SEALING TAPE BONDING WEAKLY OR NOT AT ALL ON ONE SIDE

Abstract

The invention relates to a sealing element with high sealing effect against air and moisture, which is easy to apply, and which moreover offers the possibility to reopen the sealed gap in an uncomplicated manner. Said solution is provided by an adhesive tape with differing adhesive power on the two main sides, which comprises a) a polymer foam layer and b) an outer adhesive compound layer and/or an outer thermoplastic film on one side of the polymer foam layer and is characterized in that, where the adhesive tape comprises an outer adhesive compound layer, the tape has a greater adhesive power on the side provided with the outer adhesive compound layer than on the opposing side and/or, where the adhesive tape comprises an outer thermoplastic film, the tape has a lower adhesive power on the side provided with the outer thermoplastic film than on the opposing side. The invention furthermore relates to the use of an adhesive tape according to the invention for sealing a joint between two components.

Claims

1. An adhesive tape with differing peel adhesion on both main sides, comprising a) a polymer foam layer; and b) an outer pressure-sensitive adhesive layer and/or an outer thermoplastic film on respectively one side of the polymer foam layer; wherein if the adhesive tape comprises an outer pressure-sensitive adhesive layer, it has a higher peel adhesion on its side equipped with the outer pressure-sensitive adhesive layer than on its opposite side; and/or if the adhesive tape comprises an outer thermoplastic film, it has a lower peel adhesion on its side equipped with the outer thermoplastic film than on its opposite side.

2. The adhesive tape as claimed in claim 1, wherein to an extent of at least 35 wt %, based on a total weight of the polymer foam layer, the polymer foam layer comprises one or more polymers selected from the group consisting of polyolefins; polyurethanes; polyvinyl chloride (PVC); blends of PVC and nitrile rubber; terpolymers of ethylene, propylene and a nonconjugated diene (EPDM); copolymers of ethylene and an ethylene substituted by a polar group; blends of polyethylene and a polymer of an ethylene substituted by a polar group; poly(meth)acrylates; blends of poly(meth)acrylate and synthetic rubber, and also mixtures of two or more of said polymers.

3. The adhesive tape as claimed in claim 1, wherein the polymer foam layer comprises at least one poly(meth)acrylate.

4. The adhesive tape as claimed in claim 1, wherein the polymer foam layer comprises microballoons.

5. The adhesive tape as claimed inclaim 1, wherein the adhesive tape consists of: a) a polymer foam layer; and b) an outer pressure-sensitive layer on one side of the polymer foam layer.

6. The adhesive tape as claimed in claim 1, wherein the adhesive tape consists of: a) a polymer foam layer; and b) an outer thermoplastic film on one side of the polymer foam layer.

7. The adhesive tape as claimed in claim 1, wherein the adhesive tape consists of: a) a polymer foam layer; b) an outer pressure-sensitive adhesive layer on one side of the polymer foam layer; and c) an outer thermoplastic film on the other side of the polymer foam layer.

8. A method comprising sealing a joint between two components with an adhesive tape, wherein the adhesive tape is an adhesive tape as claimed in claim 1.

9. The method as claimed in claim 8, wherein the joint between the components is a mechanically effectuated joint.

Description

EXAMPLES

[0170] Test Methods

[0171] Gel permeation chromatography for determining the molecular weight: The molecular weight data in this specification are based on a determination by gel permeation chromatography. The determination is made on 100 μl of a sample having undergone clarifying filtration (sample concentration 4 g/l). The eluent used is tetrahydrofuran with 0.1 vol % of trifluoracetic acid. Measurement takes place at 25° C. The preliminary column used is a column of type PSS-SDV, 5μ, 10 Å, ID 8.0 mm-50 mm. Separation takes place using the columns of type PSS-SDV, 5μ, 10.sup.3A and also 10.sup.5 Å and 10.sup.6 Å each of ID 8.0 mm×300 mm (columns from Polymer Standards Service; detection using Shodex R171 differential refractometer). The flow rate is 1.0 ml per minute. Calibration takes place against PMMA standards (polymethyl methacrylate calibration).

