Bio-based, curable mass for a fiber composite system, curable fiber composite system and fiber composite component

Abstract

The invention relates to a bio-based, curable mass for a fiber composite system, which is suitable for forming a resin matrix for a fiber component in the cured state, characterized in that the curable mass comprises at least one epoxy component which is biogenic and / or has at least a partially biogenic component. Furthermore, the invention relates to a curable fiber composite system and a fiber composite component for a vehicle manufactured using the curable fiber composite system.

Description

The invention relates to a bio-based, curable composition for a fiber composite system, to a curable fiber composite system and to a fiber composite component.Curable compositions for fiber composite systems are already known from the prior art. Fiber composite systems are composite materials which consist essentially of two main components, namely a fiber component and a matrix material. The fiber component is usually designed as a woven, laid scrim or knitted fabric and embedded in the matrix material.Owing to the combination of fiber component and matrix material, fiber composite systems have a high mechanical load-bearing capacity with a low weight at the same time. Furthermore, such composite systems are distinguished by high wear and corrosion resistance. Fiber composite systems are therefore preferably used as components in vehicle construction.A number of plastics are used to produce the matrix material. However, the starting raw materials for the plastics used hitherto are predominantly based on petroleum and thus contribute considerably to the CO 2- impression of the end products produced therefrom. The carbon dioxide released during the production and later disposal of the plastics contributes to the greenhouse effect, which is responsible, among other things, for global climate heating. For this reason, attempts have been made to replace petroleum-based plastics for fiber composite systems by environmentally compatible plastics.The use of environmentally compatible matrix materials in the field of fiber composite systems for vehicles has not yet become established with regard to the required reliability and the high material costs of the components produced therefrom.The object of the invention is thus to provide environmentally compatible matrix materials for use in fiber composite systems based on sustainable raw materials, which are suitable for use in curable compositions for fiber composite systems for vehicle construction.This object is achieved by a bio-based, curable composition for a fiber composite system according to claim 1, a curable fiber composite system according to claim 7 and a fiber composite component according to claim 10.Advantageous embodiments of the inventive composition, of the curable fiber composite system and of the fiber composite component are specified in the dependent claims, which can optionally be combined with one another.According to the invention, the object is achieved by a bio-based, curable composition for a fiber composite system. The composition is suitable for forming a resin matrix for a fiber component in the cured state, wherein the curable composition comprises at least one epoxy component which is biogenic and / or at least partially has a biogenic fraction.The use of an epoxy component which is biogenic and / or at least partially has a biogenic fraction makes it possible to provide bio-based, curable compositions for fiber composite systems which are durable and have a reduced CO 2- footprint during production. This makes it possible to make a substantial contribution to the climate-friendly production of bio-based, curable compositions and of the fiber composite systems produced therefrom.Furthermore, the dependence on fossil starting materials can also be reduced, whereby energy-intensive chemical reactions for producing petroleum-based starting components for the curable compositions can also be avoided. The bio-based, curable compositions proposed here for fiber composite systems are therefore also energy- or resource-saving and thus lasting and environmentally friendly.In principle, the invention is based on the finding that epoxy components which are biogenic and / or at least partially have a biogenic fraction are suitable for use in curable compositions for fiber composite systems without adversely affecting the performance requirements imposed on the curable composition and the fiber composite systems produced therefrom. In view of the high performance requirements imposed on curable compositions and the fiber composite systems produced therefrom, in particular in the field of vehicle construction, this suitability is not a matter of course.Against this background, the inventors have recognized that an epoxy component which is biogenic and / or at least partially has a biogenic fraction can be integrated into a curable composition for a fiber composite system without adversely affecting the properties of the curable composition or of the resin matrix resulting therefrom. Such compositions surprisingly meet the required performance