EP2785772A1

EP2785772A1 - Pseudothermoplastic, self-crosslinking composites

Info

Publication number: EP2785772A1
Application number: EP12790459.7A
Authority: EP
Inventors: Friedrich Georg Schmidt; Stefan Hilf
Original assignee: Evonik Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2011-11-28
Filing date: 2012-11-06
Publication date: 2014-10-08
Also published as: BR112014008332A2; US20140323001A1; DE102011087226A1; JP6141306B2; WO2013079286A1; US9169363B2; AU2012344213B2; AU2012344213A1; CA2857218A1; CN103842415A; JP6425754B2; JP2017115162A; JP2014533772A

Abstract

The invention relates to a process for producing storage-stable prepregs and shaped bodies produced therefrom (composite components). In the present process, reversibly crosslinked composites or storage-stable prepregs are produced by means of a hetero-Diels-Alder reaction (HDA) of, for example, PMMA polymers. At a slightly elevated temperature, these prepregs can be reversibly decrosslinked again by means of a retro-hetero-Diels-Alder reaction so as to become malleable. The backreaction to form crosslinked or high molecular weight products again then occurs at room temperature.

Description

Pseudo-thermoplastic, self-crosslinking composites Field of the invention

The invention relates to a process for the preparation of storage-stable prepregs and moldings produced therefrom (composite components). In the present process, hetero-Diels-Alder reactions (HDA) of e.g. PMMA polymers produced reversibly crosslinking composites or storage-stable prepregs. At a slightly elevated temperature, these prepregs can be reversibly rewetted by a retro-hetero-Diels-Alder reaction in that they become malleable. The back reaction to re-crosslinked or high molecular weight products takes place at room temperature.

State of the art

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-lay-up technology.

Industrial users of such systems require, in addition to faster cycle times and higher storage stabilities, even at room temperature, a possibility to cut the prepregs without the cutting tools being contaminated with the often sticky matrix material in the case of automated cutting and lay-up of the individual prepreg layers.

Various shaping processes, such. Reaction transfer molding (RTM) processes include incorporating the reinforcing fibers into a mold, closing the mold, introducing the crosslinkable resin formulation into the mold, and then crosslinking the resin, typically by heat. However, such a method is expensive and the prepregs as such are not storable. In addition to polyesters, vinyl esters and epoxy systems, there are a number of specialized 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, only a small impregnation of the fiber material with the

Matrix material, which in turn can lead to a non-optimal stability of the prepreg or the composite component.

Prepregs and composites based thereon based on epoxy systems are described, for example, in WO 98/5021 1, EP 309 221, EP 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 5,000 centipoise and are either thermoplastics or crosslinking polyurethane polymers.

EP 0590702 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 likewise describes the use of thermoplastics for the production of prepregs. Prepregs prepared 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 gives you

self-healing properties of the components. Analogous systems that are not based on an epoxy matrix can be found i.a. also at J.S. Park et al. (Composite Science and

Technology (2010), 70 (15), 2154-9) or at 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 classical Diels-Alder reaction is insufficiently attributed under the possible conditions, so that only small effects, such as may be sufficient for self-healing of damaged components, are possible here.

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. At least to a large extent, it can be wiped out again. At such temperatures, however, there are more quickly

Side reactions, so that the mechanism is - as described - only for recycling, but not suitable for modifying the composites.

None of the described systems can easily be reshaped after processing into the composite and the associated final cure. A rework once hardened systems is only by means of

Cropping or other irreversible process possible. task

The object of the present invention in the light of the prior art has been to provide a new prepreg technology which enables a simpler process for the production of easy-to-handle prepreg systems.

In particular, it was an object of the present invention to provide a process for the production of prepregs, which allows over the prior art significantly extended storage stability and / or processing time (potlife). In addition, the handling of prepregs over the prior art should be improved or at least comparable.

In addition, a process for the production of composite components is to be made available by which the composites should be further modified or even recyclable after completion.

solution

The tasks were solved by novel kits for the production of composites

Semi-finished products. These novel kits include

A) a fibrous carrier,

B) a first reactive component having at least two dienophilic double bonds, wherein the dienophilic double bonds are carbon-sulfur double bonds, and

C) a second reactive component having at least two diene functionalities. At least one of the components B or C contains more than two of the respective functionalities. By means of said functionalities, the first and the second reactive component can be crosslinked to each other by means of a Diels-Alder or a hetero-Diels-Alder reaction.

The term composite semi-finished products is used in the context of this invention synonymous with the terms prepreg and organo sheet. A prepreg is usually a precursor for thermoset composite components. An organic sheet is usually a precursor for thermoplastic composites.

The dienophilic double bonds are, in particular, double bonds around groups having the structure

wherein Z is a 2-pyridyl group, a phosphoryl group or a

Sulfonyl group in which R ^m is a mehrbindige organic group or a polymer and n is a number between 2 and 20.

