U.S. patent application number 10/960269 was filed with the patent office on 2005-06-23 for adhesive and its use.
Invention is credited to Hammer-Wolf, Elvira, Leder, Herbert.
Application Number | 20050133155 10/960269 |
Document ID | / |
Family ID | 34306413 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050133155 |
Kind Code |
A1 |
Leder, Herbert ; et
al. |
June 23, 2005 |
Adhesive and its use
Abstract
The invention relates to the use of a two-phase polymer
combination which is dissoluble in aqueous alkali and comprises a.
an alkali-soluble copolymer or terpolymer of an
.alpha.,.beta.-unsatura- ted monocarboxylic acid which possesses
carboxyl groups distributed essentially uniformly over the chain of
the molecule, as a continuous phase, and b. a copolymer or
terpolymer which is insoluble in aqueous alkali and contains epoxy
groups along its polymer chain, as a discontinuous finely disperse
phase, c. free epoxy groups on the surface of the polymer particles
of the discontinuous phase being linked to one another by
esterification with some of the carboxyl groups of the polymer of
the continuous phase, and the remaining carboxyl groups being
present in unchanged form, as an adhesive. The polymer combination,
which is not tacky in the dry state, can be made tacky by supplying
aqueous moisture to it.
Inventors: |
Leder, Herbert; (Sinzheim,
DE) ; Hammer-Wolf, Elvira; (Feldbrunnen, CH) |
Correspondence
Address: |
QUARLES & BRADY LLP
411 E. WISCONSIN AVENUE
SUITE 2040
MILWAUKEE
WI
53202-4497
US
|
Family ID: |
34306413 |
Appl. No.: |
10/960269 |
Filed: |
October 7, 2004 |
Current U.S.
Class: |
156/330 ;
525/89 |
Current CPC
Class: |
C08L 2666/04 20130101;
C08L 33/068 20130101; C09J 133/02 20130101; C09J 133/02 20130101;
C08L 2666/04 20130101 |
Class at
Publication: |
156/330 ;
525/089 |
International
Class: |
C09J 009/00; C08L
053/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 10, 2003 |
DE |
10348222.9 |
Claims
1. An adhesive composition dissoluble in aqueous alkali, comprising
ing a two-phase polymer combination being capable to form an
adhesive bond to substrates in moist state whereas being non-tacky
in dry state and said polymer combination consisting essentially of
a. an alkali-soluble copolymer or terpolymer of an
.alpha.,.beta.-unsaturated monocarboxylic acid which possesses
carboxyl groups distributed essentially uniformly over the chain of
the molecule, as a continuous phase, and b. a copolymer or
terpolymer which is insoluble in aqueous alkali and contains epoxy
groups along its polymer chain, as a discontinuous finely disperse
phase, wherein free epoxy groups on the surface of the polymer
particles of the discontinuous phase are linked by esterification
with some of the carboxyl groups of the polymer of the continuous
phase, and the remaining carboxyl groups are present in unchanged
form, wherein the adhesive composition can be made tacky by
addition of aqueous moisture.
2. Adhesive composition according to claim 1 wherein the aqueous
moisture is provided in form of an aqueous liquid.
3. Adhesive composition according to claim 1 wherein the polymer
combination is in the form of a film.
4. Adhesive composition according to claim 3 wherein the film is
provided for bonding on at least one side.
5. Adhesive composition according to claim 3 wherein the film is
provided for bonding over its entire area.
6. Adhesive composition according to claim 3 wherein the film is
provided for bonding only in part.
7. Adhesive composition according to claim 3 wherein the film is
transparent to milky.
8. Adhesive composition according to claim 3 wherein the film is
comprising pigments.
9. Adhesive composition according to claim 3 wherein the film is
printed.
10. Adhesive composition according to claim 3 wherein the film is a
detachable label.
11. Adhesive composition according to claim 3 wherein the film is a
protective film for smooth surfaces such as glass, metal, plastic
and also coated surfaces.
12. Adhesive composition according to claim 3 wherein the film is a
coating.
13. Adhesive composition according to claim 12 wherein the film is
a protective coating against graffitiy.
