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), a solvent-based composition is at least partially applied to the surface of the substrate in order to at least partially form a film (1) on said surface), a sealant composition is at least partially applied to the film obtained after step 1) in order 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 two different alcohols as organic solvents in an amount of at least 85.0 wt.-%, based on the total weight of the composition, as component a1), the invention relates to a method for producing a solvent-borne composition, comprising, as component a1), at least one organometallate, the metal of which is selected from Ti and Zr, as component a2), and at least one organosilane, as component a3), in an amount of at most 10.0 wt.-%, based on the total weight of the composition, sealing substrates obtainable by the method, the use of the solvent-borne composition as an adhesion-promoting composition, the solvent-borne composition itself, as an adhesion-promoting composition, the solvent-borne composition comprising, as component a2), at least one organometallate, the metal of which is selected from Ti and Zr, and at least one organosilane, as component a3). The invention also relates to a kit set containing the solvent-based 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 relevant in the field of aerospace, 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, such as 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, the chemical sealant providing 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 e.g. 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 of 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 optionally coated metal substrates. In particular, there is a need for corresponding adhesion promoting compositions, which provide excellent adhesion between a variety of different substrates, in particular metal 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 an optionally coated metal substrate. It is a particular basic object of the present application to provide adhesion promoting compositions which provide an excellent adhesion between various substrates such as metal substrates and sealants applied to the surface thereof obtainable from sealant compositions comprising polymers having thiol groups such as polysulfides and / or polysulfides, 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, but without 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 a surface of an optionally pre-coated substrate to form a film at least partially 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 selected from the group consisting of polyethers, polysulfides, polysulfides, polysulfide-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-based composition applied in step 1) comprises at least ingredients a1) to a3) which are different from each other, i.e.

[0020] at least two organic solvents as ingredient a1) in an amount of at least 85.0 wt.-%, based on the total weight of the composition, wherein said at least two organic solvents are alcohols and different from each other, and wherein at least one of the at least two alcohols has exactly one OH-group and at least one other alcohol has at least two or more OH-groups,

[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) in an amount of at most 10.0 wt.-%, based on the total weight of the composition,

[0023] wherein the sum of all ingredients present in the solvent-based composition adds up 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-based composition as 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-based composition as defined in connection with step 1) of the preceding process per se.

[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 the solvent-based composition as defined in connection with step 1) of the preceding process or the solvent-based composition of the present application, separately from each other.

[0028] It has been particularly surprising to find that the solvent borne 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 metal 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 solvent borne 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 solvent borne 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. In particular, it has been found that the solvent borne compositions disclosed above and below exhibit a flash point of > 40 °C, and thus have no or only a very low hazard potential, in particular compared to the solvent borne compositions of the prior art. It has been found that the achieved sufficiently high flash point is a result of the presence of the ingredient a1 ) according to the present application.

[0030] Furthermore, it has been particularly surprising to find that the solvent borne compositions disclosed above and below can be provided and used in a form having a lower active ingredient content, in particular with regard to ingredients a2) and / or a3), when compared to conventional adhesion promoters known in the prior art. With regard to the at least one organosilane as ingredient a3), it has been particularly found that when the amount of a3) is too high, in particular when the amount exceeds 10.0 wt.-% based on the total weight of the composition, adhesion failure can be observed after application of the solvent borne composition in step 1 ).

[0031] Furthermore, it has been surprising to find that the solvent borne compositions disclosed above and below can be applied in only a very thin layer, 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 lower. 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 solvent borne compositions, but nevertheless an excellent cohesive connection between the substrate and the sealant can be provided. DETAILED DESCRIPTION

[0032] 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.

[0033] 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.

[0034] Method of sealing optionally pre-coated substrates

[0035] 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.

[0036] Optional cleaning steps

[0037] 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.

[0038] Step 1)

[0039] In step 1), the solvent-based composition is applied at least partially to the surface of an optionally pre-coated substrate to form a film at least partially on said surface. Any kind of contact can generally be used to apply the solvent-based composition in step 1), such as dipping, wiping, brushing and / or spraying, particularly by wiping and / or brushing.