In a particular embodiment of the invention, components A and / or B are one or more polymers. These polymers 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 unhydrogenated polybutadienes, ABS, SBR, polysiloxanes and / or block, comb, star or hyperbranched copolymers of these polymers. The reactive compositions which can be used according to the invention are environmentally friendly, cost-effective, have good mechanical properties, are easy to process and, after hardening, are distinguished by a good weather resistance and by a balanced ratio between hardness and flexibility.

The principle is not limited to the polymers mentioned, but can be extended as a platform technology to other types of polymers. Thus, e.g. from BFT polymerization synthesized, difunctional polymer building blocks of the type B or C and multifunctional crosslinkers of the corresponding complementary type C or B at room temperature crosslinked systems which, when reached by the choice of

Components adjustable dewetting temperature back to their original

Components can be reversibly split, can be obtained.

One of the great advantages of the present invention is, inter alia, that with the aid of the curing mechanisms used according to the invention, a comparison with the prior art, i. compared to established composites, a significantly larger number of raw materials or

Raw material combinations can be used. This makes novel composite materials with completely new property profiles available.

In addition to the components A, B and C, the composite semifinished products may have other additives. For example, sunscreen agents such. As sterically hindered amines, or other auxiliaries, such as. As described in EP 669 353, be added in a total amount of 0.05 to 5 wt%. Fillers and pigments such. Titanium dioxide may be added in an amount of up to 30% by weight of the total composition.

For the preparation of the reactive polyurethane compositions according to the invention may also contain additives such as leveling agents, for. As polysilicones or adhesion promoters, for example, be added on an acrylate basis. Carrier A

The aforementioned fibrous supports A) are, in particular, supports which consist for the most part of glass, carbon, plastics, such as polyamide (aramid) or polyester, natural fibers, or mineral fiber materials, such as basalt fibers or ceramic fibers. The fibers are in particular as textile fabrics made of non-woven,

Knitted fabrics, knitted fabrics and knits, non-meshed packages such as fabrics, scrims or netting, as long fiber or short fiber materials.

In detail, the following embodiment is: The fiber-shaped carrier in the present invention consists of fiber-shaped material (also often called reinforcing fibers). In general, any material that makes up the fibers is suitable, but is preferably fiber material made of glass, carbon, plastics, such. As polyamide (aramid) or polyester, natural fibers or mineral fiber materials such as basalt fibers or ceramic fibers (oxide fibers based on aluminum oxides and / or silicon oxides) used. Also mixtures of fiber types, such as. B. fabric combinations of aramid and glass fibers, or carbon and glass fibers can be used. Similarly, hybrid composite components are made with prepregs

different fiber-shaped straps produced.

Glass fibers are the most commonly used fiber types mainly because of their relatively low price. In principle, here are all types of glass-based

Reinforcing fibers suitable (E-glass, S-glass, R-glass, M-glass, C-glass, ECR-glass, D-glass, AR-glass, or hollow glass fibers). Carbon fibers are generally used in high performance composites, where lower density relative to glass fiber and high strength are also important factors. Carbon fibers (also carbon fibers) are industrially produced carbon-containing fibers

Starting materials that are converted by pyrolysis into graphitic carbon. A distinction is made between isotropic and anisotropic types: isotropic fibers have only low strength and less technical importance, anisotropic fibers show high strength and stiffness with low elongation at break. Natural fibers are here all textile fibers and fiber materials, which are derived from vegetable and animal material (eg., Wood, cellulose, cotton, hemp, jute, linen, sisal, bamboo fibers). Similar to carbon fibers, aramid fibers have a negative coefficient of thermal expansion and thus contribute Heating shorter. Their specific strength and elastic modulus are significantly lower than that of carbon fibers. In conjunction with the positive expansion coefficient of the matrix resin can be manufactured dimensionally stable components. Compared to carbon fiber reinforced plastics, the compressive strength of aramid fiber composites is significantly lower. Known brand names for aramid fibers are Nomex® and Kevlar® from DuPont, or Teijinconex®, Twaron® and Technora® from Teijin. Particularly suitable and preferred are carriers made of glass fibers, carbon fibers, aramid fibers or ceramic fibers. The fiber-shaped material is a textile fabric. Suitable fabrics are nonwoven fabrics, as well as so-called knits, such as knitted fabrics and knits, but also non-meshed containers such as fabrics, scrims or braids.

In addition, a distinction long fiber and short fiber materials as a carrier. Also suitable according to the invention are rovings and yarns. All materials mentioned are suitable in the context of the invention as a fiber-shaped carrier. An overview of

Reinforcing fibers contains "Composites Technologies, Paolo Ermanni (Version 4), Script for the Lecture ETH Zurich, August 2007, Chapter 7".

