U.S. patent application number 12/377555 was filed with the patent office on 2011-09-15 for pressure-sensitive adhesive strip for moisture-insensitive peelable adhesive bonds.
This patent application is currently assigned to TESA SE. Invention is credited to Andreas Junghans, Thorsten Krawinkel.
Application Number | 20110220295 12/377555 |
Document ID | / |
Family ID | 38659809 |
Filed Date | 2011-09-15 |
United States Patent
Application |
20110220295 |
Kind Code |
A1 |
Krawinkel; Thorsten ; et
al. |
September 15, 2011 |
PRESSURE-SENSITIVE ADHESIVE STRIP FOR MOISTURE-INSENSITIVE PEELABLE
ADHESIVE BONDS
Abstract
The invention relates to a peelable adhesive strip which is
coated with a pressure-sensitive adhesive at least one side. Said
adhesive strip is constituted of the following layers: a core layer
having an elongation at tear of at least 300%, an external carrier
layer having an elongation at tear of not more than 120% and at
least some sections of which are connected to the core layer in
such a manner that it becomes detached from the core layer when the
same is stretched, a first adhesive layer at least some sections of
which are applied to the side of the external carrier layer and
which is opposite the side connected to the core layer.
Inventors: |
Krawinkel; Thorsten;
(Hamburg, DE) ; Junghans; Andreas; (Hamburg,
DE) |
Assignee: |
TESA SE
HAMBURG
DE
|
Family ID: |
38659809 |
Appl. No.: |
12/377555 |
Filed: |
August 10, 2007 |
PCT Filed: |
August 10, 2007 |
PCT NO: |
PCT/EP2007/058296 |
371 Date: |
May 27, 2011 |
Current U.S.
Class: |
156/709 ;
428/317.3; 428/354 |
Current CPC
Class: |
C09J 7/381 20180101;
C09J 183/04 20130101; C09J 2301/304 20200801; C09J 2423/105
20130101; C09J 2301/302 20200801; C09J 2483/00 20130101; C09J
2400/243 20130101; C09J 2453/00 20130101; Y10T 428/2848 20150115;
C09J 7/29 20180101; Y10T 156/1142 20150115; C09J 153/02 20130101;
B32B 43/006 20130101; C09J 7/26 20180101; C09J 2301/162 20200801;
B32B 5/04 20130101; C09J 2467/006 20130101; Y10T 428/249983
20150401; C09J 7/387 20180101; C09J 2301/308 20200801; C09J
2301/1242 20200801 |
Class at
Publication: |
156/709 ;
428/354; 428/317.3 |
International
Class: |
C09J 7/02 20060101
C09J007/02; B32B 38/10 20060101 B32B038/10; B32B 3/26 20060101
B32B003/26 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 18, 2006 |
DE |
10 2006 038719.8 |
Claims
1. A redetachable, at least single-sided pressure-sensitive
adhesive strip comprising: a) a core layer which has a breaking
extension of at least 300%, b) an outer carrier layer which has a
breaking extension of not more than 120% and which at least
sectionally is connected to the core layer such that it separates
from the core layer when the latter is extensionally stretched, and
c) a first adhesive layer which is applied at least sectionally to
the side of the outer carrier layer that is opposite the side
connected to the core layer.
2. The adhesive strip of claim 1, wherein the core layer is formed
from an adhesive which is redetachable by extensional stretching in
the bond plane.
3. The adhesive strip of claim 1, wherein the core layer protrudes
beyond the outer carrier layer at least in one region.
4. The adhesive strip of claim 3, wherein the protruding region is
made nontacky.
5. The adhesive strip of claim 1, wherein the adhesive of the core
layer is constructed on the basis of styrene block copolymers.
6. The adhesive strip of claim 1, wherein the core layer is formed
by a carrier which is redetachable by extensional stretching in the
bond plane.
7. The adhesive strip of claim 1, wherein a further adhesive layer
is applied sectionally on a side of the carrier that is opposite
the side connected to the outer carrier layer.
8. The adhesive strip of claim 6, wherein between carrier and outer
carrier layer there is a second adhesive layer.
9. The adhesive strip of claim 8, wherein the bond strengths of the
second adhesive layer and of the further adhesive layer can be
reduced by extensional stretching in the bond plane.
10. The adhesive strip of at least one of claims 6 to 9, wherein
the carrier protrudes beyond the outer carrier layer at least in
one region.
11. The adhesive strip of claim 6, wherein the carrier foam.
12. The adhesive strip of claim 1, wherein the first adhesive layer
is based on silicone and is crosslinked.
13. The adhesive strip of claim 1, wherein on the core layer and/or
on the further adhesive layer there is, at least sectionally, a
second outer carrier layer which separates from the core layer or
from the further adhesive layer when the latter is extensionally
stretched, and which is provided at least sectionally on the free
side with a third adhesive layer.
14. The adhesive strip of claim 13, wherein the outer carrier layer
and the second outer carrier layer and/or the first and the third
adhesive layers are identical.
