SH-terminated polydithioacetals for use in sealants

Abstract

The present invention relates to a polycondensation process for preparing SH-terminated polymers having at least two terminal SH groups and containing a sulfur-carbon-sulfur bond in the polymer backbone, to the polymers obtainable by this process, to a 2K sealing system comprising this polymer as one of its components, to a sealant composition obtainable therefrom, to a process for sealing a substrate with the aid of said sealant composition, and to a sealed substrate obtainable by this process, comprising the step of reacting at least one organic component a1 containing at least one carbonyl group with at least one organic component a2 containing at least two thiol groups, the component(s) a1 being selected from aldehydes having at least one aldehyde group, O-acetals of these aldehydes, ketones having at least one keto group, and mixtures thereof, the two sulfur atoms of the at least two thiol groups of the component(s) a2 being separated from each other by a linker moiety L having a chain of at least 4 atoms, and the molar ratio r of the components a1 and a2 to each other is <1.

Description

[Technical field]

[0001] The present invention relates to a method for the preparation of an SH-terminated polymer having at least two terminal SH groups, a 2K sealing system comprising this polymer as one of its components, a sealant composition obtainable therefrom, a method for sealing substrates using said sealant composition, and sealed substrates obtainable by this method. [Background technology]

[0002] Sealants are used in a wide range of applications, for example in the aircraft and aerospace sector, but also in the automotive sector. They are further used for sealing construction elements, for connecting metal sheets to existing structures, for example aircraft segments, and / or for corrosion protection where the corrosion protection layer of metal elements has been damaged or removed, for example in the region of holes. They may also perform a temporary transport function, for example during the transportation of structures to be mounted and which must then be provided with permanent supporting connection elements.

[0003] The use of polymeric thiols and their application in sealants, such as aerospace and aircraft sealants, is known in the prior art. Many synthetic routes are available for the preparation of such polymeric thiols.

[0004] The most prominent synthetic route for polythioether synthesis is the thiol-ene click chemistry route, which utilizes bis-thiols and divinyl ethers as starting materials. The corresponding SH-terminated polythioethers, which in particular have a polymer backbone with sulfur-carbon-oxygen units and more than one carbon atom between the oxygen and sulfur atoms of said units and can be obtained by said thiol-ene click reaction, are disclosed, for example, in US 6,232,401 B1. Triallyl cyanurate (TAC) can be used as a crosslinker in the thiol-ene click reaction to introduce branching into the resulting polymer. However, the availability of suitable raw materials used in this route is limited and, even if available, usually involves a relatively high cost. This route is therefore disadvantageous, at least for economic reasons.

[0005] Sulfone-containing polythioethers are disclosed in US 9,540,540B2. These polythioethers are prepared using thiol-ene prepolymers (based on bis-thiols and divinyl ethers) and divinyl sulfone. The sulfone group is introduced to enhance the thermal stability of the resulting polymer. However, the potential hazards of divinyl sulfone are high, and therefore synthetic routes employing this starting material are undesirable.

[0006] Another synthetic route for preparing polymeric thiols is the reaction of a suitable polythiol, such as a bis(thiol), with a polyhalide, such as a bis(halide), in an alkaline environment. The polymers disclosed in US 6,525,168 B2 and US 6,723,827 B2 have been prepared by this route. However, polyhalides, especially bis(halides), such as bis-chloroethyl formal, are potentially hazardous and / or toxic, and therefore synthetic routes employing this starting material are undesirable. Furthermore, when bis-chloroethyl formal is used, the resulting product is not stable to acidic conditions due to the presence of formal groups. For this reason, this route is also disadvantageous.

[0007] Further preparations of thioethers are disclosed in US 7,875,666 B2 and US 8,466,220 B2. These patents describe the synthesis of thioethers via the reaction of sodium hydrosulfide (NaHS), NaOH and bis-chloroethyl formal CH2(OCH2CH2Cl)2. First, the corresponding bis-thiol CH2(OCH2CH2SH)2 is formed, which then further reacts with additional bis-chloroethyl formal CH2(OCH2CH2Cl)2. Again, since NaHS as well as chloroethyl formal are toxic substances, the synthetic route employing this starting material is undesirable. Moreover, as mentioned above, the resulting products are not stable to acidic conditions due to the presence of the formal group. Therefore, this route is also disadvantageous.

[0008] EP3702348A1 relates to thiol compounds and synthetic methods for obtaining them. The thiol compounds disclosed in EP3702348A1 can be the reaction product of a thiol and a carbonyl compound. The thiol compounds thus obtained are not polymeric. When the non-polymeric thiol compounds disclosed in EP3702348A1 are used to prepare sealants, it is observed that the elasticity of the sealant is insufficient for aerospace applications, which is disadvantageous. Furthermore, a large amount of hardener components such as epoxide group-containing components must be used, which is economically disadvantageous and further leads to an increase in the number of OH groups present in the crosslinked network formed. This can also lead to an undesirable increase in the glass transition temperature. For these reasons, the respective sealants may not meet the requirements of the aerospace industry.

[0009] However, the methods for preparing polymeric thiols known in the prior art are not always satisfactory in all respects. In most cases, the yield is not always satisfactory. Moreover, in some cases, the methods involve more than one step, require complex handling, require the use of expensive starting materials and / or the use of toxic or at least harmful starting materials and / or chemicals, which is disadvantageous from an ecological point of view and also for safety reasons. Moreover, not all products have sufficient stability, especially under acidic conditions.

[0010] Therefore, there is a need to provide a new method for preparing polymeric thiols that does not have the disadvantages of the conventional methods. Moreover, the resulting polymers must be suitable for use in sealants, especially for the aerospace and aircraft industries, and the resulting sealants must not exhibit adverse properties, especially with regard to water and fuel resistance, and mechanical properties, and furthermore, must be capable of curing at low temperatures. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] US6,232,401B1 [Patent Document 2] US9,540,540B2 [Patent Document 3] US6,525,168B2 [Patent Document 4] US6,723,827B2 [Patent Document 5] US7,875,666B2 [Patent Document 6] US8,466,220B2 [Patent Document 7] EP3702348A1 Summary of the Invention [Problem to be solved by the invention]

[0012] The objective underlying the present invention is therefore to provide a new method for preparing polymeric thiols that is simple, easy to carry out, involves as few steps as possible, is safe, and is economically and environmentally advantageous. At the same time, the resulting polymeric thiols should have sufficient acid stability to allow curing at low temperatures when incorporated into a sealant composition, and the sealant composition should not exhibit adverse properties as far as the mechanical properties and water and fuel resistance of the resulting sealant are concerned.

[0013] This object has been solved by the subject matter of the present claims and by the preferred embodiments thereof disclosed herein, i.e. by the subject matter described herein. [Means for solving the problem]

[0014] A first subject of the present invention is a polycondensation process for preparing SH-terminated polymers having at least two terminal thiol groups and containing a sulfur-carbon-sulfur bond in the polymer backbone, comprising: The method comprises, as step 1), a step of reacting with one another at least two components, namely at least one organic component a1, which preferably has an aliphatic structure and contains at least one carbonyl group, and at least one organic component a2, which is different from component a1 and contains at least two thiol groups, to prepare an SH-terminated polymer, The component(s) a1 are selected from aldehydes having at least one aldehyde group, O-acetals of these aldehydes, ketones having at least one keto group, and mixtures thereof, the two sulfur atoms of at least two thiol groups of component(s) a2 are separated from each other by a linker moiety L having a chain of at least four atoms; and The molar ratio r of the components a1 and a2 to each other is <1 and preferably ranges from 0.82 to 0.99.

[0015] A further subject of the present invention are SH-terminated polymers obtainable by the method according to the invention.

[0016] A further subject of the present invention is a two-component (2K) sealing system comprising components (A) and (B) which are separate from one another, component (A) of which comprises at least one SH-terminated polymer according to the invention or at least one SH-terminated polymer obtainable by the process according to the invention, and component (B) of which system comprises at least one component b0 which is suitable for curing the sealant composition by at least partially bringing about a chemical transformation of at least two thiol groups of the SH-terminated polymer.

[0017] A further subject of the invention is a sealant composition obtainable by mixing together components (A) and (B) of the sealing system according to the invention.

[0018] A further subject of the present invention is a method for sealing an optionally precoated substrate, comprising at least the step of applying in portions a sealant composition according to the invention to the surface of the optionally precoated substrate, said optionally precoated substrate being preferably a substrate applicable in the aerospace and / or aircraft industry.

[0019] A further subject of the invention are encapsulated substrates obtainable by the process according to the invention.

[0020] A further subject of the present invention is the use of the sealing system of the present invention or the sealant composition of the present invention for providing a seal at least partially over the surface of any precoated substrate that can be used in the aerospace and / or aircraft industry.

[0021] Particularly surprisingly, it has been found that the method of the present invention allows the formation of SH-terminated polymers having at least two terminal thiol groups (hereinafter also referred to as polydithioacetals) in good yields in a simple and easy one-step reaction, especially from non-toxic starting materials.In most cases, the starting materials used are also volatile components, so that no purification step is even necessary after the formation of the polydithioacetals.In all other cases, it has been found that carrying out the synthesis in the presence of a filler, such as montmorillonite, is a suitable means by which the polydithioacetal synthesis can be carried out without any purification step, such as filtration, after the formation of the polydithioacetals.

[0022] Furthermore, it has been found, particularly surprisingly, that the process of the invention allows the formation of only, or at least almost only, SH-terminated polydithioacetals, without the formation of undesired cyclic dithioacetals, as observed in the case of the reaction of short-chain thiol group-containing components, such as 1,2-dimercaptoethane or 1,3-dimercaptopropane, with component a1. This has been found to be achieved both by using a molar excess of component a2 (wherein the molar ratio r defined above is <1) and by using component(s) a2 in which the two sulfur atoms of at least two thiol groups are separated from one another by a linker moiety L having a chain of at least four atoms (for example four carbon atoms), optionally one or more of which may be substituted with a heteroatom, preferably selected from O, S and N, or a corresponding heteroatom group, the heteroatom of which is preferably selected from O, S and N.

[0023] Furthermore, it has been found that the process of the present invention allows the formation of both linear and branched polydithioacetals, depending on the number of carbonyl groups present in component a1 and / or the number of thiol groups present in component a2.

[0024] Moreover, it has been found, particularly surprisingly, that the method of the present invention allows the formation of SH-terminated polydithioacetals that have very good stability against hydrolysis, i.e., that exhibit excellent water resistance.The method of the present invention therefore allows the preparation of SH-terminated polydithioacetals that can be used, inter alia, as polymeric components in sealant compositions, particularly for use in the field of aircraft and aerospace industry.

[0025] Furthermore, it has been found that polydithioacetal can be chemically crosslinked using a suitable curing component, such as a component containing two or more epoxide groups, so that a sealant with excellent properties can be obtained.In particular, it has been found that for a sealant prepared from this sealant composition and containing crosslinked polydithioacetal, no undesirable deterioration is observed after storage in water, and thus the sealant exhibits very good water resistance.

[0026] Furthermore, it has been found that the sealant composition comprising the polydithioacetal prepared according to the present invention can be used, for example, to seal the inside of an aircraft fuel tank, since the corresponding substrates sealed therewith exhibit excellent resistance to liquid media, such as organic solvents, and in particular fuels, such as jet fuel.Thus, in particular, it has been found that the sealant composition comprising the polydithioacetal prepared according to the present invention exhibits high jet fuel resistance.

[0027] Moreover, it has surprisingly been found that sealant compositions containing polydithioacetals prepared according to the present invention can provide sealed substrates that exhibit excellent physical and mechanical properties, such as tensile strength and elongation at break.

