Adhesion promoter for polysulfide and polythioether-based sealants

Abstract

The invention relates to a method for sealing a substrate, comprising at least steps 1) and 3), by applying at least part of a solvent-based composition to a surface of the substrate to at least part form a film (1) on said surface, applying at least part of a sealant composition to the film obtained after step 1) to form a sealant film (3), wherein the sealant composition is obtainable by mixing at least two components A) and B) of a sealing system, which are present separately, with one another, the solvent-borne composition applied in step 1) comprising at least one aliphatic hydrocarbon as an organic solvent component a1) in an amount of at least 70.0 wt.-%, based on the total weight of the composition, at least one organometallate as component a2) in an amount of at least 70.0 wt.-%, based on the total weight of the composition, the present invention relates to a method for preparing a solvent-borne composition comprising at least one metal acid salt, the metal of which is selected from Ti and Zr, and at least one organosilane as component a3), sealing substrates obtainable by this method, the use of this solvent-borne composition as an adhesion promoting composition, the solvent-borne composition itself, and a kit comprising said solvent-borne composition.

Description

[0001] The present invention relates to a process for sealing optionally pre-coated substrates, comprising applying a solvent-based composition as adhesion promoting composition to the surface of the substrate and subsequently applying a sealant composition, a sealed substrate obtainable by the process, the use of the aforementioned solvent-based composition as adhesion promoter, the solvent-based composition as such, and a kit-of-parts comprising the solvent-based composition. BACKGROUND

[0002] Sealants are used for a wide range of applications. They are for example related to the aerospace field, but also widely used in the automotive field. Sealants are also used for sealing construction elements, for example connecting metal plates to existing structures like aircraft cabin sections and / or for corrosion protection where the corrosion protection layer of a metal element is damaged or removed, for example in the area of a hole. They can also perform a temporary load bearing function, for example during transport of structures to be installed, for which permanent support connection elements must subsequently be provided.

[0003] It is essential that the sealant adheres sufficiently to the surface of the substrate. For this purpose, various different adhesion promoters are known in the prior art for use with various substrates, i.e. in order to provide adhesion of the substrate to the sealant applied on top.

[0004] Suitable adhesion promoters can be incorporated directly into the sealant composition used to form the sealant for this purpose. It is also possible to apply the adhesion promoter to the surface of the substrate to be sealed before the external application of the sealant in a separate step. Adhesion promoters of this type are known from US 2021 / 0402748 A1 and US 2021 / 0187922 A1 : The reference US 2021 / 0402748 A1 relates to an adhesion promoting composition for enhancing adhesion between abutting layers of a sulfur-containing sealant, the adhesion promoting composition comprising a free-radically polymerizable compound such as a functional (meth)acrylate oligomer, a free-radical initiator; and a volatile organic solvent. US 2021 / 0187922 A1 discloses a multi-layer sealant comprising a first sulfur-containing sealant layer, an adhesion promoting intermediate layer covering the first sulfur-containing sealant layer and a second sulfur-containing sealant layer covering the adhesion promoting intermediate layer, wherein the adhesion promoting intermediate layer comprises a crosslinked free-radically polymerized compound.

[0005] Another type of such adhesion promoters is disclosed in US 2021 / 0047488 A1 and US 2021 / 002514 A1, which use compositions comprising metal alkoxides. Reference US 2021 / 0047488 A1 relates to a method and composition for preparing a surface comprising a thermoplastic or thermoset material such as a polyamide material to receive a polysulfide or polythioether sealant or coating, the method comprising applying to the surface an activation composition consisting of a complex of a tetraalkoxide of a Group 4 metal and / or an alkoxide of a Group 4 metal. US 2021 / 002514 A1 relates to a composition for surface activation comprising an organic solvent and a transition metal alkoxide and optionally water. A sealant layer can be applied on top of the dried layer obtained from applying the composition.

[0006] Silanes, in particular organosilanes, are also known to be suitable as adhesion promoters for various substrates. Due to their great compatibility with many chemical systems, they can be used in a variety of different materials, including sealant materials, but also in separately applied adhesion promoting compositions. In contrast to other chemically different adhesion promoters like e.g. phenolic resins or polyolefins, silanes generally do not significantly influence the pH environment within the materials they are used in, which becomes particularly important for applications where the environmental conditions, like a constant pH environment, are crucial for the curing characteristics of the material, which is the case for example for polysulfide and / or polythioether based sealants. The use of silanes is known for example from US 2021 / 0189206 A1 and WO 2020 / 232462 A1. Reference US 2021 / 0189206 A1 relates to an adhesion promoting composition containing an organotitanate and / or zirconate, an organic solvent, and an amine- and alkenyl-functional alkoxysilane for enhancing the adhesion between a metal substrate and an overlying sealant, like a free-radically polymerizing sealant, in particular based on thiol-ene chemistry, wherein the alkenyl group of the alkenyl-functional alkoxysilane can attach to the polymeric structure of the sealant. The use of silane-based sealants is also described for example in WO 2020 / 232462 A1, which relates to a composite structure comprising a thermoplastic substrate, which in turn comprises a chemical sealant directly bonded to a surface thereof, which provides a surface suitable for adhering adhesives, coatings, and / or surface films to the thermoplastic surface.

[0007] However, the adhesion promoters known in the prior art, such as disclosed in US 2021 / 0189206 A1, do not always provide sufficient adhesion to effectively adhere the sealant to the surface of the substrate to be sealed, especially in the field of sealants for the aircraft industry, and more particularly with regard to the use of sealant compositions comprising polymers having thiol groups, such as polysulfide- and / or polysulfide ether-based sealant compositions, especially not for a variety of different substrates. In particular, when thermoplastic or glass substrates such as polycarbonate or, for example, PMMA (polymethyl methacrylate) substrates are used, sufficient adhesion is not always achieved. Further, the aforementioned adhesion promoters known in the prior art often contain a large amount of toxic materials, which is ecologically but also economically disadvantageous. Furthermore, the aforementioned adhesion promoters known in the prior art, such as the adhesion promoters disclosed in US 2021 / 0189206 A1, require a relatively high content of active ingredients, in particular at least two silanes present therein, and are further applied in a relatively high dry layer thickness of several micrometers, which is disadvantageous for both ecological and economic reasons.

[0008] Therefore, there is a need for adhesion-promoting compositions and methods for sealing substrates using the same, which do not exhibit the aforementioned disadvantages, in particular when the substrates are substrates used in the aircraft industry such as thermoplastic substrates. In particular, there is a need for corresponding adhesion-promoting compositions, which provide excellent adhesion between a variety of different substrates, in particular thermoplastic substrates, and a sealant applied to the surface thereof, wherein the sealant is obtainable from a sealant composition comprising polymers having thiol groups such as polysulfides and / or polysulfides ethers, wherein in particular compared to the adhesion-promoting compositions of the prior art, these adhesion-promoting compositions further can be provided in an ecologically and economically advantageous form, in particular in a non-toxic or at least less toxic form with a reduced concentration of active ingredients, and can be applied in a low dry layer thickness, without, however, imparting their adhesion-inducing properties.

[0009] Problem

[0010] It is therefore a basic object of the present application to provide adhesion promoting compositions and a method of sealing a substrate using such compositions, in particular when the substrate is a substrate used in the aircraft industry such as a thermoplastic substrate. It is a particular basic object of the present application to provide adhesion promoting compositions which provide an excellent adhesion between various substrates, in particular thermoplastic substrates, and sealants applied to the surface thereof, obtainable from a sealant composition comprising a polymer having thiol groups, such as a polysulfide and / or a polythioether, wherein in particular compared to the adhesion promoting compositions of the prior art, these adhesion promoting compositions further can be provided in an ecologically and economically advantageous form, in particular in a non-toxic or at least less toxic form with a reduced concentration of active ingredients, and can be applied in a low dry layer thickness, without however imparting their adhesion inducing properties.

[0011] Solution

[0012] This object has been solved by the subject matter of the claims of the present application and by the preferred embodiments thereof disclosed in the present specification, i.e. by the subject matter described herein.

[0013] A first subject matter of the present application is a method of sealing an optionally pre-coated substrate, the method comprising at least steps 1) and 3) and optionally at least one of steps 2) and / or 4), i.e.

[0014] 1) applying a solvent-borne composition at least partially onto the surface of an optionally pre-coated substrate to at least partially form a film on said surface,

[0015] 2) optionally drying and / or curing the film obtained after step 1),

[0016] 3) applying a sealant composition different from the solvent-borne composition used in step 1) at least partially onto the optionally dried and / or cured film obtained after step 1) or 2) to form a sealant film,

[0017] wherein the sealant composition is obtainable by mixing at least two separately present components A) and B) of a sealing system with each other, wherein component A) of the sealing system comprises at least one polymeric component A1) containing two or more thiol groups, the polymeric component being selected from the group consisting of polyethers, polythioethers, polysulfides, polythioether-sulfide components and mixtures thereof, and wherein component B) of the sealing system comprises at least one component B0) suitable for curing the sealant composition by at least partially inducing a chemical transformation of the two or more thiol groups of component A1), and

[0018] 4) optionally curing the sealant film obtained after step 3),

[0019] wherein the solvent-type composition applied in step 1) comprises at least ingredients a1) to a3) different from each other, i.e.

[0020] at least one aliphatic hydrocarbon as organic solvent ingredient a1) in an amount of at least 70.0 wt.-%, based on the total weight of the composition,

[0021] at least one organometallic acid salt as ingredient a2), the metal of the metal acid salt being selected from Ti and Zr, and

[0022] at least one organosilane as ingredient a3),

[0023] wherein the sum of all ingredients present in the solvent-type composition amounts to 100 wt.-%.

[0024] A further subject matter of the present application is a sealed substrate, which is obtainable by the process of the present application, which is preferably suitable for use in the aircraft and / or aerospace industry.

[0025] A further subject matter of the present application is the use of the solvent-type composition as used and defined in step 1) of the preceding process as an adhesion promoting composition, in particular for enhancing the adhesion between the surface of an optionally pre-coated substrate and a subsequently applied sealant film.

[0026] A further subject matter of the present application is the solvent-type composition as defined in connection with step 1) of the preceding process per se, wherein the at least one aliphatic hydrocarbon ingredient a1) present therein preferably has 8 to 20 carbon atoms.

[0027] A further subject matter of the present application is a kit-of-parts comprising at least a sealing system as defined in connection with step 3) of the preceding process, which sealing system comprises at least two components A) and B) separately from each other, and a solvent-type composition as defined in connection with step 1) of the preceding process or the solvent-type composition of the present application, separately from each other.

[0028] It has been particularly surprising to find that the solventborne compositions disclosed above and below can be used as adhesion promoting compositions, in particular as one-component (1 K) compositions, and provide excellent adhesion between various different substrates, in particular including thermoplastic substrates, which are used in the aircraft and / or aerospace industry, and sealants applied to the surface thereof, which are obtainable from sealant compositions comprising polymers having thiol groups, such as polysulfides and / or polysulfides, which can in particular be cured using epoxy resins, in particular when polysulfide-based sealant compositions are used, and / or metal oxides, such as manganese dioxide, in particular when polysulfide-based sealant compositions are used. Thus, the solventborne compositions can be externally applied as adhesion promoters on the various substrates prior to any sealant application and can for example be used for the assembly of aerospace and aircraft windows.

[0029] Further, it has been particularly surprising to find that the solventborne compositions disclosed above and below can be provided in an ecologically and economically advantageous form, in particular in a non-toxic form or in a form having a low, i.e. at least reduced, toxicity compared to the adhesion promoting compositions of the prior art, without imparting their adhesion inducing properties.

[0030] Furthermore, it has been particularly surprising to find that the solventborne compositions disclosed above and below can be provided and used in a form having a lower active ingredient content when compared to conventional adhesion promoters known in the prior art, in particular with regard to ingredients a2) and / or a3).

[0031] Further, it has been surprising to find that the solventborne compositions disclosed above and below can be applied in a very thin layer only, for example in a dry layer thickness of substantially below 1 pm, such as in a dry layer thickness of 300 nm or 200 nm or below. This has the particular advantage that relatively low active ingredient concentrations, in particular with regard to ingredients a2) and a3), can be used in the solventborne compositions, but nevertheless an excellent cohesive connection between the substrate and the sealant can be provided.

[0032] Further, it has been surprising to find that no undesired crazing is observed on thermoplastic substrates, such as on PMMA and polycarbonate substrates, which is advantageous since at least one aliphatic hydrocarbon, such as at least one aliphatic hydrocarbon having 2 to 20 carbon atoms or in particular having 8 to 20 carbon atoms, is used as at least one organic solvent ingredient a1), which is optionally combined with at least one alcohol having one or more, preferably exactly one OH-group, which is optionally used as one or more further organic solvent ingredient(s) a4).

