U.S. patent application number 11/233456 was filed with the patent office on 2006-11-16 for pressure-sensitive adhesives and process for preparing them.
This patent application is currently assigned to tesa Aktiengesellschaft. Invention is credited to Thilo Dollase, Aranzazu Escudero Vallejo, Bernd Luhmann.
Application Number | 20060257650 11/233456 |
Document ID | / |
Family ID | 36808845 |
Filed Date | 2006-11-16 |
United States Patent
Application |
20060257650 |
Kind Code |
A1 |
Dollase; Thilo ; et
al. |
November 16, 2006 |
Pressure-sensitive adhesives and process for preparing them
Abstract
The invention relates to a process for preparing a
pressure-sensitive adhesive based on at least one polymer, in the
course of which said at least one polymer is crosslinked, the
polymer having functional groups Y and having been admixed,
further, with at least one kind of functionalized particles which
have at least one nonpolymeric base unit, wherein the particles
having a surface modification of the base unit, the surface
modification of the particles having at least one kind of
functional groups X, and the crosslinking of the polymer being
brought about at least in part by a reaction of the functional
groups X of the particles and the functional groups Y of the
polymer, and further to pressure-sensitive adhesives based on at
least one crosslinked polymer component, the crosslinking of the
polymer component being brought about at least in part by
incorporation of the functionalized particles, the particles having
at least one nonpolymeric base unit and also a surface modification
of this base unit, and the surface modification of the particles
having at least one kind of functional groups X which are capable
of reacting with functional groups Y present in the polymer
component, and also to the use of surface-modified functionalized
particles having a nonpolymeric base unit as crosslinking reagents
for crosslinking polymers for preparing pressure-sensitive
adhesives.
Inventors: |
Dollase; Thilo; (Hamburg,
DE) ; Escudero Vallejo; Aranzazu; (Hamburg, DE)
; Luhmann; Bernd; (Norderstedt, DE) |
Correspondence
Address: |
Norris, McLaughlin & Marcus P.A.;18th Floor
875 Third Avenue
New York
NY
10022
US
|
Assignee: |
tesa Aktiengesellschaft
Hamburg
DE
|
Family ID: |
36808845 |
Appl. No.: |
11/233456 |
Filed: |
September 22, 2005 |
Current U.S.
Class: |
428/355R |
Current CPC
Class: |
C09J 2301/408 20200801;
C01P 2004/64 20130101; C09J 7/38 20180101; C01P 2004/10 20130101;
Y10T 428/2852 20150115; C09C 1/3063 20130101; C09C 3/08 20130101;
C08K 3/18 20130101; C08J 3/242 20130101; C09C 3/12 20130101; C08K
9/04 20130101; C09C 1/3081 20130101; C09J 11/04 20130101; C01P
2004/62 20130101; B82Y 30/00 20130101; C01P 2004/32 20130101 |
Class at
Publication: |
428/355.00R |
International
Class: |
B32B 7/12 20060101
B32B007/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 12, 2005 |
DE |
10 2005 022 782.1 |
Claims
1. A process for preparing a pressure-sensitive adhesive comprised
of at least one polymer, in the course of which said at least one
polymer is crosslinked, the polymer having functional groups Y and
having been admixed, further, with at least one kind of
functionalized particles which have at least one nonpolymeric base
unit, wherein the particles have a surface modification of the base
unit, the surface modification of the particles having at least one
kind of functional groups X, and the crosslinking of the polymer
being brought about at least in part by a reaction of the
functional groups X of the particles and the functional groups Y of
the polymer.
2. The process as claimed in claim 1, wherein the at least one base
unit of the at least one functionalized kind of particle is an
inorganic amorphous or crystalline oxide.
3. The process as claimed in claim 1, wherein the at least one base
unit of the at least one functionalized kind of particle is an
alkaline earth metal salt.
4. The process as claimed in claim 1, wherein the at least one base
unit of the at least one functionalized kind of particle is a
silicate-based mineral.
5. The process as claimed in claim 1, wherein the functional groups
Y of the at least one polymer and/or the functional groups X of the
at least one kind of particle have an at least partly
photoinitiating character.
6. The process as claimed in claim 1, wherein the surface
modification of the at least one functionalized kind of particle is
brought about by means of organosilanes, surfactants,
organotitanium compounds, fatty acids and/or polyelectrolytes.
7. The process as claimed in claim 1, wherein the reaction for
bringing about the crosslinking of the pressure-sensitive adhesive
is a coupling reaction, particularly one involving the formation of
covalent bonds hydrogen bonds and/or coordinative bonds.
8. The process as claimed in claim 1, wherein the crosslinking
reaction is initiated substantially by radiation.
9. The process as claimed in claim 1, wherein the at least one
functionalized kind of particle is present in the form of singular
spherical particles, singular platelet-shaped particles and/or
singular rodlet-shaped particles.
10. The process as claimed in claim 1, wherein the at least one
functionalized kind of particle is present in the form of particle
aggregates formed from a plurality of primary particles.
11. The process as claimed in claim 9, wherein the particles have a
spatial extent of not more than 1000 nm.
12. The process as claimed in claim 1, wherein the weight fraction
of functionalized particles in the pressure-sensitive adhesive is
up to 50%.
13. A pressure-sensitive adhesive comprising at least one
crosslinked polymer component, the crosslinking of the polymer
component being brought about at least in part by incorporation of
functionalized particles, the particles having at least one
nonpolymeric base unit and also a surface modification of this base
unit, and the surface modification of the particles having at least
one kind of functional groups X which are capable of reacting with
functional groups Y present in the polymer component.
14. (canceled)
15. A cross-linking reagent comprising surface-modified
functionalized particles having a nonpolymeric base unit.
16. A self-adhesive product comprising the pressure-sensitive
adhesive of claim 13.
17. The process of claim 2, wherein said particle is a metal oxide
or a semimetal oxide.
18. The process of claim 4, wherein said silicate-based mineral is
a clay mineral.
19. The process of claim 8, wherein said radiation is UV
radiation.
20. The process as claimed in claim 10, wherein the particle
aggregates have a spatial extent of not more than 1000 nm.
21. The process as claimed in claim 20, wherein the particle
aggregates have a spatial extent in at least one spatial direction
of not more than 250 nm.
22. The process as claimed in claim 21, wherein the particle
aggregates have a spatial extent in at least one spatial direction
of not more than 100 nm.
23. The process as claimed in claim 11, wherein the particles have
a spatial extent in at least one spatial direction of not more than
250 nm.
24. The process as claimed in claim 23, wherein the particles have
a spatial extent in at least one spatial direction of not more than
100 nm.
25. The process of claim 12, wherein said weight fraction of
functionalized particles is up to 20%.
26. The process of claim 21, wherein said weight fraction of
functionalized particles is up to 12%.
Description
[0001] The present invention relates to pressure-sensitive
adhesives which preferentially can be processed without solvent and
are distinguished not only by good processing properties and, in
particular, coatability but also by good product properties. The
invention embraces the composition of innovative pressure-sensitive
adhesive formulations and also their preparation, processing, and
use in self-adhesive products. Also part of this invention is an
innovative scheme allowing the combination of good processing
properties and good product properties to be realized for
pressure-sensitive adhesive formulations of this kind.
PRIOR ART
[0002] Within the field of adhesives, pressure-sensitive adhesives
(PSAs) are notable in particular for their permanent tack. A
material which has permanent tack must at any given point in time
have an appropriate combination of adhesive and cohesive
properties. This distinguishes it, for example, from reactive
adhesives, which in the unreacted state offer virtually no
cohesion. For good product properties it is appropriate to adjust
PSAs in such a way that the balance of adhesive and cohesive
properties is at an optimum. This balance is typically achieved by
converting polymer chains present in PSA formulations into
wide-meshed networks. The nature of this network has a critical
influence on the adhesive and cohesive properties of the PSA. A
material featuring pronounced crosslinking, although having good
cohesion, nevertheless has reduced pliancy, so that the material is
unable to adapt adequately to the roughness of a substrate surface.
Moreover, a material featuring pronounced crosslinking has only a
relatively low ability to dissipate deformation energy such as
occurs under load. Both phenomena reduce the bond strength. A
material with a low level of crosslinking, in contrast, although
able to flow on rough surfaces and to dissipate deformation energy,
with the consequence that the adhesion requirements may be met, is
nevertheless inadequate in its resistance to load, owing to a
reduced cohesion.
[0003] One kind of crosslinking which has an effect on the
adhesion/cohesion balance is temporary polymer-chain interlooping.
However, this is sufficient for adequate cohesion of the PSA only
when the molar mass of the polymers is sufficiently high. PSAs
based on natural rubbers may rest solely on this crosslinking
principle. Further possibilities of setting the crosslinking of the
PSA are chemical crosslinks, which are therefore irreversible.
Chemical crosslinking can also be achieved by means of radiation
treatment of the PSAs. Another possibility is to utilize physical
crosslinking principles. Examples of such crosslinks, typically
thermoreversible, in PSAs are present in thermoplastic elastomers,
such as in certain block copolymers or semicrystalline
polymers.
[0004] Besides the crosslinking principles referred to, it is also
possible to use fillers for raising the cohesion. In that case a
combination of filler/filler interactions and filler/polymer
interactions frequently leads to the desired reinforcement of the
polymer matrix. A raising of cohesion based thereon represents a
further physical crosslinking variety.
[0005] For fillers which are mentioned with a view to a reinforcing
effect in PSAs, the class of the pyrogenic (or fumed) silicas
deserves particular mention. These silicas are used, inter alia, as
thickeners, gelling agents or thixotropic agents in a very wide
variety of fluids, utilizing their effect on the rheological
properties of the fluids. The use of hydrophilic and of hydrophobic
silica is described in this context. Examples of the use of
pyrogenic silica in the field of PSAs are described in U.S. Pat.
No. 4,163,081 by Dow Corning, in U.S. Pat. No. 4,710,536 by 3M and
in DE 102 08 843 A1 by BASF AG.
[0006] As further fillers, the use of modified phyllosilicates for
improving product properties has been described in WO 02/81586 A1
by 3M, in WO 02/24756 A2 by Rohm & Haas and in JP 2002 167,557
by Sekisui.
[0007] In all of these cases the reinforcement results from the
effect of the particles on the elasticity modulus of the elastomer
composite. The interaction in this case is brought about by
physical interactions between individual particles, on the one
hand, and between particles and polymers, on the other. Often,
however, these physical interactions are not enough to withstand
even low mechanical deformations, such as may occur, for example,
when a PSA joint is loaded by shearing or peeling. This nonlinear
phenomenon is known as the Payne effect and is manifested as a loss
of elasticity modulus under deformation. A review of the
description of this effect and of various approaches as a
mechanistic explanation is given by Heinrich and Kluppel [G.
Heinrich, M. Kluppel, Adv. Polym. Sci., 2002, 160, 1-44].
[0008] In the preceding section, a variety of examples have been
given of types of crosslinking that may be employed in PSAs for
improving the product properties, especially the cohesion. For each
of these varieties of crosslinking, the question arises of to what
extent they affect the processing properties, and more particularly
the coating characteristics. This is debated below.
[0009] Besides the product properties and hence the optimum balance
of adhesive and cohesive properties in a PSA, its processing
properties are also of central importance. Generally speaking, the
processing properties of a formulation are reduced by its
crosslinking. In a majority of cases indeed, processing becomes
impossible. It is therefore advantageous to carry out or to
initiate crosslinking not until during or after processing, and in
particular during or after coating. However, where the crosslinking
state results from the mere presence of a constituent in the
formulation, as is the case with the abovementioned fillers, then
the processing characteristics are adversely affected by its very
presence. Polymers with high molar masses are likewise among
formulation constituents which by virtue of their state of
interlooping have advantageous product properties and yet, likewise
owing to their state of interlooping, may show disadvantages in
processing properties. In both cases, namely both interlooping and
fillers, the physical principles which lead to the crosslinking of
the PSA system and hence to advantageous product properties have
negative consequences for the processing characteristics,
particularly the coatability.
[0010] Traditional approaches to escaping this dilemma have been
based on the use of solvents as operating assistants. An increased
environmental awareness and the desire for evermore efficient
production techniques, however, are underlying the trend toward
solvent-free operations. In comparison to solvent processing
methods, the polymer-based PSA base compositions, in the case of
the hotmelt processes have a state of crosslinking in their melt,
as a result of the interlooping and/or filler particles, which is
associated with significantly higher viscosities and
elasticities.
[0011] In contrast to physical modes of crosslinking, chemical
crosslinking methods afford the formation of a network which can be
initiated by an appropriate operating regime only during
processing. However, the use of chemical crosslinkers is limited by
their pot-life reactivity. If the network forms in too pronounced a
way before the material has been coated, the elasticity increase
which has already taken place results in a deterioration in the
processing properties, and reduced-quality coating outcomes may
result. One particular difficulty arises in the case of
solvent-free systems, since, here, elevated temperatures are
necessary for processing, leading at the same time to an
acceleration of the chemical crosslinking reaction.
[0012] One example of a system of this kind is described in U.S.
