Macroscopically graded polymer, use and method for producing same, and kit for producing a macroscopically graded polymer

Abstract

The invention relates to a macroscopically graded polymer comprising or consisting of polybenzoxazine and / or polybenzoxazine derivative. Described is also the use of a macroscopically graded polymer according to the invention and a method for producing a macroscopically graded polymer. Described is further a kit for producing a macroscopically graded polymer according to the invention and the use of a kit according to the invention.

Description

[0001] Macroscopically graded polymer and use and method for producing the same and kit for producing a macroscopically graded polymer

[0002] The present invention relates to a macroscopically graded polymer. The invention further relates to the use of a macroscopically graded polymer according to the invention and to processes for producing a macroscopically graded polymer. The invention also relates to a kit for producing a macroscopically graded polymer according to the invention and to the use of a kit according to the invention.

[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. Where 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 otherwise apparent to the person skilled in the art from the present text.

[0004] Adapted product design to needs represents a key component of materials development. On the one hand, the increasing environmental awareness of society and industry requires consideration of recyclability in the molecular design of polymer materials. On the other hand, the longest possible service life, optimized properties, and the reduction of polymer materials are required. For applications where mechanical and chemical resistance are essential, three-dimensionally cross-linked polymers, so-called thermosets, are typically used.

[0005] In addition to structural components, thermoset-based systems also dominate in the context of load-bearing bonding, where they ensure high strength and resistance to various media. However, highly cross-linked adhesives have comparatively high stiffness and low flexibility, which limits the bond's ability to withstand complex load types. Even under ideal tensile stress, eccentric force introduction and possible notch effects can occur due to a shape discontinuity and a redirection of the force flow.

[0006] Especially with regard to different joining partners (which differ from each other, for example, in terms of material, geometry and / or mechanical properties), an initial tensile load induces a multi-axial stress state (see Fig. 1 as well as the “Handbook of Adhesive Bonding Technology” by Manfred Rasche, 1986, Carl Hanser Verlag).

[0007] A further challenge, both with thermoset components and adhesives, is process- and media-related residual stresses (see "Bonding: Fundamentals, Technologies, Applications" by Gerd Habenicht, 6th edition, Springer Verlag, Heidelberg). Residual stresses can have various causes, but draping and temporary or permanent fixation of bonded components, as well as deflection of the bonded parts outside their intended load state, are also conceivable and would lead to stresses in the adhesive bond.

[0008] The modulation of mechanical properties within a component has so far been solved, for example, by hybrid compounds, i.e. the combination of different materials within a component.

[0009] Different approaches can be used to reduce stress peaks in a bonded joint and achieve the most homogeneous stress distribution possible within an adhesive joint. Oversizing the adhesive joint can increase the load-bearing capacity of the component or connection. However, the stress peaks in the bond remain. One method to reduce stress peaks in a bonded joint and achieve the most homogeneous stress distribution possible within an adhesive joint is to combine different adhesives within an adhesive joint, so that there is a stiffer material in the middle and a more flexible material at the outer edges of the adhesive joint (see “Performance of bi-adhesive bonded aluminum lap joints” by Pires et al. in International Journal of Adhesion and Adhesives, Vol. 23, Issue 3, 2003, pp. 215-223).However, even with this method, stress peaks remain, which occur particularly at the transition point between the different adhesives.

[0010] Building on this, graded materials have been established, as shown, for example, by Sancaktar and Kumar (see “Selective use of rubber toughening to optimize lap-joint strength” by Sancaktar and Kumar in Journal of Adhesion Science and Technology, Vol. 14, No. 10, 2000, pp. 1265-1296), which modify an epoxy adhesive with a graded ratio of elastomeric components.

[0011] Another constructive solution is the design of the joining partners. However, this is on the one hand complex and on the other hand represents a limitation for the application to different components (cf. “Adhesively bonded joints in composite materials: an overview” by Banea and da Silva in Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, Vol. 223, Issue 1 , 2009).

[0012] Tsai and Morton (see “The effect of a spew fillet on adhesive stress distributions in laminated composite single-lap joints” by Tsai and Morton in Composite Structures, Vol. 32, 1995, pp. 123-131) and Rispler et al. (see “Shape optimization of adhesive fillets” by Rispler et al. in International Journal of Adhesion and Adhesives, Vol. 20, Issue 3, 2000, pp. 221-231) also show a homogenization of the stress distribution in a fiber composite overlap by filling and beveling the adhesive joint at the ends of the joining partners.

[0013] Against this background, the primary object of the present invention was to provide a material (particularly suitable for use as an adhesive) that enables local adjustment of mechanical and / or physical properties, for example, to reduce or even completely avoid the occurrence of stress peaks in bonded (composite) components in a simple and efficient manner, or to achieve more targeted and improved stress relief in bonded composite components. A further object of the present invention was to provide a method for producing such a material.

[0014] The present invention should also make it possible to use the material to be provided as an adhesive and / or in composite materials.

[0015] A further object of the present invention was to provide a kit for producing the material to be provided and to use such a kit as a multi-component adhesive.

[0016] Further objects arise from the following description and the patent claims.

[0017] The primary object of the present invention is achieved by a macroscopically graded polymer comprising or consisting of polybenzoxazine and / or polybenzoxazine derivative.

