WO2018054684A1 - Novel crosslinker unit for use in reversibly crosslinking polymer systems - Google Patents

Abstract

The invention relates to a novel crosslinker unit for use in Diels-Alder crosslinking systems for reversibly crosslinking polymer systems. According to the invention, said system can consist of a single component for the first time.

Description

 Novel crosslinker component for use in reversibly crosslinking polymer systems

Field of the invention

The invention relates to a novel crosslinker component for use in Diels-Alder crosslinking systems for reversibly crosslinking polymer systems, wherein in the present case this system can consist of only one component for the first time.

Applications for this crosslinker building block and its derivatives can be found in the production of reversibly crosslinking polymer systems for injection molding and extrusion molding compounds, for the production of foams, for applications in the field of additive manufacturing, such as, for example, with the SLS or FDM method. In addition, there are applications of this crosslinker component and its derivatives for the production of composite components, for the production or simplified

Processing of reversibly cross-linked or chain-extended polymer fibers, for the production of storage-stable prepregs and molded articles (composite components) produced therefrom, and also for adhesives and coatings. Equally applicable are these blocks for linking with

Elastomers or thermoplastic elastomers for a reversible crosslinking of

Elastomer systems.

The reversible crosslinking method allows very rapid crosslinking or conversion to higher molecular weights even at room temperature and at least to a relevant proportion solution of the joints at higher temperatures, so that a

thermoplastic processability can be recovered and e.g. the originally bonded substrates can be easily separated again. It is a particular aspect that multiple cycles of crosslinking and solution of crosslinking sites are possible with the present system.

State of the art

Methods for the reversible crosslinking of polymers are of great interest for a broad field of applications. For example, in adhesive applications are various possibilities for the

 Automotive industry or the semiconductor industry. But even in the construction of machinery, precision mechanical equipment or in the construction industry, such adhesives are interesting. In addition to adhesive applications, reversibly crosslinkable polymers can also be used in sealants,

Coating materials such as paints or inks, injection molding applications or in the production of moldings be interesting. DE 198 32 629 and DE 199 61 940 describe processes in which adhesives based on epoxy, urea, (meth) acrylate or isocyanate are thermally decomposed. The adhesive formulation from DE 199 61 940 contains a thermally unstable substance, which is activated when heated. The adhesive layer in DE 198 32 629 is destroyed by a particularly high energy input. The

Deactivation of the adhesive layer is irreversible in both cases.

 In US 2005/0159521 and US 2009/0090461 an adhesive system is described by

Irradiation with actinic radiation is radically crosslinked and destroyed by ultrasound. This method is irreversible after a gluing cycle no longer feasible.

In EP 2 062 926 thermally labile, sterically hindered urea groups are incorporated in the chains of a polyurethane for adhesive applications, which is destroyed by the entry of thermal energy and thus the adhesive effect is sufficiently reduced to dissolve the compound.

 US 2009/0280330 describes a probably reusable adhesive system which has a two-layer structure. A layer is a shape memory layer that can be thermally flexible or cured. The other layer is a dry adhesive having different adhesive strengths depending on the structure. Problem of such a system, however, is the complex structure to be built two-layer structure and the expected residual tack after heating the shape memory layer.

For several years now, mainly in the academic world, the term "click chemistry" has been used to investigate methods for the construction of block copolymers by combining two different homopolymers with linkable end groups and, for example, a Diels-Alder reaction, Diels-Alder-analogous reaction The aim of this reaction is thermally stable, linear and possibly high molecular weight

Build up polymer chains. In Inglis et al. (Macromolecules 2010, 43, pp.33-36), for example, polymers with cyclopentadienyl end groups obtainable from polymers prepared by ATRP are described for this purpose. These cyclopentadiene groups are able to react very rapidly in hetero Diels-Alder reactions with polymers bearing electron-deficient dithioesters as end groups (Inglis et al., Angew Chem Chem International, Ed., 2009, 48, pp. 241 1-2414).

The use of monofunctional RAFT polymers for attachment to monofunctional polymers containing a dihydrothiopyran group via a hetero-Diels-Alder reaction can be found in Sinnwell et al. (Chem. Comm., 2008, 2052-2054). This method can be used to realize AB diblock copolymers. Fast variants of this hetero-Diels-Alder linkage for the synthesis of AB block copolymers with a present after a RAFT polymerization

Dithioester group and a dienyl end group are described in Inglis et al. (Angew.Chem.Int. Ed. 2009, 48, p.241 1-14) and in Inglis et al. (Macromol.Rapd Commun., 2009, 30, p.1792-98). The Analogous production of multiarm star polymers can be found in Sinnwell et al. (J.Pol. Sei .: Part A: Pol.Chem., 2009, 47, p.2207-13).

