Resin formulation for producing a thermosetting plastic material, corresponding thermosetting plastic material and composite material

Abstract

The invention relates to a resin formulation for producing a thermosetting plastic material. Described is also a thermosetting plastic material. Furthermore described is the use of a resin formulation according to the invention and / or of a thermosetting plastic material according to the invention. The invention further relates to a composite material comprising a thermosetting plastic material according to the invention as the polymer matrix.

Description

[0001] Resin formulation for the production of a thermosetting plastic, corresponding thermosetting plastic and composite material

[0002] The present invention relates to a resin formulation for producing a thermosetting plastic. The invention further relates to a thermosetting plastic. The invention also relates to the use of a resin formulation according to the invention and / or a thermosetting plastic according to the invention. The invention also relates to a composite material comprising a thermosetting plastic according to the invention as the polymer matrix.

[0003] The invention is defined in the appended claims. Preferred aspects of the present invention will become apparent from the following description, including the examples. To the extent that certain embodiments are designated as preferred for one aspect of the invention, the corresponding statements also apply to the other aspects of the present invention, mutatis mutandis. Preferred individual features of aspects of the invention (as defined in the claims and / or disclosed in the description) can be combined with one another and are preferably combined with one another, unless the present text clearly indicates otherwise to the person skilled in the art. Fiber-reinforced plastics (FRP) are high-performance composite materials consisting of fibers and a surrounding polymer matrix.Due to their low weight, they are used for lightweight constructions and have replaced heavy metals in recent decades, particularly in the transportation sector. Among other things, the weight reduction has led to a significant reduction in fuel consumption. Many polymers for FRPs are currently obtained from fossil raw materials. Not only are these a limited resource, their processing also requires large amounts of energy and leads to high CO2 emissions. Furthermore, cross-linked polymer systems are primarily used for FRP production. These materials, composed of reactive systems, are extremely stable and durable, but make recycling or easy decomposition or composting of these polymers, and thus also of the FRPs produced from them, virtually impossible. For this reason, FRPs made from petroleum-based polymers have a poor environmental impact.

[0004] Due to climate change, adjustments in material selection are necessary to make FRP production more sustainable. The use of easily degradable or compostable, and preferably bio-based, polymers can enable recycling or composting of FRPs, thereby achieving closed material cycles and helping to reduce the consumption of limited resources.

[0005] In recent decades, research has been conducted into technologies that enable the recycling of cross-linked polymers. For example, cross-linked polymer systems based on unsaturated polyester resins (UP resins) can now be broken down into shorter chains through thermal or chemical treatments, or the respective monomers can be recycled. UP resins, in combination with glass fibers, are widely used in certain sectors such as automotive and shipbuilding due to their good price / performance ratio.

[0006] In addition, polymer systems made from renewable raw materials are being made usable for industrial applications. For thermosets, cross-linked polymers, bio-based UP resins based on itaconic acid, isosorbides and vegetable oils are described in the literature, some of which are slightly biodegradable. However, this biodegradability usually requires long-term storage in industrial compost. In the field of thermoplastics, which are distinguished from cross-linked systems by other processing and recycling options, bio-based alternatives are receiving increasing attention. One representative of this class is polylactide (PLA), which is known, for example, in the packaging industry as a bio-based alternative to petroleum-based polypropylene. PLA-based polymers are bio-based and, under certain conditions, simultaneously biodegradable (e.g., microbially degradable at a temperature of 52 °C (thermophilic) or 37 °C (mesophilic)).compostable (e.g., through industrial composting). A major challenge is the provision of resin formulations for the production of thermosets that

[0007] (i) have the good mechanical properties (such as high stiffness and high tensile strength) required for their use as, for example, the polymer matrix of FRP for lightweight constructions, and at the same time

[0008] (ii) are biodegradable or capable of decomposing within a foreseeable period of time under composting conditions, and

[0009] (iii) preferably also have good and easy processability (particularly in their handling for use as a polymer matrix for FRPs).

[0010] The resin formulations known to date and the thermoset systems produced therefrom often exhibit disadvantages in at least one of the three property areas mentioned above. For example, the resin compositions disclosed in document US 2008 / 0004369 A1 and the thermosets produced therefrom exhibit significant disadvantages with regard to their processability and mechanical properties, according to our own studies, which are explained in more detail below. Other resin formulations, such as the itaconic acid-based polyester resin STRUKTOL® VP3830 from Schill und Seilacher Struktol GmbH, are neither biodegradable nor compostable.

[0011] Against this background, the primary object of the present invention was to provide a resin formulation for producing a thermoset which meets the above-mentioned criteria; ie, it has advantageous mechanical properties of a thermoset system, which in particular enable its use for FRPs, but at the same time is biodegradable or compostable and is preferably also characterized by easy processability.

[0012] A further object of the present invention was to provide a corresponding thermosetting plastic with the above-mentioned advantageous combination of properties.

[0013] The present invention should also make it possible to use the resin formulation to be provided and / or the thermosetting plastic to be specified for typical applications, such as, for example, as an adhesive or as a matrix resin for a composite material (e.g., in the automotive industry).

[0014] A further task was to specify a composite material comprising the specified thermosetting plastic as a polymer matrix.

[0015] Further objects arise from the following description and the patent claims.