requirements in vehicle construction.A bio-based, curable composition is understood to mean a composition comprising at least one epoxide component, wherein the epoxide component is an epoxide component in the sense of the invention when it is biogenic and / or at least partially has a biogenic fraction.The term "at least partially biogenic" means that the epoxide component has a certain proportion of bio-based carbon.On the other hand, if the epoxy component is biogenic, then the epoxy component has a carbon content that is substantially fully bio-based.The extent to which the epoxy component has a certain proportion of bio-based carbon can be determined in particular on the basis of the ASTM 6866 standard (Standard Test Methods for Determining the Bio-based Content of Solid, Liquid, and Gaseous Samples Using Radiocarbon Analysis; ASTM International). Alternatively, the ISO 16620-2:2019-10 standard can be used to determine the bio-based carbon content of the epoxy component. The ISO 16620-2:2019-10 standard and the ASTM 6866 standard are equivalent to each other.The bio-based carbon content in a sample can be measured using the ASTM 6866 standard. The ASTM D6866 standard distinguishes carbon isotope compositions from present day biomass-based samples from fossil-contributed samples. Samples derived from biomasses have in particular an easily determinable number of carbon isotopes C14in their carbon isotope composition, which differs from other carbon isotope compositions, such as for example in fossil fuels which do not contain a carbon isotope C14.According to a first aspect of the invention, the epoxy component has a bio-based carbon content of at least 20% by weight, preferably of at least 50% by weight, particularly preferably of at least 75% by weight, based on the total content of carbon in the epoxy component.Most preferably, the epoxy component is biogenic and has a bio-based carbon content of 95 to 100 wt %, based on the total content of carbon in the epoxy component.Since the term "biogenic" relates only to the bio-based carbon content, the epoxide component can also be modified with additives which are of inorganic or fossil origin. It is therefore conceivable for the epoxide component to be halogenated or otherwise functionalized, for example.The carbon content in the non-bio-based epoxy component may be from inorganic or fossil sources.Biogenic epoxide components can be obtained in particular from renewable raw materials. The renewable raw materials are advantageously raw materials obtained from biomass. The use of biomass offers the advantage that it is available at will, resource-saving and thus lasting.In particular, an epoxy component can be used in the bio-based, curable composition that has been produced from a biogenic oil that has been at least partially or completely epoxidized.Advantageously, the biogenic oil is selected from the group consisting of dragee head oil, linseed oil, high oleic linseed oil with an oleic acid content of at least 80%, sunflower oil, high oleic sunflower oil, mustard oil, rapeseed oil, fruit kernel oil such as elderberry oil, olive oil, soybean oil and high oleic sunflower oil with an oleic acid content of at least 80% and combinations thereof.Preferred biogenic oils are dragon oil, linseed oil, high oleic linseed oil and mustard oil.The aforementioned biogenic oils can be converted into their epoxidized derivatives by known methods. For example, such oils can be reacted with hydrogen peroxide under the action of formic acid to form the corresponding epoxides.Very particular preference is given to selecting biogenic oils for epoxidation which have an iodine number of 60, preferably of at least 100, the iodine number being a measure of the content of unsaturated compounds (double bonds) in the oil. The iodine number is defined as the amount in grams of iodine that can be added to 100 g of oil. The more double bonds an oil has, the more iodine can be added and the higher the iodine number is then. In this way, the proportion of unsaturated fatty acids in an oil can be determined.Alternatively, an epoxide component can also be used which consists at least partially of biogenic monomers, preferably completely of biogenic monomers. For example, the epoxy component may comprise a mixture of biogenic and petroleum-based monomers. Preferably, the epoxide component comprises exclusively biogenic monomers. The definition of "biogenic" applies to the definition already explained above.In particular, the epoxy component is an epoxy resin.The epoxy resin may be mono- or multifunctional with respect to the epoxy group.Glycidyl-based epoxy resins are preferably used in the bio-based, curable composition.Glycidyl-based epoxy resins can be obtained, for example, by reacting a monomer precursor with a hydroxyl group and an epichlorohydrin. The monomer precursor may be a diol, polyol, phenol or a dicarboxylic acid. Preferably, phenolic compounds such as bisphenol A and novolaks are used as monomer precursors. The monomer precursor and / or the epichlorohydrin may be biogenic. Epichlorohydrin can be prepared from biogenic sources, for example, according to the article by Bruce M. Bell et