[0018] Polybenzoxazines in general, as well as the use of polybenzoxazines and their derivatives as adhesives, are already known from the state of the art. For example, reference is made to the following publications:

[0019] Shen et al., (2016) “Understanding the surface properties of polybenzoxazines: Interaction of polybenzoxazine model compounds with metal ions and wate” in J. Appl. Polym. Be.;

[0020] Tuzun et al. (2010) „Benzoxazine Containing Polyester Thermosets with Improved Adhesion and Flexibility” in Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 48, S. 4279-4284;

[0021] Li et al. (2017) „Study on benzoxazine-based film adhesive and its adhesion properties with CFPR composites“ in Journal of Adhesion Science and Technology, Vol. 31 , Nr. 16, S. 1796-1806;

[0022] Lee et al. (2018) „High-Performance Printed Circuit Board Materials Based on Benzoxazine and Epoxy Blend System” in Macromolecular Research. Vol. 26, S. 388-393; US 9,296,928 B2;

[0023] He et al. (2018) „A mussel-inspired polybenzoxazine containing catechol groups” in Polymer, Vol. 158, S. 53-58;

[0024] Higginson et al. (2019) „Bioinspired Design Provides High-Strength Benzoxazine Structural Adhesives” in Angew. Chem., Vol. 131 , S. 12399 - 12407;

[0025] Wang et al. (2016) “Latent curing systems stabilized by reaction equilibrium in homogeneous mixtures of benzoxazine and amine” in Scientific Reports 6:38584.

[0026] Approaches for the realization of materials and components with hybrid and locally bound properties can also be found, for example, in the following publications:

[0027] Chen et al. (2021) “Unified method to prepare thermoplastic / thermoset soft polyurethanes reshape-able around room temperature on-demand” in J. Polym. Res., Vol. 28, p. 201 ;

[0028] Voleppe et al. (2021) “Enhanced fracture resistance of thermoset / thermo-plastic interfaces through crack trapping in a morphology gradient” in Polymer, Vol. 218, Is. 18;

[0029] Sawaryn et al. (201 1) “Advanced chemically induced phase separation in thermosets: Polybenzoxazines toughened with multifunctional thermoplastic mainchain benzoxazine prepolymers” in Polymer, Vol. 52, Is. 15;

[0030] Estelle et al. (2017) “Manufacturing of smart composites with hyperelastic property gradients and shape memory using fused deposition” in Journal of Manufacturing Processes, Vol. 28, Part 3;

[0031] Zhang et al. (2019) “Unexpected Healability of an ortho-Blocked Polybenzoxazine Resin” in ACS Macro Lett., Vol.8, pp. 506-511 ;

[0032] Sun et al. (2015) “A curing system of benzoxazine with amine: reactivity, reaction mechanism and material properties” RSC Adv., Vol. 5, p. 19048; Zhao et al. (2018) “Significant Improvement on Polybenzoxazine Toughness Achieved by Amine / Benzoxazine Copolymerization-Induced Phase Separation” in Macromol. Chem. Phys., Vol. 219, Is. 6, p. 1700517.

[0033] Graded components are also already known from the state of the art and are described, among others, in the following documents:

[0034] US 4,650,193;

[0035] US 3,784,209;

[0036] US 6,113,831 ;

[0037] US 8,016,696 B2;

[0038] US 5,545,229.

[0039] However, a macroscopically graded polymer comprising or consisting of polybenzoxazine or a polybenzoxazine derivative is not yet known from the prior art, particularly in the context of adhesives.

[0040] In particular, it should be noted that the polymers described in the publication by Sawaryn et al. (“Advanced chemically induced phase separation in thermosets: Polybenzoxazines toughened with multifunctional thermopolastic mainchain benzoxazine prepolymers” in Polymer, Vol. 52, Issue 15, 2011) only have gradients at the nano- or microscopic level (“so-called gradient domain structures”), which do not induce any local changes in the physical, chemical and / or mechanical properties of the polymers at the macroscopic level and which are to be expressly distinguished from the macroscopic gradients or macroscopically graded polymers described in the present invention. With regard to the polymers described in the publication by Sawaryn et al.The macroscopic gradient described in the context of the present invention differs from the gradient described above both in its magnitude and in its significance for the properties of the material resulting from the gradient.

[0041] Macroscopic is defined as an area that can be detected without technical aids. Such an area can be quantitatively assigned to dimensions of > 1 mm. Regarding the description of "macroscopic properties," these are to be considered as the totality of the varying properties (structure) at the microscopic level.

[0042] For the purposes of the present invention, a macroscopically graded polymer is understood to be a polymer that exhibits a gradual change in at least one chemical, physical, and / or mechanical property that is perceptible at the macroscopic level. A macroscopically graded polymer, for the purposes of the present invention, exhibits a graded property transition in at least one spatial direction, which is characterized by the absence of a sharp interface for the changing property(ies).

[0043] Preferably, the term "macroscopically graded" in the sense of the present invention is defined as a directed change in one or more chemical, physical, and / or mechanical properties in one or more spatial directions of the polymer within a measuring section of at least 2 mm over a number of 5 to 10 measuring points evenly spaced along the measuring section. The length of the measuring section is preferably a maximum of 75 mm, particularly preferably a maximum of 50 mm, and most preferably a maximum of 25 mm. The directed change in the one or more chemical, physical, and / or mechanical properties can be determined, for example, by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR spectroscopy), energy-dispersive X-ray spectroscopy (EDX), hardness measurement, scanning electron microscopy, and / or nanoindentation.“Directed” means that the measured values ​​develop in one direction along the measuring section (i.e., starting after the starting point, they have a higher or lower value than at the previous measuring point along the measuring section).

[0044] A macroscopic gradient within the meaning of the present invention is to be distinguished from the "gradual variation of viscosity" described in "A cardanol-based polybenzoxazine vitrimer: recycling, reshaping and reversible adhesion" (Polym. Chem., 2020, 11, 7026-7034) by Trejo-Machin et al., since the "gradual variation of viscosity" described by Trejo-Machin et al. does not involve a (permanent) gradual change in properties along at least one spatial direction, but merely explains a possible (temporary) gradual change in viscosity by heating the vitrimer disclosed in the publication. Preferably, a macroscopically graded polymer within the meaning of the present invention exclusively exhibits graded property transitions.

[0045] The use of a macroscopically graded polymer according to the invention offers the following advantages compared to the solutions explained above, known from the prior art: No hybrid construction: A component or adhesive bond with locally adjustable and defined material properties can be realized using only one material. Gradable material: The graded property transition avoids sharp interfaces for property changes and the associated disadvantages (such as locally occurring stress peaks or the creation of weak points within a material system). Smaller dimensions of adhesive joints are possible.

