Sealants comprising thiol-terminated, epoxy-curable polymers and photo-latent bases

Abstract

The invention relates to a sealant system comprising at least one base component, comoprising at least one thiol- terminated polymer selected from the group consisting of polysulfides, polythioethers, polyethers and copolymers thereof; and at least one hardener component, comprising at least one polyepoxide, wherein the base component further comprises at least one non-ionic photo-latent base having the general formula (PCG)-(BG)n, wherein PCG stands for a photocleavable group; BG stands for a base group; n is 1 or 2; the base formed after cleaving the bond between PCG and BG is a non-ionic base, and possesses a pKa value of the conjugate acid of ≥ 10.0; and the non-ionic photo-latent base has a photoactivation wavelength for cleaving the bond between PCG and BG in the range of 300 nm to 420 nm.

Description

[0001] 220977W001 1 S022796PCT 1 October 07, 2025

[0002] Chemetall GmbH

[0003] SEALANTS COMPRISING THIOL-TERMINATED, EPOXY-CURABLE POLYMERS AND PHOTO-LATENT BASES

[0004] The invention relates to a sealant system, comprising a base component containing at least one thiol-terminated polymer and a photo-latent base, and hardener component containing at least one polyepoxide. The invention further relates to a sealant system comprising or consisting of a mixture of the base component and hardener component. Moreover, the invention relates to a method of sealing.

[0005] BACKGROUND OF THE INVENTION

[0006] UV-curing technology is widely known in various industries like automotive, electronic, consumer and construction industry. Products like coatings, paints, adhesives or sealants were designed as UV-curable products and enable users rapid curing processes and a high degree of automatization.

[0007] Therefore UV-technologies gained importance in aircraft industry recently. Today, the most common sealanttechnology used for aircrafts are still polysulfide-based two-component systems. These systems are mixed before usage and applied mostly manual afterwards. The required curing time is determined by the used product category and highly dependent on environmental influences like temperature or humidity.

[0008] Beside these drawbacks, the limited processing time of a mixed composition also limits the user's flexibility and leads to a high degree of unused but cured sealant, which need to be disposed. Therefore, a sealant-technology which combines short curing times with long processing times is desired.

[0009] For the sake of saving energy and profit from longer lifecycles, UV-exposure with efficient LED-lamps have become state-of-the-art in the mentioned industries. Although one need to keep in mind that this technology entails some aspects which were not relevant in case of discharging lamps. The emission spectra are way sharper compared to a discharging lamp, that requires initiators which are sensitive in the desired wavelength. Although the selective design of a suitable photo-latent base (or photo- or UV-catalyst, initiator) which provides the desired sensitivity in combination with other requirements (solubility, reactivity, storage stability) is challenging, since the absorbance spectra of the compound as such can be very different to the spectra of the pure photocleavable group.

[0010] EP 3 572 448 A1 relates to methods for making a cured sealant. The methods include depositing an uncured sealant composition on a substrate and exposing the uncured sealant composition to actinic radiation to provide a cured sealant. The uncured sealant composition includes a thiol-terminated polythioether, a polyene comprising a polyvinyl ether and / or a polyallyl compound, a hydroxy-functional vinyl ether, and a photoinitiator. Those sealants are proposed as aerospace sealant compositions. 220977W001 1 S022796PCT 2 October 07, 2025

[0011] Chemetall GmbH

[0012] EP 2 274 378 A2 discloses to thiol-ene curing compositions, which cure upon exposure to ultraviolet (UV) light and / or heat. The compositions include components having alkenyl (or "ene") functionality and components having thiol functionality, which undergo thiol-ene curing. The compositions also include a cure system. More specifically, in some embodiments, the curable compositions include a vinyl polymer bearing alkenyl or thiol terminal functional group(s) and a cross-linking agent having the opposing functionality, i.e., thiol cross-linking agents with alkenyl- terminated vinyl polymers and vinyl cross-linking agents with thiol-terminated vinyl polymers. Also provided are methods of making and using the compositions, such as for sealants for in-place gasketing applications. The cured products are supposed to be elastomeric, strong, and resistant to oils and solvents, making the compositions particularly suitable for gasketing and other sealing applications.

[0013] EP 3 478 748 A1 relates to a dual curable thiol-ene composition comprising a polythiol, an unsaturated compound, a photoinitiator, an organic hydroperoxide (thermal initiator) and optionally a nitrogen-containing base, such as e.g. an N-heterocyclic compound (together with the organic hydroperoxide a redox initiator system). A cross-linked polymer prepared therefrom. A method of making such a polymer. A cured sealant comprising such a polymer. The sealant is preferably for use in aerospace.

[0014] EP 3 114 155 A1 describes compositions comprising Michael acceptor-terminated sulfur-containing prepolymers, thiol-terminated sulfur-containing prepolymers, and phosphine catalysts useful in aerospace sealant applications. The compositions exhibit extended pot life, cure rapidly following activation, and provide cured sealants having improved properties useful in aerospace sealant applications.

[0015] US 11 , 124,674 B2 relates to a method for curing a mixture of a matrix and a curing agent based on sulfur-containing polymers on command and so rapidly that a tack-free surface results. A method for coating a substrate with the composition and of curing a sealant is also provided. The matrix and curing agent containing sulfur-containing polymers. The mixture is an uncured mixture with an isocyanate content, and the matrix is uncured and contains a mercaptan-terminated base polymer based on at least one polyether, polythioether, polysulfide or copolymers thereof. The uncured matrix, the curing agent, or both contain at least one photoinitiator based on sterical ly-inhibi ted tertiary amines, acting as photo-latent amine catalyst. The mixture cures in the temperature range of -10 to +70 °C after a high-energy actinic radiation is applied. Corresponding matrices A, mixtures B, curing agents, sealant systems, and substrates, e.g., aircraft substrates are contemplated.

[0016] Although using Isocyanates as polymer-basis leads to faster curing and tack free times in US 11 , 124,674 B2, the use of monomeric isocyanates is often not desired, since the hazard potential of the most low-molecular-weight compounds is quite high, the use of oligomeric isocyanates is preferred. On the other hand, the usage of less mobile derivatives often ends up in a decrease of curing speed.

[0017] EP 3 256 542 provides a sealing mass for coating a substrate, which is a mixture of a predominantly unhardened matrix and a hardener containing at least one epoxy compound, wherein the matrix contains a thiol-terminated 220977W001 1 S022796PCT 3 October 07, 2025

[0018] Chemetall GmbH base polymer based on polyether, polythioether, polythioethersulfide, polysulfide, copolymers thereof and / or mixtures thereof, wherein the matrix, the hardener or both contain at least one photoinitiator based on a sterically hindered nitrogen-containing organic base, and, through the effects of energy-rich actinic radiation, the at least one photoinitiator dissociates at least one radical per molecule based on a nitrogen-containing organic base, from which a nitrogen-containing organic base having a pKavalue of the conjugate acid in the region of 6 to 30 is formed, which acts as an active catalyst for the hardening of the matrix.

[0019] While the class of photo-bases described in the afore-mentioned EP 3 256 542 A1 already provide good results, several properties can further be improved. First the reactivity of the photo-bases, even in non-exposed formulations, is already high. That means that the shelf life of a mixed container, e.g., a cartridge, containing the mixed composition, is limited to a few hours.

[0020] Secondly the photo-bases described in the afore-mentioned EP 3 256 542 A1 are not sensitive for radiation with a wavelength as high as or higher than 300 nm. That leads to the need of either using a broad emitting UV-source (for example a discharging lamp) or requires the usage of photosensitizer, which can transfer the emitted energy to the initiator itself. However, this strategy suffers from the disadvantage that such compounds are known to reduce the curable thickness of an applied formulation, since they provide strong absorbance across a broad wavelength band and remain unchanged within the formulation, while the photo-base itself is decomposed with the UV- exposure.

[0021] Compared the photo-bases used in EP 3 256 542 A1 it is the aim of the present invention to provide curable composition containing photo-latent bases having superior properties in such compositions, particularly regarding their solubility, latency, curing speed, storage stability and absorption spectra.

[0022] Furthermore, longer processing times should be achievable, upon mixing the base component and hardener component, preferably processing times as high as from a few days up to one week after mixing. Such formulations would provide a maximum of flexibility to a possible operator, who can use the mixed material for a long period of time, while it still provides a save second curing mechanism and short curing times in relation to the provided application time.

[0023] While it is a desire of the present invention to provide sealant systems and sealant compositions which are suitable as sealants in the aerospace industry, particularly in sealing aerospace vehicles and parts thereof, it is not intended to limit their use to this specific field of technology. There are may other fields of use, ranging from the use in sealing land and water vehicles and parts thereof, to the use in 3D printing as UV-curable compositions.

[0024] Furthermore, the sealant compositions to be provided by the invention should be apt to cure not only in those areas which are directly exposed to UV radiation, but also in so-called "shadow areas,” which are not exposed to UV light. 220977WC01 1 S022796PCT 4 October 07, 2025

[0025] Chemetall GmbH

[0026] In addition, the aim is to be able to dispense with the use of photosensitizers in the formulation and to use LED devices for UV / Vis exposure instead of discharge lamps. A photosensitizer is usually used in most UV-formulations to allow activation when the UV-wavelength does not fit to the activation wavelength of the photo-base or initiator. However, the usage of photo-sensitizers suffers from the drawbacks of reduced excitable layer thickness as well as reduced resistance towards UV-impact throughout the products lifecycle, since a sensitizer remains un-cleaved inside an applied sealant and can catalyze undesired reactions. Furthermore, a photo sensitizer competes with the photo-initiator itself in terms of emitted photons within the wavelength-range, where both components absorb.

[0027] SUMMARY

[0028] The above problems of the prior art were solved by providing a sealant system comprising at least one base component A, the base component A comprising at least one thiol-terminated polymer A1 selected from the group consisting of polysulfides A1.1 , polythioethers A1.2, polyethers A1 .3 and copolymers thereof; and at least one hardener component B, the hardener component B comprising at least one polyepoxide B1 ; wherein the at least one base component A further comprises at least one non-ionic photo-latent base A2, the non-ionic photo-latent base A2 having the general formula (I):

[0029] (PCG)-(BG)n(I) wherein i. PCG stands for an n-valent photocleavable group; ii. BG stands for a base group; ill. n is i or 2; iv. the base formed after cleaving the bond between PCG and BG a. is a non-ionic base, and b. possesses a pKavalue of the conjugate acid of > 10.0; v. A2 has a photoactivation wavelength for cleaving the bond between PCG and BG in the range of 300 nm to 420 nm.

[0030] The above sealant system and its preferred embodiments being also denoted as "sealant system of the invention.” 220977W001 1 S022796PCT 5 October 07, 2025

[0031] Chemetall GmbH

[0032] Another subject of the present invention is a sealant composition comprising or consisting of a mixture of the base component A and hardener component B as defined in for the sealant system of the invention.

[0033] The above sealant composition and its preferred embodiments being also denoted as "sealant composition of the invention.”

[0034] Yet another subject of the invention is method of sealing comprising the steps of

[0035] (a) providing a substrate;

[0036] (b) applying the sealant composition of the invention at least onto a part of the substrate to be sealed;

[0037] (c) irradiating the applied sealant composition with light in the wavelength range from 300 to 420 nm.

