KR20150024327A - Process for metallizing nonconductive plastic surfaces - Google Patents

Abstract

The present invention relates to a method of metallizing a nonconductive plastic using an etching solution without hexavalent chromium. The etching solution is based on a sulfuric acid solution containing a source of chlorate ions. After the treatment of the plastic with the etching solution, the plastic is metallized by a known process.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of metallizing nonconductive plastic surfaces,

The present invention relates to pretreatment of nonconductive plastic surfaces prior to metallization of nonconductive plastic surfaces and can be applied in a variety of industries where decorative or functional metal coatings of plastic parts are required. The pretreatment is carried out in a hexavalent chromium-free solution.

Prior methods for pretreating nonconductive plastic surfaces prior to electroless metallization (usually electroless nickel-plating or copper-plating) of the nonconductive plastic surface include surface etching in a hexavalent chromium-containing solution, followed by surface- Activation of the palladium compound in an ionic or colloidal solution, and reduction in palladium ions or colloidal palladium particles in sodium hypophosphite solution (in most cases) or in an acid solution (usually hydrochloric acid).

The surface is hydrophilic in aqueous solution for hydrophilisation purposes so that it becomes hydrophilic at different stages of the process so that a sufficient amount of palladium salt is adsorbed and to correct the proper binding of the metal coating to the non- Etching is required during preprocessing. Activation is performed by subsequent reduction or acceleration to initiate electroless deposition of the metal on the plastic. Thereafter, electroless plating of the metal in the metallization solution takes place through self-catalysis where the metal deposited on the surface acts as a catalyst for further deposition. Metal nickel and copper are usually used for such electroless plating.

Thereafter, electrolytic or galvanic plating can be performed on the first metal layer. For example, various metals such as chromium, nickel, copper, brass, or other alloys of the above metals may be applied.

The main disadvantage of the conventional process relates to the cancerogenicity of chromic acid in the etching solution. Moreover, the metal deposited during the electroless deposition step, such as nickel, also covers the plastic-insulated rack portion, resulting in electrochemical loss of metal in the solution of the subsequent metal plating and is thus undesirable.

Various methods for overcoming this problem have been proposed in the prior art.

United States Patent Application 2005/0199587 A1 discloses a method of etching nonconductive plastic surfaces in acidic solutions containing 20-70 g / l potassium permanganate. The optimum concentration of KMnO ₄ in the above solution is close to 50 g / l. When the concentration is less than 20 g / l, the solution is ineffective and the upper limit of the concentration is determined by the solubility of potassium permanganate. Etching is followed by activation in palladium salt solution containing amine and further reduction treatment, for example, further reduction treatment in borohydride, hypophosphite or hydrazine solution.

However, this method has substantial drawbacks. The high permanganate concentration of the etching solution (about 50 g / l recommended and about 48% v / v phosphoric acid) is degraded very quickly, especially at high temperatures. The recommended temperature is 100,, or 37 캜. According to the test, at this temperature, the solution is ineffective after 4 to 6 hours, i.e. the plastic surface is not hydrophilized and remains uncoated in some areas during metallization; In the coated area, adhesion to plastics is very weak. Adjustment of solutions using new permanganate salts, which are often inexpensive, is required. Furthermore, an insoluble permanganate degradation product is formed, which contaminates the surface to be metallized.

Moreover, etching in the permanganate solution activates the surface of the plastic insulation of the rack, because it is coated with the product of the etching solution, i.e. manganese dioxide. The latter promotes the adsorption of palladium compounds on the plastisols, which tend to metallize in solution of electroless metal deposition. The formation of manganese dioxide on the surface is characteristic of the permanganate etching solution of any composition. Therefore, a very important object of the present invention is to avoid rack metallization and to avoid metal loss in subsequent metallization steps.

Lithuanian patent application LT 2008-082 also relates to pretreatment of non-conductive plastic surfaces prior to metallization. 0.005-0.2 M oxidizing solution of sulfuric acid at a concentration of 13 mol / L (about 75 vol%) to 17 mol / L (about 90 vol%), etching the polyimide, for example, , And the oxidizing agent may be KMnO ₄ , HClO ₄ , V ₂ O ₅ , KClO ₃ . For chlorate (ClO ₃ ^- , M = 83.5 g / mol) this corresponds to a concentration between 0.4 and 16.7 g / l.