14. Adhesive composition according to claim 1 wherein the adhesive
composition bonded to substrates is removable without residue from
the substrates by sufficient addition of water.
15. Adhesive composition according to claim 1 wherein the polymer
combination is in the form of particles.
16. Adhesive composition according to claim 15 wherein the polymer
combination is in the form of an aqueous dispersion.
17. Adhesive composition according to claim 1 wherein it is
processable as a hot-melt adhesive.
18. Adhesive composition according to claim 1 wherein it is
processable in a multi-stage adhesion process in which the polymer
combination is bonded moist and in a further step bonded hot.
19. Adhesive composition according to claim 1 wherein it is
processable as an adhesive in laminating operations.
20. Adhesive composition according to claim 1 wherein it is an
interlayer between at least two layers of a composite.
21. A method for bonding a two-phase polymer combination dissoluble
in aqueous alkali to a surface of at least one substrate, said
two-phase polymer combination consisting essentially of a. an
alkali-soluble copolymer or terpolymer of an
.alpha.,.beta.-unsaturated monocarboxylic acid which possesses
carboxyl groups distributed essentially uniformly over the chain of
the molecule, as a continuous phase, and b. a copolymer or
terpolymer which is insoluble in aqueous alkali and contains epoxy
groups along its polymer chain, as a discontinuous finely disperse
phase, wherein free epoxy groups on the surface of the polymer
particles of the discontinuous phase are linked by esterification
with some of the carboxyl groups of the polymer of the continuous
phase, and the remaining carboxyl groups are present in unchanged
form, comprising the steps of: providing said two-phase polymer
combination, supplying aqueous moisture to said polymer combination
and applying the moist polymer combination to said surface of said
at least one substrate.
22. Method according to claim 21 wherein the aqueous moisture is
provided in form of an aqueous liquid.
23. Method according to claim 21 wherein the application of the
moist polymer combination is followed by a drying phase.
24. Method according to claim 21 wherein the polymer combination is
applied in the form of a film.
25. Method according to claim 24 wherein aqueous moisture is
supplied to one side of the film to provide it for bonding on said
side.
26. Method according to claim 24 wherein aqueous moisture is
supplied to both sides of the film to provide it for both-side
bonding.
27. Method according to claim 24 wherein aqueous moisture is
supplied to the entire area of the film providing it for bonding
over its entire area.
28. Method according to claim 24 wherein aqueous moisture is
supplied to certain places of the film providing it for bonding
only in said places.
29. Method according to claim 21 wherein the polymer combination is
provided in the form of particles.
30. Method according to claim 29 wherein the polymer combination is
applied in the form of an aqueous dispersion.
31. Method according to claim 21, comprising a further step in
which the polymer combination is bonded as a hot melt under heat
subsequent to the application of the moist polymer combination.
32. A method to remove a two-phase polymer combination bonded to a
substrate from said substrate without residue, said two-phase
polymer combination consisting essentially of a. an alkali-soluble
copolymer or terpolymer of an .alpha.,.beta.-unsaturated
monocarboxylic acid which possesses carboxyl groups distributed
essentially uniformly over the chain of the molecule, as a
continuous phase, and b. a copolymer or terpolymer which is
insoluble in aqueous alkali and contains epoxy groups along its
polymer chain, as a discontinuous finely disperse phase, wherein
free epoxy groups on the surface of the polymer particles of the
discontinuous phase are linked by esterification with some of the
carboxyl groups of the polymer of the continuous phase, and the
remaining carboxyl groups are present in unchanged form, comprising
the step of: supplying aqueous moisture to said bonded polymer
combination.
Description
[0001] The invention relates to an adhesive based on a polymer
which can be made tacky in conjunction with aqueous moisture, and
to its use.
[0002] Industrial products having self-adhesive properties are
sufficiently well known from everyday use; examples are the wide
variety of kinds of sheets and adhesive tapes, used in the
packaging, construction or furniture sector and in the metal, glass
and automotive industries, among others, or else office products
such as adhesive strips, sticky labels or sticky notes. Common to
these products is the fact that for bonding to various substrates
they are coated with adhesive on one side or else, according to
their specific application, on both sides.