Component B

Component B is a compound, optionally a polymer, having at least two dienophilic groups having one carbon-sulfur double bond.

In general, compound A has the following form:

Z is an electron-withdrawing group, R ^m is a polyvalent organic group or a polymer and n is a number between 2 and 20. When selecting the group and its diene, it is only important that the hetero -Diels- Alder reaction at a temperature, in the case of the present invention of the

Crosslinking temperature Ti, activated below 80 ° C, at a higher temperature, which is the netnetzungstemperatur T ₂ , by means of a retro-hetero-Diels-Alder reaction traceable, and that this higher temperature possibly below the decomposition temperature of the located in the powder material components. In this case, the dienophile is particularly preferably a dithioester or a trithiocarbonate.

In a preferred embodiment, the group Z is a 2-pyridyl group, a

Phosphoryl group or a sulfphonyl group. Furthermore, cyano or trifluoromethyl groups as well as any other group Z, which greatly reduces the electron density of the C = S double bond and thus allows a rapid Diels-Alder reaction.

A detailed description of the dienophile groups for this embodiment of a (retro) hetero-Diels-Alder reaction can be found in German Patent Application 102010002987.9 (or International Patent Application PCT / EP201 1/050043). In this document, the feasibility of the reaction is shown by means of embodiments.

Component C

Component C is a diene. This diene has the general formula:

In this case, SZ is a rather electron-donating group, which may simply be hydrogen or a simple alkyl radical. R ¹ is a polyvalent organic group or a polymer and m is a number between 2 and 20. The carbon atoms of the double bonds may furthermore have further radicals.

Known groups which are particularly suitable as diene are, for example, furfuryl radicals, adducts of the sorbic alcohol or cyclopentadienyl radicals. method

Furthermore, a novel process for the production of composite semi-finished products and their further processing into moldings is part of the present invention. This process is characterized by the following process steps:

I. Optional shaping of the carrier A),

II. Preparation of a reactive composition consisting of components B) and C)

I II. direct impregnation of the fibrous carrier A) with the composition of II.

IV. Curing the composition at a crosslinking temperature T-i,

V. heating to a dewetting temperature T ₂ ,

VI. Shaping and

VII. Curing the composition at the crosslinking temperature T-i.

The crosslinking temperature Ti of the crosslinking in process steps IV and VII is preferably between 0 and 60.degree. C., more preferably between 10 and 40.degree. C. and most preferably at room temperature. At the dewetting temperature T ₂ in

Process step V, in which these crosslinking sites are at least 50%, preferably at least 70%, dissolved again by means of a retro-Diels-Alder reaction or a retro-hetero-Diels-Alder reaction, is preferably a temperature which is between 50 and 150 ° C, more preferably between 70 and 120 ° C above the

Networking temperature Ti is.

Process step II is particularly preferably carried out at a temperature T ₃ which is at least 40 ° C above the crosslinking temperature Ti. Process step IV is carried out by cooling to the crosslinking temperature Ti. Process step III, the impregnation, is carried out by soaking the fibers, fabrics or scrims with the formulation prepared in process step II. The impregnation is preferably carried out at the same temperature as process step II. This application and impregnation of the fabric / scrim in process step III takes place particularly in the low-viscosity state of the composition from process step II. The particular and great advantage, depending on the composition used, compared to thermoplastics extremely low viscosity of the unlinked juxtaposed low molecular weight building blocks.

Alternatively, the impregnation can also take place by means of a solution. In this case, drying takes place after impregnation to remove the solvent in one

Process step purple. Suitable solvents are all suitable solvents for the composition such as aromatics such as toluene, acetates such as propyl acetate, ketones such as acetone, aliphatic compounds such as heptane, alcohols such as propanol or chlorinated aliphates such as chloroform.

By using the composition of the invention of the components B and C is a very good impregnation of the fiber-shaped carrier A, due to the fact that the liquid composition of components B and C wets the carrier A very well, wherein at a sufficiently high temperature during wetting a premature crosslinking reaction is avoided. Furthermore, the process steps of milling and screening, as often required in prior art composite materials, fall into individual particle size fractions, thus providing a higher yield

impregnated fiber-shaped carrier can be achieved.

The composite semi-finished products can be brought into shape after process step II, for example in a press by pressure, preferably at a temperature which corresponds to the Entnetzungstemperatur T ₂ , but necessarily at most 20 ° C deviates from this. The use of a belt press for the production of planar "organo sheets" is particularly suitable for this purpose used for pressing tools. The demolding is preferably carried out later from the tool cooled to temperature Ti.

