DE102011111757A1 - Sealant and its use and sealed metallic substrate - Google Patents

Abstract

The invention relates to a sealant for metallic substrates, which contains an aqueous dispersion which consists of an oligosiloxane of a glycidoxysilane or an epoxyalkylsilane or an epoxycycloalkylsilane and at least one colloidal silica and optionally further additives and water. Likewise, the invention relates to a metallic substrate sealed therewith. The sealant according to the invention is used as corrosion protection of metallic substrates.

Description

The invention relates to a sealant for metallic substrates, which contains an aqueous dispersion which consists of an oligosiloxane of a glycidoxysilane or an epoxyalkylsilane or an epoxycycloalkylsilane and at least one colloidal silica and optionally further additives and water. Likewise, the invention relates to a metallic substrate sealed therewith. The sealant according to the invention is used as corrosion protection of metallic substrates.

Galvanizing has long been used for various components that are to be protected against corrosion. It was a long time, the galvanized parts u. a. Chromated with chromium-VI-containing solutions, as this significantly increased the corrosion protection. Due to the carcinogenic effect and the stricter environmental protection guidelines, chromium (VI) is now dispensed with. Instead, chromium (III) -containing solutions are used in conjunction with sealants to increase corrosion protection.

Such sealants for post-treatment of zinc and zinc alloy layers are known from DE 41 38 218 which are based on an organic solvent, titanic acid esters and / or titanium chelates and organofunctional polysiloxanes.

The disadvantage of this type of formulation are on the one hand the sometimes poor corrosion protection and on the other hand the presence of organic solvents, which are disadvantageous due to environmental and occupational safety.

Furthermore, the describes JP 5250940 a sealant containing from 0.1 to 30 water glass or sodium silicate and an organofunctional silane coupling agent in an amount of from 0.1 to 10 It is also described in the prior art that such formulations can cause film breakage in the coating of small parts.

The EP 1 070 156 B1 describes an aqueous sealant consisting of a monomeric silane derivative, 3-glycidyloxypropyltrialkoxysilane, e.g. For example, 3-glycidoxypropyltrimethoxysilane or its hydrolysis product and colloidal silica and / or colloidal silicate in the ratio silicate to silane 1: 3 to 3: 1. This formulation has the disadvantage that the corrosion protection, especially on galvanized and passivated cast iron, is not sufficient for heavily stressed components and white corrosion occurs after about 312 hours.

However, it is desirable to achieve the highest possible corrosion protection, especially for components subject to heavy wear, so that the function of the coated and sealed components is not impaired. In addition, the corrosion protection should not be drastically influenced even after a subsequent heat treatment of the sealed components. Decisive for this anti-corrosive property is the formation of a compact, adherent and dense sealing film which dries quickly, without the formulation contains volatile or only slightly volatile alcohols. Furthermore, by hydrolysis using 3-glycidoxypropyltrimethoxysilane in aqueous solution, methanol is released, which is poisonous and volatile.

Based on this, it was an object of the present invention to provide a chromium-free sealer with high corrosion protection, which also offers good storage and long-term stability.

This object is achieved by the sealing means having the features of claim 1 and the sealed metallic substrate having the features of claim 12. In claim 14, a use according to the invention is given. The other dependent claims show advantageous developments.

• a) mindestens einem Oligosiloxan von mindestens einem Glycidoxyalkylsilan und/oder mindestens einem Epoxyalkylsilan und/oder mindestens einem Epoxycycloalkylsilan,
• b) mindestens einer kolloidalen Kieselsäure sowie
• c) Wasser.

According to the invention, there is provided a metallic substrate sealant comprising an aqueous dispersion consisting of the following components:

• a) at least one oligosiloxane of at least one glycidoxyalkylsilane and / or at least one epoxyalkylsilane and / or at least one epoxycycloalkylsilane,
• b) at least one colloidal silica and
• c) water.

It has surprisingly been found according to the invention that a compact, adherent and dense film can be formed on substrates with this sealant, which also after heat treatment of the sealed parts offers a very good corrosion protection. Among other things, the adhesive strength of the layers is significantly influenced by the molar amount of the epoxy functions of the silane derivative used. The more epoxy groups are available in a molecule, the better the adhesion on the component to be sealed and the higher the corrosion protection.

