ADHESIVE ELEMENT, OPENING CLOSED OFF WITH THE ADHESIVE ELEMENT, SUCH AS A CONSTRUCTION HOLE, A BODY HOLE, A PAINT DRAIN HOLE AND/OR A PAINT DRAIN OPENING, AND SYSTEM CONSISTING OF THE ADHESIVE ELEMENT AND A CARRIER ELEMENT

Abstract

An adhesive element including a cover layer and a self-adhering sealant, wherein the self-adhering sealant is a thermoactive or thermoactivated rubber compound.

Claims

1. An adhesive element comprising a covering layer and a self-adhesive sealing composition, wherein the self-adhesive sealing composition is a thermoactive or thermoactivated rubber composition.

2. The adhesive element as claimed in claim 1, wherein the covering layer comprises a metal layer.

3. The adhesive element as claimed in claim 1, wherein the rubber composition is configured so that it is converted into a thermoactivated state by means of heating above a temperature threshold for a residence time.

4. The adhesive element as claimed in claim 1, wherein a thermoactive rubber composition comprises a first type of rubber, a second type of rubber, a hydrocarbon resin, an organic crosslinker, a catalyst, a dye, a thermal stabilizer and/or a moisture remover.

5. The adhesive element as claimed in claim 1, wherein the thermoactive rubber composition comprises a filler.

6. The adhesive element as claimed in claim 1, wherein a ratio of a proportion of rubber to the proportion of the fillers assumes a value in the range from 0.3 to 0.8.

7. The adhesive element as claimed in claim 4, wherein a proportion of the first type of rubber assumes a value in the range from 5 to 25%, a proportion of the second type of rubber assumes a value in the range from 10 to 45%, and/or a proportion of the filler assumes a value in the range from 40% to 70%.

8. The adhesive element as claimed in claim 1, wherein the adhesive element displays a penetration force of from 300 to 1200 N.

9. The adhesive element as claimed in claim 1, wherein the rubber composition is sulfur-free.

10. A process for producing an adhesive element, as claimed in claim 1, comprising the steps: provision of an adhesive element comprising a covering layer and a self-adhesive sealing composition comprising a thermoactive or thermoactivated rubber composition and introduction of thermal energy to convert the thermoactive rubber composition into a thermoactivated rubber composition.

Description

[0034] Further advantages and features may be derived from the following description of preferred embodiments of the subject matter of the invention with reference to the accompanying figures. The figures show:

[0035] FIG. 1: an adhesive element as per a preferred embodiment of the present invention,

[0036] FIG. 2: a section of FIG. 1,

[0037] FIG. 3 a graph of a satisfactory or required degree of curing as a function of a residence time and a temperature,

[0038] FIG. 4 a graph of a torque as a function of a temperature,

[0039] FIG. 5 a graph of a degree of crosslinking as a function of a temperature and

[0040] FIG. 6 a graph of a penetration force as a function of a temperature.

[0041] FIG. 1 depicts an adhesive element 1 as per an illustrative embodiment of the present invention. In particular, the adhesive element here is of the type of adhesive elements 1, for example in the form of adhesive strips or adhesive pads, which are intended for sealing or closing manufacturing-related openings of the vehicle component. Significant constituents are a covering layer and a self-adhesive sealing composition. In the present working example, the adhesive element 1 has a pad-like shape, i.e. the covering layer surrounds the sealing composition in a dome-like manner. The covering layer 7 is preferably a primary layer, for example a metal layer 5 such as an aluminum layer. The metal layer 5 preferably has a thickness viewed in the coating direction of from 0.1 to 1 mm, preferably a thickness of from 0.1 to 0.5 mm and particularly preferably a thickness of 0.2 mm. As is shown in the detail in FIG. 2, the covering layer 7 has a conversion layer 4, preferably a conversion layer 4 comprising zirconium (Zr), to avoid corrosion damage. The conversion layer 4 particularly preferably completely envelops the metal layer 5 on both sides. Furthermore, the covering layer 7 is closed off on both sides with a surface coating 6, with the surface coating 6 being, for example, cured, matt and black. Particular preference is given to the self-adhesive sealing composition of the adhesive element 1 adhering to a support element 3. The adhesive element 1 here is automatically separated when required, for example by means of a robot, from the support element 3 and subsequently automatically affixed to a component, for example to a body of a vehicle.

[0042] The support element 3, known as the liner, is in particular configured as prefabricated flat sheet on which a plurality of adhesive elements 1 are present. Here, the support element 3 is formed by paper, polyethylene or polyethylene terephthalate film having an antiadhesion layer. The sealing composition in a storage state is thus delimited on one side by the covering layer 7 and on the other side by the support element 3.

[0043] Since these adhesive elements 1 are preferably stuck on during the manufacturing process in order, for example, to avoid seeping-through of liquids, the adhesive elements 1 have to have sufficient adhesion and adhesive strength to allow the adhesive element 1 to close the opening effectively despite the stresses in the form of temperature, pressure and/or chemicals acting on the bodywork part in the manufacturing process and also in the final state.

[0044] It has surprisingly been found that an adhesive element 1 which withstands the stresses can be provided when a thermoactive or thermoactivated rubber composition 2 is used as sealing composition. Here, a person skilled in the art will, in the context of the present invention, understand a thermoactive or thermo-crosslinkable rubber composition 2 to be a composition which can be converted into the desired state by introduction of thermal energy and understand a thermoactivated rubber composition 2 to be a composition into which the thermal energy has already been introduced and is in the desired final state.

