Binder composition and its use

Abstract

To obtain a binder composition that is particularly suitable for coating metallic substrate surfaces, ensuring good adhesion of the coating to the substrate surface and improved corrosion protection, a binder composition comprising a water-based medium and a mixture of various alkoxysilanes is proposed, wherein the mixture includes: - at least one aminoalkoxysilane, - at least one vinylalkoxysilane and - at least one further alkoxysilane, selected from organofunctional water-soluble alkoxysilanes as well as water-insoluble alkoxysilanes, wherein the binder composition includes a proportion of an acid and the pH value of the binder composition is approximately 0 to approximately 3; wherein the alkoxysilanes are partially present in the form of silanols, wherein one or two of the residues of an alkoxysilane is / are replaced by a hydrogen atom; wherein furthermore a proportion of the silanols is converted to siloxanes, wherein the proportion of siloxanes leads to a solids content in the binder composition of approximately 32.5 wt.% or less.

Description

[0001] The invention relates to a binder composition and a method for coating a substrate surface using the binder composition according to the invention. The invention further relates to a substrate with a surface area coated with the binder composition according to the invention and a method for producing a material-bonded connection between a surface-coated substrate according to the invention and a layer based on liquid rubber.

[0002] Organopolysiloxane-containing compositions and their use for hydrophobizing the surfaces of mineral building materials are known from EP 0 716 127 A2 and EP 0 832 911 A1.

[0003] The object of the invention is to propose a binder composition which is particularly suitable for coating metallic substrate surfaces, so that good adhesion of the coating to the substrate surface and improved corrosion protection are achieved.

[0004] This problem is solved according to the invention with a binder composition according to claim 1, which comprises a water-based medium and a mixture of various alkoxysilanes as well as a proportion of an acid, wherein the pH value of the binder composition is approximately 0 to approximately 3.

[0005] The binder compositions according to the invention are particularly suitable for producing corrosion protection coatings on iron- or aluminum-based substrates. This corrosion protection is especially effective even under hot air exposure and also increases the oil resistance of the substrates.

[0006] In addition, such coatings produced from the binder compositions according to the invention can also have a so-called primer function, which allows the coated substrate to be coated with polymer materials, for example, acrylate ethylene rubber (AEM) or alkyl acrylate rubber (ACM), for example in the production of seals, and in particular also using sealing materials for so-called PEM (polymer electrolyte membrane) fuel cells. Such coatings according to the invention enable the bonding of sealing materials with improved adhesion to a metal component of the fuel cell. The vinyl groups of the vinyl-functionalized alkoxysilane are particularly advantageous in this respect.

[0007] Furthermore, the binder compositions according to the invention can be used for coating substrates and, in addition to corrosion protection, also form an adhesion base for elastomer coatings, in particular LSR (liquid silicon rubber) coatings.

[0008] The binder compositions according to the invention can in particular be designed to have a long shelf life, for example of 12 months or more.

[0009] Coatings made from the binder compositions according to the invention also exhibit very high resistance to aging.

[0010] The mixture of different alkoxysilanes of the binder composition according to the invention comprises at least one alkoxysilane of formula (I), at least one alkoxysilane of formula (II) and at least one further alkoxysilane of formulas (III.1), (III.2), (IV) and (V).

[0011] The alkoxysilanes of the binder composition according to the invention are partially present in the form of silanols, wherein one or two of the R groups of an alkoxysilane are replaced by a hydrogen atom.

[0012] Furthermore, a proportion of the silanols in the binder composition according to the invention are converted to siloxanes, the proportion of which leads to a solids content in the binder composition according to the invention of approximately 32.5 wt.% or less. The solids content represents the weight fraction of the binder composition obtained from a sample after drying at approximately 120 °C.

[0013] The proportion of the water-based medium in the binder composition according to the invention is preferably approximately 35 wt.% or more.

[0014] An alkoxysilane contained in the binder composition according to the invention is an aminoalkoxysilane of the following formula (I): R'HN(CH2) a' -R'' a'' -(CH2) a -Si(OR)3 Formula (I) where R represents a substituent which is individually selected from methyl, ethyl, propyl, butyl, pentyl and methoxyethyl; where independently a represents an integer value in the range of 0 to 5, a' an integer value from 0 to 5 and a'' an integer value of 0 or 1, where the sum of a+a'+a'' has a value of 1 or more; where R' represents a substituent selected from methyl, ethyl, propyl, phenyl, H and aminoalkyl, wherein the alkyl group of the substituent is aminoalkyl, methyl, ethyl, propyl or aminoalkyl; and where R'' represents a phenyl or phenylene substituent.

[0015] Preferred examples of aminoalkoxysilanes of formula (I) are 3-aminopropyltrimethoxysilane (AMMO, CAS No. 13822-56-5), 3-aminopropyltriethoxysilane (APTES / AMEO / APTS, CAS No. 919-30-2), N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (DAMO, CAS No. 1760-24-3), N-phenyl-3-aminopropyltrimethoxysilane (CAS No. 3068-76-6), diethylenetriaminepropyltrimethoxysilane (TRIAMO, CAS No. 35141-30-1), m-aminophenyltrimethoxysilane (CAS No. 33976-43-1), p-aminophenyltrimethoxysilane (CAS No. 33976-43-1), p-aminophenyltriethoxysilane (CAS No. 33976-43-1) and (Aminoethylaminomethyl)phenylethyl-trimethoxy-silane (CAS No. 74113-77-2).