[0028] Moreover, it has been surprisingly found that the cured sealants containing polydithioacetals prepared according to the invention using component a1 with an aliphatic structure have a relatively low glass transition temperature, for example below −25° C., which is advantageous insofar as the sealants are used in particular in the aerospace industry. In particular, it has been found that the cured sealants containing polydithioacetals using component a1 with an aromatic structure have a much higher glass transition temperature, which is therefore disadvantageous.

[0029] Additionally, the sealant composition has been found to provide rapid autocatalytic cure at low temperatures, such as room temperature (18-29° C.).

[0030] Finally, it has been found that the sealant compositions exhibit excellent elasticity, require the use of lower amounts of hardener components, e.g. epoxide group-containing components, which is economically advantageous, and have a sufficiently low glass transition temperature, especially when compared to sealant compositions comprising non-polymeric thiol compounds, such as those disclosed in EP 3 702 348 A1, since the number of OH groups present in the crosslinked network formed is sufficiently low. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The term "comprising" in the sense of the present invention, for example in relation to a sealant composition, preferably has the meaning "consisting of". For example, in relation to a sealant composition, in addition to any essential components present therein, it is also possible for one or more of the further optional components specified below to be included therein. All components may in each case be present in their preferred embodiments as specified below.

[0032] The proportions and amounts, expressed in wt% (mass%) of any constituents given below, present in each component of the sealing system, add up to 100% by weight in each case relative to the total weight of the respective component.Similarly, the proportions and amounts, expressed in wt% (mass%) of any constituents given below, present in the sealant composition, add up to 100% by weight in each case relative to the total weight of the composition.

[0033] Method for preparing SH-terminated polymers, components a1 and a2 The method of the present invention is a polycondensation method for preparing SH-terminated polymers having at least two terminal thiol groups and containing a sulfur-carbon-sulfur bond in the polymer backbone. The method comprises reacting with each other at least two components, namely at least one organic component a1 containing at least one carbonyl group and at least one organic component a2 different from component a1 and containing at least two thiol groups, to prepare an SH-terminated polymer. This step is also referred to as step 1) in this specification.

[0034] The terms "polymer" and "polymeric" in relation to SH-terminated polymers are known to the skilled artisan and, for the purposes of the present invention, include polycondensates. SH-terminated polymers are also referred to herein as polydithioacetals, since they are prepared via the dithioacetal route from the preferably acid-catalyzed reaction of at least components a1 and a2 with each other.

[0035] Preferably, step 1) is catalyzed by at least one acid, more preferably at least one inorganic or organic acid, even more preferably at least one inorganic acid.The acid, especially the inorganic acid, can be liquid or can be used in its liquid form, for example, in the case of hydrochloric acid, sulfuric acid and / or phosphoric acid.However, alternatively or additionally, the acid, especially the inorganic acid, can be solid and can be used in its solid form, for example, in the case of phyllosilicates.

[0036] For example, step 1) can be carried out in the presence of at least one filler material, for example a phyllosilicate material, which is used as an example of a solid acid. An example of this material is Montmorillonite® K10. This filler material can function as a solid acid to catalyze the reaction of components a1 and a2. The filler material does not necessarily have to be separated from the polymer if it is desired to later incorporate it as a filler together with the polymer into the sealing system and sealant composition. Thus, when at least one filler material, for example a phyllosilicate material, is present during the polymer synthesis, in this case filtration is not necessary. However, if desired, the material can be recovered without reducing the catalytic activity. After filtration, the material is preferably washed several times with an organic solvent, for example ethyl acetate, and then recovered. Afterwards, the material is preferably dried in a vacuum oven (90° C., 0 mbar) for 6 to 14 hours. Other examples of commercially available solid acid catalysts other than Montmorillonite® K10 include Amberlyst® 15 and Dowex® 50W X8.

[0037] Preferably, step 1) is carried out by cooling the reaction mixture containing component a2(s), optionally at least one acid and optionally at least one organic solvent to a temperature in the range of 10° C. to −10° C., for example 5° C. to −5° C., and then adding component a1, especially when the at least one acid optionally used is a liquid acid. The reaction mixture is then preferably heated at an elevated temperature, preferably in the range of 50 to 100° C., more preferably in the range of 60 to 95° C., for a certain period of time, preferably 2 to 18 hours, more preferably 2.5 to 9 hours. When the at least one acid optionally used is a solid acid, component a1 is preferably added to the reaction mixture containing component a2, at least one acid and optionally at least one organic solvent, at a temperature in the range of 15 to 35° C. After the addition of component a1, the resulting mixture is then heated at an elevated temperature, preferably in the range of 50 to 140° C., more preferably in the range of 75 to 130° C., for a certain period of time, preferably 2 to 10 hours, more preferably 2.5 to 8 hours.

[0038] Below, an exemplary procedure for carrying out the method of the invention is outlined: Preferably, component a2, for example 1,8-dimercapto-3,6-dioxaoctane (DMDO), is mixed with at least one organic solvent, for example 1,4-dioxane, and a catalytic amount of a suitable acid, for example hydrochloric acid. The reaction mixture is then cooled, preferably under stirring, for example to a temperature of about 0° C. Then, component(s) a1, for example an aldehyde, is added dropwise over a period of 15 min to 120 min, for example 44 min. Stirring is then preferably continued at 0° C., and the reaction mixture is left to stand for 1 to 16 h, before being stirred for another 1 to 18 h at elevated temperature, for example at a temperature between 60 and 100° C., for example 85° C. After evaporation of the volatile components, for example using a rotary evaporator under vacuum (-12 mbar) at 90° C., the SH-terminated polymer is obtained. Usually, purification of the polymer is not necessary, especially if the starting materials and any chemicals used are volatile.

[0039] Preferably, the number average molecular weight (M n ) is in the range of 500 to 15,000 g / mol, more preferably 600 to 10,000 g / mol, even more preferably 700 to 7,500 g / mol, even more preferably 800 to 5,000 g / mol, even more preferably 900 to 4,500 g / mol, and most preferably 1,000 to 4,000 g / mol. n is determined according to the method disclosed in the "Methods" section.

[0040] Preferably, the SH-terminated polymer has an SH content of 1.0% to 10.0% by weight, more preferably 1.1 to 9.5% by weight, even more preferably 1.2 to 9.0% by weight, also more preferably 1.3 to 8.5% by weight, even more preferably 1.4 to 8.0% by weight, also more preferably 1.5 to 7.5% by weight, even more preferably 1.5 to 7.0% by weight, even more preferably 1.5 to 6.5% by weight, and even more preferably 1.5 to 6.0% by weight, in each case relative to the total weight of the SH-terminated polymer. The SH content is determined according to the method disclosed in the "Method" section.

[0041] Preferably, the SH-terminated polymer does not contain any sulfone groups. In particular, the SH-terminated polymer is preferably prepared without using any sulfone group-containing starting material, such as divinyl sulfone.

[0042] The SH-terminated polymer preferably contains repeating sulfur-carbon-sulfur bonds in its polymer backbone. In particular, the SH-terminated polymer contains more than one sulfur-carbon-sulfur bond in its polymer backbone. At least some of these sulfur-carbon-sulfur bonds preferably have a divalent -S-CR in the backbone. x R y -S-moiety. x and R y Each of the groups preferably independently represents H, C1 to C 20 Aliphatic radicals, C1-C 20 Heteroaliphatic radicals, C3-C 20 Cycloaliphatic radicals, 3- to 20-membered heterocycloaliphatic radicals, 5- to 20-membered aryl or heteroaryl radicals, C1- 10 C3-C bonded via an aliphatic radical 20 Cycloaliphatic radicals, C1~ 10 - 3-20 membered heterocycloaliphatic radicals bonded via an aliphatic radical, and C1- 10 - 5-20 membered aryl or heteroaryl radicals bonded via an aliphatic radical, more preferably H, C1-C 20 Aliphatic radicals, C1-C 20Heteroaliphatic radicals, C3-C 20 is selected from the group consisting of cycloaliphatic radicals, 3-20 membered heterocycloaliphatic radicals, and 5-20 membered aryl or heteroaryl radicals, and even more preferably H, C1-C 20 Aliphatic radicals and C1-C 20 Heteroaliphatic radicals are preferably selected from the group consisting of R x and R y At least one of R is ≠H, more preferably x and R y The condition is that exactly one of the is ≠ H.

[0043] The molar ratio r of the components a1 or a2 to each other is <1. Preferably, the molar ratio r of the component a1 or a2 to the component a2 is in the range of 0.50 to <1, more preferably 0.51 to 0.99, even more preferably 0.52 to 0.98, still more preferably 0.53 to 0.97, also more preferably 0.54 to 0.96, and even more preferably 0.55 to 0.95. The molar ratio r is determined by the number average molecular weight (M n ) can be used to adjust / modulate. Thus, the component a2 (e.g. (bis)-thiol) containing at least two thiol groups is always used in molar excess, so that r is always <1. As r increases, M n also increases.

[0044] Preferably, the molar ratio r of the component(s) a1 to the component(s) a2 is in the range of 0.50 to <1.0, more preferably >0.50 to <1.0, also more preferably 0.60 to <1.0, still more preferably 0.70 to <1.0, also more preferably 0.80 to <1.0, still more preferably 0.82 to <1.0, even more preferably 0.85 to 0.99, also more preferably 0.86 to 0.99, still more preferably 0.87 to 0.99, and more preferably >0.87 to 0.99.

[0045] At least one organic component a1 containing at least one carbonyl group is used for the preparation of SH-terminated polymers. The component(s) a1 are selected from aldehydes having at least one aldehyde group, O-acetals of these aldehydes, ketones having at least one keto group, and mixtures thereof. Of course, it is also possible to use more than one component a1. For example, it is possible to employ two components a1 that are different from each other, for example one component a1 with exactly one carbonyl group, for example a first aldehyde, and one component a1 with two or more carbonyl groups, for example a second dialdehyde. It is also possible to use two components a1, for example one aldehyde and one ketone, each with exactly one carbonyl group, but different from each other.

[0046] The organic component a1 can have an aliphatic or aromatic structure. The aliphatic structure includes both cyclic and alicyclic structures. However, alicyclic structures are preferred. The aliphatic structure may include one or more heteroatoms and / or heteroatomic groups, and thus includes heteroaliphatic structures. The aromatic structure may include one or more heteroatoms and / or heteroatomic groups, and thus includes heteroaromatic structures. Preferred aliphatic structures are C1-C 20 Aliphatic radicals, C1-C 20 Heteroaliphatic radicals, C3-C 20 Cycloaliphatic radicals, 3-20 membered heterocycloaliphatic radicals, C1- 10 C3-C bonded via an aliphatic radical 20 Cycloaliphatic radicals, and C1~ 10 - a 3-20 membered heterocycloaliphatic radical bonded via an aliphatic radical. Preferred aromatic structures are 5-20 membered aryl or heteroaryl radicals, and C1- 10 - a 5-20 membered aryl or heteroaryl radical bonded via an aliphatic radical.

[0047] In general, components a1 having an aliphatic structure are preferred over components a1 having an aromatic structure.

[0048] Examples of aldehydes and their O-acetals include, for example, valeraldehyde, paraldehyde, 3-methoxybenzaldehyde, iso-butyraldehyde, 3,4-dimethoxybenzaldehyde, acetaldehyde diethyl acetal, formaldehyde diethyl acetal, 3-(methylthio)propionaldehyde, 3-(methylthio)butyraldehyde (each of which is an example of component a1 having one carbonyl group (aldehyde group)), and glutaraldehyde (an example of component a1 having two carbonyl groups (two aldehyde groups)). Examples of ketones include, for example, cyclohexanone and methyl-isobutyl ketone.