The preparation of a re-flexibilizable or deformable composite semifinished product is completed in process step IV by cooling to the cross-linking temperature T-i, preferably to room temperature, at which the matrix passes into the covalently crosslinked state. Upon cooling, the matrix crosslinks not only within the composite semifinished product, but optionally also between several previously assembled prepreg layers across the layer boundaries. Thus, the cross-linking takes place within the entire composite component, even if this was made up of several impregnated parts.

In a particularly preferred embodiment of the invention, the crosslinking takes place in process step IV after mixing components B and C in process step II at room temperature within 2 min. In this embodiment, process step I II is particularly preferably carried out no later than 30 s after process step I I. In the same embodiment, the cross-linking in step VII occurs spontaneously during cooling from the temperature of steps V and VI to the

Crosslinking temperature T-i, in particular to room temperature. The room temperature covalent crosslinking offers the advantage that e.g. no "creep" occurs under mechanical stress, as it is more frequently observed in thermoplastic and semi-crystalline composites.

Optionally, the composite semifinished product between the process steps I I I and IV by means of compression, e.g. under pressure or by applying a vacuum, preformed.

After the preparation of a re-flexibilizable / deformable composite semifinished product in process steps I to IV, a reactivation of the composite takes place optionally

Semi-finished products, for reshaping in process steps V to VII. A particular advantage of the present invention is that the method steps V to VII can be repeated once or several times. Thus, the composite semi-finished products according to the invention are characterized not only by the fact that they can be re-deformed several times, but also by the fact that the composite semi-finished products or the finished molded parts produced therefrom can be recycled.

The shaping in method step VI can be carried out by means of various shaping methods. In pultrusion, in particular thermoplastic pultrusion, the impregnated semi-finished product is pulled through an array of different nozzles. The cross section is gradually tapered to the geometry of the desired profile.

In the case of the thermoset or wet-winding technique, the impregnated semifinished product is wound onto a mandrel. In particular, geodetic or concave moldings can be realized with this method. By means of suitable temperature control during the winding process, a particularly good adhesion between the individual fibers can be realized.

Other geometries, in particular large-scale workpieces, can be produced by means of the Tapelegens. When tape laying impregnated semifinished products are deposited as unidirectional tapes with a laying head usually from supply spools on flat or shaped tooling. In addition, such tools are u.a. with a

Equipped cutting device.

The thermoforming of organo sheets is a pressing method. Different variants are known. When stamping with metal stamping two halves of metal molds are used as a press. In this variant, both tool sides are shaping. Especially for small series, the more flexible forming with elastomer block is used. In this variant, a tool side has a flexible, replaceable elastomer block, while the other side of the tool is shaping. A variant of this is a silicone stamp. In hydroforming, the first side of the tool instead of the elastomer block with a liquid, eg a Hydraulic oil, filled and closed with an elastic membrane chamber. In diaphragm molding, the non-forming tool side is a highly elastic membrane that acts to shape during the actual pressing operation by means of supplied gas or liquid and pressure formed therefrom after closure of the tool.

Other examples of forming methods are other winding techniques and

Rollformverfahren, in particular roll profiling, bending or forming the

Extrusion process. All methods listed by way of example are known to the person skilled in the art and can easily be applied to the semifinished products according to the invention.

The first shaping can also take place by means of a variant of the method according to the invention by means of Quicktemp molding or direct impregnation. In these processes, impregnation and the first shaping take place in the same tool. Both methods are otherwise similar to the described thermoforming of organo sheets.

In addition, in the process according to the invention in an additional process step VIII from the molded composite semifinished product by means of further compression,

Cutting, milling, polishing and / or painting or coating moldings are produced. It is also possible to use moldings of several composite semi-finished products, e.g. be glued or stitched together.

This process step VIII can after process step IV or after a

Process step VII. Irrespective of when process step VIII is carried out, further cycles of process steps V to VII may follow thereafter.

In a method step IX, the composite semifinished product according to the invention or a molded article produced therefrom can be recycled at a temperature T ₄ . This temperature T ₄ is at least as high as the dewetting temperature T ₂ . Process step IX can be carried out according to process steps IV, VII or VIII, depending on what is to be recycled at which stage of production. The composite semifinished products according to the invention or the moldings produced according to the invention can be used in various ways. In particular, these can be used for the production of composites in boatbuilding or shipbuilding, in aerospace technology, in the automotive industry, for two-wheelers - preferably motorcycles or bicycles, in the automotive, construction, medical, sports, electrical and electronics industries, as well as in power generation plants, as used for rotor blades in wind turbines.

Examples

In precursors 1 to 5, compounds with furfuryl residues were synthesized.

Precursor 1: tri-isophorone-trifurfuryl (T-IPDI-Fu) (3)

To synthesize tri-isophorone trifurfuryl (T-IPDI-Fu), furfuryl alcohol (2) is reacted with trimeric isophorone diisocyanate (T-IPDI) (1) in the presence of DBTL (dibutyltin laurate) as a catalyst in acetone.

