DE2948133A1 - METHOD FOR PRE-TREATING THE SURFACES OF CAPROLACTAMPOLYMERISATS FOR THE CHEMICAL METAL COVERING - Google Patents

Description

Patent attorneys

Dlpl.-lng. Dipt -Chem. Dipl -Ing.

E. Prince - Dr. G. Hauser - G. Leiser

Ernsbergerstrasse 19

8 Munich 60

CROWN CITY PLATING CO. November 27, 1979

4350 Temple City Blvd.

El Monte. California 91731 / V.St.A. Our symbol C 3260

Process for the pretreatment of the surfaces of caprolactam polymers for chemical metal deposition

This invention relates to chemical metallization of polymeric caprolactam substrates, and more particularly to the creation a surface of the same that is uniformly receptive to electroless nickel and copper.

The advantages of electrolessly metallized, non-conductive objects, in particular plastic objects, are known. The finished product combines the favorable properties of plastic and metal and thus offer the technical and aesthetic advantages of each one.

Polymeric substrates are usually prepared by pre-etching the surface through contact with an aqueous solution at least an organic compound effective for the preparation of the plastic surface, etching with a strong

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oxidizing acid or base, germination of the surface with a noble metal catalyst, e.g. a palladium chloride solution and immersing the germinated surface in an autocatalytic solution, which has an initial Coating of a conductive metal, e.g. copper or nickel, produced by chemical deposition, metallized. The metal deposition acts as a "bait", which is followed by the electrolytic deposition of a thicker one Metal coating allows.

Try the usual chemical plating processes Applying polymers to polyamides did not result in a uniformly adherent metal coating. After yourself the usual chemical metallization processes as proved to be ineffective, the search for a method for uniformly coating polyamides with arose chemically deposited metals.

It has now been found that the chemical metallization of caprolactam polymers, in particular filled caprolactam polymers, can be done so that a substrate made of a caprolactam polymer with an aqueous solution which brings together an organic acid soluble in water in a concentration of at least 3% by weight with 2 to contains about 10 carbon atoms. The contact time must be sufficient to make the surface receptive to a metal catalyst close. At present, a solution is preferably used which contains at least one acetic acid compound of the formula

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contains in which X, independently of one another, is in each case hydrogen, hydroxyl or halogen.

Then the surface is seeded with a catalyst for chemical metal deposition, namely with a Solution of noble metal ions or a colloidal suspension or dispersion of noble metal particles or particles of a non-precious metal.

After the nucleation and activation of the metal catalyst in the usual way, the surface can then be uniform chemically copper-plated or nickel-plated.

The contact time in the organic acid etching solution is usually about 10 seconds to 15 minutes at room temperature. The concentration of the acetic acid compound is usually at least about 3% by weight of the solution to Saturation, preferably about 5 to about 60 wt.%.

When performing the method, an alkaline solution with a pH of at least about 10 can be used to prepare the substrate, and when this happens, the temperature of this solution is preferably about 66 ^° C. up to the boiling point or up to the softening point of the plastic, depending after which is lower; preferably the temperature is 77 to about 93 ° C with contact times between about 0.5 and about 20 minutes or more, depending on the temperature and alkali concentration. The concentration is generally about 2% by weight of the solution until it is saturated, preferably about 10 to about 50% by weight. A solution of an alkali metal hydroxide, for example sodium or potassium hydroxide, is preferably used.

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In carrying out the process according to the invention, the article may by contact with an aqueous solution of an organic solvent, an alkali-soluble organic solvent for the Caprolactampolymerisat preferably.% In a concentration up to about 2 percent, be pretreated preferably up to about 1 wt.%. Ethylene glycol, phenolic compounds such as chlorophenol, cresols and salts thereof are preferred. The solvent can be used as a separate solution or as a component of the alkali solution if the alkali does not hydrolyze or otherwise degrade this organic solvent.

The solvent is used to soften the plastic for the acid etch. Contact with the solvent solution takes place before contact with the acidic etchant and can also before contact with the alkali solution.

In addition, after contact with the solution of the acetic acid compound, the substrate can be further used to remove Etching residues can be pretreated by washing with an acidic to basic washing solution.

The present invention provides a method that enables uniform chemical deposition of metals on substrates from caprolactam polymers, typically filled substrates, made possible.

The inventive method requires contacting the Caprolactamgegenstands with an etching solution containing an organic acid compound having from 2 to about 10 carbon atoms and having a solubility in water of at least 3 wt.%; the contact time must be sufficient to make the surface evenly receptive to a metal catalyst. A solution of an acetic acid compound defined below is preferably used.