[0049] As mentioned above, instead of aldehydes, their O-acetals can be used, for example, formaldehyde diethyl acetal (only flammable) can be used instead of highly toxic formaldehyde.

[0050] Preferably, the at least one organic component a1 is selected from aldehydes having at least one aldehyde group, their O-acetals and mixtures thereof, preferably at least one aldehyde and / or its O-acetal is used as a first component a1 having exactly one aldehyde group and optionally further aldehydes and / or their O-acetals are used as a second component a1 having two or more aldehyde groups, preferably exactly two aldehyde groups, the molar amount of the first component a1 preferably exceeding the molar amount of the second component a1, more preferably the molar ratio of the first component a1 to the second component a1 being in the range from 99:1 to 20:1.

[0051] For the preparation of SH-terminated polymers, at least one organic component a2 is used, which contains at least two thiol groups. Of course, it is possible to use more than one component a2. For example, it is possible to employ two components a2 that are different from each other, for example one component a2 with exactly one or two thiol groups and one component a2 with more than two thiol groups. Similarly, for example, two components a2 each with exactly two thiol groups, but different from each other, for example one aliphatic bis(thiol) and one aromatic bis(thiol) can also be used.

[0052] The two sulfur atoms of the at least two thiol groups of component(s) a2 are separated from each other by a linker moiety L having a chain of at least 4, preferably at least 5 and more preferably at least 6, 7 or 8 atoms. Preferably, the two sulfur atoms are separated from each other by a linker moiety L having a chain of at least 4, preferably at least 5, 6, 7 or 8 atoms, said atoms being carbon atoms, optionally one or more of which may be replaced by a heteroatom, preferably selected from O, S and N, or a corresponding heteroatom group, the heteroatom of said heteroatom group being preferably selected from O, S and N.

[0053] The organic component a2 can have an aliphatic or aromatic structure. The aliphatic structure includes both cyclic and alicyclic structures. However, alicyclic structures are preferred. The aliphatic structure may include one or more heteroatoms and / or heteroatomic groups, thus including heteroaliphatic structures. The aromatic structure may include one or more heteroatoms and / or heteroatomic groups, thus including heteroaromatic structures.

[0054] In general, components a2 having an aliphatic structure are preferred over components a2 having an aromatic structure.

[0055] Preferably, at least one of the components a2 used contains a divalent oxygen atom, preferably in its aliphatic portion, more preferably contains an ether segment, even more preferably of the formula -[OR a2 ] n wherein R a2 is a C2-C8 alkylene residue, and the parameter n is an integer ranging from 1 to 200. The presence of oxygen atoms in addition to sulfur atoms is advantageous for the application of SH-terminated polymers in aerospace sealants. DMDO (1,8-dimercapto-3,6-dioxaoctane) is an example of such a component a2.

[0056] Examples of compounds suitable for use as component a2 include bis(thiols) having the aliphatic structure shown below: [ka]

[0057] Particularly preferred is DMDO (1,8-dimercapto-3,6-dioxaoctane). In the case of DMDO, the linker moiety L is a divalent -C2H4-O-C2H4-O-C2H4- group, which connects the two thiol groups of DMDO as a spacer unit. In this case, L is composed of a divalent group, which is a chain having eight atoms, i.e. eight carbon atoms, two of which are replaced by heteroatoms (oxygen atoms).

[0058] Examples of compounds suitable for use as component a2 include tris(thiols) having the aliphatic structure shown below: [ka]

[0059] Further examples of aliphatic tris(thiols) used as component a2 are tris(thiols) prepared by click reaction between at least one bis(thiol), such as DMDO, and a compound as a precursor having three ethylenically unsaturated groups, such as three vinyl groups. An example of such a compound is trivinylcyclohexane (TVCH). The resulting tris(thiols) are prepared according to the scheme provided below, where R is a linker moiety L that connects the two thiol groups of the bis(thiol): [ka]

[0060] Said tris(thiols) can then be used as component a2 of the process of the invention via the dithioacetal route. Tris(thiols) can in particular be used to generate branching in the resulting polymers.

[0061] Examples of compounds suitable for use as component a2 include bis(thiols) and tris(thiols) having the aromatic structures shown below: [ka]

[0062] Further examples of aromatic tris(thiols) used as component a2 are tris(thiols) prepared by reaction of at least one bis(thiol), such as DMDO, with cyanuric chloride, preferably in the presence of a base. The resulting tris(thiols) are prepared according to the scheme provided below, where R is a linker moiety L connecting the two thiol groups of the bis(thiol): [ka]

[0063] Said tris(thiols) can then be used as component a2 of the process of the invention via the dithioacetal route. Tris(thiols) can in particular be used to generate branching in the resulting polymers, as already outlined herein.

[0064] Preferably, aromatic tris(thiol) synthesized via a click reaction between at least one bis(thiol), such as DMDO, and triaryl cyanurate (TAC) as a compound having three ethylenically unsaturated groups, is not used as component a2 in the method of the present invention. Because the polymers prepared by utilizing TAC and the corresponding tris(thiol) component a2 are not always resistant to acid hydrolysis, which is undesirable, at least when the reaction is catalyzed by liquid acid. Thus, preferably, SH termination is prepared without the use of TAC as a starting material, either in its preparation or in the preparation of the components used in the preparation of the polymer, at least when the reaction is catalyzed by liquid acid.

[0065] When present, tris(thiol) is preferably only used in addition to at least one bis(thiol) as component(s) a2. When present, the molar amount of tris(thiol) is preferably lower than the molar amount of bis(thiol), more preferably in the range of 1:99 to 1:20 ((tris)thiol:bis(thiol)).

[0066] The SH-terminated polymer can be a linear or branched polymer.

[0067] Preferably, the SH-terminated polymer is a linear polymer, preferably in which the component(s) a1 has exactly one carbonyl group and the component(s) a2 has exactly two thiol groups, or A branched polymer, which is when (i) two types of components a1 are used, and the first component a1 has exactly one carbonyl group and the second component a1 has two or more carbonyl groups, preferably exactly two carbonyl groups, preferably the molar amount of the first component a1 exceeds the molar amount of the second component a1, more preferably the molar ratio of the first component a1 to the second component a1 is in the range of 99:1 to 20:1, and the component(s) a2 have at least two thiol groups, preferably exactly two thiol groups, or (ii) the component(s) a1 have at least one carbonyl group, preferably exactly one carbonyl group, and at least one of the components a2 used has at least three thiol groups.

[0068] There are therefore two routes in particular for introducing branching into the polymer structure: the first route (i) is via the use of component(s) (a1) bearing more than one carbonyl group, and the second route (ii) is via the use of component(s) (a2) bearing more than two thiol groups.

[0069] Thus, when a carbonyl compound having one C(=O)-group is used as a1, the resulting polymer is substantially linear, which is the case when a component(s) (a2) having exactly two thiol groups is used. When a carbonyl compound having two (or more) C(=O)-groups is alternatively or additionally used as a1, the resulting polymer is branched. In addition to at least one component a1 having exactly one C(=O)-group, the use of a small amount of a carbonyl compound having two (or more) C(=O)-groups as additional component a1 is preferred in order to introduce a certain low degree of branching, which leads to improved sealant properties. Preferably, the amount of additional component a1 having two (or more) C(=O)-groups is in the range from 0.1 to 10.0 mol %, more preferably from 0.2 to 8.0 mol %, even more preferably from 0.3 to 6.0 mol %, still more preferably from 0.4 to 5.0 mol % and in particular from 0.5 to 4.0 mol %, in each case relative to the sum of all components a1 used in the preparation of the SH-terminated polymer.

[0070] Preferably, the SH-terminated polymer contains at least a repeat unit of the general formula (RU1), in particular when the polymer is a linear polymer, [ka] During the ceremony, R 1 and R 2 represent together with the carbon atoms connected to them the remainder of component a1 prior to reaction with component a2, i.e. component a1 without the oxygen atom of the carbonyl group previously present, which was the only carbonyl group present in a1; Preferably, R 1 and R 2 are, independently of each other, H, C1 to C 20 Aliphatic radicals, C1-C 20 Heteroaliphatic radicals, C3-C 20Cycloaliphatic radicals, 3- to 20-membered heterocycloaliphatic radicals, 5- to 20-membered aryl or heteroaryl radicals, C1- 10 C3-C bonded via an aliphatic radical 20 Cycloaliphatic radicals, C1~ 10 - 3-20 membered heterocycloaliphatic radicals bonded via an aliphatic radical, and C1- 10 - 5-20 membered aryl or heteroaryl radicals bonded via an aliphatic radical, more preferably H, C1-C 20 Aliphatic radicals, C1-C 20 Heteroaliphatic radicals, C3-C 20 is selected from the group consisting of cycloaliphatic radicals, 3-20 membered heterocycloaliphatic radicals, and 5-20 membered aryl or heteroaryl radicals, and even more preferably H, C1-C 20 Aliphatic radicals and C1-C 20 Heteroaliphatic radicals are preferably selected from the group consisting of R 1 and R 2 is H. More preferably, at least one of R 1 and R 2 Exactly one of the following must be ≠ H: t1 is an integer ranging from 2 to 300, more preferably from 3 to 200, and The variable A represents the remaining portion of component a2 before the reaction with component a1, i.e., component a2 that does not contain a thiol group, and there were exactly two thiol groups in a2; Preferably, A is a divalent linker moiety L having or consisting of a chain of at least 4 carbon atoms, optionally one or more of which may be replaced by a heteroatom, preferably selected from O, S and N, or a corresponding heteroatom group, the heteroatoms of which are preferably selected from O, S and N, and optionally, when the polymer is a branched polymer, further comprising at least one repeat unit (RU2), [ka] During the ceremony, R 3 and each R 4 represents the remainder of component a1 prior to reaction with component a2, i.e. component a1 without the oxygen atoms of the two carbonyl groups previously present, together with the two carbonyl groups attached thereto, which were the only carbonyl groups present in a1; Preferably, each R 4 are, independently of each other, H, C1 to C 20 Aliphatic radicals, C1-C 20 Heteroaliphatic radicals, C3-C 20 Cycloaliphatic radicals, 3- to 20-membered heterocycloaliphatic radicals, 5- to 20-membered aryl or heteroaryl radicals, C1- 10 C3-C bonded via an aliphatic radical 20 Cycloaliphatic radicals, C1~ 10 - 3-20 membered heterocycloaliphatic radicals bonded via an aliphatic radical, and C1- 10 - 5-20 membered aryl or heteroaryl radicals bonded via an aliphatic radical, more preferably H, C1-C 20 Aliphatic radicals, C1-C 20 Heteroaliphatic radicals, C3-C 20 is selected from the group consisting of cycloaliphatic radicals, 3-20 membered heterocycloaliphatic radicals, and 5-20 membered aryl or heteroaryl radicals, and even more preferably H, C1-C 20 Aliphatic radicals and C1-C 20 selected from the group comprising heteroaliphatic radicals, in particular H, Preferably, R 3 is C1~C 20 Aliphatic radicals, C1-C 20 Heteroaliphatic radicals, C3-C 20 Cycloaliphatic radicals, 3- to 20-membered heterocycloaliphatic radicals, 5- to 20-membered aryl or heteroaryl radicals, C1- 10 C3-C bonded via an aliphatic radical 20Cycloaliphatic radicals, C1~ 10 - 3-20 membered heterocycloaliphatic radicals bonded via an aliphatic radical, and C1- 10 - selected from the group consisting of 5-20 membered aryl or heteroaryl radicals bonded via an aliphatic radical, more preferably C1-C 20 Aliphatic radicals, C1-C 20 Heteroaliphatic radicals, C3-C 20 More preferably still, C1-C4 are selected from the group consisting of cycloaliphatic radicals, 3-20 membered heterocycloaliphatic radicals, and 5-20 membered aryl or heteroaryl radicals. 20 Aliphatic radicals and C1-C 20 is a divalent radical selected from the group consisting of heteroaliphatic radicals, t2 is an integer ranging from 1 to 25, more preferably from 1 to 10, also more preferably from 1 to 5, in particular from 1 to 3; and The variable A represents the remaining portion of component a2 before the reaction with component a1, i.e., component a2 that does not contain a thiol group, and there were exactly two thiol groups in a2; Preferably, A is a divalent linker moiety L having or consisting of a chain of at least 4 carbon atoms, optionally one or more of which may be replaced by a heteroatom, preferably selected from O, S and N, or a corresponding heteroatom group, the heteroatoms of which are preferably selected from O, S and N.

