U.S. patent application number 14/290514 was filed with the patent office on 2014-12-04 for packaged hot-melt pressure sensitive adhesive.
The applicant listed for this patent is H.B. FULLER COMPANY. Invention is credited to Dirk LAUKIEN, Nicholas PORRO, Peter REMMERS, Nicholas TAYLOR.
Application Number | 20140357145 14/290514 |
Document ID | / |
Family ID | 51059599 |
Filed Date | 2014-12-04 |
United States Patent
Application |
20140357145 |
Kind Code |
A1 |
REMMERS; Peter ; et
al. |
December 4, 2014 |
PACKAGED HOT-MELT PRESSURE SENSITIVE ADHESIVE
Abstract
The present invention relates to a packaged hot-melt pressure
sensitive adhesive comprising a hot-melt pressure sensitive
adhesive composition and a coextrusion coating consisting of neat
low density polyethylene, neat polypropylene, or neat ethylene
vinyl acetate. The present invention further relates to the use of
the packaged adhesive formed as individual forms in an adhesive
application process, and the use of the packaged adhesive in the
production of laminated articles, including nonwoven hygiene
articles, disposable medical drapes, and also laminate
constructions such as tapes and labels.
Inventors: |
REMMERS; Peter; (Hamburg,
DE) ; PORRO; Nicholas; (Wilmington, DE) ;
TAYLOR; Nicholas; (Oakwood, GB) ; LAUKIEN; Dirk;
(Radbruch, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
H.B. FULLER COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
51059599 |
Appl. No.: |
14/290514 |
Filed: |
May 29, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61828479 |
May 29, 2013 |
|
|
|
Current U.S.
Class: |
442/151 ;
198/717; 198/752.1; 428/343 |
Current CPC
Class: |
A61L 31/14 20130101;
B32B 27/325 20130101; D06N 2209/16 20130101; B32B 27/18 20130101;
C09J 5/06 20130101; D06N 2205/06 20130101; Y10T 428/23 20150115;
C09J 2423/003 20130101; D10B 2509/00 20130101; Y10T 428/1334
20150115; B32B 1/02 20130101; B32B 27/22 20130101; C09J 7/243
20180101; A61L 15/225 20130101; B65G 27/00 20130101; Y10T 442/2754
20150401; Y10T 428/1341 20150115; B32B 1/08 20130101; B32B 27/327
20130101; D06N 3/0086 20130101; Y10T 428/2967 20150115; B32B 27/306
20130101; B65G 19/18 20130101; Y10T 428/28 20150115; C09J 7/387
20180101; Y10T 428/1352 20150115; D06N 3/045 20130101; A61L 15/585
20130101; A61L 31/041 20130101; C09J 2301/304 20200801; D06N 3/0011
20130101; D06N 2203/042 20130101; B32B 27/32 20130101; D10B
2509/026 20130101; B32B 27/30 20130101; Y10T 428/1379 20150115 |
Class at
Publication: |
442/151 ;
198/717; 198/752.1; 428/343 |
International
Class: |
D06N 3/00 20060101
D06N003/00; B65G 27/00 20060101 B65G027/00; D06N 3/04 20060101
D06N003/04; B65G 19/18 20060101 B65G019/18 |
Claims
1. A method of using a hot melt pressure sensitive adhesive in
individual forms comprising the steps of: a.) obtaining coextruded
hot melt pressure sensitive adhesive in individual forms; and b.)
conveying the hot melt pressure sensitive adhesive to a melting
system by use of a conveying system selected from the group
consisting of a tubular drag conveying system and a melt on demand
conveying system.
2. The method of claim 1 wherein the coextruded hot melt pressure
sensitive adhesive in individual form is fed into the conveying
system by use of a vibratory feeder.
3. The method of claim 1 wherein the conveying system is a tubular
drag conveying system.
4. The method of claim 1 wherein the hot melt pressure sensitive
adhesive in individual form is a pillow with a thickness of at
least about 0.635 cms (0.250 inches).
5. The method of claim 1 wherein the hot melt pressure sensitive
adhesive comprises a propylene polymer.
6. The method of claim 1 wherein the hot melt pressure sensitive
adhesive has an average penetration number (PZ), which is between
about 20 and about 70.
7. The method of claim 1 wherein the hot melt pressure sensitive
adhesive is conveyed to more than one melting system.
8. The method of claim 1 wherein the hot melt pressure sensitive
adhesive is provided in the individual form selected from the group
consisting of a pillow, a prill and a coextruded rope.
9. The method of claim 1 wherein the hot melt pressure sensitive
adhesive composition comprises a base polymer selected from the
group consisting of polyolefins, polyolefin copolymers,
polyolefin/alpha-olefin interpolymers and synthetic rubbers.
10. A method of providing molten adhesive comprising: a. providing
a plurality of individual forms of a coextrusion coated hot melt
pressure sensitive adhesive wherein the hot melt pressure sensitive
adhesive has an average penetration number (PZ), which is between
about 20 and about 70; b. conveying the plurality of individual
forms to a melting system; c. heating the plurality of individual
forms until they become a molten adhesive; and d. applying the
molten adhesive to a substrate.
11. The method of claim 10 wherein the plurality of individual
forms have a rating of at least 3 when tested according to blocking
test 1.
12. The method of claim 10 wherein the plurality of individual
forms are continuously conveyed to the melting system so as to
maintain a consistent level of adhesive in the melting system.
13. The method of claim 10 wherein the plurality of individual
forms are conveyed with a tubular drag conveying system.
14. The method of claim 10 wherein the plurality of individual
forms are conveyed with a melt on demand conveying system.
15. The method of claim 10 wherein the coextrusion coating is neat
low-density polyethylene.
16. The method of claim 15 wherein the neat low-density
polyethylene has a melt flow index between about 20 g/10 min and
about 300 g/10 min.
17. The method of claim 10 wherein the hot melt pressure sensitive
adhesive comprises a propylene polymer.
18. The method of claim 10 wherein the substrate is a
non-woven.
19. The method of claim 10 wherein the hot melt pressure sensitive
adhesive comprises less than about 20 wt % plasticizer.
20. The method of claim 10 wherein the hot melt pressure sensitive
adhesive composition comprises a polypropylene polymer.
Description
[0001] This patent application claims the benefit of or priority to
U.S. provisional application No. 61/828,479 filed on May 29,
2013.
FIELD OF THE INVENTION
[0002] The present invention relates to a packaged hot-melt
pressure sensitive adhesive comprising a hot-melt pressure
sensitive adhesive composition and a coextrusion coating consisting
of neat low density polyethylene, neat polypropylene, or neat
ethylene vinyl acetate. The present invention further relates to
the use of the packaged adhesive formed as individual forms in an
adhesive application process, and the use of the packaged adhesive
in the production of laminated articles, including nonwoven hygiene
articles, disposable medical drapes, and also laminate
constructions such as tapes and labels.
BACKGROUND OF THE INVENTION
[0003] Hot-melt adhesive compositions are typically solid at room
temperature. Therefore, said adhesive compositions are heated and
are subsequently applied to a substrate in a molten state, which is
then placed in contact with one or more further substrates. The
hot-melt adhesive composition cools and solidifies, thereby forming
a bond between the substrates.
[0004] Hot-melt adhesive compositions can be used for a variety of
industrial adhesive applications such as packaging and labeling,
production of nonwoven hygiene and sanitary articles, such as for
the bonding of elastics, construction and core lamination or
positioning adhesive and also for other laminates such as tapes and
labels.
[0005] To prevent hot-melt adhesive compositions from agglomerating
prior to their intended use, said adhesive compositions are
typically provided in a packaged form. Packaged hot-melt adhesives
are typically composed of a base polymer, a tackifying agent and a
wax component. The base polymer provides the formulation with its
strength and adhesive characteristics. The tackifying agent allows
the polymer to be more adhesive by improving wetting during the
application, and give tack to the adhesive and also lower the
viscosity. Tack is required in most adhesive formulations to allow
for proper joining of articles prior to the hot-melt adhesive
solidifying.
[0006] A great disadvantage of currently used packaged hot-melt
pressure sensitive adhesives is that fusion of the several
packaging materials increasingly leads to agglomeration of several
particular forms during storage, which may lead to the blocking of
said individual forms during the subsequent adhesive application
processes. Such agglomeration may prevent the use of the individual
forms, because it may be very difficult to remove the packaged
hot-melt adhesive from the storage container, or it may prevent an
automatic or semi automatic processing of the individual forms,
e.g. pillows or prills, to be fed to the melting tanks. By
automating this process, the customer will have significantly
reduced handling and be able to store the adhesive at a further
distance from the melt tank and convey with reduced operator
requirement.
[0007] The packaging material of the hot-melt pressure sensitive
adhesive typically includes various coating materials such as
various portage linen blends and core polymers to avoid
agglomeration. Currently, anti-blocking powders such as talc wax or
silica are used in the discharge of hot-melts to avoid
agglomeration. However, these compounds tend to become completely
absorbed over time by the hot-melt and as a result, the residual
tack reappears. Furthermore, some of the currently used
anti-blocking agents such as silica dust are potentially harmful or
can cause serious health issues, for example, lung or respiratory
problems.
[0008] Packaged hot-melt pressure sensitive adhesives refer to
adhesives, which form a bond when pressure is applied to attach the
adhesives to the adhering substrates. Said pressure sensitive
packaged adhesives are usually designed to properly attach to the
adhering substrate at room temperature. Pressure sensitive
adhesives have a tendency to fuse together at room temperature,
which might lead to agglomeration of the pressure sensitive
adhesive during normal handling and might therefore impair the use
of the corresponding adhesives. To prevent such fusion and blocking
of packaged hot-melt pressure sensitive adhesives, powder solutions
are normally insufficient and said adhesives are typically packaged
in more advanced coating material, e.g. a plastic or metal
film.
[0009] U.S. Pat. No. 5,373,682 discloses a method for packaging
hot-melt pressure sensitive adhesives into a plastic film. However,
the method describes packaging a molten hot-melt adhesive into a
solid plastic film and thereby does not disclosure a coextrusion
process, wherein the adhesive composition and the coating are both
applied in a molten state. A particular disadvantage of the process
disclosed in U.S. Pat. No. 5,373,682 is that packaging of a molten
hot-melt adhesive into a solid plastic film results in packaged
adhesives, which are not uniformly packaged, e.g. which encompass
air inclusions, which in turn may lead to an elevated blocking and
fusion tendency of the packaged adhesives.
[0010] U.S. Pat. No. 7,572,494 B2 discloses a method for packaging
hot-melt adhesives, in particular hot-melt pressure sensitive
adhesives, which includes an extrusion process of a hot-melt
adhesive and coextrusion of a wax-based polymeric film compositions
to surround the hot-melt adhesive. However, the coextruded
wax-based polymer coating consists of a polymer composition
consisting of several different ingredients.
[0011] There remains a need in the art for packaged hot-melt
pressure sensitive adhesives, which comprise anti-blocking
coatings, which improve the handling of hot-melt adhesives and
prevents agglomeration permanently and reliably.
SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to provide a
packaged hot-melt adhesive, specifically a hot-melt pressure
sensitive adhesive composition, the individual forms of which do
not fuse together or agglomerate during their packaging,
transportation, storage or further processing. A further object is
to provide free-flowing hot-melt pressure sensitive adhesives in
individual form.
[0013] In one aspect of the invention, a packaged hot-melt adhesive
is provided, comprising a hot-melt pressure sensitive adhesive
composition (a) and a coextrusion coating (b) consisting of neat
low-density polyethylene (LDPE), neat polypropylene, or neat
ethylene vinyl acetate having a melt flow index between about 20
g/10 min and about 300 g/10 min (ASTM D 1238--190.degree. C., 2.16
kgs).
[0014] In one embodiment of the present invention, the adhesive
composition (a) comprises a base polymer selected from the group
consisting of polyolefins, polyolefin copolymers,
polyolefin/alpha-olefin interpolymers or synthetic rubbers.
[0015] In a preferred embodiment of the present invention, the
adhesive composition (a) comprises a base polymer, which is
selected from the group consisting of ethylene and propylene homo-
or copolymers.
[0016] In a preferred embodiment, the adhesive composition (a)
comprises a base polymer, selected as ethylene-octene
copolymer.
[0017] In a preferred embodiment of the present invention, the
adhesive composition (a) comprises a base polymer, which is
selected as a metallocene-synthesized polymer, preferably as a
single-site metallocene-synthesized polymer, more preferably as a
metallocene-synthesized ethylene or propylene homo- or copolymer,
even more preferably as a metallocene-synthesized polypropylene
polymer.
