DE19957325A1 - Coating composition for the production of an abrasion-corrosion and corrosion-resistant metal coatings comprises a (semi)metal alkoxide,an organosilane and a sulpur-containing organosilane. - Google Patents

Abstract

A coating composition , for the production of an abrasion resistant and corrosion resistant coating for metal, comprises 20-90 mol. % of at least one metal- or semi-metal alkoxide ,10-80 mol. % of a least one organosilane and 0.05-10 mol. % of at least one suflur containing organosilane. A coating composition (I), for the production of an abrasion resistant and corrosion resistant coating for metal, comprises (A) 20-90 mol. % of at least one metal- or semi-metal alkoxide of formula (1) and corresponding hydrolysis and condensation products (B) 10-80 mol. % of a least one organosilane of formula (2) and corresponding hydrolysis and condensation products and (C) 0.05-10 mol. % of at least one suflur containing organosilane of formula (3) and corresponding hydrolysis and condensation products. M(OR<1>)n (1) R<2>aSi(OR<3>)4-a (2) ((R<4>O)3-b(R<5>)bSi(CH2)c)2Sd (3) M = B, Al, Si, Ti, Zr; R<1>,R<3>,R<4> = 1-10C alkyl, aryl, acyl, alkoxyalkyl; n = 3-4; R<2> = 1-20C alkyl; a = 1-3; R<5> = 1-10C alkyl, aryl; b = 0-2; c = 1-8; and d = 1-12 An Independent claim is included for a process for the production of a protective layer on a metal surface by application and drying of the composition (I).

Description

The invention relates to a composition of a coating solution to create an abrasion-resistant protection layer against corrosion on metals, especially non-ferrous Metals, as well as their application.

Various methods of surface treatment have been established to protect metallic materials from corrosion. In addition to the coating of the metal with protective paints, the electrolytic deposition of base metals such as aluminum, titanium, magnesium (“anodization”), chromating and phosphating are used in particular. In practice, however, these methods have disadvantages:
Anodization requires a high energy input and phosphating often does not provide adequate corrosion protection without a further process step. Chromating is problematic from an ecological point of view due to the use of toxic and carcinogenic chromium (VI) compounds, and for this reason will soon be due to stricter laws be pushed out of the application.

As an alternative to the three methods discussed, polymer-based coatings have therefore prevailed as corrosion protection, which do not chemically change the metal, but separate it from its surroundings as well as possible. As such, polysiloxanes have found widespread use because they have a number of advantageous characteristics compared to conventional organic polymers:

• 1. Because of their higher degree of crosslinking, polysiloxanes form particularly dense networks which have a very good barrier action against substances which cause corrosion, such as water, oxygen, SO ₂ , etc.
• 2. Due to the higher mechanical compared to organic polymers Hardness and stability cause mechanical influences less easy to injure the protective layer on which the Cor rosion can start.
• 3. The necessary layer thicknesses are considerably less than with organic systems, whereby the dimensional accuracy and the optical appearance of components can be obtained and Deformations of the substrate lead less to the formation of cracks.
• 4. The decomposition temperature is significantly higher than that of most organic polymers.
• 5. The modification of polysiloxanes with organic groups Allows the coating to become hydrophobic, which means that Permeation of water through the layer further complicated becomes.

Some base metals and metal alloys such as B. iron, Aluminum, magnesium, zinc, steel, form on their air Surface of an oxide layer that the covalent attachment of Polysiloxane layers over metal-oxygen-silicon bonds enables and thus sufficient adhesion of the coating guaranteed on the untreated metal. In the opposite other metals and alloys such as B. Gold, silver, chrome, nickel, brass, none at all or none at all Linking siloxanes suitable oxide layer, so often insufficient wetting or adhesion by a polysi loxane layer can be achieved.

