MATRICES AND SEALANTS WHICH ARE BASED ON SULFUR-CONTAINING POLYMERS AND WHICH COMPRISE A PHOTOINITIATOR, CURING AND COATING METHODS, AND USE OF SAID MATRICES AND SEALANTS

Abstract

A method for curing a mixture of a matrix and a curing agent based on sulfur-containing polymers on command and so rapidly that a tack-free surface results. A method for coating a substrate with the composition and of curing a sealant is also provided. The matrix and curing agent containing sulfur-containing polymers. The mixture is an uncured mixture with an isocyanate content, and the matrix is uncured and contains a mercaptan-terminated base polymer based on at least one polyether, polythioether, polysulfide or copolymers thereof. The uncured matrix, the curing agent, or both contain at least one photoinitiator based on sterically-inhibited tertiary amines. The mixture cures in the temperature range of 10 to +70 C. after the high-energy actinic radiation is applied. Corresponding matrices A, mixtures B, curing agents, sealant systems, and substrates, e.g., aircraft are contemplated.

Claims

1-31. (canceled)

32. A sealant formed from a mixture B comprising an uncured matrix A based on sulfur-containing polymers, wherein the sulfur-containing polymers are mercapto-terminated base polymers based on polyether, polythioether, polysulfide, copolymers thereof, and/or mixtures thereof, wherein the mercapto-terminated polymer has a mercaptan content, based on the reactive SH groups to the total weight of the polymer, in the range of 0.8 to 8 wt %; and a curing agent containing isocyanate, wherein has an average functionality in the range of 1.5 to 3.2; wherein the uncured matrix A, the curing agent or both contain a photoinitiator, which is activated by exposure to high-energy actinic radiation and releases an amine radical; wherein the sealant is free of (meth)acrylate-based compounds/polymers; and wherein the sealant is formed when curing of mixture B starts.

33. An uncured matrix A based on sulfur-containing polymers, wherein the uncured matrix A contains a mercapto-terminated base polymer based on polyether, polythioether, polysulfide, copolymers thereof and/or mixtures thereof, wherein the mercapto-terminated polymer has a mercaptan content, based on the reactive SH groups to the total weight of the polymer, in the range of 0.8 to 8 wt %, and a photoinitiator that is activated on exposure to high-energy actinic radiation to form a tertiary amine compound as a catalyst after releasing an amine radical, which tertiary amine compound catalyzes a reaction between the mercapto-terminated base polymer and the isocyanate-based curing agent; wherein the matrix A is free of (meth)acrylate-based compounds/polymers.

34. An uncured mixture B, which is a mixture of an uncured matrix A, a curing agent containing isocyanate, the isocyanate having an average functionality in the range of 1.5 to 3.2, and a photoinitiator that is activated by exposure to high-energy actinic radiation and releases an amine radical, which forms an amine compound; wherein the mixture B is free of (meth)acrylate-based compounds/polymers.

35. A sealant according to claim 32, based on at least one mercapto-terminated polysulfide polymer.

36. An uncured matrix A based on sulfur-containing polymers for production of a sealant according to claim 33, comprising at least one mercapto-terminated polysulfide polymer.

37. An uncured mixture B according to claim 34, based on at least one mercapto-terminated polysulfide polymer.

38. A sealant according to claim 32, wherein the sealant contains at least one additive selected from the group consisting of photosensitizers, fillers, lightweight fillers, thixotropy agents, plasticizers, adhesion promoters, antiaging agents, water scavengers, flame retardants, crosslinking agents and organic solvents.

39. An uncured matrix A based on sulfur-containing polymers for production of a sealant according to claim 33, wherein the matrix A contains at least one additive selected from the group consisting of photosensitizers, fillers, lightweight fillers, thixotropy agents, plasticizers, adhesion promoters, antiaging agents, water scavengers, flame retardants, crosslinking agents and organic solvents.

40. An uncured mixture B according to claim 34, wherein the matrix A and/or the mixture B contain(s) at least one additive selected from the group consisting of photosensitizers, fillers, lightweight fillers, thixotropy agents, plasticizers, adhesion promoters, antiaging agents, water scavengers, flame retardants, crosslinking agents and organic solvents.

41. A sealant according to claim 32, wherein it contains a filler which is magnesium silicate hydrate, aluminum silicate, aluminum hydroxide and/or calcium silicate.

42. An uncured matrix A based on sulfur-containing polymers for production of a sealant according to claim 33, wherein it contains as the filler magnesium silicate hydrate, aluminum silicate, aluminum hydroxide and/or calcium silicate.

43. An uncured mixture B according to claim 34, wherein it contains as the filler magnesium silicate hydrate, aluminum silicate, aluminum hydroxide and/or calcium silicate.

44. A sealant according to claim 32, having a Shore A hardness of at least 10, measured 5 to 600 minutes after initiating the high-energy actinic radiation, and a Shore A hardness in the range of 30 to 60, measured 2 weeks after initiating the high-energy actinic radiation.