al: Glycerol as a renewable feed stock for epichlorohydrin production. The GTE process. Clean 36 (8), 2008; page. 657-661.Glycidyl-based epoxy resins which can be used are, for example, diglycidyl ethers of bisphenol F, bisphenol A, or mixtures of such epoxides, and novolaks thereof.The epoxy resin can have an average molecular weight of ≤2000 g / mol.The epoxy resins can have, for example, an epoxy equivalent of 120 to 2000, preferably 150 to 400. The determination can be carried out according to the DIN EN ISO 300 standard.A further aspect of the invention provides that the curable composition comprises at least one biogenic hardener and or one synthetic hardener which is suitable for epoxy curing.In principle, the choice of hardener is not restricted, and any hardener can be used which is suitable for the epoxy curing of an epoxy component which is biogenic and / or at least partially has a biogenic fraction.Biogenic means that the hardener has at least one bio-based carbon content of 20% by weight, at least 50% by weight, at least 75% by weight, based on the total content of carbon in the hardener.If the hardener is completely biogenic, then it has a bio-based carbon content of 95 to 100 wt %, based on the total content of carbon in the hardener.The bio-based carbon content in the hardener can be detected according to ASTM standard 6866.Alternatively, the hardener can be produced from petroleum-based raw materials, whereby the hardener is not of biogenic origin. Such a hardener is also referred to as a synthetic hardener.In principle, a mixture of at least one bio-based and at least one synthetic hardener can also be present in the bio-based, curable composition.In particular, the hardener, regardless of whether it is biogenic or synthetic, can be selected on the basis of anhydrides, amides or amines.As amine, diaminodiphenylmethane or diaminodiphenyl sulfone can be used, for example.As amide, dicyandiamide can be used, for example.A curing agent based on anhydrides is preferably selected from the group consisting of methyltetrahydrophtalic anhydride, hexahydrophtalic anhydride, nadic anhydride and methylhexahydrophtalic anhydride as well as combinations thereof.The curing agent is preferably present in the bio-based curable composition in powder form.According to another aspect of the invention, the curable composition comprises at least one biogenic and / or one synthetic accelerator for epoxy curing.By "biogenic" or "synthetic" is meant the same terms as already explained above. In this respect, reference is made to the above definitions.In principle, the choice of the accelerator is not restricted as long as it is suitable for epoxy curing, in particular for epoxy curing with an epoxy component as described above.Suitable accelerators are, for example, an amine, an alcohol, a metal salt, and combinations thereof.The accelerator is particularly preferably selected from the group consisting of alcohols, phenols, amines, phosphorus compounds, acids, halogenated compounds, mercaptans, UV-sensitive compounds, in particular urones, latent compounds and adducts of amines, and combinations thereof.For example, imidazoles, tert-aminophenols, organophosphines, Lewis bases, acids, such as phosphoric esters, or mixtures thereof can be used as accelerators.For example, 2,4,6-trismethylaminomethylphenol can be used as the accelerator.A further aspect of the invention provides that the curable composition comprises at least one biogenic and / or synthetic additive.The terms "biogenic" and "synthetic" are understood to mean the same terms as have already been explained above.The additive is particularly preferably selected from the group consisting of surfactants, flame retardants, toughness modifiers, elastifying agents, dyes, pigments, fluorescent agents, thixotropic agents, thickeners, stabilizers, antioxidants, plasticizers, fillers, corrosion inhibitors, diluents, catalysts, flow and wetting additives and adhesion promoters, and combinations thereof.As thixotropic agents, for example, silicic acid or hydrogenated or hydroxyalkylated castor oil can be used.Fillers which can be used are, in particular, ligninsulfonates, seed or shell flours from fruits, for example coconut shell flour, peanut shell flour, olive seed flour, vegetable coal or mixtures thereof. Furthermore, fillers such as corundum, quartz sand or quartz powder can also be added.In a further aspect of the invention, the bio-based, curable composition comprises the following components, in each case based on the total weight of components (A) to (D): (A) 20 to 100% by weight, preferably 30 to 95% by weight, of an epoxide component which is biogenic and / or at least partially has a biogenic fraction, wherein the epoxide component has a bio-based carbon content of at least 20% by weight, preferably at least 50% by weight, particularly preferably at least 75% by weight, very particularly preferably 100% by weight, based on the total content of carbon in the epoxide component; (B) optionally 3 to 60% by weight, preferably 10 to 45% by weight, of at least one hardener based on amines, amides or anhydrides, wherein the hardener can be biogenic or synthetic; (C) optionally 