U.S. patent application number 13/584944 was filed with the patent office on 2013-11-28 for sealant articles and compositions useful therein.
This patent application is currently assigned to Henkel AG & Co. KGaA. The applicant listed for this patent is Gregory A. FERGUSON, Don K. HOWARD, Jeffrey T. PACHL, Grady C. RORIE. Invention is credited to Gregory A. FERGUSON, Don K. HOWARD, Jeffrey T. PACHL, Grady C. RORIE.
Application Number | 20130312904 13/584944 |
Document ID | / |
Family ID | 39283151 |
Filed Date | 2013-11-28 |
United States Patent
Application |
20130312904 |
Kind Code |
A1 |
PACHL; Jeffrey T. ; et
al. |
November 28, 2013 |
SEALANT ARTICLES AND COMPOSITIONS USEFUL THEREIN
Abstract
A sealant article useful for sealing a substrate surface having
a first surface and a second surface is provided. The first surface
comprises a deformable composition that is capable of conforming to
a substrate surface when subjected to heat and/or pressure. The
second surface of the sealant article has been at least partially
cured by exposing said surface to an amount of radiation effective
to induce at least partial curing of the second surface of the
sealant article. Prior to such curing, the second surface also is
comprised of the deformable composition. Such at least partial
curing is effective to render the second surface less deformable
than the first surface.
Inventors: |
PACHL; Jeffrey T.; (Holt,
MO) ; HOWARD; Don K.; (Liberty, MO) ; RORIE;
Grady C.; (Ann Arbor, MI) ; FERGUSON; Gregory A.;
(Harrison Township, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PACHL; Jeffrey T.
HOWARD; Don K.
RORIE; Grady C.
FERGUSON; Gregory A. |
Holt
Liberty
Ann Arbor
Harrison Township |
MO
MO
MI
MI |
US
US
US
US |
|
|
Assignee: |
Henkel AG & Co. KGaA
Duesseldorf
DE
|
Family ID: |
39283151 |
Appl. No.: |
13/584944 |
Filed: |
August 14, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12418848 |
Apr 6, 2009 |
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13584944 |
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PCT/US2007/021340 |
Oct 4, 2007 |
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12418848 |
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60828701 |
Oct 9, 2006 |
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Current U.S.
Class: |
156/275.5 ;
522/153; 522/33; 524/531 |
Current CPC
Class: |
Y10T 428/2809 20150115;
C08K 3/26 20130101; C08L 23/0853 20130101; C08K 5/14 20130101; Y10T
428/2878 20150115; Y10T 428/31935 20150401; C09J 4/06 20130101;
Y10T 428/287 20150115; C08J 3/28 20130101; C09K 3/10 20130101; C08F
2/48 20130101; C08L 2666/04 20130101; C09K 2200/0655 20130101; C09J
167/00 20130101; C08L 23/0853 20130101; C08L 2666/04 20130101; C09J
131/04 20130101; C09K 2200/062 20130101; C09J 167/00 20130101; C09K
2200/0622 20130101; C08L 9/00 20130101; C08L 2666/04 20130101; B32B
37/14 20130101 |
Class at
Publication: |
156/275.5 ;
524/531; 522/153; 522/33 |
International
Class: |
C09J 131/04 20060101
C09J131/04; B32B 37/14 20060101 B32B037/14 |
Claims
1. A deformable composition capable of being cured by exposure to
radiation, said deformable composition comprising at least one
thermoplastic, at least one (meth)acrylate-functionalized monomer
or oligomer, at least one thermally activatable free radical
initiator, and at least one filler.
2. The deformable composition of claim 1, additionally comprising
at least one tackifier.
3. The deformable composition of claim 1, additionally comprising
at least one reactive tackifier.
4. The deformable composition of claim 1, additionally comprising
at least one liquid diene homopolymer or copolymer containing
pendant vinyl groups.
5. The deformable composition of claim 1, comprising at least one
thermally activatable free radical initiator selected from the
group consisting of organic peroxides.
6. The deformable composition of claim 1, comprising at least one
thermoplastic copolymer of ethylene and at least one comonomer
selected from the group consisting of vinyl acetate, (meth)acrylic
acid, and C1 to C6 alkyl esters of (meth)acrylic acid.
7. The deformable composition of claim 1, comprising at least one
thermoplastic that is an ethylene/vinyl acetate copolymer.
8. The deformable composition of claim 1, additionally comprising
at least one photoinitiator.
9. The deformable composition of claim 1, additionally comprising
at least one aryl-substituted ketone photoinitiator.
10. The deformable composition of claim 1, comprising at least one
(meth)acrylate-functionalized monomer or oligomer selected from the
group consisting of epoxy (meth)acrylates and urethane
(meth)acrylates.
11. The deformable composition of claim 1 comprising, as weight %
of total weight of the deformable composition: 20-45 weight %
Ethylene/Vinyl Acetate Copolymer(s) and/or Polyester(s); 1-12
weight % liquid Polybutadiene(s) 5-30 weight %
(Meth)acrylate-Functionalized Monomer(s) and/or Oligomer(s); 25-55
weight % Inorganic Particulate Filler(s); 0.1-2 weight %
Peroxide(s); and 0.1-2 weight % Photoinitiator(s).
12. The deformable composition of claim 11 wherein the
(meth)acrylate-functionalized monomer or oligomer is selected from
the group consisting of epoxy (meth)acrylates and urethane
(meth)acrylates; the epoxy (meth)acrylates essentially all epoxy
groups on the epoxy (meth)acrylates being ring-opened, the
composition being free of other epoxy compounds
13. The deformable composition of claim 1, comprising, as weight %
of total weight of the deformable composition: 20-45 weight %
ethylene/vinyl acetate copolymer(s) and/or polyester(s); 2-6 weight
% reactive tackifier; 15-20 weight % epoxy (meth)acrylate(s) and/or
urethane (meth)acrylates; 25-55 weight % inorganic particulate
filler(s); 0.1-2 weight % peroxide(s); 0.1-2 weight %
photoinitiator(s); and at least one component selected from the
group consisting of colorants, pigments, plasticizers, organic
acids, anti-oxidants, stabilizers, thixotropic agents, thickeners,
reactive diluents, adhesion promoters, coupling agents, radiation
absorbers, and radiation blocking agents.
14. A method of sealing a substrate, said method comprising
applying to a substrate surface a deformable composition according
to claim 1, said deformable composition being a solid having an
uncured first surface and a partially cured second surface opposite
said first surface, such that said first surface is in at least
partial contact with said substrate surface and said second surface
faces away from said substrate surface, wherein said first surface
is capable of conforming to the substrate surface when subjected to
heat and/or pressure and said second surface has been partially
cured by exposing said surface to an amount of radiation effective
to induce partial curing of said second surface, wherein said
partial curing is effective to render said second surface less
deformable than said first surface, rendering said second surface
capable of substantially limiting said deformable composition to a
desired area of said substrate surface when heated to a temperature
effective to cause said uncured first surface of the deformable
composition to flow.
15. A method of sealing a substrate, said method comprising
applying a solid deformable composition having an uncured first
surface and a partially cured second surface, wherein said first
surface is capable of conforming to the substrate surface when
subjected to heat and/or pressure and said second surface has been
partially cured by exposing said surface to an amount of radiation
effective to induce partial curing of said second surface, wherein
said partial curing is effective to render said second surface less
deformable than said first surface to said substrate surface such
that said first surface is in at least partial contact with said
substrate surface.
16. The method of claim 15, wherein said deformable composition
comprising said uncured first surface flows and substantially
covers a desired area of said substrate surface when said
deformable composition is heated to a temperature effective to
cause uncured portions of said deformable composition to flow.
17. A method of sealing a substrate, said method comprising
applying a sealant article having a first surface and a second
surface, wherein said first surface is comprised of a deformable
composition that is capable of conforming to a substrate surface
when subjected to heat and/or pressure and said second surface of
said sealant article has been at least partially cured by exposing
said surface to an amount of radiation effective to induce at least
partial curing of said second surface of said sealant article,
wherein said second surface prior to said curing is comprised of
said deformable composition and wherein said at least partial
curing is effective to render said second surface less deformable
than said first surface to said substrate surface such that said
first surface is in at least partial contact with said substrate
surface.
