DE2026672A1 - Metallized polyamide parts - Google Patents

Description

Patent attorney Dipl.-Cheir, F. Schrumpf

^F 516Düren 29.5.1970

Koenenifraße 20

■ p 29

Staniicarbon -IV
.ieerlen / Üederlande

Metallized polyamide parts

Priority: June 3, 1969 Miederlande No. 6908380

The invention relates to parts metallized at least in places made of polyamide which has been produced by anionic polymerization of at least one lactam .

It is known to provide plastic parts with metal coatings in whole or in part. According to a common method, the surface of the plastic is first mechanically or chemically roughened in the manufacture of such objects, whereupon metal nuclei are deposited in aqueous solutions on the surface prepared in this way and then an electrically conductive layer is applied and then a thicker metal layer is produced by galvanic means.

The adhesive strength of metal layers formed in this way, measured for example according to DIH regulation ^ 0802 is pretty with most plastics small amount. In order to improve them, the known prior art starts out from plastics, in or on which inorganic · substances are housed. To this

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Purpose is used, among other things, metal powder, titanium dioxide, zinc oxide, asbestos fibers, inorganic substances that have previously been treated with catalytically active substances, or sulfidic alkaline earth compounds. Iron powder is preferably used together with a binder, some of which consists of a polyisocyanate addition varnish. The pretreatment of the surface with organic compounds, e.g. chlorinated hydrocarbons, can also improve the adhesion to a plastic. The adhesion can also be increased by incorporating a plastic-compatible, nonionic surface-active substance. The copolymers of acrylonitrile, butadiene and styrene (ABS) are relatively easy to metallize if the butadiene chains on the surface are removed by an oxidizing pretreatment with, for example, chromosulfuric acid. The adhesion of metal layers to polyamides is poor, so that metallized nylon should not be processed into articles which are subjected to a more or less harsh treatment in use.

The invention has for its object to provide products of at least partly coated with metal polyamide, in which the adhesive strength of the metal on the polyamide, measured according to the DIN specification 40802 "at least 2.25 kg ψ a strip of 2.5 cm width is - a condition that results from the so-called Marbon requirements for metallized plastics. It must be regarded as the minimum quality for metallized plastic parts.

It has been found 'that this can be achieved if that Polyamide consists of one or more anionically polymerize lactams, which are at a temperature below the The melting point of the polyamide to be produced have been polymerized in the presence of one or more polyethers which are soluble in the molten lactam

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According to the invention, the polyamide obtained in this way is distinguished characterized in that the adhesion of the metal to the polyamide is very good and corresponds to the guidelines mentioned above. The invention thus creates a considerable technical advance in the field of metallized plastic parts.

The polyamide made up of the article can be obtained by anionic polymerization of an ω-lactam with 4-16 carbon atoms, such as butyrolactam, caprolactam, Oenanthlactam, capryllactam, decyllactam, undecyllactam or laurolactam, but mixtures of two, three or more lactams are polymerized. The structure and properties of the polyamides can be changed as desired can be influenced by the composition of the starting monomer mixture.

The amount of polyether present in the polyamide is at least 0.10% by weight of the total amount of the to be polymerized Lactam (s). If the total amount is more than 25% by weight, the polyamide is less good mechanical properties. Preferably, but not necessarily, the addition of polyether is therefore intermediate 1 and 15% by weight of the amount of lactam.

Examples of polyethers soluble in lactam are polytetra-. hydrofuran, polyepichlorohydrin, polyglycidyl ether, polyethylene glycol, Polypropylene glycol, alkylphenoxy polyethylene oxide ethanol, as well as copolymers of ethylene glycol and propylene glycol and copolymers of ethylene oxide and glycidol, and terminally substituted polyglycols such as polyethylene glycol dimethyl ether, Polypropylene glycol dibutyl ether and methyl ether of nonylphenoxy polyethylene oxide ethanol. These polyethers are soluble in molten lactam unless they have a very high molecular weight, for example

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wise mon more than 20 QOO. Such high molecular weight, ^non-: in lactam soluble Pqlyäther the polyamide can not be added to -the invention. However, the polyethers need not necessarily be restricted to organic compounds; also silicon-based polyethers. are usable. . -:

The specified polyamide is made in the way known by the way by anionic polymerization from those already mentioned Obtain lactams. As catalysts for this type of Polymerization are lactam-N-anions, the