[0016] The primary object of the present invention can be achieved by a resin formulation for producing a thermosetting plastic, a) comprising or consisting of

[0017] - at least one resin obtainable by reaction (modification) of a biodegradable and / or compostable polymer with one or more modifiers, wherein the one or more modifiers are selected from the group consisting of alcohols, ketones, aldehydes, imines, acrylonitriles, peroxides, thiocarboxylic acids, sulfonic acids, thioaldehydes, thioketones, azides, thiocyanates, furans, itaconic acid and derivatives of itaconic acid, and

[0018] - at least one hardener and / or in the case of saturated or unsaturated polyester resin as the at least one resin, at least one copolymerizable monomer (reactive diluent), wherein the at least one copolymerizable monomer in the case of polylactide modified with itaconic acid and / or itaconic acid derivatives as the saturated or unsaturated polyester resin is selected from the group consisting of styrene, dimethyl itaconate, hydroxymethyl acrylate, vinyl levulinate, vinylphenol, isoprene, cinnamic acid and derivatives thereof, and / or b) wherein the resin formulation is suitable for producing a thermosetting plastic which is decomposable within 45 days when using composting conditions according to DIN EN ISO 20200:2015, preferably is completely decomposable within 45 days when using composting conditions according to DIN EN ISO 20200:2015,particularly preferably completely decomposable within 10 days when composting conditions are applied in accordance with DIN EN ISO 20200:2015, and which has one or more of the following mechanical properties, determined in accordance with DIN EN ISO 527-4:

[0019] Young's modulus of 1700 Pa or more, preferably 2,000 MPa or more, particularly preferably 3,000 MPa or more;

[0020] Tensile strength of 20 MPa or more, preferably 25 MPa or more, particularly preferably 40 MPa or more;

[0021] Elongation at break of 1.5% or more, preferably 1.9% or more, particularly preferably 4.1% or more.

[0022] According to the invention, the stated primary object is achieved by the aforementioned resin formulation, wherein the biodegradable and / or compostable polymer is selected from the group consisting of polylactides (PLA), polycaprolactones (PCL), chitin, chitosan, polyhydroxy fatty acids (PHF, also referred to as polyhydroxyalkanoates or PHA), polyhydroxyacetic acid, starch, cellulose, lignin and derivatives thereof, and the one or more modifiers are selected from the group consisting of itaconic acid, hydroxymethylfurfural (HMF) and derivatives thereof.

[0023] Surprisingly, it has been shown that resins obtainable by reacting or modifying a biodegradable and / or compostable polymer with one or more of the aforementioned modifiers, in combination with a hardener and / or copolymerizable monomer (reactive diluent), can be used to cure thermosets that possess the desired mechanical properties, such as high rigidity and high tensile strength, while also being biodegradable or compostable. Furthermore, the corresponding resin formulations can be processed under mild reaction conditions—such as comparatively low temperatures—which allow for easy handling of the resin formulations.The plastics that can be produced from resin formulations according to the invention thus combine the material properties of a classic thermoset and are characterized by durability as well as thermal and chemical stability throughout their life cycle, but at the same time also enable recycling due to their ability to be biodegradable or compostable.

[0024] The resin formulations according to the invention are not yet cured, or at least not yet fully cured. The final curing, which leads to the formation of a thermosetting plastic, can occur with or without the addition of thermal energy (i.e., with or without heating). The resin formulations according to the invention can thus be hot-curing and / or cold-curing.

[0025] For the purposes of the present invention, the term “biodegradable polymer” refers to polymers that can be decomposed by microorganisms such as bacteria (i.e. are biodegradable).

[0026] A polymer is "compostable" within the meaning of the present invention if it can be significantly, preferably completely, decomposed under composting conditions within a specified, foreseeable period of time. For the purposes of the present invention, these are preferably compostable polymers that are decomposable within 45 days under composting conditions in accordance with DIN EN ISO 20200:2015, preferably (under composting conditions in accordance with DIN EN ISO 20200:2015) are completely decomposable within 45 days, and particularly preferably (under composting conditions in accordance with DIN EN ISO 20200:2015) are completely decomposable within 10 days.

[0027] The term "decomposable" in the context of the present invention refers to the noticeable, visually perceptible separation of individual components from a polymer or thermoset plastic. A polymer or thermoset plastic is considered "completely" decomposed in the context of the present invention if the degree of decomposition of the polymer or thermoset plastic, determined according to DIN EN ISO 20200:2015, is 100% (i.e., if no plastic material remains in the sieve even when sieving with a 2 mm sieve). As defined above and in the claims, the at least one resin of a resin formulation according to the invention is obtainable by reacting or modifying a biodegradable and / or compostable polymer with one or more of the aforementioned modifiers.The at least one resin of a resin formulation according to the invention therefore differs from those resins for the production of which a modifier is only added to the reactant or the monomer component for the production of the resin before production / polymerization of the resin.

[0028] The reaction or modification of the biodegradable and / or compostable pen with one or more of the modifiers mentioned represents an essential aspect for achieving the advantageous properties of the thermosetting plastic that can be produced from the resin formulation according to the invention, since the reaction or modification contributes substantially to the thermosetting plastic that can be produced from the resin formulation according to the invention having, in addition to its ability to be biodegradable or compostable, also the advantageous mechanical properties explained above.

[0029] The result of the reaction of the biodegradable and / or compostable polymer with one or more of the modifiers mentioned above and in the claims is always, according to the above wording and the wording of the claims, a resin (i.e., a reactive intermediate for the production of thermosetting plastics), which, in combination with a hardener and / or copolymerizable monomer, can be cured to form a thermosetting plastic. The ultimate functionality of the resin, which enables curing, can either be introduced into the compound by the modifier (for example, in the case of the choice of polylactide as the biodegradable and compostable polymer and itaconic acid as the modifier) ​​or already be present in the selected biodegradable and / or compostable polymer to be modified and merely retained during the reaction with the modifier.

[0030] The term "polymer" is to be understood broadly within the meaning of the present invention and includes both polymers with low and high degrees of polymerization, as long as they are biodegradable and / or compostable. Oligomers are understood as polymers within the meaning of the present invention and are accordingly encompassed by the term "polymer" within the meaning of the present invention. Examples of resin classes preferred within the scope of the present invention are polyester resins, preferably saturated or unsaturated polyester resins, epoxy resins, furan resins, phenolic resins, and vinyl esters.