[0040] 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 less than 1.0 pm, more preferably less than 900 nm or less than 800 nm, even more preferably less than 700 nm or less than 600 nm, still more preferably less than 500 nm or less than 400 nm, most preferably less than 300 nm or 200 nm, is produced after the optional step 2) has been carried out.

[0041] Preferably, the solvent-borne composition is applied in step 1) by wiping in the so-called "wipe-on method". Preferably, in this regard a brush, a soft lint-free wipe or a pen with a felt tip is used for applying the solvent-borne composition. The solvent-borne composition is then wiped onto the surface of the substrate.

[0042] Alternatively, the solvent-borne composition is applied in step 1) by wiping in the so-called "wipe-on / wipe-off method". Here, the solvent-borne composition is applied in excess to the surface of the substrate. Preferably, in this regard a brush, a soft lint-free wipe or a pen with a felt tip is used 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 wiped off, preferably 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.

[0043] 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.

[0044] Substrate

[0045] 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 typically substrates which can be used in the aerospace and / or aircraft industry, for example as components and / or workpieces. Most preferred are metal substrates.

[0046] Suitable as metal-containing substrates for use according to the application are all substrates which are generally used by the skilled person and are known. The metal-containing substrates for use according to the application are preferably metal-containing substrates, including substrates composed of steel, steel alloys, aluminium, aluminium alloys, titanium and / or titanium alloys. Most preferred metal-containing substrates are aluminium and / or aluminium alloy substrates and steel and / or steel alloy substrates.

[0047] Suitable thermoplastic polymers are polyalkyl(meth)acrylates (including poly(meth)acrylate methyl (PMMA), poly(butyl(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 sulfides, polyethers, polyvinyl alcohol and mixtures thereof. Polycarbonates and polyalkyl(meth)acrylates (including poly(meth)acrylate methyl (PMMA)) are especially preferred plastic substrates.

[0048] As described above, fiber-based composites such as carbon fiber composites can also be used as substrates, as well as glass substrates, in particular for windscreen applications.

[0049] 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.

[0050] 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.

[0051] The substrate can have any form, shape and geometry and can be, for example, a sheet, a foil, a plate, etc.

[0052] Solvent-borne composition used in step 1)

[0053] The solvent-borne composition applied in step 1) of the process comprises at least the constituents a1) to a3) which are different from one another, i.e.

[0054] As at least one organic solvent as constituent a1) in an amount of at least 85.0 wt.-%, based on the total weight of the composition,

[0055] As at least one organic metal salt of component a2), the metal of the metal salt is selected from the group consisting of Ti and Zr, and

[0056] As at least one organosilane of component a3) in an amount of at most 10.0 wt.-%, based on the total weight of the composition,

[0057] The sum of all components present in the solvent-borne composition adds up to 100 wt.-%.

[0058] Preferably, the solvent-borne composition is a one-component (1 K) 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).

[0059] 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 component a1) are present as the main component 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.

[0060] 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 component a3) and / or component a2) is intended to be achieved. In particular, in case component a2) is used (which reacts strongly with water such that immediate hydrolysis to Ti02or Zr02occurs), then the presence of water is not intended.

[0061] Component a1) of the solvent-borne composition

[0062] The ingredient a1 ) is at least one organic solvent, which is present in an amount of at least 85.0 wt.-%, based on the total weight of the composition. The solvent- borne composition can comprise more than one organic solvent as ingredient a1 ) and preferably comprises more than one organic solvent as ingredient a1 ). Thus, preferably, the solvent-borne composition comprises at least two or three organic solvents different from each other as ingredient a1 ). The composition can even comprise more than three, e.g. four, different organic solvents. However, preferably, the maximum number of different organic solvents present therein is four.

[0063] Preferably, the solvent-borne composition used in step 1 ) comprises at least one organic solvent as ingredient a1 ) in an amount in the range of 85.0 wt.-% to 99.0 wt.-%, more preferably 85.0 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.

[0064] Preferably, in particular when the optionally coated substrate used in step 1 ) is a metal substrate, the solvent-borne composition used in step 1 ) comprises at least one organic solvent as ingredient a1 ) in an amount in the range of 87.5 wt.-% to 99.0 wt.-%, more preferably 90.0 wt.-% to 98.0 wt.-%, even more preferably 92.5 wt.-% to 97.5 wt.-%, still more preferably 94.0 wt.-% to 97.0 wt.-%, in each case based on the total weight of the composition.