18. The method of claim 17, comprising an additional step of
exerting an amount of pressure on said sealant article effective to
conform said first surface more closely to said substrate
surface.
19. The method of claim 17, comprising an additional step of
heating said sealant article to a temperature effective to cause
said first surface to conform more closely to said substrate
surface.
Description
FIELD OF THE INVENTION
[0001] This invention pertains to sealant articles useful for
sealing and protecting joints and the like, wherein the sealant
articles are prepared using deformable compositions capable of
being radiation cured to provide a deformation-resistant and
constraining outer surface.
DISCUSSION OF THE RELATED ART
[0002] Sealants currently are employed in a wide variety of
industrial applications. For example, the automotive industry
utilizes sealants between and upon metal seams and welds. One
specific sealant application involves the use of a sealant upon the
welds in the so-called roof ditches which are formed when joining
the side panels of a vehicle body to the roof of the vehicle.
Conventionally, the roof ditch weld is covered with a bead or strip
of a plastic (e.g., PVC) molding that is covered with a metal strip
and painted. In recent years, alternative approaches have been
proposed. For example, U.S. Pat. No. 6,030,701 describes sealant
articles comprising a melt-flowable composition and a dimensionally
stable film for controlling the melt-flow behavior of the
melt-flowable composition to substantially confine the
melt-flowable composition to the desired area of the roof ditch
area to which the sealant article has been applied. In U.S. Pat.
Nos. 6,461,691, 6,277,898, 6,174,932, and 6,858,260, radiation
curable, flexible, paintable compositions produced from epoxy
compounds and one or more polyols are suggested as roof ditch
sealants.
[0003] In many cases, sealing a substrate surface, especially the
substrate surfaces typically encountered in vehicle manufacture, is
quite challenging since a variety of different requirements must be
simultaneously met. For example, welded metal joints such as those
commonly present in vehicle roof ditches often are quite uneven,
due to weld dimples, projections resulting from the design of the
parts being joined by welding, and so forth. Conventional
automotive sealants and mastics are typically formulated to be
relatively soft and flexible so that they may be readily conformed
to such surfaces and form an effective seal (e.g., prevent water
and other liquids from penetrating to the joint). However, these
characteristics also result in the outer surface of the sealant or
mastic being highly susceptible to deformation due to trapped air,
irregularities or projections in the substrate surface, or external
forces. In some cases, blow-through of the sealant or mastic may
occur, which severely compromises the effectiveness and appearance
of the seal that is sought to be achieved. As a result, it is often
difficult to provide and maintain a smooth, even, and cosmetically
attractive top surface once the sealant or mastic has been applied
to the substrate surface. However, using a less easily deformable
sealant or mastic composition would interfere with the ability to
effectively seal the substrate surface.
SUMMARY OF THE INVENTION
[0004] In one aspect of the invention, a sealant article useful for
sealing a substrate surface is provided. The sealant article has a
first surface and a second surface, wherein the first surface is
comprised of a deformable composition that is capable of conforming
to the substrate surface when subjected to heat and/or pressure.
The second surface of the sealant article has been at least
partially cured by exposing the surface to an amount of radiation
effective to induce at least partial curing of the second surface.
The second surface prior to said curing is also comprised of the
deformable composition. The at least partial curing is effective to
render the second surface less deformable than the first
surface.
[0005] The deformable composition capable of being cured by
exposure to radiation may be comprised of at least one
thermoplastic, at least one (meth)acrylate-functionalized monomer
or oligomer, at least one thermally activatable free radical
initiator, and at least one filler. A substrate may be sealed using
such sealant article, wherein the sealant article is applied to the
substrate surface such that the first surface comprised of the
deformable composition is in at least partial contact with the
substrate surface.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION
[0006] The present invention involves the use of a sealant article
to provide protective and/or aesthetically pleasing features to a
substrate. The sealant article is prepared using a deformable
composition that initially is thermoplastic in character and thus
can be readily formed after heating into a desired shape such as
relatively thin, flat sheet, tape, strip or the like. The
deformable composition is also capable of being at least partially
cured by irradiation. At least one surface of the sealant article,
such as the surface that ultimately is to be positioned facing away
from the substrate surface, is exposed to an amount of radiation
(such as ultraviolet light or electron beam radiation) effective to
achieve the desired extent of curing (crosslinking) of the
deformable composition on the selected surface of the sealant
article. The selected surface is thereby rendered more resistant
towards being deformed by external forces such as projections on
the substrate surface, air trapped under the sealant article once
applied to the substrate surface, or the pressure exerted by
fingers or tools in applying the sealant article to a surface. In
certain embodiments, the deformable composition is cured
sufficiently to make the selected surface of the sealant article
tack-free (non-tacky) and/or non-thermoplastic (i.e., not capable
of being melted). Curing a surface of the sealant using radiation
provides the additional advantage that the less cured or uncured
deformable composition in the remainder of the sealant article
remains thermoplastic and capable of flowing when heated, but the
flow of the deformable composition is restricted or constrained by
the radiation-cured surface, which exhibits less or even no flow
when heated. This feature enables the sealing of the substrate
surface by the sealant article to be controlled, thereby minimizing
dripping or running of the deformable composition and spread of the
deformable composition to areas of the substrate surface where
sealant is not desired. The radiation-cured surface of the sealant
article also imparts a smooth, aesthetically pleasing appearance to
the substrate surface, since it enables the sealant article to
effectively cover and mask surface imperfections. The present
invention does not require co-extrusion or lamination steps in the
assembly of the sealant article and thus represents an advance over
known sealants incorporating dimensionally stable carrier films,
the manufacture of which can be complicated.
[0007] The irradiation step is controlled such that at least one
other surface of the sealant article (such as the surface that
ultimately is to be brought into contact with the substrate
surface) remains deformable and therefore capable of being brought
into close conformance with the substrate surface, thereby
providing an effective seal. In one aspect of the invention, the
deformable composition proximate to such other surface remains
flowable when heated. Thus, when the sealant article is placed over
the substrate and heated, the surface of the sealant article
applied to the substrate surface softens and bonds to the substrate
(such surface thereby functions like a hot melt adhesive), with the
deformable composition resolidifying when cooled to room
temperature. In another aspect of the invention, the deformable
composition is capable of being thermally cured by incorporating
one or more heat-activated curing or crosslinking agents which,
once activated by heating, react with and/or catalyze reaction of
other components of the deformable composition, thereby forming a
thermoset polymeric matrix which is resistant to further
deformation. In one particularly desirable variation of the
invention, the deformable composition is formulated so that it
remains sufficiently thermoplastic to permit the deformable
composition to flow when heated up to a certain temperature and/or
for a certain limited period of time, but then undergo
crosslinking/curing when heated to a higher temperature or for a
longer period of time. In still another embodiment, the components
of the deformable composition are selected to render a
non-radiation cured surface of the composition sufficiently tacky
at room temperature such that the surface adheres to the substrate
surface by application of pressure to the sealant article. In this
embodiment, the deformable composition thus functions as a
pressure-sensitive adhesive.
[0008] The present invention may be used in a number of industrial
applications. For example, the sealant article can be utilized in a
process to seal metal joints in automobiles. The sealant article is
applied over the joint to be sealed. Complete sealing and bonding
would be obtained because at least a portion of the deformable
composition flows prior to hardening. As a result of the controlled
flow of the edges of the sealant article, an aesthetic outer
surface appearance is achieved. The exposed surface(s) of the
sealant article can then be painted or otherwise decorated to match
the vehicle body. The sealant articles of the present invention are
useful in sealing a variety of discontinuities such as overlap
joints or seams, butt joints or seams, depressions, indentations,
holes, gaps, channels, slots, and manufacturing defects such as
those produced when fabricating metal articles and the like.