Pat. No. 4,524,104 by Sanyo. Radiation crosslinking methods appear
advantageous in this context, since only after coating is the
formation of a network initiated deliberately, as proposed for
example in EP 377 199, by BASF. However, in order to obtain
networks having a structure satisfying the subsequent product
requirements in respect of shear strength, polymers of decidedly
high molar mass are needed, which in turn, as a result of their
state of interlooping, may have disadvantages in terms of
processing characteristics.
[0013] Typically, the processing properties of a material
deteriorate as its elasticity goes up. Formation of a network
always leads to an increase in the storage modulus and hence to
upper elasticity. Consequently, there is a deterioration in the
fluidity, which is needed for processing of the coating, or even a
complete loss of fluidity. In the case of coating, then,
inhomogeneities may occur in the coating outcome, possibly going as
far as melt fracture. A variety of authors describe this phenomena,
especially for capillary dies and extrusion dies. Literature
references on this can be found in Pahl et al. [M. Pahl, W.
Glei.beta.le, H.-M. Laun, Praktische Rheologie der Kunststoffe und
Elastomere, 4th ed., 1995, VDI Verlag, Dusseldorf, p. 191f] and
Tanner [R. I. Tanner, Engineering Rheology, 2nd ed., 2000, Oxford
University Press, Oxford, p. 523f].
[0014] Systems are therefore sought which preferably can be coated
without solvent and which exhibit a combination of good product
properties on the one hand--and here particularly in respect of
cohesion--and improved processing properties on the other,
especially coatability.
[0015] One particularly advantageous example of systems which at
least partly satisfy this combination of requirements is
represented by block copolymers comprising segments which soften at
high temperatures (known as the hard phase) and others which at
application temperature are present in melted form. The softening
temperature of the hard phase is typically adjusted, through the
use of specific monomers, such that good product properties prevail
at room temperature and yet at temperatures that are rational from
an operational standpoint the material can easily be coated from
the melt. Since these materials typically do not have high molar
masses, their melt viscosity and elasticity, as soon as the hard
phase is in softened form, are comparatively low.
[0016] A disadvantage of the above-discussed PSAs based on block
copolymers, however, is their thermal shear strength, which is
limited by the softening of the hard domains that sets in at an
elevated temperature. A further disadvantage to be cited are the
costly and inconvenient preparation conditions for block
copolymers. In order to be able to prepare polymers having the
requisite block like structure in sufficient quality, controlled or
living polymerization techniques are necessary, some of which are
complex. Moreover, not all monomer combinations can always be
easily realized. Hence the block copolymer approach, on the one
hand, therefore, is seen as not being universally flexible for
numerous polymer systems. On the other hand there is a need for
PSAs having better thermal shear strength.
[0017] It is therefore an objective of the present invention to
provide a flexible scheme which encompasses a suitable combination
of material and process so that it is possible to prepare PSAs
which can preferably be processed without solvent and which have
good processing properties and good product properties.
[0018] As has now been found, this combination of requirements,
consisting of good processing properties and good product
properties, can be obtained by preparing crosslinked PSAs using a
process in which a specific PSA formulation comprises particles
functionalized in such a way that, during or after the coating
operation, the particles can be linked to at least one kind of
polymeric constituents of the PSA formulation by exposure to
radiation energy, in particular to electromagnetic radiation, to
particulate radiation and/or to thermal energy.
DESCRIPTION
[0019] The present invention relates to a process for preparing a
crosslinked pressure-sensitive adhesive, to crosslinked
pressure-sensitive adhesives obtainable by such a process, and to
the use of such adhesives. The invention further embraces
intermediates from such a process, particularly the composition of
innovative formulations for pressure-sensitive adhesives. The
combination of the innovative PSA formulations of the invention
with the preparation process of the invention is likewise inventive
and a central component of this specification (in this regard cf.
also FIG. 1).
[0020] The invention relates to a process for preparing a
pressure-sensitive adhesive based on at least one polymer A, in the
course of which said at least one polymer A is crosslinked, the
polymer having functional groups Y and having been admixed,
further, with at least one kind of functionalized particles B (also
called "filler particles" below). The particles have at least one
nonpolymeric base unit and also a surface modification of this base
unit, the surface modification of the base unit having at least one
kind of functional groups X. In accordance with the invention the
crosslinking of the polymer is brought about at least in part by a
reaction of the functional groups X of the particles and the
functional groups Y of the polymer. Within the sense of the
invention the crosslinking may also be brought about completely by
means of the functionalized particles.
[0021] The dependent claims relate to advantageous versions of the
process of the invention.
[0022] The invention further provides a pressure-sensitive adhesive
based on at least one crosslinked polymer component A, the
crosslinking of the polymer component A being brought about at
least in part by incorporation of functionalized particles B, the
particles B having at least one nonpolymeric base unit and also a
surface modification of this base unit, and the surface
modification of the particles B having at least one kind of
functional groups X which are capable of reacting with functional
groups Y present in the polymer component A.
[0023] A pressure-sensitive adhesive of this kind is to be
presented as being in accordance with the invention particularly if
it is obtainable by the processes described as being in accordance
with the invention.
[0024] The invention additionally provides for the use of
surface-modified particles having a nonpolymeric base unit,
particularly of particles of the kind described in the context of
this specification, as crosslinking reagents of polymers for
preparing pressure-sensitive adhesives.
[0025] Also considered as being in accordance with the invention
are the polymers A which have as yet not been crosslinked but have
been admixed with the functionalized particles B. In the
pressure-sensitive adhesive to be crosslinked there may be further
components present.
[0026] The PSA formulations of the invention comprise at least one
kind of a polymer A which contains at least one kind of groups of
type Y, and also at least one kind of filler particles B containing
on their surface at least one kind of groups of type X. Groups of
type Y and of type X have been selected for the purposes of this
invention such that exposure to electromagnetic radiation,
particulate radiation and/or thermal energy forms a bond between at
least one group of type Y and at least one functional group of type
X, thereby producing an adduct of type B-X'-Y'-A (see FIG. 2). The
designation X' here denotes that the structure of the functional
group X may have altered following reaction. Similarly, the
designation Y' indicates that the structure of the functional group
Y may have altered following reaction. It is likewise in accordance
with the invention for the functional groups X and Y not to have
altered in their structure and yet still to have entered into a
linkage.
[0027] In this description the terms "electromagnetic radiation"
and "particulate radiation" are to be understood to mean all forms
of radiation, a summary having been given by V. D. McGinniss [V. D.
McGinniss in Encyclopedia of Polymer Science and Engineering, H. F.
Mark, N. M. Bikales, C. G. Overberger, G. Menges (eds.), 2nd ed.,
1986, Wiley, New York, vol. 4, p. 418ff]. These radiation forms can
be employed with preference in accordance with the invention.
[0028] Through the inventive use of the innovative formulations
described here, in combination with the process described here,
advantageously crosslinked PSAs are obtained. The functionalized
filler particles B act as polyfunctional crosslinkers. As a result
of their capacity to link two or more polymer chains in one
crosslinking point it is possible to reduce the molar mass of the
polymeric constituents of the PSA that are to be crosslinked (on
the basis of polymeric constituents for the PSA which--in relation
to customary, prior-art processes--have a reduced molar mass).
There follows an improvement in the processing characteristics.
Conversely, within the context of this invention, it is also
possible to admix the filler particles of the invention to PSAs
which comprise crosslinkable polymers of low molar mass. Following
exposure to electromagnetic radiation, particulate radiation and/or
thermal energy, different network structures are obtained than if
the filler particles of the invention had not been present. A
feature of this innovative state of crosslinking is that it
correlates with improved product properties, particularly an
increased cohesion of the PSA. Typically it is characteristic of
the innovative state of crosslinking that the adhesive properties
of the PSAs of the invention are at least at the level also
occupied by a crosslinked PSA which contains no inventive filler
particles but has been processed in a comparable way and has a
comparable gel fraction.
[0029] An advantageous approach is for the PSA formulations of the
invention, comprising at least one kind of an inventive polymer A
and at least one kind of a functionalized filler particle B, to
have good processing properties in the raw state--that is, before
processing commences. By processing properties for the purposes of
this invention are meant in particular the viscosity of the PSA
formulation and also its elasticity. The viscosity is reported as
zero-shear viscosity .eta..sub.0 for different temperatures. It can
be obtained from viscosity curves determined by capillary
viscosymmetry. The elasticity is reported in the form of the first
normal stress difference N.sub.1, again at different temperatures.
The data for the first normal stress difference, too, can be
obtained from capillary viscosymmetry experiments. Both variables,
the viscosity and the first normal stress difference, are generally
dependent on shear rates for PSA formulations. Depending on process
and the shear rates which occur therein, therefore, they may vary
for a given PSA formulation. For the description of this invention
it is sensible to limit oneself to one shear rate; however, this
does not restrict in this respect the processes which can be used
in accordance with the invention. As one such shear rate the shear
rate of 1000 s.sup.-1 is selected as a representative, advantageous
value. For the processing properties and particularly the
coatability it is very advantageous not to exceed a defined ratio
of elasticity and viscosity at the shear rate dictated by the
process. If this ratio is too high, the elastic character of the
material to be coated is predominant. A consequence of that can be
melt fracture, which is manifested in a non-homogeneous coating
pattern (M. Pahl, W. Glei.beta.le, H.-M. Laun, Praktische Rheologie
der Kunststoffe und Elastomere, 4th ed., 1995, VDI Verlag,
Dusseldorf, p. 191f).
[0030] In accordance with information gained from
capillary-viscosimetric rheology, the ratio R=N.sub.1/.tau. of
first normal stress difference N. and shear stress .tau. determines
the processing characteristics of a polymer melt [W. Glei.beta.le,
Rheol. Acta, 1982, 21, 484-487; M. Pahl, W. Glei.beta.le, H.-M.
Laun, Praktische Rheologie der Kunststoffe und Elastomere, 4th ed.,
1995, VDI Verlag, Dusseldorf, p. 320ff]. The shear stress .tau. is
the product of viscosity and shear rate. The numerator of the ratio
N.sub.1/.tau. hence describes the elastic properties of the
material, the denominator the viscous properties. The latter,
moreover, illustrates the dependence on the operating speed in the
form of the shear rate. Above a critical rate for R, flow anomalies
occur. If, therefore, at the shear rates which prevail during
processing, success is achieved in reducing N.sub.1 by a design of
material, or at least in not causing it to grow further as a result
of additional crosslinking effects, the expectation is then that
the material will be able to be coated without melt
inhomogeneities. This can be accomplished, for example, by not
initiating crosslinking until after coating, such as is possible,
for example, in the case of radiation treatment. The irradiated and
thus crosslinked material has an increased elasticity and, in
association with this, a higher first normal stress difference, and
in this state could not be processed with a good coating pattern.
The uncrosslinked melt, however, is less elastic, exhibits a lower
first normal stress difference, and can be coated successfully. For
PSAs with good cohesion there is frequently a need for polymers
having high molar masses. These polymers, however, may have high
elasticities even in the chemically uncrosslinked state, owing to
intermolecular interactions, such as interlooping, and this may
lead to disadvantages in the coating characteristics.
[0031] The innovative concept of the invention encompasses
accomplishing the cohesion of the PSA of the invention essentially
by means of an improved state of crosslinking via chemical linking
of polymers to filler surfaces. A high polymer molar mass is
therefore no longer mandatory and, consequently, the coating
characteristics are not so pronouncedly restricted as a result of
chain interlooping. The particles themselves, during processing,
are in the form of a disperse phase in the PSA formulation. Since
at this time they have not yet undergone chemical linkage with
polymeric constituents of the formulation, at this time their
contribution to the elasticity of the formulation is incomplete.
Only when the crosslinking reaction is initiated, during and/or
after coating, is the desired cohesion produced. The requirements
imposed on the PSA formulations of the invention are therefore that
the formulation in the uncrosslinked state should exhibit good
processing properties, provided for example by a low first normal
stress difference, and in particular the ratio R, and in the
crosslinked state should exhibit good cohesion, provided for
example by the holding power or the gel fraction of a self-adhesive
tape test specimen.
[0032] Advantageous PSAs of the invention, obtained by way of the
inventive coating and crosslinking operation, typically have a
holding power according to test D that is at least 50% higher,
preferably at least 100% higher, than that of a formulation coated
and crosslinked in exactly the same way but containing no filler
particles of the invention and yet having a comparable gel fraction
(test B). The adhesion, given by the bond strength according to
test C, of the PSA system of the invention is typically at least at
the same level occupied by that of the aforementioned reference
system, or preferably is in fact at least 25% higher. At the same
time, the R value of the inventive PSA in the uncrosslinked state,
at a temperature which is appropriate in a way that is specific to
the particular material, of between 25.degree. C. and 300.degree.
C., exhibits virtually no increase, likewise in comparison to a
formulation that contains no filler particles of the invention and
is also uncrosslinked, and remains at values of preferably not more
than R=3.5 (test A2). The viscosity of the PSAs of the invention at
the same temperature is no higher or only slightly higher,
specifically not more than, preferably, 25% higher, than that of a
formulation that contains no filler particles of the invention and
is also uncrosslinked (test A1).