An example is provided in Table 2 in the present application, which contains 7 mol / L (about 50 vol%) sulfuric acid and 0.2 mol / L (16.7 g / L) chlorate. However, such a high chlorate concentration leads to rapid degradation of the pretreatment solution, which is undesirable.

Therefore, the present invention is based on the problem that it has not hitherto been possible to achieve metallization of an article made of electrically non-conductive plastic in an environmentally safe manner with sufficient process reliability and adhesive strength of the subsequently applied metal layer.

It is therefore an object of the present invention to find an etching solution for the pretreatment of an electrically non-conductive plastic surface of an article, which is non-toxic but provides sufficient adhesion strength of the metal layer applied to the plastic surface.

This object is achieved by a process for the treatment of plastic surfaces prior to the electroless metallization of plastic surfaces consisting of etching of the plastic with an inorganic acid solution having an oxidizing agent, activation with a palladium salt solution, and treatment with a reducing or accelerating solution For the etching of plastics, an etching solution containing 0.2 to 15.0 g / l of soluble chlorate (based on KClO ₃ , M = 122.55, i.e. 0.0016 mol / l to 0.12 mol / l) in 50-80% v / v sulfuric acid . The etching is preferably performed at room temperature (15-28 deg. C, preferably 20-25 deg. C) but can also be done at higher temperatures up to 40 deg. C or 50 deg. C if stability of the solution is controlled. The pretreatment solution may optionally contain up to 20 g / l of other oxidant with a standard oxidation potential greater than the standard oxidation potential of the chlorate.

The etching time depends on the substrate material and its shape, and can be determined by routine experimentation. In general, it varies from 1 to 20 minutes, preferably not exceeding 10 minutes.

The source of the chlorate ion may be any water soluble salt. Sodium and potassium chlorate are most commonly used.

The concentration of chlorate ions in the etching solution is 0.0016 mol / l to 0.12 mol / l, preferably 0.03 mol / l, more preferably 0.04 mol / l or less. The preferred range is from 0.003 mol / l to 0.08 mol / l, or from 0.01 mol / l to 0.06 mol / l, or from 0.004 mol / l to 0.04 mol / l.

The concentration of sulfuric acid is 50 to 80% by volume, preferably 55 to 70% by volume, more preferably 60 to 65% by volume.

Alternatively, phosphoric acid may be included in the etching solution as an additional acid. The concentration of phosphoric acid is typically 10 to 40% by volume, preferably 15 to 25% or 30% by volume. If phosphoric acid is additionally used, the adhesion of the plated metal layer can surprisingly additionally be increased.

Particularly preferred are mixtures of 60 to 65 vol% sulfuric acid and 20 to 30 vol% phosphoric acid.

Methods of pretreating plastic surfaces prior to electroless metallization of the plastic surface include etching of the plastic in the inorganic acid solution to which the oxidizing agent is added, activation in the palladium salt solution, and treatment in a reducing or accelerating solution, Etching of the plastic surface with a solution of 0.02-15.0 g / l soluble chlorate (e.g., 0.5-5 g / l soluble chlorate) in 50-80% v / v sulfuric acid, and activation and reduction / Is characterized by an additional treatment in the alkali metal hydroxide solution prior to treatment with the solution.

The etching solution may optionally contain from 2 to 20 g / l of an additional oxidant having a standard oxidation potential greater than the standard oxidation potential of the chlorate ion.

Alkali metal chlorate and sulfuric acid form a yellow compound, and its normal oxidation potential in H ₂ SO ₄ solution medium is sufficient for reaction with plastic surfaces at room temperature. Due to this reaction, the plastic surface becomes hydrophilic and adsorbs the palladium compound with sufficient strength. The yellow product of the reaction between chlorate and sulfuric acid is poison to the palladium catalyst. This penetrates the surface layer of the plastic insulator of the rack during etching and prevents electroless metal deposition on the plastisol in the electroless metallized solution; No metallization process occurs on the nonconductive plastic surface.

