EP2673327A1

EP2673327A1 - Adhesive material with carbon material and method for its production and use

Info

Publication number: EP2673327A1
Application number: EP12705095.3A
Authority: EP
Inventors: Tim Schubert; Tomas Meinen; Christian Zenkel
Original assignee: Futurecarbon GmbH
Current assignee: Future Carbon GmbH
Priority date: 2011-02-10
Filing date: 2012-02-10
Publication date: 2013-12-18
Also published as: US20140034231A1; WO2012107548A1; US10377925B2

Abstract

The present invention relates to an adhesive material, especially an electrically and/or thermally and/or radiation-curing or curable adhesive material, having at least one adhesive constituent and/or adhesive matrix, and moreover having at least one additive in the form of a carbon material, especially based on carbon nanomaterials and/or carbon micromaterials, present in the adhesive constituent and/or adhesive matrix. The invention further relates to a method for producing, activating and/or curing an adhesive material. Finally the invention also relates to a method for adhesively bonding two substrates.

Description

description

Adhesive material with carbon material and method for its

Manufacture and use.

The present invention initially relates to an adhesive material. Furthermore, the invention also relates to a method for producing an adhesive material, a method for activating and / or curing an adhesive material and a method for bonding two substrates.

Adhesive systems of the type mentioned above are known in many different ways in the prior art. However, the adhesive systems currently used do not have sufficient electrical conductivity or

Microwave absorption in order to use this technically for the curing process can. Or else it must be added such proportions of electrically conductive additives that the adhesive properties significantly negative

be affected.

The present invention is therefore based on the object to provide solutions by means of which in particular a curing process as described above can be realized. This object is achieved by the adhesive material having the features according to the independent claims 1 and 9, the method for producing an adhesive material having the features according to the

independent claim 6, the method for activating and / or curing an adhesive material having the features according to the independent

Claim 10 and the method for bonding two substrates with the features according to independent claim 14. Further features and Details of the invention will become apparent from the dependent claims, the description, the examples and the drawings. In this case, features and details that are described in connection with a specific aspect of the invention, with regard to the disclosure, of course, always in the full extent always in the

Related to the other aspects of the invention, and vice versa.

In particular, according to the present invention, adhesive materials are provided which can be thermally activated and / or cured. This means that these adhesive materials can be activated and / or cured by means of a thermal effect. This can be realized in different ways, so that the invention is not limited to specific embodiments. For example, the thermal effect can be realized by a radiation, for example a microwave radiation. In addition, it is also possible to think about the action of UV or

Infrared radiation to thermally activate / cure the adhesive materials.

Such adhesive materials will be referred to as radiation-curing or -aktivierbar in the further course. In another embodiment, it is possible that the thermal effect is induced by an electric current.

This can be achieved by direct contacting of the layer with metallic,

possibly flat contact strips are made, or even without contact by the action of the magnetic field of an alternating current operated induction coil, which in turn generates currents in the conductive adhesive, which heat the adhesive resistive.

Such adhesive materials are referred to as electrically curing or activatable in the further course. Accordingly, it is preferable in the present invention that the adhesive material is subjected to thermal curing / activation or may be subjected. The energy required for this purpose can be provided, for example, electrically / resistively, or via radiation, such as microwave radiation.

In particular, radiation-curable adhesive materials are provided in accordance with the present invention. Furthermore, adhesive bonds, in particular with an electrically curing and / or radiation-curing

Adhesive material can be realized, for example, for use in

Automotive sector or the like.

In particular, electrically and / or radiation-curing adhesive based on carbon nanoparticles is provided. The invention is not limited to specific carbon nanoparticles

According to the present invention, basically any form of

Carbon material are used. Thus, according to the present invention, it is provided that the additive is in the form of a carbon material. In another embodiment, it may also preferably be provided that the additive is in the form of a dispersion, predispersion or the like, which is a

Has carbon material. In the case of a dispersion, the additive is preferably in a matrix material.

The currently used adhesive systems do not yet have sufficient electrical conduction or microwave absorption in order to be able to use this technically for the curing process. Or they contain so much

Amounts of conductive additives that the adhesive effect is impaired.

The basic feature of the present invention is to provide precisely this requirement by using suitable additives. However, these additives should not adversely affect the adhesive effect. The as additive used materials are mainly special carbon preparations, for example, with MWNTs (= multi-walled carbon nanotubes) as

Basic functional carrier, which are preferably incorporated into the adhesive with different dispersing methods.