0.1 to 25% by weight, preferably 0.01 to 10% by weight, of at least one biogenic and / or a synthetic accelerator for epoxy curing, wherein the accelerator is selected from the group consisting of amines, alcohols and metal salts, and combinations thereof; (D) optionally further biogenic and / or synthetic additives from the group consisting of surfactants, flame retardants, toughness modifiers, elastifying agents, dyes, pigments, fluorescent agents, thixotropic agents, thickeners, stabilizers, antioxidants, plasticizers, fillers, flame retardants, corrosion inhibitors, inert diluents, catalysts, flow and wetting additives and adhesion promoters, and combinations thereof.In principle, the bio-based, curable composition may have a composition comprising only the epoxy component (A). In this case, preferably, at least one accelerator according to component (C) can additionally be added. The addition of a curing agent according to component (B) can be dispensed with in this composition.In an alternative embodiment, component (A) is preferably present alongside component (B). The composition is particularly preferably formed from components (A) and (B). Optionally, component (C) and / or (D) may also be added.The invention further relates to a curable fiber composite system comprising a fiber component and a curable composition according to one of the above-mentioned aspects, wherein the curable composition forms a resin matrix for the fiber component, in which the fiber component is present as a laid scrim, a knitted fabric, a woven fabric or a combination thereof.A woven fabric is understood to mean a weaving of fibers, wherein two fiber directions are present (warp and weft) which are aligned at an angle, in particular a right angle, to one another. In principle, the crossing of the fibers can be carried out with different bonds. For example, canvas, twill or atlas can be used as binding types.A knitted fabric is a knitted fabric produced from yarn systems by stitch formation on a knitting machine, wherein one loop each is looped into another loop of a yarn, so that a stitch connected to one another is formed.The term "laid scrim" refers to a sheet material which consists of one or more layers of parallel extending, elongated filaments. At the crossing points, the threads can be fastened to one another chemically, for example by means of binders, thermally, for example by heat supply, or mechanically, for example with a warp stitch. Monoaxially, unidirectional, biaxially or multiaxial laid scrims may be used.In principle, the fiber component can also be present as a laid scrim in which the fibers are not interwoven with one another, but rather in each case only one fiber direction is present and the fibers are oriented parallel in one direction, wherein the fibers can be supported via an adhesive thread lattice or a sewing thread.The fiber component is preferably present as a fiber selected from the group consisting of glass fibers, aramid fibers, natural fibers, and carbon fibers, as well as combinations thereof. Natural fibers which can be used are, in particular, flax, jute or cotton fibers.One aspect of the invention provides that the fiber component is embedded in the curable composition, impregnated with the curable composition and / or coated with the curable composition.Particularly preferably, the fiber composite system is a prepreg material.It is particularly preferably a prepreg material, wherein the fiber component is coated on one side with the curable composition.According to a further aspect of the invention, the fiber composite system comprises the following components, in each case based on the total weight of the fiber composite system: (A) 22 to 75% by weight of the curable composition; and (B) 25 to 78% by weight of the fiber component.Furthermore, the invention relates to a fiber composite component for a vehicle produced using the curable fiber composite system according to one of the aspects mentioned above.The fiber composite component can be, for example, a body component.In particular, such fiber composite components for motor vehicles can be produced by means of autoclaves, pressing technology or prepreg winding methods.ExamplesThe invention is explained below with reference to examples, which however should not be interpreted in a limiting sense.Example 1:A curable composition for a fiber composite system is provided, which composition comprises the following components: 65% by weight epoxy novolac, 25% by weight cardanol-based novolak, 9% by weight dicyandiamide and 1% by weight dimethylurea, in each case based on the total weight of the components.Example 2:A curable composition for a fiber composite system is provided, which composition has the following components: 67% by weight of biodiglycod ether of bisphenol A and 33% by weight of cardanol-based amine having an amine number of 495, in each case based on the total weight of components (A) to (D).Example 3: Example 3:The curable composition according to Example 1 provides a curable fiber composite system which, in addition to the curable composition according to Example 1, comprises a fiber component in a proportion of 100 g / m 2. The curable composition is present in a proportion of 45 g / m 2 in this case.The fiber composite system is obtained by means of an autoclave synthesis.Example 4: Example 4:The curable composition according to Example 2 provides a curable fiber composite system which, in addition to the curable composition according to Example 2, comprises a fiber component in a proportion of 100 g / m 2. The curable composition is present in a proportion of 30 g / m 2 in this case.The fiber composite system is obtained by resin transfer moulding.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Cited Non-Patent LiteratureISO 16620-2:2019-10