In the dissolution of a second strong oxidizing agent such as NaBiO ₃ of between 1 and 2 g / l sodium or potassium chlorate plus 5 to 10 g / l, the etching characteristics are maintained for several days at room temperature and the solution may be used without adjustment . If only sodium / potassium chlorate is contained in the solution, the etching properties are maintained for a much shorter period (less than 24 hours).

An important feature of the proposed method to distinguish it from permanganate etching is that very high adhesion values (often greater than 1.2 to 1.3 kg / cm) are obtained between the coating and the plastic. This value depends on the composition of the activating solution, along with the composition of the etching solution and the etching time (there is an optimum etching time for each composition). Usually, when an actual activation solution is used, the resulting tack value is higher than that obtained with the colloidal activation solution.

The etching solution can be prepared as follows:

700 ml of concentrated sulfuric acid is mixed with 300 ml of deionized water. Allow the solution to cool. Then, 2 g of potassium chlorate plus 10 g of sodium perchlorate are dissolved in the solution. The solution is ready for use. The second oxidizing agent, sodium perchlorate, stronger than potassium chloride is optional. This enhances the service life of the composition, but is not required to obtain good adhesion of the subsequently plated metal layer.

If the amount of water used in the preparation of the solution exceeds 50 vol.% Relative to the sulfuric acid, no yellow plastic-oxidizing compound is formed between the chlorate ion and the sulfuric acid molecule, so the water content of the solution preferably does not exceed 50 vol% Do.

If the amount of water used in the preparation of the solution is less than 20% by volume with respect to the sulfuric acid, the surface of the plastic is decomposed during etching due to the too high concentration of sulfuric acid, and therefore no adhesion is obtained between the chemical nickel coating and the plastic.

If the amount of potassium chlorate dissolved in the solution is less than 0.5 g / l, the etching process takes longer than 15 minutes, and thus such a concentration is not tolerated.

If the amount of potassium chlorate dissolved in the solution is greater than 5.0 g / l, over-etching may be observed after a minimum etch period, say 2 to 3 minutes, resulting in a much weaker adhesion strength , So that such high concentrations of chlorate are not tolerated. However, depending on the substrate material, a higher concentration of 15 g / l or less may be tolerated and sufficient adhesion is obtained.

The object of the invention is also achieved by the following method according to the invention:

A method of metallizing an electrically non-conductive plastic surface of an article,

A) etching said plastic surface with said etching solution comprising a source of chlorate ions, wherein a concentration of chlorate ions of from 0.0016 to 0.12 mol / l in 50 - 80% v / v sulfuric acid is obtained;

B) treating the plastic surface with a solution of a metal colloid or a compound of a metal, wherein the metal is selected from a transition metal of the Periodic Table of the Elements and a metal of the Group VIII of the Periodic Table of the Elements; And

C) metallizing the plastic surface with a metallization solution

Wherein the electrically nonconductive plastic surface is metallized.

The article in the context of the present invention is understood to mean an article made from at least one electrically non-conductive plastic or covered with at least one layer of at least one electrically non-conductive plastic. Thus, the article has a surface of at least one electrically non-conductive plastic. The plastic surface is understood to mean such a surface of the article in the context of the present invention.

The process steps of the present invention are performed in the specified sequence, but are not necessarily directly contiguous. In each case it is possible that other process steps and an additional rinsing step, preferably rinsing with water, are carried out between the steps.

The plastic surface was made from at least one electrically non-conductive plastic. In one embodiment of the invention, the at least one electrically non-conductive plastic comprises an acrylonitrile-butadiene-styrene copolymer (ABS copolymer), a polyamide (PA), a polycarbonate (PC) ≪ / RTI > copolymers.

In a preferred embodiment of the present invention, the electrically adaptively nonconductive plastic is an ABS copolymer or a mixture of at least one other polymer and an ABS copolymer. The at least one other polymer is more preferably polycarbonate (PC), which means that the ABS / PC mixture is particularly preferred.