[0046] Preferably, the properties of a macroscopically graded polymer according to the invention—such as deformation, stiffness, and thermal properties—can be modified even after production, e.g., by subsequent thermal treatment (e.g., by means of warm air, heating elements, or induction). Such subsequent modification of the properties allows, for example, the adaptation of the properties of the macroscopically graded polymer to the required conditions for the respective application of the material. Furthermore, in addition to the possibility of passive stress relief (determined by the design of the gradient of the mechanical properties of the macroscopically graded polymer), this also advantageously opens up the possibility of active stress relief (i.e., the reduction of stresses arising from fixing or joining the material).

[0047] Macroscopically graded polymers according to the invention comprise or consist of a polymer backbone based on benzoxazines. The benzoxazine typically polymerizes in a thermal ring-opening polymerization with or without the addition of catalysts or initiators (such as bases, acids, or nucleophilic substances). The macroscopically graded (gradual) property changes within a macroscopically graded polymer according to the invention can be realized or adjusted in various ways. For example, property gradients within the macroscopically graded polymer according to the invention can be induced by adjusting / successively changing the stoichiometric and / or molecular composition, as well as by a (gradual) change in the conditions for the curing process of the macroscopically graded polymer along an extension direction.This allows for the targeted creation of property gradients within a macroscopically graded polymer, which can be influenced in a targeted manner. These gradients enable, for example, local flexibility, stiffening, and different temperature-sensitive regions within the macroscopically graded polymer. This can be used, for example, to compensate for stress peaks within the adhesive joint when the macroscopically graded polymer is used as an adhesive. In this context, it should be noted that even partially (not yet fully) polymerized / cured polybenzoxazines and polybenzoxazine derivatives constitute polymers within the meaning of the present invention.

[0048] Specifically, the generation of graded property transitions within the scope of the present invention can be carried out, for example, in one of the following ways:

[0049] At least two different compositions, which can be polymer compositions or monomeric or oligomeric reactants and / or reactant mixtures to be polymerized, are placed in a mold and solidified in separate locations. Heating causes the different compositions to mix at the interfaces. Heating leads to simultaneous polymerization of the monomeric or oligomeric reactants or reactant mixtures to be polymerized. Heating may also lead to further polymerization of the polymer compositions. Simultaneous application is also possible, whereby all phases can be filled into the mold or applied to the surface simultaneously.

[0050] A monomeric or oligomeric composition to be polymerized, or a polymer composition, is treated with locally differing curing temperatures, thus creating macroscopically graded property changes within the polymer, for example, with regard to hardness and modulus. Different compositions are each fully cured and can then be bonded together as desired, e.g., depending on the desired degree of hardness, using pressure and / or temperature.

[0051] Preferred is a macroscopically graded polymer according to the invention, wherein the macroscopically graded polymer is obtainable by a synthesis comprising at least one polymerization of one or more compounds of the formula (I) where

[0052] R 1 , R 2 , R 3 , R 4 , R 5 and R 9are the same or different and each represents an organic radical or H; and

[0053] R®, R 7 and R 8 are the same or different and each represents an organic radical or H or

[0054] R® and R 7 are linked together to form a covalent bond, and R 8 represents an organic residue or H or

[0055] R 7 and R 8are linked to one another to form a covalent bond, and R® represents an organic radical or H, wherein the organic radicals are preferably selected from optionally substituted aromatic and / or aliphatic, linear and / or branched, saturated and / or unsaturated carbon radicals having a respective total number of carbon atoms per organic radical in the range from 1 to 22, preferably having a respective total number of carbon atoms per organic radical in the range from 6 to 17, wherein the compounds of formula (I) particularly preferably have two or more benzoxazine structural units.

[0056] Polybenzoxazines comprising structural units based on 1,3-benzoxazine and derivatives thereof are therefore preferred within the scope of the present invention, although the scope of the invention also encompasses polybenzoxazines obtained using further or other benzoxazine isomers (such as 1,4-benzoxazine, 3,1-benzoxazine, and 2,1-benzoxazine) and / or their derivatives. In addition, the synthesis of a macroscopically graded polymer according to the invention can also be carried out using further monomers and / or conventional reagents, in particular using flexibilizing reagents.

[0057] Also preferred is a macroscopically graded polymer according to the invention, wherein the macroscopically graded polymer is obtainable by a synthesis comprising one or more benzoxazine prepolymers.

[0058] Also preferred is a macroscopically graded polymer according to the invention, wherein the macroscopically graded polymer is obtainable by a synthesis comprising at least one polymerization of one or more compounds of the formula (Ia) where R 10 and R 11 are the same or different and are each H or an alkyl group having 1 to 4 carbon atoms, preferably H or a methyl group.

[0059] Further preferred are those macroscopically graded polymers according to the invention, wherein the synthesis comprises the polymerization of at least two compounds of the formula (I) or (Ia) each having different molar masses.

[0060] As already explained above, the one or more macroscopically graded property changes within a macroscopically graded polymer according to the invention can be realized, inter alia, by changing the stoichiometric and / or molecular composition within the polymer. For this purpose, at least two compounds of formula (I) or (Ia), each with different molar masses, are preferably used for the synthesis of a macroscopically graded polymer according to the invention.

[0061] Additionally or alternatively, the change in the stoichiometric and / or molecular composition can also be realized by using, selecting and using the amount of nucleophiles preferentially involved in the synthesis.