One solution to this problem is to use orga non-functionalized silanes with hydrolyzable groups, which on the one hand has a suitable functional group with the Metal surface can interact and on the other hand by means of Silanol groups covalently integrated into the siloxane matrix become. Such reagents can be used both as "primers" treatment of the surface to be coated can be used  as well as an adhesion-promoting component of the coating medium be added. As functional groups to begin with The surface of precious metals is particularly suitable basic groups with chemically "soft" elements as Le wis base. Therefore, as an improver Thiol-functionalized monomers, especially hydrolyzable ones 3-Mercaptopropylsilane for protective metal layers on polysilox on-basis, established. Such connections are also made to bind organic polymers to the surface and noble metals because the siloxane group with the Oxide layer and the thiol group with functional groups of Polymers connects.

A major disadvantage when using this connection The reason for this is that it smells bad during processing Develop appropriate and harmful vapors. As Al alternatives to the thiols are disclosed in a published patent application (DE 28 38 495 A1) on coating solutions for silver and gold Silanolylalkyl-functionalized methyldithioethers or car boxylatoethylthioether described. These connections will be but in contrast to mercaptopropylsilanes not in large-scale African scale and are therefore uneconomical Lich and for an application of corrosion protection in large Amounts not suitable. Bis (silylorgano) sulfides, however, were so far only in adhesives for polymers on precious metal surfaces Chen and as an adhesion promoter in silica-reinforced chew used shoes.

The object of the invention is an improved coating composition with the positive properties mentioned of polysiloxane coatings, in particular especially without the use of malodorous and toxic Mer captosilanes or expensive alkyl (silyl-organyl) thioethers Production of layers with good adhesion to the various most metal surfaces, u. a. also on nickel, silver and Gold enables.  

This task is accomplished with a coating composition solved the features of claim 1. Advantageous execution Forms and uses of the invention result from the dependent claims.

The invention is based in particular on the use of Bis (silyl-organo) sulfide as an adhesion promoter between metal surface and polysiloxane.

Coating solutions according to the invention are prepared by hydrolysis and partial condensation in an organic solvent

• A) 20-90 mol% of one or a mixture of several metal or semimetal alkoxides of the general formula M (OR ¹ ) _n (M = B, Al, Si, Ti, Zr; R ¹ = alkyl C ₁ -C ₁₀ , aryl , Acyl, alkoxyalkyl), and hydrolysis and condensation products thereof,
• B) 10-80 mol% of one or a mixture of several organosilanes of the general formula R ² _a Si (OR ³ ) _4-a (R ² = alkyl C ₁ -C ₂₀ , a = 1-3, R ³ = alkyl C ₁ -C ₁₀ , aryl, acyl, alkoxyalkyl), and hydrolysis and condensation products thereof,
• C) 0.05-10 mol% of one or more sulfur-containing organodisilanes of the general formula [(R ⁴ O) _3-b (R ⁵ ) _b Si (CH ₂ ) _c ] ₂ S _d (R ⁴ = alkyl C ₁ -C ₁₀ , acyl, alkoxyalkyl, aryl; R ⁵ = alkyl C ₁ -C ₁₀ , aryl; b = 0-2; c = 1-8; d = 1-12), and hydrolysis and condensation products thereof,
• D) 0-3 mol% of one or more organosilanes with a fluorine-containing side chain, and hydrolysis and condensation products thereof,
  and mixed condensation products of components A) to D) in the given ratios,
• E) 0-10 mol% of a Re soluble in the solvent used detergent.

All solvents can be used as solvents, mixed with water and the starting compounds used  are cash. Preferred are those that do not have an extremely high ho hen boiling point that are non-toxic or carcinogenic are, which have good film-forming properties and in industrial scale can be offered inexpensively. The This profile of requirements is best met by ketones and alcohol len, especially acetone, butanone, ethanol, n-propanol, iso-propanol and n-butanol and their mixtures fulfilled.

For hydrolysis, water is at least semi-stoichiometric gene on hydrolyzable groups, but preferably stoichiome added tri-stoichiometrically to achieve a complete to ensure ge hydrolysis.