45. A sealant according to claim 32, having the following properties: no cracks or other defects in the sealant, which occur during determination of a low temperature flexibility by bending at an angle of 30 at a temperature of 552, a tensile strength in the range of 0.5 to 2.8 MPa after 168 hours of storage in a fuel at a temperature of 60 C., after 300 hours of storage in a fuel at a temperature of 100 C. and/or after 1000 hours of storage in water at a temperature of 35 C., an elongation at break in the range of 100 to 800% after 168 hours of storage in fuel at a temperature of 60 C., after 300 hours of storage in fuel at a temperature of 100 C. and after 1000 hours of storage in water at a temperature of 35 C., and/or a density in the range of 1.00 to 1.45 g/cm.sup.3.

46. A sealant according to claim 32, having the following properties after complete curing: a tensile strength in the range of 0.5 to 3 MPa, an elongation at break in the range of 100 to 900% and/or a peel resistance in the range of 50 to 300 N/25 mm.

47. A sealant as in claim 32 which is in contact with components contained in an aircraft.

48. A sealant as in claim 32 which is in contact with an aircraft, a space vehicle, an automobile, a rail vehicles, a ship, equipment, a machine, a building, furniture and an electronic device.

49. A sealant as in claim 32 which is in contact with a metallic substrate, a coated metallic substrate, a structural element, a sheet metal plate, carbon fiber reinforced plastic, or glass fiber reinforced plastic.

50. A sealant as in claim 32 which joins and/or bonds elements or seals and/or fills hollow spaces and/or interspaces of elements.

Description

EXAMPLES AND COMPARATIVE EXAMPLES

[0234] The subject matter of the invention is explained in greater detail below on the basis of exemplary embodiments.

[0235] General production and test procedure for the sealants according to the invention:

[0236] The matrix A according to the invention was prepared by first mixing polysulfide polymers such as Thiokol LP 12, Thioplast G 10 and/or Thioplast G131, molecular sieve material based on the Purmol 3ST zeolite, at least one photoinitiator based on -aminoketones, at least one photosensitizer such as, for example, benzophenone and/or isopropyl thioxanthone, a thixotropy agent, e.g., based on sepiolite and an adhesion promoter, e.g., based on a phenolic resin or based on organofunctional alkoxysilane for 10 minutes in vacuo at <50 mbar or even <10 mbar and with cooling of a planetary dissolver with cooling water at a rotational speed of approx. 2000 rpm. Next the remaining fillers, e.g., based on magnesium silicate hydrates, aluminum silicates, calcium silicates, polyamides and/or polyethylene waxes and an anti-aging agent, e.g., based on phosphorous acid ester were added and dispersed for an additional 10 to 20 minutes in vacuo at <50 mbar or even <10 mbar by means of a planetary dissolver at a rotational speed of approx. 2000 rpm. The polysulfides, polythioethers, and copolymers thereof that were used were always mercapto-terminated.

[0237] For good dispersion of the matrix, the rotational speed ranges of 500 to 2200 rpm and times of 10 to 60 minutes in particular, depending on the composition, rheological properties and equipment are suitable in particular.

[0238] The curing agent according to the invention (partial mixture II) was prepared by mixing the monomeric diphenylmethane diisocyanate, the polyisocyanate and/or the isocyanate-terminated prepolymer with the thixotropy agent based on pyrogenic silica Aerosil R202 in vacuo at <50 mbar or even <10 mbar by means of a planetary dissolver at a rotational speed of approx. 2000 rpm. The information about the molecular weights is approximate values.

[0239] For compacting, filling and/or coating construction parts and for producing test bodies, the partial mixtures I and II were combined in a mixing ratio of 100:6, for example, and then activated with high-energy actinic radiation. The sealants according to the invention will cured even without high-energy actinic radiation, but then a time in the range of 24 to 168 hours would be necessary for thorough curing, depending on the layer thicknesses in the range of 0.2 to 6 mm.

[0240] The mechanical properties of the sealants such as the Shore A hardness were determined according to ISO 7619, tensile strength and elongation at break were determined according to ISO 37, peel resistance was determined according to DIN 65262-1, after the sealant had been stored for 14 days in air at an ambient air temperature of 23 C. and 50% relative atmospheric humidity. In these tests, after initial mixing of the matrix A with the hardener in air, the mixture B was immediately applied to a substrate and irradiated with high-energy actinic radiation immediately thereafter. From then on, the mixture was stored in air. After the air storage, the mixture would then be stored in various other media (see Tables 5, 7, 10, 12 and 14).

[0241] For activation of the sealant, a UV area lamp with a Fe-doped Hg lamp with a power of 400 W was generally used. All the commercially available UV light sources including UV light-emitting diodes and fluorescent lamps or electron beam sources are suitable for curing the actinically activatable coatings. The sealants which are applied in great layer thicknesses, in particular with layers 1 to 6 mm thick can preferably be cured at a wavelength in the range of 315 to 600 nm, such as UVA and/or UVVIS, while the sealants which are applied in smaller layer thicknesses, in particular 0.1 to 1 mm, will preferably cure better at a wavelength in the range of 100 to 315 nm, such as that of UVC and/or UVB.