[0065] Suitable organic solvents for use as ingredient a1 ) 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, hydrocarbons such as aliphatic, preferably branched hydrocarbons, preferably having 5 to 20 carbon atoms, 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. Examples of aliphatic, preferably branched hydrocarbons are isoparaffins. 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.

[0066] When the optionally coated substrate used in step 1 ) is a metal substrate, very particularly suitable organic solvents for use as component a1 ) in the solvent-borne composition used in step 1 ) are alcohols, ethers, ketones and mixtures thereof, most preferably alcohols. Most preferred are alcohols, such as a mixture of at least two alcohols, in particular a mixture of at least one alcohol having exactly one OH-group, such as 1 -ethoxypropan-2-ol, and at least one alcohol having exactly two or more OH-groups, such as 2-methylpentane-2,4-diol, wherein preferably at least one alcohol having exactly one OH-group is used in excess compared to at least one alcohol having two or more OH-groups, wherein more preferably the relative weight ratio of at least one alcohol having exactly one OH-group to at least one alcohol having two or more OH-groups is in the range of 5 : 1 to 3 : 1. Such organic solvents are non-toxic or only have a low toxicity. Further, the use of such organic solvents is advantageous in terms of a good balance between flash point, which is preferably > 40 °C, and the evaporation speed of the organic solvent. If the evaporation speed is too slow, there can be delays in the production process. Preferably, each of the organic solvents for use as component a1 ) in the solvent-borne composition used in step 1 ), in particular when the optionally coated substrate used in step 1 ) is a metal substrate, has 3 to 10 carbon atoms, preferably 4 to 8 or 4 to 7 carbon atoms, and optionally carries one or more ether functional groups. The presence of ether functional groups is particularly advantageous for achieving sufficient solubility of components a2) and / or a3) and / or optional component a4) in the solvent-borne composition.

[0067] Preferably, the solvent-borne composition used in step 1 ) comprises at least two organic solvents different from each other as component a1 ), preferably wherein at least one of these at least two organic solvents is an alcohol having one or more OH-groups, which alcohol further optionally carries at least one ether segment, preferably a monomeric alcohol having one or more OH-groups, preferably a monomeric alcohol having exactly one OH-group.

[0068] Preferably, the solvent-borne composition used in step 1) comprises at least two organic solvents different from each other as component a1), i.e. at least two alcohols, each having one or more OH-groups and each preferably having 3 to 10 or 4 to 7 carbon atoms, which are preferably monomeric alcohols, wherein preferably one of the at least two alcohols exactly has one OH-group and optionally carries at least one ether segment, and at least one other alcohol has at least two or more OH-groups, thus being a diol (in case of two OH-groups) or a polyol (in case of more than two OH-groups), wherein preferably the amount in wt.-% of the at least one alcohol exactly having one OH-group exceeds the amount in wt.-% of the at least one other alcohol having at least two OH-groups, wherein more preferably, when the optionally coated substrate used in step 1) is a metallic substrate, the relative weight ratio of the at least one alcohol exactly having one OH-group to the at least one alcohol having two or more OH-groups is in the range of 5 : 1 to 3 : 1, wherein the at least two alcohols are in particular present in the solvent-borne composition.

[0069] Component a2) of the solvent-borne composition

[0070] Component a2) is at least one organometallic acid salt as component a2), the metal of which is selected from Ti and Zr. Thus, the metal acid salt corresponds to a titanate and a zirconate.

[0071] Preferably, the solvent-borne composition used in step 1) comprises component 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 component 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 component 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.

[0072] Preferably, especially when the optionally coated substrate used in step 1 ) is a metal substrate, the solvent-borne composition used in step 1 ) comprises the ingredient 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.

[0073] 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 the ingredient 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.

[0074] Preferably, the one or more organic radicals of the metal salt ingredient 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, the ingredient 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. Most preferred titanates and / or zirconates are tetra-n-butyl zirconate (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).

[0075] Preferably, the ingredient 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.

[0076] Ingredient a3) of the solvent-borne composition

[0077] Component a3) is at least one organosilane which is 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 the form of its at least partial hydrolysis. 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 failures can be observed.

