatment composition, preferably from 2 mmol/L to 40 mmol/L, more preferably from 3 mmol/L to 30 mmol/L, even more preferably from 4 mmol/L to 20 mmol/L, most preferably from 5 mmol/L to 15 mmol/L.

Preferred is a method of the present invention, wherein in the pre-treatment composition the one or more than one species of additional transition metal ions different from manganese comprise silver ions, said silver ions preferably having a total concentration in a range from 4 mmol/L to 25 mmol/L, based on the total volume of the pre-treatment composition, preferably from 6 mmol/L to 20 mmol/L, more preferably from 8 mmol/L to 17 mmol/L, most preferably from 10 mmol/L to 14 mmol/L. Very preferably, said silver ions are the only additional transition metal ions. In the context of the present invention, the aforementioned total concentration of silver ions includes silver ions with any oxidation number. Since silver ions are preferably present, halide ions, in particular chloride ions, are to be avoided to prevent precipitation. Preferred is a method of the present invention, wherein the silver ions have an oxidation number of +1 , most preferably the silver ions added to the pre-treatment composition.

(A-d) one or more than one wetting agent, preferably a fluorinated wetting agent.

Preferred is a method of the present invention, wherein the one or more than one wetting agent (preferably the fluorinated wetting agent) is present in the pre-treatment composition in a total concentration in a range from 0.001 g/L to 1.0 g/L, based on the total volume of the pre-treatment composition, preferably in a range from 0.005 g/L to 0.7 g/L, more preferably in a range from 0.01 g/L to 0.5 g/L, even more preferably in a range from 0.02 g/L to 0.3 g/L, most preferably in a range from 0.03 g/L to 0.15 g/L. Preferably, the fluorinated wetting agent is partly or fully fluorinated or a mixture thereof (if e.g. more than one wetting agent is present).

(A-e) peroxomonosulfate anions and/or peroxodisulfate anions, preferably in a total concentration in a range from 0.01 g/L to 10.0 g/L, based on the total volume of the pre-treatment composition, preferably from 0.05 g/L to 7.0 g/L, more preferably from 0.1 g/L to 4.0 g/L, even more preferably from 0.2 g/L to 2.0 g/L, most preferably from 0.1 g/L to 0.5 g/L.

In some rare cases, preferred is a method of the present invention, wherein the pre-treatment composition additionally comprises

(A-f) peroxomonophosphate anions and/or peroxodiphospate anions, preferably in a total concentration in a range from 0.01 g/L to 10.0 g/L, based on the total volume of the pre-treatment composition, preferably from 0.05 g/L to 9.0 g/L, more preferably from 0.07 g/L to 8.0 g/L, even more preferably from 0.09 g/L to 7.0 g/L, most preferably from 0.1 g/L to 5.0 g/L.

(A-g) nitrate anions, preferably in a total concentration in a range from 0.01 g/L to 20.0 g/L, based on the total volume of the pre-treatment composition, preferably from 0.05 g/L to 17.0 g/L, more preferably from 0.1 g/L to 13.0 g/L, even more preferably from 0.25 g/L to 9.0 g/L, most preferably from 0.5 g/L to 5.0 g/L. Preferably, the source of nitrate anions is silver nitrate. Most preferably, the total concentration of nitrate anions corresponds to the total concentration of silver ions. Most preferably, the only source of silver ions and nitrate anions is silver nitrate.

Preferably, aforementioned components (A-c), (A-e), (A-f), and (A-g) support the electrochemical reactions in the pre-treatment composition.

Preferred is a method of the present invention, wherein the pre-treatment composition has a density in a range from 1.50 g/cm³ to 1.90 g/cm³, referenced to a temperature of 25°C, preferably from 1.55 g/cm³ to 1.80 g/cm³, more preferably from 1.60 g/cm³ to 1.70 g/cm³, most preferably from 1.61 g/cm³ to 1.68 g/cm³. Such a density range indicates that a suitable water-balance is provided.

The contacting:

Preferred is a method of the present invention, wherein in step (A) primarily polybutadiene is pre-treated, preferably etched, if the substrate comprises, preferably is, acrylonitrile-bu- tadiene-styrene (ABS) and/or acrylonitrile-butadiene-styrene-polycarbonate (ABS-PC), most preferably polybutadiene is more pre-treated, preferably etched, than the acrylonitrile styrene.