[0009] In one embodiment of the invention, the surface of the
sealant article that is to be applied to the substrate surface is
tacky or pressure sensitive and is initially protected by a
temporary substrate such as a disposable liner or release paper.
Such a temporary substrate blocks dirt and other substances from
contaminating the sealant article surface and interfering with
adhesion of the sealant article to the substrate surface.
Additionally, a temporary substrate may facilitate storage and
handling of the sealant article (for example, the sealant article
could be in the form of a tape that is wound upon itself or a sheet
that is stacked upon another sheet with a layer of the temporary
substrate in between). Immediately before applying the sealant
article to the substrate surface, the temporary substrate is
removed to expose the sealant article surface or surfaces to be
contacted with the substrate surface.
[0010] The sealant article can be placed in a roof ditch on a
vehicle before it is painted to conceal unsightly flaws in the
metal, spot welds, and the step joint where the sheet metal of the
roof is welded to the sheet metal of the vehicle body.
[0011] In one specific embodiment, the sealant article is cut or
otherwise formed into a strip having a width equal to or slightly
greater than the width of the roof ditch and a length equal to the
length of the ditch. The sealant article is placed within the roof
ditch; typically, pressure is applied so as to bring the
non-radiation cured surface of the sealant article into at least
partial contact with the roof ditch surface. The roof ditch surface
may be unprimed, unprimed with a portion sealed with conventional
sealers, primed with conventional primers, or primed and painted.
Typically, the roof ditch surface is primed with an
electrodeposition coating prior to application of the strip. The
strip is then heated while in the ditch (for example, while the
vehicle is being passed through a paint cure oven) so the
deformable composition proximate to the surface of the roof ditch
flows and levels out over any imperfections and the step joint in
the roof ditch, thereby creating a smooth, aesthetically pleasing
appearance within the ditch. At the same time, the sealant article
also adheres to the interior surfaces of the roof ditch and
provides a protective seal in the ditch to prevent rain water,
dirt, snow, and so forth from penetrating the roof ditch and
causing rusting or corrosion. In the embodiment where the
strip-shaped sealant article has a width slightly greater than the
width of the roof ditch, the positioned and adhered strip can take
on a concave configuration along the length of the roof ditch to
provide a channel to carry water off the roof of the vehicle.
[0012] The vehicle, with the sealant article in place, may be
painted (including optionally also a protective clear coat) and put
through an oven cure cycle at about 120 to about 200 degrees C. for
about 10 to about 60 minutes. The deformable composition may be
formulated so that it melt flows to a desired extent and/or is
thermally cured through activation of curing agents/catalysts
during such oven cure cycle.
[0013] The deformable composition may be formed into the desired
sealant article shape such as a sheet using conventional forming
techniques, including extruding the deformable composition through
a heated die; molding the deformable composition while heated in a
mold of the desired configuration; heating the deformable
composition to a suitable melt temperature and knife coating onto a
release liner; curtain coating the deformable composition while
molten; or dispersing the material in a solvent, coating onto a
release liner, and drying the solvent. If the forming method
selected involves heating and the deformable composition contains a
latent (heat activated) curing agent or catalyst, care should be
taken to keep the temperature of the deformable composition below
the minimum temperature at which the curing agent or catalyst will
significantly crosslink or cure the deformable composition. Once
formed into a sheet, the deformable composition can be further
processed to provide the sealant article of the desired dimensions,
such as by die cutting or slitting the sheet. Alternatively, the
deformable composition can be directly shaped into the desired form
for placement on a substrate surface.
[0014] The thickness of the sealant article will vary depending
upon its intended end use. For most sealing applications, it is
desirable to have the sealant article thick enough to provide
sufficient material to flow and level out over dents, bumps, and
other surface imperfections or to fill in gaps between joints.
Useful thicknesses have been found to be in the range of about 0.05
mm to about 25 mm or about 0.5 to about 5 mm, for example. The
sealant article need not be uniform in thickness.
[0015] The shape of the sealant article can be varied to match the
general area and dimensions of the substrate surface which is
desired to be covered and sealed (e.g., the area proximate to a
joint between metal panels, such that the sealant article bridges
the joint).
[0016] The present invention may be practiced using any of a wide
variety of substrates, including, for example, substrates comprised
of metal, wood and other cellulosic materials, thermoset materials,
plastics, glass, concrete, ceramics, stone, and the like. In one
especially desirable aspect of the invention, the substrate is
comprised of one or more metals such as steel, including galvanized
steel, stainless steel, and cold rolled steel as well as aluminum.
The surface of the metal substrate to which the sealant article is
to be applied may be bare, pretreated (conversion coated), primed,
and/or painted. In the case of metal substrates, the sealant
articles of the present invention may be applied upon welded
joints, including joints formed by spot welding, wire welding,
laser welding and the like.
[0017] Typically, one or more surfaces of the sealant article are
radiation cured after at least partially shaping or forming the
sealant article and before applying the sealant article to the
surface of the substrate desired to be sealed. For example, the
deformable composition may be formed into a relatively flat, thin
sheet by extrusion or other suitable technique. The sheet is
exposed on one side to radiation such as ultraviolet light to cure
the surface of the sheet on that side. The sheet is then die cut or
slit to provide the sealant article, which is positioned onto the
substrate surface in the desired location with the other side of
the sealant article that has not been cured by radiation being
directed towards the substrate surface.
[0018] In one embodiment of the invention, a relatively thin skin
is formed upon the surface of the sealant article that has been
exposed to radiation, as a result of the radiation-induced
crosslinking or curing of at least certain components in the
deformable composition, e.g., the (meth)acrylate-functionalized
oligomer(s) and/or monomer(s). The surface skin serves to stabilize
the shape of the sealant article, particularly when the sealant
article is heated to a temperature effective to soften or melt the
portion of the deformable composition in the sealant article that
remains thermoplastic and substantially non-crosslinked.
[0019] Surface curing of the deformable composition can be
initiated using any suitable source of radiation, such as
ultraviolet or electron beam radiation. Where the radiation source
emits ultraviolet light, it will generally be desirable to include
one or more photoinitiators in the deformable composition. If
electron beam radiation is utilized, the presence of a
photoinitiator in the deformable composition is generally not
necessary.
[0020] One or more selected surfaces of the sealant article are
exposed to sufficient radiation in the form of ultraviolet light or
electron beam radiation to cause reaction of the radiation-reactive
components of the deformable composition (e.g., the
(meth)acrylate-functionalized oligomers and/or monomers) on the
surface. The reactive components polymerize and/or cross-link so as
to surface-harden or surface-cure the deformable composition.
Preferably, the amount of radiation is sufficient to induce
reaction of at least 90%, more preferably at least 95%, most
preferably all or essentially all of the radiation-reactive
components in that portion of the deformable composition
immediately proximate to the selected surface(s).
[0021] At the same time, the amount of radiation and the manner in
which the sealant article is exposed to the radiation are
controlled so that at least one surface of the sealant article (in
particular, the sealant article surface(s) to be applied to the
substrate surface(s) desired to be sealed) remains substantially or
completely uncured by the radiation. That is, the deformable
composition immediately proximate to such surface(s) does not cure
or crosslink to a significant extent and thus remains deformable,
i.e., more deformable than the surface(s) which has or have been
radiation cured.
[0022] The radiation-curable compositions utilized in the present
invention can be cured using conventional techniques for radiation
curing, such as irradiation of the composition layer on the
substrate surface using UV (ultraviolet) light from low, medium
and/or high pressure mercury vapor lamps, He--Cd and Ar lasers,
Xenon arc lamps, or other suitable source of radiation. The UV
light may have a wavelength of from about 200 to about 450
nanometers. The source of the electron beams (highly accelerated
electrons) can be a particle beam processing device. Such devices
are well-known in the art and are described, for example, in
published U.S. applications 2005-0233121, 2004-0089820,
2003-0235659, and 2003-0001108, each of which is incorporated
herein by reference in its entirety. Suitable electron beam
emitting devices are available, for example, from Energy Sciences,
Inc.