Composition of Inventive PSA Formulations
[0033] The PSA formulations of the invention comprise at least one
kind of polymer, A, and at least one kind of filler particle, B,
the at least one polymer kind A being able, via groups Y present in
it, to join with groups X, located on the surface of the at least
one filler particle kind B, through exposure to electromagnetic
radiation, particulate radiation and/or thermal energy during
and/or after a coating operation. The PSA of the invention may
optionally comprise further constituents in addition to polymers A
and filler particles B. This section will address the polymers A of
the invention, the fillers B of the invention, and further
constituents which may be used optionally in the PSA formulations
of the invention, and will also describe the nature of the groups X
and Y.
[0034] The PSAs of the invention contain advantageously up to 50%
by weight of at least one filler particle kind B, preferably up to
20% by weight, very preferably up to 12% by weight.
Polymers A
[0035] The at least one polymer kind A is preferably in accordance
with the invention when it has a molar mass of not more than 10 000
000 g/mol, preferably not more than 500 000 g/mol. Furthermore, the
at least one polymer kind A preferably has a softening temperature
of less than 100.degree. C., more preferably less than 20.degree.
C. The at least one polymer kind A may be of linear, branched,
star-shaped or grafted structure, to give but a few examples, and
may be in the form of a homopolymer or random copolymer. The term
"random copolymer" encompasses for the purposes of this invention
not only copolymers in which the comonomers used for the
polymerization have been incorporated in purely random fashion but
also those in which there are gradients in the comonomer
composition and/or local accumulations of individual comonomer
kinds in the polymer chains.
[0036] The molar mass is to be understood in this context as
referring to the weight average of the molar mass distribution, as
is obtainable, for example, via gel permeation chromatography
analyses. By softening temperature in this context is meant the
glass transition temperature for amorphous systems and the melting
temperature for semicrystalline systems, and may be determined, for
example, by dynamic differential calorimetry (DSC). Where numerical
values are given for softening temperatures, they relate in the
case of amorphous systems to the middle-point temperature of the
glass stage and in the case of semicrystalline systems to the
temperature at maximum heat evolution during the phase
transition.
[0037] Within the sense of this invention it is possible, moreover,
for the at least one polymer kind A to be a block copolymer. Of
particular advantage are block copolymers in which, preferably,
each of the blocks present (independently of one another) has a
molar mass of less than 1 000 000 g/mol, preferably less than 250
000 g/mol, is of linear, branched, star-shaped or grafted structure
and/or is in the form of a homopolymer or random copolymer. With
further advantage at least one kind of block has a softening
temperature of less than 100.degree. C., preferably less than
20.degree. C. The individual kinds of block occurring in the block
copolymer may differ with regard to the comonomer composition and
optionally may differ in their molar mass and/or softening
temperature and/or structure (e.g., linear or branched identity).
The different polymer arms in star-shaped and grafted systems may
be chemically different in nature: that is, may be composed of
different monomers and/or may have a different comonomer
composition.
[0038] Polymers of kind A are also preferred in accordance with the
invention when they contain at least one kind of groups Y which are
able to enter into a bond, during or after a coating operation,
with groups X present on the surface of the at least one filler
particle kind B, on exposure to electromagnetic radiation,
particulate radiation and/or thermal energy. The groups of the at
least one kind Y may be present in a diversity of ways in the at
least one polymer kind A. The at least one polymer kind A may be
constructed, for example, as a homopolymer from monomers which
contain the at least one kind of groups Y. Furthermore, the at
least one polymer kind A may also be constructed as a random
copolymer which is obtained at least from one kind of monomers
which contain the at least one kind of groups Y and, optionally,
from one or more kinds of monomers which contain no such groups. A
further possibility is for the at least one polymer kind A to
contain the at least one kind of groups Y only at certain points
along the polymer backbone. Examples of such embodiments include
groups which are located at chain ends, in the region of chain
points or blocking-agent points, in the region of branching points
or in the region of block connection points. Polymers of the at
least one kind A are particularly preferred in accordance with the
invention when the polymer molecule contains on average at least
two such groups. It is possible, furthermore, for the at least two
groups Y to be introduced into the at least one polymer A by way of
a grafting reaction. It is likewise in accordance with the
invention to introduce the at least two groups Y into the at least
one polymer kind A by carrying out a polymer-analogous reaction.
Furthermore, any desired combinations of the stated modes of
functionalization are in accordance with the invention.
[0039] As examples of polymers A, but without wishing to impose any
restriction, mention may be made of the following homopolymers and
random copolymers as being advantageous for the purposes of this
invention: polyethers, such as polyethylene glycol, polypropylene
glycol or polytetrahydrofuran, polydienes, such as polybutadiene or
polyisoprene, hydrogenated polydienes, such as
polyethylene-butylene or polyethylene-propylene, rubbers, such as
natural rubber, nitrile rubber or chloroprene rubber, butadiene
rubber, isoprene rubber, and polyisobutylene, polyolefins, such as
ethylene homopolymers or copolymers, propylene homopolymers or
copolymers, metallocene-catalyzed polyolefins, polysiloxanes,
polyalkyl vinyl ethers, polymers of unfunctionalized
.alpha.,.beta.-unsaturated esters, copolymers based on
.alpha.,.beta.-unsaturated esters, copolymers based on alkyl vinyl
ethers, and also ethylene-vinylacetate copolymers, EPDM rubbers,
and styrene-butadiene rubbers. Further random copolymers which can
be used with advantage are obtained by copolymerizing isoprene
and/or butadiene, feature 1,4, 1,2 and/or 3,4, or 1,4 and/or 1,2,
incorporation of the monomers into the polymer chain, and may be in
fully or partly hydrogenated form.
[0040] Copolymers which can be used with particular advantage for
the purposes of this invention are random copolymers based on
unfunctionalized x,p-unsaturated ethers. When they are used for the
at least one polymer kind A with copolymer character, then monomers
which can be used for their preparation are, advantageously, in
principle all compounds familiar to the skilled worker that are
suitable for polymer synthesis. Preference is given to using
.alpha.,.beta.-unsaturated alkyl esters of the general structure
CH.sub.2.dbd.CH(R.sup.1)(COOR.sup.2) (I) where R.sup.1.dbd.H or
CH.sub.3 and R.sup.2.dbd.H or represents linear, branched or
cyclic, saturated or unsaturated alkyl radicals having 1 to 30, in
particular having 4 to 18, carbon atoms.
[0041] Monomers which can be used with great preference in the
sense of general structure I for polymers A with copolymer
character include acrylic and methacrylic esters with alkyl groups
consisting of 4 to 18 carbon atoms. Specific examples of such
compounds, without wishing to be restricted by this enumeration,
include n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate,
n-pentyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate,
n-heptyl acrylate, n-heptyl methacrylate, n-octyl acrylate, n-octyl
methacrylate, n-nonyl acrylate, n-nonyl methacrylate, n-decyl
acrylate, n-decyl methacrylate, dodecyl acrylate, dodecyl
methacrylate, hexadecyl acrylate, hexadecyl methacrylate, octadecyl
acrylate, octadecyl methacrylate, their branched isomers, such as
sec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate,
tert-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl
methacrylate, and isooctyl acrylate, and also cyclic monomers such
as, for example, cyclohexyl acrylate, cyclohexyl methacrylate,
norbornyl acrylate, norbornyl methacrylate, isobornyl acrylate and
isobornyl methacrylate.
[0042] Likewise possible for use as monomers for polymers A with
copolymer character are acrylic and methacrylic esters which
contain aromatic radicals, such as phenyl acrylate, benzyl
acrylate, benzoin acrylate, phenyl methacrylate, benzyl
methacrylate or benzoin methacrylate.
[0043] A further possibility for use in accordance with the
invention are ethoxylated and propoxylated acrylates and
methacrylates. In systems of this kind the acrylate or methacrylate
side chains are composed formally of an oligomer or polymer or
ethylene oxide or of propylene oxide.
[0044] It is additionally possible, optionally, to use vinyl
monomers from the following groups: vinyl esters, vinyl ethers,
vinyl halides, vinylidene halides, and also vinyl compounds
containing aromatic rings and heterocycles in a position. For the
vinyl monomers which can be employed optionally, mention may be
made by way of example of selected monomers which can be used in
accordance with the invention: vinyl acetate, vinylformamide,
vinylpyridine, ethyl vinyl ether, 2-ethylhexyl vinyl ether, butyl
vinyl ether, vinyl chloride, vinylidene chloride, acrylonitrile,
styrene, and .alpha.-methylstyrene.
[0045] In one preferred version of this invention the at least one
polymer kind A contains its at least two groups Y in the form of at
least one specific comonomer which has been randomly copolymerized
during the polymerization of the polymer. The molar fraction
(chemical amount fraction) of this at least one specific comonomer
in relation to the composition of the total monomer mixture during
the preparation of the total polymer is up to 50% by weight,
preferably up to 20% by weight, very preferably up to 5% by weight.
The specific character of this at least one comonomer is expressed
in the fact that it carries at least one group Y which is able to
enter into a bond, during or after a coating operation, with at
least one group X, located on the surface of the at least one
filler particle kind B, on exposure to electromagnetic radiation,
particulate radiation and/or thermal energy. Examples of groups X
and Y are described in the section "Combinations of groups X and
Y". Particular preference is given to using monomers based on
.alpha.,.beta.-unsaturated esters which contain these groups. It is
also possible for groups Y to be joined by way of a
polymer-analogous reaction with the polymer A at the sites at which
these specific comonomers have been incorporated. A further
possibility is for these specific comonomers to be derivatized with
groups Y prior to polymerization; in other words, for comonomers
with functionalization which is not necessarily in accordance with
the invention to be modified, prior to polymerization and hence
preparation of a polymer kind of type A, with a chemical assembly
via which the at least one inventive group Y is incorporated into
the comonomer and, following this modification reaction and
subsequent polymerization, is available for the forming of a
linkage, in accordance with the invention, with at least one group
X.
[0046] As examples of comonomers which carry functional groups,
mention may be made--without wishing to impose any restriction--of
allyl acrylate, allyl methacrylate, tetrahydrofurfuryl acrylate,
tetrahydrofurfuryl methacrylate, 2-hydroxyethyl acrylate,
2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate,
3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate,
4-hydroxybutyl methacrylate, glycidyl acrylate, glycidyl
methacrylate, acrylated benzophenone, methacrylated benzophenone,
crotonic acid, maleic acid, maleic anhydride, itaconic acid,
itaconic anhydride, 2-dimethylaminoethyl acrylate,
2-dimethylaminoethyl methacrylate, 3-dimethylaminopropyl acrylate,
3-dimethylaminopropyl methacrylate, N-tert-butylacrylamide,
N-tert-butylmethacrylamide, N-isopropylacrylamide,
N-isopropylmethacrylamide, acrylamide, methacrylamide,
N-methylolacrylamide, N-methylolmethacrylamide, acrylic acid,
methacrylic acid, vinyl alcohol, 2-hydroxyethyl vinyl ether,
3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether and allyl
glycidyl ether.
[0047] If the at least one polymer kind A is a block copolymer then
in the simplest case the copolymers present are diblock copolymers
of the form PA-PA', composed of a block PA and a block PA', which
differ in respect of the starting monomers selected and may
optionally be different in their softening temperature and/or molar
mass and/or structure (e.g., linear or branched). Further
embodiments of polymers A with block copolymer character, without
wishing to impose any restriction, are triblock copolymers of the
type PA-PA'-PA'', block copolymers of the type PA-PA'-PA''-PA', and
higher block copolymers whose structures continue this series.
Triblock copolymers and higher block copolymers are in accordance
with the invention, in the sense of polymers A with block copolymer
character, when all blocks linked directly to one another are
different in respect of the selected starting monomers and also,
optionally, in their molar mass and/or softening temperature and/or
structure (e.g., linear or branched). Further, triblock copolymers
and higher block copolymers are in accordance with the invention,
in the sense of polymers A, if two or more of the blocks which are
not linked directly to one another are not different from one
another in respect of the selected starting monomers and also,
optionally, in their molar mass and/or softening temperature and/or
structure (e.g., linear or branched). A preferred version of a
polymer A with block copolymer character is a triblock copolymer of
the type PA-PA'-PA'', where PA and PA'' are identical in respect of
the selected starting monomers, molar mass, softening temperature,
and structure. The block linkage in polymers A with block copolymer
character may take a linear form or alternatively a star-shaped
embodiment, or a graft copolymer variant. Each individual block may
be constructed as a homopolymer block or copolymer block. The
blocks are therefore subject to the same definitions as given in
the section "Homopolymers" and "Random copolymers".
[0048] Where a block copolymer is employed as polymer A, then
preferably at least one kind of block contains functionalizations
of type Y. Particular preference is given to diblock copolymers
which contain functionalizations of type Y in only one kind of
block; symmetrical triblock copolymers which contain
functionalizations of type Y only in two end blocks; and triblock
copolymers which contain functionalities of type Y only in the
middle block.
Filler Particles B
[0049] As the at least one filler particle kind B for the purposes
of this invention use is made preferably of filler particles in
which the base units without surface modifications have softening
temperatures of greater than 200.degree. C., preferably of greater
than 500.degree. C. Furthermore, systems of the kind whose
softening temperature (based on the unmodified base units) is above
the decomposition temperature are in accordance with the invention
when the decomposition temperature is above 200.degree. C.,
preferably above 500.degree. C.
