DE102023108008A1 - Macroscopically graded polymer and use and method for producing the same and kit for producing a macroscopically graded polymer - Google Patents

Abstract

A macroscopically graded polymer comprising or consisting of polybenzoxazine and/or polybenzoxazine derivative is described. The use of a macroscopically graded polymer according to the invention and methods for producing a macroscopically graded polymer are also described. A kit for producing a macroscopically graded polymer according to the invention and the use of a kit according to the invention are also described.

Description

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 methods 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.

The invention is defined in the appended claims. Preferred aspects of the present invention also emerge from the following description, including the examples. If certain embodiments are designated as preferred for an 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 person skilled in the art in the individual case concludes otherwise from the present text.

A product design that is tailored to requirements is an essential component of material development. On the one hand, the increasing environmental awareness of society and industry requires that recyclability be taken into account in the molecular design of polymer materials. On the other hand, a usage phase that is as long as possible, properties that are optimized for requirements and the saving of polymer materials are required. For applications in which mechanical and chemical resistance are essential, three-dimensionally cross-linked polymers, so-called duromers, are typically used.

In addition to structural components, duromer-based systems also dominate in the context of load-bearing adhesives, where they ensure high strength and resistance to various media. However, highly cross-linked adhesives have a comparatively high rigidity and low flexibility, which limits an adhesive bond with regard to mostly complex types of load. Even under ideal tensile stress, an eccentric force introduction and a possible notch effect due to a shape discontinuity and a redirection of the force flow can occur.

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 stress induces a multiaxial stress state (cf. 1 as well as the “Handbook of Adhesive Technology” by Manfred Rasche, 1986, Carl Hanser Verlag).

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

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

Different approaches can be used to reduce stress peaks in an adhesive bond and to 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 the connection. However, the stress peaks in the adhesive bond remain.

One method for reducing stress peaks in an adhesive bond and achieving 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 one 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.

Building on this, graded materials have been established, as shown by Sancaktar and Kumar (cf. “ 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.

Another constructive solution is the design of the joining partners. However, this is complex and represents a limitation for the application to different components (see “ 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 ).

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. (cf. “ 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.

Against this background, the primary object of the present invention was to provide a material (particularly suitable for use as an adhesive) which enables local adjustment of mechanical and/or physical properties in order, for example, to reduce or even completely avoid the occurrence of stress peaks in (composite) components bonded together in a simple and efficient manner or to realize a more targeted and improved stress reduction in composite components bonded together.

A further object of the present invention was to provide a process for producing such a material.

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

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.

Further objects arise from the following description and the patent claims.

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

• - Shen et al., (2016) „Understanding the surface properties of polybenzoxazines: Interaction of polybenzoxazine model compounds with metal ions and wate“ in J. Appl. Polym. Sci. ;
• - 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 ;
• - 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 ;
• - 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 ;
• - He et al. (2018) „A mussel-inspired polybenzoxazine containing catechol groups“ in Polymer, Vol. 158, S. 53-58 ;
• - Higginson et al. (2019) „Bioinspired Design Provides High-Strength Benzoxazine Structural Adhesives“ in Angew. Chem., Vol. 131, S. 12399 - 12407 ;
• - Wang et al. (2016) „Latent curing systems stabilized by reaction equilibrium in homogeneous mixtures of benzoxazine and amine“ in Scientific Reports 6:38584 .

Polybenzoxazines in general and 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:

• - Shen et al., (2016) “Understanding the surface properties of polybenzoxazines: Interaction of polybenzoxazine model compounds with metal ions and wate” in J. Appl. Polym. Sci. ;
• - Tuzun et al. (2010) “Benzoxazine Containing Polyester Thermosets with Improved Adhesion and Flexibility” in Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 48, pp. 4279-4284 ;
• - 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, No. 16, pp. 1796-1806 ;
• - Lee et al. (2018) “High-Performance Printed Circuit Board Materials Based on Benzoxazine and Epoxy Blend System” in Macromolecular Research. Vol. 26, pp. 388-393 ;
• - US 9,296,928 B2 ;
• -He et al. (2018) “A mussel-inspired polybenzoxazine containing catechol groups” in Polymer, Vol. 158, pp. 53-58 ;
• - Higginson et al. (2019) “Bioinspired Design Provides High-Strength Benzoxazine Structural Adhesives” in Angew. Chem., Vol. 131, pp. 12399 - 12407 ;
• -Wang et al. (2016) “Latent curing systems stabilized by reaction equilibrium in homogeneous mixtures of benzoxazine and amine” in Scientific Reports 6:38584 .

• - 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, S. 201 ;
• - Voleppe et al. (2021) „Enhanced fracture resistance of thermoset/thermoplastic interfaces through crack trapping in a morphology gradient“ in Polymer, Vol. 218, Is. 18 ;
• - Sawaryn et al. (2011) „Advanced chemically induced phase separation in thermosets: Polybenzoxazines toughened with multifunctional thermoplastic mainchain benzoxazine prepolymers“ in Polymer, Vol. 52, Is. 15 ;
• - 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 ;
• - Zhang et al. (2019) „Unexpected Healability of an ortho-Blocked Polybenzoxazine Resin“ in ACS Macro Lett., Vol.8, S. 506-511 ;
• - Sun et al. (2015) „A curing system of benzoxazine with amine: reactivity, reaction mechanism and material properties“ RSC Adv., Vol. 5, S. 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, S. 1700517 .

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

• - 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 ;
• - Voleppe et al. (2021) “Enhanced fracture resistance of thermoset/thermoplastic interfaces through crack trapping in a morphology gradient” in Polymer, Vol. 218, Is. 18 ;
• - Sawaryn et al. (2011) “Advanced chemically induced phase separation in thermosets: Polybenzoxazines toughened with multifunctional thermoplastic mainchain benzoxazine prepolymers” in Polymer, Vol. 52, Is. 15 ;
• - 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 ;
• - Zhang et al. (2019) “Unexpected Healability of an ortho-Blocked Polybenzoxazine Resin” in ACS Macro Lett., Vol.8, pp. 506-511 ;
• - 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 .