[0023] The amount of radiation necessary to cure the deformable
composition surface(s) to the desired extent will of course depend
on the angle of exposure to the radiation, the thickness of the
deformable composition, and the concentration and reactivity of the
functional groups present in the radiation-reactive components of
the deformable composition. For example, an ultra-violet source
with a wavelength between 200 and 300 nm (e.g. a filtered mercury
arc lamp) or an electron beam source may be directed at a sealant
article carried on a conveyor system which provides a rate of
passage past the radiation source appropriate for the radiation
absorption profile of the deformable composition (which profile is
influenced by the degree and depth of surface cure desired and the
rate of polymerization/crosslinking of the composition).
[0024] As previously mentioned, in a particularly preferred
embodiment of the invention the deformable composition is comprised
of at least one thermoplastic, at least one
(meth)acrylate-functionalized monomer or oligomer, at least one
thermally activatable free radical initiator, and at least one
filler. Optionally, the deformable may contain additional
components such as tackifiers, photoinitiators, and other
additives. Such compositions may desirably be formulated so as to
be radiation-curable, thermoplastic (substantially solid or
non-flowing at room temperature, but capable of melting or
softening to at least some extent when heated up to a certain
temperature), as well as heat-curable once heated past a certain
temperature and/or for a certain period of time. In one embodiment,
the surface of the deformable composition is tacky at room
temperature but following exposure to an amount of radiation
effective to achieve at least partial curing of the surface becomes
reduced in tackiness or even entirely non-tacky at room
temperature. Preferably, the melting point (as determined by DSC)
or softening point (as determined by a ring and ball test) of the
non-irradiated deformable composition is at least 50 degrees C. In
one embodiment, the components of the deformable composition such
that the composition remains thermoplastic within the temperature
range of from about 60 degrees C. to about 100 degrees C., but then
becomes thermoset (thermally crosslinked) when heated to a higher
temperature (e.g., from about 120 degrees C. to about 200 degrees
C.).
Thermoplastics
[0025] In one embodiment of the invention, the deformable
composition is comprised of one or more thermoplastics (i.e.,
thermoplastic polymers). Polyethylenes represent a class of
thermoplastics particularly suitable for use in the present
invention. The term polyethylene is understood herein to mean both
homo- and copolymers of ethylene.
[0026] Exemplary comonomers (monomers which could be copolymerized
with ethylene) include:
alpha-olefins, particularly those having from 3 to 30 carbon atoms
(e.g., propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene,
4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene,
1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene,
1-docosene, 1-tetracosene, 1-hexacosene, 1-octacosene and
1-triacontene; such alpha-olefins can be used alone or as a mixture
of two or of more than two; unsaturated carboxylic acid esters,
such as, for example, alkyl(meth)acrylates, it being possible for
the alkyl groups to have up to 24 carbon atoms; examples of alkyl
acrylates or methacrylates are in particular methyl methacrylate,
methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl
acrylate and 2-ethylhexyl acrylate; unsaturated carboxylic acids,
such as, for example, acrylic acid and methacrylic acid; vinyl
esters of saturated carboxylic acids, such as, for example, vinyl
acetate or vinyl propionate; and dienes, such as, for example,
1,4-hexadiene, 1,4-butadiene, isoprene.
[0027] The polyethylene can comprise two or more of the above
comonomers.
[0028] Mention may be made, as examples of polyethylenes, of:
low-density polyethylene (LDPE); high-density polyethylene (HDPE);
linear low-density polyethylene (LLDPE); very low-density
polyethylene (VLDPE); polyethylene obtained by metallocene
catalysis; ethylene/alkyl(meth)acrylate copolymers (such as
ethylene/methyl acrylate and ethylene ethyl acrylate copolymers);
ethylene/(meth)acrylic acid copolymers; ethylene/(meth)acrylic acid
copolymers; ethylene/vinyl acetate copolymers; and ethylene/vinyl
acetate/(meth)acrylic acid copolymers.
[0029] Copolymers of ethylene and vinyl acetate represent an
especially useful type of thermoplastic that can be used in the
deformable compositions of the present invention. As is well known
in the art, the molar ratio of ethylene:vinyl acetate and the
molecular weight of such copolymers may be varied so as to alter
the properties of the copolymer such as melting point, ring and
ball softening point, melt flow index, and the like. Different
ethylene/vinyl acetate copolymers may be blended to achieve a
particular desired balance of properties. Termonomers, such as
unsaturated carboxylic acids, can also be introduced to further
vary or control the characteristics of the thermoplastic.
[0030] In certain embodiments of the invention, ethylene/vinyl
acetate copolymers (including ethylene/vinyl acetate/unsaturated
carboxylic acid terpolymers) or mixture of ethylene/vinyl acetate
copolymers having one or more of the following characteristics are
used in the deformable composition: about 23 to about 36 weight
percent vinyl acetate, melt index of about 200 to about 1000 g/10
min at 190 degrees C., 2.16 kg (as measured by ASTM 1238), melting
point of from about 55 to about 75 degrees C. (as measured by DSC),
and/or ring and ball softening point of from about 70 to about 90
degrees C. (as measured by ASTM E28).
[0031] Suitable thermoplastics also include polycaprolactones and
polyesters (including polyesters containing functional groups such
as terminal hydroxyl and/or carboxylic acid groups) that may be
amorphous or semi-crystalline at room temperature. A material that
is "amorphous" has a glass transition temperature but does not
display a measurable crystalline melting point as determined on a
differential scanning calorimeter (DSC). A material that is
"semi-crystalline" displays a crystalline melting point as
determined by DSC, preferably with a maximum melting point of about
200 degrees C. The melting point of the polyester may be varied as
needed to achieve the desired melt flow characteristics in the
deformable composition. For example, the melting point of the
polyester may be selected to be within the range of from about 50
degrees C. to about 150 degrees C.
[0032] The preferred polyesters are solid at room temperature.
Typically, the polyesters have a number average molecular weight of
about 7500 to 200,000, e.g., from about 10,000 to 50,000, or, e.g.,
from about 15,000 to 30,000.
[0033] Thermoplastic polyesters useful in the invention comprise
the reaction product of dicarboxylic acids (or their diester or
dihalo equivalents) and diols. The diacids (or diester or dihalo
equivalents) can be saturated aliphatic acids containing from 4 to
12 carbon atoms (including branched, unbranched, or cyclic
materials having 5 to 6 carbon atoms in a ring) and/or aromatic
acids containing from 8 to 15 carbon atoms. Examples of suitable
aliphatic acids are succinic, glutaric, adipic, pimelic, suberic,
azelaic, sebacic, 1,12-dodecanedioic, 1,4-cyclohexanedicarboxylic,
1,3-cyclopentanedicarboxylic, 2-methylsuccinic,
2-methylpentanedioic, 3-methylhexanedioic acids, and the like.
Suitable aromatic acids include terephthalic acid, isophthalic
acid, phthalic acid, 4,4'-benzophenone dicarboxylic acid,
4,4'-diphenylmethanedicarboxylic acid, 4,4'-diphenylthioether
dicarboxylic acid, and 4,4'-diphenylamine dicarboxylic acid.
Preferably the structure between the two carboxyl groups in the
diacids contains only carbon and hydrogen, and more preferably, the
structure is a phenylene group. Blends of the foregoing diacids may
be used.
[0034] The diols include branched, unbranched, and cyclic aliphatic
diols having from 2 to 12 carbon atoms. Examples of suitable diols
include ethylene glycol, 1,3-propylene glycol, 1,2-propylene
glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol,
2-methyl-2,4-pentanediol, 1,6-hexanediol,
cyclobutane-1,3-di(2'-ethanol), cyclohexane-1,4-dimethanol,
1,10-decanediol, 1,12-dodecanediol, and neopentyl glycol. Long
chain diols including poly(oxyalkylene)glycols in which the
alkylene group contains from 2 to 9 carbon atoms, preferably 2 to 4
carbon atoms, may also be used, such as polyethylene glycol,
polypropylene glycol, and polytetramethylene glycol. Blends of the
foregoing diols may be used.