[0033] Furthermore, it has been unexpectedly found that, particularly when using thermoplastic substrates such as PMMA and polycarbonate substrates, it is not necessary to activate the surface of such substrates, for example, by plasma or UV light, before applying the sealant composition. Instead, simply applying the solvent-based composition disclosed above and below as an adhesion promoter induces sufficient activation. Therefore, additional working steps, additional energy consumption, and additional expensive equipment are not necessary and are not required. Detailed Implementation

[0034] In the context of this invention, the term "comprising," for example, in relation to adhesion-promoting compositions, preferably means "consisting of." For instance, with respect to adhesion-promoting compositions, in addition to all the mandatory components present therein, one or more additional optional ingredients identified below may also be included. In each case, all components may be present in its preferred embodiment, as determined below.

[0035] The proportions and amounts of any component present in the adhesion-promoting composition given below, in wt.-% (weight %), total 100 wt.-%, based in each case on the total weight of the adhesion-promoting composition. This also applies to any other compositions disclosed herein, such as sealant compositions.

[0036] Method of sealing optionally pre-coated substrates

[0037] The first subject of the invention is a method for sealing an optionally pre-coated substrate, the method comprising at least steps 1) and 3) and optionally at least one of steps 2) and / or 4). The method may optionally include one or more additional steps performed before, between, and / or after any of the preceding steps.

[0038] Optional cleaning steps

[0039] Optionally, and preferably, the surface of the optionally pre-coated substrate is cleaned before performing step 1). Cleaning can be performed by any conventional technique, such as dipping, wiping, brushing, and / or spraying. Preferably, cleaning is performed using one or more organic solvents applied to the surface of the substrate. Appropriate solvents can be selected, for example, based on the recommendations of the substrate manufacturer for the specific substrate to be used. Preferably, the cleaning step removes any dirt, grease, oil, and / or dust from the substrate surface.

[0040] Step 1)

[0041] In step 1 ) the solvent-borne composition is at least partially applied to the surface of the optionally pre-coated substrate to at least partially form a film on said surface. Any kind of contact can generally be used for applying the solvent-borne composition in step 1 ), such as dipping, wiping, brushing and / or spraying, in particular by wiping and / or brushing.

[0042] Preferably, the solvent-borne composition is applied in a very thin layer on the surface of the substrate. In particular, the solvent-borne composition is applied such that a dry layer thickness of below 1.0 pm, more preferably below 900 nm or below 800 nm, even more preferably below 700 nm or below 600 nm, still more preferably below 500 nm or below 400 nm, most preferably below 300 nm or 200 nm, is produced after performing the optional step 2).

[0043] Preferably, the solvent-borne composition is applied in step 1 ) by wiping in a so-called "wipe-on method". Preferably, a brush, a soft lint-free wipe or a pen with a felt tip is used in this regard for applying the solvent-borne composition. The solvent-borne composition is then wiped onto the surface of the substrate.

[0044] Alternatively, the solvent-borne composition is applied in step 1 ) by wiping in a so-called "wipe-on / wipe-off method". Here, the solvent-borne composition is applied in excess to the surface of the substrate. Preferably, a brush, a soft lint-free wipe or a pen with a felt tip is used in this regard for applying the solvent-borne composition. The solvent-borne composition is then wiped onto the surface of the substrate. Within a few seconds or minutes, such as 5 seconds to 10 minutes, after the application, the excess is preferably wiped off with a soft lint-free wipe in order to allow the adhesion promoters present in the composition, such as components a2) and / or a3), for example, to undergo a hydrolysis reaction.

[0045] Step 1 ) is preferably carried out at a temperature in the range from 0 °C to 60 °C, more preferably from 5 °C to 45 °C. In particular, no heating is carried out.

[0046] Substrate

[0047] An optionally pre-coated substrate is used in step 1 ). Suitable substrates are metal-containing substrates (metal substrates), but also plastic substrates such as thermoplastic substrates, fibre-based composites (also referred to herein as fibre-reinforced composites) and glass substrates can be used. Preferred substrates are generally substrates which can be used in the aerospace and / or aircraft industry, for example as components and / or workpieces. Most preferred are plastic substrates such as thermoplastic substrates, fibre-based composites (also referred to herein as fibre-reinforced composites) and glass substrates.

[0048] Suitable metal-containing substrates for use according to the present application are all substrates which are commonly used and known by the skilled person. The metal-containing substrates for use according to the present application are preferably metal-containing substrates, including substrates composed of steel, steel alloys, aluminum, aluminum alloys, titanium and / or titanium alloys. The most preferred metal-containing substrates are aluminum and / or aluminum alloy substrates as well as steel and / or steel alloy substrates.

[0049] Preferably, in case the substrate is a plastic substrate, a thermoplastic plastic is used. Suitable thermoplastic polymers are polyalkyl (meth)acrylates, including poly(methyl) methacrylate (PMMA), polybutyl (meth)acrylate, polyethylene terephthalate, polybutylene terephthalate, polyvinylidene fluoride, polyvinyl chloride, polyesters, including polycarbonates (PC) and polyvinyl acetate, polyamides, polyolefins, such as polyethylene, polypropylene, polystyrene and also polybutadiene, polyacrylonitrile, polyacetals, polyacrylonitrile-ethylene-propylene-diene-styrene copolymers (A-EPDM), ASA (acrylonitrile-styrene-acrylate copolymer) and ABS (acrylonitrile-butadiene-styrene copolymer), polyetherimides, phenolic resins, urea resins, melamine resins, alkyd resins, epoxy resins, polyurethanes, including TPU, polyether ketones, polyphenylene sulfide, polyethers, polyvinyl alcohol, and mixtures thereof. Polycarbonates and polyalkyl (meth)acrylates, including poly(methyl) methacrylate (PMMA), are especially preferred plastic substrates.

[0050] As mentioned above, also fiber-based composites, such as carbon fiber composites, can be used as substrates, as well as glass substrates, in particular for windscreen applications.

[0051] Preferably, the optionally pre-coated substrate is selected from metal substrates, wherein the metal is preferably selected from steel, steel alloys, aluminum, aluminum alloys, titanium, titanium alloys, and mixtures thereof, or from glass substrates, thermoplastic substrates, including polycarbonate and polyalkyl (meth)acrylate substrates, and fiber-reinforced composite substrates, wherein the substrates in each case optionally bear at least one coating.

[0052] Examples of coatings which have already been present on the substrate, thus making it a pre-coated substrate, are primer layers or topcoat layers, which are obtainable from water-based (aqueous) or solvent-based (solvent-borne) primer or topcoat coatings, for example based on polyurethane or epoxy resin. The coating, if present, is preferably already cured.

[0053] The substrate can have any form, shape and geometry and can be, for example, a sheet, a foil, a plate, etc.

[0054] Solvent-borne compositions used in step 1)

[0055] The solvent-borne composition applied in step 1) of the method comprises at least the ingredients a1) to a3) which are different from each other, i.e.

[0056] at least one aliphatic hydrocarbon as organic solvent ingredient a1) in an amount of at least 70.0 wt.-%, based on the total weight of the composition,

[0057] at least one organometallic acid salt as ingredient a2), the metal of the metal acid salt being selected from Ti and Zr, and

[0058] at least one organosilane as ingredient a3), preferably in an amount of at most 10.0 wt.-%, based on the total weight of the composition,

[0059] wherein the sum of all ingredients present in the solvent-borne composition adds up to 100 wt.-%.

[0060] Preferably, the solvent-borne composition is a one-component (1K) composition. The solvent-borne composition is suitable as an adhesion promoter, i.e. as an adhesion promoting composition. Preferably, the solvent-borne composition does not represent a sealant composition. In particular, the solvent-borne composition is different from the sealant composition applied in step 3).

[0061] The composition used in step 1) is solvent-borne, i.e. a (non-aqueous) composition based on one or more organic solvents. For the purposes of the present invention, the term “solvent-borne” is in this respect preferably to be understood as meaning that one or more organic solvents (as ingredients a1) and optionally a4)) are present as the main ingredient of all solvents (including water) present in the composition. All customary organic solvents known to the person skilled in the art can be used as organic solvents. The term “organic solvent” is known to the person skilled in the art, in particular from Council Directive 1999 / 13 / EC of 11 March 1999.

[0062] The solvent-borne composition is preferably free of or essentially free of water, or, alternatively, can comprise a low amount of water. In this context, the term “essentially” preferably means that no water is intentionally added when preparing the composition. In this context, the term “low amount” preferably means that water can be present in an amount of at most 12.5 wt.-% or at most 10 wt.-% or at most 5 wt.-%, based on the total weight of the composition, in particular in case a certain level of pre-hydrolysis of the organosilane ingredient a3) and / or ingredient a2) is intended to be achieved. In particular, in case ingredient a2) is used (which reacts strongly with water such that immediate hydrolysis to TiO2 or ZrO2 occurs), then the presence of water is not intended.

[0063] ingredient a1) and optionally ingredient a4) of the solvent-borne composition

[0064] Component a1 ) is at least one aliphatic hydrocarbon as organic solvent component, which is present in an amount of at least 70.0 wt.-%, based on the total weight of the composition. The solvent-type composition can comprise one or more further organic solvents in addition to component a1 ), and preferably, for example, in the form of optional component a4). Thus, preferably, the solvent-type composition comprises at least two or three organic solvents, which are different from each other. The composition can even comprise more than three, such as four, different organic solvents. Preferably, however, the maximum number of different organic solvents present therein is four.

[0065] Preferably, the solvent-type composition used in step 1 ) comprises at least one aliphatic hydrocarbon as organic solvent component a1 ) in an amount in the range of 75.0 wt.-% or 80.0 wt.-% to 99.0 wt.-%, more preferably 82.5 wt.-% to 98.5 wt.-%, even more preferably 85.0 wt.-% to 98.0 wt.-%, still more preferably 87.5 wt.-% to 97.5 wt.-%, yet more preferably 90.0 wt.-% to 97.5 wt.-%, even more preferably 92.5 wt.-% to 97.5 wt.-%, most preferably 95.0 wt.-% to 97.0 wt.-%, in each case based on the total weight of the composition.

[0066] Suitable aliphatic hydrocarbons for use as component a1 ) are preferably branched hydrocarbons, such as isoalkanes, preferably having 2 to 20 or 5 to 20 carbon atoms. Most preferred are aliphatic hydrocarbons, such as at least one aliphatic hydrocarbon having 2 to 20 carbon atoms, more preferably 3 to 18 carbon atoms, even more preferably 4 to 17 carbon atoms, still more preferably 5 to 15 carbon atoms, yet more preferably 5 or 6 or 7 or 8 to 15 or 14 or 13 carbon atoms. Such aliphatic hydrocarbons are commercially available, for example, as Isopar® C, Isopar® E, Isopar® G, and Isopar® H (available from ExxonMobil). Most preferred is Isopar® G.

[0067] Optionally, in addition to the at least one aliphatic hydrocarbon present as component a1 ), the solvent-type composition used in step 1 ) comprises at least one further organic solvent as organic solvent component a4), which is different from component a1 ). Preferably, the at least one further organic solvent a4) is an alcohol having one or more OH-groups, which alcohol further optionally carries at least one ether segment, more preferably is a monomeric alcohol having one or more OH-groups, still more preferably is a monomeric alcohol having exactly one OH-group.

[0068] Suitable organic solvents for use as optional ingredient a4) are alcohols, preferably monomeric alcohols, including alcohols having more than one OH-group, such as diols having two OH-groups and polyols having more than two OH-groups, ethers, esters, ketones, and mixtures thereof. Examples of alcohols are 1-ethoxypropan-2-ol, 2-methylpentane-2,4-diol, ethanol, isopropanol, and isobutanol. Examples of suitable ketones are 5-methyl-2-hexan-2-one. Examples of suitable esters are ethyl acetate and butyl acetate.

[0069] Very particularly suitable organic solvents for use as optional ingredient a4) in combination with the aliphatic hydrocarbon ingredient a1) in solvent-borne compositions used in step 1) are alcohols, in particular when the optionally coated substrate used in step 1) is a thermoplastic or a fiber reinforced composite or a glass substrate. Most preferred is the combination of at least one aliphatic hydrocarbon ingredient a1) and at least one alcohol ingredient a4), in particular a mixture of at least one aliphatic hydrocarbon a1) such as at least one aliphatic hydrocarbon having 2 to 20 carbon atoms, more preferably 3 to 18 carbon atoms, even more preferably 4 to 17 carbon atoms, still more preferably 5 to 15 carbon atoms, yet more preferably 5 or 6 or 7 or 8 to 15 or 14 or 13 carbon atoms, with at least one alcohol a4) having one or more OH-groups, preferably exactly one OH-group, such as 1-ethoxy-2-propanol and / or isopropanol.