L · can be obtained, for example, from lactam metal compounds which have a metal atom on the nitrogen atom, such as sodium caprolactam. Lactam-N-anions can be formed by reaction with a lactam, for example, from metal-alkyl compounds such as diisobutylaluminum hydride, triethylaluminum, diethylaluminum chloride, triisopropylaluminum, diethylzinc and alkali alkyls, and also from alkali metals, alkaline earth metals and alkaline compounds, oxides, hydroxides of these metals, such as hydrides , Alkanolates and carbonates, as well as from. Grignard compounds such as alkyl magnesium bromide and aryl magnesium bromide, and from similar substances. The added amount of lactam-N-anion-yielding substance can vary within wide limits

w will be. Usually 0.1-5 mol%, based on the amount of lactam to be polymerized, are added, but larger proportions, for example 5-10 mol%, can also be used.

As an activator for the anionic polymerisation of the polyamide for the plastic parts according to the invention you can one or more of the substances known for this purpose. use, as long as their accelerating effect is not due to the OH groups of the dissolved in the molten lactams, Polyether is affected. The amount of. Added

1 0 901 fU7 1 2 U -. _: , r /

Activator is usually 0.1-2 mol%, based on the Laetam crowd. Examples of activators used in the Manufacture of the present polyamide can be added are acytylated lactams such as Aeetyllactam and Benzoyl lactam, compounds which can form acetylated lactams in situ, for example ketones or acid chlorides such as benzoyl chloride and adipoyl chloride Isocyanates such as phenyl isocyanate, hexamethylene diisocyanate, Tetramethylene diisocyanate, tolylene diisocyanate, 1,2-diisocyanate methylcyclobutane and triisocyanate-pheny! methane, substituted urethanes, e.g. polyurethanes, urea compounds, Carbodiimides and compounds such as tribenzamide, biscaprolactim ether and its hydrochloride, as well finally, combinations of several of these substances, in particular several isocyanates.

The temperature at which the anionic polymerization can be carried out in the temperature range of 90 to 250 C, must be chosen in each case so that the polymerization takes place at a temperature that is below the melting point of the polyamide to be produced. For example, for caprolactam there is an initial temperature from 125 - 175 ° C applied.

In the above-mentioned manner, the polymerization is great in a short time, often in less than 15 minutes, and one obtains solid macromolecular products, their dimensions correspond to those of the reaction space in which the polymerization is carried out. Mostly this one owns Reaction space is already the counter-shape of the product to be manufactured, but still another mechanical one Machining can be done before the metal is applied.

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The shape of the plastic parts is not very critical for the metallization. They can be foils or wire, for example, but complicated shapes are also possible. Examples of these are motor vehicle accessories, ship fittings, parts of electrical appliances, hinges and fittings for doors and frames, parts of household appliances, fabrics, etc. The rather high temperature resistance of the polyamide can advantageously be used for some purposes. The product can also be a polyamide plate with electrical conductor tracks (so-called printed circuit) attached to it. If necessary, the polyamide can be combined with a dimensionally stable carrier, for example phenolic resin paper or epoxy fabric. / -. ■■ · ■

After the polyamide has been brought into its final shape, its surface is completely or partially covered with metal overdrawn. All metals that can be electrodeposited, in particular, can be applied as a coating Copper, nickel, chrome, silver and gold. The metal layer can have a thickness of about 0.5 mm to about 1 mm; in principle, a much thicker metal layer can also be made to adhere. '.

According to the method of the invention, the metallization begins with a pretreatment. This pretreatment can consist of etching with a chemical agent such as chromosulfuric acid. The etchant can contain 70 to 98% sulfuric acid, in which 10-20% by weight of chromium trioxide are dissolved. The etching is performed by the parts at a temperature of 20-80 ⁰ C, about 0.5-5 minutes immersed in the etch bath. The pretreatment can also consist of mechanical processing, such as blasting with a soft material, for example with calcium carbonate or talc; if necessary, a water jet can also be used.

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Then the parts are in the usual way further treated. For this purpose, the surface is first sensitized with, for example, an aqueous stannous chloride solution, to deposit metal nuclei on it. Activation is then effected in a solution of a noble metal salt. This solution can be silver or palladium or another suitable noble metal in the form of a water-soluble Contain salt. In the next stage of the process, an electroless electrical layer is applied, for example by chemical deposition of copper on the surface, by immersion in an aqueous one Copper salt solution which has a complexing agent and a reducing |

containment agent. Nickel can also work in a similar manner to be deposited. A very thin, but well-cohesive metal layer is obtained that electrically connects the surface makes conductive.

