DE102017216514A1 - Process for producing an adhesive bond - Google Patents

Abstract

The invention relates to a method for producing an adhesive bond between at least two substrate surfaces, wherein initially a self-assembled monolayer is applied to at least a portion of the substrate surfaces. The self-assembled monolayer comprises compounds of the general formula (I) which are able to form bonds with the substrate surface and a polymerizable adhesive composition. This achieves a particularly stable adhesive bond.

Description

The invention relates to a method for producing an adhesive bond between at least two substrate surfaces, as well as the adhesive bond obtained from this method.

State of the art

In modern production processes, components are increasingly connected with the help of adhesives. This usually has the advantage of easy handling and easy automation of the process and low weight of the product. In addition, modern adhesives generally give very stable adhesive bonds which often resemble the stability of mechanical bonds.

For the stability of a bond, it is crucial that there is good contact between the surfaces to be bonded and the adhesive. This contact can be degraded by environmental influences in later use of the bonded component. If, for example, foreign substances, in particular liquids such as water or organic solvents, penetrate between the surface and the adhesive, this leads to a reduction in the stability of the adhesive bond up to failure. This is particularly problematic when it comes to adhesive joints in safety-critical areas. For example, housing parts of batteries, in particular lithium-ion battery cells, usually glued. The adhesive compounds are in this case from the inside of the battery cells forth usually with a liquid electrolyte, which comprises a polar organic solvent, in contact. From the outside, the battery cells can come into contact with water from the environment. Both liquids can reduce the stability of the bond when they penetrate between the surface of the bonded components and the adhesive layer. If water penetrates right into the battery cell, this can lead to failure of the lithium-ion battery and to self-ignition of the battery cell. The stability of the adhesive bond against the action of foreign substances, in particular liquids, is therefore of extraordinary importance.

US 2004/0043146 A1 discloses an adhesive composition comprising molecules that form a self-assembling monolayer on the surface after application of the adhesive composition. This can serve to improve the adhesion, or even allow easy detachment of the adhesive layer from the surface. A treatment tailored to the surface is not possible. For example, if surfaces made of different materials are to be joined together, it is not possible to provide different surfaces with different monolayers. In addition, this method can not ensure complete coverage of the surface with the monolayer because it depends on the distribution of self-assembling molecules in the adhesive composition as well as their diffusion to the surface. This results in a weakening of the bond.

Disclosure of the invention

1. (a) Aufbringen einer selbstorganisierenden Monoschicht einer Verbindung der allgemeinen Formel (I): R¹-(CR³R⁴)_n-R² (I) wobei

   R¹

   einen Rest darstellt, welcher mindestens eine funktionelle Gruppe umfasst, die geeignet ist mit der zu beschichtenden Substratoberfläche eine Bindung einzugehen;

   R²

   einen Rest darstellt, welcher mindestens eine funktionelle Gruppe umfasst, die geeignet ist mit mindestens einem Bestandteil einer Klebstoffzusammensetzung eine Bindung einzugehen;

   R³

   und R⁴unabhängig voneinander ausgewählt sind aus: einem Wasserstoffatom; einem Halogenatom, ausgewählt aus F, Cl, Br, I, vorzugsweise F und Cl, insbesondere F; einem linearen oder verzweigten, gesättigten oder ungesättigten Alkylrest mit 1 bis 10, insbesondere 1 bis 6 Kohlenstoffatomen, welche gegebenenfalls mit Halogenatomen, ausgewählt aus F, Cl, Br, I, vorzugsweise F und Cl, insbesondere F, substituiert sein können; einem Cycloalkylrest mit 3 bis 10, insbesondere 5 bis 7 Kohlenstoffatomen, welche gegebenenfalls mit Halogenatomen, ausgewählt aus F, Cl, Br, I, vorzugsweise F und Cl, insbesondere F, substituiert sein können; einem Arylrest mit 5 bis 12, insbesondere 6 bis 9 Kohlenstoffatomen, welche gegebenenfalls mit Halogenatomen, ausgewählt aus F, Cl, Br, I, vorzugsweise F und Cl, insbesondere F, substituiert sein können; einem Oxyalkylrest mit 1 bis 10, insbesondere 1 bis 6 Kohlenstoffatomen, welche gegebenenfalls mit Halogenatomen, ausgewählt aus F, Cl, Br, I, vorzugsweise F und Cl, insbesondere F, substituiert sein können; und

