Patent Description:
Sealants are used for a wide range of applications. They are e.g. relevant to the aerospace sector, but are also widely used in the automotive sector. Sealants are further used for sealing construction elements, connection of metal sheets, for example, to existing structures, such as segments of an airplane and/or for corrosion protection in places, where for example, in the region of holes, the corrosion protection layers of the metallic elements are damaged or removed. They may also exert a temporary carrying function, for example during transportation of structures to be mounted, which have to be subsequently provided with permanent supporting connection elements.

Silanes, in particular organosilanes, are known to work as adhesion promoter for various substrates, especially with polar surfaces like metals and glass, but also for ceramics and polymers. Due to their vast compatibility to many chemical systems, they can be used in various different materials including sealant materials. Compared to other chemically different adhesion promoters like e.g. phenolic resins or polyolefins, silanes usually do not significantly influence the pH environment within the material they are utilized in, which becomes especially important for applications, where ambient conditions such as a constant pH environment are critical for the curing properties of the material, which is, e.g. the case for polysulfide and/or polythioether based sealants. An additional advantage of the use of silanes as adhesion promoters in such materials is that they can be used along with other adhesion promoters such as e.g. polyolefins and/or organometallic compounds like titanates. Usually, the silanes used for this purpose bear an aliphatic and/or aromatic spacer (linker) attached to a functional group like an amino, thiol, hydroxy, or epoxide group, depending on the system the silane is to be used in.

<CIT> discloses specific cycloaliphatic OH-functional silanes for use as adhesion promoters and crosslinking agents. <CIT> discloses an adhesion improving agent, which is a reaction product of an isocyanate functional silane and a further silane bearing a functional group reactive towards isocyanate groups. <CIT> discloses a method of coating metallic surfaces that makes use of an aqueous composition, which contains at least one kind of Sicontaining constituents such as an organosilane. <CIT> discloses compositions comprising a combination of different silanes such as a combination of an aminohydrocarbyl alkoxy silane, an alkenyl alkoxy silane and a mercaptohydrocarbyl alkoxy silane. The composition is useful as water-based primer.

<CIT> relates to isocyanate functional silanes, which have been prepared from a reaction of e.g. amino-functional organosilanes and low volatile polyisocyanates, for use as adhesion promoters in polyurethane compositions. <CIT> relates to a <NUM> coating composition containing a compound containing alkoxy silane groups as well as succinyl urea groups.

However, the sealant systems known in the prior art not always provide sufficient adhesion properties and the silanes known in the prior art not always provide sufficient adhesion promoting properties, in particular in the field of sealants for the aircraft industry and in sealant compositions comprising polymers with thiol groups such as polysulfide and/or polythioether based sealant compositions, in particular not for a variety of different substrates. Further, the silanes known from the prior art often lead to only comparably poor processing properties when incorporated into sealant compositions containing the aforementioned polymers with thiol groups, especially as far as an undesired viscosity change such as an undesired drop of viscosity over storage time is concerned. These disadvantageous properties are in particular often observed, when amino-group containing silanes as such or silanes derived from amino-group containing precursor silanes are used such as e.g. silanes disclosed in <CIT> and <CIT>.

<CIT> relates to silane functional polyurethanes and discloses a process for preparing such polyurethanes containing silane groups. <CIT> relates to thioallophanate polyisocyanates containing silane groups and to a process for preparing them as well as to coating compositions comprising these polyisocyanates. <CIT> relates to curable compositions comprising a room temperature stable curable resin, which may comprise silyl groups, and surface treated barium sulfate, which have high strength and excellent weather and chemical resistance.

It is further known to functionalize polymers with silanes, e.g. from <CIT>, <CIT> and <CIT> as well as <CIT>: <CIT> discloses polyester polyols comprising esterified units, which in turn have been modified with an amino functional silane. These polymers can be used as adhesion promoters for urethane systems. <CIT> discloses silane-modified copolymers as adhesion improvers. <CIT> discloses a modified polyisocyanate obtainable by reacting a polyisocyanate based on <NUM>,<NUM>-diisocyanatopentan and an organosilane such as an amino functional organosilane. <CIT> discloses the preparation and use of a silane-modified butylrubber, wherein a mercapto functional silane is used for this purpose. However, the use of such modified polymers disclosed in these references necessarily requires a pre-modification step of the polymers prior to their use in materials such as sealants, which is not desired at least from an economical point of view. In addition, a prior modification of the polymers limits the flexibility of the end user with regard to degrees of freedom when formulating material compositions. As far as <CIT> is concerned, the rubbers/polymers disclosed therein are additionally not suitable for use as a sealant, in particular not as aircraft sealants, at least since they show an only poor resistance to non-polar solvents like mineral oil-based fuels. This is in particular disadvantageous for sealants used for sealing the interior of fuel tanks of aircrafts.

Thus, there is a demand for sealing systems, sealing compositions and for a method of sealing of substrates, which do not exhibit the aforementioned disadvantages, in particular, when the substrates are substrates used in the aircraft industry such as fuel tanks. In particular, there is a demand for respective sealing systems and compositions containing thiol groups containing polymers, which provide excellent adhesion properties to a variety of different substrates and surfaces, and for universally utilizable adhesion promoters to be suitable for such systems and compositions, which allow an easy and economically advantageous incorporation into these systems and compositions without imparting their processing properties.

It has been therefore an object underlying the present invention to provide sealing systems and sealing compositions containing thiol groups containing polymers and a method of sealing of substrates making use of these systems and compositions, in particular, when the substrates are substrates used in the aircraft industry such as fuel tanks, which not only provide excellent adhesion properties to a variety of different substrates and surfaces, but which additionally allow to make use of a universally utilizable adhesion promoter suitable for such systems and compositions, wherein said adhesion promoter allows an easy and economically advantageous incorporation into these systems and compositions and does not show any disadvantages as far as the processibility of these systems and compositions are concerned. At the same time the sealed substrates such as sealed interiors of fuel tanks ought to exhibit an excellent resistance to liquid media, in particular towards fuels.

This objective has been solved by the subject-matter of the claims of the present application as well as by the preferred embodiments thereof disclosed in this specification, i.e. by the subject matter described herein.

A first subject-matter of the present invention is a method of sealing an optionally pre-coated substrate comprising at least step (<NUM>) and optionally also step (<NUM>), namely.

A further subject-matter of the present invention is a sealed substrate, obtainable by the inventive method.

A further subject-matter of the present invention is a use of an organosilane constituent as defined hereinbefore and/or hereinafter when incorporated into a primer composition as defined in hereinbefore and/or hereinafter such as into a primer composition used in step (<NUM>) of the inventive method or into a sealant composition as defined hereinbefore and/or hereinafter such as into a sealant composition used in step (<NUM>) of the inventive method, in particular into component (A) of a sealing system used for preparing said sealant composition, for enhancing the adhesion of the primer composition or of the sealant composition to an optionally pre-coated substrate once applied to at least a portion of its surface.

A further subject-matter of the present invention is a sealant composition as defined hereinbefore and hereinafter, which is obtainable by mixing components (A) and (B) of a sealing system as defined hereinbefore and/or hereinafter with each other, wherein component (A) of said sealing system comprises the at least one organosilane constituent as defined hereinbefore and/or hereinafter.

A further subject-matter of the present invention is a two-component (<NUM>) sealing system comprising components (A) and (B) as defined hereinbefore and/or hereinafter, being separate from each other, wherein component (A) of said sealing system comprises the at least one organosilane constituent as defined hereinbefore and/or hereinafter.

A further subject-matter of the present invention is an organosilane constituent as defined hereinbefore and/or hereinafter, optionally being incorporated into a primer composition as defined hereinbefore and/or hereinafter. A further subject-matter of the present invention is thus also a primer composition as defined hereinbefore and/or hereinafter comprising at least an organosilane constituent as defined hereinbefore and/or hereinafter.