Preferred is a method of the present invention, wherein the substrate and pre-treated substrate, respectively, is additionally not contacted with a composition comprising permanganate ions, preferably is additionally not contacted with a composition comprising manganese (VII) species.

More preferred is a method of the present invention, wherein the substrate and pre-treated substrate, respectively, is not contacted with any composition comprising permanganate ions in a total concentration of 2 g/L or more, based on the total volume of said composition, preferably of 1 g/L or more, even more preferably of 500 mg/L or more, yet even more preferably of 250 mg/L or more, most preferably of 150 mg/L or more.

Even more preferred is a method of the present invention, wherein the substrate and pretreated substrate, respectively, is not contacted with any composition comprising manganese (VII) species. This most preferably applies if the pre-treatment composition utilized in the method of the present invention is substantially free of, preferably does not comprise, manganese (VII) species.

Preferred is a method of the present invention, wherein during step (A) substantially no, preferably no, manganese dioxide (MnC>2) is incorporated onto the pre-treated substrate. Thus, in the method of the present invention, no step is needed (and therefore not applied) in order to reduce manganese dioxide on the pre-treated substrate; i.e. in order to dissolve MnC>2 by chemical reduction through a reducing agent. Thus, preferably, the pre-treated substrate obtained after step (A) is not contacted with a respective composition comprising a reducing agent.

Instead, preferred is a method of the present invention, wherein after step (A) or prior to step (B) manganese dioxide adsorbed on the pre-treated substrate (preferably if present) is removed by rinsing, preferably by rinsing with water, more preferably by rinsing with water free of a reducing agent capable to chemically reduce manganese dioxide.

Preferred is a method of the present invention, wherein during step (A) or prior to step (B) the pre-treated substrate is not contacted with a composition comprising a reducing agent capable to chemically reduce manganese dioxide, preferably is not contacted with a composition comprising any reducing agent.

Due to the specific composition of the pre-treatment composition and how it is utilized in the method of the present invention, such a step is not required.

Preferred is a method of the present invention, wherein in step (A) the pre-treatment composition has a temperature in a range from 15°C to 60°C, preferably from 20°C to 55°C, more preferably from 27°C to 50°C, even more preferably from 34°C to 46°C, most preferably from 38°C to 43°C.

Preferred is a method of the present invention, wherein step (A) is carried out for a time ranging from 1 minute to 25 minutes, preferably from 5 minutes to 20 minutes, most preferably from 10 minutes to 18 minutes.

The electrical current:

Preferred is a method of the present invention, wherein during step (A) the electrical current is continuously applied.

Preferred is a method of the present invention, wherein during step (A) the manganese (III) species is continuously formed through the electrical current.

Preferred is a method of the present invention, wherein the electrical current has an anodic current density in a range from 0.1 A/dm² to 20 A/dm², preferably from 0.8 A/dm² to 15 A/dm², more preferably from 1 .5 A/dm² to 10 A/dm², most preferably from 2.1 A/dm² to 5.0 A/dm².

Preferred is a method of the present invention, wherein during step (A) the pre-treatment composition is exposed to a current load by the electrical current ranging from 0.5 Ah/L to 100 Ah/L, based on the total volume of the pre-treatment composition, preferably ranging from 1.0 Ah/L to 70 Ah/L, more preferably ranging from 2.0 Ah/L to 50 Ah/L, most preferably ranging from 4.0 Ah/L to 30 Ah/L.

Pre-treatment compartment:

Preferred is a method of the present invention, wherein step (A) is carried out in a pretreatment compartment comprising at least one cathode and at least one anode, preferably comprising at least one cathode, at least one anode, and at least one membrane, such that said manganese (II) species are oxidized to said manganese (III) species in the pre-treat- ment compartment.

Alternatively but more preferred is a method of the present invention, wherein step (A) is carried out in a pre-treatment compartment fluidically connected with an oxidizing compartment, the oxidizing compartment comprising at least one cathode and at least one anode, preferably comprising at least one cathode, at least one anode, and at least one membrane, such that said manganese (II) species are oxidized to said manganese (III) species in the oxidizing compartment. In such a preferred method of the present invention, the pre-treatment compartment preferably does not comprise a cathode and an anode. In such a case, the pre-treatment composition preferably circulates continually or semi-continually between the pre-treatment compartment and the oxidizing compartment.