[0031] The selection of the at least one hardener and / or - in the case of saturated or unsaturated polyester resin as the at least one resin - the at least one copolymerizable monomer is determined by the choice of resin(s) for the respective resin formulation and the suitability of the hardener / copolymerizable monomer for curing the resin(s); and vice versa. In principle, all hardeners or copolymerizable monomers suitable for curing the respective resin are suitable. The respective resins as well as hardeners or copolymerizable monomers can each have more than one type of functional group, which means that certain hardeners can also be suitable for curing different types of resins.

[0032] Below are some examples of generally preferred combinations of modifying agent and copolymerizable monomer (reactive diluent) used to produce the at least one resin of the resin formulation:

[0033] As is clear from the above explanations and the wording of the claims, a resin formulation according to the invention can comprise more than one resin as well as more than one curing agent or more than one copolymerizable monomer.

[0034] It has also been shown that by reacting the above biodegradable and / or compostable polymers with one or more of the above modifiers, resins for resin formulations for the production of thermosetting plastics with particularly advantageous properties with regard to biodegradability or compostability and, at the same time, high mechanical strength are accessible.

[0035] Based on the preferred modifier hydroxymethylfurfural (HMF), it also becomes clear that in addition to the resins and hardeners of resin formulations according to the invention, the modifiers for producing the resins for the resin formulations can of course also have more than one type of functional group.

[0036] In those cases in which the at least one resin of the resin formulation according to the invention is a polylactide modified with itaconic acid and / or itaconic acid derivatives, the selective selection of the at least one copolymerizable monomer or reactive diluent from the copolymerizable monomers specified above and in the claims has proven essential to achieving the desired advantageous properties. The choice of a suitable copolymerizable monomer is by no means trivial. Particularly surprising and contrary to the intention of the skilled person is the fact that a resin formulation for the production of thermosetting plastics can be obtained from polylactide modified with itaconic acid and / or itaconic acid derivatives using styrene as the copolymerizable monomer or reactive diluent, which exhibits excellent biodegradability and compostability.Since the skilled person would have expected to obtain a thermosetting plastic that was not biodegradable or compostable or, if at all, only poorly biodegradable, especially when using styrene as a copolymerizable monomer or reactive diluent, the skilled person would have deliberately refrained from using styrene in particular and would not have considered its use in the search for a solution to the problem posed.

[0037] Furthermore, it has been found that a compatibility of (i) a degree of composting acceptable from an ecological point of view and (ii) the necessary mechanical property window of a thermosetting plastic, in particular for use as a polymer matrix in FRPs, can be advantageously achieved by a resin formulation which, as stated above and in the claims, is suitable for producing a thermosetting plastic which is decomposable within 45 days using composting conditions according to DIN EN ISO 20200:2015 and at the same time has an E-modulus of 1700 Pa or more and / or a tensile strength of 20 MPa or more and / or an elongation at break of 1.5% or more.The Young's modulus (also known as the elastic modulus) provides information about the resistance that a material offers to elastic deformation and can therefore be considered a measure of the stiffness of a material (the higher the Young's modulus, the higher the stiffness of the material).

[0038] The fact that the properties of compostability or biodegradability and, at the same time, high mechanical strength of a thermosetting plastic can be combined by specifically adjusting and coordinating the aforementioned properties was by no means self-evident and surprising insofar as the properties of compostability or biodegradability and high mechanical strength are actually contradictory (a high mechanical strength of a material basically results from strong binding forces within the material, which in turn speak against good degradability or compostability).

[0039] A resin formulation according to the invention is preferred for producing a thermosetting plastic which meets the requirements for certification according to one or more of the following standards:

[0040] - DIN EN 13432,

[0041] - NF T51-800:2015,

[0042] - AS 5810 (2010)

[0043] - prEN 17427 (2020),

[0044] - DIN EN 14995,

[0045] - ISO 17088,

[0046] - ISO 18606,

[0047] - AS 4736.

[0048] Also preferred is a resin formulation according to the invention, wherein the resin formulation is produced partially or entirely from renewable raw materials (i.e., is bio-based). Thus, within the scope of the present invention, it is possible and preferred to select compounds from renewable raw materials for one or more of the components of the resin formulation according to the invention. For example, polylactide modified with itaconic acid (also referred to as PLA-ITA) can be used as the at least one resin of the resin formulation according to the invention, and / or dimethyl itaconate can be used as the copolymerizable monomer.

[0049] A resin formulation according to the invention is preferably suitable for producing a thermosetting plastic which (in addition to or as an alternative to its biodegradability or grainability) can be broken down into its reactants and / or monomeric components. Breaking down the thermosetting plastic into its reactants or monomeric components has the advantage that, after the breakdown, the corresponding reactants or monomeric components are directly available again as starting materials for the production of further resins, resin formulations, or other valuable chemicals, and the thermosetting plastic is thus amenable to chemical recycling.

[0050] A resin formulation according to the invention is preferred wherein the modifier is itaconic acid.

[0051] A resin formulation according to the invention is preferred, wherein the at least one resin is a saturated or unsaturated polyester resin (UP resin) and / or an epoxy resin, preferably an unsaturated polyester resin.

[0052] Also preferred is a resin formulation according to the invention, wherein the chain length of the at least one resin is in the range from 500 g / mol to 50,000 g / mol, preferably in the range from 500 g / mol to 800 g / mol.

[0053] Also preferred is a resin formulation according to the invention, wherein the proportion of hardeners and / or copolymerizable monomers (reactive diluents) in the resin formulation is 1 wt.% to 99 wt.%, preferably 10 wt.% to 50 wt.%, particularly preferably 10 wt.% to 30 wt.%, based on the total mass of the resin formulation, and / or the ratio of the total mass of hardeners and / or copolymerizable monomers (reactive diluents) to the total mass of resins in the resin formulation is 2:1. By selecting the aforementioned resin classes or by setting the aforementioned preferred chain lengths and quantitative ratios, resin formulations for producing thermosetting plastics with particularly advantageous properties with regard to biodegradability or compostability and simultaneous mechanical strength can be achieved.