[0242] In UV activation of the sealant, the UV parameters listed in Table 3 were measured. Complete curing and a quick tack-free time of the sealant were achieved at high UV doses of the UV radiation by means of an Fe-doped Hg emitter as well as at low UV doses of the UV radiation by means of a UV LED lamp.

TABLE-US-00003 TABLE 3 UV parameters for activation of the sealant and their effects. 400 W Fe 200 W Ga 100 W UV UV parameter/UV lamp surface lamp spot lamp LED lamp UV dose (mJ/cm.sup.2) UV total 6098 1037 520 UVVIS 1965 497 250 UVA 3256 540 270 UVB 868 0 0 UVC 9 0 0 UV intensity UV total 235 41 23 (mW/cm.sup.2) UVVIS 75 23 14 UVA 125 18 9 UVB 35 0 0 UVC 0 0 0 Distance from lamp 10 cm, irradiation time 30 s, layer thickness 2 mm* *Approximate data for the present patent application

[0243] The recipes for the examples according to the invention that are listed in Table 4 were prepared to determine the influence of the amount of photoinitiator on the processing properties of the matrix A, the mixture B and the curing sealant on the mechanical properties of the sealant. The matrices A according to the invention as partial mixtures I and the curing agent compositions as partial mixtures II were prepared according to the procedure given above as in all other examples and comparative examples. The two partial mixtures were mixed homogeneously in a weight ratio of 100:6, for example, then applied in a layer thickness of 2 mm to sheet metal of an aluminum alloy by extrusion from a mixer cartridge at approx. 23 C. and then irradiated using an Fe-doped UV surface lamp at wavelengths in the range of 300 to 600 nm at a UV dose of approx. 6000 mJ/cm.sup.2 and at a UV intensity of 200 mW/cm.sup.2 at a distance of 10 cm for 30 s. In doing so, the curing coating experienced a slight heating, without reaching 60 C.

[0244] Then the fully cured sealants were removed from the test molds and stored in air at a relative atmospheric humidity of 505% at 232 C. for 2 weeks before the mechanical properties such as elongation, peel resistance and tensile strength were determined.

[0245] The photoinitiator 1 used was 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-ylphenyl)-butan-1-one. The photoinitiator 2 was 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one. The photoinitiator 3 was 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one. While the photoinitiator 4 has a base of -hydroxy ketone, the photoinitiator 5 is based on phosphine oxide and the photoinitiator 6 is based on methylbenzoyl formate. Mercaptopropyltrimethoxysilane was added to the adhesion promoter 2 to function as the adhesion promoter, and (methacryloxymethyl)methyldimethoxysilane was added as the adhesion promoter 3. Hollow microspheres based on vinylidene chloride-acrylonitrile copolymers were used as the lightweight filler 4. An isocyanate-terminated prepolymer based on HDI, MDI or TDI with a molecular weight of approx. 500 to 3000 g/mol was used as the isocyanate-terminated prepolymersee Examples B12, B21, B24 and B26. The MDI-terminated prepolymer of B12 had a backbone of polysulfide and a residual monomer content of MDI approximately in the range of 0.8 and 5 wt %. The sealants of the comparative examples VB are commercially available and were acquired in a premixed form but not yet cured with high-energy actinic radiation. The main ranges of the molecular weights are given as the data on the polysulfides. The compositions in the Comparative Examples VB1 to VB3 do not contain any photoinitiator additives or any curing agent based on isocyanate.

TABLE-US-00004 TABLE 4 Composition of the masses of Examples B1 to B5 and the Comparative Examples VB1 to VB3. Content in wt %/Example Comp. Ex. B1 B2 B3 B4 B5 VB1 VB2 VB3 Partial mixture I = matrix A Matrix Naftoseal MC-...* 100 MC- 100 MC- 100 MC- 780 B- 238 B- 780 C-60 Long-chain polysulfide (3900-4400 g/mol) 71.5 70.8 70.4 69.6 70.4 Photoinitiator 1 0.1 0.8 1.2 2.0 Photoinitiator 2 1.2 Photosensitizer 1: benzophenone 1.0 1.0 1.0 1.0 Photosensitizer 2: isopropyl thioxanthone 1.0 Filler aluminum silicate 20.0 20.0 20.0 20.0 20.0 Adhesion promoter: phenolic resin 1.0 1.0 1.0 1.0 1.0 Thixotropy agent: sepiolite 3.0 3.0 3.0 3.0 3.0 Water scavenger: NaAl-based zeolite 1.0 1.0 1.0 1.0 1.0 Antiaging agent: phosphorous acid ester 2.4 2.4 2.4 2.4 2.4 Total 100 100 100 100 100 100 100 100 Partial mixture II = curing agent Monomeric isocyanate based on MDI of 95 95 95 95 95 335 g/mol Thixotropy agent pyrogenic silica 5 5 5 5 5 Naftoseal MC-... curing agent* 100 MC- 100 MC- 100 MC- 780 B- 238 A- 780 C-60 Total 100 100 100 100 100 100 100 100 Mixing ratio of matrix A:curing agent 100:6 100:6 100:6 100:6 100:6 100:10 100:12 100:10 *Products of Chemetall GmbH