[0062] Therefore, a macroscopically graded polymer according to the invention is preferred, wherein the at least one polymerization of the one or more compounds of formula (I) or (Ia) takes place in the presence and / or with the participation of one or more nucleophiles, wherein the one or more nucleophiles are preferably selected from the group consisting of amines, thiols and alcohols, particularly preferably selected from the group consisting of monofunctional amines, difunctional amines, multifunctional amines, amines bound to a polyether main chain (wherein the polyether main chain is preferably produced from ethylene oxide (EO), propylene oxide (PO), or a mixture of both oxides and epoxides), thiols and alcohols, wherein the one or more nucleophiles are very particularly preferably polyetheramines having a molar mass in the range from 600 to 2,000 g / mol, in particular polyetheramines having the formula (II) where m is an integer from 9 to 39, and

[0063] I and n are each integers, and the sum of I and n is 3 to 6. The preferential presence and / or participation of nucleophiles triggers the ring-opening reaction at lower temperatures. The nucleophile can be partially or completely incorporated into the network. Depending on the nucleophile used, the molar composition, and / or the curing temperature, a polymer is formed whose material properties are variable and definable. By using different nucleophiles and / or different molar compositions between nucleophile and benzoxazine for the production of the polymer, single-phase materials with graded properties can be obtained using a nucleophile.

[0064] A stoichiometric reaction between the one or more nucleophiles and the one or more compounds of formula (I) or (Ia) is not necessary but possible.

[0065] Also preferred is a macroscopically graded polymer according to the invention, wherein the molar ratio of compounds of formula (I) or (Ia) to nucleophiles is in the range from 1:0.01 to 1:1.5, preferably in the range from 1:0.06 to 1:1.5, particularly preferably in the range from 1:0.06 to 1:1.15.

[0066] Preferred is a macroscopically graded polymer according to the invention, comprising or consisting of structural repeat units of the formulas (III.a), (III.b) and / or (III.c)

[0067] (lll.b)

[0068] (lll.c).

[0069] Macroscopically graded polymers according to the invention comprising or consisting of the aforementioned structural units have proven to be particularly suitable for use as, for example, adhesive compounds.

[0070] Also preferred is a macroscopically graded polymer according to the invention, wherein the macroscopically graded polymer has dynamic (covalently adaptive) properties.

[0071] Dynamic covalently crosslinked polymers are those in which the covalent bonding sites can dynamically separate and reconnect as a result of an appropriate stimulus, in the case of the present invention preferably by varying the temperature and optionally the pressure (cf. "Recent advances in dynamic covalent chemistry" by Jin et al. in Chemical Society Reviews, Vol. 42, 2013, pp. 6634-6654). Due to this chemical property, such polymer networks possess self-healing properties and allow for deformation. In the case of the present invention, this dynamic behavior preferably contributes to the subsequent stress relief by means of a locally applied stimulus.

[0072] The presence of dynamic properties within the macroscopically graded polymer or the presence of a dynamic polymer network enables the circumvention and overcoming of the residual stresses of, for example, fully cross-linked polymer systems, cured adhesive joints and rigid connections.

[0073] A key cause of residual stress is the lack of relaxation capacity of cross-linked structures (see "Bonding: Fundamentals, Technologies, Applications" by Gerd Habenicht, 6th edition, Springer Verlag, Heidelberg). The use of a polymer with dynamic properties as an adhesive therefore enables stress relief after the bonding process, the draping or fixing of the bonded component, or aging under altered thermal conditions, such as cold. This opens up great potential for both significantly extending the service life of (composite) components through stress relaxation and enabling recyclability by dissolving the network points.

[0074] The self-healing properties can be used to heal damages such as (micro)cracks and delaminations in, for example, adhesives, composites and all-plastic parts after cross-linking as well as in uncured and partially cured states, as well as to integrate subsequently applied reinforcement elements onto and into components.

[0075] Without being bound to any theory, it is assumed that the self-healing mechanism is based on an exchange of covalent bonds. This can involve kinetically controlled, simultaneous exchange reactions in the form of bond breaking and bond forming reactions, or thermodynamically controlled, possibly reversible, condensation and addition reactions.

[0076] A macroscopically graded polymer according to the invention is preferred, wherein at least one mechanical or physical property of the macroscopically graded polymer changes gradually (at the macroscopic level) along at least one extension direction of the macroscopically graded polymer, wherein the at least one mechanical or physical property of the macroscopically graded polymer is preferably selected from the group consisting of

[0077] - glass transition temperature,

[0078] - Operating temperature range,

[0079] - breaking strength,

[0080] - flexural strength,

[0081] - flexural modulus,

[0082] - impact strength, and

[0083] - Hardness. The gradual change within the polymer is not necessarily limited to a linear or continuous progression. For example, the gradient of the change can vary in intensity across the direction of extension of the macroscopically graded polymer, the gradual change perceptible at the macroscopic level can extend only over a portion of the polymer, and / or the change in the property along the direction of extension can take on changing signs (e.g., the flexural strength of the macroscopically graded polymer may initially decrease and then increase again along an extension direction), whereby a periodic gradual change in a property is also conceivable and encompassed by the scope of the present invention.

[0084] The glass transition temperature and the service temperature range are defined for the purposes of the present invention as described in DIN EN ISO 6721-3 and are preferably determined as described in DIN EN ISO 6721-3.

[0085] The measurement of breaking strength and / or flexural modulus is preferably carried out by 3-point bending testing as described in DIN EN ISO 178.

[0086] Impact strength is preferably determined using Charpy impact properties, preferably as described in DIN EN 179-1.

[0087] Hardness is preferably determined according to DIN EN ISO 7619-1 and / or DIN EN ISO 7619-2. Hardness is particularly preferably determined by measuring the Shore D hardness, as described in DIN EN ISO 7619-1.

[0088] Part of the invention is also the use of a macroscopically graded polymer according to the invention or preferably according to the invention (as defined above and in the claims) as an adhesive and / or as an adhesive film and / or in composite materials (in particular in fiber-reinforced plastics, FRP), preferably in layered laminates or sandwich structures, and / or as a surface coating and / or as a matrix resin.