15. The adhesive strip of claim 1, wherein the adhesive of the core
layer, the further adhesive and/or the third adhesive are composed
of block copolymers or of a mixture thereof, especially including
polymer blocks formed from vinyl aromatics (A blocks) and those
formed by polymerization of 1,3-dienes (B blocks).
16. The adhesive strip of claim 15, wherein the vinyl aromatics are
styrene and/or the B blocks are formed by polymerization of
butadiene and/or isoprene and/or their hydrogenation products or by
polymerization of isobutylene.
17. (canceled)
18. A method of separating two substrates bonded with the adhesive
strip of claim 1 comprising stretching the core layer in the
direction of the bond plane starting from the region which has been
made nonadhesive, until the core layer releases from at least one
of the outer carrier layers so that the two substrates are
separated from one another and on at least one of the two
substrates an outer carrier layer is additionally bonded, and the
outer carrier layer together with the first adhesive layer is
peeled from the other substrate at an angle of removal of greater
than 45.degree..
19. The adhesive strip of claim 8 wherein the second adhesive layer
has the same composition as the further adhesive layer.
Description
[0001] The invention relates to an adhesive strip which is
pressure-sensitively adhesive in particular on both sides and which
can be detached again without residue or destruction in two steps,
by extensional stretching in the bond plane and subsequent peeling.
The invention further relates to the use of the adhesive strip of
the invention and also to methods of detaching the adhesive
strip.
[0002] Highly elastically or plastically extensible
pressure-sensitive adhesive strips which can be detached again
without residue or destruction by extensional stretching in the
bond plane are known from, for example, U.S. Pat. No. 4,024,312 A,
DE 33 31 016 C2, WO 92/01132 A1, WO 92/11333 A1, DE 42 22 849 A1,
WO 95/06691 A1, DE 195 31 696 A1, DE 196 26 870 A1, DE 196 49 727
A1, DE 196 49 728 A1, DE 196 49 729 A1, DE 197 08 364 A1, DE 197 20
145 A1, DE 198 20 854 A1, WO 99/37729 A1, and DE 100 03 318 A1, and
are referred to inter alia below as strippable pressure-sensitive
adhesive strips.
[0003] Strippable self-adhesive tapes of this kind are frequently
used in the form of single-sidedly or double-sidedly
pressure-sensitive adhesive-sheet strips, which preferably have a
nonadhesive grip region, from which the detachment operation is
initiated.
[0004] Particular applications of such pressure-sensitive adhesive
strips are found in DE 42 33 872 A1, DE 195 11 288 A1, U.S. Pat.
No. 5,507,464 A, U.S. Pat. No. 5,672,402 A, and WO 94/21157 A1;
specific embodiments are described in, for example, DE 44 28 587
A1, DE 44 31 914 A1, WO 97/07172 A1, DE 196 27 400 A1, WO 98/03601
A1, and DE 196 49 636 A1, DE 197 20 526 A1, DE 197 23 177 A1, DE
297 23 198 A1, DE 197 26 375 A1, DE 197 56 084 A1, DE 197 56 816
A1, DE 198 42 864 A1, DE 198 42 865 A1, WO 99/31193 A1, WO 99/37729
A1, and WO 99/63018 A1.
[0005] Fields of use of the aforementioned strippable
pressure-sensitive adhesive strips include in particular the
residuelessly and nondestructively redetachable fixing of light to
moderately heavy articles in the home, workplace, and office
segments. In these applications they replace conventional fastening
means such as, for example, drawing pins, roundhead needles, thumb
tacks, nails, screws, conventional self-adhesive tapes, and liquid
adhesives. Key to the successful use of the pressure-sensitive
adhesive strips is not only the possibility of residueless and
nondestructive redetachment of bonded articles but also their quick
and easy bonding and also their secure hold for the envisioned
period of bonding. It should be borne in mind in particular here
that the adhesive strips must function on a large number of
substrates in order to be able to serve as a universal fixing in
the home, workplace, and office segments.
[0006] Despite the fact that the literature cited above describes a
broad range of pressure-sensitive adhesives for use in strippable
self-adhesive tapes, commercial products currently on the market
(for example, Tesa.RTM. Powerstrips.RTM. from tesa AG, 3M
Command.RTM. adhesive strips from 3M, and Plastofix.RTM. Formule
Force 1000 adhesive strips from Plasto S.A.) virtually without
exception have pressure-sensitive adhesives based on styrene block
copolymers with unsaturated polydiene blocks in the elastomer
block.
[0007] These products based on the styrene block copolymers exhibit
weaknesses in bond strength under the influence of atmospheric
humidity or water. This behavior is particularly pronounced when
bonds are made on hydrophilic substrates such as glass or ceramic.
Particularly in the case of moisture exposure shortly after the
bonding of moderately heavy articles, failure of the
pressure-sensitive adhesive strips is a frequent occurrence. The
holding power under the influence of moisture is reduced in
particular in those pressure-sensitive adhesive strips which
comprise nonpolar tackifier resins such as hydrocarbon resins or
polyterpene resins.