No. 6,933,361 describes a system for the production of easily repairable, transparent moldings. The system consists of two multifunctional monomers that polymerize to a high-density network through a Diels-Alder reaction. One functionality is a maleimide and the other functionality is a furan. The thermal switching of such a high-density network serves to repair the same. The crosslinking takes place at temperatures above 100 ° C. The partial back reaction at even higher temperatures.

In Syrett et al. (Polym. Chem. 2010, DOI: 10.1039 / b9py00316a) star polymers are used for

Used as flow improver in oils. These have controllable, self-healing properties by means of a reversible Diels-Alder reaction. For this purpose, monofunctional polymethacrylate arms are combined with polymethacrylates having, in the middle of the chain, as a fragment of the initiator used, a group which can be used in a reversible Diels-Alder reaction.

EP 2 536 797 discloses a reversibly crosslinking system consisting of two components A and B. Component A is a compound having at least two dienophilic groups and component B is a compound having at least two diene functionalities. The combinations of components A and B disclosed in EP 2 536 797 are, in relation to the maximum number of possible switching cycles and the storage stability of the components

Compositions can still be optimized.

In particular, for applications of reversibly crosslinking systems in the technical field of composite materials further state of the art is of importance. Fiber reinforced prepreg materials are already being used in many industrial applications because of their ease of handling and increased processing efficiency compared to the alternative wet-layup technology.

Industrial users of such systems require, in addition to faster cycle times and higher storage stabilities - even at room temperature - an additional option, the prepregs

without the automated cutting and lay-up of the individual prepreg layers, the cutting tools are contaminated with the often sticky matrix material. Various shaping processes, such as the reaction transfer molding (RTM) process, include the Introducing the reinforcing fibers into a mold, closing the mold, introducing the crosslinkable resin formulation into the mold, and then crosslinking the resin, typically by applying heat.

 One of the limitations of such a process is the relatively difficult insertion of the

Reinforcing fibers in the mold. The individual layers of the fabric or fabric must be cut to size and adapted to the different geometries of the respective molded parts. This can be both time-consuming and complicated, especially if the moldings are also to contain foam or other cores. Preformable fiber reinforcements with easy handling and existing forming options would be desirable here.

In addition to polyesters, vinyl esters and epoxy systems, there are a number of special resins in the field of crosslinking matrix systems. These include polyurethane resins, which, because of their toughness, damage tolerance and strength, are used in particular for the production of composite profiles via pultrusion processes. A disadvantage is often called the toxicity of the isocyanates used. However, the toxicity of epoxy systems and the hardener components used there is to be regarded as critical. This is especially true for known

Sensitizations and allergies.

 Moreover, most matrix materials for preparing prepregs for composites have the disadvantage of being applied in either fibrous form, e.g., in solid form, e.g. as a powder, or as a highly viscous liquid or melt. In both cases, there is only a slight impregnation of the fiber material with the matrix material, which in turn can lead to a non-optimal stability of the prepreg or of the composite component.

 Prepregs and composites based thereon based on epoxy systems are described, for example, in WO 98/5021 1, EP 0 309 221, EP 0 297 674, WO 89/04335 and US 4,377,657. In WO 2006/043019 a process for the preparation of prepregs based on epoxy resin polyurethane powders is described. Furthermore, prepregs based on powdered thermoplastics are known as matrix.

 WO 99/64216 describes prepregs and composites and a method of making them using emulsions with polymer particles as small as to enable single-fiber coating. The polymers of the particles have a viscosity of at least 5000 centipoise and are either thermoplastics or crosslinking polyurethane polymers.

 EP 0 590 702 describes powder impregnations for the production of prepregs in which the powder consists of a mixture of a thermoplastic and a reactive monomer or prepolymer. WO 2005/091715 also describes the use of

Thermoplastics for the production of prepregs.

Prepregs made using Diels-Alder reactions and potentially activatable retro-Diels-Alder reactions are also known. In AM Peterson et al. (ACS Applied Materials & Interfaces (2009), 1 (5), 992-5) describes corresponding groups in epoxy systems. This modification provides self-healing properties of the components.

Analogous systems that are not based on an epoxy matrix can be found, inter alia. also at J.S. Park et al. (Composite Science and Technology (2010), 70 (15), 2154-9) or A.M. Peterson et al. (ACS Applied Materials & Interfaces (2010), 2 (4), 1 141-9). However, none of the listed systems makes it possible to subsequently modify the composites beyond self-healing. The classic Diels-Alder reaction is inadequate under the possible conditions

attributed, so that only small effects, as they may be sufficient for a self-healing of damaged components are possible.