[0018] In a preferred embodiment of the present invention, the
adhesive composition (a) comprises a base polymer, which is
selected as a metallocene-synthesized low molecular weight
polypropylene polymer.
[0019] In a preferred embodiment of the present invention, the
adhesive composition (a) comprises a base polymer, which is
selected from the group consisting of styrene-isoprene (SI),
styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS),
styrene-ethylene/butylene-styrene (SEBS) or
styrene-ethylene/propylene-styrene (SEPS).
[0020] A further object of the present invention is to provide
packaged hot-melt adhesives which exhibit a low content of
plasticizer to maintain an adhesive composition (a) which exhibits
an increased hardness.
[0021] According to one embodiment of the present invention, the
adhesive composition (a) additionally comprises one or more
plasticizers in an amount of less than about 30 wt %, preferably
less than about 20 wt %, more preferably less than about 15 wt %,
even more preferably less than about 10 wt % and most preferably
less than about 5 wt %, referring to the total weight of the
packaged adhesive.
[0022] In one embodiment of the present invention, the adhesive
composition (a) additionally comprises one or more tackifying
agents in an amount between about 5 wt % and about 75 wt %,
preferably between about 10 wt % and about 60 wt %, more preferably
between about 15 wt % and about 50 wt %, referring to the total
weight of the packaged adhesive.
[0023] An object of the present invention is to provide packaged
hot-melt adhesives, which provide the packaged hot-melt adhesive
with a reduced tackiness, while the other properties and the purity
of the packaged hot-melt adhesive, i.e. the components of the
hot-melt pressure sensitive adhesive composition remains
unaffected. It is also an object of the present invention to
provide hot-melt particular forms which are free-flowing and or
have a substantially tack-free surface for extended periods of
time.
[0024] In one embodiment of the present invention, the packaged
hot-melt adhesive comprises a coating (b) in an amount between
about 0.1 wt % and about 5 wt %, preferably between about 0.5 wt %
and about 3 wt %, more preferably between about 1 wt % and about 2
wt/o, and most preferably between about 1.5 wt % and about 5 wt %,
referring to the total weight of the packaged adhesive.
[0025] In one embodiment of the present invention, the packaged
hot-melt adhesive comprising a coating (b), wherein the melt flow
index (ASTM D 1238--190.degree. C., 2.16 kgs) of the coating (b) is
between about 50 g/10 min and about 180 g/10 min, preferably
between about 100 g/10 min and about 170 g/10 min and most
preferably about 150 g/10 min.
[0026] In one embodiment of the present invention, the packaged
hot-melt adhesive comprising a coating (b) has a melt temperature
(Ring and Ball, DIN EN 1427) between about 60.degree. C. and about
150.degree. C., preferably between about 100.degree. C. and about
140.degree. C. and more preferably between about 120.degree. C. and
about 130.degree. C.
[0027] In one embodiment of the present invention, the packaged
hot-melt adhesive comprising a coating (b) has a room temperature
density (ASTM D 1505) between about 0.80 g/cm.sup.3 and about 1.00
g/cm.sup.3, preferably between about 0.91 g/cm.sup.3 and about 0.93
g/cm.sup.3, and more preferably about 0.92 g/cm.sup.3.
[0028] The packaged hot-melt adhesive according to the present
invention encompasses a specific parameter range, which is
advantageous for the beneficial properties of the inventive
packaged hot-melt adhesive. Further advantageous embodiments of the
present invention are defined in the corresponding dependent
claims.
[0029] In one embodiment of the present invention, the adhesive
composition (a) has an average penetration number (PZ), which is
between about 5 and about 200, preferably between about 10 and
about 100, more preferably between about 15 and about 80, and most
preferably between about 20 and about 70.
[0030] Another object of the present invention is to provide
individual forms of the packaged hot-melt adhesive, such as pillows
or prills, as defined below, which do not agglomerate during
packaging, transportation, storage or further processing.
[0031] It would also be desirable to prevent the agglomeration of
packaged hot-melt adhesives permanently. Furthermore, it would be
desirable to provide packaged hot-melt pressure sensitive
adhesives, which allows easy de-agglomeration of temporarily
blocked individual forms of the packed hot-melt adhesive, for
example when high-pressure is applied to the packaged hot-melt
adhesive during transportation or storage, or when the packed
hot-melt adhesive is transported or stored at elevated room
temperature, for example at an average temperature of between about
25.degree. C. and about 45.degree. C., between about 25.degree. C.
and about 65.degree. C., or even of between about 25.degree. C. and
about 70.degree. C.
[0032] A further object of the present invention is to provide a
packaged hot-melt pressure sensitive adhesive, which does not
undesirably change the characteristics of the packaged hot-melt
adhesive after melting, such as bonding performance, melt
viscosity, handling, etc.
[0033] A further object of the present invention is to provide a
packaged hot-melt pressure sensitive adhesive, which is
environmentally safe and which is not harmful to health.
[0034] The object of the present invention is the provision of
packaged hot-melt adhesives, which do not agglomerate and thereby
block during the specific application processes.
[0035] According to one embodiment, the packaged hot-melt adhesive
is formed in a particular form, such as a pillow or prill.
[0036] Preferably, the particular forms, such as pillows or prills
have dimensions (length/width/height) which are from about 40
mm.times.about 30 mm.times.about 12 mm, or about 20 mm.times.about
20 mm.times.about 20 mm, preferably about 40 mm.times.about 20
mm.times.about 10 mm and most preferably about 40 mm.times.about 15
mm.times.about 7 mm.
[0037] Preferably, a plurality of individual forms such as pillows
or prills, do not fuse together and/or are mechanically separable
to induce free-flowing of the individual forms.
[0038] Preferably, a plurality of individual forms of a packaged
hot-melt adhesive, such as pillows or prills, is used in an
adhesive application process, wherein the packaged hot-melt
adhesive is conveyed to a melting system in a free-flowing and air
conveyable form before being molten and applied to a substrate.
[0039] According to another embodiment, the packaged hot-melt
adhesive is formed in a particular form, such as a coextruded
rope.
[0040] Preferably the coextruded ropes have a diameter which is
between about 0.1 cm and about 5 cm, preferably between about 1 cm
and about 3 cm, and more preferably about 2.5 cm.
[0041] Preferably, a plurality of individual forms of a packaged
hot-melt adhesive, such as a coextruded rope, is used in an
adhesive application process, wherein the packaged hot-melt
adhesive is conveyed to a melting system by pulling the coextruded
rope through a series of pulleys inside a protective cover into the
premelter.
[0042] Preferably, the plurality of individual forms such as a
coextruded rope, do not fuse together and/or are mechanically
separable to induce free-flowing of the individual forms.
[0043] For individual forms, the packaged hot-melt adhesive has a
free-flowing and/or air-conveyable form at ambient conditions.
[0044] According to the invention, the package hot-melt adhesive is
obtained by a coextrusion process.
[0045] Preferably, the packaged hot-melt adhesive according to the
present invention is obtained by a coextrusion process, wherein the
hot-melt pressure sensitive adhesive composition (a) is pumped
through the coextrusion head and wherein the coextrusion coating
(b) is added to the adhesive composition (a) such that the
coextrusion coating (b) substantially covers the adhesive
composition (a) as a cover sheet.
[0046] Furthermore, the packaged hot-melt adhesive is obtained by a
coextrusion process, wherein the coextrusion process comprises:
[0047] (i) providing one or more hot-melt components and blending
the hot-melt components to form a hot-melt pressure sensitive
adhesive composition [0048] (ii) providing a coating material
selected from neat low-density polyethylene, neat polypropylene, or
neat ethylene vinyl acetate having a melt flow index between about
20 g/10 min and about 300 g/10 min. [0049] (iii) coextruding both
(i) and (ii) such that the adhesive forms a strand substantially
surrounded by the coating material [0050] (iv) optionally cutting
the resulting, coated strand of adhesive (e.g. by forcing the
composition past rotating blades and cutting the hot-melt ribbons
to form resultant individual forms) [0051] (v) solidifying the
individuals, optionally by cooling the individuals by a liquid
cooling medium or by a dry air circulated.
[0052] In one aspect the invention covers a method of using a hot
melt pressure sensitive adhesive in individual forms comprising the
steps of: a.) obtaining coextruded hot melt pressure sensitive
adhesive in individual forms; and b.) conveying the hot melt
pressure sensitive adhesive to a melting system by use of a
conveying system selected from the group consisting of a tubular
drag conveying system and a melt on demand conveying system.
[0053] In one embodiment, the coextruded hot melt pressure
sensitive adhesive in individual form is fed into the conveying
system by use of a vibratory feeder. In another embodiment, the
conveying system is a tubular drag conveying system. In still
another embodiment, the hot melt pressure sensitive adhesive in
individual form is a pillow with a thickness of at least about
0.635 cms (0.250 inches). Alternately, the hot melt pressure
sensitive adhesive comprises a propylene polymer. In some
embodiments, the hot melt pressure sensitive adhesive has an
average penetration number (PZ), which is between about 20 and
about 70. In other embodiments, the hot melt pressure sensitive
adhesive is conveyed to more than one melting system. In still
other embodiments, the hot melt pressure sensitive adhesive is
provided in the individual form selected from the group consisting
of a pillow, a prill and a coextruded rope. In one embodiment, the
hot melt pressure sensitive adhesive composition comprises a base
polymer selected from the group consisting of polyolefins,
polyolefin copolymers, polyolefin/alpha-olefin interpolymers and
synthetic rubbers.
[0054] In one aspect, the invention provides a method of providing
molten adhesive comprising: a. providing a plurality of individual
forms of a coextrusion coated hot melt pressure sensitive adhesive
wherein the hot melt pressure sensitive adhesive has an average
penetration number (PZ), which is between about 20 and about 70; b.
conveying the plurality of individual forms to a melting system; c.
heating the plurality of individual forms until they become a
molten adhesive; and d. applying the molten adhesive to a
substrate.
[0055] In one embodiment, the plurality of individual forms have a
rating of at least 3 when tested according to blocking test 1. In
another embodiment, the plurality of individual forms are
continuously conveyed to the melting system so as to maintain a
consistent level of adhesive in the melting system. In still
another embodiment, the plurality of individual forms are conveyed
with a tubular drag conveying system, or alternately a melt on
demand conveying system.
[0056] In one embodiment, the coextrusion coating is neat
low-density polyethylene. In another embodiment, the neat
low-density polyethylene has a melt flow index (ASTM D
1238--190.degree. C., 2.16 kgs) between about 20 g/10 min and about
300 g/10 min. In still another embodiment, the hot melt pressure
sensitive adhesive comprises a propylene polymer. In one
embodiment, the substrate is a non-woven. In other embodiments, the
hot melt pressure sensitive adhesive has an average penetration
number (PZ), which is between about 20 and about 70. In still other
embodiments, the hot melt pressure sensitive adhesive composition
comprises a metallocene-synthesized low molecular weight
polypropylene polymer.
[0057] In a preferred use of the invention, the packaged hot-melt
adhesive is used for the production of hygiene and sanitary
articles, non-woven articles, labeling, elastic lamination,
construction lamination or as positioning adhesive. Preferably, the
packaged hot-melt adhesive is used for the production of nonwoven
hygiene articles including the production of diapers, adult
incontinence devices, sanitary napkins, medical drapes and also
laminate constructions such as tapes and labels.
[0058] In one aspect, the present invention is directed to an
adhesive containing container comprising a plurality of individual
forms of the packaged hot-melt adhesive according to the present
invention, wherein the container is selected from at least one of a
box, preferably a plastic bag, a pouch, a big bag, and a
supersack.
FIGURES
[0059] FIG. 1: Schematic representation of a vacuum-conveying
system.
[0060] Packaged hot-melt pressure sensitive adhesive is inserted
into a feed hopper, is introduced into the vacuum-conveying system
by a vibratory feeder and is filled into a series of hot-melt
tanks, through a discharge valve, which is controlled by electronic
level probes.
[0061] FIG. 2: Schematic representation of a tubular drag-conveying
system.
[0062] Packaged hot-melt pressure sensitive adhesive is inserted
into a tubular drag-conveying system by a vibratory feeder, wherein
the adhesive is conveyed to a plurality of hot-melt tanks by a
disc-distribution system, which is controlled by electronic level
probes.
DETAILED DESCRIPTION OF THE INVENTION
[0063] In one aspect of the present invention, a packaged hot-melt
adhesive is provided, comprising a hot-melt pressure sensitive
adhesive composition (a) and a coextrusion coating (b) consisting
of neat low-density polyethylene, neat polypropylene, or neat
ethylene vinyl acetate having a melt flow index between about 20
g/10 min and about 300 g/10 min.