Preferred is a method of the present invention, wherein said individual manganese (II), (III), and (IV) species are migrating (preferably circulating) between the pre-treatment compartment and the oxidizing compartment.

Preferred is a method of the present invention, wherein the electrical current is applied in the oxidizing compartment.

Preferred is a method of the present invention, wherein the at least one anode comprises a mixed metal anode or a graphite anode.

A preferred mixed metal anode comprises at least two of lead, tin, silver, titanium, and platinum.

A more preferred mixed metal anode comprises at least lead and tin, even more preferably at least lead, tin, and silver. Our own experiments have shown that the preparation of a respective pre-treatment composition while using anodes comprising lead, tin, and silver, is significantly shorter than using anodes comprising lead and tin but without silver.

Most preferred is a mixed metal anode comprising lead, 0.1 wt.-% to 3.0 wt.-% silver, and 1 .0 wt.-% to 10.0 wt.-% tin, based on the total weight of the mixed metal anode. Preferably, the balance to 100 wt.-% is lead. Preferred is a method of the present invention, wherein the mixed metal anode comprises 0.2 wt.-% to 2.0 wt.-% silver, based on the total weight of the mixed metal anode.

Preferred is a method of the present invention, wherein the at least one cathode is a mixed metal cathode or a graphite cathode, preferably is a mixed metal cathode, even more preferably comprising at least lead and tin, most preferably is a mixed metal cathode comprising at least lead and 1.0 wt.-% to 10.0 wt.-% tin, based on the total weight of the at least one cathode.

Preferred is a method of the present invention, wherein the at least one anode has a total anode surface and the at least one cathode has a total cathode surface, wherein the total anode surface to the total cathode surface has a ratio of 2:1 or more, preferably of 3:1 or more, more preferably of 4:1 or more, most preferably of 5:1 or more.

Step (B):

In step (B) of the method of the present invention, the pre-treated substrate is contacted with an activation composition. Step (A) includes all steps carried out prior to step (B), preferably including a rinsing and further optional steps carried out prior to and/or after step (A), e.g. a swelling and/or a conditioning step.

Particularly preferred in some cases is a method of the present invention comprising prior to step (B) but after the contacting with the pre-treatment composition a conditioning step with a conditioning composition, i.e. a contacting with a conditioning composition. Own experiments have shown that such a conditioning step significantly increases (and thereby improves) the adsorption of palladium in step (B). In other words, the total amount of palladium adsorbed and attached, respectively, on the non-metallic substrate after step (B) is finished, is significantly increased compared to a method of the present invention without such a conditioning step. In some cases, the adsorbed, respectively attached, total amount is sufficient for a subsequent so-called direct metallization. Generally, such a conditioning step reduces the amount of wasted palladium due to the increased adsorption (and therefore increased efficiency) in step (B).

Preferably, after the contacting with the conditioning composition, the non-metallic substrate is rinsed in a rinse step, preferably is at least once rinsed with water.

Preferred is a method of the present invention, wherein the conditioning composition is alkaline, preferably has a pH ranging from 9 to 14, more preferably from 10 to 13.5, even more preferably from 11 to 13, most preferably from 11.5 to 12.5.

Preferred is a method of the present invention, wherein the conditioning composition comprises an amine-compound, preferably a diamine-compound. More preferred is a method of the present invention, wherein the conditioning composition comprises at least two amine-compounds, preferably at least two diamine-compounds.

A preferred amine-compound and diamine-compound, respectively, comprises an alkyl moiety, preferably an alkyl moiety having 2 to 12 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 8 carbon atoms, most preferably 2 to 6 carbon atoms. Most preferably this denotes an alkylene, i.e. a divalent, moiety if it relates to a diamine.

A very preferred diamine-compound comprises hexane diamine, i.e. hexamethylene diamine (most preferably hexane-1 ,6-diamine) and/or ethane diamine, i.e. ethylene diamine (most preferably ethane-1 ,2-diamine).

Preferred is a method of the present invention, wherein the conditioning step is carried out for 0.1 minutes to 15 minutes, preferably for 0.2 minutes to 11 minutes, more preferably for 0.3 minutes to 8 minutes, even more preferably for 0.4 minutes to 5 minutes, most preferably for 0.5 minutes to 2.5 minutes.