EP 2 174 975 and EP 2 346 935 each describe composite materials which can be used as laminate with bis-maleimide and furan groups, which can be thermally recycled. It will be readily apparent to those skilled in the art that such a system will only reactivate at relatively high temperatures, i. be rewetted to at least a large extent, can be. In such

Temperatures, however, quickly lead to further side reactions, so that the mechanism - as described - is only suitable for recycling, but not for modifying the composites.

WO 2013/079286 describes composite materials or prepregs for their preparation which have groups for a reversible hetero-Diels-Alder reaction. These systems are reversibly cross-linkable and the molded parts are even recyclable. However, these systems can only be applied as a 100% liquid system or from an organic solution. This significantly limits the applicability of this technology.

 All systems described are based either on organic solvents or are applied as a melt or as a liquid 100% system. However, none of the described systems can be applied in the form of an aqueous dispersion. However, such aqueous systems in particular would have great advantages in terms of occupational safety and additionally available

Processing technologies in the production of prepregs or composite materials.

 Further prior art with regard to oxazoline chemistry is listed below:

 The attachment of fatty acids via the oxazoline-converted fatty acid carboxylic acid groups to carboxyl-carrying acrylate polymers with subsequent epoxidation of the double bonds and irreversible crosslinking for coatings has been described in D.L.Trumbo, J.T.Otto; J.Coat.Technol. Res., 5 (1), 107-1 1 1, 2008.

 DE 42 09 283 describes how polymers with oxazoline groups can be provided with reactive double bonds via graft reactions of an oxazoline. The polymers bearing such oxazoline groups can then be reacted with e.g. Dicarboxylic acids are irreversibly crosslinked.

 In DE 34 02 280 sealants and adhesives are described, which can be cured or crosslinked by the use of bis-oxazolines in the heat.

 US 8,258,254 discloses a long list of Diels-Alder components, among which

Cyclohexadienes are listed as diene component. These components are used for Biodegradability of a polymer. A multiple circuit between two states is not disclosed.

 US 2007/148465 discloses a similarly long list of components for use in shape memory systems. This means that it is only possible to switch between two different networked states.

 JP 2007 284643 discloses cyclohexyl dienes as diene for Diels-Alder reaction with maleimide. Again, it's about shape memory materials.

With regard to the general state of the art in composite applications, the following should be noted:

 Fiber-reinforced materials in the form of prepregs are already used in many industrial applications

Applications because of their convenient handling and increased processing efficiency compared to the alternative wet layup technology used.

 All systems described are based either on organic solvents or are applied as a melt or as a liquid 100% system. However, none of the described systems can be applied in the form of an aqueous dispersion. However, such aqueous systems in particular would have great advantages in terms of occupational safety and additionally available

Processing technologies in the production of prepregs or composite materials. task

It is an object of the present invention to provide building blocks for a novel reversible chain extension or crosslinking technology for, for example, polymers which are disclosed in US Pat

different applications and can be used in a wide range of formulations.

A further object was to find crosslinker structures which are thermally stable without protective groups such that the use of cyclopentadiene or similar structures as

Blocking agents are not required. In addition, the synthetic steps as well as the yields achieved for an economical production of the crosslinking systems should be improved to a simple and robust production method.

Optionally, the chain extension or crosslinking of the polymers should not be carried out with a diene and a corresponding dienophile, but with molecules which undergo a Diels-Alder reaction with themselves. Other tasks not explicitly mentioned emerge from the overall context of the following description, claims and examples.

solution

The objects were achieved by developing a novel formulation suitable for carrying out a reversible crosslinking mechanism, which is independent of the

Formulation ingredients such as binders for various polymers can be used.

Surprisingly, it has been found that the objects set can be solved by a novel formulation which can be implemented by means of a Diels-Alder reaction, to which end only a single, e.g. polymeric or oligomeric component must be used. Surprisingly, it was found that a combination of Diels-Alder-reactive structures in a molecule that is simultaneously diene and dienophile, the networking or

Chain extension reactions not only work simply, but also allow significant simplifications on the synthesis side. For this purpose, the present invention is characterized by a reversibly reactive formulation which is crosslinkable or chain-extending reactive by means of a Diels-Alder reaction. For this purpose, this formulation contains a component P, preferably as the predominant constituent of more than 80% by weight, which contains at least once the following structural unit Z.

having.