• - US 4,650,193 ;
• - US 3,784,209 ;
• - US 6,113,831 ;
• - US 8,016,696 B2 ;
• - US 5,545,229 .

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

• - US 4,650,193 ;
• - US 3,784,209 ;
• - US 6,113,831 ;
• - US 8,016,696 B2 ;
• - US 5,545,229 .

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.

In particular, it should be noted that the information contained in the publication of 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 expressly to be distinguished from the macroscopic gradients or macroscopically graded polymers described in the context of the present invention. In relation to the gradients described in the publication by Sawaryn et al., the macroscopic gradient described in the context of the present invention differs both in its magnitude and in its significance for the properties of the material resulting from the gradient.

Macroscopic is defined as an area that can be detected without technical aids. Such an area can be quantitatively assigned to sizes of ≥ 1 mm.

With regard to the description of “macroscopic properties”, these are to be considered as the totality of the properties (structure) that vary at the microscopic level.

For the purposes of the present invention, a macroscopically graded polymer is understood to mean a polymer which exhibits a gradual change towards visibly has at least one chemical, physical and/or mechanical property. A macroscopically graded polymer in the sense of the present invention has a graded property transition in at least one spatial direction, which is characterized by the absence of a sharp interface for the changing property(s).

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 set at equal distances in the measuring section. Preferably, the length of the measuring section is a maximum of 75 mm, particularly preferably a maximum of 50 mm, very particularly 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.

A macroscopic gradient in the sense of the present invention is that 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 represent 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 in the sense of the present invention has exclusively graded property transitions.

• - keine Hybridbauweise: Ein Bauteil oder eine Klebstoffverbindung mit lokal einstellbaren und definierten Materialeigenschaften ist mit nur einem Werkstoff realisierbar.
• - gradierbares Material: Durch den gradierten Eigenschaftsübergang lassen sich scharfe Grenzflächen für Eigenschaftsänderungen und die damit verbundenen Nachteile (wie lokal auftretende Spannungsspitzen oder die Erzeugung von Schwachstellen innerhalb eines Materialsystems) vermeiden.
• - geringere Dimensionierung von Klebefugen möglich.

The use of a macroscopically graded polymer according to the invention has the following advantages compared to the solutions known from the prior art explained above:

• - no hybrid construction: A component or an adhesive connection with locally adjustable and defined material properties can be realized with only one material.
• - Gradable material: The graded property transition makes it possible to avoid 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 possible.

Preferably, the properties of a macroscopically graded polymer according to the invention - such as the deformation, the rigidity and the thermal properties - can still be changed even after production, e.g. by subsequent thermal treatment (for example by means of warm air, heating elements or induction). Such a subsequent change in the properties allows, for example, the properties of the macroscopically graded polymer to be adapted to the required conditions for the respective application of the material. In addition, 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).

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 and by a (gradual) change in the conditions for the curing process of the macroscopically graded polymer along an extension direction. This makes it possible to generate property gradients within a macroscopically graded polymer that can be specifically influenced, for example by local flexibility, stiffening and different temperature-dependent properties. sensitive areas within the macroscopically graded polymer, for example to compensate for stress peaks within the adhesive joint when using the macroscopically graded polymer as an adhesive. In this context, it should be noted that even partially (not yet fully) polymerized/cured polybenzoxazines and polybenzoxazine derivatives represent polymers within the meaning of the present invention.

• - Mindestens zwei sich voneinander unterscheidende Zusammensetzungen, wobei es sich sowohl um Polymerzusammensetzungen als auch um zu polymerisierende monomere oder oligomere Edukte und/oder Eduktmischungen handeln kann, werden in eine Form gegeben und räumlich getrennt zum Erstarren gebracht. Durch Aufheizen vermischen sich die unterschiedlichen Zusammensetzungen in den Grenzbereichen. Das Aufheizen führt bei zu polymerisierenden monomeren oder oligomeren Edukten bzw. Eduktmischungen gleichzeitig eine Polymerisation. Durch das Aufheizen kann es ggfs. auch zu einer weiteren Polymerisation der Polymerzusammensetzungen kommen. Auch eine Simultane Applikation ist möglich, wobei alle Phasen gleichzeitig in die Form gefüllt oder auf die Oberfläche aufgetragen werden können.
• - Eine zu polymerisierende monomere oder oligomere Zusammensetzung oder eine Polymerzusammensetzung wird mit sich lokal voneinander unterscheidenden Aushärtetemperaturen behandelt, sodass makroskopisch gradierte Eigenschaftsänderungen, beispielsweise bezüglich Härte und Modulen, innerhalb des Polymers erzeugt werden.
• - Unterschiedliche Zusammensetzungen werden jeweils vollständig ausgehärtet und können im Anschluss beliebig, z.B. je nach einzustellendem Härtegrad, durch Druck und/oder Temperatur miteinander verbunden werden. Bevorzugt ist ein erfindungsgemäßes makroskopisch gradiertes Polymer, wobei das makroskopisch gradierte Polymer erhältlich ist durch eine Synthese umfassend mindestens eine Polymerisation von ein oder mehreren Verbindungen der Formel (I)
  

wobei

• - R¹, R², R³, R⁴, R⁵ und R⁹ gleich oder verschieden sind und jeweils einen organischen Rest oder H darstellen; und
• - R⁶, R⁷ und R⁸ gleich oder verschieden sind und jeweils einen organischen Rest oder H darstellen oder R⁶ und R⁷ miteinander verbunden sind, um eine kovalente Bindung zu bilden, und R⁸ einen organischen Rest oder H darstellt oder R⁷ und R^B miteinander verbunden sind, um eine kovalente Bindung zu bilden, und R⁶ einen organischen Rest oder H darstellt,