According to the first aspect of the invention, an adhesive material, in particular an electrically and / or thermally and / or radiation-curing or

curable adhesive material provided comprising at least one

Adhesive component and / or adhesive matrix, and further comprising at least one in the adhesive component and / or adhesive matrix located additive in the form of a carbon material, in particular based on

Carbon nanomaterials and / or carbon micromaterials.

Preferably, the additive may be in the form of a carbon material which is microwave-absorbent and / or based on CNT and / or based on a CNT-containing mixture of different carbon materials and / or predispersed.

Preferably, the adhesive material can be used as an additive in the form of a

Carbon material, CNT in a concentration of greater than 0.2 wt% have.

It is furthermore preferred that the adhesive material has at least one further additive, in particular at least one hardener and / or another

carbonaceous material and / or soluble CNT granules.

Basically, any combination of the following materials are conceivable. Not all components must be present at the same time.

Preferably, however, always includes a carbon material component and / or a CNT-containing component and a base adhesive component thereto. The materials mentioned are Base adhesive component. For PU adhesives, this is the polyol component

- Hardener component, such as polyisocyanates in PU adhesives

- Other additional components, for example liquid polyesters in hotmelt adhesives

- CNT dispersion, preferably aqueous or in solvents, possibly

stabilized

- Carbon material-containing dispersion, preferably aqueous or in

Solvents, possibly stabilized

- CNT granules, optionally stabilized for good dispersibility

It is further preferred that the adhesive material is one or more of those mentioned in the claims, the description, the examples or the figures

Features. The adhesive materials used, in particular the

Adhesive component and / or form the adhesive matrix may be PU-based adhesives. These adhesives are only to be seen as examples. Generally, the principle of adding CNTs / carbon materials as microwave-absorbing additives to an adhesive in order to cure them in the microwave field works for many liquid thermosetting adhesives.

Furthermore, so-called hot melt adhesives, ie, adhesives which are firmly present before melting, can be provided with CNT additives and then also activated via microwave absorption in the component. Further important aspects are, in particular, the possibility of improving the adhesive effect by CNT additives and / or microwave curing over CNT-free systems and / or conventional curing; the lifting of the

Adhesive effect during remelting in the

Microwave field / switchability of sticking and loosening, even the final one

Inactivation of the adhesive by corresponding overheating in the microwave field; the electrical conductivity of the adhesive after curing, over the pure goes beyond antistatic applications; the binding of possibly harmful moisture due to the high binding capacity of carbon nanotubes (as an option).

The peculiarity compared to previous solutions, such as metallic

Components for electrical / microwave-assisted adhesive curing consist in particular in that due to the particular absorption properties of the CNT-containing systems with good dispersion, only minor additions of additive are required and the basic properties of the adhesives are particularly well preserved. An improvement of the adhesive properties compared to a CNT-free adhesive system is documented for several material combinations.

According to a further aspect of the invention, a method is provided for producing an adhesive material, in particular an inventive adhesive material as described above, and characterized in that an adhesive component and / or adhesive matrix of adhesive material is provided, and in that an additive in the form of a carbon material, in particular based of carbon nanomaterials and / or

Carbon micromaterials introduced into the adhesive component and / or adhesive matrix, in particular dispersed and / or mixed and / or distributed.

Preferably, the additive is or will be in the form of a carbon material

predispersed, especially in an aqueous or organic solution.

Preferably, at least one further additive is added, in particular a hardener and / or another carbonaceous material and / or soluble CNT granules. With regard to the preferred materials and material combinations, reference is also made in full to the Ausführiungen above and referenced. Preferably, the method may comprise one or more method step (s) recited in the claims, the description, the figures or the examples. According to a further aspect, an adhesive material, in particular an adhesive material according to the invention as described above, which is produced or can be produced by a method according to the invention as described above is provided. According to a further aspect, a method for activating and / or

Curing an adhesive material, in particular one as above

described adhesive material according to the invention and / or a

Carbon material containing one as described above

according to the invention, characterized in that it is activated and / or cured electrically and / or thermally and / or radiation-based.

Preferably, the adhesive material is activated and / or cured by applying an electrical voltage.

Preferably, the adhesive material is activated and / or cured by being exposed to radiation, in particular microwave radiation.

Preferably, the adhesive effect of the adhesive material can be canceled by the adhesive material is again thermally treated, for example, is remelted, preferably in the microwave field.