It has been in particular surprisingly found that the aforementioned organosilane constituent represents a universally utilizable adhesion promoter when incorporated into the sealant and/or primer compositions, in particular when used in the inventive method. It has been found that said adhesion promoter can be easily incorporated into various sealant compositions and can also be easily incorporated into suitable primer compositions to be applied before the actual sealant composition is applied to the surface of the substrate. It has been found that an excellent adhesion to various substrates including metal substrates and pre-coated substrates such as metal substrates bearing at least one organic coating layer can be achieved and that the adhesion promoter can be effectively chemically incorporated into the formed polymer matrices and networks after application. It has been further surprisingly found that the organosilane constituent functions as a linker between the surface of the substrate and the applied primer/sealant.

Further, it has been in particular surprisingly found that the one or more hydrolyzable groups X of the organosilane constituent such as alkoxy groups/silyl ether groups mediate adhesion to the surface the organosilane constituent is applied to, in particular by reacting with OH-groups in a condensation reaction, whereas at the same time, the at least one NCO-group of the organosilane constituent can react with the thiol groups of constituent (a1) of the sealant composition. In particular, it has been found that a significant improvement of adhesion in the used sealant and/or primer material is a result of the at least one moiety MS present in the spacer unit of the organosilane constituent. It is assumed, that the presence of the at least one moiety MS has an additional adhesion promoting effect, which is based on the formation of hydrogen bonds. It has been found that the use of conventional organosilanes such as (<NUM>-glycidyloxypropyl)trimethoxysilane and (<NUM>-mercaptopropyl)-trimethoxysilane as well as the use of organosilanes that do not contain the at least one sulfur atom containing moiety MS such as organosilanes prepared from diisocyanates and an amino-functional silane precursor such as bis[<NUM>-(trimethoxysilyl)propyl]amine do not have the desired effect of increasing the adhesion significantly.

Moreover, it has been surprisingly found that the aforementioned organosilane constituent offers a high degree of flexibility and high degrees of freedom for formulating the sealant and primer compositions.

In particular, no pre-modification step of modifying any polymer components of the sealant compositions is necessary in order to improve adhesion, but the aforementioned organosilane constituent can instead be simply incorporated into various sealant compositions as such.

Further, it has been surprisingly found that sealant and primer compositions comprising the aforementioned organosilane constituent are in particular utilizable in the aircraft and aerospace field, e.g. as aircraft sealants, in particular for sealing the interior of fuel tanks of aircrafts, as the sealed corresponding substrates exhibit an excellent resistance to liquid media such as organic solvents and fuels, in particular non-polar solvents like mineral oil-based fuels.

Additionally, it has been surprisingly found that sealant and primer compositions comprising the aforementioned organosilane constituent are able to provide sealed substrates exhibiting excellent physical-mechanical properties such as tensile strength.

Finally, it has been surprisingly found that sealant and primer compositions comprising the aforementioned organosilane constituent show excellent processing properties and, in particular excellent viscosity properties as no undesired viscosity change such as an undesired drop of viscosity is observed over storage time.

The term "comprising" in the sense of the present invention, in connection for example with sealant composition, preferably has the meaning of "consisting of". With regard, e.g., to the sealant composition it is possible - in addition to all mandatory constituents present therein - for one or more of the further optional constituents identified hereinafter to be also included therein. All constituents may in each case be present in their preferred embodiments as identified below.

The proportions and amounts in wt. -% (% by weight) of any of the constituents given hereinafter, which are present in each of the components of the sealing system add up to <NUM> wt. -%, based in each case on the total weight of the respective component. Similarly, the proportions and amounts in wt. -% (% by weight) of any of the constituents given hereinafter, which are present in the sealant or primer composition add up to <NUM> wt. -%, based in each case on the total weight of the respective composition.

A first subject-matter of the present invention is a method of sealing an optionally pre-coated substrate comprising at least step (<NUM>) and optionally also step (<NUM>).

The at least one organosilane constituent is at least present - when optional step (<NUM>) is not performed - as constituent (a2) in component (A) of the sealing system used for preparing the sealant composition applied in step (<NUM>) or is - when step (<NUM>) is performed - at least present as a constituent in the primer composition applied in step (<NUM>).

Preferably, the organosilane constituent is present in component (A) used for preparing the sealant composition applied in step (<NUM>) and is not present in the primer composition optionally applied in step (<NUM>). Alternatively, but also preferably, the organosilane constituent is not present in component (A) used for preparing the sealant composition applied in step (<NUM>), but is present in the primer composition applied in step (<NUM>). In this case step (<NUM>) is necessarily performed. Further alternatively, but also preferably, the organosilane constituent is present in component (A) used for preparing the sealant composition applied in step (<NUM>) and is also present in the primer composition optionally applied in step (<NUM>).

Preferably, the organosilane constituent is present at least in component (A) used for preparing the sealant composition applied in step (<NUM>). In particular, the organosilane constituent is present in component (A) used for preparing the sealant composition applied in step (<NUM>) and is not present in the primer composition optionally applied in step (<NUM>).

According to optional step (<NUM>) a primer composition is applied at least in portion onto a surface of an optionally pre-coated substrate to form a primer film at least in portion on said surface. Any kind of contacting may be used for performing step (<NUM>) such as dipping, brushing and/or spraying.

Optional step (<NUM>) preferably is performed with a <NUM>-compressed air supported cartridge apparatus, with a <NUM>-low pressure or <NUM>-high pressure dosing system. It may also be done manually.

Step (<NUM>) is preferably performed at a temperature in a range of from <NUM> to <NUM>, more preferably of from <NUM> to <NUM>. In particular, no heating is performed.

Suitable substrates are metallic substrates, but also plastic substrates such as polymeric substrates and/or fiber based composites can be used. Preferred substrates are substrates utilizable in the aerospace industry such as fuel tanks. Preferably, the surface to be sealed in this case is the inner surface of a fuel tank.

Suitability as metallic substrates used in accordance with the invention are all substrates used customarily and known to the skilled person. The substrates used in accordance with the invention are preferably metallic substrates including steel substrates. Most preferred, however, are aluminum and/or aluminum alloy substrates.

Preferably, thermoplastic polymers are used in case the substrates are plastic substrates. Suitable polymers are poly(meth)acrylates including polymethyl(meth)acrylates, polybutyl (meth)acrylates, polyethylene terephthalates, polybutylene terephthalates, polyvinylidene fluorides, polyvinyl chlorides, polyesters, including polycarbonates and polyvinyl acetate, polyamides, polyolefins such as polyethylene, polypropylene, polystyrene, and also polybutadiene, polyacrylonitrile, polyacetal, polyacrylonitrile-ethylene-propylene-diene-styrene copolymers (A-EPDM), ASA (acrylonitrile-styrene-acrylic ester copolymers) and ABS (acrylonitrile-butadienestyrene copolymers), polyetherimides, phenolic resins, urea resins, melamine resins, alkyd resins, epoxy resins, polyurethanes, including TPU, polyetherketones, polyphenylene sulfides, polyethers, polyvinyl alcohols, and mixtures thereof. Polycarbonates and poly(meth)acrylates are especially preferred.

However, fiber based composites such as carbon fiber composites may also be used as substrates.

The substrates used may be subjected to a pretreatment leading to a pre-coating. For example, an epoxy based coating may be applied before optional step (<NUM>) and step (<NUM>) are performed. Preferably, the substrates used bear at least one preferably cured coating layer such as an epoxy based coating layer, before optional step (<NUM>) and step (<NUM>) are performed.

At least one organosilane constituent is at least present - when step (<NUM>) is performed - at least present as a constituent in the primer composition applied in step (<NUM>).