The etching solution of the present invention preferably does not contain any chromium or chromium compounds; The etching solution does not contain chromium (III) ions or chromium (VI) ions. Thus, the etching solution of the present invention is free of chromium or chromium compounds; The etching solution is free of chromium (III) ions and chromium (VI) ions.

In another preferred embodiment of the present invention, the following other process steps are performed between process steps A) and B):

A) i) treating the plastic surface in a solution comprising an alkaline solution.

Other process steps A i) are also referred to as neutralization processes. Any source of alkalinity may be used, and an aqueous solution of sodium hydroxide is preferred.

In another alternative embodiment of the present invention, the following other process steps are performed between process steps A) and B):

A) treating the plastic surface in a solution comprising i) a reducing agent for chlorate ions and optionally a second oxidizing agent.

Other process steps A i) are also referred to as reduction processes. This reduction process reduces the chlorate ion and optionally the second oxidant that adhere to the plastic, and facilitates the removal of such ions. The reducing agent is selected, for example, from the group comprising hydroxylammonium sulfate, hydroxylammonium chloride and hydrogen peroxide.

The method of the present invention also includes process step B) in which the plastic surface is treated with a solution of a metal colloid or a metal compound. The metal of the metal colloid or metal compound is selected from the group comprising the transition metals of the Periodic Table of the Elements (PTE) and the metals of the transition metals of the Group VIII of the PTE.

The metal of the transition group VIII of PTE is selected from the group comprising palladium, platinum, iridium, rhodium, and mixtures of two or more of these metals. Metals of the transition group I of PTE are selected from the group comprising gold, silver, and mixtures of these metals.

The preferred metal in the metal colloid is palladium. The metal colloid is stabilized with a protective colloid. Protective colloids are selected from the group comprising metal protective colloids, organic protective colloids and other protective colloids. As metal protective colloids, tin ions are preferred. The organic protective colloid is selected from the group comprising polyvinyl alcohol, polyvinyl pyrrolidone and gelatin, preferably polyvinyl alcohol.

In a preferred embodiment of the present invention, the solution of the metal colloid in process step B) is an activator solution having a palladium / tin colloid. This colloidal solution is obtained from palladium salts, tin (II) salts and inorganic acids. A preferred palladium salt is palladium chloride. A preferred tin (II) salt is tin (II) chloride. The inorganic acid may be composed of hydrochloric acid or sulfuric acid, preferably hydrochloric acid. The colloidal solution is formed through the reduction of palladium chloride to palladium with the aid of tin (II) chloride. The conversion of the palladium chloride to the colloid is completed; Thus, the colloid fluids no longer contain any palladium chloride. The concentration of palladium is from 5 mg / l to 100 mg / l, preferably from 20 mg / l to 50 mg / l, more preferably from 30 mg / l to 45 mg / l based on Pd ²⁺ . The concentration of tin (II) chloride, based on the ^{Sn 2+ 0.5 g / l - 10} g / l, preferably from 1 g / l - 5 g / l, more preferably from 2 g / l - 4 g / l to be. The concentration of hydrochloric acid is 100 ml / l - 300 ml / l (37% by weight HCl). And, the palladium / tin colloid solution additionally contains tin (IV) ions formed through the oxidation of tin (II) ions. The temperature of the colloidal solution during process step B) is between 20 ° C and 50 ° C, preferably between 35 ° C and 45 ° C. The treatment time using the activator solution is 0.5 minute to 10 minutes, preferably 2 minutes to 5 minutes, more preferably 3 minutes to 5 minutes.