[0054] In general, a higher proportion of hardeners and / or copolymerizable monomers (reactive diluents) results in stronger crosslinking. Reducing the proportion of hardeners and / or copolymerizable monomers (reactive diluents) can generally reduce the brittleness of the thermoset plastic produced from the resin formulation. Furthermore, a higher resin proportion generally has a positive effect on the biodegradability or compostability of the thermoset plastic produced from the resin formulation. The preferred ratios mentioned above make it possible to produce thermoset plastics that exhibit both particularly advantageous biodegradability or compostability and sufficiently high mechanical strength.

[0055] A resin formulation according to the invention is preferred, wherein the at least one resin is a polylactide modified with itaconic acid and / or itaconic acid derivatives and / or the at least one copolymerizable monomer is styrene.

[0056] Particularly preferred is a resin formulation according to the invention, wherein the at least one resin is a polylactide modified with itaconic acid and / or itaconic acid derivatives and the at least one copolymerizable monomer is styrene.

[0057] In addition to the fact that resin formulations according to the invention comprising polylactide modified with itaconic acid and / or itaconic acid derivatives as the resin and styrene as the copolymerizable monomer surprisingly lead to thermosetting plastics with particularly outstanding properties with regard to biodegradability or compostability and mechanical strength, their further advantage lies in the large-scale availability of these components or the starting materials for their production. For example, around 15,000 tonnes of itaconic acid are produced from molasses and 210,000 tonnes of polylactide from corn starch are produced annually. Preference is given to a resin formulation according to the invention additionally comprising one or more catalysts or catalyst systems, preferably selected from the group consisting of tin(II) 2-ethylhexanoate, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and citric acid, and / or one or more initiators, preferably thermal initiators, particularly preferably selected from the group consisting of methyl ethyl ketone peroxide (MEKP), N,N-azobisisobutyronitrile (AIBN) and dibenzoyl peroxide (BPO), and / or one or more accelerators, preferably selected from the group consisting of cobalt compounds and amine compounds, and / or one or more inhibitors, preferably selected from the group consisting of phenols, quinones and their derivatives, and / or one or more plasticizers, preferably selected from the group consisting of glycerol, epoxidized soybean oil, acetyltributyl citrate, chloroparaffins and phthalic acid esters, and / or one or more impact modifiers, preferably selected from the group consisting of rubber and styrene-butadiene block copolymers.

[0058] The catalysts mentioned above as preferred are used, for example, to produce the biodegradable and / or compostable polymer and are therefore often also included in the subsequent resin formulation.

[0059] The addition of initiators and / or accelerators and / or inhibitors serves, among other things, to influence the pot life of the resin formulation, with long pot lives being preferred. The pot life of the resin formulation can be influenced by both the type and amount of initiators, accelerators, and / or inhibitors.

[0060] More preferably, one or more of the additional components, catalysts or catalyst systems, initiators, accelerators, inhibitors, plasticizers and impact modifiers are made from renewable raw materials (i.e., bio-based).

[0061] A resin formulation according to the invention is preferred, wherein the resin formulation is single-component or multi-component, preferably two-component, wherein resins and hardeners or copolymerizable monomers are preferably present separately from one another in different components. The presence of resins and hardeners or copolymerizable monomers in different components is particularly preferred for cold-curing resin formulations.

[0062] In the case of multi-component resin formulations, the individual components can be mixed thoroughly for use, for example, by hand or with commercially available mixing equipment. In the case of multi-component resin formulations, the individual components are preferably mixed together shortly before the thermoset plastic is produced. In some cases, the production of the thermoset plastic is initiated by mixing the individual components of the multi-component resin formulation.

[0063] Also preferred is a resin formulation according to the invention, wherein the resin formulation is present as a (viscous) liquid at room temperature (25 °C) and atmospheric pressure (1.013 25 bar) and / or has a pot life of more than 10 minutes, preferably more than 30 minutes, particularly preferably more than 60 minutes.

[0064] As already mentioned above, the present invention aims to achieve a resin formulation that is preferably characterized by easy processability. Ease of processability is achieved in particular by the presence of the resin formulation in liquid or low-viscosity form at room temperature and atmospheric pressure. The resin formulations according to the invention differ from resin formulations known from the prior art in that it is easily possible to obtain a resin formulation that is liquid (low-viscosity) at room temperature.

[0065] For example, the presence of the resin formulation as a (viscous) liquid at room temperature allows it to be processed using methods commonly used in the fiber-reinforced plastics (FRP) sector, such as hand lay-up or compression molding. Furthermore, the presence of the resin formulation as a (viscous) liquid at room temperature can avoid the energy or heat input otherwise required to liquefy the resin formulation prior to processing.

[0066] The presence of the resin formulation according to the invention as a (viscous) liquid at room temperature and atmospheric pressure is particularly preferred for one-component resin formulations.

[0067] In addition, the above-mentioned preferably long pot lives can usually be achieved for resin formulations according to the invention compared to resin formulations known from the prior art, whereby a significantly longer time window for processing is usually available for resin formulations according to the invention compared to resin formulations known from the prior art.

[0068] Also preferred is a resin formulation according to the invention, wherein the temperature required for mixing the at least one resin with the at least one curing agent and / or the at least one copolymerizable monomer is less than 100 °C, preferably less than 90 °C, particularly preferably not more than 80 °C.

[0069] "Temperature required for mixing [...]" in the context of the present invention means that the viscosity of at least one of the components to be mixed is too high below this temperature to allow homogeneous mixing of resin and hardener or copolymerizable monomer. The possibility of using the lowest possible temperature for mixing resin and hardener or copolymerizable monomer is advantageous because it reduces, in particular, the evaporation of the component with a higher vapor pressure or lower boiling point, thus enabling a more precise adjustment of the desired ratio between the components and reducing the occurrence of any harmful vapors.

