Pickling agent for polyamide

Abstract

1. A process for pickling a polyamide comprising the steps of: a) contacting the polyamide with a pickling solution comprising a mixture of two or more inorganic acids, MHF2, where M is an alkali or ammonium ion, and a monocarboxylic acid having 1 to 5 carbon atoms; and b) contacting the polyamide with an organic solvent having 1 to 10 carbon atoms, wherein steps a) and b) are carried out sequentially or simultaneously.

Description

[Technical Field]

[0001] The present invention relates to a process for pickling polyamides prior to subsequent metallization, and to the pickling solutions used for this purpose. [Background technology]

[0002] The polyamide surface needs to be pickled before metallizing to allow the metal layer to adhere.

[0003] Typical plastics that are metallized (electroplated) include acrylonitrile-butadiene-styrene copolymer (ABS) and ABS polycarbonate (ABS-PC), which are used, for example, in automobiles for decorative elements, switches, display elements, etc.

[0004] Polyamide (PA) plastic surfaces are often coated with a suitable metal layer for decorative and technical reasons. Due to its special properties, polyamide (PA) is used in automotive engineering, for example, to provide sufficient strength for door handles and other safety-related components. The decorative and precious character required in this respect can be enhanced by an adhesive metal coating.

[0005] For the durability of a metal layer deposited on a polyamide surface, it is crucial to have sufficient adhesive strength on the polyamide surface. Therefore, in order to achieve the appropriate adhesive strength, it is common in the prior art to roughen / swell the polyamide surface prior to the deposition of the appropriate metal to ensure sufficient adhesive strength of the deposited metal layer. For this purpose, various methods are known in the prior art. Typically, the polyamide surface is treated with a combination of a chromium (VI)-containing pickling solution and a fluoride-containing pickling solution, followed by metallization. Such a chromium-sulfuric acid-based pickling solution may, for example, contain chromium (VI) oxide and sulfuric acid in a 1:1 weight ratio.

[0006] Typical pickling solutions for polyamides contain chromium-containing chromium(VI)-based compounds. However, because chromium(VI)-containing compounds are suspected of being carcinogenic, the handling of these compounds is subject to strict environmental protection and occupational safety regulations. REACH is expected to ban the commercial use of chromium(VI) within the European Union. Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is therefore to provide a process for pickling components made of polyamide which overcomes at least some of the mentioned drawbacks, in particular which does not contain chromium compounds. [Means for solving the problem]

[0008] This problem is solved by a process called pickling of polyamide. a) a polyamide, Mixtures of two or more inorganic acids MHF2 (wherein M is an alkali ion or an ammonium ion). Monocarboxylic acids with 1 to 5 carbon atoms contacting the substrate with a pickling solution comprising b) contacting the polymer with an organic solvent having 1 to 10 carbon atoms wherein steps a) and b) are carried out sequentially or simultaneously.

[0009] The compositions according to the invention allow pickling of polyamides for subsequent metallization without recourse to chromium, particularly chromium(VI).

[0010] The pickling solution is preferably substantially free of chromium, in particular having a chromium content of less than 1 mg / l.

[0011] In this process, the surface of the polyamide (e.g., polyamide component) is roughened and microcavities are formed.Strong mineral acids can also cleave amide bonds.

[0012] In one embodiment of the present invention, the pickling solution contains two inorganic acids, a fluoride source, and a monocarboxylic acid. After pickling, the pickled product is contacted with an organic solvent.

[0013] In another embodiment, the contacting with the acidic pickling solution and the organic solvent occurs simultaneously.

[0014] Suitable inorganic acids include, in particular, the typical mineral hydrochlorides, phosphoric acid, sulfuric acid, and nitric acid, with hydrochloric acid and phosphoric acid being preferred.

[0015] Particularly suitable fluoride sources are sodium bifluoride, potassium bifluoride and ammonium bifluoride.

[0016] Suitable monocarboxylic acids include methanoic acid, ethanoic acid, propanoic acid or mixtures thereof.