[0003] Production, handling and also the post-use disposal of these
coated self-adhesive products have a number of known drawbacks.
[0004] In the case of self-adhesives it is necessary to protect the
adhesive layer with a carrier material, such as siliconized paper,
so that it does not lose activity prior to use, as a result for
example of contamination, or, in the case of sheets, that the sheet
layers do not stick to one another. Following application the
carrier material is left as non-recyclable waste and therefore
constitutes a disposal problem.
[0005] The removal of adhesive sheets or sticky labels following
their application, from glass or porcelain products, for example,
is frequently associated with severe difficulties. Labels and
sheets, for example, can only be removed manually, while removal of
adhesive residues is often possible only with great effort, using
organic solvents.
[0006] The specific production of tacky sheets without an adhesive
coating, based on ethylene-vinyl acetate (EVA) or unplasticized
polyvinyl chloride (PVC-u) and low-density polyethylenes (LDPE)
with corresponding tackifiers, is also known. The bond strength of
these sheets is low. Their adhesion is suitable primarily for
fixing sheet to sheet, and hence they are of only limited
usefulness as wrapping sheets for industrial packaging and in the
packaging of foodstuffs.
[0007] There are also water-soluble adhesives. These adhesives have
the drawback that if too much water is used they are diluted or
become detached and then no longer stick.
[0008] The invention provides for the use of a two-phase polymer
combination which is dissoluble in aqueous alkali and comprises
[0009] a. an alkali-soluble copolymer or terpolymer of an
.alpha.,.beta.-unsaturated monocarboxylic acid which possesses
carboxyl groups distributed essentially uniformly over the chain of
the molecule, as a continuous phase, and
[0010] b. a copolymer or terpolymer which is insoluble in aqueous
alkali and contains epoxy groups along its polymer chain, as a
discontinuous finely disperse phase,
[0011] c. free epoxy groups on the surface of the polymer particles
of the discontinuous phase being linked to one another by
esterification with some of the carboxyl groups of the polymer of
the continuous phase, and the remaining carboxyl groups being
present in unchanged form,
[0012] as an adhesive.
[0013] The polymer combination has already been described in EP 0
928 316 B1, the content of which is hereby incorporated by
reference. It is known in the form of a melt, powder and films
(foils). WO 98/7778 describes alkali-dissoluble laundry detergent
pouches made from films of the polymer combination.
[0014] Surprisingly it has been found that this polymer combination
in the moist state is able to form an adhesive bond not only to
smooth surfaces but also to textured surfaces, as for example to
glass, metal surfaces, plastics, nonwovens, woven fabrics, paints,
paper or else to films of the same kind. The bond formed exhibits
an extremely high strength with respect to mechanical forces, after
drying, even to the smooth surfaces. In the dry state the polymer
itself is not tacky.
[0015] The polymer combination can be made tacky by supplying
aqueous moisture to it, but is not dissolved in the process.
Products comprising this polymer combination can be bonded without
an additional adhesive coating or can themselves act as an
adhesive. The disadvantages and restrictions described above do not
occur in the case of use in accordance with the invention.
[0016] The necessary moisture can be supplied in the form of vapour
or liquid, in the latter case by direct or indirect application
such as spreading, dropping, pouring or spraying or in atomized
form via a nozzle. Moistening in the case of a sheet can be carried
out on one or both sides, in the latter case, for example, by
complete immersion of the sheet material in water.
[0017] In powder form as well it is possible to use the polymer
combination in accordance with the invention. In that case the
powder is preferably dispersed in water and applied to the
respective substrate, in particular by spraying.
[0018] Products comprising this polymer combination are stable in
acidic and neutral, aqueous media, while in aqueous alkalis it is
possible with particular advantage to dissolve the products
completely. By acidification the polymer combination can be
reprecipitated and supplied to a recycling circuit.
[0019] The invention also relates to a method of bonding articles,
or bonding to articles, using the polymer combination.