   n

   eine ganze Zahl zwischen 1 und 30, vorzugsweise zwischen 1 und 20, insbesondere zwischen 2 und 15 ist;

   auf mindestens einem Teil mindestens einer der zu verbindenden Substratoberflächen;
2. (b) Aufbringen einer polymerisierbaren Klebstoffzusammensetzung auf mindestens einen Teil der mindestens einen selbstorganisierenden Monoschicht und/oder mindestens einen Teil der zu verbindenden Substratoberflächen;
3. (c) Aneinanderfügen der zu verbindenden Substrate; und
4. (d) Härten der Klebstoffzusammensetzung, um eine Haftverbindung zwischen den Substratoberflächen zu erreichen.

The invention relates to a method for producing an adhesive bond between at least two substrate surfaces, wherein the method comprises at least the following method steps (a) to (d):

1. (a) applying a self-assembling monolayer of a compound of the general formula (I): R ¹ - (CR ³ R ⁴ ) _n -R ² (I) in which

   R ¹

   represents a radical which comprises at least one functional group which is suitable for binding with the substrate surface to be coated;

   R ²

   a radical comprising at least one functional group capable of binding with at least one component of an adhesive composition;

   R ³

   and R ^{4 are} independently selected from: a hydrogen atom; a halogen atom selected from F, Cl, Br, I, preferably F and Cl, especially F; a linear or branched, saturated or unsaturated alkyl radical having 1 to 10, in particular 1 to 6, carbon atoms which may optionally be substituted by halogen atoms selected from F, Cl, Br, I, preferably F and Cl, in particular F; a cycloalkyl radical having from 3 to 10, in particular from 5 to 7, carbon atoms which may optionally be substituted by halogen atoms selected from F, Cl, Br, I, preferably F and Cl, in particular F; an aryl radical having 5 to 12, in particular 6 to 9 carbon atoms, which may optionally be substituted by halogen atoms selected from F, Cl, Br, I, preferably F and Cl, in particular F; an oxyalkyl radical having 1 to 10, in particular 1 to 6, carbon atoms which may optionally be substituted by halogen atoms selected from F, Cl, Br, I, preferably F and Cl, in particular F; and

   n

   an integer between 1 and 30, preferably between 1 and 20, in particular between 2 and 15;

   on at least a part of at least one of the substrate surfaces to be joined;
2. (b) applying a polymerizable adhesive composition to at least a portion of the at least one self-assembling monolayer and / or at least a portion of the substrate surfaces to be bonded;
3. (c) joining together the substrates to be joined; and
4. (d) curing the adhesive composition to achieve an adhesive bond between the substrate surfaces.

The individual process steps are explained in more detail below.

In a first process step (a), a self-assembling monolayer of a compound of the general formula (I) is applied to at least one part of at least one substrate surface.

In principle, all materials are suitable as substrates to be joined. Usually, materials are used which comprise substrate surfaces to be joined of metal, metal oxide or a plastic. These are often used as materials in components, in particular in components for housing of battery cells. Components with substrate surfaces comprising aluminum, nickel, copper, iron and / or thermoplastic polymers, such as polyolefins, polyesters, polystyrenes, polycarbonates, polyamides, as well as copolymers and mixtures of said polymers are frequently used and bonded to one another via an adhesive bond, which is produced by the process according to the invention is received.

The substrate surfaces usually have functional groups, in particular polar functional groups having at least one hydroxyl function (OH function). These polar functional groups, if an adhesive layer is conventionally applied to the substrate surface, cause polar species, such as water or organic solvents from the electrolyte, to penetrate between the substrate surface and the adhesive layer. To prevent this, at least part of the substrate surface according to the present invention is provided with a monolayer of compounds of general formula (I). These are characterized in that they can form a self-assembled monolayer on the substrate surface and have functional groups which are contained in the radical R ¹ and can form a bond with the functional groups present on the substrate surface.