[0089] Part of the invention is also a process for producing a macroscopically graded polymer according to the invention or preferably according to the invention (as defined above and in the claims), comprising the following steps: a) providing and / or, optionally partially, mixing the one or more monomeric reactants for producing the macroscopically graded polymer; b) optionally filling a mold with the one or more reactants and / or the one or more reactant mixtures or optionally applying the one or more reactants and / or the one or more reactant mixtures to a support; c) polymerizing, preferably thermally polymerizing, the one or more reactants and / or the one or more reactant mixtures, wherein the plurality of reactants and / or reactant mixtures are at least partially in contact with one another and / or are at least partially mixed with one another;wherein the time period and / or temperature selected for the polymerization in step c) differs from one another at two or more locations of the one or more reactants and / or the one or more reactant mixtures and / or the reactants and / or reactant mixtures to be polymerized in step c) have a total of at least two regions of different composition, preferably at least one region with a gradually changing composition, so that a macroscopically graded polymer results.;

[0090] Partial mixing according to the above-mentioned step a) can be understood as both an incomplete mixing of combined reactants and the production of various separate reactant mixtures from the reactants provided.

[0091] Preferably, the reactant mixtures are subjected to homogenization by brief heating. This allows an initial polymer reaction to begin within the reactant mixture, although this does not change the properties of the reactant mixture (apart from the resulting homogenization) or does not change significantly. Therefore, a reactant mixture briefly heated for the purposes of homogenization still represents a reactant mixture within the meaning of the present invention and is thus to be distinguished from a polymer or a polymeric compound.

[0092] When using multiple reactants or reactant mixtures in step b), the reactants or reactant mixtures come into contact with each other, with at least partial mixing of the reactants or reactant mixtures occurring at the respective contact surfaces. The at least partial mixing of the various reactants or reactant mixtures used causes or contributes to the formation of macroscopically graded property transitions in the subsequent polymerization step c).

[0093] By selecting different durations and / or temperatures at two or more locations of the one or more reactants and / or the one or more reactant mixtures, the mechanical and / or thermal properties can be adjusted differently at different locations and, if necessary, also subsequently changed.

[0094] As already mentioned above, to achieve the at least two ranges of different composition, several benzoxazines with different molecular weights and / or benzoxazines in combination with nucleophiles can be used, preferably varying the molar ratio of the various components within the reactant mixture to be polymerized. The process described above provides a production process for a macroscopically graded polymer according to the invention, in which the macroscopically graded polymer is produced directly from its monomeric reactants or reactant mixtures thereof. Alternatively, a macroscopically graded polymer according to the invention can also be produced by combining several previously prepared polymeric compounds selected from polybenzoxazines and polybenzoxazine derivatives, each with different properties.

[0095] Part of the invention is therefore also a process for producing a macroscopically graded polymer according to the invention or preferably according to the invention (as defined above and in the claims), comprising the following steps: i) producing or providing two or more polymeric compounds selected from polybenzoxazines and polybenzoxazine derivatives, wherein the two or more polymeric compounds each differ from one another in at least one mechanical or physical property, ii) combining the two or more polymeric compounds produced or provided in step i) to result in a macroscopically graded polymer.

[0096] The bonding of the two or more polymeric compounds produced or provided in step ii) of the process according to the invention is preferably carried out thermally and / or by applying pressure. The temperature and / or pressure must be selected to be sufficiently high to induce macroscopic flow.

[0097] Preferred is a process according to the invention as defined above, wherein one or more of the two or more polymeric compounds are provided in the form of a granulate or in the form of a film.

[0098] The starting materials for the two alternative manufacturing processes according to the invention, which differ in their properties, can each be mixed separately and stored separately or already applied in the uncured or partially cured state at room temperature in the form of bulk material, solutions, films, prepregs or cast components. The basic polymer material is suitable for various processes, such as hot pressing, RTM, vacuum infusion or hand lamination, whereby pot life, melting temperature and viscosity can be adjusted via the composition and combination of the respective monomers.Part of the invention is also a kit for producing a macroscopically graded polymer according to the invention or preferably according to the invention (as defined above and in the claims), comprising two or more polymeric compounds selected from polybenzoxazines and polybenzoxazine derivatives, preferably in granular form, wherein the two or more polymeric compounds each differ from one another in at least one mechanical or physical property, or two or more components, each comprising at least one benzoxazine or benzoxazine derivative, preferably each comprising at least one compound of the formula.

[0099] (I) or (Ia) (as defined above and in the claims), wherein one or more of the two or more components particularly preferably additionally comprises one or more nucleophiles, preferably one or more nucleophiles as defined above and in the claims, wherein the two or more components each differ from one another in their quantitative or qualitative composition, wherein the benzoxazines or benzoxazine derivatives comprised by the two or more components preferably each have different molecular weights and / or the two or more components each have different molar ratios of (i) benzoxazines or benzoxazine derivatives to (ii) nucleophiles, wherein the two or more polymeric compounds or the two or more components are each present as separate individual components.

[0100] Part of the invention is also the use of a kit according to the invention as a multi-component adhesive.

[0101] The invention is explained in more detail below using examples and the accompanying figures. The following examples are intended to describe and explain the invention in more detail without limiting its scope. They show:

[0102] Fig. 1 : Schematic representation of the stress state in a viscoelastic

[0103] Adhesive layer and tensile shear stress (not according to the invention). The stress peaks at the ends of the joint are clearly visible. Taken from "Bonding: Fundamentals, Technologies, Applications" by Gerd Habenicht, 6th edition, Springer Verlag, Heidelberg.

[0104] Fig. 2: Schematic representation of a manufactured macroscopically graded polymer according to the invention. The Shore D hardness values ​​at different locations on the macroscopically graded polymer are shown. The Shore D hardness illustrates the continuous change in the material properties over the length of the test specimen.