TABLE-US-00005 TABLE 5 Curing and properties of the sealants of Examples B1 to B5 and of Comparative Examples VB1 to VB3; RT = room temperature. Properties, Example Comparative Example B1 B2 B3 B4 B5 VB1 VB2 VB3 Density (g/cm.sup.3) 1.42 1.41 1.43 1.43 1.42 1.1 1.5 1.35 Processing time (min) 1440 180 60 30 60 30 15 3,600 Tack-free time (min) 2 2 2 2 2 240 50-120 60,000 Complete curing time for initial hardness of 720 60 40 20 40 480 90-240 86,400- Shore A 30 (min) 100,800 Shore A hardness after 14 days at RT 45 44 43 45 44 50 60 50 Tensile strength (MPa) after 14 days at RT 1.90 2.10 2.52 2.65 2.45 1.5-2.2 2.2 1.5-2.2 Elongation (%) after 14 days at RT 266 300 400 466 388 300-400 430 300-400 Peel (N/25 mm) after 14 days at RT 1.25 168 184 193 189 120-150 180 120-150 Tensile strength (MPa) after 168 hat 60 C. 1.23 1.54 2.20 2.31 2.26 1.5-2.0 1.8-2.0 1.5-2.0 storage in fuel Elongation (%) after 168 h at 60 C. storage in fuel 285 332 440 487 467 300-400 270-300 300-400 Tensile strength (MPa) after 300 h at 100 C. 0.41 0.46 0.95 1.02 0.93 1.5-2.0 1.8-2.0 1.5-2 storage in fuel Elongation (%) after 300 h at 100 C. storage in fuel 750 732 467 496 453 300-400 270-400 300-400 Tensile strength (MPa) after 1000 h at 35 C. storage 1.10 1.75 2.10 2.31 2.15 1.0-1.5 1.8-2.0 1.0-1.2 in H.sub.2O Elongation (%) after 1000 h at 35 C. storage in H.sub.2O 230 287 303 315 310 300-400 400-500 300-350 Change in volume (%) according to DIN EN 1.8 1.9 2.0 2.1 2.0 3.0 3.8 5.4 ISO 10563

[0246] It has surprisingly been found that the photoinitiators based on -aminoketones, which are otherwise conventionally used for free radical curing of acrylates and methacrylates lead to polyaddition between the sulfur-containing polymer/copolymer of the partial mixture I and the hardener based on isocyanate of partial mixture II and thereby result in curing of the sealant on demand after UV radiation. Furthermore, within a few seconds or at the latest within 2 minutes after UV radiation, a tack-free layer was formed directly on the sealant surface, with the tack-free layer rapidly advancing to greater depths and becoming thicker. Surface curing was possible very rapidly in this way, and an accelerated complete curing, i.e., the time until reaching a Shore A hardness of 30, was possible on demand, while the processing time of the matrices B according to the invention was just as long as or much longer than the processing time of a conventional fast-curing sealant (VB1 to VB3).

[0247] It was surprising that the amount of photoinitiator had no influence on the tack-free time, but instead had an influence only on the complete curing time which can evidently be explained by the fact that the UV radiation on the sealant surface contributes more to the formation of free tertiary amine at the surface than in a deeper layer and thus smaller amounts of photoinitiator are also sufficient to form a tack-free layer.

[0248] By varying the photoinitiator concentration, the processing time of the matrix according to the invention can be controlled well, and the complete curing time increases in proportion to a longer processing time.

[0249] The sealant according to the invention has surprisingly exhibit good mechanical properties even after storage in various media and at an elevated temperature such as, for example, storage in water at 35 C. or storage in fuel at 60 C. or 100 C.

[0250] An increase in the photoinitiator concentration leads to improved tensile strength values and elongation values at room temperature as well as after storage in various media.

[0251] The choice of photosensitizer had no influence on the processing properties or on the mechanical properties of the sealant according to the invention.

[0252] The compositions of the primers according to the invention listed in Table 6 were prepared to determine the influence of the chain length of the polysulfide polymers, the influence of the adhesion promoter and the influence of the different curing agents on the processing properties and on the mechanical properties. The matrices according to the invention as partial mixtures I, the curing agent compositions as partial mixtures II and the compositions of the comparative examples were prepared according to the procedure given above. The two partial mixtures were applied in a layer thickness of 2 mm to a test body and then irradiated with a Fe-doped UV surface emitter at wavelengths in the range of 300 to 600 nm for 30 s at a distance of 10 cm.