[0070] It has been found that the use of organic solvent ingredients a1) is particularly advantageous since their use does not lead to any cracking on the surface of these substrates, in particular in the case of thermoplastic substrates such as PMMA or polycarbonate. Preferably, at least one aliphatic hydrocarbon a1) is used in excess compared to at least one alcohol a4) optionally present in such a mixture. More preferably, the relative weight ratio of at least one aliphatic hydrocarbon a1) to at least one alcohol a4) if present in the solvent-borne composition is in the range of 9 : 1 to 3 : 1.

[0071] Preferably, if at least one alcohol having one or more OH-groups is present as further organic solvent ingredient a4), it is present in an amount in the range of 0 wt.-% or 0.01 wt.-% to 20.0 wt.-%, more preferably in an amount in the range of 0 wt.-% or 0.02 wt.-% to 15.0 wt.-%, even more preferably in an amount in the range of 0 wt.-% or 0.03 wt.-% to 12.5 wt.-%, still more preferably in an amount in the range of 0 wt.-% or 0.05 wt.-% to 10.0 wt.-%, in each case based on the total weight of the composition.

[0072] Preferably, the solvent-borne composition used in step 1) comprises as ingredient a1) at least one aliphatic hydrocarbon, preferably branched, preferably at least one aliphatic hydrocarbon a1) having 2 to 20 carbon atoms, more preferably 3 to 18 carbon atoms, even more preferably 4 to 17 carbon atoms, still more preferably 5 to 15 carbon atoms, yet more preferably 5 or 6 or 7 or 8 to 15 or 14 or 13 carbon atoms, and further comprises at least one alcohol a4) having one or more OH-groups and preferably having 3 to 10 carbon atoms, preferably a monomeric alcohol having one or more OH-groups, preferably a monomeric alcohol having exactly one OH-group, wherein preferably the amount of the at least one aliphatic hydrocarbon a1) in wt.-% exceeds the amount of the at least one alcohol a4) having one or more OH-groups in wt.-%, preferably wherein the relative weight ratio of the at least one aliphatic hydrocarbon a1) to the at least one alcohol a4) having one or more OH-groups is in the range of 9 : 1 to 3 : 1, and wherein the at least one aliphatic hydrocarbon a1) and the at least one alcohol a4) having one or more OH-groups are in particular present in the solvent-borne composition when the optionally coated substrate used in step 1) is a thermoplastic or a fiber-reinforced composite or a glass substrate.

[0073] Ingredient a2) of the solvent-borne composition

[0074] Ingredient a2) is at least one organometallic acid salt as ingredient a2), the metal of which is selected from Ti and Zr. Thus, the metal acid salt corresponds to a titanate and a zirconate.

[0075] Preferably, the solvent-borne composition used in step 1) comprises ingredient a2) in an amount of at least 0.5 wt.-%, more preferably at least 0.75 wt.-%, even more preferably at least 1.0 wt.-%. Preferably, the solvent-borne composition used in step 1) comprises ingredient a2) in an amount of at most 10.0 wt.-%, more preferably at most 7.5 wt.-%, even more preferably at most 5.0 wt.-%. Preferably, the solvent-borne composition used in step 1) comprises ingredient a2) in an amount in the range of 0.1 wt.-% to 15.0 wt.-%, more preferably 0.25 wt.-% to 12.0 wt.-%, even more preferably 0.5 wt.-% to 10.0 wt.-%, still more preferably 0.75 wt.-% to 7.5 wt.-%, yet more preferably 1.0 wt.-% to 5.0 wt.-%, in each case based on the total weight of the composition.

[0076] Preferably, especially when the optionally coated substrate used in step 1 ) is a metal substrate, the solvent-borne composition used in step 1 ) comprises component a2) in an amount in the range of 0.50 wt.-% to 7.50 wt.-%, more preferably 0.75 wt.-% to 5.0 wt.-%, even more preferably 1.0 wt.-% to 4.0 wt.-%, still more preferably 1.5 wt.-% to 3.5 wt.-%, in each case based on the total weight of the composition.

[0077] Preferably, especially when the optionally coated substrate used in step 1 ) is a thermoplastic or a fiber-reinforced composite material or a glass substrate, the solvent-borne composition used in step 1 ) comprises component a2) in an amount in the range of 0.25 wt.-% to 7.5 wt.-%, more preferably 0.5 wt.-% to 6.5 wt.-%, even more preferably 0.75 wt.-% to 6.0 wt.-%, still more preferably 1.0 wt.-% to 5.0 wt.-%, in each case based on the total weight of the composition.

[0078] Preferably, the one or more organic radicals of the metal salt component a2) have 1 to 20 carbon atoms. Preferably, the one or more organic radicals are bound to titanium and / or zirconium via a divalent oxygen atom. An example of such an organic radical is an acetylacetonate radical - preferably, component a2) is a metal alkoxide, more preferably, wherein each alkoxide radical represents an -O-Ci-C8 radical, more preferably an -O-C3-C8 radical. Examples of alkoxide radicals are n-butyl alkoxide, n-propyl alkoxide, isopropyl alkoxide. The most preferred titanate and / or zirconate is tetra-n-butoxyzirconate (available under the trade name Tyzor® NBZ), tetrapropyl titanate (available under the trade name Tyzor® TPT by Dorf Ketal) and titanium acetylacetonate (available under the trade names Tyzor® AA 75, Tyzor® AA 65 and Tyzor® AA 105 by Dorf Ketal).

[0079] Preferably, component a2) is a metal alkoxide, the metal of which is selected from Ti and Zr. Preferably, each alkoxide radical has 3 to 8, more preferably 3 to 6, even more preferably 3 to 4 carbon atoms.

[0080] Component a3) of the solvent-borne composition

[0081] Component a3) is at least one organosilane, which is preferably present in an amount of up to 10.0 wt.-%, based on the total weight of the composition. The at least one organosilane can be present in its at least partially hydrolyzed form. If the amount of component a3) exceeds 10.0 wt.-%, the solvent-borne composition used in step 1) can show worse adhesion promoting properties and adhesion failure can be observed.

[0082] Preferably, the solvent-borne composition used in step 1) comprises component a3) in an amount of at least 0.5 wt.-%, more preferably at least 0.75 wt.-%, even more preferably at least 1.0 wt.-%. Preferably, the solvent-borne composition used in step 1) comprises component a3) in an amount of at most 9.5 wt.-%, more preferably at most 7.5 wt.-%, even more preferably at most 5.0 wt.-%. Preferably, the solvent-borne composition used in step 1) comprises component a3) in an amount in the range of 0.1 wt.-% to 10.0 wt.-%, more preferably 0.25 wt.-% to 8.0 wt.-%, even more preferably 0.5 wt.-% to 6.0 wt.-%, still more preferably 0.75 wt.-% to 5.0 wt.-%, yet more preferably 1.0 wt.-% to 5.0 wt.-%, in each case based on the total weight of the composition.

[0083] Preferably, in particular when the optionally coated substrate used in step 1) is a thermoplastic or a fiber-reinforced composite material or a glass substrate, the solvent-borne composition used in step 1) comprises component a3) in an amount in the range of 0.25 wt.-% to 7.5 wt.-%, more preferably 0.5 wt.-% to 6.5 wt.-%, even more preferably 0.75 wt.-% to 6.0 wt.-%, still more preferably 1.0 wt.-% to 5.0 wt.-%, in each case based on the total weight of the composition.

[0084] Preferably, the molar ratio of the at least one component a2) to the at least one component a3) in the solvent-borne composition is in the range of 1 : 0.01 to 1 : 5, in particular when the optionally coated substrate used in step 1) is a thermoplastic or a fiber-reinforced composite material or a glass substrate.

[0085] A plurality of organosilanes can be used as component a3). The organosilane can be monomeric, oligomeric or polymeric. In particular, monomeric silanes are preferred when the optionally coated substrate used in step 1) is a metal substrate.

[0086] Preferably, the at least one organosilane used as component a3) contains (i) at least one hydrolysable group X and (ii) at least one non-hydrolysable organic group, which optionally and preferably carries or represents at least one functional group. The functional group (such as an OH-group) can be present in masked form, for example, it can be masked by a protecting group which can be eliminated under hydrolytic conditions. Preferably, a divalent spacer unit can be located between the functional groups, for example, within the non-hydrolysable organic group, when the functional group represents an amino group, such that the functional groups are not directly attached to the Si-atom. However, the functional group can also be directly attached to the Si-atom, for example, in case the functional group is a vinyl group. Preferably, the functional group is selected from the group consisting of amino groups (including primary and secondary amino groups), epoxy groups, thiol groups, vinyl groups and (meth)acrylic acid groups.

[0087] Preferably, the at least one organosilane used as component a3) contains (i) at least one hydrolysable group X and (ii) at least one non-hydrolysable organic group, which carries at least one functional group, more preferably at least one amino group, in particular when the optionally coated substrate used in step 1) is a metal substrate.

[0088] Preferably, the at least one organosilane used as component a3) contains (i) at least one hydrolysable group X and (ii) at least one non-hydrolysable organic group, which carries or represents, preferably represents, at least one functional group, more preferably at least one ethylenically unsaturated group, even more preferably at least one vinyl and / or (meth)acrylic acid group, in particular when the optionally coated substrate used in step 1) is a thermoplastic or a fiber-reinforced composite material or a glass substrate.

[0089] Preferably, the organosilane component a3) comprises at least two, preferably at least three, hydrolysable groups X, wherein X is preferably an alkoxy group. The hydrolysable groups X can each be identical, or at least two of these groups can each be different from one another. Preferably, the hydrolysable groups X are alkoxy groups, in particular Ci-C4alkoxy groups. Particularly preferred are methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy and tert-butoxy groups. Most preferred are ethoxy and methoxy groups.

[0090] Preferably, the at least one organosilane component a3) has a number average molecular weight in the range of 100 g / mol to 2000 g / mol, more preferably 250 g / mol to 1800 g / mol, even more preferably 300 g / mol to 1500 g / mol, still more preferably 350 g / mol to 650 g / mol.

[0091] The non-hydrolysable organic group is preferably selected from the group consisting of aliphatic groups having 1 to 24 carbon atoms, cycloaliphatic groups having 3 to 12 carbon atoms, aromatic groups having 6 to 12 carbon atoms, and araliphatic groups having 7 to 18 carbon atoms, each of these groups optionally containing or being at least one functional group, which group in turn can optionally be masked by at least one protecting group, which protecting group can be eliminated under hydrolytic conditions. Furthermore, each of the aforementioned aliphatic, cycloaliphatic, aromatic and araliphatic groups can contain one or more heteroatoms such as N, O and / or S, and / or heteroatom groups.

[0092] Examples of organosilanes having at least one non-hydrolysable organic group selected from the group consisting of aliphatic groups having 1 to 24 carbon atoms are methyltrimethoxysilane (MTMS), methyltriethoxysilane (MTES), methyltripropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, ethyltriisopropoxysilane, octyltrimethoxysilane, isobutyltriethoxysilane, isobutyltrimethoxysilane, octyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane, and decyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, and also 1,2-bis(triethoxysilyl)ethane and 1,2-bis(trimethoxysilyl)ethane. Examples of organosilanes having at least one non-hydrolysable organic group selected from the group consisting of aromatic groups having 6 to 12 carbon atoms are phenyltrimethoxysilane (PHS), phenyltriethoxysilane, phenyltripropoxysilane and phenyltriisopropoxysilane. Examples of organosilanes having at least one non-hydrolysable organic group selected from the group consisting of araliphatic groups having 7 to 18 carbon atoms are benzyltrimethoxysilane, benzyltriethoxysilane, benzyltripropoxysilane and benzyltriisopropoxysilane.

[0093] The organosilane can comprise at least one Si-containing group, such as exactly one such group (as in the case of a monosilane) or two or more such groups (as in the case of a disilane or trisilane), as in the case of 1,2-bis(triethoxysilyl)ethane. It is also possible to use organosilanes having four, five, six or more silyl groups.