Preferred is a method of the present invention, wherein in the conditioning step the conditioning composition has a temperature ranging from 25°C to 50°C, preferably from 28°C to 46°C, more preferably from 30°C to 42°C, even more preferably from 32°C to 39°C, most preferably from 34°C to 37°C.

In the method of the present invention, preferably step (B) is a step separated and independently from step (A). In other words, the pre-treatment composition utilized in step (A) is not the activation composition utilized in step (B).

Preferred is a method of the present invention, wherein in step (B) the activation composition comprises palladium, preferably dissolved palladium ions or colloidal palladium, most preferably colloidal palladium. Preferably, the colloidal palladium comprises tin.

Preferred is a method of the present invention, wherein in step (B) the activation composition comprises palladium in a total concentration ranging from 20 mg/L to 200 mg/L, based on the total volume of the activation composition, preferably ranging from 40 mg/L to 150 mg/L, even more preferably from 50 mg/L to 110 mg/L, most preferably from 55 mg/L to 80 mg/L. Preferably, this total concentration includes both dissolved palladium ions and colloidal palladium. Above concentrations are based on the element palladium.

Preferred is a method of the present invention, wherein in step (B) the activation composition has a temperature ranging from 25°C to 70°C, preferably from 30°C to 60°C, even more preferably from 36°C to 50°C, most preferably from 39°C to 46°C.

Preferred is a method of the present invention, wherein in step (B) the contacting is carried out for a time ranging from 1 minute to 15 minutes, preferably from 2 minutes to 12 minutes, even more preferably from 3 minutes to 9 minutes, most preferably from 4 minutes to 7 minutes.

Preferred is a method of the present invention, wherein step (B) comprises step

(B-1) contacting the activated substrate with an accelerator composition to modify the activated substrate, the accelerator composition comprising

- no reducing agent but at least one complexing agent for tin ions, if in step (B) the activation composition comprises colloidal palladium, or

- a reducing agent for reducing palladium ions to metallic palladium, if in step (B) the activation composition comprises palladium ions but no colloidal palladium.

Preferred is a method of the present invention, wherein in step (B-1) the accelerator composition comprises no reducing agent but at least one complexing agent for tin ions and is acidic, preferably comprising in addition sulfuric acid.

In the context of the present invention, step (B-1) as defined above is carried out after contacting the pre-treated substrate with an activation composition such that an activated substrate is obtained.

Step (C):

In step (C) of the method of the present invention, the activated substrate is metallized. Preferred is a method of the present invention, wherein step (C) comprises a contacting with at least one metalizing composition comprising nickel ions, preferably comprises a contacting with at least two distinct metalizing compositions each comprising nickel ions, most preferably prior to a contacting with a metalizing composition comprising copper ions. Most preferably the at least one, preferably the at least two, metalizing compositions are for depositing a nickel and/or a nickel alloy metal layer, respectively.

In agreement with this, preferred is a method of the present invention, wherein step (C) comprises step

(C-1) contacting the activated substrate with a first metalizing composition for electroless plating to obtain a metalized substrate having a first nickel/nickel alloy metal layer, wherein the first metalizing composition comprises nickel ions and a reducing agent for nickel ions.

Preferred is a method of the present invention, wherein in step (C-1) the first metalizing composition is alkaline, preferably has a pH ranging from 8.0 to 11.0, preferably from 8.2 to 10.2, more preferably from 8.4 to 9.3, most preferably from 8.6 to 9.0. Preferred is a method of the present invention, wherein in step (C-1) the first metalizing composition has a temperature ranging from 18°C to 60°C, preferably from 20°C to 55°C, even more preferably from 23°C to 50°C, most preferably from 26°C to 45°C.

Preferred is a method of the present invention, wherein step (C) comprises after step (C-1) step

(C-2) contacting the metalized substrate having the first nickel/nickel alloy metal layer with a second metalizing composition for electrolytic plating to obtain a metalized substrate with a second nickel/nickel alloy metal layer, wherein the second metalizing composition comprises nickel ions and is preferably substantially free of, preferably does not comprise, a reducing agent for nickel ions.

Preferred is a method of the present invention, wherein in step (C-2) the second metalizing composition is acidic, preferably has a pH ranging from 1.0 to 5.0, preferably from 2.0 to 4.5, more preferably from 2.8 to 4.0, most preferably from 3.3 to 3.7.