TABLE-US-00006 TABLE 6 Makeup of the compositions of Examples B6 to B12 and Comparative Examples VB4 to VB5. The comparative examples VB4 and VB were not cured with isocyanate but instead with curing agents based on a different chemical composition. Despite the irradiation with UV light, these comparative examples do not fully cure until after several weeks. Content in wt %, Example Comparative Example B6 B7 B8 B9 B10 B11 B12 VB4 VB5 Partial mixture I = matrix A Long-chain polysulfide (5000-6500 g/mol) 70.4 Long-chain polysulfide (3900-4400 g/mol) 58 70.4 70.4 70.4 70.4 70.4 70.4 Medium-chain polysulfide (2400-3100 g/mol) 70.4 Shod-chain polysulfide (<1100 g/mol) 12.4 Photoinitiator 1 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Photosensitizer 1: benzophenone 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Adhesion promoter 1: phenolic resin 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Adhesion promoter 2 and/or 3 2:1.0 3:1.0 Filler: aluminum silicate 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 Thixotropy agent: sepiolite 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Water scavenger: NaAl-based zeolite 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Antiaging agent: phosphorous acid ester 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 Total 100 100 100 100 100 100 100 100 100 Partial mixture II = hardener Monomeric isocyanate based on MDI 335 g/mol 95 95 95 95 95 Polyisocyanate 1 = based on MDI 800 g/mol 100 MDI-terminated prepolymer of 2000 g/mol 100 Thixotropy agent: pyrogenic silica 5 5 5 5 5 Epoxy resin E and/or organic peroxide P 100 E 100 P Total 100 100 100 100 100 100 100 100 100 Mixing ratio of matrix A:hardener 100:6 100:6 100:6 100:6 100:6 100:16 100:20 100:7.8 100:4.5

TABLE-US-00007 TABLE 7 Curing and properties of the sealants of Examples B6-B12 and Comparative Examples VB3-VB4; not determined = n.d. Properties, Example Comparative Example B6 B7 B8 B9 B10 B11 B12 VB4 VB5 Density (g/cm.sup.3) 1.42 1.42 1.42 1.42 1.42 1.42 1.42 1.42 1.42 Processing time (min) 60 100 50 180 70 480 60 >24 >24 Tack-free time (min) 2 2 2 2 2 2 1 180 >7200 Complete curing time for initial hardness of 40 50 30 120 40 240 15 >14,400 >14,400 Shore A 30 (min) Shore A hardness after 14 days at RT 45 38 45 32 43 35 50 <10 <10 Tensile strength (MPa) after 14 days at RT 1.4 2.2 1.2 1.12 1.94 1.2 2.2 <0.2 <0.2 Elongation (%) after 14 days at RT 216 450 198 830 456 420 220 <100 <100 Peel (N/25 mm) after 14 days at RT 88 170 69 93 167 56 175 <10 <10 Tensile strength (MPa) after 168 h at 60 C. 1.13 1.64 0.80 0.70 1.64 0.82 1.91 <0.2 <0.2 storage in fuel Elongation (%) after 168 h at 60 C. storage 247 476 256 870 473 497 235 <100 <100 in fuel Tensile strength (MPa) after 300 h at 100 C. 0.53 0.64 0.35 n.d. 0.73 0.56 1.13 <0.2 <0.2 storage in fuel Elongation (%) after 300 h at 100 C. storage 430 647 178 n.d. 515 570 303 <100 <100 in fuel Tensile strength (MPa) after 1000 h at 35 C. 1.05 1.27 0.75 0.61 1.55 0.75 1.83 <0.2 <0.2 storage in H.sub.2O Elongation (%) after 1000 h at 35 C. 218 357 212 892 560 436 255 <100 <100 storage in H.sub.2O

[0253] Use of polymer/prepolymers of definitely different chain lengths led to different mechanical properties but had no effect on the tack-free time.

[0254] The use of polyisocyanates based on MDI/HDI trimers, HDI biurets and isophorone diisocyanates as well as MDI-terminated prepolymers as curing agent has also proven suitable for UV curing, wherein the isocyanate-terminated prepolymer surprisingly led to an even faster complete curing of the sealant according to the invention. In this way, sealants with a layer thickness of 2 mm were completely cured within 10 to 600 minutes after UV radiation, while the processing time was kept at a minimum of 60 minutes. The tack-free time was still reached within 1 to 2 minutes after UV radiation. Furthermore, the sealant also exhibited excellent mechanical properties with and without storage in various media at elevated temperature.

[0255] Comparative examples in which a commercially available epoxy resin and a commercially available peroxide were used as the curing agents were not suitable for UV curing of the sealant because complete curing of less than 60 minutes for a 2 mm thickness to be irradiated could not be observed and it was also impossible to achieve a tack-free surface rapidly, for example, in less than 10 min, when the thickness of the sealant to be irradiated was 2 mm.

[0256] With the experimental series presented in Table 8, the speed of different UV curing sealants was tested at various layer thicknesses (2 and 5 mm).

TABLE-US-00008 TABLE 8 Processing properties of a few recipes with different layer thicknesses. Properties/Example B4 B6 B12 Layer thickness (mm) 2 5 2 5 2 5 Processing time (min) 60 60 60 60 70 70 Tack-free time (min) 2 2 2 2 2 2 Complete curing time for initial hardness of 40 300 40 360 15 60 Shore A 30 (min)

[0257] When using an isocyanate-terminated prepolymer as the curing agent (see B12), an extremely fast complete curing was surprisingly achieved in 60 minutes even with a layer thickness of the molded sealant of 5 mm, for example, while there was no influence on the tack-free time.