[0008] In the case of products comprising an intermediate foam
carrier to which adhesive is applied on both sides, the reduction
in bond strength under moisture exposure was more strongly
pronounced than in the case of adhesive strips which are composed
of just one layer of adhesive.
[0009] Failure of the bond occurs in the case of a pure peeling
load and particularly in the case of a tipping/shearing load (where
a torque is active, as in the case, for example, of the bonding of
a hook with a particular lever on which something is hung) to a
much greater extent than in the case of a pure shearing load.
[0010] DE 102 24 842 A1 describes an adhesive based on styrene
block copolymers that by virtue of addition of super-absorbents
possesses significantly improved holding power on hydrophilic
substrates such as glass under moisture conditions. Nevertheless,
the bonding performance in the case of long-lasting, very high
atmospheric humidity, but especially under running water, is
inadequate.
[0011] U.S. Pat. No. 6,569,521 B describes a redetachable adhesive
strip with a strong, extensible carrier and an adhesive based on
silicones, especially block copolymers of silicones and polyureas.
This product can be removed from the substrate again by pulling in
the bond plane; the bond strength to glass at 98% relative humidity
is increased significantly in relation to that of adhesives based
on styrene block copolymers. A disadvantage is that, owing to the
stretching of the entire product, the only adhesives that can be
used are those for which the bond strength is greatly reduced under
extension.
[0012] For a large number of pressure-sensitive adhesives (PSAs),
the bonding performance subsides considerably under the influence
of high atmospheric humidity or water. Not only is it the case that
damp or wet adhesive strips adhere much less well or even not at
all, or that they are difficult to bond to wet substrates, but also
existing bonds of an adhesive tape on a substrate can be impaired
in their load-bearing capacity, or even fail completely, under the
influence of humidity or water. This phenomenon is particularly
pronounced in the case of hydrophilic substrates such as glass or
ceramic products such as tiles. Ceramic tiles in particular are
often found in bathrooms or kitchens, where for short periods the
atmospheric humidity can rise very sharply. Hydrophilic substrates
possess the property of often having a very thin layer of adsorbed
water bound on the surface, which can be removed only at very high
temperatures. As a result of this thin layer of water, it is very
easy for moisture or water to be picked up by the glass. Owing to
the molecular structure of the glass, it is even capable of taking
water into the glass itself and not only of absorbing it on the
surface. Similar considerations apply to ceramic products too.
[0013] If an adhesive tape is bonded to ceramic products or glass,
a thin layer of water remains between the adhesive tape and the
glass. This layer is so thin that the bonding properties of the
adhesive tape are unaffected; the bond between adhesive tape and
glass can be very strong, similar to that between steel and the
same adhesive tape.
[0014] If moisture in the form of high atmospheric humidity or
water acts on the bond, the layer of water between glass and
adhesive strip may pick up further water, which causes the layer to
grow. Water may also diffuse through the glass to the bond area.
Consequently the bond performance is reduced to such an extent that
it can lead to the bond failing.
[0015] In order to prevent this failure of the bond it is standard
practice to use very soft adhesives which are able to close off all
of the pores in the glass, so that the water is no longer able to
diffuse into the intermediate layer. This route is taken, for
example, in connection with the adhesive bonding of laminated glass
sheets, where an isobutyl rubber adhesive is employed (according to
Skeist, "Handbook of Adhesives", 2nd edition, 1977).
[0016] An alternative to the very soft adhesives based on isobutyl
rubbers are adhesives based on silicones or silicone-containing
polymers. A disadvantage is that these adhesives frequently do not
loose bond strength to a sufficient extent when stretched, to allow
them to be removed from a surface.
[0017] In contrast to this, silicone compositions can frequently be
peeled effectively from the substrate to which they have been
bonded.
[0018] It is an object of the invention to develop a redetachable
adhesive strip with adhesives that are formulated on a relatively
broad formulating basis, said adhesive strip having a high bond
strength even on hydrophilic substrates under high atmospheric
humidity, and even under running water, but also being removable
again without residue.
[0019] This object is achieved by means of an adhesive strip as
recorded in the main claim. The dependent claims provide
advantageous developments of the adhesive strip, uses thereof, and
methods of detaching the adhesive strip.
[0020] The invention accordingly provides a redetachable, at least
single-sidedly pressure-sensitive adhesive strip composed at least
of the following layers: [0021] a.) a core layer which has a
breaking extension of at least 300%, preferably of at least 450%,
[0022] b.) an outer carrier layer which has a breaking extension of
not more than 120%, preferably 80%, and which at least sectionally
is connected to the core layer such that it separates from the core
layer when the latter is extensionally stretched, [0023] c.) a
first adhesive layer which is applied at least sectionally to the
side of the outer carrier layer that is opposite the side connected
to the core layer.