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To ensure the process runs smoothly, a deionized water rinse is performed between each step. That Substrate can with a dilute solution of a solvent for the caprolactam polymer, preferably one alkali-soluble solvent, to soften the surface of the substrate and thus to promote etching be pretreated. The solvent for the caprolactam polymer can be contained in a separate bath or form part of the alkaline solution, as already stated became.

In addition, the substrates can then be etched to remove any remaining on the substrate surface Residues can be contacted with an acidic or basic solution.

The caprolactam polymers to be prepared are known as nylon 6.

The essential stage of the process consists in contacting the caprolactam substrate with an organic etching solution which preferably contains at least one acetic acid compound. The currently preferred etching solution contains at least about 3 % by weight, preferably 5 to about 65% by weight and even better about 19 to about 25% by weight, based on the solution, of at least one acetic acid compound of the formula:

wherein X is independently hydroxyl, hydrogen or halogen; Halogen is preferred. The contact takes place at room temperature, although elevated temperatures can also be used. The contact times are between approx

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10 seconds and 15 minutes or more and is sufficient to etch the surface of the amide so that it becomes uniform becomes receptive to nucleation with a catalyst for chemical metal deposition.

The acetic acid compounds to be used include: trichloroacetic acid, acetic acid, hydroxyacetic acid, Dichloroacetic acid, chloroacetic acid, fluoroacetic acid, difluoroacetic acid, Trifluoroacetic acid, bromoacetic acid, dibromoacetic acid and the like. Trichloroacetic acid is preferred.

Optionally, in the process, the caprolactam substrate can also be contacted with an aqueous alkaline solution with a pH of at least 10 to pretreat the surface for contact with the acid etching solution. The alkaline solution preferably contains at least one alkali metal hydroxide, for example sodium and / or potassium hydroxide. The alkali should be used in a concentration of about 2 wt.96 to saturation, preferably between about 10 and 50 wt.96. The solution temperature is maintained at about 66 ⁰ C and the boiling point of the solution or the softening point of Caprolactamsubstrats, on the lower of the two values, preferably the temperature is 77 ° C to 93 ⁰ C. The contact time may be between about 0.5 and 20 Minutes or more, depending on the temperature and alkali concentration, although longer immersion times have been shown not to damage the substrate. In addition to the alkali metal hydroxides, alkaline compounds such as sodium metasilicate, trisodium phosphate, sodium carbonate and the like can be used alone and / or in combination with an alkali metal hydroxide.

In the process, a separate bath of the caprolactam surface can also be used before or after the alkali pretreatment emollient solvents are used or the solvent

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medium can be added to the alkaline pretreatment solution to soften the surface and thus support the attack by the alkaline solution and / or the etching solution. Typically the concentration of the solvent is up to about 2 wt.96, preferably up to about 1 weight 96. A wide variety of solvents for polyamides can be used. Preferred solvents are ethylene glycol, Phenols such as chlorophenol, cresols and the like and their salts. The solution of the solvent is preferred applied prior to acid etching, regardless of whether an alkaline pretreatment solution is used or not. The solvent serves to soften the surface of the caprolactam substrate and thus to promote the pretreatment and / or etching.

In addition, after the etching, the caprolactam substrate with an acidic or alkaline solution of a organic or inorganic base for cleaning the surface of residues, e.g. fillers and / or degraded Resin. Such solutions are usually kept at room temperature, although elevated temperatures can also be used are applicable. The concentrations are in the range up to about 20% by weight, preferably up to about 10% by weight. effective acids are e.g. hydrochloric acid, sulfuric acid, Phosphoric acid, nitric acid, formic acid, acetic acid and the like. Can also be used for pre-treatment alkaline solution or a saline solution such as a solution of borax or ammonium bifluoride can be used. The concentration of these solutions is sufficient to improve the surface quality without affecting the absorption capacity the etched surface for a metal catalyst is impaired.

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Regardless of whether the cleaning treatment is used, the object is rinsed in water, usually deionized water, and seeded with a catalyst for chemical metal deposition contained in an aqueous medium. The catalyst can be based on a noble metal or a base metal. The use of a noble metal catalyst in an aqueous medium is preferred. A noble metal catalyst contained in an aqueous medium is to be understood as meaning an ionic solution or a colloidal suspension of the free metal. Colloidal suspensions are preferred. The noble metals include gold, platinum and palladium, with palladium being preferred. Suitable base metal catalysts are described in U.S. Patent 3,958 OhB , incorporated herein by reference.

A suitable ion solution is a palladium in a concentration of about 0.2 g / liter and 3 ecm concentrated Containing hydrochloric acid per liter of solution. After germination the palladium can be converted to the free metal by immersion in a bath of a reducing agent, e.g. dimethylamine borane, be reduced.