[0258] The matrices according to the invention as listed in Table 9 were prepared according to the procedure given above and cured with UV light. The effects of the fillers, the lightweight fillers and the very large amounts of photoinitiator or photosensitizer on the mechanical properties and on the processing times were determined.

TABLE-US-00009 TABLE 9 Makeup of the compositions of Examples B13 to B17 as well as the Comparative Examples VB6 to VB8. Content in wt %, Example Comp. Example B13 B14 B15 B16 B17 VB6 VB7 VB8 Partial mixture I = matrix A Long-chain polysulfide (3900-4400 g/mol) 70.4 70.4 70.4 70.4 70.4 57.6 41.6 51.4 Photoinitiator 1 1.2 1.2 1.2 1.2 1.2 10 30 1.2 Photosensitizer 1: benzophenone 1.0 1.0 1.0 1.0 1.0 1.0 1.0 20 Filler 1: magnesium silicate hydrates 20.0 Filler 2: aluminum hydroxides 20.0 12.0 12.0 8.0 20 20.0 20.0 Lightweight filler 1: polyamide 8.0 12.0 Lightweight filler 2: polyethylene 8.0 Adhesion promoter: phenolic resin 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Thixotropy agent: sepiolite 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Water scavenger: NaAl-based zeolite 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Antiaging agent: phosphorous acid ester 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 Total 100 100 100 100 100 100 100 100 Partial mixture II = curing agent Monomeric isocyanate MDI of 335 g/mol 95.0 95.0 95.0 95.0 95.0 95.0 95.0 95.0 Thixotropy agent: pyrogenic silica 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Mixing ratio matrix A:curing agent 100:6 100:6 100:6 100:6 100:6 100:6 100:6 100:6

TABLE-US-00010 TABLE 10 Curing and properties of the sealants of Examples B13 to B17 and Comparative Examples VB5 to VB7 Properties, Example Comparative Example B13 B14 B15 B16 B17 VB6 VB7 VB8 Density (g/cm.sup.3) 1.41 1.42 1.38 1.39 1.29 1.43 1.08 1.27 Processing time (min) 60 60 760 90 100 20 10 40 Tack-free time (min) 2 2 2 2 2 2 2 2 Complete curing time for initial hardness of 40 50 50 60 70 48 56 90 Shore A 30 (min) Shore A hardness after 14 days at RT 46 42 41 38 37 35 32 33 Tensile strength (MPa) after 14 days at RT 2.3 2.05 1.84 1.92 1.45 0.6 0.4 1.6 Elongation (%) after 14 days at RT 443 560 578 610 430 900 1000 1500 Peel (N/25 mm) after 14 days at RT 150 110 101 105 135 <20 <20 <20 Tensile strength (MPa) after 168 h at 60 C. 1.82 1.71 1.63 1.73 0.92 <0.2 <0.2 <0.2 storage in fuel Elongation (%) after 168 h at 60 C. storage 610 580 605 623 442 650 690 800 in fuel Tensile strength (MPa) after 300 h at 100 C. 0.87 0.67 0.41 0.54 0.77 <0.2 <0.2 <0.2 storage in fuel Elongation (%) after 300 h at 100 C. storage 6.22 830 880 780 463 500 450 600 in fuel Tensile strength (MPa) after 1000 h at 35 C. 1.94 1.73 1.41 1.65 0.88 <0.2 <0.2 <0.2 storage in H.sub.2O Elongation (%) after 1000 h at 35 C. 565 557 720 605 295 450 530 620 storage in H.sub.2O

[0259] Examples B13 to B17 show that certain fillers such as aluminum hydroxides, polyamide, and polyethylene lead to good results with respect to processing properties and mechanical properties.

[0260] A reduction in the density of the sealant to values of less than 1.3 g/cm.sup.3 as in B17 surprisingly had no negative on rapid surface curing on demand or on the subsequent rapid complete curing. Furthermore, the sealants had very good mechanical properties, with or without storage in various media at elevated temperatures. Addition of very large amounts of photoinitiator or photosensitizer yielded very soft and incompletely cured sealants (see VB6 to VB8).