Furthermore, the sealant according to the invention has a very good storage and long-term stability.

The sealant of the invention should contain little or no methanol or other alcohols formed by hydrolysis.

mit
X unabhängig voneinander

mit
R unabhängig voneinander H oder C₁-C₆-Alkyl,
m unabhängig voneinander 0 bis 6, r unabhängig voneinander 0 bis 6 und p = 2 bis 6.Preferably, the glycidoxyalkylsilane and / or the epoxyalkylsilane and / or the epoxycycloalkylsilane has the general formula I:

With
X independently

With
R independently of one another are H or C ₁ -C ₆ -alkyl,
m are independently 0 to 6, r are independently 0 to 6 and p = 2 to 6.

Here, the units X may independently of each other and within the multiple of p in regular or irregular sequence mean the indicated functions, and m may be set independently for each monomer unit in the specified range.

The glycidoxyalkylsilane is particularly preferably selected from the group gamma-glycidoxypropyltrimethoxysilane, gamma-glycidoxypropyltriethoxysilane, gamma-glycidoxypropylmethyldiethoxysilane and combinations thereof and / or the epoxyalkylsilane selected from the group consisting of terminal and non-terminal epoxyalkylsilanes and / or the epoxycycloalkylsilane selected from the group consisting from 4,5-epoxypentyltrimethoxysilane, 5,6-epoxyhexyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, and combinations thereof.

The at least one glycidoxysilane and / or the at least one epoxyalkylsilane and / or the at least one Epoxycycloalkylsilan is preferably in an amount of 0.5 to 6.5 wt .-%, preferably from 1 to 6 wt .-% and particularly preferably of 2 to 5 wt .-%, contained.

Preferably, the dispersion is substantially free of monomers of the at least one glycidoxysilane and / or the at least one epoxyalkylsilane and / or the at least one epoxycycloalkylsilane.

The at least one colloidal silica is preferably selected from the group of silica sols and gels, polysilicate sols and gels, and mixtures thereof.

Colloidal silicas in the form of sols or gels, especially sols, are commercially available, such as under the trade names Ludox or Levasil.

These colloidal silicas are salts of silicas, preferably lithium salts, which are also known under the name of lithium polysilicate. In these colloidal silica lithium salts, the molar ratio of SiO ₂ / Li ₂ O is suitably in the range of 4.0 to 5.5, and preferably in the range of 4.6 to 5.0.

The use of such lithium polysilicate sols gives a pH of 9 to 11 of the sealant. Here, the colloidal substance can be used for pH adjustment. The use of colloidal cationic SiO ₂ sets an acidic pH. By specific mixing of lithium polysilicate and / or anionic polysilicates and / or cationic SiO ₂ , any intermediate pH can be set.

The at least one colloidal silica is preferably present in an amount of from 5 to 20% by weight, preferably from 8 to 15% by weight and more preferably from 9 to 13% by weight.

It is further preferred that the sealant contains at least one further co-polymerisable and / or co-hydrolyzable silane, in particular selected from the group vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, vinyltriisopropoxysilane, octyltriethoxysilane, propyltriethoxysilane, propyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, polyalkylene oxide-trimethoxysilane, Methacrylic trimethoxysilane, methacryltriethoxysilane, methacrylic triisopropoxysilane, or mixtures thereof.

It is also possible that the sealant contains other additives or additives. These are preferably selected from the group of corrosion inhibitors, in particular from the class of Talgalkylaminoethoxylate and Oleoylsarcosinsäuren which improve the film formation, the profile on the component surface and the corrosion protection.

Suitable corrosion inhibitors are organic compounds having at least one amine group, an ether group, a hydroxyl group, a carboxyl group, an ester or a salt thereof or a nitrogen-containing heterocyclic group. Examples thus include fatty amines such as oleylamines, hydroxyamines (eg, isopropanolamine), condensates of hydroxyamines with fatty acids (eg, products of tallow oil fatty acids with diethanolamine or with N-hydroxyethylethylenediamine), carboxylic acids, esters and salts thereof (especially as alkyl-substituted succinic acids , Esters and amines or ammonium salts, eg mono- or diesters of succinic acid and propylene oxide) as well as compounds with multiple functionalities. An example of the latter are sarcosine derivatives with amide and acid functionality. Substances containing nitrogen-containing heterocycles include triazole compounds such as tolyltriazole and triazine salts. Other corrosion inhibitors include ethoxylated phenols as well as various oxygenated materials prepared by the partial oxidation of waxes or oils, particularly paraffin oils, waxes and petroleum. Other corrosion inhibitors are organic boron compounds, such as. B. long-chain alkenyl amide borates. Likewise, corrosion inhibitors which can be used are alkali metal sulfonates, such as sodium sulfonate and sodium alkylbenzenesulfonate.