[0045] The statements and experiments set forth below concern, in particular, a rubber composition which comprises

TABLE-US-00002 7.0-10.0% of a first type of rubber 18.0-23.0% of a second type of rubber 8.0-10.0% of hydrocarbon resin 1.5-3.0% of organic crosslinker 0.5-2.0% of catalyst 0.2-0.6% of dye 2.5-4.0% of thermal stabilizers and moisture removers and 48.0-59.0% of fillers.

[0046] Here, the abovementioned constituents are mixed together and kneaded to give a highly viscous, thixotropic intermediate composition, i.e. a thermoactive rubber composition, in a production process for producing the sealing composition.

[0047] The intermediate composition is therefore advantageously suitable for a doctor blade process or calendering process by means of which the intermediate composition is processed further to give a self-adhesive film. The intermediate composition here preferably has a density in the range from 1.3 to 1.8 g/cm.sup.3.

[0048] The intermediate composition is preferably characterized by a dynamic viscosity measured at 120 C. and a shear rate of 20 1/s of from 100 to 140 Pas, a torque of 30-50 mNm, a peel strength at 100 mm/min of from 4 to 9 N/cm and heat resistance up to 240 C.

[0049] To produce the adhesive element 1, the self-adhesive film comprising the intermediate composition is preferably applied to the support element 3. On the side opposite the support element 3, this film is laminated with the covering layer 7 as described, for example, above. The adhesive elements can finally be shaped, preferably stamped, from this composite of support element 3, film comprising intermediate composition and covering layer 7.

[0050] It has advantageously been found that the intermediate composition having the above-described composition is transformed by thermal treatment into a sealing composition having desirable properties, in particular in respect of the adhesion values and impermeability of the adhesive bond, in respect of the mechanical properties such as hardness, ultimate tensile strength and/or in respect of insolubility in media such as oil, fuel, brake fluid or aqueous solutions.

[0051] FIG. 3 shows a graph of a degree of curing, in particular for the above-described composition, as a function of a residence time and a temperature. Here, the residence time is the time over which the intermediate composition, i.e. the thermoactive rubber composition, is subjected to the corresponding temperature. The closed box in the graph delimits the region in which the intermediate composition has, for the corresponding combination of temperature and residence time, led to a cured composition, i.e. to a thermoactivated rubber composition. In particular, it can be seen from the graph that the intermediate composition is thermally treated at a temperature in the range from 140 C. to 185 C. for a residence time corresponding to 45 and 10 minutes. Here, the thermal treatment of the intermediate composition brings about a course of a crosslinking process such that the self-adhesive intermediate composition is converted into a thermoset or permanently elastic, mechanically strong, rubber-like sealing composition which advantageously remains joined to the cathodically dip-coated substrate and to the metal layer 5 and/or surface coating 6 of the covering layer 7.

[0052] To achieve properties conforming to requirements, a particular combination of action of temperature and of residence time is required. In the present case, a temperature of 140 C. and a residence time of at least 30 minutes are the lowest parameters which ensure completion of the crosslinking process.

[0053] FIG. 4 shows a graph of a torque as a function of a temperature. This depiction allows conclusions to be drawn in respect of the flow behavior of the intermediate composition during the transition to the thermoactivated rubber composition. In particular, the increasing value of the torque with increasing temperature and time indicates the commencement and course of the crosslinking reaction, which brings about an increase in the viscosity and thus leads to an increase in the torque.

[0054] FIG. 5 shows a graph of a degree of crosslinking as a function of a temperature, in particular in each case for three different residence times. It can be seen that a degree of crosslinking which requires a force of more than 20 N in order to tear apart the crosslinked intermediate composition is attained at a residence time of 30 minutes and a temperature of at least 140 C., preferably a temperature of more than 160 C.

[0055] FIG. 6 shows a graph of a penetration force as a function of a temperature. In particular, the measured penetration force is shown as a function of the temperature here. It can be seen that the penetration force increases sharply at a temperature above 130 C. The penetration force is a measure of the force which is necessary to remove the adhesive element 1 from manufacturing-related openings, for example an opening in the vehicle body, and is thus a measure of the adhesion and the sealing capability of the adhesive element.

[0056] Since a penetration force of more than 500 N is preferably required, it is advantageous to treat the intermediate composition at a temperature above 160 C. so as to ensure the desired penetration force, in particular for the bodywork part, for the adhesive element 1.

[0057] After thermal activation, e.g. at a temperature of 160 C. for 20 minutes, the adhesive element 1 comprising the thermoactivated rubber composition 2 displays a penetration force in the range from 450 to 1200 N. Furthermore, the impermeability of the adhesive element 1 when closing an opening could be confirmed for a 500 mm water column. The corrosion resistance was KKK after 1000 h in accordance with DIN EN ISO 6270-2, SST after 3000 h in accordance with DIN 50021 or 20 cycles in a salt spray mist measurement in accordance with VDA 621-415. The combustability in accordance with DIN 75200 was 0-3 mm/min. In addition, the adhesive element 1 was physically and chemically resistant to fuel, oil, brake fluids, alcohol, organic solvents, dilute acids and alkalis, water and aqueous solutions.

REFERENCE NUMERALS

[0058] 1 Adhesive element [0059] 2 Rubber composition [0060] 3 Support element [0061] 4 Conversion layer [0062] 5 Metal layer [0063] 6 Surface coating [0064] 7 Covering layer