[0071] When the SH-terminated polymer is a linear polymer, it preferably has the general formula (L1) [ka] is a polymer of In the formula, R 1 and R 2 and A and t1 have the meanings given hereinbefore.

[0072] In the following scheme, an exemplary SH-terminated polymer is shown, which is linear and prepared from DMDO as component a2 and an aldehyde having an aliphatic residue R1 derivable from an aldehyde, such as, for example, acetaldehyde or valeraldehyde, having exactly one aldehyde group, as component a1, where t1 is preferably an integer ranging from 2 to 300 and A represents in each case the divalent -C2H4-O-C2H4-O-C2H4- group.

[0073] [ka]

[0074] The acid-catalyzed preparation of an exemplary linear SH-terminated polymer is also shown in the following scheme: The polymer is prepared from DMDO as component a2 and an aldehyde with an aliphatic residue R derivable from an aldehyde such as, for example, acetaldehyde or valeraldehyde with exactly one aldehyde group as component a1.

[0075] [ka]

[0076] In the following scheme, an exemplary SH-terminated polymer is shown, which is branched and prepared from DMDO as component a2 and a first aldehyde having an aliphatic residue R1 derivable from an aldehyde, such as, for example, acetaldehyde or valeraldehyde, having exactly one aldehyde group, as a first component a1, and a second aldehyde having a divalent aliphatic residue R2, such as, for example, one residue derivable from glutaraldehyde, having two aldehyde groups, as a second component a1, where A represents in each case a divalent -C2H4-O-C2H4-O-C2H4- group, and each of t1 to t4t is preferably an integer in the range of 1 to 200, where t1, t2, t3 and t4 may be identical to or different from one another.

[0077] [ka]

[0078] Glutaraldehyde as a dialdehyde in the above example connects two polymer strands via a trimethylene bridge.

[0079] Optionally, in step 1) of the method of the present invention, besides components a1 and a2, a further component a3 may be used, said component a3 being different from both components a1 and a2. For example, a component a3 having at least three ethylenically unsaturated groups, such as at least three vinyl groups, may be used. Examples of this compound include trivinylcyclohexane (TVCH), glyoxal bis(diallyl acetal) (as an example of a "4-arm crosslinker") and triallyl cyanurate (TAC). The additional presence of such a component a3 allows for a one-step (one-pot) thiol-ene and thioacetalization reaction, resulting in an SH-terminated polymer having at least three terminal thiol groups. Below is an exemplary synthesis route including DMDO as component a2, valeraldehyde as component a1 and TAC as component a3.

[0080] [ka]

[0081] Optionally, the process of the invention may comprise a further step 2), in particular when the SH-terminated polymer obtained after the first step 1) is a linear polydithioacetal. Step 2) then represents a step for branching and / or crosslinking the preferably linear SH-terminated polymer obtained after the first step 1), by further reacting the formed polymer having at least two thiol groups with at least one component a4, suitable for introducing branches and different from both components a1 and a2 (and also different from component a3). An example of this component a4 is cyanuric chloride. And such SH-terminated polymer obtained after the second step 2) has at least three terminal thiol groups. For example, an SH-terminated polymer having at least three terminal thiol groups can be prepared by reaction of at least one preferably linear SH-terminated polymer having two terminal SH-groups obtained after step 1) with cyanuric chloride, preferably in the presence of a base. The resulting SH-terminated polymer having at least three terminal thiol groups is prepared, for example, according to the scheme provided below, where R is a moiety linking two thiol groups of the preferably linear SH-terminated polymer obtained after step 1).

[0082] [ka]

[0083] SH-terminated polymer A further subject of the present invention are SH-terminated polymers obtainable by the method according to the invention.

[0084] All preferred embodiments described herein above in relation to the method of the present invention and its preferred embodiments are also preferred embodiments of the SH-terminated polymer of the present invention.

[0085] Ceiling A further subject of the present invention is a two-component (2K) sealing system comprising components (A) and (B) which are separate from one another, component (A) of which comprises at least one SH-terminated polymer according to the invention or at least one SH-terminated polymer obtainable by the process according to the invention, and component (B) of which comprises at least one component b0 suitable for curing the sealant composition by at least partially bringing about a chemical transformation of at least two thiol groups of the SH-terminated polymer. Components (A) and (B) of the sealing system can be stored separately until they are mixed with one another to prepare the sealant composition.

[0086] All preferred embodiments described herein above in relation to the inventive method and the inventive polymer and its preferred embodiments are also preferred embodiments of the inventive sealant system.

[0087] Preferably, the sealing system consists of components (A) and (B).

[0088] 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 preferred, when no organic solvent and / or water is present therein.

[0089] The amount of water present in component (A) is preferably less than 3.0% by weight, more preferably less than 2.0% by weight, even more preferably less than 1.0% by weight and more preferably less than 0.5% by weight, in each case relative to the total weight of component (A).

[0090] When at least one component b1 and / or at least one component b3 and / or at least one component b4 are present in each case as component b0 in component (B), the amount of water present in (B) is preferably less than 3.0% by weight, more preferably less than 2.0% by weight, even more preferably less than 1.0% by weight and more preferably less than 0.5% by weight, in each case relative to the total weight of component (B). Components b1, b3 and b4 are defined below.

[0091] If at least one component b2, such as manganese dioxide, is present as component b0 in component (B), the amount of water present in (B) is preferably less than 8.5% by weight, more preferably less than 7.5% by weight, even more preferably less than 7.0% by weight and more preferably less than 6.0% by weight, in each case relative to the total weight of component (B). Component b2 is defined below.

[0092] If at least one organic solvent is present, in particular if the sealant composition is a sprayable composition, the organic solvent(s) are preferably present in an amount of up to 70% by weight or up to 65% by weight, relative to the total weight of the sealant composition. In this case, the sealant composition preferably comprises an organic solvent(s) fraction of up to 60% by weight, in each case relative to the total weight of the composition. Alternatively, if at least one organic solvent is present, in particular if the sealant composition is not a sprayable composition, the organic solvent(s) are preferably present in an amount of up to 10% by weight, relative to the total weight of the sealant composition. In this case, the sealant composition preferably comprises an organic solvent(s) fraction of up to 7.5% by weight, more preferably up to 5% by weight, in each case relative to the total weight of the composition. Any conventional organic solvent known to those skilled in the art can be used as organic solvent. The term "organic solvent" is known to those skilled in the art, in particular from Council Directive 1999 / 13 / EC of 11 March 1999. Examples of such organic solvents include heterocyclic, aliphatic or aromatic hydrocarbons, mono- or polyhydric alcohols, in particular ethanol and / or propanol, ethers, esters, ketones, xylene, butanol, ethyl glycol and butyl glycol and 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 to one another or different.

[0093] Component (A) of the sealing system may additionally contain, besides the at least one SH-terminated polymer, at least one filler and / or at least one pigment.

[0094] The term "filler" is known to the skilled artisan, for example from DIN 55943 (date: October 2001). A "filler" for the purposes of the present invention is preferably a constituent which is substantially, preferably completely insoluble in the medium which surrounds it, such as each of the components (A) and (B) and the sealant composition, and which is used in particular to adjust the viscosity and thixotropy of the components and the sealant composition, to adjust the specific density of the cured sealant, and / or to increase the mechanical properties of the cured sealant. A "filler" in the sense of the present invention has a refractive index different from a "pigment", the refractive index of a filler being <1.7, whereas the refractive index of a pigment is ≧1.7. Preferably, a "filler" for the purposes of the present invention is an inorganic and / or organic filler. Examples of inorganic fillers are chalk, talcum and aluminum hydroxide. Examples of organic fillers are powders prepared from heat-resistant polymers, such as polyamides, polysulfones, polyphenylene sulfides, polyether ketones and polymeric hollow spheres.

[0095] Preferably, the amount of filler present in component (A) of the sealing system is in the range from 0 to 55.0% by weight, more preferably in the range from 0 to 50.0% by weight, even more preferably in the range from 0 to 45.0% by weight, also more preferably in the range from 0 to 40.0% by weight, still more preferably in the range from 0 to 35.0% by weight or 0 to 30.0% by weight and in particular in the range from 0 to 25.0% by weight, in each case relative to the total weight of component (A).

[0096] Preferably, the amount of any pigment present in component (A) of the sealing system is in the range of 0 to 35.0% by weight, more preferably in the range of 0 to 30.0% by weight, even more preferably in the range of 0 to 25.0% by weight, also more preferably in the range of 0 to 20.0% by weight, and still more preferably in the range of 0 to 15.0% by weight, in each case relative to the total weight of component (A).

[0097] The term "pigment" is known to the skilled person, for example from DIN 55943 (date: October 2001). "Pigment" in the sense of the present invention preferably refers to a component in powder or flake form, which is substantially, preferably completely insoluble in the medium surrounding it, such as each of components (A) and (B) and the sealant composition, and which is a colorant and / or substance that can be used as a pigment due to its magnetic, electric and / or electromagnetic properties. Preferably, "pigments" for the purposes of the present invention are inorganic and / or organic pigments. An example of an inorganic pigment is titanium dioxide.

[0098] Component (A) may additionally contain, and preferably contains, at least one curing catalyst when component (B) of the sealing system contains at least one component b1 containing two or more epoxide groups as component b0. Suitable curing catalysts are amines, in particular tertiary amines, amidines and / or guanidines. Examples include 1,4-diazabicyclo(2.2.2)octane, 1,5-diazabicyclo(4.3.0)non-5-ene (DBN) and 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU).

[0099] Component (A) of the sealing system may optionally contain one or more optional components.

[0100] An optional component may be a flame retardant such as a phosphorus-containing flame retardant, in particular at least one phosphoric acid ester. The flame retardant, if used, is preferably liquid (at 1 bar and 23° C.). If present in component (A), the flame retardant is preferably present in component (A) in an amount of 0.1 to 30.0% by weight, more preferably 1.0 to 25.0% by weight, especially 5.0 to 20.0% by weight, based on the total weight of component (A).

[0101] The optional component may be a light stabilizer, especially a UV stabilizer. Examples include, for example, sterically hindered amines (HALS: hindered amine light stabilizers). In principle, any light stabilizer commercially available from the Tinuvin® series or other manufacturers can be used. Liquid light stabilizers are preferred. If present in component (A), the light stabilizer is preferably present in component (A) in an amount of 0.05 to 5.0% by weight, more preferably 0.1 to 3.5% by weight, in particular 0.1 to 2.0% by weight, based on the total weight of component (A).