[0016] The further alkoxysilane contained in the binder composition according to the invention is a vinylalkoxysilane of formula (II): CH2=CH(CH2) b -Si(OR)3 Formula (II) where the remainder R represents a substituent as defined in connection with formula (I); and where b represents an integer value in the range of 0 to 5.

[0017] Preferred examples of vinylalkoxysilanes of formula (II) are vinylalkyalkoxysilanes, vinyl-trimethoxysilane (VTMS / VTMO, CAS No. 2768-02-7), vinyl-triethoxysilane (VTES, CAS No. 78-08-0) and vinyl-tri(methoxyethoxy)silane (VTMES, CAS No. 1067-53-4).

[0018] The at least one further alkoxysilane(s) is / are selected from organofunctional water-soluble alkoxysilanes of formulas (III.1) and (III.2) as well as water-insoluble alkoxysilanes of formulas (IV) and (V), in which the residue R represents a substituent as defined in connection with formula (I): CH2OCHCH2O(CH2) c -Si(OR)3 Formula (III.1) where c represents an integer value in the range of 1 to 5; R1CH=CH-COO(CH2) d -Si(OR)3 Formula (III.2) where d represents an integer value in the range of 1 to 5 and R1 represents a substituent selected from H and methyl; CH3(CH2) e -Si(OR)3 Formula (IV) where e represents an integer value in the range of 0 to 5; and Si(OR)4 Formula (V).

[0019] Preferred examples of alkoxysilanes of formula (III.1) are glycidyloxyalkylalkoxysilanes, e.g. (3-glycidyloxypropyl)trimethoxysilane (GOPTMS / GLYMO, CAS No. 2530-83-8) and 3-glycidyloxypropyl triethoxysilane (CAS No. 2602-34-8).

[0020] Preferred examples of alkoxysilanes of formula (III.2) are methacryloxyalkylalkoxysilanes, e.g. 3-methacryloxypropyl-trimethoxysilane (CAS No. 2530-85-0) and 3-methacryloxypropyl-triethoxysilane (CAS No. 21142-29-0), and acryloxyalkylsilanes, e.g. 3-acryloxypropyl-trimethoxysilane (CAS No. 4369-14-6).

[0021] Preferred examples of alkoxysilanes of formula (IV) are alkylalkoxysilanes, in particular n-propyltrimethoxysilane (PTMS / PTMO, CAS No. 1067-25-0) and n-propyltriethoxysilane (PTES, CAS No. 2550-02-9).

[0022] Preferred examples of alkoxysilanes of formula (V) are tetramethoxysilane (CAS No. 681-84-5) and tetraethoxysilane (CAS No. 78-10-4).

[0023] In the binder composition according to the invention, the ratio of the molecular fraction of aminoalkoxysilane of formula (I) and the corresponding silanols, based on the sum of the fractions of the alkoxysilanes of formulas (II), (III.1), (III.2), (IV) and (V) and their silanols, is preferably in the range of approximately 0.5 to approximately 3, more preferably in the range of approximately 0.75 to approximately 1.

[0024] The pH value of the binder composition according to the invention, in the range of approximately 0 to approximately 3, is preferably adjusted using an organic acid, which is particularly selected from formic acid, acetic acid, and propionic acid, and mixtures thereof. The pH value of the binder composition according to the invention is preferably approximately 0.75 to approximately 2, more preferably approximately 0.75 to approximately 1.5, and particularly approximately 1. Preferably, the acid required to adjust the pH value of the binder composition according to the invention is first added to the water-based medium, and then the alkoxysilanes for the preparation of the binder composition according to the invention are added to the acidic water-based medium.

[0025] The present invention further relates to a method for producing a coating on the surface of a substrate. The method according to the invention comprises the steps (a) Providing the substrate with a surface area to be coated which has a chemical structure with OH groups; (b) Applying a binder composition according to the invention to the surface area of ​​the substrate to be coated; and (c) Drying and curing of the applied binder composition on the surface area of ​​the substrate, forming a chemical coupling of the OH groups of the surface area of ​​the substrate with the alkoxysilanes of the binder composition, whereby the alkoxysilanes are converted to polymeric alkoxysiloxanes.

[0026] Preferably, the binder composition according to the invention is subjected to a thermally initiated reaction, preferably in a temperature range of approximately 30 °C to approximately 40 °C, before application to the surface area of ​​the substrate to be coated, for at least partial further conversion of the contained silanols into corresponding siloxanes. This conversion is preferably carried out isothermally. Furthermore, this conversion is preferably limited such that the siloxane-based solids content in the resulting binder composition according to the invention is approximately 35 wt.% or less, and more preferably in the range of approximately 25 wt.% to approximately 32.5 wt.%.

[0027] The method according to the invention is particularly suitable for coating metallic substrates.

[0028] The present invention further relates to a substrate with a coated surface area obtained according to a previously described method according to the invention.

[0029] Preferably, the coating on the substrate according to the invention is designed as a corrosion protection coating and / or as a primer coating.

[0030] Finally, the present invention relates to a method for producing a material-bonded connection between a surface-coated substrate according to the invention and a liquid rubber-based layer. This method comprises the steps (a) Applying a liquid rubber-containing mass to a coating according to the invention on the surface of the substrate; and (b) Curing of the liquid rubber-containing mass forming a chemical bond between the liquid rubber and the polymeric alkoxysiloxanes of the coating of the substrate according to the invention, in particular a coating in the form of a corrosion protection coating or a primer coating.