[0105] Fig. 3: Shore D hardness of the polybenzoxazines tested in Example 3, shown as a bar chart. The values ​​shown are the mean values ​​of five measurements for each polybenzoxazine produced. The designation on the x-axis for the individual polybenzoxazines consists of the number of the batch used to produce the polybenzoxazine ("1.1" to "1.7"; see Table 1 below for more details) and the designation for the temperature treatment used ("110°C", "150°C", or "180°C"; see Table 2 below for more details).

[0106] Fig. 4: Fig. 4 a) is a schematic representation of the production of polybenzoxazine from benzoxazine and amine and the cyclic comminution and self-healing of the material. The test specimens shown in the top left of Fig. 4 a) represent polybenzoxazine test specimens produced from batch no. 1.4 according to Example 1, with the light test specimen being produced using the temperature treatment “150°C” and the dark test specimen using the temperature treatment “180°C” (see Table 2 below for more details). Fig. 4 b) shows a test specimen which was obtained by joining two different polybenzoxazine samples (batch no. 1.4, using the temperature treatments “150°C” and “180°C” respectively) using pressure and temperature. Fig. 5: Flexural moduli of the polybenzoxazines tested in Example 5. The mean value shown is that of 5 measurements per tested sample.The designation in the x-axis for each sample consists of the designation for the temperature treatment used to produce the polybenzoxazine (110 °C, 150 °C and / or 180 °C; see Table 2 below for more details) and the number of crushing / self-healing cycles to which the respective polybenzoxazine was subjected ("0 x pr." = no crushing / self-healing cycle, "1 x pr." = one crushing / self-healing cycle, etc.).

[0107] Fig. 6 Flexural strengths of the polybenzoxazines tested in Example 5. The values ​​shown are the mean values ​​of 5 measurements per sample tested. The designation on the x-axis for the individual samples consists of the designation for the temperature treatment used to produce the polybenzoxazine (110 °C, 150 °C, and / or 180 °C; see Table 2 below for more details) and the number of comminution / self-healing cycles to which the respective polybenzoxazine was subjected ("0 x pr." = no comminution / self-healing cycle, "1 x pr." = one comminution / self-healing cycle, etc.). from benzoxazine and amine

[0108] A bisphenol-A / aniline based benzoxazine (BA-a) with trade name ARALDITE® MT 35600 (M = 462.6 g / mol) and the following structural formula was used in conjunction with an amine with the trade name Jeffamin® ED 600 (M = 600 g / mol) or Jeffamin® ED 2003 (M = 2000 g / mol), each having the following general structural formula

[0109] weighed and homogenized for approximately 10 minutes at 110 °C. The corresponding initial weights and molar ratios of benzoxazine to amine used are given in Table 1. Table 1: Initial weights and molar ratios of the mixtures used for the preparation of polybenzoxazines.

[0110] Example 2: Preparation of a macroscopically graded polymer (according to the invention):

[0111] The mixtures prepared in Example 1 using batches 1.4, 1.3, and 1.2 were placed side by side in a mold, partially mixing the individual mixtures with each other. The resulting mixture was then subjected to a heat treatment for 2 hours at 110°C and then to a further heat treatment for 2 hours at 150°C. The resulting macroscopically graded polymer according to the invention is shown schematically in Fig. 2.

[0112] The Shore D hardness was determined at several locations on the macroscopically graded polymer according to the invention, using DIN EN ISO 7619-1. The determination of the Shore D hardness reveals a change in hardness within the macroscopically graded polymer. The stoichiometry curve from the batches 1.4, 1.3, and 1.2 used is reflected in different hardnesses, ranging from comparatively hard to flexible, and can also be visually distinguished (by color). The different hardnesses also indicate different mechanical properties, ranging from comparatively stiff to flexible, within the macroscopically graded polymer.

[0113] The fact that the produced polymer exhibits more than three different Shore D hardnesses throughout its process (four hardness values ​​are shown as examples in Fig. 2), even though only three batches with different stoichiometry were used to produce the polymer, indicates that the produced polymer exhibits a macroscopically graded change in properties. A clear distinction between the three mixtures presented is no longer possible.

[0114] Example 3: Hardness measurements on polybenzoxazines treated at different temperatures

[0115] The mixtures prepared in Example 1 were each subjected to different temperature treatments. The temperature treatments described in more detail in Table 2 were used.

[0116] Table 2: Description of the temperature treatments used for the production of polybenzoxazines. The names of the temperature treatments refer to the maximum temperature applied within the respective temperature program.

[0117] The Shore D hardness of the resulting polybenzoxazines was then determined.

[0118] The Shore D hardness was determined as described in Example 2.

[0119] Fig. 3 shows the Shore D hardness values ​​for the polybenzoxazines obtained from the different starting mixtures or through different temperature treatments in the form of a bar chart. The hardness measurements demonstrate that the material system reacts sensitively to changes in stoichiometry / composition as well as to different curing conditions; thus, the physical and mechanical properties of a polybenzoxazine can be specifically influenced by changing the composition and stoichiometry of the starting materials as well as by varying the curing conditions.

[0120] Example 4: Formability and self-healing

[0121] The formability and self-healing of the polybenzoxazines used as starting material for the preparation of macroscopically graded polymers according to the invention is demonstrated using polybenzoxazines prepared from batch No. 1.4 given in Example 1 (Table 1) using the temperature treatments “150°C” and “180°C” according to Table 2 above.

[0122] Comminution and subsequent forming or curing of the produced polybenzoxazines can be achieved over at least five cycles. The comminution of the polybenzoxazines was carried out by mechanical force (at a temperature of 155 °C using a surface force of 15 kN for 10 s), which transformed the previously produced compact specimens into coarse granules.

[0123] The combination of forming temperature (155 °C) and pressure (22 kN) enables process times for bending and healing the material of approximately 15 minutes (see Fig. 4 a)). Using such pressing processes, materials of different stoichiometries and curing states (i.e., materials with different material properties) can be formed, healed, or even bonded together with the formation of macroscopically graded property changes (see Fig. 4 b)). By appropriately selecting the forming temperature and pressure, macroscopic flow of the material is enabled, whereby when two polybenzoxazines with different material properties are bonded, a partial mixing of the different materials occurs and macroscopically graded property changes develop within the resulting polymer. The resulting polymer can function directly as a component or adhesive joint.