[0020] It should be emphasized at this point that alkali-free
aqueous moisture is enough to bring about the desired adhesive
effect of the polymer combination. By adding alkaline media it is
possible to dissolve the polymer combination on the surface partly
or completely; preferably an alkaline medium is not provided for
application in accordance with the invention.
[0021] The bond of the polymer combination to the surfaces of the
aforementioned substrates is still sufficient even in a moist
environment, provided that no substantial mechanical forces act on
the bond. If, however, the bonded polymer combination is wetted
with large amounts of water, the bond can be parted again. In this
way the polymer combination can be removed without residue, and
this constitutes a substantial advantage of application in
accordance with the invention.
[0022] For films and powders comprising the polymer combination
there are a multiplicity of possible applications.
[0023] In one preferred embodiment a film of the polymer
combination is opaque, which can be achieved by incorporating
pigments into the copolymer. Thus, for example, a white coloration
is obtainable by admixing titanium dioxide. Without admixtures of
pigment the films are transparent to milky. The films can be
covered in places or entirely with at least one colour layer, in
particular by printing. Printing inks used are preferably those
which are soluble in aqueous alkali and preferably insoluble in a
neutral to acidic medium. Thus films comprising the polymer
combination can be used, for example, as labels without any need
for coating with pressure-sensitive adhesive, such as is necessary,
for example, for the labels described in EP 0 316 676 B1.
[0024] Films comprising the polymer combination can be bonded over
their entire area or only in places. They are outstandingly
suitable for use as a protective coating or locally bonded
protective covering, particularly in the case of the transportation
and temporary and long-term storage of goods and products. There is
a need for protective coverings and protective coatings in numerous
sectors and branches of industry, particularly in the
aforementioned transport, construction, sanitary or furniture
sector, or else, for example, in the glass, metal or automotive
industry.
[0025] Coatings comprising the polymer combination can be produced
either by bonding, in the form of a film, or else by application in
the form of a dispersed powder. A further possible field of
application for such coatings is that of protection against
graffiti. Preference is given here to use for protecting transport
means such as railway carriages.
[0026] If the polymer combination is employed in the form of a
film, the thickness and width of the film are guided by the
particular end use, and can be adapted accordingly. The film
thickness is generally from 10 .mu.m to 200 .mu.m; for protective
films, in particular, from 25 .mu.m to 60 .mu.m are sufficient. The
width can be chosen arbitrarily as a function of production of the
film, and is generally between 20 cm and 800 cm, in particular in
the range from 50 cm to 120 cm.
[0027] The polymer combination can also be processed in the form of
a hot-melt adhesive, particularly in combination with aqueous
bonding. In this case as well a permanent bond is formed to smooth
and textured surfaces. In conjunction with tackifying by supply of
aqueous moisture it is possible to use the polymer combination both
in the form of a film and in the form of a powder in a multi-stage
adhesion process, in which it becomes moist in a first step and in
a further step is used for hot bonding.
[0028] Moist and/or hot bonding of the polymer combination can be
employed for the production of composites, particularly in
connection with the manufacture of laminates. In that case the
polymer combination, can on the one hand, as already outlined, be
used as a straight adhesive, while on the other hand the bonded
polymer acts with particular advantage as an interlayer,
particularly as a water-vapour-permeable interlayer.
[0029] The adhesion mechanism on which the invention is based can
be described as follows:
[0030] Films and powders comprising the polymer combination
described are polar by virtue of the aforementioned free carboxyl
groups which are distributed over the whole length of the polymer
chain of the continuous phase. This means that they are
hydrophilic, and hence possess a high affinity for water.
Consequently, depending on hardness and the amount of free carboxyl
groups, they are able to absorb water. In doing so, the polymer has
incorporated into it water molecules, which act as plasticizers and
increase the mobility of the polymer chains. Films and powders
become soft and tacky and can in this state be applied to a variety
of substrate surfaces. The high polarity of the polymer combination
allows a firm bond to the substrates. As a result of the subsequent
drying process the plasticizer effect is lost and the original
state of the polymer combination is reestablished. Adhesion to the
substrate surface, however, is retained.