All can be used as catalysts for hydrolysis and condensation common acids and bases soluble in the respective system the formation of corrosion is preferred protective layers but acid catalyzed, because of acid catalyze compact, non-porous materials can be obtained. In particular strongly dissociating, non-oxidizing acids prefers that favor the formation of stable brine. Tetraal are preferred as metal or semimetal alkoxides koxysilanes and especially tetraethyl orthosilicate ("TEOS") used. The other alkoxides described are suitable for in mixtures with silanes properties of the resulting Ma terials such as adhesion behavior, polarity, degree of cross-linking, Temperature stability, flexibility, etc. to vary.

The organylsilanes used are preferably alkenyl, phenyl or alkyl silanes, especially alkyl silanes, which have a hydropho effect the coating and thus the wetting of non-polar Favor surfaces and permeation of water through minimize the layer. When coating polar surfaces However, it can be advantageous to use organylsilanes with polar functional groups in the organic part to Surface adhesion, cross-linking and processing temperature to optimize. Examples of such polar groups are  Epoxy, amino, aminoalkylamino, methacrylic, acrylic, isocya nato, cyanato, carboxylato and chloro groups.

The ratio between alkoxides (A) and organylsilanes (B) determines the degree of crosslinking of the resulting material and hence its drying behavior and flexibility. To this Way, the flexibility of coating that of the Substrates are adjusted.

The bis (silyl organo) sulfides can the reaction mixture can be added at the start of hydrolysis, but it is advantageous to add them only after the hydrolysis and Condensation of components A) and B) already largely abge is running (preferably at room temperature after at least 3 days gen), so that the adhesion-promoting sulfur groups only on the surface (and not the volume) of the sol parti formed kel are present. In this way, optimal use of the Adhesion promoter guaranteed.

Since on the one hand the rate of corrosion in coated metals depends on the permeation rate of attacking media (such as oxygen, water, SO ₂ , etc.) through the protective layer and on the other hand the first step of the permeation process is the adsorption of molecules on the coating surface, this can Corrosion behavior can be further improved by anti-adhesive treatment of the protective layer. In addition, an anti-adhesive surface leads to reduced adhesion of undesired deposits, which effectively prevents premature wear of the layer due to abrasion by dirt particles or frequent mechanical cleaning.

Particularly suitable additives for reducing the surface energy and thus to achieve an anti-adhesive effect are molecules with perfluorinated organic groups. In particular hydrolyzable silanes with fluorinated ones are particularly suitable  Side chains to polysiloxane materials with anti-adhesive Equip surfaces. The coating can optionally be added composition of this invention therefore also small amounts of Contain silyl-functionalized organofluorine compounds ten.

For residues of oxidation diffusing through the layer reduce before they arrive at the metal surface men, it may be advantageous to add the coating solution Lich a reducing agent soluble in the solvent used clog. Compounds that are known as corrosion inhibiting Re have proven means of production, z. B. thiourea and its derivatives, alkylamines, nitrites, sulfoxides, etc.

In contrast to the malodorous and unhealthy Mercaptoorganylsilanen have this here for the first time as a detention agents used in a corrosion protection coating Bis (silylorgano) sulfides have a significantly lower vapor pressure, a weaker smell and a significantly lower To xicity [e.g. B. LD50 (oral rat) = 16.4 g / kg for Bis (3-triethoxysilylpropyl) tetrasulfide (40372-72-3) versus LD50 (oral rat) = 2.38 g / kg for mercaptopropyltrimethoxysilane (4420-74-0)]. As a result, the hazard potential for the People decreased significantly.

Bis (3-triethoxysilylpropyl) tetrasulfide (40372-72-3, Handelsna me Degussa "Si69®") is a large-scale production Standard product and as such readily available and cost inexpensive to purchase, resulting in its use place the mentioned mercaptopropylsilane no host result in economic disadvantages. The adhesion-improving effect occurs with relatively small proportions Bis (silylalkyl) sulfide, so that the proportion of adhesion promoter lers the total cost of the coating is small.  