[0031] These and other advantages of the present invention will be explained in more detail below with reference to the examples and the drawing.

[0032] They show in detail: Fig. 1A to 1D IR transmission spectroscopy curves for the identification of silane, silanol and siloxane compounds at different times before and after the combination of the components of the binder composition according to the invention; Fig. 2 Solid content of binder compositions according to the invention at different sample ages; Fig.3A to 3C corrosion test samples after different exposure times in a salt spray; Fig. 4 Schematic representation of the structure of a test specimen for testing the adhesion force or tensile strength of an elastomer-metal composite according to the invention; and Fig. 5 a schematic representation of a device for producing the test specimen of the Fig. 4. EXAMPLE OF EXECUTION Production of a binder composition according to the invention

[0033] First, a reaction vessel is placed in a cooling medium to dissipate the heat of reaction. An external heat source with a stirring function is used to ensure a homogeneous distribution of the reaction components in the reaction mixture at a controlled temperature within the reaction vessel. The temperature of the reaction mixture is continuously monitored and regulated to maintain a constant temperature between approximately 30 °C and 40 °C, preferably around 35 °C.

[0034] First, the proportion of the water-based medium, in the present example distilled water, of the binder composition according to the invention is added to the reaction vessel and then an acid is added to adjust the pH value of this water-based medium to a value in the range of approximately 0.75 to approximately 3, preferably approximately 1.

[0035] In the next step, the silanes of formulas (I) and (II) as well as (III.1), (III.2) and / or (IV) are provided as an alkoxysilane mixture. The proportions of the silanes of formula (IV) can each be individually, and in particular partially, replaced by proportions of a silane of formula (V), whereby the molar ratios of the silanes remain unchanged.

[0036] In the following examples 1 to 3, a proportion of 10.2 g of formic acid (HCOOH) was added to the water-based medium in the form of 14.2 g of water at the beginning, with the formic acid acting as a catalyst.

[0037] In the following examples 4 to 6, 86.2 g of water was used as the water-based medium and a proportion of 47.4 g of formic acid (HCOOH), which acts as a catalyst, was added to adjust the pH value of the binder composition according to the invention.

[0038] The pH value of the binder compositions according to the invention is approximately 1 to approximately 2 in the examples. The pH value originally achieved in the water-based medium by adding the acid is essentially retained after adding the alkoxysilanes. Phase 1 - Drop-in:

[0039] During a drop-in phase (Phase 1), the prepared alkoxysilane mixture is added dropwise to the water-based medium already present in the reaction vessel. The resulting reaction in the mixture, i.e., a partial conversion of the silanes in the alkoxysilane mixture into silanols and siloxanes, is continuously supported by stirring. The heat of reaction from this exothermic reaction in the mixture during the dropwise addition of the alkoxysilane mixture is generally sufficient to maintain the temperature of the mixture at approximately 35 °C. The dropwise addition should be carried out as continuously and precisely as possible so that a predetermined maximum temperature of the mixture is not exceeded by the heat of reaction released during the exothermic reaction. The predetermined maximum temperature is approximately...40 °C is maintained to limit further reaction (condensation reaction) of the formed silanols to siloxanes and thus prevent gelation of the reaction mixture. Should the reaction mixture reach the specified maximum temperature, the dropwise addition of the alkoxysilane mixture must be throttled or regulated to such an extent that the specified maximum temperature is maintained and not exceeded, i.e., the released heat of reaction can be compensated for by heat dissipation into the cooling medium. Preferably, the dropwise addition phase is limited to a period of 10 minutes. Afterwards, the resulting composition can be cooled to room temperature. The mixture thus obtained represents a binder composition according to the invention and has a siloxane-based solids content of 32.5 wt.% or less. Phase 2 (optional) - Isothermal reaction:

[0040] Once the alkoxysilane mixture has been completely added dropwise to the reaction vessel (phase 1), an isothermal reaction phase (phase 2) can be initiated, if necessary, to further stabilize the binder composition according to the invention. This phase involves the partial conversion of the silanes in the alkoxysilane mixture into the corresponding mono- or disilanols within the reaction mixture. For this purpose, the temperature of the reaction mixture is maintained at a substantially constant value of approximately 30 °C to approximately 40 °C, preferably approximately 35 °C, for a predetermined reaction time using an external heat source and constant stirring. The resulting reaction mixture is a clear, slightly yellowish liquid.

[0041] The reaction time for examples 1 to 6, specified in more detail below, is approximately 2 hours at a reaction temperature of approximately 35 °C.

[0042] After the specified reaction time of approximately 2 hours has elapsed, stirring and heating can be stopped.

[0043] In this optional phase, a mixture is also obtained which corresponds to the binder composition according to the invention, in particular also with regard to the specified upper limit for the siloxane-based solids content. Phase 3 (optional) - Dilute:

[0044] Optionally, the concentration of the reaction mixture in the water-based medium can be reduced after completion of the reaction phase (phase 2), as shown in Examples 1 to 3, for example, to allow for thinner layers when applied to a metal substrate. This can be achieved by adding distilled water to the reaction mixture obtained from phase 1 or 2. The pH value increases in the process but should not exceed approximately 3. Here, too, a binder composition according to the invention is typically obtained as a result. Examples of binder compositions according to the invention

[0045] The concentration of the reaction products in the binder composition according to the invention determines, among other things, the durability of the binder composition as well as the layer thicknesses obtainable when using the binder composition for the production of coatings on substrates, the layer structure and the tendency to form films as well as the ductility of the coating that can be produced therefrom.