The bond formed between the functional groups contained in the radical R ¹ and the functional groups present on the substrate surface may in principle be a covalent or ionic bond, or else a dipole bond. Act dipole interaction. In view of the stability of the bond and a preferred reduction of free functional groups on the substrate surface, in particular the reduction of free hydroxyl groups on the substrate surface, in particular the formation of a covalent bond is preferred.

In a preferred embodiment, R ^{1 represents} a functional group which can form a bond, in particular a covalent bond, in a condensation reaction with a functional group located on the substrate surface. Thus, a particularly stable connection between the self-assembled monolayer and the substrate surface is achieved.

In view of the formation of a covalent bond between the substrate surface and the monolayer, the radical R ^{1 is} preferably selected such that it has at least one functional group which can react with a polar functional group comprising a hydroxy function on the substrate surface , For example, radicals R ¹ which contain at least one functional group selected from a carboxylic acid radical (-COOH), a carboxylic acid ester radical (-COOR ⁶ , where R ^{6 is} an alkyl radical having 1 to 5 carbon atoms), a phosphonic acid radical (-P (O ) (OH) ₂ , a thiol radical (-SH), a halosilyl radical (-SiX, wherein X is a halogen atom, preferably Cl or Br) and / or an alkoxysilyl radical (-Si (OR ⁵ ), wherein R ^{5 is} a linear alkyl radical 1 to 3 carbon atoms) comprise or consist of these.

The functional groups mentioned can react with the hydroxyl groups on the substrate surface in a condensation reaction with the deposition of small molecules such as water or alcohols and form covalent bonds between the compounds of general formula (I) and the substrate surface. The covalent bonds are spontaneous or under suitable conditions, formed in particular at a temperature of 20 to 120 ° C.

The compounds of the general formula (I) furthermore have a preferably non-polar part, which is formed by the unit - (CR ³ R ⁴ ) _n -. This is limited to a chain length of 1 to 30 carbon atoms, which allows a largely linear arrangement of the molecule on the substrate surface. Ideally, the molecules of the compound of the general formula (I) are therefore arranged on the surface parallel to one another. The terminal functional groups R ² are thus arranged adjacent to each other.

The radicals R ³ and R ⁴ are preferably independently selected from a hydrogen atom and a linear or branched, saturated or unsaturated alkyl radical having 1 to 6 carbon atoms. In a preferred embodiment, the radicals R ³ and R ^{4 represent} a hydrogen atom or a methyl radical, in particular a hydrogen atom.

The radical R ² serves to connect the self-assembled monolayer of compounds of the general formula (I) with the particular polymerizable adhesive composition used. R ² is a radical which comprises at least one functional group which is suitable for binding with at least one constituent of an adhesive composition.

The bond formed between the functional groups contained in the radical R ² and the adhesive composition may, in principle, be a covalent or ionic bond, or else a dipole-dipole interaction. In view of the stability of the bond, in particular the formation of a covalent bond is preferred.

In a preferred embodiment of the invention, the curing of the adhesive composition takes place by a polymerization reaction. It is therefore particularly preferred that the group R ^{2 represents} a functional group which participates in the polymerization reaction of the adhesive composition as a monomer or crosslinking agent.

The polymerization reaction of the adhesive composition is preferably carried out by a chain growth polymerization reaction, polycondensation reaction and / or a polyaddition reaction, in particular by a polymerization reaction and / or a polyaddition reaction. In order to achieve the formation of covalent bonds of the self-assembled monolayer to the adhesive, the radical R ² therefore preferably has at least one functional group which can participate in the polymerization reaction, in particular at least one functional group corresponding to the functional group of at least one of the participating monomers ,

In a particularly preferred embodiment of the invention, the radical R ² comprises at least one functional group based on amines or epoxides. This can be advantageously implemented with epoxy adhesives, which are obtained by the reaction of epoxy resins, for example based on bisphenol A, with amine-containing crosslinking agents. In this case, the radical R ^{2 may be incorporated} instead of an epoxy monomer as or in place of an amine-containing crosslinking agent. Particularly noteworthy are compounds of general formula (I), wherein R ^{2 is} a primary amine radical, a secondary amine radical, a primary ammonium radical, a secondary ammonium radical, an epoxy radical, or an oxyalkylepoxy. These can be incorporated into the polymer chain in a polyaddition reaction.