[0124] Example 5: Measurements of flexural modulus and flexural strength of polybenzoxazines before and after forming / self-healing

[0125] Polybenzoxazine test specimens were produced from the batch 1.4 specified in Example 1 (Table 1) using the temperature treatments "110 °C", "150 °C", and "180 °C" according to Table 2 above. Their flexural modulus and flexural strength were determined both before and after comminution and self-healing. Comminution and subsequent self-healing took place as described in Example 4. The polybenzoxazine test specimens were subjected to up to 5 comminution / self-healing cycles.

[0126] The polybenzoxazine test specimens were examined using 3-point bending tests. The results from the bending test, based on DIN EN ISO 178 (sample type A [50x10x4 mm 3]) show that the flexural modulus of the polymer samples, even after five comminution and healing cycles, remains within the error range of the flexural modulus for the respective samples prior to comminution / self-healing (see Fig. 5). The results also indicate a tendency for a comparatively higher modulus to be achieved when applying approach No. 1.4 with the temperature treatment "150 °C."

[0127] In contrast to the flexural modulus, the determination of flexural strength clearly demonstrates the influence of the process conditions applied during the comminution / self-healing cycles on the mechanical properties of the material (see Fig. 6). After the initial comminution and pressing (annealing), a significant reduction in flexural strength is evident. Strength losses are up to 70% for samples that have undergone all heat stages up to 180 °C and up to 33% for samples aged up to 150 °C. Similar to the trend for the flexural modulus, however, there is also a tendency for strength to increase or remain at the same level with an increasing number of comminution / self-healing cycles. The samples tempered for only 2 hours at 110 °C have the lowest flexural strength, averaging 20.85 MPa, which could indicate that the polymer is still incompletely crosslinked.

[0128] Another (related) invention relates to a polymer as defined in aspects 1 to 13 below:

[0129] 1 . Polymer comprising or consisting of polybenzoxazine and / or polybenzoxazine-

[0130] Derivative, wherein the polymer is obtainable by a synthesis comprising at least one polymerization of one or more compounds of formula (I) in the presence and / or with the participation of one or more polyetheramines, wherein

[0131] R 1 , R 2 , R 3 , R 4 , R 5 and R 9 are the same or different and each represents an organic radical or H; and

[0132] R 6 , R 7 and R 8 are the same or different and each represents an organic radical or H or

[0133] R 6 and R 7 are linked together to form a covalent bond, and R8 represents an organic radical or H or R 7 and R 8 are linked together to form a covalent bond, and R 6represents an organic radical or H. Polymer according to aspect 1, wherein the organic radicals of the one or more compounds of formula (I) are selected from optionally substituted aromatic and / or aliphatic, linear and / or branched, saturated and / or unsaturated carbon radicals with a respective total number of carbon atoms per organic radical in the range from 1 to 22, preferably with a respective total number of carbon atoms per organic radical in the range from 6 to 17, wherein the one or more compounds of formula (I) particularly preferably have two or more benzoxazine structural units. Polymer according to one of the preceding aspects, wherein the polymer is obtainable by a synthesis comprising at least one polymerization of one or more compounds of formula (Ia) in the presence and / or with the participation of one or more polyetheramines, where R 10 and R 11are the same or different and are each H or an alkyl group having 1 to 4 carbon atoms, preferably a methyl group. Polymer according to one of the preceding aspects, wherein the synthesis comprises the polymerization of at least two compounds of formula (I) or (Ia) each having different molar masses. Polymer according to one of the preceding aspects, wherein the one or more polyetheramines have a molar mass in the range of 600 to 2,000 g / mol. Polymer according to one of the preceding aspects, wherein the one or more polyetheramines are polyetheramines having the formula (II)

[0134] where m is an integer from 9 to 39, and

[0135] I and n are each integers and the sum of I and n is 3 to 6. 7 Polymer according to one of the preceding aspects, wherein the molar ratio of compounds of formula (I) or (Ia) to polyetheramines is in the range from 1:0.01 to 1:1.5, preferably in the range from 1:0.06 to 1:1.5, particularly preferably in the range from 1:0.06 to 1:1.15.

[0136] 8 Polymer according to any one of the preceding aspects, comprising or consisting of structural repeating units of the formulas (III.a), (III.b) and / or (III.c)

[0137] (lll.b)

[0138] (III.c). Polymer according to one of the preceding aspects, wherein the polymer has dynamic properties. Polymer according to one of the preceding aspects, wherein the polymer has one or more macroscopic gradients. Polymer according to one of the preceding aspects, wherein at least one mechanical or physical property of the polymer changes gradually along at least one extension direction of the polymer, wherein the at least one mechanical or physical property of the polymer is preferably selected from the group consisting of

[0139] - glass transition temperature,

[0140] - Operating temperature range,

[0141] - breaking strength,

[0142] - flexural strength,

[0143] - flexural modulus,

[0144] - impact strength, and

[0145] - Hardness. Use of a polymer as defined in any of the preceding aspects as an adhesive and / or as an adhesive film and / or in composite materials, preferably in layered laminates or sandwich structures, and / or as a surface coating and / or as a matrix resin.

[0146] 13. Use of a polymer as defined in any one of aspects 1 to 11 as an adhesive film with dynamic properties.

[0147] For further explanations of the individual aspects defined above and in particular the terms used therein, reference is made to the explanations and definitions of terms further above in the text, which apply mutatis mutandis to the further (related) invention described in the above aspects.