[0038] The above method of sealing and its preferred embodiments being also denoted as "method of sealing according to the invention.”

[0039] A further subject matter of the invention is the use of the sealant composition of the invention in sealing vehicles selected from the group consisting of aircrafts, spacecrafts, land vehicles, water vehicles, and parts of the aforementioned vehicles; and as printing material in 3D printing applications.

[0040] The above use and its preferred embodiments being also denoted as "use according to the invention.”

[0041] As a general remark, the term "comprising” as used in the present invention, is not limited to the meaning "comprising only” or "consisting of.” E.g., in the components of a sealant system or in a sealant composition, the term "comprising” allows the presence of further ingredients, if not defined in a more limiting way. In a method comprising method steps, further method steps may be comprised, too. However, in any case the term "comprising” includes besides the broad meaning, also the limiting meaning of "comprising only” and "consisting of.”

[0042] DETAILED DESCRIPTION

[0043] Sealant System and Sealant Composition

[0044] According to the present invention, a "sealant system” comprises a first part (base component A) comprising a thiol- terminated polymer A1 and a photo-latent base A2; and a second part (hardener component B) comprising a polyepoxide.

[0045] According to the present invention, a "sealant composition” is formed by combining the base component A and the hardener component B of a sealant system. 220977W001 1 S022796PCT 6 October 07, 2025

[0046] Chemetall GmbH

[0047] Base component A and hardener component B are preferably liquid at 23 °C. The term "liquid” as used herein is used in a broad meaning and encompasses highly viscous and even pasty compositions.

[0048] Base Component A

[0049] The base component A mandatorily comprises thiol-terminated Polymers A1 and a photo-latent base A2.

[0050] Thiol-terminated Polymers A1

[0051] The thiol-terminated polymers are preferably selected from thiol-terminated polysulfides, thiol-terminated polythioethers, thiol-terminated polyethers, and their copolymers, such as polyether-polythioether, polyetherpolysulfide and / or polythioether-polysulfide, and mixtures thereof. According to "IUPAC, Pure and Applied Chemistry 81 (2009) pp. 1169, 1171” polysulfides are polymer composed of macromolecules containing sulfursulfur linkages in the backbone: -Sx- with x > 1 , while polythioethers are polymers composed of macromolecules containing thioether (sulfide) linkages in the backbone: -Sx- with x = 1.

[0052] Any of the herein below mentioned ranges for any ingredients A1 to A11 and B1 to B8 can selected independently of each other to further specify the ingredients with respect to their amounts. However, it is particularly preferred to combine the preferred ranges of at least the mandatory ingredients A1 , A2 and B1 , or more preferred to combine the first more preferred ranges, or even more preferred to combine the second even more preferred ranges, and so on, and so on for each preference level. The same applies for the optional ingredients, if one or more of them are combined with the mandatory ingredients.

[0053] Preferably, the amount of thiol-terminated polymers A1 , based on the total weight of the base component A is preferably in the range from 35 to 99.8 wt.-%, more preferred in the range from 45 to 98 wt.-%, even more preferred in the range from 50 to 95 wt.-%, most preferred preferred in the range from 55 to 90 wt.-%, such as from 65 to 85 wt.-%. Based on the total weight of the sealant composition (i.e., base component A plus hardener component B) the amount of thiol-terminated polymers A1 is preferably in the range from 45 to 95 wt.-%, more preferred in the range from 50 to 90 wt.-% and most preferred in the range from 55 to 85 wt.-%.

[0054] Preferably, the thiol-terminated polymers have a thiol content, based on the reactive SH groups to the total base polymer, in the range from 0.5 to 10 wt.-%, more preferred in the range from 0.8 to 8 wt.-%, and most preferred in the range from 1 to 6 wt- %. The thiol content can be determined by titration methods.

[0055] Preferably, the thiol-terminated polymers have a total sulfur content in the range of 1 to 50 wt.-%, more preferred in the range from 2 to 45 wt.-%, most preferred in the range from 10 to 38 wt.-%. Typically, the fuel resistance improves with a higher sulfur content. 220977W001 1 S022796PCT 7 October 07, 2025

[0056] Chemetall GmbH

[0057] The thiol-terminated polymers preferably have an average thiol group functionality in the range of 1.5 to 2.5 or 1.9 to 2.2. Especially preferably no other functionalities than reactive thiol terminal groups are present as terminal groups.

[0058] The thiol-terminated polymers preferably have a glass transition temperature Tgin the range of -80 °C to -30 °C, or -60 °C to -40 °C, measured according to AITM 1-0003 Airbus Industry Test Method of June 1995.

[0059] Thiol-terminated Polysulfides A1. 1

[0060] Long-chain polymers with a number-average molecular weight in particular in the range of 2800 to 9000 g / mol are preferably used as the thiol-terminated polysulfide polymers in the compositions according to the invention. An example of such commercially available thiol-terminated polysulfides is Thioplast® G131. Especially preferable with a number-average molecular weight in the range of 3300 to 5000 g / mol such as Thioplast® G10, Thioplast® G12, Thioplast® G1 , Thiokol® LP 32 and / or Thiokol® LP 12, for example. The number-average molecular weights of all thiol-terminated polymers used in the invention can be determined by gel permeation chromatography using a polystyrene standard and, e.g., THF as eluent.

[0061] Short-chain thiol-terminated polysulfides with a number-average molecular weight in the range of 100 to 3200 g / mol in particular, from 400 to 2800 g / mol and / or from 500 to 1200 g / mol, are for example commercially available under the tradenames Thiokol® LP3, Thioplast® G4, Thioplast® G22 or Thioplast® G44.

[0062] Preferably, a combination of long-chain polymers preferably with a number-average molecular weight in the range of 2800 to 9000 g / mol, more preferred with a number-average molecular weight in the range of 3300 to 5000 g / mol, and short-chained polymers preferably with a number-average molecular weight in the range of 400 to 2800 g / mol or from 500 to 1200 g / mol are used as thiol-terminated polysulfide polymers. Such combination is, e.g., the combination of Thioplast® G10 with Thioplast® G44.

[0063] The weight ratio of the long-chain polymer(s) to the short-chain polymer(s) is preferably in the range of 25:1 to 0.5: 1 , from 10: 1 to 1 :1 or from 6:1 to 2:1.

[0064] Thiol-terminated Polythioethers Al.2

[0065] In the compositions according to the invention preferably liquid polymers with a number-average molecular weight in particular in the range from 500 to 6000 g / mol, especially preferably with a number-average molecular weight in the range of 1000 to 3000 g / mol are used as the thiol-terminated polythioether polymers.

[0066] Thiol-terminated Polyethers A1.3 220977WC01 1 S022796PCT 8 October 07, 2025

[0067] Chemetall GmbH

[0068] Preferably liquid polymers with a number-average molecular weight preferably in the range from 100 to 7000 g / mol, more preferably in the range from 500 to 6000 g / mol, even further preferred in the range from 1000 to 3000 g / mol are used as the thiol-terminated polyether polymers in the compositions according to the invention.

[0069] Thio-terminated Copolymers A1.4 of the afore-mentioned thiol-terminated polymers

[0070] The thiol-terminated copolymers are preferably selected from polyether-polythioethers, polyether-polysulfides and / or polythioether-polysulfides. Preferably liquid copolymers have a number-average molecular weight preferably in the range from 100 to 7000 g / mol, more preferably in the range from 500 to 6000 g / mol, even further preferred in the range from 1000 to 3000 g / mol.

[0071] Photo-latent Bases A2

[0072] It has been found by the present inventors that the photo-latent base A2 needs to be non-ionic as such to be homogenously distributed in the sealant system and sealant composition of the present invention. The non-ionic photo-latent base A2 as used sealant system and sealant composition has the general formula (I):

[0073] (PCG)-(BG)n(I)

[0074] In this formula (I) PCG stands for an n-valent photocleavable group, and BG stands for a base group, wherein n is 1 or 2. If n = 1 , group PCG is monovalent group to which one base group BG is bound. If n = 2, group PCG is divalent group to which two base groups BG are bound.

[0075] The base formed after cleaving the bond between PCG and BG is a non-ionic base, which is also important for a homogeneous distribution of the base in the sealant composition. The base, liberated upon photoactivation of photo-latent base A2, possesses a pKavalue of the conjugate acid of > 10.0, preferably > 11.0, more preferred > 12.0, and most preferred > 13.

[0076] The pKavalues of the conjugate acids of the photo-latent bases and the conjugate acids of the bases formed after cleavage are determined in the present invention by a pH-metric titration method at 25 °C in water or a watersolvent mixture, and in the latter case, subsequent extrapolation of the apparent pKavalue according to the Yasuda- Shedlovsky method. Details are described in the experimental part. The "pKavalues” as referred to in the present invention also simply denominated "pKavalue (in water at 25°C).”

[0077] In the present invention it is necessary that the photo-latent base A2 has a photoactivation wavelength for cleaving the bond between PCG and BG in the wavelength range of 300 nm to 420 nm, preferably 320 nm to 420 nm, more preferably 350 nm to 420 nm, and most preferably 375 nm to 420 nm, such 380 to 420 nm. The photoactivation wavelength being in the above ranges include UV radiation as well as low wavelength VIS radiation (visual radiation 220977W001 1 S022796PCT 9 October 07, 2025

[0078] Chemetall GmbH up to a wavelength of 420 nm). If, in the context of the present invention, the term "UV radiation” or "UV curing” or a similar term is used, it encompasses the above wavelengths ranges including the low wavelength VIS radiation. The cleavage in the afore-mentioned ranges allows, to strongly reduce or even omit the use of photosensitizers in the sealant system and sealant composition to form the free base. It further allows the use of LED omitting light in this wavelength range and furthermore a deep penetration of the omitted light through the applied sealant is possible, thus curing samples having a thickness of 2 mm and more, such as 3, 4 or 5 mm is possible.

[0079] In any case, it is particularly preferred that the difference between the pKavalues of the conjugate acids of the photo-latent bases of formulae (la), (lb) and (II) and the conjugate acids of the respective bases formed (ApKa), i.e. after cleaving the bond between the respective photocleavable group and the base group is as high as possible. Such difference between the pKavalues of the conjugate acids of the photo-latent bases of formulae (la), (lb) and (II) and the conjugate acids of the respective bases formed, is denominated ApKa. ApKais preferably > 3, more preferred > 4, even more preferred > 5 and most preferred > 6.

[0080] Preferably the photo-latent base according the invention possesses a pKavalue of the conjugate acid being > 10.0, more preferred > 11.0, and most preferred > 12.0, while the difference between the pKavalues of the conjugate acids of the photo-latent bases of formulae (la), (lb) and (II) and the conjugate acids of the respective bases formed (ApKa) is preferably > 5, more preferred > 6.

[0081] As preferred bases, strong bases such as

[0082] 1 ,5-Diazabicyclo[4.3.0]non-5-ene (DBN); pKa= 13.7

[0083] G» corresponding to base group BG1 :

[0084] QO

[0085] 1 ,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD); pKa= 15.1 220977W001 1 S022796PCT 10 October 07, 2025

[0086] Chemetall GmbH corresponding to base group BG2:

[0087] 1 , 1 ,3,3-tetramethylguanidine (TMG); pKa= 13.6 corresponding to base group BG3: have been identified by the inventors. The bicyclic bases DBN and TBD being most preferred amongst the aforementioned bases, DBN being even more preferred.