Other possible corrosion inhibitors are esters of hydroxy acids, such as tartaric acid, citric acid, maleic acid, lactic acid, oxalic acid, glycolic acid, hydroxypropionic acid and hydroxyglutaric acid. Examples of these are esters, in particular tartaric acid esters of C ₆ - to C ₁₂ - or C ₆ - to C ₁₀ - or C ₈ - to C ₁₀ -alcohols, eg. As isotridecyl tartrate, 2-ethylhexyl tartrate and mixtures of linear C ₁₂ - to C ₁₄ -alcohols or branched C ₁₃ -alcohols. Amides and bimides of these substances are equally applicable.

The sealant preferably has a pH in the range of 8.5 to 12. Particularly preferred is a pH in the range of 9 to 11.

• a) 3 bis 5 Gew.-% des mindestens einen Oligosiloxans von mindestens einem Glycidoxysilan und/oder des mindestens einen Epoxyalkylsilans und/oder des mindestens einen Epoxycycloalkylsilans,
• b) 6 bis 12 Gew.-% der mindestens einen Kieselsäure,
• c) 0 bis 1 Gew.-% Talgalkylaminoethoxylate, sowie Oleoylsarcosinsäure
• d) 82 bis 91 Gew.-% Wasser.

The sealant preferably has the following composition:

• a) 3 to 5% by weight of the at least one oligosiloxane of at least one glycidoxysilane and / or the at least one epoxyalkylsilane and / or the at least one epoxycycloalkylsilane,
• b) 6 to 12% by weight of the at least one silica,
• c) 0 to 1 wt .-% Talgalkylaminoethoxylate, and Oleoylsarcosinsäure
• d) 82 to 91% by weight of water.

Also provided in accordance with the present invention is a sealed metallic substrate that has been treated with the sealant described above.

The substrate is preferably selected from the group aluminum, zinc, iron and its alloys.

The sealant of the invention is used as a corrosion protection coating of metallic substrates.

The sealant according to the invention has the advantage that it has no or only a very small proportion of alcohols, which is due to the hydrolysis of the corresponding functionalities of the oligosiloxanes. Even with a further hydrolytic curing, the release of alcohol is almost completely suppressed due to the very low number of alkoxy groups. This is a significant advantage in view of the monomers used in the prior art.

The sealant according to the invention further distinguishes the high adhesive strength of the layers, which is influenced by the molar amount of the epoxy functionalities or glycidoxy functionalities of the oligosiloxanes used. The higher the number of epoxy or glycidoxy groups in a molecule, the better the adhesion to the substrate to be sealed, which increases the corrosion protection.

The sealants of the invention are stable for months and show a high tolerance to the working temperature, so such sealants at temperatures of 10 to 90 ° C, preferably at 20 to 30 ° C, operated.

Reference to the following examples and figures, the subject invention is to be explained in more detail, without wishing to limit this to the embodiments shown here.

1 Figure 9 shows a ²⁹ Si NMR spectrum of a monomeric silane as in the prior art ( EP 1 070 156 B1 ) known sealant is used.

2 Figure 9 shows a ²⁹ Si NMR spectrum of an oligosiloxane as used in the sealant of the present invention.

In 1 Figure imgb0005 Figure imgb0005 Figure imgb0005 Figure imgb0005 Figure imgb0005 A ²⁹ Si NMR spectrum of 3-glycidyloxypropyltrimethoxysilane taken with the Bruker Avance 400 MHz NMR Spectrometer (25 ° C) spectrometer is shown. The measurement was carried out directly with the silane without addition of a solvent. The silane was a clear, colorless and oily liquid.

The ²⁹ Si NMR spectrum shows a sharp peak at δ 42.79 ppm attributable to 3-glycidyloxy-propyltrimethoxysilane.