[0094] Organic silanes containing at least one primary and / or secondary amino group (which are particularly preferred when the optionally coated substrate used in step 1) is a metal substrate) are, for example, 3-aminopropyltrimethoxysilane (APS), 3-aminopropyltriethoxysilane, 3-aminopropyltriisopropoxysilane, 2-aminoethyltrimethoxysilane, 2-aminoethyltriethoxysilane, 2-aminoethyltriisopropoxysilane, aminomethyltrimethoxysilane, aminomethyltriethoxysilane, aminomethyltriisopropoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane (AEAPS), 3-(2-aminoethyl)aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltriisopropoxysilane, 2-(2-aminoethyl)aminoethyltrimethoxysilane, 2-(2-aminoethyl)aminoethyltriethoxysilane, 2-(2-aminoethyl)aminoethyltriisopropoxysilane, 3-(3-aminopropyl)aminopropyltrimethoxysilane, 3-(3-aminopropyl)aminopropyltriethoxysilane, 3-(3-aminopropyl)aminopropyltriisopropoxysilane, diethylenetriaminopropyltrimethoxysilane, diethylenetriaminopropyltriethoxysilane, N-(n-butyl)-3-aminopropyltrimethoxysilane, N-(n-butyl)-3-aminopropyltriethoxysilane, N-cyclohexylaminomethyltriethoxysilane, N-cyclohexylaminomethyltrimethoxysilane, N-ethyl-γ- aminoisobutyltrimethoxysilane, N-ethyl-γ-aminoisobutyltriethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, N-phenyl-γ- aminopropyltrimethoxysilane, N-phenyl-γ-aminopropyltriethoxysilane, γ-ureidopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, N-methyl-[3-(trimethoxysilyl)propyl]carbamate, and / or N-trimethoxysilylmethyl-O-methylcarbamate, and also bis[γ-(triethoxysilyl)propyl]amine, bis[y-(trimethoxysilyl)propyl]amine.

[0095] Organic silanes containing at least one thiol group are, for example, 3-mercaptopropyltrimethoxysilane (MPTMS), 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltriisopropoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane and / or 2-mercaptoethyltriisopropoxysilane.

[0096] Organosilanes containing at least one epoxy group (as an example for a hydroxyl group masked by a protecting group which can be eliminated under hydrolytic conditions) are, for example, 3-glycidyloxypropyltrimethoxysilane (GLYMO), 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltriisopropoxyoxysilane, 2-glycidyloxyethyltrimethoxysilane, 2-glycidyloxyethyltriethoxysilane, 2-glycidyloxyethyltriisopropoxyoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and / or β-(3,4-epoxycyclohexyl)ethyltriethoxysilane. Corresponding products are, for example, commercially available under the names Silquest® A-186 and A-187.

[0097] As organosilanes, preference is given to using at least one alkoxysilane having the structural formula (I)

[0098] A-R-Si(R') x (OR'')3- x

[0099] (I),

[0100] wherein

[0101] A is a functional group which is optionally masked by a protecting group which can be eliminated under hydrolytic conditions, or is H,

[0102] R is an aliphatic radical having 1 to 24 carbon atoms or having 1 to 12 carbon atoms, a cycloaliphatic radical having 3 to 12 carbon atoms, an aromatic radical having 6 to 12 carbon atoms or an araliphatic radical having 7 to 18 carbon atoms,

[0103] The R' radical is selected from the group of C1- to C 12 alkyl radicals,

[0104] R" is an aliphatic radical having 1 to 4 carbon atoms, and

[0105] x = 0 to 2.

[0106] Aliphatic radicals R mean in this context organic radicals which do not have aromatic groups, such as, for example, phenyl. Aliphatic radicals R can have 1 to 24 or 1 to 12 carbon atoms. Preferably, aliphatic radicals R have 2 to 12, more preferably 3 to 10 carbon atoms. Cycloaliphatic radicals R mean organic radicals which do not have aromatic groups, such as, for example, phenyl. Cycloaliphatic radicals R can have 3 to 12 carbon atoms, such as, for example, in the case of cyclopropyl or cyclohexyl. Aliphatic and cycloaliphatic radicals can also be saturated or unsaturated. An example of such an unsaturated aliphatic radical is vinyl, such as, for example, in the case of vinyltrimethoxysilane and / or vinyltriethoxysilane. Aromatic radicals R mean organic radicals which consist of aromatic groups, such as, for example, phenylene. Aromatic radicals R can have 6 to 12 carbon atoms. Aryl-aliphatic radicals R mean organic radicals which have not only aromatic groups but also aliphatic groups. Aryl-aliphatic radicals R can have 7 to 18 carbon atoms. In addition to carbon and hydrogen, the radicals R, like the aliphatic radicals R, can also contain heteroatoms, such as oxygen, nitrogen or sulfur. Furthermore, in each case further functional groups, such as ester groups or carbamato groups, can also be present. More preferably, R is an aliphatic radical having 1 to 12 carbon atoms or having 1 to 10 carbon atoms, very preferably 1 to 8 carbon atoms, and especially 1 to 6 carbon atoms. It is clear to the skilled person that the radicals R are divalent radicals.

[0107] Most preferred organosilanes are N-(2-aminoethyl)-3-aminopropylmethyl- dimethoxysilane (available from Evonik under the trade name Dynasylan® 1401 or from Momentive under the trade name Silquest A-2120), 3-aminopropyltrimethoxysilane (available under the trade name Dynasylan® AMMO), and 3-aminopropyltriethoxysilane (available under the trade name Dynasylan® AMEO or Silquest A-1100), in particular when the optionally coated substrate used in step 1) is a metal substrate.

[0108] Most preferred organosilanes are also vinyl-functional oligomeric silanes, in particular when the optionally coated substrate used in step 1) is a thermoplastic or a fiber-reinforced composite or a glass substrate. These are, for example, available from Evonik under the trade names Dynasylan® 6490, Dynasylan® 6498 and Dynasylan® 6598. Vinyltrimethoxysilane (Dynasylan® VTMO), vinyltriethoxysilane (Dynasylan® VTEO) and 3-methacryloyloxypropyltrimethoxysilane (Dynasylan® MEMO) are particularly preferred.

[0109] Preferably, the molar ratio of the one or more ingredients a2) to a3) to each other is in the range of 1 : 0.01 to 1 : 5.

[0110] Further optional ingredients of the solventborne composition

[0111] The solventborne composition can comprise one or more further optional ingredients, which are different from each other and also from ingredients a1) to a3) and optional ingredient a4).

[0112] Optionally, the composition comprises at least one colorant as ingredient a6), preferably in an amount in the range of 0 wt.-% or 0.01 wt.-% to 1.5 wt.-%, more preferably in an amount in the range of 0 wt.-% or 0.02 wt.-% to 1.0 wt.-%, even more preferably in an amount in the range of 0 wt.-% or 0.03 wt.-% to 0.75 wt.-%, still more preferably in an amount in the range of 0 wt.-% or 0.05 wt.-% to 0.5 wt.-%, in each case based on the total weight of the composition, in particular when the optionally coated substrate used in step 1) is a metal substrate.

[0113] Examples of colorants are pigments and dyes. The use of dyes is particularly preferred. The colorant can be inorganic or organic, preferably organic. Most preferred are organic dyes.

[0114] The colorant can be any colorant, in particular a colorant which is soluble in the one or more organic solvents present as ingredient a1). Red colorants are most preferred for externally applied adhesion promoters in the aerospace industry. For example, rhodamine colorants, such as rhodamine B, and azo colorants, such as Macrolex® Red H by Lanxess or Keyplast® Red H by Milliken, can be used.

[0115] The colorant is preferably added such that after the solventborne composition has been applied as adhesion promoter, it is visible where the solventborne composition has been applied. Furthermore, the operator can see on the color shade whether the amount of adhesion promoter applied is correct. If too much adhesion promoter is applied, the color shade is too dark, if too little adhesion promoter is applied, the color shade is too light.

[0116] However, for some applications, in particular when the optionally coated substrate used in step 1) is a thermoplastic or a fiber reinforced composite or a glass substrate, the presence of a colorant is not necessarily desirable, for example for window assembly applications: after assembly, some parts of the applied adhesion promoter layer can still be visible on the transparent substrate.

[0117] Optionally, the composition comprises at least one additive selected from the group consisting of reactive diluents and resins such as polymeric resins and mixtures thereof as component a5), preferably in an amount in the range of 0 wt.-% or 0.01 wt.-% to 7.5 wt.-%, more preferably in an amount in the range of 0 wt.-% or 0.02 wt.-% to 6.0 wt.-%, even more preferably in an amount in the range of 0 wt.-% or 0.03 wt.-% to 5.0 wt.-%, yet more preferably in an amount in the range of 0 wt.-% or 0.05 wt.-% to 4.0 wt.-%, in each case based on the total weight of the composition, in particular when the optionally coated substrate used in step 1) is a thermoplastic or a fiber reinforced composite or a glass substrate.

[0118] Reactive diluents with at least one epoxide group are particularly preferred. Examples are neopentyl glycol diglycidyl ether, 1,6-hexanediol-di-glycidyl ether and trimethylolpropane polyglycidyl ether. Preferably, the reactive diluents do not carry carbon-carbon double bonds. Nevertheless, such reactive diluents can generally also be used.

[0119] Resins which can be used are in particular rosin resins (which can be used in modified form, as in the case of maleic acid-modified rosin resins), colophonium resins, polyesters and polyurethanes. The resins can be solid or liquid. In the case of solid resins, they are preferably first dissolved in at least one organic solvent before being added to the composition.

[0120] Very preferred solvent-borne compositions, in particular when the optionally coated substrate used in step 1) is a thermoplastic or a fiber reinforced composite or a glass substrate, are solvent-borne compositions comprising, preferably consisting of:

[0121] at least one aliphatic hydrocarbon as organic solvent component a1) in an amount in the range of 75.0 wt.-% or 80 wt.-% to 99.0 wt.-%, more preferably 85.0 wt.-% to 98.5 wt.-%, even more preferably 85.0 wt.-% to 98.0 wt.-%, yet more preferably 87.5 wt.-% to 97.5 wt.-%, in each case based on the total weight of the composition,

[0122] component a2) in an amount in the range of 0.25 wt.-% to 7.5 wt.-%, more preferably 0.5 wt.-% to 6.5 wt.-%, even more preferably 0.75 wt.-% to 6.0 wt.-%, yet more preferably 1.0 wt.-% to 5.0 wt.-%, in each case based on the total weight of the composition,

[0123] component a3) in an amount in the range of 0.25 wt.-% to 7.5 wt.-%, more preferably 0.5 wt.-% to 6.5 wt.-%, even more preferably 0.75 wt.-% to 6.0 wt.-%, still more preferably 1.0 wt.-% to 5.0 wt.-%, in each case based on the total weight of the composition,

[0124] Optionally, and preferably, at least one alcohol having one or more OH-groups as further organic solvent component a4) in an amount in the range of 0 wt.-% or 0.01 wt.-% to 20.0 wt.-%, more preferably in an amount in the range of 0 wt.-% or 0.02 wt.-% to 17.5 wt.-%, even more preferably in an amount in the range of 0 wt.-% or 0.03 wt.-% to 15.0 wt.-%, still more preferably in an amount in the range of 0 wt.-% or 0.05 wt.-% to 12.5 wt.-%, in each case based on the total weight of the composition, and

[0125] Optionally, and preferably, component a5), i.e. at least one additive selected from the group consisting of reactive diluents and resins, such as polymeric resins, and mixtures thereof as component a5) in an amount in the range of 0 wt.-% or 0.01 wt.-% to 7.5 wt.-%, more preferably in an amount in the range of 0 wt.-% or 0.02 wt.-% to 6.0 wt.-%, even more preferably in an amount in the range of 0 wt.-% or 0.03 wt.-% to 5.0 wt.-%, still more preferably in an amount in the range of 0 wt.-% or 0.05 wt.-% to 4.0 wt.-%, in each case based on the total weight of the composition.

[0126] Optional step 2)

[0127] In optional step 2), the film obtained after step 1) is dried and / or cured.

[0128] In the sense of the present application, "drying" preferably means physical drying by at least partial evaporation of the organic solvent(s) component a1) present in the composition used, while "curing" further comprises chemical reactions between at least two components originally present in the composition and / or between at least one component originally present in the composition and suitable functional groups present on the surface of the substrate.

[0129] Drying and / or curing can preferably be carried out, for example, at temperatures in the range from 15 °C to 80 °C, more preferably at temperatures in the range from 18 °C to 60 °C, in particular at temperatures in the range from 20 °C or 23 °C to 50 °C. Preferably, however, drying and / or curing is carried out simply at room temperature (15 °C to 23 °C), preferably by blowing. Drying and / or curing is preferably carried out for a period of 5 minutes to 30 minutes, more preferably 10 minutes to 30 minutes. The length to be chosen depends on the ambient temperature and humidity. The dried and / or cured film represents the layer.