[0064] In a further aspect of the present invention, a plurality of
individual forms of a packaged adhesive in accordance with the
present invention are provided, which may be used in an adhesive
application process, wherein the packaged adhesive is conveyed to a
melting system in a free-flowing and air conveyable form before
being molten and applied to a substrate.
[0065] In the following, the hot-melt pressure sensitive adhesive
composition (a) and the coextrusion coating (b), and the
anti-blocking characteristics of the packaged hot-melt adhesive,
e.g. the individual forms, will be described in more detail, as
well as individual forms comprising said packaged hot-melt
adhesive.
[0066] Unless otherwise specified, the following abbreviations and
definitions are used in the context of the present invention.
[0067] The undefined article "a" or "an" means one or more of the
species designated by the term following said article. For example,
"a individual form" encompasses one or more individual forms.
[0068] The term "about" in the context of the present application
means a value within 15% (.+-.15%) of the value recited immediately
after the term "about," including any numeric value within this
range, the value equal to the upper limit (i.e., +15%) and the
value equal to the lower limit (i.e., -15%) of this range. For
example, the phrase "about 100" encompasses any numeric value that
is between 85 and 115, including 85 and 115 (with the exception of
"about 100%", which always has an upper limit of 100%). A further
exception is the phrase "about 0" or "about 0%", which always has a
lower limit of 0 or 0%). In a preferred aspect, "about" means
.+-.10%, even more preferably .+-.5%, even more preferably .+-.1%
or less than .+-.%.
[0069] The amount of a specific component, which is added to
packaged hot-melt adhesive comprising a hot-melt pressure sensitive
adhesive composition (a) and a coextrusion coating (b) may be
defined as the weight per weight percentage as defined by the
following ratio: wt %=(g of specific component)/(g of composition
comprising specific components). For example, when 2.5 g of
plasticizer in 100 g of a packaged hot-melt adhesive are used, this
results in a ratio of 2.5 wt % (2.5/100) of plasticizer.
[0070] For the purpose of the present invention, the term
"hot-melt" or "hot-melt composition" refers to a solvent free
product which is more or less solid at room temperature, e.g. at a
temperature between about 20.degree. C. and about 25.degree. C.
When heated the hot-melt becomes tacky and preferably liquid
(molten) and can be applied, for example to a substrate to provide
an adhesive surface.
[0071] The hot-melt adhesive composition (a) of the present
invention is a hot-melt "pressure sensitive adhesive" composition.
The term "pressure-sensitive adhesive" means an adhesive that is
aggressively and permanently tacky at room temperature and firmly
adheres to a variety of dissimilar surfaces upon mere contact
without the need of more than finger or hand pressure, i.e. a
hot-melt adhesive composition that retains surface tackiness over
time including when cooled.
A. The Hot-Melt Pressure Sensitive Adhesive Composition (a)
[0072] A hot-melt pressure sensitive adhesive typically comprises
at least one thermoplastic base polymer, at least one plasticizer
and at least one tackifying agent.
[0073] Generally, the invention's hot-melts will additionally
contain one or more tackifying resins, plasticizers or oils and
optionally waxes plus customary additives and adjutants such as
stabilizers, antioxidants, pigments, UV stabilizers or absorbers,
fillers etc. Materials used in hot-melt adhesives are known.
[0074] The packaged hot-melt adhesive according to the present
invention comprises a hot-melt pressure sensitive adhesive
composition (a), which predominantly determines the adhesive
properties of the packaged hot-melt adhesive.
[0075] The hot-melt pressure sensitive adhesive composition (a)
comprises a base polymer. The present invention is not specifically
limited with respect to the base polymer being used. Rather, any
polymer that in principle can be used in hot-melt compositions is
suitable according to the present invention. Typically, base
polymers include thermoplastic polymers selected from e.g.
polyolefins, polyolefin copolymers or polyolefin/alpha-olefin
interpolymers, as well as amorphous poly-.alpha.-olefins such as
atactic propylene, and propylene copolymers with ethylene, butene,
hexene, and octane, or ethylene and propylene homo- or copolymers
and mixtures thereof. Also useful are polyamides and polyesters,
polyurethanes, or synthetic rubbers, such as styrene block
copolymers.
[0076] The hot-melt pressure sensitive adhesive composition (a)
will preferably comprise at least one ethylene polymer, and may
comprise a blend of two or more polymers. The term ethylene polymer
as used herein refers to homopolymers, copolymers and terpolymers
of ethylene.
[0077] In the present invention, the base polymer can be selected
from the group consisting of ethylene copolymers. In a preferred
embodiment, the base polymer is selected as ethylene vinyl acetate,
ethylene methyl acrylate, ethylene n-butyl acrylate, ethylene
n-hexyl acrylate, ethylene-2-ethylhexyl acrylate, ethylene butene,
ethylene octene, ethylene acrylic acid, or ethylene methacrylic
acid copolymers. Even more preferred, the base polymer is selected
as ethylene-octene copolymer.
[0078] Also, the base polymer is selected from the group consisting
of polyolefin/alpha-olefin interpolymers, in particular ethylene
copolymers, such as ethylene-octene. A particular preferred polymer
such as ethylene octene has a melt flow index between about 0.1
g/10 min and about 4,000 g/10 min, preferably between about 1 g/10
min and about 10 g/10 min and most preferably about 5 g/10 min. A
particular preferred polymer such as ethylene octene has a density
between about 0.7 g/cm.sup.3 and about 1.0 g/cm.sup.3, preferably
between about 0.8 g/cm.sup.3 and about 0.9 g/cm.sup.3, most
preferably about 0.87 g/cm.sup.3. More than one ethylene copolymer
may be used to optimize the melt flow index and density of the
polymer. A preferred example of ethylene copolymer includes ENGAGE
8200 available from Dow Chemical Company, US. A second polymer may
be added in addition to the first to further optimize properties
e.g. an ethylene vinyl acetate polymer may be used in combination
with ethylene octene.
[0079] In another option of the present invention, the base polymer
can be selected as a low molecular weight polypropylene polymer.
These base polymers can either be homopolymers of propylene or
copolymers of propylene with one or more .alpha.-olefin comonomer,
such as for example ethylene, 1-butene, 1-hexene, or 1-octene. The
average molecular weight of the low molecular weight polypropylene
polymers in the scope of the present invention may be in the range
between about 4,000 g/mol and about 150,000 g/mol, preferably
between about 10,000 g/mol and about 100,000 g/mol, more preferably
between about 30,000 g/mol and about 60,000 g/mol and most
preferably about 45,000 g/mol. Said polymers may have a Vicat
softening point between about 80.degree. C. and about 170.degree.
C., preferably about 90.degree. C. Polypropylene polymers are
usually predominantly amorphous without a well-defined melting
point. Preferred examples of polypropylene homopolymers or
copolymers of propylene include VISTAMAX 6202 available from EXXON
MOBILE CHEMICALS, US and MODU S-400 available from Idemitsu Kosan
Co., JP.
[0080] Other polymers that may be useful in the hot-melt
composition of the present invention include so-called metallocene
or single-site catalyzed polymers, including homopolymers and
interpolymers of ethylene, propylene, or butane including
homopolymers and interpolymers of ethylene with at least one
C.sub.2 to C.sub.20-.alpha.-olefin. In a preferred option, the
basic polymer is selected as a metallocene-synthesized low
molecular weight polypropylene polymer. Metallocene polymers are
prepared using a constrained geometry or single site metallocene
catalyst. Useful metallocene polymers include, e.g. a homogeneous
linear or substantially linear polymers that are interpolymers of
ethylene and at least one C.sub.3-C.sub.20-.alpha.-olefin including
e.g., ethylene/.alpha.-olefin/diene terpolymers. The term
"homogenous" as used with respect to the metallocene polymer
indicates that any comonomer is randomly distributed within a given
interpolymer molecule and substantially all of the interpolymer
molecules have the same ethylene/comonomer ratio within that
interpolymer. Linear ethylene interpolymers are interpolymers that
have an interpolymer backbone substituted with less than 0.01 long
chain branches per 1000 carbons. The substantially linear ethylene
interpolymers are interpolymers that include long chain branching.
The long chain branches have the same comonomer distribution as the
polymer backbone and can be as long as about the same length as the
length of the polymer backbone. Suitable substantially linear
ethylene interpolymers have a polymer backbone substituted with
from about 0.1 to about 3 long chain branches per 1000 carbons.
Useful C.sub.3-C.sub.20-.alpha.-olefins used in the preparation of
ethylene interpolymers include, e.g., propylene, isobutylene,
1-butene, 1-hexene, 4-methyl-1-pentene, I-heptene, I-octene,
cyclopentene, cyclohexene, cyclooctene and combinations thereof.
The dienes suitable as comonomers, particularly in the making of
ethylene/.alpha.-olefin/diene terpolymers, are typically
non-conjugated dienes having from 6 to 15 carbon atoms. Useful
examples of suitable non-conjugated dienes include: (1) straight
chain acyclic dienes including, e.g., 1,4-hexadiene,
1,5-heptadiene, and 1,6-octadiene; (2) branched chain acyclic
dienes including, e.g., 5-methyl-1,4-hexadiene,
3,7-dimethyl-1,6-octadiene, and 3,7-dimethyl-1,7-octadiene, (3)
single ring alicyclic dienes including, e.g., 4-vinylcyclohexene,
1-allyl-4-isopropylidene cyclohexane, 3-allylcyclopentene, 4-allyl
cyclohexene, and 1-isopropenyl-4-butenylcyclohexene; and (4)
multi-ring alicyclic fused and bridged ring dienes including, e.g.,
dicyclopentadiene, and cycloalkylidene-substituted norbornenes
including, e.g., 5-methylene-2-norboraene,
5-methylene-6-methyl-2-norbornene,
5-methylene-6,6-dimethyl-2-norbornene, 5-propenyl-2-norbornene,
5-(3-cyclopentenyl)-2-norbornene, 5-ethylidene-2-norbornene, and
5-cyclohexylidene-2-norbornene. Useful homogenous linear or
substantially linear ethylene polymers have a narrow molecular
weight distribution (M.sub.w/M.sub.n) including, e.g., from 1.5 to
3.5, or even from 1.8 to 2.8.
[0081] Examples of useful metallocene polymers are described in
U.S. Pat. Nos. 5,324,800, 5,548,014, 5,530,054 and 6,207,748 and
incorporated herein.
[0082] Useful metallocene polymers are commercially available under
the AFFINITY series of trade designations including EG 8200
polyolefin plastomer from Dow Chemical Company (Midland, Mich.),
and linear ethylene polymers are commercially available under the
EXACT series of trade designations from ExxonMobil (Texas).
[0083] The metallocene polymer is preferably present in the
hot-melt adhesive composition in an amount from about 0% wt % to
about 80 wt %, from about 5% wt % to about 70 wt %/o, from about 10
wt % to about 60 wt %, or even from about 15 wt % to about 50 wt %.
In some embodiments the amount of metallocene polymer, which is
present in the hot-melt adhesive composition may be higher,
preferably up to about 90 wt % and more preferably the hot-melt
adhesive composition may be neat metallocene polymer.
[0084] Metallocene polymer present in the adhesive composition (a)
may exhibit some degree of crystallinity. For example, there are
some grades of commercial low molecular weight polypropylene
polymers having a low degree of crystallinity. Preferably, the
adhesive composition (a) has a low degree of crystallinity and the
coextrusion coating (b) according to the present invention has a
high degree of crystallinity.
[0085] One other class of thermoplastic base polymers suitable for
use in the pressure-sensitive hot-melt adhesive composition (a)
together with the coextrusion coating (b) is thermoplastic
elastomers. Suitable thermoplastic elastomers include block
copolymers having at least one A block that includes a vinyl
aromatic compound and at least one B block that includes an
elastomeric conjugated diene, including hydrogenated,
unhydrogenated conjugated dienes, and combinations thereof. The A
blocks and the B blocks may bind to one another in any manner of
binding such that the resulting copolymer is random, block,
straight-chained, branched, radial, or a combination thereof. The
block copolymer can exhibit any form including, e.g., linear A-B
block, linear A-B-A block, linear A-(B-A)n-B multi-block, and
radial (A-B)n-Y block where Y is a multivalent compound and n is an
integer of at least 3, tetrablock copolymer, e.g., A-B-A-B, and
pentablock copolymers having a structure of A-B-A-B-A. The adhesive
composition can include blends of at least two different block
copolymers.