In another embodiment of the present invention, in process step B), a solution of a metal compound is used in place of the metal colloid. The solution of the metal compound used is a solution containing an acid and a metal salt. The metal salt of the metal salt consists of at least one of the above metals of Group I and VIII of the PTE. The metal salt may be a palladium salt, preferably palladium chloride, palladium sulfate or palladium acetate, or silver salt, preferably silver acetate. The acid is preferably hydrochloric acid. Alternatively, it is also possible to use palladium complex salts such as metal complexes such as palladium-aminopyridine complexes. The metal compound in process step B) is present at a concentration of from 40 mg / l to 80 mg / l based on the metal. The solution of the metal compound may be employed at a temperature of 25 캜 to 70 캜, preferably 25 캜. The treatment time using the solution of the metal compound is 0.5 minutes to 10 minutes, preferably 2 minutes to 6 minutes, more preferably 3 minutes to 5 minutes.

Between process steps A) and B), the following other process steps may be performed:

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

It is desirable to perform process step Aii) between process steps Ai) and B). If, in the method according to the invention, the protection of the rack is followed by the process step A i), then the process step A ii) is preferably carried out between the protection of the rack and the process step B).

The treatment of the plastic surface in process step A ii) is also referred to as preceding dipping, and the aqueous acidic solution used is also referred to as the preceding immersion solution. The preceding immersion solution has the same composition as the colloid solution of process step B), without the presence of the metal in the colloid and its protective colloid. In the case of the use of a palladium / tin colloid solution in process step B), if the colloidal solution similarly comprises hydrochloric acid, the preceding immersion solution contains only hydrochloric acid. In the case of prior immersion, immersion for a short time in the preceding immersion solution at ambient temperature is sufficient. Without rinsing the plastic surface, the plastic surface is further processed directly into the colloidal solution of process step B) after treatment in the preceding immersion solution.

Process step A ii) is preferably carried out when process step B) involves the treatment of the plastic surface with a solution of the metal colloid. Process step A ii) can also be done when process step B) involves the treatment of the plastic surface with a solution of the metal compound.

After treatment of the plastic surface with the metal colloid or metal compound in process step B), the plastic surface may be rinsed.

In another embodiment of the present invention, the following other process steps are performed between process steps B) and C):

B i) treating the plastic surface in an aqueous acidic solution, and

B ii) electroless metallizing the plastic surface in the metallization solution.

The embodiments are shown schematically in Table 1. [

These other process steps B i) and B ii) are employed when the article has to be metallized by an electroless metallization process, i.e. when the first metal layer has to be applied to the plastic surface by an electroless process.

When the activation in process step B) is carried out with a metal colloid, the plastic surface is treated with an accelerator solution in process step B i) to remove the colloid components of the colloid solution from the plastic surface, do. If the colloid of the colloidal solution in process step B) is a palladium / tin colloid, then the accelerator solution used is preferably an aqueous solution of an acid. The acid is selected, for example, from the group comprising sulfuric acid, hydrochloric acid, citric acid and tetrafluoroboric acid. In the case of palladium / tin colloids, the accelerator solution helps to remove tin compounds that serve as protective colloids.

Alternatively, in process step B i), when in process step B) a solution of a metal compound is used instead of a metal colloid for activation, a reductor treatment is performed. And, the reductant solution used for this purpose includes hydrochloric acid and tin (II) chloride if the solution of the metal compound is a hydrochloric acid solution of palladium chloride or an acid solution of silver salt. The reductant solution may also contain other reducing agents such as NaH ₂ PO ₂ or borane or borohydride such as alkali metal borane or alkaline earth metal borane or dimethyl aminoborene. It is preferable to use NaH ₂ PO ₂ in the reductant solution.

After processing or accelerating with the rejector solution in process step B i), the plastic surface can be rinsed first.

Process step B i) and optionally followed by one or more rinse steps, followed by process step B ii) wherein the plastic surface is electroless metallized. Electroless nickel plating is achieved, for example, using a conventional nickel bath comprising nickel sulfate as a reducing agent, a sodium hypophosphite, such as sodium hypophosphite, and also an organic complexing agent and a pH adjusting agent (e.g., buffer). Similarly, the reducing agent used may be a mixture of dimethylaminoborane or hypophosphite and dimethylaminoborane.