[0046] The originally clear, slightly yellow reaction mixture can, in some cases, lead to the formation of an undesirably high solids content as a result of dilution, i.e., a solids content of more than approximately 32.5 wt%, and become cloudy.

[0047] This clouding can be avoided if the originally used water-based medium already contains the necessary total amount of water at the beginning, i.e., even before the drop-in phase (phase 1), as shown in examples 4 to 6 below. Phase 3 is then omitted accordingly. With this approach, the reaction mixture of phase 2, i.e., the thermally treated binder composition, remains clear and does not become cloudy even after long standing times, for example, 4 weeks or more.

[0048] The binder composition according to the invention contains the silane of formula (I) at least partially as mono- and / or di-silanols. The silanols of formulas (II), (III) and (IV) are also preferably present partially as mono- and / or disilanols, i.e., as compounds with a maximum of two Si-OH groups, in the reaction mixture or the binder composition according to the invention. This can be controlled, firstly, by the predetermined reaction time in the isothermal reaction phase (phase 2) and / or by the predetermined reaction temperature.

[0049] Parts of the amount of silanol of formula (IV) according to the following examples can also be replaced by silanols of formula (V), in particular to an extent of approximately 50% of the proportion of silanol of formula (IV) or less.

[0050] The molar ratios of the other components of the composition remain unchanged.

[0051] The degree of conversion of the silane derivatives of formulas (I) to (V) can be easily monitored using infrared spectroscopy (FTIR or ATR), as shown in Fig. 1 is illustrated.

[0052] The spectral curve A in Fig. Sample 1A was taken from the mixture of alkoxysilanes according to Example 1 before the start of Phase 1, i.e., before being added dropwise to the water-based medium, and shows that no silanols are present before the addition to the water-based medium. This is evident from the fact that in the spectral range of approximately 3400 cm⁻¹ -1 No band attributable to a Si-OH group is present. The strong band is located in the 1000 cm⁻¹ range. -1 up to 1100 cm -1 is assigned to the Si-OR groups of the alkoxysilanes.

[0053] After the addition of the silanes to the water-based medium, the Si-OH band forms, as can be seen from the spectral curve B ( Fig.1B). The first siloxanes also form at this time, with bands appearing at approximately 1000 cm. -1 up to approximately 1200 cm -1 These can be assigned. Spectral curve B was recorded at the end of phase 1. The band is located in the range of approximately 1700 cm. -1 is to be assigned to the C=O group of the formic acid present in the composition.

[0054] After gelation of the composition at a time when a siloxane-based solids content of more than approximately 32.5 wt% is present, the following results are obtained, as shown in the spectral curve C ( Fig. 1C) shows a very prominent Si-OH band in the spectral range of approximately 3400 cm⁻¹. -1 as well as barriers in the area of ​​approximately 1000 cm -1 up to approximately 1200 cm -1 , which are attributable to the siloxanes that are still present.

[0055] In Fig. 1D are the spectral curves of the Fig.1A to 1C are shown together again, offset vertically for better comparison. Example recipes

[0056] In the following examples 1 to 6, the following silanes were used in the recipes: Alkoxysilane of formula (I): 3-Aminopropyltriethoxysilane (APTES), available as AMEO from Evonik; Alkoxysilanes of formula (II) 3-Vinylpropyltrimethoxysilane (VTMS), available as VTMO from Evonik; Vinyl-tri-(2-methoxyethoxy)silane (VTMES), available as VTMOEO from Evonik; 3-Vinylpropyl triethoxysilane (VTES), available as VTEO from Evonik; Alkoxysilane of formula (III.1) 3-Glycidylpropyl-trimethoxysilane (GOPTMS), available as GLYMO from Evonik; Alkoxysilane of formula (III.2) 3-Methacryloxypropyl-trimethoxysilane (MPTMS), available as a MEMO from Evonik; alkoxysilane of formula (IV) Propyl trimethoxysilane (PTMS), available as PTMO from Evonik.

[0057] The silanes used in the following individual examples and their quantities in [g] can be found in Table 1 below: Table 1 Example APTES VTES VTMS VTMES GOPTMS MPTMS PTMS H2O Formic acid 1 33,2 9,5 11,8 12,4 8,2 14,2 +72,0 10,2 2 33,2 7,4 11,8 12,4 8,2 14,2 +72,0 10,2 3 33,2 14,0 11,8 12,4 8,2 14,2 +72,0 10,2 4 33,2 9,5 11,8 12,4 8,2 86,2 47,4 5 33,2 19,0 11,8 12,4 8,2 86,2 47,4 6 16,6 9,5 5,9 6,2 4,1 86,2 47,4

[0058] In examples 1, 2, and 3, 14.2 g of distilled water were initially used, and after the isothermal reaction phase (phase 2), a further 72 g of distilled water was added to dilute the reaction mixture (phase 3). The pH value remained below approximately 2.