[0024] In a first advantageous embodiment of the invention the core
layer is formed from an adhesive which is redetachable by
extensional stretching especially in the bond plane.
[0025] As a highly stretchable core layer it is possible to employ
adhesives which are both pressure-sensitively adhesive and
non-pressure-sensitively adhesive--which, for example, must be
activated thermally.
[0026] The thickness of the core layer comprising the adhesive is
preferably between 300 and 1500 .mu.m.
[0027] With further preference the core layer protrudes beyond the
outer carrier layer at least in one region. This region serves as a
grip tab, at which pulling takes place in order to obtain the
extensional stretching especially in the bond plane of the core
layer, and it is therefore preferably made non-adhesive on both
sides, especially by the application of pieces of film, foil or
paper.
[0028] In another advantageous development the region can be
generated by irradiation, powdering or neutralization of the
adhesive. Alternatively a varnish or primer may be applied at the
corresponding points.
[0029] The surface can then be modified by chemical treatment such
as etching in order in each case to produce nonadhesive zones.
[0030] In a further advantageous development of the invention, the
adhesive of the core layer is constructed on the basis of styrene
block copolymers.
[0031] Adhesives of this kind are described for example in DE 42 33
872 A1 or in DE 195 11 288 A1 and are available commercially as
teas Powerstrips.RTM..
[0032] In a further advantageous embodiment of the invention the
core layer is formed by a carrier which is redetachable by
extensional stretching especially in the bond plane.
[0033] With further preference a further adhesive layer is applied
at least sectionally on the side of the carrier that is opposite
the side connected to the outer carrier layer.
[0034] Between carrier and outer carrier layer there is
advantageously a second adhesive layer which preferably has the
same composition as the further adhesive layer.
[0035] Furthermore, it ought to be possible to reduce the bond
strengths of the second adhesive layer and of the further adhesive
layer by extensional stretching especially in the bond plane, in
order to obtain an adhesive strip of particularly advantageous
design.
[0036] With further preference the carrier protrudes beyond the
outer carrier layer at least in one region. This region serves
again as a grip tab, on which adhering takes place in order to
obtain the extensional stretching especially in the bond plane of
the core layer.
[0037] In a further advantageous embodiment of the invention the
carrier is composed of foam, in particular of homopolymers and
copolymers of ethylene, in particular of low-density and very
low-density polyethylenes (LDPE, LLDPE, VLDPE), of ethylene-vinyl
acetate copolymers and also of mixtures of aforementioned polymers
and/or of films of polyvinyl acetates, polypropylenes,
polyurethanes based on aromatic and aliphatic diisocyanates,
polystyrene, impact-modified polystyrenes, PVC, acrylate
copolymers.
[0038] The foams can be employed in crosslinked or noncrosslinked
form.
[0039] The thicknesses of the foams used are in particular between
175 .mu.m and 10 mm, preferably between 250 .mu.m and 5 mm, more
preferably between 350 .mu.m and 3 mm. The densities may be 20 to
400 kg/m.sup.3, preferably 25 to 250 kg/m.sup.3, more preferably
from 25 to 150 kg/m.sup.3. The foam structure may be closed-cell,
open-cell or mixed-cell. Skinned or unskinned foams of integral or
nonintegral structure may be utilized. In accordance with the
invention it is likewise possible to employ laminates of two or
more foams.
[0040] To generate sufficient anchorage of the PSAs employed on the
foams the latter are advantageously subjected to a pretreatment
during production and/or prior to their coating with PSA. Suitable
pretreatment techniques include fluorine pretreatment, corona
pretreatment, plasma pretreatment, and flame pretreatment, the
latter in particular by means of an electrically polarized flame.
Pretreatment methods may be applied alone or in combination. In the
case of skinned foams and in the case of integral foams, the foam
may be primer-treated in order further to improve the anchorage of
adhesive. Open-cell and mixed-cell foams may be subjected to
impregnation.
[0041] The foam carriers may be subjected to pretreatment or injury
by means, for example, of perforating, cutting or punching. Such
pretreatment may be carried out before or after the coating with
adhesive. The result of the pretreatment is, in particular,
incisions in the foam-containing carrier, or the extraction of
material from the foam-containing carrier, thereby reducing the
mechanical strength of the carrier.
[0042] Examples of corresponding pretreatments are incisions,
punches and perforations. These may cover the whole area of the
foam-containing carriers or else be present in confined regions.
They may have a regular structure and/or repetition sequence or be
irregular.
[0043] A distinction may be made between pretreatments where the
original form of the foam-containing carrier materials is retained,
and those where, as a result of removal of material (extractive
punching, for example) or as a result of thermal treatment
(melting, for example), regions free of material are produced, in
the form for instance of hole-like or channel-like openings in the
carrier. Incisions and also regions free of material may penetrate
the foam-containing carrier only partly or else completely, or
alternatively be present in a hybrid form. They may be made on one
side or on both sides into the foam-containing carrier.
[0044] Between the foam and PSAs it is possible optionally to
integrate a barrier layer in order to reduce the travel of
migratable materials between PSAs and foam.