The organosilane constituent contains (i) at least one hydrolyzable group X, (ii) at least one isocyanate group, and (iii) a spacer unit positioned between the at least one hydrolyzable group X and the at least one isocyanate group, wherein said spacer unit comprises the aforementioned at least one moiety MS.

Said organosilane constituent, which can be present in the primer composition applied in step (<NUM>), is further described in more detail hereinafter in connection with its optional presence as constituent (a2) in the sealant composition applied in step (<NUM>). This relevant disclosure with respect to constituent (a2) similarly applies to the organosilane constituent when it is present in the primer composition.

Preferably, the organosilane constituent - if at least present as a constituent in the primer composition applied in step (<NUM>) - is present therein in an amount in a range of from <NUM> to <NUM> wt. -%, preferably of from <NUM> to <NUM> wt. -%, more preferably of from <NUM> to <NUM> wt. -%, even more preferably of from <NUM> to <NUM> wt. -%, still more preferably of from <NUM> to <NUM> wt. -%, in each case based on the total weight of the primer composition.

The primer composition is different from the sealant composition applied in step (<NUM>). Preferably, it may contain each of constituents (a3) to (a6) identified and discussed hereinafter in connection with the sealant composition. Preferably, it does not contain any constituent (a1), i.e. it does not contain any polymeric constituents containing two or more thiol groups selected from polyether, polythioether, polysulfide, polythioether-sulfide constituents and mixtures thereof. Preferably, it does not contain any constituent (b) either, and in particular it does not contain any of constituents (b1) to (b4).

Preferably, the primer composition is an organic solvent(s)-based (solventborne, non-aqueous) composition. The term "solventborne" or "non-aqueous" is understood preferably for the purposes of the present invention in this regard to mean that organic solvent(s), as solvent(s) and/or as diluent(s), is/are present as the main constituent of all solvents and/or diluents present in the primer composition. Preferably, organic solvent(s) are present in an amount of at least <NUM> wt. -%, based on the total weight of the primer composition. A solventborne primer composition preferably includes an organic solvent(s) fraction of at least <NUM> or <NUM> wt. -%, more preferably of at least <NUM> or <NUM> wt. -%, very preferably of at least <NUM> or <NUM> wt. -%, based in each case on the total weight of the composition. All conventional organic solvents known to those skilled in the art can be used as organic solvents. The term "organic solvent" is known to those skilled in the art, in particular from Council Directive <NUM>/<NUM> / EC of <NUM> March <NUM>. Examples of such organic solvents would include heterocyclic, aliphatic, or aromatic hydrocarbons, mono- or polyhydric alcohols, especially ethanol and/or propanol, ethers, esters, ketones, xylene, 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. A solventborne composition preferably is free or essentially free of water. The term "essentially" in this context preferably means that no water is added on purpose when preparing the composition.

Preferably, the primer composition comprises a non-alcohol organic solvent(s) fraction of at least <NUM> or <NUM> wt. -%, more preferably of at least <NUM> or <NUM> wt. -%, very preferably of at least <NUM> wt. -%, based in each case on the total weight of the composition. Most preferred are aromatic hydrocarbons such as xylene and/or aliphatic hydrocarbons such as petrol ether.

Preferably, the primer composition comprises an alcohol organic solvent(s) fraction of <NUM> to <NUM> wt. -%, more preferably of <NUM> or <NUM> wt. -%, very preferably of <NUM> to <NUM> wt. -%, based in each case on the total weight of the composition. Most preferred are isopropylalcohol, butanol and/or methoxypropanol.

Besides the at least one organosilane constituent it may and preferably does contain at least one further adhesion promoting agent such as at least one further organsilane being different from the aforementioned organosilane constituent. Examples are e.g. (<NUM>-aminopropyl)trimethoxysilane, (<NUM>-aminopropyl)triethoxysilane, N-<NUM>-aminoethyl-<NUM>-aminopropyltrimethoxysilane, (<NUM>-mercaptopropyl)trimethoxysilane, (<NUM>-mercaptopropyl)triethoxysilane, (<NUM>-glycidyloxypropyl)trimethoxysilane and/or (<NUM>-glycidyloxypropyl)triethoxysilane, vinyltrimethoxysilane. Additionally or alternatively, other adhesion promoters may be used, e.g., titanates such as titanium acetylacetonate (TAA) and/or Ti-n-butanolate (TnBt) and/or isopropyl titanate, as well as e.g. zirconates. In case an additional adhesion promoter is present, it is preferably present in the primer composition an amount of from <NUM> to <NUM> wt. -%, more preferably of from <NUM> to <NUM> wt. -%, in particular of from <NUM> to <NUM> wt. -%, based on the total weight of the composition. Most preferably, at least one additional titanate and/or zirconate is present in one of the aforementioned amounts.

According to step (<NUM>) a sealant composition is applied at least in portion onto a surface of an optionally pre-coated substrate in case optional step (<NUM>) is not performed or onto the primer film in case optional step (<NUM>) is performed.

Any kind of contacting may be used for performing step (<NUM>) such as extrusion brushing and/or spraying. Step (<NUM>) is preferably performed at a temperature in a range of from <NUM> to <NUM>, more preferably of from <NUM> to <NUM>. In particular, no heating is performed.

Preferably, step (<NUM>) is performed with a <NUM>-compressed air supported cartridge apparatus, with a <NUM>-low pressure or <NUM>-high pressure dosing system. It may also be done manually.

The sealant composition is different from the primer composition optionally applied in step (<NUM>) and is obtainable by mixing the components of a sealing system with each other, said sealing system being a two-component (<NUM>) sealing system comprising, preferably consisting of, two components (A) and (B) being separate from each other. 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.

Each of the two components (A) and (B) of the sealing system may contain water and/or at least one organic solvent. However, it is also possible and even preferably if no organic solvents and/or water are present therein.

The amount of water present in component (A) preferably is less than <NUM> wt. -%, more preferably less than <NUM> wt. -%, even more preferably less than <NUM> wt. -%, still more preferably less than <NUM> wt. -%, in each case based on the total weight of component (A).

The amount of water present in component (B) when at least one constituent (b1) and/or at least one constituent (b3) and/or at least one constituent (b4) is present in each case as constituent (b) in (B) preferably is less than <NUM> wt. -%, more preferably less than <NUM> wt. -%, even more preferably less than <NUM> wt. -%, still more preferably less than <NUM> wt. -%, in each case based on the total weight of component (B). Constituents (b1), (b3) and (b4) will be defined hereinafter.

The amount of water present in component (B) when at least one constituent (b2) such as manganese dioxide is present as constituent (b) in (B) preferably is less than <NUM> wt. -%, more preferably less than <NUM> wt. -%, even more preferably less than <NUM> wt. -%, still more preferably less than <NUM> wt. -%, in each case based on the total weight of component (B). Constituent (b2) will be defined hereinafter.

If at least one organic solvent is present therein, organic solvent(s) are preferably present in an amount of up to <NUM> wt. -% or up to <NUM> 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 includes an organic solvent(s) fraction of up to <NUM> wt. -%, based in each case 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, organic solvent(s) are preferably present in an amount of up to <NUM> wt. -%, based on the total weight of the sealant composition. The sealant composition in this case preferably includes an organic solvent(s) fraction of up to <NUM> wt. -%, more preferably of up to <NUM> wt. -%, based in each case on the total weight of the composition. All conventional organic solvents known to those skilled in the art can be used as organic solvents. The term "organic solvent" is known to those skilled in the art, in particular from Council Directive <NUM>/<NUM> / EC of <NUM> March <NUM>. Examples of such organic solvents would include heterocyclic, aliphatic, or aromatic hydrocarbons, mono- or polyhydric alcohols, especially ethanol and/or propanol, ethers, esters, ketones, xylene, 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 may be identical or different from one another.