[0088] As photocleavable groups PCG the following groups are most preferred: PCG1 (R3=R4=H), PCG2 (R3and R4form C=O) wherein R1and R2are selected from hydrogen; CN; NO2; NHRAwith RAbeing hydrogen or an alkyl group with 1 to 12 carbon atoms; ORBwith RBbeing an alkyl group with 1 to 12 carbon atoms; F; SO3H; BG1; BG2; BG3, or R1and R2form together a group O-CH2-O; R3and R4are hydrogen or form together a C=O group; and at least one of R1and R2being hydrogen, preferably R1being hydrogen; 220977W001 1 S022796PCT 11 October 07, 2025

[0089] Chemetall GmbH wherein R5and R6form together a group O-CH2-O, or R5= H and R6= OH; PCG5, wherein R7is selected from ON; COORCwith Rcbeing an alkyl group with 1 to 12 carbon atoms, preferably 1 to 5 carbon atom and even more preferred 1 to 3 carbon atoms;

[0090] If R3= R4= H, the photocleavable group is PCG1 and has the following structure: PCG1.

[0091] If R3and R4together form a C=O group, the photocleavable group is PCG1 and has the following structure:

[0092] If in PCG1 or PCG2 the residues R1and R2together form a group O-CH2-O the resulting structure is as follows:

[0093] In analogy, in PCG4, residues R5and R6together form a group O-CH2-O, thus constituting 5-membered ring.

[0094] The non-ionic photo-latent base is preferably selected from (BG1)-(PCG1)n, (BG1)-(PCG2)n, (BG1)-(PCG3)n, (BG1)-(PCG4)n, (BG1)-(PCG5)n, (BG2)-(PCG1)n, (BG2)-(PCG2)n,

[0095] (BG2)-(PCG3)n, (BG2)-(PCG4)n, (BG2)-(PCG5)n, (BG3)-(PCG1)n, (BG3)-(PCG2)n,

[0096] (BG3)-(PCG3)n, (BG3)-(PCG4)n, (BG3)-(PCG5)n, n being 1 or 2. Most preferably it is selected from (BG1)-(PCG1)n, (BG1)-(PCG2)n, (BG1)-(PCG3)n, (BG1)-(PCG4)n, (BG1)-(PCG5)nwith n being 1 or 2. The explicitly mentioned combinations of BG with PCG as described herein in combination with the base composition A and hardener composition B, are also subject of the present invention, as such. 220977WC01 1 S022796PCT 12 October 07, 2025

[0097] Chemetall GmbH

[0098] The amount of the photo-latent base A2 based on the total weight of the base component A is preferably in the range from 0.2 to 10 wt.-%, more preferred in the range from 0.3 to 5 wt.-%, even more preferred from 0.5 to 4 wt.- %, most preferred from 0.6 to 3 wt.-%. Based on the total weight of the sealant composition (i ,e. , base component A plus hardener component B) the amount of the photo-latent base A2 is preferably in the range from 0.15 to 9 wt.- %, more preferred in the range from 0.2 to 4.5 wt.-%, even more preferred from 0.3 to 3.5 wt.-%, most preferred from 0.4 to 2.5 wt.-%.

[0099] The non-ionic photo-latent bases BG-PCG, as described above, have photocleavable groups PCG1 , PCG2; PCG3, PCG4 and PCG5, all possessing a "CH moiety to which the base groups BG1 , BG2 and BG3 are attached. The non-ionic photo-latent bases BG-PCG can be synthesized by reacting the respective strong base with the halomethyl compound corresponding to the photocleavable group. Such halomethyl compounds possess instead of the "CH moiety, a "CH2Br” or "CH2CI” group. Thus, the photocleavable bond between the base group BG and the photocleavable group PCG may be formed by reaction between the base and the halomethyl compound in that HBr of HCI is eliminated.

[0100] More particularly, the corresponding compounds PCG1-Hal to PCG5-Hal, with Hal = Cl or Br, preferably Br can be used as first starting compounds. Thus, the CH2 radical of the respective PCG1 to PCG5 is a CH2Hal group in the corresponding first starting compound. This also applies to all photocleavable groups comprising a CH2 radical.

[0101] Such first starting compounds can be reacted with a second starting compound, being a base preferably corresponding to the base structures BG2 and BG3. Such bases contain a secondary amino group (-NH-) or an imino group (NH=). The base underlying the BG1, i.e., DBN, first needs to be reduced to obtain an NH group. Such reduction can, e.g., be carried out by use of lithium aluminum hydride, as shown in the examples of the experimental part.

[0102] To form a photo-latent base of formula (I), as a first starting compound, a compound consisting of a CH2 radical containing photocleavable group wherein the CH2 radical is bound to Br or Cl is reacted with a second starting compound, being a base containing a secondary amino group or an imino group.

[0103] Thus, the following reaction leads to the photo latent bases of formula (I):

[0104] RPCG-CH2Hal + HNRBG-> RPGG-CH2NRBG+ HHal wherein RPCGstands for a CH2 radical containing photocleavable group PCG deprived of its CH2 radical, and RBGstand for a secondary amino group or imino group containing base deprived of its secondary amino group or imino group, and Hal = Br or Cl. 220977WC01 1 S022796PCT 13 October 07, 2025

[0105] Chemetall GmbH

[0106] Thus, it is provided a method of preparing a photo-latent base of formula (I) as defined herein above, comprising reacting a compound of formula RPCG-CH2Hal with a compound of formula HNRBGto obtain a compound of formula RPCG-CH2NRBG, thereby eliminating HHal, wherein RPCGstands for a CH2radical containing photocleavable group PCG deprived of its CH2radical, and RBGstand for a secondary amino group or imino group containing base deprived of its secondary amino group or imino group, and Hal = Br or Cl. Preferably, RPCG-CH2Hal is one of PCG1- Hal, PCG2-Hal, PCG3-Hal, PCG4-Hal, and PCG5-Hal, Hal preferably being Br; and preferably HNRBGis one of H- BG2 and H-BG3, or reduced H-BG1 , i.e., the bases corresponding to the respective base groups BG.

[0107] Preferably the reaction is carried out in solvents like alkyl cyclic or acyclic carbonates, cyclic or acyclic ethers, chlorinated solvents, cyclic or aromatic nitriles at 0 °C to 35 °C for 2 to 48 hours.

[0108] Numerous examples of such reactions are shown in the experimental part of this invention. The halomethyl compounds may be synthesized in accordance with the examples, or are commercially available. The bases used herein in the formation of the photo-latent bases are commercially available.

[0109] Further Monomers, Oligomers and Polymers A3

[0110] The base composition optionally comprises further comprises monomers, oligomers, or polymers, which differ from any other ingredients, and which preferably comprise one or more hydroxy groups, preferably one hydroxyl group.

[0111] Such monomers are, e.g., saturated monoalcohols preferably comprising 1 , 2, or 3 to 12 carbon atoms, particularly alkane mono alcohols with 1 , 2, or 3 to 12 carbon atoms. If comprised, they are preferably comprised in an amount from 0 to 10 wt.-% based on the total weight of the sealant composition.

[0112] Adhesion Promoters A4

[0113] Adhesion promoters A4, such as silanes may be added to the base composition. Such silanes, which are suitable in the base composition have preferably an at least partially alkoxy lated silane groups and additionally a functional group which is reactive towards epoxy groups but inert towards thiol groups, preferably inert towards thiol groups under storage conditions. Such functional groups are preferably thiol groups. Examples of such silane adhesion promoters are y-mercaptopropyl trimethoxysilane (commercially available as Dynasylan® MTMO or Geniosil® GF 70), y-mercaptopropyl methyldimethoxysilane (commercially available as SISIB® PC2320 or Dow Corning Z-6044), and y-mercaptopropyl triethoxysilane (commercially available as SISIB® PC2310 or Dow Corning AY43-062).

[0114] The amount of the adhesion promoter A4 based on the total weight of the base component A is preferably in the range from 0 to 10 wt.-%, more preferred in the range from 0 to 8 wt.-%. Based on the total weight of the sealant composition (i.e., base component A plus hardener component B) the amount of the adhesion promoter A4 is preferably in the range from 0 to 9 wt.-%, more preferred in the range from 0 to 7 wt.-%. 220977WC01 1 S022796PCT 14 October 07, 2025

[0115] Chemetall GmbH

[0116] The combined amount of adhesion promoters A4 and B3 as described herein below, both preferably being silanes, is also preferably in the range from 0 to 9 wt.-%, more preferred in the range from 0.1 to 7 wt.-% based on the total weight of the sealant composition.

[0117] Photosensitizers A5

[0118] The base component A may comprise a photosensitizer A5 from the group comprising anthracene-type photosensitizers, thioxanthone-type photosensitizers, and perylene-type photosensitizers. If such photosensitizers are contained, their amount based on the total weight of the base component A is preferably in the range from 0 to 3 wt.-%, more preferred in the range from 0 to 1 wt.-% and most preferred 0 wt.-%. If such photosensitizers are contained, their amount based on the total weight of the sealant composition (i.e. , base component A plus hardener component B) is preferably in the range from 0 to 2 wt.-%, more preferred in the range from 0 to 0.5 wt.-% and most preferred 0 wt.-%.

[0119] Further curinci catalysts A6

[0120] Particularly, base component A may optionally contain further curing catalysts A6, differing from the non-ionic photo-latent bases A2, which are apt to catalyze the reaction between thiol groups and epoxy groups. Such further curing catalysts A6 do not need an activation by radiation, or liberation by any sustained release mechanism, but act as such. Such non-latent curing catalysts are preferably being selected from bases, more preferably from tertiary amines.

[0121] While the present invention does not necessarily make use of the employment of tertiary amines, there are some application scenarios where it is preferred that further curing catalysts A6 are employed in the sealant composition. For example, if there is a desire or need to adjust the processing time of the sealant composition of the invention.

