Fiber-reinforced composite panel with flame-retardant and smoke-suppressing finish

Abstract

The invention relates to a fiber-reinforced composite panel obtainable by pressing a matrix material with a flame-retardant and smoke-suppressing textile material, wherein the textile material is smoke-retardant using a boron-containing trialkoxysilane of formula I wherein R1 is a straight-chain or branched alkyl group with up to 6 C atoms, n is an integer from 1 to 5 and R2 is a boron-containing organic residue bonded to the trialkoxysilane via an N atom, in a sol-gel process.

Description

[0001] The invention relates to a fiber-reinforced composite panel which is obtainable by pressing a matrix material with a smoke-suppressing textile material.

[0002] Composite panels based on a combustible matrix are widely known. A common problem with these panels is their flammability. Even with flame-retardant treatment, which prevents continued burning after the ignition source has been removed, heavy smoke is almost always produced. Smoke is toxic and hinders rescue efforts in the event of a fire. This is especially true for composite panels based on a plastic matrix with textile reinforcement.

[0003] On the other hand, composite panels have found application in many areas, for example, in construction and the furniture industry. When a plastic matrix is ​​combined with a textile fabric, such composite panels offer excellent flexibility combined with high strength and resilience. However, their use is limited by fire safety regulations.

[0004] The object of the invention is therefore to provide composite panels with smoke-suppressing properties, and in particular, agents with smoke-suppressing properties that can be used in such composite panels and make them suitable for use in fire-prone environments. Preferably, such composite panels should also be flame-retardant.

[0005] Surprisingly, it was found that flame-retardant and smoke-suppressant finishing of textile materials is suitable for imparting the desired properties to such composite materials.

[0006] Accordingly, the invention relates to a fiber-reinforced composite material panel of the type mentioned at the outset, in which the textile material is provided with a boron-containing trialkoxysilane of the formula Iwherein R1 is a straight-chain or branched alkyl group having up to 6 C atoms, n is an integer from 1 to 5 and R2 is a boron-containing radical which is bonded to the trialkoxysilane via an N atom.

[0007] The matrix material of the fiber-reinforced composite panel according to the invention is, in particular, a plastic material, for example, polypropylene or an epoxy resin. A textile fabric, especially a natural fiber fabric, is preferably used as the textile material. Fiber materials containing hydroxyl groups, such as flax, cotton, wool, and viscose, are particularly suitable. The matrix material and the textile material are generally pressed together in two or more layers to form the composite panel.

[0008] For the smoke-suppressant treatment of the composite material, it is sufficient to provide the textile material with an appropriate finish. The above-mentioned boron-containing trialkoxysilanes of formula I, as defined above, have proven particularly suitable. R1 in the trialkoxysilane is preferably methyl or ethyl, and n is 2. Organic radicals derived from boric acid, for example -B(OH)2, B(OR1)2, and 1,3,2-dioxaborolanes, have proven particularly suitable boron-containing radicals. Groups of formulas II and III are particularly suitable as boron-containing radicals R2:

[0009] The invention further relates to compounds of the formulas IV and V:which have proven particularly suitable for the smoke-suppressing finishing of textile materials in fiber composite panels, and their use for these purposes.

[0010] It is understood that the boron-containing organic radicals, such as those of formulas II and III, as used according to the invention, are bonded to the trialkoxysilane via nitrogen atoms.

[0011] The composite panels according to the invention are also, in particular, flame-retardant. For this purpose, the textile materials are advantageously treated with phosphorus-containing radicals. Preferred for this purpose are trialkoxysilanes of the formula I', in which n is 1 to 5 and R2' is a phosphorus-containing radical bonded to the trialkoxysilane directly or via one or more nitrogen atoms.

[0012] Suitable phosphorus-containing organic radicals include, in particular, radicals derived from phosphoric acid, as well as phosphonates, thiophosphonates, phosphonites, arylphosphines, phosphonamides, and the like. Particular preference is given to radicals of the following formulas VI to XIV.

[0013] Where R3 is C1-C3 alkyl and Z is oxygen or sulfur.

[0014] With regard to the phosphorus-containing organic residues of formulas VI to XIV and their attachment to a trialkoxysilane group, explicit reference is made to DE 10 2021 110 402 A1 and DE 10 2020 132 465 A1. These residues are intended for use as flame-retardant impregnation for textiles, which are applied to a textile using the sol-gel process.