Component (A) of the sealing system comprises at least one polymeric constituent (a1) containing two or more thiol groups (mercapto groups) selected from polyether, polythioether, polysulfide, polythioether-sulfide constituents and mixtures thereof, preferably is selected from polythioether, polysulfide, polythioether-sulfide constituents and mixtures thereof, more preferably is selected from polythioether, polysulfide constituents and mixtures thereof, in particular is selected from polysulfide constituents.

The terms "polymer" and "polymeric" are known to the person skilled in the art and, for the purposes of the present invention, encompasses polyadducts and polymerizates as well as polycondensates. The term "polymer" includes both homopolymers and copolymers.

Due to the presence of the thiol groups, (a1) is necessarily a sulfur atoms containing constituent. The thiol groups of (a1) can be chemically reacted with constituent (b) or part of it, e.g. with suitable functional groups thereof. For example, when a constituent (b1) is present as constituent (b) the epoxide groups thereof can be reacted and at least one of hydroxythioether, hydroxythioethersulfide and/or hydroxysulfide moieties are formed. For example, when a constituent (b2) is present as constituent (b) such as contains manganese oxide, S-S-bonds are formed.

Preferably, polymeric constituent (a1) contains terminal thiol groups. Constituent (a1) may be branched or linear. Preferably, polymeric constituent (a1) is liquid at ambient conditions (<NUM> to <NUM>, <NUM>% relative humidity).

Polymeric constituents suitable for use as (a1) are e.g. disclosed in <CIT> and <CIT> as well as in <CIT>.

If at least one polythioether is used as (a1) it preferably is a liquid (at ambient conditions) polythioether. The polythioether may contain possibly up to about <NUM> mol-% of disulfide groups within the molecule. The respective polymers may then be named polythioethersulfides. Preferred compounds of this kind are described in <CIT>.

Preferably, polymeric constituent (a1) has a number average molecular weight in a range of from <NUM> to <NUM><NUM>/mol, more preferably of from <NUM> to <NUM>/mol. Most preferred is a number average molecular weight in a range of from <NUM> to <NUM><NUM>/mol, more preferably of from <NUM> to <NUM>/mol, especially when (a1) is at least one polysulfide. Examples for such polymers are e.g. polysulfides commercially available, e.g. under Thioplast® G131, Thioplast® G10, Thioplast® G12, Thiokol® LP <NUM> and/or Thiokol® LP <NUM>. Preferred is also a polymer constituent (a1) having a number average molecular weight in a range of from <NUM> to <NUM><NUM>/mol, more preferably of from <NUM> to <NUM>/mol or <NUM> to <NUM>/mol. In this case examples for such polymers are e.g. polysulfides commercially available, e.g. under Thiokol® LP3, Thioplast® G4, or Thioplast® G44.

Optionally, at least two kinds of constituents (a1) are present in component (A) having a different number average molecular weight: Long-chain polymers with a number average molecular weight in particular in the range from <NUM> to <NUM>/mol, particularly preferably in the range from <NUM> to <NUM>/mol, may be present besides short chain polymers with a number average molecular weight in particular in the range from <NUM> to <NUM>/mol, particularly preferably in the range from <NUM> to <NUM>/mol. Optionally, at least one of the aforementioned short chain polymers used in combination with the at least one aforementioned long chain polymer may be replaced by at least one polymeric, oligomeric or monomeric mercaptane, which preferably is solid or liquid, having three thiol groups and a number average molecular weight in a range of from <NUM> to <NUM>/mol. Alternatively, said mercaptane may be further added to the combination of the at least one short chain polymer and the at least one long chain polymer. Examples of such suitable mercaptanes are thiocyanuric acid (<NUM>,<NUM>,<NUM>-triazine-<NUM>,<NUM>,<NUM>-trithiol) and benzene-<NUM>,<NUM>,<NUM>-trithiol (<NUM>,<NUM>,<NUM>-trimercaptobenzene). In case said mercaptane used is non-polymeric, it formally represents a constituent (a6) of component (A). Preferably, said at least one mercaptane - if present - is present in an amount in a range of from <NUM> to <NUM> wt. -%, based on the total weight of component (A).

The sulfur containing polymeric constituents (a1) preferably have a mercaptan content referred to reactive SH-groups with respect to the total weight of (a1) in the range of from <NUM> to <NUM> wt. -%, more preferably of from <NUM> to <NUM> wt. -%, in particular of from <NUM> to <NUM> wt. The mercaptan content can be determined by direct titration of the SH-terminated polymers with an iodine solution: The polymers are dissolved in a solvent mixture composed of <NUM>% in volume of pyridine and <NUM>% in volume of benzene, and are titrated by stirring with a benzene iodine solution, until a weak yellow coloration remains.

Preferably, constituent (a1) has a total sulfur content in the range of from <NUM> to <NUM> wt. -%, more preferably of from <NUM> to <NUM> wt. -%, in particular of from <NUM> to <NUM> wt.

Preferably, constituent (a1) has an average functionality as reactive end groups of mercapto-groups per molecule in the range from <NUM> to <NUM> or from <NUM> to <NUM>. The functionality indicates the average number of mercapto groups per molecule. It is calculated as the ratio of molecular weight to equivalent weight and may be determined by NMR.

Preferably, constituent (a1) has an average glass transition temperature Tg in the range of from -<NUM> to -<NUM>° C or of from -<NUM> to -<NUM>° C. , measured according to the AITM <NUM>-<NUM> Airbus Industrie Test Method, June <NUM>.

Preferably, component (A) and the sealant composition as such are free from any constituents comprising (meth)acrylate groups (methacrylate and/or acrylate groups).

Preferably, constituent (a1) is present in the sealant composition obtained after having mixed components (A) and (B) of the sealing system with each other in an amount in a range of from <NUM> to <NUM> wt. -%, based on the total weight of the sealant composition.

At least one organosilane constituent is at least present - when optional step (<NUM>) is not performed - as constituent (a2) in component (A) of the sealing system used for preparing the sealant composition applied in step (<NUM>).

Preferably, the organosilane constituent - if at least present as constituent (a2) in component (A) of the sealing system used for preparing the sealant composition applied in step (<NUM>) - is present therein in an amount in a range of from <NUM> to <NUM> wt. -%, more preferably of from <NUM> to <NUM> wt. -%, still more preferably of from <NUM> to <NUM> wt. -%, even more preferably of from <NUM> to <NUM> wt. -%, still more preferably of from <NUM> to <NUM> wt. -%, in each case based on the total weight of component (A).

Preferably, the organosilane constituent - if at least present as constituent (a2) in component (A) of the sealing system used for preparing the sealant composition applied in step (<NUM>) - is present therein in an amount in a range of from <NUM> to <NUM> wt. -%, preferably of from <NUM> to <NUM> wt. -%, more preferably of from <NUM> to <NUM> wt. -%, even more preferably of from <NUM> to <NUM> wt. -%, still more preferably of from <NUM> to <NUM> wt. -%, in each case based on the total weight of the sealing composition obtainable by mixing at least components (A) and (B) of the sealing system with each other.

The organosilane constituent contains (i) at least one hydrolyzable group X, (ii) at least one isocyanate group, and (iii) a spacer unit positioned between the at least one hydrolyzable group X and the at least one isocyanate group, wherein said spacer unit comprises at least one moiety MS, which comprises at least one sulfur atom and which is preferably selected from the group consisting of thiocarbamate, thiourea, thioester, thioketo, thiourethane and thioamide moieties. Each of the moieties MS is preferably a divalent moiety present within the spacer unit. The term thiocarbamate preferably comprises O-thiocarbamates (-O-C(=S)-N-) and S-thiocarbamates (-S-(C=O)-N-). Preferably, a thiocarbamate moiety is a S-thiocarbamate moiety. Preferably, moiety MS thus at least contains at least one divalent -C(=X)-group, with X being a chalcogen atom selected from oxygen and sulfur. Preferably, the organosilane constituent contains precisely one moiety MS.