[0017] Suitable organic solvents having 1 to 10 carbon atoms include, for example, n-butanol, isobutanol, t-butanol, isopropanol, n-propanol, and glycol ethers, such as 1-methoxy-2-propanol, 2-butoxyethan-1-ol, 2-(2-butoxyethoxy)ethanol, 2-(2-methoxyethoxy)ethanol, dipropylene glycol methyl ether, and mixtures thereof. Compounds having 3 to 8 carbon atoms are preferred. Preferably, the organic solvent is selected from alcohols and ethers.

[0018] Suitable concentrations are e.g. A mixture of inorganic acids in a concentration of 1-5 mol / l in the pickling agent MHF2 5-50g / l Monocarboxylic acids: 50-300g / L Optionally, the organic solvent is 30-100g / l is. Volumes are measured at 23°C.

[0019] The mixture of two inorganic acids may contain the two inorganic acids independently in the range of 0.5 to 3 mol / l, and preferably contains them at a total concentration of 1 to 4 mol / l or 2 to 4 mol / l.

[0020] Contact with the polyamide is typically carried out in a suitable manner at a temperature of 20 to 50° C. A suitable contact time is about 3 to 15 minutes.

[0021] When carrying out the process of the present invention, it is not necessary to move the pickling solution or the product in the pickling solution. In some embodiments, the pickling solution or the product is agitated in the pickling solution.

[0022] It is recommended to carry out one or more rinsing steps before proceeding with post-pickling treatment.

[0023] In many cases, it makes sense to perform two rinse steps. A particularly suitable process is one in which a first hot rinse step is performed at a temperature above 25°C, followed by a cold rinse step at room temperature. A suitable temperature range for the hot rinse step is 30-40°C.

[0024] For both the hot and cold rinse steps, a surfactant may be included in the rinse solution to improve surface wetting. A surfactant may be included in the hot rinse step, and no surfactant may be included in the cold rinse step. Typical exposure times for the rinse step are 3 to 10 minutes.

[0025] One or more rinse steps may be performed as an alkaline rinse step to neutralize the surface. During the hot rinse step, the cleaning solution may be agitated by air injection. The cold rinse step is typically performed without bath agitation.

[0026] A typical further step is to deposit metal nuclei on the pickled surface by contact with a catalyst. Such processes are known to those skilled in the art and can be used for surfaces pickled according to the present invention. Common metals for this purpose are, for example, palladium, platinum, silver, or ruthenium. These are typically contacted with the pickled surface as colloids. Processes in which metal nuclei are deposited by acids and alkalis are known.

[0027] This is usually followed by electroless metallization using a copper or nickel layer by reduction from their metal salts. In principle, other electroless plating processes are also known for depositing, for example, cobalt, copper / nickel, nickel / cobalt, or gold layers. In some embodiments, an ammonium-free electroless nickel process is used.

[0028] It may then be coated with further layers after metallization without external current, as known to those skilled in the art for other plastics.

[0029] Thus, preferably, the process according to the invention comprises the following steps: Pickling with the pickling agent of the present invention, Catalytic separation of metal nuclei; electrolessly plating a first metal layer, and Plating further metal layers as required.

[0030] It is also an object of the present invention to provide a pickling solution comprising: Mixtures of two or more inorganic acids MHF2 (wherein M is an alkali ion or an ammonium ion). ·Monocarboxylic acids having 1 to 5 C atoms.

[0031] The object of the present invention is also the use of a pickling solution for pickling polyamides, in particular PA6. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is an SEM image of Example 1 of the present invention. [Figure 2] FIG. 2 is an SEM image of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be explained in more detail by the following examples. The disclosure of the present invention may include the following aspects. (Aspect 1) A process for pickling polyamide a) a polyamide, a mixture of two or more inorganic acids, MHF 2 (wherein M is an alkali ion or an ammonium ion), Monocarboxylic acids with 1 to 5 carbon atoms contacting the substrate with a pickling solution comprising b) contacting the polymer with an organic solvent having 1 to 10 carbon atoms Including, The process wherein steps a) and b) are carried out sequentially or simultaneously. (Aspect 2) 2. The process according to aspect 1, wherein the inorganic acid is hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid, in particular hydrochloric acid and phosphoric acid. (Aspect 3)