R 1 is hydrogen, an alkylene radical having 1 to 20, preferably 1 to 10, more preferably 1 to 5 carbon atoms, a polyether radical having a degree of polymerization between 1 and 50, preferably between 1 and 10, a hydroxy, amino, , Epoxy, isocyanate, carboxyl or oxazoline group, the latter being able to represent exclusively the R1 or to be bonded to an abovementioned alkyl or polyether radical. In this case, more than one functional group or combinations of different of these groups may be present in the latter compounds. R 2 is hydrogen, an alkyl group having 1 to 5 carbon atoms, optionally having one or more hydroxyl groups, or a hydroxyl group or alkoxy group having 1 to 12 carbon atoms. Preferred alkoxy groups would be methoxy or ethoxy. R3, R4, R5 and R6 independently of one another or at least partially identical to one another are hydrogen, linear or branched alkyl or alkylene groups having 1 to 20

Carbon atoms which may optionally have one or more hydroxy, amine, halogen, epoxy, isocyanate, carboxyl or oxazoline groups or directly bonded hydroxy, amine, halogen, epoxy, isocyanate, carboxyl or oxazoline groups.

The reve ma:

 The formulation according to the invention can be used in two different embodiments. In the first embodiment, component P has one or at most two of the

Structural units Z on. This formulation can react reversibly under a chain extension and molecular weight increase by means of a Diels-Alder reaction, with no crosslinking.

The second embodiment is characterized in that the component P has more than two of the structural units Z, and that the formulation is reversibly crosslinkable by means of a Diels-Alder reaction.

Regardless of the embodiment, it is particularly preferred if at least one, preferably one of the groups R3, R4, R5 and R6 by means of a functional group with a further compound A, a polymer or an oligomer, optionally further structural units Z comprising, together forming the component A. , connected is.

The polymer or oligomers are preferably polyacrylates,

Polymethacrylates, polystyrenes, copolymers of acrylates, methacrylates and / or styrenes, polyacrylonitrile, polyethers, polyesters, polylactic acids, polyamides, polyesteramides, polyurethanes, polycarbonates, amorphous or partially crystalline poly-α-olefins, EPDM, EPM, hydrogenated or non-hydrogenated polybutadienes, ABS , SBR, polysiloxanes and / or block, comb and / or star copolymers of these polymers. In this case, the connection to the polymers or oligomers to be crosslinked or linked generally takes place via hydroxyl, amine, halogen, epoxy, oxazoline, isocyanate or carboxy functionalities of the structural unit Z. The polymer or oligomer is particularly preferably a polyether, a polyamide, a polyester or a polycarbonate which, as component A, is at least one

 Structural unit Z have. Often, the structural unit is terminal and there is thus a mixture of mono- and bifunctional chains or a purely mono- or bifunctional component.

In a particularly suitable embodiment of the present invention, one of the functional groups R 1 to R 6, preferably the functional group R 3, is an initial acid or ester group or an alkyl group of 1 to 20

 Carbon atoms, having an acid or ester group as a functional group, which is subsequently added e.g. was reacted with an a-hydroxylamine of the formula H2N-CR7R8-CH20H to form an oxazoline. Subsequently, this oxazoline group was reacted with a carboxyl function of another compound A, e.g. a polymer for attachment of the structural unit Z to the

endem Scheme: be ebunden:

Wherein in these structural formulas, according to the nomenclature of the present invention as a constituent of the radicals R1 and R3 present acid group is shown separately.

The second reaction step then takes place in another alternative, for example according to the following scheme:

These are the reaction with bisoxazolines, e.g. 1, 3-phenylenebisoxazoline to the corresponding oxazolines.

In the best case, the formulation is crosslinkable at room temperature and the formed crosslink can be reversed at a higher temperature to at least 50%. In another embodiment that can possibly be combined with the other, polymers having multiple carboxy functionalities, for example (meth) acrylate (co) polymers with (meth) acrylic acid units or branched (co) polyesters, polyethers, polyamides, Polycarbonates or elastomers with, for example, polymerized monomers with carboxy functionalities with the structural unit Z provided. For example, such starting polymers are as follows:

In this case, a reversible crosslinking can be supplied via the reaction with the epoxy- or oxazoline-functionalized not yet bound components Z which dimer at room temperature. The same applies to grafted building blocks with carboxy functionalities, e.g. via grafting with (meth) acrylic acid, maleic acid or fumaric acid.

Similarly, there is another embodiment which is that polymers having multiple hydroxyl or amine functionalities, e.g. (Meth) acrylate (co) polymers having hydroxy-alkyl (meth) acrylate units or branched (co) polyesters, polyethers, polyamides, polycarbonates or even elastomers with optionally copolymerized monomers with hydroxyl or amine -Functionalities can be supplied via the reaction with the carboxyl or isocyanate-functionalized Diels-Alder building blocks of the invention a reversible crosslinking. The same applies to grafted building blocks with hydroxyl functionalities, e.g. via grafting with hydroxyalkyl (meth) acrylates or other graftable building blocks, e.g. the ethylene glycol diester of maleate or fumaric acid.