[0122] Suitable tertiary amine catalysts are preferably selected from the following group, comprising or consisting of N,N- dimethylethanolamine, triethylene diamine (TED A), bis(2-dimethylaminoethyl)ether (BDMAE), N-ethylmorpholine, N', N'-dimethylpiperazine, N,N,N',N',N'- pentamethyl-diethylene-triamine (PMDETA), N,N-dimethylcyclohexylamine (DMCHA), N,N-dimethylbenzylamine (DMBA), N,N-dimethylcethylamine, N,N,N',N",N"-pentamethyl-dipropylene- triamine (PMDPTA), triethylamine, 1-(2-hydroxypropyl)imidazole, l,4-diazabicyclo[2.2.2]octane (DABCO®, commercially available from Air Products, Chemical Additives Division, AUentown, Pa.) and DMP-30® (an accelerant composition including 2,4,6-tris(dimethylaminomethyl)phenol, dimethylethanolamine (DMEA), bis-(2- dimethylaminoethyl)-ether, N-ethylmorpholine, triethylamine, 1 ,8-diazabicyclo[5.4.0]undecene-7 (DBU), 1 ,5- diazabicyclo[4.3.0]non-5-ene (DBN), benzyldimethylamine (BDMA), NNN'-trimethyl-N'-hydroxyethyl- bis(aminoethyl)ether, N'-(3-(dimethylamino)propyl)-N,N-dimethyl-1 ,3-propanediamine, imidazole, 2- methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-undecylimidazole, 2-dodecylimidazole, 2- phenylimidazole, 2-ethyl-4-methyl-imidazole, 2-benzylimidazole, 2,4,5-trimethylimidazole, 2,4-dimethylimidazole, 220977WC01 1 S022796PCT 15 October 07, 2025

[0123] Chemetall GmbH butylimidazole, 2-heptadecenyl-4-methylimidazole, 1-vinyl-2-methylimidazole, 2-n-heptadecylimidazole, 2- heptadecylimidazole, 1-benzyl-2- methylimidazole, 1-propyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl- 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-guanaminoethyl-2- methylimidazole and addition products of an imidazole and trimellitic acid, 2-n-heptadecyl-4-methylimidazole; phenylimidazole, benzylimidazole, 2-methyl-4,5-diphenylimidazole, 2,3,5-triphenylimidazole, 2-styrylimidazole, 1- (dodecyl benzyl)-2-methylimidazole, 2-(2-hydroxyl-4-t-butylphenyl)-4,5-diphenylimidazole, 2-(2-methoxyphenyl)- 4,5-diphenylimidazole, 2-(3-hydroxyphenyl)-4,5-diphenylimidazole, 2-(p-dimethylaminophenyl)-4,5- diphenylimidazole, 2-(2-hydroxyphenyl)-4,5-diphenylimidazole, di(4,5-diphenyl-2-imidazole)-benzene-1,4,2- naphthyl-4,5-diphenylimidazole, 1-benzyl-2-methylimidazole, and 2-p-methoxystyrylimidazole. Particularly preferred are DABCO and DBN.

[0124] If contained, the further curing catalyst(s) A6 is / are employed in the sealant composition in an amount of preferably 0 to < 50 wt.-%, more preferably < 40 wt.-%, even more preferred < 30 wt.-%, particularly preferred < 20 wt.-%, such as < 15 wt.-% based on the combined total weight of the non-ionic photo-latent base(s) A2 and further curing catalyst(s) A6. Preferably, if contained, the minimum amount of the further curing catalyst(s) A6, based on the combined total weight of the non-ionic photo-latent base(s) A2 and further curing catalyst(s) A6, is > 1 wt.-%, more preferably > 2 wt.-%, even more preferably > 5 wt.-% and most preferred > 10 wt.-%. Thus, if contained, it is preferred that the further curing catalyst(s) A6 is / are employed in the sealant composition based on the combined total weight of the non-ionic photo-latent base(s) A2 and further curing catalyst(s) A6 in an amount ranging from 1 to 50 wt.-%, more preferably 2 to 40 wt.-%, even more preferred 5 to 30 wt.-% most preferred 10 to 20 wt.-%, such as 10 to 15 wt.-%.

[0125] Hardener Component B

[0126] The hardener component B mandatorily comprises at least one polyexpoxide B1.

[0127] Polyepoxides B1 (Curing Agent B1)

[0128] The sealant composition of the invention cures by reaction with epoxy groups, namely by use of a polyepoxide, which can be monomeric, oligomeric or polymeric, and which is preferably oligomeric or polymeric. The polyepoxide may be aromatic or aliphatic. A "polyepoxide” as defined herein preferably possesses on average at least two epoxy groups, e.g., in form of glycidyl groups.

[0129] The amount of the polyepoxides B1 based on the total weight of the hardener component B is preferably in the range from 50 to 100 wt.-%, more preferred in the range from 60 to 99 wt.-%, even more preferred 70 to 97 wt.-% and most preferred 80 to 95 wt.-%. Based on the total weight of the sealant composition (i.e., base component A plus hardener component B) the amount of the polyepoxides B1 is preferably in the range from 1 to 20 wt.-%, more 220977W001 1 S022796PCT 16 October 07, 2025

[0130] Chemetall GmbH preferred in the range from 2 to 18 wt.-%, even more preferred in the range from 4 to 16 wt.-% and most preferred in the range from 6 to 14 wt.-%.

[0131] The polyepoxides are preferably only added to the hardener component. As polyepoxides, preferably di-functional or multifunctional epoxy resins are used, more preferably having epoxy groups functionalities F of F = 2 to F = 5. If mixtures of polyepoxides are used, the average epoxy group functionality of the mixture is preferably F = 2.0 to 3.0 or 2.2 to 2.8.

[0132] Preferably, the epoxy equivalent weight of the polyepoxides lies in the range from 120 to 700 g / eq, particularly preferably in the range from 140 to 400 g / eq, and most preferably in the range from 170 to 250 g / eq.

[0133] All polyepoxides are preferably mixable with each other. Mixing is facilitated when all polyepoxides are liquid at room temperature (23 °C). Among the polyepoxides may exist, which are solid also at room temperature, however, which may be melted, or which may be "dissolved” in the liquid polyepoxides.

[0134] The polyepoxides, preferably used are as follows: diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, aliphatic polyglycol diglycidyl ether, hydantoin-epoxy derivatives, epoxidized unsaturated and / or phenolic resins, epoxy novolac resin, more preferably cross-linked epoxy novolac resin and / or an epoxy resin, which is based on several of the above classes. An example for the latter one is a bisphenol F novolac resin. However, it is preferred that the curing agent is free of cycloaliphatic epoxy resins such as hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol A diglycidyl ether oligomers, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol F diglycidyl ether and 3,4-oligomers-epoxycyclohexyl-methyl-3,4-epoxycyclohexyl carboxylate.

[0135] The following polyepoxides are particularly preferred: 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 novolac resins such as DEN 431 , DEN 438, DEN 439 (Olin Epoxy); epoxyterminated prepolymers based on polysulfide and / or polythioether such as Thioplast EPS 25 (Akzo Nobel) and epoxy-terminated reactive diluent based on alcohol / glycols such as 1 ,4-butanediol diglycidyl ether (DER 731 ; Olin Epoxy), 1 ,6-hexanediol diglycidyl ether (DER 734; Olin Epoxy), 2-ethylhexyl diglycidyl ether (DER 728; Olin Epoxy), C12-C14 glycidyl ether (DER 721 ; Olin Epoxy).

[0136] Most particularly preferred are polyepoxides based on bisphenol A epoxy resins having an epoxy equivalent weight in the range from 170 to 200 g / eq, based on bisphenol F resin having an epoxy equivalent weight in the range from 150 to 180 g / eq and based on epoxy novolac resins having an epoxy equivalent weight in the range from 160 to 220 g / eq. Depending on the desired properties and concrete application, however, all epoxy resins can be used. it is preferred that the curing agent not contain any cycloaliphatic epoxy resin such as hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol A diglycidyl ether oligomers, hydrogenated bisphenol F diglycidyl ether, 220977WC01 1 S022796PCT 17 October 07, 2025

[0137] Chemetall GmbH hydrogenated bisphenol F diglycidyl ether oligomers and 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexyl carboxylate

[0138] Further Curing Agents B2

[0139] The sealant composition is preferably free of co-curing agents which differ from polyepoxides, such as for example isocyanates and ethylenically unsaturated compounds, such as vinyl compounds.

[0140] Adhesion Promoters B3

[0141] Adhesion promoters B3, such as silanes may be added to the hardener composition. Such silanes, which are suitable in the hardener composition have preferably an at least partially alkoxylated silane groups and additionally a functional group which is reactive towards thiol groups but inert towards epoxy groups, preferably inert towards epoxy groups under storage conditions. Such functional groups are preferably epoxy groups, more preferred as glycidyl groups. Examples of such silane adhesion promoters are y-glycidoxy propyl trimethoxysilane (commercially available as Dynasylan® GLYMO or Geniosil® GF 80), y-glycidoxypropyl methyldimethoxysilane (commercially available as SiSiB® PC3400 or Dow Corning Z-6044), y-glycidoxypropyl triethoxysilane (commercially available as Dynasylan® GLYEO or Geniosil® GF 82), and y-glycidoxypropyl methyldiethoxysilane (commercially available as SiSiB® PC3300 or Dow Corning Z-6042).

[0142] The amount of the adhesion promoter B3 based on the total weight of the hardener component B is preferably in the range from 0 to 20 wt.-%, more preferred in the range from 0 to 10 wt.-%. Based on the total weight of the sealant composition (i.e., base component A plus hardener component B) the amount of the adhesion promoter A4 is preferably in the range from 0 to 2 wt.-%, more preferred in the range from 0 to 1 wt.-%.

[0143] Further Optional Ingredients of the Base Component A and / or the Hardener Component B

[0144] The base component A, the hardener component B as well as the sealant produced by mixing those, may preferably contain ingredients which are not negatively interfering with the UV-cure of the sealant, i.e., which absorb UV light only to a minimum extent. Particularly, this applies to fillers which are often used in high amounts in the base component A and / or hardener component B.

[0145] Fillers Al and B4

[0146] With the fillers, attention should preferably be paid to the fact that they are as permeable as possible for the selected UV radiation wavelengths. While electron beams usually penetrate through the ingredients of a sealant to a much greater extent than UV light, it is preferred to select those fillers that absorb little or none of the selected type of UV 220977W001 1 S022796PCT 18 October 07, 2025

[0147] Chemetall GmbH light, even more preferred they have permeability as high as practicable for the selected type of radiation with which curing is to be initiated. They preferably exhibit little or no absorption in the range of the UV light spectrum or of the UV light used for the incident radiation. Fillers are usually comprised in the sealant to achieve better mechanical properties. Fillers based on calcium carbonate, titanium dioxide, silica, quartz powder and micro-hollow beads of glass or plastic in particular should be tested for their radiation permeability as needed. Fillers are preferably contained in the base composition, more preferably in the base composition only.

[0148] The amount of the fillers A7 or B4 based on the total weight of the base component A and hardener component B, is preferably, for each, the base component A and hardener component B, in the range from 0 to 60 wt.-%, more preferred in the range from 10 to 40 wt.-%, most preferred in the range from 15 to 35 wt.-%. Based on the total weight of the sealant composition (i.e., base component A plus hardener component B) the amount of fillers A7 plus B4 is preferably in the range from 5 to 50 wt.-%, more preferred in the range from 15 to 35 wt.-%.

[0149] Pigments A8 and B5

[0150] Pigments A8 and B5 may also be comprised in the base composition and / or der hardener composition and thus in the sealant. The same considerations as for the fillers also apply to the pigments. If UV light absorbing pigments are used, their content should be preferably be in a very low range such as 0 to 5 wt.-%, more preferably in the range from 0.01 to 3 wt.-%, even more preferred in the range from 0.02 to 1 wt.-%, such as 0.02 to 0.5 wt.-% or 0.02 to 0.2 wt.-%, based on the combined weight of the base composition and hardener composition being typically the same as the total weight of the sealant composition. Most preferably no UV-light absorbing pigments are contained. For strongly UV absorbing pigments, such as carbon black their amount does preferably not exceed 0.01 to 0.1 wt.-%, more preferred 0.02 to 0.05 wt.-% based on the combined weight of the base composition and hardener composition being typically the same as the total weight of the sealant composition.