In a further preferred embodiment, the radical R ² comprises at least one functional group which has an olefinic carbon-carbon double bond. These can be used advantageously in the polymerization of acrylate adhesives and can be incorporated into the polymer chain in an anionic and / or free-radical polymerization reaction.

wobei R⁷, R⁸, R⁹ und R¹⁰ ausgewählt jeweils unabhängig ein Wasserstoffatom oder einen Kohlenwasserstoffrest mit 1 bis 5, vorzugsweise 1, 2 oder 3 Kohlenstoffatomen darstellen können.Particularly preferred radicals R ² can be selected from:

wherein R ⁷ , R ⁸ , R ⁹ and R ^{10 are} each independently a hydrogen atom or a hydrocarbon radical having from 1 to 5, preferably 1, 2 or 3 carbon atoms.

In addition, polyurethanes and polysiloxanes may be mentioned as further adhesive components. Both can be reacted, for example, with radicals R ² , which OH groups, in particular two OH groups, for example a radical R ² = -Si- (OH) ₂ , have. These can advantageously participate in a polycondensation.

• (a-1) Bereitstellen einer Verbindung der allgemeinen Formel (I). Um einen möglichst guten Kontakt der Substratoberfläche mit der Verbindung der allgemeinen Formel (I) zu erreichen, wird diese vorzugsweise in Form einer Flüssigkeit oder einer flüssigen Lösung bereitgestellt. Eine Lösung wird vorzugsweise in einem Lösungsmittel oder Lösungsmittelgemisch bereitgestellt, in welchem die Verbindung der allgemeinen Formel (I) löslich ist und welches einen Dampfdruck aufweist, welcher es ermöglicht, das Lösungsmittel kontrolliert und vollständig zu entfernen, nachdem sich die gewünschte selbstorganisierte Monoschicht ausgebildet hat. Zusätzlich unterstütz das Lösungsmittel vorzugweise die Reaktion zwischen der Substratoberfläche und der Verbindung der allgemeinen Formel (I). Die Löslichkeit der Verbindung der allgemeinen Formel (I) in dem jeweiligen Lösungsmittel bzw. Lösungsmittelgemisch liegt vorzugsweise in einem Bereich von 0,01 g bis 10 g der Verbindung der allgemeinen Formel (I) pro 1 g Lösungsmittel. Der Dampfdruck des Lösungsmittels bzw. Lösungsmittelgemischs beträgt bei 40°C vorzugsweise mindestens 2 hPa. Als geeignete Lösungsmittel sind insbesondere Wasser, Tetrahydrofuran, Aceton, Cyclohexan und Dimethylformamid zu nennen.
• (a-2) Aufbringen der Verbindung der allgemeinen Formel (I) gemäß Schritt (a-1), gegebenenfalls in Form der gemäß Schritt (a-1) erhaltenen Lösung, auf mindestens einem Teil der Substratoberfläche, um eine selbstorganisierte Monoschicht der Verbindung der allgemeinen Formel (I) auf der Substratoberfläche zu bilden. Dies erfolgt vorzugsweise durch eintauchen der Substratoberfläche in die Verbindung der allgemeinen Formel (I) bzw. in die Lösung der Verbindung der allgemeinen Formel (I) über einen Zeitraum von 1 Sekunde bis 24 h, vorzugsweise 1 min bis 10 h, insbesondere 10 min bis 5 h. Vorzugsweise findet dieser Verfahrensschritt bei 10 bis 50°C, insbesondere bei 15 bis 30°C statt.
• (a-3) gegebenenfalls Waschen der Substratoberfläche. Dieser Schritt erfolgt in der Regel nur dann, wenn durch die Reaktion der funktionellen Gruppen auf der Substratoberfläche mit den funktionellen Gruppen des Rests R¹ der Verbindung der allgemeinen Formel (I) bereits Bindungen ausgebildet wurden. Dies ist von der Wahl des Lösungsmittels, der Natur der Verbindung der allgemeinen Formel (I) und den Reaktionsbedingungen abhängig.
• (a-4) gegebenenfalls Erwärmen des mit der selbstorganisierten Monoschicht der Verbindung der allgemeinen Formel (I) auf der Substratoberfläche versehenen Substrats auf eine Temperatur, welche die Ausbildung einer Bindung, insbesondere einer kovalenten Bindung, zwischen der Substratoberfläche und der Verbindung der allgemeinen Formel (I) ermöglicht. Die Temperatur liegt beispielsweise in einem Bereich von 20 bis 120°C, vorzugsweise in einem Bereich von 40 bis 100°C, insbesondere in einem Bereich von 50 bis 90°C. Die Reaktionsdauer liegt in einem Bereich von 1 min bis 10 h, insbesondere 2 min bis 180 min. Dieser Schritt kann auch in Schritt (d) des erfindungsgemäßen Verfahrens durchgeführt werden.
• (a-5) gegebenenfalls Waschen und Trocknen der beschichteten Substratoberfläche, um Reste von nicht umgesetzten Verbindungen der allgemeinen Formel (I) zu entfernen. Dies könnte sonst gegebenenfalls der Haftung abträglich sein.