[0086] Useful vinyl aromatic compounds include, e.g., styrene,
alpha-methylstyrene, o-methylstyrene, m-methylstyrene,
p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene,
2,4,6-trimethylstyrene, diphenylethylenes including stilbene, vinyl
naphthalene, vinylanthracene, vinyltoluene (a mixture of meta- and
para-isomers of methylstyrene), vinylxylene, and combinations
thereof. Suitable conjugated dienes include, e.g., butadiene (e.g.,
polybutadiene), isoprene (e.g., polyisoprene),
2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and
combinations thereof, and hydrogenated versions thereof including,
e.g., ethylene, propylene, butylene and combinations thereof.
[0087] Useful block copolymers include polyvinyl aromatic in an
amount between about 0 wt % and about 50 wt %, between about 5 wt %
and about 50 wt %, between about 15 wt % and about 35 wt %, or even
between about 20 wt % and about 30 wt %. Suitable block copolymers
have a melt flow index between about 3 g/10 min and about 50 g/10
min, or between about 5 g/10 min and about 20 g/10 min, as
determined by ASTM-D 1238.
[0088] The A block can also include a small amount (e.g. no greater
than 10 wt % based on the weight of the A block) of a structural
unit derived from unsaturated monomers other than the vinyl
aromatic compounds including, e.g., I-butene, pentene, hexene,
butadiene, isoprene, methyl vinyl ether, methyl methacrylate, vinyl
acetate and combinations thereof. The B block can also include a
small amount (e.g., no greater than 10 wt % based on the amount of
the B block) of a structural unit derived from unsaturated monomers
other than the conjugated diene including, e.g., I-butene,
I-pentene, 1-hexene, methyl vinyl ether, styrene, methyl
methacrylate, and combinations thereof.
[0089] Useful elastomeric polymers include, e.g., rubber
(polyisoprene), polybutadiene, synthetic polyisoprene, random
styrene-butadiene polymers, styrene-butadiene block copolymers,
multiarmed and repeating styrene-butadiene copolymers,
styrene-butadiene-styrene block copolymers, styrene-isoprene block
copolymers, styrene-isoprene-styrene block copolymers,
styrene-multiarmed styrene-isoprene (SI).sub.x block copolymers,
styrene-ethylene-butylene-styrene block copolymers,
styrene-isobutylene-styrene block copolymers,
styrene-ethylene-ethylene-propylene-styrene block copolymers,
styrene-ethylene-propylene-styrene block copolymers and
combinations thereof.
[0090] Useful block copolymers are commercially available under the
KRATON D and G series of trade designations from Shell Chemical
Company (Houston, Tex.) including, e.g., KRATON D 1163 and 1117 and
KRATON G 1652 and 1726, EUROPRENE Sol T trade designation from
EniChem (Houston, Tex.), SEPTON trade designation from Septon
Company of America (Pasadena, Tex.) including SEPTON S 1001
styrene-ethylene-propylene-styrene block copolymer, and SEPTON
4030, 4033, 4044, 4055 and 4077 block copolymers, and VECTOR series
of trade designations from Dexco (Houston, Tex.) including VECTOR
4211 styrene-isoprene-styrene block copolymer.
[0091] The elastomer is present in the adhesive composition in an
amount between about 0 wt % and about 35 wt %, between about 5 wt %
and about 35 wt %, between about 10 wt % and about 30 wt %, or even
between about 15 wt % and about 25 wt %.
[0092] Alternatively, the base polymer can be selected from the
group consisting of synthetic rubbers. Preferably, the base polymer
is selected from the group consisting of butadiene styrene,
styrene-acrylonitrile, acrylonitrile-butadiene-styrene,
styrene-butadiene rubbers, butadiene-styrene elastomers,
styrene-isoprene (SI), styrene-isoprene-styrene (SIS),
styrene-butadiene-styrene (SBS), styrene-ethylene/butylene-styrene
(SEBS) or styrene-ethylene/propylene-styrene (SEPS). More
preferred, the base polymer is selected from the group consisting
of styrene-isoprene (SI), styrene-isoprene-styrene (SIS),
styrene-butadiene-styrene (SBS), styrene-ethylene/butylene-styrene
(SEBS) or styrene-ethylene/propylene-styrene (SEPS).
[0093] In a preferred embodiment the synthetic rubbers have melt
flow index between about 0.1 g/10 min and about 4,000 g/10 min,
preferably between about 10 g/10 min and about 60 g/10 min and most
preferably between about 25 g/10 min and about 40 g/10 min. A
particular preferred polymer such as styrene-isoprene (SI) or
styrene-isoprene-styrene (SIS) has a density between about 0.8
g/cm.sup.3 and about 1.0 g/cm.sup.3, preferably between about 0.92
g/cm.sup.3 and about 0.96 g/cm.sup.3. More than one
styrene-isoprene (SI) or styrene-isoprene-styrene (SIS) may be used
to optimize the melt flow index and density of the polymer.
Preferred examples of styrene-isoprene (SI) or
styrene-isoprene-styrene (SIS) include KRATON D1117 and KRATON
D11161 NS, available from Kraton Polymers, US, VECTOR 4114A and
VECTOR 4411 A from Dexco Polymers, USA.
[0094] The base polymers according to the present invention may be
functionalized, e.g. by using (co-)monomers with at least one
functional group, e.g. by an unsaturated monomer, which is
functionalized by carboxylic acids, dicarboxylic acids, organic
esters, organic anhydrides, organic alcohols, organic acid halides,
organic peroxides, amides or imides.
[0095] An object of the present invention is to provide a packaged
hot-melt adhesive, which provides an increased structural
resistance of the adhesive, which is referred hereto as
hardness.
[0096] A measure of the hardness of a specific material is obtained
by allowing a weighted needle of specified dimensions to penetrate
into the material under specific test conditions, e.g. at a defined
temperature. The penetration number (PZ) is usually recorded as the
number of units of depth which the needle penetrates in a given
time. The harder a specific material, the lower is its penetration
number. The penetration number according to the present invention
is determined by needle penetration according to the test procedure
is described in DIN 51579 at a temperature of 25.degree. C. (see
also examples section).
[0097] In accordance with the present invention, the packaged
hot-melt adhesive has an average penetration number (PZ), which is
between about 5 and about 200, preferably between about 10 and
about 100, more preferably between about 15 and about 80, and most
preferably between about 20 and about 70.
[0098] Another parameter to determine the properties of a packaged
hot-melt adhesive according to the present invention is the
viscosity. Typically polymers partially display non-Newtonian
viscosity properties. This means that their viscosity does not
remain constant over a given range of shear rates. Polymer
viscosity rates are typically referred to in correlation with the
corresponding temperature, wherein said viscosity rates have been
measured. The polymer viscosity according to the present invention
is determined according to method ASTM D-3236 (see also examples
section).
[0099] The hot-melt pressure sensitive adhesive composition (a)
according to the present invention can be formulated to exhibit a
suitable viscosity. Useful packaged hot-melt adhesives according to
the present invention exhibit a viscosity measured at 150.degree.
C. of between about 200 mPas and about 20,000 mPas, preferably
between about 500 mPas and about 10,000 mPas, more preferably
between about 100 mPas and about 5,000 mPas and most preferably
between about 2,000 mPas and about 4,000 mPas.
[0100] The packaged hot-melt adhesive according to the present
invention comprises a hot-melt pressure sensitive adhesive
composition (a) and a coextrusion coating (b), which typically
consist of different materials, which in turn may have different
viscosities.
[0101] The packaged hot-melt adhesive according to the present
invention is characterized by various parameters. The melting point
of the packaged adhesive according to the present invention is
determined by the Ring and Ball method (DIN EN 1427) (see Example
section).
[0102] The packaged adhesive according to the present invention may
have a melting point according to DIN EN 1427 between about
60.degree. C. and about 130.degree. C., preferably between about
70.degree. C. and 110.degree. C.
[0103] Also, the packaged adhesive according to the present
invention may have a room temperature density between about 0.80
g/cm.sup.3 and about 1.00 g/cm.sup.3, preferably between about 0.85
g/cm.sup.3 and about 0.95 g/cm.sup.3 and more preferably about 0.91
g/cm.sup.3.
[0104] The packaged hot-melt adhesive comprising a hot-melt
pressure sensitive adhesive composition (a) may additionally
comprise further, optional, additives such as tackifying agents,
plasticizers, stabilizers, antioxidants, pigments, dyes,
ultraviolet light absorbers, anti-slip agents and combinations
thereof.
[0105] In one aspect of the present invention, the packaged
hot-melt adhesive comprising a hot-melt pressure sensitive adhesive
composition (a) and a coextrusion coating (b) additionally
comprises one or more plasticizers.
[0106] Suitable plasticizers may include naphthenic oils,
paraffinic oils (e.g., cycloparaffin oils), mineral based oils,
phthalate esters, adipate esters, olefin oligomers (e.g., oligomers
of polypropylene, polybutene, and hydrogenated polyisoprene),
polybutenes, polyisoprene, hydrogenated polyisoprene,
polybutadiene, benzoate esters, animal oil, plant oils (e.g. castor
oil, soybean oil), derivatives of oils, glycerol esters of fatty
acids, polyesters, polyethers, lactic acid derivatives and
combinations thereof. A "plasticizer" in the meaning of the present
invention is a typically organic composition that can be added to
thermoplastics, rubbers and other resins to improve extrudability,
flexibility, workability and stretchability in the finished
adhesive. Any material which flows at ambient temperatures and is
compatible with the block copolymer may be useful. The most
commonly used plasticizers are oils which are primarily hydrocarbon
oils that are low in aromatic content and are paraffinic or
naphthenic in character. The oils are preferably low in volatility,
transparent and have as little color and odor as possible.
Furthermore, olefin oligomers, low molecular weight polymers,
vegetable oils and their derivatives and similar plasticizing oils
may be used as plasticizers.
[0107] Also, the plasticizer can be selected from the group
consisting of napthenic process oils and paraffinic process oils,
such as NYFLEX 222B available from Nynas AB, SE and KRYSTOL 550
available from Petrochem Carless Ltd., UK.
[0108] Useful commercially available plasticizers include KAYDOL
OIL from Sonneborn (Tarrytown N.Y.) PARAPOL polybutene from Exxon
Mobil Chemical Company (Houston, Tex.), OPPANOL polyisobutylene
from BASF (Ludwigsjhafen, Germany), KRYSTOL 550 mineral oil from
Petrochem Carless Limited (Surrey, England) and PURETOL 15 mineral
oil from Petro Canada Lubricants Inc. (Mississauga, Ontario).
[0109] Preferably, the amount of plasticizer in the hot-melt
pressure sensitive adhesive composition (a) is less than about 30
wt % referring to the total weight of the packaged hot-melt
adhesive, more preferably less than about 20 wt %, even more
preferably less than about 15 wt %, even more preferably less than
about 10 wt %, and most preferably less than about 5 wt %.
[0110] The packaged hot-melt adhesive comprising a hot-melt
pressure sensitive adhesive composition (a) and a coextrusion
coating (b) may additionally or alternatively comprise one or more
tackifying agents.
[0111] The tackifying agent can be at least partially hydrogenated
in order to improve stability for bulk handling. Useful tackifying
agents have Ring and Ball softening point of less than about
140.degree. C., less than about 130.degree. C., less than about
100.degree. C., or even between about 100.degree. C. to about
140.degree. C. The tackifying agent can be fluid or solid at room
temperature. Suitable classes of tackifying agents include, e.g.,
aromatic, aliphatic and cycloaliphatic hydrocarbon resins, mixed
aromatic and aliphatic modified hydrocarbon resins, aromatic
modified aliphatic hydrocarbon resins, and hydrogenated versions
thereof; terpenes, modified terpenes and hydrogenated versions
thereof; natural rosins, modified rosins, rosin esters, and
hydrogenated versions thereof; low molecular weight polylactic
acid; and combinations thereof. Examples of useful natural and
modified rosins include gum rosin, wood rosin, tall oil rosin,
distilled rosin, hydrogenated rosin, dimerized rosin and
polymerized rosin. Examples of useful rosin esters include e.g.,
glycerol esters of pale wood rosin, glycerol esters of hydrogenated
rosin, glycerol esters of polymerized rosin, pentaerythritol esters
of natural and modified rosins including pentaerythritol esters of
pale wood rosin, pentaerythritol esters of hydrogenated rosin,
pentaerythritol esters of tall oil rosin, and phenolic-modified
pentaerythritol esters of rosin.
[0112] Examples of useful polyterpene resins include polyterpene
resins having a melting point, as determined by DIN EN 1427 (Ring
and Ball) of from about 10.degree. C. to about 180.degree. C.,
hydrogenated polyterpene resins, and copolymers and terpolymers of
natural terpenes (e.g. styrene-terpene, alpha-methyl
styrene-terpene and vinyl toluene-terpene). Examples of useful
aliphatic and cycloaliphatic petroleum hydrocarbon resins include
aliphatic and cycloaliphatic petroleum hydrocarbon resins having
Ring and Ball softening points of from about 10.degree. C. to about
140.degree. C. (e.g., branched and unbranched C5 resins, C9 resins,
and C10 resins) and the hydrogenated derivatives thereof.