[0031] The preparation of the acrylic and/or methacrylic acid
polymer takes place as described in patent EP 0 928 316 B1, it
being possible to give preference, rather than a polymerization in
the melt, to a solution polymerization in organic solvents, which
can lead to molecular sizes which are favourable, in particular for
the adhesive properties.
[0032] The polymer combination is preferably compounded, as
described in EP 0 928 316 B1, in the melt.
[0033] Further features of the invention will emerge from the
following description of preferred embodiments in conjunction with
the dependent claims. In these embodiments the individual features
may each be realised individually, or two or more thereof in
combination with one another, in an embodiment of the
invention.
EXAMPLES
[0034] The hardness and the hydrophilic nature of the two-phase
polymer compound can be adjusted by way, inter alia, of the
composition of the COOH-containing matrix polymer (cf. Table 1). In
the monomer mixture the fraction of .alpha.,.beta.-unsaturated
carboxylic acids is generally 20-40% by weight, preferably 25-35%.
Esters of .alpha.,.beta.-unsaturated carboxylic acids are present
in a fraction of 20-60% by weight, preferably 40-60%, and the
fraction of styrene, if present, is 5-50% by weight, in particular
15-25%. As the styrene content goes up, for example, there is also
a decrease in the water vapour permeability and the water
absorbency of the films adjusted accordingly.
1TABLE 1 Composition and properties of the carboxyl-containing
matrix polymer. Matrix polymer 1 2 3 4 Butyl acrylate in % 57.5 52
48 20 Acrylic acid in % 27.5 29 30 33 (methacrylic acid) Styrene in
% 15 19 22 47 Carboxyl content in % 16 17 18 18 Tg in .degree. C.
45 50 61 110
[0035] The weight ratio of COOH-containing polymer to
epoxy-containing impact modifier in the film is from 9:1 to 1:1, in
particular from 5:1 to 1.8:1.
[0036] The compounding of the carboxyl-containing polymer with the
impact modifier takes place under computer control, it being
possible to add very-low-density polyethylene (VLDPE),
anti-blocking agents such as silica or talc, lubricants such as
stearic acid, stearamide or ethylenamines and processing
stabilizers from the class of the sterically hindered phenols to
the mixture, at up to 10% by weight.
2TABLE 2 Composition and properties of films of the two-phase
polymer combination. Film compound 1 2 3 4 5 Carboxyl-containing
55.5 61 58 62 58 matrix polymer in % Epoxy-containing impact 40 35
40 35 40 component in % VLDPE in % 2 2 2 Lubricant in % 1 2 1 2
Anti-blocking agent in % 0.5 2 Stabilizer in % 1 Film A Film B Film
C Film D Tensile strength MD/CD 20/18 24/24 20/18 24/20 29/31
N/mm.sup.2 Breaking elongation 250/300 240/180 170/180 230/190 6/7
MD/CD % Water absorption % 16 10 10 14 <1 Water vapour 85 40 50
66 <5 permeability g/m.sup.2/24 h Tg in .degree. C. 46 46 50 59
98
[0037] Selected films were used for adhesive tests with neutral
water, the results being as follows:
3TABLE 3 Assessment of adhesion: 1 - film undetachable; 2 - film
difficult to detach, partially fractures; 3 - film difficult to
detach, no fracture; 4 - film easy to detach; 5 - no adhesion. Film
(% styrene) A (8) B (11) C (14) D (30) Glass 1 2 2 5 Aluminium 1 3
4 5 LDPE 4 5 5 PP nonwoven 5 Stationery paper 4 High-gloss paper 4
Steel, stainless 2 Steel sheet, galvanized 2
[0038] Further experiments investigated the adhesion which occurred
when bonding film to film.
4TABLE 4 "Film-to-film" adhesion tests. Adhesion is assessed as in
Table 3. Film on film A B C D A 1 1 1 1 B 1 1 1 1 C 1 2 4 5 D 1 1 5
5
[0039] By moistening with 0.5% strength sodium hydroxide solution
it is also possible for films A, B and C to be bonded effectively
to aluminium, stationery paper and galvanized steel sheet. The
adhesion is unaffected by accelerated drying in a drying cabinet at
40.degree. C.
* * * * *