[0078] 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.

[0079] Preferably, in particular when the optionally coated substrate used in step 1) is a metal substrate, the solvent-borne composition used in step 1) comprises component a3) 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.

[0080] Preferably, the molar ratio of the at least one component a2) to the at least one component a3) in the solvent-borne composition to each other is in the range of 1 : > 1.0 to 1 : 3.0, more preferably 1 : 1.2 to 1 : 2.8, in particular when the optionally coated substrate used in step 1) is a metal substrate.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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 150 g / mol to 1800 g / mol, even more preferably 180 g / mol to 1500 g / mol, still more preferably 200 g / mol to 650 g / mol.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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, N-(2-aminoethyl)-3- aminopropylmethyldimethoxysilane, 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.

[0091] 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.

[0092] 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.

[0093] As organosilanes, preference is given to using at least one alkoxysilane having the structural formula (I)

[0094] A-R-Si(R') x (OR'')3- x

[0095] (I),

[0096] wherein

[0097] A is a functional group which is optionally masked by a protecting group which can be eliminated under hydrolytic conditions, or is H,

[0098] 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,

[0099] The R' radical is selected from the group of C1- to C 12 alkyl radicals,

[0100] R" is an aliphatic radical having 1 to 4 carbon atoms, and

[0101] x = 0 to 2.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] Preferably, the molar ratio of the one or more ingredients a2) to a3) to each other is in the range of 1 : > 1.0 to 1 : 3.0, more preferably 1 : 1.2 to 1 : 2.8.

[0106] Further optional ingredients of the solvent-borne composition

[0107] The solvent-borne composition can comprise one or more further optional ingredients, which are different from each other and also from the ingredients a1) to a3).

[0108] Optionally, the composition comprises at least one colorant as ingredient a4), 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.

[0109] 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.

[0110] 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, a rhodamine colorant, such as rhodamine B, and an azo colorant, such as Macrolex® Red H by Lanxess or Keyplast® Red H by Milliken, can be used.

[0111] The colorant is preferably added such that it is visible where the solvent-borne composition as adhesion promoter has been applied after it 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.

[0112] However, for some applications, especially when the optionally coated substrate used in step 1) is a thermoplastic or a fiber reinforced composite or a glass substrate, the presence of the colorant is not necessarily desirable, for example for window assembly applications: some parts of the applied adhesion promoter layer can still be visible on the transparent substrate after assembly.

[0113] 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, especially when the optionally coated substrate used in step 1) is a thermoplastic or a fiber reinforced composite or a glass substrate.

[0114] 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.

[0115] 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.

[0116] Very preferred solvent-borne compositions, especially when the optionally coated substrate used in step 1) is a metal substrate, are solvent-borne compositions comprising, preferably consisting of:

[0117] The at least one organic solvent as component a1) is in an amount in the range of 87.5 wt.-% to 99.0 wt.-%, more preferably 90.0 wt.-% to 98.0 wt.-%, even more preferably 92.5 wt.-% to 97.5 wt.-%, yet more preferably 94.0 wt.-% to 97.0 wt.-%, in each case based on the total weight of the composition,

[0118] 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,

[0119] component a3) 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, and

[0120] Optionally, and preferably, component a4) 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.-%.

[0121] Optional step 2)

[0122] In optional step 2), the film obtained after step 1) is dried and / or cured.

[0123] In the sense of the present application, “drying” preferably means a physical drying by at least partial evaporation of the organic solvent(s) component a1) present in the composition used, while “curing” further comprises a chemical reaction 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.

[0124] Drying and / or curing can preferably be carried out, for example, at temperatures in the range of 15 °C to 80 °C, more preferably at temperatures in the range of 18 °C to 60 °C, in particular at temperatures in the range of 20 °C or 23 °C to 50 °C. Preferably, however, drying and / or curing is simply carried out 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.

[0125] Preferably, by performing optional step 2), ingredients a2) and / or a3) bind to the substrate surface and a hydrolysis reaction occurs. 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.

[0126] Step 3)

[0127] 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.

[0128] Any kind of contact can be used for the application according to step 3), such as brushing and / or spraying. Step 3) is preferably performed at a temperature in the range of 0 °C to 60 °C, more preferably 5 °C to 45 °C. In particular, no heating is performed.