For the synthesis, 0.490 mol (355.78 g) of T-IPDI are dissolved in 500 ml of acetone in a 2000 ml three-necked flask and heated to 60 ° C. after addition of 0.01% by weight of dibutyltin laurate (DBTL). Subsequently, 1.478 mol (145.02 g) of furfuryl alcohol are added dropwise to the acetone solution over a dropping funnel over a period of 30 minutes. The NCO content of the reaction solution is 6.07% at the beginning of the synthesis. After 2.5 h reaction times at 60 ° C, the NCO content of the reaction solution is determined to monitor the progress of the reaction. It is around 0.35%. After a further 2.25 h, the NCO content is determined again. He is now at 0.14%. The reaction is stopped at this NCO content. The solvent is removed in a vacuum oven at 25 ° C overnight. What remains is a crystalline, slightly yellowish solid with one

Melting point of T _m = 123 ° C. The unambiguous characterization of the product was carried out by means of infrared spectroscopy and by means of ¹ H NMR and ¹³ C NMR spectroscopy.

Precursor 2: tri-hexamethylene-trifurfuryl (T-HDI-Fu) In the second precursor is trimeric hexamethylene diisocyanate (T-HDI) (4) with

Furfuryl alcohol (5) reacted in a urethane reaction to tri-hexamethylene-trifurfuryl (T-HDI-Fu) (6). The background for using T-HDI is that this

Crosslinking component provides because of their long alkyl chains for more flexibility in the network and thus the production of a flexible matrix for the prepreg production even better.

For synthesis, 0.574 mol (331, 42 g) of the clear, oily-viscous T-HDI are weighed into a 2000 ml three-necked flask, dissolved in 500 g of acetone and admixed with 0.01% by weight DBTL catalyst. The solution is then heated under reflux to 60 ° C, with 1.244 mol (169.0 g) of furfuryl alcohol are added dropwise within 60 min via a dropping funnel. The NCO content of the reaction solution is 7.22% at the beginning of the synthesis. In the course of the reaction, a sample is taken after 3.5 h reaction time at 60 ° C to determine the NCO content and the progress of the reaction. The content is 0.055%. After another hour of reaction time, the reaction is terminated at an NCO content of 0.050%. Subsequently, the solvent and unreacted starting material be at 100 ° C and approximately 5 ^* 10 ^"1 mbar. What remains is a slightly yellowish solid product at room temperature. The clear characterization was carried out of the product by

Infrared spectroscopy and by means of ¹ H-NMR and ¹³ C-NMR spectroscopy.

Precursor 3: Fu-IPDI-Voranol (12) As a third compound, monomeric isophorone diisocyanate (IPDI) (7) is reacted in a ratio of 3 to 2 with a bifunctional polyetherol (8) in acetone to give the intermediate (9). Subsequently, the still free isocyanate groups of the intermediate are reacted in a second reaction step with furfuryl alcohol (1: 1). This molecule is intended for flexibilization and used in combination with compound (3) as a matrix component.

For synthesis, 0.321 mol (691, 91 g) of Voranol 2000L (8) is added to a 2000 ml

Weighed out three-necked flasks and dissolved in 500 g of acetone. After addition of 0.01% by weight of DBTL catalyst, the solution is heated under reflux to 60 ° C., 0.484 mol (108.96 g) of IPDI being added dropwise to the reaction solution over a dropping funnel over the course of 45 minutes. The NCO content of the reaction solution is 2.69% at the beginning of the synthesis. After 2.5 h reaction time at 60 ° C, the NCO content of the solution is determined. It is 0.91%. Since the theoretical calculated final NCO number is 0.897%, we continue the reaction. After a further 1.5 h reaction time, the NCO content is determined to be 0.896%, whereupon the reaction is terminated. The solvent and unreacted starting material are stripped off at 100 ° C and 5 ^* 10 ^"1 mbar. What remains is a clear, brownish viscous oil was carried unambiguous characterization of the product by.

Infrared spectroscopy and by means of ¹ H-NMR and ¹³ C-NMR spectroscopy.

In the second reaction step, 0.1 19 mol (678.25 g) of product (10) are weighed into a 2000 ml three-necked flask and dissolved in 700 g of acetone. After addition of 0.01% by weight DBTL, the solution is heated under reflux to 60 ° C, with 0.241 mol (23.61 g) of furfuryl alcohol are added dropwise within 60 min via a dropping funnel. The NCO content of the reaction solution is determined at the beginning of the synthesis at 0.716%. For the reaction control, the NCO content is determined after 1 h reaction time. This amounts to 0.184%. After another 4.5 h reaction time of the NCO content in solution is only 0.045%, which speaks for a nearly complete reaction.