Preferred is a method of the present invention, wherein in step (C-2) the second metalizing composition has a temperature ranging from 25°C to 70°C, preferably from 35°C to 65°C, even more preferably from 45°C to 61 °C, most preferably from 52°C to 58°C.

Preferred is a method of the present invention, wherein in step (C-2) the contacting is carried out for a time ranging from 1 minute to 10 minutes, preferably from 2 minutes to 8 minutes, most preferably from 2.5 minutes to 5.5 minutes.

Preferred is a method of the present invention, wherein in step (C-2) an electrical current is applied, preferably ranging from 0.3 A/dm² to 10.0 A/dm², preferably ranging from 0.5 A/dm² to 8.0 A/dm², more preferably ranging from 0.8 A/dm² to 6.0 A/dm², even more preferably ranging from 1.0 A/dm² to 4.0 A/dm², most preferably ranging from 1 .3 A/dm² to 2.5 A/dm².

Preferred is a method of the present invention, wherein in step (C-2) the second metalizing composition comprises chloride ions and/or (preferably and) boric acid.

Preferred is a method of the present invention, wherein in step (C-2) the second metalizing composition is a Watts Nickel composition. Thus, preferred is a method of the present invention, wherein in step (C-2) the second metalizing composition comprises chloride ions, sulfate ions, and boric acid.

Although significantly less preferred, preferred is an alternative method of the present invention, wherein step (C) comprises after step (C-1) step

(C-2) contacting the metalized substrate having the first nickel/nickel alloy metal layer with a second metalizing composition to obtain a metalized substrate with a copper/ copper alloy metal layer on the first nickel/nickel alloy metal layer, wherein the second metalizing composition comprises copper ions and is preferably an immersion copper metallization composition.

However, as shown below in the examples, in this alternative in some cases an undesired blistering is observed.

Preferred is a method of the present invention, wherein step (C) comprises after step (C-2), most preferably if (C-2) involves nickel, step

(C-3) contacting the metalized substrate having the second nickel/nickel alloy metal layer with a third metalizing composition to obtain a metalized substrate with a copper/copper alloy metal layer, wherein the third metalizing composition comprises copper ions.

Preferred is a method of the present invention, wherein in step (C) at least one metalizing composition of the one or more than one metalizing composition comprises trivalent chromium ions such that a chromium or chromium alloy metal layer, respectively, is deposited. Most preferably, the chromium or chromium alloy metal layer, respectively, is the outermost metallic layer. Thus, most preferably the method of the present invention is for metalizing a non-metallic substrate, wherein the metalizing comprises a chromium deposition, preferably a decorative chromium deposition.

Specifically preferred is a method of the present invention, wherein step (C) comprises after step (C-3) a further step

(C-x) contacting the metalized substrate obtained after a step prior to step (C-x) with a further metalizing composition to obtain a metalized substrate with a chro- mium/chromium alloy metal layer, wherein the further metalizing composition comprises trivalent chromium ions.

The advantages coming along with the present invention are typically observed and recognized on the chromium/chromium alloy layer.

The present invention furthermore refers to a specific pre-treatment composition comprising

(A-a) Mn(ll) ions, Mn(lll) ions, and colloidal manganese (IV) species,

(A-b) one, two or more than two acids,

(A-c) silver ions, wherein the pre-treatment composition has - a density in a range from 1 .50 g/cm³ to 1 .90 g/cm³, referenced to a temperature of 25°C, and

- an absorbance in a range from 1.1 to 2.1 , referenced to a wavelength of 400 nm and preferably a path length of 1 cm, with the proviso that the pre-treatment composition

- is substantially free of, preferably does not comprise, methane sulfonic acid, salts thereof, and chloride ions,

- is substantially free of, preferably does not comprise, permanganate ions, or comprises permanganate ions only up to a total concentration of 100 mg/L, based on the total volume of the pre-treatment composition and the element manganese, preferably only up to a total concentration of 75 mg/L, more preferably only up to a total concentration of 50 mg/L, even more preferably only up to a total concentration of 35 mg/L, most preferably only up to a total concentration of 20 mg/L, even most preferably only up to a total concentration of 10 mg/L.

The aforementioned regarding the method of the present invention and in particular regarding the pre-treatment composition utilized in the method of the present invention applies mutatis mutandis to the pre-treatment composition of the present invention (if technically applicable).

Examples

The invention will now be illustrated by reference to the following non-limiting example.