[0129] Preferably, step 3) is performed 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.

[0130] Sealant composition used in step 3)

[0131] The sealant composition used in step 3) can be obtained by mixing at least two separately present components A) and B) of a 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).

[0132] 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 therein.

[0133] 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.

[0134] If at least one organic solvent is present therein, the amount of the organic solvent(s) present is preferably 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 organic solvent(s), 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 amount of the organic solvent(s) present is preferably 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 organic solvent(s), 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 solvent. 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, dimethylbenzene, butanol, ethyl glycol 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.

[0135] 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.

[0136] Component A) of the sealing system

[0137] Component A1)

[0138] Component A) of the sealing system comprises at least one polymeric component A1) containing two or more thiol groups (mercapto groups), which is selected from the group consisting of polyethers, polythioethers, polysulfides, polythioether-sulfide components and mixtures thereof, preferably from the group consisting of polythioethers, polysulfides, polythioether-sulfide components and mixtures thereof, more preferably from the group consisting of polythioethers, polysulfide components and mixtures thereof, in particular from the group consisting of polysulfide components. The terms “polymer” and “polymeric” are known to the person skilled in the art and encompass for the purposes of the present invention polyadducts and polymerizates as well as polycondensates. The term “polymer” includes both homopolymers and copolymers.

[0139] Due to the presence of thiol groups, A1) is necessarily a sulfur atom containing component. The thiol groups of A1) can chemically react with component B0) or a part thereof, for example with a suitable functional group thereof. For example, when component B1) is present as component 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 component B2) is present as component B0) (as containing manganese oxide), an S-S-bond is formed.

[0140] Preferably, the polymeric component A1) contains terminal thiol groups. Component A1) can be branched or linear. Preferably, the polymeric component A1) is liquid at ambient conditions (18 °C to 23 °C, 50% relative humidity).

[0141] Polymeric components suitable for use as A1) are for example disclosed in US 2004 / 097643 A1 and WO 2016 / 128548 A1 and WO 2015 / 014876 A2.

[0142] 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. The corresponding polymer can then be designated as polythioether sulfide. Preferred compounds of this class are described in WO 2015 / 014876 A2.

[0143] 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 polythiofide. Examples of such polymers are for example commercially available polythiofides, 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 polythiofides, for example commercially available as Thiokol® LP3, Thioplast® G4, or Thioplast® G44.

[0144] Optionally, at least two species of component A1 ) are present in component (A) which have 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 thiol, which is preferably solid or liquid, has three thiol groups and a number average molecular weight in the range of 160 g / mol to 1200 g / mol. Alternatively, said thiol 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 thiols are thiocyanuric acid (1,3,5-triazine-2,4,6-trithiol) and benzene-1,3,5-trithiol (1,3,5-trimercaptobenzene). In case said thiol used is non-polymeric, it formally represents an optional component A6) of component A) which will be defined in the following. Preferably, said at least one thiol, 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).

[0145] 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 .

[0146] Preferably, component A1 ) and the sealant composition as such are free of any ingredient comprising (meth)acrylate groups (methacrylate and / or acrylate groups).

[0147] 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.

[0148] Optional ingredients present in component A)

[0149] 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.

[0150] 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.

[0151] Component A) of the sealing system can contain one or more optional ingredients A5 and / or A6).

[0152] 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).

[0153] 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).

[0154] Component B) of the sealing system

[0155] Component B0)

[0156] 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.

[0157] 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).

[0158] 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).

[0159] component B1)

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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).

[0165] Preferably, the molar ratio of all components B1 ) to all components A1 ) is in the range of 0.90 : 1 to 2 : 1.

[0166] Component B2)

[0167] 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.

[0168] 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).

[0169] Component B3)

[0170] Component B3) is at least one organic peroxide. An example of a suitable organic peroxide is an organic hydroperoxide, such as cumene hydroperoxide.

[0171] 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).

[0172] Component B4)

[0173] 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.

[0174] Preferably, component B4) is present in component B) of the sealing system used 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).

[0175] 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.

[0176] Optional components B5) and B6) and B7)

[0177] 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).