For work-up, the acetone is removed on a rotary evaporator at 60 ° C. and 5 ^× 10 ^-1 mbar, leaving behind a yellowish oil, which is analyzed for characterization by means of ¹ H-NMR and ¹³ C-NMR, as well as infrared spectroscopy.

Precursor 4: Isophorone difurfuryl (IPDI-Fu)

As a fourth compound, isophorone difurfuryl (IPDI-Fu) (15) is synthesized from isophorone diisocyanate (IPDI) (13) and furfuryl alcohol (14) in acetone. The product can be used, for example, as a crosslinking component for the reversible DA / rDA reaction of maleate-functionalized poly (methyl methacrylate) Compolymeren. Furthermore, it may e.g. used in combination with trifunctional cross-linkers to the

Reduce crosslink density and thus increase the flexibility of the matrix.

For synthesis, 1. 092 mol (267.77 g) of IPDI are placed in a 2000 ml three-necked flask

weighed and then dissolved in 300 g of acetone. After addition of 0.01% by weight DBTL, the solution is heated to 60 ° C, 2.377 mol (233.25 g) of furfuryl alcohol are added dropwise within 60 min. The NCO content of the reaction solution is 12.45% at the beginning of the synthesis. After 4.5 h reaction time, the NCO content is determined to determine the progress of the reaction. It is 0.506%. Another hour later, the reaction is terminated at an NCO content of 0.20%. The solvent is removed on a rotary evaporator at 100 ° C. and 5 ^× 10 ^-1 mbar, leaving behind a very viscous, brownish oil at room temperature The unambiguous characterization of the product was carried out by means of infrared spectroscopy and by means of ¹ H-NMR and ¹³ C-NMR spectroscopy. Precursor 5: tri-methylhexamethylene-difurfuryl (TMDI-Fu)

As the fifth furfuryl-functionalized compound, trimethylhexamethylene difurfuryl (TMDI-Fu) (18) is prepared from 2,2,4-trimethylhexanemethylene diisocyanate (TMDI) (16) and furfuryl alcohol (17) in acetone at reflux.

For the synthesis, 1, 210 mol (262.64 g) of TMDI are weighed into a 2000 ml three-necked flask and then dissolved in 500 g of acetone. After addition of 0.01% by weight of DBTL, the solution is heated to 60 ° C., while 2.470 mol (242.38 g) of furfuryl alcohol are added dropwise within 60 min. The NCO content of the reaction solution is 10.16% at the beginning of the synthesis. After a reaction time of 7.5 hours, the NCO content is determined to be the

Proceeding to determine. The salary has dropped to 0.43%. After a further 7.5 h, the NCO content is determined to be 0.30%. After 9.5 h, the reaction is terminated at an NCO content of 0.08%. The solvent and unreacted furfuryl alcohol are ^{"distilled 1} mbar in a rotary evaporator at 90 ° C and 5 ^× 10. What remains is a brown liquid at room temperature to slightly viscous oil was carried unambiguous characterization of the product by ¹ H-NMR and ¹³ C. NMR spectroscopy. Precursor 6: furfuryl-modified polymethacrylate

In precursor 6, furfuryl-modified polymethacrylates were synthesized by way of example. A copolymer of butyl methacrylate, methyl metharylate and furfuryl methacrylate was prepared by free radical solution polymerization by free radical solution polymerization and ATRP polymerization.

Alternatively, the desired polymer can be prepared by the well-known techniques of solution polymerization, suspension polymerization or emulsion polymerization, and bulk polymerization and all controlled radical, ionic or coordinative polymerization methods compatible with the desired monomer mixture.

For further purposes, for example, two polymers each having 6.5 mol .-% and 13 mol .-% of furfuryl groups were synthesized.

Precursor 6a Synthesis of furfuryl-functionalized polymethacrylate by ATRP

(66-x / 2) parts by weight of n-butyl methacrylate (nBA), (34-x / 2) parts by weight

Methyl methacrylate acrylate, x parts by weight of furfuryl methacrylate 0.5 parts by weight of 1, 4-bis (bromoisobutyryloxy) butane, 0.05 parts by weight of copper (I) bromide, 0.006 parts by weight of copper (II) bromide and 0.125 parts by weight of PMDETA in a 1 L three-necked flask with magnetic stirrer, Nitrogen inlet and reflux condenser submitted. The corresponding x value is shown in the respective results in Table 3. Add so much acetone to the mixture that there is 500 mL of a 50 vol% solution. Existing oxygen is removed by passing nitrogen through for 40 minutes. The mixture is then heated to 60 ° C under nitrogen in an oil bath. After 4 h of polymerization, this is terminated by cooling to room temperature and supply of atmospheric oxygen. The copper card analyzer is removed by electrochemical deposition on zinc dust according to the method described in WO 2012/007213. The polymer is recovered by evaporation of the solvent. The composition of the polymer was determined by ¹ H-NMR spectroscopy. Precursor 6b Synthesis of Furfuryl-Functionalized Polymethacrylate by Free Radical Solution Polymerization