Alternatively, it is possible to use an electroless plating bath for electroless copper-plating and the electroless plating bath typically comprises a copper salt, such as copper sulfate or copper hypophosphite, and a reducing agent such as formaldehyde or a hypophosphite One or more complexing agents such as salts, such as alkali metal or ammonium salts, or hypophosphorous acid, and additionally, tartaric acid, and pH adjusting agents such as sodium hydroxide.

Thus, a conductive surface can be subsequently metallized more electrolytically to obtain a functional or decorative surface.

Step C) of the process according to the invention is metallization of the plastic surface using a metallization solution. Metallization in process step C) can be carried out electrolytically. It is possible to use any desired metal deposition bath for the electrolytic metallization, for example for the deposition of nickel, copper, silver, gold, tin, zinc, iron, lead or their alloys. Such deposition is familiar to those of ordinary skill in the art. As a bright nickel bath, a Watts nickel bath is typically used, which includes nickel sulfate, nickel chloride and boric acid and also includes saccharin as an additive. An example of a composition used as a bright copper bath is a composition comprising copper sulfate, sulfuric acid, sodium chloride, and an organosulfur compound, such as an organic sulfide or disulfide, in which sulfur is in a low oxidation state as an additive.

The effect of the metallization of the plastic surface in process step C) is that the plastic surface is coated with a metal selected from the metals mentioned above for the deposition bath.

In another embodiment of the present invention, after process step C), the following other process steps are performed:

C i) storing the metallized plastic surface at elevated temperature.

The adhesion strength between the metal and the plastic surface increases in the first period after application of the metal layer, as in all electroplating processes wherein the non-conductor is coated with a metal by wet chemical means. At room temperature, the process is complete after about 3 days. Which can be significantly accelerated by storage at elevated temperatures. The process is completed after about 1 hour at 80 占 폚. It is presumed that the initial low adhesive strength is caused by a thin water layer lying at the interface between the metal and the nonconductive substrate and hinders the formation of electrostatic force.

Thus, the method according to the invention makes it possible to achieve metallization of the electrically non-conductive plastic surface of the article with good adhesion strength and good process reliability of the subsequently applied metal layer. The adhesive strength of the metal layer applied to the plastic surface is 2.7 N / mm or less (corresponding to approximately 2.7 kg / cm, 1 kg / cm = 0.98 N / mm) or more. Thus, the achieved adhesion strength is much higher than that obtainable according to the prior art after etching of the plastic surface with chromosulfuric acid (see Examples 2 and 3).

In general, for industrial applications, an adhesion value of more than 0.8 N / mm is required, and an uncomplicated shaped article should be plated. Generally, the higher the tack value, the better the stability of the deposited material.

And, by the method according to the invention, only the flat plastic surface is not metallized with high adhesive strength; Instead, a heterogeneously shaped plastic surface (e.g., a showerhead) is provided with a homogeneous and strongly adherent metal coating.

The treatment of the plastic surface by the method according to the invention is preferably carried out in a conventional immersion process by continuously immersing the article in a solution of the container in which each treatment takes place. In this case, the article may be fixed to the rack or immersed in the solution contained in the drum. Fixation to the rack is desirable. Alternatively, the article can be processed in what is referred to as a conveyor plant, for example by being continuously conveyed through a conveyor plant in a horizontal direction, elevated to a tray.

Example

The embodiments described below are intended to describe the invention in detail.