TABLE-US-00011 TABLE 11 Makeup of the compositions of examples B18 to B26, wherein the isocyanate in B21 has a backbone based on polysulfide and a residual TDI monomer content of less than 0.1 wt %, while the isocyanate of B24 has a backbone based on polythioether and also has a residual TDI monomer content of less than 0.1 wt %, The isocyanate of B26 has a backbone based on polysulfide and a residual MDI monomer content of less than 1 wt %. Content in wt %/example comparative example B18 B19 B20 B21 B22 B23 B24 B25 B26 Partial mixture I = matrix A Long-chain polysulfide (3900-4400 g/mol) 70.4 70.4 70.4 70.4 70.4 70.4 70.4 55.4 70.4 Photoinitiator 1 + photosensitizer 1: benzophenone 1.2 + 1.0 Filler 2: aluminum hydroxides 22.2 22.2 22.2 22.2 22.2 22.2 22.2 20.0 22.2 Flame retardant based on phosphate ester 15.0 Adhesion promoter phenolic resin 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Thixotropy agent: sepiolite 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Water scavenger: NaAl-based zeolite 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Antiaging agent B: phosphorous acid ester 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 Total 100 100 100 100 100 100 100 100 100 Partial mixture II = curing agent Monomeric isocyanate based on MDI of 335 g/mol 72.0 72.0 95.0 Monomeric isocyanate based on TDI of 175 g/mol 72.0 Isocyanate prepolymer based on TDI of 1900 g/mol 77.0 Monomeric isocyanate based on HDI of 170 g/mol 72.0 Isocyanate trimer based on HDI of 360 g/mol 72.0 Isocyanate prepolymer based on TDI of 3000 g/mol 77.0 Isocyanate prepolymer based on MDI of 2500 g/mol 77.0 Thixotropy agent: pyrogenic silica 5.0 5.0 5.0 5.0 5.0 5.0 Photoinitiator 1 13.0 13.0 13.0 13.0 13.0 13.0 13.0 13.0 Photosensitizer 1: benzophenone 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Mixing ratio of matrix A:curing agent 100:9 100:9 100:5 100:56 100:5 100:11 100:83 100:5 100:60

TABLE-US-00012 TABLE 12 Curing and properties of the sealants of examples B18 to B26. Properties/example comparative example B18 B19 B20 B21 B22 B23 B24 B25 B26 Density (g/cm.sup.3) 1.39 1.30 1.40 1.40 1.39 1.41 1.41 1.42 1.39 Processing time (min) 80 160 300 800 1000 1000 1200 80 500 Tack-free time (min) 2 2 2 2 2 2 2 2 2 Complete curing time for initial hardness of 60 90 180 300 500 600 700 45 180 Shore A 30 (min) Shore A hardness after 14 days at RT 45 45 40 45 30 33 50 40 46 Tensile strength (MPa) after 14 days at RT 2.1 2.3 2.0 1.6 1.3 1.4 2.7 1.7 2.5 Elongation (%) after 14 days at RT 540 420 620 340 440 450 410 630 400 Peel (N/25 mm) after 14 days at RT 115 140 100 150 80 85 146 120 138 Tensile strength (MPa) after 168 h at 60 C. 1.8 1.7 1.4 1.3 1.1 1.0 1.1 1.5 1.8 storage in fuel Elongation (%) after 168 h at 60 C. storage 570 530 430 320 300 250 200 450 320 in fuel Tensile strength (MPa) after 300 h at 100 C. 0.8 0.7 0.5 0.8 0.4 0.5 0.9 0.6 1.0 storage in fuel Elongation (%) after 300 h at 100 C. storage 790 400 490 280 200 250 230 230 410 in fuel Tensile strength (MPa) after 1000 h at 35 C. 1.69 1.2 1.3 0.8 0.7 0.6 0.9 0.9 1.3 storage in H.sub.2O Elongation (%) after 1000 h at 35 C. 545 300 330 220 230 270 200 200 270 storage in H.sub.2O

[0261] In the case of Example B18, a composition and a method were selected according to B14 in which the corresponding amounts were selected in a similar manner, but in this method the photoinitiator 1 was added to the curing agent instead of being added to the matrix A. This also resulted in good properties in example B18.

[0262] The sealants of Examples B20 to B24 and B26 were prepared according to the general production and test procedure, cured with UV light and tested. The influence of different isocyanate ethers such as toluene diisocyanate, hexamethylene diisocyanate and their prepolymers and/or trimers on the processing properties and on the mechanical properties were determined.

[0263] Examples B25 and B31 show, that the addition of liquid flame retardants based on phosphate esters or phosphonate surprisingly leads to results comparable to those obtained with the sealants according to the invention, as was the case with the other sealants according to the invention, and even permitted a particularly rapid curing. Liquid flame retardant based on phosphate esters or phosphonate is capable of partially replacing the mercapto-terminated base polymer and is particularly suitable as an additive in the range of 0.1 to 30 wt %. For example, polyphosphates, tris-(2-ethylhexyl) phosphate, triethyl phosphates, triaryl phosphates, triaryl polyphosphates and dimethylpropane phosphonate are especially suitable here. This yields a fire prevention behavior that is significantly improved.

[0264] The matrices presented in Table 13 were prepared according to the aforementioned procedure and then cured with UV light, thereby releasing prepolymers having different basic structures and molecular weights (see B27 to B29); and various photoinitiators that do not release tertiary amines (see VB9 to VB11) were tested with respect to their mechanical properties and the processing properties of the sealants.