In 2 a ²⁹ Si NMR spectrum of the inventively used oligosiloxane MP 200 is shown, which was recorded with the spectrometer Bruker Avance 400 MHz NMR spectrometer (25 ° C). The oligosiloxane was a clear, colorless and viscous liquid. Therefore, the oligosiloxane was diluted with methanol-d ₄ (CD ₃ OD) in the ratio 3: 1 (v / v).

The ²⁹ SI NMR spectrum shows two major peaks at δ 51.25 ppm and δ 60.25 ppm attributable to the oligosiloxane.

Furthermore, two broad signals can be recognized at δ 59.05 ppm and δ 69.91 ppm, which indicate the presence of branched-chain polysiloxanes.

Similarly, a sharp peak at δ is 42.79 ppm attributable to 3-glycidyloxy-propyltrimethoxysilane. This shows that the oligosiloxane has only small residues of the monomer.

example 1

Compositions according to the invention

The following compositions are embodiments according to the present invention.

Composition 1 Hydrolyzed CoatOSil MP 200 20wt .-% lithium polysilicate 40% by weight water 40% by weight Tallow alkyl amino ethoxylates and / or Oleoylsarcosinsäure 0-1% by weight

Composition 2 Hydrolyzed CoatOSil MP 200 10% by weight lithium polysilicate 50% by weight water 40% by weight Tallow alkyl amino ethoxylates and / or Oleoylsarcosinsäure 0-1% by weight

Composition 3 Hydrolyzed CoatOSil NP 200 8% by weight lithium polysilicate 45% by weight water 47% by weight Tallow alkylaminoethaxylates and / or Oleoylsarcosinsäure 0-1% by weight

Composition 4 Hydrolyzed 3-glycidyloxypropyl trimethoxysilane 5% by weight lithium polysilicate 45% by weight water 50% by weight Tallow alkyl amino ethoxylates and / or Oleoylsarcosinsäure 0-1% by weight

Example 2

Preparation of the sealant

The sealant consists of several raw materials which in part have to go through a certain process during the production process.

The Silan Oligomer MP 200 must be brought into a water-soluble form before the actual formulation. For this purpose, for. B. 50 g MP 200 with stirring with 1 g of phosphoric acid 85% mixed. Thereafter, 49 g of water are added and stirred for about 3 h. It must be stirred until the solution is completely clear and a homogeneous mixture is achieved. Thereafter, the hydrolyzed MP 200 must be processed within 24 hours, as the system polymerizes completely over time. For further processing, the following procedure must be followed:
The required amounts of hydrolyzed MP 200 are slowly adjusted to pH 7.5 with stirring with 85% triethanolamine. This amount is then added with stirring to the required amount of lithium polysilicate and stirred until everything has completely dissolved each other. This solution will be referred to as solution 1 below.

Solution 2 is prepared by simply stirring together from the required amount of water and the possibly required amounts of excipients from the group Talgalkylaminoethoxylate and / or Oleoylsarcosinsäure.

Now solution 2 is slowly mixed with solution 1 with stirring. The resulting solution is the sealant.

The sealant is filtered to separate any resulting precipitated products. The sealant now has a solids content between 14 and 15% and a pH between 9 and 11.

Example 3

Procedure for the sealing of components with the sealant according to the invention

In Table 1, the individual process steps in the sealing of components with the corresponding process parameters are briefly listed.

This procedure is exemplary and must be adapted to the respective basic materials or system properties.

The indication of the concentration of the sealant refers to the solids used in the working container. The applicable concentrations are dependent on the conditions of use such. B. drum product or rack goods. Racks are preferably coated in the range of 3-9% solids. Drum product in the range 7-14 The higher solids content must be used here as drumware is usually dried in centrifuges where the sealant is spun off. In order to ensure adequate corrosion protection, it is therefore necessary to work with higher concentrations in order to retain enough sealant on the surface.

In certain cases, a temperature treatment of the finished sealed components is required. For this purpose, the finished components are again exposed in an oven for several hours (1-24 h) temperatures of 100-250 ° C.