Claims

Patent claims:

1. Macroscopically graded polymer comprising or consisting of polybenzoxazine and / or polybenzoxazine derivative.

2. Macroscopically graded polymer according to claim 1, wherein the macroscopically graded polymer is obtainable by a synthesis comprising at least one polymerization of one or more compounds of the formula (I) where R 1 , R 2 , R 3 , R 4 , R 5 and R 9 are the same or different and each represents an organic radical or H; and R®, R 7 and R 8 are the same or different and each represents an organic radical or H or R® and R 7 are linked together to form a covalent bond, and R 8 represents an organic residue or H or R 7 and R 8are linked together to form a covalent bond, and R® represents an organic radical or H, wherein the organic radicals are preferably selected from optionally substituted aromatic and / or aliphatic, linear and / or branched, saturated and / or unsaturated carbon radicals having a respective total number of carbon atoms per organic radical in the range from 1 to 22, preferably having a respective total number of carbon atoms per organic radical in the range from 6 to 17, wherein the compounds of formula (I) particularly preferably have two or more benzoxazine structural units.

3. Macroscopically graded polymer according to one of the preceding claims, wherein the macroscopically graded polymer is obtainable by a synthesis comprising at least one polymerization of one or more compounds of formula (Ia) where R 10 and R 11are the same or different and are each H or an alkyl group having 1 to 4 carbon atoms, preferably a methyl group.

4. Macroscopically graded polymer according to one of claims 2 or 3, wherein the synthesis comprises the polymerization of at least two compounds of formula (I) or (Ia) each having different molar masses.

5. Macroscopically graded polymer according to one of claims 2 to 4, wherein the at least one polymerization of the one or more compounds of formula (I) or (Ia) takes place in the presence and / or with the participation of one or more nucleophiles, wherein the one or more nucleophiles are preferably selected from the group consisting of amines, thiols and alcohols, particularly preferably selected from the group consisting of monofunctional amines, difunctional amines, multifunctional amines, amines bound to a polyether main chain, thiols and alcohols, wherein the one or more nucleophiles are very particularly preferably polyetheramines having a molar mass in the range of 600 to 2,000 g / mol, in particular polyetheramines having the formula (II) (II), where m is an integer from 9 to 39, and I and n are each integers and the sum of I and n is 3 to 6.

6. Macroscopically graded polymer according to one of claims 2 to 5, wherein the molar ratio of compounds of formula (I) or (Ia) to nucleophiles is in the range from 1:0.01 to 1:1.5, preferably in the range from 1:0.06 to 1:1.5, particularly preferably in the range from 1:0.06 to 1:1.

15.

7. Macroscopically graded polymer according to any one of the preceding claims, comprising or consisting of structural repeating units of the formulas (lll.a), (lll.b) and / or (III. c) (lll.b) (lll.c).

8. A macroscopically graded polymer according to any one of the preceding claims, wherein the macroscopically graded polymer has dynamic properties.

9. Macroscopically graded polymer according to one of the preceding claims, wherein at least one mechanical or physical property of the macroscopically graded polymer changes gradually along at least one extension direction of the macroscopically graded polymer, wherein the at least one mechanical or physical property of the macroscopically graded polymer is preferably selected from the group consisting of - glass transition temperature, - Operating temperature range, - breaking strength, - flexural strength, - flexural modulus, - impact strength, and - Hardness.

10. Use of a macroscopically graded polymer as defined in any one of the preceding claims as an adhesive and / or as an adhesive film and / or in composite materials, preferably in layered laminates or sandwich structures, and / or as a surface coating and / or as a matrix resin.

11. A process for producing a macroscopically graded polymer as defined in any one of the preceding claims 1 to 9, comprising the following steps: a) providing and / or, optionally partially, mixing the one or more monomeric reactants for producing the macroscopically graded polymer; b) optionally filling a mold with the one or more reactants and / or the one or more reactant mixtures or optionally applying the one or more reactants and / or the one or more reactant mixtures to a support; c) polymerizing, preferably thermally polymerizing, the one or more reactants and / or the one or more reactant mixtures, wherein the plurality of reactants and / or reactant mixtures are at least partially in contact with one another and / or are at least partially mixed with one another;wherein the time period and / or temperature selected for the polymerization in step c) differs from one another at two or more locations of the one or more reactants and / or the one or more reactant mixtures and / or; the reactants and / or reactant mixtures to be polymerized in step c) have a total of at least two regions of different composition, preferably at least one region with a gradually changing composition, so that a macroscopically graded polymer results.

12. A process for producing a macroscopically graded polymer as defined in any one of the preceding claims 1 to 9, comprising the following steps: i) producing or providing two or more polymeric compounds selected from polybenzoxazines and polybenzoxazine derivatives, wherein the two or more polymeric compounds each differ from one another in at least one mechanical or physical property, ii) combining the two or more polymeric compounds produced or provided in step i) to result in a macroscopically graded polymer.

13. The method of claim 12, wherein one or more of the two or more polymeric compounds are provided in the form of granules or in the form of a film.

14. Kit for producing a macroscopically graded polymer as defined in any one of the preceding claims 1 to 9, comprising two or more polymeric compounds selected from polybenzoxazines and polybenzoxazine derivatives, preferably in granular form, wherein the two or more polymeric compounds each differ from each other in at least one mechanical or physical property, or two or more components, each comprising at least one benzoxazine or benzoxazine derivative, preferably each comprising at least one compound of formula (I) or (Ia) as defined in one of the preceding claims 2 or 3, wherein one or more of the two or more components particularly preferably additionally comprises one or more nucleophiles, preferably one or more nucleophiles as defined in one of the preceding claims 5, wherein the two or more components each differ from one another in their quantitative or qualitative composition, wherein the benzoxazines or benzoxazine derivatives comprised by the two or more components preferably each have different molecular weights and / or the two or more components each have different molar ratios of (i) benzoxazines or benzoxazine derivatives to (ii) nucleophiles, wherein the two or more polymeric compounds or the two or more components are each present as separate individual components.

15. Use of a kit as defined in claim 14 as a multi-component adhesive.

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