Note: Descriptions are shown in the official language in which they were submitted.
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COVERED, PRESSURE-SENSITIVE SELE-ADHESIVE CARRIERS,
AND A PROCESS FOR THR PRODUCTION THEREOF
Back~ro _d of the Invention
Field of the Invention
The invention relates to materials which have been
provided with a self-adhesive coating and have been
rendered pressure-sensitive; such as adhesive tapes.
The materials are provided on their self-adhe~ive
surEace with a covering which can easily be removed,
wherein the covering contains no silicone, has high
strength, and is recyclable.
The invention also relates to a process o~
producing such covered materials and to a process of
using such a covering.
Description of Related Art
Materials which have been provided with a self-
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adhesive coating and have been rendered pressure-sensi-
tive, for example adhesive tapes, must frequently be
reversibly covered on their adhesive or active surface
during production, transport, and storage in order to
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prevent them from sticking to themselves. In addition,
these coverings enable the rolling resistance to be
modified in a specific manner, which is of crucial
impor~ance, in particular, when adhesive tape rolls are
used in automatic packaging machines.
Conventional reversible coverings for adhesive
tapes usually have silicone-containing coatings which
are adhesive-repellent. However, silicone-containing
coverings o~ this type have a number of disadvantages.
Firstly, traces of the silicone remain adhered to the
adhesive layer when the covering is removed. The
~; adhered silicone reduces the adhesion of the adhesive
- when in contact with a new substrate. Secondly, the
silicone in the covering prevents recovery and reuse of
the pure material used as the covering. Accordingly,
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recycliny of the covering is imprac-tical, and disposal
of materia:Ls which have been siliconized in this way
must be accomplished hy landfilling or incineration.
Also, another disadvantage of silicone-containiny
covers is tha-t -thermal converslon is not generally
possible for silicone-con-tainin~ material.
Summary of the_Invention
An ob~ec-t of the present invention is to provide a
covering for adhesive tapes and other materials having
a pressure-sensitive surface or coating which is in no
way inferior -to siliconized carriers with respect to
its proper-ty profile, but which does not have the
above-described disadvantages of siliconized carriers.
It is also an object of the present invention to
provide a process for the production of the covered
carrier.
- It is also an object of the present invention to
provide a process for the use of an embossed film as a
covering film for self-adhesive carriers.
In accomplishing the foregoing objectives, there
has been provided, in accordance with one aspect of the
present invention, a covered carrier comprising a
carrier having a surface which is pressure-sensitive
and self-adhesive, and an embossed material covering
said surface.
In accordance with another aspect of the invention
there has been provided a process for using an embossed
material as a covering, comprising the step of applying
the embossed material to a pressure-sensitive, self-
adhesive surface of a carrier.
In accordance with another aspect of the
invention, there has been provided a process for the
`~ production of a covered carrier, which comprises
applying an embossed material to a surface of a carrier
which is pressure-sensitive and self-adhesive.
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Further ob~ects, ~eatures, and advantages of the
present invention will become apparen-t from the
cletailed description of preferred embodiments tha-t
follows.
Detailed Description of the Preferred Embodiments
As the material having the pressure-sensitive,
self-adhesive surface, any such material can be used.
In particular, pressure-sensitive, self-adhesive
carriers, which are sufficiently well known and are
described, for example, in EP-A-0 028 771 which is
hereby incorporated by reference, can be used.
As -the embossed structure, any structure, such as
a thermoplastic film, having elevations, can be used.
- For example, useful embossable polyester films are
described in EP-A-0 115 033, which is ecluivalent to
U.S. Paten-t No. 4,734,335, which is hereby incorporated
by reference in its entirety.
V.S. Patent Application 07/947,173 proposes
employing the embossed film of EP-A-0 115 033 as a
release film for the production of decorative layers
with a structured surface. There is no inclication in
this application of any possible use of such embossed --
films as a covering for self-adhesive carriers.
A covering in the sense of the invention means a
~- 25 material which protec-ts the adhesive surface of a
carrier which has been provided with an adhesive
coating. The covering can be removed, if desired,
without significantly damaging the adhesive layer
and/or the carrier.
In the present invention, a carrier means a
structure which inherently has or is provided with, at
least on one surface, a self-adhesive coating which
bonds the carrier more or less strongly to a substrate
by simple exertion of pressure, e.g., in a pressure-
sensitive manner. Any such carrier having the
described adhesive surface or coating can be used in
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the present invention. :Ln particu:Lar, che carrier may
be an aclhesive tape film, which usually comprises a
single- or multilayer thermoplas-t:ic, such as polyvinyl
chloride, polypropylene or polyethylene terephthalate,
and has been coated on one sicle with a pressure-
sensi-tive adhesive. Any known pressure-sensitive
adhesives can be used to coat the carrier. Throuyhout
the specification and claims, the term "pressure-
sensitive" means tha-t the adhesive effec-t is achieved
simply by the action of pressure without increasing the
tempera-ture or adding any addi-tives.