[0035] Useful thermoplastic polyesters that are commercially
available include various saturated linear, semi-crystalline
copolyesters available from Degussa America, Inc. such as DYNAPOL
S1401, DYNAPOL S1402, DYNAPOL S1358, DYNAPOLS1359, DYNAPOL S1227,
and DYNAPOL S1229. Useful saturated, linear amorphous copolyesters
available from Degussa America, Inc. include DYNAPOL S1313 and
DYNAPOL S1430.
[0036] The amount of thermoplastic present should be sufficient to
assist in rendering the deformable composition solid at room
temperature and preferably melt-flowable at an elevated
temperature. Typically, the deformable composition contains at
least about 10 weight percent but no greater than about 60 weight
percent (e.g., 20-45 weight percent) thermoplastic. More than one
type of thermoplastic can be present; for example, a combination of
a polyethylene and a polyester can be utilized. All amounts herein,
unless otherwise stated, are expressed in terms of percent by
weight of the total weight of the deformable composition.
(Meth)Acrylate-Functionalized Monomers and Oligomers
[0037] The deformable compositions of the present invention may
comprise one or more radiation curable
(meth)acrylate-functionalized oligomers. These are oligomeric
substances of low to moderate molecular weight (e.g., from about
300 to about 10,000 number average molecular weight) having one or
more acrylate and/or methacrylate groups attached to the oligomeric
backbone. The (meth)acrylate functional groups may be in a terminal
position on the oligomer and/or may be distributed along the
oligomeric backbone. In one embodiment of the invention, at least a
portion of the (meth)acrylated functionalized oligomers have two or
more (meth)acrylate functional groups per molecule. Examples of
such oligomers include (meth)acrylate-functionalized urethane
oligomers (sometimes also referred to as "acrylated urethanes" or
"urethane (meth)acrylates") such as (meth)acrylate-functionalized
polyester urethanes and (meth)acrylate-functionalized polyether
urethanes, (meth)acrylate-functionalized polyepoxide resins,
(meth)acrylate-functionalized polybutadienes, (meth)acrylic polyol
(meth)acrylates (also known as "poly(meth)acrylate (meth)acrylates"
or "(meth)acrylated poly(meth)acrylates"), polyester (meth)acrylate
oligomers (also known as "polyester (meth)acrylates"), polyamide
(meth)acrylate oligomers, polyether (meth)acrylate oligomers (also
known as "polyester (meth)acrylates"), polysiloxane (meth)acrylate
oligomers and the like. Such (meth)acrylate-functionalized
oligomers and their methods of preparation are disclosed in, for
example, U.S. Pat. Nos. 4,574,138; 4,439,600; 4,380,613; 4,309,526;
4,295,909; 4,018,851, 3,676,398; 3,770,602; 4,072,529; 4,511,732;
3,700,643; 4,133,723; 4,188,455; 4,206,025; 5,002,976; and
published U.S. applications 2004/0127594 and 2005/0065310. Such
materials are available from numerous commercial sources, including
the UVITHANE resins from Morton International, certain oligomers
sold under the brand name PHOTOMER by Cognis Corporation, the CN
oligomer resins from Sartomer Company, the GENOMER resins from Rahn
Inc., and the EBECRYL resins from the Cytec Surface Specialties
Division of Cytec Industries, Inc.
[0038] Suitable (meth)acrylate-functionalized monomers which may be
present in the radiation-curable deformable composition include
monomers having single (meth)acrylate groups such as
tetrahydrofurfuryl (meth)acrylate, hydroxyethyl (meth)acrylate,
hydroxypropyl (meth)acrylate, isobornyl (meth)acrylate, methyl
(meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate,
isooctyl (meth)acrylate, octyl (meth)acrylate, decyl
(meth)acrylate, (meth)acrylic acid, n-hexyl (meth)acrylate, stearyl
(meth)acrylate, allyl (meth)acrylate, 2(2-ethoxyethoxy)ethyl
(meth)acrylate, 2-phenoxyethyl (meth)acrylate, ethoxylated nonyl
phenol (meth)acrylates, (meth)acrylated monomers such as those
described in U.S. Pat. No. 4,652,274, monomethoxy tripropylene
glycol monoacrylate (available from Cognis Corporation under the
designation PHOTOMER 8061), neopentylglycol propoxylate (2)
methylether monoacrylate (available from Cognis Corporation under
the designation PHOTOMER 8127), and the like. Other suitable
(meth)acrylate-functionalized monomers include carboxylic
acid-functionalized ester-containing (meth)acrylate monomers, e.g.,
compounds containing at least one carboxylic acid group
(--CO.sub.2H), at least one ester linkage (in addition to at least
one acrylate or methacrylate group) and at least one acrylate or
methacrylate group per molecule. Such substances are well-known in
the art and may be prepared using any suitable synthetic method.
For example, one such method involves reacting a compound
containing both a hydroxyl group and a (meth)acrylate group with an
anhydride. Carboxylic acid-functionalized ester-containing
(meth)acrylate monomers suitable for use in the present invention
are available from commercial sources, including, for example, ECX
4046 from Cognis Corporation and the series of specialty oligomers
sold by the Sartomer Company under the brand name SARBOX.
[0039] Suitable monomers having plural (meth)acrylate functionality
(i.e., two or more (meth)acrylate groups per molecule) include, for
example, 1,3-butylene glycol di(meth)acrylate, diethylene glycol
di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol
di(meth)acrylate, triethylene glycol di(meth)acrylate,
tetraethylene glycol di(meth)acrylate, dipropylene glycol
di(meth)acrylate, tripropylene glycol di(meth)acrylate, trimethylol
propane ethoxylate tri(meth)acrylate, pentaerythritol
tetra(meth)acrylate, tripropylene glycol di(meth)acrylate,
trimethylol propane tri(meth)acrylate, ethoxylated bisphenol A
di(meth)acrylates, ethoxylated hexanediol di(meth)acrylates,
tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate, ditrimethylol
propane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate,
propoxylated glycerol tri(meth)acrylates, pentaerythritol
tri(meth)acrylate, and the like. In one embodiment of the
invention, the deformable composition comprises one or more
alkoxylated polyol poly(meth)acrylates containing at least three
(meth)acrylate groups per molecule. The polyol may be an organic
compound containing three or more hydroxyl groups
trimethylolethane, trimethylolpropane, pentaerythritol,
dipentaerythritol, sugar alcohols, or the like. The polyol is
reacted with one or more alkylene oxides such as ethylene oxide or
propylene oxide (typically, from about 1 to about 20 moles of
alkylene oxide per mole of polyol) to form an alkoxylated polyol,
then esterified with acrylic acid, methacrylic acid, or a
derivative thereof to obtain the alkoxylated polyol
poly(meth)acrylate.
[0040] Epoxy (meth)acrylates, including aromatic and aliphatic
epoxy (meth)acrylates, are one especially preferred class of
compounds suitable for use in the deformable compositions of the
present invention. Epoxy (meth)acrylates are the beta-hydroxy
esters which are generated by the reaction of acrylic acid and/or
methacrylic acid (or an equivalent thereof, such as an anhydride)
with an epoxy compound, preferably an epoxy compound having an
epoxy functionality of two or greater. Suitable epoxy
(meth)acrylates include the relatively low viscosity epoxy
(meth)acrylates derived from diglycidyl ethers obtained by reaction
of epichlorohydrin with an aliphatic alcohol containing two or more
hydroxyl groups per molecule. Suitable aliphatic alcohols include,
for example, glycols such as ethylene glycol, 1,2-propanediol,
1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,6-hexanediol,
neopentyl glycol and other linear and branched C2-C10 aliphatic
diols, triols such as glycerin, trimethyolpropane,
trimethylolethane, butanetriols, pentanetriols, and the like,
tetrols such as pentaerythritol, as well as other polyfunctional
alcohols such as dipentaerythritol, sugar alcohols and the like and
alkoxylated derivatives thereof (where the alcohol has been reacted
with an alkylene oxide such as ethylene oxide or propylene oxide,
including both oligomeric species such as diethylene glycol or
tripropylene glycol as well as polymeric species such as
polyethylene glycols or polypropylene glycols or block, capped or
random copolymers of ethylene oxide and propylene oxide). The
alcohol may also be an aromatic alcohol such as bisphenol A,
bisphenol F, or the like. The epoxy compound reacted with the
(meth)acrylic acid may also be an epoxidized unsaturated
triglyceride such as epoxidized soybean oil or epoxidized linseed
oil. Preferably, all or essentially all of the epoxy groups on the
epoxy compound are ring-opened with the (meth)acrylic acid.