wobei die organischen Reste vorzugsweise ausgewählt sind aus gegebenenfalls substituierten aromatischen und/oder aliphatischen, linearen und/oder verzweigten, gesättigten und/oder ungesättigten Kohlenstoffresten mit einer jeweiligen Gesamtzahl an Kohlenstoffatomen pro organischem Rest im Bereich von 1 bis 22, bevorzugt mit einer jeweiligen Gesamtzahl an Kohlenstoffatomen pro organischem Rest im Bereich von 6 bis 17,
wobei die Verbindungen der Formel (I) besonders vorzugsweise zwei oder mehr Benzoxazin-Struktureinheiten aufweisen.
Polybenzoxazine umfassend Struktureinheiten auf Basis von 1,3-Benzoxazin und deren Derivaten sind somit im Rahmen der vorliegenden Erfindung bevorzugt, wobei jedoch vom Umfang der Erfindung auch Polybenzoxazine umfasst sind, welche unter Verwendung weiterer oder anderer Benzoxazin-Isomere (wie beispielsweise 1,4-Benzoxazin, 3,1-Benzoxazin und 2,1-Benzoxazin) und/oder deren Derivaten erhalten werden. Zusätzlich kann die Synthese eines erfindungsgemäßen makroskopisch gradierten Polymers auch unter Einsatz weiterer Monomere und/oder fachüblicher Reagenzien, insbesondere unter Einsatz flexibilisierender Reagenzien, erfolgen.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:

• - At least two different compositions, which can be polymer compositions as well as 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 in the boundary areas. Heating leads to simultaneous polymerization of the monomeric or oligomeric reactants or reactant mixtures to be polymerized. Heating can 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 at the same time.
• - A monomeric or oligomeric composition to be polymerized or a polymer composition is treated with locally differing curing temperatures so that macroscopically graded property changes, for example with regard to hardness and moduli, are produced within the polymer.
• - Different compositions are each completely cured and can then be bonded together as desired, e.g. depending on the degree of hardness to be set, by pressure and/or temperature. A macroscopically graded polymer according to the invention is preferred, 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 ⁶ , R ⁷ and R ⁸ are the same or different and each represents an organic radical or H, or R ⁶ and R ⁷ are joined together to form a covalent bond and R ⁸ represents an organic radical or H, or R ⁷ and R ^B are joined together to form a covalent bond and R ⁶ 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.
Polybenzoxazines comprising structural units based on 1,3-benzoxazine and their derivatives are thus preferred within the scope of the present invention, although the scope of the invention also includes polybenzoxazines which are obtained using further or other benzoxazine isomers (such as e.g. 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 other monomers and/or standard reagents, in particular using flexibilizing reagents.

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.

wobei R¹⁰ und R¹¹ gleich oder verschieden sind und jeweils H oder eine Alkylgruppe mit 1 bis 4 Kohlenstoffatomen, vorzugsweise H oder eine Methylgruppe, sind.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.

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

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

Additionally or alternatively, the change in the stoichiometric and/or molecular composition can also be realized by the use, selection and amount of nucleophiles preferentially involved in the synthesis.

wobei
m eine ganze Zahl von 9 bis 39 bedeutet, und
I und n jeweils ganz Zahlen bedeuten und die Summe aus I und n 3 bis 6 beträgt.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 made from ethylene oxide (EO), propylene oxide (PO), or a mixture of both oxides 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
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 created that is variable and definable in its material properties. By using different nucleophiles and/or different molar compositions between nucleophile and benzoxazine to produce the polymer, single-phase materials with graded properties can be obtained using a nucleophile.

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

Also preferred is a macroscopically graded polymer according to the invention, wherein the molar ratio of compounds of the formula (I) or (I.a) 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.

Erfindungsgemäße makroskopisch gradierte Polymere umfassend oder bestehend aus den vorgenannten Struktureinheiten haben sich als besonders geeignet für den Einsatz als z.B. Klebstoffverbindung erwiesen.Preference is given to 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)

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.

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

Covalently cross-linked polymers are referred to as dynamic in which, as a result of an adequate stimulus, in the case of the present invention preferably by varying the temperature and given under pressure, the covalent bonding sites can dynamically separate and reconnect (see “ 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 have self-healing properties and allow for deformation. In the case of the present invention, this dynamic preferably contributes to the subsequent stress relief by means of a locally introduced stimulus.

The presence of dynamic properties within the macroscopically graded polymer or the presence of a dynamic polymer network makes it possible to bypass and overcome the residual stress of, for example, fully cross-linked polymer systems, cured adhesive joints and rigid connections.

A major cause of residual stress is the lack of relaxation capacity of cross-linked structures (cf. "Bonding: Basics, 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 storage under changed thermal conditions, such as cold. This opens up great potential for significantly extending the service life of (composite) components through stress relaxation and also for enabling recyclability by dissolving the network points.

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

Without being bound to a theory, it is assumed that the self-healing mechanism is based on an exchange of covalent bonds. Kinetically controlled, simultaneous exchange reactions in the form of bond breaking and bond closing reactions or thermodynamically controlled, possibly reversible, condensation and addition reactions can take place.

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 (on a macroscopic level) along at least one extension direction of the macroscopically graded polymer,

• - Glasübergangstemperatur,
• - Gebrauchs-Temperaturbereich,
• - Bruchfestigkeit,
• - Biegefestigkeit,
• - Biegemodul,
• - Schlagzähigkeit, und
• - Härte.

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.

The gradual change within the polymer is not necessarily limited to a linear or continuous course. For example, the gradient of the change can be of varying intensity across the direction of expansion of the macroscopically graded polymer, the gradual change perceptible at the macroscopic level can also extend over only a portion of the polymer and/or the change in the property along the direction of expansion can take on changing signs (i.e., for example, the flexural strength of the macroscopically graded polymer can initially decrease and then increase again along an expansion direction), whereby a periodic gradual change in a property is also conceivable and is included in the scope of the present invention.