[0070] Also preferred is a resin formulation according to the invention wherein the viscosity required for mixing the at least one resin with the at least one curing agent and / or the at least one copolymerizable monomer is 1 Pa*s. The viscosity is determined using a rheological test. This can be isothermal or temperature-dependent. Usually, the temperature-dependent test is performed first, followed by the isothermal test.

[0071] The invention also relates to a thermosetting plastic, a) obtainable by curing, preferably thermal curing, of a resin formulation according to the invention or preferably according to the invention (as defined above and in the claims) and / or b) wherein the thermosetting plastic is decomposable within 45 days, preferably completely decomposable within 45 days, particularly preferably completely decomposable within 10 days, using composting conditions according to DIN EN ISO 20200:2015 and has one or more of the following mechanical properties, determined according to DIN EN ISO 527-4:

[0072] Young's modulus of 1700 MPa or more, preferably 2000 MPa or more, particularly preferably 3000 MPa or more;

[0073] Tensile strength of 20 MPa or more, preferably 25 MPa or more, particularly preferably 40 MPa or more;

[0074] Elongation at break of 1.5% or more, preferably 1.9% or more, particularly preferably 4.1% or more.

[0075] With regard to the advantages and effects associated with such a thermosetting plastic according to the invention or preferably according to the invention, reference is made to the above statements on resin formulations according to the invention and preferably according to the invention, which apply mutatis mutandis to thermosetting plastics according to the invention.

[0076] The invention also relates to the use of a resin formulation according to the invention or preferably according to the invention (as defined above and in the claims) and / or a thermosetting plastic according to the invention (as defined above and in the claims), as a plastic and / or as an adhesive and / or as a matrix resin for a composite material, preferably for a fiber-reinforced plastic and / or in one or more of the following areas:

[0077] automotive industry,

[0078] aerospace,

[0079] Construction of rail vehicles,

[0080] Shipbuilding,

[0081] Furniture construction and exhibition stand construction.

[0082] In particular, resin formulations according to the invention or thermosetting plastics according to the invention are suitable for the production of pipes and / or tanks for the transport and storage of molecular hydrogen (H2).

[0083] Due to the combination of high mechanical strength and effective biodegradability or compostability, resin formulations according to the invention or thermosetting plastics according to the invention are particularly suitable for products that are used only once and yet must withstand high mechanical loads during their service life.

[0084] The invention also relates to a composite material, preferably a fiber-reinforced plastic, comprising a thermosetting plastic according to the invention (as defined above and in the claims) as a polymer matrix. As already explained above, the thermosetting plastics according to the invention are particularly suitable and interesting as a polymer matrix for corresponding composite materials due to their exceptional material properties.

[0085] The invention is explained in more detail below using examples and the accompanying figures. The examples provided below are intended to describe and explain the invention in more detail without limiting its scope.

[0086] They show:

[0087] Fig. 1 to Fig. 3 Comparison of the modulus of elasticity of the tensile strength and the elongation at break of a non-inventive fiber composite plastic produced using the commercially available UP resin VP3830 from Schill and Seilacher Struktol GmbH (designated with the sample number “1”) and a fiber composite plastic according to the invention produced using a resin formulation according to the invention comprising itaconic acid-modified polylactide as resin and styrene as copolymerizable monomer (designated with the sample number “3”).

[0088] Fig. 4 Mechanical properties of thermoset plastics obtained by curing resin formulations comprising either (i) itaconic acid modified polylactide as resin (referred to as “PLA-ITA” in Fig. 4) or (ii) the commercially available UP resin VP3830 from Schill and Seilacher Struktol GmbH (referred to as “Struktol” in Fig. 4) and a mixture of styrene and dimethyl itaconate as copolymerizable monomers.

[0089] Fig. 5 to Fig. 7 Comparison of the modulus of elasticity of the tensile strength and the elongation at break of a thermosetting plastic, produced from a (non-inventive) resin formulation comprising the commercially available UP resin VP3830 from Schill und Seilacher Struktol GmbH as the resin and styrene as the copolymerizable monomer (designated with sample number "1"); a thermosetting plastic, produced from a (inventive) resin formulation comprising itaconic acid-modified polylactide as the resin and styrene as the copolymerizable monomer (designated with sample number "3"); and a thermosetting plastic, produced from a (non-inventive) resin formulation comprising a resin obtained from the polymerization of L-lactic acid and itaconic acid and styrene as the copolymerizable monomer (designated with sample number "5"). Materials used:

[0090] The materials used for the experiments described here are specified in more detail in the table below.

[0091] Example 1: Preparation of a resin formulation comprising itaconic acid-modified polylactide as resin and styrene as copolymerizable monomer (according to the invention). 240 g of lactide were melted at approximately 100°C, and 42.23 g of propylene glycol were added with stirring. Once a homogeneous liquid was obtained, 1.2 g of tin(II) 2-ethylhexanoate were slowly added dropwise with vigorous stirring. The reaction solution was then stirred for 1 h at 120°C and then for 3 h at 150°C. 280 g of the resulting polylactide (PLA) were dried at 80°C with stirring under an oil pump vacuum. Subsequently, the vacuum was replaced with a protective gas atmosphere, and 193 mL of toluene, 107.58 g of itaconic acid, 193.2 mg of p-methoxyphenol, and 1.94 g of p-toluenesulfonic acid were added successively. The temperature of the reaction mixture was gradually increased from 80 °C to 180 °C within one hour, and this temperature was maintained for a further 20 h.The resulting water was distilled off and collected in a suitable apparatus; it served as an indicator of the reaction progress. As soon as no more water was formed, the reaction was complete. The toluene was then removed using a rotary evaporator at 80 °C.

[0092] The product was dried at 80 °C for 18 hours in a vacuum oven and then for a further 2 hours under stirring with a KPG stirrer in an oil pump vacuum. A protective gas atmosphere was then introduced, and the heat source was removed. A proportion of 33% (based on the total mass) of styrene was gradually added to the resulting bio-based resin as a copolymerizable monomer or reactive diluent, and the mixture was stirred with the KPG stirrer until a homogeneous liquid was obtained. After cooling to room temperature, the mixture was filled into UV-protected storage containers.