To synthesize the copolymer, a mixture of (66-x / 2) parts by weight of n-butyl methacylate, (24-x / 2) parts of methyl methacrylate and x parts by weight of furfuryl methacrylate is dissolved in 35 parts by weight of xylene and 4 parts by weight

Mercaptoethanol added and degassed by passing nitrogen. The corresponding x value is shown in the respective results in Table 3. In another container, a 10% by weight solution of α, α'-azobis (isobutyric acid 2-hydroxyethylamide (3 parts by weight) is prepared, the two templates being added in a constant ratio over a period of five hours to 1 ° to 10 ° C tempered glass double jacket reactor with thermostat added under nitrogen and allowed to polymerize After the dosing is heated for an additional hour (1 10 ° C) and the resulting

Polymer solution cooled and discharged. A viscous clear polymer solution is obtained, the composition of which is determined by 1 H NMR spectroscopy.

H ₃ C 1, 6-bismaleimide-2,2,4-trimethylhexane (TMD-BMI)

The TMD-BMI was purchased from Evonik Industries AG / TechnoChemie Dossenheim.

Example: general procedure for the production of prepregs and laminates

The laminates are produced in a heated, hydraulic press. They are built up from prepregs layer by layer, whereby usually between 9 to 15 prepregs are pressed into a laminate about 2 mm thick.

As a reinforcing material for the fiber composites produced in this work, a standard fabric from. WELA is used, which is performed under the trade number 7628. This fabric has a basis weight of 202 g / m ² and is provided for better further processing with a size and a non-explained finish name TF 970. The finish generally provides good fiber-matrix adhesion by forming a covalent bond between matrix and tissue. To prepare the prepregs, an approximately 55% by weight acetone solution consisting of the Diels-Alder starting materials is prepared so that they are combined in molar equivalent of the DA functional groups. By Diels-Alder educts in this context are meant the dienes from Examples 1 to 6 and 1,6-bismaleimide-2,2,4-trimethylhexane as the dienophile. The polymer solution is preferred to each

Impregnation freshly prepared, since the starting materials also crosslink in solution and at RT after a few hours or days.

The cut glass fiber fabrics are now individually soaked in the polymer solution.

Subsequently, the tissues are dried at 65 ° C for 1 h in a drying oven, the DA reaction starts and the solvent evaporates. The resulting prepreg Materials are storage stable due to their fully crosslinked matrix, but still have sufficient flexibility to be stored in rolled form.

In the press, the prepregs are pressed above the retro-Diels-Alder temperature at about 150 ° C and 150 bar for 1 h. At this temperature, the matrices of the individual prepregs become thermoplastic because the Diels-Alder adduct reversibly cleaves back. At the

Cooling cross-links the matrix to a hard composite to rebuild the Diels-Alder adduct.

Characterization of matrices, prepregs and laminates The characterization of different matrices, prepregs and laminates is performed by mechanical analysis and differential scanning calorimetry (DSC), which is used to determine the glass transition temperature of the matrices.

The mechanical analyzes show, for example, in the tensile test, the stress-strain behavior, the modulus of elasticity and the maximum tensile strength o _max and the maximum elongation at break e _{max of} the laminate according to DIN EN ISO 527.

The three-point bending test according to DIN EN 2563 determines the interlaminar shear strength (ILSF) of the laminate, which also provides information about the fiber-matrix connection. The resistance of the laminate against interlaminar shear stress is determined which acts parallel to the individual layers. The determination of the Charpy impact strength of the laminate according to DIN ISO 179-1 / 1 eU describes the ability of the laminate to absorb impact energy and dissipate without breaking.

Based on the above-described and ongoing analysis of composite materials, it is attempted to create a Diels-Alder based fiber composite that can compete in mechanical, thermal and optical properties with conventional epoxy based fiber composites. Table 1: Modulus of Elasticity of Various Laminates of 9 Prepregs (2mm Thickness) Furfuryl Maleimide Base.

Table 2: Shear strength of various laminates of 9 prepregs (2mm thickness) based on furfuryl-maleimide.

Determination modulus of elasticity from tensile test; Apparent interlaminar shear strength according to the three-point method with short beams according to DIN EN ISO 14130)

In summary, the mere manufacturability of a durable and shear-stable laminate between the prepreg layers is direct evidence of the reversibility of the cross-linking, as this requires a disruption of the cross-linked structure.

Table 3: Mechanical properties of the laminates of 14 prepregs (2 mm) based on polyacrylate furfuryl / bismaleimide.