[0130] Preferably, by carrying out optional step 2), the ingredients a2) and / or a3) bind to the surface of the substrate and a hydrolysis reaction takes place. The hydrolyzed ingredients then form the adhesion-promoting layer. As already outlined above in connection with step 1), the resulting dry layer thickness is preferably below 1.0 pm, more preferably below 900 nm or below 800 nm, even more preferably below 700 nm or below 600 nm, still more preferably below 500 nm or below 400 nm, most preferably below 300 nm or 200 nm.

[0131] Step 3)

[0132] In step 3), a sealant composition different from the solvent-based composition used in step 1) is at least partially applied to the optionally dried and / or cured film obtained after step 1) or 2) to form a sealant film.

[0133] Any kind of contact can be used for the application according to step 3), such as brushing and / or spraying. Step 3) is preferably carried out at temperatures in the range from 0 °C to 60 °C, more preferably 5 °C to 45 °C. In particular, no heating is carried out.

[0134] Preferably, step 3) is carried out with a 2K compressed air supported cartridge equipment with a 2K low pressure or 2K high pressure dosing system. It can also be done manually.

[0135] Sealant composition used in step 3)

[0136] The sealant composition used in step 3) can be obtained by mixing the at least two separately present components A) and B) of the sealing system with each other. Preferably, the sealing system consists of components A) and B). For example, components A) and B) of the sealing system can be stored separately until they are mixed with each other in order to prepare the sealant composition. Component A) of the sealing system comprises at least one polymeric ingredient A1) containing two or more thiol groups, which is selected from the group consisting of polyethers, polythioethers, polysulfides, polythioether-sulfide ingredients and mixtures thereof, and component B) of the sealing system comprises at least one ingredient B0) which is suitable for curing the sealant composition by at least partially inducing a chemical transformation of the two or more thiol groups of ingredient A1).

[0137] Each of the two components A) and B) of the sealing system can contain water and / or at least one organic solvent. However, it is also possible and even preferred that no organic solvent and / or water is present.

[0138] The amount of water present in component A) is preferably less than 3.0 wt.-%, more preferably less than 2.0 wt.-%, even more preferably less than 1.0 wt.-%, still more preferably less than 0.5 wt.-%, in each case based on the total weight of component A). When at least one ingredient B1) and / or at least one ingredient B3) and / or at least one ingredient b4) is present in B) as ingredient B0) in each case, the amount of water present in component (B) is preferably less than 3.0 wt.-%, more preferably less than 2.0 wt.-%, even more preferably less than 1.0 wt.-%, still more preferably less than 0.5 wt.-%, in each case based on the total weight of component B). Ingredients B1), B3) and B4) will be defined hereinafter. When at least one ingredient B2) as manganese dioxide is present in B) as ingredient B0), the amount of water present in component B) is preferably less than 8.5 wt.-%, more preferably less than 7.5 wt.-%, even more preferably less than 7.0 wt.-%, still more preferably less than 6.0 wt.-%, in each case based on the total weight of component B). Ingredient B2) will be defined hereinafter.

[0139] If at least one organic solvent is present therein, the one or more organic solvents are preferably present in an amount of at most 70 wt.-% or at most 65 wt.-%, based on the total weight of the sealant composition, in particular when the sealant composition is a sprayable composition. In this case, the sealant composition preferably comprises a fraction of at most 60 wt.-% of the one or more organic solvents, in each case based on the total weight of the composition. Alternatively, if at least one organic solvent is present therein, in particular when the sealant composition is not a sprayable composition, the one or more organic solvents are preferably present in an amount of at most 10 wt.-%, based on the total weight of the sealant composition. In this case, the sealant composition preferably comprises a fraction of at most 7.5 wt.-%, more preferably at most 5 wt.-% of the one or more organic solvents, in each case based on the total weight of the composition. All customary organic solvents known to the person skilled in the art can be used as organic solvents. The term "organic solvent" is known to the person skilled in the art, in particular from Council Directive 1999 / 13 / EC of 11 March 1999. Examples of such organic solvents include heterocyclic, aliphatic or aromatic hydrocarbons, mono- or polyhydric alcohols (especially ethanol and / or propanol), ethers, esters, ketones, xylene, butanol, ethyl and butyl glycol and also their acetates, butyl diglycol, diethylene glycol dimethyl ether, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetone, isophorone or mixtures thereof. The solvents present can be the same as or different from one another.

[0140] Preferably, the sealant composition is obtainable by mixing components A) and B) in a weight ratio (component A) / component B) in the range of 100 : 1 to 1 : 1. More preferably, the mixing is in a weight ratio in the range of 100 : 1 to 1.1 : 1, even more preferably in a weight ratio in the range of 100 : 1 to 2 : 1, in particular in a weight ratio in the range of 100 : 1 to 3 : 1, most preferably in a weight ratio in the range of 20 : 1 to 4 : 1.

[0141] Component A) of the sealing system

[0142] Component A1)

[0143] Component A) of the sealing system comprises at least one polymeric ingredient A1 ) containing two or more thiol groups (mercapto groups), which is selected from the group consisting of polyethers, polythioethers, polysulfides, polythioether-sulfide ingredients and mixtures thereof, preferably from the group consisting of polythioethers, polysulfides, polythioether-sulfide ingredients and mixtures thereof, more preferably from the group consisting of polythioethers, polysulfide ingredients and mixtures thereof, in particular from the group consisting of polysulfide ingredients. The terms "polymer" and "polymeric" are known to the person skilled in the art and encompass polyadducts and polymerizates as well as polycondensates for the purpose of the present application. The term "polymer" includes both homopolymers and copolymers.

[0144] Due to the presence of thiol groups, A1 ) is necessarily a sulfur atom containing ingredient. The thiol groups of A1 ) can chemically react with ingredient B0) or a part thereof, e.g. with a suitable functional group thereof. For example, when ingredient B1 ) is present as ingredient B0), its epoxy groups can react and at least one of a hydroxyl thioether, a hydroxyl thioether sulfide and / or a hydroxyl sulfide moiety is formed. For example, when ingredient B2) is present as ingredient B0) (as containing manganese oxide), an S-S-bond is formed.

[0145] Preferably, polymeric ingredient A1 ) contains terminal thiol groups. Ingredient A1 ) can be branched or linear. Preferably, polymeric ingredient A1 ) is liquid at ambient conditions (18 °C to 23 °C, 50 % relative humidity).

[0146] Polymeric ingredients suitable for use as A1 ) are for example disclosed in US 2004 / 097643 A1 and WO 2016 / 128548 A1 and WO 2015 / 014876 A2.

[0147] If at least one polythioether is used as A1 ), it is preferably a liquid (at ambient conditions) polythioether. The polythioether can contain within the molecule up to about 50 mol-% of disulfide groups only. The corresponding polymer can then be named polythioether sulfide. Preferred compounds of this kind are described in WO 2015 / 014876 A2.

[0148] Preferably, the polymeric ingredient A1 ) has a number average molecular weight in the range of 500 g / mol to 10 000 g / mol, more preferably 900 g / mol to 5000 g / mol. Most preferred is a number average molecular weight in the range of 2500 g / mol to 6 000 g / mol, more preferably 3300 g / mol to 5000 g / mol, especially when A1 ) is at least one polysulfide. Examples of such polymers are for example commercially available polysulfides, for example commercially available as Thioplast® G131, Thioplast® G10, Thioplast® G12, Thiokol® LP 32 and / or Thiokol® LP 12. Also preferred is a polymeric ingredient A1 ) having a number average molecular weight in the range of 500 g / mol to 2 500 g / mol, more preferably 700 g / mol to 2000 g / mol or 800 g / mol to 1200 g / mol. In this case, examples of such polymers are for example commercially available polysulfides, for example commercially available as Thiokol® LP3, Thioplast® G4, or Thioplast® G44.

[0149] Optionally, at least two kinds of ingredient A1 ) are present in component (A) having different number average molecular weights: In addition to short chain polymers having a number average molecular weight in particular in the range of 500 g / mol to 2500 g / mol, particularly preferably in the range of 800 g / mol to 1500 g / mol, long chain polymers having a number average molecular weight in particular in the range of 2500 g / mol to 6000 g / mol, particularly preferably in the range of 3300 g / mol to 5000 g / mol can be present. Optionally, at least one of the aforementioned short chain polymers used in combination with at least one of the aforementioned long chain polymers can be replaced by at least one polymeric, oligomeric or monomeric mercaptan, which is preferably solid or liquid, has three mercaptan groups and a number average molecular weight in the range of 160 g / mol to 1200 g / mol. Alternatively, said mercaptan can be added further to the combination of at least one short chain polymer and at least one long chain polymer. Examples of such suitable mercaptans are thiocyanuric acid (1,3,5-triazine-2,4,6-trithiol) and benzene-1,3,5-trithiol (1,3,5-trimercaptobenzene). In case said mercaptan used is non-polymeric, it formally represents an optional ingredient A6) of component A), which will be defined below. Preferably, said at least one mercaptan, if present, is present in an amount in the range of 0.05 wt.-% to 3.0 wt.-% based on the total weight of component A).

[0150] The sulphur-containing polymer ingredient A1 ) preferably has a mercaptan content, referred to as reactive SH-groups, in the range of 0.5 wt.-% to 10.0 wt.-%, more preferably 0.8 wt.-% to 8.0 wt.-%, in particular 1.2 wt.-% to 7.0 wt.-%, relative to the total weight of A1 ). The mercaptan content can be determined by direct titration of the SH-terminated polymer with an iodine solution: the polymer is dissolved in a solvent mixture consisting of 40% by volume of pyridine and 60% by volume of benzene and titrated by stirring with a benzene iodine solution until a weak yellow colouring remains. Preferably, ingredient A1 ) has a total sulphur content in the range of 1 wt.-% to 50 wt.-%, more preferably 5 wt.-% to 45 wt.-%, in particular 12 wt.-% to 36 wt.-%. Preferably, ingredient A1 ) has an average functionality of reactive end groups per molecule of mercapto group in the range of 1.5 to 2.5 or 1.9 to 2.2. The functionality indicates the average number of mercapto groups per molecule. The functionality is calculated as the ratio of molecular weight to equivalent weight and can be determined by NMR. Preferably, ingredient A1 ) has an average glass transition temperature Tg measured according to AIRTECHNICAL TEST METHODS, June 1995, in the range of −80 °C to −30 °C or −60 °C to −40 °C. g .

[0151] Preferably, component A1 ) and the sealant composition as such are free of any ingredient comprising (meth)acrylate groups (methacrylate and / or acrylate groups).

[0152] Preferably, ingredient A1 ) is present in the sealant composition obtained after mixing components A) and B) of the sealing system with each other in an amount in the range of 50 wt.-% to 95 wt.-%, based on the total weight of the sealant composition.

[0153] Optional ingredients present in component A)

[0154] Component A) can optionally additionally contain at least one organosilane A2), at least one filler A3) and / or at least one pigment A4). The organosilane A2) can be the same or different from ingredient a3) as defined hereinabove and hereinafter.

[0155] The term "filler" is known to the skilled person, e.g. from DIN 55943 (date: October 2001). A "filler" for the purposes of the present application is preferably an ingredient which is essentially, preferably completely, insoluble in its surrounding medium, e.g. like each of components A) and B) and the sealant composition, and which is used in particular to adjust the viscosity and thixotropy of the components and the sealant composition, to adjust the specific density of the cured sealant and / or to improve the mechanical properties of the cured sealant. A "filler" differs from a "pigment" in the sense of the present application in their refractive index, the refractive index of a filler < 1.7, whereas the refractive index of a pigment > 1.7. Preferably, a "filler" for the purposes of the present application is an inorganic and / or organic filler. Examples of inorganic fillers are chalk and talc. Examples of organic fillers are powders made from temperature-resistant polymers such as polyamides, polysulfones, polyphenylene sulfides, polyether ketones and polymer hollow spheres. Preferably, the amount of filler present in component A) of the sealing system is in the range of 0 wt.-% to 55.0 wt.-%, more preferably in the range of 0 wt.-% to 50.0 wt.-%, even more preferably in the range of 0 wt.-% to 45.0 wt.-%, yet more preferably in the range of 0 wt.-% to 40.0 wt.-%, yet more preferably in the range of 0 wt.-% to 35.0 wt.-% or 0 wt.-% to 30.0 wt.-%, in particular in the range of 0 wt.-% to 25.0 wt.-%, in each case based on the total weight of component A). Preferably, the amount of any pigment present in component A) of the sealing system is in the range of 0 wt.-% to 35.0 wt.-%, more preferably in the range of 0 wt.-% to 30.0 wt.-%, even more preferably in the range of 0 wt.-% to 25.0 wt.-%, yet more preferably in the range of 0 wt.-% to 20.0 wt.-%, yet more preferably in the range of 0 wt.-% to 15.0 wt.-%, in each case based on the total weight of component A). The term "pigment" is known to the skilled person from e.g. DIN 55943 (date: October 2001). A "pigment" in the sense of the present application preferably means a component in the form of a powder or flake which is essentially, preferably completely, insoluble in its surrounding medium, e.g. like each of components A) and B) and the sealant composition, and which is a colouring agent and / or a substance which can be used as a pigment due to its magnetic, electrical and / or electromagnetic properties. Preferably, a "pigment" for the purposes of the present application is an inorganic and / or organic pigment. An example of an inorganic pigment is titanium dioxide.