[0023] Aspect 3. The process of aspect 1 or aspect 2, wherein the organic solvent is selected from n-butanol, isobutanol, t-butanol, isopropanol, n-propanol, and glycol ethers, such as 1-methoxy-2-propanol, 2-butoxyethan-1-ol, 2-(2-butoxyethoxy)ethanol, 2-(2-methoxyethoxy)ethanol, dipropylene glycol methyl ether, and mixtures thereof. (Aspect 4) The MHF 2 However, NaHF 2 , KHF 2 or a mixture thereof. (Aspect 5) Aspect 5. The process of any one of aspects 1 to 4, wherein the monocarboxylic acid is methanoic acid, ethanoic acid, propanoic acid, or a mixture thereof. (Aspect 6) The concentration in the pickling solution is Mixtures of inorganic acids are 1-5 mol / l, MHF 2 is 10-60g / l, Monocarboxylic acids: 50-300g / l; Optionally, the organic solvent is 30 to 100 g / l The process according to any one of embodiments 1 to 5, wherein (Aspect 7) The process of any one of the preceding embodiments, wherein the contacting is carried out at 20 to 50°C. (Aspect 8) The process of any one of the preceding embodiments, wherein the contacting is performed for 3 to 15 minutes. (Aspect 9) The process of any one of the preceding embodiments, wherein one or more rinsing steps are used. (Aspect 10) The process of any one of the preceding embodiments, followed by a step comprising a catalyst. (Aspect 11) 11. The process of embodiment 10, followed by an electroless nickel plating step. (Aspect 12) a mixture of two or more inorganic acids, MHF 2 (wherein M is an alkali ion or an ammonium ion), Monocarboxylic acids with 1 to 5 carbon atoms A pickling solution containing (Aspect 13) 13. The pickling solution of claim 12, further comprising an organic solvent having 1 to 5 carbon atoms. (Aspect 14) The concentration in the pickling solution is Mixtures of inorganic acids are 1-5 mol / l, MHF 2 is 10-60g / l, Monocarboxylic acids: 50-300g / l; Optionally, the organic solvent is 30 to 100 g / l 14. The pickling solution of claim 12 or 13, wherein (Aspect 15) Aspect 15. The pickling solution according to any one of Aspects 12 to 14, wherein the inorganic acid is selected from the group consisting of hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid. (Aspect 16) Aspect 15. The pickling solution according to any one of Aspects 12 to 14, wherein the inorganic acid comprises hydrochloric acid and phosphoric acid. (Aspect 17) 17. Use of the pickling solution according to any one of aspects 12 to 16 for pickling polyamide. [Example]

[0034] Example 1: Pickling The components were treated with a pickling solution of the following composition: HCl 37%-ig: 150ml / L H3PO4 85%-ig: 100ml / L 2-(2-butoxyethoxy)ethanol: 50ml / L Ammonium bifluoride: 35g / L Formic acid: 100ml / L Remaining amount: Water The plate was pickled at 40°C for 5 minutes. Acid-washed polyamide, size 3dm 2 The specimens were PA6M40.

[0035] For comparison, the same polyamide was pickled with a commercial chromium (VI) pickling agent (CrO3 380 g / l, H2SO4 380 g / l).

[0036] Two SEM images of an example according to the present invention and a comparative example are shown in FIGS.

[0037] The surface structure is differently invaded, and qualitative differences are virtually impossible to assess at this level.

[0038] Example 2 Flushing and Activation The surface was first rinsed at 35°C for 5 minutes with air agitation, then cooled at room temperature for 2 minutes without agitation and without the addition of a wetting agent, and activated with a palladium-containing catalyst at a palladium concentration of 40 mg / L for 4 minutes at 40°C. The amount of palladium deposited on the surface was then measured. For polyamides etched according to the present invention, the palladium concentration was >0.3 mg / dm 2 and 0.3 mg / dm for the comparison product. 2 The higher the loading of palladium, the more electroless plating of the layer is promoted.

[0039] Example 3: Electroless deposition The product thus obtained was then coated with nickel solution plating without external current in the next step.

[0040] Example 4: Analysis The products according to the invention can achieve peel strengths of more than 15 N / cm in the pull-off test according to DIN 53494, compared with 8 N / cm for comparative products. Determining the peel force of the metal layer of zinc-plated plastic parts according to this standard allows a comparative evaluation of the process on test specimens with smooth, flat surfaces and an investigation of the influence of process parameters. The peel force in this standard refers to the force in N required to peel a 25 mm wide strip of a 40 μm thick copper layer perpendicular to the sample surface.