In a preferrecl embodiment of the present
invention, -the embossable structure is a film which is
a stretched ancl thermofixed multilayer film made from
polyesters having different melting points, comprising
two outer polyester layers of polyethylene
terephthalate, between which a lower-melting polyester
layer made from copolyesters containing ethylene
terephthalate and ethylene isophthalate units is
embedded. An embossable multilayer film of this type
;~ is described in U.S. Patent 4,734,335 the disclosure of
which is incorporated by reference. This multilayer
film can be produced, for example as an unembossed
film, be laminated onto a carrier, for example a book
cover, and subsequently embossed under the action of
pressure and temperature, producing the desired relief-
like pattern.
It has now been found, surprisingly, that this
embossable film is highly suitable as a covering film
for pressure-sensitive, self-adhesive carriers. To
this end, the embossable film of U.S. Patent 4,734,335
is embossed with the desired pattern, for example small
elevations uniformly distributed over the film surface.
The embossing may be accomplished in any desired
manner. The advantage of this film as compared to
previously used coverings is, in particular, that it
a) contains no silicone,
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b) achieves low aclhesion between the adhesive layer
and the covering film by minimi~ing the contact
area between covering and adhesive due to the
small elevations (embossing) of the covering,
~; 5 c) has high strength, and
d) is made of a sinyle type material, i.e.,
polyesters, and is thus recyclable.
The preferred embossable polyester film is a
multilayer film whose features are that the film is
biaxially stretched and that the middle layer comprises
a copolyester preferably containing between about 5 and
about 95%, more preferably between about 5 and about
` 50% by weight, of ethylene isophthalate units. The two
outer layers are arranged such tha-t the outer polyester
layer from which the embossing proceeds is preferably
thinner than the other outer polyester layer.
It has been found that covering the middle layer,
which has -the lower melting point, by the higher-
melting polyester layers makes the embossability very
good, that there is no tendency for film to stick to
the tool during the embossing process, and -that
elevated temperatures can be used during the embossing
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--; process so that the embossing depth is retained even on
- exposure to elevated temperatures.
The outer layers are preferably made of the same
~-~ or different polyethylene terephthalate having a
melting point of between about 240 and about 260C and
~- the middle layer is preferably made from a copolyester
having a melting point of between about 190 and about
230C.
~; The multilayer embossable film preferably has an
asymmetrical structure; that is, the outer polyester
layer from which the embossing is carried out (i.e., to
which the embossing tool is applied) is thinner than
the other outer polyester layer, which is arranged
opposite the side from which the embossing is carried
out. The thickness of the multilayer film is generally
from about 5 to about 1000 ~m, preferably from about 10
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- to about 350 ~lm, particularly preferably Erom about lO
to about 200 ~lm. The outer polyester layer from which
-the embossing proceeds yenerally has a thickness of a-t
least abou-t 0.01 ~m, preferably from about 0.1 to abou-t
lO ~m, very particularly preferably from about 0.1 to
about 5 ~m. The thickness of the middle layer is
~ generally a-t least about 0.5 ~m, preferably between
- about 1 and about 100 ~m, particularly preferably
between about 2 and about 40 ~m. The second ou-ter
polyes-ter layer arranged opposlte the side from which
the embossing is carried ou-t generally has a thickness
of at least about l ~lm, preferably from about 1 -to
about 100 ~m, particularly preferably from about 5 to
about 50 ~m.
The preferred embossable film described above can
be produced in any desired manner such as coextrusion,
biaxially stretching, and thermofixing by conventional
processes which are known per se.
The embossing may be accomplished in any desired
manner. It is only important that the embossed cover
has a surface having raised structures such that only
the raised structures contact the adhesive surface of
the carrier, allowing easier removal of the cover
layer. A preferred procedure is to bring the
embossable structure or film under sufficient pressure
into contact with a structured surface, preferably a
roller, whose structure is then transferred to the
three-layer film.
Suitable structures have proven to be punctiform
or linear elevations having a height of from about 5 to
about 50 ~m and a mean diameter or width of from about
5 to about 20 ~m, distributed uniformly over the entire
length and width of the embossing film. The number of
- these elevations per mm2 should generally be from about
25 -to about 100, depending on the diameter/width of the
elevation. In order to produce linear elevations, the
embossing film can be provided with a groove-like or
corrugated profile in the form of, for example,
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concentric ~ings, or the like. The crucial factor is
that the total contact area of the cover to the
adhesive surface of the carrier is reduced by
impressing or embossiny regions on -the surface of -the
carrier, so that a surface carrying only punctiform or
web-like elevations is formecl. The form of this
embossing is of secondary importance.
The application of the covering to the surface
provided with a pressure-sensitive, self-adhesive
coating is expediently carried out by bringing the two
surfaces into contact. In the case of adhesive tapes
provided with a self-adhesive coating, the covering is
expediently fed to the adhesive tape, as a film tape of
the same width as the adhesive tape, on the side coated
with adhesive, af-ter produc-tion of the tape and just
before it is rolled up. The covered carrier is then
rolled up together with the adhesive tape and the
covering.
Compared with conventional coverings for self-
adhesive carriers or compared with adhesive tapes
themselves provided on the back with an abherent, the
novel combination of embossed covering film and
adhesive tape has the following advantages:
a) the entire system contains no silicone,
b) the covering film can be reused or recycled,
c) the adhesion between the self-adhesive carrier and
- the covering film can be modified within broad
limits by appropriate embossing of the covering
film, and
d) the covering film used has high strength.
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