[0059] The siloxane-based solids content originally contained in the binder compositions according to the invention can be found in Table 1A: Table 1A Example 1 2 3 4 5 6 Solids content [wt.%] 27,0 30,3 28,8 25,7 25,2 25,2

[0060] The solids content according to Table 1A was determined using samples of the binder compositions according to the invention from Examples 1 to 6, which were dried in a dryer (e.g., a Mettler Toledo HR83-P halogen dryer) at approximately 120 °C until a constant mass was achieved. The solids content was then determined gravimetrically. Durability test of the binder composition according to the invention

[0061] The storability of these binder compositions according to the invention, which are designed as adhesion promoters, was verified in long-term tests in which samples were dried at predetermined intervals (initially weekly and then at longer intervals, e.g., monthly) – as already described – in a dryer (e.g., a Mettler Toledo HR83-P halogen dryer) at approximately 120 °C until a constant mass was achieved, and their solids content was subsequently determined gravimetrically. The measured solids content corresponds essentially to the proportion of alkoxysilanes that gelled during drying, forming siloxanes. The storage conditions were as follows: Storage temperature 23 °C; the samples were stored sealed in a container to prevent exposure to air.

[0062] The results of the shelf-life test for examples 1 to 6 are in Fig. 2 is reproduced. In the diagram of the Fig. Figure 2 shows the results of the lifetime investigation of the binder compositions according to the invention, which can be used as adhesion promoters. The solids content present in each sample was plotted against the sample age. Table 2 Example 1 2 3 4 5 6 curve A B C D E F

[0063] It is evident that the binder compositions according to the invention (here designed as adhesion promoters), which were produced according to the examples, exhibit high durability and long shelf life. The adhesion promoters show virtually no gelation and can be processed over extended periods. In some cases, shelf lives of over 12 months can be achieved (for example, with compositions of Examples 1, 2, and 4). Production of a substrate coated with the binder composition

[0064] In the following examples, which relate to the production of substrates coated on a first predetermined surface area with a binder composition according to the invention, a metal substrate (sheet) made of steel (available as DC04 + LC-MB-RL C EN 10139 / 10141) was pretreated differently and then coated with a binder composition according to the invention (samples A to C) or with a conventional silane adhesion promoter (Megum 3290-1 from Dow Chemicals; comparison samples D and E). The application rates of the binder composition according to the invention or of the conventional adhesion promoter in the comparison examples are approximately 0.05 g / cm² each. 2 A second surface area of ​​samples A to E remained uncoated. For a comparison sample F, an uncoated stainless steel sheet (available as EN 10088-2 / ISO 9445 High T X6 CR 17 + C850 + 2H pickled) was used. Sample A based on Example 1:

[0065] For this test, the sheet metal was degreased and phosphated. Then the binder composition from Example 1 was applied. Sample B based on Example 2:

[0066] For this test, the sheet metal was only degreased. Then the binder composition from Example 2 was applied. Sample C based on Example 3:

[0067] For this test, the sheet metal was only degreased. Then the binder composition from Example 3 was applied. Comparison sample D:

[0068] For this test, the sheet metal was degreased and phosphated. Then the conventional adhesion promoter (Megum 3290-1 from Dow Chemicals) was applied. Comparison sample E:

[0069] For this test, the sheet metal was only degreased. Then a conventional adhesion promoter (Megum 3290-1 from Dow Chemicals) was applied.

[0070] The metal substrates of samples A to C and the comparison samples D and E were degreased using an alkaline process. For this purpose, the metal substrates were immersed in an aqueous alkaline Builder surfactant solution (available from SurTec Deutschland GmbH) with a pH of approximately 12 for 3 minutes at 60 °C.

[0071] In both sample A and the comparison sample D, the metal substrate was phosphated after degreasing. For this purpose, the metal substrates were immersed in a phosphoric acid solution with a pH of approximately 4.5 for 3 minutes at 45 °C.

[0072] The prepared metal substrates of samples A to C and the comparison samples D and E were then immersed in the respective binder compositions or adhesion promoters for at least 30 seconds, with a section of the surface area to be coated being immersed. Another section remained untreated. The immersed sections of the metal substrates were then withdrawn from the binder composition or adhesion promoter at a speed of approximately 1 mm / sec. The excess binder or adhesion promoter was allowed to drip off.

[0073] In samples A to C, the binder composition adhering to the metal substrate was cured at an elevated temperature of approximately 175 °C for approximately 20 minutes.

[0074] The comparison samples D and E were pretreated analogously to samples A and B, respectively, and then the conventional adhesion promoter (Megum 3290-1 from Dow Chemicals) was applied. The adhesion promoter was also cured for 20 minutes at approximately 175 °C. Corrosion resistance tests

[0075] The testing of samples A to C based on examples 1 to 3 was carried out in accordance with DIN EN ISO 9227 at a chamber temperature of 35 °C and a brine concentration in the spray mist of 5 wt% NaCl in distilled water.

[0076] The samples and control samples were subsequently subjected to a corrosion test for 3 h, 6 h and 10 h. The results are in the Fig. 3A to 3C are illustrated and summarized in the following Table 3.