Further metal layers made of the same or a different metal can then be electroplated using customary methods be applied. The method described above is known per se and is described, for example, in "Metal Finishing" November 1964, pp. 52-59. The treatment solutions for a particular embodiment of this process are commercially available and are described, for example, in a publication by Schering AG., ™ Berlin, with the title "Noviganthverfahren for the galvanic coating of plastic materials ^. The described However, treatment stages are not required for the application of a metal layer to the specified polyamide compulsory. Other modifications are possible.

The invention is illustrated below by means of comparative examples explained in more detail. The polyamides required for the examples were obtained as follows:

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Sample I.

0.42 g of hexaemethylene diisocyanate are added to 56.5 g of molten ceprolactam. 0.12 g of sodium hydride are dissolved in an equal amount of lactam. Both solutions are maintained at a temperature of 100 ⁰ G .. They are then assembled and placed in a 160 ° C. held flat cast aluminum shape. After 20 minutes the shaped plate is removed from the mold *

Sample II

Sample II is made in the same way, however 11.3 g of polypropylene glycol (2000) are dissolved in the part of lactam to which the sodium hydride was added, that is 10% by weight of the amount of caprolactam.

Sample III

1.47 g of biscaprolactx ether hydrochloride are dissolved in 56.5 g of melted caprolactam. This solution is kept at a temperature of 150 ^° C. for half an hour. Then a solution of 0.36 g NaH in 56.5 g ceprolactam is added at the same temperature. The whole is poured into a maintained at 160 ⁰ C flat aluminum mold. After 20 minutes the molded panels are removed from the mold.

Sample IV

Sample IV is made like Sample III, however 11.3 g of polyethylene oxide dimethyl ether were added.

The test panels are made from the polyamides thus obtained then metallized. They were treated in the same way as follows; ■ ■

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1. Pretreatment at room temperature for 1 minute in a solution of 400 ml H ₂ SO ₁₊ (96%) and 60 g K ₃ Cr ₂ O ₇ in 1200 ml. H ₂ O;

2. Sensitize at room temperature for 3 minutes in a solution of 18 g SnCl ₂ . 2 H ₂ O and 61 ml HCl (cone.) In 1500 ml H ₂ O;

3. at a temperature of 40 ⁰ C for 3 minutes in a solution of 0.25 g of PdCl ₃ and H ml HCl in 1500 ml H ₂ O;

4. Electroless copper plating at room temperature for 20 minutes in a mixture of the following solutions: 163 g of Seignette salt and 29 g of NaCO ₃ in 400 ml of H ₂ O, in which 34 g of CuSO ₄ in 400 ml of H ₃ O and

24 ml of NH ₄ OH (2%) are dissolved in 560 ml of H ₃ O.

5. Etching at room temperature for 5 seconds in a solution of 75 ml H ₂ SO ₄ (95%) in 1425 ml H ₃ O;

6. Galvanic copper plating at a temperature of 27 ° C,

60 minutes with a current density of 4 amps per din in the following solution:
220 g CuSO ₁₊
60 g H ₂ SO ₄ (96%)

2.5 ml Cupralid A

2.5 ml Cupralid B

0.06 g NaCl in, 1 liter H ₂ O

If necessary, neutralization was carried out between these treatments or rinsed. Shiny plates with a copper layer 45 μm thick were obtained.

The adhesion of the metal is then carried out on the samples measured, according to DIN regulation 40802. The Results' were as follows:

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sample I. 0.1 kg sample II 4.8 kg sample III 1.2 kg sample IV 3.5 kg

each to a width of 2.5 cm.

These results show that the adhesion of metal to a sample prepared according to the invention
can be considerably higher than the values determined according to the Marbon requirements of 2.25 kg by 2.5 cm in width. The measurement of the adhesive strength of sample II even resulted in local rupture of the polyamide instead of separation of the metal.

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Claims (2)

- li - claims 1. At least partially metallized parts made of polyamide, which was produced by anionic polymerization of at least one lactam, characterized in that that the lactam is at a temperature below the melting point of the polyamide in the presence of one or several polyether soluble in the molten lactams is polymerized. 2. Polyamide parts according to Claim 1, characterized in that that the amount of the polyether (s) present is 0.1-25% by weight, preferably 1-15% by weight, based on the amount of lactam is. 109810/2124