Example 1

In a 45% v / v phosphoric acid solution containing 50 g / l KMnO ₄ at 37 ° C for 5 minutes (for ABS) or 15 minutes (for PC / ABS) or 0.5% at 20 ° C for 1 to 12 minutes to about 5.0 g / l KClO ₃ and having an oxidizing agent was added from 50 to 80% v / v sulfuric acid solution, according to US Patent Application 2005/0199587 A1, ABS (acrylonitrile-butadiene-styrene copolymer) and PC / ABS (A mixture of 45% polycarbonate and 55% acrylonitrile butadiene styrene copolymer) is etched. At the time of etching, the plastic is immersed in a neutralization solution at room temperature containing 10 g / l NaOH for 1 to 2 minutes and then the palladium compound is removed from the solution (5 minutes at 20 DEG C) or colloidal (2 minutes at 35 DEG C) (The colloidal solution is a registered solution of the DOW Chemical Company ("DOW")). The actual solution had a PdCl ₂ concentration of 0.1 g / l and a solution pH of 2.7. At the time of activation in the actual Pd solution, the plastic is maintained in a solution containing 20 g / l of sodium hypophosphite at 60 DEG C and pH 9 for 5 minutes. Upon activation in the registered colloidal solution, the plastic is treated with the registered accelerating solution of DOW at 40 占 폚 for 2 minutes. Plastics are then nickel plated using DOW's Niposit-PM nickel-plating process. The coating quality is assessed based on factors such as fully / incompletely plated plastic surfaces, plated or unplated plastic insulated racks, and adhesion strength of electroless nickel with plastics. To evaluate the adhesion, the Ni plating is thickened in a galvanic copper bath and the strength required to peel a 1 cm wide strip from the plastic is measured (kg / cm). For the ABS specimen, the etching time in the permanganate solution was 5 minutes, and for the PC / ABS specimen it was 15 minutes. The etch time in the chlorate solution was 5 minutes for all specimens. The conditions of the plastic pretreatment for metallization and the results of metallization (electroless nickel-plating) are shown in Table 2 below.

Specimens 1 to 4 show that, in the case of permanganate-based etching, the plastisol insulation of the rack is partially coated with electroless nickel, while in the case of chlorate-based etching, the insulation remains clean. Moreover, the adhesion between the Ni coating and the ABS is significantly higher in the case of chlorate etching for both ionic and colloidal activating solutions.

The same results were observed in the case of electroless nickel-plating of PC / ABS (specimens 5 to 8): in the chlorate etching process, the plastisol insulation was not coated at all and the tack values, particularly when the ionic activating solution was used It is considerably higher.

When the KClO ₃ concentration of the etching solution is less than 0.5 g / l, ABS is not coated with electroless nickel or is incompletely coated (P 9). When the KClO ₃ concentration is greater than 5 g / l (specimen 10), overetching occurs after 5 minutes of etching, and thus the coating adhesion value is significantly lower (practically insufficient for application). Similar results are obtained for PC / ABS metallizations when the recommended KClO ₃ concentration values are exceeded (PESTS 11 and 12).

If the H ₂ SO ₄ concentration of the etching solution is lower than 50% v / v, the etchant is not sufficiently effective, and thus the plastic is not coated at all with electroless nickel or is incompletely coated (P 13). When the H ₂ SO ₄ concentration is higher than 80% v / v (specimen 14), plastic overetching occurs and adhesion between the chemical nickel coating and the plastic is insufficient.

Example 2

A disk of ABS plastic (Novodur P2MC from Ineos) with a diameter of 7 cm was mounted on a stainless steel wire. Then, the substrate was immersed in various pretreatment etching solutions according to the present invention as shown in Table 4 at a temperature of 22 캜 for 4 minutes (the process sequence is shown in Table 3). Subsequently, the substrate was rinsed in running water for about 1 minute. Subsequent immersion in a solution of 300 ml / l 36% hydrochloric acid (process step A ii)) followed by a rinsing, neutralization (process step A i) and a colloidal active agent based on palladium colloid (Adhemax Aktivator NA from Atotech, 100 ppm palladium) (process step B).

Following a subsequent rinse, the protective shell of the palladium particles was removed at 40 占 폚 for 3 minutes (Adhemax ACC1 accelerator from Atotech, process step Bi)). Subsequently, the substrate was nickel-plated (Adhemax LFS from Atotech, process step B ii) at 45 ° C without external current for 10 minutes, rinsed and copper-plated at 3.5 A / dm 2 at room temperature for 70 minutes Cupracid HT, process step C)). After rinsing, the panels were stored at 70 占 폚 for 60 minutes (process step C i)). Subsequently, a knife was used to cut a strip of the metallized plastic substrate about 1 cm wide, and a tensile tester (manufactured by Instron) was used to remove the metal layer from the plastic (ASTM B 533 1985 Reapproved 2009). The adhesive strength as shown in Table 4 was obtained.