[0178] 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 B). In particular, in case at least one plasticizer is present, its amount is preferably in the range of 10.0 wt.-% to 70.0 wt.-% based on the total weight of component B).

[0179] Component B) can additionally and preferably contains at least one curing catalyst B6).

[0180] 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).

[0181] 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).

[0182] 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).

[0183] 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.

[0184] 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).

[0185] Optional step 4)

[0186] 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.

[0187] 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.

[0188] 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.

[0189] Sealing substrates

[0190] 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.

[0191] 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.

[0192] Use as adhesion promoters

[0193] 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.

[0194] 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.

[0195] 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.

[0196] Solvent-borne compositions

[0197] A further subject-matter of the present application is a solvent-borne composition as defined in connection with step 1 ) of the preceding method itself.

[0198] 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 solvent-borne composition of the present application.

[0199] Kit of parts

[0200] 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 method and a solvent-borne composition as defined in connection with step 1 ) of the preceding method or the solvent-borne composition of the present application, separated from each other, preferably consisting of at least a sealing system as defined in connection with step 3) of the preceding method and a solvent-borne composition as defined in connection with step 1 ) of the preceding method or the solvent-borne composition of the present application, separated from each other, the sealing system comprising at least two components A) and B), separated from each other.

[0201] 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.

[0202] Method

[0203] 1. Peel test

[0204] Peeling was produced and tested in a manner equivalent to DIN 65262-1 (07-2017) after curing for 14 days at room temperature (23 °C) and 50% relative humidity. It was assessed whether cohesive failure or adhesive failure occurred.

[0205] 2. Number average molecular weight

[0206] The number average molecular weight of the components A21 ) and B1 ) was determined by GPC (gel permeation chromatography) against polystyrene standards. THF (tetrahydrofuran) was used as mobile phase. The number average molecular weight of the silane components A2) and a3) was determined by NMR spectroscopy in the case of monomeric and oligomeric components and by GPC in the case of polymeric components.

[0207] 3. Flash point

[0208] The apparatus Miniflash FLPL was used for determining the flash point according to ASTM D6450.

[0209] 4. Dry layer thickness

[0210] The dry layer thickness is measured using REM / EDX (scanning electron microscope / energy dispersive X-ray analysis), in particular the dry layer thickness of the film obtained after optional step 2) of the inventive process. Examples

[0211] The following examples further illustrate the present application, but should not be construed as limiting its scope. 'Pbw' means parts by weight. If not otherwise defined, 'parts' means 'parts by weight'.

[0212] 1. Adhesion promoting compositions

[0213] 1.1 The exemplary composition E1 is prepared by mixing the ingredients listed in table 1.1 with each other in the order given in table 1.1.

[0214] Table 1.1 - Composition E1

[0215]

[0216] A commercial product containing zirconium tetra-n-butoxide (87 wt.-%) in n-butanol is used as zirconate 1. A commercially available xanthene-based colorant is used as dye 1. Silane 1 is a commercially available organosilane, namely N-(2-aminoethyl)-3- aminopropylmethyldimethoxysilane.

[0217] The composition E1 is prepared as follows: The used organic solvents are weighed into a closable glass bottle. Then, the zirconate 1 is added. The glass bottle is closed and carefully shaken. Next, the silane 1 is added. The glass bottle is closed and carefully shaken. Finally, the dye 1 is added. The glass bottle is closed and carefully shaken.

[0218] 1.2 The further exemplary compositions E2 and E3 as well as the comparative composition C1 are prepared by mixing the ingredients listed in table 1.2 with each other in the order given in table 1.2.

[0219] Table 1.2 - Compositions E2, E3 and C1

[0220]

[0221] A commercial product containing zirconium tetra-n-butoxide (87 wt.-%) in n-butanol is used as zirconate 1. A commercially available azo-based red colorant is used as dye 2. Silane 1 is a commercially available organosilane, namely N-(2-aminoethyl)-3- aminopropylmethyldimethoxysilane.

[0222] In the composition C1 the used diol is completely replaced by a monoalcohol compared to the composition E3.

[0223] 1.3 Additional comparative compositions C2, C3 and C4 are prepared by mixing the ingredients listed in Table 1.3 with each other in the order given in Table 1.3.