[0151] The amount of the pigments A8 or B5 based on the total weight of the base component A and hardener component B, is preferably, for each, the base component A and hardener component B, in the range from 0 to 3 wt.-%, more preferred in the range from 0 to 1 wt.-%. Based on the total weight of the sealant composition (i.e., base component A plus hardener component B) the amount of pigments A8 plus B5 is preferably in the range from 0 to 3 wt.-%, more preferred in the range from 0 to 1 wt.-%.

[0152] Plasticizers A9 and B6

[0153] Plasticizers A9 and B6 might optionally be employed in the base component and / or hardener component. Preferred plasticizers are selected from the group containing phthalic acid esters, such as butylbenzylphthalate and octylbenzylphthalate; chloroparaffines, preferably having a carbon chain length of 10 to 18, more preferred 14 to 18 carbon atoms, and preferably a chlorine content of 40 wt.-% or higher; and polyoxyalkylenes. Preferably, plasticizers are not contained. 220977W001 1 S022796PCT 19 October 07, 2025

[0154] Chemetall GmbH

[0155] The amount of the plasticizers A9 or B6 based on the total weight of the base component A and hardener component B, is preferably, for each, the base component A and hardener component B, in the range from 0 to 20 wt.-%, more preferred in the range from 0 to 10 wt.-%. Based on the total weight of the sealant composition (i.e., base component A plus hardener component B) the amount of plasticizers A9 plus B6 is preferably in the range from 0 to 18 wt.-%, more preferred in the range from 0 to 8 wt.-%.

[0156] Thixotropic Agents A10 and B7

[0157] Preferably, thixotropic agents are employed in the base component and / or hardener component, preferably thixotropic agents are contained in the base component. Preferred thixotropic agents are selected from hydrogenated castor oil; layered silicates, preferably being organically modified; and pyrogenic and / or precipitated silica, preferably being organically modified; or organic thixotropic agents.

[0158] The amount of the thixotropic agents A10 or B7 based on the total weight of the base component A and hardener component B, is preferably, for each, the base component A and hardener component B, in the range from 0 to 10 wt.-%, more preferred in the range from 0.5 to 7 wt.-%. Based on the total weight of the sealant composition (i.e., base component A plus hardener component B) the amount of thixotropic agents A10 plus B7 is preferably in the range from 0 to 9 wt.-%, more preferred in the range from 0.2 to 6 wt.-%.

[0159] Solvents A11 and B8

[0160] The base component and / or hardener component may comprise one or more organic solvents A11 and B8, but is preferably substantially free of water. "Substantially free of water” means that the amount of water should preferably be 0 wt.-%, or in the range from 0 wt.-% to less than 5 wt.-%, more preferred less than 4 wt.-% and most preferred less than 2 wt.-%, based on the total weight of the sealant composition, i.e., the combined weight of base component A and hardener component B.

[0161] The amount of organic solvents A11 or B8 based on the total weight of the base component A and hardener component B, is preferably, for each, the base component A and hardener component B, in the range from 0 to 5 wt.-%, more preferred in the range from 0 to 4 wt.-%. Based on the total weight of the sealant composition (i.e., base component A plus hardener component B) the amount of organic solvents A11 or B8 is preferably in the range from 0 to 5 wt.-%, more preferred in the range from 0 to 4 wt.-%. 220977W001 1 S022796PCT 20 October 07, 2025

[0162] Chemetall GmbH

[0163] Mixing Ratio of base component A with hardener component B

[0164] For curing, the base component A and the hardener component B of the sealant system are mixed in a way that preferably an overstoichiometric number of epoxy group over the number of thiol groups is present. The excess is more preferably 1 to 80 mol % or 5 to 50 mol % or 10 to 30 mol %. This way, a sealant composition can be prepared.

[0165] A sealant composition is also a subject matter of the invention and is formed by mixing base component A with hardener component B, preferably in the way as described in the preceding paragraph. Thus, the sealant composition contains a mixture of base component A with hardener component B. All preferred features and embodiments described for the sealant system are also valid for the sealant composition.

[0166] Method of Sealing

[0167] Another subject of the present invention is a method of sealing comprising the steps of

[0168] (a) providing a substrate;

[0169] (b) applying a sealant composition of the invention at least onto a part of the substrate to be sealed;

[0170] (c) irradiating the applied sealant composition with light in the wavelength range from 300 nm to 420 nm.

[0171] Step (a)

[0172] The sealant compositions of the invention may be applied to any of a variety of substrates. Examples of substrates to which a composition may be applied include metals such as titanium, stainless steel, steel alloy, aluminum, and aluminum alloy, any of which may be anodized, primed, organic-coated or chromate-coated; epoxy; urethane; graphite; fiberglass composite; Kevlar®; acrylics; and polycarbonates. Particularly preferred substrates are such as typically used in sealing aircrafts or spacecrafts, or any parts thereof, even more preferred parts comprising or consisting of aluminum and aluminum alloy. However, since the application is not limited to sealing in the aircraft / spacecraft, other substrates can also be sealed, such as bodies and parts of land and water vehicles, or any other parts to be sealed, which comprise or consist of the above materials.

[0173] Step (b)

[0174] The sealant compositions of the present invention can exhibit specific viscosities suitable for a particular method of application. Thus, the term "applying” comprises several application techniques depending on the viscosity of the respective sealant composition. The viscosity can, as known to one of skill in the art, can, e.g. be adjusted by the solids content of the sealant composition, the molecular weight of the resins, the amounts of pigments and fillers, plasticizers, and thixotropic agents, and / or the processing temperature. 220977WC01 1 S022796PCT 21 October 07, 2025

[0175] Chemetall GmbH

[0176] Sealants can generally be classified into 3 classes - A, B and C. For example, a Class A sealant composition, which is suitable for brush-on applications, which is, e.g., suitable to be used as an overcoat sealant on fasteners, can be characterized by a viscosity from preferably 0.1 Pa s to 50 Pa s. A Class B sealant composition, which is, e.g., suitable for fillet seal applications, can be characterized by a viscosity from preferably 450 Pa s to 2000 Pas. And a Class C sealant composition, which is, e.g., suitable for interfay seal applications, can be characterized by a viscosity from preferably 50 Pas to 450 Pas.

[0177] Figure 1 shows application examples for Class A, Class B and Class C sealant compositions. In this figure it is shown that the Class A sealant is applied on bolts and exposed to the radiation accordingly, while the Class B sealant is applied at edges of two mounted substrates and exposed accordingly. The Class C is applied to a first substrate (bottom substrate) and exposed to the radiation, followed by mounting and fixing the second substrate (top substrate) thereon.

[0178] Further for coating applications, the curable sealant composition may preferably have a viscosity, for example, from 0.2 Pas to 0.8 Pa s. For sprayable coating and sealant compositions, a curable composition preferably has a viscosity, for example, from 0.015 Pas to 0.1 Pa s, such as from 0.02 Pa s to 0.08 Pas. Sprayable sealants are typically denoted as Class S sealants.

[0179] The application of the sealant composition to a substrate by use of 3D printing methods is also possible, and may be used for sealing operations. However, the sealant compositions may also be used as printing material for printing of 3D objects.

[0180] The viscosities can be measured according to Section 5.3 of SAE Aerospace Standard AS5127 / 1C published by SAE International Group.

[0181] To obtain the sealant composition in a ready-to-be-applied state, the two components of the sealant system are combined and mixed, and filled into an application container, such as a cartridge. In the present invention it is distinguished between the processing time in an unexposed condition and the curing time after exposure to radiation in the above wavelength range. The processing time (application time) is the maximum time the sealant composition can be applied after mixing and being stored in the dark (such as in a cartridge). The application time is determined as described in the experimental part of the application.

[0182] In case the sealant composition contains the optional further curing catalyst A6, curing will start directly after mixing the two parts of the sealant system. The use of a further curing catalyst A6 as described above is particularly preferred for Class C sealants in interfay sealing, since after the application of the sealant composition to the first substrate and the subsequent exposure to radiation, a second substrate is placed on the sealant covered first substrate. Thus, unlike the other applications, no sun light can reach the sealant material between the first and 220977W001 1 S022796PCT 22 October 07, 2025

[0183] Chemetall GmbH second parts after mounting and fixing the second substrate on the first substrate, and full curing may be adjusted or facilitated by the presence of a further curing catalyst A6.

[0184] Step Cc)

[0185] The light used for cleaving the bond between the photocleavable group (PCG) and the base group (BG) is in the range from 300 nm to 420 nm, preferably in the range from 320 nm to 420 nm, more preferably in the range from 350 nm to 420 nm and most preferably in the range from 375 nm to 420 nm, such as in the range from 380 to 420 nm. Preferably the light being emitted in the afore-mentioned wavelength ranges is emitted by one or more lightemitting diodes (LEDs).

[0186] In this step curing is initiated, unless some cure already occurs if a further curing catalyst A6 is present in the sealant composition. The curing time after exposure is determined by measuring the Shore A-value. A sealant composition was defined as "cured” when the sealant material reached a Shore A-value of 30. Details are found in the experimental part of the application. After a sealant has cured to a hardness of Shore 30 A it can take several days for a curable sealant composition to fully cure. A composition is considered fully cured when the hardness no longer increases. Depending on the formulation, a fully cured sealant can exhibit, for example, a hardness in the range from Shore 40 A to Shore 70 A, determined according to ISO 868.

[0187] Use of the Sealant Composition

[0188] The sealant compositions of the present invention are suitable in all fields of sealing such as fastener sealing, fillet sealing and interfay sealing, but also as a sprayable sealant compositions for coating applications. The main technical fields are sealing aircraft and spacecrafts, and parts thereof; sealing land vehicles such as automobiles, trucks, and parts thereof; and sealing water vehicles, such as boats, ships, and submarines, and parts thereof.

[0189] However, the sealant composition may also be used as printing material for 3D printing either to seal substrates or for printing 3D objects without the purpose of sealing.

[0190] In the following the invention will be further described by means of working examples and comparative examples.

[0191] EXPERIMENTAL SECTION

[0192] Determination of pKaValues

[0193] The pKavalues of the conjugate acids of the photo-latent bases and the bases after cleavage are determined by pH-metric titration (at 25 °C) in water, or in water-solvent mixtures where the mere water solubility of the sample is 220977WQ01 1 S022796PCT October 07, 2025

[0194] Chemetall GmbH too low for pH-metric titration (lower than 104M). If water-solvent mixtures are used, the measured pKavalues are so-called apparent pKavalues, which are extrapolated to zero organic solvent content by Yasuda-Shedlovsky extrapolation. The procedure and conditions are described in detail by Avdeef, A., et al. in "PH-metric log P 11 . pKadetermination of water-insoluble drugs in organic solvent-water mixtures," Journal of pharmaceutical and biomedical analysis 20.4 (1999): 631-641 , to which it is referred herein. Preferred organic solvent in the above- mentioned water-solvent mixtures is tetrahydrofurane. The pKavalues as reported herein can also be denominated as "pKavalues (in water, 25 °C)” irrespective of their measurement in water only, or in the respective extrapolation of the apparent pKavalue according to the Yasuda-Shedlovsky method, if measure in a water-solvent mixture.