According to yet another aspect, there is provided a method for bonding two substrates, in particular using an adhesive material according to the invention as described above and / or produced, characterized in that the adhesive material on the first and / or second Substrate is applied and / or brought between the two substrates, that the two substrates are brought together and that the adhesive material is activated and / or cured, in particular by a method according to the invention as described above.

A substrate is generally a component or device

Preferably, the substrate has a support, such as a pad or base for something else. In another embodiment, a substrate may also be such a support.

However, as with other aspects of the invention, the

Adhesive effect by carbon additives, in particular CNT additives and / or microwave curing over CNT-free systems and / or conventional curing can be improved.

Preferably, the adhesive effect by re-melting or

Melting, for example in the microwave field, reduced or even canceled. It is preferably provided that by the possibility of melting, in particular a temporary melting, a switchability of gluing and loosening can be generated.

For example, it is also possible that a final inactivation of the

Adhesive can be achieved, for example by a corresponding

Overheating, for example in the microwave field.

In addition, an electrical conductivity of the adhesive, in particular after curing, can be achieved, which goes beyond purely antistatic applications; The binding of optionally harmful moisture by the high binding capacity of the carbon material, in particular carbon nanotubes can be achieved. Preferably, the methods of the invention described above may comprise one or more of the method steps (e) recited in the claims, the description, the figures or the examples.

In the invention represented by the various aspects mentioned above, carbon nanomaterial may preferably be used as the carbon material.

This can be present for example in the form of carbon nanotubes or used. Carbon Nanotubes (CNTs) consist in particular of cylinder-wound, closed graphene layers. Single tubes are called "single wall carbon nanotubes" (SWCNT), particles of concentrically stacked tubes of increasing diameter become "multiwall carbon nanotubes".

(MWCNT). CNT can be produced by various methods. The best known are the arc process, the laser ablation process and the catalytically assisted vapor deposition (CCVD). The latter method is suitable for large-scale production of CNT. The CNTs are produced from gaseous carbon sources (hydrocarbons, alcohols, CO, CO2) on metallic, catalytically active substrates. Commercially available SWCNT have diameters of 0.5 - 4nm, MWCNT have diameters between 6 - 100nm. The length of CNT can be up to several mm. The physical properties of CNT largely correspond to those of graphite along basal planes. CNTs are used today as a mechanical reinforcement, as an electrically and thermally conductive additive in polymers, ceramics and metals. For this purpose, the CNTs are often chemically modified on their surface in order to meet the requirements of good dispersibility and connection to the matrix. As a rule, the CNTs are added to the matrix material. Due to the high

Aspect ratio and the high surface area are only composites with relatively low CNT content representable. In another embodiment, the carbon nanomaterial may be in the form of carbon nanofibers. Carbon nanofibers (CNF) consist of graphene layers stacked along the filament axis. The angle (orientation) of the graphene planes with respect to the filament axis is taken as a rough distinction. So-called 'herringbone' CNF have graphene planes which are arranged at an angle of 90 °. These CNFs can be massive or hollow. Their diameters are in the range 50nm-1 pm and their lengths can be up to mm. In the case that the graphene layers are arranged at an angle = 90 ° to the filament axis one speaks of 'Platelet'

CNF. Their diameters are in the range 50nm-500nm and their lengths can be up to 50pm. These CNFs are usually manufactured via CVD. Their applications are found primarily in catalysis as catalyst supports and as active additives in Li-ion batteries or in gas storage.

Carbon particles, for example carbon nanoparticles, for example

Carbon nanotubes (CNTs) have special electrical, thermal and mechanical properties. Thus, CNTs have a very high electrical conductivity, which can go into the range of a metallic conductivity. The thermal conductivity of the CNT can theoretically reach up to 6000 W / mK. The mechanical properties of CNT are extreme. For example, tensile strengths and moduli of elasticity that are 1000 times higher than those achieved by steel are achieved. Therefore, carbon nanoparticles are of particular interest as additives in various matrix materials for improving electrical conductivity, thermal conductivity, mechanical properties and much more in the chemical industry

Mechanical engineering, in the automotive industry, aerospace and also the

Medical technology and other industries. By using CNT dispersions, the heating rates in the microwave field can be further increased by a factor of 2-3 and the attainable final temperatures increase. With increasing power, the positive aspect of the CNTs decreases due to the self-heating of the matrix system, the heating rates do not increase

proportional to the introduced microwave power and become more independent of the CNT content. On locally too high CNT proportions or accidentally too high

Microwave power responds the system so tolerant, this is a principle technically usable self-limitation of the system.