[0050] The materials on which the base unit of the at least one
filler particle kind B is based may be inorganic in nature or may
be an organic/inorganic hybrid material and may have an amorphous,
partly crystalline or crystalline character. Base units of organic
nature can also be used for the purposes of the invention.
[0051] In terms of their structure, the filler particles may be
present preferably in spherical form, rodlet form or platelet form.
Separate particles, often also called primary particles, are in
accordance with the invention just as much as aggregates formed
from a plurality of primary particles. Such systems often exhibit a
fractal superstructure. Where the particles are formed from
crystallites, the primary particle form depends on the nature of
the crystal lattice. Platelet form systems can also be present in
the form of layer stacks.
[0052] In one advantageous embodiment of this invention the at
least one functionalized filler kind is present in the
pressure-sensitive adhesive substantially in the form of singular
spherical particles. In that case the particle diameters have
values of less than 500 nm, preferably of less than 100 nm, very
preferably of less than 25 nm. In a further advantageous version of
this invention the at least one functionalized filler kind is
present in the pressure-sensitive adhesive substantially in the
form of singular platelet-shaped particles. The layer thickness of
such platelets then has values of preferably less than 10 nm and a
greatest diameter of preferably less than 1000 nm. In a further
advantageous version of this invention the at least one filler kind
is present in the pressure-sensitive adhesive substantially in the
form of singular rodlet-shaped particles. In this case these
rodlets have a diameter of less than 100 nm and a length of less
than 15 .mu.m. The rodlets may also be curved and/or flexible.
Furthermore, it is possible with advantage for the purposes of this
invention for the at least one filler kind to be present in the
pressure-sensitive adhesive in the form of primary particle
aggregates. These aggregates have a gyration radius (to be
understood in analogy to the term "radius of gyration" as known
from polymers) of less than 1000 nm, preferably of less than 250
nm. Particular preference is given for the purposes of this
invention to using filler particles of the kind whose spatial
extent in at least one direction is less than 250 nm, preferably
less than 100 nm, very preferably less than 50 nm. It is possible
for the purposes of this invention, furthermore, to use
combinations of the aforementioned types of filler.
[0053] Typical classes of compound, advantageous in accordance with
the invention, of which the base unit of the at least one filler
particle kind B is composed are oxides of inorganic
nature--particularly metal oxides and/or semimetal oxides--salts of
alkaline earth metals, and silicate-based minerals, especially clay
minerals and clays. The amorphous or crystalline metal oxides that
can be used in accordance with the invention include, for example,
silicon dioxide, aluminum oxide, titanium dioxide, zirconium
dioxide, and zinc oxide. The skilled worker is familiar with
further systems, which may likewise be used in accordance with the
invention. Alkaline earth metal salts include, for example,
carbonates, sulfates, hydroxides, phosphates, and hydrogen
phosphates of magnesium, of calcium, of strontium, and of barium.
The clay minerals and clays which can be used in accordance with
the invention include, in particular, silicatic systems such as
serpentines, kaolins, talc, pyrophyllite, smectites such as
particularly montmorillonite, vermiculites, illites, mica, brittle
mica, chlorites, sepiolite, and palygorskite. Additionally it is
possible to use synthetic clay minerals such as hectorites and also
systems related thereto, such as Laponite.RTM. from Laporte, and
fluorohectorites and systems related thereto, such as Somasif.RTM.
from Co-Op, in accordance with the invention.
[0054] The at least one filler particle kind B is in a
surface-modified form. Surface modification reagents that are
typical and advantageous in accordance with the invention are
organosilanes and surfactants, but also organotitanium compounds,
fatty acids or polyelectrolytes such as, for example, short-chain
polymers having a high acrylic acid fraction. The primary function
of these surface modification reagents is to create compatibility
between the particle surface and the matrix into which the
particles are to be dispersed. As a further function, surface
modification reagents are used in order to prevent relatively small
particles coming together to form larger objects. It is very
advantageous for the purposes of the invention to use at least one
kind of surface modification reagent which in addition to the
compatibilizing and aggregation-preventing function also affords
the possibility of entering, via at least one group X incorporated
in the at least one kind of surface modification reagent, into a
connection with at least one group Y, present in at least one
polymer kind A, on exposure to electromagnetic radiation,
particulate radiation and/or thermal energy, during or after a
coating operation. A filler particle carries on its surface
preferably at least 10 groups of the at least one kind X, more
preferably at least 50.
[0055] Filler particles which in their natural form (in the form of
the base unit without surface modification) contain hydroxide
groups on the surface afford the possibility, preferably, of a
reaction with chlorosilanes or alkoxysilanes. Hydrolysis of the
silane is followed by condensation of silanol groups with the
hydroxide groups on the particle surface. If at least one
substituent on the central silicon atom of the silane is an organic
radical, then in the case of complete surface coverage with silane
molecules an organophilic casing is linked covalently in this way
to the filler particle, and hence the particles are made compatible
with the polymer matrix. The concepts and typically used classes of
material which can be employed for the purposes of this invention
are described, for example by R. N. Rothon [R. N. Rothon (ed.),
"Particulate-Filled Polymer Composites" 2nd ed., 2003, Rapra
Technology, Shawbury, 153-206].
[0056] Two classes of silanes can be distinguished in particular
for the purposes of this invention: on the one hand, those which,
in addition to the groups capable of reaction with the base
surface, carry exclusively organic radicals which are chemically
inert (see structure II); on the other, those which, in addition to
the groups capable of reaction with the base surface, contain at
least one organic radical which carries at least one group X that
is able to enter into a bond with at least one group Y present in
at least one polymer kind A on exposure to electromagnetic
radiation, particulate radiation and/or thermal energy, during or
after a coating operation (see structure III). In silane II at
least one of substituents A, B, and D is a hydrolyzable group,
i.e., a chlorine atom or an alkoxy group, for example. At least one
of substituents B, C, and D is an organic radical which is composed
of a linear, branched or cyclic hydrocarbon, which may also be
aromatic and is of low molecular mass or oligomeric or polymeric in
nature. If there is more than one hydrolyzable group among
substituents A, B, and D, then the groups involved may be
chemically identical or different, or meeting the above definition
of hydrolyzable groups. If there is more than one organic radical
among substituents B, C, and D, then these radicals may likewise be
chemically identical or different, or meeting the above definition
of organic radicals. In silane III at least one of substituents A,
E, and F is a hydrolyzable group, i.e., a chlorine atom or an
alkoxy group, for example. At least one of substituents E, F, and G
is an organic radical which is composed of a linear, branched or
cyclic hydrocarbon, which may also be aromatic and is of low
molecular mass or oligomeric or polymeric in nature and which
additionally contains at least one group X which is able, during or
after a coating operation, to enter into a bond with at least one
group Y present in at least one polymer kind A on exposure to
electromagnetic radiation, particulate radiation and/or thermal
energy. If there is more than one hydrolyzable group among
substituents A, E, and F, then the groups involved may be
chemically identical or different. If there is more than one
organic radical among substituents E, F, and G, then the radicals
involved may likewise be chemically identical or different, or
meeting the above definition of organic radicals. ##STR1##
[0057] Advantageous embodiments of silanes of structure II that are
useful in accordance with the invention are those in which only A
is employed as a hydrolyzable group and B, C, and D are organic
radicals, of which B and D are chemically identical and C is
chemically different. Further advantageous embodiments of silanes
of structure II that are useful in accordance with the invention
are those in which A and B are employed as chemically identical
hydrolyzable groups and C and D are chemically identical organic
radicals. Further advantageous embodiments of silanes of structure
II that are useful in accordance with the invention are those in
which A, B, and D are employed as chemically identical hydrolyzable
groups and C is an organic radical.
[0058] Advantageous embodiments of silanes of structure III that
are useful in accordance with the invention are those in which only
A is employed as a hydrolyzable group and E, F, and G are organic
radicals, of which E and F are chemically identical and G is
chemically different. G contains the at least one group X which,
during or after a coating operation, is able to enter into a bond
with at least one group Y present in at least one polymer kind A on
exposure to electromagnetic radiation, particulate radiation and/or
thermal energy. Further advantageous embodiments of silanes of
structure III that are useful in accordance with the invention are
those in which A, E, and F are employed as chemically identical
hydrolyzable groups and G is an organic radical which contains the
at least one group X which, during or after a coating operation, is
able to enter into a bond with at least one group Y present in at
least one polymer kind A on exposure to electromagnetic radiation,
particulate radiation and/or thermal energy.
[0059] Hydrolyzable groups A, B, D, E, and F which may be employed
with advantage in silanes II and silanes III are halogen atoms,
especially chlorine, and/or alkoxy groups, such as methoxy, ethoxy,
n-propoxy, isopropoxy, n-butoxy, sec-butoxy or tert-butoxy groups.
Acetoxy groups are a further possibility for use. The additional
examples of hydrolyzable groups, known to the skilled worker, may
likewise be employed for the purposes of this invention.
[0060] The organic radicals B, C, D, E, and F which may be employed
in silanes II and silanes III include by way of example, with no
claim to completeness, methyl, ethyl, n-propyl, isopropyl, n-butyl,
sec-butyl, and tert-butyl groups, pentyl groups and also the
branched isomers, hexyl groups and also the branched isomers,
heptyl groups and also the branched isomers, octyl groups and also
the branched isomers, nonyl groups and also the branched isomers,
decyl groups and also the branched isomers, undecyl groups and also
the branched isomers, dodecyl groups and also the branched isomers,
tetradecyl groups and also the branched isomers, hexadecyl groups
and also the branched isomers, octadecyl groups and also the
branched isomers, and eicosyl groups and also the branched isomers.
The organic radicals of the invention may, furthermore, contain
cyclic and/or aromatic moieties. Representative structures are
cyclohexyl, phenyl, and benzyl groups. It is further in accordance
with the invention if as at least one organic radical use is made
of oligomers or polymers which contain at least one hydrolyzable
silyl group.
[0061] The organic radicals E, F, and G in which there is at least
one group X which, during or after a coating operation, is able to
enter into a bond with at least one group Y present in at least one
polymer kind A on exposure to electromagnetic radiation,
particulate radiation and/or thermal energy include, for example,
the compounds compiled in the following list (the list makes no
claim to completeness): methyl, ethyl, n-propyl, isopropyl,
n-butyl, sec-butyl, and tert-butyl groups, pentyl groups and also
the branched isomers, hexyl groups and also the branched isomers,
heptyl groups and also the branched isomers, octyl groups and also
the branched isomers, nonyl groups and also the branched isomers,
decyl groups and also the branched isomers, undecyl groups and also
the branched isomers, dodecyl groups and also the branched isomers,
tetradecyl groups and also the branched isomers, hexadecyl groups
and also the branched isomers, octadecyl groups and also the
branched isomers, and eicosyl groups and also the branched isomers.
The organic radicals of the invention may, furthermore, contain
cyclic and/or aromatic moieties. Representative structures are
cyclohexyl, phenyl, and benzyl groups. It is further in accordance
with the invention if as at least one organic radical use is made
of oligomers or polymers which contain at least one hydrolyzable
silyl group. Where a radical from the above list is employed as one
or more of radicals E, F, and G, it is additionally modified by a
chemical moiety which contains at least one group X.
[0062] Examples of silanes of structure II that can be used with
preference for the purposes of this invention are
methyltrimethoxysilane, methyltriethoxysilane,
dimethyldimethoxysilane, dimethyldiethoxysilane,
trimethylethoxysilane, ethyltrimethoxysilane,
propyltrimethoxysilane, propyltriethoxysilane,
isobutyltrimethoxysilane, isobutyltriethoxysilane,
octyltrimethoxysilane, octyltriethoxysilane,
isooctyltrimethoxysilane isooctyltriethoxysilane,
hexadecyltrimethoxysilane, hexadecyltriethoxysilane,
octadecylmethyldimethoxysilane, phenyltrimethoxysilane,
phenyltriethoxysilane, cyclohexylmethyldimethoxysilane, and
dicyclopentyldimethoxysilane.
[0063] An example of silyl-functionalized oligomers or polymers
which can be employed in accordance with the invention is
polyethylene glycol which has been linked with a trimethoxysilane
group.