Preferably, the organosilane constituent comprises at least two, preferably at least three, hydrolyzable groups X, wherein X preferably is an alkoxy group. The hydrolyzable groups X may each be identical or at least two of these groups may each be different from one another. Preferably, the hydrolyzable groups X are alkoxy groups, in particular C<NUM>-C<NUM> alkoxy groups. Particularly preferred are methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, sec-butoxy and tert-butoxy groups. Most preferred are ethoxy groups and methoxy groups.

The organosilane constituent can be monomeric, oligomeric or polymeric. Preferably, it is non-polymeric, more preferably monomeric.

Preferably, the at least one organosilane constituent has a number average molecular weight in a range of from <NUM> to <NUM>/mol, more preferably of from <NUM> to <NUM>/mol, even more preferably of from <NUM> to <NUM>/mol, still more preferably of from <NUM> to <NUM>/mol.

Preferably, the spacer unit positioned between the at least one hydrolyzable group X and the at least one isocyanate group and containing the at least one moiety MS is a trivalent or divalent, more preferably divalent, non-hydrolzyable organic residue, which preferably is aliphatic including cycloaliphatic, heteroaliphatic including heterocycloaliphatic and/or aromatic including heteroaromatic. The residue preferably is selected from the group comprising C<NUM>-C<NUM> aliphatic radicals, C<NUM>-C<NUM> heteroaliphatic radicals, C<NUM>-C<NUM> cycloaliphatic radicals, <NUM>-<NUM> membered heterocycloaliphatic radicals, <NUM>-<NUM> membered aryl or heteroaryl radicals, C<NUM>-C<NUM> cycloaliphatic radical bonded via a C<NUM>-<NUM> aliphatic radical, <NUM>-<NUM>-membered heterocycloaliphatic radicals bonded via a C<NUM>-<NUM>-aliphatic radical, <NUM>-<NUM>-membered aryl or heteroaryl radicals bonded via a C<NUM>-<NUM>-aliphatic radical. The moiety MS is additionally positioned within each of these residues. Preferably, the spacer unit has a chain length separating the at least one hydrolyzable group X and the at least one isocyanate group of at least six carbon and/or heteroatoms, preferably including at least one atom of moiety MS within the chain.

Preferably, the at least one moiety MS of the spacer unit of the organosilane constituent represents a thiocarbamate and/or thiourea moiety. Preferably, a thiocarbamate moiety is a S-thiocarbamate moiety.

Preferably, the at least one organosilane constituent comprises precisely one isocyanate group.

Preferably, the at least one organosilane constituent is preferably obtainable from a reaction of at least one diisocyanate and/or polyisocyanate with at least one organosilane precursor comprising at least one functional group that is reactive towards isocyanate groups, wherein said at least one functional group that is reactive towards isocyanate groups is preferably a thiol group. Diisocyanates have precisely two NCO-groups, whereas polyisocyanates have more than two NCO-groups. Suitable polyisocyanates are e.g. isocyanurates such as isophororone diisocyanate (IPDI) and HMDI (hexamethylene diisocyanate) trimers. Suitable diisocyanates are aliphatic and cycloaliphatic diisocyanates such as isophororone diisocyanate (IPDI) and HMDI (hexamethylene diisocyanate), HMDI and/or IPDI uretdiones and/or allophanates as well as hydrogenated MDI (methylene diphenyl isocyanate). Aromatic diisocyanates such as TDI and XDI are also suitable. However, the use of aliphatic and cycloaliphatic diisocyanates is preferred.

Preferably, the at least one organosilane constituent is preferably obtainable from a reaction of at least one diisocyanate with at least one organosilane precursor comprising at least one functional group that is reactive towards isocyanate groups, wherein said at least one functional group that is reactive towards isocyanate groups is preferably a thiol group, in particular when the at least one diisocyanate and the at least one organosilane precursor are used each in about equimolar amounts. Suitable diisocyanates are aliphatic and cycloaliphatic diisocyanates such as isophororone diisocyanate (IPDI) and HMDI (hexamethylene diisocyanate). Aromatic diisocyanates such as TDI and XDI are also suitable. However, the use of aliphatic and cycloaliphatic diisocyanates is preferred.

Preferably, the at least one organosilane constituent is obtainable from a reaction of at least one preferably aliphatic and/or cycloaliphatic diisocyanate with at least one organosilane precursor comprising at least one thiol group as functional group that is reactive towards isocyanate groups.

The at least one organosilane precursor preferably is a monosilane, which preferably has at least two, particularly preferably three hydrolyzable groups X, and/or is at least one bis(silane), which preferably has at least four, particularly preferably six hydrolyzable groups X.

Preferably, at least one organosilane precursor of general formulae (I) and/or (II) is used for reaction with the at least one diisocyanate,.

Si(X)<NUM>-z(T)z-(RA)-Si(X)<NUM>-z(T)z     (II),.

wherein in the case of general formula (I).

Component (A) may additionally contain at least one filler (a3) and/or at least one pigment (a4).

The term "filler" is known to the skilled person, from DIN <NUM> (date: October <NUM>), for example. A "filler" for the purposes of the present invention is preferably a constituent, which is substantially, preferably entirely, insoluble in the medium surrounding them, such as each of components (A) and (B) and the sealant composition, for example, and which is used in particular for adjusting the viscosity and thixotropy of the components and the sealant composition, for adjusting the specific density of the cured sealant and/or for increasing the mechanical properties of the cured sealant. "Fillers" in the sense of the present invention differ from "pigments" in their refractive index, which for fillers is < <NUM>, while the refractive index for pigments is ≥ <NUM>. Preferably, a "filler" for the purposes of the present invention is an inorganic and/or organic filler. Examples of inorganic fillers are chalk and talcum. Examples of organic fillers are powders prepared from temperature resistant polymers such as polyamides, polysulfones, polyphenylene sulfides, polyetherketones and polymeric hollow spheres.

Preferably, the amounts of fillers present in component (A) of the sealing system is in the range of from <NUM> to <NUM> wt. -%, more preferably in the range of from <NUM> to <NUM> wt. -%, even more preferably in the range of from <NUM> to <NUM> wt. -%, still more preferably in the range of from <NUM> to <NUM> wt. -%, yet more preferably in the range of from <NUM> to <NUM> wt. -% or of from <NUM> to <NUM> wt. -%, in particular in the range of from <NUM> to <NUM> wt. -%, in each case based on the total weight of component (A).

Preferably, the amounts of any pigments present in component (A) of the sealing system is in the range of from <NUM> to <NUM> wt. -%, more preferably in the range of from <NUM> to <NUM> wt. -%, even more preferably in the range of from <NUM> to <NUM> wt. -%, still more preferably in the range of from <NUM> to <NUM> wt. -%, yet more preferably in the range of from <NUM> to <NUM> wt. -%, in each case based on the total weight of component (A).

The term "pigment" is known to the skilled person from DIN <NUM> (date: October <NUM>), for example. A "pigment" in the sense of the present invention refers preferably to components in powder or flake form which are substantially, preferably entirely, insoluble in the medium surrounding them, such as each of components (A) and (B) and the sealant composition, for example, and which is a colorant and/or substance which can be used as pigment on account of their magnetic, electrical and/or electromagnetic properties. Preferably, a "pigment" for the purposes of the present invention is an inorganic and/or organic pigment. An example of an inorganic pigment is titanium dioxide.