Die reversible Vernetzung, die mit der erfindungsgemäßen Formulierung möglich ist, ermöglicht eine sehr schnelle Umsetzung schon bei einer niedrigen ersten Temperatur und eine Lösung der

The reversible crosslinking, which is possible with the formulation according to the invention, enables a very rapid conversion even at a low first temperature and a solution of

Crosslinking points at significantly higher temperatures, so that ideally a thermoplastic processability is recovered or at least a relevant material property, such as the cohesion in an adhesive, is changed so that other processing, such as the detachment of a splice, becomes available. Furthermore, e.g. the originally networked layers when used in the field of

Laminates pressed single layers in composites easily separated again or e.g. the crosslinked individual layers, which are present for example as prepregs, reshaped and pressed into a laminate can be. It is a particular aspect that multiple cycles of crosslinking and solution of crosslinking sites are possible with the present system. The crosslinker or chain extender molecules described are stable as pure substances with temperature increase so that they do not have to be blocked with protective groups.

The formulations according to the invention have in particular the following special advantages:

 · There are no protecting groups / blocking groups for the reactive dienophile in the

Synthesis required.

 Very simple and robust synthesis with inexpensive starting materials and high yield The formulation is thermally stable even without protective groups to over 200 ° C The retro-Diels-Alder reaction takes place at temperatures, the melting point or

 Allow glass temperatures of the entire system of greater than 100 ° C.

In another possible embodiment, component A is a bifunctional polymer prepared by atom transfer radical polymerization (ATRP). In this case, the functionalization with the structural units Z is carried out by a polymer-analogous or during the termination carried out substitution of terminal halogen atoms. This substitution can be carried out, for example, by adding dieno functionalized mercaptans.

Another aspect of the present invention is the process for the reversible crosslinking of the formulations according to the invention. In carrying out this process, a formulation comprising components A is crosslinked by means of a Diels-Alder reaction at room temperature, this step generally being carried out already in the synthesis of component A. In a second process step, at a higher temperature of more than 100 ° C., at least 10%, preferably at least 15% and particularly preferably at least 50% of the crosslinking sites are dissolved again by means of a retro-Diels-Alder reaction. In addition to networking, the procedure can also - and, as already mentioned above

Performed formulations - also serve to increase molecular weight.

Further formulation ingredients may be added to the formulation, for example in the form of a

Coating or adhesive composition. According to the invention, the composition optionally additionally comprises components added in addition to the component A. These additional components may be additives specially selected for the respective application, such as, for example, fillers, pigments, additives,

Compatibility promoters, co-binders, plasticizers, impact modifiers, thickeners, defoamers, dispersing additives, rheology improvers, adhesion promoters, scratch-resistant additives, catalysts or stabilizers and optional further additives act.

In another alternative embodiment, the formulation contains a catalyst that lowers the activation temperature of the retro-Diels-Alder reaction. These catalysts may be, for example, iron or an iron compound.

FIG. 1 shows, by way of example, the reaction scheme for crosslinking and for feedback. These are the binding of oxazoline-terminated Diels-Alder structures to terminal carboxyl groups of the polymers and subsequently the thermally induced retro-Diels-Alder reaction and the recombination of the polymers on cooling.

The structures, formulations or processes according to the invention can be used in a wide variety of fields of application. The following list exemplifies some preferred applications, without limiting the invention in any way.

 Such preferred applications are adhesives, sealants, injection moldable or extrudable molding compounds, lacquers, paint, coatings, (fiber reinforced) composites, polymer fibers, materials for additive manufacturing (3D-printing, SLS, FDM), inks or oil additives such as flow improvers.

These inks are, for example, compositions which are applied thermally and cure on the substrate. When using conductive oligomers or additives to provide conductivity in general, an electrically conductive ink is obtained, e.g. can be processed by bubble-jet method.

 Examples of injection-moldable or extrudable molding materials are polyester, polycarbonate or polyamide, in which a high-temperature retro-Diels-Alder decoupling of the (existing at lower temperature and forming on cooling)

Polymer chain linkage (crosslinking or chain extension) advantageous for the plastic injection reduced viscosity or only emerging fluidity enabled. The at lower Temperature and on re-forming polymer chain linkages increase, for example, the mechanical properties.

 Examples from the application areas paints, coatings and paint are

Compositions, e.g. porous materials in the low-viscosity state can soak or wet particularly well and result in highly coherent materials as a result of the coupling reaction.

Similar characteristics are important for adhesives which should have high cohesion and yet readily wet the surfaces of the materials to be bonded.

Another application in the field of gluing is, for example, a temporary, later to be solved addition, as in various production processes, for example in the

Automotive or in mechanical engineering may occur.