Suitable preferred epoxy (meth)acrylates thus have two, three, or
more (meth)acrylate groups and two, three, or more hydroxyl groups
per molecule. Specific illustrative examples of suitable epoxy
compounds include bisphenol A diglycidyl ethers, bisphenol F
diglycidyl ethers, hexanediol diglycidyl ethers, neopentyl glycol
diglycidyl ethers, and butanediol diglycidyl ethers.
[0041] The deformable compositions of the present invention contain
one or more urethane (meth)acrylate oligomers. The use of such
urethane (meth)acrylate oligomers in place of epoxy (meth)acrylates
has been found to significantly improve the moisture/humidity
resistance of the deformable composition. Absorption of water into
the deformable composition is generally undesirable, since a
composition containing absorbed water tends to exhibit foaming
during baking or curing. Urethane (meth)acrylate oligomeric
materials contain at least one urethane linkage (in some
embodiments, two or more urethane linkages) within the backbone of
the oligomeric molecule and at least one acrylate and/or
methacrylate functional groups (in some embodiments, two or more
acrylate and/or methacrylate functional groups) pendent to the
oligomeric molecule. The (meth)acrylate functional groups provide
unsaturated double bonds capable of reaction when the deformable
composition is exposed to radiation, thereby inducing curing of the
composition. Typically, the urethane (meth)acrylate oligomer is
liquid at room temperature or at least is liquid at the temperature
at which the deformable composition is to be processed, although
higher melting oligomers which are solubilized by the other
components of the adhesive may also be used. The (meth)acrylate
functional group(s) may be on the terminal position(s) of the
oligomeric molecule and/or distributed along the backbone of the
oligomeric molecule. Typically, the number average molecular weight
of the urethane (meth)acrylate oligomer is from about 1000 to about
6000.
[0042] Urethane (meth)acrylate oligomers are well-known in the art
and may be readily synthesized by a number of different procedures.
For example, a polyfunctional alcohol may be reacted with a
polyisocyanate (preferably, a stoichiometric excess of
polyisocyanate) to form an NCO-terminated preoligomer, which is
thereafter reacted with a hydroxy-functional (meth)acrylate. The
polyfunctional alcohol may be any compound containing two or more
OH groups per molecule and may be a monomeric polyol (e.g., a
glycol), a polyester polyol, a polyether polyol, a (meth)acrylic
polyol or the like. The urethane (meth)acrylate oligomer in one
embodiment of the invention is an aliphatic urethane (meth)acrylate
oligomer. In another embodiment of the invention, the urethane
(meth)acrylate oligomer is a polyester urethane (meth)acrylate
oligomer.
[0043] For example, a polyester polyol may be prepared by a
condensation polymerization involving one or more diols and one or
more diacids, anhydrides or diesters, with the stoichiometry of the
reactants and the reaction conditions adjusted so as to provide
terminal OH groups on the polyester thereby formed. The polyester
polyol molecular weight may be, for example, from about 300 to
about 10,000. Suitable diols include, for example, aliphatic
glycols such as ethylene glycol, propane-1,2-diol,
propane-1,3-diol, 2-methyl-1,3-propanediol, neopentyl glycol,
1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, and the like.
Suitable diacids and diesters include aliphatic and aromatic
dicarboxylic acids and esters thereof such as, for example,
succinic acid, adipic acid, suberic acid, azelaic acid, glutaric
acid, glutaric anhydride, phthalic acid, isophthalic acid,
terephthalic acid, phthalic anhydride, tetrahydrophthalic
anhydride, maleic acid, maleic anhydride, fumaric acid, dimer fatty
acids, and mixtures thereof. The hydroxyl groups of the polyester
polyol may then be reacted with an aliphatic or aromatic
diisocyanate, preferably in stoichiometric excess so as to provide
an isocyanate-tipped preoligomer. Suitable diisocyanates include,
but are not limited to, diphenylmethane diisocyanate (MDI) isomers,
hydrogenated MDI isomers, xylylene diisocyanate, tetramethyl
xylylene diisocyanate (TMXDI), isophorone diisocyanate (IPDI),
hexane-1,6-diisocyanate (HDI), toluene diisocyanate (TDI) isomers,
cyclohexane diisocyanate and the like. The isocyanate groups of the
preoligomer are then reacted with a hydroxyl- and
(meth)acrylate-functionalized compound to provide the urethane
(meth)acrylate oligomer. The compound containing a hydroxyl group
and a (meth)acrylate group may, for example, be selected from the
following: 2-hydroxyethyl (meth)acrylate;
2-hydroxpropyl(meth)acrylate; 2-hydroxybutyl(meth)acrylate;
2-hydroxy 3-phenyloxpropyl(meth)acrylate; 1,4-butanediol
mono(meth)acrylate; 4-hydroxycyclohexyl (meth)acrylate;
1,6-hexanediol mono(meth)acrylate; neopentylglycol
mono(meth)acrylate; trimethylolpropane di(meth)acrylate;
trimethylolethane di(meth)acrylate; pentaerythritol
tri(meth)acrylate; dipentaerythritol penta(meth)acrylate; and other
hydroxy functional (meth)acrylates such as the hydroxy terminated
(meth)acrylate monomers based on caprolactone sold under the brand
name TONE by Dow Chemical (e.g. TONE M-100, M-101, and M-20).
[0044] Alternatively, a polyether polyol (with a number average
molecular weight of from about 400 to about 6000, for example)
could be substituted for the polyester polyol in the aforedescribed
synthetic procedure. Suitable polyether polyols may be obtained by
reaction of low molecular weight polyalcohols (e.g., ethylene
glycol, glycerin, 1,4-butanediol, trimethylolpropane) with alkylene
oxides (e.g., epoxides such as ethylene oxide, propylene oxide
and/or butene oxide). Polytetramethylene glycols prepared by
ring-opening polymerization of tetrahydrofuran could also be
used.
[0045] In yet another embodiment, a (meth)acrylic polyol may be
reacted with a polyisocyanate and then with a hydroxy functional
(meth)acrylate to provide the urethane (meth)acrylate oligomer. The
preparation of such oligomers is described, for example, in U.S.
published application 2005-0065310, incorporated herein by
reference in its entirety. Suitable urethane(meth)acrylate
oligomers are available from commercial sources, including, for
example, ECX 6026, PHOTOMER 6210, PHOTOMER 6008, PHOTOMER 6010,
PHOTOMER 6019, PHOTOMER 6363, PHOTOMER 6572, PHOTOMER 6891,
PHOTOMER 6892 and PHOTOMER 6893-20R from Cognis Corporation and
PE230 Block Resin from the Liofol Division of Henkel Corporation.
The Sartomer Company also sells a wide variety of
urethane(meth)acrylate oligomers, including, for example, CN961,
CN962, CN963, CN964, CN965, CN966, CN980, CN981, CN9001, CN9002,
CN9004, CN929, CN968, CN9788, CN983 CN984, CN9893, CN996, CN1963,
CN972, CN975, CN978, CN9782, CN9783, CN991, CN992, CN994, CN997,
and CN999. Other suppliers of suitable urethane (meth)acrylate
oligomers include Rahn Inc. (under the brand name GENOMER) and UCB
Chemicals (under the brand name EBECRYL). Certain suppliers sell
admixtures of urethane (meth)acrylate oligomers and other
components that can also be suitable for use in the present
invention, provided the other components are also desirable for
incorporation into the radiation-curable laminating adhesive or, at
a minimum, do not interfere with the intended use and function of
the deformable composition. Examples of such admixtures include
CN3100 and CN966H90 from Sartomer.