[0045] An assembly comprising second adhesive, further adhesive,
and carrier, consisting of a highly stretchable, strong carrier and
two identical adhesives which loose their bond strength on
extensional stretching, is described in WO 92/11333 A1, for
example. In an inventive development, that assembly can be utilized
as a basis in an adhesive strip of the invention.
[0046] With further preference the first adhesive layer is based on
silicone and in particular is crosslinked. This achieves optimum
bond strengths on hydrophilic substrates, even under humid and wet
conditions.
[0047] The adhesive may be composed of a silicone-containing
polymer and/or a silicone resin. In this context it is possible to
employ blends of silicone resins and silicone rubbers, and also
reaction products of the two, through condensation crosslinking or
addition crosslinking, for example.
[0048] With regard to the resins it is possible to employ those
based on R.sub.3SiO.sub.1/2 and SiO.sub.4/2, but there may also, in
addition, be monomers of the form R.sub.2Si.sub.2/2 or RSiO.sub.3/2
present, as described, for example, in U.S. Pat. No. 2,676,182 A,
U.S. Pat. No. 3,627,851 A or U.S. Pat. No. 5,110,890 A.
[0049] Silicone polymers may be constructed on the basis of
polydimethylsiloxanes or polydiphenylsiloxanes. The use of block
copolymers of silicones and polyureas is also possible. These block
copolymers may be obtained from polyorganosiloxanediamines and
diisocyanates.
[0050] For the crosslinking of the silicone polymers and of the
silicone resins there are in principle two methods available. In
the case of condensation crosslinking, silanol-containing silicone
polymers react with silanol-containing resins either by addition of
a catalyst or as a result of increased temperature.
[0051] For the addition crosslinking, silicone polymers containing
alkenyl groups are crosslinked with silicone resins containing
either silicone-bonded hydrogen or alkenyl groups, through the use
of platinum catalysts.
[0052] The silicone adhesives may comprise fillers or pigments, as
elucidated in detail below.
[0053] In a further advantageous embodiment of the invention there
is, at least sectionally, a second outer carrier layer on the core
layer and/or on the further adhesive layer which separates from the
core layer or from the further adhesive layer when the latter is
extensionally stretched, and which is preferably provided at least
sectionally on the free side with a third adhesive layer. The
second outer carrier layer as well preferably has a maximum
breaking extension of 120%, especially 80%.
[0054] On extensional stretching of the core layer, the outer
carrier layers separate therefrom, and there remain two
single-sidedly bonded adhesive strips on the respective substrate,
which can be peeled off.
[0055] With further preference the outer carrier layer and the
second outer carrier layer and/or the first and the third adhesive
layers are identical.
[0056] The adhesive of the core layer, the further adhesive and/or
the third adhesive are preferably composed of block copolymers or
of a mixture thereof, especially including polymer blocks formed
from vinyl aromatics (A blocks) and those formed by polymerization
of 1,3-dienes (B blocks).
[0057] Advantageously the vinyl aromatics are styrene and/or the B
blocks are formed by polymerization of butadiene and/or isoprene
and/or their hydrogenation products or by polymerization of
isobutylene.
[0058] Resultant block copolymers may comprise identical or
different B blocks, which may be hydrogenated partly, selectively
or completely. The block copolymers may have a linear A-B-A
structure. It is likewise possible to employ block copolymers of
radial design and also star-shaped and linear multiblock
copolymers. A further component present may be A-B diblock
copolymers. Block copolymers of vinyl aromatics and isobutylene can
likewise be employed. All of the aforementioned polymers may be
utilized alone or in a mixture with one another.
[0059] In lieu of styrene-butadiene block copolymers and
styrene-isoprene block copolymers and their hydrogenation products,
thus styrene-ethylene/butylene block copolymers and
styrene-ethylene/propylene block copolymers, it is likewise
possible to employ block copolymers and their hydrogenation
products that utilize further polydiene-containing elastomer
blocks, such as, for example, copolymers of two or more different
1,3-dienes. Use may additionally be made of functionalized block
copolymers, where the block copolymer is a maleic
anhydride-modified or silane-modified styrene block copolymer
[0060] Typical use concentrations for the block copolymer are
situated in a concentration in the range between 20% and 70% by
weight, in particular in the range between 30% and 60% by weight
and in the range of 35% and 55% by weight.
[0061] Further polymers present may be those based on pure
hydrocarbons, for example, unsaturated polydienes such as naturally
or synthetically generated polyisoprene or polybutadiene,
substantially chemically saturated elastomers such as, for example,
a saturated ethylene-propylene copolymer, an .alpha.-olefin
copolymer, a polyisobutylene, a butyl rubber, an ethylene-propylene
rubber or a chemically functionalized hydrocarbon such as a
halogen-containing, acrylate-containing or vinyl ether-containing
polyolefin, which may replace the vinyl aromatic-containing block
copolymers at up to about 100 phr (parts per hundred parts of
resin), based on the styrene block copolymer.