[0102] Optional components may be additional adhesion promoters. In particular, organic silanes different from component (a2) may be used. Examples include, for example, (3-aminopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, (3-mercaptopropyl)trimethoxysilane, (3-mercaptopropyl)triethoxysilane, (3-glycidyloxypropyl)trimethoxysilane and / or (3-glycidyloxypropyl)triethoxysilane, vinyltrimethoxysilane. Additionally or alternatively, other adhesion promoters may be used, for example, titanates and / or zirconates, such as titanium acetylacetonate (TAA) and / or Ti-n-butanolate (TnBt) and / or isopropyl titanate. The additional adhesion promoter, if present in component (A), is preferably present in component (A) in an amount of 0.05 to 5.0 mass %, more preferably 0.1 to 3.5 mass %, especially 0.1 to 2.0 mass %, based on the total mass of component (A).

[0103] The optional components may be additives selected from the group consisting of antifoams, 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, and mixtures of these additives. The at least one additive, if present in component (A), is preferably present in component (A) in an amount of 0.05 to 40.0% by weight, more preferably 0.1 to 30.0% by weight, in particular 0.1 to 20.0% by weight, relative to the total weight of component (A). Specifically, if at least one antifoam is present, its amount is preferably in the range of 0.1 to 2.5% by weight, relative to the total weight of component (A). Specifically, if at least one reactive diluent is present, its amount is preferably in the range of 0.1 to 20.0% by weight, relative to the total weight of component (A). Specifically, when at least one rheological additive is present, its amount is preferably in the range of 0.1 to 5.0% by weight, based on the total weight of component (A). Specifically, when at least one plasticizer is present, its amount is preferably in the range of 0.1 to 2.5% by weight, based on the total weight of component (A). Specifically, when at least one viscosity reducer is present, its amount is preferably in the range of 0.1 to 20.0% by weight, based on the total weight of component (A).

[0104] Component (B) of the sealing system comprises at least one component b0, which is suitable for curing the sealant composition by at least partially inducing a chemical transformation of at least two thiol groups of the SH-terminated polymer. In other words, component b0 or a part thereof is capable of chemically reacting with the thiol groups of said polymer. Component b0 thus represents a curing agent. The resulting chemical transformation may apply to all thiol groups of the polymer or to only some of the thiol groups of the polymer. However, preferably, the chemical transformation is not only partially but also substantially induced to all thiol groups of the SH-terminated polymer.

[0105] Preferably, the at least one component b0 is selected from the group consisting of components comprising two or more epoxide groups (component b1), components which are metal oxides and / or metal peroxides, in particular manganese dioxide (component b2), components which are organic peroxides (component b3), components which comprise two or more vinyl groups (component b4), and mixtures thereof, more preferably from the group consisting of components comprising two or more epoxide groups (component b1), components which are metal oxides and / or metal peroxides, in particular manganese dioxide (component b2), and mixtures thereof, in particular representing as component b1 at least one component comprising two or more epoxide groups or as component b2 at least one metal oxide and / or metal peroxide, in particular manganese dioxide.

[0106] Preferably, component b0 is present in component (B) of the sealing system in an amount ranging from 30 to 100% by weight, based on the total weight of component (B).

[0107] Component b1 contains two or more epoxide groups. Preferably, the epoxide groups are present in b1 as terminal groups. Component b1 can be monomeric, oligomeric or polymeric. Preferably, b1 is aliphatic and / or aromatic.

[0108] Preferably, component b1 is present in component (B) of the sealing system in an amount ranging from 50 to 100% by weight, based on the total weight of component (B).

[0109] Preferably, b1 has an epoxide functionality of from 2.0 to 5.0, more preferably from 2.0 to 3.0, especially from 2.0 to 2.8.

[0110] Component b1 is in particular selected from diglycidyl ethers of bisphenol A, diglycidyl ethers of bisphenol F, and aliphatic polyglycols and / or hydantoin epoxy derivatives. Epoxy-terminated polythioethers or polythioether sulfides and / or epoxidized polysulfides may also be used. Particularly preferred is at least one epoxy novolac resin (epoxidized phenol formaldehyde resin), preferably a crosslinked epoxy novolac resin. It is also possible to use more than component (b1), for example bisphenol A / F epoxy resins or bisphenol F novolac resins, based on some of the above classes. Component (B) may additionally contain a diluent, for example to adjust the viscosity and flexibility. Examples of diluents include 1,4-butanediol diglycidyl ether, 2-ethylhexyl-glycidyl ether, 1,1,1-trimethylolpropane triglycidyl ether and 1,6-hexanediol diglycidyl ether.

[0111] Preferably, b1 is at least one epoxide-terminated polysulfide polymer and / or polythioether polymer and / or polythioether sulfide polymer having no terminal mercapto groups and functioning as a hardener by virtue of its two terminal epoxide groups, said polymer being preferably present as a liquid or highly viscous polymer, in particular with an epoxy equivalent in the range of 200 to 800 g / eq.

[0112] Preferably, the epoxy(epoxide) equivalent of b1 is in the range of 120 to 800 g / eq, particularly preferably in the range of 140 to 700 g / eq, and most preferably in the range of 170 to 400 g / eq.

[0113] Most particularly preferred are components b1 based on bisphenol A epoxy resins having an epoxy equivalent in the range from 170 to 200 g / eq, based on bisphenol F resins having an epoxy equivalent in the range from 150 to 180 g / eq and based on epoxy novolac resins having an epoxy equivalent in the range from 160 to 220 g / eq.

[0114] Suitable commercially available examples include, for example, bisphenol F epoxy resins such as DEN 354 (Olin Epoxy), bisphenol A resins such as DER 336, DER 331 (Olin Epoxy), bisphenol A / F epoxy resins such as DER 351, DER 324, DER 335 (Olin Epoxy), epoxy novolac resins such as DEN 431, DEN 438, DEN 439 (Olin Epoxy), epoxy-terminated prepolymers based on polysulfides and / or polythioethers such as Thioplast EPS 25 (Akzo Nobel), epoxy-terminated reactive diluents based on alcohols / glycols such as 1,4-butanediol diglycidyl ether (DER 731; Olin Epoxy), and 1,6-hexanediol diglycidyl ether (DER 734; Olin Epoxy).

[0115] Preferably, the molar ratio of any component b1 to any SH-terminated polymer present is in the range of 0.90:1 to 2:1.

[0116] Component b2 is at least one metal oxide and / or metal peroxide, in particular manganese dioxide. Manganese dioxide means manganese(IV) oxide. Another suitable component b2 is calcium peroxide.

[0117] Preferably, component b2 is present in component (B) of the sealing system in an amount ranging from 30 to 90% by weight, based on the total weight of component (B).

[0118] Component b3 is at least one organic peroxide. Examples of suitable organic peroxides are organic hydroperoxides, such as cumenyl hydroperoxide.

[0119] Preferably, component b3 is present in component (B) of the sealing system in an amount ranging from 30 to 100% by weight, based on the total weight of component (B).

[0120] Component b4 contains two or more vinyl groups. Preferably, the vinyl groups are present in b4 as end groups. Component b4 can be monomeric, oligomeric or polymeric, and is preferably monomeric. Preferably, b4 is aliphatic and / or aromatic. Examples of component b4 are divinyl ethers, such as diethylene glycol divinyl ether, triethylene glycol divinyl ether and butanediol divinyl ether.

[0121] Preferably, component b4 is present in component (B) of the sealing system in an amount ranging from 30 to 100% by weight, based on the total weight of component (B).

[0122] When component b4 is used as component (b) of component (B), it is preferably present in combination with at least one radical generator. Examples of suitable radical generators are 1-hydroxycyclohexyl phenyl ketone and 2-hydroxy-2-methyl-1-phenylpropan-1-one.

[0123] Component (B) of the sealing system may contain one or more optional components b5. Component b5 may be an additive selected from the group consisting of reactive diluents, such as bis-oxazolidines and / or aldimines, and plasticizers, such as phthalates. In particular, at least one plasticizer component b5 is present in component (B) of the sealing system when it comprises at least one component b2, in particular manganese dioxide.

[0124] Specifically, when at least one reactive diluent is present, its amount is preferably in the range of 0.1 to 20.0% by weight, based on the total weight of component (B). Specifically, when at least one plasticizer is present, its amount is preferably in the range of 10.0 to 70.0% by weight, based on the total weight of component (B).

[0125] Component (B) may additionally contain, and preferably does contain, at least one curing catalyst b6.

[0126] As outlined above, when component (B) of the sealing system comprises, as component b0, at least one component b1 containing two or more epoxide groups, at least one curing catalyst, if present, is preferably present as a component in component (A) and not in component B. Suitable curing catalysts in this case are amines, in particular tertiary amines, amidines and / or guanidines. Examples include 1,4-diazabicyclo(2.2.2)octane, 1,5-diazabicyclo(4.3.0)non-5-ene (DBN) and 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU).

[0127] If component (B) of the sealing system comprises at least one component b2 as component b0, then at least one curing catalyst b6 is preferably present in component (B). Suitable curing catalysts in this case are, for example, tetrabenzyl thiuram disulfide, diphenyl guanidine and / or zinc bis(diethyldithiocarbamate).

[0128] If component (B) of the sealing system comprises at least one component b3 as component b0, then at least one curing catalyst b6 is preferably present in component (B). A suitable curing catalyst in this case is, for example, zinc diethylcarbamate.

[0129] If component (B) of the sealing system comprises at least one component b4 as component b0, then 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 acetophenone, benzoin ether and / or benzoyl oxime. Curing is preferably carried out via UV light.

[0130] Component (B) may additionally contain at least one flame retardant b7. Component b7 may be a phosphorus-containing flame retardant, in particular at least one phosphoric acid ester. The flame retardant, if used, is preferably liquid (at 1 bar and 23° C.). If present in component (A), the flame retardant is preferably present in an amount of 5.0 to 65.0% by weight, more preferably 25.0 to 65.0% by weight, in particular 40.0 to 65.0% by weight, in each case relative to the total weight of component (B).

[0131] Sealant Composition A further subject of the invention is a sealant composition obtainable by mixing together components (A) and (B) of the sealing system according to the invention.

[0132] The resulting sealant composition may, but need not be, sprayable.

[0133] Preferably, the sealant composition is obtainable by mixing components (A) and (B) in a mass ratio (component (A) / component (B)) in the range of 100:1 to 1:1. More preferably, the mixing is carried out in a mass ratio in the range of 100:1 to 1.1:1, even more preferably in a mass ratio in the range of 100:1 to 2:1, in particular in a mass ratio in the range of 100:1 to 3:1, and most preferably in a mass ratio in the range of 20:1 to 4:1.

[0134] All preferred embodiments described hereinabove in connection with the inventive method, the inventive polymer and the inventive sealing system and their preferred embodiments are also preferred embodiments of the inventive sealant composition.

[0135] How to seal A further subject of the present invention is a method for sealing an optionally precoated substrate, comprising at least the step of applying in portions to a surface of the optionally precoated substrate a sealant composition according to the invention, said optionally precoated substrate being preferably a substrate that can be used in the aerospace and / or aircraft industry.

[0136] All preferred embodiments described herein above in connection with the inventive method, the inventive polymer and the inventive sealing system and sealant composition, and preferred embodiments thereof, are also preferred embodiments of the inventive sealing method.

[0137] The substrate may be optionally precoated. For example, a primer film may already be formed at least partially on its surface. The substrate used may additionally or alternatively be subjected to a pretreatment that leads to another precoating. For example, an epoxy-based coating may be applied, so that the substrate used has at least one preferably cured coating layer, such as an epoxy-based coating layer.

[0138] Suitable substrates are metal substrates, but plastic substrates, such as polymeric substrates and / or fiber-based composites, can also be used. Preferred substrates are substrates available in the aerospace and / or aircraft industry, such as fuel tanks. Preferably, the sealed surface in this case is the inner surface of the fuel tank.