Component (A) may additionally contain and preferably contains at least one curing catalyst (a5), when component (B) of the sealing system comprises at least one constituent (b1) comprising two or more epoxide groups as constituent (b). Suitable curing catalysts are amines, in particular tertiary amines, amidines and/or guanidines. Examples are <NUM>,<NUM>-diazabicyclo(<NUM>. <NUM>)octane, <NUM>,<NUM>-diazabicyclo(<NUM>. <NUM>)non-<NUM>-ene (DBN) and <NUM>,<NUM>-diazabicyclo(<NUM>. <NUM>)undec-<NUM>-ene (DBU).

Component (A) of the sealing system may contain one or more optional constituents (a6).

Constituent (a6) may be a flame retardant such as a phosphorous-containing flame retardants, in particular at least one phosphate ester. If a flame retardant is used, it preferably is liquid (at <NUM> bar and <NUM>). In case a flame retardant is present in component (A), it is preferably present therein in an amount of <NUM> to <NUM> wt. -%, more preferably of <NUM> to <NUM> wt. -%, in particular of <NUM> to <NUM> wt. -%, based on the total weight of component (A).

Constituent (a6) may be a light stabilizer, in particular a UV stabilizers. Examples are for instance sterically hindered amines (HALS: hindered amine light stabilizer). 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 <NUM> to <NUM> wt. -%, more preferably of <NUM> to <NUM> wt. -%, in particular of <NUM> to <NUM> wt. -%, based on the total weight of component (A).

Constituent (a6) may be an additional adhesion promoter besides the aforementioned organosilane constituent. In particular, organosilanes different from constituent (a2) can be used. Examples are e.g. (<NUM>-aminopropyl)trimethoxysilane, (<NUM>-aminopropyl)triethoxysilane, N-<NUM>-aminoethyl-<NUM>-aminopropyltrimethoxysilane, (<NUM>-mercaptopropyl)trimethoxysilane, (<NUM>-mercaptopropyl)triethoxysilane, (<NUM>-glycidyloxypropyl)trimethoxysilane and/or (<NUM>-glycidyloxypropyl)triethoxysilane, vinyltrimethoxysilane. Additionally or alternatively, other adhesion promoters may be used, e.g., titanates and/or zirconates, such as titanium acetylacetonate (TAA) and/or Ti-n-butanolate (TnBt) and/or isopropyl titanate. In case an additional adhesion promoter is present in component (A), it is preferably present therein in an amount of <NUM> to <NUM> wt. -%, more preferably of <NUM> to <NUM> wt. -%, in particular of <NUM> to <NUM> wt. -%, based on the total weight of component (A).

Constituent (a6) may be an additive selected from the group consisting of defoamers, rheological additives, plasticizers such as phthalates, and viscosity reducers, in particular non-reactive viscosity reducers such as hydrocarbon mixtures based on naphthalene derivatives and/or indene-coumarone resins, tall oil and rapeseed methyl ester (biodiesel) and rapeseed oil and/or other ester-based diluents, as well as mixtures of such additives. In case at least one additive is present in component (A), it is preferably present therein in an amount of <NUM> to <NUM> wt. -%, more preferably of <NUM> to <NUM> wt. -%, in particular of <NUM> to <NUM> wt. -%, based on the total weight of component (A). Specifically, in case at least one defoamer is present, its amount is preferably in the range of from <NUM> to <NUM> wt. -%, based on the total weight of component (A). Specifically, in case at least one reactive diluent is present, its amount is preferably in the range of from <NUM> to <NUM> wt. -%, based on the total weight of component (A). Specifically, in case at least one rheological additive is present, its amount is preferably in the range of from <NUM> to <NUM> wt. -%, based on the total weight of component (A). Specifically, in case at least one plasticizer is present, its amount is preferably in the range of from <NUM> to <NUM> wt. -%, based on the total weight of component (A). Specifically, in case at least one viscosity reducer is present, its amount is preferably in the range of from <NUM> to <NUM> wt. -%, based on the total weight of component (A).

As outlined hereinbefore in connection with constituent (a1), constituent (a6) may further be at least one non-polymeric mercaptane having three thiol groups and a number average molecular weight in a range of from <NUM> to <NUM>/mol. Preferably, said at least one non-polymeric mercaptane - if present - is present as constituent (a6) in an amount in a range of from <NUM> to <NUM> wt. -%, more preferably of from <NUM> to <NUM> wt. -%, in each case based on the total weight of component (A).

Component (B) of the sealing system comprises at least one constituent (b), which is suitable for hardening the sealant composition by at least partially inducing a chemical transformation of the two or more thiol groups of constituent (a1). In other words, constituent (b) or part of it can be chemically reacted with the thiol groups of constituent (a1). Constituent (b) thus represents a curing agent. The resulting chemical transformation may apply to all thiol groups of constituent (a1) or to only part of the thiol groups of constituent (a1). Preferably, however, a chemical transformation is not only induced partially, but substantially to all thiol groups of constituent (a1).

Preferably, the least one constituent (b) is selected from the group consisting of constituents comprising two or more epoxide groups (constituents (b1)), constituents, which are metal oxides and/or metal peroxides, in particular manganese dioxide, (constituents (b2)), constituents, which are organic peroxides (constituents (b3)), constituents comprising two or more vinyl groups (constituents (b4), and mixtures thereof, more preferably is selected from the group consisting of constituents comprising two or more epoxide groups (constituents (b1)), constituents, which are metal oxides and/or metal peroxides, in particular manganese dioxide, (constituents (b2)), and mixtures thereof, in particular represents either at least one constituent comprising two or more epoxide groups as constituent (b1) or represents at least one metal oxide and/or metal peroxide, in particular manganese dioxide, as constituent (b2).

Preferably, constituent (b) is present in component (B) of the sealing system used for preparing the sealant composition applied in step (<NUM>) in an amount in a range of from <NUM> to <NUM> wt. -%, based on the total weight of component (B).

Constituent (b1) comprises two or more epoxide groups. Preferably, the epoxide groups are present in (b1) as terminal groups. Constituent (b1) can be monomeric, oligomeric or polymeric. Preferably, (b1) is aliphatic and/or aromatic.

Preferably, constituent (b1) is present in component (B) of the sealing system used for preparing the sealant composition applied in step (<NUM>) in an amount in a range of from <NUM> to <NUM> wt. -%, based on the total weight of component (B).

Preferably, (b1) has an epoxide functionality of from <NUM> to <NUM>, more preferably of from <NUM> to <NUM>, in particular of from <NUM> to <NUM>.

Constituent (b1) is particularly selected from diglycidyl ethers of bisphenol A, diglycidyl ethers of bisphenol F and aliphatic polyglycol and/or hydantoin epoxy derivatives. Also, epoxy-terminated polythioether or polythioethersulfide and/or epoxidized polysulfides may be used. Particularly preferred is also at least one epoxy-novolac resin (epoxidized phenol formaldehyde resin), preferably a crosslinked epoxy novolac resin. It is also possible that more than constituents (b1) can be used based on several of the abovementioned classes, for example, bisphenol A/F epoxy resin or bisphenol F novolac resin. Component (B) may additionally contain diluting agents in order to adjust the viscosity and flexibility, for example. Examples of diluting agents are <NUM>,<NUM>-butanediol diglycidyl ether, <NUM>-ethylhexyl-glycidyl ether and <NUM>,<NUM>-hexanediol diglycidyl ether.

Preferably, (b1) is at least one epoxide-terminated polysulfide polymer and/or polythioether polymer and/or polythioethersulfide polymer without terminal mercapto groups, which serves as a curing agent due to its two terminal epoxide groups. This polymer is preferably present as a liquid or highly viscous polymer with an epoxy equivalent weight in particular in the range from <NUM> to <NUM>/eq.

Preferably, the epoxy (epoxide) equivalent weight of (b1) is in the range of from <NUM> to <NUM>/eq, particularly preferably in the range of from <NUM> to <NUM>/eq, and most preferably in the range of from <NUM> to <NUM>/eq.