[0093] The following describes the production of a fiber-reinforced plastic from a flax fiber semi-finished product and the resin formulation prepared in Example 1.

[0094] For production, the resin formulation prepared in Example 1 was mixed with 2 wt.% of the thermal initiator methyl ethyl ketone peroxide. The textile semi-finished product was then impregnated with the resin formulation by hand lamination. The fiber volume content was 30%. The semi-finished product impregnated with the resin formulation was first heated to 180°C in a mold with a pressure of 90 kN at a heating rate of 10 K / min and then held at this temperature for 30 minutes. The mold was then cooled to 30°C, and the fiber-reinforced plastic, comprising the thermosetting plastic obtained by curing the resin formulation as the polymer matrix, was removed. The resulting fiber-reinforced plastic was then post-cured outside the press for 2 hours at 180°C.

[0095] As a reference material, a fiber-reinforced plastic was produced from the flax fiber semi-finished product used in Example 2 and the commercially available UP resin VP3830 from Schill und Seilacher Struktol GmbH. The system, with the product name VP3830 from Schill und Seilacher Struktol GmbH, is a bio-based UP resin based on itaconic acid, which, however, unlike the resin produced in Example 1, does not contain PLA.

[0096] A proportion of 30% (based on the total mass) of styrene as a copolymerizable monomer or reactive diluent was gradually added to the UP resin VP3830, the mixture was stirred with a KPG stirrer until a homogeneous liquid was obtained and then cooled to room temperature.

[0097] The fiber composite plastic was produced from the resin formulation thus prepared and the flax fiber semi-finished product analogously to the production method explained in Example 2, whereby the resin formulation was cured for 2 h at 80 °C and then for a further 2 h at 120 °C.

[0098] The modified curing conditions for resin formulations according to the invention and those not according to the invention are due to the fact that the advantageously short curing times for the resin formulation prepared in Example 1 cannot be applied to the commercial UP resin. Instead, longer curing times at lower temperatures are required for curing the commercial UP resin. Furthermore, it was observed that the resin formulation according to the invention according to Example 1 exhibits significantly lower shrinkage during curing compared to the non-inventive resin formulation according to Example 2. The reduced shrinkage, together with the shorter curing time of resin formulations according to the invention, represents a significant advantage in the industrial manufacturing process.

[0099] Example 4: Mechanical properties of the fiber-reinforced plastics produced in Examples 2 and 3. Samples were cut from the fiber-reinforced plastics produced according to Examples 2 and 3 to determine the Young's modulus, tensile strength, and elongation at break. The cut samples were first dried for 15 hours at 30 °C to remove any moisture absorbed during cutting and then tested in a climate-controlled test laboratory (52% humidity, 23 °C). The Young's modulus, tensile strength, and elongation at break were determined in accordance with DIN EN ISO 527-4.

[0100] The results of the investigations are shown in Fig. 1 to Fig. 3. The results illustrate that the mechanical properties of the fiber-reinforced plastic produced using the resin formulation according to the invention comprising itaconic acid-modified polylactide as resin and styrene as copolymerizable monomer (designated in the figures with sample number 3) and the fiber-reinforced plastic produced using the commercially available UP resin VP3830 (designated in the figures with sample number 1) are in a similar range of values, with the fiber-reinforced plastic according to the invention having a higher tensile strength and a higher elongation at break in comparison.

[0101] Example 5: Investigation of the biodegradability and compostability of the fiber-reinforced plastics produced in Examples 2 and 3

[0102] The biodegradability and compostability of the fiber-reinforced plastics manufactured according to Examples 2 and 3 were investigated using decomposition tests under simulated composting conditions according to DIN EN ISO 20200:2015. For each sample, a compost was prepared from sawdust, rabbit feed, mature compost, corn starch, sucrose, corn oil, and urea, and samples of the fiber-reinforced plastics manufactured according to Examples 2 and 3 were stored therein for 4 weeks at a temperature of 55 °C and 95% relative humidity.

[0103] After 4 weeks, the non-inventive samples prepared with the commercially available UP resin VP3830 show no change. In contrast, the inventive samples prepared with itaconic acid-modified polylactide as the resin show very strong decomposition, and even the smallest residues can only be detected by sieving the compost. extensively modified with itaconic acid and as bare monomers Resin formulations were prepared analogously to Example 1, using a mixture of styrene and dimethyl itaconate as the copolymerizable monomers or reactive diluent. The proportion of dimethyl itaconate was varied. The resin formulations were cured at 80 °C for 4 hours and for a further 2 hours at 120 °C in a mold with a pressure of 90 kN. The Young's modulus, tensile strength, and elongation at break of the resulting thermoset plastics were determined according to DIN EN ISO 527-4.

[0104] As a comparative sample, a non-inventive resin formulation was also prepared according to Example 3, for which a mixture of styrene and dimethyl itaconate was also used as the copolymerizable monomers or reactive diluent. The comparative sample was cured at 80 °C for 2 h and for a further 2 h at 120 °C in a mold with a pressure of 90 kN. The elastic modulus, tensile strength, and elongation at break of the thermoset plastic obtained from this resin formulation were also determined according to DIN EN ISO 527-4.

[0105] The results of these investigations are shown in Fig. 4. The results show that mechanically resilient workpieces can also be obtained by using the bio-based dimethyl itaconate as a copolymerizable monomer. a mixture of L-lactic acid and itaconic acid and manufacturing plastics from this

[0106] Based on Example 9 of US 2008 / 0004369 A1, a resin was first prepared by polymerizing a mixture comprising L-lactic acid and itaconic acid. The reactor used was a glass apparatus consisting of a distillation bridge and two glass flasks connected to a diaphragm pump. The heating rates were adjusted using a hot plate and a temperature sensor. Water was formed as a byproduct of the esterification. This was permanently removed during the reaction by vacuum distillation.