[0046] Materials capable of being utilized as the
urethane(meth)acrylate oligomer component of the present invention
are also described in published United States application US
2004/0127594, incorporated herein by reference in its entirety.
See, in particular, structures (I) and (II) of the aforementioned
published application.
[0047] The deformable composition should contain sufficient
(meth)acrylate-functionalized oligomer and/or monomer to allow a
selected surface of the sealant article prepared therefrom to be
crosslinked/cured by radiation to the desired extent. Such amount
will vary depending upon the particular
(meth)acrylate-functionalized oligomer(s)/monomer(s) selected, but
typically will be at least about 1 weight percent but no greater
than about 40 weight percent (e.g., 5-30 weight percent).
Thermally Activatable Free Radical Initiators
[0048] In certain embodiments, the deformable composition is
comprised of one or more thermally activatable (latent) free
radical initiators. Such initiators include substances capable of
inducing free radical reactions, in particular organic peroxides
including ketone peroxides, diacyl peroxides, peresters, perketals,
hydroperoxides and others such as cumene hydroperoxide, t-butyl
peroxide, bis(tert-butylperoxy)diisopropylbenzene, di(tert-butyl
peroxyisopropyl)benzene,
1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, dicumyl
peroxide, t-butylperoxybenzoate, di-alkyl peroxydicarbonates,
di-peroxyketals (such as
1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane), ketone
peroxides (e.g., methylethylketone peroxide),
2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, dibenzoyl peroxide, and
4,4-di-tert-butylperoxy n-butyl valerate. The thermally activatable
free radical initiator is preferably essentially inert or
non-reactive within the temperature range of room temperature
through the temperature at which the sealant article is to be
fabricated (by extrusion of the deformable composition, for
example), e.g., about 25 degrees C. to about 100 degrees C., but is
activated by heating to an elevated temperature (for example, a
temperature within the range of from about 120 degrees C. to about
200 degrees C.). In one embodiment, the peroxide free radical
initiator has a ten minute half life temperature of from about 140
to about 180 degrees C. The aforedescribed free radical initiators
are believed to assist in cross-linking the various polymeric
components of the deformable compositions of the present invention
(in particular, the one or more thermoplastics), thereby improving
and/or modifying the physical and/or mechanical characteristics of
such compositions and the cured sealant articles obtained
therefrom. The deformable composition may, for example, typically
contain from about 0.05 to about 5 or about 0.1 to about 2 weight %
free radical initiator.
[0049] Coagents can be used with peroxides to modify the thermal
curing characteristics of the deformable composition. Suitable
coagents include, for example, metal salts of unsaturated
carboxylic acids having from 3 to 8 carbon atoms. Particularly
suitable metal salts include, for example, one or more metal salts
of acrylates, diacrylates, methacrylates, and dimethacrylates,
wherein the metal is selected from magnesium, calcium, zinc,
aluminum, lithium, and nickel. In a particular embodiment, the
coagent is selected from zinc salts of acrylates, diacrylates,
methacrylates, and dimethacrylates. In another particular
embodiment, the coagent is zinc diacrylate. Although the use of a
coagent is optional, typically the deformable composition may
comprise up to about 10 weight percent of one or more coagents
(e.g., 0.5 to 8 weight percent coagent).
Fillers
[0050] In certain embodiments of the invention, the deformable
composition contains one or more fillers, especially inorganic
fillers in finely divided (powdered) form. Examples of suitable
fillers include talc, ground and precipitated chalks, silica,
titanium dioxide, magnesium carbonate, barium sulfate, calcium
carbonate, calcium-magnesium carbonates, alumina, zirconia, zinc
oxides, and other inorganic metal oxides, sulfides, sulfates and
carbonates, clays, zeolites, glass beads (including hollow glass
microspheres), glass fibers, polymeric fibers, mica, carbon black,
barite and silicate fillers of the aluminium-magnesium-calcium
type, such as wollastonite and chlorite. In one aspect, the
deformable composition contains a substantial amount of one or more
fillers, e.g., at least about 20 weight % filler, although
typically the composition will not contain more than about 60
weight % filler.
Photoinitiators
[0051] Where the deformable composition is to be cured using
ultraviolet radiation, the composition additionally preferably
contains at least one photoinitiator, which may be employed alone
or in combination with a photosensitizer. Suitable photoinitiators
are any of those known to those skilled in the art for use with
radiation (including visible and ultraviolet light) curable
(meth)acrylate systems. Exemplary of such photoinitiators are
acetophenone and its derivatives such as dichloroacetophenone,
trichloroacetophenone, dialkoxyacetophenone,
2,2-dimethoxy-2-phenylacetophenone and 4-dialkylaminoacetophenone;
benzophenone and its derivatives such as
4,4'-bis(dimethylamino)benzophenone (Michler's ketone) and
4,4'-bis(diethylamine)benzophenone; benzil; benzoin and its
derivatives such as benzoin alkyl ether; benzildimethylketal;
benzoylbenzoate; alphaacyloxime esters; thioxanthone and its
derivatives such as 2-chlorothioxanthone and diethylthioxanthone;
azo-compounds such as azobisisobutyronitrile; benzoyl peroxide;
camphoquinone; phosphine oxides such as
diphenyl-2,4,6-trimethylbenzoylphosphine oxide and the like.
Especially preferred photoinitiators include aryl-substituted
ketones and benzoyl-substituted phosphine oxides. Examples of
commercially available photoinitiators suitable for use in the
present invention include DAROCUR 1173, DAROCUR 4265, IRGACURE 651,
IRGACURE 2959, and IRGACURE 819. The precise concentration of
photoinitiator(s) in the deformable composition is not believed to
be particularly critical, although a sufficient amount should be
used to effectively accomplish curing of the
(meth)acrylate-functionalized oligomers and monomers within the
desired period of time upon exposing the composition to light
radiation. Typically, photoinitiator concentrations of from about
0.01 to about 5 weight percent (e.g., about 0.1 to about 2 weight
percent) are utilized.
Tackifiers
[0052] In some cases, it has proved to be of advantage to add at
least one tackifier to the deformable composition. In the context
of the invention, a "tackifier" is understood to be a resin which
makes the deformable composition tacky so that other articles
adhere firmly to it after light pressure has been briefly applied.
They themselves do not have to be tacky at room temperature.
Suitable tackifiers generally have relatively low number average
molecular weights of around 200 to 3,000, with relatively broad
molecular weight distributions. Reactive and well as non-reactive
tackifiers may be utilized. Exemplary types of tackifiers include
rosin derivatives (e.g., derivatives of wood rosins and tall oil
rosins, including hydrogenated and/or esterified derivatives
thereof), coumarone-indene resins, terpene oligomers, aliphatic
petroleum resins (including the hydrocarbon resins obtained by
oligomerization of the C5 and C6 fractions of petroleum and
hydrogenated derivatives thereof), copolymers of
alpha-methylstyrene and vinyltoluene, and alkyl-modified phenolics.
Especially suitable reactive tackifiers include liquid diene
polymers and copolymers (e.g., liquid polybutadienes), particularly
those having a relatively high (e.g., over 70%) vinyl content.
[0053] Although the deformable composition does not necessarily
need to include a tackifier, typically tackifiers will be used at a
concentration of at least 0.5 weight percent but no more than about
20 weight percent (e.g., 1 to 12 weight percent).