The following basic technologies may be related to the

For example, a heating by electrical resistive heating can be carried out. By applying an electrical voltage to a conductive material, electrical current can be converted into heat by means of the electrical resistance of the material, which makes it possible to activate temperature-crosslinking systems. The

Heating power depends on both the surface resistivity and the applied electrical voltage, which is hot of the flowing current. In the case of electrically heated layers, in addition to the conductive material used, the layer thickness additionally plays a role, since the conductivity increases until a specific volume conductivity value is reached, depending on the layer thickness. Another important value is the percolation limit, which must be reached or exceeded in order for the conductive particles in the matrix to form an electrically conductive network. For contacting the applied heatable layer, commercially available metallic contacting tapes can be used, which are applied before the application of the layer. In order to ensure a homogeneous heating of the layer - that is, a uniform heating - on the one hand, the layer thickness must be as constant as possible and on the other hand, the arrangement of the contact strips parallel to each other. This creates between the Electrodes of equal length "current paths" with identical conductance values, which ensures a uniform current flow throughout the entire layer, in order to achieve a low contact resistance or contact resistance

ensure the contact bands are preferably incorporated into the material and can be removed only with considerable effort from the components again. For this reason, a whereabouts of the electrode strips in the respective component is to be considered.

Another form of heating may be by means of a microwave field. In principle, four possible reactions of a material or a sample can be distinguished in particular from microwave radiation.

On the one hand, the sample can be permeable to microwaves, which is usually the case with electrical insulators. Furthermore, it can reflect the radiation, or with the electric or magnetic field in

Interacting. In contrast to conventional heating methods in which heat is supplied to the material or specimen indirectly from the outside by heat radiation, convection or heat conduction, heating with microwaves generates heat directly inside the sample. This also reverses the conventional temperature gradient in conventional heating processes, that is, the material is heated from the inside. If a substance can either interact with the magnetic or electrical part of the microwave radiation, it can be heated with it, whereby different mechanisms are important for conductors and dielectrics.

Conductive and inductive heating takes place in electrically conductive materials. In the case of conductive heating, the oscillating electrical part of the field generates a current in the material, which in turn heats up the sample by ohmic losses. In inductive heating, the oscillating E field is generated by the externally acting magnetic field component of the microwave radiation. The resulting circulating currents cause warming. It is important to note the field lines are located on the surface of the specimen by field displacement and the penetration depth is of the order of only 10 ^"6 m for metallically conductive materials

Materials, as in the case of the CNT-containing adhesive systems, the radiation penetrates into the entire volume of the adhesive film.

If the dielectric is polar, which is the case for example in the case of water, the statistically distributed elementary dipoles can be aligned by the external field, which is referred to as orientation polarization (maximum in the range 105-109 Hz, but also effective in the frequency range used). This mechanism is also due to the water content of many adhesives - especially before

Curing, relevant for the heating process.

A good overview of microwave radiation, in particular

Absorption mechanisms as well as interaction of matter-electromagnetic fields is described in "T. Gerdes. Microwave sintering of metal-ceramic composites - Dissertationsschrift, Progress Reports VDI, Dusseldorf, 1996. "This disclosure content is included in the disclosure of the present patent application in this respect.

Is a mixture of substances, for example a dispersion of CNTs in one

Solvent, a resin, a polymer or the like, so there are locally different gradients of the electric field, the electrical conductivity and / or a locally different absorption behavior, which can lead to different degrees of heating.

In the range of low temperature, especially the conductive components of the mixture contribute to the heating, the matrix component, if so

Microwave transparent or less absorbing, is then indirectly heated by the conductive particles, causing an anisotropic heating. By good dispersion of the CNTs, as well as by the good thermal conductivity of the used Additive spontaneous dissemination of the resulting heat, but it usually comes to a rapid and efficient homogenization of the temperature

Adhesive film. If this temperature equalization is made possible by a limited field strength, thus not too rapid heating rate, so-called "hot spots" can be completely avoided.