TABLE-US-00013 TABLE 13 Makeup of the compositions of Examples B27 to B31 and Comparative Examples VB9 to VB11. Content in wt %, Example Comparative Example B27 B28 B29 B30 B31 VB9 VB10 VB11 Partial mixture I = matrix A Polythioether (3900-4100 g/mol) 70.4 70.4 57.6 70.4 70.4 70.4 Polythioether (2000-2200 g/mol) 70.4 Polythioether-polysulfide (1800-2000 g/mol) 70.4 Photoinitiator no. 1:1.2 1:1.2 1:1.2 3:1.2 4:1.2 5:1.2 6:1.2 Photosensitizer based on benzophenone 1 1 1 1 1 1 1 Flame retardant based on phosphate ester 15.0 Filler: aluminum silicate 22.2 22.2 22.2 22.2 20.0 22.2 22.2 22.2 Adhesion promoter phenolic resin 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Thixotropy agent: sepiolite 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Water scavenger: NaAl-based zeolite 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Antiaging agent B: phosphorous acid ester 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 Total 100 100 100 100 100 100 100 100 Partial mixture II = curing agent Monomeric isocyanate based on 95.0 95.0 95.0 95.0 72.0 95.0 95.0 95.0 MDI of 335 g/mol Photoinitiator 1 13.0 Photosensitizer based on benzophenone 10.0 Thixotropy agent: pyrogenic silica 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Total 100 100 100 100 100 100 100 100 Mixing ratio of matrix A:curing agent 100:6 100:9 100:5 100:6 100:9 100:6 100:6 100:6

TABLE-US-00014 TABLE 14 Curing and properties of the sealants of Examples B27-B31 and Comparative Examples VB9-VB11. Propenies, Example Comparative Example B27 B28 B29 B30 B31 VB9 VB10 VB11 Density (g/cm.sup.3) 1.31 1.31 1.34 1.31 1.35 1.31 1.31 1.31 Processing time (min) 120 110 115 120 90 >1440 >1440 >1440 Tack-free time (min) 2 2 2 2 2 >1440 >1440 >1440 Complete curing time for initial hardness of 80 70 60 90 45 >14,400 >14,400 >14,400 Shore A 30 (min) Shore A hardness after 14 days at RT 48 52 55 47 42 <1 <1 <1 Tensile strength (MPa) after 14 days at RT 2.0 2.2 2.3 2.0 1.6 <0.1 <0.1 <0.1 Elongation (%) after 14 days at RT 350 250 200 300 640 <1 <1 <1 Peel (N/25 mm) after 14 days at RT 180 175 160 190 130 <1 <1 <1 Tensile strength (MPa) after 168 h at 60 C. 1.7 2.0 2.0 1.8 1.5 <1 <1 <1 storage in fuel Elongation (%) after 168 h at 60 C. storage 220 200 170 220 440 <1 <1 <1 in fuel Tensile strength (MPa) after 300 h at 100 C. 1.3 1.2 1.4 1.2 0.7 <1 <1 <1 storage in fuel Elongation (%) after 300 h at 100 C. storage 250 230 240 260 450 <1 <1 <1 in fuel Tensile strength (MPa) after 1000 h at 35 C. 1.0 0.9 1.1 1.0 1.2 <1 <1 <1 storage in H.sub.2O Elongation (%) after 1000 h at 35 C. 280 240 260 290 369 1 1 1 storage in H.sub.2O

[0265] The photoinitiators 4 to 6 are suitable specifically for acrylate-based polymer systems but not for the mercapto-terminated base polymers according to the present patent application (see VB9 to VB11). They do not release any radicals based on tertiary amine and are therefore unsuitable for use according to the present invention.

[0266] In addition to the speed record for the extremely rapid curing of high quality sealants, there is also a record in terms of properties which is associated with the extraordinary reduction in the so-called shrinkage in curing.

[0267] With conventional aviation sealants based on mercapto-terminated polymers, the shrinkage in volume of the cured sealant with respect to the volume of the original mixture B is usually 4 to 9 vol % at the start of curing. In the case of the sealants according to the present patent application, however, shrinkage is usually only 1 to 2.5 vol %. The lower shrinkage here seems to be associated with the lack of plasticizer content and with the type of crosslinking. In comparison with that, the (meth)acrylate-based sealants, however, even have a volume shrinkage in the range of approximately 8 to 15 vol %. To determine the shrinkage of the sealant, the volume change method according to DIN EN ISO 10563 is used.

[0268] Curing agents based on manganese dioxide always require a plasticizer content of approx. 5 to 10 wt % relative to the total sealant composition. These plasticizers often result in a volume shrinkage of approx. 2 to 10%. These plasticizers can escape into the environment and may be washed out especially at an elevated temperature.

[0269] Another advantageous property relates to the stability of the sealants during storage in water. Water storage of a conventionally cured sealant for more than 1000 hours at 35 C., for example, typically has a marked influence on the mechanical properties of a sealant cured with manganese dioxide (see VB1 and VB2), while the mechanical properties of the sealants according to the invention show a much smaller decline.

[0270] On the whole, the high quality properties of the conventional aviation sealants such as the high resistance to various media such as a fuel resistance at 60 C., for example, measured after 168 hours and 100 C., for example, a water resistance at 35 C., measured after 1000 hours, hydraulic fluid, water of condensation and deicing fluid, a high temperature stability, high cold flexibility, high weather resistance, high peel resistance on different substrates, high elongation at break and high tensile strength have been achieved here to a large extent or to the full extent, despite the extreme shortening of the curing time.