 Another conceivable application is the bonding of components which, over the lifetime of the entire product, have a high probability of replacement, and should therefore be removed as simply as possible and without residue. An example of such an application is the bonding of automotive windshields. Further examples are manufacturing processes in the field of electronics, information technology, in the construction or furniture industry. Another interesting application for a low-temperature decoupling according to the invention could be in the field of medical technology or orthopedic technology.

 A particular example of adhesives or sealants is the use in food packaging, which can be solved automatically during heating, for example in a microwave or open.

An example of rapid prototyping applications for the crosslinking and de-entangling materials described herein are FDM (Fused Deposition Modeling) or low-viscosity melt inkjet 3D printing.

The present invention is particularly suitable for the preparation of reversibly crosslinking polymer structures and in particular a novel system which represents a storage-stable dosage form when using high molecular weights of the polymers used or in highly reactive systems. The crosslinked with the structures according to the invention e.g. dispersible polymers may be e.g. for the impregnation of fibrous material, e.g. Carbon fibers, glass fibers or polymer fibers for the production of prepregs can be used by known methods.

 The invention also relates in particular to emulsion polymers which are compatible with the

Crosslinker molecules according to the invention are crosslinked intraparticularly by means of the Diels-Alder mechanism. The crosslinked polymers can then be wholly or partially dewatered by thermal processing, for example as a composite matrix, by means of a retro-Diels-Alder reaction or retro-hetero-Diels-Alder reaction and crosslinked again interparticleically on cooling. As a result, storage-stable prepregs for composite can be displayed. But also other materials that have duroplastic properties at useful temperature, but thermoplastic at higher temperatures

Processing properties can be realized in this way. Examples

In the following, a selection of syntheses for concrete examples of novel Diels-Alder crosslinking systems, as well as possibilities for generating a functionality for attachment to polymers are described.

Example 1: Synthesis of 6- (hydroxy) -2,6-dimethylcyclohexa-2,4-dien-1-one (CHD-OH) 2,6-dimethylphenol (1.00 g, 8.18 mmol, 1 , 0 eq.) Was suspended in a mixture of 150 ml of water and 50 ml of THF. Subsequently, a solution of 3.50 g of Nal04 (16.37 mmol, 2.0 eq.) In 50 mL of water was added, whereupon the solution turned yellow. After stirring for 1 h, the solution cleared and the reaction was stopped by addition of dichloromethane. The aqueous phase was then extracted three times with 200 mL dichloromethane each time. The combined organic phases were dried over MgSO 4 and the solvent removed under reduced pressure. The

 Crude product was an orange oil to which 5 mL of cyclohexane was added to precipitate white crystals. These were filtered off and washed with toluene. The yield was 53% (0.59 g, 4.30 mmol). Example 2: Synthesis of 6- (hydroxy) -2,6-dimethylcyclohexa-2,4-dien-1-one acetate (CHD-Ac)

A solution of 10 mL ethyl acetate (EtOAc), 0, 1 mL H2SO4 and 0.4 mL acetylacetonate (AcOAc) was prepared with stirring. After 10 minutes, another 2 mL of AcOAc was added to the solution. Subsequently, 3 ml of this solution were added to 495.6 mg of the product from Example 1 (1.79 mmol, 1.0 eq.) And this mixture was shaken for 4 min. The reaction mixture was then washed five times with 20 mL each of 1 M HCl, then with 20 mL saturated NaHCO 3 and finally with 20 mL saturated brine. After removal volatile

In vacuo and vacuum dried, white crystals were obtained as product with a yield of 49. 16% (316.8 mg, 0.88 mmol).

Example 3: Synthesis of 6- (ethylene oxide) -cyclohexa-2,4-dien-1-one (CHD-epoxy)

In a round-bottomed flask, 1 00 g of 2-hydroxybenzyl alcohol (8.06 mmol, 1.0 eq.) Was suspended in 60 mL of water with very vigorous stirring. Subsequently, 2.00 g of Nal04 (9.35 mmol 1, 16 eq., Dissolved in 40 mL of water) was slowly added to the solution. The reaction solution turned yellow. After stirring for a further 5 minutes, a yellow-brown solid precipitated. The reaction was stopped after a further 30 minutes and finally a pale pink solid was recovered by filtration as a product. The yield was 65% (0.64 mg, 5.24 mmol). Example 4: Synthesis of 6- (hydroxy) -6- (azidomethyl) -cyclohexa-2,4-dien-1-one (CHD-azide)

1.00 g of the reaction product from Example 3 (4.09 mmol, 1.0 eq.), 1.35 g NaN3 (20.75 mmol, 5.07 eq.) And 1.13 g NhUCI (21, 12 mmol , 5.16 eq.) Were taken up in a mixture of 25 ml of methanol and 5 ml of water. While heating and stirring at 80 ° C for 2 hours, the solution cleared. After cooling, the aqueous phase was extracted three times with 10 mL each of ethyl acetate. The combined organic phases were dried over MgSC and the solvent removed under reduced pressure. The product was obtained as an orange-brown solid in 85% yield (1.17 g, 3.54 mmol).