[0107] The test procedure according to Example 9 of US 2008 / 0004369 A1 was only deviated from insofar as the pressure specified in Example 1 of US 2008 / 0004369 A1 was applied for the test (since Example 9 could not otherwise be reproduced). The pressure was applied to a diaphragm pump according to Example 1 of US 2008 / 0004369 A1.

[0108] The resin obtained differs in particular from the at least one resin used in resin formulations according to the invention in that the resin obtained here was not obtained by reaction (modification) of a biodegradable and / or compostable polymer with one or more modifiers, but the modifier (itaconic acid) was added to the monomer (L-lactic acid) for the preparation of the polymer before the start of the polymerization and the polymerization of the monomer took place directly in the presence of the modifier.

[0109] Using the obtained resin, resin formulations were prepared by

[0110] (i) a part of the resin, in accordance with Example 11 of US 2008 / 0004369 A1 , with methacrylic anhydride as copolymerizable monomer, and

[0111] (ii) a further portion of the resin was blended with styrene as a copolymerizable monomer.

[0112] Processing the resin proved to be complicated, as mixing it with methacrylic anhydride or styrene required heating the resin to at least 130 °C. Below 130 °C, the resin was not sufficiently fluid for processing, and demixing was observed when attempting to mix it with copolymerizable monomer.

[0113] When using the 160 °C specified in Example 11 of US 2008 / 0004369 A1 for mixing the resin with methacrylic anhydride, a brittle resin formulation was obtained that could not be remelted but began to decompose at 180 °C. The resulting resin formulation was not suitable for producing a thermosetting plastic or even for producing fiber-reinforced plastics.

[0114] The production of a thermosetting plastic from the resin and methacrylic anhydride was only possible by adding the methacrylic anhydride directly to the resin after heating to a temperature of 130 °C, along with the initiator methyl ethyl ketone peroxide (MEKP, 2 wt%). However, the pot life of the resin formulation in this case was less than 2 minutes, which further complicated processing. After adding methacrylic anhydride and MEKP, the resin formulation was immediately poured into a mold and cured for 3 hours at 160 °C.

[0115] To mix the resin with styrene, the resin was first heated to 130 °C and then homogeneously mixed with 30 wt.% styrene (based on the total mass). The resulting mixture was then cooled to room temperature, leaving a viscous mixture. The necessary heating of the resin to 130 °C for mixing with styrene made processing extremely complicated, as styrene has a high vapor pressure and a boiling point of 145 °C, and therefore a large amount of styrene evaporated when the resin and styrene were mixed (for comparison: mixing the itaconic acid-modified polylactide with styrene according to Example 1 above requires only a temperature of 80 °C). To produce a thermosetting plastic, methyl ethyl ketone peroxide (MEKP, 2 wt.%) was added as an initiator to the mixture of resin and styrene and the mixture was then cured at 120°C for 30 min.

[0116] Example 8: Investigation of the mechanical properties and biodegradability or compostability of thermosetting plastics according to the invention and not according to the invention

[0117] The mechanical properties as well as the biodegradability and compostability of the following “pure” (i.e., not containing reinforcing fibers) thermosetting plastics were investigated:

[0118] (i) thermosetting plastic according to the invention, prepared from the resin formulation described in Example 1 above (according to the invention) comprising itaconic acid-modified polylactide as resin and styrene as copolymerizable monomer using the curing conditions explained in Example 2 above;

[0119] (ii) non-inventive thermosetting plastic, produced from the resin formulation described in Example 3 above (non-inventive) comprising the commercially available UP resin VP3830 from Schill and Seilacher Struktol GmbH as resin and styrene as copolymerizable monomer using the curing conditions explained in Example 3 above;

[0120] (iii) the thermosetting plastic not according to the invention prepared in Example 7 using methacrylic anhydride as copolymerizable monomer;

[0121] (iv) the thermosetting plastic not according to the invention prepared in Example 7 using styrene as copolymerizable monomer.

[0122] The mechanical properties were investigated by determining the modulus of elasticity, tensile strength, and elongation at break according to DIN EN ISO 527-4, as explained in more detail in Example 4 above. Biodegradability and compostability were investigated using decomposition tests under simulated composting conditions according to DIN EN ISO 20200:2015, as explained in more detail in Example 5 above.

[0123] For the thermoset plastic produced in Example 7 using methacrylic anhydride as the copolymerizable monomer, defect-free, standard-compliant test specimens could not be produced due to the short pot life. Therefore, determination of the Young's modulus, tensile strength, and elongation at break according to DIN EN ISO 527-4 was not possible for this plastic. The values ​​for Young's modulus, tensile strength, and elongation at break for the other thermoset plastics tested are shown in Figs. 5 to 7. In Figs. 5 to 7,7 is the thermosetting plastic prepared from the resin formulation comprising the commercially available UP resin VP3830 as the resin and styrene as the copolymerizable monomer designated by sample number "1"; the thermosetting plastic prepared from the resin formulation comprising itaconic acid-modified polylactide as the resin and styrene as the copolymerizable monomer designated by sample number "3"; and the thermosetting plastic prepared in Example 7 using styrene as the copolymerizable monomer designated by sample number "5".

[0124] The mechanical tests show that the thermosetting plastic according to the invention, produced from the resin formulation comprising itaconic acid-modified polylactide as resin and styrene as copolymerizable monomer, has excellent mechanical properties and, compared to the other materials tested, has a significantly higher modulus of elasticity and a significantly higher tensile strength, and its elongation at break is comparable to that of the thermosetting plastic produced in Example 7 using styrene as copolymerizable monomer.