With the coating solution described, thin, transparent, flexible, mechanically resistant, corrosion resistant protective layers on various metals and Metal alloys (or metallized solid surfaces) realize. The coating can be applied in different ways Techniques such as diving, spraying, knife coating, flooding, etc. are successful The protective layers and their manufacture are also Subject of the invention.

Embodiments example 1

In an Erlenmeyer flask (300 ml), 200 ml of isopropanol, 40 ml tetraethyl orthosilicate ("TEOS", 179.1 mmol), 10 ml Iso butyltrimethoxysilane ("IBTMO", 52.3 mmol), 12.5 ml distill t water and 12.5 ml 0.1 N trifluoroacetic acid (1.25 mmol) mixed and stirred for three hours at room temperature. After three days, 3 ml of egg are added to 60 ml of the brine formed solution of 10% by volume bis (triethoxysilylpropyl) tetrasulfide ("Si69", 0.6 mmol) in acetone was added and the Mi stirred for an hour. After one day of storage at room temperature, the solution is ready to use.

Example 2

Analogous to example 1, but hydrolyzed with 10 ml of distilled Water and 10 ml of 0.1 N ortho-phosphoric acid.

Example 3

Analogously to Example 1, in addition to 60 ml of the formed Soles with 3 ml of a solution of 10% by volume Bis (triethoxysilylpropyl) tetrasulfide ("Si69", 0.6 mmol) in Acetone 0.15 ml of heptafluorobutyramidopropyltriethoxysilane added give. After one day of storage at room temperature, the sol solution ready for use.  

Examples 4-11

Small components made of various metal alloys were immersed in the solution from Example 1, then air-dried for 10 minutes and then cured at 130 ° C. for 25 minutes. The metal alloys were:
4) brass (CuZn39Pb)
5) Brass (CuZn), nickel-plated
6) aluminum (AlCuBiPb)
7) aluminum (AlCuMgPb)
8) steel (9SMnPb)
9) Steel (9SMnPb), galvanized and blue chromated
10) Die-cast zinc (GD-ZnAl4Cu1)
11) Die-cast zinc (GD-ZnAl4Cu1), galvanized and blue chromated.

Good wetting and adhesion were achieved on all parts. All metal parts coated in this way were subjected to the following corrosion tests:

• A) Warm-cold aging (120 ° C / -20 ° C)
• B) Moisture change climate test (DIN 50017)
• C) Kasternich test (DIN 50018)
• D) Salt spray test (DIN 50021).

The test specimens (6-11) showed no change after 50 cycles of test A) and no signs of corrosion after every 72 Hours of tests B, C and D.

Examples 12-19

The small components from the metal alloys mentioned under 4) -11) were immersed in the solution from Example 3, then air-dried for 10 minutes and then cured at 130 ° C. for 25 minutes:
12) brass (CuZn39Pb)
13) Brass (CuZn), nickel-plated
14) aluminum (AlCuBiPb)
15) aluminum (AlCuMgPb)
16) steel (9SMnPb)
17) Steel (9SMnPb), galvanized and blue chromated
18) Zinc die casting (GD-ZnAl4Cu1)
19) Die-cast zinc (GD-ZnAl4Cu1), galvanized and blue chromated.

The surface energy of the components was reduced by the coating by 2-12 mN / m, in detail:
12) from 44 to 32 mN / m, 13) from 38 to 36 mN / m, 14) from 43 to 37 mN / m, 15) from 45 to 36 mN / m, 16) from 45 to 36 mN / m, 17) from 44 to 32 mN / m, 18) from 45 to 35 mN / m, 19) from 41 to 32 mN / m.

Example 20

A gold-coated polycarbonate plate was in solution dipped from Example 2, then air-dried for 5 minutes net and then cured for 30 minutes at 120 ° C. It became a hard, transparent layer with a grid Get cut liability of 100%.