[0156] Component A) of the sealing system can contain one or more optional ingredients A5 and / or A6).

[0157] When component B) of the sealing system comprises at least one ingredient B1 ) comprising two or more epoxy groups as ingredient B0), component A) can additionally contain and preferably contains at least one curing catalyst A5). Suitable curing catalysts are amines, in particular tertiary amines, amidines and / or guanidines. Examples are 1,4-diazabicyclo(2.2.2)octane, 1,5-diazabicyclo(4.3.0)non-5-ene (DBN) and 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU).

[0158] Component A6) can be a flame retardant, such as a phosphorus-containing flame retardant, in particular at least one phosphate ester. If a flame retardant is used, it is preferably liquid (at 1 bar and 23 °C). In case a flame retardant is present in component A), it is preferably present therein in an amount of 0.1 wt.-% to 30.0 wt.-%, more preferably 1.0 wt.-% to 25.0 wt.-%, in particular 5.0 wt.-% to 20.0 wt.-%, based on the total weight of component A). Component A6) can be a light stabilizer, in particular a UV stabilizer. Examples are, for example, sterically hindered amines (HALS: hindered amine light stabilizers). In principle, all commercially available light stabilizers of the Tinuvin® series or from other manufacturers can be used. Liquid light stabilizers are preferred. In case a light stabilizer is present in component A), it is preferably present therein in an amount of 0.05 wt.-% to 5.0 wt.-%, more preferably 0.1 wt.-% to 3.5 wt.-%, in particular 0.1 wt.-% to 2.0 wt.-%, based on the total weight of component A). In addition to the optionally present aforementioned organosilane component A2), component A6) can be a further adhesion promoter. Additionally or alternatively, other adhesion promoters can be used, such as the adhesion promoters subsumed under component a2) defined hereinbefore and hereinafter. In case a further adhesion promoter is present in component A), it is preferably present therein in an amount of 0.05 wt.-% to 5.0 wt.-%, more preferably 0.1 wt.-% to 3.5 wt.-%, in particular 0.1 wt.-% to 2.0 wt.-%, based on the total weight of component A). Component A6) can be an additive selected from the group consisting of antifoams, rheological additives, plasticizers such as phthalic acid esters and viscosity reducers, in particular non-reactive viscosity reducers such as hydrocarbon mixtures based on naphthalene derivatives and / or indan-coumarone resins, tall oil and rapeseed oil methyl ester (biodiesel) and rapeseed oil and / or other ester-based diluents, and mixtures of such additives. In case at least one additive is present in component A), it is preferably present therein in an amount of 0.05 wt.-% to 40.0 wt.-%, more preferably 0.1 wt.-% to 30.0 wt.-%, in particular 0.1 wt.-% to 20.0 wt.-%, based on the total weight of component A). In particular, in case at least one antifoam is present, its amount is preferably in the range of 0.1 wt.-% to 2.5 wt.-%, based on the total weight of component A). In particular, in case at least one reactive diluent is present, its amount is preferably in the range of 0.1 wt.-% to 20.0 wt.-%, based on the total weight of component A). In particular, in case at least one rheological additive is present, its amount is preferably in the range of 0.1 wt.-% to 5.0 wt.-%, based on the total weight of component A).In particular, in the presence of at least one plasticizer, the amount thereof is preferably in the range of 0.1 wt.-% to 2.5 wt.-%, based on the total weight of component A). In particular, in the presence of at least one viscosity-reducing agent, the amount thereof is preferably in the range of 0.1 wt.-% to 20.0 wt.-%, based on the total weight of component A). As outlined above in connection with component A1 ), component A6) can further be at least one non-polymeric mercaptan having three mercaptan groups and a number average molecular weight in the range of 160 g / mol to 800 g / mol. Preferably, the at least one non-polymeric mercaptan, if present, is present as component A6) in an amount in the range of 0.05 wt.-% to 3.0 wt.-%, more preferably 0.05 wt.-% to 1.5 wt.-%, in each case based on the total weight of component A).

[0159] Component B) of the sealing system

[0160] Component B0)

[0161] Component B) of the sealing system comprises at least one component B0) which is suitable for hardening the sealant composition by at least partially inducing a chemical transformation of two or more mercaptan groups of component A1 ). In other words, component B0) or a part thereof can chemically react with the mercaptan groups of component A1 ). Thus, component B0) denotes a curing agent. The chemical transformation produced can apply to all mercaptan groups of component A1 ) or only a part of the mercaptan groups of component A1 ). However, preferably, not only partially, but essentially all mercaptan groups of component A1 ) are induced to chemical transformation.

[0162] Preferably, the at least one component B0) is selected from the group consisting of a component comprising two or more epoxy groups (component B1 ), a component which is a metal oxide and / or metal peroxide, in particular manganese dioxide (component B2), a component which is an organic peroxide (component B3), a component comprising two or more vinyl groups (component B4), and mixtures thereof, more preferably from the group consisting of a component comprising two or more epoxy groups (component B1 ), a component which is a metal oxide and / or metal peroxide, in particular manganese dioxide (component B2), and mixtures thereof, in particular denoting at least one component comprising two or more epoxy groups as component B1 ), or at least one metal oxide and / or metal peroxide, in particular manganese dioxide, as component B2).

[0163] Preferably, component B0) is present in component B) of the sealing system for preparing the sealant composition applied in step 3) in an amount in the range of 30 wt.-% to 100 wt.-%, based on the total weight of component B).

[0164] component B1)

[0165] Component B1) comprises two or more epoxy groups. Preferably, the epoxy groups are present as end groups in B1). Component B1) can be monomeric, oligomeric or polymeric. Preferably, B1) is aliphatic and / or aromatic.

[0166] Preferably, component B1) is present in component B) of the sealing system for preparing the sealant composition applied in step 3) in an amount in the range of 50 wt.-% to 100 wt.-%, based on the total weight of component B). Preferably, B1) has an epoxy functionality of 2.0 to 5.0, more preferably 2.0 to 3.0, in particular 2.2 to 2.8.

[0167] Component B1) is in particular selected from the group consisting of diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F and aliphatic polyglycols and / or hydantoin epoxy derivatives. Furthermore, epoxy-terminated polysulfides or polysulfide sulfides and / or epoxidized polysulfides can be used. Also particularly preferred are at least one epoxy- novolak resin (epoxidized phenol formaldehyde resin), preferably a crosslinked epoxy novolak resin. It is also possible that more than one component B1) can be used based on several of the above categories, for example a bisphenol A / F epoxy resin or a bisphenol F novolak resin. For example, component B) can additionally contain diluents in order to adjust the viscosity and flexibility. Examples of diluents are 1,4-butanediol diglycidyl ether, 2-ethylhexyl- glycidyl ether and 1,6-hexanediol diglycidyl ether.

[0168] Preferably, B1) is at least one epoxy-terminated polysulfide polymer and / or polysulfide polymer and / or polysulfide sulfide polymer without terminal mercapto groups, which acts as a curing agent due to the two terminal epoxy groups. Such polymers are preferably present as liquid or highly viscous polymers, which have an epoxy equivalent weight in particular in the range of 200 to 800 g / eq. Preferably, the epoxy / epoxide equivalent weight of B1) is in the range of 120 g / eq to 800 g / eq, particularly preferably in the range of 140 g / eq to 700 g / eq, and most preferably in the range of 170 g / eq to 400 g / eq.

[0169] Most especially preferred is component B1 ) based on a bisphenol A epoxy resin having an epoxy equivalent weight in the range of 170 g / eq to 200 g / eq, a bisphenol F resin having an epoxy equivalent weight in the range of 150 g / eq to 180 g / eq and an epoxy novolak resin having an epoxy equivalent weight in the range of 160 g / eq to 220 g / eq. Examples of suitable commercial products are for example bisphenol F epoxy resins such as DEN 354 (Olin Epoxy), bisphenol A resins such as DER 336, DER 331 (Olin Epoxy), bisphenol A / F epoxy resins such as DER 351, DER 324, DER 335 (Olin Epoxy), epoxy novolak resins such as DEN 431, DEN 438, DEN 439 (Olin Epoxy), epoxy-terminated prepolymers based on polysulfide and / or polythioether such as Thioplast EPS 25 (AkzoNobel), epoxy-terminated reactive diluents based on alcohol / glycol such as 1,4-butanediol diglycidyl ether (DER 731 ; Olin Epoxy), and 1,6-hexanediol diglycidyl ether (DER 734; Olin Epoxy).

[0170] Preferably, the molar ratio of all components B1 ) to all components A1 ) is in the range of 0.90 : 1 to 2 : 1.

[0171] Component B2)

[0172] Component B2) is at least one metal oxide and / or metal peroxide, in particular manganese dioxide. Manganese dioxide means manganese (IV) oxide. Another suitable component B2) is calcium peroxide.

[0173] Preferably, component B2) is present in component B) for preparing the sealing system of the sealant composition applied in step 3) in an amount in the range of 30 wt.-% to 90 wt.-%, based on the total weight of component B).

[0174] Component B3)

[0175] Component B3) is at least one organic peroxide. An example of a suitable organic peroxide is an organic hydroperoxide, such as cumene hydroperoxide.

[0176] Preferably, component B3) is present in component B) for preparing the sealing system of the sealant composition applied in step 3) in an amount in the range of 30 wt.-% to 100 wt.-%, based on the total weight of component B).

[0177] Component B4)

[0178] Component B4) comprises two or more vinyl groups. Preferably, the vinyl groups are present as end groups in B4). Component B4) can be monomeric, oligomeric or polymeric and is preferably monomeric. Preferably, B4) is aliphatic and / or aromatic. Examples of component B4) are divinyl ethers such as diethylene glycol divinyl ether, triethylene glycol divinyl ether and butanediol divinyl ether.

[0179] Preferably, component B4) is present in component B) of the sealing system for preparing the sealant composition applied in step 3) in an amount in the range of 30 wt.-% to 100 wt.-% based on the total weight of component B).

[0180] If component B4) is used as component B0) of component B), it is preferably present in combination with at least one radical generator. Examples of suitable radical generators are 1-hydroxycyclohexyl phenyl ketone and 2-hydroxy-2-methyl-1-phenylpropan-1-one.

[0181] Optional components B5) and B6) and B7)

[0182] Component B) of the sealing system can contain one or more optional components B5). Component B5) can be an additive selected from the group consisting of reactive diluents such as bisoxazolidines and / or aldehyde imines and plasticizers such as phthalates. In particular, when component B) of the sealing system comprises at least one component B2), in particular manganese dioxide, at least one plasticizer component B5) is present in component B).

[0183] In particular, in case at least one reactive diluent is present, the amount thereof is preferably in the range of 0.1 wt.-% to 20.0 wt.-% based on the total weight of component B). In particular, in case at least one plasticizer is present, the amount thereof is preferably in the range of 10.0 wt.-% to 70.0 wt.-% based on the total weight of component B).

[0184] Component B) can additionally and preferably contains at least one curing catalyst B6).

[0185] As outlined above, when component B) of the sealing system comprises at least one ingredient B1 ) which in turn comprises two or more epoxy groups as ingredient B0), at least one curing catalyst, if present, is preferably present in component A) as ingredient A5) and is not present in component B). In this case, suitable curing catalysts are amines, in particular tertiary amines, amidines and / or guanidines. Examples are 1,4-diazabicyclo(2.2.2)octane, 1,5-diazabicyclo(4.3.0)non-5-ene (DBN) and 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU).

[0186] When component B) of the sealing system comprises at least one ingredient B2) as ingredient B0), at least one curing catalyst B6) is preferably present in component B). In this case, suitable curing catalysts are, for example, tetrabenzylthiuram disulfide, diphenylguanidine and / or zinc bis(diethyldithiocarbamate).

[0187] When component B) of the sealing system comprises at least one ingredient B3) as ingredient B0), at least one curing catalyst B6) is preferably present in component B). In this case, suitable curing catalysts are, for example, zinc bis(diethyldithiocarbamate).