[0125] The biodegradability and compostability tests show that the thermosetting plastic according to the invention, produced from the resin formulation comprising itaconic acid-modified polylactide as the resin and styrene as the copolymerizable monomer, decomposes completely within 10 days, so that residual pieces of it are no longer found in the compost. Complete decomposition within 10 days was also observed for the non-inventive thermosetting plastic produced in Example 7 using methacrylic anhydride as the copolymerizable monomer.For the non-inventive thermosetting plastic produced from the resin formulation comprising the commercially available UP resin VP3830 as resin and styrene as copolymerizable monomer, as well as for the non-inventive thermosetting plastic produced in Example 7 using styrene as copolymerizable monomer, no perceptible decomposition is detectable even after 40 days under composting conditions.

[0126] In summary, it can be stated that thermosetting plastics and fiber-reinforced plastics can be obtained only by using the resin formulation according to the invention investigated, which are characterized by both high mechanical strength and good biodegradability and grain postability. What is particularly surprising here is that the resin formulation according to the invention shows good biodegradability and grain postability despite the use of styrene as the copolymerizable monomer. That this was not to be expected is clear from the lack of compostability of the other thermosetting plastics produced with styrene as the copolymerizable monomer. The resin formulation according to the invention investigated is also characterized by short curing times and easy processability at low temperatures compared to the other non-inventive resin formulations investigated.

Claims

1 . Resin formulation for producing a thermosetting plastic, a) comprising or consisting of - at least one resin obtainable by reacting a biodegradable and / or compostable polymer with one or more modifiers, wherein the biodegradable and / or compostable polymer is selected from the group consisting of polylactides, polycaprolactones, chitin, chitosan, polyhydroxy fatty acids, polyhydroxyacetic acid, starch, cellulose, lignin and derivatives thereof, and the one or more modifiers are selected from the group consisting of itaconic acid, hydroxymethylfurfural and derivatives thereof, and - at least one hardener and / or in the case of saturated or unsaturated polyester resin as the at least one resin, at least one copolymerizable monomer, wherein the at least one copolymerizable monomer in the case of polylactide modified with itaconic acid and / or itaconic acid derivatives as the saturated or unsaturated polyester resin is selected from the group consisting of styrene, dimethyl itaconate, hydroxymethyl acrylate, vinyl levulinate, vinylphenol, isoprene, cinnamic acid and derivatives thereof, and / or b) wherein the resin formulation is suitable for producing a thermosetting plastic which is decomposable within 45 days using composting conditions according to DIN EN ISO 20200:2015 and which has one or more of the following mechanical properties, determined according to DIN EN ISO 527-4: Young's modulus of 1700 Pa or more; Tensile strength of 20 MPa or more; Elongation at break of 1.5% or more.

2. Resin formulation according to claim 1, wherein the modifier is itaconic acid.

3. Resin formulation according to claim 1 or claim 2, wherein the at least one resin is a saturated or unsaturated polyester resin and / or an epoxy resin, preferably a saturated or unsaturated polyester resin.

4. Resin formulation according to one of the preceding claims, wherein the chain length of the at least one resin is in the range from 500 g / mol to 50,000 g / mol, preferably in the range from 500 g / mol to 800 g / mol.

5. Resin formulation according to one of the preceding claims, wherein the proportion of hardeners and / or copolymerizable monomers in the resin formulation is 1 wt.% to 99 wt.%, preferably 10 wt.% to 50 wt.%, particularly preferably 10 wt.% to 30 wt.%, based on the total mass of the resin formulation, and / or the ratio of the total mass of hardeners and / or copolymerizable monomers to the total mass of resins in the resin formulation is 2:

1.

6. Resin formulation according to one of the preceding claims, wherein the at least one resin is a polylactide modified with itaconic acid and / or itaconic acid derivatives and / or the at least one copolymerizable monomer is styrene.

7. Resin formulation according to one of the preceding claims, additionally comprising one or more catalysts or catalyst systems, preferably selected from the group consisting of tin(II) 2-ethylhexanoate, 1,5,7-triazabicyclo[4.4.0]dec-5-ene and citric acid, and / or one or more initiators, preferably thermal initiators, particularly preferably selected from the group consisting of methyl ethyl ketone peroxide, N,N-azobisisobutyronitrile and dibenzoyl peroxide, and / or one or more accelerators, preferably selected from the group consisting of cobalt compounds and amine compounds, and / or one or more inhibitors, preferably selected from the group consisting of phenols, quinones and their derivatives, and / or one or more plasticizers, preferably selected from the group consisting of glycerol, epoxidized soybean oil, acetyltributyl citrate, chloroparaffins and phthalic acid esters, and / or one or more impact modifiers, preferably selected from the group consisting of rubber and styrene-butadiene block copolymers.

8. Resin formulation according to one of the preceding claims, wherein the resin formulation is in the form of a liquid at room temperature and atmospheric pressure and / or has a pot life of more than 10 minutes, preferably more than 30 minutes, particularly preferably more than 60 minutes.

9. Thermosetting plastic a) obtainable by curing, preferably thermal curing, a resin formulation as defined in any one of claims 1 to 8 and / or b) wherein the thermosetting plastic is decomposable within 45 days, preferably completely decomposable within 45 days, particularly preferably completely decomposable within 10 days, when composting conditions according to DIN EN ISO 20200:2015 are applied, and has one or more of the following mechanical properties, determined according to DIN EN ISO 527-4: Young's modulus of 1700 MPa or more, preferably 2000 MPa or more, particularly preferably 3000 MPa or more; Tensile strength of 20 MPa or more, preferably 25 MPa or more, particularly preferably 40 MPa or more; Elongation at break of 1.5% or more, preferably 1.9% or more, particularly preferably 4.1% or more.

10. Use of a resin formulation as defined in any one of claims 1 to 8 and / or a thermosetting plastic as defined in claim 9 as a plastic and / or as an adhesive and / or as a matrix resin for a composite material, preferably for a fiber-reinforced plastic and / or in one or more of the following areas: automotive industry, aerospace, Construction of rail vehicles, Shipbuilding, furniture construction and trade fair construction.

11. Composite material, preferably fiber-reinforced plastic, comprising as polymer matrix a thermosetting plastic as defined in claim 9.

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