[0015] Like the boron-containing organic residues, the phosphorus-containing organic residues can also be bonded to the trialkoxysilane group via a nitrogen-containing bridge function. Suitable nitrogen-containing bridge functions include amines, triazines, and triazoles. The high nitrogen content of these groups leads to nitrogen release upon decomposition, which reduces flammability.

[0016] The textile materials used in the fiber composite panels according to the invention are treated in a known manner using a sol-gel process. For this purpose, the compounds of formula I and I' are hydrolyzed in the presence of water to form a trihydroxysilane, which is then consolidated with the elimination of water to form a crosslinked silicon oxide in gel form according to the following reaction sequence.

[0017] The resulting aqueous gel is applied to the textile material and thermally fixed, forming covalent bonds through a condensation reaction between the silyl hydroxy groups and the hydroxy groups of the textile material. The thus-treated textile material is then pressed into a fiber composite panel with a polymer matrix—for example, polypropylene or an epoxy resin. The fiber composite panels thus treated are self-extinguishing in the event of a fire and exhibit significantly reduced smoke development.

[0018] The fiber composite panels according to the invention generally have a layer thickness of 1.5 to 4 mm, in particular approximately 2 mm. The fiber volume fraction is in the range of 20 to 50%.

[0019] The impregnation of the textile material with smoke suppressants is in the range of 1.0 to 4.0 wt.%, preferably in the range of 1.0 to 3.0 wt.%. Flame retardants are generally applied in an amount of 12 to 25 wt.%, especially 15 to 20 wt.%.

[0020] The weight ratio of smoke suppressant to flame retardant in the finish is generally 1:2 to 1:24, preferably 1:3 to 1:20 and particularly preferably 1:9 to 1:18.

[0021] The invention is explained in more detail by the following examples. Synthesis Example 1Di(methylboronic acid pinacol ester)aminopropyltrimethoxysilane

[0022] In a 250 ml three-neck round-bottom flask fitted with a reflux condenser with a bubble counter, a pressure-equalizing dropping funnel, and a gas stopcock, 3.13 ml (2.29 g / 22.6 mmol / 2 eq) of triethylamine were dissolved in 100 ml of THF. 2 ml (2.03 g / 11.3 mmol / 1 eq) of 3-aminopropyltrimethoxysilane were added, and the reaction vessel was cooled with an ice bath. Nitrogen was passed through the apparatus via the gas stopcock for a few minutes. A solution of 2-(bromomethyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (3.96 ml / 5 g / 22.6 mmol / 2 eq) in 20 ml of THF was slowly added dropwise (30 min) via the dropping funnel while stirring. The reaction mixture was stirred overnight at room temperature, and the resulting precipitate was filtered off using a fluted filter. The filtrate was collected, and the solvent was removed using a rotary evaporator. Synthesis example 2N-(3-phenylboronic acid)-N'-(propyltrimethoxysilane)urea

[0023] In a 250 ml three-neck round-bottom flask fitted with a reflux condenser with a bubble counter, a pressure-equalizing dropping funnel, and a gas stopcock, 2.5 g (18.25 mmol / 1 eq) of 3-aminophenylboric acid were dissolved in 50 ml of dioxane. Nitrogen was passed through the apparatus via the gas stopcock for a few minutes. Subsequently, a solution of 3.75 g (18.25 mmol / 1 eq) of 3-isocyanatopropyltrimethoxysilane dissolved in 10 ml of dioxane was added dropwise. The reaction mixture was stirred overnight at 70°C, filtered, and the solvent from the filtrate was removed using a rotary evaporator. Fiber composite panels

[0024] A polymer matrix based on polypropylene was bonded with 4 layers of a flax fabric (twill weave; 300 g / m 2ampliTex 5040 was pressed into a multilayer structure with alternating layers of fabric and polymer. The flax fabric was treated with 26 wt.% of a sol-gel made from the compound from Synthesis Example 1, as well as with a conventional flame retardant; the fiber content in the composite panel was 26.5 vol.%. The fiber composite panel was self-extinguishing and emitted only minimal smoke.