[0062] Adhesives based on natural rubber can also be employed.
[0063] The adhesive may be crosslinked by chemical means, in
particular by radiation chemical means, as for example by UV
irradiation, .gamma. irradiation or by irradiation using rapid
electrons.
[0064] The adhesives of the present invention are optionally those
whose pressure-sensitive adhesiveness is generated only by thermal
or solvent activation.
[0065] The tackifier is a tackifier resin which is compatible with
the elastomer block of the styrene block copolymers. Suitable
tackifier resins include, among others, preferably unhydrogenated,
partially hydrogenated or fully hydrogenated resins based on rosin
or on rosin derivatives, hydrogenated polymers of
dicyclopentadiene, unhydrogenated, partially, selectively or fully
hydrogenated hydrocarbon resins based on C.sub.5, C.sub.5/C.sub.9
or C.sub.9 monomer streams, polyterpene resins based on
.alpha.-pinene and/or .beta.-pinene and/or .delta.-limonene, a
hydrogenated polymer of pure C.sub.8 or C.sub.9 aromatics.
Aforementioned tackifier resins may be used both alone and in a
mixture.
[0066] The mixture preferably comprises at least one additive. To
stabilize the adhesives it is typical to add antioxidants.
Additives may be primary or secondary antioxidants; primary
antioxidants employed in particular include sterically hindered
phenols, and secondary antioxidants employed in particular include
phosphites or thiols. C-radical scavengers may be added.
[0067] As an additive it is also possible, however, to use light
stabilizers such as, for example UV absorbers or sterically
hindered amines. The addition may likewise take place of
antiozonants, metal deactivators, processing assistants or end
block-reinforcing resins.
[0068] Further possible additives may be plasticizing agents.
Plasticizing agents may be liquid resins, plasticizer oils or low
molecular mass liquid polymers which possess a low molecular mass
polyisobutylene having a molar mass <1500 g/mol or a liquid EPDM
(ethylene/propylene-diene terpolymer) type having a maximum
proportion of 20% by weight.
[0069] Fillers, such as, for example, silicon dioxide, glass
(ground or in the form of beads), aluminum oxide, zinc oxide,
calcium carbonate, titanium dioxide or carbon black, to name but a
few, and also color pigments and dyes, and also optical
brighteners, may likewise be used.
[0070] The outer adhesives, in other words the first adhesive, the
third adhesive layer if appropriate, the further adhesive, and the
core layer, when the latter is composed of an adhesive, may be
provided with an easy-release liner. Suitable for lining the
further adhesive and also the core layer is a paper or a film of
siliconization; for the first or third adhesive, a
fluorosiliconization is advisable.
[0071] The following layer thicknesses have proven advantageous:
[0072] the outer carrier layer(s): up to 100 .mu.m, especially 20
to 100 .mu.m. [0073] the first, second, third, and further
adhesives: 20 to 100 g/m.sup.2.
[0074] Unless noted otherwise, the breaking extension measurements
are made by a method based on DIN 53504, using dumbbell specimens
of size S3 and a separation speed of 300 mm/min.
[0075] In view of the properties outlined, the adhesive strip of
the invention can be used with outstanding effects to bond an
article to a hydrophilic surface.
[0076] With particular advantage, in accordance with the method
below, two substrates bonded with the adhesive strip of the
invention can be separated by stretching the core layer in the
direction of the bond plane, and doing so more particularly
starting from the region which has been made nonadhesive, until the
core layer from at least one of the outer carrier layers, so that
the two substrates are separated from one another and on at least
one of the two substrates an outer carrier layer is additionally
bonded, and the outer carrier layer together with the first
adhesive layer is peeled from the other substrate at an angle of
removal of greater than 45.degree..
[0077] Using the below-described figures and examples, particularly
advantageous embodiments of the invention are illustrated, without
any intention thereby to subject the invention to unnecessary
restriction.
[0078] FIG. 1 shows the pressure-sensitive adhesive strip of the
invention, wherein the core layer is composed of an adhesive,
[0079] FIG. 2 shows the pressure-sensitive adhesive strip of the
invention, wherein the core layer is composed of a carrier,
[0080] FIG. 3 shows the pressure-sensitive adhesive strip of the
invention, wherein the core layer is composed of an adhesive, and
which has a second outer carrier layer,
[0081] FIG. 4 shows the pressure-sensitive adhesive strip of the
invention, wherein the core layer is composed of a carrier, and
which has a second outer carrier layer,
[0082] FIG. 5 shows how an article is bonded with an adhesive strip
according to FIG. 1 to a hydrophilic substrate,
[0083] FIG. 6 shows the first step in the method for detaching the
article bonded with the pressure-sensitive adhesive strip, and
[0084] FIG. 7 shows the second step in the method for detaching the
article bonded with the pressure-sensitive adhesive strip.