¹ thermal aftertreatment of the composite for 7 h at 80 ° C in a rocking cabinet

Apparent interlaminar shear strength according to the three-point method with short beams according to DIN EN ISO 14130; Impact strength according to Charpy DIN EN ISO 179-1 / 1 eU; Tensile test according to DIN EN ISO 527

A significant increase in the Tg of the Materix material through the crosslinking of the material is also evidence of the crosslinking of the matrix

Claims

claims:

1 . Kit for the production of composite semi-finished products comprising

A) a fibrous carrier,

B) a first reactive component comprising at least two dienophilic double bonds, wherein the dienophilic double bonds are carbon-sulfur double bonds, and

C) a second reactive component comprising at least two diene functionalities, wherein at least one of the components B or C more than two of the respective

Has functionalities, and the first and the second reactive component with each other by means of a Diels-Alder or a hetero-Diels-Alder reaction can be crosslinked.

2. Kit according to claim 1, characterized in that the fibrous carrier A)

consist largely of glass, carbon, plastics such as polyamide (aramid) or polyester, natural fibers, or mineral fiber materials such as basalt fibers or ceramic fibers, and the fibers thereby as a textile fabric of non-woven,

Knitted fabrics, knitted fabrics and knits, non-meshed packages such as fabrics, scrims or netting, long fiber or short fiber materials.

3. Kit according to claim 1, characterized in that it is the dienophilic double bonds to groups having the structure

where Z is a 2-pyridyl group, a phosphoryl group or a sulfonyl group, R ^m is a polyvalent organic group or a polymer and n is a number between 2 and 20. Kit according to claim 1, characterized in that components A and / or B are one or more polymers.

Kit according to Claim 4, characterized in that the polymers are

Polyacrylates, polymethacrylates, polystyrenes, copolymers of acrylates,

Methacrylates and / or styrenes, polyacrylonitrile, polyethers, polyesters, polylactic acids, polyamides, polyester amides, polyurethanes, polycarbonates, amorphous or partially crystalline poly-α-olefins, EPDM, EPM, hydrogenated or non-hydrogenated polybutadienes, ABS, SBR, polysiloxanes and / or Block, comb, star or hyperbranched copolymers of these polymers.

Composite or semifinished product, characterized in that they have been produced with a kit according to at least one of claims 1 to 5.

Process for the production of composite semi-finished products and their further processing into molded parts, characterized by the following process steps

I. optional shaping of the support A) according to claim 1,

II. Preparation of a reactive composition consisting of components B) and C) according to claim 1,

III. direct impregnation of the fibrous carrier A) with the composition of II.,

IV. Curing the composition at a crosslinking temperature T-i,

V. heating to a dewetting temperature T ₂ ,

VI. reshaping and

VII. Re-curing of the composition at the cross-linking temperature Ti.

8. The method according to claim 7, characterized in that the crosslinking temperature T-i of the crosslinking in the process steps IV. And VI I. between 0 and 60 ° C, preferably between 10 and 40 ° C.

9. The method according to claim 7 or 8, characterized in that the crosslinking in the process steps IV. And VII. At room temperature, that in

At the dewetting temperature T _2, these crosslinking sites are redissolved at least 50% by means of a retro-Diels-Alder reaction or a retro-hetero-Diels-Alder reaction, and the dewetting temperature T _{2 is} between 50 and 150 ° C. above the crosslinking temperature ΤΊ is located.

10. The method according to claim 7, characterized in that the crosslinking in

Process step IV. After mixing the components B and C in

Process step II. At room temperature within 2 min, and that process step I I I. carried out no later than 30 s after process step I I.

1 1. Method according to claim 7, characterized in that method step II. Is carried out at a temperature T ₃ which is at least 40 ° C above the

Crosslinking temperature ΤΊ is, and that process step IV. By cooling to the crosslinking temperature Ti occurs.

12. The method according to any one of claims 7 to 1 1, characterized in that the method steps V. to VI I. are repeated once or several times.

13. The method according to any one of claims 7 to 12, characterized in that in a process step VIII. From the composite semi-finished by means of

Cutting, milling, polishing and / or painting or coating a molding is produced.

14. The method according to any one of claims 7 to 12, characterized in that in a method step VIII., The composite semifinished product according to at least one of claims 6 to 1 1 or a molded article produced therefrom

Claim 13 is recycled at a temperature T ₄ , wherein the temperature T _{4 is} at least as high as the Entnetztstemperatur T ₂ .

15. The use of the composite semifinished products, which were produced according to at least one of claims 7 to 12 or the molding, which were prepared according to claim 13, for the production of composites in boat and shipbuilding, in the aerospace industry, in the automotive industry, For two-wheelers preferred motorcycles and bicycles, in the areas of automotive, construction, medical, sports, electrical and bicycle

Electronics industry, power generation equipment, such as for rotor blades

Wind turbines.