Other Components
[0054] The deformable compositions of the present invention may
also contain one or more additional components or additives, such
as, for example, colorants, pigments, plasticizers, processing
aids, organic acids (e.g., fatty acids), anti-oxidants,
stabilizers, thixotropic agents, thickeners, reactive diluents,
adhesion promoters, coupling agents, and the like. Radiation
absorbers or blocking agents may be incorporated into the
deformable composition for the purpose of limiting the depth of
radiation cure in the sealant article, e.g., controlling such
curing so that substantially only the deformable composition on and
immediately proximate to the selected surface is fully cured.
[0055] In one aspect of the invention, the deformable composition
is free or essentially free of any volatile organic compounds
(VOCs) such as solvents and the like. The deformable composition
may also be formulated such that it is free or essentially free of
epoxy compounds.
[0056] In one aspect of the invention, the deformable composition
corresponds to the following composition (the amounts being
expressed as weight % of the total weight of the deformable
composition, it being understood that additional components besides
those mentioned below may also be present):
TABLE-US-00001 Ethylene/Vinyl Acetate Copolymer(s) and/or
Polyester(s) 20-45 Reactive Tackifier(s), e.g., Liquid
Polybutadiene(s) 1-12 (Meth)acrylate-Functionalized Monomer(s)
and/or 5-30 Oligomer(s), e.g., Epoxy (Meth)acrylate(s) and/or
Urethane (Meth)acrylates Inorganic Particulate Filler(s) 25-55
Organic Peroxide(s) 0.1-2 Photoinitiator(s) 0.1-2
[0057] The composition may be blended, extruded into a sealant
article having a specific desired shape such as a tape, and then
exposed to a source of radiation such as ultraviolet light or
electron beam radiation under conditions effective to cure
(crosslink) one surface of the sealant article to an extent
sufficient to render such surface resistant to deformation while
leaving the opposite surface of the sealant article essentially
uncured and still capable of being readily deformed. The sealant
article may then be applied over a substrate such as a welded metal
joint (as might be found in a vehicle roof ditch, for example) and
pressed into position such that at least a portion of the
deformable opposite surface of the sealant article is in contact
with at least a portion of the substrate surface. The sealant
article can be exposed to a temperature effective to cause the
deformable composition to thermally cure and to come into closer
conformance with the substrate surface through softening/melting of
the deformable composition. The substrate surface is thereby
effectively sealed. Prior to heating of the sealant article, the
deformation-resistant, radiation-cured surface of the sealant
article helps to make the sealant article easier to handle and
manipulate than an analogous sealant article where such surface has
not been cured by exposure to radiation. Additionally, the
radiation cured surface, which is typically positioned facing away
from the substrate surface to which the sealant article is applied,
improves the resistance of the sealant article towards being
deformed due to air trapped beneath the sealant article or blown
through the substrate to be sealed (e.g., where the substrate
surface includes one or more openings) or due to an uneven
substrate surface.
EXAMPLES
Example 1
[0058] A deformable composition in accordance with the present
invention may be formulated using the following components (the
amounts being expressed as weight percent based on the total weight
of the deformable composition):
TABLE-US-00002 Ethylene/Vinyl Acetate Copolymer.sup.1 33.25 Liquid
Polybutadiene.sup.2 5.54 Epoxy (Meth)acrylate.sup.3 16.07 Carbon
Black 0.01 Barium Sulfate 27.71 Calcium Carbonate 16.62
Peroxide.sup.4 0.36 Photoinitiator.sup.5 0.44 .sup.111.08% ELVAX
205W (DuPont) and 22.16% K2102 .sup.2RICON 154 (Sartomer)
.sup.3EBECRYL 3700 (UCB) .sup.40.03% VULCUP + 0.33% VAROX 130-XL
dialkyl. 2,5-dimethyl-2,5-Di-(t-.butylperoxy)hexyne-3 (R. T.
Vanderbilt) .sup.5IRGACURE 651 alpha,
alpha-dimethoxy-alpha-phenylacetophenone (Ciba)
[0059] The components may be mixed at a temperature of from about
70 degrees C. to about 90 degrees C. using any suitable
conventional mixer of the type utilized in the plastics and rubber
industry. The deformable composition may be formed into a
relatively thin, flat sheet and then surface-cured on one side of
the sheet by exposing the sheet to ultraviolet radiation. For
example, in a laboratory environment, a single UV lamp having an
output of 0.82 W/cm.sup.2, 0.350 J/cm.sup.2, at slowest setting may
be utilized. In a production environment, three lamps having an
output of 0.112 W/cm.sup.2, 0.431 J/cm.sup.2, at a speed of 350
inches per minute may be used. The sealant article thereby obtained
may be applied to a substrate surface, with the surface-cured side
of the sheet facing away from the substrate surface, and then
heated at a temperature of from about 325 degrees F. (165 degrees
C.) to about 375 degrees F. (190 degrees C.) to soften the uncured
portion of the sealant article in contact with the substrate
surface, thereby accomplishing effective sealing of such surface.
Heating at such temperature also activates the organic peroxide and
promotes thermal crosslinking/curing of the deformable composition,
in particular the polymeric components of the composition such as
the ethylene/vinyl acetate copolymer.
Example 2
[0060] Another deformable composition in accordance with the
present invention may be formulated using the following components
(the amounts being expressed as weight percent based on the total
weight of the deformable composition):
TABLE-US-00003 Barium Sulfate 27.93 Calcium Carbonate 16.76
Ethylene Vinyl Acetate Copolymer.sup.1 33.51 Polybutadiene 5.59
Urethane (Meth)acrylate.sup.2 15.08 Carbon Black 0.01 Organic
Peroxide.sup.3 0.67 Photoinitiator.sup.4 0.45 .sup.118.43% EVATANE
33-400 (Arkema) + 15.08% ELVAX 46 (DuPont) .sup.25.03% CN 991 +
10.05% CN 965 (Sartomer) .sup.30.45% LUPERCO 130XL (Arkema) + 0.22%
VAROX 230XL (R. T. Vanderbilt) .sup.4IRGACURE 651 (Ciba)
[0061] The deformable composition thereby obtained has improved
moisture/humidity resistance, as compared to the composition of
Example 1, but exhibits similar radiation curing, thermal curing,
and melt flow characteristics. Absorption of water during storage
under ambient conditions tends to cause the deformable composition
to expand when baked, which normally is undesirable. It is believed
that the marked and unexpected improvement in humidity/moisture
resistance exhibited by the composition of Example 1 is due to the
use of urethane (meth)acrylate in place of the epoxy (meth)acrylate
in the composition of Example 1.
Example 3
[0062] A deformable composition in accordance with the present
invention may be formulated using the following components (the
amounts being expressed as weight percent based on the total weight
of the deformable composition):
TABLE-US-00004 Zinc Diacrylate 3.94 Calcium Carbonate 32.80
Copolyester.sup.1 22.96 Ethylene Vinyl Acetate Copolymer.sup.2
16.40 Polybutadiene.sup.3 2.62 Urethane (Meth)Acrylate.sup.4 19.68
Carbon Black 0.01 Stearic Acid 0.39 Organic Peroxide.sup.5 0.66
Photoinitiator.sup.6 0.52 .sup.1DYNAPOL S1402 (Degussa) .sup.2ELVAX
46 (DuPont) .sup.3RICON 154 (Sartomer) .sup.49.84% CN 991 + 9.84%
CN 965 (Sartomer) .sup.5VAROX 230XL (R. T. Vanderbilt)
.sup.6IRGACURE 651 (Ciba)
[0063] The deformable composition can be formed into a sheet and
surface-cured on one side by exposure to radiation in accordance
with the procedures described in Example 1. The sealant article
thereby obtained may be applied to a substrate surface, with the
surface-cured side of the sheet facing away from the substrate
surface, and then heated at a temperature of from about 255 degrees
F. (125 degrees C.) to about 320 degrees F. (160 degrees C.) to
soften the uncured portion of the sealant article in contact with
the substrate surface, thereby accomplishing effective sealing of
such surface. The sealant article also undergoes thermal curing
within this temperature range, as certain components contained in
the sealant article experience a thermoset reaction when so
heated.
* * * * *