The following method for metallizing a non-metallic substrate was repeatedly carried out for at least 3 months with parameters as described below.

A respective pre-treatment composition was prepared as follows in an oxidizing compartment comprising all together 6 tin/lead/silver anodes, 12 lead/tin (97 wt.-% I 3 wt.-%) anodes, and 9 tin/lead cathodes with a total cathodic surface to a total anodic surface of approximately 1 :2:

First, a mixture of sulfuric and phosphoric acid was added to the compartment. Manganese (II) sulfate and silver nitrate were added and dissolved in the acid mixture such that the concentration of Mn(ll) ions (i.e. the manganese (II) species) is exceeding 5 g/L but below 6 g/L. The silver concentration was about 12 mmol/L.

Second, a current in a range from 1.2 A/dm² to 1.5 A/dm² was applied in order to oxidize Mn(ll) ions to manganese (III) species. After 48 hours the pre-treatment composition reached an absorbance at 400 nm of about 1 .0. The absorbance was measured via LIV/VIS spectroscopy with a path length of 1 cm.

Third, further amounts of manganese sulfate were added in intervals and dissolved under the effect of the applied current such that finally after about 96 hours an absorbance at 400 nm of more than 1 .2 was reached. The density of the pre-treatment composition was finally about 1.65 g/L.

The so obtained pre-treatment composition utilized in the method of the present invention does not comprise methane sulfonic acid and no intentionally added compounds/ions comprising chromium; in particular no hexavalent chromium compounds. Furthermore, the pretreatment composition is free of chloride ions and free of intentionally added permanganate compounds/ions.

The oxidizing compartment was fluidically connected with a pre-treatment compartment (tank volume approximately 5400 liters) such that the pre-treatment composition was allowed to constantly circulate between the pre-treatment compartment and the oxidizing compartment. In the pre-treatment compartment no anodes and no cathodes were installed.

In step (A) of the method of the present invention, a plurality of non-metallic plastic substrates (ABS or ABS-PC having surface dimensions ranging from 0.1 dm² to 10 dm² with varying production qualities) was used. Prior to contacting with the prepared pre-treatment composition in the pre-treatment compartment, the substrates were cleansed with Uniclean 151 (product of Atotech) and afterwards air dried.

Table 1 , composition and pre-treatment parameters during step (A)

denotes: determined by LIV/VIS spectroscopy

Concentrations of manganese species are in g/L, based on the total volume of the pretreatment composition and based on the element manganese.

During step (A) an electrical current of 1.2 - 1.5 A/dm² was constantly applied to the pre- treatment composition in the oxidizing compartment.

It is noteworthy that during the entire method, all substrates were contacted with manganese species only in step (A) with the pre-treatment composition as defined in Table 1. No additional contacting was carried out with a further manganese species-containing composition. Thus, step (A) is a one-step contacting with manganese species and the only con- tacting step with manganese species throughout the entire method. This is a general and important feature of the method of the present invention as a whole.

After step (A), pre-treated substrates were obtained with an etch pattern, showing an exceptionally fine sponge-like structure after removal of polybutadiene spheres contained in the surface of the ABS and ABS-PC, respectively, substrates. Own analysis confirmed that in the substrates primarily the polybutadiene frame work was etched wherein the acrylonitrile styrene of the substrates remained primarily intact. As a result, a very fine-pored surface was obtained after step (A), which was significantly less strongly etched compared to substrates contacted with e.g. permanganate ions but still providing sufficient adhesion. It was therefore an excellent balance obtained between etching and adhesion.

Prior to step (B) a rinsing was carried out with water. If any manganese dioxide particles are present on the substrate, they are simply rinsed away with water since no strong adherence of manganese dioxide is observed.

In step (B) the pre-treated substrates were contacted with an activation composition comprising colloidal palladium (approximately: 55 mg/L to 80 mg/L Pd, temperature 42°C, contact time 5 minutes).

Furthermore, step (B) comprises step (B-1), wherein the pre-treated substrate was contacted with an acidic accelerator composition to modify the activated substrate, the accelerator composition comprising at least one complexing agent for tin ions, since in step (B) the activation composition comprises colloidal palladium.

Prior to step (C) a rinsing was carried out with water.

In step (C) the activated substrate is contacted with more than one metalizing composition in order to obtain a metalized substrate.