[0195] Synthesis of Photo-latent Bases

[0196] Synthesis of a coumarin-DBN derivative E1

[0197] DBN Intermediate 1

[0198] Step 1: Reduction of DBN

[0199] In a 2L multi neck round bottom flask, 50 g (403 mmol, 1.0 eq) 1 ,5-diazabicyclo[4.3.0]non-5-ene (DBN) was dissolved in 400 mL of dry 2-methyl tetrahydrofuran (2-MeTHF) under N2. The solution was stirred at 50 °C followed by addition the of 7.5 g (201 ,5mmol,0.5eq) of lithium aluminum hydride (LAH) in tablet form, slowly over period of 2.5 h. The initial addition of LAH led to a slightly exothermic reaction, then there was no exotherm observed. After complete addition, the reaction mixture was stirred at same temperature for 1 h. Then reaction mixture was cooled to room temperature and stirred for 16 h. The progress of the reaction was monitored by thin layer chromatography (TLC) and gas chromatography (GC). After stirring for 16 h the reaction mass was cooled to 20 °C then the reaction was quenched by using saturated sodium sulfate (1 vol, 50ml) solution which was added very slowly maintaining temperature around 20 °C. Quenching was highly exothermic with H2 gas evolution with exotherm of 10-12 °C for initial 20 % addition. The color of the reaction mass changes from ash color to white which indicates the complete quenching of LAH. Then the reaction mass filtered through celite bed (or sintered funnel). Residues on the funnel were washed with 2-MeTHF (150 ml). The filtrate was evaporated under vacuum up to complete dryness to yield 4 5g (yield: 88.5 %) of product as light brown liquid. 220977WC01 1 S022796PCT 24 October 07, 2025

[0200] Chemetall GmbH

[0201] 1H-NMR (500Hz, CDCI3): 5 3.06 (m,2H), 2.8 (m,1 H), 2.46 (d,1 H), 2.23-1.98 (m,3H), 1.9-1.5 (m,6H) ppm.

[0202] Step-2: Alkylation

[0203] In 500 ml 3-neck round bottom flask, 8.4 g (66.6 mmol, 1.0 eq) of reduced DBN (intermediate 1) was taken in 50 ml dichloromethane (DOM). 8 g (33.3 mmol, 0.5 eq) of 7-bromomethyl coumarin dissolved in 200 ml DCM (200ml) were added to the reaction mixture, slowly at room temperature. After addition of 7-bromomethyl coumarin, the reaction mixture was stirred at room temperature for 2 h. The progress of the reaction was monitored by TLC. After 2 h the reaction was quenched with 100 ml of water and extracted with DCM. The organic layer was separated dried over sodium sulfate and evaporated to dryness. Crude compound was purified by column chromatography in methanol: Chloroform as an eluent. 4.3 g (yield 45 %) of the product were obtained as light yellow solid.

[0204] 1H-NMR (500Hz, CDCI3): 5 7.68 (d,1 H) 7.42-7.32 (m,3H), 6.4 (m,1 H), 4.0 (m,1 H), 3.26 (m,1 H), 3.5 (d, 1 H), 3.16 (m, 1 H), 3.1-1.5 (m, 13H) ppm.

[0205] Synthesis of an anthraquinone-DBN derivative E2

[0206] DBN Intermediate 1

[0207] In 1L 3-neck round bottom flask, 5.5 g (43.6 mmol, 1.0 eq) of reduced DBN (intermediate 1) were taken in DCM (50 ml). 6.5 g (21.8 mmol) of 2-bromomethyl anthraquinone were dissolved in DCM (300 ml), which was added to the reaction mixture slowly at room temperature. After completion of the addition, the reaction mixture was stirred at room temperature for 2 h. After stirring for 2 h, 100 ml of water were added to the reaction mixture to wash the DCM layer. The organic layer was separated, dried, and evaporated to dryness. The crude compound obtained was purified by column chromatography in methanol: chloroform as an eluent. 4.1 g (yield 51 %) of the product were obtained as a greenish yellow solid.

[0208] 1H-NMR (500Hz, CDCI3): 8.2-8.0 (m,4H) 7.95-7.8 (m,3H), 3.9 (d, 1 H), 3.4 (d,1 H), 3.1-1.5 (m, 13H) ppm.

[0209] Synthesis of DBN-Benzophenone derivative E3 220977W001 1 S022796PCT 25 October 07, 2025

[0210] Chemetall GmbH

[0211] In a 1 L 3-neck round bottom flask 30.0 g (152. 9mmol, 1.0 eq) methyl benzophenone was dissolved in 300 ml of dimethyl carbonate under nitrogen. Thereto, 40.8 g (175.84 mmol, 1.15 eq) N-bromosuccinimide (NBS) were added in one lot followed by azobis(isobutyronitril) Al BN. The reaction mixture was stirred at 70 °C for 2 h. The reaction progress was monitored by liquid chromatography / mass spectrometry (LC-MS). After stirring for 2 h the starting material was consumed. The reaction mixture was cooled to room temperature and extracted with 300 ml of water. The aqueous layer was washed with 100 ml dimethyl carbonate. The combined organic layers were dried over sodium sulfate and distilled under vacuum to give 31.0 g (yield 74 %) of a white solid compound which was purified by 1 vol of acetone at room temperature. The pure compound was analyzed by1H-NMR.

[0212] 1H-NMR (500MHz CDCI3): 5 7.8 (m,4H), 7.4-7.6 (m, 5H), 4.53 (s, 2H) ppm.

[0213] In a 50ml 3-neck round bottom flask 12.7 g (101.3 mmol, 2.0 eq) of reduced DBN was dissolved in 150 ml of 2- MeTHF under nitrogen. Thereto, 15 g (50.6 mmol, 1.0 eq) of the bromomethyl benzophenone obtained in step-2 were added slowly at 0 to 5 °C. The reaction mixture was stirred at the same temperature for 6 to 7 h. After stirring for 7 h the reaction mass was diluted with 150 ml of water. The organic layer was separated. The aqueous layer was washed with 100 ml of 2-MeTHF. The combined organic layers were dried over sodium sulfate and distilled under vacuum to give a crude product which was purified by column chromatography using DCM and methanol as an eluent. 14 g (yield 80 %) of an off-white solid product were obtained

[0214] 1H-NMR (500MHz DMSO): 5 7.7-7.6 (m, 5H ), 7.58-7.55 ( m, 2H ), 7.5 ( m, 2H ), 3.8 (d, 1 H ), 3.2 ( d, 1 H ), 2.99 ( m, 2H ), 2.77 ( d, 1 H ), 2.17 ( q, 1 H ), 2.05( q, 1 H ), 1.9 (m, 2H ), 1.5-1.8 (m, 4H ), 1.4 (m, 1 H ) ppm.

[0215] Synthesis of a Sesamol / Coumarin-DBN derivative E4 220977WC01 1 S022796PCT 26 October 07, 2025

[0216] Chemetall GmbH

[0217] In a 100 ml 3-neck round bottom flask, 5.0 g (36.2 mmol, 1.0 eq) of sesamol (3,4-methylendioxyphenol) were dissolved in 100 ml of 70 % aqueous H2SO4 at room temperature under nitrogen to which 11.3 g (54.34 mmol, 1.5 eq) ethyl bromo acetoacetate were added slowly to the reaction mass at room temperature. Then the reaction mixture was stirred at the same temperature for 16 h. After stirring for 16 h the reaction mass was quenched with water, solids were precipitated, which were filtered through a sintered funnel and dried under vacuum, which was purified by washing with 50 ml of acetonitrile to give 7.0 g (yield 68.3 %) of a pure product (brown solid) which was analyzed by1H-NMR.

[0218] 1H-NMR (500MHz DMSO- d6): 5 7.39 (s,1 H), 7.04 (s,1 H), 6.6 (s,1 H), 6.15 (s,2H), 4.8 (s,2H) ppm.

[0219] In a 250 ml 3-neck round bottom flask 6.24 g (36.2 mmol, 2.05 eq) of reduced DBN were dissolved in 50 ml DCM under nitrogen to which 5.0 g (17.66 mmol, 1.0 eq) of the bromo compound obtained in step 2 were added slowly. Then reaction was stirred at room temperature for 16 h. The reaction progress was monitored by TLC. After stirring for 16 h, DCM was washed with 50 ml of water. The organic layer was dried over sodium sulfate and distilled under vacuum to give a brown solid which was purified by column chromatography using DCM: MeOH as an eluent to get brown solid. Pure compound which was analyzed by1H-NMR. 2.5 g (yield 30.78 %) of the product were obtained.

[0220] 1H NMR (300 MHz, DMSO-d6): 5 7.43 (s, 1 H), 7.08 (s, 1 H), 6.37 (s, 1 H), 6.16 (s, 2H), 3.90 (d, J = 15.7 Hz, 1 H), 3.30 (d, J = 15.7 Hz, 2H), 3.04 - 2.91 (m, 2H), 2.80 (d, J = 11.6 Hz, 1 H), 2.61 (t, J = 6.8 Hz, 1 H), 2.25 - 2.05 (m, 2H), 1.97 (tt, J = 14.4, 5.3 Hz, 2H), 1.72 (td, J = 14.6, 14.2, 5.3 Hz, 2H), 1.64 - 1.48 (m, 2H), 1.39 (d, J = 12.9 Hz, 1 H) ppm. 220977WC01 1 S022796PCT 27 October 07, 2025

[0221] Chemetall GmbH

[0222] Synthesis of sesamol benzophenone-DBN derivative E5

[0223] In a 100 ml 3-neck round bottom flask 3.0 g (24.5 mmol, 1.0 eq) benzodixole and 4.64 g (24.5 mmol, 1.0 eq) 4- chloro methyl benzoyl chloride were dissolved in 30 ml ethy lenedicloride (EDO) under nitrogen at room temperature. The reaction mixture was cooled to 0 °C. 2.0 g (14.7 mmol, 0.6 eq) zinc dichloride was slowly added over a period of 5 to 10 mins. After addition, the reaction mass was allowed to warm to room temperature, and was then stirred for 7 h. The reaction progress was monitored by TLC. After 7 h, the reaction mass was quenched with 1 N HCI and extracted with DCM. The organic layer was washed with brine and dried over sodium sulfate. The organic layer was distilled under vacuum to give a crude compound which was purified by column chromatography using Heptane: EtOAC as an eluent.

[0224] 3 g (yield 44.4%) of a white solid compound were obtained.

[0225] 1H NMR (300 MHz, Chloroform-d): 5 7.67 (d, 2H), 7.46 - 7.38 (m, 3H), 7.34 - 7.26 (m, 2H), 6.00 (s, 2H), 4.57 (s, 2H) ppm.