[0064] Representatives of silanes of structure III which can be
used with particular preference for the purposes of this invention
and which carry at least one functionalization are, for example,
N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,
N-(2-aminoethyl)-3-amino-propyltriethoxysilane,
3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane,
3-aminopropyldiethoxymethylsilane,
N-(2-aminoethyl)-3-aminopropyldimethoxymethylsilane,
(N-butyl)-3-aminopropyltrimethoxysilane,
3-(N-ethylamino)-2-methylpropyltrimethoxysilane,
4-amino-3,3-dimethylbutyltrimethoxysilane,
4-amino-3,3-dimethylbutyldimethoxymethylsilane,
(N-cyclohexyl)aminomethyldimethoxymethylsilane,
(N-cyclohexyl)-aminomethyltrimethoxysilane,
(N-phenyl)-3-aminopropyltrimethoxysilane,
(N-phenyl)amino-methyldimethoxymethylsilane,
(N-benzyl-2-aminoethyl)-3-aminopropyltrimethoxysilane
[2-(N-benzyl-N-vinylamino)ethyl]-3-aminopropyltrimethoxysilane
hydrogen chloride,
[2-(N-benzyl-N-vinylamino)ethyl]-3-aminopropyltrimethoxysilane,
bis(3-propyltriethoxysilyl)amine, vinyltrimethoxysilane,
vinytriethoxysilane, vinyltri(2-methoxyethoxy)silane,
vinyltriisopropoxysilane, vinyldimethoxymethylsilane,
vinyltriacetoxysilane, 3-triethoxysilylpropylsuccinic anhydride,
3-glycidyloxypropyltrimethoxysilane,
3-glycidyloxy-propyltriethoxysilane,
2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,
3-glycidyloxy-propyldiethoxymethylsilane,
3-methacryloyloxypropyltrimethoxysilane,
3-methacryloyloxypropyltriethoxysilane,
3-methacryloyloxypropyltriisopropoxysilane,
3-methacryloyloxypropyldimethoxymethylsilane,
3-methacryloyloxypropyldiethoxymethylsilane,
3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane,
3-isocyanatopropyltrimethoxysilane,
3-isocyanatopropyltriethoxysilane,
isocyanatomethyltrimethoxysilane,
isocyanatomethyldimethoxymethylsilane,
tris[3-(trimethoxysilyl)propyl]isocyanurate,
3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane,
2-hydroxy-4-(3-triethoxysilylpropoxy)benzophenone,
4-(3'-chlorodimethylsilylpropoxy)benzophenone,
3-mercaptopropyltrimethoxysilane,
3-mercaptopropyldimethoxymethylsilane,
bis(3-triethoxysilylpropyl)disulfane,
bis(3-triethoxysilylpropyl)tetrasulfane,
bis(triethoxysilylpropyl)polysulfane, and
octadecylaminodimethyltrimethoxysilylpropylammonium chloride.
[0065] Silanes which are disclosed in WO 00/43539 by Biochip
Technologies or in EP 281 941 B1 by Ciba Geigy, and those published
by Kolar et al. [A. Kolar, H. F. Gruber, G. Greber, JMS Pure Appl.
Chem., 1994, A31, 305-318], may likewise be employed for the
purposes of this invention as silanes of structure III. It is also
possible to use organic titanium compounds, optionally in
conjunction with silanes.
[0066] It is likewise of advantage in accordance with the invention
to use silanes of structure III which have been derivatized with a
chemical assembly which contains at least one group X. By this is
meant that silanes of structure III with non inventive
functionalization are modified, before and/or after the surface
modification reaction with the filler particles, with a chemical
assembly which introduces the at least one inventive group X into
the silane and after this silane modification reaction and the
surface modification reaction is available to form a bond with at
least one group Y.
[0067] The surface modification may take place completely by means
of at least one representative of the silanes III. It is also
possible, though, to use a combination of silanes III and silanes
II. Such a combination is inventive if at least 1% by weight,
preferably at least 5% by weight, of at least one representative of
the silanes III is used.
[0068] Silanes are used with particular preference for the purposes
of this invention as surface modifiers if filler particles are
employed which, at least in the state of the non-surface-modified
base unit, carry hydroxyl groups on the surface. Examples of this
kind of filler particles are metal oxides, especially amorphous
silicon dioxide. An exemplary possibility of realizing a surface
modification is given by Bauer and coworkers (F. Bauer, H. Ernst,
U. Decker, M. Findeisen, H.-J. Glasel , H. Langguth, E. Hartmann,
R. Mehnert, C. Peuker, Macromol. Chem. Phys., 2000, 201, 2654-2659]
and Rothon [R. N. Rothon (ed.), Particulate Filled Polymer
Composites, 2nd ed., 2003, Rapra Technology, Shawbury, pp.
153-206].
[0069] Particles which in the state of the non-surface-modified
base unit carry ionic groups on the surface can be modified
preferably using surfactants and/or fatty acids.
[0070] As surfactants it is possible in general to employ all
quaternary ammonium compounds, protonated amines, organic
phosphonium ions, and amino carboxylic acids that exhibit
amphiphilic behavior. Advantageous use may be made of ammonium
compounds which carry at least three organic radicals, such as
alkylammonium salts, trimethylalkylammonium salts,
dimethyldialkylammonium salts, methylbenzyldialkylammonium salts,
dimethylbenzylalkylammonium salts or alkylpyridinium salts.
Furthermore, alkoxylated quaternary ammonium compounds may be
employed.
[0071] Two classes of surfactants may be distinguished for the
purposes of this invention: on the one hand,.those which, in
addition to the groups capable of interaction with the base
surface, carry exclusively organic radicals which are chemically
inert (see structure IV); on the other, those which, in addition to
the groups capable of linking with the base surface, contain at
least one organic radical which carries at least one group X which,
during or after a coating operation, is able to enter into a bond
with at least one group Y present in at least one polymer kind A on
exposure to electromagnetic radiation, particulate radiation and/or
thermal energy (see structure V). In surfactant IV the substituents
A, B, and D may independently of one another be organic radicals or
hydrogen; the substituent C is a long-chain organic radical. Any
anions can be employed as counterions. Examples are chloride,
bromide, hydrogen sulfate, dihydrogen phosphate, and
tetrafluoroborate. The skilled worker is aware of others which may
likewise be employed for the purposes of this invention.
Independently of one another, the organic radicals may be linear or
branched, saturated or unsaturated, may be composed of aliphatic,
olefinic and/or aromatic elements, and may contain 1 to 22 carbon
atoms. Typical substituents used as organic radicals include methyl
groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl
groups, sec-butyl groups, tert-butyl groups, linear or branched
pentyl groups, linear or branched hexyl groups, linear or branched
heptyl groups, linear or branched octyl groups, benzyl groups, or
groups with higher numbers of carbon atoms. Long-chain organic
radicals employed include, preferably, dodecyl groups, tetradecyl
groups, hexadecyl groups, octadecyl groups or eicosyl groups in
saturated or unsaturated form. Since the starting materials for
surfactant manufacture are frequently natural products, alkyl
substituents with only one length of chain are rarely encountered.
Instead there is frequently a mixture of alkyl chains different in
length. Particularly preferred long-chain organic radicals used are
tallow radicals (unsaturated) or hydrogenated tallow radicals
(saturated). It is also in accordance with the invention for the
surfactant function to be taken on by oligomers or polymers which
have been functionalized such that they carry at least one cationic
group. ##STR2##
[0072] Examples which may be used with preference for the purposes
of this invention as surfactants of structure IV are
hexadecyltrimethylammonium chloride or bromide,
methylditallowylammonium chloride or bromide, in which the tallow
radicals ("tallowyl") may be saturated or unsaturated,
dimethyltallowylbenzylammonium chloride or bromide, in which the
tallowyl radicals may be saturated or unsaturated,
dimethyltallowyl(2-ethylhexyl)ammonium chloride or bromide, in
which the tallowyl radicals may be saturated or unsaturated, and
dimethylditallowylammonium chloride or bromide, in which the
tallowyl radicals may be saturated or unsaturated.
[0073] Surfactants which are disclosed in EP 900 260 B1 by Akzo
Nobel, U.S. Pat. No. 5,739,087 by Southern Clay, U.S. Pat. No.
5,718,841 by Rheox, U.S. Pat. No. 4,141,841 by Procter &
Gamble, and by H Gro.beta.mann [H. Gro.beta.mann in Katalysatoren,
Tenside und Mineraloladditive, H. Falbe, U. Hasserodt (ed.), 1978.
G. Thieme, Stuttgart, p. 135ff] may likewise be employed for the
purposes of this invention as surfactants of structure IV.
[0074] Advantageous embodiments of surfactants of structure V that
are useful in accordance with the invention are those in which the
substituents E, F, and G independently of one another may be
organic radicals or hydrogen and the substituent C is a long-chain
organic radical. Any anions can be employed as counterions.
Examples are chloride, bromide, hydrogen sulfate, dihydrogen
phosphate, and tetrafluoroborate. Independently of one another, the
organic radicals may be linear or branched, saturated or
unsaturated, may be composed of aliphatic, olefinic and/or aromatic
elements, and may contain 1 to 22 carbon atoms. Typical
substituents used as organic radicals include methyl groups, ethyl
groups, n-propyl groups, isopropyl groups, n-butyl groups,
sec-butyl groups, tert-butyl groups, linear or branched pentyl
groups, linear or branched hexyl groups, linear or branched heptyl
groups, linear or branched octyl groups, benzyl groups, or groups
with higher numbers of carbon atoms. Long-chain organic radicals
employed include, preferably, dodecyl groups, tetradecyl groups,
hexadecyl groups, octadecyl groups or eicosyl groups in saturated
or unsaturated form. With regard to the starting materials for
manufacturing surfactant V as well, natural products are frequently
employed, so that rarely are alkyl substituents of a single chain
length present; instead, a mixture of alkyl chains of different
lengths is present. Particularly preferred long-chain organic
radicals used are tallow radicals (unsaturated) or hydrogenated
tallow radicals (saturated). It is also in accordance with the
invention for the surfactant function to be taken on by oligomers
or polymers which have been functionalized such that they carry at
least one cationic group. With regard to the surfactants V at least
one of substituents E, F, G, and C contains at least one group X
which, during or after a coating operation, is able to enter into a
bond with at least one group Y present in at least one polymer kind
A on exposure to electromagnetic radiation, particulate radiation
and/or thermal energy. Surfactants disclosed in EP 900 260 B1 by
Akzo Nobel, U.S. Pat. No. 5,739,087 by Southern Clay, U.S. Pat. No.
5,718,841 by Rheox, U.S. Pat. No. 4,141,841 by Procter &
Gamble, and by H Gro.beta.mann [H. Gro.beta.mann in Katalysatoren,
Tenside und Mineraloladditive, H. Falbe, U. Hasserodt (ed.), 1978.
G. Thieme, Stuttgart, p. 135ff] may likewise be employed for the
purposes of this invention as surfactants of structure V, provided
they have been modified with at least one group X, in addition,
under certain circumstances, to the structure disclosed.
[0075] Examples which can be employed with preference for the
purposes of this invention as surfactants of structure V are
methyltallowyldi(2-hydroxyethyl)ammonium. chloride or bromide,
allyldimethyltetradecyl chloride or bromide,
allyldimethylhexadecylammonium chloride or bromide, and
allyldimethylhexadecylammonium chloride or bromide.
[0076] For the purposes of this invention it is possible with
preference to use a combination, of surfactants IV and surfactants
V. In this embodiment of the invention, representatives of
surfactants V are present at a level of at least 1% by weight,
preferably at least 5% by weight, among all of the surfactants
employed. Furthermore, it is possible to use surfactants IV or V in
combination with cationic compounds which, though not themselves
surfactants, carry at least one group X which is able, during or
after a coating operation, to enter into a bond with at least one
group Y present in at least one polymer kind A on exposure to
electromagnetic radiation, particulate radiation and/or thermal
energy. At least 1% by weight, preferably at least 5% by weight, of
a cationic compound of this kind is used in accordance with the
invention in combination with surfactants IV and/or V. Where
cationic compounds of this kind are employed, the sum of
surfactants IV and V employed is not more than 99% by weight,
preferably not more than 95% by weight, it being possible for
surfactants V to be replaced entirely by surfactants IV. Examples
of such cationic compounds are
(2-acryloyloxyethyl)(4-benzoylbenzyl)dimethylammonium chloride or
bromide, 3-trimethyl-ammoniopropylmethacrylamide chloride or
bromide, 2-trimethylammmonioethyl methacrylate chloride or bromide,
3-dimethylalkylammoniopropylmethacrylamide chloride or bromide, and
2-dimethylalkylammoniomethyl methacrylate chloride or bromide.
[0077] Surfactants are used with particular preference for the
purposes of this invention if the filler particles employed have
negative charges or partial charges on the surface (in the state of
the non-surface-modified base unit). Examples of this kind of
filler particles are certain clay minerals, particularly smectites,
in which intercalated cations may be replaced by surfactants. One
principle whereby such replacement may take place has been
formulated by Lagaly [G. Lagaly in Tonminerale und Tone, K.
Jasmund, G. Lagaly (ed.), 1993, Steinkopff, Darmstadt, p.
366ff].
[0078] It is possible, furthermore, to use combinations of
inventive silanes and inventive surfactants. At least one of the
surface modification reagents employed contains at least one group
X which, during or after a coating operation, is able to enter into
a bond with at least one group Y present in the polymer kind A on
exposure to electromagnetic radiation, particulate radiation and/or
thermal energy.
Further Constituents
[0079] It is additionally in accordance with the invention to use,
optionally, polymers C containing at least one group of type X,
and/or polymers C containing at least one group X and at least one
group of type Y, and/or polymers C containing neither type-X nor
type-Y groups. The composition of those polymers, employable
optionally, that contain no groups of type X or Y are subject to
the same details in terms of construction, composition, choice of
monomers, softening temperature, and structure as contained in the
definition of the polymers A, apart from the details given there in
respect of groups Y. Optionally employable polymers containing at
least one group X are subject to the details given for polymers A,
but such polymers C contain groups of kind X and not groups of kind
Y and can therefore, during or after a coating operation, enter
into a bond with at least one group Y of the at least one polymer
of kind A by exposure to electromagnetic radiation, particulate
radiation and/or thermal energy. The incorporation of groups X into
polymers C is subject to the same details given for groups Y in the
polymers A. Where polymers are employed that carry groups X and Y,
then the same details, in terms of construction, composition,
choice of monomers, softening temperature, and structure, apply as
contained in the definition of the polymers A, but with the
addition that there is also at least one group X present in the
polymer. For the incorporation of groups X and Y into polymers C
which carry both kinds of groups, the details which apply are the
same as those given for the groups Y in the polymers A.