Example 21

A silver-coated polyester film became in solution dipped from Example 2, then air-dried for 5 minutes net and then cured for 30 minutes at 120 ° C. It became a hard, transparent layer with a grid Get cut liability of 100%.

Example 22

Solution from Example 2 was on polyethylene terephthalate film cast (wet layer thickness 22 µm), fixed at 90 ° C and 10 mi grooves hardened at 130 ° C. It became transparent Received layer. The surface gloss (20 °) of this film went after 100 cycles of the Taber Abraser test (2.5 N, CS10, DIN 52347) 5.4% of the initial value, compared to 81.0% loss of gloss for uncoated polyethylene terephthalate.

Claims (13)

1. Coating composition for producing an abrasion-resistant protective layer against corrosion on metals, characterized by a mixture with the following substance ratios:

• A) 20-90 mol% of one or a mixture of several metal or semimetal alkoxides of the general formula M (OR ¹ ) _n (M = B, Al, Si, Ti, Zr; R ¹ = alkyl C ₁ -C ₁₀ , aryl , Acyl, alkoxyalkyl, n = 3-4), and hydrolysis and condensation products thereof,
• B) 10-80 mol% of one or a mixture of several organosilanes of the general formula R ² _a Si (OR ³ ) _4-a (R ² = alkyl C ₁ -C ₂₀ , a = 1-3, R ³ = alkyl C ₁ -C ₁₀ , aryl, acyl, alkoxyalkyl), and hydrolysis and condensation products thereof, and
• C) 0.05-10 mol% of one or more sulfur-containing organodisilanes of the general formula [(R ⁴ O) _3-b (R ⁵ ) _b Si (CH ₂ ) _c ] ₂ S _d R ⁴ = Alkyl C ₁ -C ₁₀ , acyl, alkoxyalkyl, aryl; R ⁵ = alkyl C ₁ -C ₁₀ , aryl; b = 0-2; c = 1-8; d = 1-12), and hydrolysis and condensation products thereof, and
  mixed condensation products of components A) to C).

2. Coating composition according to claim 1, the additional Lich as component D) up to 3 mol% of one or more Or ganosilane with fluorine-containing side chain, as well as hydrolysis and Condensation products thereof. 3. Coating composition according to at least one of the An claims 1 or 2, which additionally as component E) up to 10 mol% a reduction soluble in the solvent used means contains.   4. Coating composition according to at least one of the An claims 1 to 3, in which as organosilane of component B) Methyl, ethyl, propyl, butyl, isobutyl, hexyl and / or Octyl trialkoxysilane is included. 5. Coating composition according to at least one of the An Proverbs 1 or 4, in which the compo as bis (silylalkyl) sulfide nente C) bis (3-triethoxysilylpropyl) tetrasulfide (40372-72-3) is included. 6. Coating composition according to at least one of the An sayings 1 to 5, in the case of metal or semimetal alkoxide component A) is at least partially a silicon alcoholate is included. 7. Coating composition according to at least one of the An Proverbs 2 to 6, in the case of organosilane with fluorine Side chain of component D) a fluoroalkylsilane, perfluorpo contain lyersilane or a (perfluoroalkylamido) alkylsilane is. 8. Coating composition according to at least one of the An Proverbs 1 to 7, the solvent acetone, butanone, metha nol, ethanol, propanol, isopropanol, butanol and / or mixture contains from these. 9. Coating composition according to at least one of the An Proverbs 1 to 8, which is an aqueous dilute acid for catalysis which contains hydrolysis and condensation. 10. Method of making a protective layer on a Metal surface by applying and drying a coating  tion composition according to at least one of claims 1 to 9 on the metal surface. 11. The method of claim 10, wherein the applied Be coating composition at a temperature above 90 ° C. is hardened. 12. Use of a coating composition according to at least least one of claims 1 to 9 for the production of a Protective layer on a metal surface. 13. Use of a bis (silyl organo) sulfide as an adhesion promoter between a metallic solid surface and poly siloxane.