Example 4

Comparison of oligosiloxane with monomeric silane derivative

In Table 2, the different properties of the oligosiloxane (MP 200) with the monomeric silane derivative (3-glycidoxypropyltrimethoxysilane) are listed by comparison. Table 2 3-Glycidoxypropyltrimethaxysilan MP 200 Methanol content ¹ 41% 22% Epoxy (meq / g) 4,145 4,785 Corrosion protection ² 312 h 480 h

The methanol content of 3-glycidoxypropyltrimethoxysilane was calculated from the molar ratios over the theoretical amount of methanol. The values for MP 200 (oligosiloxane) were determined after hydrolysis in water by gas chromatography (taken from Coat-O-Sil MP 200 Product characteristics).

The corrosion test after DIN EN ISO 9227 was performed on 8 μm acid-galvanized cast iron followed by thick-layer passivation, sealing and heat treatment (2 h / 150 ° C). The corrosion test with subsequent thick-film passivation and sealing was carried out according to Table 1.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4138218 [0003]
• JP 5250940 [0005]
• EP 1070156 B1 [0006, 0037]

Cited non-patent literature

• DIN EN ISO 9227 [0061]

Claims (15)

Sealant for metallic substrates containing an aqueous dispersion consisting of a) at least one oligosiloxane of at least one Glycidoxyalkylsilan and / or at least one epoxyalkylsilane and / or at least one Epoxycycloalkylsilan and b) at least one colloidal silica, c) water. Sealant according to claim 1, characterized in that the glycidoxyalkylsilane and / or the epoxyalkylsilane and / or the epoxycycloalkylsilane has the general formula I.

with X independently

with R independently of one another H or C ₁ -C ₆ -alkyl m independently of one another 0 to 6, r independently of one another 0 to 6 and p = 2 to 6. Sealant according to one of the preceding claims, characterized in that the at least one Glycidoxyalkylsilan is selected from the group γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldi-ethoxysilane and combinations thereof and / or the at least one cycloaliphatic epoxy-silane is selected from the group β- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) -ethyltriethoxysilane and combinations thereof. Sealant according to one of the preceding claims, characterized in that the at least one oligosiloxane of at least one glycidoxysilane and / or at least one epoxyalkylsilane and / or at least one Epoxycycloalkylsilan in an amount of 0.5 to 6.5 wt .-%, preferably from 1 to 6 wt .-% and particularly preferably from 2 to 5 wt .-% is contained. Sealant according to one of the preceding claims, characterized in that the dispersion is substantially free of monomers of the at least one glycidoxysilane and / or the at least one cycloaliphatic Epoxyalkylsilans and / or the at least one Epoxycycloalkylsilan. Sealant according to one of the preceding claims, characterized in that the at least one colloidal silicic acid is selected from the group of silica sols and gels, Polysilikatsole and gels, in particular Lithiumpolysilikatsol. Sealant according to one of the preceding claims, characterized in that the at least one colloidal silica in an amount of 5 to 20 wt .-%, preferably from 8 to 15 wt .-% and particularly preferably from 9 to 13 wt .-% is included , Sealant according to one of the preceding claims, characterized in that the sealant contains at least one further co-polymerizable and / or co-hydrolyzable silane, in particular selected from the group vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, vinyltriisopropoxysilane, octyltriethoxysilane, propyltriethoxysilane, propyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane , Polyalkylene oxide-trimethoxysilane, methacryl-trimethoxysilane, methacryltriethoxysilane, methacryltriisopropoxysilane or mixtures thereof. Sealant according to one of the preceding claims, characterized in that corrosion inhibitors, in particular from the class of Talgalkylaminoethoxylate, Oleoylsarcosinsäure are included as further additives or additives. Sealant according to one of the preceding claims, characterized in that the sealant has a pH in the range from 8.5 to 12, in particular from 9 to 11. Sealant according to one of the preceding claims, having the following composition: a) from 3 to 5% by weight of the at least one oligomer of at least one glycidoxysilane and / or at least one cycloaliphatic epoxysilane, b) from 6 to 12% by weight of at least one silica, c) 0 to 1 wt .-% of the corrosion inhibitor, and d) 82 to 91% by weight of water. A sealed metallic substrate treated with the sealant of any one of the preceding claims. Sealed substrate according to the preceding claim, characterized in that the substrate consists of aluminum, zinc, iron and their alloys. Use of the sealant according to one of claims 1 to 11 for coating metallic substrates. Use according to the preceding claim, characterized in that the substrate consists of aluminum, zinc, iron and its alloys.

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