[0077] The tests show that the coatings according to the invention, made from the binder compositions of Examples 1 to 3, are superior to the commercial systems (comparison samples D and E). Even after a test period of 3 hours ( Fig. 3A) With conventional adhesion promoters, it is no longer possible to distinguish on which section of the metal substrate the adhesion promoter was applied. Table 3 Sample / Comparison sample Condition after 3 hours ( Fig. 3A) Condition after 6 h( Fig. 3B) Condition after 10 hours ( Fig. 3C) A Heavy rust formation on the untreated section; surface of the treated section without visible rust formation. Heavy rust formation on the untreated section; rust formation begins in the edge areas of the treated section; otherwise largely corrosion-free. Excessive rust formation on the untreated section; advanced rust formation on the treated section from the edges towards the center of the sample. B Heavy rust formation on the untreated section; surface of the treated section without visible rust formation. Heavy rust formation on the untreated section; rust formation begins in the edge areas of the treated section; otherwise largely corrosion-free. Excessive rust formation on the untreated section; advanced rust formation on the treated section from the edges towards the center of the sample. C Heavy rust formation on the untreated section; surface of the treated section without visible rust formation. Heavy rust formation on the untreated section; rust formation begins in the edge areas of the treated section; otherwise largely corrosion-free. Excessive rust formation on the untreated section; advanced rust formation on the treated section from the edges towards the center of the sample. D Heavy rust formation across the entire surface of the control sample; no visible difference between the treated and untreated areas. Termination of the corrosion test E Heavy rust formation across the entire surface of the control sample; no visible difference between the treated and untreated areas. Termination of the corrosion test

[0078] The corrosion test was therefore not continued for the comparison samples D and E. Meanwhile, after 3 hours, the metal substrates on the sections coated with the binder composition according to the invention show impressive corrosion protection. In contrast, the uncoated sections are already completely covered with rust, while the coated sections show no signs of rust whatsoever.

[0079] This condition is essentially maintained even after 6 hours ( Fig. 3B). Only after a corrosion test period of 10 h do corrosion marks appear at the edges of the coating on samples coated according to the invention ( Fig. 3C), signs of rust.

[0080] A comparison of the vinylsilanes shows that the vinylsilane VTMS (Sample B; Example 2) exhibits somewhat poorer corrosion resistance. After 10 hours, significantly stronger corrosion is observed compared to the VTES-based formulation (Sample A; Example 1). Slightly poorer corrosion resistance is also observed for the VTMES-based formulation (Sample C; Example 3).

[0081] Similar results to those obtained for Example 1 (Sample A) are obtained for the recipes in Examples 4 to 6.

[0082] In the further comparison sample F, a sheet of stainless steel (EN 10088-2 / ISO 9445 High T X6 CR 17 + C850 + 2H pickled) was used unchanged. Under the same test conditions as samples A to E, no corrosion whatsoever was detected in this sample (not shown). Production of substrates according to the invention, which are additionally coated with a liquid rubber layer.

[0083] For a production of the in Fig.In the four schematically shown substrate samples 100 according to the invention, two stainless steel plates 12, 12' (material available as EN 10088-2 / ISO 9445 High T X6 CR 17 + C850 + 2H pickled) with dimensions of 100 mm x 24 mm are produced. The thickness of the stainless steel plates 12, 12' can be varied, but should not exceed approximately 1 mm. The stainless steel plates 12, 12' are pretreated (for example, by alkaline degreasing and optionally phosphating, as described above in the examples) and then immersed in a binder composition according to the invention at room temperature to a depth of at least 30 mm for approximately 30 s and subsequently withdrawn at a withdrawal rate of approximately 1 mm / s.

[0084] After application of the binder composition (approx. 0.05 g / cm²) 2The stainless steel plates 12, 12' are tempered for approximately 15 minutes in a convection oven at approximately 175 °C. The binder composition according to the invention is then present as cured gel layers 14, 14' on the stainless steel plates 12, 12'. The stainless steel plates 12, 12' prepared in this way can then be used to bond them together by means of a two-component liquid elastomer layer 20 (LSR). In the following examples, the commercially available Elastosil LR 3005 / 40 from Wacker Chemie AG is used as the LSR material.

[0085] For this purpose, one of the stainless steel plates, here the stainless steel plate 12', is first placed in a device 200 ( Fig. 5) to prepare substrate samples 100 in a so-called sandwich form, as in Fig. 4 schematically shown, placed on a lower clamping block 210 and then the liquid elastomer is applied as layer 20 to the upper cured gel layer 14'.

[0086] The mass of the two-component liquid elastomer layer 20 is applied evenly to the upper gel layer 14' of the stainless steel plate 12' using a mixing unit. The second stainless steel plate 12 is then placed onto the liquid elastomer layer 20 with the gel layer 14 facing downwards. An excess of liquid elastomer should be used. This ensures that, with complete coverage, a surface as flat as possible and a layer of uniform thickness is formed, and that the amount of elastomer and the resulting layer thickness (approx. 5 mm) of layer 20 between the stainless steel plates 12 and 12' remain as consistent as possible across the contact area (increasing reproducibility).

[0087] After the second metal plate 12 has been applied and placed, hold-down clamps 216, 218 are placed on the stainless steel plates 12 and 12' respectively and pressed and clamped against the clamping block 210 by means of fixing screws 212, 214. The overlapping surfaces of the two metal plates 12, 12' relevant for the tensile test (see Fig. 5) each amount to 600 mm 2 Typically, fixing screws 212, 214 are used on both sides of the samples 100 (in Fig. 5 shows only the respective front fixing screw 212 or 214).