[0226] In a 100 ml 3-neck round bottom flask reduced 5.5 g (43.68 mmol, 2.0 eq) of DBN were dissolved in 55 ml DCM to which 6.0 g (21 .84 mmol, 1 .0 eq) of the chloro compound obtained in step-2 were added. The reaction mixture was stirred at room temperature for 16 h. The reaction progress was monitored by TLC. After stirring for 16 h the reaction mass was diluted with DCM and extracted with water. The organic layer was again, washed with DCM. The combined organic layers were dried over sodium sulfate and distilled under vacuum to give a crude compound which was purified by column chromatography using DCM and methanol as an eluent. The pure compound was analyzed by1H-NMR. 3 g (yield 50%) of a white solid product were obtained. 220977W001 1 S022796PCT 28 October 07, 2025

[0227] Chemetall GmbH

[0228] 1H NMR (500 MHz, DMSO-d6): 6 7.66 (d, 2H), 7.48 (d,2H), 7.29 (d,2H), 7.06 (d,1 H), 6.17 (d,2H), 5.76 (d, 2H), 3.88 (d, 1 H), 3.19 (dd,1 H), 2.98 (s, 1 H), 2.76 (d,1 H), 2.17 (d, 1 H), 2.04 (d,1 H), 1.96 (s, 1 H), 1.89 (t, 1 H), 1.71 (s, 1 H), 1.60 (s, 1 H), 1.40 (d, 1 H) ppm.

[0229] Synthesis of a hydroxy coumarin-DBN derivative E6

[0230] In 100 ml 3-neck round bottom flask 1.0 g (9.09 mmol, 1.0 eq) resorcinol were dissolved in 20 ml of a 70% aqueous H2SO4 solution at room temperature under nitrogen to which 2.08 g (13.6 mmol, 1.5 eq) ethyl bromo acetoacetate were added slowly at room temperature. Then reaction mixture was stirred at the same temperature for 16 h. After stirring for 16 h the reaction mass was quenched with water, solid was precipitated which was filtered through a sintered funnel and dried under vacuum. The crude reaction product was purified by washing with 10 ml of acetonitrile to give a pure compound which was analyzed by1H-NMR. 0.72g (yield 31%) of the product were obtained.

[0231] 1H-NMR (500MHz DMSO): 5 10.7 (s, 1 H), 7.72 (d,1 H), 6.91 (m, 1 H), 6.74 (s,1 H), 6.37 (s, 1 H), 4.8 (s,2H).

[0232] In a 50 ml 3-neck round bottom flask, 0.99 g (2.0 eq, 7.841 mmol) reduced DBN were dissolved in 10 ml acetonitrile under nitrogen. Thereto, 1.0 g (1.0 eq, 3.921 mmol) of the bromo hydroxy coumarin derivative obtained in step 2 were added slowly, then the reaction mixture was stirred at room temperature for 16 h. The progress of the reaction was monitored by TLC. After stirring for 16 h, acetonitrile was removed under vacuum to give a crude solid which was purified by acetone washing to afford an off-white solid which was analyzed by1H-NMR. 0.9 g of the product were obtained.

[0233] 1H-NMR (500MHz DMSO-d6): 3 8.32 (s, 1 H), 7.8 (d, 1 H ), 6.8 (d, 1 H ), 6.7 (s, 1 H ), 6.3 (s, 1 H), 3.94 ( d, 1 H ), 3.4 (d, 2H ), 3.05 (m, 2H ), 2.8 (m, 1 H ), 2.6 ( m, 1 H ), 2.2-2.1 (m ,4H ), 1.95 (m , 1 H ), 1.4-1.7 (m, 3H ) ppm. 220977WC01 1 S022796PCT 29 October 07, 2025

[0234] Chemetall GmbH

[0235] Synthesis of Di-DBN Benzophenone derivative E7

[0236] In a 2L 3-neck round bottom flask 50.0 g (238 mmol, 1.0 eq) of 4,4' dimethyl benzophenone was dissolved in 500 ml of dry chloroform under nitrogen. Thereto, 93.2 g (523.6 mmol, 2.2 eq) NBS were added in one lot followed by 0.03 eq AIBN and the reaction mixture was stirred at reflux temperature for 3 h. The reaction progress was monitored by TLC. After stirring for

[0237] 3 h the starting material was consumed. The reaction mixture was cooled to room temperature. The reaction mass was distilled under vacuum to its half quantity. A solid was precipitated, which was filtered, mother liquor was diluted with 500 ml chloroform and extracted with 500 ml of water. The aqueous layer was washed with 300 ml DCM. The combined organic layers were dried over sodium sulfate and distilled under vacuum to give white solid compound which was purified by washing with heptane to give mixture of di-bromo and mono-bromo compounds, which was used for next step without purification.

[0238] In a 2L 3-neck round bottom flask 10.2 g (81.5 mmol, 2eq) reduced DBN was dissolved in 150 ml of DMF:Toluene (7:3) to which 12.3 g (89.6 mmol, 2.2 eq) potassium carbonate was added and stirred for 15 min followed by addition of di-Bromo compound 15 g (40.7 mmol, 1.0 eq). Then the reaction mixture was stirred at room temperature for 7 h. The reaction progress was monitored by TLC. After stirring for 7 h the reaction mass was filtered through a sintered funnel to remove the solid. Mother liquor was distilled under vacuum. Crude compound was diluted with 150 ml of water and extracted with 150 ml of DCM. The aqueous layer was washed with DCM. The combined organic layers were washed twice with water and dried over sodium sulfate and distilled under vacuum to give a crude brown oil, which was purified by heptane washing.

[0239] 1H NMR (500 MHz, DMSO-d6): 5 7.70 (d, 4H), 7.50 (d,4H), 3.90 (d,2H), 3.25 (d,2H), 3.01 (s, 2H), 2.77 (d,2H), 2.61 (s, 1 H), 2.24 (s, 1 H), 2.13 (s, 1 H), 1.95 (d,3H), 1.72 (s, 2H), 1.63 (s, 2H), 1.43 (d,2H). 220977WC01 1 S022796PCT October 07, 2025

[0240] Chemetall GmbH

[0241] Synthesis of Cyano Benzophenone DBN derivative E8 2h at RT

[0242] In a 250 ml 3-neck round bottom flask 5.0 g (34 mmol, 1 .0 eq) of 4-cyanobenzoic acid was dissolved in toluene (50 ml) under nitrogen. 4.7 g (37.4 mmol, 1.1 eq) of oxalyl chloride were added followed by addition of 0.025 eq of dimethyl formamide (DMF) and the reaction mixture was stirred at 25 °C for 2 h. The reaction progress was monitored by HPLC by quenching reaction mass in methanol. After complete reaction of the acid, 4.9 g (37.4 mmol, 1.1 eq) AICI3 were added and the reaction mixture was stirred at 100 °C for 2 h. The reaction progress was monitored by HPLC. After stirring for 2 h the reaction mass was cooled to 75 °C and quenched with 50 ml of an aqueous sodium sulphate solution. After quenching, the reaction mass was stirred at same temperature for 10 min. Then it was allowed to stand for layer separation. The aqueous layer was removed, and the organic layer was cooled to 10 °C. A solid precipitated, which was filtered through a sintered funnel and dried under vacuum to give an off-white solid. The pure solid was analyzed by1H-NMR. 5.1 g (yield 72.5 %) of the off-white solid were obtained.

[0243] 1H NMR (300 MHz, Chloroform-d): 5 7.88 (d, 1 H), 7.80 (d, 1 H), 7.79 - 7.67 (m, 1 H), 7.33 (d, J = 8.0 Hz, 1 H), 2.48 (s, 2H) ppm.

[0244] In 100 ml 3-neck round bottom flask 5.0 g (23.69 mmol, 1 eq) 4-methyl cyano benzophenone was dissolved in 50 ml of dimethyl carbonate to which 0.025 eq Al BN were added in one lot and reaction was stirred at 75 °C. At that temperature 5.0 g (28.4 mmol, 1.2 eq) NBS were added in 4 lots (each lot after an interval of 10 min). Then the reaction mixture was stirred at 75 °C until the starting material was consumed (2 h) which was monitored by LC- MS. LC-MS shows 80 % of monobromo and 12.5 % dibromo compounds, the rest was starting material. After stirring for 2 h, the reaction mixture was cooled to room temperature and then diluted with 50 ml of water. The organic layer was washed with 25 ml of water. The organic layer was distilled under vacuum to give white crude solid. The crude solid was dissolved in 10 vol of methanol and stirred at 50 °C solution. As it became clear it was cooled to 10°C to precipitate a white solid which was filtered and dried under vacuum to give white solid which was analyzed by LC-MS. The reaction yielded 7 g of the crude product. 220977W001 1 S022796PCT October 07, 2025

[0245] Chemetall GmbH

[0246] In a 50 ml 3-neck round bottom flask 4.2 g (33.7 mmol, 2.0 eq) of reduced DBN was dissolved in 50 ml of 2-MeTHF under nitrogen which was cooled to 5 to 8 °C. Thereto, 5.0 g (16.8 mmol, 1 .0 eq) of the bromo compound obtained in step-3 was added slowly at the same temperature. The reaction mixture was stirred at 5 to 8 °C for 16 h. After stirring for 16 h the reaction mass was diluted with 50 ml of water. The organic layer was separated. The aqueous layer was washed with 25 ml of 2-MeTHF. The combined organic layers were dried over sodium sulfate and distilled under vacuum to give a crude product, which was purified by washing with 5 vol of methyl-tert-butylether (MTBE) (5 vol). The pure compound obtained was analyzed by1H-NMR. 4.3 g (yield 75%) of an off-white solid were obtained.

[0247] 1H NMR (500 MHz, DMSO-d6) : 5 8.07 - 8.01 (m, 2H), 7.89 - 7.84 (m, 2H), 7.75 - 7.70 (m, 2H), 7.54 - 7.49 (m, 2H), 3.88 (d, 1 H), 3.22 (d, J = 14.1 Hz, 1 H), 2.98 (td, 2H), 2.74 (d, 1 H), 2.17 (q,1 H), 2.06 (t,1 H), 1.93 (dtd,2H), 1.75 - 1 .64 (m, 2H), 1 .59 (ddt,2H), 1 .44 - 1 .36 (m, 1 H)ppm.

[0248] Synthesis of TBD alkylated with 4-Cyanobenzyl bromide E9

[0249] To a three-neck round bottom flask, fitted with an N2 inlet, stopper and thermometer pocket were added 3.0 g (21.52mmol) of TBD and 30.0 ml tetrahydrofuran. Then the reaction mixture was cooled to 10.0 °C. 0.95 g (23.7 mmol) of sodium hydride was added slowly keeping the temperature below 10.0 °C. Then the reaction mixture was heated to 45.0 °C and stirred for 2.0 hours. The reaction mixture was cooled to 15.0 °C and then a solution of 4- cyano benzyl bromide (4.11 g 21.52 mmol in 30.0 ml of THF) was added slowly for period of 30.0 min. the reaction mixture was stirred for 2.0 hours and progress was monitored by thin layer chromatography (TLC). After consumption of the starting material, the reaction mixture was cooled to 0 °C to 5 °C, and quenched by water (20.0 ml). The aqueous layer was extracted by ethyl acetate (3 times 20.0 ml). The combined organic layers were dried over sodium sulfate, concentrated, and analyzed by NMR spectroscopy. Yield: 5.2 g, (94.8%). 220977WQ01 1 S022796PCT 32 October 07, 2025

[0250] Chemetall GmbH

[0251] 1HNMR(DMSO-D6): 7.76-7.74 (d,2H), 7.43-7.41 (d,2H), 4.58(s,1 H), 3.10-3.16 (t,1 H), 3.02-3.10 (m,4H), 1.86-1.88 (t,2H), 1.69-1.71 (t,2H).

[0252] In analogy with the above procedures any further non-ionic photo-latent bases can be obtain by use of the corresponding bases such as DBN, TBC and TMG in combination with the halomethyl compound corresponding to the photo cleavable group.