Most particularly preferred are constituents (b1) based on bisphenol A epoxy resins having an epoxy equivalent weight in the range from <NUM> to <NUM>/eq, based on bisphenol F resin having an epoxy equivalent weight in the range from <NUM> to <NUM>/eq and based on epoxy novolac resins having an epoxy equivalent weight in the range from <NUM> to <NUM>/eq.

Examples of suitable commercial products are e.g. bisphenol F epoxy resins such as DEN <NUM> (Olin Epoxy), bisphenol A resins such as DER <NUM>, DER <NUM> (Olin Epoxy), bisphenol A/F epoxy resins such as DER <NUM>, DER <NUM>, DER <NUM> (Olin Epoxy), epoxy novolac resins such as DEN <NUM>, DEN <NUM>, DEN <NUM> (Olin Epoxy), epoxy-terminated prepolymers based on polysulfide and/or polythioether such as Thioplast EPS <NUM> (Akzo Nobel), epoxy-terminated reactive diluents based on alcohol/glycols such as <NUM>,<NUM>-butanediol diglycidyl ether (DER <NUM>; Olin Epoxy), and <NUM>,<NUM>-hexanediol diglycidyl ether (DER <NUM>; Olin Epoxy).

Preferably, the molar ratio of all constituents (b1) to all constituents (a1) is in a range of from <NUM>:<NUM> to <NUM>:<NUM>.

Constituent (b2) is at least one metal oxide and/or metal peroxide, in particular manganese dioxide. Manganese dioxide means manganese (IV) oxide. Another suitable constituent (b2) is calcium peroxide.

Preferably, constituent (b2) is present in component (B) of the sealing system used for preparing the sealant composition applied in step (<NUM>) in an amount in a range of from <NUM> to <NUM> wt. -%, based on the total weight of component (B).

Constituent (b3) is at least one organic peroxide. Examples of suitable organic peroxides are organic hydroperoxides such as cumenyl hydroperoxide.

Preferably, constituent (b3) is present in component (B) of the sealing system used for preparing the sealant composition applied in step (<NUM>) in an amount in a range of from <NUM> to <NUM> wt. -%, based on the total weight of component (B).

Constituent (b4) comprises two or more vinyl groups. Preferably, the vinyl groups are present in (b4) as terminal groups. Constituent (b4) can be monomeric, oligomeric or polymeric, and preferably is monomeric. Preferably, (b4) is aliphatic and/or aromatic.

Examples of constituent (b4) are divinyl ethers such as diethyleneglycol divinyl ether, triethyleneglycol divinyl ether and butandiol divinyl ether.

Preferably, constituent (b4) is present in component (B) of the sealing system used for preparing the sealant composition applied in step (<NUM>) in an amount in a range of from <NUM> to <NUM> wt. -%, based on the total weight of component (B).

If constituent (b4) is used as constituent (b) of component (B), it preferably is present in combination with at least one radical generator. Examples of suitable radical generators are <NUM>-hydroxycyclohexyl phenylketone and <NUM>-hydroxy-<NUM>-methyl-<NUM>-phenylpropane-<NUM>-one.

Component (B) of the sealing system may contain one or more optional constituents (b5). Constituent (b5) may be an additive selected from the group consisting of reactive diluents such as such as bis-oxazolidines and/or aldimines, and plasticizers such as phthalates. In particular, at least one plasticizer constituent (b5) is present in component (B), when component (B) of the sealing system comprises at least one constituent (b2), in particular manganese dioxide.

Specifically, in case at least one reactive diluent is present, its amount is preferably in the range of from <NUM> to <NUM> wt. -%, based on the total weight of component (B). Specifically, in case at least one plasticizer is present, its amount is preferably in the range of from <NUM> to <NUM> wt. -%, based on the total weight of component (B).

Component (B) may additionally contain and preferably contains at least one curing catalyst (b6).

As outlined hereinbefore, when component (B) of the sealing system comprises at least one constituent (b1) comprising on turn two or more epoxide groups as constituent (b), at least one curing catalyst if present is preferably present in component (A) as constituent (a5) and is not present in component (B). Suitable curing catalysts in this case are amines, in particular tertiary amines, amidines and/or guanidines. Examples are <NUM>,<NUM>-diazabicyclo(<NUM>. <NUM>)octane, <NUM>,<NUM>-diazabicyclo(<NUM>. <NUM>)non-<NUM>-ene (DBN) and <NUM>,<NUM>-diazabicyclo(<NUM>. <NUM>)undec-<NUM>-ene (DBU).

When component (B) of the sealing system comprises at least one constituent (b2) as constituent (b), at least one curing catalyst (b6) is preferably present in component (B). Suitable curing catalysts in this case are e.g. tetrabenzylthiuram disulfide, diphenylguanidine, and/or zinc bis(diethyldithiocarbamate).

When component (B) of the sealing system comprises at least one constituent (b3) as constituent (b), at least one curing catalyst (b6) is preferably present in component (B). Suitable curing catalysts in this case are e.g. zinc diethycarbamate.

When component (B) of the sealing system comprises at least one constituent (b4) as constituent (b), at least one curing catalyst (b6) is preferably present in component (B). Suitable curing catalysts in this case are in particular suitable photoinitiators such as acetophenones, benzoin ethers and/or benzoyl oximes. Curing preferably takes place via UV light.

Component (B) may additionally contain at least one flame retardant (b7). Constituent (b7) may be a phosphorous-containing flame retardant, in particular at least one phosphate ester. If a flame retardant is used, it preferably is liquid (at <NUM> bar and <NUM>). In case a flame retardant is present in component (A), it is preferably present therein in an amount of <NUM> to <NUM> wt. -%, more preferably of <NUM> to <NUM> wt. -%, in particular of <NUM> to <NUM> wt. -%, based in each case on the total weight of component (B).

Preferably, the inventive method further comprises a curing step (<NUM>), namely (<NUM>) curing at least the sealant composition applied in step (<NUM>) at ambient temperature (<NUM> to <NUM>) or at an elevated temperature such as <NUM> for <NUM> hours to <NUM> days.

Preferably, curing according to step (<NUM>) means chemical curing such as chemical crosslinking, at ambient temperature or at an elevated temperature. In case of using at least one constituent (b1) or (b4) as constituent (b), curing may additionally or alternatively be induced via UV light.

Preferably, the sealant composition is applied in a dry layer thickness in the range of from <NUM> to <NUM>, more preferably of from <NUM> to <NUM>, in particular of from <NUM> to <NUM>.

All preferred embodiments described above herein in connection with the inventive method and the preferred embodiments thereof, are also preferred embodiments of the inventive sealed substrate.

A further subject-matter of the present invention is a use of an organosilane constituent as defined hereinbefore when incorporated into a primer composition as defined in hereinbefore such as into a primer composition used in step (<NUM>) of the inventive method or into a sealant composition as defined hereinbefore such as into a sealant composition used in step (<NUM>) of the inventive method, in particular into component (A) of a sealing system used for preparing said sealant composition, for enhancing the adhesion of the primer composition or of the sealant composition to an optionally pre-coated substrate once applied to at least a portion of its surface.

All preferred embodiments described above herein in connection with the inventive method and the inventive sealed substrate and the preferred embodiments thereof, are also preferred embodiments of the inventive use.

A further subject-matter of the present invention is a sealant composition as defined hereinbefore, which is obtainable by mixing components (A) and (B) of a sealing system as defined hereinbefore with each other, wherein component (A) of said sealing system comprises the at least one organosilane constituent as defined hereinbefore.

The obtained sealing composition may be sprayable, but does not have to be.