[0224] Table 1.3 - Compositions C2, C3 and C4

[0225]

[0226] A commercial product containing tetra-n-propylzirconium (74 wt.-%) in n- propyl alcohol is used as zirconium salt 2. A commercially available azo-based red colorant is used as dye 2. Silane 1 is a commercially available organosilane, namely N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane. Silane 2 is a commercially available organosilane, namely N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0227] 2. Investigation of properties of adhesion promoting compositions

[0228] The flash point of each of the adhesion-promoting compositions E2, E3 and C1 to C4 is determined according to the method disclosed in the ‘Methods’ section. The results are shown in Table 2. The higher the flash point, the lower the potential hazard. Therefore, a higher flash point, in particular a flash point of > 40 °C, is desirable.

[0229] Table 2 - Flash points

[0230]

[0231] As is apparent from Table 2, the use of a mixture of diol and monool as organic solvent in compositions E2 and E3 leads to a sufficiently high flash point of > 40 °C, i.e. 41 °C in both cases. The comparison between E2 and E3 shows that the reduction of the amount of zirconium salt and silane has no influence on the flash point.

[0232] The comparison between E3 and C1 shows that the use of a monool only and no diol leads to an undesired drop of the flash point below 40 °C (i.e. to 37 °C). The use of a different zirconium salt or a different silane does not influence this, as is apparent from the comparison of the flash points of C1, C2 and C3. The use of isopropanol as the only alcohol present leads to a further severe drop of the flash point and to a very low flash point of only 16 °C, as is apparent from the comparison of the flash points of C1 and C4.

[0233] 3. Preparation of sealing substrates and investigation of their properties

[0234] Sealing substrates prepared by using exemplary adhesion-promoting composition E1

[0235] A number of substrates S1 to S8 were provided, namely titanium grade 5 (S1 ), stainless steel 304 (S2), aluminium 2024 T3 clad (S3), a carbon fibre composite (CFC) material, namely HexPly® M21 E (S4), a substrate S3 coated with a commercially available primer coating, namely coated with Mankiewicz Seevenax 313-02 (S5), a substrate S3 coated with a commercially available primer coating, namely coated with Akzo® 37092 (S6), a substrate S3 coated with a commercially available polyurethane topcoat, namely coated with Akzo® HS 67348 (S7) and a substrate S3 coated with a commercially available polyurethane topcoat, namely coated with Akzo® C21 / 100 (S8).

[0236] Each of the substrates S1 to S8 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 prior to the subsequent application of the adhesion promoting composition.

[0237] The adhesion promoting composition E1 was then applied to the cleaned surface of each substrate in a very thin layer (dry layer thickness < 200 nm) by the "wipe-on / wipe-off" method. This method means that the adhesion promoting composition E1 is applied in excess onto this surface of the substrate by means of a brush, a soft lint-free wipe or by means of a suitable pen with a felt tip. Within a few seconds or minutes (depending on the substrate used), the excess is wiped off with a soft lint-free wipe, followed by a flash-off time during which at least a portion of the organic solvents present can evaporate and a hydrolysis reaction involving the ingredients present in the applied composition E1 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.

[0238] Afterwards, 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 polysulphide sealant.

[0239] 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 the peel test according to the method disclosed in the 'Methods' section. The results are summarised in Table 3 below. C.f. means cohesive failure.

[0240] Table 3 - Peel test results

[0241]

[0242] As is apparent from Table 3, by using the adhesion promoting composition E1, 100% adhesion can be achieved for the various tested different substrates S1 to S8 (no adhesion failure observed, cf. only). In comparison to other adhesion promoters on the market (e.g. in comparison to Naftoseal® MC-110 and Naftoseal® MC-115), E1 has a lower toxicity and further, even though E1 has a lower active ingredient content in comparison to Naftoseal® MC-110 and Naftoseal® MC-115, it performs equally efficiently. Furthermore, E1 has a higher flash point, i.e. > 40°C, in comparison to each of Naftoseal® MC-110 and Naftoseal® MC-115, which each have a flash point of < 40°C.