If one increases the concentration of the CNTs, then the

Improve heating properties by reaching the percolation threshold. When the threshold is exceeded, the conductivity of the mixture increases significantly, while the penetration depth of the MW radiation decreases. While below the

Percolation threshold, the absorption behavior of the individual particles is decisive for the heating, now occurs - in addition - on the communicating overall system related absorption of the microwaves. The behavior of the penetration depth during heating depends on the materials, so the conductivity decreases

Carbon increases with increasing temperature, which is why the penetration depth decreases. For splices that have only a small film thickness, this is technologically not a relevant limitation. For heating processes, the optimum in terms of heating behavior is usually in a range which has a high electrical conductivity, but again not too high, so not by a limited

Penetration depth is heated only the surface of the body.

In the case of microwave heating of various adhesive systems, it should be noted that many adhesives are not transparent to the microwave, meaning that dissipation and heating of the adhesive takes place even without CNT content. To make these technically usable for a curing process and to accelerate, the addition of strong Mikrowellenstrahlenabsorbierender components, such as CNTs, advantageous.

In anticipation of the results described below, it can be concluded that

· Additization of adhesives with carbon-based microwaves

absorbent materials is feasible, • in particular carbon nanotubes are suitable for this,

• the fast and efficient heating in the microwave field works,

This heating leads to the desired curing of the adhesive,

• An industrially acceptable solution for microwave-based adhesive curing using said additives is feasible.

In the further course, the invention will now be described with reference to preferred

Embodiments described, with particular reference is also made to the accompanying drawings. Show it

Figure 1 various CNT-containing adhesive systems;

Figure 2 shows the schematic structure of a microwave band dryer for

Implementation of inventive method;

FIG. 3 shows the absolute temperature profile of various heating attempts; FIG. 4 shows the plot of the heating over a recorded period of time; and Figure 5 is a rating table.

In the following, various investigations are described by way of example for the dispersion of CNT in an adhesive matrix of a PU-based adhesive-as a first exemplary embodiment which does not limit the entire invention. The results of the investigations were as follows:

1 . Creating reference samples (without CNT)

- is glued:

PC ABS (polycarbonate / acrylonitrile-butadiene-styrene copolymer)

• Planware thin (leather) as upper material

2. Improved dispersion of CNTs

3. Surface modified CNTs to improve the dispersion 4. Mixing back-soluble CNT granules to further improve the dispersion of CNTs in the adhesive

5. Testing Dispersants

6. introduction of various CNT concentrations, for example 0.5 wt%, 1, 0 wt%, 1, 5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt% ,

7. Use of CarboDis, which are: predispersed, stabilized CNT dispersions, for better dispersion of the CNTs in the adhesive.

The results of the dispersing tests initially showed that the CNTs used were difficult to incorporate into the adhesive from time to time irrespective of the respective mixing ratio and even when using established

Mixed technologies still agglomerates. These mixing difficulties were attributable to the fact that CNTs are even more likely to be considered hydrophobic even after an upstream purification, which clearly makes dispersing in diols difficult, in particular. Further improvement of the dispersion could be achieved in such cases by transferring high shear forces to the CNT agglomerates in the highly viscous systems, thereby dispersing them more finely in the adhesive matrix. In order to improve the dispersibility of the CNT in the matrix, further experiments were carried out with dispersing aids, whereby the viscosity of the

Systems adhesives / CNT, however, continued to increase. This increase is due to the better distribution of CNT in the matrix, as finely divided CNTs have an extraordinary ability to bind liquids. The question of viscosity is of importance for the homogeneous dispersion of CNTs in solvent and matrix systems: As the viscosity increases, shear force transmission is improved, depending on the dispersion techniques used. This can, by appropriate shearing of CNT agglomerates, these successively crush and lead to a homogeneous distribution of CNTs in the adhesive.

On the other hand, too high a viscosity means a more difficult one

Processability and inferior functionality of the adhesive, so it is a parameter to be optimized. In the sense of the described binding capacity of the CNTs and the increase in viscosity, it was possible to achieve a better-optically detectable-better distribution by the addition of surface-oxidized CNTs from a concentration of 1.5 wt% CNTs. The adhesive became highly viscous. The following are the results of the processability of the adhesive mixtures with the different proportions by weight.