First, step (C) included step (C-1), wherein the activated substrate was contacted with an alkaline (pH approximately 8.6 to 9.0) first metalizing composition (having a temperature of approximately 26°C to 45°C; contact time about 10 minutes) for electroless nickel plating. The first metalizing composition comprised approximately 3.5 g/L nickel ions and approximately 15 g/L hypophosphite ions as a reducing agent for nickel ions to obtain a metalized substrate having a first nickel alloy metal layer.

Second, step (C) included after step (C-1) step (C-2), wherein the metallized substrate having the first nickel alloy metal layer was contacted for approximately 2.5 to 5 min with an acidic second metalizing composition (pH approximately 3.3 to 3.7; temperature 55°C, current density approximately 1.5 A/dm²) comprising nickel sulfate, nickel chloride, and boric acid (Watts-Nickel composition). Thus, step (C-2) is an electrolytic deposition of nickel.

Afterwards, the metalized substrate with the second nickel metal layer was rinsed with water.

Afterwards, the respective substrates were contacted in a step (C-3) with a third metalizing composition (acidic pH) in order to obtain a metalized substrate having a copper layer with a layer thickness of more than 30 pm (contact time about 45 min, 32.5°C, 40 g/L copper ions).

Subsequently, further metallization steps were carried out to prepare chromium deposition.

In a final metallization step (C-x), the respective substrates were contacted with a further metalizing composition in order to obtain a metalized substrate having a chromium layer, the further metalizing composition comprising 15 g/L to 30 g/L trivalent chromium and boric acid (acidic pH, 25°C to 60°C).

Finally, the optical quality of the chromium layer was evaluated by analyzing coverage and optical defects. As a result, no haze and no other optical defects were observed. In particular, the chromium layer showed a very homogeneous optical distribution.

For adhesion tests, the substrates obtained after contacting with the third metalizing composition (i.e. plated with copper) were subjected to adhesion tests. Typically, the adhesion for ABS was above 1 .0 N/mm and for ABS-PC in a range from 0.5 to 0.8 N/mm.

Compared to comparative examples depositing copper in steps (C-1) and/or (C-2) instead of nickel as carried out in the example above, the method of the present invention showed a significantly higher adhesion (at least 10%) and in addition a reduced tendency to form blisters. This was particularly observed for substrates, wherein in step (C-2) a copper layer was deposited by immersion plating.

Furthermore, compared to comparative examples utilizing permanganate in a respective etching composition (e.g. as described in WO 2018/095998 A1), the method of the present invention includes basically a single-step pre-treatment sequence, which significantly reduces the time for the entire pre-treatment procedure because no contacting with a composition comprising a reducing agent and/or no second contacting step with a second or further manganese species is needed.

As a result of the present invention, a significantly lower degradation of the acrylonitrilestyrene matrix of the substrate is obtained leading to a much less aggressive etching result. This is significant. Own experiments with samples of lower manufacturing quality have shown that the etching result obtained with the method of the present invention is sufficiently homogeneous and still leads to a very acceptable optical quality. Surprisingly, in our own experiments even substrates of significantly lower quality showed a very homogeneous metallization because defects in the substrate were less pronounced during the pretreatment step compared to other known pre-treatment methods, in particular including permanganate ions. This benefit most preferably applies to polybutadiene-comprising substrates as investigated in our own experiments.