[0113] Useful tackifying agents are commercially available under a
variety of trade designations including, e.g., the ESCOREZ series
of trade designations from Exxon Mobil Chemical Company (Houston,
Tex.) including ESCOREZ 1310 LC, ESCOREZ 5400, ESCOREZ 5415,
ESCOREZ 5600, ESCOREZ 5615, and ESCOREZ 5690, the EASTOTAC series
of trade designations from Eastman Chemical (Kingsport, Tenn.)
including EASTOTAC H-100R, EASTOTAC H-100L, and EASTOTAC H130W, the
WINGTACK series of trade designations from Cray Valley HSC (Exton,
Pa.) including WINGTACK 86, WINGTACK EXTRA, and WINGTACK 95, the
PICCOTAC and KRISTALEX series of trade designations from Eastman
Chemical Company (Kingsport, Tenn.) including, e.g., PICCOTAC 8095
and KRISTALEX 3100, ARKON M-100 of trade designations from Arakawa
Europe GmbH, Germany, SUKOREZ SU-100 of trade designations from
Kolon Industries Inc., Korea, and SYLVARES 7115 and SYLVARES SA 140
of trade designatons from Arizona Chemical, USA.
[0114] Preferably, the amount of tackifying agent in the hot-melt
pressure sensitive adhesive composition (a) is between about 5 wt %
and about 75 wt %, preferably between about 10 wt % and about 60 wt
%, more preferably between about 15 wt % and about 50 wt %,
referring to the total weight of the packaged adhesive.
[0115] The packaged hot-melt adhesive comprising a hot-melt
pressure sensitive adhesive composition (a) and a coextrusion
coating (b) may additionally or alternatively comprise one or more
antixodiants and/or more stabilizers.
[0116] Useful antioxidants are, e.g., high molecular weight
hindered phenols and multifunctional phenols. Useful stabilizers
are, e.g., phosphites, such as tris-(p-nonylphenyl)-phosphite
(TNPP) and
bis(2,4-di-tert-butylphenyl)4,4'-diphenylene-diphosphonite and
di-stearyl-3,3'-thiodipropionate (DSTDP). Useful antioxidants are,
e.g., commercially available under trade designation IRGANOX,
including IRGANOX 1010, from Ciba (Terrytown, N.Y.), and under the
trade designation BNX, including BXN 1010, from Mayzo, Inc.
(Norcross, Ga.). Useful anti-slip agents are, e.g., silicone oils.
Examples thereof are commercially available, e.g., under the trade
designation Tegiloxan and available from Goldschmidt Industrial
Specialties.
[0117] The amount of antioxidant and/or stabilizer in the hot-melt
pressure sensitive adhesive composition (a) may be between about
0.1 wt % and about 5.0 wt % referring to the total weight of the
packaged hot-melt adhesive, more between about 0.1 wt % and about
3.0 wt %, more preferably between about 0.1 wt % and about 2.0 wt %
even more preferably less than about 0.2 wt % and about 1 wt %.
B. The Coextrusion Coating (b)
[0118] According to the present invention, the packaged hot-melt
adhesive comprises a coextrusion coating (b), which provides for
the anti-blocking properties of the packaged hot-melt adhesive.
[0119] The inventors surprisingly found out that the coextrusion
coating (b) as defined in the present invention, which is made of
neat polymers instead of conventionally used compounded coextrusion
material, effectively prevents the agglomeration of packaged
hot-melt adhesives, e.g. individual forms, over extended periods of
time. Furthermore, the addition of a coextrusion coating (b) to a
hot-melt pressure sensitive adhesive composition (a) allows for an
easy de-agglomeration of potentially blocked individual forms. It
was also found that coextruded coatings (b) are particularly useful
for the anti-blocking properties of polyolefins, polyolefin
copolymers or polyolefin/alpha-olefin interpolymers, as well as
amorphous poly-.alpha.-olefins, which typically possess some
residual or permanent tack, particularly at elevated ambient
temperatures. In particular, the inventors found that the
anti-blocking properties of the coextrusion coating (b) of the
packaged hot-melt adhesive are not adversely affected when the
hot-melt is exposed to higher ambient temperatures (e.g. between
about 25.degree. C. and about 70.degree. C.), for example during
storage or transportation. This makes the anti-blocking properties
of the inventive coextrusion coating (b) very reliable.
[0120] To provide hot-melt pressure sensitive adhesives with
anti-blocking properties, powdered coating materials or compounded
coextrusion coating are conventionally applied.
[0121] Powdered coating materials are conventionally loaded onto
the hot-melt pressure sensitive adhesive in a subsequent step after
adhesive formation. A major problem for hot-melt pressure sensitive
adhesives with powdered coating materials is that the diffusion of
the components of the powdered coating material into the adhesive
may occur over time. Such a diffusion of components into the
adhesive may alter the composition of the adhesive significantly,
which in turn might impair the functional properties of the
adhesive and the anti-blocking property is lost during extended
storage.
[0122] Some compounded coextrusion coatings are known. Compounded
coextrusion coatings are typically coextruded with the adhesive
composition and typically consist of various components, which in
their combination provide for the anti-blocking and anti-tacking
properties of the hot-melt pressure sensitive adhesive. Problems
with migration of ingredients of the compounded coextrusion
coatings occurs to a lesser extended in comparison to powdered
coating material, but migration of components from the compounded
coextrusion coating into the hot-melt pressure sensitive adhesive
composition continues to pose a major problem for compounded
coextrusion coatings, especially during long-term storage.
[0123] The coextrusion coating (b) according to the present
invention provides significant advantages in comparison with
conventional used anti-blocking additives, which are conventionally
added to the corresponding adhesive composition, such as powdered
coating materials or compounded coextrusion coatings. A major
difference between the different systems is that the coextrusion
coating (b) according to the present invention is applied to the
hot-melt pressure sensitive adhesive composition (a) during the
coextrusion process, by coextruding a hot-melt pressure sensitive
adhesive composition (a) together with the coating (b). Thereby,
the coextrusion process according to the present invention does not
require an additional step of adding anti-blocking agents, but
instead allows for the provision of the packaged hot-melt adhesive
according to the present invention in a one-step process.
[0124] Another important aspect of the coextrusion coating (b) of
the present invention is that the coating consists of "neat"
polymers.
[0125] Without being bound to a specific theory, it is believed
that the effectiveness of the anti-blocking properties of the
coextrusion coating (b) is a result of the chemical and physical
characteristics of the neat coating film materials. This is
supported by the fact that the coextrusion coating (b) is not
penetrated over time during storage and migration of adhesive
components into the coating is avoided. Also, with the use of neat
polymer extrusion coatings, deterioration of anti-blocking
properties of the coating by migration of components of the coating
composition into the adhesive is excluded. In this regard it is
noted that conventional powdered coated hot-melt compositions
during storage at high room temperatures (25-70.degree. C.) tend to
"absorb" the anti-tack powders, thus deteriorating the anti-tack
effectiveness. It was observed that this does not happen with the
coextruded coating (b).
[0126] Furthermore, some of the conventional anti-blocking agents
such as silica create inhalable dusts that are potentially harmful
or can cause serious health issues, for example lung or respiratory
problems. The coextruded coating (b) is not inhalable. This reduces
health risks and expenses for filters and air cleaning equipment.
Consequently, coextruded coating (b) provide a favorable,
environmentally friendly and safe alternative to silica as an
anti-blocking agent for individual forms of packaged hot-melt
adhesives.
[0127] A particular advantage of the "neat" coating polymers in
comparison to previously used anti-tack coatings is that uniform
"neat" coating material can be designed and manufactured, which can
be applied to different adhesive compositions. Conventional
anti-tack coatings have the disadvantage that the type and amount
of components present in said anti-tack coatings have to be
separately adjusted for each individual type of adhesive
composition to meet their specific properties. In contrast, the
"neat" coating polymers according to the present invention
encompass a single component, which does not diffuse into the
adhesive composition, and could therefore be pre-designed and
manufactured in large quantities, and be subsequently applied to a
large variety of different adhesive compositions. Therefore, the
use of "neat" coating polymers according to the present invention
provides a resource- and cost-efficient way to provide coextrusion
coatings for packaged hot-melt adhesives.
[0128] In one aspect of the present invention, the packaged
hot-melt adhesive comprises a hot-melt pressure sensitive adhesive
composition (a) and a coextrusion coating (b) of consisting of neat
low-density polyethylene, neat polypropylene, or neat ethylene
vinyl acetate having a melt flow index between about 20 g/10 min
and about 300 g/10 min (ASTM D 1238--190.degree. C., 2.16 kgs).
[0129] The term "neat" according to the present invention, which
refers to neat polymers, encompasses exclusively one type of
polymer, which do not contain any additional polymers, beside the
stated polymers. Thereby, any blends of polymers with additional
copolymers or additives are excluded from the definition of "neat"
polymers according to the present invention.
[0130] A "neat" low-density polyethylene coating (b) according to
the present invention refers to a low-density polyethylene with a
melt flow index between about 20 g/10 min and about 300 g/10 min.
Said "neat" low-density polyethylene has a density between about
0.80 g/cm.sup.3 and about 1.00 g/cm.sup.3, preferably between about
0.85 g/cm.sup.3 and about 0.95 g/cm.sup.3, more preferably between
about 0.90 g/cm.sup.3 and about 0.93 g/cm.sup.3, even more
preferably between about 0.91 g/cm.sup.3 and about 0.92 g/cm.sup.3
and most preferably about 0.92 g/cm.sup.3. Said "neat" low-density
polyethylene has a melting point between about 60.degree. C. and
about 130.degree. C., preferably between about 80.degree. C. and
110.degree. C. and most preferably between about 95.degree. C. and
about 110.degree. C., which has been determined according to the
Exxon Mobil method.
[0131] Preferably, a "neat" low-density polyethylene coating (b)
includes a low-density polyethylene with a melt flow index between
about 20 g/10 min and about 120 g/10 min, preferably between about
20 g/10 min and about 60 g/10 min, more preferably between about 26
g/10 min and about 40 g/10 min.
[0132] Alternatively, a "neat" low-density polyethylene coating (b)
may also include a low-density polyethylene with a melt flow index
between about 120 g/10 min and about 300 g/10 min, preferably
between about 140 g/10 min and about 160 g/10 min, more preferably
between about 150 g/10 min.
[0133] A neat low-density polyethylene coating (b) with a melt flow
index between about 20 g/10 min and about 300 g/10 min may be
combined with any hot-melt pressure sensitive adhesive composition
(a) according to the present invention, preferably with an adhesive
composition (a), which comprises a base polymer selected from
polyolefins, polyolefin copolymers, polyolefin/alpha-olefin
interpolymers, more preferably selected from the group consisting
of ethylene and propylene homo- or copolymers.
[0134] Also preferably, a neat low-density polyethylene coating (b)
according to the present invention may be combined with an adhesive
composition (a), which comprises a base polymer selected as
metallocene-synthesized polymer, preferably a
metallocene-synthesized ethylene or propylene homo- or copolymer,
more preferably a metallocene-synthesized propylene polymer.
[0135] Also preferably, a neat low-density polyethylene coating (b)
according to the present invention may be combined with an adhesive
composition (a), which comprises a base polymer selected as
ethylene vinyl acetate.
[0136] Also preferably, a neat low-density polyethylene coating (b)
according to the present invention may be combined with an adhesive
composition (a), which comprises a base polymer selected from
synthetic rubbers.
[0137] A "neat" polypropylene coating (b) according to the present
invention may also refer to a polypropylene with a melt flow index
between about 20 g/10 min and about 300 g/10 min. Said "neat"
polypropylene has a room temperature density between about 0.80
g/cm.sup.3 and about 1.00 g/cm.sup.3, preferably between about 0.85
g/cm.sup.3 and about 0.95 g/cm.sup.3, more preferably between about
0.88 g/cm.sup.3 and about 0.92 g/cm.sup.3, even more preferably
between about 0.89 g/cm.sup.3 and about 0.91 g/cm.sup.3 and most
preferably about 0.90 g/cm.sup.3. A preferred example of neat"
low-density polyethylene includes EXXON Mobil PP 7905E1 Exxon Mobil
Chemical.
[0138] Optionally, a "neat" polypropylene coating (b) may refer to
a polypropylene with a melt flow index between about 50 g/10 min
and about 150 g/10 min, preferably between about 80 g/10 min and
about 120 g/10 min, more preferably between about 100 g/10 min.