• 0.5% by weight low viscosity

• 1, 0% by weight low viscous

»1, 5% by weight still easy to process

• 2.0% by weight extreme limit

• 2.5% by weight no longer flowable

• 3.0% by weight no longer flowable A very good distribution could be achieved by the addition of soluble CNT granules, which are highly dispersible, especially in aqueous systems. The additive used for this purpose is a dispersible in polar systems granules, which is characterized by a particularly low

Agglomerationsneigung (in contrast to "conventional" CNTs) is characterized, however, acts in this particular case, a surfactant contained herein in the overall system electrically insulating, so that at higher concentrations of the electric Conductive resistance of the adhesive increases, which prevents electrical curing of the samples. Finally, attempts to deliver CNTs to the adhesive system in powder form have at least resulted in a moderately homogeneous distribution of the CNTs, or they have not shown sufficient effect by the insulating action of the surfactant used (in the case of soluble granules if they contain such surfactants) electric conductivity. In particular, according to the present invention, it is possible to disperse CNT directly in the adhesive. For example, the use of CNT may be in powder form. Preferably, pre-dispersed CNTs can be used, which in particular are easier to handle.

For these reasons, the present invention has also pursued the further novel approach which works with already excellently dispersed CNTs in aqueous or organic or solvent-based media. Several corresponding products were used. FIG. 1 shows CNT-containing adhesive systems having an improved dispersing quality by using CarboDis materials. The CarboDis materials are aqueous predispersed CNTs. The greatest success in dispersing CNTs has been achieved with CarboDis TA. CarboDis TA is a single-dose dispersion of CNTs that are anionically stabilized. A difficulty of compatibility between hardener and the hydrous dispersion did not exist for the prefabricated CNT dispersion used.

Various electrical curing tests were carried out, the results of which were as follows:

1 . Sample processing:

· Knife the glue

• Dry for 20 minutes at 40 ° C • Crosslinking at 80 ° C for 20 min

2. Resistance measurement and electrical curing with ready-mixed mixtures (adhesive / CNT / hardener) on contacted sample plates

Results of the investigations on the electrical curing of the adhesive matrix were as follows:

The coated with the adhesive / CNT / hardener mixture plates were contacted on two opposite sides with copper metal bands and measured the respective resistors with a digital multimeter. The respective values are shown below.

Specific resistance

Adhesive without CNTs 844 Ω cm

Adhesive with 0.5% CNTs 705 Ω cm

Glue with 1, 0% CNTs 677 Ω cm

Glue with 1, 5% CNTs 654 Ω cm

Glue with 2.5% CarboGran 741 Ω cm

Glue with 3.5% CarboGran 770 Ω cm

Glue with 1% surfactant u. 1.5% CNTs 728 Ω cm

Glue with 40% CarboDis TA

(a 2.5% CNTs and 2.5% surfactant),

corresponding to CNT content in adhesive: 1% 600 Ω cm Subsequently, the contacts were charged with a voltage of 80 V to cure the adhesive.

In the further course were also different attempts - second

Embodiment - performed for microwave curing. The heating tests of the specimens were carried out in a conveyor belted microwave arrangement (microwave belt drier), as used more widely in industrial processes for drying goods. The components of the system, their function and the schematic structure of the microwave belt dryer can also be seen in FIG. 2.

Figure 2 shows the schematic construction of a microwave belt dryer 10. This comprises a magnetron 1 1, a waveguide coupling 12, a directional coupler 13, a circulator 14, a tuner 15, a water load 16, a detection diode 17 and a cavity 18 with product load.

This device 10 generates microwave radiation with a frequency of 2.45 GHz and a maximum power of 2 kW. The sample passes through the applicator on a Teflon-coated belt and lingers for 30 seconds per pass in the electromagnetic field. When the sample leaves the cavity 18, its

Temperature can be measured with the help of an infrared thermometer. The

Microwave radiation is generated in a magnetron 1 1.

In addition, a tuning unit 15 is installed to optionally a

Field matching to maximize the power absorbed by the sample. The applicator takes the material to be heated, the load, and in addition to its procedural tasks, possibly reactor, furnace and the like, also adapted to electromagnetic concerns, such as resonator. In the microwave belt dryer 10 used, the applicator is passed through by a belt on which the samples have been placed. Preliminary tests for

Heating behavior was in an adapted, infinitely adjustable

Laboratory microwave device performed. Various experiments were carried out, such as one above

described adhesive material can be activated and / or cured. 1 . Sample processing:

• squeegee the glue

• Optional, clamping the sample in the press plates

2. Microwave drying at different powers, nominal

Total power (3,2kW):

C NT concentration [wt%]

· 0

• 0.5

• 1, 0

Level of performance [%], relative to 3,2kW

· 20

• 30

• 40

Results of the investigations on the microwave-assisted curing of the adhesive matrix were as follows.