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.

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.

The impact strength is preferably determined using the Charpy impact properties, preferably as described in DIN EN 179-1.

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

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 (especially in fiber-reinforced plastics, FRP), preferably in layered laminates or sandwich structures,
and/or
as a surface coating
and/or
as matrix resin.

1. a) Bereitstellen und/oder, gegebenenfalls teilweises, Mischen der ein oder mehreren monomeren Edukte für die Herstellung des makroskopisch gradierten Polymers;
2. b) gegebenenfalls Befüllen einer Form mit den ein oder mehreren Edukten und/oder der ein oder mehreren Eduktmischungen oder gegebenenfalls Applizieren der ein oder mehrerer Edukte und/oder der ein oder mehreren Eduktmischungen auf einem Träger;
3. c) Polymerisieren, vorzugsweise thermisches Polymerisieren, der ein oder mehrerer Edukte und/oder der ein oder mehreren Eduktmischungen, wobei die mehreren Edukte und/oder Eduktmischungen zumindest teilweise miteinander in Kontakt stehen und/oder zumindest teilweise miteinander vermischt sind;

wobei
sich die für das Polymerisieren in Schritt c) gewählte Zeitdauer und/oder Temperatur an zwei oder mehr Stellen der ein oder mehrerer Edukte und/oder der ein oder mehreren Eduktmischungen voneinander unterscheidet
und/oder
die in Schritt c) zu polymerisierenden Edukte und/oder Eduktmischungen insgesamt mindestens zwei Bereiche unterschiedlicher Zusammensetzung, vorzugsweise mindestens einen Bereich mit sich graduell ändernder Zusammensetzung, aufweisen,
so dass ein makroskopisch gradiertes Polymer resultiert.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:

1. a) providing and/or, optionally partially, mixing the one or more monomeric reactants for the preparation of the macroscopically graded polymer;
2. b) if necessary, filling a mold with the one or more reactants and/or the one or more reactant mixtures or, if necessary, applying the one or more reactants and/or the one or more reactant mixtures to a carrier;
3. 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;

where
the time period and/or temperature selected for 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,
resulting in a macroscopically graded polymer.

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

Preferably, the reactant mixtures are subjected to homogenization by brief heating. This can cause an initial polymer reaction within the reactant mixture, but this does not affect the properties of the reactant mixture (apart from the resulting homo genization) does not change or does not change noticeably. A reactant mixture heated for a short time for the purposes of homogenization therefore 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.

When using several reactants or reactant mixtures in step b), the reactants or reactant mixtures come into contact with one another, with at least partial mixing of the reactants or reactant mixtures taking place at the respective contact surfaces. The at least partial mixing of the various reactants or reactant mixtures used causes the formation of macroscopically graded property transitions in the subsequent step c) of polymerization or contributes to this.

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.

As already mentioned above, in order 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, wherein preferably the molar ratio of the various components within the reactant mixture to be polymerized is varied.

The method described above provides a production method for a macroscopically graded polymer according to the invention, in which the macroscopically graded polymer is produced directly from its monomeric starting materials or starting material mixtures thereof. Alternatively, a macroscopically graded polymer according to the invention can also be produced by combining several previously produced polymeric compounds selected from polybenzoxazines and polybenzoxazine derivatives, each with different properties.

• i) Herstellen oder Bereitstellen von zwei oder mehr polymeren Verbindungen ausgewählt aus Polybenzoxazinen und Polybenzoxazin-Derivaten, wobei die zwei oder mehr polymeren Verbindungen sich jeweils in mindestens einer mechanischen oder physikalischen Eigenschaft voneinander unterscheiden,
• ii) Verbinden der in Schritt i) hergestellten oder bereitgestellten zwei oder mehr polymeren Verbindungen, so dass ein makroskopisch gradiertes Polymer resultiert.

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 differ from each other in at least one mechanical or physical property,
• ii) combining the two or more polymeric compounds prepared or provided in step i) to form a macroscopically graded polymer.

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 high enough for macroscopic flow to occur.

Preference is given to 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.

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 for a short time in an 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 the pot life, melting temperature and viscosity can be adjusted via the composition and combination of the respective monomers.

• zwei oder mehr polymere Verbindungen ausgewählt aus Polybenzoxazinen und Polybenzoxazin-Derivaten, vorzugsweise in granulärer Form, wobei die zwei oder mehr polymeren Verbindungen sich jeweils in mindestens einer mechanischen oder physikalischen Eigenschaft voneinander unterscheiden,

oder

• zwei oder mehr Komponenten, jeweils umfassend mindestens ein Benzoxazin oder Benzoxazin-Derivat,
  • vorzugsweise jeweils umfassend mindestens eine Verbindung der Formel (I) oder (I.a) (wie oben und in den Ansprüchen definiert),
    • wobei eine oder mehrere der zwei oder mehr Komponenten besonders vorzugsweise zusätzlich ein oder mehrere Nukleophile umfasst, bevorzugt ein oder mehrere Nukleophile wie oben und in den Ansprüchen definiert,
• wobei die zwei oder mehr Komponenten sich jeweils in ihrer quantitativen oder qualitativen Zusammensetzung voneinander unterscheiden, wobei die von den zwei oder mehr Komponenten umfassten Benzoxazine oder Benzoxazin-Derivate vorzugsweise jeweils unterschiedliche Molmassen besitzen und/oder die zwei oder mehr Komponenten jeweils unterschiedliche molare Verhältnisse von (i) Benzoxazinen oder Benzoxazin-Derivaten zu (ii) Nukleophilen aufweisen,

wobei die zwei oder mehr polymeren Verbindungen oder die zwei oder mehr Komponenten jeweils als separate Einzelkomponenten vorliegen.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 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 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 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 molar masses 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 each exist as separate individual components.