[0080] As further constituents the PSA formulations of the
invention May comprise tackifier resins, plasticizers, rheological
additives, catalysts, initiators, stabilizers, compatibilizers,
coupling reagents, crosslinkers, antioxidants, other aging
inhibitors, light stabilizers, flame retardants, pigments, dyes,
further fillers, especially those not included in at least one
filler particle kind B, and/or expandants.
Combinations of Groups X and Y
[0081] The PSAs of the invention comprise at least one polymer kind
A and at least one filler particle kind B. Polymers A contain at
least two groups Y; filler particles B contain at least one kind of
groups X. Groups X and Y are chosen for the purposes of this
invention such that between these groups X and Y or by way of these
groups X and Y it is possible to bring about coupling between
polymers A and filler particles B. The coupling is initiated during
or after the coating operation by exposure to electromagnetic
radiation, particulate radiation and/or thermal energy. The
coupling involves at least one group X and at least one group Y. By
coupling of at least one group X and at least one group Y is meant
for the purposes of this invention, in particular [0082] a chemical
reaction in which the at least one group X reacts with the at least
one group Y and leads to the formation of a covalent bond, [0083]
the formation of hydrogen bonds between the at least one group X
and the at least one group Y, and/or [0084] the formation of a
coordinative bond as a result, for example, of formation of a
complex, involving the at least one group X and the at least one
group Y, so that at least one donor/acceptor bond is formed.
[0085] The coupling in this case may take place between the groups
X and Y directly or else by mediation through one or more further
substances, such as coupling reagents or crosslinkers. The position
and number of groups X and Y in the polymers A and filler particles
B that can be used in accordance with the invention are subject to
the same definitions given for the polymers A and the filler
particles B.
[0086] Where the coupling of the invention between the at least one
polymer kind A and the at least one filler particle kind B is to
proceed via the groups Y and X as a chemical reaction, the groups X
and Y involved are defined in particular in accordance with the
following remarks.
[0087] The PSAs of the invention comprise at least one constituent
which comprises at least one kind of inventive segments having the
general structure (R.sup.oR.sup.ooR.sup.oooC)--X. R.sup.o, R.sup.oo
and R.sup.ooo may independently of one another be saturated or
unsaturated, aliphatic or aromatic hydrocarbon radicals which may
also be linked to one another and may be identical or different.
For the purposes of this invention it is also possible for the
carbon atom in (R.sup.oR.sup.ooR.sup.oooC)--X itself to be
unsaturated. In that case said carbon atom is linked only to X and
to one or two of the radicals R.sup.o, R.sup.oo or R.sup.ooo. The
radicals R.sup.o, R.sup.oo, and R.sup.ooo may independently of one
another include any number of heteroatoms. The radicals R.sup.o,
R.sup.oo, and R.sup.ooo may be of low molecular mass or may be
polymeric in nature. Up to two of the radicals R.sup.o, R.sup.oo,
and R.sup.ooo may also be hydrogen atoms, moreover. At least one of
the radicals R.sup.o, R.sup.oo, and R.sup.ooo is linked by a
chemical or ionic bond, by chemisorption or physisorption, to a
filler particle of kind B. The group needed for the coupling
reaction is designated X.
[0088] The at least one inventive segment of structure
(R.sup.oR.sup.ooR.sup.oooC)--X can be reacted with at least one
segment which is present in at least one further constituent of the
PSA of the invention and which has the general structure
(R*R**R***C)--Y. R*, R** and R*** may independently of one another
be saturated or unsaturated, aliphatic or aromatic hydrocarbon
radicals which may also be linked to one another and may be
identical or different. For the purposes of this invention it is
also possible for the carbon atom in (R*R**R***C)--Y itself to be
unsaturated. In that case said carbon atom is linked only to Y and
to one or two of the radicals R*, R** or R***. The radicals R*,
R**, and R*** may independently of one another include any number
of heteroatoms. The radicals R*, R**, and R*** may be of low
molecular mass or may be polymeric in nature. Up to two of the
radicals R*, R**, and R*** may also be hydrogen atoms, moreover. At
least one of the radicals R*, R**, and R*** is linked by a chemical
bond, to a polymer chain of kind A. The group needed for the
coupling reaction is designated Y. In specific versions of this
invention, single or plural radicals R*, R** or R*** may be of the
same identity as R.sup.o, R.sup.oo or R.sup.ooo. It is also in
accordance with the invention if group X and group Y are identical.
In this specific case the coupling takes place advantageously by
means of a coupling reagent or by the action of a catalyst or
initiator. For the purposes of this invention it is particularly
advantageous if the coupling reaction is initiated by exposure to
electromagnetic radiation and/or particulate radiation.
[0089] For the purposes of this invention it is possible to use an
arbitrarily large number of further groups, which may react with a
group X and/or with a group Y.
[0090] A coupling reaction may proceed by chemical reaction
directly between the groups X and Y, so forming a species
(R.sup.oR.sup.ooR.sup.oooC)--X'-Y'-(CR*R**R***) (see FIG. 2). In
the case of a chemical reaction, X' and Y' are the reaction
products of the groups X and Y respectively. In specific cases the
coupling of groups X and Y requires a coupling reagent
X.sup.a--Y.sup.a or X.sup.a--R.sup.a--Y.sup.a. X.sup.a and Y.sup.a
are groups capable of reaction with groups X and Y, respectively,
and may be identical or different. It is also possible,
furthermore, to link two groups X via coupling reagent
Y--R.sup.b--Y and also two groups Y via a coupling reagent
X--R.sup.b--X. R.sup.a and R.sup.b can be saturated or unsaturated,
aliphatic or aromatic hydrocarbon radicals and may contain an
arbitrary number of heteroatoms. The radicals R.sup.a and R.sup.b
may be of low molecular mass or may be polymeric in nature.
[0091] Table 1 lists a number of examples of X and Y which can be
used in accordance with the invention. Combinations of groups which
can be used with advantage are marked with a cross. In certain
circumstances, additional reagents and/or special conditions are
needed for the reaction between the groups indicated. Reagents of
this kind are then added to the PSA formulation (see "Further
constituents" section). Specific conditions such as temperature or
radiation also come within the intention of this invention. The
table does not make any claim to completeness, but is intended
merely to indicate examples of groups which can be employed for the
purposes of this invention, and combinations of groups that can be
employed. Further groups and combinations, known to the skilled
worker, for corresponding reactions may likewise be employed in
accordance with the invention. The radicals R.sup.1, R.sup.2
R.sup.3, R.sup.4, R.sup.5, and R.sup.6 and also R.sup.a, R.sup.b,
R.sup.c, R.sup.d, R.sup.e and R.sup.f in Table 1 may independently
of one another be saturated or unsaturated, aliphatic or aromatic
hydrocarbon radicals, which may contain any number of heteroatoms
and may be of low molecular mass or may be polymeric in nature,
and/or, alternatively, may be hydrogen atoms. In accordance with
the definition above, the radicals may be identical or different in
construction. The radicals R.sup.1, R.sup.2, and R.sup.3 may be
linked to one another, the radicals R.sup.5 and R.sup.6 may be
linked to one another, the radicals R.sup.a, R.sup.b, and R.sup.c
may be linked to one another, and the radicals R.sup.e and R.sup.f
may be linked to one another. Cyclic acid anhydrides such as maleic
anhydride or succinic anhydride may be attached arbitrarily as a
chemical group to polymers A or filler particles B. Maleic
anhydride offers the possibility, furthermore, of being
incorporated as a comonomer in polymers A.
[0092] The entry "-PI" in Table 1 refers to a group which is
possessed of a photoinitiator function. Irradiation with UV light
of appropriate wavelength activates the group and, depending on the
nature of the photoinitiator, a free-radical reaction or a cationic
reaction is initiated. Suitable representatives of such groups are
type-I photoinitiators, in other words .alpha.-cleaving initiators
such as benzoin derivatives and acetophenone derivatives, benzil
ketals or acylphosphine oxides, type-II photoinitiators, in other
words hydrogen abstractors such as benzophenone derivatives and
certain quinones, diketones and thioxanthones, and cationic
photoinitiators, such as "photoacid generators" such as arylated
sulfonium or iodonium salts and dimerized arylated imidazole
derivatives. Further, triazine derivatives can be used to initiate
free-radical and cationic reactions.
[0093] Photoinitiating groups X and/or Y of type I include for the
purposes of this invention, preferably, benzoin, benzoin ethers
such as, for example, benzoin methyl ether, benzoin isopropyl
ether, benzoin butyl ether, benzoin isobutyl ether, methylolbenzoin
derivatives such as methylolbenzoin propyl ether,
4-benzoyl-1,3-dioxolane and its derivatives, benzil ketal
derivatives such as 2,2-dimethoxy-2-phenylacetophenone or
2-benzol-2-phenyl-1,3-dioxolane,
.alpha.,.alpha.-dialkoxyacetophenones such as
.alpha.,.alpha.-dimethoxyacetophenone and
.alpha.,.alpha.-diethoxyactophenone, .alpha.-hydroxyalkyl phenones
such as 1-hydroxycyclohexyl phenyl ketone,
2-hydroxy-2-methyl-1-phenylpropanone and
2-hydroxy-2-methyl-1-(4-isopropylphenyl)propanone,
4-(2-hydroxyethoxy)phenyl-2-hydroxy-2-methyl-2-propanone and its
derivatives, .alpha.-aminoalkylphenones such as
2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-2-one and
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one,
acylphosphine oxides such as
2,4,6-trimethylbenzoyldiphenylphosphine oxide and
ethyl-2,4,6-trimethylbenzoylphenylphosphinate, and
O-acyl-.alpha.-oximino ketones.
[0094] Photoinitiating groups of type II that can be used with
preference in accordance with the invention are based for example
on benzophenone and its derivatives such as
2,4,6-trimethylbenzophenone or 4,4'-bis(dimethylamino)benzophenone,
thioxanthone and its derivatives such as 2-isopropylthioxanthone
and 2,4-diethylthioxanthone, xanthone and its derivatives, and
anthraquinone and its derivatives.
[0095] Type-II photoinitiators are used with particular advantage
in combination with nitrogen-containing coinitiators, known as
amine synergists. For the purposes of this invention it is
preferred to use tertiary amines. Furthermore, in combination with
type-II photoinitiators, hydrogen atom donors are employed
advantageously. Examples thereof are substrates which contain amino
groups. Examples of amine synergists are methyldiethanolamine,
triethanolamine, ethyl 4-(dimethylamino)benzoate, 2-n-butoxyethyl
4-(dimethylamino)-benzoate, isoacryloyl 4-(dimethylamino)benzoate,
2-(dimethylaminophenyl)ethanone, and also unsaturated tertiary
amines copolymerizable therewith, (meth)acrylated amines,
unsaturated, amine-modified oligomers and polymers based on
polyester or polyether, and amine-modified (meth)acrylates. For the
purposes of this invention it is possible for such chemical
assemblies to be linked to polymers and/or fillers. For the
purposes of this invention it is also possible to use any desired
combinations of different varieties of type-I and/or type-II
photoinitiating groups.
[0096] In one particularly preferred version of this invention,
groups of photoinitiating character are present as groups Y in at
least one kind of polymers A.
[0097] In a further particularly preferred version of this
invention, groups of photoinitiating character are present as
groups X in at least one kind of functionalized filler particles
B.
[0098] When the coupling of the invention between the at least one
polymer kind A and the at least one filler particle kind B proceeds
via the groups Y and X by way of the formation of hydrogen bonds,
the groups X and Y involved are defined in accordance with the
following remarks. In this regard see, for example, D. Philp, J. F.
Stoddard, Angew. Chem., 1996, 108, 1242-1286 or C. Schmuck, W.
Wienand, Angew. Chem., 2001, 113, 4493-4499.
[0099] The PSAs of the invention comprise in this case at least one
constituent which comprises one kind of segments having the general
structure (R.sup.#R.sup.##R.sup.###C)--X.sup.#. R.sup.#, R.sup.##
and R.sup.### may independently of one another be saturated or
unsaturated, aliphatic or aromatic hydrocarbon radicals which may
also be linked to one another and may be identical or different.
For the purposes of this invention it is also possible for the
carbon atom in (R.sup.#R.sup.##R.sup.###C)--X.sup.# itself to be
unsaturated. In that case said carbon atom is linked only to
X.sup.# and to one or two of the radicals R.sup.#, R.sup.190 # or
R.sup.#. The radicals R.sup.#, R.sup.##, and R.sup.### may
independently of one another include any number of heteroatoms. The
radicals R.sup.#, R.sup.190 #, and R.sup.### may be of low
molecular mass or may be polymeric in nature. Up to two of the
radicals R.sup.#, R.sup.190 #, and R.sup.### may also be hydrogen
atoms, moreover. At least one of the radicals R.sup.#, R.sup.##,
and R.sup.### is linked by a chemical or ionic bond, by
chemisorption or physisorption, to a filler particle of kind B. The
group needed for the coupling reaction is designated X.sup.#.