[0017] DIN EN ISO 300

[0036]

Claims

Bio-based, curable composition for a fiber composite system, which is suitable for forming a resin matrix for a fiber component in the cured state, characterized in that the curable composition comprises at least one epoxy component which is biogenic and / or at least partially has a biogenic fraction.Curable composition according to Claim 1, characterized in that the epoxy component has a bio-based carbon content of at least 20% by weight, preferably of at least 50% by weight, more preferably of at least 75% by weight, very preferably of 95 to 100% by weight, based on the total content of carbon in the epoxy component.Curable composition according to Claim 1 or 2, characterized in that the curable composition comprises at least one biogenic and / or one synthetic hardener which is suitable for epoxy curing, preferably a hardener based on anhydrides or amines.Curable composition according to any of the preceding claims, characterized in that the curable composition comprises at least one biogenic and / or a synthetic accelerator for epoxy curing, wherein the accelerator is selected from the group consisting of amines, alcohols and metal salts and combinations thereof.Curable composition according to any of the preceding claims, characterized in that the curable composition comprises at least one biogenic and / or a synthetic additive, the additive preferably being selected from the group consisting of surfactants, flame retardants, toughness modifiers, elastifying agents, dyes, pigments, fluorescent agents, thixotropic agents, thickeners, stabilizers, antioxidants, plasticizers, fillers, corrosion inhibitors, diluents, catalysts, flow and wetting additives and adhesion promoters, and combinations thereof.Curable composition according to any of the preceding claims, characterized in that the curable composition comprises the following components, in each case based on the total weight of components (A) to (D): (A) 20 to 100% by weight, preferably 50 to 95% by weight, of an epoxide component which is biogenic and / or at least partially has a biogenic fraction, wherein the epoxide component has a bio-based carbon content of at least 20% by weight, preferably of at least 50% by weight, particularly preferably of at least 75% by weight, very particularly preferably of 95 to 100% by weight, based on the total content of carbon in the epoxide component; (B) optionally 3 to 60% by weight, preferably 10 to 45% by weight, of at least one hardener based on amines, amides or anhydrides, wherein the hardener can be biogenic or synthetic; (C) optionally 0.1 to 25% by weight, preferably 0.01 to 10% by weight, of at least one biogenic and / or a synthetic accelerator for epoxy curing, wherein the accelerator is selected from the group consisting of amines, alcohols and metal salts and combinations thereof; and (D) optionally further biogenic and / or synthetic additives from the group consisting of surfactants, flame retardants, toughness modifiers, elastifiers, dyes, pigments, fluorescent agents, thixotropic agents, thickeners, stabilizers, antioxidants, plasticizers, fillers, flame retardants, corrosion inhibitors, inert diluents, catalysts, flow and wetting additives and adhesion promoters and combinations thereof;Curable fibre composite system comprising a fibre component and a curable composition according to any one of the preceding claims, wherein the curable composition forms a resin matrix for the fibre component, in which the fibre component is present as a laid scrim, a knitted fabric, a woven fabric or a combination thereof, wherein the fibre component preferably comprises at least one fibre selected from the group consisting of glass fibres, aramid fibres, natural fibres and carbon fibres and combinations thereof.Curable fiber composite system according to Claim 7, characterized in that the fiber component is embedded in the curable composition, impregnated with the curable composition and / or coated with the curable composition, more preferably in that the fiber component is coated on one side with the curable composition.Curable fiber composite system according to Claim 7 or 8, characterized in that the fiber composite system comprises the following components, in each case based on the total weight of the fiber composite system: (A) 22 - 75% by weight of the curable composition; and (B) 25 - 78% by weight of the fiber component.A fiber composite component for a vehicle produced using the curable fiber composite system according to any one of claims 7 to 9.