[0085] In FIG. 1 the pressure-sensitive adhesive strip 10 of the
invention is shown, wherein the core layer 1 is composed of an
adhesive which is redetachable by extensional stretching especially
in the bond plane.
[0086] The core layer 1 protrudes beyond the outer carrier layer 4
at least in a region which serves as a grip tab, which is pulled in
order to obtain the extensional stretching especially in the bond
plane of the core layer 1. This region is made non-adhesive on both
sides by the application of preferably siliconized pieces of film,
foil or paper 6.
[0087] The outer carrier layer 4 is connected to the core layer 1,
owing to the adhesive character of said core layer 1, in such a way
that is separates from the core layer 1 when the latter is
subjected to extensional stretching.
[0088] Applied over the full area of the outer carrier layer 4 is a
first adhesive layer 5, in particular a pressure-sensitive silicone
adhesive, specifically on the side opposite that connected to the
core layer 1.
[0089] In FIG. 2 the pressure-sensitive adhesive strip 10 of the
invention is shown, wherein the core layer 1 is composed of a
carrier which is redetachable by extensional stretching especially
in the bond plane. Connected to the carrier 1 is an outer carrier
layer 4, the connection being such that the layer 4 separates from
the core layer 1 when the latter is subjected to extensional
stretching. The bond is ensured by a second adhesive layer 3.
[0090] On the side of the carrier 1 opposite to the side connected
to the outer carrier layer 4, the further adhesive layer 2 is
applied, and preferably has the same composition as the second
adhesive layer 3.
[0091] Moreover, the bond strengths of the second adhesive layer 3
and of the further adhesive layer 2 can be reduced by extensional
stretching especially in the bond plane.
[0092] In FIG. 3 the pressure-sensitive adhesive strip 10 of the
invention is shown, wherein the core layer 1 is composed of an
adhesive which is redetachable by extensional stretching especially
in the bond plane.
[0093] The core layer 1 protrudes beyond the outer carrier layer 4
at least in a region which serves as a grip tab, which is pulled in
order to obtain the extensional stretching especially in the bond
plane of the core layer 1. This region is made non-adhesive on both
sides by the application of preferably siliconized pieces of film,
foil or paper 6.
[0094] The outer carrier layer 4 is connected to the core layer 1,
owing to the adhesive character of said core layer 1, in such a way
that it separates from the core layer 1 when the latter is
subjected to extensional stretching.
[0095] Applied over the full area of the outer carrier layer 4 is a
first adhesive layer 5, in particular a pressure-sensitive silicone
adhesive, specifically on the side opposite that connected to the
core layer 1.
[0096] Present on the core layer 1 is a second outer carrier layer
7, which separates from the core layer 1 when the latter is
subjected to extensional stretching, and which is provided on the
free side with a third adhesive layer 8, in particular a
pressure-sensitive silicone adhesive.
[0097] In FIG. 4 the pressure-sensitive adhesive strip 10 of the
invention is shown, wherein the core layer 1 is composed of a
carrier which is redetachable by extensional stretching especially
in the bond plane.
[0098] On the side of the carrier 1 which is opposite to the side
connected to the outer carrier layer 4 the further adhesive layer 2
is applied.
[0099] Connected to the carrier 1 is an outer carrier layer 4, the
connection being such that the layer 4 separates from the core
layer 1 when the latter is subjected to extensional stretching. The
bond is ensured by a second adhesive layer 3, which preferably has
the same composition as the further adhesive layer 2.
[0100] Present on the further adhesive layer 2 is a second outer
carrier layer 7 which, on extensional stretching of the core layer
1 or of the further adhesive layer 3, separates therefrom, and
which is provided on the free side with a third adhesive layer 8,
in particular a pressure-sensitive silicone adhesive.
[0101] FIG. 5 shows how an article 11 is bonded with an adhesive
strip 10 according to FIG. 1 to a hydrophilic substrate 12. The
article 11 is a hook.
[0102] It is important that the first adhesive layer 5, in
particular a pressure-sensitive silicone adhesive, is located on
the substrate.
[0103] FIG. 6 shows the first step in the method for detaching the
article 11 bonded with the pressure-sensitive adhesive strip
10.
[0104] First of all the grip tab of the core layer 1 is pulled in
the direction of the bond plane, leading to stretching of the core
layer 1. Owing to the stretching, the core layer loses bond
strength, and thus parts from the outer carrier layer 4, which by
virtue of the first adhesive 5 continues to remain bonded to the
substrate 12.
[0105] At the same time the pressure-sensitive adhesive strip 10
parts from the article 11.
[0106] The stretching of the core layer 1 is continued until
separation of the core layer 1 from the outer carrier layer 4 and
from the article 11 is complete.
[0107] FIG. 7 shows the second step in the method for detaching the
article 11 bonded with the pressure-sensitive adhesive strip
10.
[0108] To detach the outer carrier layer 4, it is peeled, along
with the first adhesive layer 5, from the substrate 12 at an angle
of removal of greater than 45.degree..