Colloidal suspensions of precious metals are disclosed in U.S. Patent 3,011,920, which are incorporated herein by reference. The preferred colloidal suspension contains about 1.7 moles of hydrochloric acid (HCl). Such suspensions are colloids in which the noble metal colloid is kept in suspension by a protective colloid, i.e. stannic acid colloid will. After germination, the colloid is removed by immersion in an acidic or alkaline accelerator solution the protective colloid and to expose the absorbed precious metal.

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Although less preferred, a germination method can also be used can be applied in which the etched object with a sensitizing solution containing stannous chloride contacted and then immersed in an activator solution, e.g. a palladium chloride solution, in which the palladium ions on the surface of the substrate to the free metal can be reduced.

After activation, the item can then be used in the usual way Way to be chemically metallized. Chemical copper plating and nickel plating compositions such as those described in U.S. patents 3,011,920 and 3,874,072 can be used. Chemical copper plating solutions are usually based on a soluble copper salt, e.g. copper sulfate, a complexing agent for the cupric ions, e.g. Rochelle salt, an alkali hydroxide to adjust a certain pH value, a carbonate radical as Buffer and a reducing agent for the cupric ions, e.g. formaldehyde.

After chemical metallization, the substrate can then be electrolytically coated with copper, nickel, gold, Silver, chrome and the like can be plated to achieve the desired final finish of the article.

example

A molded item made from Capron ^ 'XPM-1030, a Filled nylon 6, manufactured and sold by Allied Chemical Corporation, was made at a 15% w / v% contacted aqueous solution of trichloroacetic acid at room temperature for 5 minutes. After rinsing with deionized Water became the article by contact with a tin-palladium colloidal catalyst such as that described in the US patent 3 011 920 and the one acid molarity

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of about 1.7, germinates. An alkaline accelerator was used to expose the palladium metal. The catalyst was maintained at about 49 ⁰ C and the accelerator at about ⁰ C AO. The seeded article was then electrolessly metallized using Cuposite PM-990 manufactured and sold by the Shipley Company. The chemical plating solution was kept at room temperature.

After the chemical metallization, the object was rinsed with deionized water, in an alkaline one Cleaner introduced, sent through a counter-current cleaner, with acidic electrolytic copper plating and Nickel plating solutions and finally treated with a chrome plating solution.

The plated article was subjected to a test cycle to determine its adhesive strength under thermal stress. In this test, the plated article was held for 1 hour at a temperature of 82 ⁰ C, then cooled to room temperature and held for 30 minutes at this temperature, whereupon it was cooled to -29 ° C and 1 hour, kept at this temperature. The test was passed.

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Claims (1)

Patent attorneys Dipl Int) Dipl.-ChGin Dipl.-Ing E. Prince - Dr. G. Hauser - G. Leiser Ernsbergeistrasse 19 O Munich 60 CROWN CITY PLATING CO. November 27, 1979 Temple City Blvd. El Monte. California 91731 / V.St.A. Our sign; C 3260 Patent claims I 1. A process for the pretreatment of the surfaces of PoIycaprolactampolymerisaten for the chemical metallization, characterized in that the Caprolactamsubstrat is etched with an aqueous etching solution containing at least an organic in a concentration of at least 3 wt.% Soluble acid compound having 2 to 10 carbon atoms, the concentration of which in the solution is sufficient to make the caprolactam substrate receptive to a metal catalyst for chemical metallization. 2. The method according to claim 1, characterized in that the polycaprolactam substrate prior to contact with the aqueous Etching solution with a dilute aqueous solution of an organic solvent for caprolactam until softened its surface is contacted. Dr Ha / Ma 030026/0626 3. The method according to claim 1 or 2, characterized in that an aqueous etching solution is used, which at least an acetic acid compound of the formula X, C - contains, wherein X is independently hydrogen, hydroxyl or halogen. H. Process according to Claim 3 »characterized in that a filled polycaprolactam is used as the substrate. 5. The method according to claim 3, characterized in that the total concentration of the acetic acid compound of Etching solution about 3 wt.96 of the solution until saturation amounts to. 6. The method of claim 3 »characterized in that the total concentration of the acetic acid compound of the etching solution is about 5 to 60 wt.% Of the solution. 7. The method according to claim 3, characterized in that the caprolactam substrate with the etching solution for about 10 seconds contacted for up to 15 minutes. 8. The method according to one or more of claims 1 to 7t characterized in that trichloroacetic acid is used as the organic acid compound. 9. The method according to claim 8, characterized in that the concentration of trichloroacetic acid is about 5 wt.% To saturation of the solution. 030026/0625