The method step (a) of the method for producing an adhesive bond preferably comprises the following substeps:

• (a-1) Providing a compound of the general formula (I). In order to achieve the best possible contact of the substrate surface with the compound of general formula (I), this is preferably provided in the form of a liquid or a liquid solution. A solution is preferably provided in a solvent or solvent mixture in which the compound of general formula (I) is soluble and which has a vapor pressure which allows the solvent to be controlled and completely removed after the desired self-assembled monolayer has formed. In addition, the solvent preferably promotes the reaction between the substrate surface and the compound of the general formula (I). The solubility of the compound of general formula (I) in the respective solvent or solvent mixture is preferably in a range of 0.01 g to 10 g of the compound of general formula (I) per 1 g of solvent. The vapor pressure of the solvent or solvent mixture is preferably at least 2 hPa at 40 ° C. Suitable suitable solvents are, in particular, water, tetrahydrofuran, acetone, cyclohexane and dimethylformamide.
• (a-2) Applying the compound of the general formula (I) according to the step (a-1) optionally in the form of the solution obtained in the step (a-1) on at least a part of the substrate surface to form a self-assembled monolayer of the compound of general formula (I) on the substrate surface. This is preferably done by immersing the substrate surface in the compound of general formula (I) or in the solution of the compound of general formula (I) over a period of 1 second to 24 hours, preferably 1 minute to 10 hours, especially 10 minutes 5 h. This process step preferably takes place at 10 to 50.degree. C., in particular at 15 to 30.degree.
• (a-3) optionally washing the substrate surface. As a rule, this step takes place only when bonds have already been formed by the reaction of the functional groups on the substrate surface with the functional groups of the radical R ^{1 of} the compound of the general formula (I). This depends on the choice of solvent, the nature of the compound of general formula (I) and the reaction conditions.
• (a-4) optionally heating the substrate provided with the self-assembled monolayer of the compound of the general formula (I) on the substrate surface to a temperature which permits the formation of a bond, in particular a covalent bond, between the substrate surface and the compound of the general formula ( I). The temperature is, for example, in a range of 20 to 120 ° C, preferably in a range of 40 to 100 ° C, in particular in a range of 50 to 90 ° C. The reaction time is in a range of 1 min to 10 h, in particular 2 min to 180 min. This step can also be carried out in step (d) of the method according to the invention.
• (a-5) optionally washing and drying the coated substrate surface to remove residues of unreacted compounds of general formula (I). Otherwise, this might be detrimental to liability.

The resulting self-assembled monolayer of molecules of the compound of the general formula (I) is bonded to the substrate surface and has a layer thickness of preferably 0.1 to 10 nm, more preferably 0.5 to 5, and especially 1 to 2 nm. Preferably, the bond is covalent.