[0100] The at least one inventive segment of structure
(R.sup.#R.sup.##R.sup.###C)--X.sup.# is able to form hydrogen bonds
with at least one functional segment which is present in at least
one further constituent and which has the general structure
(R.sup..about.R.sup..about..about.R.sup..about..about..about.C)--Y.sup..a-
bout.. R.sup..about., R.sup..about..about. and
R.sup..about..about..about. may independently of one another be
saturated or unsaturated, aliphatic or aromatic hydrocarbon
radicals which may also be linked to one another and may be
identical or different. For the purposes of this invention it is
also possible for the carbon atom in
(R.sup..about.R.sup..about..about.R.sup..about..about..about.C)--Y.sup..a-
bout. itself to be unsaturated. In that case said carbon atom is
linked only to Y.sup..about. and to one or two of the radicals
R.sup..about., R.sup..about..about. or R.sup..about..about..about..
The radicals R.sup..about., R.sup..about..about., and
R.sup..about..about..about. may independently of one another
include any number of heteroatoms. The radicals
R.sup..about.R.sup..about..about., and R.sup..about..about..about.
may be of low molecular mass or may be polymeric in nature. Up to
two of the radicals R.sup..about., R.sup..about..about., and
R.sup..about..about..about. may also be hydrogen atoms, moreover.
At least one of the radicals R.sup..about., R.sup..about..about.,
and R.sup..about..about..about. is linked by a chemical bond, to a
polymer chain of kind A. The group needed for the coupling reaction
is designated Y.sup..about.. In specific versions of this
invention, single or plural radicals R.sup..about.,
R.sup..about..about., and R.sup..about..about..about. may be of the
same identity as R.sup.#, R.sup.## or R.sup.###. It is also in
accordance with the invention if group X.sup.# and group
Y.sup..about. are identical. In this specific case the coupling
takes place by means of a coupling reagent.
[0101] For the purposes of this invention it is possible to use an
arbitrarily large number of further groups, which may enter into a
bond with at least one group X and/or at least one group Y.
[0102] A coupling reaction may proceed by formation of hydrogen
bonds directly between the groups X.sup.# and Y.sup.# so forming a
species
(R.sup.#R.sup.##R.sup.###C)--X.sup.#--Y.sup..about.--(CR.sup..about.R.sup-
..about..about.R.sup..about..about..about.) (see FIG. 2). In
specific cases the coupling of groups X.sup.# and Y.sup..about.
requires a coupling reagent X.sup.#a--Y.sup..about.a or
X.sup.#a--R.sup.a'--Y.sup..about.a. X.sup.#a and Y.sup..about.a are
groups capable of forming hydrogen bridges with groups X.sup.# and
Y.sup..about., respectively, and may be identical or different. It
is also possible, furthermore, to link two groups X.sup.# via
coupling reagent Y.sup..about.--R.sup.b--Y.sup..about. and also two
groups Y- via a coupling reagent
X.sup..about.--R.sup.b'--X.sup..about.. R.sup.a' and R.sup.b' can
be saturated or unsaturated, aliphatic or aromatic hydrocarbon
radicals and may contain an arbitrary number of heteroatoms. The
radicals R.sup.a' and R.sup.b' may be of low molecular mass or may
be polymeric in nature.
[0103] The coupleable groups may be unidentate or, preferably
multidentate. Denticity refers in this case to the capacity of a
group to form a certain number of hydrogen bonds. Hydrogen bonds
between unidentate or, preferably, multidentate functional
segments, as structure-forming elements, are known from a variety
of examples. In nature, hydrogen bonds between complementary
functional segments are used for the construction, of
deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). A specific
combination of donor and acceptor sites makes it possible for
couplings to be able to take place only in accordance with the
lock-and-key principle. Where, for example, the functional segments
.alpha. ("key" type) and .beta. ("lock" type) are complementary
segments which are able to form hydrogen bonds, then a compound is
possible between .alpha. and .beta. but not between .alpha. and
.alpha. or between .beta. and .beta.. With regard to the selection
of the functional segments, nature, when constructing DNA,
restricts itself to the two organic base pairs adenine/thymine (or
uracil instead of thymine in RNA) as bidentate segments and
cytosine/guanine as tridentate segments.
[0104] For the purposes of this invention it is possible to use
polymers A and filler particles B having groups based on adenine,
thymine, uracil, cytosine, guanine, derivatives thereof, and also
further compounds capable of forming hydrogen bonds by the
lock-and-key principle, such as, for example, 2-ureido-4-pyrimidone
and its derivatives, 2,6-diacetylaminopyridine and its derivatives,
diacetylpyrimidine and its derivatives, and ureidoacylpyrimidine
and its derivatives. This listing makes no claim to completeness.
Instead, the skilled worker is aware of further systems which can
be used in accordance with the invention. When this kind of
functionalization is chosen, then, for the purposes of this
invention, either the at least one polymer kind A carries groups of
the "key" type and the at least one filler particle B carries
groups of the "lock" type, or vice versa. FIG. 3 shows two examples
of the coupling of reactive constituents via formation of hydrogen
bonds, by using two complementary groups; on the one hand, the
direct coupling of polymer A and filler particle B, and, on the
other, the coupling of polymer A and filler particle B using a
coupling reagent.
[0105] Likewise possible in accordance with the invention is the
coupling of groups via coordinate bonds. Examples of coordinate
bonds are ligand-central atom bonds in complexes, i.e., the
formation of a coordinate bond with metal atoms which may be
present in elemental form, in the form of metal salts and/or in the
form of metal complexes, and also all other donor-acceptor bonds
(in this regard see, for example, D. Philp, J. F. Stoddard, Angew.
Chem., 1996, 108, 1242-1286; M. Rehahn, Acta Polym., 1998, 49,
201-224 or B. G. G. Lohmeijer, U. S. Schubert, J. Polym. Sci. A
Polym. Chem., 2003, 41, 1413-1427).
[0106] If this coupling principle is chosen for the purposes of
this invention, then the PSA comprises filler particles of kind B
which contain groups having the general structure
(R.sup.517R.sup..sctn..sctn.R.sup..sctn..sctn..sctn.C)--X.sup..sctn..
R.sup..sctn., R.sup..sctn..sctn. and R.sup..sctn..sctn..sctn. may
independently of one another be saturated or unsaturated, aliphatic
or aromatic hydrocarbon radicals which may also be linked to one
another and may be identical or different. For the purposes of this
invention it is also possible for the carbon atom in
(R.sup..sctn.R.sup..sctn..sctn.R.sup..sctn..sctn..sctn.C)--X.sup..sctn.
itself to be unsaturated. In that case said carbon atom is linked
only to X.sup..sctn. and to one or two of the radicals
R.sup..sctn., R.sup..sctn. or R.sup..sctn..sctn..sctn.. The
radicals R.sup..sctn., R.sup..sctn..sctn., and
R.sup..sctn..sctn..sctn. may independently of one another include
any number of heteroatoms. The radicals R.sup..sctn.,
R.sup..sctn..sctn., and R.sup..sctn..sctn..sctn. may be of low
molecular mass or may be polymeric in nature. Up to two of the
radicals R.sup..sctn., R.sup..sctn..sctn., and
R.sup..sctn..sctn..sctn. may also be hydrogen atoms, moreover. At
least one of the radicals R.sup..sctn., R.sup..sctn..sctn., and
R.sup..sctn..sctn..sctn. is linked by a chemical or ionic bond, by
chemisorption or physisorption, to a filler particle of kind B. The
group needed for the coupling reaction is designated X.sup.517 . At
the same time the PSA comprises polymers of kind A which contain
groups having the general structure
(R.sup..dbd.R.sup..dbd..dbd.R.sup..dbd..dbd..dbd.C)--Y.sup..dbd..
R.sup..dbd., R.sup..dbd..dbd. and R.sup..dbd..dbd..dbd. may
independently of one another be saturated or unsaturated, aliphatic
or aromatic hydrocarbon radicals which may also be linked to one
another and may be identical or different. For the purposes of this
invention it is also possible for the carbon atom in
(R.sup..dbd.R.sup..dbd..dbd.R.sup..dbd..dbd..dbd.C)--Y.sup..dbd.
itself to be unsaturated. In that case said carbon atom is linked
only to Y.sup..dbd. and to one or two of the radicals R.sup..dbd.,
R.sup..dbd..dbd. or R.sup..dbd..dbd..dbd.. The radicals
R.sup..dbd., R.sup..dbd..dbd., and R.sup..dbd..dbd..dbd. may
independently of one another include any number of heteroatoms. The
radicals R.sup..dbd., R.sup..dbd..dbd., and R.sup..dbd..dbd..dbd.
may be of low molecular mass or may be polymeric in nature. Up to
two of the radicals R.sup..dbd., R.sup..dbd..dbd., and
R.sup..dbd..dbd..dbd. may also be hydrogen atoms, moreover. At
least one of the radicals R.sup..dbd., R.sup..dbd..dbd., and
R.sup..dbd..dbd..dbd. is linked by a chemical bond, to a polymer
chain of kind A. The group needed for the coupling reaction is
designated Y.sup..dbd.. The groups X.sup..sctn. and Y.sup..dbd. may
be identical or different. If they are different, then one of the
varieties of groups takes on the donor function and the other the
acceptor function that are necessary for the formation of
coordinate bonds. If both groups are of the same kind, then the
coordinate bond is formed by way of a coupling reagent.
[0107] The groups in the polymers A and filler particles B are
advantageously constructed such that they are capable of being able
to form coordinate bonds with metals of type M, which may be in
elemental form, in metal salt form or in the form of metal
complexes. Metal complexes may also be polynuclear. Unidentate or
multidentate segments may be employed. The coupling principle is
depicted diagrammatically in FIG. 4. At least two groups of the
"key" type couple by coordination of M, which takes on the "lock"
function. During the formation of the coordinate bond, the
structure of M may alter to become M'. This may be manifested in
altered oxidation states or else in an altered ligand structure
and/or ligand composition. When using metal atoms it is
particularly advantageous for the purposes of this invention to
take special precautions to disperse M in the PSA. This is
preferably accomplished by choosing particularly suitable
counterions, in the case of metal salts, or particularly suitable
complex ligands, in the case of metal complexes. Suitable
counterions and complex ligands therefore take on the function of
compatibilizers and dispersing assistants. It is particularly
advantageous to disperse the metal atom M in a meltable matrix that
contains no constituents able to enter into coordinate bonds with
M. This mixture is metered into the rest of the PSA formulation,
comprising at least one polymer kind A and at least one filler
particle kind B, not until immediately before the coating
operation.
[0108] Particular preference is given to coupling using chelating
segments. Examples of ligands which may be employed as groups are
bipyridine and terpyridine and also their derivatives,
acetylacetonate and its derivatives, ethylenediaminetetraacetic
acid and its derivatives, nitrilotriacetic acid and its
derivatives, hydroxyethylethylenediaminetriacetic acid and its
derivatives, diethylenetriaminepentaacetic acid and its
derivatives, and carboxylic acids. This listing makes no claim to
completeness. Instead, the skilled worker will be aware of further
systems which may be used in accordance with the invention. These
groups are not reactive with one another. All constituents
containing these groups can therefore be used in one mass stream.
The coupling of the groups takes place as soon as the mixture
comprising metal atom M is admixed to the mass stream, which for
the purposes of this invention takes place immediately prior to the
coating operation.
[0109] Suitable metal atoms for the purposes of this invention are
all those chemical elements capable of acting as an acceptor for
coordinate bonds. These are alkaline earth metals, preferably Ca
and/or Mg, transition metals, preferably Ti, Mn, Fe, Co, Ni, Cu,
Zn, Mo, Ru, Rh, Pd, W, Re, Os, Ir and/or Pt, and also Al and
lanthanoids. Examples of suitable compatibilizers and dispersing
assistants for these metal atoms which can be used in accordance
with the invention are alkoxides of aliphatic or aromatic,
saturated or unsaturated molecules containing any desired number of
heteroatoms, it being possible for these molecules to be of low
molecular mass or to be polymeric in nature. Additionally suitable
are open-chain or cyclic unsaturated hydrocarbons which contain any
number of heteroatoms and may be of low molecular mass or may be
polymeric in nature. Further dispersing assistants and
compatibilizers for M, useful in accordance with the invention, are
low molecular mass chelating compounds of organic identity.
[0110] Generally speaking, M can be an acceptor group ("key") which
in conjunction with a donor group of the "lock" type is able to
form a coordinate bond. In this case the acceptor group may be
attached to polymer A and filler particle B or else may be used in
the form of coupling reagents. This general case is depicted
diagrammatically in FIG. 5. It is further in accordance with the
invention to use filler particles B and polymers A furnished with
acceptor groups in combination with coupling reagents which carry
donor groups.
[0111] For the purposes of this invention it is possible for any
desired combinations of different sorts of coupling reactions to be
employed. In accordance with the invention at least one kind of
coupling reaction is used.
Methods of Producing Self-Adhesive Products
[0112] The production of self-adhesive products of the invention
embraces the operating steps of formulating/compounding, of
coating, and of crosslinking.