Example 5: Synthesis of 6- (hydroxy) -6- (hydroxymethyl) -cyclohexa-2,4-dien-1-one (CHD-CL-OH)

200 mg of the reaction product of Example 3 (0.82 mmol, 1.0 eq.) And 232.5 mg of NhUCI (4.23 mmol, 5.16 eq.) Were suspended in a mixture of 25 mL of methanol and 5 mL of water , After two hours of stirring at 80 ° C and then cooling, the aqueous phase was extracted three times with 50 mL of ethyl acetate. The combined organic phases were dried over MgSC and the solvent removed under reduced pressure. The product was obtained as a light brown solid in 62% yield (144 mg, 0.51 mmol).

Naturally, all the products of the preceding examples were present as dimers after work-up. This also applies to the respective corresponding starting materials in Examples 2, 3 and 5.

Example 8 below is characterized by the incorporation of the linker into a polymer. Examples 6 and 7 describe the synthesis of the linker for Example 8.

Example 6: Synthesis of 6- (ethylene oxide) -cyclohexa-2,4-dien-1-one (CHD-epoxy, alternative synthesis)

In a round bottom flask, 12.4 g of 2-hydroxybenzyl alcohol (100 mmol, 1.0 eq.) Was suspended in 750 mL of water with very vigorous stirring. Subsequently, 25.7 g of NalC (120 mmol 1.2 eq.) Was added to the solution within 10 min. The reaction solution turned yellow. Upon further stirring, a yellow-brown solid precipitated. The reaction was stopped after stirring for a total of 30 minutes after the addition of all starting materials, filtered off and washed with a total of 400 ml of water. After drying under reduced pressure at 60 ° C, a pale won pink solid. The yield was 65.4% (7.99 g). This crude product was finally recrystallized in methanol.

Example 7: Synthesis of 6- (hydroxy) -6- (hydroxymethyl) -cyclohexa-2,4-diene-1-one (CHD-CL-OH;

1.22 g of the reaction product from example 6 (5 mmol, 1.0 eq.) Were dissolved in ACN and then this solution was admixed with 1.34 g of NhUCI (25.0 mmol, 5.00 eq.). After 17 hours of stirring at 90 ° C and then cooling, the aqueous phase was separated, the organic phase was concentrated to 5 mL and extracted three times with 50 mL of ethyl acetate. The combined organic phases were washed with 100 ml and then concentrated brine and finally dried over MgSC. This was followed by recrystallization in tert-butyl methyl ether. Finally, the solvent was removed in vacuo at 50 ° C. The product was obtained as a light brown solid in a yield of 71.3% (1.3 g).

 Naturally, all the products of the preceding examples were present as dimers after work-up. Example 8: Synthesis of a CHD functional polyurethane

In a glove box, three parallel syntheses according to Tab.1 were used. For this, the product from Example 7 was dissolved in each case in 600 ml of DMF and admixed with 336.4 mg (1.0 eq) of hexamethylene-1,6-diisocyanate (HMDI) and 0.1 eq of DABCO. The reaction mixtures were each stirred for 60 min at 90 ° C, then cooled to room temperature and treated with 1, 6-hexanediol according Tab.1. The reaction mixtures were stirred for a further 20 minutes at 80 ° C., for 20 minutes at 90 ° C. and finally for 10 minutes at 100 ° C. The successful incorporation of CHD-CI-OH into the polyurethane was detected by H NMR spectroscopy in DMSO-d6.

Hochtemperatur-NMR-Messungen zum Nachweis der entkoppelten Bindungen Table 1

High-temperature NMR measurements for the detection of decoupled bonds

To investigate the reversibility associated with the retro-Diels-Alder reaction, temperature-dependent NMR spectroscopic measurements were performed and the Diels-Alder adduct was converted to the monomers / open species by heating via the retro-Diels-Alder reaction blocked by a maleimide to prevent re-dimerization on cooling.

Execution:

To prepare the high-temperature NMR measurements, the respective component was dissolved in d6-DMSO (c = 40 mg / L), filled in a pressure-resistant NMR tube and preheated to the subsequent measurement temperature. During heating, 1 H NMR spectra were recorded at different temperatures. The measurements were started at room temperature (20 ° C) and heated in steps of 20 ° C to a maximum temperature of 140 ° C. After cooling again to room temperature, another spectrum was measured. For evaluation, the resonance shifts of the vinyl protons between 5.5 and 6.5 ppm were determined. These signals are a suitable indicator for the opening of the dimeric structures. The integration of the signals also provides information about the percentage of binding opening. For example, for Example 1, this fraction was about 18% open at 140 ° C.