[0139] A neat polypropylene coating (b) with a melt flow index
between about 20 g/10 min and about 300 g/10 min may be combined
with any hot-melt pressure sensitive adhesive composition (a)
according to the present invention, preferably with an adhesive
composition (a), which comprises a base polymer selected from
polyolefins, polyolefin copolymers, polyolefin/alpha-olefin
interpolymers, more preferably selected from the group consisting
of ethylene and propylene homo- or copolymers.
[0140] Also preferably, a neat polypropylene coating (b) according
to the present invention may be combined with an adhesive
composition (a), which comprises a base polymer selected as
metallocene-synthesized polymer, preferably a
metallocene-synthesized ethylene or propylene homo- or copolymer,
more preferably a metallocene-synthesized propylene polymer.
[0141] Also preferably, a neat polypropylene coating (b) according
to the present invention may be combined with an adhesive
composition (a), which comprises a base polymer selected as
ethylene vinyl acetate.
[0142] Also preferably, a polypropylene coating (b) according to
the present invention may be combined with an adhesive composition
(a), which comprises a base polymer selected from synthetic
rubbers.
[0143] A "neat" ethylene polyvinyl acetate (EVA) coating (b)
according to the present invention is ethylene polyvinyl acetate
with a melt flow index between about 20 g/10 min and about 300 g/10
min. Said EVA polymer has a room temperature density between about
0.80 g/cm.sup.3 and about 1.00 g/cm.sup.3, preferably between about
0.90 g/cm.sup.3 and about 0.96 g/cm.sup.3, more preferably between
about 0.91 g/cm.sup.3 and about 0.95 g/cm.sup.3 and most preferably
about 0.935 g/cm.sup.3. In the ethylene vinyl acetate the vinyl
acetate content is between about 2 wt % and about 25 wt %,
preferably between about 5 wt % and about 20 wt %, more preferably
between about 10 wt % and about 15 wt %. Said "neat" low-density
ethylene polyvinyl acetate has a melting point between about
60.degree. C. and about 130.degree. C., preferably between about
70.degree. C. and about 110.degree. C. and most preferably between
about 85.degree. C. and about 95.degree. C. A preferred example of
ethylene vinyl acetate copolymers includes Ateva 1360 available by
M. Holland.
[0144] A neat ethylene polyvinyl acetate coating (b) with a melt
flow index between about 20 g/10 min and about 300 g/10 min may be
combined with any hot-melt pressure sensitive adhesive composition
(a) according to the present invention, preferably with an adhesive
composition (a), which comprises a base polymer selected from
polyolefins, polyolefin copolymers, polyolefin/alpha-olefin
interpolymers, more preferably selected from the group consisting
of ethylene and propylene homo- or copolymers.
[0145] Also preferably, a neat ethylene polyvinyl acetate coating
(b) according to the present invention may be combined with an
adhesive composition (a), which comprises a base polymer selected
as metallocene-synthesized polymer, preferably a
metallocene-synthesized ethylene or propylene homo- or copolymer,
more preferably a metallocene-synthesized propylene polymer.
[0146] Also preferably, a neat ethylene polyvinyl acetate coating
(b) according to the present invention may be combined with an
adhesive composition (a), which comprises a base polymer selected
as ethylene vinyl acetate.
[0147] According to the present invention, the coextrusion coating
(b) comprises neat low-density polyethylene, neat polypropylene, or
neat ethylene vinyl acetate having a melt flow index between about
20 g/10 min and about 300 g/10 min.
[0148] The melt flow index of the coextrusion coating material
correlates with its physical properties. At low melt flow index of
less than about 20 g/10 min, the coextrusion coating material
displays a high viscosity and a poor melting behaviour, which leads
to a partially inhomogeneous melt and at least partially prevents
proper mixing of the adhesive components.
[0149] On other hand, a high melt flow index of more than 300 g/10
min correlates with poor anti-blocking properties, e.g. barrier
properties, of the corresponding packaged adhesive, which in turn
leads to individual forms, which tend to agglomerate during the
melting process and are not free-flowing.
[0150] Therefore, the melt flow index between about 20 g/10 min and
about 300 g/10 min of the neat low-density polyethylene, neat
polypropylene, or neat ethylene vinyl acetate coating materials
covers an optimal range for the coating (b) to display its
properties.
[0151] The inventors surprisingly found that packaged hot-melt
adhesives wherein the coextrusion coating (b) consisting of neat
low-density polyethylene, neat polypropylene, or neat ethylene
vinyl acetate, which comprises a melt flow index between about 20
g/10 min and about 80 g/10 min display excellent anti-blocking
properties, e.g. barrier properties, which include particular forms
of packaged hot-melt adhesives, which are free-flowing and or have
a substantially tack-free surface for extended periods of time. It
might be advantageous to combine said coextrusion coating
materials, which comprises a melt flow index between about 20 g/10
min and about 80 g/10 min with a higher plasticizer content, which
may be added to the hot-melt pressure sensitive adhesive
composition (a).
[0152] In the present invention, the coextrusion coating (b) of the
packaged hot-melt adhesives in accordance with the present
invention consist of neat low-density polyethylene, neat
polypropylene, or neat ethylene vinyl acetate, which comprises a
melt flow index between about 20 g/10 min and about 80 g/10 min,
preferably between about 20 g/10 min and about 50 g/10 min, more
preferably between about 20 g/10 min and about 30 g/10 min, and
most preferably about 20 g/10 min.
[0153] The inventors surprisingly found out that the packaged
hot-melt adhesives consisting of neat low-density polyethylene,
neat polypropylene, or neat ethylene vinyl acetate, which comprises
a melt flow index between about 120 g/10 min and about 300 g/10 min
display a low viscosity and an optimal normal melting behavior,
leading to a homogenous melt. It may be advantageous to combine
said coextrusion coating materials, which comprise a melt flow
index between about 120 g/10 min and about 300 g/10 min with a
reduced amount of plasticizer, which may be included in the
hot-melt pressure sensitive adhesive composition (a).
[0154] In the present invention, the coextrusion coating (b) of the
packaged hot-melt adhesives in accordance with the present
invention consist of neat low-density polyethylene, neat
polypropylene, or neat ethylene vinyl acetate, which comprises a
melt flow index between about 150 g/10 min and about 300 g/10 min,
preferably between about 170 g/10 min and about 280 g/10 min, more
preferably between about 180 g/10 min and about 250 g/10 min, and
most preferably about 220 g/10 min.
[0155] The coextrusion coating (b) at least partially, preferably
substantially completely, covers the surface of the hot-melt
pressure sensitive adhesive composition (a), e.g. by a film layer
on the surface of the hot-melt individual forms. For the purpose of
the present invention, the term "at least partially covers" means
that at least 10%, preferably more than 25%, more preferably more
than 50%, and most preferably more than 75% or more than 90% of the
surface of the individual forms are covered by the coextrusion
coating (b) in accordance with the present invention. Most
preferably, the coextrusion coating (b) completely covers the
surface of the hot-melt pressure sensitive adhesive composition
(a).
[0156] In particular, the coextrusion coating (b) consists of a
crystalline material, which tends to be come easily meltable.
Preferably, the coextrusion coating (b) has a high
crystallinity.
[0157] In one embodiment, the coextrusion coating (b) may be
present in an amount between about 0.1 wt % and about 5 wt %,
referring to the total weight of the packaged hot-melt adhesive.
Preferably, the coextrusion coating (b) may be present in amount
between about 0.5 wt % and about 3 wt %. More preferably, the
coextrusion coating (b) may be present in amount between about 1.0
wt % and about 3.0 wt %. In an even more preferred embodiment, the
co-extrusion coating (b) may be present in amount between about 1.5
wt % and about 5.0 wt %. In an even more preferred embodiment, the
co-extrusion coating (b) may be present in amount between about 1.5
wt % and about 2.5 wt %. In a most preferred embodiment, the
co-extrusion coating (b) may be present in amount between about 1.5
wt % and about 2.0 wt %, referring to the total weight of the
packaged hot-melt adhesive.
[0158] If the base polymer present in the hot-melt pressure
sensitive adhesive composition (a) is selected as a synthetic
rubber, the coextrusion coating (b) may be present in an amount
between about 0.5 wt % and about 3 wt %, preferably, between about
1.0 wt % and about 3.0 wt %, more preferably between about 1.5 wt %
and about 3.0 wt %, even more preferably between about 1.5 wt % and
about 2.5 wt % and most preferably between about 1.5 wt % and about
2.0 wt %, referring to the total weight of the packaged hot-melt
adhesive.
[0159] If the base polymer present in the hot-melt pressure
sensitive adhesive composition (a) is selected as a polyolefin,
polyolefin copolymer, polyolefin/alpha-olefin interpolymer, the
coextrusion coating (b) may be present in a higher amount in
relation to the amount of coating (b) present if the base polymer
is selected as a synthetic rubber, preferably in an amount between
about 0.1 wt % and about 3 wt %, more preferably between about 0.5
wt % and about 3 wt %/o, even more preferably between about 1.0 wt
% and about 3 wt %, even more preferably between about 1.0 wt % and
about 2.5 wt %, even more preferably between about 1.0 wt % and
about 2.0 wt % and most preferably between about 1.5 wt % and about
2.0 wt %, referring to the total weight of the packaged hot-melt
adhesive.
[0160] The coextrusion coating (b) may have a melting temperature
between about 60.degree. C. and about 170.degree. C., between about
60.degree. C. and about 150.degree. C., preferably between about
100.degree. C. and about 140.degree. C. and more preferably between
about 120.degree. C. and about 130.degree. C. The melting
temperature has been measured according to the Ring and Ball
softening point method (DIN EN 1427).
[0161] The coextrusion coating (b) may have a room temperature
density between about 0.80 g/cm.sup.3 and about 1.00 g/cm.sup.3,
preferably between about 0.91 g/cm.sup.3 and about 0.93 g/cm.sup.3
and more preferably about 0.92 g/cm.sup.3.
C. Individual Forms
[0162] The packaged hot-melt adhesives according to the present
invention may be in any form suitable for their use, including any
"individual forms", irrespective of size. For the purpose of the
present invention the term "individual forms" comprise packaged
hot-melt adhesives in the form of granules, blocks, pillows,
prills. For another purpose of the present invention the term
"individual forms" comprise elongated ropes or rods, or any other
known form of hot-melts. The elongated ropes or rods can be of any
length, and, e.g., can be wound onto a reel, spool or can be freely
laid inside a box or other container and applied from there.
Preferred "individual forms" such as blocks, pillows, elongated
ropes or rods may have a size, in the longest dimension, in the
range of centimeters, for example up to about 15 cm or up to about
20 cm. In certain embodiments, the packaged hot-melt adhesives are
in the form of smaller sized "individual forms", such as particles,
prills, chips, flakes, spheres, beads, slugs, e.g. sausage shaped
slugs, or pellets.
[0163] The "individual forms" may be selected from a plurality of
pillows or prills. A "prill" in the meaning of the present
invention refers to a substantially spherical bead, while a
"pillow" refers to a substantial prismatic geometric object, such
as obtained by cutting off pieces from a cylindrical strand, which
optionally contains rounded edges and/or corners. In a preferred
embodiment, said pillows may have a substantial prismatic
rectangular form with average dimensions (length/width/height) of
about 40 mm.times.about 30 mm.times.about 12 mm, or about 20
mm.times.about 20 mm.times.about 20 mm. In a more preferred
embodiment, said pillows may have average dimensions
(length/width/height) of about 40 mm.times.about 20 mm.times.about
10 mm, most preferably of about 40 mm.times.about 15 mm.times.about
7 mm.
[0164] An individual form can weigh less than about 15 grams, or
even less than about 10 grams.
[0165] Alternatively, the pillows may have a substantially cube
like form. Also such pillows may have rounded corners, thereby
forming almost a spherical shape.
[0166] In another embodiment of the present invention, the
"individual forms" are selected from at least one of coextruded
ropes or rods, which do can be of any length. Preferably, the
coextruded ropes or rods may have a length between about 1 m and
about 100 m, and more preferably between about 5 m and about 50 m.
In a preferred embodiment, the coextruded ropes or rods may have a
diameter between about 0.1 cm and about 5 cm, preferably between
about 1 cm and about 3 cm, and more preferably about 2.5 cm.
Preferably the coextruded ropes or rods are wound onto a reel or
spool or are freely laid inside a box or other container.
