Stock material or miscellaneous articles – Layer or component removable to expose adhesive
Reexamination Certificate
2000-08-11
2004-01-20
Ahmad, Nasser (Department: 1772)
Stock material or miscellaneous articles
Layer or component removable to expose adhesive
C428S041700, C428S042100, C428S042200, C428S192000, C428S194000, C428S201000, C428S212000, C428S214000, C428S220000
Reexamination Certificate
active
06680096
ABSTRACT:
The invention relates to an adhesive film strip and to its use; the invention relates in particular to a strippable, high-peel-strength, adhesive film strip having a first adhesive film strip region of high cross-sectional area, preferably realized by means of a large adhesive strip width, and adjacent to this first adhesive film strip region a second adhesive film strip region with strong spontaneous tapering of the adhesive film cross-sectional area, in association with one or more adhesive film strip ends which run to a point, the said strip featuring only very low transfer to a bonded article of the energy stored elastically in the adhesive film strip in the course of the detachment process, and so, at the end of the detachment process, in the case of double-sidedly adhesive film strips, causing no significant catapulting of the assembly comprising one of the bonded articles and the adhesive film strip, even when one of the two articles bonded to one another is not fixed during the detachment process. At the same time, the adhesive film strip in the invention features a significantly reduced drop in the energy stored elastically in it at the end of the detachment process.
INTRODUCTION/PRIOR ART
The invention relates to a high-peel-strength, double-sided adhesive film strip for a bond redetachable without residue or destruction, the said strip being removable from a joint by stretching extending essentially in the bond plane such that the debonding of the two adherends proceeds very substantially simultaneously and, at the end of the detachment process, there is no significant catapulting of the assembly comprising one of the bonded articles with the adhesive strip. At the same time, the adhesive film strip of the invention features only a very slight drop in the elastic energy stored in it during the detachment process.
The invention further relates to a high-peel-strength, single-sided adhesive film strip for a bond redetachable without residue or destruction, the said strip being detachable by stretching extending essentially in the bond plane such that at the end of the detachment process there is only a very slight drop in the energy stored elastically in the said strip, as a result of which there is only a very low transfer to the bonded article of the energy stored elastically in the adhesive strip during the detachment process.
Highly elastically or plastically extensible (strippable) self-adhesive tapes which are redetachable without residue or destruction by stretching extending essentially in the bond plane are known from U.S. Pat. No. 4,024,312, DE 33 31 016, WO 92/11332, WO 92/11333, DE 42 22 849, WO 95/06691, DE 195 31 696, DE 196 26 870, DE 196 49 727, DE 196 49 728, DE 196 49 729 and DE 197 08 366.
They are frequently used in the form of single- or double-sided adhesive film strips (adhesive tape strips, adhesive strips), which preferably have a nonadhesive grip-tab region from which the detachment process is initiated. Particular applications of such self-adhesive tapes may be found, inter alia, in DE 42 33 872, DE 195 11 288, U.S. Pat. Nos. 5,507,464, 5,672,402 and WO 94/21157. Specific embodiments are described, for example, in DE 44 28 587, DE 44 31 914, WO 97/07172, DE 196 27 400, WO 98/03601 and DE 196 49 636.
A highly advantageous quality criterion of abovementioned strippable adhesive film strips is their capacity to develop a reduced adhesion under stretching, including that involved in the detachment process, as a result of which the friction of the adhesive strips on the edges of the adherends, and thus the mechanical load on the adhesive strips in these potential contact regions, when corresponding double-sided adhesive film strips are removed from the joint, are low. An essential factor, especially for the redetachable bonding of rigid adherends, is a reduction in the thickness of the adhesive film strip during detachment, which is the primary prerequisite for the ability to remove double-sided adhesive tapes from a joint.
The realization of strippable self-adhesive tapes which on the one hand have high peel strength by virtue of a large adhesive-strip width and on the other hand may be reliably redetached without residue, destruction or tearing in all cases, even from very sensitive substrates, is a complex undertaking and requires further preconditions. With regard to redetachment without residue, destruction or tearing, DE 44 31 914 and DE 196 49 636 address in particular the problem of tears in the grip-tab region and, respectively, in the adhesive-strip region directly adjacent to the grip-tab region. DE 44 28 587 describes an adhesive film strip for a rereleasable bond removable from a joint by pulling in the direction of the bond plane, characterized in that the bond area decreases towards the end of the adhesive film strip (the end which disappears in the joint) (see claim
1
). DE 44 28 587 describes pointed, zigzag, convexly curved, and corrugated adhesive film strip ends. Essential in each case is a reduction in the bond area at the end of the adhesive strip (column 1, lines 63 and 64). Correspondingly shaped adhesive film strips, in comparison to adhesive film strips whose bond area does not decrease at the end, exhibit a significantly reduced tendency to tear in the end region of the adhesive strips. At the same time, there is a marked reduction in instances of substrate damage, so that even very sensitive substrates may be reversibly bonded with such adhesive film strips.
A further problem may be the transfer to an adherend of the energy stored elastically during the stripping process in the adhesive strip which it is intended to detach. In the case of double-sided adhesive film strips, there may be catapulting of the assembly comprising adhesive strip for detachment and one of the bonded articles, and this catapulting may cause not inconsiderable damage. Furthermore, the spontaneous elastic release of, in particular, highly elastic strippable self-adhesive tapes at the end of the stripping process (viz, at the end of the detachment process, the drop in the energy stored elastically in the adhesive strip during the detachment process) may result in the adhesive tape snapping back against the fingers, which may have very painful consequences.
WO 97/07172 addresses the specific problems of the catapulting of articles bonded with strippable double-sided self-adhesive tapes and of the spontaneous snap-back of aforementioned self-adhesive tapes from the joint at the end of the detachment process. Catapulting of bonded articles may occur when, at the end of the detachment process, the adhesive strip for detachment has separated only from one of the adherends, e.g. the wall, and the second adherend is not adequately fixed. The energy elastically stored in the self-adhesive strip in the course of its stretching then causes the assembly comprising adhesive strip and the unfixed article, still bonded to the adhesive film strip, to catapult in the direction of detachment. The solution described by WO 97/07172 is a strippable self-adhesive strip which on one adhesive surface at the end of the adhesive strip has a region of no adhesion or else significantly reduced adhesion (differential adhesive strip end). If this self-adhesive strip surface is directed towards the bonded article, then when the adhesive strip is detached there is first of all complete separation of the adhesive strip from the bonded article, so that the latter is detached from the bond substrate and can be removed therefrom, and on further stretching of the self-adhesive tape the same then detaches from the second substrate, e.g. the wall. Aforementioned adhesive strips therefore permit controllable sequential detachment of an adhesive bond. The thus-controlled sequential detachment process likewise reduces the snap-back of the adhesive film strip from the joint by virtue of the absence of one adherend (which has in fact already undergone detachment).
Without a non-adhesive or significantly adhesion-reduced end region, the detachment sequence of two bonded articles is normal
Franck Achim
Junghans Andreas
Lühmann Bernd
Ahmad Nasser
Norris & McLaughlin & Marcus
tesa AG
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