Trapping experiment

In a round-bottomed flask, 56.0 mg of the product of Example 2 (the "Ac-dimer", 0; 16 mmol, 1; 0 eq.) And 56.46 mg of phenylmaleimide (0.33 mmol, 2.1 eq.). dissolved in 3.5 mL DMSO-d6. This solution was heated in an oil bath preheated to 190 ° C (± 2 ° C). Samples were taken at 5 minute intervals and measured by 1 H NMR and ESI-MS. The resonance shift of the vinyl proton between 5.5 and 6.5 ppm is a strong indication of the proportion of closed (ie dimeric) structures. After 35 min at 190 ° C, it could be shown that complete trapping of the open structures of the cyclohexadienone Structures with the maleimide is done.

Claims

PATENT CLAIMS 1. Reversibly reactive formulation, characterized in that the formulation is crosslinkable or chain-extending reactive by means of a Diels-Alder reaction, that the formulation contains a component P which at least once contains the following structural unit Z

has, where Ri is hydrogen, an alkylene radical with 1 to 20 carbon atoms, a polyether radical with a degree of polymerization between 1 and 50, a hydroxy, amino, epoxy, isocyanate, carboxyl or oxazoline group or at least one an alkylene radical containing a hydroxy, amino, epoxy, isocyanate, carboxyl and/or oxazoline group with 1 to 20 carbon atoms, a polyether radical with a degree of polymerization between 1 and 50, R2 is hydrogen, an alkyl radical 1 to 5 carbon atoms, optionally having one or more hydroxyl groups or an ether group O-R2 ' R2' or is a hydroxyl group or alkoxy group with 1 to 12 carbon atoms, and R3, R4, R5 and R6 are independently or at least partially identical to hydrogen, linear or branched alkyl or alkylene groups with 1 to 20 carbon atoms, which may optionally have one or more hydroxy, alkoxy, amine, halogen, epoxy, isocyanate, carboxyl or oxazoline groups or to hydroxy, alkoxy, amine, halogen, epoxy, isocyanate , carboxyl or oxazoline groups. 2. Formulation according to claim 1, characterized in that component P has one or two of the structural units Z, and that the formulation is reversible by means of a Diels-Alder reaction with chain extension and Molecular weight increase reacts. 3. Formulation according to claim 1, characterized in that component P has more than two of the structural units Z, and that the formulation is reversibly crosslinkable by means of a Diels-Alder reaction. 4. Formulation according to claim 2 or 3, characterized in that at least one of Groups Ri, R3, R4, R5 and R6 by means of a functional group with a further compound A, a polymer or an oligomer, optionally further structural units Z having component A is connected to form. 5. Formulation according to claim 4, characterized in that the polymer or oligomer is polyacrylates, polymethacrylates, polystyrenes, copolymers of acrylates, methacrylates and / or styrenes, polyacrylonitrile, polyethers, polyesters, polylactic acids, polyamides, polyesteramides, polyurethanes, polycarbonates , amorphous or semi-crystalline poly-oolefins, EPDM, EPM, hydrogenated or non-hydrogenated Polybutadienes, ABS, SBR, polysiloxanes and/or block, comb and/or Star copolymers of these polymers. 6. Formulation according to at least one of claims 1 to 5, characterized in that one of the functional groups Ri to R6 is an original acid or ester group or an alkyl group with 1 to 20 carbon atoms, having an acid or ester group as a functional group which is then converted into an oxazoline and this oxazoline group is then combined with a carboxyl function of another compound A to bind the Structural unit Z was converted to the compound A. 7. Formulation according to at least one of claims 1 to 6, characterized in that the formulation is crosslinkable at room temperature and the crosslinking can be reversed to at least 50% at a higher temperature. 8. Formulation according to claim 2 or 3, characterized in that it is Component A, a polyether, a polyamide, a polyester or a Polycarbonate, having at least one structural unit Z. 9. Process for reversible implementation, characterized in that a Formulation according to at least one of claims 1 to 9 is crosslinked or implemented to increase the molecular weight by means of a Diels-Alder reaction at room temperature and at a higher temperature of more than 100 ° C at least 15% of the crosslinking points are dissolved again by means of a retro-Diels-Alder reaction become. 10. Use of a formulation according to at least one of claims 1 to 8 in adhesives, sealants, molding compounds, foams, varnishes, paints, coatings or inks. 1. Use of a formulation according to at least one of claims 1 to 8 Composites for applications in the construction, automotive, aerospace industries, energy technology, such as wind turbines, in boat or shipbuilding.