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

The invention is explained in more detail below using examples and the attached figures. The examples given below are intended to describe and explain the invention in more detail without limiting its scope.

• 1: Schematische Darstellung des Spannungszustands in einer viskoelastischen Klebstoffschicht und der Zugscherbelastung (nicht erfindungsgemäß). Deutlich zu sehen, die Spannungsspitzen an den Enden der Fügeverbindung. Entnommen aus „Kleben: Grundlagen, Technologien, Anwendungen“ von Gerd Habenicht, 6. Auflage, Springer Verlag, Heidelberg.
• 2: Schematische Darstellung eines hergestellten erfindungsgemäßen makroskopisch gradierten Polymers. Angegeben sind jeweils die Shore-D-Härten an unterschiedlichen Stellen des makroskopisch gradierten Polymers. Die Shore D-Härte verdeutlich die stetige Veränderung der Materialbeschaffenheit über die Länge des Probekörpers.
• 3: Shore-D-Härten der in Beispiel 3 untersuchten Polybenzoxazine, dargestellt als Säulendiagramm. Dargestellt ist jeweils der Mittelwert aus 5 Messungen je hergestelltem Polybenzoxazin. Die Bezeichnung in der x-Achse für die einzelnen Polybenzoxazine setzt sich jeweils aus der Nummer des für die Herstellung des Polybenzoxazins verwendeten Ansatzes („1.1“ bis „1.7“; vgl. Tabelle 1 weiter unten für mehr Details) und der Bezeichnung für die angewendete Temperaturbehandlung („110°C“, „150°C" oder „180°C"; vgl. Tabelle 2 weiter unten für mehr Details) zusammen.
• 4: 4 a) ist eine schematische Darstellung der Herstellung des Polybenzoxazins aus Benzoxazin und Amin und der zyklischen Zerkleinerung und Selbstheilung des Materials. Die oben links in 4 a) dargestellten Prüfkörper stellen aus dem Ansatz Nr. 1.4 gemäß Beispiel 1 hergestellte Prüfkörper aus Polybenzoxazin dar, wobei der helle Prüfkörper unter Anwendung der Temperaturbehandlung „150°C" und der dunkle Prüfkörper unter Anwendung der Temperaturbehandlung „180°C" (vgl. Tabelle 2 weiter unten für mehr Details) hergestellt wurde. 4 b) zeigt einen Prüfkörper, welcher durch Verbinden zweier unterschiedlicher Polybenzoxazin-Proben (Ansatz Nr. 1.4, unter Anwendung der Temperaturbehandlung „150°C" bzw. „180°C") mittels Druck und Temperatur erhalten wurde.
• 5: Biegemodule der in Beispiel 5 untersuchten Polybenzoxazine. Dargestellt ist jeweils der Mittelwert aus 5 Messungen je untersuchter Probe. Die Bezeichnung in der x-Achse für die einzelnen Proben setzt sich jeweils aus der Bezeichnung für die angewendete Temperaturbehandlung zur Herstellung des Polybenzoxazins (110 °C, 150 °C und/oder 180 °C; vgl. Tabelle 2 weiter unten für mehr Details) und der Anzahl an Zerkleinerungs/Selbstheilungs-Zyklen, welchen das jeweilige Polybenzoxazin unterzogen wurde („0 x pr.“ = die Durchführung keines Zerkleinerungs/Selbstheilungs-Zyklusses, „1 x pr." = die Durchführung eines Zerkleinerungs/Selbstheilungs-Zyklusses, usw.), zusammen.
• 6 Biegefestigkeiten der in Beispiel 5 untersuchten Polybenzoxazine. Dargestellt ist jeweils der Mittelwert aus 5 Messungen je untersuchter Probe. Die Bezeichnung in der x-Achse für die einzelnen Proben setzt sich jeweils aus der Bezeichnung für die angewendete Temperaturbehandlung zur Herstellung des Polybenzoxazins (110 °C, 150 °C und/oder 180 °C; vgl. Tabelle 2 weiter unten für mehr Details) und der Anzahl an Zerkleinerungs/Selbstheilungs-Zyklen, welchen das jeweilige Polybenzoxazin unterzogen wurde („0 x pr.“ = die Durchführung keines Zerkleinerungs/Selbstheilungs-Zyklusses, „1 x pr." = die Durchführung eines Zerkleinerungs/Selbstheilungs-Zyklusses, usw.), zusammen.

They show:

• 1 : Schematic representation of the stress state in a viscoelastic adhesive layer and the tensile shear load (not according to the invention). The stress peaks at the ends of the joint are clearly visible. Taken from "Bonding: Basics, Technologies, Applications" by Gerd Habenicht, 6th edition, Springer Verlag, Heidelberg.
• 2 : Schematic representation of a macroscopically graded polymer produced according to the invention. The Shore D hardnesses are given at different points on the macroscopically graded polymer. The Shore D hardness illustrates the constant change in the material properties over the length of the test specimen.
• 3 : Shore D hardness of the polybenzoxazines investigated in Example 3, shown as a bar chart. The mean value of 5 measurements for each polybenzoxazine produced is shown. 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).
• 4 : 4 a) is a schematic representation of the preparation of polybenzoxazine from benzoxazine and amine and the cyclic comminution and self-healing of the material. The top left in 4 a) The test specimens shown represent polybenzoxazine test specimens produced from batch No. 1.4 according to Example 1, whereby the light test specimen was produced using the temperature treatment "150°C" and the dark test specimen was produced using the temperature treatment "180°C" (see Table 2 below for more details). 4 b) shows a test specimen which was obtained by joining two different polybenzoxazine samples (approach no. 1.4, using the temperature treatment "150°C" or "180°C") by means of pressure and temperature.
• 5 : Flexural moduli of the polybenzoxazines investigated in Example 5. The mean value of 5 measurements per sample investigated is shown. The designation in 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 crushing/self-healing cycles to which the respective polybenzoxazine was subjected ("0 x pr." = no crushing/self-healing cycle was carried out, "1 x pr." = one crushing/self-healing cycle was carried out, etc.).
• 6 Flexural strengths of the polybenzoxazines tested in Example 5. The mean value of 5 measurements per sample tested is shown. The designation on the x-axis for the individual pro ben 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 was carried out, "1 x pr." = one crushing/self-healing cycle was carried out, etc.).