[0041] As another comparison product, a product obtained from ATO was used. Treat with 400ml / l of PA Sweller Concentrate and 130ml / l of PA conditioner at 40°C for 5 minutes. Rinse at 40°C for 8 minutes. Rinse twice more in cold water for 4 minutes each Here, only the nickel layer with a peel strength of 6.9 N / cm could be achieved.

[0042] The results show that superior adhesion levels to the state of the art are achieved despite the use of environmentally friendly, chromium-free pickling agents.

[0043] Example 5: Solvent Variations The type of solvent was changed as shown below. The surface energy was measured according to DIN 55660-2, Determination of the free surface energy of solid surfaces by measuring the contact angle. Kruss Advance software was used.

[0044] [Table 1]

[0045] Subsequent rinsing, activation, and subsequent deposition were performed as described above. After activation, palladium uptake was measured, and after deposition, adhesion was monitored over time. Finally, impact testing (100°C for 1 hour, followed by quenching) was performed up to three times and visually assessed.

[0046] [Table 2]

[0047] Impact tests have shown that coatings vary in stability, and for some applications, passing cycles is not necessary to be suitable for that application.

[0048] Example 6: Ingredient Relationships These experiments were carried out using 2-(2-butoxyethoxy)ethanol as the solvent.

[0049] [Table 3]

[0050] Further analysis was carried out as in Example 5.

[0051] [Table 4]

[0052] Example 7: Concentration Variation

[0053] [Table 5]

[0054] [Table 6]

Claims

1. A process for pickling polyamide a) a polyamide, a mixture of two or more inorganic acids; MHF ２ (wherein M is an alkali ion or an ammonium ion), Monocarboxylic acids having 1 to 5 carbon atoms contacting the substrate with a pickling solution comprising b) contacting the mixture with an organic solvent having 1 to 10 carbon atoms; Including, The process wherein steps a) and b) are carried out sequentially or simultaneously.

2. 2. The process of claim 1, wherein the inorganic acids are hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid.

3. 3. The process of claim 1 or claim 2, wherein the organic solvent is selected from n-butanol, isobutanol, t-butanol, isopropanol, n-propanol, and glycol ethers.

4. The MHF ２ However, NaHF ２ , K.H.F. ２ or a mixture thereof.

5. 5. The process of any one of claims 1 to 4, wherein the monocarboxylic acid is methanoic acid, ethanoic acid, propanoic acid, or a mixture thereof.

6. The concentration in the pickling solution is Mixture of inorganic acids: 1-5 mol / l; MHF ２ is 10 to 60 g / l, Monocarboxylic acids: 50 to 300 g / l The process according to any one of claims 1 to 5, wherein

7. The process of any one of claims 1 to 6, wherein the contacting is carried out at 20 to 50°C.

8. The process of any one of claims 1 to 7, wherein the contacting is carried out for 3 to 15 minutes.

9. The process of any one of claims 1 to 8, wherein one or more rinsing steps are used.

10. The process of any one of claims 1 to 9, followed by a step involving a catalyst.

11. 11. The process of claim 10 followed by an electroless nickel plating step.

12. a mixture of two or more inorganic acids; MHF ２ (wherein M is an alkali ion or an ammonium ion), Monocarboxylic acids having 1 to 5 carbon atoms 1. A pickling solution for polyamides comprising:

13. 13. The pickling solution of claim 12, further comprising an organic solvent having 1 to 5 carbon atoms.

14. The concentration in the pickling solution is Mixture of inorganic acids: 1-5 mol / l; MHF ２ is 10 to 60 g / l, Monocarboxylic acids: 50 to 300 g / l 14. The pickling solution according to claim 12 or claim 13, wherein

15. The pickling solution according to any one of claims 12 to 14, wherein the inorganic acid is selected from the group consisting of hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid.

16. The pickling solution according to any one of claims 12 to 14, wherein the inorganic acid comprises hydrochloric acid and phosphoric acid.

17. Use of the pickling solution according to any one of claims 12 to 16 for pickling polyamides.

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