[0172] Water Permeability:

[0173] Strips 5 mm wide were cut from the adhesive tape under investigation and were adhered to a square metal plate (external dimensions 80 mm×80 mm×5 mm). The strips were arranged so as to form a closed square contour. The ends of a strip were each joined flush with the side face of the next strip end.

[0174] In the inside of the square, a paste (KMnO.sub.4) was then applied which undergoes a marked color change to violet on contact with water. An identical metal plate was then placed onto the construction and screw-connected. The screws were located outside the square of adhesive tape strips. The distance between the metal plates were set at exactly 2 mm by means of 2 shims each 1 mm thick. This construction ensured that the water-reactive paste is in a closed space within the adhesive tape strips. Penetration of water would be apparent from a color change and would imply a lack of imperviousness of the adhesive tape.

[0175] The entire sample was then placed into a water bath which was subsequently placed into an autoclave. Initially a small superatmospheric pressure of 0.3 bar was applied; in a second test, a superatmospheric pressure of 3 bar then simulated a water column of 30 m. After 30-minutes storage under water in the autoclave, the superatmospheric pressure was let down, the assembly was withdrawn, and the sample was studied for color change of the KMnO.sub.4. A change in color indicates water permeability of the adhesive tape; no change in color indicates imperviousness to water (result “water-permeable yes/no”).

[0176] Redetachability of the bonded substrate (simulating the redetachment of a bonded battery cover; reopenability):

[0177] The adhesive tape was applied once around by the more strongly adhering side to an aluminum plate (450×250 mm, 2.5 mm thickness) at a distance of 30 mm from the plate edge. A further aluminum plate (450×250 mm, 1 mm thickness) with identical dimensions was applied to the free side (from above). Shims 2 mm thick were inserted into the joints on each side, after which the assembly was compressed in a screw clamp. The aluminum plates were thereafter screwed to one another, utilizing holes present for that purpose in the corners of the plates.

[0178] The resultant assembly was stored for 10 days in a conditioned chamber at 40° C. and 100% relative humidity. Following removal it was reconditioned for 24 h at 23° C. and 50% relative humidity.

[0179] The screws and shims were then removed, and on one of the shorter sides a tensioning strap was inserted into the joint, this strap being connected to a testing machine (Zwick). The upper (1 mm) plate was pulled off at an angle of 90° and a velocity of 300 mm/min, and a measurement was made of the maximum force required for this purpose. Table 1 reports the average value from three measurements.

[0180] Adhesive Tapes Used

[0181] A—Tesa® 61102 (closed-cell EPDM rubber foam, coated on one side with an acrylate adhesive, to total thickness 3200 μm; tesa)

[0182] B—Tesa® ACXU.sup.plus 70730 High Resistance (double-sided acrylate foam tape, coated on both sides with acrylate PSA, total thickness 2900 μm; tesa), laminated on one side with a thermoplastic polyurethane film (Platilon® U04/PE, 30 μm; Bayer)

[0183] C—Tesa® ACXP's 70730 High Resistance, with the acrylate PSA applied only one side, the acrylate foam therefore lying exposed on one side (see B, total thickness 2850 μm; tesa)

[0184] D—Tesa® 92111 HiP—High initial Performance, bonded to itself 3×, total thickness 3300 μm; tesa); laminated on one side with a thermoplastic polyurethane film (Platilon® U04/PE, 30 μm; Bayer)

[0185] E—Tesa® ACX.sup.plus 70730 High Resistance (double-sided acrylate foam tape, coated on both sides with acrylate PSA, total thickness 2900 μm; tesa); comparative example

TABLE-US-00001 TABLE 1 test results Water Water Adhesive permeability at permeability at tape 0.3 bar 3 bar Redetachability A No Yes B No No Measurement not required; the bond could be parted very easily by hand C No No 148 N D No No Measurement not required; the bond could be parted very easily by hand E (comp.) No No >500 N comp. = comparative example