[0188] When component B) of the sealing system comprises at least one ingredient B4) as ingredient B0), at least one curing catalyst B6) is preferably present in component B). In this case, suitable curing catalysts are, in particular, suitable photoinitiators, such as acetophenone, benzoin ethers and / or benzoyl oximes. Curing is preferably carried out by UV light.

[0189] Component B) can contain at least one flame retardant B7). Ingredient B7) can be a phosphorus-containing flame retardant, in particular at least one phosphate ester. If a flame retardant is used, it is preferably liquid (at 1 bar and 23 °C). In the case of a flame retardant present in component A), it is preferably present therein in an amount of 5.0 wt.-% to 65.0 wt.-%, more preferably 25.0 wt.-% to 65.0 wt.-%, in particular 40.0 wt.-% to 65.0 wt.-%, in each case based on the total weight of component B).

[0190] Optional step 4)

[0191] In optional step 4), the sealing agent film obtained after step 3) is cured. Preferably, curing is carried out at ambient temperature (18 °C to 23 °C) or at elevated temperature (such as 80 °C) for 0.5 hours to 14 days.

[0192] Preferably, the curing according to optional step 4) means chemical curing, such as chemical crosslinking, at ambient temperature or at elevated temperature. In case at least one ingredient B1) or B4) is used as ingredient B0), the curing can additionally or alternatively be induced by UV light.

[0193] Preferably, the sealant composition is applied in a dry layer thickness in the range of 15 pm to 20 mm, more preferably 50 pm to 15 mm, in particular 0.5 mm to 10 mm.

[0194] Sealing substrates

[0195] A further subject matter of the present application is a sealed substrate, which is obtainable by the method of the present application, which is preferably suitable for use in the aircraft and / or aerospace industry.

[0196] All preferred embodiments described above in connection with the method of the present application and its preferred embodiments are also preferred embodiments of the sealed substrate of the present application.

[0197] Use as adhesion promoters

[0198] A further subject matter of the present application is the use of the solvent-type composition as used and defined in step 1) of the preceding method as an adhesion promoting composition, in particular for enhancing the adhesion between the surface of an optionally pre-coated substrate and a subsequently applied sealant film.

[0199] All preferred embodiments described above in connection with the method of the present application and the sealed substrate of the present application and its preferred embodiments are also preferred embodiments of the use of the present application.

[0200] The sealant film is preferably obtained in the manner as defined in step 3) of the preceding method, in particular by applying a sealant composition obtainable by mixing at least two separately present components A) and B) of a sealing system with each other to a film already present on the surface of an optionally pre-coated substrate, wherein component A) of the sealing system comprises at least one polymeric ingredient A1) containing two or more thiol groups, which is selected from the group consisting of polyethers, polythioethers, polysulfides, polythioether-sulfide ingredients and mixtures thereof, and wherein component B) of the sealing system comprises at least one ingredient b) suitable for curing the sealant composition by at least partially inducing chemical transformation of the two or more thiol groups of ingredient A1), said film having been formed by at least partially applying a solvent-type composition as defined in step 1) of the preceding method to said surface.

[0201] Solvent-borne compositions

[0202] A further subject-matter of the present application is the solvent-type composition as defined in connection with step 1) of the preceding method itself, wherein the at least one aliphatic hydrocarbon constituent a1) present therein preferably has 8 to 20 carbon atoms.

[0203] All preferred embodiments described above in connection with the method of the present application, the sealed substrate of the present application and the use of the present application and preferred embodiments thereof are also preferred embodiments of the solvent-type composition of the present application.

[0204] Kit of parts

[0205] A further subject-matter of the present application is a kit-of-parts comprising at least the sealing system as defined in connection with step 3) of the preceding method and the solvent-type composition as defined in connection with step 1) of the preceding method or the solvent-type composition of the present application, separated from each other, preferably consisting of at least the sealing system as defined in connection with step 3) of the preceding method and the solvent-type composition as defined in connection with step 1) of the preceding method or the solvent-type composition of the present application, separated from each other, which sealing system comprises at least two components A) and B) separated from each other.

[0206] All preferred embodiments described above in connection with the method of the present application, the sealed substrate of the present application, the use of the present application and the composition of the present application and preferred embodiments thereof are also preferred embodiments of the kit-of-parts of the present application.

[0207] Method

[0208] 1. Peel test

[0209] Peeling test I:

[0210] After curing for 14 days at room temperature (23 °C) and 50% relative humidity, the peeling is produced and tested in a manner equivalent to DIN 65262-1 (07-2017). It is assessed whether a cohesive failure or an adhesive failure occurs.

[0211] Peeling test II:

[0212] After applying the sealant to the surface of the substrate tested, a small strip of wire mesh is positioned inside the sealant so that the sealant is pushed through the wire mesh, laid parallel to the substrate with a rough distance of 1-2 mm. Some sealant is applied on top and evenly formed. After curing for 14 or 21 days at room temperature (23 °C) and 50% relative humidity, the wire mesh is pulled at an angle of approximately 180°, similar to the appropriate peeling test according to DIN 65262-1 (07-2017). It is assessed whether a cohesive failure or an adhesive failure occurs.

[0213] 2. Number average molecular weight

[0214] The number average molecular weight of the components A21) and B1) is determined by GPC (gel permeation chromatography) against polystyrene standards. THF (tetrahydrofuran) is used as mobile phase. The number average molecular weight of the organosilane components A2) and a3) is determined by NMR spectroscopy in case of monomeric and oligomeric components and by GPC in case of polymeric components.

[0215] 3. Flash point

[0216] The flash point is determined using the apparatus Miniflash FLPL according to ASTM D6450.

[0217] 4. Dry layer thickness

[0218] REM / EDX (scanning electron microscope / energy dispersive X-ray analysis) is used to measure the dry layer thickness, in particular of the film obtained after optional step 2) of the process of the present application.

[0219] 5. Crazing

[0220] The craze test is performed according to ASTM F-484:2008 using a PMMA substrate (type C). Examples

[0221] The following examples further illustrate the present application, but are not to be construed as limiting its scope. ‘Pbw’ means parts by weight. If not otherwise defined, ‘parts’ means ‘parts by weight’.

[0222] 1. Adhesion promoting compositions

[0223] 1.1 A number of exemplary compositions E1a to E1h are prepared by mixing the ingredients listed in Tables 1a and 1b with each other in the order given in Tables 1a and 1b.

[0224] Table 1a - Compositions E1a to E1d

[0225]

[0226] A commercially available C 9-12 The isoparaffin mixture is used as isoparaffin 1. A commercial product containing tetra-n-butoxyzirconium (87 wt.-%) in n-butanol is used as zirconate. NPGDE is neopentyl glycol diglycidyl ether. HDDGE is 1,6-hexanediol diglycidyl ether. TMPPGE is trimethylolpropane polyglycidyl ether. A commercially available oligomeric siloxane containing vinyl and ethoxy groups is used as silane 1. A commercial organosilane, namely 3-methacryloyloxypropyltrimethoxysilane, is used as silane 2.

[0227] Table 1 b - Compositions E1 e to E1 h

[0228]

[0229] The compositions E1 a to E1 h were prepared as follows: The organic solvent used was weighed into a closable glass bottle. Then, the zirconate was added. The glass bottle was closed and carefully shaken. Next, if applicable, one of NPGDE, HDDGE, or TMPPGE was added. The glass bottle was closed and carefully shaken. Then, silane 1 or a mixture of silane 1 and silane 2 was added. The glass bottle was closed and carefully shaken. The resulting composition was carefully shaken from time to time to dissolve all ingredients. After at most 24 h, in all cases a solution was obtained.

[0230] 1.2 A number of further exemplary compositions E2a to E2d were prepared by mixing the ingredients listed in Table 2 with each other in the order given in Table 2. The preparation was carried out in the manner described above in item 1.1. The comparative exemplary composition E2e was prepared in the same manner.

[0231] As zirconate a commercial product, namely tetraisopropyl titanate, was used.

[0232] Table 2 - Compositions E2a to E2d and E2e

[0233]

[0234] E2e differs from E2c in that isoalkane 1 has been replaced by isopropanol.

[0235] 1.3 A number of exemplary compositions E3a to E3h were prepared by mixing the ingredients listed in Tables 3a and 3b with each other in the order given in Tables 3a and 3b.

[0236] Table 3a - Compositions E3a to E3d

[0237]

[0238] As zirconate a commercial product was used, namely tetra-n-butoxy zirconium (87 wt.-%) contained in n-butanol. Resin 1 is a commercially available dispersion comprising 75 wt.-% of a modified polyurethane resin in ethyl acetate. Resin 2 is a commercially available maleic acid-modified rosin resin. Resin 3 is a commercially available low viscosity rosin resin. Resin 4 is a commercially available resin ester. Resin 5 is a commercially available modified adhesive resin. Resin 6 is a commercially available modified rosin resin. Resin 7 is a commercially available polymeric rosin gum resin.

[0239] Table 3b - Compositions E3e to E3h

[0240]

[0241] 2. Preparation of sealed substrates and investigation of their properties

[0242] 2.1 Sealed substrates prepared by using exemplary adhesion promoting compositions E1a to E1h

[0243] A substrate S1, namely Europlex® F7 (S1 ), was provided. Europlex® F7 is a substrate sheet made of fireproof polycarbonate.

[0244] The substrate S1 was cleaned with the appropriate solvent (mixture) according to the recommendations of the substrate manufacturer. In this way, any dirt, grease, oil or dust was removed from the substrate surface before the subsequent application of the adhesion promoting composition.

[0245] One of the adhesion promoting compositions E1a to E1h was then applied to the cleaned surface of the substrate S1 in a very thin layer (dry layer thickness < 200 nm) by the “wiping-on” method. This method means that the adhesion promoting composition used is applied to this surface of the substrate by brush, soft lint-free wiping cloth or by a suitable pen with a felt tip, followed by a flash-off time during which at least a part of the organic solvents present can evaporate and a hydrolysis reaction involving the ingredients present in the applied composition is allowed to take place. The length of the flash-off time depends on the ambient temperature and humidity. Here, a flash-off time of 30 minutes was used.

[0246] After that, an aerospace sealant was applied on top. In all cases, the commercially available sealant Naftoseal® MC-238M B-2 (available from Chemetall GmbH) was used, which is a two-component manganese dioxide-cured liquid polysulfide sealant.

[0247] After application to the surface of the substrate, the applied sealant was cured for 21 days at room temperature (23 °C) and 50% relative humidity. The sealed substrate S1 was then subjected to a peel test according to the method disclosed in the ‘Methods’ section (Peel Test II therein). The results are summarized in Table 4.1 below. C.f. means cohesive failure.

[0248] Table 4.1 - Peel test results

[0249]

[0250] From Table 4.1 it is evident that for all tested substrates excellent adhesion could be achieved (no adhesive failure observed, only c.f.).

[0251] 2.2 Sealed substrates prepared by using exemplary adhesion promoting compositions E2a to E2d

[0252] Two substrates S1 and S2 were provided, namely Europlex® F7 (S1) and stretched PMMA (MIL-P-25690) (S2). Stretched PMMA (MIL-P-25690) is a stretched polymethyl methacrylate material. The substrates were cleaned in the same way as described in project 2.1 and then one of the adhesion promoting compositions E2a to E2d was applied to the cleaned surface of each substrate in the same way as described in project 2.1. Then, a sealant was applied in the same way as described in project 2.1.

[0253] After application to the surface of the substrates, the applied sealant was cured for 14 days at room temperature (23 °C) and 50% relative humidity. The sealed substrates were then subjected to a peel test according to the method disclosed in the 'Methods' section (Peel Test I therein). The results are summarized in Table 4.2 hereinafter.

[0254] Table 4.2 - Peel test results

[0255]

[0256] From Table 4.2 it is evident that by using the adhesion promoting compositions E2a to E2d, 100% adhesion could be achieved for all tested different substrates S1 and S2 (no adhesion failure observed, cf. only).

[0257] 2.3 Sealed substrates prepared by using exemplary adhesion promoting compositions E3a to E3g

[0258] Different kinds of substrates were provided, namely substrate S1 and S3, S4 and S5. S3 is PMMA GS 249 (commercially available crosslinked polymethyl methacrylate material). S4 is Lexan® 9030 (commercially available polycarbonate sheet). S5 is Exolon® GP (commercially available polycarbonate material). The substrates were cleaned in the same way as described in project 2.1 and then some of the adhesion promoting compositions E3a to E3g were applied to the cleaned surface of some of the substrates in the same way as described in project 2.1. Then, a sealant was applied in the same way as described in project 2.1.