Preferably, the sealing composition is obtainable by mixing components (A) and (B) in a weight ratio (component (A)/component (B)) in the range of from <NUM>:<NUM> to <NUM>:<NUM>. More preferably, mixing is performed in a weight ratio in the range of from <NUM>:<NUM> to <NUM>:<NUM>, even more preferably in a weight ratio in the range of from <NUM>:<NUM> to <NUM>:<NUM>, in particular in a weight ratio in the range of from <NUM>:<NUM> to <NUM>:<NUM>, most preferred in a weight ratio in the range of from <NUM>:<NUM> to <NUM>:<NUM>.

A further subject-matter of the present invention is a two-component (<NUM>) sealing system comprising components (A) and (B) as defined hereinbefore, being separate from each other, wherein component (A) of said sealing system comprises the at least one organosilane constituent as defined hereinbefore.

All preferred embodiments described above herein in connection with the inventive method, the inventive sealed substrate and the inventive use and the preferred embodiments thereof, are also preferred embodiments of the inventive sealant composition and the inventive sealing system.

Preferably, the sealing system consists of components (A) and (B).

A further subject-matter of the present invention is an organosilane constituent as defined hereinbefore, optionally being incorporated into a primer composition as defined hereinbefore.

All preferred embodiments described above herein in connection with the inventive method, the inventive sealed substrate, the inventive use, the inventive sealant composition and the inventive sealing system, and the preferred embodiments thereof, are also preferred embodiments of the inventive organosilane constituent.

A further subject-matter of the present invention is a primer composition as defined hereinbefore comprising at least the at least one organosilane constituent as defined hereinbefore.

All preferred embodiments described above herein in connection with the inventive method, the inventive sealed substrate, the inventive use, the inventive sealant composition and the inventive sealing system, and the inventive organosilane constituent, and the preferred embodiments thereof, are also preferred embodiments of the inventive primer composition.

The peel test was performed according to AMS-C-<NUM>.

The immersion test was performed according to AMS <NUM> (type <NUM> for <NUM> days).

The number average molecular weight of constituents (a1) and (b1) is determined through GPC (gel permeation chromatography) against polystyrene standards. THF (tetrahydrofurane) is used as a mobile phase. The number average molecular weight of organosilane constituent (a2) is determined through NMR spectroscopy in case of monomeric and oligomeric constituents and is determined via GPC in case of polymeric constituents.

The following examples further illustrate the invention. 'Pbw' means parts by weight. If not defined otherwise, 'parts' means 'parts by weight'.

OS1 was prepared by adding IPDI (isophorone diisocyanate) slowly dropwise under stirring to bis[<NUM>-(trimethoxysilyl)propyl]amine. IPDI and bis[<NUM>-(trimethoxysilyl)propyl]-amine were used in equimolar amounts. The resulting product was used as OS1 without purification.

OS2 was prepared by heating an equimolar mixture of IPDI and (<NUM>-mercaptopropyl)methyldimethoxysilane additionally containing <NUM> mol <NUM>,<NUM>-dimethylpiperazine under stirring under inert gas atmosphere to <NUM> for <NUM> hours. The resulting product was used as OS2 without purification. OS2 had an NCO-content of <NUM> wt.

OS3 was prepared by heating an equimolar mixture of HMDI (hexamethylene diisocyanate) and (<NUM>-mercaptopropyl)trimethoxysilane additionally containing <NUM> mol <NUM>,<NUM>-dimethylpiperazine under stirring under inert gas atmosphere to <NUM> for <NUM> hours. The resulting product was used as OS3 without purification. OS3 had an NCO-content of <NUM> wt.

OS4 was prepared by heating an equimolar mixture of IPDI and (<NUM>-mercaptopropyltrimethoxysilane additionally containing <NUM> mol <NUM>,<NUM>-dimethylpiperazine under stirring under inert gas atmosphere to <NUM> for <NUM> hours. The resulting product was used as OS4 without purification. OS4 had an NCO-content of <NUM> wt.

<NUM> A number of exemplary sealant compositions were prepared. Each of the sealant compositions was prepared from mixing two components (A) and (B) of a two-component sealing system with each other. The composition of component (A) of each of the sealing systems is given in Table <NUM>. Component (A) is prepared from mixing the constituents listed in Table <NUM> with each other in the order given in Table <NUM>.

Thioplast® LP12 and Thioplast® LP33 are commercially available SH-groups containing polysulfides. Filler <NUM> and Filler <NUM> are commercially available fillers. Pigment <NUM> is a commercially available pigment. Rheological additive <NUM> is commercially available hydrophobic fumed silica. OS is one of NCO-functionalized organosilanes OS1 to OS4 or one of commercially organosilanes (<NUM>-glycidyloxypropyl)trimethoxysilane (COS1) and (<NUM>-mercaptopropyl)trimethoxysilane (COS2).

Depending on which of organosilanes OS1 to OS4, COS1 and COS2 has been used, different components "A" of a sealing system were obtained in this manner, namely SC-A-OS1, SC-A-OS2, SC-A-OS3, SC-A-OS4, SC-A-COS1 and SC-A-COS2.

<NUM> <NUM> parts by weight of each of the components "A" SC-A-OS1, SC-A-OS2, SC-A-OS3, SC-A-OS4, SC-A-COS1 and SC-A-COS2 was mixed with <NUM> parts by weight of a hardener component "B". Component "B" contains a manganese dioxide hardener. A commercially available product was used as component (B) in each case (Naftoseal® MC <NUM> B-<NUM> hardener from Chemetall GmbH).

<NUM> After each of the components "A", namely SC-A-OS1, SC-A-OS2, SC-A-OS3, SC-A-OS4, SC-A-COS1 and SC-A-COS2 had been mixed with component "B" the resulting sealant compositions obtained after mixing, namely SC-OS1, SC-OS2, SC-OS3, SC-OS4, SC-COS1 and SC-COS2, were applied in each case to a substrate by applying air pressure to a cartridge. The following substrates S1 to S3 were used:.

After having been applied to one of the substrates the applied sealant compositions were cured for <NUM> days at room temperature (<NUM>) and <NUM>% relative humidity. The sealed substrates were then subjected to a number of tests as it will be outlined hereinafter.

Some properties of the sealed and cured substrates have been investigated. The measurements have been performed according to the methods disclosed in the 'methods' section. The results are displayed in Table <NUM>.

Claim 1:
A method of sealing an optionally pre-coated substrate comprising at least step (<NUM>) and optionally also step (<NUM>), namely
(<NUM>) optionally applying a primer composition at least in portion onto a surface of an optionally pre-coated substrate to form a primer film at least in portion on said surface,
(<NUM>) applying a sealant composition at least in portion onto a surface of an optionally pre-coated substrate in case optional step (<NUM>) is not performed or onto the primer film in case optional step (<NUM>) is performed,
wherein the sealant composition is different from the primer composition optionally applied in step (<NUM>) and is obtainable by mixing the components of a sealing system with each other, said sealing system being a two-component (<NUM>) sealing system comprising two components (A) and (B) being separate from each other,
wherein component (A) of the sealing system comprises at least one polymeric constituent (a1) containing two or more thiol groups selected from polyether, polythioether, polysulfide, polythioether-sulfide constituents and mixtures thereof, and
wherein component (B) of the sealing system comprises at least one constituent (b), which is suitable for hardening the sealant composition by at least partially inducing a chemical transformation of the two or more thiol groups of constituent (a1),
characterized in that at least one organosilane constituent, which contains
(i) at least one hydrolyzable group X,
(ii) at least one isocyanate group, and
(iii) a spacer unit positioned between the at least one hydrolyzable group X and the at least one isocyanate group, wherein said spacer unit comprises at least one moiety MS, which comprises at least one sulfur atom,
is at least present - when optional step (<NUM>) is not performed - as constituent (a2) in component (A) of the sealing system used for preparing the sealant composition applied in step (<NUM>) or is - when step (<NUM>) is performed - at least present as a constituent in the primer composition applied in step (<NUM>).