[0139] Suitable metal substrates for use according to the present invention are any substrates commonly used and known to those skilled in the art. The substrates for use according to the present invention are preferably metal substrates, including steel substrates and titanium substrates. However, most preferred are aluminum and / or aluminum alloy substrates.

[0140] Preferably, when the substrate is a plastic substrate, use thermoplastic polymer.Suitable polymers are poly(meth)acrylate, including polymethyl(meth)acrylate, poly(meth)acrylate, polyethylene terephthalate, polybutylene terephthalate, polyvinylidene fluoride, polyvinyl chloride, polyester, including polycarbonate and polyvinyl acetate, polyamide, polyolefin, such as polyethylene, polypropylene, polystyrene, and also polybutadiene, polyacrylonitrile, polyacetal, polyacrylonitrile-ethylene-propylene-diene-styrene copolymer (A-EPDM), ASA (acrylonitrile-styrene-acrylic acid ester copolymer) and ABS (acrylonitrile-butadiene-styrene copolymer), polyetherimide, phenolic resin, urea resin, melamine resin, alkyd resin, epoxy resin, polyurethane, including TPU, polyetherketone, polyphenylene sulfide, polyether, polyvinyl alcohol, and mixtures thereof. Polycarbonates and poly(meth)acrylates are particularly preferred.

[0141] However, as outlined above, fibre-based composites, such as carbon fibre composites, may also be used as the substrate.

[0142] Preferably, the sealing method of the present invention further comprises a curing step, i.e. curing at least the applied sealant composition at ambient temperature (18-23° C.) or at an elevated temperature, such as 80° C., for 0.5 hours to 14 days. Preferably, curing means chemical curing, e.g. chemical crosslinking, at ambient or elevated temperature. When at least one component (b1) or (b4) is used as component (b), curing may additionally or alternatively be induced via UV light.

[0143] Preferably, the sealant composition is applied in a dry layer thickness in the range of from 15 μm to 20 mm, more preferably from 50 μm to 15 mm, especially from 0.5 to 10 mm.

[0144] Encapsulated Substrate A further subject of the invention are encapsulated substrates obtainable by the process according to the invention.

[0145] All preferred embodiments described herein with respect to the inventive method, the inventive polymer, the inventive sealing system and sealant composition, and the inventive sealing method and preferred embodiments thereof are preferred embodiments of the inventive sealed substrate.

[0146] Method of use according to the present invention A further subject of the present invention is the use of the sealing system of the present invention or the sealant composition of the present invention for providing a seal at least partially to the surface of an optionally precoated substrate, which can preferably be used in the aerospace and / or aircraft industry.

[0147] All preferred embodiments described herein above in connection with the inventive method, the inventive polymer and the inventive sealing system and sealant composition, and the inventive sealing method and the inventive sealed substrate, and preferred embodiments thereof, are also preferred embodiments of the inventive use method described above.

[0148] method 1.Hardness Shore A hardness was measured according to AITM1-0033, ISO48-4, and ISO868.

[0149] 2. Tensile strength and elongation at break Tensile strength and elongation were measured according to ISO37, Type 2.

[0150] 3. Immersion test Immersion tests were performed according to AIMS04-05-001, AIMS04-05-007 at either 60°C (H2O) or 100°C (JetA1).

[0151] 4.DMTA Measurements DMTA (Dynamic Mechanical Thermal Analysis) measurements were performed using a GABO Qualimeter and the software Eplexor 8.375. The following measurement parameters were applied: measurement frequency: 10 Hz, heating rate: 2 K / min, temperature range: -50 / -50 °C to +30 °C. Samples with a thickness of 3 mm, width of 10 mm and length of 35-40 mm were tested in tensile mode. Prior to the measurements, the samples were cured at 23 °C and 50% rF for 14 days. The Tg peak is defined as the temperature at which tan δ has its maximum. The Tg-onset is defined as the intersection temperature of the extrapolated tangent drawn from the points on the curve before and after the drop in the storage modulus E'.

[0152] 5. Number average molecular weight (M n ) Number average molecular weights were determined by GPC (gel permeation chromatography) against polystyrene standards, using THF (tetrahydrofuran) as the mobile phase or calculated relative to SH content.

[0153] 6.SH content The SH content in mass % was determined by titration. Terminal SH groups are oxidized by iodine to disulfide groups. The SH content can then be calculated from the iodine consumption. EXAMPLES

[0154] The following examples further illustrate the invention but should not be construed as limiting its scope. "pbw" means parts by weight. Unless otherwise defined, "parts" means parts by weight.

[0155] 1. Synthesis of SH-terminated polydithioacetals 1.1 Examples 1a, 1b and 1d (inventive examples) and 1c and 1e (comparative examples) Example 1a: Synthesis of linear polydithioacetals using liquid acid catalysts In a 500 ml three-neck flask equipped with a dropping funnel, a condenser and a gas control valve (for argon introduction), 75.33 g (0.413 mol) of 2,2'-(ethylenedioxy)diethanethiol (DMDO), 80 mL of 1,4-dioxane and 6.1 g of 37% aqueous HCl were mixed and stirred under argon. The mixture was cooled to 0° C. in an ice bath. Valeraldehyde (32.14 g, 0.362 mol) was slowly added dropwise to the solution with stirring. After complete addition, the dropping funnel was washed with 20 mL of 1,4-dioxane. The mixture was further stirred at 0° C. for 2 h. The mixture was then heated to 85° C. and stirred under argon for 10 h. The reaction mixture was then cooled to room temperature and evaporated in a vacuum at 85° C. / 12 mbar. 101.07 g of a viscous oil was obtained, which had an SH of 3.6% by weight (calculated: 3.4% by weight) and n The calculated value was approximately 1830 g / mol.

[0156] Examples 1b, 1d (inventive examples) and 1c and 1e (comparative examples) Example 1a was repeated, except that valeraldehyde was replaced by equimolar amounts of paraldehyde (acetaldehyde trimer; 3 moles of acetaldehyde are equivalent to 1 mole of paraldehyde, so 1 / 3 the amount of paraldehyde must be used as the amount of acetaldehyde; Example 1b), 3-methoxybenzaldehyde (Example 1c), and iso-butyraldehyde (Example 1d) and 3,4-dimethoxybenzaldehyde (Example 1e). In the case of Example 1c, the SH was 2.1% by weight, and the M n An oily product was obtained with a calculated value of about 3140 g / mol. In the case of example 1e, a glassy polymeric product was obtained, which could not be further processed.

[0157] 1.2 Examples 2a and 2b (inventive examples) Example 2a: Synthesis of linear polydithioacetals using liquid acid catalysts In a 250 ml three-neck flask equipped with a dropping funnel, a condenser and a gas control valve (for argon introduction), 20.30 g (0.111 mol) of 2,2'-(ethylenedioxy)diethanethiol (DMDO), 50 ml of 1,4-dioxane, 4 ml of H2O and 2.27 g of 37% aqueous HCl were mixed and stirred under argon. The mixture was cooled to 0°C in an ice bath. Acetaldehyde diethyl acetal (11.51 g, 0.0974 mol) was slowly added dropwise to the solution with stirring. After complete addition, the dropping funnel was washed with 15 ml of 1,4-dioxane. The mixture was further stirred at 0°C for 2 h. The mixture was then heated to 85°C and stirred under argon for 10 h. The reaction mixture was then cooled to room temperature and evaporated in a vacuum at 85°C / 12 mbar. 22.94 g of a viscous oil was obtained, which had a SH of 3.4% by weight (calculated value: 4.01% by weight) and n The calculated value was approximately 1940 g / mol.

[0158] Example 2b Example 2a was repeated except that the acetaldehyde diethyl acetal was replaced with an equimolar amount of formaldehyde diethyl acetal (after storage at room temperature the product went from liquid to waxy).

[0159] 1.3 Examples 3a to 3e (inventive examples) Example 3a: Synthesis of branched polydithioacetals using liquid acid catalysts In a 500 ml three-neck flask equipped with a dropping funnel, a condenser and a gas control valve (for argon introduction), 60.00 g (0.329 mol) of 2,2'-(ethylenedioxy)diethanethiol (DMDO), 180 mL of 1,4-dioxane and 1.37 g of 50% by weight aqueous glutaraldehyde solution were mixed and stirred under argon. The mixture was cooled to 0°C in an ice bath. A mixture of 7 g of 37% aqueous HCl and 12 g of H2O was slowly dripped into the solution with stirring. The mixture was further stirred at 0°C for 2 hours. Acetaldehyde diethyl acetal (35.00 g, 0.296 mol) was slowly dripped into the solution with stirring. After complete addition, the dropping funnel was washed with 20 mL of 1,4-dioxane. The mixture was further stirred at 0°C for 2 hours. The mixture was then heated to 85°C and stirred under argon for 10 hours. The reaction mixture was then cooled to room temperature and evaporated in vacuum at 85° C. / 12 mbar: 68.24 g of a viscous oil was obtained, which had a SH of 1.8% by weight (calculated: 1.85% by weight).

[0160] Examples 3b, 3c, 3d and 3e Example 3a was repeated, except that a larger amount of 50% by weight aqueous glutaraldehyde solution was used, i.e., an amount equivalent to 2.5 mol% glutaraldehyde (Example 3b) or 2.9 mol% (Example 3c) or 3.2 mol% (Example 3d; in this case, a solid product was obtained). More specifically, for Example 3b, 60 g DMDO (0.329 mol), 1.60 g (0.008 mol) of 50% by weight aqueous glutaraldehyde solution, 34.74 g (0.294 mol) of acetaldehyde diethyl acetal, 200 mL of 1,4-dioxane, 7 g of 37% aqueous HCl solution, and 12 g of HO were used. For example, 3c used 60 g DMDO (0.329 mol), 1.80 g (0.009 mol) of 50% by weight glutaraldehyde aqueous solution, 34.51 g (0.292 mol) of acetaldehyde diethyl acetal, 200 mL of 1,4-dioxane, 7 g of 37% HCl aqueous solution, and 12 g of H2O. For example, 3d used 60 g DMDO (0.329 mol), 2.06 g (0.010 mol) of 50% by weight glutaraldehyde aqueous solution, 34.20 g (0.289 mol) of acetaldehyde diethyl acetal, 200 mL of 1,4-dioxane, 10.5 g of 37% HCl aqueous solution, and 18 g of H2O. Example 3a was repeated (Example 3e), except that no solvent (1,4-dioxane) was used.

[0161] 1.4 Examples 4a to 4k (invention examples) Example 4a: Synthesis of linear polydithioacetals using solid acid catalysts 9.87g DMDO (54.1mmol) and 0.49g Montmorillonite K10 were charged into a 100ml three-neck flask. The reaction mixture was stirred at room temperature under nitrogen flush for 20 minutes. Then 4g valeraldehyde (46.4mmol) was added dropwise over 45 minutes. After complete addition of valeraldehyde, the reaction mixture was heated to 95°C and then held at 95°C for 6 hours or held for 3 hours and held at 115°C for another 3 hours. The reaction mixture was then cooled to room temperature and the catalyst was filtered off via vacuum filtration. To obtain a quantitative yield, the catalyst was washed with ethyl acetate after the filtration step and the product of Example 4a was recovered after evaporating the ethyl acetate using a rotary evaporator.