[0025] Another fiber composite panel was made of a polypropylene matrix and a flame-retardant and smoke-retardant viscose fabric (plain weave; 450 g / m 2 ; M4 150 02; 3 layers). The finish accounted for 24% by weight of the textile material. The fiber content in the composite panel was 44% by volume. This fiber composite panel was also self-extinguishing and emitted only a small amount of smoke. Tests

[0026] Fiber composite panels were manufactured by pressing flax and Cordenka fabric for 2 minutes at 185°C and 5 bar, and for 5 minutes at 190°C and 20 bar. Greenpoxy 33, an epoxy resin, and polypropylene served as the matrix. Table 1 Flax / GP, Flax / PP Cordenka / GP, Cordenka PP Number of fabric layers 4 3 Plate thickness in mm 2,0 2,0 Fiber volume fraction in % 44,4 45,0 Density in g / cm 3 1,22 1,29

[0027] The fabric layers were treated according to Table 2 (wt.%). The weight ratio of the two impregnating agents is given in parentheses. Table 2 equipment - FSM1 FSM3 FSM1 + FSM3 Flax / GP33 - 18,1 3,0 19,6 (18:1) Flax / PP - 17,9 3,0 21,8 (18:1) Cordenka / GP33 - 13,8 3,0 21,4 (18:1) Cordenka / PP - 13,2 2,5 21,2 (18:1) Cordenka / GP33 20,1 (9:1)

[0028] The maximum smoke density was determined for each sample using standard procedures. The values ​​indicate the transmittance (in %) for light with a wavelength of 633 nm. Table 3 equipment - FSM 1 FSM 3 FSM 1 + FSM 3 Flax / GP 33 53 64 57 80 Flax / PP 7 19 7 31 Cordenka / GP33 37 67 24 74 Cordenka / PP 10 22 2 29 Cordenka / GP33 59 QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 110 402 A1

[0014] DE 10 2020 132 465 A1

[0014]

Claims

[1] Fiber-reinforced composite panel, obtainable by pressing a matrix material with a flame-retardant and smoke-suppressing textile material, characterized by that the textile material is produced using a boron-containing trialkoxysilane of the formula I wherein R1 is a straight-chain or branched alkyl group with up to 6 C atoms, n is an integer from 1 to 5 and R2 is a boron-containing organic residue bonded to the trialkoxysilane via an N atom, smoke-retardant in a sol-gel process is equipped. [2] Fiber-reinforced composite panel according to claim 1, characterized by that the textile material is a textile fabric, in particular a natural fibre fabric. [3] Fiber-reinforced composite panel according to claim 1 or 2, characterized by that the matrix material is a polymer, preferably polypropylene or an epoxy resin. [4] Fiber-reinforced composite panel according to one of the preceding claims, characterized by that R1 is methyl or ethyl. [5] Fiber-reinforced composite panel according to one of the preceding claims, characterized by that n is 2. [6] Fiber-reinforced composite panel according to one of the preceding claims, characterized by that the organic radical derived from boric acid is a radical of the formula -B(OH)2, -B(OR1)2 or a 1,3,2-dioxaborolane of the formula II. [7] Fiber-reinforced composite panel according to one of claims 1 to 5, characterized by that the organic radical R2 derived from boric acid is a 3-aminophenylboronic acid group of formula III. [8] Boron-containing compound with smoke suppressant effect of formulas IV and V: [9] Fiber-reinforced composite panel according to one of claims 1 to 7, characterized bythat the textile material is further treated with a phosphorus-containing organic residue with flame-retardant effect. [10] Fiber-reinforced composite panel according to claim 9, dg, that the phosphorus-containing organic radical is a radical of the formula I'wherein R1 and n are as defined above and R2' is a phosphorus-containing radical. [11] Fiber-reinforced composite panel according to claim 10, characterized in that the phosphorus-containing radical is a group of the formula VI to XIV where R3 is in each case C1-C3-alkyl and Z is in each case O or S. [12] Fiber-reinforced composite panel according to claim 11, characterized in that the group of formula VI to XIV is bonded directly to the trialkoxysilane via a triazole, a triazine or an amine. [13] Fiber-reinforced composite material panel according to one of claims 1 to 7, 9 or 10 with at least 2, preferably at least 3 layers of the textile material pressed with the matrix material.