[0259] After application to the surface of the substrates, the applied sealant was cured for 14 days at room temperature (23 °C) and 50% relative humidity. The sealed substrates were then subjected to a peel test according to the method disclosed in the 'Methods' section (Peel Test II therein). The results are summarized in Table 4.3 hereinafter.

[0260] Table 4.3 - Peel test results

[0261]

[0262] As is apparent from Table 4.3, for all tested substrates, excellent adhesion can be achieved with the adhesion-promoting compositions E3a to E3h containing a resin (no adhesion failure observed, cf. only).

[0263] 2.4 Substrates treated with one of the exemplary adhesion-promoting compositions E2c and E2e

[0264] The substrate S2 (stretched PMMA; MIL-P-25690) is provided, cleaned in the same manner as described in item 2.1, and then one of the adhesion-promoting compositions E2c and E2e is applied to the cleaned surface of the substrate in the same manner as described in item 2.1.

[0265] After having been applied to the surface of the substrate, the chipping test is carried out according to the method disclosed in the ‘Methods’ section. In the case of the composition E2e (comparative), the test is stopped after 22 minutes, since substantial and intolerable chipping on the substrate has been observed. In the case of the composition E2c, the test does not need to be stopped, and only no to very little chipping is observed. This demonstrates the importance of the presence of an aliphatic hydrocarbon in the composition: in the case of replacing the aliphatic hydrocarbon with isopropyl alcohol, as in the case of the composition E2e, it leads to substantial and unwanted chipping.

Claims

1. A process for sealing an optionally pre-coated substrate, which process comprises at least steps 1) and 3) and optionally at least one of steps 2) and / or 4), namely 1) applying at least partially a solvent-borne composition onto the surface of an optionally pre-coated substrate to form at least partially a film on said surface, 2) optionally drying and / or curing the film obtained after step 1), 3) applying at least partially a sealant composition different from the solvent-borne composition used in step 1) onto the optionally dried and / or cured film obtained after step 1) or 2) to form a sealant film, wherein the sealant composition is obtainable by mixing with each other at least two separately present components A) and B) of a sealing system, wherein component A) of the sealing system comprises at least one polymeric ingredient A1) containing two or more thiol groups, the polymeric ingredient being selected from the group consisting of polyethers, polythioethers, polysulfides, polythioether-sulfide ingredients and mixtures thereof, and wherein component B) of the sealing system comprises at least one ingredient B0) suitable for curing the sealant composition by at least partially inducing a chemical transformation of the two or more thiol groups of ingredient A1), and 4) optionally curing the sealant film obtained after step 3), wherein the solvent-borne composition applied in step 1) comprises at least ingredients a1) to a3) different from each other, namely at least one aliphatic hydrocarbon as organic solvent ingredient a1) in an amount of at least 70.0 wt.-%, based on the total weight of the composition, at least one organometallic acid salt as ingredient a2), the metal of the metal acid salt being selected from the group consisting of Ti and Zr, and at least one organosilane as ingredient a3), wherein the sum of all ingredients present in the solvent-borne composition adds up to 100 wt.-%.

2. The method of claim 1, wherein, The solvent-borne composition used in step 1) comprises the at least one aliphatic hydrocarbon as organic solvent ingredient a1) in an amount in the range of 75.0 wt.-% or 80.0 wt.-% to 99.0 wt.-%, preferably 82.5 wt.-% to 98.5 wt.-%, even more preferably 85.0 wt.-% to 98.0 wt.-%, still more preferably 87.5 wt.-% to 97.5 wt.-%, yet more preferably 90.0 wt.-% to 97.5 wt.-%, even more preferably 92.5 wt.-% to 97.5 wt.-%, most preferably 95.0 wt.-% to 97.0 wt.-%.

3. The method according to claim 1 or 2, characterized in that, The solvent-type composition used in step 1) comprises, in addition to the at least one fatty hydrocarbon present therein as component a1), at least one further organic solvent as organic solvent component a4) which is different from component a1), preferably wherein the at least one further organic solvent a4) is an alcohol having one or more OH-groups, which alcohol further optionally carries at least one ether segment, which alcohol is more preferably a monomeric alcohol having one or more OH-groups, still more preferably a monomeric alcohol having exactly one OH-group.

4. The method according to one or more of the preceding claims, characterized in that, The at least one preferably branched fatty hydrocarbon present as component a1) has 2 to 20 carbon atoms, more preferably has 3 to 18 carbon atoms, even more preferably has 4 to 17 carbon atoms, still more preferably has 5 to 15 carbon atoms, yet more preferably has 5 or 6 or 7 or 8 to 15 or 14 or 13 carbon atoms, and / or is characterized in that The solvent-type composition used in step 1) comprises, in addition to the at least one fatty hydrocarbon present therein as component a1), a monomeric alcohol having preferably one or more OH-groups, more preferably exactly one OH-group, as at least one further organic solvent component a4), which monomeric alcohol preferably has 3 to 10 carbon atoms, wherein preferably the amount of the at least one fatty hydrocarbon a1) in wt.-% exceeds the amount of the at least one alcohol a4) in wt.-%, preferably wherein the relative weight ratio of the at least one fatty hydrocarbon a1) to the at least one alcohol a4) having one or more OH-groups is in the range of 9 : 1 to 3 :

1.

5. The method according to one or more of the preceding claims, characterized in that, The solvent-type composition used in step 1) comprises component a2) in an amount in the range of 0.1 wt.-% to 15.0 wt.-%, preferably 0.25 wt.-% to 12.0 wt.-%, even more preferably 0.5 wt.-% to 10.0 wt.-%, still more preferably 0.75 wt.-% to 7.5 wt.-%, yet more preferably 1.0 wt.-% to 5.0 wt.-%, in each case based on the total weight of the composition.

6. The method according to one or more of the preceding claims, characterized in that, The solvent-type composition used in step 1) comprises component a3) in an amount in the range of 0.1 wt.-% to 10.0 wt.-%, more preferably 0.25 wt.-% to 8.0 wt.-%, even more preferably 0.5 wt.-% to 6.0 wt.-%, still more preferably 0.75 wt.-% to 5.0 wt.-%, yet more preferably 1.0 wt.-% to 5.0 wt.-%, in each case based on the total weight of the composition.

7. The method according to one or more of the preceding claims, characterized in that, The solvent-based composition used in step 1 ) further comprises as ingredient a5) at least one additive selected from the group consisting of reactive diluents and resins such as polymeric resins and mixtures thereof, in an amount in the range of 0 wt.-% or 0.01 wt.-% to 7.5 wt.-%, preferably in an amount in the range of 0 wt.-% or 0.02 wt.-% to 6.0 wt.-%, more preferably in an amount in the range of 0 wt.-% or 0.03 wt.-% to 5.0 wt.-%, still more preferably in an amount in the range of 0 wt.-% or 0.05 wt.-% to 4.0 wt.-%, in each case based on the total weight of the composition.

8. The method according to one or more of the preceding claims, characterized in that, The solvent-based composition used in step 1 ) comprises, preferably consists of: at least one aliphatic hydrocarbon as organic solvent ingredient a1 ) in an amount in the range of 75.0 wt.-% or 80.0 wt.-% to 99.0 wt.-%, preferably 82.5 wt.-% to 98.5 wt.-%, more preferably 85.0 wt.-% to 98.0 wt.-%, still more preferably 87.5 wt.-% to 97.5 wt.-%, in each case based on the total weight of the composition, ingredient a2) in an amount in the range of 0.25 wt.-% to 7.5 wt.-%, preferably 0.5 wt.-% to 6.5 wt.-%, more preferably 0.75 wt.-% to 6.0 wt.-%, still more preferably 1.0 wt.-% to 5.0 wt.-%, in each case based on the total weight of the composition, ingredient a3) in an amount in the range of 0.25 wt.-% to 7.5 wt.-%, more preferably 0.5 wt.-% to 6.5 wt.-%, even more preferably 0.75 wt.-% to 6.0 wt.-%, still more preferably 1.0 wt.-% to 5.0 wt.-%, in each case based on the total weight of the composition, optionally, and preferably, at least one alcohol having one or more OH-groups as organic solvent ingredient a4) in an amount in the range of 0 wt.-% or 0.01 wt.-% to 20.0 wt.-%, preferably in an amount in the range of 0 wt.-% or 0.02 wt.-% to 15.0 wt.-%, more preferably in an amount in the range of 0 wt.-% or 0.03 wt.-% to 12.5 wt.-%, still more preferably in an amount in the range of 0 wt.-% or 0.05 wt.-% to 10.0 wt.-%, in each case based on the total weight of the composition, and Optionally, and preferably, at least one additive selected from the group consisting of reactive diluents and resins, such as polymeric resins, and mixtures thereof, as component a5), in an amount in the range of 0 wt.-% or 0.01 wt.-% to 7.5 wt.-%, preferably in an amount in the range of 0 wt.-% or 0.02 wt.-% to 6.0 wt.-%, more preferably in an amount in the range of 0 wt.-% or 0.03 wt.-% to 5.0 wt.-%, still more preferably in an amount in the range of 0 wt.-% or 0.05 wt.-% to 4.0 wt.-%, in each case based on the total weight of the composition, in particular when the optionally coated substrate used in step 1) is a thermoplastic or a fiber reinforced composite material or a glass substrate.

9. The method according to one or more of the preceding claims, characterized in that, The solvent borne composition is applied in step 1) such that a dry layer thickness of preferably below 1.0 pm, preferably below 900 nm or below 800 nm, even more preferably below 700 nm or below 600 nm, still more preferably below 500 nm or below 400 nm, most preferably below 300 nm or 200 nm, is produced after performing optional step 2).

10. The method according to one or more of the preceding claims, characterized in that, Component B) for preparing the sealing system of the sealant composition used in step 3) comprises at least one ingredient B0) selected from the group consisting of ingredients comprising two or more epoxy groups (ingredient B1), ingredients being metal oxides and / or metal peroxides, in particular manganese dioxide (ingredient B2), ingredients being organic peroxides (ingredient B3), ingredients comprising two or more vinyl groups (ingredient B4), and mixtures thereof, preferably selected from the group consisting of ingredients comprising two or more epoxy groups (ingredient B1), ingredients being metal oxides and / or metal peroxides, in particular manganese dioxide (ingredient B2), and mixtures thereof, more preferably representing at least one ingredient comprising two or more epoxy groups as ingredient B1), or at least one metal oxide and / or metal peroxide, in particular manganese dioxide, as ingredient B2).

11. The method according to one or more of the preceding claims, characterized in that, The optionally pre-coated substrate is selected from metal substrates, wherein the metal is preferably selected from steel, steel alloys, aluminum, aluminum alloys, titanium, titanium alloys, and mixtures thereof, or from glass substrates, thermoplastic substrates including polycarbonate and polyalkyl (meth)acrylic substrates, and fiber reinforced composite substrates, wherein the substrates in each case optionally carry at least one coating layer, most preferably in that the optionally pre-coated substrate is selected from glass substrates, thermoplastic substrates including polycarbonate and polyalkyl (meth)acrylic substrates, and fiber reinforced composite substrates, wherein the substrates in each case optionally carry at least one coating layer.

12. A sealed substrate, obtainable by the method according to one or more of the preceding claims, which is preferably suitable for use in the aircraft and / or aerospace industry.

13. Use of a solventborne composition as defined in one or more of claims 1 to 9 as adhesion promoting composition, in particular for enhancing the adhesion between the surface of an optionally pre-coated substrate and a subsequently applied sealant film, which sealant film is obtained by applying a sealant composition obtainable by mixing with each other at least two separately present components A) and B) of a sealing system onto a film already present on the surface of the optionally pre-coated substrate, wherein component A) of the sealing system comprises at least one polymeric ingredient A1) containing two or more thiol groups, which polymeric ingredient is selected from the group consisting of polyethers, poly sulfides, poly sulfides, poly sulfide-sulfide ingredients and mixtures thereof, and wherein component B) of the sealing system comprises at least one ingredient B0) suitable for curing the sealant composition by at least partially inducing chemical transformation of the two or more thiol groups of ingredient A1), said film having been formed by at least partially applying onto said surface a solventborne composition according to one or more of the preceding claims.

14. A solvent-borne composition as defined in one or more of claims 1 to 9, wherein, The at least one aliphatic hydrocarbon ingredient a1) present therein has 8 to 20 carbon atoms.

15. A kit-of-parts comprising at least separately from each other A sealing system as defined in one or more of claims 1, 10 or 13, which sealing system comprises two components A) and B) separately from each other, and A solventborne composition as defined in one or more of claims 1 to 9 or according to claim 14. A sealing system as defined in one or more of claims 1, 10 or 13, which sealing system comprises two components A) and B) separately from each other, and

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