Preliminary tests for microwave-assisted curing were carried out with a laboratory microwave oven in preparation for the band microwave. This already allows infinite power control. Various CNT concentrations (0% by weight, 0.5% by weight, 1.0% by weight) were tested in conjunction with the PU-based adhesive with the performance levels P = 20%; P = 30%; P = 40% (corresponding to 640W, 960W, 1280W).

It was found that the CNTs with a low power input in the microwave field - as an intermediate result - within the short heating time cause a respectable increase in temperature of the matrix system and thus harden the adhesive.

This intermediate result was brought to a much better level in the last step, by using CNT dispersions, by using the

Heating rates were again increased by a factor of 2 - 3 and the achievable final temperatures increased.

With increasing power, the positive aspect of the CNTs decreases due to the self-heating of the matrix system, the heating rates do not increase

The total energy expenditure that has to be applied for curing the adhesive by means of microwaves can be significantly reduced by carbon-containing additives, in particular CNTs. In Figure 3, the absolute temperature profile (temperature in ° C) of the heating tests of the adapted adhesive in the microwave field at different powers

shown.

FIG. 4 shows the plot of the heating (temperature difference ΔT) over the detected period of time - the temperature before heating was set as the reference (= 0).

The diagrams shown here (absolute temperature T or temperature difference ΔΤ over the course of heating) describe the adhesive system for a PU adhesive used in the test. Overall, two different PU adhesive used. There are no big differences between the two tested PU adhesives.

The preparation of the adhesive dispersions and their curing took place under the same conditions. With the samples were subsequently

Curing experiments in the band microwave, which gives the possibility of a

continuous process, each carried out with and without contact force. It became clear that the curing in the microwave, even without an applied contact force, causes a very good bonding, which can be improved by applying the defined pressure. Eie appropriate

Rating table is shown in FIG.

In the further course, various adhesive samples were also created. The preparation of the adhesive dispersion was realized as follows:

- Weighing the glue

- Add the hardener

- Mix by spatula

Weighing the CarboDis TA (2.5% CNTs / 2.5% surfactant)

- Add the CarboDis TA while stirring

- homogenizing / venting

The coating and curing was as follows: Since the coating experiments by knife had a better reproducibility than those applied with an existing spray apparatus, the adhesive was in all cases aufgerakelt. However, in principle the spraying application does not represent any problem industrially. The samples were pre-dried for 5 minutes at 30 ° C. in order to dry out the additional water introduced by CarboDis. The curing took place within 5 minutes in the band microwave at nominally about 1200W (at reduced order within 5 minutes 30 seconds).

The experiments and results as described above in their general form and in the form of the two embodiments mentioned can be summarized as follows.

First, a breakthrough with microwave curing became CNT-additive

Adhesive systems achieved. It has been successfully demonstrated that adhesive systems with carbon materials, in particular carbon nanotubes (CNTs), can be used to cure microplates in the microwave field. Adopting the adhesives with carbon-based microwave-absorbent materials is feasible using suitable mixing technologies. Due to the extraordinary absorption properties with respect to electromagnetic radiation, carbon nanotubes and CNT-containing mixtures of different carbon materials are particularly suitable for this purpose. The high electrical conductivity of the CNTs and other carbon materials, but especially the achievement of an electrical percolation in the adhesive system with already small amounts of additives is crucial for success. The fast and efficient heating in the microwave field works for the additive-based adhesive systems, this also applies to thin adhesive films that have only a small total mass

(Order of magnitude 0.5-2g / dm ² ) of the uncured adhesive. Especially with high quality of the dispersion (the best possible distribution of the additives in

Adhesive system) can be realized high, but controllable heating rates with microwave-induced heating. By the generated heating of the adhesive in the microwave field, the desired curing can be realized. The curing is homogeneous and you can not avoid completely cured weak spots / zones. Energetically, through the

Focusing the heating process solely on the splice, resulting in significant benefits. The processability of the adhesives can be obtained. The

Adhesive effect is due to the additives used, according to the previously available Results, in no way impaired and remains fully intact. In addition, an electrical conductivity of the splice is achieved, which is advantageous for the prevention of static charges. The central result of the present invention is that an industrially suitable solution for microwave-based adhesive curing using said additives is feasible - all the relevant foundations for a realization have been found and developed in the context of the present invention. An essential aspect here is the quality of the additive dispersion in the adhesive.