[0088] The prepared substrate samples 100 are placed in a strained state ( Fig. 5) placed in a preheated convection oven at 150 °C for two hours.

[0089] In a final step, any excess elastomer mass is removed from the side edges of the substrate samples 100 using a razor blade.

[0090] After that, the substrate samples can be 100 ( Fig.4) (possibly after media storage) subject to a tensile test (also called peel test), whereby tensile forces are applied in the direction of the Fig. Arrows I and II, as shown in the diagram, are applied parallel to the planes of the stainless steel plates 12, 12'. The test speed is 10 mm / min until a pre-force of 1 N is reached. After reaching the pre-force, the tensile forces are applied at a tensile test speed of 50 mm / min.

[0091] For this tensile test, the different binder compositions of examples 1 to 3 were initially used for the production of the gel layers 14, 14'.

[0092] Additionally, two bare, i.e., uncoated, stainless steel plates 12, 12' were directly bonded using an LSR layer 20 as a reference (comparative sample). The results of the tensile test, i.e., the measured tensile force, are shown in Table 4. The measured tensile force represents the value of the tensile force at which the bond between the two stainless steel plates breaks or tears. Table 4: Comparison of the results of the adhesion tests for various vinylsilane-modified adhesion promoters according to the invention, examples 1 to 3, and a reference sample Example 1 Example 2 Example 3 comparison sample Tear strength [N] 903 1050 871 469

[0093] The results from Table 4 show that the adhesion of the stainless steel plates 12, 12' can be significantly improved by using a binder composition according to the invention in the form of the gel layers 14, 14' as an adhesion promoter, compared to the untreated stainless steel plates of the reference sample. The trials with different vinylsilanes from Examples 1 to 3 result in a tensile strength at a very similar, but significantly higher level.

[0094] Taking into account the results of the corrosion resistance tests ( Fig. For 3A to 3C, the following investigations were carried out using further binder compositions based on Example 1, as specified in more detail in Examples 4 to 6 (Table 1) above. The results of this study are presented in Table 5. Table 5: Comparison of the results of the adhesion tests for adhesion promoters according to the invention with samples based on Examples 4, 5 and 6 Example 4 Example 5 Example 6 Tear strength [N] 903 1305 1415

[0095] The values ​​in Table 5 show that both adjustments to the process and adjustments to the formulation (Examples 5 and 6) result in an improvement in tensile strength. The increase in tensile strength observed in Examples 5 and 6 is primarily due to the increased proportion of vinyltriethoxysilane.

[0096] The storage studies described below were therefore continued with samples based on Example 6.

[0097] The embedding processes were carried out using both a stainless steel metal substrate (available as EN 10088-2 / ISO 9445 High T X6 CR 17 + C850 + 2H pickled) and an AlMg substrate (B046 [EN AW-AL Mg 3(EN AW-5754)], material no. 3.3535.25). Hot air (150 °C) and distilled water (90 °C) were used as the embedding media. Both embedding processes were carried out over a period of 168 hours.

[0098] Table 6 shows the results of the depositions for the stainless steel substrates. Table 7 shows the results of the depositions for the aluminum substrates. Table 6: Tensile forces after storage of the stainless steel samples based on Example 6 Tensile strength Initial values ​​[N] After storage in water[N] Δ to initial value [%] After storage in hot air[N] Δ to initial value [%] Average 1273 42 - 96,7 624 - 51,0 minimum 1080 35 608 maximum 1480 49 483 Table 7: Tensile strength after storage of the AlMg samples based on Example 6 Tensile strength Initial values ​​[N] After storage in water[N] Δ to initial value [%] After storage in hot air[N] Δ to initial value [%] Average 1109 78 - 93,0 1065 - 4,0 minimum 948 59 984 maximum 1320 129 1130

[0099] The coatings according to the invention, based on the binder compositions according to the invention, exhibit very good resistance to hot air on stainless steel and, in particular, also on AlMg. The respective combination of metal substrates and adhesion promoters according to the invention is therefore particularly well suited for use in hot, dry environments. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 0 716 127 A2

[0002] EP 0 832 911 A1

[0002]

Claims

[1] Binder composition comprising a water-based medium and a mixture of various alkoxysilanes, wherein the mixture comprises: at least one aminoalkoxysilane of formula (I) R'HN(CH2) a' -R'' a'' (CH2) a -Si(OR)3 Formula (I) where R in formula (I) as well as in the following formulas (II), (III.1), (III.2), (IV) and (V) represents a substituent which is individually selected from methyl, ethyl, propyl, butyl, pentyl and methoxyethyl; where independently a represents an integer value in the range of 0 to 5, a' an integer value from 0 to 5 and a'' an integer value of 0 or 1, where the sum of a+a'+a'' has a value of 1 or more; where R' represents a substituent selected from methyl, ethyl, propyl, phenyl, H and aminoalkyl, wherein the alkyl group of the substituent aminoalkyl is selected from methyl, ethyl, propyl and aminoalkyl; and where R'' represents a phenyl or phenylene substituent; at least one vinylalkoxysilane of formula (II) CH2=CH(CH2) b -Si(OR)3 Formula (II) where b represents an integer value in the range of 0 to 5; and at least one further alkoxysilane selected from organofunctional water-soluble alkoxysilanes of formulas (III.1) and (III.2) and water-insoluble alkoxysilanes of formulas (IV) and (V): CH2OCHCH2O(CH2) c -Si(OR)3 Formula (III.1) where c represents an integer value in the range of 1 to 5; R1CH =CH-COO(CH2) d -Si(OR)3 Formula (III.2) where d represents an integer value in the range of 1 to 5 and R1 represents a substituent selected from H and methyl; CH3(CH2) e -Si(OR)3 Formula (IV) where e represents an integer value in the range of 0 to 5; Si(OR)4 Formula (V); wherein the binder composition includes a proportion of an acid and the pH value of the binder composition is approximately 0 to approximately 3; wherein the alkoxysilanes are partially present in the form of silanols, wherein one or two of the R groups of an alkoxysilane are replaced by a hydrogen atom; furthermore, a proportion of the silanols is converted to siloxanes, the proportion of siloxanes resulting in a solids content in the binder composition of approximately 32.5 wt.% or less. [2] Binder composition according to claim 1, wherein the pH is adjusted using an organic acid selected from formic acid, acetic acid and propionic acid and mixtures thereof. [3] Binder composition according to claim 1 or 2, wherein the pH value is approximately 0.75 to approximately 2, in particular approximately 0.75 to approximately 1.