Claims

27 A method for metallizing a non-metallic substrate, the method comprising the steps(A) contacting the non-metallic substrate with a pre-treatment composition such that a pre-treated substrate is obtained, wherein the pre-treatment composition comprises (A-a) individual manganese (II), (III), and (IV) species, (B) contacting the pre-treated substrate with an activation composition such that an activated substrate is obtained, and (C) contacting the activated substrate with one or more than one metalizing composition such that a metalized substrate is obtained, with the proviso that - in the pre-treatment composition, the total concentration of manganese (IV) species is higher than the combined concentration of manganese (II) and (III) species,- an electrical current is applied to the pre-treatment composition such that manganese (II) species are oxidized to manganese (III) species, and - in step (A) contacting said substrate with manganese species is carried out in a single step. The method of claim 1 , wherein in step (A) the pre-treatment composition is substantially free of, preferably does not comprise, permanganate ions, or only up to a total concentration of 100 mg/L, based on the total volume of the pre-treatment composition and the element manganese, preferably only up to a total concentration of 75 mg/L, more preferably only up to a total concentration of 50 mg/L, even more preferably only up to a total concentration of 35 mg/L, most preferably only up to a total concentration of 20 mg/L, even most preferably only up to a total concentration of 10 mg/L. The method of claim 1 or 2, wherein in the pre-treatment composition manganese (III) species disproportionate to manganese species comprising manganese (IV) species. The method of any one of claims 1 to 3, wherein the electrical current has an anodic current density in a range from 0.1 A/dm2 to 20 A/dm2, preferably from 0.8 A/dm2 to 15 A/dm2, more preferably from 1.5 A/dm2 to 10 A/dm2, most preferably from 2.1 A/dm2 to 5.0 A/dm2. The method of any one of claims 1 to 4, wherein during step (A) or prior to step (B) the pre-treated substrate is not contacted with a composition comprising a reducing agent capable to chemically reduce manganese dioxide, preferably is not contacted with a composition comprising any reducing agent. The method of any one of claims 1 to 5, wherein during step (A) in the pre-treatment composition the total amount of all manganese species is more than 5.0 g/L, based on the total volume of the pre-treatment composition and the element manganese, preferably is 5.4 g/L or more, even more preferably is 5.8 g/L or more, most preferably is 6.0 g/L or more. The method of any one of claims 1 to 6, wherein the pre-treatment composition additionally comprises (A-b) one, two or more than two acids, preferably inorganic acids, most preferably at least a combination of sulfuric acid and phosphoric acid. The method of claim 7, wherein the pre-treatment composition comprises at least a combination of sulfuric acid and phosphoric acid, wherein the phosphoric acid has a higher concentration than the sulfuric acid, preferably the molar ratio of phosphoric acid to sulfuric acid is in a range from 1.1 : 1 to 3 : 1 , more preferably is in a range from 1.3 : 1 to 2.6 : 1 , even more preferably is in a range from 1.4 : 1 to 2.4 : 1 , yet even more preferably is in a range from 1.5 : 1 to 2.1 : 1 , most preferably is in a range from 1.6 : 1 to 2.0 : 1. The method of any one of claims 1 to 8, wherein the pre-treatment composition has an absorbance of more than 1.0, referenced to a wavelength of 400 nm and a path length of 1 cm, preferably in a range from 1.1 to 2.1 , more preferably from 1.2 to 2.0, most preferably from 1.3 to 1 .7. The method of any one of claims 1 to 9, wherein the pre-treatment composition additionally comprises (A-c) one or more than one species of additional transition metal ions different from manganese. The method of any one of claims 1 to 10, wherein the pre-treatment composition has a density in a range from 1.50 g/cm3 to 1.90 g/cm3, referenced to a temperature of 25°C, preferably from 1.55 g/cm3 to 1.80 g/cm3, more preferably from 1.60 g/cm3 to 1.70 g/cm3, most preferably from 1.61 g/cm3 to 1.68 g/cm3. The method of any one of claims 1 to 11 , wherein step (C) comprises a contacting with at least one metalizing composition comprising nickel ions, preferably comprises a contacting with at least two distinct metalizing compositions each comprising nickel ions, most preferably prior to a contacting with a metalizing composition comprising copper ions. The method of any one of claims 1 to 12, wherein step (C) comprises step

(C-1) contacting the activated substrate with a first metalizing composition for electroless plating to obtain a metalized substrate having a first nickel/nickel alloy metal layer, wherein the first metalizing composition comprises nickel ions and a reducing agent for nickel ions. The method of claim 13, wherein step (C) comprises after step (C-1) step

(C-2) contacting the metalized substrate having the first nickel/nickel alloy metal layer with a second metalizing composition for electrolytic plating to obtain a metalized substrate with a second nickel/nickel alloy metal layer, wherein the second metalizing composition comprises nickel ions and is preferably substantially free of, preferably does not comprise, a reducing agent for nickel ions. A pre-treatment composition comprising

(A-a) Mn(ll) ions, Mn(lll) ions, and colloidal manganese (IV) species,

(A-b) one, two or more than two acids,

(A-c) silver ions, wherein the pre-treatment composition has

- a density in a range from 1 .50 g/cm³ to 1 .90 g/cm³, referenced to a temperature of 25°C, and

- an absorbance in a range from 1.1 to 2.1 , referenced to a wavelength of 400 nm and a path length of 1 cm, with the proviso that the pre-treatment composition