Example 1: Preparation of mixtures of benzoxazine and amine

wurde jeweils zusammen mit einem Amin mit Handelsnamen Jeffamin® ED 600 (M = 600 g/mol) oder Jeffamin® ED 2003 (M = 2000 g/mol), aufweisend jeweils folgende allgemeine Strukturformel

eingewogen und für etwa 10 Minuten bei 110 °C homogenisiert. Die entsprechenden Einwaagen und verwendeten molaren Verhältnisse von Benzoxazin zu Amin sind in Tabelle 1 angegeben. Tabelle 1: Einwaagen und molaren Verhältnisse der für die Herstellung von Polybenzoxazinen verwendeten Mischungen. Ansatz Nr. Einwaage Benzoxazin (ARALDITE® MT 35600) [g] Einwaage Jeffamin® ED 600 [g] Einwaage Jeffamin® ED 2003 [g] molares Verhältnis Benzoxazin:Amin 1.1 6,020 8,980 - 1:1,15 1.2 6,530 8,470 - 1:1 1.3 9,099 5,901 - 1:0,5 1.4 11,327 3,673 - 1:0,25 1.5 7,205 - 7,795 1:0,25 1.6 10,470 - 4,530 1:0,1 1.7 12,332 - 2,668 1:0,05 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 together 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

weighed and homogenized for about 10 minutes at 110 °C. The corresponding weights and molar ratios of benzoxazine to amine used are given in Table 1. Table 1: Weights and molar ratios of the mixtures used for the production of polybenzoxazines. Approach No . Sample weight of benzoxazine (ARALDITE® MT 35600) [g] Initial weight Jeffamin® ED 600 [g] Initial weight of Jeffamin® ED 2003 [g] molar ratio benzoxazine:amine 1.1 6,020 8,980 - 1:1.15 1.2 6,530 8,470 - 1:1 1.3 9,099 5,901 - 1:0.5 1.4 11,327 3,673 - 1:0.25 1.5 7,205 - 7,795 1:0.25 1.6 10,470 - 4,530 1:0.1 1.7 12,332 - 2,668 1:0.05

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

The mixtures prepared in Example 1 with batches 1.4, 1.3 and 1.2 were placed next to each other in a mold, whereby a partial mixing of the individual mixtures took place. The mixture thus obtained was then subjected to a temperature treatment for 2 hours at 110 °C and then to a further temperature treatment for 2 hours at 150 °C. The macroscopically graded polymer according to the invention thus obtained is shown schematically in 2 shown.

The Shore D hardness was determined at several points 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 course of the stoichiometries from the approaches 1.4, 1.3 and 1.2 used is reflected in different hardnesses from comparatively hard to flexible and can also be distinguished visually (by color). The different hardnesses also indicate different mechanical properties, from comparatively stiff to flexible, within the macroscopically graded polymer.

The fact that the polymer produced has more than three different Shore D hardnesses over its course (in 2 4 hardness values are given as examples), although only 3 batches with different stoichiometry were used to produce the polymer, indicates that the polymer produced shows a macroscopically graded change in properties. A clear distinction between the three mixtures presented is no longer possible.

Example 3: Hardness measurements on polybenzoxazines treated at different temperatures

The mixtures produced in Example 1 were each subjected to different temperature treatments. The temperature treatments explained in more detail in Table 2 were used. Table 2: Explanation of the temperature treatments used for the production of polybenzoxazines. The names of the temperature treatments refer to the maximum temperature used in the respective temperature program. name of the temperature treatment Applied temperature program "110°C" 110 °C for 2 h "150°C" or "110_150°C" 110 °C for 2 h and 150 °C for 2 h "180°C" or "110_150_180°C" 110° C for 2h, 150 °C for 2 and 180 °C for 2 h

The Shore D hardness of the polybenzoxazines thus obtained was then determined. The Shore D hardness was determined as described in Example 2.

In 3 The Shore D hardnesses for the polybenzoxazines obtained from the different starting mixtures or through different temperature treatments are given in the form of a bar chart. The hardness measurements show that the material system reacts sensitively to changes in the stoichiometry/composition as well as sensitively to different curing conditions; the physical and mechanical properties of a polybenzoxazine can therefore be specifically influenced by changing the composition and stoichiometry of the starting materials as well as by varying the curing conditions.

Example 4: Malleability and self-healing

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 which were 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.

The polybenzoxazines produced can be crushed and then reshaped or cured over at least five cycles. The polybenzoxazines were crushed in each case by applying mechanical force (at a temperature of 155 °C using a surface force of 15 kN for 10 s), which converted the previously produced compact test specimens into coarse granules.

The combination of forming temperature (155 °C) and pressure (22 kN) enables process times for bending and healing the material of approx. 15 minutes (cf. 4 a) ). Using such pressing processes, materials of different stoichiometries and curing states (i.e. materials with different material properties) can be transformed, healed or even bonded together with the formation of macroscopically graded property changes (cf. 4 b) ). By selecting the appropriate forming temperature and pressure, macroscopic flow of the material is enabled, which allows partial mixing of the different materials with each other and macroscopically graded property changes develop within the resulting polymer. The resulting polymer can function directly as a component or adhesive joint.