[0167] According to the present invention, the packaged hot-melt
adhesive has a substantially tack-free surface and/or is
free-flowing, preferably for extended periods of time, such as a
month, 3 months, 6 months, a year, or more than a year. The
packaged hot-melt adhesive may have a tack-free surface and/or may
be free-flowing at ambient conditions or room temperature, i.e. at
temperatures from about 20.degree. C. to about 25.degree. C.,
and/or at elevated ambient temperatures, i.e. at temperatures from
about 25.degree. C. to about 70.degree. C. The term "free-flowing"
as used in the present invention means that "individuals" of the
packaged hot-melt adhesive are able to move freely and without any
difficulty and/or any agglomeration. Included in the definition
"free-flowing" individuals are individuals, which do not fuse
together and/or are able to move freely with none or minimal
mechanical action and/or are mechanical separable.
E. Preparation of Individual Forms of a Packaged Hot-Melt
Adhesive
[0168] The individual forms of a packaged hot-melt adhesive
according to the present invention comprise a hot-melt pressure
sensitive adhesive composition (a), which is covered by a
coextrusion coating (b). The inventive individual forms,
particularly pillows or ropes may be substantially tack-free and/or
free-flowing.
[0169] According to one embodiment of the present invention, a
method for preparing individual forms of a packaged hot-melt
adhesive according to the present invention comprises the first
step of providing a hot-melt pressure sensitive adhesive
composition (a), and the second step of coextruding said adhesive
composition (a) together with a coating (b) in such way that the
coating (b) at least partially covers the surface of the hot-melt
pressure sensitive adhesive composition (a), thereby forming the
individual forms of the packaged hot-melt adhesive and optionally
cutting the individual forms into pillows or prills.
[0170] The inventive method allows the preparation of tack-free
and/or free flowing individual forms of the packaged hot-melt
adhesive.
[0171] Individual forms of the packaged hot-melt adhesive,
particularly pillows or prills, may be particularly suitable for
use e.g. in vacuum feeders or similar conveying equipment due to
their small size and weight. However, due to the larger surface of
pillows or prills compared to larger blocks, pillows or prills may
have a higher tendency to agglomerate. Thus, the present invention
is specifically advantageous with small sized forms such as pillows
or prills, although it may equally work with pellets, flakes,
blocks or any other form of individuals of the inventive packaged
hot-melt adhesive.
[0172] The production of the individual forms of the packaged
hot-melt adhesive, e.g. pillows or prills, may require multiple
passes through a co-rotating twin screw extruder to homogenize the
hot-melt pressure sensitive adhesive composition (a), followed by
an coextrusion of the adhesive composition (a) together with the
coating (b) through a coextrusion system, followed by a solidifying
process optionally followed by the calibration of the granules
size.
[0173] Preferably, the packaged hot-melt adhesive according to the
present invention is obtained by a coextrusion process, wherein the
hot-melt pressure sensitive adhesive composition (a) is pumped
through the coextrusion head and wherein the coextrusion coating
(b) is added to the adhesive composition (a) such that the
coextrusion coating (b) substantially covers the adhesive
composition (a) as a cover sheet.
[0174] Furthermore, the packaged hot-melt adhesive is obtained by a
coextrusion process, wherein the coextrusion process comprises:
[0175] (i) providing one or more hot-melt components and blending
the hot-melt components to form a hot-melt pressure sensitive
adhesive composition [0176] (ii) providing a coating material
selected from neat low-density polyethylene, neat polypropylene, or
neat ethylene vinyl acetate having a melt flow index between about
20 g/10 min and about 300 g/10 min. [0177] (iii) coextruding both
(i) and (ii) such that the adhesive forms a strand substantially
surrounded by the coating material [0178] (iv) optionally cutting
the resulting, coated strand of adhesive (e.g. by forcing the
composition past rotating blades and cutting the hot-melt ribbons
to form resultant individual forms) [0179] (v) solidifying the
individuals, optionally by cooling the individuals by a liquid
cooling medium or by a dry air circulated.
[0180] Preferably, the individuals produced from this method are
pillows or prills.
[0181] Hot-melt pressure sensitive adhesive compositions are
suitable for preparing the inventive hot-melt individuals as
described above. Optionally, the packaged hot-melt adhesive
individuals may comprise additional components such as described
above.
E. Use of Individual Forms
[0182] In one aspect of the present invention, a plurality of
individual forms of a packaged hot-melt adhesive according to the
present invention may be used in an adhesive application process,
wherein the packaged hot-melt adhesive is conveyed to a melting
system in a free-flowing and/or air conveyable form before being
molten and applied to a substrate.
[0183] A disadvantage of individual forms of packaged hot-melt
adhesives previously used is that said particular forms may fuse
together inside the adhesive containing containers, e.g. during
storage. Such fusion of individual forms may occur, when said
individual forms are conventionally bulk packaged, e.g. packaged in
huge quantities in pouches or boxes. The elevated temperature,
which may be present in warehouses, combined with the weight of the
pouches themselves, if stacked upon each other, may cause that the
conventional individual forms fuse together into a large entity or
agglomerate. This complete fusion of individual forms may result in
that the corresponding packaged hot-melt adhesives may not be used
in an adhesive application process, e.g. by conveying the packaged
hot-melt adhesive to a melting system, a feeder or the like.
[0184] Therefore, it is an object of the present invention to
provide individual forms of the packaged hot-melt adhesive, which
do not tack or fuse together during the shipping or storage process
both at room temperature, as well as elevated temperatures and over
time during storage. It is a further object of the present
invention to modify the coextrusion coating (b) of the packaged
hot-melt adhesive to obtain individual forms of the adhesive which
have a significantly reduced fusion/blocking tendency, such that
said individual forms stay loose and/or can be easily separated. It
is a further object of the present invention to improve the
individual forms of packaged hotmelt adhesives, in such a way that
these adhesives can be packaged and automatically processed during
an adhesive application process, i.e. during conveying said
individual forms during a melting process.
[0185] The individual forms of the package hot-melt adhesive
according to the present invention do not tack or fuse together in
a storage device at 45.degree. C. and remain substantially loose
and free-flowing.
[0186] The term "substantially loose" means that the particles do
not stick together or may be easily separated from each other if
temporarily blocking, by application of mechanical forces such as
kicking against the container or vibration, or any other suitable
methods.
[0187] With the packaged adhesive of the present invention, the
plurality of individual forms does not fuse together as determined
by a blocking test.
[0188] In one embodiment of the present invention the individual
forms of the packaged hot-melt adhesive may be stored in an
adhesive containing container, e.g. a cardboard carton, a box,
preferably a plastic box, a plastic bag, a pouch, a big bag or a
supersack. These containers might contain between about 100 kg and
about 1,000 kg of individual forms, preferably between about 400 kg
and about 1,000 kg.
[0189] One aspect of the present invention encompasses an adhesive
containing container, comprising a plurality of individual forms of
the packaged adhesive according to the present invention, wherein
the container is selected from at least one of a box, preferably a
plastic box, plastic bag, a pouch, a big bag, and a supersack.
[0190] The term "big bag" as used herein also encompasses the terms
"super sack", or "bulk bag", which could be alternatively used in
the context of the present invention, and refers to bags made of
textile or other flexible material usable for shipping, handling
and storing of flowable products. Such big bags are commercially
available from e.g. PEMA Verpackung GmbH, Germany, preferably PEMA
Article number 40-09999hb, in various sizes and are conventionally
used for larger amounts of individual materials, such as greater
100 kg to metric tons. Such big bags also include reusable,
recyclable and/or returnable versions of big bags.
[0191] In one embodiment, the adhesive containing package bag
comprises sealed bags. In a preferred embodiment, the adhesive
containing package bag may be chosen as a conical bottomed bulk
bag/supersack or full drop or open bottom system, protected with
s-flaps bulk bag/supersack. Preferably, said bags are made from out
of coated 180+30 gr./sqm pp-woven-fabric.
[0192] In a typical adhesive application process, the individual
forms are provided from the container into a melting system,
wherein said individual form are being transferred to the melter,
wherein the individual forms are molten and applied to a
substrate.
[0193] In one embodiment of the present invention, the plurality of
individual forms is conveyed to the melting system by vacuum
conveying, tubular drag conveying, a big bag conveying method, melt
on demand, or any combination thereof.
[0194] The vacuum conveying system is depicted in FIG. 1 and
includes packaged hot-melt pressure sensitive adhesive which is
inserted, e.g. by a big bag (1), into a feed hopper (2) and the
vibratory feeder (3). A vacuum pump (4) generates a vacuum in the
vacuum conveyors separator tanks (5) and thereby sucks in air
through the inlet point at the feed hopper (2), which in turn
causes the packaged hot-melt adhesive to be aspirated and carried
in the corresponding air stream. Inside the separator tanks (5), a
filter unit (6) separates the packaged hot-melt adhesive from the
air, wherein the adhesive is contained in the separator tanks (5).
When the separator tanks (5) are filled with adhesive, the vacuum
pump switches off, the pressure in the separator tanks is adjusted
to the surrounding pressure and the adhesive material is discharged
through a discharge valve (7) directly into the hot-melt tank (8)
to be charged. The discharge step is controlled by a load cell (9),
which determines that the desired amount of adhesive is loaded into
the hot-melt tanks (8). After the discharge step, the discharge
valve (7) directly closes and the complete conveying cycle restarts
again.
[0195] An exemplary tubular drag conveying method, which refers to
a disc conveying system according to Cablevey Company, US, is
depicted in FIG. 2 and consists of a pipe (4) with the diameter of
from about 7 cms to about 13 cms, typically about 10 cm, through
which the individual forms (6) are conveyed. The pipes are
preferably stainless steel. The super sack (1) containing
individual forms (6) can be discharged into a conical bottom feed
hopper (2). Below the hopper discharge (2) is an inclined vibratory
feeder (3). It can be useful to put a limit switch on the vibratory
feeder to control the rate at which the individual forms are fed
into the tubular drag conveying system If the individual forms are
fed in too quickly, blockages can occur. When the level in the
adhesive melt tank (8) drops, the level transmitter sends a signal
to a controller and the controller then activates the vibratory
feeder (3). Individual forms will flow out of the hopper (2), down
the vibratory feeder (3) and into the tubular drag conveyor system.
This system consists of a drive motor, pulleys and a cable (7).
Every about 15 cm to about 20 cm, along the length of the cable (7)
are positioned plastic discs (5) that are roughly about 10 cm in
diameter. The pillows (6) fill in the voids between the discs (5).
The discs (5) are pulled slowly through the pipe line (4),
conveying the individual forms (6) toward the melt tanks (9). The
system can feed multiple melt tanks (9). Above each melt tank (9)
is a rotating valve and drop section of pipe (8), down to the melt
tank (9). If that tank level is calling for feed, the valve spins
(8) open and the pillows (6) fall into that melt tank (9). When the
level in the melt tank reaches a "full" set point, the
controller/load cell (10) signals the valve (8) to spin closed and
the flow of pillows to that tank stops. If the other melt tanks (9)
on this same system are also full, then the controller/load cell
(10) will also turn off the vibratory feeder (3) and the disc
conveyor system. When the next melt tank requires additional
adhesive the system turns on and completes the next cycle of feed.
This tubular drag conveying system is very gentle on the individual
forms, and this is important because the individual forms should
not be damaged in any conveying system, or risk to spill out the
adhesive and gumming up the feed system.
[0196] It has been found that when using a tubular drag conveying
system for conveying individual adhesive forms, running at a lower
than maximum capacity provides sufficient throughput while
decreasing the possibility of adhesive plugs. The tubular drag
conveying system can be run at less than about 50% capacity, less
than about 30% capacity, less than about 20% capacity or even from
about 5% to about 50% capacity.
[0197] The individual form conveyed in the tubular drag conveying
method can be a pillow. In embodiments, it is helpful if the pillow
has a minimum thickness to prevent getting squeezed between the
disc and the wall of the tube. It is useful if the pillow has a
thickness of greater than about 0.318 cms (0.125 inches), at least
about 0.635 cms (0.250 inches), or even from about 0.350 cms (0.138
inches) to about 1.5 cms (0.591 inches).
[0198] An exemplary big bag conveying method according to the
present invention involves an adhesive containing container,
selected e.g. as a big bag or supersack, wherein the adhesive
content of the container is manually or automatically, e.g. by a
crane or forklift, placed above a conical feed hopper. Typically,
the big bag or supersack may contain manufactured fracture sites in
the material, which may cause the material to fracture, such that
the big bag or supersack opens up at a defined location, e.g. at
the bottom of the bag. The fractures sites are typically generated
in a way that the fracture only occurs upon a specific impulse,
e.g. by pulling a rope, which is attached to the fracture sites. By
opening the bottom of the supersack, the adhesive flows into the
canonical feed hopper and from there directly into the pre-melter
or into a further conveying system to reach the pre-melters. In the
further adhesive application process, a fully or partially working
automated system similar to the systems described in the vacuum and
tubular drag conveying method described above may be employed.