[0162] Examples 4b to 4k Example 4a was repeated, except that 0.98 g (Example 4b), 1.96 g (Example 4c), 0.29 g (Example 4d) or 0.098 g (Example 4e) of Montmorillonite K10 was used. Example 4a was repeated, except that 1.96 g (Example 4f) or 0.49 g (Example 4g) of Amberlyst® 15, or 1.96 g (Example 4h) or 0.49 g (Example 4i) of Dowex® 50W X8 was used for Montmorillonite K10, and in each case 10 mL of 1,4-dioxane was used as solvent. Example 4a was repeated, except that 11.64 g of DMDO, 3.95 g of iso-butyraldehyde, and 0.57 g of Montmorillonite K10 were used. The aldehyde was added at room temperature in 45 minutes, and then the mixture was heated at 95° C. for 6 hours (Example 4j). Example 4a was repeated, except that 11.47 g DMDO, 4.0 g butyraldehyde, and 0.57 g Montmorillonite K10 were used. The aldehyde was added at room temperature in 45 minutes, and then the mixture was heated at 95° C. for 6 hours (Example 4k).

[0163] 1.5 Examples 5a to 5f (inventive examples) Example 5a: Synthesis of branched polydithioacetals using solid acid catalysts 9.87g DMDO (54.1mmol), 0.24g glutaraldehyde (50% solution in H2O) and 0.49g montmorillonite K10 were charged into a 100ml three-neck flask. The reaction mixture was stirred at room temperature under nitrogen flush for 20 minutes. Then 4g valeraldehyde (46.4mmol) was added dropwise over 45 minutes. After complete addition of valeraldehyde, the reaction mixture was heated to 95°C and held for 3 hours, and then heated to 115°C and held for another 3 hours. The reaction mixture was then cooled to room temperature and the catalyst was filtered off via vacuum filtration. To obtain a quantitative yield, the catalyst was washed with ethyl acetate after the filtration step, and the product of Example 4a was recovered after evaporating the ethyl acetate using a rotary evaporator.

[0164] Examples 5b to 5g Example 5a was repeated, except that 0.98g (Example 5b), 1.96g (Example 5c) or 0.29g (Example 5d) of Montmorillonite K10 was used. Example 5a was repeated, except that 0.29g of glutaraldehyde (50% solution in H2O) was used (Example 5e). Example 5e was repeated, except that 10mL of 1,4-dioxane was used as the solvent (Example 5f). Example 5a was repeated, except that 4.0g of valeraldehyde and 0.18g of terephthalaldehyde were used instead of glutaraldehyde (50% solution in H2O) (Example 5g).

[0165] 1.6 Examples 6a and 6b (inventive examples) Example 6a: In a 250 ml three-neck flask equipped with a dropping funnel, a condenser and a gas regulator (for argon introduction), 21.15 g (0.116 mol) of 2,2'-(ethylenedioxy)diethanethiol (DMDO), 40 ml of 1,4-dioxane and 1.14 g of 37% aqueous HCl were mixed and stirred under argon. The mixture was cooled to 0° C. in an ice bath. Valeraldehyde (8.74 g, 0.0984 mol) was slowly added dropwise to the solution with stirring. After complete addition, the dropping funnel was washed with 20 ml of 1,4-dioxane. The mixture was further stirred at 0° C. for 2 hours. The mixture was then heated to 85° C. and stirred under argon for 10 hours. The reaction mixture was then cooled to room temperature and evaporated in a vacuum at 85° C. / 12 mbar. 28.2 g of a viscous oil was obtained, which had a SH of 4.1% by weight (calculated: 3.4% by weight) and n The calculated value was approximately 1610 g / mol.

[0166] Example 6b: In a 100 ml three-neck flask equipped with a dropping funnel, a condenser and a gas regulator (for argon introduction), 10.57 g (0.0058 mol) of 2,2'-(ethylenedioxy)diethanethiol (DMDO), 20 mL of 1,4-dioxane and 0.57 g of 37% aqueous HCl were mixed and stirred under argon. The mixture was cooled to 0° C. in an ice bath. Valeraldehyde (4.51 g, 0.0508 mol) was slowly added dropwise to the solution with stirring. After complete addition, the dropping funnel was washed with 10 mL of 1,4-dioxane. The mixture was further stirred at 0° C. for 2 hours. The mixture was then heated to 85° C. and stirred under argon for 10 hours. The reaction mixture was then cooled to room temperature and evaporated in a vacuum at 85° C. / 12 mbar. 14.12 g of a viscous oil was obtained, which had a SH of 3.4% by weight (calculated: 2.5% by weight) and n The calculated value was approximately 1940 g / mol.

[0167] 2. Preparation of the sealant composition 2.1 A number of exemplary sealant compositions were prepared. Each sealant composition was prepared by mixing together two components (A) and (B) of a two-component sealing system. Sealant Examples S-1a, S-3a, S-3b, S-3c, S-2a, S-2b, S-1d, S2a1d, S-6a, and S-6b are examples according to the present invention. Sealant Example S1c is a comparative example.

[0168] 2.2 Sealant Example S-1a The composition of component (A) of sealing system S-1a is shown in Table 1. Component (A) was prepared by mixing together the components shown in Table 1 in the order shown in Table 1.

[0169] [Table 1]

[0170] Dabco 33LV was used as the amine catalyst, and aluminum hydroxide was used as the filler.

[0171] 92.2g of component "A" was mixed with hardener component "B" (consisting of 12.48g of a commercially available epoxy resin (Novolak DEN431)).

[0172] 2.3 Sealant Example S-3a The composition of component (A) of sealing system S-3a is shown in Table 2. Component (A) was prepared by mixing together the components shown in Table 2 in the order shown in Table 2.

[0173] [Table 2]

[0174] Dabco 33LV was used as the amine catalyst, and aluminum hydroxide was used as the filler.

[0175] 85.32g of component "A" was mixed with hardener component "B" (consisting of 5.95g of a commercially available epoxy resin (Novolak DEN431)).

[0176] 2.4 Sealant Example S-3b The composition of component (A) of sealing system S-3b is shown in Table 3. Component (A) was prepared by mixing together the components shown in Table 3 in the order shown in Table 3.

[0177] [Table 3]

[0178] Dabco 33LV was used as the amine catalyst, and aluminum hydroxide was used as the filler.

[0179] 79.98g of component "A" was mixed with hardener component "B" (consisting of 5.57g of a commercially available epoxy resin (Novolak DEN431)).

[0180] 2.5 Sealant Example S-3c The composition of component (A) of sealing system S-3c is shown in Table 4. Component (A) was prepared by mixing together the components shown in Table 4 in the order shown in Table 4.

[0181] [Table 4]

[0182] Dabco 33LV was used as the amine catalyst, and aluminum hydroxide was used as the filler.

[0183] 85.62g of component "A" was mixed with hardener component "B" (consisting of 6.28g of a commercially available epoxy resin (Novolak DEN431)).

[0184] 2.6 Sealant Example S-2a The composition of component (A) of sealing system S-2a is shown in Table 5. Component (A) was prepared by mixing together the components shown in Table 5 in the order shown in Table 5.

[0185] [Table 5]

[0186] DBU was used as the amine catalyst.

[0187] 6.83g of component "A" was mixed with hardener component "B" (consisting of 1.22g of a commercially available epoxy resin (Novolak DEN431)).

[0188] 2.7 Sealant Example S-2b The composition of component (A) of sealing system S-2b is shown in Table 6. Component (A) was prepared by mixing together the components shown in Table 6 in the order shown in Table 6.

[0189] [Table 6]

[0190] DBU was used as the amine catalyst.

[0191] 7.16g of component "A" was mixed with hardener component "B" (consisting of 1.28g of a commercially available epoxy resin (Novolak DEN431)).

[0192] 2.8 Sealant Example S-1c The composition of component (A) of sealing system S-1c is shown in Table 7. Component (A) was prepared by mixing together the components shown in Table 7 in the order shown in Table 7.

[0193] [Table 7]

[0194] DBU was used as the amine catalyst.

[0195] 9.38 g of component "A" was mixed with hardener component "B" (consisting of 1.03 g of a commercially available epoxy resin (Novolak DEN431)).

[0196] 2.9 Sealant Example S-1d The composition of component (A) of sealing system S-1d is shown in Table 8. Component (A) was prepared by mixing together the components shown in Table 8 in the order shown in Table 8.

[0197] [Table 8]

[0198] DBU was used as the amine catalyst.

[0199] 8.07g of component "A" was mixed with hardener component "B" (consisting of 1.36g of a commercially available epoxy resin (Novolak DEN431)).

[0200] 2.10 Sealant Example S-2a1d The composition of component (A) of sealing system S-2a1d is shown in Table 9. Component (A) was prepared by mixing together the components shown in Table 9 in the order shown in Table 9.

[0201] [Table 9]

[0202] DBU was used as the amine catalyst.

[0203] 6.70 g of component "A" was mixed with hardener component "B" (consisting of 1.25 g of a commercially available epoxy resin (Novolak DEN431)).

[0204] 2.11 Sealant Examples S-6a and S-6b The composition of component (A) of sealing system S-6a is shown in Table 10. Component (A) was prepared by mixing together the components shown in Table 10 in the order shown in Table 10.

[0205] [Table 10]

[0206] DBU was used as the amine catalyst.

[0207] 7.43g of component "A" was mixed with hardener component "B" (consisting of 1.6g of a commercially available epoxy resin (Novolak DEN431)).

[0208] The composition of component (A) of sealing system S-6b is shown in Table 11. Component (A) was prepared by mixing together the components shown in Table 11 in the order shown in Table 11.

[0209] [Table 11]

[0210] DBU was used as the amine catalyst.

[0211] 6.29g of component "A" was mixed with hardener component "B" (consisting of 1.12g of a commercially available epoxy resin (Novolak DEN431)).

[0212] 2.12 Each of the aforementioned components "A" was mixed with component "B" using a speed mixer, and the resulting mixture was then poured into a Teflon mold, and the resulting sealant composition was allowed to cure in the mold for 14 days at room temperature (23°C) and 50% relative humidity. The resulting test specimens were then subjected to a number of tests as outlined below.

[0213] 3. Investigating the properties of the encapsulated substrate 3.1 Some properties of some of the encapsulated and cured substrates were also investigated. Measurements were performed according to the methods disclosed in the "Methods" section. The results are shown in Table 12.

[0214] [Table 12]

[0215] 3.2 Some further properties of the encapsulated and cured substrates were investigated. Measurements were performed according to the methods disclosed in the "Methods" section. The results are shown in Table 13.

[0216] [Table 13]

[0217] A preliminary mass loss test was conducted to understand the jet fuel resistance (JetA1) of the prepared sealants. Samples with a thickness of 3 mm, width of 10 mm, and length of 60 mm were tested. Prior to the measurements, the samples were cured at 23°C and 50% rF for 14 days. To evaluate the jet fuel resistance, the mass of the listed samples was measured on an analytical balance. The samples were then stored in JetA1 at 100°C for 7 days. After immersion, the mass of the samples was measured again on an analytical balance. The mass loss (comparing the mass before and after immersion in jet fuel) gave an idea about the jet fuel resistance of the prepared samples.

[0218] As is evident from Tables 12 and 13, each of the sealants of the present invention prepared from component a1 having an aliphatic structure exhibits excellent low T values ​​measured by DMTA in the range of -29°C to -44°C. g In contrast, the comparative sealant S-1c showed a significantly higher T g The onset values ​​were not suitable for use as a sealant, particularly in the aerospace industry.

Claims

1. 1. A polycondensation method for preparing an SH-terminated polymer having at least two terminal thiol groups and containing a sulfur-carbon-sulfur bond in the polymer backbone, comprising: The process comprises, as step 1), a step of preparing said SH-terminated polymer by reacting with each other at least two components, namely at least one organic component a1 having an aliphatic structure and containing at least one carbonyl group and at least one organic component a2 different from component a1 and containing at least two thiol groups, component a1 is selected from aldehydes having at least one aldehyde group, O-acetals of these aldehydes, ketones having at least one keto group, and mixtures thereof; the two sulfur atoms of the at least two thiol groups of component a2 are separated from each other by a linker moiety L having a chain of at least 4 atoms; and The molar ratio r of components a1 and a2 to each other is in the range of 0.82 to 0.99; method.