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

Polybenzoxazine test specimens were produced from the batch 1.4 given in Example 1 (Table 1) using the temperature treatments "110 °C", "150 °C" and "180 °C" according to Table 2 above, and their flexural modulus and flexural strength were determined both before and after comminution and self-healing (healing). The 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.

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 bending modulus of the polymer samples, even after five crushing and healing cycles, is within the error range of the bending modulus for the respective samples before crushing/self-healing (cf. 5 ). The results also show a tendency that a comparatively higher modulus can be achieved when approach No. 1.4 is used with the temperature treatments “150 °C”.

In contrast to the flexural modulus, the determination of the flexural strength makes clear the influence of the process conditions applied during the crushing/self-healing cycles on the mechanical properties of the material (cf. 6 ). After the first crushing and pressing (healing), a significant reduction in flexural strength can be seen. The loss of strength is up to 70% for samples that have been through 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, there is also a tendency for strength to increase or remain at the same level with an increasing number of crushing/self-healing cycles. The samples tempered for only 2 hours at 110 °C have the lowest flexural strength with an average of 20.85 MPa, which could indicate that the polymer is still incompletely cross-linked.

1. 1. Polymer umfassend oder bestehend aus Polybenzoxazin und/oder Polybenzoxazin-Derivat, wobei das Polymer erhältlich ist durch eine Synthese umfassend mindestens eine Polymerisation von ein oder mehreren Verbindungen der Formel (I)
   
   in Anwesenheit und/oder unter Beteiligung von ein oder mehreren Polyetheraminen, wobei
   • - R¹, R², R³, R⁴, R⁵ und R⁹ gleich oder verschieden sind und jeweils einen organischen Rest oder H darstellen; und
   • - R⁶, R⁷ und R⁸ gleich oder verschieden sind und jeweils einen organischen Rest oder H darstellen oder R⁶ und R⁷ miteinander verbunden sind, um eine kovalente Bindung zu bilden, und R⁸ einen organischen Rest oder H darstellt oder R⁷ und R⁸ miteinander verbunden sind, um eine kovalente Bindung zu bilden, und R⁶ einen organischen Rest oder H darstellt.
2. 2. Polymer nach Aspekt 1, wobei die organischen Reste der ein oder mehreren Verbindungen der Formel (I) ausgewählt sind aus gegebenenfalls substituierten aromatischen und/oder aliphatischen, linearen und/oder verzweigten, gesättigten und/oder ungesättigten Kohlenstoffresten mit einer jeweiligen Gesamtzahl an Kohlenstoffatomen pro organischem Rest im Bereich von 1 bis 22, bevorzugt mit einer jeweiligen Gesamtzahl an Kohlenstoffatomen pro organischem Rest im Bereich von 6 bis 17, wobei die ein oder mehreren Verbindungen der Formel (I) besonders vorzugsweise zwei oder mehr Benzoxazin-Struktureinheiten aufweisen.
3. 3. Polymer nach einem der vorangehenden Aspekte, wobei das Polymer erhältlich ist durch eine Synthese umfassend mindestens eine Polymerisation von ein oder mehreren Verbindungen der Formel (I.a)
   
   in Anwesenheit und/oder unter Beteiligung von ein oder mehreren Polyetheraminen, wobei R¹⁰ und R¹¹ gleich oder verschieden sind und jeweils H oder eine Alkylgruppe mit 1 bis 4 Kohlenstoffatomen, vorzugsweise eine Methylgruppe, sind.

• 4. Polymer nach einem der vorangehenden Aspekte, wobei die Synthese die Polymerisation von mindestens zwei Verbindungen der Formel (I) oder (I.a) mit jeweils unterschiedlichen molaren Massen umfasst.
• 5. Polymer nach einem der vorangehenden Aspekte, wobei die ein oder mehreren Polyetheramine eine molare Masse im Bereich von 600 bis 2.000 g/mol aufweisen.
• 6. Polymer nach einem der vorangehenden Aspekte, wobei die ein oder mehreren Polyetheramine Polyetheramine mit der Formel (II)
  
  sind, wobei m eine ganze Zahl von 9 bis 39 bedeutet, und I und n jeweils ganz Zahlen bedeuten und die Summe aus I und n 3 bis 6 beträgt.
• 7. Polymer nach einem der vorangehenden Aspekte, wobei das molare Verhältnis von Verbindungen der Formel (I) oder (I.a) zu Polyetheraminen im Bereich von 1:0,01 bis 1:1,5 liegt, vorzugsweise im Bereich von 1:0,06 bis 1:1,5, besonders vorzugsweise im Bereich von 1:0,06 bis 1:1,15.
• 8. Polymer nach einem der vorangehenden Aspekte, umfassend oder bestehend aus strukturellen Wiederholeinheiten der Formeln (III.a), (III.b) und/oder (III.c)
  
  
  
• 9. Polymer nach einem der vorangehenden Aspekte, wobei das Polymer dynamische Eigenschaften aufweist.
• 10. Polymer nach einem der vorangehenden Aspekte, wobei das Polymer ein oder mehrere makroskopische Gradienten aufweist.
• 11. Polymer nach einem der vorangehenden Aspekte, wobei sich mindestens eine mechanische oder physikalische Eigenschaft des Polymers entlang mindestens einer Ausdehnungsrichtung des Polymers graduell ändert, wobei die mindestens eine mechanische oder physikalische Eigenschaft des Polymers vorzugsweise ausgewählt ist aus der Gruppe bestehend aus
  • - Glasübergangstemperatur,
  • - Gebrauchs-Temperaturbereich,
  • - Bruchfestigkeit,
  • - Biegefestigkeit,
  • - Biegemodul,
  • - Schlagzähigkeit, und
  • - Härte.
• 12. Verwendung eines Polymers, wie in einem der vorangehenden Aspekte definiert, als Klebstoff und/oder als Klebstofffolie und/oder in Verbundwerkstoffen, vorzugsweise in Schichtlaminaten oder Sandwichstrukturen, und/oder als Oberflächenbeschichtung und/oder als Matrixharz.
• 13. Verwendung eines Polymers, wie in einem der Aspekte 1 bis 11 definiert, als Klebstofffolie mit dynamischen Eigenschaften.