Compounding Methods
[0113] The formulations of the invention can be produced using
solvents in solvent kneading apparatus or else, for example, by
using high-speed dispersers. Preferably, however, formulations of
this kind are produced solventlessly. Appropriate for this purpose
are kneading apparatus, in batch operation, and extruders, such as
twin-screw extruders, in continuous operation. Suitable compounding
units for the purposes of this invention are those which contain
dispersive and, optionally, distributive mixing elements.
Dispersive mixing elements ensure very fine distribution of the
filler particles in the formulation, while the distributive
elements homogenize melted constituents such as resins or polymers
in the mixture of the PSA formulation. Particularly appropriate in
solventless batch operation are Banbury mixers and also kneading
apparatus of Buss or Baker-Perkins type. In continuous operation,
twin-screw extruders in corotating mode can be used with
preference.
Coating Methods
[0114] Coating methods which can be employed for the purposes of
this invention include knife coating methods, nozzle knife coating
methods, rolling rod nozzle methods, extrusion nozzle methods,
casting nozzle methods, and caster methods. Likewise in accordance
with the invention are application methods such as roll application
methods, printing methods, screen-printing methods, patterned roll
methods, ink-jet methods, and spraying methods. For the feeding of
the coating unit of the invention it is possible as an option to
include a conveying and/or mixing assembly, e.g., a single-screw or
twin-screw extruder, between metering system and mixing system. The
extruder which can be used alternatively is separately
heatable.
Crosslinking Methods
[0115] It is particularly preferred to initiate the crosslinking of
the PSA following the operation of applying it by coating.
Particularly advantageous for this purpose is a radiation process.
One very preferred variant that may be mentioned, and that be used
for the purposes of this invention, is that of crosslinking with
ultraviolet radiation. By means of brief exposure to light in a
wavelength range between 200 to 400 nm, the coated material, which
in this version of the invention contains the photoinitiator
functions preferably as groups X and/or groups Y, is irradiated and
hence crosslinked. Employed in particular for this purpose are
high-pressure or medium-pressure mercury lamps at a power of 80 to
240 W/cm. Other radiation sources which can be used for the
purposes of this invention are those familiar to the skilled
worker. Alternatively, the emission spectrum of the lamp is adapted
to the photoinitiator used, or the type of photoinitiator is
adapted to the lamp's spectrum. The intensity of irradiation is
adapted to the respective quantum yield of the UV photoinitiator,
to the degree of crosslinking that is to be set, and to the web
speed.
[0116] Furthermore, it is possible with preference to crosslink the
PSA formulations of the invention with electron beams after they
have been applied by coating. This may also take place in
combination with a UV crosslinking operation. Typical irradiation
equipment that may be employed includes linear cathode systems,
scanner systems, and segmented cathode systems where electron beam
accelerators are concerned. Typical acceleration voltages are
situated in the range between 50 kV and 1 MV, preferably between 80
kV and 300 kV. The radiation doses employed are situated between 5
to 250 kGy, in particular between 20 and 100 kGy.
[0117] For the purposes of this invention it is additionally
possible with preference to realize the crosslinking by exposure to
thermal energy. This can be done optionally in combination with one
or more radiation methods. Where thermal energy is used to initiate
the crosslinking reaction, care must be taken to ensure that,
during the coating operation, the crosslinking process has not
progressed too far, since this alters the coating characteristics
of the formulation. Particular preference is given in this case to
producing a compound which already comprises filler particles of
kind B and polymers of kind A, but with the groups X and Y selected
such that they are able to react not directly with one another but
rather only through the intermediacy of a crosslinker or a coupling
reagent. In that case, crosslinkers or coupling reagents are
preferably metered into the otherwise fully homogenized compound
immediately prior to the coating operation, and are mixed with said
compound. With particular preference a two-component or
multicomponent operation is conducted in which all of the raw
materials have been divided up between at least two mass reservoirs
in such a way as to ensure the physical separation, up until
immediately prior to the coating operation, of all those raw
materials that are capable of a thermal reaction with one another.
The thermal energy is then either taken from the preheated mass
streams, made available by setting a temperature of the coating
unit, or realized by way of a heating tunnel and/or an infrared
section after the coating operation. It is likewise possible in
accordance with the invention to utilize the thermal energy given
off in one or more exothermic reactions in order for this thermal
reaction to proceed. Combinations of these methodological
possibilities particularly with the radiation crosslinking methods
are possible within the context of this invention.
[0118] With great preference in the context of this invention,
self-adhesive products of the invention are produced in a
continuous operation in the, course of which the steps of
compounding, of coating, and of crosslinking are coupled directly
and hence in which an inline operation is employed.
Self-Adhesive Products
Product Constructions
[0119] The pressure-sensitive adhesives prepared by the processes
of the invention can be utilized for constructing different kinds
of self-adhesive products such as, for example, self-adhesive tapes
or self-adhesive sheets. Inventive constructions of self-adhesive
products are depicted in FIG. 6. Each layer in the self-adhesive
tape constructions of the invention may, as an alternative, be in
foamed form.
[0120] In the simplest case a self-adhesive product of the
invention is composed of the pressure-sensitive adhesive (PSA) in
single-layer construction (construction in FIG. 6.1). This
construction may optionally be lined on one or both sides with a
release liner, e.g., a release film or release paper. The layer
thickness of the PSA is, typically between 1 .mu.m and 2000 .mu.m,
preferably between 5 .mu.m and 1000 .mu.m.
[0121] The PSA may additionally be on a backing, in particular a
film or paper backing or a sheetlike textile structure
(construction in FIG. 6.2). The backing in this case may have been
pretreated in accordance with the prior art on the side facing the
PSA, so that, for example, an improvement in PSA anchorage is
obtained. The side may also have been provided with a functional
layer which can act, for example, as a barrier layer. The reverse
of the backing may have been pretreated in accordance with the
prior art so as to achieve, for example, a release effect. The
reverse of the backing may also have been printed. The PSA may
optionally be lined with a release paper or release film. The PSA
has a typical layer thickness of between 1 .mu.m and 2000 .mu.m,
preferably between 5 .mu.m and 1000 .mu.m.
[0122] In the case of the construction according to FIG. 6.3 the
self-adhesive product is a double-sided product comprising as its
middle layer, for example, a backing film, a backing paper, a
sheetlike textile structure or a backing foam. In this
construction, PSAs of the invention of identical or different kind
and/or of identical or different layer thickness are employed as
top and bottom layers. The backing (or carrier) may in this case
have been pretreated in accordance with the prior art on one or
both sides, thereby achieving, for example, an improvement in PSA
anchorage. It is also possible for one or both sides to have been
provided with a functional layer which connect, for example, as a
barrier layer. The PSA layers may optionally be lined with release
papers or release films. The layers of PSA typically have
thicknesses, independently of one another, of between 1 .mu.m and
2000 .mu.m, preferably between 5 .mu.m and 1000 .mu.m.
[0123] As a further double-sided self-adhesive product, the
construction according to FIG. 6.4 is an inventive variant. A PSA
layer of the invention carries on one side a further PSA layer
which, however, may be of any desired nature and therefore need not
be inventive. The construction of this self-adhesive product may be
lined optionally with one or two release films or release papers.
The layers of PSA typically have thicknesses, independently of one
another, of typically between 1 .mu.m and 2000 .mu.m, preferably
between 5 .mu.m and 1000 .mu.m.
[0124] As in the case of the construction in FIG. 6.4, the
construction according to FIG. 6.5 is a double-sided self-adhesive
product which comprises a PSA of the invention and also one other
PSA of any kind. In FIG. 6.5, however, two PSA layers are separated
from one another by a backing (or carrier), a backing film, backing
paper, a sheetlike textile structure or a backing foam. The backing
in this case may have been pretreated in accordance with the prior
art on one or both sides, thereby achieving, for example, an
improvement in PSA anchorage. It is also possible for one or both
sides to have been provided with a functional layer which connect,
for example, as a barrier layer. The PSA layers may optionally be
lined with release paper or release film. The PSA layers have
thicknesses, independently of one another, of typically between 1
.mu.m and 2000 .mu.m, preferably between 5 .mu.m and 1000
.mu.m.
[0125] The self-adhesive product of the invention according to FIG.
6.6 comprises a layer of inventive material as a middle layer,
which is provided on both sides with any desired PSAs of identical
or different type. One or both sides of the middle layer may have
been provided with a functional layer which connect, for example,
as a barrier layer. For the outer PSA layers it is not necessary
for inventive PSAs to be employed. The outer PSA layers may
optionally be lined with release paper or release film. The outer
PSA layers have thicknesses, independently of one another, of
typically between 1 .mu.m and 2000 .mu.m, preferably between 5
.mu.m and 1000 .mu.m. The thickness of the middle layer is
typically between 1 .mu.m and 2000 .mu.m, preferably between 5
.mu.m and 1000 .mu.m.
Test Methods
[0126] In the description of this invention, numerical values are
given for systems of the invention and reference is made to test
methods by means of which such data can be determined. These test
methods are collated below.
Determination of Processing Properties (Test A)
[0127] Melt viscosities (Test A1) and first normal stress
differences are determined for solvent-free, uncrosslinked test
specimens as a function of shear rate and temperature by means of a
PC-controlled high-pressure capillary rheometer from Gottfert
(model: Rheograph 2002) from the pressure drops measured in the
steady-state flow range. The capillary used is, for example, a flat
slot with geometry of 23 mm.times.25 mm.times.0.16 mm
(L.times.W.times.H). Values for the shear rates, viscosities, and
first normal stress differences indicate that in this description
are corrected data. The shear rate chosen for the tests is 1000
s.sup.-1. The measurement temperature depends on the nature of the
material under investigation and is reported together with the
results. From the data for shear rate, viscosity, and first normal
stress difference, the R value is determined as a ratio between the
first normal stress difference and the product of viscosity and
shear rate (Test A2).
Determining the Gel Fraction (Test B)
[0128] Coated and crosslinked, solvent-free PSA samples are welded
into a nonwoven polyethylene pouch. Soluble constituents are
extracted with toluene for a period of three days, the solvent
being replaced daily. The difference in sample weights before and
after extraction gives the gel index, as the percentage weight
fraction of the polymer which cannot be extracted with toluene.
Determining the Bond Strength (Test C)
[0129] The peel strength (bond strength) is tested in accordance
with PSTC-1. A PSA layer 50 .mu.m thick is applied to a PET film 25
.mu.m thick. A strip of this specimen 2 cm wide is adhered to a
sanded steel plate by rolling over the specimen back and forth five
times using a 5 kg roller. The plate is clamped in and the
self-adhesive strip is pulled off from its free end on a tensile
testing machine at a peel angle of 180.degree. and a speed of 300
mm/min.
Determining the Holding Power (Test D)
[0130] The test takes place in accordance with PSTC-7. A PSA layer
50 .mu.m thick is applied to a PET film 25 .mu.m thick. A strip of
this specimen 1.3 cm wide is adhered to a polished steel plaque
over a length of 2 cm using a 2 kg roller, the specimen being
rolled over back and forth twice. The plaques are equilibrated
under test conditions (temperature and atmospheric humidity) for 30
minutes, but without a load. Then the test weight is hung on,
thereby producing a shearing stress parallel to the surface of the
bond, and a measurement is made of the time taken for the bond to
fail. TABLE-US-00001 TABLE 1 Functional groups Functional groups of
type Y of type X --CR.sup.a.dbd.CR.sup.bR.sup.c
--OC(.dbd.O)CR.sup.d.dbd.CR.sup.aR.sup.b
--OCR.sup.a.dbd.CR.sup.bR.sup.c ##STR3## --NCO --NR.sup.aR.sup.b
--N.sub.3 --OH --CR.sup.1.dbd.CR.sup.2R.sup.3 X X X X
--OC(.dbd.O)CR.sup.4.dbd.CR.sup.1R.sup.2 X X X X X
--OCR.sup.1.dbd.CR.sup.2R.sup.3 X X X X ##STR4## X X X X --NCO X X
X X --NR.sup.1R.sup.2 X X X --N.sub.3 X X X --OH X X --SH X X X
--C(.dbd.O)R.sup.1 X --C(.dbd.O)--OH X X X X
--C(.dbd.O)--O--C(.dbd.O)R.sup.1 X X Cyclic acid anhydride X X --PI
X X X X --C.ident.CR.sup.1 X --CR.sup.5R.sup.6H X X X Functional
groups of type Y Functional groups Cyclic of type X --SH
--C(.dbd.O)R.sup.a --C(.dbd.O)--OH --C(.dbd.O)--O--C(.dbd.O)R.sup.a
acid anhydride --PI --C.ident.CR.sup.a --CR.sup.eR.sup.fH
--CR.sup.1.dbd.CR.sup.2R.sup.3 X X X
--OC(.dbd.O)CR.sup.4.dbd.CR.sup.1R.sup.2 X X
--OCR.sup.1.dbd.CR.sup.2R.sup.3 X X ##STR5## X X X --NCO X X
--NR.sup.1R.sup.2 X X X X --N.sub.3 X --OH X X X --SH X X X
--C(.dbd.O)R.sup.1 --C(.dbd.O)--OH X X
--C(.dbd.O)--O--C(.dbd.O)R.sup.1 X X Cyclic acid anhydride X X --PI
X X --C.ident.CR.sup.1 X --CR.sup.5R.sup.6H X
* * * * *