In a second process step (b), a polymerizable adhesive composition is applied to at least a portion of the at least one self-assembling monolayer and / or at least a portion of the substrate surfaces to be bonded. As already explained, this is an adhesive composition which is capable of undergoing a polymerization reaction with at least one functional group of the radical R ² . Preferably, the polymerizable adhesive composition comprises an epoxy adhesive composition, an acrylate adhesive composition, a urethane adhesive composition, or a siloxane adhesive composition. Most preferably, it is an epoxy adhesive composition or an acrylate adhesive composition.

In a subsequent process step (c), the substrate surfaces of the substrates to be joined are joined together after at least a portion of one of the substrate surfaces has been treated according to the method described in steps (a) and (b).

Finally, in step (d), the curing of the adhesive composition follows to achieve an adhesive bond between the substrate surfaces. This step serves the actual polymerization reaction of the adhesive composition. At the same time, the - preferably covalent - bond between the adhesive and the self-assembled monolayer is formed via the functional groups of the radical R ² . The temperature is selected in process step (d) so that a rapid and controlled polymerization is achieved. The temperature is, for example, in a range of 20 to 120 ° C, preferably in a range of 40 to 100 ° C, in particular in a range of 50 to 90 ° C. The reaction time is in a range of 0.1 min to 10 h, in particular 1 min to 5 h.

In one embodiment, two substrate surfaces S and S 'are bonded together, with the substrate surfaces S and S' comprising different materials. In order to achieve the best possible connection, the substrate surfaces S and S 'are therefore reacted with different compounds of the formulas (I) or (I'): R ¹ - (CR ³ R ⁴ ) _n -R ² (I) respectively. R ^{1 '} - (CR ³ R ⁴ ) _n -R ² (I')

This differs in particular in the nature of the radical R ^{1 '} in order to achieve the best possible adhesion to the respective substrate surface. The radicals R ² to R ⁴ have the same meaning as defined above. R ^{1 '} has the same meaning previously defined as R ¹ , with the proviso that the radicals R ¹ and R ^{1' are} not identical. The radicals R ² are preferably identical in each case since these functional groups each react with the same adhesive composition and should form bonds, preferably covalent bonds. This allows a stable as possible adhesive bond.

The invention also relates to the use of the method according to the invention for producing an adhesive bond between at least two substrate surfaces, the adhesive bond being in contact with polar compounds from the environment, e.g. Water or organic solvents.

In a preferred embodiment, the method is used for the production of security-relevant adhesive bonds, in particular for the production of adhesive bonds between housing parts of a battery cell, in particular a lithium-ion battery cell.

Furthermore, the subject matter of the invention is a battery cell whose housing has been produced by means of a method according to the invention.

Advantages of the invention

The inventive method offers the advantage that an adhesive bond between two substrate surfaces can be produced, which is characterized in that between the substrate surfaces and the adhesive layer, a uniform and area-covering self-assembled monolayer is arranged, which is bonded to the substrate surface and to the adhesive layer. Thus, a particularly stable compound is obtained, which also prevents the penetration of foreign substances such as water or electrolyte between the substrate and adhesive. In addition, the hydroxyl groups located on the substrate surface are completely or at least predominantly reacted and can thus no longer participate in undesired chemical or electrochemical reactions. The hydrophobic part - (CR ³ R ⁴ ) _n - forms a barrier which prevents the penetration of polar compounds, in particular polar liquids, between the adhesive layer and the substrate surface.

list of figures

Embodiments of the invention will be explained in more detail with reference to the drawings and the description below.

• 1 Eine beispielhafte Auswahl möglicher Ausführungsformen der Verbindungen der allgemeinen Formel (I).
• 2 Die Bildung einer selbstorganisierten Monoschicht einer Ausführungsform der Verbindung der allgemeinen Formel (I) auf einer Substratoberfläche.
• 3 Die graphische Darstellung der Scherfestigkeit verschiedener verklebter Bauteile.