5. [4] Binder composition according to any one of claims 1 to 3, wherein the solids content is approximately 30 wt.% or less, in particular approximately 27.5 wt.% or less. [5] Binder composition according to one of claims 1 to 4, wherein the ratio of the molecular fraction of aminoalkoxysilane of formula (I) and the corresponding silanols, based on the sum of the fractions of the alkoxysilanes of formulas (II), (III.1), (III.2), (IV) and (V) and their corresponding silanols, is approximately 0.5 to approximately 3, in particular approximately 0.75 to approximately 1. [6] Binder composition according to any one of claims 1 to 5, wherein the aminoalkoxysilane of formula (I) is selected from 3-aminopropyl-trimethoxysilane, 3-aminopropyl-triethoxysilane, N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane, N-phenyl-3-aminopropyl-trimethoxysilane, diethylenetriaminopropyl-trimethoxysilane, m-aminophenyl-trimethoxysilane, p-aminophenyl-trimethoxysilane, p-aminophenyltriethoxysilane, and (aminoethylaminoethyl)-phenylethyl-trimethoxysilane. [7] Binder composition according to any one of claims 1 to 6, wherein the vinylalkoxysilane of formula (II) is selected from vinylalkylalkoxysilanes, vinyl-trimethoxysilane, vinyl-triethoxysilane and vinyltri(methoxyethoxy)silane. [8] Binder composition according to any one of claims 1 to 7, wherein the further alkoxysilane is selected in the form of the water-soluble alkoxysilane of formula (III.1) from glycidyloxyalkyl alkoxysilanes, in particular 3-glycidyloxypropyl triethoxysilane and 3-glycidyloxypropyl triethoxysilane, or of the water-soluble alkoxysilane of formula (III.2) is selected from methacryloxyalkyl alkoxysilanes, in particular 3-methacryloxypropyl triethoxysilane and 3-methacryloxypropyl triethoxysilane, and acryloxysilanes, in particular 3-acryloxypropyl triethoxysilane. [9] Binder composition according to any one of claims 1 to 8, wherein the water-insoluble alkoxysilanol derivative of formula (IV) is selected from alkylalkoxysilanes, in particular n-propyl-trimethoxysilane and n-propyl-triethoxysilane; and / or wherein the water-insoluble alkoxysilane of formula (V) is selected from tetramethoxysilane and tetraethoxysilane. [10] Method for producing a coating on a surface of a substrate, comprising the steps (d) Providing the substrate with a surface area to be coated which has a chemical structure with OH groups; (e) Applying a binder composition according to any one of claims 1 to 9 to the surface area of ​​the substrate to be coated; and (f) Drying and curing of the applied binder composition on the surface area of ​​the substrate, forming a chemical coupling of the OH groups of the surface area of ​​the substrate with the alkoxysilanols of the binder composition, wherein the alkoxysilanols are converted to polymeric alkoxysiloxanes. [11] Method according to claim 10, wherein the binder composition is subjected to a thermal reaction, in particular an isothermal reaction, in a temperature range of approximately 30 °C to approximately 40 °C before application to the surface area to be coated, for at least partial further conversion of the silanols contained in the binder composition into corresponding siloxanes. [12] Method according to claim 11, wherein the isothermal reaction is carried out at approximately 35 °C. [13] Method according to any one of claims 10 to 12, wherein the solids content of the binder composition is approximately 35 wt.% or less, in particular approximately 25 wt.% to approximately 32.5 wt.%. [14] Method according to any one of claims 10 to 13, wherein the substrate is a metallic substrate. [15] Substrate with a coated surface area obtained according to a method of claims 10 to 14. [16] Substrate according to claim 15, wherein the coating is designed as a corrosion protection coating and / or as a primer coating. [17] Method for producing a material-bonded composite between a surface-coated substrate according to claims 15 or 16 and a liquid rubber-based layer, comprising the steps (a) Applying a liquid rubber-containing mass to the coated surface of the substrate; and (b) Curing the liquid rubber-containing mass to form a chemical bond between the liquid rubber and the polymeric alkoxysiloxanes of the coating of the substrate formed according to any one of claims 10 to 14, in particular in the form of a corrosion protection coating or a primer coating.

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