The initial results showed that conductivity and homogeneous microwave coupling are dependent on the addition of CNTs. This is generally true even with simple additives, which leads to CNT contents of about 2% by weight in the range of incipient percolation. However, the effect was significantly increased in the further course, after a uniform distribution of CNT in the matrix - and thus complete electrical percolation - was achieved. The conducted microwave experiments have shown that it is possible, the present adhesive system by adding CNT even at low

Harden services and the desired effects, heating by microwaves, and the accelerated heating again by CNT addition, occur. In particular, the use of predispersed CNT dispersions was advantageous. The improvements could be achieved by predispersing the CNT in a water / surfactant mixture (introduction of an aqueous dispersion) (CarboDis), which was already supplied in this form to the adhesive. This was a very manageable and functional mixture can be found.

The focus of the present invention is on the microwave-curing process, since this is a particularly uniform coupling to all the

Available particles allowed. Furthermore, it could be found that the quality of the adhesive bond was slightly improved by the microwave irradiation compared with comparative oven experiments. An essential conclusion of the present invention is that the switching of the previous method to the microwave curing is possible and offers several advantages over the previous process (process duration, heating only the splice, energetic aspects and the like). In summary, the present invention shows a high potential for the process of

Convert adhesive curing to a microwave process. In this case, in particular, the shortening of the process times is preferred, since in the first place only the bond area is heated, and as a result long cooling times, for example of tools (previous heat and contact force transfer), are not incurred. The heating itself can easily be done in the single-digit minute range, which also includes the cooling phase already.

Claims

claims

Adhesive material, in particular electrically and / or thermally and / or radiation-curing or curable adhesive material, comprising at least one adhesive component and / or adhesive matrix, and furthermore comprising at least one additive in the form of a carbon material, in particular based on the adhesive component and / or adhesive matrix Carbon nanomaterials and / or

Carbon micro materials.

Adhesive material according to claim 1, characterized in that the additive is in the form of a carbon material which is microwave absorbing and / or based on CNT and / or based on a CNT-containing mixture of different carbon materials and / or predispersed.

Adhesive material according to claim 1 or 2, characterized in that the adhesive material as an additive in the form of a carbon material CNT in a concentration of greater than 0.2 wt% has.

Adhesive material according to one of claims 1 to 3, characterized in that it comprises at least one further additive, in particular at least one hardener and / or another carbonaceous material and / or soluble CNT granules.

Adhesive material according to one of claims 1 to 4, characterized in that the adhesive component and / or the adhesive matrix is formed PU-based.

6. A method for producing an adhesive material, in particular an adhesive material according to one of claims 1 to 5, characterized

in that an adhesive component and / or adhesive matrix of adhesive material is provided, and in that at least one additive in the form of a carbon material, in particular based on

Carbon nanomaterials and / or carbon micro-materials are introduced into the adhesive component and / or adhesive matrix, in particular dispersed and / or mixed and / or distributed.

7. The method according to claim 6, characterized in that the additive is or is predispersed in the form of a carbon material, in particular in an aqueous or organic solution.

8. The method according to claim 6 or 7, characterized in that at least one further additive is added, in particular a hardener and / or another carbonaceous material and / or soluble CNT granules.

9. adhesive material, in particular adhesive material according to one of claims 1 to 5, producible by a method according to claims 6 to 8.

10. A method for activating and / or curing an adhesive material,

in particular an adhesive material according to one of claims 1 to 5 or 9 and / or an adhesive material produced by means of a method according to any one of claims 6 to 8, characterized in that it is activated and / or cured electrically and / or thermally and / or radiation-based becomes.

1 1 .Method according to claim 10, characterized in that the

Adhesive material is activated by applying an electrical voltage and / or cured.

12. The method according to claim 10 or 1 1, characterized in that the adhesive material is activated and / or cured by a

Radiation, in particular microwave radiation is exposed.

13. The method according to any one of claims 10 to 12, characterized in that the adhesive effect of the adhesive material is canceled by the adhesive material is again thermally treated, for example, is remelted, preferably in the microwave field.

14. A method for bonding two substrates, in particular using an adhesive material according to one of claims 1 to 5 or 9 and / or one by means of a method according to one of claims 6 to 8

produced adhesive material, characterized in that the

Adhesive material is applied to the first and / or second substrate and / or brought between the two substrates, that the two substrates are brought together and that the adhesive material is activated and / or cured, in particular according to a method according to any one of claims 10 to 13.