It shows:

• 1 An exemplary selection of possible embodiments of the compounds of general formula (I).
• 2 The formation of a self-assembled monolayer of one embodiment of the compound of general formula (I) on a substrate surface.
• 3 The graphic representation of the shear strength of various bonded components.

Embodiments of the invention

The present invention makes it possible to bond substrate surface to each other with simple means and stable against the action of foreign substances. This is accomplished by providing the surfaces with self-assembled monolayers comprised of compounds covalently bonded to the substrate surfaces and to the adhesive layers. A selection of suitable compounds of general formula (I), ie, compounds which form the self-assembled monolayer on the substrate surface, is disclosed in U.S. Pat 1 shown. It should be noted that the individual regions of the compound of the general formula (I), ie the functional groups -R ¹ and -R ² , and the nonpolar spacer - (CR ³ R ⁴ ) _n -, are in principle freely selectable and free with one another can be combined. In the 1 combinations shown are therefore chosen purely by way of example. The person skilled in the art therefore recognizes that the compound of the general formula (I) can be ideally adapted to the respective requirements with regard to the nature of the substrate surface and the selected adhesive composition.

2 shows an exemplary representation of the formation of a monolayer on a Substratobarfläche the example of a Phosphonsäurederivats. This is covalently bound to the substrate surface with elimination of water. The remaining free epoxide moiety on the molecule is now able to be incorporated into it in a crosslinking reaction of an epoxy adhesive. The same applies, for example, analogously for terminal amine functions.

3 shows a graphical representation of the shear strength S of two samples. The maximum shear strength S in Newton [N] is plotted on the y-axis. The data are based on the average values of 10 tensile shear tests each according to DIN EN 1465: 2009-07 were carried out. The bar (a) shows the shear strength S of a conventional glued component of two aluminum sheets, with an intermediate adhesive layer of an epoxy adhesive. The shear strength S is more than 5000 N. The bonded component was then stored for 1 week at 85 ° C and 85% relative humidity and the measurement was carried out again. Bar (b) in 3 shows the significant drop in shear strength S to less than 4500 N.

In contrast, bar (c) shows the fatigue strength S (determined according to DIN EN 1465: 2009-07 ) of a component after 1 week storage at 85 ° C and 85% relative humidity, which according to the present invention was obtained as follows:

Aluminum sheets (Al 3.3547) were cleaned, placed in a solution of 0.2 mL of [3- (2,3-epoxypropoxy) propyl] trimethoxysilane in 200 mL of acetone and allowed to stand at room temperature for 20 minutes without stirring. A self-assembled monolayer forms on the surface of the aluminum sheets. The sheets are then removed from the solution and baked in an oven for 40 minutes at 80 ° C. Thus, the formation of covalent bonds between the monolayer and the surface of the aluminum sheet is supported, and the solvent and the condensation products (especially methanol) are removed. Finally, on one of the thus-obtained surfaces, an epoxy adhesive composition comprising an epoxy and an amine-containing crosslinking agent was coated, a second aluminum sheet was laid, and the epoxy adhesive composition was baked in the oven at 80 ° C for 180 minutes. The resulting component was then stored for 1 week at 85 ° C and 85% relative humidity and the maximum shear strength S according to DIN EN 1465: 2009-07 measured. The value was higher than the shear strength S of the sample (a).

The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, within the scope given by the claims a variety of modifications are possible, which are within the scope of expert action.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• US 2004/0043146 A1 [0004]

Cited non-patent literature

• DIN EN 1465: 2009-07 [0039, 0040, 0041]

Claims (12)