[0253] Sealant Systems and Sealant Composition

[0254] Base Components AC1 and AC2

[0255] In Tables 1 and 2 base components AC1 and AC2 are described. The amount of ingredients is in parts by weight. Base component AC1 makes use of a thiol-terminated polythioether polymer as thiol-terminated polymer, while base component AC2 makes use of a thiol terminated polysulfide as a thiol-terminated polymer.

[0256] Further, base components AC1’ and AC2’ were prepared which differ from base components AC1 and AC2, respectively, only in that the 0.1 parts by weight of the photosensitizer contained in AC1 and AC2 were omitted, and in case of AC1’, additionally 0.1 parts by weight of the thiol-terminated polythioether polymer were added, while in case of AC2’, additionally 0.1 parts by weight of the thiol-terminated polysulfide polymer 1 (Thioplast® G10) were added.

[0257] Table 1 - Base Component AC1 (thiol-terminated Polythioether) 220977WC01 1 S022796PCT 33 October 07, 2025

[0258] Chemetall GmbH

[0259] Table 2 - Base Component AC2 (thiol-terminated Polysulfides)

[0260] *SH content: approx. 1 .4 wt.-%; Mn: approx. 4550 g / mol

[0261] **SH content: approx. 6.5 wt.-%; Mn: s 1150 g / mol

[0262] Table 3 - Photo-latent Bases 220977WC01 1 S022796PCT 34 October 07, 2025

[0263] Chemetall GmbH

[0264] Hardener Component BC1

[0265] In Table 4 hardener component BC1 is described. The amount of ingredients is in parts by weight. Hardener component BC1 makes use of two different polyepoxides as curing agents, namely DEN 431 and DER 331.

[0266] Table 4 - Hardener Component BC1 (polyepoxide)

[0267] Sealant Composition

[0268] The ready-to-use sealant composition was obtained by mixing 90 parts by weight of the respective Base Component AC1 / AC1’ with 10 parts by weight of the Hardener Component BC1.

[0269] Application of the Sealant Composition onto a Substrate and Testing

[0270] For testing the sealant compositions on whether they require a photosensitizer, to determine the processing time of the non-UV-exposed mixture of the base component and the hardener component, and to determine the curing time after UV exposure, the ready-to-use sealant composition was investigated as follows. 220977W001 1 S022796PCT 35 October 07, 2025

[0271] Chemetall GmbH

[0272] To determine the processing time in an unexposed condition, both components were mixed in and the cartridge extrusion rate was measured by applying a defined air-pressure on the cartridge backside. Extrusion rate is then determined by:

[0273] The extrusion rate at the end of the application time shall not exceed 15 g / min.

[0274] To determine whether a photosensitizer is required to initiate UV-curing, a sealant composition containing a photosensitizer (making use of base composition AC1) was compared with a sealant composition, which does not contain a photosensitizer (making use of base composition ACT). For each sealant composition the ready-to-use sealant was applied onto a PTFE-mold with a 3 mm deep cavity and cured with UV radiation (wavelength: 395 nm) using a Phoseon FireJet ONE with 14 W / cm2of power. Distance was set to 50 mm between substrate and lamp surface. Exposure time was set to 10 seconds.

[0275] To determine the curing time after exposure the sealant compositions comprising base composition were applied onto a PTFE-mold with a 3 mm deep cavity and cured with UV radiation (wavelength: 395 nm) using a Phoseon FireJet ONE with 14 W / cm2of power. Distance was set to 50 mm between substrate and lamp surface. Exposure time was set to 10 seconds. Curing time was determined by measuring the Shore A-value. Sealant was defined as "cured” when material reached a Shore A-value of 30.

[0276] Results

[0277] In Table 5 the results of the afore-mentioned tests are summarized.

[0278] Table 5 - Results

[0279] It is clearly shown that the comparative sealant CS1, making use of comparative photo-latent base C1 is only curable, if a photosensitizer is present in the sealant composition. 220977W001 1 S022796PCT 36 October 07, 2025

[0280] Chemetall GmbH

[0281] For all inventive sealants IS1 to IS4 no photosensitizers are required for curing. Surprisingly, the curing time for inventive sealant IS3 is the same even without photosensitizer compared to the comparative sealant composition CS1 containing a photosensitizer, or even much shorter, particularly for inventive sealant compositions IS2 and IS4 being in the range from 1 to 8 min with photosensitizer or 1 to 10 min without photosensitizer.

[0282] The inventive sealant IS3 (without photosensitizer) having a similar curing time range as comparative sealant composition CS1 (with photosensitizer), has a much longer processing time in the unexposed state, namely 72 h compared to 24 h. For inventive sealant composition IS3 it was further observed that the maximum curable layer thickness was in the range from 6 to 7 mm, while the comparative sealant composition was, although requiring a photosensitizer, only curable up to a layer thickness of about 4 to 5 mm.

Claims

1. 220977WC01 1 S022796PCT 37 October 07, 2025Chemetall GmbHCLAIMS1 . A sealant system comprising at least one base component A, the base component A comprising at least one thiol-terminated polymer A1 selected from the group consisting of polysulfides A1.1, polythioethers A1.2, polyethers A1.3 and copolymers A1.4 thereof; and at least one hardener component B, the hardener component B comprising at least one polyepoxide B1; characterized in that the at least one base component A further comprises at least one non-ionic photo-latent base A2, the non-ionic photo-latent base A2 having the general formula (I):(PCG)-(BG)n(I) whereinI. PCG stands for a photocleavable group;II. BG stands for a base group; ill. n is i or 2; iv. the base formed after cleaving the bond between PCG and BG a. is a non-ionic base, and b. possesses a pKavalue of the conjugate acid of > 10.0 v. A2 has a photoactivation wavelength for cleaving the bond between PCG and BG in the range of 300 nm to 420 nm.

2. The sealant system according to claim 1, characterized in that the non-ionic photo-latent base A2 has the general formula (I) wherein the base group BG is one of the following groups:220977W001 1 S022796PCT October 07, 2025Chemetall GmbH the photocleavable group PCG is one of the following groupsPCG1 (R3=R4=H),PCG2 (R3and R4form C=O), wherein R1and R2are selected from hydrogen; CN; NO2; NHRAwith RAbeing hydrogen or an alkyl group with 1 to 12 carbon atoms; ORBwith RBbeing an alkyl group with 1 to 12 carbon atoms; F; SO3H; BGI-CH2; BG2-CH2;BG3-CH2, or R1and R2form together a group O-CH2-O; R3and R4are hydrogen or form together a C=O group; and at least one of R1and R2being hydrogen, preferably R1being hydrogen;wherein R5and R6form together a group O-CH2-O, or R5= H and R6= OH;PCG5, wherein R7is selected from ON; COORCwith Rcbeing an alkyl group with 1 to 12 carbon atoms.

3. The sealant system according to claim 1 or 2, characterized in that the non-ionic photo-latent base is selected from (BG1)-(PCG1)n, (BG1)-(PCG2)n, (BG1)-(PCG3)n, (BG1)-(PCG4)n, (BG1)-(PCG5)n, (BG2)- (PCG1)n, (BG2)-(PCG2)n, (BG2)-(PCG3)n, (BG2)-(PCG4)n, (BG2)-(PCG5)n, (BG3)-(PCG1)n, (BG3)- (PCG2)n, (BG3)-(PCG3)n, (BG3)-(PCG4)n, (BG3)-(PCG5)n, n being 1 or 2.

4. The sealant system according to any one or more of the preceding claims, characterized in that the pKavalue of the conjugate acid is > 11.0, more preferred > 12.0, and220977W001 1 S022796PCT 39 October 07, 2025Chemetall GmbH the difference between the pKavalues of the conjugate acids of the photo-latent bases of formulae (I) and the conjugate acids of the respective bases formed (ApKa) is > 5, more preferred > 6.

5. The sealant system according to any one or more of the preceding claims, characterized in that the at least one thiol-terminated polymer A1 is selected from thiol-terminated polysulfides, thiol-terminated polythioethers, thiol-terminated polyethers, and their copolymers, and mixtures thereof, and / or the at least one polyepoxide B1 is selected from monomeric, oligomeric or polymeric polyepoxides B1 , which are aromatic or aliphatic and possess at least two epoxide groups.

6. The sealant system according to claim 5, characterized in that the at least one thiol-terminated polymer A1 is selected from thiol-terminated polysulfides, thiol-terminated polythioethers, and their copolymers, and mixtures thereof; and / or the at least one polyepoxide B1 is selected from the group consisting of diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, aliphatic polyglycol diglycidyl ether, hydantoin-epoxy derivatives, epoxidized unsaturated and / or phenolic resins, epoxy novolac resin, including cross-linked epoxy novolac resins and / or an epoxy resins.

7. A sealant composition containing or consisting of a mixture of base component A and hardener component B, both as defined in the preceding claims.

8. A sealant composition according to claim 7, comprising, based on the total weight of the sealant composition45 to 95 wt.-% of the at least one thiol-terminated polymer A1 ,0.15 to 9 wt.-% of the at least one non-ionic photo latent bases A2, and1 to 20 wt.-% of the at least one polyepoxides B1.

9. A sealant composition according to claim 8, further comprising, based on the total weight of the sealant composition, one or more or the following ingredients in an amount of more than 0 wt.-%:0 to 9 wt.-% of at least one adhesion promotor, preferably a silane adhesion promotor,0 to 2 wt.-% of at least one photosensitizer,0 to 60 wt.-% of at least one filler,0 to 3 wt.-% of at least one pigment,0 to 18 wt.-% of at least one plasticizer,220977W001 1 S022796PCT 40 October 07, 2025Chemetall GmbH0 to 9 wt.-% of at least one thixotropic agent, and 0 to 5 wt.-% of at least one organic solvent.

10. A sealant composition according to any of claims 7 to 9, further comprising1 to 50 wt.-% of at least one curing catalyst for the reaction between thiol groups and epoxy groups, which differs from the non-ionic photo-latent bases A2, the amount of the at least one curing catalyst being based on the combined amounts of the at least one curing agent and the non-ionic photo-latent bases A2.11 . A method of sealing comprising the steps of(a) providing a substrate;(b) applying a sealant composition as defined in any of claims 7 to 10 at least onto a part of the substrate to be sealed;(c) irradiating the applied sealant composition with light in the wavelength range from 300 to 420 nm.

12. The method according to claim 11 , characterized in that the light in the wavelength range from 300 to 420 nm, preferably in the range from 320 to 420 nm, more preferably in range from 350 to 420 nm and most preferably in range from 375 to 420 nm is emitted by a light-emitting diode (LED).

13. The method according to any one of claims 11 or 12, characterized in that the substrate is selected from the group consisting of aircrafts, spacecrafts, land vehicles, water vehicles, and parts of the aforementioned vehicles.

14. Use of the sealant composition as defined in claims 7 to 10 as fastener sealing, fillet sealing, interfay sealing, and / or sprayable sealant; or as printing material in 3D printing applications.

15. The use of the sealant composition as defined in claim 14, in sealing vehicles selected from the group consisting of aircrafts, spacecrafts, land vehicles, water vehicles, and parts of the afore-mentioned vehicles.

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