[0199] An exemplary melt on demand conveying method according to
the present invention involves the individual forms being fed into
an extruder (e.g. a single screw extruder) or other melting
apparatus and then pumped through a heated hose into at least one
melt tank and optionally many melt tanks found on separate
manufacturing lines in the same location. Optionally, the molten
adhesive can be fed directly in to one or more adhesive nozzles.
The individual forms can be fed into the extruder in any possible
way including by use of a vibratory feeder.
[0200] In the present invention, the individual forms used in the
vacuum, tubular drag and/or big bag conveying system according to
the present invention are selected from the group consisting of
pillows, prills, flakes or chips, preferably pillows.
[0201] Another aspect of the vacuum, tubular drag conveying and
melt on demand methods of the present invention is to avoid cross
contamination. During a manual feeding process of individual forms
of the packaged hot-melt adhesive, there is a possibility that the
operator might feed the wrong grade of adhesive or a different
adhesive into the melt tank. In the above described automated
conveying system, a bar coding or scanning element may be included
in the system that will alarm and minimize the likelihood of using
the wrong adhesive.
[0202] Another aspect of contamination is to allow ambient plant
dust to enter the melt tanks. This could result in "charring" and
discoloration of the hot-melt adhesive as it's applied to the
customer's product. Every time the operator now opens the lid on
the hot-melt tank, dust or other foreign could enter the tank. The
above-described automatic feed system would essentially be a closed
system, thus minimizing the occurrence of contamination. With the
current, manual feed practice, the melt tank levels are typically
cycled from full to fairly empty until being refilled. This results
in a thin film of adhesive along the walls of the heated tanks that
are exposed to significant heat history and could result in
charring of the adhesive over time. In the described automatic feed
system, the level of adhesive is automatically controlled to
maintain the level consistently thereby avoiding high and low
levels, and thereby minimizing the thin film heat history.
F. General Use of Packaged Adhesive
[0203] The packaged hot-melt adhesive according to the present
invention can be used in the production of typical nonwoven hygiene
articles, sanitary devices, care articles, disposable medical
drapes, paper, packaging, tapes and labels, furniture, textiles,
footwear, in woodworking or in construction industries e.g. for
roofing membranes or for other construction type lamination.
[0204] Further, the packaged hot-melt adhesive according to the
present invention can be used in the production of nonwoven hygiene
and sanitary articles, non-woven articles, labeling, elastic
lamination, construction and core lamination or positioning
adhesive. Also, the packaged hot-melt adhesive according to the
present invention is used in the production of diapers, adult
incontinence devices, sanitary napkins and disposable medical
drapes.
[0205] The packaged hot-melt adhesive according to the present
invention may also be used in the production of disposable
articles. Preferably, the packaged hot-melt adhesive according to
the present invention is used in the production of at least part of
the core of the disposable article or at least part of an elastic
attachment attached to the disposable article.
[0206] The invention will now be described by way of the following
examples. All parts, ratios, persons and amounts stated are by
weight unless otherwise specified.
EXAMPLES
[0207] In the context of the present invention, unless indicated
otherwise, the melt flow index (MI) is determined in accordance
with ASTM D 1238 at a standard temperature of 190.degree. C. and at
2.16 kg load.
[0208] The viscosity is determined similar to method ASTM D-3236 as
follows. The viscosity of a sample is determined using a Brookfield
Laboratories DVH, DV-II, or DV-III Viscometer. The spindle used may
be a SC-21, SC-27, SC-29 or SC-34 hot-melt spindle suitable for
measuring viscosities in a range between about 100 mPas and about
4,000,000 mPas. The sample is placed in a pre-warmed measuring
cell, which in turn is inserted into the heating element/container
and is locked into place. The sample is heated until it is melted
with additional sample being added until the melted sample is about
5 mm higher than the cylinder of the measuring spindle. The
viscometer apparatus is lowered and the spindle is submerged into
the sample. The viscometer is turned on and set to a shear rate
that leads to a torque reading in the range of from 30% to 60%.
Readings are taken every minute for about 15 minutes or until the
values stabilize. The final reading can be obtained after 30 min
and is recorded in mPas.
[0209] The molecular weight of all materials mentioned in this
description, if not expressly stated otherwise, is determined by
the method ASTM D 4001-93/2006.
[0210] The melting point is determined according to DIN EN 1427
(Ring and Ball) with the Ring and Ball instrument MC753 as
summarized as follows. Two shouldered rings are heated to melt
temperature and are placed onto a silicon-papered glass-plate and
the melted substance is poured into the rings. After cooling, the
excess materials were cut off and the samples were placed into the
sample holder of the apparatus and the ball-centering guide with
the balls is placed above the samples. A 600 ml NF beaker is filled
with 500 ml Glycerin and is placed on the heating plate of the MC
753 apparatus. The frame, which is ready for measurement with the
shouldered rings, is placed into the beaker in such a way that it
is centered on the pins. The temperature sensor is adjusted in the
therefore designed opening in the frame and the MC 753 apparatus is
activated by choosing the measuring point (keyboard 1-10, basic
unit). After a certain pre-heating time, the program automatically
runs with a heating rate of 5.degree. C. per minute until the balls
fall. The measurement is completed when both balls have fallen down
and two temperatures are shown on the display.
[0211] Polymer density is determined according to method ASTM D
1505.
[0212] The penetration number (PZ, "Penetrationszahl") is
determined by needle penetration according to the test procedure is
described in DIN 51579. About 100 g of sample polymer is melted
until a temperature about 10 to 15.degree. C. above the melting
temperature. The homogeneous melt is filled into a corresponding
examination cylinder, cooled at room temperature for about 1 hour
and incubated at 25.degree. C. for 1 hour. The melt-containing
cylinder is placed in a pre-adjusted needle penetration device
(mass: 100 g, time: 5 sec, temperature: 25.degree. C.). The needle
is automatically positioned at the melt surface, the measuring
process is started and the penetration depth is recorded. For
reproducibility three consecutive measurements are performed and
the average value of the three measurements is recorded. The
penetration number indicates the hardness of the polymer
composition and is referred to as 1/10 mm. Thereby a high
penetration number refers a soft material, wherein the low
penetration number refers to a hard material.
[0213] The blocking test 1 according to the present invention is
performed by placing 5 kg of coextruded individuals (e.g. pillows)
of the product in 3 bags. The particular containing bags were
placed at 45.degree. C. in a forced air chamber for 2 hours. After
the incubation period, the bags were stacked on top of each other.
A 5 kg weight was placed on top of the stack of bags for 1 hour.
Afterwards, the weight was removed and the individual in the bags
were evaluated according to the criteria set out below.
[0214] The blocking test 2 according to the present invention is
performed by placing 15 kg of coextruded individuals (e.g. pillows)
of the product in a corrugated box with a lid. The box was placed
at 30.degree. C. in an oven for 1 week. After the incubation
period, the box was removed from the oven and the pillows were
dumped out and evaluated.
[0215] A rating system was developed, ranging from 1 to 5, to
classify the potential of co-extruded individual to not block
during the further application in the melting process.
1: individual forms are completely fused together 2: individual
forms are mostly fused together 3: individual forms partially fused
together, cannot be separated by mechanical force 4: individual
forms are partially fused together, can be separated by mechanical
force 5: no fusion of individual forms observed
Example 1
[0216] A packaged hot-melt adhesive was prepared by using 1 wt %
low density polyethylene (LDPE) with a melt flow index of 150 g/10
min and a room temperature density of 0.913 as the coextrusion
coating material on a standard hot-melt pressure sensitive adhesive
having a mineral oil content of 20.6 wt % and a 15 wt % polystyrene
containing linear styrene-isoprene-styrene block copolymer (MW
220,000, coupling efficiency 81%, Kraton D-1161 NS). The results
are shown in Table 1 below.
Example 2
[0217] A packaged hot-melt adhesive was prepared by using 2 wt %
low density polyethylene (LDPE) with a melt flow index of 150 g/10
min and a room temperature density of 0.913 as the coextrusion
coating material on a standard hot-melt pressure sensitive adhesive
having a mineral oil content of 27 wt % and ethylene-octene
copolymer (ENGAGE 8200, Dow Chemical Company). The results are
shown in Table 1 below.
Example 3
[0218] A packaged hot-melt adhesive was prepared by using 2 wt %
low density polyethylene (LDPE) with a melt flow index of 150 g/10
min and a room temperature density of 0.913 as the coextrusion
coating material on a standard hot-melt pressure sensitive adhesive
having a mineral oil content of 16 wt % and a
metallocene-synthesized low molecular weight polypropylene polymer
(L-MODU S-400, Idemitsu Kosan Co., Ltd.). The results are shown in
Table 1 below.
[0219] The following comparative examples are included.
Comparative Example 1
[0220] A packaged hot-melt pressure sensitive adhesive was prepared
by coextruding a standard hot-melt pressure sensitive adhesive
having 26.5 wt % of mineral oil and ethylene-octene copolymer
(ENGAGE 8200, Dow Chemical Company) coextruded with 2 wt % of a
coating composition, which in turn comprises 40.0 wt % hydrogenated
microwax (Shell Microcrystalline Wax HMP, Shell), 35.9 wt % of
cycloaliphatic hydrocarbon resin tackifing agent (ESCOREX 5320,
Exxon Mobil Company), 23.9 wt % of styrene ethylene butylene
styrene block copolymer (SEPTON 8007, Kuraray America, Inc.). The
results are shown in Table 1 below.
TABLE-US-00001 TABLE I Example No. 1 2 3 Comp. 1 Viscosity at
150.degree. C. 2,800 4,800 5,900 4,800 [mPas] Melting point
[.degree. C.] 93 94 104 94 Melt index of polymer 150 150 150 --
coating Blocking test results (1).sup.x -- 3 5 1 Blocking test
results (2).sup.x -- 5 -- 1 .sup.xBlocking test results 1:
individual forms are completely fused together 2: individual forms
are mostly fused together 3: individual forms are partially fused
together, cannot be separated by mechanical force 4: individual
forms are partially fused together, can be separated by mechanical
force 5: no fusion of individual forms observed
[0221] According to table 1, the neat LDPE coating according to the
present invention, which is used in Examples 1, 2 and 3 in an
amount of 1 wt % and 2 wt % results in superior results in blocking
tests compared to the conventional coating composition used in
Comparative Examples 1 and 2, irrespectively of the base polymer
used.
[0222] Moreover, a direct comparison of the composition of Example
2 with the composition of comparative example 1, wherein the type
of base polymer and the amount of plasticizer of the hot-melt
pressure sensitive adhesive are identical, shows improvement in
blocking test of the neat LDPE coating in comparison with the
conventional coating materials.
[0223] The following table 2 provides comparative examples A, B, C
and D with examples 1, 2 and 3, and discloses different polymers,
comprising varying amounts of plastizicer in relation to the
corresponding penetration numbers (PZ).
TABLE-US-00002 TABLE II Example No. Comp. A 3 Comp. C Comp. D 2
Comp. E 1 Polymer Kraton L- Vector Taipol EG- Vector Kraton type
D1117.sup.1 MODU 4411.sup.3 SBS- 8200.sup.4 4114A.sup.5 D1161
S400.sup.2 320 NS.sup.6 Plasticizer 5 16 18 25 26 26 21-26 content
[wt %] PZ [25.degree. C.] 63 32 34 62 51 132 117 PZ:
Penetrationszahl/Penetration number .sup.1Kraton D1117 - available
from Kraton Polymers U.S. LLC; 17% Styrene, MFR = 33 g/10 min
@200.degree. C., 5 kg; 33% diblock .sup.2L-MODU S-400 - metallocene
catalyzed polypropylene available from Indemitsu Kosan Co. Ltd.
Viscosity @190 C. = 7000 cp .sup.3Vector 4411A - available from
Dexco Polymers; 44% Styrene, MFR = 40 g/10 min @ 200.degree. C., 5
kg; <1% diblock .sup.4EG-8200 - metallocene catalyzed ethylene
octene available from Dow Chemical Company, MI = 5.0 g/10 min,
190.degree. C., 2.16 kg .sup.5Vector 4114A - SIS available from
Dexco Polymers; 15% Styrene, MFR = 25 g/10 min @ 200.degree. C., 5
kg; diblock content = 42% .sup.6Kraton D 1161NS - SIS available
from Kraton Polymers U.S. LLC; 15% Styrene, MFR = 9 g/10 min @
200.degree. C., 5 kg; diblock content = 33%
[0224] The above specific examples are not intended to limit the
present invention. Rather, other embodiments are within the
appended claims.
* * * * *