A process for producing an adhesive bond between at least two substrate surfaces, said process comprising at least the following process steps (a) to (d): (a) applying a self-assembling monolayer of a compound of general formula (I): R ¹ - (CR ³ R ⁴ ) _n -R ² (I) wherein R ^{1 represents} a radical comprising at least one functional group capable of binding with the substrate surface to be coated; R ^{2 is} a radical comprising at least one functional group capable of bonding with at least one component of an adhesive composition; R ³ and R ^{4 are} independently selected from: a hydrogen atom; a halogen atom selected from F, Cl, Br, I, preferably F and Cl, especially F; a linear or branched, saturated or unsaturated alkyl radical having 1 to 10, in particular 1 to 6, carbon atoms which may optionally be substituted by halogen atoms selected from F, Cl, Br, I, preferably F and Cl, in particular F; a cycloalkyl radical having from 3 to 10, in particular from 5 to 7, carbon atoms which may optionally be substituted by halogen atoms selected from F, Cl, Br, I, preferably F and Cl, in particular F; an aryl radical having 5 to 12, in particular 6 to 9 carbon atoms, which may optionally be substituted by halogen atoms selected from F, Cl, Br, I, preferably F and Cl, in particular F; an oxyalkyl radical having 1 to 10, in particular 1 to 6, carbon atoms which may optionally be substituted by halogen atoms selected from F, Cl, Br, I, preferably F and Cl, in particular F; and n is an integer between 1 and 30, preferably between 1 and 20, in particular between 2 and 15; on at least a part of at least one of the substrate surfaces to be joined; (b) applying a polymerizable adhesive composition to at least a portion of the at least one self-assembling monolayer and / or at least a portion of the substrate surfaces to be bonded; (c) adhering the substrate surfaces to be bonded after at least a portion of one of the substrate surfaces has been treated according to the method described in steps (a) and (b); and (d) polymerizing the adhesive composition to achieve an adhesive bond between the substrate surfaces. Method according to Claim 1 wherein the radical R ¹ comprises a functional group which can form a covalent or ionic bond and / or a dipole-dipole interaction in a condensation reaction with a functional group located on the substrate surface. Method according to Claim 1 or 2 wherein the curing of the adhesive composition is by a polymerization reaction. Method according to Claim 3 wherein the radical R ² comprises a functional group which participates in the polymerization reaction of the adhesive composition as a monomer or crosslinking agent. Method according to one of Claims 1 to 4 wherein the radicals R ³ and R ^{4 are} independently selected from a hydrogen atom and a linear or branched, saturated or unsaturated alkyl radical having 1 to 6 carbon atoms. Method according to one of Claims 1 to 5 wherein the process step (a) comprises the following substeps: (a-1) providing a compound of the general formula (I); (a-2) applying the compound of the general formula (I) according to the step (a-1) on at least a part of the substrate surface to form a self-assembled monolayer of the compound of the general formula (I) on the substrate surface; (a-3) optionally washing the substrate surface; (a-4) optionally heating the substrate provided with the self-assembled monolayer of the compound of the general formula (I) on the substrate surface to a temperature which enables formation of a bond between the substrate surface and the compound of the general formula (I). Method according to one of Claims 1 to 6 wherein the substrate surface comprises a metal, a metal oxide or a plastic. Method according to one of Claims 1 to 7 wherein the adhesive composition is an epoxy adhesive composition, an acrylate adhesive composition, a urethane adhesive composition or a siloxane adhesive composition. Method according to one of Claims 1 to 8th wherein R ^{1 represents} a radical having at least one functional group selected from a carboxylic acid radical (-COOH), a carboxylic acid ester radical (-COOR ⁶ , wherein R ^{6 represents} an alkyl radical having 1 to 5 carbon atoms), a phosphonic acid radical (-P (O ) (OH) ₂ ), a thiol radical (-SH), a halosilyl radical (-SiX, where X is a halogen atom, preferably Cl or Br) and / or an alkoxysilyl radical (- Si (OR ⁵ ) wherein R ^{5 is} a linear alkyl group of 1 to 3 carbon atoms). Method according to one of Claims 1 to 9 wherein R ² represents a group comprising at least one functional group selected from a primary amine group, a secondary amine group, a primary ammonium group, a secondary ammonium group, an epoxy group, an oxyalkylepoxy group and an olefin group. Use of the method according to one of Claims 1 to 10 for producing an adhesive bond between at least two substrate surfaces, wherein the adhesive bond is in contact with polar compounds. Use after Claim 11 for the production of security-relevant adhesive bonds, in particular for the production of adhesive bonds between housing parts of a battery cell.

Images