It can be seen from Table 4 that a very high tack value can be obtained by careful selection of the concentration of chlorate with sulfuric acid. Specimen No. 1 was 0.2 g / l by a low concentration of potassium chlorate ^- shows that (ClO ₃ of 0.0016 mol / l corresponding to concentration) is sufficient to obtain a good adhesion. A maximum value is obtained in the range of about 1.5 g / l potassium chlorate. Therefore, a decrease in the adhesive strength can be observed. Compositions comprising a mixture of sulfuric acid and phosphoric acid (Table 4, Specimen Nos. 9 to 16) generally exhibit higher adhesion values at the same chlorate ion concentration compared to etching in solutions containing only sulfuric acid and are therefore particularly preferred.

Claims (15)

A method of metallizing an electrically non-conductive plastic surface of an article,
A) etching the plastic surface with an aqueous etching solution;
B) treating the plastic surface with a solution of a metal colloid or a compound of a metal, wherein the metal is selected from a transition metal of the Periodic Table of the Elements and a metal of the Group VIII of the Periodic Table of the Elements; And
C) metallizing the plastic surface with a metallization solution
Lt; / RTI >
Characterized in that the etching solution comprises a source of chlorate ions in which a concentration of 50-80% v / v sulfuric acid and chlorate ions of 0.0016 to 0.12 mol / l is obtained. Way. The method according to claim 1,
Characterized in that the source of the chlorate ion of the etching solution of step A) is selected from sodium and potassium chlorate. 3. The method according to claim 1 or 2,
Characterized in that the concentration of the chlorate ion is from 0.003 to 0.08 mol / l. 3. The method according to claim 1 or 2,
Characterized in that the concentration of the chlorate ion is from 0.01 to 0.06 mol / l. 3. The method according to claim 1 or 2,
Characterized in that the concentration of the chlorate ion is from 0.004 to 0.04 mol / l. 6. The method according to any one of claims 1 to 5,
Characterized in that the sulfuric acid ion concentration is 60 to 70% by volume. 7. The method according to any one of claims 1 to 6,
Characterized in that the etching solution further comprises a second oxidant having a standard oxidation potential greater than the standard oxidation potential of the chlorate ion in an amount of 2 to 20 g / l. Way. 8. The method according to any one of claims 1 to 7,
Characterized in that the etching solution further comprises phosphoric acid. ≪ Desc / Clms Page number 12 > 9. The method of claim 8,
Characterized in that the concentration of said phosphoric acid is from 10 to 30% by volume. 10. The method according to any one of claims 1 to 9,
Wherein the metal of step B) is palladium. ≪ RTI ID = 0.0 > 8. < / RTI > 11. The method according to any one of claims 1 to 10,
Wherein the plastic surface is made of at least one electrically nonconductive plastic, and the at least one electrically nonconductive plastic comprises an acrylonitrile-butadiene-styrene copolymer, a polyamide, a polycarbonate, and at least one other polymer and an acrylonitrile Lt; RTI ID = 0.0 > of-butadiene-styrene copolymer. ≪ / RTI > 12. The method according to any one of claims 1 to 11,
Between step A) and step B), the following additional steps:
A) treating the plastic surface in a solution comprising a reducing agent for chlorate ions
The method comprising the steps of: providing an electrically non-conductive plastic surface of the article; 13. The method of claim 12,
Wherein the reducing agent is selected from the group consisting of hydroxylammonium sulfate, hydroxylammonium chloride and hydrogen peroxide. 14. The method according to any one of claims 1 to 13,
Between step A) and step B), the following additional steps:
A i) treating the plastic surface in a solution comprising a neutralizing agent containing a source of hydroxide ions
The method comprising the steps of: providing an electrically non-conductive plastic surface of the article; 15. The method according to any one of claims 1 to 14,
Between step B) and step C), the following additional steps:
B i) treating said plastic surface in an aqueous acidic solution, and
B ii) electroless metallizing the plastic surface in a metallization solution
The method comprising the steps of: providing an electrically non-conductive plastic surface of the article;