2. 2. The process according to claim 1, wherein the molar ratio r of component a1 to component a2 is in the range of 0.85 to 0.99, more preferably 0.86 to 0.99, even more preferably 0.87 to 0.99, and more preferably >0.87 to 0.

99.

3. The number average molecular weight (M ｎ 3. The method according to claim 1 or 2, wherein the molecular weight of the polymer is in the range of 500 to 15000 g / mol, more preferably 600 to 10000 g / mol, even more preferably 700 to 7500 g / mol, still more preferably 800 to 5000 g / mol, also more preferably 900 to 4500 g / mol, and most preferably 1000 to 4000 g / mol.

4. 3. The method according to claim 1 or 2, wherein the SH-terminated polymer has an SH content of 1.0% to 10.0% by weight, preferably 1.1 to 9.5% by weight, more preferably 1.2 to 9.0% by weight, also more preferably 1.3 to 8.5% by weight, still more preferably 1.4 to 8.0% by weight, also more preferably 1.5 to 7.5% by weight, even more preferably 1.5 to 7.0% by weight, still more preferably 1.5 to 6.5% by weight, and also more preferably 1.5 to 6.0% by weight, these weight percentages being in each case relative to the total weight of the SH-terminated polymer.

5. 3. The method according to claim 1 or 2, wherein step 1) is catalyzed via at least one acid, which may be a liquid or solid acid, preferably at least one inorganic acid.

6. At least a portion of the sulfur-carbon-sulfur bonds present in the polymer backbone are divalent -S-CR ｘ R ｙ present as an -S- moiety, In the formula, R ｘ and R ｙ Each of the groups is independently H, C １ ~C ２０ Aliphatic radical, C １ ~C ２０ Heteroaliphatic radicals, C ３ ~C ２０ Cycloaliphatic radicals, 3- to 20-membered heterocycloaliphatic radicals, C １ ~ １０ C bonded via an aliphatic radical ３ ~C ２０ Cycloaliphatic radicals, C １ ~ １０ - selected from the group consisting of 3-20 membered heterocycloaliphatic radicals bonded via an aliphatic radical, more preferably H, C １ ~C ２０ Aliphatic radical, C １ ~C ２０ Heteroaliphatic radicals, C ３ ~C ２０ cycloaliphatic radicals, 3- to 20-membered heterocycloaliphatic radicals, and even more preferably H, C １ ~C ２０ Aliphatic radicals, and C １ ~C ２０ is selected from the group consisting of heteroaliphatic radicals, Preferably, R ｘ and R ｙ At least one of the conditions must be H.

3. The method according to claim 1 or 2.

7. The SH-terminated polymer Preferably, it is a linear polymer, where component a1 has exactly one carbonyl group and component a2 has exactly two thiol groups, or (i) when two components a1 are used and the first component a1 has exactly one carbonyl group and the second component a1 has two or more carbonyl groups, preferably exactly two carbonyl groups, preferably the molar amount of the first component a1 exceeds the molar amount of the second component a1, more preferably the molar ratio of the first component a1 to the second component a1 is in the range of 99:1 to 20:1, and component a2 has at least two thiol groups, preferably exactly two thiol groups, or (ii) when component a1 has at least one carbonyl group, preferably exactly one carbonyl group, and at least one of the components a2 used has at least three thiol groups.

3. The method according to claim 1 or 2.

8. 3. The method according to claim 1 or 2, characterized in that the two sulfur atoms of the at least two thiol groups of component a2 are separated from each other by a linker moiety L having a chain of at least 4, preferably at least 5, atoms, said atoms being carbon atoms, optionally one or more of which may be replaced by a heteroatom, preferably selected from O, S and N, or a corresponding heteroatom group, the heteroatom of which is preferably selected from O, S and N.

9. At least one of the components a2 used preferably contains a divalent oxygen atom in its aliphatic portion, more preferably contains an ether segment, even more preferably has the formula -[O-R ａ２ ] ｎ wherein R ａ２ is C ２ ~C ８ and the parameter n is an integer in the range of 1 to 200.

10. The SH-terminated polymer, particularly when the polymer is a linear polymer, contains at least a repeating unit of the general formula (RU1), 【Chemistry 1】 During the ceremony, R １ and R ２ represent together with the carbon atoms connected to them the remainder of component a1 prior to reaction with component a2, i.e. component a1 without the oxygen atom of the carbonyl group previously present, which was the only carbonyl group present in a1, Preferably, R １ and R ２ are, independently of each other, H, C １ ~C ２０ Aliphatic radical, C １ ~C ２０ Heteroaliphatic radicals, C ３ ~C ２０ Cycloaliphatic radicals, 3- to 20-membered heterocycloaliphatic radicals, C １ ~ １０ C bonded via an aliphatic radical ３ ~C ２０ Cycloaliphatic radicals, C １ ~ １０ - selected from the group consisting of 3-20 membered heterocycloaliphatic radicals bonded via an aliphatic radical, more preferably H, C １ ~C ２０ Aliphatic radical, C １ ~C ２０ Heteroaliphatic radicals, C ３ ~C ２０ cycloaliphatic radicals, 3- to 20-membered heterocycloaliphatic radicals, and even more preferably H, C １ ~C ２０ Aliphatic radicals, and C １ ~C ２０ Heteroaliphatic radicals are preferably selected from the group consisting of R １ and R ２ At least one of R is ≠H. １ and R ２ is H, t1 is an integer ranging from 2 to 300, more preferably from 3 to 200, and The variable A represents the remaining portion of the component a2 before the reaction with the component a1, i.e., the component a2 that does not contain a thiol group, and there were exactly two thiol groups in a2; Preferably, A is a divalent linker moiety L having or consisting of a chain of at least 4 carbon atoms, optionally one or more of which may be replaced by a heteroatom, preferably selected from O, S and N, or a corresponding heteroatom group, the heteroatoms of said heteroatom group being preferably selected from O, S and N, and, when the SH-terminated polymer is a branched polymer, it optionally further comprises at least one repeating unit (RU2), 【Chemistry 2】 During the ceremony, R ３ And each R ４ represents, together with the two carbon atoms attached thereto, the remainder of component a1 prior to reaction with component a2, i.e. component a1 without the oxygen atoms of the two carbonyl groups previously present, which were the only carbonyl groups present in a1; Preferably, each R ４ are, independently of each other, H, C １ ~C ２０ Aliphatic radical, C １ ~C ２０ Heteroaliphatic radicals, C ３ ~C ２０ Cycloaliphatic radicals, 3- to 20-membered heterocycloaliphatic radicals, C １ ~ １０ C bonded via an aliphatic radical ３ ~C ２０ Cycloaliphatic radicals, C １ ~ １０ - selected from the group consisting of 3-20 membered heterocycloaliphatic radicals bonded via an aliphatic radical, more preferably H, C １ ~C ２０ Aliphatic radical, C １ ~C ２０ Heteroaliphatic radicals, C ３ ~C ２０ cycloaliphatic radicals, 3- to 20-membered heterocycloaliphatic radicals, and even more preferably H, C １ ~C ２０ Aliphatic radicals, and C １ ~C ２０ selected from the group comprising heteroaliphatic radicals, in particular H, Preferably, R ３ is C １ ~C ２０ Aliphatic radical, C １ ~C ２０ Heteroaliphatic radicals, C ３ ~C ２０ Cycloaliphatic radicals, 3- to 20-membered heterocycloaliphatic radicals, C １ ~ １０ C bonded via an aliphatic radical ３ ~C ２０ Cycloaliphatic radicals, C １ ~ １０ - selected from the group comprising 3-20 membered heterocycloaliphatic radicals bonded via an aliphatic radical, more preferably C １ ~C ２０ Aliphatic radical, C １ ~C ２０ Heteroaliphatic radicals, C ３ ~C ２０ cycloaliphatic radicals, 3- to 20-membered heterocycloaliphatic radicals, even more preferably C １ ~C ２０ Aliphatic radicals and C １ ~C ２０ is a divalent residue selected from the group consisting of heteroaliphatic radicals, t2 is an integer ranging from 1 to 25, more preferably from 1 to 10, also more preferably from 1 to 5, in particular from 1 to 3, and The variable A represents the remaining portion of the component a2 before the reaction with the component a1, i.e., the component a2 that does not contain a thiol group, and there were exactly two thiol groups in a2; Preferably, A is a divalent linker moiety L having or consisting of a chain of at least 4 carbon atoms, optionally one or more of which may be replaced by a heteroatom, preferably selected from O, S and N, or a corresponding heteroatom group, the heteroatoms of said heteroatom group being preferably selected from O, S and N; The method according to claim 1 or 2.

11. characterised in that in step 1) besides components a1 and a2 at least one further component a3 is used, said component a3 being different from both components a1 and a2 and having at least 3 ethylenically unsaturated groups, preferably at least 3 vinyl groups, the additional presence of component a3 making it possible to carry out thiol-ene and thioacetalisation reactions in a one-step reaction within step 1) of the process and producing SH-terminated polymers having at least 3 terminal thiol groups, and / or the method comprises a further step 2), in particular when the SH-terminated polymer obtained after the first step 1) is linear, which step 2) represents a step for branching and / or crosslinking the preferably linear SH-terminated polymer obtained after the first step 1) by further reacting it with at least one component a4, suitable for introducing branches and different from both components a1 and a2 and also from any component a3, e.g. cyanuric chloride, characterized in that the SH-terminated polymer obtained after this second step 2) has at least three terminal thiol groups, The method according to claim 1 or 2.

12. 3. An SH-terminated polymer obtainable by the method according to claim 1 or 2.

13. 13. A two-component (2K) sealing system comprising components (A) and (B) which are separate from each other, wherein component (A) of said sealing system comprises at least one SH-terminated polymer obtainable by the method according to claim 12 or according to claim 1 or 2, and wherein component (B) of said sealing system comprises at least one component b0 which is suitable for curing a sealant composition by at least partially causing a chemical transformation of at least two thiol groups of said SH-terminated polymer.

14. 14. The sealing system according to claim 13, characterized in that the at least one component b0 present in component (B) and suitable for curing the sealant composition is selected from the group consisting of components comprising two or more epoxide groups (component b1), components which are metal oxides and / or metal peroxides, in particular manganese dioxide (component b2), components which are organic peroxides (component b3), components which comprise two or more vinyl groups (component b4), and mixtures thereof, preferably selected from the group consisting of components comprising two or more epoxide groups (component b1), components which are metal oxides and / or metal peroxides, in particular manganese dioxide (component b2), and mixtures thereof, in particular representing as component b1 at least one component which comprises two or more epoxide groups or as component b2 at least one metal oxide and / or metal peroxide, in particular manganese dioxide.

15. A sealant composition obtainable by mixing together components (A) and (B) of a sealing system as defined in claim 14.

16. 16. A method for sealing an optionally precoated substrate comprising at least the step of applying at least a portion of a sealant composition as defined in claim 15 to a surface of the optionally precoated substrate, said optionally precoated substrate being preferably a substrate usable in the aerospace and / or aircraft industries.

17. An encapsulated substrate obtainable by the method according to claim 16.

18. 16. Use of the sealing system according to claim 14 or the sealant composition according to claim 15 for providing sealing over at least a portion of a surface of an optionally precoated substrate that can be used in the aerospace and / or aircraft industries.

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