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

1. 1. Polymer comprising or consisting of polybenzoxazine and/or polybenzoxazine 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
   • - 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 ⁶ , R ⁷ and R ⁸ are the same or different and each represents an organic radical or H or R ⁶ and R ⁷ are joined together to form a covalent bond and R ⁸ represents an organic radical or H or R ⁷ and R ⁸ are joined together to form a covalent bond and R ⁶ represents an organic radical or H.
2. 2. Polymer according to aspect 1, wherein the organic radicals of the one or more compounds of the 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 the formula (I) particularly preferably have two or more benzoxazine structural units.
3. 3. 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 the formula (Ia)
   
   in the presence and/or with the participation of one or more polyetheramines, wherein 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 a methyl group.

• 4. Polymer according to any 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.
• 5. Polymer according to any 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.
• 6. Polymer according to any one of the preceding aspects, wherein the one or more polyetheramines are polyetheramines having the formula (II)
  
  where m is an integer from 9 to 39, I and n are each integers and the sum of I and n is 3 to 6.
• 7. Polymer according to any 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.
• 8. Polymer according to one of the preceding aspects, comprising or consisting of structural repeat units of the formulas (III.a), (III.b) and/or (III.c)
  
  
  
• 9. A polymer according to any preceding aspect, wherein the polymer has dynamic properties.
• 10. A polymer according to any preceding aspect, wherein the polymer has one or more macroscopic gradients.
• 11. 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
  • - glass transition temperature,
  • - Operating temperature range,
  • - breaking strength,
  • - flexural strength,
  • - flexural modulus,
  • - impact strength, and
  • - Hardness.
• 12. 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.
• 13. Use of a polymer as defined in any of aspects 1 to 11 as an adhesive film with dynamic properties.

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 up in the text, which apply mutatis mutandis to the further (related) invention described in the above aspects.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 9296928 B2 [0019]
• US 4650193 [0021]
• US 3784209 [0021]
• US 6113831 [0021]
• US 8016696 B2 [0021]
• US 5545229 [0021]

Cited non-patent literature

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• 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, No. 16, pp. 1796-1806 [0019]
• Lee et al. (2018) “High-Performance Printed Circuit Board Materials Based on Benzoxazine and Epoxy Blend System” in Macromolecular Research. Vol. 26, pp. 388-393 [0019]
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• Higginson et al. (2019) “Bioinspired Design Provides High-Strength Benzoxazine Structural Adhesives” in Angew. Chem., Vol. 131, pp. 12399 - 12407 [0019]
• -Wang et al. (2016) “Latent curing systems stabilized by reaction equilibrium in homogeneous mixtures of benzoxazine and amine” in Scientific Reports 6:38584 [0019]
• 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 [0020]
• Voleppe et al. (2021) “Enhanced fracture resistance of thermoset/thermoplastic interfaces through crack trapping in a morphology gradient” in Polymer, Vol. 218, Is. 18 [0020]
• Sawaryn et al. (2011) “Advanced chemically induced phase separation in thermosets: Polybenzoxazines toughened with multifunctional thermoplastic mainchain benzoxazine prepolymers” in Polymer, Vol. 52, Is. 15 [0020]
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• Sun et al. (2015) “A curing system of benzoxazine with amine: reactivity, reaction mechanism and material properties” RSC Adv., Vol. 5, p. 19048 [0020]
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Claims (15)

Macroscopically graded polymer comprising or consisting of polybenzoxazine and/or polybenzoxazine derivative. 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 represent an organic radical or H; and - R ⁶ , R ⁷ and R ⁸ are the same or different and each represent an organic radical or H or R ⁶ and R ⁷ are linked to one another to form a covalent bond and R ⁸ represents an organic radical or H or R ⁷ and R ⁸ are linked to one another to form a covalent bond and R ⁶ 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 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 compounds of the formula (I) particularly preferably have two or more benzoxazine structural units. 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 the formula (Ia)

wherein 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 a methyl group. Macroscopically graded polymer according to one of the 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. Macroscopically graded polymer according to one of the Claims 2 until 4 , wherein the at least one polymerization of the one or more compounds of the 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 functional 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 with a molar mass in the range of 600 to 2,000 g/mol, in particular polyetheramines with the formula (II)

where m is an integer from 9 to 39, I and n are each integers and the sum of I and n is 3 to 6. Macroscopically graded polymer according to one of the Claims 2 until 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. Macroscopically graded polymer according to one of the preceding claims, comprising or consisting of structural repeat units of the formulas (III.a), (III.b) and/or (III.c)

A macroscopically graded polymer according to any one of the preceding claims, wherein the macroscopically graded polymer has dynamic properties. 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, - service temperature range, - breaking strength, - flexural strength, - flexural modulus, - impact strength, and - hardness. 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. A process for producing a macroscopically graded polymer as in any of the preceding Claims 1 until 9 defined, comprising the following steps: a) providing and/or, optionally partially, mixing the one or more monomeric reactants for the production of 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 carrier; 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. A process for producing a macroscopically graded polymer as in any of the preceding Claims 1 until 9 defined, 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 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. procedure according to claim 12 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. Kit for the preparation of a macroscopically graded polymer as described in any of the preceding Claims 1 until 9 defined comprising two or more polymeric compounds selected from polybenzoxazines and polybenzoxazine derivatives, preferably in granular form, wherein the two or more polymeric compounds 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 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 in one of the preceding claim 5 defined, 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 molar masses 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 each exist as separate individual components. Using a kit as in claim 14 defined as a multi-component adhesive.

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