[0109] Residues of adhesive remain neither on the substrate 12 nor
on the article 11.
EXAMPLES
Preparation of the Adhesive for Forming the Core Layer, the Further
Adhesive, and the First and Third Adhesives
[0110] The preparation and processing of the adhesives may take
place from solution and also from the melt. Fabrication from the
melt has proven advantageous for the further adhesive and for the
adhesive for forming the core layer, while fabrication from
solution is preferred for the first and third adhesives.
Converting
[0111] Typical converted forms of the pressure-sensitive adhesive
strips of the invention are adhesive-tape rolls and adhesive
strips, of the kind obtained in the form of diecuts, for
example.
[0112] Preferably all of the layers have essentially the shape of a
rectangular block. With further preference all of the layers are
connected to one another over their full area.
[0113] For the purposes of this invention the general expression
"adhesive tape" encompasses all sheetlike structures such as
two-dimensionally extended sheets or sheet sections, tapes with
extended length and limited width, tape sections, diecuts, labels,
and the like.
Example 1
[0114] 1.8% by weight of the catalyst SYL-OFF 4000 from Dow Corning
Corporation is mixed with 98.2% by weight of Dow Corning 7657
polydimethylsiloxane adhesive solution and the mixture is coated
out onto a PET film with a thickness of 36 .mu.m and dried at
140.degree. C. for 10 min. After drying, the thickness of the
adhesive layer is 60 g/m.sup.2. The film thus coated is cut to
appropriate size and then adhered by its uncoated side to the
following adhesive strip in such a way that the grip-tab region
remains free.
Composition:
[0115] 51.5 parts by weight of linear SIS triblock copolymer having
a block polystyrene content of 29% by weight and a hardness,
measured by the Shore A method, of 60 (Vector 4211) [0116] 47.0
parts by weight of partly hydrogenated aromatic C.sub.9 hydrocarbon
resin having a Ring & Ball softening point of 100.degree. C.
(Regalite S 260) [0117] 1.0 part by weight of phenolic antioxidant
(Irganox 1010) [0118] 0.5 part by weight of light stabilizer
(polymeric sterically hindered amine)
[0119] The ingredients are kneaded at 160.degree. C. in a
Sigma-blade mixer until homogeneous. The resulting
pressure-sensitive hot-melt adhesive is coated at 160.degree. C. in
a coat thickness of 410 .mu.m from a slot die onto a double-sidedly
siliconized release film 80 .mu.m thick and composed of monoaxially
oriented polypropylene.
[0120] The resulting bale product (consisting of double-sided
pressure-sensitive adhesive tape with single-sided release-film
liner) is processed to sheet product (adhesive strips) on a unit
consisting of two laminating stations, a delaminating station, two
further laminating stations, a longitudinal slitting device, and a
separation unit (format punch). For this purpose, a 20 mm wide and
15 .mu.m thick polyethylene terephthalate film is laminated
centrally onto the release-film-free side (front face) of 120 mm
width at the first laminating station. At the second laminating
station, siliconized polyethylene release film in a width of 120 mm
is laminated on in such a way that the release film projects beyond
the adhesive by 2.5 mm on either side. Following the release-film
lining of the reverse face at a delaminating station, the same
linings (20 mm wide polyethylene terephthalate film centrally, 125
mm wide siliconized polyethylene film over the full area with a 2.5
mm projection on either side) are performed for the reverse face.
Separation to form sheet product with a length of 62.5 mm and a
width of 19 mm is accomplished by means of slitting (in
longitudinal direction) and by diecutting by a format
diecutter.
[0121] The ring-and-ball method is the customary method for
ascertaining softening points. Details can be taken from ASTM E 28
and DIN EN 1238, hereby incorporated by reference.
[0122] The resulting adhesive assembly is adhered with the silicone
adhesive side to a vertical glass wall and pressed on with a force
of 100 N. Bonded to the Powerstrips side is a steel hook with
dimensions of 4.times.2 cm, projecting vertically from which there
is a pin to which a weight can be affixed. The bond is made such
that the grip tab of the Powerstrip projects from the adhesive
joint. Subsequently a weight of 500 g is hung on the
above-described pin at a distance of 30 mm from the wall.
Comparative Example
[0123] As described in example 1, an adhesive strip as per claim 1
is bonded without additional outer carrier layer and adhesive, and
the pin is loaded with the same weight.
[0124] In the case of both examples, 10 min after adhesive bonding,
the atmospheric humidity in the room is increased to 85% relative
humidity. While the unimproved strip often falls off even within
the first hour, the adhesive strip from example 1 continues to hold
after several days.
[0125] The adhesive strip from example 1 can be parted again
without problems. This is done by pulling on the grip tab of the
core layer, the detachment force being comparable with that of a
normal adhesive bond with the adhesive strip without an additional
outer carrier layer and adhesive. In the process of parting by
extensional stretching, the core layer parts from the PET film,
which remains with the silicone composition on the tab. This can
then be peeled off easily without leaving residues on the
glass.
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