Claims

1. A method of sealing an optionally pre-coated substrate, which method comprises at least steps 1) and 3) and optionally at least one of steps 2) and / or 4), i.e. 1) applying at least partially a solvent-borne composition onto the surface of the 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, 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 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, i.e. as ingredient a1) at least two organic solvents in an amount of at least 85.0 wt.-% based on the total weight of the composition, wherein said at least two organic solvents are alcohols and different from each other, and wherein at least one of the at least two alcohols exactly has one OH-group and at least one other alcohol has at least two or more OH-groups, as ingredient a2) at least one organometallic acid salt, the metal of which is selected from the group consisting of Ti and Zr, and as ingredient a3) at least one organosilane in an amount of at most 10.0 wt.-% based on the total weight of the composition, 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 two organic solvents as ingredient a1) in an amount in the range of 85.0 wt.-% to 99.0 wt.-%, preferably 85.0 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 at least two organic solvents as ingredient a1) each have 3 to 10 or 4 to 7 carbon atoms.

4. The method according to one or more of the preceding claims, characterized in that, The amount of the at least one alcohol having exactly one OH-group in wt.-% exceeds the amount of the at least one other alcohol having at least two OH-groups in wt.-%, wherein preferably the relative weight ratio of the at least one alcohol having exactly one OH-group to the at least one alcohol having two or more OH-groups is in the range of 5 : 1 to 3 : 1, wherein the at least two alcohols are in particular present in the solvent-borne composition when the optionally coated substrate used in step 1) is a metal substrate.

5. The method according to one or more of the preceding claims, characterized in that, The solvent-borne composition used in step 1) comprises the ingredients 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-borne composition used in step 1) comprises the ingredients 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-borne composition used in step 1) further comprises at least one colorant as ingredient a4), preferably in an amount in the range of 0.01 wt.-% to 1.5 wt.-% based on the total weight of the composition, in particular when the optionally coated substrate used in step 1) is a metal substrate, and / or at least one additive selected from the group consisting of reactive diluents and resins such as polymeric resins and mixtures thereof as ingredient 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.

8. The method according to one or more of the preceding claims, characterized in that, The solvent-borne composition used in step 1) comprises, preferably consists of: the at least two organic solvents as ingredient a1) in an amount in the range of 87.5 wt.-% to 99.0 wt.-%, preferably 90.0 wt.-% to 98.0 wt.-%, more preferably 92.5 wt.-% to 97.5 wt.-%, still more preferably 94.0 wt.-% to 97.0 wt.-%, in each case based on the total weight of the composition, component a2) in an amount in the range of 0.50 wt.-% to 7.50 wt.-%, preferably 0.75 wt.-% to 5.0 wt.-%, 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, component a3) in an amount in the range of 0.50 wt.-% to 7.50 wt.-%, preferably 0.75 wt.-% to 5.0 wt.-%, 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, and optionally, and preferably, as component a4) at least one colorant 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 particular when the optionally coated substrate used in step 1) is a metal 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 carrying out optional step 2).

10. The method according to one or more of the preceding claims, characterized in that, Component B) for producing 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 which are metal oxides and / or metal peroxides, in particular manganese dioxide (ingredient B2), ingredients which are 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 which are 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 a metal substrate, wherein the metal is preferably selected from steel, steel alloys, aluminum, aluminum alloys, titanium, titanium alloys and mixtures thereof, or from a glass substrate, a thermoplastic substrate including polycarbonate and polyalkyl (methyl) acrylate substrates, and a fiber reinforced composite substrate, wherein the substrate in each case optionally bears at least one coating, most preferably in that the optionally pre-coated substrate is selected from a metal substrate, wherein the substrate optionally bears at least one coating.

12. A sealed substrate, obtainable by the process 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 solvent-borne composition as defined in one or more of claims 1 to 9 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, which is preferably 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 is selected from 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 chemical transformation of the two or more thiol groups of ingredient A1), said film having been formed by at least partially applying a solvent-borne composition according to one or more of the preceding claims onto said surface.

14. A solvent-borne composition as defined in one or more of claims 1 to 9.

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 comprises two components A) and B) separately from each other, and a solvent-borne composition as defined in one or more of claims 1 to 9 or according to claim 14.

16. Use of a solvent-borne composition as defined in one or more of claims 1 to 9 for the preparation of a sealing system as defined in one or more of claims 1 to 10.

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